WO2004072472A1 - Control valve arrangement - Google Patents

Control valve arrangement Download PDF

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Publication number
WO2004072472A1
WO2004072472A1 PCT/GB2004/000603 GB2004000603W WO2004072472A1 WO 2004072472 A1 WO2004072472 A1 WO 2004072472A1 GB 2004000603 W GB2004000603 W GB 2004000603W WO 2004072472 A1 WO2004072472 A1 WO 2004072472A1
Authority
WO
WIPO (PCT)
Prior art keywords
valve
fuel
valve member
control valve
arrangement
Prior art date
Application number
PCT/GB2004/000603
Other languages
French (fr)
Inventor
Matthew E. Moore
Original Assignee
Delphi Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Delphi Technologies, Inc. filed Critical Delphi Technologies, Inc.
Publication of WO2004072472A1 publication Critical patent/WO2004072472A1/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012Valves
    • F02M63/0014Valves characterised by the valve actuating means
    • F02M63/0015Valves characterised by the valve actuating means electrical, e.g. using solenoid
    • F02M63/0017Valves characterised by the valve actuating means electrical, e.g. using solenoid using electromagnetic operating means
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M47/00Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
    • F02M47/02Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
    • F02M47/027Electrically actuated valves draining the chamber to release the closing pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/20Varying fuel delivery in quantity or timing
    • F02M59/36Varying fuel delivery in quantity or timing by variably-timed valves controlling fuel passages to pumping elements or overflow passages
    • F02M59/366Valves being actuated electrically
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0003Fuel-injection apparatus having a cyclically-operated valve for connecting a pressure source, e.g. constant pressure pump or accumulator, to an injection valve held closed mechanically, e.g. by springs, and automatically opened by fuel pressure
    • F02M63/0007Fuel-injection apparatus having a cyclically-operated valve for connecting a pressure source, e.g. constant pressure pump or accumulator, to an injection valve held closed mechanically, e.g. by springs, and automatically opened by fuel pressure using electrically actuated valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012Valves
    • F02M63/0031Valves characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details
    • F02M63/004Sliding valves, e.g. spool valves, i.e. whereby the closing member has a sliding movement along a seat for opening and closing
    • F02M63/0042Sliding valves, e.g. spool valves, i.e. whereby the closing member has a sliding movement along a seat for opening and closing combined with valve seats of the lift valve type
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012Valves
    • F02M63/0031Valves characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details
    • F02M63/0045Three-way valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012Valves
    • F02M63/007Details not provided for in, or of interest apart from, the apparatus of the groups F02M63/0014 - F02M63/0059
    • F02M63/0073Pressure balanced valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/40Fuel-injection apparatus with fuel accumulators, e.g. a fuel injector having an integrated fuel accumulator

Definitions

  • the present invention relates to a control valve arrangement for use in a fuel injection system. It relates particularly, although not exclusively, to a control valve arrangement for use in a fuel injection system that is generally of the common rail type for delivering fuel to a combustion space of an internal combustion engine. The invention also relates to a fuel injection system incorporating a control valve arrangement.
  • a fuel injector with a nozzle control valve which is arranged to control movement of a fuel injector valve needle relative to a seating so as to control the delivery of fuel from the injector.
  • a known electronic unit injector includes a dedicated pump having a cam-driven plunger for raising fuel pressure within a pump chamber, and an injection nozzle through which fuel is injected into an associated engine cylinder.
  • a spill valve is operable to control the pressure of fuel within the pump chamber. When the spill valve is in an open position, the pump chamber communicates with a low pressure fuel reservoir so that fuel pressure within the pump chamber is not substantially affected by movement of the plunger and fuel is simply drawn into and displaced from the pump chamber as the plunger reciprocates. Closure of the spill valve causes fuel pressure in the pump chamber to rise as the plunger is driven to reduce the volume of the pump chamber.
  • the EUI also includes an electronically controlled nozzle control valve which is arranged to control the timing of injection of fuel.
  • a single pump is arranged to charge an accumulator volume (or common rail) with high pressure fuel for supply to a plurality of injectors.
  • the timing of injection is controlled by means of a respective nozzle control valve of each injector.
  • One advantage of the common rail system is that the timing of injection of high pressure fuel is not dependent upon a cam drive, and so fast and accurate timing of injection can be achieved with the nozzle control valves alone.
  • achieving very high injection pressures within a common rail system is problematic and the high levels to which fuel must be pressurised can cause high stresses within the pump and within the rail.
  • the rail must therefore be provided with a relatively thick wall for pressure containment, making it heavy and bulky. Parasitic fuel losses can also be high.
  • a nozzle control valve is used for the control of initiation and termination of injection.
  • a control valve arrangement suitable for use in an engine fuel injection system having first, second and third fuel volumes, the control valve arrangement including an inner valve member that is slidably movable within an outer valve member to provide for the control valve arrangement (i) a first valve position in which the first fuel volume communicates with the second fuel volume, (ii) a second valve position in which communication between the first fuel volume and the second fuel volume is broken and (iii) a third valve position in which one of the first and second fuel volumes communicates with the third fuel volume.
  • the inner valve member slides within the outer valve member, so that at least a part of the outer surface of the inner valve member is in direct sliding contact with a part of an inner surface of the outer valve member e.g. the internal bore of a tubular outer valve member.
  • the fuel system enables injection of fuel from either the first or second fuel volume in dependence upon the position of the control valve arrangement, and the third fuel volume takes the form of a low pressure drain or reservoir.
  • the fuel volumes may take the form of chambers, passages, channels, pump chambers or any other type of "reservoir” for fuel storage or through which fuel flows.
  • control valve arrangement is incorporated within a fuel injection system having an accumulator volume (the first fuel volume) for fuel at a first injectable pressure level and pump means (the second fuel volume) for increasing fuel pressure to a second injectable pressure level.
  • control valve arrangement includes an inner valve member that is slidably mounted within the outer valve member to provide for the control valve arrangement (i) a first valve position in which the accumulator volume communicates with the pump means, (ii) a second valve position in which communication between the accumulator volume and the pump means is broken and (iii) a third valve position in which the pump means communicates with a low pressure fuel drain (the third fuel volume), thereby to enable injection of fuel at either the first or second pressure level in dependence upon the position of the control valve arrangement.
  • the fuel injection system may alternatively be configured so that any one of the first, second or third fuel volumes is the low pressure fuel drain, the pump means or the accumulator volume.
  • the inner valve member is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
  • the outer valve member is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
  • the control valve arrangement has particular application in a fuel injection system of the hybrid EUI-common rail type, such as that described in our co-pending PCT and EP applications, WO 03/093671 and EP 1359316 A, in which an injection control means in the form of a nozzle control valve is typically provided to control movement of a valve needle of an injection nozzle so as to control the timing of commencement and termination of fuel injection.
  • an injection control means in the form of a nozzle control valve is typically provided to control movement of a valve needle of an injection nozzle so as to control the timing of commencement and termination of fuel injection.
  • Fuel injection at a first pressure can be achieved with the control valve arrangement in the first valve position
  • fuel injection at the second pressure level can be achieved with the control valve arrangement in the second valve position and termination of injection may be effected or aided by spilling fuel to low pressure with the control valve arrangement in the third valve position.
  • One advantage of the present invention is that its use in such a fuel system enables rapid termination of fuel injection, thus providing improved engine performance and an ability to reduce emissions levels.
  • the system permits fuel injection to be terminated in such a way that the injector valve needle need not be seated against a high fuel pressure within the injector at the end of injection, due to the facility to provide a spill-end of injection .
  • the inner valve member is therefore substantially pressure balanced to fuel in the second fuel volume, that is the pump means, when the second valve position is adopted. More preferably, the outer valve member is substantially pressure balanced to fuel in the fuel volume, that is the pump means, when the second valve position is adopted.
  • both the inner and outer valve members are pressure balanced to fuel at the injectable pressure level that is delivered through a high pressure supply line to the injector.
  • the control valve arrangement can be conveniently sized and requires only one actuator to control movement of both the inner and outer valves .
  • an electromagnetic actuator arrangement which may comprise an energisable solenoid or winding (commonly referred to as a stator), and an armature.
  • the winding preferably has three states: a first state where the winding is not energised, a second state that results from partial energisation of the winding to a first partial energisation level, and a third state that results from energisation of the winding to a higher, partial energisation level or full energisation of the winding.
  • One of the inner or the outer valve members is preferably coupled to the armature so that, upon energisation (or de-energisation) of the winding, the inner and outer valve members are movable relative to and co-operable with one another, and engageable with valve seatings, so as to control the passage of fuel through the control valve arrangement.
  • the control valve arrangement preferably comprises a first fluid chamber which is fluidly communicable with the fuel accumulator volume, a second fluid chamber which is fluidly communicable with the pump means and the first fluid chamber, a third fluid chamber which is fluidly communicable with the second fluid chamber and a fourth fluid chamber which is fluidly communicable with the low pressure fuel drain.
  • fluidly communicable it is meant that fluid is able to flow selectively from one chamber to another.
  • the second fluid chamber may be communicable with the third fluid chamber by means of a first radial fluid passage defined in the outer valve member.
  • the outer valve member takes the form of a tubular member or sleeve having a valve bore or passageway through which at least a part of the inner valve member extends.
  • the outer valve member is preferably movable within a housing bore provided in a valve housing.
  • the first chamber is defined by an inner surface of the outer valve member and an outer surface of the inner valve member.
  • the second chamber is defined by an inner surface of the outer valve member and an outer surface of the inner valve member.
  • the third fluid chamber is preferably defined by a surface of the housing bore and an outer surface of the outer valve member.
  • the fourth fluid chamber is preferably defined by a surface of the housing bore and an outer surface of the outer valve member.
  • one or both of the third and fourth fluid chambers may be defined by a recess or recesses provided in the housing bore and/or the outer surface of the outer valve member.
  • the inner valve member is coupled to the armature.
  • the first valve seating is preferably positioned between the first and second fluid chambers, and the second valve seating is preferably positioned between the third and fourth fluid chambers.
  • the first valve seating is conveniently defined by a surface of the valve bore provided in the outer valve member.
  • the second valve seating is conveniently defined by a surface of the housing bore provided in the valve housing.
  • the inner valve member is engaged with a first valve seating when the control valve arrangement is in the second and third valve positions
  • the outer valve member is engaged with a second valve seating when the control valve arrangement is in the first and second valve positions.
  • the first and second valve seatings are preferably of substantially conical form, for engagement with substantially conical seating surfaces of the engageable parts of the inner and outer valve members respectively.
  • the differential angles at the first and second valve seatings are preferably selected so as to ensure the inner and outer valve members are substantially pressure balanced to fuel at the injectable pressure level when at least the second valve position is adopted.
  • no energisation of the winding corresponds to the control valve arrangement being in the first valve position.
  • the outer valve member is engaged with the second valve seating so that the third and fourth fluid chambers are fluidly disconnected, and the inner valve member is not engaged with the first valve seating such that the first and second chambers are fluidly connected.
  • fuel may therefore pass between the pump means and the fuel accumulator volume when the control valve arrangement is in the first valve position.
  • the control valve arrangement is in the second valve position, for example corresponding to partial energisation of the winding to the first, partial energisation level
  • the inner valve member is preferably engaged with the first valve seating so that the first and second fluid chambers are disconnected, and the outer valve member is advantageously engaged with the second valve seating so as to disconnect the third and fourth fluid chambers. In this manner, communication between the pump means and the accumulator volume is broken, and with the control valve arrangement in this second valve position injection of fuel at the second, higher pressure level can be achieved.
  • the inner valve member In the third valve position, for example corresponding to energisation of the winding to a full (or higher, partial) energisation level, the inner valve member is preferably engaged with the first valve seating, and the outer valve member is now spaced apart from the second valve seating thereby fluidly connecting the third and fourth fluid chambers. Fuel from the pump means may therefore flow from the second chamber into the third chamber, and then to the fourth chamber whereupon it may flow to the low pressure drain.
  • the outer valve member is coupled to the armature.
  • the first valve seating is preferably positioned between the first and second fluid chambers. There may also be provided a third valve seating positioned between the third and fourth fluid chambers.
  • the first valve seating is conveniently defined by an outer surface of the inner valve member.
  • the second valve seating is conveniently defined by a surface of a housing.
  • the third valve seating is conveniently defined by a housing bore provided in a valve housing.
  • the first and third valve seatings are preferably of substantially conical form, for engagement with substantially conical seating surfaces of the engageable parts of the outer valve member.
  • the differential angles at the first and third valve seatings are preferably selected so as to ensure the inner and outer valve members are substantially pressure balanced to fuel at the injectable pressure level when the second valve position, at least, is adopted.
  • the outer valve member is engaged with the first valve seating when the control valve arrangement is in the second and third valve positions.
  • the outer valve member is engaged with the second valve seating when the control valve arrangement is in the first valve position. More preferably, the outer valve member is engaged with the third valve seating when the control valve arrangement is in the second valve position.
  • the inner valve member is preferably and advantageously provided with at least one cross-drilling, or cut-away section, at an end thereof, so as to define a passage for fuel flow through the inner valve member between the fourth chamber and the low pressure drain when the outer valve member is spaced away from the second valve seating.
  • the inner valve member When the control valve arrangement is in the first valve position, for example corresponding to no energisation of the winding, the inner valve member is spaced apart from the first valve seating so that the first and second fluid chambers are fluidly connected, and the outer valve member is not in engagement with the third valve seating such that the third and fourth fluid chambers are fluidly connected. However, the outer valve member is engaged with the second valve seating such that fuel may not pass from the fourth fluid chamber to the low pressure drain.
  • fuel When the control valve arrangement is in this first valve position, fuel may therefore flow from the pump means to the fuel accumulator volume, and in this operating condition injection can be achieved at the first injectable pressure level.
  • the control valve arrangement When the control valve arrangement is in the second valve position (e.g.
  • the outer valve member is caused to move away from the second valve seating and into engagement with the first valve seating, thereby fluidly disconnecting the first and second fluid chambers.
  • the outer valve member is moved so far as to bring in into engagement with the inner valve member at the first valve seating, and to cause the inner valve to move with it.
  • the outer valve member is also moved so far as to bring it into engagement with the third valve seating and the third and fourth fluid chambers are disconnected, resulting in communication between the accumulator volume and the pump means being broken. This is the condition for injection at the second higher pressure level as fuel is not permitted to flow through the valve arrangement.
  • the outer valve member When the control valve arrangement is in the third valve position, for example partial energisation of the winding to the partial energisation level, the outer valve member is moved into engagement with the first valve seating, thereby disconnecting the first and second fluid chambers.
  • the outer valve member is moved only part way through its range of travel, however, and so is preferably spaced apart from both the second and third valve seatings, thereby fluidly connecting the second, third and fourth fluid chambers.
  • the inner valve member remains engaged with an inner valve stop as it is not caused to move with the outer valve member.
  • Fuel from the pump means is permitted to pass from the third chamber to the fourth chamber whereupon it may flow through the passage(s) in the inner valve member to the low pressure drain, even though the inner valve member remains seated against the inner valve stop.
  • Resilient spring means such as springs, may also be provided in the control valve arrangement to act on the inner and outer valve members to oppose the force applied to these parts by means of energisation of the winding.
  • Resilient spring means such as springs
  • the inner valve member when the inner valve member is in the first valve position it is urged by means of an inner valve spring into engagement with the inner valve stop and away from the first valve seating defined by the valve bore in the outer valve member.
  • the outer valve member is urged into engagement with the second valve seating by an outer valve spring.
  • the outer valve member remains urged into engagement with the second valve seating by virtue of the force due to the outer valve spring.
  • the second embodiment of the invention preferably utilises an inner valve spring arranged to urge the inner valve member into engagement with the inner valve stop when the control valve arrangement is in the first and third valve positions.
  • the fluid chambers are substantially annular chambers which preferably communicate with fuel system components via fluid passages defined in the valve housing.
  • the outer valve member may have a radial passage defined therein for linking the first fluid chamber to the fuel accumulator volume.
  • a fuel injector for use in delivering fuel to an internal combustion engine at first and second injectable pressure levels, the fuel injector comprising the aforedescribed control valve arrangement.
  • the fuel injector may further comprise said pump means for increasing fuel pressure to at least one of the first and second injectable pressure levels.
  • a third aspect of the invention provides a fuel injection system for supplying pressurised fuel to an injection nozzle, the fuel injection system comprising: an accumulator volume for supplying fuel at a first injectable pressure (PI) to the injection nozzle; pump means for increasing the pressure of fuel supplied to the injection nozzle to a second injectable pressure level (P2); and a control valve arrangement operable between a first valve position in which the accumulator volume communicates with the pump means and fuel at the first injectable pressure level (PI) is supplied to the injection nozzle, a second valve position in which communication between the pump means and the accumulator volume is broken so as to permit fuel at the second injectable pressure (P2) to be supplied to the injection nozzle, and a third valve position in which the communication between the pump means and the accumulator volume is broken and the pump means communicates with a low pressure drain, thereby to aid, or execute, termination of injection.
  • PI injectable pressure
  • P2 second injectable pressure level
  • the fuel injection may, but need not, include a high pressure fuel pump for supplying fuel at the first injectable pressure level to the accumulator volume. If no high pressure fuel pump is provided, the pump means itself serves to increase fuel to the first pressure level by actuating the control valve arrangement to adopt its first valve position.
  • control valve arrangement of the first aspect of the invention may be included alone or in appropriate combination in the second or third aspects of the invention.
  • Figure 1 is a schematic diagram of a hybrid EUI-common rail fuel injection system
  • Figure 2a is a schematic diagram of a control valve arrangement according to a first embodiment of the invention, for use in the fuel injection system of Figure 1;
  • Figure 2b is a schematic diagram of a control valve arrangement according to a second embodiment of the invention, for use in the fuel injection system of Figure 1;
  • Figure 3 is a sectional view of the control valve arrangement of the first embodiment
  • Figures 4a and 4b are sectional views of selected parts of the control valve arrangement of the first embodiment
  • Figures 5 a, 5b and 5 c are sectional views of the control valve arrangement of the first embodiment in its first, second and third positions, respectively;
  • Figure 6 is a sectional view of the control valve arrangement of the second embodiment
  • Figures 7 a and 7b are sectional views of selected parts of the control valve arrangement of the second embodiment
  • Figures 8a, 8b and 8c are sectional views of the control valve arrangement of the second embodiment in its first, third and second positions, respectively;
  • Figures 9a and 9b are tables showing information regarding the positions of the control valve arrangements of the first and second embodiments, respectively.
  • a fuel injection system 10 comprising a fuel injector, referred to generally as 12, and an associated high pressure supply passage 16.
  • the high pressure fuel passage is arranged to deliver fuel to an injection nozzle 20 of the injector 12.
  • the injection nozzle 20 includes a valve needle 14 that is engageable with a valve needle seating (not shown), in use, so as to control the delivery of fuel from the nozzle 20.
  • the injector 12 also includes a needle control valve (NCN) 18, also referred to as a nozzle control valve, to control movement of the valve needle 14, whereby movement of the needle 14 away from the seating permits fuel to flow through the nozzle 20 into an engine cylinder or other combustion space.
  • NCN needle control valve
  • the ⁇ CN 18 is operable between a first position (hereinafter referred to as a "closed” position), in which an injector control chamber 22 communicates with the high pressure supply passage 16, and a second position (hereinafter referred to as an "open” position) in which the control chamber 22 communicates with a low pressure reservoir (not shown) and communication between the high pressure supply passage 16 and the control chamber 22 is broken.
  • a spring 23 is arranged in the injector control chamber 22 to urge the valve needle into engagement with its seating.
  • a common rail pump 24 supplies fuel at a moderately high and injectable pressure level (e.g. between about 300 and 1000 bar) to an accumulator volume in the form of a common rail 26.
  • a pressure regulator 28 serves to maintain the pressure of fuel within the common rail 26 at a substantially constant level (referred to as "rail pressure").
  • the common rail 26 supplies pressurised fuel to a supply passage 30 (or common rail line) in communication with a pump chamber 32 arranged within, and communicating with, the high pressure supply passage 16 under the control of an electro-magnetically controlled three-position control valve arrangement 34.
  • the pump chamber 32 forms part of pump means 36, including a plunger 38 which is driven by means of a cam drive arrangement 40.
  • the plunger 38 has a pumping stroke (during which the volume of the pump chamber 32 is reduced and fuel may be injected), and a return or retraction stroke (during which the volume of the pump chamber 32 is increased and the pump chamber 32 can be filled).
  • the three-position valve arrangement 34 also controls the passage of fuel to a low pressure drain 42 via a low pressure supply passage 44.
  • Each injector has a dedicated plunger 38 and pump chamber 32, as shown in Figure 1 for the injector 12, and the pump chambers communicate with the common rail 26 through respective three-position valves, such as 34.
  • the plunger 38 is driven by means of a cam drive arrangement having a cam or cam member 40.
  • the valve arrangement 34 may be an electro-magnetically operable valve that is actuated in response to an electronic control signal provided by an engine controller to move between first, second and third valve positions so as to control whether pressurisation of fuel within the pump chamber 32 occurs as the plunger 38 reciprocates under the influence of the cam 40, or whether fuel at high pressure is "spilled" to the low pressure drain 42 to terminate injection.
  • the valve 34 may take the form of a first control valve arrangement 34a, as shown in Figure 2a.
  • first valve arrangement 34a When the valve adopts its first valve position, the high pressure passage 16, and hence the pump chamber 32, communicates with the common rail 26. In this position, the passage of fuel from the high pressure passage 16 to the low pressure drain 42 is prevented. Under such circumstances, reciprocating movement of the plunger 38 has substantially no effect on fuel pressure within the chamber 32, and thus the fuel pressure does not increase above rail pressure.
  • the valve 34a in the first position the pressure of fuel supplied to the injector 12 through the passage 16 is therefore determined by the pressure of fuel within the common rail 26 which, typically, will be between 300 and 1000 bar.
  • moderate pressure level PI
  • the NCN 18 In order to inject fuel at this first, moderate pressure level (PI), the NCN 18 is moved into its open position, causing fuel pressure within the control chamber 22 to be reduced as it flows to low pressure and thereby enabling the valve needle 14 to lift.
  • the timing of injection of fuel at the second, higher pressure level (P2) is controlled by operation of the ⁇ CN 18 while the valve 34a is in the second valve position, in which circumstances the pump arrangement 36 serves to increase the pressure of fuel within the pump chamber 32 to the second, higher pressure level for delivery through the high pressure supply passage 16
  • the ability to provide injection at two different pressure levels is particularly useful for providing a pilot injection of fuel at a lower pressure level followed by a main injection of fuel at a higher pressure level. This can be achieved by switching the control valve arrangement 34 between its first and second valve positions, and actuating the ⁇ CN 18 to cause an injection of fuel for both the first and second valve positions.
  • Termination of fuel injection in the system 10 may be achieved when the control valve arrangement is in a third valve position, whereby the high pressure supply passage 16 communicates with the low pressure drain 42 and communication between the pump chamber 32 and the common rail 26 is broken.
  • the valve 34a is moved to the third valve position to "spill" fuel in the high pressure passage 16 to the low pressure drain 42.
  • the reduction in pressure in the passage 16 reduces the force acting on the valve needle 14 in an opening direction and the spring 23 in the injector control chamber 22 exerts a high enough force on the needle 14 so that it seats to end fuel injection. This is referred to as “spill end of injection”, or “spill-type end of injection”, as it is the spilling of fuel to the low pressure drain 42 that causes the valve needle 14 to seat.
  • the first control valve arrangement 34a is illustrated in further detail in Figures 3, 4a and 4b, and comprises three housing sections: an upper housing section 52 which defines a substantially cylindrical spring chamber 58, a first valve housing section 54 that is provided with a bore 51 that opens into a chamber or gallery 68 at an upper end of the housing section 54 and a second valve housing section 56 which is provided with a through housing bore 48.
  • the gallery 68 houses an armature 59 that is coupled to an elongate cylindrical inner valve member 50, which extends through the bore 51 in the first valve housing 54 and projects, at its upper end, through the gallery 68 and at least part way into the spring chamber 58.
  • the spring chamber 58 also contains an inner valve return spring 60 which receives the upper end portion of the inner valve member 50.
  • a winding 61 is disposed within the upper housing section 52, above the armature 59 in the orientation shown in Figure 3, and is energisable and de-energisable to cause movement of the armature 59, and hence the inner valve member 50, within the gallery 68.
  • An outer valve member 64 which takes the form of a profiled sleeve or tube, is slidably mounted within the through bore 48 in the second valve housing 56.
  • the outer valve member 64 is provided with a through bore 47 within which a lower portion of the inner valve member 50 is concentrically received and slidably mounted.
  • the inner 50 and outer 64 valve members are arranged such that they can move relative to one another, or can move together, so as to control fluid communication between fluid passages and fluid chambers formed in the valve arrangement 34a in dependence on the energisation level of the winding 61.
  • the inner valve member 50 is dimensioned to form a close sliding fit with the bore 47 of the outer valve member 64, and the outer valve member is dimensioned to form a close sliding fit with the inner surface of the housing bore 48.
  • the inner valve member 50 therefore slides directly within the outer valve member 64 so that the outer surface of the inner valve member 50 contacts with one the inner surface of the outer valve member 64.
  • the inner valve spring 60 serves to urge the inner valve member 50 into engagement with an inner valve stop 62 defined by a further housing section (not shown) which mates with the second valve housing 56, at its lower end.
  • a neck region 98 is formed at the lower end of the outer valve member 64.
  • the outer valve member 64 also has an annular lip 66 at its upper end which is disposed within a second annular gallery 70 formed at an enlarged upper end of the bore 48.
  • the outer portion of the gallery 70 opens upwards to an annular spring chamber 74 defined in the lower part of the first valve housing 54.
  • the spring chamber 74 houses an outer valve return spring 70 which abuts the top face of the outer valve member lip 66 at one spring end, and a shim (not identified) located within the spring chamber 74 at the other spring end.
  • the second valve housing 56 has defined therein a first fluid passage 76 which leads to (or forms part of) the common rail supply passage 30. Also defined in the second valve housing 56 is a second fluid passage 78 which leads to (or forms part of) the high pressure passage 16, and a third fluid passage 80 which leads to (or forms part of) the low pressure drain 42.
  • a neck 82 is formed in the inner valve member 50 which defines a first annular fluid chamber 84 between the inner valve member 50 and the inner surface of the outer valve member 64. Both ends of the first neck 82 flare so as to form respective upper 82a and lower 82b shoulders, the lower shoulder 82b being engageable with a first annular valve seating 92 of conical form, that is positioned on the inner surface of the outer valve member 64. Below the first valve seating 92, the inner surface of the outer valve member 64 and the outer surface of the inner valve member 50 together define a second annular fluid chamber 86 which communicates with the mouth of the passage 78 (and hence with the high pressure passage 16).
  • the first annular chamber 84 communicates with the first passage 76 via radial fluid passages (not identified) defined in the outer valve member 64.
  • the second 84 annular chamber communicates with the second passage 78 via further radial fluid passages (not identified) defined in the outer valve member 64.
  • a second valve seating 94 of conical form is defined by a surface of the bore 48 in the second valve housing 56, which disconnects the second annular chamber 86 from the third fluid passage 80 to the drain 42 when the outer valve member 64 is engaged therewith.
  • the outer valve member 64 is permitted to move within the housing bore 48 over a limited range, as determined by an outer valve lift stop 102 defined by a surface of a piece located in the spring chamber 58 (uppermost end of travel) and the position of the second valve seating 94 defined by the housing bore 48 (lowermost end of travel).
  • the winding 61 has three different energisation states. In its first state, the winding 61 is not energised and hence the armature 59 sits at its lowermost position in the armature gallery 68. In this condition the inner valve member 50 is urged into engagement with the valve stop 62 by the inner valve return spring 60, and is thus spaced apart from the first valve seating 92. The outer valve member 64 is urged against the second valve seating 94 by the outer valve return spring 72. Under such circumstances, the first 84 and second 86 chambers are in fluid communication, and fuel is permitted to flow from the high pressure supply passage 16 to the common rail supply passage 30, or vice versa. This is the first valve position of the control valve arrangement 34a.
  • the armature 59 Upon partial energisation of the winding 61, the armature 59 is moved to an intermediate position and enough force is generated to overcome the force due to the inner valve return spring 60 to cause the inner valve member 50 to move away from the stop 62, as shown in Figure 5b. The result of this action is that the inner valve 50 is moved to be positioned against the first valve seating 92, thereby closing communication between the first 84 and second 86 fluid chambers.
  • the force due to the outer valve return spring 72 is, however, high enough to keep the outer valve member 64 against the second valve seating 94 during partial energisation of the winding 61, and thus the second annular chamber 86, and hence the second passage 78, remains disconnected from the low pressure drain 42.
  • the pump chamber 32 may also be filled from the reservoir 42 during the plunger retraction phase.
  • That part of the outer valve member 64 which engages with the conical second valve seating 94 is of substantially conical form.
  • the differential cone angle i.e. the difference in cone angle between the conical seating surface on outer valve member 64 and the conical second valve seating 94
  • the differential cone angle is selected so that the outer valve member 64 seats on its outer diameter at the second valve seating 94.
  • the outer valve member 64 is therefore substantially pressure-balanced to high pressure fuel within the supply passage 16 when seated against the second valve seating 94 (i.e. in the first and second valve positions).
  • the shoulder 82b of the inner valve member 50 and the first valve seating 92 are shaped so that the differential cone angle between their respective conical surfaces ensures the inner valve member 50 seats on its outer diameter at the first valve seating 92.
  • the second control valve arrangement 34b comprises three sections: an upper housing section 52 which defines a substantially cylindrical spring chamber 58 having a stepped profile, a valve housing 56 defining a housing bore 48 which communicates with the spring chamber 58, and a lower housing section 57.
  • the valve housing 56 also has formed therein respective passageways which lead to the first 76 and second 78 fluid passageways defined in the lower housing section 57.
  • the first fluid passage 76 leads to (or forms part of) the common rail supply passage 30 and the second fluid passage 78 leads to (or forms part of) the high pressure supply passage 16.
  • a third passage 80 is also defined in the lower housing section 57.
  • the third passage 80 communicates with the low pressure drain 42.
  • the valve housing 56 houses a reciprocable armature 59 sited in an annular gallery 68 which opens into the housing bore 48.
  • the armature 59 is coupled to an outer valve member 64 (or sleeve) which is located in the housing bore 48, and which itself is provided with a through bore 47.
  • the top face of the armature 59 is in contact with an outer valve return spring 72 situated in the lower, wide section of the spring chamber 58.
  • An energisable winding 61 is disposed within the upper housing section 52, above the armature 59 in the orientation shown.
  • An elongate cylindrical inner valve member 50 extends through the bore 47 in the outer valve member 64 and projects at least part of the way into the narrow, upper section of the spring chamber 58, and is received there by an inner valve return spring 60.
  • the inner valve member 50 is dimensioned to form a close sliding fit within the bore 47 of the outer valve member 64 so that the surfaces thereof are in direct sliding contact with one another.
  • the outer valve member 64 is dimensioned to form a close sliding fit with the wall of the housing bore 48.
  • the inner surface of the bore 47 in the outer valve member 64 has an annular "cut away" portion, thereby defining a first annular fluid chamber 84 defined by the inner surface of the outer valve member 64 and an outer surface of the inner valve member 50.
  • a neck 82 is formed in the lower portion of the inner valve member 50 to define a second annular fluid chamber 86 located below the first fluid chamber 84 and defined between the inner surface of the outer valve member 64 and the outer surface of the inner valve member 50. Both ends of the neck 82 flare so as to form respective upper 82a and lower 82b shoulders.
  • the upper shoulder 82a of the inner valve member 50 defines a first annular valve seating 92 of substantially conical form with which a conical seating surface of the outer valve member 64 is engageable.
  • first annular chamber 84 communicates with the first fluid passage 76 by an upper radial passage (not identified) defined in the outer valve member 64.
  • a lower radial passage (not identified) is also defined in the outer valve member 64, and this connects the second annular chamber 86 with the mouth of the second passage 78.
  • a neck is defined at the base of the outer valve member 64, and the end surface of the outer valve neck is engageable with a second valve seating 94 defined by the upper face of the lower housing section 57.
  • the lower housing section 57 also defines the stop 62 for the inner valve member 50.
  • the neck of the outer valve member 64 defines, together with the housing bore 48, a third annular chamber 90.
  • the inner valve member 50 is provided with one or more cut-away sections 81 at the end thereof to define a flow passage for fuel between the third annular chamber 90 and the third passage 80 when the inner valve member 50 is disengaged from the stop 62.
  • the inner valve member 50 may also be provided with a cross-drilling(s) for the same purpose.
  • a third valve seating 96 of substantially conical form is defined in the wall of the housing bore 48.
  • a conical seating surface of the outer valve member 64 is engageable with the third valve seating 94. Engagement between the third valve seating 96 and the outer valve member 64 serves to disconnect or separate the second annular chamber 86 from the third annular chamber 90 and, hence, breaks communication between the second passage 78 and the low pressure drain 42.
  • the winding 61 has three operating states.
  • the winding 61 is not energised and hence the armature 59 sits at its lowermost position in the annular gallery 68.
  • the outer valve member 64 also sits in its lowermost position in abutment with the second valve seating 94.
  • the inner valve member 50 is urged against the inner valve stop 62 by the inner valve return spring 60.
  • the outer valve member 64 is spaced apart from the first valve seating 92 so that the first and second annular chambers 84, 86 are connected.
  • the armature 59 upon partial energisation of the winding 61, the armature 59 is raised to its intermediate position (i.e. the third valve position in Figure 2b). Enough force is generated on the armature 59 to overcome the force due to the outer valve return spring force, and hence the outer valve member 64 is raised and urged against the first valve seating 92. This discomiects the first annular chamber 84 from the second annular chamber 86. As the third valve seating 96 is disengaged from the outer valve member 64, the second annular chamber 86 communicates with the third chamber 90.
  • the "intermediate" position of the valve 34b of this second embodiment when the winding 61 is partially energised is functionally equivalent to the third valve position of the valve 34a of the first embodiment when the winding 61 is fully energised.
  • the high pressure passage 16 that communicates with the pump chamber 32 is able to communicate with the low pressure drain 42.
  • the force due to the inner valve return spring 60 is high enough to keep the inner valve member 50 against the valve stop 62 with the winding 61 only partially energised, due to the cut away sections 81 defined at the base of the inner valve member 50 fuel is nonetheless permitted to flow from the third annular chamber 90, through the cut away sections 81 and into the passage 80 which leads to the low pressure drain 42.
  • control valve arrangement to adopt the third valve position therefore permits the spilling of fuel to the low pressure drain 42 and, thus, permits termination of injection in a spill-end manner, as described previously. Additionally, filling of the pump chamber 32 during the plunger retraction phase or return stroke is also permitted with the control valve arrangement in the third valve position.
  • Figure 8c shows the second valve position where the winding 61 is fully energised (i.e. the second valve position in Figure 2b), and the armature 59 is caused to be raised to its uppermost position. Enough lifting force is generated on the armature 59 for the outer valve member 64 to overcome the force due to both the outer and inner valve returns springs 60, 72 and hence lift the outer valve member 64 to be positioned against the third valve seating 96. h doing so, movement of the outer valve member 64 is coupled to the inner valve member 50 by virtue of their engagement at the first seating 92, and so the inner valve member 50 is also raised.
  • the differential cone angle at the first seating 92 i.e. the difference in cone angle between the first valve seating 92 on the inner valve member 50 and the engageable seating surface of the outer valve member 64
  • the differential cone angle at the first seating 92 is selected so that the outer valve member 64 seats on its inner diameter at the first valve seating 92.
  • the third valve seating 96 and the seating surface of the outer valve member 64 which engages with the third valve seating 96 are shaped so that the outer valve member 64 seats on the inner diameter of the third valve seating 96.
  • the pump means 36 may be arranged to supply the rail 26 with pressurised fuel at the first, injectable (rail) pressure.
  • a low pressure pump may replace the low pressure drain 42, with the passage 44 providing a fill/spill passage between the pump chamber 32 and the low pressure pump.
  • the low pressure pump may take the form of a transfer pump for supplying fuel to the pump means 36 at a pressure dependent upon engine speed.
  • control valve arrangement 34 may be moved into its third valve position to bring the high pressure passage 16, and hence the pump chamber 32, into communication with the low pressure pump through the passage 44, thereby enabling the pump chamber 32 to be filled with low pressure fuel.
  • Moving the control valve arrangement into its second position brings the pump chamber 32 into communication with the common rail 26, allowing the rail to fill with fuel at the first injectable pressure level. Injection can then be achieved at this first pressure level through operation of the NCN 18, as described previously.
  • control valve arrangement 34 may be moved into the third valve position to break communication between the common rail 26 and the pump chamber 32, thereby permitting fuel within the pump chamber 32 and the high pressure passage 16 to be returned to the low pressure pump. This permits a spill end of injection, as described previously.
  • the rate of termination of injection may be varied by providing springs 60, 72 of different sizes, or by the use of shims or spacers within the chamber 58, 74 for the springs.
  • the control valve arrangement may be configured such that the winding 61 may be de-energised (rather than energised) to cause movement of the valve members 50, 64 to provide the three required valve operating positions.
  • control valve arrangement of the present invention may be used in fuel injection systems other than those of the EUI-common rail hybrid type for permitting injection at two different pressure levels.

Abstract

A control valve arrangement (34) intended particularly for use in a fuel injection system having an accumulator volume (26) for fuel at a first injectable pressure level and pump means (32) for increasing fuel pressure to a second injectable pressure level. The control valve arrangement includes an the inner valve member (50) that co-operates with an outer valve member (64) to provide for the control valve arrangement (i) a first valve position in which the accumulator volume (26) communicates with the pump means (32), (ii) a second valve position in which communication between the accumulator volume (26) and the pump means (26) is broken and (iii) a third valve position in which the pump means (26) communicates with a low pressure fuel drain (42). The control valve arrangement (34) therefore enables injection of fuel at either the first or second pressure level in dependence on the position of the control valve arrangement (34).

Description

CONTROLVALVE ARRANGEMENT
The present invention relates to a control valve arrangement for use in a fuel injection system. It relates particularly, although not exclusively, to a control valve arrangement for use in a fuel injection system that is generally of the common rail type for delivering fuel to a combustion space of an internal combustion engine. The invention also relates to a fuel injection system incorporating a control valve arrangement.
In fuel injection systems, it is known to provide a fuel injector with a nozzle control valve which is arranged to control movement of a fuel injector valve needle relative to a seating so as to control the delivery of fuel from the injector.
A known electronic unit injector (EUI) includes a dedicated pump having a cam-driven plunger for raising fuel pressure within a pump chamber, and an injection nozzle through which fuel is injected into an associated engine cylinder. A spill valve is operable to control the pressure of fuel within the pump chamber. When the spill valve is in an open position, the pump chamber communicates with a low pressure fuel reservoir so that fuel pressure within the pump chamber is not substantially affected by movement of the plunger and fuel is simply drawn into and displaced from the pump chamber as the plunger reciprocates. Closure of the spill valve causes fuel pressure in the pump chamber to rise as the plunger is driven to reduce the volume of the pump chamber. The EUI also includes an electronically controlled nozzle control valve which is arranged to control the timing of injection of fuel.
In common rail (CR) fuel injection systems, a single pump is arranged to charge an accumulator volume (or common rail) with high pressure fuel for supply to a plurality of injectors. As in an EUI system, the timing of injection is controlled by means of a respective nozzle control valve of each injector. One advantage of the common rail system is that the timing of injection of high pressure fuel is not dependent upon a cam drive, and so fast and accurate timing of injection can be achieved with the nozzle control valves alone. However, achieving very high injection pressures within a common rail system is problematic and the high levels to which fuel must be pressurised can cause high stresses within the pump and within the rail. The rail must therefore be provided with a relatively thick wall for pressure containment, making it heavy and bulky. Parasitic fuel losses can also be high.
Significant improvements in combustion quality and efficiency may be achieved by rapidly varying the injection pressure level and rate. Such pressure variations are difficult and/or inefficient to achieve with CR systems. These limitations have been somewhat alleviated by a fuel injection system of the hybrid EUI-common rail type, as described in the Applicant's co-pending PCT and EP applications, WO 03/093671 and EP 1359316 A. This system comprises an accumulator volume for supplying fuel at a moderate injectable pressure level to the fuel injector, a pump for increasing the pressure of fuel supplied to the injector to a high injectable pressure level, and a valve arrangement for switching between the moderate and high injectable pressure levels.
In our proposed hybrid EUI-common rail system, a nozzle control valve is used for the control of initiation and termination of injection. However, it is a feature of using a nozzle control valve to terminate injection that the fuel spray formation is degraded as the injector valve needle is seated against a high fuel pressure at the end of injection.
It is an object of the invention to provide a control valve arrangement that when used in a hybrid EUI-common rail fuel injection system enables an improved injection characteristic to be achieved. Another object of the invention is to provide a hybrid EUI- common rail fuel injection system which provides an improvement in termination of fuel injection characteristics.
According to a first aspect of the present invention there is provided a control valve arrangement suitable for use in an engine fuel injection system having first, second and third fuel volumes, the control valve arrangement including an inner valve member that is slidably movable within an outer valve member to provide for the control valve arrangement (i) a first valve position in which the first fuel volume communicates with the second fuel volume, (ii) a second valve position in which communication between the first fuel volume and the second fuel volume is broken and (iii) a third valve position in which one of the first and second fuel volumes communicates with the third fuel volume.
The inner valve member slides within the outer valve member, so that at least a part of the outer surface of the inner valve member is in direct sliding contact with a part of an inner surface of the outer valve member e.g. the internal bore of a tubular outer valve member.
In a preferred embodiment, the fuel system enables injection of fuel from either the first or second fuel volume in dependence upon the position of the control valve arrangement, and the third fuel volume takes the form of a low pressure drain or reservoir.
The fuel volumes may take the form of chambers, passages, channels, pump chambers or any other type of "reservoir" for fuel storage or through which fuel flows.
In a preferred application of the invention, the control valve arrangement is incorporated within a fuel injection system having an accumulator volume (the first fuel volume) for fuel at a first injectable pressure level and pump means (the second fuel volume) for increasing fuel pressure to a second injectable pressure level. Preferably, the control valve arrangement includes an inner valve member that is slidably mounted within the outer valve member to provide for the control valve arrangement (i) a first valve position in which the accumulator volume communicates with the pump means, (ii) a second valve position in which communication between the accumulator volume and the pump means is broken and (iii) a third valve position in which the pump means communicates with a low pressure fuel drain (the third fuel volume), thereby to enable injection of fuel at either the first or second pressure level in dependence upon the position of the control valve arrangement.
The fuel injection system may alternatively be configured so that any one of the first, second or third fuel volumes is the low pressure fuel drain, the pump means or the accumulator volume. Preferably, the inner valve member is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
More preferably, the outer valve member is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
The control valve arrangement has particular application in a fuel injection system of the hybrid EUI-common rail type, such as that described in our co-pending PCT and EP applications, WO 03/093671 and EP 1359316 A, in which an injection control means in the form of a nozzle control valve is typically provided to control movement of a valve needle of an injection nozzle so as to control the timing of commencement and termination of fuel injection. By providing the fuel injection system with a control valve arrangement having the first, second and third valve positions, termination of fuel injection by spilling to low pressure can be achieved through actuation of the control valve arrangement to the third valve position. Fuel injection at a first pressure can be achieved with the control valve arrangement in the first valve position, fuel injection at the second pressure level can be achieved with the control valve arrangement in the second valve position and termination of injection may be effected or aided by spilling fuel to low pressure with the control valve arrangement in the third valve position.
One advantage of the present invention is that its use in such a fuel system enables rapid termination of fuel injection, thus providing improved engine performance and an ability to reduce emissions levels. The system permits fuel injection to be terminated in such a way that the injector valve needle need not be seated against a high fuel pressure within the injector at the end of injection, due to the facility to provide a spill-end of injection .
In a preferred embodiment, the inner valve member is therefore substantially pressure balanced to fuel in the second fuel volume, that is the pump means, when the second valve position is adopted. More preferably, the outer valve member is substantially pressure balanced to fuel in the fuel volume, that is the pump means, when the second valve position is adopted.
In this way, whether fuel at the first or second injectable pressure level is to be injected, when the second position of the control valve arrangement is adopted both the inner and outer valve members are pressure balanced to fuel at the injectable pressure level that is delivered through a high pressure supply line to the injector.
The control valve arrangement can be conveniently sized and requires only one actuator to control movement of both the inner and outer valves .
Preferably the movement of the inner and outer valve members is controlled by means of an electromagnetic actuator arrangement which may comprise an energisable solenoid or winding (commonly referred to as a stator), and an armature.
The winding preferably has three states: a first state where the winding is not energised, a second state that results from partial energisation of the winding to a first partial energisation level, and a third state that results from energisation of the winding to a higher, partial energisation level or full energisation of the winding.
One of the inner or the outer valve members is preferably coupled to the armature so that, upon energisation (or de-energisation) of the winding, the inner and outer valve members are movable relative to and co-operable with one another, and engageable with valve seatings, so as to control the passage of fuel through the control valve arrangement.
The control valve arrangement preferably comprises a first fluid chamber which is fluidly communicable with the fuel accumulator volume, a second fluid chamber which is fluidly communicable with the pump means and the first fluid chamber, a third fluid chamber which is fluidly communicable with the second fluid chamber and a fourth fluid chamber which is fluidly communicable with the low pressure fuel drain. By "fluidly communicable", it is meant that fluid is able to flow selectively from one chamber to another.
Preferably, the second fluid chamber may be communicable with the third fluid chamber by means of a first radial fluid passage defined in the outer valve member.
In a preferred embodiment, the outer valve member takes the form of a tubular member or sleeve having a valve bore or passageway through which at least a part of the inner valve member extends. The outer valve member is preferably movable within a housing bore provided in a valve housing.
Most preferably the first chamber is defined by an inner surface of the outer valve member and an outer surface of the inner valve member.
Most preferably the second chamber is defined by an inner surface of the outer valve member and an outer surface of the inner valve member.
The third fluid chamber is preferably defined by a surface of the housing bore and an outer surface of the outer valve member.
The fourth fluid chamber is preferably defined by a surface of the housing bore and an outer surface of the outer valve member.
For example, one or both of the third and fourth fluid chambers may be defined by a recess or recesses provided in the housing bore and/or the outer surface of the outer valve member.
In a first embodiment of the invention, the inner valve member is coupled to the armature. In this embodiment of the control valve arrangement, the first valve seating is preferably positioned between the first and second fluid chambers, and the second valve seating is preferably positioned between the third and fourth fluid chambers.
The first valve seating is conveniently defined by a surface of the valve bore provided in the outer valve member.
The second valve seating is conveniently defined by a surface of the housing bore provided in the valve housing.
Preferably, the inner valve member is engaged with a first valve seating when the control valve arrangement is in the second and third valve positions, and the outer valve member is engaged with a second valve seating when the control valve arrangement is in the first and second valve positions.
The first and second valve seatings are preferably of substantially conical form, for engagement with substantially conical seating surfaces of the engageable parts of the inner and outer valve members respectively. The differential angles at the first and second valve seatings are preferably selected so as to ensure the inner and outer valve members are substantially pressure balanced to fuel at the injectable pressure level when at least the second valve position is adopted.
In one embodiment, no energisation of the winding corresponds to the control valve arrangement being in the first valve position.
Preferably, when the first valve position is adopted, the outer valve member is engaged with the second valve seating so that the third and fourth fluid chambers are fluidly disconnected, and the inner valve member is not engaged with the first valve seating such that the first and second chambers are fluidly connected. In this manner, fuel may therefore pass between the pump means and the fuel accumulator volume when the control valve arrangement is in the first valve position. When the control valve arrangement is in the second valve position, for example corresponding to partial energisation of the winding to the first, partial energisation level, the inner valve member is preferably engaged with the first valve seating so that the first and second fluid chambers are disconnected, and the outer valve member is advantageously engaged with the second valve seating so as to disconnect the third and fourth fluid chambers. In this manner, communication between the pump means and the accumulator volume is broken, and with the control valve arrangement in this second valve position injection of fuel at the second, higher pressure level can be achieved.
In the third valve position, for example corresponding to energisation of the winding to a full (or higher, partial) energisation level, the inner valve member is preferably engaged with the first valve seating, and the outer valve member is now spaced apart from the second valve seating thereby fluidly connecting the third and fourth fluid chambers. Fuel from the pump means may therefore flow from the second chamber into the third chamber, and then to the fourth chamber whereupon it may flow to the low pressure drain.
In a second embodiment of the present invention, the outer valve member is coupled to the armature.
In this embodiment of the control valve arrangement, the first valve seating is preferably positioned between the first and second fluid chambers. There may also be provided a third valve seating positioned between the third and fourth fluid chambers.
The first valve seating is conveniently defined by an outer surface of the inner valve member.
The second valve seating is conveniently defined by a surface of a housing.
The third valve seating is conveniently defined by a housing bore provided in a valve housing. The first and third valve seatings are preferably of substantially conical form, for engagement with substantially conical seating surfaces of the engageable parts of the outer valve member. The differential angles at the first and third valve seatings are preferably selected so as to ensure the inner and outer valve members are substantially pressure balanced to fuel at the injectable pressure level when the second valve position, at least, is adopted.
In this second embodiment, preferably the outer valve member is engaged with the first valve seating when the control valve arrangement is in the second and third valve positions. Preferably, the outer valve member is engaged with the second valve seating when the control valve arrangement is in the first valve position. More preferably, the outer valve member is engaged with the third valve seating when the control valve arrangement is in the second valve position.
The inner valve member is preferably and advantageously provided with at least one cross-drilling, or cut-away section, at an end thereof, so as to define a passage for fuel flow through the inner valve member between the fourth chamber and the low pressure drain when the outer valve member is spaced away from the second valve seating.
When the control valve arrangement is in the first valve position, for example corresponding to no energisation of the winding, the inner valve member is spaced apart from the first valve seating so that the first and second fluid chambers are fluidly connected, and the outer valve member is not in engagement with the third valve seating such that the third and fourth fluid chambers are fluidly connected. However, the outer valve member is engaged with the second valve seating such that fuel may not pass from the fourth fluid chamber to the low pressure drain. When the control valve arrangement is in this first valve position, fuel may therefore flow from the pump means to the fuel accumulator volume, and in this operating condition injection can be achieved at the first injectable pressure level. When the control valve arrangement is in the second valve position (e.g. at the full or higher partial energisation level), the outer valve member is caused to move away from the second valve seating and into engagement with the first valve seating, thereby fluidly disconnecting the first and second fluid chambers. The outer valve member is moved so far as to bring in into engagement with the inner valve member at the first valve seating, and to cause the inner valve to move with it. The outer valve member is also moved so far as to bring it into engagement with the third valve seating and the third and fourth fluid chambers are disconnected, resulting in communication between the accumulator volume and the pump means being broken. This is the condition for injection at the second higher pressure level as fuel is not permitted to flow through the valve arrangement.
When the control valve arrangement is in the third valve position, for example partial energisation of the winding to the partial energisation level, the outer valve member is moved into engagement with the first valve seating, thereby disconnecting the first and second fluid chambers. The outer valve member is moved only part way through its range of travel, however, and so is preferably spaced apart from both the second and third valve seatings, thereby fluidly connecting the second, third and fourth fluid chambers. The inner valve member remains engaged with an inner valve stop as it is not caused to move with the outer valve member. Fuel from the pump means is permitted to pass from the third chamber to the fourth chamber whereupon it may flow through the passage(s) in the inner valve member to the low pressure drain, even though the inner valve member remains seated against the inner valve stop.
Resilient spring means, such as springs, may also be provided in the control valve arrangement to act on the inner and outer valve members to oppose the force applied to these parts by means of energisation of the winding. For example, in the first embodiment, when the inner valve member is in the first valve position it is urged by means of an inner valve spring into engagement with the inner valve stop and away from the first valve seating defined by the valve bore in the outer valve member. The outer valve member is urged into engagement with the second valve seating by an outer valve spring. For the second valve position, the outer valve member remains urged into engagement with the second valve seating by virtue of the force due to the outer valve spring.
The second embodiment of the invention preferably utilises an inner valve spring arranged to urge the inner valve member into engagement with the inner valve stop when the control valve arrangement is in the first and third valve positions.
Most preferably the fluid chambers are substantially annular chambers which preferably communicate with fuel system components via fluid passages defined in the valve housing. For example, the outer valve member may have a radial passage defined therein for linking the first fluid chamber to the fuel accumulator volume.
According to a second aspect of the invention, there is provided a fuel injector for use in delivering fuel to an internal combustion engine at first and second injectable pressure levels, the fuel injector comprising the aforedescribed control valve arrangement.
The fuel injector may further comprise said pump means for increasing fuel pressure to at least one of the first and second injectable pressure levels.
A third aspect of the invention provides a fuel injection system for supplying pressurised fuel to an injection nozzle, the fuel injection system comprising: an accumulator volume for supplying fuel at a first injectable pressure (PI) to the injection nozzle; pump means for increasing the pressure of fuel supplied to the injection nozzle to a second injectable pressure level (P2); and a control valve arrangement operable between a first valve position in which the accumulator volume communicates with the pump means and fuel at the first injectable pressure level (PI) is supplied to the injection nozzle, a second valve position in which communication between the pump means and the accumulator volume is broken so as to permit fuel at the second injectable pressure (P2) to be supplied to the injection nozzle, and a third valve position in which the communication between the pump means and the accumulator volume is broken and the pump means communicates with a low pressure drain, thereby to aid, or execute, termination of injection. The fuel injection may, but need not, include a high pressure fuel pump for supplying fuel at the first injectable pressure level to the accumulator volume. If no high pressure fuel pump is provided, the pump means itself serves to increase fuel to the first pressure level by actuating the control valve arrangement to adopt its first valve position.
It will be appreciated that any of the aformentioned preferred or optional features of the control valve arrangement of the first aspect of the invention may be included alone or in appropriate combination in the second or third aspects of the invention.
The invention will be described, by way of example only, with reference to the accompanying drawings, in which: -
Figure 1 is a schematic diagram of a hybrid EUI-common rail fuel injection system;
Figure 2a is a schematic diagram of a control valve arrangement according to a first embodiment of the invention, for use in the fuel injection system of Figure 1;
Figure 2b is a schematic diagram of a control valve arrangement according to a second embodiment of the invention, for use in the fuel injection system of Figure 1;
Figure 3 is a sectional view of the control valve arrangement of the first embodiment;
Figures 4a and 4b are sectional views of selected parts of the control valve arrangement of the first embodiment;
Figures 5 a, 5b and 5 c are sectional views of the control valve arrangement of the first embodiment in its first, second and third positions, respectively;
Figure 6 is a sectional view of the control valve arrangement of the second embodiment; Figures 7 a and 7b are sectional views of selected parts of the control valve arrangement of the second embodiment;
Figures 8a, 8b and 8c are sectional views of the control valve arrangement of the second embodiment in its first, third and second positions, respectively; and
Figures 9a and 9b are tables showing information regarding the positions of the control valve arrangements of the first and second embodiments, respectively.
Referring to Figure 1, there is shown a fuel injection system 10 comprising a fuel injector, referred to generally as 12, and an associated high pressure supply passage 16. The high pressure fuel passage is arranged to deliver fuel to an injection nozzle 20 of the injector 12. The injection nozzle 20 includes a valve needle 14 that is engageable with a valve needle seating (not shown), in use, so as to control the delivery of fuel from the nozzle 20. The injector 12 also includes a needle control valve (NCN) 18, also referred to as a nozzle control valve, to control movement of the valve needle 14, whereby movement of the needle 14 away from the seating permits fuel to flow through the nozzle 20 into an engine cylinder or other combustion space. The ΝCN 18 is operable between a first position (hereinafter referred to as a "closed" position), in which an injector control chamber 22 communicates with the high pressure supply passage 16, and a second position (hereinafter referred to as an "open" position) in which the control chamber 22 communicates with a low pressure reservoir (not shown) and communication between the high pressure supply passage 16 and the control chamber 22 is broken. A spring 23 is arranged in the injector control chamber 22 to urge the valve needle into engagement with its seating.
A common rail pump 24 supplies fuel at a moderately high and injectable pressure level (e.g. between about 300 and 1000 bar) to an accumulator volume in the form of a common rail 26. A pressure regulator 28 serves to maintain the pressure of fuel within the common rail 26 at a substantially constant level (referred to as "rail pressure"). The common rail 26 supplies pressurised fuel to a supply passage 30 (or common rail line) in communication with a pump chamber 32 arranged within, and communicating with, the high pressure supply passage 16 under the control of an electro-magnetically controlled three-position control valve arrangement 34. The pump chamber 32 forms part of pump means 36, including a plunger 38 which is driven by means of a cam drive arrangement 40. The plunger 38 has a pumping stroke (during which the volume of the pump chamber 32 is reduced and fuel may be injected), and a return or retraction stroke (during which the volume of the pump chamber 32 is increased and the pump chamber 32 can be filled). The three-position valve arrangement 34 also controls the passage of fuel to a low pressure drain 42 via a low pressure supply passage 44.
For clarity, only one fuel injector is shown in the system of Figure 1, although in practice a plurality of injectors would be supplied with fuel from the common rail 26 in a multi- cylinder engine. Each injector has a dedicated plunger 38 and pump chamber 32, as shown in Figure 1 for the injector 12, and the pump chambers communicate with the common rail 26 through respective three-position valves, such as 34. The plunger 38 is driven by means of a cam drive arrangement having a cam or cam member 40.
The valve arrangement 34 may be an electro-magnetically operable valve that is actuated in response to an electronic control signal provided by an engine controller to move between first, second and third valve positions so as to control whether pressurisation of fuel within the pump chamber 32 occurs as the plunger 38 reciprocates under the influence of the cam 40, or whether fuel at high pressure is "spilled" to the low pressure drain 42 to terminate injection.
The valve 34 may take the form of a first control valve arrangement 34a, as shown in Figure 2a. When the valve adopts its first valve position, the high pressure passage 16, and hence the pump chamber 32, communicates with the common rail 26. In this position, the passage of fuel from the high pressure passage 16 to the low pressure drain 42 is prevented. Under such circumstances, reciprocating movement of the plunger 38 has substantially no effect on fuel pressure within the chamber 32, and thus the fuel pressure does not increase above rail pressure. With the valve 34a in the first position, the pressure of fuel supplied to the injector 12 through the passage 16 is therefore determined by the pressure of fuel within the common rail 26 which, typically, will be between 300 and 1000 bar. In order to inject fuel at this first, moderate pressure level (PI), the NCN 18 is moved into its open position, causing fuel pressure within the control chamber 22 to be reduced as it flows to low pressure and thereby enabling the valve needle 14 to lift.
Where the second position of the valve 34a is adopted, communication between the common rail supply passage 30 and the pump chamber 32 is broken. With the valve 34a is in the second valve position, reciprocal movement of the plunger 38 under the influence of the cam 40 will cause fuel within the pump chamber 32 to be increased to a second injectable pressure level (P2), which is greater than the first pressure level (PI). Typically, the second pressure level is between 2000 and 2500 bar. By moving the ΝCN 18 into its open position the valve needle is lifted from its seating to permit injection at this higher pressure level, P2. The timing of injection of fuel at the first, moderate pressure level (PI) is therefore controlled by operation of the ΝCN 18 when the valve 34a is in the first valve position. The timing of injection of fuel at the second, higher pressure level (P2) is controlled by operation of the ΝCN 18 while the valve 34a is in the second valve position, in which circumstances the pump arrangement 36 serves to increase the pressure of fuel within the pump chamber 32 to the second, higher pressure level for delivery through the high pressure supply passage 16
The ability to provide injection at two different pressure levels is particularly useful for providing a pilot injection of fuel at a lower pressure level followed by a main injection of fuel at a higher pressure level. This can be achieved by switching the control valve arrangement 34 between its first and second valve positions, and actuating the ΝCN 18 to cause an injection of fuel for both the first and second valve positions.
Termination of fuel injection in the system 10 may be achieved when the control valve arrangement is in a third valve position, whereby the high pressure supply passage 16 communicates with the low pressure drain 42 and communication between the pump chamber 32 and the common rail 26 is broken. Thus, when the desired amount of fuel has been injected, the valve 34a is moved to the third valve position to "spill" fuel in the high pressure passage 16 to the low pressure drain 42. The reduction in pressure in the passage 16 reduces the force acting on the valve needle 14 in an opening direction and the spring 23 in the injector control chamber 22 exerts a high enough force on the needle 14 so that it seats to end fuel injection. This is referred to as "spill end of injection", or "spill-type end of injection", as it is the spilling of fuel to the low pressure drain 42 that causes the valve needle 14 to seat.
The first control valve arrangement 34a is illustrated in further detail in Figures 3, 4a and 4b, and comprises three housing sections: an upper housing section 52 which defines a substantially cylindrical spring chamber 58, a first valve housing section 54 that is provided with a bore 51 that opens into a chamber or gallery 68 at an upper end of the housing section 54 and a second valve housing section 56 which is provided with a through housing bore 48.
The gallery 68 houses an armature 59 that is coupled to an elongate cylindrical inner valve member 50, which extends through the bore 51 in the first valve housing 54 and projects, at its upper end, through the gallery 68 and at least part way into the spring chamber 58. The spring chamber 58 also contains an inner valve return spring 60 which receives the upper end portion of the inner valve member 50. A winding 61 is disposed within the upper housing section 52, above the armature 59 in the orientation shown in Figure 3, and is energisable and de-energisable to cause movement of the armature 59, and hence the inner valve member 50, within the gallery 68.
An outer valve member 64, which takes the form of a profiled sleeve or tube, is slidably mounted within the through bore 48 in the second valve housing 56. The outer valve member 64 is provided with a through bore 47 within which a lower portion of the inner valve member 50 is concentrically received and slidably mounted. The inner 50 and outer 64 valve members are arranged such that they can move relative to one another, or can move together, so as to control fluid communication between fluid passages and fluid chambers formed in the valve arrangement 34a in dependence on the energisation level of the winding 61. The inner valve member 50 is dimensioned to form a close sliding fit with the bore 47 of the outer valve member 64, and the outer valve member is dimensioned to form a close sliding fit with the inner surface of the housing bore 48. The inner valve member 50 therefore slides directly within the outer valve member 64 so that the outer surface of the inner valve member 50 contacts with one the inner surface of the outer valve member 64. The inner valve spring 60 serves to urge the inner valve member 50 into engagement with an inner valve stop 62 defined by a further housing section (not shown) which mates with the second valve housing 56, at its lower end.
A neck region 98 is formed at the lower end of the outer valve member 64. The outer valve member 64 also has an annular lip 66 at its upper end which is disposed within a second annular gallery 70 formed at an enlarged upper end of the bore 48. The outer portion of the gallery 70 opens upwards to an annular spring chamber 74 defined in the lower part of the first valve housing 54. The spring chamber 74 houses an outer valve return spring 70 which abuts the top face of the outer valve member lip 66 at one spring end, and a shim (not identified) located within the spring chamber 74 at the other spring end.
The second valve housing 56 has defined therein a first fluid passage 76 which leads to (or forms part of) the common rail supply passage 30. Also defined in the second valve housing 56 is a second fluid passage 78 which leads to (or forms part of) the high pressure passage 16, and a third fluid passage 80 which leads to (or forms part of) the low pressure drain 42.
As can be seen most clearly in Figures 4a and 4b, a neck 82 is formed in the inner valve member 50 which defines a first annular fluid chamber 84 between the inner valve member 50 and the inner surface of the outer valve member 64. Both ends of the first neck 82 flare so as to form respective upper 82a and lower 82b shoulders, the lower shoulder 82b being engageable with a first annular valve seating 92 of conical form, that is positioned on the inner surface of the outer valve member 64. Below the first valve seating 92, the inner surface of the outer valve member 64 and the outer surface of the inner valve member 50 together define a second annular fluid chamber 86 which communicates with the mouth of the passage 78 (and hence with the high pressure passage 16). The first annular chamber 84 communicates with the first passage 76 via radial fluid passages (not identified) defined in the outer valve member 64. The second 84 annular chamber communicates with the second passage 78 via further radial fluid passages (not identified) defined in the outer valve member 64.
A second valve seating 94 of conical form is defined by a surface of the bore 48 in the second valve housing 56, which disconnects the second annular chamber 86 from the third fluid passage 80 to the drain 42 when the outer valve member 64 is engaged therewith.
The outer valve member 64 is permitted to move within the housing bore 48 over a limited range, as determined by an outer valve lift stop 102 defined by a surface of a piece located in the spring chamber 58 (uppermost end of travel) and the position of the second valve seating 94 defined by the housing bore 48 (lowermost end of travel).
The winding 61 has three different energisation states. In its first state, the winding 61 is not energised and hence the armature 59 sits at its lowermost position in the armature gallery 68. In this condition the inner valve member 50 is urged into engagement with the valve stop 62 by the inner valve return spring 60, and is thus spaced apart from the first valve seating 92. The outer valve member 64 is urged against the second valve seating 94 by the outer valve return spring 72. Under such circumstances, the first 84 and second 86 chambers are in fluid communication, and fuel is permitted to flow from the high pressure supply passage 16 to the common rail supply passage 30, or vice versa. This is the first valve position of the control valve arrangement 34a.
As the second valve seating 94 is closed, fluid cannot pass between the second annular chamber 86 and the lower pressure drain 42 through the third passage 80. This configuration is illustrated by Figure 5a. During operation of the fuel system 10 with the control valve arrangement 34a in this position, the pump chamber 32 communicates with the common rail supply passage 30 and so the plunger 38 does not increase the pressure of the fuel above the rail pressure (PI) during pumping.
Upon partial energisation of the winding 61, the armature 59 is moved to an intermediate position and enough force is generated to overcome the force due to the inner valve return spring 60 to cause the inner valve member 50 to move away from the stop 62, as shown in Figure 5b. The result of this action is that the inner valve 50 is moved to be positioned against the first valve seating 92, thereby closing communication between the first 84 and second 86 fluid chambers. The force due to the outer valve return spring 72 is, however, high enough to keep the outer valve member 64 against the second valve seating 94 during partial energisation of the winding 61, and thus the second annular chamber 86, and hence the second passage 78, remains disconnected from the low pressure drain 42. With both the first and second valve seatings 92, 94 respectively closed, the high pressure passage 16 is connected to neither the common rail 26, nor the low pressure drain 42. This is the second valve position of the control valve arrangement 34a, and in which position movement of the plunger 38 reduces the volume of the chamber 32 to increase the fuel pressure above rail pressure (P2). The condition for injection at a peak injection pressure is therefore fulfilled.
Finally, when the winding 61 is fully energised, the armature 59 is in its uppermost raised position. In this condition enough lifting force is generated on the armature 59 to overcome the force due to both the inner and outer valve return springs 60, 72, and hence the outer valve member 64 is caused to move by virtue of its engagement with the inner valve member 50. Coupled movement of the outer valve member 64 with the inner valve member 50 causes the outer valve member 64 to be lifted from the second seating 94. The lift of the outer valve member 64 is limited by the outer valve lift stop 102, which is placed above the top face of the outer valve member lip 66. In this position, the inner valve member 50 remains in abutment with the first seating 92, and so communication between the first 84 and second 86 fluid chambers remains closed. However, the second chamber 86 and the fluid passage 80 are now fluidly connected so that fuel is permitted to flow from the high pressure passage 16, past the second valve seating 94, and through the passage 80 to the low pressure drain 42. This is the third valve position of the control valve arrangement 34a.
By adopting this configuration, the pressure in the high pressure passage 16 is decreased or 'spilt'. In this position of the control valve arrangement, a spill end of injection is permitted, whereby the spring 23 acting on the valve needle 14 overcomes the reduced hydraulic force acting to keep the valve needle 14 open and, hence, the valve needle seats to terminate injection. This spill end of injection may be implemented on its own to terminate injection, or may be implemented simultaneously with the NCN 18 being opened to synchronise the reduction of fuel pressure within the passage 16 with a reduction in fuel pressure in the injector control chamber 22. In both cases, spill end of injection provides an advantage as the valve needle 14 is not forced to seat against a high fuel pressure within the injector 12. It has been found that this provides an advantage in terms of the fuel spray formation at the end of injection, and emissions levels are improved.
With the control valve arrangement 34a in the third valve position, the pump chamber 32 may also be filled from the reservoir 42 during the plunger retraction phase.
Although not visible in the scale shown in Figures 4a and 4b, that part of the outer valve member 64 which engages with the conical second valve seating 94 is of substantially conical form. The differential cone angle (i.e. the difference in cone angle between the conical seating surface on outer valve member 64 and the conical second valve seating 94) is selected so that the outer valve member 64 seats on its outer diameter at the second valve seating 94. By selecting the differential cone angle so that the outer valve member 64 seats on its outer diameter there is substantially no out-of-balance axial component of the hydraulic force acting on the outer valve member 64 due to high pressure fuel in the supply passage 16 when the outer valve member 64 is seated against the second valve seating 94. The outer valve member 64 is therefore substantially pressure-balanced to high pressure fuel within the supply passage 16 when seated against the second valve seating 94 (i.e. in the first and second valve positions). Similarly, the shoulder 82b of the inner valve member 50 and the first valve seating 92 are shaped so that the differential cone angle between their respective conical surfaces ensures the inner valve member 50 seats on its outer diameter at the first valve seating 92. By selecting the differential cone angle at the first valve seating 92 so that the inner valve member 50 seats on its outer diameter, there is substantially no out-of-balance axial component of the hydraulic force due to high pressure fuel within the passage 16 acting on the inner valve member 50 when it is seated against the first valve seating 92. The inner valve member 50 is therefore substantially pressure-balanced to high pressure fuel within the high pressure supply passage 16 when seated against the first valve seating 92 (i.e. in the second and third valve positions).
Referring now to Figures 6 to 8 (and Figure 2b) there is shown an alternative embodiment of the control valve arrangement 34b, in which equivalent features to that of the first control valve arrangement 34a of the first embodiment are identified with like reference numerals.
With reference to Figure 6, the second control valve arrangement 34b comprises three sections: an upper housing section 52 which defines a substantially cylindrical spring chamber 58 having a stepped profile, a valve housing 56 defining a housing bore 48 which communicates with the spring chamber 58, and a lower housing section 57. It will be appreciated that, in comparison with the first embodiment in Figure 2, the intermediate valve housing section 54 is not required in the second embodiment. The valve housing 56 also has formed therein respective passageways which lead to the first 76 and second 78 fluid passageways defined in the lower housing section 57. The first fluid passage 76 leads to (or forms part of) the common rail supply passage 30 and the second fluid passage 78 leads to (or forms part of) the high pressure supply passage 16. A third passage 80 is also defined in the lower housing section 57. The third passage 80 communicates with the low pressure drain 42. The valve housing 56 houses a reciprocable armature 59 sited in an annular gallery 68 which opens into the housing bore 48. The armature 59 is coupled to an outer valve member 64 (or sleeve) which is located in the housing bore 48, and which itself is provided with a through bore 47. The top face of the armature 59 is in contact with an outer valve return spring 72 situated in the lower, wide section of the spring chamber 58. An energisable winding 61 is disposed within the upper housing section 52, above the armature 59 in the orientation shown.
An elongate cylindrical inner valve member 50 extends through the bore 47 in the outer valve member 64 and projects at least part of the way into the narrow, upper section of the spring chamber 58, and is received there by an inner valve return spring 60. The inner valve member 50 is dimensioned to form a close sliding fit within the bore 47 of the outer valve member 64 so that the surfaces thereof are in direct sliding contact with one another. The outer valve member 64 is dimensioned to form a close sliding fit with the wall of the housing bore 48.
The inner surface of the bore 47 in the outer valve member 64 has an annular "cut away" portion, thereby defining a first annular fluid chamber 84 defined by the inner surface of the outer valve member 64 and an outer surface of the inner valve member 50. A neck 82 is formed in the lower portion of the inner valve member 50 to define a second annular fluid chamber 86 located below the first fluid chamber 84 and defined between the inner surface of the outer valve member 64 and the outer surface of the inner valve member 50. Both ends of the neck 82 flare so as to form respective upper 82a and lower 82b shoulders. The upper shoulder 82a of the inner valve member 50 defines a first annular valve seating 92 of substantially conical form with which a conical seating surface of the outer valve member 64 is engageable. Engagement between the outer valve member 64 and the first valve seating 92 serves to disconnect the first fluid chamber 84 from the second fluid chamber 86 when the winding 61 is energised to move the outer valve member 64. As shown more clearly in Figures 7a and 7b, the first annular chamber 84 communicates with the first fluid passage 76 by an upper radial passage (not identified) defined in the outer valve member 64. A lower radial passage (not identified) is also defined in the outer valve member 64, and this connects the second annular chamber 86 with the mouth of the second passage 78. A neck is defined at the base of the outer valve member 64, and the end surface of the outer valve neck is engageable with a second valve seating 94 defined by the upper face of the lower housing section 57. The lower housing section 57 also defines the stop 62 for the inner valve member 50.
The neck of the outer valve member 64 defines, together with the housing bore 48, a third annular chamber 90. The inner valve member 50 is provided with one or more cut-away sections 81 at the end thereof to define a flow passage for fuel between the third annular chamber 90 and the third passage 80 when the inner valve member 50 is disengaged from the stop 62. The inner valve member 50 may also be provided with a cross-drilling(s) for the same purpose.
A third valve seating 96 of substantially conical form is defined in the wall of the housing bore 48. A conical seating surface of the outer valve member 64 is engageable with the third valve seating 94. Engagement between the third valve seating 96 and the outer valve member 64 serves to disconnect or separate the second annular chamber 86 from the third annular chamber 90 and, hence, breaks communication between the second passage 78 and the low pressure drain 42.
As described for the first control valve arrangement 34a, the winding 61 has three operating states. In the first state, the winding 61 is not energised and hence the armature 59 sits at its lowermost position in the annular gallery 68. By virtue of the force of the outer valve return spring 72, the outer valve member 64 also sits in its lowermost position in abutment with the second valve seating 94. The inner valve member 50 is urged against the inner valve stop 62 by the inner valve return spring 60. In this position (i.e. the first valve position in Figure 2b), the outer valve member 64 is spaced apart from the first valve seating 92 so that the first and second annular chambers 84, 86 are connected. As the outer valve member 64 is in its lowermost position, it is disengaged from the third valve seating 96 but seated against the second seating 94. As the outer valve member 64 is seated against the second valve seating 94, no fuel is permitted to flow from the third annular chamber 90, into the third passage 80 and, hence, to the low pressure drain 42. Fuel is therefore able to flow from the high pressure supply passage 16 to the common rail supply passage 30. This results in the plunger 38 not increasing the pressure above rail pressure (PI) as it performs its pumping stroke, and thus fuel may be injected at this moderate rail pressure. The above configuration is shown in Figure 8a.
Referring to Figure 8b, upon partial energisation of the winding 61, the armature 59 is raised to its intermediate position (i.e. the third valve position in Figure 2b). Enough force is generated on the armature 59 to overcome the force due to the outer valve return spring force, and hence the outer valve member 64 is raised and urged against the first valve seating 92. This discomiects the first annular chamber 84 from the second annular chamber 86. As the third valve seating 96 is disengaged from the outer valve member 64, the second annular chamber 86 communicates with the third chamber 90.
It will be appreciated that the "intermediate" position of the valve 34b of this second embodiment when the winding 61 is partially energised is functionally equivalent to the third valve position of the valve 34a of the first embodiment when the winding 61 is fully energised. In this third valve position the high pressure passage 16 that communicates with the pump chamber 32 is able to communicate with the low pressure drain 42. Although the force due to the inner valve return spring 60 is high enough to keep the inner valve member 50 against the valve stop 62 with the winding 61 only partially energised, due to the cut away sections 81 defined at the base of the inner valve member 50 fuel is nonetheless permitted to flow from the third annular chamber 90, through the cut away sections 81 and into the passage 80 which leads to the low pressure drain 42. Operating the control valve arrangement to adopt the third valve position therefore permits the spilling of fuel to the low pressure drain 42 and, thus, permits termination of injection in a spill-end manner, as described previously. Additionally, filling of the pump chamber 32 during the plunger retraction phase or return stroke is also permitted with the control valve arrangement in the third valve position.
Finally, Figure 8c shows the second valve position where the winding 61 is fully energised (i.e. the second valve position in Figure 2b), and the armature 59 is caused to be raised to its uppermost position. Enough lifting force is generated on the armature 59 for the outer valve member 64 to overcome the force due to both the outer and inner valve returns springs 60, 72 and hence lift the outer valve member 64 to be positioned against the third valve seating 96. h doing so, movement of the outer valve member 64 is coupled to the inner valve member 50 by virtue of their engagement at the first seating 92, and so the inner valve member 50 is also raised. By adopting this configuration, the connection between the first 84 and second 86 fluid chambers is closed, and so too is the connection between the second annular chamber 86 and the third chamber 90. Fluid is therefore not permitted to flow between the high pressure passage 16 and the low pressure drain 42, nor between the high pressure passage 16 and the common rail supply passage 30. This is the condition for peak injection, in which fuel within the pump chamber 32 is increased to the second, peak injector pressure (P2) during the plunger pumping stroke.
Although not visible in the scale shown in Figures 7a and 7b, the differential cone angle at the first seating 92 (i.e. the difference in cone angle between the first valve seating 92 on the inner valve member 50 and the engageable seating surface of the outer valve member 64) is selected so that the outer valve member 64 seats on its inner diameter at the first valve seating 92. By selecting the differential cone angle so that the outer valve member 64 seats on its inner diameter at the first valve seating 92, there is substantially no out-of- balance axial component of the hydraulic force acting on the inner valve member 50 due to high pressure fuel in the supply passage 16 when the outer valve member 64 is seated against the first valve seating 92. The inner valve member 50 is therefore substantially pressure-balanced to high pressure fuel within the supply passage 16 when the second and third valve positions are adopted.
Similarly, the third valve seating 96 and the seating surface of the outer valve member 64 which engages with the third valve seating 96 are shaped so that the outer valve member 64 seats on the inner diameter of the third valve seating 96. By selecting the differential cone angle at the third valve seating 96 so that the outer valve member 64 seats on the inner diameter of the third valve seating 96, there is substantially no out-of-balance axial component of the hydraulic force due to high pressure fuel within the passage 16 acting on the outer valve member 64 when in this position. The outer valve member 64 is therefore substantially pressure-balanced to high pressure fuel within the high pressure supply passage 16 when seated against the third valve seating 96 (i.e. in the second valve position).
Tables summarising the three positions of the control valve arrangements 34a and 34b positions (and associated information) are shown in Figures 9a and 9b, respectively.
As an alternative to providing the fuel system in Figure 1 with high pressure pump 24 for pressuring the common rail 26, the pump means 36 may be arranged to supply the rail 26 with pressurised fuel at the first, injectable (rail) pressure. In this embodiment, a low pressure pump may replace the low pressure drain 42, with the passage 44 providing a fill/spill passage between the pump chamber 32 and the low pressure pump. Typically, the low pressure pump may take the form of a transfer pump for supplying fuel to the pump means 36 at a pressure dependent upon engine speed.
During the plunger return stroke, the control valve arrangement 34 may be moved into its third valve position to bring the high pressure passage 16, and hence the pump chamber 32, into communication with the low pressure pump through the passage 44, thereby enabling the pump chamber 32 to be filled with low pressure fuel. Moving the control valve arrangement into its second position brings the pump chamber 32 into communication with the common rail 26, allowing the rail to fill with fuel at the first injectable pressure level. Injection can then be achieved at this first pressure level through operation of the NCN 18, as described previously.
During the plunger pumping stroke, the control valve arrangement 34 may be moved into the third valve position to break communication between the common rail 26 and the pump chamber 32, thereby permitting fuel within the pump chamber 32 and the high pressure passage 16 to be returned to the low pressure pump. This permits a spill end of injection, as described previously.
Having described particular preferred embodiments of the invention, it is to be appreciated that the embodiments in question are exemplary only and that variations and modifications such as will occur to those possessed of the appropriate knowledge and skills may be made without departure from the scope of the invention as set forth in the appended claims. By way of example, the rate of termination of injection may be varied by providing springs 60, 72 of different sizes, or by the use of shims or spacers within the chamber 58, 74 for the springs. It will also be appreciated that the control valve arrangement may be configured such that the winding 61 may be de-energised (rather than energised) to cause movement of the valve members 50, 64 to provide the three required valve operating positions.
It will also be appreciated that the control valve arrangement of the present invention may be used in fuel injection systems other than those of the EUI-common rail hybrid type for permitting injection at two different pressure levels.

Claims

1. A control valve arrangement (34a, 34b) suitable for use in an engine fuel injection system having first, second and third fuel volumes (26, 32, 42), the control valve arrangement including an inner valve member (50) which is slidably movable within an outer valve member (64) to provide for the control valve arrangement (i) a first valve position in which the first fuel volume (26) communicates with the second fuel volume (32), (ii) a second valve position in which communication between the first fuel volume (26) and the second fuel volume (32) is broken and (iii) a third valve position in which one of the first and second fuel volumes (26, 32) communicates with the third fuel volume (42).
2. A control valve arrangement (34a, 34b) according to claim 1, wherein the inner valve member (50) is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
3. A control valve arrangement (34a, 34b) according to claim 1 or claim 2, wherein the outer valve member (64) is substantially pressure balanced to fuel in one of the first, second or third fuel volumes when the second valve position is adopted.
4. A control valve arrangement (34a, 34b) according to any one of claims 1 to 3, for use in a fuel injection system having an accumulator volume (26) for fuel at a first injectable pressure level and pump means (32) for increasing fuel pressure to a second injectable pressure level, wherein the inner valve member (50) is slidably movable within the outer valve member (64) to provide for the control valve arrangement (i) the first valve position in which the accumulator volume (26) communicates with the pump means (32), (ii) the second valve position in which communication between the accumulator volume (26) and the pump means (26) is broken and (iii) the third valve position in which the pump means (26) communicates with a low pressure fuel drain (42), thereby to enable injection of fuel at either the first or second pressure level in dependence on the position of the control valve arrangement (34).
5. . A control valve arrangement (34a,34b) according to claim 4, wherein the outer valve member (64) takes the form of a tubular member having a valve bore (47) through which at least part of the inner valve member (50) extends so that an outer surface of the inner valve member (5) is in sliding contact with an inner surface of the tubular member (64).
6. A control valve arrangement (34a,34b) according to claim 4 or claim 5, wherein the outer valve member (64) is movable within a housing bore (48) provided in a valve housing (56).
7. A control valve arrangement (34a,34b) according to claim 6, including an electromagnetic actuator arrangement having an armature (59) that is movable in response to energisation and de-energisation of a winding (61), whereby movement of the inner and outer valve members (50, 64) is controlled by means of the electromagnetic actuator arrangement.
8. A control valve arrangement (34a,34b) according to claim 7, wherein the wmding (61) has a first state where it is not energised, a second state that results from partial energisation of the winding (61) to a first partial energisation level, and a third state that results from energisation of the winding (61) to a higher partial or full energisation level, wherein one of the inner or outer valve members (50, 64) is coupled to the armature (59) and whereby upon energisation or de-energisation of the winding said coupled valve member is movable relative to and co-operable with the other valve member to provide the first, second and third valve positions.
9. A control valve arrangement (34a,34b) according to claim 8, whereby no energisation of the winding (61) corresponds to the control valve arrangement being in the first valve position.
10. A control valve arrangement (34a,34b) according to any one of claims 7 to 9, whereby energisation of the winding (61) to the first partial energisation level corresponds to the control valve arrangement being in the second valve position.
11. A control valve arrangement (34a,34b) according to any one of claims 7 to 9, whereby energisation of the winding (61) to the first partial energisation level corresponds to the control valve arrangement being in the third valve position.
12. A control valve arrangement (34a,34b) according to claim 10, wherein the inner valve member (50) is coupled to the armature (59) and is movable relative to the outer valve member (64) into engagement with a first valve seating (92) defined by the outer valve member (64) upon energisation of the winding (61) to the first partial energisation level to provide the second valve position, said movement being coupled to the outer valve member (64) upon energisation of the winding to the higher partial or full energisation level to provide the third valve position.
13. A control valve arrangement (34a,34b) according to claim 12, wherein the first valve seating (92) is defined by a surface of the valve bore (47) provided in the outer valve member (64).
14. A control valve arrangement (34a,34b) according to claim 12 or claim 13, wherein a second valve seating (94) for the outer valve member (64) is defined by a surface of the housing bore (48), said outer valve member (64) being disengaged from the second valve seating (94) when the control valve arrangement is in the third valve position.
15. A control valve arrangement (34a,34b) according to claim 11, wherein the outer valve member (64) is coupled to the armature (59) and is movable relative to the inner valve member (50) into engagement with a first valve seating (92) defined by the inner valve member upon energisation of the winding (61) to the first partial energisation level to provide the third valve position, said movement being coupled to the inner valve member (50) upon energisation of the winding (61) to the higher partial or full energisation level to provide the second valve position.
16. A control valve arrangement (34a,34b) according to claim 15, wherein a third valve seating (96) for the outer valve member (64) is defined by a surface of the housing bore (48), whereby the outer valve member (64) is moved into engagement with the third valve seating (96) upon energisation of the winding (61) to the higher partial or full energisation level to provide the second valve position.
17. A control valve arrangement (34a, 34b) according to claim 15 or claim 16, wherein a second valve seating (94) for the outer valve member (64) is defined by a surface of a further housing (57) mounted adjacent to the valve housing (56).
18. A control valve arrangement (34a,34b) according to any one of claims 15 to 17, wherein the inner valve member (50) is provided with at least one cut-away section (81) at an end thereof to define a flow passage for fuel flow through the inner valve member (50) to low pressure when the control valve arrangement adopts the third valve position.
19. A control valve arrangement (34a,34b) according to any one of claims 7 to 18, including spring means (60, 72) that act on the inner and outer valve members (50, 64) to oppose the force applied to said inner and outer valve members (50, 64) due to energisation of the winding (61).
20. A control valve arrangement (34a,34b) according to claim 19, including an inner valve spring (60) that acts on the inner valve member (50) and an outer valve spring (72) that acts on the outer valve member (64), said springs (60, 72) urging their associated valve members towards the positions in which the first valve position of the control valve arrangement is provided.
21. A fuel injector for use in delivering fuel to an internal combustion engine at a first or second injectable pressure levels, the fuel injector comprising a control valve arrangement (34a, 34b) according to any one of claims 1 to 20 for controlling whether injection occurs at the first or second injectable pressure level.
22. A fuel injection system for supplying pressurised fuel to an injection nozzle, the fuel injection system comprising: an accumulator volume (26) for supplying fuel at a first injectable pressure (PI) to the injection nozzle (20), pump means (32) for increasing the pressure of fuel supplied to the injection nozzle (20) to a second injectable pressure level (P2) and a control valve arrangement (34a, 34b) which is operable between a first valve position in which the accumulator volume (26) communicates with the pump means (32) and fuel at the first injectable pressure level (PI) is supplied to the injection nozzle (20), a second valve position in which communication between the pump means (32) and the accumulator volume (26) is broken so as to permit fuel at the second injectable pressure (P2) to be supplied to the injection nozzle (20), and a third valve position in which the pump means (32) communicates with a low pressure drain (42), thereby to aid or execute termination of inj ection.
PCT/GB2004/000603 2003-02-17 2004-02-17 Control valve arrangement WO2004072472A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP03250956 2003-02-17
EP03250956.4 2003-02-17

Publications (1)

Publication Number Publication Date
WO2004072472A1 true WO2004072472A1 (en) 2004-08-26

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2004/000603 WO2004072472A1 (en) 2003-02-17 2004-02-17 Control valve arrangement

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4118236A1 (en) * 1990-06-06 1991-12-12 Avl Verbrennungskraft Messtech Cyclic-delivery fuel injection system for combustion engine - employs two control valves in low-pressure system supplying nozzle with fuel also during pre-injection period
US5687693A (en) * 1994-07-29 1997-11-18 Caterpillar Inc. Hydraulically-actuated fuel injector with direct control needle valve
US6119960A (en) * 1998-05-07 2000-09-19 Caterpillar Inc. Solenoid actuated valve and fuel injector using same
DE19939419A1 (en) * 1999-08-20 2001-03-01 Bosch Gmbh Robert Fuel injector

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4118236A1 (en) * 1990-06-06 1991-12-12 Avl Verbrennungskraft Messtech Cyclic-delivery fuel injection system for combustion engine - employs two control valves in low-pressure system supplying nozzle with fuel also during pre-injection period
US5687693A (en) * 1994-07-29 1997-11-18 Caterpillar Inc. Hydraulically-actuated fuel injector with direct control needle valve
US6119960A (en) * 1998-05-07 2000-09-19 Caterpillar Inc. Solenoid actuated valve and fuel injector using same
DE19939419A1 (en) * 1999-08-20 2001-03-01 Bosch Gmbh Robert Fuel injector

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