WO1999049229A1

WO1999049229A1 - A friction-type coupling arrangement

Info

Publication number: WO1999049229A1
Application number: PCT/SE1999/000255
Authority: WO
Inventors: Arnold Englund
Original assignee: Lysholm Technologies Ab
Priority date: 1998-03-26
Filing date: 1999-02-24
Publication date: 1999-09-30
Also published as: SE9801025D0; SE9801025L

Abstract

The present invention relates to a friction-type coupling arrangement comprising a fluid actuated pressure means (16) which when activated actuates a pressure plate (28) for pressing together the discs of a driving coupling part (10, 15) and a driven coupling part (9, 14). According to the invention, the pressure plate (28) actuates the pressure means (16) through the medium of a force-amplifying lever means (26) that has a relatively long lever arm (26b) connected to the pressure means (16) and a shorter lever arm (26a) connected to the driven coupling part (9).

Description

A FRICTION-TYPE COUPLING ARRANGEMENT

The present invention relates to a friction-type coupling arrangement of the kind defined in the preamble of the following Claim 1. Background Art A coupling, or clutch, arrangement of this kind can be used for both connecting and disconnecting a mechanical brake device and for purely coupling purposes. The coupling arrangement will normally include oil-lubricated and oil-cooled coupling discs and is very suitable for use in connecting and disconnecting a supercharger of an internal combustion engine. Since the coupling must be lubricated with oil to this end, it is convenient to use a piston controlled by the same oil for moving the first coupling part towards and into engagement with the other coupling part. The available oil pressure determines the piston area required to obtain the requisite pressure force on the displaceable coupling part. It has earlier been suggested in this regard that the engine pressure oil system is used to supply the coupling arrangement with oil. The use of a pressure oil source that is intended for some other purpose involves the risk that an oil pressure might be accepted that will be initially at a rather low level and become insufficient in the passage of time due to wear, for instance. This can, of course, be avoided by ensuring initially that the piston is given a sufficiently large area to deliver the requisite force should the oil pressure become low, as feared. However, the diameter of the piston of the coupling arrangement would then be so large as to make its inclusion in the coupling arrangement problematic. Alternatively, a pressure amplifying means can be included in the pressure line for raising the pressure acting on the piston. This solution, however, is not an ideal solution because the pressure amplifying means would require a separate space in the coupling arrangement, and is relatively expensive and requires maintenance. 2 Summary of the Invention

The object of the present invention is to provide a coupling arrangement, or clutch arrangement, of the aforesaid kind with which the aforesaid drawbacks are avoided in a simple and effective manner. This object is achieved in accordance with the invention with a coupling arrangement that has the characteristic features set forth in the following Claim 1. Thus, in accordance with the invention, there is not only a force amplification that is achieved directly between the pressure means and the coupling part actuated by said pressure means, through the action of the lever means, but the lever means is also coupled to the non-rotating, driven coupling part and the normally non-rotating piston and pressure means when the coupling arrangement is deactivated. The lever means will not begin to rotate until the coupling arrangement is activated, which is a desirable functional feature. The lever means can be readily produced and fitted. Ideally, the lever means will comprise three equidistantly spaced lever arms, which can be pressed from sheet metal and reinforced by profiling the arms. The lever arms can be readily placed in position as loose inserts when assembling the coupling arrangement, or may be interconnected by an annular holder, in accordance with Claim 2 and 3, respectively.

Brief Description of the Drawings

The invention will now be described in more detail with reference to an exemplifying embodiment of an inventive coupling arrangement and also with reference to the accompanying drawings, in which Figure 1 is a longitudinal sectioned view of the coupling arrangement; Figure 2 shows the lever means from above; and Figure 3 shows a modified lever means from above. Description of Preferred Embodiments

Fig. 1 illustrates a coupling arrangement for a supercharger of the screw- compressor type. The arrangement includes a housing 1 mounted on one side wall 2 of the supercharger, said supercharger including two screw rotors whose shafts 3, 4 are mounted at one end in bearings 5, 6 in the side wall 2. The shafts 3, 4 typically carry two co-acting, synchronizing cog wheels 7, 8. A driven coupling part 9 is fixedly mounted on the cog wheel 7. A driving coupling part 10 is constructed integrally with a driving shaft 11 , whose inner end is mounted in a radial bearing 12 accommodated in a recess in the central part of the cog wheel 7. The other end of the shaft 11 projects out of the housing 1 and is mounted in an angle bearing 13 and carries on said end a belt pulley 31 by means of which the supercharger is driven from the crank shaft of the internal combustion engine (not shown) via a toothed belt (also not shown).

Between the coupling parts 9 and 10, which each have the form of a sleeve, are typically provided annular coupling discs 14, 15 which are interfoliated and non-rotatably connected to the coupling parts 9 and 10 respectively.

The housing 1 also houses an annular piston 16 which is mounted for axial movement in a cylinder chamber 17 that is concentrical with the shaft 11. Connected to the cylinder chamber 17 is a pressure oil line 18 which communicates with the pressure oil system of the engine (not shown) via a pipe means 19 and a magnetic valve 20.

A bearing 21 having an outer ring 22 is mounted on the side of the piston 16 proximal to the coupling parts 9, 10. The inner ring 23 of the bearing 21 is freely rotatable. The driven coupling part 9 has an outwardly projecting end-part 24 that has a ring-shaped recess 25 on its inner surface. As will also be seen from Fig. 2, a lever means that includes three members 26 is fitted between this recess 25 and the inner ring 23 of the bearing 21. Each lever unit 26 has a knee 27 that abuts against a pressure plate 28 located above the uppermost disc 14 of the driven coupling part 9. A short lever arm 26a is located on one side of the knee 27 and a longer lever arm 26b is located on the other side of said knee. Coil springs 29 are disposed around the circumference of the coupling parts 9, 10 and function to urge said parts away from each other.

When the engine is running, the driving shaft 11 of the coupling arrangement will be rotated by the belt pulley 14 and the driving coupling part 10 carrying the discs 15 will thus also rotate. When the valve 20 is opened, pressure oil is delivered through the line 18 to the cylinder space 17 above the piston 16, which is therewith pressed against the end of the lever arm 26b via the inner ring 23 of the bearing 21. Since the end of the lever arm 26a is disposed in the recess 25, which acts as a counterpressure means, the knee 27 will be pressed hard against the pressure plate 28 so as to press the discs 14, 15 into engagement with one another with a force that is dependent on the proportional length between the lever arms 26a and 26b, therewith activating the coupling and causing the coupling part 9, the inner ring 23 of the bearing 21 , the lever units 26, the cog wheels 7, 8 and the shafts 3, 4 to rotate. When the ratio between the lengths of the lever arms 26a, 26b is 1 :4 and the piston exerts a force of 50 kp on the free end of the lever arm 26b, the knee 27 will be pressed against the pressure plate 28 with a force of 250 kp.

In order to prevent the pressure force on the discs 14, 15 from becoming dangerously high should the oil pressure become higher than intended for some reason or another, a pressure limiter may be included in the hydraulic oil line to the coupling arrangement for limiting line pressure in a known manner. Fig. 2 shows one embodiment of a lever means 26. The lever means is comprised of three identical units which are disposed equidistantly around the recess 25 in the coupling part 9. The shorter lever arm 26a of each unit is in engagement with the recess 25 at the chain line 26c, while the two legs of the forked, longer lever arm 26b are in abutment with the bearing ring 23 at the locations marked with respective crosses 26d. The knee 27 abuts the pressure plate 28 (not shown).

Fig. 3 illustrates a modification of the lever means 26 of Fig. 2. In this modified version, the three lever units are held together by an annular holder 30, thereby facilitating fitting of the lever means and holding the three units securely in place between the pressure plate 28 and the inner ring 23 of the bearing 21. It will be understood that the invention is not restricted to the illustrated and described embodiments thereof, and that modifications can be made within the scope of the invention as defined in the Claims. This applies particularly to the pressure means 16, which has the form of an hydraulic piston in the illustrated case but which may, alternatively, have the form of a screw mechanism with a tangentially disposed hydraulic piston for rotating said screw mechanism. The screw mechanism may include a screw thread or have oblique grooves in which balls are intended to roll and the like.

Claims

5 I CLAIM:

1. A friction-type coupling arrangement having a housing (1) in which there is mounted a drive shaft (11), an axially movable first coupling part (9, 14) and a second coupling part (10, 15) which acts as a counterpressure means, wherein both coupling parts include friction surfaces that are intended to be pressed together when the first coupling part is moved axially into engagement with the second coupling part by means of a fluid-actuated pressure means (16) mounted for axial movement in said housing (1) and located coaxially with said drive shaft (11), which engagement of said first coupling part (9, 14) with said second coupling part by means of said pressure means (16) is arranged to take place through the medium of a lever means (26) that includes a plurality of relatively short lever arms (26a) whose end parts are each connected to a respective holding means (25) and corresponding longer lever arms (26b) whose end parts are coupled to the pressure means (16) in contact with a freely rotatable bearing ring (23) of a bearing (21) mounted in the pressure means (16), characterized in that the first coupling part includes an outer sleeve (9) which is connected to a driven shaft (3) and which has inwardly lying ring- shaped coupling discs (14) non-rotatably connected thereto, and in that the second coupling part includes a ring-shaped inner sleeve (10) which is connected to the drive shaft (11) and with which outwardly lying, ring-shaped coupling discs (15) are non-rotatably connected interfoliated with the first- mentioned discs (14), and actuated by the lever means (26), the ends of the relatively short lever arms (26a) of which being mounted in said outer sleeve (9).

2. A coupling arrangement according to Claim 1 , characterized in that the lever means (26) includes three mutually identical units disposed equidistantly around the first coupling part (9).

3. A coupling arrangement according to any one of Claims 1-2, characterized in that the ends of the shorter lever arms (26a) connected to the first coupling part (9) are interjoined by an annular holder (30).

4. A coupling arrangement according to any one of Claims 1-3, characterized in that the end-parts of the longer lever arms (26b) coupled to the pressure means (16) are fork-shaped with a respective abutment part (26d) in abutment with the pressure means (16).