DE4301591A1 - - Google Patents

Abstract

A motor vehicle has a continuously variable automatic transmission, an automatic clutch provided between the engine and the automatic transmission, an antilock brake system (ABS). An ABS signal is produced when the ABS is operated. In response to the ABS signal, the automatic clutch is released so as to efficiently operate said antilock brake system without belt slipping. The idling speed of the engine may be increased when the clutch is disengaged to ensure sufficient pressure output from the pump supplying the controlling hydraulic system. An air conditioner may also be turned off to reduce the load on the engine.

Description

The present invention relates to a system for Controlling a continuously variable transmission (CVT) for a motor vehicle with automatic clutch and esp special to a control system that controls an automati gearbox in conjunction with an anti-lock braking system stem is suitable.

It has become common to have motor vehicles with an anti-lock Brake system (hereinafter referred to as ABS) to equip to prevent the wheels from locking when the vehicle is on on a road with a low coefficient of friction and thereby the directional stability and manageability to improve the vehicle. The ABS controls electronically a brake oil pressure to prevent the wheels from locking ren. In a vehicle with continuously changing ge however, where transmission ratio and oil pressure correspond  Precisely controlled according to the wheel speed and other factors ABS operation strongly influences the transmission control. Therefore, when operating the ABS, both the ABS is preferably controlled the transmission as well. ABS-Be drove the pressure of a brake oil supplied to the brake system decreased to release the wheel so that the wheels begin to turn. However, the drive wheels are over the automatic clutch and gearbox directly with the engine connected. Consequently, the wheel rotation is caused by the inertial mass of the engine difficult. As a result, the recoverers can delay the setting of the wheel speed and thereby the effect deteriorate ABS.

Japanese Patent Application Laid-Open 62-2 47 928 has an engine speed control system. In this system a throttle valve of the engine controls the engine speed to keep at a set speed when a driver choose an optimal gear ratio. The system serves however, to regulate an engine speed when the engine is engaged Clutch. After the system is not turned on for ABS control is aimed, it cannot un as an engine speed control system ter ABS can be used with the clutch disengaged.

The object of the present invention is a control system to make available, which prevents the effects ABS deteriorates.

Is made available according to the present invention a system for controlling a continuously changing Gearbox for a motor vehicle with an engine, an auto matic coupling, provided between the engine and the Ge drives, wheel speed sensors for detecting the wheel speed of the Vehicle, a hydraulic control system comprising a Oil pump and a hydraulic circuit to control the transmission, and an anti-lock braking system that operates on an output of the Wheel speed sensor responds to reduce the brake pressure.  

The system includes determining means based on the wheel speed respond to an ABS signal to operate the anti-lock To produce braking system, and disengaging means that on the Activate ABS signal to disengage the automatic clutch.

A speed increase means is preferably provided, that responds to the ABS signal to rotate the engine idle number increase, and stop responsive to the ABS signal medium to stop the operation of an air conditioner operating in the Motor vehicle is installed.

Other objects and features of the present invention from the following description with reference to the accompanying drawings obvious.

Fig. 1 Shows a schematic diagram of a continuier Lich variable belt-drive transmission and a hydraulic control circuit thereof according to the present invention,

Fig. 2 shows a block diagram of a control unit of the present invention;

FIGS. 3 and 3f show operating characteristics of an ABS;

Fig. 4 is a flowchart showing the clutch release operation according to the present invention;

Fig. 5 is a schematic diagram of a second embodiment of the present invention;

Fig. 6 is a block diagram of a control unit of the second embodiment.

Referring to Fig. 1, a continuously variable (belt) automatic transmission for a motor vehicle to which the present invention is applied includes an automatic clutch 2 to the power of an engine 1 via a shift mechanism 3 to the continuously variable transmission 4 transfer.

The continuously variable transmission 4 has a main shaft 5 and an output shaft 6 which is arranged parallel to the main shaft. 5 A drive pulley (primary pulley) 7 and a driven pulley (secondary pulley) 8 are attached to the main shaft 5 and the output shaft 6 , respectively. A fixed conical disc 7a of the drive pulley 7 forms with the main shaft 5 a one unit. An axially movable conical disk 7 b is axially slidably attached to the drive shaft 5 . The movable conical disc 7 b also slides in a cylinder 9 which is formed on the main shaft 5 to provide a servo device.

A fixed conical pulley 8 a of the driven belt pulley 8 is formed on the output shaft 6 relative to the movable conical pulley 7 b. A movable koni cal disc 8 b is slidably mounted on the shaft 6 opposite the disc 7 a. The movable conical disc 8 b has a cylindrical part which slidably engages in a cylinder 10 of the output shaft 6 to form a Servovor direction. A belt 11 connects the drive pulley 7 and the driven pulley 8th

The cylinder 9 of the drive pulley 7 has a pressure receiving area that is larger than that of the cylinder 10 of the driven pulley 8 . Depending on the driving conditions, a running diameter of the belt 11 on the pulleys 7 and 8 is changed.

On the output shaft 6 , a drive gear 12 a is fixed, which engages in an intermediate reduction gear 12 on an inter mediate shaft 13 . An intermediate gear 14 a on the shaft 13 engages with a final reduction gear fourteenth Rotation of the Enduntersetzungszahnrades 14 is transmitted via a differential 15 to the axles 17 of vehicle driving wheels sixteenth

In a hydraulic control circuit, oil is supplied from an oil reservoir 30 by an oil pump 20 via an oil pressure connection 21 to an oil pressure control valve 22 . The oil pump 20 is also connected to the cylinder 10 of the driven pulley 8 via a connection 21 b. The oil pressure control valve 22 is connected via a connection 21 a to the transmission ratio control valve 23 . At the Zy cylinder 9 of the drive pulley 7 is under pressure of the oil, through the connection 21 , the oil pressure control valve 22 , the connection 21 a, the transmission ratio control valve 23 and a connection 24th A connection 25 connects the oil pressure control valve 22 and a solenoid-operated on-off valve 27 . A connection 26 connects the gear ratio control valve 23 and a solenoid-operated on-off valve 28 . The solenoid-operated valve 27 is connected to the pump 20 through a connection 21 c with an opening 27 a opening. The valve 28 is connected to a connection 21 a through a connection 21 d, which has an opening 28 a.

The solenoid-operated valve 27 can be operated by electrical signals from a control unit 40 to generate the control pressure. The control pressure is applied to the oil pressure control valve 22 . The oil pressure control valve 22 is connected to a sensor shoe 29 via a spring lock. The sensor shoe 29 is engaged with the movable sheave 7b of the drive pulley 7, so as to an actual translation ratio i detected. Thus, the oil pressure P _L is regulated according to the gear ratio i and the engine torque Te.

Also, the solenoid-operated valve 28 is driven by the electrical signal's and generates a reduced pressure which is applied to the gear ratio control valve 23 to slide a spool of the gear ratio control valve 23 into an oil supply and an oil drain position ben. Thus, the cylinder 9 of the pulley 7 is supplied or discharged by the oil flow Q controlled to provide an optimal gear ratio i.

A braking system with ABS will now be described. A brake pedal 31 is connected to a master cylinder 32 to testify to fluid pressure corresponding to depression of the brake pedal. The master cylinder 32 is connected via a line 33 a to a pair of modulators 34 of the ABS. A line 33 b extends from each of the modulators 34 and is connected to a braking device 35 of one drive wheel 16 each. The modulator 34 is also connected to a braking device of the driven wheels (not shown) via a line 33 c connected to a metering valve 36 for adjusting the pressure on the driven wheels. The modulator 34 has various solenoid valves to reduce, increase or maintain the pressure, and thus to control the brake fluid pressure when the anti-lock brake system is in accordance with a signal from the control unit 40 in operation.

Referring to Fig. 2 which shows an electronic system of the control unit 40, the system is provided with an on drive pulley rotational speed sensor 41, a speed sensor 42 of the driven pulley, a throttle position sensor 43, a gear position sensor 44, an accelerator pedal scarf ter 45, an engine speed sensor 48 , a front wheel speed sensor 46 and a rear wheel speed sensor 47 .

Output signals N _P and N _{S of} the sensors 41 , 42 and an output signal R, which gives an opening degree of a throttle valve, which is taken up by the throttle position sensor 43 , leads to a transmission ratio control module 50 . The control module 50 calculates the actual gear ratio i and a target gear ratio id according to the input signals. A gear ratio change speed di / dt is calculated from the difference between the actual gear ratio i and the target gear ratio id. A power ratio D, determined by the gear ratio change speed (di / dt), is supplied to the solenoid-operated on-off valve 28 .

The engine speed signal Ne and the throttle valve opening degree R are supplied to an oil pressure control assembly 51 . In the oil pressure control assembly 51 , the engine torque Te is estimated based on the engine speed Ne and the throttle opening degree R ge. A power ratio D _L , which, depending on the engine torque Te, corresponds to a desired oil pressure, is determined and leads to the solenoid-operated on-off valve 27 .

The engine speed Ne, the speed N _{S of} the driven pulley, which represents the vehicle speed, one of the output signals of the shift position sensor 44 , and an output signal of the accelerator pedal switch 45 , which represents the position of the accelerator pedal, are supplied to a clutch control module 52 . The control assembly 52 determines an operation of the automatic clutch 2 , according to the driving conditions of the vehicle. When the vehicle starts up or if it is preferable to fully engage the clutch, a clutch current is applied to the clutch 2 with a strength suitable for the respective mode of operation. When the vehicle speed is lower than a predetermined reference speed, the clutch current is automatically cut off, thereby preventing the engine 1 from dying.

To control the ABS a vehicle speed computer 53, a front wheel speed NF from the front wheel speed sensor 46 and a rear wheel speed NR from the rear wheel speed sensor 47 is supplied. The vehicle speed V is calculated as the mean of the wheel speeds NF and NR. The wheel speeds NF and NR are fed to a wheel lock determination module 54 in order to recognize the locking of the wheels. The wheels can be blocked if the decelerations dN / dt of the wheel speeds NF or NR are extremely large. A blocking signal from the determination module 54 , the vehicle speed V and the wheel speeds NF and NR are applied to a hydraulic pressure controller 54 in order to control the modulator 34 via an output controller 56 .

If the wheel speed NF or NR of the wheel is less than a pseudo vehicle speed Vc so that the wheel could be locked, the controller 55 generates a pressure reduction signal to reduce the hydraulic pressure for the brake device.

When the wheel speed recovers, a signal to increase the hydraulic pressure is generated. The output controller 56 supplies the solenoid valves in the modulator 34 with an ABS signal based on these signals.

A system to maintain the effectiveness of the ABS and to provide a sufficient delivery of the pump 20 is described below. If the hydraulic pressure of the brake system falls during the operation of the ABS, the restoration of the wheel speed can be delayed due to the inertial mass of the engine 1 , whereby the effectiveness of the ABS deteriorates. When the automatic clutch 2 is released, on the other hand, the engine speed Ne drops to an idle speed, so that the flow rate of the engine geared NEN oil pump 20 decreases rapidly, causing a drop in oil pressure. At the same time, the oil pressure, which acts on the drive pulley of the continuously variable transmission, decreases with the oil line pressure, so that the belt 41 slips on the pulley. In addition, when an air conditioner installed in the vehicle is operated while the engine is idling, a compressor (not shown) of the air conditioner applies a load to the engine. She is happy to disturb or delay the engine speed Ne.

The control unit 40 is provided with a disengagement determination group 60 , which is fed the ABS signal from the output controller 56 . The disengagement determination group 60 generates a disengagement signal corresponding to the ABS signal that is input to the clutch control group 52 to thereby disengage the clutch 2 .

The decoupling signal is also supplied to an idle speed control group 61 , which serves to actuate an actuator 62 attached to the throttle valve 1 a of the engine 1 in order to increase the engine speed Ne at idle.

The control unit 40 is also provided with an air conditioner controller 65 to which an output signal of the idle speed control group 61 is supplied to control a clutch 63 for connecting the air conditioner compressor to the engine 1 and a condenser fan 64 . In accordance with the input signal from the idle speed control group 61 , the controller 65 is operated to disengage the clutch 63 and stop the condenser fan 64 .

The operation of the system is described below. When the accelerator pedal is depressed in the driving range, the clutch current increases, increasingly with an increase in the engine speed Ne. The automatic clutch 2 is gradually engaged, whereby it transfers the engine power to the drive pulley 7 . The power of the engine 1 is transmitted at the largest gear ratio by the drive belt 11 and the driven pulley 8 to the output shaft 6 , and further via the intermediate shaft 13 and the differential 15 on the axles 17 of the drive wheels 16 . So the vehicle starts. When the vehicle speed (output signal N _S ) exceeds a predetermined value, the clutch 2 is fully engaged. The pump 20 driven by motor 1 feeds the oil line pressure control valve 22 to the oil. If the engine torque Te is large in the low engine speed range, the desired oil line pressure is large. The solenoid-operated on-off valve 27 is operated at a power ratio D _L corresponding to the desired oil pressure, thus increasing the oil pressure P _L. When the engine torque Te decreases in the high engine speed range, the oil pressure P _{L is} reduced. The power is transmitted through the transmission without the belt 11 slipping.

The oil pressure P _L is supplied to the cylinder 10 of the drive pulley 8 and the gear ratio control valve 22 . In the translation control module 50 of the control unit 40 , the target gear ratio id is determined depending on the corresponding driving conditions. The ratio Ratio change rate di / dt is calculated based on the actual ratio i and the target ratio ratio id, so that the power ratio D for the translation control valve 23 is obtained.

The solenoid-operated valve 28 is operated via the Leistungsver ratio D and to push produces reducing pressure which is applied to the transmission ratio control valve 23 to the spool of the valve 23 in an oil supply and an oil discharge position. Thus, the cylinder 9 of the pulley 7 supplied or discharged oil flow depending on the gear ratio change speed di / dt controlled to generate a primary pressure. Thus, the barrel diameter of the belt 11 is changed by the drive pulley 7 to variably control the gear ratio.

When the brake pedal 37 is depressed while driving, the master cylinder 32 generates brake fluid pressure, which is supplied to the brake devices 32 to brake the wheels. As a result, the vehicle speed and the rotational speed N _{S of} the driven pulley are reduced, so that the gear ratio control group 50 operates the gear ratio control valve 23 to reduce the gear ratio.

On the other hand, it is determined at the eraser lock determination group 54 when the wheels are about to lock NF or NR when the wheel speed drops rapidly. Namely, when the vehicle is braked on a road with a low coefficient of friction as shown in FIG. 3a, the front wheel speed NF or the rear wheel speed NR drops rapidly as shown in FIG. 3b. The hydraulic pressure controller 55 he generates an ABS signal, as shown in Fig. 3a 'to increase, maintain or decrease the liquid pressure according to the difference between the wheel speed NF or NR and the pseudo or reference vehicle speed Vc (calculated from previously measured wheel speeds). The ABS signal is applied to the modulator 34 via the output controller 56 to regulate the pressure. Thus, the fluid pressure for the braking device 35 is modulated, as shown in FIG. 3c. Thus, the wheel speed NF or NR is reduced in accordance with the actual vehicle speed VB without causing the wheels to lock.

Thereafter, the program shown in the flowchart of Fig. 4 is executed. When the ABS is not operating, the engine idle speed is controlled normally. When the ABS is in operation, the ABS signal is also applied to the disengagement determining group 60 which determines the disengagement of the clutch 2 and generates an disengagement signal.

The disengaging signal is fed to the clutch control group 52 to force the clutch 2 to be released as shown in FIG. 3d and thereby prevent the inertial mass of the engine from acting on the wheels. On the other hand, the idle speed control group 61 is provided with the disengagement signal ver in order to generate an output signal which is supplied to the air conditioning system controller 65 . The controller 65 serves to disengage the clutch 63 of the air conditioning system and to stop the condenser fan 65 , and thus to stop the air conditioning system, as shown in FIG. 3f. So the load on the engine 1 is reduced. In this state, the actuating member 62 is actuated by the control group 61 , so that the throttle valve 1 a is opened further to increase the idle speed. Consequently, the idle speed is prevented from decreasing; it can because of the disengagement of the automatic clutch 2 , as shown by a dotted line in Fig. 3e. Thus, the engine speed Ne and thus the delivery rate of the pump 20 are obtained, as shown by a solid line.

Accordingly, the oil pressure control valve 22 can be operated to provide an optimal oil pressure in accordance with the slow drop in the delivery rate of the pump 20 . Thus, Sicherheitge is provided that the belt 11 engages the pulleys 7 and 8 .

When the clutch is disengaged, the gear ratio ratio in the same way as in a conventional one Control unit controlled.

Referring to FIGS. 5 and 6, which show the second embodiment, the system has a hydraulic control unit 67 and a hydraulic circuit 68. The hydraulic circuit 68 is conventionally Lich, as disclosed in US Patent 49 48 370. The hydraulic circuit 68 includes an oil pressure control valve and a translation ratio control valve, which are controlled by a Pitot pressure from a Pitot tube 69 , which reflects the engine speed, the position of an accelerator pedal 70 and a selector position of a gear selector lever 71 . Thus, the gear ratio and the oil pressure are controlled according to the driving conditions of the vehicle.

The rest of the structure and other operations are as in the first embodiment.

From what has been said it is clear that the present invention is a continuously variable transmission for a vehicle with ABS provides by preventing the ABS effectiveness by disengaging the clutch during the ABS operation deteriorated. At the same time, the idle speed increases to a rapid drop in pump delivery to prevent performance, and thereby slipping of the To prevent straps.

After the engine load is stopped by stopping the air conditioner is reduced, the engine idle speed increased without delay and thus effectively prevented, that the oil pressure drops.

Claims (4)

1. System for controlling a continuously variable transmission ( 4 ) for a motor vehicle with an engine ( 1 ), an automatic clutch ( 2 ), provided between the engine and the transmission, wheel speed sensors ( 46 , 47 ) for recording the wheel speed of the vehicle, a A hydraulic control system comprising an oil pump ( 20 ) and a hydraulic circuit for controlling the gear ratio, and an anti-lock braking system (ABS) which is responsive to an output of the wheel speed sensors ( 46 , 47 ) to reduce brake pressure, characterized in that that the system encompasses

• - determining means ( 54 ) for generating an ABS signal for operating the anti-lock braking system; and
• - Disengaging means ( 52 , 60 ) that respond to the ABS signal to the automatic clutch ( 2 ) so that the anti-lock braking system will operate effectively without slipping a belt ( 11 ).

2. System according to claim 1, characterized by speed increasing means ( 61 ) responsive to the ABS signal to increase the idle speed of the engine ( 1 ) without delay, and thereby effectively prevent a drop in the oil pressure. 3. System according to claim 1, characterized in that the determining means ( 54 ) comprises a blocking determining means which responds to the wheel speed recorded by the wheel speed sensors ( 46 , 47 ) in order to determine a rapid deceleration of the wheel and to generate a wheel blocking signal , and hydraulic pressure control means ( 55 ) responsive to the wheel lock signal to generate the ABS signal. 4. System according to claim 2, characterized by stop means ( 65 ) which respond to the ABS signal to stop the operation of an air conditioning system installed in the vehicle.