GB1599526A

GB1599526A - Motor vehicle clutch control mechanisms

Info

Publication number: GB1599526A
Application number: GB15659/77A
Authority: GB
Original assignee: Vandervell Products Ltd
Current assignee: Federal Mogul Shoreham Ltd
Priority date: 1977-04-14
Filing date: 1977-04-14
Publication date: 1981-10-07
Also published as: FR2387137A1; IT1108652B; IT7867852A0

Description

(54) IMPROVEMENTS IN OR RELATING TO MOTOR VEHICLE CLUTCH CONTROL MECHANISMS (71) We, VANDERVELL PRODUCTS LIMITED, a British Company of Norden Road, Maidenhead, Berkshire, do hereby declare the invention for which we pray that a patent be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to motor vehicle clutch control mechanisms.

It has already been proposed to control a friction clutch of a motor vehicle in response to parameters such as engine speed and the fact that a gear change mechanism is being operated and arrangements of this kind make it unnecessary to provide a vehicle with a clutch pedal.

One situation in which an arrangement of this kind is particularly desirable is for a vehicle to be used by an invalid.

In a typical vehicle transmission which does not incorporate a clutch pedal, some form of clutch other than or additional to the conventional coil spring or diaphragmspring friction clutch is required. For this reason it is not normally practical to convert a vehicle with conventional clutch operation to operation without a clutch pedal because of the expense and difficulty associated with installing a different or additional clutch or similar mechanism.

An object of the present invention is to provide a clutch control mechanism which can remove the requirement for a clutch pedal whilst maintaining a conventional clutch.

According to the present invention there is provided a motor vehicle clutch control mechanism comprising power means arranged to release a clutch when the power means is actuated, fust control means to cause actuation of the power means while a gear selection mechanism is being operated and second control means to actuate the power means in response to a combination of the engine speed being below a predetermined level and the vehicle service brakes being in the applied condition, said first and second control means comprising electrical control systems to actuate said power means for operating said clutch, the first electrical control system comprising a switch operable in conjunction with operation of said gear selection mechanism to actuate said power means for operating said clutch, the second control system comprising means responsive to a vehicle brake light circuit and an engine speed below a predetermined level to actuate said power means to disengage said clutch when said brake light circuit is in operation and the vehicle speed is below said predetermined level, wherein the speed responsive means comprises means which generates a first electric signal in accordance with the actual engine speed, means to generate a reference signal of predetermined magnitude and a comparator to compare said signals and transmit a further signal to actuate said power means and disengage said clutch when the vehicle brake light circuit is energised and the engine speed is below said predetermined speed.

The second control means is provided to disengage the clutch when the vehicle is stationery or travelling very slowly and by making this control means dependent on the application of the vehicle service brakes, a differentiation is established between the situation where the vehicle is being slowed down and the situation where the vehicle is being accelerated gently from rest with a low engine speed. If the second control means were dependent solely on engine speed, the clutch could disengage inadvertently as the vehicle is being accelerated gently from rest because the initial clutch engagement could apply sufficient load to the engine to reduce its speed below that at which the clutch becomes disengaged.

In the case where the clutch control mechanism is intended for use with a gear box having a manually operated gear lever for effecting gear selection, the first electrical control system may comprise a switch operable in conjunction with operation of a gear lever to actuate the power means for operating the clutch.

Preferably, there is provided throttle overridding means operable to ensure that the throttle is in an idle condition whenever the clutch is in a disengaged condition.

The throttle control means may comprise a Bowden cable having an inner cable connected to a throttle valve and an outer casing mounted on a moveable anchorage adjacent the throttle valve, the throttle over-riding means being arranged to move the anchorage from a normal position to ensure that the throttle valve is in an idle position when the clutch is disengaged.

A stop may be provided to define a normal position of the anchorage and spring means may be provided for biassing the anchorage towards the stop against the action of the throttle over-riding means to provide a fast idle setting for the throttle.

The power means for operating the clutch may comprise a servo controlled by both said first and second control means and a clutch operating mechanism actuated by the servo.

The servo may be a vacuum servo.

The servo may be connected to the clutch through a hydraulic system including a master cylinder operated by the servo and a slave cylinder for operating the clutch.

The following is a description of a specific embodiment of the invention and some possible modifications reference being made to the accompanying diagrammatic drawings in which: Figure 1 shows a motor vehicle clutch control system including a solenoid operated control valve for a servo-system, and Figure 2 is a more detailed view of the control valve.

A motor vehicle engine 10 has a conventional clutch 11, an inlet manifold 12 and a carburettor 13 with a throttle valve 14 and a venturi 15 upstream of the throttle valve.

The clutch 11 is a conventional motor vehicle friction clutch which is engaged by coil springs or a diaphragm spring forming part of the clutch and can be disengaged by operation of a conventional throw-out fork 1 la.

The clutch 11 is disengaged by a servo unit 16 having a diaphragm 17 connected by a pushrod 18 to the throw-out fork 1 la. The servo unit 16 has a vacuum line 19 for connection to a source of vacuum to disengage the clutch and a return spring 1 7a for the diaphragm 17.

The vacuum line 19 is connected through a control valve assembly 20 having a solenoid control 21 and through a further vacuum line 22 to a vacuum reservoir 23. The valve assembly 20 is also connected to a vacuum line 24 to the engine inlet manifold 12 to create the vacuum in the reservoir 23 and the supply may be augmented or substituted by an engine or electrically driven vacuum pump 25 in the vacuum line 24. The control valve assembly 20 as shown in Figure 2 comprises a first two position pneumatic valve 26 having a slide movable by the solenoid 21. With the solenoid de-energised, the valve 26 connects the vacuum line 19 from the servo unit 16 through a line 27 to atmosphere so that the clutch is engaged.

With the solenoid energised, the valve 26 connects the vacuum line 19 to the further vacuum line 22 to the vacuum reservoir to operate the servo unit to disengage the clutch. The vacuum line 24 connected to the inlet manifold is branched from the line 22 and contains a check valve 28 to create and maintain the vacuum in the reservoir 23.

The air line 27 to atmosphere contains a two position valve 29 for opening and closing the air line. The valve 29 is operated by a diaphragm unit 30 having a return spring 31. The diaphragm unit 30 is connected by a vacuum line 32 to the carburettor venturi 15. A by-pass line 33 around the valve 29, has a restriction 34 to permit restricted air flow through the line 27 to the servo unit when the valve 29 is closed.

When the throttle valve 14 is opened a relatively small amount, the relatively small air flow through the venturi 15 applies a relatively low vacuum to the diaphragm unit 30 so that the valve 29 remains closed. Air can then bleed through the line 27 only through the restriction 34 and thence to the servo unit 16 so that a relatively slow engagement of the clutch takes place. When the throttle opening is relatively large the resulting high air flow through the venturi 15 produces a high vacuum in the diaphragm unit 30 which moves the valve 29 to the open position allowing air to pass directly through the valve 29 along the air line 27, through the valve 26 and then through the vacuum line 19 to servo unit 16 to allow a rapid re-engagement of the clutch. The changeover from slow to fast clutch re-engagement may be set to occur at an engine speed of about 1200 rpm. The volume and proportions of the various passages and valves is such that when the solenoid is de-energised on small throttle openings, fast initial movement towards engagement of the clutch occurs as the air pressure in these passages and valves equalises with the high vacuum in the servo before a slow completion of engagement controlled by restriction 34.

The electrical control system for the solenoid 21 will now be described with reference to Figure 1 of the drawings. The vehicle has a battery 40, a gear box 41, a gear lever 42 having a control knob 43, a gear change mechanism 44 between the gear lever 42 and gear box 41, an ignition distributor 45, a brake light circuit 46 having brake lights 47 and a conventional service brake operated switch 48 for the brake lights and hand brake lever 49. One terminal of solenoid 21 is connected to the battery by a lead 50. The other terminal may be earthed to energise the solenoid through a switch 51 mounted between the gear lever 42 and gear lever knob 43 and arranged to be closed by pressure applied to the knob 43 to engage or disengage a gear or to change gear. The other side of the switch is connected to earth. Thus the solenoid 21 is energised whenever pressure is applied to the gear lever knob 43 and energis ing of the solenoid causes the servo to be operated to disengage the clutch.

When a gear[or neutral] has been selected and the knob 43 is released, the switch 51 opens de-energising the solenoid 21 and the clutch is reengaged at a rate determined by the throttle opening as described above.

When the vehicle is on the move and a gear change is to be made, the knob 43 is pushed in the desired direction causing the clutch to disengage and the gear lever 42 can then be moved to select the required gear. On release of the knob 43 the clutch is re-engaged at a rate dependent on throttle opening.

When braking the vehicle to rest, it is desirable that the clutch should disengage automatically without the gear lever switch having to be operated. It is not practicable to disengage the clutch solely in response to a low engine speed because a low engine speed can occur while the vehicle is starting gently from rest and clutch dis-engagement in these conditions would make a gentle start impossible.

For this reason the combined criteria of low engine speed and service brakes applied is selected to disengage the clutch as the vehicle comes to rest with a gear engaged.

When the service brakes are applied, the switch 48 is closed to operate the brake lights 47 and energise an electronic speed switch assembly 52. The speed switch assembly comprises a pulse counter 53 which is connected to the low tension side of the ignition distributor 45 and converts ignition pulses into a voltage signal. A pre-set trimming device 54 gives a constant reference signal corresponding to the engine speed at which it is desired to energise the solenoid. This may for example be about 900 rpm. The two signals from the counter and the trimming device are compared in a comparator circuit 55 which in turn operates an output device 56 in the form of a relay or a transistor switch when the voltage signal from device 53 is less than or equal to the reference voltage. The output device 56 is arranged to connect the solenoid 21 to earth. Thus when the brakes are operated and the engine speed is below the predetermined level the solenoid 21 is energised to disengage the clutch. If the brakes are operated but the engine speed is above the predetermined level, the clutch does not dis-engage so that, for example, when the vehicle is braked to reduce speed for a corner, the clutch does not disengage.

An additional switch assembly 58 may be fitted to the handbrake lever 49 in parallel with the switch 48 so that the speed circuit is energised while the handbrake is on unless the conventional ratchet release mechanism of the hand brake is also operated. Then, immediately before a hill start, with a gear engaged and the hand brake on, clutch reengagement can be initiated by operation of the ratchet release mechanism and hand brake release can be synchronised with clutch reengagement.

A mechanism is also providecd to ensure that the carburettor throttle valve 14 is moved to a normal idling position defined by a stop 60 giving, say 600 rpm whenever the clutch is disengaged, regardless of the position of the accelerator. The throttle valve 14 is connected by a lever system 61 to one end of the inner cable 62 of a Bowden cable having an outer casing 63. A throttle return spring 64 is connected to the lever to bias the lever towards the stop 60 and thereby close the throttle when the accelerator pedal is released. The outer casing 63 of the Bowden cable mechanism carries a threaded adjuster 63a screwed into a lever 65 which is pivotally mounted at 66.

The lever 65 is connected by a link 67 to a vacuum servo unit 68 connected by vacuum line 69 to the vacuum line 19 leading to the servo unit 16. Vacuum in the servo unit 68 pivots the lever 65 in a direction to draw the outer casing 63 of the Bowden cable in a direction which slackens the cable 62 and allows the spring 64 to return the lever system 61 to the stop 60. Thus whenever the vacuum line 19 is opened by the solenoid 21 to disengage the clutch, the throttle control lever 61 is returned to the stop 60 and the engine then idles. The lever 65 is biassed in the opposite direction by a tension spring 70 which biasses the lever 65 into engagement with a stop 71 mounted adjacent the pivotal mounting 66 and in this position the engine idles at a higher speed of say 1100 rpm. Thus when the vehicle is at rest with the foot brake applied and the gear lever is moved to select first gear, the clutch is disengaged and the servo unit 68 operated to allow the throttle lever 61 to move to its stop 60 to give the normal slow idle speed. Once the gear lever knob is released and the brake released and the clutch is allowed to re engage, the lever 65 is restored to its stop 71, thus opening the throttle to the fast idle speed. If the clutch is allowed to re-engage without the accelerator being depressed the vehicle creeps forward with the engine running at the fast idle speed and this is particularly convenient for manoeuvring in confined spaces. The adjustment of the diaphragm unit 30 is such that valve 29 remains closed at fast idle speed so that the clutch re-engages slowly. Of course as soon as the service brakes are applied at such low speeds the clutch disengages under the action of the speed switch assembly 52.

The above arrangement provides a simple and relatively un-complicated automatic clutch control mechanism which can be applied to the majority of conventional motor vehicles having normally manually operated clutches without the need of a torque converter or other special clutching arrangement and without splitting the engine from the gear-box to provide access to the clutch. The clutch mechanism also enables a fully automatic gear box to be provided in which gear selection is automatically controlled in which case the switch associated with the gear lever knob in the arrangement described above forms part of the control system for automatic gear slection for the gear box.

Many modifications may be made to the above described embodiment without departing from the scope of the invention. For example, the diaphragm type servo unit 16 could be replaced by a servo unit incorporating a bellows capsule or a piston and cylinder.

Also the direct mechanical link between the servo unit and clutch could be replaced by a hydraulic system comprising a master cylinder operated by the servo unit, a hydraulic fluid circuit and a slave cylinder connected to the clutch.

The arrangement lends itself to any motor vehicle where automatic clutch operation is required including vehicles intended to be used by disabled drivers.

WHAT WE CLAIM IS: 1. A motor vehicle clutch control mechanism comprising power means arranged to release a clutch when the power means is actuated, first control means to cause actuation of the power means while a gear selection mechanism is being operated and second control means to actuate the power means in response to a combination of the engine speed being below a predetermined level and the vehicle service brakes being in the applied condition, said first and second control means comprising electrical control systems to actuate said power means for operating said clutch, the first electrical control system comprising a switch operable in conjunction with operation of said gear selection mechanism to actuate said power means for operating said clutch, the second control system comprising means responsive to a vehicle brake light circuit and an engine speed below a predetermined level to actuate said power means to disengage said clutch when said brake light circuit is in operation and the vehicle speed is below said predetermined level, wherein the speed responsive means comprises means which generates a first electric signal in accordance with the actual engine speed, means to generate a reference signal of predetermined magnitude and a comparator to compare said signals and transmit a further signal to actuate said power means and disengage said clutch when the vehicle brake light circuit is energised and the engine speed is below said predetermined speed.

2. A clutch control mechanism as claimed in claim 1 in which there is provided throttle over-riding means operable to ensure that the throttle is in an idle condition whenever the clutch is in a dis-engaged condition.

3. A clutch control mechanism as claimed in claim 2 in which the throttle control means comprises a Bowden cable having an inner cable connected to a throttle valve and an outer casing mounted on a moveable anchorage adjacent the throttle valve, the throttle overriding means being arranged to move the anchorage from a normal position to ensure that the throttle is in an idle position when the clutch is dis-engaged.

4. A clutch control mechanism as claimed in claim 3 in which a stop is provided to define a normal position of the anchorage and spring means are provided for biassing the anchorage towards the stop against the action of the throttle over-riding means to provide a fast idle setting for the throttle.

5. A clutch control mechanism as claimed in any preceding claim in which the power means for operating the clutch comprises a servo controlled by both said first and second control means, and a clutch operating mechanism actuated by the servo.

6. A clutch control mechanism as claimed in claim 5 in which the servo is a vacuum servo.

7. A clutch control mechanism as claimed in claim 5 or claim 6 in which the servo is connected to the clutch through a hydraulic system including a master cylinder operated by the servo and a slave cylinder for operating the clutch.

8. A motor vehicle clutch control mechanism substantially as described with reference to and as illustrated by the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. provided in which gear selection is automatically controlled in which case the switch associated with the gear lever knob in the arrangement described above forms part of the control system for automatic gear slection for the gear box. Many modifications may be made to the above described embodiment without departing from the scope of the invention. For example, the diaphragm type servo unit 16 could be replaced by a servo unit incorporating a bellows capsule or a piston and cylinder. Also the direct mechanical link between the servo unit and clutch could be replaced by a hydraulic system comprising a master cylinder operated by the servo unit, a hydraulic fluid circuit and a slave cylinder connected to the clutch. The arrangement lends itself to any motor vehicle where automatic clutch operation is required including vehicles intended to be used by disabled drivers. WHAT WE CLAIM IS:

1. A motor vehicle clutch control mechanism comprising power means arranged to release a clutch when the power means is actuated, first control means to cause actuation of the power means while a gear selection mechanism is being operated and second control means to actuate the power means in response to a combination of the engine speed being below a predetermined level and the vehicle service brakes being in the applied condition, said first and second control means comprising electrical control systems to actuate said power means for operating said clutch, the first electrical control system comprising a switch operable in conjunction with operation of said gear selection mechanism to actuate said power means for operating said clutch, the second control system comprising means responsive to a vehicle brake light circuit and an engine speed below a predetermined level to actuate said power means to disengage said clutch when said brake light circuit is in operation and the vehicle speed is below said predetermined level, wherein the speed responsive means comprises means which generates a first electric signal in accordance with the actual engine speed, means to generate a reference signal of predetermined magnitude and a comparator to compare said signals and transmit a further signal to actuate said power means and disengage said clutch when the vehicle brake light circuit is energised and the engine speed is below said predetermined speed.