GB2254121A - Clutch actuating mechanism - Google Patents

Abstract

A transverse clutch-actuating shaft 24 has a helical portion 28 of a pro-load spring 27 encircling it, the pro-load spring 27 being operatively connected by a first limb 29 to a forked lever 25 used to connect the actuating shaft 24 to a release bearing 22. A second limb 30 of the spring 27 reacts against an end face of a gearbox 23 and provides a stop in the form of a U-shaped end portion 31 which prevents the spring 27 acting on the lever 24 beyond a certain position. The limb 29 may be hooked to the lever 25 at 32 or may engage a hole therein (Fig. 3). <IMAGE>

Description

A TRANSMISSION FOR A MOTOR VEHICLE This invention relates to a transmission for a motor vehicle and in particular to a clutch release mechanism for a transmission.

It is known to provide a transmission having a gearbox, a friction clutch and a clutch release mechanism to disengage the clutch in which the clutch release mechanism has a clutch release bearing slidingly located on a hollow tube through which extends an input shaft of the gearbox to be driven, the clutch release bearing being movable along the axis of said input shaft to selectively engage or disengage the drive from the clutch to said input shaft by means of the action thereon of a pair of spaced apart arms attached to an actuation shaft extending transversely to the axis of the input shaft, the actuation snaft being adapted at one end for connection to driver responsive actuation means such as a cable linkage.

In such a prior art transmission rotation of the actuation shaft in one direction will cause the clutch release bearing to be urged towards the clutch and rotation of the actuation shaft in the opposite direction will allow the clutch release bearing to move away from the clutch.

It is usual to provide as part of the cable linkage a spring to provide a small preload to said release bearing to maintain it in contact with the clutch to prevent excessive travel in the clutch release mechanism and to reduce wear within the release bearing and between the clutch release bearing and the clutch.

Such pre-load means have the disadvantage that if the clutch needs to be replaced there is a risk of the clutch release bearing being dislodged from the hollow tube unless the cable linkage is disconnected which is time consuming.

It is an object of this invention to overcome the disadvantage of the prior art.

According to the invention there is provided a transmission for a motor vehicle of the type having a gearbox, a friction clutch arranged between the gearbox and a source of motive power to provide a selectable coupling therebetween and a clutch release mechanism to selectively disengage the friction clutch in response to an input from an operator responsive actuation means, the clutch release mechanism comprising a clutch release bearing movable from a first position to a second position along a first axis towards said friction clutch to disengage said friction clutch and movable from the second position to the first position to engage said friction clutch, an actuating shaft rotatable about a second axis arranged substantially perpendicular to the first axis and adapted at one end for connection to said operator responsive actuation means and connecting means to provide an operable connection between the actuating shaft and the release bearing wherein a spring acting on the connecting means is provided to bias the release bearing towards the friction clutch only when the release bearing is at or near said first position. Preferably, said spring has a helical portion encircling the actuating shaft, a first limb extending away from the helical portion to a position where it is operably connected to said connecting means and a second limb extending away from the helical portion for reaction against an abutment.

Advantageously, the second limb extends from the abutment to provide a stop means for the first limb allowing the application of a biasing force from the first limb to the connecting means only when the release bearing is at or near said first position.

The stop means may be a U-shaped portion at the end of the second limb which is hooked around the first limb.

The connecting means may be a forked lever fixed to the actuating shaft.

The first limb may be bent over near its free end to form a hook used to operatively connect it to the lever.

Alternatively, the first limb may be bent over for engagement with an aperture in the lever to provide said operable connection.

The abutment may be an end face of a gearbox casing.

The invention will now be described by way of example with reference to the accompanying drawing of which: Figure 1 is a schematic drawing of a known clutched transmission including a transverse shaft clutch release mechanism; Figure 2 is a pictorial representation of a transmission according to the invention showing in particular a clutch release mechanism; Figure 3 is a scrap view showing a first modification to the clutch release mechanism shown in Figure 2.

With reference to Figure 1 there is shown an engine 12, a gearbox 13 and a casing 6 joining the engine 12 to the gearbox 13.

A flywheel 7 of the engine 12 has a diaphragm spring clutch 8 mounted thereon to provide a selectable driving connection between a source of motive power in the form of the engine 12 and the gearbox 13.

A release bearing 11 is slidably mounted on a tubular extension of the gearbox 13.

An input shaft (not shown) of the gearbox 13 extends through the tubular extension of the gearbox 13 for engagement with a driven plate of the clutch 8.

The clutch 8 has in addition to the driven plate a pressure plate and a diaphragm spring. The driven plate is positioned between the flywheel and the pressure plate. The pressure plate is urged towards the flywheel by the normal action of the diaphragm spring thus clamping the driven plate to the flywheel to provide a drive from the flywheel to the input shaft of the gearbox.

The diaphragm spring has a plurality of radially inwardly directed fingers which if deflected in the direction of the flywheel by the action of the release bearing 11 cause the clamping load to be reduced thereby disengaging the clutch and allowing relative rotation of the flywheel 7 with respect to the input shaft.

The clutch release bearing 11 is axially movable by means of a forked lever in the form of two spaced apart arms 15 attached to an actuating shaft 14.

The actuating shaft 14 is rotatably supported at each end by the casing 6 and extends along an axis substantially perpendicular to the longitundinal axis of the input shaft for the gearbox 13.

A lever 9 is fixed to one end of the actuating shaft 14 to provide a connection to a driver responsive actuation means in the form of a cable 3 and pedal 5. The foot pedal 5 being attached to a part of the bodywork 2 of the motor vehicle to which the engine 12 and gearbox 13 are fitted.

A spring 4 is provided to ensure that the release bearing 11 is kept in contact with the fingers of the diaphragm spring of the clutch 8.

With no load applied to the pedal 5 the full clamping effect of the diaphragm spring minus the bearing pre-load is supplied and the flywheel 7 and input shaft will rotate at the same speed thereby transmitting drive from the engine 12 to the gearbox 13.

When the pedal 5 is urged in the direction of arrow 'r' by the application of a load by an operator of the vehicle this causes the lever 9 to be moved in the direction of arrow 'c' causing anti-clockwise rotation of the actuating shaft 14 which is transferred by the arms 15 to the release bearing 11 urging it from a first position towards the flywheel 7. Such movement against the action of the diaphragm spring will reduce the clamping load thus exerted until at a second position the flywheel 7 becomes disengaged from the input shaft of the gearbox and no drive is transmitted from the engine 12 to the gearbox 13.

With reference to Figure 2 the transmission is substantially as hereinbefore described.

Figure 2 shows an actuating shaft 24, a release bearing 22, an input shaft 20 to a gearbox 23 forming part of a transmission of a motor vehicle, a hollow extension 21 to the gearbox 23, a forked lever in the form of a pair of arms 25 connected to the actuating shaft 24 to operatively connect the shaft 24 to the release bearing 22 and a pre-load means in the form of a spring 27.

The actuating shaft 24 extends along a second axis substantially perpendicular to a longitudinal or first axis of a gearbox input shaft 20 and is adapted at one end for connection to operator responsive actuation means (not shown).

The input shaft 20 extends through the hollow extension 21 and has a splined portion 26 near one end for engagement with a driven plate of a clutch (not shown) to be actuated.

The spring 27 has a helical portion 28 wrapped around the actuating shaft 24 and first and second limbs 29 and 30 extending from said helical portion 28.

The first limb 29 extends away from the helical portion 28 and is operatively connected at its free end to one of the arms 25 by being bent over near its free end to form a hook 32 which is hooked onto the said arm 25.

The second limb 30 extends away from the helical portion 28 to abut an end face of the gearbox 23 at a position 'X'. The second limb 30 extends from the abutment at position 'X' towards the first limb 29 and has a U-shaped end portion 31 hooked around the first limb 29 at position substantially midway along the first limb 29 to form a stop.

With the clutch removed as is shown in Figure 2 the release bearing 22 is moved away from a first position until the biasing force of the first limb 29 is reacted against the second limb 30 by the contact of the first limb 29 with the U-shaped end portion 31.

In such a situation no load can be applied by the first limb 29 to the arm 25 urging the release bearing 22 towards the end of the input shaft 20.

The length of the second limb 30 between the U-shaped portion 31 and the position 'X' being subjected to a bendina moment and the portion of the second limb 30 between position 'X' and its juncture with the helical portion 28 being subjected to a torsional moment.

When the clutch is assembled on to the input shaft 20 the release bearing 22 is pushed back towards the gearbox 23 to the first position by contact with the diaphragm spring of the clutch.

In this first position the first limb 29 is no longer in contact with the U-shaped end portion 31 but is free to react through the hook 32 against the arm 25 causing it to bias the release bearing 22 towards the clutch.

As the clutch wears there is a tendency for the diaphragm spring to move the first position of the release bearing 22 further towards the gearbox 23 with no release load being applied to the actuating shaft 24.

This movement causes an increase in the load applied by the first limb 29 due to the greater deflection of the first limb 29.

However, as the clutch wears there is also an increase in the force needed to release the clutch and so this increase in pre-load partially compensates for this increase in release force.

Operation of the clutch release mechanism is as described with reference to Figure 1 namely rotation of the actuating shaft 24 will cause the release bearing 22 to be moved from the first position along the hollow extension 21 by the action of the arms 25 on the release bearing 22 towards a second position in which the clutch is disengaged. During this movement the load of the spring 27 is applied to the arm 25 until the first limb 29 abuts the end portion 31.

After this initial movement from the first position the only force applied to the release bearing is the actual force from the actuating shaft 24 transferred via the arms 25 in response to an operator input to the actuating shaft 24.

With reference to Figure 3 there is shown a first modification to the invention. In this modification one of the arms 25a has an aperture 39 formed in it into which is located a bent over end 38 of the first limb to provide said operable connection with the arm 25a.

Apart from this modification the clutch release mechanism is as hereinbefore described.

It will be appreciated that if the stop means provided by the U-shaped portion of the second limb were not present the displacement from the first position over which a pre-load could be supplied by the spring to the release bearing is still limited but is not so accurately controlled.

Claims (10)

1. A transmission for a motor vehicle of the type having a gearbox, a friction clutch arranged between the gearbox and a source of motive power to provide a selectable coupling therebetween and a clutch release mechanism to selectively disengage the friction clutch in response to an input from an operator responsive actuation means, the clutch release mechanism comprising a clutch release bearing movable from a first position to a second position along a first axis towards said friction clutch to disengage said friction clutch and movable from the second position to the first position to engage said friction clutch, an actuating shaft rotatable about a second axis arranged substantially perpendicular to the first axis and adapted at one end for connection to said operator responsive actuation means and connecting means to provide an operable connection between the actuating shaft and the release bearing wherein a spring acting on the connecting means is provided to bias the release bearing towards the friction clutch only when the release bearing is at or near said first position.

2. A transmission as Claimed in Claim 1 in which said spring has a helical portion encircling the actuating shaft, a first limb extending away from the helical portion to a position where it is operably connected to said connecting means and a second limb extending away from the helical portion for reaction against an abutment.

3. A transmission as claimed in claim 2 in which the second limb extends from the abutment to provide a stop means for the first limb allowing the application of a biasing force from the first limb to the connecting means only when the release bearing is at or near said first position.

4. A transmission as claimed in claim 3 in which said stop means is a U-shaped portion at the end of the second limb which is hooked around the first limb.

5. A transmission as claimed in any preceding claim in which the connecting means is a forked lever fixed to the actuating shaft.

6. A transmission as claimed in Claim 5 in which the first limb is bent over near its free end to form a hook used to operatively connect it to the lever.

7. A clutch release mechanism as claimed in claim 5 in which the first limb is bent over near its free end for engagement with an aperture in the lever to provide said operable connection.

8. A clutch release mechanism as claimed in any preceding claim in which the release bearing is slidably supported by a hollow tubular extension connected to an end face of a gearbox casing forming part of the transmission.

9. A clutch release mechanism as claimed in any preceding claim in which said abutment is an end face of a gearbox casing forming part of the transmission.

10. A transmission for a motor vehicle substantially as described herein with reference to the accompanying drawing.