Clutch assembly with wear compensation adjustment

A clutch assembly and control having an automatic adjustment for friction lining wear and a lash control which essentially removes the forces on the clutch release bearing when the clutch is engaged. This is accomplished through a load sensitive releasable drive mechanism which provides the drive connection between the clutch pedal and the clutch cable during lash take-up in the system. The load sensitive releasable drive mechanism permits removal of forces on the clutch release bearing by allowing relative movement between the clutch pedal and the clutch cable if any forces are applied to the clutch release bearing while the clutch is engaged. During the lash take-up movement of the clutch, if the clutch release bearing forces are excessive, the load sensitive drive mechanism permits relative motion to lessen the bearing forces which are indicative of clutch wear.

This invention relates to clutch assemblies and more particularly to clutch 
assemblies having an automatic wear adjustment and lash control mechanism. 
It is an object of this invention to provide an improved clutch assembly 
wherein the forces on the clutch bearing are removed when the clutch is 
engaged. 
It is another object of this invention to provide an improved clutch 
assembly having a wear compensating mechanism and a lash control mechanism 
permitting the clutch assembly to be self-compensating for clutch plate 
wear and for controlling the clutch spring load on the clutch release 
bearing when the clutch is engaged.

Referring to the drawings wherein like characters represent the same or 
corresponding parts that are seen in FIG. 1, a clutch pedal 10 is 
rotatably supported on an axis 12 which is secured to the vehicle body. 
The clutch pedal 10 is resiliently drivingly connected to a gear segment 
14 through a torsion spring 16. The gear segment 14 is connected at 18 to 
one end of a control cable 20. The control cable 20 is a conventional type 
sheathed cable the other end 21 of which is connected to a lever 22, which 
lever 22 in turn is connected to a rock shaft 24 which operates a 
conventional manually controlled transmission input clutch generally 
designated 26. As is well known in conventional clutch arrangements, a 
release bearing, such as 28, is operated by the rock shaft 24 to control 
the spring load engaging the friction clutch between the engine and 
transmission. 
The cable 20 has the outer sheath 25 secured to the vehicle body at 30 and 
32 such that movement of end 18 results in movement of the lever 22 as 
long as the sheath remains stationary, as it is well-known in the art. The 
lever 22 is urged in the clutch engaging direction by a lash control 
tension spring 34, thus the end 21 of cable 20 connected thereto is also 
urged in the clutch engaging direction. The end 18 of cable 20 is urged in 
the clutch disengaging direction by the torsion spring 16 and the clutch 
pedal 10 is urged in the clutch engaging position by a tension spring 34 
which may be considered a clutch pedal return spring. 
FIG. 1a diagrammatically shows the conventional clutch arrangement 26 in 
which a flywheel 37 is secured to an engine crankshaft 39. A friction 
plate or clutch disc 41 is splined to a clutch output shaft 43 which in 
turn is connected to a transmission, not shown, in a conventional manner. 
The clutch 26 is engaged by a conventional Belleville-type apply spring 45 
acting through a pressure plate 47 driven by the flywheel 37 through a 
housing 49. The clutch 26 is disengaged through movement of the lever 22 
and rock shaft 24 which moves the fork 51, disposed in a groove 53 formed 
in release bearing 28, to the left to engage and more the fingers of apply 
spring 45 and remove the engaging force from the pressure plate 47. 
A wear compensating and lash take-up assembly 38 is rotatably mounted on 
the clutch pedal 10 and is best seen in FIG. 2. As can be seen in FIG. 2, 
the assembly 38 consists of a lash pawl or coupling member 40 and a 
compensating pawl or coupling member 42. Both coupling members 40, 42 are 
urged into engagement with the gear sector 14 by a torsion spring 44. In 
the clutch engaged position shown, the coupling 42 is held out of 
engagement with the gear sector 14 by a stop member 46 which is secured to 
the vehicle body. The clutch pedal 10 also contacts the stop member 46 in 
the engaged position shown in FIGS. 1 and 2. As shown in phantom lines in 
FIG. 2, when the clutch pedal is moved towards the disengaging position, 
the coupling 42 is removed from the stop member 46 such that the torsion 
spring 44 will enforce engagement between the gear sector 14 and the 
coupling 42. The coupling 40 is always urged into engagement with gear 
sector 14 by the torsion spring 44. 
As can be seen in FIG. 3, the clutch pedal 10 is mounted on a tube member 
48 which is rotatably supported on a bearing 50, which is mounted on a 
fastener 52 secured to a frame member 54 along axis 12. The gear sector 14 
is rotatably supported on the tube 48 and is drivingly connected to the 
clutch pedal 10 by the torsion spring 16. 
As shown in FIG. 1, the clutch pedal 10 and, therefore, the clutch 26 are 
biased to the engaged position by the return spring 34. The coupling 42 is 
engaged by the stop member 46 thereby placing the coupling 42 in a 
released position relative to the gear sector 14. The coupling 40 is 
locked into engagement with the gear segment 14 to prevent relative 
movement between the gear segment 14 and the clutch pedal 10 in a 
disengaging direction and to permit relative movement therebetween in the 
clutch engaging direction if the forces imposed on the cable 20 by spring 
34 and the clutch apply spring forces on release bearing 28 are greater 
than the forces imposed on cable 20 by the torsion spring 16. If these 
forces are balanced, there will be no relative motion. The system is 
designed such that any release bearing forces which are present create an 
unbalance in the system which requires the gear sector 14 to rotate 
counterclockwise, as viewed in FIG. 2, and the coupling 40 will ratchet on 
the gear segment 14 during this relative movement. During movement of the 
clutch pedal 10, through the angle A, only the coupling 40 engages the 
gear segment 14. During travel through angle B, both couplings 40 and 42 
engage the gear segment 14. Whenever coupling 40 alone is engaging the 
gear segment 14 relative movement in a counterclockwise direction by 
segment 14 will be permitted. This rotation of gear segment 14 relative to 
pedal 10 permits the clutch to compensate for any wear which has occurred 
during previous engaging and disengaging operations. When the clutch pedal 
10 is moved from the disengaged position to the engaged position through 
angle B, there is no relative motion between sector 14 and the pedal 10 
due to the engagement of coupling 42, and when the clutch pedal 10 is 
moved through the angle A, if the net spring forces are balanced, the gear 
sector 14 will continue to move with the clutch pedal 10 permitting the 
cable 20 to also move which will ensure some lash in the system and the 
alleviation of external forces on the clutch release bearing 28. 
When the clutch pedal 10 is moved in a disengaging direction through angle 
A, the engaged coupling 40 ensures that the pedal 10 and gear segment 14 
move as a unit to take up the lash and provide a light contact bearing 
force at a zero lash between the release bearing 28 and the clutch apply 
spring in clutch assembly 26, if the net force of torsion spring 16 and 
the force of spring 34 acting on the gear segment 14 are in proper 
balance. If wear has not occurred since the last clutch engagement, lash 
take-up will occur at the same release bearing position and segment 14 
will not move relative to coupling 40 and the clutch pedal 10. If there 
has been wear on the clutch friction plate since the last clutch 
engagement, the apply spring in clutch assembly 26 will have a greater 
travel and the release bearing force will be at a higher value than the 
net spring force for proper balance during the lash take-up movement 
through angle A to cause the release of coupling 40 and permit rotation of 
gear segment 14 in an engaging or wear compensating direction relative to 
clutch pedal 10 to re-establish the bearing force at the desired level. As 
has been previously stated, during this lash take-up and wear compensating 
movement, stop member 46 holds the coupling 42 disengaged from the gear 
segment 14. 
On further movement of clutch pedal 10 in the disengaging direction, the 
coupling 42 moves away from stop 46 and engages the gear segment 14 to 
move the gear segment 14, connecting cable 20, lever 22, rock shaft 24 and 
release bearing 28 as a unit with the clutch pedal 10 disengaging the 
clutch 26. 
When the clutch pedal 10 is returned in the engaging direction, the 
coupling 42 remains engaged with gear segment 14 so that the clutch pedal 
10 and gear segment 14 move as a unit through angle B. At the transition 
point, between angles A and B, stop 46 engages and releases the coupling 
42. 
If there has been sufficient wear so that there is an increase in the 
bearing force when the clutch pedal 10 reaches the transition point, the 
coupling 40 will be released from the gear segment 14 due to the excess 
load to permit relative movement of the gear segment until the desired 
balance of forces occurs, at which time compensation for the clutch wear 
has been made. Upon continued movement of clutch pedal 10 through angle A, 
the coupling 40 moves the gear segment 14 to provide lash between the 
apply spring in clutch assembly 26 and the release bearing 28. 
The embodiment shown in FIGS. 4 and 5 includes a clutch pedal 10 which is 
pivotally supported on a member 56 secured to the vehicle housing. A lever 
or link 58 is also rotatably supported on the member 56 and has one end 
thereof connected to the cable 20. The other end of link 58 is connected 
by a pin 60 to an adjustor strip 62 which extends between a pair of wear 
compensating rollers 64 and a pair of lash rollers 66 to a spring seat 68. 
The spring seat 68 supports a coil spring 70 which is compressed between 
spring seat 68 and a spring seat 72 which is biased by the spring 70 
against a cam housing 74, and in which cam housing 74 are disposed the 
rollers 64 and 66. As can be seen in FIG. 4, the cam housing 74 has 
sloping sides such that in the downward direction or clutch disengaging 
direction the rollers 66 are urged into engagement with the adjusting 
strip 62 and in the upward clutch engaging direction the rollers 64 are 
urged into engagement with the adjusting strip 62. The rollers 64 and 66 
are urged in a separating direction by a pair of coil springs 76. The cam 
housing 74 is secured to the clutch pedal 10 and has formed therein a slot 
78 through which extends an unloading lever 80 which is bifurcated at one 
end to pass by either side of the adjusting strip 62. The unloading lever 
80 extends outside of the cam housing 74 to be abutted by a stop member 82 
when the clutch is in the engaged position shown. The unloading member 80 
abuts the rollers 64 to prevent their engagement with the adjusting strip 
62. The stop member 82 is engaged when the clutch travels through the lash 
control angle A which is the same as that shown in FIG. 2. The unloading 
member 80 is out of abutment with the stop member 82 when the clutch pedal 
10 is moved through the clutch control angle B. When the clutch pedal 10 
is being moved through the clutch control angle B, the rollers 64 are 
forced into engagement with the adjusting strip 62 by the cam housing 74 
such that unitary motion between the clutch pedal 10, lever 58 and cable 
20 will occur. The cable 20 is, of course, connected to a conventional 
friction clutch assembly in a manner similar to that shown in FIG. 1. When 
the clutch pedal 10 is in engaged position under the bias of spring 34, 
the lash rollers 66 lock under the force of the adjustor spring 70 minus 
the force of the spring 34. At this time, there is lash between the clutch 
release bearing and the clutch apply spring. Initially depressing clutch 
pedal 10, there is no clutch release bearing force and then a low clutch 
release bearing force ensuring contact with the clutch apply spring 
occurs. The force in adjusting spring 70 is greater than and then equal to 
the sum of the force in spring 34 and the clutch release bearing force on 
the cable 20. Thus the lash rollers 66 remain locked to the cam housing 
74. The lash is taken up and the clutch release bearing force increases to 
a low value when contact with the clutch apply spring occurs. Upon further 
rotation of the clutch pedal 10, the wear compensating rollers 64 are 
moved away from the unloading member 80 and are locked to the adjustor 
strip 62 by the cam housing 74. Further movement of the clutch pedal 10 in 
the disengaging direction, transmits the load to cam housing 74 and the 
adjusting strip 62 to the cable 20 to provide clutch disengagement. 
When the clutch pedal 10 is moved to the engaged position, the unloading 
member 80 will engage the wear compensating rollers 64, when the clutch 
reaches the engaged position, that is after travel through angle B has 
occurred. This forces the wear compensator rollers 64 out of engagement 
with the cam housing 74 unlocking the adjustor strip 62 from the clutch 
pedal 10. The adjusting strip 62, link 58 and cable 20 are free to move in 
the engaging direction relative to the pedal if the load thereon is 
greater than the load on the adjusting spring 70. This condition will 
exist when the clutch disc has worn such that the clutch apply spring is 
engaging the clutch release bearing. The adjusting strip 62 will be moved 
relative to the pedal 10 since the lash control rollers 66 will permit 
movement in one direction, that is, toward clutch engagement. The wear 
adjustment occurs very quickly when the wear compensator rollers 64 engage 
the unloading member 80 so that, on continued movement of the clutch pedal 
10, the cable 20 continues to move providing a lash condition in the 
clutch release bearing. This is caused by the lock feature of the lash 
rollers 66 to the adjusting strip 62 when the correct force balance occurs 
between the springs 70 and 34. 
If no significant wear of the clutch friction material has occurred, the 
clutch apply spring height remains the same and the wear compensator 
rollers 64, lash rollers 66 and the spring forces maintain the same 
relative position between the clutch pedal 10 and link 58. Wear adjustment 
may normally occur during clutch engagement as described above but may 
also occur during clutch disengagement. 
Obviously, many modifications and variations are possible in light of the 
above teaching. It is, therefore, to be understood that within the scope 
of the appended claims the invention may be practiced otherwise and as 
specifically described.