192 clutches and power-stop control – Clutches – Axially engaging
Reexamination Certificate
2000-04-19
2001-12-04
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Axially engaging
C192S111400
Reexamination Certificate
active
06325193
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of friction clutches, and more particularly to friction clutches having automatic adjustment mechanisms.
BACKGROUND OF THE INVENTION
Known friction clutches provide a releasable torsional connection between a motor vehicle engine flywheel and an associated transmission. Repeated clutch disengagement and engagement cycles wear the friction material of the clutch driven disc. The wear results in a change in the axial location of the pressure plate in the engaged position. The shift in axial location results in a progressive decrease of the clutch engagement force or clamping load. Clutches are commonly provided with adjustment mechanisms to compensate for such wear.
The clutch clamping load is generated by a spring acting directly or indirectly against the pressure plate and reacting directly or indirectly against the clutch cover.
One type of spring configuration commonly employed is a diaphragm spring having an annular portion with radially inwardly directed fingers extending from the annular portion. The radially innermost tips of the fingers engage a release assembly. The fingers bow with a movement of the tips to deflect the annular portion, and thereby release the clutch, when the release assembly is axially displaced.
As the friction material wears, the engaged position of the finger tips, and the release assembly, move closer to the flywheel. Adjustment mechanisms disposed between the cover and the levers or between the pressure plate and the diaphragm spring compensate for this change.
One type of known adjustment mechanism relies on the relative rotation of two annular cams, each having inclined cam surfaces in engagement with each other. The relative rotation of the cams compensates for wear of the friction material. The cams are biased to rotate in a direction that increases a combined height or thickness of the cams. A rotative biasing force is induced by a torsional biasing spring functionally disposed between the two cams. A number of different spring configurations can be employed in this capacity, including coil tension springs, torsional round wire springs, and torsional flat wire springs.
It is also known to provide adjustment limiting devices which prevent the cams from overadjusting when the release bearing is moved too far. One such device relies on the use of pins frictionally engaged with the pressure plate to limit cam adjustment. However, such a mechanism relies on establishing a precise frictional relationship between the pins and the pressure plate to provide the desired adjustment limitation without interfering with the operation of the clutch. Further, the frictionally retained pins contribute to a reduction in the clamping load transferred to the friction material by the pressure plate.
It is desired to provide a mechanism for limiting the relative rotation of the cams which does not rely on overcoming a frictional relationship between the pressure plate and pins disposed therein.
SUMMARY OF THE INVENTION
A friction clutch for a motor vehicle includes a cover, a pressure plate, a diaphragm spring, an adjustment mechanism, and an adjustment limiting mechanism. The cover has an axis of rotation. The pressure plate is coupled to the cover for rotation therewith about the axis, and has a frictional engagement surface substantially normal to the axis. The diaphragm spring is interposed between the cover and the pressure plate and biases the pressure plate toward an engaged pressure plate position. The adjustment mechanism is centered about the axis. The adjustment mechanism includes a first annular cam, a second annular cam, and a cam spring. The first annular cam is rotatably fixed with respect to the pressure plate and the cover. The second annular cam is rotatable relative to the first annular cam. Both the first and second annular cams each have a plurality of mutually engaged cam surfaces configured such that rotation of the second cam relative to the first cam in a first direction increases a height of the adjustment mechanism. The second annular cam also defines a cam lock engagement surface which extends radially inwardly of the cam surfaces, faces the pressure plate and is concentric with the axis. The cam spring is connected to the second annular cam and is connected to the first annular cam so as to induce relative rotation therebetween. The adjustment limiting mechanism includes a guide pin, a cam lock and a bias spring. The guide pin is fixed in the pressure plate and axially extends from the pressure plate on a side opposite the frictional engagement surface. The cam lock has a radially extending cam lock flange. The cam lock flange is axially disposed between the pressure plate and the cam lock engagement surface. The cam lock flange defines a flange engagement surface facing and complementary to the cam lock engagement surface. The cam lock has an aperture therein slidably receiving the guide pin. The bias spring engages the cam lock and biases the cam lock away from the pressure plate. When the clutch is in a released condition, the flange engagement surface is biased into engagement with the cam lock engagement surface by the bias spring with sufficient force to prevent rotation of the second cam relative to the first cam.
There is also an improvement in a friction clutch for a motor vehicle having a cover, a pressure plate, a diaphragm spring, and an adjustment mechanism. The cover has an axis of rotation. The pressure plate is coupled to the cover for rotation therewith about the axis and has a frictional engagement surface substantially normal to the axis. The diaphragm spring is interposed between the cover and the pressure plate and biases the pressure plate toward an engaged pressure plate position. The adjustment mechanism is centered about the axis. The adjustment mechanism includes a first annular cam, a second annular cam, and a cam spring. The first annular cam is rotatably fixed with respect to the pressure plate and the cover. The second annular cam is rotatable relative to the first annular cam. The first and second annular cams each have a plurality of mutually engaged cam surfaces configured such that rotation of the second cam relative to the first cam in a first direction increases a height of the adjustment mechanism. The cam spring is connected to the second annular cam and is connected to the first annular cam so as to induce relative rotation therebetween. The improvement includes the second annular cam having a cam lock engagement surface extending radially inwardly of the cam surfaces, facing the pressure plate and concentric with the axis. The improvement also includes a guide pin, a cam lock, and a bias spring. The guide pin is fixed in the pressure plate and axially extends from the pressure plate on a side opposite the frictional engagement surface. The cam lock has a radially extending cam lock flange. The cam lock flange is axially disposed between the pressure plate and the cam lock engagement surface. The cam lock flange defines a flange engagement surface facing and complementary to the cam lock engagement surface. The cam lock has an aperture therein slidably receiving the guide pin. The bias spring engages the cam lock and biases the cam lock away from the pressure plate. When the clutch is in a released condition, the flange engagement surface is biased into engagement with the cam lock engagement surface by the bias spring with sufficient force to prevent rotation of the second cam relative to the first cam.
The disclosed clutch provides a mechanism for limiting the relative rotation of the cams which does not rely on overcoming a frictional relationship between the pressure plate and pins disposed therein.
REFERENCES:
patent: 5069322 (1991-12-01), Mizukami et al.
patent: 5450934 (1995-09-01), Maucher
patent: 5632365 (1997-05-01), Maucher
patent: 5636721 (1997-06-01), Weidinger
patent: 5667049 (1997-09-01), Weidinger et al.
patent: 5690203 (1997-11-01), Link et al.
patent: 5695036 (1997-12-01), Gochenour et al.
patent: 5715920 (1998-02-01
Eaton Corporation
Hinman Kevin M.
Lorence Richard M.
Uthoff Jr. Loren H.
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