192 clutches and power-stop control – Clutches – Axially engaging
Reexamination Certificate
1999-08-05
2001-02-27
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Axially engaging
C192S03000R, C192S111400
Reexamination Certificate
active
06193039
ABSTRACT:
The present invention concerns a friction clutch, in particular for motor vehicles, and more particularly a clutch equipped with a device for taking up wear of the friction linings in particular, referred to hereinafter as the wear take-up device.
A conventional friction clutch generally includes a reaction plate, which may be in two parts to form a damper flywheel or a flexible flywheel, constrained to rotate with a first shaft, usually a driving shaft such as the crankshaft of the internal combustion engine, its outside periphery supporting a cover to which at least one pressure plate is attached.
The pressure plate is constrained to rotate with the cover and the reaction plate but can be moved axially by axially acting clutch engaging spring means operated by clutch release means; the clutch engaging means can be coil springs or one or two Belleville washers disposed in series or in parallel acted on by clutch release levers forming the clutch release means; the clutch engaging and clutch releasing means generally form part of the same component, for example a metal diaphragm bearing on the cover; the diaphragm can be disposed in series or in parallel with a Belleville washer to assist the clutch release force, as described in document FR-A-2 753 758, for example.
A friction disk carrying friction linings at its outside periphery and constrained to rotate with a shaft, usually a driven shaft such as the input shaft of the gearbox, is disposed between the pressure plate and the reaction plate and is gripped between them when the clutch is engaged. The clutch engaging means cause axial displacement of the pressure plate when they are operated by a clutch release thrust bearing through the intermediary of the clutch release means.
During the service life of a clutch of the above kind the friction linings and the materials against which they bear (pressure plate and reaction plate) wear, which varies the position of the pressure plate and those of the axially acting clutch engaging means and the clutch release thrust bearing; this varies the force with which the friction disk is clamped between the pressure and reaction plates because the working conditions of the clutch release means are modified and it also affects the force needed to release the clutch. Providing a clutch of the above kind with a wear take-up device eliminates these drawbacks, the clutch engaging means and the clutch release thrust bearing, usually bearing at all times against the clutch release means, occupying the same position when the clutch is engaged.
A friction clutch equipped with a wear take-up device is adapted so that one of the supports of the clutch engaging means, whether this is the support joined directly or indirectly to the cover or the support joined directly or indirectly to the pressure plate, can be offset axially, compensator means being provided to bring about this offsetting, in association with actuator means for actuating said compensator means and trigger means selectively authorizing operation of the actuator means. A wear take-up device is controlled by detector means responsive to wear of the linings, directly or indirectly, for example responsive to the position of at least one of the components of the clutch affected by such wear, said detector means operating on said compensator means, said actuator means or said trigger means.
Various types of wear take-up device are known per se.
For example, document FR-A-2 753 503 describes a clutch in which the wear take-up device includes ramp means disposed circumferentially, constituting the compensator means, disposed axially between the offsettable support and the pressure plate and adapted to be rotated by teeth at their periphery which cooperate with a tangential lead screw, means for rotating the lead screw being rendered operational by wear of the friction linings, and non-return means preventing the lead screw turning in the direction opposite to that in which it is rotated by the rotation drive means, when operational, the lead screw, the non-return means and the rotation drive means of the lead screw being carried by a support attached to the cover and the axially acting clutch engaging spring means comprising a diaphragm. The lead screw rotation drive means are actuated by the diaphragm; the ramp means comprise a ring including the offsettable support of the diaphragm and circumferentially distributed inclined ramps and the pressure plate has studs or ramps adapted to cooperate with the ramps of the ramp means; the lead screw is adapted to be slid along its axis by take-up spring means constituting the actuator means and when it is displaced along its axis it drives circumferential rotation of said ramp means. The lead screw rotation drive means comprise a ratchet wheel attached to the lead screw and the non-return means comprise a pawl that cooperates with the ratchet wheel. Here the detector means comprise a tongue operated by the diaphragm and adapted to cooperate with the ratchet wheel, its travel increasing with the wear until, when the clutch is engaged, it can push a tooth of the ratchet wheel and turn the screw, compressing the take-up spring means; the trigger means are represented by a reduction of the load on the supporting bead, on releasing the clutch, the take-up spring means allowing the inclined ramps to move and therefore axial offsetting of the plate support when its spring force is sufficient to overcome the friction forces.
Accordingly the detector means, here the tongue operated by the diaphragm, operate via the ratchet wheel on the actuator means, here the take-up spring means, producing an actuation force: triggering occurs on a subsequent clutch release operation.
In document GB-A-2 294 983 the clutch engaging means comprise a diaphragm and the support that can be offset is also the plate support; the take-up means again comprise ramps; the actuator means comprise a spring operative at all times between ramps and counter-ramps in the direction of increasing axial thickness; again triggering is effected during the clutch release operation by a reduction in the load on the support bead while the pressure plate moves, according to the wear, relative to a pin bearing on the reaction plate, said pin passing with friction through the pressure plate and constituting the detector means. The pin carries an abutment in the form of a lever cooperating with the ramp means; the detector means therefore operate on the compensator means.
In document GB-A-2 294 301 the clutch engaging means also comprise a diaphragm, the compensator means comprise ramps and the actuator means comprise a spring operative at all times between the ramps and the cover; the support that can be offset is the primary support carried by the cover; the clutch is of the push type and triggering is obtained by sinking of the secondary support, facing the primary support on the pressure plate side, and mounted elastically, the maximal clutch release load increasing with the wear, this constituting the detector means which, through sinking, constitute the triggering means. The detector means therefore operate on the triggering means, a clearance appearing between the primary and secondary supports as the secondary support sinks, said clearance being compensated by movement of the primary support by actuator means.
In the
FIG. 10
embodiment of document U.S. Pat. No. 5,564,541 the detector means comprise a pin disposed with clearance between the cover and the reaction plate and passing with friction through the pressure plate, the force needed to move the pin relative to the pressure plate being greater than the pressure plate return force, here produced by tangential tongues; the actuator means comprise a spring operative at all times between the pressure plate and the ramps that constitute the take-up means; it is the plate support that can be offset, the clutch device being of the pull type. Here the clutch release travel varies: the completely released position is fixed so that triggering occurs at the end of the clutch release operation, a
Despres Dominique
Doremus Oliver
Travers Jean-Luc
Bonck Rodney H.
Liniak Berenato Longacre & White
Valeo
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