1. Field of the Invention
The present invention is directed to a thrust plate assembly, especially for a motor vehicle friction clutch with automatic wear compensation. Such an assembly comprises a housing which can be fixed or is fixed to a flywheel for joint rotation about an axis of rotation. A pressure plate is arranged in the housing so as to be fixed with respect to rotation relative to it and axially displaceable relative to it. An energy accumulator, preferably a diaphragm spring, is supported at the housing on one side and is supported at the pressure plate on the other side and presses the pressure plate in the direction of a side of the housing provided for connection with the flywheel. A wear adjustment device is arranged in the support path of the energy accumulator between the energy accumulator and a component of the housing and pressure plate. The wear adjustment device has at least one adjustment element which is displaceable for purposes of wear adjustment and is pretensioned in a wear adjusting direction. At least one play sensor arrangement for detecting wear in friction facings or friction linings of a clutch disk can be clamped or is clamped between the pressure plate and the flywheel. The play sensor arrangement comprises: a locking/detection element which is arranged on one component and which is pretensioned against the wear adjustment device with a locking portion and acts upon this wear adjustment device in order to prevent a movement of the at least one wear adjustment element in the wear adjusting direction and which interacts or can be made to interact by a detection portion with another component or assembly for detection of wear. The latter component or assembly is displaceable with respect to the first component when wear occurs. The locking/detection element can be brought into a position for releasing the at least one adjustment element for movement in the wear adjusting direction when wear occurs by means of the interaction with the other component or assembly.
2. Discussion of the Prior Art
A thrust plate arrangement constructed in the manner described above is known from the prior art, wherein the play sensor arrangement is constructed as follows: An axial through-opening is provided in the pressure plate and is penetrated by a pin-like detection portion of a play sensor. The pin-like detection portion is easily tiltable in the through-opening. A leaf spring element is fixedly arranged at one end of this pin-like detection portion, this end being situated at a distance from the flywheel, wherein the leaf spring element extends in the direction of the wear adjustment device so that the wear adjustment device is clamped between the pressure plate and the leaf spring element. Due to the support of the leaf spring element at the wear adjustment device, the pin-like detection portion is tilted in its through-opening due to the spring elasticity of the leaf spring element, and is accordingly pretensioned in a friction clamping fit. If wear occurs in friction linings of a clutch disk which are located between the pressure plate and flywheel, the pressure plate moves in the direction of the flywheel until the pin-like detection portion stands up at the flywheel. In so doing, this detection portion is displaced in its through-opening axially with respect to the pressure plate against the pretensioning action and friction clamping fit. This means that its end by which it is connected with the leaf spring element is pushed away from the pressure plate so that the pretensioning force by which the leaf spring element acts upon the wear adjustment device decreases. When the force of the diaphragm spring exerted on the wear adjustment device is reduced or released in a subsequent disengagement process, the at least one adjustment element can move in the wear adjusting direction accompanied by increasing tensioning of the leaf spring element until the pretensioning force by which the at least one wear adjustment element is pretensioned in the wear adjustment position and the force applied by the leaf spring element balance one another, and a further movement of the at least one wear adjustment element is blocked in the wear adjusting direction by the leaf spring. This means that in this arrangement, the play sensor formed of the pin-like detection portion and the leaf spring element is displaced to an increasing extent with respect to the pressure plate and there takes place a successive relaxing of the leaf spring element (when wear is detected) and tensioning of the leaf spring element (when wear is compensated).
In order to carry out wear compensation in an arrangement of this kind to an extent which exactly corresponds to the wear of the friction linings detected by the play sensor, the spring elasticity or spring constant of the leaf spring element must be provided in a highly precise manner. If the leaf spring element is somewhat too soft, there is a risk that overcompensation of wear can take place; if the leaf spring element is too stiff, there is a risk that the wear will not be sufficiently compensated and that the interaction of the different components cannot take place in the provided manner.