The present invention relates to a self-adjusting clutch actuator for wear compensation in clutches.

Clutches, in particular vehicle clutches which are configured as friction clutches, establish a torque-proof connection between an input shaft, which is connected, for example, to an engine, and an output shaft, which is guided, for example, into a transmission, by means of a frictionally locking connection which takes place by way of contact of friction faces, in order to transmit a torque between the two shafts via said torque-proof connection.

In order to establish the frictionally locking connection, for example, the friction faces of the clutch are loaded with a spring-based pressing force which is strong enough that the required torque can be transmitted via said frictionally locking connection. In order to release the frictionally locking connection of the clutch and, as a result, to decouple the two shafts from one another, a force is introduced into the clutch by means of a clutch actuator, which force counteracts the pressing force of the clutch and overcomes said force, with the result that the frictionally locking connection is released.

During operation of the clutch, without a sufficient frictionally locking connection, relative movements between the friction faces which are in contact here at the same time can occur, which leads to abrasion of the friction faces arising. Said increasing abrasion brings about the production of wear in the clutch, which wear becomes correspondingly greater as the operating time of the clutch increases.

In order to counteract said problem, clutch actuators with an automatic length compensation means are known, which length compensation means is configured to automatically displace a transmission element, which applies the force to the clutch, with respect to a second element, which experiences an introduced actuating force, in order thus to compensate for the wear. Here, the length compensation means is released only when no actuating force is applied. If said actuating force is applied, the length compensation means is locked, as a result of which the transmission element and the second element, for example, are blocked, and the actuating force can be applied to the clutch.

Here, the locking action is brought about by way of the frictionally locking contact of two elements which otherwise perform a relative movement on account of the relative displacement of the actuating element.

Clutch actuators of this type have the disadvantage that, in order to achieve a sufficient locking action, they require great areas on the corresponding elements for the frictionally locking contact. As an alternative or in addition, great spacings of the rubbing faces from a rotational axis are also required. This results in a relatively great extent of the elements and therefore of the clutch actuator in a direction which can bring about problems with regard to the required installation space.

It is therefore an object of the present invention to provide a self-adjusting clutch actuator which has the above-described functionality without the associated problems.

Said object is achieved by way of the subject matter of the independent patent claim. Advantageous developments are the subject matter of the subclaims.

According to the invention, a self-adjusting clutch actuator for actuating a clutch is provided, with:a transmission element which is provided such that it can be displaced in a displacement direction;a compensation mechanism, with a piston which is provided such that it can be displaced in the displacement direction of the transmission element,the compensation mechanism being configured to enable a relative displacement of the transmission element in the displacement direction with respect to the piston if no actuating force is introduced into the clutch actuator, and to block the relative displacement in the displacement direction if an actuating force is introduced into the clutch actuator, by a friction element being brought into contact in a frictionally locking manner with a mating element,the friction element being configured to carry out a relative movement with respect to the mating element if the relative displacement is not blocked by way of the compensation mechanism, anda transmission mechanism being provided between the transmission element and the piston, which transmission mechanism is configured to bring about the relative movement by way of the relative displacement in the displacement direction of the transmission element with respect to the mating element, andthe friction element having a fixed connection to the transmission element in the direction of the relative movement.

The friction element is preferably provided such that it can be displaced, particularly preferably such that it can be displaced in the displacement direction, in order to be brought into contact with the mating element.

The piston is preferably configured in the form of a basket. The piston is particularly preferably configured about at least one axis as a rotationally symmetrical body.

The transmission element is preferably configured as a piston rod. The displacement direction is particularly preferably configured substantially parallel to an axis of the piston rod.

Here, the relative displacement of the transmission element with respect to the piston is oriented substantially parallel to the displacement direction of the transmission element, with the result that the transmission element and the piston are configured to preferably move along said displacement direction.

The transmission element, which is configured, in particular, as a piston rod, and the piston are particularly preferably arranged coaxially, further, non-coaxial designs also being conceivable.

Here, the relative movement of the friction element with respect to the mating element is preferably configured as a rotational movement which particularly preferably takes place about the axis of the transmission element. Rectilinear movements or movements with a rectilinear and rotational component are also possible in further embodiments, however.

The compensation mechanism is preferably configured to bring at least one face of the friction element into contact with the mating element directly and/or via intermediate elements.

The contact between the friction element and the mating element or further friction elements preferably takes place here via a part of the at least one face of the friction element, which face is denoted in the further text as a locking face.

Said locking face is preferably of special configuration for improving a frictionally locking contact, for example by way of the application of special friction linings which have a higher coefficient of friction than the material of the friction elements. Suitable configurations for this purpose are known to a person skilled in the art from the prior art.

The mating element also preferably has a comparable locking face.

The mating element is preferably the piston. This can advantageously achieve a situation where a separate component is saved, and a direct frictionally locking connection can be established between the piston and the friction element and therefore between the piston and the transmission element in the direction of the relative movement.

The piston is preferably configured as a basket, the friction element particularly preferably being arranged within the basket. There is therefore the possibility for the compensation mechanism to be configured within the piston.

The clutch actuator or the compensation mechanism is preferably configured in such a way that the relative movement of the friction element with respect to the mating element is at most as large as, preferably smaller than, the relative displacement in the displacement direction of the transmission element with respect to the piston.

In the case of a rectilinear relative movement, this means that the relative displacement X of the transmission element with respect to the piston brings about a relative movement Y of the friction element with respect to the mating element, the magnitude of which relative movement Y is likewise at most as great as that of the relative displacement X.

If, in contrast, the relative movement Y is a rotational movement or a movement at least with a rotational component, a reference point on the friction element or the mating element is to be selected, the travel through which said reference point passes then being considered as a relative movement Y.

In the case of a purely rotational movement, a point can preferably be selected which is situated on an effective diameter of the locking face.

An effective diameter is to be understood to mean the diameter, on which all the individual friction forces of the locking face would act in a concentrated manner, in order to achieve said locking action.

As an alternative, any desired point on the friction element, preferably on the external diameter or the circumference, can also be selected.

Here, the configuration of the friction element and/or the mating element as a body which is rotationally symmetrical about at least one axis, preferably the rotational axis, is not absolutely necessary.

A relative movement Y can then be calculated in accordance with the circular segment passed through by the selected point.

The following applies in every case:
Yfriction element−mating element≤Xtransmission element−piston

Regardless of whether there is a translational or rotational relative movement, it is preferred that the relative displacement X and the relative movement Y correspond in terms of their magnitudes, that is to say are of equal magnitude:
Yfriction element−mating element=Xtransmission element−piston

The clutch actuator, in particular the compensation mechanism, preferably has an activation element. The latter preferably has a clamping element which is configured to bring the friction element into a frictionally locking connection with the mating element and/or with further elements.

Here, the clamping element is preferably configured as a floating piston.

The activation element, particularly preferably the clamping element, is preferably configured to establish the contact between the friction element and the mating element if an actuating force is introduced into the clutch actuator.

The activation element, particularly preferably the clamping element, is preferably provided such that it can be displaced, and is provided on or in the piston. The activation element, particularly preferably the clamping element, particularly preferably has an end position relative to the piston, particularly preferably an end stop position.

Here, the activation element, in particular the floating piston, can be displaced in the piston preferably in the displacement direction of the transmission element. In the case of a displacement in said direction, the activation element is preferably configured to bring the at least one friction element and the mating element into contact.

In one preferred embodiment, at least one friction element which is connected to the transmission element is brought into contact in this way by way of at least one face with the mating element and by way of at least one further face with the activation element, in particular with the clamping element, as the result of which a frictionally locking connection is produced on at least two faces of the friction element. As a result, a locking action of the compensation mechanism can be realized in an effective way in a comparatively small installation space.

The transmission mechanism between the transmission element and the piston preferably has a thread, in particular a transmission thread, the transmission element and the piston being in contact with one another via the thread.

In this way, a relative displacement of the transmission element with respect to the piston can be converted into a rotational movement. The friction element which is connected to the transmission element fixedly in the direction of the relative movement therefore rotates with the transmission element relative to the piston and therefore the mating element. Therefore, a relative movement of the friction element with respect to the mating element can be achieved.

The clutch actuator, in particular the compensation mechanism, preferably has at least one friction element which is connected to the piston fixedly in the direction of the relative movement and which is configured to be brought into contact with at least one friction element which is connected to the transmission element fixedly in the direction of the relative movement. The friction element which is connected to the piston fixedly in the direction of the relative movement is preferably provided such that it can be displaced, particularly preferably such that it can be displaced in the direction of the relative displacement.

The clutch actuator preferably has at least one further friction element which is connected to the transmission element fixedly in the direction of the relative movement and is configured to be brought into contact with at least one friction element which is connected to the piston fixedly in the direction of the relative movement, and/or with the mating element. Said at least one further friction element is preferably provided such that it can be displaced, particularly preferably such that it can be displaced in the direction of the relative displacement.

The friction elements which are provided in the piston and/or on the transmission element preferably have at least one locking face which is configured as described above.

The activation element, particularly preferably the clamping element, preferably has at least one locking face which is configured as described above.

Therefore, by way of the provision of further friction elements which are preferably arranged in an alternating manner along the axis of the transmission element, the number of locking faces which can be brought into contact can be increased, as a result of which the resulting friction force is increased per locking face contact. As a result, the locking action of the compensation mechanism is increased.

The friction elements are preferably arranged in an alternating manner in the displacement direction, and/or the friction elements are preferably flanked by the piston, particularly preferably by the mating element, and the activation element, in particular the clamping element.

As a result of the flanking of the friction elements by way of the piston and the activation element, all the friction elements can be connected to the piston and/or the mating element and the clamping element in a frictionally locking manner, in particular in the direction of the relative movement.

The clutch actuator preferably has at least one spring element, in particular a spiral spring, which is preferably configured, if no actuating force is introduced into the clutch actuator, to load the transmission element with a force counter to the force of a diaphragm spring of the clutch.

The spring element is preferably supported directly or via intermediate elements between the transmission element and the piston.

The spring element can thus advantageously be used to counteract the force of the diaphragm spring of the clutch and to prestress the compensation mechanism if it is not blocked, with the result that, in the case of application of an actuating force, an immediate introduction of the actuating force into the clutch can take place.

A spring element is preferably provided which is configured to load the activation element, in particular the clamping element, with a force which loads the activation element, in particular the clamping element, away from the at least one friction element.

The spring element is preferably configured as a cup or spiral spring, and/or as an elastic ring element, preferably with a hollow profile, particularly preferably with a rectangular profile, which is particularly preferably supported within the piston.

This can advantageously achieve a situation where the activation element, in particular the clamping element, if no actuating force is applied, is spaced apart from the at least one friction element and is transferred into an end position, preferably into an end stop position. As a result, the compensation mechanism is not blocked, and the length compensation of the transmission element can take place.

The activation element, in particular the clamping element, is preferably configured such that it can be loaded with an actuating force, or, in addition to the activation element, the piston is configured such that it can be loaded with the actuating force. Here, the activation element and/or the piston form/forms elements which are configured for the introduction of an actuating force.

The actuating force can preferably be applied mechanically and/or pneumatically and/or hydraulically and/or electrically and/or magnetically.

The clutch actuator which is described in this manner can be loaded in this way with an actuating force in various ways, which allows the clutch actuator to be provided in different systems, in particular in different drive systems.

The clutch actuator preferably has a housing which, with the piston, configures a pressure space which is configured to be connected to a pressure source, in order to apply the actuating force to the activation element, in particular the clamping element, or to the piston and the activation element, in particular the clamping element.

In this preferred embodiment, a hydraulic or pneumatic actuation of the clutch actuator can be realized in this way, as a result of which the attachment of the clutch actuator to further elements, such as, for example, a pressure control valve or a pressure accumulator, can take place in a relatively flexible manner on account of bendable pressure lines.

A stop is preferably provided in the housing, against which stop the piston can be brought to bear in its end stop position.

The piston is preferably received in the housing such that it can be displaced in the displacement direction.

Furthermore, it is to be noted that a piston and a piston rod are always used for the release of the clutch in the embodiments which have been described up to now. Here, the term “piston” is not to be interpreted narrowly. A person skilled in the art usually understands a piston to be an element from mechanical engineering which is preferably configured such that it can be displaced in a housing in one direction, the piston and the housing configuring a pressure space which can be loaded with a pressure force by means of a pressure medium which is situated in said pressure space or introduced into said pressure space. The piston is moved by means of the pressure force, generally in a manner guided by the housing. The term “piston” is to be interpreted more broadly in the case of the present invention, however. This is generally an element which is configured for absorbing an actuating force, in order to transmit said actuating force to the piston rod. The absorbing of the actuating force can preferably take place here by way of pressurization, but also by means of other possibilities, as described further above. Said actuating force can be applied to the piston directly or via intermediate elements. Accordingly, an element of this type can therefore be configured, in particular, as a disk or merely as a projection, to which the actuating force can be transmitted. As a consequence, the piston rod is also generally to be considered as a rod or bar with an axis. Here, the piston rod is provided such that it can be displaced along its axis.

