The invention relates to a clutch actuator, comprising a housing having a recess, a piston arranged in the recess and configured to move along an axis between an uncoupled position and a coupled position, when actuated by an actuation force, a clutch release bearing carrier, operatively coupled to the piston, a clutch release bearing mounted to the clutch release bearing carrier, wherein the clutch release bearing has a bearing ring configured to rotate in relation to the axis, wherein the bearing ring has a contact surface for being engaged by a clutch spring when the piston is actuated by the actuation force. In particular, the present invention relates to a concentric pneumatic clutch actuator with improvements in e.g., a fixation member.

Clutch actuators for the pneumatic actuation of the clutch are well-known in the prior art. They are used for the temporary separation of the internal combustion engine from the transmission of the driveline of a motor vehicle, when using a mechanical clutch.

With a clutch actuation system, the driver controls the power transmission by pressing or releasing the pedal.

In the motor vehicle, an input shaft of the gear box is connected to the engine, spinning at the same rotation speed. Further, an output shaft is operatively coupled to the gears and determining the rotation speed of the wheels. Based on the actuation on the foot pedal a fly wheel of a crank shaft of the motor vehicle is engaged or disengaged with the clutch or in particular a clutch pressure plate.

Clutches and in particular dry clutches are distinguished in push and pull systems. In a pull-type clutch, the action of pressing the pedal pulls the release bearing, pulling on a spring and disengaging the clutch. In a push-type clutch, the action of pressing the pedal pushes the release bearing, pushing on a spring and disengaging the clutch.

The clutch is connected to the crank shaft of the engine and to the input shaft of the gearbox. The release bearing is connected to the clutch actuator the clutch actuator is connected to the gearbox. In order to compensate for the tolerances between the crank shaft and the bearing, the possibility of a radial movement is required. This radial movement is needed for a push-type clutch as well as a pull-type clutch.

It was hence an object of the invention to provide a fixation of the clutch release bearing being coupled to the clutch and the clutch release bearing carrier that prevents an axial movement of the clutch release bearing and enables an elastic and in particular reversible radial movement.

As regards the clutch actuator, the object is achieved by the invention with a clutch actuator according to claim 1 . It is suggested that the actuator comprises a fixation member operatively coupled to the clutch release bearing carrier and the clutch release bearing, the fixation member being configured to prevent axial movement of the clutch release bearing and to enable a radial or rotational movement of the clutch release bearing relative to the axis. The operative coupling may advantageously be achieved by clamping, preferably with a predetermined clamping force. According to the invention, the clutch release bearing is secured in the axial direction preventing any axial movement of the clutch release bearing as well as the clutch, and to enable radial or rotational movement in order to compensate radial forces acting on the clutch, reasoned by tolerances between the crank shaft and the bearing. Further, the clutch release bearing is easy to dispose and/or connect to the clutch release bearing carrier, wherein the final fixation on the axial direction is provided by the fixation member providing at the same time a predefined radial or rotational movement of the bearing.

It will be understood, that the axis describes the symmetry axis of the cylindrical housing as well as the symmetry axis of the cylindrical piston and of the clutch bearing assembly. It will further be understood, that the deflection of the clutch release bearing resulting in a deflection of a symmetry axis of the clutch release bearing is insignificant with regard to the dimensions of the clutch actuator.

Preferably the cylindrical housing and the cylindrical piston are defining a gap between them, in particular a combustion chamber, configured to be pressurized in order to actuate the piston.

Preferably, the fixation member is at least partly elastic to tolerate a resilient radial or resilient rotational movement of the clutch release bearing. The embodiment advantageously recognizes that the at least partly elastic fixation member provides a high energy absorption and enables a radial or rotational movement at the same time. It will be understood that being at least partly elastic can be provided by a fixation member comprising different parts made of different materials as well as monolithic part providing special treated areas with an increased elasticity. Accordingly, a directional elasticity of the fixation member can be reached by such a treatment in order to prevent the axial movement of the clutch release bearing. It will also be understood that the fixation member according to this embodiment can be formed as a fully elastic part.

In a preferred embodiment, the fixation member is coupled between the clutch release bearing carrier and the clutch release bearing in a positive fit. The embodiment advantageously recognizes that by coupling the fixation member in the positive fit, the number of wear parts is reduced and the assembling is simplified. Furthermore, connecting via positive fit is in general more temperature resistant as for example a chemical bonding.

Preferably, the fixation member has a number of elastically deformable legs configured to engage the clutch release bearing carrier. Advantageously, the embodiment recognizes that a number of elastic legs provide a high elastic deformability solely through their geometry, enabling the use of wear resistant materials providing a comparatively low elastic deformability. The legs are preferably biased against the bearing ring and apply a load against the inner bearing ring such that a friction force occurs between the clutch release bearing carrier and the inner bearing ring, still leaving the possibility of radial or rotational movement of the bearing assembly under a predetermined, specific movement force.

In a particularly preferred embodiment, the fixation member has at least one annular seat surface, wherein the seat surface is oriented perpendicularly to the axis and configured to abut at least partially against the clutch release bearing carrier. Thus, by providing a seat surface, the twisting or tipping of the fixation member caused by forces in axial and radial direction is impeded.

Preferably, the fixation member has the first seat surface and at least one second seat surface being spaced apart from the first seat surface, wherein the second seat surface abuts at least partially against the clutch release bearing. Preferably, the second seat surface is oriented perpendicularly to the axis. In order to impede twisting or tipping, the first seat surface abuts at least partly against the clutch release bearing carrier and the second seat surface abuts at least partly against the clutch release bearing. Thus, the embodiment advantageously recognizes that abutting at least partly against two vertical spaced apart surfaces, namely against a seat surface of the clutch release bearing carrier and a seat surface of the clutch release bearing, provides an increased safety against tipping or twisting.

When assembling the clutch actuator, the fixation plate is pressed in its position in order to couple between the clutch release bearing carrier and the clutch bearing in a positive fit by applying a pressing force. By providing two seat surfaces, the pressing force can be applied locally only in the region of the fixation member abutting at the seat surface of the clutch release bearing carrier, to protect the clutch release bearing from damage.

In a preferred embodiment, the maximal radial or rotational movement or the force created because of such a movement is tolerated by the fixation member is defined as a function of at least one of the stiffness or compressive strength of the fixation member. Thus, the embodiment advantageously recognizes that determining the maximal radial or rotational movement is necessary for the construction of the clutch actuator and in particular the whole clutch assembly. By providing a homogenous fixation plate made of solid material, the radial or rotational movement is determined by the stiffness and the compressive strength of the fixation plate. Accordingly, just by adapting or selecting a fixation plate, the clutch actuator and in particular the clutch release bearing carrier and bearing can be assimilated according to changing requirements.

Preferably, the clutch release bearing has an outer annular groove, configured to engage with the fixation member in a positive fit. By providing a groove, preferably adjacent to the seat surface of the clutch release bearing, the embodiment advantageously recognizes that a groove is easy to manufacture and provides a sufficient security against axial movement, while at the same time being cost-effective.

In a particularly preferred embodiment the clutch release bearing and the clutch release bearing carrier define an annular chamber between them, and wherein the fixation member is disposed in the annular chamber. Advantageously, the embodiment allows a repeatable positioning and guidance during assembling of the clutch actuator.

Preferably, the clutch release bearing carrier has an inner annular edge, configured to engage with the fixation member in a positive fit. By providing an annular edge, preferably adjacent to the seat surface of the clutch release bearing, the embodiment advantageously recognizes that an annular edge provides a sufficient security against axial movement, while at the same time being cost-effective with regard to the manufacturing costs.

In a particularly preferred embodiment, the clutch release bearing carrier and the cylindrical piston are formed as one monolithic part. The embodiment advantageously recognizes that forming the cylindrical piston and the clutch release bearing carrier in a monolithic part simplifies the sealing and increases the wear resistance by the reduction of wear parts assembled in the clutch actuator. Further, the transmission of the actuation forces is supported and the service life is increased.

For a more complete understanding of the invention, the invention will now be described in detail with reference to the accompanying drawing. The detailed description will illustrate and describe what is considered as a preferred embodiment of the invention. It should of course be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention may not be limited to the exact form and detail shown and described herein, nor to anything less than the whole of the invention disclosed herein and as claimed hereinafter. Further, the features described in the description, the drawings and the claims disclosing the invention may be essential for the invention considered alone or in combination. In particular, any reference signs in the claims shall not be construed as limiting the scope of the invention. The wording “comprising” does not exclude other elements or steps. The wording “a” or “an” does not exclude a plurality.

This invention will now be described with reference to the accompanying drawings which illustrate, by way of example and not by way of limitation, one of several possible embodiments of the clutch actuator proposed herein, and wherein:

Fig. 1 shows a clutch actuator 100 in principle in a sectional view,

Fig. 2 shows a detail of the sectional view according to Figure 1 ,

Fig. 3 shows in detail the fixation of the clutch release bearing according to Figure

1 ,

Fig. 4 shows in detail the fixation member according to Figure 1 ,

Fig. 5 shows a pressing tool for manufacturing the fixation member of the clutch actuator according to Figure 1 , and Fig. 6 shows an anti-rotation lock for the clutch actuator according to Figure 1 .

Figure 1 shows a clutch actuator 100 in principle. The clutch actuator 100 comprises a cylindrical housing 10 having a recess 12 configured to receive a piston 20, a cylindrical piston 20 mounted in the recess 12 and movable along an axis 30, and a clutch release bearing assembly 40.

The cylindrical housing 10 and the cylindrical piston 20 are in particular coaxially arranged to each other, wherein the axis 30 describes the symmetry axis of the cylindrical housing 10 as well as the symmetry axis of the cylindrical piston 20 and of the clutch bearing assembly 40. It will be understood that the deflection of the clutch release bearing 44 resulting in a deflection of a symmetry axis of the clutch release bearing is insignificant with regard to the dimensions of the clutch actuator 100.

The cylindrical piston 20 and the clutch release bearing carrier 42 are formed as one monolithic part being movably mounted in the cylindrical housing 10 and configured to receive the clutch release bearing.

The clutch release bearing assembly 40 comprises a clutch release bearing carrier 42, operatively coupled to the piston 20, and a clutch release bearing 44 mounted at the clutch release bearing carrier 42.

The clutch release bearing 44 comprises an outer bearing ring 46 configured to rotate in relation the axis 30 together with the clutch.

The clutch actuator 100 further comprises a clutch spring element 50 configured to engage a contact surface 49 of the outer bearing ring 46 when the piston 20 is actuated by the actuation force, cf. fig. 6.

As can further be seen in fig. 6, the clutch actuator 100 comprises a anti rotation lock 21 arranged on the clutch release bearing assembly 40 and on a lateral surface of the housing 10. It is configured to secure the clutch release bearing assembly 40 against rotation, such as those caused by rotations of outer bearing ring 46. The clutch actuator 100 further comprises a fixation member 60 operatively coupled to the clutch release bearing carrier 42 and the clutch release bearing 44, configured to prevent axial movement of the clutch release bearing 42 and to enable an elastic and in particular reversible radial or rotational movement of the clutch release bearing 44.

The fixation member 60 is disposed in an annular chamber 70 formed between the clutch release bearing 44 and the clutch release bearing carrier 42.

The actuation force configured to actuate the movement of the cylindrical piston 20 is applied by a tension spring 80 being operatively coupled with the piston 20 and disposed within the cylindrical housing 10. By way of example, the actuation force can also or in addition be applied by a pneumatic pressure.

Preferably the cylindrical housing 10 and the cylindrical piston 20 are defining a gap 82 between them, in particular a combustion chamber. The pneumatic pressure is applied when the gap 82 is pressurized in order to actuate the piston 20.

Figure 2 shows a detail of the sectional view shown in Figure 1 . The clutch release bearing assembly 40 comprises the clutch release bearing carrier 42 operatively coupled to the piston 20, the clutch release bearing 44 having the outer bearing ring 46 configured to rotate together with the clutch in relation to the axis 30, and a rolling element 48 being in rolling contact with the outer bearing ring 46.

The piston 20 movably mounted in the cylindrical housing 10 is guided by at least one guiding element 84.

The release bearing assembly 40 further comprises as rigid member an inner bearing 47 configured to be operatively coupled with the clutch release bearing carrier 42 by means of the fixation member 60.

The clutch release bearing carrier 42 and the clutch release bearing 44, in particular the inner bearing ring 47, are defining an annular chamber 70, configured to receive the fixation member 60. The clutch release bearing carrier and in particular an inner side wall defining the side wall of the annular chamber 70 has an annular edge 74 configured to be engaged with a fixation member 60.

The fixation member 60 comprises a plurality of elastic legs 62 configured to be engaged with the clutch release bearing carrier 42.

The clutch actuator 100 and in particular the inside of the cylindrical housing 10 is protected against environmental dirt and dust by at least one sealing element 86 disposed between the cylindrical piston and/or the clutch release bearing carrier 42 and the cylindrical housing 10.

Figure 3 shows in detail the annular chamber 70 and the fixation member 60 disposed therein.

The fixation member 60 comprises a plurality of elastic legs 62 extending along an inner wall of the release bearing carrier 42 and engaging an annular edge 74 of the clutch release bearing carrier 42.

The fixation member 60 further comprises a first seat surface 64 and a second seat surface 66. The first seat surface 64 is in contact with the clutch release bearing carrier 42 and configured to secure the fixation member from twisting and tipping. The second seat surface 66 is in contact with the inner bearing ring 47 of the clutch release bearing 44 and configured to arrange the fixation member 60 in an upward position in the annular chamber 70.

As in particular shown in Figure 4, the first seat surface 64 and the second seat surface 66 of the fixation member 60 are spaced apart from each other in the vertical direction and extending in particular parallel to each other. The first seat surface 64 is abutting against the surface of the clutch release bearing carrier 42 and the second seat surface 66 is abutting against the surface of the clutch release bearing 44 and in particular the inner bearing ring 47 of the clutch release bearing 44.

In the following, the function of the clutch actuator is described as an illustrative example.

In order to disengage the clutch, an actuation force applied actuating the piston 20 to move in the housing 10 in the direction of the clutch spring 50 until the contact surface 49 of the outer bearing ring 46 is engaged by the clutch spring 50.

The actuation force is induced by the tension spring 80 and/or by a pneumatic pressure applied in a chamber defined between the piston 20 and the cylindrical housing 10.

The outer bearing ring 46 and the clutch are rotating in relation to axis 30. Clutch release bearing 40 is fixed with its inner bearing ring 47 in the clutch release bearing carrier 42 such that it is axially and radially secured by fixation plate 60. The radial fixation results from an axial force applied from the fixation plate 60 and acts towards to the inner bearing ring 47. This allows a wanted, predetermined radial or rotational movement of the complete bearing within a specified force window. With this function unwanted misalignments between clutch and bearing will be reliably compensated.