EP1690017A1

EP1690017A1 - Clutch actuators

Info

Publication number: EP1690017A1
Application number: EP04798900A
Authority: EP
Inventors: Yannick Frank Thoephile Emile Christiaens
Original assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG; LuK Lamellen und Kupplungsbau GmbH
Current assignee: Schaeffler Buehl Verwaltungs GmbH; LuK Lamellen und Kupplungsbau GmbH
Priority date: 2003-11-27
Filing date: 2004-11-18
Publication date: 2006-08-16
Also published as: DE112004002198T5; GB0327574D0; WO2005052401A1

Abstract

A concentric slave cylinder type clutch actuator in which an annular piston (12) slides in sealed contact with an annular bore defined between inner (29) and outer (28) cylinder walls of a cylinder body (11) to provide an annular actuating chamber (13) into which fluid is introduced to displace the piston relative to the cylinder to move a clutch release bearing (21) carried by the piston or body for engagement with associated clutch release fingers (27) of an associated clutch. The release bearing is carried by the cylinder body (11) and the piston is adapted to be fixed to a suitable abutment on the transmission/clutch housing of the associated vehicle. The cylinder body (11) carries the release bearing (21) in an encircling cavity (22) and is guided on an axially extending tube (23) which encircles the transmission input shaft.

Description

CLUTCH ACTUATORS

This invention relates to clutch actuators and in particular to so-called concentric slave cylinders (CSCs) [hereinafter referred to as of the type described] in which an annular piston slides in sealed contact with an annular bore defined between inner and outer cylinder walls of a cylinder body to provide an annular actuating chamber into which fluid is introduced to displace the piston relative to the cylinder to move a clutch release bearing carried by the piston or body for engagement with associated clutch release fingers of the associated clutch.

CSCs of the type described are well known and generally a very effective means of actuating a vehicle clutch since the CSC can conveniently surround the input shaft of an associated transmission into which the clutch is to transmit drive.

It is important to guide the piston/cylinder sliding contact and cater for radially misalignment of the release bearing.

It is an object of the present invention to provide an improved form of CSC of the type described.

Thus according to the present invention there is provided a CSC of the type described in which the release bearing is carried by the cylinder body and the piston is adapted to be fixed to a suitable abutment on the transmission/clutch housing of the associated vehicle, the cylinder body carrying the release bearing in an encircling cavity and being guided on an axially extending tube which encircles the transmission input shaft.

This arrangement enables the diameter of the piston to be increased without increasing the overall diameter of the cylinder. The axially extending guide tube may be carried by the piston and may slide over a guide formation carried by the cylinder as the cylinder is displaced relative to the piston.

In the alternative arrangement the axially extending guide tube is carried by the cylinder and slides over a guide formation carried by the piston as the cylinder is displaced relative to the piston.

Preferably the release bearing is mounted on the cylinder via a self-centring arrangement which allows transverse movement of the bearing relative to the cylinder. This allows self-centring without any increase in diameter.

The piston may be biased away from the cylinder body (to provide a preload between the release bearing and the associated clutch release fingers) by a spring which encircles the axially extending guide tube.

Preferably an outer annular seal carried by the piston makes sealed sliding contact with the outer cylinder wall and an inner annular seal carried by the inner cylinder wall makes sealed sliding contact with the piston.

With such a seal arrangement both annular seals are in circumferential tension, the outer seal being in tension around an outer surface of the piston and the inner seal around the inner cylinder wall. Having both seals under slight circumferential tension is the best operating condition and helps to overcome problems which can arise if either seal is in circumferential compression, as is normal, since compression of a seal tends to result in bunching of the seal in its support groove which can lead to wear problems when the seal projects irregularly from its support groove.

In a preferred arrangement the outer seal is mounted in a groove formed in the outer surface of the piston and the inner seal is mounted in a groove formed in the inner cylinder wall of the body. One or both of the piston and body may be formed from plastics material.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is an axial section through a concentric slave cylinder in accordance with the present invention;

Figure 1a shows details of a self-centring release bearing arrangement;

Figure 2 is a view on a larger scale of the sealing arrangement of Figure 1 , and

Figure 3 is an axial section through an alternative concentric slave cylinder in accordance with the present invention.

Referring to the drawing the concentric slave cylinder (CSC) 10 has a cylindrical body 11 formed from plastics material and an annular piston 12, also of plastics material, slideable relative to the body 11 to define an annual actuating chamber 13.

In the arrangement shown in the drawings, the piston 12 is provided with a mounting flange 14 which is secured by bolts or other fasteners (not shown) to a suitable mounting surface on an associated transmission or clutch housing.

The piston 12 is sealed to the body 11 by an outer annular O-ring seal 15 received in a groove 16 formed in the outer surface 17 of piston 12. The sealing is completed by an inner annular O-ring type seal 18 carried in a groove 19 formed in the inner cylinder wall 20 of body 11.

As will be appreciated, both the outer seal 15 and the inner seal 18 being supported in grooves 16 and 19 respectively can be arranged to be under slight circumferential tension within their associated grooves. This provides the best possible operating situation for the seals and helps prevent problems due to bunching and irregular projection from the seal support groove which could occur if one or both seals were in circumferential compression in their associated support grooves. Also, only surfaces 28 and 29 which are contacted by seals 15 and 18 respectively need to be of a high quality finish. This further simplifies production of the CSC.

A clutch release bearing 21 is carried in a cavity 22 formed in cylinder body 11 with a self-centring arrangement 31 therebetween. The self-centring arrangement (see figure 1a) comprises a metal Z-section washer 32 which receives the outer race 21a of bearing 21 and a cranked belleville spring 33 which reacts against the surrounding lip 11a of body 11 and applies an axial damping pressure to washer 32. Thus washer 32 and hence bearing 21 is free to move laterally relative to spring 33 and hence body 11 to accommodate radial misalignment when the cylinder is mounted in its operational position.

The cylinder body 11 is also guided form sliding movement relative to piston 12 by an axially extending steel tube 23 having a radially extending flange 24 which is received in a recess 25 formed in mounting flange 14. As cylinder body 11 is displaced relative to fixed piston 12 guide formation 30 on body 11 slides along tube 23. This provides good and accurate axially sliding of the body 11 relative to piston 12 and reduces any loads associated with sliding which may be applied to seals 15 and 18. Arcuate locating formations 14a on flange 14 engage a circular groove cut into the associated transmission or clutch housing to locate cylinder 10 in its correct position.

Also, a coil compression spring 26 is located between the guide tube 23 and the piston 12. This spring biases the piston 12 away from the body 11 and provides a preload of the release bearing 21 on the associated clutch release fingers 27 of the associated clutch. Located in this position the spring 26 is well protected and no additional dust protection for the cylinder is necessary. As will be appreciated, the clutch is released by pressurising actuating chamber 13 in the normal manner which displaces body 11 to the left as viewed in the drawing thus moving the release fingers in the direction of the arrow X.

With the cylinder arrangement described above the diameter of piston 12 can be increased without increasing the overall diameter of the cylinder as compared to arrangements in which the bearing is carried by the piston. Also the self-centring arrangement can be incorporated with no increase in diameter and the stop controlling movement of the cylinder towards the body can be provided by contact between the body and flange 14. No seal is necessary between the sliding guide formation 30 and the tube 23 as the hydraulic system is sealed by seals 15 and 18. Also, is desired, rotation of body 11 relative to piston 12 can be controlled by inter- engaging anti-rotation formations on the body 11 and piston 12.

Figure 3 shows an alternative CSC in accordance with the present invention in which components of a similar function to those shown in Figure 1 have been similarly numbered.

In the arrangement shown in Figure 3 the bearing 21 is again carried by cylinder body 11 via a self-centring arrangement 31. Piston 12 is again sealed to body 11 via seals 15 and 18 received in their respective grooves 16 and 19. In this arrangement the seals are spaced at opposite axial ends of the piston and are again in circumferential tension.

Piston 12 carries an integrally formed axially extending tube 40 which carries at its free end an inner circumferential lip 41. Body 11 also carries an axially extending tube 42 which carries at its free end an annular snap-on guide washer 43. As the body 11 moves axially relative to the piston 12 the inner lip 41 on tube 40 slides along internal surface 44 of tube 42 and the guide washer 43 slides along the inner surface 45 of tube 40 to guide the body accurately relative to the piston 12 and hence reduce seal wear. As previously the spring 26 is protected being located between the body 11 and the tube 40.

Claims

1. A CSC of the type described in which the release bearing is carried by the cylinder body and the piston is adapted to be fixed to a suitable abutment on the transmission/clutch housing of the associated vehicle, the cylinder body carrying the release bearing in an encircling cavity and being guided on an axially extending tube which encircles the transmission input shaft.

2. A CSC according to claim 1 in which the axially extending guide tube is carried by the piston and slides over a guide formation carried by the cylinder as the cylinder is displaced relative to the piston.

3. A CSC according to claim 1 or 2 in which the axially extending guide tube is carried by the cylinder and slides over a guide formation carried by the piston as the cylinder is displaced relative to the piston.

4. A CSC according to any one of claims 1 to 3 in which the release bearing is mounted on the cylinder via a self-centring arrangement which allows transverse movement of the bearing relative to the cylinder.

5. A CSC according to any one of claims 1 to 4 in which the piston is biased away from the cylinder body (to provide a preload between the release bearing and the associated clutch release fingers) by a spring which encircles the axially extending guide tube.

6. A CSC according to any one of claims 1 to 5 in which an outer annular seal carried by the piston makes sealed sliding contact with the outer cylinder wall and an inner annular seal carried by the inner cylinder wall makes sealed sliding contact with the piston.

7. A CSC according to claim 6 in which the outer seal is mounted in a groove formed in the outer surface of the piston and the inner seal is mounted in a groove formed in the inner cylinder wall of the body.

8. A CSC according to claim 6 or 7 in which one or both of the piston and body are formed from plastics material.

9. A CSC of the type described constructed and arranged substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or Figure 3 of the accompanying drawings.