WO2005045271A1

WO2005045271A1 - Clutch actuators

Info

Publication number: WO2005045271A1
Application number: PCT/IB2004/003545
Authority: WO
Inventors: Yannick Frank Thoephile Emile Christiaens
Original assignee: Luk Lamellen Und Kupplungsbau Beteiligungs Kg
Priority date: 2003-11-07
Filing date: 2004-10-27
Publication date: 2005-05-19
Also published as: GB0326018D0

Abstract

A clutch actuator of the so-called concentric slave cylinder (CSC) type is provided in which an annular piston (13) slides in sealed contact with an annular bore defined between inner (12) and outer (11) cylinder walls to provide an annular actuating chamber (1 Oa) into which fluid is introduced to displace the piston relative to the cylinder to move a clutch release bearing (16) carried by the piston for engagement with associated clutch release fingers (18) of an associated clutch. The piston (13) is split axially into two parts, one part (20) of the piston carries the clutch release bearing (16) and is able to tilt axially relative to the other part (21) of the piston to accommodate any angular misalignment (A) between the longitudinal axis (Y) of the CSC and axis of rotation (X) of the associated clutch.

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 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 for engagement with associated clutch release fingers of an 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.

Problems can arise due to angular misalignment between the release bearing carried by the CSC and the clutch release fingers. The longitudinal axis of the CSC and the axis of rotation of the clutch are designed to be in angular alignment with each other. However, since the clutch is supported from a flywheel of the associated engine and the CSC is supported on the transmission housing angular misalignment between the longitudinal axis of the CSC and the associated clutch is not uncommon when the transmission is mounted on the engine. This angular misalignment can significantly affect the operation of the CSC and the clutch and can lead to excessive clutch release bearing noise and early failure of the release bearing and CSC dues to asymmetrical loading.

It is an object of the present invention to provide a CSC which overcomes the above problem of angular misalignment.

Thus according to the present invention there is provided a CSC of the type described in which the piston is split axially into two parts, one part of the piston carries the clutch release bearing and is able to tilt axially relative to the other part of the piston to accommodate any angular misalignment between the longitudinal axis of the CSC and axis of rotation of the associated clutch.

Preferably the two parts of the piston have co-operating part-spherical surfaces which slide over each other to allow the tilting.

The part of the piston which carries the release bearing preferably has a double tapering internal bore to provide a contact zone relative to the inner cylinder wall on which that part of the piston can tilt and clearance either side of this contact zone to allow the tilting.

The two parts of the piston may both be formed from metal or one or both parts could 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 shows an axial section through a CSC in accordance with the invention, and

Figure 2 shows details of the piston of the CSC of Figure 1 on a larger scale.

Referring to the drawings, the CSC comprises a cylinder body 10 having an outer cylinder part 11 moulded from plastics material and an inner cylinder part 12 pressed from metal. These two cylinder parts co-operate to receive a piston 13 therebetween which is sealed to the cylinder body 10 by a seal 14 carried in a carrier 15 which abuts the end of piston 13. Piston 13 carries a release bearing 16 which has an outer race member 17 which contacts associated clutch release fingers 18 in a plane of contact generally indicated at Z and defined by the face 17a of member 17. The clutch is released by pressurising working chamber 10a in the conventional manner to displace piston 13 to the right and hence push on release fingers 18 via release bearing 16. In accordance with the present invention the piston 13 is divided axially into two parts with one part 20 which carries the release bearing 16 and the other part 21 which makes contact with seal carrier 15.

The part 20 of piston 13 which carries the release bearing 16 can tilt relative to the other part 21 of the piston to accommodate angular misalignment(see angle A in Figure 1) of the axis of rotation X of the associated clutch (not shown) and the longitudinal axis Y of the CSC which would result in the contact plane Z no longer being at rights angles to the clutch axis X. The bearing 16 is held on piston part 20 by a spring steel sleeve 22 which has tabs 23 which engage behind a shoulder 24 on part 20 and a flange portion 25 which engages around an inner race member 16a of bearing 16.

As explained earlier, ideally the contact plane Z should be at right angles to the axis of rotation X of the clutch. The tilting of piston part 20 relative to piston part 21 is accommodated by providing both the parts of the piston with co-operating part spherical surfaces 20a and 21a respectively. The radius of curvature of these part spherical surfaces is equal to the mean radius 'R' of the area of contact 19 between the fingers 18 and the contact member 17 from the axis Y.

To accommodate this tilting of the piston part 20 relative to piston part 21 internal bore of piston part 20 has a double tapering configuration which provides a contact zone 20b where the piston part 20 contacts the inside surface of the inner cylinder part 12 and tapering portions 20c and 20d (see figure 2) either side of the contact zone 20b which provide tilting clearance p and q respectively.

As will be appreciated, if the axes of the clutch and CSC are not angularly aligned as designed, the piston part 20 can tilt slightly relative to the piston part 21 to accommodate this misalignment thus avoiding asymmetrical loading of the release bearing with the consequent noise and accelerated wear problems etc. Any lateral misalignment (see distance B in Figure 1) between the axes of the clutch and the CSC is taken care of by the lateral movement of the bearing 16 relative to the spring steel sleeve 22.

Claims

1. A concentric slave cylinder of the type described in which the piston is split axially into two parts, one part of the piston carries the clutch release bearing and is able to tilt axially relative to the other part of the piston to accommodate any angular misalignment between the longitudinal axis of the CSC and axis of rotation of the associated clutch.

2. A cylinder according to claim 1 in which the two parts of the piston have cooperating part-spherical surfaces which slide over each other to allow the tilting.

3. A cylinder according to claim 1 or 2 in which the part of the piston which carries the release bearing preferably has a double tapering internal bore to provide a contact zone relative to the inner cylinder wall on which that part of the piston can tilt and clearance either side of this contact zone to allow the tilting.

4. A cylinder according to any one of claims 1 to 3 in which the two parts of the piston are both formed from metal or one or both parts is formed from plastics material.

5. A cylinder according to any one of claims 1 to 4 in which the release bearing is free to move laterally relative to the piston through a limited distance to accommodate lateral misalignment of the axes of the CSC and the associated clutch.

6. A concentric slave cylinder of the type described constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.