WO2014191741A1

WO2014191741A1 - Clutch actuator

Info

Publication number: WO2014191741A1
Application number: PCT/GB2014/051627
Authority: WO
Inventors: Michael Lamperth; Mark CORDNER
Original assignee: Gkn Evo Edrive Systems Limited
Priority date: 2013-05-28
Filing date: 2014-05-28
Publication date: 2014-12-04
Also published as: GB2516415A; GB201309521D0

Abstract

A clutch actuator (1) comprising an actuation assembly (2), a hydraulic piston (4) and at least one retention member (8). The actuation assembly comprises an elongate shaft (3) defining a longitudinal axis (Z). The hydraulic piston assembly (4) provides a channel (5) for receiving the elongate shaft (3) of the actuation assembly. The at least one retention member (8) is arranged to provide releasable mounting of the actuation assembly and the hydraulic piston on application of an axial force.

Description

CLUTCH ACTUATOR

The present invention relates to a clutch actuator and a clutched drivetrain for a motorised vehicle with improved ability for assembly and/or disassembly in confined spaces.

Background of the Invention A clutch assembly is typically disposed between a flywheel of an engine and a transmission of an automotive vehicle. The clutch assembly engages, disengages and transmits torque from the engine (i.e. the power source) to a transmission (i.e. driven system) which itself may also be combined with an auxiliary power source (e.g. an electric machine). As illustrated in Figure 1 , conventional "pull-type" friction clutch actuators comprise a non-rotating element 40 and a rotating element 42 which are arranged about the shaft 30, for example a transmission shaft. The non-rotating element 40 is configured to move substantially parallel to the shaft 30 axis. The rotating element 42 is configured to move together with the non-rotating element 40 (i.e. substantially parallel to the shaft 30 axis) whilst also accommodating rotation of the rotating element relative to the non- rotating element. Consequently the rotating element moves parallel to and concentrically about the shaft 30 axis. A diaphragm spring 44 is mounted within a clutch cover. The clutch cover is also mounted to a flywheel. The flywheel 48 is mounted and driven by the ending. The diaphragm spring 44 provides the load required to engage the clutch and may include a thrust plate for actuation purposes. The clutch actuator's rotating element contacts the clutch diaphragm spring 44 and/or thrust plate, allowing an axial load to be applied to the clutch's rotating parts. The axial load disengages (actuates) the clutch. The flywheel and clutch are typically pre-installed on the engine prior to assembly with the transmission and/or auxiliary power source 46. The shaft 30 is typically pre-installed within the transmission and/or auxiliary power source housing prior to assembly with the engine. In one implementation a retention device 70 such as for example a clip, for maintaining the mounting between the rotating- and non-rotating-elements of the clutch actuator is located within the housing and is inaccessible using conventional tools. As a result, the conventional pull type clutch actuators are difficult to assemble and/or disassemble in confined or enclosed spaces where tool access is limited or restricted. Summary of the Present Invention

According to one aspect of the present invention, there is provided a clutch actuator comprising: an actuation assembly comprising an elongate shaft defining a longitudinal axis; a hydraulic piston assembly providing a channel for receiving the elongate shaft of the actuation assembly; and at least one retention member arranged to provide releasable mounting of the actuation assembly and the hydraulic piston on application of an axial force.

The retention member(s) preferably enables the actuation assembly to be dismounted from the hydraulic piston on application of an axial force by the hydraulic piston to the retention member.

The axial force is preferably applied in a direction substantially parallel to the longitudinal axis of the elongate shaft of the actuation assembly. The axial force may place the retention member(s) under tension or compression, depending on the configuration adopted. The retention member(s) may deform in shape when subjected to the axial force.

According to a further aspect of the present invention, there is provided a clutched drivetrain for a motor vehicle comprising: a drive unit; a transmission unit; and a clutch actuator as herein described located between the drive unit and the transmission unit.

The clutch actuator is preferably a pull type clutch actuator, such as used for example with a pulled diaphragm spring clutch. The transmission unit may incorporate an auxiliary power source.

The drive unit may for example be an internal combustion engine. The clutch actuator may comprise apart capable of driving the clutch diaphragm sping. The clutch actuator may further comprise a part connected to the transmission/auxiliary power source housing. The elongate shaft is preferably arranged to receive the retention member at or adjacent a first end of the elongate shaft. For example, the elongate shaft provides at least one recess for receiving the retention member. The at least one recess may for example be located at or adjacent the first end of the elongate shaft.

The retention member(s) is preferably received within the recess(es) such that portions of the retention member(s) protrude beyond the surfaces of both the elongate shaft and the hydraulic piston. The retention member(s) is preferably arranged to extend circumferentially about the elongate shaft.

The retention member(s) may be any suitable device capable of retaining the hydraulic piston and the actuation assembly in the mounted position. For example the retention member may be a snap ring.

The retention member(s), for example a retention ring, may be located between the flex plate and the shaft. The shaft may comprise at least one slit for receiving the retention member(s). The slit(s) and/or the retention member(s) may be deformable.

The elongate shaft of the actuation assembly preferably further comprises a rotating element located at or adjacent a second end of the elongate shaft. The rotating element contacts the clutch diaphragm spring The channel of the hydraulic piston preferably comprises a first end which in the mounted position is arranged to be located adjacent the first end of the elongate shaft. The second end of the channel of the hydraulic piston is preferably in the mounted position arranged to be located adjacent the second end of the elongate shaft. Preferably, both the first and second ends of the channel are open. The actuation assembly and the hydraulic piston may be arranged such that in the mounted position the first end of the elongate shaft and the retention member extend beyond the first end of the channel of the hydraulic piston assembly such that the retention member abuts the hydraulic piston assembly to transfer load between the hydraulic piston and the actuation assembly.

The channel of the hydraulic piston may have any suitable shape. For example, at least a portion of the inner surface of the channel provided by the hydraulic piston assembly is of reduced cross-sectional dimension. For example at least a portion of the inner surface of the channel tapers inwardly to provide a ramp. The inner surface of the channel preferably tapers inwardly between the second end and the first end of the channel.

The at least one retention member is preferably arranged to engage or contact the inner surface of the channel of the actuation assembly.

The clutch actuator of the present invention is able to be assembled and/or disassembled in confined or enclosed spaces, for example in spaces where full tool access is not possible.

Brief Description of the Drawings Figure 1 is a cross-sectional view of a system incorporating a clutch actuator according to one embodiment of the present invention;

Figure 2 is a cross-sectional view of a clutch actuator according to one embodiment of the present invention (including a section of the clutch diaphragm spring for reference);

Figures 3a-b are cross-sectional views of the process of mounting the actuation assembly and hydraulic piston assembly of the clutch actuator of Figure 2;

Figure 4 is a cross-sectional view of the clutch actuator during operation;

Figures 5a-b are cross-sectional views of the process of dismounting the actuation assembly and the hydraulic piston assembly of the clutch actuator of Figure 2.

Detailed Description of the Preferred Embodiments With reference to Figure 2, the clutch actuator 1 comprises an actuation assembly 2 comprising an elongate shaft 3 defining a longitudinal axis Z. The elongate shaft 3 is substantially circular in cross-section. It is however to be understood that the shaft may have any suitable shape. The clutch actuator 1 further comprises a hydraulic piston assembly 4 providing a channel 5 for receiving the elongate shaft 3 of the actuation assembly 2. The channel 5 is substantially circular in cross-section. It is however to be understood that the channel 5 may have any suitable shape for receiving the elongate shaft 3 of the actuation assembly 2. The elongate shaft 3 comprises a first end 6 providing a recess 7 extending circumferentially around the shaft 3. The recess 7 is located adjacent the first end 6 of the shaft 3. The recess 7 is shaped and dimensioned to receive a retention member 8. The retention member 8 and the recess 7 may be shaped and dimensioned to ensure that at least a portion of the retention member 8 protrudes beyond the external surface of the shaft 3. The retention member 8 may have any suitable cross-sectional shape. For example, the retention member 8 may have a square or circular cross-section. The retention member 8 is a snap ring. The snap ring 8 extends circumferentially around the external surface of the shaft 3. The retention member 8 is arranged to provide releasable mounting of the actuation assembly 2 and the hydraulic piston 4 on application of an axial force. Releasable mounting is used herein to refer to the mounting and dismounting of the actuation assembly and the hydraulic piston.

The axial force is applied in a direction extending substantially parallel to the longitudinal axis Z of the elongate shaft 3 of the actuation assembly 2.

The elongate shaft 3 of the actuation assembly 2 further comprises a rotating element 9 located at or adjacent a second end 10 of the elongate shaft 3.

The channel 5 of the hydraulic piston assembly 4 comprises a first open end 1 1 which in the mounted position is arranged to be located adjacent the first end 6 of the elongate shaft 3 of the actuation assembly 2. The channel 5 further comprises a second open end 12 which in the mounted position is arranged to be located adjacent the second end 10 of the elongate shaft 3. The hydraulic piston assembly 4 further comprises an annular hydraulic piston assembly 15.

The inner surface 13 of the channel 5 of the hydraulic piston assembly 4 tapers inwardly to provide ramp 14. The inner surface 13 of the channel 5 tapers inwardly between the second end 12 and the first end 1 1 of the channel 5. The ramp 14 is preferably an annular ramp. The channel 5 may however provide a plurality of spaced apart ramps extending along the inner surface of the channel 5. The ramp 14 may taper inwardly at any suitable angle. With reference to Figures 3a-b, during mounting of the hydraulic piston assembly 4 and the actuation assembly 2, the first end 6 of the elongate shaft 3 of the actuation assembly 2 is inserted into the second open end 12 of the channel 5 of the hydraulic assembly 4. The actuation assembly 2 is inserted in a direction extending substantially parallel to the longitudinal axis Z of the elongate shaft 3. The spring clip 8 protrudes beyond the external surface of the elongate shaft 3. During insertion into the channel 5, the spring clip 8 engages and follows ramp 14. The spring clip 8 is compressed into recess 7. The amount of force required in order to mount the hydraulic piston assembly 4 and the actuation assembly 2 depends on the design off the ramp angle. The greater the ramp angle, the greater the force required in order to mount the two components.

The actuation assembly 2 continues to be inserted in an axial direction into the channel 5 of the hydraulic assembly 4. The first end 6 of the elongate shaft 3 extends beyond the first end 11 of the channel 5 of the actuation assembly 2. The compressive force on the spring clip 8 is removed and the spring clip 8 expands and protrudes beyond the external surface of the elongate shaft 3. The spring clip 8 therefore contacts and abuts the shoulder 16 of the hydraulic piston assembly 4. The spring clip 8 is held under tension of the clutch diaphragm spring 9. With reference to Figure 4, during operation of the clutch actuator 1 the spring clip 8 transfers load between the hydraulic piston assembly 4 and the clutch actuation assembly 2 as shown in Figure 3d.

With reference to Figures 5a-5b, the clutch actuator 1 is disassembled when the hydraulic piston assembly 4 travels a maximum distance relative to the actuation assembly 2. The first end 6 of the elongate shaft 3 of the assembly 2 engages a static feature, such as for example a housing wall 20. As shown in Figure 5b, the housing wall 20 exerts an axial force in a direction extending substantially parallel to the longitudinal axis of the elongate shaft 3. The axial force exerted on the spring clip 8 by the static feature is sufficient to cause the spring clip 8 to deform sufficiently so as to no longer abut the shoulder 16 of the hydraulic piston assembly 4. The spring clip 8 can then be dislodged thereby releasing the actuation assembly 2. The clutch diaphragm spring 9 ejects the actuation assembly 2 from the hydraulic piston assembly 4. The clutch actuator 1 can therefore be assembled and disassembled on the application of axial force. The clutch actuator 1 can also be assembled and disassembled in locations where access to the retention member by for example tools is limited and/or restricted.

Although aspects of the invention have been described with reference to the embodiment shown in the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment shown and that various changes and modifications may be effected without further inventive skill and effort.

Claims

1. A clutch actuator comprising: an actuation assembly comprising an elongate shaft defining a longitudinal axis; a hydraulic piston assembly providing a channel for receiving the elongate shaft of the actuation assembly; and at least one retention member arranged to provide releasable mounting of the actuation assembly and the hydraulic piston on application of an axial force.

2. An actuator as claimed in claim 1 , in which the axial force is applied in a direction substantially parallel to the longitudinal axis of the elongate shaft of the actuation assembly.

3. An actuator as claimed in either of claims 1 and 2, in which the hydraulic piston assembly is arranged to apply axial force to the at least one retention member so as to enable dismounting of the actuation assembly from the hydraulic piston assembly.

4. An actuator as claimed in any preceding claim, in which the clutch actuator is a pull type clutch actuator.

5. An actuator as claimed in any preceding claim, in which the elongate shaft is arranged to receive the at least one retention member at or adjacent a first end of the elongate shaft.

6. An actuator as claimed in claim 5, in which the elongate shaft provides at least one recess for receiving the at least one retention member, in which the at least one recess is located at or adjacent the first end of the elongate shaft.

7. An actuator as claimed in claim 6, in which the at least one retention member is received within the at least one recess such that at least a portion of the at least one retention member protrudes beyond the surface of the elongate shaft.

8. An actuator as claimed in any preceding claim, in which the at least one retention member is arranged to extend circumferentially about the elongate shaft.

9. An actuator as claimed in any preceding claim, in which the at least one retention member is a snap ring.

10. An actuator as claimed in any preceding claim, in which the at least one retention member is composed of material which is deformable when subjected to an axial force.

11. An actuator as claimed in any preceding claim, in which the elongate shaft of the actuation assembly further comprises a rotating element located at or adjacent a second end of the elongate shaft.

12. An actuator as claimed in any preceding claim, in which the channel comprises a first end which in the mounted position is arranged to be located adjacent the first end of the elongate shaft, and a second end which in the mounted position is arranged to be located adjacent the second end of the elongate shaft.

13. An actuator as claimed in claim 12, in which the actuation assembly and the hydraulic piston are arranged such that in the mounted position the first end of the elongate shaft and the retention member extend beyond the first end of the channel of the hydraulic piston assembly such that the retention member abuts the hydraulic piston assembly to transfer load between the hydraulic piston and the actuation assembly.

14. An actuator as claimed in either of claims 12 and 13, in which at least a portion of the inner surface of the channel provided by the hydraulic piston assembly tapers inwardly to provide a ramp.

15. An actuator as claimed in claim 14, in which the inner surface of the channel tapers inwardly between the second end and the first end of the channel.

16. An actuator as claimed in any preceding claim, in which the retention member is arranged to engage the inner surface of the channel of the actuation assembly.

17. A clutched drivetrain of a motor vehicle comprising: a drive unit; a transmission unit; and a clutch actuator as claimed in any one of claims 1 to 16 located between the drive unit and the transmission unit.