WO1990007656A1

WO1990007656A1 - Friction clutch assembly

Info

Publication number: WO1990007656A1
Application number: PCT/GB1990/000002
Authority: WO
Inventors: Per Ola Svenke
Original assignee: Kongsberg Automotive A/S; Brunner, Michael, John
Priority date: 1989-01-05
Filing date: 1990-01-02
Publication date: 1990-07-12
Also published as: GB8900153D0

Abstract

A pressure plate (17) for a clutch assembly (1) has an annular rim (16), one side of which engages the clutch disk (13) in use. In order to cool the pressure plate in use the rim has a plurality of radially outwardly extending passages (20) for air to flow therethrough on rotation of the pressure plate.

Description

DESCRIPTION

FRICTTON CLUTCH ASSEMBLY

The present invention relates to friction clutch assemblies in drive train systems such as those commonly found in motor vehicles to selectively engage or disengage the drive train to the wheels from the engine. Such friction clutch assemblies conventionally comprise a generally C-shaped supporting cover which carries a sp ing-loaded pressure plate for forcing a friction clutch disk into engagement with a rotatable member such as the flywheel of the engine. Conventionally, the biasing force is provided by coil springs arranged circumferentially around the pressure plate and engaging the housing, but more recently a diaphragm spring has been used instead.

Due to the frictional coupling and de-coupling of the clutch in use when the engine is rotating, heat is generated at the friction surfaces on either side of the clutch disk, on one side heat being conducted through the relatively large mass of the flywheel into the engine and on the other side being conducted into the pressure plate. Unfortunately, the lower mass of the pressure plate, in relation to the flywheel, results in a greater degree of heating of the pressure plate and this can lead to high temperatures during heavy clutch work. High temperatures in the pressure plate lead to increased wearing of the engaging faces of the pressure plate and the clutch disk and, ultimately, to reduced life time of the clutch assembly.

Furthermore, distortion may occur. In an automatic clutch control system which requires accurate control of the torque transmitted to the pressure plate, further problems may be experienced in regard to consistency of operation as this may vary with clutch usage as a result of the heat, resulting in inaccurate operation and control.

Accordingly, it would be desirable to increase the heat dissipation from the pressure plate in order to lower the temperature of both the pressure plate and the clutch disk, thus resulting in reduced wear and greater accuracy of operation.

According to the present invention therefore there is provided a clutch assembly for a motor vehicle engine or the like, the assembly having a spring-loaded pressure plate for forcing a friction clutch disk into engagement with a rotatable member, the pressure plate having an annular rim, one side of which engages the clutch disk in use, the rim having a plurality of radially outwardly extending passages for air to flow therethrough to cool the pressure plate in use.

When the engine is turning and the clutch assembly is rotated, carrying the pressure plate with it, centrifugal action results in the effective pumping of air through the passages to the outside of the clutch cover.

The invention also includes a pressure plate for a clutch assembly, the pressure plate having an annular rim, one side of which engages the clutch disk in use, the rim having a plurality of radially outwardly extending passages for air to flow therethrough to cool the pressure plate in use. Preferably, the passages are arranged to exit the radially outer edge of the pressure plate in alignment with the side openings in the clutch assembly cover and appropriate axial apertures or holes are arranged radially inwardly of the rim of the pressure plate in the housing in order to enable the passage of air substantially along the axis of rotation of the clutch assembly in order that air can be drawn in close to the axis, passed radially outwardly through the passages in the pressure plate and exit the cover through the above mentioned openings. The precise form and disposition of the passages in the pressure plate will vary from clutch assembly to clutch assembly and it is envisaged that the passages may extend at an angle to radial lines through the pressure plate in order to increase the pumping effect on the air passing therethrough. Likewise, the passages may be curved if so desired and may be angled to the plane normal to the rotational axis of the clutch assembly. Alternatively, or additionally, the surfaces of the passages may include cooling fins to increase heat dissipation.

In a conventional clutch assembly with axially extending compression coil springs the cover has a generally central aperture through which air may be passed to the radially inner side of the pressure plate rim. However, in a clutch assembly having diaphragm spring operation of the pressure plate, the area of this central opening may be reduced by the presence of the diaphragm spring itself and passages may need to be formed through and/or between the springs in order to provide for a sufficient flow of air to achieve the design cooling.

One example of a clutch assembly constructed in accordance with the present invention will now be briefly described with reference to the accompanying informal drawing which is an axial section through the clutch assembly.

The clutch assembly 1 is shown mounted on the face of a flywheel 2 which in turn is mounted on the end of a crankshaft 3 of an internal combustion engine. The clutch assembly 1 has a metal cover 4 which is secured to the face of the flywheel 2 by means of bolts (not shown) . The cover 4 has a generally axially central aperture 5 and located therein is a thrust bearing 6, axial movement of which is controlled by a lever arm 7 in turn operated by a connecting rod 8 from a clutch slave cylinder or cable (not shown), the lever 7 pivoting about a pivot pin 9. The thrust bearing 6 surrounds the end of a drive shaft 10 which, through a gear box, drives the wheels of the vehicle or the like, the end of the drive shaft 10 having a reduced diameter and carrying splines 11 which engage with a similarly splined hub 12 of a friction clutch disk 13. The clutch disk 13 has a pair of annular friction linings 14, 15, one of which engages the surface 2¹ of the flywheel 2. The other friction lining 15 engages the annular rim 16 of a pressure plate 17 which is located within the cover 4 by means of a plurality of leaf spring elements 22. A diaphragm spring 18 is mounted on support brackets 19 and is able to pivot and flex on the support 19 under the action of the thrust bearing 6 in order to control the engagement of the pressure plate with the friction clutch plate and hence with the flywheel, engagement transferring motion from the flywheel to the drive shaft 10. The diaphragm spring 18 is arranged so as normally to force the pressure plate into engagement with the clutch plate and the operation of the slave cylinder or clutch cable through the arm 7 and the thrust plate 6 is arranged to cause the diaphragm spring to pivot and flex so as to relieve the biasing force on the pressure plate.

In order to cool the pressure plate 17 generally _r radially extending passages 20 are formed in the rim of the pressure plate, air being allowed to flow from the outside, to the centre of the pressure plate 17 through the diaphragm spring 18

(through holes in them or between them if desired) and thence to the passages 20, rotation of the clutch assembly on the flywheel in. use effectively pumping air through the passages 20, and in turn, due to the result of heat exhange, cooling the pressure plate 17. In order to improve the escape of air from the passages 20 additional openings 21 are formed in the annular side wall 4*. Restriction of the air flow through the centre opening 5 should be reduced as far as possible and, if desired, modification of the shape, and design, etc of the diaphragm spring 18 may be required to achieve this. The design should be optimised for maximum airflow axially in through the diaphragm spring and radially outwardly through the clutch cover, for example, the diaphragm . spring having a maximum flow area between its constituent fingers, and the clutch cover having a maximum area of side openings and apertures.

Claims

1. A pressure plate (17) for a clutch assembly, the pressure plate having an annular rim (16) , one side of which engages the clutch disk (13) in use, characterised in that: the rim has a plurality of radially outwardly extending passages (20) for air to flow therethrough to cool the pressure plate in use.

2. A pressure plate according to claim 1, wherein the passages (20) extend at an angle to radial lines through the pressure plate in order to increase the pumping effect on the air passing therethrough.

3. A pressure plate according to claim 1, wherein the passages (20) are curved.

4. A pressure plate according to any of claims 1 to 3, wherein the passages (20) are angled to the plane normal to the rotational axis of the pressure piate.

5. A pressure plate according to any of claims 1 to 4, wherein the surfaces of the passages (20) include cooling fins to increase heat dissipation.

6. A clutch assembly (1) for a motor vehicle engine or the like, the assembly having a spring-loaded pressure plate (17), for forcing a friction clutch disk (13) into engagement with a rotatable member (2), the clutch plate being formed according to any of claims 1 to 5.

7. A clutch assembly according to claim 6, wherein the passages (20) are arranged to exit the radially outer edge of the pressure plate in alignment with side openings (21) in a clutch assembly cover (4) .

8. A clutch assembly according to claim 6 or claim 7, wherein axial apertures or holes are arranged radially inwardly of the rim of the pressure plate in the housing in order to enable the passage of air substantially along the axis of rotation of the clutch assembly.

9. A clutch assembly according to any of claims 6 to 8, having diaphragm springs (18) for operation of the pressure plate, air passages being provided through and/or between the springs.