GB2298251A

GB2298251A - Friction clutch

Info

Publication number: GB2298251A
Application number: GB9604043A
Authority: GB
Inventors: Achim Link; Reinhold Weidinger
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1995-02-25
Filing date: 1996-02-26
Publication date: 1996-08-28
Anticipated expiration: 2016-02-26
Also published as: FR2731056B1; ES2130011B1; GB2298251B; DE19506698A1; DE19506698C2; GB9604043D0; ES2130011A1; FR2731056A1

Description

1 FRICTION CLUTCH 2298251 The invention relates to a friction clutch for a

motor vehicle of the kind comprising a clutch housing secured to a flywheel, and rotatable therewith about an axis, a pressure plate rotatable with the clutch housing and axially movable relative thereto, a clutch plate with friction linings arranged between the pressure plate and the flywheel, and a diaphragm spring engaging the pressure plate and the clutch housing to urge the pressure plate towards the flywheel, the diaphragm spring engaging the pressure plate through an automatic wear adjuster allowing axial movement of the pressure plate away from the diaphragm spring to compensate for wear of the friction linings.

DE-A-43 06 688 shows a motor vehicle friction clutch with an automatic adjuster compensating for the wear in the friction linings, the adjuster having radially movable conical structural elements which, on the occurrence of wear, cause a corresponding increase in the spacing between diaphragm spring and pressure plate by a radial outward movement. Such an adjuster functions without problems if several circumferentially distributed clearance-providing devices are provided.

DE-A-44 12 107 shows an automatic adjuster for compensating for wear comprising two ring elements arranged concentric with the axis and springloaded relative to one another in a circumferential direction, and which engage one another through spaced inclined surfaces, so that on the occurrence of wear they increase correspondingly the spacing between diaphragrn spring and pressure plate.

It is an aim of the present invention to provide a friction clutch of the kind set forth with an automatic wear adjuster, which can be 2 manufactured as inexpensively as possible and which has trouble-free operation.

According to the present invention, in a friction clutch of the kind set forth at least one clearance-providing device is provided, each clearance -providing device being mounted in an axial opening in the pressure plate for axial movement and being adapted to be held by friction in the opening, and including an axial stop secured to the clutch housing to limit movement of the device in a direction towards the flywheel, and an actuating lever acting on part of the automatic adjuster, the arrangement being such that on clutch withdrawal following the occurrence of wear there is an increased axial spacing between the clearance- providing device and the pressure plate which is taken up by operation of the automatic adjuster, the automatic adjuster comprising at least one ring element which is concentric with the axis, engages circumferentially on a guide diameter on the pressure plate, is stiff in an axial direction and has circumferentially spaced inclined surfaces, and a spring means urging the ring element circumferentially to rotate it to increase its axial length.

Using this construction, it has been found that the number of clearanceproviding devices can be reduced without reducing the reliability of operation of the adjuster. In most cases one clearanceproviding device is sufficient but in some clutches two clearance- providing devices are necessary, arranged approximately diagonally opposite one another. This simplification is made possible because the ring element is guided accurately on a guide diameter of the pressure plate, is concentric with the axis of rotation and is made stiff in an axial direction. This ensures that it operates properly, even with only one clearance-providing device. The ring element can be guided on an inside 3 diameter, and it can then be circumferentially open. It is also possible to guide it on an outside diameter but then a circumferentially closed ring element is preferred.

In order to increase the axial length of the adjuster, opposing circumferentially spaced inclined surfaces are provided on an adjacent component. The opposing surfaces may be arranged on the pressure plate. Alternatively they may be provided on the diaphragm spring. A further alternative is the provision of a second ring element which is arranged in axial alignment with the first, the opposing surfaces being arranged on the second ring element. In the first two embodiments only one ring element is necessary, so that the number of parts involved is reduced. With the third embodiment, although two ring elements are used assembly is simplified in that the spring means provided for the relative movement of the two ring elements can be pre-assembled with the ring elements.

Advantageously the ring element has a rectangular cross-section with the longer edge extending axially and guided on the guide diameter on the pressure plate, so that the ring element can be easily manufactured from a metal strip, for example by stamping.

It is furthermore proposed that each clearance-providing device should be acted on by a locking spring tending to lock the device in the opening in the pressure plate. The locking spring causes tilting of the clearance-providing device in the opening in the pressure plate to produce a self-locking action during all conditions of operation apart from the adjustment of wear.

4 The locking spring preferably abuts the actuating lever and the pressure plate. It can produce a sufficient locking action by appropriate choice of the abutment points, even if it only has a low spring force.

Preferably each clearance-providing device has a setting spring in the region of the opening in the pressure plate acting to urge the clearanceproviding device axially towards the flywheel. This setting spring serves substantially to achieve the basic setting on assembly of the clutch, in that each clearance-providing device is brought into engagement with a component fixed to the housing, such as the flywheel.

Advantageously the opening comprises a bore, and the clearance-providing device includes a sliding pin extending parallel to the axis and the setting spring is arranged concentrically around the sliding pin and bears against the pressure plate and the sliding pin. In this way the spring is reliably guided and is mounted in a manner taking up little space. The pin may have a head providing an abutment for the setting spring.

In a further feature each clearance-providing device has detent means preventing rotation in the opening, in the form of a peg parallel to the opening and radially spaced from it. This ensures that the clearanceproviding device stays in its operating position with respect to the pressure plate despite being subjected to centrifugal force.

Preferably the locking spring is arranged concentrically around the peg, and urges the actuating lever away from the pressure plate. The peg has the two functions of securing against rotation and guiding the locking spring.

The actuating lever may act directly or indirectly on the part of the automatic adjuster. Preferably the actuating lever extends radially inwards from the opening on the pressure plate.

The diaphragm spring conveniently engages the pressure plate at an outer radial region, and the clutch housing at an intermediate radial region.

An embodiment of the invention is illustrated by way of example in the accompanying drawings, of which the single Figure is a longitudinal section through part of a friction clutch.

The friction clutch 1 shown in the Figure is for a motor vehicle (not shown) and is adapted to be located in the drive train between the vehicle engine and the gearbox.

The clutch 1 is secured on a flywheel 2 of the engine rotatable about an axis 3. It comprises a clutch housing 6 which is bolted to the flywheel 2 in the usual manner. A pressure plate 4 is disposed between flywheel 2 and clutch housing 6. The pressure plate 4 is connected to the clutch housing 6 to rotate with it but is guided to be axially displaceable.

Tangential leaf springs (not shown) are used for this purpose. A clutch plate 5 having friction linings 23 is arranged between the pressure plate 4 and the flywheel 2. A diaphragm spring 7 engages between the pressure plate 4 and the clutch housing 6. The diaphragm spring 7 is tiltably mounted in the region of an intermediate diameter through a number of spacer pins 8 secured on the clutch housing 6, and it acts in the region of its outside diameter against the pressure plate 4 to urge it towards the flywheel 2, to cause clamping of the friction linings 23 between the pressure plate 4 and the flywheel 2. The diaphragm spring 7 is provided 6 at its radially inner region with spring tongues 17 which can be actuated by a withdrawal system, not shown. An automatic wear adjuster is arranged between the diaphragm spring 7 and the pressure plate 4 for automatically taking up wear in the friction linings 23.

The adjuster comprises two ring elements, 18, 18a concentric with the axis 3 and axially aligned. The outer diameters of the ring elements are guided on a guide diameter 22 on the pressure plate 4. The ring element 18a abuts the pressure plate 4 and the ring element 18 is engaged by the diaphragm spring 7. A portion of the ring element 18 is illustrated in plan view. It has a straight circumferential edge, and on the opposing edge there are a number of circumferentially spaced inclined surfaces 20 which are adapted to engage with matching opposing surfaces on the ring element 18a. A spring 21 is arranged between the two ring elements 18, 18a to urge them circumferentially. Each ring element 18, 18a has openings 19 to receive the end of the spring 21. The spring 21 acts on them to cause the surfaces 20 on ring element 18 and the opposing surfaces on element 18a to ride up one another so as to increase the axial space occupied by the two ring elements 18, 18a.

The clutch 1 is provided with at least one clearance-providing device 9 which has a sliding pin 10 extending through an opening in the pressure plate 4 parallel to the axis 3. The pin 10 is round and the opening in the pressure plate 4 is accordingly in the form of a bore 24.

The sliding pin 10 has a head 15 on its end adjacent the flywheel 2.

Between this head 15 and the pressure plate 4 there is arranged a first or setting spring 13 which urges the clearance -prov id i ng device 9 towards the flywheel 2. The pin 10 is provided on its end remote from the flywheel with an actuating lever 12 which extends radially inwards.

Normally, the lever 12 acts to lock the clearance-providing device 9 in the 7 bore 24 by appropriate tilting. This tilting is supported by a second or locking spring 14 which is arranged around a peg 11 located in the pressure plate parallel to the axis 3. The peg 11 also serves as detent means for preventing rotation of the actuating lever 12, in that it passes through an appropriate opening in the lever 12. The radially inner end of the lever 12 extends, looking in an axial direction, between the outside diameter region of the diaphragm spring 7 and the pressure plate 4 as far as the ring element 18. For this purpose the ring element 18, as shown in the separate illustration, is provided with a corresponding notch 25.

With the clutch in its withdrawn condition the locking between the clearance-providing device 9 and the bore 24 in the pressure plate 4 is assisted by the spring 21 and the surfaces 20.

The clutch 1 operates as follows. On assembly, with the clutch plate 5 in place and with the clutch in its engaged condition, it is ensured that the head 15 of the clearance -providing device 9 bears against the flywheel 2. The ring element 18 is adjusted in opposition to the force of the spring 21 so that during assembly it has a minimum axial spacing from the radially inner end of the actuating lever 12. After assembly the ring element 18 is released and it turns under the action of the force of the spring 21 until the axial space between the pressure plate 4 and the actuating lever 12 is filled by the ring element 18. In this state the diaphragm spring 7 bears against the edge of the ring element 18 remote from the pressure plate 4 and is spaced from the actuating lever 12. The inclination of the surfaces 20 is chosen to ensure that the force of the diaphragm spring 7 cannot move the spring element 18 circumferentially. When the friction linings 23 wear due to use, the force of the diaphragm spring 7 moves the pressure plate 4 together with the ring elements 18, 18a through the amount of the wear in a direction towards the flywheel 2.

Because of the engagement of the head 15 of the sliding pin 10 against the 8 flywheel 2 the clearance-providing device 9 cannot follow this relative movement of the pressure plate 4 towards the flywheel 2. In this position the frictional clamping between the sliding pin 10 and the bore 24 is relieved by the force of the diaphragm spring 7. A clearance corresponding to the wear of the friction linings 23 thus arises between the radially inner end of the actuating lever 12 and the ring element 18 in the region of the notch 25. On the subsequent withdrawal sequence when the spring tongues 17 are moved towards the flywheel 2 by the withdrawal system and the outer diameter of the diaphragm spring moves in the opposite direction - the force of the spring 21 causes relative rotation of the ring elements 18, 18a about the axis 3. As a result of the inclined surfaces 20 the clearance with respect to the actuating lever 12 is taken up and the lever 12 is once again connected to the pressure plate 4 without any axial clearance. On the next clutch engaging sequence the axial spacing between the radially outer region of the spring 7 and the pressure plate 4 is increased by the amount of the wear that has occurred so that in the engaged state of the clutch the diaphragm spring 7 maintains its original installed position. This ensures that the diaphragm spring 7 always operates in the same force region, the actuating forces are always maintained at the same level and the torque-transmitting capacity of the clutch is substantially constant.

In a modification (not shown) the radially inner end regions of the actuating levers 12 may be arranged so that they engage the face of the diaphragm spring 7 remote from the flywheel 2. The levers 12 then control the compensating movement of the ring element 18 indirectly. In such an arrangement the actuating levers 12 serve simultaneously for the forced releasing movement of the pressure plate 4 during the withdrawal sequence. The remaining functions remain unaltered.

9 In a further modification (not shown) a single ring element 18 is provided. The surfaces which oppose the inclined surfaces 20 can then be arranged either on the pressure plate 4 or on the diaphragm spring 7. The ring elements 18, 18a can be stamped out in a particularly simple manner from sheet metal strip, bent around to form a ring and in the example illustrated can be in the form of an open ring. However, where the guiding diameter 22 is in the form of an external diameter, the ring element 18 is better in the form of a closed ring. The ring element 18 can be made relatively stiff despite its simple construction, so that in most 10 cases it functions as required with a single clearance-providing device 9. In exception cases it might be necessary to provide two circumferentially spaced clearance -prov i ding devices 9.

Claims

1. A friction clutch of the kind set forth in which at least one clearance-providing device is provided, each clearance-providing device being mounted in an axial opening in the pressure plate for axial movement and being adapted to be held by friction in the opening, and including an axial stop secured to the clutch housing to limit movement of the device in a direction towards the flywheel, and an actuating lever acting on part of the automatic adjuster, the arrangement being such that on clutch withdrawal following the occurrence of wear there is an increased axial spacing between the clearance-providing device and the pressure plate which is taken up by operation of the automatic adjuster, the automatic adjuster comprising at least one ring element which is concentric with the axis, engages circumferentially on a guide diameter on the pressure plate, is stiff in an axial direction and has circumferentially spaced inclined surfaces, and a spring means urging the ring element circumferentially to rotate it to increase its axial length.

2. A friction clutch as claimed in claim 1, in which the ring element is guided on its outside diameter, and is circumferentially closed.

3. A friction clutch as claimed in claim 1 or claim 2, in which opposing circumferentially spaced inclined surfaces are arranged on the pressure plate.

4. A friction clutch as claimed in claim 1 or claim 2, in which opposing circumferentially spaced inclined surfaces are arranged on the diaphragm spring.

11

5. A friction clutch as claimed in claim 1 or claim 2, in which opposing circumferentially spaced inclined surfaces are arranged on a second ring element in axial alignment with the first.

6. A friction clutch as claimed in any preceding claim, in which the ring element has a rectangular cross-section, with the longer edge extending axially and guided on the guide diameter on the pressure plate.

7. A friction clutch as claimed in any preceding claim, in which each clearance-providing device is acted on by a locking spring tending to lock the device in the opening in the pressure plate.

8. A friction clutch as claimed in claim 7, in which the locking spring abuts the actuating lever and the pressure plate.

9. A friction clutch as claimed in any preceding claim, in which each clearance-providing device has a setting spring in the region of the opening in the pressure plate acting to urge the clearance-providing device axially.

10. A friction clutch as claimed in claim 9, in which the opening comprises a bore and the clearance-providing device includes a sliding pin extending parallel to the axis and the setting spring is arranged concentrically around the sliding pin and bears against the pressure plate and the sliding pin.

11. A friction clutch as claimed in claim 10, in which the pin has a head providing an abutment for the setting spring.

12 12. A friction clutch as claimed in any preceding claim, in which each clearance-providing device has detent means preventing rotation in the opening, in the form of a peg parallel to the opening and spaced radially from it.

13. A friction clutch as claimed in claim 12 in combination with claim 7 or claim 8, in which the locking spring is arranged concentrically around the peg and urges the actuating lever away from the pressure plate.

14. A friction clutch as claimed in any preceding claim, in which the actuating lever acts indirectly on the part of automatic adjuster.

15. A friction clutch as claimed in any preceding claim, in which the actuating lever extends radially inwards from the opening in the pressure 15 plate.

16. A friction clutch as claimed in any preceding claim, in which the diaphragm spring engages the pressure plate at an outer radial region, and the clutch housing at an intermediate radial region.

17. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in the accompanying drawings.