GB2296541A

GB2296541A - Friction clutch

Info

Publication number: GB2296541A
Application number: GB9526455A
Authority: GB
Inventors: Joachim Lindner; Gunther Esly; Michael Weiss; Heiko Schulz-Andres; Achim Link; Reinhold Weidinger
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1994-12-24
Filing date: 1995-12-22
Publication date: 1996-07-03
Anticipated expiration: 2015-12-22
Also published as: GB2296541B; GB9526455D0

Abstract

A friction clutch (1) has a rotatable clutch housing (3), a pressure plate (6) rotatable with the clutch housing (3) but axially movable, a clutch plate (8) with friction linings, a diaphragm spring (9) urging the pressure plate (6) to clamp the clutch plate (8) to a flywheel, and a withdrawal system. A second spring (14) is arranged in the clutch to apply little or no force in a clutch release direction when the clutch is engaged and an increasing release force with increasing clutch withdrawal travel. The second spring (14) has inwardly extending tongues (21) through which it is connected to the diaphragm spring (9). <IMAGE>

Description

FRICTION CLUTCH The invention relates to a friction clutch of the kind for use in a drive train of a motor vehicle and comprising a clutch housing secured to a flywheel of an internal combustion engine and rotatable with the flywheel 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, a diaphragm spring engaging the pressure plate and the clutch housing and urging the pressure plate towards the flywheel to generate an actuating force and a withdrawal element of a withdrawal system acting on the radially inner region of the diaphragm spring.

DE-C-39 91 022 shows a friction clutch of the kind set forth with an additional spring element acting with increasing wear of the friction linings to oppose the spring force of the diaphragm spring. This affects the increase in spring force, typical in a diaphragm spring in the wear region, so as to make substantially uniform the actuating force exerted by the diaphragm spring. This arrangement cannot reduce the actuating force; it simply ensures that the withdrawal forces exerted by the withdrawal system do not increase.

DE-C-944 050 shows a clutch actuating system in which an auxiliary spring is introduced as an over-centre spring through a number of intermediate levers and pivot points in such a way that a reduction in the actuating force takes place with increasing actuating travel of the clutch pedal. This construction is relatively expensive to manufacture and has a limited possibility of use.

It is an aim of the present invention to produce a reduction in the actuating force in a clutch of the kind set forth using the simplest possible means.

According to the present invention a friction clutch of the kind set forth includes an automatic adjuster for taking up the wear of the friction linings to maintain substantially constant an installed position of the diaphragm spring and the actuating force, and an annular spring member engaging an axially stationary component and another component of an actuating chain between and including the pressure plate and the withdrawal system, the annular spring member being so constructed and arranged to apply little or no force in a clutch release direction when the clutch is engaged, and an increasing release force with increasing clutch withdrawal travel.

The automatic adjuster maintains the installed position of the diaphragm spring and the actuating force while the annular spring member which, with the clutch engaged, applies little or no release force and with increasing withdrawal travel applies an increasing release force, allows an optimum association of the characteristic of the annular spring member with the characteristic of the diaphragm spring. This results in an effective reduction in the actuating force within the range of the withdrawal travel. The annular spring member can be arranged at any point in the actuating chain. It may be a diaphragm spring or a plate spring.

Preferably the annular spring member comprises a spring body having radially inwardly extending tongues, the spring body engaging the clutch housing in the region of its outside diameter, and the tongues acting on faces of spring tongues of the diaphragm spring remote from the pressure plate. This construction and arrangement of the annular spring member provides both easy assembly and also the possibility of undertaking an exact tuning or matching of the spring forces.

To secure the annular spring member, with the clutch in its engaged condition, against snapping over as a consequence of passing through zero or the neutral position, it is proposed to provide the annular spring member with individual tongues extending radially outwards from the spring body and engaging the diaphragm spring. In this way, the annular spring member is held in a simple manner in permanent engagement with the diaphragm spring and cannot lift away from the diaphragm spring with the clutch in its engaged condition, for example as a result of variations in tolerances.

Where the diaphragm spring is secured radially by a plurality of spacer pins arranged in the clutch housing concentric with the axis, the annular spring member can also be retained in the region outside its outside diameter by means of the spacer pins, both radially and axially, and preferably it has a plurality of noses, each being arranged circumferentially between two adjacent tongues of the annular spring member, and being hooked into stepped openings in corresponding spring tongues of the diaphragm spring. The annular spring member can therefore be secured in position in relation to the spring tongues of the diaphragm spring, without any additional components.

The openings in the spring tongues of the diaphragm spring are preferably formed by widened-out portions of the slots between two respective spring tongues of the diaphragm spring.

The assembly of the annular spring member and the diaphragm spring is achieved by resilient comical deformation of one or both springs, and in the assembled condition a mechanical inter-engagement of their shapes prevents separation. Assembly in this way is very simple.

Where the diaphragm spring is secured in the clutch housing by a plurality of spacer pins concentric with the axis, it is proposed that at least one tongue of the annular spring member should be held in engagement against the spring tongues of the diaphragm spring by a separate component. The withdrawal thrust race of the withdrawal system can be used as the separate component, if at least one tongue of the annular spring is extended radially inwards so far that it is clamped axially between the spring tongues of the diaphragm spring and the withdrawal thrust race. This means that the withdrawal thrust race, which is already present, can be made of use for locating the annular spring member.

Alternatively, at least one tongue of the annular spring member may be riveted to a corresponding spring tongue of the diaphragm spring.

Such a construction is easily achieved, and is flexible in use, as the most suitable point can be used for the riveting.

Alternatively the separate component may comprise a ring concentric with the axis and so constructed and arranged that it holds the tongues of the annular spring member in engagement with the spring tongues of the diaphragm spring.

In one embodiment the body of the ring engages the side of the tongues of the annular spring member remote from the spring tongues of the diaphragm spring and has axially extending arms passing through slots between the spring tongues of the diaphragm spring, the arms being staked on their rear faces. In this construction all the tongues can be secured using one component.

Alternatively the body of the ring may comprise an axially resilient wavy disc which engages the spring tongues of the diaphragm spring on the sides remote from the annular spring member and has axially directed arms extending through slots between the spring tongues of the diaphragm spring and radially outwardly bent lugs engaging over at least one tongue of the annular spring member, which are arranged so that they overlie the slots circumferentially. This construction ensures that relative movements between the tongues and the spring tongues can be handled, by means of the axially resilient action of the wavy disc.

Various embodiments of the invention are illustrated by way of example in the accompanying drawings, in which: Figure 1 is a longitudinal section through the friction clutch; and Figures 2 to 8 show variants of the spring for assisting the withdrawal force.

Figure 1 shows a friction clutch 1, of which the construction is known in principle for use in a motor vehicle. Thus a clutch housing 3 is rigidly attached to a flywheel (not shown) of an internal combustion engine and is rotatable with the flywheel about an axis 5. A pressure plate 6 is rotatable with the clutch housing 3 but is axially movable. A diaphragm spring 9 is located in the housing 3, and in the engaged position of the clutch applies an actuating force A to the pressure plate 6 so that the clutch plate 8 with its friction linings is clamped between the flywheel and the pressure plate 6 with the actuating force A. The diaphragm spring 9 engages in the region of its outer periphery against the pressure plate 6 and in the region of an intermediate diameter it engages against the clutch housing 3 through a number of circumferentially spaced spacer pins 16.Radially inwards of this the diaphragm spring 9 is provided with individually circumferentially spaced spring tongues 11 engaged by a withdrawal system, not shown. The clutch 1 is a so-called push-to-release clutch, in which the withdrawal system pushes the spring tongues 11 to withdraw the clutch. Between the outside diameter region of the spring 9 and the pressure plate 6 there is an automatic wear adjuster 12 for the friction linings.The adjuster 12 includes adjusting element 13 which, when wear occurs in the friction linings on the clutch plate 8, ensure that on displacement of the pressure plate 6 in the direction of arrow A with wear, the spacing between the pressure plate 6 and the radially outer region of the spring 9 is increased, dependant on the wear, so that over the entire working life of the friction linings on the clutch plate 8 the spring 9 can apply a constant actuating force A to the pressure plate 6. A more detailed description of the adjuster 12 will not be provided here as there are various embodiments of it, such as can be seen for example in DE-A-35 18 781. the clutch 1 also has an annular spring member, such as a diaphragm spring or plate 14 which acts to reduce the forces applied for withdrawal of the clutch.This diaphragm or plate spring 14 is so constructed and arranged that with the clutch 1 in the engaged position illustrated it exerts little or no release force on the spring 9. On increasing withdrawal movement - that is a movement of the spring tongues 11 of the spring 9 in the direction of the arrow A and a movement of the radially outer edge of the spring 9 in the opposite direction - the diaphragm or plate spring 14 exerts an increasingly large withdrawal force on the diaphragm spring 9 so that the actuating forces for the clutch 1 can be significantly reduced.

The spring characteristics of the springs 9, 14 are arranged so that the neutral point of the spring 14 is when the clutch is engaged, rather than at a position in the withdrawal travel. However, as the characteristics of mass-produced springs of this kind vary, there could be combinations of springs in which the neutral point is in the withdrawal travel. The diaphragm or plate spring 14 would then snap over with the clutch in the engaged condition and would be inoperative. For this reason the spring 14 in Figure 1 is arranged so that it cannot snap over into its inoperative state, as it is held in the region of its radially outer diameter by the housing 3 and at its radially inner diameter by spring tongues 11 of the diaphragm spring 9.The spring 14 engages in the region of its outside diameter in a recess 19 formed between the inside of the clutch housing 3 and a corresponding edge on the individual spacer pins 16. The recess 19 corresponds substantially to the thickness of the material of the spring 14. The radially inner diameter of the spring 14 has a circumferential engaging region 20 by which it engages the outer (front) face of the spring tongues 11. The spring 14 has individual retaining elements 21 integral with the spring 14, each of which extends into a circumferential gap between two spring tongues 11 and engages behind a respective spring tongue. In this way the spring 14 cannot reach its inoperative state and on every withdrawal sequence it will augment the withdrawal force with increasing spring force. The retaining elements 21 may be separate from the spring 14 if required.

Figure 2 shows a section through the diaphragm spring 9 of Figure 1 with a modified annular spring 30, which may be a diaphragm or plate spring. The two springs 9, 30 are connected in the region of radially inwardly projecting tongues 41 of the spring 30 by a separate component 49. The component 49 comprises a ring which can be produced from a sheet metal strip. The ring is arranged concentric with the axis and engages the side of the tongues 41 remote from the spring tongues 11 of the diaphragm spring 9. The ring 49 also has axially extending arms 51 which pass through slots 35 between the spring tongues 11, and are bent over or staked on the rear faces of the spring tongues 11. The ring component 49, as illustrated in the section A-A, holds the spring tongues 11 and the tongues 41 in mutual axial engagement.The ring component 49 has a body 50 which is stamped out of a continuous strip and bent round to form a ring.

A modification of Figure 2 is shown in Figure 3. In Figure 3 a ring component 52 similar to a wavy spring is provided. The ring 52 has a body 53 comprising a ring concentric with the axis and having spring characteristics formed by axial peaks and troughs. A plurality of circumferentially spaced arms 54 are formed from the body 53 and extend radially through the slots 35 in the spring tongues 11, and are radially outwardly bent over on the side adjacent the diaphragm or plate spring 30.

These bent over lugs hold the tongues 41 of the spring 30 in their relative position with respect to the diaphragm spring 9, the tongues 41 being so constructed and arranged that they circumferentially overlie respective slots between the spring tongues 11. The resilient nature of the ring component 52 means that relative movements between the spring tongues 11 and the tongues 41 are possible.

Figure 4 shows a further modification, in which the tongues 41 on the spring 30 are secured by rivets 55 which are inserted in the spring tongues 11 of the diaphragm spring 9. Not all the spring tongues 11 need to be provided with a rivet 55 but individual rivets 55 are sufficient.

Figure 5 shows a further modification in which a diaphragm or plate spring 38 is provided, in addition to the radially inwardly extending tongues 41, with one or more radially outwardly extending tongues 41 which engage against the body of the diaphragm spring 9. The spring 38 is therefore held in permanent engagement against the diaphragm spring 9 without additional components, and over the whole range of deflection of the diaphragm spring 9.

In a modification of Figure 6 an existing component is also used to hold the diaphragm or plate spring 39 in position with respect to the diaphragm spring 9. Tongues 43 extending radially inwards from the body of the spring 39 are provided with extensions which project between the spring tongues 11 of the diaphragm spring 9 and the withdrawal bearing or thrust race 28 of the withdrawal system 27. The spring 39 is therefore secured in position in relation to the diaphragm spring 9 in all operating conditions.

Figures 7 and 8 show further modifications. The central part of Figure 7 shows a section through the upper half of a friction clutch with clutch housing 3, diaphragm spring 9 and spacer pins 16 which hold the spring 9 fixed. A diaphragm or plate spring 36 is arranged between radially inwardly projecting spring tongues 11 of the diaphragm spring 9 and the clutch housing 3. The spring 36 has a spring body 44 and inwardly extending tongues 41. The spring 36 is axially and radially fixed by the outside diameter of its spring body 44 on the clutch housing 3 and on the spacer pins 16. The spring body extends radially inwards and merges into the tongues 41 which, in the engaged position shown in the drawing, engage from outside against the spring tongues 11 of the diaphragm spring 9. The left hand part shows a portion of the diaphragm spring 9 viewed from the spring 36. The spring 36 has, circumferentially between each two adjacent tongues 41, one or more noses 45 each of which projects through a slot 35 between two circumferentially adjacent spring tongues 11 of the diaphragm spring 9 and is hooked into a stepped opening 47 in the spring tongue 11. The circumferential extent of each nose 45 is matched to the opening 47 and in the installed condition they engage behind the steps between the openings 47 and the slot 35. The assembly of the spring 36 and the diaphragm spring 9 is shown in the right hand part of Figure 7, in which one or both of the two springs 9, 36 are brought into a conical position (e.g. an unstressed position), so that the noses 45 can be threaded into the openings 47.This produces, in the assembled condition, a mechanical interengagement between the two springs so that with the clutch in the engaged state the spring 36 cannot snap inadvertently into its inoperative state.

Figure 11 shows another modification. In Figure 11 the diaphragm or plate spring 37 is similar to the spring 36 of Figure 10, and is installed with its spring body 44 and the radially inwardly projecting tongues 41 between the diaphragm spring 9 and the clutch housing 3 and is fixed by the spacer pins (not shown). In contrast to Figure 10 openings 48 in the spring tongues 11 of the diaphragm spring 9 have a minimum radial extent and the end regions of noses 46 on the spring 37 are matched to the openings 48, whilst the region connecting the tongues 41 to the spring body 44 is matched to the slot 35 between two circumferentially adjacent spring tongues 11. For assembly the noses 46 are inserted through the openings 48, and then in the assembled condition they are moved radially outwards so that they are hooked behind the slot 35 radially outwards of the openings 48. The operation of this arrangement corresponds to that of Figure 10.

Claims

1. A friction clutch of the kind set forth, including an automatic adjuster for taking up the wear of the friction linings to maintain substantially constant an installed position of the diaphragm spring and the actuating force, and an annular spring member engaging an axially stationary component and another component of an actuating chain between and including the pressure plate and the withdrawal system, the annular spring member being so constructed and arranged to apply little or no force in a clutch release direction when the clutch is engaged, and an increasing release force with increasing clutch withdrawal travel.

2. A friction clutch as claimed in Claim 1, in which the annular spring member comprises a spring body with radially inwardly extending tongues, the spring body engaging the clutch housing in the region of its outside diameter and the tongues acting on faces of spring tongues of the diaphragm spring remote from the pressure plate.

3. A friction clutch as claimed in Claim 2, in which the annular spring member has individual tongues extending radially outwards from the spring body and engaging the diaphragm spring.

4. A friction clutch as claimed in Claim 2, in which the diaphragm spring is secured by a plurality of spacer pins arranged in the clutch housing concentric with the axis, and the annular spring member is retained axially in the region of its outside diameter between the clutch housing and the spacer pins and has a plurality of noses, each being arranged circumferentially between two adjacent tongues of the annular spring member and being hooked into stepped openings in corresponding spring tongues of the diaphragm spring.

5. A friction clutch as claimed in Claim 4, in which the openings are formed by widened-out portions of the slots between two respective spring tongues of the diaphragm spring.

6. A friction clutch as claimed in Claim 4 or Claim 5, in which assembly of the annular spring member and the diaphragm spring is achieved by resilient conical deformation of one or both springs and in the assembled condition, a mechanical inter-engagement of their shapes prevents separation.

7. A friction clutch as claimed in Claim 2, in which the diaphragm spring is secured in the clutch housing by a plurality of spacer pins concentric with the axis, and at least one tongue of the annular spring member is held in engagement with the spring tongues of the diaphragm spring by a separate component.

8. A friction clutch as claimed in Claim 7, in which at least one tongue of the annular spring member is extended radially inwards so far that it is clamped axially between the spring tongues of the diaphragm spring and a withdrawal thrust race of the withdrawal system.

9. A friction clutch as claimed in Claim 7, in which at least one tongue of the annular spring member is riveted to a corresponding spring tongue of the diaphragm spring.

10. A friction clutch as claimed in Claim 7, in which the separate component comprises a ring concentric with the axis and so constructed and arranged that it holds the tongues of the annular spring member in engagement with the spring tongues of the diaphragm spring.

11. A friction clutch as claimed in Claim 10, in which the body of the ring engages the side of the tongues of the annular spring member remote from the spring tongues of the diaphragm spring, and has axially extending arms passing through slots between the spring tongues of the diaphragm spring, the arms being staked on their rear faces.

12. A friction clutch as claimed in Claim 10, in which the body of the ring comprises an axially resilient wavy disc which engages against the spring tongues of the diaphragm spring on the sides remote from the annular spring member, and has axially directed arms extending through slots between the spring tongues of the diaphragm spring, and radially outwardly bent lugs engaging over at least on tongue of the annular spring member, which are arranged so that they overlie the slots circumferentially.

13. A friction clutch as claimed in any preceding claim, in which the annular spring member comprises a diaphragm spring.

14. A friction clutch as claimed in any of claims 1 to 12, in which the annular spring member comprises a plate spring.

15. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

16. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 2 of the accompanying drawings.

17. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 3 of the accompanying drawings.

18. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.

19. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 5 of the accompanying drawings.

20. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 6 of the accompanying drawings.

21. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 7 of the accompanying drawings.

22. A friction clutch of the kind set forth substantially as described herein with reference to and as illustrated in Figure 8 of the accompanying drawings.