GB2251052A

GB2251052A - Clutch disc with friction damping

Info

Publication number: GB2251052A
Application number: GB9127009A
Authority: GB
Inventors: Norbert Ament; Harald Raab
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1990-12-19
Filing date: 1991-12-19
Publication date: 1992-06-24
Anticipated expiration: 2011-12-19
Also published as: BR9105474A; GB2251052B; GB9127009D0; ES2051184B1; ES2051184A2; ES2051184R; FR2670853A1; FR2670853B1; DE9017106U1

Abstract

The clutch disc for a friction clutch comprises substantially disc-shaped input parts (7, 8) provided with friction linings (9), a substantially disc-shaped output part (12) provided with a hub (11) and adapted for limited rotation in relation to the input parts (7, 8) and a plurality of damper springs (10) coupling the output part (12) in torsionally elastic manner to the input part (7, 8). Friction means (14, 18, 25) are disposed in the area radially between the damper springs (10) and the axis of rotation (6) and comprise a control disc part (14) coupled to at least one of the damper springs (10) and which together with a friction ring (25) is disposed in the path of force of an axially acting annular spring (18) which is concentric with the axis of rotation (6). The annular spring (18) is disposed axially between the control disc part (14) on the one hand and the input part (7, 8) or output part on the other and forms with one of these parts a metal-on-metal friction element of the friction means. The friction ring (25) is disposed on the side of the control disc part (14) remote from the spring (18) and has a low coefficient of friction. The spring (18) has a mean friction radius (R) greater than the mean friction radius (r) of the friction ring (25). The disc may include an idling damper (Figs 4 and 5) and the input parts (7, 8) and the output part (12) may be reversed (Fig 7). <IMAGE>

Description

A clutch disc with a two-stage friction means The invention relates to a clutch disc for a friction clutch.

For example, known from German Patent Application No. P 29 16 868 is a clutch disc in which a control disc part or control plate permits of a friction force which increases step-wise over the torsion angle, many different component parts participating in the build-up of friction force.

The object of the present invention is to produce a graded friction device having the fewest possible component parts and being of simple construction, this friction device offering a high degree of operational safety and effective life.

This problem is resolved by the features of the main claim. On the one hand, the joint use of an annular spring as the friction element and the provision of a large mean friction radius for this spring with its greater friction value compared with a friction ring of the friction device ensures that it is possible to achieve a sufficiently great jump in friction force in the friction device. In the circumstances, the entire arrangement manages with the minimum of component parts which can be very space-savingly accommodated in an axial direction. By varying the mean friction radii and the friction coefficient of the friction ring, it is very easily possible to vary the differences in friction force to a very great extent.

In order to define the friction side or also the diameter, it is advantageous to have the rings engage via lugs in a peripheral direction and substantially without clearance into corresponding apertures in the disc-shaped part.

In a particularly advantageous way, an undulating spring is suggested for this purpose. It is indeed readily possible to use a plate spring but this must be rotationally rigidly disposed so that its effective friction radius is defined. In addition, the plate spring is more susceptible to wear and tear without additional measures being taken.

The undulating spring is advantageously provided with plane portions in those zones which bear on the disc-like input or output part. By increasing the area of contact through plane portions, it is possible to maintain within very narrow limits the wear and tear on this portion of the undulating spring.

According to a feature of the invention, it is advantageous so to construct the undulating spring that it has plane portions which bear both on the control disc part and also on the disc-shaped input or output part.

Thus, it is possible to provide areas which are defined in respect of both parts and which serve to generate an even friction force and also to limit wear and tear.

It is proposed to provide the undulating spring, in the region of its portions which bear on the disc-like input or output part with lugs extending obliquely in the direction of the disc-shaped part and which engage corresponding apertures in a peripheral direction and in a substantially clearance-free manner. Consequently, on the one hand the undulating spring is definitively fixed and generates its friction force in relation to the control disc part while on the other the lugs project from the plane portions to establish a rotationally rigid connection so that they cannot have any repercussions on the spring properties.

Peripherally, at least twice three plane portions are provided.

A preferred embodiment comprises four plane portions opposite the control disc part and four opposite the disc-like input or output part, the portions on each side being offset to one another by 90 while the portions on both sides are offset to one another by 45 . The result is a very even application of the undulating spring on both sides.

Advantageously, in the case of a preferred clutch disc, its lining carrier is guided axially and radially on the hub via a guide ring and on the opposite side are the friction ring, the control disc part and the undulating spring. The result is a balanced distribution of the component parts between the lining carrier or the cover plate on the one hand and the hub disc on the other.

In the case of another preferred clutch disc, the control disc part, the friction ring and the undulating spring are advantageously parts of a load damper. Thus, the graded friction device only comes into use after passage through the torsion angle for the idling damper so that this latter can if necessary be equipped with its own friction force device.

In the case of a further preferred clutch disc, the friction means, consisting of friction ring, control disc part and undulating spring, may be disposed between the hub and one of the side plates, while a further friction ring is provided between the hub and the other side plate. Where this embodiment is concerned, the hub disc serves as an input part of the torsion vibration damper and the two cover plates with the hub serve as the output part.

The design will be explained in greater detail hereinafter with reference to examples of embodiment which are shown in detail in the accompanying drawings in which: Fig. 1 shows a partially axial longitudinal section through a clutch disc with a lining carrier and a cover plate as the input part; Fig. 2 shows a detail of Fig. 1 with a plate spring for generating the friction force; Fig. 3 is a view and cross-section through an undulating spring as shown in Fig. 1; Figs. 4 and 5 are partly axial longitudinal sections through clutch discs with load and idling damper; Fig. 6 shows a view and a cross-section through an undulating spring in Fig. 5 and Fig. 7 is a partial axial longitudinal section through a clutch disc, in which the hub disc serves as an input part while two cover plates together with a hub serve as the output part.

Fig. 1 shows a partial axial longitudinal section through a clutch disc 1 with a hub 11 disposed concentrically in relation to a common axis of rotation 6 and with a radially outwardly projecting hub disc 12, the said hub 11 being rotationally rigidly fitted by means of internally cut teeth onto a transmission shaft, not shown.

On one side of the hub disc 12 there is one lining carrier 7 which is provided in the region of its outer periphery with friction linings 9. The lining carrier 7 is in the region of its inner periphery axially and radially guided in relation to the hub 11 by a guide ring 13 which is substantially L-shaped in its toroidal cross-section. On the other side of the hub disc 12 is a cover plate 8 which is rotationally rigidly connected and spaced apart from the lining carrier 7 via spacing rivets 36. The spacing rivets 36 pass through corresponding apertures in the hub disc 12. On a middle diameter, in windows both in the hub disc 12 and also in the lining carrier 7 and cover plate 8, there are damping springs 10 which are more or less compressed when torque is applied to the clutch disc.

While this is happening, there is a relative rotation between the lining carrier 7 and the cover plate 8 on the one hand and the hub 11 and hub disc 12 on the other.

In the axial space between the hub disc 12 and the cover plate 8 and radially within the area of the damper springs 10 there is a two-stage friction device. This consists on the one hand of a control disc part 14 the basic body of which is disposed in the indicated space and can be connected via radially outwardly directed projections 15 to one of the damper springs 10.

Furthermore, there may be provided on the control disc part axially angled-over lugs 16 which engage corresponding apertures 17 in the hub disc 12. Both parts 15 and 16 may be provided for the controlled actuation of the control disc part 14. Between the basic body of the control disc part 15 and the hub disc 12 there is a friction ring 25 which has a lower coefficient of friction than metal. Between the control disc part and the cover plate 8 there is an undulating spring 18 which in order to generate a friction force can be installed with an axial initial tension and which, for rotationally rigid connection to the cover plate 8, is provided with extending lugs 20 for which purpose it has appropriate apertures 22.As can also be seen from Fig. 3, the undulating spring 18 is provided with an encircling basic body having distributed over its periphery a plurality of plane portions 24 by which it can bear on the cover plate 8, obliquely radially inwardly extending lugs 20 projecting from these plane areas 24. Thus, the undulating spring 18 has a plurality of flat portions 24 by which it bears on the cover plate 8 to which it is rotationally rigidly connected via the lugs 20. As Fig. 1 shows, the undulating spring 18 has a mean friction radius R which is greater than the mean friction radius r of the friction ring 25.At the same time, the coefficient of friction between the control disc part 14 and the undulating spring 18 - since both parts are of metal - is clearly greater than the coefficient of friction between the control disc part 14 or hub disc 12 and the friction ring 25 which may consist of a synthetic plastics material.

Due to the illustrated disposition and choice of materials, it is thus possible in a first portion of the torsion angle - starting from the inoperative position of the clutch disc - to generate a friction force which is created by a relative movement between lining carrier 7 and control disc part 14 on the one hand and the hub disc 12 on the other, through an interposed guide ring 13 and friction ring 25 and which is low.In this first part of the torsion angle, in fact, the control disc part 14 must be regarded as rotationally rigidly connected to the cover plate 8, since the control disc part must be regarded as a rotationally rigid unit connected to the cover plate 8 via the higher friction force of the undulating spring 18. After a predetermined torsion angle, the control disc part 14 is prevented for instance by its lugs 16 in the apertures 17 from further rotation so that it is therefore held fast in relation to the hub disc 12. Thus the effect of the friction ring 25 is deactivated and the friction between the control disc part 14 and the undulating spring 18 becomes ineffective. The jump in friction force during this transition can be controlled by the differences in the friction coefficient of the participating friction surfaces and by the difference in the mean friction radii r and R.The participating components are simple to produce and are easily fitted and they occupy very little space, particularly in their axial direction.

Fig. 2 shows by way of a detail the friction means in Fig. 1 with a plate spring 39 instead of the undulating spring. Since, now, the plate spring 39 is axially supported with a larger and a smaller diameter, it is vital to provide it with a safeguard against rotation in respect of one of the two parts. In the present case, the safeguard against rotation is, as in Fig. 1, provided by lugs 40 which point radially inwardly and which engage apertures 22 in the cover plate 8 in a substantially rotationally rigid manner. The plate spring 39 in the present instance has its entire outer edge bearing on the control disc plate 14 and counteracts this as a friction element. Thus, in this case the mean friction radius R of the plate spring 39 is established by its outside diameter.

In Fig. 4, a partial section through a clutch disc 2 shows how the previously described friction device can be disposed in the case of a clutch disc with an integrated idling damper 30. A hub disc 26 is so disposed on the hub 11 via a backlash type of tooth system 27 that the idling damper 30 takes effect in the region of reciprocal clearance. When this clearance is exceeded, the load damper comes into effect and the idling damper is bridged. The load damper comprises the cover plate 8 which is rigidly connected to the lining carrier 7, both parts being operatively connected to the hub disc 26 via damper springs 10.Between the hub disc 26 and the lining carrier 7 there is an idling damper 30 the individual parts of which are in principle constructed in the same way as the clutch disc according to Fig. 1, consisting of two cover plates and a hub disc as well as damper springs in windows of both sub-assemblies, a separate friction means also being possibly provided. Between the hub disc 26 and the cover plate 8 is inserted the already explained friction means, consisting of the control disc part 14 with its projections 15 and lugs 16, the undulating spring 18 and the friction ring 25. The lining carrier 7 is thereby guided in respect of the hub 11 by a guide ring 37. Furthermore, a friction ring 28 is provided between the lining carrier 7 and the components of the idling damper 30 which are rotationally rigidly connected to the hub disc 26.The undulating spring corresponds to the embodiment shown in Fig. 3 and by means of projecting lugs 20 it is rotationally rigidly connected to the cover plate 8 by engagement with apertures 22 therein. It exerts an axial force which clamps together all the components which are provided with friction elements. Within the rotary clearance made possible by the backlash type tooth system 27, only the friction device 38 for the idling range together with the friction effect of the guide ring 37 is effective, like the corresponding pre-tensioning force of the springs for the idling damper 30.After compensating for the clearance in the backlash type tooth system 27, the load damper comes into use and this means firstly the friction forces generated by the friction rings 25 and 28, since in this working range the control disc part 14 is still connected to the cover plate 8 by means of the greater friction compared with the undulating spring 18.

Once the portion of the angle of rotation which is relevant to this low friction has been passed through, the control disc part 14 is held fast in relation to the hub disc 26 and the friction jumps to a substantially higher value which is determined by the coefficient of friction between the control disc part 14 and the undulating spring 18 and by the difference between the mean friction radii r and R as in Fig. 1.

Fig. 5 shows a clutch disc 3 which in terms of action corresponds to the clutch disc 2 shown in Fig. 4 in which certainly the idling damper 30 is disposed outside the components of the load damper. The clutch disc 3 corresponds within the scope of its load damper substantially to the construction of clutch disc 1 in Fig.

1, the hub 11 being fitted via a backlash type tooth system 27 on an inner hub 29, which is in turn fitted onto the transmission shaft, not shown. The idling damper 30 is laterally disposed and acts between the two hubs 11 and 29. The load damper comprises an undulating spring 19 a view of and cross-section through which are shown in Fig.

6. In contrast to the undulating spring 18 in Fig. 1, it has radially outwardly projecting lugs 21 which engage corresponding apertures 22 in the lining carrier 7. The other component parts are already described with reference to Fig. 1.

The move of operation of this clutch disc 3 corresponds to that of the clutch disc 2 in Fig. 4.

Certainly, the undulating spring 19 is provided opposite the lining carrier 7 and also opposite the control disc part 14 with flat portions 23, 24 so that a very clearly defined contact of the friction zones is provided in respect of the control disc part 14. These flat portions 23 opposite the control disc part 14 reduce wear and tear at this location since there is a clearly defined surface contact.

Fig. 7 shows a clutch disc 4 in which the principle of the design of the disc-like parts - input part and output part - is changed around in comparison with the embodiment shown in Fig. 1. The two cover plates 32 are connected to the hub 33 rigidly by rivets 35 while the hub disc 31 with the friction linings 9 forms the input part and is guided to be rotatable against the force of the torsion springs 10 and in respect of the hub 33 and the two cover plates 32. Radially within the damper springs 10 between the hub disc 31 and one cover plate 32 there is a friction ring 34 while on the other side there is the friction means consisting of the control disc part 14, the friction ring 25 and the undulating spring 18.

The undulating spring 18 is thereby constructed as shown in Fig. 3 and can in addition to the plane portions 24 on the side of the cover plate 32 still have plane portions 23 on the side of the control disc part. The function corresponds to that already described hitherto, and in this case also after a predetermined angle of rotation has been exceeded, the generation of friction force by the friction ring 25 is cancelled out and instead the friction force is generated by the undulating spring 18 which is larger in keeping with the difference in the coefficients of friction and the difference in the middle friction radius.

Claims

CLAIMS:

1. A clutch disc for a friction clutch, comprising a substantially disc-shaped input part (7, 8, 31) provided with friction linings (9), a substantially disc-shaped output part (12, 32) provided with a hub (11, 33) and adapted for limited rotation relative to the input part (7, 8, 31) and about a common axis of rotation (6), a plurality of damper springs (10) coupling the output part (12, 32) in torsionally elastic manner to the input part (7, 8, 31), and, disposed in an area radially between the damper springs (10) and the axis of rotation (6), friction means (14, 18, 25; 14, 25, 39; 14, 19, 25) which become effective during relative rotation of input part (7, 8, 31) and output part (12, 32) and of which at least one comprises a control disc part (14) coupled to at least one of the damper springs (10) and is disposed, together with a friction ring (25), in the force path of an axially acting annular spring (18, 19, 39) concentric with the axis of rotation (6), characterised in that the annular spring (18, 19, 25) is disposed axially between the control disc part (14) on the one hand and the input part (7, 8) or the output part (32) on the other and forms with one of these parts a metal-to-metal friction element of the friction means (14, 18, 25; 14, 25, 39; 14, 19, 25), and in that the friction ring (25) is disposed on the side of the control disc part (14) remote from the annular spring (18, 19, 25) and has a lower friction coefficient than metal and in that the annular spring (18, 19, 25) has a mean friction radius (R) which is greater than the mean friction radius (r) of the friction ring (25).

2. A clutch disc according to Claim 1, characterised in that the control disc part (14) consists of metal and in that the annular springs (18, 19, 31) and the friction ring (25) bear directly on respectively opposite sides of the control disc part (14).

3. A clutch disc according to Claim 1 or 2, characterised in that the annular spring (18, 19, 39) is biased on that side of the input part (7, 8) or output part (32) which is axially remote from the control disc part (14) and has on this side lugs (20, 21, 40) which in the peripheral direction engage substantially without clearance in apertures (22) in the input part (7, 8) or output part (32j.

4. A clutch disc according to Claim 3, characterised in that the control disc part (14) has lugs (16) which in the peripheral direction engage with clearance in apertures (17) in the input part (7, 8) or output part (32), whichever is not connected to the annular spring (18, 19, 39) by the lugs (20, 21, 40) thereon.

5. A clutch disc according to one of Claims 1 to 4, characterised in that the annular spring is constructed as an undulating spring (18, 19), of which the annular member has, distributed in the peripheral direction, a plurality of plane portions (23, 24) by which the annular member bears on the input part (7, 8) or on the output part (32) on the one hand and/or on the control disc part (14) on the other.

6. A clutch disc according to Claim 5, characterised in that from at least some of the plane portions on the annular member lugs (20, 21) project obliquely to the axis of rotation (6) and engage substantially without clearance in the peripheral direction in apertures (22) in the input part (7, 8) or output part (32).

7. A clutch disc according to Claim 5 or 6, characterised in that distributed in the peripheral direction there are provided on the annular member at least three pairs of alternately successively disposed plane portion (24) bearing on the input part (7, 8) or the output part (32) and a plane portion (23) bearing on the control disc part (14).

8. A clutch disc according to Claim 7, characterised in that four pairs of plane portions (23, 24) are provided all of which are offset by 25 in respect of one another.

9. A clutch disc according to one of Claims 1 to 8, characterised in that the input part has, rigidly connected to each other and disposed at an axial distance from each other and guided for rotation on the hub (11), two side discs (7, 8) of which one (7) forms a friction lining carrier, the output part having a hub disc (12) disposed between the side discs (7, 8), and in that one (7) of the side discs (7, 8), particularly the lining carrier disc, is guided radially on the hub (11) by means of a guide ring (13) and in that the friction ring (25), the control disc part (14) and the axially acting spring (18) is disposed axially between the hub disc (12) and the other (8) of the two side discs.

10. A clutch disc according to one of Claims 1 to 8, characterised in that the input part has a hub disc (31) rotatably guided on the hub (33) while the output part has two side plates (32) rigidly connected to the hub (33) and disposed axially on either side of the hub disc (31), and in that the friction ring (25), the axially acting spring (18) and the control disc part (14) are disposed axially between the hub disc (31) and one of the side discs (32) and in that a further friction ring (34) is disposed between the hub disc (31) and the other of the two side discs (32).

11. A clutch disc according to one of Claims 1 to 10, characterised in that separate damper systems (7, 8, 10, 12, 30) are provided for idling operation and for load operation, each of which comprises damper springs and at least one friction means and in that the control disc part (14), the friction ring (25) and the annular spring (18) are constituent parts of the damper system dimensioned for load operation.

12. A clutch disc substantially as described with reference to Figures 1 and 2, Figures 1 and 3, Figure 4, Figure 5 or Figure 7 of the accompanying drawings.