GB2045380A

GB2045380A - Clutch release bearing assembly

Info

Publication number: GB2045380A
Application number: GB8005107A
Authority: GB
Original assignee: SKF Compagnie dApplications Mecaniques SA
Current assignee: SKF Compagnie dApplications Mecaniques SA
Priority date: 1979-03-29
Filing date: 1980-02-14
Publication date: 1980-10-29
Also published as: JPH0129288Y2; JPS55140129U; ES489960A1; FR2452633B1; IT8067351A0; DE3012215A1; DE3012215C2; FR2452633A1; GB2045380B; IT1129405B; BR8001921A

Abstract

A clutch release bearing assembly comprises a composite guide sleeve 19 in the form of an annular metal disc-like part 20 which is surface hardened and on to which is moulded a cylindrical part 18 made of filled plastics material. A resilient self- aligning action of the assembly is ensured by an elastomeric sleeve 16 which comprises a number of radial ribs 17 which are in contact with the outer surface of the guide sleeve 19. The outer surface of the sleeve 16 carries the inner ring 1 of a ball bearing 4 and the outer ring 10 of the bearing acts on the clutch to disengage it. The plastics part 18 ensures that the assembly can slide freely on a guide tube 13 while the hardened metal part 20 takes the thrust from a clutch operating fork and resists wear. The part 20 also helps, by its contact with the fork, to hold the axis of the assembly parallel to the axis of the guide tube 13 and prevent the assembly from rocking when it is operated. <IMAGE>

Description

SPECIFICATION Clutch withdrawal bearing assembly This invention relates to clutch withdrawal bearing assemblies having resilient self-aligning guiding means for use with plate clutches and particularly diaphragm clutches.

The assembly comprises a rolling contact bearing, for example a ball bearing, resilient means for effecting self-alignment of the bearing with the clutch and a guide sleeve which in use, slides on a tubular guide. The resilient selfalignment means permits radial displacement of the assembly and, in particular, of the bearing ring which is in contact with the diaphragm or other clutch operating member, to produce a selfaligning action radially of the bearing relative to the diaphragm or other member each time the clutch is disengaged.

In such clutch withdrawal bearing assemblies, one of the two rings of the bearing transmits the force which is applied to effect clutch disengagement, by moving into a position in which it bears directly against the diaphragm or other member, or by remaining in continuous contact with the diaphragm or other member, while the other bearing ring receives a thrust from a clutch disengaging fork or other clutch operating mechanism. The bearing ring which comes into contact with or which remains in contact with, the diaphragm or other member, for example the outer ring of the bearing has a contact surface which is of generally annular shape. The assembly is not precisely centred on the tubular guide, nor is it in perfect alignment with respect to the axis of rotation of the diaphragm or other member of the clutch.Further, the geometrical axis of the clutch diaphragm, its axis of rotation, and the axis of the tubular guide or of a gearbox input shaft do not always exactly coincide with one another, which makes it still more necessary to make provision for radial movement of the withdrawal bearing at the time of each clutch disengaging operation.

In existing clutch withdrawal bearing assemblies, which are self-aligning, resilient elements, the shape of which may vary, are inserted between one of the bearing rings and the tubular guide. Thus, in our French Patent Application No. 75 21447, the bearing assembly comprises a resilient sleeve which is provided with radial ribs which come into direct contact with the tubular guide and are constructed in such a way as to impart at the same time the rigidity and flexibility which are required for correct and repeated operation of the withdrawal bearing when the clutch is being operated.

It has already been proposed, in order to prevent any rocking movement of the bearing when clutch disengagement takes place, as such rocking movement would result in premature wear of the contact surface of the diaphragm, in our French Patent Application No. 77 09095 to incorporate, in a clutch withdrawal bearing assembly, guide means which are constituted by a guide sleeve which is made of a rigid material, preferably metallic, which, in use extends at least partially between the inner bearing ring and the tubular guide.

In this assembly, and also in other self-aligning clutch withdrawal bearing assemblies in which the resilient means lie between one of the bearing rings and a metal guide bushing (such as are described in French Patent 73 43651), operation of the bearing assembly is not satisfactory owing to friction between the metal guide sleeve and the tubular guide during each disengagement of the clutch.

The object of the present invention is to provide a clutch withdrawal bearing assembly having a resilient guided self-aligning action and comprising a guide sleeve, in which rocking movement during clutch disengagement is avoided and in which also better operation of the bearing is effected by a reduction in friction occurring during axial movement of the bearing assembly on the tubular guide.

To this end, according to this invention, we provide a clutch withdrawal bearing assembly, which is adapted to be guided on a cylindrical tubular guide and has means to enable-it to be self-aligning of the guide, the assembly comprising a rolling contact bearing having inner and outer thin-walled bearing rings, a rigid guide sleeve extending at least partially inside the inner bearing ring and, in use, between this ring and the guide on which it is a sliding fit, and resilient means permitting the self-alignment of the assembly, wherein the guide sleeve is formed by two separate parts, which are fixed relative to one another, the first part being of generally cylindrical shape and, in use, surrounding and sliding on the tubular guide to effect guidance of the assembly on the tubular guide with a low frictional drag, and the second part being of generally annular shape and serving, in use, to maintain parallelism between the axis of the assembly and the axis of the tubular guide and also acting to transmit force applied by a clutch operating member to the bearing, and wherein the resilient means is formed by a resilient sleeve positioned between the inner bearing ring and the outer surface of the first part of the guide sleeve.

The second, annular part is conveniently shaped as a substantially flat disc lying in a plane normal to the axis of the assembly and in contact with a radially extending portion of one of the rings of the bearing.

With a view to facilitating the self-aligning action each time the assembly is operated, the resilient sleeve preferably comprises a number of ribs extending parallel to the axis of the assembly.

These ribs may come into direct contact with the tubular guide, preferably through suitable openings formed in the first, cylindrical part of the guide sleeve. In other embodiments, the ribs of the resilient sleeve may come into contact with the outer surface of the first, cylindrical part of the guide sleeve. These two embodiments may be combined by providing two sets of ribs, some of these ribs come, in use, into direct contact with the tubular guide and the other ribs come into contact with the outer surface of the first, cylindrical part of the guide sleeve. In all these embodiments the ribs of the resilient sleeve are preferably inclined relative to the radial direction and their profile tapers from the sleeve to the free edges of the ribs in such a way as to facilitate their deformation during clutch disengagement operations.

The two parts, which together form the guide sleeve, can be locked together by any suitable means subject to the proviso that a right-angled relationship can be maintained between the axis of the first cylindrical part and the plane of the second flat disc-like annular part of the composite guide sleeve.

In the first embodiment, the second, annular part is locked to the first, cylindrical part by moulding the plastics material of which the first cylindrical part is preferably made to the metal of which the second, annular part is preferably made.

In a modification of this embodiment, the annular part is locked to the cylindrical part by snap-engaging an inner circular edge of the annular part in a circular recess formed in one of the ends of the cylindrical part. To ensure that the right-angled relationship of the annular part is preserved, the above-mentioned recess is preferably defined, on its side adjacent the bearing, by an annular support edge or rim.

In a further modification the annular part is locked to the cylindrical part by means of a bayonet joint. For this reason projecting tongues are provided on the edge of the first, cylindrical part and these tongues co-operate with radial tongues or projections formed on the inner edge of the second, annular part. The cylindrical part may comprise a resilient locking tab, which cooperates with a notch formed on the inner edge of the annular part for the purpose of holding the annular part angularly in position after the rotary movement for engaging the bayonet joint has taken place.

In another embodiment the annular part which is preferably made of smooth sheet metal, is locked to the cylindrical part by screwing it on to a screwthread on the cylindrical part.

In all the embodiments, the cylindrical part of the guide sleeve is preferably made of plastics material, preferably filled or reinforced plastics material, which has a low coefficient of friction with respect to the tubular guide. The second, annular part is preferably constituted by a flat metal disc which is preferably surface hardened.

In one practical embodiment of the invention, the means used for attachment of the member required for operation of the clutch withdrawal bearing assembly is provided directly on the second annular part. Otherwise the attachment means are formed as appendages on one of the bearing rings of the bearing as is usually the case in clutch withdrawal bearing assemblies.

A number of examples of clutch withdrawal bearing assemblies in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a longitudinal sectional view of a first example; Figure 2 is a longitudinal sectional view of a second example; Figure 3 is a cross-section taken along the line Ill-IllofFigure 1; Figure 4 is a cross-section taken along the line IV--IV of Figure 2; Figure 5 is a longitudinal section of a third example in which two elements of a guide sleeve are connected together by a bayonet joint; Figure 6 is an end elevation of the example shown in Figure 5; and, Figure 7 is a cross-sectional detail taken along the line VIl-VIl of Figure 6.

As seen in Figures 1 and 3, the clutch withdrawal or release bearing assembly comprises an inner bearing ring or race 1, which has a thin wall and is formed by flanging a sheet metal element or tube, and has a tubular portion 2 and an annular raceway 3 for a set of bearing balls 4.

In this example the tubular portion 2 of the ring 1 is outwardly extended by way of a radial flange 5, which in its turn is axially extended in the form of two lugs 6 extending parallel to the axis of the release bearing and each comprising an opening 7, which can co-operate with a rod which holds a control fork, used for operating the withdrawal bearing assembly. The control fork is not shown in the drawings. It will of course be understood that other means may be used for attachment of the control fork.

The ball bearing of the assembly is completed by an outer bearing ring or race 10, which is also in the form of a thin walled tube and is formed by flanging a sheet metal tube. The outer ring 1 D comprises an annular portion 11 which, in use, comes into contact with the surface of a clutch diaphragm (not shown in the drawings) when the bearing assembly is moved longitudinally along a tubular guide 13, which is shown in chain-dotted lines in Figure 1 and inside which a gearbox input shaft rotates. The bearing balls are held in place by a retaining cage 14, and the bearing is protected buy a cheek plate 15.

A sleeve 16, which is made of resilient material e.g. an elastomer or natural rubber, is positioned within the tubular part 2 of the inner ring 1. The resilient sleeve 16 comprises a number of ribs 17, which lie parallel to the axis of the assembly and are inwardly directed. As seen in Figure 3, the ribs 1 7 are slightly inclined with respect to the radial direction. The profile of the ribs 1 7 tapers in the direction from the sleeve 1 6 towards the free edges of the ribs 1 7. As can be seen in Figure 1, the ribs 1 7 have parallel bevels at their two ends 17a, 17b.

The free ends of the ribs 1 7 are in contact with part of the outer surface of a cylindrical part 18 of a composite rigid guide sleeve, generally designated as 1 9. The cylindrical part 1 8 is made of moulded and filled rigid plastics material. In this way a cylindrical surface is obtained in sliding contact with the outer surface of the tubular guide 1 3. The frictional force entailed in this sliding contact is low, while at the same time the longitudinal movement of the assembly is given correct guidance during each operation to disengage the clutch and rocking movement of the assembly is avoided.

The guide sleeve 1 9 is completed by a second part 20 of annular shape and in the form of a plane disc. The part 20 is in contact with the radial flange 5 of the inner ring 1. The first, cylindrical part 18 and the second, annular part 20, which together constitute the composite guide sleeve 19, are locked together by moulding the part 1 8 of plastics material, on to the metal disc-like part 20.

The part 20, which is preferably surface-hardened, has an inner, circular edge 21 which is bent over in the direction of the bearing and is insert moulded into an annular bead 22 formed at one of the ends of the cylindrical part 18, substantially opposite the radial flange 5 of the inner bearing ring 1. The bead 22, the outer diameter of which is greater than that of the cylindrical part 18, is used for ensuring the correct positioning of the part 20, and also ensures that a strictly right-angled positional relationship is maintained between the part 20 and the axis of the tubular guide 13. Due to the presence of the bead 22, with its conical inner surface 22a, the adjacent ends of the ribs 1 7 are bevelled as indicated at 1 7b.To ensure that the provision of this bevel will not reduce the total supporting length of each rib 1 7, a parallel and identical bevel 17a is also provided, as has been mentioned, at the other end of each rib 1 7.

The cylindrical part 1 8 comprises, at its end remote from the end receiving the annular part 20, studs 23, which are distributed equidistantly around its periphery and project radially outwardly beyond the internal surface of the inner bearing ring 1. However, there is a slight clearance between the studs 23 and the peripheral edge of the inner bearing ring 1. In this way it is possible to prevent the guide bush 19 from becoming accidentally dislodged, after it has been fitted in position by a resilient snap engagement of the studs 23 within the ring 1.

When an assembly constructed as illustrated in Figure 1, is brought into operation, the mechanism controlling the assembly, that is to say the control fork which, as has already been mentioned, is held by a retaining rod, which co-operates with the openings 7 in the lugs 6, comes into contact with the outer surface of the annular part 20, which has been surface hardened. Under the thrust of the control fork, used for effecting clutch disengagement, on the annular element 20, the guide sleeve 19 slides along the tubular guide 13 and carries with it, by way of the inner bearing ring 1, the ball bearing of the assembly. The annular portion 11 of the outer bearing ring 10 acts on the diaphragm, and initiates the operation of clutch disengagement.When clutch disengagement is carried out, the bearing undergoes the required self-alignment by moving radially relative to the axis of the tubular guide 13. This radial movement is possible due to the deformation of the ribs 1 7 of the resilient sleeve 16, the bearing of the assembly shifting radially relative to the guide sleeve 19.

The guide sleeve 19, which is of composite construction and is formed by assembling the first part 18, of generally cylindrical shape, and the second part 20, which is of generally annular shape, not only ensures guidance on the guide 1 3 with little friction, account being taken of the material of which the cylindrical part 1 8 is made, this being selectable, but also ensures the required parallelism between the axis of the bearing and the axis of the tubular guide. The guide sleeve 1 9 also effects transmission of the force applied by the clutch control member due to the provision of the second, annular element 20, which has a high degree of hardness.Thus, the fact that the guide sleeve 1 9 is composed of two parts enables the two functions to be performed by this guide sleeve to be separated, and enables each of these parts to be excellently adapted to the function which it is intended to fulfil.

The example illustrated in Figure 2 is a modification of the assembly illustrated in Figure 1. As seen in Figures 2 and 4, in which components identical to those shown in the example of Figure 1 have the same reference numerals, a resilient sleeve 24 is fitted inside the inner ring 1. It may be held inside the ring 1 by any means, such as by sticking it in place with an adhesive, by moulding the sleeve 24 inside the ring 1, or by press fitting the sleeve 24 inside the inner ring 1. The sleeve 24 has a portion 24a which lies adjacent a cylindrical portion 2 of the inner ring 1 and is provided with a number of ribs 25 which are of the same shape as the ribs 17 of the example shown in Figure 1.Further, the resilient sleeve 24 has an additional portion 24b which lies substantially adjacent the raceway 3 and extends as far as the edge of the inner ring 1.

The additional portion 24b may even extend a short distance beyond the edge of the inner ring 1.

The additional portion 24b of the resilient sleeve 24 comprises a radial flange 24c by means of which the resilient sleeve 24 is reliably fixed in position axially in the ring 1. The portion 24b of the resilient sleeve 24 has a number of ribs 26 which, like the ribs 25, have a profile which tapers from the base towards the free edge. The ribs 26, which are also parallel to the axis of the guide tube 13, are arranged in groups, which are separated by portions free of ribs; this is clear from Figure 4.

It will be observed that, again, the ribs 26 are inclined with respect to the radial direction, as are the ribs 25.

In the example shown in Figure 2, the composite guide sleeve 27 comprises an annular part 20 on to which is moulded, through a bead 22, a cylindrical part 28 which has a number of openings 29 registering with the groups of ribs 26 in such a way that these ribs 26 pass through the openings and can come into direct contact with the outer surface of the tubular guide 13.

Thus, in this example, the resilient self-aligning means of the sleeve 24 are constituted, firstly by a first series of ribs 25 which lie at regular intervals around the inner periphery of the resilient sleeve 24 and come into contact with the outer surface of the cylindrical part 28 of the guide sleeve 27 and, secondly, a number of groups of ribs 26 which come into direct contact with the outer surface of the tubular guide 13.

In this example, it is ensured that the guide sleeve 27 cannot become dislodged from the other parts of the assembly owing to the provision of the openings 29 and the ribs 26. The operation of the example illustrated in Figure 2 is identical to that of the example shown in Figure 1.

The example shown in Figures 5 to 7 is a modification of the assemblies illustrated in Figures 1 and 2. In this example, in which the same components are given the same reference numerals, a composite guide sleeve 30 comprises an annular part 31 , which is shaped from sheet metal and is locked, through a bayonet joint to a cylindrical part 32 which is made of plastics material. To this end one of the ends of the cylindrical element 32 has, in this example, four tongues 33, each of which is in the form a radial projecting portion defining a circular recess 34 with an edge 35 defining a radial supporting surface, extending outwardly, and having an outer diameter which is greater than the outer diameter of the cylindrical portion of the part 32. The inner, circular edge 37 of the annular part 31 has four radial tongues 36.The portions of the inner, circular edge 37 lying between these tongues 36 are of an inner diameter which is the same as the outer diameter of the tongues 33. Accordingly, and it is apparent from Figure 6, the annular part 31 can be introduced into the recess 34 and can then be rotated relative to the cylindrical part 32 so as to lock the annular element 31 inside the recess 34 due to co-operation between the tongues 33 and the tongues or projections 36.

The right-angled relationship to the axis of the assembly of the plane of the annular part 31, which comes into contact with the radial flange 5, is ensured by the radial supporting surface of the edge 35.

In order to lock the annular part 31 relative to the cylindrical part 32, in the position shown in Figure 6, the cylindrical part 32 also comprises a resilient locking tab 38, which is formed by moulding and co-operates with a notch 39 formed in each of the tongues or projections 36. The provision of a notch 39 in each of the tongues 36 ensures that the required locking action can be effected, by means of the tongue 38, in any position of the annular part 31.

In the example shown in Figure 5, the resilient, self-aligning means are constituted by a resilient sleeve 40 which is secured, by any suitable means, within the inner bearing ring 1. The resilient sleeve 40 comprises a number of ribs 41, which are of the same general shape as the ribs 17 of the example of Figure 1, and come into contact with the outer surface of the cylindrical part 32 of the composite guide sleeve 30. The resilient sleeve 40 has an end bead 42, which engages round the end edge of the inner ring 1, and reduces the clearance, so as to afford a certain measure of protection to the ball bearing through preventing any penetration of contaminants between the inner bearing ring 1 and the outer bearing ring 10.Similarly, in all the examples shown in Figures 2 to 6, the resilient sleeve 20 or 40 can be provided with an extended portion which is not shown and which extends close to the bore of the outer bearing ring 10, only a small clearance being provided for the purpose of preventing penetration of contaminants.

The end of the cylindrical part 32 has an annular rim 43, which is provided to ensure that the guide sleeve 30 will not become accidentally dislodged from the resilient sleeve 40.

In the examples of Figures 1 and 2 the attachment means for the member used for operating the clutch withdrawal bearing assembly are provided on two mutually diametrically opposed lugs which are integral with the inner ring of the bearing. In distinction to this in the example of Figure 5, the attachment means are directly carried by the annular part 31 of the composite guide sleeve 30. For this purpose, the annular element 31 comprises two diametrically opposed flanges 44 which are bent over axially and are provided with openings 45 by means of which the operating member can be secured in place and which, as in the preceding example assumes a position in which it bears against the outer surface of the annular part 31.

Other attachment means can of course be envisaged for locking together the two parts which together constitute the composite guide sleeve in accordance with the invention. In particular, it is possible to resiliently snap-engage an annular element, such as the part 31 shown in Figure 6, on an element such as the cylindrical part 32, which is also shown in Figure 5. In this case the rotary movement required for locking together the elements by means of a bayonet joint is replaced by simply axially pushing one element on to the other As another modification the annular element may be assembled on the cylindrical element through inserting the annular element through the other end of the cylindrical element, the locking action taking place in a recess similar to the annular recess 34 shown in Figure 5. The locking action may be effected by means of a bayonet joint or by resilient snap engagement, the annular element then assuming a position in which its surface lying adjacent the ball bearing bears against a radial supporting rim.

The two elements or parts of the composite sleeve may also be locked together by screwing one element or part on to the other.

Claims

1. A clutch withdrawal bearing assembly, which is adapted to be guided on a cylindrical tubular guide and has means to enable it to be selfaligning on the guide, the assembly comprising a rolling contact bearing having inner and outer thin-walled bearing rings, a rigid guide sleeve extending at least partially inside the inner bearing ring and, in use, between this ring and the guide on which it is a sliding fit, and resilient means permitting the self-alignment of the assembly, wherein the guide sleeve is formed by two separate parts, which are fixed relative to one another, the first part being of generally cylindrical shape and in use, surrounding and sliding on the tubular guide to effect guidance of the assembly on the tubular guide with a low frictional drag, and the second part being of generally annular shape and serving, in use, to maintain parallelism between the axis of the assembly and the axis of the tubular guide and also acting to transmit force applied by a clutch operating member to the bearing, and wherein the resilient means is formed by a resilient sleeve positioned between the inner bearing ring and the outer surface of the first part of the guide sleeve.

2. An assembly according to Claim 1, in which the second part is shaped as a substantially flat disc lying in a plane normal to the axis of the assembly and in contact with a radially extending portion of one of the rings of the bearing.

3. An assembly according to Claim 2, in which the second, annular part is in contact with a radially outwardly directed portion of the inner bearing ring.

4. An assembly according to Claim 2 or Claim 3, in which the resilient sleeve comprises a number of ribs extending parallel to the axis of the assembly.

5. An assembly according to Claim 4, in which the ribs are inwardly directed and are in contact with the outer surface of the first, cylindrical part of the guide sleeve.

6. An assembly according to Claim 4 or Claim 5, in which the resilient sleeve comprises a number of ribs which are inwardly directed and, in use, are in direct contact with the outer surface of the tubular guide.

7. An assembly according to Claim 6, in which the resilient sleeve comprises a first group of ribs which are in contact with the outer surface of the first, cylindrical part of the guide sleeve, and a series of several groups of resilient ribs which, in use, are in direct contact with the outer surface of the tubular guide.

8. An assembly according to Claim 7, in which the first, cylindrical part of the guide sleeve has openings through which the series of groups of ribs extend inwards and, in use, into contact with the tubular guide.

9. An assembly according to any one of Claims 4 to 8, in which the ribs are inclined with respect to the radial direction, and are of a profile which tapers from the sleeve towards the free edges of the ribs.

10. An assembly according to any one of Claims 2 to 9, in which the second, annular part of the guide sleeve is fixed to the first, cylindrical part by moulding the first cylindrical part onto the annular part.

11. An assembly according to any one of the preceding Claims, in which the first, cylindrical part is made of filled or reinforced plastics material, and the second, annular part is of surface hardened metal.

12. An assembly according to Claim 10, in which the second, annular part has an inner circular edge which is bent over and is moulded into an annular bead of the first, cylindrical part, the bead being positioned at one end of the first, cylindrical part adjacent the radially extending portion of the one of the rings of the bearing.

13. An assembly according to any one of Claims 2 to 9, in which the second, annular part is attached to the first, cylindrical part by snap engagement of an inner circular edge of the said second, annular part in a circular recess at one end of the first, cylindrical part, the recess being delimited by an annular supporting edge which supports the second annular part.

14. An assembly according to any one of Claims 2 to 9, in which the second, annular part is attached to the first, cylindrical part by a bayonet joint formed by projecting tongues on the edge of the first, cylindrical part co-operating with radial tongues or projections on an inner circular edge of the second annular part.

1 5. An assembly according to Claim 14, in which the first, cylindrical part further comprises a resilient locking tab which fits in a notch formed on the inner edge of the second, annular part.

1 6. An assembly according to any one of the preceding Claims, in which the first, cylindrical part has, at its end remote from the end to which the second annular part is fixed, at least one radial tongue, or an annular rim, which limits the axial movement of the bearing relative to the guide sleeve.

17. An assembly according to any one of the preceding Claims, in which the second, annular part includes means for attachment of a clutch operating member.

1 8. An assembly according to any one of Claims 6 to 8, in which the resilient sleeve has a portion which projects axially beyond the inner bearing ring and terminates closely adjacent the outer bearing ring.

19. An assembly according to Claim 1, substantially as described with reference to Figures 1 and 3, or Figures 2 and 4, or Figures 5 and 7 of the accompanying drawings.