GB2045381A

GB2045381A - Clutch release bearing assembly

Info

Publication number: GB2045381A
Application number: GB8008760A
Authority: GB
Original assignee: SKF Compagnie dApplications Mecaniques SA
Current assignee: SKF Compagnie dApplications Mecaniques SA
Priority date: 1979-03-30
Filing date: 1980-03-14
Publication date: 1980-10-29
Also published as: ES489959A0; IT8067352A0; FR2452634B1; ES8101733A1; DE3012216A1; FR2452634A1

Abstract

A clutch release bearing assembly comprises a guide sleeve 16 having a cylindrical element 17 which surrounds a tubular guide 13 and by means of which the guide sleeve 16 can slide on the tubular guide with only a small frictional drag. The guide sleeve 16 also comprises a radially extending element 19 which is in contact with a radial flange 5 of an inner bearing ring 1 so as to guide the movement of the bearing in a radial plane. Resilient self-alignment of the assembly on the guide 13 is ensured by the provision of a number of ribs 18, which are an integral part of the cylindrical element 17 of the guide sleeve, and which are in contact with the bore of the inner bearing ring 1. <IMAGE>

Description

SPECIFICATION Clutch withdrawal bearing assembly The present invention relates to clutch withdrawal bearing assemblies, for use with plate clutches, and more particularly with diaphragm clutches, the assembly comprising a bearing e.g. a ball bearing, a rigid guide sleeve which in use, slides axially on a tubular guide, and also resilient means permitting alignment of the bearing with the axis of rotation of the clutch during disengagement or withdrawal operation.

Preferably, such withdrawal assemblies comprisng a ball or other rolling contact bearing are provided with resilient means adapted to permit a certain movement of the bearing assembly relative to a gearbox shaft of the vehicle to which the clutch is fitted and relative to a tubular guide on which the bearing assembly moves axially. Thus, one of the two bail or roller bearing rings of such as assembly, that is the ring which transmits to the clutch the force to effect clutch disengagement, bears directly upon the diaphragm or upon a clutch withdrawal member during disengagement, or is in continuous contact therewith, while the other bearing ring receives the thrust of the clutch operating fork or other clutch operating member.The bearing ring which comes into or remains in contact with the diaphragm or withdrawal member, which is commonly the outer bearing ring, has a substantially part-toroidai contact face. The bearing is not precisely centred on the gearbox shaft or tubular guide, nor is it perfectly aligned relative to the axis of rotation of the diaphragm or withdrawal member. Further, the geometrical axis of the clutch diaphragm or plates, their axis of rotation and the axis of the gearbox shaft or of the tubular guide, do not always exactly coincide. This makes it still more necessary to make provision for movement of the withdrawal bearing assembly during each clutch disengagement operation.

Clutch withdrawal bearings as described above and comprising means capable of ensuring automatic alignment with the clutch during disengagement are known. One such assembly comprises a resilient sleeve which is equipped with radial ribs. The ribs are adapted to come into direct contact with the tubular guide and the sleeve is so constructed as to provide both the rigidity and the pliability necessary for correct and repeated operation of the assembly when the vehicle clutch is operated.In this clutch withdrawal bearing assembly provision is made for incorporating a rigid guide sleeve, which comprises a radially extending portion which is in contact with a radial section of one of the rings of the bearing to prevent any rocking movement of the bearing when the clutch is operated, as such rocking movement of the bearing would result in premature wear of the contact surface of the diaphragm or other clutch withdrawal member.

It is the object of the present invention to provide a self-aligning clutch withdrawal bearing assembly in which the number of component elements is reduced below that previously used and the manufacture of the assembly is simplified.

According to the present invention, a selfaligning clutch withdrawal bearing assembly comprises a rolling contact bearing having thinwalled inner and outer bearing rings, and a rigid guide sleeve extending within the inner bearing ring and arranged to surround and slide along a tubular guide, the guide sleeve comprising a radially extending portion, which is in contact with a radially extending part of one of the bearing rings, and resilient means permitting selfalignment of the assembly to take place on the tubular guide, wherein the resilient means, which permit the self-alignment to take place, are integral parts of the guide sleeve and are in contact with the inner surface of the inner bearing ring.

In a preferred embodiment the resilient means comprise a plurality of ribs which extend parallel to the axis of the bearing and are inclined with respect to radii of the bearing, the ribs tapering in cross-section from their bases adjacent the sleeve to their free ends.

In another embodiment the resilient means comprise a plurality of substantially axially extending tongues.

Although the guide sleeve may be in the form of a single unit, it is preferably in the form of two elements which are fixed relative to each other.

The first element, which is of substantially cylindrical shape, has the resilient means formed integrally on its outer surface and, in use, surrounds the tubular guide so that, subject to slight friction, it permits sliding movement of the assembly on the tubular guide. The second element which is substantially annular, causes the parallel relationship between the axis of the bearing and the axis of the tubular guide to be maintained and also acts to transmit force from a clutch operating member to the bearing. The second element may have the general shape of a flat disc which is radially disposed and is in contact with a radially outwardly extending part of the inner bearing ring. In this case the first element of the guide sleeve has its inner surface in contact with the tubular guide.

In another embodiment the second element of the guide sleeve has a radially extending portion, which is in contact with the radially outwardly extending portion of the inner bearing ring, and a cylindrical portion, which, in use, is in direct contact with the tubular guide over the greater part of the length of the sleeve.

The two elements of the guide sleeve can be locked to one another by any suitable means, for example, mutual snap engagement, a bayonet joint, or screwing, can be used for this purpose.

However, in a preferred embodiment, the two elements are locked to one another by moulding the first element, which is made of plastics material or of an elastomer, on to the second element, which is made of metal and is preferably surface-hardened.

Three examples of assemblies in accordance with the invention are illustrated in the accompanying drawings in which: Figure 1 is an axial section through a first example; Figure 2 is an axial section through a second example; Figure 3 is an axial section through a third example; Figure 4 is a cross-section along the line IV--IV of Figure 1, Figure 5 is a cross-section along the line V-V of Figure 2; and, Figure 6 is a cross-section along the line VI--VI of Figure 3.

As shown in Figures 1 and 4, a clutch withdrawal bearing assembly comprises an inner bearing ring 1 which is of thin-walled construction and is made by pressing a sheet metal tube. The ring 1 has a tubular portion 2 and a part-toroidal raceway 3 for a set of bearing balls 4. The tubular portion 2 is outwardly extended in the form of a radial flange 5, which is itself axially extended in the form of two diametrically opposed lugs 6 which are parallel to the axis of the bearing and each of which has an opening 7 which cooperates with a rod 8 adapted to retain a control fork 9. The fork 9 is shown in broken lines in Figure 1. It is of course understood that other means may be used for retaining the control fork which forms a clutc.i operating member.

The ball bearing of the assembly is completed by an outer bearing ring 10, which is also thinwalled and is formed by pressing a sheet metal tube. The outer bearing ring comprises a parttoroidal portion 11, which can come into contact with the surface of a clutch diaphragm 1 2 shown in broken lines in Figure 1, when the control fork 9 has caused the assembly to move longitudinally along a tubular guide 12, which is shown in broken lines in Figure 1, and within which a gearbox shaft rotates. The bearing balls are held in place by a cage 14, and the bearing is protected by a cheek plate 1 5.

A composite, part-rigid guide sleeve 16, which is formed by the combination of a first element 17, of generally cylindrical shape, and a second element 19, of generally annular shape, is interposed between the inner bearing ring 1 and the tubular guide 1 3. The composite guide sleeve 1 6 comes into contact with the outer surface of the tubular guide 1 3 by means of the inner surface of the cylindrical element 1 7. The annular element 19, which is in the shape of a flat radial disc, is in frictional contact with the radial flange 5, so that the bearing can only be moved in a radial plane relative to the sleeve.A number of ribs 18, which extend parallel to the axis of the assembly and are integral with the cylindrical element 17, are positioned round the outer periphery of the cylindrical element 17, and are in contact with the inner surface of the tubular portion 2 of the inner bearing ring 1. As is particularly clear from the cross-sectional view of Figure 4, the ribs 18 have a cross-sectional shape which tapers from their bases adjacent the element 1 7 to their free ends.

In the example of Figures 1 and 4 this shape is substantially triangular. It will be seen that the ribs 18 are steeply inclines relative to radii of the bearing. Further, the bases of the ribs have, on the side of the acute angle which the ribs include with the outside surface of the cylindrical element 17, a groove 1 8a which facilitates flexural deformation of the ribs 1 8. Despite the necessary rigidity of the synthetic plastics material of which the cylindrical element 17 is composed, it is thus possible to provide the individuai ribs 1 8 with pliability to ensure self-alignment of the bearing with the axis of rotation of the diaphragm 12 while the clutch is disengaged.

The second element 1 9 is locked to the cylindrical element 1 7 by moulding the latter onto a circular inner edge 20, which is bent over towards the bearing, of the element 1 9. In order to ensure that the right-angled relationship of the annular element 1 9 to the axis of the bearing is correctly maintained, the cylindrical element 1 7 has-an annular bead 21 near its end which receives the annular inner edge 20.

At its opposite end the cylindrical element 1 7 has retaining studs 22, which restrict the possible extent of movement of the bearing relative to the sleeve 1 6 in the axial direction. A clearance is left between the inner faces of the studs 22 and the end face of the inner bearing ring 1. The provision of the retaining studs 22 ensures that the guids sleeve 4S cannot be accidntally d Jso iged from within the bearing ring 1.

By virtue of the provision of the ribs 1 8 and of the annular element 1 9 in contact with the flange 5, the assembly automatically undergoes selfalignment without being subjected to any pivotal movement when the clutch operating fork 9 comes into direct contact with the front, outer surface of the annular element 19 (as can be seen in Figure 1).

The example shown in Figure 2 is a modification of the example shown in Figure 1. In the example of Figure 2, in which identical components are given the same reference symbols as in the example of Figure 1, the composite guide sleeve, which is generally designated as 23, again comprises a cylindrical element 24 and an annular element 19. These two elements 24 and 1 9 are positioned as in the previous example. However, in the example shown in Figure 2, the resilient self-aligning means comprise a number of tongues 25 which extend substantially axially from the bead 21. As is clear from Figure 2, the cross-sectionai shape of these tongues tapers from their bases to their free ends which are directed towards the bearing. Further, and as is clear from the cross-sectional view of Figure 5, these tongues are laterally curved. This curved shape facilitates contact of the tongues with the bore of the inner bearing ring 1. As in the example of Figure 1 , the annular element 19 is locked to the cylindrical element 24 by moulding the latter on to the flat metal disc constituting the annular element 1 9.

It will be understood that these two elements, which together constitute the composite guide sleeve, can be locked together by other suitable means. Thus, an annular recess may be provided in a portion similar to the bead 21 of the cylindrical element 17 or 24, the annular element being introduced into this annular recess and being secured in position by a suitable locking means, or by snap engagement.

The example of Figure 3 is another modification of the example of Figure 1. In the example of Figure 3, in which identical components bear the same reference symbols as in the first example, the guide sleeve, generally designated as 26, comprises an annular element 27 which has a radial portion 27a with the radial flange 5, and a cylindrical portion 27b which is in direct contact with the tubular guide 13 for the greater part of the length of the assembly and beyond the raceway 3 (as is clear from Figure 3).Moulded onto the cylindrical portion 27b is an elastomer element 28 which, in particular, covers the outer cylindrical surface of the portion 27b and carries, in this area and round the whole of its periphery a number of ribs 29 which extend parallel to the axis of the sleeve, are inclined with respect to radii of the bearing, and have a cross-sectional shape which tapers from their bases towards their free ends (as can be seen in the cross-ssctional view of Figure 6). As the ribs 29 of elastomeric material are more pliable than the ribs 18 of the example of Figure 1, it is apparent from Figure 6 that their thickness may be greater and that they may have a trapezoidal cross-section. The smaller side of the trapezoidal section is in contact with the bore of the tubular portion 2 of the inner bearing ring. The moulded, elastomer element 28 is completed, beyond the cylindrical portion 27b, by a bead 30, which comes into contact with the outer surface of the tubular guide 13, and also by retaining studs, or an annular rim 31, which has the same profile, and performs the same function, as the studs 22 of the example shown in Figure 1. The portion 28, which is moulded on to the element 27b, is completed at the opposite end of the guide sleeve 26 by a second bead 32 which again is in contact with the outer surface of the tubular guide 13. The two beads 31 and 32 serve to wipe off lubricant when the guide sleeve slides on the tubular guide.

Although the drawings illustrate assemblies which have composite guide sleeves, it will be understood that the invention can also be applied to an assemblies which have guide sleeves which are constituted as single units.

Claims

1. A self-aligning clutch withdrawal bearing assembly comprising a rolling contact bearing having thin-walled inner and outer bearing rings, and a rigid guide sleeve extending within the inner bearing ring and arranged to surround and slide along a tubular guide, the guide sleeve comprising a radially extending portion, which is in contact with a radially extending part of one of the bearing rings, and resilient means permitting selfalignment of the assembly to take place on the tubular guide, wherein the resilient means which permit the self-alignment to take place, are integral parts of the guide sleeve and are in contact with the inner surface of the inner bearing.

2. An assembly according to Claim 1, in which the resilient means comprise a plurality of ribs which extend parallel to the axis of the bearing and are inclined with respect to radii of the bearing, the ribs taper in cross-section from their bases adjacent the sleeve to their free ends.

3. An assembly according to Claim 2, in which the ribs are longitudinally grooved at their bases to facilitate lateral deformation of the ribs, the grooves being located on the flanks of the ribs which form an acute angle with the outside of the sleeve.

4. An assembly according to Claim 1, in which the resilient means comprise a plurality of substantially axially extending tongues.

5. An assembly according to any one of the preceding Claims, in which the guide sleeve comprises two elements which are fixed relative to each other, the first element being of generally cylindrical shape, having the resilient means formed integraily on its outer surface and being arranged to surround the tubular guide and to slide axially on the guide, and the second element being of generally annular shape and serving, in use, to maintain parallelism between the axis nf the bear ng and the axis of the tubular guide, and also to transmit force appiied by en operating member to the bearing.

6. An assembly according to Claim 5, in which the second element is shaped as a substantially flat disc which extends radially outwards from the first element and is in contact with a radially outwardly directed flange on the inner bearing ring.

7. An assembly according to Claim 5 or Claim 6, in combination with a tubular guide, in which the inner surface of the first element is in contact with the tubular guide.

8. An assembly according to Claim 5, in combination with a tubular guide in which the second element has a radially extending portion which is in contact with a radially outwardly directed portion of the inner bearing ring and a cylindrical portion of which is in contact with the tubular guide over the greater part of the length of the sleeve.

9. An assembly according to any one of Claims 5 to 8, in which the first element is locked to the second element by one of the elements being moulded on to the other element.

10. An assembly according to any one of Claims 5 to 8, in which the two elements are locked to one another by mutual snap engagement.

11. An assembly according to Claim 8, in which the first element comprises two beads arranged one at each end of the cylindrical portion of the second element, the beads being in contact with the tubular guide and acting to wipe away lubricant from the guide as the sleeve moves along the guide.

12. An assembly according to any one of the preceding Claims, in which, at its end remote from its radially extending portion, the guide sleeve has at least one radial stud or annular rim which limits the extent of axial movement of the bearing relative to the guide sleeve.

13. An assembly according to Claim 1, substantially as described with reference to Figures 1 and 4, or Figures 2 and 5, or Figures 3 and 6, of the accompanying drawings.

14. A motor vehicle having a clutch, a tubular guide, and an assembly in accordance with any of Claims 1 to 6 mounted on the tubular guide.