GB2084671A

GB2084671A - Assembly for forming a freewheel or unidirectional clutch

Info

Publication number: GB2084671A
Application number: GB8129182A
Authority: GB
Original assignee: SKF Compagnie dApplications Mecaniques SA
Current assignee: SKF Compagnie dApplications Mecaniques SA
Priority date: 1980-10-02
Filing date: 1981-09-28
Publication date: 1982-04-15
Also published as: DE3139307A1; FR2491566A1

Abstract

An assembly for forming a freewheel or unidirectional clutch is formed as a separate unit, which, in use, is inserted between the surfaces of a bore (1) and a shaft (3). The assembly acts both as a freewheel and as a roller bearing for supporting the shaft and the bore concentrically. The assembly comprises: a series of bearing rollers (5) and a series of sprags (6) arranged alternately, a continuous strip spring (7) which has tongues (9) biasing the sprags (6) towards wedging positions and clearance openings (11) for the rollers 5, and a cage (8) comprising a cylindrical ring (12) having undersize apertures (13) for the sprags (6) and windows (14) for the rollers (5). The ring 12 has an inwardly bent edge (16) terminating in a series of lugs (18) which are bent parallel to the ring (12) after the rollers (5) and the spring (7) have been placed in position. The rollers (5) are thus held captive between the ring (12) and the lugs (18) and cannot escape and the sprags (6) are prevented from escaping radially inwardly by the ring (12) and radially outwardly by the tongues (10). <IMAGE>

Description

SPECIFICATION Assembly for forming a freewheel or unidirectional clutch This invention relates to cam-Wpe freewheels or unidirectional clutches in which, in use, one of the components which are connected by the clutch is mounted to float, that is to say is not centred with respect to the geometrical axis of the clutch. This is the case in particular in the reaction stage or stages in hydrokinetic torque converters and in disc clutches in automatic change-speed gearboxes.

The freewheel or unidirectional clutch takes the place of both a freewheel and a bearing to centre one of the components with respect to the other, at least for moderate loads.

In order to enable the freewheel or unidirectional clutch to perform this dual function and setting aside the obvious solution which consists in placing side by side a conventional freewheel and conventional roller bearings, two arrangements have been proposed. The first consists in arranging a cage which locates cams and a spring of the clutch in such a way that it also forms a plain bearing between the faces of the two components on which the cams act. This arrangement offers the advantage of simplicity and is suitable for very moderate loads but is never free from wear.

The second arrangement consists in providing the cage with a series of wedging cams and rolling members arranged alternately. In certain arrangements such as this, the rolling members are balls and the cage is an ordinary ball-cage to which cheeks are attached to receive the wedging members. However, the two races for the balls on the two components consist of grooves which are not suitable for the wedging cams to act on. For this reasons, the cams are placed at the side of the balls and this produces an assembly which is complicated and bulky and makes it necessary to supply a complete assembly comprising the cage, balls and cams together with composite inner and outer races.

This is the case in particular with the devices disclosed in French Patents Nos. 1,516,632, 2,029,011 and 2,281,830. Furthermore, the operating temperature conditions, in particular those in torque converters, prohibit the employment of plastics material as is made use of in the device described in French Patent No. 1,516,632.

In other arrangements such as that described in French Patent No. 2,078,922, rollers are provided which serve both as bearing rolling members and as wedging members by cooperating as wedging members with fixed ramps which are incorporated in the cage. Hence this arrangement is not properly speaking, a cam-type freewheel or unidirectional clutch and the very complicated assembly must likewise be supplied complete because the various components of the cage as well as the rollers are not captive.

Finally, in other arrangements such as those disclosed in U.S. Patents Nos. 2,883,023 and 3,776,335, an arrangement of alternating rollers and cams of special types is provided. These cooperate directly with a circular spring without there being any cage. Hence, in this case it is still necessary to supply the assembly complete with its inner and outer races.

The aim of the present invention is to overcome the above-mentioned disadvantages and to provide a separate cage assembly including an alternation of rollers and cams, the assembly being arranged so that it can be used with bearing races or tracks for both rolling and for wedging which are common and preferably also the cams cannot escape from the assembly when the assembly is delivered by itself without the races.

To this end, according to this invention, we provide an assembly forming a unit for insertion between cylindrical surfaces of a bore and of an inner body to form a freewheel or unidirectional clutch and a roller bearing between the bore and the body to hold the bore and body concentric, the assembly comprising a series of bearing rollers and a series of wedging cams which are interspersed with each other and are regularly circumferentially spaced apart to act, when in use, on the same cylindrical paths in the bore and on the body, a spring in the form of a continuous strip having deformations and resilient tongues acting on the cams to exert a torque on each cam to bias it towards a wedging position, the spring having clearance openings for the rollers, and a cage comprising a cylindrical ring having apertures receiving the cams and windows receiving the rollers, each window being so dimensioned that it prevents the escape from the cage of is roller in one radial direction, the ring having a radial extension at one edge and a series of lugs on the extension, the lugs being bent parallel to the ring after the rollers have been set in position, and the spacing of the lugs being such that they prevent the escape of the assembly of the cams in one radial direction and the spring prevents their escape in the other radial direction.

Preferably the rollers and cams are of the same axial dimension. The windows, preferably include chamfers which ensure the lubrication of the rollers and their retention in the one radial direction.

Two examples of assemblies in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a partial sectional view of a first example as seen in the direction of the arrows on the line I-I in Figure 2; Figure 2 is a radial sectional view of the first example as seen in the direction of the arrows on the line ll-ll in Figure 1; and, Figures 3 and 4 are views similar to Figures 1 and 2 but of a second example.

The assembly in accordance with the invention is intended to be inserted between the cylindrical surface 1 of a bore machined in an outer part 2, and a likewise cylindrical surface 3 forming the periphery of an inner part 4. These two parts do not normally form part of the assembly as supplied and may be machined directly in the mechanical parts which it is required to centre and drive unidirectionally with respect to one another.

Of course, if that proves necessary, it is possible, for example to overcome problems of hardness or accuracy, to include the parts 1 and 2 as rings which form part of the assembly. Subsequently the surfaces 1 and 3 and the parts 2 and 4will simply be designated as the bore 1 and the shaft 3.

Hence the product supplied is a separate assembly comprising roller-bearing rollers 5, wedging cams 6, a continuous strip spring 7 for the cams 6, and a cage 8 which unites all these components in a captive manner during transport and the manipulations which precede insertion of the assembly between the bore and the shaft.

The rollers 5 are ordinary roller-bearing rollers, the diameter of which corresponds with the width of the gap between the shaft 3 and the bore 1.

The wedging cams 6 are of a known design and cooperate with a continuous strip or band spring 7 which both retains the cams in place and exerts a torque on each cam to bias it towards its wedging position. The cams are dimensioned to act between the bore and the shaft to produce a wedging action in one direction and to slide in the other direction.

Thus their overall radial dimension is close to the diameter of the rollers 5. The axial dimension of the cams 6 is preferably equal to that of the rollers 5.

The continuous spring 7 includes from place to place wavy deformations 9 and bearing tongues 10 each of which acts on one of the cams 6 in a known manner. Additionally the spring 7 includes from place to place clearance openings 11 at the locations of the rollers 5. The width of the spring 7, as is evident from Figure 2, is greater than the common axial length of the rollers 5 and the cams 6 so that a band of continuous material remains on opposite sides of the openings 11 and also on opposite sides of openings for the cams 6 to pass through the deformations 9. This ensures the continuity of the spring.

The cage 8 which is of metal in order to withstand the temperatures which occur in use, may advantageously be manufactured by stamping from a metal sheet. It comprises essentially a cylindrical ring 12 which includes the usual apertures 13 for the passage of the cams 6. The apertures 13 are substantially rectangular with in addition a notch at one side to provide a clearance from the tongues 10, and the dimension of the main rectangular portion in the circumferential direction is less than the corres ponding dimension of the portion of the cam situated at the periphery of the assembly in order to prevent the cam from passing through the aperture.

The spring 7 is then placed on the inside of the ring 12. The ring 12 includes in addition windows 14 at the locations of the rollers 5. The windows 14 are likewise substantially rectangular, having on the opposite edges which cooperate with the cylindrical surfaces of the rollers, chamfers 15 which extend over part of the length of the rollers. The direction and spacing of the two opposite chamfers 15 is such that the roller 5 cannot pass through the opening and is retained in one radial direction.

In the example of Figure 1, the chamfers 15 are made by deformation and are directed in the radial inward direction to prevent the rollers 5 from escaping radially outwards.

In the example of Figure 3, on the other hand, the chamfers 15 are formed by bending back in a radial inward direction a narrow tab 15a and hence the chamfers are directed in the radial outward direction in order to prevent the roller from escaping radially inwards from the ring 12.

The ring 12 has a radially directed extension 16 along one edge. The extension extends inwards in the example of Figures 1 and 2 or outwards in the example of Figures 3 and 4. The ring 12 preferably also has a second extension 17 along its opposite ' edge, the extension 17 extending in the opposite direction to that of the edge 16.

In both cases the extension 16 has extending from it small bars or lugs 18 which are initially directed radially inwards in the example of Figures 1 and 2 and radially outwards in the example of Figures 3 and 4.

After putting the rollers 5 in place, in both cases these small bars or lugs 18 are bent over parallel to the ring 12 and their spacing is such that they prevent the rollers escaping inwards in the example of Figures 1 and 2 and outwards in the example of Figures 3 and 4. Hence the cooperation of two small bars 18 and the two corresponding chamfers 15 traps the rollers completely and thus ensures centring of the cage between the bore 1 and the shaft 3.

Of course, the small bars 18 are arranged so that they do not interfere with the movement of the cams 6.

In the example of Figures 1 and 2, the spring 7 is advantageously placed in the gap between the ring 12 and the small bars 18 as is shown, and in this case the placing of the spring must necessarily occur before the bending over of the small bars 18. On the other hand in the example of Figures 3 and 4, the spring is arranged inside the ring and hence may easily be introduced after the bending of the small bars 18.

The cams 6 may be introduced at any time after the fitting of the spring by introducing them in the usual way from the outside into the windows 13 in which they are retained by the spring 7 and in particular by its tongues 10. The cams 6 cannot escape inwards because of the insufficient width of the windows 13 as explained above, nor outwards because of the retention effected elastically by the wavy portions 9 and the tongues 10.

Hence the assembly so formed is relatively simple and robust and all its components are captive. This enables it to be transported and handled without risk of it coming apart up to the time when it is inserted between the bore 1 and the shaft 3 as explained above.

The assembly constitutes an effective freewheel or undirectional clutch thanks to the number and diameter of the rollers 5. Of course, depending upon the requirements, the numbers and dimensions of the rollers 5 and ofthe cams 6 may be chosen at will and it is not necessary that the number of rollers be equal to the number of cams as in the examples shown.

Instead, for example, there may be only one roller for two, three or four cams, or vice versa depending upon the characteristics to be obtained. There may otherwise be a sequence including successions of any number of cams alternating with successions of any number of rollers. The assembly is suited to withstanding long use even under difficult temperature conditions, and produces only an extremely low drag in the direction of relative movement between the bore and the shaft allowed by the cams.

Claims

1. An assembly forming a unitforinsertion between cylindrical surfaces of a bore and of an inner body to form a freewheel or unidirectional clutch and a roller bearing between the bore and the body to hold the bore and body concentrio, the assembly comprising a series of bearing rollers and a series of wedging cams which are interspersed with each other and are regularly circumferentially spaced apart to act, when in use, on the same cylindrical paths in the bore and on the body, a spring in the form of a continuous strip having deformations and resilient tongues acting on the cams to exert a torque on each cam to bias it towards a wedging position, the spring having clearance openings for the rollers, and a cage comprising a cylindrical ring having apertures receiving the cams and windows receiving the rollers, each window being so dimensioned that it prevents the escape from the cage of its roller in one radial direction, the ring having a radial extension at one edge and a series of lugs on the extension, the lugs being bent parallel to the ring after the rollers have been set in position, and the spacing of the lugs being such that they prevent the escape of the rollers in an opposite radial direction.

2. An assembly according to Claim 1, in which the apertures are so dimensioned that they prevent the escape from the assembly of the cams in one radial direction and the spring prevents their escape in the other radial direction.

3. An assembly according to Claim 1 or Claim 2, in which the edges of the windows which extend axially of the rollers have, along at least part of their length a chamfer facing towards the said opposite radial direction.

4. An assembly according to Claim 3, in which each of the chamfers is formed by a permanent deformation of a protruberance on the said edge.

5. An assembly according to Claim 3, in which each of the chamfers is formed by a bent tab extending from the said edge towards the interior of the window.

6. An assembly according to anyone of the preceding Claims, in which the radial extension and the lugs are situated radially inwardly of the ring and the spring is situated between the ring and the lugs.

7. An assembly according to anyone of Claims 1 to 5, in which the radial extension and the lugs are situated radially outwardly of the ring and the spring is applied to the inside of the ring.

8. An assembly according to anyone of the preceding Claims, in which the bearing rollers and the cams have the same axial lengths as each other.

9. An assembly according to anyone of the preceding Claims, in which the ring has a second radial extension at its opposite edge, that is the edge remote from that at which the first radial extension is situated, two extensions extending in opposite radial directions from each other, that is one extending radially inwardly and the other radially outwardly.

10. An assembly according to any one of the preceding Claims, in which the rollers and the cams are arranged in a sequence around the assembly with successions of one or more rollers alternating with successions of one or more cams.

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

12. The combination of a cylindrical bore, a body having a cylindrical surface within the bore and an assembly in accordance with any one of the preceding Claims interposed between the cylindrical surfaces of the bore and the body, the assembly forming a freewheel or unidirectional clutch and a roller bearing between the bore and the body to hold the cylindrical surfaces of the bore and the body concentric.