WO2009150496A1

WO2009150496A1 - Female element for constant-velocity joint, assembly and corresponding constant-velocity joint

Info

Publication number: WO2009150496A1
Application number: PCT/IB2008/053483
Authority: WO
Inventors: Michel Margerie
Original assignee: Gkn Driveline S.A.
Priority date: 2008-06-09
Filing date: 2008-06-09
Publication date: 2009-12-17

Abstract

This female element for a constant-velocity joint extends about a female central axis (A-A) and comprises a pair of races (16) that extend symmetrically about a central plane (M-M) and that define a radial zone (30) having a reference plane (P1). The element comprises a race end wall (32) having an outer end wall surface (36). The female element defines in each reference plane (P1 ) a wall thickness Em. Each of the races (16) is at a centre distance DM from the central plane and comprises a closed end (16F). The outer end wall surface (36) lies, in the reference plane (P1 ), exclusively in a preferred zone (ZP1 ). The preferred zone is defined by an annular half-disc of minimum radius r = DM and maximum radius R = (DM. + Em.) x 1.9. The centre Cr of the radius r is situated at the intersection between the central plane and the closed ends. Applicable to constant-velocity joints for motor vehicle transmissions.

Description

Female element for constant-velocity joint, assembly and corresponding constant-velocity joint

The present invention relates to a female element for a constant-velocity joint, of the type

- extending about a female central axis,

- comprising at least one pair of races that extend opposite each other, that extend symmetrically about a central plane and that define a radial zone relative to the female central axis,

- having at least one first reference plane perpendicular to the central plane, parallel to the female central axis and extending in the radial zone, and

- comprising a race end wall having an outer end wall surface and an inner end wall surface connecting the races in the radial zone, the female element defining, in each reference plane, a wall thickness Em measured at the junction between the race and the race end wall, each of the races being at a centre distance DM measured in the first reference plane under consideration, from the central plane, and each of the races having a closed end which meets the race end wall.

The invention applies particularly to tripod-type constant-velocity joints for motor vehicle transmissions.

Tripod-type constant-velocity joints generally comprise a female element having a plurality of pairs of races extending parallel to a central axis. The female element has an end wall and an opening into which a male element fitted with rollers is inserted. The end wall is integral with a drive shaft.

The end wall of the female element is at all points generally perpendicular to the central axis of the female element and is connected to the races by a small radius of curvature. This female element uses a large amount of material to create races of a workable length. Consequently, if the female element is a forging, it is difficult to forge and the forging tools suffer rapid wear. Equally, the known female element uses a large amount of grease.

It is an object of the invention to solve at least one of these problems by providing a female element for a constant-velocity joint that uses little material. To this end, the subject of the invention is a female element of the type indicated above, in which the outer end wall surface lies, in the or each first reference plane (P1 ), exclusively in a first preferred zone, and the first preferred zone is defined for each first reference plane by an annular half-disc having a minimum radius r = DM and having a maximum radius R = (DM. + Em. ) x 1^9, a centre Cr of the minimum radius r being situated at the intersection between the central plane and the closed ends.

In accordance with individual embodiments, the female element has one or more of the following features: - the minimum radius r = DM + Em;

- the outer end wall surface comprises, in the first reference plane under consideration, at least two part-circular portions of radius RR;

- the two part-circular portions are connected by a straight portion;

- the two part-circular portions are adjacent; - the two part-circular portions form a semicircle of centre C1 ;

- the centre C1 of the semicircle is offset from the centre Cr of the minimum radius, and the outer end wall surface comprises, in the first reference plane under consideration, straight portions, particularly portions parallel to the female central axis A-A; - the inner end wall surface extends, in the first reference plane under consideration, exclusively in a second preferred zone, and the second preferred zone is defined, for each first reference plane, by an inner limit of radius ri = DM and by an outer limit defined by the outer end wall surface, and the inner end wall surface has a part-circular portion whose radius of curvature is greater than 4 mm and preferably greater than 6 mm;

- the radius ri = 1 .05 DM;

- in each first reference plane, the inner end wall surface is concave at all points;

- in each first reference plane, the inner end wall surface is joined continuously to the races;

- the female element comprises an arch connecting the races of a pair of races and a connecting portion connecting the arch and the race end wall, the arch has an outer arch surface and defines a circumferential zone extending on both sides of the central plane between the races of the pair of races, the female element defines at least one second reference plane extending radially relative to the female central axis, the arch having an outer arch radius RVE in the second reference plane under consideration, the connecting portion has an outer connecting surface situated, in the or each second reference plane, exclusively in a third preferred zone, this third preferred zone is defined by a partial annular disc whose centre is on the female central axis and which is aligned with the closed ends of the races, and this partial annular disc has a maximum radius RMV that is 1.10 times the outer arch radius RVE in the second reference plane under consideration;

- the connecting portion has a partially spherical inner connecting surface;

- the partially spherical inner connecting surface has a centre CS situated on the female central axis;

- the outer connecting surface of the connecting portion is continuously joined to the arch;

- the outer connecting surface has a partially spherical portion whose centre CS2 is offset from the centre CS of the inner connecting surface;

- the outer connecting surface comprises a chamfered portion;

- the female element comprises an intermediate race part extending between two adjacent pairs of races, and an intermediate end wall part extending between the intermediate race part and the female central axis A-A, and the intermediate end wall part comprises an intermediate inner surface whose profile in an arc of a circle extends from the female central axis A-A to the intermediate race part; and - it is a forging.

The invention also relates to an assembly comprising a female element for a constant-velocity joint having a pair of races, and a roller suitable for rolling in the races, said assembly being characterized in that the female element is a female element as defined above, and when the roller is on the closed end of a race, the roller is against the inner end wall surface at a point lying in the central plane.

Lastly, the invention relates to a constant-velocity joint comprising a male element having at least one arm defining an arm axis, characterized in that it also comprises an assembly as defined above, and in that the roller is mounted rotatably on the arm about the arm axis.

In individual embodiments of the invention, the constant-velocity joint has one or more of the following features: - the roller is rotatable about at least one axis perpendicular to the arm axis; and

- the roller is rotatable exclusively about the arm axis.

A clearer understanding of the invention will be gained from reading the following description, which is given purely by way of example and refers to the accompanying drawings, in which:

- Figure 1 is a half-view in cross section through a transmission joint in a first embodiment of the invention, in the in-line position;

- Figure 2 is a perspective view in partial cross section of the female element of the joint seen in Figure 1 ; - Figure 3 is a cross section through the female element and roller, taken on the plane marked Ill-Ill in Figure 1 ;

- Figure 4 is a half-view in cross section of a joint in a second embodiment of the invention, the view being similar to that of Figure 1 ; and

- Figure 5 is a view in longitudinal section taken on the plane marked V-V in Figure 4.

Figure 1 shows a constant-velocity joint in a first embodiment of the invention, denoted by the general reference 2. The constant-velocity joint 2 comprises:

(1 ) A male element or tripod 4 having a hub 6 with a male central axis X-X, from which project three radial arms 8 spaced out at angles of 120°. The end part of each arm 8 is an integrally formed spherical bearing 10 whose centre lies on the axis Y-Y of the corresponding arm 8. This male element 4 is integral with a first rotary shaft 12.

(2) A female element or tulip 14 whose female central axis A-A, in the in- line position of the joint illustrated, coincides with the male central axis X-X. On either side of each arm 8, this female element 14 has two opposing races 16. This female element 14 is mounted on a second rotary shaft 18 (see Figure 2). (3) For each arm 8, a rolling-contact bearing assembly 20 with an axis Z-Z of revolution, this axis Z-Z coinciding with the axis Y-Y of the corresponding arm 8 in the in-line position shown in Figure 1.

In the following description, the terms "radial", "axial", "circumferential", "longitudinal", and "transverse" are to be understood as being with respect to the central axis A-A of the female element 14.

The three rolling-contact bearing assemblies 20 are identical, so only one will be described below.

The assembly 20 comprises: - a cylindrical inner ring 22 of axis Z-Z,

- a generally axisymmetric outer roller 24 of axis Z-Z surrounding, at a distance, the inner ring 22,

- a circle of needle rollers 26 between the inner ring 22 and the outer roller 24, and - washers 28 for the radial retention of the outer roller 24 and of the circle of needle rollers 26 with respect to the inner ring 22.

The outer roller 24 has an outer rolling-contact surface in the form of a partial torus.

The female element 14 defines an opening 14A through which the male element 8 is inserted.

As shown in Figure 2, the female element 14 defines for each pair of races 16 a central plane M-M. This central plane M-M passes through the female central axis A-A and is the plane of symmetry of that particular pair of races 16.

Each race 16 comprises an end opening 16O directed towards the opening 14A, and a closed end 16F directed axially towards the second shaft 18. When observed along the female central axis A-A, the races 16 have a concave arc-of-a- circle profile.

Each pair of races 16 occupies a radial height JHR and defines on this height HR a radial zone 30 of races relative to the central axis A-A. The female element 14 defines a plurality of first reference planes £1, each of which is perpendicular to the central plane M-M, is parallel to the female central axis A-A, and is in the radial race zone 30. Each track 16 is at a centre distance DM from this central plane M-M (see Figure 3) in one of the first reference planes P1_.

The female element 14 comprises, for each pair of races 16, a race end wall 32 connecting the races 16 where they come towards the second shaft 18. This race end wall 32 extends radially across the radial zone 30, and defines an inner end wall surface 34 and an outer end wall surface 36. The inner end wall surface 34 connects two races 16.

The explanation of the geometrical relationships which follows refers to one of the first reference planes P1_. The female element 14 defines a plurality of these first reference planes, each first reference plane £1 being either identical or parallel to the plane of Figure 3 and lying within the associated radial zone 30.

The outer end wall surface 36 lies exclusively within a first preferential zone ZP1 and the inner end wall surface 34 lies exclusively within a second preferential zone ZP2 (see Figure 3) for at least one, and preferably each, first reference plane £1.

The outer end wall surface 36 defines with the inner end wall surface 34 a maximum wall thickness EM- and a minimum wall thickness Em. The minimum wall thickness Em- occurs at the junction between the race end wall 32 and the races 16, while the maximum wall thickness EM occurs at that portion of the race end wall 32 which is furthest from the races 16. The maximum wall thickness EM is preferably less than 1.70 times the minimum wall thickness Em.

The first preferential zone ZP1 is defined for each first reference plane P1 by an annular half-disc having a minimum radius r = DM and having a maximum radius R = (DM + Em.) x UJ. The centre Cr of the minimum radius r is situated at the intersection between the central plane M-M and the closed ends 16F of the races 16 meeting the race end wall 32.

Preferably, the minimum radius r = DM + Em.

The outer end wall surface 36 comprises, in the reference plane P1 under consideration, two part-circular portions 37 of radius RR. This radius RR is preferably DM + Em. In the embodiment shown in Figure 3, the two part-circular portions 37 are adjacent and form a semicircle whose centre is C1.

The centre C1 of this semicircle is offset away from the centre Cr towards the shaft 18 of the female element. The outer end wall surface 36 comprises straight portions 38 which are parallel to the central axis A-A and connect the two part-circular portions 37 to the outer surface of the female element situated in the location of the races.

In a variant which is not illustrated, the two part-circular portions 37 are connected by a straight portion of the end wall surface 36.

The second preferred zone ZP2 is defined by a part-circular inner limit of radius ri = DM and by an outer limit which is the outer end wall surface 36. The centre of the radius ri lies on the intersection between the central plane M-M and the closed ends 16F meeting the race end wall 32. In general terms, the inner limit is inside the outer limit.

The centre distance DM is always measured in the first reference plane P1 under consideration.

The radius ri is preferably 1.05 x DM.

Thus, in the first reference plane PJ. under consideration, the inner end wall surface 34 is preferably concave throughout and has a profile which is an arc of a circle. The inner end wall surface 34 advantageously makes a continuous join with the races 16. In the case shown in Figure 3, the inner end wall surface 34 has a semicircular profile whose radius is the same as DM. The inner end wall surface 34 has at least one part-circular portion 35 whose radius of curvature is greater than 4 mm, preferably greater than 6 mm.

Also shown in Figure 3 is the outer roller 24, in its position at the closed ends 16F of the races 16. In this position the whole of the outer roller 24 is away from the inner end wall surface 34. However, owing to the shape of the inner end wall surface 34, the latter very closely follows the roller 24, thus defining a small unoccupied space for the lubricant.

The roller 24 has an outer radius RG measured in the first reference plane El under consideration. This outer radius RG is smaller than the radius of the semicircular profile of the inner end wall surface 34.

Referring again to Figure 1 , the female element 14 also has an arch 50 extending axially by the races 16 and connecting each of the two races 16 of each pair of races in a generally circumferential direction. The arch 50 defines an arch outer surface and a circumferential zone 52 extending on either side of the central plane M-M between the races 16 of a pair of races. The female element defines a plurality of second reference planes P2 which are radial with respect to the female central axis A-A and extend inside the circumferential zone 52 under consideration.

One of these second reference planes P2 is illustrated in Figure 1 and coincides with the central plane M-M.

In each second reference plane P2 the arch 50 is associated with an outer arch radius RVE measured with respect to the female central axis A-A.

The female element 14 also comprises a connecting portion 54 connecting the arch 50 to the race end wall 32 (see Figure 2). The female element 14 is preferably forged in steel.

Another feature of the invention will be described with reference to a second embodiment of the invention shown in Figures 4 and 5.

Figure 4 shows a constant-velocity joint in this second embodiment, Figure 4 being analogous to Figure 1. In contrast to the constant-velocity joint described above, this joint 2 comprises a male element 4 having three arms 8 whose bearings 10 are cylindrical about the axis Z-Z. The rolling-contact bearing assembly 20 has no inner ring 22 but consists of an outer roller 24 surrounding the circle of needle rollers 26. Consequently the circle of needle rollers 26 is in direct contact with the cylindrical bearing 10 and the outer roller 24.

In addition, the free end of the arm 8 has a groove in which a circlip 60 is engaged to retain a ring 62 which retains the rolling-contact bearing assembly 20.

The outer roller 24 is thus rotatable only about the axis Y-Y of the arm 8 and not rotatable about axes perpendicular to the axis Y-Y. The roller 24 can furthermore slide along the axis Y-Y.

Referring to Figure 5, the connecting portion 54 will be seen to comprise an inner connecting surface 56 and an outer connecting surface 58.

The inner connecting surface 56 is at least partly shaped like a partial sphere whose centre CS is situated on the female central axis A-A and aligned with the closed end 16F of the races.

The outer connecting surface 58 is situated exclusively inside a third preferred zone ZP3. This third preferred zone ZP3 is defined, in the or each second reference plane P2, by a partial annular disc whose centre is situated on the central axis A-A and aligned with the closed end 16F of the races 16.

The partial annular disc of the preferred third zone ZP3 has an outer radius

RMV which is 1.1 O x RVE. This partial annular disc has an inner radius RM- which is 0.90 x RVE. The outer connecting surface 58 is preferably shaped like a partial sphere whose centre CS2 is offset from the centre CS of the inner connecting surface 56 towards the shaft 18 of the female element.

The outer connecting surface 58 is joined continuously to the arch 50.

In a variant shown in broken lines in Figure 5, the outer connecting surface 58 comprises a portion shaped like a partial sphere and a flat chamfered portion 60 which is inclined relative to the axis A-A. This chamfered portion 60 is adjacent to the race end wall 32.

The female element 14 also comprises an intermediate race part 100 extending between two races 16 and connecting two races 16 of each set of two pairs of adjacent races. This intermediate race part 100 is situated facing an arch 50.

The female element 14 comprises an intermediate end wall part 102 extending from the intermediate race part 100 to the female central axis A-A.

The intermediate end wall part 102 extends circumferentially between two adjacent race end walls 32.

The intermediate end wall part 102 has an intermediate inner surface 104 and an intermediate outer surface 106. The intermediate inner surface 104 comprises a profile in the form of an arc of a circle extending from the female central axis A-A to the intermediate race part 100. This arc of a circle extends preferably through 90° and in particular exactly 90°. This arc-of-a-circle profile has a radius RII which is equal to the distance between the intermediate part 100 and the female axis A-A.

The intermediate outer surface 106 also has a profile in the form of an arc of a circle, preferably extending through at least 90°. The geometrical features described above make it possible further to reduce the amount of material necessary to produce the female element and the amount of lubricant lost. By means of the invention, the radii of curvature in the race end wall 32 are relatively long, which translates into reduced wear on the forging tools, if this element is produced as a forging.

This shape also makes it possible to use little material for races 16 of a given length.

The space "lost" between the female part and the rollers is also relatively small, so that the constant-velocity joint requires little lubricant.

The features of one of the embodiments can of course also be implemented in the other embodiment. In a variant, the constant-velocity joint has two or more than three arms.

It should be observed that the preferred zones described above are absolute limits for the corresponding surfaces. The actual shaping of the surfaces is of course governed in addition to other constraints, such as the wall thickness, the material, and other process parameters.

Claims

1. Female element for a constant-velocity joint, of the type

- extending about a female central axis (A-A), - comprising at least one pair of races (16) that extend opposite each other, that extend symmetrically about a central plane (M-M) and that define a radial zone (30) relative to the female central axis (A-A),

- having at least one first reference plane (P1 ) perpendicular to the central plane (M-M), parallel to the female central axis (A-A) and extending in the radial zone (30), and

- comprising a race end wall (32) having an outer end wall surface (36) and an inner end wall surface (34) connecting the races in the radial zone (30), the female element defining, in each reference plane (P1 ), a wall thickness Em measured at the junction between the race (16) and the race end wall (32), each of the races (16) being at a centre distance DM, measured in the first reference plane (P1 ) under consideration, from the central plane (M-M) and each of the races having a closed end (16F) which meets the race end wall (32), said female element being characterized in that the outer end wall surface (36) lies, in the or each first reference plane (P1 ), exclusively in a first preferred zone (ZP1 ), and in that the first preferred zone is defined for each first reference plane

(P1 ) by an annular half-disc having a minimum radius r = DM and having a maximum radius R = (DM- + Em-) x 1J3, a centre Cr of the minimum radius r being situated at the intersection between the central plane (M-M) and the closed ends (16F).

2. Female element according to Claim 1 , characterized in that the minimum radius r = DM + Em.

3. Female element according to any one of the preceding claims, characterized in that the outer end wall surface (36) comprises, in the first reference plane (P1 ) under consideration, at least two part-circular portions (37) of radius RR.

4. Female element according to Claim 3, characterized in that the two part-circular portions are connected by a straight portion.

5. Female element according to Claim 3, characterized in that the two part-circular portions (37) are adjacent.

6. Female element according to Claim 5, characterized in that the two part-circular portions (37) form a semicircle of centre C1.

7. Female element according to the preceding claims, characterized in that the centre C1 of the semicircle is offset from the centre Cr of the minimum radius, and in that the outer end wall surface (36) comprises, in the first reference plane under consideration, straight portions (38), particularly portions parallel to the female central axis A-A.

8. Female element according to Claims 1 to 7, characterized in that the inner end wall surface (34) extends, in the first reference plane (P1 ) under consideration, exclusively in a second preferred zone (ZP2), and in that the second preferred zone is defined, for each first reference plane (P1 ), by an inner limit of radius ri = DM and by an outer limit defined by the outer end wall surface (36), and in that the inner end wall surface (34) has a part- circular portion whose radius of curvature is greater than 4 mm and preferably greater than 6 mm.

9. Female element according to Claim 8, characterized in that the radius ri = 1.05 DM.

10. Female element according to Claim 8 or 9, characterized in that, in each first reference plane (P1 ), the inner end wall surface (34) is concave at all points.

11. Female element according to any one of Claims 8 to 10, characterized in that, in each first reference plane (P1 ), the inner end wall surface (34) is joined continuously to the races (16).

12. Female element according to any one of the preceding claims, characterized in that the female element comprises an arch (50) connecting the races (16) of a pair of races and a connecting portion (54) connecting the arch and the race end wall (32), in that the arch (50) has an outer arch surface and defines a circumferential zone (52) extending on both sides of the central plane (M-M) between the races (16) of the pair of races, in that the female element defines at least one second reference plane (P2) extending radially relative to the female central axis, the arch having an outer arch radius RVE in the second reference plane under consideration, in that the connecting portion (54) has an outer connecting surface (58) situated, in the or each second reference plane (P2), exclusively in a third preferred zone (ZP3), in that this third preferred zone is defined by a partial annular disc whose centre is on the female central axis (A-A) and which is aligned with the closed ends (16F) of the races, and in that this partial annular disc has a maximum radius RMV that is 1.10 times the outer arch radius RVE in the second reference plane (P2) under consideration.

13. Female element according to Claim 12, characterized in that the connecting portion (54) has a partially spherical inner connecting surface (56).

14. Female element according to Claim 13, characterized in that the partially spherical inner connecting surface (56) has a centre CS situated on the female central axis (A-A).

15. Female element according to Claim 14, characterized in that the outer connecting surface (58) of the connecting portion (54) is continuously joined to the arch (50).

16. Female element according to any one of Claims 12 to 15, characterized in that the outer connecting surface (58) has a partially spherical portion whose centre CS2 is offset from the centre CS of the inner connecting surface (56).

17. Female element according to any one of Claims 12 to 16, characterized in that the outer connecting surface (58) comprises a chamfered portion (60).

18. Female element according to any one of Claims 12 to 17, characterized in that the female element (14) comprises an intermediate race part (100) extending between two adjacent pairs of races (16), and an intermediate end wall part (102) extending between the intermediate race part (100) and the female central axis A-A, and in that the intermediate end wall part (102) comprises an intermediate inner surface (104) whose profile in an arc of a circle extends from the female central axis A-A to the intermediate race part (100).

19. Female element according to any one of Claims 1 to 18, characterized in that it is a forging.

20. Assembly comprising: - a female element (14) for a constant-velocity joint having a pair of races

(16), and

- a roller (24) suitable for rolling in the races (16), said assembly being characterized in that the female element is a female element (14) according to any one of the preceding claims, and when the roller is on the closed end (16F) of a race, the roller is against the inner end wall surface (34) at a point lying in the central plane (M-M).

21 . Constant-velocity joint comprising a male element (4) having at least one arm (8) defining an arm axis (Y-Y), characterized in that it also comprises an assembly according to Claim 19, and in that the roller (24) is mounted rotatably on the arm (8) about the arm axis.

22. Constant-velocity joint according to Claim 21 , characterized in that the roller (24) is rotatable about at least one axis perpendicular to the arm axis.

23. Constant-velocity joint according to Claim 21 , characterized in that the roller (24) is rotatable exclusively about the arm axis.