FIELD OF THE INVENTION

[0001] The present invention relates to the differentials.

DESCRIPTION OF THE PRIOR ART

[0002] Differentials are used in power transmission systems, particularly of vehicles, to distribute the torque supplied from a power source to a pair of outputs. In the conventional vehicle application, the differential acts to transfer torque received from the engine and transmission to each of the wheels on an axle. The differential contains an arrangement of gearing that balances the torque supplied to each of the outputs. In this manner, a differential rotational speed of each output can be accommodated, allowing the vehicle to negotiate a curve without undue stress on the drive shafts or wheels. Differentials may also be used to distribute torque between a pair of axles in a vehicle in a similar manner.

[0003] A differential therefore is a critical component in the power transmission system of a vehicle or other machinery, and, as with many other similar components, there is a continued demand to reduce the expense and mass associated with such components whilst retaining their overall performance. Conventionally, a differential will include a housing to support the differential gearing and receive each of the output shafts. The housing is connected to an input drive member, typically a ring gear or hypoid gear, so that the power flows from the input drive member to the housing and through the differential gears to the output shaft. The differential housing is a relatively complex component that is typically cast and subsequently machined.

[0004] It has previously been proposed to support the differential gearing on the input drive member and to support the output shafts on housings connected to the drive member. European patent 1803972 and German application 4441163 each show an arrangement in which a cross shaft extends diametrically across a ring gear with differential pinions mounted on the cross shaft. A pair of housings are connected to the ring gear and support output pinions that mesh with the differential pinions. The half shafts are connected to the output pinions. Similar arrangements may be found in US patent 5,584,777 and German patent application 4042173.

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22460882.2 [0005] In the arrangement shown in the German reference 4441163, the differential pinion acts against a bearing that absorbs the axial thrust imposed on the differential pinion. The bearing is located on a radial flange of the ring gear so as to be held against rotation relative to the ring gear. This arrangement of bearing complicates assembly and manufacture, in that the pinion must be slid axially along the cross shaft after installation of the cross shaft on the ring gear. This requires manipulation of several components from both sides of the assembly.

[0006] It is therefore an object of the present invention to provide a differential assembly in which the above disadvantages are obviated or mitigated.

SUMMARY OF THE INVENTION

[0007] In general terms, the present invention provides a differential to transfer torque between input and a pair of outputs. The differential comprises an annular input member and a pair of housings disposed on oppositely directed faces of the input member. Each of the housings has a surface that engages the opposite sides of the input member and extends radially inwardly beyond the input member to provide a pair of opposed abutment surfaces. A pair of output pinions are rotatably supported in respective ones of the housings and a pair of differential pinions are rotatably supported on a cross shaft extending diametrically across the input member. The differential pinions mesh with the output pinions to provide a torque transmitting path between the input member and the output pinions. A bearing member is disposed between each of the differential pinions and the input member. The bearing member has a projection that extends radially outwardly and is received between the opposed abutment surfaces of the housings. The engagement of the projection with the housings inhibits rotation of the bearing relative to the input member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] An embodiment to the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0009] Figure 1 is a front elevation of a differential assembly;

[0010] Figure 2 is perspective view of a section through the differential assembly of Figure 1 ;

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22460882.2 [0011] Figure 3 is an exploded view showing the components of the differential assembly of Figure 1 ;

[0012] Figure 4 is a section on the line IV- IV of Figure 1 ;

[0013] Figure 5 is a perspective view of a component used in the assembly of Figure 1 ;

[0014] Figure 6 is a perspective view of a bearing component used in the assembly of Figure 1;

[0015] Figure 7 is a view on the line VII- VII of Figure 4;

[0016] Figure 8 is a view on the line VIII- VIII of Figure 4; and

[0017] Figure 9 is a section on the line IX- IX of Figure 4.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring therefore to Figures 1 and 2, a differential 10 includes an annular input member 12 that is driven from a prime mover (not shown) such as an internal combustion engine or electric motor. The annular input member 12 has a radially outer surface 13 and a cylindrical radially inner surface 14. In the embodiment, the drive member 12 is formed as a ring gear with gear teeth 16 formed on the radially outer surface 13. It will be understood that the gear teeth 16 mesh with a complementary gear indicated G in Figure 1 driven by the prime mover. It will also be understood that other forms of drive may be used, such as a hypoid gear set or a belt, either toothed or friction drive, and that the outer surface 13 will have the appropriate form to receive such a drive.

[0019] As best seen in Figures 2,4 and 8, the drive member 12 includes a web 18 that extends radially inwardly from the outer surface to an enlarged annular boss 20. The boss 20 has a pair of oppositely directed support surfaces 22 that merge with the radially inner surface 14. Transverse holes 24 are uniformly distributed about the boss 20.

[0020] The boss 20 is formed with a pair of diametrically opposed notches 26 (Figure 3) that receive opposite ends of a cross shaft 28 that extends diametrically across the input member 12 . Opposite ends of the cross shaft 28 are machined to provide a pair of flats 30 that are spaced apart the width of the notch 26. The flats 30 allow the cross shaft 28 to be slid into the notches 26 and inhibit rotation of the cross shaft 28 within the drive member 12.

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22460882.2 [0021] The cross shaft 28 rotatably supports a pair of differential pinions 32. The pinions 32 are formed with beveled gears 34 and a spherical outer face 36. A bearing 38 is located on the cross shaft 28 so as to be interposed between the differential pinion 32 and the radially inner surface 14 of the boss 20. Referring to Figure 6, the bearing 38 is square in plan with peripheral edges 39 and a bore 48 that extends through the bearing 38 to receive the cross shaft 28. The bearing 38 has an inwardly directed spherical surface 40 that is complementary to the spherical surface 36 on the differential pinion and of sufficient area to support the differential pinion. An oppositely facing support surface 42 has a central band 44 formed as a radial projection from the surface 42. The band 44 has a pair of oppositely directed flanks 46 and an outer surface 47. The surface 47 is part cylindrical with a radius corresponding to that of the inner surface 14 of the driver member 12. The surface 42 extends to either side of the band 44 to provide a pair of shoulders 45. The shoulders 45 are preferably found as a part cylindrical or part conical surface to facilitate the forming or machinery of the surface 42.

[0022] Returning to Figure 1, 3 and 7, the pinions 32 mesh with a pair of output pinions 50 that are rotatably supported within respective ones of a pair of housings 52. The pinions 50 each have a collar 54 that is rotatably received within a counter bore 56 of the housing 52. A thrust washer 58 is located between the output pinion 50 and the housing 52 to absorb axial loads. The output pinions 50 are provided with an internal bore 59 which is splined to receive drive shafts (D in Figure 1) or other suitable form of torque transmitting engagement.

[0023] The housing 52 has a cylindrical boss 68 that is machined to receive a bearing (B in Figure 1) that supports the housing 52 within a support structure, typically a transmission housing. The body of housing 52, as shown in Figure 5, is generally hemispherical and terminates in a flange 60. The flange 60 has a series of holes 62 distributed about the circumference corresponding to the holes 24 formed in the boss 20. A lip 64 projects from the flange 60 and has a radially outer diameter corresponding to the diameter of the inner surface 14 of the drive member 12.

[0024] The lip 64 is interrupted by a pair of slots 66 at diametrically opposite positions on the housing 52. The slot 66 may be formed in situ when the housing is cast or forged and/or may be machined to the required dimensions post forming. As shown, the slot 66 extends through the wall of the housing 52 to facilitate oil flow around the pinions, but it will be

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22460882.2 appreciated that an enclosed housing may be used where required. The circumferential extent of the slot 66 corresponds to that of the bearing 38 and the depth of the slot 66 corresponds to the spacing between the flank 46 and the outer edge 39 of the bearing 38 so that the bearing is snugly received in the slot 66. The radially outer extent, 68, of the slot is part cylindrical and of the same nominal radius as that of the surface 47.

[0025] To assemble the differential 10, one of the output pinions 50 is located within the corresponding housing 52 with the thrust bearing 56 interposed between the pinion 50 and the housing 52. The drive member 12 is then positioned on the housing and located by the lip 64. The drive member 12 is oriented so that the recesses 26 are centrally located in the slots 66 which of course is facilitated by alignment of the holes 24, 62.

[0026] The pinions 32 are located on the cross shaft 28 and the respective bearings 38 positioned radially outwardly of the pinions. The cross shaft 28 is then inserted into the drive member 12 with the flats 30 aligned with the notches 26. The differential pinions 32 engage the output pinion 50 to maintain the radial spacing between the differential pinions.

[0027] The insertion of the cross shaft into the notches 26 causes the bearing 38 to be received within the notch 66. With the bearing snugly received within the notch 66, the flank 46 of the projection 44 abuts the flange 60 and therefore provides an abutment surface for the bearing 38 to inhibit rotation relative to the drive member 12.

[0028] The second of the output pinions 50 may then be located on the differential pinions 32 and the other housing 52 located on the opposite face of the drive member 12. The assembly may then be connected with bolts 70 passing through each of the housing 52 and the boss 20. The lip 64 of the second housing is located within the radially inner surface 14 of the drive member 12 and the notches 66 receive the bearings 38. The flank 46 of the projection 44 is again located against the flange 60 so that rotation of the bearing 38 is inhibited. The surface 47 of the projection 44 is a sliding fit with the inner surface 14 so that the bearing 32 is properly supported.

[0029] In operation, drive is transmitted through the input member 12 and torque is transferred into the cross shaft 28. Assuming that an equal torque can be accommodated on each of the outputs, the differential pinions 32 and output pinions 50 rotate in unison with the drive member 12 on the bearings B so as to rotate the output shafts. If the torque on one of

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22460882.2 the output pinions 50 is greater to that of the other, a rotation of the differential pinion 32 will be induced about the cross shaft 28 to balance the torque in each of the outputs. As the pinion 32 rotates, the bearing 38 is held stationary by the engagement of the flanks 46 with the flanges 60 so that relative rotation occurs between the spherical faces 36 and 42. The abutment provided by the flanks 46 of the projection 44 inhibits rotation to the bearing 38 and thereby ensures that premature wear of the drive member and housings does not occur.

[0030] It will be seen therefore that the provision of the projection 44 and the engagement of that projection with the flanges of the housings 52 facilitates assembly of the differential and provides proper support for the rotation of the differential pinions. It will also be noted that as the bearing 38 is held against rotation relative to the drive member by the engagement of the abutment surfaces, the surfaces 42 and 47 need only be machined as a cylindrical surfaces as opposed to a spherical surfaces which further facilitates the manufacture of the components. The thickness of the shoulders 45, that is the spacing between the surfaces 40, 42, is chosen to provide the requisite stiffness to properly support the differential pinions with the band 44 being fully supported against the inner surface 14 of the input member 12.

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22460882.2