WO2013043202A1

WO2013043202A1 - Low axial bearing arrangement for straddle mounted hypoid pinion

Info

Publication number: WO2013043202A1
Application number: PCT/US2011/053187
Authority: WO
Inventors: Joseph Palazzolo; Jason Bock
Original assignee: Gkn Driveline North America, Inc.
Priority date: 2011-09-25
Filing date: 2011-09-25
Publication date: 2013-03-28

Abstract

Disclosed is an exemplary differential axle assembly that includes a pinion gear attached to a pinion shaft for concurrent rotation therewith. The pinion gear includes a distal end and a proximal end. A bearing pocket is formed in the proximal end of the pinion gear. A first bearing member is mounted on the pinion shaft, and is configured to support a thrust load in a first axial direction. A second bearing member is mounted on the pinion shaft and is configured to support a thrust load in a second axial direction. A third bearing member disposed in the bearing pocket of the pinion gear and is configured to support a radial load.

Description

LOW AXIAL BEARING ARRANGEMENT FOR

STRADDLE MOUNTED HYPOID PINION

Background Art

Automotive differential assemblies are typically configured to transmit an input drive torque from a pinion gear to a ring gear and associated bevel pinions mounted in an axle housing. The bevel pinions mesh with corresponding output bevel gears attached to two output or half-shafts that extend one on each side of the ring gear. In a typical "straddle mount configuration", the pinion gear is mounted on a pinion shaft and supported on two axially spaced bearing assemblies carried by a housing of the differential assembly. A first bearing assembly typically supports a first end portion of the pinion shaft normally associated with a vehicle drive shaft, and a second bearing assembly, located on an opposite side of the pinion gear from the first bearing assembly, supports a second end portion of the pinion shaft located adjacent the ring gear of the differential assembly. The second bearing assembly is supported on an internal flange that extends from the differential assembly housing and is mounted on a pin extending axially outward from an end of the pinion gear. To provide sufficient clearance between the flange supporting the second bearing and the axle housing, a rotational axis of the pinion gear is typically offset a distance from a rotational axis of the ring gear. However, this generally has the effect of decreasing the efficiency of the pinion gear and ring gear. Generally speaking, reducing the offset between the axis of rotation of the pinion gear and the axis of rotation of the ring gear results in a corresponding improvement in the operating efficiency of the ring gear and pinion gear.

Brief Description of Drawings

FIG. 1 is a partial cross-sectional view of an exemplary vehicle differential assembly employing a straddle mounted pinion gear;

FIG. 2 is a partial cross-sectional view of the pinion gear taken along section 2-2 of

FIG. 1 ;

FIG. 3 is a schematic side elevational view of the ring gear and the pinion gear of the exemplary vehicle differential assembly of FIG. 1 ; and

FIG. 4 is a schematic side elevational view of a straddle mounted pinion gear employing a support bearing mounted on a pin extending axially outward from an end of the pinion gear. Detailed Description

Referring to FIGS. 1 and 2, a vehicle differential assembly 10 may include a differential 1 1 disposed within a differential assembly housing 12. Differential assembly 10 may include a pinion gear 14 fixedly attached to a pinion shaft 16 for concurrent rotation therewith. Pinion shaft 16 and pinion gear 14 may be formed as a single unitary pinion gear assembly, for example, as illustrated in FIGS. 1 and 2. Alternatively, pinion gear 14 and pinion shaft 16 may formed as separate components that may fixedly connected together to form the pinion gear assembly.

Pinion gear 14 may be straddle mounted on the pinion shaft 16 and supported by a pinion gear bearing assembly 17 and a straddle bearing 19. The term "straddle mounted," as used throughout this specification, is intended to cover differential assemblies in which a pinion gear is mounted on a pinion shaft supported on axially spaced bearing assemblies (e.g., pinion gear bearing assembly 17 and straddle bearing 19 carried by the housing 12).

The pinion gear bearing assembly 17 may include a head bearing 18a and a tail bearing 18b received in an aperture 22 formed in housing 12. To support the relatively high thrust load transferred by the pinion shaft 16, the head and tail bearings 18a and 18b of the pinion gear bearing assembly 17 may be configured as tapered roller bearings. Tapered roller bearings employ a conical geometry that permits greater loads to be carried than with other bearing configurations, such as ball bearings, and can typically handle both large axial forces (e.g., thrust load) and large radial forces (e.g., radial load). Tapered roller bearings, however, are typically capable of supporting axially loads in only one direction. To support axial loads equally in either direction, head bearing 18a and tail bearing 18b are arranged in opposite directions on pinion shaft 16. For example, head bearing 18a may be orientated on pinion shaft 16 to support an axial thrust load "A", whereas tail bearing 18b may be orientated to support an axial thrust load "B" applied in a direction opposite to axial thrust "A". In practice, the positioning and/or orientation of head bearing 18a and tail bearing 18b may be reversed. For example, head bearing 18a and tail bearing 18b may swap positions on pinion shaft 16 and/or the orientation of the bearings may be reversed, provided the bearings are arranged in opposite directions so as to support axial forces in both directions. Head bearing 18a and tail bearing 18b include rolling elements 21 having an axis of rotation arranged obliquely relative to an axis of rotation of pinion gear 14.

With continued reference to FIGS. 1 and 2, the pinion gear 14 meshes with a ring gear assembly 24 that includes a ring gear 25 having ring teeth 27. Pinion gear 14 includes a plurality of pinion gear teeth 20 that meshingly engage the corresponding plurality of ring gear teeth 27 associated with ring gear 25. Ring gear assembly 24 may be mounted to an axle housing 38 having an outer wall 45. Axle housing 38 may be carried by ring gear bearings 26 mounted in the housing 12. Drive torque may be transmitted from the ring gear assembly 24 via bevel pinions 28 mounted on a transverse shaft 30 to bevel gears 32, which are splined to output shafts 34 and 35 of the differential assembly 10. The output shafts 34 and 35 may be supported in the housing 12 by shaft bearing assemblies 36 and 37.

The pinion gear 14 is disposed within the differential assembly housing 12 and rotatably extends about a pinion axis A₁ (FIG. 3). The pinion gear 14 includes a distal end 46 and a proximal end 48. The plurality of pinion gear teeth 20 extend between the distal end 46 and the proximal end 48 at an oblique angle relative to pinion axis A₁. The distal end 46 may have a larger diameter than the proximal end 48. The proximal end 48 is generally arranged adjacent to the outer wall 45 of the axle housing 13. The pinion shaft 16 and pinion gear 14 include a common axis of rotation corresponding to pinion axis A₁. Pinion shaft 16 extends generally perpendicular to the distal end 46 of the pinion gear 14.

The pinion gear 14 includes a bearing cavity 52 arranged at the proximal end 48 for receiving the straddle bearing 19. The bearing cavity 52 is defined by a generally cylindrical side wall 56 and an end wall 57 arranged opposite a bearing cavity opening 58 in proximal end 48. The bearing cavity 52 is open to the proximal end 48 through opening 58 and is substantially centered about the pinion axis A₁.

Referring in particular to FIG. 2, the straddle bearing 19 has a width W₁ and is disposed in the bearing cavity 52. The straddle bearing 19 includes a first end 74 arranged adjacent to end wall 57 of bearing cavity 52, and a second opposite end 75 arranged adjacent to the proximal end 48 of pinion gear 14. End 75 of the straddle bearing 19 may be aligned substantially flush with, or recessed from the proximal end 48 of the pinion gear 14. The straddle bearing 19 has an inner diameter D₃. Since substantially the entire axial thrust load transferred through pinion shaft 16 is supported by head bearing 18a and tail bearing 18b, straddle bearing 19 may be configured to primarily support a radial load caused by the meshing of ring gear teeth 27 with pinion gear teeth 20. Not having to support a substantial thrust load allows straddle bearing 19 to be configured as cylindrical roller bearing, needle bearing, or spherical bearing, rather than a tapered roller bearing. A cylindrical roller bearing may have a smaller physical size than a corresponding tapered roller bearing configured to have a similar load carrying capacity, which may allow for a smaller diameter pinion gear than may possible when using a tapered roller bearing. Stradle bearing 19 includes a plurality of rolling elements 59 having an axis of rotation aligned substantially parallel to pinion axis A-i .

Straddle bearing 19 may be supported by a bearing support member 60 that includes a boss 54 that extends into bearing cavity 52. The boss 54 may extend from the opening 58 at the proximal end 48 of the pinion gear 14 to the end wall 57. The boss 54 may engage an inner race of the straddle bearing 19. The support member 60 may be arranged adjacent the proximal end 46 of the pinion gear 14, and may have a thickness T (FIG. 1 ) and a width W₂ (FIG. 2). The diameter of boss 54 may be substantially equal to width W₂ of support member 60. The support member 60 extends along the proximal end 48 of the pinion gear 14, but generally does not extend above an outer circumference of the boss 54. As illustrated in FIG. 1 , the thickness T of the support member 60 may be less than a maximum width W₁ of the straddle bearing 19. Further, the thickness T and the width W₂ of the support member may be less than the inner diameter D₃ (FIG. 2) of the straddle bearing 19. Support member 60 is separated from axle housing 13 by a distance D₁.

Referring to FIGS. 3 and 4, wall 45 of axle housing 13 may define a differential envelope 62. Ring gear 25 is generally arranged outside of the envelope 62. The ring gear 25 rotates about an axis of rotation A₂. To provide clearance between support member 60 and axle housing 13 the pinion axis A₁ may be offset from the axis A_2, by a distance D₂. To maximize efficiency it is desirable to have pinion axis A₁ arranged as close to axis A₂ as possible. Generally, the efficiency of the differential assembly 10 increases as the distance D₂ between pinion axis A₁ and the axis A₂ decreases. As the distance D₂ decreases, the engagement between pinion gear teeth 20 and ring gear teeth 27 decreases, which tends to decrease the frictional forces between the teeth. Decreasing the frictional forces tends to decrease the heat generation caused by the meshing of the gears. This may increase long term durability of the differential assembly and reduce its complexity by eliminating the need for an external cooling system.

The clearance between the outer wall 45 and the support member 60 is indicated as D₁. Because the boss 54 is disposed substantially within bearing cavity 52 of the pinion gear 14, the maximum width W₁ of the bearing 56 may be greater than the thickness T of the support member 60. Decreasing the thickness T of the support member 60 provides additional clearance (D-i) between support member 60 and axle housing 13. The additional clearance may allow pinion axis Ai to be moved closer to axis A₂, thereby increasing the efficiency of the differential assembly. Thus, the ability to decrease the thickness T of the support member 60 may enable the axis of rotation A₁ of pinion gear 14 to be moved closer to the axis of rotation A₂ without having the support member 60 contacting the outer wall 45 of the axle housing 13.

With continued reference to FIGS. 3 and 4, recessing straddle bearing 19 within bearing cavity 52 may also enable a wider variety of manufacturing options to be employed for forming pinion gear teeth 20. For example, FIGS. 3 and 4 illustrate a gear cutter tool path C that may be followed by a gear cutting tool when forming pinion gear teeth 20. With straddle bearing 19 recessed in bearing cavity 52, as illustrated in FIG. 3, there is no additional material extending from the proximal end 48 of pinion gear 14 that may interfere with the travel of the gear cutting tool. However, mounting straddle bearing 19 on a boss extending from the proximal end 48 of pinion gear 48, for example, as illustrated in FIG. 4, may cause the gear cutting tool to contact the boss during manufacturing, which may adversely effect the cutting of the gear teeth 20.

It will be appreciated that the exemplary axel assembly described herein has broad applications. The foregoing configurations were chosen and described in order to illustrate principles of the methods and apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize methods and apparatuses in various configurations and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of the disclosed container have been explained and illustrated in exemplary configurations.

It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that the disclosed axel assembly may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the configuration described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the disclosed container should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as "a," "the," "said," etc., should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the device and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the device is capable of modification and variation and is limited only by the following claims.

Claims

1. An axle assembly comprising:

a pinion shaft;

a pinion gear fixedly attached to the pinion shaft for concurrent rotation therewith, the pinion gear having a distal end and a proximal end, the pinion gear including a bearing pocket formed in the proximal end;

a first bearing member mounted on the pinion shaft, the first bearing member configured to support a thrust load in a first axial direction;

a second bearing member mounted on the pinion shaft, the second bearing member configured to support a thrust load in a second axial direction; and

a third bearing member disposed in the bearing pocket of the pinion gear, the third bearing member configured to support a radial load.

2. The axle assembly of claim 1 , wherein the first and second bearing members are tapered roller bearings.

3. The axle assembly of claim 2, wherein the third bearing member is at least one of a cylindrical roller bearing and a needle bearing.

4. The axle assembly of claim 1 , wherein the third bearing member includes a rolling element having an axis of rotation aligned substantially parallel to an axis of rotation of the pinion shaft.

5. The axle assembly of claim 4, wherein at least one of the first and second bearing members includes a rolling element having an axis of rotation arranged obliquely relative to the axis of rotation of the pinion shaft.

6. The axle assembly of claim 1 further comprising a support member including a boss disposed within the bearing pocket in the proximal end of the pinion gear.

7. The axle assembly of claim 6, wherein the boss engages an inner race of the third bearing member.

8. The axle assembly of claim 1 , wherein at least one of a width and a thickness of the support member is less than an inner diameter of the third bearing member.

9. The axle assembly of claim 8, wherein both the width and thickness of the support member is less than the inner diameter of the third bearing member.

10. The axle assembly of claim 1 , wherein the first and second bearing members are arranged on a first side of the distal end of the pinion gear and the third bearing member is arranged on an opposite second side of the distal end of the pinion gear.

1 1. The axle assembly of claim 1 , wherein the third bearing member is at least one of a cylindrical roller bearing, a needle bearing and a spherical bearing.

12. The axle assembly of claim 1 , wherein substantially the entire third bearing member is disposed between the distal and proximal ends of the pinion gear.

13. The axle assembly of claim 1 , wherein the distal end of the pinion gear has a larger diameter than the proximal end of the pinion gear.

14. An axle assembly comprising:

a pinion shaft;

a pinion gear fixedly attached to the pinion gear for concurrent rotation therewith, the pinion gear having a distal end and a proximal end, the pinion gear including a bearing cavity formed in the proximal end;

a first bearing member attached to the pinion shaft, the first bearing member configured to support an axial thrust load; and

a second bearing member engaging the bearing cavity in the pinion gear, the second bearing member including a rolling element having an axis of rotation aligned substantially parallel to an axis of rotation of the pinion shaft.

15. The axle assembly of claim 14 further comprising a third bearing member attached to the pinion shaft, the first and third bearing members arranged on the same side of the distal end of the pinion gear.

16. The axle assembly of claim 15, wherein the third bearing member includes a rolling element having an axis of rotation arranged obliquely relative to the axis of rotation of the pinion shaft.

17. The axle assembly of claim 14, wherein the first bearing member includes a rolling element having an axis of rotation aligned obliquely relative to the axis of rotation of the pinion shaft.

18. The axle assembly of claim 14 further comprising a support member including a boss disposed within the bearing cavity.

19. The axle assembly of claim 14, wherein the boss engages an inner race of the second bearing member.

20. The axle assembly of claim 14, wherein a thickness of the support member is less than a width of the bearing.

21. The axle assembly of claim 14, wherein substantially the entire second bearing member is arranged between the proximal and distal ends of the pinion gear.

22. The axle assembly of claim 14, wherein the distal end of the pinion gear has a larger diameter than that of the proximal end.