WO2004009392A1

WO2004009392A1 - Inter-axle differential having improved bearing arrangement

Info

Publication number: WO2004009392A1
Application number: PCT/US2003/021368
Authority: WO
Inventors: James F. Ziech
Original assignee: Dana Corporation
Priority date: 2002-07-19
Filing date: 2003-07-09
Publication date: 2004-01-29
Also published as: AU2003248871A1

Abstract

An inter-axle differential is provided that reduces end play of the input shaft and improves lubrication of bearing surfaces on the input shaft. The differential (30) includes an input shaft (36), a spider (38) coupled to the input shaft and supporting a differential pinion gear (40), an output gear (44) in mesh with the pinion differential gear and an output shaft (48) extending from the output gear and configured for rotation with the output gear. A tapered bearing (50) is disposed between the input shaft and the output gear. The tapered bearing limits axial and radial movement of the input shaft and increases the opening available for splash lubrication of the input shaft.

Description

INTER-AXLE DIFFERENTIAL HAVING AN IMPROVED BEARING

ARRANGEMENT

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to inter-axle differentials and, in particular, to an improved inter-axle differential for use in a tandem axle assembly.

2. Discussion of Related Art

A conventional tandem axle assembly includes forward and rear axle assemblies and an intermediate drive shaft assembly connecting the two axle assemblies. The forward and rear axle assemblies each include a pair of axle half shafts extending therefrom on wliich one or more wheels of a vehicle are mounted. Each of the forward and rear axle assemblies further include a wheel differential that allows the vehicle wheels on each axle assembly to rotate at different speeds. Each of the differentials includes a pinion gear in mesh with a ring gear (wliich in turn drives a plurality of bevel gears to cause rotation of the axle half shafts). The pinion gears of the forward and rear axle assemblies are driven by an inter-axle differential generally housed within the forward axle assembly (with the pinion gear in the rear axle assembly being driven by the inter-axle differential through the intermediate drive shaft assembly).

An inter-axle differential for a conventional tandem axle assembly includes an input shaft extending into a housing of the forward axle assembly and a spider mounted on the input shaft and supporting a plurality of bevel pinion gears. The differential further includes a pair of side gears in mesh with, and driven by, the pinion bevel gears. One side gear, or input gear, is used to drive the pinion gear of the forward axle assembly wheel differential. The other side gear, or output gear, is coupled to an output shaft that extends outwardly from the forward axle assembly housing and drives the intermediate drive shaft assembly.

The output gear of a conventional inter-axle differential is typically supported on the rearward end of the input shaft for relative rotation with the input shaft using a plain bearing or a set of needle roller bearings. In each case, the bearings extend parallel to the axis of rotation of the input shaft and output gear. These conventional differentials have suffered from several problems. First, the input shaft is subject to a relatively large amount of end play. Second, the manufacture of the differential is relatively expensive and requires close tolerances. In particular, precise control of the input shaft diameter is required as well as a relatively smooth finish, a precisely shaped crown, and/or the addition of oil flats without sharp edges. Third, the rearward end of the input shaft is difficult to lubricate during spinout because the opening for splash lubrication is relatively small thereby increasing the risk of a part failure.

The inventors herein have recognized a need for an inter-axle differential that will minimize and/or eliminate one or more of the above-identified deficiencies.

SUMMARY OF THE INVENTION

The present invention provides an inter-axle differential.

An inter-axle differential in accordance with the present invention includes an input shaft, a spider supported on the input shaft, and a differential pinion gear coupled to the spider. The differential further includes an output gear in mesh with the differential pinion gear and an output shaft extending from the output gear and configured for rotation with the output gear. Finally, the differential includes a tapered bearing disposed between the input shaft and the output gear. In accordance with one embodiment of the invention, the tapered bearing includes a plurality of bearings supported between a cone and a cup. The cone is disposed about the input shaft and defines an inner race for the bearings. The cup is disposed against the output gear and defines an outer race for the bearings, h accordance with another embodiment of the invention, the tapered bearing includes a cone as described above and a plurality of bearings supported between the cone and the output gear. The output gear itself defines an outer race for the bearing.

An inter-axle differential in accordance with the present invention is advantageous. The inventive differential reduces end play in the input shaft by limiting axial and radial movement of the input shaft. This increases the life of components of the inter-axle differential including gears and seals. The inventive differential also is less expensive to manufacture because special processing of the input shaft is reduced and/or eliminated. Finally, the inventive suspension reduces friction and also increases the opening available for splash lubrication of the input shaft thereby preventing spinout failures. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view of a tandem axle assembly. Figure 2 is a partial cross-sectional view of the forward axle assembly of the tandem axle assembly of Figure 1 showing an inter-axle differential in accordance with one embodiment of the present invention.

Figure 3 is an enlarged, cross-sectional view of a portion of the forward axle assembly of Figure 2.

Figure 4 is an enlarged view of a portion of a forward axle assembly for a tandem axle assembly illustrating an inter-axle differential in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views, Figure 1 illustrates a tandem axle assembly 10. Axle assembly 10 is provided to support the frame (not shown) of a vehicle on a plurality of wheels (not shown). Assembly 10 is particularly adapted for use in medium and heavy trucks. It should be understood, however, that the present invention is not limited to use in medium and heavy trucks and may be used in a wide variety of vehicles. Assembly 10 includes a rear axle assembly 12, an intermediate drive shaft assembly 14, and a forward axle assembly 16.

Rear axle assembly 12 is provided to drive wheels (not shown) supported on either side of assembly 12 on axle half shafts (not shown) extending from axle assembly 12 and is conventional in the art. Assembly 14 is provided to transfer torque from an output shaft of forward axle assembly 16 to rear axle assembly 12 and is also conventional in the art. Assembly 14 may include an output yoke 18 at a forward end, an input yoke 20 at a rear end, an intermediate drive shaft 22 between yokes 18, 20 and conventional universal joints 24, 26 for coupling drive shaft 22 to yokes 18, 20. Forward axle assembly 16 is provided to drive wheels (not shown) supported on either side of assembly 16 on axle half shafts (not shown) extending from axle assembly 16. Referring now to Figure 2, axle assembly 16 may include a housing 28, an inter-axle differential 30 for dividing power between assembly 12 and assembly 16, a differential locking device, such as clutch 32 and a wheel differential assembly 34.

Housing 28 provides structural support for the other components of assembly 16. Housing 28 also protects the other components of assembly 16 from foreign objects and elements. Housing 28 may be made from conventional metals and metal alloys such as steel and may include multiple members (only one of which is shown in Figure 2) that are sized relative to components of assembly 16 and coupled together using conventional fasteners.

Inter-axle differential 30 is provided to divide power between assemblies 12, 16. Differential 30 may include an input shaft 36, a spider 38, differential pinion gears 40, an input gear 42, and output gear 44, a pump 46, and an output shaft 48. In accordance with the present invention, differential may further include a bearing 50. hiput shaft 36 is provided to transmit power from a power input shaft (not shown) at the forward end of forward axle assembly 16 to differential gears 40 and is conventional in the art. Input shaft 36 is driven by the power input shaft through a conventional input yoke 52. The input yoke 52 may be splined to the forward end of input shaft 36 and may be retained thereon by a nut (not shown) and a washer (not shown) which are disposed about a threaded stud that extends from the forward end of shaft 36 and is integral therewith. A cap 54 is disposed about the input yoke 52 and is received within an opening in housing 28. Shaft 36 is journalled for rotation within an opening in cap 54 and housing 28 by a tapered roller bearing 56 disposed within the opening. As best shown in Figure 3, input shaft 36 may include a pilot portion 58 extending from a rearward end of input shaft 36 forming a shoulder 60.

Spider 38 provides a mounting arrangement for differential pinion gears 40 and is conventional in the art. Spider 38 is supported on input shaft and may be coupled to input shaft 36 for rotation therewith using a spline connection or in other ways customary in the art. Alternatively, spider 38 maybe made integral with input shaft 36.

Differential pinion gears 40 are provided to divide and transfer torque from input shaft 36 to gears 42, 44. Gears 40 are conventional in the art and may be made from conventional metals and metal alloys. Gears 40 are coupled to spider 38 for rotation with spider 38 and input shaft 36. The teeth on gears 40 engage corresponding teeth on gears 42, 44.

Input and output gears 42, 44 transfer torque from differential pinion gears 40 to wheel differential assembly 34 and output shaft 48, respectively. Gears 42, 44 are conventional in the art and may be made from conventional metals and metal alloys. Gear 42 is disposed about input shaft 36 and is freely rotatable thereon, being journalled on shaft by bearings (not shown). Gear 42 includes a first set of teeth on a forward planar surface which form a first member of clutch 32 and a second set of teeth disposed on a rear planar surface that mesh with the teeth of differential gears 40. Gear 42 further includes a third set of teeth disposed about the radial periphery of gear for engagement with a corresponding gear in assembly 34. Gear 44 is disposed about output shaft 48 near the forward end of shaft 48 and may be coupled thereto by mating splines (not shown) on gear and shaft. Alternatively, gear 44 may be integral with shaft 48. Gear 44 is journalled for rotation within housing by a tapered roller bearing 62. As best shown in Figure 3, in accordance with one embodiment of the present invention, gear 44 defines a shoulder 64 complementary to shoulder 60 of on input shaft 36.

Pump 46 is provided to lubricate the components of differential 30. Pump 46 may be located between input shaft 36 and output shaft 48 within a bore defined in output gear 44 as set forth in commonly assigned U.S. Patent Application Serial No. 09/791,724 filed on January 18, 2001, the entire disclosure of which is incorporated herein by reference.

Output shaft 48 is provided to transmit a portion of the power provided by input shaft 36 to the intermediate drive shaft assembly 14. Shaft 48 is coaxially disposed relative to input shaft 36 and extends outwardly from gear 44. Shaft 48 rotates with gear 44. Shaft 48 extends through openings in housing 28 and is journalled within one opening of housing 28 by bearings 66, 68.

Referring to Figure 3, bearing 50 provides bearing support allowing relative rotation of input shaft 36 and output shaft 48. In accordance with one embodiment of the present invention, bearing 50 includes a cone 70, a cup 72, and one or more tapered roller bearings 74 disposed between cone 70 and cup 72. Cone 70 defines an inner race for bearings 74. Cone 70 is disposed about pilot portion 58 of input shaft 36 and is abuts against shoulder 60. Cone 70 tapers in a rearward direction. Cup 72 defines an outer race for bearings 74. Cup 72 is also disposed about pilot portion 58 of input shaft 36 radially outwardly of cone 70 and abuts against shoulder 64 formed in output gear 44. Cup 72 opens in a forward direction. Referring to Figure 4, in accordance with another embodiment of the present invention, a bearing 50' includes only a cone 70 and one more tapered roller bearings 74 disposed between the cone 70 and an output gear 44'. Gear 44' defines a tapered surface that defines an outer race for bearings 74.

The use of a tapered bearing 50 in differential 30 provides significant advantages as compared to conventional inter-axle differentials. Bearing 50 limits both axial and radial movement of input shaft 38 thereby increasing component life in differential 30. Bearing 50 also provides improved anti-friction characteristics and provide a larger opening for splash lubrication of input shaft 36 and other components of differential 30. In this manner, bearing 50 reduces the change of a component failure during spinout conditions. Finally, shaft 36 can be manufactured less expensively because a smooth finish is not required.

Clutch 32 is provided to selectively lock differential 30 and is conventional in the art. In the illustrated embodiment, clutch 32 comprises a conventional sliding dog clutch that may be engaged by sliifting a clutch member 76 with a first set of teeth into engagement with a clutch member (gear 40 in the illustrated embodiment) having a second set of teeth using a shifting fork.

Wheel differential assembly 34 is provided to transfer torque from input shaft 36 to vehicle wheels (not shown) and to allow the wheels to rotate at different speeds. Assembly 34 is conventional in the art and may include a pinion shaft 78, a pinion gear 80, a driven gear 82, bearing sets 84, 86, a ring gear (not shown), and a conventional differential gear assembly (not shown).

Pinion shaft 78 transmits torque to pinion gear 80 and is conventional in the art. Shaft 78 is supported for rotation within housing 28 by bearing sets 84, 86. A forward axial end of shaft 78 may define an integral threaded stud configured to receive a nut 88 used to retain bearing sets 84, 86 and gear 82 in position on shaft 78.

Pinion gear 80 transfers torque from pinion shaft 78 to a ring gear (not shown). Pinion gear 80 may be made from conventional metals and metal alloys and may comprise a hypoid gear. Gear 80 is disposed about shaft 78 and may be mounted thereto using a conventional spline connection or in other ways customary in the art.

Driven gear 82 transmits torque from input gear 40 of inter-axle differential 30 to pinion shaft 78. Driven gear 82 may comprise a helical gear having teeth disposed about its radial periphery which engage corresponding teeth on input gear 40.

Bearings 84, 86 enable rotation of pinion shaft 78 relative to housing 28. Bearings 84, 86 are conventional in the art and may include tapered roller bearings.

While the invention has been shown and described with reference to one or more particular embodiments thereof, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

CLAIMSWe claim:

1. An inter-axle differential, comprising: an input shaft; a spider supported on said input shaft; a differential gear coupled to said spider; an output gear in mesh with said differential gear; an output shaft extending from said output gear and configured for rotation therewith; and, a tapered bearing disposed between said input shaft and said output gear.

2. The inter-axle differential of claim 1 wherein said input shaft includes a pilot portion extending from one end and said tapered bearing is disposed between said pilot portion of said input shaft and said output gear.

3. The inter-axle differential of claim 1 wherein said tapered bearing includes: a cone supported on said input shaft and defining an inner race; a cup disposed against said output gear and defining an outer race; and, a plurality of bearings disposed between said cone and said cup.

4. The inter-axle differential of claim 3 wherein said cone abuts against a shoulder of said input shaft and said cup abuts against a complementary shoulder of said output gear.

5. The inter-axle differential of claim 1 wherein said tapered bearing includes: a cone supported on said input shaft and defining an inner race; and, a plurality of bearings disposed between said cone and said output gear, said output gear defining an outer race.

6. The inter-axle differential of claim 1 wherein said tapered bearing comprises a tapered roller bearing.

7. An axle assembly, comprising: a housing; an inter-axle differential having: an input shaft supported for rotation within said housing by a first tapered bearing; a spider supported on said input shaft; a differential gear coupled to said spider; an output gear in mesh with said differential gear and supported for rotation within said housing by a second tapered bearing; an output shaft extending from said output gear and configured for rotation therewith; and, a third tapered bearing disposed between said input shaft and said output gear.

8. The axle assembly of claim 7 wherein said input shaft includes a pilot portion extending from one end and said third tapered bearing is disposed between said pilot portion of said input shaft and said output gear.

9. The axle assembly of claim 7 wherein said third tapered bearing includes: a cone supported on said input shaft and defining an inner race; a cup disposed against said output gear and defining an outer race; and, a plurality of bearings disposed between said cone and said cup.

10. The axle assembly of claim 9 wherein said cone abuts against a shoulder of said input shaft and said cup abuts against a complementary shoulder of said output gear.

11. The axle assembly of claim 7 wherein said third tapered bearing includes: a cone supported on said input shaft and defining an inner race; and, a plurality of bearings disposed between said cone and said output gear, said output gear defining an outer race.

12. The axle assembly of claim 7 wherein said third tapered bearing comprises a tapered roller bearing.