GB2208689A

GB2208689A - Axle unit for motor vehicle

Info

Publication number: GB2208689A
Application number: GB8814915A
Authority: GB
Inventors: Brian Edward Cherrington
Original assignee: GKN Axles Ltd
Current assignee: Dana Spicer Europe Ltd
Priority date: 1987-07-01
Filing date: 1988-06-23
Publication date: 1989-04-12
Also published as: GB2208689B; GB8814915D0; GB8715418D0

Abstract

An axle unit for a motor vehicle, comprising a housing containing a crown wheel and pinion gearing, the pinion (14) being provided at the end of an input shaft supported in the housing by a first bearing (16) adjacent the pinion and a second bearing (17) remote from the pinion. Between the bearings (16, 17) the housing defines a chamber (31) surrounding the input shaft, and oil is fed to such chamber in use by a passage (32). A formation (34) extends into the chamber (31) to provide a retaining wall to maintain a level of oil in bearing assembly (17) and an oil circulation passage (36) when not in use, to ensure lubrication of the bearing assembly (17) under start up conditions. <IMAGE>

Description

AXLE UNIT FOR MOTOR VEHICLE This invention relates to an axle unit for a motor vehicle, comprising a housing containing a crown wheel and pinion gearing. The axle unit may form part of a live rigid axle, or may be arranged to be fixed to the structure of the vehicle and drive the vehicle's wheels through laterally extending universally jointed drive shafts.

In a motor vehicle axle unit, it is usual to arrange for lubrication of the moving parts thereof, which comprise the crown wheel and pinion themselves, a differential gearing associated with the crown wheel, bearings by which the crown wheel and differential gearing are supported, and an input shaft carrying the pinion and supported by bearings, by oil which is splashed and impelled within the housing by rotation of the crown wheel. The housing has a sump portion which contains sufficient oil for the crown wheel to dip into it in use and thus impel the oil. There have been many proposals for arrangements of passages within the housing, to ensure that all the operating parts of the axle unit are adequately lubricated.

The bearings by which the input shaft is supported in the housing are subject to high loads in use. It is usual to provide two bearings spaced along such input shaft, and lubrication of the bearing which is farthest away from the pinion presents particular difficulties.

Whilst such bearing can be adequately lubricated when the unit is operating and a steady circulation of oil has been established, the bearing may suffer from lack of lubrication when first started from rest, because it takes an appreciable time after starting before oil reaches it and oil previously in the bearing may have drained therefrom during a long rest period. The problem arises particularly in an axle unit wherein the axis of the input shaft is offset from and disposed above the axis of the crown wheel.

An example of an axle unit in which there is provided means for distributing lubricant to the working parts thereof is disclosed in British Patent 1 124 697.

The axle unit contains an inter-axle differential mechanism and a crown wheel and pinion mechanism for driving one axle, the crown wheel and pinion mechanism being disposed in the lower part of the housing of the unit such that the level of lubricant in the housing is approximately level with the bearings of the pinion.

Thus the pinion bearings are effectively lubricated both at start-up and in continuous running.

An example of an axle unit wherein the casing affords passages to direct lubricant to the bearings of a pinion which may be above the static level of lubricant in the housing is disclosed in British Patent 2 015 095.

However, the above described problem of lubricating the pinion bearings under start-up conditions still exists.

It is the object of the present invention to overcome this disadvantage.

According to the invention, we provide an axle unit for a motor vehicle, comprising a housing containing a crown wheel and pinion gearing, the pinion being provided at the end of an input shaft supported in the housing by a first bearing adjacent the pinion and a second bearing remote from the pinion, the crown wheel being supported in the housing for rotation about an axis extending transversely relative to the axis of said input shaft and for connection, by way of a differential gearing, to two output elements, the housing being provided with a formation arranged to receive from the crown wheel oil carried thereby during rotation thereof in use and a passage arranged to deliver such oil to a space surrounding the input shaft between the bearings thereof, wherein the housing includes a formation arranged to retain oil in the second bearing of the input shaft when the crown wheel is not rotating.

By virtue of the provision of a formation to retain oil in the second bearing of the input shaft, lubrication of such bearing is ensured even under start up conditions, before supply of oil to such bearing is established.

The housing may provide a space at the side of the second bearing of the input shaft remote from the pinion, and a passage leading from such space to the space between the bearings at the side of said formation adjacent the second bearing. Where, as is usually the case, the bearings of the input shaft comprise taper roller bearings, such passage provides for circulation of oil through the second bearing from starting until oil circulation is established from the main quantity of oil contained in the housing.

The invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a horizontal section through part of an axle unit according to the invention; Figure 2 is a vertical section through the part unit.

The illustrated axle unit comprises a housing, part of which is indicated at 10. The housing supports, by bearing means 9, for rotation about an axis which extends transversely of the vehicle in use, a differential gearing. The differential gearing comprises a carrier 11, planet bevel gears of which one is seen at 7, and side gears 6 which have splined bores for connection to half shafts or other output elements. The carrier is secured, by circumferentially spaced bolts 12, to a crown wheel 13. The crown wheel 13 meshes with a pinion 14, provided at the end of an input shaft 15. The shaft 15 is supported in the housing part 10 by two taper roller bearing assemblies 16, 17. The bearing assembly 16 has an inner race 18 which abuts the pinion 14, an outer race 19 which abuts a shoulder 20 in the housing with the interposition of shims 21, and taper rollers 22.The bearing assembly 17 comprises an outer race 23 which abuts a shoulder 24 in the housing, taper rollers 25, and an inner race 26 which is abutted by a drive flange 27 held on a splined end portion of the shaft 15 by a nut 28. An oil seal 29 engages a cylindrical portion 30 of the drive flange 27.

Between the bearing assemblies 16, 17, the housing 10 defines an annular chamber 31 surrounding the shaft 15. A passage 32 is provided in the housing and leads into the chamber 31, the passage 32 having an entrance opening 33 which is aligned with the crown wheel 13.

Between the bearing assemblies, the housing has a formation 34 which extends upwardly into the chamber 31, approximately level with the centre of the adjacent end of the lowermost roller 25 in the bearing assembly 17.

At the opposite side of the bearing assembly 17, a space 35 is defined between the bearing assembly and the oil seal 29, and a passage 36 extends downwardly from such space and upwardly into the chamber 31 adjacent the formation 34.

In use, oil contained in the lower part of the housing, into which the crown wheel dips, is impelled by the crown wheel 13 and thrown therefrom to enter the passage 32 through its opening 33. Oil is thus delivered to the chamber 31 surrounding the shaft 15 between the bearing assemblies 16, 17. In use, it will be appreciated that taper roller bearing assemblies act as pumps, each tending to pump oil from the smaller diameter end to the larger diameter end thereof, so that oil is circulated through the bearing assembly 17, returning to the chamber 31 by way of passage 36. Oil passes from chamber 31 back to the main part of the housing through the bearing assembly 16. When we refer to oil being impelled by the crown wheel, it will be appreciated that in some designs of axle unit the crown wheel may be provided with or connected to a member specifically intended for impelling oil to ensure effective lubrication, and such provision is intended to be included within the scope of the present invention and the claims hereof.

When not in use, formation 34 acts as a retaining wall or weir, to retain oil up to the level of the formation 34, in the bearing assembly 17, space 35 and passage 36. Thus lubrication of such bearing assembly is assured when starting from rest, or at very low speeds when oil circulation is not established in the assembly.

The axle unit above described is one wherein the axis of rotation of the input shaft carrying the pinion is offset above the axis 8 of the crown wheel and differential gearing carrier. The provision of formation 34 and passage 36 is particularly advantageous in such an axle unit, but it will be appreciated that the invention is not applicable solely to such a unit. The axis of rotation of the input shaft may be below that of the crown wheel, and yet the bearings of the input shaft still be above the level of the oil in the housing; in such an arrangement the invention is also beneficial.

Claims

1. An axle unit for a motor vehicle, comprising a housing containing a crown wheel and pinion gearing, the pinion being provided at the end of an input shaft supported in the housing by a first bearing adjacent the pinion and a second bearing remote from the pinion, the crown wheel being supported in the housing for rotation about an axis extending transversely relative to the axis of said input shaft and for connection, by way of a differential gearing, to two output elements, the housing being provided with a formation arranged to receive from the crown wheel oil carried thereby during rotation thereof in use and a passage arranged to deliver such oil to a space surrounding the input shaft between the bearings thereof, wherein the housing includes a formation arranged to retain oil in the second bearing of the input shaft when the crown wheel is not rotating.

2. An axle unit according to Claim 1 wherein the first and second bearings of the input shaft comprise taper roller bearings.

3. An axle unit according to Claim 2 wherein the housing provides a space at the side of the second bearing of the input shaft remote from the pinion, and a passage leading from such space to the space between the bearings, at the side of said formation adjacent the second bearing.

4. An axle unit according to any one of the preceding claims wherein the axis of the input shaft is above the axis of the crown wheel.

5. An axle unit substantially as hereinbefore described with reference to the accompanying drawings.