GB2059523A

GB2059523A - A Locking Differential Gear for the Driving Axle of a Motor Vehicle

Info

Publication number: GB2059523A
Application number: GB8031173A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1979-09-26
Filing date: 1980-09-26
Publication date: 1981-04-23

Abstract

A friction clutch (2) is arranged between two half axle shafts (1, 3) of the driving axle, preferably between only one (3) of the half axle shafts and the differential carrier (4), so as to "cut-out" the differential, e.g. when one wheel is on ice. Means are provided for actuating the friction clutch (2) manually, e.g. via a sliding sleeve (23) and actuating fork (24), or in an alternative embodiment via a pivoting actuating fork. The fork (24) may be operated by a pneumatic cylinder 26 which may be controlled by a regulator valve as a function of vehicle speed or gear ratio. <IMAGE>

Description

SPECIFICATION A Locking Differential Gear for the Driving Axle of a Motor Vehicle This invention relates to a locking differential gear for the driving axle of motor vehicle, particularly of a bus having a friction clutch arranged between half axle shafts of the driving axle.

In winter, buses, as opposed to long distance coaches, often have to stand with their near-side driving wheel on ice or snow (e.g. in a bus-stop layby) while their off-side driving wheel may be resting on a cleared or gritted portion of the road.

When the bus starts, therefore, especially from bus stops, the differential gear will be subjected to extremely severe loads when the near-side driving wheel is spinning. Where such load conditions are encountered frequently, the differential gear will tend to wear out prematurely.

The practice has been to eliminate excessive loads on the differential gear, especially when caused by wheel spinning, by means of claw-type actuating clutches arranged between the half axle shafts. Such manually-controlled locking differential gears are used, especially in off-road vehicles. Such locking differential gears, however, can only prevent the differential action altogether or completely allow it. Such a manually-controlled locking differential will not solve the problem encountered with buses as described above, because the driver would either have to operate the differential gear much too often, which would be at every bus stop, or because friction losses, fuel consumption, tyre wear and differential gear wear would all be excessive should the driver prefer to leave the differential locking gear engaged, at full locking effect, throughout driving operations.

A publication designated G 4061 P-NG 675003, by Zahnradfabrik Friedrichshafen AG, describes a self-locking differential gear of restricted locking action, where a disc-type clutch arranged between the half axle shafts serves to produce a locking effect between the half axle shafts which varies with the drive torque applied at the differential carrier. Such devices provide an advantage over the manually-controlled locking devices as described above in that the bus driver will not continually have to engage and disengage the locking device when road conditions vary, because the locking action is controlled automatically.However, such a self-locking differential gear cannot be turned off, so that considerable friction losses will have to be accepted at the time that friction between the road and the driving wheels is high, which is most of the time a vehicle is on the road.

An object of the present invention is to provide a locking differential gear which can be adapted in a simple fashion to the road conditions prevailing at the moment such that losses and/or wear are prevented or at least significantly reduced.

The invention provides a locking differential gear for a driving axle of a motor vehicle comprising a friction clutch arranged between two half axle shafts, wherein means are provided for manually controlling the friction clutch.

The prime advantage afforded by the present invention is that when the coefficients of friction between the road and the driving wheels are high, the locking action can be eliminated completely, so that for a great portion of the time the vehicle is on the road, wear and losses are eliminated.

When friction is low in adverse weather, the differential locking device can be allowed to stay on continuousiy, considering that the locking action is to some degree adjustable via the friction clutch.

Preferably, the friction clutch is arranged between the differential carrier and only one of the half axle shafts. With a view to the space required for the locking differential gear this arrangement provides an advantage in that the friction clutch can then be arranged laterally outside the differential carrier.

A special advantage is provided when the friction clutch is arranged outside the differential casing, because use can then be made of conventional, production-type differential casings, which are subsequently fitted with manually controlled locking devices. A locking device arranged outside the differential casing will afford an advantage also in terms of ease of installation.

The invention will now be described with reference to embodiments shown by way of example in the accompanying drawings, wherein: Figure 1 is a part-sectional view of the axle box of a motor vehicle having a locking differential gear in accordance with the present invention, Figure 2 is an enlarged view of part of Figure 1 showing a different locking device, and Figure 3 is an enlarged view of part of Figure 1 showing a different actuating device.

Figure 1 illustrates the central portion of an axle box for a rigid drive axle of a motor vehicle having an axle tube 8 and a differential casing 6.

A differential carrier 4 is rotatably mounted within the differential casing 6 in antifriction bearings 61. A crown wheel 41 is fixedly bolted to the differential carrier 4 and meshes with a bevel pinion 62 also mounted in the differential casing 6. Half axle shafts 1 and 3 are to be balanced by the differential gear. A locking device is provided between one half axle shaft 3 and the differential carrier 4 and is in the form of a friction clutch 2.

The friction clutch 2 is a disc clutch having two friction liners 21 with an intermediate disc 22 arranged therebetween and splined to the half axle shaft 3. As may be seen from the drawing, the friction clutch 2 is arranged within the axle tube 8 but is still outside the differential casing 6.

This severely limits the outer diameter of the friction clutch 2, and in order to be able to transmit the requisite forces of friction between the half axle shaft 3 and the differential carrier 4, it may be necessary to use, in lieu of the single intermediate disc 22 and two friction liners 21, a larger number of intermediate discs and friction liners. In the embodiment of Figure 2 the friction clutch is a cone clutch 2a, which gives more coupling area for the same, maximum total diameter of the clutch. The remaining components of Figure 2 are indicated by the same reference numerals used in Figure 1.

With reference again to Figure 1 the friction clutch 2 is operated via a sleeve 23 and an actuating fork 24, the sleeve 23 being connected to the fork 24 by means of a release bearing (antifriction members 28). In the embodiment of Figure 1 the actuating fork 24 is slidably carried on a guide pin 25 and parallel to the centre-line of the half axle shaft 3. The contact pressure for the friction clutch 2 is generated in a pneumatic cylinder 26, which is carried on or in the axle casing. Charging of the pneumatic cylinder 26 with compressed air from a compressed-air reservoir 92 is controlled by means of a pressure regulator valve 9 shown in broken line in Figure 3.

In this arrangement the pressure regulator valve 9 can be operated as a function of vehicle speed or of the shifting position of a change speed gear.

Actuation of the regulator valve 9 is indicated by arrowhead 91 in Figure 3.

Unlike the arrangement of Figure 1, where the fork 24 undergoes a translatory movement in a direction parallel to the centre-line of the half axle shaft 3, the fork of the embodiment shown in Figure 3 is a one-armed lever 24a. This onearmed lever abuts against a stop 81 of the axle tube 8. This arrangement obviates the need for sliding guidance and guide bolts 25 (Figure 1).

The advantage of providing the fork in the shape of a one-armed lever is that, with the appropriate leverage, great contact pressure of the friction clutch can be achieved.

Claims

1. A locking differential gear for a driving axle of a motor vehicle comprising a friction clutch arranged between two half axle shafts, wherein means are provided for manually controlling the friction clutch.

2. A locking differential gear as claimed in claim 1, wherein the friction clutch is arranged between the differential carrier and only one of the half axle shafts.

3. A locking differential gear as claimed in claim 1 or 2, wherein the friction clutch is arranged outside a casing of the differential.

4. A locking differential gear as claimed in claim 1, 2-or 3, wherein the friction clutch is operated via a sleeve and an actuating fork.

5. A locking differential gear as claimed in claim 4, wherein the actuating fork is a singlearmed lever.

6. A locking differential gear as claimed in any one of claims, wherein the clutch, or the actuating fork, is operated via a pneumatic cylinder.

7. A locking differential gear as claimed in claim 6, wherein actuating pressure is variable by means of a pressure regulating valve provided for the pneumatic cylinder.

8. A locking differential gear as claimed in claim 7, wherein the actuating pressure is variable as a function of vehicle speed.

9. A locking differential gear as claimed in claim 7, wherein the actuating pressure is applied as a function of the gear position of a change speed gear.

10. A locking differential gear as claimed in any one of claims 1 to 9, wherein the friction clutch is a cone-type clutch.

11. A locking differential gear as claimed in any one of claims 1 to 9, wherein the friction clutch is a disc-type clutch.

12. A locking differential gear for a driving axle of a motor vehicle, substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.

1 3. A motor vehicle having a locking differential gear as claimed in any one of the preceding claims.