GB2199907A - Limited slip differential conversion - Google Patents

Abstract

A standard bevel gear differential is modified by boring out the casing to receive belleville washers (6) and thrust washer (8). A thrust block spacer (7) is located between two sum gears (3), preferably having an elongated hole to allow floating on a mounting pin (5) of the plant gears. Shims are added behind the thrust washer (8) to take up wear. <IMAGE>

Description

LIMITED SLIP DIFFERENTIAL CONVERSION This information relates to a limited slip differential conversion for a motor vehicle.

Limited slip differentials are used widely in motor sport and in off road vehicles to increase the grip of the vehicle to the road surface and to increase the road holding. These differentials limit the amount a wheel can spin when it loses grip and hence transfer more torque to the wheel at the other end of the axle.

Usually friction is the means used to limit the amount of wheel spinning. Many different types of vehicle are used in motorsport but some, particularly those used by newcomers to the sport, are not fitted with limited slip differentials because they are very costly new and almost unobtainable on the 'second-hand' market.

It is essential to have a limited slip differential fitted in order to be competitive.

This invention utilizes the standard parts of a vehicle differential in combination with new components to produce a limited slip differential.

The casing and end plate are bored to provide space for belleville washers and thrust washers and shims.

A thrust block spacer is added and the sun gears and output shafts may be modified to produce a bearing surface.

The complete assembly can be bolted together with different combinations of belleville washers and shims to allow the static slipping torque to be set between 15lbft (2.073kgm) and 120lbft (16.588kgm).

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in cross section the assembled differential with the new parts fitted in their respective positions and the clearances which need to be machined in parts land 2; Figure 2 shows in perspective an exploded view of the parts illustrating how they fit together; Figure 3 illustrates in orthographic views the spacer which is the essential part of the conversion; and Figure 4 shows in orthographic views the thrust washer which prevents wear on the casing.

Referring to the drawing the differential conversion comprises a thrust spacer 7 which is squeezed between the two sun gears 3 by belleville washers 6 which bear on thrust washer 8. Shims can be added behind the thrust washers to take up wear when required. The spacer has an elongated hole through it to allow it to float when wear occurs and to assist assembly of the parts.

In order to fit the belleville washers and thrust washer into the assembly, clearance has to be made by machining the differential case at end plate as shown in Figure 1A and B.

In order to assemble the differential, the belleville washers in the casing 2, may require to be compressed before the planet gears and thrust washers, spacer and differential pin can be inserted. Once this has been done the differential is assembled in the usual manner and bolted together.

The assembly can now be fitted to the gearbox, axle, etc.

Claims (7)

1 A limited slip differential conversion comprises of a thrust block spacer, belleville washers, shims and any relevant modification to the differential case and end plate and interBal gears, output shafts and differential pins.

2 A limited slip differential conversion as claimed in Claim 1 wherein the thrust block spacer has an elongated hole through it which allows it to float on the differential pin.

3 A limited slip differential conversion as claimed in Claim 1 or Claim 2 wherein the thrust block spacer has hard bearing surfaces where it contacts the sun gears or output shafts.

4 A limited slip differential conversion as claimed in Claim 1 or Claim 2 or Claim 3 wherein the thrust block spacer is such a shape and made with such a material that it can withstand the compression forces placed upon it.

5 A limited slip differential conversion as claimed in Claim 1 wherein the thrust washers are prevented from revolving.

6 A limited slip differential conversion as claimed in Claim 1 or Claim 5 wherein the thrust washers are made from a suitably hard or hardened material so as to reduce frictional wear on their surfaces.

7 A limited slip differential conversion as claimed in Claim 1 wherein belleville washers are used to produce thrust induced friction. This is achieved by fitting the shims and belleville washer to the modified casing followed by the output shaft/sun gear followed by the spacer and planet gears which are held in position by a dummy pin of smaller diameter.

The other output shaft/sun gear and belleville washers are assembled onto the modified crownwheel/end plate and the unit is bolted together thus compressing the belleville washers and moving the spacer into position such that the original pin can be drifted into situation. The unit now has a preload applied to it and it will only operate as a bevel gear differential when the preload is overcome. The preload can be adjusted by fitting gaskets between the crownwheel/end plate and the casing which reduces the preload and slipping torque and by the addition of shims between the thrust washer and the casing, which increases the preload and slipping torque.

7 A limited slip differential conversion as claimed in Claim 1 wherein belleville washers are used to produce thrust induced friction.

8 A limited slip differential conversion as claimed in Claim 1 wherein shims may be used behind the thrust washers to repack the differential after wear has occured.

9 A limited slip differential conversion as described in Claim 1 wherein some internal parts of the differential may have to be welded or machined or both.

10 A limited slip differential conversion as described herein with reference to Figures 1 - 5.

Amendments to the claims -have been filed as follows CLAIMS 1 A limited slip differential conversion is a method of converting a standard bevel gear differential to a limited slip differential by incorporating a thrust block spacer, belleville washers and shims into the original unit.

The original casing will have to be bored to accept the belleville washers and shims and the crownwheel will also have to be bored to accept belleville washers if it acts as the end plate to the unit. A special end plate may have to be produced if the crownwheel is of the ring type.

2 A limited slip differential conversion as claimed in Claim 1 wherein the thrust block spacer has an elongated hole through it which allows it to float on the differential pin and to facilitate assembly of the unit.

3 A limited slip differential conversion as claimed in Claim 1 or Claim 2 wherein the thrust block spacer has hard bearing surfaces where it contacts the sun gears or output shafts.

4 A limited slip differential conversion as claimed in Claim 1 or Claim 2 or Claim 3 wherein the thrust block spacer is such a shape and made with such a material that it can withstand the compression forces placed upon it.

5 A limited slip differential conversion as claimed in Claim 1 wherein the thrust washers are prevented from revolving by the addition of tabs on the outer edges which locate in grooves or protrude through the casing.

6 A limited slip differential conversion as claimed in Claim 1 or Claim 5 wherein the thrust washers are made from a suitably hard or hardened material so as to reduce frictional wear on their surfaces.