GB2462363A

GB2462363A - Differential having a clutch control lever with an adjustable fulcrum

Info

Publication number: GB2462363A
Application number: GB0913505A
Authority: GB
Inventors: Richard Michael Tracy
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-05
Filing date: 2009-08-03
Publication date: 2010-02-10
Also published as: GB0913505D0

Abstract

A differential comprises a differential casing 1 containing a set of sun 5, 6 and planetary gears 8 which are freely rotatable on one or more cross-shafts 7. Limited slip is provided via a clutch 12 between the differential casing 1 and a sun gear 5, 6 providing torque to a half shaft 3. The extent of clutch 12 actuation is controlled by a sleeve 10 splined to the differential casing 1 and slidable in an axial direction of the half shaft 3. An axial position of the sleeve is determined by cramming action between the cross-shafts 7 and a ramp (20, fig 3) carried by the sleeve 10. The sleeve 10 bears against and rotates levers 19 which about a fulcrum26 so as to apply a pressure to the clutch 12 to control its actuation. A position of the fulcrum 19 is adjustable from outside the differential casing 1 by a nut and screw arrangement or another linkage. In other embodiments the sleeve 10 may be replaced without stripping down the differential 1 and/or the sleeve 10 may be segmented.

Description

INTELLECTUAL

. .... PROPERTY OFFICE Application No. GB09 13505.4 RTM Date:20 November 2009 The following terms are registered trademarks and should be read as such wherever they occur in this document: Peugeot Allen Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk

DIFFERENTIAL

This disclosure relates to differential gears, often simply termed: differentials.

Differentials are installed on vehicle axles where independent torque is required for the drive to either side of the vehicle on that axle.

Limited slip differentials such as those disclosed in GB 1414290 Automobile Peugeot and WO 03/0898 12 M & Tec Corp have a differential casing containing sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts.

Limited slip is provided via an intervening clutch between the differential casing and the sun gears providing torque to half shafts to drive wheels on the two sides of the vehicle.

Actuation of the clutches is controlled by sleeves splined to the casing and slidable in the axial direction of the half shafts, the axial position of the sleeves being determined by camming action between the cross-shaft(s) and ramps carried by the sleeves.

Such limited slip differentials have found a use both in the field of motor sports and sports cars where the differential is desired to be locked when static and to become free at high torque, and for off road vehicles for which it is desired to lock the differential at high torque conditions off-road. Between these extremes, a degree of slip is provided.

In order to utilise a limited slip differential to its best potential, namely to gain the best available traction, it should be set up or tuned for the particular circuit or track conditions. For example: a dry tarmac road needs a quite different setting to a gravel track or a wet tarmac circuit. The requirements can also change in the course of a race or rally, so that often a compromise has to be selected that will mean that often the limited slip differential will not be operating under ideal conditions.

Heretofore, in those situations where there was provision for adjustment of the differential, this entailed stripping the differential from the axle before a race, totally disassembling its components, and then rebuilding the differential with those components judged best suited to the expected conditions.

It will be appreciated that this is a time consuming procedure, prone to errors, such as poor choice of tuning parts, and unexpected changes in conditions, for example caused by the weather. In practice, it was not readily feasible to change the differential settings in the course of an event.

As will become apparent from the detailed description below, we have devised embodiments of limited slip differential in which adjustment of the differential is feasible without having to strip it from the axle. As further explained, our teachings enable remote adjustment of the differential settings in some embodiments, making manual adjustment by the driver or automatic adjustment feasible in the course of an event, even while the vehicle is moving.

In accordance with a first aspect of this disclosure, there is provided a differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the axial position of which sleeve is determined by camming action between the or a said cross-shaft and a ramp carried by the sleeve, the sleeve bearing against at least one lever adapted for rotation about a fulcrum to apply a pressure depending upon the rotational position of the lever about its fulcrum to the clutch to control its actuation, and the position of the fulcrum being adjustable from outside the differential casing.

Preferred embodiments have one or more of the following features. The lever applies pressure to the clutch via a pressure plate and clutch spring. The or each said fulcrum is provided by a nut slidable along a groove under the control of a worm drive, against which nut the or a said lever bears. In an alternative arrangement, there are a plurality of levers with respective fulcrums, each said fulcrum being constrained for movement radially of the half shaft axis and coupled via a respective linkage to a ring moveable in the axial direction of the half shaft thereby to move all said fulcrums together in the radial direction.

When the lever is a lever of the first class, sliding of the sleeve away from the cross-shaft, which occurs on increasing torque through the camming action between the ramps and cross-shaft, will tend to increase clutch action, whereas when the lever is a lever of the second class, this same sliding motion will tend to reduce clutch action.

Generally similar differentials may thus be employed for motor sports, where the aim is to free the differential with increasing torque, and for off-road vehicles, where the aim is increasingly to lock the differential as torque increases.

The slidable sleeves are preferably provided with replaceable ramp angle plates, and the differential casing is provided with windows located over the axial ends of the cross-shafts to serve both as a lubrication window and for access to the ramp angle plates to allow them to be replaced without having to strip down the differential. This feature is believed novel in its own right for differential gears.

Accordingly, in a second and alternative aspect of this disclosure, there is provided a differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the axial position of which sleeve is determined by camming action between the or a said cross-shaft and a ramp provided by replaceable ramp angle plates carried by the sleeve, the differential casing being provided with windows located over the axial ends of the cross-shaft(s) for access to the ramp angle plates to allow them to be replaced without having to strip down the differential.

Whether the differential gear is in accordance with the first or second aspects of this disclosure, the sleeve may comprise a plurality of sleeve segments, the segments being disposed relative to each other angularly about the axis of the half-shaft and being axially slidable relative to each other in the axial direction of the half-shaft, and said one or more cross-shafts being disposed relative to the sleeve segments so that each said cross-shaft is positioned for camming action between that cross-shaft and a ramp carried by one said sleeve segment during acceleration and between that cross-shaft and a ramp carried by an adjacent sleeve segment slidable relative to the said one sleeve segment during deceleration. This feature is also believed novel in its own right for differential gears.

Accordingly, in a third alternative aspect of this disclosure, there is provided a differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the sleeve comprising a plurality of sleeve segments, the segments being disposed relative to each other angularly about the axis of the half-shaft and being axially slidable relative to each other in the axial direction of the half-shaft, and said one or more cross-shafts being disposed relative to the sleeve segments so that each said cross-shaft is positioned for camniing action between that cross-shaft and a ramp carried by one said sleeve segment during acceleration and between that cross-shaft and a ramp carried by an adjacent sleeve segment slidable relative to the said one sleeve segment during deceleration.

Preferred embodiments have one or more of the following features: The said one sleeve segment bears against a lever adapted for rotation about a fulcrum to apply a pressure depending upon the rotational position of the lever about its fulcrum to the clutch to control its actuation, and the position of the fulcrum being adjustable from outside the differential casing, and the said adjacent sleeve segment bears against a second lever adapted for rotation about a second fulcrum to apply a pressure depending upon the rotational position of the second lever about its fulcrum to the clutch to control its actuation, and the position of the second fulcrum being adjustable from outside the differential casing. The sleeve comprises two sets of sleeve segments, the cross-shaft(s) bearing against ramps carried by sleeve segments of one said set during acceleration and against ramps carried by sleeve segments of the other said set during deceleration. The fulcrums of levers against which said one set of sleeve segments bear being adjustable together, and the fulcrums of levers against which said other set of sleeve segments bear being adjustable together but separately from those of levers against which said one set of sleeve segments bear. Each ramp is provided by a replaceable ramp angle plate carried by its sleeve segment. Windows are located over the axial ends of the cross-shaft(s) for access to the ramp angle plates to allow them to be replaced without having to strip down the differential.

Preferred embodiments of differential gear are described below by way of example only with reference to the accompanying drawings, in which:-Fig. 1 is a longitudinal sectional view of an embodiment of differential gear; Fig. 2 is an axial end view of the differential gear of Fig. 1 as seen from the right in that Figure, with its crown wheel gear omitted; Fig. 3 is a partially cut-away and partially sectional view of a second embodiment of the differential gear, shown with its crown wheel gear omitted; Fig. 4 is a view generally similar to Fig. I for a third embodiment; Fig. 5 is a view similar to Fig. 1 for a fourth embodiment; Fig. 6 is a partially cut-away and partially sectional view of an embodiment of differential gear, shown with its crown wheel gear omitted, and comprising a modification of the embodiment shown in Fig. 3, here shown in acceleration mode; Fig. 7 is a similar view of the embodiment of Fig. 6 in deceleration mode; and Fig. 8 is an isometric view of a segmented sleeve and cross-shafts in isolation.

Referring first to Figs. I and 2, a differential gear comprises a differential casing 1, which carries a crown wheel gear 2 via which drive is transmitted to the differential.

The differential drives respective half shafts 3, 4, which each carry a sun gear 5, 6, and which are arranged to provide drive to respective wheels on opposite sides of a vehicle.

One or more cross-shafts 7 carry freely rotatable planetary gears 8 which mesh with the sun gears 5, 6. Distal ends 9 of cross-shafts 7 bear against a sleeve 10, which is slidable in the axial direction of the half shafts away from the cross-shaft. Sleeve 10 rotates with the differential casing, being splined in grooves 11 on the inside surface of the differential casing. The sleeve 10 is also coupled to the sun gear 5 on the same side of the vehicle via a clutch 12 comprising a first set of clutch plates 13, slidable in the axial direction in a plurality of grooves 14 formed on the inner side of the sleeve 10, and a second set of clutch plates 15 carried by the sun gear 5. Clutch plates 15 are here shown connected to shaft 16 of sun gear 5, but may be axially slidable in longitudinal grooves formed on the outer side of the sun gear shaft. The clutch plates 15, 16 are here shown biased together by a spring 17, here a Belleville disc washer, and pressure plate 18. In alternative embodiments, the pressure plate may be omitted, or another form of spring, such as one or more compression springs, may be substituted, or both spring and pressure plate may be omitted. A plurality of levers 19 bear against the rear of pressure plate 18 for a purpose to be explained below.

The illustrated embodiment has only one slidable sleeve 10 and only one clutch 12 to provide limited slip, as explained below, an arrangement which works perfectly well.

However, many limited slip differentials, such as the Peugeot and M & Tec prior arrangements mentioned above, have a second slidable sleeve and a second clutch on the other side of the cross-shaft. We contemplate both the single-sided arrangements illustrated and double-sided arrangements in which exactly similar components will be provided on the other side of the cross-shaft.

As the differential is rotated via the crown wheel gear 2, torque is created between the half shafts 3, 4, which causes sliding sleeve 10 to be forced away from cross-shaft 7, by camming action of the distal end 9 of the cross-shafts against ramps 20 providing what is in effect a V-shaped notch in the sleeve 10, as best shown in Fig. 3. Indeed, the ramps may consist of no more than a V-shaped notch in the arrangement of Figs. 1 and 2.

However, we prefer to provide the ramps 20 by interchangeable ramp angle plates 21 replaceably mounted to the sleeve 10, as shown in Fig. 3. Again, as shown in Fig. 3, in that embodiment, the ramp angle plates 21 are mounted in recessed locations on the edge of sleeve 10 by means of fIxings 22. The ramp angle plates may be accessible through windows 23 provided in the differential casing 1 at the axial ends of the cross-shafts 7, as shown in Fig. 3. This allows the ramp angles to be selected without needing to strip down the differential. Different angles of ramp will alter the performance of the differential, changing the rate at which the differential locks or is freed, and there may be different angles for acceleration and for braking.

As sliding sleeve 10 is forced in the axial direction away from the axis of cross-shaft 7, it forces against the clutch 12, creating rotational friction between sun gear 5 and sliding sleeve 10, which rotates with differential casing 1, to cause a degree of lock between the half shafts 3 and 4, by slowing down the movement, or differential of the planetary gears 8. As sliding sleeve 10 continues to move, its proximal end forces against a series of radially spaced pivoting levers 19 located in slots 24 in the sleeve 10. The levers 19 pivot on respective fulcrums 26 to transfer the force back against the clutch 12 via pressure plate 18 and spring 17. The pressure forcing the clutch 12 and sun gear 5 back maintains sun gear 5 in its correct mesh position with planetary gears 8, as opposed to becoming partially disengaged as in the arrangement of the Peugeot Patent mentioned above. This reduces wear, reduces noise and increases strength and longevity of the differential.

In embodiments that lack the pressure plate andlor spring, the levers 19 are still caused to rotate to apply pressure to the clutch pack.

Each lever 19 pivots against a fulcrum 26, the position of which is adjustable.

Movement of the fulcrum towards or away from the axis of the half shafts will alter the pressure exerted on the clutch plates via their spring, which will significantly affect the characteristics of the differential, such as the speed and amount of lock up achieved. In the embodiments of Figs. 1 to 3, the fulcrums are provided by nuts 27 constrained by sides 28 of a groove and threadedly mounted on respective threaded adjusters 29, which on being turned drive their nut along the groove in the manner of a worm drive. Adjuster 29 has a head 30, the underside of which has a plurality of shallow depressions 31 allowing it to be indexed by a spring and ball 32. Indexing may also be provided by an index mark 33 and numerals 34, as shown in Fig. 3. Indexing ensures that all of the fulcrums are positioned at the same distance from the axis of the half shafts, and hence that their levers work together. Each head 31 is here shown with a central depression 35 adapted to receive an Allen key, but may be configured for cooperation with other mechanisms, including a simple screwdriver, for turning the adjuster head. A locating screw 36 extending skew to the axis of the adjuster, cooperates with a circumextending groove 36a in the adjuster (best shown in Fig. 3) to locate the adjuster in its axial direction.

Levers 19 shown in Figs. 1 and 3 are levers of the first class, lobe 37 which bears against the rear of pressure plate 18 being located on the opposite side of the fulcrum from the point of action of the sleeve 10 against the lever. Thus increased displacement of sleeve 10 axially from the axes of the cross-shafts as a result of increased torque results in increased pressure against pressure plate 18 and hence on the clutch. The differential is accordingly increasingly locked as torque increases, which is what is desired in an off-road vehicle.

Fig. 4 illustrates a differential suitable for motor sport. Like reference numerals are used for like parts. While superficially similar to the embodiment of Fig. 1, in the static condition of this differential, the clutch plates 13, 15 are compressed together between clutch spring 17 and an annular washer 37 behind the head of sun gear 5, causing the sun gear to be held stationary and locking the differential. Under increasing torque, the sliding sleeve 10 transmits pressure away from the cross-shaft 7 by camming of the cross-shafts on ramps 20, as before. Pressure is transmitted by the proximal end of sleeve to a plurality of radially spaced pivoting levers. In this embodiment, each such lever 38 is a lever of the second class. Its lobe 39, which bears against the rear of pressure plate 18, lies between the fulcrum 26 and the point of action of sleeve 10 on lever 38. As a result, with increasing torque, sleeve 10 slides to the right in Fig. 4, causing the lever to rotate, reducing the pressure of lever 38 against the pressure plate 18, to release pressure from the clutch pack, allowing the differential to slip and eventually to turn freely. As in the embodiments of Figs. 1 and 3, the rate of release on acceleration or of re-establishment of lock on braking will depend on the position of adjustable fulcrum 26. A locating spring washer 25 returns the lever as the sliding sleeve returns to its initial position as torque is reduced. In alternative embodiments, washer 25 is replaced by one or more compression springs.

The positions of the fulcrums may be adjusted in other ways from the exterior of the differential casing. Thus, in Fig. 5, a radial ring 40 is coupled by suitable linkages 41 to respective rods 42 attached to each fulcrum 26 and slidable in radial grooves 43.

Reciprocation of an actuator arm 44 coupled to the ring 40 to move the ring in the axial direction of the half shafts will cause the rods 42 to move in and out to adjust the radial position of the fulcrums 26. Actuator arm 44 is coupled to ring 40 by a stirrup or fork 45 of the kind commonly employed in gearbox selectors. Movement of the actuator arm may be controlled. It will readily be appreciated that movement of rods 42 or of actuator arm 44 may be controlled by devices such as pneumatic systems, cables, motors, servos, screw threads and solenoids. Indeed any electronic device or mechanical control capable of producing or controlling movement may be employed. Accordingly, adjustment of the position of the fulcrum, which in turn can adjusts operation of the differential, may be achieved from a location remote from the differential, such as a switch or dial on a dash-board of the vehicle, a lever on the exterior of the differential housing, or automatically by a traction control device.

Numerous variations may be made in the embodiments illustrated, but in all cases, the preload and lock up speed/pressure may be adjusted by moving the fulcrums.

Different shapes of lever may be employed resulting in different characteristics. In all the illustrated embodiments, the positions of the fulcrums are shown adjustable in the radial direction relative to the axis of the half-shaft, but this is not necessary. Movement of the fulcrums may be in other directions. The illustrated single-ended arrangements have the slidable sleeve at the end of the differential casing that mounts the crown wheel gear, but both double-ended arrangements and single-ended arrangements in which the opposite end of the differential casing is provided with the slidable sleeve are contemplated. The Belleville disc washer 17 illustrated may be replaced with radially spaced compression springs. The pressure plate 18 is optional. The remote adjusting mechanism may include springs or clutches to move the fulcrum only in a neutral power state. Thus, the pivot may be under considerable load and unable to be moved when a fulcrum movement is initiated. A spring loaded mechanism may be provided to take up and store a preload force, which mechanism will then apply the necessary force and cause movement in the linkage when the fulcrum is able to be moved, such as when the vehicle's clutch is depressed, momentarily to remove torque.

An electronically controlled system may control the adjustment to automatically select predetermined settings upon certain conditions being detected, for example: different settings for hard acceleration or hard braking.

The difference between the embodiment illustrated in Figs. 6, 7 and 8 and that of Fig. 3 is to be found in sleeve 10 which, as best shown in Fig. 8 is segmented, comprising, in this embodiment, eight segments Si, S2, S3, S4, S5, S6, S7 and S8, each splined via a respective groove 46 to differential casing 1, so that adjacent segments disposed angularly relative to each other about the axis of the half-shafts 3, 4 are slidable relative to each other in the axial direction. With rotation in the sense of arrow A during forward acceleration of the vehicle, the cross-shafts 7 will bear against ramps 20, 203, 205 and 207 respectively carried by segments Si, S3, S5 and S7 during acceleration, and against ramps 202, 204, 206 and 208 respectively carried by segments S2, S4, S6 and S8 during deceleration. The ramps 20 may either be provided by the segments themselves, as shown for Segments S2 and S3 in Fig. 3, or may be provided by respective interchangeable ramp angle plates 21, as exemplified by ramp angle plates 212 and 213 for ramps 202 and 203 shown in Figs. 6 and 7. The remaining ramps, other than ramp 2Og, and ramp angle plates are not visible in the views of Figs. 6, 7 and 8.

In the embodiment of Fig. 3, levers 19 bear against the rear of a pressure plate 18, and the angular position of the levers 19 about their fulcrums 26 is determined by the axial position of the sleeve 10. However, in the case of Figs. 6, 7 and 8, each segment of sleeve 10 will have its own lever 19. Accordingly, during acceleration, sleeve segments SI, S3, S5 and S7 will bear against their respective levers 19, 193, 195 and 197, of which only lever I 9 is shown in Fig. 6, to cause them to rotate about their respective fulcrums.

In this embodiment, pressure plate 18 will also be segmented, so that levers 19k, 193, 19 and 19 will bear against respective plate segments 18k, 183, l8 and 187, of which only plate segment 18 is shown in Fig. 6, to control actuation of a clutch 12. Similarly, during deceleration, sleeve segments S2, S4, S6 and S8 will bear against their respective levers 192, 194, 196 and 1 9g (not visible in the drawings) to cause them to rotate about their respective fulcrums. These levers 192, 194, 196 and 198 will bear against respective plate segments 182, 184, 186 and 188 (not visible in the drawings) to control actuation of clutch 12.

The fulcrum 26 for each lever 19 is adjustable from outside the differential casing as in the previously described embodiments. Preferably the levers 19 of each of the two sets of slidable segments are adjusted to the same extent, and may be adjusted in common.

Where the ramps 20 are provided by interchangeable ramp angle plates 21, then, respective windows 23 may be provided in the differential casing for access and replacement without any need to strip the differential as a whole.

Persons skilled in this field will readily appreciate that other features of the differentials shown in Figs. 1 to 5 may also be employed in arrangements with a segmented sleeve 10. In particular, the levers need not be levers of the first class, but may be levers of the second class as in the arrangement of Fig. 4. The differential may be single-sided as in the arrangements illustrated in Figs. 6, 7 and 8, or may be double sided with a second sleeve, clutch and associated parts on the opposite side of the sun and planet gears. The fulcrums of the levers 19 may also adjusted in different ways, as explained above.

Not all the fulcrums need be adjustable. Thus the fulcrums for those levers actuated during acceleration may have adjustable fulcrums, while the fulcrums for the levers that operate only upon deceleration may be fixed.

It will also be appreciated that arrangements with segmented sleeves to give different characteristics on acceleration and deceleration are not restricted to limited slip differentials of the kind described with reference to Figs. I to 5, but may also be applied in a similar manner in other kinds of limited slip differentials, for example, but without restriction, those disclosed in the prior Peugeot and M & Tee Corp arrangements to which reference is made above, where the extent of actuation of an intervening clutch between the differential casing and a sun gear of a set of sun and planetary gears is controlled by a slidable sleeve.

Thus, the use of segmented sleeves in a limited slip differential is considered both novel and inventive in its own right.

Claims

Claims 1. A differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the axial position of which sleeve is determined by camming action between the or a said cross-shaft and a ramp carried by the sleeve, the sleeve bearing against at least one lever adapted for rotation about a fulcrum to apply a pressure depending upon the rotational position of the lever about its fulcrum to the clutch to control its actuation, and the position of the fulcrum being adjustable from outside the differential casing.
2. A differential gear according to Claim 1, wherein the lever applies pressure to the clutch via a pressure plate and clutch spring.
3. A differential gear according to Claim 1 or Claim 2, wherein the or each said fulcrum is provided by a nut slidable along a groove under the control of a worm drive, against which nut the or a said lever bears.
4. A differential gear according to Claim 1 or Claim 2, wherein there are a plurality of levers with respective fulcrums, each said fulcrum being constrained for movement radially of the half shaft axis and coupled via a respective linkage to a ring moveable in the axial direction of the half shaft thereby to move all said fulcrums together in the radial direction.
5. A differential gear according to any preceding Claim, wherein the lever is a lever of the first class, whereby sliding of the sleeve away from the cross-shaft, which occurs in use of the gear on increasing torque through the camming action between the ramps and cross-shaft, will tend to increase clutch action.
6. A differential gear according to any of Claims I to 4, wherein the lever is a lever of the second class, whereby sliding of the sleeve away from the cross-shaft, which occurs in use of the gear on increasing torque through the camming action between the ramps and cross-shaft, will tend to reduce clutch action.
7. A differential gear according to any preceding Claim, wherein the slidable sleeves are provided with replaceable ramp angle plates, and the differential casing is provided with windows located over the axial ends of the cross-shafts to serve both as a lubrication window and for access to the ramp angle plates to allow them to be replaced without having to strip down the differential.
8. A differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the axial position of which sleeve is determined by camming action between the or a said cross-shaft and a ramp provided by replaceable ramp angle plates carried by the sleeve, the differential casing being provided with windows located over the axial ends of the cross-shaft(s) for access to the ramp angle plates to allow them to be replaced without having to strip down the differential,
9. A differential according to any preceding Claim, wherein the sleeve comprises a plurality of sleeve segments, the segments being disposed relative to each other angularly about the axis of the half-shaft and being axially slidable relative to each other in the axial direction of the half-shaft, and said one or more cross-shafts being disposed relative to the sleeve segments so that each said cross-shaft is positioned for camming action between that cross-shaft and a ramp carried by one said sleeve segment during acceleration and between that cross-shaft and a ramp carried by an adjacent sleeve segment slidable relative to the said one sleeve segment during deceleration.
10. A differential gear of the kind comprising a differential casing containing a set of sun and planetary gears, the planetary gears being freely rotatable on one or more cross-shafts, and limited slip being provided via an intervening clutch between the differential casing and a sun gear providing torque to a half shaft for providing drive to a wheel of a vehicle; the extent of clutch actuation being controlled by a sleeve splined to the differential casing and slidable in the axial direction of the half shaft, the sleeve comprising a plurality of sleeve segments, the segments being disposed relative to each other angularly about the axis of the half-shaft and being axially slidable relative to each other in the axial direction of the half-shaft, and said one or more cross-shafts being disposed relative to the sleeve segments so that each said cross-shaft is positioned for camming action between that cross-shaft and a ramp carried by one said sleeve segment during acceleration and between that cross-shaft and a ramp carried by an adjacent sleeve segment slidable relative to the said one sleeve segment during deceleration.
11. A differential gear according to Claims 9 or 10, wherein the said one sleeve segment bears against a lever adapted for rotation about a fulcrum to apply a pressure depending upon the rotational position of the lever about its fulcrum to the clutch to control its actuation, and the position of the fulcrum being adjustable from outside the differential casing, and the said adjacent sleeve segment bears against a second lever adapted for rotation about a second fulcrum to apply a pressure depending upon the rotational position of the second lever about its fulcrum to the clutch to control its actuation, and the position of the second fulcrum being adjustable from outside the differential casing.
12. A differential gear according to any of Claims 9, 10 or 11, wherein the sleeve comprises two sets of sleeve segments, the cross-shaft(s) bearing against ramps carried by sleeve segments of one said set during acceleration and against ramps carried by sleeve segments of the other said set during deceleration.
13. A differential gear according to both Claim 11 and Claim 12, wherein the fulcrums of levers against which said one set of sleeve segments bear being adjustable together, and the fulcrums of levers against which said other set of sleeve segments bear being adjustable together but separately from those of levers against which said one set of sleeve segments bear.
14. A differential gear according to Claims 12 or 13, wherein each ramp is provided by a replaceable ramp angle plate carried by its sleeve segment, and wherein windows are located over the axial ends of the cross-shaft(s) for access to the ramp angle plates to allow them to be replaced without having to strip down the differential.
15. A differential gear substantially as hereinbefore described with reference to and as shown in Figs. 1 to 5 the accompanying drawings.
16. A differential gear substantially as hereinbefore described with reference to and as shown in Figs. 6, 7 and 8 of the accompanying drawings.