Combined coupling and differential assemblies

Abstract

A combined coupling and differential assembly 100 for a vehicle 10 (fig 1) comprising; a differential 120; an engageable coupling 130; a common housing assembly 140; and a hydraulic actuation mechanis

Description

Technical Field The present disclosure relates to combined coupling and differential assemblies and is particularly, although not exclusively, concerned with combined coupling and differential assemblies which provide improved torque distribution. Background During normal operation of a motor vehicle, the motor vehicle, e.g. a transmission assembly of the motor vehicle, may be configured to supply drive torque to either the front road wheels or the rear road wheels of the motor vehicle. The motor vehicle may be provided with an all-wheel drive assembly, which may be operable to distribute drive torque to the front and rear wheels of the motor vehicle. The all-wheel drive assembly may be configured to enable a driver to selectively supply drive to both the front and rear wheels of the motor vehicle. For example, if the motor vehicle is being operated over more difficult terrain, or if the driven road wheels of the motor vehicle being to slip, the driver may operate the all-wheel drive assembly to supply drive torque to additional road wheels, so that the motor vehicle can continue driving over the more difficult terrain. It may be desirable to configure the all-wheel drive system such that torque is distributed evenly between the road wheels on either side of the motor vehicle when the all-wheel drive system is operating. Statements of Invention According to an aspect of the present disclosure, there is provided a combined coupling and differential assembly for a motor vehicle, the combined coupling and differential assembly comprising: a differential; an engageable coupling; a common housing assembly, in which the differential and the engageable coupling are housed; and a hydraulic actuation mechanism for engaging and disengaging the engageable coupling; wherein the common housing comprises: an outer housing assembly rotatable about a central axis of rotation by means of a ring gear drivingly attached to the outer housing assembly; and an inner housing assembly disposed within the outer housing and rotatable about the central axis relative to the outer housing, wherein the differential is driven by the inner housing, wherein the engageable coupling is arranged 5 to selectively couple the inner housing to the outer housing, so that the inner housing rotates about the central axis together with the outer housing, and wherein the hydraulic actuation mechanism comprises: an actuator piston disposed outside of the common housing assembly; and a thrust transfer element to transfer force from the actuator piston to the engageable coupling in order to engage and / or disengage the 10 engageable coupling. The engageable coupling comprises a coupling drum, a coupling hub and an engagement mechanism for selectively connecting the coupling drum and coupling hub. The coupling drum is coupled to or formed by the outer housing assembly, and the coupling hub is coupled to or formed by the inner housing assembly. The engageable coupling is a friction clutch and the engagement mechanism 15 comprises a number of clutch plates, wherein alternating ones of the clutch plates are coupled to the clutch hub and the clutch drum, wherein the clutch plates are selectively engageable to provide a dis-connectable connection between the coupling drum and the coupling hub. 20 The differential may comprise a pinion shaft connected to the inner housing assembly rotatably supporting a pair of pinion gears; and a pair of side gears arranged in meshing engagement with the two pinion gears. Each of the side gears may have a respective axis of rotation arranged coaxially with the axis of rotation of the common housing assembly. Each of the side gears may be drivingly connected to a respective 25 one of first and second output shafts. The engageable coupling may be arranged between the outer housing and the inner housing. For example, the coupling hub may be coupled to the inner housing by a splined connection. The first output shaft many extend from the differential through an 30 inner bore of the coupling hub. The thrust transfer element may comprise a thrust ring. The thrust transfer element, or one or more portions thereof, may extend through one or more openings in a wall of 35 the outer housing assembly between the actuator piston and the engageable clutch. The actuator piston is received within a recess formed in a transmission housing for the motor vehicle. For example, the actuator piston may be received within a recess formed in a cover of a transmission housing for the motor vehicle. The inner housing assembly may comprise a first inner housing part and a second inner housing part coupled to the first inner housing part. The differential may be at least partially received within the second inner housing part. The engageable coupling may be at least partially disposed about the first inner housing part. The first inner housing part may comprise a radially extending flange. The engageable coupling may be arranged on a first axial side of the radially extending flange and the differential may be at least partially arranged on a second axial side of the radially extending flange, e.g. opposite the first side. The assembly further may comprise first and second drive shafts operatively connected to first and second side gears of the differential respectively, A number of frictional interfaces between the first side gear and first drive shaft, and the common housing assembly may be the same as a number of frictional interfaces between the second side gear and second drive shaft, and the common housing assembly. The frictional interfaces between the first side gear and first drive shaft, and the common housing assembly may be configured similarly to, e.g. geometrically and mechanically the same as, the frictional interfaces between the second side gear and second drive shaft, and the common housing assembly. A motor vehicle may comprise an engine and a transmission assembly including the above-mentioned combined coupling and differential. The transmission assembly may comprise a transmission housing. The combined coupling and differential assembly may be rotatably supported by the transmission housing. The motor vehicle may comprise first and second output shafts drivingly connected to the differential, and first and second road wheels. The first output shaft may provide a drive path to the first road wheel of the motor vehicle and the second output shaft may provide a drive path to the second road wheel of the motor vehicle. To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention. For example, features described in relation to the first mentioned aspect may be combined with the features of the second mentioned aspect. Brief Description of the Drawings For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic plan view of a motor vehicle having a combined coupling and differential assembly according to arrangements of the present disclosure; Figure 2 is an isometric view of an auxiliary drive gear system forming part of a transmission assembly for a motor vehicle, the view showing the auxiliary drive system driving a combined coupling and differential assembly in accordance with the present disclosure; Figure 3 is a sectional view of a combined coupling and differential assembly according to arrangements of the present disclosure; and Figure 4 is another section view of the combined coupling and differential assembly shown in Figure 3. Detailed Description With reference to Figures 1 and 2, a vehicle 10, such as a motor vehicle, according to arrangements of the present disclosure, may comprise an engine 11, which may be arranged longitudinally in the motor vehicle 10. In Figures 1 and 2, a forward direction of motion for the motor vehicle 10 is indicated by arrow “F” and a rear direction of motion is indicated by arrow “R”. The vehicle 10 may comprise a transmission assembly 12, which may be mounted on the rear of the engine 11 via a bell housing (not shown). An input shaft 30 from a clutch (not shown) may be interposed between the engine 11 and the transmission assembly 12 and may drive a transmission main shaft 35. The transmission assembly 12 may be arranged with its primary drive connected to rear wheels 7L, 7R of the motor vehicle, which may be driven by the transmission main shaft 35 (see Fig 2) via a conventional prop shaft 13. The motor vehicle 10 may further comprise a rear axle 20 including a rear differential unit 21 and rear drive shafts 22L, 22R. The transmission assembly 12 may further comprise an auxiliary final drive gear system 14. The auxiliary final drive gear system 14 may comprise a transmission housing 117 for housing components of the auxiliary final drive gear system 14 described below. The auxiliary drive for road front wheels 6L, 6R of the motor vehicle may be taken off the main shaft 35 via the auxiliary final drive gear system 14. With particular reference to Figure 2, the auxiliary final drive gear system 14 may comprise a transfer gear 37 that meshes with a gear 36 mounted on the main shaft 35. The transfer gear 37 may be mounted on a transfer shaft 38 and may further mesh with a driven gear 41 mounted on an auxiliary shaft 40. The auxiliary shaft 40 may comprise a first bevel gear 42 mounted, e.g. fixedly mounted, on an opposite end of the auxiliary shaft 40 from the driven gear 41. A second bevel gear 52 and a pinion gear 51, e.g. a helical pinon gear, may be coupled, e.g. fixedly coupled, on a transverse shaft 50. The first bevel gear 42 may be meshed with the second bevel gear 52 so as to drive the transverse shaft 50, and hence, the pinion gear 51. The pinion gear 51 may be meshingly engaged with a ring gear 112, e.g. a helical ring gear, of a combined coupling and differential assembly 100, according to arrangements of the present disclosure. As described in greater detail below and with reference to Figure 3, the combined coupling and differential assembly 100 comprises a differential 120, and an engageable coupling 130. The combined coupling and differential assembly 100 is configured to selectively provide drive torque to the front wheels 6L, 6R via respective first and second drive shafts 101,102. As described below, when the engageable coupling 130 of the combined coupling and differential assembly 100 is engaged, drive torque supplied to the ring gear 112 may be transferred to the differential 120 in order to supply drive torque to the first and second drive shafts 101, 102. In this way, the auxiliary final drive gear system 14 may be configured to drive the front road wheels 6L, 6R of the vehicle 10. As depicted, the transverse shaft 50 may be arranged perpendicular to the transmission main shaft 35. In other words, a longitudinal axis of rotation of the transverse shaft 50 may be arranged perpendicular to a longitudinal axis of the transmission main shaft 35. The transverse shaft 50 may be arranged parallel with a central axis X-Xof the combined coupling and differential assembly 100, about which the ring gear 112 and the differential 120 rotate. Returning to Figure 1, the first, left hand drive shaft 101 may comprise inner and outer parts 101i, 101o, which may be respectively joined together by a constant velocity or universal joint 103. The second, right hand drive shaft 102 may similarly comprise inner and outer parts 102i, 102o, with may be respectively joined together by a constant velocity or universal joint 103. The vehicle 10 may further comprise an actuation system for the engageable coupling 130 of the combined coupling and differential assembly 100. The actuation system may be an electro-hydraulic actuation system and may comprise a source of hydraulic power 15 controlled by an electronic controller 16. A human machine interface 17 may also be provided to allow an operator of the motor vehicle 10 operate the electro-hydraulic actuation system, e.g. to select or deselect drive to the front wheels 6L, 6R. The source of hydraulic power 15 may be connected to an actuator of the combined coupling and differential assembly 100 by a pipe or conduit 18. In one or more arrangements, the source of hydraulic power 15 may comprises a pump and / or a reservoir, and optionally one or more electro-hydraulic valves controlled by the electronic controller 16. When the vehicle 10 is driving normally along a road, the primary drive is through the differential 21 and rear axle 20. In this configuration, the engageable coupling 130 of the combined coupling and differential assembly 100 may be in a disengaged state. The front wheels 6L, 6R may therefore rotate freely, because there is no drive through the combined coupling and differential assembly 100 to the front wheels 6L, 6R. If in a particular situation, the rear wheels 7L, 7R begin to slip, then the engageable coupling 130 of the combined coupling and differential assembly 100 can be engaged either automatically by the electronic controller 16 or by a user of the vehicle 10 using the human machine interface 17, e.g. depending upon the configuration and construction of the vehicle 10. When the engageable coupling 130 of the combined coupling and differential assembly 100 is engaged, drive is transmitted, as will be described in more detail below, to the front wheels 6L, 6R from the engine 11 via the transmission assembly 12, auxiliary final drive gear system 14, differential 120 and first and second front drive shafts 101,102, so as to supplement the drive from the rear wheels 7L, 7R. With reference to Figure 3, the combined coupling and differential assembly 100, according to arrangements of the present disclosure, will now be described in greater detail. The combined coupling and differential assembly 100 comprises the differential 120, the engageable coupling 130 and a common housing assembly 140, in which the differential 120 and engageable coupling 130 are housed. The combined coupling and differential assembly 100 further comprises a hydraulic actuation mechanism 150 for engaging and disengaging the engageable coupling 130, e.g. in response to the operation of the actuation system described above. The common housing 140 comprises an outer housing assembly 142 and an inner housing assembly 144. The outer housing assembly 142 may comprise a first outer housing part 142a and a second outer housing part 142b, which may be coupled together by a number of fasteners, e.g. bolts 106. The ring gear 112 may be coupled to a radially outer flange of the outer housing assembly 142. As depicted, the ring gear 112 may be coupled to the outer housing assembly 142 by the same fasteners used to coupling the first and second outer housing parts 142a, 142b together. The outer housing assembly 142 may be supported in the transmission housing 117 for rotation about the central axis of rotation X-X of the combined coupling and differential assembly. For example, the outer housing 142 may be supported in the transmission housing 117 by two spaced apart bearings 108, 109. A first bearing 108 may have an inner race engaged with a nose portion of the first outer housing part 142a and an outer race engaged with a first bearing recess 119 in the transmission housing 117. A second bearing 109 may have an inner race engaged with a nose portion of the second outer housing part 142b and an outer race engaged with a second bearing recess 116 in the transmission housing 117. The inner housing assembly 144 is disposed inside of the outer housing assembly 142 and is supported, e.g. by the outer housing assembly, for rotation about the central axis X-X relative to the outer housing assembly 142 and / or transmission housing 117. The inner housing assembly 144 may comprise a first inner housing part 144a and a second inner housing part 144b. The first and second inner housing parts 144a, 144b may be coupled together by a number of fasteners, e.g. bolts and / or pins 107. As depicted, the first inner housing part 144a may comprise a substantially cylindrical portion 144c and a radially extending flange portion 144d, e.g. at one end of the cylindrical portion. The first inner housing part 144a may be coupled to the second inner housing part 144b at the radially extending flange portion 144d of the first inner housing part. As depicted, the differential 120 may be arranged at least partially within the second inner housing part 144b. A shape of the second inner housing part 144b may be configured to house components of the differential, e.g. the pinion shaft, pinion gear and side gears described below. The engageable coupling 130 may be disposed at least partially about the first inner housing part 144a, e.g. about the substantially cylindrical part 144c of the first inner housing part. As depicted in Figure 3, the engageable coupling 130 may be arranged on an opposite side of the radially extending flange 144d from the second inner housing part 144b. The front drive shafts 101, 102 may be supported within the inner housing assembly 144, outer housing assembly 142 and the transmission housing 117 for rotation about the central axis X-X. As depicted, the drive shafts 101, 102 may extend from the differential 120 in opposite directions along the central axis X-X to exit the inner and outer housings 142, 144 at opposing sides. The ring gear 112, the inner housing assembly 144, the outer housing assembly 142 and the inner portions 101 i, 102i of the drive shafts 101, 102 may therefore be all coaxially arranged for rotation about a common axis, which is the central axis of rotation X-X. It will be appreciated that if constant velocity joints or universal joints, such as those shown on Fig. 1, are fitted to the drive shafts 101, 102 then the axes of rotation of the outer portions 101o, 102o of the drive shafts 101,102, outboard of these joints may not correspond to the axes of rotation of the inner portions 101 i, 102i of the drive shafts 101, 102 inboard of the joints. The differential 120 may comprise a pinion shaft 122 and a pair of pinion gears 121, 123 rotatably mounted on the pinion shaft 122. Both ends of the pinion shaft 122 may be coupled to the second inner housing part 144b, such that the pinion shaft 122 has a longitudinal axis Y-Y arranged perpendicular to the central axis X-X of the combined coupling and differential assembly 100. The pinion shaft 122 may be secured relative to the second inner housing part 144b by one or more drive pins 126, which may be disposed at one or both ends of the pinion shaft 122. The pinion gears 121, 123 may be arranged at opposing ends of the pinion shaft, e.g. adjacent to an inner wall of the inner housing assembly 144. The differential 120 may further comprise a pair of side gears 124, 125, which may be arranged on opposite sides of the pinion shaft from one another and may be arranged for rotation about the central axis X-X. The pair of side gears 124, 125 may be meshingly engaged with the pair of pinion gears. As depicted, a first side gear 124 may be at least partially received within a recess 144e formed in the first inner housing part 144a. Additionally or alternatively, the first side gear 124 may be at least partially supported within the inner housing assembly by the first inner housing part 144a. As depicted, a first side gear thrust bearing 129a may be provided between the first side gear 124 and the first inner housing part 144a. A second side gear 125 may be at least partially received within a recess 144f formed in the second inner housing part 144b. Additionally or alternatively, the second side gear 125 may be at least partially supported by the second inner housing part 144b. As depicted, a second side gear thrust bearing 129b may be provided between the second side gear 125 and the second inner housing part 144b. The first drive shaft 101 may be coupled to the first side gear 124, so that the first drive shaft rotates about the central axis X-X together with the first side gear 124. The second drive shaft 102 may be coupled to the second side gear 125, so that the second drive shaft rotates about the central axis X-X together with the second side gear 124. For example, the side gears 124, 125 may each comprise an internally splined bore 127 in which complementary splined ends of the first and second drive shafts are respectively received, to form a driving connection between the first and second drive shafts 101, 102 and the first and second side gears 124, 125. As depicted, one or both of the drive shafts 101, 102, such as the first drive shaft 101, may comprise a circumferentially extending groove at least partially aligned with a corresponding groove formed in the particular side gear 124 to which the drive shaft is coupled. An axial retaining element 128 may be received within the groove and corresponding groove to axially locate and / or retain the drive shaft relative to the particular side gear to which is it coupled. The engageable coupling 130 may comprise a coupling drum 132 and coupling hub 136. As depicted, the coupling hub 136 may be arranged radially inside of the coupling drum 132. The coupling drum 132 may be drivingly connected to the outer housing 142, and the coupling hub 136 may be drivingly connected to the inner housing 144. For example, the coupling hub 136 may be drivingly connected to the inner housing 144, e.g. the cylindrical portion 144c of the inner housing 144, via a splined connection. The engageable coupling 130 further comprises a coupling mechanism 134 for selectively coupling the coupling drum 132 with the coupling hub 136 when the engageable coupling is engaged. When the engageable coupling 130 is engaged, torque may be transferred between the coupling drum 132 and the coupling hub 136. When the engageable coupling is not engaged, less torque, such as substantially no torque, may be transferred between the coupling drum 132 and the coupling hub 136. In this way, engagement of the engageable clutch 130 may act to connect the inner and outer housing assemblies 142, 144, such that torque can be transmitted between the inner and outer housing assemblies and the inner and outer housing assemblies rotate together, e.g. relative to the transmission housing 117, about the central axis X-X. In the arrangement depicted, the engageable coupling 130 is a conventional plate clutch, such as a multi-plate clutch. In such arrangements, the coupling mechanism 134 comprises alternate outer and inner clutch plates 138 respectively connected with the clutch drum 132 and the clutch hub 136. When the engageable coupling is engaged, the alternating plates of the clutch are forced to engage one another and transmit drive torque between the outer and inner clutch plates via friction, to thereby transfer toque between the coupling drum 132 and the coupling hub 136. In other arrangements, the engageable coupling 130 may be any other type of coupling suitable for selectively connecting the outer and inner housing and transmitting drive torque between them. As depicted, the first drive shaft 101 may extend from the first side gear 124 through a bore 144g formed in the inner housing 144, e.g. the cylindrical part 144c, which passes through, e.g. inside of, the coupling hub 136 of the engageable coupling. As mentioned above, the hydraulic actuation mechanism 150 is configured for engaging and disengaging the engageable coupling. The hydraulic actuation mechanism 150 comprises an actuator piston 152. The actuator piston 152 may be an annular actuator piston. As depicted, the actuator piston may be slidingly located within a recess 118, e.g. an annular recess, formed in the transmission housing 117. In some arrangements, the recess 118 may be formed in a housing cover part 117a of the transmission housing 117. The actuator piston 152 is therefore located outside of the common housing assembly 140, e.g. outside of the inner and outer housing assemblies 142, 144. The hydraulic actuation mechanism 150 further comprises a thrust transfer element 154, such as a thrust ring, for transferring force from the actuator piston 152 to the engageable coupling 130. As depicted, the thrust transfer element may be slideably supported by the outer housing assembly, e.g. the first outer housing part. For example, one or more portions of the thrust transfer element 154 may extend through one or more, e.g. respective, openings 142c in a wall of the outer housing assembly 142 between the actuator piston 152 and the engageable clutch 130. The hydraulic actuation mechanism 150 and the engageable coupling 130 are configured such that when force is transferred from the actuator piston 152 to the engageable coupling, the coupling is caused to engage so that torque is transferred between the outer housing assembly 142 and the inner housing assembly 144 by the engageable coupling 130. For example, when the engageable coupling comprises a conventional plate clutch, the clutch is configured such that force transferred from the hydraulic actuator to the clutch causes the alternating clutch plates to engage one another. The engageable coupling 130 is further configured such that when force is not transferred from the actuator piston to the engageable coupled, the engageable coupling returns to a disengaged condition. As depicted, the hydraulic actuation mechanism 150 may further comprise one or more thrust bearings 156, e.g. located on either side of the thrust transfer element 154. The thrust transfer element 154 may be arranged to engage with the actuator piston 152 and the engageable coupling 130, e.g. the coupling mechanism 134, via respective thrust bearings 156. In order to actuate the actuator piston 152, a supply of pressurized hydraulic fluid may be selectively supplied to the recess 118 in the transmission housing 117, e.g. from the source of hydraulic pressure 15 via the pipe or conduit 18. Operation of the combined coupling and differential assembly 100 will now be described. During normal operation of the vehicle 10, hydraulic fluid may not be supplied to the recess 118 and hence, force may not be transferred to the engageable coupling 130 via the thrust ring 154 and the engageable coupling 130 may therefore be in a disengaged condition. In the disengaged condition, no torque, e.g. substantially no torque, may be transferred between the outer and inner housing assemblies 142, 144. For example, the torque transferred between the outer and inner housing assemblies may be less than friction forces acting against rotation of the outer housing assembly 142, inner housing assembly 144 and / or drive shafts 101, 102. The differential 120 is therefore not driven by auxiliary final drive system 14, and the drive shafts 101, 102 are not driven by the differential. When the engageable coupling is in the disengaged condition, the drive shafts 101, 102 may be substantially free to rotate. When pressurised hydraulic fluid is supplied to the recess 118 from the source of hydraulic pressure, e.g. based on automatic control by the electronic controller 16 or manual control by the operator of the vehicle 10 via the human machine interface 17, the actuator piston 152 slides within the recess 118 and force is transferred from the actuator piston to the engageable clutch 130 via the thrust transfer elements 154 to cause the engageable coupling to engage. For example, when the engageable coupling comprises a plate clutch, the force may cause the inner and outer clutch plates to engaged on another to form a driving connection between the coupling drum 132 and the coupling hub 136. Engagement of the engageable coupling 130 enables torque to be transferred from the outer housing assembly 142 to the inner housing assembly 144. The differential 120 can thereby be driven by the auxiliary final drive system 14 via the ring gear 112 coupled to the outer housing assembly 142. The differential 120 acts to balance torque supplied to the inner housing assembly 144 between the first and second side gears 124, 125, and hence, the first and second drive shafts 101, 102. Therefore, any torque supplied to the ring gear 112 is distributed through the differential 120 to the first and second drive shafts 101, 102 when the engageable coupling 130 is engaged. The torque is then transferred, by the first and second drive shafts, to the first and second front road wheels 6L, 6R respectively. As depicted in Figure 4, the inner housing assembly 144 may experience a frictional force at its interface 402 with the outer housing assembly 142, e.g. where the inner housing assembly 144 is supported by the outer housing assembly 142. Additionally, the first and second side gears 124, 125 may experience frictional forces at their respective interfaces 404, 406 with the inner housing assembly 144, e.g. where they are supported by the inner housing assembly 144 via the side gear thrust bearings 129a, 129b. The frictional force acting at the interface 402 between the inner housing assembly and the outer housing assembly does not affect the balance of torque supplied by the differential 120 to the first and second drive shafts 101, 102 when the engageable coupling 130 is engaged. The frictional forces acting at the interface 404, 406 between the first and second side gears 124, 125 and the inner housing assembly 144 may be substantially the same as one another, e.g. due to the similarity of the interfaces between the first and second side gears 124, 125 and the inner housing assembly 144. For example, the design of both of the side gear thrust bearings 129a, 129b may be similar, e.g. the same. The interfaces between the first and second side gears 124, 125 and the inner housing assembly 144 may therefore be geometrically and / or mechanically similar. Hence, torque may be distributed substantially equally between the first and second drive shafts 101, 102 by the differential 120, notwithstanding the friction forces acting on the first and second side gears 124, 125. Returning to Figure 3, when hydraulic pressure is no longer supplied to the recess 118 and / or hydraulic pressure within the recess 118 is allowed to decay, the actuator piston 152 may return or retract into the recess 118 and the engageable coupling 130 may return to a disengaged configuration so that torque is no longer transferred from the ring gear 112 to the differential 120. It will be appreciated that the source of hydraulic power 15 may include a relief valve, e.g. an electronically controlled relief valve, or a separate relief valve may be provided under the control of the electronic controller 16. Although the invention has been described with respect to a combined coupling and differential assembly used to selectively connect the front wheels of a motor vehicle to form an all-wheel drive vehicle it will be appreciated that it could also be used to selectively connect rear wheels of a motor vehicle if the front wheels are permanently driven. It will be appreciated by those skilled in the art that although the invention has been 5 described by way of example, with reference to one or more exemplary examples, it is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

1. A combined coupling and differential assembly for a motor vehicle, the combined coupling and differential assembly comprising:5 a differential; an engageable coupling; a common housing assembly, in which the differential and the engageable coupling are housed; and a hydraulic actuation mechanism for engaging and disengaging the engageable coupling; wherein the common housing comprises:an outer housing assembly rotatable about a central axis of rotation by means of10 a ring gear drivingly attached to the outer housing assembly; andan inner housing assembly disposed within the outer housing and rotatable about the central axis relative to the outer housing, wherein the differential is driven by the inner housing, wherein the engageable coupling is arranged to selectively couple the inner housing to the outer housing, so that the inner housing rotates about the central15 axis together with the outer housing, and wherein the hydraulic actuation mechanismxlqj comprises:an actuator piston disposed outside of the common housing assembly; and a thrust transfer element to transfer force from the actuator piston to the engageable coupling in order to engage and / or disengage the engageable coupling, wherein the20 engageable coupling comprises a coupling drum, a coupling hub and an engagement mechanism for selectively connecting the coupling drum and coupling hub, wherein the coupling drum is coupled to or formed by the outer housing assembly, and wherein the coupling hub is coupled to or formed by the inner housing assembly, wherein the engageable coupling is a friction clutch and wherein the engagement mechanism25 comprises a number of clutch plates, wherein alternating ones of the clutch plates are coupled to the clutch hub and the clutch drum, and wherein the clutch plates are selectively engageable to provide a dis-connectable connection between the coupling drum and the coupling hub.30 2. The combined coupling and differential assembly of claim 1, wherein thedifferential comprises a pinion shaft connected to the inner housing assembly rotatably supporting a pair of pinion gears; and a pair of side gears arranged in meshing engagement with the two pinion gears, wherein each of the side gears has a respective axis of rotation arranged coaxially with the axis of rotation of the common housing35 assembly and is drivingly connected to a respective one of first and second output shafts.

3. The combined coupling and differential assembly of claim 1 or 2, wherein the engageable coupling is arranged between the outer housing and the inner housing.5 4. The combined coupling and differential assembly of any of the preceding claims,wherein the coupling hub is coupled to the inner housing by a splined connection.

5. The combined coupling and differential assembly of any of the preceding claims, wherein the first output shaft extends from the differential through an inner bore of the 10 coupling hub.

6. The combined coupling and differential assembly of any of the preceding claims, wherein the thrust transfer element extends through one or more openings in a wall of the outer housing assembly between the actuator piston and the engageable clutch.

157. The combined coupling and differential assembly of any of the preceding claims, wherein the thrust transfer element comprises a thrust ring8. The combined coupling and differential assembly of any of the preceding claims, 20 wherein the actuator piston is received within a recess formed in a transmission housing for the motor vehicle.

9. The combined coupling and differential assembly of any of the preceding claims, wherein the actuator piston is received within a recess formed in cover of a25 transmission housing for the motor vehicle.

10. The combined coupling and differential assembly of any of the preceding claims, wherein the inner housing assembly comprises a first inner housing part and a second inner housing part coupled to the first inner housing part, wherein the differential is at30 least partially received within the second inner housing part and the engageable coupling is at least partially disposed about the first inner housing part.

11. The combined coupling and differential assembly of claim 10, wherein the first inner housing part comprises a radially extending flange, wherein the engageable35 coupling is arranged of a first axial side of the radially extending flange and the14 05 24differential is at least partially arranged on a second axial side of the radially extending flange.

12. The combined coupling and differential assembly of any of the preceding claims, 5 wherein the assembly further comprises first and second drive shafts operatively connected to first and second side gears of the differential respectively, wherein a number of frictional interfaces between the first side gear and first drive shaft, and the common housing assembly is the same as a number of frictional interfaces between the second side gear and second drive shaft, and the common housing assembly.1013. The combined coupling and differential assembly of claim 12, wherein the frictional interfaces between the first side gear and first drive shaft, and the common housing assembly are configured similarly to the frictional interfaces between the second side gear and second drive shaft, and the common housing assembly.1514. A motor vehicle comprising an engine and a transmission assembly including the combined coupling and differential assembly according to any of claims 1 to 13.

15. The motor vehicle of claim 14, wherein the transmission assembly comprises a 20 transmission housing, wherein the combined coupling and differential assembly is rotatably supported by the transmission housing.

16. The motor vehicle of claim 14 or 15, wherein the motor vehicle comprises first and second output shafts drivingly connected to the differential, and first and second 25 road wheels, wherein the first output shaft provides a drive path to the first road wheel of the motor vehicle and the second output shaft provides a drive path to the second road wheel of the motor vehicle.

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