GB2438609A

GB2438609A - Four wheel drive hybrid vehicle with motor in final drive housing

Info

Publication number: GB2438609A
Application number: GB0706861A
Authority: GB
Inventors: Andrew Julian Burrows; Simon Mark Brereton
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-04-07
Filing date: 2007-04-10
Publication date: 2007-12-05
Anticipated expiration: 2027-04-10
Also published as: GB2438609B; GB0706861D0; GB0607046D0

Abstract

In a motor vehicle having an internal combustion engine driving a front final drive unit connected to a pair of front wheels and a pair of rear wheels 21 driven through the rear final drive unit 18 by a longitudinal propshaft 19, the rear final drive unit 18 houses an electric motor/generator (35 see fig 2) which can also drive the rear wheels through an epicyclic reduction gear (39 see fig 4), a pinion shaft (32 see fig 4) having a bevel pinion 31 and a crown wheel and differential. The motor/generator (35) has a rotor (36 see fig 4) fast with a sun gear (37 see fig 4), meshing with planet gears (38 see fig 4) which are each rotatable on a carrier (41 see fig 4). The planet gears (38) also mesh with a ring gear (43 see fig 4). A ratio change clutch (44 see fig 4) has a low ratio position where the ring gear (43) is grounded to the casing (23 see fig 4) and a high ratio position where the ring gear (43) is connected to the pinion shaft (32), thereby providing a reduction ratio and a direct drive. A control clutch 33 controls the connection from the propshaft 19 to the pinion shaft (32) while a disconnect clutch (42 see fig 4) controls the connection from the motor/generator (35) to the pinion shaft (32).

Description

Hybrid Electric Motor Vehicles The invention relates to hybrid electric

motor vehicles, particularly but not exclusively of the kind where an internal combustion (IC) engine provides power to a four wheel drive transmission which has an electric motor/generator in the drive to one pair of wheels.

It is known from EP-A-0584090 to provide a hybrid electric motor vehicle in which a motor/generator is mounted on the nose of a rear final drive unit where a propshaft connects an engine and transmission unit to the rear final drive unit, the motor/generator providing additional drive torque or braking torque as required. However, the motor/generator is a direct drive unit in which the rotor rotates with the propshaft so that the range of torque and power is limited by the speed range of the propshaft, i.e. by the ratio of the final drive unit. It is also known from US-A-5443130 to provide an electric motor drive in which an electric traction motor is arranged transversely on a final drive unit, the motor having a hollow rotor which drives a differential through an epicyclic reduction gear, the differential driving one of the wheels through a shaft which extends concentrically through the rotor. a

The present invention has an object of providing a hybrid electric motor vehicle in S...

S... . . . . . which a motor/generator unit is mounted on a final drive unit and wherein the range of torque and power that can be provided by the motor/generator unit is improved.

: According to a first aspect of the invention there is provided a hybrid electric motor vehicle having an internal combustion engine, a transmission to transmit power from the engine to a front pair of wheels through a front final drive unit and to a rear pair of wheels through a rear final drive unit and an electric motor/generator in the drive to one of said pairs of wheels, the motor/generator being arranged in one of the final drive units and comprising a casing, a stator and a rotor, the stator being fast with the casing and the rotor driving the final drive unit through a reduction gear providing a reduction ratio and a direct drive.

Conveniently, the reduction gear comprises an epicyclic reduction gear having four gear elements comprising a sun gear fast with the rotor, at least one planet gear, a carrier rotatable about the axis of the sun gear and a ring gear, the or each planet gear being rotatable on the carrier and meshing with the sun gear and the ring gear, one of the ring gear and the carrier being connected to the final drive unit, and the epicyclic reduction gear being arranged so that two of the gear elements can be locked together to provide the direct drive.

The epicyclic reduction gear may be provided with a ratio change clutch, the ratio change clutch having one state wherein one of the carrier and the ring gear is grounded to the casing and another state wherein two of the gear elements are locked together to provide the direct drive.

When the ratio change clutch is in the one state, the ring gear may be grounded to the casing and the carrier connected to the final drive unit. In such a case, when the ratio change clutch is in the other state, the carrier may be connected to ring gear or the sun gear may be connected to the ring gear. I. *. *..

Alternatively, when the ratio change clutch is in the one state, the carrier may be *..s grounded to the casing and the ring gear connected to the final drive unit, in which case in * the other state of the ratio change clutch the carrier may be connected to the ring gear. S.

The vehicle may be arranged so that said one final drive unit comprises a differential, an input shaft arranged longitudinally in the vehicle and which can transmit power from the transmission to the differential and wherein the motor/generator has a hollow rotor arranged concentrically with the input shaft with the input shaft extending through the rotor.

In such an arrangement, the casing may form part of the final drive unit such that the motor/generator, the epicyclic reduction gear and one part of the casing form a unit which is interchangeable with a final drive unit of a motor vehicle in which an engine is connected to the final drive unit through a propshaft. The final drive unit may incorporate a crown wheel and pinion, the pinion being part of the unit comprising the motor/generator, the epicyclic reduction gear and said one part of the casing.

Alternatively, the vehicle may be arranged so that the said one final drive unit comprises a differential and the motor/generator is arranged transversely on said one final drive unit, the rotor of the motor/generator being hollow such that a drive shaft connecting the differential to one of said one pair of wheels extends concentrically through the rotor. In such an arrangement, the reduction gear may comprise an epicyclic reduction gear which may comprise two sets of gear elements arranged in series. Also, the reduction gear may comprise a layshaft reduction gear train including a spur input gear driven by the motor/generator, a large diameter spur gear and a small diameter spur gear fixed on a layshaft and a large diameter driving gear fast with the differential, the large diameter spur gear meshing with the input gear and the small diameter spur gear meshing with the driving gear.

The layshaft may include a disconnect clutch to selectively disconnect the large diameter spur gear and the small diameter spur gear and a direct drive clutch provided to selectively connect the input gear and the differential. This allows for a direct 1:1 drive : ** between the spur input gear and the differential. S...

Preferably, an input shaft is arranged longitudinally in the vehicle to transmit power from the transmission to the differential, the input shaft having a final drive bevel pinion * . which meshes with a crownwheel fast with the large diameter spur gear.

The invention will now be described by way of example and with reference to the accompanying drawings, in which:-Fig. 1 is a schematic diagram of one example of a hybrid electric motor vehicle according to the invention; Fig.2 is a schematic diagram of a motor/generator assembly and a final drive unit shown in Fig.1 in simplified form; Fig.3 is a schematic diagram showing a first example of a motor/generator assembly for use in the hybrid electric motor vehicle shown in Fig.1; Fig.4 is a schematic diagram showing a modification to the motor/generator assembly shown in Fig.3; Fig.5 is a schematic diagram showing a second example of a motor/generator assembly for use in the hybrid electric motor vehicle shown in Fig.1; Fig.6 is a schematic diagram showing a third example of a motor/generator assembly for use in the hybrid electric motor vehicle shown in Fig. 1; Fig.7 is a schematic diagram showing a fourth example of a motor/generator assembly for use in the hybrid electric motor vehicle shown in Fig.1; Fig.8 is a schematic diagram of a motor/generator assembly and a final drive unit for another example of a hybrid electric motor vehicle according to the invention in which the motor/generator assembly is arranged transversely; and Fig.9 is a schematic diagram a further example of motor/generator assembly and a final drive unit for a hybrid electric motor vehicle of the kind where the motor/generator :.: assembly is arranged transversely. s.

Referring to Figs. 1 and 2, a hybrid electric motor vehicle 11 has an IC engine 12 driving a transmission 13 (which may be a manual gearbox, or any type of automatic : transmission) which in turn drives a front final drive unit 14 connected to a pair of front wheels 15 by front driveshafts 16. The front final drive unit 14 also drives a rear drive take-off unit 17 which is connected to a rear final drive unit 18 by a longitudinal propshaft 19.

The rear final drive unit 18 is connected to a pair of rear wheels 21 by rear driveshafts 22.

The rear final drive unit 18 has a casing 23 which comprises a rear casing part 24 and a front casing part 25, the casing parts being connected at a flange face 26. The rear casing part 24 carries the inboard ends of the rear driveshafts 22 and a crownwheel 27 which drives the rear driveshafts 22 through a differential 28. The front casing part 25 carries a bevel pinion 31 which meshes with the crownwheel 27 and is part of an input or pinion shaft 32 which is journalled in the front casing part 25 and arranged longitudinally in the vehicle. The rear end of the propshaft 19 is also journalled in the front casing part 25 and carries a control clutch 33 which controllably couples the propshaft 19 to the pinion shaft 32.

As described so far, the vehicle 11 is of a generally known type. In the present invention, the front casing part 25 also houses the stator 34 of an electric motor/generator whose rotor 36 is rotatable about the axis of the pinion shaft 32. The rotor 36 is fast with a sun gear 37 which meshes with planet gears 38 of an epicyclic reduction gear 39 to form a motor/generator assembly 40. The planet gears 38 are each rotatable on a carrier 41 which is rotatable about the axis of the pinion shaft 32 and is selectably coupled to the pinion shaft 32 by a disconnect clutch 42. The planet gears 38 also mesh with a ring gear 43 which is also rotatable about the axis of the pinion shaft 32.

As shown in Figs.3 and 4, the epicyclic reduction gear 39 is arranged so that two of the gear elements can be locked together to provide a direct drive from the rotor 36 to the final drive bevel pinion 31. In the example shown in Fig.3, this is achieved by the use of a : * ratio change clutch 44 having a low ratio position C2a where the ring gear 43 is grounded S...

to the casing 23 and a high ratio position C2b where the ring gear 43 is connected to the pinion shaft 32. In the low ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 provides a reduction ratio between the speed of the rotor 36 and that of * the pinion shaft 32 in the range 2.5:1 and 5:1, depending on the detail design (i.e. the number of teeth of the sun gear 37, the planet gears 38 and the ring gear 43). In the high ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 is effectively locked to provide a direct drive from the rotor 36 to the pinion shaft 32, i.e. a 1:1 ratio.

The rear casing part 24 carrying the inboard ends of the rear driveshafts 22 and the crownwheel 27 can be the same as would be provided for a conventional non-hybrid motor vehicle with the same general power train layout as is shown in Fig.1 while the front casing part 25 can be interchangeable with a similar unit which simply carries a bevel pinion 31 to mesh with the crownwheel 27 and a control clutch 33 to connect the pinion shaft 32 to the propshaft 19. Either there is an appropriate adjustment to the length of the propshaft 19 or the overall length is kept the same.

The motor/generator 35 is controlled by an electronic control unit (ECU) 51. Power is generated by the motor/generator 35 and by another motor/generator, conveniently referred to as the integrated starter generator 29, driven by (or driving) the engine 12. Both the motor/generator 35 and the integrated starter generator 29 draw current from or supply current to a traction battery 61 and to an auxiliaries battery 62. The traction battery 61 would ordinarily be a high voltage unit while the auxiliaries battery 62 would be 12V for the supply & control of the normal vehicle electrical systems.

In normal on-road use of the vehicle lithe engine 12 can drive the front wheels 15 through the transmission 13, the front final drive unit 14 and the front driveshafts 16 while also driving the rear wheels 21 through the rear take-off unit 17, the propshaft 19, the rear final drive unit 18 and the rear driveshafts 22. The rear take-off unit 17 is driven in a direct :. ratio of the drive to the front wheels 15, the control clutch 33 allowing drive torque to the rear wheels 21 as required to maintain an appropriate torque split between the front and * rear wheels 15, 21. Under gentle low speed driving conditions, the electric motor generator can be used with the ratio change clutch 44 in the low ratio position C2a to drive the *.s vehicle with the engine 12 stopped, in which case the control clutch 33 would be : disengaged and drive would be to the rear wheels 21 only through the epicyclic reduction 25 gear 39. Under more severe low speed driving conditions, such as pulling away from junctions or driving off-road, the motor generator 35 can be used with the ratio change clutch 44 in the low ratio position C2a to supplement the power supplied by the engine, the torque provided by the rotor 36 being multiplied in accordance with the gear ratio of the epicyclic reduction gear 39.

For higher road speeds, particularly out of town driving, the engine 12 would drive as described above with the integrated starter generator 29 and, where needed, the electric motor generator 35 supplying current to the batteries 61 and 62. Under these conditions, the ratio change clutch 44 would be in the high ratio position to provide a direct drive from the rotor 36 to the pinion shaft 32. This would reduce the rotational speed of the rotor 36 to reduce windage losses and prevent overspeeding.

Fig.4 shows a modification to the motor/generator assembly 40 shown in Fig.3, the ratio change clutch 44 having a low ratio position C2a where the nng gear 43 is grounded to the casing 23 and a high ratio position C2b where the ring gear 43 is connected to the carrier 41.

In the example shown in Fig.5, two of the gear elements can be locked together to provide a direct drive from the rotor 36 to the final drive bevel pinion 31 by the use of a ratio change clutch 44 having a low ratio position Cib where the ring gear 43 is grounded to the casing 23 and a high ratio position Cia where the ring gear 43 is connected to the sun gear 37. As in the Fig.3 example, in the low ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 provides a reduction ratio between the speed of the rotor 36 :.::: and that of the pinion shaft 32 in the range 2.5:1 and 5:1 and in the high ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 is effectively locked to provide a direct drive from the rotor 36 to the pinion shaft 32. S.

I

. : In the examples shown in Figs. 6 and 7 the epicyclic reduction gear 39 differs from that shown in Figs. I to 5 in that the ring gear 43 is connected to the pinion shaft 32, either directly as shown in Fig.6 or through a disconnect clutch 42 as shown in Fig.7. As with the examples shown in Figs. 4 and 5, two of the gear elements can be locked together to provide a direct drive from the rotor 36 to the final drive bevel pinion 31. In these Figs. 6 and 7 examples, the ratio change clutch 44 has a high ratio position Cia where the ring gear 43 is connected to the carrier 41 and a low ratio position Cib where the carrier 41 is grounded to the casing 23. In the low ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 provides a reduction ratio between the speed of the rotor 36 and that of the pinion shaft 32 in a range between -1.5:1 and -4:1, depending on the detail design (i.e. the number of teeth of the sun gear 37, the planet gears 38 and the ring gear 43). The reduction ratio is negative because the direction of drive is reversed. In the high ratio position of the ratio change clutch 44, the epicyclic reduction gear 39 is effectively locked to provide a direct drive from the rotor 36 to the pinion shaft 32, i.e. a 1:1 ratio.

The ratio change clutch 44 can be of any known type, e.g. dog clutches, synchromesh, friction clutches, powder clutches, etc. The motor/generator assembly 40 and the final drive unit 18 shown in Fig.8 differ from those shown in Figs. 1 to 7 in that the motor/generator assembly 40 is arranged transversely on the final drive unit 18. In other respects, the motor/generator assembly 40 is substantially similar to the motor/generator assemblies 40 shown in Figs. 3 to 7 so that where applicable the same references are used.

The motor/generator assembly 40 includes a motor/generator 35 having a hollow rotor 36 which drives a differential 28 in the final drive unit 18 through an epicyclic reduction gear 39 which is similar to that shown in Fig.4 except that there are two sets of gear elements arranged in series. In the first set, a sun gear 37A is directly connected to the rotor 36 of the motor/generator 35 and meshes with planet gears 38A rotatable on a carrier 41A. The planet gears 38A also mesh with a ring gear 43 while the carrier 41A is directly connected *:*. to a sun gear 37B of the second set. This sun gear 37B meshes with planet gears 38B rotatable on a second carrier 41 B, the planet gears 38B also meshing with the ring gear 43 which is thus common to both sets of gear elements. The second carrier 41 B connects to the crownwheel 27 of the final drive unit 18 through a disconnect clutch 42.

The crownwheel 27 drives the rear wheels 21 through the differential 28 and drive shafts 22, one of which extends concentrically through the rotor 36. This same drive shaft 22 also extends concentrically through the sun gears 37A and 37B. As in the example shown in Fig.4, a control clutch 33 controllably couples the propshaft 19 to the input shaft 32 which, in this example, drives a final drive bevel pinion 31 though a spur gear train 46.

As in the example shown in Fig.4, a ratio change clutch 44 allows the ring gear 43 to be locked to the output carrier 41 B or to a casing 23.

Operation of the motor/generator assembly 40 and the final drive unit 18 shown in Fig.8 is substantially the same as that described in relation to Fig.4. The use of an additional set of epicyclic gear elements provides an additional gear ratio reduction which corresponds to that obtained when the motor/generator 35 in the examples shown in Figs. 3 to 7 drives through the epicyclic reduction gear 39 and the final drive pinion 31 and crownwheel 27. However, it will be appreciated that other arrangements of epicyclic reduction gear can be used, in particular those shown in and described in relation to Figs. 5 to 7 and also that the use of an additional set of epicyclic gear elements would allow for more gear elements to be locked together or grounded to the casing 23 to allow for additional gear ratios. * S

Fig.9 shows a further example of a motor/generator assembly 40 arranged transversely on a final drive unit 18. The motor/generator assembly 40 comprises a motor/generator 35 having a hollow rotor 36 which drives a differential 28 in the final drive unit 18 through an epicyclic reduction gear 39 which is similar to that shown in Fig.4, there *** being only one set of gear elements. A sun gear 37 is directly connected to the rotor 36 of the motor/generator 35 and meshes with planet gears 38 rotatable on a carrier 41. The planet gears 38 also mesh with a ring gear 43 while the carrier 41 is connected to a spur -10-input gear 64 of a layshaft reduction gear train 65 through a first disconnect clutch 42 (Cia). This input gear 64 meshes with a large diameter spur gear 66 fixed on a layshaft 67 which also has a small diameter spur gear 68 fixed on it. The small diameter spur gear 68 meshes with a large diameter driving gear 69 fast with a differential 28 which drives the rear wheels by means of drive shafts 22, one of which extends concentrically through the rotor 36, the first disconnect clutch 42 and the sun gear 37.

A control clutch 33 (C3) controllably couples a propshaft 19 to an input shaft 32 which drives a final drive bevel pinion 31 which meshes with a crownwheel 27 fast with the large diameter spur gear 66. A second disconnect clutch 71 (CIb) is in the layshaft 67 to disconnect drive between the large diameter spur gear 66 and the small diameter spur gear 68 while a lock-up or direct drive clutch 72 (Ci c) is provided to directly couple the motor generator 35 to the differential 28 via the epicyclic reduction gear 39.

As in the example shown in Fig.4, a ratio change clutch 44 allows the ring gear 43 to be locked to the output carrier 41 B (C2b) or to a casing 23 (C2a).

Operation of the motor/generator assembly 40 and the final drive unit 18 shown in Fig.9 is substantially the same as that described in relation to Figs. 4 and 8. Normally the motor/generator 35 drives the differential through the layshaft 67, i.e., the small diameter spur gear 68 drives the large diameter spur gear 66 through the layshaft 67 with the : ** second disconnect clutch 71 engaged so that the layshaft in turn drives the differential " 20 through the small diameter spur gear 68 and the large diameter driving gear 69. * S. * . S S...

The layshaft 67 provides an additional gear reduction ratio which corresponds to that . : obtained when the motor/generator 35 in the examples shown in Figs. 3 to 7 drives through the epicyclic reduction gear 39 and the final drive pinion 31 and crownwheel 27. It will be appreciated that other arrangements of epicyclic reduction gear can be used, in particular those shown in and described in relation to Figs. 5 to 7. -11 -

The second disconnect clutch 71 allows the motor/generator 35 to be directly coupled to the differential 28 through the epicyclic reduction gear 39, the first disconnect clutch 42 and the direct drive clutch 72 with the second disconnect clutch 71 (CIb) disengaged. This allows for additional gear ratios, including a direct 1:1 drive between the rotor 36 and the differential 28. However, it will be appreciated that the second disconnect clutch 71 and the direct drive clutch 72 may be omitted. Also, the epicyclic reduction gear 39 may be omitted so that the motor/generator 35 can be directly coupled to the differential 28 through the direct drive clutch 72 with the second disconnect clutch 71 (Cib) disengaged or drive the differential through the layshaft 67 as described above.

It will be appreciated that where the motor/generator assembly 40 is arranged transversely on the final drive unit 18 as in Figs. 8 and 9, the casings 23 will support the various shafts and gear elements and provide lubrication and cooling where appropriate.

In the detail design of these arrangements, the propshaft 19 and input shaft 32 would be arranged on a substantially central longitudinal axis of the vehicle and the casings 23 of the motor/generator assembly 40 and the final drive unit 18 arranged to be packaged as compactly and centrally as reasonably possible. The drive shafts 22, while being shown here diagrammatically as one piece, would normally each comprise an inner shaft extending inside the casing 23 and an outer shaft outside the casing 23 extending towards the respective wheel 21, universal joints connecting the inner and outer shafts and the outer shaft and the wheel. * * ****

* In all of the examples and modifications described above, the control clutch 33 may form part of the front drive take-off unit 17 instead of forming part of the rear final drive unit 18. Indeed, the front drive take-off unit 17 may incorporate a centre differential which splits the torque between the front wheels 15 and the rear wheels 21 and in such a case the * 25 control clutch 33 may be omitted. -12-

While the vehicle 11 has been described as having the engine 12 towards the front, other layouts may be applicable, e.g., a rear engine and transmission or a front engine arranged longitudinally with a transmission behind it. Hence references to front and rear are used primarily for convenience to describe the relative positions of components. S. * S * S.. * . S... * S. * S S S... S..

S S. * * S. * S. S. S

S S S 0.

Claims

CLAIMS

1. A hybrid electric motor vehicle having an internal combustion engine, a transmission to transmit power from the engine to a front pair of wheels through a front final drive unit and to a rear pair of wheels through a rear final drive unit and an electric motor/generator in the drive to one of said pairs of wheels, the motor/generator being arranged in one of the final drive units and comprising a casing, a stator and a rotor, the stator being fast with the casing and the rotor driving the final drive unit through a reduction gear providing a reduction ratio and a direct drive.
2. A vehicle according to claim I wherein the reduction gear comprises an epicyclic reduction gear having four gear elements comprising a sun gear fast with the rotor, at least one planet gear, a carrier rotatable about the axis of the sun gear and a ring gear, the or each planet gear being rotatable on the carrier and meshing with the sun gear and the ring gear, one of the ring gear and the carrier being connected to the final drive unit, and the epicyclic reduction gear being arranged so that two of the gear elements can be locked together to provide the direct drive.
3. A vehicle according to claim 2 wherein the epicyclic reduction gear is provided with a ratio change clutch, the ratio change clutch having one state wherein one of the carrier and the ring gear is grounded to the casing and another state wherein two of the gear elements are locked together to provide the direct drive. *...

S S S...

: *.
4. A vehicle according to claim 3 wherein, when the ratio change clutch is in the one state, the ring gear is grounded to the casing and the carrier is connected to the final ::::!. drive unit.

5. A vehicle according to claim 4 wherein, when the ratio change clutch is in the other state, the carrier is connected to the ring gear.

-14 - 6. A vehicle according to claim 4 wherein, when the ratio change clutch is in the other state, the sun gear is connected to the ring gear.

7. A vehicle according to claim 3 wherein, when the ratio change clutch is in the one state, the carrier is grounded to the casing and the ring gear is connected to the final drive unit.

8. A vehicle according to claim 7 wherein, when the ratio change clutch is in the other state, the carrier is connected to the ring gear.

9. A vehicle according to any preceding claim wherein said one final drive unit comprises a differential, an input shaft arranged longitudinally in the vehicle and which can transmit power from the transmission to the differential and wherein the motor/generator has a hollow rotor arranged concentrically with the input shaft with the input shaft extending through the rotor.

10. A vehicle according to claim 9 wherein the casing forms part of the final drive unit such that the motor/generator, the reduction gear and one part of the casing form a unit which is interchangeable with a final drive unit of a motor vehicle in which an engine is connected to the final drive unit through a propshaft.

11. A vehicle according to claim 10 wherein the final drive unit incorporates a crown wheel and pinion, the pinion being part of the unit comprising the motor/generator, the : ** reduction gear and said one part of the casing.

12. A vehicle according to any of claims 1 to 8 wherein the said one final drive unit :: comprises a differential and the motor/generator is arranged transversely on said one final drive unit, the rotor of the motor/generator being hollow such that a drive shaft connecting the differential to one of said one pair of wheels extends concentrically through the rotor.

13. A vehicle according to claim 12 wherein the reduction gear comprises an epicyclic reduction gear.

14. A vehicle according to claim 13 wherein the epicyclic reduction gear comprises two sets of gear elements arranged in series.

15. A vehicle according to any of claims 12 to 14 wherein the reduction gear comprises a layshaft reduction gear train including a spur input gear driven by the motor/generator, a large diameter spur gear and a small diameter spur gear fixed on a layshaft and a large diameter driving gear fast with the differential, the large diameter spur gear meshing with the input gear and the small diameter spur gear meshing with the driving gear.

16. A vehicle according to claim 15 wherein the layshaft includes a disconnect clutch to selectively disconnect the large diameter spur gear and the small diameter spur gear and a direct drive clutch to selectively connect the input gear and the differential.

17. A vehicle according to claim 15 or claim 16 wherein an input shaft is arranged longitudinally in the vehicle to transmit power from the transmission to the differential, the input shaft having a final drive bevel pinion which meshes with a crownwheel fast with the large diameter spur gear. I. * S * SSS S...

18. A hybrid electric motor vehicle substantially as described herein with reference to Figs. : ** 1 to 3, or as modified with reference to Fig.4, or as described with further reference to *.SS Figs. 5, 6, 7, 8 or 9 of the accompanying drawings. S. I * . . * SI * *

S S S S *S