GB2345041A

GB2345041A - Motor vehicle transmission assembly

Info

Publication number: GB2345041A
Application number: GB9828320A
Authority: GB
Inventors: David Charles Nesbitt; David John Tickle
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-12-23
Filing date: 1998-12-23
Publication date: 2000-06-28
Anticipated expiration: 2018-12-23
Also published as: GB9828320D0; GB2345041B

Abstract

A transmission assembly 23 for a vehicle having a longitudinally mounted engine and front wheel drive includes a change speed transmission 25 connected to a spiral bevel final drive 26 carried in a final drive casing 54. The transmission assembly 23 is connected to the engine by an adapter casing 24 which is integral with the final drive casing 54, thereby avoiding connecting the final drive casing to the engine lower structure (crankcase and sump).

Description

Motor Vehicle Transmission Assemble The invention relates to transmission assemblies for motor vehicles of the kind in which an engine is mounted longitudinally in the vehicle adjacent an end thereof.

One proposal for a transmission assembly of the kind referred to above is described in GB 912 675. In this arrangement a change speed transmission is mounted generally in line with the engine and is driven through a flywheel and clutch and a final drive assembly is mounted on one side of the engine crankcase and driven through gears by a final drive input shaft arranged parallel to the crankshaft. A similar arrangement is described in somewhat greater detail in US 5,046,578. In these arrangements, the final drive casing becomes part of the engine lower structure, i. e. the part which generally includes a crankcase and a sump. Whilst this arrangement has certain advantages, there needs to be substantial reinforcement of the crankcase and sump to provide the required stiffness. This adds cost to the engine and creates tolerance and assembly problems.

US 3,052,313 shows an arrangement in which the final drive casing is on one side of the engine lower structure without being structurally attached to it directly. In this case the final drive casing is bolted to an intermediate casing which in turn is attached to a change speed transmission mounted at the rear of and to one side of the engine. Such an arrangement is generally unable to provide a necessary stiffness to meet modern requirements.

It is an object of the invention to provide a transmission assembly for a motor vehicle having a longitudinally mounted engine and which avoids the problems outlined above.

According to the present invention there is provided a transmission assembly for a motor vehicle having a pair of front wheels and a pair of rear wheels, an engine mounted longitudinally in the vehicle adjacent an end thereof and having a crankshaft, a drive coupling at one end of the crankshaft and an engine lower structure comprising a crankcase and an oil sump, the transmission assembly including an adapter casing comprising an annular spacer which, in use, is mounted on the engine and encircles the drive coupling, a change speed transmission mounted on the annular spacer at an end thereof which, in use, is opposite the engine, the change speed transmission including a transmission input shaft drivably connected to the drive coupling and a transmission output shaft parallel to the input shaft, and a final drive disposed, in use, between one of said pairs of wheels and drivably connected thereto and including a final drive input gear drivably connected to the transmission output shaft and rotatably supported in a final drive casing which is integral with the adapter casing and is positioned on one side of the engine lower structure without being structurally attached thereto except by the adapter casing.

Conveniently the change speed transmission includes an intermediate casing which is attached to the adapter casing.

The transmission output shaft may have a transmission output gear which meshes with a transfer gear coaxial with and drivably connected to the final drive input gear, in which case, where an intermediate casing is provided, the transfer gear may be supported in a bearing in the intermediate casing.

The final drive casing may be pan-shaped with a generally tubular portion extending parallel to and merging with the annular spacer and a dished portion arranged perpendicular to the tubular portion and having an open rim closed by a cover plate.

Conveniently the final drive input gear is the bevel pinion of a bevel gear set comprising the bevel pinion and a bevel crownwheel, in which case, where the final drive casing is pan-shaped, the final drive bevel pinion may be carried in bearings in the tubular portion of the final drive casing and the bevel crownwheel carried in one bearing in the dished portion of the final drive casing and another bearing in the cover plate.

The final drive bevel crownwheel may be carried on a final drive differential arranged to drive said one pair of wheels, in which case the differential may be arranged to drive one universal joint which, in use, is on the same side of the engine lower structure and another universal joint which, in use, is on the other side of the engine lower structure. Said other universal joint may be rotatably supported in a bracket which is integral or fast with the adapter casing without being structurally attached to the engine lower structure except by the adapter casing. The other universal joint may be connected to the differential by an intermediate drive shaft which, in use, extends transversely through the engine lower structure.

The change speed transmission may include rotary drive components and selector components substantially identical to those produced for a change speed transmission used in a front wheel drive motor vehicle with a transverse engine and change speed transmission Furthermore, the change speed transmission may include a casing component substantially identical to one produced for such a change speed transmission.

An auxiliary output may be drivably connected to the transfer gear and arranged, in use, to drive the other of said pairs of wheels, thereby providing four wheel drive. in such a case the transfer gear may be drivably connected to the auxiliary output and to the final drive input gear by a centre differential which itself may be mounted on the transfer gear.

A plurality of selectable ratios may be provided in the drive between the transmission output shaft and the final drive input gear, particularly if four wheel drive is provided for. In such a case, where the transmission output shaft has a transmission output gear which meshes with a transfer gear coaxial with and drivably connected to the final drive input gear, the transmission output shaft may have a plurality of transmission output gears arranged to each drive a respective transfer gear.

The invention will now be described by way of example and with reference to the accompanying drawings, of which: Fig. 1 is a diagrammatic plan view of a motor vehicle incorporating a transmission assembly according to the invention; Fig. 2 is a cross-section through the transmission assembly shown in Fig. l through a generally horizontal plane; Fig. 3 is a perspective view of the transmission assembly shown in Fig. 1 in the general direction of arrow A; Fig. 4 is another perspective view of the transmission assembly shown in Fig. l in the general direction of arrow B; Fig. 5 is another perspective view of the transmission assembly shown in Fig. l in the general direction of arrow C; Fig. 6 is a vertical cross-section on the line VI-VI in Fig. 1; Fig. 7 is a view based on Fig. 2 and showing an auxiliary output; Fig. 8 is a side elevation of an alternative rear cluster for the change speed transmission shown in Fig. 2; Fig. 9 is a perspective of the gear cluster shown in Fig. 8; and Fig. 10 is an end elevation viewed on arrow D of the gear cluster shown in Fig. 7.

Referring to Figs. 1 to 5, a motor vehicle has a pair of front wheels 11,12, a pair of rear wheels 13,14 and an engine 15 mounted longitudinally in the vehicle adjacent its front end. The engine 15 has a conventional crankshaft 16, at one end of which is mounted a drive coupling in the form of a conventional flywheel 17 and clutch 18. The engine has a conventional lower structure comprising a crankcase 21 and a sump 22.

A transmission assembly 23 is fastened to the rear of the engine 15 and includes an adapter casing 24, a change speed transmission 25 and a final drive 26. The change speed transmission 25 includes a transmission input shaft 27 having a number of drive gears 28 which are integral with or secured to the shaft 27. Meshing with the drive gears 28 are driven gears 29 which are rotatable on a transmission output shaft 31 so that individual gear ratios can be selected by conventional synchromesh assemblies 32.

The transmission input shaft 27 and transmission output shaft 31 are carried in a main transmission casing 33, an end casing 34 and an end plate 35. As described so far, the change speed transmission 25 is conventional, being based on one produced for a front wheel drive vehicle with transverse engine and transmission. Indeed, all the components of the change speed transmission 25 mentioned so far can be identical to such a transmission, as can the selector mechanism (not shown).

The final drive 26 includes a bevel gear type differential 26 housed in a differential housing or cage 37 to which is secured the crown wheel 38 of a spiral bevel gear set which also includes a bevel pinion 39. The bevel pinion 39 is formed at one end of a final drive input shaft 41 which is carried on bearings 42,43 in the adapter casing 24. The bevel pinion shaft 41 has splines 44 at the opposite end to the bevel pinion 39 to take drive from a transfer gear 45 which meshes with a transmission output gear fixed to the change speed transmission output shaft 31.

The transfer gear 45 is secured to a pair of flanged hubs 47 and 48, hub 47 being carried in a bearing 49 in the transmission end plate 35 and the hub 48 being carried in a bearing 51 in an intermediate casing 52 interposed between the adapter casing 24 and the transmission end plate 35.

The adapter casing 24 includes an annular spacer 53 which is mounted on and secured to the engine so as to encircles the flywheel 17 and clutch 18. The bearings 42 and 43 which support the bevel pinion shaft 41 are carried in a final drive casing 54 which is integral with the adapter casing 24 and positioned at one side of the engine crankcase 21 and sump 22. The final drive casing 54 is pan-shaped with a generally tubular portion extending parallel to and merging with the annular spacer 53 and a dished portion 56 arranged perpendicular to the tubular portion 55. The dished portion 56 of the final drive casing 54 has an open rim 57 closed by a cover plate 58. The bevel pinion shaft bearings 42 and 43 are in the tubular portion 55 and the differential cage 37 is carried by one bearing 59 in the dished portion 56 and another bearing 61 in the cover plate 58.

The differential 36 is arranged to drive one universal joint 62 on the same side of the engine crankcase 21 and another universal joint 63 which is on the other side of the crankcase 21. To support the other universal joint 63 a bracket 64 is secured to the adapter casing 24 and has a bearing 65 which supports an intermediate drive shaft 66 which extends transversely through a tube which extends from one side wall 68 of the crankcase 21 to the other side wall 69. The other end of the intermediate drive shaft 66 is supported by the differential cage 37. As shown in Fig. 6 the left hand universal joint 63 has a drive pot 71 which is integral with the intermediate drive shaft 66, although these components can be separate if required.

By making the final drive casing 54 integral with the adapter casing 24 there is adequate strength and stiffness in the support for the differential cage 37 and the bevel pinion shaft 41 without a need to structurally attach the final drive casing to the lower structure (crankcase 21 or sump 22) of the engine 15. This removes tolerance and alignment problems and avoids a direct noise path from the transmission assembly 23 to the engine sump 22. The bracket 64 may also be integral with the adapter casing 24 if required.

In the modified transmission assembly shown in Fig. 7 the parts which are identical to or similar to those shown in Figs. 1 to 6 carry the same reference numeral with the addition of 100. The transfer gear 145 is carried on a centre differential 181 which has one output connected to the bevel pinion shaft 141 (not shown) and the other output to a flanged stop shaft 182 which connects to a rear universal joint driving a rear differential propshaft 185 to provide drive to the rear wheels 13 and 14 as shown in dotted lines in Fig. 1.

Figs. 8, 9 and 10 show the gear clusters of an alternative transmission assembly to that shown in Figs. l to 6. Similar parts carry the same reference numeral with the addition of 200. Here it is shown as a generally conventional arrangement of gears and synchromesh assemblies in which one synchromesh assembly 232 is carried on the transmission output shaft 231 whereas the other synchromesh assembly 291 are carried on the transmission input shaft 227. Also shown are the selector rails 292 for the selector forks 293 and the fact that the axis of the input shaft 227 the output shaft 246 and the transfer gear 245 are laterally offset as well as vertically offset, as particularly shown in Fig. 10. Also shown is a reverse gear idler pinion 294.

Other forms of change speed transmission may be employed, for example an epicyclic automatic transmission, or continuously variable transmissions (CVTs) of either the belt and pulley type or the toroidal type or any other type which is engineered to replace the conventional type of synchromesh change speed transmitter 25 or 225. One example of such a substitution is shown in GB 2 304 659 A (hereby incorporated by reference) which shows another adaptation of a transmission normally used for a front wheel drive transverse engine and transmission for the purposes of a longitudinal engine and transmission. Also shown in GB 2 304 659 A are arrangements for providing a plurality of selectable ratios in the drive between the transmission output shaft and the final drive input gear, including an illustration of two transmission output gears arranged to each drive a respective transfer gear. It will be appreciated that the intermediate casing 52 may be modified to accommodate such an arrangement of plurality of ratios or alternative change speed transmissions without a need to modify the adapter casing 24.

In place of the centre differential 181, the rear universal joint 183 may be directly connected to the transfer gear 145 and a viscous coupling or similar speed sensitive device fitted in the drive to the rear wheels 13,14.

Other conventional forms of final drive may be used in place of the spiral bevel and bevel differential shown, e. g. a hypoid drive or a Torsen (Trade Mark) type of differential.

Although described with particular reference to vehicles with the engine at the front of the vehicle, the invention may also be applied to mid or rear engine vehicles. In the case of the mid engine vehicle, an engine and transmission based on those shown in Figs. 1 to 6 would be located at the rear of the vehicle but with the engine 15 still being in front of the change speed transmission 23. In the case of the rear engine vehicle, an engine and transmission based on those shown in Figs. 1 to 6 would be located at the rear of the vehicle but reversed, effectively inverting the layout shown in Fig. 1, the engine 15 being behind the change speed transmission 23. Such a layout would still have the option of four wheel drive.

Claims

CLAIMS 1. A transmission assembly for a motor vehicle having a pair of front wheels and a pair of rear wheels, an engine mounted longitudinally in the vehicle adjacent an end thereof and having a crankshaft, a drive coupling at one end of the crankshaft and an engine lower structure comprising a crankcase and an oil sump, the transmission assembly including: an adapter casing comprising an annular spacer which, in use, is mounted on the engine and encircles the drive coupling; a change speed transmission mounted on the annular spacer at an end thereof which, in use, is opposite the engine, the change speed transmission including a transmission input shaft drivably connected to the drive coupling and a transmission output shaft parallel to the input shaft; and a final drive disposed, in use, between one of said pairs of wheels and drivably connected thereto and including a final drive input gear drivably connected to the transmission output shaft and rotatably supported in a final drive casing which is integral with the adapter casing and is positioned on one side of the engine lower structure without being structurally attached thereto except by the adapter casing.
2. A transmission assembly according to claim 1 wherein the change speed transmission includes an intermediate casing which is attached to the adapter casing.
3. A transmission assembly according to claim 1 or claim 2 wherein the transmission output shaft has a transmission output gear which meshes with a transfer gear coaxial with and drivably connected to the final drive input gear.
4. A transmission assembly according to claim 3 when dependent on claim 2 wherein the transfer gear is supported in a bearing in the intermediate casing.
5. A transmission assembly according to any preceding claim wherein the final drive casing is pan-shaped with a generally tubular portion extending parallel to and merging with the annular spacer and a dished portion arranged perpendicular to the tubular portion and having an open rim closed by a cover plate.
6. A transmission assembly according to any preceding claim wherein the final drive input gear is the bevel pinion of a bevel gear set comprising the bevel pinion and a bevel crownwheel.
7. A transmission assembly according to claim 6 when dependent upon claim 5 wherein the final drive bevel pinion is carried in bearings in the tubular portion of the final drive casing and the bevel crownwheel is carried in one bearing in the dished portion of the final drive casing and another bearing in the cover plate..
8. A transmission assembly according to claim 6 or claim 7 wherein the final drive bevel crownwheel is carried on a final drive differential arranged to drive said one pair of wheels.
9. A transmission assembly according to claim 8 wherein the differential is arranged to drive one universal joint which, in use, is on the same side of the engine lower structure and another universal joint which, in use, is on the other side of the engine lower structure.
10. A transmission assembly according to claim 9 wherein said other universal joint is rotatably supported in a bracket which is integral or fast with the adapter casing without being structurally attached to the engine lower structure except by the adapter casing.
11. A transmission assembly according to claim 9 or claim 10 wherein said other universal joint is connected to the differential by an intermediate drive shaft which, in use, extends transversely through the engine lower structure.
12. A transmission assembly according to any preceding claim in which the change speed transmission includes rotary drive components and selector components substantially identical to those produced for a change speed transmission used in a front wheel drive motor vehicle with a transverse engine and change speed transmission.
13. A transmission assembly according to claim 8 in which the change speed transmission includes a casing component substantially identical to one produced for a change speed transmission used in a front wheel drive motor vehicle with a transverse engine and change speed transmission.
14. A transmission assembly according to any preceding claim and including an auxiliary output drivably connected to the transfer gear and arranged, in use, to drive the other of said pairs of wheels.
15. A transmission assembly according to claim 14 wherein the transfer gear is drivably connected to the auxiliary output and to the final drive input gear by a centre differential.
16. A transmission assembly according to claim 15 wherein the centre differential is mounted on the transfer gear.
17. A transmission assembly according to any preceding claim wherein a plurality of selectable ratios is provided in the drive between the transmission output shaft and the final drive input gear.
18. A transmission assembly according to claim 17 when dependent upon claim 3 wherein the transmission output shaft has a plurality of transmission output gears arranged to each drive a respective transfer gear.
19. A transmission assembly substantially as described herein with reference to Figs. 1 to 6 or as modified with reference to Fig. 7 or Figs. 8 to 10 of the accompanying drawings.