GB2270661A

GB2270661A - Vehicle transmission assembly.

Info

Publication number: GB2270661A
Application number: GB9314605A
Authority: GB
Inventors: Patrick Weismann
Original assignee: McLaren Cars NV
Current assignee: McLaren Cars NV
Priority date: 1992-07-31
Filing date: 1993-07-14
Publication date: 1994-03-23
Anticipated expiration: 2013-07-14
Also published as: GB9314605D0; GB9216310D0; GB2270661B

Abstract

A transmission assembly (14), particularly for a mid-engined car has a short longitudinal extent. The clutch output shaft (30) is connected by gears (32) to a transversely extending lay shaft (34) which engages a transfer gear shaft (36) which, in its turn, engages, and is arranged to rotate, a final drive gear (38). The axis of rotation (R) of the final drive gear (38) is substantially transverse to a longitudinal axis (L) of the transmission assembly (14), and the gears (32) are laterally offset relative to the longitudinal axis (L). Thus, the final drive gear (38) and the clutch assembly (22) overlap so that the length (F) of the transmission assembly (14) is very much smaller than is traditional. <IMAGE>

Description

A TRANSMISSION ASSEMBLY FOR A VEHICLE The present invention relates to a transmission assembly for a vehicle.

It is generally very important to minimise the length of the wheel base of a mid-engined car where the engine is longitudinally mounted for stability; This requires that the length of the transmission assembly should be kept short, and attempts to reduce the length thereof had been made in the past. For example, previous designs have included placing the transmission assembly underneath or to the front of the engine, or placiny the clutch assembly at the rear of the transmission assembly. All of the previously known solutions are complicated and in most cases carry weight, centre of mass and packaging penalties.

It is an object of the present invention to provide a transmission assembly for a vehicle which as well as having a restricted length is simple and light and no more complex than a conventional transmission assembly.

According to the present invention there is provided a transmission assembly for a vehicle comprising a clutch assembly having an output shaft, a final drive gear arranged to be coupled to drive wheels, and gear means for coupling the output shaft of the clutch assembly to said final drive gear, wherein the said output shaft extends substantially parallel to a longitudinal axis of said transmission assembly, and the final drive gear has an axis of rotation which extends substantially perpendicular to said longitudinal axis, and wherein said final drive gear extends along one side of the clutch assembly such that the final drive gear and the clutch assembly overlap in the longitudinal direction, generally parallel to the longitudinal axis, of the transmission assembly whereby the longitudinal extent of the transmission assembly is kept small.

The overlapping arrangement of the clutch assembly and final drive gear of a transmission assembly according to an embodiment of the invention enables the rotation axis of the final drive gear to be closer to the clutch assembly than hitherto. It is in this manner that the longitudinal extent of the transmission assembly is kept small.

In a preferred embodiment, the gear means is offset transversely relative to said longitudinal axis. This offset position of the gear means provides space for the overlapping final drive gear without it being necessary to increase the transverse dimension of the transmission assembly.

As is conventional, the final drive gear is coupled to the drive wheels by way of a differential arranged within a differential housing. Respective half shafts couple the differential to drive wheels, these half shafts being substantially equal in length.

Said gear means coupling said clutch assembly output shaft to the final drive gear is preferably arranged such that the drive of said output shaft is turned through substantially 1800 before it is coupled to said final drive gear. It will be appreciated that, by this means, the drive is effectively coupled back on itself, that it extends along three sides of a square or rectangle. Again this arrangement aids in the reduction of the overall length of the transmission assembly.

In a preferred embodiment said output shaft is arranged to extend above or below said differential housing, is coupled by way of bevel gear means to a first shaft arranged above or below a second shaft, said first and second shafts being in engagement, and the second shaft being also in engagement with said final drive gear.

In a preferred embodiment, said output shaft extends below said differential housing and is coupled by way of said bevel gear means to said first shaft, which is transversely extending and which is in engagement with said second shaft, which is also transversely extending and which is arranged above said first shaft.

An embodiment of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a mid-engined car, Figure 2 shows an enlarged view of the engine and transmission- assembly of the car of Figure 1, Figure 3 shows a plan view of a transmission assembly of the present invention, Figure 4 shows an end elevation of the transmission assembly of Figure 3, and Figure 5 shows an end elevation of a conventional transmission assembly for comparison with that of Figure 4.

The invention is described and illustrated herein with specific reference to a mid-engined car. However, although a transmission assembly of the invention has been specifically designed for such use, it will be appreciated that the transmission assembly may be incorporated in any vehicle if required.

Figure 1 shows a plan view of a mid-engined car 10 having a longitudinally mounted engine 12, and a transmission assembly, generally referenced 14, arranged to transfer drive to rear wheels 16. The car 10 also has an occupant cabin 18 and front wheels 20. It will be seen that the car 10 of Figure 1 has a wheel base length A, a sizeable proportion of which is attributable to a length B. Figure 2 shows in closer detail the components contributing to the length B, namely an engine 12, which has a length C, a clutch assembly 22, which has a length D, and a final drive 24 which contributes a length E.

In the design of such a mid-engined car as 10, efforts are made to ensure that the length C of the engine 12 and the length D of the clutch assembly 22 are kept to a minimum.

Various solutions have also been proposed to try to minimise the length E between the clutch assembly 22 and the rotation axis of the final drive 24. For example, it has been proposed to place the transmission assembly underneath or in front of the engine, or to place the clutch assembly at the rear of the transmission assembly. However, such proposals are generally complicated and provide other problems.

Figures 3 and 4 show a plan view and a side elevation of an embodiment of a transmission assembly 14 of the present invention. In Figures 3 and 4 features which are the same or similar to those of Figures 1 and 2 have been accorded the same reference numerals. The transmission assembly 14 comprises the clutch assembly 22 which has an output shaft 30.

This output shaft 30 is connected by way of bevel gears 32 to a transversely extending primary or lay shaft 34. The lay shaft 34 engages a second transversely extending secondary or transfer gear shaft 36. The transfer gear shaft 36 engages, and is arranged to rotate, a final drive gear 38.

It will be seen that the final drive gear 38 has an axis of rotation R which is substantially transverse to a longitudinal axis L of the transmission assembly 14. It will also be seen that the output shaft 30 of the clutch assembly 22 extends substantially parallel to, but laterally offset with respect to, the longitudinal axis L. Furthermore, the gear means 32 is laterally offset relative to the longitudinal axis L. This enables the final drive gear 38 to extend radially along one side of the clutch assembly 22 such that the final gear 28 and the clutch assembly 22 overlap as is clearly shown in Figure 4. It will thus be seen that the length F that the transmission assembly 14 of Figures 3 and 4 contributes to the length B is very much smaller than the traditional dimension of D+E. In fact, the dimension F is substantially the sum of the length of the clutch assembly 22 and of the radius of a differential housing 40. In this respect, the differential housing 40 is conventional and houses a differential (not visible) coupled by respective half shafts (not visible) to drive the rear wheels. The half shafts are arranged to be substantially equal in length.

Figure 4 shows an end elevation the conventional arrangement of a transmission assembly of Figure 2 showing the dimension F which is made up of the lengths D+E. It will be appreciated that the contribution of the dimension E to the final length B in the embodiment of the invention has been reduced by approximately half.

It will be appreciated that variations to and modifications of the invention as illustrated above may be made within the scope of this application.

Claims

1. A transmission assembly for a vehicle comprising a clutch assembly having an output shaft, a final drive gear arranged to be coupled to drive wheels, and gear means for coupling the output shaft of the clutch assembly to said final drive gear, wherein the said output shaft extends substantially parallel to a longitudinal axis of said transmission assembly, and the final drive gear has an axis of rotation which extends substantially perpendicular to said longitudinal axis, and wherein said final drive gear extends along one side of the clutch assembly such that the final drive gear and the clutch assembly overlap in the longitudinal direction, generally parallel to the longitudinal axis, of the transmission assembly whereby the longitudinal extent of the transmission assembly is kept small.

2. A transmission assembly for a vehicle as claimed in Claim 1, wherein said gear means is offset transversely relative to said longitudinal axis.

3. A transmission assembly as claimed in Claim 1 or 2, wherein the final drive gear is coupled to the drive wheels by way of a differential arranged within a differential housing, and wherein respective half shafts couple the differential to drive wheels, these half shafts being substantially equal in length.

4. A transmission assembly as claimed in any preceding claim, wherein said gear means coupling said clutch assembly output shaft to the final drive gear is arranged such that the drive of said output shaft is turned through substantially 180C before it is coupled to said final drive gear.

5. A transmission assembly as claimed in any preceding claim, wherein the final drive gear is coupled to the drive wheels by way of a differential arranged within a differential housing, and wherein said output shaft is arranged to extend above or below said differential housing, is coupled by way of bevel gear means to a first shaft arranged above or below a second shaft, said first and second shafts being in engagement, and the second shaft being also in engagement with said final drive gear.

6. A transmission assembly as claimed in Claim 5, wherein said output shaft extends below said differential housing and is coupled by way of said bevel gear means to said first shaft, which is transversely extending and which is in engagement with said second shaft, which is also transversely extending and which is arranged above said first shaft.

7. A transmission assembly for a vehicle substantially as hereinbefore described with reference to the accompanying drawings.

8. A vehicle incorporating a transmission assembly as claimed in any preceding claim.

9. A vehicle as claimed in Claim 8, wherein said vehicle is a mid-engined car.