GB2294019A - Mounting of vehicle power pack ie power source and final drive - Google Patents

Abstract

A power pack for a motor vehicle had a power source (engine and gearbox unit) connected to a final drive unit (15) incorporating reduction gearing by a transmission means (17) enabling relative movement therebetween, so that the power source may be mounted to the vehicle structure by mountings softer than those by which the final drive unit is mounted. <IMAGE>

Description

Title: VEHICLE POWER PACKS Description of Invention This invention relates to a power pack for a motor vehicle. By a power pack, we mean the combination, in close proximity to one another, of a power source having an output; and a final drive means having an input connected to the output of the power source and at least one output for connection to at least one road wheel of the vehicle, the final drive means incorporating reduction gearing means effective between its input and output or outputs. The power source preferably comprises an engine (which usually will be an internal combustion engine) and a gearbox.The gearbox may be a conventional manual gearbox in which case a clutch will usually be interposed between the engine and gearbox, or alternatively may be any type of automatic or semi-automatic gearbox, a continuously variable transmission means of any type, an hydrostatic or hydrodynamic transmission means, e.g. a torque converter, or any combination of the aforesaid and/or other devices enabling a change in transmission ratio to be effected between an output of the engine and the output of the gearbox.

The invention has been devised in relation to such a power pack intended for installation at the front of a front wheel drive vehicle such as a passenger car or light commercial vehicle. In such a power pack, the final drive means has two outputs for connection to respective universally-jointed drive shafts extending laterally to the front wheels of the vehicle. The final drive means may also have an auxiliary output providing either a permanent or disconnectable drive for the rear wheels of the vehicle. In some vehicles, a similar power pack is disposed at the rear or mid-region of the vehicle for driving the rear wheels thereof.

The usual form of power pack has the engine, gearbox and final drive means bolted rigidly to one another to form a unit which is flexibly mounted relative to the structure of the vehicle. Flexible mountings which are soft and compliant are used in order to isolate engine-generated vibration from the vehicle's structure as far as possible. However, the performance of the mountings of the power pack unit is compromised by the need to react the torque created at the power pack unit, equal to the torque which is transmitted to the wheels of the vehicle by way of the drive shafts. When the gearbox is providing a high ratio reduction between the engine and its output, and the final drive means is providing a further reduction, the torque reaction at the power pack unit can be very high.The mountings for the power pack unit must not permit the unit to move relative to the structure of the vehicle more than a predetermined distance, whilst sudden changes in torque reacted through soft power pack unit mountings will give rise to a movement of the power pack which is detectable by persons travelling in the vehicle as a low frequency vibration known as "shunt".

Accordingly, it is an object of the present invention to provide a vehicle power pack which enables the above described difficulties with conventional power pack units to be overcome.

According to the present invention, we provide a vehicle power pack wherein the power source and final drive means are adapted to be separately mounted to the vehicle structure, and a transmission means is provided between the output of the power source and input of the final drive means and providing for relative movement therebetween.

The transmission means provided between the power source output and the final drive means input conveniently comprises a universally-jointed drive shaft.

A vehicle power pack in accordance with the invention presents advantages over conventional power pack units as described above. The torque reaction at the power source is less than that at the final drive means, by virtue of the fact that the final drive means incorporates reduction gearing means. Thus the power source can be connected to the vehicle structure by mountings which are relatively soft and compliant compared with those which for the reasons aforesaid have to be provided for conventional power pack units. Thereby isolation of engine-generated vibration from the vehicle structure is improved.

The final drive means requires mountings which are less soft and compliant, but this is not of such importance in terms of vibration isolation since a final drive means does not generate vibration to the same extent as an internal combustion engine in the power source. Further, the separation of the final drive means from the power source provides greater freedom of design in respect of where the final drive means is mounted in the vehicle.

In one-piece power pack units, it is frequently the case that the final drive means is not disposed centrally between the sides of the vehicle, so that unequal-length drive shafts extending from its output to the wheels are necessary, giving rise to torque-steer effects and, in the case of the shorter drive shaft, high angles of articulation occurring in the universal joints of the drive shaft when the wheel is steered and suspension movement takes place. In a power pack in accordance with the invention, however, the final drive means may be able more conveniently to be centrally disposed, enabling relatively long and equal-length drive shafts to be used, with minimal angular change in their universal joints with wheel steering and suspension movement and a reduction in torque steer effects.

According to another aspect of the invention, we provide a vehicle incorporating a power pack in accordance with the first aspect of the invention as above set forth. Prtferably there are respective resilient mounting means for the power source and for the final drive means, the mounting means for the power source being softer than the mounting means for the final drive means.

Preferably the vehicle is a front wheel drive vehicle.

The invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic perspective view of a typical installation in a motor vehicle of a power pack in accordance with the invention; Figure 2 shows diagrammatically, in front view, the power pack installation of Figure 1.

Referring to the drawings, an engine, e.g. a spark- or compressionignition internal combustion engine, is indicated at 10. At one end of the engine there is a clutch housing 11 followed by a gearbox casing 12, these being rigidly connected to one another and to the crankcase/cylinder structure of the engine.

The gearbox casing 12 includes an upwardly and rearwardly extending portion 13 containing transfer gearing means by which a driving connection is provided with an output member rotatable about an axis 14 at the uppermost end of the casing portion 13.

A final drive means comprises a housing 15 with an input rotatable about axis 16. A drive shaft 17 with constant velocity ratio universal joints 18, 19 at its ends provides a driving connection between the output from the gearbox and the input of the final drive means. The final drive means 15 comprises a differential gearing whose outputs are connected by way of constant velocity ratio universal joints 20, 21 to drive shafts 22, 23 respectively, and a reduction gearing means between the input of the final drive means and the differential gearing incorporated therein.

The drive shafts 22, 23 have further constant velocity ratio universal joints 24, 25 respectively at their outboard ends, providing driving connections to wheel carriers 26, 27 supported by swivel hubs 28, 29 at the lowermost ends of suspension struts indicated generally at 30, 31, respectively. Lower suspension arms, wishbones, or the like, not shown, would normally be provided to provide additional connections between the swivel hubs 28, 29 and the vehicle structure wherein the power pack is to be installed.

The engine and gearbox unit 10, 11, 12 is mounted by resilient mountings 32, 33 and possibly other mountings not shown to a sub-frame 34 adapted to be connected to the structure of the vehicle. The final drive means 15 is mounted to the sub-frame by a flexible mounting 35. The drive shaft 17 with universal joints 18, 19 connecting the output from the gearbox to the input to the final drive means enables these two units to move relative to one another and to the sub-frame 34.

The mountings 32, 33 connecting the power source unit 10, 11, 12 to the sub-frame may be more compliant than the mounting 35 of the final drive means. Thereby improved isolation of engine-generated vibration from the vehicle structure may be obtained. Driving torque applied to the wheels 40 of the vehicle is reacted at the mounting 35 or mountings of the final drive means 15, whilst the mountings 32, 33 have only to react gearbox output torque which is less than the former torque by virtue of the reduction gearing incorporated in the final drive means.

It will further be noted that the final drive means 15 is substantially centrally disposed between the wheels of the vehicle, so that the drive shafts 22, 23 are of equal lengths and as long as possible.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (7)

1. A power pack for a motor vehicle, comprising a power source having an output; and a final drive means disposed close to the power source and having an input connected to the output of the power source, at least one output for connection to at least one road wheel of the vehicle, and reduction gearing means effective between its input and output or outputs; wherein the power source and final drive means are adapted to be separately mounted to the structure of the vehicle and a transmission means is provided between the output of the power source and the input of the final drive means and providing for relative movement therebetween.

2. A power pack according to Claim 1 wherein the transmission means between the power source and final drive means comprises a universally-jointed drive shaft.

3. A motor vehicle having a power pack according to Claim 1 or Claim 2.

4. A motor vehicle according to Claim 3 comprising respective resilient mounting means for the power source and for the final drive means, the mounting means for the power source being softer than the mounting means for the final drive means.

5. A vehicle according to Claim 3 or Claim 4 wherein the final drive means is disposed substantially centrally between the sides of the vehicle, and has outputs connected to respective road wheels of the vehicle by universally jointed drive shafts of substa.ially equal length to one another.

6. A vehicle power pack substantially as hereinbefore described with reference to the accompanying drawings.

7. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.