GB2149732A

GB2149732A - Vehicle transmission

Info

Publication number: GB2149732A
Application number: GB08425720A
Authority: GB
Inventors: Richard Thomas Knowles
Original assignee: Quest 80 Ltd
Current assignee: Quest 80 Ltd
Priority date: 1983-11-14
Filing date: 1984-10-11
Publication date: 1985-06-19
Also published as: GB8425720D0; GB8330325D0

Abstract

An under floor transmission system for an omnibus vehicle, wherein the vehicle engine 10 is mounted beneath the vehicle floor and a drive transmission shaft extends rearwardly from the engine, comprises chain and sprocket gearing and helical gear wheels contained in a housing 26. An output shaft extends forwardly from housing 26 to a change-speed gearbox 23 connected to the driven rear axle 7 of the vehicle. The transmission system may incorporate overdrive gearing. A petrol tank 11 laterally counterbalances the weight of the engine 10. <IMAGE>

Description

SPECIFICATION Improvements in or relating to vehicles This invention has reference to vehicles and has particular reference to transmission systems for underfloor vehicles more especially for underfloor omnibuses.

It is known for underfloor omnibuses to have an underfloor engine positioned to the rear of the driving axle of the omnibus. The known arrangement has the disadvantage of being applicable only to omnibuses having a relatively long length because of the necessity to have an overhang to the rear of the driving axle of 60% compared to the length of the wheel base. In this construction the drive is transferred from the engine (or from a gear box driven by the engine) by a transmission shaft extending forwardly of the vehicle to the rear axle.

This construction necessitates the use of a cantilever construction which is relatively expensive.

It is also known for underfloor omnibuses to have an underfloor engine mounted crosswise of the length of the vehicle and drivingly connected to the differential on the rear driving axle of the omnibus by a driving shaft arranged at an inclined angle to the length of the omnibus. With this arrangement the overhang of the vehicle to the rear of the driving axle can be arranged to be relatively short but the wheel base will be consequently short as well.

It is an object of the present invention to provide an improved transmission system for an underfloor vehicle and more particularly for an omnibus.

It is a further object of the present invention to provide an improved transmission for an omnibus which is available for a wide range of wheel bases and does not entail having to mount the engine by a special cantilever construction mounting.

According to the present invention a transmission system for an underfloor vehicle has the vehicle engine mounted at one outer side of the vehicle frame and adjacent to one end of the vehicle and the drive transmission shaft extends from the engine towards the adjacent end of the vehicle and a drive system is provided for transferring the drive from a direction towards that end of the vehicle to the opposite direction to connection with the driving axle of the vehicle.

Preferably a gear box is located between the drive system and the rear driving axle and an overdrive mechanism is included in the drive system.

A transmission system in accordance with the present invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a diagrammatic view of an omnibus vehicle frame including the transmission system but not showing the vehicle body, and Figures 2 and 3 are plan view and end view respectively of part of the transmission system.

Referring to Fig. 1 there is shown the frame of an underfloor omnibus vehicle but not including the vehicle body. As shown the chassis frame 1 supports the vehicle driving position 2. The front axle 3 with front wheels 4 and steering system 5 is mounted on the chassis frame with an air bag suspension system 6.

The rear driving axle 7 of the vehicle with driving wheels 8 is also mounted on the chassis frame 1 and is mounted by an air bag suspension system 9. The vehicle engine 10 is mounted on the chassis frame 1 on the offside of the vehicle outside the chassis frame and beneath the floor of the vehicle and between the rear axle and the rear of the vehicle. A cross chassis frame member la helps to support the engine.

To counterbalance the weight of the engine 10 on the vehicle the petrol tank 11 is mounted on the nearside of the vehicle on the outside of the chassis frame 1. The air bag suspension system 9 accommodates for differences in the weight of the engine 10 and the petrol tank 11 for example as the petrol is used up.

It is arranged that the engine 10 has its drive take off at the end of the engine facing the rear of the vehicle. The drive take off has a drive shaft 12 (see Fig. 2). The rearward end of the drive shaft 12 is rotatable in a bearing 13 and is solidly connected to a series of three sets of three separate sprocket wheels 14 and each separate sprocket wheel 14 has a chain 15 engaging the teeth in the sprocket wheel. The chains may comprise three chains each chain having three sets of links. Each chain 15 also passes around a respective sprocket wheel 16 which sprocket wheels are mounted on a single idle shaft 17 mounted in bearings 18.The arrangement of the sprocket wheels is that the numbers of teeth on respective sprocket wheels 14 are the same and likewise the numbers of teeth on the respective sets of sprocket wheels 16 are the same to that the respective sprocket wheels drive and are driven in synchronism. A chain tensioning means 15a cooperates with the chains for adjusting the tension of the three chains.

The shaft 17 also carries a helical gear wheel 19 and this gear wheel meshes with another helical gear wheel 20 solid on a shaft 21 and this shaft is solid with a drive shaft 22 which connects to a gearbox 23 (Fig. 1) which in turn connects to a transmission shaft 24 which serves as an input to the differential mechanism 25 on the rear drive axle 7. The provision of the gear wheel 20 serves to change the direction of rotation of the transmission shaft 24 but being able to use traditional components.

The connection between the input shaft 12 and the output shaft 22 including the sprocket wheels 14 and 16 and chains 15 is contained in a housing 26. This connection has a 1-1 gear ratio but an overdrive mechanism may be included in the drive connection to reduce torque in the gearbox 23 and to give a higher top speed.

Although it is preferred to position the enging 10 on the offside of the vehicle and thereby offset the weight of the engine of the offside of the vehicle by taking into account the camber on the road, it is possible to have the engine 10 on the nearside of the vehicle. This is appropriate when the parts of the engine which are liable to require most fre quent maintenance are on the side of the engine away from the chassis frame.

By this invention we are able to provide an improved construction of vehicle in which the rear overhand of the vehicle is reduced compared to the wheelbase in comparison with other vehicles.

Furthermore because of being able to position the engine near the rear driving axle the weight of the engine near the axle gives a more firm contact between the driving road wheels and the road.

Claims

1. A transmission system for an underfloor vehicle wherein the vehicle engine is mounted at one outer side of the vehicle frame and adjacent one end of the vehicle and the drive transmission shaft extends from the engine towards the adjacent end of the vehicle and a drive system is provided to transfer the drive from a direction towards that end of the vehicle to the opposite direction to connect with the driving axle of the vehicle.

2. A transmission system according to claim 1 wherein the transfer drive system includes a pair of gears having the same number of teeth connected by an endless chain drive and an additional gear in mesh with a gear connected to one of the endless chain gears.

3. A transmission system according to claim 1 or 2 wherein the vehicle engine is mounted adjacent the rear end of the vehicle and the drive axle is the rear axle of the vehicle.

4. A tranmission system according to claim 3 wherein the engine is mounted on the overhang of the vehicle to the rear of the driving axle.

5. A transmission system according to any one of the preceding claims wherein a gear box is located between the drive system and the rear driving axle and an overdrive mechanism is included in the drive system.

6. A transmission system according to claim 2 wherein the drive system includes an endless chain drive with a pair of sprockets each sprocket including three sets of sprocket wheels and the sets of sprocket wheels being connected by an endless chain having nine sets of endless chains.

7. A transmission system according to claims 2 and 6 wherein the additional gear is in mesh with a gear sited on a shaft on which one series of the three sets of sprocket wheels are mounted.

8. A transmission system for an underfloor vehicle wherein the vehicle engine is mounted at one outer end of the vehicle frame and adjacent one end of the vehicle and the transmission system includes a drive system to transfer the drive in the vehicle from one direction to an opposite direction and which includes an input drive shaft and an output drive shaft and a pair of sprocket gears having the same number of teeth connected by an endless chain sprocket drive as well as an additional gear in mesh with a gear connected to one of endless chain gears and in which one of the drive shafts is connected to the additional gear and the other drive shaft is connected to the gear connected through the chain drive to the gear meshing with the additional gear.

9. A transmission system constructed arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.