GB2103160A

GB2103160A - Two to four wheel drive vehicle conversion

Info

Publication number: GB2103160A
Application number: GB08123368A
Authority: GB
Inventors: Barry William Talman; David Robert Frederick Tapp
Original assignee: County Commercial Cars Ltd
Current assignee: County Commercial Cars Ltd
Priority date: 1981-07-30
Filing date: 1981-07-30
Publication date: 1983-02-16
Also published as: GB2103160B

Abstract

For converting a two wheel drive tractor to four wheel drive the outer half shaft housings 14 are detached from the transmission housing 13 and interposed therebetween are intermediate gear housings 20. Each housing 20 mounts a take-off mechanism which provides a take-off outlet for a respective front steerable wheel 27 but which transmits drive to the respective half shaft 43. Propeller shafts 24 convey power to the front wheels 27. <IMAGE>

Description

SPECIFICATION Two to four wheel drive vehicle conversion This invention relates to the conversion of two wheel drive land vehicles to four wheel drive.

The invention provides a method of converting from two wheel drive to four wheel drive a land vehicle having a rear wheel drive mechanism comprising a differential gear mechanism and two half shafts driven by the differential mechanism and drivingly connected to respective rear land wheels, the method comprising the steps of disengaging the half shafts from the differential mechanism, engaging a pair of take-off mechanisms with the differential mechanism one on each side thereof, each take-off mechanism comprising a drive outlet and a take-off outlet, engaging each half shaft with the drive outlet of the respective take-off mechanism so as to be drivably connected to the differential mechanism through the take-off mechanism, and providing a drive transmission between each outlet and a respective front land wheel whereby the front land wheels are drivably connected to the differential mechanism through their respective take-off mechanisms.

The invention further provides apparatus for converting from two wheel drive to four wheel drive a land vehicle having a rear wheel drive mechanism comprising a differential gear mechanism and two half shafts driven by the differential mechanism and drivingly connected to respective rear land wheels, the apparatus comprising a pair of take-off mechanisms each comprising a drive inlet for drivable connection to the differential mechanism, a drive outlet for driving connection to a respective one of the half shafts, and a take-off outlet for driving connection to a respective front land wheel, whereby in use the front and rear land wheels of the converted vehicle are all driven by the differential mechanism through their corresponding take-off mechanism.

Where the differential mechanism is housed in an inner housing with each half shaft housed in an outer housing attached in the unconverted vehicle to the inner housing, each take-off mechanism is preferably housed in an intermediate housing, the method comprising the steps of detaching the outer housings from the inner housing, attaching the intermediate housings to the inner housing one on each side thereof, and attaching each outer housing to the respective intermediate housing.

Each take-off mechanism preferably comprises a transfer shaft engageable with the differential mechanism to provide the engagement of the take-off mechanism with the differential mechanism. Each such transfer shaft may be drivably engageable between the respective output gear of the differential mechanism and the respective half shaft, each take-off mechanism also comprising a take-off shaft driven by the transfer shaft and providing the take-off outlet.

In the case where there is a splined joint between each half shaft and the respective output gear in the unconverted vehicle, the ends of each transfer shaft are preferably similarly splined so as to provide similar splined joints between the transfer shaft and each of the output gear and the half shaft. Each output gear and the outer end of each transfer shaft may be provided with external splines, with the inner end of each transfer shaft and each half shaft formed with corresponding internal splines.

Each take-off shaft is preferably orientated generally longitudinally of the vehicle and may have an axis which is lower than that of the rear land wheels.

Each take-off mechanism may comprise a first spur gear secured to the transfer shaft and a second spur gear driven by the first gear through an idler gear, the take-off shaft being driven by the second spur gear. Each such second spur gear may be secured to a first bevel gear which meshes with a second bevel gear mounted on the respective take-off shaft. The external splines provided for the outer end of each transfer shaft may be formed directly in the respective first spur gear.

An example of the invention will now be described with reference to the accompanying drawings, in which; Figure 1 shows in outline a side elevation of a typical two wheel drive tractor; Figure 2 shows a plan view of the same tractor; Figure 3 shows in outline a side elevation of the tractor of Figure 1 after conversion to four wheel drive according to the invention; Figure 4 shows a plan view of the converted tractor; Figure 5 is an enlarged sectional side elevation taken generally along the line V-V of Figure 4; and Figure 6 is an enlarged sectional plan view taken along the line VI--VI of Figure 5.

Referring first to Figures 1 and 2, the two wheel drive tractor 1 has an engine 10, change speed gearbox 12, inner transmission housing 13 and outer half shaft housings 14 attached together to form a solid unitary structure. Rear land wheels 1 5 are attached to axle shafts (not shown) which are rotatably mounted in the outer housings 14.

Steerable front wheels 1 6 are rotatably attached to an axle beam 17 which is mounted by means of a horizontai longitudinal pivot (not shown) on to a cross member 1 8. The cross member 1 8 is attached rigidly to the engine 10.

Referring now also to Figures 3 and 4, the engine 10, change speed gearbox 12 and transmission housing 13 remain as in the two wheel drive tractor solidly attached together. The outer housings 14 are detached from the transmission housing 13 and interposed therebetween are intermediate gear housings 20.

The housings 13, 20 and 14 are secured together so as to form a complete new rear housing.

Mounted in each intermediate housing 20 is a take-off mechanism having an output coupling 22 on a take-off shaft forming a take-off outlet.

Telescopic propeller shafts 24 are then connected to the couplings 22 via universal joints 23 and are connected up to front drive housings 25 for transmitting power to new front wheels 27, the wheels 27 being rotatably mounted to the housings 25. The front housings 25 are pivotably mounted within C shape members 26 so as to be free to pivot about a generally upright axis within the C shape members 26 in order to steer. The C shape members 26 are attached to a beam structure 28 which is pivotably mounted about a longitudinal horizontal axis to a cross member 29, the cross member 29 being attached rigidly to the engine 10.

The propeller shafts 24 are connected to stub shafts 31 by universal joints 32 and drive the wheels 27 through bevel pinions 33 mounted on the shafts 31 and meshing with bevel crown wheels 34 which are fast with the wheels 27 or drivably connected to them via planetary reduction gears.

Referring now to Figures 5 and 6, the output drive shaft 37 from the change speed gearbox 12 has fixedly mounted thereon a bevel pinion 38.

This bevel pinion 38 meshes with a bevel crown wheel 39 driving a differential gear assembly of conventional design, having planetary gears 40 and output gears 41. In the unconverted two wheel drive tractor, half shafts 43 are splined directly into the output gears 41. During conversion the half shafts 43 are disengaged from the output gears 41 and with the interposal of the take-off mechanisms between the differential mechanism and the half shafts 43, transfer shafts 44 which are formed with external splines similar to those on the half shafts 43 are engaged in respective output gears 41. The outer end of each transfer shaft 44 provides a spigot end flange mounting into which a first spur gear 46 fits and is bolted.An internally splined portion in each gear 46 reproduces the spline in each differential output gear 41 and thus provides the mating drive connection with the half shaft 43. Mounted on each half shaft 43 is a disc brake 47. During the conversion the output drive shaft 37, bevel pinion 38 and differential gear mechanism remain as in the two wheel drive tractor.

Each take-off mechanism also includes a second spur gear 50 driven by the first spur gear 46 through an idler gear 51. A bevel gear 52 secured to the second spur gear 50 meshes with a second bevel gear 53 mounted on an output (take-off) shaft 54 to which the coupling 22 is secured. The shafts 44, 54 and gears 46, 51 and 50 with 52 are mounted in bearings in the housings 20.

It will be seen that by the method described above a standard conventional two wheel drive tractor may be simply and economically converted to a four wheel drive tractor utilising the maximum number of the original tractor components.

Claims

1. A method of converting from two wheel drive to four wheel drive a land vehicle having a rear wheel drive mechanism comprising a differential gear mechanism and two half shafts driven by the differential mechanism and drivingly connected to respective rear land wheels, the method comprising the steps of disengaging the half shafts from the differential mechanism, engaging a pair of take-off mechanisms with the differential mechanism one on each side thereof, each take-off mechanism comprising a drive outlet and a take-off outlet, engaging each half shaft with the drive outlet of the respective take-off mechanism so as to be drivably connected to the differential mechanism through the take-off mechanism, and providing a drive transmission between each outlet and a respective front land wheel whereby the front land wheels are drivably connected to the differential mechanism through their respective takeoff mechanisms.

2. A method as claimed in Claim 1, the differential mechanism being housed in an inner housing, each half shaft being housed in an outer housing attached in the unconverted vehicle to the inner housing, and each take-off mechanism being housed in an intermediate housing, the method comprising the steps of detaching the outer housings from the inner housing, attaching the intermediate housings to the inner housing one on each side thereof, and attaching each outer housing to the respective intermediate housing.

3. A method as claimed in either Claim 1 or Claim 2 wherein each take-off mechanism comprises a transfer shaft engageable with the differential mechanism to provide the engagement of the take-off mechanism with the differential mechanism.

4. A method as claimed in Claim 3 wherein each transfer shaft is drivably engageable between the respective output gear of the differential mechanism and the respective half shaft, each take-off mechanism also comprising a take-off shaft driven by the transfer shaft and providing the take-off outlet.

5. A method as claimed in Claim 4, there being a splined joint between each half shaft and the respective output gear in the unconverted vehicle, in which method the ends of each transfer shaft are similarly splined so as to provide similar splined joints between the transfer shaft and each of the output gear and the half shaft.

6. A method as claimed in Claim 5 wherein each output gear and the outer end of each transfer shafts are provided with external splines and the inner end of each transfer shaft and each half shaft are formed with corresponding internal splines.

7. A method as claimed in any one of Claims 4 to 6 wherein each take-off shaft is orientated generally longitudinally of the vehicle.

8. A method as claimed in any one of Claims 4 to 7 wherein each take-off mechanism comprises a first spur gear secured to the transfer shaft and a second spur gear driven by the first gear through an idler gear, the take-off shaft being driven by the second spur gear.

9. A method as claimed in Claim 8 as dependent on Claim 7 wherein each second spur gear is secured to a first bevel gear which meshes with a second bevel gear mounted on the respective take-off shaft.

10. A method as claimed in either Claim 8 or Claim 9 wherein Claim 6 is depended upon wherein the external splines provided for the outer end of each transfer shaft are formed directly in the respective first spur gear.

11. Apparatus for converting from two wheel drive to four wheel drive a land vehicle having a rear wheel drive mechanism comprising a differential gear mechanism and two half shafts driven by the differential mechanism and drivingly connected to respective rear land wheels, the apparatus comprising a pair of take-off mechanisms each comprising a drive inlet for drivable connection to the differential mechanism, a drive outlet for driving connection to a respective one of the half shafts, and a take-off outlet for driving connection to a respective front land wheel, whereby in use the front and rear land wheels of the converted vehicle are all driven by the differential mechanism through their corresponding take-off mechanisms.

12. Apparatus as claimed in Claim 11 further comprising a pair of intermediate housings each having a respective one of the take-off mechanisms mounted therein, each housing being for interposal between an inner housing in which the differential mechanism is housed and a respective outer housing in which the respective half shaft is housed.

13. A method of converting a land vehicle from two wheel drive to four wheel drive substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

14. Apparatus for converting a land vehicle from two wheel drive to four wheel drive substantially as hereinbefore described with reference to and as shown in the accompanying drawings.