GB2220247A

GB2220247A - Drive transfer apparatus

Info

Publication number: GB2220247A
Application number: GB8913475A
Authority: GB
Inventors: Brian Brown; Graham Beck
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-15
Filing date: 1989-06-12
Publication date: 1990-01-04
Also published as: GB8913475D0; GB8814230D0; GB2220247B

Abstract

Apparatus for transferring drive between a crankshaft and a camshaft gear 12 of a vehicle engine comprises a casing 1 adapted for attachment to fixed structure of the engine or engine housing and dimensioned to house first and second gear wheels 11, 12 carried respectively by the crankshaft and camshaft of the engine and rotatable therewith. An idler gear wheel 8 is positioned to mesh with each of the first and second gear wheels to transmit drive therebetween and the casing 1 includes a closure plate 3 adapted to receive or at least partially to support one end of a spindle or shaft 7 on which the idler gear is located. A further idler gear 9 may be provided to transfer drive to a gear wheel 14 driving a pump. For timing purposes keyways are formed within the gears 11, 12 and 14. <IMAGE>

Description

Drive Transfer Apparatus This invention relates to apparatus for transferring drive between drive and driven shafts of a reciprocating piston engine and more especially to gear trains by which such drive can be transferred. The invention has particular application to a kit of parts for replacing a drive belt or other timing mechanism of a vehicle engine.

In petrol driven or diesel driven recriprocating piston engines working on a multi-stroke cycle, each spring biased valve through which combustible and combusted mixtures respectively enter and leave the working cylinders of the engine must open once every one or more revolutions of the crankshaft. In a four stroke engine, for example, each valve must open once every two revolutions of the crankshaft. The opening and closing of these valves is normally effected by cams carried by a camshaft driven at one half of the rotational speed of the crankshaft through a flexible belt or a timing chain.

For vehicles subjected to higher than average mileages, the increased wear engenered can lead to belt or chain breakage with consequent loss of drive and inherent possibility of consequential damage to engine parts. In addition, in use, a drive belt tends to stretch so reducing the torque transmitted with consequent loss of power and engine efficiency. Idler gears have been used previously in place of timing chains or belts but have achieved limited success.

The present invention sets out to provide apparatus for transferring drive between crankshaft and camshaft gears which does not suffer from or at least alleviates the disadvantages referred to in the preceding paragraph.

The invention further sets out to provide a conversion kit by which the timing mechanism of a suitable vehicle can be replaced in a relatively simple manner by an assembly in accordance with the invention.

According to the present invention in one aspect, there is provided apparatus for transferring drive between a crankshaft and a camshaft gear of a vehicle engine, the assembly comprising a casing adapted for attachment to fixed structure of the engine or engine housing and dimensioned to house first and second gear wheels carried respectively by the crankshaft and camshaft of the engine and rotatable therewith, and an idler gear wheel positioned to mesh with each of the first and second gear wheels to transmit drive therebetween, the casing including a closure plate adapted to receive or at least partially to support one end of a spindle or shaft on which the idler gear is located.

The casing may additionally house a third gear wheel carried by and rotatable with the driven shaft of an injector pump, this third gear wheel being positioned to mesh with a second idler gear wheel operable to transfer drive from the camshaft gear wheel to the injector pump gear wheel. This second idler gear wheel may also be carried by a spindle or shaft one end of which is received within a recess formed in the closure plate or is at least partially supported by the closure plate. Additional gear wheels may be housed within the casing.

The casing may include a closable inlet port for admitting lubricant to the casing interior and a drain for removing spent lubricant therefrom. Alternatively or additionally the teeth of the gear wheels housed within the casing may be coated with a material such as teflon; one such coating material is that marketed under the name Xylan 1052.

The shaft or spindle of the or each idler gear wheel may be supported at one end within bearing races set in recesses formed in the internal surface of the closure plate of the casing and at its other end within bearing races supported by the internal surface of the casing itself. Alternatively, the shaft or spindle of the or each idler gear wheel may be supported by or formed integral with a mounting plate positioned within the casing, the end of the shaft or spindle remote from the mounting plate being supported within bearing races set in recesses formed in the internal surface of the closure plate of the casing.

In another arrangement, the or each idler gear is mounted on spigots protruding from the internal surface of the casing. The spigots are preferably formed integrally with the casing and may be cast therewith. In this arrangement, the free end of the or each idler gear seats within a complementary recess formed in the internal surface of the closure plate of the casing. The or each idler gear is supported on needle bearing races carried by the or each spigot.

In a further aspect, the invention provides a kit of parts for replacing a timing mechanism of a vehicle engine, the kit comprising a casing adapted for attachment to fixed structure of the engine or engine housing and dimensioned to house first and second gear wheels carried by the crankshaft and camshaft of the engine, and an idler gear wheel positioned to mesh with each of the first and second gear wheels to transmit drive therebetween, the casing including a closure plate which additionally serves to receive one end of or at least partially to support a spindle or shaft on which the idler gear is located.

In another aspect, the invention provides a vehicle engine in which the timing mechanism thereof is replaced by a kit of parts as set out in the preceding paragraph.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which: Figures 1 and 2 are respectively plan and side elevational views of an assembly in accordance with the invention; Figures 3 and 4 are plan and side views to a larger scale of a mounting plate illustrated in Figures 1 and 2; and Figures 5 and 6 are respectively plan and side elevational views of an alternative assembly in accordance with invention.

The apparatus illustrated in Figures 1 to 4 of the drawings includes a metal casing 1 including spot faced holes 2 for receiving threaded bolts by which it can be secured rigidly to a fixed structure of an engine housing (not shown). The casing 1 includes a closure plate 3 which seats against the rim of the casing to provide a seal therefor. The closure plate is secured to the casing by threaded bolts which pass into apertures 4. A mounting plate 5 is supported internally within the casing and includes two cylindrical spindles 6 protruding therefrom.

The plate 5 is shown in greater detail in Figures 3 and 4.

The spindles 6 are preferably induction hardened and may be formed integrally with the mounting plate 5 (e.g. by a turning procedure) or may be secured thereto by any conventional means. Bearing races 7 are carried by the solid spindles 6.

As will be seen more clearly from Figure 2, one spindle provides a bearing surface for an idler gear wheel 8 and the other spindle provides a bearing surface for an idler gear wheel 9. The idler gear wheels 8, 9 are retained on the circumference of their respective shaft members by means of the closure plate 3. The closure plate 3 is recessed at 10 to provide additional support for the spindles 6 and the respective bearing races 7.

The idler gear wheels 8, 9 are so positioned within the casing 1 that gear wheel 8 meshes with and transfers drive between gear wheels 11, 12 carried respectively by the crankshaft and camshaft of the engine; and gear wheel 9 meshes with and transfers drive between the gear wheel 12 and a further gear wheel 14 carried by the drive shaft of an injector pump of a water pump housed within a side casing 21. For timing purposes keyways are formed within the camshaft gear, the crankshaft gear, and the injector gear.

The gear wheels are coated with a material such as a teflon, e.g. the material known in the trade as Xylan 1052 which has properties which avoid the need for the presence of lubricant within the casing. In an alternative construction, means are provided to introduce and extract lubricant from the casing. In this construction, the shaft members and gears may include discrete passageways for the flow of lubricant.

The gears employed in the embodiment described are spur gears; however, other species of gears may be used, these including helical gears.

In the embodiment illustrated in Figures 5 and 6, (in which the same integers bear the same reference numerals used in the preceding Figures) the casing 1 is provided with an oil filler port 15 and the closure plate 3 with a drain 16 for the oil. The drain 16 can alternatively be positioned in the casing. Thus, in this particular embodiment, the casing 1 is, in use, at least partially filled with a lubricant such as oil. As will be seen from Figure 6 of the drawings, the idler gear wheels 8, 9 are mounted on stub shafts 17, 18 respectively which are supported within ball bearing races 19 located within recesses set in the inside surface of the closure plate 3 and races 20 carried by the casing 1.

As for the previous embodiment, the gear wheels may be either of the spur or helical construction.

In an unillustrated embodiment, the closure plate 3 is formed with recesses to receive the free ends of solid spigots which protrude from the internal surface of the casing 1 and which define spindles on which the idler gears 8, 9 are mounted, the idler gears being supported on needle roller bearing races. In this arrangement, the closure plate 3 does not include any provision for bearings, the plate merely including two counterbored holes to receive and at least partially support the free ends of the two solid spigots. These spigots are preferably formed integrally with the casing and may be cast therewith. One advantage of this arrangement is that the closure plate 3 can readily be removed from the casing 1 without disturbing the gears contained within the casing.In this arrangement, the casing is formed with a small aperture through which oil can be pumped under pressure directly into the casing. In addition, a hooded aperture may be provided to prevent oil leaving the casing until it reaches a predetermined height.

The invention has especial application as a conversion kit for replacing timing mechanisms such as chains and belts used in reciprocating piston engines. In such engines, and in particular those used to power high mileage vehicles, the conversion essentially entails removing the existing timing belt or chain, securing the casing to a suitable engine structure and locating the casing such that the idler gear wheels mesh with and transfer drive between the crankshaft, the camshaft and the pump shaft.

It will be appreciated that the foregoing is merely exemplary of one embodiment of the invention and that various modifications can be made thereto without departing from the true scope of the invention. Thus, additional gear wheels may be housed within the casing 1.

Such gear wheels may be driving, driven or idler gear wheels. One or more of the spindles which carry the gear wheels may protrude through the casing to provide drive to or be driven by an external component. Additionally, the closure plate may be adapted to accept a Jabsco raw water pump driven by an injector pump gear. Means may also be provided to lock the pump gear in position to facilitate removal of the injector pump.

Claims

Claims:

1. Apparatus for transferring drive between a crankshaft and a camshaft gear of a vehicle engine, the assembly comprising a casing adapted for attachment to fixed structure of the engine or engine housing and dimensioned to house first and second gear wheels carried respectively by the crankshaft and camshaft of the engine and rotatable therewith, and an idler gear wheel positioned to mesh with each of the first and second gear wheels to transmit drive therebetween, the casing including a closure plate adapted to receive or at least partially to support one end of a spindle or shaft on which the idler gear is located.

2. Apparatus as claimed in Claim 1 wherein the casing additionally houses a third gear wheel carried by and rotatable with the driven shaft of an injector pump, this third gear wheel being positioned to mesh with a second idler gear wheel operable to transfer drive from the camshaft gear wheel to the injector pump gear wheel.

3. Apparatus as claimed in Claim 2 wherein-the second idler gear wheel is carried by a spindle or shaft, one end which is received within a recess formed in or at least partially supported by the closure plate.

4. Apparatus as claimed in any one of Claims 1 to 3 wherein the casing includes a closable inlet port for admitting lubricant to the casing interior and a drain for removing spent lubricant therefrom.

5. Apparatus as claimed in any one of Claims 1 to 4 wherein the teeth of the gear wheels housed within the casing are coated with a self-lubricating material such as teflon.

6. Apparatus as claimed in Claim 5 wherein the coating material is that marketed under the name Xylan 1052.

7. Apparatus as claimed in any one of Claims 1 to 6 wherein the shaft or spindle of the or each idler gear wheel is supported at one end within bearing races set in recesses formed in the internal surface of the closure plate of the casing and at its other end within bearing races supported by the internal surface of the casing itself.

8. Apparatus as claimed in any one of Claims 1 to 6 wherein the shaft or spindle of the or each idler gear wheel is supported by or formed integral with a mounting plate positioned within the casing, the end of the shaft or spindle remote from the mounting plate being supported within bearing races set in recesses formed in the internal surface of the closure plate of the casing.

9. Apparatus as claimed in any one of Claims 1 to 6 wherein the or each idler gear is mounted on spigots protruding from the internal surface of the casing.

10. Apparatus as claimed in Claim 9 wherein the spigots are formed integrally with the casing.

11. Apparatus as claimed in Claim 9 wherein the spigots are cast with the casing.

12. Apparatus as claimed in any one of Claims 9 to 11 wherein the free end of the or each idler gear seats within a complementary recess formed in the internal surface of the closure plate of the casing.

13. Apparatus as claimed in any one of Claims 1 to 12 herein the or each idler gear is supported on needle bearing races carried by the or each spigot.

14. A kit of parts for replacing a timing mechanism of a vehicle engine, the kit comprising a casing adapted for attachment to fixed structure of the engine or engine housing and dimensioned to house first and second gear wheels carried by the crankshaft and camshaft of the engine, and an idler gear wheel positioned to mesh with each of the first and second gear wheels to transmit drive therebetween, the casing including a closure plate which additionally serves to receive one end of or at least partially to support a spindle or shaft on which the idler gear is located.

15. A vehicle engine in which the timing mechanism thereof is replaced by a kit of parts as claimed in Claim 14.

16. Apparatus for transfering drive between a crankshaft and a camshaft of a vehicle engine substantially as herein described and as described with reference to Figures 1 to 4 or Figures 5 and 6 of the accompanying drawings.