GB2193273A

GB2193273A - Motorcycle reversing gearing mechanism

Info

Publication number: GB2193273A
Application number: GB08713751A
Authority: GB
Inventors: Stephen Carl Henderson
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-06-13
Filing date: 1987-06-12
Publication date: 1988-02-03
Also published as: GB8713751D0; GB8614383D0

Abstract

A drive gear (7) is in fixed rotary relationship with the motorcycle drive sprocket (3), a driven gear (9) is in fixed rotary relationship with a wheel hub (17) of the motorcycle, intermediate gears (8) engages the drive and driven gears and are mounted for rotation about an axis which is free to move relative to both the drive and driven gears, and clutch means (31, 32, 34) enable that axis of rotation to be selectively fixed relative to the drive gear or the driven gear on the one hand, thereby to permit the motorcycle to be driven in a first direction, or relative to the body of the motorcycle on the other hand, thereby to permit the motorcycle to be driven in the opposite direction. The drive gear (7) is preferably a ring gear, the driven gear (9) a sun gear and the intermediate gears (8) are preferably spur planet gears. The mechanism may alternatively comprise planetary bevel gears. A single axially acting clutch plate (13) preferably controls reverse action. <IMAGE>

Description

SPECIFICATION Motorcycle reversing mechanism The present invention is a reversing mechanism for a motorcycle.

In general it has not been considered necessary or even advantageous to provide a reversing mechanism on other than the heavier motorcycles. The motorcycles are sufficiently manoeuvrable to require no driven reversing facility. However some situations do exist wherein a reverse gear would be an advantage. For example in cross-country competitive riding, in particular in trials riding, it may be inconvenient or even against competition rules to move the motorcycle backwards by the rider placing his feet on the ground. The only alternative would then be a driven reversing mechanism, such as is not generally available.

It is therefore an object of the present invention to provide a reversing mechanism for a motorcycle, and in particular a reversing mechanism which may be simply and smoothly engaged and disengaged in practical operation.

The motorcycle reversing mechanism according to the present invention comprises a drive gear in fixed rotary relationship with the motorcycle drive sprocket, a driven gear in fixed rotary relationship with a wheel hub of the motorcycle, an intermediate gear engaging both said drive gear and said driven gear and mounted for rotation about an axis which is free to move relative to both said drive and driven gears, and clutch means enabling said axis of rotation of said intermediate gear to be selectively fixed relative to said drive gear or said driven gear on the one hand or relative to the body of the motorcycle on the other.

The operation of the reversing mechanism according to the present invention may be readily explained. When the clutch means is operated to fix the axis of the intermediate gear relative to either the drive gear or the driven gear, rotation of the drive gear with the motorcycle drive sprocket causes the driven gear and the associated wheel hub to be rotated, via the intermediate gear, in the same direction as the drive sprocket. Thus a positive forward drive is transmitted to the wheel and the motorcycle is caused to move forward in the conventional manner, subject still to operation of the normal motorcycle controls of accelerator, gear change and main clutch.

When, however, the clutch means of the reversing mechanism is operated to fix the axis of the intermediate gear relative to the body of the motorcycle, the intermediate gear does not move bodily with the drive gear or the driven gear but simply rotates about its axis and thereby transmits the drive from the drive gear to the driven gear, reversing the direction of rotation of the drive as it does so. That is, when the drive sprocket and drive gear together rotate in one rotational direction, the driven gear and wheel hub are now caused to rotate in the opposite rotational direction.

Thus normal forward rotation of the drive sprocket now causes the motorcycle to be driven in reverse.

The gear train upon which the reversing mechanism of the present invention is based may be an epicyclic gear system or a system of bevel gears. The above description of the method of operation is equally applicable to either of these forms of the invention. In either case, the intermediate gear preferably comprises at least two gear wheels, especially four such gear wheels, all engaging both the drive gear and the driven gear. In one form of the invention, the drive gear is an internal circular gear, the driven gear is a sun gear and the intermediate gear takes the form of a plurality of planet gears distributed uniformly about the circumference of the sun gear.

The axes of the intermediate gear wheels may be held in the desired relatively spaced relationship by a disc or preferably by an annular control plate and the operation of the mechanism overall, that is the selecting of forward or reverse drive of the motorcycle, may be achieved by locking the disc or plate in frictional or other engagement with, say, the wheel hub on the one hand or the motorcycle frame on the other. Thus the clutch means may comprise clutch plates fixed relative to the wheel hub and the motorcycle frame respectively and each able to engage the aforesaid disc or control plate or different parts or faces of that disc or control plate.In one embodiment of this form of the invention, the disc or control plate is urged by spring means into frictional engagement with that one of those two clutch plates which gives forward drive of the motorcycle but can be moved axially out of that engagement by pressure applied via the clutch plate which is fixed relative to the frame of the motorcycle.

The invention will now be further described with reference to the accompanying drawings, wherein: Fig. 1 is an exploded perspective view showing the components of a first embodiment of a motorcycle reversing mechanism according to the present invention; Fig. 2 is a sectional view of a detail of the mechanism of Fig. 1 in assembled form; Fig. 3 is an exploded sectional view showing the components of a second embodiment of a motorcycle reversing mechanism according to the present invention; and Fig. 4 is a sectional view showing the mechanism of Fig. 3 in assembled form.

Referring firstly to Figs. 1 and 2 of the drawings, the numeral 3 indicates the drive sprocket, mounted about the axis of the rear wheel 4 of the motorcycle and driven from the motorcycle gearbox via a drive chain 5.

One of the spokes 6 of the rear wheel 4 is seen in Fig. 2.

The internal cylindrical face of the sprocket 3 carries a drive gear 7 (of which the individual teeth are not shown in detail) and this drive gear is in permanent mesh with four planet gears 8. The planet gears are also permanently in mesh with a sun gear 9 and are held in fixed relationship to each other by a control plate 10, which supports the spindles 11 of the planet gears 8. A Belleville washer 12 presses upon the ends of the spindles 11 and in turn brings the control plate 10 into frictional contact with a clutch plate 13 fixed with respect to the wheel hub 17.In this way, during normal running of the motorcycle, the spindles 11 and control plate 10 are in turn fixed relative to the wheel hub 17, with the result that rotation of the drive sprocket 3 causes the planet gears 8, the sun gear 9 and the wheel hub 17 to rotate together as a single body and drive the motorcycle forward.

When it is desired to drive the motorcycle in reverse, a hand lever or pedal control is operated and thereby a second clutch plate 14 is brought into contact with the outer part of the face of the control plate 10. The clutch plate 14 is rotationally fixed relative to the frame of the motorcycle via stops 15 which locate against the swinging arm 16 which forms part of the frame. Thus the clutch plate 14 initially acts against the rotational drive transmitted by the clutch plate 13 and has a braking effect on the forward drive of the vehicle.

Further pressure on the clutch plate 14 moves the control plate 10 and planet gears 8 out of contact with the clutch plate 13 (against the pressure of the Belleville washer 12) and effectively holds the planet gears 8 against any movement transverse to their axes. The gears 8 can therefore only rotate upon their axes. Since disengagement of the clutch plate 13 allows the planet gears to move relative to the sun gear 9, the gears 8 now transmit the rotary drive from the sprocket 3 to the sun gear 9, reversing the drive in doing so and therefore driving the motorcycle towards the rear.

It will be seen that the manner of co-operation of the two clutch plates 13 and 14 allows an easily-controlled, smooth transition from forward drive to reverse drive. Removal of the pressure applied to clutch plate 14 allows the washer 12 to bring the control plate 10 into re-engagement with the clutch plate 13 and thereby restore the forward drive.

Referring now to Figs. 3 and 4 of the drawings, the motorcycle reversing mechanism there illustrated functions in a manner which is generally similar to that of the first illustrated embodiment but the gear train uses a system of bevel gears. The drive to the mechanism is provided from the motorcycle gear box via a conventional drive chain engaging a drive sprocket 20, supported by a bearing 21 upon a stationary spindle 22.

Secured to the drive sprocket mounting is a tapered drive gear 23, which is in mesh with an intermediate gear in the form of three bevel gears disposed uniformly around the circumference of a support ring 36. The bevel gears 24 are in turn in mesh with a tapered driven gear 25 mounted within the wheel hub 26 of the motorcycle rear wheel. The driven gear 25 is normally held in engagement with the intermediate gear 24 by a Belleville washer 27 acting between an annular stop plate 28 and a clutch plate 29 frictionally linked via further clutch plates 30 to the interior surface of the wheel hub 26.With the components in the relative positions described and illustrated, the assembly comprising drive gear 23, intermediate gear 24 and driven gear 25 rotates as a whole and the drive from the driven chain is transmitted directly to the wheel hub 26 and thereby moves the motorcycle in a forward direction.

The reversing of the drive is achieved by means of two frustoconical clutch plates 31 and 32. By operation of a control lever 33, a ring cam 34 is moved through a small rotational angle relative to the stationary spindle 22 and thereby moves the clutch plates 31, 32 apart. The clutch plate 31 is linked by a ciip 35 to the clutch plate 29 with the result that, when the clutch plate 31 is moved leftwards, it causes the clutch plate 29 to move in the same direction against the pressure of the Belleville washer 27 and thereby disengage the forward drive to the whole hub.

Meanwhile, the movement of the clutch plate 32 towards the right locks the intermediate gear ring to the fixed spindle 22 and thereby prevents the gears 24 from moving around the axis of the mechanism. The gears 24, still in engagement with the drive gear 23, therefore rotate about their individual axes and transmit the drive to the driven gear 25, reversing the direction of the drive in doing so.

Claims

1. A motorcycle reversing mechanism comprising a drive gear in fixed rotary relationship with the motorcycle drive sprocket, a driven gear in fixed rotary relationship with a wheel hub of the motorcycle, an intermediate gear engaging both said drive gear and said driven gear and mounted for rotation about an axis which is free to move relative to both said drive and driven gears, and clutch means enabling said axis of rotation of said intermediate gear to be selectively fixed relative to said drive gear or said driven gear on the one hand or relative to the body of the motorcycle on the other.

2. A motorcycle reversing mechanism as claimed in claim 1, wherein said drive gear, intermediate gear and driven gear form an epi cyclic gear system.

3. A motorcycle reversing mechanism as claimed in claim 2. wherein said drive gear is an internal circular gear, said driven gear is a sun gear and said intermediate gear is a plurality of planet gears distributed uniformly about the circumference of the sun gear.

4. A motorcycle reversing mechanism as claimed in claim 1, wherein said drive gear, intermediate gear and driven gear are each be vel gears.

5. A motorcycle reversing mechanism as claimed in any of the preceding claims, wherein a plurality of intermediate gear wheels are held in spaced relationship by a disc or an annular control plate and the disc or plate may be selectively locked in engagement with the wheel hub on the one hand or the motorcycle frame on the other.

6. A motorcycle reversing mechanism as claimed in claim 5, wherein the clutch means comprises clutch plates fixed relative to the wheel hub and the motorcycle frame respectively and each able to engage said disc or plate.

7. A motorcycle reversing mechanism as claimed in claim 6, wherein said disc or control plate is urged by spring means into frictional engagement with the clutch plate which gives forward drive of the motorcycle and can be moved axially out of that engagement by pressure applied via the clutch plate which is fixed relative to the motorcycle frame.

8. A motorcycle reversing mechanism substantially as hereinbefore described with reference to, and as illustrated in, Fig. 1 and 2 of the accompanying drawings.

9. A motorcycle reversing mechanism substantially as hereinbefore described with reference to, and as illustrated in, Figs. 3 and 4 of the accompanying drawings.