GB2239499A

GB2239499A - Continuously variable speed gear apparatus comprising first and second differential gear assemblies

Info

Publication number: GB2239499A
Application number: GB9027153A
Authority: GB
Inventors: Leonard Ainslie Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-12-15
Filing date: 1990-12-14
Publication date: 1991-07-03
Also published as: GB8928410D0; GB9027153D0

Abstract

Variable speed gear apparatus (2) comprising a first differential gear assembly (4) having first and second in-line shafts (6, 8), a second differential gear assembly (10) having first and second in-line shafts (12, 14), first motion transmitting means (16) for transmitting rotary motion from the first differential gear assembly (4) to the first and second in-line shaft (12, 14) of the second differential gear assembly (10), and second motion transmitting means (18) for transmitting rotary motion from the second differential gear assembly (10) to the first or the second in-line shaft (6, 8) of the first differential gear assembly (4). The motion transmitting means may be spur gearing as shown, bevel gearing, chain and sprocket, or a solid connection. A fly wheel (42) is preferably provided on one of the shafts. The output speed may be controlled by load. <IMAGE>

Description

CONTINUOUSLY VARIABLE SPEED GEAR APPARATUS This invention relates to variable speed gear apparatus.

Variable speed gear apparatus in accordance with the present invention comprises a first differential gear assembly having first and second in-line shafts, a second differential gear assembly having first and second in-line shafts, first motion transmitting means for transmitting rotary motion from the first differential gear assembly to the first or the second in-line shaft of the second differential gear assembly, and second motion transmitting means for transmitting rotary motion from the second differential gear assembly to the first or the second in-line shaft of the first differential gear assembly.

The variable speed gear apparatus is such that in operation, the output speed varies according to load.

Thus, with a prime mover in the form of an internal combustion engine, the engine can be made to operate at or close to its most efficient speed, whilst all gears remain continuously in mesh.

For road vehicle applications, the variable speed gear apparatus may operate such that at a very light load as, for example with a road vehicle having minimum passenger and/or other load, travelling along a smooth level road surface, the engine speed can be kept at, or close to that, giving maximum engine efficiency for that load. When the load rises, as when the level road gives way to an uphill gradient, wheel and engine speeds tend to fall. However, the engine speed can be raised to an efficient level by use of the engine accelerator. The wheel speed then adjusts to a level such that the rate of work corresponds to the engine power, less losses in the transmission to the wheels.

Thus the process of adaptation to varying loads is achieved solely by accelerator control (i.e. throttle control) and there is no intermediate stage during which any gears which are normally in mesh are required to come out of mesh.

The first and the second differential gear assemblies may each comprise a pair of opposed differential gear wheels, and a pair of opposed pinions, the first and the second in-line shafts being connected one to each of the opposed differential gear wheels.

Various types of first and second motion transmitting means may be employed. Thus, for example, the first and second motion transmitting means may each comprise a spur gear and pinion arrangement, a bevel gear and connecting shaft arrangement, a sprocket and chain drive, or a solid connection. Witch a chain and sprocket drive, all drives remain positive.

Usually, the first and the second motion transmitting means will be of the same general type, but different types of first and second motion transmitting means may be employed if desired.

The variable speed gear apparatus will usually include a flywheel.

Preferably the flywheel is constructed to give a high moment of inertia relative to the weight of the flywheel.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows first variable speed gear apparatus; Figure 2 shows in detail part of the variable speed gear apparatus shown in Figure 1; Figure 3 shows second variable speed gear apparatus; Figure 4 shows third variable speed gear apparatus; and Figure 5 illustrates connections made in Figure 4.

Referring to Figure 1, there is shown variable speed gear apparatus 2 comprising a first differential gear assembly 4. The first differential gear assembly 4 has a first shaft 6 and a second shaft 8. The first and the second shafts 6, 8 are in-line shafts as shown.

The variable speed gear apparatus 2 has a second differential gear assembly 10. The second differential gear assembly 10 has a first shaft 12 and a second shaft 14. The first and the second shafts 12, 14 are in-line shafts as shown.

The variable speed gear apparatus 2 further comprises first motion transmitting means 16 for transmitting rotary motion from the first differential gear assembly 4 to the first shaft 12 of the second differential gear assembly 10. The variable speed gear apparatus 2 further comprises second motion transmitting means 18 for transmitting rotary motion from the second differential gear assembly 10 to the second shaft 8 of the first differential gear assembly 4.

Figure 2 shows in more detail the first differential gear assembly 4. For ease of illustration, the first differential gear assembly 4 has been rotated through 900 in Figure 2. As can be seen, the first differential gear assembly 4 comprises a pair of opposed differential gear wheels 20, 22 and a pair of opposed pinions 24, 26. The pinions 24, 26 may be star or differential pinions. As can be seen from Figure 2, the first and the second in-line shafts 6, 8 are connected one to each of the opposed differential gear wheels 20, 22. The gear wheels 20, 22 and the pinions 24, 26 are housed in a differential casing 28.

The second differential gear assembly 10 is constructed similarly to the first differential gear assembly 4.

The first motion transmitting means 16 comprises a spur gear wheel 30 which is arranged to be coaxial with the first shaft 6. The first motion transmitting means 16 further comprises a pinion 32 and a spur gear wheel 34 arranged to be in line with the first shaft 12.

Thus the pinion 32 is positioned between the two spur gear wheels 30 and 34. Similarly, the second motion transmitting means 18 comprises a pinion 36 positioned between two spur gear wheels 38, 40.

The variable speed gear apparatus 2 comprises a flywheel 42. The flywheel 42 is constructed to give a high moment of inertia relative to the weight of the flywheel 42.

The variable speed gear apparatus 2 comprises a plurality of bearings which are each marked with a "x". The number of bearings employed may vary with the actual configuration employed.

Input from a prime mover such for example as a vehicle engine (not shown) can be applied to an input shaft 44. The output to load is then via an output shaft 46.

Figure 3 shows second variable speed gear apparatus 2 which is similar to that shown in Figure 1. Similar parts have therefore been given the same reference numerals for ease of comparison and understanding. In Figure 3, it will be seen that an alternative arrangement for the input is shown, with the input from the prime mover being applied to an input shaft 48.

The different types of variable speed gear apparatus 2 shown in the drawings can be made to operate as above with the output speed varying according to load0 The weight penalty for achieving the continuously variable speed is minimal because the weight of the first and second differential gear assemblies 4, 10 and the weight of the flywheel 42, the varying shafts and the bearings "x" can be made comparable to that of a conventional gear box. The moment of inertia of the flywheel is important, rather than the weight of the flywheel and, as indicated above, the flywheel can be designed such that its moment of inertia is high relative to its weight.

The performance of the variable speed gear apparatus 2 depends upon energy transfer as required to deal with load variations, either from or to the flywheel 42 and other rotating items. The variable speed gear apparatus 2 acts as a mechanical analogue of a gear box/ fluid flywheel combination, in which the fluid flywheel function is to perform a smooth bridge between successive gear ratios. The variable speed gear apparatus 2 however requires no brakes or other means to achieve its performance.

Referring now to Figure 4, there is shown third variable speed gear apparatus 2 in which similar parts as in previous Figures have been given the same reference numerals for ease of comparison and understanding. The various in-line shafts referred to herein may be regarded as half-shafts.

The first differential gear assembly 4 has a casing 50, and the second differential gear assembly 10 has a casing 52. As will be seen from Figure 4, there are three shafts which are concentric with the first shaft 6 and these three shafts are the shaft 8 carrying the output, the shaft 12 carrying the flywheel 42 and one pinion of the second differential gear assembly 10, and the shaft 14 carrying the other pinion of the second differential gear assembly 10, and bonded to the casing 50 of the first differential gear assembly 4. This arrangement is shown schematically in Figure 5 for ease of understanding.

As will be understood from Figures 4 and 5, the variable speed gear apparatus 2 is such that the rotary motion is transmitted by solid bonding means. The various solid bonds are indicated on Figure 4. The various shafts are axially aligned as shown.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of- example only and that modifications may be effected Thus, for example, any suitable and appropriate ratio may be employed between the casing of the differential gear assemblies 4, 10 and the in-line shaft of the other differential gear assemblies 4, 10. Thus, for example, the ratio may be 1:1 or any other desired ratio.

The first and second motion transmitting means 16, 18 can transmit the rotary motion to either in-line shaft of the other differential gear assembly 4, 10.

As an alternative to using the illustrated first and second motion transmitting means 16, 18, bevel gears and a connecting shaft, or a spocket and chain drive may be employed.

The variable speed gear apparatus may be used in a wide variety of situations. Thus, for example, it may be used on road vehicles with internal combustion engines, and it may also be used on rail vehicles such for example as diesel locomotives and diesel-engined multiple unit rolling stock, where the current practice is to use a gear box. Bicycles may also be provided with the variable speed gear apparatus 2. The variable speed gear apparatus 2 may also be employed in tractors, agricultural machinery, cranes and earth moving equipment. The prime mover may be an internal combustion engine, pedal power, a hydraulic drive or an electric motor as may be desired and appropriate depending upon the precise equipment in which the variable speed gear apparatus 2 is employed.

Claims

1. Variable speed gear apparatus comprising a first differential gear assembly having first and second in-line shafts, a second differential gear assembly having first and second in-line shafts, first motion transmitting means for transmitting rotary motion from the first differential gear assembly to the first or the second in-line shaft of the second differential gear assembly, and second motion transmitting means for transmitting rotary motion from the second differential gear assembly to the first or the second in-line shaft of the first differential gear assembly.

2. Variable speed gear apparatus according to claim 1 in which the first and the second differential gear assemblies each comprise a pair of opposed differential gear wheels, and a pair of opposed pinions, the first and the second in-line shafts being connected one to each of the opposed differential gear wheels.

3. Variable speed gear apparatus according to claim 1 or claim 2 in which the first and second motion transmitting means each comprises a spur gear and pinion arrangement.

4. Variable speed gear apparatus according to claim 1 or claim 2 in which the first and second motion transmitting means each comprises a bevel gear and connecting shaft arrangement.

5. Variable speed gear apparatus according to claim 1 or claim 2 in which the first and second motion transmitting means each comprises a sprocket and chain drive.

6. Variable speed gear apparatus according to claim 1 or claim 2 in which the first and second motion transmitting means each comprises a solid connection.

7. Variable speed gear apparatus according to any one of the preceding claims in which the first and the second motion transmitting means are of the same general type.

8. Variable speed gear apparatus according to any one of the preceding claims and including a flywheel.

9. Variable speed gear apparatus substantially as herein described with reference to the accompanying drawings.