GB2452710A

GB2452710A - Toric transmission with epicyclic output drive

Info

Publication number: GB2452710A
Application number: GB0717624A
Authority: GB
Inventors: Forbes George De Brie Perry
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-09-11
Filing date: 2007-09-11
Publication date: 2009-03-18
Also published as: GB0717624D0

Abstract

A drive system comprises a variable rolling-traction toroidal-race transmission unit 1 including a main shaft 3, at least one input disc 4, driven by the main shaft 3, and an output disc 5. An output epicyclic drive 2 comprises an annulus 8a, a sun 7a, and planets 9 disposed between the sun 7a and the annulus 8a and held by a common carrier 10. The annulus 8a is driven by the main shaft 3, the sun 7a is driven by the output disc 5 and an output member 14 is driven by the carrier 10. Sun 7a may be integral with the output disc 5 or it may be connected to the output disc 5 by a frame (42, fig 3) when the toroidal-race transmission unit 1 is a double-sided unit with two input and output discs (34, 34a, 36, 36a). The sun 7a, annulus 8a and planets 9 may be either rolling elements or geared elements.

Description

Toric Transmissions with Epicyclic Output Drives

S

This invention relates to toric transmissions, i.e. rolling traction transmission of the kind which includes at least one pair of discs, which define a toroidal race and between which is a set of rollers which transmit torque from one disc to another and of which the attitudes relative to the discs are controllable to alter the transmission speed ratio between the discs.

It is known to provide a drive system comprising a variable rolling-traction toroidal-race transmission unit including a main shaft, at least one input disc, driven by the main shaft, and an output disc; and an output epicyclic drive which comprises an annulus, a sun and planets disposed between the sun and the annulus and held by a common carrier; in which the sun is driven by the main shaft, the annulus is driven by the output disc and an output member is driven by the carrier.

The invention provides various embodiments in which the variable speed output disc is connected to the sun of the epicyclic.

In one embodiment the output disc constitutes the sun of the epicyclic. In a different embodiment the sun of the epicyclic is connected to the output disc by a frame coupled to a sleeve mounted on the main shaft and supporting the sun. The variable rolling-traction toroidal-race transmission unit may be a double-sided unit with two input discs arid an output disc between the input discs.

The sun, annulus and planets may be rolling elements. For a higher-power system, the sun, annulus and planets may be geared elements.

Reference will be made hereinafter to the accompanying drawings, in which: Figure 1 illustrates a known system of a variable rolling traction unit and an epicyclic output drive.

Figure 2 illustrates one embodiment of a variable rolling traction unit and an epicyclic output drive according to the invention.

Figure 3 illustrates another embodiment of a variable rolling traction unit and an epicyclic output drive according to the invention.

It is known to employ an epicyclic output drive for variable speed rolling traction (toric) transmissions, as exemplified in the published patent applications GB- 2395759-A and GB-2208 I 78-A. An epicyclic comprises an annulus, a sun and a set of planets between the annulus and the sun and mounted in a common carrier. In these transmissions, the output is taken from the carrier, the annulus is driven from the variable speed rolling traction unit and the sun is attached to a main shaft.

Figure 1 illustrates an example of such a transmission. The rolling traction unit is generally denoted I and the epicyclic is generally denoted 2. The transmission has a main (input) shaft 3 which directly drives an input disc 4 of the rolling traction unit 1.

An output disc 5 of the rolling traction unit I defines with the input disc a toroidal drive region and is driven at a variable speed ratio with respect to the input disc 4 by a set of rollers (exemplified by the roller 6); the transmission ration varies according to the attitude of the rollers. The attitude may be changes by any suitable means, as for example shown in the aforementioned documents.

In this example the annulus (7) of the epicyclic is constituted by the output disc 5 and in particular by a rear surface thereof. The sun 8 is driven by the main shaft. Between the sun 8 and the annulus 7 is a set of planets, indicated by the planet 9. The planets are mounted in a common, rotatable carrier 10. This carrier has an output pinion 11 which provides output to a reversing and reducing gear train 12.

An output speed N0 from an arrangement as shown in Figure 1 may be expressed as: N0fN1 (Rv*Er_l)/(Er+l) where N, is the input speed, R is the transmission ration of the unit I and Er is the train ratio between annulus and sun.

If for example R varies between 0.4 and 1.6 and E is typically 1.3, the output ratio varies from + 0.21 in reverse (the same direction as the input) to -0.47 for forward drive. For a vehicle such as a tractor these ratios suit a separate back axle with a further final drive reduction of between 3: 1 and 5:1.

For a passenger car, Er is typically 2.3 and N0 then varies from a reverse of+ 0.08 x input at an R of 0.4 to a forwards drive of-0.812 at an R of 1.6. Back axle gearing corrects the rotational directions.

For small passenger vehicles, however, it is preferred to provide a transaxie type of transmission and it is convenient to provide a larger speed reduction in the rolling assembly and less final drive reduction, so as to reduce the diameters of components in a line of half-shafts. In it also convenient to have the feed to the final drive in the same direction as the engine's input so that (for example) a single chain may be used instead of a reversing train of gears.

Figure 2 illustrates one embodiment of a system in which the major part of the output torque is taken by connection to the main (input) shaft and only the minor part is reacted through the set of variable speed rollers (6).

In the embodiment shown in Figure 2, the rear of the output disc 5 has a frusto-conical surface 8a engaged by the planets (9) and constitutes the sun wheel of the epicyclic. The annulus 8a is driven by the main shaft 3. In this embodiment the box 13 denotes a simple cam drive (which may comprise a set of balls and ramps) which drives the annulus from the shaft 3 and provides an end load for the rolling assembly.

The output is taken from the carrier 10, but in this embodiment the carrier in connected to a chain wheel 14 which is connected by a chain loop (not illustrated) to a chain wheel 15 connected to an output shaft 16 The output speed No is now given by: NJN1 (E1Rv)/(Er+ 1) For the same set of values as indicated for the system shown in Figure 1, the output is now in the same direction as the input for a forwards drive of 0.39 x input with R at 0.4. A reverse of -0.13 x input is given when the roric transmission is in an overdrive condition wherein R = I.6.

The configuration shown in Figure 2 exhibits lower losses than usual in forwards drive but higher losses in reverse, where they are not so important.

For higher power systems, the epicyclic may be a bevel-gear epicyclic instead of a roller epicyclic. An example is shown in Figure 3.

The system shown in Figure 3 comprises a double-sided toric transmission 31 and an epicyclic 32, which in this embodiment is separate from the toric transmission unit 1, not having a component in common with it such as the disc 5 in Figure 2. The main shaft 33 directly drives two opposite input discs 34 and 34a. Between the input discs is a double- sided output disc 35, there being a set of rollers 36 between the input disc 34 and one side of the output disc 35 and another set of rollers 36a between the input disc 35a and the other side of the output disc 35.

The annulus 37 of the epicyclic is driven by the main shaft 33. The planets 39 are supported by a carrier 40 which is connected to an output shaft 41. The sun 38 of the epicyclic is connected to the output disc 35 by way of a frame 42 and a sleeve 43, which is mounted for rotation on and with respect to the main shaft 33.

As is shown, the planets 39 are bevel gears and the sun 38 and annulus 37 are geared accordingly.

The end loads are required merely for the needs of the end-load balanced, two-set variable roller assembly 31, which is typically taking only about a third of the transmitted torque. The losses in forward drive are again quite low and the efficiency of the whole drive is correspondingly increased.

Claims

Claims 1. A drive system comprising a variable rolling-traction toroidal-racc transmission Unit including a main shaft, at least one input disc, driven by the main shaft, and an output disc; and an output epicyclic drive which comprises an annulus, a sun and planets disposed between the sun and the annulus and held by a common carrier; in which the annulus is driven by the main shaft, the sun is driven by the output disc and an output member is driven by the carrier.
2. A drive system according to claim I in which the output disc constitutes the sun of the epicyclic.
3. A drive system according to claim 2 in which the sun of the epicyclic is connected to the output disc by a frame coupled to a sleeve mounted on the main shaft and supporting the sun.
4. A drive system according to claim 3 in which the variable rolling-traction toroidal-race transmission unit is a double-sided unit with two input discs and an output disc between the input discs.
5. A drive system according to any of claims I -4 in which the sun, annulus and planets are rolling elements.
6. A drive system according to any of claims i - in which the sun, annulus and planets are geared elements