WO1995033146A1

WO1995033146A1 - Continuous, and infinitely variable transmission

Info

Publication number: WO1995033146A1
Application number: PCT/AU1995/000307
Authority: WO
Inventors: Jock Clunne
Original assignee: Conitorque Pty. Ltd.
Priority date: 1994-05-26
Filing date: 1995-05-26
Publication date: 1995-12-07
Also published as: AUPM589394A0

Abstract

A continuous variable ratio transmission (CVT) (100) has first and second conical gears (120, 121) rotatable about spaced, parallel shafts (110, 111), the gears (120, 121) having their apexes oppositely directed. An idler gear (130), on an idler shaft (140), is rotatable about an idler axis transverse to the shafts (110, 111) and movable along a translational axis (150) inclined at an angle a° to the shafts (110, 111), the angle a° being one-half of the included angles of the gears (120, 121).

Description

TITLE : CONT I NUOUS , AND INFINI TELY VARI ABLE

TRANSMISSION BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

THIS INVENTION relates to a continuous, variable ratio transmission. The transmission is preferably designed to transmit torque from a power source to an apparatus where the gearing ratio can be changed within a stepless range on a continuous basis.

2. PRIOR ART Traditionally, mechanical transmissions have relied upon gears, planetary devices, chains, belts, clutch packs or the like to transmit the torque. Such transmissions require a substantial number of components, which are often expensive to manufacture and/or assemble, and which cause significant power loss due to friction, heat and/or vibration. Generally, such transmissions permit only a limited number of stepped ratios.

Proposals for continuous variable ratio, transmissions have been disclosed in:

1. AU-B-24240/77 (512192) (Vadatech S.A.) ;

2. AU-A-74718/91 (= WO 92/15803) (Priem); and

3. AU-A-74155/91 (Smyth). in Smyth (3.), torque is transmitted via friction between two cone-shaped wheels by a connecting wheel rotating about, and movable along, an axis in the same plane, but inclined to, the parallel axes of the cone wheels. While a continuous, variable ratio, transmission is produced, only very limited torque can be transmitted.

Priem (2.) discloses a transmission where a gear (2) engages a cone wheel (1) , where the axis of the gear is at an angle to the axis of the cone wheel. While greater torque can be transmitted than is possible with Smyth, it is not a practical solution.

Vadatech (1.) provides a transmission to convert power developed in reciprocating pistons to a rotary output over a variable speed range and relies on roller engaging cones on the output shaft. SUMMARY OF THE INVENTION

The present invention is provided to enable even very high torque levels to be transmitted between a power source and an apparatus over a continuous, variable ratio, range of speeds.

In a preferred object, the invention only requires three moving parts.

It is a further preferred object to provide a transmission which is reversible over the whole range of ratios.

It is a still further preferred object to provide a transmission which can incorporate additional elements to increase the variable ratio range. Other preferred objects will become apparent from the following description.

In one aspect, the present invention resides in a continuous, variable ratio, transmission (CVT) including: a first cone-shaped gear rotatable about a first axis; a second cone-shaped gear rotatable about a second axis parallel to, but spaced from, the first axis, the first and second gears being oppositely convergent to their apex(es); and an idler gear, in engagement with both the first and second gears, rotatable about an idler axis interposed between, but transverse to, the first and second axes, the idler gear being movable between the first and second gears to vary the transmission ratio between the first and second gears.

Preferably, each gear has a helical screw- thread ground or otherwise machined (or formed) on its peripheral surface and each gear is fixed to, or formed integrally with, a respective shaft.

Preferably, the gears are identical and the idler axis is equidistant between the gears.

Preferably, the idler axis is movable along a translational axis which is inclined at an angle which is equal to one half of the included angle of the gears.

In a preferred embodiment, a third gear and second idler is provided to increase the ratio range, and further gears may be added, eg. for n gears, there will be (n-1) idler gears. In a further preferred embodiment, each gear may have two conical formations, which are opposed in convergence, to provide a reversible transmission. Alternatively, three gears and two idler gears may be provided, where the input power is supplied to the centre gear and the outer gears are selectively connected to an output shaft, e . by mechanical, electrical, magnetic, hydraulic or li. e clutches.

The idler gear may be offset so that the respective points of contact between the idler gear and the conical gears lie outside the plane defined by the first and second axles.

In a second aspect, the present invention resides in a continuous, variable ratio transmission including: a first cone-shaped gear rotatable about a first axis; a second cone-shaped gear rotatable about a second axis parallel to, but spaced from the first axis, the first and second gears being oppositely convergent to their apex(es); and an idler gear, having respective first and second convergent portions, in engagement with the first and second gears, rotatable about an idler axis interposed between, but inclined to, the first and second axes, the idler gear being movable between the first and second gears to vary the transmission ratio between the first and second gears.

Preferably the first and second portions of the idler gear are oppositely convergent to their apex(es) .

Preferably, as the idler gear is moved, the movement of the idler gear has one vector component parallel to, and one vector component transverse to, the first and second axes. BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, preferred embodiments will now be described with reference to the accompanying drawings, in which:

FIGS. 1 to 4 are respective perspective, side elevational, plan and end elevational views of a first embodiment;

FIGS. 5 and 6 are respective perspective and side elevational views of a second embodiment;

FIG. 7 is a side elevational view of a third embodiment;

FIGS. 8 and 9 are respective perspective and side elevational views of a fourth embodiment;

FIGS. 10 and 11 are respective side elevational and end elevational views of a fifth embodiment;

FIGS. 12 and 13 are plan and end elevational views of a sixth embodiment; and

FIGS. 14 and 15 are side elevational views of the conical gears of the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4, the transmission

100 has parallel, spaced, input and output shafts 110,

111, on which are fixed respective conical gears 120 and

121, which are oppositely, but equally, convergent. A helical screw-thread is formed on the faces of each gear

120, 121.

An idler gear 130 is mounted on a shaft 140 and engages both gears 120, 121. The shaft 140 is transverse to shafts 110, 111 and can move along a translational axis 150 (axis x-y) which is inclined at angle a° to the axes of the shafts 110, 111, the angle a° being one half the included angle at the apexes of gears 120, 121 and is equal to the angle produced when a line is projected from the peripheries of the gears 120, 121 and interconnects the axes of rotation.

The idler gear 130 is moved along the axis 150 (by a yoke 160) so that its points of contact with the gears 120, 121 are varied. As the gears are inversely convergent, this varies the ratios of circumferential contact between the gears 120, 121 and the idler gear 130 and thereby the transmission ratio between the limiting parameters R_x and R₂, which are the respective minimum and maximum circumferences of the gears 120,

121. For example, where R--.:R₂=1:4, so that the ratio range can extend from 0.25:1 to 1:4, ie. a total overall range of 16:1.

As shown in FIGS. 5 and 6, transmission 200 has a second idler gear 231 (and shaft 241) and third gear 222 (and shaft 212), which are incorporated to expand the ratio range by a further factor (eg. of 4) so that the overall ratio range could be 64:1. (In this example, shaft 210 would be the input shaft, shaft 222 would be the output shaft, and the idler shafts 240, 241 could be translationally moved separately or simultaneously. ) The transmission 300 (see FIG. 7) provides continuous, variable ratio, outputs in both forward and reverse directions.

Input shaft 331 has a gear 332 operably connected to gears 334, 336 (on shafts 333, 335) on opposite sides of gear 332, and with opposed handed screw-threads, via idler gears 337, 338. The input shaft 331 is supported by bearings 331a co-axially in a gear 340 on output shaft 339. Electromagnetic clutches 341, 342 operably connect shafts 333, 335 to respective gears 343, 344 both in constant mesh with gear 340. Control means (not shown) only allow one electromagnetic clutch 341, 342 to be engaged at any time. The control means also controls the translational movement of the idler gears 337, 338 relative to gears 332, 334 and 332, 336, respectively.

As gears 337, 338 are of opposite hand, they rotate in opposite directions and the idler gears 337, 338 provide the full ratio range. Where only two gears and one idler gear are allowed in a reversible transmission 400 (see FIGS. 8 and 9), each gear 442, 444 has a double cone formation (eg. 442A, 442B), where the cones are convergent to the ends of gear 442, and to the centre of gear 444, and the cone formations of one gear (442) are of opposite hand. By moving the idler gear 446 from the neutral position (FIG. 8), forward or reverse drive can be provided at different ratios.

At all times, as the idler gears move along their translational axes, they remain in operative driving engagement with the cone gears to enable full torque transfer over the variable ratio range.

For practical limits, the ratio R₂:Rι may have a maximum of 4:1, so that the overall ratio range is 16:1 for two gears and an idler gear. Each additional gear and idler gear enables the range to be expanded, with minimal additional moving parts. Similarly, a reversing gearbox can be easily produced.

In all of the above embodiments, the points of contact between the, or each, idler gear and its associated conical gears lie in a plane defined by the shafts of the conical gears.

As shown in FIGS. 10 and 11, the idler gear 530 in transmission 500 may be "offset" relative to the shafts 510, 511 of gears 520, 521. It will be noted that the points of contact 560, 561 between the gears 520 and idler gear 530 and between gear 521 and idler gear 530 respectively, do not lie in the plane defined by the shafts 510, 511. The axis of idler shaft 540 remains transverse to the plane defined by the shafts 510, 511.

Referring now to FIGS. 12 to 15, transmission 600 has an idler gear 630, on idler shaft 640, where the idler gear 630 has conical portions 630A and 630B with their apexes convergent. In addition, the idler shaft 640 is inclined, and not transverse, to the shafts 610, 611 of the conical gears 620, 621 and the idler shaft 640 moves in the direction of the arrows 649. (As hereinbefore described, the shaft 640 moves in a plane at an angle to the plane defined by the shafts 610, 611, equal to the angle of the helical threads on the conical gears 620, 621 and the idler gear 630.) The movement of the idler gear 630 relative to the conical gears 620, 621 has vector components parallel and transverse to the axes of the shafts 610, 611 (ie. in the direction of arrows V-c and V_τ in FIG 22).

With this arrangement, a muc^*. wider ratio range (eg 16:1) can be achieved than w_ch the simple idler (eg idler 130, 530) of earlier embodiments. It will be readily apparent to the skilled addressee that the present invention provides a simple, yet efficient, means to provide a transmission which can have a wide ratio range and yet is based on only three moving parts (ie, the two conical gears and the idler gear).

It will be readily apparent to the skilled addressee that the included angle of the conical gears (and idler gears), the profile of the teeth and the angle of the teeth to the axes of the gears, and the number of starts of the teeth (eg. 1, 2, 4, 6, etc.) can all be varied to suit the particular intended application of the invention. For example, while several of the gears are illustrated with "square" profile teeth, the teeth may have, eg. triangular, trapezoidal, semi-circular or like profiles. By increasing the included angle of the gears, the ratio range achievable with the gears is increased.

Intended applications for the transmission include vehicle transmissions, machinery drives and the like.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

Claims

CLAIMS:

1. A continuous, variable ratio, transmission (CVT) including: a first cone-shaped gear rotatable about a first axis; a second cone-shaped gear rotatable about a second axis parallel to, but spaced from, the first axis, the first and second gears being oppositely convergent to their apex(es); and an idler gear, in engagement with both the first and second gears, rotatable about an idler axis interposed between, but transverse to, the first and second axes, the idler gear being movable between the first and second gears to vary the transmission ratio between the first and second gears.

2. A transmission as claimed in Claim 1 wherein: the first gear, and the second gear each has a helical screw-thread ground or otherwise machined (or formed) on its peripheral surface and each gear is fixed to, or formed integrally with, a respective shaft.

3. A transmission as claimed in Claim 2 wherein: the first and second gears are identical and the idler axis is equidistant between the first and second gears.

4. A transmission as claimed in Claim 3 wherein: the idler axis is movable along a translational axis which is inclined at an angle which is equal to one half of the included angle of the first and second gears.

5. A transmission as claimed in any one of Claims

1 to 4 and further including: a third gear and second idler gear provided to increase the ratio range.

6. A transmission as claimed in Claim 5 wherein: further gears are added, where for n gears. there are (n-1) idler gears.

7. A transmission as claimed in any one of Claims 1 to 6 wherein: each gear has two conical formations, which are opposed in convergence, to provide a reversible transmission.

8. A transmission as claimed in any one of Claims 1 to 6 wherein: three gears and two idler gears are provided, where the input power is supplied to a centre gear and the outer gears are selectively connected to an output shaft, by mechanical, electrical, magnetic, hydraulic or like clutches.

9. A transmission as claimed in Claim 1 wherein: the idler gear is offset so that the respective points of contact between the idler gear and the first and second gears lie outside the plane defined by the first and second axes.

10. A continuous, variable ratio transmission including: a first cone-shaped gear rotatable about a first axis; a second cone-shaped gear rotatable about a second axis parallel to, but spaced from, the first axis, the first and second gear being oppositely convergent to their apex(es); and an idler gear, having respective first and second convergent portions, in engagement with the first and second gears, rotatable about an idler axis interposed between, but inclined to, the first and second axes, the idler gear being movable between the first and second gears to vary the transmission ratio between the first and second gears.

11. A transmission as claimed in Claim 10 wherein: the first and second portions of the idler gear are oppositely convergent to their apex(es).

12. A transmission as claimed in Claim 10 or Claim

11 wherein: as the idler gear is moved, the movement of the idler gear has one vector component parallel to, and one vector component transverse to, the first and second axes.