GB2215415A

GB2215415A - Variable speed transmission with variable-throw crank

Info

Publication number: GB2215415A
Application number: GB8805028A
Authority: GB
Inventors: Peter Goss; Anthony Bryan Shaw; Graham Stephen Poulter; Ivor Joseph Jones; Michael William John Alderson
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-02
Filing date: 1988-03-02
Publication date: 1989-09-20
Anticipated expiration: 2008-03-02
Also published as: GB8805028D0; GB2215415B

Abstract

A variable transmission has an output shaft 80 driven through gears 78 and 76 from a planet carrier 38, 36, 34, 32 having planet gears 42 in engagement with a stationary sun gear 26. The planet gears 42 are driven through one-way clutches 46 by variable throw cranks 56 driving crank shafts 50. The cranked portion 54 of each crank shaft 50 is longitudinally offset with respect to that of the other shafts. The crank throw is varied by a slider 58 having a cylindrical periphery and a slot engaging flat portions of the input shaft 24. By means of a nut-and-screw device 60, 61, a shaft 62 may be rotated to move the slider laterally of the shaft 24 whilst it is being rotated by shaft 24. The shaft 24 is driven through gears 28 and 20 from a drive shaft 18, and the shaft 62 is rotated through a differential device 64. The cranked portions 54 of oppositely crank shafts 50 are oppositely circumferentially disposed, the sliders 58 being operable in opposite directions to vary the eccentricity of the input shaft ends of the cranks 56. <IMAGE>

Description

VARIABLE SPEED TRANSMISSION This invention relates to variable speed transmissions and in particular to those providing a ratio of input to output speed which is infinitesimally variable between finite limits, usually referred to as infinitely variable.

There has been previously proposed, in United States Patent No. 4,194,407, a variable speed transmission in which the output is taken from a planet carrier having planet gears in engagement with a stationary sun gear, the planet gears being driven through one-way clutches by variable throw cranks driven from the input. The arrangement was complicated and unwieldy and never satisfied the demand for a wide range of output speeds from a relatively constant speed input from a transmission capable of high torque.

According to the invention, therefore, there is provided in a variable speed transmission in which the output is taken from a planet carrier having planet gears in engagement with a stationary member of an epicyclic gear, the planet gears being driven through one-way clutches by variable throw cranks driven from the input, seperate means to vary the throw of each crank, operable simultaneously by common means. By this arrangement, the throw variation movement of the input driven ends of the cranks may be in opposite directions for oppositely disposed one-way clutch input shafts. This enables a simple construction and tends to balance out the forces involved.

Although the present invention comprises any novel and inventive combination of features disclosed in the application, from one aspect, the invention includes an epicyclic gear including a planet carrier having planet gears in engagement with a stationary member or the epicyclic gear, the planet gears having input shafts connected through one-way clutches to intermediate shafts rotatably mounted in the planet carrier, each intermediate shaft having an input cranked portion, the cranked portions being offset from each other longitudinally of the intermediate shafts, a connecting crank for each intermediate shaft connected at one end to the cranked portion thereof and at the other end thereof to a crank throw variation means mounted on an input shaft, the seperate crank throw variation means being operable simultaneously by common means.

Preferably, the input shaft is central and the cranked portions of oppositely disposed intermediate shafts are oppositely circumferentially disposed, the crank throw variation means being operable in opposite directions to vary the eccentricity of the input shaft ends of the cranks.

Advantageously, the crank throw variation is limited so as not to permit full revolution of the cranked portions of the intermediate shafts.

Conveniently, the intermediate shafts are rotatably mounted in support members forming part of the planet carrier and rotatably mounted on either side of the crank throw variation means on the input shaft. The planet gears may be mounted on shafts rotatably mounted in support members rotatably mounted on either side of the stationary member of the epicyclic gear. In such case, the one-way clutches may be disposed between the planet gear shaft support members and the intermediate shaft support members.

The cranked portions of the intermediate shafts may have counter-balance portions on the opposite sides of the shafts to the crank-engaged portions.

The connecting cranks may be in the form of connecting rods with big ends encircling the throw variation means and little ends encircling the cranked portions of the intermediate shafts. The crank throw variation means may include a slider having a substantially cylindrical periphery and a bifurcated inside portion engaging flat portions of the input shaft to allow sliding movement of the throw variation slider on the input shaft, whilst ensuring rotation of the slider by the input shaft.

The input shaft may be rotatably supported on either side of the crank throw variation means in stationary parts of the transmission.

The stationary member of the epicyclic gear is preferably a sun gear. In this case, the input shaft is conveniently central and rotatably supported at one end in the sun gear.

How the invention can be carried into effect is hereinafter particularly described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of one embodinent of variable speed transmission according to the invention; Figure 2 is a transverse section on the lines II-II of Figure 1 and; Figure 3 is a scrap view, to an enlarged scale, of the central portion of Figure 2.

In the preferred embodimentof variable speed transmission according to the invention shown in Figure 1, a casing 10 includes two spaced end plates 12 and 14 and a spaced internal partition 16. A drive shaft 18 adapted to be driven by an internal combustion engine, an electric motor or other prime mover, is rotatably supported in bearings in the end plate 14 and partition 16. The drive shaft 18 projects on either side of the partition 16 and plate 14 and an input gear 20 is keyed to its end beyond the partition 16. To the inside of the plate 12 is secured a block 22 which has a central recess for the end of an input shaft 24 carried in a bearing in the block 22. A sun gear 26 is formed on the surface of the block 22 around the input shaft bearing portion, which sun gear is stationary and forms part of an epicyclic gear.The input shaft 24 is also carried in a bearing in the partition 16 and a gear 28 is keyed to the shaft 24 close to the partition 16 and is in mesh with the input gear 20. A planet carrier 30, forming part of the epicyclic gear, includes four spaced plates 32, 34, 36 and 38 with four planet gear assemblies spaced around the input shaft 24. One end plate 32 is rotatably supported on a bearing on the part of the input shaft 24 adjacent the gear 28. The other end plate 38 is rotatably supported on a bearing on the block 22 on the side of the sun gear 26 nearer to the end plate 12 of the casing 10. The plate 36 is rotatably on a bearing on the input shaft 24 on the other side of the sun gear 26. The plate 34 is also rotatably supported on a bearing on the input shaft 24 but spaced from the plate 36 by a bolted spacer 40.

Each of the four planet gear assemblies includes a planet gear 42 in mesh with the stationary sun gear 26 and keyed to a shaft 44 carried in bearings in the plates 36 and 38. The shaft 44 extends beyond the plate 36 and is there formed as, or connected to, a housing 46 for a one-way clutch 48. The one-way clutch 48 is preferably of the sprag type, having an input shaft 50 and sprags 52. The sprags 52 are so arranged that rotation of the shaft 50 in one direction causes the shaft 50 to drive the housing 46 in the same direction, whilst rotation of the shaft 50 in the opposite or reverse direction causes no drive of the housing 46, but is allowed even when the housing 46 is rotating in the one direction. Thus, if the shaft 50 is driven in the one direction faster than the housing 46, the sprags 52 are locked up and transmit torque to the housing 46.If the shaft 50 is not driven faster than the housing 46 in the one direction or is driven in the opposite reverse direction, the housing 46 continues to rotate in the one direction. The intermediate shaft 50 is rotatably supported in a bearing in the plate 34 on either side of which it projects, and in a bearing in the plate 32, the plates 32 and 34 acting as support members for the shaft 50. Between the plates 32 and 34, the shaft 50 has a cranked portion 54. The cranked portion 54 comprises a cylindrical part, parallel to the shaft 50 and offset therefrom, and two transverse parts connecting the cylindrical part to the shaft. The two transverse parts extend beyond the shaft 50 from the cylindrical part to form counter-balance portions 55 (Figure 2).The cranked portions 54 of the individual planet gear assemblies are set at different positions along the lengths of the shafts 50 between the plates 32 and 34. Rotatably supported upon the cylindrical part of the cranked portion 54 is the little end of a connecting crank rod 56 whose big end surrounds a middle portion of the input shaft 24. Each of the big ends of the four connecting rods 56 surrounds a different part of that middle portion. Within each big end of a connecting rod 56 is a slider 58 with a bearing 59 therebetween. The four sliders 58 are arranged side-by-side between end spacers 57 on the input shaft 24. The middle portion of the input shaft 24 is of rectangular cross-section (Figure 2), the flat end portions being slidably engaged by the flat opposed inner faces of a bifurcated part of the slider 58 which has a substantially cylindrical periphery.

Thus each slider 58 is forced to rotate with the input shaft 24, but is free to slide thereon so that the centre of the cylindrical outer surface of the slider 58 and of the bearing 59 is eccentric to the axis of rotation of the shaft 24.

The transverse position of a slider 58 upon the shaft 24 is determined by two threaded bolts 60 which pass through transverse holes in the shaft 24 and are parallel to the flat faces thereof. The bolts 60 are fixed in the slider 58 and each is engaged by a nut 61 in a slotted part of the input shaft 24. The nuts 61 are externally threaded for engagement by a threaded worm shaft 62 in a central aperture in the input shaft 24. The threaded shaft 62 is driven through a differential assembly 64 whose input bevel gear 66 is driven from the drive shaft 18 through a train of gears.

The differential assembly 64 has an output bevel gear 68 connected to the threaded shaft 62 and an intermediate bevel gear 70 mounted rotatably on a ring gear 72 whose position can be adjusted by an external handle 74 through a gearwheel 76. The arrangement is such that the threaded shaft 62 normally rotates with the input shaft 24 but can be rotated relative thereto by rotation of the handle 74. Such relative rotation rotates the nuts 61 which drive the threaded bolts 60 transversely of the shaft 24. This displaces the sliders 58, thus positioning the big ends of the connecting rods 56 eccentrically or altering their eccentricity. Thus the transmission has variable throw cranks with means to vary the crank throws which operate seperately but simultaneously by means of a common shaft 62.

As described below, the sliders 58 are so arranged that two move in one direction and two in the opposite direction.

The cranked portions 54 of the shafts 50 are also so arranged that two are disposed to one side and two to the other side of their shafts, so that the effect is as though the sliders moved in the same direction.

With the sliders displaced from their central positions on the input shaft 24, the big ends of the connecting rods 56 are moved in a circular path during rotation of the input shaft 24. The effect of this is to cause angular pivotation of the intermediate shafts 50 through their cranked portions 54 in the little ends. The extent of the angular pivotation is determined by the extent of the eccentricity of the sliders 58 and this is preferably limited so as not to permit full rotation of the cranked portions 54 of the intermediate shafts 50. The angular movement of the shaft 50 in one direction is passed on to the planet-gear carrying shaft 44 through the one-way clutch 48 when the speed of rotation is greater than that of the housing 46.The disposition of the sliders 58 and cranked portions 54 of the shafts 50 is such that the planet gears 42 are successively driven in the direction of rotation permitted by the one-way clutches 48. As the planet gears 42 are in mesh with the stationary sun gear 26, the planet carrier 30 is driven round at a corresponding speed. The end plate 38 of the carrier 30 has a hub-like extension encircling the block, to which extension is keyed a gear 76.

The gear 76 is in mesh with an output gear 78 keyed to an output shaft 80 rotatably supported in the end plate 12 of the casing 10.

With the input shaft 24 driven by rotation of the drive shaft 18 and the sliders 58 in their central positions, as shown in Figure 2, the sliders 58 rotate freely within the big ends of the connecting crank rods 56, so that no movement of the rods or of the shafts 50 occurs. When the shaft 62 is rotated by the handle 74 and differential assembly 64, the sliders 58 are displaced from their central positions and become offset from the central axis of the rotating shaft 24. The sliders 58 continue to be rotated by the shaft 24 and the central axes of the sliders 58, which are also the central axts of the bearings 59 and of the big ends of the connecting rods 56, rotate about the central axis of the shaft 24 in a circular path whose radius is determined by the amount of offset.This movement of the big ends of the connecting rods 56 causes the central axqs of the little ends of the rods to move about the axts of the shafts 50, carrying with them the cranked portions 54 of the shafts and pivoting the latter. This pivotation is an oscillation in two directions during a single revolution of the input shaft 24. In one of these directions, each, shaft 50 will turn the planet gear shaft 44 through the one-way clutch 48, assuming that the planet gear 42 is stationary. This starts rotation of the planet gears 42 and consequent rotation of the planet carrier 30 around the stationary sun gear 26. As the planet carrier 30 begins to rotate, it carries with it in the plates 32 and 34 the intermediate shafts 50 with their cranked portions 54 and the little ends of the connecting rods 56.This reduces the throw of the little ends of the connecting rods 56 due to the movement of the big ends. The shafts 50 continue to turn the planet gear shafts 44 through the one-way clutches 48, whilst the planet gears are rotating at a speed less than that of the shafts. The speed of rotation of the carrier 30 increases until the reduced effect of rotation of the big ends of the connecting rods upon the shafts 50 is balanced by the rotation of the planet gears 42. Thereafter, the transmission ratio remains stable, provided that the input drive is sufficient for the output load. Variation of the transmission ratio is effected by movement of the shaft 62 to move the sliders 58 on the input shaft 24 and thus to vary the throw of the cranks. Although a handle 74 is shown as the external means to effect such crank throw variation, it will be appreciated that other means may be used, for example an automatic control responsive to output speed and power setting.

As the input shaft 24 rotates with the sliders 58 offset, the connecting rods 56 pull or push on the cranked portions 54 of the intermediate shafts 50, the movement of the little ends being approximately sinusoidal. Thus, when running at speed, the rotational speed of the shafts 50 tends to exceed the rotational speed of the planet gear shaft 44 for only part of half a revolution. For the best effect, therefore, there are at least four intermediate shafts 50, and for reasons of balance, these are best arranged in pairs on opposite sides of the input shaft 24. The crank throw variation should be such that the effective strokes of the connecting rods to pivot the shafts 50 in the one direction are sequential and overlapping.If the sliders 58 were all to be moved in the same direction to achieve this with similarly disposed cranked portions 54 on the shafts 50, there would be a degree of imbalance which would drastically reduce the practicability of the transmission.

Accordingly, the crank throw variation sliders of pairs of opposite shafts 50 are movable in opposite directions by selection of the threaded bolts 60, whilst the cranked portions 54 are oppositely circumferentially disposed on the shafts 50, as shown in Figure 2. The effect of this arrangement is that the connecting rods 56 move in opposite directions and the unbalancing forces from one are substantially balanced by those from the other. In the case of four intermediate shafts, the crank throw variation sliders of the other pair are similarly movable. If more than two pairs are used, the directions of slider movement are adjusted to give the necessary sequential and overlapping drives to the intermediate shafts. It will also be appreciated that,as the movement of the individual sliders of the pairs of sliders 58 is equal and opposite, the arrangement remains balanced during crank throw variation.

Claims

1. A variable speed transmission in which the output is taken from a planet carrier having planet gears in engagement with a stationary member of an epicyclic gear, the planet gears being driven through one-way clutches by variable throw cranks driven from the input, including seperate means to vary the throw of each crank, operable simultaneously by common means.

2. A variable speed transmission comprising an epicyclic gear including a planet carrier having planet gears in engagement with a stationary member of the epicyclic gear, the planet gears having input shafts connected through one-way clutches to intermediate shafts rotatably mounted in the planet carrier, each intermediate shaft having an input cranked portion, the cranked portions being offset from each other longitudinally of the intermediate shafts, a connecting crank for each intermediate shaft connected at one end to the cranked portion thereof and at the other end thereof to a crank throw variation means mounted on an input shaft, the separate crank throw variation means being operable simultaneously by common means.

3. A transmission according to claim 2, wherein the input shaft is central and the cranked portions of oppositely disposed intermediate shafts are oppositely circumferentially disposed, the crank throw variation means being operable in opposite directions to vary the eccentricity of the input shaft ends of the cranks.

4. A transmission according to claim 2 or 3, wherein the crank throw variation is limited so as not to permit full revolution of the cranked portions of the intermediate shafts.

5. A transmission according to claim 2, 3 or 4, wherein the intermediate shafts are rotatably mounted in support members forming part of the planet carrier and rotatably mounted on either side of the crank throw variation means on the input shaft.

6. A transmission according to claim 2, 3, 4 or 5, wherein the planet gears are mounted on shafts rotatably mounted in support members rotatably mounted on either side of the stationary member of the epicyclic gear.

7. A transmission according to claim 6, as appendant to claim 5, wherein the one-way clutches are disposed between the planet gear shaft support members and the intermediate shaft support members.

8. A transmission according to any one claims 2 to 7, wherein the cranked portions of the intermediate shafts have counter-balance portions on the opposite sides of the shafts to the crank-engaged portions.

9. A transmission according to any one claims 2 to 8, wherein the connecting cranks are in the form of connecting rods with big ends encircling the throw variation means and little ends encircling the cranked portions of the intermediate shafts.

10. A transmission according to any one of claims 2 to 9, wherein the crank throw variation means includes a slider having a substantially cylindrical periphery and a bifurcated inside portion engaging flat portions of the input shaft to allow sliding movement of the throw variation slider on the input shaft, whilst ensuring rotation of the slider by the input shaft.

11. A transmission according to any one claims 2 to 10, wherein the input shaft is rotatably supported on either side of the crank throw variation means in stationary parts of the transmission.

12. A transmission according to any one preceding claim, wherein the stationary member of the epicyclic gear is a sun gear.

13. A transmission according to claim 12, wherein the input is a central shaft rotatably supported at one end in the sun gear.

14. A variable speed transmission substantially as hereinbefore particularly described with reference to the accompanying drawings.

15. Any novel integer or combination of integers, hereinbefore disclosed and/or shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of any of the preceding claims.