CONTINUOUSLY VARIABLE GEAR TRANSMISSION

Abstract

A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.

Claims

1. An apparatus for facilitating control of the ratio of a continuously variable transmission (CVT), the apparatus comprising: a first member having a first plurality of radial grooves arranged angularly about an axis, the first plurality of radial grooves engaging a first end of ball axles of a plurality of traction balls of the CVT, wherein the first member is non-rotatable; a second member having a second plurality of radial grooves arranged angularly about the axis, the second plurality of radial grooves engaging a second end of the ball axles; and an actuator for rotating the first and second members relative to one another such that during operation of the CVT the first plurality of radial grooves can be angularly misaligned relative to the second plurality of grooves through a plane lying through the shaft, wherein an angular misalignment of the first and second plurality of radial grooves corresponds to a tilting of the ball axles in the first and second pluralities of radial grooves.

2. The apparatus of claim 1, wherein the first member comprises a stationary member, and wherein the second member is rotated relative to the first member.

3. The apparatus of claim 2, wherein the second member comprises a support plate configured for rotation relative to the first member.

4. The apparatus of claim 1, wherein the first member comprises a housing member.

5. The apparatus of claim 4, wherein the second member comprises a support plate.

6. The apparatus of claim 5, further comprising an actuator housing and an actuator arm, the actuator housing coupled to the support plate, and the actuator arm coupled to a mechanism for tilting the plurality of traction balls of the CVT.

7. The apparatus of claim 1, further comprising an input disc in contact with the plurality of traction balls, and wherein a clockwise rotation of the input disc and a clockwise rotation of the second plurality of radial grooves results in the ball axles being tilted in a first direction in the radial grooves.

8. The apparatus of claim 7, wherein the second plurality of grooves is further characterized in that a counterclockwise rotation of the second plurality of grooves results in the ball axles being tilted in a second direction in the radial grooves.

9. The apparatus of claim 1, further characterized by a support plate having a minor rotational play around its ideal aligned position.

10. A method for facilitating control of a speed ratio of a continuously variable transmission (CVT) having a shaft, a plurality of traction balls arrayed angularly about a longitudinal axis of the shaft, each traction ball including a ball axle about which the traction ball rotates, and a pre-spanning ring contacting the plurality of traction balls, the method comprising: providing a first plurality of radial grooves for engaging a first end of each of the ball axles, the first member being non-rotatable; providing a second plurality of radial grooves for engaging a second end of each of the ball axles; and arranging the first and the second plurality of radial grooves relative to one another such that during operation of the CVT the first plurality of radial grooves can be misaligned relative to the second plurality of radial grooves through a plane lying through the shaft, wherein an angular misalignment of the first and the second plurality of radial grooves corresponds to a tilting of the ball axles in the first and second pluralities of radial grooves.

11. The method of claim 10, wherein the first plurality of radial grooves is part of a housing.

12. The method of claim 11, wherein the second plurality of radial grooves is part of a support plate.

13. The method of claim 12, further comprising providing an actuator housing and an actuator arm, the actuator housing being coupled to the support plate, and the actuator arm being coupled to a mechanism for tiling the plurality of traction balls.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the invention will be described more fully below with reference to the drawing, in which

[0021] FIG. 1 shows a sectional view of a continuous variable transmission according to the invention seen in the direction A-A in FIG. 2,

[0022] FIG. 2 shows a side view of the continuously variable transmission showing the radial grooves in the support plate,

[0023] FIG. 3 shows the iris plate with spiral grooves,

[0024] FIG. 4A shows a sectional view of the axial force generator,

[0025] FIG. 4b shows an exploded view of the axial force generator,

[0026] FIG. 5A shows a sectional view of the pre-spanning ring and a traction ball, in the constant ratio state,

[0027] FIG. 5B shows a sectional view of the pre-spanning ring and a traction ball after a quick tilt of the traction balls axles

[0028] FIG. 6A shows the iris plate with modified grooves and ramps for the alternative embodiment with disengagement mechanism,

[0029] FIG. 6B shows the iris plate of FIG. 6a in a perspective view more clearly showing the ramps,

[0030] FIG. 7 shows the clutch plate and control pins used in the alternative embodiment

[0031] FIG. 8 shows a sectional view of the continuously gear transmission in accordance with the alternative embodiment with the disengagement mechanism cut through a traction ball,

[0032] FIG. 9 shows a sectional view corresponding to FIG. 8, but cut between the traction balls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 1 shows a section through a continuously variable transmission according to an embodiment of the invention. The transmission comprises an input shaft 1 whose rotation is to be converted into rotation of an output shaft 10, whose one end extends out of the gear, said output shaft 10 being axially aligned with the input stub shaft 1. As shown in FIGS. 4A and 4B, the input shaft 1 is connected by an axial force generator to an input disc 8. The axial force generator consists of a number of ramps 14 on the input shaft 1, a number of ramps 15 on the input disc 8 and in between a number of balls 16. This axial force generator provides an axial force varying with the torque of the input shaft 1. The slope of the ramps 14, 15 is calculated to create an axial force to result in the needed normal force on the traction balls 2 to give the required traction.

[0034] This axial force presses the traction balls 2 towards the pre-spanning ring 11. When the input shaft 1 rotates the traction balls 2, they will start spinning, and the contact point between traction balls 2 and pre-spanning ring 11 will move to the axial centre of the pre-spanning ring 11, where the inner diameter is largest, as shown in FIG. 5A. When the traction balls 2 are tilted rapidly, the pre-spanning ring will follow axially and the contact point will move to a point with a smaller inner diameter of the pre-spanning ring 11, as shown in FIG. 5B, which results in a larger normal force at the contact points of the traction balls 2.

[0035] The positions of the traction balls are defined by the three contact points with the input disc 8, pre-spanning ring 11 and output disc 9, and the axles are supported by the grooves in the housing 5 and the support plate 6 shown in FIG. 2.

[0036] The iris plate 7 shown in FIG. 3 controls the angle of the traction ball axles 3. The axles 3 of the traction balls 2 supported by the radial grooves 4 in the housing 5 and the support plate 6 passes through the grooves 13 in the iris plate 7. When the iris plate 7 turns, the axles 3 will tilt, in order to make it possible for the axles 3 to pass through the grooves 13 at an angle, the grooves 13 in the iris plate 7 are wider than the diameter of the friction ball axles 3. To prevent play, the friction ball axles 3 are equipped with iris rollers 17, which have the same diameter as the grooves 13 in the iris plate.

[0037] The iris plate 18 shown in FIGS. 6A and 6B comprises grooves 19, the inner part of which maintain a constant radius, in order to provide the minimum transmission ratio in connection with disengagement. The disengagement is provided by means of the ramps 20 on the iris plate 18, said ramps 20 forcing the clutch plate 21 shown in FIG. 7 towards the thrust bearing 22, when the iris plate 18 is turned further onwards after reaching the minimum transmission ratio. The thrust bearing 22 will thus push the input disc 8 away from its engagement with the traction balls 2 whereby the driven unit is disengaged from the driving unit. In this situation i.e. the disengaged position of the input disc 8, the torque on the input shaft 1 will be close to zero and thus if an axial force generator is present, the axial force will be at a minimum, further supporting the disengagement of the transmission. The rotational position of the clutch plate 21 may be controlled by means of pins 23 inserted in the housing, whereby the movement of the clutch plate 21 is limited to an axial movement.

[0038] The FIGS. 8 and 9 show different cross-sectional views of the transmission with the disengagement mechanism implemented. In FIG. 8 the cross-sectional view is provided through a traction ball 1 and in FIG. 9 a cross-sectional view is provided between the traction balls 1.

[0039] Above the invention has been described in connection with a preferred embodiment, however, many deviations may be envisaged without departing from the scope of the following claims, such as having the pre-spanning ring positioned on the inside of the traction balls 2 and the input and output discs positioned with contact on the outside of the traction balls 2, or other possible mechanisms for tilting the traction balls 2, etc.