Systems and methods for controlling rollback in continuously variable transmissions

Patent metadata

Field	Value
Publication number	US-11306818-B2
Application number	US-202117177046-A
Country	US
Kind code	B2
Filing date	Feb 16, 2021
Priority date	Jan 15, 2016
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

A continuously variable transmission capable of operating in a forward direction or reverse direction may be controlled in the reverse direction by providing an initial skew angle in a first skew direction, followed by a set or sequence of skew angle adjustments in an opposite direction to prevent runaway or other unintended consequences. A continuously variable transmission may include a timing plate to maintain all planets at an angle or within a range of an angle in forward and reverse operations.

First claim

What is claimed:

1. A method for controlling tilt angle in a ball planetary continuously variable transmission (CVT) comprising a first carrier comprising a plurality of first slots and a second carrier comprising a plurality of second slots and at least one planet axle extending from a first particular slot of the plurality of first slots to a second particular slot of the plurality of second slots, the method comprising:
operating the CVT in a design direction of rotation, including rotating the first carrier of the CVT in a first direction to a first skew angle of the planet axle associated with a desired tilt angle of the planet axle; and
operating the CVT in a reverse direction of rotation, including
rotating the first carrier of the CVT in a second direction opposite the first direction to a second skew angle of the planet axle;
monitoring the CVT to determine a change in a tilt angle of the planet axle; and
rotating the first carrier in the first direction to a third skew angle of the planet axle, the third skew angle resulting in the CVT having the desired tilt angle of the planet axle.

2. The method of claim 1 , further comprising determining when the CVT has switched from the design direction to the reverse direction.

3. The method of claim 1 , wherein operating the CVT in the reverse rotation further comprises causing a series of additional changes to the skew angle of the planet axle in the first direction.

4. The method of claim 3 , further comprising:
determining, based on one or more of the dimensions of the plurality of first slots in the first carrier of the CVT and the dimensions of the plurality of second slots in the second carrier of the CVT, at least one additional change of the series of additional changes; and
causing the at least one additional change.

5. The method of claim 1 , wherein the CVT further comprises an array of planets orbital about a center axis of the CVT, each planet having an axis of rotation, and wherein the method further comprises determining the skew angle based on the rate of change of a planet axis skew angle and the rate of rotation of the planets.

6. The method of claim 1 ,
further comprising determining a load change,
wherein the skew angle of the planet axle is further changed to offset a bias caused by the load change, and
wherein the bias causes the CVT to adjust a transmission ratio to either an overdrive condition or an underdrive condition.

7. A continuously variable transmission (CVT), comprising:
a variator, comprising an array of planets orbital about a longitudinal axis, each planet having a planet axle defining a planet axis of rotation, a first ring in contact with the array of planets and orbital about the longitudinal axis, the first ring being on a first side of the array of planets, a second ring in contact with the array of planets and orbital about the longitudinal axis, the second ring being on a second side of the array of planets, a sun located radially inward of and in contact with the array of planets, a first carrier comprising a plurality of first slots, each first slot configured for receiving a first end of a planet axle, and a second carrier opposite the first carrier and comprising a plurality of second slots, each second slot configured for receiving a second end of the planet axle;
an actuator coupled to at least one of the first carrier and the second carrier; and
a controller communicatively coupled to the actuator, the controller comprising a processor and memory storing a set of instructions executable by the processor to perform determining if the variator is operating in a design direction or a reverse direction; the controller being configured to, when the variator is operating in a design direction, determine a desired tilt angle for the array of planets and send a signal to the actuator to rotate the first carrier in a first direction to a first skew angle; and the controller being configured to, when the variator is operating in a reverse direction, determine the desired tilt angle for the array of planets, send a first signal to the actuator to rotate the first carrier in a second direction opposite the first direction to a second skew angle, monitor the CVT to determine a change in the tilt angle, and send a second signal to rotate the first carrier in the first direction to a third skew angle that adjusts the CVT to the desired tilt angle.

8. The CVT of claim 7 , wherein the set of instructions executable by the processor includes instructions for sending a series of additional signals to change the skew angle in the first direction.

9. The CVT of claim 7 , wherein the set of instructions executable by the processor includes instructions for periodically changing the skew angle to offset a bias of the planets to tilt towards reduction.

10. The CVT of claim 7 , wherein the controller is configured to send an instruction to advance the skew angle.

11. The CVT of claim 7 , wherein when the CVT is stopped, the controller is configured to preset the variator to operate in the reverse direction.

12. The CVT of claim 7 , wherein the controller is configured to change the skew angle based on one or more of the dimensions of the plurality of first slots of the first carrier and the dimensions of the plurality of second slots of the second carrier.

13. The CVT of claim 7 , wherein a change in the skew angle after a first rotation is based on a rate of change of planet axis skew angle and a rate of rotation of the planets.

14. The CVT of claim 7 , wherein the set of instructions executable by the processor includes instructions for determining a load change, and wherein the skew angle is further changed to offset bias of the planets to tilt towards reduction caused by the load change.

Assignees

• Fallbrook Ip Co Llc

Inventors

• Thomassy Fernand A
• Lohr Charles B
• Pohl Brad P
• Jackson David Brian

Classifications

• F16H61/66 Primary

  specially adapted for continuously variable gearings (control of exclusively fluid gearing F16H61/38) · CPC title

• F16H61/664 Primary

  Friction gearings · CPC title

• B60W10/108

  Friction gearings · CPC title

• B60W2510/1005

  Transmission ratio engaged · CPC title

• F16H15/52

  in which a member of uniform effective diameter mounted on a shaft may co-operate with different parts of another member · CPC title