SYSTEMS AND METHODS FOR CONTROLLING ROLLBACK IN CONTINUOUSLY VARIABLE TRANSMISSIONS

• US 20170204969A1
• Filed: 01/15/2016
• Published: 07/20/2017
• Est. Priority Date: 01/15/2016
• Status: Active Grant

• Current Assignee: Fallbrook Intellectual Property Company LLC (Fallbrook Technologies Incorporated)
• Original Assignee: Fallbrook Intellectual Property Company LLC (Fallbrook Technologies Incorporated)
• Inventors: Jackson, David Brian, Pohl, Brad P., Thomassy, Fernand A., Lohr, Charles B.
• Granted Patent: US 10,047,861 B2
• Time in Patent Office: Days
• CPC Class Codes: B60W 10/108 Friction gearings
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: B60W 30/18036 Reversing
• CPC Class Codes: F16H 15/28 with external friction surface
• CPC Class Codes: F16H 15/52 in which a member of uniform effective diameter mounted on a shaft may co-operate with different parts of another member
• CPC Class Codes: F16H 61/66 specially adapted for continuously variable gearings control of exclusively fluid gearing F16H61/38
• CPC Class Codes: F16H 61/664 Friction gearings

Abstract

A continuously variable transmission capable of operating in a forward direction or reverse direction maybe 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.

Claims

1. A method for controlling rollback in a continuously variable transmission (CVT) capable of operating in a design direction of rotation and a reverse direction of rotation, wherein when the CVT is operating in a reverse direction, the method comprises:

rotating, a carrier in the CVT in a first direction to a first skew angle;

monitoring the CVT to determine a change in a tilt angle; and

rotating the carrier in an opposite direction to a second skew angle, wherein the second skew angle results in the CVT having a zero tilt angle.

2. The method of claim 1, wherein the continuously variable transmission is preset to operate in the reverse direction.

3. The method of claim 1, further comprising causing a series of additional changes to the skew angle.

4. The method of claim 1, wherein at least one additional change of the series of additional changes is determined based on one or more of the dimensions of a first plurality of slots in a first carrier of the CVT and the dimensions of a second plurality of slots in a second carrier of the CVT.

5. The method of claim 1, wherein the CVT 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 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. The method of claim 1, wherein the CVT comprises an array of planets orbital about a center axis of the CVT, each planet having an axis of rotation, wherein each of the first and second skew angles are measured between a projection of a skew guide feature of the CVT and a radial line L_R normal to the center axis of the CVT, wherein the projection plane is normal to the center axis, and wherein the tilt angle is a projection of an angle measured between a planet axis of rotation and the center axis of the CVT, wherein the planet axis of rotation is projected onto a plane containing both axes.

8. A variator, comprising:

an array of planets orbital about a longitudinal axis, each planet having an axle;

a first ring in contact with the army 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 army of planets and orbital about the longitudinal axis, the second ring being on a second side of the array of planets;

a first carrier having a plurality of carrier slots oriented in a first direction, each carrier slot configured for receiving a first end of a planet axle of the array of planets;

a second carrier opposite the first carrier and having a plurality of carrier slots oriented in the first direction, each carrier slot configured for receiving a second end of the planet axle of the array of planets;

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 a memory storing a set of instructions executable by the processor to perform;

determining the variator is operating in a reverse direction;

initiating a first rotation to cause the variator to operate based on the reverse direction, wherein the array of planets are biased to tilt towards reduction; and

changing a skew angle to change a tilt angle of the array of planets.

9. The variator of claim 8, wherein the set of instructions executable by the processor includes instructions to periodically change the skew angle to offset the bias of the planets to tilt towards reduction.

10. The variator of claim 8, wherein the controller is configured to advance the skew angle to change the skew angle.

11. The variator of claim 8, wherein the controller is configured to preset the variator to operate in a reverse direction.

12. The variator of claim 8, wherein the controller is configured to change the skew angle based on one or more of the dimensions of the plurality of carrier slots of the first carrier and the dimensions of the plurality of carrier slots of the second carrier.

13. The variator of claim 8, wherein a change in the skew angle after the first rotation is based on a rate of change of planet axis skew angle and the rate of rotation of the planets.

14. The variator of claim 8, wherein the set of instructions executable by the processor includes instructions to determine 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.

15. A drivetrain comprising:

a power source;

a variator coupled to the power source, the variator comprising;

an array of planets orbital about a longitudinal axis;

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 power load;

an actuator coupled to at least one of a first carrier and a second carrier; and

a controller communicatively coupled to the actuator, the controller comprising a processor and a memory storing a set of instructions executable by the processor to perform;

initiating a first rotation to cause the variator to operate in a reverse direction, wherein the variator is biased to rotate to a maximum reduction; and

changing the skew angle to offset the bias of the variator to rotate.

16. The drivetrain of claim 15, wherein the controller is configured to advance the skew angle to change the skew angle.

17. The drivetrain of claim 15, wherein the controller is configured to preset the variator to operate in a reverse direction.

18. The drivetrain of claim 15, wherein the controller is configured to change the skew angle based on one or more of the dimensions of a first plurality of slots in the first carrier and the dimensions of a second plurality of slots in the second carrier.

19. The drivetrain of claim 15, wherein a change in the skew angle after the first rotation is based on the rate of change of planet axis skew angle and the rate of rotation of the planets.

20. The drivetrain of claim 15, wherein the set of instructions executable by the processor includes instructions to determine a load change, wherein the skew angle is further changed to offset bias of the variator to rotate caused by the load change.