Method and apparatus for controlling a contiuously variable transmission

• US 20080009389A1
• Filed: 07/06/2006
• Published: 01/10/2008
• Est. Priority Date: 07/06/2006
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Jacobs, Craig S.
• Granted Patent: US 7,479,090 B2
• Time in Patent Office: Days
• US Class Current: 477/37
• CPC Class Codes: F16H 61/66254 controlling of shifting being influenced by a signal derived from the engine and the main coupling
• CPC Class Codes: F16H 61/66259 using electrical or electronical sensing or control means

Abstract

A method of controlling the ratio of a continuously variable transmission (CVT) that is controlled by a CVT controller is provided. The method includes determining the torque produced by an engine, calculating an acceleration limit value based upon the torque value and the engine inertia value and a calibrated acceleration limiting ratio. The acceleration limit value is compared to the desired engine speed value to determine a command engine speed value. The CVT ratio is then calculated by dividing the command engine speed value by a measured vehicle speed value. The calculated CVT ratio is compared to a measured CVT ratio and a control signal is sent to an actuator of a CVT. Torque provided to the engine to overcome the engine inertia is limited by the method so that the step change in torque provided to the vehicle wheels, as the engine approaches the command engine speed value, is reduced.

Claims

1. A method of controlling the ratio of a continuously variable transmission (CVT) that is controlled by a CVT controller, comprising:

determining the torque produced by an engine to develop a torque value;

calculating an acceleration limit value by dividing the torque value by an engine inertia value and multiplying by a limiting ratio;

comparing the acceleration limit value to a desired engine speed value to determine a command engine speed value;

calculating the CVT ratio by dividing the command engine speed value by a measured vehicle speed value;

comparing the CVT ratio to a measured CVT ratio; and

sending a control signal to an actuator of a CVT, whereby torque provided to the engine to overcome the engine'"'"'s inertia is limited so that the step change in torque provided to a plurality of wheels of a vehicle as the engine approaches the command engine speed is reduced.

2. The method of claim 1 wherein the step of determining the torque is performed by monitoring the engine torque value that is obtained from a datalink that monitors engine performance.

3. The method of claim 1 wherein the engine inertia value is a constant that is programmed into the CVT controller.

4. The method of claim 1 wherein the limiting ratio is programmed into the CVT controller as a constant value.

5. The method of claim 4 wherein the constant engine inertia value programmed for the limiting ratio is between 5 and 10%.

6. The method of claim 1 wherein the limiting ratio programmed into the CVT controller is obtained from a look-up table with reference to an additional input signal.

7. The method of claim 6 wherein the additional input signal is obtained from a signal source selected from the group consisting of:

a throttle position switch that indicates the relative position of the throttle;

a mode switch that is controlled by an operator to select a mode of operation of the CVT controller;

or

a grade switch that indicates the grade angle of a road on which the vehicle is traveling.

8. The method of claim 1 wherein the desired engine speed value is a programmed value corresponding to the desired engine speed.

9. The method of claim 1 wherein the step of comparing the acceleration limit value to a desired engine speed value to determine a command engine speed value is performed in a rate limiter circuit element that has a reset mechanism that is activated at vehicle launch.

10. The method of claim 1 wherein the step of comparing the CVT ratio to a measured CVT ratio is performed iteratively in a feedback control circuit that compares the CVT ratio output of the CVT ratio generator to the measured CVT ratio of the CVT.

11. The method of claim 1 wherein the measured CVT ratio is obtained from the CVT controller and is provided to a feedback control circuit.

12. A system for controlling a continuously variable transmission (CVT), comprising:

an engine that produces torque that is determined to be a torque value;

a CVT controller that calculates an acceleration limit value by dividing the torque value by an engine inertia value and multiplying by a limiting ratio, the CVT controller compares the acceleration limit value to a desired engine speed value to determine a command engine speed value, the CVT controller calculates a CVT ratio by dividing the command engine speed value by a measured vehicle speed value, the CVT controller compares the CVT ratio to a measured CVT ratio and sends a control signal to an actuator of the CVT, whereby the torque provided to the engine to overcome the engine'"'"'s inertia is limited to reduce the step change in torque provided to a plurality of wheels of a vehicle as the engine approaches a command engine speed.

13. The system of claim 12 wherein the step of determining the torque is performed by monitoring the engine torque value that is obtained from a datalink that monitors engine performance.

14. The system of claim 12 wherein the engine inertia value is a constant that is programmed into the CVT controller.

15. The system of claim 12 wherein the limiting ratio is programmed into the CVT controller as a constant value.

16. The system of claim 12 wherein the limiting ratio programmed into the CVT controller is obtained from a look-up table with reference to an additional input signal.

17. The system of claim 16 wherein the additional input signal is obtained from a signal source selected from the group consisting of:

a throttle position switch that indicates the relative position of the throttle;

a mode switch that is controlled by an operator to select a mode of operation of the CVT controller;

or

a grade switch that indicates the grade angle of a road on which the vehicle is traveling.

18. The system of claim 12 wherein the desired engine speed value is a programmed value corresponding to the desired engine speed.

19. The system of claim 12 wherein the step of comparing the acceleration limit value to a desired engine speed value to determine a command engine speed value is performed in a rate limiter circuit element that has a reset mechanism that is activated at vehicle launch.

20. The system of claim 12 wherein the step of comparing the CVT ratio to a measured CVT ratio is performed iteratively in a feedback control circuit that compares the CVT ratio output of the CVT ratio generator to the measured CVT ratio of the CVT.

21. The system of claim 12 wherein the measured CVT ratio is obtained from the CVT controller and is provided to a feedback control circuit.