Method for controlling gear ratio changes in an automatic transmission

• US 20100121543A1
• Filed: 11/12/2008
• Published: 05/13/2010
• Est. Priority Date: 11/12/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Steinlage, Justin L., Dickrell, David E., Landes, James W.
• Granted Patent: US 8,145,398 B2
• Time in Patent Office: Days
• US Class Current: 701/54
• CPC Class Codes: F16H 2059/743 using engine performance or power for control of gearing transmission input torque F16H2059/147
• CPC Class Codes: F16H 2061/0234 Adapting the ratios to special vehicle conditions
• CPC Class Codes: F16H 59/60 Inputs being a function of ambient conditions
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals
• CPC Class Codes: F16H 61/12 Detecting malfunction or potential malfunction, e.g. fail safe in control of hydrostatic gearing F16H61/4192; Circumventing or fixing failures

Abstract

A method of controlling an automatic transmission of a machine includes a step of identifying an upcoming gear ratio change from a current gear ratio to a proposed gear ratio. An estimated power output value, based on the proposed gear ratio and a current engine speed, is determined. The estimated power output value is adjusted based on a derated operating condition. If the estimated power output value is greater than or equal to a current power output value, a gear evaluation identifier is set to a first value. If the estimated power output value is less than the current power output value, the gear evaluation identifier is set to a second value.

Claims

1. A method of controlling an automatic transmission of a machine, comprising:

identifying an upcoming gear ratio change from a current gear ratio to a proposed gear ratio;

determining an estimated power output value based on the proposed gear ratio and a current engine speed;

adjusting the estimated power output value based on a derated operating condition;

setting a gear evaluation identifier to a first value if the estimated power output value is greater than or equal to a current power output value; and

setting the gear evaluation identifier to a second value if the estimated power output value is less than the current power output value.

2. The method of claim 1, further including:

changing the current gear ratio to the proposed gear ratio if the gear evaluation identifier is the first value; and

maintaining the current gear ratio if the gear evaluation identifier is the second value.

3. The method of claim 1, wherein the identifying step includes identifying an upcoming upshift from a lower gear ratio to a higher gear ratio.

4. The method of claim 1, wherein the determining step includes communicating a request for the estimated power output value from a transmission electronic controller to an engine electronic controller.

5. The method of claim 4, wherein the determining step further includes selecting the estimated power output value corresponding to the proposed gear ratio and the current engine speed from a lug curve stored in a memory.

6. The method of claim 4, wherein the adjusting step includes adjusting the estimated power output value by a value corresponding to the derated operating condition.

7. The method of claim 6, wherein the adjusting step further includes adjusting the estimated power output value based on at least one parasitic load.

8. The method of claim 6, further including communicating the estimated power output value from the engine electronic controller to the transmission electronic controller after the adjusting step.

9. The method of claim 1, wherein the determining, adjusting, and setting steps are performed only if the derated operating condition is detected.

10. A machine, comprising:

an electronically controlled automatic transmission having at least two gear ratios;

an internal combustion engine coupled to the electronically controlled automatic transmission; and

at least one electronic controller in communication with the electronically controlled automatic transmission and the internal combustion engine, wherein the at least one electronic controller is configured to identify an upcoming gear ratio change from a current gear ratio to a proposed gear ratio;

determine an estimated power output value based on the proposed gear ratio and a current engine speed;

adjust the estimated power output value based on a derated operating condition;

change the current gear ratio to the proposed gear ratio if the estimated power output value is greater than or equal to a current power output value; and

maintain the current gear ratio if the estimated power output value is less than the current power output value.

11. The machine of claim 10, wherein the upcoming gear ratio change includes an upshift from a lower gear ratio to a higher gear ratio.

12. The machine of claim 11, further including an engine electronic controller and a transmission electronic controller, wherein the transmission electronic controller is configured to communicate a request for the estimated power output value to the engine electronic controller.

13. The machine of claim 12, wherein the engine electronic controller is configured to select the estimated power output value corresponding to the proposed gear ratio and the current engine speed from a lug curve stored in a memory.

14. The machine of claim 12, wherein the engine electronic controller is configured to adjust the estimated power output value by a value corresponding to the derated operating condition.

15. The machine of claim 14, wherein the engine electronic controller is further configured to adjust the estimated power output value based on at least one parasitic load corresponding to the current engine speed.

16. The machine of claim 14, wherein the engine electronic controller is further configured to communicate the estimated power output value to the transmission electronic controller.

17. The machine of claim 16, wherein the transmission electronic controller is further configured to delay the upshift if the estimated power output value is less than the current power output value.

18. A method of reducing an occurrence of a gear hunting event in an automatic transmission of a machine, comprising:

identifying an upcoming gear ratio change from a current gear ratio to a proposed gear ratio based on a predetermined shift point;

determining an estimated power output value based on the proposed gear ratio and a current engine speed;

adjusting the estimated power output value based on a derated operating condition;

changing the current gear ratio to the proposed gear ratio if the estimated power output value is greater than or equal to a current power output value; and

adjusting the predetermined shift point if the estimated power output value is less than the current power output value.

19. The method of claim 18, wherein the step of adjusting the predetermined shift point includes maintaining the current gear ratio.

20. The method of claim 19, further including delaying the upcoming gear ratio change until the estimated power output value is greater than or equal to the current power output value.