System and Method for Controlling Transmission Shift Points Based on Vehicle Weight

• US 20090036267A1
• Filed: 08/02/2007
• Published: 02/05/2009
• Est. Priority Date: 08/02/2007
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Bellinger, Steven M.
• Granted Patent: US 7,966,115 B2
• Time in Patent Office: Days
• US Class Current: 477/97
• CPC Class Codes: F16H 2061/0232 Selecting ratios for bringing engine into a particular state, e.g. for fast warming up or for reducing exhaust emissions
• CPC Class Codes: F16H 2061/216 by using exhaust brakes
• CPC Class Codes: F16H 59/52 dependent on the weight of the machine, e.g. change in weight resulting from passengers boarding a bus
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals
• CPC Class Codes: F16H 61/143 using electric control means
• CPC Class Codes: Y10S 700/90 Special robot structural element

Abstract

A system and method of controlling shift points of a transmission coupled to an internal combustion engine by modifying at least one transmission shift point schedule may comprise determining a weight of a vehicle carrying the engine and the transmission, modifying the at least one transmission shift point schedule as a function of the weight of the vehicle, and controlling automatic shifting between two or more gear ratios of the transmission in accordance with the modified at least one transmission shift point schedule.

Claims

1. A system for controlling shift points of a transmission carried by a motor vehicle, comprising:

means for determining a weight of the vehicle,

a memory unit having stored therein at least one transmission shift point schedule and having stored therein at least one set of instructions, and

a control circuit configured to execute the at least one set of instructions to modify the at least one transmission shift point schedule as a function of the weight of the vehicle and to control automatic shifting between two or more gear ratios of the transmission in accordance with the modified at least one transmission shift point schedule.

2. The system of claim 1 wherein the transmission includes a tailshaft coupled to at least one wheel of the vehicle,

and wherein the control circuit is configured to determine a throttle position as a function of user-requested fueling,

and wherein the at least one transmission shift point schedule comprises at least one default transmission shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a vehicle weight that is one of or between a minimum weight of the vehicle and a maximum weight of the vehicle

and wherein the control circuit configured to execute the at least one set of instructions to determine the modified at least one transmission shift point schedule as a function of the at least one default transmission shift point schedule.

3. The system of claim 2 wherein the at least one default transmission shift point schedule comprises a default upshift schedule,

and wherein the control circuit is configured to execute the at least one set of instructions to modify the default upshift schedule by extrapolating the default upshift schedule to lower rotational speeds of the tailshaft than those of the default upshift schedule if the weight of the vehicle is below that upon which the default upshift schedule is based, and by extrapolating the default upshift schedule to higher rotational speeds of the tailshaft than those of the default upshift schedule if the weight of the vehicle is above that upon which the default upshift schedule is based.

4. The system of claim 3 further comprising a torque converter positioned between an internal combustion engine carried by the vehicle and the transmission, the torque converter operable in either of a lockup mode wherein a drive shaft of the engine is coupled directly to an input shaft of the transmission and a torque converter mode wherein the drive shaft of the engine is fluidly coupled to the input shaft of the transmission.

5. The system of claim 4 wherein the default upshift schedule corresponds to a default lockup upshift schedule when the torque converter is operating in lockup mode.

6. The system of claim 4 wherein the default upshift schedule corresponds to a normal default upshift schedule when the torque converter is operating in torque converter mode.

7. The system of claim 2 wherein the at least one default transmission shift point schedule comprises a default downshift schedule,

and wherein the control circuit is configured to execute the at least one set of instructions to modify the default downshift schedule by extrapolating the default downshift schedule to higher rotational speeds of the tailshaft than those of the default downshift schedule if the weight of the vehicle is above that upon which the default downshift schedule is based, and by extrapolating the default downshift schedule to lower rotational speeds of the tailshaft than those of the default downshift schedule if the weight of the vehicle is above that upon which the default downshift schedule is based.

8. The system of claim 7 further comprising a torque converter positioned between an internal combustion engine carried by the vehicle and the transmission, the torque converter operable in either of a lockup mode wherein a drive shaft of the engine is coupled directly to an input shaft of the transmission and a torque converter mode wherein the drive shaft of the engine is fluidly coupled to the input shaft of the transmission.

9. The system of claim 8 wherein the default downshift schedule corresponds to a default lockup downshift schedule when the torque converter is operating in lockup mode.

10. The system of claim 8 wherein the default downshift schedule corresponds to a normal default downshift schedule when the torque converter is operating in torque converter mode.

11. The system of claim 7 further comprising an engine brake system configured when activated to selectively apply a retarding force to an internal combustion engine coupled to the transmission,

wherein the default downshift schedule corresponds to an engine brake default downshift schedule when the engine brake system is activated.

12. The system of claim 1 wherein the transmission includes a tailshaft coupled to at least one wheel of the vehicle,

and wherein the control circuit is configured to determine a throttle position as a function of user-requested fueling,

and wherein the at least one transmission shift point schedule comprises a low speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a minimum weight of the vehicle, and a high speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a maximum weight of the vehicle, the low speed shift point schedule being defined at lower rotational speeds of the tailshaft than the high speed shift point schedule

and wherein the control circuit configured to execute the at least one set of instructions to determine the modified at least one transmission shift point schedule as a function of at least one of the low speed shift point schedule and the high speed shift point schedule.

13. The system of claim 12 wherein the control circuit is configured to execute the at least one set of instructions to modify the at least one transmission shift point schedule by extrapolating between the low speed shift point schedule and the high speed shift point schedule as a function of the weight of the vehicle.

14. The system of claim 13 wherein the control circuit is configured to execute the at least one set of instructions to control shifting between the two or more gear ratios of the transmission in accordance with the low speed shift point schedule if the weight of the vehicle is within a first threshold weight range of the minimum weight of the vehicle.

15. The system of claim 13 wherein the control circuit is configured to execute the at least one set of instructions to control shifting between the two or more gear ratios of the transmission in accordance with the high speed shift point schedule if the weight of the vehicle is within a second threshold weight range of the maximum weight of the vehicle.

16. The system of claim 13 further comprising a torque converter positioned between an internal combustion engine carried by the vehicle and the transmission, the torque converter operable in either of a lockup mode wherein a drive shaft of the engine is coupled directly to an input shaft of the transmission and a torque converter mode wherein the drive shaft of the engine is fluidly coupled to the input shaft of the transmission.

17. The system of claim 16 wherein the low speed shift point schedule corresponds to a low speed lockup upshift schedule and the high speed shift point schedule corresponds to a high speed lockup upshift schedule when the torque converter is operating in lockup mode.

18. The system of claim 16 wherein the low speed shift point schedule corresponds to a low speed normal upshift schedule and the high speed shift point schedule corresponds to a high speed normal upshift schedule when the torque converter is operating in lockup mode.

19. The system of claim 16 wherein the low speed shift point schedule corresponds to a low speed lockup downshift schedule and the high speed shift point schedule corresponds to a high speed lockup downshift schedule when the torque converter is operating in lockup mode.

20. The system of claim 16 wherein the low speed shift point schedule corresponds to a low speed normal downshift schedule and the high speed shift point schedule corresponds to a high speed normal downshift schedule when the torque converter is operating in lockup mode.

21. The system of claim 13 further comprising an engine brake system configured when activated to selectively apply a retarding force to an internal combustion engine coupled to the transmission,

wherein the low speed shift point schedule corresponds to a low speed engine brake downshift schedule and the high speed shift point schedule corresponds to a high speed engine brake downshift schedule when the engine brake system is activated.

22. The system of claim 1 wherein the vehicle further includes an accelerator pedal, and further comprising:

a speed sensor configured to produce a speed signal corresponding to rotational speed of the tailshaft, and

a position sensor configured to produce a position signal corresponding to a position of the accelerator pedal relative to a reference position,

wherein the control circuit is configured to control automatic shifting of the transmission between the two or more gear ratios according to the modified at least one transmission shift point schedule based on the speed signal and the position signal.

23. A system for controlling shift points of a transmission coupled to an internal combustion engine and having a number of automatically selectable gear ratios, the system comprising:

a first control circuit configured to control operation of the engine and to determine a weight of a motor vehicle carrying the engine and the transmission,

a memory unit having stored therein at least one transmission shift point schedule and at least one set of instructions, and

a second control circuit configured to receive from the first control circuit the weight of the vehicle and to execute the at least one set of instructions to modify the at least one transmission shift point schedule as a function of the weight of the vehicle and to control shifting between two or more of the automatically selectable gear ratios in accordance with the modified at least one transmission shift point schedule.

24. The system of claim 23 further comprising a communications interface via which the first and second control circuits exchange information.

25. The system of claim 23 wherein the transmission includes a tailshaft coupled to at least one wheel of the vehicle,

and wherein the control circuit is configured to determine a throttle position as a function of user-requested fueling,

and wherein the at least one transmission shift point schedule comprises at least one default transmission shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a vehicle weight that is one of or between a minimum weight of the vehicle and a maximum weight of the vehicle

and wherein the control circuit configured to execute the at least one set of instructions to determine the modified at least one transmission shift point schedule as a function of the at least one default transmission shift point schedule.

26. The system of claim 25 wherein the second control circuit is configured to execute the at least one set of instructions to modify tailshaft rotational speed values of the at least one default transmission shift point schedule as a function of the weight of the vehicle relative to that upon which the at least one default transmission shift point schedule is based.

27. The system of claim 23 wherein the transmission includes a tailshaft coupled to at least one wheel of the vehicle,

and wherein the control circuit is configured to determine a throttle position as a function of user-requested fueling,

and wherein the at least one transmission shift point schedule comprises a low speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a minimum weight of the vehicle, and a high speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a maximum weight of the vehicle, the low speed shift point schedule being defined at lower rotational speeds of the tailshaft than the high speed shift point schedule

and wherein the control circuit configured to execute the at least one set of instructions to determine the modified at least one transmission shift point schedule as a function of at least one of the low speed shift point schedule and the high speed shift point schedule.

28. The system of claim 27 wherein the second control circuit is configured to execute the at least one set of instructions to extrapolate between the low speed shift point schedule and the high speed shift point schedule as a function of the weight of the vehicle.

29. The system of claim 23 wherein the vehicle includes an accelerator pedal, and further comprising:

a speed sensor configured to produce a speed signal corresponding to rotational speed of the tailshaft, and

a position sensor configured to produce a position signal corresponding to a position of the accelerator relative to a reference position,

wherein the second control circuit is configured to execute the at least one set of instructions to control automatic shifting of the transmission between the two or more gear ratios according to the modified at least one transmission shift point schedule based on the rotational speed of the tailshaft and on the accelerator pedal position.

30. A method of controlling shift points of a transmission coupled to an internal combustion engine by modifying at least one transmission shift point schedule, the transmission having a number of automatically selectable gear ratios, the method comprising:

determining a weight of a vehicle carrying the engine and the transmission,

modifying the at least one transmission shift point schedule as a function of the weight of the vehicle, and

controlling automatic shifting between two or more gear ratios of the transmission in accordance with the modified at least one transmission shift point schedule.

31. The method of claim 30 further comprising storing in a memory unit the at least one transmission shift point schedule in the form of at least one default transmission shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of user-requested fueling in the form of a throttle position, rotational speed of the tailshaft and a vehicle weight that is one of or between a minimum weight of the vehicle and a maximum weight of the vehicle,

wherein modifying at least one transmission shift point schedule comprises modifying tailshaft rotational speed values of the at least one default transmission shift point schedule as a function of the weight of the vehicle relative to that upon which the at least one default transmission shift point schedule is based.

32. The method of claim 30 further comprising storing in a memory unit the at least one transmission shift point schedule in the form of a low speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of user-requested fueling in the form of a throttle position, rotational speed of the tailshaft and a minimum weight of the vehicle, and a high speed shift point schedule defining transmission shift points between two or more gear ratios of the transmission as a function of the throttle position, rotational speed of the tailshaft and a maximum weight of the vehicle,

wherein the low speed shift point schedule is defined at lower rotational speeds of the tailshaft than the high speed shift point schedule,

and wherein modifying at least one transmission shift point schedule comprises determining the modified at least one transmission shift point schedule as a function of at least one of the low speed shift point schedule and the high speed shift point schedule.

33. The method of claim 32 wherein determining the modified at least one transmission shift point schedule comprises extrapolating between the low speed shift point schedule and the high speed shift point schedule as a function of the weight of the vehicle.

34. The method of claim 32 further including controlling automatic shifting between two or more gear ratios of the transmission in accordance with the low speed shift point schedule if the weight of the vehicle is within a first threshold weight range of the minimum weight of the vehicle.

35. The method of claim 34 further including controlling automatic shifting between two or more gear ratios of the transmission in accordance with the high speed shift point schedule if the weight of the vehicle is within a second threshold weight range of the maximum weight of the vehicle.

36. The method of claim 35 wherein the first threshold weight range is different from the second threshold weight range.

37. The method of claim 35 wherein the first threshold weight range is equal to the second threshold weight range.

38. The method of claim 30 further comprising:

determining a rotational speed of a tailshaft coupled to the transmission,

determining a position of an accelerator pedal relative to a reference position, and

controlling automatic shifting of the transmission between the two or more gear ratios in accordance with the modified at least one transmission shift point schedule based on the rotational speed of the tailshaft and on the accelerator pedal position.