System for determining an equivalent throttle valve for controlling automatic transmission shift points

• US 6,308,124 B1
• Filed: 11/16/1998
• Issued: 10/23/2001
• Est. Priority Date: 11/16/1998
• Status: Expired due to Term

• Current Assignee: Cummins Engine Company Incorporated (Cummins Incorporated)
• Original Assignee: Cummins Engine Company Incorporated (Cummins Incorporated)
• Inventors: West, Stephen, Kresse, John P.
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): To, Tuan C
• Application Number:
  US09/193,057
• Time in Patent Office: 1,072 Days
• Field of Search: 701/53, 180/175, 180/177, 123/361, 477/408
• US Class Current: 701/53
• CPC Class Codes: F16H 59/24 dependent on the throttle opening
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals

Abstract

A system is disclosed for determining an effective throttle value of an internal combustion engine for controlling automatic transmission shift points. In one embodiment, the system is operable to determine an effective throttle value as a function of commanded fueling and engine speed under operating conditions wherein engine torque is requested by a system/component other than manual throttle control to thereby provide a throttle value indicative of what throttle position or percentage would be under present operating conditions if engine torque was being requested via manual throttle control. The present invention accordingly overcomes deficiencies in known automatic transmission shift point control systems by continuously computing an equivalent throttle percentage whenever fueling or requested torque values are not dominated by actual throttle (e.g. accelerator pedal) percentage. The equivalent throttle parameter value is approximately what the throttle percentage would be if manual throttle percentage was the dominant source of requested torque. Transmission shift point logic may resultantly be simplified by basing transmission shift points on the equivalent throttle parameter during non-manual fueling control just as transmission shift points are based on throttle percentage during manual fueling conditions.

Claims

1. System for determining an equivalent throttle value, comprising:

means for determining engine speed of an internal combustion engine and producing an engine speed signal corresponding thereto;

an accelerator pedal responsive to manual actuation thereof to produce a first torque request signal;

means for producing a second torque request signal; and

a control computer producing a fueling command as a function of a dominant one of said first and second torque request signals, said control computer producing an equivalent throttle value as a function of said engine speed signal and said fueling command when said second torque request signal is dominant over said first torque request signal, said equivalent throttle value corresponding to a relative position of said accelerator pedal otherwise required to produce engine operating conditions defined by said engine speed signal and said fueling command.

2. The system of claim 1 wherein said control computer is operable to produce a real throttle value corresponding to a relative position of said accelerator pedal when said first torque request signal is dominant over said second torque request signal.

3. The system of claim 1 wherein said means for producing a second torque request includes a power-take-off (PTO) unit.

4. The system of claim 1 wherein said means for producing a second torque request includes a cruise control unit.

5. The system of claim 1 further including:

a transmission operatively connected to said engine, said transmission having a number of automatically selectable gear ratios; and

a transmission control computer associated with said transmission, said transmission control computer responsive to said equivalent throttle value to control engine speed shift points of said number of automatically selectable gear ratios as a function thereof when said second torque request signal is dominant over said first torque request signal.

6. The system of claim 5 wherein said control computer is an engine control computer operable to control operation of said engine.

7. The system of claim 1 further including a transmission operatively connected to said engine, said transmission having a number of automatically selectable gear ratios;

and wherein said control computer is a transmission control computer associated with said transmission, said transmission control computer controlling engine speed shift points of said number of automatically selectable gear ratios as a function of said equivalent throttle value when said second torque request signal is dominant over said first torque request signal.

8. The system of claim 1 wherein said control computer includes a memory having stored therein a look-up table of equivalent throttle values, said control computer operable to produce said equivalent throttle value by mapping said fueling command and said engine speed signal to an appropriate one of said equivalent throttle values stored in said memory.

9. The system of claim 1 wherein said control computer includes a tracking estimator control loop having as inputs said engine speed signal and said fueling command, said tracking estimator control loop determining said equivalent throttle value based on said fueling command and said engine speed signal.

10. The system of claim 9 wherein said tracking estimator control loop includes:

means responsive to said engine speed signal for computing an average engine speed value;

means responsive to a first error value corresponding to a difference between said fueling command and an equivalent fueling value for computing an equivalent engine speed value;

means responsive to a second error value corresponding to a difference between said equivalent engine speed value and said average speed value for computing a first fueling value as a function of a throttle droop value;

means responsive to said equivalent engine speed value for computing a second fueling value as a function thereof;

means for computing said equivalent fueling value as a function of said first and second fueling values; and

means responsive to said equivalent engine speed value for computing said equivalent throttle value.

11. The system of claim 10 wherein said system further includes a cooling system associated with said engine, said cooling system having a coolant medium therein and a coolant sensor operable to determine a temperature of said coolant medium and produce a coolant temperature signal corresponding thereto;

and wherein said tracking estimator control loop further includes means responsive to said coolant temperature signal for computing a third fueling value as a function thereof;

and wherein said means for computing said equivalent fueling value as a function of said first and second fueling values further includes means for computing said equivalent fueling value as a function of said first, second and third fueling values.

12. The system of claim 1 further including a data bus connected to said control computer;

and wherein said control computer is operable to broadcast said equivalent throttle value over said data bus.

13. The system of claim 12 wherein said serial data bus is a SAE J1939 data bus.

14. The system of claim 1 further including a fuel system responsive to said fueling command to supply fuel to said engine.

15. The system of claim 3 wherein said control computer is operable to increase said effective throttle value as a function of said engine speed signal and a reference speed of said PTO unit if said fueling command indicates that output torque of said engine is limited by a maximum engine torque value at a present engine speed indicated by said engine speed signal and said reference speed of said PTO unit is greater than said present engine speed.

16. The system of claim 15 wherein said control computer is operable to determine a speed error as a difference between said reference speed of said PTO unit and said present engine speed and further determine a rate of change of said effective throttle value as a function of said speed error if said speed error greater than zero.

17. The system of claim 15 wherein said control computer is operable to decrease said effective throttle value at said rate of change of said effective throttle value until said speed error is substantially eliminated if said speed error is less than zero.

18. The system of claim 4 further including means for determining vehicle speed and producing a vehicle speed signal corresponding thereto;

and wherein said control computer is operable to increase said effective throttle value as a function of said vehicle speed signal and a reference speed of said cruise control unit if said fueling command indicates that output torque of said engine is limited by a maximum engine torque value at a present engine speed indicated by said engine speed signal and said reference speed of said cruise control unit is greater than a present vehicle speed indicated by said vehicle speed signal.

19. The system of claim 18 wherein said control computer is operable to determine a speed error as a difference between said reference speed of said cruise control unit and said present vehicle speed and further determine a rate of change of said effective throttle value as a function of said speed error if said speed error greater than zero.

20. The system of claim 19 wherein said control computer is operable to decrease said effective throttle value at said rate of change of said effective throttle value until said speed error is substantially eliminated if said speed error is less than zero.

22. The method of claim 16 further including the step of basing engine speed shift points of a transmission coupled to said engine on said equivalent throttle value when said second fueling request is dominant over said first fueling request.

21. A method of producing an equivalent throttle value, comprising the steps of:

determining an engine speed value corresponding to engine speed of an internal combustion engine;

determining a first torque request corresponding to manual actuation of an accelerator pedal;

determining a second torque request corresponding to actuation of a torque requesting device separate from said accelerator pedal;

producing a fueling command as a function of a dominant one of said first and second torque requests; and

producing an equivalent throttle value as a function of said fueling command and said second torque request when said second torque request is dominant over said first torque request, said equivalent throttle value corresponding substantially to a relative position of said accelerator pedal otherwise required to produce engine operating conditions defined by said engine speed and said fueling command.