System and method for controlling engine torque

• US 6,279,531 B1
• Filed: 08/09/1999
• Issued: 08/28/2001
• Est. Priority Date: 08/09/1999
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pallett, Tobias John, Robichaux, Jerry Dean
• Primary Examiner(s): Kwon, John
• Application Number:
  US09/370,234
• Time in Patent Office: 750 Days
• Field of Search: 123/339.19, 123/350, 123/352, 123/353, 123/354, 123/355, 123/361, 180/197
• US Class Current: 123/339.19
• CPC Class Codes: F02D 2041/0017 by simultaneous control of throttle and exhaust gas recirculation
• CPC Class Codes: F02D 2041/1409 using at least a proportional, integral or derivative controller
• CPC Class Codes: F02D 2041/1422 Variable gain or coefficients
• CPC Class Codes: F02D 2200/1004 Estimation of the output torque
• CPC Class Codes: F02D 2200/1006 Engine torque losses, e.g. friction or pumping losses or losses caused by external loads of accessories
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/083 taking into account engine load variation, e.g. air-conditionning
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine
• CPC Class Codes: F02P 5/1504 with particular means during a transient phase, e.g. acceleration, deceleration, gear change during starting F02P5/1506
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system and method for controlling an engine include determining a desired engine brake torque and modifying the desired engine brake torque based on current engine operating conditions to determine a requested engine brake torque prior to determination of control parameters, including at least one of an airflow and a fuel quantity, to effect the requested engine brake torque. Preferably, the desired engine brake torque is modified by combining the desired engine brake torque with an idle speed torque to generate a first intermediate torque, comparing the first intermediate torque to an actual engine brake torque to generate a second intermediate torque, generating a feedback correction torque based on the second intermediate torque, and combining the first intermediate torque, the feedback correction torque, and a third intermediate torque to determine the requested engine brake torque, where the third intermediate torque represents accessory load or a frictional torque loss which varies with temperature.

Claims

1. A method for controlling an engine, the method comprising:

determining a desired engine brake torque based on accelerator pedal position, barometric pressure and speed;

adjusting the desired engine brake torque to generate a requested engine brake torque based on current operating conditions; and

controlling at least one operating parameter of the engine based on the requested engine brake torque to deliver the desired engine brake torque.

2. The method of claim 1 wherein the speed comprises a vehicle speed.

3. The method of claim 1 wherein the speed comprises an engine speed.

4. The method of claim 1 wherein the step of adjusting the desired engine brake torque comprises:

combining the desired engine brake torque with an idle speed torque, the idle speed torque determined at least in part based on a desired engine speed.

5. The method of claim 1 wherein the step of adjusting the desired engine brake torque comprises:

determining an actual engine brake torque; and

comparing the actual engine brake torque to the desired engine brake torque to generate a torque error.

6. The method of claim 5 wherein the step of determining an actual engine brake torque comprises estimating an actual engine brake torque based on current engine operating parameters.

7. The method of claim 6 wherein the step of estimating an actual engine brake torque comprises estimating an actual engine brake torque based on at least engine speed, engine temperature, airflow, ignition angle, and relative camshaft timing.

8. The method of claim 5 wherein the step of adjusting the desired engine brake torque further comprises generating a requested brake torque based on the torque error to drive the torque error toward zero.

9. The method of claim 8 wherein the step of generating a requested brake torque based on the torque error comprises applying the torque error to a PID feedback controller.

10. The method of claim 8 wherein the PID feedback controller includes a proportional term, an integral term, and a derivative term, and wherein the proportional and derivative terms are set to zero and the integral term is held constant during transient torque control modes.

11. The method of claim 10 wherein the transient torque control modes include a traction assist mode and an idle speed control mode.

12. The method of claim 1 wherein the step of adjusting the desired engine brake torque comprises combining an accessory brake torque with the desired engine brake torque.

13. The method of claim 12 wherein the accessory brake torque includes an estimate of torque required to operate an air conditiong compressor.

14. The method of claim 12 wherein the accessory brake torque includes an estimate of frictional losses based on engine temperature and engine speed.

15. The method of claim 1 wherein the step of controlling at least one operating parameter comprises controlling airflow.

16. The method of claim 1 wherein the step of controlling at least one operating parameter comprises controlling fuel delivery.

17. The method of claim 1 wherein the step of controlling at least one operating parameter comprises controlling air/fuel ratio.

18. A method for controlling an engine, the method comprising:

determining a desired engine brake torque; and

modifying the desired engine brake torque based on current engine operating conditions to determine a requested engine brake torque prior to determination of control parameters, including at least one of an airflow and a fuel quantity, to effect the requested engine brake torque by combining the desired engine brake torque with an idle speed torque to generate a first intermediate torque, comparing the first intermediate torque to an actual engine brake torque to generate a second intermediate torque, generating a feedback correction torque based on the second intermediate torque, and combining the first intermediate torque, the feedback correction torque, and a third intermediate torque to determine the requested engine brake torque.

19. The method of claim 18 wherein the third intermediate torque represents torque required to operate at least one engine accessory.

20. The method of claim 18 wherein the third intermediate torque varies as a function of temperature and engine speed.

21. The method of claim 18 wherein the step of comparing the first intermediate torque comprises estimating the actual engine brake torque based on ignition angle, air/fuel ratio, engine coolant temperature, engine speed, air flow, and accessory load.

22. The method of claim 18 wherein the step of generating a feedback correction torque comprises:

determining proportional, integral, and derivative terms wherein the proportional and derivative terms are set to zero and the integral term is held constant during at least one engine control mode.