Apparatus and methods for controlling idling speed of an internal combustion engine by reducing torque fluctuations

• US 6,085,723 A
• Filed: 09/03/1999
• Issued: 07/11/2000
• Est. Priority Date: 03/06/1997
• Status: Expired due to Fees

• Current Assignee: Isad Electronic Systems GmbH & Co. KG
• Original Assignee: Isad Electronic Systems GmbH & Co. KG
• Inventors: Revermann, Klaus, Pels, Thomas, Zeyen, Klaus-Peter
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US09/389,546
• Time in Patent Office: 312 Days
• Field of Search: 123/192.1, 123/192.2, 123/339.1, 123/339.22, 123/339.24, 123/406.24, 123/406.25, 123/436, 290/40 A, 701/111
• US Class Current: 123/339.22
• CPC Class Codes: F02B 75/06 Engines with means for equalising torque
• CPC Class Codes: H02P 29/0016 Control of angular speed of one shaft without controlling the prime mover

Abstract

Apparatus and methods are disclosed for controlling the idling speed of an internal combustion engine by reducing torque fluctuations experienced by the engine. In the disclosed apparatus, an electric machine is coupled to the drive shaft of an internal combustion engine. The electric machine is controlled such that it applies a varying torque substantially in counterphase to the torque fluctuations to reduce such fluctuations. The amplitude of the torque variations applied by the electric machine in the cold state of the internal combustion engine are greater than in the warm state. An idle control system functions to maintain the reference idling speed of the internal combustion engine in the cold state below or at the same level set in the warm state. The reference idling speed can be reduced relative to the idling speeds set in prior art systems to achieve enhanced engine performance.

Claims

1. For use with a vehicle having an internal combustion engine that exhibits torque fluctuations during idling, the internal combustion engine having a cold temperature state and a warm temperature state, an apparatus comprising:

at least one electric machine coupled to the internal combustion engine for applying a torque with a varying amplitude to the internal combustion engine to reduce the torque fluctuations, the amplitude of the torque applied to the internal combustion engine by the electric machine being greater when the internal combustion engine is in the cold temperature state than when the internal combustion engine is in the warm temperature state; and

an idle control system for setting an average target idling speed for the internal combustion engine, wherein the idle control system sets the average target idling speed at a first level when the internal combustion engine is in the warm temperature state and at a second level when the internal combustion engine is in the cold state, the second level being the same or lower than the first level.

2. An apparatus as defined in claim 1 wherein the control system sets an average target idling speed of the internal combustion engine that is closer to a critical speed of the internal combustion engine then could be set in the absence of the varying torque applied by the electric machine.

3. An apparatus as defined in claim 1 wherein the torque applied to the internal combustion engine by the at least one electric machine includes a constant torque component and a varying torque component which is superimposed on the constant torque component.

4. An apparatus as defined in claim 1 wherein the amplitude of the varying torque is selected based on a temperature associated with the internal combustion engine, and the torque adjustment is performed via at least one of closed loop control and open loop control.

5. An apparatus as defined in claim 1 wherein the torque adjustment is performed via closed loop control.

6. An apparatus as defined in claim 1 wherein the average target idling speed set by the idle control system is substantially the same in the cold temperature state and the warm temperature state.

9. A method as defined in claim 6 further comprising the steps of:

(a) measuring the torque fluctuation experienced by the internal combustion engine;

(b) comparing the measured torque fluctuation to a predetermined value;

(c) if the measured torque value exceeds the predetermined value, determining a new expected torque fluctuation value; and

(d) employing at least one of the new expected torque fluctuation value and a value derived from the new expected torque fluctuation value instead of the at least one expected torque fluctuation value read from the database to control the electric machine coupled to the internal combustion engine to apply a varying torque to the internal combustion engine to thereby reduce torque fluctuations associated with the internal combustion engine.

10. A method as defined in claim 9 wherein at least the steps (a) and (b) are performed periodically.

7. A method of controlling the idling speed of an internal combustion engine comprising the steps of:

measuring a temperature associated with the internal combustion engine;

reading at least one expected torque fluctuation value associated with the measured temperature from a torque fluctuation database;

employing the at least one expected torque fluctuation value to control an electric machine coupled to the internal combustion engine to apply a varying torque to the internal combustion engine to thereby reduce torque fluctuations associated with the internal combustion engine; and

setting a first average target idling speed for the internal combustion engine when the measured temperature indicates that the internal combustion engine is in a warm state; and

setting a second average target idling speed when the measured temperature indicates that the internal combustion engine is in a cold state, the second average target idling speed being the same or lower than the first average target idling speed.

8. A method as defined in claim 7 wherein the torque fluctuation database is representative of a map.

11. For use with a vehicle having an internal combustion engine that exhibits torque fluctuations during idling, the internal combustion engine having a drive shaft, a cold state and a warm state, an apparatus comprising:

a temperature sensor positioned to detect a temperature associated with the internal combustion engine;

an electric machine operatively coupled to the drive shaft for applying a torque thereto;

a memory storing a torque fluctuation database associating expected torque fluctuation values with temperatures; and

a control circuit in communication with the temperature sensor, the electric machine and the memory, the control circuit retrieving an expected torque fluctuation value associated with a measured temperature from the memory and controlling the electric machine to produce a varying torque which is at least initially based on the retrieved expected torque fluctuation value to thereby reduce the torque fluctuations of the internal combustion engine, the control circuit being adapted to set an average target idling speed for the internal combustion engine that is independent of the sensed temperature.

12. An apparatus as defined in claim 11 wherein the control circuit applies a varying torque to the internal combustion engine in both the warm state and the cold state.

13. An apparatus as defined in claim 12 wherein the varying torque applied during the warm state has a smaller amplitude than the varying torque applied during the cold state.

14. An apparatus as defined in claim 11 wherein the control system sets an average target idling speed of the internal combustion engine that is closer to a critical speed of the internal combustion engine then could be set in the absence of the varying torque while maintaining a substantially unchanged safety margin between a critical speed and the lowest expected instantaneous idling speed.

15. An apparatus as defined in claim 11 wherein the control system sets an average target idling speed employing an increased safety margin relative to a safety margin required in the absence of the varying torque.

16. An apparatus as defined in claim 11 wherein the control circuit comprises a microcontroller.

17. An apparatus as defined in claim 11 wherein the control circuit periodically (a) measures the torque fluctuation experienced by the internal combustion engine;

(b) compares the measured torque fluctuation to a predetermined value;

(c) if the measured torque fluctuation value exceeds the predetermined value, determines a new expected torque fluctuation value; and

(d) employs at least one of the new expected torque fluctuation value and a value derived from the new expected torque fluctuation value instead of the expected torque fluctuation value read from the memory to control the electric machine coupled to the internal combustion engine to apply a varying torque to the internal combustion engine to thereby reduce torque fluctuations associated with the internal combustion engine.

18. An apparatus as defined in claim 11 wherein the retrieved expected torque fluctuation value comprises a magnitude value and a phase value.

19. An apparatus as defined in claim 11 further comprising an energy storage device for temporarily storing energy developed by the electric machine when the varying torque acts as a braking torque and for providing energy to the electric machine when the varying torque acts as a driving torque.

20. An apparatus as defined in claim 11 further comprising a rotational position sensor located to sense an angular position of the drive shaft wherein the control circuit receives signals from the rotational position sensor, and the control circuit employs the received signals to apply the varying torque in counterphase to the torque fluctuations of the internal combustion engine.

21. A method of controlling the idling speed of an internal combustion engine comprising the steps of:

controlling an electric machine coupled to the internal combustion engine to apply a varying torque having a first amplitude to the internal combustion engine when the internal combustion engine is in a cold temperature state to thereby reduce torque fluctuations associated with the internal combustion engine;

controlling an electric machine coupled to the internal combustion engine to apply a varying torque having a second amplitude to the internal combustion engine when the internal combustion engine is in a warm temperature state to thereby reduce torque fluctuations associated with the internal combustion engine, the first amplitude being greater than the second amplitude;

setting a first average target idling speed for the internal combustion engine when the internal combustion engine is in a warm state; and

setting a second average target idling speed when the internal combustion engine is in a cold state, the second average target idling speed being the same or lower than the first average target idling speed.