Engine control method

• US 5,909,724 A
• Filed: 03/25/1997
• Issued: 06/08/1999
• Est. Priority Date: 03/29/1996
• Status: Expired due to Fees

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Taga, Junichi, Nishimura, Hirofumi, Watanabe, Tomomi, Imada, Michihiro
• Primary Examiner(s): Solis, Erick R.
• Application Number:
  US08/826,806
• Time in Patent Office: 805 Days
• Field of Search: 123/295, 123/436, 123/679
• US Class Current: 123/436
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 2200/1015 Engines misfires
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: G01M 15/046 by monitoring revolutions for detecting misfire G01M15/11
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

An engine combustion condition judging method for detecting a crank angle speed of a multiple cylinder engine, for judging a combustion condition of each of cylinders of the engine based on the detection of the crank angle speed, wherein the improvement includes the steps of setting a predetermined crank angle range selectively determined within a range between a crank angle at which a combustion substantially terminate in a given cylinder and another crank angle at which a combustion substantially start in the next cylinder for detecting a crank angle speed property, and judging the combustion condition based on said crank angle speed property within the predetermined crank angle range. The combustion condition can be obtained reliably so that an appropriate A/F control can be accomplished irrespective of the engine operating condition.

Claims

1. An engine combustion condition judging method for detecting a crank angle speed of a multiple cylinder engine to judge a combustion condition of each of cylinders of the engine based on the detection of the crank angle speed, wherein the improvement comprises steps of;

setting a predetermined crank angle range selectively determined within a range between a crank angle at which a combustion substantially terminates in a given cylinder and another crank angle at which a combustion substantially starts in the next cylinder to the given cylinder in an engine cycle for detecting a crank angle speed property, and judging the combustion condition based on said crank angle speed property within said predetermined crank angle range.

2. A method as recited in claim 1 wherein said predetermined crank angle range for detecting the crank angle speed property is determined in a second half of an expansion stroke of the engine cycle.

3. A method as recited in claim 1 wherein said predetermined crank angle range is determined within a range of 100°

crank angle to 200°

crank angle after a top dead center of the second half of the expansion stroke.

4. A method as recited in claim 1 wherein said the predetermined crank angle range is set not smaller than 60°

crank angle.

5. A method as recited in claim 1 wherein a crank angle speed or equivalent thereof is measured for detecting the crank angle speed property, and wherein frequency components corresponding to an engine explosive rotation degree are excluded in detecting the crank angle speed property.

6. A method as recited in claim 1 wherein the engine is provided with multiple cylinders, each of which combustion condition is judged, wherein a crank angle speed or equivalent thereof is measured for detecting the crank angle speed property, and wherein frequency components corresponding to an engine explosive rotation degree are excluded in detecting the crank angle speed property.

7. A method as recited in claim 1 wherein the frequency components corresponding to the explosive rotation degree of the engine can be removed by obtaining a difference in the detected data of the crank angle speed between the current cycle and the precedent cycle to obtain a crank angle speed change profile.

8. A method as recited in claim 6 wherein the frequency components corresponding to the engine explosive rotation degree is removed only in the high engine speed range.

9. A method as recited in claim 6 wherein a crank angle speed or equivalent thereof is measured for detecting the crank angle speed property, and wherein frequency components having degrees lower than 0.5 of the engine rotation is excluded in detecting the crank angle speed property.

10. An engine control method comprising steps of;

detecting a crank angle speed of a multiple cylinder engine, for judging a combustion condition of each of cylinders of the engine based on the detection of the crank angle speed,

setting a predetermined crank angle range selectively determined within a range between a crank angle at which a combustion substantially terminates in a given cylinder and another crank angle at which a combustion substantially starts in the next cylinder for detecting a crank angle speed property, and judging the combustion condition based on said crank angle speed property within the predetermined crank angle range, and

controlling an air fuel ratio based on the judgment of the combustion condition in a lean burn operation in which the air fuel ratio is controlled to a value greater than the theoretical value in a predetermined operating range of the engine.

11. A method as recited in claim 10 wherein an air fuel control ratio gain is controlled based on the combustion condition.

12. An engine control system, comprising;

crank angle speed detecting means for detecting a crank angle speed or equivalent thereto of an engine in a predetermined crank angle range selectively determined within a range between a crank angle at which a combustion substantially terminates in a given cylinder and another crank angle at which a combustion substantially starts in the next cylinder for detecting a crank angle speed property,

combustion condition judging means for judging the combustion condition based on said crank angle speed property within the predetermined crank angle range, and,

air fuel ratio control means for controlling an air fuel ratio of the engine in accordance with the judgment of the combustion condition judging means.

13. An engine control system as recited in claim 12 further comprising detected data processing means for excluding frequency components corresponding to an engine explosive rotation degree and those having degrees lower than 0.5 degree of the engine rotation.

14. An engine control system as recited in claim 12 wherein the air fuel ratio control means comprises an air fuel control gain setting means for setting a target air fuel control gain which provides a greater air fuel ratio than a theoretical air fuel ratio in a predetermined lean burn operation range and an air fuel ratio control gain compensation means for compensating the air fuel control gain base on the judgement to the combustion condition judgement means.

15. An engine control system as recited in claim 12 wherein the combustion condition judging means judges the combustion condition in the cylinder by comparing the crank angle speed change property with a first set value and a second set value lower than the first set value, the air fuel ratio compensation means compensates the air fuel ratio control gain to make an intake gas mixture rich when the crank angle speed fluctuation is greater than the first set value, and make the intake gas mixture lean when the crank angle speed fluctuation is smaller than the second set value.

16. An engine control system as recited in claim 12 wherein the crank angle speed detecting means detects the crank angle speed property or equivalent there to of the engine in the predetermined crank angle range selectively determined within the crank angle range between 100°

crank angle and 200°

crank angle after top dead center in the expansion stroke.