Method and apparatus for controlling air-fuel ratio in an internal combustion engine by corrective feedback control

• US 4,853,862 A
• Filed: 01/22/1986
• Issued: 08/01/1989
• Est. Priority Date: 01/23/1985
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Shiraishi, Takashi, Hasegawa, Taiji
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/820,739
• Time in Patent Office: 1,287 Days
• Field of Search: 364/431.05, 364/431.06, 364/830, 364/831, 123/440, 123/489
• US Class Current: 701/108
• CPC Class Codes: F02D 41/1483 Proportional component

Abstract

A method of controlling air-fuel ratio in which addition or subtraction is carried out on the basis of the output of an exhaust gas sensor to determine a feedback constant by which the air-fuel ratio is feedback-controlled. The feedback constant is changed at a given regular interval.

Claims

1. An air-fuel ratio control system for an engine comprising:

exhaust gas sensor means for detecting a state of exhaust gas so as to produce an output signal indicating a state of an air-fuel ratio of the engine;

a processor unit for calculating a control value on the basis of the state of the exhaust gas by;

(a) comparing said output signal of said exhaust gas sensor with a predetermined value so as to produce a comparison result;

(b) generating in response to said comparison result a control signal having a first proportional correction component at a first period and a predetermined integral slope; and

(c) correcting said control signal by periodically adding a second proportional correction component thereto at a second period which is longer than said first period; and

means for controlling said air-fuel ratio on the basis of said corrected control signal.

2. A system according to claim 1, wherein said first period is of a fixed predetermined length and said second period varies with engine speed.

3. A system according to claim 1, wherein said further proportional correction component has a value which varies with engine speed.

4. A system according to claim 1, wherein said further proportional correction component has a value which varies with engine load.

5. A system according to claim 1, wherein said processor unit operates to add said second proportional correction component at a selected interval which is not related to the timing of the output of said exhaust gas sensor, while maintaining the value of said predetermined integral slope without change.

6. A method of controlling an air-fuel ratio for an engine comprising the steps of:

(a) detecting an output of an O₂ sensor;

(b) comparing an output of said O₂ sensor which indicates a state of an air-fuel ratio of the engine with a predetermined value so as to produce a comparison result;

(c) generating a control signal having a first proportional correction component and a predetermined integral slope based on said comparison result of the comparison in step (a), said steps (a), (b) and (c) being executed periodically at a first period;

(d) adding a second proportional correction component to said control signal generated in step (c), to produce a corrected control signal, said step (d) being executed periodically at a second period which is longer than said first period; and

(e) controlling the air-fuel ratio on the basis of said corrected control signal.

7. A method according to claim 6, wherein said second proportional correction component is added to said control signal while maintaining said predetermined integral slope without change.

8. A method according to claim 6, wherein said second proportional correction component has a value which varies with engine speed.

9. A method according to claim 6, wherein said second proportional correction component has a value which varies with engine load.