Method and apparatus for discriminating operativeness/inoperativeness of an air-fuel ratio sensor

• US 4,677,955 A
• Filed: 10/30/1985
• Issued: 07/07/1987
• Est. Priority Date: 11/30/1984
• Status: Expired due to Term

• Current Assignee: Nippondenso Company Limited 1-1 Showa-Cho Kariya-Shi Aichi Japan
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Takao, Mitsunori
• Primary Examiner(s): Argenbright, Tony M.
• Application Number:
  US06/792,929
• Time in Patent Office: 615 Days
• Field of Search: 123/440, 123/489
• US Class Current: 123/688
• CPC Class Codes: F02D 41/1474 by detecting the commutation time of the sensor
• CPC Class Codes: F02D 41/1479 Using a comparator with variable reference

Abstract

In an air-fuel ratio feedback control system for an engine having an air-fuel ratio sensor, operativeness/inoperativeness of the air-fuel ratio sensor is discriminated. An output signal of the air-fuel ratio sensor is compared and a difference thereof from a reference level is integrated for a predetermined internal of time. Integration value is compared with a discrimination reference so that a feedback control is disabled when the integration value does not attain the discrimination reference indicating inoperativeness of the air-fuel ratio sensor.

Claims

1. An apparatus for discriminating operativeness/inoperativeness of an air-fuel ratio sensor which produces an output signal indicative of air-fuel ratio, provided in an exhaust passage of an internal combustion engine so that an air-fuel ratio of mixture to said engine is feedback-controlled in response to an output signal of said air-fuel ratio sensor, said apparatus comprising:

means for comparing the output signal of said air-fuel ratio sensor with a predetermined reference level;

means for calculating a difference between the output signal of said air-fuel ratio sensor and said predetermined reference level;

means for integrating, for a predetermined interval of time, the difference calculated by said calculating means to produce an integration value;

means for comparing the integration value produced by said integrating means with a predetermined discrimination reference, so that operativeness/inoperativeness of said air-fuel ratio sensor is discriminated in response to a comparison output of said comparing means; and

means for enabling said difference calculating means to calculate said difference in response to an output of said output signal comparing means indicative of an attainment of the output signal of said air-fuel ratio sensor at the predetermined reference level.

2. An apparatus according to claim 1 further comprising means for disabling feedback control of the air-fuel ratio of mixture in response to the comparison output indicative of the inoperativeness of said air-fuel ratio sensor.

3. An apparatus according to claim 1, wherein said predetermined interval of time is longer than a cycle period in which said air-fuel ratio sensor, when operative, changes the output signal thereof across the predetermined reference level.

4. A method for discriminating operativeness/inoperativeness of an air-fuel ratio sensor which produces an output signal indicative of feedback control, provided in an exhaust passage of an internal combustion engine so that an air-fuel ratio of mixture to said engine is feedback-controlled in response to an output signal of said air-fuel ratio sensor, said method comprising the steps of:

comparing the output signal of said air-fuel ratio sensor with a predetermined reference level;

calculating a difference between the output signal of said air-fuel ratio sensor and the predetermined reference level;

integrating, for a predetermined interval of time, the difference calculated by said calculating step;

comparing an integration value produced by said integrating step with a predetermined discrimination reference, so that operativeness/inoperativeness of said air-fuel ratio sensor is discriminated in response to a comparison output of said comparing step; and

disabling said difference calculating step, and calculating a difference in the response to an output of said output comparing step which indicates that the output signal of said air-fuel ratio sensor is below the predetermined reference level.

5. A method according to claim 4, wherein said predetermined interval of time is determined so that said air-fuel ratio sensor, when operative, changes the output signal thereof across the predetermined reference level repeatedly.

6. An apparatus for discriminating operativeness/inoperativeness of an air-fuel ratio sensor which produces an output signal provided in an exhaust passage of an internal combustion engine so that air-fuel ratio of mixture to said engine is feedback-controlled in response to an output signal of said air-fuel ratio sensor, said apparatus comprising:

means for subtracting the output signal of said air-fuel ratio sensor from a predetermined reference level to obtain a difference therebetween;

means for integrating the difference obtained by said subtracting means during an integration interval to produce an integration value;

means for measuring said integration interval during which said integrating means integrates said difference; and

means for comparing the integration value produced by said integrating means with a predetermined discrimination reference when the integration interval attains a predetermined value, so that operativeness/inoperativeness of said air-fuel ratio sensor is discriminated in response to a comparison output of said comparing means.

7. An apparatus according to claim 6 further comprising:

means for comparing the output signal of said air-fuel ratio sensor with the predetermined reference level;

means for enabling said integrating means to continue integrating the difference, in response to an output of said output signal comparing means indicative of attainment of the output signal of said air-fuel ratio sensor at the predetermined reference level; and

means for disabling feedback control of the air-fuel ratio of mixture in response to the comparison output indicative of the inoperativeness of said air-fuel ratio sensor.

8. A method for discriminating operativeness/inoperativeness of an air-fuel ratio sensor which produces an output signal provided in an exhaust passage of an interval combustion engine so that air-fuel ratio of mixture to said engine is feedback-controlled in response to an output signal of the air-fuel ratio sensor, comprising the steps of:

subtracting the output signal of the air-fuel ratio sensor from a predetermined reference level to derive a difference therebetween;

integrating the difference derived in said subtracting step;

measuring an integration interval during which said integrating step continues integrating; and

comparing an integration value produced during said integrating step with a predetermined discrimination reference when the measured integration interval attains a predetermined value, so that operativeness/inoperativeness of the air-fuel ratio sensor is discriminated in response to a comparison output of the comparing step.

9. A method according to claim 8, further comprising the steps of:

comparing the output signal of the air-fuel ratio sensor with the predetermined reference level;

enabling said integrating step to continue integrating the difference in response to an output of output signal comparing step indicative of attainment of the output signal of said air-fuel ratio sensor at the predetermined reference level; and

disabling feedback control of the air-fuel ratio of mixture in response to the comparison output indicative of the inoperativeness of the air-fuel ratio sensor.