Diagnostic method and control apparatus for gas sensor
First Claim
1. A gas sensor diagnostic method of diagnosing an improper condition of a gas sensor for producing a gas sensor output representing a concentration of a specified gas component in an exhaust gas mixture of an internal combustion engine, comprising:
- a sensor output obtaining step of obtaining sensor output values of the gas sensor output at regular time intervals of a predetermined obtaining period;
an interruption detecting step of detecting a fuel supply interruption to the engine;
an extremum determining step of determining local extreme values each of which is an extremum in a series of sensor output values obtained consecutively by the sensor output obtaining step during a fuel supply interruption period during which the fuel supply interruption is detected by the interruption detecting step;
an extremum comparing step of comparing each of the local extreme values with a first predetermined threshold level; and
a diagnosing step of determining whether the gas sensor is in the improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level when a number of the local extreme values obtained from the gas sensor output becomes equal to a predetermined first number.
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Accused Products
Abstract
A gas sensor diagnostic method (or apparatus) is arranged to periodically obtain sensor output values of a gas sensor such as an oxygen sensor for an internal combustion engine, and to determine local extreme values from the sensor output values obtained during a period of interruption of fuel supply to the engine. Moreover, the local extreme values are compared with a first predetermined threshold level. When the number of the local extreme values reaches a predetermined first number, a diagnosis is performed to determine whether the gas sensor is in an improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level.
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Citations
16 Claims
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1. A gas sensor diagnostic method of diagnosing an improper condition of a gas sensor for producing a gas sensor output representing a concentration of a specified gas component in an exhaust gas mixture of an internal combustion engine, comprising:
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a sensor output obtaining step of obtaining sensor output values of the gas sensor output at regular time intervals of a predetermined obtaining period; an interruption detecting step of detecting a fuel supply interruption to the engine; an extremum determining step of determining local extreme values each of which is an extremum in a series of sensor output values obtained consecutively by the sensor output obtaining step during a fuel supply interruption period during which the fuel supply interruption is detected by the interruption detecting step; an extremum comparing step of comparing each of the local extreme values with a first predetermined threshold level; and a diagnosing step of determining whether the gas sensor is in the improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level when a number of the local extreme values obtained from the gas sensor output becomes equal to a predetermined first number. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A gas sensor control apparatus to diagnose an improper condition of a gas sensor for producing a gas sensor output representing a concentration of a specified gas component in an exhaust gas mixture of an internal combustion engine, comprising:
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a sensor output obtaining section to obtain sensor output values of the gas sensor output at regular time intervals of a predetermined obtaining period; an interruption detecting section to detect a fuel supply interruption to the engine; an extremum determining section to determine local extreme values each of which is an extremum in a series of sensor output values obtained consecutively by the sensor output obtaining section during a fuel supply interruption period during which the fuel supply interruption is detected by the interruption detecting section; an extremum comparing section to compare each of the local extreme values with a first predetermined threshold level; and a diagnosing section to determine whether the gas sensor is in the improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level when a number of the local extreme values obtained from the gas sensor output becomes equal to a predetermined first number. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification