Catalyst deterioration-determining system for internal combustion engines using compressed natural gas
First Claim
1. In a catalyst deterioration-determining system for an internal combustion engine using a compressed natural gas and having an exhaust system, catalyst means arranged in the exhaust system, for purifying exhaust gases emitted from said engine, oxygen concentration-detecting means arranged in said exhaust system at a location downstream of said catalyst means, for detecting concentration of oxygen present in said exhaust gases, and air-fuel ratio control means for controlling an air-fuel ratio of an air-fuel mixture supplied to said engine in a feedback manner in response to an output from said oxygen concentration-detecting means, said catalyst deterioration-determining system including catalyst deterioration-determining means for determining that said catalyst means is deteriorated when a period of change of said output from said oxygen concentration-detecting means during execution of air-fuel ratio feedback control by said air-fuel ratio control means is shorter than a predetermined determination reference value,the improvement comprising:
- influence degree-detecting means for detecting a degree of influence of oxidation of a particular component of said compressed natural gas in a vicinity of said oxygen concentration sensor; and
determination reference value-setting means for setting said predetermined determination reference value, in dependence on the degree of influence of oxidation of said particular component detected by said influence degree-detecting means.
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Abstract
A catalyst deterioration-determining system for an internal combustion engine has a catalyst arranged in the exhaust system, for purifying exhaust gases emitted from the engine, an oxygen concentration sensor arranged in the exhaust system at a location downstream of the catalyst, for detecting the concentration of oxygen present in the exhaust gases, and an ECU which controls the air-fuel ratio of an air-fuel mixture supplied to the engine in a feedback manner in response to the output from the oxygen concentration sensor. Determination of deterioration of the catalyst is carried out based on the output from the oxygen concentration sensor during execution of air-fuel ratio feedback control. An inversion period parameter representative of a repetition period of change in the output from the oxygen concentration sensor over a predetermined diagnosis period is measured, and a determination parameter is calculated by averaging values of the inversion period parameter measured over different diagnosis periods as the predetermined diagnosis period. The determination of deterioration of the catalyst is carried out based on the determination parameter.
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4 Claims
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1. In a catalyst deterioration-determining system for an internal combustion engine using a compressed natural gas and having an exhaust system, catalyst means arranged in the exhaust system, for purifying exhaust gases emitted from said engine, oxygen concentration-detecting means arranged in said exhaust system at a location downstream of said catalyst means, for detecting concentration of oxygen present in said exhaust gases, and air-fuel ratio control means for controlling an air-fuel ratio of an air-fuel mixture supplied to said engine in a feedback manner in response to an output from said oxygen concentration-detecting means, said catalyst deterioration-determining system including catalyst deterioration-determining means for determining that said catalyst means is deteriorated when a period of change of said output from said oxygen concentration-detecting means during execution of air-fuel ratio feedback control by said air-fuel ratio control means is shorter than a predetermined determination reference value,
the improvement comprising: -
influence degree-detecting means for detecting a degree of influence of oxidation of a particular component of said compressed natural gas in a vicinity of said oxygen concentration sensor; and determination reference value-setting means for setting said predetermined determination reference value, in dependence on the degree of influence of oxidation of said particular component detected by said influence degree-detecting means. - View Dependent Claims (2, 3, 4)
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Specification