Diagnostic system for a secondary air supplier in an engine

Claim 1

A diagnostic system for a secondary air supplier in an engine, the engine including a cylinder; an intake passage; an exhaust passage; an injector for injecting fuel into one of the cylinder and the intake passage; a sensor for detecting an air-fuel ratio (A/F) of the exhaust gas within the exhaust passage; an engine controller for executing feedback control of an amount of fuel injected by the injector, in such a way that the air-fuel ratio (A/F) approaches a theoretical air-fuel ration, wherein the amount of fuel injected is a function of a changeable feedback correction factor (FAF); and wherein the engine controller is equipped with a memory unit for changing and storing the value of the feedback correction factor (FAF), the secondary air supplier including an air supply unit for supplying secondary air from the intake passage to the exhaust passage, so that the secondary air mixes with existing exhaust gas to change the air-fuel ratio of the exhaust gas; a detection unit for detecting a condition of the engine; and a control unit for controlling the air supply unit in accordance with the engine condition, whereby the secondary air is supplied to the exhaust passage by means of the air supply unit when the engine is in a predetermined condition in which the engine controller interrupts the feedback control of the amount of the fuel injected, the diagnostic system comprising: command means for instructing the secondary air supplier to temporarily supply air to the exhaust passage when the engine controller executes the feedback control of the amount of fuel injected; sampling means for sampling the changeable feedback correction factor (FAF) from the memory unit, said sampling means detecting a first feedback correction factor before the secondary air is supplied based on the instruction of said command means, and a second feedback correction factor after the secondary air has been supplied; calculation means for calculating a deviation value (ΔFAF) between said first and said second feedback correction factors; and diagnostic means for determining that the secondary air supplier is malfunctioning when said deviation value is smaller than a predetermined value (α).

Claim 5

A method for diagnosing a secondary air supplier in an engine, the engine including a cylinder; an intake passage; an exhaust passage; an injector for injecting fuel into one of the cylinder and the intake passage; a sensor for detecting an air-fuel ratio (A/F) of the exhaust gas within the exhaust passage; an engine controller for executing feedback control of an amount of fuel injected by the injector, in such a way that the air-fuel ratio (A/F) approaches a theoretical air-fuel ratio, wherein the amount of fuel injected is a function of a changeable feedback correction factor (FAF); and wherein the engine controller is equipped with a memory unit for changing and storing the value of the feedback correction factor (FAF), the secondary air supplier including an air supply unit for supplying secondary air from the intake passage to the exhaust passage, so that the secondary air mixes with existing exhaust gas; to change the air-fuel ration of the exhaust gas; a detection unit for detecting a condition of the engine; and a control unit for controlling the air supply unit in accordance with the engine condition, whereby the secondary air is supplied to the exhaust passage by means of the air supply unit when the engine is in a predetermined condition in which the engine controller interrupts the feedback control of the amount of fuel injected, the method comprising the steps of: A. determining whether the engine is in a predetermined condition suitable for diagnosing the secondary air supplier; B. instructing the secondary air supplier to temporarily supply air to the exhaust passage, when the engine is in said predetermined condition suitable for diagnosis, and when the engine controller executes the feedback control of the amount of fuel injected; C. detecting a first feedback correction factor before the secondary air is supplied to the exhaust passage, based on said instruction; D. detecting a second feedback correction factor after the secondary air has been supplied to the exhaust passage, based on said instruction; E. calculating a deviation value (ΔFAF) between said first and said second feedback correction factors; and F. determining that the secondary air supplier is malfunctioning when said deviation value is smaller than a predetermined value (α).

Claim 6

A method for diagnosing a secondary air supplier in an engine, the engine including a cylinder; an intake passage; an exhaust passage; an injector for injecting fuel into one of the cylinder and the intake passage; a sensor for detecting an air-fuel ratio (A/F) of the exhaust gas within the exhaust passage; an engine controller for executing feedback control of an amount of fuel injected by the injector, in such a way that the air-fuel ratio (A/F) approaches a theoretical air-fuel ratio, wherein the amount of fuel injected is a function of a changeable feedback correction factor (FAF); and wherein the engine controller is equipped with a memory unit for changing and storing the value of the feedback correction factor (FAF), the secondary air supplier including an air supply unit for supplying secondary air from the intake passage to the exhaust passage, so that the secondary air mixes with existing exhaust gas; to change the air-fuel ration of the exhaust gas; a detection unit for detecting a condition of the engine; and a control unit for controlling the air supply unit in accordance with the engine condition, whereby the secondary air is supplied to the exhaust passage by means of the air supply unit when the engine is in a predetermined condition in which the engine controller interrupts the feedback control of the amount of fuel injected, the method comprising the steps of: A. determining whether the engine is in a predetermined condition suitable for diagnosing the secondary air supplier; B. instructing the secondary air supplier to temporarily supply air to the exhaust passage, when the engine is in said predetermined condition suitable for diagnosis, and when the engine controller executes the feedback control of the amount of fuel injected; C. detecting a first feedback correction factor before the secondary air is supplied to the exhaust passage, based on said instruction; D. detecting a second feedback correction factor after the secondary air has been supplied to the exhaust passage, based on said instruction; E. calculating a deviation value (ΔFAF) between said first and said second feedback correction factors; and F. determining that the secondary air supplier is malfunctioning when said deviation value is smaller than a predetermined value (α).