Diagnosis apparatus for internal combustion engine
View Patent ↗In a diagnosis apparatus for an internal combustion engine which determines the abnormality of a linear A/F sensor which is disposed on the upstream side of a catalyst of the engine and detects the A/F of exhaust gas, the apparatus includes a response/gain deterioration detection unit that separately detects the response deterioration in which the response of the linear A/F sensor is delayed and the gain deterioration in which the detection sensitivity of the linear A/F sensor is abnormal.
1. A diagnosis apparatus for an internal combustion engine which diagnoses a linear A/F sensor which is disposed within an exhaust pipe of the engine and detects an A/F of exhaust gas, comprising:
a unit which separately detects response deterioration and gain deterioration of the linear A/F sensor.
2. A diagnosis apparatus for an internal combustion engine according to claim 1 , further comprising:
a control mode for controlling the A/F; and
a diagnosis mode for diagnosing the linear A/F sensor, wherein
the diagnosis mode includes a diagnosis signal generation unit which applies an A/F deviation at a frequency lower than that of the control mode.
3. A diagnosis apparatus for an internal combustion engine according to claim 2 , wherein
the frequency of the A/F deviation of the diagnosis mode for diagnosing the linear A/F sensor in the diagnosis signal generation unit is in a range which is larger than 0 Hz and equal to or less than 1 Hz.
4. A diagnosis apparatus for an internal combustion engine according to claim 2 , wherein
the frequency of the A/F deviation of the diagnosis mode for diagnosing the linear A/F sensor in the diagnosis signal generation unit is in a range which is equal to or larger than 0.3 Hz and equal to or less than 1 Hz.
5. A diagnosis apparatus for an internal combustion engine according to claim 2 , wherein
it is determined to be the gain deterioration when a ratio (hereinafter referred to a gain deterioration index) between a peak value of an A/F detected by the linear A/F sensor and a peak value of the A/F deviation controlled by the diagnosis signal generation unit is out of a predetermined range.
6. A diagnosis apparatus for an internal combustion engine according to claim 5 , wherein
gain characteristics of the linear A/F sensor is corrected based on the gain deterioration index.
7. A diagnosis apparatus for an internal combustion engine according to claim 2 , wherein
it is determined to be the response deterioration when a ratio (hereinafter referred to a response deterioration index) between a period of an A/F detected by the linear A/F sensor and a period of the A/F deviation controlled by the diagnosis signal generation unit is larger than a predetermined value.
8. A diagnosis apparatus for an internal combustion engine according to claim 7 , wherein
gain characteristics of the linear A/F sensor is corrected based on the response deterioration index.
9. A diagnosis apparatus for an internal combustion engine according to claim 1 , wherein
the diagnosis of the linear A/F sensor is inhibited when an abnormality of a fuel system of the engine is detected.