| 摘要 |
<p>PURPOSE:To obtain an abnormality detection device which can grasp the extent of abnormalities of a secondary air supply mechanism, and estimate the abnormal portions. CONSTITUTION:An abnormality detection device has an air flow meter 43, an engine speed sensor 42, an oxygen sensor 46, and a CPU 48 which detects abnormalities based on detection signals of the above stated sensors. The CPU 48 calculates an actual secondary air supply amount based on an intake air amount when the output signal of the oxygen sensor 46 is abruptly varied. In addition, the CPU 48 calculates the secondary air amount to be supplied from secondary air supply mechanism 25 against back pressure in an exhaust passage 10 when the secondary air supply mechanism is normally operated, based on the intake air amount and engine speed, and sets the secondary air supply amount to be a judgment value for abnormality detection. The CPU 48 judges the secondary air supply mechanism 25 to be abnormal when the deviation between the secondary air supply amount and the judgment value is larger than a specified value.</p> |
