| 摘要 |
PURPOSE:To detect sensor fail precisely down to a low rotation area by detecting a knock sensor output signal as a sample, detecting its maximum value by replacing the signal sequentially and deciding the sensor fail by the number of times of replacement and the size of the maximum value. CONSTITUTION:The vibration of an internal combustion engine is detected by the knock sensor 35 and its output signal is inputted to an MPU34 through an envelope detecting part and A/D converted. The digital value is compared with the maximum value every A/D conversion, a larger knock data is replaced by the preceding maximum value and the number of times of replacement is counted up. When the counted number of times is larger than a prescribed value, the maximum value is compared with a decision value. If the maximum value is smaller than the decision value, a deterioration disconnection signal of the knock sensor is outputted to a display part 37, and when the maximum value is larger than the decision value, a normal signal of the sensor 35 is outputted. When the number of times of replacement is smaller than the prescribed value, the knock signal is discriminated as an influence due to a noise and the maximum value is turned to ''0'', so that the maximum value < the decision value is formed and the deterioration disconnection signal is outputted. |
