| 摘要 |
PURPOSE:To detect a misfire by intactly using a vibration sensor already mounted. CONSTITUTION:A signal having a frequency band including vibration components at a misfire is taken out, by a lowpass filter 2, from an engine vibration detected by a vibration sensor 1. After this signal is converted to a digital quantity by an A-D converter 3, it is passed through a digital filter 4 to extract a misfire vibration component. In a misfire detection section 11, the moving average value of the differences between maximum values and the minimum values, in level, of the output signal from the digital filter corresponding to one ignition timing is multiplied by a constant determined from a vehicle speed, a number of engine revolutions, and intake negative pressure, to thereby determine a misfire decision value and decide that a misfire occurs, on the basis of this decision value. |
