| 摘要 |
PURPOSE:To sufficiently increase a difference between a level of vibration at sensor fail time and a level at normal time so as to detect sensor fail surely by changing a noise gate period for detecting a noise level in the case of realizing a condition that the noise level during its detection period is decreased. CONSTITUTION:In a microcomputer 5 at engine operation time, whether a condition of decreasing a noise level is realized or not is decided by using detection signals of for instance, an engine speed and air pressure in an intake manifold or a cooling water temperature, and when the concerned condition is realized, a noise gate is changed from 100 deg. to 120 deg. in a period where an influence of valve seating vibration or the like appears in an output signal of a vibration sensor 1 despite presence of knocking, that is, in a period where a large difference is generated between output levels from the vibration sensor 1 at sensor fail time and normal time. An angle change of this noise gate is realized by changing a preset value of a timer for creating the noise gate. Sensor fail is detected based on the noise level in the noise gate. |
