| 摘要 |
PROBLEM TO BE SOLVED: To detect spike noise and residual magnetic noise superposed on an ion current detection signal. SOLUTION: An ion current detection signal A is divided into a knocking signal B in a specified frequency band and a noise signal C in other frequency bands by a BPF 33 and a BEF 34. It is determined whether or not spike noise and residual magnetic noise are occurred in a knocking determination zone, based on whether or not peak hold values PH1, PH2 of the signals B and C are in the specified zone. The noise determination is carried out immediately after starting the knocking determination zone and immediately before ending it. When the specified noise is detected immediately after starting the knocking determination zone, residual magnetic noise is determined. When the specified noise is detected immediately before ending the knocking determination zone, the spike noise is determined. In addition, when occurrence frequency of the residual magnetic noise is a specified value or more, residual magnetic abnormality is determined. When the occurrence frequency of the spike noise is a specified value or more, abnormality of an ignition plug 17 is determined. |
