| 摘要 |
PURPOSE:To expand the width of frequency detection, to improve an S/N ratio and to improve sensitivity by providing plural resonance points in a knocking frequency band by each piezoelectric vibration detector. CONSTITUTION:Components 21a-21d are piezoelectric vibration detecting platelike elements having resonance frequencies in either one of 4-10kHz or 11-13kHz knocking frequency; they are stacked and their one-side ends are fixed to projected part 22c by screws 26 and press plate 25. Detector 2 is fitted tightly to an engine block and knocking vibrations are transmitted to respective piezoelectric elements 21a-21c via housing 22. Since piezoelectric elements 21a-21c are connected in series, an electric signal with three composite resonance characteristics is led out. The number of the resonance characteristics depends upon the number of the piezoelectric elements, and knocking can easily be detected with high sensitivity over the entire knocking frequency band by providing proper resonance points. |
