| 摘要 |
PURPOSE:To measure a knocking detection signal of high frequency directly by performing A-D conversion after the knocking detection signal crosses a specific level and exceeds the peak of >=1 signal waveform. CONSTITUTION:The output signal of a knocking detector 1 is sent to a filter circuit 2 to extract only a frequency component characteristic to knocking and the component is sent to an A-D converter 5. A microcomputer 6 generates a timing signal for the start of the A-D conversion according to a signal from a comparing function for a threshold value given the converter 5, averages the output signal of the converter 5 to calculates a knocking decision level, and also compares the knocking decision level with the maximum value of a digital signal within a specific time to decide whether knocking occurs or not. For example, the rise cross point 311 of the knocking detection signal is detected, and then the peak P1 of the 1st signal waveform is skipped and the waveform nearby the next peak P2 is converted from analog to digital to take a measurement, thereby securing a necessary time DELTAD up to the start of the A-D conversion. |
