| 摘要 |
Knocking sounds in an internal combustion engine are detected by a transducer, amplified, filtered to the knock frequencies, rectified and integrated to provide for each knock a DC pulse representative of the intensity of the knock. This DC pulse is fed to an up/down counter to step up the counter output voltage in proportion to the knock rate. After a delay the voltage in the counter is stepped down at a controlled rate by signals derived from the engine distributor. A net positive output of the up/down counter and knock intensity operate to proportionately retard the spark, which returns to its normal setting when the counter output is counted down to zero. Additionally an integrated knock signal is fed back to the signal amplifier to control amplifier gain as engine running noise varies. The time constants of the feedback circuit are sufficiently slow, and the amplifier gain control is inhibited by the presence of knock, such that amplifier gain is not modified by the short knock pulses. Thus knock pulses are amplified above a noise level which is otherwise maintained constant by the feedback circuit. |
