Abstract: A device for detecting knocking of an internal combustion engine which, even when spike noise is generated, does not erroneously detect it as knocking. An ionic current signal detected by an ionic current detecting unit 17 is separated into a knocking frequency component passing through a band-pass filter 32 and frequency components other than the knocking frequency component passing through a low-pass filter 321 and a high-pass filter 322. When the knocking frequency component is higher than a predetermined level, it is determined that the knocking is occurring. When the frequency component other than the knocking frequency component is higher than the predetermined level, it is regarded that the spike noise is generating, so that the generation of spike noise will not be erroneously determined as knocking.

Abstract: A device for detecting knocking in an internal combustion engine capable of preventing accuracy for detecting knocking from being deteriorated by noise when resetting the LC resonance masking unit. An ionic current signal detected by an ionic current detecting unit is supplied to a buffer amplifier 5 via an LC resonance masking unit 31. To a first operational amplifier 51 of the buffer amplifier is connected a capacitor 513 for rejecting noise in parallel with a first feedback resistor 512. A second operational amplifier inverts again the ionic current signal inverted by the first operational amplifier. The buffer amplifier prevents a stepwise change on the input to the band-pass filtering unit when the masking of the LC resonance masking unit is reset, and suppresses a reduction in accuracy for detecting the knocking.

Abstract: An ignition device for an internal combustion engine capable of suppressing not only a decrease in the discharge energy of the spark plug but also the LC resonance itself. When an igniter 13 is turned on by an ignition timing control unit 14 and a current flows into a primary coil 111 of the igniter 11, a FET 31 is turned off by the ignition timing control unit 14, whereby the primary coil is cut off from an LC resonance-absorbing resistor 32 to prevent a decrease in the current flowing into the primary coil. The ignition timing control unit 14 turns the igniter 13 off and turns the FET 31 on a predetermined period after the start of discharge of the secondary coil 112, whereby the primary coil and the LC resonance-absorbing resistor are connected together to absorb LC resonance after the discharge of the secondary coil, in order to suppress the occurrence of noise caused by LC resonance.

Abstract: A device for a detecting a combustion state in an internal combustion engine, capable of preventing the background from increasing while the fuel is being cut. A peak value of ionic current detected by the ionic current detecting unit 19 is supplied to an ignition timing control unit 14 via an LC resonance masking unit 31, a band-pass filter unit 32 and a peak-holding unit 33. An average of peak values is used as a background, and it is so determined that knocking has occurred when the peak value becomes larger than the product of a predetermined coefficient and the background (BG). Impulse noise (IM) easily occurs while the fuel is being cut. In order to prevent BG from being increased by IM, therefore, a limiting means is provided to limit BG to a value calculated before the fuel was cut, so that the detecting precision will not be deteriorated after the fuel-cut is terminated.

Abstract: A device for detecting knocking in an internal combustion engine which, when spike noise or noise due to disturbance in the flame in low-load running are generated, does not erroneously detect it as knocking. Knocking frequency components passing through a band-pass filter 32 and frequency components lower than the knocking frequency and passing through a low-load noise band-pass filter 321 are picked from the ionic current detected by an ionic current detecting unit 17. When the level of the low-frequency components is larger than a predetermined value, it is regarded that the noise is generated due to unstable combustion during the low-load operation or the spike noise is generated due to corona discharge of a spark plug 16, and the determination of the occurrence of knocking is prevented. This constitution makes it possible to prevent erroneous detection of knocking.