Mitsubishi Denki Kabushiki Kaisha

Mituru Koiwa

Yutaka Ohashi

Koichi Okamura

Takeshi Shimizu

Yasuhiro Takahashi

Shingo Morita

There is provided a combustion state detecting device for an internal combustion engine even in the case where disconnection of a secondary current path or misfire in an ignition plug occurs. A voltage developed at the secondary winding low voltage side is suppressed so that the high voltage can be prevented from being leaked. The combustion state detecting device for an internal combustion engine includes a capacitor,for charging a positive bias voltage necessary for detecting ions generated when an ignition plug,discharges upon application of the ignition high voltage, a resistor,disposed between the low voltage side of the secondary winding and the capacitor for suppressing the drop of the bias voltage, ion current detecting means,for detecting a discharge current from the capacitor as an ion current flowing through the ignition plug, an ECU,for detecting a combustion state in the ignition plug on the basis of a detection value of the ion current detecting means, and a Zener diode,for suppressing a voltage developed when a path in which the ion current flows is disconnected.

Combustion state detecting device for an internal combustion engine

A combustion state detecting device for an internal combustion engine is obtained which is capable of preventing noises from being superimposed on an ion current, and surely obtaining a desired peak value of the ion current. The combustion state detecting device for the internal combustion engine includes an ignition coil which develops an ignition high voltage, an ignition plug to which the ignition high voltage is applied through a high-voltage path connected to a plurality of output terminals of the ignition coil, bias means for charging a bias voltage necessary for detecting ions which are discharged and generated from the ignition plug, discharge current limiting means for discharging the bias voltage, ion current detecting means for detecting the discharge of the bias voltage as an ion current that flows through the ignition plug, and an ECU for detecting a combustion state in the ignition plug on the basis of a detection value of the ion current, wherein the discharge current limiting means is disposed between an ignition current path formed by discharging the ions from the ignition plug and the bias means.

A combustion state detecting device for an internal combustion engine enables diverse combustion state detection by obtaining a plurality of currents analogous to an ion current. The combustion state detecting device includes a bias circuit,that applies an ion current detection voltage to an ignition plug,disposed in a cylinder of the internal combustion engine, an ion current signal distributor circuit,made up of a current mirror circuit for detecting the ion current on the basis of a voltage from the bias circuit, and current-voltage converter circuits,and,, to thereby produce a plurality of currents analogous to the ion current by the ion current signal distributor circuit.

For a purpose of improving detecting performance toward knocking in small and middle intensity which must be detected as a top priority to conduct regulation of ignition timing, a device is provided to vary an output gain of an alternating component included in an ion current in accordance with ion current quantity. An ion current detector to detect the ion current to be generated surrounding an ignition plug just after mixed gas inside a cylinder has been ignited with a spark discharge having occurred at the ignition plug due to a voltage generated by an ignition coil, comprises a bias voltage generating part to generate a high voltage for an ion current detection to be applied to the ignition plug via the ignition coil, an ion current-to-voltage conversion part to convert an ion current having flowed between electrodes of the ignition plug by the high voltage into a voltage, and a knock signal generator to extract and amplify a frequency band resembling knocks on the basis of voltage conversion effect.

Ion current detector

To obtain a combustion state detecting device in which a detection range is optimized to thereby make it possible to improve the S/N ratio, thereby making it possible to enhance the accuracy in detection of the combustion state of the internal combustion engine, in particular, the accuracy in knock detection. The combustion state detecting device for an internal combustion engine includes an ignition plug 4 which discharges by application of the ignition high voltage to fire a fuel-air mixture within a cylinder of an internal combustion engine, a bias circuit,for applying a bias voltage to the ignition plug, a current detector circuit,for detecting an ion current corresponding to the quantity of ions which are generated within the cylinder in which the fuel-air mixture is being burned as an ion current detection signal, knock signal processing means,to,for producing a knock decision signal representative of a knock occurrence state of the internal combustion engine on the basis of the ion current detection signal, and an ECU,for detecting the combustion state in the ignition plug on the basis of the ion current detection signal and the knock decision signal. The knock signal processing means sets a detection period of the knock decision signal on the basis of an integral value of the ion current detection signal.

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Tokyo, Japan

Mituru Koiwa