Enhancement of knocking detection accuracy by an ion-current sensor integrated in the ignition system

Abstract

Enhancement of knocking detection accuracy by an ion-current sensor integrated in the ignition systemAbstract Abnormal combustion such as pre-ignition and knocking is becoming one of the biggest problems in the latest gasoline engines that have a higher compression ratio and boosting for higher efficiency. An ion-current sensor integrated in an ignition system is used for accurately detecting knocking cycles. First, the problem for accurate knocking detection with an ion-current sensor was clarified in the test engine. The oscillation in the ion-current signal was observed in knocking cycles as is commonly known in the previous research. However, heavy oscillation in the ion-current signal can be observed occasionally even in the small knocking cycles. This phenomenon leads to the misdetection of knocking cycles with the conventional signal-processing method, which defines the oscillation intensity of the change amount in the ion-current signal as a knocking indicator. Second, to solve the problem mentioned above, a new signal-processing method is proposed on the basis of the thermal characteristics of ion-current signals. This method defines the oscillation intensity of the "normalized ion-signal change rate" as a knock indicator in order to suppress the effect of temperature dependency in ion-current signals. Finally, the proposed method was applied to an actual gasoline engine, and the knocking detection performance was evaluated. The method enabled the misdetection of the knocking cycles to be avoided and enhanced the correlation factor with knock intensity compared with the conventional method.

Control Technologies for Advanced Engines and Powertrains: A Review

“…Ion current has been used to obtain flame information and detect misfires (41)(42)(43) , and studies have shown that it can be used to obtain the combustion state even for compression ignition at lean conditions in HCCI (44)(45)(46) engines. In addition, the detection of abnormal combustion, knocking and pre-ignition (47)(48)(49)(50)(51) , and the possibility of detecting precursors to preignition (52,53) have also been reported. Kumano et al (52) investigated the characteristics of ignition precursor phenomena in gasoline engines with a high compression ratio by using an ion current sensor integrated into the spark ignition coil.…”

“…In addition, the detection of abnormal combustion, knocking and pre-ignition (47)(48)(49)(50)(51) , and the possibility of detecting precursors to preignition (52,53) have also been reported. Kumano et al (52) investigated the characteristics of ignition precursor phenomena in gasoline engines with a high compression ratio by using an ion current sensor integrated into the spark ignition coil. They identified the feature values of the ion current signal that correlated with the ignition precursor phenomena.…”

Pre-ignition-prevention control method in spark-ignition engines by detecting precursory cycles with an ion-current sensor

“…Ion current sensors for integration in the ignition coil and dedicated spark plugs for ion-current sensing were investigated. [21][22][23][24][25] Doi et al 24 enhanced the durability and sensitivity of ion current sensing by modifying the initial dimensions of electrodes. Bogin et al 25 showed that increasing the surface area of the positive center electrode of a spark plug greatly improved the peak ion signal.…”

“…Zhang et al 28 applied a wavelet transform and designed wavelets to detect knocking from the ion current waveform. In our previous study, 23 we proposed a normalization method of ion-current oscillation intensity regarding the thermal characteristics of the ion-current signal to enhance knocking-detection accuracy.…”