Study on Effects of Common Rail Injector Drive Circuitry with Different Freewheeling Circuits on Control Performance and Cycle-by-Cycle Variations

This paper provides a new common rail injector drive circuitry for practical use. The new drive circuitry with variable freewheeling circuit was developed based on the requirements for the rate of current drop in the peak-and-hold solenoid model. The variable freewheeling circuit exhibited superior performance in the control accuracy compared to the conventional circuit with a resistor in series with diode (RD) freewheeling circuit. Furthermore, the current cutting process was 30 mu s shorter, and the control accuracy of the cycle fuel injection mass was improved by at least 0.36% or exactly 2.86% when a small fuel injection mass was used. In addition, the variable freewheeling circuit consumed less power because the drive power charging was done through the feedback from electromagnetic energy to electrical energy. When the fuel injection mass was large, the fall range of the driving power voltage became 1 V smaller, its recovery time was 1ms shorter, and the highest temperature of the drive circuitry was only 37 degrees C, which was 127 degrees C lower than that of the RD freewheeling due to the decrease in energy consumption. Finally, experimental tests with a multi-cylinder engine showed that the variable freewheeling circuit reduced the cycle-by-cycle combustion variations by 0.5%, and lessened the NOx and soot emissions significantly by 3.5% and 4%, respectively, in comparison to the RD freewheeling circuit.