Fuel injection rate variation of a piezoelectric injector according to the charge current patterns

The effects of charge current patterns on the injected fuel mass per stroke (IFMPS) were investigated. The charge and discharge currents supplied to a piezo injector are basically controlled by the peak and hold method. The hold current is controlled by PWM (pulse width modulation) control of the driving power supplied to the injector. The duty ratios of the PWM signal used for hold current control are varied. A variety of charge and discharge current waveforms to drive the piezo injector were generated by combining duty ratio control of the PWM waveform with the driving power source. An optimal piezo injector charge control condition to minimize the variation of the IFMPS under given fuel rail pressure and fuel injection duration values was investigated. When the fuel injection duration was short, the effect of the duty ratio of hold control on the average IFMPS deviation % from the average IFMPS was increased. The standard deviation of average IFMPS and average IFMPS deviation % can be reduced by lowering the peak charge current to obtain the target IFMPS.