US Patent 7828228 Fuel injection apparatus

An inflection point sensing arrangement of an electronic drive unit, which drives a fuel injection valve, senses an inflection point in a pressure-changing process of the pressure in the control chamber. A charging and discharging condition changing arrangement of the electronic drive unit changes a charging condition for charging of the electric current to a piezoelectric actuator of the fuel injection valve or a discharging condition for discharging of the electric current from the piezoelectric actuator upon sensing of the inflection point, which is sensed with the inflection point sensing arrangement.