Patent ID: 7828228

Claim:
A fuel injection apparatus comprising: a nozzle that has a fuel injection hole, which extends through a wall of a distal end portion of the nozzle, and a valve seat, which surrounds an inlet of the fuel injection hole; a needle that has a valve element at a distal end side of the needle and is axially reciprocable in a first axial direction and an opposite second axial direction relative to the valve seat; a control chamber that receives pressure conducting fluid, which exerts a pressure to the needle to axially drive the needle; a piezoelectric actuator that expands and contracts depending on a drive voltage thereof, which is increased and is decreased through charging of electric current to the piezoelectric actuator and discharging of electric current from the piezoelectric actuator, respectively, wherein one of expansion and contraction of the piezoelectric actuator results in an increase in the pressure of the pressure conducting fluid in the control chamber to axially move the needle in the first axial direction away from the valve seat, and the other one of the expansion and the contraction of the piezoelectric actuator results in a decrease in the pressure of the pressure conducting fluid in the control chamber to axially move the needle in the second axial direction toward the valve seat; an inflection point sensing means for sensing an inflection point in a pressure-changing process of the pressure in the control chamber; and a charging and discharging condition changing means for changing a charging condition for the charging of the electric current to the piezoelectric actuator or a discharging condition for the discharging of the electric current from the piezoelectric actuator upon sensing of the inflection point, which is sensed with the inflection point sensing means.