Patent ID: 8342424

Claim:
A fuel injection apparatus comprising: a nozzle body that includes a fuel passage, to which fuel is supplied from an external fuel source, and an injection hole, which is located on a downstream side of the fuel passage and is adapted to inject the fuel outside of the nozzle body; a needle that is received in the nozzle body and is adapted to reciprocate relative to the injection hole in a reciprocating direction to open and close the injection hole; a first urging member that has one end, which is installed to an inner wall of the nozzle body, and the other end, which urges the needle in a closing direction toward the injection hole; a pressure control arrangement that includes: a pressure chamber, which receives the fuel and exerts a pressure against the needle in an opening direction away from the injection hole against an urging force of the first urging member upon increasing of the pressure of the fuel in the pressure chamber; and a damper, which is actuated upon increasing of the pressure in the pressure chamber to increase a volume of the pressure chamber; a pressurizing piston that is received in the nozzle body and is adapted to reciprocate in the nozzle body to increase and decrease the pressure in the pressure chamber; a second urging member that urges the pressurizing piston in a decreasing direction to decrease the pressure of the pressure chamber; and a piezoelectric driver that has one end fixed to the nozzle body and is extendable in response to an amount of electric power supply to the piezoelectric driver to urge the pressurizing piston against an urging force of the second urging member in an increasing direction, which is opposite from the decreasing direction, to increase the pressure of the pressure chamber, wherein: the needle has a large diameter potion, which is slidable along an inner wall of the nozzle body; the pressure control arrangement further includes a back pressure chamber that is located on one side of the large diameter portion, which is opposite from the pressure chamber in the reciprocating direction of the needle; the back pressure chamber is communicated with the fuel passage; and the back pressure chamber exerts a pressure against the needle in a closing direction toward the injection hole upon increasing of a pressure of the fuel in the back pressure chamber.