Abstract: A body 600 of a fuel injector 1000 according to the present invention includes: a needle valve mechanism 200 including a needle valve 252 provided near a nozzle portion 250, and a fuel chamber 254; a needle valve actuator 230 mounted with a piston 235 on a center, wherein a spring 240 is disposed into the piston 235; a booster 300 disposed between the needle valve mechanism 200 and a pilot valve 400, and having only a spring-free piston 350; the pilot valve 400 operating by a pressure difference between supplied fuel pressure and working pressure of a solenoid valve 500; and the solenoid valve 500 controlling working pressure of fuel to operate the needle valve actuator 230.

Abstract: A fuel injector according to the present invention includes a needle valve mechanism including a needle valve provided near a nozzle portion, and a fuel chamber; a needle valve actuator mounted with a piston, wherein a spring is disposed into the piston; a booster formed with first through third chambers in an upper portion, a middle portion, and a lower portion, respectively, based on a piston, and having only the spring-free piston; a pilot valve operating by a pressure difference between pressure for injection of the fuel chamber and working pressure of a solenoid, having a spool and a spacer mounted above the spool and formed with a second orifice on one side thereof; and a solenoid valve controlling working pressure of fuel to operate the needle valve actuator or the pilot valve.