HYDRAULIC OPERATION TYPE FUEL INJECTOR

PROBLEM TO BE SOLVED: To improve the combustion efficiency by interposing a compression spring between an amplifier piston and a plunger of a fuel injector, and urging the compression spring so as to separate a piston apart from the plunger by the prescribed distance before each injection phenomenon is started. SOLUTION: When a control valve 22 mounted in an injector body is lifted from a seat 24 against a return spring 25 by excitation of a solenoid 26, the high pressure working fluid flows into a working fluid cavity 23 through an inlet 21. When the solenoid 26 is demagnetized the control valve 22 is returned to the seat 24 side by the urging force of the return spring 25 to close the working fluid inlet 21. The working fluid introduced in the cavity 23 lowers a plunger 40 through an amplifier piston 30, and the high pressure fuel is ejected from a nozzle port 58 by pressing a needle check 60.