To enhance oil-tightness by reducing a sliding part clearance, and to improve controllability and durability by eliminating a defect due to friction of a piston sliding part, in a fuel injection valve having a displacement enlarging mechanism.
The fuel injection valve 1 controls the back pressure of a nozzle needle 5 which opens and closes an injection hole 51 to inject fuel supplied from a high pressure passage 121, by a valve body 4 to be driven via the displacement enlarging mechanism. The displacement enlarging mechanism comprises a large-diameter piston 31 to be driven by a piezo-actuator 2, a small-diameter piston 32 whose end pushes down the valve body 4, and a displacement enlarging chamber 3 formed between these pistons. The sliding surfaces of the large-diameter and small-diameter pistons 31 and 32 are coated with coating films 31a and 31b which consist of a low friction material. As a result, the pistons are constructed so that their friction resistance is not increased even in non-lubrication environment where a circumferential clearance is reduced.
KUROYANAGI MASATOSHI
MATSUMOTO SHUICHI
