Fuel injector for an internal combustion engine

Claim 1

In a fuel injector for an internal combustion engine including a cylindrical valve housing provided with an injection port at its forward end, a valve body fixed on the rear outer periphery of said valve housing and extending rearwardly from said valve housing, a rod-like valve member accommodated in said valve housing and adapted to reciprocate axially, a solenoid coil provided and arranged rearwardly from said valve housing, a fixed iron core accommodated within said solenoid coil and fixed to said valve body, said fixed iron core being arranged coaxially with said valve member, an armature facing towards said fixed iron core with a clearance normally defined between itself and said fixed iron core, mechanical biasing means interposed between said armature and said fixed iron core, said valve member being movable in respective axial directions by respectively conducting or cutting off an electric current to said solenoid coil and respectively opening or closing said injection port of said valve housing at its forward end to intermittently inject fuel through said port; an improvement wherein at least one of said armature secured to said valve member and said fixed iron core is made of a permanent magnet, and including circuit means, coupled to said solenoid coil, for producing a pulse shape of the electric current applied to said solenoid coil of said fuel injector in a stepped wave shape, the electric current in an initial stage of current application being larger than that in a later stage.