Fuel injector with adjustable metering servo-valve for an internal-combustion engine

摘要

The injector (1) with adjustable-metering servo valve (7) has a shutter (45) actuated by an armature (16) of an electromagnet (15). The armature (16) is mobile for an opening stroke defined by a surface (19) of the core (18) of the electromagnet (15), which is fixed in the casing (2) by means of a ring nut (40) and a hollow support (20) of the core (18) itself. The support (20) has a first contact surface (51) that acts on a flange (52) of the core (18). Set between the surface (19) and a shoulder (49) of the casing (2) is a shim (48) having a hardness different from that of the core (18) or of the casing (2). An annular projection (53), having a second contact surface (54), is set between the polar surface (19) and a shoulder (49) of the casing (2), the second contact surface (54) being contained at least in part in the area corresponding to the first contact surface (51), so that the stroke of the armature (16) is adjusted by means of a plastic deformation of the shim (48) or of the surface (19) of the core (18) as a function of the tightening torque of the ring nut (40).