Electronically controlled fuel injector

A fuel injector for intermittently injecting fuel into the combustion chamber of an internal combustion engine, comprising a housing (14) with a valve seat (22) and at least one discharge orifice (24), an elongated injector valve member (18) provided with a piston member (26) and mounted within said housing (14) for engagement with said valve seat (22) for closing said discharge orifice (24), said injector valve member (18) being shiftable in its axial direction to be momentarily lifted from said valve seat (22) to open said discharge orifice (24), to allow for the injection of a desired quantity of fuel into the combustion chamber of the related internal combustion engine, a control chamber (40) provided in said housing (14) and being connectable to a fuel supply line (12);

• the fuel pressure in said control chamber (40) acting upon said piston member (26) of said injector valve member (18) forcing the latter against said valve seat (22), means (34, 38, 44, 46;
• 172, 182) for quickly reducing and quickly restoring the fuel pressure in said control chamber (40) to allow for the momentary axial movement of said injector valve member (18), said reducing or restoring means including a first orifice (34) and a second orifice (38) opening into said control chamber (40), electromagnetically controlled pilot valve means (46;
• 182) for closing and temporarily opening one end of said second orifice (38) and a solenoid (44;
• 172) for opening said pilot valve means (46;
• 182) depending upon applied electric pulses of a predetermined duration;
• said solenoid (44;
• 172) having pole faces (148, 150) and being formed by a round body (122) with an outer round section (126), an inner round section (138) and a stator plate (124), both inner and outer round sections (126, 138) being part of one work piece and being connected together at the side opposite to said pole faces (148, 150) of said solenoid (44;
• 172), said stator plate (124) being placed and positioned in said outer round section (126) and defining with an outer surface together with at least a planar surface of said inner round section (138) a common plane being perpendicular to the circumferential surface (146) of said solenoid (44;
• 172) and being generally parallel to a surface (52a) of said solenoid (44, 172) provided on the side opposite to the solenoid pole faces (148, 150) said pilot valve means (46, 182) being provided with an armature or pilot valve plate (62;
• 176) having an outer diameter substantially smaller compared to the diameter of said circumferential surface (146), one of said pole faces (148) being formed between an inner portion of said stator plate (124) and an outer portion of said armature or pilot valve plate (62;
• 176), the other of said pole faces (150) being formed by an inner portion of said armature or pilot valve plate (62;
• 176) and said planar surface of said inner round section (138) of said round body (122), a solenoid coil (130) of said solenoid (44;
• 172) being placed in an inner space of said round body (122) delimited by the circumferential surface of said inner round section (138), the inner circumferential surface of said outer round section (126) and the inner surface of said stator plate (124).