Fuel injector with balanced metering servovalve, for an internal combustion engine

摘要

The injector (1) comprises a balanced metering servovalve (5) for controlling a rod (10) for opening/closing a nozzle. The servovalve (5) has a valve body (7) with a control chamber (26) fitted with an outlet passage (42a) that is opened/closed by an axially mobile shutter (47). The shutter (47) is integral with a sleeve (41) separate from the armature (17) and is made of a harder material, machined with extreme precision. The sleeve (41) is guided by an axial stem (38), provided with a lateral surface (39) to which a discharge channel (42) in communication with the outlet passage (42a) runs. The shutter (47) is coupled to the stem (38) in an axially sliding manner such that it is substantially balanced when it closes the channel (42). The shutter (47) comprises a sharp edge (45) able to close an annular chamber (46) in communication with the outlet passage (42), so as to keep the sleeve (41) in contact with the armature (17) when this is operated by the electro-actuator (15).