Patent ID: 8231105

Claim:
An adjustable metering servovalve and an internal combustion engine fuel injector, said fuel injector comprising: a control rod configured to be movable to control a pin shutter configured to close and open a fuel injection nozzle; the servovalve being housed in a casing of said fuel injector and comprising: a valve body; a control chamber which permanently communicates with an inlet via a passage to receive pressurized fuel and which is bounded axially at an end thereof by the control rod; the control chamber communicating with a draining passage; a shutter sliding along an axis between a forward position and a withdrawn position, where said shutter is defined by a sleeve integral with an armature; said sleeve sliding on a rod having at least one radial hole of the draining passage; an actuator for controlling said shutter, the actuator comprising: a) an electromagnet comprising a magnetic core having a polar surface perpendicular to said axis; and b) said armature performing a given travel defined by a pair of opposite stop members; one of said stop members being formed by said polar surface and being fixed inside said casing by a threaded member with the interposition of at least one shim; a support which holds in position said electromagnet; said threaded member being a threaded ring nut, which engages an annular shoulder of said support and is screwed with a predetermined tightening torque to a thread of said casing to fix said electromagnet inside said casing and to produce a corresponding tightening load on said shim; the bottom end of said support engaging an annular shoulder of said magnetic core; and said shim being located between said polar surface and a shoulder of a cavity of said casing and being deformable elastically by said threaded ring nut, as a function of said tightening torque, so as to adjust the travel of said armature, wherein said shim is defined by a ring made of elastically deformable material and wherein said ring has a cross section such that the ring is predominantly bendable.