Flexural element for positioning an armature in a fuel injector

A fuel injector for use in an internal combustion engine, comprising:

• an injector body having a through extending fuel flow passage;
• a magnetic pole fixed within the body and defining a portion of the passage;
• a solenoid coil surrounding the pole;
• a valve seat having a discharge opening and fixed at an outlet end of the passage;
• and
• a valve assembly including an injection valve biased toward the valve seat to close fuel flow through the passage, a magnetic armature movable with the valve and responsive to action of the coil for movement between open and closed positions and a flexural element connecting the armature with the injector body and restricting radial movement while allowing axial movement of the armature within the fuel passage, wherein the flexural element is unloaded when the valve is in the closed position and the flexural element is resiliently flexed and biases the valve in a closing direction when the valve is in the open position;
• and
• the flexural element is a disc-shaped ring having an open center and at least two resilient beams connected with the ring and extending radially into and angularly within the open center, the beams bending resiliently to allow axial motion of the armature.

A method for setting a valve stroke in a fuel injector of an internal combustion engine, the fuel injector having an injector body carrying an inner pole at least partially defining an axially extending fuel passage therein, the method comprising the steps of:

• providing the injector body with an upper cylindrical portion and an enlarged lower cylindrical portion connected by a radial flange surface forming an outer pole, wherein the enlarged lower cylindrical portion is configured to house a valve assembly and a valve seat;
• positioning a lower surface of the inner pole coplanar with the radial flange surface of the outer pole;
• inserting a valve assembly and a valve seat in the enlarged lower cylindrical portion of the body, the valve assembly having an armature with a flat upper surface, a valve element in the armature engagable with the valve seat and a disk shaped flexural element of constant thickness and including an outer ring with an open center and a plurality of resilient beams extending from the outer ring into and angularly about the center, the beams being connected to the flat upper surface of the armature at positions of the beams distal from their connections with the outer ring, the outer ring forming a spacer positioning the valve seat such that the valve stroke from the closed to the open position equals the thickness of the flexural element;
• and
• fixing the valve assembly and seat in the valve body.