Injection nozzle

Claim 1

A fuel injection nozzle for supplying fuel to an internal combustion engine comprising a body part, a stepped bore defined in the body part, said bore communicating at one end with an outlet opening extending to the exterior of the body part, a seating defined at said one end of the bore, a valve member movable in the bore, the valve member being shaped for co-operation with said seating, resilient means acting to urge the valve member into contact with said seating, a fuel inlet passage through which in use fuel under pressure can be supplied to act on a surface of the valve member to move the valve member away from the seating thereby to allow fuel flow through said outlet opening, an annular member surrounding the valve member, means on the annular member engageable with said valve member, said annular member being subjected to fuel under pressure so as to generate a force which is applied to said valve member to assist the movement thereof away from the seating and means for limiting the movement of the annular member, said annular member comprising a sleeve defining a further bore and being slidable in said bore in the body part, the valve member being slidably mounted in said further bore, the sleeve being provided with passage means whereby the fuel pressures in use in the working clearances between the inner wall of the sleeve and the valve member and the outer wall of the sleeve and the wall of said bore in the body part, are substantially equal.