Fuel injection nozzles

Claim 1

A fuel injection nozzle for supplying fuel to a compression ignition internal combustion engine and of the kind comprising a nozzle body, a bore defined in the body, an outlet at one end of the bore, a seating defined in the bore adjacent said outlet, a valve member slidable in said bore, said valve member being shaped for co-operation with said seating, resilient means biasing the valve member into contact with the seating, a fuel supply passage in the body, said passage communicating with said bore, and the valve member defining a surface against which in use, fuel under pressure in said passage can act to lift the valve member from the seating thereby to allow fuel flow from the supply passage through said outlet, characterized by a variable area restrictor in a flow passage extending from said supply passage to a drain, said variable area restrictor being constituted by a port in said flow passage opening into said bore and the valve member, said port being progressively covered by said valve member as the valve member is lifted from its seating, whereby the degree of restriction offered by said restrictor is dependent upon the axial position of the valve member in the bore and the flow area of the restrictor decreases as the valve member moves away from the seating.