Fuel injection nozzle units

Claim 1

A fuel injection nozzle unit of the kind intended to be mounted to direct fuel into a combustion chamber of an internal combustion engine and comprising in combination a body having a chamber and an end wall, said chamber being in communication with a fuel pump for delivering fuel thereto, a valve member mounted for axial movement in the chamber, a seating for the end wall with which said valve member cooperates to prevent the flow of fuel through an orifice of the end wall communicating with the combustion chamber said valve member having an abutment surface against which the fuel under pressure in the chamber can act to move said valve member axially away from the seating, a resiliently loaded stop located in the path of axial movement of the valve member for limiting the extent of movement of the valve member under the action of the fuel pressure acting on said abutment surface away from the seating, the valve member when in contact with said stop acting to permit fuel to flow through said orifice at a restricted rate and an axially displaceable annular piston located in the chamber, said valve member being slidably mounted within the annular piston, and resilient means operably related to said piston urging said piston and said valve member in the direction of the end wall to prevent fuel flow through the orifice, the annular piston resting upon the abutment surface on the valve member so that the resilient means serves to maintain the valve member in closed position on the seating, and upon the fuel pump supplying fuel to the chamber, the pressure acting on the piston removes the action of the resilient means so that the valve member engages the stop to allow fuel flow through the orifice at a restricted rate, and as the pressure of fuel delivered to the chamber increases, the pressure rise in the chamber is minimized by movement of the piston so that fuel continues to flow at a restricted rate through the orifice, a second abutment surface on the valve member spaced axially from the first abutment surface, and a fixed stop in the path of movement of the valve member located at a greater distance from the seating and the resiliently loaded stop, whereby as fuel pressure within the chamber increases, the piston continues its movement against the action of the resilient means away from the end wall until it engages the second abutment surface on the valve member so that the piston prevents an excessive rise in fuel pressure and upon the fuel pressure increasing beyond a predetermined value, the valve member and resiliently loaded stop move together until the valve member engages the fixed stop to permit substantially unrestricted flow of fuel through the orifice.