GB1406216A - Fuel injection nozzle units - Google Patents

Abstract

1406216 Fuel injection nozzles CAV Ltd 17 Oct 1972 [30 Oct 1971] 50534/71 Heading F1B A liquid fuel injection nozzle unit in which a valve member shaped to co-operate with a seat is moved by fuel pressure against resilient means away from the seat, is characterized in that a fluid pressure operable means is provided to which fuel under pressure, leaking between the valve member and a bore in which it runs, is led,the means being coupled to the valve member so that the fuel under pressure assists the action of the resilient means in closing the valve member on to its seating valve means being provided for controlling the pressure of fuel applied to the fluid pressure operable means. The unit comprises a body 10 against the lower end face of which a nozzle head 12 is held by a screw cap 13. A valve member 14 slides in a bore in the body and cooperates with a seating in the head 12. A fuel space 16, communicates by passage 15 with pump 30. Fuel pressure lifts valve member 14 against a spring 19. Fuel which leaks past valve member 14 is conducted by a passage 23 to the chamber 20 and acts on piston 18, the lower end of which bears against push rod 21, so that the fluid pressure produces a force acting in the same direction as the spring. The maximum pressure in the chamber 20 is limited by a valve 24 consisting of piston 25 which is moved to the right (in the Fig.), by the fluid pressure, against a spring. Excessive pressure moves the piston so that fluid exhausts between the edge of a formation in the piston and the shoulder formed by a step in the cylinder. Fluid from the chamber beneath the piston 18, drains through a passage 26 at a rate controlled by a restriction 27. When the engine is started from rest, only the spring 19 resists the valve opening movement, the fluid pressure in chamber 20 increasing with engine speed. In a modification the piston 18 is replaced by a diaphragm.