GB1178486A - Improvements in and relating to Fuel Injection Valves - Google Patents

Abstract

1,178,486. Fuel injectors. ROBERT BOSCH G.m.b.H. March 29, 1967 [March 30, 1966], No.14263/67. Heading F1B. In a fuel injection valve having a fuel pressure opened valve needle 8 moving against a spring 24 variably loaded by a piston 7 which is acted upon by fuel pressure and controls a main injection supply channel 20, a fixed pressure-moved preinjection piston 6 displaces a pre-injection quantity into a pressure chamber 17 until its movement is limited by a stop after further increase of fuel pressure and thereby increases the spring force before still further rise in pressure causes the opening of the valve needle for the main injection, the unthrottled fuel pressure acts constantly on the pre-injection and loading pistons and the effective area of the valve needle is greater or less than the effective area of the loading piston when the needle valve is respectively closed or open. Operation: Fuel from passage 9 passes via passages 10, 11 to move the pre-injection piston against spring 12 until it abuts sleeve 13. The fuel displaced lifts the valve needle 8 off its seat to inject the pre-injection quantity and also increases the force applied by spring 24 on the loading piston 7. When the pressure in chamber 17 falls the valve needle 8 recloses. A non- return valve 21 prevents the pressure in chamber 17 from acting directly on the loading piston 7. When the pressure in passage 9 exceeds the preinjection pressure the loading piston 7 is moved into contact with stop 1a to permit fuel flow via passage 20 into the pressure chamber 17, the needle valve 8 being unseated to start the main injection. The movement of the loading piston compresses the spring 24 to increase the main injection pressure above the pre-injection pressure. Excess pressures in chamber 17 are relieved through non-return valve 15.