GB1390422A - Fuel injection systems for internal combustion engines - Google Patents

Abstract

1390422 Fuel injection systems; electromagnetic fuel injectors ROBERT BOSCH GmbH 26 May 1972 [28 May 1971] 24833/72 Heading F1B In a fuel injection system a pump nozzle has a pump piston 25, Fig. 1, driven by a bigger servopiston 24, pressurized fuel being supplied to a pump working chamber 52 via a supply valve 27, Fig. 2 and to a servo pressure chamber 29 in which a servopiston face is exposed, a valve slide 18 regulated by a solenoid valve 17 and movable by fuel branched off from the pressure source, the solenoid valve in a first switching position controlling the fuel flow to the servo pressure chamber and in a second position controlling the flow from the servo pressure chamber to a return flow line 59, the return stroke of the servopiston 24 the beginning of the filling stroke of the pump piston and the filling stroke speed being controlled by a throttle and the fuel injection quantity being controlled by the variable switching time of the solenoid valve. Operation. Before the start of injection the servopiston 24, Fig. 3, engages stop 88 at the end of the preceding filling stroke. Solenoid valve 17 is opened so that ball 63 engages seat 66 to pass fuel into servopressure chamber 29 causing the servopiston to move pump piston 25 downwards into its, Fig. 1, position. Pump piston 25 forces fuel from the pump working chamber 52 through channel 51, Fig. 2, to the nozzle opening 55. The fuel pressure causes needle 35 to commence injection. After injection the solenoid valve 17 closes with ball 63 blocking fuel flow to the control pressure chamber 21 and the latter discharges via line 65, valve seat 66 and bore 67 to line 59 leading to tank 98. Spring 19 moves valve 18 into the Fig. 1, position so that groove 74 connects servopressure chamber 29 to line 59. Pressure drops in the servopressure chamber 29 and the pump working chamber 52, supply valve 27 opens and pressurized fuel forces pump piston 25 upwardly on its filling stroke in a filling time controlled by the throttle 26 until the solenoid switch 17 is again opened. The pressure source may be an engine driven gear pump 93 whose feed pressure is controlled by a pressure control valve 94 which may be speed and/or load dependent. The load dependence is achieved by altering its spring tension in dependence of a driving throttle control position or by rotating a movable valve member of valve 94. The sytem includes a pressure reservoir 95 and filter 97. Fuel leakage to spring cavity 36 passes via lines 77, 78 to line 59.