GB1394280A - Pump zozzles for fuel injection systems - Google Patents

Abstract

1394280 Electromagnetically controlled fuel injectors ROBERT BOSCH GmbH 26 May 1972 [28 May 1971] 24831/72 Heading F1B A fuel injection pump nozzle comprises a pump piston 15 Fig. 1 driven by a larger servopiston 14, the nozzle being connectible to a pressurized fuel source arranged to feed fuel to the pump piston, servopiston and to a valve spool 12 via an electromagnetically operable valve 18, Fig.2 operable in synchronism with an I.C. engine, the valve spool controlling the flow of fuel to and from the servopiston to control the pumping and return stokes of the pump piston 15 which has an oblique control edge 21 co-operating with a control bore 23 to control the termination of injection and injection quantity in dependence on the rotary position of the pump piston. The pump working chamber 24, Fig.3 is fed via line 26 through a throttling gap 'a' at the end of the return stroke (T.D.C.) and returns fuel to the reservoir through bore 23 entraining any bubbles present in working chamber 24. During the pumping stroke of piston 15 the fuel passes through valve 37 and lines 49, 51 to chamber 52 where fuel pressure acts on surface 53 to open the valve needle 44. Chambers 45, 55, 56 and groove 54 communicate with bore 57 to return leakage fuel. Operation: In the Fig. 3 position the servo pressure chamber 95 is connected to a pressure source 105, the pressure of which may be engine speed or load dependent, so that servopiston 14 moves pump piston 15 downwardly against spring 65. The gap "a" and then bore 23 is closed to commence injection. Injection is terminated when edge 21 opens bore 23, Fig. 4 to relieve chamber 24 to reservoir 111 via groove 32 and line 33. Valve 17 retains a predetermined pressure in lines 49 and 51. With the termination of injection the solenoid valve 18 is changed to its Fig.4 position by a signal from an electronic control device 115. The latter determines the switching times of the valve 18 in dependence on a speed signal from tachogenerator 116 a pump piston position signal from position sensor 117 and a desired value signal from a regulator 119. In a modification the connections to the solenoid valve 18 and valve spool 12 are arranged so that the electromagnet is energized during the pressure stroke. In another modification the solenoid valve return line 79, Fig. 2 is led back to chamber 96.