GB1422422A - Electromagnetic fuel injectio- valves for internal combustion engines - Google Patents

Abstract

1422422 Electromagnetic fuel injectors ROBERT BOSCH GmbH 2 March 1973 [3 March 1972] 10261/73 Heading F1B The valve member 12 is biased against a seat 15 by a spring 35 and is connected to an electromagnet armature 33 and a compensating piston 41. The fuel supply pressure acting on the member 12 acts on one end-face 44 of the piston 41, the other end-face 43 being effectively subject to substantially atmospheric pressure. The piston diameter DKI is equal or substantially equal to the diameter DSI of the member 12 at the maximum diameter of seat engagement and thus with the member seated the fuel pressure forces acting to open and close the injector are substantially equal. A spring wire 45 connecting the piston 41 and armature 33 and the member 34 articulated to the armature 33 and the member 12 permit slight misalignment of the axes of the guide bores of the piston, armature and member. A restrictor 31 in the fuel flow-path to the injector chamber 22 provides, when the injector is open, a pressure less than the supply pressure in the chamber to compensate for the increased cross-sectional area of the valve member subject to fuel pressure and tending to open the injector. The fuel may be supplied to the injector 10 by an engine-driven gear or piston pump 19 with a pressure regulating valve 23 to provide a desired supply pressure, e.g. 200 or 400 bar. The valve 23 may be combined with a pressure accumulator. The compensating piston (93), Fig. 3 (not shown), and the restrictor (82) may be mounted in a bush (95) mounted in the injector body and formed in a threaded part (81) mounted in the valve member (67), respectively, for interchangeability. The valve member (67) may have a throttling pintle (74), Fig. 3a (not shown), at its downstream end and the member may have line contact with the valve seat (71). The compensating piston (138), Fig. 5 (not shown), may be connected between the armature and the valve member (132), the connecting rod (155) between the piston and member may be coupled thereto by ball and socket joints (161, 163, 162, 164). The injector discharge openings may be provided in a pin portion of the valve member downstream of the seat engaging surface. A pintle portion of the valve member downstream of the seat engaging surface may be spaced from a surrounding bore in the injector body and at least one bore extend through the pintle portion. The space and bore provide parallel fuel flow-paths.