GB1122886A - Improvements in fuel injection pumps for internal combustion engines - Google Patents

Abstract

1,122,886. Fuel injection pumps. ROBERT BOSCH G.m.b.H. May 9, 1967 [May 9, 1966], No.21471/67. Heading F1A. In a fuel injection pump of the type in which a spill valve is actuated by liquid delivered by an auxiliary pump, the cam drive of the auxiliary pump pistons is ineffective at start-up speeds. In the embodiment shown in Fig. 1 a rotary pump head 4 has an injection pump cylinder 8 and an auxiliary pump cylinder 9 and is combined with a rotary valve and distributer 3. The cylinder 8 is connected to a bore 18 terminating in a groove 19 connected with inlet grooves 20 and an outlet groove 22; the bore 18 also connects with a groove 42 in communication with a passage 33 leading to the cylinder of the spill valve 15. A groove 28 connects by passages 29 with the cylinder 9 and by passages 39 and throttle passage 40 with the actuating chamber 32 of the spill valve 15. The groove 28 and hence the cylinder 9 is connected on the suction stroke of the auxiliary pump to an inlet 26 and through a valve 31 to the chamber 32, by the grooves 27. The inlet chamber 7 is fed by feed pump 45 with liquid at a pressure variable with speed. Fuel passes through a pressure maintenance valve 52 to a chamber 55 to lubricate the cam mechanism and passes from the chamber 55 through a pressure maintenance valve 56. One of the auxiliary pump pistons 16 has a spring 58 therein which engages the tappet 11 so that without pressure in the inlet chamber 7 and cylinder 9 the pistons 16, 16a engage and reciprocate together so that no pressure is generated to operate the valve 15 is that maximum fuel is delivered. When pressure builds up in the chamber 7 and cylinder 9 the pistons 16, 16a are pushed into engagement with their cam followers and liquid is delivered to the chamber 32 of the valve 15 to regulate the spill. In a modification, Fig. 4, the auxiliary pump chamber 25a is formed in one of the injection pump pistons 10a and the auxiliary pump piston 16b is disposed in coaxial bores in the pistons 10a, 10b, a spring 58a being disposed between the pistons 10b and 16b. In addition to the spring loading the auxiliary pistons 16, 16b are subjected to the pressure in the chamber 55 which pressure may be varied by setting the valves 52, 56, so that the point of delivery by the auxiliary pump may be varied.