GB1187074A - Improvements in or relating to Fuel Injection Pumps for Internal Combustion Engines. - Google Patents

Abstract

1,187,074. Fuel injection pumps. ROBERT BOSCH G.m.b.H. July 13, 1967 [July 19, 1966], No.32185/67. Heading F1A. In a fuel injection pump of the type in which output is regulated by means of a by-pass or spill valve actuated by pressure generated by an auxiliary pump, return flow of the actuating liquid and hence the return of the valve towards its initial position being controlled by a throttle, a second by-pass passage is opened by the pump plunger before the by-pass valve opens, during conditions under which the by-pass valve returns to its initial position. The plunger 1 is reciprocated and rotated and comprises an injection portion 1a operating in an axially adjustable cylinder 2 and controlling inlet ports 46, a distributing portion 1C having a port 12 distributing to outlets 13 in succession and a portion 1b forming the auxiliary pump and having grooves 16 controlling the flow and return of actuating liquid to the by-pass valve 5 which regulates the spill from the chamber 3 via the passages 9, groove 6, passages 30a and 31 to the inlet chamber 11. The groove 6 also communicates with grooves 7 which appropriately connect with inlet 10 from chamber 11. The groove 6 also connects with a groove 33 towards the end of the plunger stroke providing a second spill or by-pass valve, groove 33 connecting via passage 32, normally open valve 34 and passage 32a with the chamber 11. Valve 34 is held open during normal running by pressure in the chamber 11 but during starting is held closed so that maximum fuel is delivered. The arrangement is such that the by-pass 6, 33 opens before the by-pass 30a, 30b when the valve 5 starts from its stop 28 or from a point closely adjacent thereto i.e. under low speed operation of the engine. In a modification Fig. 3 (not shown) the auxiliary pump chamber is by-passed through a passage throttled by the valve 34 during starting so that the valve 5 cannot be operated. Should the valve 34 stick the throttled aperture would allow the valve 5 to operate before excessive speed is reached. In a further modification Fig. 4 (not shown) the plunger portion 1a has ports which function as the second spill or by-pass, which ports co-operate with normally open ports in the cylinder 2. During starting these latter ports are closed by a spring pressed sleeve surrounding the cylinder 2 but which is raised to open the ports by the pressure from the feed pump.