GB583897A - Improvements in fuel-injection systems for internal-combustion engines - Google Patents

Abstract

583,897. Valve gear. MUNTZ & CO., Ltd., A., and BEALE, E. S. L. March 29, 1944, No. 5834. [Class 7 (vi)] In a fuel-injection system in which fuel is supplied from a continuous source at high pressure, the beginning and end of the injection period are determined by a "flash" valve of the piston type which overruns ports in the valve easing while moving at high speed and disabling means associated with the valve prevent' a second injection on the return stroke of the plunger. A supply pump 22; Fig. 1 delivers fuel to a reservoir 20 adapted to feed the fuel at constant pressure to a timing valve unit 29 and the timing valve both determines the time of operation of a metering or "flash" valve 28 of the piston type and ensures that the flash valve shall not operate on the return stroke of the piston. The flash valve supplies one or more injection nozzles 64. At starting, a priming pump 24 driven by compressed air is adapted to charge 'the fuel reservoir 20 to working pressure at a single stroke. Fuel delivered from the reservoir 20 through a pipe 18 to ports 35, Fig. 2, in the timing valve 29 flows to a transfer pipe 51 when an engine driven cam 31 displaces a spring - pressed hollow tappet 32 far enough to bring a helical slot 34 in a plunger 30 operatively connected to the tappet opposite the inlet ports 35, the fuel traversing a passage 49 in the plunger to a reduced section 50 always open to the transfer pipe 51. The slot 34 is formed as a double helix to co-operate with oppositely disposed inlet ports 35 and the incidence of the flow may be varied by rotating the plunger through a rack 37 and pinion 38 manually by a lever arrangement 42, 41, 45 or automatically as described in Specification 579,734. Fuel flow continues until release ports 36 are uncovered by the slot 34 whereupon the fuel escapes through a restricted orifice 89, which minimises cavitation, and passages 48, 47 to a reservoir 46 containing an elastic capsule 90 adapted to damp out pulsations in the flow. Part of the fuel in the transfer passage 51 traverses a pipe 81 and passage 80 to displace an hydraulic plunger 72 which engages a hollow spring-pressed tappet 73 connected to the plunger 52 of the flash valve unit 28. This plunger is similar to the plunger 50 and may be rotated to adjust the quantity of fuel delivered. It is subjected to rapidly accelerating movement 'by the hydraulic plunger 72, ports 57 in the transfer passage 51 being open to the helical slot 56 in the plunger and, through the axial passage 55, with a reduced portion 53 thereof. When the plunger is moving rapidly, the portion 53 uncovers delivery ports 54 leading to the injection nozzles and the end of the plunger closes ports 83 opening into the release passage 47. The end of the cylinder in which the plunger slides comprises a dashpot 84 from which fluid can escape only through an orifice 85 adjustable to regulate the speed of the plunger which keeps substantially constant. If the pressure in the pipe 51 is low, the length of the injection period increases, as the plunger 52 moves less quickly, to compensate therefor. On the return stroke of the plunger 52, which occurs some time after the engine pistons have passed their inner dead centre positions at a time determined by the timing valve 29, the plunger 50 of the timing valve cuts off the transfer passage 51 from the source of pressure and, there being no pressure in the flash valve 28, no fuel is delivered to the nozzles. An air cushion, operative against the hollow tappet 73, damps the return stroke of the plunger 52. Fuel is delivered to the nozzles through an unloading valve to prevent dribble. For remote operation, a master timing valve is connected by equal lengths of piping to assemblies each comprising a pressure reservoir, a timing and a flash valve, the timing valves being actuated by pressure fluid controlled by the master valve. Specifications 536,671, [Group XXVIII], and 578,436 also are referred to.