GB1507919A - Fuel pumping apparatus - Google Patents

Abstract

1507919 Fuel injection pumps; starting fuel injection engines LUCAS INDUSTRIES Ltd 28 June 1975 27441/75 Headings F1A and F1B [Also in Division G3] A fuel injection pumping apparatus for an internal combustion engine includes a valvemember 58 operable to vary the timing of the injection pump in response to a force which varies in accordance with the axial setting of a member 34 and a pressure signal dependent upon the square of the speed N of a feedpump 26. The latter is provided with a relief valve 29 which is both spring and fluid biased towards a closed position such that the feedpump outlet pressure in line 27 varies as N<SP>2</SP> + a constant K. Line 27 is in constant communication with a groove 44 in member 34, the groove and port 43 in fixed sleeve 33 constituting an adjustable orifice through which fuel is supplied via shut-off valve 32 to a rotary distributer 10. Member 34 is acted on by engine driven centrifugal weights 40 tending to displace the member axially in opposition to a bias set by operating lever 38 acting via plunger 37, spring 36 and valve closure member 35. The latter restricts the open end of a blind bore 41 within member 34 and supplied via restricted orifice 42 from the feed pump outlet 27. Thus the pressure in bore 41 varies as N<SP>2</SP> and is communicated as the fluid bias to the relief valve plunger 30. This pressure is also communicated directly, or indirectly via valve arrangement 61, 64, to act on the lower end of valve spool 58. The latter has a land co-operating with a passage 57 through piston 54 to control flow of fuel at feedpump output pressure via non- return valve 60 to and from a chamber below servopiston 54. Increase or decrease in pressure thus causes piston 54 to move upwards or downwards to rotate the attached annular cam ring 13 of the injection pump in a direction to respectively advance or retard the injection timing. Valve spool 58 is also subject via spring 59 to the fuel flow acting above piston 52. This flow is maintained at constant pressure by a valve 45 and since it passes through a variable orifice constituted by port 49 and groove 51 in member 34, the position of piston 52 is dependent upon the axial setting of member 34, i.e. upon the quantity of fuel supplied to the engine. The flow to piston 52 is prevented when the pressure in bore 41 is unsufficient to open switch valve 50. To retard the injection timing at starting, the application of pressure to the lower end of valve spool 58 may be delayed by operating a latch 63 of valve arrangement 61, 64 to enable an annular rib on the top of spring-biased piston 61 to engage resilient seat 64 and initially block the flow to the spool. Piston 61 also carries a contoured stop surface 62 for a shuttle 19 associated with rotary distributer 10, the surface 62 determining the maximum amount of fuel for any engine speed and being shaped to provide extra fuel at starting after operation of latch 63.