GB564303A - Improvements in regulating devices for controlling the supply of fuel to internal combustion engines - Google Patents

Abstract

564,303. Regulating. HOBSON (AIRCRAFT & MOTOR) COMPONENTS, Ltd., H. M., and STOKES, P: H. June 22, 1943, No. 10053. [Class 7(vi)] [Also in Group XXIX] The pressure difference across a fuel metering orifice through which fuel is pumped to the engine is independent of the engine speed and the effective area of the orifice is varied as a function thereof. A pump 10, Fig. 1, feeds fuel through a pipe 14 past a pressure-regulating valve 12 and metering device 11'to an injection nozzle 18, the valve 21 of which is opened by fuel pressure acting upon a diaphragm 19 against pressure of a spring 20 in a chamber exposed to atmospheric or boost pressure. The regulating-valve 12 remains closed until the pump has built up sufficient pressure around it to lift a diaphragm 15, connected to the valve, against the pressure of a spring 23 in a chamber communicating with the passage 14 on the remote side of the metering device 11 by a passage 17, the valve then permitting fuel to flow back along a conduit 16 to the input side of the pump. The metering device 11 comprises two nested cylinders 43, 44 having ports 41, 42 which overlap to an extent determined on the one hand by a centrifugal governor 45 which moves the inner cylinder 44 vertically and on the other hand by a servomotor 46 which rotates the outer cylinder 43, overlapping outlet ports on the opposite side of the cylinders being arranged to provide an outlet of constant area. The cylinder 43 is rigid with a sleeve 49, Fig. 3, carrying the vanes 47 of the servomotor 46. A scroll valve 50 within the sleeve 49 controls the supply of fuel or other pressure fluid to inlet and outlet ports 56, 57 in the sleeve 49, fuel being admitted to rotate the vanes 47 when a rod 77 carrying the scroll valve 50 is raised or lowered to register slots 51, 54 in the valve with the ports 56, 57. The rod 77 is secured to a capsule housed in a chamber 65 to which boost pressure is communicated through an inlet 66. The lower part 59 of the capsule is evacuated to make it responsive to the boost pressure while the smaller upper part 60 is exposed to the exhaust back pressure. The top of the capsule is positioned by a lever 64 set by a Bourdon tube 63 actuated by a thermometer bulb 69 in the induction pipe. A slow-running nozzle 127 and cock 27, in a pipe 28 forming a byepass for the metering device 11, permit adjustment of the mixture strength during slow-running, the cock 27 being linked at 29 to the pilot's throttle 30. The link 29 also actuates an acceleration pump comprising a diaphragm 33 adapted to be displaced to the right to create a depression in a chamber 37, the opposite wall of which consists of a diaphragm 34 connected to an additional fuel valve 35, the fuel flowing past this valve until leakage into the chamber 37 through a restricted orifice 39 has restored pressure therein. The actual pressure difference across the metering orifice may be varied by a cam 25 which depresses the spring 23 of the pressure-regulating valve 12 and is linked to the pilot's control lever 30. The cam 25 may be arranged to take over the functions of the slow-running control 27, 127 or to reduce the fuel flow when it is desired to introduce anti-detonants &c. thereto. The mixture strength may be varied by shaping the ports 41, 42 and the rod 77 be rotated manually to bring the shaped portions into operation. As shown in Fig. 5, the metering orifice 73 is controlled by a needle valve 74 operated by a slotted lever 75 connected at its other end to the capsule 59, 60 and rocked about an adjustable pivot 79 formed by the end of a cranked rod 80. The major arm of the cranked rod 80 is moved axially by the centrifugal governor 45 acting through a cam slot 81 which converts the relationship of fuel supply to speed to a linear one. Specification 419,113 is referred to.