Patent GB-1478294-A (GB)
Title: Liquid fuel injection pumping apparatus
IPC: F02D1/12
Filed: 1973-07-14
Abstract: 1478294 Fluid-pressure servomotor systems CAV Ltd 8 July 1974 [14 July 1973] 33670/73 Heading G3P [Also in Division F1] In fuel injection pumping apparatus wherein a feedpump 25 delivers fuel to the pumping chamber 11 of a fuel injection pump, the amount of fuel supplied being controlled by an adjustable throttle valve 40, 4,1 having a groove 54 connected to the feedpump outlet 27 and co-operable with a port 55 leading via a line 21 to the injection pump; the delivery pressure of the feedpump, the centrifugal operation of the throttle valve 40, 41 and the provision of fixed and variable restrictors 47 and 52/60 are arranged to produce a pressure in a branch conduit 45 for effecting adjustment of an injection pump component 13, the pressure thereby being dependent on the speed at which the apparatus is driven and on the setting of the throttle valve. The throttle valve comprises a fixed sleeve 40 in which slides a rod member 41 acted on at one end by centrifugal governor weights 43 and at the other end by a valve-member 48 loaded by a spring 49. The force of the spring 49 is adjustable by an operator controlled member 51. The injection pump is of the radial cylinder rotary distributer type in which the throttle valve controls the charging of fuel to one end of a bore containing a shuttle 19, the latter being moved by feedpump pressure admitted to the other end of the bore to displace the fuel into the pumping chamber 11. The pressure established in the branch conduit 45 acts on a servo-piston 38 controlling a piston 39 movable to adjust the angular position of the injection pump cam ring 13 and thus alter the injection timing. Fuel from the pump 27 not entering the line 21 flows through communicating ports 59, 60 in the sleeve 40 to a groove 52 in permanent communication with the branch conduit 45, the pressure established in the conduit 45 being dependent on the degree of alignment of the groove 52 with the port 60, i.e. the size of the variable restrictor 52/60, and the rate at which fuel flows from the groove 52 through the restrictor 47 to a right hand axial bore in the rod 41. The pressure in the right hand axial bore is proportional to the square of the speed due to the combined action of the weights 43 and the valve-member 48, the actual pressure being lower than the output pressure of the feedpump since the right hand bore pressure passes through a port 56 to act with a spring 57 in loading a valve-member 58 towards a position in which it prevents relief of the feedpump delivery. In the embodiment shown the right hand axial bore receives the feedpump pressure through a fixed resistor 53 as well as through the restrictor 47, but the restrictor 53 need not be provided. In a modification Fig. 5 (not shown) special adjustment of the cam ring 13 during idling is achieved by connecting the conduit 45 directly to the feedpump through a groove (69) in an abutment 50, when the operator controlled member 51 is in the idling position. Alternatively Fig. 7 (not shown) the groove (74) in the abutment 50 may be arranged so that when the member 51 is in the idling position it connnects a conduit (73) to drain, the conduit (73) leading to a cylinder supplied with feedpump pressure through a restriction (72) and containing a piston (71) acting on the spring loading the servo-piston 38. To modify the branch conduit pressure speed characteristic additional restrictors (75, 76), Fig. 8 (not shown) or (79), Fig. 10 (not shown) may be provided.