GB963069A - Improvements in fuel injection systems for internal combustion engines with automatic variation of the advance of fuel injection - Google Patents

Abstract

963,069. Fluid-pressure servomotor systems. SOC. ANON. POUR L'EXPLOITATION DES PROCEDES CHIMIQUES ET PHYSIQUES. Dec. 6, 1960 [Dec. 10, 1959; Sept. 19, 1960], No. 41999/60. Heading G3P. [Also in Division F1] A device for automatically varying the advance of fuel ignition in a fuel supply system for an internal combustion engine comprises a threaded sleeve 20 coupling the shaft 3 of the injection pump 1 with the engine driving shaft 16 and capable of being moved axially by a hydraulic ram the piston 23 of which is displaced by a variable pressure against the action of a return spring 27 characterized in that the variable pressure is produced by a volumetric pump 31, 32 driven at a speed proportional to that of the engine feeds in parallel arrangement fuel to the cylinder 2 of the injection pump and to the hydraulic ram and wherein in the delivery conduit 33 leading from the pump to the ram there is provided a leak 34 in the form of an outlet the cross-section of which increases when the delivery pressure increases and inversely so that the variation of section of the leak outlet, as a function of the speed, produces a moderation of the variation of the pressure acting upon the ram piston 23. The piston 1 of the ejection pump is actuated, via a roller 5 and slider 6, by a cam 4 provided on the shaft 3 which is connected to the engine driving shaft 16 by a helical thread 21, 22 formed in the coupling sleeve 20, a shoulder 51 on the latter being urged by the spring 27 into contact with a shoulder formed on the piston 23. In operation, fuel is fed by the pump 31, 32 into the cylinder 2 of the ejection piston 1, the excess fuel being fed via a pipe 33 and leak 34 back to the reservoir, the leak orifice being controlled by a spring loaded valve 56. At low speeds fuel is prevented from acting on the piston 23 and thereby advancing the injection, by a spring loaded valve 59. When the speed increases above a certain value, pressure in the pipe 33 increases and acts on the valve 59 to thereby permit the fuel to act on the piston 23 and so advance the injection. In order to control the flow of fuel from the cylinder 2 to the injectors, the piston 1 is formed with a larger piston 37 which, during each reciprocation of the latter piston, forces fuel, via a non-return valve, to act on a spool valve 36, the latter then permitting excess fuel in the cylinder 2 to be returned to the reservoir via a passage 40. The return of the spool valve 36 is controlled by a dash-pot effect adjusted by a throttle valve 43 in order that, during high speed operation of the engine, the spool is maintained in its upper position and thus permit the excess fuel in the cylinder 2 to be returned to the reservoir. In a modification, in order that the fuel injection may be advanced, if necessary, at slow speeds when the engine is under load, the passage 40,Fig. 2, leading to the reservoir is connected to an accumulator 44 so that the excess fuel from the cylinder 2 is fed into the latter before being returned to the reservoir via a throttle valve 34a; the reservoir is connected with a pipe 33a which provides communication with the piston 23. By adjusting the throttle valve 34a, a pressure may be built up in the pipe 33a in order to actuate the piston 23 at low speed. The piston 1 is rotated by a gear arrangement 35, 45 in order to distribute the fuel to a number of injectors.