GB784425A - Improvements relating to fuel injection pumps - Google Patents

Abstract

784,425. Fluid-pressure servomotor-control systems. S.U. CARBURETTER CO., Ltd. Jan. 17, 1956 [Feb. 24, 1955], No. 5527/55. Class 135. In a fuel injection pump for spark-ignition internal-combustion engines the spring-loaded plungers 5, Fig. 1, are operated by a wobbleplate 4 controlled by a piston and associated skew shaft 1 longitudinally slidable on a driveshaft 3. The shaft 3 has a central passage 8 having inlet ports 7 and outlet ports 9, the latter being controlled by a sleeve valve member 13. A spring 14 is located between the piston 1 and the member 13 and acts on the latter through a thrust race 15. The valve member 13 is supported by the forked end of a pivoted lever 16, the other end of which is connected by thrust pins 18, 19 to a bellows 20 in a chamber connected by a port 22 to the induction manifold of the engine. Pressurized oil is supplied through an inlet 6 to the upper side of the piston 1 and passes through the ports 7, the passage 8, the ports 9 and ports 13A in the member 13 to the chamber 10 at the other side of the piston. Oil continually leaks from the chamber 10 to the sump, either through a port 11 or through the port 27, the passage 28 and the port 29. To increase the speed with which the sleeve 13 moves to a position in which the pressures on both sides of the piston 1 balance after a sudden decrease in the induction manifold pressure, the rate of leakage from the chamber 10 is momentarily increased. To this end the outlet passage 28 in the shaft 3 is provided with additional inlet ports 26 which are normally closed by the valve member 13. If the induction manifold pressure suddenly drops, the bellows 20 expands and the sleeve 13 is moved upwardly to uncover the ports 26 so that the leakage rate is momentarily increased and the sleeve 13 moves to establish equilibrium. In a modification the lower edge 30, Fig. 3, of the member 13 has a notch 31 which in normal operation successively uncovers the ports 26 to provide a permanent leak from the chamber 10. Upon a sudden reduction of manifold pressure the sleeve 13 is moved to uncover all ports 26 so momentarily increasing the leakage rate. Specifications 533,596 and 552,547, [both in Group XXVIII], are referred to.