GB946741A - Improvements in or relating to fuel injection pumps - Google Patents

Abstract

946,741. Fuel-injection pumps. MONO-CAM Ltd. Feb. 15, 1960 [Feb. 24, 1959; April 7, 1959], Nos. 6403/59 and 11779/59. Heading F1A. A fuel injection pump comprises at least one piston and cylinder pumping assembly in which the effective length of the delivery stroke of the piston is controlled by governor means exposed during the injection stroke of the piston to a liquid pressure which moves the governor means to connect the pumping chamber to a spill passage when the engine speed exceeds that for which the pump is set and wherein the time during which the governor means is exposed to liquid pressure is a function of the time between the commencement of the injection stroke and the end of the immediately preceding injection stroke. As shown in Fig. 1, a piston 1 slidable and rotatable in a cylinder bore 2 to deliver fuel to a four cylinder compression-ignition - engine is formed with an enlargement 20 movable in an enlarged portion 19 of the bore 2. On the injection stroke of the piston 1, fuel admitted to the enlarged portion 19 through an inlet 23 is pumped up a passage 21 and through a non- return valve 22 to admit the fuel beneath a valve body 10 loaded by a spring 12. When the pressure of this fuel reaches a predetermined value the valve body 10 moves upwardly to connect the pump chamber through a passage 7 and an annular chamber 13 to a spill passage 14 whence pump delivery through axial and radial passages 24, 25, and an elongated slot 26 in the piston and a delivery passage 27 ceases. At the same time axial and radial passages 15, 16 in the valve body 10 connect the underside of the valve body with a spill port 51 to prevent any further upward movement of the valve body during the remainder of the injection stroke. On the suction stroke of the piston, the non-return valve 22 closes and fuel from beneath the valve body 10 passes through a restricted outlet adjusted on rotation of the valve body provided by a crescent-shaped valve body recess 17, and a passage 18 to the enlargement 20. If, e.g., the engine speed is in excess of that set by the pump the time between injection strokes is decreased with the result that less fuel passes through the restricted outlet and downward travel of the valve body 10 is reduced so that at the next injection stroke the valve body 10 has less distance to travel before the spill passage 14 is opened resulting in earlier cut-off of pump delivery and consequent reduction in engine speed. Helical grooves 31 in the piston 1 and a spill passage 32 are provided to control spill for the associated engine cylinder at maximum engine load. In a modification, the valve body 10, Fig. 3, is disposed at right angles to the axis of the cylinder bore 2 and an adjustable plug 37 and a control rod 38 adjustable with respect to the plug are fitted to provide a control for maximum engine load. When starting the engine the rod 38 is withdrawn to allow increased travel of the valve body 10 and increased fuel to the engine.