GB956561A - Variable delivery pumps - Google Patents

Abstract

956,561. Fuel injection pumps. C.A.V. Ltd. Dec. 16, 1960 [Dec. 31, 1959], No. 44446/59. Heading F1A. A variable delivery pump e.g. for fuel injaction to a single cylinder engine comprises a shuttle c movable in a bore and, in part, defining at opposite sides thereof a pair of chambers b, d, a plunger e reciprocable in the chambers d during alternating filling and discharge of the chamber b, an adjustable throttle valve o for proportioning the simultaneous flow to both chambers through respective spring-loaded ball valves m, k, during the filling of the chamber b, a further spring-loaded ball valve h for controlling an outlet from the chamber b, and a spill port p which is uncovered by the shuttle during each discharge stroke of the plunger e and permits escape of liquid from the chamber d, thereby terminating discharge from the chamber b. In a modification, (Fig. 2 not shown), for a four cylinder engine the camshaft is connected to the plunger through gearing whereby the plunger constitutes a rotary distributer. In a further modification, Fig. 3, the shuttle 23 is located in the axial bore of a cylindrical rotary distributer, and fuel fed by a pump 2 passes to both sides of the shuttle 23 by annular chambers 14, axially adjustable throttle 20 and supply ports 16, 17 with which supply passages 18, 19 communicate during the rotation. In a modification, Fig. 8, of this embodiment, a spring loaded valve piston 27 uncovers an additional supply port 26, to the side of the shuttle feeding the plungers 7 of the injection pump, by an amount determined by the feed pressure in the chamber 14, and thereby causes the plungers to move further outwardly into reliefs in the eccentric (Fig. 11 not shown). The commencement of the injection stroke is thus varied in accordance with the feed pressure i.e. the engine speed. A further spring loaded valve piston connects the chamber 14 directly to each passage 19 in turn, to deliver a quantity of fuel dependent on the feed pressure, i.e. on the engine speed. Since the total quantity of fuel fed to the bore of the distributer is constant, the amount passing through the throttle 20 decreases with engine speed, and hence the fuel fed to the engine decreases with increasing engine speed. The opposite effect can be achieved instead by suitable arrangement of the piston valve. In a further modification (Fig. 13 not shown) the throttle is angularly adjustable to vary the distribution of fuel between ports 16 and 17. In a further modification, (Fig. 18 not shown) the supply passages 19 are widened at their outer ends, to remain connected with the port 17 after the corresponding passages 18 have moved out of register with the port 16, thus feeding an additional charge of fuel to the plungers, moving them into the reliefs in the eccentric and thereby advancing the injection; alternatively the injection may be retarded by the modification in Figs. 19 (not shown) and 20, where a separate timing port 34 is provided to register in turn with the passages 19 after the passages 18 have moved out of register with the port 16, the port 34 communicating with the port 16 through a passage. In a further modification, (Fig. 21 not shown), a separate port, equivalent to the port 34, is in direct communication with the throttle and is fed thereby in amounts determined by the axial setting of the throttle, such that, by a change of throttle plug, it can be predetermined whether a light load for a given engine speed should result in advance or retard of injection, as compared with a heavy load at the same speed.