US3487783A - Liquid fuel injection pumps - Google Patents

Description

Jan. 6, 1970 Filed June 14, 1968 J. P. s. CURRAN ETAL LIQUID FUEL INJECTION PUMPS 2 Sheets-Sheet 1 V J 2 5 IN ENTOR awn awe.

1970 J. P. s. CURRAN ETAL 3,487J&

LIQUID FUEL INJECTION PUMPS Filed June 14, 1968 2 Sheets-Sheet 2 INVE TOR 7 21.01.10? kuwcm L) cflaudd United States Patent 3,487,783 LIQUID FUEL INJECTION PUMPS John Patrick Stewart Curran, Tuifley, and David Elliot, Stroud, England, assignors to Bryce Berger Limited, Gloucestershire, England Filed June 14, 1968, Ser. No. 737,143 Int. Cl. F0411 13/042, 17/00; F15b 11/08 U.S. Cl. 10350 4 Claims ABSTRACT OF THE DISCLOSURE A fuel injection pump comprising a reciprocable plunger which during inward movement displaces fuel until a spill port is opened, a piston being provided to effect inward movement of the plunger and the piston having fluid pressure applied thereto from a source by way of a valve and a flow regulator, the flow regulator acting to limit the rate of flow of fluid when the port is opened.

This invention relates to liquid fuel injection pumps for supplying fuel to a combustion space of an internal combustion engine and of the kind comprising in combination, a pump plunger which during a pumping stroke displaces fuel from a pumping chamber to the engine, the termination of discharge to the engine being effected by the uncovering of a spill port by the plunger at a predetermined position during the pumping stroke, and a fluid pressure operable piston contained within a cylinder for imparting movement to the plunger, said cylinder being arranged to receive fluid under pressure from a source in timed relationship with the engine.

With such a pump when the spill port is opened, the force which opposes movement of the plunger and piston is suddenly reduced with the result that rapid acceleration of the plunger and piston occurs. The plunger and piston must eventually be arrested, and the object of the present invention is to provide in such a pump means whereby the sudden acceleration is minimised.

According to the invention in a pump of the kind specified, a flow regulator is provided to control the flow of fluid into said cylinder, said flow regulator being adjusted so that when the resistance to the flow of fluid decreases, as a result of the spill port being uncovered by the plunger, the flow regulator moves to restrict the rate of flow of fluid into the cylinder, thereby limiting the acceleration of the plunger and piston.

In the accompanying drawings:

FIGURE 1 is a sectional side elevation showing one example of a pump in accordance with the invention, and

FIGURE 2 is a view of part of the pump shown in FIGURE 1 to an enlarged scale.

Referring to the drawings there is provided a pumping plunger which is accommodated within a cylindrical bore formed in the body part of the pump. The inner end of the bore is in communication with an outlet 11, and for controlling the flow of fuel through this outlet, there is provided a non-return delivery valve 12. In use, the outlet is connected to a fuel injection nozzle 13 which is arranged to direct fuel into a combustion space of an engine with which the pump is associated.

Formed in the wall of the bore is a spill part 14 which is in communication with a fuel supply chamber 15 formed in the body part and which, in use, is connected to a source of liquid fuel. Formed on the periphery of the plunger is a helical groove 16 which is in communication with the pumping chamber defined by the bore. In use, during inward movement of the plunger 10, fuel is expelled from the pumping chamber by way of the outlet 11 until the helical groove 16 is exposed to the spill port 14, whereafter the delivery of fuel to the engine ceases, and the remaining fuel in the pumping chamber is expelled through the spill port. During outward movement of the plunger, as soon as the port 14 is uncovered, fuel from the supply chamber 15 flows into the pumping chamber and completely fills same.

The plunger is loaded in the outward direction by means of a coiled compression spring 17 and for moving the plunger inwardly against the action of the spring, a fluid pressure operable piston 18 is provided. This is located within a cylinder 19 which may be formed in the body part of the pump or in a part adapted to be secured thereto.

There is also provided a source 20 of fluid under pressure and this may comprise a pump which is driven by the engine and which supplies fluid to an accumulator. Fluid under pressure is supplied to the cylinder under the control of a valve 21 which is operated in timed relationship to the engine, and the arrangement is such that when the valve is opened, fluid under pressure acts on the piston 18 to effect inward movement of the plunger 10.

The return motion of the piston 18 and the plunger 10 is effected by closing the valve 21 and opening a valve 25 which is operated in synchronism with the valve 21. The valve 25 when opened allows fluid to flow from the cylinder 19 to a drain.

Such systems are fairly well known, and one of the problems with such a system is the fact that as soon as the spill port 14 is opened to the helical groove 16, the force restraining the inward movement of the plunger and piston is reduced, with the result that rapid acceleration occurs, and the plunger and piston attain a high velocity and eventually must be stopped either by positive stops or by means of dash pots.

In the present system a flow regulator 23 is provided to control the flow of fluid into the cylinder. As shown in FIGURE 2 the flow regulator comprises an elongated cylindrical chamber 30, the opposite ends of which are closed by adjustable plugs 31, 32. The plug 31 constitutes a stop, and the other plug constitutes an abutment for a coiled compression spring 33. Intersecting the chamber is a flow passage 34 through which fluid is arranged to flow to the cylinder containing the piston, and slidably accommodated within the chamber is a regulator element 35 upon one end of which acts the spring. The regulator element is of reduced section intermediate its ends and at a position corresponding to the flow passage. Moreover, the end of the element upon which the spring 33 acts is exposed to the pressure at the downstream end of the flow passage, and the other end of the valve element is exposed to the pressure at the upstream end of the flow passage.

In use, the plugs 31, 32 are adjusted so that the regulator offers little restriction to the flow of fluid to the cylinder 19 when the spill port 14 is closed. However, when the spill port is opened and the resistance to the flow of fluid suddenly decreases, the pressure drop which occurs between the ends of the flow passage increases sufficiently to move the regulator element 35 against the action of the spring. This movement restricts the effective area of the flo'w passage so that the rate at which fluid can pass to the cylinder is also restricted, and the acceleration of the piston and plunger is limited. Furthermore, because of the increased restriction to flow, the pressure drop also increases, the final result being complete closure of the flow passage. Adjustment of the plug 32 enables the regulator to be adjusted to operate at a given pressure drop, whilst adjustment of the plug 31 serves to enable the regulator to be adjusted to operate at a given flow.

Having thus described our invention, what We claim as new, and desire to secure by Letters Patent is:

1. A liquid fuel injection pump for supplying fuel to a combustion space of an internal combustion engine and of the kind comprising in combination, a body in which is defined a bore, a pump plunger slidable within the bore and which during a pumping stroke displaces fuel from the bore to the engine, a spill port which is uncovered by the plunger at a predetermined position during the pumping stroke to terminate the discharge of fuel to the engine, a fluid pressure operable piston contained within a cylinder for imparting movement to the plunger, and a flow regulator for controlling the flow of fluid into said cylinder from a source, said flow regulator being adjusted so that when the resistance to the flow of fluid decreases, as a result of the spill port being uncovered by the plunger, the flow regulator moves to restrict the rate of flow of fluid into the cylinder, thereby limiting the acceleration of the plunger and piston.

2. A pump as claimed in claim 1 including a first valve operable in synchronism with the engine to admit fluid under pressure from said source to the cylinder through said flow regulator and a second valve operable in synchronism with the engine to permit fluid to escape from said cylinder.

3. A pump as claimed in claim 1 in which said flow regulator comprises a spring loaded regulator element slidable within a chamber defined in a body part, a flow passage defined in said body part and through which fluid flows from said source to the cylinder, said chamber in- K tersecting said flow passage and the element defining a restriction to the flow of fluid through the flow passage, means biasing the element towards one end of the chamber, passage means through which said one end and the other end of the chamber are in communication with the upstream and downstream ends of the flow passage respectively whereby the element is exposed to the pressure drop across the restriction the arrangement being that when said pressure drop increases due to the reduced resistance to the flow of fluid when the spill port opens, the element will move to restrict the rate of flow of fluid through the flow passage.

4. A pump as claimed in claim 3 including a pair of adjustable plugs serving to close the opposite ends of the chamber, the plug at said one end of the chamber defining a stop for the valve element whereby the degree of restriction to the flow of fluid through the flow passage can be adjusted, and the plug at the other end of the chamber defining an abutment for the spring whereby the force exerted by the spring can be adjusted.

References Cited UNITED STATES PATENTS 1,956,612 5/1934 Brun 103150 2,033,579 3/1936 Koster 10337 2,662,476 12/1953 French 103-50 2,756,724 7/1956 Stewart et al. 91447 2,879,745 3/1959 Brown 91-447 3,168,010 2/1965 Thomas 91447 WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 9l447; 103-37

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