US2038311A - Fuel injection pump - Google Patents

Description

April 21, 1936,. F. l.. PARSONS FUEL INJECTION PUMP Filed Aug. 6, 1954 UNITED STATES This invention relates to fuel injection pumps for use with Diesel engines and the like, and the object is to provide a simple and'rugged construction of pump whereby a desired quantity of fuel may be injected at a desired time into the engine cylinder.

The nature of my invention and the advantages resultant from its use will be well understood by those skilled in the art by reference to the following description of the illustrative embodiment thereof shown by way of example in the accompanying drawing which shows the pump in longitudinal section with the parts at the beginning of the injection stroke.

Referring to the drawing, the operating parts of the pump may be organized in connection with a suitable base or body 5 having an intake passage 1 adapted to communicate with a fuel supply and a discharge passage 9, herein shown as connected by means of a pipe I I with an injection nozzle I3 carrying a check valve I5 normally held closed by a spring I1 which provides a determined resistance to the injection .of fuel into the cylinder (not shown). Herein I have shown the body 5 as supporting a suitable liner I9 having a cylindrical bore in which works a piston hereinafter to be referred to and provided -with a passage 2| forming a continuationv of the intake passage 1 and opening to the inner cylindrical lbore of the liner and with' a passage 23 opening from that bore and extending to the discharge passage 9. The junction of the passages in the body and the liner is made at the meeting face 25 of the opposed annular shoulders of the body and the liner which are held pressed together by the threaded collar 21. 'I'his arrangement', as will be apparent in the drawing, facilitates the formation of the rpassages referred to. The body and the liner also provide a passage 29 from intake 1 to the inner bore of the liner for a purpose hereinafter to be referred to, this passage opening at a distance from the opening of the passage 2|.

Working in the liner I provide a piston 3| in the form of a cylindrical sleeve closed at the lower end by the plugs 33 and 35. The piston thus takes the form of a hollow cylinder with an open inner end, and for the sake of brevity I shall hereinafter refer to such a construction as a barrel piston. This piston is reciprocated in the liner by power and herein a spring 31 interposed between the overhanging flange at the upper end of collar 21 and a bearing ring 39 supported at the lower end of the piston tends to thrust it downwardly and holds it in cooperating relation with a cam 4| on a shaft 43. 'I'he cam in the example PATENT OFFICE FUEL INJECTION PUMP Frederick L. Parsons, Reading, Mass., assigner to Benjamin Howe, trustee, Reading, Mass.

Application August 6, 1934, Serial No. 738,577

5 Claims. (Cl. 193-37) illustrated is in the form of a simple eccentric which is desirable notably for engines operating at relatively high speeds. Herein the cam acts against the base of a cup-like member 45 telescoping within collar 21 and cooperating therewith to enclose the spring and which aids in guiding the parts axially.

Telescoping within the barrel piston 3| is a counter-piston 41, the lower face of this piston and the opposed face of the barrel piston formed by plug 33 defining between them a working chamber to receive a charge of liquid-to be injected on each cycle. Opening from this chamber laterally through the circumferential walls of the barrel piston are intake and discharge ports I9 and 5| respectively which preferably, for reasons which will appear, take the form of circumferentially disposed slots rectangular in outline. Since herein the openings of the intake and discharge passages 2| and 23 to the bore of the liner are vertically spaced, the ports 49 and 5| are disposed opposite each other and at the outer extremity of the stroke of the barrel piston, as shown in the drawing, port I9 is in communication with passage 2|, whereas on or about the other extreme of the/stroke the discharge port 5| is presented to the discharge passage 23. The counter-piston' 41 is normally urged inwardlyr (downwardly in the figure) by a light spring 55 interposed between the upper end of the piston and an abutment screw 51 by means of which the tension of the spring may be adjusted. Inward movement of the piston under the influence of this spring is limited, however, by contact of the collar 59 with adjustable stop arms 6| mounted on a transverse pin or shaft 63 and adjustably supported at their other ends by the eccentrics '65 on a shaft 61 which may be manually or automatically rotated as desired. This adjustment limiting the inward movement of the counter-piston toward the bottom of the barrel piston in the position of the latter shown in the drawing determines the size of the working chamber and thus the volume of the charge of fuel handled by the pump on each cycler Supported by a shoulder in the casing 5 is a cup-like member 69 pressed downwardly bya .heavy spring 1| of substantially greater effective force l;than the spring I1 of the nozzle,l which spring is interposed between the bottom of the cup and the screw cap 13. In the outward or upward movement of the ounter-piston when pressed in the manner herein more fully described by the mechanically driven barrel piston acting through an interposed column of liquid in the working chamber of the pump, the collar 59 during the latter portion of the stroke of the counter-piston makes contact with cup 69 and compresses the spring 1l.

I have now described more or less arbitrarily the exemplary mechanical construction illustrated in the drawing. I will now describe the operation of the pump shown. Assuming the parts to be in the position shown in the drawing,

the barrel piston is in its extreme outward position on the low point of the cam 4I and the counter-piston is supported in the position shown by the stop arms 6l against the stress of spring forming a Working chamber between the opposed faces of the pistons, which we may suppose lled with liquid supplied through intake passage 2| and port 49. As the barrel piston 3l now rises, port 49 is first carried out of alignment with passage 2|, thus trapping in the chamber a charge of liquid. As the barrel piston continues to rise, it moves outwardly before it the counterpiston 41, the former acting on the latter through the incompressible column of fluid trapped within the working chamber. The initial'portion of this movement is, in the construction shown, an easy one against the light spring 55, thus assuring a positive cut-off action at port 49. The counterpiston 41 continues to move outwardly or upwardly as the cam rotates and collar 59 compresses spring 1l placing the tension of the latter on the imprisoned column of fluid. Toward the end of the stroke the port 5I is brought into alignment with the passage 23, spring 1I expands powerfully and quickly, overcoming the tension of spring I1 on the check valve l5 of the injection nozzle, and quickly and powerfully injects the charge of fuel through the check valve and into the cylinder. The counter-piston, no longer supported by the uid column, descends within the barrel piston.

Preferably I provide the counter-piston with a passage 'I5 opening from the lower face thereof laterally to the side and the wall of the barrel piston with a port 11, the arrangement of the parts being such that as the injecting action under the stress of the spring 1l just described takes place the port 11 is in alignment with the passage 29 Ileading to the intake, and when the counter-piston has descended into contact with or to a predetermined clearance from the bottom of the barrel piston the passage 15 aligns with the port 11. It will be noted that the alignment of the various passages depends on the position of the barrel piston and the xed determined throw of the cam 4I thereon. At the end of the injection stroke, therefore, the pressure is relieved regardless of speed or load, permitting the valve l5 to snap shut. There are thus no pressure waves ensuing upon the cut-off which might tend to secondary discharges, there is no residual H pressure in the high pressure line which might of the drawing, the port 49 in alignment withl passage 2|y provides for drawing a new charge of fuel into the working chamber.

The injection of the fuel under the pressure of spring 1l provides a uniform but controllable injection pressure` at all speeds, avoiding overaoeasl 1 straining of the mechanism, and a rapid injection at low speeds to insure atomization. It permits in many instances of the use of a. simple eccentric as here shown or other low acceleration cam with consequent low structural loading on the pump parts. The valve action provided for by the ports 49 and 5I is particularly simple and permits the use of a rectangular port giving rapid operation with large effective areas and avoiding clogging. The intake and delivery are positiver;

claims rather than to the foregoing description to indicate the scope of the invention.

I claim:-

1. A fuel injection pump for delivering fuel te an engine against a determined resistance cornprising a casing having intake and discharge passages, a power-reciprocated barrel piston working therein having a bore and provided with lateral ports opening to said bore adapted to register respectively with said passages adjacent the ex tremes of the piston stroke, a counter-piston telescoping within the bore of said barrel piston to define a liquid-receiving chamber therein, means providing an adjustably variable clearance between the opposed faces of the pistons in the outward position of the barrel piston, a resilient resistance relatively strong as compared with. said determined resistance opposing outward movement of said counter-piston during the latter portion of its outward stroke .under drive of said barrel piston through a charge of liquid in the chamber, and means in said counter-piston placing said chamber in communication with the intake side of the pump substantially at the inward limit of movement of the counter-piston under said strong resistance after the inward movement of the barrel piston has placed the chamber in communication with the discharge passage.

2. A fuel injection pump for delivering fuel to an engine against adetermined resistance comprising a casing having intake and discharge passages, a power-reciprocated barrel piston working therein with lateral ports adapted to register respectively with said passages adjacent the extremes of the piston stroke, a counter-piston telescoping in said barrel piston to denne a liquidreceiving chamber therein, means providing an adjustably variable clearance between the opposed faces oi' the pistons in the outward position of the barrel piston, a resilient resistance relatively strong as compared with saiddetermined resistance opposing outward movement of said counter-piston during the latter portion of its outward stroke under drive of said barrel piston through a charge of liquid in the chamber, a passage leading from the inner end of the counterpiston, and means comprising a port in the barrel piston and a passage in the casing to open said counter-piston passage to the intake side of the pump substantially at the inward limit of movement of the counter-piston under said strong resistance after the inward movement of the barrel piston has placed the chamber in communication l with the discharge passage.

an engine against a determined resistance comprising a casing, a power-reciprocated piston working therein, a counter-piston, a spring relatively strong as compared with said resistance against which spring said counter-piston is moved during the latter part of its outward travel byA force of the power reciprocated piston exerted through an interposed column of uid, port means providing for discharge of said column located to be opened independently of the position of the counter-piston, and a. venting passage for the space between the pistons opened to the intake side of the pump consequentially to completion of the movement of said counter-piston under its spring consequent on opening ofsaid port means.

4. A fuel injection pump comprising a casing having intake and discharge passages, a power4 reciprocated barrel piston working therein having an intake port adapted to register with said intake passage at the outward position of the piston, a spring-supported counter-piston telescoping in said barrel piston to provide a iiuidreceiving chamber between them, means providing an adjustably variable clearance between the opposed faces of the pistons in the outward position of the barrel piston, the barrel piston having a lateral port adapted to cooperate with said discharge passage at a definite time in its stroke independently of the position of the counter-piston, and means providing a connection from said chamber through the counterpiston to the intake side of the pump opened when said piston faces approximate one another at the conclusion of the discharge.

5. A fuel injection pump for delivering fuel to an engine against a determined resistance comprising a casing having intake and discharge passages, a power-reciprocated barrel piston working therein having a bore and provided with lateral ports opening to said bore adapted to register respectively with said passages adjacent the extremes of the piston stroke, a counterpiston telescoping within the bore of said barrel piston to define a liquid-receiving chamber therein, means to determine the volume of liquid to be delivered from between said pistons on their ejection movement, a resilient resistance relatively strong as compared with said determined resistance opposing outward movement of said counter-piston during the latter portion of its outward stroke under drive of said barrel piston through a charge of liquid in the chamber, and means in said counter-piston placing said chamber in communication with the intake side of the pump substantially at the inward limit of movement of the counter-piston under said strong resistance after the inward movement of the barrel piston has placed the chamber in com-

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