US3368491A - Fuel injection pump - Google Patents

Description

Feb. 13, 1968 D. E. SHOOK ET AL 3,368,491

FUEL INJECTION PUMP Filed June 22, 1966 2 Sheets-Sheei 1 DAVID E. SHOOK ROBERT J. DUNLAP BY INVENTORS.

Feb. 13, 1968 D. E. SHOOK ET AL 3,368,491

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United States Patent C 3,368,491 FUEL INJECTION PUMP David E. Shook and Robert J. Dunlap, Milwaukee, Wis., assignors to Murphy Diesel Cmpany,-Milwaukee, Wis., a corporation of Delaware Filed June 22, 1966, Ser. No. 559,509 2 Claims. (Cl. 103-41) ABSTRACT OF THE DISCLOSURE A fuel'injection pump of the type employing a plunger in a cylindrical member having an inlet port and a pressure release port connecting with a'source of fuel, and a pressure relief port in the cylindrical member disposed to be uncovered by the plunger 'just ahead of the uncovering of the pressure release port.

This invention relates to a fuel injection pump for internal combustion engines generally of the diesel type.

The invention is based upon the discovery that pressure surges in the pump chamber after cut-off and which sometimes cause after dribble in fuel injection may be substantially eliminated by providing a minute pressure relief for the pump chamber just ahead of the pressure release by the plunger.

The invention avoids the attempts to solve after dribble by special needle valve constructions and heavier spring actuated check valves for control of the injection, and makes it possible to employ normal check valves with lighter actuating springs.

The accompanying drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIGURE 1 is an axial section of a typical fuel injection pump employing the invention;

FIG. 2 is a transverse section taken through the pump plunger on line 22 of FIG. 1;

FIG. 3 is a left side elevation of the lower portion of the pump plunger;

FIG. 4 is a right side elevation of the lower portion of the pump plunger;

FIG. 5 is a sectional view similar to FIG. 1 showing the pump plunger in its downward pressure stroke and with the check valves open injecting fuel into the engine cylinder;

FIG. 6 is a view similar to FIG. 5 showing initial opening of the relief port; and

FIG. 7 is a similar view upon opening of the cut-off port.

Referring to the drawing, the fuel injection pump comprises a hollow generally cylindrical body 1 having a pump plunger actuator 2 in one end thereof and a cap or tip nut 3 threaded into the other end thereof.

A tubular cylinder 4 is disposed within body 1 and receives the pump plunger 5 which reciprocates therein and which has its free end extending upwardly for connection with the actuator 2.

The tip nut 3 contains the valve cartridge 6 which preferably has the construction described and illustrated in the copending application of David E. Shook, one of the present co-inventors, Ser. No. 555,545 filed June 6, 1966 and assigned to a common ass-ignee herewith.

The spacer block 7 of the valve cartridge 6 presses against the adjacent end of cylinder 4 and holds the latter con-fined against an inner shoulder 8 of body 1.

The pump chamber 9 is principally formed by the inner end portion of cylinder 4 and the plunger 5 at one end of the chamber and the spacer block 7 at the other end of ice the chamber. The chamber 9 has an additional volume by reason of the connecting axial passage 10, cross passage 11 and diagonal transfer passages 12 and 13 in plunger '5, and also by reason of the axial passage through spacer which is substantially lower than the necessary injection pres-sure, and enters the body v1 through passage 16 to a cylindrical spacer or chamber 17 surrounding the major portion of the cylinder 4 and in direct communication "with inlet port 15.

A suitable coil spring 18 is carried by body 1 and en gages a flange 19 on actuator 2 to bias the latter upwardly and normally maintain plunger 5 in its upper position except when being actuated against the spring for injecting fuel into the engine cylinder.

A suitable sleeve 20 may be provided in fuel chamber 17 to prevent undue erosion of the ports and body.

The release port 21 is disposed in cylinder 4 above and on the opposite side from inlet port 1 5 to discharge directly into the fuel chamber 17 at the time for release of the pressure injection, and which is governed by the diagonal transfer passage 1'3 registering with port 21 as the plunger 5 approaches the bottom of its stroke.

Rotational adjustment of plunger 5 as by the rack 22 engaging teeth 23 on the upper portion of plunger 5 determines the release time for the injection.

In carrying out the present invention an initial pressure relief is provided just ahead of the main release by a small orifice 24 preferably located above the inlet port 15 and on the opposite side of plunger 5 from release port 21.

The diagonal transfer passage 12 in plunger '5 is disposed on the opposite side from passage 13 and is adapted to uncover relief orifice 24 just ahead of the uncovering of release port 21 by passage 13.

Referring to FIGS. 5-7 it will be noted that as plunger 5 moves downwardly in its charging stroke from the position of FIG. 1, the end of the plunger first cuts off inlet 15, and further movement of the plunger immediately compresses the liquid fuel filling chamber 9, thereby effecting opening of the first check valve 14 and then of the second check valve 2 5 as shown in FIG. 5 with a resulting discharge of fuel through orifices 26 of tip 27 into the engine cylinder.

As the time for release approaches, the diagonal transfer port 12 uncovers orifice 24 and provides a very slight initial pressure relief prior to final release, as shown in FIG. 6. At this point it is believed that valves 14 and 2 5 are open but possibly start to close. It may be that they complete their closing by the time transfer passage 13 starts to uncover release port 21.

In any event, the effect of the initial pressure relief orifice 24 is to substantially eliminate the secondary surge in pressure in chamber 9 following release and to prevent re-opening of valves 1'4 and 25 with resulting afterdribble. Tests have indicated that this is so regardless of whether the release is timed to occur at 25%, 50% or of complete charge.

It is believed that the orifice 24 effects a more gradual closing of check valves 14 and 25 which may have some improvement in engine efiiciency by reason of a change in heat release characteristics of the engine. While it has generally been thought that a sharp cut off is desirable, more recently attempts have been made to vary the cutoff rate by employing release ports of different shapes. Such attempts result in high erosion of the port with unpredictable engine performance. The present separate orifice has been found to avoid erosion and to provide the needed control of cut-01f.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. In a fuel injection pump of the class described having a cylindrical member with inlet, outlet, leakage collection, and release ports connecting to a fuel supply and adapted to be covered and uncovered by a pump plunger operating within the cylindrical member to provide a pump chamber at one end, a pressurerelief orifice in said cylindrical member on a side opposite said release port and also connecting to said fuel supply, and passage means in the plunger directly connecting said relief orifice to said pump chamber and disposed to uncover said orifice just ahead of the uncovering of said release port by the plunger in its pressure stroke.

2. The construction of claim 1 in which said plunger has a separate diagonal transfer passage disposed on the side corresponding to each said release port and said pressure relief orifice, and means to rotationally adjust said plunger relative to said member to control the timing of opening of both said release port and said relief orifice, said diagonal transfer passages being correlated in position further apart than the correlation in position between said release port and said relief orifice axially of said member to provide a pressure relief for the pump chamber momentarily prior to cut-off of injection.

References Cited UNITED STATES PATENTS 2,420,164 5/1947 Bremser 10341 2,521,224 9/1950 Kammer 299107.5 2,551,053 5/1951 Rogers 10341 2,571,501 10/1951 Truxell 239 X 2,628,866 2/ 1953 Purchas 23990 2,890,657 6/1959 May 103-41 2,985,378 5/1961 Falberg 239--92 X 3,075,707 1/1963 Rademaker 23990 3,115,304 12/1963 Humphries 230-90 3,216,359 11/1965 Teichert 103-41 DONLEY J. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

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