US1926743A - Fuel injection pump for internal combustion engines of the diesel type - Google Patents

Description

Sept. 12, 1933. H, D, 1,926,743

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES OF THE DIESEL TYPE Filed Sept. 30, 1929 ATTO RN EYS Patented Sept. 12, 1933 UNITED STATES PATENT OFFICE TYPE Harry D.. Hill, Lansing, Mich., assignor to Hill Diesel Engine Company, Lansing, Mich., a corporation of Michigan Application september so, 1929 Serial No. 396,340

l Claim.

The invention relates to fuel pumps for internal combustion engines. and more particularly for use with engines of the Diesel type. It is usual to inject the fuel into a combustion chamber through a sprayer nozzle and to produce the required pressure for such injection by the opera-v tion of a plunger pump. As this `pump is frequently located at a point removed from the point of injection it is necessary to provide a connecting conduit between the pump and the nozzle in which the fluid is conveyed und'er high pressure. There is also usually a valve at the discharge end of the conduit which closes after each injection and remains closed during the portion of the cycle intermediate successive injections.

The quantity of fuel injected in successive operations of the pump is controlled by the operation of a governor, while the timing of the injection is determined by the injection stroke of the plunger. There is, however, a certain lag in the timing of the injection due to the resiliency of the fluid and the conduit through which it passes which stores 'a certain amount of energy and continues movement of the uid after the plunger4 has reached the end of its injection stroke.

It is the object of the present invention to obtain a more positive and accurately timed injection of the fuel and closingof the nozzle valve. This I have accomplished by the provisionof means operating at the end of the injection stroke of the plunger for instantaneously relieving the high pressure on the uid. The construction is such that after this release of pressure the fuel kinjection conduit is again sealed and remains in i this condition until the succeeding period of fuel injection. The invention-thereforev consists in the novel construction as hereinafter described and shown in the drawing in which Figure 1 is a longitudinal section through my improved fuel injection pump;

Figures 2 and 3 show the plunger respectively at the beginning and at the end of the injection stroke;

As shown, A is the cam shaft Whichoperates and times the fuel injection, B is a suitable casing in which .is located the' pump barrel C and D is the plunger operating in this barrel.v The plunger is actuated by a cam follower E which is slidably secured in the casing B and which as shown is cup-shaped to embrace the plunger. F

is la spring for actuating the plunger in its return stroke, one end of said spring bearing against a collar G on the plunger D and the other end engaging an abutment on the casing.

The fuel inlet to the barrel C is through a lateral port H which is uncovered b'y the plunger as it approaches the end of its return stroke. The port H connects with a chamber I supplied with fuel under low pressure by any suitable means (not shown). The quantity of fuel passing through the port H is, however, regulated by the adjustment of a metering pin J on a shank K slidable in a bearing L, the tapering portion of said pin engaging the mouth or entrance tube M leading to the port H. The position of the metering pin is regulated by a rock arm N on a shaft O which is rocked into different positions by the operations of a governor (not shown). Thus the quantity of' fuel which is permitted .to pass into the barrel C during the brief interval in which the port H is uncovered is determined by the restriction of the tube M by the metering pin J.

The discharge of the liquid from the pump barrel is through a port controlled by the check valve P closed by the spring P and after passing theseV valves the fluid is conveyed-through a conduit Q to the sprayer nozzle R.. This is preferably a finely apertured disk through which fluid is forced and adjacent to this disk is the check valve S yieldably forced to its seat by the spring S so that after each injection these valves P and S are intended to automatically close.

As has been stated, the liquid fuel when forced through the conduit Q under high pressure due to the plunger D will store a certain amount of energy either by compression of the fluid or expansion of the conduit, and this will continue the discharge through the nozzle after the plunger has reached the end of its injection stroke. Inasmuch as the mechanism is designed to time the injection by the cam and plunger operated thereby, it is obvious that this lag in the discharge of the uid will interfere with the accuracy of the result. To avoid this defect, I have provided means for instantaneously releasing the pressure at the end of the' injection stroke of the plunger which is preferably constructed as follows:

'I'he plunger D is provided with a port which comes into registration with a relief port near the end of the injection stroke. As shown, the plunger has an annular vgroove T located to register with the port H near the end of the injection stroke and this annular groove communicated through a lateral bore T' with an axial bore T2 extending to the end of the plunger. Thus as soon as the plunger moves to a position where the groove T and port H register, the highpressure on the uid in the conduit Q is instantaneously released, dropping to the pressure within the chamber I. As this pressure is relatively low and much less than the pressure in the combustion chamber, the discharge through the nozzle will stop and the valves will be permitted to close.

The operation of the fuel pump occurs during the limited portion of the engine cycle and during the remainder of said cycle said pump remains inactive. To avoid holding the relief port open during all of this inactive portion of the cycle, the cam A is so constructed that immediately after the completion of its ejection stroke it will permit of the slight retraction of the plunger sufficient to close the relief passage. Thus as shown the portion A of the cam which reciprocates the plunger has a peak A2 corresponding to the limit of the ejection stroke and immediately adjacent to this peak is a cut-away portion A3 which permits suiiicient retraction of the plunger to close the relief port. There is then a concentric portion A4 of the cam which extends to the point where the portion A begins. Therefore, with this construction the relief of pressure is only an instantaneouscifect and is immediately followed by a closure ofthe relief ports which continue closed during the remainder of the cycle. -As has been stated, the amount of fuel which is admitted to the barrel is determined by the position of the tapering metering pin J during the interval in which the passage H is open to the barrel. The stroke of the plunger D is constant but due to the fact that the quantity of fuel admitted varies and also because of the resistance of the spring closed valves S and P the timing of initial injection 'will be varied. This is a desirable feature for when the engine is operating under full load it is advantageous to advance the time of ignition as is automatically accomplished by my construction.

What I claim as my invention is:

A fuel injection pump for internal combustion engines comprising a reciprocable plunger, a barrel in which said plunger reciprocates provided with a lateral inlet passage uncovered by said plunger when in its retracted position, a conduit leading from said barrel to the injection nozzle, a relief passage having co-operating portions in said plunger and said barrel adapted to register at the completion of the ejection stroke, and means for operating said plunger during a. portion of the engine cycle in the sequence of first retracting and then advancing the plunger to the completion of its ejection stroke immedi.

ately followed by a slight retraction sufficient to quickly close the relief port and for holding the plunger stationary in this position during the remainder of the cycle.'

HARRY D. HILL.

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