US2374614A - Liquid fuel injection apparatus - Google Patents

Description

April 1945. w. M. NICHOLS LIQUID FUEL INJECTION APPARATUS Filed May 20, 1943 INVENTOR Patented Apr. 24, 1945 UNITED STATES PATENT OFFICE LIQUID FUEL INJECTION APPARATUS William M. Nichols, Auburn, N. Y., assignor to American Locomotive Company, New York. N. Y., a corporation of New York Application May 20, 1943, Serial No. 487,739

, 1 Claim.

I gines, to employ a fuel injection apparatus in which the valve of the injector is closed, not only by the usual valve spring, but also by some auxiliary closing means which augments the. closing force of the valve spring and insures a quick closing of the valve, effecting a sharp cut-oil of the fuel then being injected at a high pressure. This sharp cut-off prevents dribbling of fuel into the cylinder at the end of injection, which dribbling would result in poor atomization of the fuel in the cylinder, and poor combustion, accompanied by poor economy and operation of the engine.

It has been proposed to employ hydraulic means to provide the force augmenting the force of the usual valve spring, and various attempts have been'made previously to provide a satisfactory hydraulic feature. The present invention is directed to hydraulically augmenting the usual valve-closing spring in a simple, economical manner necessitating only a slight change in the usual fuel injector.

An object of the present invention is to proa fuel injection apparatus for one cylinder of -an oil (Diesel) engine, shown in vertical central section, parts being shown in full and parts being broken away.

The fuel injection apparatus includes a fuel pump I, a fuel injector 2, and a constant residual pipe-line pressure device 3 connected to the'delivery end of the pump A pipe-line 4 connects the device 3 with a fuel passage 5 of the in- J'ector 2.

The pump is of conventional design, and includes a fuel inlet G'opening into a cylinder 1, a plunger 8 disposed in the cylinder, and a fuel delivery port 9. Control edges l0 and II on the plunger are adapted to control ports l2 and I3 of fuel inlet 6 in the usual manner as will later morefully appear.

The device 3 includes a cylinder l4 connected at oneend to the pump and in communication with port 9, and a slidable piston |5 disposed in the cylinder l4. A spring l8 engages the piston l5 and the opposed lower end of the cylinder l4 for forcing the piston |5 away'from the pump. A fitting I1 is secured to the other end of the cylinder M. It is provided with a passage l8 adapted to be controlled by piston l5, as will presently appear.

Piston I5 is made in two pieces, as is clearly shown in the drawing, this being for convenience in manufacture. It has a central bore for the passage of fuel, the bore being enlarged intermediate its ends to provide a chamber is, the reduced portion below the chamber 19 forming a guide 20 for a valve stem, as will presently appear, a valve seat 2| being formed on the shoulder between the guide 20 and chamber IS. The shoulder between the chamber [9 and the upper reduced portion of the bore provides a valve spring seat 22.

A valve, 23 is disposed in chamber l3, normally seated on valve seat 2|. It includes a fluted stem 24 disposed in guide 20. A spring 25, compressed between valve 23 and seat 22, normally holds valve 23 in closed position.

Spring l6 normally holds piston IS in full upward position so that the upper end of the piston acts as a valve closing the upper end of cylinder M from passage |8, the upper end of the piston engaging the adjacent face of the fitting Thus the portion of this face surrounding passage I8 provides a valve seat for the piston upper end. An external longitudinal groove 28 is formedin the piston, for by-passing the piston and connecting passage l8 with port 3. This by-passing will be later more fully referred to.

The fuel injector includes a casing 21 open at both ends and provided adjacent its lower end with a shoulder 28. A nozzle 29 is carried by the casing and seats against the shoulder 28 and projects through the open lower end of the easing. The nozzle includes the usual injection jets 30, injection port 3|, injection fuel chamber 32, passage 33 leading thereto, groove 34 in its upper face in' communication with passage 33, cylinder 35, valve 36 controlling port 3|, and plunger '31, formed integral with valve 36 and being slidably disposed in the cylinder 35. Plunger 31 has a shoulder 38 providing a working pressure face disposed in chamber 32.

A spring housing member 39 is disposed in the casing above and seating on the nozzle 29. It has a. passage 40 in communication with groove 34, a large loading fuel and spring chamber 4|,

and a small passage 42 connecting chamber 4| with cylinder 35. A stem 43 forming an integral part of plunger 31 extends upwardly through passage 42 and supports a spring seat 44 disposed in chamber 4|. A spring 45 is disposed between seat 44 and a seat 46, later to be referred to. Stem 43 is of smaller diameter than passage 42, the part of plunger 31 in cylinder 35 providing a shoulder 41 therewith. Shoulder 41 provides part of an upper working pressure face for the plunger 31, the remainder being provided by the seat 44 supported on the stem 43.

An oriflced head 48 is disposed in the casing and held therein by a threaded sleeve 49, head 46 engaging the upper face of member39 and closing chamber 4|, and being connected against rotation relative. to member 39 by a dowel 50. Head 48 is threaded at its upper end and a pipe fitting 5| is secured thereto, pipe-line 4 being connected to fitting 5|. Passage 5 is formed partly in fitting 5| and partly in head 48 and connects pipe-line 4 with passage 40, as is clearly shown in the drawing. Head 48 has a concave seat 52 in its lower face, in which seats the spring seat 46, seat 46 having a convex surface 53 coinciding with the seat 52.

The present invention ontemplates the filling of the chamber 4| with fuel for augmenting the loading of the spring-loaded plunger 31. It is contemplated that this fuel may enter the chamber 4| by passage between the plunger 31 and the wall of cylinder 35, sufiicient clearance being provided for this. However, it has-been found more satisfactory to provide asmall port connecting the loading fuel chamber 4| with the passage 5 or with a passage connected to the passage 5. For instance chamber 4| might be connected to passage 40 or 33, or cylinder 35 above plunger 31 might be connected to any suitable one of these passages.

In the drawing a port 54 is shown connecting chamber 4| with passage 5. This port is relative 1y small in diameter. During delivery periods (injection periods) of the pump, the passage 5 is full of high pressure fuel. Port 54 serves to let fuel enter chamber 4| from passage 5 during such periods, but reduces the pressure thereof by throttling, the pressure in T'chamber 4| thereby then being below that in passage 5 so that plunger 31 may be lifted by the pressure differential (delivery pressure). Between delivery periods the constant residual pipe-line pressure device maintains a constant pressure in the delivery passage between valves 23 and 36 lower than delivery pressure, but sufficiently high so that engine cylinder pressure developed during the compression stroke can not raise plunger 31, and port 54 permits the pressure in chamber 4| to be lowered by substantially equalizing with the residual pipe-line pressure. 6

The operation of the fuel injection apparatus is as follows: When the pump plunger 8 is at the end of its suction stroke, as shown in the.drawing, the space above the plunger 8 is in communication with the fuel inlet 6 for supply of fuel and the chambers and passages of the injector will be full of fuel at a constant pressure due to the constant residual pipe-line pressure device. The plunger 8 will be moved upwardly by the usual cam (not shown) and until edge Ill covers ports I2 and I3, the fuel above the plunger-8 will be forced back into the fuel inlet 6. When ports |2 and I3 are covered, the plunger 8 will then force the fuel thereabove toward the injector. This delivery will continue until edge uncovers port I3, at'which time the fuel above the piston will spill" back into port l3, terminating injection, all in the usual manner. The period between closing of ports l2 and I3 by edge l0 and opening of port l3 by edge II is known as the delivery period. This may be adjusted by rotating plunger 8 in a well-known manner, edge being helical.

During the delivery period, fuel is forced into the device 3,v pushing valve 23 off seat 2| anddelivering fuel through passage I8, pipe-line 4 and passages 5, 4D and 33. Thus chamber 32 is filled with injection fuel at injection pressure, and this, acting on shoulder 38, lifts plunger 31, effecting injection of fuel into the engine cylinder.

/ The injection pressure initially acts only against the area of the shoulder 38 to lift the plunger 31. At this time, plunger 31 is being forceddownward by the pressure of spring 45 and by the pressure of the fuel oil in loading fuel chamber 4|, which at the beginning of the delivery period is at substantially the constant residual pipeline pressure.

Raising of the plunger 31 compresses the fuel in chamber 4| a small amount. The pressure of the fuel in chamber 4| is further raised during the delivery period due to communication,

by means of port 54, between the chamber 4| and the passage 5, which is then full of fuel at high pressure.

At the end of the delivery period, there is a sharp drop in pressure in passage 5 and chamber 32 due to the aforementioned spill of fuel back into port l3 and the return of the delivery valve 23 to its seat 2|. Plunger 31 is therefore quickly and abruptly returned to its lowermost position closing port 3|. This is accomplished by the closing force of the spring 45 augmented by the closing force of the fuel compressed in chamber 4|. This quick closing of port 3| abruptly terminates the injection of fuel into the engine cylinder, stopping injection while the pressure of the fuel in chamber 32 is suflicient to provide complete atomization, and thereby preventing dribbling of fuel into the engine cylinder with its accompanied poor combustion results.

As soon as the delivery valve 23 engages its seat 2|, the fuel trapped between the valves 23 and 36 adjusts itself to a predetermined constant residual pipe-line pressure by exerting a moving force against piston-l5, moving it downward against the pressure of spring I6, and opening passage l8 to groove 26. Thus a small amount of fuel is bypassed frompassage I8 to port 9 decreasing the pressure between valves 23 and 36 sufficiently so that spring "5 can return piston |5 to its uppermost position closing passage l8 from groove 26.

Thus device 3 is adapted to maintain a predetermined constant residual pipe-line pressure.

Between the delivery periods, the chamber 4| again substantially equalizes the pressure therein with the residual pipe-line pressure through the port 54 It will be seen from the foregoing that at the beginning of the injection into the engine cylinder, the plunger 31 is moved upward to initially open port 3| against a predetermined pressure, i. e., the pressure of spring 45 augmented by the pressure (constant residual pipe-line pressure) of the fuel in chamber 4|. This pressure is always the same for the beginning of each injection. However, at the end of injection, plunger 31 spring 45 augmented by an increased pressure of the fuel in chamber 4|, the fuel pressure then is forced downward by the pressure of here 32 and 4|.

being increased by compression due to raising of plunger 31', and also by an increase in pressure due to the flow of high pressure fuel through port 54' during the delivery period. Therefore valve 36 is opened against a relatively low pressure, and closed b a relatively high pressure. This results in a clear-cut injection period, starting by a quick opening of the valve, preventing initial dribbling, and ending by an abrupt closing of the valve, preventing dribbling at the end of injection.

The aforedescribed operation of the apparatus applies also to the injector not provided with the port 54, wherein the space between the plunger 31 and cylinder 35 permits passage of loading I fuel to chamber ll and equalization of pressures,

between delivery periods, of the fuel in cham- The space between the plunger 31 and cylinder 35 performs the functions of the port 54.

While there has been hereinbefore described an approved embodiment of this invention, it will be understood that many and various changes and modifications in form, arrangement of parts and details of construction thereof ,may be made without departing from the spirit of the invention and that all such changes and modifications as fall withinthe scope of the appended claim are contemplated as a part of this invention.

The invention claimed and desired to be secured by LettersPatent is:

A liquid fuel injection apparatus comprising a fuel injection pump of the unloading type having a pumping element for delivering pressure fuel for injection; a fuel injector having a casing pro vided at one end with a valve seat, an injector valve for said seat housed in said-casing for reciprocating axial movement and having a working pressure face between its ends for raising said valve by fuel pressure and another working pressure face at the end thereof remote from said valve seat, means forming a continually fuel-full chamber open at one end to said valve remote end face, a spring in said chamber loading said valve for closing said valve, said valve remote end being imperforate for completely closing said chamber at its said end preventing fuel pressure drop in said chamber due to passage of fuel from said'chamber past said valve; a fuel delivery passage having a portion extending through said injector casing to said valve seat, another portion extending through said pump to said pumping element, and a portion connecting said two first mentioned portions; and a constant residual fuel pressure device forming part of said passage and disposed between said valve seat and said pumping element, including a check valve in said passage openable away from said pumping element, said check valve being open during said pump pressure stroke, and means for reducing the fuel pressure to a predetermined constant residual pressure in said passage between said injector valve seat and said check valve when said injector valve is closed, the passage between said. injector valve seat and said check valve being continually full of fuel under pressure, said injector valve being raised on said pressure stroke of said pump for fuel injection simultaneously with said stroke, said injector 'valve automatically closing at unloading of said pump, said casing having a throttie aperture connecting said passage between said valve seat and said device with said chamber for obtaining equalization of pressures therebetween, said chamber pressure facilitating injector valve opening when at said constant residual pressure and enhancing said injector valve closing when at injection pressure.

WILLIAM M. NICHOLS.

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