US3195465A - Fuel injection pump - Google Patents

Description

July 20, 1965 HANS-RUDOLF HUG 3,195,465

I FUEL INJECTION PUMP Filed July 31, 1963 ,i Al.

Jnvenfor: H/ws-Runmf Hue BY Arrok/vfy United States Patent O 3,195,465 FUEL INEECTHQN PUMP Hans-Rudolf Hug, Winterthur, Switzerland, assigner to Schweizerische Lokomotivund Maschinenfabrik, `Winterthur', Switzerland, a firm of Switzerland Filed `luly 31, 1963, Ser. No. 298,959 Claims priority, appiication Switzerland, Aug. 9, 1962, 9,499/62 1 Claim. (Cl. 10S-41) The invention relates to a fuel injection pump for internal combustion engines, particularly for diesel engines, for pumping fuel into a pipe terminating in a fuel injection valve connected to a cylinder of 4the internal combustion engine.

In the conventional fuel injection systems of diesel engines there is, upon completion of the injection operation, a sudden drop of pressure in the part of the pipe connecting the fuel pump and the fuel injection valve or nozzle, which part is close to the pump. Due to the elasticity of the fuel in said pipe and of the pipe itself, this sudden pressure drop causes undulations which frequently effect a brief opening of the injection valve and an undesired dripping lor spraying of fuel into the engine cylinder. Since this fuel is injected at low pressure and too late into the engine cylinder, the fuel is insufficiently atomized and combustion is unsatisfactory, causing smoking of the engine and coking of the injection nozzles and reduction of the operating efficiency.

For suppressing the above-described undulations in the pipe line between the fuel pump and the injection valve, usually a space is provided accommodating a certain amount of fuel. For this purpose the pressure or outlet f valve element forming part of the fuel pump is provided with a cylindrical portion upstream of the valve seat whereby the outlet valve is closed before the valve element is seated on the valve seat. This causes withdrawing of a predetermined volume of fuel from the pipe connecting the fuel pump and the fuel injection valve, before the pressure valve of the fuel pump is fully closed. This conventional arrangement reduces the undulations in the fuel pipe if the amount of injected fuel is relatively small, and avoids undesired post-injection. This conventional arrangement, however, fails at greater rates of fuel injection as they occur at full load operation of supercharged engines.

It is an object of the presen-t invention to provide an arrangement in the fuel injection system of internal combustion engines, particularly diesel engines, which avoids the aforedescribed disadvantages of conventional systems. According to the invention a small leakage through the pressure valve of the fuel pump is provided so that when this pressure valve is fully closed and sits tightly on its seat a limited amount of fuel may pass from the pipe downstream of the fuel pump into the pump chamber.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claim. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in connection with the accompanying drawing wherein:

FIG. l is a longitudinal section of a fuel injection pump according to the invention.

FIG. 2 is a part-sectional large scale View of a modified part of the fuel pump shown in FIG. l.

FIG. 3 is a longitudinal sectional View of the part j' shown in FIG. 2 provided with a check valve.

Referring more particularly to FIG. 1 of the drawing, numeral 1 designates the casing of a fuel injection valve provided with a bushing 2 wherein a piston 3 recipro- Patented July 20, 1965 cates. The piston 3 is moved against the action of a spring 6 by a cam 5 acting on a movable part 4 interposed between the cam 5 and the piston 3. The latter is provided with inclined control edges in the conventional manner and is rotatable about its longitudinal axis, the rotation being effected by a worm drive arrangement 7. Fuel is supplied t-o the casing 1 through a supply conduit 8. The fuel ows through apertures 1t) in the bushing Z into a pump chamber or cylinder 9. The upper end of the cylinder 9 is closed by a fuel discharge valve comprising a valve body 12 and a seat element 11. The seat element 11 is pressed by means of a nipple 13 through a packing 14 onto the bushing 2. A spring 15 is interposed between the nipple 13 and 4the valve member 12. A pipe 16 terminating in an injection valve of the irlternal combustion engine, not shown, is connected in the conventional manner to the nipple 13. According to the invention the seat element 11 is provided with a bore 17 which connects the spaces upstream and downstream of the fuel discharge valve and permits by-passing of a predetermined amount of fuel around the valve.

During the downward or inward movement of the piston 3 caused by the cam 5 fuel oil is drawn into the chamber 9 through the openings 1li and pressed during the upward or outward movement Iof the piston 3 past the lifted valve 12 into the pipe 16. Upon reaching a predetermined pressure the injection valve of the engine cylinder is lifted and fuel is sprayed from the pipe 16 into the engine cylinder. This fuel injection is terminated in the conventional manner when the lower control edge of the piston 3, illustrated in FIG. 1, moves into the region of the openings 1@ so that the pipe 16 is connected to the fuel supply conduit S. This causes a sudden drop of the pressure in the pipe 16 effecting sudden closure of the injection valve. This sudden pressure drop and closing of the injection valve initiates a pressure wave in the pipe 16. In the conventional arrangements this pressure wave is reflected at the closed discharge valve and causes a subsequent lifting of the injection valve and the aforedescribed undesired dripping or postspray.

ln the arrangement according to the invention the bypass bore 17 provides a connection between the spaces upstream and downstream of the discharge valve, also when this valve is closed. In this way there is always a certain leakage permitted between the spaces ups-tream and downstream of the discharge valve which, as eX- perience has shown, prevents the undesired reflection of the pressure wave in the pipe 16 and postdripping.

FIGS. 2 and 3 show different means for providing an artificial leakage in the pump outlet valve. FIG. 2 shows in enlarged scale a valve body 1S corresponding to the valve element 12 in FIG. l. The valve body 18 has a cylindrical portion provided with an annular groove 2i? separating a guide portion 21 of the valve body from a cylindrical portion or collar 22. Adjacent to the collar .2 is a relatively large diameter collar 23 forming a valve seat surface 24. The valve body 18 shown in FIG. 2 is provided with a central bore 25 having a small diameter part 26 at the outlet end of the valve body. Transverse bores 27 connect the bore 25 to the groove 2t). The outlet end of the valve body 1S -is provided with a cylindrical boss 2S extending into one end 0f the spiral spring 15. The bore 26 replaces the bore 17 in the valve seat element according -to FIG. l. The bore 17 may be omitted when using the structure shown in FIG. 2.

1f, during a pressure stroke the groove 20 is above the valve seat in the seat element 11, there is a connection between the pump chamber 9 and the pipe 16 through the bores 25, 27 and 26 and fuel is conducted through these bores into the pipe 16. During the closing movement of the valve body 18 the lower edge of the collar 22 passes the valve seat in the element 11. At lthis moment connectionbetween the bores 27 and the pipe 16 is in-,

of fuel corresponding to the volume of the cylindrical portion or collar 2.2 is drawn from the pressure pipe 16 up' to thev moment the seats'urface 24`comes to rest on -the valve seat element 1,1. In the arrangement accordf ing' to the invention a limited'connection of the spaces up-Y stream and downstream fY the valve element 18 is pro- Y vided by the bore 26 which hasa considerable throtjtling aad- It is alsol possible to provide a check l duit by-passing the pump outlet valve, the check valve being adapted to open at 'a flow of fuel oil in the direction `toward the pump chamber 9. FIG. 3 shows a valve body 30 whichy correspondsiothe valve body 1.8 shown in FIG. 2. A check valve comprising a ball 31 and a coill *springV 3 2 are located within the bore 25. One end of the Spring 3 2fabutsagainst a tubular element 33 screwed intothe element 30; the second end of the spring abuts agaiujstkvthe ball 31; I

The structure shown in FIG. 3 provides a connection of the spaces downstream and upstream of the pump outlet 'valve duringa limited'period of time. The connectionis in eifect only if, due 'to a pressure wave ini'glie pipe 16, the pressure therein rise'sabov'e a predetermined value.l Otherwise, the effect of the modification shown in,

FIG. 3 is the same as that of kthe modicationshown in FIGS. 1 and '2. f f Y It is obvious that the structure according to the invention is not limited tol an arrangement simultaneously usingthe well-known backow volume principle which is implemented bythe'collar 22..' v

' The extent of the artiiicial leakage of the pump outlet valve, i.e. `the Vflowarea ofthe by-pass conduit, dependsA on thelocal operating eonditions of Ythe engine and iS, preferably ascertained by tests.;v V.Ihn av commercial fuel in; j ection pump wherein the inr'ler diameter ofv the valve seat was 1Q mm. and wherein'a valve body according toy FIG. 2'was used, it has beenffouud that reiiections in the pressure pipe were'entirely sujrspressedv and postdripping was eliminatedv if the diameter o f the :bore 26,Y amountedy to 1.2 mm. l

The artificial leakage of the outlet valve of kthe fuel pumpgmayV befpr'oduced byother means'thanrbores in the valve elements. Grooves may be providedfin 'the valve in the'conl valve seat.. 'Thepump housing maybe providedwith af conduit by-passing the valve seat element and, if desired,

anl adjustable throttling device may be interposed in the A' by-pass conduit whereby the leakage can be adjusted during operation.

I claim:

In a fuel injection pump having a pump cylinder having an open fuelrdelivery end and a plunger reciprocable in said pump cylinder: Y t l a discharge valve Iassembly adjacentvr said open end and Y Y havingvan inlet at said open end and an outlet distant from said open end,

said dischargefvalve assembly having :a valve housing connected to said pump cylinder and having a conical valve seat distant from said open end,`Y

i a bore in said valvehousing coaxial of said( pumpY cylinder, y a spring-biased valve body'having a cylindrical portion axially movably ttedin said bore, a collar projecting YfromY said cylindrical portion distant from said Vopfen end andhaving a conical shoulder opposite said conical 'valve seat for being seated thereon, and an I annular recess in said cylindricalv portion, spaced from Ysaid collar, l a rst bore extending through said valve body coaxial with's'aidborle insaid valve housing, o a second bore extending at said lannular recess through said valvel body in a direction normal to the longitudinal airis of said first bore and connecting said rst bore tosaid recess, and t f a checlg 'valve disposedin said first; bore between said second bore and the end of said valve vbody which end' is distant from -said lopen end of said pump cylinder, for allowing Yflow of fuel throughsaid first bore in a direction from said end of said valve body which is'distant from the vopen 'end of said pump cylinder t-owardsaid open end ofsaid pump lcylinder and preventing fuel flow in the opposite direction.k

References Cited bythe Examiner j -UNrjran STAT-Es PATENTS lijflfrnqry Examiner. LAURENCE Y, EFNER, Examiner.

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