US2959360A - Fuel injectors - Google Patents

Description

Nov. 8, 1960 w. M. NICHOLS FUEL INJECTORS Filed Sept. 20, 1957 M '3 m M f m n ma a M L Mk w ATTORNEY' United States Patent FUEL INJECTORS William M. Nichols, Schenectady, N.Y., assignor to Alco Products, Incorporated, New York, N.Y., a corporation of New York Filed Sept. 20, 1957, Ser. No. 685,351

6 Claims. (Cl. 239-533) This invention relates to fuel injectors for internal combustion engines and particularly to fuel injectors of the accumulator type.

'Fuel injection through injectors having inwardly opening spring controlled nozzle valves has been improved by the provision of a fuel accumulator chamber within the injector body. During the delivery stroke of the pump in such a construction, check valve means between the delivery line and the chamber is opened by the pressure of the fuel to permit fuel to pass into the chamber. The nozzle valve is kept closed at the same time by the same pressure exerted on the top or pump end of the nozzle valve. This end pressure plus the force of the spring is suflicient to offset the fuel pressure exerted on the valve opening differential surface located adjacent the nozzle end of the valve. Hence, during delivery stroke of the pump, fuel is supplied to the accumulator chamber but injection is prevented. Upon the completion of the pump delivery stroke, pressure on the check valve means and on the pump end of the nozzle valve is relieved so that the accumulator chamber is cut off from the pump delivery line and the nozzle valve is opened by the pressure of the fuel in the accumulator chamber acting on the valve-opening differential surface. Injection continues as long as the nozzle valve remains open and the nozzle valve remains open until the pressure in the accumulator chamber drops sufiiciently for the force of the spring to seat the valve. The construction described so far is known in the art.

In constructions such as described, it should be observed that after the valve is opened or unseated, additional valve surface becomes exposed to the pressure of the fuel. This includes the seating surface of the valve and the area at the end of the valve encircled by the seating surface. The additional lifting force thus produced must be added to the force exerted on the valveopening differential surface to determine the total force to be overcome by the spring to seat the valve. It follows of course that the greater this additional surface, the greater will be the drop in fuel pressure in the accumulator chamber before the spring is able to close the valve. Such a pressure drop is undesirable since fuel will be supplied at too low a pressure at the end of injection and dribbling will result. Furthermore, in some instances, the pressure drop will be great enough so that valve opening pressure will not be restored to the accumulator chamber by the next delivery stroke of the pump, particularly when the engine is operating at idle or at low load, thus fuel injection will not occur until valve-opening pressure is restored to the accumulator chamber.

The principal object of the present invention, therefore, is to provide in a fuel injector of the class which has an inwardly opening spring controlled nozzle valve and a fuel accumulator, a construction which shortens the period during which the valve remains open in response to fuel pressure.

A further object is to provide in such an injector additional differential pressure surface to offset in part the differential surface exposed to valve-opening pressure after the valve has been opened by fuel pressure in the accumulator chamber.

Still another object is to provide within the'body of the nozzle valve of such an injector a cylinder and plunger, the cylinder being in communication with the fuel accumulator chamber and having a defining area which functions as a differential surface when fuel pressure is permitted to enter the chamber by the movement of the piston after the nozzle valve has opened in response to the pressure of fuel in the accumulator chamber.

Other and further objects of the present invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings, Fig. l is a view in section of the fuel injector of the present invention; Fig. 2 is a partial view in section on an enlarged scale of the fuel injector of Fig. 1; and, Fig. 3 is a sectional view taken on line 3- of Fig. 2.

Referring now to the drawings, the fuel injector to which the invention has been applied comprises a cylindrical main body 10 having a downward extension consisting of two cylindrical portions 11 and 12 of reduced diameter. The upper of the two extension portions is threaded for the engagement of nozzle 13. Nozzle 13 has an axial bore 14 into the upper part of which body portions 11 and 12 project. The periphery of portion 12 is spaced from the bore wall to form an annular passage 15, the purpose of which will be later described. Bore 14 beyond portion 12 forms a chamber 16 which communicates with a smaller coaxial duct 17, the bore 14 and duct 17 being connected by a conical shoulder or valve seat 18. Duct 17 supplies the injector orifices 19 in the nozzle tip 20.

Disposed in chamber 16 and extending downward through bore 14 is a needle valve 21 formed with a conical shoulder 22 at its lower end shaped to mate with valve seat 18. The lower portion of valve 21 is splined to form a series of axial passages 23 leading from chamber 16 to the lower end of bore 14. Spaced from seating shoulder 22 is a second shoulder 24 on the valve which serves as a differential pressure surface as later appears. Passages 23 open at their lower end through shoulder 24 into a small chamber 25. An enlargement 26 is formed on the valve at the pump end of the splined passages 23 and the end walls 27 of the passages formed in the valve body adjacent the enlargement also serve as differential pressure surfaces as later appears. A cuff 28 having an axial bore 29 is slidably mounted on the upper end of needle valve 21. The lower end of the cuff is shouldered to form a spring seat 30. A coil spring 31 is arranged between spring seat 39 and a washer 32 disposed atop enlargement 26 and normally maintains the valve in seated position and the cuff in closed position against body portion 12. The pump end of the cuff 28 is fiat and is formed with an annular rib 33 the top surface of which is also flat so that the cuff is adapted to seat flush against the flat end wall 34 of body portion 12. Rib 33 defines an annular compartment 35 in communication with the cuff bore 29.

Needle valve 21 has an axial passage 36 terminating at its lower end short of the valve tip where it communicates with a plurality of ducts 37. angularly disposed within the valve tip and opening through the conical end 22 of the valve opposite the valve seat 18 when the valve is in seated position. The upper end of passage 36 is of enlarged diameter and forms a cylinder 38 within which is disposed a reciprocable plunger 39. The end of plunger 39 remote from the nozzle is adapted to abut the bottom face 34 of portion 12. The opposite end 39a ofthen un er enicallxsliarerl and. s. adapted. 9. seat 44 opens throughthe end Wall'34 of themainbody portion 12,,and is in communicatiQn with the chamber .315 formed between cufi 28 and the b od y portion 34 when he tLis seated V The operation of the device is as follows: When fuel is deliveredby the pump through passage 44 into the chamber 35 its pressure increasesuntil it forces cuff 28 downwardly against the bias of springfi l. This fuel pressure also' acts on the top end of needle valve 21, including plunger 3 9,, to force the valve downwardly to 'seatedposition', thus to prevent the flow of fuel through thenozz'le. The plunger is also forced into seated position against conical shoulder 40. Fuel advances over rib SSfiintochamber 16.and.is accumulatedtherein at increasing pressure as the pump completes its delivery stroke. Chamber 16 and the communicating passages between it and chamber 41 are likewise subjected to the fuel pressure on each pumping stroke. When the pump spills, the pressure in line 44 drops abruptly and the pressure on cuff 28 and piston 39 is relieved. Cuff 28 is snapped shut by the pressure of the fuel in the chamber 16. The upper end ofneedle valve 21 is'now cut ofsfrom the fuel pressure in the chamber so that the valve is lifted or unseated by the pressure offuel on the diiferentialsurfaces on shoulder 24 andendwalls 27. Injection takes place through orifices 19. 'When'the valve is lifted from its seat, the ducts 37are open to the pressure of the fuel passing from the chamber 16 to the nozzle orifices and a part of the fuel advanceslupwardly through passage 36 into cylinder 38. Plunger 39 isflforced upwardly and its seat 40' becomes exposed to the pressure of the fuel. The plunger seat then functionsasa differential surface for pressure of fuel toward the nozzle. Fuel pressure upon the plunger is transmitted through portion 34 to the injector body and hence does not function as a differential surface. This additional differential surface provides means for,creat ingaforce to offset the additional force which acts upon the valve in opposition to the spring when fuel pressure is applied to the additional surface exposed when the valveha's been unseated. A much more rapid seating of thevalveresults. If the additional differential surface is equal in area to. theadditionalsurface exposed when the valve has been unseated, then offsetting will be complete, Insuch a case, the pressure required'to open. the valve is substantially equal to the pressure. at which the valve is closed. If desired, the additional difierential surface may be lessin area to the area of the additional surface exposed when the valve is unseated. In this case, the pressure at which the valve is closed is less, to the extent determined by the decrease in offset between the1 two surfaces, than the pressure required to open the va ve.

While there has been hereinbefore described an approved embodiment of this invention, it. will be understgod thatmany and various changes and modifications inform, arrangement of parts and details of construction the sef, ma he masm t qqt departin 29 2. s iri of the invention, and that all such changes and modifications as fall within the scope of the appended claims are contemplated as a part of this invention.

What I claim is: i

1. In a fuel injector of theclass which has an in wardly opening spring return nozzle valve disposed in a fuel accumulator chamber, saidvalve having a surface thereon responsive to pressure of fuel in the chamber to open the valvenpo'ncgmpletion of the delivery stroke of a pump; valve control means comprisin a, second surface on the valve out of communication with the fuel in the accumulator chamber-when the valve is closed but in communication with such fuel when the valve is opened, said surface providing cumulative pressure responsive means urging the valve toward open position when sub jected to the pressure of the fuel in the chamber; a surface within the body ofthe valveresponsive, to fuel .pressureto urge.thesharew e.cia eap smb fuel pas, sage means extending from said'secondsurfaceio the pressure responsive surface within the valve body, and meansjclosin'g siiiifuellpeissag means, said means op n ing said: passa'gfmeans when the valve isv unseated.

2 Valvef control means; according to claim 1, which thesecondsurface isthe valve seat.

"3, Valve control means, according to claim 1 in which. the secondis urfac e is equal in area to the surface withinthe body oflth e valve. i

"'4: Valve control, means, according to claim 1, in which thesecond surface i'sgreat er in areathan thearea of the surface within the body or the valve.

'5. In a fuel injector of the class which hasan accumu lator chamberand an inwardly opening spring controlled nozzlefvalve, valve controlmeanscomprisiug fuel dis cliarg'e means leading from the accumulator chaniber and controlled by thevalve; an inwardly acting pressure, re} sponsive surface on the, valve in communicationwith the accumulator chamber, said valve being openable. in response to: fuel pressure on saidsurface; an outwardly acting pressure responsive surface. within. the valve; and f fls s s n e a ye tendi s the u ard v ing surfaceto the. exterior surfaceof the valve, means closing said passage at the exterior surface ofthevalve, h r e nt f he lems ts, in such at s d wer bPencdtathe umul e? h mb hen he valve is unsealed.

A eli ig qr of h y e s r ed. wmn i n a nozzle body having a valve seat therein; an injection valve in said ngzzle body, said-valvehaving a seating shoulder thereon. adaptedto engage said valve seat; spring means urging 'the valve against said seat; a fuel passage to supplyfuel tolthenozzlebody; a second shoulderon said valve' responsive tq said fuel pressure to urge e al e w tsii peu aq it n; a u ace Within the valve responsiveto fuel pressure, to urge the valve to- War s q ed pcq i i n rassase exte n fr m .Said u face tothevalveseating shpulder; means-closing said passage at said shoulder, the shoulder being movable away from the closing meansupon opening ofthevalve IQ Pe m t s e i f i ai pa s r t valve ql l er- References Cited in ,th e fileofthis patent V UNITED STATES PATENTS

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