US2711720A

US2711720A - Device for fuel injection in internal combustion engines

Info

Publication number: US2711720A
Application number: US229018A
Authority: US
Inventors: Friedrich K H Nallinger
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1950-05-31
Filing date: 1951-05-31
Publication date: 1955-06-28
Anticipated expiration: 1972-06-28

Description

June 1955 -F. K. H. NALLINGER 2,711,720

DEVICE FOR FUEL INJECTION IN INTERNAL COMBUSTION ENGINES Filed May 31, 1951 United States Patent DEVICE FOR FUEL INJECTION IN INTERNAL COMBUSTION ENGINES Friedrich K. H. Nallinger, Stuttgart, Germany, assignor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Application May 31, 1951, Serial No. 229,018

Claims priority, application Germany May 31, 1950 7 Claims. (Cl. 123-119) This invention relates to a method and device for fuel injection in internal combustion engines.

Fuel injection without the employment of compressed air, i. e., by the solid injection method, has the disadvantage that very small injection nozzles or injection nozzles with very small spray holes must be used which are liable to choke very easily.

On the other hand, the use of compressed air for the injection of fuel is, in the hitherto usual injection methods, attended by the disadvantage of requiring an additional expenditure for the means for compressing the air. Furthermore, a relatively high pressure must be employed in order to ensure a sufliciently thorough atomizing of the fuel.

It is a primary object of the present invention to overcome these disadvantages of the known fuel injection systems and, at the same time, to combine the advantages of both methods.

A further object of the present invention is to bring about an effective preparation of the mixture to be burned by simple inexpensive means requiring, at the most, but few additional parts.

A feature of the present invention therefore essentially lies therein that air is admixed to the fuel prior to, or while it is put under pressure, or also subsequently to that period, and the fuel-air mixture, eventually in the form of a fuel-air emulsion, is delivered to the injection nozzle under pressure.

According to another feature of the present invention the fuel-air mixture is accurately metered and delivered to the injection nozzle by means of an injection pump which is so constructed that the mixture volume inducted by the injection pump is completely. displaced from the pump space.

One particular advantage of the present invention is that, on the one hand, additional means for producing compressed air is rendered almost superfluous thus eflfecting considerable saving of expense and, on the other hand, a very eiiective intimate mixing of fuel and air is already eifected prior to their passage through the crosssectional area of the injection nozzle and, furthermore, very small nozzle cross-sections which are difficult to manufacture and liable to choke easily are obviated owing to the increased injection volume as compared with that of purely solid injection.

The accompanying drawings illustrate one embodiment of the present invention. The fuel is drawn from a reservoir 1 through a fuel line 2 and a suction valve 3 by a piston 4 of a delivery pump 5 and delivered to an injection pump 8 through a delivery valve 6 and a fuel line 7. The injection pump 8 comprises in a known manner two

pistons

9 and 10 of which the piston 9 is operated on the up-stroke by a cam on a pump shaft 11 and on the down-stroke by a spring 12. The piston 9 is permanently inserted into or-secured to a sleeve 13 which forms a part of the piston and in its upper portion extends beyond the piston 9. In this sleeve-like extension the piston 10 slides with friction. The down-stroke of the latter is limited by a settable stop 14 and the up-stroke by a resilient stop 15. A delivery line 16 leads to the injection nozzle 17 which, for example, is held on its seat by means of a spring 18. The pumpspace 22 formed mainly by the

pistons

9 and 13 is provided with a suction opening 21 and a pressure opening 23.

Provision is made in the suction system of the ,injec tion pump for means whereby air can be admixed to the inducted fuel. In the diagram illustrated on the drawing this mixture is accomplished, for example, by the delivery pump 5, the pump space of which is in communication with the atmosphere by means of an additional suction valve 19 and for example, a settable throttle 20. Consequently, during the suction stroke of the delivery pump 5 air will be inducted or drawn in through the throttle bore 20 and suction valve 19 at the same time as the fuel through the valve 3, and then the ensuing mixture is delivered through the line 7 to the injection pump. By employing appropriately proportioned springs which exert their tension upon the valve 3 and 19 to hold them on the seats, or by adjusting, or exchanging the throttle bore 29 the fuel-air mixture can then be regulated so as to have the most suitable proportion for injection.

Instead of a throttle bore 20 on the pump 5 there may, of course, be employed a separate, for example, foamforming mixing device consisting of sieves or the like, and this mixing device may be arranged on the delivery pump, or on another point of the suction system of the injection pump, eventually, just in the delivery line thereof.

The injection pump 8 operates in a manner whereby on the down-stroke of the

pistons

9 and 13, under the action of the spring 12, the upper piston 10 is carried with it by friction in the manner of a dummy piston until it is arrested by the stop 14 thereby effecting, during the continuing downward travel of the piston 9, induction of the fuel-air mixture into the pump space 22 through the opening 21 in the sleeve 13. Subsequent to the closing of the suction opening 21 leading towards the line 7 the fuel-air mixture, enclosed in the pump space 22, is moved upwardly on the up-stroke of the

pistons

9 and 13 in that the piston 10 is carried with it until the latter, after opening of the pressure bore 23, pushes against the re siiient stop 15 whereby the air volume enclosed in the pump space 22 is displaced towards the injection nozzle by the reciprocating motion of both

pistons

9 and 10 and then injected into the combustion chamber after the injection valve has been opened. The spring of the stop 15 is so proportioned that the requisite pressure for the displacement may be built up in the pump space 22. By

such an arrangement, which will bring about that the pistons 9 and 14} are brought very close together, the eifect is obtained that no residue of the fuel-air mixture will remain in the pump space whereby an accurate control of the amount of fuel is rendered possible notwithstanding the admixture of air. The fuel control is preferably accomplished by setting the stop 14, for example by means of a rack (not shown) whereby the upper piston 10 is retained in a more or less low position during the suction stroke of the pump.

Any other type of injection pump may also be employed instead of the double piston pump 8 but preferably only such a pump which again fully displaces the inducted fuelair volume from the pump space into the delivery line, or eventually into a by-pass line.

. Injection into the combustion chamber may, moreover, also be accomplished by the employment of additional compressed air which, for example, is delivered directly to the nozzle 17 in such a manner that the fuel-air mixture, metered and delivered by the injection pump, is

mixed with the compressed air, which has been delivered to the nozzle, and atomized into the combustion chamber.

Along with this the delivery of the fuel-air mixture may take place at such a point in the compressed air stream in which acceleration is imparted thereupon.

Mixing of fuel and air prior, during, or consecutively to the time they are subjected to pressure may take place in such a manner and in such a proportion that an emulsion of fuel and air is produced.

The invention is applicable to Diesel engines having direct, or pre-combustion chamber fuel injection, or also to engines having fuel distributing systems for the injection of light (volatile) fuels. It is suitable for all purposes, for example, also for automotive-type engines.

It will be obvious that the details of construction may be varied from those shown in the drawings. I therefore do not limit myself to such details.

What is claimed is:

1. Device for fuel injection in internal combustion engines comprising, a fuel supply, an injection pump, an injection nozzle, adjustable valve means for mixing atmospheric air with the fuel fed to said injection pump between said fuel supply and said injection pump to deliver a mixture of fuel and air to the pump, said injection pump comprising a cylinder, two spaced plungers in alignment with each other, said plungers sliding in said cylinder and enclosing the pump space therebetween, the stroke of one of said plungers being adjustable, a delivery pipe extending to said injection nozzle, and operating means for impelling both plungers in such a manner that both plungers are positioned closely one adjacent the other at the end of the compression stroke of the pump to thoroughly displace the mixture from said pump space into said delivery line.

2. Fuel injection device according to claim 1 wherein said impelling means for said pump plungers comprise, a cam-shaft for impelling one of said plungers, a spring for returning said one plunger, a sleeve connected with said one plunger and operative to carry the other piston with it by means of friction, an adjustable stop means for varying the injected quantity of fuel mixture delivered by said injection pump by detaining said second plunger during the suction stroke of said first plunger at a variable distance from said first plunger, and a further resilient stop means for detaining said second plunger on the compression stroke of said first plunger and to thereby effect that both plungers are positioned closely one adjacent another at the end of the compression stroke.

3. Fuel injection device according to claim 1 wherein said adjustable valve means for mixing fuel and air comprise, a delivery pump housing, a delivery pump member adapted to form a variable pump space, an induction pipe for the fuel extending to said pump space and having a arranged reciprocably within said pump housing and r suction valve, a delivery pipe having a delivery valve extending from said pump space to said injection pump, and an additional opening in communication with the atmosphere and extending into said pump space having a suction valve for admixing air to the fuel.

4. An injection pump for fuel injection in internal combustion engines comprising a housing, cam means operable in said housing, spaced aligned pistons reciprocable in said housing and operable by said cam means, sleeve means connected to one of said pistons, the second piston being slidable in said sleeve means and being in frictional engagement with said sleeve means for common movement therewith during at least a part of the movement of said sleeve means, said sleeve means having a pair of openings therein, tension means for the piston connected with said sleeve means to retract the same to the idling position thereof, stop means to limit said common movement of said second piston in both directions, the stop means for one direction being adjustable, inlet means for fuel air mixture entering through one of said openings and delivery means extending from the other of said openings.

5. A device for fuel injection in an internal combustion engine comprising a fuel supply, an injection pump including metering means and compressing means to vary the amount of fuel introduced with each stroke and subject the same to pressure, communicating means between said fuel supply and said injection pump, and means for admixing air to said fuel in said communicating means, said metering and compressing means being operative to displace the fuel and air completely from said compressing means upon each stroke.

6. A device according to claim 5, wherein said admixing means is operative to draw in air into said fuel.

7. A device for fuel injection in an internal combustion engine comprising a fuel supply and means for delivering fuel from said supply to said engine including means for initially admixing air to said fuel to produce a fuel mixture, means having variable quantity control means for metering said fuel mixture and for subsequently subjecting the same to pressure, means for completely displacing said metered fuel mixture from said last-named means and means for injecting said completely displaced metered fuel mixture into said engine.