US2672329A - Carburetor of combustion engines with automatic fuel regulation - Google Patents

Description

March 16, 1954 w. ZARNACK 2,672,329 CARBURETOR OF COMBUSTION ENGINES WITH AUTOMATIC FUEL REGULATION Filed July 6, 1950 INVENTOR.

WERNER ZARA 145K L Z/W AFFORNEJ Patented Mar. 16, 1954 OMBUSTION ENGINES WITH AUTOMATIC FUEL REGULATIUN Werner Zarnack, Lockstedter Lager-Nord, Germany Application July 6, 1950, Serial No. 172,249

Claims priority, application Switzerland July 13, 1949 CARBURETOR OF C 3 Claims.

Carburetors are used for the regulation and formation of the combustible mixture in socalled Otto-engines in which the proportion of mixture of air and fuel is determined thereby that the effective pressure produced in an air nozzle, air funnel or the like is transmitted to a calibrated fuel nozzle in such a way that the two effective pressures are equal and therewith the proportion of mixture equals to the proportion of the cross-section of the air and fuel nozzle. If the mentioned two cross-sections remain constant also a substantially constant proportion of mixture would result independent of the load of the engine and of the number of revolutions. This supposition essentially also prevails if, as in the so-called foam nozzle carburetors, additional or correcting air is added to the fuel before its exit into the air funnel where in the most cases the mixing of air and fuel happens, provided that the dimensioning of the spraying tubes and the forming of the nozzles correctly considers the rules of the mechanics of flow. Then approximately the following conditions exist:

Herein means:

Gr=weight of the air sucked in per time unit,

Gse=weight of the fuel sucked in per time unit,

jz.=narrowest cross-section of the air funnel,

fa==narrowest cross-section of the fuel nozzle,

yz.=specific gravity of the air sucked in,

'yse=specific gravity of the fuel.

In connection with carburetor of vehicles the variability of '11. may be neglected, While the variability of 'yi. requires special regulating devices in connection with carburetors of aeroplanes.

For the purpose to balance alterations of the load of the engine mostly a throttle valve or a sliding valve is provided behind the place where the combustible mixture is formed; or, if the throttle valve is arranged in the direction of the air flow before the air funnel, mechanical devices are known regulating the feeding of the fuel according to an empirically found law or said devices act in a similar way as the depth rudder of carburetors of aeroplanes.

For small engines, especially engines of motor cycles, carburetors are usual in which the place where the combustible mixture is formed coincides with the throttling place. The controlling of such carburetors is made fully empirically by considering the variable air cross-section on the mixture forming place by simultaneously changing the cross-section of the fuel nozzle. In consequence, however, of the very small fuel crosssections the desired regularity cannot be reached. The described methods of regulating and forming the combustible mixture have great disadvantages.

If the carburetors are provided with a constant air measuring and fuel measuring crosssection a quadratic decrease of the effective pressure results from a decreasing load, so that the suction effect of the carburetor and therewith the atomizing of the fuel rapidly decreases. By

this regularity for example also the arrange-r ment of a device for running without load became necessary, ending on the edge of the throttling valve and constituting a second mixing place of air and fuel. Thereby the fuel supply depends upon the depression on that mixing place following very complicated rules. Thus it happens that the simple relation between the quantity of fuel and air is very considerably disturbed by the added device for running without load. The regulation of fuel and air will therefore not have approximately equal results for all loads but essentially depends also upon the position of the throttling valve. Further especially within the region of transition from running without load to running with artial load very undesired discontinuities of the proportion of mixture result.

A further considerable disadvantage of these mostly used carburetors arises during the forming of the combustible mixture. The formin of the combustible mixture should suitably take place on the place of the greatest air speed because there the mixture is the most intimate and perfect. Instead of that, here the mixture is again deposited in these carburetors behind the place of forming the mixture, the throttling valve being partially closed, and the mixture must be formed anew when passing through the throttling place. As further in consequence of the different circumstances of flow the passage through the throttling valve is quite different on the two halves related to the axis also the mixture behind'the throttle valve is very differently concentrated. The mixture is stripped.

The quality of the atomizing further depends upon the rate of decrease in pressure on the nozzle at a given cross-section. Now, as the rate of decrease in pressure becomes smaller in the square of the load also for this reason the fuel preparing on the exit of the nozzle becomes bad if there is a partial load.

These circumstances are an essential reason for the bad consumption of partially loaded engines working with the usual carburetors. In this respect the conditions on the usual carburetors of motor cycles are more favorable as here the forming of the combustible mixture takes place in fact on the place of the greater speed of flow.

There is however the difficulty to correctly dimension the jet needle destined to change the cross-section of the fuel nozzle proportionally to the alteration of the cross-section on the mixture forming place. In consequence of the high speed of flow at the throttling place the coefficients of flow resulting in a deviation from the quadratic rule of flowing are of considerable importance so that it is impossible to shape the jet needle so much approximate that the desired constant proportion of mixture or the required dependency of the proportion of mixture on the air quantity results with every load.

Further it is clear that the air slide which mostly is cylindrically shaped in combination with the air suction pipe socket of the carburetor ar-' ranged rectangularly thereto on the narrowest place does not form a cross-section formation adapted to be inserted into the equation of flow as measuring cross-section fr, so that the effective pressure happening on the fuel nozzle is not at all a measure for the flowing air volume. The proportion of mixture, therefore, is very fluctuating with the load and the number of rotations even if the jet needle is accurately shaped. Also in that case a high consumption results with par tial load.

The improved device according to the invention removes the above described disadvantages of the mentioned two systems. of carburetors by the fact that the, forming of the mixture takes place at the place of the highest speed of flow, i..e. on the throttling place, itself. Further ac-.- cording, to the invention is automatically made by a simple controller in dependenc on t r fl ct pres ur m asured in an a r fu nel havi n. h ari ab e cr ect on.

The al m suri P 3? ma be ar an e n. that a a e qr th thro t in la f he ir. a actwh h is o b nre rrc n ons qu nc of the so reached greater measuring exactness, or:

behind he h ottl n p ac in a ficien t n e. if the variable air density is correspondingly considered. In the improved carburetor the construction of the thr ttl n p a s of n nflu nc at all to the measuring. exactness, of the device as the fuel measuring nozzle is, arranged between the float chamber and the controller in such a way that it remains free of all. disturbance .fac-.

tors of the air flow. It is further without any importance whether there are arranged for example twisting devices behind the controller, in the flow-- ing direction of the fuel for the purpose for ameliorating the atomizing. The proportion of mixture is determined in every case only by the cross-section of themain nozzle and. the crosssection of the air funnel. This assumption naturally is only correct if the decrease of pressure on the throttling valve is sufficiently high to overthe meterin of the fuel come the flowing resistances of the mixture of fuel and atomizer air between the regulating valve and the spraying nozzle.

As with decreasing load until a smallest partial load (10-20% of the full load) the action of the regulator intermits in consequence of the quadratically decreasing effective pressure a no-load device of the usual form is necessary. But also this device does not influence the proportion of mixture if the regulator starts with increasing partial load as the quantity of fuel escaping from the slow running jet is also measured by the main nozzle and the regulator only allows so much fuel to pass as required on both nozzles altogether.

So it is also possible to arrange only one regulator and one main measuring nozzle in multicylinder motors and to provide any number of throttling places. or mixture forming places on different places of the suction tube. In this case only one air measuring place may be provided or the measuring tube lines of a plurality of air measuring places may be conducted to one sole regulator.

The new regulator becomes very simple especially by the fact that the effective pressures A101. and AZJBe are divided. The negative pres y sures are conducted to the two sides of amenifully opened the narrowest cross section of the; carburetor must be of such size that the decrease of pressure from the air funnel until the throttling place is greater than the loss of pressure of. the fuel from the place behind the fuel measuring nozzle until the exit of the spraying nozzle. including the exit losses.

The drawing shows by way of example two embodiments of the, invention, Fig. 1 being a diagrammatioal illustration of theone and Fig. 2. of. the other embodiment.

According to Fig. 1 the air enters through the air suction pipe socket l and flows through the air funnel 2 to the throttling and mixture forming place 3. throttling valve or. throttling slide 8 of any desirable construction is provided. The valve or slide is operated by any suitable leverage not shown and described.

The fuel is delivered from the fuel container not shown in the drawing through the opening 5 and over the throttling needle 1 into the float chamber 8 ofknown construction, and from there to the main fuel nozzle 8 and over the throttling needle 9 of the regulator to the spraying nozzle H. When partially loaded with a small loador when idly running the regulator closes automatically, in a ivenc se n e he ect onof the. smalr clditional spring. 12, said spring beingsimultaneously. a valuablemeans for influencing the characteristic; of the regulator. In thisieventthe fuelescapes through the slow running jet l3 which if desired, may be controlled by aneedle IA. The atomizing in: the sprayingpipe. maybe effectively.

ameliorated by additional airentering through the, nozzle R5, or by twisting deviceson the exitof; the fuelwithout the re u at on. ei nfiuencedthereby.

take pipe. This velocity difference is brought:

For limiting the output or power a Downstream of the intersection of the pipe I!v with the funnel 2, the latter still further converges or is reduced, in order to yield a further pressure drop at the point of fuel ejection by the nozzle ll even when the throttle 4 is fully opened. The pressure drop must be large enough so that air 7 may also be taken in through the auxiliary air nozzle l5.

The negative pressure on the fuel nozzle is conducted through the pipe line i into the chamber l8 and the negative pressure on the air nozzle through the pipe line H into the chamber l 9, the two chambers being separated from each other by a membrane. The positive pressures are short circuited by the pipe lin to. The regulator operates as follows:

During idling, the throttle 4, as best shown in Fig. 1, is closed so that only a small amount of air will pass through the funnel 2. During this idling the pressure drop between the points of intersection with the socket and funnel with the pipes and I! is correspondingly small. For this.

reason, the spring l2 will be made sufl'iciently strong to close the throttling needle 9 of the regulator. The fuel needed for idling is being calibrated accordingly by the nozzle 53 and, where there isprovided a regulation for said nozzle S3, for instance the needle 14, the calibration is also aided thereby. Where there is provided no needle M, the idling fuel feed will be regulated by the size of the nozzle l3 and the size of the auxiliary air nozzle 15.

When the throttle 4 is opened wider and therefore the flow of air through the funnel 2 is increased, the regulator will be opened. The throttling needle 9 of the regulator will admit an amount of fuel necessary to cover the fuel required in addition to that fed through the nozzle l3, for ejection through the nozzle l l. The calibration of the amount of that fuel is made by the nozzle 8. Thereby the quantity of fuel increases until the pressure behind the fuel nozzle 8 is exactly as great as the pressure in the air funnel 2 so that the regulator is again balanced.

Another embodiment of invention in which a plurality of mixture forming places are combined with one sole regulator is shown in Fig. 2. In this figure 2| designates the float chamber and 22 the fuel regulator connected with the negative pressure of the fuel nozzle 24 by the pipe line 23, while the negative pressure of the air measuring nozzle 25 is connected with the regulator by the connecting pipe 26 and the assembling pipe line 21. In the pipe line 21 therefore the average pressure of the measurements in the air funnels 25 prevails so that also an average pressure is adjusted on the common fuel measuring nozzle. By the pipe line 28 the positive pressure of the air measuring nozzle 25 is connected with the float chamber. Exactly as described with respect to the negative pressures of the air measuring nozzles also here the two pressures may be combined to an average value. In the pipeline of the fuel also the common atomizing nozzle 29 is provided. The fuel flows through the admitting socket 30 into the float chamber 2| and over the main measuring nozzle 24 to the regulator 22. After passing the regulating valve the fuel flows into the assembling pipe 3| and from there to the spraying nozzles of which any desirable number may be' especially simple by using only one regulator and only on float chamber.

Having thus particularly described the nature of my invention and the manner in which the same is to be performed what I wish to have covered by Letters Patent is:

1. In a carburetor, for use in connection with a combustion engine, in combination, an air pipe having a wide section, a converging section adjacent thereto abruptly narrowing the width of said pipe as compared to said wide section, a narrow section spaced from said converging section and constituting the smallest width throughout said pipe, and a funnel section extending between said converging and narrow sections and continuously converging between the widths thereof, whereby air flowing through said pipe from said wide section to said narrow section will undergo a first pressure drop between said wide and said converging sections and will undergo a second pressure drop between said converging and said narrow sections, throttle means disposed in said narrow section and operable for reducing th Width thereof, a fuel conduit comprising a float chamber structure including a regulatable inlet pipe, means operable in response to the amount of fuel prevailing at any moment in said chamber for regulating the amount of fluid delivered by said inlet pipe and comprising a valve, a float for opening and closing said valve, and an interconnection be-- tween said wide section of said air pipe and the upper portion of said chamber structure, a fuel pipe connected to the lower portion of said chamber structure and interconnected to said narrow section of said air pipe and operable for delivering controlled amounts of fuel sidewise thereto, and means connected to said fuel pipe for controlling the amount of fuel passing therethrough comprising a valve and a regulator interconnected to said converging section and being operable to actuate said valve in response to predetermined values of differentials between the pressure of the fuel flowing in said fuel pipe and the pressure prevailing in said converging section.

2. In a carburetor, for use in connection with a combustion engine, in combination, an air pipe having a wide section, a converging section adjacent thereto abruptly narrowing the width of said pipe as compared to said wide section, a narrow section spaced from said converging section and constituting the smallest width throughout said pipe, and a funnel section extending between said converging and narrow sections and continuously converging between the widths thereof, whereby air flowing through said pipe from said wide section to said narrow section will undergo a first pressure drop between said wide and said converging sections and will undergo a second pressure drop between said converging and said narrow sections, throttle means disposed in said narrow section and operable for reducing the width thereof, a fuel conduit comprising a float chamber structure including an inlet pipe and a float having a valve needle, said float floating in the fuel within said structure and being operable for closattests ii'i with said needle said inlet when the level of said fuel sure a predetermined height inside of the strut store, an air chamber formed in said structure above the level of the fluid thereof and intereemznunieatmg with said wide section of saidair pipe, a fuel pipe eonneeted to the underside of said sweaters and operable for oiive' iih' said tile} and ifielii'diiie a first fiiel nozzle, a second file! riezzieadjacent said narrow seetioii of "said air needed beiifg des rable for delivering sidewise fuel into said narrow section; and a valve inter= iiidiatesaid ii'oiz'le's operable for interrupting the between said rioi'zls, means actuable new f tiel for operating said valve in'response to said pres-- sure drops comprising a ho sing, a diaphragm ea titiohi-iig said housing into two compartments in driving eeaneetms said valve; partmeilt nearest said valve beans inter tifa'iletdto said reei pipe to ieeive real that said first time and the other compartfi fifit acing with said eenveeging" seii'tioil pine, an air intake nozzle adi liit said 'soflii nozzle;

3: a earburetor {of use in connection With a cifiib'ustioii engine in oorflbi'l'iation, an air leaving it Wi'ti seetren it eenv'ersing section ad jaeent thereto abruptly narrowing the width of said pipe as tempered to said wide section, a naarow spaced from said converging seeden and constituting the smallest width throughout said lpipe, and a funnel section ex-tendingbe= tween said converging and narrow sections and continuously converging between the widths thereoftwhereby air flowing through said pipe rrem said Wide Section to said narrow section will undergo a first pressure drop between said wide and said converging sections and will undergo a second pressure drop between said converging and said narrow sections, throttle means disposed in said narrow section and operable for reducing the width thereof, a fuel conduit comprising a floateh'amber structure mcluding an inlet pipe and being this i3 3? and a floatliaving a valve needle, said float float ingin the fuel within said structure and. being operable for closing with said needle said inlet when the level or said :uel surpasses a predetermined height inside of the structure, an air chamber formed in said structure above the level of he ruel thereof and intercommunicatins with said Wide section of- Said air pipe, a fuel pipe eonnested to the underside of said structure and op stable for conveying said fuel and indiudirig a first fuel nozzle, a second fuel nozzle adjacent said narrow section of said air pipe and being operable for delivering sidewi'se fuel into said narrow sec tion, and a valve intermediate said nozzles openable for interrupting the new of fuel between said ne'zzles, means actuable for operating said valve in response to said pressure drops comprising a housing, a diaphragm partitioning said housing into two compartments and being in driving'cenn'ztiori with saidvalv'e, the Compartment nearest said Via-I've being} interoonnected to said fuel pipe to receive fuel that passed said first nozzle and the other eem' artment interoommunicatifig with said conver in section of said air pipe, and a re;- uiatabl third fuel nozzle connected to said fuel pipe and operable to receive ruel from said first nozzle and intereommuineating with said narrow section of said air pipe for delivering 'sidewise a resold-table amount of fuel thereto, and an air intake nozzle adjacent said second nozzle.

WERNER ZARNACK;

References Cited in the file of this patent UNiTE'D STATES PA'I'ENT'S

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