US2852240A - Carburetor - Google Patents

Description

sept 16, 1958 ,A c. R. GooDYEAR 2,852,240

CARBURETOR Filed DeG. 19, 1955 INVENTOR CHARLES R. GOODYEAR W wi/Nwww ATTORNE S United States Patent xO CARBURETOR 'Charles'.R. Goodyear, Detroit, Mich., assignor to Holley Carburetor Company, Van l)yke,Mich., a corporation :of Michigan Application December '19,' 1955, VSerial No. 554,053

4 Claims. (Cl. 261.41)

The present invention relates to a carburetor and more particularly, to improvements therein relating to `the tcontrol of idle air bleed in the idle transfer system.

`It is an object of the present invention to provide `in a carburetor an idleair. bleed including bleed passages Aconnected to the idle fuel passage and extending' into the ithroat or throats of a venturi or venturis yin the carburetor.

It isa further object of the present invention to provide an idle system in a carburetor which eliminates the usual air bleed connected to -a source ,of air at substantially .atmospheric pressure and substituting therefor an air bleed connected to a source of air atthe vacuum existing inthe throat of the venturi, which air bleed under certain conditions operates to deliver-fuel to the yventuriof 'the carburetor.

It isa further object ofthe present invention tojprovide in a carburetor a transfer system having a plurality of transfer ports connected by passages to a chamber, and a restricted air passage connectingsaid chambergto ithe idle `fuel passage of the carburetor.

Other objects and features of the invention willbecome apparent as the description proceeds, especially lwhen taken in conjunction with the accompanying drawings, wherein:

'Figure l is a diagrammatic sectional View of a conven- 'tional carburetor illustrating essential operating features thereof as employed prior to the present invention.

Figure 2 is a'diagrammatic sectional view of'a Acarburetor embodying the features of the presentinvention therein.

In Figure l the carburetor ycomprises a-ba1rel`f10 having its interior formed to provide a main-venturi Y12 therein Aand including a manuallyoperable throttle 14 located downstream from the venturi. As illustrated hereinfthe throttle 14 is'provided in a separatebody-portionflibut lthis is of course not essential. In proximitytolthebarrel ,is `a fuel bowl '18 containing aninletvalve controlled ,by aeoat of usual type which is therefore noty illustrated. :The barrel 10 is formedY with a verticallyextendingpassage forming a main vwell 20 communicatingwiththe lower portion of the bowl 18 through a-metering orifice22. If pressure within the `well equalspressure `within-the bowl it will be appreciated thatfuel will llthewell to the same level as existing in the bowl.

The carburetor in thepresent instanceis provided with a booster venturi 24, the outlet -thereof-which is located substantially in the throat ofthe-mainventuriflZ and which is `adapted to establish-a-highergvacuum1in its throat. Adjacent the throat of the boosterA venturi-124 isa main fuel nozzle 26 communicating by intersecting lpassages 27 and 28 with the interior ofa main tube 3 0, -the lower end of which isopen and extends toward the -bottom of the main well 20.

As is well understood, air=drawn through thefbarrel kofthe carburetor bythe action ofthe internal combustion :engine to whichV the carburetor is attached,-producesa ireduced pressure or vacuum withinl the `yen-turis. "This through the booster venturi. lpressure or a pressure approaching atmospheric exists a 2,852,240 Patented Sept. 16, 1958 fice lvacuum existing at the end of the main nozzle 26 causes liquid fuel to be discharged from Athe nozzle where it is broken up or atomized by the rapid movement of air Generally, ,atmospheric within thebowl and the pressure differential between :the

-pressure ofthe bowl and `the pressure at the outlet of passages 34 'and36 to the idle tube-38 which terminates in af restricted metering inlet orifice 40, located in the Alower portion of the well 20. Communicating with the passage 30 is an air bleed 42. The air bleed 42 serves a number of separate functions. T hese functions are (A) to provide air to form an emulsion of fuel `and air `for discharge by the idleport 32 and the ports provided by the transfer passages 46 and'48; l(B) to control the metering pressure dilferential at lthel idle fuel oriice40; and (C) to provide a syphon break at a high point in the idle system passages. 'i

When'the throttle is closed as illustrated in 'Figure 1, the high vacuum maintained beneath t he throttle causes fuel to ow from the well 20 past :the restricted inlet oriliceiii of the idle tube'38, throught-the passages 36 from fully closed toward open position, a pair of transferfpassages 46 and 48 are provided-which terminate in transferports located just upstreamv from an-'edge of the throttle when the throttle is in fully closed position. The ports thus provided are arranged tobe sequentially traversed-by the edge of the throttle `and vthustransferred inetfect ,from upstream of .the throttle to downstream thereof. Thus, asthe throttle is rnovedtin arclockwise :direction toward open position, fuel first flows through :the'pasasge 46 and then through the. passagelythus supplementing the fuel flowing through the idleport 32 and causes an acceleration of the .engineasfthethrottle i opened from its curb idle position.

Withthe throttle in its fully closed..position,it. will be/appreciated that substantially atmosphericpressure existslinthe barrelof the carburetor above the:throttle andaccordingly, the passages 46 and .4S at thistime `operate as air bleeds, bleeding air intot'helfuel-air mixture `or emulsion owing through the passage134.

Movement of the throttle to a-positioninwhichtit sequentially traverses the ports provided by the passages A6 and 48 also has the effectof causing the idle port 32 to discharge a richer mixture intofthe manifoldsincethe .airbleeding function of the portsv 46 and48 is eliminated as-,they tbecome subjected tol the `reduced pressure or higher vacuum existing below the partially openthrottle. Referring now to Figure 2, certain specific .c hangesin thecarburetor structure areillustrated and the purpose and function of these changes will bedescribedin detail. Insofar as'the carburetor parts shown inFigure-Z are identical withthose shown in'Figure l, the Vsame reference numerals have been applied.

@In order to cause the carburetor -to delivera leaner mixture in thetransfer range than isy possibleorfpractical selves relatively small and afford a restriction to owrof f fuel or air therethrough. inasmuch as communication of the chamber 50 with the idle passage 34 is further restricted by the orifice member S2., it will of course be apparent that the flow from the passage 46 and/or the passage 48 to the passage 34 is doubly restricted. As a result, during periods of curb idle fuel is delivered to the engine through the idle port 32. The fuel-air mixture delivered to the idle port 32 by the improved construction illustrated in Figure 2 is richer than would be delivered by the system shown in Figure l. This results from the fact that the air bleed from the passages 46 and 48 is further restricted by the restricted orifice member 52. This being the case, needle valve 44 will require adjustment to decrease the area of the port 32 so that the total idling air-fuel ratio for the engine remains the same as in Figure l.

During the idle transfer operation when the throttle 14 opens sutiiciently to subject the transfer passages 46 and 48 to the reduced pressure existing in the engine manifold, the amount of fuel which is discharged from the transfer passages 46 and 48 is also less than would normally be delivered since the supply of fuel to these passages under the described conditions is restricted the orifice member 52. At the same time, the enrichment of the fuel discharged from the idle port 32 under these conditions is reduced, since the original amount of air bled through the transfer passages had previously been reduced.

In other words, with the modification illustrated in Figure 2, a restriction of the passage leading to the idle port by the needle valve 44 is required because less air is bled into the idle fuel mixture through the passages 46 and 4S. At the same time, when the throttle is opened to place the transfer passages 46 and 48 below the throttle and thus, subject to the increased manifold vacuum, less fuel is supplied than would be the case with the prior art structure illustrated in Figure l. At the same time, there is less enrichment of the. fuel supplied through the idle port 32 as a result of transfer operation of the passages 46 and 4S so that a leaner mixture is delivered. Thus, the mixture delivered under curb idle conditions tends to be richer than would be delivered from the prior art system shown in Figure l, but in the transfer range a leaner mixture is delivered.

It is further pointed out that the arrangement of the plurality of transfer passages 46 and 48 in association with a chamber 5t) connected through the restricting orifice member 52 provide a new and improved construction. In the present stage of development of modern carburetors, there is a practical limit to the smallness of size of passages which may be drilled or otherwise formed in the parts. One obvious limitation is in the actual production of the small passages. Secondly, a problem of maintaining extremely small passages free and clear of obstruction is another limitation. In the present construction the passages 46 and 48 are of relatively small size but both of these passages are in series with the restricted passage provided through the orifice member 52. Thus, the net result of the system accompanied by the seriesarrangement of the restricting orifice member 52 and the transfer passages is the same as if the transfer passages themselves were of substantially smaller size. By this arrangement it isthus possible to provide passages of a size practical to produce by drilling much smaller size due to their series arrangement with one or more additional restrictions.

Referring again to Figure l, it will be recalled that air bleeds into the idle system through the passage 42 when the throttle is fully closed in curb idle position. At this time air is also bled into the'idle system through the transfer passages 46 and 43. As the throttle 14 is opened, the vacuum below the throttle diminishes and, due to increased air flow, a vacuum is produced at the throat of the main venturi 12 and an even greater vacuum is produced at the throat of the booster venturi 24. Under these conditions air is admitted into the idle system through the passage 42 and the mixture of fuel and air is discharged both through the idle port 32 and the ports provided by the transfer passages 46 and 48.

As the throttle 14 is opened still further, air pressure below the throttle increases and the air pressure in the throats of the venturis diminishes with an increase in air ilow. Eventually, the air pressure at the venturis 12 and 24, and consequently the pressure existing at the main fuel discharge nozzle 26, becomes the lowest pressure in the system. When this occurs, air from all higher pressure areas connected thereto will flow toward the main nozzle. Thus, air will flow from the interior of the barrel through the idle port 32, Athe transfer passages 46 and 48, and the air bleed passage 42 into the idle system and thence through the idle tube 3S and the idle fuel restriction 40 into the main Well 20 from where it is drawn and discharged through the main nozzle 26.

The foregoing described operation, known as back bleed, is sometimes undesirable in that it may adversely affect the desired metering characteristics of the carburetor. This is overcome in the impro-ved construction shown in Figure 2. In this construction it will be observed that the air bleed 42 has been completedly omitted and instead, an air bleed passage 54 provided which extends from adjacent the throat of the booster venturi to the idle fuel passage 36. Preferably also, a second bleed passage 56 is provided extending through a restricted portion 53 to adjacent the throat of the main venturi 12.

It will be appreciated that either the bleeds S4 or 56 may be employed, or if desired, both may be provided. With the bleeds 54 and S6 in the position shown, the requirement (A), (B) and (C) previously described are fulfilled during the idle and idle transfer positions of thc throttle valve 14. During periods of increased air consumption by the engine on which the carburetor is mounted, the idle air bleeds 54 and/or 56 are subjected to the reduced pressure or increased vacuum produced by the operation of the venturis in which they are located. Thus, as the main discharge nozzle 26' is subjected to reduced pressure, the bleeds are subjected to equally reduced pressure with the consequent reduction or elimination of the previously described back bleed action.

By proper proportioning of the passages, bleeds and restrictions of the idle system, the passages 54 and 56 operate to discharge fuel at high throttle openings and thus, to supplement the discharge of the main fuel supply system through the nozzle 26.

The drawings and the foregoing specification constitute a description of the improved carburetor in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A carburetor comprising an air passage including a venturi, a main nozzle in said venturi, a throttle in said air passage downstream from said nozzle, an adjustably restricted idle port in said passage downstream from said throttle whenrsaid throttle is in closed position, a plurality of restricted transfer ports in said passage upstream from said throttle when said throttle is closed but close enough together to be sequentially traversed by one edge of said throttle to become downstream therefrom upon initial opening movement of said throttle, a chamber with which said transfer ports communicate, an idle fuel supply passage having branches connecting respectively to said idle port and said chamber, said idle fuel supply passage and the branch connecting to said idle port being substantially unrestricted, and a restriction in the branch leading to said chamber.

2. A carburetor comprising an air passage including a venturi, a main nozzle in said venturi, a throttle in said air passage downstream from said nozzle, an adjustably restricted idle port in said passage downstream from said throttle when said throttle is in closed position, a restricted transfer port in said passage upstream from said throttle when said throttle is closed but close enough together to be traversed by one edge of said throttle to become downstream therefrom upon initial opening movement of said throttle, an idle fuel supply passage having branches connecting respectively to said idle port and said transfer port, said idle fuel supply passage and the branch connecting to said idle port being substantially unrestricted, a restriction in the branch leading to said transfer port, and a bleed passage connecting said fuel supply passage to the throat of said venturi.

3. A carburetor comprising an air passage including a venturi, a main nozzle in said venturi, a throttle in said air pasasge downstream from said nozzle, an adjustably restricted idle port in said passage downstream from said throttle when said throttle is in closed position, a plurality of restricted transfer ports in said passage upstream from said throttle when said throttle is closed but close enough together to be sequentially traversed by one edge of said throttle to become downstream therefrom upon initial opening movement of said throttle, a chamber with which said transfer ports communicate, an idle fuel supply passage having branches connecting respectively to said idle port and said chamber, said idle fuel supply 6 passage and the branch connecting to said idle port being substantially unrestrained, a restriction inthe branch leading to said chamber, and a bleed passage connecting said fuel supply passage to the throat of said venturi.

4. A carburetor comprising an air passage including a venturi, a main nozzle in said venturi, a well, a fuel supply'passage connecting said well to said nozzle, a throttle in said air passage downstream from said nozzle, an adjustably restricted idle port in said passage downstream from said throttle when said throttle is in closed position, a plurality of restricted transfer ports in said passage upstream from said throttle when said throttle is closed but close enough together to be sequentially traversed by one edge of said throttle to become downstream therefrom upon initial opening movement of said throttle, a chamber with which said transfer ports communicate, an idle fuel supply passage extending from said well and having branches connecting respectively to said idle port and said chamber, said idle fuel supply passage and the branch connecting'to said idle port being substantially unrestricted, a restriction in the branch leading to said chamber, and a bleed passage connecting said idle fuel 4supply passage to the throat of said venturi to deliver fuel thereto under open throttle conditions.

References Cited in the le of this patent UNITED STATES PATENTS 1,416,858 Mock May 23, 1922 2,035,681 Udale Mar. 31, 1936 2,127,444 f Emerson Aug. 16, 1938 2,621,030 Henning Dec. 9, 1952 2,674,443 Bracke Apr. 6, 1954 2,676,004 Bimberg Apr. 20, 1954 2,689,115 Olson Sept. 14, 1954 2,771,282 Olson et al. Nov. 20. 1956

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