US2821373A - Carburetor fuel feeding device - Google Patents

Description

Jan. 28, 1958 E. OLSON 2,821,373

' CARB'URETOR FUEL FEEDING DEVICE Filed April 30, 1956 Vacuum. x(vemuri) ATTORNEY INVENTOR I United States Patent CARBURETOR FUEL FEEDING DEVICE Elmer Olson, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich.,' a corporation of Delaware Application April 30, 1956, Serial No. 581,597

2 Claims. (Cl. 261-78) The present invention relates to an improved fuel feeding device for a carburetor. More specifically, the present invention relates to means whereby the transition from idling to normal fuel feed flow is made more smoothly particularly under light throttle loading.

It has been found that in progressing from idle to normal operation under light throttle loading, the air flow through the conventional booster venturi is too low to create enough vacuum to adequately start the flow of fuel through-the main fuel nozzle. Accordingly, the engine is starved for fuel with a consequent fall-off in power until such time as the throttle is opened sufiicient- 1y to increase air flow through'the induction passages and in turn increase the booster venturi vacuum.

It is the purpose of the present invention to provide a device for more quickly starting the flow of fuel through the main fuel nozzle under low air flow conditions as during the aforementioned transition from idling to normal running conditions. Pursuant to this purpose a vacuum multiplying means has been developed which can replace the conventional booster venturi.

A description of the present invention is hereinafter set i forth in detail.

. In the drawings:

Figure 1 is a fragmentary sectional elevation of a carburetor embodying the improved fuel feeding device.

Figure 2 is a' fragmentary showing of a conventional booster venturi.

Figure 3 is a graphic representation of a typical carburetor flow curve.

Figure 4 is a graphic comparison of the vacuum obtainable with the subject device as compared with a conventional venturi of the type shown in Figure 2.

Referring to the fragmentary view of a carburetor shown generally at 10 in Figure 1, a casing 12 includes a fuel bowl 14, and a main fuel well 24. Well 24 is interconnected with the fuel bowl through a restricted passage formed in a plug 16. A portion of an induction passage 18 is formed in casing 12 and includes a main venturi 20 having a throat 22.

A throttle body casing is shown at 26 and includes a throttle valve 28, as well as the remaining portion of induction passage 18.

Usually formed separately from casing 12 but mounted thereon is a fuel supplying casting or cluster 30. Cluster 30 is mounted super-adjacent the main fuel well 24 and dependingly supports a fuel nozzle 32. Nozzle 32 is of sufficient length to extend below the normal fuel level in well 24. Nozzle 32 is suitably perforated below the fuel level to permit fuel to flow interiorly thereof.

The upper or supported end of nozzle 32 projects with in an aspirating passage 36 and terminates in a bevelled portion 38 which, as will be hereinafter explained, opens downwind with respect to normal airflow. Passage 36 is open to substantially atmospheric pressure at end 40 which actually communicates with the induction passage 18 anterior of the main venturi 20. The other end of passage 36 is, under normal operating conditions, ex-

posed to sub-atmospheric pressures, therefore, air flows from end 40 past the bevelled portion 38 of fuel nozzle 32 into the main venturi 20.

Air in thus flowing through the passage 36 has an aspirating or educting effect on the nozzle 32 causing the fuel therein to be drawn into passage 36 at a rate proportional to the velocity of air flow through said passage. The fuel is, of course, mixed with air in aspirating passage 36 to provide, what is at this point, an over-rich mixture of fuel and air to the main venturi entrance.

In order to provide an adequate supply of fuel to the main venturi 20, it is normal practice to provide means to insure that the velocity of air flow through passage is sufficient for normal operating conditions. Referring momentarily to Figure 2 in conjunction with the general environment of Figure 1, this air flow has normally been assured by the provision of a booster or auxiliary venturi 44 which is supported from the inner end of passage 36' and projects centrally within the upper end of the main venturi 20. I

Under normal operating conditions the flow of air through booster venturi 44 creates sufficient sub-atmospheric pressure or vacuum in the venturi end of passage 36 to insure an adequate supply of fuel. It has been found, however, that during conditions of low air flow through the induction passage 18, particularly as occurs during the transition from idling to normal operating conditions With throttle 28 only partially open, the booster venturi does not provide sufficient vacuum to draw the requisite amount of fuel through the main nozzle 32 for smooth engine operation. As a consequence, the engine is starved for fuel and there is a perceptible drop off in power until the situation is rectified by further throttle opening. I

This condition. canbe. graphically represented in Fig ure 3 in which a portioniof a typical carburetor flow curve is represented at 48. In this case air-fuel ratio- A/Fis plotted against airflow. The portionof curve 48 between lines A and B is intended to illustrate the part of the curve. theoretically involved in making ,th e transi; tion from idle to normal operation. As already noted, however, under light throttle loading with a conventional booster venturi, air and fuel flow are quantitatively reduced to an amount which results in a sag, indicated by broken line 50, below the normal curve portion AB. The sag is functionally manifested in the loss of power already referred to above.

It is to eliminate this loss of power under the frequently occurring conditions noted, that the present invention is dedicated. Having determined the cause for the loss of power, particularly during the transition from idle to normal operation with light throttle loading, a novel vacuum multiplying mechanism 60 has been developed, a preferred form of which is shown in Figure 1.

Mechanism 60 is intended when necessary to replace the traditional booster of the type shown and described in relation to Figure 2. Mechanism 60 is designed particularly to provide a relatively high vacuum during conditions of low air flow.

The vacuum multiplying mechanism 60 includes a cylindrical sleeve 62 formed integrally, or otherwise supported, upon passage 36. The sleeve 62 has open ends 64 and 66 aligned in the direction of air flow through induction passage 18. End 66 of sleeve 62 extends with in venturi 20 and terminates proximate throat 22 thereof. It has been found preferable to provide the inner wall of sleeve 62 with a slight restriction at 68 just posterior of the junction of the sleeve with passage 36. The portion of the inner Wall of sleeve 62 posterior of restriction 68 is slightly divergent. The inner wall anterior of restriction 68 as well as the outer wall are substantially cylindricalv "To insure the relatively high vacuum, referred to above,

is substantially diametrically co-extensive with end. 64

of sleeve 62, in a smoothly curving fashion to terminate in a restricted portion 74 proximate sleeve restriction 68.

As thus constructed and arranged, the inner end of passage 36, sleeve 62 and nozzle 70 cooperate to define a downwardly opening annular vacuum chamber 78'. Further, the smoothly curving entrance of nozzle 70 relatively efiiciently converts the pressure head of air flowing therethrough to a velocity head. Unlike a venturi which again gradually diverges from the restricted portion or throat, nozzle 70 discharges the high velocity air into the appreciably and abruptly larger sleeve 62 with a resultant high turbulence and correspondingly high eductive effect on chamber 78 and creating therewithin a relatively high vacuum even through the quantitative flow of air through the nozzle may be low.

The result of this novel arrangement is to insure a higher vacuum and a consequently greater quantity of fuel fiow under low air flow conditions than is possible with a conventional secondary or booster venturi.

The difference in the vacuum obtainable under the conditions set forthis illustrated graphically in Figure 4 in which vacuum is plotted against air fiow. Curves X and Y respectively depict in a general way the vacuumair flow relationships through a venturi and through the subject nozzle. Again the lines A and B depict the portions of the curves involved during the transition from idle to normal operation under light throttle loading. It will thus be seen that between A and B a higher vacuum is realizable for a given air flow with the subject nozzle than is the case with a venturi.

Inasmuch as nozzle 70 is preferably an insertable member which is adapted to be removably mounted in sleeve 62, it is apparent that nozzles of the general type shown but having different flow characteristics may be utilized 7 in a given carburetor. In this way, it is possible to more closely match nozzle characteristics with a particular engine. Further, the versatility of the present fuel feeding device is greatly enhanced as well as providing a simply and inexpensively manufactured sub-assembly.

I claim:

1. A carburetor comprising an induction passage, venturi means in said passage, a fuel bowl, a perforate nozzle projecting within said fuel bowl, passage means communicating said nozzle with said venturi, and a fuel cluster, said fuel cluster including a mixture passage connected at one end with said nozzle and terminating at the other end in an open-ended cylindrical sleeve disposed within said venturi, said sleeve being disposed centrally of said venturi and having one of its open ends terminating proximate the venturi throat, said sleeve having a portion of reduced cross-section posterior to the junction of said sleeve and fuel passage, and a nozzle supported from the other end of said sleeve and projecting therewithin in radially spaced relation to the inner wall of said sleeve, the other end of said nozzle terminating adjacent the reduced portion of said sleeve.

2. A carburetor comprising an induction passage, venturi means in said passage, a fuel bowl, a perforate nozzle projecting within said fuel bowl, passage means communicating said nozzle with said venturi and a fuel cluster, said fuel cluster including a mixture passage connected at one end with said nozzle and terminating at the other end in an open-ended sleeve disposed within said venturi, said sleeve being disposed centrally of said venturi and having an internal portion of reduced cross section posterior to the junction of said sleeve and fuel passage, and a tapered nozzle supported from the anterior end of said sleeve and projecting therewithin in radially spaced relation to the inner wall of said sleeve, the most restricted end of said nozzle terminating proximate the reduced portion of said sleeve.

References Cited in the file of this patent

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