US2807449A

US2807449A - Carburetor construction

Info

Publication number: US2807449A
Application number: US454507A
Authority: US
Inventors: Jr William O Manning
Original assignee: Holley Carburetor Co
Current assignee: Holley Performance Products Inc
Priority date: 1954-09-07
Filing date: 1954-09-07
Publication date: 1957-09-24
Anticipated expiration: 1974-09-24

Description

Sept. 24, 1957 w. o. MANNING, JR

CARBURETOR CONSTRUCTION Filed Sept. 7, 1954 h mm MM VA mM 0. M M M H/ w Y I B I 1 W I I United States Patent Ofitice 2,807,449 Patented Sept. 24, 1957 CARBURETOR CONSTRUCTION William O. Manning, In, Detroit, Mich., assignor to Holley Carburetor Company, Detroit, Mich., a corporation of Michigan Application September 7, 1954, Serial No. 454,507

2 Claims. (Cl. 26,141)

This invention relates generally to carburetors of the type employed for feeding fuel mixture to internal combustion engines and refers more particularly to an improved idling or low speed jet system for carburetors.

Internal combustion engines employed to propel Vehicles are usually provided with a carburetor of the down draft type having an idling jet communicating with the fuel mixture supply passage at the down stream side of the throttle valve and also communicating with the upper end of an idling tube to receive fuel from the latter. The lower end of the idling tube ordinarily extends into a fuel well which is connected by a main metering jet to a fuel supply or float bowl of the carburetor.

The primary function of the idling system is to assure delivery of an ample supply of fuel mixture to the engine when the throttle valve is closed or substantially closed. However, in many installations the fuel supply bowl occupies such a position that rapid deceleration of the vehicle resulting from closure of the throttle valve while the vehicle is moving forward, causes the supply of fuel in the bowl to surge in a direction away from the main metering jet and this surging action has a tendency to effect a reverse flow of fuel through the main metering jet with a corresponding lowering of the fuel level in the well which communicates with the lower end of the idling tube. This reverse flow of fuel through the main metering jet produces a force which opposes the intake manifold vacuum tending to draw fuel through the idling jet and in severe cases this force becomes sufiicient to cause stalling of the engine.

With the above in view, it is an object of this invention to overcome the tendency for the vehicle to stall upon deceleration by providing the idling tube with an air bleed situated to interrupt the fuel passage extending from the idling discharge jet to the fuel Well at the bottom of the idling tube. As a result, the force tending to produce reverse flow upon deceleration is reduced to a negligible quantity in the portion of the fuel passage between the idling discharge jet and point of interruption.

It is another object of this invention to locate the air bleed as closely as possible to the normal level of the fuel in the well communicating with the lower end of the idling tube so that the maximum volume of fuel is available in the portion of the passage extending from the idling discharge jet to the air bleed. Hence, ample supply of fuel is available at the idling jet to maintain operation of the engine during the relatively short surging period of the fuel in the supply bowl.

It is a further object of this invention to locate and so proportion the size of the air bleed in the idling tube that it serves the additional purpose of enrichening the fuel mixture in the idling fuel passage at the time the main fuel nozzle begins to flow. Thus, the metering characteristics of the carburetor are improved and superior performance is assured regardless of changing conditions.

The foregoing as well as other objects will be made more apparent as this description proceeds especially when considered in connection with the accompanying drawing, wherein:

Figure 1 is a semi-diagrammatic sectional view of a carburetor of the down draft type and embodying the features of this invention; and

Figure 2 is an enlarged sectional view of a part of the carburetor shown in Figure 1. V v

The carburetor selected for the purpose of illustration is of the down draft type having a housing 10 formed to provide a vertically extending passage 11 and a float bowl 12. The lower end of the passage 11 communicates with an intake manifold of an internal combustion engine (not shown) and the upper end of the passage 11 communicates with the atmosphere or an air supply. A venturi 13 is provided in the passage 11 intermediate the ends thereof and a throttle valve 14 is supported in the passage 11 at the downstream side of the venturi 13. A choke or air control valve 15 is suitably mounted in the passage 11 at the upstream side of the venturi 13 for regulating the amount of air drawn into the system to facilitate starting the engine when the latter is cold.

The float bowl 12 communicates with the passage 11 above the choke valve 15 and is adapted to contain a supply of fuel determined by a float 16. Fuel is supplied to the bowl 12 through a passage 17 and the quantity of fuel admitted to the bowl 12 is regulated by a valve 18 operatively connected to the float 16 for actuation by the latter. A main metering jet or restriction 19 establishes communication between the bowl 12 and a well 20 in a manner such that the level of the fuel in the well is normally the same as the level of the fuel in the bowl 12.

The well 20 communicates at a point above the normal level of the fuel therein with a main fuel discharge nozzle 21 positioned in the throat or restricted area of the venturi 13 to discharge fuel in a downward direction toward the throttle valve 14. The arrangement is such that when the throttle valve 14 is opened substantially, considerable suction is produced in the Venturi throat and fuel is drawn upwardly from the well 20 through the main nozzle 21.

When the throttle valve 14 is closed or practically closed, the suction at the Venturi throat drops considerably and very little, if any, fuel is drawn through the main nozzle 21. In order to assure the supply of fuel required to maintain operation of the engine at closed or practically closed throttle conditions, a low speed jet or idling nozzle 22 is provided at the downstream side of the throttle valve 14 where the suction is relatively high under these conditions. A needle valve 23 is threadably supported on the housing 10 in a position to regulate the flow'through the idling jet 22 in accordance with conventional practice.

Fuel is supplied to the idling-jet 22 by a passage.24

formed in one wall of the housing Ill and extending upwardly from the idling jet 22 to a point above the venturi 13. The upper end of the passage 24 extends forwardly across the passage 11 and communicates with the well 20 at a point spaced above the point of communication of the main fuel discharge nozzle 21 with the well 24 Fuel is admitted to the upper end of the passage 24 from the Well 20 through an idling tube 25 having a head 26 at the upper end threadably mounted in the well 20 above the point of communication between the passage 24 and well 20. The lower end of the tube 25 is reduced in diameter and projects downwardly to a point below the normal level of the fuel in the well 28. The vertical passage through the tube 25 is indicated by the numeral 27 and terminates short of the head 26. The head 26 has an annular groove 23 in registration with the intake end of the passage 24 and a bore 29 is formed in the side of the head to connect the groove 28 to the passage 27.

flowing .upwardly through the tube 25 during operation of the idling jet 22.

As stated above, when thethrottle valve 14 is closed or practically closed, the manifold suction at the throat of 1 the venturi 13 or' at the main discharge jet 21. drops 1 substantially so that very little, if "any, fuel is'drawn from the well 20 through the main discharge jet 21. However, the suction in the passage .11 at the downstream side of the throttle valve 14 is increased to such an extent that fuel is drawn from the well through the idling tube 25 and passage 24 to the idling discharge jet 22.. Also, a small quantity of air is drawn into the fuel stream through the bleed 30 and the resulting emulsion is discharged into the passage 11 through the jet 22. Supplemental jets 31 may be, and preferably are provided at the upstream side of the jet 2 2. The supplemental jets 31 function when the throttle valve 14 is practically closed to admit additional airinto the passage 24 and when the throttle valve 14 is opened farther to admit additional fuel mixture into the passage 11. By reason of the above arrangement, the socallcd fiat spot-is eliminated in the mixture-ratio curve within the range of speeds where the delivery was taken over from the idling nozzle 22 by the main nozzle 21.

In the present instance, the carburetor is installed With the bowl 12 in such a position that when the vehicle is rapidly decelerated, the fuel contained in the bowl 12 and well 26 surges forwardly or in a direction to cause reverse flow of fuel in the main metering jet 19. However, the force produced by such reverse fiow through the jet 19 is dissipated or materially reduced at the air bleed orifice 30 in the idling tube 25 so that it has little or no effect on the fuel mixture contained in the length of the passage extending from the idling jet 22 to the air bleed orifice 30. Hence, any opposition that this force produces on normal flow of the fuel mixture through the idling jet 22 by the manifold vacuum is negligible. Moreover, since the air bleed 30 is located inclose proximity to the normal level of the fuel in the well 20, ample fuel mixture is available beyond the bleed orifice 30 to assure maintaining operation of the engine during the relatively short time required for the fuel to return to its normal level in both the bowl 12 and well 20.

The location of the air bleed 30 in the side of the idling tube 25 above the normal level of the fuel in the well 20 also renders it possible to improve the metering characteristics of the carburetor. In this connection, it will be understood that when the throttle valve 14 is moved from its idling position toward its open position, the manifold vacuum at the restriction of the venturi is greatly increased with the result that the suction created at the main discharge jet 21 becomes sufficient to draw, fuel upwardly from the well 20 into the venturi. In other words, the level of the fuel in the well 20 is raised to the point of communication of the main discharge jet 21 with the well 20 by the increased suctionresulting from opening 4 the throttle'valve 14. As shown in Figure 1 of the drawing, the air bleed 30 in the idling tube 25 is positioned slightly above the point of communication of the main discharge jet 21 with the well 20. Actually, the air bleed 3% is located in such a position with respect to the point of communication of the main discharge jet 21 with the well 26 that it bleeds the idling tube 25 with an emulsion of fuel and air at the time the main nozzle 21 starts its flow. In other words, the fuel mixture in the idling system is enriched at the time the main fuel discharge nozzle 21 becomes operative and this is desirable in that it assures more satisfactory distribution of fuel to the engine when the throttle valve 14 is opened. It will also be understood that the size of the bleed orifice 30 may be varied to obtain the most desirable metering characteristics for a given set of conditions.

What i claim as my invention is:

1. A carburetor for an internal combustion engine of an automotive vehicle comprising a body having an induction passage for fuel mixture, a float chamber in said body, a vertically elongated well in said body, a fuel metering jet connecting the chamber and well adjacent the bottom of the well, a main nozzle in said induction passage, a throttle valve in said induction passage downstream from said main nozzle, an idle tube in said well defining an annular chamber between the inner surface of said well and the outer surface of said tube, said tube having an intake opening adjacent its lower end, a main supply passage connecting said main nozzle to said annular chamber adjacent the top of said well, an idle nozzle in the side of said induction passage adjacent said throttle, an elongated idle passage connecting said idle nozzle to the top of said tube, means mounting said carburetor in position such that deceleration resulting from throttle valve closure while the vehicle is moving in a forward direction displaces fuel in said float chamber in a direction to draw fuel through said metering jet from the bottom of said well, and a bleed orifice in the side of said tube closely adjacent the juncture between said well and said main supply passage and forming a direct connection between said annular chamber and the interior of saididle tube.

2. A carburetor as defined in claim 1 in which said bleed orifice is just above the juncture between said ,well

F and said main supply passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,631,716 Bavcry June 7, 1927 1,821,012 Guthrie Sept. 1, 1931 1,881,256 Ball et al. Oct. 4, 1932 2,419,956 Kuzelka May 6, 1947 2,615,696 Winkler Oct. 28, 1952 2,628,826 Worden Feb. 17, 1953 2,656,166 Foster Oct. 20, 1953 2,676,004 Bimberg Apr. 20, 1954 2,689,115 Olson Sept. 14, 1954