US2395554A - Carburetor - Google Patents

Description

Feb. 26, 1946.

M. E. JONES CARBURETOR Filed June 50, 1943 25 i =54 ,I/ ga '5. 24 D P-i a, 1' 59,

38 FIG.2. v

INVENTOR MALDWYN E. JONES ATTORNEY Patented Feb. 26, 1946 CARBURETOR Maldwyn E. Jones, Ferguson, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware- Application June 30, 1943, Serial N 0. 492,954

.6 Claims.

This invention relates to carburetors for internal combustion engines and consists particularly in novel means for insuring the delivery of fuel and air in proper proportions under varying load conditions and positions of the throttle.

The use of an air bled main nozzle in a carburetor has the advantage that it facilitates the lifting of fuel under lowest suction conditions and also tends to lean out the mixture when the carburetor is operating at a high speed with substantially opened throttle. In other words, the fuel mixture proportion curve of such a carburetor, with the throttle in wide open position, is desirably rich at the inner or low suction end and tends to drop toward the outer or'high speed end.

However, the air bleed has certain disadvantages in connection with the fuel supply under part throttle conditions. One such disadvantage is that where the main metering jet is reduced by a metering valve, as is the usual case under part throttle conditions, the air and fuel tend to emerge from the main nozzle in spurts and this is reflected in the uneven running of the engine known as surging. Furthermore, the part throttle mixture curve should remain substantially constant throughout the economy range operation of the engine, but if the nozzle is air bled, the part throttle curve tends to become leaner as the speed increases at an even greater rate than the full throttle curve of an air bled nozzle. The excessive leaning effect at the outer end of the part throttle curve can be partially corrected by the use of a properly shaped metering valve, but a valve having a plurality of different steps or tapers is undesirable where the valve is controlled by a suction responsive device, particularly a diaphragm, because of the somewhat erratic movement of the diaphragm under varying suction conditions. Because of this erratic response of the diaphragm, it is desirable that the metering valve apply a constant restriction to the fuel supply throughout the part throttle range so that the erratic hunting of the diaphragm cannot adversely aifect the normal metering of the fuel by suction applied to the main nozzle under the influence of varying engine suctions. When the carburetor suction drops to or below approximately three inches of mercury, as when the throttle valve is substantially wide open, a smaller portion thereof should enter the metering orifice to provide for a richer, power mixture.

An object of the present invention is to provide a carburetor having the advantages of an air bled main nozzle throughout the full throttleor power range of operation, while eliminating the disadvantages of the air bleed in the part throttle or economy range.

A more detailed object .is to provide a main nozzle air bleed which is effective only during the full throttle or power range operation.

Another detailed object is to provide an idling system fed from the main nozzle passage in such away that all fuel cannot be swept out of the idling system because of the superior suction in the main nozzle passage.

These objects and other objects hereafter appearing are attained substantially by the structure illustrated in the accompanying drawing in which:

Fig. 1 is a top view of a carburetor having the invention applied thereto.

Fig. 2is a side view partly in section better illustrating the invention.

Fig. 3 shows mixture quality curves graphically illustrating the advantages of the invention.

The carburetor shown has a downdraft mixture conduit or barrel including an air inlet horn H) at the upper extremity, the passage of air through which is controlled by a butterfly choker valve H. At the lower or outlet end of the barrel there is provided a butterfly throttle valve l2 for controlling the discharge of mixture from the carburetor. Between the two valves there are provided the venturis l3 forming part of the mixing chamber. A fuel bowl i4 is formed adjacent the j barrel and contains a float I5 controlling needle valve It for maintaining the fuel at a substantially constant level. In the lower part of the fuel bowl there is provided a main metering orifice element I! through which gasoline is supplied to upwardly extending fuel passage l8 and main nozzle I 9 discharging into the smallest or primary venturi l3. Fuel is also supplied to a cross passage 20 which is intersected by a second vertical extends downwardly past cross passage 20 into well 25.

A casing member 30 is attached to the outer wall of the fuel chamber for securing a diaphragm 3| in position. The space to the right hand side of the diaphragm forms a suction chamber which An idle metering tube 25 is mounted in passage 2! and" is connected by a passage 32 to the mixture conduit posterior to throttle 24. The diaphragm is gripped between a pair of cup washers 33 and 34,

the latter forming a stop for abutting casing member 30 to limit the rightward movement of I the diaphragm. The diaphragm is constantly urged to the left against the efiect of suction by acoiled spring 35. An actuator stem 35 extends through and issecured to the diaphragm. This stem projects adjacent a pivoted lever 31 which is connected by a link 38 to throttle lever 39. Lever 39 has a perforation 40 for attachment of a link extending to the usual accelerator pedal located in the drivers compartment.

A metering pin 45 is connected to and extends leftwardly of plunger rod 36 and has an intermediate stepped portion 46 extending through and restricting the effective opening in metering orifice element ll. Pin 45 extends into lower cross fuel passage 25 and past idling jet tube 26 which is mounted off center of passage 20 to permit this.

Extending upwardly from the left'hand extremity of cross passage 20 is an upwardly extending air bleed passage 48 which communicates with the atmosphere above the fuel bowl through a restriction 49. Passage 2!) adjacent its intersection with air passage 58 is shouldered to form a valve seat normally receiving a disk valve 50 urged toward this seat by a coiled spring compressed between the disk valve and a threaded plug 52 secured in and sealing the end of passage 23. An actuating pintle' 53 projects right- Wardly from disk valve 56.

In operation, with the throttle valve in idling position, diaphragm 3| is held in its right hand position, as shown, against spring 35, by the engine suction. As the throttle valve is opened, lever 31 is rotated clockwise so as to push rod 35 and the diaphragm to the left and, in turn, move metering portion 46 of the metering pin through the metering orifice element. Until the throttle valve arrives at a substantially open position, be-

tween three-fourths and full open, a straight or cylindrical portion of the metering pin is positioned in the metering orifice so that the efiective size thereof is not varied. However, as thetively rich inner end portion, as at 10, and descending intermediate and outer end portions.

The curve C illustrates the operation of the carburetor in the part throttle range with a solid" fuel main nozzle, while the curve D shows the functioning of the same type of nozzle in the full throttle range. The curve C is satisfactorily fiat and regular in its intermediate portion, but the curve D is relatively weak or lean at its inner end portion and ascends outwardly to indicate increasing richness.

By the use of the invention, the carburetor delivers fuel of the proportions represented by the curve C during the part throttle range and by the curve B in the full throttle range. The positions of the curves on the flow sheets can, of

course, be adjusted by means of the various fixed The invention may be modified in these and other respects as will occur to those skilled in the art without departing from the spirit thereof and the exclusive use of all modifications as come within the scope of the appended claims is con- I templated.

throttle is farther opened, the smaller step of p so as to open air bleed passage 48. Thereafter,

air enters thefuel stream in main fuel passage 18 and nozzle !9, whereas in the part throttle range, the main nozzle discharges "solid fuel,

no air being admitted.

In case the load on the engine and, consequently, its speed, is varied for a fixed setting of the throttle valve, diaphragm 3| can respond independently of the throttle linkage to vary the position of the metering pin and, if the suction drops low enough, to open air bleed valve disk 50.

The mixture quality or proportion curve shown in Fig. 3 graphically illustrates the advantages of the invention. These curves represent proportions of air to fuel in the mixture supplied as the rate of air flow increases. The curve A is the part throttle curve of an air bled main nozzle carburetor and becomes excessively lean at the outer end. The curve B is obtained for full throttle operation with an air bled main nozzle. While the curve A is undesirably lean at the outer end, curve B is satisfactory, exhibiting a firm, rela- Iclaim:

1. In a carburetor, a mixture conduit having a venturi, a throttle in said conduit, a main fuel passage discharging into said venturi and having a metering orifice element, an economizer valve controlling said element, an air bleed duct open ing into said fuel passage, a normally closed valve controlling said duct, and means responsive to movement of said throttle to a substantially wide open position for opening aid duct valve. 7

2. In a carburetor. a mixture conduit havin a venturi, a throttle in said conduit, an idle pas-' age for feeding fuel to a port in the Wall of said conduit adjacent the edge of said throttle when closed, a main fuel passage discharging into said venturi and having a metering orifice element, an economizer valve controlling said element, air bleed means opening into said main fuel passage. a valve controlling said bleed means, and means responsive to relatively low suction in said conduit posterior to said throttle for opening said bleed means whereby said passage supplies solid fuel in the high suction range and a mixture of fuel and air in the low suction range.

3. In a carburetor, a mixture conduit having a venturi and a throttle therein, a main fuel passage discharging into said venturi and having a metering orifice element, air bleed means opening into said fuel passage below the normal level therein, an economizer valve controlling said orifice and having lean and rich positions, a valve for closing said bleed means, a suction operated device, and operative connections between said device and said valves constructed and arranged to move said economizer valve to its rich position and to open said bleed valve responsive to rela tively low suction in saidconduit posterior to said throttle.

4. In a carburetor, a mixture conduit having a throttle and a venturi therein, a main fuel passage discharging into said venturi and having a metering orifice element, an air bleed duct opening into said fuel passage, an economizer valve controlling said orifice and having lean and rich positions, a valve controlling said duct and positioned to be actuated by said economizer valve, and an operative connection between said throttle and said economizer valve constructed and arranged for moving said economizer valve to its rich position and opening said duct valve when said throttle is substantially fully opened.

5. In a carburetor, a mixture conduit, a throttle therein, a main fuel passage discharging into said conduit and having a metering orifice element, air

, bleed means opening into said passage, a normally closed first valve controlling said bleed means, a second valve controlling said metering orifice element, an economizer device, an operative connections between said device and said valves for opening said first valve and moving said second valve to its rich position when the carburetor is operating in the power range.

6. In a carburetor, a mixture conduit having a throttle therein, a main fuel passage discharging into said conduit and having a metering orifice element, air bleed means opening into said fuel passage below the normal level therein, a metering pin controlling said orifice and having lean and rich positions, a valve for closing said bleed means, and throttle operated means for actuating said metering valve to increase the richness of the mixture supplied by the carburetor, as said throttle is opened, said bleed valve being engageable by said pin when said throttle is moved to its substantially wide open position for opening said bleed valve to cause air to be entrained with the fuel discharged from said passage during full throttle operation.

MALDWYN E. JONES.

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