US2341694A - Carburetor - Google Patents

Description

Feb. 15, 1944. 1. E. COFFEY 2,341,694

GARBURETOR Filed Oct. 12, 1940 INVENTOR IRVEN E. COFFEY @Mufg- ATTORNEY Tip-- Patented Feb. 15, 1944 CABBURETOR Irven E. Coffey, Normandy, Mo., assignor to Carfor Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application October 12, 1940, Serial No. 360,979

11 Claims.

- This invention relates to carburetors for internal combustion engines and, more particularly, to compensating means for variations in flow of volatile liquid fuel due to temperature change.

Carburetors in general and particularly downdraft carburetors, due to their location with respect to the engine, become heated to such extent due to high speed driving on warm days that the usually available fuels, upon being received in the carburetor constant level chamber, immediately become charged with vapor bubbles. It will be readily appreciated in view of this that the amount of fuel, by weight, in this condition which will pass the relatively small fuel metering orifices, which control the flow to the carburetor mixture conduit, will be less than if the fuel were cool and not boiling. This, obviously, results in a leaning out of the mixture, and frequently, in practice, causes objectionable irregularity of engine operation known as surging.

It is the primary object of the present invention to provide an improved carburetor including automatic means for increasing the volume of fuel discharged into the mixture conduit when said fuel becomes charged with vapor due to heating.

It is a further object of the present invention to provide a carburetor of the above character in which restriction of the flow of fuel from the constant level chamber to the mixture conduit is automatically decreased as the fuel reaches a temperature whereby its flow, by weight, to said mixture conduit is decreased by reason of its boiling.

It is a further object of the present invention to provide a carburetor of the above character having air bled fuel jets and including tempera- 'ture-responsive means for reducing the air bleeding of the jet as the fuel reaches a temperature whereby its flowby weight through the jet is decreased by reason of its boiling.

Further objects and advantages will become apparent upon reference to the following description and accompanying drawing referring to which:

Fig. 1 is a diagrammatic view of a downdraft carburetor embodying a form of the present invention.

Fig. 2 is a fragmentary view of the carburetor shown in Fig. 1 showing a modification of the metering device.

Numeral 1 indicates a main carburetor body member having a mixture conduit 2 formed therethrough. The lower end of body .I is equipped with a flange 3 for attaching the carburetor to the intake manifold of an internal combustion engine. The mixture conduit is provided with a venturi formed restriction 4 and two concentric Venturi tubes 5 and 6 suspended therein. The outlet of the mixture conduit is controlled by a plate-type throttle valve I mounted for rotation with a throttle shaft 8. ,Adjacent the mixture conduit and formed as an integral part of body member I is a constant level fuel chamber 9 equipped with a float III which acts upon the intake needle valve H to maintain a substantial constant level of fuel as indicated by the dot-dash line A-A.

Attached to the upper end of body member I is a combination air inlet and fuel chamber cover casting [2 having an air inlet l3 to the mixture conduit formed therein. For control of the air inlet an unbalanced plate-type choke valve ll rigidly attached to'a rotatable choke shaft I5 is provided. Enclosed in a housing IE on the far side of casting I2 is a bi-metallic temperature responsive spiral ll which has its inner end attached to shaft l4 and its outer end abutting a stop l8. The element I1 is so constructed as to tend to unwind with decreasing temperature thereby urging the valve 14 in a counter-clock wise direction toward a closed position.

Discharging into the Venturi tube 6 is a main fuel nozzle l9 which receives fuel from chamber 9 through the metering orifice 20 and passage 43. Extending through the orifice 20 is a stepped and tapered metering rod 2| arranged to be moved vertically to vary the net opening of the orifice. Link mechanism is provided for positioning the metering rod in accordance with the position of the throttle valve comprising a lever 22, which is pivoted at 23, a link 24, and a lever 25 which is rigidly attached to the throttle valve shaft 8. In order to compensate for the reduction in flow through orifice 20 at high bowl temperatures and ,at which the fuel becomes charged with vapor bubbles, the metering rod 2| is constructed in two sections which are joined by the bi-metal temperature responsive loop 26. Element 26 is so constructed as to raise the lower end of rod 2| with increasing temperatures and thereby increase the net opening of orifice 20 for any given position of the throttle valve.

Fuel is supplied to the mixture conduit for low speed operation through an idling system comprising an idling fuel jet .21, a passage 28, an air bleed 29, a restricted passage 30, an air bleed 3|, a passage 32, 33 and discharge ports 34 and 35. In order to compensate for the reduction in flow, through the small idling jet 21, due to boiling of fuel, a thermo-control of the air bleed 3| is provided. This control comprises a ball valve 36 adapted to be seated on a valve seat 31 at the upper end of passage 32 thereby closing bleed 31. The ball 36 is supported on a bi-metal temperature responsive helix 38 which is so constructed as to extend with increasing temperatures thereby urging ball 36 toward the seat 31 and reducing the effectiveness of the air bleed therepast. It will be understood that the element 38 by reason of its structure provides a yielding support for ball 36 and its tension, while varying with the temperatures, likely to be encountered, will, under any fuel temperature, permit the unseating of ball 36 when acted upon by abnormally high engine manifold vacuums which are communicated to passage 32 through ports 34 and 36. By "abnormally high manifold vacuum" is meant vacuum in excess of that necessary to hold the engine at a normal idling speed, such high vacuums are encountered when a motor vehicle is travelling at a high rate of speed down an incline with the throttle substantially closed. The manner of forming and the operation of helical coil 38 is more fully explained in the patent to F. A. Parsons 2,121,259 for a thermostatic element similar to that employed in the present invention. Thermostatic, elements of this construction are commercially produced at present.

In the modification shown-in Fig. 2 a second fuel orifice 39 is provided feeding the passage." and is controlled by a metering rod 40. The rod 40 has a comparatively large diameter portion 40a which substantially restricts the orifice 39 when in the position shown. It will be seen that as the rod 40 is moved either upward or downward the restriction of orifice 39 will decrease. The rod 40 is attached at its upper end to a Sylphon type temperature responsive element 4| which in turn is rigidly attached to the carburetor at 42. The element M is so constructed as to expand with increasing temperatures to, move rod 40 downward and is so calibrated as to assume the position shown in Fig. 2 during normal operating temperatures. At abnormally low temperatures the element 4| will retract and move rod 46 upward thereby augmenting the flow through orifice 20. Also at abnormally high temperatures the rod 40 will be moved downward to a less restricting position thereby permitting an increased flow by volume when the fuel is charged with vapor. In this arrangement the metering rod 2| is formed in one piece, the temperature responsive element 26 being omitted.

In operation upon starting a cold engine, choke valve M will be in a partially or fully closed position by reason of heat responsive element l1 and as a result an abnormally rich mixture for starting and warming up of the engine will be delivered to the-mixture conduit by reason of this choking effect. As the engine attains a normal operating temperature, the element l1 will relax its tension by reason of heat absorption from the engine and permit the oif-set valve II to assume a wide open position after which it will have no enriching eilfect upon the mixture as supplied to the normal operating calibration. If, however, the engine is operated at high speed or under load and temperature conditions resulting in suflicient heating of the engine and the attached carburetor to cause the. fuel in bowl 9 to boil, the element 26 will respond to lift the lower portion of rod 20 to some degree and the element 38 will respond to move ball 36 toward its seat thereby compensating for the normal leaning out due to the boiling of the fuel as heretofore explained.

The foregoing description and accompanying drawing are intended to be illustrative and not limiting and the use of all modifications within the scope of the appended claims is contemplated.

I claim:

1. In a carburetor having a mixture conduit and a constant level fuel chamber, a fuel passageway for conveying fuel from said chamber to said conduit, a regulable metering orifice in said passageway calibrated to pass the correct amount, by weight, of liquid fuel to said mixture conduit for normal temperature operation, and a temperature therefor responsive element submerged in and responsive to the temperature of the fuel acting to maintain predetermined restriction of said orifice during normal operating temperatures and to increase the net opening in said orifice when the boiling temperature of the fuel is reached so as to compensate to some degree for the reduction in fuel flow therethrough by weight due to the presence of bubbles in the fuel.

2. In a carburetor having a mixture conduit, a throttle valve in said conduit, a constant level fuel chamber, a fuel passageway for conveying fuel from said chamber to said conduit, a fuel metering valve for regulating said fuel passageway, link mechanism connecting said metering valve and said throttle valve, and a temperature responsive element interposed in said link mechanism and responsive to boiling temperature of the fuel to increase the opening of said metering valve for a given throttle position to compensate for the formation of bubbles in the fuel.

3. In a carburetor, a fuel passageway, a metering orifice in said passageway, a metering rod extending through said orifice. said rod having an extended portion of its length of such diameter as to uniformly restrict said orifice and having portions of lesser diameter at either end thereof whereby when said rod is moved in either direction from its greatest restricting position the net opening of said orifice will be increased, and means responsive to the fuel temperature for moving said rod to less restricting positions when the fuel temperature is below normal and also when boiling temperature of the fuel is reached.

4. In a carburetor, a constant level fuel chamber, a mixture conduit, a liquid fuel passageway leading from said chamber to said conduit, 9. metering orifice in said passageway, a valve in said orifice, and a thermostatic element normally submerged in said fuel chamber and connected to said valve, said element being constructed and arranged to move said valve toward a less restricting position as the fuel temperature exceeds the point where bubbles form therein.

5. In a carburetor having a mixture conduit and a constant level fuel chamber, a fuel passageway for conveying fuel from said chamber to said conduit, valve means for said passageway, and a. temperature responsive device submerged in the fuel and connected to said valve, said de-,- vice being responsive to boiling temperature of the fuel to move said valve to a more open position so as to permit a greater flow by volume through said passageway when vapor bubbles are formed in the fuel.

6. In a carburetor, an induction conduit, a fuel bowl, a fuel passage connecting said bowl and said conduit, an air bleed duct connecting with said passage, a valve seat and a valve therefor in said duct, and a thermostatic spring responsive to boiling temperature of the fuel to urge said valve toward its seat with increasing force so as to reduce said bleed and thereby compensate for the reduction in weight of fuel drawn through said passages due to boiling.

7. In a carburetor, a fuel passageway, a valve controlling said passageway, and a thermostat responsive to the fuel temperature and acting on said valve to restrict said passageway at normal operating temperatures and to reduce said restriction at lower fuel temperatures to enrich the mixture and also at the boiling temperature of the fuel to compensate for the formation of bubbles in the fuel.

'8. In a carburetor, an induction conduit, 9. fuel passageway disposed to discharge into said conduit according to the suction therein, and a thermostatic valve device controlling said orifice and responsive to normal operating fuel temperatures to restrict said orifice and responsive to lower fuel temperatures and also to the boiling temperature of the fuel to increase the net opening in said orifice.

9. The method of maintaining stable proportioning of fuel and air in the combustible mixture supplied to an internal combustion engine which consists in metering the fuel supply in accordance with suction under normal fuel temperature conditions and utilizing a fuel temperature responsive device for increasing the volume of the fuel supplied, responsive to heating of the fuel above the boiling point thereof to compensate for the reduction in density of such fuel due to the formation of bubbles therein.

10. In a carburetor, an induction conduit, a fuel bowl, a fuel passage connecting said bowl and said conduit, an air bleed for said passage, a valve controlling said bleed, and a thermostat controlling said valve and responsive to the boiling temperature of the fuel to decrease the effectiveness of said bleed so as to compensate for the reduction in quantity of fuel supplied due to the formation'of bubbles therein.

11. In a carburetor, an induction conduit, a throttle valve therein, a fuel bowl, main and idling fuel passages discharging-into said conduit, respectively, anterior and posterior to said throttle valve when closed, an air'bleed opening into said idling passage, a valve controlling said bleed, and a thermostatic spring located in said idling passage andresponsive to the boiling temperature of the fuel therein to increase the closing pressure applied to said valve and thereby decrease the effectiveness of said bleed so as to compensate for the reduction in quantity of fuel supplied through said idling passage due to the formation of bubbles therein.

, IRVEN E. COFFEY.

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