US2877753A - Method of preventing cold stalling and means therefor - Google Patents

Description

March 17, 1959 o. E. LARSEN METHOD OF PREVENTING COLD STALLING AND MEANS THEREFOR Filed April 18, 1956 INLET FOR HEATING FLUID TO PASSAGE 42 OUTLET FOR HEATING FLUID FROM PASSAGE 42 IGNITION SWITCH ZNVENTOR. O. E. LAR S E N A TTORNEVS United States Patent METHOD OF PREVENTING COLD STALLING AND MEANS THEREFOR Olaf E. Larsen, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application April 18, 1956, Serial No. 579,031 10 Claims. (Cl. 123122) This invention relates to the operation of carburetorequipped internal combustion engines. In one of its aspects this invention relates to preventing cold stalling of an internal fuel combustion, carburetor-equipped engine by heating the initial air bleed section or passageway of the carburetor. In another of its aspects, this invention relates to an improved carburetor device comprising a heater means located in or adjacent to the initial air bleed section or passageway of the carburetor.

It has been observed that an internal combustion engine, having a carburetor, will stall while being warmed up when certain combinations of atmospheric temperature and humidity exist. This phenomenon has been referred to as cold stalling and has been thought to be caused by the formation of ice on the throttle plate and adjacent parts of the carburetor, for example around the idling jet and throttle plate. The ice formation results from the cooling effect derived from the vaporization of fuels within the carburetor operative upon the moisture contained in the air admitted to the carburetor.

, I have now discovered that cold stalling resulting from carburetor icing is mainly caused by ice which forms in the initial air bleed section of the idle fuel system of the carburetor and not primarily by the ice which forms on the throttle plate and around the idle ports, as heretofore believed. The present day carburetor usually consists of a float chamber, a nozzle with metering orifice, a venturi, a throttle valve, a choke valve, and a low speed or idle fuel system. The idle fuel system of a carburetor controls and delivers a rich fuel/ air mixture to the induction system of the engine where it is mixed to the correct mixture ratio with air coming past the throttle plate. The idle fuel system also functions during light load operation so as to give a nearly constant fuel/ air mixture during the transition period between idling and full operation of the high speed system. Maximum flow of fuel and air through the idle system ordinarily occurs between -35 miles per hour. The idle fuel system usually comprises an idle well, a low speed jet, an air bleed opening or openings, an idle air mixture needle valve, and port openings located near the throttle plate. The air bleed or bleeds, which are located above the idle well, serve two functions. First the air bleed serves as a syphon break to prevent the flow of unmetered fuel. Second, the air supplied by the air bleeds, break up the liquid fuel mass so that pre-mixed. air and fuel are supplied to the manifold. When two air bleeds are present, there is usually a restriction in the idle passage between the bleeds which further helps to break up the liquid fuel mass and to premix the fuel and air.

With reference to the construction of the carburetor and its operation, as just described, I have found that the flow of humid air into the idle fuel system of the carburetor will deliver to said system a quantity of moisture which, due to vaporization of fuel or gasoline which is occurring at or near said opening or openings, will cause ice to form on the surfaces of the idle passage, restrictions, and air bleed opening or openings. This ice builds up rapidly and actually throttles or chokes off the required flow of air-fuel mixture to maintain the engine at idling speed.

It is an object of'this-invention to provide an improved method of operating an internal combustion engine of the carburetor type. It isanother object of this invention to'p'rovide an improved carburetor for internal combus- ICC tion engines. A further object of this invention is to. provide an improved carburetor wherein cold stalling resulting from carburetor icing is eliminated or substantially minimized.

Other aspects, objects, as well as the several advantages of the invention, are apparent from a study of this disclosure, the drawings, and the appended claims.

Cold stalling ordinarily is encountered whenever the weather conditions, in which the engine is used, are such as to provide a relatively high humidity, for example above about 60 percent, and a temperature above about 30 F. but below about 60 F. As noted, it has been commonly believed that cold stalling is caused by ice formation on the throttle plate and around the idle ports. Although ice does form on the throttle plate and around the idle ports of the carburetor, this is not now thought to be the major or controlling factor in cold stalling of engines. Thus, cold stalling still occurs to an appreciable degree even when the throttle plate and idle ports are heated.

According to the present invention, cold stalling resulting from carburetor icing is eliminated or substantially minimized by heating the initial air bleed or idle fuel system of a carburetor at a place at which the air bled. into the idle fuel system first'comes into contact with idle fuel being admixed therewith.

Since the initial air bleed section is ordinarily positioned between an idle well and idle ports and is usually located in a top section of the carburetor, it has been found that by placing a heater, for example an electrical heater, in the vicinity of the idle air bleed section of the carburetor, cold stalling is substantially reduced and in some cases is entirely eliminated.

In the drawing there is shown a conventional type carburetor as modified by application thereto of an electrical heater and a control circmuit, which will now be described.

Referring to the drawing, numeral 10 refers generally to a carburetor having a mixture conduit 11 with an air inlet opening 12 and outlet 13 communicating with intake manifold 14. Air inlet 12 is controlled by a choke valve (not shown), which is rotatably journalled in the mixture conduit wall structure. Outlet 13 is controlled by a throttle valve 17 mounted on shaft 18, which is also rotatably journalled in the wall structure of mixture con duit 11. Venturi stack 19 is formed on the mixture conduit anterior to the throttle valve. A constant level fuel chamber 22 is provided for supplying fuel to main nozzle passage 23, 20 through metering orifice 25, controlled by metering pin 27.

Fuel from fuel chamber 22 enters the idle well after passing through the high speed circuit metering rod jet 25. The fuel passes up through passage 28 and a calibrated restriction 29. After passing through restriction 29 the gasoline mixes with a stream of air coming in through air bleed opening 30 (a small hole leading into the bore of the carburetor). This tends to break up or partially atomize the gasoline. In addition, the idle bleed opening 30 is required in the system to act as a syphon break to prevent the flow of unmetered fuel. The gaso? line and air mixture now passes through a small restriction 29a in the idle passage and then combines with a second stream of air coming in through another idle air bleed passage 31. This tends to further break up the gasoline particles. This mixture flows downward through idle passage 33 to the idle port 32 and mixes with air coming past the almost closed throttle valve 17; thence, air and fuel are discharged from the lower portion of the idle port 32 and to idle mixture valve 41 and then out idle port 40. The idle port is slotted so that as the throttle valve opens, it will not only allow more air to come past A the valve, but will also uncover more of the idle port,

allowing a greater quantity of gasoline and air mixture to flow from the idle system. As the edge of the throttle plate clears the idle port slot, the induced vacuum on the idle system diminishes, and when the pressure differential becomes zero, the idle system ceases to function. The low speed circuit supplies the gasoline for idling and light loads up to approximately 20 miles per hour; it partially controls supply for light loads up to 30 miles per hour, since it gradually fades out as the high speed circuit cuts in.

It has been thought previously that cold stalling is caused by the ice which forms on the throttle valve 17 and the idle ports 32 and 40. I have discovered, contrary to the prior thinking on the subject, that cold stalling is caused only partially by the ice which forms on the throttle valve and idle ports, and that the ice which forms in the initial idle air bleed section of the idling system, in other words at or near openings 30 and 31, is the main cause of cold stalling. During my experimental work described in the examples, I have observed ice formation in the idle air bleed openings of the carburetor under test. To eliminate ice formation in the initial idle air bleed section of the idle fuel system, I have provided an electrical heater 34 between air bleeds 30 and 31. The heater need not be very large, and in most cases, a to 40 watt heater will be suflicient;however, larger or smaller heaters may be used, if desired. The operation of heater 34 is controlled by an electrical circuit, for example, comprising an electrical energy source 35, engine ignition switch 36 and a bimetallic element 37. The bi-metal element 37 is preferably attached to the carburetor wall or body by silver solder, and contact 38 is suitably insulated from the carburetor body. When the ignition switch 36 is turned to the on" position, the heater begins to heat the wall area around air bleeds 30 and 31. After the car is started and begins to warm-up, the bi-metallic element 37 moves toward the carburetor wall, and breaks the circuit to the heater. In actual operation the electrical circuit is broken only after the carburetor has picked up enough heat from the engine that icing is no longer a problem. Thus, the formation of ice is prevented in the air bleed section of the idle system. Laboratory tests have shown that engine operation is practically normal and very few cold stalls occur when the initial air bleed section of the idle fuel system of the carburetor is locally heated above its icing temperature. If desired, the bimetallic element 37 can be placed into or in close proximity to the idle air passage. As shown, the switch is mounted on the carburetor and will interrupt the current when the temperature of the carburetor is such that the temperature in the passage is above a stalling temperature.

While the present invention has been primarily concerned with the use of an electrical heater located in the vicinity of the idle air bleed openings of a carburetor, it is obvious that other means can be provided to accomplish the same result. For example, passage 42 can be located along side of the idle system passages so that exhaust gases or heated air can be passed through these passages. Engine coolant can be passed through the passage if desired provided that a sufficient volume of the coolant is employed to maintain the adjacent carburetor parts above the icing temperature. The amount of heat exchange fluid passed through the passages can be controlled with an electrical circuit similar to the one described for the drawing. Or an electrical system can be provided to control a valve which, in turn, will control the amount of coolant or heat exchange material passed through the passages. Alternatively, the valve can be mechanically linked to the bimetallic strip so that no electrical system is necessary. Also, instead of using a thermal switch, such as a bimetallic type of unit, to control heating of the idle air bleed section, a thermocouple and One skilled in the art in possession of this disclosure will understand that the invention is applicable to all those cases in which cold stalling occurs regardless of the nature of the fuel or oxidant which may be employed. Thus, the point of the invention is in the discovery of the locus at which the lowering of temperature causes a temporary ice obstruction or restriction of flow of the air.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawings, and the appended claims to the invention, the essence of which is that an improved method and apparatus for the operation of an internal combustion engine of the carburetor type have been provided wherein, as described, the initial air bleed section of the carburetor is heated.

I claim:

1. In an automotive internal combustion engine which when said ignition switch is closed.

amplifier, for example, may be used. Neither is the present invention limited to the carburetor shown in the drawing. I a

2. A carburetor system as described in claim 1 wherein said heater is connected to a thermal responsive switch sensing the temperature of said carburetor and operative to cut off flow of current whenever the temperature in said passage is above a predetermined maximum stalling temperature.

3. An anti-stalling carburetor device for an internal combustion engine comprising an idle air bleed passage and a heater in heat exchange relation with the passage.

4. A device according to claim 3 wherein said heater is an electrical heater.

5. An anti-stalling carburetor device comprising in combination an idle air passage formed within the body of said carburetor, and a heating medium flow passageway in indirect heat exchange relationship with said idle air passage.

6. A method of operating an air-fuel carburetor subject to cold stalling which comprises heating the air in the initial air bleed section of the idle fuel system of said carburetor.

7. A method of preventing cold stalling of an internal combustion engine due to ice formation in an air-fuel carburetor zone which has an initial air bleed section located in an idle fuel supply zone which comprises heating the walls of said initial air bleed section.

8. A method according to claim 7 wherein the initial air bleed section is heated by passing hot heating medium into heat exchange relationship with said section.

9. In a carburetor adapted to produce an air-fuel mixture for an internal combustion engine, in combination, an idling system comprising a passageway for conducting fuel through a calibrated restriction into admixture with initial bleed air, a bleed air passageway communicating with the atmosphere surrounding said carburetor and a locus adjacent said calibrated restriction for admitting air into admixture with said fuel and an indirect heat exchange means for heating at least one wall of the locus at which the initial air bled into the carburetor and the fuel come into contact each with the other.

10. An apparatus according to claim 9 wherein the heating means is an electrical heater, said heater is operatively connected to a source of electrical current, said source of electrical current is controlled by a switch and there is positioned upon the line of flow of current a thermal responsive element adapted to open the circuit to the heater whenever the carburetor has reached a temperature above which stalling will not occur.

References Cited in the file of this patent UNITED STATES PATENTS 2,715,520 Boyce Aug. 16, 1955

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