EP0110877A1 - Liquid fuel carburetion system - Google Patents

Abstract

Fuel system for metering the fuel supplying an internal combustion engine. Liquid fuel (26) is metered into a metering system with a single connecting port. Fuel flows through a metering port (36) in response to a reduction in pressure that results from the sum of a reduction in venturi pressure and a reduction in auxiliary pressure. Fuel (26) is supplied through a bypass line (38) from the metering system to the air intake (12) downstream of the throttle (22) when the engine load is small. Fuel is supplied to the intake (12) through the other bypass duct (22) upstream of the throttle (22) when the engine load is great. The flow of fuel divides between the bypass conduits (38, 32) automatically in response to pressure differences in the metering system. The fuel which is supplied downstream of the restrictor (22) can be heated by the heater (40) or can flow through a nozzle (42) for better vaporization. An air purge valve can be used to precisely control the fuel mixture.

Description

LIQUID FUEL CARBURETION SYSTEM

BACKGROUND OF THE INVENTION

The principal functions of carburetion systems in general are to accurately meter fuel for efficient engine operation at the various engine loads, and to provide a well-mixed homogeneous mixture of the fuel and air. There should be maximum fuel vaporization, and any liquid fuel droplets should be as small as possible.

Previous carburetor designs typically employ three essentially separate fuel metering systems to meter fuel for the various engine operating conditions; There is an idle system which meters fuel and delivers it to the air inlet downstream from the throttle. A main system uses a venturi pressure reduction to meter fuel for large load conditions. Finally, a transfer system meters fuel for operation above idle when venturi airflow is too small for main system activation.

These previous carburetor designs have dif¬ ficulty metering fuel accurately at engine operating conditions where the carburetor is transitioning between the different systems. The result is in- accurate fuel metering, which results in engine fuel inefficiency.

The present invention^' is a carburetor having essentially a single metering system that is divided into two branches. A venturi pressure reduction acts to meter fuel for all engine operating conditions, including idle. An auxiliary pressure reduction adds to the venturi pressure reduction for metering the correct amount of fuel for idle and small engine loads. The provision of the single metering system allows the invention to avoid the metering problems of conventional carburetors.

There have been several previous attempts to design carburetors with single metering systems. One well-known design is the variable venturi carburetor, which uses a mechanica the venturi pressure reduction for accurate fuel metering. However, the variable venturi carburetor is mechanically complex, expensive to manufacture, and subject to malfunction. Other previous designs require specially shaped interaction zones, difficult locations of duct connections, and impractical requirements for minimizing the height difference between the fuel level and the metering conduits. The carburetor of the present invention has a useful characteristic in that it allows fuel for small and medium engine loads to be processed, with little adverse effect on accurate fuel metering. This processing can include heating, vaporizing, and treat- ment of the fuel with high velocity airstreams for optimum droplet size. These processing techniques have been attempted with previous carburetor designs, but without much practical success.

Another very useful characteristic of the present invention is that the fuel/air mixture ratio can be easily varied during operation by means of a simple controllable air bleed. This allows the in¬ vention to be responsive to the various electronic control systems that have been developed. Thus, the carburetor of the present invention is very effective, simple and inexpensive to construct, and avoids many of the problems to which previous carburetors were susceptible.

SUMMARY OF^* THE INVENTION^* The present invention provides a carburetor which has an essentially fixed venturi. Liquid fuel is metered in a branched single metering system. The metering function is achieved by a pressure reduction that is the sum of a venturi pressure reduction and an auxiliary pressure reduction. The auxiliary pressure reduction is specifically predetermined such that the correct amount of fuel is metered, especially at idle and small engine loads. The metering system is branched downstream from the throttle at small and medium engine loads, and the other branch delivers fuel to the air inlet upstream from the throttle at large engine loads. In some embodiments, fuel flowing to the engine downstream from the throttle can be processed.

In construction, the carburetor of the present invention has an air inlet with a venturi portion of essentially fixed configuration. A throttle valve is located downstream from the venturi. A main conduit has a connection to the venturi region of the air inlet. A fuel conduit is connected to the main conduit and to fuel in a fuel reservoir. An auxiliary conduit has a connection to the main conduit, and a connection to the air inlet downstream from the throttle. The connection of the auxiliary conduit to the main conduit is at a location such that air flows out of the main conduit through the auxiliary conduit to the air inlet, downstream from the throttle, at small and medium engine loads. The main conduit has a fluid flowing capacity that is specifically proportioned to the fluid flowing capacity of the auxiliary conduit such that the magnitude of the auxiliary pressure reduction is specifically determined. The fluid flowing capacity of the fuel conduit is specifically predetermined such that the correct amount of fuel flows to the engine in response to the action of the venturi and auxiliary pressure reductions.

In operation, air flows into the engine through the venturi region of the air inlet. The amount of air flowing is regulated by a throttle located in the air inlet downstream from the venturi region. When the throttle is partially open, the pressure in the air inlet downstream from the throttle is less than the pressure upstream from the throttle. Air flowing through the venturi region creates a proportional venturi pressure reduction according to the principle of the Italian scientist Venturi. This venturi pres¬ sure reduction is applied to the main conduit through the connection of the main conduit with the air inlet. The auxiliary conduit is connected to the main conduit and to the air inlet downstream from the throttle. Therefore, when there is a substantial pressure dif¬ ference across the throttle, air flows out of the main conduit, through the auxiliary conduit, to the air inlet downstream from the throttle. Because air is being removed from the main conduit in this manner, a pressure reduction is generated in the main conduit. This pressure reduction is named the auxiliary pressure reduction. This auxiliary pressure reduction sums, or cooperates, in the main conduit with the venturi pressure reduction. This cooperation causes a resultant pressure reduction in the main conduit which meters fuel from the fuel reservoir through the fuel conduit into the main conduit. Fuel metered from the fuel conduit into the main conduit at small and medium engine load conditions flows into the auxiliary conduit, and is subsequently delivered to the air inlet down¬ stream from the throttle. Fuel metered from the fuel conduit into the main conduit at large engine loads continues through the main conduit and is delivered to the air inlet upstream from the throttle. In response to the auxiliary pressure reduction, air flows- from the air inlet into the main conduit. This air flow resists fuel flow from the main conduit into the air inlet at small and medium engine loads, when such flow is not desirable. For most engine operating conditions, there is a strong pressure difference across the auxiliary conduit. This allows fuel flowing through the auxiliary conduit to be processed, without much adverse effect on the relatively small metering pressure reductions in the main conduit. The metering pressure reduction in the main conduit can be attenuated by admitting controlled amounts of air into the main conduit from a variable air source. This action moderates fuel flow from the fuel conduit into the main conduit. By this means, the fuel to air mixture ratio can be precisely controlled. This is especially by an electronic control means that is responsive to engine operating conditions.

Many advantages of the present invention will become more apparent from the following detailed description of the invention when considered in con¬ junction with the accompanying Figures, wherein like reference numerals refer to like parts throughout. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a representational cross section of a carburetor embodying the present invention;

Fig. 2 is a representational cross section of another carburetor embodying the present invention;

Fig. 3 is a representational cross section, which includes a heater; Fig. 4 is a representational cross section, which includes a heater with an air conduit;

Fig. 5 is a representational cross section, which includes a diffuser to vaporize the fuel;

Fig. 6 is a representational cross section, which includes an air bypass about the throttle and a diffuser; and

Fig. .7 is a representational cross section, which includes a control valve to modulate the fuel/air mixture. DETAILED DESCRIPTION OF

THE PREFERRED EMBODIMENTS Referring to Fig. 1, there is provided a carburetor body, indicated generally at 10. Air inlet conduit 12 is located in the carburetor body 10. Air necessary for operating the engine with the present invention flows to the engine through the inlet 12, in the direction from upstream end 8 to downstream end 16, as indicated by the arrows at 14. The up¬ stream end 8 opens to the atmosphere, preferably through a conventional air filter. The downstream end 16 is connected to the intake of the internal combustion engine. Venturi region 18 is located in inlet 12, and is preferably formed as a constriction for increasing the speed of the air flowing therethrouc A compound or booster venturi 20 is situated in the venturi 18 in the conventional manner. Throttle valve 22, shown schematically as a butterfly-type throttle, is located in inlet 12 downstream from venturi 18.

A fuel reservoir is indicated generally at 24. Liquid fuel 26 is maintained at a nearly constant level in reservoir 24, preferably by conventional float valve means (not illustrated) . Fuel is provided to reservoir 24 from an external source (not illustrated) through inlet 28. Reservoir vent 30 connects the volume above the liquid fuel in the reservoir 24 to essentially atmospheric pressure at a location pref¬ erably near the upstream end 8 of inlet 12. A main conduit 32 has a connection 100 with inlet 12 at es¬ sentially the most narrow part of venturi 20. A fuel conduit 34 is connected to the liquid fuel 26 in the reservoir 24. Fuel conduit 34 has a connection 102 with the main conduit 32. Calibrated metering orifice 36 controls the amount of fuel flowing through conduit 34 in response to metering pressure reductions.

An auxiliary conduit is indicated at 38. Auxiliary conduit 38 is connected to main conduit 32 at connection 104. Auxiliary conduit 38 is connected to air inlet 12 at a location 106 that is downstream from the throttle 22. An auxiliary conduit flow adjustment valve 44 is adjustable to control the flow through auxiliary conduit 38. Main conduit 32 has a predetermined fluid flowing capacity, and auxiliary conduit 38 has a predetermined fluid flowing capacity. The fluid flowing capacity of main conduit 32 is specifically related to the fluid flowing capacity of auxiliary conduit 38.

There are five pressure regions of specific interest that pertain to the operation of the carburetor. Indicated at A is the pressure region at the upstream end 8 of the inlet 12. The pressure at A remains essentially constant at or near atmospheric pressure for all carburetor operating conditions. Indicated at C is the pressure region in the venturi region 18 of the inlet 12. Indicated at B is the pressure region in the most narrow part of the booster venturi 20. The pressure at B is a pressure reduction that is proportional to the quantity of air flowing through inlet 12 according to the principle of Venturi. Indicated at E is the pressure region in the inlet 12 downstream from the throttle 22. Indicated at D is the pressure in the main conduit 32 in the region of the connection 102. The pressure at D will be herein referred to as the metering pressure re¬ duction.

The reservoir vent 30 maintains the pressure of the fuel 26 in the reservoir 24 at essentially the pressure of region A. The venturi pressure re¬ duction at B is applied to conduit 32 through con¬ nection 100. The pressure at region E varies depend¬ ing on the amount of opening of the throttle. When the' throttle valve 22 is closed or only partially open, E is at a strong pressure reduction (vacuum) .

As the throttle valve is opened, there is less pressure reduction at E. When the throttle is completely open, the pressure at E approaches the pressure at A. The pressure at D serves to meter fuel 26 from reservoir 24 through orifice 36 into fuel conduit 34.

In operation, first it will be assumed that the engine has not yet been started. Under these conditions, there is no air flow through inlet 12. Therefore, there is no venturi pressure reduction at B. The pres- sure at B is the same as the pressure at A (atmospheric) . The pressure at E is the same as at A. The pressure at D is the same as at A. There will be a fuel level M in the fuel conduit 34. Fuel level M is at essentially the same level as the fuel in the reservoir. When the engine has been started and is running at idle load, the throttle valve is closed or almost closed and there is a small flow of air through the venturi region . There will be a very small venturi pressure reduction at B, which is applied to main -8- conduit 32 through the connection 100. There will be a very strong pressure reduction in region E due to the engine intake acting against the almost closed throttle 22. The strong pressure reduction at E is applied to the auxiliary conduit 38 through the con¬ nection 106. Under these circumstances, the pressure at connection 106 is less than the pressure at connection 104, since the venturi pressure reduction is small. Therefore, there is a pressure difference across the auxiliary conduit 38. In response to this pressure difrerence, air flows out of main conduit 32, through connection 104 into auxiliary conduit 38, through auxiliary conduit 38, and into the air inlet 12 through connection 106. Some important pressure and flow relationships associated with the above-mentioned airflows can now be examined. Air flowing out of main conduit 32 into auxiliary conduit 38 through connection 104 causes a pressure reduction to be generated in main conduit 32. This pressure reduction will herein be referred to as the auxiliary pressure reduction. In response to the auxiliary pressure reduction, air flows out of the inlet 12 into main conduit 32 through connection 100. This airflow is shown by the arrow 46. The pressure in conduit 32 is less than atmospheric pressure, because the venturi pressure reduction at B is applied to conduit 32 through the connection 100. Therefore, the auxiliary pressure reduction causes a total pressure reduction in conduit 32 that is even stronger than the venturi pressure reduction. In this manner, the venturi pressure reduction and the auxiliary pressure reduction cooperate, or sum, in the auxiliary conduit 38 to generate a metering pressure reduction. This metering pressure reduction is shown at the region D in conduit 32. Thus, the auxiliary pressure reduction and the venturi pressure reduction are both components of the metering pressure reduction. The auxiliary pressure reduction component is especially significant at small The metering pressure reduction at D acts on the connection 102 where the main conduit 32 is connected to fuel conduit 34. Since the fuel reservoir is at atmospheric pressure because of conduit 30, the metering pressure reduction causes a pressure difference across fuel conduit 34. In response to this pressure difference, fuel 26 is forced from reservoir 24 through orifice 36 into fuel conduit 34. The predetermined fluid flowing capacity of main conduit 32 is specifically related to the pre¬ determined fluid flowing capacity of auxiliary conduit 38 such that the magnitude of the auxiliary pressure reduction is specifically determined. This very important aspect of the invention allows the auxiliary pressure reduction to be determined such that any desired magnitude can be achieved. For example, in¬ creasing the flow capacity of conduit 32 would decrease the magnitude of the auxiliary pressure reduction. Likewise, increasing the capacity of the auxiliary conduit 38 would increase the magnitude of the auxiliary pressure reduction. Accordingly, the valve 44 can be adjusted to determine the fluid flowing capacity of auxiliary conduit 38. This allows adjustment of the magnitude of the auxiliary pressure reduction. • ^• When the auxiliary pressure reduction is adjusted to the proper value, the fuel level in conduit 34 will rise to the level shown at N, and sufficient fuel for engine idling will flow into main conduit 32. Fuel flowing into conduit 32 will flow to the connection 104, and then be drawn into auxiliary conduit 38 by the strong flow of air that is flowing into conduit 38. Fuel will not be able to flow in conduit 32 substantially beyond connection 104 because of the strong counter-flow of air as indicated by the arrow 46. Fuel flowing from conduit 32 into conduit 38 will be carried by conduit 38 to the inlet 12, down¬ stream from the throttle 22, via the connection 106.

When more engine power is desired, the throttle valve 22 is moved to a more open position. More air then flows through the inlet 12 to the engine. The airflow through the venturi is greater, so the venturi pressure reduction becomes proportionally stronger. This increases the magnitude of the metering pressure reduction, so a proportionally greater amount of fuel flows through fuel conduit 34 to conduit 32. This increase in fuel flow is carried through conduit 38 to the air inlet 12, downstream from the throttle 22, via connection 106. In this manner, the engine re- ceives a correct increase in fuel flow to correspond with the increase in air flow which occurred when the throttle was opened. The invention thus maintains a correct fuel to air mixture ratio.

As the throttle 22 is opened much more, for large engine load conditions, the pressure reduction at E becomes weaker. There is a large amount of fuel flowing through main conduit 32 and into auxiliary conduit 38. The large quantity of fuel flowing into conduit 38 approaches the flow capacity of conduit 38, so much less air flows out of main conduit 32. This significantly reduces the magnitude of the auxiliary pressure reduction. Additionally, the flow through conduit 38 is reduced because the pressure reduction at E is less. Since less air flows into conduit 38, the air flow shown at arrow 46 becomes much less. Thus, at large engine loads, the auxiliary pressure reduction becomes weaker and becomes a smaller component of the metering pressure reduction.

As the throttle 22 is opened even more, the vacuum at E becomes greatly reduced. The pressure across conduit 38 is much less, and the fluid flowing capacity of conduit 38 is insufficient to transport all of the fuel flowing out of conduit 34 into conduit 32. For these conditions, the air flow shown by arrow 46 is very small or zero. Therefore, fuel in excess of the capacity of conduit 38 flows through main conduit 32, through connection 100, and into inlet 12. At this point, the magnitude of the auxiliary pressure reduction is virtually zero. For maximum engine load, the throttle is opened fully. The pressure at E may actually be greater than the pressure at B, so there will be virtually no fluid flow through auxiliary conduit 38. Essentially all fuel metered through conduit 34 will flow through conduit 32 and into inlet 12 through connection 100.

The auxiliary pressure reduction is of special importance. By specifically relating the fluid flowing capacities of the main conduit 32 and the auxiliary conduit 38, the magnitude of the auxiliary pressure reduction can be set over a very wide range of values. As can be seen from Fig. _1, the fuel level rests at M in conduit 34 when the engine is not operating. When the engine is started, the fuel must be raised to the level at N. A significantly strong metering pressure reduction is necessary to achieve this. A venturi pressure reduction acting alone could not raise the fuel level substantially above the level M at idle or small load conditions. In the present invention, the auxiliary pressure reduction augments the venturi pressure reduction. Therefore, the auxiliary pressure reduction can be adjusted so that the metering pressure reduction is strong enough to raise the fuel to a level N that can be as high as desired above the level M. Another interesting characteristic is the bi¬ directional fluid flowing capability of the main conduit 32. At small and medium engine loads, conduit 32 flows air out of the inlet 12. At large engine loads, conduit 32 flows fuel into the inlet 12. This assists in controlling the flow of fuel through conduit 32.

The auxiliary pressure reduction has significant magnitude at small and medium engine loads, but diminishes as the engine load becomes larger. This permits the fuel/air mixture ratio to be higher for idle and small engine loads, but lower for cruising power levels. This results in smooth operation at small and medium loads, and economy at cruising levels. One of the most significant advantages of the present invention is that the venturi pressure reduction and the auxiliary pressure reduction cooperate to generate a metering pressure reduction that can function to meter fuel for all engine operating conditions including idle load. Thus, fuel metering for all engine load conditions, including idle, can be achieved in a basic single metering system. ■ Metering in a single metering system avoids the difficulties associated with conventional carburetors employing separate idle, intermediate, and high speed metering systems.

Fig. 2 illustrates a slightly different embodi¬ ment of the invention. In Fig. 2, the fuel conduit 34 is located centrally in the fuel reservoir 24. The main conduit 32 is connected to fuel conduit 34 at connection 102 which is located over the fuel reservoir. Auxiliary conduit 38 is connected to main conduit 32 at connection 104 which is centered over the fuel level in reservoir 24. With connection 104 centered over the fuel, changes in the angle of the fuel level of the fuel 26 do not adversely affect the height of the level N of fuel in conduit 34. Also in Fig. 2, the booster venturi 20 is not used- A satisfactory venturi pressure reduction is generated at region B of inlet 12. The functioning of this embodiment is otherwise identical to the functioning of the embodiment of Fig. 1.

Fig. 3 illustrates another embodiment of the invention. In the configuration of Fig. 3, the auxiliary conduit 38 delivers liquid fuel to a heater, shown schematically at 40. This heater 40 heats and partially or completely vaporizes the fuel. Vapor , conduit 42 carries the fuel and fuel vapor to annular channel 45. A plurality of ports 43 are located around channel 45. The ports 43 transport fuel and fuel vapor to the inlet 12 and distribute the fuel evenly into inlet 12. The operation of the embodiment of Fig. 3 is otherwise identical to the operation of the embodi¬ ment of Fig. 1. The valve 44 is used to adjust the flow through auxiliary conduit 38 so that the of_. the auxiliary pressure reduction can be determined. The flow capacity of conduit 42 must be considered when determining the necessary flow capacity for the auxiliary conduit 38. The flow capacity of vapor conduit 42 should be great enough so that there is no interference with the ^"capability of conduit 38 to generate a useful auxiliary pressure reduction. The source of heat for the heater 40 can include engine exhaust gasses, heat from engine cooling liquids, electrical heat, and other sources. The invention as in Fig. 3 is especially useful when the various alcohols are used for fuel. The heater 40 can cause essentially complete vaporization of the fuel. The result is excellent fuel/air mixing and excellent combustion efficiency.

Fig. 4 is a variation of the invention illustra¬ ted in Fig. 3. In Fig. 4, the connection 104 is located centrally over the fuel 26 in the reservoir 24. A heater, shown schematically at 40, heats and vaporizes fuel flowing through auxiliary conduit 38. The vapor conduit 42 of Fig. 3 has been replaced in Fig. 4 by an extension of the auxiliary conduit 38. Air conduit 64 is connected to inlet 12 upstream from throttle 22 at connection 108. Conduit 64 transports air frominlet 12 through connection 108 into heater

40. Air entering the heater 40 from conduit 64 lowers the partial pressure of the fuel vapor, and assists in evaporation of the fuel. Air, fuel, and fuel vapor flow from heater 40 to inlet 12 through connection 106. The air flow capacity of air conduit 64 can be adjusted so that approximately the correct amount of air for engine idling flows through air conduit 64. This allows the throttle 22 to be completely closed for engine idle load conditions. Fig. 5 illustrates another embodiment of the invention that is especially useful for supplying to an engine liquid fuel that is finely divided into very small droplets. Conduit 38 has a connection

110 to a nozzle means generally indicated at 68. The nozzle means consists of vapor conduit 42 and air conduit 64A. Vapor conduit 42 is constructed with a divergent cross section to function as a diffuser, for recovering the kinetic energy of flowing fluids as static pressure. Air from a source at or near atmospheric pressure is supplied to conduit 64A. Conduit 42 is normally at a very low pressure from region E. Therefore, air flows from conduit 64A, past connection 110, and through conduit 42 to inlet 12. The air flow in the region of connection 110 will be at extremely high speed, possibly at or near sonic speed. This causes a strong pressure reduction at connection 110, which causes fluid flow through auxiliary conduit 38. Thus, there will be an auxiliary pressure reduction generated in conduit 32, which functions as previously described for the invention of Fig. 1. The nozzle 68 can be designed with a diffuser con¬ figuration for conduit .42 such that the pressure re¬ duction at the connection 110 remains very strong and essentially constant for wide variations of the pressure reduction at region E. The result of this is a very stable auxiliary pressure reduction for a variety of engine operating conditions. Fuel is discharged from conduit.38 into conduit 42 at the connection 110. The very high speed of the air flow¬ ing through connection 110 from conduit 64A causes the fuel to be very finely divided into small droplets. This results in very good combustion efficiency in the engine. The air supplied to conduit 64A can originate from inlet 12 upstream from throttle 22, in a similar manner as for conduit 64 in the embodiment of Fig. 4.

Fig. 6 illustrates yet another embodiment of the invention. In Fig. 6, a conduit 64 transports air out of the inlet 12 upstream from the throttle 22. Auxiliary conduit 38 has a connection 112 with conduit 64. Conduit 64 has a convergent-divergent configura¬ tion to function as a diffuser. Connection 112 is in the region of the most narrow part of conduit 64. Air flows out of the inlet 12 throu h conduit 64 -15- then through conduit 42, and then flows back into inlet 12 downstream from the throttle 22. The conduit 42 is subject to strong pressure reduction from region E. Therefore, there is a strong flow of air through the conduit 64, then through conduit 42 and into the inlet 12. Air from conduit 64 flows at very high speed past the connection 112. There is a very strong pressure reduction at the connection 112, causing a strong flow in auxiliary conduit 38. This generates an auxiliary pressure reduction in conduit 32 that functions identically to the auxiliary pressure re¬ duction that was described in detail with respect to Fig. 1. The high speed air flow from conduit 64 through connection 112 can remain stable for wide variations in the pressure reduction at region E.

This results in a stable auxiliary pressure reduction for many engine load conditions. Fuel from conduit 38 is discharged into conduit 64 at connection 112. This fuel flows through conduit 42 and into inlet 12 downstream from the throttle 22. A heater, shown schematically at 40, transfers heat to the fuel and air flowing in conduit 42. This heat assists in vaporizing the fuel in conduit 42.

Fig. 7 illustrates another embodiment of the invention, in which the fuel to air ratio is adjustable during engine operation. This embodiment can utilize advanced control techniques, which are responsive to engine operating conditions, to maintain optimum fuel to air ratios for all engine operating conditions, including idle. It is to be understood from the prior discussion herein that fuel is metered in the present invention by the action of a metering pressure reduction. The metering pressure reduction is generated in the main conduit by the cooperation (or summing) of a venturi pressure reduction and an auxiliary pressure reduction. As will be seen, Fig. 7 further shows that if air is admitted to the main conduit from another source of higher pressure, the air so admitted will attenuate the metering pressure reduction in approximate proportion to the quantity of air so admitted. In Fig. 7, therefore, there is provided a modulating conduit 90. Modulating conduit 90 is connected to main conduit 32 at connection 120. Modulating conduit 90 is also connected to the air inlet 12 at connection 122 in the vicinity of pressure region A. A valve 92 is adjustable to control the quantity of air flow¬ ing in conduit 90. A control means 94 is adapted to control the valve 92. The valve 92 is preferably set to a nominal position to allow conduit 90 to flow approximately one-half of its air flowing capacity. This establishes a nominal value for the metering pressure reduction for the various engine operating conditions. If a higher fuel/air ratio is desired (more fuel) , the control means 94 adjusts the valve 92 to reduce the air flowing from conduit 90 into main conduit 32. Therefore, there is less attenuation of the metering pressure reduction due to air from conduit 90. If a lower fuel/air ratio is desired (less fuel) , the control means 94 adjusts the valve 92 to increase the air flowing from conduit 90 into conduit 32. Therefore, there is more attenuation of the metering pressure reduction due to air from conduit 90. A plurality of modulating conduits such as conduit 90 could be connected to the main conduit 32. Possibly, each such conduit could be responsive to some operating condition to flow air to independently modulate the metering pressure reduction. In this manner, the independent actions of all of the modulating conduits would result in a metering pressure reduction that would meter the exact amount of fuel required for each unique condition of engine operation. It should be realized that the high pressure source of air for the modulating conduit 90 is not restricted to the specific location of pressure region A. The conduit 90 could receive air from virtually any source of pressure that is higher than the pressure of the metering pressure reduction. For example, the conduit 90 could have a source of air from the venturi 18, near the region of pressure B. This could be used to advantage for exerting a different modulating influence on conduit 32. Also, there could be a plural air source, such as a simultaneous connection with the pressure regions A and B. This would provide a source pressure . for conduit 90 that is mid-way between the pressures of A and B. The source of air for conduit 90 could also be a source of air from outside the carburetor. One particular advantage to admitting air to main conduit 32, from a source such as modulating conduit 90, is that the air tends to form a fuel-air emulsion in conduit 32. This assists the flow of fuel through conduit 32, especially at large load engine operating conditions. This action is like the action of the device used in conventional carburetors that is commonly called an "air bleed".

Many common carburetor features and enhance¬ ments can be used advantageously in conjunction with the present invention. Such features include the accelerator pump, for providing extra fuel during opening motion of the throttle; the choke valve, located upstream from the venturi for increasing fuel flow for cold engine operation; and the power valve; sensitive to intake vacuum for increasing fuel flow at large engine loads.

The present invention is most advantageous since all. fuel for all engine operating conditions can be metered and delivered in a single metering system that is bifurcated into two branches. However, the invention can be usefully employed in conjunction with a separate conventional idle system for special applications. However, such applications require an adjustment of the auxiliary pressure reduction to compensate, for any fuel provided by any other additional metering system used in conjunction with the present invention.

In view of the above teachings, it is to be understood that many changes and modifications are possible within the scope of the present invention, and that the invention is not restricted to the specific embodiments described herein. The specific details described herein are intended to be illustrative and not limiting, the scope of the invention being as defined by the claims appended hereto.

Claims

CLAIMS 1. A carburetion system, for metering fuel for operating an internal combustion engine, comprising: a carburetor body; air inlet means having upstream and down¬ stream ends, for admitting air to said engine; venturi means of essentially fixed con¬ figuration disposed in said air inlet means, for causing a venturi pressure reduction that varies essentially in proportion to the amount of air flowing therethrough; throttle valve means disposed in said air inlet means downstream from said venturi means, for regulating the amount of air flowing through said ven¬ turi means; fuel reservoir means adapted to contain a level of liquid fuel therein; main conduit means of predetermined fluid flowing capacity, for flowing air out of said inlet means and flowing fuel into said inlet means; said main conduit means connected to said air inlet means at a location proximate said venturi means; fuel conduit means, for transporting fuel from said reservoir to said main conduit means; said fuel conduit means being connected to said main conduit means; said fuel conduit means being connected to said fuel reservoir such that fuel from said reservoir can flow into said fuel conduit means; auxiliary conduit means of predetermined fluid flowing capacity, for flowing fuel and air out .. of said main conduit means;

.said auxiliary conduit means being connected to said air inlet means at a location that is down¬ stream from said throttle valve means when said throttle valve means is at a position of essentially minimum opening; said auxiliary conduit means being connected to said main conduit means at a location such that air is flowed out of said main conduit means into said auxiliary conduit means when said throttle valve is at a position of essentially minimum opening; said air flowed out of said main conduit means into said auxiliary conduit means generating an auxiliary pressure reduction of predetermined magni¬ tude in said main conduit means; said predetermined fluid flowing capacity of said main conduit means being specifically related to said predetermined fluid flowing capacity of said aux¬ iliary conduit means to specifically determine said predetermined magnitude of said auxiliary pressure reduction; said auxiliary pressure reduction causing air to flow out of said air inlet means into said main conduit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction being ap¬ plied to said main conduit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction and said auxiliary pressure reduction cooperating in said main conduit means to generate a.metering pressure re¬ duction in said main conduit means; and said metering pressure reduction acting on said fuel conduit means to cause fuel to flow from said reservoir into said fuel conduit means.

2. A method for metering fuel in a car¬ buretor, said fuel being metered to an internal com¬ bustion engine, said carburetor having: air inlet means; venturi means of essentially fixed configur¬ ation disposed in said air inlet means; liquid fuel reservoir means adapted to con¬ tain liquid fuel; main conduit means of predetermined fluid flowing capacity; said main conduit means being connected to said air inlet means proximate said venturi means; fuel conduit means; said fuel conduit means being connected to said fuel reservoir means so that said liquid fuel from said reservoir means can flow into said fuel conduit means; said fuel conduit means being connected to said main conduit means; auxiliary conduit means of predetermined fluid flowing capacity; said auxiliary conduit means being connected to said main conduit means such that air can flow out of said main conduit means into said auxiliary conduit means; said method comprising: flowing air to said engine through said air inlet means; generating a venturi pressure reduction in said venturi means, said venturi pressure reduction varying essentially in proportion to the quantity of air flowing to said engine through said air inlet means; applying said venturi pressure reduction to said main conduit means; flowing air out of said main conduit means into said auxiliary conduit means; generating an auxiliary pressure reduction of predetermined magnitude in said main conduit means in response to said air flowing out of said main conduit means into said auxiliary conduit means; specifically determining said predetermined magnitude of said auxiliary pressure reduction by specif¬ ically relating said predetermined fluid flowing capacity of said main conduit means to said predetermined fluid flowing capacity of said auxiliary conduit means; generating a metering pressure reduction in said main conduit means by summing said venturi pressure reduction and said auxiliary pressure reduction in said main conduit means; and flowing fuel from said fuel reservoir into said fuel conduit means in response to said metering pressure reduction.

3. A carburetion system, for metering fuel for operating an internal combustion engine, comprising: a carburetor body; air inlet means having upstream and down¬ stream ends, for admitting air to said engine; venturi means of essentially fixed con¬ figuration disposed in said air inlet means, for causing a venturi pressure reduction that varies essentially in proportion to the amount of air flowing therethrough; throttle valve means disposed in said air inlet means downstream from said venturi means, for regulating the amount of air flowing through said ven¬ turi means; fuel reservoir means adapted to contain a level of liquid fuel therein; main conduit means of predetermined fluid flowing capacity, for flowing air out of said inlet means and flowing fuel into said inlet means; said main conduit means connected to said air inlet means at a location proximate said venturi means; fuel conduit means, for transporting fuel from said reservoir to said main conduit means; said fuel conduit means being connected to said main conduit means; said fuel conduit means being connected to said fuel reservoir such that fuel from said reservoir can flow into said fuel conduit means; auxiliary conduit means of predetermined fluid flowing capacity, for flowing fuel and air out of said main conduit means; said auxiliary conduit means being connected to said main conduit means at a location such that air is flowed out of said main conduit means into said aux¬ iliary conduit means when said throttle valve is at a position of essentially minimum opening; into said auxiliary conduit means generating an aux¬ iliary pressure reduction of predetermined magnitude in said main conduit means; fuel heating means for transporting liquid fuel and adapted to transfer heat to said fuel; said auxiliary conduit means being connec¬ ted to said fuel heating means such that fluids flow¬ ing through said auxiliary conduit means are flowed into said fuel heating means; vapor conduit means having sufficient fluid flowing capacity to flow at least all fluids flowing through said auxiliary conduit means; said vapor conduit means being connected to said fuel heating means such that fluids flowed into said fuel heating means from said auxiliary con¬ duit means are flowed out of said fuel heating means in¬ to said vapor conduit means; said vapor conduit means being connected to said air inlet means at a location that is downstream from said throttle valve means when said throttle valve means is at a position of essentially minimum opening; said predetermined fluid flowing capacity of said main conduit means being specifically related to said predetermined fluid flowing capacity of said auxiliary conduit means to specifically determine said predetermined magnitude of said auxiliary pressure re¬ duction; said auxiliary pressure reduction causing air to flow out of said air inlet means into said main con¬ duit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction being applied to said main conduit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction and said aux¬ iliary pressure reduction cooperating in said main con¬ duit means to generate a metering pressure reduction in said main conduit means; and said metering pressure reduction acting said fuel conduit means to cause fuel to flow from said reservoir into said fuel conduit means.

4. A carburetion system, for metering fuel for operating an internal combustion engine, compris¬ ing: a carburetor body; air inlet means having upstream and down¬ stream ends, for admitting air to said engine; venturi means of essentially fixed con¬ figuration disposed in said air inlet means, for causing a venturi pressure reduction that varies es¬ sentially in proportion to the amount of air flowing therethroug ; throttle valve means disposed in said air in¬ let means downstream from said venturi means, for regu¬ lating the amount of air flowing through said venturi means; fuel reservoir means adapted to contain a level of liquid fuel therein; main conduit means of predetermined fluid flowing capacity, for flowing air out of said inlet means and flowing fuel into said inlet means; said main conduit means connected to said air inlet means at a location proximate said venturi means; fuel conduit means, for transporting fuel from said reservoir to said main conduit means; said fuel conduit means being connected to said main conduit means; said fuel conduit means being connected to said fuel reservoir such that fuel from said reservoir can flow into said fuel conduit means; auxiliary conduit means of predetermined fluid flowing capacity, for flowing fuel and air out of said main conduit means; said auxiliary conduit means being connected to said main conduit means at a location such that air is flowed out of said main conduit means into said aux¬ position of essentially minimum opening; said air flowed out of said main conduit means into said auxiliary conduit means generating an auxiliary pressure reduction of predetermined magnitude in said main conduit means; said predetermined fluid flowing capacity of said main conduit means being specifically related to said predetermined fluid flowing capacity of said auxiliary conduit means to specifically determine said predetermined magnitude of said auxiliary pressure re¬ duction; said auxiliary pressure reduction causing air to flow out of said-air- inlet means into said main conduit means through the connection of said main conduit means with said air inlet means; air conduit means; said air conduit means being connected to said air inlet means at a location upstream from said throttle valve means; vapor conduit means; said vapor conduit means being connected to said air inlet means at a location that is downstream from said throttle valve means when said throttle valve means is at a position of essentially minimum opening; said vapor conduit means being connected to said air conduit means; said auxiliary conduit means being connected to said vapor conduit means at essentially the location of the connection of said air conduit means with said vapor conduit means; air being flowed out of said air, inlet means into and through said air conduit means; air flowing through said air conduit means flowing into and through said vapor conduit means; said venturi pressure reduction being applied to said main conduit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction and said auxiliary pressure reduction cooperating in said main conduit means to generate a metering pressure reduc¬ tion in said main conduit means; and said metering pressure reduction acting on said fuel conduit means to cause fuel to flow from said reservoir into said fuel conduit means.

5.- The carburetion system according to Claim 4 including: said air conduit means having a convergent configuration portion for accelerating the air flowing ' therein; said vapor conduit means having a divergent configuration portion acting as a diffuser to recover, as static pressure, the kinetic energy of fluids flow¬ ing therein; and said auxiliary conduit means being connected to said vapor conduit means at a location that is between said convergent portion of said air inlet . means and said divergent portion of said vapor conduit means.

6. A carburetion system according to Claim 3 including: air conduit means; said air conduit means being connected to .said air inlet means at a location upstream from said throttle valve means; said air conduit means being connected to said fuel heating means; and air being flowed out of said air inlet means, through said air conduit means, and into said fuel heating means.

7. A carburetion system, for metering fuel for operating an internal combustion engine, comprising: a carburetor body; air inlet means having upstream and down¬ stream ends, for admitting air to said engine; venturi means of essentially fixed config¬ uration disposed in said air inlet means, for causing a venturi pressure reduction that varies essentially in proportion to the amount of air flowing therethrough; throttle valve means disposed in said air inlet means downstream from said venturi means, for regulating the amount of air flowing through said venturi means; fuel reservoir means adapted to contain a level of liquid fuel therein; main conduit means of predetermined fluid flowing capacity, for flowing air out of said inlet means and flowing fuel into said inlet means; said main conduit means connected to said air inlet means at a location proximate said venturi means; fuel conduit means, for transporting fuel from said reservoir to said main conduit means; said fuel conduit means being connected to said main conduit means; said fuel conduit means being connected to said fuel reservoir such that fuel from said reservoir can flow into said fuel conduit means; auxiliary conduit means of predetermined fluid flowing capacity, for flowing fuel and air out of said main conduit means; said auxiliary conduit means being connec¬ ted to said air inlet means at a location that is down¬ stream from said throttle valve means when said throttle valve means is at a position of essentially minimum opening; said auxiliary conduit means being connected to said main conduit means at a location such that air is flowed out of said main conduit means into said auxiliary conduit means when said throttle valve is at a position of essentially minimum opening; said air flowed out of said main conduit means into said auxiliary conduit means generating an auxiliary pressure reduction of predetermined magni¬ tude in said main conduit means; said predetermined fluid flowing capacity of said main conduit means being specifically related to said predetermined fluid flowing capacity of said auxiliary conduit means to specifically determine said predetermined magnitude of said auxiliary pressure reduction; said auxiliary pressure reduction causing air to flow out of said air inlet means into said main conduit means through the connection of said main conduit means with said air inlet means; said venturi pressure reduction being ap¬ plied to said main conduit means through the con¬ nection of said main conduit means with said air inlet means; said venturi pressure reduction and said auxiliary pressure reduction cooperating in said main conduit means to generate a metering pressure reduc¬ tion in said main conduit means; modulating conduit means; said modulating condui means being con¬ nected to said main conduit means; said modulating conduit means being con¬ nected to a source of air pressure that is higher than the pressure of said metering pressure reduction. said modulating conduit means flowing air into said main conduit means for attenuating said metering pressure reduction; and - said metering pressure reduction acting on said fuel conduit means to cause fuel to flow from said reservoir into said fuel conduit means.

8. The method according to Claim 2 in¬ cluding the step of flowing air into said main conduit means through a modulating conduit means for the pur¬ pose of attenuating said metering pressure reduction.

9. The carburetion system according to Claim 4 including: adjustable valve means for ad¬ justing the flow of fluids through said auxiliary conduit means.