Fuel metering apparatus for a carburetor

Abstract

An improved fuel metering apparatus for a carburetor which provides an optimum air/fuel ratio at all engine speeds and loads. The air/fuel ratio is adjusted by means of a valve sensitive to intake manifold pressure which modulates the amount of bleed air mixed with the fuel prior to the aerated fuel being introduced into the venturi throat of the carburetor.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to carburetors of the type used with internal combustion engines. More particularly, the invention is directed to an apparatus for matching the air/fuel ratio delivered by a carburetor to the requirements of an engine operating at various speeds and loads.

2. Description of the Prior Art

Precise air/fuel ratio control, especially on engines operating very lean at part load, is absolutely necessary for good driveability and optimum emissions. When a carburetor is used to mix and meter the air and fuel, it is designed to match as closely as possible the particular requirements of the engine. In addition to a primary fuel metering system which generally comprises an air induction pipe, a venturi throat, a fuel nozzle and a throttle plate, it is not uncommon to employ other systems to tailor the output of the carburetor to the requirements of the engine. For example, choke systems are often incorporated to improve cold starting and running characteristics of the engine, idle systems are used to facilitate low speed engine operation and accelerator pump systems are sometimes used to prevent stalling by injecting an additional quantity of fuel when the throttle plate is rapidly opened.

The primary fuel metering system cross sectional, leaning out of the mixture can be achieved for part load conditions by disposing the springs 76 so that the valve 170 will start moving to the left with small decreases in manifold vacuum as would result from light increases in load. In this manner the air/fuel ratio can be leaned out to a point such as 96 in FIG. 5, nearly corresponding to the largest total area opened by a combination of apertures 72 and 80. From this point, if it is desirable to start enriching the mixture to accommodate higher loads, further throttle opening resulting in manifold vacuum decreases causes further movement of the diaphragm 58 and the valve 170 to the left. In this way the so-called "fuel hook" or air/fuel ratio to engine load curve (FIG. 5) can be tailored exactly to the requirements of the engine.

As manifold pressures pressure varies with variation in load, the diaphragm 58 continually moves back and forth to provide the optimum fuel/air ratio called for by the engine.

It has been found that the apparatus of the present invention acts as an anti-stall device especially when used in conjunction with venturis of relatively small size. If the engine is running at a particular speed and the load increases, the engine speed drops and the manifold vacuum decreases. In a normal construction, especially if the engine is operating at very lean air/fuel ratios, the engine would stall because not enough fuel can be pulled into the intake manifold. In the construction of the present invention, the air manifold diaphragm moves to a closed position and this provides a richer mixture which avoids stalling.

When an internal combustion engine equipped with a conventional carburetor system is coupled with a turbocharger (as illustrated in phantom in FIG. 1 at 108) having its compressor discharge upstream of the carburetor, the conventional power jet and bleed air systems do not function properly. When the engine is required to deliver high power the power jet system kicks in and the compressor begins to create a positive manifold pressure. The fixed bleed air inlet orifice 54 is designed to properly control the air flow only at normal atmospheric pressures. The compressor 108 actually forces excessive quantities of air through the bleed air inlet 32 into the emulsifying well 26 excessively leaning the air/fuel mixture.

The fuel metering system of the present invention allows the proper positioning of the carburetor between the air compressor 108 and the inlet manifold while providing the desired air/fuel ratio without detrimental effects. It will be understood by those familiar with the art that the apparatus must be "matched" to these turbocharged operations, by proper positioning and sizing of the apertures in the regulating valve 70, and by proper selection of the spring 66 or, if preferred by providing a spring 77 as shown in FIG. 4. An additional spring 76 may be required according to the application, for proper air/fuel ratio modulation during the periods when the engine operates with a positive pressure in the intake manifold. If so desired, the apparatus can also be used as a "power limiter" if the valve 70 is prevented from restricting the flow of all bleed air through the apertures 72, thus allowing a controlled and limited amount of bleed air into the emulsifying well 26. In this fashion, the maximum amount of fuel drawn by the engine can be controlled and the engine power can be effectively checked.

Although an air valve means has been described which utilizes a diaphragm responsive to manifold pressure it should be apparent that other means sensing engine load and operating the air valve in response to changes in such load could be used as well. It should also be understood that the system of the present invention could with modifications be used to regulate air/fuel flow in a fuel injection system rather than the carburetor system shown.

It will also be understood by those familiar with the art, that the device of the present invention can also be used with a natural gas or LPG carburetor, either as an air modulator or fuel modulator, or both, to provide the correct air/fuel ratio, as desired.

It should also be understood that an air modulator of the present invention could be provided with appropriate means, such as an aneroid or temperature sensing means, to regulate the air/fuel ratio in response to changes in altitude or temperatures.

Although the system of the present invention has been described with the pipe 68 connected to the emulsifying well 26 and the pipe 74 connected to the air induction pipe 10 it should be understood that these connections can be reversed. With such reversed connections air from the induction pipe 10 would pass through the apertures 72, the chamber 62 and the pipe 74 to the emulsifying well 26.

The system of the present invention is provided with relatively large fuel and air apertures. This reduces the likelihood of clogging and reduces manufacturing costs by diminishing the need to adhere to close tolerances. The relatively rugged design with few operating parts also reduces such costs while at the same time reducing maintenance requirements.

From the foregoing detailed description it will be evident that there are a number of changes, adaptations, and modifications of the present invention which come within the province of those skilled in the art, however, it is intended that all such variations not departing from the spirit of the invention be considered as within the scope thereof as limited solely by the appended claims.

Claims

1. In combination: an internal combustion engine having an intake manifold, an air induction pipe, a venturi throat disposed within said air induction pipe, a fuel reservoir, a fuel nozzle means connecting said fuel reservoir and said fuel nozzle means including an emulsifying well disposed intermediate said fuel reservoir and said fuel nozzle means, said fuel nozzle means disposed in said venturi throat for introducing fuel into a stream of air flowing through said air induction pipe,

said emulsifying well including a passage means for directing air into the fuel whereby the fuel delivered to said venturi throat is mixed with air.

means in communication with the interior of said intake manifold for sensing the pressure therein; and

valve means connected intermediate said air induction pipe, upstream of said fuel nozzle means, and said emulsifying well, said valve means being connected to and responsive to said manifold pressure sensing means to regulate air flow through an outlet to said emulsifying well to decrease the amount of air introduced into said fuel upon a predetermined increase in the pressure in said intake manifold and to increase the amount of air introduced into said fuel upon a predetermined decrease in the pressure in said intake manifold whereby a predetermined optimum air/fuel mixture is provided for said internal combustion engine over a wide range of engine speeds and loads said valve means comprising a tubular member having apertures therein connecting the interior thereof in the area adjacent said manifold pressure sensing means to said outlet.

2. The improved fuel metering apparatus described in claim 1 wherein said manifold pressure sensing means is a vacuum diaphragm unit.

3. The fuel metering apparatus as defined in claim 1 and in which said valve means comprises a housing defining a first chamber and a second chamber separated by a diaphragm, means connecting said second chamber to the intake manifold of an internal combustion engine whereby said diaphragm is actuated in response to changes in the manifold pressure of said engine, an inlet connecting said first chamber with a source of air and said outlet connected with said emulsifying well and said valve member carried by said diaphragm and operable to variably regulate air flow through said outlet in response to movement of said diaphragm.

4. The fuel metering apparatus as defined in claim 3 and in which said valve member extends into said outlet.

5. The fuel metering apparatus as defined in claim 4 and in which said valve member further comprises a tubular member open at the end toward said outlet.

6. The fuel metering apparatus as defined in claim 4 and in which said valve member further comprises a tubular member closed at the end toward said outlet.

7. The fuel metering apparatus defined in claim 1 and including a turbocharger having its compressor discharge upstream of the fuel nozzle.

8. A fuel metering system for an internal combustion engine, said system comprising an air induction pipe, a fuel reservoir, a fuel nozzle means fluidly connected with said fuel reservoir, a fuel/air mixing means fluidly connected with said fuel nozzle, said fuel nozzle means disposed in said air induction pipe for introducing a fuel/air mixture fuel into a stream of air flowing through said air induction pipe,

means for sensing engine operation conditions,

variable valve means fluidly connected with said fuel/air mixing means, to vary the amount of air introduced into said fuel in said fuel/air mixing means, said valve means being operatively connected to and responsive to said means for sensing engine operating conditions, said valve means further comprising a housing having an interior chamber, an air inlet connected to said interior chamber and conduit means for connecting said interior chamber with said fuel/air mixing means, a portion of said conduit means adjacent said housing forming a tubular valve seat, a tubular valve member having a plurality of longitudinally spaced apertures formed therethrough, said valve member being longitudinally slidably engaged with said valve seat so that the number of apertures in the valve member open to both the interior of the valve seat and the interior chamber is dependent upon the longitudinal position of the valve member with respect to the valve seat, wherein said sensing means is connected to and controls the longitudinal position of said valve member.

9. A fuel metering system for an internal combustion engine, said system comprising an air induction pipe, a fuel reservoir, a fuel nozzle means fluidly connected with said fuel reservoir, fuel/air mixing means fluidly connected with said fuel nozzle means, said fuel nozzle means disposed in said induction pipe for introducing fuel into a stream of air flowing through said air induction pipe,

means for sensing ambient conditions, and

valve means for varying the amount of air introduced into said fuel upon a change in the ambient conditions as sensed by said ambient condition sensing means, said valve means further comprising a housing having an interior chamber, an air inlet connected to said interior chamber and conduit means for connecting said interior chamber with said fuel/air mixing means, a portion of said conduit means adjacent said housing forming a tubular valve seat, a tubular valve member having a plurality of longitudinally spaced apertures formed therethrough, said valve member being longitudinally slidably engaged with said valve seat so that the number of apertures in the valve member open to both the interior of the valve seat and the interior chamber is dependent upon the longitudinal position of the valve member with respect to the valve seat, wherein said sensing means is connected to and controls the longitudinal position of said valve member.

10. A fuel metering system for an internal combustion engine, said system comprising an air induction pipe, a venturi throat disposed within said air induction pipe, a fuel reservoir, a fuel/air mixing means fluidly connected with said fuel reservoir, fuel nozzle means fluidly connected with said fuel/air mixing means whereby a fuel/air mixture is delivered to said fuel nozzle means, said fuel nozzle means disposed in said venturi throat for introducing said fuel/air mixture into a stream of air flowing through said air induction pipe,

means for sensing engine operating conditions,

valve means connected intermediate said air induction pipe and said air mixing means, upstream of said fuel nozzle means, to vary the amount of air introduced into said fuel in accordance with a variation in the operating conditions of said engine, said valve means further comprising a housing having an interior chamber, an air inlet connected to said interior chamber and conduit means for connecting said interior chamber with said fuel/air mixing means, a portion of said conduit means adjacent said housing forming a tubular valve seat, a tubular valve member having a plurality of longitudinally spaced apertures formed therethrough, said valve member being longitudinally slidably engaged with said valve seat so that the number of apertures in the valve member open to both the interior of the valve seat and the interior chamber is dependent upon the longitudinal position of the valve member with respect to the valve seat, wherein said sensing means is connected to and controls the longitudinal position of said valve member.

11. A fuel metering system for an internal combustion engine, said engine having an intake manifold, said system comprising an air induction pipe, fuel/air mixing means and means fluidly connecting said fuel/air mixing means with said air induction pipe, means introducing air into said fuel/air mixing means and including valve means operable when actuated to vary the rate of air delivered to said fuel/air mixing means, and means sensing changes in engine operating conditions and actuating said valve means to regulate the rate of air delivered to said fuel/air mixing means in accordance with changes in the operating conditions of said engine, said valve means further comprising a housing having an interior chamber, an air inlet connected to said interior chamber and conduit means for connecting said interior chamber with said fuel/air mixing means, a portion of said conduit means adjacent said housing forming a tubular valve seat, a tubular valve member having a plurality of longitudinally spaced apertures formed therethrough, said valve member being longitudinally slidably engaged with said valve seat so that the number of apertures in the valve member open to both the interior of the valve seat and the interior chamber is dependent upon the longitudinal position of the valve member with respect to the valve seat, wherein said sensing means is connected to and controls the longitudinal position of said valve member.

12. The system as defined in claim 11 and in which said engine condition sensing means comprises means sensing the manifold pressure of said engine.

13. The invention as defined in claim 11 wherein said valve member is slidably received within the interior of the valve seat.