Carburetor, control apparatus and method for internal combustion engines

Abstract

A carburetor and associated control apparatus for an internal combustion engine. The carburetor includes a carburetor head having a fuel inlet conduit and an air inlet conduit communicating with a fuel mixing chamber. The carburetor further includes metering means for controlling the amount of fuel and air entering the mixing chamber. The mixing chamber connects to an expansion chamber through a control orifice in the carburetor head. The carburetor also includes a carburetor housing having a throat that communicates with the expansion chamber and with an air delivery passage. Air entering the throat is metered with an air valve that is moved with respect to the air delivery passage in correspondence with the fuel metering means.1. Technical FieldThis invention relates generally to fluid distribution apparatus having multiple valves and, more particularly, to carburetors and associated control apparatus for internal combustion engines.2. Background ArtCarburetors perform three functions for internal combustion engines when delivering a gaseous mixture of fuel and air to the cylinders. The first function is to control the speed of the engine by controlling the absolute pressure in the intake manifold of the engine. The second function is to introduce and meter the fuel into the air stream going to the cylinders. The third function is to mix the fuel with the air so that a uniform mixture is produced.One problem with conventional carburetors is that the fuel within the fuel reservoir or float bowl is subject to inertial and gravity forces. The inertial forces are generated by cornering, stopping, and accelerating. The gravity forces stem from hill climbing and from operating at different attitudes. Both sets of forces place operating limitations on engines because they vary the relationship of the fuel and float bowl with respect to the main jets.A further problem with conventional carburetors is the emission of unburned hydrocarbons from the carburetor. When fuel enters the float bowl and drops in pressure to atmospheric pressure, a portion of the fuel is immediately vaporized and can be released unburned to the atmosphere. In addition, heat from an engine that is not in operation can boil the fuel remaining in the float bowl and likewise cause the emission of unburned hydrocarbons.An additional problem with conventional carburetors is in providing a uniform mixture to the engine. One aspect of this problem stems from using a butterfly valve to control the pressure drop across the carburetor. At any angle less than wide open throttle, the butterfly valve deflects the flow through the carburetor. Also, when fuel impinges on the butterfly valve, the denser parts of the mixture tend to come off the lower side of the butterfly valve. Another aspect of the problem occurs at idle and low speeds when there is not sufficient air flow through the carburetor to operate the main venturi system. In this case fuel is introduced into the air stream in the carburetor via an idle port located below the butterfly valve and via a transfer slot located just above the idle port. The idle port and the transfer slot are located on just one side of the throat and hence cannot provide a uniform distribution of fuel across the throat of the carburetor.A typical four barrel carburetor contains more than one hundred parts and is consequently complicated to manufacture and to assemble. These carburetors also require critical adjustments both during installation and at subsequent times. This complexity means that conventional carburetors are expensive and may be subject to frequent repair.Recently there has been wide interest in converting carburetors over to alternative fuels such as ethanol and methanol. The stoichiometric air fuel ratio for these popular alcohol mixtures is much higher than for gasoline. In other words, as the percentage of alcohol is increased in the fuel, the engine tends to run leaner. In order to use a gasoline fuel containing more than ten percent (10%) alcohol, the fuel passages in a conventional carburetor must be substantially enlarged and the jets changed. Such a conversion almost mandates replacement of a conventionally constructed carburetor.Work in this area of technology includes U.S. Pat. No. 4,137,284 entitled "Carburetor", issued Jan. 30, 1979 to Barbee, and U.S. Pat. No. 3,943,205 entitled "Internal Combustion Engine", issued Mar. 9, 1976 to Oliver.The present invention is directed to overcoming one or more of the problems as set forth above.DISCLOSURE OF THE INVENTIONIn one aspect of the present invention a carburetor for an internal combustion engine is contemplated. This carburetor includes a carburetor head having a fuel inlet conduit and an air inlet conduit communicating with a fuel mixing chamber. The carburetor further includes metering means for controlling the amount of fuel and air entering the mixing chamber. The mixing chamber connects to an expansion chamber through a control orifice in the carburetor head. The carburetor also includes a carburetor housing having a throat that communicates with the expansion chamber and with an air delivery passage. Air entering the throat is metered with an air valve that is moved with respect to the air delivery passage in correspondence with the fuel metering means.In the present invention the problem of inertial and gravitational forces acting on the fuel in the fuel bowl is overcome by eliminating the fuel bowl and all other fuel reservoirs in the carburetor. Fuel metering is no longer affected by inertia and the carburetor can be operated at any attitude without disturbing the process of fuel metering. Elimination of the fuel bowl also alleviates the problem of emitting unburned hydrocarbons. In the present invention vapor is not allowed to escape to the atmosphere.The present invention provides a uniform fuel mixture to the engine by first premixing the fuel with air first in a mixing chamber, and secondly in a centrally located expansion chamber and then lowering the momentum of the mixture so that it can flow radially outward and mix with the primary air along a 360.degree. circular front. This technique results in an extremely uniform mixture reaching the intake manifold of the engine.One feature of the present invention is the precise fuel metering that can be obtained. A single fuel metering circuit is used to provide all of the fuel to the carburetor from idle through full throttle. No artificial enrichment devices are required, such as idle feed circuits, low speed circuits, and accelerator pumps. In addition, the transitions between such circuits are avoided.A further feature of the present invention is its mechanical simplicity and use of few moving parts. The apparatus disclosed herein is less expensive to manufacture and to maintain than presently available carburetors. The use of only one fuel metering circuit also permits this carburetor to be easily controlled electronically and to be easily converted over to the use of alternative fuels.The present invention is adapted to incorporate a solenoid operated fuel valve. Fuel flow to the carburetor is terminated either when the engine is decclerated or when the ignition key is turned off. This feature substantially reduces fuel consumption.Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure, and the appended claims.

Description

Claims

1. A carburetor for an internal combustion engine, comprising:

(a) a carburetor head having a fuel mixing chamber;

(b) a fuel inlet conduit in the head for communicating fuel to the fuel mixing chamber;

(c) means, in the fuel inlet conduit, for metering the fuel entering the fuel mixing chamber;

(d) an air inlet conduit in the head for communicating air to the fuel mixing chamber;

(e) means, in the air inlet conduit, for metering the air entering the fuel mixing chamber;

(f) an expansion chamber in the carburetor head communicating with the mixing chamber in series through a control orifice;

(g) a carburetor housing attached to the carburetor head and having a throat communicating directly with the expansion chamber, said housing being mountable on an internal combustion engine with the throat in communication with an intake passage thereof;

(h) an air delivery passage in the carburetor for communicating air to the throat at a location adjacent to an outlet of said expansion chamber;

(i) an air valve in the carburetor head for metering the air entering the throat from the air delivery passage; and

(j) means, connected to the carburetor, for moving the air valve with respect to the air delivery passage in correspondence with the fuel metering means.

2. A carburetor as in claim 1 wherein the fuel and air from the mixing chamber flow through the control orifice and into the expansion chamber in a stream, said expansion chamber pre-mixes the fuel and air in the stream together and reduces the velocity thereof before said fuel and air enter the throat.

3. A carburetor as in claim 1 wherein said carburetor has a central axis of symmetry and said expansion chamber is an elongate passage in the carburetor head coincident with said central axis and said control orifice is received in the passage proximate to the mixing chamber and coincident with the central axis.

4. A carburetor as in claim 1 wherein said air valve has the shape generally of a right circular cylinder with an annular cross section and with an annular top margin and wherein said expansion chamber has a length and width sufficiently large that the fuel passing therethrough is so reduced in velocity that when the fuel flows out of the expansion chamber the fuel flows radially outward and mixes with air from the air delivery passage proximate to the top margin of the air valve.

5. A carburetor as in claim 1 wherein the air valve has the shape of a right circular cylinder with an annular top margin and wherein the carburetor head has a stationary annular seat that is engaged by said margin of the air valve.

6. A carburetor as in claim 1 including an idle fuel enrichment conduit for fuel in the head communicating with the fuel mixing chamber in parallel with the fuel inlet conduit.

7. A carburetor as in claim 1 wherein said air valve moving means includes a cam with a profile such that the air valve and the fuel metering means move together in a sinesoidal relationship.

8. A carburetor as in claim 1 wherein said air metering means includes a flow restrictor that maintains a vacuum in the mixing chamber for the fuel metering means.

9. Apparatus for an internal combustion engine for regulating the pressure of fuel from the output of a fuel pump, comprising:

(a) an elongate, upright housing;

(b) a vertically elongate chamber within the housing having bottom, medial, and upper sections;

(c) a fuel input conduit connectable to the output of a fuel pump and communicating with the upper section of the chamber, said conduit having a restriction therein which accelerates the fuel and causes any vapor in the fuel to form in the upper and medial sections of the chamber;

(d) a fuel output conduit communicating with the lower section of the chamber so that liquid fuel is passed therethrough;

(e) a return conduit for vapor and fuel communicating with the medial section of the chamber;

(f) a spool valve centrally received in the housing and vertically movable with respect thereto, said valve controlling the flow of fuel and vapor from the chamber into the return conduit; and

(g) a spring loaded diaphragm actuating said spool valve and sensitive to the pressure of fuel in the chamber such that when the pressure of fuel exceeds a predetermined value, said fuel and vapor are directed into the return conduit by the spool valve, thereby regulating the pressure of fuel in the fuel output conduit.

10. An apparatus as in claim 9 further including a piston that biases the diaphragm on command to increase the pressure of the fuel in the fuel output conduit.

11. An apparatus as in claim 9 further including a second diaphragm sensitive to vacuum from an exterior source and operatively connected to the spring loaded diaphragm such that when the vacuum from the exterior source decreases, the spring loaded diaphragm is biased to reduce the pressure of fuel in the fuel output conduit.

12. Carburetion apparatus for an internal combustion engine, comprising:

(a) a carburetor having therein a fuel mixing chamber, fuel and air inlet conduits communicating with the fuel mixing chamber, means for metering the fuel and air entering the fuel mixing chamber, an expansion chamber communicating with the mixing chamber through a controlled orifice, a throat communicating with the expansion chamber and with the internal combustion engine, an air delivery passage communicating with the throat, an air valve for metering air entering the throat from the air delivery passage, and means for moving the air valve with respect to the air delivery passage in correspondence with the fuel metering means;

(b) a fuel pressure regulator connected to the fuel inlet conduit of the carburetor and having therein a vertically elongate chamber having bottom, medial and upper sections, a fuel input conduit connectable to the output of a fuel pump and communicating with the upper section of the chamber, said conduit having a restriction therein which accelerates said fuel and causes any vapor in the fuel to form in the upper and medial sections of the chamber, a return conduit communicating with the medial section of the chamber, a spool valve centrally received in the regulator and vertically movable with respect thereto for controlling the flow of fuel and vapor from the chamber to the return conduit, a spring loaded diaphragm actuating said spool valve and sensitive to the pressure of fuel in the chamber such that when the pressure exceeds a predetermined value, said fuel and vapor are directed into the return conduit by the spool valve, and a vacuum controlled piston that biases the diaphragm to increase the pressure of fuel in the fuel output conduit;

(c) a source of vacuum;

(d) means, connectable to an internal combustion engine, for sensing the operating temperature thereof; and

(e) means, connected to the temperature sensing means and to the fuel pressure regulator, for actuating said vacuum controlled piston and biasing the diaphragm to increase the pressure of fuel in the fuel output conduit of the fuel pressure regulator when the operating temperature of the internal combustion engine is less than a predetermined value.

13. Carburetion apparatus for an internal combustion engine, comprising:

(a) a carburetor having therein a fuel mixing chamber, fuel and air inlet conduits communicating with the fuel mixing chamber, means for metering the fuel and air entering the fuel mixing chamber, an expansion chamber communicating with the mixing chamber through a controlled orifice, a throat communicating with the expansion chamber and with the internal combustion engine, an air delivery passage communicating with the throat, an air valve for metering air entering the throat from the air delivery passage, and means for moving the air valve with respect to the air delivery passage in correspondence with the fuel metering means;

(b) an electrically actuated valve in the fuel inlet conduit to the carburetor for interrupting and restoring a flow of fuel thereto;

(c) valve control means, connected to said valve, for electrically actuating said valve; and

(d) an ignition switch means for said internal combustion engine having an on position and an off position and connected to the valve control means, said ignition switch means causing said valve control means to interrupt said flow of fuel to the carburetor through said valve when the ignition switch means is in the off position, and said valve control means causing said valve to interrupt said flow of fuel to said carburetor when the ignition switch means is in its on position and the engine is not running.

14. Carburetion apparatus for an internal combustion engine having an intake manifold, comprising:

(a) a carburetor having therein a fuel mixing chamber, fuel and air inlet conduits communicating with the fuel mixing chamber, means for metering the fuel and air entering the fuel mixing chamber, an expansion chamber communicating with the mixing chamber through a controlled orifice, a throat communicating with the expansion chamber and with the internal combustion engine, an air delivery passage communicating with the throat, an air valve for meteing air entering the throat from the air delivery passage, and means for moving the air valve with respect to the air delivery passage in correspondence with the fuel metering means;

(b) an electrically actuated valve in the fuel inlet conduit to the carburetor for interrupting and restoring a flow of fuel thereto;

(c) valve control means, connected to said valve, for electrically actuating said valve;

(d) means, connected to the intake manifold of an internal combustion engine and the valve control means, for sensing the vacuum in the intake manifold and for actuating the valve control means to interrupt the flow of fuel to the carburetor when the vacuum in the intake manifold exceeds a first predetermined value and including means for actuating the valve control means to restore a flow of fuel to the carburetor after first being interrupted and after the vacuum diminishes below a second predetermined value; and

(e) means, connected to the valve control means, for sensing the rate of change of the speed of the internal combustion engine and for varying the first predetermined value if the rate of change exceeds a third predetermined value.

15. An apparatus as in claim 14 including means, connected to the valve control means, for sensing the gate of change of the speed of the internal combustion engine and for varying the second predetermined value if the rate of change exceeds a fourth predetermined value.

16. An apparatus as in claim 14 including a throttle linkage connected to the carburetor and means, connected to the throttle linkage, for overriding said fuel interrupting means when said throttle linkage is actuated.

17. Method for providing a mixture of fuel and air to an internal combustion engine, comprising the steps of:

(a) metering fuel and air into a mixing chamber of a carburetor;

(b) maintaining a vacuum in said mixing chamber by passing said fuel and air through a control orifice in a stream flowing along a first axis;

(c) expanding said stream in an expansion chamber and thereby substantially decreasing the velocity of the stream along said axis;

(d) thereafter further expanding and directing said stream radially outward from said axis in a plane orthogonal to said axis;

(e) thereafter introducing primary air into the stream and thereby mixing said fuel and air together in a mixture; and

(f) thereafter directing said fuel and air mixture back into a stream flowing along said first axis into an internal combustion engine.

18. A method as in claim 17 wherein the step of introducing primary air into the stream includes introducing said air into the fuel along a 360.degree. circular front lying in said orthogonal plane.

19. A method as in claim 17 including the steps of:

(a) metering the primary air introduced into the stream and;

(b) sinesoidally coordinating the primary air metering with the fuel metering.

20. A method as in claim 17 including the steps of:

(a) regulating the pressure of the fuel prior to fuel metering and;

(b) removing any vapor in the fuel prior to fuel metering.

21. A method as in claim 17 including the steps of:

(a) providing fuel to the carburetor at a first predetermined pressure when the internal combustion engine operates at normal temperature and;

(b) providing fuel to the carburetor at a second higher pressure when the internal combustion engine operates at a temperature below a predetermined value.

22. Method of providing and regulating a mixture of fuel and air to a manifold of an internal combustion engine, comprising the steps of:

(a) providing a flow of fuel at a regulated pressure to a carburetor through an input fuel line;

(b) metering air and said fuel into a mixing chamber in the carburetor;

(c) maintaining a vacuum in said mixing chamber by passing said fuel and air through a control orifice in a stream flowing along a first axis;

(d) expanding said stream in an expansion chamber and thereby substantially decreasing the velocity of the stream along said axis;

(e) thereafter further expanding and directing said stream radially outward from said axis;

(f) thereafter introducing primary air into the stream along a 360.degree. circular front and thereby mixing said fuel and air together in a mixture;

(g) thereafter directing said fuel and air mixture back into a stream flowing along said first axis into a manifold of an internal combustion engine; and

(h) interrupting the flow of fuel to the carburetor when said internal combustion engine decelerates in engine speed at more than a predetermined rate.

23. A method as in claim 22 including the step of restoring the flow of fuel to the carburetor after first being interrupted and when the internal combustion engine is accelerated.

24. A method as in claim 22 including the step of restoring the flow of fuel to the carburetor after first being interrupted and before said engine dies.

25. A method as in claim 24 wherein the step of restoring the flow of fuel includes the steps of:

(a) measuring the rate of change of engine speed of the internal combustion engine and

(b) restoring the flow of fuel if the rate of change decreases below a predetermined value.

26. A method as in claim 22 including the step of terminating the flow of fuel to the carburetor by de-energizing a valve in the fuel input line.

27. A method as in claim 26 wherein said terminating step includes the step of de-energizing an electrically operated solenoid valve in the fuel input line by de-energizing an ignition circuit of the internal combustion engine.

28. A carburetor for communicating an air-fuel mixture to an intake passage of an internal combustion engine comprising

premixing chamber means for forming a first air-fuel mixture therein,

fuel supply means for metering liquid fuel to said premixing chamber means,

air supply means for metering air to said premixing chamber means,

primary air intake means for communicating ambient air internally of said carburetor,

throat means for receiving and mixing said first air-fuel mixture with ambient air from said primary air intake means to form a second air-fuel mixture for communication to the intake passage of said engine,

expansion chamber means for receiving and expanding said first air-fuel mixture therein and for communicating and further expanding it into said throat means, and

orifice means for metering said first air-fuel mixture from said premixing chamber means into said expansion chamber means.

29. In a carburetor for communicating an air-fuel mixture to an intake passage of an internal combustion engine, said carburetor comprising a mixing chamber adapted to form an air-fuel mixture therein, a primary air intake for communicating ambient air internally of said carburetor, and a throat intercommunicating between said mixing chamber and the intake passage of said engine, the improvement comprising

means, including an orifice and an expansion chamber in series between said mixing chamber and said throat, for sequentially (1) receiving and expanding the air-fuel mixture from said mixing chamber, and (2) further expanding said air-fuel mixture into said throat to further mix ambient air from said primary intake therewith.

30. The carburetor of claim 29 wherein said means further expands said air-fuel mixture radially outwardly into said ambient air from said primary intake.