Carburetor, control apparatus and method for internal combustion engines

Abstract

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 Field This 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 Art Carburetors 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 INVENTION In 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° 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.

Inventors

• 👤 William Highfield

Bibliographic Details