FUEL SYSTEM FOR A TWO-CYCLE INTERNAL COMBUSTION ENGINE

Abstract: A fuel system for internal combustion, two-cycle or four-cycle engines in which hot combustion gases are introduced under pressure to the cylinder to be next fired along with raw fuel injection. The purpose is to preheat and atomize the fuel to obtain more efficient and more complete combustion. The respective cylinders are connected by cross-passages whereby hot gases from the combustion in one cylinder will be transferred along with heated vaporized fuel to an adjacent cylinder at proper timing with an electrically triggered fuel injection valve or device.

Description: The present invention relates to a fuel system for a two-cycle internal combustion engine having two or more cylinders with reciprocating pistons each comprising a circumferential wall and having a top stroke position and a bottom stroke position, a fuel inlet at the top of each cylinder, an exhaust outlet in each cylinder positioned to be uncovered by each piston as it reaches the lowest point of its stroke, air transfer ports in each cylinder also uncovered by each piston as it reaches the lowest point of its stroke, a wall port in each cylinder positioned between the top and bottom stroke positions of each piston, a transfer conduit connecting each said wall port of one cylinder with the fuel inlet of a second cylinder, and a fuel injector in each said conduit, whereby in the operation of the engine hot exhaust gases are transferred from one cylinder in which a piston is descending in a power stroke to a second cylinder in which a piston is ascending in a compression stroke, said transferring gases also preheating and atomizing fuel from said fuel injectors. A fuel system of this type has been disclosed in FR-A-901.122. In this prior art system a cam-controlled inlet valve is arranged at the outlet-end of each transfer conduit. Hot combustion gases at high pressure are utilized to deliver the fuel from the fuel injector which is arranged to inject the fuel into a small chamber at the outlet end of each transfer conduit. Due to the volatility of the fuel, it is partially vaporized by the hot gases and atomized due to the high velocities created by the relatively high pressure of the combustion gas source. It is an object of the present invention to provide an improved fuel system in which the combustion heat of the engine can be utilized not only to heat the volatile fuel being introduced but to utilize the force of pressures from the engine to assist in the injection and the mixing of the fuel. Another object is the stratification of fuel to increase the efficiency of combustion. To this end a fuel system of the above identified type is characterized in that each piston has an opening in its circumferential wall to register with a wall port in a respective cylinder to selectively relieve pressure in each said transfer conduit as each piston reaches its top position. So the present invention provides means for avoiding an undue pressure increase in the transfer conduit in its inoperative condition. The system of the present invention can utilize various types of a fuel control or injection devices, and it can be utilized with most multi-cylinder two-cycle engines. Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable a person skilled in the art to practice the invention, or in connection with the best mode presently contemplated for the invention. The drawings accompany the disclosure and the various views thereof may be briefly described as: Fig. 1, a diagrammatic view of a two-cylinder, two-cycle engine incorporating the present invention, Fig. 2, a view of a fuel injector. In FIG. 1, two cylinders 20, 22 of a two-cycle engine are shown. Each cylinder has an exhaust port 24 and 26 respectively. Cylinder 20 is shown with a piston 30 in a down position with the exhaust port 24 open. Cylinder 22 is shown with a piston 32 in the firing position with the exhaust port 26 closed. Spark plugs 34 and 36 are provided respectively for each cylinder. Each piston will have a connecting rod 38 suitably connected to a crankshaft in a conventional manner. A cylinder head 40 carries the spark plugs. At cylinder 20 a fuel inlet conduit 42 opens to the combustion chamber, while at cylinder 22 a fuel inlet conduit 43 opens to the combustion chamber. Conduit 42 is connected to a port 44 in the wall of cylinder 22. Conduit 43 is connected to a port 46 in the wall of the cylinder 20. A fuel injector 50 of standard construction discharges into conduit 42 leading to cylinder 20. A fuel injector 52 discharges into conduit 43 leading to cylinder 22. In FIG. 2, a fuel injector body 50, 52 is illustrated having a fuel inlet 54 leading from a fuel pump and a return fuel passage 56. The fuel injector discharges at properly timed intervals into the respective passages 42 and 43. Each cylinder has air transfer ports 60 and 62, respectively, which function as in a standard two-cycle engine for scavenging and air transfer from the crankcase to the combustion cylinder. Each piston has a wall opening 64 which registers with the ports 44, 46 when the piston is at top dead center to relieve pressure in lines 42 and 43. Each line 42 and 43 has a one-way check valve 72 and 73, respectively, to prevent combustion pressure entering from a cylinder to which it is connected. IN THE OPERATION in FIG. 1, as the piston 30 is descending during the power stroke, it has opened the port 46 to allow combustion pressure and hot gases to enter conduit 43 through check valve 73 into the combustion chamber of cylinder 22. At the same time, fuel has been injected by injector 52 and this combination of fuel and hot gases reaches the combustion chamber above piston 32 at the proper time for firing. Thus, the fuel is preheated, atomized, and forced into the cylinder 22. When piston 30 is in the down position, exhaust gas will have been partially exhausted through port 24 and air will be entering the air inlet port 60 to the space above the piston. After firing in cylinder 22, the same function will take place in cylinder 20.

Claims: A fuel system for a two-cycle internal combustion engine having two or more cylinders (20,22) with reciprocating pistons (30,32) each comprising a circumferential wall and having a top stroke position and a bottom stroke position, a fuel inlet at the top of each cylinder (20,22), an exhaust outlet (24,26) in each cylinder (20,22) positioned to be uncovered by each piston (30,32) as it reaches the lowest point of its stroke, air transfer ports (60,62) in each cylinder (20,22) also uncovered by each piston (30, 32) as it reaches the lowest point of its stroke, a wall port (44,46) in each cylinder (20,22) positioned between the top and bottom stroke positions of each piston (30,32), a transfer conduit (42, 43) connecting each said wall port (44,46) of one cylinder with the fuel inlet of a second cylinder, and a fuel injector (50,52) in each said conduit (42,43), whereby in the operation of the engine hot exhaust gases are transferred from one cylinder in which a piston is descending in a power stroke to a second cylinder in which a piston is ascending in a compression stroke, said transferring gases also preheating and atomizing fuel from said fuel injectors, characterized in that each piston (30,32) has an opening (64) in its circumferential wall to register with a wall port (44,46) in a respective cylinder (20,22) to selectively relieve pressure in each said transfer conduit (42,43) as each piston (30,32) reaches its top position. A fuel system as defined in claim 1 which said wall ports (44,46) are positioned substantially half-way between said top and bottom stroke positions of said pistons (30,32). A fuel system as defined in claim 1 or claim 2 in which a one-way check valve (72,73) is located in each transfer conduit (42,43) to pass fuel and hot exhaust gases to the fuel inlet port of a cylinder.

Inventors: TUCKEY CHARLES HENRY
Applicants: WALBRO CORPORATION (CORPORATION OF DELAWARE)
Application year: 1987
Main classification: F02M67
IPC codes: F02F1, F02B75, F02B13, F02M63, F02M67, F02B15