US3734072A

US3734072A - Fuel control means for a model engine

Info

Publication number: US3734072A
Application number: US00263460A
Authority: US
Inventors: S Yamda
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-10-20
Filing date: 1972-06-16
Publication date: 1973-05-22
Anticipated expiration: 1990-05-22
Also published as: JPS4850718U; JPS5115879Y2; DE2235913A1

Abstract

Fuel control means for a model engine in which intake air is pre-compressed in a crank chamber of the engine, said fuel control means comprising a pressure responsive fuel control valve provided between a fuel tank and fuel injection nozzle means of the engine, the pressure in the crank chamber being introduced into the valve so as to control its opening in accordance with the crank chamber pressure. The crank chamber pressure is also introduced into the fuel tank so that the fuel in the tank is forced under pressure through the pressure responsive fuel control valve into the engine.

Description

United States Patent 91 Yamda 1 May 22,1973

[54] FUEL CONTROL MEANS FOR A 221 Filed: June 16, 1972 211 App]. No.: 263,460

[30] Foreign Application Priority Data Oct. 20, 1971 Japan ..46/96879 [52] U.S. Cl ..123/73 A, 123/73 DA, 123/139 AJ, 123/DIG. 3, l23/DIG. 5 [51] Int. Cl ..F02b 33/04 [58] Field of Search ..l23/73 A, 73 DA, 123/139 AJ, DIG. 5, DIG. 3

[56] References Cited UNITED STATES PATENTS 2,733,694 2/1956 Brebeck ..123/DIG. 3

2,722,208 11/1955 Conroy et al ..123/DIG. 5

FOREIGN PATENTS OR APPLICATIONS 747,534 4/1956 Great Britain ..l23/73 A Primary ExaminerAl Lawrence Smith Assistant ExaminerDennis Toth Attorney-Karl W. Flocks [57] ABSTRACT Fuel control means for a model engine in which intake air is pre-compressed in a crank chamber of the engine, said fuel control means comprising a pressure responsive fuel control valve provided between a fuel tank and fuel injection nozzle means of the engine, the pressure in the crank chamber being introduced into the valve so as to control its opening in accordance with the crank chamber pressure. The crank chamber pressure is also introduced into the fuel tank so that the fuel in the tank is forced under pressure through the pressure responsive fuel control valve into the engme.

4 Claims, 1 Drawing Figure FUEL CONTROL MEANS FOR A MODEL ENGINE The present invention relates to a model engine, and more particularly to an automatic fuel control system fora model engine.

In a conventional model engine, supply of fuel to the engine has been controlled by a throat or Venturi passage provided in an air intake passage of the engine for providing a suction pressure therein in accordance with the amount of air flow in the intake passage so that fuel is taken under the action of the suction pressure from a fuel tank through a suitable conduit and a fuel injection nozzle into the engine. This known arrangement, however, has a lot of disadvantages. For example, when a throttle valve in the air intake passage is closed to provide a low speed operation, the suction pressure in the throat passage is reduced in correspondence with the decrease in air flow therein, so that a stable fuel supply cannot be ensured. Further, when the throttle valve is rapidly opened, the fuel flow into the engine cannot increase as rapid as the air flow does.

Further, when theengine is mounted on a model plane or a model boat, the fuel tank is always subjected to the influence of centrifugal force or inertia force due to the movement of the model plane or the model boat. Particularly, in case of a model plane which is expected to perform movements in three dimensional directions, the engine is expected to take various attitudes and the position of the fuel tank with respect to the engine may always chahge. Therefore, the amount of fuel supply cannot be uniform when the fuel is taken into the engine under a suction pressure.

As an effective solution for increasing the engine output, an increased amount of fuel-air mixture may be taken into the engine. For this purpose, it may be conceived to increase the cross-sectional area of the intake Venturi portion and that of the hollow interior of engine crankshaft which constitutes a portion of the intake passage. However, since the increased crosssectional area of the intake Venturi portion will correspondingly reduce the suction pressure produced therein, the stable fuel supply cannot be ensured anymore when the cross-sectional area of the Venturi portion is excessively increased. Thus, there is a practical limit in increasing the engine output in the conventional arrangement. l i

The present invention has a primary object to eliminate the aforementioned disadvantages of the conventional model engine.

Another object of the present invention is to provide I a fuel control means for a model engine which can provide a stable fuel supply throughout the operation range of the engine.

A further object of the present invention is to provide a fuel control means which can provide an increased engine output.

According to the present invention, there is provided a fuel control means for a model engine having a cylinder, a crankcase defining a crank chamber, a piston disposed in said cylinder for reciprocating movement, a crank shaft connected with said piston through a connecting rod, an intake passage which is in communication with the crank chamber, intake port means communicating with the crank chamber and opening into the cylinder, exhaust port means opening into the cylinder, and fuel injection nozzle means provided in the intake passage, said fuel control means comprising a pressure responsive fuel control valve provided between a fuel tank and said fuel injection nozzle means, and means for introducing the pressure in the crank chamber of the engine to the pressure responsive fuel control valve so that the opening of the valve is increased in accordance with the increase in the pressure in the crank chamber.

According to a further aspect of the present invention, said fuel tank is a shielded tank and means is provided for introducing the pressure in the crank chamber into the fuel tank through non-return valve means so that the fuel in the tank is forced by the pressure through said control valve into the engine.

The pressure responsive fuel control valve may include a pressure responsive diaphragm which is connected to a valve member for controlling the fuel passage into the engine.

These and other objects and features of the present invention will become apparent from the following descriptions of a preferred embodiment thereof taking reference to the accompanying drawing which is a diagrammatical view, partially in section of a model engine and its fuel control means embodying the features of the present invention.

Referring to the drawing, the reference numeral 1 generally designates a model engine of substantially known type having a cylinder 2 and a crank case 3 defining a crank chamber 4. Within the cylinder 2, there is desposed a piston 5 for reciprocating movement therein. The cylinder 2 and the piston 5 define a combustion chamber in the cylinder as is well known in the art. The reference numeral 6 shows a crank shaft having a crank end connected through a connecting rod 7 with the piston 5. The other end of the crank shaft 6 has secured thereto a propeller 8 of a model plane or a model boat. As seen in the drawing, the crank shaft 6 passes through a cylindrical bearing portion 9 integrally formed with the crank case 3 and having an air intake conduit 10 including a throat or Venturi portion 11. The crank shaft 6 is formed adjacent to its end connected to the rod 7 with an axial bore 12 opening to the crank chamber 4. The crank shaft 6 is further formed with a slot 13 connecting the interior of the axial bore to the exterior of the crank shaft 6. The position of the slot 13 is such that during the compression stroke of the engine, that is, when the piston 5 is moving up, it is brought into communication with the conduit 10 whereby an intake passage to the crank chamber 4 is completed. Further, the engine is also provided with scavenging ports 14 which are opened to the cylinder wall and connect the crank chamber 4 with the combustion chamber at a suitable timing during the expansion stroke or downward movement of the piston 5. The engine is further provided with exhaust ports 15 as is well known in the art. In the conduit 10, there is dis posed a fuel injection nozzle 16 and a butterfly type throttle valve 17. The reference numeral 18 designates an ignition plug.

The operation of the engine of this type is widely known in the art, so that the detailed descriptions thereof will be omitted.

According to a feature of the present invention, the cylindrical bearing portion 9 is provided with a pressure take-off port 19 in such a position that it comes into communication with the slot 13 formed in the crank shaft 6 at a suitable timing during the downward stroke of the piston 5. Thus, the pressure in the crank chamber 4 is taken out through the slot 13 and the port 19 and introduced into a pressure responsive fuel control valve which is generally designated by the reference numeral 20 and disposed in a fuel supply line between a fuel tank 21 and the fuel injection nozzle 16.

The fuel control valve 20 includes a pressure responsive diaphragm 22 which divides a chamber in a casing 25 into a pressure chamber 23 and a low pressure chamber 24. The diaphragm 22 is connected with a valve member 26 which co-operates with a valve seat 27 formed in the fuel flow passage in the casing 25 so as to control the fuel flow in accordance with the position of the valve member 26. The pressure in the crank chamber 4 taken out through the slot 13 in the crank shaft 6 and the port 19 is transmitted through a line 27 into the pressure chamber 23 of the fuel control valve 20. A spring 28 acting on the valve member 26 serves to urge the valve member 26 toward the closed position, while the pressure acting on the diaphragm 22 serves to urge the valve member toward the open position. The spring is seated on an adjustable plug member 29 threadably inserted into the casing 25. Thus, the position of the valve member 26 is determined by the pressure introduced into the pressure chamber 23 and the adjustment of the plug member 29.

The pressure in the crank chamber 4 is further introduced through the line 27 and a further line 30 into the top space of the fuel tank 21. The reference numeral 31 designates a non-return valve provided at the entrance of the crank chamber pressure into the fuel tank 21. The fuel from the tank 21 is introduced through a line 33 into the inlet 34 of the fuel line in the casing 25 of the fuel control valve 20. The fuel from the outlet 35 of the fuel line in the fuel control valve 20 is passed through a line 36 into the fuel injection nozzle 16.

Thus, in operation of the engine as described above, the positive pressure in the crank chamber 4 is introduced through the slot 13, the port 19 and the line 27 into the pressure chamber 23 of the fuel control valve 20, so that the opening of the valve is controlled in accordance with the pressure in the crank chamber. Therefore, it is possible to increase the fuel flow in accordance with the increase in the opening of the throttle valve 17. Further, the positive pressure in the crank chamber is also introduced into the fuel tank 21 through the line 30 and the non-return valve 31. Therefore, the fuel is forced under pressure from the tank 21 into the fuel control valve 20 and then into the fuel injection valve 16. This feature is effective to ensure positive fuel supply irrespective of the change in attitude of the model plane or the model boat on which the engine is mounted. Further, according to the features of the present invention, it is possible to increase the crosssectional area of the throat or Venturi portion without having any adverse effect on the supply of fuel since the fuel is forced under pressure from the fuel tank to provide a positive fuel flow. Therefore, it is possible to provide an engine of increased output by an air intake passage of increased cross-sectional area.

Although the invention has been illustrated and described with reference to a preferred embodiment, it should be noted that the invention is not limited to the details of the structure but changes and modifications can be made without departing from the scope of the appended claims. For example, the fuel control valve 20 should not necessarily be separated from the engine 1 but can be directly secured to the crank case of the engine if desired.

1 claim:

1. Fuel control means for a model engine including a cylinder, at crankcase defining a crank chamber, a piston disposed in said cylinder for reciprocating movement, a crank shaft connected with said piston through a connecting rod, an intake passage which is in communication with the crank chamber, and an intake port means communicating with the crank chamber and opening into the cylinder whereby fuel-air mixture is passed through the intake passage into the crank chamber to be compressed therein and thereafter through the intake port means into the cylinder, characterized by the fact that said fuel control means comprises a pressure responsive fuel control valve provided between a fuel tank and fuel injection nozzle means of the engine, and means for introducing the pressure in the crank chamber of the engine to the pressure responsive fuel control valve so that the opening of the valve is increased in accordance with the increase in the crank chamber pressure.

2. Fuel control means in accordance with claim 1, in which said fuel tank is a shielded tank and means is provided for introducing the pressure in the crank chamber into the fuel tank through non-return valve means so that the fuel in the tank is forced under pressure through said control valve into the engine.

3. Fuel control means in accordance with claim 1 in which said pressure responsive fuel control valve includes a pressure responsive diaphragm which is connected to a valve member for controlling the opening of the valve in accordance with the crank chamber pressure.

4. Fuel control means in accordance with claim 1 in which said crank shaft is formed with an axial bore opening into the crank chamber and a slot is formed in the crank shaft in such a position that it connects the intake passage to the crank chamber at a suitable timing during the compression stroke of the engine, and said means for introducing the crank chamber pressure into the fuel control valve includes a port provided in the engine at such a position that it is brought into communication with said slot in the crank shaft at least when positive pressure is produced in the crank chamber.

Claims

1. Fuel control means for a model engine including a cylinder, a crankcase defining a crank chamber, a piston disposed in said cylinder for reciprocating movement, a crank shaft connected with said piston through a connecting rod, an intake passage which is in communication with the crank chamber, and an intake port means communicating with the crank chamber and opening into the cylinder whereby fuel-air mixture is passed through the intake passage into the crank chamber to be compressed therein and thereafter through the intake port means into the cylinder, characterized by the fact that said fuel control means comprises a pressure responsive fuel control valve provided between a fuel tank and fuel injection nozzle means of the engine, and means for introducing the pressure in the crank chamber of the engine to the pressure responsive fuel control valve so that the opening of the valve is increased in accordance with the increase in the crank chamber pressure.