Two-stroke cycle engine

A two-stroke cycle engine using a preceding air-layer for scavenging, comprising:

• an exhaust port on the side of the cylinder;
• a scavenging port on the side of the cylinder;
• an intake port on the side of the cylinder fuel passage, which supplies fuel-air mixture through a mixture control valve on the carburetor to the crank chamber during the time of the elevation of the piston;
• a scavenger passage opened to said scavenging port;
• an air supply port, which supplies scavenging air from the air cleaner to said scavenger passage;
• a cam which is interlocked with said mixture control valve;
• a cam follower which engages with said cam;
• and
• an air control valve in the upstream of an air passage which controls the diameter of said air passage, and said air control valve being operated by said cam and said cam follower in such a way as to supply a quantity of scavenging air proportional to the quantity of fuel-air mixture determined by the opening of said cam and the mixture control valve to control the fuel-air mixture.

A two-stroke cycle engine using a preceding air-layer for scavenging, comprising:

• an exhaust port on the side of the cylinder;
• a scavenging port on the side of the cylinder;
• a fuel passage, which supplies fuel-air mixture to the crank chamber through the intake port on the side of the cylinder during the time of the elevation of the piston;
• a scavenger passage to be connected to said scavenging port;
• an air passage, which supplies scavenging air from the air cleaner toward the inner side of said engine;
• an insulator, in which said fuel passage and said air passage run in parallel;
• a non-return valve, which is provided on said insulator facing toward the inner side of said engine, to open or close said air passage by means of the negative pressure in said scavenger passage:
• and
• a connecting passage with a small diameter to link said air passage and said fuel passages so that negative pressure in said air passage forces the fuel-air mixture in said fuel passage into said air passage.

A two-stroke cycle engine, comprising:

• an exhaust port on the sidewall of the cylinder, which opens into the cylinder;
• a scavenging port on the sidewall of the cylinder positioned a slight distance apart in the circumferential direction from said exhaust port, which also opens into the cylinder;
• an intake port, which opens to supply fuel-air mixture to the crankcase according to the action of the piston;
• and
• a scavenger passage, which connects the crankcase and said scavenging port;
• wherein a blow-up angle (α) of said scavenger passage, which is defined by an angle between the upper wall which connects to said scavenging port and a perpendicular line to the axis of the cylinder, varies along the circumferential direction of the cylinder, and if said blow-up angle in a location nearer said exhaust port is defined as (α1) and said blow-up angle in a location nearer said intake port is defined as (≢2), then α1<α2.

A two-stroke cycle engine, comprising:

• a scavenging port on the side of the cylinder, which opens into the cylinder;
• and
• a scavenger passage, which connects the crank chamber in a crankcase and said scavenging port, and supplies the fuel-air mixture in the crank chamber to said scavenging port;
• wherein said crankcase is configured in such a way that the front and rear portions, which are separated by a block at a right angle to the crankshaft which entails the axis of the cylinder, are fixed to each other by mounting hardware, a scavenger passage is provided inside both said front and rear portions of said crankcase, and the cylinder, whose scavenger passage connects to said scavenger passage in said crankcase, is fixed by mounting hardware to the mounting surface on the top of said crankcase in such a way that said scavenger passage runs through the mounting surface.

A two-stroke cycle engine, comprising:

• a scavenger passage which connects the crankcase and the scavenging port on the side of the cylinder;
• an air passage connected to the midpoint of the scavenger passage, which supplies scavenging air from an air cleaner to the scavenger passage;
• and
• a fuel passage, which supplies the fuel-air mixture produced in the carburetor to the crankcase;
• wherein said air cleaner has two air passages running from it in parallel, the first one is connected to said air passage, and the second one is connected to the air inlet of the carburetor to provide air for said fuel passage, and a choke valve on the air cleaner is provided to open and close both of said first and second air passages.

A two-stroke cycle engine, comprising:

• a rotary valve installed on the case in such a way that it is free to rotate which, when rotated, opens and closes the two air passages;
• and
• a rotary knob which operates the valve;
• wherein the front surface of said rotary valve comprises a sheet which covers or uncovers the inlets of the two air passages, a sealing ring consisting of an elastic material presses the flat surface of the valve against the openings of the inlets by elastic force and forms a fluid seal around the valve shaft with respect to the interior of the case.