Abstract: A cylinder bore (4) of a two-stroke internal combustion engine (1) has first scavenging ports (12) and second scavenging ports (13) inside. The first scavenging ports (12) are nearer to an exhaust port (11) of the engine (1) than the second scavenging ports (13). In each scavenging stroke, the second scavenging ports (13) are opened earlier than the first scavenging ports (12) and introduce fuel-free air (A) from the second scavenging ports (13) into a combustion chamber (6). The first scavenging ports (12) are opened later and introduce an air-fuel mixture (M) pre-compressed in a crank chamber (8) into the same combustion chamber (6). Thus, harmful substances contained in exhaust gas discharged from the engine (1) are reduced.

Abstract: A cylinder bore (4) of a two-stroke internal combustion engine (1) has first scavenging ports (12) and second scavenging ports (13) inside. The first scavenging ports (12) are nearer to an exhaust port (11) of the engine (1) than the second scavenging ports (13). In each scavenging stroke, the second scavenging ports (13) are opened earlier than the first scavenging ports (12) and introduce fuel-free air (A) from the second scavenging ports (13) into a combustion chamber (6). The first scavenging ports (12) are opened later and introduce an air-fuel mixture (M) pre-compressed in a crank chamber (8) into the same combustion chamber (6). Thus, harmful substances contained in exhaust gas discharged from the engine (1) are reduced.

Abstract: A two-stroke internal combustion engine that emits exhaust gases with reduced amounts of noxious components, such as HC, and has less blow-by of unburned air-fuel mixture has a crank chamber located below a piston and a combustion actuating chamber located above the piston. Either one pair or two pairs of scavenging passageways communicate the crank chamber with the combustion actuating chamber, the scavenging passageways of the one pair or of each of the two pairs being disposed symmetrically with respect to a plane that bisects an exhaust port so as to form a Schnürle-type scavenging system. Each scavenging passageway is throttled at a location proximate to a scavenging inlet port thereof.

Abstract: A two-stroke internal combustion engine that emits exhaust gases with reduced amounts of noxious components, such as HC, and has less blow-by of unburned air-fuel mixture has a crank chamber located below a piston and a combustion actuating chamber located above the piston. Either one pair or two pairs of scavenging passageways communicate the crank chamber with the combustion actuating chamber, the scavenging passageways of the one pair or of each of the two pairs being disposed symmetrically with respect to a plane that bisects an exhaust port so as to form a Schnürle-type scavenging system. Each scavenging passageway is throttled at a location proximate to a scavenging inlet port thereof.

Abstract: A two-stroke internal combustion engine having a Schnürle scavenging system includes a pair of first scavenging ports and a pair of second scavenging ports. An inner horizontal scavenging angle formed close to an exhaust port and an outer horizontal scavenging angle formed remote from the exhaust port by a pair of scavenging flows blown out of the pair of the first scavenging ports are both set to an angle in the range of from 116 to 124 degrees. An inner horizontal scavenging angle formed close to the exhaust port and an outer horizontal scavenging angle formed remote from the exhaust port by a pair of scavenging flows blown out of the pair of the second scavenging ports are set to angles in the ranges of from 126 to 134 degrees and from 146 to 154 degrees, respectively.

Abstract: A loop scavenge two-cycle internal combustion engine that includes a partial wall partition disposed between a scavenging path and a cylinder bore, with a cooling port formed in the partial wall partition for enabling fresh gas in the scavenging path to contact directly with a peripheral wall of a piston in the cylinder. The fresh gas in the scavenging path directly contacts and efficiently cools the peripheral surface of the piston to prevent heat rise and distortion within the engine. The partial wall partition and cooling port maximize both cooling efficiently and cylinder strength and durability.

Abstract: A two-cycle internal combustion engine comprising a cylinder including an exhaust outlet and scavenging paths formed in the inner wall thereof, and a piston including openings formed in its peripheral wall at positions near respective piston-pin bosses thereof, the respective upper ends of the scavenging paths serving as scavenging ports which are opened and closed through reciprocating movement of the piston and the openings being so arranged as to communicate with the scavenging paths at positions nearer to the exhaust outlet of the cylinder.