Two-cycle internal combustion engine

A two-cycle internal combustion engine comprising:

• a cylinder head having at least one intake port for introducing fresh air into a combustion chamber and at least one exhaust port for discharging exhaust gas from said combustion chamber;
• an air charging means for supplying compressed fresh air to said intake port;
• intake and exhaust valves for opening and closing said intake and exhaust ports, respectively;
• and a valve operating means operated in response to a crank angle;
• characterized in that said engine further comprises:
• a piston having a concavity on the top face thereof;
• said valve operating means including a means for opening said exhaust valve earlier than said intake valve, when the speed of the downward movement of the piston is relatively high, so that a part of exhaust gas in said exhaust port flows back to said combustion chamber;
• and,
• a swirl forming means including a masking provided on the inner wall of the cylinder head and around said exhaust valve, for forming an exhaust gas swirl rotating around a cylinder axis of the combustion chamber when the exhaust gas flows from said exhaust port back to the combustion chamber;
• said valve operating means further including a means for opening said intake valve so as to slowly introduce fresh air onto said exhaust gas swirl in the combustion chamber in the idling or light laod condition.

A two-cycle internal combustion engine comprising:

• a cylinder head having at least one intake port for introducing fresh air into a combustion chamber and first and second exhaust ports for discharging exhaust gas from said combustion chamber;
• an air charging means for supplying compressed fresh air to said intake port;
• an intake valve and first and second exhaust valves for opening and closing said intake port and said first and second exhaust ports, respectively;
• and a valve operating means operated in response to a crank angle;
• characterized in that said engine further comprises:
• a piston having a concavity on the top face thereof;
• said concavity having a bottom face inclined in such a way that the depth of the concavity is larger at the side near said exhaust valves;
• said valve operating means including a means for opening said first exhaust valve earlier than said second exhaust valve and said intake valve, when the speed of the downward movement of the piston is relatively high, so that a part of exhaust gas in said first exhaust port flows back to said combustion chamber;
• and,
• a swirl forming means including a masking provided on the inner wall of the cylinder head and around said first exhaust valve, for forming an exhaust gas swirl rotating around a cylinder axis of the combustion chamber when the exhaust gas flows from said first exhaust port back to the combustion chamber;
• said valve operating means further including a means for opening said intake valve so as to slowly introduce fresh air onto said exhaust gas swirl in the combustion chamber in the idling or light load condition.