Internal-combustion engine and drive system

An internal combustion engine comprising an intake port with an intake valve and an exhaust port with an exhaust valve, in which the intake valve alternately opens and closes the intake port, and the exhaust valve alternately opens and closes the exhaust port, when a piston reciprocates in a cylinder,

• wherein provided is a valve opening/closing mechanism made for controlling opening/closing of each of the intake valve and the exhaust valve in a manner repeatedly performing the following as one repeating cycle in sequence, during three reciprocations of the piston:
• a first-stage intake stroke in which intake is performed by opening the intake valve and moving down the piston;
• a first-stage compression stroke in which compression is performed by moving up the piston in a state where the intake valve and exhaust valve are closed;
• a first-stage ignition stroke in which first-stage ignition is performed when the piston reaches a top dead center or the vicinity of the top dead center;
• a first-stage combustion stroke in which combustion is performed by the first-stage ignition, and the piston moves down;
• a first-stage exhaust stroke in which exhaust is performed by opening the exhaust valve when the piston moves down;
• a scavenging and intake stroke in which scavenging and intake is performed until the piston moves up again by opening the intake valve in a state where the exhaust valve is open and before the piston reaches a bottom dead center;
• a second-stage compression stroke in which compression is performed by closing both of the exhaust valve and the intake valve and moving up the piston;
• a second-stage ignition stroke in which ignition is performed when the piston reaches the top dead center or the vicinity of the top dead center;
• a second-stage combustion stroke in which combustion is performed by the second-stage ignition and the piston moves down;
• and
• a second-stage exhaust stroke in which exhaust is performed by opening the exhaust valve when the piston moves down,
• wherein at the first-stage exhaust stroke and the second-stage exhaust stroke, the valve opening/closing mechanism opens the exhaust valve before the piston reaches a bottom dead center while the intake valve is closed, and at the scavenging and intake stroke, the valve opening/closing mechanism opens the intake valve before the piston reaches the bottom dead center while the exhaust valve is open,
• wherein the internal combustion engine repeatedly performs, using the piston, the foregoing operations in sequence as one repeating cycle corresponding to three reciprocations of the piston.