An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins.

An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins.

An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins.

An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins.

The invention discloses a two-stroke internal combustion engine having an engine housing with a crankcase in which a crankshaft is connected to a piston moving in a cylinder, an exhaust port leading from the cylinder space and opening at the level of the lower dead center of the crankshaft, the exhaust port is configured to be closed by a piston when the crankshaft is in its top dead center position, characterized in that it further has a rotary disk with an opening or recess on a part of its circumference, or with a protrusion on a part of its circumference, the rotary disk extending with its circumference into the exhaust port so that the exhaust port is completely closable by the rotary disk.

The invention discloses a two-stroke internal combustion engine having an engine housing with a crankcase in which a crankshaft is connected to a piston moving in a cylinder, an exhaust port leading from the cylinder space and opening at the level of the lower dead center of the crankshaft, the exhaust port is configured to be closed by a piston when the crankshaft is in its top dead center position, characterized in that it further has a rotary disk with an opening or recess on a part of its circumference, or with a protrusion on a part of its circumference, the rotary disk extending with its circumference into the exhaust port so that the exhaust port is completely closable by the rotary disk.

A two-stroke internal combustion engine includes:—a base;—a head, fixed to the base, and having a cylindrical cavity;—a piston slidable in the cylindrical cavity, to define a combustion chamber and a pumping chamber, and movable in the cylindrical cavity between a bottom and a top dead center;—a transfer duct having an inlet mouth in fluid communication with the pumping chamber, and an outlet mouth in fluid communication with the combustion chamber;—an exhaust duct having an inlet mouth in fluid communication with the combustion chamber,—a crank shaft partially housed in the pumping chamber;—a connecting rod connecting the piston to the crank shaft;—a movable partition housed inside the pumping chamber operatively connected to the crank shaft to occlude the transfer duct inlet mouth and to put in fluid communication the transfer duct inlet mouth with the pumping chamber.

A two-stroke internal combustion engine has a crankshaft disposed at least in part in a crankcase, and a cylinder block connected to the crankcase and defining a cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid. A piston is movably disposed within the cylinder and is operatively connected to the crankshaft. The piston is movable along a cylinder axis in a reciprocating motion including an upstroke and a downstroke. An exhaust valve assembly is operatively connected to and rotates with the crankshaft. The exhaust valve assembly has a shaft rotatably supported by the cylinder block and a valve configured to cyclically obstruct the exhaust port. The valve is operable to move clear of the exhaust port before the piston uncovers the exhaust port during its downstroke, and at least partially close the exhaust port before the piston fully covers the exhaust port during its upstroke.

A two-stroke internal combustion engine has a crankshaft disposed at least in part in a crankcase, and a cylinder block connected to the crankcase and defining a cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid. A piston is movably disposed within the cylinder and is operatively connected to the crankshaft. The piston is movable along a cylinder axis in a reciprocating motion including an upstroke and a downstroke. An exhaust valve assembly is operatively connected to and rotates with the crankshaft. The exhaust valve assembly has a shaft rotatably supported by the cylinder block and a valve configured to cyclically obstruct the exhaust port. The valve is operable to move clear of the exhaust port before the piston uncovers the exhaust port during its downstroke, and at least partially close the exhaust port before the piston fully covers the exhaust port during its upstroke.

The present invention concerns a method in a two-stroke engine comprising at least one cylinder (1) with a reciprocating piston (2), a delimited combustion space (5), at least one outlet port (7) and an inlet port (9) which are both uncovered at the bottom dead center position of the piston, an actuator (8) which activates a valve (17) to open and introduce combustion air via an inlet pipe (6), a control system (15) which controls the actuator to open the valve in order to introduce combustion air via the inlet port. The invention is characterized in that the inlet port is closed by the piston after the outlet port has been closed, thus the opposite compared to the two-stroke engines of today.