An engine (2) is a four-flow scavenging type engine. Four scavenging ports (34) include: first right and left scavenging ports (34(lef-1) and 34(ref-1)) that lie on a side relatively away from an exhaust port (22) and that lie facing each other with a cylinder (4) in between; and second right and left scavenging ports (34(lef-2) and 34(ref-2)) that lie closer to the exhaust port (22) than first right and left scavenging ports do and that lie facing each other with the cylinder (4) in between. The second left scavenging port and the first right scavenging port that make up a first mutually diagonal set (Diag-No. 1) have different opening timings from those of the first left scavenging port and the second right scavenging port that make up a second mutually diagonal set (Diag-No. 2).

Two-cycle engine includes cylinder block formed with a cylinder and crank chamber. The cylinder block includes: an exhaust passage leading to a combustion chamber in the cylinder through an exhaust port opened to an inner circumferential surface of the cylinder; a scavenging port opened to the inner circumferential surface of the cylinder; a communication passage extending from the scavenging port in a radial direction of the cylinder; and a scavenging passage extending in an axial direction of the cylinder, communicating with the crank chamber, and having an opening portion formed in a bottom surface of the communication passage. A ceiling surface of the communication passage is inclined toward a cylinder head with increasing distance from a scavenging passage side thereof toward the scavenging port. A bottom surface of the communication passage is inclined toward the crank chamber with increasing distance from a scavenging passage side thereof toward the scavenging port.

Among multiple scavenging passages 14 included in a cylinder, a scavenging passage connected to at least one scavenging port 16 constitutes a variable scavenging passage 14(ch). An upper end portion of the variable scavenging passage 14(ch) has a guide surface 50 defining a discharge direction of a scavenging gas discharged from a variable scavenging port 16(ch) connected thereto on a horizontal plane. The guide surface 50 includes at least a first guide portion 50(H) defining a first discharge direction of the scavenging gas and a second guide portion 50(L) defining a second discharge direction of the scavenging gas. The discharge direction of the scavenging gas is changed from the first discharge direction to the second discharge direction on the horizontal plane by the first and second guide portions 50(H) and 50(L) in the scavenging stroke.

Among multiple scavenging passages 14 included in a cylinder, a scavenging passage connected to at least one scavenging port 16 constitutes a variable scavenging passage 14(ch). An upper end portion of the variable scavenging passage 14(ch) has a guide surface 50 defining a discharge direction of a scavenging gas discharged from a variable scavenging port 16(ch) connected thereto on a horizontal plane. The guide surface 50 includes at least a first guide portion 50(H) defining a first discharge direction of the scavenging gas and a second guide portion 50(L) defining a second discharge direction of the scavenging gas. The discharge direction of the scavenging gas is changed from the first discharge direction to the second discharge direction on the horizontal plane by the first and second guide portions 50(H) and 50(L) in the scavenging stroke.

Provided is a two-stroke internal combustion engine, including: a fuel injection valve configured to supply a fuel to a crank chamber; an intake passage configured to allow only air to be sucked thereinto under a negative pressure generated when a piston is actuated; and a scavenging passage that allows communication between the crank chamber and a combustion chamber. The intake passage is branched into a first intake passage and a second intake passage. The first intake passage communicates with the crank chamber. The second intake passage communicates with the scavenging passage. The fuel injection valve is configured to inject the fuel toward at least one of the first intake passage or the crank chamber. Further, air stagnant in the scavenging passage at end of air suction serves as leading air to contribute to scavenging.

Provided is a two-stroke internal combustion engine, including: a fuel injection valve configured to supply a fuel to a crank chamber; an intake passage configured to allow only air to be sucked thereinto under a negative pressure generated when a piston is actuated; and a scavenging passage that allows communication between the crank chamber and a combustion chamber. The intake passage is branched into a first intake passage and a second intake passage. The first intake passage communicates with the crank chamber. The second intake passage communicates with the scavenging passage. The fuel injection valve is configured to inject the fuel toward at least one of the first intake passage or the crank chamber. Further, air stagnant in the scavenging passage at end of air suction serves as leading air to contribute to scavenging.

Two-cycle engine includes cylinder block formed with a cylinder and crank chamber. The cylinder block includes: an exhaust passage leading to a combustion chamber in the cylinder through an exhaust port opened to an inner circumferential surface of the cylinder; a scavenging port opened to the inner circumferential surface of the cylinder; a communication passage extending from the scavenging port in a radial direction of the cylinder; and a scavenging passage extending in an axial direction of the cylinder, communicating with the crank chamber, and having an opening portion formed in a bottom surface of the communication passage. A ceiling surface of the communication passage is inclined toward a cylinder head with increasing distance from a scavenging passage side thereof toward the scavenging port. A bottom surface of the communication passage is inclined toward the crank chamber with increasing distance from a scavenging passage side thereof toward the scavenging port.

The invention pertains to gas exchange in internal combustion engines using low to zero-emission fuels. The combustion engine has the ability to regulate the quantity of air/fuel mixture in the cylinder using one or more exhaust valve(s) (2) that can have adjustable opening times in order to control the gas exchange in the cylinder so that exhaust and alternatively also air can be expelled into the exhaust system. By reducing the quantity of air and thus the quantity of fuel for each cycle, that combined with reduced compression pressure means that engines can operate with a higher expansion ratio by leaving the exhaust valve(s) (2) open through a part of the compression stroke to reduce the amount of air to the combustion and reduce compression and then pressure rise before combustion. Air volume and gas exchange are regulated by compressor(s) (5) as well as opening and closing of exhaust valve(s) (2) with the exhaust valve control (4); alternatively, also intake valves for 4-stroke engines.

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 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.