An internal combustion engine optimizing small-size arrangement of the valve drive mechanism, considering that the exhaust valve diameter is smaller than the intake valve diameter.

Intake and exhaust valves are in a radial arrangement, intake and exhaust cam surfaces are inclined relative to intake and exhaust cam axes, intake and exhaust rocker arm support members are inclined correspondingly in the same way and disposed between an intake camshaft and an exhaust camshaft. Pivotal support base portions of intake rocker arms and pivotal support base portions of exhaust rocker arms are disposed such that the distances thereof from a joining surface joining a cylinder head and a cylinder body are different.

An opposed-piston internal combustion engine is configured so that one cylinder is provided with two pistons and these pistons reciprocate symmetrically with each other. The engine comprises: an expanded chamber formed at part of a wall of the cylinder positioned between the two pistons when a volume between the two pistons is the minimum and extending in a radial direction of the cylinder; an intake passage communicated with the expanded chamber; an exhaust passage communicated with the expanded chamber; an intake valve opening and closing the intake passage with respect to the expanded chamber; an exhaust valve opening and closing the exhaust passage with respect to the expanded chamber, and crankshafts respectively connected to the pistons. The expanded chamber formed so as to stick out from a wall surface of the cylinder in the same direction as axes of rotation of the crankshafts.

A pushrod valvetrain combustion system assembly for an internal combustion engine includes a two-valve pushrod assembly and a cylinder top that forms a portion of a cylinder head. The cylinder top has a single intake port, a single exhaust port, a spark plug bore, and a fuel injector bore. The pushrod assembly includes an intake valve positioned in the intake port and an exhaust valve positioned in the exhaust port. The intake port and exhaust port are positioned adjacent each other and are positioned along an axis that intersects a center point of each of the ports. The intersecting axis is rotated relative to a centerline of the crankshaft of the engine, providing space for the spark plug bore and fuel injector bore to both be located in the cylinder top on a same side of the intersecting axis.

A pushrod valvetrain combustion system assembly for an internal combustion engine includes a two-valve pushrod assembly and a cylinder top that forms a portion of a cylinder head. The cylinder top has a single intake port, a single exhaust port, a spark plug bore, and a fuel injector bore. The pushrod assembly includes an intake valve positioned in the intake port and an exhaust valve positioned in the exhaust port. The intake port and exhaust port are positioned adjacent each other and are positioned along an axis that intersects a center point of each of the ports. The intersecting axis is rotated relative to a centerline of the crankshaft of the engine, providing space for the spark plug bore and fuel injector bore to both be located in the cylinder top on a same side of the intersecting axis.

Internal combustion engines having non-circular, preferably rectangular, cross-section pistons and cylinders are disclosed. The pistons may include a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The pistons also may have a domed piston head with depressions thereon to facilitate the movement of air/charge in the cylinder. The engines also may use multi-stage poppet valves in lieu of conventional poppet valves, and a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.

An opposed-piston internal combustion engine is configured so that one cylinder is provided with two pistons and these pistons reciprocate symmetrically with each other. The engine comprises: an expanded chamber formed at part of a wall of the cylinder positioned between the two pistons when a volume between the two pistons is the minimum and extending in a radial direction of the cylinder; an intake passage communicated with the expanded chamber; an exhaust passage communicated with the expanded chamber; an intake valve opening and closing the intake passage with respect to the expanded chamber; an exhaust valve opening and closing the exhaust passage with respect to the expanded chamber, and crankshafts respectively connected to the pistons. The expanded chamber formed so as to stick out from a wall surface of the cylinder in the same direction as axes of rotation of the crankshafts.

An internal combustion engine optimizing small-size arrangement of the valve drive mechanism, considering that the exhaust valve diameter is smaller than the intake valve diameter. Intake and exhaust valves are in a radial arrangement, intake and exhaust cam surfaces are inclined relative to intake and exhaust cam axes, intake and exhaust rocker arm support members are inclined correspondingly in the same way and disposed between an intake camshaft and an exhaust camshaft. Pivotal support base portions of intake rocker arms and pivotal support base portions of exhaust rocker arms are disposed such that the distances thereof from a joining surface joining a cylinder head and a cylinder body are different.

Internal combustion engines having non-circular, preferably rectangular, cross-section pistons and cylinders are disclosed. The pistons may include a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The pistons also may have a domed piston head with depressions thereon to facilitate the movement of air/charge in the cylinder. The engines also may use multi-stage poppet valves in lieu of conventional poppet valves, and a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.