Internal combustion engine

A compression ignition internal combustion engine comprising:

• a cylinder;
• a piston reciprocably received within the cylinder;
• a pair of contra-rotating crankshafts rotatably mounted relative to the cylinder;
• a pair of connecting rods each having a first end connected to a crank journal of a respective one of the crankshafts and a second end connected to the piston by a piston connector;
• a crankshaft throw radius described between an axis of rotation of each crankshaft and its crank journal;
• an effective crankshaft offset described by the offset between the axis of rotation of each crankshaft and the piston connector to which its connecting rod is connected;
• wherein the effective crankshaft offset is between 1.6 and 1.7 times the crankshaft throw radius;
• and
• wherein the engine is configured such that the piston stroke in a first direction toward the crankshafts causes each crankshaft to rotate by a first angle and the piston stroke in a second direction opposite the first direction causes each crankshaft to rotate by a second angle which is between 26 and 42 degrees less than the first angle.

A compression ignition internal combustion engine comprising:

• a cylinder;
• a piston reciprocably received within the cylinder;
• a pair of contra-rotating crankshafts rotatably mounted relative to the cylinder;
• a pair of connecting rods each having a first end connected to a crank journal of a respective one of the crankshafts and a second end connected to the piston by a piston connector;
• an inlet valve for introducing air and/or fuel into the cylinder;
• an exhaust valve for exhausting a gas from the cylinder;
• wherein the engine is configured such that the piston stroke in a first direction toward the crankshafts causes each crankshaft to rotate by a first angle and the piston stroke in a second direction opposite the first direction causes each crankshaft to rotate by a second angle different from the first angle;
• and
• wherein the engine is configured such that the inlet valve opens between 15 and 25 degrees before the piston reaches a top dead centre position and closes between 40 and 50 degrees after the piston reaches a bottom dead centre position and the exhaust valve opens between 40 and 50 degrees before the piston reaches the bottom dead centre position and closes between 15 and 25 degrees after the piston reaches the top dead centre position.