Internal combustion engine

An internal combustion engine comprising:

• two parallel crankshafts positioned in crankcases;
• a pair of cylinders provided to sides of both crankshafts and to a side of the crankcases so as to be aligned with a cylinder axis;
• pistons movably disposed within each of the cylinders;
• and
• connecting rods linked to each of the pistons and extend from the two crankshafts to the side of each of the cylinders in the pair,
• wherein positions at which the crankshafts and the pistons are linked to the corresponding connecting rods linked to the corresponding pistons are constantly kept symmetrical with respect to a cylinder axis when the two crankshafts rotate in opposite directions, and the pistons in the pair each move horizontally.

An internal combustion engine comprising:

• first and second cylinders provided to the side of crankcases;
• first and second crankshafts positioned in parallel in the crankcases;
• a first connecting rod linked at one end to the first crankshaft via a first crankpin;
• a first piston movably disposed within the first cylinder and linked to another end of the first connecting rod;
• a second connecting rod linked at one end to the second crankshaft via a second crankpin;
• and
• a second piston movably disposed within the second cylinder and linked to another end of the second connecting rod,
• a distance from an axis of the first crankshaft to the first crankpin and a distance from an axis of the second crankshaft to the second crankpin being equivalent,
• wherein the internal combustion engine further comprises:
• pairs of first crank arms provided to the first crankshaft, formed in a tapered shape and supported on a tip by the first crankpin;
• and pairs of second crank arms provided to the second crankshaft, formed in a tapered shape and supported on a tip by the second crankpin, and
• wherein the first crank arms and the second crank arms are positioned in parallel, a length of the second crankpin is equivalent to a length of the first crankpin or is longer than the length of the first crankpin, or, alternatively, the length of the first crankpin is equivalent to the length of the second crankpin or is longer than the length of the second crankpin, and the first crank arms are capable of passing through an inner side of the second crank arms and the second crank arms are capable of passing through an inner side of the first crank arms when the first crankshaft and the second crankshaft are rotating.