Patent ID: 7392781

Claim:
A crankshaft mechanism, comprising: an upper link having a first end that is adapted to be connected to a piston through a piston pin; a crankshaft having a crank pin and at least one counterweight, the at least one counterweight and the crank pin formed on opposite sides of a main journal center of the crankshaft; a control link having a first end that is adapted to be rotatably supported on an eccentric cam provided at a control shaft supported by a cylinder block; and a lower link rotatably mounted on the crank pin, and having a first end that is adapted to be connected to a second end of the upper link through an upper pin, a second end that is adapted to be connected to a second end of the control link through a control pin, in which the crank pin is arranged to be located between the upper pin and the control pin; wherein the upper pin is disposed on the right of the control pin when viewed in an axial direction of the crankshaft where the crankshaft rotates counterclockwise, and a center of gravity of the at least one counterweight of the crankshaft existing at a forward side in the direction of rotation of the crankshaft.