Patent ID: 8671894

Claim:
A variable compression ratio internal engine constituted by at least two block portions connected to each other so as to be able to move relative to each other and constituted such that the mechanical compression ratio in the combustion chamber can be varied by moving one of the block portions relative to the other block portion, comprising: a cam shaft having a cam for driving an intake or exhaust valve positioned on one of the block portions; a crank shaft positioned on the other block portion; an output gear for outputting the rotation of the crank shaft; and an input gear for inputting the rotation output from the output gear to the cam shaft; the engine being constituted such that the input gear moves relative to the output gear along with the movement of the one block portion when the one block portion is moved relative to the other block portion, wherein the engine further comprises a rotation transmission shaft for transmitting the rotation output from the output gear to the input gear, wherein the rotation transmission shaft has a crank shaft side gear meshed with the output gear on one end thereof and a cam shaft side gear meshed with the input gear on the other end thereof, wherein the output gear and the crank shaft side gear are meshed with each other such that the rotation transmission shaft is rotated around the axis thereof by the rotation of the crank shaft and the cam shaft side gear and the input gear are meshed with each other such that the cam shaft is rotated around the axis thereof by the rotation of the rotation transmission shaft, wherein the input gear and the rotation transmission shaft are constituted to be able to slide relative to each other or the output gear and the rotation transmission shaft are constituted to be able to slide relative to each other in the direction of the movement of the one block portion relative to the other block portion such that the meshing between the input gear and the cam shaft side gear or the meshing between the output gear and the crank shaft side gear is maintained when the one block portion is moved relative to the other block portion, wherein the input gear and the cam shaft side gear are constituted to be able to slide relative to each other in the direction of the movement of the one block portion relative to the other block portion such that the meshing between the input gear and the cam shaft side gear is maintained when the one block portion is moved relative to the other block portion, and wherein the cam shaft side gear is a spur gear.