Patent ID: 7047917

Claim:
A variable compression ratio mechanism in which a cylinder block and a crankcase of an internal combustion engine are coupled with each other for relative movement, and one or more camshafts are rotatably mounted on bearing portions at which said cylinder block and said crankcase are coupled with each other, so that said cylinder block and said crankcase are caused to move relative to each other in accordance with a rotation of said camshafts thereby to change a compression ratio of said internal combustion engine, said mechanism comprising: a rotation device driving said camshafts to rotate; wherein: said cylinder block has one or more cylinders; a pair of said camshafts are disposed between said cylinder block and said crankcase on opposite sides of said cylinders in a parallel relation; each of said camshafts has a shaft portion, a cam portion fixedly secured to said shaft portion, and a movable bearing portion rotatably mounted on said shaft portion; said cam portion of each camshaft is received in a cam receiving hole formed in one of said cylinder block and said crankcase; said shaft portion of each camshaft, on which said movable bearing portion is rotatably mounted, is received in a shaft receiving hole formed in said movable bearing portion; said movable bearing portion of each camshaft is received in a bearing receiving hole formed in the other of said cylinder block and said crankcase; and said rotation device drives said camshafts to rotate whereby said cylinder block is caused to move relative to said crankcase in an axial direction of said cylinders thereby to change the compression ratio in said cylinders; and an oil film forming device that forms oil films between said camshafts and the bearing portions rotatably supporting said camshafts.