Variable compression ratio mechanism

In a variable compression ratio mechanism that serves to change the compression ratio of an internal combustion engine (1) by rotating camshafts (9) so as to cause relative movement between a cylinder block (3) and a crankcase (4), an oil film forming device (21) forms oil films on the sliding portions of camshafts (9). In a variable compression ratio mechanism that serves to change the compression ratio of an internal combustion engine (1) by rotating camshafts (9) so as to cause relative movement between a cylinder block (3) and a crankcase (4), an oil film forming device (21) forms oil films on the sliding portions of camshafts (9).