and compress the bearing members 18 then the first contact rings 18 b of the bearing members 18 are brought into contact with the first contact part 16 a of the control cams 16 of the rotary adjuster 14 and the second contact rings 18 c of the bearing members 18 are brought into contact with the second contact parts 22 a of the rocker arms 22 in this case the valve lift and the opening duration of the intake and exhaust valves 10 depend on and vary with the profiles of the cams 12 a the profiles of the first contact parts 16 a of the control cams 16 of the rotary adjuster 14 and the profiles of the second contact parts 22 a of the rocker arms 22 for example as shown in fig8 when the rotating angle of the rotating shaft 14 a of the rotary adjuster 14 is at 0 u00b0 variation of valve lift and opening duration of the intake and exhaust valves 10 by the rotation of the cam shaft 12 is smallest as shown in fig9 and 10 when the rotating shaft 14 a of the rotary adjuster 14 is rotated at 10 u00b0 and 25 u00b0 in a counterclockwise direction that is when the rotating angle of the rotating shaft 14 a of the rotary adjuster 14 is increased valve lift and opening duration of the intake and exhaust valves 10 are also gradually.