A valve mechanism 90A of a conventional example 1 (Patent Document 1) illustrated in FIG. 8 includes a cam 92 formed on a camshaft 91 and a roller arm 95 including a roller 95a and configured to swing to drive a valve 7 when the roller 95a is pressed by the cam 92.
A variable valve mechanism 90B of a conventional example 2 (Patent Document 2) illustrated in FIG. 9 and a variable valve mechanism 90C of a conventional example 3 (Patent Document 3) illustrated in FIG. 10 are the same as that of the conventional example 1 in including the cam 92 and the roller arm 95, but are different therefrom in including a variable arm 94 interposed between the cam 92 and the roller 95a. The variable arm 94 is operated by a variable device 96, whereby the drive state (the lift amount and the action angle) of the valve 7 is continuously changed.