ACTUATOR FOR INTERNAL COMBUSTION ENGINE LINK MECHANISM AND WAVE GEAR SPEED REDUCER

Provided are an actuator for an internal combustion engine link mechanism, and a wave gear speed reducer that are capable of increasing both input efficiency and drive efficiency. According to the present invention, in a wave gear speed reducer in which, by means of a wave motion generator that is rotated by an input shaft, a flexible external gear is deformed into an elliptical shape to cause anexternal tooth of the flexile external gear to partially engage with an internal tooth of an internal gear part, and the engaged part between the flexible external gear and the internal gear part is rotated, the curvature of the external tooth at the contact part between the internal tooth and the external tooth is set larger than that of the inner tooth. 提供能够提高输入效率以及驱动效率这两方的内燃机用连杆机构的促动器以及波动齿轮减速机。在本发明中，在利用通过输入轴旋转的波动发生器使挠性外齿轮挠曲成椭圆形、使挠性外齿轮的外齿局部啮合于内齿轮部的内齿、并且使挠性外齿轮与内齿轮部的啮合位置旋转的波动齿轮减速机中，使内齿与外齿的接触部分的外齿的曲率比内齿大。