REDUCTION GEAR AND ACTUATOR OF VARIABLE COMPRESSION MECHANISM OF INTERNAL COMBUSTION ENGINE

To provide a reduction gear which is suppressed in the enlargement of a gear device and an increase of the number of part items, and an actuator of a variable compression mechanism of an internal combustion engine.SOLUTION: An actuator of a variable compression mechanism has: a drive motor having a motor shaft at which a sun gear is arranged; a wave motion generator whose contour of a cross section in an orthogonal direction of a rotation axial line is non-circular, and which has first inner teeth at an internal periphery; a flexible outer gear having a cylindrical flank part having flexibility which is deflected into a non-circular shape by the wave motion generator, and outer teeth arranged at an external peripheral face of the flank part; an inner gear member having second inner teeth which are engaged with the outer teeth of the deflected and deformed flank part; a housing into which the inner gear member is fixed; an output shaft which rotates integrally with the flexible outer gear, and changes a posture of the variable compression mechanism of the internal combustion engine by rotation; a plurality of support shafts held to the output shaft or the housing, or the flexible outer gear; and a plurality of planetary gears which are rotatably arranged at the plurality of support shafts, respectively, and engaged with the sun gear and the first inner teeth.SELECTED DRAWING: Figure 5 【課題】歯車装置の大型化や部品点数の増大を抑制した減速機及び内燃機関の可変圧縮機構のアクチュエータを提供すること。【解決手段】可変圧縮機構のアクチュエータは、太陽歯車が設けられたモータ軸を有する駆動モータと、回転軸線の直角方向断面の外形が非円形であって、内周に第１内歯を有する波動発生器と、波動発生器により非円形に撓む可撓性を有する筒状の胴部、胴部の外周面に設けられた外歯、を有する可撓性外歯車と、撓み変形された胴部の外歯と噛み合う第２内歯車を有する内歯車部材と、内歯車部材が固定されるハウジングと、可撓性外歯車と一体に回転すると共に、回転によって内燃機関の可変圧縮比機構の姿勢を変更する出力軸と、出力軸又はハウジング又は可撓性外歯車に保持された複数の支持軸と、複数の支持軸にそれぞれ回転可能に配置され、太陽歯車と第１内歯と噛み合う複数の遊星歯車と、を有する。【選択図】図５