Strain wave gearing

A strain wave gearing provided with a rotation-transmitting member for transmitting rotation in a direction orthogonal to a rotation central axis, the strain wave gearing comprising:

• a rigid internally toothed gear;
• a flexible externally toothed gear arranged coaxially inside the internally toothed gear, the externally toothed gear being cup-shaped and being capable of flexing in a radial direction;
• a wave generator fitted inside the externally toothed gear, the wave generator causing the externally toothed gear to flex into a non-circular shape and partially mesh with the internally toothed gear;
• an input shaft extending coaxially from the wave generator toward a first side, which is one side in an axial direction that follows the rotation central axis;
• an output shaft coaxially attached from the first side in the axial direction to a boss defining a central portion of a bottom section of the cup shape of the externally toothed gear;
• a cover plate attached to the internally toothed gear from a second side, which is opposite from the first side in the axial direction, the cover plate covering the internally toothed gear, the externally toothed gear, and the wave generator from the second side, and
• a first bearing and a second bearing for rotatably supporting the input shaft,
• wherein
• the input shaft is provided with a shaft end section extending from the wave generator and a shaft distal-end section extending from the shaft end section toward the first side through a central through hole formed in the boss;
• the rotation-transmitting member is provided with a shaft part protruding toward the second side, and a central hole formed in the shaft part opening toward the second side;
• the shaft distal-end section of the input shaft is fitted coaxially into the central hole of the shaft part of the rotation-transmitting member;
• the shaft end section of the input shaft is rotatably supported by the boss of the externally toothed gear via the first bearing positioned between the wave generator and the boss in the axial direction;
• and
• the shaft distal-end section of the input shaft is rotatably supported by the output shaft via the second bearing, the second bearing being mounted between the shaft part of the rotation-transmitting member and the output shaft, and the output shaft, the second bearing and the shaft part of the rotation-transmitting member being disposed concentrically in the radial direction.