Robot power transmission mechanism for transmitting rotational force and robot drive unit

A power transmission mechanism for a robot, comprising:

• a shaft configured to transmit a rotational force of an electric motor;
• and
• a strain wave gear reducer configured to amplify the rotational force of the electric motor, wherein
• the strain wave gear reducer includes a wave generating member including a cam having an elliptical shape when viewed from a direction of a rotation axis, an elastic tubular member including a plurality of first tooth parts at an outer circumferential surface and being elastically deformable, and an annular member including a plurality of second tooth parts at an inner circumferential surface,
• part of the plurality of first tooth parts of the elastic tubular member and part of the plurality of second tooth parts of the annular member are engaged with each other,
• the shaft includes a spline shaft part at which a plurality of protrusions are formed in a circumferential direction of an outer circumferential surface,
• the wave generating member includes an insertion hole into which the spline shaft part is inserted and that has recesses having a shape corresponding to a shape of the protrusions of the spline shaft part,
• the spline shaft part and the insertion hole have a shape in which a gap in a radial direction is present between the spline shaft part and the insertion hole, and
• the gap has a size such that a rotation center axis of the wave generating member is always movable and alignment is possible due to elasticity of the elastic tubular member in a direction in which an eccentricity with respect to a center axis of the elastic tubular member is canceled.