Strain wave gearing and actuator

A strain wave gearing comprising:

• a device housing;
• a rigid internally toothed gear;
• a flexible externally toothed gear that is made to flex into a non-circular shape to partially mesh with the internally toothed gear;
• and
• a wave generator for generating a wave motion that repeatedly flexes each part in a circumferential direction of the externally toothed gear in a radial direction so that partial meshing positions of the externally toothed gear with the internally toothed gear move in a circumferential direction of the internally toothed gear,
• wherein the wave generator has a plurality of wave-generating members mounted to the device housing at fixed positions at a prescribed angular interval along the circumferential direction of the externally toothed gear;
• and
• each of the wave-generating members has an outer circumferential cam surface for facing each part of the externally toothed gear in the radial direction and for repeatedly flexing each part of the externally toothed gear in the radial direction with a prescribed amplitude when the wave-generating member rotates centered on the rotation center line that is parallel to a center axis line of the externally toothed gear;
• wherein the outer circumferential cam surface of each of the wave-generating members is eccentric with respect to a respective rotation center line of each of the wave-generating members.