Strain wave gearing

A strain wave gearing comprising:

• a rigid internally toothed gear;
• a flexible externally toothed gear;
• a wave generator for flexing the externally toothed gear in a radial direction to form meshing portions thereof with the internally toothed gear in positions that are separated in a circumferential direction and for moving the meshing portions in the circumferential direction;
• and
• a non-meshing region formed in part of each of the meshing portions in a tooth trace direction,
• wherein the internally toothed gear and the externally toothed gear are spur gears, or helical gears having a single tooth trace;
• the wave generator has a wave bearing for supporting the externally toothed gear from a radially inner side thereof;
• and
• the non-meshing region is a region that has a width in the tooth trace direction so as to include a support center of the wave generator for supporting the externally toothed gear;
• wherein the non-meshing portion is defined, in the tooth trace direction, by a portion where no external teeth are formed.

A strain wave gearing comprising:

• a rigid internally toothed gear;
• a flexible externally toothed gear;
• a wave generator for flexing the externally toothed gear in a radial direction to form meshing portions thereof with the internally toothed gear in positions that are separated in a circumferential direction and for moving the meshing portions in the circumferential direction;
• and
• a non-meshing region formed in part of each of the meshing portions in a tooth trace direction,
• wherein the internally toothed gear and the externally toothed gear are spur gears, or helical gears having a single tooth trace;
• the wave generator has a wave bearing for supporting the externally toothed gear from a radially inner side thereof;
• and
• the non-meshing region is a region that has a width in the tooth trace direction so as to include a support center of the wave generator for supporting the externally toothed gear;
• wherein the non-meshing region is defined, in the tooth trace direction, by a relieving portion where relieving is applied to external teeth of the externally toothed gear so that a tooth-depth dimension or a tooth-thickness dimension thereof becomes small.