Strain wave gearing

A strain wave gearing comprising:

• a rigid internal gear;
• a flexible external gear disposed coaxially inside the internal gear;
• and
• a wave generator that flexes the external gear into a non-circular shape to partially mesh with the internal gear, and moves a meshing position between the two gears in a circumferential direction,
• wherein the external gear has a cylindrical external-tooth forming portion that is flexible in a radial direction and is provided with at least one end being an open end;
• and the wave generator is mounted coaxially inside the external-tooth forming portion,
• wherein the wave generator has:
• a wave-generator plug that is a rigid body having a non-circular contour;
• a wave-generator bearing mounted between a non-circular plug outer peripheral surface of the wave-generator plug and an inner peripheral surface of the external-tooth forming portion;
• and
• a foreign-matter intrusion preventing mechanism that covers a space formed between the wave-generator plug and an inner peripheral surface of the external gear,
• wherein the foreign-matter intrusion preventing mechanism has:
• an annular filter capable of capturing foreign matters mixed in a lubricant passing therethrough;
• and
• a lubricant-impermeable filter attachment plate,
• wherein the filter attachment plate is attached to the wave-generator plug so as to rotate integrally therewith;
• and
• the filter is attached to the filter attachment plate so as to rotate integrally therewith, and is in contact with the inner peripheral surface of the external-tooth forming portion in a slidable state, and
• wherein the filter is provided with a non-circular filter outer peripheral surface similar in shape to a non-circular plug outer peripheral surface,
• the filter is attached to the filter attachment plate so that the non-circular filter outer peripheral surface is in a same phase as the non-circular plug outer peripheral surface, and
• the non-circular filter outer peripheral surface is in contact with the inner peripheral surface of the external-tooth forming portion.

A strain wave gearing comprising:

• a rigid internal gear;
• a flexible external gear disposed coaxially inside the internal gear;
• and
• a wave generator that flexes the external gear into a non-circular shape to partially mesh with the internal gear, and moves a meshing position between the two gears in a circumferential direction,
• wherein the external gear has a cylindrical external-tooth forming portion that is flexible in a radial direction and is provided with at least one end being an open end;
• and the wave generator is mounted coaxially inside the external-tooth forming portion,
• wherein the wave generator has:
• a wave-generator plug that is a rigid body having a non-circular contour;
• a wave-generator bearing mounted between a non-circular plug outer peripheral surface of the wave-generator plug and an inner peripheral surface of the external-tooth forming portion;
• and
• a foreign-matter intrusion preventing mechanism that covers a space formed between the wave-generator plug and an inner peripheral surface of the external gear,
• wherein the foreign-matter intrusion preventing mechanism has:
• an annular filter capable of capturing foreign matters mixed in a lubricant passing therethrough;
• and
• a lubricant-impermeable filter attachment plate,
• wherein the filter attachment plate is attached to the wave-generator plug so as to rotate integrally therewith;
• and
• the filter is attached to the filter attachment plate so as to rotate integrally therewith, and is in contact with the inner peripheral surface of the external-tooth forming portion in a slidable state, and
• wherein the filter attachment plate is provided with a non-circular attachment-palate outer peripheral surface similar in shape to a non-circular plug outer peripheral surface of the wave-generator plug;
• the filter attachment plate is attached to the wave-generator plug in a same phase as the non-circular plug outer peripheral surface;
• and
• the filter is attached to the non-circular attachment-plate outer peripheral surface and is in contact with the inner peripheral surface of the external-tooth forming portion in a state being flexed into a non-circular shape.