Bending meshing type gear device

1. A bending meshing gear device comprising:

an internal gear;

an external gear which meshes with the internal gear;

a wave generator which bends and deforms the external gear; and

a wave generator bearing which is disposed between an outer peripheral surface of the wave generator and an inner peripheral surface of the external gear,

wherein the wave generator bearing comprises:

an outer ring, and

a plurality of rolling bodies which roll with an inner peripheral surface of the outer ring as a rolling surface,

wherein the outer ring is disposed radially inside the external gear,

wherein a pressure is generated between:

the inner peripheral surface of the external gear, and

an outer peripheral surface of the outer ring at a long axis position, the long axis position is at which a distance from a rotation center to a peripheral surface of the wave generator is longest, and

wherein a minimum inner peripheral length of the external gear is larger than a maximum outer peripheral length of the outer ring.

2. The bending meshing gear device according to claim 1 ,

wherein a gap is provided over an entire length of the external gear in an axial direction between the external gear and the outer ring at a short axis position at which the distance from a rotation center to a peripheral surface of the wave generator is shortest.

3. A bending meshing gear device comprising:

an internal gear;

an external gear which meshes with the internal gear;

a wave generator which bends and deforms the external gear; and

a wave generator bearing which is disposed between the wave generator and the external gear,

wherein the wave generator bearing comprises a rolling body and an outer ring, and

wherein a minimum inner peripheral length of the external gear is larger than a maximum outer peripheral length of the outer ring,

wherein an escape portion which is recessed from a surface where the outer ring and the external gear face each other is provided in the outer ring, the external gear, or both thereof, and

wherein an axial length A of a contact portion between the external gear and the outer ring at a long axis position at which a distance from a rotation center to a peripheral surface of the wave generator is longest, a radial length B of a gap g between the external gear and the outer ring at a short axis position at which the distance from the rotation center to the peripheral surface of the wave generator is shortest, and an area C of the escape portion in a cross section passing through the rotation center satisfy a relationship of A×B<C.

4. A bending meshing gear device comprising:

an internal gear;

an external gear which meshes with the internal gear;

a wave generator which bends and deforms the external gear; and

a wave generator bearing which is disposed between the wave generator and the external gear,

wherein the wave generator bearing comprises a rolling body and an outer ring,

wherein a minimum inner peripheral length of the external gear is larger than a maximum outer peripheral length of the outer ring, and

wherein when the outer ring and the external gear are concentrically disposed such that an outer periphery of the outer ring and an inner periphery of the external gear become a perfect circle in a cross section perpendicular to a rotation center and the rolling body is disposed to come into contact with an outer peripheral surface of a cylinder which is concentrically disposed with the outer ring and has a peripheral length of the wave generator, a radial length of a gap between the outer ring and the external gear is larger than a minimum radial length of a gap between the rolling body and the outer ring.

5. The bending meshing gear device according to claim 1 ,

wherein the wave generator has an elliptical outer shape in a cross section perpendicular to a rotation axis, and

wherein the wave generator bearing is disposed between the outer peripheral surface of the wave generator and the inner peripheral surface of the external gear.

6. The bending meshing gear device according to claim 1 ,

wherein the rolling body of the wave generator bearing rolls with the outer peripheral surface of the wave generator as a rolling surface.