A gearing includes an internal gear, a flexible external gear partially meshing with the internal gear and relatively rotating about a rotation axis to the internal gear, and a wave generator provided inside of the external gear and moving a mesh position between the internal gear and the external gear in a circumferential direction about the rotation axis, wherein the external gear includes an external tooth having an external tooth surface, the external tooth surface has an external tooth convex pattern including a first convex portion and a second convex portion extending in directions crossing directions of a tooth trace of the external tooth and arranged adjacent to each other in the directions of the tooth trace, and a distance between the first convex portion and the second convex portion is from 80 μm to 520 μm.

The present application discloses a double-flexspline harmonic reducer, comprising a strong flexspline (3) , a weak flexspline (2), a wave generator (1), and a deformation stopper (4) of the strong flexspline; the strong flexspline and the weak flexspline are coaxially fixed axially and radially, the strong flexspline and the weak flexspline are respectively provided with teeth that can engage with each other; the number of teeth of the strong flexspline and the weak flexspline are different; the wave generator is used to make the weak flexspline to undergo non-circular elastic deformation and partially engage with the strong flexspline; the contact part of the strong flexspline and the weak flexspline is subjected to the radial pressure of the weak flexspline to generate a non-circular elastic deformation, a flexible tubular wall of the strong flexspline has a toothless surface, and a limiting contact surface is processed on the toothless surface.

Provided is a plate harmonic reducer, and more particularly, a plate harmonic reducer, in which design may be further simplified and a manufacturing cost may be reduced.

The present invention relates to a harmonic gear device in which a first similarity curve obtained by similarly transforming a reference curve representing a moving locus of an external tooth with respect to an internal tooth in a non-deflected state and a second similarity curve generated by similarly transforming the first similarity curve are used as a criterion for generating a tooth profile, wherein the present invention may provide the harmonic gear device that enlarges a first curve represented by a moving locus of positive deflection located above the apex of the reference curve among the moving loci of positive deflection of the external teeth on the basis of the reference curve to approximate an approximate reference point arranged on the second similarity curve to create a second curve, and uses the second curve as the top of the tooth profile of the external tooth.

There is provided a technique capable of increasing support rigidity of a bearing when a support member expands due to moisture absorption. A power transmission device includes: a rotary shaft; a support member disposed outside the rotary shaft in a radial direction; a bearing disposed between the rotary shaft and the support member; and a fitting member fitted to an outer peripheral portion of the support member. The fitting member is made of a material having lower hygroscopicity than hygroscopicity of a material of the support member.

A gear includes a tubular portion and a diaphragm portion. The diaphragm portion extends in a direction including a radial component from one axial end portion of the tubular portion. The portion includes a first portion and a second portion. The first portion is on one axial side of the portion. The second portion is on another axial side relative to the first portion. The second portion includes teeth protruding radially outward. A maximum value of a thickness of the diaphragm portion is equal to or less than twice a distance from radially outer ends of the teeth to a radially inner surface of the second portion, and a minimum value of a thickness of the first portion is equal to or less than half the maximum value of the thickness of the diaphragm portion.

An externally toothed gear of a cup-type strain wave gearing has external teeth, the tooth profile of which gradually changes in the tooth-trace direction. The external teeth are formed with an external teeth portion capable of meshing with internal teeth of an internally toothed gear, a first external teeth extension portion and a second external teeth extension portion, in which the first and second external teeth extension portions do not mesh with the internal teeth. The second external teeth extension portion has a narrowing tapered tooth profile so that the second external teeth extension portion serves as a guide when the external teeth is inserted into the internal teeth. The work of assembling the externally toothed gear in the internally toothed gear is made easier.

An elastic transmission element is used in a strain wave gear. Such strain wave gears are also referred to as Harmonic Drives. The elastic transmission element is also referred to as a flexspline. Outer toothing is formed on the elastic transmission element. Furthermore, at least one strain gauge for measuring a mechanical strain of the elastic transmission element is arranged on the elastic transmission element. The at least one strain gauge is formed as a coating directly on a metallic surface of the elastic transmission element.

A relieving portion is formed between a first external tooth portion and a second external tooth portion in the external teeth of a flexible externally toothed gear of a flat strain wave gearing. The length L1 of the relieving portion in the tooth trace direction is within the range of 0.1 to 0.5 of the tooth width L of the external teeth. The maximum relieving amount t from the tooth top land of an external tooth in the relieving portion is 3.3×10.sup.−4<t/PCD<6.3×10.sup.−4 where the PCT is defined as the pitch circle diameter of the external teeth. The tooth face load distribution of the external tooth in the tooth trace direction can be equalized, and a flat strain wave gearing having a high transmitted-load capacity can be achieved.

Provided is a double-flexspline harmonic reducer, comprising a strong flexspline (3), a weak flexspline (2) and a wave generator (1). The strong flexspline (3) and the weak flexspline (2) are coaxially fixed in an axial direction and a radial direction, and teeth which can be engaged with each other and are different in the number thereof are provided on the strong flexspline (3) and the weak flexspline (2) respectively. The wave generator (1) causes the weak flexspline (2) to undergo non-circular elastic deformation and then to partially engage with the strong flexspline (3), and a contact portion of the strong flexspline (3) and the weak flexspline (2) undergoes non-circular elastic deformation under a radial pressure from the weak flexspline (2). A wall thickness of the strong flexspline (3) is greater than or equal to 2 times and less than 5 times that of the weak flexspline (2).