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.

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 mechanism includes a gear including external teeth, the external teeth including a plurality of tooth parts defined by a cycloid curve, a plurality of contacting members disposed on an outer side and in a circumferential direction of the external teeth, the external teeth being brought into pressure contact with the plurality of contacting members, and a mechanism configured to eccentrically move the gear. A plurality of through holes penetrating the gear in a thickness direction of the gear are formed in the gear in the circumferential direction of the gear, the cycloid curve extends outward from an ideal cycloid curve without the external teeth interfering with the plurality of contacting members, the plurality of contacting members being in contact with the ideal cycloid curve.

A harmonic gear device includes a rigid internal gear, a flexible external gear and a wave generator. The rigid internal gear is an annular component having internal teeth. The flexible external gear is an annular component, which has external teeth and is configured on an inner side of the rigid internal gear. The wave generator is configured on an inner side of the flexible external gear, and deflects the flexible external gear. The harmonic gear device deforms the flexible external gear along with the rotation of the wave generator taking a rotation axis as the center, such that some of the external teeth mesh with some of the internal teeth. The flexible external gear rotates relative to the rigid internal gear in accordance with the difference between the numbers of teeth of the flexible external gear and the rigid internal gear.

The tooth profile contours of a rigid internally toothed gear and a flexible externally toothed gear in this strain wave gearing are stipulated by: meshing portions which each mesh with the opposing gear; tooth-crest-side convex surface portions which, respectively, are smoothly connected to the addendum-side ends of the meshing portions and extend from said ends to the apices of the tooth crests; and tooth-bottom-side concave surface portions which, respectively, are smoothly connected to the dedendum-side ends of the meshing portions and extend from said ends to the deepest parts of the tooth bottoms. The meshing portions and tooth-crest-side convex surface portions are machined portions that are simultaneously machined by topping gear cutting, and there are no edges on the teeth of either gear on the tooth-crest side.

Provided is a method for producing a gear including an intermediate product forming process of solidifying a fluid material to form a gear intermediate product, and a tooth forming process of cutting the gear intermediate product to form teeth.

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.

A system and method for registration of rotary drive shaft in a high-torque environment. The system utilizes a pair of connected harmonic drives to allow the clocking or registration of the rotary drive shaft without backlash and without requiring gearing changes as a result of a single harmonic drive. The pair of connected harmonic drives is coupled together by a tandem coupling.

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).

A three-dimensional tooth profile of internal teeth in a strain wave gearing is a basic internal-teeth tooth profile at an internal-teeth outer end, and is a reduced tooth profile, in which the basic internal-teeth tooth profile is proportionally reduced only in the lateral direction, at other tooth-trace-direction positions. A three-dimensional tooth profile of external teeth is a basic external-teeth tooth profile at an external-teeth outer end, and is an increased tooth profile, in which the basic external-teeth tooth profile is proportionally increased only in the lateral direction, at other tooth-trace-direction positions. Tooth cutting process becomes easier than when only the external teeth employ a three-dimensional tooth profile. Since the tooth profiles, which are proportionally reduced and increased only in the lateral direction along the tooth trace direction, are employed, it is further easier in tooth cutting process.