Abstract: A wave bearing of a wave generator of a strain wave gearing is provided with steel or stainless steel cylindrical hollow rollers between an inner-race-side raceway surface and an outer-race-side raceway surface, the hollow rollers serving as rolling elements. The ratio Di/Do of the inner diameter Di to the outer diameter Do of the hollow rollers is set to 0.95 or more. The relative radius of curvature of hollow rollers that have been flexed into an ellipsoidal shape increases with respect to the inner-race raceway surface and the outer-race raceway surface with which the hollow rollers are in contact, and the Hertz maximum contact stress is reduced. The hardness of the hollow rollers, the inner-race raceway surface, and the outer-race raceway surface can be reduced.

Abstract: A restraint mechanism for limiting the movement of the flexible external gear of a flat strain wave gearing in the axial direction has a first restraining member installed in a floating state in a first recess and a second restraining member installed in a floating state in a second recess. The restraining member is able to limit the movement of the flexible external gear in the axial direction to a range in which there are no difficulties during actual use. Moreover, compared with when movement of the flexible external gear is limited using members that are disposed at fixed positions, it is possible to reduce the sliding abrasion that occurs between the flexible external gear and the first and second restraining members.

Abstract: A wave gear device includes a circular spline that has an annular shape and rigidity; a flex spline that has an annular shape and flexibility, and is disposed in the circular spline; and a wave generator that is disposed in the flex spline, is configured to cause the flex spline to be distorted in a radial direction and is configured to partially mesh with the circular spline, and is configured to move a meshing position between the circular spline and the flex spline in a circumferential direction. The ratio of the Vickers hardness on an inner circumferential surface of the flex spline to the Vickers hardness on an outer circumferential surface of the wave generator is 1.2 or more and 1.7 or less.

Abstract: In a wave generator for a strain wave gearing, a plug outer peripheral surface of a rigid wave plug has a non-circular profile and is fixed to an inner-race inner peripheral surface of a wave bearing by press-fitting and using an adhesive. The plug outer peripheral surface is a groove formation surface in which microgrooves are formed as adhesive-retaining grooves that can retain the adhesive. When the wave plug is press-fitted into the wave bearing, the amount of adhesive that is scraped out from therebetween is reduced and the bonding strength therebetween can be increased while also preventing unevenness of the bonding strength.

Abstract: A strain wave gearing wherein the outer circumferential surface of an outer ring of a wave generator is in contact with an inner-circumferential-surface portion of a flexible externally toothed gear, and a release groove, which is not in contact with the outer circumferential surface, is formed in the inner-circumferential-surface portion. The release groove is formed in a region containing a ball raceway groove. The groove depth of the release groove gradually increases from both sides of the groove in the groove width direction toward a deepest portion of the groove provided at an intermediate portion in the groove width direction. By providing the release groove, it is possible to smooth the distribution of pressing force of the wave generator acting on the externally toothed gear in the tooth-trace direction. In addition, the tooth root fatigue strength and the transmission torque capacity of the externally toothed gear can be improved.

Abstract: In a rotation transmission mechanism that transmits the rotational driving force of a motor to a load-side member via a speed reducer, a strain wave gearing is used as the speed reducer, and the allowable load torque of members in the powertrain other than the strain wave gearing is greater than a predetermined upper-limit load torque. The allowable load torque of the strain wave gearing is dictated by the ratcheting torque, which is set so as not to exceed the upper-limit load torque. In an overload state, ratcheting is generated in the strain wave gearing, so that the strain wave gearing functions as a mechanical fuse. Other power transmission members can be protected from an overload state without adding a separate member such as a torque limiter.

Abstract: A rotary actuator has a hollow motor and hollow reduction gears arranged coaxially on either side of the hollow motor. A rotary shaft is arranged so as to pass through a hollow motor shaft of the hollow motor. The hollow reduction gears have hollow input shafts connected to the shaft ends on either sides of the hollow motor shaft. The hollow reduction gears have hollow output shafts connected to sections of the rotary shaft protruding from both ends of the hollow motor shaft. The connection position of the hollow output shaft with respect to the rotary shaft can be adjusted in the rotational direction. A load is rotationally driven by the rotary shaft. By increasing the axial length of the hollow motor, it is possible to obtain a small-diameter rotary actuator having a rotational output with large torque.

Abstract: A strain wave gearing has a wave generator which flexes an externally toothed gear in a radial direction to form meshing portions thereof with an internally toothed gear in positions that are separated along a circumferential direction of the externally toothed gear. When the wave generator rotates, the meshing portions move in the circumferential direction. Non-meshing regions are formed in part of the meshing portions along the tooth trace direction thereof. The non-meshing regions are those of a prescribed width including the support center of a wave bearing in the tooth trace direction. The concentration of stress in the tooth root of the externally toothed gear can be alleviated, and the tooth-root fatigue strength of the externally toothed gear can be increased.

Abstract: A wave generator of a wave gear device flexes an externally toothed gear into a shape along an elliptical closed curve to form engaging portions of the externally toothed gear with an internally toothed gear at two places, namely at both ends of the major axis, and to move the engaging portions in the circumferential direction. The elliptical closed curve has a non-point symmetric shape. For example, the elliptical closed curve is a line symmetric closed curve that is not symmetric about the minor axis, and is symmetric about only the major axis. In the non-point symmetric state, the engaging portions are formed at both ends in the major axis direction. By selecting different shapes for the engaging portions at the two locations of the major axis, vibration attributed to a secondary angular transmission error component generated along with the rotation of the wave generator can be reduced.

Abstract: A wave generator for a strain wave gearing is provided with a rigid plug having an ellipsoidal plug-outer-circumferential surface, and a ring-shaped displacement body that is flexed to an ellipsoidal shape by the plug. The ring-shaped displacement body is provided with a plurality of radially arranged displacing sections. The plug-contacting surfaces of the displacing sections are in sliding contact with the plug-outer-circumferential surface and when the plug rotates, the displacing sections are repeatedly displaced in the radial direction. By the displacement of the displacing sections, wave motion is generated in an external gear. It is possible to achieve a wave generator capable of generating wave motion in the external gear with a small rotational torque.

Abstract: A wave gear device includes a circular spline that has an annular shape and rigidity; a flex spline that has an annular shape and flexibility, and is disposed in the circular spline; and a wave generator that is disposed in the flex spline, is configured to cause the flex spline to be distorted in a radial direction and is configured to partially mesh with the circular spline, and is configured to move a meshing position between the circular spline and the flex spline in a circumferential direction. The ratio of the Vickers hardness on an inner circumferential surface of the flex spline to the Vickers hardness on an outer circumferential surface of the wave generator is 1.2 or more and 1.7 or less.

Abstract: A strain wave gearing has a rigid internally toothed gear, a flexible externally toothed gear, and a sliding-contact type wave generator. The wave generator has: a plurality of gear pressing members that flexes the externally toothed gear in the radial direction at positions at equal angular intervals in the circumferential direction to form plurality of meshing portions which mesh with the internally toothed gear; and piezoelectric elements that generate ultrasonic vibration of 20 kHz to 80 kHz in the gear pressing members in the radial direction. Ultrasonic vibration is applied at contact sites where the gear pressing members and the externally toothed gear contact each other. As a result of a squeeze film effect, the apparent friction coefficient of each contact surface at the contact sites can be greatly reduced and rotational torque, of the wave generator can be reduced.

Abstract: In a rotation transmission mechanism that transmits the rotational driving force of a motor to a load-side member via a speed reducer, a strain wave gearing is used as the speed reducer, and the allowable load torque of members in the powertrain other than the strain wave gearing is greater than a predetermined upper-limit load torque. The allowable load torque of the strain wave gearing is dictated by the ratcheting torque, which is set so as not to exceed the upper-limit load torque. In an overload state, ratcheting is generated in the strain wave gearing, so that the strain wave gearing functions as a mechanical fuse. Other power transmission members can be protected from an overload state without adding a separate member such as a torque limiter.

Abstract: In a rotation transmission mechanism that transmits the rotational driving force of a motor to a load-side member via a speed reducer, a strain wave gearing is used as the speed reducer, and the allowable load torque of members in the powertrain other than the strain wave gearing is greater than a predetermined upper-limit load torque. The allowable load torque of the strain wave gearing is dictated by the ratcheting torque, which is set so as not to exceed the upper-limit load torque. In an overload state, ratcheting is generated in the strain wave gearing, so that the strain wave gearing functions as a mechanical fuse. Other power transmission members can be protected from an overload state without adding a separate member such as a torque limiter.

Abstract: A wave generator of a strain wave gearing is provided with a rigid plug, a wave bearing mounted to the ellipsoidal outer peripheral surface of the rigid plug, and four elastic claws that rotate integrally with the rigid plug. The balls of the wave bearing include balls in a loose state and balls in a tight state. The loose-state balls adjacent to the tight-state balls are applied with braking force by the elastic claws immediately before they transition into a tight state, and the orbital motion thereof is temporarily prevented or suppressed, whereby the gaps between the loose-state balls and the adjacent tight-state balls are secured. It is possible to prevent increase in rotational torque, damage to the balls or other defects due to ball-to-ball contact by the tight-state balls.

Abstract: A wave generator for a strain wave gearing makes a flexible externally toothed gear to flex into an elliptical shape and mesh with rigid internally toothed gears, and makes meshing positions of the flexible externally toothed gear with the both gears to move in a circumferential direction. On the inner side of a rigid plug of the wave generator, a plug support ring is secured and integrated. The rigid plug is formed from an iron-based material, and the plug support ring is formed from a high-rigidity material that is more rigid than the iron-based material. Since deformation of the rigid plug is suppressed, the wave generator provided with a large hollow part can be obtained.

Abstract: A strain wave gearing has a cup-shaped externally toothed gear that is provided with a body formed with external teeth, a diaphragm extending from an end of the body, and a rigid boss integrally formed in the diaphragm. The ratio B/A is set equal to or less than 0.59 where A is the reference pitch circle diameter of the external teeth and B is the outer diameter of the boss. The radial length from the inner peripheral edge of the diaphragm to the outer peripheral edge thereof in the present externally toothed gear is large. This enables to reduce bending stress generated in each part of the externally toothed gear due to coning, and a meshing state of the external teeth with the internal teeth in the tooth trace direction can also be improved, whereby further flattening of the externally toothed gear can be realized.

Abstract: In a silk hat-shaped external gear for a strain wave gearing, t(A)>t(C)>t(D)>t(B) is satisfied, where the thicknesses of the inner circumferential end (A), the middle part (B) and the outer circumferential end (C) of the diaphragm body portion of a diaphragm are t(A), t(B) and t(C), and where the thickness of the barrel-side end part (D) of the curved portion of the diaphragm is t(D). With reference to the thickness of the middle part (B), the thickness of the inner circumferential end (A) of the diaphragm is set so as to be thicker than conventional silk hat-shaped external gears. It is possible to realize an externally toothed gear capable of preventing diaphragm rupture due to thrust force at high load torque and having high fatigue strength.

Abstract: The wave generator of a strain wave gearing is provided with an ellipsoidally contoured wave generator plug and a wave generator bearing. The wave generator bearing is provided with an annular body fitted between inner and outer races in a sliding contact state. The annular body is composed of an endless coil spring and has a rigidity that is able to maintain a constant gap between the inner and outer races. The annular body also has a specified overall flexibility in the radial direction so that the annular body can be flexed into an ellipsoidal shape by the wave generator plug. Since sliding occurs between the annular body and the inner race when the wave generator plug rotates, it is possible to generate a wave motion in an externally toothed gear with a small rotational torque.

Abstract: A strain wave gearing has a rigid internally toothed gear, a flexible externally toothed gear, and a wave generator. Before being flexed by the wave generator, the externally toothed gear has a cylindrical body part, an inside diameter of which is such that the inside diameter D is smallest at a rear end thereof and increases gradually from the rear end to an opening end thereof. After being flexed by the wave generator, D1?D is satisfied where D1 is the minor diameter of an elliptical inner circumferential surface of the opening end of the cylindrical body part. The externally toothed gear, which is provided with such a tapered cylindrical body part, is suitable for manufacturing by die molding such as casting, and can also alleviate excessive uneven contact thereof with a wave bearing.