Harmonic Drive Systems Inc.

Sumitomo Electric Sintered Alloy, Ltd.

Harmonic Drive Aktiengesellschaft

Masaru Kobayashi

Tatsuro Hoshina

Yoshihide Kiyosawa

Toshihiko Kaji

Yoshihiro Tanioka

Yusuke Shibamoto

Rolf Slatter

Daisuke Orii

Hideo Asawa

Junichi Kurogi

Stéphanie Moune

Akira Maruyama

Akira Nagai

Yuki Honda

Hiroshi Takizawa

A strain wave gearing has a detection mechanism that detects thrust force generated between a wave generator and an externally toothed gear. The detection mechanism is provided with a strain gauge or piezoelectric load meter, and a transmission mechanism that transmits thrust force from the wave generator to the load meter. Only rotational force is transmitted to the wave generator from a from a motor shaft side, and axial force is not transmitted. The load meter and the transmission mechanism provide a small and compact detection mechanism that can be incorporated inside the externally toothed gear. In the strain wave gearing into which the detection mechanism is incorporated, operation control according to detected thrust force becomes possible using thrust force information during operation.

Strain wave gearing and actuator

A strain wave gearing includes a wave generator that creates a state in which a flexible externally toothed gear is flexed into a non-circular shape and partially meshes with a rigid internally toothed gear, and that includes a wave plug having a non-circular outer peripheral surface and a wave bearing attached to the non-circular outer peripheral surface of the wave plug. The wave bearing includes an outer ring having an inner peripheral surface and an outer-ring-side raceway surface formed on the inner peripheral surface, an inner ring having an outer peripheral surface and an inner-ring-side raceway surface formed on the outer peripheral surface, and a plurality of rolling elements rotatably inserted between the outer-ring-side raceway surface and the inner-ring-side raceway surface.

Strain wave gearing

In the interior of a device housing of a strain wave gearing, a detection mechanism is incorporated at a site on the outer peripheral side of a hub of a wave generator. The hub of the wave generator is linked to a motor shaft so that axial force does not act thereon. The detection mechanism detects minute displacements in the axial direction that occur in the hub of the wave generator due to thrust acting on the wave generator. Thrust acting on the wave generator is obtained on the basis of the detected minute displacements. With this strain wave gearing in which the detection mechanism is incorporated, operation control that is responsive to sensed thrust is possible through the use of thrust information during operation.

In a strain wave gearing, a thrust force applied on an externally toothed gear during an increased-speed operation causes the externally toothed gear to move along an axis in a first direction, and the output-side end surface thereof is pressed, by a prescribed force, against a friction surface of a friction plate integrated with a rotating shaft part of a strain wave generator. Torque transmission efficiency can be reduced only during increased-speed operation, by means of a friction loss occurring between the externally toothed gear and the friction plate. When large load torque is applied from an output shaft which is an output-side member during reduced-speed operation, retention torque of the strain wave generator which is an input-side member during speed-reduction operation can be reduced.

A powder supply mechanism, which is provided with a press-molded article obtained by consolidating a solid lubricant powder in advance, is incorporated into an inner-side space of an externally toothed gear of a strain wave gearing. While the strain wave gearing is operating, the press-molded article is worn down by the friction plate, whereby the powder supply mechanism can incrementally supply very small amounts of a solid lubricant abrasion powder from the press-molded article over an extended period. It is possible to suppress any reduction in efficiency caused by loss torque produced due to a large amount of the solid lubricant powder infiltrating gaps in, inter alia, a contact section of a wave generator rotating at high speed. Thus, it is possible to extend the service life of the powder-lubricated strain wave gearing while keeping the efficiency consistently high.

Powder lubrication method of strain wave gearing

A strain wave gearing is lubricated by a non-hydrophobized powder enclosed in an internal space until the strain wave gearing is fully broken in, and the non-hydrophobized powder is transferred to contact surfaces of contact parts to form a lubricating film. During operation under load, the strain wave gearing is lubricated by a hydrophobized powder enclosed in the internal space instead of the non-hydrophobized powder. Each of the powders used is a powder of an ionic crystalline compound (MoS2, WS2, etc.) having a layered crystal structure. By lubricating the strain wave gearing with the hydrophobized powder during operation under load, any temporary decrease in efficiency at the start of operation is minimized and stable operation of the strain wave gearing can be maintained.

Method for lubricating strain wave gearing

In a strain wave gearing, in order to regulate axial-direction movement of an externally toothed gear thereof, first balls are directly interposed between a first annular end surface and a device housing, whereby the first annular end surface and the device housing are in rolling contact with one another. Similarly, second balls, are directly interposed between a second annular end surface and an output shaft, whereby the second annular end surface and the output shaft are in rolling contact with one another. No contact occurs other than rolling contact of contact portions. Additionally, pressure is applied in the axial direction to the portions that make rolling contact, and axial-direction rattling is eliminated, whereby axial-direction movement of the externally toothed gear is reliably suppressed, and generation of high thrust force is prevented.

A push-pull solenoid is provided with a cylindrical guide member that is fixed to a case. A circular outer peripheral surface of a plunger is in contact with a friction guide surface formed on a circular inner peripheral surface of the guide member, and slides along the friction guide surface. Frictional force due to contact with the friction guide surface is always acting on the plunger, so it is possible to suppress impact-like contact of the plunger with an object to be manipulated during suctioning, and vibration and noise caused thereby. Moreover, over-recovery and falling-out of the plunger after suction is released can also be prevented.

Push-pull solenoid

A strain wave gearing has a wave generator provided with a plurality of rollers mounted between an ellipsoidal outer peripheral surface of a plug and an inner peripheral surface of an externally toothed gear. The plug is formed with recesses along the ellipsoidal outer peripheral surface. The recesses open in a first end surface of the plug facing toward a diaphragm of the externally toothed gear. The radial rigidity of the plug is relatively low in the side having the first end surface in the direction of a plug axis. When viewed along the direction of the plug axis, the respective rollers can be brought into linear contact with the inner peripheral surface of the externally toothed gear at positions on the long axis (Lmax) of the elliptically-flexed externally toothed gear, so as not to occur one-sided contact state.

Strain wave gearing having roller-bearing-type wave generator

The flat strain wave gearing is provided with an axially arranged rigid gear, flexible gear and wave generator. The flexible gear forms a flat truncated cone shape, has a tooth formation portion connected via a bellows-shaped cross-sectional diaphragm to a rigid boss which is an output shaft linking part. The flat strain wave gearing can ensure axial flexibility of the tooth formation portion, and can enable teeth of the flexible gear to mesh favorably with teeth of the rigid gear in the axial direction in each position in the tooth trace direction. Local bias of the load torque in the meshing portion in the tooth formation portion can also be suppressed.

Flat strain wave gearing

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.

Wave generator and strain wave gearing

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.

Sliding contact-type wave generator and strain wave gearing

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.

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.

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.

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Azumino, Japan

Masaru Kobayashi