Harmonic Drive Systems Inc.

Harmonic Ad, Inc.

Matsushita Electric Industrial Co., Ltd.

Norio Shirokoshi

Yoshihide Kiyosawa

Hiroshi Yamazaki

Syuhei Kobayashi

Daisuke Orii

Harushige Aoyagi

Satoshi Kishi

Naomi Shirasawa

Yuya Murayama

Satoru Kimura

Yoshitomo Mizoguchi

Hiroshi Kameda

Yoshihiro Tanioka

Hiroshi Nakagawa

Yasushi Ono

In each of tooth tip surfaces of internal teeth of an internally toothed gear and external teeth of an externally toothed gear of a strain wave gearing, lubricant passage grooves are formed at fixed intervals along the tooth trace direction. Each of the lubricant passage grooves is an inclined groove that extends in a direction inclined to one side in the tooth trace direction. The inclined grooves facilitate the flow of the lubricant such as grease confined in gaps between the internal teeth and the external teeth and thus the lubricant is efficiently supplied to the tooth surfaces of both teeth.

Lubricating structure for gear tooth surface

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.

Strain wave gearing provided with three-dimensional tooth profile

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. The tooth tip circle of an internal-teeth inner-end-side portion of the internal teeth is larger than that of other portions and does not interfere with the external teeth. The external teeth and the internal teeth mesh three-dimensionally, the teeth do not interfere at the internal-teeth inner-end side.

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.

Strain wave gearing

An outer-ring lubrication groove pattern formed in an outer-race raceway surface and an inner-race lubrication groove pattern formed in an inner-race raceway surface of a wave generator bearing of a strain wave gearing device are patterns in which linear lubrication grooves having very small widths and depths of several micrometers or less are arranged at fine pitches of several micrometers or less. The inner-race lubrication groove pattern includes a second groove pattern formed in long-axis-side inner-race raceway surface portions to hold the lubricant, and a first groove pattern formed in short-axis-side inner-race raceway surface portions to hold the lubricant and guide the lubricant to the second groove pattern. This configuration improves the contact state between balls and the inner-race and outer-race raceway surfaces of the wave generator bearing, thus reducing the coefficient of friction therebetween.

Wave generator of strain wave gearing device

In a strain wave gearing device, fine first and second lubricant-holding grooves for holding lubricant are formed at fine pitches in an outer-race external peripheral surface of a wave generator bearing and an outer-race-contacting internal peripheral surface portion of an externally toothed gear in contact therewith. Fine lubricant-guiding grooves for guiding the lubricant to the outer-race-contacting internal peripheral surface portion are formed at fine pitches in a second internal peripheral surface portion, which adjoins the outer-race-contacting internal peripheral surface portion, of an internal peripheral surface of the externally toothed gear. This configuration improves the contact state between the outer-race-contacting internal peripheral surface portion of the externally toothed gear and the outer-race external peripheral surface, thus suppressing fretting wear occurring in these surfaces.

Strain wave gearing device

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.

Wave generator for strain wave gearing

When a strain wave gearing is used in an application for an operation of repeating startup/stopping, an outer-side lubrication portion and an inner-side lubrication portion, which are lubricated using different types of grease, remain in a communicating state without being divided using a seal member or the like. The outer-side lubrication portion is supplied with a much smaller amount of grease than the amount that would be required if used in an application such as a steady operation. Similarly, the inner-side lubrication portion is also supplied with a much smaller amount of grease than the amount that would be required if used in an application such as a steady operation. Essentially, the outer-side lubrication portion and the inner-side lubrication portion can be lubricated appropriately using different types of grease, without the grease becoming mixed.

Method for lubricating strain wave gearing

A cup-type strain wave gearing having a unit structure and having: a stationary-side part including a unit housing and an internally toothed gear; a driving-side part including an output member and an externally toothed gear; and a sliding bearing supporting the stationary-side part and the driving-side part in the radial direction and the thrust direction in a state in which relative rotation is possible. The sliding bearing has a cylindrical bushing accommodated in a radial gap, and annular bushings accommodated respectively in thrust gaps. Thus, it is possible to provide an advantageous strain wave gearing having a unit structure that is more lightweight and compact than when a rolling bearing is used.

Strain wave gearing having unit structure

In a unit-type strain wave gearing, a rotating-side member, which is constituted by a second internally toothed gear and an output shaft is supported, via a first sliding bearing and a second sliding bearing, on a fixed-side member so as to be capable of relative rotation, the fixed-side member being constituted by a unit housing and a first internally toothed gear. Sliding bearing surfaces of the first sliding bearing and sliding bearing surfaces of the second sliding bearing are defined by a conic surface having a central axis line as a center line. It is possible to realize a unit-type strain wave gearing which is advantageous in making smaller and more compact than when a roller bearing is used. It is also easier to adjust the gap between the sliding bearing surfaces because a radial sliding bearing having no function to adjust the radial gap is obviated.

Unit-type strain wave gearing

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.

A cup-shaped strain wave gearing has an externally toothed gear formed with a cylindrical extension portion extending from an end of an external tooth forming portion of the externally toothed gear. A space between the external peripheral surface of the cylindrical extension portion and an end face of an internally toothed gear is sealed by an oil seal. A space between an outer-side lubrication portion on the outer side of the externally toothed gear and an inner-side lubrication portion on the inner side of the externally toothed gear is blocked by a lubricant-mixing-prevention part configured from the cylindrical extension portion and the oil seal. The mixing of different types of lubricants supplied to the outer-side and inner-side lubrication portions can be effectively prevented.

Strain wave gearing provided with lubricant-mixing-prevention part

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, D&#x2264;D is satisfied where Dis 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.

Cup-type strain wave gearing

A strain wave gearing wherein the tooth profile of an external teeth of a cup-shaped or silk-hat-shaped external gear is set as follows. The tooth-tip tooth thickness decreases gradually from an external-teeth outer end toward an external-teeth inner end along an external tooth trace direction. In addition, a pressure angle at a pitch point (P) increases gradually from the external-teeth outer end toward the external-teeth inner end along the external tooth trace direction. Thus, it is possible to realize a cup-type or silk-hat-type strain wave gearing in which external teeth mesh with internal teeth in a wide range along the tooth trace direction, rather than only in one cross-section perpendicular to the axis in the tooth trace direction.

Strain wave gearing having 3-dimensional meshing tooth profile

In a planetary gear device series composed of eight kinds of planetary gear devices with gear reduction ratios of 3 to 10, the planetary gear device of each gear reduction ratio uses an internal gear with 108 teeth or a slightly different number of teeth, and the module is common among the planetary gear devices of all gear reduction ratios. The combinations of the sun gear teeth number Za and the internal gear teeth number Zc in the planetary gear device of each reduction ratio are given in Table 1 of this application.

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Azumino, Japan

Norio Shirokoshi