Harmonic Drive Systems Inc.

Kabushiki Kaisha Hasegawa Haguruma

Panasonic Corporation

Shoichi Ishikawa

Noboru Takizawa

Yoshihide Kiyosawa

Satoshi Tsuchiya

Jun Nakai

Takashi Okohira

Shunsuke Sasanabe

Yusuke Shibamoto

Kiyoshi Kotake

Seishi Honma

Takahiro Arima

In a strain wave gearing, the addendum tooth profile of an inner gear is defined by a formula and that of an outer gear is by another formula at a principal cross-section located at a tooth-trace-direction center of the outer gear, on the basis of a movement locus (Mc) of &#x3ba;=1 by the teeth of the outer gear with respect to those of the inner gear. The tooth profiles of the dedenda of each of the inner gear and the outer gear are set to any shape that does not interfere with the tooth profile of the addendum of the other gear. It is possible to avoid superimposed flexion-induced bending stresses and tensile stresses caused by load torque arising at the long-axis locations of the outer gear, and the transmission torque capacity of a strain wave gearing can be improved.

Two stress-separation strain wave gearing

The dedendum tooth profiles of the internal teeth and external teeth of a strain wave gearing are prescribed by a first homothetic curve BC and a second homothetic curve AC obtained from a curve segment from a point A, at which the angle formed by the tangent to a movement locus Mc when meshing is approximated by rack meshing and the major axis is &#x398;A, to a low point B. The dedendum tooth profile of the internal teeth is prescribed by a curve formed on the internal teeth in the course of the addendum tooth profile of the external teeth moving from an apex of the movement locus to point A. The dedendum tooth profile of the external teeth is prescribed by a curve formed on the external teeth when the addendum tooth profile of the internal teeth moves from the apex to arrive at point A.

Strain wave gearing with compound meshing that involves congruity of tooth surfaces

In a strain wave gearing, the addendum tooth profile of an internal gear is defined by the formula a and that of an external gear is by the formula b at a principal cross-section located at a tooth-trace-direction center of the external gear, on the basis of a movement locus (Mc) of &#x3ba;=1 by the teeth of the external gear with respect to those of the internal gear. It is possible to avoid superimposition of flexion-induced bending stresses and tensile stresses caused by load torque at the major-axis locations of the external gear, and the transmission torque capacity of a strain wave gearing can be improved.

Strain wave gearing with full separation of two stresses

In a strain wave gearing, the addendum tooth profile of an internal gear is defined by the formula a and that of an external gear is by the formula b at a principal cross-section located at a tooth-trace-direction center of the external gear, on the basis of a movement locus (Mc) of &#x3ba;=1 of the teeth of the external gear with respect to those of the internal gear in the principle cross-section taken at the center of the tooth trace of the external gear obtained when the tooth meshing is approximated by rack meshing. It is possible to avoid superimposition of flexion-induced bending stresses and tensile stresses caused by load torque at the major-axis locations of the external gear, and the transmission torque capacity of a strain wave gearing can be improved.

A strain wave gearing is a negative deflection strain wave gearing. The tooth profile shape for the internally toothed gear is defined by using a convex, basic tooth profile curve, which is a curve portion from an inflection point (A) to a bottom-part point (B) of a moving locus (Mc) of an externally toothed gear with regard to an internally toothed gear obtained by a rack meshing approximation. The tooth profile shape for the externally toothed gear at a principal cross section is defined by a concave, basic tooth profile curve, which is generated in the externally toothed gear by the convex, basic tooth profile curve of the internally toothed gear moving from an apex (C) to an inflection point (A) of the moving locus (Mc). Passing-type meshing that is effective in lubrication is established, and bending stress in the tooth-bottom rim of the externally toothed gear can be reduced.

Passing-type-meshing negative-deflection strain wave gearing

A strain wave gearing includes a rigid internally toothed gear, a flexible externally toothed gear disposed coaxially within the internally toothed gear, and a wave generator fitted within the externally toothed gear. The internally toothed gear and the externally toothed gear are spur gears having module m; and the number of teeth of the externally toothed gear is 2n less than the number of teeth of the internally toothed gear, where n is a positive integer. Taking a transverse cross-section at a prescribed position along a tooth trace direction of the external teeth as a main cross-section, a degree of flexing, with respect to a rim-neutral circle of the externally toothed gear prior to ellipsoidal flexing, of a rim-neutral line of the ellipsoidally flexed externally toothed gear is set, at a position on the major axis in the main cross-section, to 2mn.

Strain wave gearing having continuous-contact tooth profile formed using arcuate tooth profile

The addendum tooth profile of the inner teeth and outer teeth of a strain wave gearing is stipulated by a first and second similar curve obtained from the curve segment from an inflection point to a low point in a movement trajectory when the meshing of both teeth is approximated by rack meshing. The addendum tooth profile of the inner teeth is stipulated by a curve generated at the inner teeth in the process of the addendum profile of the outer teeth moving from the inflection point to the apex of the movement trajectory. The addendum tooth profile of the outer teeth is stipulated by a curve generated at the outer teeth when the addendum profile of the inner teeth moves from the inflection point to the apex. The addendum profile of the outer teeth makes double contact with the addendum profile and dedendum profile of the inner teeth.

Strain wave gearing having double-contact negative deflection tooth profile

With a wave gear device, the gears employ homothetic curve tooth profiles AD, BE. Furthermore, a transposition is applied to the external teeth along the tooth trace such that the movement loci M, Mof the external teeth in a section perpendicular to the axis, from the aperture end to the inner end, share the movement locus Mof the aperture end and bottom portion thereof, and a continuous meshing of the teeth in the tooth trace direction is achieved. Furthermore, the tooth bottom rim thickness of the aperture end of the external teeth is optimized using a modified Goodman diagram, and a tooth bottom rim thickness which takes into account the relationship between the tooth profile and the transmitted torque from the aperture end to the inner end is employed for the flexible external gear.

Wave gear device having tapered flexible external gear

In the strain wave gearing, an involute positive deflection tooth profile of a low pressure angle of less than 20&#xb0; is used as the basic tooth profile for the rigid internal spur gear and the flexible external spur gear in order to increase the effective tooth depth. Continuous meshing of the two gears in the tooth trace direction is made possible by shifting the external teeth so that the linear parts of the rack tooth profiles coincide when viewed along the tooth trace direction. The root rim thickness of the front end of the external teeth of the flexible external spur gear is set to an optimal thickness and the root rim thicknesses at various positions other than the front end of the external teeth in the tooth trace direction are set to appropriate values.

Strain wave gearing with involute positive deflection tooth profile taking rim thickness into consideration

In a wave gear device, an involute tooth profile with the low pressure angle &#x3b1; (&#x3c;20&#xb0;) is employed as a basic tooth profile of external teeth of a flexible external gear. In the principal section of the external teeth, the tooth depth thereof satisfies 2&#x3ba;mn=2(1+c) mn (deflection coefficient &#x3ba;=1+c, 0&#x3c;c&#x3c;0.5), which is larger than the standard one. The shifting of the teeth which takes into account coning is performed along the tooth trace direction of the external teeth, so that straight portions of a rack tooth profile on the respective sections perpendicular to the axis in the tooth trace direction of the external teeth are conformed as viewed along the tooth trace direction. The rack tooth profile of the involute tooth profile is a straight line.

Wave gear device having three-dimensional contacting involute positive deflection tooth profile

In a wave gear device, similarity-curve tooth profiles BC and AC are adopted as addendum tooth profile shapes for gears, the tooth profiles being derived from a movement trajectory Mof an external tooth of a flexible externally toothed gear having zero deviation (&#x3ba;=1), in relation to an internal tooth at a main cross-section. Profile shifting is performed on the external tooth along the tooth trace for a movement trajectory Mof the external tooth to share a bottom portion with the movement trajectory Mat the main cross-section from the main cross-section to an inner edge. Profile shifting is performed on the external tooth along the tooth trace for the movement trajectory of the straight-line tooth-profile portion of the external tooth from the main cross-section to the outer edge to be consistent with the movement trajectory of the straight-line tooth-profile portion of the main cross-section.

Wave gear device having three-dimensional-contact tooth profile

In an elliptical rim neutral line of each axially perpendicular cross section in a tooth trace direction of a flexible externally toothed gear of a wave gear device, external teeth are applied with addendum modification along the external teeth tooth trace direction so that the bending stress generated at the root rim surface of the external teeth that is caused by flexing of the flexible externally toothed gear is averaged out, the maximum value thereof can be reduced, and the transferred torque of the wave gear device can be increased.

Wave gear device provided with tapered flexible externally toothed gear

Disclosed is a wave gear device () for setting the flexible state of the principal section () of a flexible external gear in a normal-deflection state (at a deflection coefficient &#x3ba;=1). The moving locus of a tooth profile in the principal section () is determined by a rack approximation, and a similar curve (BC), which is obtained by similarly transforming a curve (AB) cut from that moving locus, is used to define the fundamental addendum shape of the tooth profile in the principal section. The portion of the tooth profile of the flexible external gear other than the principal section is shifted so that both each negative-deflection side moving locus (M), which is obtained in each plane of rotation to deflect in a negative deflection state (at the deflection coefficient &#x3ba;&#x3c;1) closer to the diaphragm side than the principal section and each positive-deflection side moving locus (M), which is obtained in each plane of rotation to deflect in a positive deflection state (at the deflection coefficient &#x3ba;&#x3e;1) closer to the front end opening side than the principal section, may become curves (Mand M) to contact at the bottom (a point (P)) of a normal-deflection moving locus (M). The partial meshing engagement can also be held at the section other than the principal section in the tooth trace direction, so that the load torque performance of the wave gear device can be advantageously improved.

Wave gear device having three-dimensionally contactable shifted tooth profile

In a wave gear device (), radial deflection of a flexible external gear () is set at 2&#x3ba;mn (&#x3ba;&#x3e;1) which is larger than a normal deflection of 2nm (&#x3ba;=1), and the tooth depth of both gears () is set larger than a standard tooth depth (in case of &#x3ba;=1). Meshing movement locus of both gears () is approximated by a rack in case of &#x3ba;&#x3e;1, and using similarity-transformation curves (AC, AD) obtained by similarly enlarging a curve (AB) on the unmeshing side at the post-stage of meshing from the vertex (deepest meshing position)(A) of the movement locus (M), the dedendum tooth profile portion () of a rigid internal gear () and the addendum tooth profile portion () of the flexible external gear () are defined and then both gears () are brought into continuous contact.

Wave gear device having compound tooth profile of positive deflection meshing

In a wave gear device, similarity curve tooth profiles for defining the tooth-face tooth profile of each of a flexible externally toothed gear and a rigid internally toothed gear is determined from the movement trajectory, relative to a tooth of the rigid internally toothed gear, of a tooth of the flexible externally toothed gear at a main cross-section at which the deflection factor is &#x3ba;=1. Tooth profile curves, which have been subjected to profile shifting corresponding to the difference between the deflection factor &#x3ba;(&#x3e;1) of the opening-end cross-section of the flexible externally toothed gear and the deflection factor &#x3ba; of the main cross-section, are determined from the similarity curves; and the tooth profile curves are used to form the tooth-face tooth profile portions of the two gears. High-gear-tooth compound tooth profiles, defined from the tooth-face tooth profile portions, straight-line tooth profile portions continuing from the tooth-face tooth profile portions, and appropriate tooth-flank tooth profile portions for avoiding interference are used as tooth profiles of the internal teeth and the external teeth. Also, taking coning of the flexible externally toothed gear into account, negative profile shifting is applied from an opening-end cross-section to an inner-end cross-section of the flexible externally toothed gear, and rational meshing between the two gears is obtained along the entire tooth trace.

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Yokohama, Japan

Shoichi Ishikawa