Harmonic Drive Systems Inc.

Harminic Drive Systems Inc.

Noboru Takizawa

Yoshihide Kiyosawa

Jun Handa

Xin Yue Zhang

Shoichi Ishikawa

XinYue Zhang

Keiji Ueura

Stéphanie Moune

Naomi Shirasawa

Yusuke Shibamoto

Takahiro Arima

Go Kuroiwa

Yutaka Miyazawa

Takahiro Oukura

Stephanie Moune

Yoshito Yamamoto

A hollow strain-wave gear device () has a wave generator (), a wave generator plug () of which is integrally formed in a portion of a hollow rotating shaft (). A plug reinforcement part (), which is adjacent to the wave generator plug (), has a thickness larger than that of the wave generator plug (), and is integrally formed in the hollow rotating shaft (). The wave generator plug () is reinforced by the highly rigid plug reinforcement part () formed adjacently to the wave generator plug (). It is thus possible to prevent or suppress a decline in the rigidity of the wave generator plug () when the hollow rotating shaft has a thin thickness in order to reduce the weight of the hollow rotating shaft () and increase the diameter of the hollow portion thereof. Consequently, it is possible to suppress a decline in ratcheting torque.

Hollow strain-wave gear device

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different teeth numbers, and a gap formed between these teeth as a cutter clearance area for tooth cutters. The maximum width Lof the gap is 0.1 to 0.3 times the width L of the externally toothed gear. The depth from the tooth top land of the first external teeth to the deepest part of the gap is 0.9 to 1.3 times the depth of the first external teeth, and the depth from the tooth top land of the second external teeth to the deepest part of the gap is 0.9 to 1.3 times the depth of the second external teeth. The tooth bottom fatigue strength of the externally toothed gear provided with differing numbers of first and second external teeth is increased.

Dual-type strain wave gearing

In a silk hat-shaped external gear for a strain wave gearing, t(A)&#x3e;t(C)&#x3e;t(D)&#x3e;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.

Externally toothed gear for strain wave gearing

A relieving portion is formed between a first external tooth portion and a second external tooth portion in the external teeth of a flexible externally toothed gear of a flat strain wave gearing. The length Lof the relieving portion in the tooth trace direction is within the range of 0.1 to 0.5 of the tooth width L of the external teeth. The maximum relieving amount t from the tooth top land of an external tooth in the relieving portion is 3.3&#xd7;10&#x3c;t/PCD&#x3c;6.3&#xd7;10where the PCT is defined as the pitch circle diameter of the external teeth. The tooth face load distribution of the external tooth in the tooth trace direction can be equalized, and a flat strain wave gearing having a high transmitted-load capacity can be achieved.

Flat strain wave gearing

In the cup-shaped externally toothed gear, the outside end face profile of the diaphragm is defined by a first concave circular arc having a first radius, a second concave circular arc that has a second radius and is smoothly connected to the first concave circular arc, an inclined straight line that is smoothly connected to the second concave circular arc and is inclined toward an inside straight line with respect to the center axis line, the inside straight line defining the outside profile of the diaphragm. The second radius is larger than the first radius, and the thickness of the diaphragm is gradually decreased from the side of the boss to the side of the cylindrical body. The stress concentration in the boss-side joint portion of the diaphragm can be relieved, whereby enhancing fatigue strength of the flexible externally toothed gear.

Cup-shaped flexible externally toothed gear and cup-type strain wave gearing

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different teeth numbers, and is flexed into an ellipsoidal shape by a wave generator. When the theoretical values of the radial flexing amounts at major-axis positions of the first and second external teeth flexed into the ellipsoidal shape are expressed by d1=m1n1 and d2=m2n2 (m1 and m2 represent the modules of the first and second external teeth, and n1 and n2 represent positive integers), the radial flexing amounts of the first and second external teeth flexed by the wave generator satisfy d1a=&#x3c9;d1 and d2a=&#x3c9;d2, where 1.25&#x2264;&#x3c9;&#x2264;3. Accordingly, a dual-type strain wave gearing can be achieved with which the first and second external teeth having different numbers can be suitably flexed to form excellent mating states with respective internally toothed gears.

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different tooth numbers, and is flexed into an ellipsoidal shape by a wave generator. When the theoretical values of the radial flexing amounts at major-axis positions of the first and second external teeth flexed into the ellipsoidal shape are expressed by d=mnand d=mn(mand mrepresent the modules of the first and second external teeth, and nand nrepresent positive integers), the radial flexing amount of the first and second external teeth flexed by the wave generator satisfies d=(d+d)/&#x3c9;(1.4&#x2264;&#x3c9;&#x2264;2.6). Accordingly, a dual-type strain wave gearing can be achieved with which the first and second external teeth having different numbers can be suitably flexed to form excellent mating states with respective internally toothed gears.

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different teeth numbers, and is flexed into an ellipsoidal shape by a wave generator. When t() represents the tooth bottom rim wall thickness of the first external teeth, and t() represents the tooth bottom rim wall thickness of the second external teeth, the ratio of t()/t() is set to a value satisfying 0.5&#x3e;t()/t()&#x3c;1.5. Accordingly, a dual-type strain wave gearing can be achieved with which the first and second external teeth having different teeth numbers can be suitably flexed to form excellent meshing states with respective internally toothed gears.

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different teeth numbers. The first and second external teeth are flexed by a wave generator by the same flexing amount, into an ellipsoidal shape. The tooth depth of tooth profiles of the first external teeth having a low teeth number is smaller than the tooth depth of tooth profiles of the second external teeth having a high teeth number. A dual-type strain wave gearing can be achieved with which the first and second external teeth having different teeth numbers can be suitably flexed to form excellent meshing states with respective internally toothed gears.

An externally toothed gear of a dual-type strain wave gearing is provided with first and second external teeth having different teeth numbers. The first and second external teeth are flexed by a wave generator by the same flexing amount, into an ellipsoidal shape. The average pressure angle of main-tooth-surface sections of tooth profiles of the first external teeth having a low teeth number is less acute than the average pressure angle of main-tooth-surface sections of tooth profiles of the second external teeth having a high teeth number. Accordingly, a dual-type strain wave gearing can be achieved with which the first and second external teeth having different teeth numbers can be suitably flexed to form excellent meshing states with respective internally toothed gears.

A cup-shaped flexible externally toothed gear of a wave gear device, wherein a diaphragm plate slopes from a diaphragm internal peripheral edge portion contiguous to a boss part toward a diaphragm external peripheral edge portion contiguous to a cylindrical body portion in a direction in which the diaphragm external peripheral edge portion is at greater distance from an open end of the cylindrical body portion with respect to an orthogonal plane orthogonal to a central axis line of the device. The length dimension of the diaphragm plate and the length dimension of the cylindrical body portion in the axial direction can be increased. Therefore, the fatigue strength of the diaphragm plate and the load capacity of the wave gear device in which the flexible externally toothed gear has been incorporated can be increased.

Flexible externally toothed gear for wave gear device

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

A rigid internal gear and a flexible external gear of a wave gear drive are spur gears of module m. The number of teeth of the external gear is smaller by 2n (n is a positive integer) than that of the internal gear. The deflection of the major axis of the elliptical rim neutral line on the principal cross-section of the external gear is set at 2&#x3ba;mn (&#x3ba;&#x3c;1). On the principal cross-section, the meshing of both gears is approximated by rack meshing. The locus M of movement of a tooth of the external gear caused by the rotation of a wave generator is determined. A part AC of the locus M of movement from the inflection point A of the locus M of movement to the deepest position B of meshing is determined on the entering side of meshing of the teeth toward the major axis of the locus M of movement. A first similar curve FG generated by multiplying the curve part AC by &lgr; is employed as the tooth profile of the external gear, and a second similar curve DE generated by multiplying the curve part AC by (&lgr;+1) is employed as the tooth profile of the internal gear. The tooth whole depth is increased wherever possible so that the range of the tooth profile of the internal gear may be the greatest at which the tooth tip touches the locus M of movement of the tip of tooth of the external gear, thus realizing a wave gear drive of high ratcheting torque.

Wave gear drive having negative deflection meshing tooth profile

A wave gear drive comprises a circular rigid internal gear and a flexible external gear inside the rigid internal gear. A wave generator in the flexible external gear flexes the flexible external gear into an elliptical shape. The cross-section of the flexible external gear perpendicular to the axis at a point in the tooth trace direction of the flexible external gear is set as the main cross-section. The rigid internal gear and flexible external gear are gears with a module m, and the flexible external gear has a number of teeth that is smaller than the number of teeth of the rigid internal gear. The moving route M of a tooth of the flexible external gear with respect to a tooth of the rigid internal gear that accompanies rotation of the wave generator when meshing of the teeth in the main cross-section is approximated by rack meshing. On the entering side of the meshing of the teeth to the major axis of the moving route M, a first similar curve AC is obtained by similarity transformation of a pressure angle .alpha. orthogonal to the direction of the moving route M. The first similar curve AC is employed as the basic addendum tooth profile of the rigid internal gear. A second similar curve CB is obtained by rotating the first similar curve AC 180&#xb0; about endpoint C, and by a similarity transformation in which the first similar curve AC is multiplied by a ratio of similitude (1&#x2212;&#x3bb;)/&#x3bb;. The second similar curve CB is employed as the basic addendum tooth profile of the flexible external gear.

Wave gear drive with continuous meshing, high ratcheting torque tooth profile

A diaphragm of a cup-shaped flexible external gear of a cup-shaped wave gear device having a high reduction ratio of 100 or higher is given a thickness t in a position of a radius r of the diaphragm whereby the thickness t is a value that satisfies the expression A/rwhen A is a constant. The constant A is preferably a value that satisfies the expression 0.0014 D&#x3c;A&#x3c;0.0026 D, where D is a pitch diameter of the flexible external gear, and the range of the radius r whereby the thickness t is defined as described above in the diaphragm is preferably set to satisfy the expression 0.6 d&#x3c;r&#x3c;0.4 D, where d is a diameter of a discoid rigid boss made continuous with an internal peripheral end of the diaphragm. Stress concentration can be alleviated, and it is possible for the allowable transmission torque to be increased compared to the prior art.

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Azumino, Japan

Noboru Takizawa