JP7319822B2 - Strain wave gearing - Google Patents

Description

The present invention relates to strain wave gearing.

A strain wave gearing (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100002) is sometimes adopted as a speed reducer in a drive mechanism of a handling robot or the like.
A strain wave gear device consists of an annular rigid internal gear (circular spline) with internal teeth on the inner peripheral surface, a flexible external gear (flex spline) with external teeth on the outer peripheral surface, and a wave generator (wave generator ). The number of external teeth of the flexible external gear is less than the number of internal teeth of the rigid internal gear. The wave generator elliptically bends the flexible external gear arranged inside the rigid internal gear so that the external teeth of the flexible external gear mesh with the internal teeth of the rigid internal gear. match. Further, the wave generator rotates to move the meshing positions of the external teeth and the internal teeth in the circumferential direction. The flexible external gear rotates relative to the rigid internal gear based on the difference in the number of teeth between the internal and external teeth. The rotational speed of the flexible external gear is less than the rotational speed of the wave generator. As a result, the strain wave gearing can obtain a reduced rotational output from the flexible external gear.

JP-A-10-318338

By the way, in a wave gear device, if the rotation of the wave generator suddenly changes such as when the wave generator suddenly stops, an excessive load such as an impact acts on the flexible external gear. In this case, the flexible external gear deforms in the radial direction due to an excessive load, causing tooth skipping with respect to the rigid internal gear (unintentional deviation of the meshing position between the internal teeth and the external teeth). There is a problem that

The present invention provides a wave gear device capable of suppressing tooth jumping.

A strain wave gearing according to an aspect of the present invention includes an annular rigid internal gear having internal teeth on an inner peripheral surface, and an external ring disposed inside the rigid internal gear and having an outer peripheral surface capable of meshing with the internal teeth. a flexible external gear having teeth; and a flexible external gear disposed inside the flexible external gear, wherein the external teeth mesh with the internal teeth by radially bending the flexible external gear. a first wave generator for moving the meshing position between the external teeth and the internal teeth in the circumferential direction; a second wave generator that meshes the external teeth with the internal teeth by bending the external teeth and moves the meshing position between the external teeth and the internal teeth in the circumferential direction; The generator and the second wave generator are each formed in an elliptical shape when viewed from the axial direction, so that the flexible external gear is deformed into an elliptical shape by bending the flexible external gear in the radial direction. The teeth are meshed with the internal teeth at two different locations in the circumferential direction, and the major axis directions of the first wave generator and the second wave generator are offset from each other in the circumferential direction, thereby generating the first wave. and the second wave generator radially bend different portions of the flexible external gear in the circumferential direction .

By configuring in this way, it is possible to increase the meshing positions between the internal teeth of the rigid internal gear and the external teeth of the flexible external gear as compared with the case where there is only one wave generator. Therefore, the internal teeth and the external teeth can be meshed firmly. As a result, even if a large load acts on the flexible external gear due to, for example, a sudden change in the rotation of the wave generator, the flexible external gear jumps relative to the rigid internal gear. can be suppressed.

In addition, with this configuration, the first meshing position between the internal teeth and the external teeth by the first wave generator and the second meshing position between the internal teeth and the external teeth by the second wave generator. , are offset from each other in the circumferential direction. As a result, the internal teeth and the external teeth can be meshed more firmly. Therefore, it is possible to effectively suppress tooth jumping of the flexible external gear with respect to the rigid internal gear.

In the above configuration, even if the first wave generator and the second wave generator bend radially the portions of the flexible externally toothed gear that are shifted from each other by 90 degrees in the circumferential direction. good.

By configuring in this way, the first meshing position between the internal teeth and the external teeth by the first wave generator and the second meshing position between the internal teeth and the external teeth by the second wave generator can be changed around the circumference. can be evenly spaced in all directions. Therefore, it is possible to effectively strengthen the engagement between the internal teeth and the external teeth. Therefore, it is possible to more effectively suppress tooth jumping of the flexible external gear with respect to the rigid internal gear.

In the above configuration, the distance between the first wave generator and the second wave generator in the axial direction is equal to or greater than the thickness of the first wave generator or the second wave generator in the axial direction. There may be.

With this configuration, the first meshing position between the internal teeth and the external teeth generated by the first wave generator and the second meshing position between the internal teeth and the external teeth generated by the second wave generator can be aligned with each other. direction away from each other. Therefore, the stress generated in the flexible externally toothed gear due to the meshing positions of the internal teeth and the external teeth of the first and second wave generators being different from each other in the circumferential direction can be alleviated.

In the above configuration, a plurality of rolling elements arranged in the circumferential direction between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator ; a retainer that holds a gap between the rolling elements in the radial direction between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator in the radial direction; You may prepare .

With this configuration, the cage reduces the radial distance between the inner circumference of the flexible externally toothed gear and the outer circumference of the wave generator in the region between the rolling elements adjacent to each other in the circumferential direction. can be suppressed. Therefore, even if a large load is applied to the flexible external gear due to a sudden change in the rotation of the wave generator, the flexible external gear will move radially in the region between the rolling elements. Inward deformation can be suppressed by the retainer. As a result, it is possible to suppress tooth jumping of the flexible external gear with respect to the rigid internal gear.

In the above configuration, the length of shrinkage of the retainer that shrinks in the radial direction when the retainer receives a compressive force in the radial direction is greater than the length of engagement between the inner teeth and the outer teeth in the radial direction. It can be small.

With this configuration, the cage is contracted and deformed in the radial direction by an external force, and the flexible external gear is radially inward in the region between the rolling elements by the length of the contraction of the cage. Even if deformed, the external teeth of the flexible external gear can be prevented from coming off the internal teeth of the rigid internal gear. That is, it is possible to prevent the flexible external gear from jumping with respect to the rigid internal gear.

In the above configuration, the dimension of the retainer in the radial direction is L2, and the gap between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator in the radial direction L1 is the dimension of L1, and H1 is the meshing length between the internal teeth and the external teeth in the radial direction.
L1-H1≤L2≤L1
may be satisfied.

With this configuration, even if the flexible external gear is deformed inward in the radial direction in the region between the rolling elements, the external teeth of the flexible external gear move away from the internal teeth of the rigid internal gear. You can prevent it from coming off. That is, it is possible to prevent the flexible external gear from jumping with respect to the rigid internal gear.

With the above configuration, the cage may include a plurality of holding members that are separately formed and arranged between the adjacent rolling elements.

With this configuration, the retainer in which the plurality of holding members are formed separately can improve the material yield compared to the retainer in which the plurality of holding members are integrally fixed.

In the above configuration, a plurality of first rolling elements arranged in the circumferential direction between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator and a second rolling element group having a plurality of second rolling elements arranged in the circumferential direction adjacent to the first rolling element group and alternately arranged in the circumferential direction with the first rolling element group , may be further provided .

By comprising in this way, a 1st rolling element and a 2nd rolling element can be put in order without gap in the circumferential direction. Therefore, even if a large load acts on the flexible external gear due to a sudden change in the rotation of the wave generator, etc., the flexible external gear is prevented from deforming inward in the radial direction. can. As a result, it is possible to suppress tooth jumping of the flexible external gear with respect to the rigid internal gear.

In the strain wave gearing described above, it is possible to suppress tooth jumping of the flexible external gear with respect to the rigid internal gear.

1 is a sectional view of a strain wave gearing according to a first embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1; FIG. 2 is a cross-sectional view taken along line III-III in FIG. 1; It is a figure which shows the principal part of the strain wave gearing based on 2nd embodiment of this invention. FIG. 11 is a schematic view of a bearing provided in a strain wave gearing device according to a third embodiment of the present invention, viewed from the radial direction;

[First Embodiment]
A first embodiment of the present invention will be described below with reference to FIGS.
As shown in FIGS. 1 to 3, the strain wave gearing 1 according to the first embodiment includes a rigid internal gear 2, a flexible external gear 3 meshing with the rigid internal gear 2, and a flexible external gear. and a wave generator 4 for flexurally deforming the tooth gear 3 . The strain wave gearing 1 of the first embodiment also includes a bearing 5 .

The rigid internal gear 2 is formed in an annular shape. The rigid internal gear 2 has internal teeth 21 on its inner peripheral surface. A plurality of internal teeth 21 are arranged in the circumferential direction. The rigidity of the rigid internal gear 2 is higher than that of the flexible external gear 3 described later. The rigid internal gear 2 preferably has such rigidity that it does not deform even when subjected to an external force.

The flexible external gear 3 is formed in a cylindrical shape. The flexible external gear 3 is arranged inside the rigid internal gear 2 . The flexible external gear 3 has external teeth 31 on its outer peripheral surface. A plurality of external teeth 31 are arranged in the circumferential direction. The external teeth 31 are meshable with the internal teeth 21 of the rigid internal gear 2 . The circumferential length of the outer peripheral surface of the flexible external gear 3 is smaller than the circumferential length of the inner peripheral surface of the rigid internal gear 2 . The number of external teeth 31 of the flexible external gear 3 is less than the number of internal teeth 21 of the rigid internal gear 2 .

The flexible external gear 3 is elastically flexurally deformable. By applying an external force in the radial direction of the flexible external gear 3, the radial dimension in the first radial direction orthogonal to the axial direction is changed to the radial dimension in the second radial direction orthogonal to the axial direction and the first radial direction. elastically deforms to become larger than That is, the flexible external gear 3 elastically deforms into an elliptical shape by bending in its radial direction.

The external teeth 31 of the flexible external gear 3 of this embodiment are separated into a plurality of parts in the axial direction. That is, a plurality of external teeth 31 are arranged at intervals in the axial direction of the flexible external gear 3 . The number of the external teeth 31 arranged in the axial direction may be three or more, but is two in this embodiment.

A wave generator 4 is arranged inside the flexible external gear 3 . The wave generator 4 meshes the external teeth 31 of the flexible external gear 3 with the internal teeth 21 of the rigid internal gear 2 by radially bending the flexible external gear 3 . The wave generator 4 moves the meshing position EP between the external teeth 31 and the internal teeth 21 in the circumferential direction. The strain wave gearing 1 of this embodiment includes two wave generators 4 , that is, a first wave generator 41 and a second wave generator 42 .

The first and second wave generators 41 and 42 are each formed in an elliptical shape when viewed from the axial direction. The first and second wave generators 41 and 42 are arranged axially spaced from each other. The first and second wave generators 41 and 42 are arranged so as to be positioned radially inward of the two axially arranged external teeth 31, respectively. By arranging the wave generators 41 and 42 inside the flexible external gear 3, the flexible external gear 3 bends in the radial direction and deforms into an elliptical shape. In addition, the external teeth 31 positioned at both ends in the radial direction of the flexible external gear 3 corresponding to the longitudinal direction of the wave generators 41 and 42 mesh with the internal teeth 21 of the rigid internal gear 2 . As the wave generators 41 and 42 rotate, the engagement position EP between the inner tooth 21 and the outer tooth 31 moves in the circumferential direction.

The shape and size of the first and second wave generators 41 and 42 seen from the axial direction are equal to each other. The thicknesses of the first and second wave generators 41, 42 in the axial direction may, for example, be different from each other, but are equal to each other in this embodiment.

Since the first and second wave generators 41 and 42 are arranged in the axial direction, different portions of the flexible external gear 3 are bent in the axial direction. A distance D1 between the first wave generator 41 and the second wave generator 42 in the axial direction is equal to or greater than the thickness t1 of the first wave generator 41 or the thickness t2 of the second wave generator 42 .
The first and second wave generators 41 and 42 are connected to each other by a shaft 43 . As a result, the first and second wave generators 41 and 42 rotate together.

In addition, the first and second wave generators 41 and 42 radially bend different portions of the flexible external gear 3 in the circumferential direction. Particularly in this embodiment, the first and second wave generators 41 and 42 bend portions of the flexible externally toothed gear 3 that are shifted from each other by 90 degrees in the circumferential direction.
Specifically, the major diameter directions of the first and second wave generators 41 and 42 are shifted 90 degrees from each other in the circumferential direction. As a result, the two first meshing positions EP1 of the internal teeth 21 and the external teeth 31 by the first wave generator 41 and the two second meshing positions EP1 of the internal teeth 21 and the external teeth 31 by the second wave generator 42 are generated. The matching position EP2 is located with a 90 degree shift from each other in the circumferential direction. That is, four meshing positions EP between the inner tooth 21 and the outer tooth 31 by the two wave generators 41 and 42 are evenly positioned in the circumferential direction.

The bearings 5 are provided between the inner circumference of the flexible external gear 3 and the outer circumferences of the wave generators 41 and 42, respectively. The bearing 5 of this embodiment comprises a plurality of rolling elements 51 circumferentially arranged between the inner circumference of the flexible external gear 3 and the outer circumferences of the wave generators 41 and 42 . The rolling bodies 51 may be spherical or cylindrical. The bearing 5 allows the inner circumference of the flexible external gear 3 and the outer circumferences of the wave generators 41 and 42 to smoothly rub against each other.

In the strain wave gearing 1 of the first embodiment configured as described above, when the two wave generators 41 and 42 rotate, the engagement position EP between the internal teeth 21 and the external teeth 31 moves in the circumferential direction. Here, since the number of the external teeth 31 is smaller than the number of the internal teeth 21, the rigid internal gear 2 and the flexible external gear 3 rotate relatively with the movement of the engagement position EP. This relative rotation speed is slower than the rotation speed of the wave generator 4 . That is, the rotation of the flexible external gear 3 or the rigid internal gear 2 can be output in response to the input rotation of the wave generator 4 .

Thus, the strain wave gearing 1 of the first embodiment includes the first wave generator 41 and the second wave generator 42 . This makes it possible to increase the meshing positions EP between the internal teeth 21 of the rigid internal gear 2 and the external teeth 31 of the flexible external gear 3, compared to the case where there is only one wave generator 4. . Therefore, the internal teeth 21 and the external teeth 31 can be meshed firmly. Therefore, even if a large load acts on the flexible external gear 3 due to a sudden change in the rotation of the wave generator 4 or the like, the flexible external gear 3 is Tooth jumping can be suppressed. That is, the impact resistance and vibration characteristics of the strain wave gearing 1 can be improved.
By improving the shock resistance and vibration characteristics of the strain wave gearing 1, the strain wave gearing 1 can be used in a severe environment (for example, an environment in which a handling robot is quickly moved) in which the rotation of the wave generator 4 is abruptly changed. becomes possible.

In addition, the first and second wave generators 41 and 42 radially bend different portions of the flexible external gear 3 in the circumferential direction. In this case, a first meshing position EP1 between the internal teeth 21 and the external teeth 31 by the first wave generator 41 and a second meshing position EP2 between the internal teeth 21 and the external teeth 31 by the second wave generator 42. are offset from each other in the circumferential direction. As a result, the internal teeth 21 and the external teeth 31 can be meshed more firmly. Therefore, it is possible to effectively suppress tooth jumping of the flexible external gear 3 with respect to the rigid internal gear 2 . That is, the impact resistance and vibration characteristics of the strain wave gearing 1 can be further improved.

In addition, the first and second wave generators 41 and 42 radially bend portions of the flexible external gear 3 that are shifted from each other by 90 degrees in the circumferential direction. In this case, a first meshing position EP1 between the internal teeth 21 and the external teeth 31 by the first wave generator 41 and a second meshing position EP2 between the internal teeth 21 and the external teeth 31 by the second wave generator 42. can be evenly distributed in the circumferential direction. Therefore, the engagement between the internal teeth 21 and the external teeth 31 can be effectively strengthened. Therefore, it is possible to more effectively suppress tooth jumping of the flexible external gear 3 with respect to the rigid internal gear 2 . That is, the impact resistance and vibration characteristics of the strain wave gearing 1 can be further improved.

A distance D1 between the first wave generator 41 and the second wave generator 42 in the axial direction is equal to or greater than the thickness of the first wave generator 41 or the thickness of the second wave generator 42 . Therefore, a first meshing position EP1 between the internal teeth 21 and the external teeth 31 generated by the first wave generator 41 and a second meshing position EP2 between the internal teeth 21 and the external teeth 31 generated by the second wave generator 42 are established. can be axially separated from each other. This relaxes the stress generated in the flexible external gear 3 due to the meshing positions EP of the internal teeth 21 and the external teeth 31 by the first and second wave generators 41 and 42 being different in the circumferential direction. can.

In the first embodiment described above, the angle at which the first meshing position EP1 and the second meshing position EP2 are shifted from each other in the circumferential direction is not limited to 90 degrees, and may be any angle.

In the above-described first embodiment, the first and second wave generators 41 and 42 may radially bend the same portion of the flexible external gear 3 in the circumferential direction, for example. That is, the angle at which the first meshing position EP1 and the second meshing position EP2 are displaced from each other in the circumferential direction may be 0 degree.

In the first embodiment described above, the number of wave generators 4 arranged in the axial direction may be, for example, three or more. Also, the three or more wave generators 4 may radially bend different portions of the flexible external gear 3 in the circumferential direction. In this case, the plurality of portions of the flexible externally toothed gear 3 where the plurality of wave generators 4 bend should preferably be shifted by an angle θ defined below from each other in the circumferential direction.
θ=180 degrees/n, (where n is the number of wave generators 4)
With such a configuration, a plurality of meshing positions EP between the inner teeth 21 and the outer teeth 31 by the plurality of wave generators 4 can be evenly arranged in the circumferential direction.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIG. In the second embodiment, the same reference numerals are given to the same constituent elements as in the first embodiment, and the explanation thereof is omitted.

As shown in FIG. 4, a strain wave gearing 1A of the second embodiment includes a rigid internal gear 2, a flexible external gear 3, a wave generator 4, and a bearing 5A, as in the first embodiment. The number of wave generators 4 may be plural as in the first embodiment, but may be, for example, one.

A bearing 5A of the second embodiment includes a plurality of rolling elements 51 and a retainer 52A. A plurality of rolling elements 51 are arranged in the circumferential direction between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4, as in the first embodiment. The retainer 52A maintains a gap between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4 in the radial direction between the rolling elements 51 in the circumferential direction.

52 A of retainers are provided with 53 A of several holding members distribute|arranged between the rolling elements 51 which adjoin. Each holding member 53A is arranged between the rolling elements 51 in the circumferential direction. The holding member 53A should be formed so as to hold at least the gap between the inner periphery of the flexible external gear 3 and the outer periphery of the wave generator 4 . Each holding member 53A may be arbitrarily formed, for example, in a rod-like shape radially extending from the inner periphery of the flexible external gear 3 to the outer periphery of the wave generator 4 .

53 A of holding members of this embodiment are formed so that the clearance gap between rolling elements 51 comrades in the circumferential direction may be filled. Specifically, the rolling elements 51 are circular when viewed from the axial direction. Therefore, the interval between the rolling elements 51 in the circumferential direction increases from the intermediate portion in the radial direction toward both end portions (the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4). On the other hand, the surfaces on both sides in the circumferential direction of the holding member 53A are formed so as to correspond to the circular shape of the rolling element 51 . That is, the dimension of the holding member 53A in the circumferential direction increases from the intermediate portion toward the both end portions in the radial direction.
The plurality of holding members 53A may be connected to each other, for example, but are formed separately in this embodiment.

A dimension L2 of the holding member 53A (retainer 52A) in the radial direction preferably satisfies the following inequality, for example.
L1-H1≤L2≤L1
L2: Dimension of the holding member 53A (retainer 52A) in the radial direction L1: Dimension of the gap between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4 in the radial direction H1: The inner tooth 21 in the radial direction 4, the dimension L2 of the holding member 53A is equal to the dimension L1 of the gap.

The holding member 53A (retainer 52A) may be, for example, a rigid body that does not deform against external force, but may deform against external force, for example. In this case, the length of contraction of the holding member 53A (retainer 52A) in the radial direction when the holding member 53A (retainer 52A) receives a compressive force in the radial direction is the length of meshing between the internal teeth 21 and the external teeth 31 in the radial direction. It is preferable that it is smaller than the length H1.

A bearing 5</b>A of this embodiment has an inner ring 54 and an outer ring 55 . The inner ring 54 has properties similar to those of the wave generator 4 , ie has a higher stiffness than the flexible externally toothed gear 3 . The inner ring 54 is fixed to the outer circumference of the wave generator 4 . Therefore, the inner ring 54 of the bearing 5A substantially forms the outer circumference of the wave generator 4. As shown in FIG. The outer ring 55 has properties similar to those of the flexible external gear 3, that is, it is elastically flexurally deformable. The outer ring 55 is fixed to the inner periphery of the flexible external gear 3 . Therefore, the outer ring 55 of the bearing 5A substantially forms the inner circumference of the flexible externally toothed gear 3 .

The strain wave gearing 1A of the second embodiment includes a retainer 52A that holds a gap between the inner periphery of the flexible external gear 3 and the outer periphery of the wave generator 4 in the radial direction between the rolling elements 51 in the circumferential direction. Prepare. Therefore, the retainer 52A reduces the distance between the inner periphery of the flexible external gear 3 and the outer periphery of the wave generator 4 in the radial direction in the region between the rolling elements 51 adjacent in the circumferential direction. can be suppressed. As a result, even if a large load acts on the flexible external gear 3 due to, for example, a sudden change in the rotation of the wave generator 4 , the flexible external gear 3 does not move in the area between the rolling elements 51 . The retainer 52A can suppress radially inward deformation in the . As a result, it is possible to prevent the flexible external gear 3 from jumping with respect to the rigid internal gear 2 . That is, the shock resistance and vibration characteristics of the strain wave gearing 1A can be improved.

Further, in the strain wave gearing 1A of the second embodiment, the dimension L2 of the retainer 52A, the dimension L1 of the gap, and the meshing length H1 are
L1-H1≤L2≤L1
meets Therefore, even if the flexible external gear 3 is deformed inward in the radial direction in the region between the rolling elements 51 , the external teeth 31 of the flexible external gear 3 do not move the internal teeth 21 of the rigid internal gear 2 . You can prevent it from coming off. That is, it is possible to prevent the flexible external gear 3 from jumping with respect to the rigid internal gear 2 .

Further, in the strain wave gearing 1A of the second embodiment, the contraction length of the retainer 52A, which contracts in the radial direction when the retainer 52A receives a compressive force in the radial direction, is the same as the inner tooth 21 and the outer tooth 31 in the radial direction. is smaller than the length H1 of meshing with. In this case, the retainer 52A is contracted and deformed in the radial direction by an external force, and the flexible external gear 3 is deformed radially inward in the region between the rolling elements 51 by the length of the shrinkage of the retainer 52A. However, it is possible to prevent the external teeth 31 of the flexible external gear 3 from coming off the internal teeth 21 of the rigid internal gear 2 . That is, it is possible to prevent the flexible external gear 3 from jumping with respect to the rigid internal gear 2 .

Further, in the strain wave gearing device 1A of the second embodiment, the retainer 52A includes a plurality of holding members 53A that are separately formed and arranged between the adjacent rolling elements 51 . The retainer 52A in which the plurality of holding members 53A are individually formed can improve the material yield compared to the retainer in which the plurality of holding members 53A are integrally fixed.

In the second embodiment described above, the bearing 5A may not include the inner ring 54 and the outer ring 55, for example. That is, the rolling elements 51 may contact the inner periphery of the flexible external gear 3 and the outer periphery of the wave generator 4 .

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the same reference numerals are assigned to the same components as in the first embodiment, and the description thereof is omitted.

The strain wave gearing of the third embodiment includes a rigid internal gear 2, a flexible external gear 3 and a wave generator 4 (see FIGS. 1 to 3) similar to those of the first embodiment, and bearings shown in FIG. 5B. The number of wave generators 4 may be plural as in the first embodiment, but may be, for example, one.

The bearing 5B is provided between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4, like the bearing 5 of the first embodiment.
The bearing 5B of this embodiment includes a first rolling element group 501 and a second rolling element group 502 . The first rolling element group 501 includes a plurality of first rolling elements 511 arranged in the circumferential direction (vertical direction in FIG. 5) between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4. have. The second rolling element group 502 is located between the inner circumference of the flexible external gear 3 and the outer circumference of the wave generator 4, and is adjacent to the first rolling element group 501 in the axial direction (horizontal direction in FIG. 5). and has a plurality of second rolling elements 512 arranged in the circumferential direction. The second rolling elements 512 are arranged alternately with the first rolling elements 511 in the circumferential direction. That is, the first rolling elements 511 and the second rolling elements 512 are arranged in a zigzag or staggered manner.

The first rolling element 511 and the second rolling element 512 are arranged in a line without a gap in the circumferential direction. That is, the interval between the first rolling elements 511 adjacent in the circumferential direction is smaller than the dimension of the second rolling elements 512 in the circumferential direction. Also, the interval between the second rolling elements 512 adjacent in the circumferential direction is smaller than the dimension of the first rolling elements 511 in the circumferential direction.
The first and second rolling bodies 511 and 512 may be, for example, cylindrical bodies extending in the axial direction (horizontal direction), but the first and second rolling bodies 511 and 512 of this embodiment are spherical bodies. Also, the sizes of the first and second rolling elements 511 and 512 may be different from each other, for example, but they are the same in this embodiment.

The external teeth 31 of the flexible external gear 3 extend axially so as to overlap both the first and second rolling elements 511 and 512 in the radial direction (the direction perpendicular to the plane of the paper in FIG. 5). Therefore, the external teeth 31 of the flexible external gear 3 are supported from the inside in the radial direction by both the first and second rolling elements 511 and 512 .

The strain wave gearing of the third embodiment includes a first rolling element group 501 having a plurality of first rolling elements 511 arranged in the circumferential direction, and a first rolling element group 501 arranged in the circumferential direction adjacent to the first rolling element group 501. It has a moving body 511 and a second rolling element group 502 having a plurality of second rolling elements 512 alternately arranged in the circumferential direction. In particular, the first rolling element 511 and the second rolling element 512 are arranged without any gap in the circumferential direction. Therefore, even if a large load is applied to the flexible external gear 3 due to a sudden change in rotation of the wave generator 4, the flexible external gear 3 is deformed radially inward. can be suppressed. For example, the portion of the flexible external gear 3 located between two first rolling elements 511 adjacent in the circumferential direction is the second rolling element 512 located between the two first rolling elements 511 in the circumferential direction. supported from the radially inner side by As a result, even if a large load acts on the flexible external gear 3, it is possible to prevent the flexible external gear 3 from deforming inward in the radial direction. Therefore, it is possible to suppress the flexible external gear 3 from jumping with respect to the rigid internal gear 2 . That is, the impact resistance and vibration characteristics of the strain wave gearing can be improved.

The bearing 5B of the third embodiment described above may include, for example, a retainer 52A (see FIG. 4) similar to that of the second embodiment.

Although the details of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

The bearings in the strain wave gearing of the present invention may be slide bearings, for example. Even in this case, it is possible to prevent the flexible external gear from jumping with respect to the rigid internal gear, as in the above embodiment.

Reference Signs List 1, 1A... Strain wave gearing, 2... Rigid internal gear, 3... Flexible external gear, 4... Wave generator, 5, 5A, 5B... Bearing, 21... Internal tooth, 31... External tooth, 41... First wave generator 42 Second wave generator 51 Rolling element 52A Cage 53A Holding member 501 First rolling element group 502 Second rolling element group 511 First roller Moving body 512 Second rolling element D1 Spacing EP Engagement position EP1 First engagement position EP2 Second engagement position

Claims (8)

an annular rigid internal gear having internal teeth on its inner peripheral surface;
a flexible external gear disposed inside the rigid internal gear and having external teeth on an outer peripheral surface that can mesh with the internal teeth;
The flexible external gear is arranged inside the flexible external gear, and by bending the flexible external gear in the radial direction, the external teeth are meshed with the internal teeth, and the external teeth and the internal teeth are engaged. a first wave generator for moving the meshing position in the circumferential direction;
The flexible external gear is arranged inside the flexible external gear, and by bending the flexible external gear in the radial direction, the external teeth are meshed with the internal teeth, and the external teeth and the internal teeth are engaged. a second wave generator for moving the engagement position in the circumferential direction;
with
The first wave generator and the second wave generator are each formed in an elliptical shape when viewed from the axial direction, so that the flexible external gear is radially deformed into an elliptical shape. and meshing the external teeth with the internal teeth at two different points in the circumferential direction,
The longitudinal directions of the first wave generator and the second wave generator are offset from each other in the circumferential direction, so that the first wave generator and the second wave generator are arranged in the flexible external gear. A strain wave gearing that radially bends different portions in the circumferential direction . 2. The wave motion according to claim 1, wherein said first wave motion generator and said second wave motion generator flex radially portions of said flexible externally toothed gear that are positioned 90 degrees apart from each other in said circumferential direction. Gear device. said first wave generator and said second wave generator being axially spaced from each other;
2. The distance between the first wave generator and the second wave generator in the axial direction is equal to or greater than the thickness of the first wave generator or the second wave generator in the axial direction . 3. A wave gear device according to item 2 . a plurality of rolling elements circumferentially arranged between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator ;
a retainer that holds a gap between the rolling elements in the circumferential direction and between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator in the radial direction;
The strain wave gearing according to any one of claims 1 to 3, comprising: 5. The retainer according to claim 4 , wherein a shrinkage length of the retainer that shrinks in the radial direction when the retainer receives a compressive force in the radial direction is smaller than a meshing length of the inner teeth and the outer teeth in the radial direction. strain wave gearing. L2 is the dimension of the cage in the radial direction, L1 is the dimension of the gap between the inner periphery of the flexible external gear and the outer periphery of the first wave generator and the second wave generator in the radial direction Let H1 be the length of meshing between the internal teeth and the external teeth in the direction,
The dimension L2 of the retainer, the dimension L1 of the clearance, and the length H1 of engagement are
L1-H1≤L2≤L1
6. The strain wave gearing according to claim 4 or 5 , which satisfies The strain wave gearing according to any one of claims 4 to 6, wherein the retainer comprises a plurality of holding members that are separately formed and arranged between the adjacent rolling elements. A first rolling element having a plurality of first rolling elements arranged in the circumferential direction between the inner circumference of the flexible external gear and the outer circumferences of the first wave generator and the second wave generator. flock and
a second rolling element group having a plurality of second rolling elements arranged in the circumferential direction adjacent to the first rolling element group and alternately arranged in the circumferential direction with the first rolling element group;
The strain wave gearing according to any one of claims 1 to 7, comprising:

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