JP2018091414A - Flexible meshing-type gear unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible meshing-type gear unit excellent in lubricity.SOLUTION: A flexible meshing-type gear unit includes: an excitation body 15; an external gear 13 flexibly deformed by the excitation body; a first internal gear 11 meshed with the external gear; and a second internal gear 12 arranged adjacently to the first internal gear in an axial direction D, and meshed with the external gear. The first internal gear has an extension part 111 extending to the second internal gear side along the axial direction. The extension part has a first extension part 112 positioned outward in a radial direction of an interval d between the first internal gear and the second internal gear, and a second extension part 113 positioned outward in a radial direction of the second internal gear. A maximum inner diameter R1max of the first extension part is made larger than a minimum inner diameter of the second extension part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a flexure meshing gear device.

DESCRIPTION OF RELATED ART For a long time, the bending meshing type gear apparatus provided with the bending gear is known (for example, refer FIG. 2 of patent document 1).
This flexure meshing gear device includes an external gear that can be flexibly deformed, a transmission shaft that bends and deforms the external gear, two internal gears that mesh with the external gear, and a motor that applies torque to the transmission shaft. I have.
When the motor is driven, the transmission shaft imparts periodic bending deformation to the external gear from the inside, and one of the unfixed internal gears is imparted with a rotational operation that is decelerated from the transmission shaft. .

JP 58-180858 A

In such a gear mechanism, in order to perform a smooth meshing operation, a lubricant is supplied between the members that perform the operation.
However, in the conventional gear mechanism, there is a possibility that the lubricant is moved by driving and the lubricity between members is lowered.

  An object of the present invention is to provide a flexibly meshing gear device having excellent lubricity.

The present invention includes an oscillator, an external gear that is bent and deformed by the oscillator, a first internal gear that meshes with the external gear, and an axial direction relative to the first internal gear. A flexibly meshing gear device comprising a second internal gear disposed adjacently and meshing with the external gear,
The first internal gear has an extending portion extending toward the second internal gear along the axial direction;
The extension part is located on the radially outer side of the second internal gear and the first extension part located on the radially outer side of the gap between the first internal gear and the second internal gear. A second extension part,
The maximum inner diameter of the first extending portion is configured to be larger than the minimum inner diameter of the second extending portion.

  According to the present invention, it is possible to improve the lubricity in the apparatus.

It is a longitudinal cross-sectional view which shows the bending meshing type gear apparatus which concerns on 1st embodiment of this invention. 2A is a side view of the flexure meshing gear device viewed in the axial direction, and FIG. 2B is a partially enlarged view of FIG. 2A. It is a disassembled perspective view which shows the mechanism of the gear periphery of a bending meshing type gear apparatus. It is a partial expanded sectional view of the 1st internal gear and the 2nd internal gear of a flexure meshing gear device. It is a partial expanded sectional view of the 1st internal gear and the 2nd internal gear of the flexible meshing gear device concerning a 2nd embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 is a longitudinal sectional view showing a flexure meshing gear device according to a first embodiment of the present invention. FIG. 2A is a side view of the flexure meshing gear device 1 according to the first embodiment as viewed in the rotation center line direction (axial direction), and FIG. 2B is a partially enlarged view thereof. The rotation center line direction D is a direction parallel to a rotation center line O of a first internal gear 11 described later of the flexure meshing gear device 1.
FIG. 3 is an exploded perspective view showing a mechanism around the gear of the flexible meshing gear device 1 according to the first embodiment.

  A flexure meshing gear device 1 (hereinafter, referred to as “gear device 1”) according to a first embodiment of the present invention rotates at a high reduction ratio by arranging an input shaft and an output shaft on the same axis. It can be used as a speed reducer that transmits motion.

  As shown in FIGS. 1 to 3, the gear device 1 includes a first internal gear 11 and a second internal gear 12, an external gear 13 as a bending gear, a bearing 14, and an eccentricity as a vibration generator. And a cam 15. The first internal gear 11 and the second internal gear 12 are coaxially aligned along the rotation center line O, and the external gear 13, the bearing 14, and the eccentric cam 15 are sequentially arranged inside these radial directions. ing. In FIG. 3, only the first internal gear 11, the second internal gear 12, the external gear 13, and the outer ring 14 a of the bearing 14 are shown.

  The first internal gear 11 and the second internal gear 12 are cylindrical gears having rigidity. The first internal gear 11 and the second internal gear 12 are provided with tooth portions 11a and 12a over the entire inner circumference. The tooth portion 11a of the first internal gear 11 and the tooth portion 12a of the second internal gear 12 are provided on substantially the same radius around the rotation center line O. The number of teeth of the first internal gear 11 and the number of teeth of the second internal gear 12 are set to different values. One of the first internal gear 11 and the second internal gear 12 is typically fixed, and the other is connected to the output shaft (or driven member).

Either the first internal gear 11 or the second internal gear 12 may be fixed, but here, a case where the second internal gear 12 is fixed will be described as an example.
The term “fixed” as used herein refers to the support structure in a state in which a host device incorporating the flexure meshing gear device 1 as a power transmission mechanism supports the flexure meshing gear device 1 with the support structure. Shows a fixed state.

  The eccentric cam 15 is a rigid body having rigidity, and has a cam surface 15 a that is eccentric about the rotation center line O. The cam surface 15a has a curvature that is eccentric in the circumferential direction around the rotation center line O, while having no curvature in the axial direction of the rotation center line O. The cross-sectional shape perpendicular to the axis of the cam surface 15a is a shape close to an ellipse having a major axis La and a minor axis Lb, as shown in FIG. The midpoint of the long axis La and the midpoint of the short axis Lb intersect at the rotation center line O. The long axis La has a length that meshes the external gear 13 with the first internal gear 11 and the second internal gear 12, while the short axis Lb has the external gear 13, the first internal gear 11, and The second internal gear 12 has a length that allows the second internal gear 12 to be separated so as not to mesh.

  The eccentric cam 15 is provided with, for example, a connection hole 15b, and an external shaft of the gear device 1 is connected to the eccentric cam 15. The eccentric cam 15 is typically connected to an input shaft (a motor shaft or a shaft that is rotationally driven by a motor).

  The external gear 13 is a flexure gear that bends and deforms and meshes with the first internal gear 11 and the second internal gear 12, and is configured to be flexibly deformable in a direction in which the curvature in the circumferential direction is changed. . The external gear 13 includes a cylindrical base portion 13b and a tooth portion 13a provided on the outer periphery of the base portion 13b. The tooth portion 13a is disposed over the entire circumference on the outer peripheral side of the base portion 13b in an arrangement facing the tooth portions 11a and 12a of the first internal gear 11 and the second internal gear 12. The external gear 13 is deformed along the cam surface 15a of the eccentric cam 15, and the area around the extended line of the long axis La of the eccentric cam 15 that rotates is in the range around the first internal gear 11 and the second internal gear. 12 and the remaining range is separated from the first internal gear 11 and the second internal gear 12 so as not to mesh.

  The bearing 14 is interposed between the external gear 13 and the eccentric cam 15, and regulates the external gear 13 to a shape along the eccentric cam surface 15a of the eccentric cam 15, while the external gear 13 and the eccentric cam. 15 for realizing a relative rotational movement with respect to 15 with a small resistance. The bearing 14 is, for example, a roller bearing, and includes a cylindrical outer ring 14a, a plurality of rollers 14b, and a cage 14c that holds the intervals between the plurality of rollers 14b. The inner ring of the bearing 14 is provided integrally with the eccentric cam 15. The cam surface 15 a of the eccentric cam 15 is in contact with the inside of the bearing 14, and the inner peripheral surface of the external gear 13 is in contact with the outside of the bearing 14.

  The outer ring 14a is made of a member that has high hardness with respect to a force compressing in the thickness direction, but can be elastically deformed in a direction in which the curvature in the circumferential direction is changed. The outer ring 14a is provided to reduce the rolling resistance of the plurality of rollers 14b. The outer ring 14 a comes into contact with the inner peripheral surface of the external gear 13, flexes and deforms integrally with the external gear 13, and rotates integrally with the external gear 13 when the external gear 13 rotates.

  The bearing 14 may have an inner ring between the plurality of rollers 14b and the eccentric cam 15. In this case, the inner ring contacts the cam surface of the eccentric cam 15 and rotates integrally with the eccentric cam 15.

[Lubricant holding structure]
FIG. 4 is an enlarged cross-sectional view along a cross section passing through the rotation center line O of the first internal gear 11 and the second internal gear 12 of the gear mechanism 1.
Generally, in the case of a flexure meshing gear device, when there is a place where sliding or wear occurs between members during operation, a lubricant such as grease or lubricating oil is applied between the members in advance. Supply is made and the operation is facilitated.
However, if the operation is continuously performed, the lubricant flows and retreats from a portion where the lubricant is necessary, for example, lubrication of the meshing portion of the external gear 13 and the first and second internal gears 11 and 12. May decrease.
For this reason, in the flexure meshing gear device 1, a lubricant holding structure is provided between the first internal gear 11 and the second internal gear 12 described above.

As shown in FIG. 4, the first internal gear 11 includes a main body 110 having a tooth portion 11 a and a second along the rotation center line direction D from the end of the main body 110 on the second internal gear 12 side. And a substantially cylindrical extending portion 111 extending toward the internal gear 12 side. The inside of the extending portion 111 has a lubricant holding structure.
The main body part 110 and the extending part 111 are integrally formed, and the outer diameters thereof are equal and the outer diameter is larger than that of the second internal gear 12. And the extension part 111 has the internal diameter larger than the outer diameter of the 2nd internal gear 12, and the said 2nd internal gear 12 is arrange | positioned on the inner side.

The second internal gear 12 has the same width as the main body 110 of the first internal gear 11 in the rotation center line direction D, and the outer diameter is uniform over the entire length in the rotation center line direction D.
A gap d having a constant width is formed between the end surface on the second internal gear 12 side in the main body 110 of the first internal gear 11 and the end surface on the first internal gear 11 side in the second internal gear 12. Is formed.

  The extending part 111 is provided on the radially outer side of the first extending part 112 and the second internally toothed gear 12 that are located radially outside the gap d between the first internal gear 11 and the second internal gear 12. It has the 2nd extension part 113 located. That is, the first extending portion 112 has the same width as the gap d in the rotation center line direction D, and the second extending portion 113 has the same width as the second internal gear 12 in the rotation center line direction D.

The first extending portion 112 has a maximum inner diameter R1max larger than the minimum inner diameter R2min of the second extending portion 113, and the inner diameter of the first extending portion 112 is uniform over the entire length in the rotation center line direction D. It is.
On the other hand, the second extending portion 113 has a portion 113a in which the inner diameter is constant in the rotation center line direction D and the maximum inner diameter R2max, and the inner diameter is constant in the rotation center line direction D and the minimum inner diameter R2min. Part 113b.
The inner diameter of the end portion of the second extending portion 113 on the first extending portion 112 side is the maximum inner diameter R2max, and the maximum inner diameter R2max of the second extending portion 113 and the maximum inner diameter R1max of the first extending portion 112 are equal. Further, the boundary between the portion 113a having the maximum inner diameter R2max and the portion 113b having the minimum inner diameter R2min of the second extending portion 113 is an end surface perpendicular to the rotation center line direction D.

Since the first extending portion 112 and the portion 113a having the maximum inner diameter R2max of the second extending portion 113 have the same inner diameter, they make one round of the inner peripheral surface of the extending portion 111 and go outward in the radial direction. Thus, a groove-shaped region M that is concave is formed.
At the time of driving the flexure meshing gear device 1, the lubricant applied or supplied to various places in the device is moved outward from the center of rotation, but the extending portion 111 has the second inner teeth. Since the gear 12 is surrounded, the lubricant is trapped in the groove-shaped region M.
Further, since there is a portion 113b that becomes the minimum inner diameter R2min of the second extending portion 113 on the second internal gear 12 side with respect to the groove-shaped region M, the lubrication captured in the groove-shaped region M is present. The agent is restrained from moving toward the opening end of the extending portion 111 and can be held in the groove-shaped region M.

Note that the minimum inner diameter R2min of the second extending portion 113 is preferably set to a size close to the outer diameter of the second internal gear 12 within a range that does not cause interference with the second internal gear 12. Thereby, the passage of the lubricant can be narrowed, and the movement of the extending portion 111 toward the opening end can be further reduced.
Further, the rotation center line O of the flexure meshing gear device 1 is not essential, but a direction inclined with respect to the vertical vertical direction is preferable, and further, it is more preferably directed to a horizontal or substantially horizontal state.

[Operation of flexible meshing gear unit]
Next, the operation of the gear device 1 will be described. As described above, here, the configuration in which the eccentric cam 15 is connected to the input shaft (drive source side), the first internal gear 11 is connected to the output shaft, and the second internal gear 12 is fixed will be described. . Although not particularly limited, the number of teeth of the first internal gear 11 and the external gear 13 is the same, and the number of teeth of the second internal gear 12 and the external gear 13 is different. Shall. The relationship between the number of teeth of the first internal gear 11 and the second internal gear 12 may be reversed.

  When the eccentric cam 15 is rotated by the rotational drive of the input shaft, the movement of the eccentric cam 15 is transmitted to the external gear 13 via the bearing 14. Since the external gear 13 is partially engaged with the fixed second internal gear 12, the external gear 13 does not rotate following the rotation of the eccentric cam 15. On the other hand, a motion in which the eccentric cam 15 rotates relatively is obtained. At this time, since the external gear 13 is regulated to a shape along the cam surface 15 a of the eccentric cam 15, the external gear 13 bends and deforms as the eccentric cam 15 rotates. Specifically, the positions of the portion where the curvature of the external gear 13 is increased and the portion where the curvature is decreased are deformed so as to periodically move. The period of this deformation is proportional to the high-speed rotation period of the eccentric cam 15.

As described above, when the external gear 13 is deformed by the rotation of the eccentric cam 15, the meshing position of the external gear 13 and the second internal gear 12 changes in the rotation direction according to the rotation of the long axis La of the eccentric cam 15. . Here, if there is a difference in the number of teeth between the external gear 13 and the second internal gear 12, the corresponding relationship between the tooth portions 13a and 12a that are meshed every time the meshing position makes a round shifts. Thus, relative rotation occurs between the external gear 13 and the second internal gear 12. Here, since the second internal gear 12 is fixed, the external gear 13 rotates.
For example, if the number of teeth of the second internal gear 12 is 102 and the number of teeth of the external gear 13 is 100, the rotational movement of the eccentric cam 15 is decelerated at a reduction ratio of 100: 2 and transmitted to the external gear 13. Is done.

  On the other hand, since the external gear 13 meshes with the first internal gear 11 in the same manner, the position where the external gear 13 and the first internal gear 11 mesh with each other in the rotational direction due to the rotation of the eccentric cam 15. Change. Since the number of teeth of the first internal gear 11 and the number of teeth of the external gear 13 are the same, the external gear 13 and the first internal gear 11 do not rotate and move relatively, and the external gear 13. Is transmitted to the first internal gear 11 at a reduction ratio of 1: 1. Thereby, the 1st internal gear 11 rotates and the rotational motion decelerated from the output shaft is output.

[Technical effect of flexure meshing gear]
In the bending meshing gear device 1, the first internal gear 11 has an extending portion 111, and the extending portion 111 is a gap d between the first internal gear 11 and the second internal gear 12. The first extending portion 112 positioned on the radially outer side of the second internal gear 12 and the second extending portion 113 positioned on the radially outer side of the second internal gear 12 have a maximum inner diameter R1max of the first extending portion 112. , Larger than the minimum inner diameter R2min of the second extending portion 113.
For this reason, when driving the flexure meshing gear device 1, the portion of the first extending portion 112 having the maximum inner diameter R1max captures the lubricant in the device that moves outward from the center of rotation. And since the part 113b used as the minimum internal diameter R2min of the 2nd extension part 113 exists in the outer side of the 2nd internal gear 12, it suppresses that the capture | acquired lubricant moves outside the extension part 111. In addition, the lubricant can be held in the apparatus. When the rotation stops, the retained lubricant returns to the meshing portion.
Therefore, in the flexibly meshing gear device 1, in particular, the lubricity of the meshing portion is improved, and high lubricity can be maintained for a longer time.

  Further, when the first internal gear 11 is a gear that outputs a rotation decelerated from the input rotation by the gear device 1, the first internal gear 11 is held within the maximum inner diameter R1max of the first extending portion 112. Further, the lubricant can be moved by gravity by the rotation of the first internal gear 11, and a part of the lubricant can be refluxed to a place where the lubricant is required in the apparatus.

  In addition, when the inner diameter of the first extending portion 112 is constant over the entire length in the rotation center line direction D, more lubricant can be retained, and high lubricity can be maintained even longer. It becomes possible.

  Further, when the second extending portion 113 has a portion 113b having the minimum inner diameter R2min in a certain range along the rotation center line direction D, the first extending portion 112 has the maximum inner diameter R1max. It is possible to further suppress the lubricant trapped in the portion from moving to the outside of the extending portion 111 and to hold the lubricant in the apparatus more effectively.

  In addition, when the maximum inner diameter R1max of the first extension portion 112 and the maximum inner diameter R2max of the second extension portion 113 are equal, more lubricant can be retained, and high lubricity is maintained for a longer time. It becomes possible.

[Second Embodiment]
Another example different from the lubricant holding structure shown in FIG. 4 will be described with reference to FIG. FIG. 5 is an enlarged cross-sectional view along a cross section passing through the rotation center line O of the first internal gear 11A and the second internal gear 12A.
In the following description, only differences from the above-described flexure meshing gear device 1 will be mainly described, and description of common parts will be omitted. Moreover, the same code | symbol is used about the same structure as each structure of the bending meshing gear apparatus 1 mentioned above, and the overlapping description is abbreviate | omitted.

As shown in FIG. 5, the first internal gear 11 </ b> A includes a main body 110 having a tooth portion 11 a, and a second along the rotation center line direction D from the end of the main body 110 on the second internal gear 12 </ b> A side. A substantially cylindrical extending portion 111 </ b> A extending toward the internal gear 12 side. The inside of the extending portion 111A has a lubricant holding structure.
The main body 110 and the extending portion 111A are integrally formed, and the outer diameters thereof are equal and the outer diameter is larger than that of the second internal gear 12A. The extending portion 111A has the second internal gear 12A disposed on the inner side, and the inner diameter of each portion in the rotation center line direction D of the extending portion 111A does not interfere with the second internal gear 12A. ing.

The extending portion 111A has a first extending portion 112A located on the radially outer side of the gap d between the first internal gear 11A and the second internal gear 12A, and a radially outer side of the second internal gear 12A. It has the 2nd extension part 113A located.
Also in the case of the first extending portion 112A, the maximum inner diameter R1max is larger than the minimum inner diameter R2min of the second extending portion 113A.

In the extending portion 111A, the inner diameter of the end on the main body 110 side (left side in FIG. 5) in the rotation center line direction D is the maximum inner diameter R1max.
Further, the extending portion 111A has a uniform inner diameter at the end on the second internal gear 12 side (right side in FIG. 5) in the rotation center line direction D and a constant width in the rotation center line direction D at the minimum inner diameter R2min. The same-diameter portion 114A is formed.

In the range from the end where the maximum inner diameter R1max of the extending portion 111A reaches the constant diameter portion 114A, the reduced diameter portion 115A is formed from the first extending portion 112A to the second extending portion 113A. Has been.
As for this diameter-reduced portion 115A, the inner diameter gradually decreases at a constant rate toward the second internal gear 12 side in the rotation center line direction D. That is, the reduced diameter portion 115A has a cross-sectional shape that is linearly inclined with respect to the rotation center line direction D, and the inner peripheral surface of the reduced diameter portion 115A is a conical surface. The first extending portion 112A and the second extending portion 113A are connected by this conical surface.

The second internal gear 12A has the same outer diameter at the end of the first internal gear 11A (left side in FIG. 5) in the rotation center line direction D within the constant range of the rotation center line direction D. It has an equal-diameter portion 121A.
The second internal gear 12A gradually increases from the smallest outer diameter to the largest outer diameter on the second internal gear 12A side (right side in FIG. 5) in the rotation center line direction D adjacent to the equal-diameter portion 121A. It has an enlarged diameter portion 122A. That is, the cross-sectional shape of the enlarged diameter portion 122A is inclined with respect to the rotation center line direction D, and the outer peripheral surface of the enlarged diameter portion 122A is a conical surface.
The maximum outer diameter of the enlarged diameter portion 122A (which is also the maximum outer diameter of the second internal gear 12A) is smaller than the minimum inner diameter R2min of the extending portion 111A described above, and the first internal gear 11A and the second internal gear It does not interfere with the relative rotation of the tooth gear 12A.

Also in the case of the first internal gear 11A, the minimum inner diameter R2min of the second extending portion 113A is the maximum outer diameter of the second internal gear 12A as long as it does not interfere with the second internal gear 12A. It is preferable that the size is close.
Further, also in the case of the first internal gear 11A and the second internal gear 12A, it is more preferable that the rotation center line O be directed in a direction inclined with respect to the vertical direction, and further in a horizontal or substantially horizontal state.

Thus, also in the case of the first internal gear 11A, since the maximum inner diameter R1max of the first extending portion 112A is larger than the minimum inner diameter R2min of the second extending portion 113A, the lubricant is held in the apparatus, It is possible to improve and maintain the lubricity.
In addition, since the constant-diameter portion 114A having the minimum inner diameter R2min of the second extending portion 113A has a certain range along the rotation center line direction D, the movement of the lubricant to the outside of the extending portion 111A is suppressed, and lubrication is performed. It becomes possible to hold | maintain an agent in an apparatus more effectively.

  Further, when the inner periphery of the extending portion 111A has a reduced diameter portion 115A in which the inner diameter decreases linearly from the first internal gear 11A toward the second internal gear 12A side, The lubricant trapped in the existing portion 111A can be returned to the first internal gear 11A side, and high lubricity can be maintained for a longer time.

  Further, the end of the second internal gear 12A on the side opposite to the first internal gear 11A side than the outer diameter of the end on the first internal gear 11A side (the outer diameter of the equal diameter portion 121A). When the outer diameter (maximum outer diameter) is increased, more lubricant can be retained, and high lubricity can be maintained for a longer time.

[Others]
As shown in FIG. 4, the first internal gear 11 and the second internal gear 12 described above have the positions of the end portions on the second internal gear 12 side (right side in FIG. 4) in the respective rotation center line directions D. Although the aligned state is illustrated, the present invention is not limited to this. That is, the end positions of the first internal gear 11 and the second internal gear 12 are inconsistent with respect to the rotation center line direction D, and one of the end positions extends further along the rotation center line direction D. May be. Further, the width in the rotation center line direction D of the main body 110 of the first internal gear 11 and the second internal gear 12 may not be equal. The same applies to the first internal gear 11A and the second internal gear 12A shown in FIG.

  At the boundary between the first extending portion 112 and the second extending portion 113 in the extending portion 111 of the first internal gear 11 described above, the inner diameter is from the first internal gear 11 toward the second internal gear 12. A gradually decreasing conical surface may be provided.

  The first internal gears 11 and 11A both have a portion having the same inner diameter with a minimum inner diameter, but this is not essential. For example, you may comprise the whole internal peripheral surface of the 1st internal gear 11 and 11A by one or several conical surfaces.

In the configuration of FIG. 4, instead of the second internal gear 12, the outer diameter of the end portion on the opposite side (right side of FIG. 4) is larger than the outer diameter of the end portion on the first internal gear 11 side (left side of FIG. 4). A second internal gear having a larger diameter may be provided.
Similarly, in the configuration of FIG. 5, a second internal gear having a uniform outer diameter over the entire length in the rotation center line direction D may be provided instead of the second internal gear 12 </ b> A.

Further, the lubricant is not limited to a paste-like material such as grease, and a liquid material may be used.
In addition, the details shown in the embodiments can be changed as appropriate without departing from the spirit of the invention.

1 Gear device (flexure meshing gear device)
11, 11A First internal gear 11a Tooth portion 12, 12A Second internal gear 12a Tooth portion 13 External gear 13a Tooth portion 14 Bearing 15 Eccentric cam (vibrator)
110 Body portion 111, 111A Extension portion 112, 112A First extension portion 113, 113A Second extension portion 113a Maximum inner diameter portion 113b Minimum inner diameter portion 114A Same diameter portion 115A Reduced diameter portion 121A Same diameter portion 122A Diameter expansion part D Rotation center line direction (axial direction)
d Gap M Region O Rotation center line
R1max, R2max Maximum inner diameter
R2min Minimum inner diameter

Claims (7)

A vibrator,
An external gear to which bending deformation is imparted by the vibrator,
A first internal gear that meshes with the external gear;
A second internal gear that is disposed next to the first internal gear in the axial direction and meshes with the external gear;
A flexure meshing gear device comprising:
The first internal gear has an extending portion extending toward the second internal gear along the axial direction;
The extension part is located on the radially outer side of the second internal gear and the first extension part located on the radially outer side of the gap between the first internal gear and the second internal gear. A second extension part,
A flexure meshing gear device in which a maximum inner diameter of the first extending portion is larger than a minimum inner diameter of the second extending portion.   2. The flexure meshing gear device according to claim 1, wherein the first internal gear is a gear that outputs rotation decelerated from input rotation by the gear device.   3. The flexible meshing gear device according to claim 1, wherein the first extending portion has a constant inner diameter over the entire length in the axial direction.   The flexibly meshing gear device according to any one of claims 1 to 3, wherein the second extending portion has a portion having the minimum inner diameter in a certain range along the axial direction.   The flexure meshing gear device according to any one of claims 1 to 4, wherein a maximum inner diameter of the first extending portion is equal to a maximum inner diameter of the second extending portion.   6. The inner periphery of the extension part has a portion in which an inner diameter linearly decreases from the first internal gear toward the second internal gear side. Bending gear system.   7. The second internal gear has a larger outer diameter at an end opposite to the first internal gear than at an outer diameter at the end on the first internal gear. The flexure meshing gear device according to any one of the above.

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