JP2020122563A - Flexible external gear and wave gear device - Google Patents

Abstract

To provide a technique that can easily manufacture a flexible external gear that meets required properties of each part.SOLUTION: A flexible external gear comprises external teeth in an outer peripheral surface. The external teeth partially engage with internal teeth of an annular rigid internal gear. The flexible external gear rotates relatively with respect to the rigid internal gear while moving an engagement position between the internal teeth and the external teeth in its circumferential direction by being pushed in association with rotation of an imperfectly circular cam. The flexible external gear comprises a first part 27 and a second part 28. The first part includes a cylindrical flexible thin-walled part 25 in which the external teeth are formed. The second part includes a flat plate part 26 spreading in a direction perpendicular to a rotation center axis of the external teeth. The first part and the second part are materials different from each other.SELECTED DRAWING: Figure 3

Description

The present invention relates to a flexible external gear and a wave gear device.

Conventionally, a wave gear device including a flexible external gear is known. This type of wave gear device is mainly used as a speed reducer. Regarding a conventional wave gear device, for example, Japanese Patent Laid-Open No. 2011-2011
No. 196,423. The wave gear device disclosed in Japanese Unexamined Patent Application Publication No. 2011-196423 includes a rigid internal gear having internal teeth, a flexible external gear having external teeth, and a flexible external gear. Wave generation that generates relative rotational motion between the rigid internal gear and the flexible external gear by flexing in the radial direction and engaging the external teeth with the internal teeth and moving the engagement position in the circumferential direction And a container.

Further, the flexible external gear described in JP2011-196423A includes a body portion and a disc portion. External teeth are formed on the outer peripheral surface of the body. The disk portion forms a plane perpendicular to the rotation center axis of the external tooth. An output shaft for fixing the relative rotational movement to the outside is fixed to the center of the disc portion.
JP, 2011-196423, A

In the flexible external gear having such a configuration, the body portion is a portion that repeats the elliptical flexural deformation due to the driving of the wave generator, and thus is formed in a thin-walled shape that easily undergoes flexural deformation. on the other hand,
Since the disc portion is a portion for fixing the output shaft, the disc portion is formed in a thick shape having high rigidity.

In the flexible external gear, the body portion and the disc portion are generally integrally formed by forging. However, with forging, it is difficult to accurately manufacture a member having a plurality of portions having different wall thicknesses. Therefore, after the forging process, it is necessary to finish the flexible external gear by cutting in order to optimize the characteristics such as flexibility and rigidity of each part.

In Japanese Unexamined Patent Application Publication No. 2011-196423, in order to improve the durability of the flexible externally toothed gear, the body portion and the disc portion are separately engaged with each other. However, if the body portion and the disc portion are separate bodies, it is considered difficult to drive the wave gear device with high accuracy while suppressing local rattling.

An object of the present invention is to provide a technique capable of easily manufacturing a flexible external gear that satisfies the required characteristics of each part.

The flexible external gear of the present invention has external teeth on its outer peripheral surface that partially mesh with the internal teeth of a ring-shaped rigid internal gear, and its internal peripheral surface allows rotation of a non-round cam. By being pushed along with it, the inner teeth and the outer teeth rotate relative to the rigid internal gear while moving the meshing position of the internal teeth in the circumferential direction. This flexible external gear has at least a first portion and a second portion. The first portion includes a tubular flexible thin portion in which the external teeth are formed. The second portion includes a flat plate portion that spreads in a direction perpendicular to the rotation center axis of the external tooth. The second part is integrated with the first part by being joined to the first part. The first part and the second part are made of different materials.

According to the aspects of the present invention, it is possible to easily manufacture a flexible external gear that satisfies the required characteristics of each part.

FIG. 1 is a vertical cross-sectional view of a wave gear device according to a first embodiment. FIG. 2 is a cross-sectional view of the wave gear device according to the first embodiment. FIG. 3 is a vertical cross-sectional view of the flexible external gear according to the first embodiment. FIG. 4 is an exploded vertical cross-sectional view of the flexible external gear according to the first embodiment. FIG. 5 is a vertical cross-sectional view of the flexible external gear according to the first modification of the first embodiment. FIG. 6A is a vertical cross-sectional view of a flexible external gear according to Modification 2 of the first embodiment. FIG. 6B is a vertical cross-sectional view of a flexible external gear according to Modification 2 of the first embodiment.

Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings. In the present application, the direction parallel to the central axis of the wave gear device is "axial direction", the direction orthogonal to the central axis of the wave gear device is "radial direction", and the arc is centered on the central axis of the wave gear device. The directions are referred to as “circumferential directions”, respectively.

Further, in the present application, the “parallel direction” also includes a substantially parallel direction. In the present application,
The “orthogonal direction” also includes a substantially orthogonal direction.

<1. First Embodiment>
<1-1. Structure of wave gear device>
Hereinafter, the configuration of the wave gear device 100 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a vertical cross-sectional view of a wave gear device 100 according to the first embodiment. FIG. 2 is a transverse sectional view of the wave gear device 100 when viewed from the position II-II in FIG.

The wave gear device 100 of the present embodiment is a device that shifts the input rotational movement by utilizing a differential between a rigid internal gear 10 and a flexible external gear 20 described later. The wave gear device 100 is incorporated in a joint of a small robot, for example, and is used as a speed reducer for reducing the power obtained from a motor.

As shown in FIGS. 1 and 2, the wave gear device 100 includes a rigid internal gear 10, a flexible external gear 20, and a wave generator 30.

The rigid internal gear 10 is an annular member centered on the rotation center axis C. Rigidity The rigidity of the internal gear 10 is much higher than the rigidity of the flexible thin portion 25 described later. Therefore, the rigid internal gear 10 can be regarded as a substantially rigid body. The rigid internal gear 10 has a plurality of internal teeth on its inner peripheral surface. The plurality of inner teeth 11 are arranged at a constant pitch along the circumferential direction. The rigid internal gear 10 is fixed to the frame of the device in which the wave gear device 100 is mounted.

The flexible external gear 20 is a member having a flexible thin portion 25 and a flat plate portion 26. The flexible thin portion 25 is a cylindrical portion that can bend in the radial direction. The flat plate portion 26 is a flat plate portion that is less likely to bend than the flexible thin portion 25. As shown in FIGS. 1 and 2, the flexible external gear 20 is arranged inside the rigid internal gear 10. The flexible thin portion 25 has a plurality of outer teeth 21 on the outer peripheral surface. The plurality of outer teeth 21 are arranged at a constant pitch along the circumferential direction. The number of internal teeth 11 included in the rigid internal gear 10 and the number of external teeth 21 included in the flexible external gear 20 are slightly different from each other. An output shaft (not shown) for extracting power after deceleration is fixed to the center of the flat plate portion 26.

The wave generator 30 is a mechanism for flexibly deforming the flexible external gear 20. The wave generator 30 includes a non-round cam 31 and a wave bearing 33.

The non-round cam 31 of this embodiment has an elliptical cam profile. As shown in FIGS. 1 and 2, the non-round cam 31 is arranged inside the flexible thin portion 25 of the flexible external gear 20 in the radial direction. An input shaft (not shown) is fixed to the center of the non-round cam 31 so as not to rotate relative to it. The input shaft and the non-round cam 31 are rotated by the power obtained from an external motor (not shown) at the rotation speed before deceleration.

The wave bearing 33 includes an inner ring 331, a plurality of balls 332, and an elastically deformable outer ring 333. The inner ring 331 is fixed to the outer peripheral surface of the non-round cam 31. The outer ring 333 is fixed to the inner peripheral surface of the flexible thin portion 25 of the flexible external gear 20. The plurality of balls 332 are interposed between the inner ring 331 and the outer ring 333 and arranged along the circumferential direction. The outer ring 333 elastically deforms (deflects and deforms) via the inner ring 331 and the balls 332 so as to reflect the cam profile of the rotated non-round cam 31.

In the wave gear device 100 having such a configuration, when power is supplied to the input shaft, the input shaft and the non-round cam 31 rotate integrally. Further, as the non-round cam 31 rotates, the inner peripheral surface of the flexible thin portion 25 of the flexible externally toothed gear 20 is pushed via the wave bearing 33, whereby the flexible thin portion 25. Deforms into an elliptical shape. As a result, as shown in FIG. 2, the outer teeth 21 and the inner teeth 11 mesh with each other at two positions on both ends of the major axis of the ellipse formed by the flexible thin portion 25. At this time, the outer teeth 21 and the inner teeth 11 do not mesh with each other at phase positions other than the two positions of the ellipse.

When the non-round cam 31 rotates, the position of the major axis of the ellipse moves in the circumferential direction, so that the meshing position between the outer teeth 21 and the inner teeth 11 also moves in the circumferential direction. Here, as described above, the number of the internal teeth 11 of the rigid internal gear 10 is slightly different from the number of the external teeth 21 of the flexible external gear 20. Therefore, the meshing position of the inner teeth 11 and the outer teeth 21 slightly changes for each rotation of the non-round cam 31. As a result, the flexible external gear 20 and the output shaft rotate with respect to the rigid internal gear 10 at a reduced rotation speed.

<1-2. Structure of flexible external gear>
Next, the configuration of the flexible external gear 20 will be described more specifically with reference to FIGS. 3 and 4. FIG. 3 is a vertical cross-sectional view of the flexible external gear 20 according to the first embodiment. FIG. 4 is an exploded vertical cross-sectional view for explaining the first portion 27 and the second portion 28 that form the flexible external gear 20 of FIG.

As shown in FIGS. 3 and 4, the flexible external gear 20 of the present embodiment has a flexible thin portion 25, a flat plate portion 26, and a tubular arm portion 29.

The flexible thin portion 25 is a tubular portion that can be flexibly deformed in the radial direction. The thickness of the flexible thin portion 25 in the radial direction is smaller than the thickness of the flat plate portion 26 in the axial direction. The plurality of outer teeth 21 are formed on the outer peripheral surface of the flexible thin portion 25. The flat plate portion 26 is a disc-shaped portion having higher rigidity than the flexible thin portion 25. The flat plate portion 26 extends perpendicularly to the rotation center axis C (see FIG. 1). Further, the flat plate portion 26 expands radially inward with respect to the flexible thin portion 25.

The tubular arm portion 29 is a cylindrical portion that connects one end portion in the axial direction of the flexible thin portion 25 and the outer peripheral portion of the flat plate portion 26. The radial thickness of the tubular arm portion 29 is smaller than the axial thickness of the flat plate portion 26. By providing the tubular arm portion 29 between the flexible thin portion 25 and the flat plate portion 26, even if the flexible thin portion 25 repeats the elliptic flexural deformation, the flexible external gear 20 is hooked. It is possible to mitigate that the stress distribution is locally concentrated. The axially intermediate portion of the tubular arm portion 29 is an area where the distribution of stress applied when the non-round cam 31 is rotated is relatively small. As shown in FIGS. 3 and 4, the tubular arm portion 29 is formed across the first portion 27 and the second portion 28. Here, the first part side of the tubular arm part 29 is referred to as a first arm part 29A, and the second part side thereof is referred to as a second arm part 29B. That is, the first portion 27 has the first arm portion 29A connected to the flexible thin portion 25, and the second portion 28 has the second arm portion 29B connected to the flat plate portion 26.

As shown in FIG. 4, the flexible external gear 20 is formed by fixing the first portion 27 and the second portion 28 to each other. The flexible thin portion 25 and the first arm portion 29A that is a part of the tubular arm portion 29 are included in the first portion 27. The flat plate portion 26 and the second arm portion 29B, which is a portion other than the portion of the tubular arm portion 29, are included in the second portion 28. Here, the first arm portion 29A is a portion where the second arm portion 29B contacts each other when the first portion 27 and the second portion 28 are fixed to each other.

<1-3. Manufacturing process of flexible external gear>
When manufacturing the flexible externally toothed gear 20, first, the first portion 27, which is a part of the flexible externally toothed gear 20, is manufactured by casting (step S1). By manufacturing by casting, a gear having a complicated gear shape can be manufactured more efficiently than by cutting. The radial outer peripheral surface of the first portion is preferably an inclined surface that is radially inward toward the opening side. This not only improves the releasability at the time of casting, but also improves the meshing with the rigid internal gear 10 when the flexible external gear 20 is pressed and deformed by the non-round cam 31.

Simultaneously with or before and after step S1, the second part 28 which is another part of the flexible external gear 20 is manufactured by forging (step S2). More specifically, the second portion 28 is processed into a rough shape by forging, and then detailed processing is performed by cutting. In addition, the joint surface 28A is polished and polished to a mirror surface.

Then, the 1st arm part 29A of the 1st part 27 and the 2nd arm part 29B of the 2nd part 28 contact and are mutually fixed (step S3). That is, the flexible external gear 20 is manufactured by fixing the 1st part 27 and the 2nd part 28 mutually. The fact that the first portion 27 and the second portion 28 are fixed to each other is not limited to the case where the first portion 27 and the second portion 28 are joined to each other to form a single connected member. That is, as long as the first portion 27 and the second portion 28 are in contact with each other so that they can rotate together, the first portion 27 and the second portion 28 may be separate members.

When the first part 27 and the second part 28 are combined and fixed to each other, various methods such as caulking, bonding, press fitting, welding, fitting, and insert molding may be used.

The first arm portion 29A of the first portion 27 has unevenness more than the tooth width of the flexible external gear 20, and the second arm portion 29B of the second portion 28 has unevenness that meshes with the unevenness of the first portion 27. It is preferable to have. Accordingly, when the first portion 27 and the second portion 28 are combined and fixed, the uneven portion serves as a rotation stop, and idling is suppressed.

If the flexible external gear 20 is manufactured by such a process, it is advantageous in the following points. That is, since the flexible thin portion 25 is a portion where the elliptical flexural deformation is repeated, high flexibility (flexibility) is required. On the other hand, the flat plate portion 26 is generally a portion to which the output shaft is fixed by using a fastener such as a screw, and therefore high rigidity and a certain thickness or more are required. According to the manufacturing process described above, it is possible to manufacture a plurality of parts that require different flexibility and rigidity as described above in individual processes (steps S1 and S2). Therefore, it becomes easy to employ materials having different elastic moduli for the first part 27 and the second part 28, or to perform different processing treatments on the first part 27 and the second part 28. As a result, the flexible external gear 20 that satisfies the characteristics of each part can be easily manufactured.

An amorphous metal is preferably used as the material of the first portion 27. The dimensional accuracy of the flexible external gear can be improved. For example, a metal such as iron is used as the material of the second portion 28. In addition, it is preferable to use a material having a smaller elastic modulus (more easily deformed) than that of the second portion 28 for the first portion 27. With this configuration, the flexible thin portion 25 having the outer teeth 21 can be easily bent, while the rigidity of the flat plate portion 26 to which the output shaft is fixed can be easily increased.

Further, in the flexible external gear 20 of the present embodiment, the first portion is provided in the middle portion of the tubular arm portion 29, which is a region where the distribution of stress applied when the non-round cam 31 is rotated is relatively small. The fixing portion 23, which is a portion where the portion 27 and the second portion 28 are fixed to each other, is formed. More specifically, the fixed portion 23 is a portion where the first arm portion 29A and the second arm portion 29B are fixed to each other. That is, the fixing portion 23 is formed at a position apart from both the flexible thin portion 25 where the outer teeth 21 are formed and the flat plate portion 26. This can prevent the flexible external gear 20 from being divided into the first portion 27 and the second portion 28 by applying an excessive force to the fixing portion 23. Thus, even if the flexible thin portion 25 of the flexible external gear 20 is repeatedly flexed and deformed, the fixing portion 23 is formed in a portion where stress is less likely to concentrate, so that the flexible external gear 20 The durability of can be improved.

As described above, according to this embodiment, the so-called cup-shaped flexible external gear 20 having both the flat plate portion 26 requiring rigidity and the flexible thin portion 25 requiring flexibility is efficiently manufactured. can do.

<Modification 1>
Below, with reference to Drawing 5, the composition of flexible external gear 40 concerning modification 1 of a 1st embodiment is explained. FIG. 5 is a vertical cross-sectional view of the flexible external gear 40 according to the modified example 1 of the first embodiment. In the following description, the same members and parts as those already described in the first embodiment will be designated by the same reference numerals as in the first embodiment, and detailed description thereof will be omitted. ..

The first arm portion 49A of the first portion 47 of the flexible externally toothed gear 40 according to the first modification of the first embodiment has a base portion 41 connected to the flexible thin portion 65, and an extension extending from the base portion and having a taper shape. It has a section 42. The second arm portion 49B of the second portion 48 has an outer ring 43 arranged radially outside the first portion 27 and an inner ring 44 arranged radially inside the first portion 47 and the outer ring 43.

Here, the extending portion 42 of the first portion 47 is arranged between the outer race 43 and the inner race 44 of the second portion 48. The extending portion 42, the outer ring 43, and the inner ring 44 are fixed to each other, and the first portion 47 and the second portion 48 are fixed more firmly. More specifically, in a state where the extending portion 42 is arranged between the outer ring 43 and the inner ring 44, the extending portion 42 is moved so as to narrow the gap between the outer ring 43 and the inner ring 44, and the extending portion is sandwiched and fixed. At this time, they may be fixed by simply sandwiching them, or may be combined with adhesion or welding. In addition, the radially inner surface of the outer ring 43 and the radially outer surface of the inner ring 44 may be provided with irregular shapes (not shown) to sandwich and fix the extending portion 42. At this time, the extending portion 42 may be deformed.

<Modification 2>
Below, with reference to Drawing 6A and Drawing 6B, composition of flexible external gear 60 concerning modification 2 of a 1st embodiment is explained. FIG. 6A is a cross-sectional view of the flexible externally toothed gear 60 according to the second modification of the first embodiment, which is in a state before the first portion 67 and the second portion 68 are integrated. In the following description, the same members and parts as those already described in the first embodiment will be designated by the same reference numerals as in the first embodiment, and detailed description thereof will be omitted. ..

A groove portion 70 is provided at an end portion of the second arm portion 69B of the second portion 68. At least a part of the first portion 67 is accommodated in the groove portion 70. Then, the wall surface forming the groove portion 70 is deformed, and the first portion 68 and the second portion 68 are caulked and fixed. FIG. 6B is a cross-sectional view of the first portion 67 and the second portion 68 in a state where they are fixed by crimping. When crimping and fixing, there is no need to raise the temperature unlike welding, so the temperature rise of the first portion 67 during fixing can be small. This characteristic makes it easy to select, as the material of the first portion 67, a material such as metallic glass that deteriorates due to temperature rise. If necessary, a fixing method such as adhesion or welding may be used together.

<3. Other modifications>
Although the exemplary embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

In the above embodiment, the flexible external gear is manufactured by fixing the first part and the second part. However, the flexible external gear may be manufactured by fixing three or more members including the first part and the second part.

Further, in the above-described embodiment, it has been described that materials having different elastic moduli are used for the first part and the second part. However, materials having different properties other than the elastic modulus may be used for the first part and the second part. For example, materials having different spring properties, pressure resistance, resistance against repeated load, or hardness may be used for the first part and the second part.

Moreover, in the above-mentioned embodiment, the second part was manufactured by forging. However, the second part may be manufactured by another method such as press working.

The radial inner side surface of the second arm portion was fixed by contacting the radial outer side surface of the first arm portion, but the radial inner side surface of the first arm portion was fixed to the radial outer side surface of the second arm portion. It may be fixed by contact. In addition, the second arm portion may contact and be fixed below the first arm portion.

The first part and the second part were fixed by contacting the first arm part and the second arm part, but not limited to this. The flexible thin portion and the flat portion may be in contact and fixed.

Moreover, in the manufacturing process of the flexible external gear shown in the above-mentioned embodiment, the order of each process may be partially replaced, or another process may be added.

In the above embodiment, the flexible external gear has been described by giving directions such as “vertical”, “horizontal”, “bottom”, etc., but these indicate the direction when the wave gear device is used. It is not limited.

Further, the detailed shape and the like of the wave gear device may be different from those shown in the drawings of the present application. Further, the respective elements appearing in the above-described embodiment or modification may be appropriately combined within the range where no contradiction occurs.

The present application can be applied to a flexible external gear and a wave gear device.

10 Rigid Internal Toothed Gear 11 Internal Tooth 20, 40, 60, Flexible External Toothed Gear 21 External Tooth 23, 43, 63 Fixed Part 25 Flexible Thinned Part 26, 46, 66 Flat Plate Part 27, 47, 67 1st Part 28, 48, 68 Second part 29 Cylindrical arm part 30 Wave generator 31 Non-round cam 33 Wave bearing 100: Wave gear device

Claims (11)

The outer peripheral surface has outer teeth that partially mesh with the inner teeth of the annular rigid internal gear, and the inner peripheral surface is pushed by the rotation of the non-round cam, so that A flexible external gear, which rotates relative to the rigid internal gear while moving a meshing position with the external teeth in the circumferential direction,
A first portion including a tubular flexible thin portion on which the external teeth are formed;
A flat portion that extends in a direction perpendicular to the rotation center axis of the external tooth, and a second portion that is integrated with the first portion,
The said 1st part and the said 2nd part are flexible external gears which are mutually different materials. The flexible external gear according to claim 1,
The first part is a flexible external gear that is an amorphous metal. The flexible external gear according to claim 1 or 2, wherein
The said 1st part and the said 2nd part are separate members mutually, and are the flexible external gears which are contacting rotatably. The flexible external gear according to claim 1,
The radially outer peripheral surface of the first portion is an inclined surface that is radially inward toward the opening side. The flexible external gear according to claim 1,
The first portion has a first arm portion connected to the flexible thin portion,
The second portion has a second arm portion connected to the flat plate portion,
The first part and the second part are integrated by the first arm part and the second arm part. The flexible external gear according to claim 1,
The second portion is located on the radially outer peripheral surface of the first portion. The flexible external gear according to claim 1,
The second part is in contact with the lower part of the first part. The flexible external gear according to claim 6,
At the contact portion between the first portion and the second portion, the first portion is arranged outside the second portion. The flexible external gear according to claim 1,
The flexible thin portion of the first portion has an uneven portion smaller than the tooth width of the external tooth. The flexible external gear according to claim 1,
The first portion has a first arm portion extending from the flexible thin portion, and has a tapered base portion,
The second part has an outer ring arranged radially outside the first part, and an inner ring arranged radially inside the first part and the outer ring,
The base portion radially overlaps with the outer ring and the inner ring. The flexible external gear according to claim 1,
The second portion has a wall portion that is connected to the flat plate portion and extends in a direction parallel to the rotation center axis of the external tooth,
The end of the wall has a groove,
The groove portion accommodates at least a part of the flexible thin portion.

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