Flexible bending meshing type gear device

Abstract

An object of the presently disclosed technology is to provide a flexural meshing type gear device capable of suppressing a decrease in strength and durability of teeth of an external gear. The flexural meshing type gear device includes a wave generator, an external gear flexibly deformed by the wave generator, a first internal gear meshing with the external gear, and a second internal gear arranged so that the second internal gear and the first internal gear are arranged in an axial direction and mesh with the external gear. The external gear includes a first external tooth portion meshing with the first internal gear and a second external tooth portion meshing with the second internal gear. The second external tooth portion includes a second thickest external tooth portion where a tooth thickness is the largest, and a second external tooth inner side tooth thickness decreasing portion where the tooth thickness decreases from the second thickest external tooth portion toward an inner side in the axial direction.An inner tooth portion of the second internal gear includes a second thickest inner tooth portion in which a tooth thickness is largest, and a second inner tooth inner side tooth thickness decreasing portion in which the tooth thickness decreases from the second thickest inner tooth portion toward the inner side in the axial direction.

Description

Technical area

[0001] The present invention relates to a flexural engagement type gear device. State of the art

[0002] A flexural engagement type gear device including a wave generator, an external gear flexibly deformed by the wave generator, a first internal gear meshing with the external gear, and a second internal gear arranged such that the second internal gear and the first internal gear are arranged in an axial direction and meshing with the external gear is known (for example, see PTL 1).

[0003] In PTL 1, a technique of suppressing excessive wear of teeth of an external gear, a first internal gear, and a second internal gear in a flat type flexural meshing type gear device by designing a tooth track shape of the external gear is disclosed. Citation listPatent literature

[0004] [PTL 1] Japanese Unexamined Patent Publication No. 2019-120325 Summary of the inventionTechnical problem

[0005] In the case of the flexural meshing type gear device of PTL 1, an effect of suppressing excessive wear of the teeth of the external gear, the first internal gear, and the second internal gear is achieved. However, there is room for improvement in the strength and durability of the external gear teeth.

[0006] An object of the present invention is to provide a flexural meshing type gear device capable of suppressing a decrease in strength and durability of teeth of an external gear. Solution to problem

[0007] According to one aspect of the present invention, there is provided a flexural engagement type gear device comprising: a wave generator, an external gear that is flexibly deformed by the wave generator, a first internal gear meshing with the external gear, and a second internal gear arranged such that the second internal gear and the first internal gear are arranged in an axial direction and meshes with the external gear, wherein the external gear includes a first external tooth portion engaging with the first internal gear and a second external tooth portion engaging with the second internal gear, the second outer tooth portion includes a second thickest outer tooth portion in which a tooth thickness is the largest, and a second outer tooth portion with decreasing inner tooth thickness in which the tooth thickness decreases from the second thickest outer tooth portion toward an inner side in the axial direction, and an inner tooth portion of the second internal gear includes a second thickest inner tooth portion in which a tooth thickness is largest, and a second inner tooth thickness decreasing inner tooth portion in which the tooth thickness decreases from the second thickest inner tooth portion toward the inner side in the axial direction. Advantageous effects of the invention

[0008] According to the present invention, it is possible to provide a flexural engagement type gear device capable of suppressing a decrease in strength and durability of teeth of an external gear. Brief description of the drawings Fig. 1 is a sectional view showing a bending engagement type gear device according to Embodiment 1. Fig. 2 is a view for describing the tooth trace shapes of an external gear, a first internal gear and a second internal gear of Fig. 1. Fig. 3 is a view for describing the tooth tip shapes of the external gear, the first internal gear and the second internal gear of Fig. 1. Fig. 4 is a view for describing the tooth trace shapes of an external gear, a first internal gear, and a second internal gear of a flexural engagement type gear device according to Embodiment 2. Fig. 5 is a view for describing the tooth tip shapes of the external gear, the first internal gear, and the second internal gear of the flexural engagement type gear device according to Embodiment 2. Fig. 6 is a view for describing the tooth trace shapes of an external gear, a first internal gear, and a second internal gear of a flexural engagement type gear device according to Embodiment 3. Description of embodiments

[0009] One or more embodiments will be described below with reference to the drawings, and the features and technical effects of the embodiments will be understood from the following detailed description and the drawings. However, the scope of the present invention is not limited to the embodiments disclosed below. The drawings are provided only for the purpose of providing examples, and the scope of the present invention is not limited to the examples in the drawings. The same reference numeral is assigned to the same or equivalent component, element, and process shown in each drawing, and duplicate descriptions are omitted where appropriate. The dimensions of elements in each drawing have been enlarged or reduced where appropriate for ease of understanding.In each drawing, some elements that are not important for describing the embodiment are omitted. Furthermore, while terms with ordinal numbers such as "first" and "second" are used to describe various components, the ordinal numbers of such terms are used only to distinguish one component from another, and no component is limited by the ordinal numbers of such terms. (Embodiment 1)

[0010] Fig. 1 is a sectional view showing a bending engagement type gear device 100 according to Embodiment 1. The bending engagement type gear device 100 reduces the rotational speed input thereto and then outputs the rotation. The bending engagement type gear device 100 is a so-called flat type bending engagement type gear device (a flat type may be referred to as a tubular type). Furthermore, the present invention is also applicable to, for example, a so-called cup-type or cylinder-hat type bending engagement type gear device instead of the flat type bending engagement type gear device 100.

[0011] The flexural engagement type gear device 100 includes a wave generating unit 2, an external gear 4 flexibly deformed by the wave generating unit 2, a first internal gear 6 meshing with the external gear 4, a second internal gear 8 arranged so that the second internal gear 8 and the first internal gear 6 are arranged in an axial direction (so that they are adjacent to each other) and meshing with the external gear 4, a housing 10, a first regulating member 12, a second regulating member 14, a main bearing 16, a first bearing housing 18, and a second bearing housing 20. The flexural engagement type gear device 100 is filled with a lubricant (for example, grease). The lubricant lubricates portions of the external gear 4, the first internal gear 6 and the second internal gear 8 that mesh with each other, each of bearings and the like.

[0012] The wave generator unit 2 includes a wave generator shaft 22, a first wave generator bearing 21a disposed between the wave generator shaft 22 and the external gear 4 (specifically, a first external tooth portion 4a of the external gear 4), and a second wave generator bearing 21b disposed between the wave generator shaft 22 and the external gear 4 (specifically, a second external tooth portion 4b of the external gear 4). The first wave generator bearing 21a includes a plurality of first rolling elements 24a, first retainers 26a that retain the plurality of first rolling elements 24a, and a first outer ring member 28a internally fitted into the external gear 4. The second shaft generator bearing 21b includes a plurality of second rolling elements 24b, second holders 26b that hold the plurality of second rolling elements 24b, and a second outer ring member 28b that is internally fitted into the external gear 4.The wave generator shaft 22 is a drive shaft, is connected to a rotational drive source such as a motor, and rotates about a rotation axis R. The wave generator shaft 22 is formed integrally with a wave generator 22a, a portion of which perpendicular to the rotation axis R has an approximately oval shape.

[0013] Each of the plurality of first rolling elements 24a has an approximately columnar shape, and the plurality of first rolling elements 24a are provided at intervals in a circumferential direction in a state where axial directions thereof are approximately parallel to a direction along the rotation axis R. The first rolling elements 24a are rollably held by the first holders 26a and roll on an outer peripheral surface 22b of the wave generator 22a. That is, an inner ring of the first wave generator bearing 21a is formed integrally with the outer peripheral surface 22b of the wave generator 22a. However, the present invention is not limited to this, and a dedicated inner ring separate from the wave generator 22a may be provided. The second rolling elements 24b are configured in the same manner as the first rolling elements 24a.The plurality of second rolling elements 24b are rollably held by the second retainers 26b and roll on the outer peripheral surface 22b of the wave generator 22a, and the second retainers 26b are arranged such that the second retainers 26b and the first retainers 26a are arranged in the axial direction. That is, an inner ring of the second wave generator bearing 21b is formed integrally with the outer peripheral surface 22b of the wave generator 22a. However, the present invention is not limited to this, and a dedicated inner ring separate from the wave generator 22a may be provided. Hereinafter, the first rolling elements 24a and the second rolling elements 24b may be collectively referred to as "rolling elements 24." Furthermore, the first retainers 26a and the second retainers 26b may be collectively referred to as "retainer 26."

[0014] The first outer ring member 28a surrounds the plurality of first rolling elements 24a. The first outer ring member 28a is flexible and is bent into an oval shape by the wave generator 22a with the plurality of first rolling elements 24a interposed therebetween. As the wave generator 22a (i.e., the wave generator shaft 22) rotates, the first outer ring member 28a is continuously flexibly deformed in accordance with the shape of the wave generator 22a. The second outer ring member 28b is configured in the same manner as the first outer ring member 28a. The second outer ring member 28b is formed as a body separate from the first outer ring member 28a. The second outer ring member 28b may be formed integrally with the first outer ring member 28a. Hereinafter, the first outer ring member 28a and the second outer ring member 28b may be collectively referred to as "outer ring members 28."

[0015] The external gear 4 is a flexible annular member, and the wave generator 22a, the rolling elements 24, and the outer ring elements 28 are fitted into the external gear 4. The external gear 4 is bent into an oval shape when the wave generator 22a, the rolling elements 24, and the outer ring elements 28 are fitted into the external gear 4. As the wave generator 22a rotates, the external gear 4 is continuously flexibly deformed in accordance with the shape of the wave generator 22a. The external gear 4 includes the first external tooth portion 4a positioned outside the first outer ring element 28a, the second external tooth portion 4b positioned outside the second outer ring element 28b, and a base material 4c. The first outer tooth portion 4a and the second outer tooth portion 4b are formed on the base material 4c, which is a single base material, and have the same number of teeth.

[0016] The first internal gear 6 is a rigid annular body, and a first internal tooth portion 6a is formed on an inner periphery thereof. The first internal tooth portion 6a surrounds the first external tooth portion 4a of the external gear 4 bent into an oval shape and meshes with the first external tooth portion 4a in two predetermined regions near a main axis of the wave generator 22a. The first internal tooth portion 6a has a larger number of teeth than the first external tooth portion 4a.

[0017] The second internal gear 8 and the first internal gear 6 are arranged so as to be arranged in the axial direction, and the second internal gear 8 is adjacent to the first internal gear 6. The second internal gear 8 is a rigid cylindrical member, and a second internal tooth portion 8a is formed on an inner periphery thereof. The second internal tooth portion 8a surrounds the second external tooth portion 4b of the external gear 4, which is bent in an elliptical shape, and meshes with the second external tooth portion 4b in a predetermined range in a major axis direction of the wave generator 22a. The second internal tooth portion 8a has the same number of teeth as the second external tooth portion 4b. Therefore, the second internal gear 8 rotates synchronously with the rotation of the second external tooth portion 4b, that is, the external gear 4.

[0018] The first regulating element 12 is a flat annular element and is arranged between the external gear 4, the first outer ring element 28a, the first retainers 26a, and the first bearing housing 18. The second regulating element 14 is a flat annular element and is arranged between the external gear 4, the second outer ring element 28b, the second retainers 26b, and the second bearing housing 20. The first regulating element 12 and the second regulating element 14 regulate movement of the external gear 4, the outer ring elements 28, and the retainers 26 in the axial direction. The first regulating element 12 and the second regulating element 14 may be referred to as pressure plates.

[0019] The housing 10 is a roughly cylindrical member and surrounds the second internal gear 8. The first internal gear 6 is splined to the housing 10, and the first internal gear 6 is integrally mounted with the housing 10 by a bolt (not shown). The main bearing 16 is disposed between the housing 10 and the second internal gear 8. The main bearing 16, in the present embodiment, is a crossed roller bearing and includes a plurality of rollers (rolling elements) 46 provided at intervals in the circumferential direction. The plurality of rollers 46 roll on rolling surfaces 8b of the second internal gear 8 and rolling surfaces 10a of the housing 10. That is, an outer peripheral side of the second internal gear 8 functions as an inner ring of the main bearing 16, and an inner peripheral side of the housing 10 functions as an outer ring of the main bearing 16. The housing 10 supports the second internal gear 8 via the main bearing 16 so that the second internal gear 8 can rotate relatively.It should be noted that the bearing type of the main bearing 16 is not particularly limited, and the main bearing 16 may be, for example, a four-point contact ball bearing.

[0020] The first bearing housing 18 is an annular member and surrounds the wave generator shaft 22. Similarly, the second bearing housing 20 is an annular member and surrounds the wave generator shaft 22. The first bearing housing 18 and the second bearing housing 20 are arranged such that the external gear 4, the rolling elements 24, the retainers 26, the outer ring members 28, the first regulating member 12, and the second regulating member 14 are interposed therebetween in the axial direction. The first bearing housing 18 is journaled with respect to the first internal gear 6 and fixed with screws. The second bearing housing 20 is journaled with respect to the second internal gear 8 and fixed with screws. A bearing 30 is installed in an inner periphery of the first bearing housing 18, and a bearing 32 is installed in an inner periphery of the second bearing housing 20.The shaft generator shaft 22 is supported so that it is rotatable with respect to the first bearing housing 18 and the second bearing housing 20 via the bearing 30 and the bearing 32.

[0021] An oil seal 40 is disposed between the wave generator shaft 22 and the first bearing housing 18, an O-ring 34 is disposed between the first bearing housing 18 and the first internal gear 6, an O-ring 36 is disposed between the first internal gear 6 and the housing 10, an oil seal 42 is disposed between the housing 10 and the second internal gear 8, an O-ring 38 is disposed between the second internal gear 8 and the second bearing housing 20, and an oil seal 44 is disposed between the second bearing housing 20 and the wave generator shaft 22. Accordingly, it is possible to suppress lubricant leakage in the flexural engagement type gear device 100.

[0022] The first regulating member 12 is interposed between an outer ring of the bearing 30 and the external gear 4. A thickness T12 of the first regulating member 12 is set in accordance with the size of a clearance between the outer ring of the bearing 30 and the external gear 4 in the axial direction, taking into account the size of a clearance between the internal gear 6 and the internal gear 8 along the axial direction. For example, a thrust plate having a thickness corresponding to the size of the clearance between the outer ring of the bearing 30 and the external gear 4 in the axial direction is selected from a plurality of thrust plates whose thicknesses differ from each other, and the selected thrust plate is interposed between the external gear 4, the first outer ring member 28a, the first retainers 26a, the first bearing housing 18, and the outer ring of the bearing 30. The selected thrust plate is the first regulating member 12.The size of the interval between the outer ring of the bearing 30 and the external gear 4 in the axial direction can be measured at the time of assembling the flexure engagement type gear device 100, or can be calculated from the size of each component and each assembled article measured at the time of assembling the flexure engagement type gear device 100. Note that the thickness T12 of the first regulating member 12 can be adjusted according to the size of a clearance between the first bearing housing 18 and the external gear 4 in the axial direction.

[0023] The second regulating member 14 is interposed between an outer ring of the bearing 32 and the external gear 4. A thickness T14 of the second regulating member 14 is set in accordance with the size of a clearance between the outer ring of the bearing 32 and the external gear 4 in the axial direction, taking into account the size of a clearance between the internal gear 6 and the internal gear 8 along the axial direction. For example, a pressure plate having a thickness corresponding to the size of the clearance between the outer ring of the bearing 32 and the external gear 4 in the axial direction is selected from a plurality of pressure plates whose thicknesses differ from each other, and the selected pressure plate is interposed between the external gear 4, the second outer ring member 28b, the second retainers 26b, the second bearing housing 20, and the outer ring of the bearing 32. The selected pressure plate is the second regulating member 14.The size of the clearance between the outer ring of the bearing 32 and the external gear 4 in the axial direction can be measured at the time of assembly of the flexure engagement type gear device 100, or can be calculated from the size of each component and each assembled article measured at the time of assembly of the flexure engagement type gear device 100. Note that the thickness T14 of the second regulating member 14 can be adjusted in accordance with the size of a clearance between the second bearing housing 20 and the external gear 4 in the axial direction.

[0024] The thickness T14 of the second regulating element 14 may differ from the thickness T12 of the first regulating element 12. The thickness T14 of the second regulating element 14 may be equal to the thickness T12 of the first regulating element 12.

[0025] The manner in which the flexural engagement type gear device 100 configured as described above operates will be described. A case where the number of teeth of the first external tooth portion 4a is 100, the number of teeth of the second external tooth portion 4b is 100, the number of teeth of the first internal tooth portion 6a is 102, and the number of teeth of the second internal tooth portion 8a is 100 will be described here as an example. Furthermore, a case where the second internal gear 8 and the second bearing housing 20 are connected to a driven member will be described as an example.

[0026] When the wave generator shaft 22 rotates in a state where the first external tooth portion 4a meshes with the first internal tooth portion 6a at two positions in a major axis direction of an oval shape, positions where the first external tooth portion 4a and the first internal tooth portion 6a mesh with each other move in the circumferential direction in accordance with the rotation of the wave generator shaft 22. In this case, since the number of teeth of the first external tooth portion 4a and the number of teeth of the first internal tooth portion 6a are different from each other, the first external tooth portion 4a rotates relative to the first internal tooth portion 6a. Since the first internal gear 6 and the first bearing housing 18 are in a state of being fixed, the first external tooth portion 4a rotates according to a difference in the number of teeth.That is, the rotation of the wave generator shaft 22 is significantly reduced in speed and then transmitted to the first external gear portion 4a. The reduction ratio in this case is as follows. The reduction ratio = (the number of teeth of the first outer tooth section 4a − the number of teeth of the first inner tooth section 6a) / the number of teeth of the first outer tooth section 4a = (100 − 102) * 100 = − 1 / 50

[0027] The second external tooth portion 4b rotates integrally with the first external tooth portion 4a because the second external tooth portion 4b is formed integrally with the first external tooth portion 4a. Since the number of teeth of the second external tooth portion 4b and the number of teeth of the second internal tooth portion 8a are the same, the second external tooth portion 4b and the second internal tooth portion 8a rotate integrally with each other without relative rotation. Therefore, rotation identical to the rotation of the first external tooth portion 4a is output to the second internal tooth portion 8a. As a result, output obtained by reducing the rotational speed of the wave generator shaft 22 to -1 / 50 can be taken out from the second internal gear 8.

[0028] Next, the configurations of the external gear 4, the first internal gear 6, and the second internal gear 8 will be described in more detail. Note that in the present embodiment, the external gear 4, the first external tooth portion 4a, the second external tooth portion 4b, the first internal gear 6, the first internal tooth portion 6a, the second internal gear 8, and the second internal tooth portion 8a each correspond to an external gear, a first external tooth portion, a second external tooth portion, a first internal gear, a first internal tooth portion, a second internal gear, and a second internal tooth portion in the claims.In this regard, the external gear 4, the first external tooth portion 4a, the second external tooth portion 4b, the first internal gear 6, the first internal tooth portion 6a, the second internal gear 8, and the second internal tooth portion 8a in the present embodiment can be regarded as corresponding to the external gear, the second external tooth portion, the first external tooth portion, the second internal gear, the second internal tooth portion, the first internal gear, and the first internal tooth portion, respectively, in the claims. <zahnspurform>

[0029] Fig. Fig. 2 is a view for describing the tooth trace shapes of the external gear 4, the first internal gear 6 and the second internal gear 8 of Fig. 1. Fig. Figure 2 shows cross-sectional views of the external gear 4, the first internal gear 6 and the second internal gear 8, taken along an imaginary cylinder passing through a pitch circle of the external gear 4. In Fig. 2 shows an external tooth of the external gear 4 and two internal teeth adjacent to the external tooth in the circumferential direction. For ease of understanding, Fig. 2, the first internal tooth portion 6a and the second internal tooth portion 8a are shown in a state in which they are shifted in the circumferential direction so as to be separated from the external gear 4, and the tooth trace shapes of the first external tooth portion 4a, the second external tooth portion 4b, the first internal tooth portion 6a, and the second internal tooth portion 8a are shown in an enlarged manner. The horizontal axis in Fig. 2 is parallel to the axial direction, and the horizontal axis indicates an axial position relative to a specific reference position. The axial direction and a tooth trace direction are parallel to each other, and the axial direction can also be referred to as the tooth trace direction. The vertical axis indicates a dimension in the circumferential direction. That is, it can be said that the vertical axis serves to indicate the tooth thickness of an external tooth of the external gear 4.

[0030] In the present embodiment, each of the first external tooth portion 4a and the first internal tooth portion 6a has an area in the axial direction, the area of ​​the first external tooth portion 4a is larger than the area of ​​the first internal tooth portion 6a, and the first internal tooth portion 6a meshes with the first external tooth portion 4a over the entire area thereof. Each of the second external tooth portion 4b and the second internal tooth portion 8a has an area in the axial direction, the area of ​​the second external tooth portion 4b is wider than the area of ​​the second internal tooth portion 8a, and the second internal tooth portion 8a meshes with the second external tooth portion 4b over the entire area thereof.

[0031] The first outer tooth portion 4a may have a shape that is symmetrical with respect to a tooth thickness center plane S4 of the first outer tooth portion 4a, or may include a partially asymmetrical portion. The tooth thickness center plane S4 refers to a plane passing through the center of a thickest portion, where the tooth thickness of the first outer tooth portion 4a is the largest, in a tooth thickness direction and the rotation axis R. A tooth thickness of the first outer tooth portion 4a means a distance from the tooth thickness center plane S4 to a tooth surface.

[0032] Similarly, the second outer tooth portion 4b may have a shape that is symmetrical with respect to a tooth thickness center plane of the second outer tooth portion 4b, or may include a partially asymmetrical portion. The tooth thickness center plane of the second outer tooth portion 4b coincides with the tooth thickness center plane S4 of the first outer tooth portion 4a.

[0033] Similarly, the first inner tooth portion 6a may have a shape that is symmetrical with respect to a tooth thickness center plane S6 of the first inner tooth portion 6a, or may include a partially asymmetric portion.

[0034] Similarly, the second inner tooth portion 8a may have a shape that is symmetrical with respect to a tooth thickness center plane S8 of the second inner tooth portion 8a, or may include a partially asymmetrical portion. Since the number of teeth of the first inner tooth portion 6a and the number of teeth of the second inner tooth portion 8a are different from each other, the tooth thickness center plane S8 of the second inner tooth portion 8a does not coincide with the tooth thickness center plane S6 of the first inner tooth portion 6a. <<Zahnspurform von erstem Außenzahnabschnitt 4a und erstem Innenzahnabschnitt 6a> >

[0035] The tooth track shapes of the first outer tooth portion 4a and the first inner tooth portion 6a are described with reference to Fig. 2. In the following description, tooth trace shapes of the first outer tooth portion 4a and the first inner tooth portion 6a in a cylindrical cross section along the pitch circle are representatively described. However, tooth trace shapes of the first outer tooth portion 4a and the first inner tooth portion 6a in a cylindrical cross section that is shifted along the pitch circle in a radial direction from the cylindrical cross section are the same as the tooth trace shapes described in the following description.The tooth trace shape of the first external tooth portion 4a described in the following description may be entirely reflected in a range from a tooth root of the first external tooth portion 4a to the vicinity of a tooth tip of the first external tooth portion 4a, or may be partially reflected in a portion of the range from the tooth root of the first external tooth portion 4a to the vicinity of the tooth tip of the first external tooth portion 4a. The tooth trace shape of the first internal tooth portion 6a described in the following description may be entirely reflected in a range from a tooth root of the first internal tooth portion 6a to the vicinity of a tooth tip of the first internal tooth portion 6a, or may be partially reflected in a portion of the range from the tooth root of the first internal tooth portion 6a to the vicinity of the tooth tip of the first internal tooth portion 6a.

[0036] When the first outer tooth portion 4a is divided in the axial direction, the first outer tooth portion 4a includes a first outer tooth thickest portion 4a1, a first outer tooth inner side tooth thickness reduction portion 4a2, and a first outer tooth outer side tooth thickness reduction portion. The first outer tooth inner side tooth thickness reduction portion 4a2 is positioned axially inward of the first thickest outer tooth portion 4a1, and the first outer tooth outer side tooth thickness reduction portion 4a3 is positioned axially outward of the first thickest outer tooth portion 4a1. Here, an inward direction in the axial direction means a direction toward the center of a space between the first outer tooth portion 4a and the second outer tooth portion 4b in the axial direction. An outward direction in the axial direction means a direction away from the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b in the axial direction.Furthermore, the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b represents a boundary between the axial direction range of the first outer tooth portion 4a and the axial direction range of the second outer tooth portion 4b. An imaginary plane P0 perpendicular to the axial direction and passing through the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b is referred to as a center plane P0. The position of the center plane P0 in the axial direction is between the first inner tooth portion 6a and the second inner tooth portion 8a.

[0037] The tooth thickness of the first outer tooth portion 4a changes in the axial direction. Specifically, the tooth thickness of the first thickest outer tooth portion 4a1 corresponds to the maximum tooth thickness of the first outer tooth portion 4a, the tooth thickness of the first outer tooth inner side tooth thickness decreasing portion 4a2 gradually decreases in the axial direction from the first thickest outer tooth portion 4a1 toward the inner side, and the tooth thickness of the first outer tooth outer side tooth thickness decreasing portion 4a3 gradually decreases in the axial direction from the first thickest outer tooth portion 4a1 toward the outer side.

[0038] When the first inner tooth portion 6a is divided in the axial direction, the first inner tooth portion 6a includes a first thickest inner tooth portion 6a1 and a first inner tooth inner side tooth thickness reduction portion 6a2. The first inner tooth inner side tooth thickness reduction portion 6a2 is positioned axially inward of the first thickest inner tooth portion 6a1.

[0039] The tooth thickness of the first inner tooth portion 6a changes in the axial direction. Specifically, the tooth thickness of the first thickest inner tooth portion 6a1 corresponds to the maximum tooth thickness of the first inner tooth portion 6a, and the tooth thickness of the first inner tooth inner side tooth thickness decreasing portion 6a2 gradually decreases in the axial direction from the first thickest inner tooth portion 6a1 toward the inner side.

[0040] The first thickest outer tooth portion 4a1 may have a region with a predetermined width in the axial direction or may be a single point without a region in the axial direction. Fig. 2, the first thickest outer tooth portion 4a1 is a single point without any area in the axial direction.

[0041] The first thickest inner tooth portion 6a1 may have a region with a predetermined width in the axial direction or may be a single point without a region in the axial direction. Fig. 2, the first thickest inner tooth portion 6a1 has a region in the axial direction. Note that an axially outer end of the first thickest inner tooth portion 6a1 corresponds to an axially outer end of the first inner tooth portion 6a in a case where the first thickest inner tooth portion 6a1 has a region in the axial direction, and the first thickest inner tooth portion 6a1 corresponds to the axially outer end of the first inner tooth portion 6a in a case where the first thickest inner tooth portion 6a1 is a single point without a region in the axial direction.

[0042] As in Fig. 2, in a case where the first thickest outer tooth portion 4a1 is a single point without a range in the axial direction and the first thickest inner tooth portion 6a1 has a range in the axial direction, the position of the first thickest outer tooth portion 4a1 in the axial direction is within the range of the first thickest inner tooth portion 6a1. Note that in a case where the first thickest outer tooth portion 4a1 has a range in the axial direction and the first thickest inner tooth portion 6a1 is a single point without a range in the axial direction, the position of the first thickest inner tooth portion 6a1 in the axial direction may be within the range of the first thickest outer tooth portion 4a1.Furthermore, in a case where the first thickest outer tooth portion 4a1 has a region in the axial direction and the first thickest inner tooth portion 6a1 has a region in the axial direction, the region of the first thickest outer tooth portion 4a1 and the region of the first thickest inner tooth portion 6a1 may partially or completely overlap with each other. In a case where the first thickest outer tooth portion 4a1 is a single point without a region in the axial direction and the first thickest inner tooth portion 6a1 is a single point without a region in the axial direction, the positions of the first thickest outer tooth portion 4a1 and the first thickest inner tooth portion 6a1 in the axial direction may be aligned with each other.

[0043] The first outer tooth inner side tooth thickness reduction portion 4a2 has an area in the axial direction. In a case where the first thickest inner tooth portion 6a1 has an area in the axial direction, as in the Fig. 2, the area of ​​the first outer tooth inner side tooth thickness reduction portion 4a2 partially overlaps with the area of ​​the first thickest inner tooth portion 6a1. Note that an axially inner end of the first outer tooth inner side tooth thickness reduction portion 4a2 corresponds to the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b.

[0044] The first inner tooth inner lateral tooth thickness reduction portion 6a2 has an area in the axial direction. The area of ​​the first inner tooth inner lateral tooth thickness reduction portion 6a2 is smaller than the area of ​​the first outer tooth inner lateral tooth thickness reduction portion 4a2, and the entire area of ​​the first inner tooth inner lateral tooth thickness reduction portion 6a2 lies within the area of ​​the first outer tooth inner lateral tooth thickness reduction portion 4a2. The area of ​​the first outer tooth inner lateral tooth thickness reduction portion 4a2 reaches a position closer to the inner side in the axial direction than an axially inner end of the area of ​​the first inner tooth inner lateral tooth thickness reduction portion 6a2. In this regard, however, an axially inner end of the portion of the first outer tooth inner side tooth thickness decreasing portion 4a2 may be positionally aligned with the axially inner end of the portion of the first inner tooth inner side tooth thickness decreasing portion 6a2.The portion of the first outer tooth inner side tooth thickness reduction portion 4a2 reaches a position closer to the outside in the axial direction than an axially outer end of the portion of the first inner tooth inner side tooth thickness reduction portion 6a2. Note that an axially inner end of the first inner tooth inner side tooth thickness reduction portion 6a2 corresponds to an axially inner end of the first inner tooth portion 6a.

[0045] The tooth thickness reduction rate of the first inner tooth inner side tooth thickness reduction section 6a2 is higher than the tooth thickness reduction rate of the first outer tooth inner side tooth thickness reduction section 4a2. Therefore, in a cross section as shown in Fig. 2, a tooth trace curve drawn along the first inner tooth inner lateral tooth thickness decreasing portion 6a2 is steeper than a tooth trace curve drawn along the first outer tooth inner lateral tooth thickness decreasing portion 4a2. Here, the tooth thickness decreasing rate of the first inner tooth inner lateral tooth thickness decreasing portion 6a2 means a result obtained by dividing the amount of decrease in tooth thickness of the first inner tooth inner lateral tooth thickness decreasing portion 6a2 in the case of displacement over the unit distance in the tooth trace direction, specifically, an axially inward direction, by a unit distance. That is, the tooth thickness decreasing rate of the first inner tooth inner lateral tooth thickness decreasing portion 6a2 can also be referred to as the amount of decrease in tooth thickness of the first inner tooth inner lateral tooth thickness decreasing portion 6a2 per unit distance in the tooth trace direction.The tooth thickness reduction rate of the first external tooth inner side tooth thickness reduction portion 4a2 means a result obtained by dividing the amount of reduction in tooth thickness of the first external tooth inner side tooth thickness reduction portion 4a2 with decreasing inner side tooth thickness in the case of displacement over the unit distance in the tooth trace direction, specifically, the axially inward direction, by the unit distance. The tooth thickness reduction rate of the first external tooth inner side tooth thickness reduction portion 4a2 may also be referred to as the amount of reduction in tooth thickness of the first external tooth inner side tooth thickness reduction portion 4a2 per unit distance in the tooth trace direction.

[0046] The maximum tooth thickness reduction amount of the first inner tooth inner lateral tooth thickness reduction portion 6a2 is greater than the maximum tooth thickness reduction amount of the first outer tooth inner lateral tooth thickness reduction portion 4a2. Regarding a ratio between the maximum tooth thickness reduction amount of the first inner tooth inner lateral tooth thickness reduction portion 6a2 and the maximum tooth thickness reduction amount of the first outer tooth inner lateral tooth thickness reduction portion 4a2, a relationship of "the maximum tooth thickness reduction amount of the first outer tooth inner lateral tooth thickness reduction portion 4a2:the maximum tooth thickness reduction amount of the first inner tooth inner lateral tooth thickness reduction portion 6a2 = 1:2 to 4" is satisfied.Here, the maximum tooth thickness reduction amount of the first internal tooth inner lateral tooth thickness reduction portion 6a2 means a result obtained by subtracting the minimum tooth thickness of the first internal tooth inner lateral tooth thickness reduction portion 6a2 at an axially inner end of the first internal tooth inner lateral tooth thickness reduction portion 6a2 from the maximum tooth thickness of the first internal tooth inner lateral tooth thickness reduction portion 6a2 at an axially outer end of the first internal tooth inner lateral tooth thickness reduction portion 6a2.The maximum tooth thickness reduction amount of the first external tooth inner side tooth thickness reduction portion 4a2 means a result obtained by subtracting the minimum tooth thickness of the first external tooth inner side tooth thickness reduction portion 4a2 at an axially inner end of the first external tooth inner side tooth thickness reduction portion 4a2 m from the maximum tooth thickness of the first external tooth inner side tooth thickness reduction portion 4a2 at an axially outer end of the first external tooth inner side tooth thickness reduction portion 4a2.

[0047] The first outer tooth outer side tooth thickness reduction portion 4a3 has an area in the axial direction. In a case where the first thickest inner tooth portion 6a1 has an area in the axial direction, as in the case shown in Fig. 2, the area of ​​the first outer tooth outer side tooth thickness reduction portion 4a3 partially overlaps with the area of ​​the first thickest inner tooth portion 6a1. The area of ​​the first outer tooth outer side tooth thickness reduction portion 4a3 reaches a position closer to the outside in the axial direction than the first thickest inner tooth portion 6a1. Note that an axially outer end of the first outer tooth outer side tooth thickness reduction portion 4a3 corresponds to an axially outer end of the first outer tooth portion 4a.

[0048] The tooth thickness reduction rate of the first external tooth outer side tooth thickness reduction section 4a3 is higher than the tooth thickness reduction rate of the first external tooth inner side tooth thickness reduction section 4a2. Therefore, in the cross section as shown in Fig. 2, a tooth trace curve drawn along the first external tooth outer side tooth thickness decreasing portion 4a3 is steeper than the tooth trace curve drawn along the first external tooth inner side tooth thickness decreasing portion 4a2. Here, the tooth thickness decreasing rate of the first external tooth outer side tooth thickness decreasing portion 4a3 means a result obtained by dividing the amount of decrease in tooth thickness of the first external tooth outer side tooth thickness decreasing portion 4a3 in the case of displacement over the unit distance in the tooth trace direction, specifically, an axially outward direction, by the unit distance. The tooth thickness decreasing rate of the first external tooth outer side tooth thickness decreasing portion 4a3 may also be referred to as the amount of decrease in tooth thickness of the first external tooth outer side tooth thickness decreasing portion 4a3 per unit distance in the tooth trace direction. <<Zahnspurformen von zweitem Außenzahnabschnitt 4b und zweitem Innenzahnabschnitt 8a>>

[0049] The tooth trace shapes of the second outer tooth portion 4b and the second inner tooth portion 8a will be described. In the following description, the tooth trace shapes of the second outer tooth portion 4b and the second inner tooth portion 8a in a cylindrical cross section along the pitch circle will be representatively described. However, the tooth trace shapes of the second outer tooth portion 4b and the second inner tooth portion 8a in a cylindrical cross section that is shifted along the pitch circle in a radial direction from the cylindrical cross section are the same as the tooth trace shapes described in the following description.The tooth trace shape of the second external tooth portion 4b described in the following description may be entirely reflected in a range from a tooth root of the second external tooth portion 4b to the vicinity of a tooth tip of the second external tooth portion 4b, or may be partially reflected in a portion of the range from the tooth root of the second external tooth portion 4b to the vicinity of the tooth tip of the second external tooth portion 4b. The tooth trace shape of the second internal tooth portion 8a described in the following description may be entirely reflected in a range from a tooth root of the second internal tooth portion 8a to the vicinity of a tooth tip of the second internal tooth portion 8a, or may be partially reflected in a portion of the range from the tooth root of the second internal tooth portion 8a to the vicinity of the tooth tip of the second internal tooth portion 8a.

[0050] When the second outer tooth portion 4b is divided in the axial direction, the second outer tooth portion 4b includes a second outer tooth thickest portion 4b1, a second outer tooth inner side tooth thickness reduction portion 4b2, and a second outer tooth outer side tooth thickness reduction portion 4b3. The second outer tooth inner side tooth thickness reduction portion 4b2 is positioned axially inward of the second thickest outer tooth portion 4b1, and the second outer tooth outer side tooth thickness reduction portion 4b3 is positioned axially outward of the second thickest outer tooth portion 4b1.

[0051] The tooth thickness of the second outer tooth portion 4b changes in the axial direction. Specifically, the tooth thickness of the second thickest outer tooth portion 4b1 corresponds to the maximum tooth thickness of the second outer tooth portion 4b, the tooth thickness of the second outer tooth inner side tooth thickness decreasing portion 4b2 gradually decreases in the axial direction from the second thickest outer tooth portion 4b1 toward the inner side, and the tooth thickness of the second outer tooth outer side tooth thickness decreasing portion 4b3 gradually decreases in the axial direction from the second thickest outer tooth portion 4b1 toward the outer side.

[0052] When the second inner tooth portion 8a is divided in the axial direction, the second inner tooth portion 8a includes a second thickest inner tooth portion 8a1 and a second inner tooth inner side tooth thickness reduction portion 8a2. The second inner tooth inner side tooth thickness reduction portion 8a2 is positioned axially inward of the second thickest inner tooth portion 8a1.

[0053] The tooth thickness of the second inner tooth portion 8a changes in the axial direction. Specifically, the tooth thickness of the second thickest inner tooth portion 8a1 corresponds to the maximum tooth thickness of the second inner tooth portion 8a, and the tooth thickness of the second inner tooth inner side tooth thickness decreasing portion 8a2 gradually decreases in the axial direction from the second thickest inner tooth portion 8a1 toward the inner side.

[0054] The second thickest outer tooth portion 4b1 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 2, the second thickest outer tooth portion 4b1 is a single point without any area in the axial direction.

[0055] The second thickest inner tooth portion 8a1 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 2, the second thickest inner tooth portion 8a1 has a region in the axial direction. Note that an axially outer end of the second thickest inner tooth portion 8a1 corresponds to an axially outer end of the second inner tooth portion 8a in a case where the second thickest inner tooth portion 8a1 has a region in the axial direction, and the second thickest inner tooth portion 8a1 corresponds to an axially outer end of the second inner tooth portion 8a in a case where the second thickest inner tooth portion 8a1 is a single point without a region in the axial direction.

[0056] As in Fig. 2, in a case where the second thickest outer tooth portion 4b1 is a single point without a range in the axial direction and the second thickest inner tooth portion 8a1 has a range in the axial direction, the position of the second thickest outer tooth portion 4b1 in the axial direction is within the range of the second thickest inner tooth portion 8a1. Note that in a case where the second thickest outer tooth portion 4b1 has a range in the axial direction and the second thickest inner tooth portion 8a1 is a single point without a range in the axial direction, the position of the second thickest inner tooth portion 8a1 in the axial direction may be within the range of the second thickest outer tooth portion 4b1.Furthermore, in a case where the second thickest outer tooth portion 4b1 has a region in the axial direction and the second thickest inner tooth portion 8a1 has a region in the axial direction, the region of the second thickest outer tooth portion 4b1 and the region of the second thickest inner tooth portion 8a1 may partially or completely overlap with each other. In a case where the second thickest outer tooth portion 4b1 is a single point without a region in the axial direction and the second thickest inner tooth portion 8a1 is a single point without a region in the axial direction, the positions of the second thickest outer tooth portion 4b1 and the second thickest inner tooth portion 8a1 in the axial direction may be aligned with each other.

[0057] The second outer tooth inner side tooth thickness reduction portion 4b2 has an area in the axial direction. In a case where the second thickest inner tooth portion 8a1 has an area in the axial direction, as in the Fig. 2, the area of ​​the second outer tooth inner side tooth thickness reduction portion 4b2 partially overlaps with the area of ​​the second thickest inner tooth portion 8a1. Note that an axially inner end of the second outer tooth inner side tooth thickness reduction portion 4b2 corresponds to the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b.

[0058] The second inner tooth inner lateral tooth thickness reduction portion 8a2 has an area in the axial direction. The area of ​​the second inner tooth inner lateral tooth thickness reduction portion 8a2 is smaller than the area of ​​the second outer tooth inner lateral tooth thickness reduction portion 4b2, and the entire area of ​​the second inner tooth inner lateral tooth thickness reduction portion 8a2 lies within the area of ​​the second outer tooth inner lateral tooth thickness reduction portion 4b2. An axially inner end of the area of ​​the second outer tooth inner lateral tooth thickness reduction portion 4b2 is positionally aligned with an axially inner end of the area of ​​the second inner tooth inner lateral tooth thickness reduction portion 8a2. In this regard, however, the portion of the second outer tooth inner side tooth thickness decreasing portion 4b2 may reach a position closer to the inner side in the axial direction than the axially inner end of the portion of the second inner tooth inner side tooth thickness decreasing portion 8a2.The portion of the second outer tooth inner side tooth thickness reduction portion 4b2 reaches a position closer to the outside in the axial direction than an axially outer end of the portion of the second inner tooth inner side tooth thickness reduction portion 8a2. Note that an axially inner end of the second inner tooth inner side tooth thickness reduction portion 8a2 corresponds to an axially inner end of the second inner tooth portion 8a.

[0059] The tooth thickness reduction rate of the second inner tooth inner side tooth thickness reduction section 8a2 is higher than the tooth thickness reduction rate of the second outer tooth inner side tooth thickness reduction section 4b2. Therefore, in the cross section as shown in Fig. 2, a tooth trace curve drawn along the second inner tooth inner lateral tooth thickness decreasing portion 8a2 is steeper than a tooth trace curve drawn along the second outer tooth inner lateral tooth thickness decreasing portion 4b2. Here, the tooth thickness decreasing rate of the second inner tooth inner lateral tooth thickness decreasing portion 8a2 means a result obtained by dividing the amount of decrease in tooth thickness of the second inner tooth inner lateral tooth thickness decreasing portion 8a2 in the case of displacement over the unit distance in the tooth trace direction, specifically, an axially inward direction, by a unit distance. The tooth thickness decreasing rate of the second inner tooth inner lateral tooth thickness decreasing portion 8a2 may also be referred to as the amount of decrease in tooth thickness of the second inner tooth inner lateral tooth thickness decreasing portion 8a2 per unit distance in the tooth trace direction.The tooth thickness reduction rate of the second external tooth inner side tooth thickness reduction portion 4b2 means a result obtained by dividing the amount of reduction in tooth thickness of the second external tooth inner side tooth thickness reduction portion 4b2 in the case of displacement over the unit distance in the tooth trace direction, specifically, the axially inward direction, by the unit distance. The tooth thickness reduction rate of the second external tooth inner side tooth thickness reduction portion 4b2 may also be referred to as the amount of reduction in tooth thickness of the second external tooth inner side tooth thickness reduction portion 4b2 per unit distance in the tooth trace direction.

[0060] The maximum tooth thickness reduction amount of the second inner tooth inner lateral tooth thickness reduction portion 8a2 is greater than the maximum tooth thickness reduction amount of the second outer tooth inner lateral tooth thickness reduction portion 4b2. Regarding a ratio between the maximum tooth thickness reduction amount of the second inner tooth inner lateral tooth thickness reduction portion 8a2 and the maximum tooth thickness reduction amount of the second outer tooth inner lateral tooth thickness reduction portion 4b2, a relationship of "the maximum tooth thickness reduction amount of the second outer tooth inner lateral tooth thickness reduction portion 4b2:the maximum tooth thickness reduction amount of the second inner tooth inner lateral tooth thickness reduction portion 8a2 = 1:2 to 4" is satisfied.Here, the maximum tooth thickness reduction amount of the second internal tooth inner lateral tooth thickness reduction portion 8a2 means a result obtained by subtracting the minimum tooth thickness of the second internal tooth inner lateral tooth thickness reduction portion 8a2 at an axially inner end of the second internal tooth inner lateral tooth thickness reduction portion 8a2 from the maximum tooth thickness of the second internal tooth inner lateral tooth thickness reduction portion 8a2 at an axially outer end of the second internal tooth inner lateral tooth thickness reduction portion 8a2.The maximum tooth thickness reduction amount of the second external tooth inner side tooth thickness reduction portion 4b2 means a result obtained by subtracting the minimum tooth thickness of the second external tooth inner side tooth thickness reduction portion 4b2 at an axially inner end of the second external tooth inner side tooth thickness reduction portion 4b2 from the maximum tooth thickness of the second external tooth inner side tooth thickness reduction portion 4b2 at an axially outer end of the second external tooth inner side tooth thickness reduction portion 4b2.

[0061] The maximum tooth thickness reduction amount of the second inner tooth inner side tooth thickness reduction portion 8a2 is larger than the maximum tooth thickness reduction amount of the first inner tooth inner side tooth thickness reduction portion 6a2.

[0062] The second outer tooth outer side tooth thickness reduction portion 4b3 has an area in the axial direction. In a case where the second thickest inner tooth portion 8a1 has an area in the axial direction, as in the Fig. 2, the area of ​​the second outer tooth outer side tooth thickness reduction portion 4b3 partially overlaps with the area of ​​the second thickest inner tooth portion 8a1. The area of ​​the second outer tooth outer side tooth thickness reduction portion 4b3 reaches a position closer to the outer side in the axial direction than the second inner leg thickest portion 8a1. Note that an axially outer end of the second outer tooth outer side tooth thickness reduction portion 4b3 corresponds to an axially outer end of the second outer tooth portion 4b.

[0063] The tooth thickness reduction rate of the second external tooth outer side tooth thickness reduction section 4b3 is higher than the tooth thickness reduction rate of the second external tooth inner side tooth thickness reduction section 4b2. Therefore, in the cross section as shown in Fig. 2, a tooth trace curve drawn along the second external tooth outer side tooth thickness decreasing portion 4b3 is steeper than the tooth trace curve drawn along the second external tooth inner side tooth thickness decreasing portion 4b2. Here, the tooth thickness decreasing rate of the second external tooth outer side tooth thickness decreasing portion 4b3 means a result obtained by dividing the amount of decrease in tooth thickness of the second external tooth outer side tooth thickness decreasing portion 4b3 in the case of displacement over the unit distance in the tooth trace direction, specifically, an axially outward direction, by the unit distance. The tooth thickness decreasing rate of the second external tooth outer side tooth thickness decreasing portion 4b3 may also be referred to as the amount of decrease in tooth thickness of the second external tooth outer side tooth thickness decreasing portion 4b3 per unit distance in the tooth trace direction. <zahnspitzenform>

[0064] Fig. 3 is a view for describing the tooth tip types of the external gear 4, the first internal gear 6 and the second internal gear 8 of Fig. 1. Fig. 3 shows tooth tips of the first outer tooth portion 4a and the second outer tooth portion 4b and tooth tips of the first inner tooth portion 6a and the second inner tooth portion 8a when viewed in the circumferential direction. Fig. 3, for easier understanding, the tooth tips of the first internal tooth portion 6a and the tooth tips of the second internal tooth portion 8a are shown in a state in which they are shifted so as to be separated radially outward from the external gear 4, and the tooth tip shapes of the first external tooth portion 4a, the second external tooth portion 4b, the first internal tooth portion 6a, and the second internal tooth portion 8a are shown in an enlarged manner. In Fig. 3, the horizontal axis represents an axial position relative to a specific reference position. The vertical axis is used to indicate a dimension in a radial direction. <<Zahnspitzenformen von erstem Außenzahnabschnitt 4a und erstem Innenzahnabschnitt 6a> >

[0065] The tooth tip shapes of the first outer tooth portion 4a and the first inner tooth portion 6a are described with reference to Fig. 3. Note that the first outer tooth portion 4a and the first inner tooth portion 6a may not have the tooth tip shapes described below while having the tooth trace shapes described above. In a case where the first outer tooth portion 4a and the first inner tooth portion 6a do not have the tooth tip shapes described below, the tooth tip shapes of the first outer tooth portion 4a and the first inner tooth portion 6a may be, for example, flat shapes.

[0066] When a tooth tip of the first outer tooth portion 4a is divided in the axial direction, the first outer tooth portion 4a includes a first outer tooth maximum outer diameter portion 4a6, a first outer tooth inner outer diameter decreasing portion 4a7, and a first outer tooth outer diameter decreasing portion 4a8. The first outer tooth inner outer diameter portion 4a7 is positioned axially inward of the first outer tooth maximum outer diameter portion 4a6, and the first outer tooth outer diameter decreasing portion 4a8 is positioned axially outward of the first outer tooth maximum outer diameter portion 4a6.

[0067] The outer diameter of the first external tooth portion 4a changes in the axial direction. Specifically, the outer diameter of the first external tooth maximum outer diameter portion 4a6 corresponds to the maximum outer diameter of the first external tooth portion 4a, the outer diameter of the first external tooth inner side outer diameter decreasing portion 4a7 gradually decreases from the first external tooth maximum outer diameter portion 4a6 toward the inner side in the axial direction, and the outer diameter of the first external tooth outer side outer diameter decreasing portion 4a8 gradually decreases from the first external tooth maximum outer diameter portion 4a6 toward the outer side in the axial direction. The outer diameter of the first external tooth portion 4a means a distance from the rotation axis R to the tooth tip of the first external tooth portion 4a.

[0068] When a tooth tip of the first inner tooth portion 6a is divided in the axial direction, the first inner tooth portion 6a includes a first inner tooth minimum inner diameter portion 6a6 and a first inner tooth inner diameter increasing portion 6a7. The first inner tooth inner diameter increasing portion 6a7 is positioned axially inward of the first inner tooth minimum inner diameter portion 6a6.

[0069] The inner diameter of the first inner tooth portion 6a changes in the axial direction. Specifically, the inner diameter of the first inner tooth minimum inner diameter portion 6a6 corresponds to the minimum inner diameter of the first inner tooth portion 6a, and the inner diameter of the first inner tooth inner diameter increasing portion 6a7 gradually increases in the axial direction from the first inner tooth minimum inner diameter portion 6a6 toward the inner side. The inner diameter of the first inner tooth portion 6a means a distance from the rotation axis R to the tooth tip of the first inner tooth portion 6a.

[0070] The first outer tooth maximum outer diameter portion 4a6 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 3, the first outer tooth maximum outer diameter portion 4a6 is a single point without a region in the axial direction.

[0071] The first internal tooth minimum inner diameter portion 6a6 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 3, the first internal tooth minimum inner diameter portion 6a6 has a range in the axial direction. Note that an axially outer end of the first internal tooth minimum inner diameter portion 6a6 corresponds to an axially outer end of the first internal tooth portion 6a in a case where the first internal tooth minimum inner diameter portion 6a6 has a range in the axial direction, and the first internal tooth minimum inner diameter portion 6a6 with minimum inner diameter corresponds to the axially outer end of the first internal tooth portion 6a in a case where the first internal tooth minimum inner diameter portion 6a6 is a single point without a range in the axial direction.

[0072] As in Fig. 3, in a case where the first outer tooth maximum outer diameter portion 4a6 is a single point without a range in the axial direction and the first inner tooth minimum inner diameter portion 6a6 has a range in the axial direction, the position of the first outer tooth maximum outer diameter portion 4a6 in the axial direction is within the range of the first inner tooth minimum inner diameter portion 6a6. Note that in a case where the first outer tooth maximum outer diameter portion 4a6 has a range in the axial direction and the first inner tooth minimum inner diameter portion 6a6 is a single point without a range in the axial direction, the position of the first inner tooth minimum inner diameter portion 6a6 in the axial direction may be within the range of the first outer tooth maximum outer diameter portion 4a6.Furthermore, in a case where the first outer tooth maximum outer diameter portion 4a6 has a range in the axial direction and the first inner tooth minimum inner diameter portion 6a6 has a range in the axial direction, the range of the first outer tooth maximum outer diameter portion 4a6 and the range of the first inner tooth minimum inner diameter portion 6a6 may partially or completely overlap with each other. In a case where the first outer tooth maximum outer diameter portion 4a6 is a single point without a range in the axial direction and the first inner tooth minimum inner diameter portion 6a6 is a single point without a range in the axial direction, the positions of the first outer tooth maximum outer diameter portion 4a6 and the first inner tooth minimum inner diameter portion 6a6 with minimum inner diameter in the axial direction may be aligned with each other.

[0073] The first outer tooth inner side outer diameter reduction portion 4a7 has a range in the axial direction. In a case where the first inner tooth minimum inner diameter portion 6a6 has a range in the axial direction, as in the Fig. 3, the area of ​​the first outer tooth inner side outer diameter reduction portion 4a7 partially overlaps with the area of ​​the first inner tooth minimum inner diameter portion 6a6. Note that an axially inner end of the first outer tooth inner side outer diameter reduction portion 4a7 corresponds to the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b.

[0074] The first inner tooth inner diameter increasing portion 6a7 has an area in the axial direction. The area of ​​the first inner tooth inner diameter increasing portion 6a7 is smaller than the area of ​​the first outer tooth inner outer diameter decreasing portion 4a7, and the entire area of ​​the first inner tooth inner diameter increasing portion 6a7 lies within the area of ​​the first outer tooth inner outer diameter decreasing portion 4a7. The area of ​​the first outer tooth inner outer diameter decreasing portion 4a7 reaches a position closer to the inside in the axial direction than an axially inner end of the area of ​​the first inner tooth inner inner diameter increasing portion 6a7.However, an axially inner end of the portion of the first outer tooth inner side outer diameter decreasing portion 4a7 may be positionally aligned with the axially inner end of the portion of the first inner tooth inner side inner diameter increasing portion 6a7. The portion of the first outer tooth inner side outer diameter decreasing portion 4a7 reaches a position closer to the outside in the axial direction than an axially outer end of the portion of the first inner tooth inner side inner diameter increasing portion 6a7. Note that an axially inner end of the first inner tooth inner side inner diameter increasing portion 6a7 corresponds to an axially inner end of the first inner tooth portion 6a.

[0075] The inner diameter increase rate of the first inner tooth inner diameter increase portion 6a7 is greater than the outer diameter decrease rate of the first outer tooth inner outer diameter decrease portion 4a7. Therefore, Fig. 3, a tooth tip curve drawn along the first inner tooth inner diameter increasing portion 6a7 is steeper than a tooth tip curve drawn along the first outer tooth inner outer diameter decreasing portion 4a7. Here, the inner diameter increasing rate of the first inner tooth inner inner diameter increasing portion 6a7 means a result obtained by dividing, by a unit distance, the amount of increase in the inner diameter of the first inner tooth inner inner diameter increasing portion 6a7 in the case of displacement over the unit distance to the inner side in the axial direction. The inner diameter increasing rate of the first inner tooth inner inner diameter increasing portion 6a7 may also be referred to as the amount of increase in the inner diameter of the first inner tooth inner inner diameter increasing portion 6a7 per unit distance in the axial direction.The outer diameter reduction rate of the first outer tooth inner side outer diameter reduction portion 4a7 means a result obtained by dividing the amount of outer diameter reduction of the first outer tooth inner side outer diameter reduction portion 4a7 in the case of displacement over the unit distance to the inner side in the axial direction by the unit distance. The first outer tooth inner side outer diameter reduction portion 4a7 may also be referred to as the amount of inner diameter reduction of the first outer tooth inner side outer diameter reduction portion 4a7 per unit distance in the axial direction.

[0076] The maximum inner diameter increase amount of the first inner tooth inner diameter increase portion 6a7 is greater than the maximum outer diameter decrease amount of the first outer tooth inner outer diameter decrease portion 4a7. Regarding a relationship between the maximum inner diameter increase amount of the first inner tooth inner inner diameter increase portion 6a7 and the maximum outer diameter decrease amount of the first outer tooth inner outer diameter decrease portion 4a7, a relationship of "the maximum outer diameter decrease amount of the first outer tooth inner outer diameter decrease portion 4a7:the maximum inner diameter increase amount of the first inner tooth inner inner diameter increase portion 6a7 = 1:2 to 4" is satisfied.Here, the maximum inner diameter increase amount of the first inner tooth inner side inner diameter increase portion 6a7 means a result obtained by subtracting the minimum inner diameter of the first inner tooth inner side inner diameter increase portion 6a7 at an axially outer end of the first inner tooth inner side inner diameter increase portion 6a7 from the maximum inner diameter of the first inner tooth inner side inner diameter increase portion 6a7 at an axially inner end of the first inner tooth inner side inner diameter increase portion 6a7.The maximum outer diameter reduction amount of the first outer tooth inner side outer diameter reduction portion 4a7 means a result obtained by subtracting the minimum outer diameter of the first outer tooth inner side outer diameter reduction portion 4a7 at an axially inner end of the first outer tooth inner side outer diameter reduction portion 4a7 from the maximum outer diameter of the first outer tooth inner side outer diameter reduction portion 4a7 at an axially outer end of the first outer tooth inner side outer diameter reduction portion 4a7.

[0077] The first outer tooth outer diameter reduction portion 4a8 has a range in the axial direction. In a case where the first inner tooth minimum inner diameter portion 6a6 has a range in the axial direction, as in the Fig. In the example shown in FIG. 3, the region of the first outer tooth outer diameter reduction portion 4a8 partially overlaps with the region of the first inner tooth minimum inner diameter portion 6a6. The region of the first outer tooth outer diameter reduction portion 4a8 reaches a position closer to the outside in the axial direction than the first inner tooth minimum inner diameter portion 6a6. Note that an axially outer end of the first outer tooth outer diameter reduction portion 4a8 corresponds to an axially outer end of the first outer tooth portion 4a.

[0078] The outer diameter decreasing rate of the first outer tooth outer side outer diameter decreasing portion 4a8 is greater than the outer diameter decreasing rate of the first outer tooth inner side outer diameter decreasing portion 4a7. Therefore, in the cross section as shown in Fig. 3, a tooth tip curve drawn along the first outer tooth outer diameter decreasing portion 4a8 is steeper than the tooth tip curve drawn along the first outer tooth inner diameter decreasing portion 4a7. Here, the outer diameter decreasing rate of the first outer tooth outer diameter decreasing portion 4a8 means a result obtained by dividing the amount of outer diameter decrease of the first outer tooth outer diameter decreasing portion 4a8 in the case of displacement over the unit distance to the outside in the axial direction by the unit distance. <<Zahnspitzenformen von zweitem Außenzahnabschnitt 4b und zweitem Innenzahnabschnitt 8a> >

[0079] The tooth tip shapes of the second outer tooth portion 4b and the second inner tooth portion 8a will be described. Note that the second outer tooth portion 4b and the second inner tooth portion 8a may not have the tooth tip shapes described below while having the tooth tip shapes described above. In a case where the second outer tooth portion 4b and the second inner tooth portion 8a do not have the tooth tip shapes described below, the tooth tip shapes of the second outer tooth portion 4b and the second inner tooth portion 8a may be, for example, flat shapes.

[0080] When a tooth tip of the second outer tooth portion 4b is divided in the axial direction, the second outer tooth portion 4b includes a second outer tooth maximum outer diameter portion 4b6, a second outer tooth inner outer diameter decreasing portion 4b7, and a second outer tooth outer diameter decreasing portion 4b8. The second outer tooth inner outer diameter decreasing portion 4b7 is positioned axially inward of the second outer tooth maximum outer diameter portion 4b6, and the second outer tooth outer diameter decreasing portion 4b8 is positioned axially outward of the second outer tooth maximum outer diameter portion 4b6.

[0081] The outer diameter of the second outer tooth portion 4b changes in the axial direction. Specifically, the outer diameter of the second outer tooth maximum outer diameter portion 4b6 corresponds to the maximum outer diameter of the second outer tooth portion 4b, the outer diameter of the second outer tooth inner side outer diameter decreasing portion 4b7 gradually decreases in the axial direction from the second outer tooth maximum outer diameter portion 4b6 toward the inner side, and the outer diameter of the second outer tooth outer side outer diameter decreasing portion 4b8 gradually decreases in the axial direction from the second outer tooth maximum outer diameter portion 4b6 toward the outer side. The outer diameter of the second outer tooth portion 4b means a distance from the rotation axis R to the tooth tip of the second outer tooth portion 4b.

[0082] When the second inner tooth portion 8a is divided in the axial direction, the second inner tooth portion 8a includes a second inner tooth minimum inner diameter portion 8a6 and a second inner tooth inner diameter increasing portion 8a7. The second inner tooth inner diameter increasing portion 8a7 is positioned axially inward of the second inner tooth minimum inner diameter portion 8a6.

[0083] The inner diameter of the second inner tooth portion 8a changes in the axial direction. Specifically, the inner diameter of the second inner tooth minimum inner diameter portion 8a6 corresponds to the minimum inner diameter of the second inner tooth portion 8a, and the inner diameter of the second inner tooth inner diameter increasing portion 8a7 gradually increases in the axial direction from the second inner tooth minimum inner diameter portion 8a6 toward the inner side. The inner diameter of the second inner tooth portion 8a means a distance from the rotation axis R to the tooth tip of the second inner tooth portion 8a.

[0084] The second outer tooth maximum outer diameter portion 4b6 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 3, the second outer tooth maximum outer diameter portion 4b6 is a single point without a region in the axial direction.

[0085] The second internal tooth minimum inner diameter portion 8a6 may have a region in the axial direction or may be a single point without a region in the axial direction. Fig. 3, the second internal tooth minimum inner diameter portion 8a6 has a range in the axial direction. Note that, in a case where the second internal tooth minimum inner diameter portion 8a6 has a range in the axial direction, the second internal tooth minimum inner diameter portion 8a6 corresponds to an axially outer end of the second internal tooth portion 8a6 of the second internal tooth portion 8a, and in a case where the second internal tooth minimum inner diameter portion 8a6 is a single point without a range in the axial direction, the second internal tooth minimum inner diameter portion 8a6 corresponds to the axially outer end of the second internal tooth portion 8a.

[0086] As in Fig. 3, in a case where the second outer tooth maximum outer diameter portion 4b6 is a single point without a range in the axial direction and the inner tooth minimum inner diameter portion 8a6 has a range in the axial direction, the position of the second outer tooth maximum outer diameter portion 4b6 in the axial direction is within the range of the inner tooth minimum inner diameter portion 8a6. Note that in a case where the second outer tooth maximum outer diameter portion 4b6 has a range in the axial direction and the inner tooth minimum inner diameter portion 8a6 is a single point without a range in the axial direction, the position of the inner tooth minimum inner diameter portion 8a6 in the axial direction may be within the range of the outer tooth maximum outer diameter portion 4b6.Furthermore, in a case where the second outer tooth maximum outer diameter portion 4b6 has a range in the axial direction and the inner tooth minimum inner diameter portion 8a6 has a range in the axial direction, the range of the second outer tooth maximum outer diameter portion 4b6 and the range of the inner tooth minimum inner diameter portion 8a6 may partially or completely overlap with each other. In a case where the second outer tooth maximum outer diameter portion 4b6 is a single point without a range in the axial direction and the inner tooth minimum inner diameter portion 8a6 is a single point without a range in the axial direction, the positions of the second outer tooth maximum outer diameter portion 4b6 and the inner tooth minimum inner diameter portion 8a6 may be aligned with each other in the axial direction.

[0087] The second outer tooth inner side outer diameter reduction portion 4b7 has a range in the axial direction. In a case where the second inner tooth minimum inner diameter portion 8a6 has a range in the axial direction, as in the Fig. 3, the area of ​​the second outer tooth inner side outer diameter reduction portion 4b7 partially overlaps with the area of ​​the second inner tooth minimum inner diameter portion 8a6. Note that an axially inner end of the second outer tooth inner side outer diameter reduction portion 4b7 corresponds to the center of the space between the first outer tooth portion 4a and the second outer tooth portion 4b.

[0088] The second inner tooth inner diameter increasing portion 8a7 has an area in the axial direction. The area of ​​the second inner tooth inner diameter increasing portion 8a7 is smaller than the area of ​​the second outer tooth inner outer diameter decreasing portion 4b7, and the entire area of ​​the second inner tooth inner diameter increasing portion 8a7 lies within the area of ​​the second outer tooth inner outer diameter decreasing portion 4b7. An axially inner end of the area of ​​the second outer tooth inner outer diameter decreasing portion 4b7 is positionally aligned with an axially inner end of the area of ​​the second inner tooth inner inner diameter increasing portion 8a7.In this regard, however, the portion of the second external tooth inner side outer diameter decreasing portion 4b7 can reach a position closer to the inner side in the axial direction than the axially inner end of the portion of the second internal tooth inner side inner diameter increasing portion 8a7. The portion of the second external tooth inner side outer diameter decreasing portion 4b7 reaches a position closer to the outer side in the axial direction than an axially outer end of the portion of the second internal tooth inner side inner diameter increasing portion 8a7. Note that an axially inner end of the second internal tooth inner side inner diameter increasing portion 8a7 corresponds to an axially inner end of the second internal tooth portion 8a.

[0089] The inner diameter increase rate of the second inner tooth inner diameter increase portion 8a7 is greater than the outer diameter decrease rate of the second outer tooth inner outer diameter decrease portion 4b7. Therefore, Fig. 3, a tooth tip curve drawn along the second inner tooth inner diameter increasing portion 8a7 is steeper than a tooth tip curve drawn along the second outer tooth inner outer diameter decreasing portion 4b7. Here, the inner diameter increasing rate of the second inner tooth inner inner diameter increasing portion 8a7 means a result obtained by dividing the amount of increase in the inner diameter of the second inner tooth inner inner diameter increasing portion 8a7 in the case of displacement over the unit distance to the inner side in the axial direction by a unit distance. The inner diameter increasing rate of the second inner tooth inner inner diameter increasing portion 8a7 may also be referred to as the amount of increase in the inner diameter of the second inner tooth inner inner diameter increasing portion 8a7 per unit distance in the axial direction.The outer diameter reduction rate of the second outer tooth inner side outer diameter reduction portion 4b7 means a result obtained by dividing the amount of outer diameter reduction of the second outer tooth inner side outer diameter reduction portion 4b7 in the case of displacement over the unit distance to the inner side in the axial direction by the unit distance. The outer diameter reduction rate of the second outer tooth inner side outer diameter reduction portion 4b7 may also be referred to as the amount of outer diameter reduction of the second outer tooth inner side outer diameter reduction portion 4b7 per unit distance in the axial direction.

[0090] The maximum inner diameter increase amount of the second inner tooth inner diameter increase portion 8a7 is greater than the maximum outer diameter decrease amount of the second outer tooth inner outer diameter decrease portion 4b7. Regarding a ratio between the maximum inner diameter increase amount of the second inner tooth inner inner diameter increase portion 8a7 and the maximum outer diameter decrease amount of the second outer tooth inner outer diameter decrease portion 4b7, a relationship of "the maximum outer diameter decrease amount of the second outer tooth inner outer diameter decrease portion 4b7 : the maximum inner diameter increase amount of the second inner tooth inner inner diameter increase portion 8a7 = 1 : 2 to 4" is satisfied.Here, the maximum inner diameter increase amount of the second inner tooth inner side inner diameter increase portion 8a7 denotes a result obtained by subtracting the minimum inner diameter of the second inner tooth inner side inner diameter increase portion 8a7 at an axially outer end of the second inner tooth inner side inner diameter increase portion 8a7 from the maximum inner diameter of the second inner tooth inner side inner diameter increase portion 8a7 at an axially inner end of the second inner tooth inner side inner diameter increase portion 8a7.The maximum outer diameter reduction amount of the second outer tooth inner side outer diameter reduction portion 4b7 means a result obtained by subtracting the minimum outer diameter of the second outer tooth inner side outer diameter reduction portion 4b7 at an axially inner end of the second outer tooth inner side outer diameter reduction portion 4b7 from the maximum outer diameter of the second outer tooth inner side outer diameter reduction portion 4b7 at an axially outer end of the second outer tooth inner side outer diameter reduction portion 4b7.

[0091] The maximum inner diameter increase amount of the second inner tooth inner diameter increase portion 8a7 is larger than the maximum tooth thickness decrease amount of the first inner tooth inner diameter increase portion 6a7.

[0092] The second outer tooth outer diameter reduction portion 4b8 has a range in the axial direction. In a case where the second inner tooth minimum inner diameter portion 8a6 has a range in the axial direction, as in the Fig. 3, the area of ​​the second outer tooth outer diameter decreasing portion 4b8 partially overlaps with the area of ​​the second inner tooth minimum inner diameter portion 8a6. The area of ​​the second outer tooth outer diameter decreasing portion 4b8 reaches a position closer to the outside in the axial direction than the second inner tooth minimum inner diameter portion 8a6. Note that an axially outer end of the second outer tooth outer diameter decreasing portion 4b8 corresponds to an axially outer end of the second outer tooth portion 4b.

[0093] The outer diameter decreasing rate of the second outer tooth outer side outer diameter decreasing portion 4b8 is greater than the outer diameter decreasing rate of the second outer tooth inner side outer diameter decreasing portion 4b7. Therefore, Fig. 3, a tooth trace curve drawn along the second outer tooth outer diameter decreasing portion 4b8 is steeper than the tooth trace curve drawn along the second outer tooth inner diameter decreasing portion 4b7. Here, the outer diameter decreasing rate of the second outer tooth outer diameter decreasing portion 4b8 means a result obtained by dividing the amount of outer diameter decrease of the second outer tooth outer diameter decreasing portion 4b8 in the case of displacement over the unit distance to the outside in the axial direction by the unit distance. The outer diameter decreasing rate of the second outer tooth outer diameter decreasing portion 4b8 may also be referred to as the amount of outer diameter decrease of the second outer tooth outer diameter decreasing portion 4b8 per unit distance in the axial direction. <Vorteilhafte technische Effekte>

[0094] The tooth thickness of the first external tooth inner side tooth thickness reduction portion 4a2 of the first external tooth portion 4a gradually decreases in the axial direction toward the inner side. Therefore, a tooth surface of the first external tooth portion 4a smoothly contacts a tooth surface of the first internal tooth portion 6a, a partial contact load acting on an axially inner end of the first external tooth portion 4a is reduced, and excessive wear of the first external tooth portion 4a and the first internal tooth portion 6a can be reduced. The fact that the tooth thickness of the first internal tooth inner side tooth thickness reduction portion 6a2 gradually decreases in the axial direction toward the inner side of the first internal tooth portion 6a leads to the same effect.

[0095] Since the first external tooth portion 4a and the first internal tooth portion 6a each include the first external tooth inner side tooth thickness reduction portion 4a2 and the first internal tooth inner side tooth thickness reduction portion 6a2, the tooth thicknesses of the first external tooth portion 4a and the first internal tooth portion 6a are not excessively small. That is, the maximum tooth thickness reduction amount of the first external tooth inner side tooth thickness reduction portion 4a2 and the maximum tooth thickness reduction amount of the first internal tooth inner side tooth thickness reduction portion 6a2 do not need to be excessively large. Therefore, excessive wear of both the first external tooth portion 4a and the first internal tooth portion 6a can be reduced while the first external tooth portion 4a and the first internal tooth portion 6a have adequate strengths in a balanced manner, resulting in an improvement in the durability of the external gear 4 and the first internal gear 6.Such an effect is noticeable in a case where a relationship of "the maximum tooth thickness reduction amount of the first outer tooth inner side tooth thickness reduction portion 4a2:the maximum tooth thickness reduction amount of the first inner tooth inner side tooth thickness reduction portion 6a2 = 1:2 to 4" is satisfied.

[0096] Since one or both of the first thickest outer tooth portion 4a1 and the first thickest inner tooth portion 6a1 have a region over a predetermined width in the axial direction, the first thickest outer tooth portion 4a1 and the first thickest inner tooth portion 6a1 contact each other even in the case where there is a position error of the first internal gear 6 in the axial direction. Therefore, rattle caused by the first outer tooth portion 4a and the first inner tooth portion 6a meshing with each other does not occur.

[0097] The second outer tooth portion 4b and the second inner tooth portion 8a have the same effect as the first outer tooth portion 4a and the first inner tooth portion 6a.

[0098] Even in a case where each component of the bending engagement type gear device 100 has a dimensional error, the above-described advantageous technical effects are reliably achieved by the regulating members 12 and 14. This is because the thickness T12 of the first regulating member 12 is optimally adjusted in accordance with the distance between the outer ring of the bearing 30 and the external gear 4 in the axial direction, and the thickness T14 of the second regulating member 14 is optimally adjusted in accordance with the distance between the outer ring of the bearing 32 and the external gear 4 in the axial direction. That is, since the thicknesses T12 and T14 of the regulating members 12 and 14 determine the relative positions of tooth traces (see Fig. 2) of the external gear 4 in relation to tooth marks (see Fig. 2) of the internal gears 6 and 8 are appropriately determined, a partial contact load acting on the axially inner end of the first external tooth portion 4a is reliably reduced, and excessive abrasion of the first external tooth portion 4a and the first internal tooth portion 6a can be reliably reduced. (Embodiment 2)

[0099] Embodiment 2 will be described with reference to Fig. 4 and Fig. 5. Embodiment 2 is modified from Embodiment 1 in the following points, and Embodiment 2 and Embodiment 1 are the same except for the following description.

[0100] With respect to a tooth track of the second inner tooth portion 8a, as shown in Fig. 4, the second internal inner tooth thickness decreasing portion 8a2 includes an outer portion 8a2o and an inner portion 8a2i. The inner portion 8a2i is positioned axially inward of the outer portion 8a2o. The axial direction portion of the inner portion 8a2i occupies an axially inner side of the entire axial direction portion of the second internal tooth thickness decreasing portion 8a2, and the axial direction portion of the outer portion 8a2o occupies an axially outer side of the entire axial direction portion of the second internal tooth thickness decreasing portion 8a2. The tooth thickness of the outer portion 8a2o gradually decreases from the second thickest internal tooth portion 8a1 toward the inner side in the axial direction, and the tooth thickness of the inner portion 8a2i gradually decreases from the outer portion 8a2o toward the inner side in the axial direction.The tooth thickness reduction rate of the inner region 8a2i is higher than the tooth thickness reduction rate of the outer region 8a2o.

[0101] Since the second internal tooth inner side tooth thickness reduction portion 8a2 includes the outer region 8a2o and the inner region 8a2i, it is possible to suppress tooth thickness reduction at a center of the second internal tooth portion 8a in the axial direction while reducing the tooth thickness of the second internal tooth portion 8a beyond the axially inner end thereof. Therefore, the rigidity of the second internal gear 8 is improved, and the torsional rigidity of the flexural meshing type gear device 100 is improved.

[0102] In a Fig. In the example shown in Figure 4, the second inner tooth inner lateral tooth thickness decreasing portion 8a2 includes the outer region 8a2o and the inner region 8a2i. Similarly, the first inner tooth inner lateral tooth thickness decreasing portion 6a2 may include an outer region and an inner region positioned axially inward from the outer region, and the tooth thickness decreasing rate of the inner region may be higher than the tooth thickness decreasing rate of the outer region.

[0103] With respect to a tooth tip of the second inner tooth portion 8a, as shown in Fig. 5, the second inner tooth inner diameter increasing portion 8a7 includes an outer portion 8a7o and an inner portion 8a7i. The inner portion 8a7i is positioned axially inward of the outer portion 8a7o. The axial direction region of the inner portion 8a7i occupies an axially inner side of the entire axial direction region of the second inner tooth inner diameter increasing portion 8a7, and the axial direction region of the outer portion 8a7o occupies an axially outer side of the entire axial direction region of the second inner tooth inner diameter increasing portion 8a7. The inner diameter of the outer portion 8a7o gradually increases from the second inner tooth minimum inner diameter portion 8a6 toward the inner side in the axial direction, and the inner diameter of the inner portion 8a7i gradually increases from the outer portion 8a7o toward the inner side in the axial direction.The inner diameter increase rate of the inner region 8a7i is higher than the inner diameter increase rate of the outer region 8a7o.

[0104] In a Fig. In the example shown in Figure 5, the second inner tooth inner diameter increasing portion 8a7 includes the outer region 8a7o and the inner region 8a7i. Similarly, the first inner tooth inner diameter increasing portion 6a7 may include an outer region and an inner region positioned axially inward from the outer region, and the inner diameter increasing rate of the inner region may be higher than the inner diameter increasing rate of the outer region. (Embodiment 3)

[0105] Embodiment 3 will be described with reference to Fig. 6. Embodiment 3 is modified from Embodiment 1 in the following points, and Embodiment 3 and Embodiment 1 are the same except for the following description.

[0106] Similar to the first external tooth portion 4a including the first external tooth outer side tooth thickness reduction portion 4a3, the first internal tooth portion 6a further includes a first internal tooth outer side tooth thickness reduction portion 6a3. The first internal tooth outer side tooth thickness reduction portion 6a3 is positioned axially outward from the first thickest internal tooth portion 6a1. The tooth thickness of the first internal tooth outer side tooth thickness reduction portion 6a3 gradually decreases from the first thickest internal tooth portion 6a1 toward the outside in the axial direction. The first internal tooth outer side tooth thickness reduction portion 6a3 has a range in the axial direction, and the range of the first internal tooth outer side tooth thickness reduction portion 6a3 partially or completely overlaps with the range of the first external tooth outer side tooth thickness reduction portion 4a3.

[0107] Similar to the second outer tooth portion 4b including the second outer tooth outer side tooth thickness reduction portion 4b3, the second inner tooth portion 8a further includes a second inner tooth outer side tooth thickness reduction portion 8a3. The second inner tooth outer side tooth thickness reduction portion 8a3 is positioned axially outward from the second thickest inner tooth portion 8a1. The tooth thickness of the second inner tooth outer side tooth thickness reduction portion 8a3 gradually decreases from the second thickest inner tooth portion 8a1 toward the outside in the axial direction. The second inner tooth outer side tooth thickness reduction portion 8a3 has a range in the axial direction, and the range of the second inner tooth outer side tooth thickness reduction portion 8a3 partially or completely overlaps with the range of the second outer tooth outer side tooth thickness reduction portion 4b3.

[0108] The first inner tooth outer side tooth thickness reduction portion 6a3 contributes to smooth contact between a tooth surface of the first inner tooth portion 6a and a tooth surface of the first outer tooth portion 4a and to reducing partial contact load acting on the axially outer end of the first inner tooth portion 6a. The second inner tooth outer side tooth thickness reduction portion 8a3 contributes to smooth contact between a tooth surface of the second inner tooth portion 8a and a tooth surface of the second outer tooth portion 4b and to reducing partial contact load acting on the axially outer end of the second inner tooth portion 8a.

[0109] Note that a configuration in which the first inner tooth portion 6a includes the first inner tooth outer side tooth thickness decreasing portion 6a3 can be applied to Embodiment 2. Similarly, a configuration in which the second inner tooth portion 8a includes the second inner tooth outer side tooth thickness decreasing portion 8a3 can be applied to Embodiment 2.

[0110] Furthermore, the first inner tooth portion 6a may include a first inner tooth outer side inner diameter increasing portion in addition to the first inner tooth minimum inner diameter portion 6a6 and the first inner tooth inner side inner diameter increasing portion 6a7. The first inner tooth outer side inner diameter increasing portion is positioned axially outward from the first inner tooth minimum inner diameter portion 6a6, and the inner diameter of the first inner tooth outer side inner diameter increasing portion gradually increases from the first inner tooth minimum inner diameter portion 6a6 toward the outside in the axial direction. A configuration in which the first inner tooth portion 6a includes the first inner tooth outer side inner diameter increasing portion can be applied to Embodiment 2.

[0111] Furthermore, the second inner tooth portion 8a may include a second inner tooth outer side inner diameter increasing portion in addition to the second inner tooth minimum inner diameter portion 8a6 and the second inner tooth inner side inner diameter increasing portion 8a7. The second inner tooth inner side inner diameter increasing portion is positioned axially outward from the second inner tooth minimum inner diameter portion 8a6, and the inner diameter of the second inner tooth inner side inner diameter increasing portion gradually increases from the inner tooth minimum inner diameter portion 8a6 toward the outside in the axial direction. A configuration in which the second inner tooth portion 8a includes the second inner tooth inner side inner diameter increasing portion can be applied to Embodiment 2. List of reference symbols 4 external gear 4a first outer tooth section 4a1 first thickest outer tooth section 4a2 first outer tooth-inner posterior tooth thickness reduction section 4a3 first outer tooth outer lateral tooth thickness reduction section 4a6 first outer tooth maximum outer diameter section 4a7 first external tooth inner diameter reduction section 4a8 first external tooth outer diameter reduction section 4b second outer tooth section 4b1 second thickest outer tooth section 4b2 second outer tooth-inner posterior tooth thickness reduction section 4b3 second outer tooth outer side tooth thickness reduction section 4b6 second outer tooth maximum outer diameter section 4b7 second external tooth inner side outer diameter reduction section 4b8 second external tooth outer diameter reduction section 6 first internal gear 6a first inner tooth section 6a1 first thickest inner tooth section 6a2 first inner tooth inner posterior tooth thickness reduction section 6a3 first inner tooth-outer lateral tooth thickness reduction section 6a6 first inner tooth section with minimum inner diameter 6a7 first internal tooth inner diameter increase section 8 second internal gear 8a second inner tooth section 8a1 second thickest inner tooth section 8a2 second inner tooth inner posterior tooth thickness reduction section 8a2i interior 8a2o outdoor area 8a3 second inner tooth-outer tooth thickness reduction section 8a6 second internal tooth minimum inner diameter section 8a7 second internal tooth inner diameter increase section 8a7i interior 8a7o outdoor area 8b Rolling surface 22 Shaft generator shaft 22a Wave generator 100 Gear device of bending engagement type QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-120325

[0004] < / zahnspitzenform> < / zahnspurform>

Claims

[1] A bending engagement type gear device comprising: a wave generator; an external gear that is flexibly deformed by the wave generator; a first internal gear meshing with the external gear; and a second internal gear arranged such that the second internal gear and the first internal gear are arranged in an axial direction and meshes with the external gear, wherein the external gear includes a first external tooth portion engaging with the first internal gear and a second external tooth portion engaging with the second internal gear, the second outer tooth portion includes a second thickest outer tooth portion in which a tooth thickness is the largest, and a second outer tooth inner side tooth thickness decreasing portion in which the tooth thickness decreases from the second thickest outer tooth portion toward an inner side in the axial direction, and an inner tooth portion of the second internal gear includes a second thickest inner tooth portion in which a tooth thickness is largest, and a second inner tooth inner side tooth thickness decreasing portion in which the tooth thickness decreases from the second thickest inner tooth portion toward the inner side in the axial direction. [2] A bending engagement type gear device according to claim 1, wherein the first outer tooth portion includes a first thickest outer tooth portion in which a tooth thickness is the largest, and a first outer tooth inner tooth thickness decreasing portion in which the tooth thickness decreases from the first thickest outer tooth portion toward the inner side in the axial direction, and an inner tooth portion of the first internal gear includes a first thickest inner tooth portion in which a tooth thickness is largest, and a first inner tooth inner side tooth thickness decreasing portion in which the tooth thickness decreases from the first thickest inner tooth portion toward the inner side in the axial direction. [3] The flexural engagement type gear device according to claim 2, wherein the number of teeth of the first external tooth portion and the number of teeth of the first internal gear are different from each other, the number of teeth of the second external tooth portion and the number of teeth of the second internal gear are equal to each other, and the second internal tooth inner side tooth thickness decreasing portion is larger than the first internal tooth inner side tooth thickness decreasing portion in terms of maximum tooth thickness decreasing amount. [4] The flexural engagement type gear device according to any one of claims 1 to 3, wherein the second outer tooth portion includes a second outer tooth portion outer side tooth thickness decreasing portion in which the tooth thickness decreases from the second thickest outer tooth portion toward an outer side in the axial direction. [5] The flexural engagement type gear device according to any one of claims 1 to 3, wherein the inner tooth portion of the second internal gear includes a second inner tooth portion outer side tooth thickness decreasing portion in which the tooth thickness decreases from the second thickest inner tooth portion toward an outer side in the axial direction. [6] The flexural engagement type gear device according to any one of claims 1 to 3, wherein at least one of the second thickest outer tooth portion and the second thickest inner tooth portion is provided over a predetermined width in the axial direction. [7] The flexural engagement type gear device according to any one of claims 1 to 3, wherein the second internal tooth inner side tooth thickness decreasing portion is larger than the second external tooth inner side tooth thickness decreasing portion in an amount of decrease in tooth thickness per unit distance in a tooth trace direction. [8] A flexural engagement type gear device according to any one of claims 1 to 3, wherein the second inner tooth portion inner side tooth thickness decreasing portion includes an outer region continuing from the second thickest inner tooth portion and an inner region positioned axially inward of the outer region, and the inner region is larger than the outer region in terms of an amount of decrease in tooth thickness per unit distance in a tooth track direction.

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