DE102018132806A1 - Transmission device of the bending engagement type - Google Patents

Abstract

The present invention provides a bending engagement type transmission device which can suppress the excessive wear of a gear. A bending engagement type transmission device includes a shaft generator, an outer gear bent and deformed by the shaft generator, a first inner gear meshing with the outer gear and a second inner gear arranged so as to be in an axial direction is aligned with the first inner gear and meshes with the outer gear. The outer gear includes a first outer tooth portion that meshes with the first inner gear and a second outer tooth portion that mesh with the second inner gear. The first outer tooth portion includes a first outer thickest tooth portion having a maximum tooth thickness, a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the first outer thickest tooth portion, and a first inner portion decreasing in tooth thickness a tooth thickness decreasing axially inwardly from the first outer thickest tooth portion, the second outer tooth portion having a second outer thickest tooth portion having a maximum tooth thickness; a second outer portion having decreasing tooth thickness having a tooth thickness of the second outer thickest tooth portion decreases axially outwardly, and a second inner portion of decreasing tooth thickness, which has a tooth thickness which decreases axially inwardly from the second outer thickest tooth portion contains.

Description

BACKGROUND OF THE INVENTION

Field of the invention

Certain embodiments of the present invention relate to a flexure engagement type transmission device.

It will be the priority of Japanese Patent Application No. 2018-000804 , filed January 5, 2018, the contents of which are hereby incorporated by reference in their entirety.

Description of the Prior Art

A bending engagement type transmission device is known as a transmission device which is small in size and lightweight and can obtain a high speed reduction ratio. In the prior art, there is proposed a so-called flat-type bending engagement type transmission device comprising a shaft generator, an outer gear bent and deformed by the shaft generator, a first inner gear meshing with the outer gear, and a second inner gear. which is arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear (eg, International Publication No. WO2016 / 21011 ).

SUMMARY OF THE INVENTION

In the international publication no. WO2016 / 21011 In the gear mechanism of the bending engagement type disclosed, misalignment is generated in a gear by an external torque load, and thus partial gear contact occurs and the gear is excessively worn.

The present invention has been made in view of the circumstances described above, and its object is to provide a bending engagement type transmission device which can suppress excessive wear of the gear.

In order to achieve the object described above, according to one aspect of the present invention, there is provided a bending engagement type transmission device including: a wave generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, the outer gear having a first outer gear portion meshing with the first inner gear and a first outer gear portion second outer tooth portion, which engages with the second inner gear includes. The first outer tooth portion includes a first outer thickest tooth portion having a maximum tooth thickness, a first outer portion with decreasing tooth thickness having a tooth thickness decreasing axially outwardly from the first outer thickest tooth portion, and a first inner portion decreasing in tooth thickness having a tooth thickness decreasing axially inward from the first outer thickest tooth portion. The second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness, a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second outer thickest tooth portion, and a second inner portion decreasing in tooth thickness which has a tooth thickness decreasing axially inwardly from the second outer thickest tooth portion.

According to another aspect of the present invention, there is provided a bending engagement type transmission device including: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, wherein an inner gear portion of the first inner gear has a first inner thickest gear portion having a maximum tooth thickness a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outwardly from the first inner thickest tooth portion, and a first inner portion of decreasing tooth thickness having a tooth thickness axially inward of the first inner thickest tooth portion decreases. An inner tooth portion of the second inner gear includes a second inner thickest tooth portion having a maximum tooth thickness, a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second inner thickest tooth portion, and a second inner portion decreasing tooth thickness having a tooth thickness decreasing axially inward from the second inner thickest tooth portion.

In accordance with still another aspect of the present invention, there is provided a bending engagement type transmission device including: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, the outer gear having a first outer gear portion connected to a first inner gear portion of the first inner gear meshes, and a second outer tooth portion, which engages with a second inner tooth portion of the second inner gear includes. The first outer tooth portion includes a first outer thickest tooth portion having a maximum tooth thickness and a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the first outer thickest tooth portion. The second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness and a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second outer thickest tooth portion. The first inner tooth portion includes a first inner thickest tooth portion having a maximum tooth thickness, and a first inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inward from the first inner thickest tooth portion. The second inner tooth portion includes a second inner thickest tooth portion having a maximum tooth thickness, and a second inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inwardly from the second inner thickest tooth portion.

In accordance with still another aspect of the present invention, there is provided a bending engagement type transmission device including: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, the outer gear having a first outer gear portion connected to a first inner gear portion of the first inner gear meshes, and a second outer tooth portion, which engages with a second inner tooth portion of the second inner gear includes. The first outer tooth portion includes a first outer thickest tooth portion having a maximum tooth thickness and a first inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inwardly from the first outer thickest tooth portion. The second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness, and a second inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inwardly from the second outer thickest tooth portion. The first inner tooth portion includes a first inner thickest tooth portion having a maximum tooth thickness and a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the first inner thickest tooth portion. The second inner tooth portion includes a second inner thickest tooth portion having a maximum tooth thickness, and a second outer portion with decreasing tooth thickness having a tooth thickness decreasing axially outward from the second inner thickest tooth portion.

In accordance with still another aspect of the present invention, there is provided a bending engagement type transmission device including: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, the outer gear having a first outer gear portion connected to a first inner gear portion of the first inner gear meshing and having the number of teeth different from that of the first inner tooth portion and a second outer tooth portion meshing with a second inner tooth portion of the second inner gear and having the number of teeth the same as that of the second inner tooth Teeth section is included. The second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness, and a second inner portion of decreasing tooth thickness having a tooth thickness continuously decreasing axially inwardly from the second outer thickest tooth portion. The second inner portion of decreasing tooth thickness occupies 80% or more of an axial portion of the second outer tooth portion.

In accordance with still another aspect of the present invention, there is provided a bending engagement type transmission device including: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, the second inner gear having a second inner gear portion connected to a second outer gear portion of the outer gear meshes with each other and has the number of teeth that is the same as that of the second outer tooth portion. The second inner tooth portion includes an inner thickest tooth portion having a maximum tooth thickness, and an inner portion of decreasing tooth thickness having a tooth thickness continuously decreasing axially inward from the inner thickest tooth portion. The inner portion of decreasing tooth thickness occupies 80% or more of an axial portion of the second inner tooth portion.

In addition, aspects of the present invention include any combination of the constituent elements described above and mutual replacement of the constituent elements or terms of the present invention among the methods, devices, systems, or the like.

According to the present invention, it is possible to provide a bending engagement type transmission device capable of suppressing excessive wear of a gear.

list of figures

• 1 FIG. 10 is a sectional diagram showing a bending engagement type transmission device according to an embodiment. FIG.
• 2 Fig. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear according to 1 ,
• 3A and 3B are graphical representations that show simulation results.
• 4 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a second embodiment. FIG.
• 5 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a third embodiment. FIG.
• 6 FIG. 10 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a fourth embodiment. FIG.
• 7 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a fifth embodiment. FIG.
• 8th FIG. 10 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a sixth embodiment. FIG.
• 9 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a seventh embodiment. FIG.
• 10 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to an eighth embodiment. FIG.
• 11 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a ninth embodiment. FIG.
• 12 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a tenth embodiment. FIG.
• 13 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to an eleventh embodiment. FIG.
• 14 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a twelfth embodiment. FIG.
• 15 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a modification example of the first embodiment. FIG.
• 16 FIG. 10 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the second embodiment. FIG.
• 17 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the third embodiment. FIG.
• 18 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the fourth embodiment. FIG.
• 19 FIG. 10 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a modification example of the fifth embodiment. FIG.
• 20 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to another modification example of the fifth embodiment. FIG.
• 21 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the sixth embodiment. FIG.
• 22 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a modification example of the seventh embodiment. FIG.
• 23 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the eighth embodiment. FIG.
• 24 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the ninth embodiment. FIG.
• 25 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a modification example of the tenth embodiment. FIG.
• 26 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear, and a second inner gear of a bending engagement type transmission device according to a modification example of the eleventh embodiment. FIG.
• 27 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to another modification example of the eleventh embodiment. FIG.
• 28 FIG. 12 is a diagram for explaining the shapes of an outer gear, a first inner gear and a second inner gear of a bending engagement type transmission device according to a modification example of the twelfth embodiment. FIG.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the same reference numerals are assigned to the same or equivalent constituent elements, elements and processes shown in each drawing, wherein overlapping descriptions suitably omitted. In addition, the dimensions of the elements in each drawing are appropriately enlarged and reduced to promote understanding. Moreover, in each drawing, a portion of the elements that are not important for explaining an embodiment is omitted, so that it is not shown.

In the first to sixth embodiments, an example focusing mainly on the shapes of the tooth surfaces of the gears will be described.

In the seventh to twelfth embodiments, examples mainly focusing on the outer diameters of the tooth portions of the outer gears or the inner diameters of the tooth portions of the inner gears will be described. The technical concepts of the first to sixth embodiments and the technical concepts of the seventh to twelfth embodiments may be used by combining as long as they do not contradict each other. Hereinafter, each embodiment will be described.

First Embodiment

1 is a sectional diagram illustrating a transmission device 100 of the bending engagement type according to a first embodiment. The transmission device 100 of the bending engagement type reduces an input rotation and outputs the reduced rotation. The transmission device 100 of the bending engagement type is a so-called flat-type bending engagement type transmission device, and includes a shaft generating unit 2 , an outer gear 4 that through the wave generation unit 2 bent and deformed, a first inner gear 6 that with the outer gear 4 meshes, a second inner gear 8th that is disposed so as to be in an axial direction with the first inner gear 6 is aligned (the first inner gear is adjacent) and with the outer gear 4 meshes, a housing 10 , a first rule element 12 , a second rule element 14 , a main camp 16 , a first bearing housing 18 and a second bearing housing 20 , The transmission device 100 of the bending engagement type is filled with a lubricant (eg, a grease). The lubricant lubricates the mating portions between the outer gear 4 and the first inner gear 6 and between the outer gear 4 and the second inner gear 8th , every warehouse and the like.

The wave generation unit 2 contains a wave generator wave 22 , a first wave generator bearing 21a that between the wave generator shaft 22 and a (first outer tooth portion 4a) of the outer gear 4 is arranged, and a second wave generator bearing 21b that between the wave generator shaft 22 and a (second outer tooth portion 4b) of the outer gear 4 is arranged. The first wave generator bearing 21a contains several first rolling elements 24a , a first holder 26a , which is the first multiple rolling elements 24a holds, and a first outer ring member 28a inside the outer gear 4 is fitted. The second wave generator bearing 21b contains several second rolling elements 24b , a second holder 26b that has the several second rolling elements 24b holds, and a second outer ring member 28b inside the outer gear 4 is fitted. The wave generator wave 22 is z. B. an input shaft is connected to a rotary drive source, such. As a motor, connected and is about a rotation axis R turned. A wave generator 22a whose cross-section orthogonal to the axis of rotation R is about elliptical, is with the wave generator wave 22 formed in one piece.

Each of the several first rolling elements 24a has an approximately columnar shape, wherein the plurality of first rolling elements 24a are provided at intervals in a circumferential direction in a state in which an axial direction of each of the plurality of first rolling elements 24a a direction is the direction of the axis of rotation R is about parallel. The first rolling elements 24a are through the first holder 26a Rollably held and roll on an outer peripheral surface 22b of the wave generator 22a , That is, an inner ring of the first shaft generator bearing 21a is with the outer peripheral surface 22b of the wave generator 22a one-piece configured. However, the present invention is not limited to this, wherein the inner ring may include a dedicated inner ring of the wave generator 22a is disconnected. The second rolling elements 24b are similar to the first rolling elements 24a configured. The several second rolling elements 24b are through the second holder 26b held rollable, which is arranged so that it is on the first holder 26a is aligned in the axial direction, and roll on the outer peripheral surface 22b of the wave generator 22a , That is, an inner ring of the second wave generator bearing 21b is with the outer peripheral surface 22b of the wave generator 22a one-piece configured. However, the present invention is not limited to this, wherein the inner ring may include a dedicated inner ring of the wave generator 22a is disconnected. The following are the first rolling elements 24a and the second rolling element 24b collectively as a "rolling element 24 " designated. In addition, the first holder 26a and the second holder 26b collectively as a "keeper 26 " designated.

The first outer ring element 28a surrounds the first plurality of rolling elements 24a , The first outer ring element 28a has elasticity and is generated by the wave generator 22a over the several first rolling elements 24a distracted elliptically. If the wave generator 22a (ie, the wave generator wave 22 ) is rotated, the first outer ring member 28a according to the shape of the wave generator 22a continuously bent and deformed. The second outer ring element 28b is to the first outer ring member 28a similarly configured. The second outer ring element 28b is from the first outer ring element 28a trained separately. In addition, the second outer ring member 28b in one piece with the first outer ring element 28a be educated. The following will be the first outer ring member 28a and the second outer ring member 28b together as an "outer ring element 28 " designated.

The outer gear 4 is an annular element with elasticity, wherein the wave generator 22a , the rolling element 24 and the outer ring member 28 in the outer gear 4 are fitted. The wave generator 22a , the rolling element 24 and the outer ring member 28 are in the outer gear 4 fitted, thus the outer gear 4 is distracted elliptically. If the wave generator 22a is turned, the outer gear becomes 4 according to the shape of the wave generator 22a continuously bent and deformed. The outer gear 4 contains the first outer tooth section 4a that is outside the first outer ring element 28a is positioned, the second outer tooth portion 4b that is outside the second outer ring element 28b is positioned, and a base material 4c , The first outer tooth section 4a and the second outer tooth portion 4b are on the base material 4c formed, which is a single base material, and have a same number of teeth.

The first inner gear 6 is a ring-shaped element with rigidities, wherein a first inner tooth portion 6a on an inner circumference of the first inner gear 6 is trained. The first inner tooth section 6a surrounds the first outer tooth section 4a of the elliptically deflected outer gear 4 and engages in a predetermined area (two areas) near a long axis of the wave generator 22a with the first outer tooth portion 4a each other. The number of teeth of the first inner tooth section 6a is larger than that of the first outer tooth portion 4a ,

The second inner gear 8th is disposed so as to be in the axial direction with the first inner gear 6 is aligned (the first inner gear 6 is adjacent). The second inner gear 8th is a cylindrical member with rigidities, with a second inner tooth portion 8a on an inner circumference of the second inner gear 8th is trained. The second inner tooth section 8a surrounds the second outer tooth portion 4b of the elliptically deflected outer gear 4 and grips in a predetermined area (two areas) in a direction of the long axis of the wave generator 22a with the second outer tooth portion 4b each other. The number of teeth of the second inner tooth section 8a is the same as that of the second outer tooth portion 4b , Accordingly, the second inner gear becomes 8th synchronous with the rotations of the second outer tooth section 4b and the outer gear 4 turned.

The first rule element 12 is a flat annular element and is between the outer gear 4 , the first outer ring element 28a and the first holder 26a and the first bearing housing 18 arranged. The second rule element 14 is a flat annular element and is between the outer gear 4 , the second outer ring member 28b and the second holder 26b and the second bearing housing 20 arranged. The first rule element 12 and the second rule element 14 regulate the axial movements of the outer gear 4 , the outer ring element 28 and the owner 26 ,

The housing 10 is an approximately cylindrical element and surrounds the second inner gear 8th , The first inner gear 8th is by a pin on the housing 10 attached so that it by a (not shown) bolt with the housing 10 is integrated. The main camp 16 is between the case 10 and the second inner gear 8th arranged. In the present embodiment, the main bearing 16 a cross roller bearing, where there are several rollers (rolling elements) 46 contains, which are provided at intervals in the circumferential direction. The multiple roles 46 roll on a rolling surface 8b of the second inner gear 8th and a rolling surface 10a of the housing 10 , That is, an outer peripheral side of the second inner gear 8th works as an inner ring of the main bearing 16 while an inner peripheral side of the housing 10 as an outer ring of the main bearing 16 is working. The housing 10 supports the second inner gear 8th about the main camp 16 in a relatively rotatable state. In addition, a type of main bearing 16 not particularly limited, wherein z. B. the main bearing can be a four-point contact ball bearings.

The first bearing housing 18 is an annular element and surrounds the wave generator shaft 22 , Similar is the second bearing housing 20 an annular element and surrounds the wave generator shaft 22 , The first bearing housing 18 and the second bearing housing 20 are arranged so that the outer gear 4 , the rolling element 24 , the holder 26 , the outer ring element 28 , the first rule element 12 and the second rule element 14 are arranged in the axial direction therebetween. The first bearing housing 18 is by a pin on the first inner gear 6 attached so that it by a bolt on the first inner gear 6 is attached. The second bearing housing 20 is by a pin on the second inner gear 8th attached so that it by a bolt on the second inner gear 8th is attached. A warehouse 30 is in the inner circumference of the first bearing housing 18 taken, a camp 32 is in the inner circumference of the second bearing housing 20 recorded and the wave generator wave 22 is about the camp 30 and the camp 32 through the first bearing housing 18 and the second bearing housing 20 rotatably supported.

Between the wave generator shaft 22 and the first bearing housing 18 is an oil seal 40 arranged between the first bearing housing 18 and the first inner gear 6 is an O-ring 34 arranged between the first inner gear 6 and the housing 10 is an O-ring 36 arranged between the housing 10 and the second inner gear 8th is an oil seal 42 arranged between the second inner gear 8th and the second bearing housing 20 is an O-ring 38 arranged and between the second bearing housing 20 and the wave generator shaft 22 is an oil seal 44 arranged. Accordingly, it is possible to prevent a lubricant in the transmission device 100 of the bending engagement type exits.

It becomes an operation of the transmission device 100 of the bending engagement type configured as described above. Here is a case where the number of teeth of the first outer tooth section 4a 100 is the number of teeth of the second outer tooth portion 4b 100 is the number of teeth of the first inner tooth section 6a 102 is and the number of teeth of the second inner tooth section 8a 100 is described as an example. In addition, a case where the second inner gear 8th and the second bearing housing 20 connected to a driven element are described as an example.

If the wave generator shaft 22 rotates in a state in which the first outer tooth portion 4a with the first inner tooth section 6a engages at two elliptical locations in the longitudinal direction, the engagement position moves between the first outer tooth portion 4a and the first inner tooth section 6a also in accordance with the rotation of the wave generator shaft 22 in the circumferential direction. The number of teeth of the first outer tooth section 4a and the number of teeth of the first inner tooth portion 6a are different from each other, and thus in this case the first outer tooth portion 4a with respect to the first inner tooth section 6a relatively turns. The first inner gear 6 and the first bearing housing 18 are fixed, thus being the first outer tooth portion 4a by an amount equivalent to the difference in the number of teeth. That is, the rotation of the wave generator shaft 22 is greatly reduced and becomes the first outer tooth portion 4a output. A speed reduction ratio is as follows. $$\begin{array}{l}\text{Speed reduction ratio}=(\text{Number of teeth of the first <figure-callout id="4a" label="outer Tooth portion" filenames="DE102018132806A1\_0007.png,DE102018132806A1\_0008.png" state="{{state}}">outer </figure-callout>}& \\ \text{Tooth portion}\text{4a}-\text{Number of teeth of the first <figure-callout id="6a" label="inner tooth section" filenames="DE102018132806A1\_0007.png,DE102018132806A1\_0008.png" state="{{state}}">inner tooth section</figure-callout>}\\ \text{6a})\text{/ Number of teeth of the first <figure-callout id="4a" label="outer tooth portion" filenames="DE102018132806A1\_0007.png,DE102018132806A1\_0008.png" state="{{state}}">outer tooth portion</figure-callout> 4a}\\ =\left(100-102\right)\text{/}100=-1/\mathrm{50th}\end{array}$$

The second outer tooth section 4b is with the first outer tooth section 4a formed in one piece, thus forming the second outer tooth portion 4b and the first outer tooth portion 4a rotate in one piece with each other. The number of teeth of the second outer tooth section 4b and the number of teeth of the second inner tooth portion 8a are equal to each other, consequently, therebetween no relative rotation is generated therebetween and the second outer tooth portion 4b and the second inner tooth portion 8a rotate in one piece with each other. Accordingly, the same rotation as the rotation of the first outer tooth portion 4a to the second inner tooth portion 8a output. As a result, it is possible to move from the second inner gear 8th extract the output by reducing the rotation of the wave generator shaft 22 to -1/50.

Continuing the configurations of the outer gear 4 , the first inner gear 6 and the second inner gear 8th described in more detail. 2 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th to 1 , 2 is a sectional diagram showing the outer gear 4 , the first inner gear 6 and the second inner gear 8th shows, which are cut by an imaginary cylinder, which by a pitch circle of the outer gear 4 passes. To promote understanding, shows 2 a state in which the first inner tooth portion 6a and the second inner tooth portion 8a slide in a circumferential direction so that they from the outer gear 4 are separated, showing a state in which the shapes of the tooth surfaces of the tooth portions are exaggerated. In 2 a horizontal axis is an axial position from a certain reference position. A vertical axis indicates a circumference dimension scale (a scale is 10 μm) for reference. Additionally is in 2 a level P1 an imaginary plane leading to the (in 2 not shown), and an imaginary plane passing through an axial center of an engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a passes. In the present embodiment, an axial length of the first inner tooth portion 6a shorter than an axial length of the first outer tooth portion 4a wherein the first inner tooth portion 6a over the entire area in the axial direction with the first outer tooth portion 4a interlocked. Accordingly, an axial length of the engagement portion between the first outer tooth portion 4a and the first inner tooth section 6a the same as the axial length of the first inner tooth section 6a , where the plane P1 through the axial center of the first inner tooth section 6a passes. In addition, a level P2 an imaginary plane orthogonal to the rotation axis R, and an imaginary plane passing through an axial center of an engagement portion between the second outer teeth portion 4a and the second inner tooth portion 8a passes. In the present embodiment, an axial length of the second inner tooth portion 8a shorter than an axial length of the second outer tooth portion 4b wherein the second inner tooth portion 8a over the entire area in the axial direction with the second outer tooth portion 4b comes together. Accordingly, an axial length of the engagement portion between the second outer tooth portion 4b and the second inner tooth portion 8a the same as the axial length of the second inner tooth portion 8a , where the plane P2 through the axial center of the second inner tooth section 8a passes.

The first outer tooth section 4a includes a first outer thickest tooth portion 4a7 having a thickest tooth thickness at a tooth height position, a first outer portion 4a8 decreasing tooth thickness having a tooth thickness from that of the first outer thickest tooth portion 4a7 axially outward (ie, in a direction that is from a center between the first outer tooth portion 4a and the second outer tooth portion 4b is separated), and a first inner section 4a9 decreasing tooth thickness having a tooth thickness from that of the first outer thickest tooth portion 4a7 axially inward (ie, in a direction close to the center between the first outer tooth portion 4a and the second outer tooth portion 4b) decreases, a few tooth height positions (ie, radial positions). Preferably, the first outer tooth portion includes 4a the first outer thickest tooth portion 4a7 , the first outer section 4a8 with decreasing tooth thickness and the first inner section 4a9 with decreasing tooth thickness at the tooth height positions, with the first inner tooth portion 6a intermesh, typically at the center positions in a tooth height direction. In the present embodiment, the first outer tooth portion includes 4a the first outer thickest tooth portion 4a7 , the first outer section 4a8 with decreasing tooth thickness and the first inner section 4a9 with decreasing tooth thickness at all tooth height positions from a tooth head position to a tooth root position.

The first outer tooth section 4a has a shape with respect to a center surface S ₄ is symmetrical in the tooth thickness. Here, the "center surface in the tooth thickness" indicates a surface including the rotation axis R and a surface passing through a center of a thickest portion having a thickest tooth thickness in the tooth thickness direction. The first outer tooth section 4a is formed so that the distances between the two tooth surfaces of the first outer tooth portion 4a and the center area S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 in the first outer section 4a8 with decreasing tooth thickness decrease axially outward and the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 in the first inner section 4a9 Slacken axially with decreasing tooth thickness.

The first outer thickest tooth section 4a7 is out of the plane P1 positioned, ie, is outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a positioned, in other words, is outside the axial center of the first inner tooth portion 6a positioned. In addition, in the present embodiment, the first outer thickest tooth portion 4a7 outside the axial center of the first outer tooth section 4a positioned. The first outer section 4a8 with decreasing tooth thickness is like that configured its tooth thickness from the first outer thickest tooth portion 4a7 arched axially decreases towards the outside, ie, that the distances between the two tooth surfaces of the first outer tooth portion 4a and the center area S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 in the first outer section 4a8 Curved with decreasing tooth thickness axially decrease towards the outside. The first inner section 4a9 with decreasing tooth thickness is configured so that its tooth thickness is from the first outer thickest tooth portion 4a7 curved axially inwardly decreases, ie, that the distances between the two tooth surfaces of the first outer tooth portion 4a and the center area S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 in the first inner section 4a9 Curved with decreasing tooth thickness axially inward decrease. In addition, the first inner section 4a9 configured with decreasing tooth thickness so that it extends to a portion of a gap 7 between the first inner gear 6 and the second inner gear 8th corresponds (faces). Moreover, the first outer section 4a8 with decreasing tooth thickness and the first inner section 4a9 configured with decreasing tooth thickness such that a decrease ratio (= decrease amount of the tooth thickness / axial movement amount) of the tooth thickness in the axial direction increases when the first outer portion 4a8 with decreasing tooth thickness and the first inner section 4a9 decreasing tooth thickness from the first outer thickest tooth portion 4a7 away. In other words, in the first outer section 4a8 with decreasing tooth thickness and the first inner section 4a9 with decreasing tooth thickness are the two tooth surfaces of the first outer tooth portion 4a is configured such that the decreasing ratios (= decrease amount of the distance between the tooth surface and the center surface in the tooth thickness / axial movement amount) of the distances between the two tooth surfaces of the first outer tooth portion 4a and the center area S ₄ increase in the tooth thickness in the axial direction when the two tooth surfaces of the first outer tooth portion 4a from the first outer thickest tooth portion 4a7 away.

The second outer tooth section 4b includes a second outer thickest tooth portion 4B7 having a thickest tooth thickness at a tooth height position, a second outer portion 4B8 decreasing tooth thickness having a tooth thickness from that of the second outer thickest tooth portion 4B7 decreases axially outwards, and a second inner portion 4b9 decreasing tooth thickness having a tooth thickness from that of the second outer thickest tooth portion 4B7 axially decreasing inwards, at some tooth height positions. Preferably, the second outer tooth portion includes 4b the second outer thickest tooth portion 4B7 , the second outer section 4B8 with decreasing tooth thickness and the second inner section 4b9 with decreasing tooth thickness at the tooth height positions, with the second inner tooth portion 8a intermesh, typically at the center positions in a tooth height direction. In the present embodiment, the second outer tooth portion includes 4b the second outer thickest tooth portion 4B7 , the second outer section 4B8 with decreasing tooth thickness and the second inner section 4b9 with decreasing tooth thickness at all tooth height positions from a tooth head position to a tooth root position.

The second outer tooth section 4b has a shape with respect to the center surface S ₄ is symmetrical in the tooth thickness. That is, in the second outer tooth portion 4b the two tooth surfaces are formed so that the distances between the two tooth surfaces of the second outer tooth portion 4b and the center area S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 in the second outer section 4B8 decrease axially outward with decreasing tooth thickness, and the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 in the second inner section 4b9 Slacken axially with decreasing tooth thickness.

The second outer thickest tooth section 4B7 is out of the plane P2 positioned, ie, is outside an axial center of an engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a positioned, in other words, is outside an axial center of the second inner tooth portion 8a positioned. In addition, in the present embodiment, the second outer thickest tooth portion 4B7 outside the axial center of the second outer tooth section 4b positioned. The second outer section 4B8 with decreasing tooth thickness is configured so that its tooth thickness is from the second outer thickest tooth portion 4B7 curved axially decreases towards the outside. That is, in the second outer section 4B8 with decreasing tooth thickness are the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 curved axially decrease to the outside. The second inner section 4b9 with decreasing tooth thickness is configured so that its tooth thickness is from the second outer thickest tooth portion 4B7 arched axially decreases inwards. That is, in the second inner section 4b9 with decreasing tooth thickness are the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 curved axially inward decrease. In addition, the second inner section 4b9 configured with decreasing tooth thickness so that it extends to a portion of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Moreover, the second outer section 4B8 with decreasing Tooth thickness and the second inner section 4b9 configured with decreasing tooth thickness such that a decrease ratio of the tooth thickness in the axial direction increases when the second outer portion 4B8 with decreasing tooth thickness and the second inner section 4b9 decreasing tooth thickness from the second outer thickest tooth portion 4B7 away. In other words, in the second outer section 4B8 with decreasing tooth thickness and the second inner portion 4b9 with decreasing tooth thickness are the two tooth surfaces of the second outer tooth portion 4b configured so that the decrease ratios (= decrease amount of the distance between the tooth surface and the center surface S ₄ in the tooth thickness / axial amount of movement) of the distances between the two tooth surfaces and the center surface S ₄ increase in tooth thickness when the two tooth surfaces of the second outer tooth portion 4b from the second outer thickest tooth portion 4B7 away. The decrease ratio of the tooth thickness in the axial direction of the second outer portion 4B8 with decreasing tooth thickness is larger than the decrease ratio of the tooth thickness in the axial direction of the first outer portion 4a8 with decreasing tooth thickness.

In addition, in each decreasing section of the first outer section 4a8 with decreasing tooth thickness, the first inner section 4a9 with decreasing tooth thickness, the second outer portion 4B8 with decreasing tooth thickness and the second inner portion 4b9 With decreasing tooth thickness, each of the two tooth surfaces is configured so that the decrease ratio of the distance between each tooth surface and the center surface S ₄ in the tooth thickness in the axial direction satisfies the following expression. $$\begin{array}{l}\text{loss ratio}=\text{decrement}\left(\text{mm}\right)\text{the distance between the}\\ \text{Tooth surface and the center tooth thickness / axial movement amount}\left(\text{mm}\right)\le 0.05\end{array}$$

Here, in a case of chamfering, generally, the decrease ratio of the distance between the tooth surface and the center surface is satisfied S4 in the tooth thickness in the axial direction, the following expression $$\begin{array}{l}\text{decrement}\left(\text{mm}\right)\text{the distance between the tooth surface and the <figure-callout id="4" label="center surface S" filenames="DE102018132806A1\_0013.png,DE102018132806A1\_0018.png" state="{{state}}">center surface </figure-callout>}& \\ {\text{S}}_{}{}_{\text{4}}\text{in the tooth thickness by the taper / axial movement amount}\left(\text{mm}\right)\ge 0.5\end{array}$$

Accordingly, the orders of magnitude of each section with decreasing tooth thickness and bevel are different from each other and clearly different from each other.

The first inner tooth section 6a is symmetrical about a center area (not shown) in the tooth thickness and is configured so that the tooth thickness in the axial direction is substantially constant. Similar is the second inner tooth section 8a to a center area (not shown) in the tooth thickness symmetrical and configured so that the tooth thickness in the axial direction is substantially constant.

According to the transmission device described above 100 The bending engagement type of the present embodiment is the first outer tooth portion 4a configured so that the tooth thickness of the first outer thickest tooth portion 4a7 axially outwardly and inwardly decreases, and is the second outer tooth portion 4b configured so that the tooth thickness of the second outer thickest tooth portion 4B7 decreases axially outwards and inwards. Accordingly, it is possible to have one at a tooth width end (a position corresponding to an axial end portion of an inner tooth) of the first outer tooth portion 4a and the second outer tooth portion 4b To reduce generated unilateral load, and it is possible to reduce excessive wear of the gear.

In addition, according to the transmission device 100 bending engagement type of the present embodiment, each outer thickest tooth portion of the outer gear 4 positioned outside the axial center of the engagement region between the outer tooth portion and the inner tooth portion. Accordingly, in comparison with a case where each outer thickest tooth portion is positioned in the axial center of the engagement portion or within the axial center thereof, it is possible to further reduce the single-sided load.

Moreover, according to the transmission device 100 of the bending engagement type of the present embodiment, each of the first inner portion 4a9 with decreasing tooth thickness and the second inner portion 4b9 configured with decreasing tooth thickness so that it extends to the portion of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the external gear that shifts with respect to the internal gear in the axial direction.

The inventors of the present invention conducted a simulation to confirm the effects. 3A FIG. 16 shows the simulation results of a bending engagement type transmission device according to a comparative example during FIG 3B the simulation results of the transmission device 100 of the bending engagement type according to the present embodiment. In the 3A and 3B a horizontal axis indicates an axial position of the outer gear 4 while a vertical axis one at the axial position on the outer gear 4 indicates exerted radial load. In addition, in the bending engagement type transmission device according to the comparative example, each of the first outer teeth portion, the second outer teeth portion, the first inner tooth portion, and the second inner tooth portion is configured so that the tooth thickness in the axial direction is substantially constant.

As in 3A 4, it is recognized in the bending-engagement type transmission device according to the comparative example that the radial load on the tooth width end (a portion surrounded by a broken line) of the outer gear is relatively large and the partial contact occurs.

As in 3B Meanwhile, in the transmission device, meanwhile, is shown 100 of the bending engagement type according to the present embodiment recognizes that the radial load on the tooth width end of the outer gear is relatively small and the part contact decreases. In addition, takes in the transmission device 100 of the bending engagement type according to the present embodiment not only decreases the radial load acting on the tooth width end, but also takes on the outer gear 4 acting radial load as a whole. Therefore, according to the present embodiment, it is recognized that the excessive wear of the gear can decrease.

Second Embodiment

4 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a second embodiment. 4 corresponds to 2 the first embodiment. As main differences from the first embodiment, in the second embodiment, a tooth thickness of the outer tooth portion in the axial direction is not changed, but a tooth thickness of the inner tooth portion is changed in the axial direction. The following are the differences between the transmission device 100 of the bending engagement type according to the first embodiment and the transmission device of the bending engagement type according to the second embodiment are mainly described.

The first outer tooth section 4a is to the (in 4 not shown) center surface S ₄ is symmetrical in tooth thickness and is configured so that the tooth thickness is substantially constant in the axial direction. Similarly, the second outer tooth portion 4b to the center area S ₄ in the tooth thickness symmetrical, being configured so that the tooth thickness in the axial direction is substantially constant. Both the first outer tooth section 4a as well as the second outer tooth portion 4b are configured to extend to a section of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent.

The first inner tooth section 6a includes a first inner thickest tooth portion 6a7 which has a thickest tooth thickness in the first inner tooth section 6a has a first outer portion 6A8 decreasing tooth thickness having a tooth thickness from that of the first inner thickest tooth portion 6a7 axially outwardly decreases, and a first inner portion 6A9 decreasing tooth thickness having a tooth thickness from that of the first inner thickest tooth portion 6a7 decreases axially inwards.

The first inner thickest tooth section 6a7 is out of the plane P1 positioned, ie, is outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a positioned, in other words, is outside the axial center of the first inner tooth portion 6a (which is a shorter axial length from the first outer tooth portion 4a and the first inner tooth section 6a has positioned). The first outer section 6A8 with decreasing tooth thickness is configured so that its tooth thickness is from the first inner thickest tooth portion 6a7 curved axially decreases towards the outside. That is, in the first outer section 6A8 with decreasing tooth thickness are the two tooth surfaces of the first inner tooth portion 6a configured so that the distances between the two tooth surfaces and a center surface S ₆ in the tooth thickness of the first inner thickest tooth portion 6a7 curved axially decrease to the outside. The first inner section 6A9 with decreasing tooth thickness is configured so that its tooth thickness is from the first inner thickest tooth portion 6a7 arched axially decreases inwards. That is, in the first inner section 6A9 with decreasing tooth thickness are the two tooth surfaces of the first inner tooth portion 6a configured so that the distances between the two Tooth surfaces and the center surface S ₆ in the tooth thickness of the first inner thickest tooth portion 6a7 curved axially inward decrease. In addition, the first inner section 6A9 configured with decreasing tooth thickness such that a decrease ratio (= decrease amount of the tooth thickness / axial amount of movement) of the tooth thickness in the axial direction increases when the first inner portion 6A9 decreasing tooth thickness from the first inner thickest tooth portion 6a7 is disconnected. In other words, in the first inner section 6A9 with decreasing tooth thickness are the two tooth surfaces of the first inner tooth portion 6a is configured such that the decrease ratios (= decrease amount of the distance between the tooth surface and the center surface in the tooth thickness / axial movement amount) of the distances between the two tooth surfaces of the first inner tooth portion 6a and the center area S ₆ increase in the tooth thickness in the axial direction when the two tooth surfaces of the first inner tooth portion 6a from the first inner thickest tooth portion 6a7 away.

The second inner tooth section 8a includes a second inner thickest tooth portion 8A7 , which has a thickest tooth thickness in the second inner tooth portion 8a has a second outer portion 8A8 decreasing tooth thickness having a tooth thickness from that of the second inner thickest tooth portion 8A7 decreases axially outwards, and a second inner portion 8A9 decreasing tooth thickness having a tooth thickness from that of the second inner thickest tooth portion 8A7 decreases axially inwards.

The second inner thickest tooth section 8A7 is out of the plane P2 positioned, ie, is outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a positioned, in other words, is outside the axial center of the second inner tooth portion 8a (Which is the shorter axial length of the second outer tooth portion 4b and the second inner tooth portion 8a has positioned). The second outer section 8A8 with decreasing tooth thickness is configured so that its tooth thickness is from the second inner thickest tooth portion 8A7 curved axially decreases towards the outside. That is, in the second outer section 8A8 with decreasing tooth thickness are the two tooth surfaces of the second inner tooth portion 8a configured so that the distances between the two tooth surfaces and a center surface S ₈ in the tooth thickness of the second inner thickest tooth portion 8A7 curved axially decrease to the outside. The second inner section 8A9 with decreasing tooth thickness is configured so that its tooth thickness is from the second inner thickest tooth portion 8A7 arched axially decreases inwards. That is, in the second inner section 8A9 with decreasing tooth thickness are the two tooth surfaces of the second inner tooth portion 8a configured so that the distances between the two tooth surfaces and the center surface S ₈ in the tooth thickness of the second inner thickest tooth portion 8A7 curved axially inward decrease. In addition, the second inner section 8A9 configured with decreasing tooth thickness such that a decrease ratio of the tooth thickness in the axial direction increases when the second inner portion 8A9 decreasing tooth thickness from the second inner thickest tooth portion 8A7 is disconnected. In other words, in the second inner section 8A9 with decreasing tooth thickness are the two tooth surfaces of the second inner tooth portion 8a configured so that the decreasing ratios of the distances between the two tooth surfaces of the second inner tooth portion 8a and the center area S ₈ increase in the tooth thickness in the axial direction when the two tooth surfaces of the second inner tooth portion 8a from the second inner thickest tooth portion 8A7 away.

In addition, in each decreasing section of the first outer section 6A8 with decreasing tooth thickness, the first inner section 6A9 with decreasing tooth thickness, the second outer portion 8A8 with decreasing tooth thickness and the second inner portion 8A9 With decreasing tooth thickness, each of the two tooth surfaces is configured so that the decrease ratio of the distance between each tooth surface and the center surface in the tooth thickness in the axial direction satisfies Expression 1 described above.

According to the above-described bending engagement type transmission device of the present embodiment, the first inner tooth portion 6a configured so that the tooth thickness of the first inner thickest tooth portion 6a7 axially inwardly and axially outwardly decreases while the second inner tooth portion 8a is configured such that the tooth thickness of the second inner thickest tooth portion 8A7 axially outwardly and axially inwardly decreases. Accordingly, it is possible that at the tooth width end of the first outer tooth portion 4a and the second outer tooth portion 4b To reduce generated unilateral load, and it is possible to reduce the excessive wear of the gear.

In addition, according to the bending engagement type transmission device of the present embodiment, both in the first inner gear 6 as well as in the second inner gear 8th the inner thickest tooth portion is positioned outside the axial center of the engagement portion between the outer tooth portion and the inner tooth portion. Accordingly, it is compared to a case in which the inner thickest tooth portion is positioned in the axial center of the engaging portion or within the axial center, it is possible to further reduce the unilateral load.

Moreover, according to the bending engagement type transmission device of the present embodiment, both the first outer teeth portion are 4a as well as the second outer tooth portion 4b configured to extend to the section that is the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the external gear that shifts with respect to the internal gear in the axial direction.

Third Embodiment

5 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a third embodiment. 5 corresponds to 2 the first embodiment. As the main differences from the first embodiment, in the third embodiment, both the outer tooth portion and the inner tooth portion have portions whose tooth thicknesses change in the axial direction. The following are the differences between the transmission device 100 of the bending engagement type according to the first embodiment and the transmission apparatus of the bending engagement type according to the third embodiment are mainly described.

The first outer tooth section 4a contains the first outer thickest tooth section 4a7 and the first outer section 4a8 decreasing tooth thickness similar to that of the first embodiment. That is, the first outer tooth portion 4a does not have the first inner portion of decreasing tooth thickness, with the first outer thickest tooth portion 4a7 instead from a position outside the plane P1 that is, a position outside the axial center of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the first inner tooth portion 6a to one with the second outer tooth portion 4b that is, a section that is the gap 7 between the first inner gear 6 and the second inner gear 8th corresponds, connected position extends axially. The first outer tooth section 4a may also include the first inner section of decreasing tooth thickness.

The second outer tooth section 4b contains the second outer thickest tooth portion 4B7 and the second outer section 4B8 decreasing tooth thickness similar to that of the first embodiment. That is, the second outer tooth portion 4b does not have the second inner portion of decreasing tooth thickness, with the second outer thickest tooth portion 4B7 instead from a position outside the plane P2 that is, a position outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the second inner tooth portion 8a to one with the first outer tooth portion 4a that is, a section that is the gap 7 between the first inner gear 6 and the second inner gear 8th corresponds, connected position extends axially. The second outer tooth section 4b may also include the second inner section with decreasing tooth thickness.

The first inner tooth section 6a contains the first inner thickest tooth section 6a7 and the first inner section 6A9 decreasing tooth thickness similar to that of the second embodiment. That is, the first inner tooth portion 6a does not have the first outer portion of decreasing tooth thickness, with the first inner thickest tooth portion 6a7 instead from a position outside the plane P1 that is, a position outside the axial center of the first outer tooth portion 4a extends axially outwards. The first inner tooth section 6a may also include the first outer section with decreasing tooth thickness.

The second inner tooth section 8a contains the second inner thickest tooth section 8A7 and a second inner section 8A9 decreasing tooth thickness similar to that of the second embodiment. That is, the second inner tooth portion 8a does not have the second outer portion with decreasing tooth thickness, with the second inner thickest tooth portion 8A7 instead from a position outside the plane P2 that is, a position outside the axial center of the second outer tooth portion 4b , extends axially outwards. The second inner tooth section 8a may also include the second outer portion with decreasing tooth thickness.

An axial position of a boundary between the first outer thickest tooth portion 4a7 and the first outer section 4a8 with decreasing tooth thickness is substantially in an axial position a boundary between the first inner thickest tooth portion 6a7 and the first inner section 6A9 coincide with decreasing tooth thickness. Additionally, the boundaries are out of the plane P1 that is, outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the first inner tooth section 6a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the first outer tooth portion 4a positioned.

Similarly, an axial position coincides with a boundary between the second outer thickest tooth portion 4B7 and the second outer portion 4B8 decreasing tooth thickness substantially at an axial position of a boundary between the second inner thickest tooth portion 8A7 and the second inner section 8A9 coincide with decreasing tooth thickness. Additionally, the boundaries are out of the plane P2 that is, outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the second inner tooth section 8a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the second outer tooth portion 4b positioned.

According to the bending engagement type transmission device of the present embodiment, the outer tooth portion similar to the first embodiment includes the outer decreasing portion. Meanwhile, unlike the first embodiment, the outer tooth portion does not include the inner decreasing portion. The inner tooth portion, however, and instead includes the inner portion with decreasing tooth thickness. Therefore, according to the bending-engagement-type transmission device of the present embodiment, the functional effects obtained by the transmission device are obtained 100 of the bending engagement type according to the first embodiment are similar in function effects.

Fourth Embodiment

6 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a fourth embodiment. 6 corresponds to 2 the first embodiment. As the main differences from the first embodiment, in the fourth embodiment, both the outer tooth portion and the inner tooth portion have portions whose tooth thicknesses change in the axial direction. The following are the differences between the transmission device 100 of the bending engagement type according to the first embodiment and the transmission apparatus of the bending engagement type according to the fourth embodiment are mainly described.

The first outer tooth section 4a contains the first outer thickest tooth section 4a7 and the first inner section 4a9 decreasing tooth thickness similar to that of the first embodiment. That is, the first outer tooth portion 4a does not have the first outer portion of decreasing tooth thickness, with instead the first outer thickest tooth portion 4a7 from a position outside the plane P1 that is, a position outside the axial center of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the first inner tooth portion 6a , extends axially outwards. The first outer tooth section 4a may also include the first outer section with decreasing tooth thickness.

The second outer tooth section 4b contains the second outer thickest tooth portion 4B7 and the second inner section 4b9 decreasing tooth thickness similar to that of the first embodiment. That is, the second outer tooth portion 4b does not have the second outer portion with decreasing tooth thickness, with instead the second outer thickest tooth portion 4B7 from a position outside the plane P2 that is, a position outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the second inner tooth portion 8a , extends axially outwards. The second outer tooth section 4b may also include the second outer portion with decreasing tooth thickness.

The first inner tooth section 6a contains the first inner thickest tooth section 6a7 and the first outer section 6A8 decreasing tooth thickness similar to that of the second embodiment. That is, the first inner tooth portion 6a does not have the first inner portion of decreasing tooth thickness, with instead the first inner thickest tooth portion 6a7 from a position outside the plane P1 that is, a portion outside the axial center of the engagement portion between the first outer tooth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the first inner tooth section 6a , extends axially inwards. The first inner tooth section 6a may also include the first inner section of decreasing tooth thickness.

The second inner tooth section 8a contains the second inner thickest tooth section 8A7 and the second outer section 8A8 decreasing tooth thickness similar to that of the second embodiment. That is, the second inner tooth portion 8a does not have the second inner portion of decreasing tooth thickness, with instead the second inner thickest tooth portion 8A7 from a position outside the plane P2 that is, a portion outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the second inner tooth portion 8a , extends axially inwards. The second inner tooth section 8th may also include the second inner section with decreasing tooth thickness.

An axial position of a boundary between the first outer thickest tooth portion 4a7 and the first inner section 4a9 with decreasing tooth thickness substantially coincides with an axial position of a boundary between the first inner thickest tooth portion 6a7 and the first outer section 6A8 coincide with decreasing tooth thickness. Additionally, the boundaries are out of the plane P1 that is, outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the first inner tooth section 6a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the first outer tooth portion 4a positioned.

Similarly, an axial position coincides with a boundary between the second outer thickest tooth portion 4B7 and the second inner section 4b9 decreasing tooth thickness substantially at an axial position of a boundary between the second inner thickest tooth portion 8A7 and the second outer portion 8A8 coincide with decreasing tooth thickness. Additionally, the boundaries are out of the plane P2 that is, outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the second inner tooth section 8a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the second outer tooth portion 4b positioned.

According to the bending engagement type transmission device of the present embodiment, the outer tooth portion similar to the first embodiment includes the inner portion with decreasing tooth thickness. Meanwhile, unlike the first embodiment, the outer tooth portion does not include the outer portion with decreasing tooth thickness. Instead, however, the inner tooth portion includes the outer portion with decreasing tooth thickness. Therefore, according to the bending-engagement-type transmission device of the present embodiment, the functional effects obtained by the transmission device are obtained 100 of the bending engagement type according to the first embodiment are similar in function effects.

Fifth Embodiment

7 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a fifth embodiment. 7 corresponds to 2 the first embodiment. As the main differences from the first embodiment, in the fifth embodiment, only the tooth thickness of the second outer teeth portion becomes 4b changed in the axial direction. The following are the differences between the transmission device 100 of the bending engagement type according to the first embodiment and the transmission apparatus of the bending engagement type according to the fifth embodiment are mainly described.

The first outer tooth section 4a has the number of teeth, that of the first inner tooth portion 6a is different. In addition, the first outer tooth portion 4a configured to point to the center area S ₄ in the tooth thickness is symmetrical, that it has a tooth thickness which is substantially constant in the axial direction, and that it has the same tooth thickness as a minimum tooth thickness of the second outer tooth portion 4b having.

The second outer tooth section 4b that has the same number of teeth as the second inner tooth section 8a includes the second outer thickest tooth portion 4B7 and the second inner section 4b9 with decreasing tooth thickness. That is, the second outer tooth portion 4b does not contain the second outer section with decreasing tooth thickness. The second outer thickest tooth section 4B7 is positioned at an axially outer end portion. The second inner section 4b9 with decreasing tooth thickness occupies 80% or more (about 100% in the example shown) of an axial portion of the second outer tooth portion 4b , The second inner section 4b9 with decreasing tooth thickness is configured so that the tooth thickness of the second outer thickest tooth portion 4B7 axially inwardly decreases continuously, the tooth thickness decreases specially curved. That is, in the second inner section 4b9 with decreasing tooth thickness are the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 decrease continuously axially inwards, with the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness specially curved decrease.

The first inner tooth section 6a is to the (in 7 not shown) center surface S ₆ is symmetrical in tooth thickness and is configured so that the tooth thickness is substantially constant in the axial direction. Similar is the second inner tooth section 8a to the (in 7 not shown) center surface S ₈ in the tooth thickness symmetrical, being configured so that the tooth thickness in the axial direction is substantially constant.

According to the bending engagement type transmission device of the present embodiment, the second outer teeth portion 4b that has the same number of teeth as the second inner tooth section 8a ie, the second outer tooth portion 4b , which is a driven-side gear, the tooth thickness, that of the second outer thickest tooth portion 4B7 decreases axially inwardly, with the decreasing portion (ie, the second inner portion 4b9 with decreasing tooth thickness) 80% or more of the axial portion of the second outer tooth portion 4b busy. Accordingly, it is possible that at the tooth width end of the second outer tooth portion 4b That is, the driven side outer tooth portion on which a load is easily exerted to reduce generated unilateral load, and it is possible to reduce excessive wear of the gear.

In addition, according to the bending engagement type transmission device of the present embodiment, both the first outer teeth portion 4a as well as the second outer tooth portion 4b (In particular the second inner section 4b9 with decreasing tooth thickness) configured to extend to the portion that is the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the external gear that shifts with respect to the internal gear in the axial direction.

Sixth Embodiment

8th Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a sixth embodiment. 8th corresponds to 4 the second embodiment. As the main differences from the second embodiment, in the sixth embodiment, only the tooth thickness of the second inner teeth portion becomes 8a changed in the axial direction. Hereinafter, the differences between the bending engagement type transmission device according to the second embodiment and the bending engagement type transmission device according to the sixth embodiment will be mainly described.

The first outer tooth section 4a is to the (in 8th not shown) center surface S ₄ is symmetrical in tooth thickness and is configured so that the tooth thickness is substantially constant in the axial direction. Similarly, the second outer tooth portion 4b to the center area S ₄ in the tooth thickness symmetrical, being configured so that the tooth thickness in the axial direction is substantially constant.

The first inner tooth section 6a has the number of teeth, that of the first outer tooth portion 4a is different. In addition, the first inner tooth section 6a configured to point to the center area S ₈ is symmetrical in the tooth thickness, has a tooth thickness that is substantially constant in the axial direction, and the same tooth thickness as a minimum tooth thickness of the second inner tooth portion 8a having.

The second inner tooth section 8a that has the same number of teeth as the second outer tooth section 4b includes the second inner thickest tooth portion 8A7 and the second inner section 8A9 with decreasing tooth thickness. That is, the second inner tooth portion 8a does not contain the second outer section with decreasing tooth thickness. The second inner thickest tooth section 8A7 is positioned at an axially outer end portion. The second inner section 8A9 with decreasing tooth thickness occupies 80% or more (about 100% in the example shown) of the axial portion of the second inner tooth portion 8a , The second inner section 8A9 with decreasing tooth thickness is configured so that the tooth thickness of the second inner thickest tooth portion 8A7 axially decreasing continuously inward, the tooth thickness decreases with a special arch. That is, in the second inner section 8A9 with decreasing tooth thickness are the two tooth surfaces of the second inner tooth portion 8a configured so that the distances between the two tooth surfaces and the center surface S ₈ in the tooth thickness of the second inner thickest tooth portion 8A7 decrease continuously axially inwards, in particular the distances between the two tooth surfaces and the center surface S ₈ Dented in the tooth thickness decrease.

According to the bending engagement type transmission device of the present embodiment, the functional effects similar to the operational effects exerted by the bending engagement type transmission device according to the fifth embodiment are obtained.

(Seventh Embodiment)

9 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a seventh embodiment. In 9 are a tooth tip of the first outer tooth section 4a of the outer gear 4 , a tooth tip of the second outer tooth section 4b , a tooth tip of the first inner tooth section 6a of the first inner gear 6 and a tooth tip of the second inner tooth portion 8a of the second inner gear 8th when viewed in a circumferential direction. To promote understanding, are in 9 the tooth tip of the first inner tooth section 6a and the tooth tip of the second inner tooth portion 8a shown pushed radially outwards so that they are from the outer gear 4 are separated. In 9 a horizontal axis is the position in the axial direction from a predetermined reference position. In a vertical axis is shown for reference a radial dimension scale (a scale is 10 microns). Additionally is in 9 a midline C1 one to the (in 9 not shown) rotation axis R orthogonal line, indicating a line passing through the axial center of the engagement portion between the first outer tooth portion 4a and the first inner tooth section 6a passes. In the present embodiment, the axial length of the first inner tooth portion 6a shorter than the axial length of the first outer tooth portion 4a wherein the first inner tooth portion 6a in the entire region of the axial direction with the first outer tooth portion 4a comes together. Accordingly, an axial length of an engagement portion between the first outer tooth portion 4a and the first inner tooth section 6a the same as the axial length of the first inner tooth section 6a , where the midline C1 through the axial center of the tooth tip of the first inner tooth section 6a passes. In addition, there is a center line C2 a line orthogonal to the rotation axis R, indicating a line passing through the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a passes. In the present embodiment, the axial length of the second inner tooth portion 8a shorter than the axial length of the second outer tooth portion 4b wherein the second inner tooth portion 8a in the entire area in the axial direction with the second outer tooth portion 4b comes together. Accordingly, the axial length of an engagement portion between the second outer tooth portion 4b and the second inner tooth portion 8a the same as the axial length of the second inner tooth portion 8a , where the midline C2 through the axial center of the tooth tip of the second inner tooth section 8a passes.

The tooth tip of the first outer tooth section 4a includes a first outermost diameter section 4a1 in the first outer tooth section 4a has a maximum outer diameter, a first outer portion 4a2 decreasing outer diameter having an outer diameter of the first outermost diameter portion 4a1 axially outward (ie, in a direction away from a center between the first outer tooth portion 4a and the second outer tooth portion 4b) decreases, and a first inner section 4a3 decreasing outer diameter having an outer diameter of the first outermost diameter portion 4a1 axially inward (ie, in a direction close to the center between the first outer tooth portion 4a and the second outer tooth portion 4b) decreases.

The first outermost diameter section 4a1 is outside the center line C1 that is, outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the tooth tip of the first inner tooth section 6a positioned. In addition, in the present embodiment, the first outermost diameter portion 4a1 outside the axial center of the tooth tip of the first outer tooth portion 4a positioned. The first outer section 4a2 with decreasing outer diameter is configured so that its outer diameter from the first outermost diameter portion 4a1 curved axially decreases towards the outside. The first inner section 4a3 with decreasing outer diameter is configured so that its outer diameter from the first outermost diameter portion 4a1 arched axially decreases inwards. additionally is the first inner section 4a3 configured with decreasing outer diameter so that it extends to a portion of a radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th corresponds (ie, faces). In addition, both are the first outer section 4a2 with decreasing outer diameter as well as the first inner portion 4a3 configured with decreasing outer diameter so that the decrease ratios (= decrease of the outer diameter / axial movement amount) of the outer diameter increase in the axial direction, like the first outer portion 4a2 with decreasing outer diameter and the first inner section 4a3 decreasing in outer diameter from the first outermost diameter portion 4a1 away.

The tooth tip of the second outer tooth section 4b includes a second outermost diameter section 4b1 in the second outer tooth section 4b has a maximum outer diameter, a second outer portion 4b2 decreasing outer diameter having an outer diameter of the second outermost diameter portion 4b1 decreases axially outwards, and a second inner portion 4b3 decreasing outer diameter having an outer diameter of the second outermost diameter portion 4b1 decreases axially inwards.

The second outermost diameter section 4b1 is outside the center line C2 that is, outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the tooth tip of the second inner tooth section 8a positioned. In addition, in the present embodiment, the second outermost diameter portion 4b1 outside the axial center of the tooth tip of the second outer tooth portion 4b positioned. The second outer section 4b2 with decreasing outer diameter is configured so that its outer diameter from the second outermost diameter portion 4b1 curved axially decreases towards the outside. The second inner section 4b3 with decreasing outer diameter is configured so that its outer diameter from the second outermost diameter portion 4b1 arched axially decreases inwards. In addition, the second inner section 4b3 configured with decreasing outer diameter so that it extends to a portion of the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. In addition, both the second outer section 4b2 with decreasing outer diameter as well as the second inner portion 4b3 configured with decreasing outer diameter so that the decrease ratios of the outer diameter increase in the axial direction, when the second outer portion 4b2 with decreasing outer diameter and the second inner portion 4b3 decreasing in outer diameter from the second outermost diameter portion 4b1 away. The second outer section 4b2 with decreasing outer diameter and the first outer portion 4a2 with decreasing outer diameter are configured so that the decrease ratio of the outer diameter of the second outer portion 4b2 with decreasing outer diameter in the axial direction larger than that of the first outer portion 4a2 with decreasing outer diameter in the axial direction.

Moreover, each is the first outer section 4a2 with decreasing outer diameter, the first inner portion 4a3 with decreasing outer diameter, the second outer portion 4b2 with decreasing outer diameter and the second inner portion 4b3 configured with decreasing outer diameter such that the decrease ratio of the outer diameter in the axial direction satisfies the following expression. $$\begin{array}{l}\text{loss ratio}=\text{decrement}\left(\text{mm}\right)\text{of the outside diameter}\\ \left(\text{diameter}\right)\text{/ axial movement amount}\left(\text{mm}\right)\le 0.1\end{array}$$

Here, in general, in a case of a taper, the decrease ratio of the outer diameter in the axial direction satisfies the following expression. $$\begin{array}{l}\text{decrement}\left(\text{mm}\right)\text{of the outside diameter}\left(\text{diameter}\right)\text{the}\\ \text{Bevel / axial movement amount}\left(\text{mm}\right)\ge 1.15\end{array}$$

Accordingly, the orders of magnitude of each decreasing outer diameter and tapered portion are different from each other and are clearly differentiated from each other.

The tooth head of the first inner tooth section 6a is configured so that its inner diameter is substantially constant in the axial direction. Similar is the tooth tip of the second inner tooth section 8a configured so that its inner diameter is substantially constant in the axial direction.

According to the bending engagement type transmission device of the above-described present embodiment, the tooth tip of the first outer tooth portion is 4a configured so that the outer diameter of the first outermost diameter portion 4a1 axially outwardly and axially inwardly decreases, the tooth tip of the second outer tooth portion 4b is configured so that the outer diameter of the second outermost diameter portion 4b1 axially outwardly and axially inwardly decreases. Accordingly, it is possible that at the tooth width end (a position corresponding to the axial end portion of the inner tooth) of the first outer tooth portion 4a and the second outer tooth portion 4b to reduce generated unilateral load, whereby it is possible to reduce the excessive wear of the gear.

Moreover, according to the transmission device 100 of the bending engagement type of the present embodiment, each outermost diameter portion of the outer gear 4 positioned outside the axial center of the engagement region between the outer tooth portion and the inner tooth portion. Accordingly, in comparison with a case where each outermost diameter portion is positioned at the axial center of the engagement portion or within its axial center, it is possible to further reduce the single-sided load.

In addition, according to the bending engagement type transmission device of the present embodiment, each of the first inner portion is 4a3 with decreasing outer diameter and the second inner portion 4b3 configured with decreasing outer diameter so that it extends to the portion of the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the displacement of the outer gear in the axial direction with respect to the inner gear.

(Eighth Embodiment)

10 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to an eighth embodiment. 10 corresponds to 9 the seventh embodiment. As the main differences from the seventh embodiment, in the eighth embodiment, the diameter of the tooth tip of the outer tooth portion is not changed while the diameter of the tooth tip of the inner tooth portion is changed in the axial direction. Hereinafter, the differences between the bending engagement type transmission device of the seventh embodiment and the bending engagement type transmission device of the eighth embodiment will be mainly described.

The tooth tip of the first outer tooth section 4a is configured so that its outer diameter is substantially constant in the axial direction. Similarly, the tooth tip of the second outer tooth portion 4b configured so that its outer diameter is substantially constant in the axial direction. Both the first outer tooth section 4a as well as the second outer tooth portion 4b are configured to extend to the portion of the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent.

The tooth head of the first inner tooth section 6a includes a first innermost diameter section 6a1 having a minimum inner diameter in the first inner tooth portion 6a has a first outer portion 6a2 with increasing inner diameter having an inner diameter, that of the first innermost diameter portion 6a1 axially outwardly increases, and a first inner portion 6a3 with increasing inner diameter having an inner diameter, that of the first innermost diameter portion 6a1 increases axially inwards.

The first innermost diameter section 6a1 is outside the center line C1 that is, outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the tooth tip of the first inner tooth section 6a (which is the shorter axial length of the first outer tooth portion 4a and the first inner tooth section 6a has) positioned. The first outer section 6a2 with increasing inner diameter is configured so that its inner diameter of the first innermost diameter section 6a1 arched axially outward increases. The first inner section 6a3 with increasing inner diameter is configured so that its inner diameter of the first innermost diameter section 6a1 arched axially inward increases. In addition, the first inner section 6a3 with increasing inner diameter so configured such that an increase ratio (= increase of the inner diameter / axial movement amount) of the inner diameter in the axial direction increases when the first inner portion 6a3 with increasing inner diameter of the innermost diameter portion 6a1 is disconnected.

The tooth head of the second inner tooth section 8a contains a second innermost diameter section 8a1 having a minimum inner diameter in the second inner tooth portion 8a has a second outer portion 8a2 with increasing inner diameter having an inner diameter of the second innermost diameter portion 8a1 axially outwardly increases, and a second inner portion 8a3 with increasing inner diameter having an inner diameter of the second innermost diameter portion 8a1 increases axially inwards.

The second innermost diameter section 8a1 is outside the center line C2 that is, outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the tooth tip of the second inner tooth section 8a (which has a shorter axial length from the second outer tooth portion 4b and the second inner tooth portion 8a has) positioned. The second outer section 8a2 with increasing inner diameter is configured so that its inner diameter of the second innermost diameter section 8a1 arched axially outward increases. The second inner section 8a3 with increasing inner diameter is configured so that its inner diameter of the second innermost diameter section 8a1 arched axially inward increases. In addition, the second inner section 8a3 configured with increasing inner diameter so that the increasing ratio of the inner diameter increases in the axial direction when the second inner portion 8a3 with increasing inner diameter of the second innermost diameter portion 8a1 is disconnected.

Moreover, each is the first outer section 6a2 with increasing inner diameter, of the first inner portion 6a3 with increasing inside diameter, the second outer portion 8a2 with increasing inner diameter and the second inner portion 8a3 configured with increasing inner diameter such that the increasing ratio of the inner diameter in the axial direction satisfies the following expression. $$\begin{array}{l}\text{increase ratio}=\text{increasing amount}\left(\text{mm}\right)\text{of the outside diameter}\\ \left(\text{diameter}\right)\text{/ axial movement amount}\left(\text{mm}\right)\le 0.1\end{array}$$

Accordingly, similarly to each decreasing outer diameter portion of the seventh embodiment, the sizes of each increasing and decreasing inner diameter and taper portion are different from each other and are clearly differentiated from each other.

According to the bending engagement type transmission device of the above-described present embodiment, the tooth tip of the first inner tooth portion is 6a configured so that the inner diameter of the first innermost diameter section 6a1 axially outwardly and axially inwardly increases while the tooth tip of the second inner tooth section 8a is configured such that the inner diameter of the second innermost diameter portion 8a1 axially outwardly and axially inwardly increases. Accordingly, it is possible that at the tooth width end of the first outer tooth portion 4a and the second outer tooth portion 4b to reduce generated unilateral load, whereby it is possible to reduce the excessive wear of the gear.

Moreover, according to the bending engagement type transmission device of the present embodiment, in each of the first inner gear 6 and the second inner gear 8th the innermost diameter portion is positioned outside the axial center of the engagement portion between the outer tooth portion and the inner tooth portion. Accordingly, in comparison with a case where the innermost diameter portion is positioned at the axial center of the engagement portion or within its axial center, it is possible to further reduce the one-sided load.

In addition, according to the bending engagement type transmission device of the present embodiment, each of the tooth tips of the first outer teeth portion is 4a and the tooth tip of the second outer tooth portion 4b configured to extend to the portion of the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the displacement of the outer gear in the axial direction with respect to the inner gear.

Ninth Embodiment

11 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a ninth embodiment. 11 corresponds to 9 the seventh embodiment. As the main differences from the seventh embodiment, both the outer tooth portion and the inner tooth portion have portions in which the diameters of the tooth tips change in the axial direction. Hereinafter, the differences between the bending engagement type transmission device of the seventh embodiment and the bending engagement type transmission device of the ninth embodiment will be mainly described.

The tooth tip of the first outer tooth section 4a contains the first outermost diameter section 4a1 and the first outer section 4a2 decreasing outer diameter similar to that of the seventh embodiment. That is, the tooth tip of the first outer tooth portion 4a does not include the first inner section of decreasing outer diameter, with instead the first outermost diameter section 4a1 from a position outside the centerline C1 That is, an off-center position in the axial direction of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the tooth tip of the first inner tooth portion 6a , extends in the axial direction to a position coincident with the tooth tip of the second outer tooth portion 4b That is, a section that is the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th corresponds, is connected. The tooth tip of the first outer tooth section 4a may also include the first inner section with decreasing outer diameter.

The tooth tip of the second outer tooth section 4b contains the second outermost diameter section 4b1 and the second outer section 4b2 decreasing outer diameter similar to that of the seventh embodiment. That is, the tooth tip of the second outer tooth portion 4b does not include the second inner portion as the outer diameter decreases, with the second outer diameter portion instead instead 4b1 from a position outside the centerline C2 that is, a position outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the tooth tip of the second inner tooth portion 8a , extends axially to a position corresponding to the tooth tip of the first outer tooth portion 4a ie, the section that is the radial inside of the gap 7 between the first inner gear 6 and the second inner gear 8th corresponds, is connected. The tooth tip of the second outer tooth section 4b may also include the second inner section with decreasing outer diameter.

The tooth head of the first inner tooth section 6a contains the first innermost diameter section 6a1 and the first inner section 6a3 with increasing inside diameter similar to that of the eighth embodiment. That is, the tooth tip of the first inner tooth portion 6a does not include the first outer portion as the inner diameter increases, with the first innermost diameter portion instead 6a1 from a position outside the centerline C1 that is, a position outside the axial center of the tooth tip of the first outer tooth portion 4a , extends axially outwards. The tooth head of the first inner tooth section 6a may also include the first outer portion with increasing inner diameter.

The tooth head of the second inner tooth section 8a contains the second innermost diameter section 8a1 and the second inner section 8a3 with increasing inside diameter similar to that of the eighth embodiment. That is, the tooth tip of the second inner tooth portion 8a does not include the second outer portion as the inner diameter increases, with the second innermost diameter portion instead instead 8a1 from a position outside the centerline C2 That is, a position outside the axial center of the tooth tip of the second outer tooth portion 4b , extends axially outwards. The tooth head of the second inner tooth section 8a may also contain the second outer portion with increasing inner diameter.

An axial position of a boundary between the first outermost diameter portion 4a1 and the first outer section 4a2 with decreasing outer diameter substantially coincides with an axial position of a boundary between the first innermost diameter portion 6a1 and the first inner section 6a3 coincide with increasing inner diameter. In addition, the boundaries are outside the centerline C1 that is, outside the axial center of the engagement region between the first outer tooth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the tooth tip of the first inner tooth section 6a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the tooth tip of the first outer tooth portion 4a positioned.

Similarly, an axial position coincides with a boundary between the second outermost diameter portion 4b1 and the second outer portion 4b2 decreasing in outer diameter substantially with an axial position of a boundary between the second innermost diameter portion 8a1 and the second inner section 8a3 coincide with increasing inner diameter. In addition, the boundaries are outside the centerline C2 that is, out of center in the axial direction of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the tooth tip of the second inner tooth section 8a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the tooth tip of the second outer tooth portion 4b positioned.

Similarly to the seventh embodiment, in the bending engagement type transmission device according to the present embodiment, the tooth tip of the outer tooth portion includes the outer portion with decreasing outer diameter. Meanwhile, unlike the seventh embodiment, the tooth tip of the outer tooth portion does not include the inner portion with decreasing outer diameter. Instead, however, the tooth tip of the inner tooth portion includes the inner portion as the inner diameter increases. Therefore, according to the bending engagement type transmission device of the present embodiment, the functional effects similar to the operational effects exerted by the bending engagement type transmission device of the seventh embodiment are obtained.

Tenth Embodiment

12 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a tenth embodiment. 12 corresponds to 9 the seventh embodiment. As the main differences from the seventh embodiment, both the outer tooth portion and the inner tooth portion have portions in which the diameters of the tooth tips are changed in the axial direction. Hereinafter, the differences between the bending engagement type transmission device of the seventh embodiment and the bending engagement type transmission device of the tenth embodiment will be mainly described.

The tooth tip of the first outer tooth section 4a contains the first outermost diameter section 4a1 and the first inner section 4a3 decreasing outer diameter similar to that of the seventh embodiment. That is, the tooth tip of the first outer tooth portion 4a does not include the first outer section of decreasing outer diameter, with instead the first outermost diameter section 4a1 from a position outside the centerline C1 that is, a position outside the axial center of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the tooth tip of the first inner tooth portion 6a , extends axially outwards. The tooth tip of the first outer tooth section 4a may also include the first outer section with decreasing outer diameter.

The tooth tip of the second outer tooth section 4b contains the second outermost diameter section 4b1 and the second inner section 4b3 decreasing outer diameter similar to that of the seventh embodiment. That is, the tooth tip of the second outer tooth portion 4b does not include the second outer portion as the outer diameter decreases, with the second outer diameter portion instead instead 4b1 from a position outside the centerline C2 , ie, a position outside the axial center of the engagement portion between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the tooth tip of the second inner tooth portion 8a , extends axially outwards. The tooth tip of the second outer tooth section 4b may also include the second outer section with decreasing outer diameter.

The tooth head of the first inner tooth section 6a contains the first innermost diameter section 6a1 and the first outer section 6a2 with increasing inside diameter similar to that of the eighth embodiment. That is, the tooth tip of the first inner tooth portion 6a does not include the first inner portion as the inner diameter increases, with the first innermost diameter portion instead 6a1 from a position outside the centerline C1 that is, a position outside the axial center of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, a position outside the axial center of the tooth tip of the first inner tooth portion 6a , extends axially inwards. The tooth head of the first inner tooth section 6a may also include the first inner portion with increasing inner diameter.

The tooth head of the second inner tooth section 8a contains the second innermost diameter section 8a1 and the second outer section 8a2 with increasing inside diameter similar to that of the eighth embodiment. That is, the tooth tip of the second inner tooth portion 8a does not include the second inner portion as the inner diameter increases, with the second innermost diameter portion instead 8a1 from a position outside the centerline C2 that is, a position outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a in other words, a position outside the axial center of the tooth tip of the second inner tooth portion 8a , extends axially inwards. The tooth head of the second inner tooth section 8a may also contain the second inner portion with increasing inner diameter.

An axial position of a boundary between the first outermost diameter portion 4a1 and the first inner section 4a3 with decreasing outer diameter substantially coincides with an axial position of a boundary between the first innermost diameter portion 6al and the first outer portion 6a2 coincide with increasing inner diameter. In addition, the boundaries are outside the centerline C1 that is, out of center in the axial direction of the engagement portion between the first outer teeth portion 4a and the first inner tooth section 6a in other words, outside the axial center of the tooth tip of the first inner tooth section 6a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the tooth tip of the first outer tooth portion 4a positioned.

Similarly, an axial position coincides with a boundary between the second outermost diameter portion 4b1 and the second inner section 4b3 decreasing in outer diameter substantially with an axial position of a boundary between the second innermost diameter portion 8a1 and the second outer portion 8a2 coincide with increasing inner diameter. In addition, the boundaries are outside the centerline C2 that is, outside the axial center of the engagement region between the second outer tooth portion 4b and the second inner tooth portion 8a in other words, outside the axial center of the tooth tip of the second inner tooth section 8a , positioned. In addition, in the present embodiment, the boundaries are outside the axial center of the tooth tip of the second outer tooth portion 4b positioned.

Similar to the seventh embodiment, in the bending engagement type transmission device according to the present embodiment, the tooth tip of the outer tooth portion includes the inner portion with decreasing outer diameter. Meanwhile, the tooth tip of the outer tooth portion unlike the seventh embodiment does not include the outer diameter decreasing portion. Instead, however, the tooth tip of the inner tooth portion includes the outer portion as the inner diameter increases. Therefore, according to the bending engagement type transmission device of the present embodiment, the functional effects similar to the operational effects exerted by the bending engagement type transmission device of the seventh embodiment are obtained.

Eleventh Embodiment

13 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to an eleventh embodiment. 13 corresponds to 9 the seventh embodiment. As the main differences from the seventh embodiment, in the eleventh embodiment, only the diameter of the tooth tip of the second outer tooth portion changes 4b in the axial direction. Hereinafter, the differences between the bending engagement type transmission device of the seventh embodiment and the bending engagement type transmission device of the eleventh embodiment will be mainly described.

The outer diameter in the axial direction of the tooth tip of the first outer tooth portion 4a which has the number of teeth, that of the first inner tooth portion 6a is different, is substantially constant, with the tooth tip of the first outer tooth portion 4a is configured to have an outer diameter the same as the minimum outer diameter of the second outer tooth portion 4b is.

The tooth tip of the second outer tooth section 4b which has the number of teeth which are the same as that of the second inner tooth portion 8a is, contains the second outermost diameter section 4b1 and the second inner section 4b3 with decreasing outside diameter. That is, the tooth tip of the second outer tooth portion 4b does not contain the second outer section with decreasing outer diameter. The second outermost diameter section 4b1 is positioned at an axial outer end portion. The second inner section 4b3 with decreasing outer diameter occupies 80% or more (occupies about 100% in the example shown) of the axial portion of the tooth tip of the second outer tooth portion 4b and is configured such that the outer diameter of the second outermost diameter portion 4b1 decreases axially inwardly continuously, the outer diameter decreases specially curved.

The tooth head of the first inner tooth section 6a is configured such that the inner diameter is substantially constant in the axial direction. Similar is the tooth tip of the second inner tooth section 8a configured such that the inner diameter is substantially constant in the axial direction.

According to the bending engagement type transmission device of the present embodiment, the tooth tip of the second outer tooth portion 4b the number of teeth that are the same as that of the second inner tooth portion 8a is, ie, the tooth tip of the second outer tooth portion 4b which is a driven-side gear, has the outer diameter, that of the second outermost diameter portion 4b1 axially inwardly decreasing, and is configured so that the portion decreases as the outer diameter decreases (ie, the second inner portion 4b3 with decreasing outer diameter) 80% or more of the axial portion of the tooth tip of the second outer tooth portion 4b busy. Accordingly, it is possible that at the tooth width end of the second outer tooth portion 4b which is a driven side outer tooth portion on which a load is easily exerted to reduce unilateral load, whereby it is possible to reduce the excessive wear of the gear.

In addition, according to the bending engagement type transmission device of the present embodiment, each of the tooth tips of the first outer teeth portion is 4a and the tooth tip (especially the second inner portion 4b3 with decreasing outer diameter) of the second outer tooth portion 4b configured to extend to the section of the gap 7 between the first inner gear 6 and the second inner gear 8th equivalent. Accordingly, it is possible to absorb the influences of the displacement of the outer gear in the axial direction with respect to the inner gear.

Twelfth Embodiment

14 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a twelfth embodiment. 14 corresponds to 10 the eighth embodiment. As a major difference from the eighth embodiment, in the twelfth embodiment, only the diameter of the tooth tip of the second inner tooth portion changes 8a in the axial direction. Hereinafter, the differences between the bending engagement type transmission device of the eighth embodiment and the bending engagement type transmission device of the twelfth embodiment will be mainly described.

The tooth tip of the first outer tooth section 4a is configured so that the outer diameter is substantially constant in the axial direction. Similarly, the tooth tip of the second outer tooth portion 4b configured so that its outer diameter is substantially constant in the axial direction.

The inner diameter in the axial direction of the tooth tip of the first inner tooth portion 6a which has the number of teeth, that of the first outer tooth portion 4a is different, is substantially constant, with the tooth tip of the first inner tooth portion 6a is configured to have an inner diameter the same as the minimum inner diameter of the second inner tooth portion 8a is.

The tooth head of the second inner tooth section 8a having the number of teeth which are the same as that of the second outer tooth portion 4b is, contains the second innermost diameter section 8a1 and the second inner section 8a3 with increasing inside diameter. That is, the tooth tip of the second inner tooth portion 8a does not contain the second outer portion as the inner diameter increases. The second innermost diameter section 8a1 is positioned at an axial outer end portion. The second inner section 8a3 As the inner diameter increases, it occupies 80% or more (occupies about 100% in the example shown) of the axial portion of the tooth tip of the second inner one tooth portion 8a and is configured such that the inner diameter of the second innermost diameter portion 8a1 increases axially inwardly continuously, the inner diameter increases specially curved.

According to the bending engagement type transmission device of the present embodiment, the functional effects similar to the operational effects exerted by the bending engagement type transmission device of the eleventh embodiment are obtained.

Above, the bending engagement type transmission devices according to the embodiments have been described. It will be appreciated by those skilled in the art that the embodiments are examples, that various modifications may be made to the combinations of the constituent elements and the respective processing processes, and that the modifications are also within the scope of the present invention.

(Modification Example 1)

In the first to sixth embodiments, the case where the portion decreases with decreasing tooth thickness is described. However, the present invention is not limited to this, and the decreasing tooth thickness portion may linearly decrease.

15 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the first embodiment. 15 corresponds to 2 the first embodiment. In the present modification example, the first outer portion is 4a8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward, while the first inner portion 4a9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specific are in the first outer section 4a8 with decreasing tooth thickness, the two tooth surfaces of the first outer tooth portion 4a configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly outwardly in the tooth thickness, wherein in the first inner portion 4a9 with decreasing tooth thickness, the two tooth surfaces are configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly in the tooth thickness axially inwards. In addition, the second outer section 4B8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward while the second inner portion decreases linearly 4b9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specifically, in the second outer section 4B8 with decreasing tooth thickness, the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly outward in the tooth thickness, while in the second inner portion 4b9 with decreasing tooth thickness, the two tooth surfaces are configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly in the tooth thickness axially inwards. At least one tooth surface of the first inner portion 4a9 with decreasing tooth thickness and the second inner portion 4b9 with decreasing tooth thickness includes two linear portions having different inclinations in the axial direction, in other words, two linear portions having different angles with respect to the rotation axis R (see FIG 1 ) respectively. In the two linear portions of the inner portion with decreasing tooth thickness, the inclination of the outer positioned linear portion, that is, the inclination of the linear portion near the outer thickest tooth portion, is smaller than the inclination of the inner positioned linear portion, that is, the inclination of the linear one Section away from the outer thickest tooth portion. That is, the angle of the linear portion positioned outside with respect to the rotation axis R is smaller than the angle of the linear portion positioned inside with respect to the rotation axis R. In addition, FIG 15 a case in which each of the two tooth surfaces of the first inner portion 4a9 with decreasing tooth thickness and the second inner portion 4b9 with decreasing tooth thickness contains two linear sections, which have different inclinations.

16 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the second embodiment. 16 corresponds to 4 the second embodiment. In the present modification example, the first outer portion is 6A8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward, while the first inner portion 6A9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specific are in the first outer section 6A8 with decreasing tooth thickness, the two tooth surfaces of the first inner tooth portion 6a configured so that the distances between the two tooth surfaces and the center surface S ₆ decrease linearly outward in the tooth thickness, while in the first inner section 6A9 with decreasing tooth thickness, the two tooth surfaces are configured so that the distances between the two tooth surfaces and the center surface S ₆ decrease linearly in the tooth thickness axially inwards. In addition, the second outer section 8A8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward while the second inner portion decreases linearly 8A9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specifically, in the second outer section 8A8 with decreasing tooth thickness, the two tooth surfaces of the second inner tooth portion 8a configured so that the distances between the two tooth surfaces and the center surface S ₈ decrease linearly outward in the tooth thickness, while in the second inner portion 8A9 with decreasing tooth thickness, the two tooth surfaces are configured so that the distances between the two tooth surfaces and the center surface S ₈ decrease linearly in the tooth thickness axially inwards. At least one tooth surface of the first inner portion 6A9 with decreasing tooth thickness and the second inner portion 8A9 with decreasing tooth thickness includes two linear portions having different inclinations in the axial direction, in other words, two linear portions which are relative to the axis of rotation R have different angles (see 1 ). In the two linear portions of the inner portion with decreasing tooth thickness, the inclination of the outwardly positioned linear portion, that is, the inclination of the linear portion near the inner thickest tooth portion, is smaller than the inclination of the inner positioned linear portion, that is, the inclination of the linear one Section away from the inner thickest tooth portion. That is, the angle of the linear portion positioned outside with respect to the rotation axis R is smaller than the angle of the linear portion positioned inside with respect to the rotation axis R , Additionally shows 16 a case in which each of the two tooth surfaces of the first inner portion 6A9 with decreasing tooth thickness and the second inner portion 8A9 with decreasing tooth thickness contains two linear sections, which have different inclinations.

17 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the third embodiment. 17 corresponds to 5 the third embodiment. In the present modification example, the first outer portion is 4a8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward, while the first inner portion 6A9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specific are in the first outer section 4a8 with decreasing tooth thickness, the two tooth surfaces of the first outer tooth portion 4a configured so that the distances between the both tooth surfaces and the center surface S ₄ decrease linearly outward in the tooth thickness, while in the first inner portion 6A9 with decreasing tooth thickness, the two tooth surfaces of the first inner tooth portion 6a are configured so that the distances between the two tooth surfaces and the center surface S ₆ decrease linearly in the tooth thickness axially inwards. In addition, the second outer section 4B8 configured with decreasing tooth thickness such that the tooth thickness decreases linearly axially outward while the second inner portion decreases linearly 8A9 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially. Specifically, in the second outer section 4B8 with decreasing tooth thickness, the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly outward in the tooth thickness, while in the second inner portion 8A9 with decreasing tooth thickness, the two tooth surfaces of the second inner tooth portion 8a are configured so that the distances between the two tooth surfaces and the center surface S ₈ decrease linearly in the tooth thickness axially inwards.

18 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the fourth embodiment. 18 corresponds to 6 the fourth embodiment. In the present modification example, the first inner portion 4a9 configured with decreasing tooth thickness such that the tooth thickness decreases linearly inward axially while the first outer portion 6A8 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly outward axially. Specifically, in the first inner section 4a9 with decreasing tooth thickness, the two tooth surfaces of the first outer tooth portion 4a configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly inwardly in the tooth thickness, while in the first outer portion 6A8 with decreasing tooth thickness, the two tooth surfaces of the first inner tooth portion 6a are configured so that the distances between the two tooth surfaces and the center surface S ₆ decrease linearly in the tooth thickness axially outward. In addition, the second inner section 4b9 configured with decreasing tooth thickness such that the outer diameter linearly decreases axially inward, while the second outer portion 8A8 is configured with decreasing tooth thickness such that the tooth thickness decreases linearly outward axially. Specifically, in the second inner section 4b9 with decreasing tooth thickness, the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ decrease linearly inwardly in the tooth thickness, while in the second outer portion 8A8 with decreasing tooth thickness, the two tooth surfaces of the second inner tooth portion 8a are configured so that the distances between the two tooth surfaces and the center surface S ₈ decrease linearly in the tooth thickness axially outward.

19 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the fifth embodiment. 19 corresponds to 7 the fifth embodiment. In the present modification example, the second inner portion is 4b9 with decreasing tooth thickness configured so that the outer diameter of the second outer thickest tooth portion 4B7 axially inwardly decreases linearly. Specifically, in the second inner section 4b9 with decreasing tooth thickness, the two tooth surfaces of the second outer tooth portion 4b configured so that the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 decrease axially inwards in a linear manner.

20 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to another modification example of the fifth embodiment. 20 corresponds to 7 the fifth embodiment. In the present modification example, the second inner portion is 4b9 with decreasing tooth thickness configured so that the tooth thickness of the second outer thickest tooth portion 4B7 axially inwardly decreases linearly. Specifically, in the second inner section 4b9 with decreasing tooth thickness, the two tooth surfaces of the second outer tooth portion 4b configured so that the distance between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the second outer thickest tooth portion 4B7 axially inwardly decreases linearly. In addition, in the present modification example, the first outer tooth portion includes 4a the first outer thickest tooth portion 4a7 and the first inner section 4a9 with decreasing tooth thickness. The first outer thickest tooth section 4a7 extends in the axial direction. The first inner section 4a9 with decreasing tooth thickness is configured so that the tooth thickness of the first outer thickest tooth portion 4a7 axially inwardly decreases linearly. Specifically, in the first inner section 4a9 with decreasing tooth thickness, the two tooth surfaces of the first outer tooth portion 4a configured so that the distances between the two tooth surfaces and the center surface S ₄ in the tooth thickness of the first outer thickest tooth portion 4a7 decrease axially inwards in a linear manner. In particular, the first inner section 4a9 with decreasing tooth thickness configured to have an axial dimension D1 hereof smaller than an axial dimension D2 of the second inner section 4b9 with decreasing tooth thickness.

21 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the sixth embodiment. 21 corresponds to 8th the sixth embodiment. In the present modification example, the second inner portion is 8A9 with decreasing tooth thickness configured so that the tooth thickness of the second inner thickest tooth portion 8A7 axially inwardly decreases linearly. Specifically, in the second inner section 8A9 with decreasing tooth thickness, the two tooth surfaces of the second inner tooth portion 8a configured so that the distances between the two tooth surfaces and the center surface S ₈ in the tooth thickness of the second inner thickest tooth portion 8A7 decrease axially inwards in a linear manner.

In the modification examples according to the 15 to 21 For example, each decreasing tooth thickness section is configured such that the decrease ratio of the distance between each of the two tooth surfaces and the center surface in the tooth thickness in the axial direction satisfies Expression 1 described above.

According to the modification examples according to the 15 to 21 For example, the functional effects similar to the operational effects exerted by the bending-engagement type gear apparatuses of the first to sixth embodiments are obtained. In addition, according to the present modification examples, a processing machine that can work only on a tooth portion having a linear shape of the tooth surface, that is, a processing machine that can not machine a tooth portion having a curved shape of the tooth surface can be used to grind the teeth To produce gears.

(Modification Example 2)

In the first embodiment, the case has been described in which both the first outer thickest tooth portion 4a7 as well as the second outer thickest tooth portion 4B7 outside the axial centers of the Engagement portions are positioned between the respective outer tooth portions and inner tooth portions. However, the present invention is not limited to this, with only one of the first outer thickest tooth portion 4a7 and the second outer thickest tooth portion 4B7 can be positioned outside the axial center of the engagement region between the corresponding outer tooth portion and inner tooth portion. The second outer tooth section 4b that has the same number of teeth as the second inner tooth section 8a ie, only the second outer thickest tooth portion 4B7 of the second outer tooth portion 4b which is the driven side gear, may be outside the axial center of the engaging portion between the second outer teeth portion 4b and the second inner tooth portion 8a be positioned.

Similarly, in the second embodiment, the case has been described in which both the first inner thickest tooth portion 6a7 as well as the second inner thickest tooth section 8A7 are positioned outside the axial centers of the engaging portions between the respective outer teeth portions and inner teeth portions. However, the present invention is not limited to this, with only one of the first inner thickest tooth portion 6a7 and the second inner thickest tooth portion 8A7 can be positioned outside the axial center of the engagement region between the corresponding outer tooth portion and inner tooth portion.

In addition, in the third and fourth embodiments, the case has been described in which both the boundary between the first outer tooth portion 4a and the first inner tooth section 6a as well as the boundary between the second outer tooth portion 4b and the second inner tooth portion 8a are positioned outside the axial centers of the engaging portions between the respective outer teeth portions and inner teeth portions. However, the present invention is not limited to this, with only one of the boundary between the first outer tooth portion 4a and the first inner tooth section 6a and the boundary between the second outer tooth portion 4b and the second inner tooth portion 8a can be positioned outside the axial center of the engagement portion of the corresponding outer tooth portion and inner tooth portion.

(Modification Example 3)

In the first to sixth embodiments, the case has been described in which each outer tooth portion and each inner tooth portion are symmetrical to the center surface in the tooth thickness. However, the present invention is not limited to this, wherein each outer tooth portion and each inner tooth portion may be asymmetric to the center surface in the tooth thickness. In a case where the wave generator wave 22 rotates in one direction, comes in each outer tooth portion and each inner tooth portion z. B. only one tooth surface of the two tooth surfaces with the other tooth portion in contact. In this case, the tooth surface which comes into contact with the other tooth portion is formed as in the 2 and 4 to 8th is shown, wherein the shape of the tooth surface, which does not come into contact with the other tooth portion, is not particularly limited. Accordingly, the tooth surface, which does not come into contact with the other tooth portion, z. B. be formed so that a distance between the tooth surface and the central surface in the tooth thickness in the axial direction is constant.

(Modification Example 4)

In the seventh to twelfth embodiments, the case has been described in which the outer diameter or the inner diameter of each of the outer diameter decreasing portion and the inner diameter decreasing portion decreases or increases in a curved manner. However, the present invention is not limited to this, wherein the outer diameter or the inner diameter can decrease or increase linearly.

22 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the seventh embodiment. 22 corresponds to 9 the seventh embodiment. In the present modification example, the first outer portion is 4a2 configured with decreasing outer diameter so that the outer diameter decreases linearly outward axially while the first inner portion 4a3 is configured with decreasing outer diameter so that the outer diameter decreases linearly inward axially. In addition, the second outer section 4b2 configured with decreasing outer diameter so that the outer diameter linearly decreases axially outward, while the second inner portion 4b3 is configured with decreasing outer diameter so that the outer diameter decreases linearly inward axially. At least one of the first inner section 4a3 With decreasing outer diameter and the second inner portion 4b3 with decreasing outer diameter includes two linear portions having different inclinations in the axial direction, in other words, two linear portions having different angles with respect to the rotational axis R (please refer 1 ) respectively. In the two linear portions of the outer diameter decreasing inner portion, the inclination of the outer positioned linear portion, ie, the inclination of the linear portion near the outermost diameter portion, is smaller than the inclination of the inner positioned linear portion, ie, the inclination of the linear portion from the outermost diameter section. That is, the angle of the linear portion positioned outside with respect to the rotation axis R is smaller than the angle of the linear portion positioned inside with respect to the rotation axis R. In addition, FIG 9 a case where each of the first inner portion 4a3 with decreasing outer diameter and the second inner portion 4b3 with decreasing outer diameter contains two linear sections, which have different inclinations.

23 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the eighth embodiment. 23 corresponds to 10 the eighth embodiment. In the present modification example, the first outer portion is 6a2 configured with increasing inner diameter so that the inner diameter increases linearly axially outwards, while the first inner portion 6a3 is configured with increasing inner diameter so that the inner diameter increases linearly inward axially. In addition, the second outer section 8a2 configured with increasing inner diameter so that the inner diameter increases linearly axially outward, while the second inner portion 8a3 is configured with increasing inner diameter so that the inner diameter increases linearly inward axially. At least one of the first inner section 6a3 with increasing inner diameter and the second inner portion 8a3 As the inner diameter increases, it includes two linear portions having different inclinations in the axial direction, in other words, two linear portions having different angles with respect to the rotational axis R (please refer 1 ) respectively. In the two linear portions of the inner portion as the inner diameter increases, the inclination of the outer positioned linear portion, ie, the inclination of the linear portion near the innermost diameter portion, is smaller than the inclination of the inner positioned linear portion, that is, the inclination of the linear portion away from the innermost diameter section. That is, the angle of the linear portion positioned outside with respect to the rotation axis R is smaller than the angle of the linear portion positioned inside with respect to the rotation axis R , Additionally shows 23 a case where each of the first inner portion 6a3 with increasing inner diameter and the second inner portion 8a3 with increasing inner diameter contains two linear sections, which have different inclinations.

24 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the ninth embodiment. 24 corresponds to 11 the ninth embodiment. In the present modification example, the first outer portion is 4a2 configured with decreasing outer diameter so that the outer diameter decreases linearly outward axially while the first inner portion 6a3 is configured with increasing inner diameter so that the inner diameter increases linearly inward axially. In addition, the second outer section 4b2 configured with decreasing outer diameter so that the outer diameter linearly decreases axially outward, while the second inner portion 8a3 is configured with increasing inner diameter so that the inner diameter increases linearly inward axially.

25 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the tenth embodiment. 25 corresponds to 12 the tenth embodiment. In the present modification example, the first inner portion 4a3 configured with decreasing outer diameter so that the outer diameter decreases linearly inward axially while the first outer portion 6a2 is configured with increasing inner diameter so that the inner diameter increases linearly axially outward. In addition, the second inner section 4b3 configured with decreasing outer diameter so that the outer diameter decreases linearly inward axially, while the second outer portion 8a2 is configured with increasing inner diameter so that the inner diameter increases linearly axially outward.

26 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a transmission device of the bending engagement type according to a modification example of the eleventh embodiment. 26 corresponds to 13 the eleventh embodiment. In the present modification example, the second inner portion is 4b3 with decreasing outer diameter configured so that the outer diameter of the second outermost diameter portion 4b1 axially inwardly decreases linearly.

27 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to another modification example of the eleventh embodiment. 27 corresponds to 13 the eleventh embodiment. In the present modification example, the second inner portion is 4b3 with decreasing outer diameter configured so that the outer diameter of the second outermost diameter portion 4b1 axially inwardly decreases linearly. In addition, in the present modification example, the first outer tooth portion includes 4a the first outermost diameter section 4a1 and the first inner section 4a3 with decreasing outside diameter. The first outermost diameter section 4a1 extends in the axial direction. The outer diameter of the first inner section 4a3 with decreasing outer diameter decreases from the first outermost diameter portion 4a1 axially inward linearly. In particular, the first inner section 4a3 with decreasing outer diameter configured so that the axial dimension D1 smaller than the axial dimension D2 of the second inner section 4b3 with decreasing outside diameter.

28 Fig. 12 is a diagram for explaining the shapes of the external gear 4 , the first inner gear 6 and the second inner gear 8th a bending engagement type transmission device according to a modification example of the twelfth embodiment. 28 corresponds to 14 the twelfth embodiment. In the present modification example, the second inner portion is 8a3 configured with increasing inner diameter such that the inner diameter of the second innermost diameter section 8a1 increases axially inward linearly.

In the modification examples according to the 22 to 28 For example, each decreasing outer diameter portion is configured so that the decrease ratio of the outer diameter in the axial direction satisfies Expression 1 described above, while each increasing inner diameter portion is configured so that the increasing ratio of the inner diameter in the axial direction satisfies Expression 2 described above ,

According to the modification examples according to the 22 to 28 For example, the functional effects similar to those of the flexing engagement type transmission device according to the seventh through twelfth embodiments are obtained. In addition, according to the present modification examples, a processing machine that can machine only a tooth portion having a linear shape of the tooth tip, that is, a processing machine that can not machine a tooth portion having a domed shape of the tooth head, can be used to grind the teeth To produce gears.

(Modification Example 5)

In the seventh embodiment, the case has been described in which both the first outermost diameter portion 4a1 as well as the second outermost diameter section 4b 1 are positioned outside the axial centers of the engagement portions of the respective outer teeth portions and inner teeth portions. However, the present invention is not limited to this, with only one of the first outermost diameter portion 4a1 and the second outermost diameter portion 4b 1 except for axial center of the engagement portion between the corresponding outer tooth portion and inner tooth portion may be positioned. It can, for. B. the second outer tooth portion 4b that has the same number of teeth as the second inner tooth section 8a ie, only the second outermost diameter section 4b1 of the second outer tooth portion 4b which is the driven side gear, outside the axial center of the engagement portion between the second outer teeth portion 4b and the second inner tooth portion 8a be positioned.

Similarly, in the eighth embodiment, the case where both the first innermost diameter portion 6a1 and the second innermost diameter portion 8al are positioned outside the axial centers of the engagement portions of the respective outer teeth portions and inner teeth portions. However, the present invention is not limited to this, with only one of the first innermost diameter portion 6a1 and the second innermost diameter portion 8a1 can be positioned outside the axial center of the engagement region between the corresponding outer tooth portion and inner tooth portion.

In addition, in the ninth and tenth embodiments, the case has been described in which both the boundary between the first outer tooth portion 4a and the first inner tooth section 6a as well as the boundary between the second outer tooth portion 4b and the second inner tooth portion 8a are positioned outside the axial centers of the engaging portions between the respective outer teeth portions and inner teeth portions. However, the present invention is not limited to this, with only one of the boundary between the first outer tooth portion 4a and the first inner tooth section 6a and the boundary between the second outer tooth portion 4b and the second inner tooth portion 8a can be positioned outside the axial center of the engagement region between the corresponding outer tooth portion and inner tooth portion.

(Modification Example 6)

In the first to twelfth embodiments and the modification examples described above, the case where the axial length of the inner teeth portion is shorter than the axial length of the outer teeth portion has been described. However, the present invention is not limited to this. The axial length of the outer tooth portion may be shorter than the axial length of the inner tooth portion, and thus the outer tooth portion may be configured to mesh with the inner tooth portion over the entire region in the axial direction. That is, the axial length of the engagement portion between the outer teeth portion and the inner teeth portion may be the same as the axial length of the outer teeth portion. In this case, z. For example, each outer thickest tooth portion in the first embodiment, each inner thickest tooth portion in the second embodiment, each boundary between the outer thickest tooth portion and the outer portion with decreasing tooth thickness in the third embodiment and any boundary between the outer thickest tooth portion and the inner portion with decreasing tooth thickness in the fourth embodiment, positioned outside the axial centers of the engagement portions of the respective outer teeth portions and inner teeth portions, in other words outside the axial centers of the corresponding outer teeth portions. In addition, z. For example, each outermost diameter portion in the seventh embodiment, each innermost diameter portion in the eighth embodiment, each boundary between the outermost diameter portion and the outer portion with decreasing outer diameter in the ninth embodiment and each boundary between the outermost diameter portion and the inner portion with decreasing outer diameter of the tenth embodiment is positioned outside the axial centers of the engagement portions of the respective outer teeth portions and inner teeth portions, in other words, outside the axial centers of the tooth tips of the respective outer teeth portions.

LIST OF REFERENCE NUMBERS

4:

outer gear

4a:

first outer tooth section

4b:

second outer tooth section

4a7:

first outer thickest tooth section

4a8:

first outer section with decreasing tooth thickness

4a9:

first inner section with decreasing tooth thickness

4B7:

second outer thickest tooth section

4B8:

second outermost section with decreasing tooth thickness

4b9:

second inner section with decreasing tooth thickness

6:

first inner gear

8th:

second inner gear

22a:

wave generator

100:

Transmission device of the bending engagement type

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• JP 2018000804 [0002]
• WO 2016/21011 [0003, 0004]

Claims (9)

A bending engagement type transmission device comprising: a wave generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear, wherein the outer gear includes a first outer tooth portion that meshes with the first inner gear and a second outer tooth portion that mesh with the second inner gear, wherein the first outer tooth portion has a first outer thickest tooth portion having a maximum tooth thickness, a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outwardly from the first outer thickest tooth portion, and a first inner portion decreasing in tooth thickness which has a tooth thickness decreasing axially inwardly from the first outer thickest tooth portion, and wherein the second outer tooth portion has a second outer thickest tooth portion having a maximum tooth thickness, a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second outer thickest tooth portion, and a second inner portion decreasing in tooth thickness which has a tooth thickness decreasing axially inwardly from the second outer thickest tooth portion. Transmission device of the bending engagement type according to Claim 1 wherein, in the first outer portion, as the tooth thickness decreases, a distance between each of the two tooth surfaces of the first outer tooth portion and a center surface in a tooth thickness decreases axially outwardly from the first outer thickest tooth portion, and a distance between each in the first inner portion as the tooth thickness decreases in the second outer portion, as the tooth thickness decreases, a distance between each of the two tooth surfaces of the second outer tooth portion and a center surface in a tooth thickness of the second outer thickest tooth portion decreases axially outward and axially decreasing in the second inner portion with decreasing tooth thickness, a distance between each of the two tooth surfaces and a center surface in a tooth thickness of the second outer thickest tooth portion n decreases. Transmission device of the bending engagement type according to Claim 1 or 2 wherein at least one of the first outer thickest tooth portion and the second outer thickest tooth portion is positioned outside an axial center of a tooth portion having a smaller axial width of an outer tooth portion and an inner tooth portion which mesh with each other. Transmission device of the bending engagement type according to one of Claims 1 to 3 wherein a tooth tip of the first outer tooth portion has a first outermost diameter portion having a maximum outer diameter, a first outer portion of decreasing outer diameter having an outer diameter decreasing axially outward from the first outermost diameter portion, and the first inner portion decreasing Outer diameter having an outer diameter decreasing axially inwardly from the first outermost diameter portion, and wherein a tooth tip of the second outer tooth portion has a second outermost diameter portion having a maximum outer diameter, a second outer portion with decreasing outer diameter, an outer diameter which decreases axially outwardly from the second outermost diameter portion, and the second inner diameter decreasing portion having an outer diameter that is different from the second outer diameter portion outer diameter portion decreases axially inwardly contains. A bending engagement type transmission device, comprising: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged to align with the first inner gear in an axial direction and mesh with the outer gear, wherein an inner gear portion of the first inner gear has a first inner thickest gear portion having a maximum tooth thickness a first outer section of decreasing tooth thickness, the one Tooth thickness, which decreases axially outwardly from the first inner thickest tooth portion, and a first inner portion of decreasing tooth thickness, which has a tooth thickness which decreases axially inwardly from the first inner thickest tooth portion, and wherein an inner tooth portion of the second inner gear has a second inner thickest tooth portion having a maximum tooth thickness, a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second inner thickest tooth portion, and a second inner portion decreasing in tooth thickness, the one Tooth thickness, which decreases axially inwardly from the second inner thickest tooth portion contains. A bending engagement type transmission device comprising: a wave generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear, wherein the outer gear includes a first outer tooth portion that meshes with a first inner tooth portion of the first inner gear and a second outer tooth portion that meshes with a second inner tooth portion of the second inner gear; wherein the first outer tooth portion includes a first outer thickest tooth portion having a maximum tooth thickness, and a first outer portion with decreasing tooth thickness having a tooth thickness decreasing axially outward from the first outer thickest tooth portion; wherein the second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness, and a second outer portion with decreasing tooth thickness having a tooth thickness decreasing axially outward from the second outer thickest tooth portion; wherein the first inner tooth portion includes a first inner thickest tooth portion having a maximum tooth thickness, and a first inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inward from the first inner thickest tooth portion, and wherein the second inner tooth portion includes a second inner thickest tooth portion having a maximum tooth thickness and a second inner portion decreasing in tooth thickness having a tooth thickness decreasing axially inwardly from the second inner thickest tooth portion. A bending engagement type transmission device, comprising: a shaft generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear, wherein the outer gear includes a first outer tooth portion that meshes with a first inner tooth portion of the first inner gear and a second outer tooth portion that mesh with a second inner tooth portion of the second inner gear, the first outer tooth portion having a first outer thickest A tooth portion having a maximum tooth thickness, and a first inner portion of decreasing tooth thickness having a tooth thickness decreasing axially inward from the first outer thickest tooth portion, the second outer tooth portion having a second outer thickest tooth portion having a maximum tooth thickness Tooth thickness, and a second inner portion of decreasing tooth thickness, which has a tooth thickness, which decreases axially inwardly from the second outer thickest tooth portion includes, wherein the first inner tooth portion has a first inner thickest tooth portion which has a m aximum tooth thickness, and a first outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the first inner thickest tooth portion, and wherein the second inner tooth portion has a second inner thickest tooth portion having a maximum tooth thickness; and a second outer portion of decreasing tooth thickness having a tooth thickness decreasing axially outward from the second inner thickest tooth portion. A bending engagement type transmission device comprising: a wave generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear, wherein the outer gear has a first outer tooth portion that meshes with a first inner tooth portion of the first inner gear and has the number of teeth different from that of the first inner tooth portion and a second outer tooth portion that meshes with a second inner tooth portion of the first inner tooth portion second internal gear and has the number of teeth, which is the same as that of the second inner tooth portion contains, wherein the second outer tooth portion includes a second outer thickest tooth portion having a maximum tooth thickness and a second inner portion of decreasing tooth thickness having a tooth thickness continuously decreasing axially inwardly from the second outer thickest tooth portion; wherein the second inner portion occupies 80% or more of an axial portion of the second outer tooth portion as the tooth thickness decreases. A bending engagement type transmission device comprising: a wave generator; an outer gear that is bent and deformed by the wave generator; a first inner gear meshing with the outer gear; and a second inner gear arranged so as to be aligned with the first inner gear in an axial direction and mesh with the outer gear, wherein the second inner gear includes a second inner gear portion which meshes with a second outer gear portion of the outer gear and has the number of teeth that is the same as that of the second outer gear portion, wherein the second inner tooth portion includes an inner thickest tooth portion having a maximum tooth thickness and an inner portion of decreasing tooth thickness having a tooth thickness continuously decreasing axially inward from the inner thickest tooth portion, and wherein the inner portion occupies 80% or more of an axial portion of the second inner tooth portion as the tooth thickness decreases.

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