POWER TRANSMISSION DEVICE AND METHOD FOR MANUFACTURING POWER TRANSMISSION DEVICE

Abstract

Power transmission device (10), comprising: a rotating shaft (50); a support element (52A, 52B, 52C, 52D, 52E) which is arranged outside the rotating shaft (50) in a radial direction; a bearing (54A, 54B, 54C, 54D, 54E) arranged between the rotating shaft (50) and the support element (52A, 52B, 52C, 52D, 52E); and a fitting element (56A, 56B, 56C, 56D) that is adapted to an outer circumferential section of the support element (52A, 52B, 52C, 52D, 52E), wherein the fitting element (56A, 56B, 56C, 56D) is made of a material that has a lower hygroscopicity than the hygroscopicity of a material of the support element (52A, 52B, 52C, 52D, 52E), the support element (52A, 52B, 52C, 52D, 52E) is made of a resin-based material, and the fitting element (56A, 56B, 56C, 56D) is a gear made of a resin-based material which has lower hygroscopicity than the hygroscopicity of the resin-based material which forms the support element (52A, 52B, 52C, 52D, 52E).

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present disclosure relates to a power transmission device. Description of the state of the art

[0002] Japanese Unexamined Patent Publication No. 2018-155313 discloses a power transmission device including a rotary shaft; a support member disposed outside the rotary shaft in a radial direction; and a bearing disposed between the support member and the rotary shaft. According to JP 2020-190306 A, such a power transmission device further includes a fitting member. SUMMARY OF THE INVENTION

[0003] The inventors of this application have investigated the power transmission device and, as a result, have identified the following new problems. The support member of the power transmission device may expand due to moisture absorption, depending on the material of the support member. When the support member expands due to moisture absorption, the support member typically tends to bulge and deform excessively in a radially outward direction. As a result, a gap between the support member and the bearing widens, causing a reduction in the support rigidity of the bearing, which is a problem. A technique to address this problem has not yet been proposed, and a proposal for the technique is desired.

[0004] One of the objects of the present disclosure is to provide a technique capable of increasing support rigidity of a bearing when a support member expands due to moisture absorption.

[0005] This object is achieved by a power transmission device according to claim 1 and a method according to claim 7. A power transmission device of the present disclosure includes: a rotary shaft; a support member disposed outside the rotary shaft in a radial direction; a bearing disposed between the rotary shaft and the support member; and a fitting member fitted to an outer peripheral portion of the support member. The fitting member is made of a material having a lower hygroscopicity than a hygroscopicity of a material of the support member.

[0006] According to the present disclosure, it is possible to increase the support rigidity of the bearing when the support member expands due to moisture absorption. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is a side cross-sectional view of a power transmission device of a first embodiment. Fig. 2A is a view showing a state in which a support member of a reference mold is expanded, and Fig. 2B is a view showing a state in which a support member of the first embodiment is expanded. Fig. 3 is a psychrometric chart showing temperature and humidity in a use environment of the power transmission device. Fig. 4 is a view showing a state in the middle of a fitting process for the support member and a fitting member. Fig. 5 is a side cross-sectional view of a power transmission device of a second embodiment. Fig. 6 is a side cross-sectional view of a power transmission device of a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Embodiments are described below. The same components are denoted by the same reference numerals, and duplicate descriptions are avoided. In each drawing, components are omitted, enlarged, or reduced where appropriate to simplify description. The drawings should be viewed according to the directions of reference numerals. (First embodiment)

[0008] With reference to Fig. 1, a power transmission device 10 of the present embodiment is a gear device. The power transmission device 10 includes a drive shaft 12; a gear mechanism 14 that transmits rotation of the drive shaft 12; an output member 16 that outputs output rotation extracted from the gear mechanism 14 to a driven machine; and a housing 18 that houses the gear mechanism 14. Furthermore, the power transmission device 10 of the present embodiment includes a first cover 20A disposed on one side in an axial direction (right side in the drawing) with respect to the gear mechanism 14, and a second cover 20B disposed on the other side in the axial direction (left side in the drawing) with respect to the gear mechanism 14. The output member 16 of the present embodiment is the second cover 20B.The drive shaft 12 functions as a rotary shaft 50 to be described later. In this description, an axial direction, a radial direction, and a circumferential direction of the rotary shaft 50 are simply referred to as an “axial direction,” a “radial direction,” and a “circumferential direction,” respectively.

[0009] The transmission mechanism 14 of the present embodiment is a flexure engagement type transmission mechanism. The transmission mechanism 14 includes an external gear 24 and internal gears 26A and 26B that mesh with each other, one of which serves as a flexure gear 22. The transmission mechanism 14 can bend and deform the flexure gear 22 to rotate one of the external gear 24 and the internal gears 26A and 26B and to extract an axial rotation component thereof from the output member 16 as output rotation. In the present embodiment, the external gear 24 serves as the flexure gear 22, and the external gear 24 can be rotated. The transmission mechanism 14 of the present embodiment is a tubular flexure engagement type transmission mechanism that uses the first internal gear 26A and the second internal gear 26B.

[0010] The drive shaft 12 is rotatable by rotational force transmitted from a drive source (not shown). The drive source is, for example, a motor, a gear motor, a machine, or the like.

[0011] The drive shaft 12 of the present embodiment is a wave generator shaft. The drive shaft 12, which is a wave generator shaft, includes a wave generator 30 that bends and deforms the flexural gear 22, and shaft portions 32 provided on both sides in the axial direction with respect to the wave generator 30. An outer peripheral shape of the wave generator 30 is an elliptical shape in a cross section perpendicular to the axial direction of the drive shaft 12. The "ellipse" in the present description is not limited to a geometrically exact ellipse, but also includes a substantially elliptical shape. An outer peripheral shape of the shaft portions 32 is a circular shape in a cross section perpendicular to the axial direction of the drive shaft 12.

[0012] The flexure gear 22 is rotatably supported by the wave generator 30 through wave generator bearings 34. The flexure gear 22 is a tubular member that exhibits flexibility. The wave generator bearings 34 correspond to a plurality of the respective internal gears 26A and 26B and are individually arranged within the respective internal gears 26A and 26B.

[0013] The first internal gear 26A is arranged on one side in the axial direction (right side in the drawing), and the second internal gear 26B is arranged on the other side in the axial direction (left side in the drawing). The first internal gear 26A has a different number of internal teeth (for example, 102) than the number of external teeth (for example, 100) of the external gear 24 serving as the flexure gear 22, and the second internal gear 26B has the same number of internal teeth as the number of external teeth of the external gear 24.

[0014] The housing 18 includes a first housing member 36, which also serves as the first internal gear 26A, and a second housing member 38, which is arranged radially outwardly of the second internal gear 26B. The first housing member 36 and the second housing member 38 are connected and integrated with each other. A main bearing 40 is arranged between the second housing member 38 and the second internal gear 26B.

[0015] The first cover 20A covers an interior of the housing 18, which houses the gear mechanism 14, from one side in the axial direction. The second cover 20B covers the interior of the housing 18, which houses the gear mechanism 14, from the other side in the axial direction. The first cover 20A is connected to the first internal gear 26A by a first screw member 42A and is integrated with the first internal gear 26A. The second cover 20B is connected to the second internal gear 26B by a second screw member 42B and is integrated with the second internal gear 26B.

[0016] An operation of the above-described power transmission device 10 will be described. When the drive shaft 12 is rotated by a drive source, the transmission mechanism 14 operates. When the transmission mechanism 14 operates, the output rotation shifted (here, reduced) relative to the rotation of the drive shaft 12 is extracted from the transmission mechanism 14 through the output member 16 and output to the driven machine.

[0017] In the power transmission device 10 using the gear mechanism 14 of a flexural engagement type, the flexural gear 22 is bent and deformed into an elliptical shape according to the shape of the wave generator 30 when the wave generator shaft, which is the drive shaft 12, rotates. When the flexural gear 22 is bent and deformed in this manner, the meshing position of the external gear 24 and the internal gear 26A changes in a rotational direction of the wave generator 30. At this time, meshing teeth of the external gear 24 and the first internal gear 26A, which differ in the number of teeth, are shifted in the circumferential direction each time the meshing position thereof makes one revolution. As a result, the external gear 24 or the first internal gear 26A (the external gear 24 in the present embodiment) rotates.In the present embodiment, since the external gear 24 and the second internal gear 26B have the same number of teeth, the external gear 24 and the second internal gear 26B are synchronized without relative rotation, even if the engagement position thereof makes one revolution. For this reason, an axial rotation component of the external gear 24 is extracted from the second cover 20B as the output member 16 by the second internal gear 26B, which is synchronized with the external gear 24.

[0018] Here, the power transmission device 10 includes the rotary shaft 50; support members 52A and 52B arranged outside the rotary shaft 50 in the radial direction; rotary shaft bearings 54A and 54B arranged between the support members 52A and 52B and the rotary shaft 50; and fitting members 56A and 56B fitted to outer peripheral portions of the support members 52A and 52B, respectively.

[0019] The rotating shaft 50 is rotatable when the power transmission device 10 is operating. The rotating shaft 50 of the present embodiment is the shaft generator shaft (drive shaft 12). The rotating shaft 50 of the present embodiment can rotate to move a driven gear 58 of the transmission mechanism 14. The driven gear 58 in the present embodiment is the flexure gear 22.

[0020] The support members 52A and 52B support the rotary shaft 50 through the rotary shaft bearings 54A and 54B, respectively. The support members 52A and 52B of the present embodiment include the first support member 52A formed from the first cover 20A and the second support member 52B formed from the second cover 20B, respectively. The support members 52A and 52B each have a disk shape as a whole. The support members 52A and 52B include respective bearing mounting portions 60 on which the rotary shaft bearings 54A and 54B are arranged.

[0021] The rotary shaft bearings 54A and 54B allow the support members 52A and 52B and the rotary shaft 50 to rotate relative to each other. The rotary shaft bearings 54A and 54B of the present embodiment include, respectively, the first rotary shaft bearing 54A disposed between the first support member 52A and the rotary shaft 50, and the second rotary shaft bearing 54B disposed between the second support member 52B and the rotary shaft 50.

[0022] The rotary shaft bearings 54A and 54B of the present embodiment each include a plurality of rolling elements 54a; an outer ring 54b and an inner ring 54c on which the plurality of rolling elements 54a roll, respectively; and a seal member 54d that seals an interior of each of the rotary shaft bearings 54A and 54B. The outer ring 54b of the present embodiment is provided separately from the support members 52A and 52B as a dedicated component for each of the rotary shaft bearings 54A and 54B. Alternatively, each of the support members 52A and 52B may also serve as the outer ring 54b. The inner ring 54c of the present embodiment is provided separately from the rotary shaft 50 as a dedicated component for each of the rotary shaft bearings 54A and 54B. Alternatively, the rotary shaft 50 may also serve as the inner ring 54c.

[0023] The fitting members 56A and 56B of the present embodiment respectively include the first fitting member 56A formed from the first internal gear 26A and the second fitting member 56B formed from the second internal gear 26B. The fitting members 56A and 56B of the present embodiment each have a disk shape as a whole.

[0024] The support members 52A and 52B include respective outer peripheral fitting portions 70 provided on outer peripheral portions of the support members 52A and 52B. The fitting members 56A and 56B include respective inner peripheral fitting portions 72 provided on inner peripheral portions of the fitting members 56A and 56B. The outer peripheral fitting portions 70 (outer peripheral portions) of the support members 52A and 52B are fitted to the respective inner peripheral fitting portions 72 (inner peripheral portions) of the fitting members 56A and 56B. Fitting positions (the outer peripheral fitting portions 70 and the inner peripheral fitting portions 72) between the support members 52A and 52B and the fitting members 56A and 56B and the rotary shaft bearings 54A and 54B supported by the support members 52A and 52B overlap each other when viewed in the radial direction.

[0025] The support members 52A and 52B include respective annular projections 74 projecting in the axial direction from axial side portions of the support members 52A and 52B toward a side on which the fitting members 56A and 56B are disposed, to which the support members 52A and 52B are fitted. The fitting members 56A and 56B include respective recessed portions 76 at axial side portions of the fitting members 56A and 56B, the recessed portions 76 being recessed in the axial direction opposite the support members 52A and 52B, which are fitted to the fitting members 56A and 56B. The annular projections 74 of the support members 52A and 52B are fitted in a tenon-like manner into the respective recessed portions 76 of the fitting members 56A and 56B.The outer peripheral fitting portions 70 of the support members 52A and 52B of the present embodiment are provided at respective outer peripheral portions of the annular projections 74, and the inner peripheral fitting portions 72 of the fitting members 56A and 56B are provided at respective inner peripheral portions of the recessed portions 76.

[0026] The support members 52A and 52B include respective through-holes 78 at central portions in the radial direction of the rotary shaft 50, with the through-holes 78 penetrating the respective support members 52A and 52B in the axial direction. Both the first support member 52A and the second support member 52B of the present embodiment also include the respective through-holes 78.

[0027] The support members 52A and 52B are respectively fixed to the fitting members 56A and 56B by the screw members 42A and 42B. The first cover 20A serving as the first support member 52A is fixed to the first internal gear 26A serving as the first fitting member 56A by the first screw member 42A. The second cover 20B serving as the second support member 52B is fixed to the second internal gear 26B serving as the second fitting member 56B by the second screw member 42B. The screw members 42A and 42B are inserted into respective insertion holes 80 of the support members 52A and 52B and are screwed into respective internal threaded holes 82 of the fitting members 56A and 56B.

[0028] In the present embodiment, both the support members 52A and 52B and the fitting members 56A and 56B are made of a resin-based material. The resin-based material mentioned here refers to a material of which the main material is resin. The resin used here is, for example, general engineering plastic, special engineering plastic, or the like. The resin-based material may be composed only of resin as a main material, or it may be composed of a composite of resin as a main material and another material. The composite material is, for example, a carbon fiber reinforced resin, a glass fiber reinforced resin, or the like.

[0029] The fitting elements 56A and 56B are made of a material having lower hygroscopicity than the support elements 52A and 52B fitted to the fitting elements 56A and 56B. The first fitting element 56A is made of a material having lower hygroscopicity than the first support element 52A. Furthermore, the second fitting element 56B is made of a material having lower hygroscopicity than the second support element 52B.

[0030] To quantitatively evaluate a high / low hygroscopicity relationship between the support members 52A and 52B and the fitting members 56A and 56B, a moisture absorption rate obtained by a measurement test in accordance with Method A of JIS K7209 can be used. In the measurement test, a test piece cut to a predetermined dimension is first prepared. The test piece is cut into a square flat plate shape or a curved plate shape specified in JIS K7209. Next, the test piece is dried in an oven set at 50.0 ± 2.0 °C for 24 ± 1 hours. A mass m1 (mg) of the test piece immediately after drying is measured. The test piece is then placed in a desiccator, cooled to room temperature, and then immersed in distilled water at 23.0 °C ± 1.0 °C for 24 ± 1 hours. The mass m2 (mg) of the test piece immediately after immersion is measured.A moisture absorption rate c (%) can be obtained from the following equation (1) using the masses m1 and m2. c={(m2−m1) / m1}×100

[0031] The measurement test assumes that a resin-made element is the measurement target. However, a material with hygroscopicity other than resin can also be measured for a moisture absorption rate as a measurement target of the same measurement test. Furthermore, if a material to be measured (for example, a metal such as steel) does not exhibit hygroscopicity, the moisture absorption rate can be considered zero.

[0032] The fitting members 56A and 56B of the present embodiment are made of, for example, a material having a moisture absorption rate of 1 / 2 or less of the moisture absorption rate of the material of the support members 52A and 52B. When this condition is met, the moisture absorption rate of the fitting members 56A and 56B can be zero. When this condition is met, the support members 52A and 52B are made of, for example, a resin such as polyamide (PA) or polyphthalamide (PPA). Further, the fitting members 56A and 56B are made of, for example, a resin such as polyetheretherketone (PEEK). The moisture absorption rate in the case of using PEEK is, for example, 0.1 or less, and the moisture absorption rate in the case of using PA is, for example, 1.3 to 2.5.

[0033] A high / low hygroscopicity relationship between the first fitting member 56A and the second fitting member 56B does not play a particular role. The first fitting member 56A and the second fitting member 56B of the present embodiment have the same hygroscopicity (the same moisture absorption rate), but both may differ in hygroscopicity. Similarly, a high / low hygroscopicity relationship between the first support member 52A and the second support member 52B does not play a particular role. The first support member 52A and the second support member 52B have the same hygroscopicity (the same moisture absorption rate), but both may differ in hygroscopicity.

[0034] The power transmission device 10 is a combination of resin elements made of a resin-based material and metal elements made of a metal-based material. The resin elements of the present embodiment are the housing 18, the covers 20A and 20B, the internal gears 26A and 26B, and the like. The metal elements of the present embodiment are the drive shaft 12 (rotation shaft 50), the flexure gear 22 (external gear 24), the shaft generator bearings 34, the main bearing 40, the rotation shaft bearings 54A and 54B, and the like.

[0035] The metal-based material mentioned here refers to a material whose main material is metal. The metal used here is, for example, an iron-based material such as cast iron or steel, or an aluminum-based material such as an aluminum alloy. The metal-based material may consist of only metal as a main material, or it may consist of a composite of metal as a main material and another material. The composite material mentioned here is, for example, an alloy, a fiber-reinforced metal, or the like. A metal-based material with higher thermal conductivity than a resin-based material may be used.

[0036] In the present embodiment, the resin members other than the fitting members 56A and 56B may be made of resin only. Since the fitting members 56A and 56B mesh with the external gear 24, which is a metal member, the fitting members 56A and 56B are made of PEEK containing carbon fiber from the viewpoint of improving strength. The metal members of the present embodiment are made of metal only (specifically, steel). Accordingly, metal members with higher thermal conductivities than those of the resin members are used together with the resin members, so that heat generated within the power transmission device 10 can be easily transferred through the metal members. Consequently, the number of heat dissipation sites in the power transmission device 10 is increased, so that good heat dissipation can be achieved.

[0037] Effects of the above-described power transmission device 10 will be described.

[0038] With reference to Fig. 2A, a configuration of the first support member 52A, the first rotary shaft bearing 54A, and the first fitting member 56A and the second support member 52B, the second rotary shaft bearing 54B, and the second fitting member 56B will be described below with reference to the drawings. Fig. 2A and the like, for the convenience of description, states before and after bulging and deforming of the support member 52A are shown in an exaggerated manner.

[0039] Consider a case where the support members 52A and 52B tend to expand due to moisture absorption in a state where the deformation of the support members 52A and 52B is not restricted by other members. In this case, generally, the entirety of the support members 52A and 52B tends to bulge and deform in a radially outward direction Da. Fig. In FIG. 2A, the state before warping is shown by a line alternating between one long and two short dashes, and the state after warping is shown by a solid line. Due to warping, the bearing assembly portions 60 of the support members 52A and 52B are displaced in the radially outward direction. Accordingly, a gap between the support members 52A and 52B and the rotary shaft bearings 54A and 54B widens, causing a decrease in the support rigidity of the rotary shaft bearings 54A and 54B. In particular, the higher the absolute humidity of the use environment becomes, the greater the amount of warping of the support members 52A and 52B in the radially outward direction becomes.As a result, the higher the humidity of the use environment becomes, the wider the gap between the rotary shaft bearings 54A and 54B and the support members 52A and 52B becomes, so that the support rigidity of the rotary shaft bearings 54A and 54B is likely to decrease.

[0040] With reference to Fig. 2B, since the power transmission device 10 of the present embodiment includes the fitting members 56A and 56B respectively fitted to the outer peripheral portions of the support members 52A and 52B, and the fitting members 56A and 56B are made of a material having lower hygroscopicity than the support members 52A and 52B, the following advantages are achieved.

[0041] (A) Consider a case where the support members 52A and 52B and the fitting members 56A and 56B tend to expand in a fitted state due to moisture absorption, so that the outer peripheral fitting portions 70 of the support members 52A and 52B and the inner peripheral fitting portions 72 of the fitting members 56A and 56B tend to bulge and deform in the radially outward direction. In this case, since the fitting members 56A and 56B have lower hygroscopicity than the support members 52A and 52B, an expansion amount of the fitting members 56A and 56B caused by moisture absorption is smaller than an expansion amount of the support members 52A and 52B caused by moisture absorption.For this reason, a displacement amount of the inner peripheral fitting portions 72 of the fitting members 56A and 56B in the radially outward direction is smaller than a displacement amount of the outer peripheral fitting portions 70 of the support members 52A and 52B in the radially outward direction. As a result, the camber deformation of the support members 52A and 52B, which tends to cause the displacement amount of the outer peripheral fitting portions 70 to be greater than the displacement amount of the inner peripheral fitting portions 72, is restricted by the inner peripheral fitting portions 72.

[0042] The warpage deformation of the support members 52A and 52B in the radially outward direction is restricted in such a way that the support members 52A and 52B can bulge and deform to deflect in a radially inward direction Db. For this reason, the bearing assembly portions 60 of the support members 52A and 52B can be displaced in the radially inward direction. As a result, a gap around the rotary shaft bearings 54A and 54B between the support members 52A and 52B and the rotary shaft 50 can be closed. The "gap around the rotary shaft bearings 54A and 54B" mentioned here refers to the gap between the rotary shaft bearings 54A and 54B and the support members 52A and 52B, and to a gap between the rotary shaft bearings 54A and 54B and the rotary shaft 50.

[0043] The gap around the rotary shaft bearings 54A and 54B is closed in such a way that the interference of the rotary shaft bearings 54A and 54B with the support members 52A and 52B and with the rotary shaft 50 can be increased. As a result, when the support members 52A and 52B expand due to moisture absorption, the support rigidity of the rotary shaft bearings 54A and 54B can be increased. Consequently, the shaft runout of the rotary shaft 50 supported by the rotary shaft bearings 54A and 54B can be reduced.

[0044] Furthermore, according to the present embodiment, the higher the absolute humidity of the use environment becomes, the greater the amount of warpage deformation of the support member 52A in the radially inward direction is likely to become. Therefore, even if the absolute humidity of the use environment has increased, the state in which the gap around the rotary shaft bearings 54A and 54B is closed is maintained, so that the state in which the support rigidity of the rotary shaft bearings 54A and 54B is increased can be maintained, which is an advantage.

[0045] Furthermore, as in the present embodiment, when the driven gear 58 is moved by the rotating shaft 50, the shaft runout of the rotating shaft 50 is reduced, so that an engagement state between the driven gear 58 and other gears (here, the external gear 24 and the internal gears 26A and 26B) can be stabilized. Accordingly, contact pressure on the tooth surfaces of the driven gear 58 and the other gears can be made uniform, and the service life thereof can be extended.

[0046] Furthermore, when each of the support members 52A and 52B and the fitting members 56A and 56B is made of a resin-based material, the higher the hygroscopicity, the lower the component cost is. Therefore, compared to when the support members 52A and 52B are made of a resin-based material with the same hygroscopicity as the fitting members 56A and 56B, the component cost is likely to be reduced to the extent that a material with high hygroscopicity is used for the support members 52A and 52B, which is also an advantage.

[0047] (B) The support members 52A and 52B are made of a resin-based material, and the fitting members 56A and 56B are gears made of a resin-based material with lower hygroscopicity than that of the resin-based material constituting the support members 52A and 52B. Therefore, when the power transmission device 10 is a gear device, a weight reduction of the gear device can be achieved compared to when the fitting members 56A and 56B and the support members 52A and 52B are made of a metal-based material.

[0048] (C) The support members 52A and 52B include the respective through-holes 78 at the center portions in the radial direction, and the through-holes 78 penetrate the respective support members 52A and 52B in the axial direction. Therefore, when the support members 52A and 52B tend to bulge and deform in the radial inward direction due to expansion caused by moisture absorption, the bulging deformation is unlikely to be restrained by itself. As a result, the support members 52A and 52B are likely to bulge and deform in the radial inward direction, so that the gap around the rotary shaft bearings 54A and 54B can be easily closed.

[0049] (D) The fitting positions (outer peripheral fitting portions 70 and inner peripheral fitting portions 72) between the support members 52A and 52B and the fitting members 56A and 56B, and the rotary shaft bearings 54A and 54B overlap each other when viewed in the radial direction. Therefore, in a state where the warpage deformation in the radially outward direction is kept restricted at the fitting positions between the fitting members 56A and 56B and the support members 52A and 52B, the bearing assembly portions 60 of the support members 52A and 52B are likely to be displaced straight inward along the radial direction. Consequently, a radial load not considered in the design is unlikely to be applied from the bearing arrangement portions 60 of the support members 52A and 52B to the rotary shaft bearings 54A and 54B, and the rotary shaft 50 is easily and stably supported by the rotary shaft bearings 54A and 54B.

[0050] Next, other inventive points of the power transmission device 10 will be described. In the power transmission device 10 of the present embodiment, in an environment where the absolute humidity is 0.003 (kg / kg) or higher, the support members 52A and 52B expand due to moisture absorption in a state where the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other, so that a tightening load F (see Fig. 2B) acts from the support members 52A and 52B to the rotary shaft bearings 54A and 54B. The tightening load F acts from the support members 52A and 52B in the radial direction inward. This means that the tightening load F acts due to expansion caused by the moisture absorption of the support members 52A and 52B in the environment where the absolute humidity is 0.003 or higher. This condition is met at least when the support members 52A and 52B and the fitting members 56A and 56B are in an equilibrium state in which the moisture absorption amount does not change in the environment where the absolute humidity is 0.003 or higher and the atmospheric pressure is normal atmospheric pressure (= 1.0 atm).

[0051] The support members 52A and 52B expand due to moisture absorption compared to the outer dimensions immediately after fitting the support members 52A and 52B and the fitting members 56A and 56B in an assembly process (to be described later) of assembling the power transmission device 10, so that the tightening load F acts. In a case where the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other by tightening, the tightening load from the support members 52A and 52B can act on the rotary shaft bearings 54A and 54B even if there is no expansion of the support members 52A and 52B caused by moisture absorption. In this case, in the environment described above, the support members 52A and 52B may bulge and deform further in the radially inward direction compared to immediately after the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other, so that the tightening load F increases.

[0052] With reference to Fig. 3 shows Fig. 3 shows a psychrometric diagram in an environment with normal atmospheric pressure. In the use environment of the power transmission device 10, the temperature is normally in a range of 15 °C to 30 °C, and the relative humidity (RH) is in a range of 30% to 70%. A hatched area in Fig. 3 indicates the usage environment, and the absolute humidity is in a range of 0.003 or higher. Therefore, when the tightening load F acts in the environment where the absolute humidity is 0.003 or higher, it is possible to make the tightening load F act in a normal usage environment regardless of the temperature and relative humidity.

[0053] Consider a case where the temperatures of a use environment and an installation environment of the power transmission device 10 are the same specific temperature. In this case, the support members 52A and 52B may expand at the specific temperature due to moisture absorption in an environment where the relative humidity is 30% or higher, so that the tightening load F acts on the rotary shaft bearings 54A and 54B. This means that the support members 52A and 52B may expand at the specific temperature due to moisture absorption in the environment where the relative humidity is 30% or higher, so that the tightening load F acts on the rotary shaft bearings 54A and 54B.For example, if the temperature in the use environment and the assembly environment are the same, it is assumed that both the use environment and the assembly environment are temperature-controlled environments. Accordingly, it is possible to apply the tightening load F at the specific temperature regardless of the relative humidity (30% to 70%) in the normal use environment.

[0054] Next, a method for manufacturing the above-described power transmission device 10 will be described.

[0055] First, a drying process of drying at least the support elements 52A and 52B is performed. During the drying process, it is irrelevant whether other components (e.g., the fitting elements 56A and 56B) of the power transmission device 10 need to be dried or not.

[0056] The specific example of a method for drying an object to be dried in the drying process is not particularly limited. The object to be dried can be dried, for example, by leaving it in an environment in which the object to be dried can be dried. Assume that the drying method is, for example, vacuum drying, constant humidity drying, or the like. In the case of vacuum drying, the object to be dried is dried by leaving it in a vacuum environment depressurized by vacuum drying. In the case of constant humidity drying, the object to be dried is dried by leaving it in a constant humidity environment controlled to a predetermined humidity.In addition to these methods, the object to be dried can be dried by supplying a drying-accelerating medium to the object to be dried to promote drying. This method is assumed to be, for example, hot air drying, far-infrared drying, ultrasonic drying, or the like. The drying-accelerating medium is, for example, hot air in hot air drying, a far-infrared ray in far-infrared drying, and an ultrasonic wave in ultrasonic drying.

[0057] A predetermined humidity assumed in the use environment of the power transmission device 10 is referred to as a reference humidity. The reference humidity is, for example, a lower limit humidity of an absolute humidity range assumed in the use environment, but may be a humidity higher than the lower limit humidity. Furthermore, a moisture absorption amount of the support members 52A and 52B when they are in an equilibrium state in an environment having the reference humidity is referred to as a reference moisture absorption amount. In this case, in the drying process, the support members 52A and 52B are dried to have a moisture absorption amount smaller than the reference moisture absorption amount.Accordingly, the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other in the subsequent assembly process, and then simply left in a usage environment where the humidity is the reference humidity or higher, so that the support members 52A and 52B can absorb moisture until the moisture absorption amount reaches the reference moisture absorption amount. Consequently, the support members 52A and 52B can stably expand due to moisture absorption compared to the external dimensions immediately after the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other.As described above, when the power transmission device 10 is used in the use environment where the absolute humidity is 0.003 or higher, in the drying process, the support members 52A and 52B can be dried so that the moisture absorption amount is lower than the moisture absorption amount (reference moisture absorption amount) of the support members 52A and 52B when they are in an equilibrium state in an environment where the absolute humidity is 0.003 (reference humidity).

[0058] Next, the assembly process of assembling the power transmission device 10 is performed using the components of the power transmission device 10. Referring to Fig. 4, the assembly process includes a fitting process of fitting the support members 52A and 52B, which are dried in the drying process, and the fitting members 56A and 56B. In the fitting process, the outer peripheral fitting portions 70 of the support members 52A and 52B and the inner peripheral fitting portions 72 of the fitting members 56A and 56B are fitted to each other.

[0059] In the fitting process, the support members 52A and 52B, which keep the moisture absorption amount lower than the reference moisture absorption amount, are fitted to the fitting members 56A and 56B. Fig. 4, a state after drying in the drying process is shown by a solid line, and a state before drying in the drying process is shown by a line alternating between one long and two short dashes. Since the support members 52A and 52B are dried in the drying process, compared to when the support members 52A and 52B are not dried, the amount of warpage deformation in the radially outward direction when the support members 52A and 52B expand due to moisture absorption can be reduced, and the outer peripheral fitting portions 70 of the support members 52A and 52B can be displaced in the radially inward direction.Consequently, in comparison with when the support members 52A and 52B are not dried, when the support members 52A and 52B and the fitting members 56A and 56B are fitted to each other, work can be performed in a state where the interference between them is reduced or in a state where the gap between them is left, and good workability can be obtained.

[0060] Apart from that, the assembly process is the same as an assembly process used in a normal method for manufacturing the power transmission device 10. That is, the power transmission device 10 is assembled using an intermediate product obtained by fitting the support members 52A and 52B and the fitting members 56A and 56B, and the other components of the power transmission device 10. Since this process itself is known, a detailed description thereof will not be repeated. (Second embodiment)

[0061] With reference to Fig. 5, the power transmission device 10 of the present embodiment includes a first carrier 100A disposed on one side in the axial direction (right side in the drawing) with respect to the gear mechanism 14; a second carrier 100B disposed on the other side in the axial direction (left side in the drawing) with respect to the gear mechanism 14; and a cover 20C disposed on one side in the axial direction with respect to the first carrier 100A, in addition to the input shaft 12, the gear mechanism 14, the output member 16, and the housing 18 described above. The output member 16 of the present embodiment is the second carrier 100B.

[0062] The gear mechanism 14 of the present embodiment differs from that of the first embodiment in that the gear mechanism 14 is an eccentric oscillating type gear mechanism. The gear mechanism 14 includes the external gear 24 and an internal gear 26C meshing with each other, one of which serves as an oscillating gear 106. The gear mechanism 14 can oscillate the oscillating gear 106 to rotate one of the external gear 24 and the internal gear 26C and extract an axial rotation component thereof from the output member 16 as output rotation. In the present embodiment, the external gear 24 serves as the oscillating gear 106, and the external gear 24 can be rotated.

[0063] The drive shaft 12 of the present embodiment is a crankshaft including a plurality of eccentric bodies 108. The eccentric bodies 108 have axial centers CL2 eccentric with respect to a rotational center line CL1 of the drive shaft 12 and can rotate about the rotational center line CL1 to oscillate the oscillating gear 106 (external gear 24). The plurality of eccentric bodies 108 have different eccentric phases from each other. When the number of eccentric bodies 108 is M (two in the present embodiment), the eccentric phases of the plurality of eccentric bodies 108 are offset from each other by (360° / M). The number of eccentric bodies 108 is not particularly limited and can be one, three, or more.

[0064] The oscillating gear 106 is individually provided to correspond to each of the plurality of eccentric bodies 108 and is rotatably supported by the corresponding eccentric body 108 through an eccentric body bearing 110.

[0065] The internal gear 26C of the present embodiment is integrated with the housing 18. The main bearing 40 is arranged between the housing 18 and the carriers 100A and 100B.

[0066] The carriers 100A and 100B are integrated with a plurality of pins 112 projecting from the carriers 100A and 100B in the axial direction. The plurality of pins 112 penetrate the external gear 24 in an axial direction X and can synchronize the axial rotation component of the external gear 24 with the carriers 100A and 100B. The "synchronization with the axial rotation component" mentioned here refers to maintaining the axial rotation component of the external gear 24 and the axial rotation components of the carriers 100A and 100B at the same magnitude within a numerical range including zero.

[0067] An operation of the above-described power transmission device 10 will be described. In the present embodiment, the oscillating gear 106 is oscillated by the eccentric bodies 108 of the crankshaft constituting the drive shaft 12. As the oscillating gear 106 oscillates, an engagement position of the external gear 24 and the internal gear 26C changes in the circumferential direction. As a result, one (in the present embodiment, the external gear 24) of the external gear 24 and the internal gear 26C rotates, and an axial rotation component thereof is extracted from the output member 16 as output rotation.

[0068] The power transmission device 10 of the present embodiment includes, in addition to the above-described rotary shaft 50, a support member 52C, a rotary shaft bearing 54C, and a fitting member 56C. A main function of the support member 52C, the rotary shaft bearing 54C, and the fitting member 56C is common to that of a combination of the support member 52A, the rotary shaft bearing 54A, and the fitting member 56A described in the first embodiment. Differences will be mainly described below.

[0069] The rotating shaft 50 of the present embodiment is a crankshaft (drive shaft 12). The driven gear 58, which is moved by the rotation of the rotating shaft 50 of the present embodiment, is the oscillating gear 106.

[0070] The support member 52C of the present embodiment is the second carrier 100B (driven member 16). The second carrier 100B of the present embodiment is made of a resin-based material, for example, a resin such as polyamide (PA) or polyphthalamide (PPA). The support member 52C includes a bearing arrangement portion 114 provided at an outer peripheral portion of the support member 52C, on which the main bearing 40 is arranged. The support member 52C of the present embodiment does not include the through-hole 78 described in the first embodiment, but includes a central recessed portion 116 recessed in the axial direction at a central portion of the support member in the radial direction. The bearing arrangement portion 60 of the support members 52A and 52B is provided at an inner peripheral portion of the central recessed portion 116.

[0071] The rotary shaft bearing 54C is arranged between the support member 52C and the rotary shaft 50.

[0072] The fitting member 56C of the present embodiment is formed from the main bearing 40, which is arranged between the housing 18 and the second carrier 100B. The main bearing 40 includes a plurality of rolling elements 40a and an outer ring 40b and an inner ring 40c, on which the rolling elements 40a roll, respectively. The outer ring 40b of the present embodiment is provided separately from the housing 18 as a dedicated component for the main bearing 40. The inner ring 40C of the present embodiment is provided separately from the support member 52C as a dedicated component for the main bearing 40.

[0073] The outer peripheral fitting portion 70 of the support member 52C is formed from the bearing assembly portion 114 of the support member 52C. The inner peripheral fitting portion 72 of the fitting member 56C is provided on an inner peripheral portion of the inner ring 40c of the main bearing 40. Also in the present embodiment, the inner peripheral fitting portion 72 of the fitting member 56C and the outer peripheral fitting portion 70 of the support member 52C are fitted to each other.

[0074] The main bearing 40, which forms the fitting member 56C, is made of a metal-based material. In the present embodiment, the rolling elements 40a, the outer ring 40b, and the inner ring 40c of the main bearing 40 are all made of a metal-based material, particularly steel. As described above, the fitting member may have lower hygroscopicity than the support member. The specific example of the material is not limited to a resin-based material, and the fitting member may be made of a metal-based material as in the present embodiment.

[0075] The power transmission device 10 of the present embodiment also includes the fitting member 56C fitted to the outer peripheral portion of the support member 52C, and the fitting member 56C is made of a material having lower hygroscopicity than that of the support member 52C. Therefore, similar to the description in (A) of the first embodiment, the support rigidity of the rotary shaft bearing 54C can be increased.

[0076] The power transmission device 10 of the present embodiment also further includes the components described in (D) described above, and an effect corresponding to the description can be obtained.

[0077] Furthermore, according to the present embodiment, the warpage deformation of the support member 52C is restricted by using the main bearing 40 made of a metal-based material and constituting the fitting member 56C, so that, similar to the above description, the support rigidity of the rotary shaft bearing 54C can be increased. From the viewpoint of obtaining such an effect, the bearing constituting the fitting member 56C is not limited to the main bearing 40 and may be another bearing.

[0078] The power transmission device 10 of the present embodiment is also a combination of resin elements and metal elements. The resin elements of the present embodiment are the oscillating gear 106 (external gear 24), the first carrier 100A, the second carrier 100B, and the housing 18. The metal elements of the present embodiment are the crankshaft (rotating shaft 50), the rotating shaft bearing 54C, the internal gear 26C, and the like. (Third embodiment)

[0079] With reference to Fig. 6, the power transmission device 10 of the present embodiment is a motor device. The power transmission device 10 includes a rotor shaft 120; a motor 122 that generates a rotating magnetic field to rotate the rotor shaft 120; a motor housing 124 to which a stator 128 of the motor 122 is fixed; and covers 20D and 20E that cover the motor 122 in the axial direction. The covers 20D and 20E respectively include the first cover 20D disposed on one side in the axial direction (counter-load side and the right side in the drawing) with respect to the motor 122, and the second cover 20E disposed on the other side in the axial direction (load side and the left side in the drawing) with respect to the motor 122.

[0080] The rotor shaft 120 can output rotational power to a driven device. The motor 122 includes the stator 128 and a rotor 130 that rotates integrally with the rotor shaft 120.

[0081] The power transmission device 10 of the present embodiment also includes the above-described rotary shaft 50, support members 52D and 52E, rotary shaft bearings 54D and 54E, and a fitting member 56D. A main function of the support member 52D, the rotary shaft bearing 54D, and the fitting member 56D is common to that of a combination of the support member 52A, the rotary shaft bearing 54A, and the fitting member 56A described in the first embodiment. Furthermore, a main function of the support member 52E, the rotary shaft bearing 54E, and the fitting member 56D is common to that of a combination of the support member 52B, the rotary shaft bearing 54B, and the fitting member 56B described in the first embodiment. Differences will be mainly described below.

[0082] The rotating shaft 50 of the present embodiment is the rotor shaft 120.

[0083] The support members 52D and 52E of the present embodiment are the covers 20D and 20E. The covers 20D and 20E of the present embodiment are made of a resin-based material, for example, a resin such as polyamide (PA) or polyphthalamide (PPA). The support members 52D and 52E respectively include the first support member 52D, which is the first cover 20D, and the second support member 52E, which is the second cover 20E. Both the first support member 52D and the second support member 52E include respective through-holes 78, similar to the support members 52A and 52B of the first embodiment.

[0084] The rotary shaft bearings 54D and 54E respectively include the first rotary shaft bearing 54D disposed between the support member 52D and the rotary shaft 50, and the second rotary shaft bearing 54E disposed between the support member 52E and the rotary shaft 50.

[0085] The fitting member 56D of the present embodiment is the motor housing 124. The motor housing 124 of the present embodiment is made of a metal-based material, for example, an aluminum alloy.

[0086] The outer peripheral fitting portions 70 of the support members 52D and 52E of the present embodiment are provided at outer peripheral portions of the annular projections 74, and the inner peripheral fitting portion 72 of the fitting member 56D is provided at an inner peripheral portion of the recessed portion 76.

[0087] The power transmission device 10 of the present embodiment also includes the fitting member 56D fitted to outer peripheral portions of the support members 52D and 52E, and the fitting member 56D is made of a material with lower hygroscopicity than that of the support members 52D and 52E. Therefore, similar to the description in (A) in the first embodiment, the support rigidity of the rotary shaft bearings 54D and 54E can be increased.

[0088] The power transmission device 10 of the present embodiment also further includes the components described in (C) and (D) described above, and effects corresponding to the description can be obtained.

[0089] Further, according to the present embodiment, the warpage deformation of the covers 20D and 20E is restricted using the motor housing 124 in the motor device, so that similarly to the above description, the supporting rigidity of the rotary shaft bearings 54D and 54E can be increased.

[0090] The power transmission device 10 of the present embodiment is also a combination of resin elements and metal elements. The resin elements of the present embodiment are the first cover 20D and the second cover 20E. The metal elements of the present embodiment are the rotor shaft 120 (rotation shaft 50), the rotation shaft bearings 54D and 54E, the motor 122, the motor housing 124, and the like.

[0091] Further modification forms of each component will be described. Hereinafter, when the components (support member, etc.) are collectively referred to with "A, B, C, ..." at the ends of the reference numerals, the letters appended to the ends of the reference numerals are omitted.

[0092] The specific example of the gear mechanism 14 is not particularly limited. The gear mechanism 14 may be, for example, a planetary gear mechanism, a perpendicular-axis gear mechanism, a parallel-axis gear mechanism, or the like.

[0093] As a specific type of the eccentric oscillating type transmission mechanism, a center-crank type has been described in which the crankshaft (drive shaft 12) is arranged at an axial center of the internal gear 26. This type is not particularly limited and may, for example, be a distributor type in which a plurality of the crankshafts are arranged at respective positions offset from the axial center of the internal gear 26 in the radial direction. When the external gear 24 serves as the oscillating gear 106 in the eccentric oscillating type transmission mechanism, the housing 18 may further serve as the output member 16. Furthermore, instead of the external gear 24, the internal gear 26 may serve as the oscillating gear 106.

[0094] The tubular type has been described as a specific type of the flexure engagement type transmission mechanism. The type is not particularly limited and can be, for example, a pot type or a cylinder type. When the external gear 24 serves as the flexure gear 22 in the flexure engagement type transmission mechanism, the housing 18 can also serve as the output member 16. Furthermore, instead of the external gear 24, the internal gears 26 can also serve as the flexure gear 22.

[0095] As the rotating shaft 50, the drive shaft in the power transmission device 10 of the first and second embodiments and the rotor shaft 120 in the third embodiment were described as examples. The specific example is not particularly limited. The rotating shaft 50 may be, for example, the output shaft that outputs rotation to the driven device, or an intermediate shaft that transmits the rotation of the drive shaft to the output shaft.

[0096] The fitting member 56 may be fitted to the outer peripheral portion of the support member 52, and the specific example is not particularly limited. The "outer peripheral portion of the support member 52" mentioned here is not necessarily an outermost peripheral portion forming an outermost peripheral surface of the support member 52. For example, as shown in Fig. 1, the second support member 52B of the first embodiment includes, in addition to an outermost peripheral portion 140 constituting an outermost peripheral surface of the second support member 52B, an annular groove portion 142 provided inside the outermost peripheral portion 140 in the radial direction. An outer peripheral portion of the annular groove portion 142 constitutes the outer peripheral portion of the annular projection 74 of the second support member 52B. It is intended that the "outer peripheral portion of the support member 52B" mentioned here may be the outer peripheral portion of the annular groove portion 142 constituting the outer peripheral portion of the support member 52B.

[0097] The specific example of a combination of the support member 52 and the fitting member 56 is not particularly limited. In the example of the first embodiment, when the support member 52 serves as the cover 20, the fitting member 56 may be formed from a part of the housing 18 provided separately from the internal gear 26, or may be provided separately from the housing 18 and the internal gear 26. In the example of the second embodiment, when the support member 52 serves as the carrier 100, the fitting member 56 may be a retaining ring 144 (see Fig. 5) which limits the movement of the main bearing 40 in the axial direction.

[0098] In the first embodiment, an example was described in which a gear constituting the fitting member 56A made of a resin-based material is the internal gear 26, but the specific example is not particularly limited. The gear may be, for example, an external gear, a bevel gear, or the like.

[0099] When the fitting element 56 serves as a bearing, the specific example of the material is not limited to a metal-based material. The material may, for example, be a resin-based material.

[0100] The support member 52 may expand due to moisture absorption in an environment where the absolute humidity is less than 0.003, so that the tightening load F acts from the support member 52 to the rotary shaft bearing 54.

[0101] The support member 52 of the first and third embodiments may not include the through-hole 78, and the support member 52 of the second embodiment may include the through-hole 78.

[0102] The fitting position between the support member 52 and the fitting member 56 and the rotary shaft bearing 54 may not overlap each other when viewed in the radial direction.

[0103] The power transmission device 10 to which the manufacturing method described in the first embodiment is applied is not particularly limited. The manufacturing method can be used for the power transmission device 10 of the second and third embodiments, and can be used for other power transmission devices 10.

[0104] The embodiments and modifications described above are provided as examples. The technical concept abstracted from the embodiments and modifications should not be construed as being limited to the contents of the embodiments and modifications. Various design changes, such as changing, adding, and omitting components, can be made to the contents of the embodiments and modifications. In the embodiments described above, contents to which such design changes can be made are highlighted with a designation "Embodiment." However, design changes to contents without such a designation are also permitted. The hatching applied to the cross-sections of the drawings does not limit the material of a hatched object.The structures and numerical values ​​mentioned in the embodiments and modification forms naturally include those that can be considered equivalent taking into account manufacturing errors and the like. Brief description of the reference symbols 10 Power transmission device 20A, 20B, 20C, 20D, 20E cover 26A, 26B gear 50 rotating shaft 52A, 52B, 52C, 52D, 52E support element 54A, 54B, 54C, 54D, 54E bearings 56A, 56B, 56C, 56D fitting element 78 through hole 122 engine 124 engine housing 128 Stator

Claims

[1] Power transmission device (10), comprising: a rotating shaft (50); a support member (52A, 52B, 52C, 52D, 52E) arranged outside the rotary shaft (50) in a radial direction; a bearing (54A, 54B, 54C, 54D, 54E) arranged between the rotary shaft (50) and the support member (52A, 52B, 52C, 52D, 52E); and a fitting element (56A, 56B, 56C, 56D) adapted to an outer peripheral portion of the support element (52A, 52B, 52C, 52D, 52E), wherein the fitting element (56A, 56B, 56C, 56D) is made of a material having lower hygroscopicity than the hygroscopicity of a material of the support element (52A, 52B, 52C, 52D, 52E), the support element (52A, 52B, 52C, 52D, 52E) is made of a resin-based material, and the fitting element (56A, 56B, 56C, 56D) is a gear made of a resin-based material having lower hygroscopicity than the hygroscopicity of the resin-based material forming the support element (52A, 52B, 52C, 52D, 52E). [2] The power transmission device (10) according to claim 1, wherein the fitting member (56A, 56B, 56C, 56D) is a bearing made of a metal-based material. [3] Power transmission device (10) according to claim 1, wherein the support member (52A, 52B, 52C, 52D, 52E) is a cover covering a motor (122) in an axial direction, and the fitting element (56A, 56B, 56C, 56D) is a motor housing (124) to which a stator (128) of the motor (122) is attached. [4] The power transmission device (10) according to any one of claims 1 to 3, wherein in an environment where an absolute humidity is 0.003 (kg / kg) or higher, the support member (52A, 52B, 52C, 52D, 52E) expands due to moisture absorption in a state where the support member (52A, 52B, 52C, 52D, 52E) and the fitting member (56A, 56B, 56C, 56D) are fitted to each other, so that a tightening load from the support member (52A, 52B, 52C, 52D, 52E) acts on the bearing (54A, 54B, 54C, 54D, 54E). [5] The power transmission device (10) according to any one of claims 1 to 4, wherein the support member (52A, 52B, 52C, 52D, 52E) includes a through hole (78) at a central portion in the radial direction of the rotary shaft (50), the through hole (78) penetrating through the support member (52A, 52B, 52C, 52D, 52E) in an axial direction. [6] The power transmission device (10) according to any one of claims 1 to 5, wherein a fitting position between the support member (52A, 52B, 52C, 52D, 52E) and the fitting member (56A, 56B, 56C, 56D) and the bearing (54A, 54B, 54C, 54D, 54E) overlap each other when viewed in the radial direction of the rotary shaft (50). [7] A method of manufacturing the power transmission device (10) according to any one of claims 1 to 6, the method comprising: a drying process of drying at least the support element (52A, 52B, 52C, 52D, 52E); and a fitting process of fitting the support member (52A, 52B, 52C, 52D, 52E) dried in the drying process and the fitting member (56A, 56B, 56C, 56D) together.

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