JP2019183981A - Damping device - Google Patents

Abstract

To provide a new structure of a damping device.SOLUTION: A shaft member 11 comprises a shaft part 11a, a first spherical body part 11b provided at one end of the shaft part, and a second spherical body part 11c provided at another end of the shaft part. A first receiving member 12 comprises a concave first spherical surface part 12a for receiving the first spherical body part. A second receiving member 13 comprises a concave second spherical surface part 13a for receiving the second spherical body part. A first viscoelastic body 14 is arranged between the first spherical body part and the first spherical surface part, and deforms depending on a relative displacement between the first spherical body part and the first spherical surface part. A second viscoelastic body 15 is arranged between the second spherical body part and the second spherical surface part, and deforms depending on a relative displacement between the second spherical body part and the second spherical surface part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vibration damping device.

  For example, Japanese Patent Application Laid-Open No. 2011-190879, Japanese Patent Application Laid-Open No. 2001-207552, Japanese Patent Application Laid-Open No. 2001-107600, and the like have been proposed as vibration damping devices that can exhibit a damping force with respect to displacement between support members. Yes. In addition, since the structure of the damping device disclosed by these differs from the damping device proposed in this application, detailed description is abbreviate | omitted.

JP 2011-190879 A JP 2001-207552 A JP 2001-107600 A

  We propose a new structure of damping device that can exert damping force against displacement between support members.

The vibration damping device proposed here includes a shaft member, a first receiving member, a second receiving member, a first viscoelastic body, and a second viscoelastic body.
The shaft member includes a shaft portion, a first sphere portion provided at one end of the shaft portion, and a second sphere portion provided at the other end of the shaft portion.
The first receiving member has a concave first spherical surface portion that receives the first spherical body portion.
The second receiving member has a recessed second spherical surface portion that receives the second sphere portion.
A 1st viscoelastic body is arrange | positioned between a 1st spherical body part and a 1st spherical surface part, and deform | transforms according to the relative displacement of a 1st spherical body part and a 1st spherical surface part.
The second viscoelastic body is disposed between the second sphere portion and the second spherical portion, and is deformed in accordance with the relative displacement between the second sphere portion and the second spherical portion.

  According to the vibration damping device, the first viscoelastic body and the second viscoelastic body are deformed according to the relative displacement between the first receiving member and the second receiving member, and the displacement is suppressed to be small, and This contributes to early damping of vibrations associated with the displacement.

FIG. 1 is a front view of a vibration damping device 10 proposed here. FIG. 2 is a front view of the vibration damping device 10 in which the opposing support members A1 and A2 are relatively displaced in the horizontal direction. FIG. 3 is a front view showing another embodiment of the vibration damping device 10.

  Hereinafter, the damping device proposed here will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment. Each drawing is drawn schematically and does not necessarily reflect the real thing. Each drawing shows only an example and does not limit the present invention unless otherwise specified. Moreover, the same code | symbol is suitably attached to the member and site | part which show | plays the same effect | action, and the overlapping description is abbreviate | omitted.

FIG. 1 is a front view of a vibration damping device 10 proposed here.
The vibration damping device 10 proposed here includes a shaft member 11, a first receiving member 12, a second receiving member 13, a first viscoelastic body 14, and a second viscoelastic body 15.

  The shaft member 11 includes a shaft portion 11a, a first sphere portion 11b, and a second sphere portion 11c. The first sphere portion 11b is provided at one end of the shaft portion 11a. The 2nd spherical body part 11c is provided in the other end of the axial part 11a. A recess 11b1 for attaching the first viscoelastic body 14 is formed in the first sphere portion 11b. A recess 11c1 for attaching the second viscoelastic body 15 is formed in the second sphere portion 11c.

  The first receiving member 12 has a concave first spherical surface portion 12a that receives the first spherical body portion 11b. In this embodiment, the 1st receiving member 12 is comprised by the rectangular or circular block. A substantially spherical cavity 12 d is formed at the center of the first receiving member 12. An opening 12b is formed in one direction in the spherical cavity of the first receiving member 12. The first spherical surface portion 12 a is formed along the inner surface of the spherical cavity 12 d of the first receiving member 12. The 1st receiving member 12 has the junction part 12c set so that the 1st spherical surface part 12a might be divided | segmented into at least two. In this embodiment, the joint 12c is set in the first receiving member 12 so that the cavity 12d is divided into two substantially hemispherical cavities along the direction in which the opening 12b is formed. A recess 12a1 for attaching the first viscoelastic body 14 is formed in the first spherical surface portion 12a. Although illustration is abbreviate | omitted, the junction part 12c is good to join so that isolation | separation is possible with a volt | bolt nut etc., for example.

  The second receiving member 13 has a recessed second spherical surface portion 13a that receives the second spherical body portion 11c. In this embodiment, the 2nd receiving member 13 is equipped with the form substantially the same as the 1st receiving member 12 mentioned above. The second receiving member 13 is configured by a rectangular or circular block. A substantially spherical cavity 13 d is formed at the center of the second receiving member 13. An opening 13 b is formed in one direction in the spherical cavity 13 d of the second receiving member 13. The second spherical surface portion 13 a is formed along the inner surface of the spherical cavity 13 d of the second receiving member 13. The 2nd receiving member 13 has the junction part 13c set so that the 2nd spherical part 13a might be divided | segmented into at least two. In this embodiment, the joint 13c is set in the second receiving member 13 so that the cavity 13d is divided into two substantially hemispherical cavities along the direction in which the opening 13b is formed. In the second spherical surface portion 13a, a recess 13a1 for attaching the second viscoelastic body 15 is formed. Although illustration is abbreviate | omitted, the junction part 12c is good to join so that isolation | separation is possible with a volt | bolt nut etc., for example.

  The 1st viscoelastic body 14 is arrange | positioned between the 1st spherical body part 11b and the 1st spherical surface part 12a. The 1st viscoelastic body 14 deform | transforms according to the relative displacement of the 1st spherical body part 11b and the 1st spherical surface part 12a. In this embodiment, two first viscoelastic bodies 14 are arranged between the first spherical body portion 11b and the first spherical surface portion 12a. The 1st viscoelastic body 14 is arrange | positioned so as to oppose the radial direction with respect to the center part of the 1st spherical body part 11b and the 1st spherical surface part 12a. It is not limited to this form, It is good to arrange | position between the 1st spherical body part 11b and the 1st spherical surface part 12a so that the some 1st viscoelastic body 14 may act with sufficient mechanical balance. The number and arrangement of the first viscoelastic bodies 14 are not particularly limited.

  In this embodiment, the 1st viscoelastic body 14 is arrange | positioned between the 1st steel material 14a and the 2nd steel material 14b, and is adhere | attached on the 1st steel material 14a and the 2nd steel material 14b. The first steel material 14a is a member attached to the first sphere portion 11b. The second steel material 14 b is a member attached to the first spherical surface portion 12 a of the first receiving member 12. In this case, the first viscoelastic body 14 may be disposed between the first steel material 14a and the second steel material 14b, and may be bonded to the first steel material 14a and the second steel material 14b. The first receiving member 12 may be configured separately. In this case, the 1st viscoelastic body 14 is good to arrange | position and shape | mold between the 1st steel material 14a and the 2nd steel material 14b, for example, and shaping | molding of the 1st viscoelastic body 14 becomes easy.

  In this embodiment, the 1st steel material 14a is mounted | worn with the hollow 11b1 of the 1st spherical body part 11b. The second steel material 14b is attached to the recess 12a1 of the first spherical surface portion 12a. Specifically, the first sphere portion 11b and the first steel material 14a are mounted in the recess 11b1 of the first sphere portion 11b, and the second steel material 14b is mounted in the recess 12a1 of the first spherical surface portion 12a. A first viscoelastic body 14 is disposed between the first spherical surface portion 12a. When the 1st viscoelastic body 14 is arrange | positioned, the 1st receiving member 12 is good to be divided | segmented suitably. And it is good for the junction part 12c of the 1st receiving member 12 to be joined in the state where the 1st viscoelastic body 14 is arrange | positioned between the 1st spherical body part 11b and the 1st spherical surface part 12a. In this case, it is not necessary to directly bond the first viscoelastic body 14 to the first spherical body portion 11b and the first spherical surface portion 12a, and the first viscoelastic body 14 can be easily manufactured and attached.

  The 2nd viscoelastic body 15 is arrange | positioned between the 2nd spherical body part 11c and the 2nd spherical surface part 13a. The 2nd viscoelastic body 15 deform | transforms according to the relative displacement of the 2nd spherical body part 11c and the 2nd spherical surface part 13a. In this embodiment, two second viscoelastic bodies 15 are disposed between the second sphere portion 11c and the second spherical portion 13a. The 2nd viscoelastic body 15 is arrange | positioned so as to oppose the radial direction with respect to the center part of the 2nd spherical body part 11c and the 2nd spherical surface part 13a. It is not limited to this form, It is good to arrange | position between the 2nd spherical body part 11c and the 2nd spherical surface part 13a so that the several 2nd viscoelastic body 15 may act with sufficient mechanical balance. The number and arrangement of the second viscoelastic bodies 15 are not particularly limited.

  In this embodiment, the 2nd viscoelastic body 15 is arrange | positioned between the 3rd steel material 15a and the 4th steel material 15b, and is adhere | attached on the 3rd steel material 15a and the 4th steel material 15b. The 3rd steel material 15a is a member attached to the 2nd spherical body part 11c. The fourth steel material 15 b is a member that is attached to the second spherical surface portion 13 a of the second receiving member 13. In this case, the second viscoelastic body 15 is preferably disposed between the third steel material 15a and the fourth steel material 15b and bonded to the third steel material 15a and the fourth steel material 15b. The first receiving member 12 may be configured separately. In this case, for example, the second viscoelastic body 15 may be disposed and molded between the third steel material 15a and the fourth steel material 15b, and the second viscoelastic body 15 can be easily molded.

  Here, as the first viscoelastic body 14 and the second viscoelastic body 15, so-called high damping rubber or the like can be appropriately employed. The performance of the first viscoelastic body 14 and the second viscoelastic body 15 can be adjusted by adjusting the blending of the additives. The first viscoelastic body 14 and the first steel material 14a and the second steel material 14b may be bonded by vulcanization when the first viscoelastic body 14 is formed. The second viscoelastic body 15 and the third steel material 15a and the fourth steel material 15b may be bonded by vulcanization when the second viscoelastic body 15 is formed.

  In this embodiment, the 3rd steel material 15a is mounted | worn with the hollow 11c1 of the 2nd spherical body part 11c. The fourth steel material 15b is mounted in the recess 13a1 of the second spherical surface portion 13a. Specifically, the third steel material 15a is mounted in the recess 11c1 of the second sphere portion 11c, and the fourth steel material 15b is mounted in the recess 13a1 of the second spherical surface portion 13a. A second viscoelastic body 15 is disposed between the second spherical surface portion 13a. When the 2nd viscoelastic body 15 is arrange | positioned, the 2nd receiving member 13 is good to be divided | segmented suitably. And it is good for the junction part 13c of the 2nd receiving member 13 to be joined in the state where the 2nd viscoelastic body 15 is arrange | positioned between the 2nd spherical body part 11c and the 2nd spherical surface part 13a. In this case, it is not necessary to directly bond the second viscoelastic body 15 to the second spherical body portion 11c and the second spherical surface portion 13a, and the second viscoelastic body 15 can be easily manufactured and attached.

  That is, the first viscoelastic body 14 is formed between the first steel material 14a, the second steel material 14b, the first steel material 14a and the second steel material 14b, and is added to the first steel material 14a and the second steel material 14b. Sulfur bonded. For this reason, it is good to arrange | position the 1st steel material 14a and the 2nd steel material 14b in a metal mold | die, and shape | mold the 1st viscoelastic body 14 between the 1st steel material 14a and the 2nd steel material 14b. The first viscoelastic body 14 can be easily molded. Moreover, in the attachment of the 1st viscoelastic body 14, the 1st steel material 14a is engage | inserted in the hollow 11b1 formed in the 1st spherical body part 11b, and the 2nd steel material 14b is inserted in the hollow 12a1 formed in the 1st spherical surface part 12a. It is good to be. For this reason, it is not necessary to vulcanize and bond the viscoelastic body directly to the first spherical body portion 11b or the first spherical surface portion 12a, and the manufacture becomes easy. In this case, the adhesive strength of the viscoelastic body is also kept high. Similarly, the second viscoelastic body 15 is easy to manufacture and attach.

  The number and arrangement of the first viscoelastic bodies 14 may be three, for example, between the first spherical body portion 11b and the first spherical surface portion 12a. One may be arranged. As for the 1st viscoelastic body 14, more 1st viscoelastic bodies 14 may be arrange | positioned between the 1st spherical body part 11b and the 1st spherical surface part 12a. Further, the arrangement of the first viscoelastic body 14 is not limited to one circumferential direction, and may be arranged at an arbitrary position between the first spherical body portion 11b and the first spherical surface portion 12a. As described above, the first steel material 14a and the second steel material 14b may be formed with a viscoelastic body interposed therebetween, and may be fitted into the recesses 11a1 and 12a1 formed in the first sphere portion 11b and the first spherical surface portion 12a. For this reason, compared with the case where a viscoelastic body is directly vulcanized and bonded to the 1st spherical body part 11b or the 1st spherical surface part 12a, the number of the 1st viscoelastic bodies 14 and the freedom degree of arrangement | positioning become high. The same applies to the second viscoelastic body 15.

  As shown in FIG. 1, the vibration damping device 10 is disposed between the supporting members A1 and A2 facing each other. The opposing support members A1, A2 can be, for example, a building floor slab and an upper floor slab. That is, the vibration damping device 10 can be installed on an arbitrary floor. Note that the vibration damping device 10 is disposed between members that are relatively displaced in response to vibration or the like, can suppress the displacement of the relatively displaced member, and can attenuate the vibration at an early stage. The vibration damping device 10 can be used for various applications from this viewpoint.

  FIG. 2 is a front view of the vibration damping device 10 in which the opposing support members A1 and A2 are relatively displaced in the horizontal direction. As shown in FIG. 2, when the supporting members A1 and A2 facing each other are relatively displaced in the horizontal direction, the vibration damping device 10 has a shaft member 11 according to the displacement of the supporting members A1 and A2. Tilts. Further, when the shaft member 11 is tilted, the first spherical body portion 11 b rotates with respect to the first spherical surface portion 12 a of the first receiving member 12. At this time, shear deformation is applied to the first viscoelastic body 14 disposed between the first spherical portion 11b and the first spherical portion 12a in accordance with the relative displacement between the first spherical portion 11b and the first spherical portion 12a. Arise. Similarly, shear deformation occurs in the second viscoelastic body 15 disposed between the second spherical portion 11c and the second spherical portion 13a as the shaft member 11 tilts. By the reaction force according to the shear deformation of the first viscoelastic body 14 and the second viscoelastic body 15, and by the energy absorbed according to the shear deformation of the first viscoelastic body 14 and the second viscoelastic body 15. The horizontal displacement generated in the supporting members A1 and A2 facing each other is suppressed to be small, and the vibration is attenuated early. For this reason, the vibration damping device 10 contributes to, for example, suppressing the shaking generated in the building at the time of an earthquake to a small level and quickly attenuating it.

  Thus, shear deformation is repeatedly input to the first viscoelastic body 14 and the second viscoelastic body 15 according to the shear displacement of the supporting members A1 and A2 facing each other. At this time, the first viscoelastic body 14 and the second viscoelastic body 15 can absorb energy corresponding to a hysteresis loop drawn according to shear deformation. Here, the first viscoelastic body 14 and the second viscoelastic body 15 may be made of a material that generates a required damping force according to shear deformation. As materials used for the first viscoelastic body 14 and the second viscoelastic body 15, styrene-based, urethane-based, acrylic-based, isobutylene-based, isoprene-based, silicon-based, and diene-based elastomers are suitable. In particular, a material with less temperature dependency is more preferable, and a rubber material called a so-called high damping rubber can be employed.

  Although not shown, the vibration damping device 10 suppresses not only the relative horizontal displacement of the opposing support members A1 and A2 but also the axial direction and the torsional direction of the shaft member 11 to reduce vibrations. Contributes to the early decay of For this reason, the vibration damping device 10 can be used as a vibration damping device that supports any vibration in the three-dimensional direction of the opposing support members A1 and A2.

The vibration damping device 10 proposed here is not limited to the form shown in FIG.
The vibration damping device 10 may include a shaft member 11, a first receiving member 12, a second receiving member 13, a first viscoelastic body 14, and a second viscoelastic body 15.
The shaft member 11 includes a shaft portion 11a, a first sphere portion 11b provided at one end of the shaft portion 11a, and a second sphere portion 11c provided at the other end of the shaft portion 11a.
The first receiving member 12 has a concave first spherical surface portion 12a that receives the first spherical body portion 11b.
The second receiving member 13 has a recessed second spherical surface portion 13a that receives the second spherical body portion 11c.
The 1st viscoelastic body 14 is arrange | positioned between the 1st spherical body part 11b and the 1st spherical surface part 12a, and deform | transforms according to the relative displacement of the 1st spherical body part 11b and the 1st spherical surface part 12a.
The 2nd viscoelastic body 15 is arrange | positioned between the 2nd spherical body part 11c and the 2nd spherical surface part 13a, and deform | transforms according to the relative displacement of the 2nd spherical body part 11c and the 2nd spherical surface part 13a.

  According to the vibration damping device 10, the first viscoelastic body 14 and the second viscoelastic body 15 are deformed according to the relative displacement between the first receiving member 12 and the second receiving member 13. Since the first viscoelastic body 14 and the second viscoelastic body 15 are deformed, energy for displacing the first receiving member 12 and the second receiving member 13 is absorbed. The relative displacement with respect to the receiving member 13 is kept small, and the vibration accompanying the displacement is attenuated early.

  As described above, the vibration damping device 10 proposed here has been variously described, but the vibration damping device proposed here is not limited to the above-described embodiment unless specifically mentioned.

  For example, as for the shaft member 11, the shaft part 11a, the 1st spherical body part 11b, and the 2nd spherical body part 11c may be formed integrally. Further, the shaft portion 11a, the first sphere portion 11b, and the second sphere portion 11c are manufactured separately, and the first sphere portion 11b and the second sphere portion 11c are attached to one end of the shaft portion 11a. May be.

  In the form shown in FIG. 1, the first viscoelastic body 14 is disposed between the first steel material 14a attached to the first sphere portion 11b and the second steel material 14b attached to the first spherical surface portion 12a. And bonded to the first steel material 14a and the second steel material 14b. It is not limited to such a form. The same applies to the second viscoelastic body 15 and is not limited to the form shown in FIG.

  FIG. 3 is a front view showing another embodiment of the vibration damping device 10. As shown in FIG. 3, the first viscoelastic body 14 is disposed between the first sphere portion 11b and the first spherical portion 12a, and is bonded to the first sphere portion 11b and the first spherical portion 12a. May be. Thereby, the 1st viscoelastic body 14 may be comprised so that it may deform | transform according to the relative displacement of the 1st spherical body part 11b and the 1st spherical surface part 12a. The 2nd viscoelastic body 15 may be arrange | positioned between the 2nd spherical body part 11c and the 2nd spherical surface part 13a, and may be adhere | attached on the 2nd spherical body part 11c and the 2nd spherical surface part 13a. Thereby, the 2nd viscoelastic body 15 may be comprised so that it may deform | transform according to the relative displacement of the 2nd spherical body part 11c and the 2nd spherical surface part 13a. In this case, the portions 11b2 and 12a2 where the first viscoelastic body 14 is bonded to the first spherical body portion 11b and the first spherical surface portion 12a may not be spherical surfaces. In FIG. 3, the 1st spherical body part 11b and the 1st spherical surface part 12a are made into the flat surface in the site | part to which the 1st viscoelastic body 14 is adhere | attached. In order to increase the bonding area, the flat surface may be further uneven. The same applies to the portions 11c2 and 13a2 where the second viscoelastic body 15 is bonded to the second spherical portion 11c and the second spherical portion 13a.

  In addition, the first spherical body portion 11 b of the shaft member 11 may move smoothly through the first viscoelastic body 14 in the first spherical surface portion 12 a formed on the first receiving member 12. From this viewpoint, the cavity 12d formed in the first receiving member 12 is not limited to a spherical shape, and the first spherical surface portion 12a is not limited to a strictly spherical surface. Further, the first sphere portion 11b corresponding to this does not need to be a strict spherical shape.

  In addition, the second spherical portion 11 c of the shaft member 11 may move smoothly through the second viscoelastic body 15 in the second spherical surface portion 13 a formed on the second receiving member 13. From this viewpoint, the cavity 13d formed in the second receiving member 13 is not limited to a spherical shape, and the second spherical surface portion 13a is not limited to a strictly spherical surface. Further, the second sphere portion 11c corresponding to this does not need to be a strict spherical shape. Thus, “spherical surface”, “spherical body”, etc. do not strictly specify the shape of the member.

  In addition, the shape of the first receiving member 12 that receives the first sphere portion 11b of the shaft member 11, the number of the first receiving members 12 divided, the setting of the joint portion 12c, and the like are described above unless otherwise specified. The form is not limited. The shape of the second receiving member 13 that receives the second spherical portion 11c of the shaft member 11, the number of the second receiving members 13 that are divided, the setting of the joint portion 13c, and the like are also in the above-described embodiment unless otherwise specified. It is not limited. Further, the position where the cavity 12 d is formed in the first receiving member 12 is not limited to the exact center of the first receiving member 12. The position where the cavity 13 d is formed in the second receiving member 13 is not limited to the exact center of the second receiving member 13.

  For example, in the above-described embodiment, the first viscoelastic body 14 is substantially centered between the first spherical portion 11b and the first spherical portion 12a, between the first spherical portion 11b and the first spherical portion 12a. They are arranged symmetrically with respect to the point. Thereby, the reaction force of the plurality of first viscoelastic bodies 14 acts in a mechanically balanced manner between the first spherical body portion 11b and the first spherical surface portion 12a. The first viscoelastic body 14 is generally arranged between the first spherical body portion 11b and the first spherical surface portion 12a from the viewpoint of causing the reaction forces of the plurality of first viscoelastic bodies 14 to work in a balanced manner. It is not limited to being arranged point-symmetrically with respect to the center, and may be arranged asymmetrically. Moreover, the magnitude | size, thickness, rigidity, etc. of the 1st viscoelastic body 14 may be changed for every position between the 1st spherical body part 11b and the 1st spherical surface part 12a. About these points, it is the same also about the 2nd viscoelastic body 15 arrange | positioned between the 2nd spherical body part 11c and the 2nd spherical surface part 13a. Further, in order to prevent the first viscoelastic body 14 and the second viscoelastic body 15 from creeping due to the weight of the shaft member 11, a support member for supporting the weight of the shaft member 11 may be provided separately.

DESCRIPTION OF SYMBOLS 10 Damping apparatus 11 Shaft member 11a Shaft part 11b 1st spherical body part 11b1 hollow 11c 2nd spherical body part 11c1 hollow 12 1st receiving member 12a 1st spherical surface part 12a1 hollow 12b opening 12c joining part 12d formed in the 1st receiving member 12 Cavity 13 Second receiving member 13a Second spherical surface portion 13a1 Depression 13b Opening 13c Joint portion 13d Cavity 14 formed in second receiving member 13 First viscoelastic body 14a First steel material 14b Second steel material 15 Second viscoelastic body 15a 3rd steel material 15b 4th steel material A1 Support member A2 Support member

Claims (5)

A shaft member comprising: a shaft portion; a first sphere portion provided at one end of the shaft portion; and a second sphere portion provided at the other end of the shaft portion;
A first receiving member having a recessed first spherical surface portion for receiving the first spherical body portion;
A second receiving member having a recessed second spherical surface portion for receiving the second sphere portion;
A first viscoelastic body disposed between the first sphere part and the first spherical part and deformed in accordance with a relative displacement between the first sphere part and the first spherical part;
A vibration damping device comprising a second viscoelastic body disposed between the second sphere part and the second spherical part and deformed in accordance with a relative displacement between the second sphere part and the second spherical part. apparatus. The first viscoelastic body is:
It is arrange | positioned between the 1st steel material attached to the said 1st spherical body part, and the 2nd steel material attached to the said 1st spherical surface part, and is adhere | attached on the said 1st steel material and the said 2nd steel material, Item 1. The vibration damping device according to item 1.   3. The vibration damping device according to claim 2, wherein the first receiving member has a joint portion that is set so that the first spherical surface portion is divided into at least two. The second viscoelastic body is
The third steel material attached to the second sphere portion and the fourth steel material attached to the second spherical surface portion are disposed and bonded to the third steel material and the fourth steel material. To 3. The vibration damping device according to any one of items 3 to 3.   5. The vibration damping device according to claim 4, wherein the second receiving member has a joint portion that is set so that the second spherical surface portion is divided into at least two.

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