Shock absorber and shaft coupling structure

Abstract

To suppress abnormal noise or wear caused by collision between a first shaft member and a second shaft member connected to each other.SOLUTION: The damping device 30 is used for damping between a first shaft member and a second shaft member including a cylindrical connection end part surrounding the first shaft member. The shock absorber 30 includes the elastically deformable cylindrical elastic body 50 and the cylindrical support body 60 that has higher rigidity than the elastic body 50 and surrounds the elastic body 50, the inner peripheral surface 70 of the elastic body 50 includes the first inner surface 71 that comes into contact with the outer peripheral surface of the first shaft member and the second inner surface 72 that has a larger inner diameter than the first inner surface 71 and comes into contact with the outer peripheral surface of the coupling end portion, and one or more groove portions 75 extending along the axial direction are formed in at least one of the first inner surface 71 and the second inner surface 72.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a structure for connecting a plurality of shaft members. [Background technology]

[0002] For example, in a power transmission mechanism for a moving body such as an automobile, multiple shaft members are coaxially connected to one another. Patent Document 1 discloses a structure in which a rotating shaft and a drive shaft are connected to one another by engagement between an internal spline formed on the inner periphery of the rotating shaft and an external spline formed on the outer periphery of the drive shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5671829 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, gaps are formed in the radial and circumferential directions between the internal spline of the rotating shaft and the external spline of the drive shaft. Therefore, there is a problem that abnormal noise or wear occurs due to a collision between the rotating shaft and the drive shaft. In consideration of the above circumstances, one aspect of the present disclosure aims to suppress abnormal noise or wear caused by a collision between a first shaft member and a second shaft member. [Means for solving the problem]

[0005] In order to solve the above problems, a buffer device according to one embodiment of the present disclosure is a buffer device used for buffering between a first shaft member and a second shaft member including a cylindrical connecting end portion surrounding the first shaft member, and comprises an elastically deformable cylindrical elastic body and a cylindrical support body that is more rigid than the elastic body and surrounds the elastic body, the inner surface of the elastic body includes a first inner surface that contacts the outer surface of the first shaft member and a second inner surface that has an inner diameter larger than that of the first inner surface and contacts the outer surface of the connecting end portion, and at least one of the first inner surface and the second inner surface is formed with one or more groove portions extending along the axial direction.

[0006] A shaft connecting structure according to one embodiment of the present disclosure comprises a first shaft member, a second shaft member including a cylindrical connecting end portion surrounding the first shaft member, and a buffer device used for buffering between the first shaft member and the second shaft member, wherein the buffer device comprises an elastically deformable cylindrical elastic body and a cylindrical support body surrounding the elastic body and having higher rigidity than the elastic body, the inner surface of the elastic body including a first inner surface that contacts the outer surface of the first shaft member and a second inner surface that has an inner diameter larger than the first inner surface and contacts the outer surface of the connecting end portion, and at least one of the first inner surface and the second inner surface is formed with one or more grooves extending along the axial direction. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of a shaft connection structure according to a first embodiment. [Figure 2] 1 is a cross-sectional view of a shock absorber according to a first embodiment. [Figure 3] FIG. [Figure 4] 10A to 10C are explanatory diagrams of a procedure for manufacturing the shaft connection structure. [Figure 5] FIG. 10 is a cross-sectional view of a shock absorber according to a second embodiment. [Figure 6] FIG. 10 is a plan view of a shock absorber according to a second embodiment. [Figure 7] 10A to 10C are explanatory views of a process of inserting a second shaft member into the shock absorber. [Figure 8]FIG. 10 is a cross-sectional view of a shock absorber according to a third embodiment. [Figure 9] FIG. 10 is a plan view of a shock absorber according to a third embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a shock absorber according to a fourth embodiment. [Figure 11] FIG. 10 is a cross-sectional view of a shock absorber according to a modified example. [Figure 12] FIG. 10 is a cross-sectional view of a shock absorber according to a modified example. [Figure 13] FIG. 10 is a cross-sectional view of a shock absorber according to a modified example. [Figure 14] FIG. 10 is a cross-sectional view of a shock absorber according to a modified example. [Figure 15] FIG. 10 is a cross-sectional view of a shock absorber according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. Furthermore, the embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0009] A: First embodiment 1 is a cross-sectional view of a shaft connection structure 100 according to a first embodiment of the present disclosure. The shaft connection structure 100 is used in a power transmission mechanism that transmits power generated by a power source such as an internal combustion engine or an electric motor to a drive mechanism such as a transmission or a differential gear in a moving body such as an automobile.

[0010] As illustrated in FIG. 1 , the shaft connection structure 100 includes a first shaft member 10, a second shaft member 20, a shock absorber 30, a bearing device 41, and a sealing device 42. In the following description, the direction along the central axis Z of the first shaft member 10 and the second shaft member 20 will be referred to as the "axial direction." The axial direction is divided into the Z1 direction and the Z2 direction. The Z1 direction is one direction along the central axis Z, and the Z2 direction is the direction opposite to the Z1 direction. Furthermore, the direction along the circumference of an imaginary circle of any diameter centered on the central axis Z will be referred to as the "circumferential direction," and the direction of the radius of the imaginary circle will be referred to as the "radial direction." In the radial direction, the direction toward the central axis Z will be referred to as the "inner side," and the direction away from the central axis Z will be referred to as the "outer side."

[0011] The first shaft member 10 is a cylindrical shaft that can rotate around a central axis Z. The Z1-direction end of the first shaft member 10 is connected to the rotating shaft of a power source such as an internal combustion engine or an electric motor. The first shaft member 10 includes a shaft main body 11 and a connecting end 12. The shaft main body 11 and the connecting end 12 are integrally formed. The connecting end 12 is the portion of the first shaft member 10 that includes the end in the Z2 direction. The shaft main body 11 is the portion of the first shaft member 10 other than the connecting end 12. The outer diameter of the connecting end 12 is smaller than the outer diameter of the shaft main body 11. The bearing device 41 is a ball bearing that supports the shaft main body 11 of the first shaft member 10.

[0012] The second shaft member 20 is a cylindrical shaft that can rotate around a central axis Z. The Z2-direction end of the second shaft member 20 is connected to a rotating shaft of a drive mechanism such as a transmission or a differential device. The second shaft member 20 includes a shaft main body 21 and a connecting end 22. The shaft main body 21 and the connecting end 22 are integrally formed. The connecting end 22 is a cylindrical portion of the second shaft member 20 that includes the end of the second shaft member 20 in the Z1 direction. The shaft main body 21 is the cylindrical portion of the second shaft member 20 other than the connecting end 22.

[0013] The connecting end 22 of the second shaft member 20 surrounds the first shaft member 10. Specifically, the outer peripheral surface 14 of the shaft main body 11 of the first shaft member 10 and the inner peripheral surface 25 of the connecting end 22 of the second shaft member 20 face each other with a small gap between them. The sealing device 42 is an annular seal for sealing the annular space formed between the outer peripheral surface 14 of the shaft main body 11 and the inner peripheral surface 25 of the connecting end 22. Specifically, an attachment groove 16 is formed in the outer peripheral surface 14 of the shaft main body 11 of the first shaft member 10, spanning the entire circumference of the shaft main body 11, and the sealing device 42 is attached to the attachment groove 16. An O-ring is an example of the sealing device 42.

[0014] A connecting structure 13 is formed on the outer peripheral surface of the connecting end 12 of the first shaft member 10. The connecting structure 13 is, for example, an external spline structure in which a plurality of grooves or a plurality of protrusions are arranged in the circumferential direction. On the other hand, a connecting structure 23 is formed on the inner peripheral surface 25 of the connecting end 22 of the second shaft member 20. The connecting structure 23 is, for example, an internal spline structure in which a plurality of grooves or a plurality of protrusions are arranged in the circumferential direction. The engagement between the connecting structure 13 and the connecting structure 23 restricts rotation of one of the first shaft member 10 and the second shaft member 20 relative to the other. In other words, the first shaft member 10 and the second shaft member 20 rotate integrally.

[0015] There are minute gaps between the connecting structure 13 and the connecting structure 23 in the circumferential and radial directions. Therefore, when the first shaft member 10 or the second shaft member 20 rotates, the connecting structure 13 and the connecting structure 23 may collide with each other when they are spaced apart from each other. The shock absorber 30 of the first embodiment is a device used to cushion the impact between the first shaft member 10 and the second shaft member 20. That is, the shock absorber 30 suppresses the impact between the first shaft member 10 and the second shaft member 20. As illustrated in FIG. 1 , the first shaft member 10 and the second shaft member 20 are inserted into the shock absorber 30. Specifically, the shock absorber 30 surrounds the portion where the first shaft member 10 and the second shaft member 20 are connected. The central axis Z is also referred to as the central axis of the shock absorber 30.

[0016] FIG. 2 is a cross-sectional view of the shock absorber 30. FIG. 3 is a plan view of the shock absorber 30 as viewed in the Z1 direction. As illustrated in FIGS. 2 and 3, the shock absorber 30 includes an elastic body 50 and a support body 60. The elastic body 50 is a cylindrical structure that is elastically deformable. The support body 60 is a cylindrical structure that surrounds the elastic body 50. In other words, the elastic body 50 is supported inside the support body 60.

[0017] The elastic body 50 is formed of an elastic material such as a rubber material. Examples of rubber materials that can be used for the elastic body 50 include various rubber materials such as chloroprene rubber (CR), silicone rubber (SR), acrylic rubber (ACM), urethane rubber (U), polyurethane rubber (PUR), vinyl methyl silicone rubber (VMQ), ethylene propylene diene rubber (EPDM), and fluororubber (FKM). The elastic body 50 may also be formed of a low-rigidity resin material.

[0018] The support body 60 is a cylindrical structure having higher rigidity than the elastic body 50. The support body 60 is, for example, a metal ring made of a metal material. Examples of metal materials used for the support body 60 include stainless steel, SPCC (Steel Plate Cold Commercial), and SPHC (Steel Plate Hot Commercial). The support body 60 may also be made of, for example, a highly rigid resin material.

[0019] The shock absorber 30 is formed by, for example, injection molding. For example, a fluid elastic material is supplied to a mold in which the support body 60 is attached, and the elastic material is cooled to form the elastic body 50 bonded to the support body 60. Alternatively, an adhesive may be applied to the support body 60 attached to the mold, and the support body 60 and the elastic body 50 may be bonded together by heating with the fluid elastic material, causing the adhesive to react. For example, the elastic body 50 and the support body 60 may be bonded together by vulcanization. The method for manufacturing the shock absorber 30 is not limited to the above examples.

[0020] As illustrated in FIG. 2, the elastic body 50 includes a first part 51, a second part 52, and a connecting part 53. The first part 51 and the second part 52 are cylindrical parts centered on the central axis Z. The connecting part 53 is an annular part located between the first part 51 and the second part 52 and connects the first part 51 and the second part 52. The first part 51 is located in the Z1 direction with respect to the connecting part 53, and the second part 52 is located in the Z2 direction with respect to the connecting part 53. The elastic body 50 is a molded product in which the first part 51, the second part 52, and the connecting part 53 are integrally formed.

[0021] As illustrated in FIG. 2, the elastic body 50 is a cylindrical structure including an inner peripheral surface 70 and an outer peripheral surface 80. The inner peripheral surface 70 of the elastic body 50 includes a first inner surface 71, a second inner surface 72, and a stepped surface 73. The first inner surface 71 and the second inner surface 72 are cylindrical surfaces centered on the central axis Z. The first inner surface 71 is located in the Z1 direction with respect to the second inner surface 72.

[0022] The first inner surface 71 is a region extending over the first part 51 and the connecting part 53 of the inner peripheral surface 70 of the elastic body 50. On the other hand, the second inner surface 72 is a region corresponding to the second part 52 of the inner peripheral surface 70 of the elastic body 50. As illustrated in FIGS. 2 and 3, the inner diameter Da1 of the first inner surface 71 is smaller than the inner diameter Da2 of the second inner surface 72 (Da1 < Da2). That is, the second inner surface 72 has a larger inner diameter than the first inner surface 71. The inner diameter Da l is the inner diameter of the first part 51 and the connecting part 53. The inner diameter Da2 is the inner diameter of the second part 52.

[0023] As illustrated in FIG. 1, the first inner surface 71 contacts the outer peripheral surface 14 of the first shaft member 10 (specifically, the shaft main body 11). Specifically, the first inner surface 71 contacts a region of the outer peripheral surface 14 of the first shaft member 10 that is located in the Z1 direction with respect to the end surface in the Z1 direction of the second shaft member 20 (hereinafter referred to as the "front end surface 26"). The inner diameter Da1 of the first inner surface 71 is smaller than the outer diameter of the shaft main body 11 of the first shaft member 10. Therefore, the first inner surface 71 closely adheres to the outer peripheral surface 14 of the first shaft member 10 with a predetermined interference fit.

[0024] On the other hand, the second inner surface 72 contacts the outer peripheral surface 24 of the second shaft member 20 (specifically, the connecting end 22). Specifically, the second inner surface 72 contacts an area of ​​the connecting end 22 of the second shaft member 20 that extends over a predetermined length in the Z2 direction from the tip surface 26 of the first shaft member 10. The inner diameter Da2 of the second inner surface 72 is smaller than the outer diameter of the connecting end 22 of the second shaft member 20. Therefore, the first inner surface 71 tightly contacts the outer peripheral surface 24 of the connecting end 22 with a predetermined interference.

[0025] As illustrated in FIGS. 2 and 3 , the step surface 73 of the inner circumferential surface 70 of the elastic body 50 is an annular flat surface perpendicular to the axial direction, and is located between a first inner surface 71 and a second inner surface 72. Specifically, the inner periphery of the step surface 73 is connected to the first inner surface 71, and the outer periphery of the step surface 73 is connected to the second inner surface 72. The portion where the step surface 73 and the first inner surface 71 are continuous is a curved surface (R-shaped). Similarly, the portion where the step surface 73 and the second inner surface 72 are continuous is a curved surface (R-shaped). Furthermore, as illustrated in FIG. 1 , the tip surface 26 of the second shaft member 20 contacts the step surface 73 of the elastic body 50.

[0026] The length L1 of the first inner surface 71 in the axial direction is greater than the length L2 of the second inner surface 72 (L1>L2). The length L1 of the first inner surface 71 is the distance from a first edge E1 of the first inner surface 71 in the Z1 direction to the step surface 73. The length L2 of the second inner surface 72 is the distance from a second edge E2 of the second inner surface 72 in the Z2 direction to the step surface 73.

[0027] As described above, in the first embodiment, the elastic body 50 is installed inside the support body 60, and the first inner surface 71 of the inner circumferential surface 70 of the elastic body 50 contacts the outer circumferential surface 14 of the first shaft member 10, and the second inner surface 72 of the inner circumferential surface 70 contacts the outer circumferential surface 24 of the second shaft member 20. In the above configuration, the shock absorber 30 suppresses rotation of one of the first shaft member 10 and the second shaft member 20 relative to the other. In other words, the elastic body 50 buffers the collision between the first shaft member 10 and the second shaft member 20. Therefore, abnormal noise or wear caused by the collision between the first shaft member 10 and the second shaft member 20 can be suppressed.

[0028] In the first embodiment, since the tip surface 26 of the connecting end portion 22 of the second shaft member 20 contacts the stepped surface 73 on the inner peripheral surface 70 of the elastic body 50, the second shaft member 20 is stably held by the elastic body 50. Therefore, the elastic body 50 can effectively buffer the collision between the first shaft member 10 and the second shaft member 20.

[0029] As illustrated in FIG. 2, the outer peripheral surface 80 of the elastic body 50 includes a first outer surface 81, a second outer surface 82, and a stepped surface 83. The first outer surface 81 and the second outer surface 82 are cylindrical surfaces centered on the central axis Z. The first outer surface 81 is located in the Z1 direction with respect to the second outer surface 82.

[0030] The first outer surface 81 is located outside the first inner surface 71. Specifically, the first outer surface 81 is a region corresponding to the first portion 51 of the outer peripheral surface 80 of the elastic body 50. On the other hand, the second outer surface 82 is located outside the second inner surface 72. Specifically, the second outer surface 82 is a region extending over the second portion 52 and the connecting portion 53 of the outer peripheral surface 80 of the elastic body 50. The outer diameter Db1 of the first outer surface 81 is smaller than the outer diameter Db2 of the second outer surface 82 (Db1 < Db2). That is, the second outer surface 82 has a larger outer diameter than the first outer surface 81. The outer diameter Db1 is the outer diameter of the first portion 51 of the elastic body 50. The outer diameter Db2 is the outer diameter of the second portion 52 and the connecting portion 53 of the elastic body 50.

[0031] The relative size between the outer diameter Db1 of the first portion 51 and the inner diameter Da2 of the second portion 52 is arbitrary. That is, a configuration in which the outer diameter Db1 is greater than the inner diameter Da2, a configuration in which the outer diameter Db1 is smaller than the inner diameter Da2, or a configuration in which the outer diameter Db1 is equal to the inner diameter Da2 is assumed.

[0032] The stepped surface 83 is an annular plane orthogonal to the axial direction and is located between the first outer surface 81 and the second outer surface 82. Specifically, the inner periphery of the stepped surface 83 is connected to the first outer surface 81, and the outer periphery of the stepped surface 83 is connected to the second outer surface 82. Note that the portion where the stepped surface 83 and the first outer surface 81 are continuous is curved (R-shaped). Similarly, the portion where the stepped surface 83 and the second outer surface 82 are continuous is curved (R-shaped).

[0033] As illustrated in FIG. 2, the distance between the first inner surface 71 and the first outer surface 81 corresponds to the thickness T1 of the first portion 51 of the elastic body 50. The distance between the second inner surface 72 and the second outer surface 82 corresponds to the thickness T2 of the second portion 52 of the elastic body 50. The thickness T1 of the first portion 51 is smaller than the thickness T2 of the second portion 52 (T1 <T2)。

[0034] As described above, in the first embodiment, the outer diameter Db1 of the first outer surface 81 located outside the first inner surface 71 is smaller than the outer diameter Db2 of the second outer surface 82 located outside the second inner surface 72. Therefore, compared to a configuration in which the outer diameter Db1 of the first outer surface 81 and the outer diameter Db2 of the second outer surface 82 are equal (for example, the configuration in FIG. 13 ), the thickness of the first portion 51 of the elastic body 50 is reduced. Specifically, as described above, the thickness T1 of the first portion 51 of the elastic body 50 is smaller than the thickness T2 of the second portion 52. In the above configuration, the rigidity of the first portion 51 exceeds the rigidity of the second portion 52. That is, the fastening force from the first portion 51 to the first shaft member 10 can be maintained higher than the fastening force from the second portion 52 to the second shaft member 20. Therefore, the possibility of co-rotation, that is, the entire elastic body 50 including the first portion 51 and the second portion 52 rotating relative to the first shaft member 10 and the second shaft member 20, can be reduced.

[0035] Furthermore, in the first embodiment, the length L1 of the first inner surface 71 in the axial direction exceeds the length L2 of the second inner surface 72, so the fastening force from the first inner surface 71 to the first shaft member 10 can be maintained higher than the fastening force from the second inner surface 72 to the second shaft member 20. Therefore, the possibility of co-rotation, that is, the entire elastic body 50 including the first portion 51 and the second portion 52 rotates relative to the first shaft member 10 and the second shaft member 20, can be reduced.

[0036] 2, the support body 60 includes a first cylindrical portion 61, a second cylindrical portion 62, and a connecting portion 63. The first cylindrical portion 61 and the second cylindrical portion 62 are cylindrical portions centered on the central axis Z. The connecting portion 63 is an annular portion located between the first cylindrical portion 61 and the second cylindrical portion 62, and connects the first cylindrical portion 61 and the second cylindrical portion 62. The first cylindrical portion 61 is located in the Z1 direction relative to the connecting portion 63, and the second cylindrical portion 62 is located in the Z2 direction relative to the connecting portion 63.

[0037] The second cylindrical portion 62 has a larger diameter than the first cylindrical portion 61. Specifically, the inner diameter of the second cylindrical portion 62 is larger than the inner diameter of the first cylindrical portion 61, and the outer diameter of the second cylindrical portion 62 is larger than the outer diameter of the first cylindrical portion 61. The first cylindrical portion 61, the second cylindrical portion 62, and the connecting portion 63 are integrally formed. For example, the support body 60 is manufactured by pressing a metal plate. Therefore, the thickness of the entire support body 60 (the first cylindrical portion 61, the second cylindrical portion 62, and the connecting portion 63) is constant.

[0038] 2, the inner circumferential surface of the support body 60 contacts the outer circumferential surface 80 of the elastic body 50. The inner circumferential surface of the support body 60 and the outer circumferential surface 80 of the elastic body 50 are joined to each other. Specifically, the inner circumferential surface 64 of the first tubular portion 61 contacts the first outer surface 81 of the elastic body 50, and the inner circumferential surface 65 of the second tubular portion 62 contacts the second outer surface 82 of the elastic body 50. Specifically, the inner circumferential surface 64 is joined to the first outer surface 81, and the inner circumferential surface 65 is joined to the second outer surface 82. In addition, the surface of the connecting portion 63 of the support body 60 in the Z2 direction contacts the surface of the connecting portion 53 of the elastic body 50 in the Z1 direction.

[0039] In the above configuration, the shock absorber 30 rotates in conjunction with the first shaft member 10 and the second shaft member 20. Centrifugal force acts on the elastic body 50 during rotation, but deformation of the elastic body 50 toward the outside in the radial direction (i.e., radial expansion) is restricted by the support body 60 that surrounds the elastic body 50. Specifically, deformation of the first portion 51 of the elastic body 50 toward the outside in the radial direction is restricted by the first cylindrical portion 61 of the support body 60, and deformation of the second portion 52 of the elastic body 50 toward the outside in the radial direction is restricted by the second cylindrical portion 62 of the support body 60.

[0040] As a result of suppressing deformation of the elastic body 50 during rotation as described above, according to the first embodiment, the fastening force from the elastic body 50 on the first shaft member 10 and the second shaft member 20 can be maintained compared to a configuration in which the support body 60 is not provided. In other words, a decrease in fastening force due to rotation of the shock absorber 30 can be suppressed. Therefore, according to the first embodiment, the elastic body 50 can effectively hold the first shaft member 10 and the second shaft member 20. Specifically, the configuration in which the elastic body 50 is surrounded by the support body 60 makes it possible to maintain the fastening force from the first portion 51 on the first shaft member 10 and the fastening force from the second portion 52 on the second shaft member 20.

[0041] [Assembly procedure for shaft connection structure 100] 4 is an explanatory diagram of a procedure for manufacturing the shaft connection structure 100. The procedure in FIG. 4 can also be expressed as a procedure for assembling the first shaft member 10, the second shaft member 20, and the shock absorber 30.

[0042] 4, the first shaft member 10 is inserted into the shock absorber 30. Specifically, the first shaft member 10, which is positioned in the Z1 direction relative to the shock absorber 30, is moved in the Z2 direction, whereby the first shaft member 10 is press-fit into the first portion 51 of the shock absorber 30. When step P1 is performed, the first inner surface 71 of the elastic body 50 of the shock absorber 30 comes into contact with the outer peripheral surface 14 of the first shaft member 10 (shaft main body portion 11) with a predetermined interference.

[0043] In step P2 after step P1 is performed, the second shaft member 20 is inserted into the shock absorber 30. Specifically, by moving the second shaft member 20, which is positioned in the Z2 direction relative to the shock absorber 30, in the Z1 direction, the second shaft member 20 is press-fit into the second portion 52 of the shock absorber 30 with the connecting end portion 22 of the second shaft member 20 surrounding the first shaft member 10. The second shaft member 20 is inserted in the Z1 direction until the tip surface 26 abuts against the stepped surface 73 of the elastic body 50. When step P2 is performed, the second inner surface 72 of the elastic body 50 of the shock absorber 30 comes into contact with the outer peripheral surface 24 of the second shaft member 20 (connecting end portion 22) with a predetermined interference.

[0044] In step P1, the first portion 51 and the connecting portion 53 of the elastic body 50 are deformed in the Z2 direction due to the frictional force from the first shaft member 10. On the other hand, in step P2, the step surface 73 is pressed in the Z1 direction by the tip surface 26 of the second shaft member 20, which makes it possible to reduce the deformation of the first portion 51 and the connecting portion 53 in step P1.

[0045] B: Second embodiment A second embodiment of the present disclosure will be described. Note that, for elements in the following exemplary aspects that have the same functions as those in the first embodiment, the same reference numerals as those in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.

[0046] Fig. 5 is a cross-sectional view of the shock absorber 30 according to the second embodiment. Fig. 6 is a plan view of the shock absorber 30. Fig. 6 shows a plan view of the shock absorber 30 as seen in the Z1 direction.

[0047] 5 and 6, in the shock absorber 30 of the second embodiment, a plurality of first groove portions 75a are formed in the inner circumferential surface 70 of the elastic body 50. The configuration is the same as that of the first embodiment except that a plurality of first groove portions 75a are formed in the inner circumferential surface 70. Therefore, the second embodiment also achieves the same effects as the first embodiment.

[0048] Each of the multiple first groove portions 75a is a depression of a predetermined width formed in the inner circumferential surface 70 of the elastic body 50. Specifically, each first groove portion 75a extends linearly along the axial direction. The multiple first groove portions 75a have the same groove width and depth.

[0049] In the second embodiment, a plurality of first grooves 75a are formed in a first inner surface 71 of the inner circumferential surface 70 of the elastic body 50. Each of the first grooves 75a extends along the axial direction over the entire first inner surface 71 in the axial direction. Specifically, each of the first grooves 75a extends in the axial direction from a first edge E1 in the Z1 direction of the first inner surface 71 to the step surface 73. That is, each of the first grooves 75a is continuous with the step surface 73.

[0050] 6, the multiple first groove portions 75a are formed at equal intervals in the circumferential direction around the central axis Z. In the second embodiment, three first groove portions 75a are formed on the first inner surface 71 of the elastic body 50. Therefore, each first groove portion 75a is formed at an interval of 120° in the circumferential direction around the central axis Z.

[0051] 7 is an explanatory diagram of the process in which the second shaft member 20 is inserted into the shock absorber 30 in step P2 described above. During the period from when the second shaft member 20 is inserted into the elastic body 50 until the tip surface 26 abuts against the stepped surface 73, as illustrated in FIG. 7, a space S is formed between the tip surface 26 and the stepped surface 73. The space S is an annular space surrounded by the outer peripheral surface 14 of the first shaft member 10, the stepped surface 73 of the elastic body 50, the second inner surface 72, and the tip surface 26 of the second shaft member 20. Air is present in the space S.

[0052] In the process of moving the second shaft member 20 in the Z1 direction, the air in the space S is compressed by the tip surface 26 of the second member. In a configuration in which the first groove portion 75a is not formed in the inner circumferential surface 70 of the elastic body 50 (for example, the first embodiment), the space S is sealed, and therefore a repulsive force in the Z2 direction acts on the second shaft member 20 from the air in the space S. In order to move the second shaft member 20 in the Z1 direction against this repulsive force, a sufficient load (press-fit load) in the axial direction Z1 is required.

[0053] In the second embodiment, first grooves 75a are formed on the inner circumferential surface 70 of the elastic body 50. Each of the first grooves 75a communicates with the space S. Therefore, in the process of moving the second shaft member 20 in the Z1 direction, the air in the space S flows in the Z1 direction via each of the first grooves 75a as shown by the arrows in FIG. 7 and is ultimately discharged to the external space of the shock absorber 30. In other words, each of the first grooves 75a functions as a flow path for discharging the air in the space S.

[0054] As a result of the air being discharged from the space S as described above, according to the second embodiment, the repulsive force acting on the second shaft member 20 from the air in the space S is suppressed. That is, in the second embodiment, the press-fit load required to move the second shaft member 20 in the Z1 direction is reduced compared to the first embodiment. Therefore, according to the second embodiment, it is possible to facilitate the assembly of the first shaft member 10, the second shaft member 20, and the shock absorber 30.

[0055] In addition, in a configuration in which the sealing device 42 is installed between the outer peripheral surface 14 of the first shaft member 10 and the inner peripheral surface 25 of the second shaft member 20, the space S is highly sealed, and therefore the repulsive force acting on the second shaft member 20 from the air in the space S becomes particularly pronounced. Therefore, the present disclosure is particularly effective in that the formation of the first groove portion 75a on the inner peripheral surface 70 of the elastic body 50 can suppress the repulsive force acting on the second shaft member 20 from the air in the space S.

[0056] Furthermore, in the second embodiment, the first groove portion 75a is formed on the first inner surface 71 of the elastic body 50. This reduces the contact area between the first inner surface 71 of the elastic body 50 and the outer peripheral surface 14 of the first shaft member 10, compared to a configuration (e.g., the first embodiment) in which the first groove portion 75a is not formed on the first inner surface 71. This therefore reduces the press-fit load required to insert the first shaft member 10 into the first portion 51 of the elastic body 50 in step P1 described above. This means that the work of inserting the first shaft member 10 into the shock absorber 30 can be simplified. Furthermore, as a result of the reduction in the contact area between the first inner surface 71 of the elastic body 50 and the outer peripheral surface 14 of the first shaft member 10, the load (removal load) required to remove the first shaft member 10 from the shock absorber 30 is also reduced. This therefore makes it easier to remove the first shaft member 10 from the shock absorber 30 for maintenance, such as repair or inspection.

[0057] In a configuration in which the multiple first grooves 75a are unevenly distributed in a specific circumferential region of the inner circumferential surface 70 of the elastic body 50, the fastening force from the elastic body 50 to the first shaft member 10 and the second shaft member 20 may differ significantly depending on the circumferential position. Therefore, eccentricity (i.e., misalignment of the central axes) may occur between the first shaft member 10 and the second shaft member 20. In the second embodiment, the multiple first grooves 75a are formed at equal intervals on the inner circumferential surface 70 of the elastic body 50. Therefore, compared to a configuration in which the multiple first grooves 75a are unevenly distributed in a specific region of the inner circumferential surface 70, the fastening force from the elastic body 50 to the first shaft member 10 and the second shaft member 20 is uniform throughout the circumferential direction. Therefore, according to the second embodiment, eccentricity between the first shaft member 10 and the second shaft member 20 due to the uneven distribution of the first grooves 75a can be suppressed.

[0058] C: Third embodiment In the second embodiment, a configuration has been exemplified in which a plurality of first groove portions 75a are formed on the first inner surface 71 of the elastic body 50. In the third embodiment, a plurality of second groove portions 75b are formed on the second inner surface 72 of the elastic body 50.

[0059] Fig. 8 is a cross-sectional view of the shock absorber 30 according to the third embodiment. Fig. 9 is a plan view of the shock absorber 30 as viewed in the Z1 direction. As illustrated in Figs. 8 and 9, in the third embodiment, a plurality of second groove portions 75b are formed in the second inner surface 72 of the inner circumferential surface 70 of the elastic body 50. The groove width and depth are common to the plurality of second groove portions 75b.

[0060] Each of the multiple second groove portions 75b extends along the axial direction over the entire second inner surface 72 in the axial direction. Specifically, each second groove portion 75b extends linearly along the axial direction from a second edge portion E2 in the Z2 direction of the second inner surface 72 to the step surface 73. That is, each second groove portion 75b is continuous with the step surface 73. As illustrated in FIG. 9 , the multiple second groove portions 75b of the third embodiment are formed at equal intervals in the circumferential direction around the central axis Z, similar to the multiple first groove portions 75a of the second embodiment.

[0061] The third embodiment also achieves the same effects as the first embodiment. Furthermore, in the third embodiment, during step P2 of moving the second shaft member 20 in the Z1 direction, the air in the space S is discharged to the external space through each second groove 75b. That is, each second groove 75b functions as a flow path for discharging the air in the space S. Therefore, in the third embodiment, as in the second embodiment, the repulsive force acting on the second shaft member 20 from the air in the space S is suppressed. That is, in the third embodiment, the press-fit load required to move the second shaft member 20 in the Z1 direction can be reduced compared to the first embodiment. Therefore, as in the second embodiment, it is possible to simplify the assembly of the first shaft member 10, the second shaft member 20, and the shock absorber 30.

[0062] Furthermore, in the third embodiment, a second groove portion 75b is formed in the second inner surface 72 of the elastic body 50. Therefore, compared to a configuration (for example, the first embodiment) in which the second groove portion 75b is not formed in the second inner surface 72, the contact area between the second inner surface 72 of the elastic body 50 and the outer circumferential surface 24 of the second shaft member 20 is reduced. The load required to insert or remove the second shaft member 20 into or from the second portion 52 of the elastic body 50 can be reduced.

[0063] D: Fourth embodiment 10 is a cross-sectional view of a shock absorber 30 according to a fourth embodiment. The shock absorber 30 according to the fourth embodiment differs from that according to the first embodiment in the shape of the first inner surface 71 of the elastic body 50. The shock absorber 30 according to the fourth embodiment is the same as that according to the first embodiment except for the shape of the first inner surface 71. Therefore, the fourth embodiment also achieves the same effects as the first embodiment.

[0064] 10 , the first inner surface 71 of the elastic body 50 in the fourth embodiment is an inclined surface (i.e., a tapered surface) inclined with respect to the central axis Z. That is, in the fourth embodiment, the inner diameter Da1 of the first inner surface 71 changes depending on the axial position on the first inner surface 71. Specifically, the first inner surface 71 linearly reduces in diameter in the Z2 direction. That is, the closer the point on the first inner surface 71 is to the second inner surface 72, the smaller the inner diameter Da1.

[0065] That is, the inner diameter Da11 at the first edge E1 on the side of the first inner surface 71 opposite to the second inner surface 72 is larger than the inner diameter Da12 at the third edge E3 on the first inner surface 71 closer to the second inner surface 72 (Da11 > Da12). That is, the first inner surface 71 of the first embodiment constitutes a cylindrical rotating surface, while the first inner surface 71 of the fourth embodiment constitutes a frustum-shaped rotating surface centered on the central axis Z. For example, the inner diameter Da11 is larger than the inner diameter Da12 and less than 1.2 times the inner diameter Da12 (Da12 < Da11 < 1.2×Da12). More preferably, the inner diameter Da11 is larger than the inner diameter Da12 and less than 1.1 times the inner diameter Da12 (Da12 < Da11 < 1.1×Da12).

[0066] As described above, in the fourth embodiment, the inner diameter Da11 at the first edge E1 of the first inner surface 71 is larger than the inner diameter Da12 at the third edge E3. In the above configuration, in the process of the procedure P1 of moving the first shaft member 10 in the Z2 direction and inserting it into the first part 51 of the buffer device 30, the press-fitting weight required to move the first shaft member 10 in the axial direction Z2 gradually increases. That is, immediately after the insertion of the first shaft member 10 into the buffer device 30 is started, the press-fitting load is sufficiently reduced. Therefore, the operation of inserting the first shaft member 10 into the elastic body 50 of the buffer device 30 is facilitated.

[0067] E: Modified Example Specific modified aspects added to the aspects exemplified above are exemplified below. Two or more aspects arbitrarily selected from the following examples may be appropriately combined within a non-conflicting range.

[0068] (1) In the second embodiment, a configuration in which a first groove portion 75a is formed on the first inner surface 71 of the elastic body 50 is exemplified, and in the third embodiment, a configuration in which a second groove portion 75b is formed on the second inner surface 72 of the elastic body 50 is exemplified. The second and third embodiments may be combined. That is, as illustrated in FIG. 11 , a groove portion 75 extending in the axial direction from the first inner surface 71 to the second inner surface 72 of the elastic body 50 may be formed on the inner circumferential surface 70 of the elastic body 50. Specifically, each groove portion 75 in FIG. 11 extends in the axial direction from a first edge portion E1 of the first inner surface 71 in the Z1 direction to a second edge portion E2 of the second inner surface 72 in the Z2 direction. As illustrated above, in one aspect of the present disclosure, one or more groove portions 75 (75a, 75b) extending along the axial direction are formed on at least one of the first inner surface 71 and the second inner surface 72.

[0069] (2) The second to fourth embodiments may be combined as appropriate. For example, as illustrated in Fig. 12, in the configuration of the fourth embodiment in which the first inner surface 71 of the elastic body 50 is inclined with respect to the central axis Z, a first groove portion 75a extending in the axial direction may be formed on the first inner surface 71. In the configuration of Fig. 12, the diameter of the first inner surface 71 decreases in the Z2 direction, and therefore the lateral width of the first groove portion 75a decreases in the Z2 direction.

[0070] In addition, Figure 12 illustrates a configuration in which the first groove portion 75a is formed on the first inner surface 71, but for the fourth embodiment in which the first inner surface 71 is inclined with respect to the central axis Z, the configuration of the third embodiment (Figure 8) in which the second groove portion 75b is formed on the second inner surface 72, or the configuration of Figure 12 in which the groove portion 75 is formed across the first inner surface 71 and the second inner surface 72 may also be applied.

[0071] (3) In the second and third embodiments, a configuration in which multiple grooves 75 (75a, 75b) are formed on the inner circumferential surface 70 of the elastic body 50 has been illustrated. However, the number of grooves 75 formed on the inner circumferential surface 70 is not limited to the above examples. For example, a configuration in which one or two grooves 75 are formed on the inner circumferential surface 70, or a configuration in which three or more grooves 75 are formed on the inner circumferential surface 70 is also conceivable. Note that a configuration in which three or more grooves 75 are formed on the inner circumferential surface 70 of the elastic body 50 has the advantage of more easily maintaining uniformity in the fastening force from the elastic body 50 to the first shaft member 10 and the second shaft member 20 compared to a configuration in which the total number of grooves 75 is two or less. Furthermore, a configuration in which three or more grooves 75 are formed on the inner circumferential surface 70 has the advantage of efficiently discharging air from the space S to the external space.

[0072] (4) In the above-described embodiments, the outer peripheral surface 80 of the elastic body 50 includes a first outer surface 81 and a second outer surface 82, but the shape of the outer peripheral surface 80 is not limited to the above examples. For example, as illustrated in Fig. 13, the outer peripheral surface 80 of the elastic body 50 may be a simple cylindrical surface. In the configuration of Fig. 13, the outer diameter of the elastic body 50 is constant throughout from the first edge E1 to the second edge E2.

[0073] (5) In the above-described embodiments, the length L1 of the first inner surface 71 in the axial direction is greater than the length L2 of the second inner surface 72. However, the relationship between the length L1 of the first inner surface 71 and the length L2 of the second inner surface 72 is not limited to the above examples. For example, as illustrated in Fig. 14, a configuration is also envisioned in which the length L1 of the first inner surface 71 in the axial direction is less than the length L2 of the second inner surface 72. A configuration is also envisioned in which the length L1 of the first inner surface 71 and the length L2 of the second inner surface 72 are equal to each other.

[0074] (6) As illustrated in Figure 15, the end surface 55 of the elastic body 50 in the Z2 direction is not limited to a flat surface perpendicular to the central axis Z. For example, the end surface 55 of the elastic body 50 may be an inclined surface inclined with respect to the central axis Z. Specifically, the end surface 55 in Figure 15 is a truncated conical surface of revolution whose diameter increases in the Z2 direction. The configuration in Figure 15 facilitates the operation of inserting the second shaft member 20 into the shock absorber 30 (the second portion 52 of the elastic body 50) in step P2 described above.

[0075] (7) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of manufacture, etc., based on the term "nth."

[0076] F: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0077] A buffer device according to one aspect (aspect 1) of the present disclosure is a buffer device used for buffering between a first shaft member and a second shaft member including a cylindrical connecting end portion surrounding the first shaft member, and comprises an elastically deformable cylindrical elastic body and a cylindrical support body that is more rigid than the elastic body and surrounds the elastic body, the inner surface of the elastic body includes a first inner surface that contacts the outer surface of the first shaft member and a second inner surface that has an inner diameter larger than the first inner surface and contacts the outer surface of the connecting end portion, and at least one of the first inner surface and the second inner surface has one or more groove portions extending along the axial direction formed therein.

[0078] In the above-described embodiment, an elastic body is installed inside the support body, and a first inner surface of the elastic body contacts the outer surface of the first shaft member, and a second inner surface of the elastic body contacts the outer surface of the second shaft member (connecting end portion). Therefore, the elastic body buffers the collision between the first shaft member and the second shaft member. In other words, noise or wear caused by the collision between the first shaft member and the second shaft member can be suppressed.

[0079] Here, assume a process in which a first shaft member is inserted into a first portion of the elastic body corresponding to the first inner surface, and a second shaft member is inserted into a second portion of the elastic body corresponding to the second inner surface. During this process, the air in the space surrounded by the outer circumferential surface of the first shaft member, the second inner surface of the elastic body, and the tip surface of the connecting end is compressed by the second shaft member. In the configuration disclosed herein, one or more grooves extending along the axial direction are formed in at least one of the first inner surface and the second inner surface. The air in the space surrounded by the outer circumferential surface of the first shaft member, the second inner surface of the elastic body, and the tip surface of the connecting end is discharged to the outside through the one or more grooves. In other words, the repulsive force acting from the air in the space on the second shaft member is suppressed. Therefore, compared to a configuration in which grooves are not formed, assembly of the first shaft member, the second shaft member, and the shock absorber is facilitated.

[0080] In a specific example (Aspect 2) of Aspect 1, the inner circumferential surface of the elastic body further includes a stepped surface between the first inner surface and the second inner surface, and the stepped surface contacts the tip end surface of the connecting end. In the above aspect, the tip end surface of the connecting end of the second shaft member contacts the stepped surface on the inner circumferential surface of the elastic body, so the second shaft member is stably held by the elastic body. Therefore, the elastic body can effectively cushion the collision between the first shaft member and the second shaft member.

[0081] In a specific example (Aspect 3) of Aspect 2, the one or more grooves include a first groove extending axially from a first edge of the first inner surface opposite the stepped surface to the stepped surface. In the above aspect, the first groove extends axially from the first edge of the first inner surface to the stepped surface. Therefore, air in the space between the tip surface of the connecting end and the stepped surface can be discharged to the outside through the first groove. Furthermore, as a result of the first groove being formed on the first inner surface, the contact area between the first inner surface and the outer circumferential surface of the first shaft member is reduced. Therefore, the load required to insert or remove the first shaft member from the first portion of the elastic body corresponding to the first inner surface is reduced.

[0082] In a specific example (Aspect 4) of Aspect 2 or Aspect 3, the one or more grooves include a second groove extending axially from a second edge of the second inner surface opposite the stepped surface to the stepped surface. In the above aspect, the second groove extends axially from the second edge of the second inner surface to the stepped surface. Therefore, air in the space between the tip surface of the connecting end and the stepped surface can be discharged to the outside through the second groove. Furthermore, as a result of the second groove being formed on the second inner surface, the contact area between the second inner surface and the outer circumferential surface of the second shaft member is reduced. Therefore, the load required to insert or remove the second shaft member from the second portion of the elastic body corresponding to the second inner surface is reduced.

[0083] In a specific example (Aspect 5) of any of Aspects 1 to 4, the one or more grooves are a plurality of grooves, and the plurality of grooves are formed at equal intervals in the circumferential direction. In the above aspects, the plurality of grooves are formed at equal intervals on the inner circumferential surface of the elastic body. Therefore, compared to an embodiment in which the grooves are unevenly distributed in a specific region in the circumferential direction on the inner circumferential surface of the elastic body, the tightening force from the elastic body to the first shaft member or the second shaft member is equalized throughout the entire circumferential direction. Therefore, eccentricity between the first shaft member and the second shaft member due to uneven distribution of the grooves can be suppressed.

[0084] In a specific example (Aspect 6) of Aspect 5, the one or more grooves are three or more grooves. In the above aspect, three or more grooves are formed at equal intervals on the inner circumferential surface of the elastic body. Therefore, compared to an aspect in which two or fewer grooves are formed on the inner circumferential surface of the elastic body, it is easier to maintain uniformity in the tightening force from the elastic body to the first shaft member and the second shaft member.

[0085] In a specific example (Aspect 7) of any of Aspects 1 to 6, the first inner surface is an inclined surface in which a first inner diameter at a first edge portion of the first inner surface opposite the second inner surface is greater than a second inner diameter at a third edge portion of the first inner surface closer to the second inner surface. In the above aspects, the load required to insert the first shaft member into the first portion of the elastic body corresponding to the first inner surface gradually increases. This facilitates the operation of inserting the first shaft member into the elastic body.

[0086] A shaft connection structure according to one embodiment (embodiment 8) of the present disclosure includes a first shaft member, a second shaft member including a cylindrical connecting end portion surrounding the first shaft member, and a shock absorber used to cushion between the first shaft member and the second shaft member. The shock absorber includes an elastically deformable cylindrical elastic body and a cylindrical support body having higher rigidity than the elastic body and surrounding the elastic body. The inner circumferential surface of the elastic body includes a first inner surface that contacts the outer circumferential surface of the first shaft member and a second inner surface that has a larger inner diameter than the first inner surface and contacts the outer circumferential surface of the connecting end portion. At least one of the first inner surface and the second inner surface has one or more grooves extending along the axial direction. In the above embodiment, the elastic body is installed inside the support body. The first inner surface of the inner circumferential surface of the elastic body contacts the outer circumferential surface of the first shaft member, and the second inner surface of the inner circumferential surface contacts the outer circumferential surface of the second shaft member (connecting end portion). Therefore, a collision between the first shaft member and the second shaft member is cushioned by the elastic body. That is, it is possible to suppress abnormal noise or wear caused by a collision between the first shaft member and the second shaft member.

[0087] In a specific example (Aspect 9) of Aspect 8, the device further includes a sealing device installed between the outer circumferential surface of the first shaft member and the inner circumferential surface of the connecting end. In a configuration in which a sealing device is installed between the outer circumferential surface of the first shaft member and the inner circumferential surface of the connecting end, the space enclosed by the outer circumferential surface of the first shaft member, the second inner surface of the elastic body, and the tip surface of the connecting end is highly sealed, so the repulsive force acting from the air in the space on the second shaft member becomes particularly significant. Therefore, the present disclosure is particularly effective in that the repulsive force acting from the air in the space on the second shaft member can be suppressed by forming one or more grooves on the inner circumferential surface of the elastic body. [Explanation of symbols]

[0088] 100...shaft connecting structure, 10...first shaft member, 11...shaft main body portion, 12...connecting end portion, 13...connecting structure, 14...outer peripheral surface, 16...mounting groove, 20...second shaft member, 21...shaft main body portion, 22...connecting end portion, 23...connecting structure, 24...outer peripheral surface, 25...inner peripheral surface, 26...tip surface, 30...shock absorber, 41...bearing device, 42...sealing device, 50...elastic body, 51...first part, 52...second part, 53...connecting portion, 60...support body, 61...first cylindrical portion, 62...second cylindrical portion, 63...connecting portion, 70...inner peripheral surface, 71...first inner surface, 72...second inner surface, 73...step surface, 80...outer peripheral surface, 81...first outer surface, 72...second outer surface, 73...step surface.

Claims

1. A shock absorber used for shock absorbing between a first shaft member and a second shaft member including a cylindrical connecting end portion surrounding the first shaft member, an elastically deformable cylindrical elastic body; a cylindrical support body having a higher rigidity than the elastic body and surrounding the elastic body; The inner circumferential surface of the elastic body is a first inner surface that contacts an outer peripheral surface of the first shaft member; a second inner surface having an inner diameter larger than that of the first inner surface and in contact with an outer circumferential surface of the connecting end portion; At least one of the first inner surface and the second inner surface is formed with one or more grooves extending along the axial direction. Buffer device.

2. The inner circumferential surface of the elastic body is further including a step surface between the first inner surface and the second inner surface, The step surface contacts the tip surface of the connecting end portion. The shock absorber of claim 1.

3. The one or more grooves include a first groove extending in the axial direction from a first edge portion of the first inner surface opposite to the stepped surface to the stepped surface. The shock absorber of claim 2.

4. The one or more grooves include a second groove extending in the axial direction from a second edge portion of the second inner surface opposite to the stepped surface to the stepped surface. The shock absorber according to claim 2 or 3.

5. the one or more grooves are a plurality of grooves, The plurality of grooves are formed at equal intervals in the circumferential direction. The shock absorber according to claim 1 (or any one of claims 1 to 4).

6. The one or more grooves are three or more grooves. The shock absorber of claim 5.

7. The first inner surface is an inclined surface in which a first inner diameter at a first edge portion of the first inner surface opposite to the second inner surface is larger than a second inner diameter at a third edge portion of the first inner surface close to the second inner surface. The shock absorber according to claim 1 (or any one of claims 1 to 6).

8. A first shaft member; a second shaft member including a cylindrical connecting end portion surrounding the first shaft member; a shock absorber used for shock absorption between the first shaft member and the second shaft member, The shock absorber is an elastically deformable cylindrical elastic body; a cylindrical support body having a higher rigidity than the elastic body and surrounding the elastic body; The inner circumferential surface of the elastic body is a first inner surface that contacts an outer peripheral surface of the first shaft member; a second inner surface having an inner diameter larger than that of the first inner surface and in contact with an outer circumferential surface of the connecting end portion; At least one of the first inner surface and the second inner surface is formed with one or more grooves extending along the axial direction. Axial connection structure.

9. a sealing device disposed between the outer peripheral surface of the first shaft member and the inner peripheral surface of the connecting end portion; The shaft coupling structure of claim 8, further comprising:

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