Damper mounting structure in seismic isolation devices

Abstract

To suppress a phenomenon that the deterioration of a damper is early progressed at a peripheral portion of an insertion port of an insertion hole of an attachment base part, in a "damper attachment structure of a seismic isolator".SOLUTION: In a damper attachment structure 10, a damper 1 is fixed to an attachment base part 2 by a plurality of axial fixing tools 23 which penetrate the attachment base part 2 and a center axis of the damper 1. In the damper 1, with respect to an effective cross section area S of a cross section in a diameter direction of a portion which is penetrated with the axial fixing tools 23, an effective cross section area S1 of a cross section in the diameter direction located in a position which is close to an insertion port 212 of a damper insertion hole 211 is equal to or larger than an effective cross section area S2 of a cross section in the diameter direction located in a position which is far from the insertion port 212, and the effective cross section area S1 of a cross section in the direction which is the nearest from the insertion port 212 is larger than an effective cross section area S3 of a cross section in the diameter direction which is the farthest from the insertion port 212.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to a damper mounting structure for a seismic isolation device. More specifically, this invention relates to a damper mounting structure for a seismic isolation device, which is an elastoplastic hysteresis damper that utilizes the plastic deformation of metal, and in which a U-shaped curved portion is formed between a pair of straight portions. [Background technology]

[0002] As an example of a seismic isolation device that is placed between the superstructure and substructure of a building to absorb vibrational energy such as earthquakes, there is a known seismic isolation device that utilizes the plastic deformation of metal to provide an elastoplastic type hysteretic seismic isolation damper, which has a U-shaped curved section having a pair of straight sections and a curved section connecting them, as a vibrational energy absorption section (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-107225 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] A widely adopted mounting structure for attaching a damper having a U-shaped curved section to a building frame is one in which the straight section of the damper is inserted into a block-shaped mounting base that can be joined directly to the frame or via another base plate, and the damper is then fixed to the mounting base with fasteners such as mounting bolts (see Figures 1 and 2; however, in Figure 1, the "bolts" are not shown).

[0005] However, in damper mounting structures where the inserted damper is fastened with a axial through member such as a bolt, as described above, a phenomenon was observed where the damper deteriorated relatively quickly around the bolt fastening portion, which is located closer to the insertion hole of the mounting base, on the straight section of the damper.

[0006] The present invention relates to a damper mounting structure for seismic isolation devices, in which the straight portion of a damper having a U-shaped curved section is inserted into an insertion hole in a block-shaped mounting base and fixed with fasteners such as mounting bolts. The objective is to suppress the phenomenon in which the damper deteriorates prematurely around the insertion opening of the insertion hole in the mounting base. [Means for solving the problem]

[0007] The inventors of the present invention have come to the realization that the above problem can be solved by optimizing the effective cross-sectional area of ​​the diameter cross-section at each part of the straight section of the damper, by adjusting the diameter of the portion of the shaft-shaped fastener, such as a bolt, that penetrates the damper to a different diameter for each individual bolt than usual, thereby completing the present invention. More specifically, the present invention provides the following.

[0008] (1) A damper mounting structure in a seismic isolation device, comprising a damper having a pair of parallel straight sections and a curved section connecting one end of each of the straight sections, and a mounting base having a damper insertion hole into which a part of the straight section of the damper is inserted, wherein the damper is fixed to the mounting base by a plurality of axial fasteners that pass through the mounting base and the central axis of the damper, with a part of the straight section inserted into the damper insertion hole of the mounting base, and the damper In a damper mounting structure, in each portion through which the shaft-shaped fixing device penetrates, the effective cross-sectional area of ​​the diametrical cross-section, which is the area of ​​the portion excluding the cross-sectional area of ​​the space through which the shaft-shaped fixing device penetrates, is such that the effective cross-sectional area of ​​one diametrical cross-section is equal to or greater than the effective cross-sectional area of ​​another diametrical cross-section located further away from the insertion opening of the damper insertion hole, and furthermore, the effective cross-sectional area of ​​the diametrical cross-section closest to the insertion opening is greater than the effective cross-sectional area of ​​the diametrical cross-section furthest from the damper insertion hole.

[0009] According to the damper mounting structure of (1), in a "damper mounting structure for seismic isolation devices" in which the straight portion of a damper having a U-shaped curved portion is inserted into an insertion hole in a block-shaped mounting base and fixed with fasteners such as mounting bolts, it is possible to suppress the phenomenon in which the damper deteriorates relatively quickly in the area around the insertion opening of the damper insertion hole in the mounting base.

[0010] (2) The damper mounting structure according to (1), wherein L is defined as the distance from the insertion opening of the mounting base to the central axis of the foremost axial fixing device that is closest to the insertion opening, and D is the diameter of the damper, and L / D is a value of 1.0 or more.

[0011] According to the damper mounting structure of (2), when there is a certain amount of clearance between the inner surface of the damper insertion hole and the damper, the above-mentioned effects of the damper mounting structure of (1) can be realized with high precision. In addition, it is possible to effectively suppress the occurrence of premature fracture near the through-hole through which the foremost axial fixing device, which is located closest to the insertion opening of the damper insertion hole, passes, which is caused by the presence of clearance.

[0012] (3) The damper mounting structure according to (1) or (2), wherein the shape of the diametrical cross-section is circular.

[0013] According to the damper mounting structure of (3), by forming the vibration energy absorbing part of the seismic isolation device with a round bar-shaped member, it is possible to reduce the anisotropy of seismic isolation performance due to differences in the direction of vibration.

[0014] (4) The damper mounting structure according to (1) or (2), wherein the shape of the diametrical cross-section is a polygonal shape other than circular.

[0015] According to the damper mounting structure of (4), by forming the vibration energy absorbing part of the seismic isolation device with a rod-shaped member having a polygonal cross-section, the bending moment in a direction perpendicular to the length direction of the damper (see Figure 3) can be more stably borne at the fitting part. [Effects of the Invention]

[0016] According to the present invention, in a mounting structure in which the straight portion of a damper having a U-shaped curved portion is inserted into an insertion hole of the block-shaped mounting base and fixed with fasteners such as mounting bolts, it is possible to suppress the phenomenon in which the deterioration of the damper progresses relatively quickly in the area surrounding the insertion hole of the mounting base. [Brief explanation of the drawing]

[0017] [Figure 1]It is a perspective view showing an example of a seismic isolation device including a damper attachment structure in the seismic isolation device of the present invention. [Figure 2] It is a perspective view of a damper attachment structure in the seismic isolation device of the present invention. [Figure 3] It is a partially enlarged view showing in more detail the joint portion between the damper and the attachment base portion in the damper attachment structure of FIG. 3. [Figure 4] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in the damper attachment structure in the seismic isolation device of the present invention. [Figure 5] It is a cross-sectional view taken along the line A-A, B-B, and C-C of FIG. 4. [Figure 6] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in the damper attachment structure (a particularly preferred embodiment in the case of a large clearance) in the seismic isolation device of the present invention. [Figure 7] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in another embodiment of the damper attachment structure in the seismic isolation device of the present invention. [Figure 8] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in another embodiment of the damper attachment structure in the seismic isolation device of the present invention. [Figure 9] It is a drawing for explaining the shape of the counter bore in another embodiment of the damper attachment structure shown in FIG. 8. [Figure 10] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in another embodiment (an embodiment using a rivet) of the damper attachment structure in the seismic isolation device of the present invention. [Figure 11] It is a cross-sectional view of the joint portion between the damper and the attachment base portion in another embodiment (an embodiment using a pin) of the damper attachment structure in the seismic isolation device of the present invention.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the embodiments described below.

[0019] <Seismic isolation device> First, an example of an embodiment of the present invention, the overall configuration of a "seismic isolation device" that can be constructed using the damper mounting structure of the present invention, will be described with reference to the drawings.

[0020] As shown in Figure 1, the seismic isolation device 100, which includes the "damper mounting structure in a seismic isolation device" (hereinafter also simply referred to as the "damper mounting structure") of the present invention, has dampers 1 (1A to 1D) made of elastoplastic material joined to an upper base plate 3 connected to the superstructure of a building and a lower base plate 4 connected to the substructure via mounting base parts 2 (2A to 2D). In this seismic isolation device 100, vibration energy is absorbed by the elastoplastic deformation of the dampers 1 (1A to 1D) for the seismic isolation device when an earthquake occurs.

[0021] The dampers 1 (1A~1D) constituting the seismic isolation device 100 are U-shaped dampers having a pair of parallel straight sections 12 (12A~12D) and curved sections 11 (11A~11D) connecting one end of each of the straight sections 12 (12A~12D), as shown in Figures 1 and 2. Furthermore, various metal materials used in conventional seismic isolation dampers can be used without particular limitation as the elastoplastic members forming the dampers 1. These metal materials can be steel, which has been widely used in the past, or non-ferrous metals such as copper or aluminum, or alloys of these metals. In the damper 1, the curved section 11 is formed by bending a rod-shaped elastoplastic member made of the above-mentioned metal material near the center.

[0022] The damper 1 is preferably made of a rod-shaped elastoplastic member whose cross-section perpendicular to its longitudinal direction (cross-section 13 in Figure 2; in this specification, this cross-section is referred to as the "diametrical cross-section") is circular or a polygonal shape other than circular. For example, the length of the straight section 12 of the damper 1 is 700 mm, the radius of the curved section 11 is 200 mm, and the shape of the cross-section 13 is circular with a radius of 80 mm. However, these shapes and sizes can be any size depending on the required seismic isolation performance.

[0023] Furthermore, as shown in Figure 2, it is more preferable that the cross-sectional shape of the damper 1 is circular. By making the cross-sectional shape of the vibration energy absorbing part circular, when it is arranged at an angle as shown in Figure 1, the difference in mechanical properties for all horizontal deformations can be reduced, thereby contributing to reducing the anisotropy of the vibration energy absorption performance.

[0024] Alternatively, the damper 1 can have a polygonal shape other than a circle in its diametrical cross-section. In this case, the damper insertion hole 211 of the mounting base 2 will also have the same polygonal shape, and the bending moment around the x-axis (see Figure 3) on the damper 1 can be more stably borne at the fitting portion between the straight section 12 of the damper 1 and the damper insertion hole 211 of the mounting base 2.

[0025] <Damper mounting structure in seismic isolation devices> The "damper mounting structure in a seismic isolation device" of the present invention refers to a partial structure for attaching a U-shaped damper made of an elastoplastic material, which functions as a vibration energy absorption part, to the building frame in a seismic isolation device 100, and is a part (damper mounting structure 10) composed of a U-shaped damper 1 and a mounting base 2.

[0026] In the damper mounting structure 10, as shown in Figure 2, with a portion of both ends of the straight section 12 of the damper 1 inserted into the damper insertion hole 211 of the mounting base 2, both straight sections 12 of the damper 1 are fixed to the mounting base 2 by a plurality of axial fasteners (e.g., bolts and nuts) 23 that pass through the mounting base 2 and the central axis of the damper 1.

[0027] As shown in Figures 2 and 3, the mounting base portion 2 may consist of a damper insertion portion 21 in which a damper insertion hole 211 is formed, and a joining plate portion 22 that serves as the joint between the upper substrate 3 and the lower substrate 4, or it may be a block-shaped member in which the parts capable of performing each of these functions are integrally formed.

[0028] The axial fastener 23 in the damper mounting structure 10 may be a bolt as shown in Figures 2 to 4, or it may be another fastener (for example, the rivet 25 shown in Figure 10 or the pin 26 shown in Figure 11) that can fasten and secure the mounting base 2 and the central axis of the damper 1 in such a manner that the axial portion penetrates both.

[0029] The damper mounting structure 10 according to the present invention is optimized so that the effective cross-sectional areas S (S1, S2, S3) of each diametrical cross-section (AA cross-section, BB cross-section, CC cross-section) (see Figure 4) in the portion through which each axial fixing device 23 (23a, 23b, 23c) in the damper 1 penetrates have a specific relative magnitude relationship (see Figure 5).

[0030] Here, in this specification, the "effective cross-sectional area" of the "diametrical cross-section" of the damper refers to the area S(S1, S2, S3) of the diametrical cross-section of the portion through which each axial fastener 23 penetrates, excluding the cross-sectional area of ​​the space through which the axial fastener 23 penetrates. In this specification, the "effective cross-sectional area" of the "diametrical cross-section" of the damper refers to the area of ​​the space through which the axial fastener 23 penetrates.

[0031] The effective cross-sectional area S (S1, S2, S3) of the diametrical cross-section of the portion through which each axial fixture 23 penetrates in the straight portion 12 of the damper 1 of the damper mounting structure 10 is specifically the effective cross-sectional area S of the cross-section closer to the insertion port 212 of the damper insertion hole 211 a (As an example, S1 in FIG. 5) is equal to or greater than the effective cross-sectional area S of the diametrical cross-section at a position farther from the insertion port 212 compared to that cross-section (a+1) (As an example, S2 in FIG. 5)) (S a ≧S (a+1 )), and moreover, the effective cross-sectional area S of the rearmost cross-section at the position farthest from the insertion port 212 n (As an example, S3 in FIG. 5) is smaller than the effective cross-sectional area S1 (as an example, S1 in FIG. 5) of the cross-section closest to the insertion port 212 (S n <S1), which is the main feature. The diameter of the space portion through which the axial fixture 23 penetrates is approximately the same as the diameter φ (φ a、 φ b 、φ c ) of the shaft portion 231 (231a, 231b, 231c) of each axial fixture 23. Therefore, the diameter φ of the shaft portion 231 of each axial fixture 23 is the diameter φ of the shaft portion 231c of the rearmost axial fixture 23c, which is the largest and farthest from the insertion port 212 c becomes the largest.

[0032] As an example, in the damper mounting structure 10 shown in Figures 3 and 4, there are three axial fasteners 23 (n=3). In this damper mounting structure 10, when a force P acts in the x direction, the load on the cross-section of the damper 1 at the point where the a-th axial fastener 23 penetrates is P × (3-a+1) / n. Specifically, in the damper mounting structure 10 shown in Figures 3 and 4, the largest load P is applied to the point where the first axial fastener 23a (counting from the insertion opening 212 side of the damper insertion hole 211) penetrates, and the smallest load (P / n) is applied to the cross-section at the bolt position at the point where the axial fastener 23c (farthest from the insertion opening 212 of the damper insertion hole 211) penetrates. Therefore, to ensure that uniform stress is generated in each cross-section including the space through which each axial fastener 23 penetrates, the effective cross-sectional area of ​​each cross-section is set to S a = a / n × S n This allows for the maximum possible load to be borne.

[0033] Therefore, the effective cross-sectional area S in each of the above cross-sections of the damper mounting structure 10 is calculated as follows, where n is the number of axial fasteners (mounting bolts) 23, Sa is the effective cross-sectional area of ​​the straight section 12 of the damper 1 at the a-th bolt position counting from the side of the insertion opening 212 of the damper insertion hole 211, and Sn is the effective cross-sectional area at the n-th bolt position. a = a / n × S n It is preferable to do so.

[0034] Furthermore, in the damper mounting structure 10, the forces in the Y and Z directions shown in Figure 3 are borne by the fitting structure between the straight section 12 of the damper 1 and the damper insertion hole 211, so the load on the axial fixing device (mounting bolt) 23 is very small. As for the force in the X direction shown in Figure 3, the stress on each of the above cross-sections can be further reduced by increasing the number (n) of the axial fixing device (mounting bolt) 23.

[0035] Furthermore, in the damper mounting structure 10, for example, as the rod-shaped elastoplastic member forming the damper 1, a special shaped rod material (a rod material with an uneven diameter cross-section) is used, in which the area of ​​the "diameter cross-section" at each bolt position is appropriately changed at any part as needed, thereby reducing the diameter of the shaft portion 231 at each position (φ a、 φ b , φ c While it is theoretically possible to adjust the overall structure so that the effective cross-sectional area S of the damper at each position satisfies the above conditions, while keeping the ) uniform, such specially shaped rods are costly to obtain and process, and the fitting manner between the damper 1 and the mounting base 2 must also be complex, which in turn leads to a significant increase in manufacturing and maintenance costs. In contrast, the present invention can be implemented at a lower cost by using general-purpose rods with a uniform "diameter cross-section" without using such specially shaped rods. In this respect as well, the present invention has advantages over the prior art.

[0036] In the damper mounting structure 10, as shown in Figure 6, a small clearance δ may occur between the inner circumferential surface of the damper insertion hole 211 and the outer circumferential surface of the straight portion 12 of the damper 1. In the state shown in Figure 6, bending deformation may occur in the rod-shaped member made of the elastoplastic material that forms the damper 1, even in the portion of the straight portion 12 of the damper 1 that is inserted into the damper insertion hole 211. On the other hand, the rod-shaped member made of the elastoplastic material has less strength in the area surrounding the part through which the shaft-shaped fixing device 23 passes, compared to other parts, because the cross-sectional area (effective cross-sectional area) is smaller. As a result, in the rod-shaped member made of the elastoplastic material that forms the damper 1, the bending deformation described above may act on the area near the through-hole through which the foremost shaft-shaped fixing device 23a, which is located closest to the insertion opening 212 of the damper insertion hole 211, can pass, causing premature fracture to occur near the through-hole.

[0037] As shown in Figure 6, in the damper mounting structure 10, when L is defined as the distance from the insertion opening 212 of the damper insertion hole 211 of the mounting base 2 to the central axis of the foremost axial fixing device 23a that is closest to the insertion opening 212, and D is the diameter of the damper 1, it is preferable that the value of L / D be 1.0 or more, and more preferably 1.4 or more. Specifically, it is preferable to position the foremost axial fixing device 23a at a position where the value of L / D satisfies L / D ≥ 1.0, and more preferably at a position where the same value satisfies L / D ≥ 1.4. This reduces the influence of the bending deformation described above that occurs in the diametrical cross-section of the portion through which the foremost axial fixing device 23a that is closest to the insertion opening 212 of the damper insertion hole 211 penetrates, and thus suppresses the occurrence of the above-mentioned fracture of the member forming the damper 1, which is particularly likely to occur in the vicinity of this position.

[0038] For example, in the damper mounting structure for testing designed with L / D=0.56 (comparative example), fracture occurred prematurely in the "repeated loading test" described below, particularly when a load was applied in the Y direction as shown in Figure 3. This fracture occurred in the portion extending from the insertion opening 212 of the damper insertion hole 211 to the through-hole of the foremost axial fixing device 23a, which is closest to the insertion opening 212. In contrast, in the damper mounting structure for testing designed with L / D=1.44, without changing any other conditions (example), it was confirmed that no fracture occurred in the portion inserted into the damper insertion hole 211, including the area around the through-hole, even in the ultimate state where the damper was loaded until it fractured, in the same "repeated loading test" as described above.

[0039] In this specification, the "repeated loading test" refers to a test in which alternating positive and negative loading is applied to a test damper, causing relative displacement of the upper substrate 3 and the lower substrate 4 in the X or Y direction in Figure 3 at a constant amplitude over a predetermined number of repetitions. In this specification, the above description is based on test results when the loading is repeated until the damper breaks and loses a predetermined function. It should be noted that the direction of seismic motion experienced by the actual device is not limited to the two directions of X and Y, but the effects of the present invention are, of course, effective for any direction of applied load.

[0040] Furthermore, if the diametrical cross-section of damper 1 is a polygonal shape other than a circle, the diameter D of the damper cannot be defined. In this case, the diametrical cross-section is defined by the equivalent cross-sectional diameter Deq. The definition of Deq is as shown in the following equation (Equation 1).

[0041]

number

[0042] The damper mounting structure of the present invention can also be implemented as damper mounting structure 10A shown in Figure 7, as an example of an embodiment. In damper mounting structure 10A, bolts 23a, 23b, and 23c are used as axial fasteners 23. Each of these bolts passes through holes formed in both the mounting base portion 2 and the damper 1, and engages with a female thread formed in the mounting base portion 2, thereby fastening and fixing the mounting base portion 2 and the damper 1.

[0043] As another embodiment, the damper mounting structure of the present invention can also be implemented as damper mounting structure 10B shown in Figure 8. In damper mounting structure 10B, as the shaft-shaped fixing device 23, bolts 23a, 23b, 23c and nuts 232 (232a, 232b, 232c) that are screwed with these are used, similar to the shaft-shaped fixing device 23 of damper mounting structure 10 shown in Figure 6.

[0044] In this damper mounting structure 10B, bolts 23a, 23b, and 23c pass through holes formed in both the mounting base 2 and the damper 1, and are fastened with nuts 232 inside counterbores 24 formed on the structural side of the mounting base 2, thereby fixing the mounting base 2 and the damper 1. In the damper mounting structure 10B, the nuts 232 are positioned on the structural side, but the relative positions of the bolts and nuts may be reversed.

[0045] In the damper mounting structure 10B, once the damper is attached to the seismic isolation device 100, it becomes impossible to access the internal components of the counterbore 24, and therefore, there is essentially no way to retighten the bolts if they loosen. However, as shown in Figure 9, by making the shape of the counterbore 24 such that the width across flats W is smaller than the width across flats w of the nut 232, relative rotation of the nut 232 with respect to the mounting base 2 can be suppressed. With this configuration, even if the bolts loosen, it becomes possible to retighten only the head of the bolt 23 by applying torque using a torque wrench or the like.

[0046] As another embodiment, the damper mounting structure of the present invention can also be implemented as damper mounting structure 10C shown in Figure 10. In damper mounting structure 10C, rivets 25 (25a, 25b, 25c) are used as shaft-shaped fasteners 23.

[0047] In this damper mounting structure 10C, the rivets 25 (25a, 25b, 25c) pass through holes formed in both the mounting base 2 and the damper 1. Furthermore, by crushing the sides of the crimping portions 252 (252a, 252b, 252c) of the rivets, which are originally straight round rods, they are deformed into a flat shape. Simultaneously, plastic flow fills the clearance between the mounting base 2, the damper 1 and the rivets 25 (25a, 25b, 25c), thereby stably fixing the mounting base 2 and the damper 1. In the example shown in Figure 10, the rivet heads 251 are positioned on the building structure side, but the heads may be on the opposite side.

[0048] As another embodiment, the damper mounting structure of the present invention can also be implemented as the damper mounting structure 10D shown in Figure 11. In the damper mounting structure 10D, pins 26 (26a, 26b, 26c) are used as shaft-shaped fixing devices 23.

[0049] In this damper mounting structure 10D, the pins 26 (26a, 26b, 26c) pass through holes formed in both the mounting base 2 and the damper 1, and the fixing parts are prevented from falling out by passing cotter pins through holes formed near the tips of the pins 26 (26a, 26b, 26c). In the example shown in Figure 11, a head is formed on one side of the pins 26 (26a, 26b, 26c), but this head may be omitted and both sides may be secured with cotter pins. Alternatively, the cotter pins may be replaced with snap rings. Or, without using cotter pins or heads, a straight pin shape can be used by combining it with a method that uses negative clearance, such as press-fitting, shrink-fitting, or cold-fitting. [Explanation of Symbols]

[0050] 1 (1A~1D) Damper 11 (11A~11D) Curved section 12(12A~12D) Straight section 13(13a, ~13c) Diameter cross section 2 (2A~2D) Mounting base 21 Damper insertion section 211 Damper insertion hole 212 Insertion port 22 Joint plate part 23 (23a, 23b, 23c) Shaft-shaped fastener (bolt) 231(231a, 231b, 231c) Shaft 232 nuts 24 Counterbore 25 (25a, 25b, 25c) rivets 251(251a, 251b, 251c) Head 252 (252a, 252b, 252c) Crimping part 26 (26a, 26b, 26c) pins 3. Upper circuit board 4 Lower circuit board 10 (10A, 10B) Damper mounting structure 100 seismic isolation devices S(S1, S2, S3) Effective cross-sectional area of ​​the diameter cross-section of the damper δ clearance

Claims

1. A damper mounting structure in a seismic isolation device, A damper having a pair of parallel straight sections and a curved section connecting one end of each of the straight sections, It consists of a mounting base having a damper insertion hole into which a part of the straight portion of the damper is inserted, The damper is fixed to the mounting base by a plurality of axial fasteners that pass through the mounting base and the central axis of the damper, with a portion of the straight section inserted into the damper insertion hole of the mounting base. In the damper, in the portion through which each of the axial fasteners passes, Regarding the effective cross-sectional area of ​​the diametrical cross-section, which is the area of ​​the portion excluding the cross-sectional area of ​​the space through which the axial fixing device passes, the effective cross-sectional area of ​​one diametrical cross-section is equal to or greater than the effective cross-sectional area of ​​another diametrical cross-section located further away from the insertion opening of the damper insertion hole, and furthermore, the effective cross-sectional area of ​​the diametrical cross-section closest to the insertion opening is greater than the effective cross-sectional area of ​​the diametrical cross-section furthest from the damper insertion hole. Damper mounting structure.

2. When L is defined as the distance from the insertion opening of the mounting base to the central axis of the foremost axial fixing device that is closest to the insertion opening, and D is the diameter of the damper, then L / D is a value of 1.0 or greater. The damper mounting structure according to claim 1.

3. The shape of the diametrical cross-section is circular. The damper mounting structure according to claim 1 or 2.

4. The shape of the diametrical cross-section is a polygon other than a circle. The damper mounting structure according to claim 1 or 2.

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