Vibration isolator and shock absorber

Abstract

To provide a vibration isolator and a shock absorber having a simple structure.SOLUTION: The vibration isolation device 10 includes a spring element 20 and a negative stiffness body 30 whose restoring behavior exhibits a negative stiffness characteristic, and the negative stiffness body 30 includes a stretchable structure 32 having a negative Poisson's ratio and stretchable, a first plate-like member 34a provided on one side of the stretchable structure 32, and a second plate-like member 34b provided on the other side of the stretchable structure 32. The stretchable structure 32 is preferably an auxetic structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to vibration isolation and damping devices. [Background technology]

[0002] Patent Document 1 describes a vibration isolation device that includes a first elastic body for suppressing vibrations applied to an object to be isolated from vibrations, and a second elastic body (excluding those arranged so that the longitudinal direction of the second elastic body is perpendicular to the direction of vibration) whose static restoring behavior after buckling exhibits negative stiffness characteristics and for suppressing vibrations applied to the object to be isolated from vibrations, and the second elastic body deforms in a single buckling mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7352272 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure describes vibration isolators and dampers of simple construction. [Means for solving the problem]

[0005] A vibration isolation device according to one aspect of the present disclosure is a vibration isolation device including a spring element and a negative stiffness body whose restoring behavior exhibits negative stiffness characteristics, wherein the negative stiffness body includes a stretchable structure having a negative Poisson's ratio and capable of stretching and contracting, a first plate-like member provided on one side of the stretchable structure and supporting an object to be isolated, and a second plate-like member provided on the other side of the stretchable structure and supporting the object to be isolated.

[0006] In a vibration isolation device according to another aspect of the present disclosure, the expansion and contraction structure is an auxetic structure.

[0007] In another aspect of the present disclosure, the vibration isolation device has an auxetic structure having cell-forming members that form a plurality of cells of substantially the same shape arranged side by side, and when a compressive force is applied in the direction of vibration, the cell-forming members deform and the auxetic structure contracts in a direction intersecting the vibration direction.

[0008] In a vibration isolation device according to another aspect of the present disclosure, the spring constant of the spring element is set to a value that can offset the negative stiffness characteristic of the negative stiffness body.

[0009] In a vibration isolation device according to another aspect of the present disclosure, the vibration direction is a vertical direction, and the device further includes a guide section that guides the object to be isolated in the vertical direction.

[0010] A shock absorber according to one aspect of the present disclosure includes a stretchable structure having a negative Poisson's ratio, a first plate-like member provided on one side of the stretchable structure, and a second plate-like member provided on the other side of the stretchable structure.

[0011] In a shock absorber according to another aspect of the present disclosure, the expansion structure is an auxetic structure. [Effects of the Invention]

[0012] The vibration isolation device and shock absorber according to the present disclosure have a simple structure. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration diagram of a vibration isolation device according to a first embodiment. [Figure 2A] FIG. 2 is a front view illustrating the structure of a negative stiffness body. [Figure 2B] FIG. 2 is a perspective view showing the details of the structure of a negative stiffness body. [Figure 2C] FIG. 10 is an explanatory diagram showing an example of dimensions of cell forming members that form cells of an auxetic structure. [Figure 3] 10(A) to 10(C) are explanatory diagrams showing how a negative stiffness body undergoes buckling deformation. [Figure 4]10 is a graph showing the restoring force after buckling of a negative stiffness body. [Figure 5] 10 is a graph showing the tangential stiffness of a negative stiffness body and a vibration isolation device after buckling. [Figure 6] 10 is a graph showing the restoring force of the vibration isolation device. [Figure 7] 10 is a graph showing an example of frequency response characteristics of vibration transmissibility of the vibration isolation device according to a simulation. [Figure 8] FIG. 10 is a configuration diagram of a vibration isolation device according to a second embodiment. [Figure 9] 10 is a graph showing the tangential stiffness of a low stiffness body. [Figure 10] FIG. 10 is an explanatory diagram showing another example of an expandable structure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that in the drawings, parts that are not relevant to the description may be omitted.

[0015] [First embodiment] The vibration isolation device 10 according to the first embodiment can suppress vertical vibrations (see arrows in FIG. 1) that are applied to the object 14 to be isolated from the base 12, which is a vibration source. The vibration isolation device 10 comprises a coil spring 20, a negative stiffness body 30, and a guide part (not shown), and the object 14 to be isolated is supported via the vibration isolation device 10 by an upper fixed part 122 of the base 12 arranged at a distance in the vertical direction and a lower fixed part 124 which holds the upper fixed part 122.

[0016] The coil spring (an example of a spring element) 20 is, for example, a tension coil spring. One end of the coil spring 20 is attached to the upper fixed part 122, and the other end is attached to the upper surface of the object 14 to be isolated from vibrations, thereby suppressing vibrations acting on the object 14 to be isolated from vibrations. The spring element is not limited to the coil spring 20.

[0017] The negative stiffness body 30 is a shock absorber whose restoration behavior after buckling exhibits negative stiffness characteristics, and as shown in FIGS. 2A and 2B, includes an expansion and contraction structure 32, a plate-like member 34a, and a plate-like member 34b. The expansion structure 32 has a rectangular parallelepiped outer shape. The expansion structure 32 is expandable in the vibration direction and in a direction intersecting the vibration direction, and exhibits a negative Poisson's ratio.

[0018] Specifically, the stretchable structure 32 is an auxetic structure, and is made of a material such as resin. Here, the auxetic structure has a cell forming member 322 that forms a plurality of cells S, and exhibits a negative Poisson's ratio. Each cell S is arranged side by side when viewed from the front, and has substantially the same shape when not stretched or contracted. However, each cell S is not limited to having the same shape, and cells of different shapes and sizes may be included.

[0019] When a compressive force is applied to such an auxetic structure in the direction of vibration (vertical direction), the cell-forming members 322 deform, and the auxetic structure contracts in a direction intersecting the vibration direction (horizontal direction). On the other hand, when a tensile force is applied to the auxetic structure in the direction of vibration (vertical direction), the cell-forming members 322 deform, and the auxetic structure expands in a direction intersecting the vibration direction (horizontal direction).

[0020] The plate-like member (an example of a first plate-like member) 34a is a beam element that extends in the vibration direction (vertical direction) and supports the object 14 to be isolated from vibration. The upper end of the plate-like member 34a is fixed to the object 14 to be isolated from vibrations, and the lower end is fixed to the lower fixing portion 124. The plate-like member 34a is, for example, a thin metal plate.

[0021] Plate-like member 34b (an example of a second plate-like member) is a beam element that extends in the vibration direction (vertical direction) and supports object 14 to be isolated from vibration, and is provided on the other side of expansion structure 32. That is, when viewed from the front, plate-like member 34b is provided on the opposite side of plate-like member 34a across expansion structure 32. The upper end of the plate-like member 34b is fixed to the object 14 to be isolated from vibrations, and the lower end is fixed to the lower fixing portion 124. Plate-shaped member 34b is, for example, a thin metal plate, and has the same thickness as plate-shaped member 34a. Note that "same" here does not mean "same" in the strict sense. In other words, "same" means "substantially the same," allowing for design and manufacturing errors. In addition, the lower surface of the object 14 to be isolated from vibrations is supported only by the plate-like members 34a and 34b.

[0022] The guide portion (not shown) can restrain displacement of the object 14 to be isolated from vibration in a direction intersecting the direction of vibration, and can guide the object 14 to be isolated from vibration in the vertical direction. The guide portion is, for example, a linear guide extending in the vertical direction. [Example]

[0023] Next, it will be explained that the negative stiffness body 30 provided in the vibration isolation device 10 is effective as a vibration isolation element and can be applied to a passive vibration isolation system.

[0024] The inventors performed static mechanical analysis on a finite element model of the negative stiffness body 30 provided in the vibration isolation device 10 to investigate the restoring force characteristics.

[0025] The finite element model of the negative stiffness body 30 has a width dimension W of 36 mm, a height dimension L of 180 mm, and a thickness t of 10 mm as shown in FIG. 2A. The expandable structure 32 is an auxetic structure made of resin. The cell-forming member 322 shown in FIG. 2C has a width dimension Ws of 6 mm, a height dimension Ls of 9 mm, and a thickness ts of 0.5 mm. The two plate-like members 34a and 34b are made of metal, and the plate thickness Tp1 of the plate-like member 34a and the plate thickness Tp2 of the plate-like member 34b shown in FIG. 2A are each 0.5 mm.

[0026] The two plate-like members 34a, 34b were completely fixed at the top and bottom ends, and the expandable structure 32 and the plate-like members 34a, 34b were bonded at three points: the top and bottom ends and the center (a total of six points for the two plate-like members 34a, 34b). When compressive displacement was applied to the two plate-like members 34a and 34b in the longitudinal direction, causing the plate-like members 34a and 34b to buckle, the relationship between the applied longitudinal displacement and the restoring force of the plate-like members 34a and 34b was examined using finite element analysis. The material properties of each structure used in the analysis are shown in Table 1.

[0027] [Table 1]

[0028] Furthermore, when buckling the plate-like members 34a and 34b, an initial external lateral force was applied so that both plates were bent in the direction of the stretchable structure 32. However, once buckling began, the external lateral force was removed. This deformation caused a large deformation of the stretchable structure (auxetic structure) 32, which resulted in a change in the resistance to buckling of the plate-like members 34a and 34b, with the intention of producing negative stiffness in the restoring force characteristics of the structure consisting of the stretchable structure 32 and the plate-like members 34a and 34b.

[0029] In the finite element model of the negative stiffness body 30 constructed in this manner, when displacements of 0.049 mm, 0.1 mm, and 0.2 mm were applied to the plate-like members 34a and 34b in the vertical compression directions, they deformed as shown in Figures 3(A) to 3(C), respectively, and when displacements of 0.1 mm and 0.2 mm were applied (see Figures 3(B) and 3(C), respectively), buckling of the stretchable structure (auxetic structure) 32 was confirmed in addition to buckling of the plate-like members 34a and 34b.

[0030] Furthermore, when the relationship between compressive displacement and longitudinal restoring force is calculated, negative stiffness appears in the displacement range of approximately 0.05 mm or more, as shown in Figure 4. In Figure 4, the horizontal axis is displacement [mm] and the vertical axis is restoring force [N].

[0031] Furthermore, the tangential stiffness kd calculated from the analysis results in Fig. 4 is shown by black dots in Fig. 5. In Fig. 5, the horizontal axis is displacement [mm] and the vertical axis is tangential stiffness [N / mm]. From Figure 5, a negative stiffness of approximately -340 N / mm to -73 N / mm is obtained, and considering the relationship between Figures 3, 4 and 5, the negative stiffness appears in a displacement region of approximately 0.05 mm or more, and it can be understood that the negative stiffness is manifested by the occurrence of buckling in the stretch structure (auxetic structure) 32.

[0032] When applying the negative stiffness body 30 to a passive vibration isolation system, it is theoretically possible to achieve quasi-zero stiffness by adding in parallel a coil spring 20 with a positive stiffness sufficient to offset the negative stiffness. In other words, quasi-zero stiffness is achieved by setting the spring constant of the coil spring 20 to a value that can offset the negative stiffness characteristic of the negative stiffness body 30.

[0033] For example, since the tangent stiffness kd is -72.5 N / mm when the displacement is 0.2 mm, if a coil spring 20 with a spring constant ks of 72.6 N / mm is added in parallel, the tangent stiffness will be as shown by the white circle in Figure 5, and the overall tangent stiffness at the 0.2 mm position will be 0.1 N / mm.

[0034] The overall restoring force characteristics of the vibration isolation apparatus 10 are shown by the white circles in Fig. 6. The black circles in Fig. 6 represent the restoring force characteristics after buckling of the negative stiffness body 30 shown in Fig. 4. At this time, the restoring force of the vibration isolation apparatus 10 at 0.2 mm is 98.4 N, and if the object 14 to be isolated is attached to the top of the plate-like members 34a and 34b and a static displacement of 0.2 mm is applied by the weight of the object 14, the mass m of the object 14 to be isolated is m = 98.4 / 9.8 = 10.0 kg. Therefore, when this system is simplified as a one-degree-of-freedom model, the natural frequency fn is calculated by the following equation (1), and it has been found that the vibration isolation device 10 can reduce the first-order natural frequency.

[0035]

number

[0036] where kd is the tangential stiffness of the negative stiffness body 30, ks is the spring constant of the coil spring 20, and m is the mass of the object 14 to be isolated from vibration.

[0037] In this way, it was confirmed that the negative stiffness body 30 exhibits negative stiffness, and it became clear that by combining it with a coil spring 20 having an appropriate positive stiffness, a natural frequency of 1 Hz or less can be achieved. [Example]

[0038] Next, an example will be shown that demonstrates the vibration isolation performance of the vibration isolation device 10, and the effects of the vibration isolation device 10 will be described more specifically.

[0039] The inventors determined the frequency response characteristics of the vibration isolation apparatus 10 in order to confirm the vibration isolation performance of the vibration isolation apparatus 10. The finite element model of the vibration isolation apparatus 10 used was a model in which a coil spring 20 with a spring constant ks of 90 N / mm and an initial tension of 0.932 N was added in parallel to the model of the negative stiffness body 30 used in Example 1. The mass m of the object 14 to be isolated from vibrations was 10.35 kg. As a result, the frequency characteristics shown in Fig. 7 were obtained. In Fig. 7, the horizontal axis represents frequency [Hz], and the vertical axis represents transmissibility [dB]. It was found from FIG. 7 that the vibration isolation device 10 based on the finite element model had a primary natural frequency of about 1.1 Hz, and had good vibration isolation performance in the range of several Hz to about 60 Hz.

[0040] Second Embodiment Next, a vibration isolation device 50 according to a second embodiment will be described. As shown in FIG. 8, the vibration isolation device 50 according to the second embodiment includes a low-rigidity body 70 corresponding to the negative-rigidity body 30 and a guide portion (not shown), and unlike the vibration isolation device 10 according to the first embodiment, does not include a coil spring 20 (see FIG. 1).

[0041] The low-rigidity body 70 is a shock absorber having the expandable structure 32, the plate-like members 34a and 34b, and the lower ends of the plate-like members 34a and 34b are fixed to the base 52. The structure of the low stiffness body 70 itself is substantially the same as that of the negative stiffness body 30, but the characteristics of the tangential stiffness may differ.

[0042] The guide portion (not shown) can restrain displacement of the object 14 to be isolated from vibration in a direction intersecting the direction of vibration, and can guide the object 14 to be isolated from vibration in the vertical direction. The guide portion is, for example, a linear guide extending in the vertical direction.

[0043] The inventors performed static mechanical analysis on the low-rigidity body 70 provided in such an anti-vibration device 50, and investigated the change in tangential rigidity due to differences in plate thickness by changing the plate thicknesses tp1 and tp2 (see Figure 2A) of the plate-like members 34a and 34b. The finite element model of the low-rigidity body 70 is the same as the negative-rigidity body 30 shown in the above-described Example 1, except for the plate thicknesses tp1 and tp2 and the width dimension Ws and height dimension Ls of the cell forming member 322 (see FIG. 2C). The width dimension Ws and height dimension Ls, which are different from those of the negative-rigidity body 30, are each 10 mm. Note that instead of changing the plate thicknesses tp1 and tp2, changes in the plate thicknesses tp1 and tp2 were simulated by changing the Young's modulus as shown in Table 2.

[0044] [Table 2]

[0045] The set Young's modulus E was calculated based on the following formula (2).

[0046] E = 200×(h / 0.5) 3 Formula (2) Here, h is the plate thickness tp1 or the plate thickness tp2.

[0047] When the tangential stiffness was calculated for each low-stiffness body 70 with plate thicknesses tp1 and tp2 set to 0.5, 0.6, 0.8, 1.0, and 1.2 mm, the results shown in Figure 9 were obtained, and it became clear that the characteristics changed depending on the plate thicknesses tp1 and tp2, as shown below. In Figure 9, the horizontal axis is displacement [mm] and the vertical axis is tangential stiffness [N / mm].

[0048] (1) When plate thickness tp1 and tp2 are 0.5 mm Negative stiffness appears in the region where the displacement is approximately 0.13 to 0.8 mm, and the low stiffness body 70 behaves as a negative stiffness body.

[0049] (2) When plate thickness tp1 and tp2 are 0.6 mm In the region of displacement of 0.6 mm or more, a very small value of positive stiffness is stably exhibited, and the vibration isolation device 50 can suppress vibrations even though it does not have a coil spring 20 like the vibration isolation device 10 of the first embodiment.

[0050] (3) When the plate thickness tp1 and tp2 are 0.8 mm or more A stable, small positive stiffness is exhibited at least in the region of 0.3 mm or more, and depending on the mass of the object 14 to be isolated from vibration, it is possible to obtain a vibration isolation device 50 that exhibits a certain level of performance.

[0051] In this way, the low-rigidity body 70 can function as a shock absorber whose tangential rigidity characteristics change by changing the plate thicknesses tp1 and tp2. It is presumed that the tangential rigidity characteristics of the low-rigidity body 70 depend not only on the plate thicknesses tp1 and tp2 but also, for example, on the relationship between the magnitude of the buckling load and bending rigidity of the plate-like members 34a and 34b and the restoring force of the expansion and contraction structure 32. In other words, by changing the relationship between the magnitude of the buckling load and bending rigidity and the restoring force of the expansion and contraction structure 32, a shock absorber and vibration isolation device 50 can be configured in which the tangential rigidity characteristics can be changed.

[0052] As described above, the vibration isolation devices 10, 50 and the shock absorber have a simple structure. The negative stiffness body 30 and the low stiffness body 70 are not limited to use in vibration isolation devices, but can be used for any purpose as shock absorbers.

[0053] Furthermore, the stretchable structure 32 of the negative stiffness body 30 or low stiffness body 70 is not limited to the shape shown in Figures 2A and 2B. Any stretchable structure may be used as long as it exhibits a negative Poisson's ratio and, when combined with plate-like members 34a, 34b, provides a negative stiffness body 30 or low stiffness body 70 that exhibits the required tangential stiffness. Another stretchable structure is, for example, an auxetic structure, which is a stretchable structure 32a shaped as shown in Figure 10. [Explanation of symbols]

[0054] 10, 50 Vibration isolator 12, 52 Basics 122 Upper fixed part 124 Lower fixed part 14 Object to be isolated from vibration 20 Coil spring 30 Negative rigid body 32, 32a Stretchable structure 34a, 34b plate-shaped members 322 Cell forming member 70 Low rigidity body S Cell

Claims

1. a spring element; a negative stiffness body whose restoring behavior exhibits negative stiffness characteristics, the negative rigidity body is a stretchable structure having a negative Poisson's ratio; a first plate-like member provided on one side of the expandable structure and supporting an object to be isolated from vibration; a second plate-like member provided on the other side of the expandable structure and supporting the object to be isolated from vibrations.

2. 2. The vibration isolation device according to claim 1, The vibration isolation device, wherein the expansion and contraction structure is an auxetic structure.

3. 3. The vibration isolation device according to claim 2, the auxetic structure has cell forming members that form a plurality of cells arranged side by side; An anti-vibration device in which, when a compressive force is applied in the direction of vibration, the cell-forming member deforms and the auxetic structure contracts in a direction intersecting the vibration direction.

4. 4. The vibration isolation device according to claim 3, A vibration isolation device in which the spring constant of the spring element is set to a value that can offset the negative stiffness characteristic of the negative stiffness body.

5. 5. The vibration isolation device according to claim 4, The vibration direction is an up-down direction, The vibration isolation device further comprises a guide portion that guides the object to be isolated in the vertical direction.

6. a stretchable structure having a negative Poisson's ratio and capable of stretching; a first plate-like member provided on one side of the stretchable structure; a second plate-shaped member provided on the other side of the expandable structure.

7. 7. The shock absorber according to claim 6, A shock absorber wherein the elastic structure is an auxetic structure.

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