Vibration damping structure

Abstract

To provide a vibration-damping structure that can be applied to an area with a curved face and a narrow limited internal space.SOLUTION: A vibration-damping structure includes a metal vibration-damping plate 1, which includes a wedge-shaped part 11 with its plate thickness gradually decreasing in one direction, and a base part 12 connected to its thick end 11A. The wedge-shaped part 11 has its plate thickness that changes in accordance with the following formula (1). The wedge-shaped part 11 includes a vibration-damping member 2 at the thin end 11B side and also includes, in plan view, at least one folding part T1 somewhere between the thick end 11A and the thin end 11B. The wedge-shaped part 11 forms, as a whole, a bending shape that fits within a rectangular area having long and short sides. In the formula (1): h(x)=ε xn + h0, x denotes a distance (mm) measured along the bending shape from the thin end of the wedge-shaped part to the thick end, h(x) denotes a plate thickness(mm) in the distance x, h0 denotes the plate thickness (mm) of the thin end of the wedge-shaped part, ε denotes a positive constant and n denotes a real number of 1 or greater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a vibration damping structure, and more particularly to a vibration damping structure that utilizes the acoustic black hole effect. [Background technology]

[0002] It is known that vibration-damping structures utilizing the acoustic black hole effect are used as countermeasures against vibration and noise. This vibration-damping structure has a wedge-shaped structure in which the plate thickness decreases towards the tip. As vibrations (waves) propagating through the wedge-shaped section approach the tip, the amplitude increases and the propagation speed slows down. At the tip of the wedge, where the plate thickness approaches 0 (zero), the propagation speed approaches 0, and vibrations are hardly reflected. However, it is difficult to completely eliminate vibration reflection by making the plate thickness at the tip of the wedge 0, so vibration damping material is provided at the tip of the wedge to reduce vibration reflection as much as possible. Furthermore, the longer the wedge-shaped section of the above vibration-damping structure, the more effectively low-frequency vibrations can be suppressed.

[0003] Non-Patent Document 1 discloses a vibration damping structure formed by bending a wedge-shaped portion in the thickness direction of the plate, so that the overall structure has a vertical spiral shape. Non-Patent Document 2 discloses a vibration damping structure formed by bending a wedge-shaped portion in the width direction, so that the overall structure has a horizontal spiral shape. [Prior art documents] [Patent Documents]

[0004] [Non-Patent Document 1] Seongmin Park et al., Vibration damping of plates using waveguide absorbers based on spiral acoustic black holes, journal of Sound and Vibration, 521(2022)116685 [Non-Patent Document 2] T.Zhou, L.Cheng, Planar Swirl-Shaped Acoustic Black Hole Absorbers for Multi-directional Vibration Suppression, journal of Sound and Vibration, 526(2022)116500 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the vibration damping structure described in Non-Patent Document 1, for example, protrudes significantly from the panel when fixed to a panel due to its wedge-shaped portion. Similarly, the vibration damping structure described in Non-Patent Document 2, when fixed to a panel, extends significantly along the panel due to its wedge-shaped portion. For these reasons, these vibration damping structures could not be applied to automobile body panels, such as those with curved surfaces and limited internal space, because the wedge-shaped portion would easily come into contact with the panel or other structures.

[0006] The present invention has been made in view of the problems of the prior art described above, and aims to provide a vibration damping structure that can be applied to locations with curved surfaces and narrow, limited internal spaces, such as automobile body panels, and that can exhibit a compact and reliable vibration damping function. [Means for solving the problem]

[0007] The vibration damping structure according to the present invention comprises a metal vibration damping plate having a wedge-shaped portion whose thickness gradually decreases in one direction and a base portion continuous with the thick end of the wedge-shaped portion. The thickness of the wedge-shaped portion changes in accordance with the following formula (1). Furthermore, the vibration damping structure is characterized in that the wedge-shaped portion has a vibration damping material at the end on the thin end side, and in a plan view, has at least one folded portion between the thick end and the thin end, and as a whole has a bent shape that fits within a rectangular region having a long side and a short side. h(x) = ε·x n + h0...Equation (1) However, in equation (1), x: Distance (mm) measured along the bend shape from the thin end to the thick end of the wedge-shaped portion. h(x): Plate thickness (mm) at a distance x measured along the bend shape from the thin end to the thick end of the wedge-shaped portion. h0: Thickness of the thin-walled end of the wedge-shaped portion (mm) ε: positive constant n: a real number greater than or equal to 1 [Effects of the Invention]

[0008] The vibration damping structure according to the present invention can be applied to locations with curved surfaces and narrow, limited internal spaces, such as the body panels of automobiles, and can exhibit a compact and reliable vibration damping function. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view showing a first embodiment of a vibration damping structure according to the present invention. [Figure 2] These are side views of the vibration damping structure on the shorter side (A) and the longer side (B). [Figure 3] This is a side view showing the vibration damping structure fixed to the panel. [Figure 4] This is a side view showing the relationship between the vibration damping structure and the radius of curvature of the panel. [Figure 5] This is a plan view showing a second embodiment of the vibration damping structure. [Figure 6] This is a plan view showing a third embodiment of the vibration damping structure. [Figure 7] This is a plan view illustrating the vibration damping structure of the embodiment. [Figure 8] This graph shows the inertance measurement results of the vibration damping structure in the example. [Modes for carrying out the invention]

[0010] <First Embodiment> The vibration damping structure A shown in FIGS. 1 and 2 includes, as a basic configuration, a metal vibration damping plate 1 having a long wedge-shaped portion 11 with a gradually decreasing plate thickness in one direction and a base portion 12 continuous with the thick end 11A of the wedge-shaped portion 11. Further, the base portion 12 includes a pedestal portion 13 that maintains the wedge-shaped portion 11 in a state separated from the panel member P that is the vibration damping object.

[0011] The wedge-shaped portion 11 has a thick end 11A as a fixed end and a thin end 11B as a free end, and by changing its plate thickness so as to satisfy the following formula (1), an acoustic black hole effect can be obtained.

[0012] h(x) = ε·x n + h0 ··· Formula (1) However, in Formula (1), x: The distance (mm) measured along the shape of the wedge-shaped portion 11 from the thin end 11B to the thick end 11A of the wedge-shaped portion 11 h(x): The plate thickness (mm) at the distance x measured along the shape of the wedge-shaped portion 11 from the thin end 11B to the thick end 11A of the wedge-shaped portion 11 h0: The plate thickness (mm) of the thin end 11B of the wedge-shaped portion 11 ε: A positive constant n: A real number of 1 or more

[0013] And the vibration damping structure A has a vibration damping material 2 at the end on the thin end 11B side of the wedge-shaped portion 11, and in a plan view, has at least one folded-back portion between the thick end 11A and the thin end 11B, and as a whole, forms a bent shape that fits within a rectangular region (L1 > L2) having a long side of length L1 and a short side of length L2.

[0014] The wedge-shaped portion 11 of the metal vibration damping plate 1 in the vibration damping structure A of this embodiment has a first straight portion S1 extending from the thick end 11A, a first folded-back portion T1 continuous with the end of the first straight portion S1, and a second straight portion S2 continuous with the first folded-back portion T1. Further, the wedge-shaped portion 11 has a second folded-back portion T2 continuous with the end of the second straight portion S2 and passing behind the base portion 12, and a third straight portion S3 continuous with the second folded-back portion T2 and reaching the thin end 11B.

[0015] The first to third straight sections S1 to S3 are elongated in the direction along the longer side of the rectangular region, arranged in three rows with the first straight section S1 in the center, and parallel to each other with gaps in between. The first and second folded sections T1 and T2 are arranged along the shorter side of the rectangular region. In this embodiment, folded sections T1 and T2 have right-angle corners, but corners may be rounded or curved folded sections may be provided.

[0016] The above vibration damping structure A is a metal vibration damping plate 1, and the base 12 The vibration (wave) incident from the front propagates toward the thin-walled end 11B where the plate thickness of the wedge-shaped section 11 is minimum, and as it approaches the thin-walled end 11B, the amplitude increases and the propagation speed slows down.

[0017] Therefore, by providing a metal damping plate 1 having a wedge-shaped portion 11, even if the plate thickness (h0) of the thin end 11B of the metal damping plate 1 is not 0, the propagation speed of vibrations transmitted to the thin end 11B becomes smaller and less likely to be reflected, resulting in the thicker portion 11A and even the base portion 12 This can suppress vibrations. However, since the vibration damping structure cannot completely eliminate vibration reflection by making the plate thickness of the thin-walled end 11B zero, vibration reflection can be further reduced by providing vibration damping material 2 at the end of the wedge-shaped section 11 on the thin-walled end 11B side.

[0018] Furthermore, as shown in Figure 3, when the panel member P, which is the object to be damped, is curved, the vibration damping structure A is positioned so that the direction along the shorter side of the rectangular area (left-right direction in Figure 3) aligns with the direction along the concave curve of the panel member P on the concave curved surface of the panel member P. In this case, the vibration damping structure, with the configuration of the straight sections S1 to S3 and folded sections T1 and T2 described above, has the base section 13 positioned in the center along the shorter side of the rectangular area, as shown in Figure 2(A).

[0019] Furthermore, as shown in Figure 4, in the vibration damping structure A, when T is the distance from the fixed center (0) of the base portion 13 of the panel member P to the wedge-shaped portion 11 (height of the base portion 13) and R is the radius of curvature of the panel member P, the length L2 of the shorter side of the wedge-shaped portion 11 is 2√2TR-R 2 Smaller than (L2 < 2√2TR - R 2 It has a ) structure.

[0020] The vibration damping structure A, having the above configuration, can be applied to the interior of various vehicle body panels such as door panels, engine hood panels, trunk lid panels, and hood panels of automobiles.

[0021] In other words, the vibration damping structure A comprises a metal vibration damping plate 1 having a wedge-shaped portion 11 and a base portion 12 continuous with its thick end 11A. The wedge-shaped portion 11 has folded portions T1 and T2 between the thick end 11A and the thin end 11B in a plan view, and as a whole, it has a bent shape that fits within a rectangular region having a long side and a short side.

[0022] As a result, vibration damping structure A can be applied to areas with curved surfaces and narrow, limited internal spaces, such as the body panels of automobiles, and can exhibit a compact and reliable vibration damping function. In automobiles to which the above vibration damping structure A is applied to the body panels, vibrations of the body panels can be reduced, resulting in a comfortable cabin space.

[0023] Furthermore, in the above-described vibration damping structure A, the object to be damped is a curved panel member P, and the structure is positioned such that the direction along the shorter side of the rectangular area on the concave surface of the panel member P is aligned with the direction along the concave surface of the panel member P. This makes it easier to prevent interference between the vibration damping structure A and the panel member P, making it more desirable for application to vehicle body panels.

[0024] Furthermore, since the vibration damping structure A has a base portion 13 that supports the wedge-shaped portion 11 in a state where it is spaced apart from the panel member P, the contact portion with the curved panel member P is minimized, interference with the panel member P is reliably prevented, so-called rattling noise is prevented, and a vibration damping effect is reliably achieved.

[0025] Furthermore, since the vibration damping structure A has a base portion 13 in the center along the shorter side of the rectangular area, it is a structure that is less likely to interfere with the curved panel member P, and a stable mounting position can be obtained.

[0026] Furthermore, with respect to the wedge-shaped portion 11, the vibration damping structure A has a length L2 of the shorter side in the rectangular region, where L2 < 2√2TR-R 2 This allows the vibration damping structure A described above to minimize the height (T) of the base portion 13 and prevent interference between the panel member P and the wedge-shaped portion 11, even when the radius of curvature R of the panel body P is different. This makes it even more suitable for applications in areas with limited internal space, such as vehicle body panels.

[0027] Figures 5 and 6 illustrate second and third embodiments of the vibration damping structure according to the present invention. In these embodiments, the same reference numerals are used for the same components as in the first embodiment, and detailed descriptions are omitted.

[0028] <Second Embodiment> The vibration damping structure A shown in Figure 5 has a base 12 and a pedestal 13 in the center of the long side of a rectangular region, and a wedge-shaped portion 11 continuous with the base 12 has a first straight portion extending from the thick end 11A in the direction along the long side, a first folded portion T1, a second straight portion S2, a second folded portion T2, and a third straight portion S3 reaching the thin end 11B. In this embodiment, the wedge-shaped portion 11 has the first to third straight portions S1 to S3 arranged in order in the direction along the short side of the rectangular region when viewed from above, and as a whole, it has a bent shape that fits within a rectangular region having a long side of length L1 and a short side of length L2.

[0029] Similar to the first embodiment, the vibration damping structure A described above can be applied to locations with curved surfaces and narrow, limited internal spaces, such as the body panels of automobiles, and can exhibit a compact and reliable vibration damping function.

[0030] <Third Embodiment> The vibration damping structure A shown in Fig. 6 has a base portion 12 and a pedestal portion 13 at the center of the short side in a rectangular region, and the wedge portion 11 is continuous in a zigzag shape (angular wave shape) along the long side of the rectangular region in a plan view, and as a whole, it forms a bent shape that fits within a rectangular region having a long side of length L1 and a short side of length L2.

[0031] Even in the above-described vibration damping structure A, similar to each of the above-described embodiments, it can be applied to a location having a curved surface like an automobile body panel and having a narrow and limited internal space, and exhibits a compact and reliable vibration damping function.

[0032] <Example> A test (CAE vibration analysis) was performed using the vibration damping structure A shown in Fig. 7. The vibration damping structure A has a base portion 12 arranged at the center in the direction along the long side of a rectangular region and a wedge portion 11 continuous with the base portion 12, similar to that shown in the second embodiment. The wedge portion 11 has a total length of 218 mm in the direction along the long side of the rectangular region, a total width of 62 mm in the direction along the short side, a width of the wedge portion 11 of 18 mm, and a plate thickness of the base portion 12 of 5 mm.

[0033] The wedge portion 11 has a plate thickness of 4.5 mm at the thick end 11A, a plate thickness of 3.75 mm at the first folded-back portion T1, and a plate thickness of 2.05 mm at the second folded-back portion T2. Also, a vibration damping material 2 having a length of 60 mm, a width of 18 mm, and a thickness of 1 mm was arranged at the end portion on the thin end 11B side of the third straight portion S3. The first to third straight portions S1 to S3 gradually reduced the plate thickness as follows according to the formula of the acoustic black hole.

[0034] First straight portion S1: h(x)=(0.75 / 82 2 )x 2 +3.75 (0≦x≦82) Second straight portion S2: h(x)=(1.7 / 182 2 )x 2 +2.05 (0≦x≦182) Third straight portion S3: h(x)=(I.85 / 200 2 )x 2 +0.2 (0≦x≦200)

[0035] As a comparative example, a sample was prepared in which the planar shape was the same as that of the example, and the plate thickness of the portion corresponding to the wedge-shaped part 11 was constant at 4.5 mm.

[0036] In actual testing, for example, the vibration-damping structures of the examples and comparative examples are freely supported, an acceleration sensor (PCB 356A01) is attached to the thickened section 11A, and the thickened end 11A is used as the excitation point and response point, and vibration is applied in the thickness direction using an impulse hammer (PCB 086C03 (hard chip)). The force of the impulse hammer (input) and the acceleration of the acceleration sensor (response) are input into an FFT analyzer (Siemens SCADAS III) and a Fourier transform is performed to obtain the acceleration / force transfer function (inertance), and the inertance is measured by repeating the impact five times and averaging it.

[0037] In this example, computer analysis was performed, and a mode damping coefficient of 0.0008 was derived from the full width at half maximum of the inertance measurement results. This coefficient was then applied to all modes in the following vibration analysis.

[0038] Specifically, the vibration-damping structures of the above-described examples and comparative examples were modeled and given free support. The thick-walled end 11A was defined as the excitation point and response point, and the response acceleration in the thickness direction was calculated when an excitation force of 1000 mN in the thickness direction was applied to the excitation point in the frequency range of 0 to 6000 Hz, and the inertance was calculated. The software used for vibration analysis was NX-Nastran (SIEMENS). The parameters of the members (materials) used in the calculations are shown in Table 1, and the analysis results are shown in Figure 8.

[0039] [Table 1]

[0040] Figure 8 shows that the vibration level decreases as the gain of the resonance peak decreases. As is clear from the figure, the vibration damping structure of the embodiment exhibits a vibration damping effect compared to the comparative example, with lower vibration levels from low frequencies of approximately 200 Hz to high frequencies due to the acoustic black hole.

[0041] The vibration damping structure according to the present invention is not limited to the above-described embodiments, and its configuration can be appropriately modified without departing from the spirit of the present invention, depending on the object to be damped and the application location. [Explanation of symbols]

[0042] 1. Metal vibration damping plate 2 Damping material 11 Wedge-shaped part 11A thick end 11B Thin end 12 Base 13. Base S1~S3 Straight section T1, T2 Folded section

Claims

1. The metal vibration damping plate comprises a wedge-shaped portion in which the plate thickness gradually decreases in one direction, and a base portion that is continuous with the thick end of the wedge-shaped portion. The plate thickness of the wedge-shaped portion changes while satisfying the following formula (1): The vibration damping structure is characterized in that the wedge-shaped portion has a vibration damping material at the end on the thin-walled end side, and in a plan view, has at least one folded portion between the thick-walled end and the thin-walled end, and as a whole has a bent shape that fits within a rectangular region having a long side and a short side. h(x) = ε・x ｎ + h ０ ... Equation (1) However, in equation (1), x: Distance (mm) measured along the bend shape from the thin end to the thick end of the wedge-shaped portion. h(x): Plate thickness (mm) at the aforementioned distance x h ０ : The thickness of the thin-walled end of the wedge-shaped portion (mm) ε: a positive constant n: a real number greater than or equal to 1

2. The object to be damped is a curved panel member, The vibration damping structure according to claim 1, characterized in that the direction along the short side of the concave curved surface of the panel member is aligned with the direction along the concave curved surface of the panel member.

3. The vibration damping structure according to claim 2, characterized in that the base portion has a pedestal portion that supports the wedge-shaped portion in a state separated from the panel member.

4. The vibration damping structure according to claim 3, characterized in that the base portion is positioned in the center in the direction along the short side.

5. When T is the distance from the fixed center of the base portion of the panel member to the wedge-shaped portion, and R is the radius of curvature of the panel member, the length L2 of the shorter side of the wedge-shaped portion is 2√2TR - R ２ Smaller than (L2 < 2√2TR - R ２ ) The vibration-damping structure according to claim 4.

6. An automobile characterized by having a vibration damping structure according to any one of claims 1 to 5 provided on the vehicle body panel.

Images