JPH01220741A - Dynamic absorption type vibration suppressor - Google Patents

Abstract

PURPOSE:To suppress even complex vibration well by arranging mass bodies through intervals at plural positions on a resilient substrate thereby distributing a plurality of dynamic vibration absorbers having inherent vibration to be determined by the mass of the mass body and the spring constant of the resilient body. CONSTITUTION:In a resilient substrate 1 to be jointed to a vibration body 3, mass bodies 2A, 2B having different mass are buries through intervals at plural positions, and a plurality of dynamic vibration absorbers having inherent vibration to be determined by the mass of the mass body and the spring constant of the resilient body around the mass are distributed in a plane. Since the dynamic vibration absorbers are positioned at or near the peak position of vibration, the vibration is suppressed effectively. When more than two types of mass body 2 are provided and dynamic vibration absorbers having different inherent vibration are distributed, the vibration can be reduced effectively over a wide vibration range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dynamic vibration absorber type damping material, and particularly to a vibration damping material in which dynamic vibration absorbers are formed that are distributed in a plane.

[Prior Art] When a plate-like body, a membrane-like body, or a shell-like body generates elastic vibrations, most of them have relatively high frequencies and large vibration levels, and effective reduction of these vibrations is an effective way to reduce noise. This has become a strong requirement in social life and industrial technology that requires prevention.

Conventionally, measures to prevent such vibrations include changing the thickness, weight, shape of the aperture, etc. of the plate-shaped body to shift its natural frequency from the problematic frequency, or using a material with a relatively large damping coefficient. A method has been adopted, such as constructing a vibration damping material and attaching it to the vibrating body.

[Problems to be Solved by the Invention] However, the above-mentioned method of shifting the frequency is not a fundamental measure for vibration prevention, and therefore unexpected problems may occur at the shifted frequency.

On the other hand, the method of using a damping material is preferable in that it directly suppresses vibrations, but despite many years of efforts, no damping material that exhibits a significant effect has yet been reported.

The present invention attempts to solve this problem with a vibration damping material of a new structure that forms a dynamic vibration absorber, and is effective in reducing the vibration of a vibrating body that makes complex planar vibrations, such as a plate-like body or a shell-like body. The purpose of the present invention is to provide a dynamic vibration absorber type vibration damping material that can prevent

[Means for Solving the Problems] The dynamic vibration absorber type vibration damping material of the present invention has an elastic substrate 1 joined to a vibrating body 3, and a plurality of masses are arranged at intervals within the substrate 1. The bodies 2A and 2B are provided. Therefore, a plurality of dynamic vibration absorbers each having a natural frequency determined by the mass of the mass bodies 2A, 2B and the spring constant of the elastic body are distributed and formed in a plane by the above-mentioned mass bodies 2A, 2B and the elastic bodies around them. has been done.

In some cases, two or more types of the above-mentioned mass bodies having different masses are provided.

[It is effective to install a co-dynamic vibration absorber at the peak position of vibration, but in plate-shaped bodies, etc., there are multiple peak positions of vibration, and it is often difficult to determine the position.

Here, in the vibration damping material of the present invention, since the dynamic vibration absorbers are distributed in a planar manner, some of the dynamic vibration absorbers can be placed at the peak position or It is located at the periphery of the ring and effectively suppresses and reduces vibration.

In addition, in general, vibrating bodies often have higher-order natural vibrations in addition to their fundamental vibrations, but by providing two or more types of mass bodies to form a dynamic vibration absorber with different natural frequencies, it is possible to widen the range of vibration frequencies. Vibration is effectively suppressed and reduced in the range.

[Example] In FIGS. 1 and 2, an elastic substrate 1 made of, for example, soft urethane foam is attached to the top surface of a rectangular plate-shaped vibrating body 3 over the entire surface excluding the peripheral edge. 1
Inside there are two large and small spherical mass bodies 2 made of iron or lead.
A and 2B are embedded at equal intervals in a plane approximately at the center in the thickness direction.

Here, the diameter and mass of each of the mass bodies 2A and 2B are dl, d2, ml, and m2, respectively, the interval between the mass bodies is g, and the thickness of the elastic body located below the mass body is h.

Each of the above-mentioned mass bodies 2A and 2B constitutes a dynamic vibration absorber with an elastic body existing around it, and its natural frequency fre,s is determined by the movement of the elastic body, with the mass of the mass body being m. It is determined by the following formula, where K is the spring constant.

By the way, FIG. 3 shows the range of the elastic body that contributes to determining the dynamic spring constant of the dynamic vibration absorber.

In the figure, line X, line y, and line 2 indicate that the mass body is buried at the center position in the thickness direction of the elastic plate, or that the mass body is buried so that the top surface of the mass body is parallel to the top surface of the elastic plate. Or, it shows the change in the dynamic spring constant when a mass body is placed exposed on the upper surface of the elastic body plate, and the horizontal axis is the size a of one side of the square elastic body plate and the diameter d of the mass body. The ratio (
a/d) Toshishita. Note that the thickness h of the elastic body located below the mass body is constant.

As can be seen from the figure, although the elastic bodies on the sides and top of the mass body also contribute to the determination of the dynamic spring constant to some extent (
Line X, line y>, 80% or more is determined by the lower elastic body (line 2).

Note that when a/d exceeds about 8.4 (broken line in the figure), the dynamic spring constant does not change even if the elastic plate is made larger. Therefore, only the elastic body within an area approximately 8.4 times the diameter of the mass body around the mass body contributes to determining the dynamic spring constant.

Therefore, when we examine the relationship between the thickness h of the elastic body below the mass body and the dynamic spring constant, we find that, regardless of the diameter d of the mass body, the ratio of this diameter d to the above thickness h (d/h) Therefore, the above dynamic spring constant lies on one curve.

This is shown in FIG. 4, where the black circles, white circles, and triangular marks are measured values when d=6.0 mm, 8.3 mm, and 10.0 mm, respectively.

When the equation of the above curve is determined by the least squares method from the measured values shown in FIG. 4, the following equation is obtained.

(d/h) K= α・C1・Ks・□・・・・・・(2) (d/h
) +C2 Here, α: Dynamic magnification KS: Static spring constant of the elastic body C1, C2: Constant If the natural frequency fres of the dynamic vibration absorber is made to match the resonant frequency of the vibrating body, the vibration of the vibrating body can be effectively reduced. Therefore, by determining the frequency fres of the resonance vibration to be suppressed, the static spring constant Ks of the elastic substrate, and the thickness h of the elastic body at the bottom of the mass body, from the above equations (1) and (2), The diameter d and mass m, ie the specific gravity, of the mass body are determined.

As an example, in FIG. 1, a plate-shaped vibrating body is
An iron plate with a thickness of 1.0 mm and a thickness of 1.0 mm was used, and a soft urethane foam with a thickness of 30W11 was bonded to the upper surface of this plate as an elastic substrate, and at the center of the thickness of the urethane foam, ml = 0
．． 71g, di = 6.0mm, m2 = 0.31g,
Two types of lead balls 2A and 2B with different masses and diameters of d2 = 4.5 mm are placed at an interval J! When the vibration damping material was constructed by burying six damping materials alternately in the order of =140, the 3rd and 6th natural vibrations at 107Hz and 167Hz were effectively suppressed, as shown by the line X in Figure 5. There is. Note that in the figure, line y indicates the case where no damping material is provided.

In addition, in the vibration damping material of the present invention, even if the mass bodies are not positioned to completely coincide with the vibration peak position of the vibrating body, some of the plurality of mass bodies are positioned in the vicinity surrounding the above-mentioned peak position. Therefore, the vibration suppressing effect does not decrease that much. This is shown in FIG. 6, in which the line X represents the case where the mass body completely coincides with the vibration peak position, and the line y represents the case where it does not completely coincide.

Furthermore, the greater the number of mass bodies installed per unit area, the better the vibration damping effect will be. This is shown in FIG.

In the figure, line W indicates the case where no damping material is provided, and line x
, y, and z are obtained by increasing the number of mass bodies per unit area in this order.

However, since increasing the number of mass bodies installed increases the weight of the vibration damping material, the mass body installation density is limited within the weight allowed for the vibration damping material.

In this case, since the vibration damping material of the present invention utilizes the anti-resonance effect of a dynamic vibration absorber, a relatively light mass body can be used, and even if the installation density is increased, the conventional vibration damping material can be used. It is often lighter than other materials.

In the above embodiment, the lead balls can be easily embedded in the foamed urethane substrate by integral molding. Alternatively, the mass body can be added after the substrate is provided.

In the above embodiment, two types of mass bodies are provided to suppress the two resonance vibrations of the vibrating body, but the number of mass bodies can be one to three or more depending on the number of resonance vibrations to be suppressed.

Of course, the shape of the mass body is not limited to a sphere,
The material can also be appropriately selected depending on the required specific gravity. Also,
The mass body does not necessarily need to be embedded within the elastic substrate.

[Effect] According to the damping material according to the first aspect, it is possible to satisfactorily damp the vibration of a vibrating body that vibrates in a complex manner with peaks at a plurality of positions on a surface such as a plate-shaped body.

In this case, since a relatively light mass body can be used to constitute the dynamic vibration absorber, the weight of the rotating part can be significantly reduced compared to conventional vibration damping materials.

According to the damping material according to the second aspect, it is possible to effectively suppress higher-order vibrations in addition to basic vibrations.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a plate-shaped vibrating body to which the damping material of the present invention is attached, Fig. 2 is a cross-sectional view thereof, taken along line ■-n in Fig. 1, and Fig. 3 is an elastic body. Figure 4 shows the change in the dynamic spring constant with respect to the ratio of the size of the plate and the diameter of the mass body; Figure 4 is a diagram showing the change in the dynamic spring constant with respect to the ratio of the diameter of the mass body and the thickness of the elastic body at the bottom of the mass body; Figure 5 7 to 7 are diagrams showing the damping effect of the damping material of the present invention. 1...Elastic body substrate 2A, 2B...Mass body 3...Vibrating body Fig. 1 R2 to J Z Fig. 3 Ratio a/d 4th!2I Ratio d/b Vibration transmission magnification (dB ) Vibration transmission magnification (dB) Vibration transmission magnification (dB)

Claims (2)

[Claims] (1) It has an elastic substrate that is joined to the vibrating body, and mass bodies are provided at multiple positions at intervals within the substrate, and the mass of the mass body is A dynamic vibration absorber-type damping material formed by distributing a plurality of dynamic vibration absorbers in a planar manner, each having a natural frequency determined by the spring constant of an elastic body. (2) The dynamic vibration absorber type vibration damping material according to claim 1, wherein two or more types of mass bodies having different masses are provided.