JPS5830546A - Vibration damper - Google Patents

Abstract

PURPOSE:To obtain not only a vibration damping effect but also excellent acoustical properties by a method wherein a solid restraint layer is attached to one surface of a board-like foamed material while the other surface thereof is attached to a vibrating body. CONSTITUTION:A foamed material 1 is made of normal polyurethane foam, polyvinyl chloride or the like and having a modulus of 100g/cm<2> or less when it is compressed by 25%. As the solid restraint layer 2 attached to the foamed material 1 by an adhesive or the like, a heavy material giving a restraining property to the foam under an using temperature substantially and which will never flow easily by itself may be employed. The density ratio of the solid restraint layer 2 to the foamed material 1 is preferable to be more than five, and more preferably more than ten. The opposite surface of the foamed material 1 is adhered to a vibrating body 4 to use it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 7-ohm composite damping material that exhibits a significant vibration damping effect due to the presence of a solid constraining layer.

More specifically, by bonding a specific solid restraining layer to one surface of the plate-shaped foam material and bonding the other surface of the plate-shaped foam to the vibrating body, it not only has a remarkable vibration damping effect but also has excellent sound absorption performance. In addition, the present invention relates to an extremely practical allocation material that can be made thinner and lighter, and has a large cost reduction effect.

First, the present inventors formed polyurethane, which has low vibration damping performance as a solid material, into a foam. (1) The vibration damping performance was slightly improved. A large frequency dependence appears in the (i+) allocation performance. Based on this knowledge, we conducted further research and discovered excellent vibration damping performance by adding powdered filler to polyurethane foam.
A patent application was filed (Japanese Patent Application No. 55-184215).

However, when a filler is added during foaming of polyurethane, an increase in viscosity due to blending with the filler is unavoidable, and therefore there is a problem in that there is a limit to the amount of filler to be used.

As a result of further research in consideration of the above points, the present inventors found that
The inventors have discovered that a foam composite vibration damping material having extremely excellent vibration damping performance can be obtained using a method completely different from that of the above-mentioned invention, and have thus arrived at the present invention. In other words, the damping material of the present invention takes a method of maximizing the vibration damping performance of the foam itself by bonding a specific constraining layer to a specific foam, and does not use polymers or other materials used in conventional damping materials. This method is completely different from methods that utilize the damping properties of solid viscoelastic materials such as asphalt.

That is, the main point of the present invention is to derive vibration damping performance from the foam alone by attaching the foam directly to the vibrating body and further bonding the restraining layer to the foam (FIG. 1A). In other words, the allocation performance of the foam is small if it is simply attached to a vibrating body as an unrestricted type, but when used as a restrained type, the amount of deformation of the foam in response to vibration is greatly expanded, and The vibration damping effect is dramatically improved by the occurrence of shear deformation. Therefore, when considering the mechanism by which such damping performance occurs, it is naturally desirable to use a soft foam material, and conversely, by using such a soft foam, a constraint type foam composite damping material with excellent low frequency vibration damping performance can be obtained. sell.

On the other hand, the solid material that serves as a constraining layer does not need to have an allocating performance by itself in principle, and may simply be a heavy material that can exert a constraining property on the foam. However, if the constraining layer itself has a very large damping effect, this effect is added and the damping performance of the foam composite damping material as a whole is slightly improved. At this time, it is important to note that when using a solid restraining layer, if it is very hard, such as a metal plate, the vibration damping performance will drop significantly in a certain frequency range from low to medium frequencies. Therefore, in order to exhibit excellent vibration damping performance in a wide frequency range from low frequencies to medium frequencies, the restraining layer must also be flexible.

By the way, when looking at the damping material of the present invention from the perspective of sound absorption performance,
It is natural that the foam has sound absorbing properties since it is based on ions, but the presence of a solid constraining layer bonded to the foam surface tends to improve low frequency sound absorbing performance while decreasing high frequency sound absorbing performance. However, the sound absorption performance of foam material decreases as the thickness of the foam becomes thinner.

Since there is a tendency for sumo wrestlers to deteriorate extremely in the low frequency range, the use of the restraint type foam composite damping material of the present invention helps to improve the sound absorption performance in the low to medium frequency range, which is the most important as a practical sound absorbing material. (see example). Of course, in this case, it is possible to control the frequency dependence of the sound absorption performance by providing an appropriate number of through holes in the constraint layer.

Now, in order to comprehensively and effectively implement noise countermeasures, it is necessary to exhibit both a vibration allocation effect and a sound absorption effect, but materials that have both of these performances are other than the filler-filled foam according to the aforementioned pending invention. It is currently not found. Therefore, as a practical solution, commercially available products have both properties by attaching a solid damping material to the vibration source and then attaching a foam on top of it (Figure 1B).
.

In this case, of course, the damping performance is almost entirely due to the solid damping material.

On the other hand, sound absorption performance is affected by the foam.

Therefore, in the case of such a bonded composite (commercially available), it is necessary to use a large amount of expensive damping material in order to obtain sufficient vibration damping performance, and when the material cost of the foam is added to this, the product cost increases. becomes very high.

Compared to such commercially available laminated composites.

As mentioned above, the foam composite vibration damping material of the present invention is completely different not only in form but also in the mechanism of expression of the 2-frequency vibration performance.
, which should be strictly distinguished from commercially available bonded composites. Furthermore, in terms of cost, (1) the solid constraint layer only needs to be an inexpensive and heavy material; (1+) the foam thickness can be reduced as the weight of the solid constraint layer increases; From these points of view, considerable cost reductions are possible. Furthermore, by using an appropriate material as a restraining layer, it is useful for improving flame retardancy, oil resistance, durability, etc. In this way, the foam composite vibration damping material of the present invention is not only novel, but also has many practical uses. It can be said that it is a soundproofing material with the following advantages.

By the way, when using foam as a sound absorbing material.

The surface of the foam is finished with a thin film of aluminum or plastic, and low-frequency sound absorption performance is improved.Furthermore, various thin films are applied to the surface of the foam as interior materials. Pasting is being done. In this case, it is desirable that the thickness of the thin film be less than bOμ' in order not to impair sound absorption performance at high frequencies (Architectural Acoustics Series <Materials Edition>)
L Sound Absorbing Materials 1 Edited by Japan Acoustic Materials Association.

Masaru Koyasu 56P). In all of these cases, no attention was paid to the distribution performance of the foam material, and from a performance standpoint, the thin film acts as a constraining layer because the weight ratio between the thin film and the foam is about 0.1 to 0.5. In other words, it is hardly possible to expect an improvement in damping performance by using a thin film.9 This is clearly distinguishable from the foam composite damping material of the present invention.0 The foam material used in the present invention is 25% The modulus (M, ,) when compressed is 1 oor/i or less.

Preferably soy/(j or less, more preferably 50t
lcr& or less is desirable. However, in order to particularly improve the vibration damping performance in the low frequency range, it is preferable that the MNS of the foam is 2of/cr/I or less.In this case, if the MNS of the foam exceeds 1009/cd, the effect of the constraining layer becomes difficult to appear. Foam materials used include 1 normal polyurethane foam, polyvinyl chloride, polyethylene, polystyrene,
Various plastic foams such as phenolic resin, foams made by adding fillers, plasticizers, flame retardants, etc. to these foams, impregnated foams made by adding an impregnating liquid to general foams, and compressed foams obtained by compressing general foams. Although any type of foamed material may be used, foams with continuous pores are preferable in view of having excellent sound absorption performance.

Particularly preferred is polyurethane foam.

As a solid restraint layer, in principle, it provides restraint to the foam at the operating temperature.1. (and naturally) may be a heavy material that does not flow easily, but preferably satisfies the following conditions. That is, the dynamic storage modulus E of the solid constrained layer at 25C is E≦I×106, preferably 4-2, preferably E≦6×10′V4Zcrl, and more preferably E≦4XIO′/d. Further, it is desirable that the density ratio between the solid constrained layer and the foam is 5 or more, preferably 10 or more.

Furthermore, these solid substances function as a constraining layer when the weight ratio of the constraining layer to the foam is 2.0 to 1. OX1
A range of 0.08 is preferred. That is, when considering the direction perpendicular to the bonding surface between the solid object and the foam, if the ratio of the weight of the solid object to the weight of the foam per unit area of the bonding surface is less than 2.0, no improvement in vibration damping performance will be observed. On the other hand, if it exceeds 1.0×10B, the foam will be crushed and will not function properly. However, more preferably the weight ratio of both is 8.5 or more.

It is 8.0×102 or less. Furthermore, from the standpoint of sound absorption performance, it is desirable that the solid constraining layer has an appropriate number of through holes with an appropriate diameter.

These solid substances are applied to the foam surface by (1) spraying or using a trowel as a liquid substance;

(11) Bonding by itself as a sheet-like product or using an adhesive; (fit) bonding as a woven fabric, non-woven fabric, or net-like material; (fit) bonding by integrally molding when foaming Qφ foam;

The foam composite vibration damping material thus obtained is used by pasting its foam side surface onto a vibrating body, but it may also be melt-bonded or integrally molded during foam foaming.

The foam composite damping material of the present invention can be used in vehicles and ships.

As an allocation material for automobiles, aircraft, etc., as well as railway rails, home appliances, metal processing machines, etc.

Furthermore, it is widely used for buildings such as residences, offices, and factories, and as a vibration damping and sound absorbing material for office equipment, computers, sound systems, etc.

Next, the present invention will be explained in more detail based on Examples.

Example 1. Comparative examples 1 to 8 The sample shown in the table has a thickness of Imp and a width of 25 mm.

It was pasted on a galvanized iron plate with a length of 800 mm to serve as a test specimen, and the loss coefficient (η) was measured using a vibration analysis device (mechanical impedance method) manufactured by Akashi Seisakusho ■. Note that the frequency used is lθ~5'0OOHz.

The condition of room temperature (29tll') measurement is common to all Examples and Comparative Examples except Example 12.

- Example 1 and Comparative Example 1 have the same composition and shape for both the foam and the constraint layer, but Example 1 is of type A in FIG. 1 in accordance with the gist of the present invention.

Comparative Example 1 was a type B shown in FIG. 1, which is the same as a commercially available bonding material, and was bonded to a vibration source (iron plate).

On the other hand, comparative example 2. Comparative Example 8 is the same as each of the above-mentioned Examples 1. Only the foam and only the constraint layer used in Comparative Example 1 were attached to the vibration source, and the results obtained for these samples are shown in FIG.

The value of η of Comparative Example 1 is given as approximately the sum of each η of the foam and constraint layer used in Comparative Example 2 and Comparative Example 8.

On the other hand, in the case of Example 1, η is much higher than that of Comparative Example 1.
value, i.e. its constituent factors form and constrained layer η
It shows a high η value that cannot be estimated from the value, and η≧0.05, which is a guideline for good allocation performance. (preferably η≧0
．． It is at a level that sufficiently exceeds 1). This confirms the special damping performance mechanism of the foam composite damping material of the present invention.

Table 1 Umbrella 1 c/f- = 1 density ratio of the garden layer and the foam JThe modulus (M!!1) of the foam at 25% compression was determined by placing a circular pressure plate with a diameter of 200mm on the test piece for 100s+
The disk was compressed at a speed of ψin, and when the amount of strain reached 25%, the disk was stopped, and the stress value was obtained after 20 seconds of stopping.

Example z, 8. Comparative Example 4 The samples shown in Table 2 were of type A in Fig.
Figure 8 shows the frequency dependence of η when pasted as 0 type).
It can be seen that the damping performance at low frequencies deteriorates significantly.

Table 2 Examples 4 and 5. Comparative Example 5 The η-frequency curves of the samples given in Table 8 are shown in FIG. Compared to the damping performance of ohm only (comparative example 5),
When using the restraint type, as the weight of the restraint layer increases, η
The value of is significantly improved (Examples 4 and 5).

Table 8 Example 6. Comparative Example 6 The effect of the softness of the foam itself was measured using the samples given in Table 4, and the results are shown in FIG. It can be seen that even if the same constraint layer is used, the vibration damping performance is significantly improved in the case of a soft foam.

Table 4 Examples 7 to 9 As another example, the η-frequency curve of the system given in Table 5 is shown in FIG. In all cases, excellent damping performance is exhibited over a fairly wide frequency range.Table 5 Examples 10 and 11. Comparative example? Table 6 shows the frequency dependence of the normal incidence sound absorption coefficient at room temperature (ZOR) for representative samples as shown in FIG.

In this case, the sound absorption performance was measured using a vertical projection method, with the material in close contact with a rigid wall (however, in the case of a constraint type foam composite damping material, it was set so that the sound was incident from the solid constraint layer).

In the case of only a foam without a constraining layer (Comparative Example 7), as can be seen in Figure 2, the low frequency sound absorption coefficient is extremely low. When a constraint layer is attached to this, the sound absorption performance in the practically important low and medium frequency ranges is improved (Example 10), and this curve can be further controlled by making appropriate holes in the constraint layer (
Example 11).

Example 12 There are two types of foam as samples: urethane foam +
Mgs 16t/al e thickness 5n, type filler filled PVO as constraining layer, E 2X10' to 4/
A material consisting of d, c/r zs was used. This foam composite vibration damping material was attached to a 1 fl thick iron plate and then vibrated, the sound pressure level was measured and compared with the case of only the iron plate, as shown in FIG.

Figure 8 shows that the foam composite damping material of the present invention has excellent vibration allocation performance, especially in the low frequency and medium frequency regions, and it was confirmed that it is extremely useful as a vibration damping material. .

[Brief explanation of the drawing]

FIG. 1 shows a cross section of the distribution material, where A is the foam composite distribution material of the present invention, and B is a conventional distribution material and a 7-ohm bonded material (commercially available product). Figures 2-6 are examples given in each table. The frequency dependence of the loss coefficient (η) measured at room temperature (29C) using a comparative example as a sample is shown. Figure 7 shows room temperature (29
The frequency dependence of the normal incidence sound absorption coefficient in C) is shown. FIG. 8 shows the effect of reducing the sound pressure level at 25C by using the foam composite damping material. 1... Form 2... Solid constraint layer color... Damping material 4... Vibration source patent applicant Patent attorney for Brideston Tire Co., Ltd. Shi Ito Akira 1 (A) (B);〉−Ne i′ cicada ÷ m,,＜斗guφitem (Me)

Claims (2)

[Claims] (1) A foam material with a compression modulus of 10017 cd or less at 25% has a dynamic storage modulus of lX10'J at 25C on the surface opposite to the surface to be attached to the vibrating body.
l/d or less, the density ratio with the foam is 5 or more,
and a vibration damping material combined with a solid constraining layer whose weight ratio with the foam is 20 or more and lXl0' or less. (2) The 25% compression modulus is 80 P/cd or less, the dynamic storage modulus at 25C' of the solid constrained layer is 6 x 10' Kp/lI or less, and the density ratio with the foam is 10 or more. and the weight ratio with the foam is 2
5 or more and 8XlO” or less, the damping material according to claim (1)