Soundproofing materials

Abstract

To provide soundproofing materials that offer excellent durability and sound insulation. [Solution] A soundproofing member 1 made of polyurethane foam is disposed on at least a portion of the outer surface of the sound source 2, comprising: one skin layer 5 with an open cell structure located on one side facing the sound source 2 and in contact with the sound source 2 when in use; and another skin layer 6 with a closed cell structure located on the other side opposite to the side facing the sound source 2.

Description

Technical Field

[0001] The present invention relates to a soundproof member made of polyurethane foam.

Background Art

[0002] Conventionally, for example, as a soundproof member, there is an engine cover for reducing noise emitted from a vehicle engine. As such an engine cover, one formed of polyurethane foam is known. In this configuration, the inner surface facing the engine as the sound source is a skin layer in a closed cell state, and the outer surface is a skin layer in an open cell state (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of the above-described engine cover, since the skin layer on the outer surface is in an open cell state, chemical liquids and the like easily penetrate, and the resistance when receiving an external load is not sufficient. Further, since the inner surface in a closed cell state is interposed between the core part that absorbs sound and the engine, it is difficult to directly absorb the sound from the engine.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a soundproof member excellent in durability and soundproof performance.

Means for Solving the Problems

[0007] According to the present invention, durability and sound insulation are excellent. [Brief explanation of the drawing]

[0008] [Figure 1] (a) is a schematic cross-sectional view showing a sound-insulating member according to the first embodiment of the present invention, and (b) is a schematic cross-sectional view showing an enlarged portion of the other side of (a). [Figure 2] This is a schematic cross-sectional view showing the manufacturing method of the soundproofing member described above, in the order of (a) and (b). [Figure 3] This is a schematic cross-sectional view showing a soundproofing member according to a second embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view showing a soundproofing member according to a third embodiment of the present invention. [Figure 5] This is a schematic cross-sectional view showing a soundproofing member according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

[0010] In Figure 1(a), 1 represents a soundproofing member. The soundproofing member 1 absorbs and reduces sound S emitted from the sound source 2. In this embodiment, the sound source 2 is, for example, the engine that powers the vehicle, and the soundproofing member 1 is an example of an engine cover, which is a soundproofing member for vehicles. However, the sound source 2 may be a motor that powers the vehicle, or any other sound source may be arbitrarily selected.

[0011] The soundproofing member 1 is made of polyurethane foam that covers at least a portion of the sound source 2, and integrally has one skin layer 5 and another skin layer 6. The soundproofing member 1 is formed to conform to the outer shape of the sound source 2, and in the illustrated example, the bottom is open and it is formed in a lid-like shape that covers the top and sides of the sound source 2.

[0012] The first skin layer 5 is a foamed layer that forms the inner surface of the soundproofing member 1, on the side facing the sound source 2. In this embodiment, the first skin layer 5 constitutes the entire inner surface of the soundproofing member 1. The first skin layer 5 has an open-cell structure. The first skin layer 5 is formed to be thicker than the other skin layers 6. The first skin layer 5 comes into contact with the sound source 2 when in use.

[0013] The other skin layer 6 is on the opposite side from the side facing the sound source 2, that is, it forms the outer surface of the soundproofing member 1. The other skin layer 6 has a closed-cell structure. That is, the other skin layer 6 is denser and harder than the first skin layer 5, and has lower breathability. In this embodiment, the other skin layer 6 constitutes the entire outer surface of the soundproofing member 1.

[0014] Preferably, as shown in Figure 1(b), the soundproofing member 1 is formed such that the amount of air bubbles gradually decreases from the inside to the outside toward the other skin layer 6 which forms the outer surface, with the hardness, i.e., density, increasing. That is, the soundproofing member 1 is formed such that the amount of air bubbles and hardness increase in a gradient from one skin layer 5 to the other skin layer 6 as shown in Figure 1(a), with the other skin layer 6 being the hardest urethane layer.

[0015] When manufacturing the soundproofing member 1, mold molding is performed using metal or other molds 10 and 11 as shown in Figures 2(a) and 2(b). For example, the upper mold, mold 10, is the core (movable mold), and the lower mold, mold 11, is the cavity (fixed mold). The resin raw material 14 filled in the cavity, which is a molding space that defines the outer shape of the soundproofing member 1 formed between the mold surface 12 of mold 10 and the mold surface 13 of mold 11, is heated to foam it. In other words, mold 10 forms one skin layer 5 side of the soundproofing member 1, and mold 11 forms the other skin layer 6 side of the soundproofing member 1.

[0016] For example, Figure 2 shows an example of open molding in which the resin raw material 14 is injected before the mold is closed, but it is not limited to this, and closed molding in which the resin raw material is injected into a pre-closed mold is also acceptable.

[0017] The resin raw material 14 uses a polyol and an isocyanate, and is further mixed with additives such as a foaming agent, foam stabilizer, and catalyst in a mixing head 15 before being filled into the cavity between the mold surface 12 of the mold 10 and the mold surface 13 of the mold 11. A suitable release agent may be applied to the mold surfaces 12 and 13. Then, a foaming reaction and a resinification reaction occur simultaneously within this cavity, causing foaming and hardening to form the soundproofing member 1.

[0018] Here, by controlling the heat absorption of the mold 10 and the mold 11 by the temperatures of the mold surface 12 and the mold surface 13, one skin layer 5 and another skin layer 6 are formed. In the present embodiment, by making the temperature of at least the mold surface 12 of the mold 10 higher than the temperature of at least the mold surface 13 of the mold 11, the resinization reaction rate of the polyol and the isocyanate on the mold 10 side is made faster than that on the mold 11 side. Therefore, on the mold 10 side where the temperature is relatively high, the absorption of the reaction heat H is suppressed, so that a hard urethane layer is not formed and an open-cell structure one skin layer 5 is formed. On the mold 11 side where the temperature is relatively low, the absorption of the reaction heat H becomes relatively large, so that the shape gradually becomes less bubbly and harder toward the mold surface 13 of the mold 11, and another skin layer 6 having a closed-cell structure is formed at the portion adhering to the mold surface 13.

[0019] And the demolded soundproof member 1 is arranged and used so that one skin layer 5 contacts, preferably adheres closely to, the outer surface of the sound source 2. Here, the close adhesion means not only the state where the shape of the outer surface of the sound source 2 and one skin layer 5 of the soundproof member 1 facing this outer surface completely coincides and adheres closely without a gap, but also the state where the shape of the outer surface of the sound source 2 and one skin layer 5 generally coincides and adheres closely with a slight gap.

[0020] Thereby, the sound S emitted from the sound source 2 is absorbed by entering from one skin layer 5 of the soundproof member 1 facing the outer surface of the sound source S into the soundproof member 1. Further, since the outer surface of the soundproof member 1 is the other skin layer 6 having a closed-cell structure, the sound S passing through one skin layer 5 is less likely to leak to the outside of the soundproof member 1, and for the sound S reflected to the sound source 2 side by the other skin layer 6, it is further absorbed by passing through one skin layer 5 again.

[0021] Thus, by making one skin layer 5, which is located on one side facing the sound source 2 and contacts the sound source 2 in the use state, an open cell structure, and making another skin layer 6, which is located on the other side opposite to the side facing the sound source 2, a closed cell structure, the shape retention of the soundproof member 1 is maintained by the other skin layer 6 that contributes to the product rigidity, and resistance to loads on the outer surface such as liquid repellency is obtained, resulting in excellent durability. At the same time, the sound S is directly incident on one skin layer 5 that contacts the sound source 2, and the sound S can be absorbed by the one skin layer 5, resulting in excellent soundproofing performance.

[0022] In addition, since the other side portion of the soundproof member 1 is formed such that the bubbles gradually decrease and the hardness increases from the inside to the outside toward the other skin layer 6, high-frequency sound S is absorbed at locations with many bubbles and low hardness, and low-frequency sound S can be absorbed at locations with few bubbles and high hardness. Therefore, it becomes possible to absorb sound S in various frequency bands before it is reflected by the other skin layer 6.

[0023] Note that although the example of covering the upper side of the sound source 2 is given for the soundproof member 1, it is not limited to this. For example, as in the second embodiment shown in FIG. 3, by using a plurality of soundproof members 1 to cover the entire sound source 2, the soundproofing performance may be further enhanced.

[0024] Regarding the other skin layer 6, it is not limited to covering the entire outer surface of the soundproof member 1. For example, after molding, a part may be removed by cutting, polishing, etc., so that, as in the third embodiment shown in FIG. 4, it may form a part of the outer surface of the soundproof member 1 according to the location of the sound source 2 where soundproofing is particularly desired. In this case, since the sound emitted from an external sound source different from the sound source 2 directly enters the one skin layer 5, the sound absorption performance of the external sound source can also be enhanced.

[0025] Furthermore, as in the fourth embodiment shown in FIG. 5, the sound insulation characteristics may be changed by varying the thickness of the other skin layer 6 according to the magnitude and frequency characteristics of the sound S at each part of the sound source 2. For example, the other skin layer 6 is provided with a portion 6a having a large thickness and a portion 6b having a small thickness. The greater the thickness of the other skin layer 6, the better the soundproofing performance. [Industrial applicability]

[0026] The present invention can be suitably used, for example, as an engine cover that reduces noise emitted from an automobile engine. [Explanation of Symbols]

[0027] 1. Soundproofing material 2 Sound sources 5. One skin layer 6 Other skin layers

Claims

1. A soundproofing member made of polyurethane foam, which is placed on at least a portion of the outer surface of a sound source, A skin layer with an open cell structure located on one side facing the sound source and in contact with the sound source during use, Another skin layer with a closed-cell structure located on the opposite side from the side facing the aforementioned sound source, A soundproofing member characterized by comprising the following features.

2. The other side is formed such that the number of air bubbles gradually decreases and the hardness increases from the inside out toward the other skin layer. The soundproofing member according to feature 1.

3. This is a cover used for the power source of a vehicle, which is used as a sound source. The soundproofing member according to claim 1 or 2, characterized by the above.

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