JP7492847B2 - Soundproof cover - Google Patents

Description

The present invention relates to a soundproof cover, and more specifically, to a soundproof cover that is attached to a noise source in an automobile.

Conventionally, various soundproof covers have been proposed that are attached to noise sources such as automobile engines in order to reduce such noise. Among them, a soundproof cover that has a soundproof layer made of a hard resin molded body and a sound absorbing layer made of a foam molded body such as urethane foam and bonded to the soundproof layer facing the noise source is known (see, for example, Patent Documents 1 and 2). In such a soundproof cover, the soundproof layer blocks noise from the noise source, and the sound absorbing layer absorbs noise from the noise source.

JP 2002-28934 A JP 2009-108789 A

In recent years, hybrid and electric vehicles, which are much quieter than conventional gasoline vehicles, have become more common, and as a result, there is a demand to block out as much noise as possible from noise sources. To meet this demand, a soundproof cover can be installed to cover the entire outer surface of the noise source, which is one way to improve the soundproofing effect. However, the soundproof cover described above requires multiple covers to accommodate the three-dimensional outer shape of the noise source. This not only increases the mass of the resin molded body and the overall mass of the cover, but also increases the labor required for installation and manufacturing costs. Furthermore, due to its structure, it is difficult to cover the entire outer surface of the noise source with a foam molded body without any gaps, so the expected soundproofing effect cannot be obtained.

Therefore, the object of the present invention is to provide a soundproof cover that is lightweight, inexpensive, and has high soundproofing performance.

In order to achieve the above-mentioned object, the soundproof cover of the present invention has two cover parts connected by a hinge part consisting of an integral hinge and molded to cover the entire outer surface of a noise source when closed at the hinge part , and the two cover parts have a laminated structure including a first fiber layer as a surface layer, a sound-insulating layer, and a second fiber layer as a sound-absorbing layer facing the noise source .

With this type of soundproof cover, the use of a fiber layer can suppress an increase in the mass of the entire soundproof cover. In addition, since the entire outer surface of the noise source is covered with multiple cover parts that are connected together, not only can soundproofing performance be improved, but also costs can be reduced by improving installation workability.

As described above, the present invention can provide a soundproof cover that is lightweight, inexpensive, and has high soundproofing performance.

1 is a perspective view of a soundproof cover according to an embodiment of the present invention; 2 is a cross-sectional view taken along line AA in FIG.

The following describes an embodiment of the present invention with reference to the drawings. In this specification, the soundproof cover of the present invention is described using an example in which it is applied to a vehicle drive motor mounted on a hybrid vehicle or electric vehicle, but the use of the soundproof cover of the present invention is not limited to this. Examples of noise sources to which the soundproof cover of the present invention can be applied include compressors for car air conditioners.

Figure 1 is a perspective view of a soundproof cover according to one embodiment of the present invention, with Figures 1(a) and 1(b) being perspective views of the soundproof cover in an open state as seen from opposite sides, and Figure 1(c) being a perspective view of the soundproof cover in a closed state. Figure 2 is a cross-sectional view taken along line A-A in Figure 1(a). Note that the front-rear, left-right, and top-bottom directions shown in Figure 1(c) are for convenience only and do not limit the position of the soundproof cover of this embodiment when in use.

The soundproof cover 10 is attached to a vehicle drive motor to reduce noise generated by the motor, and is composed of two cover sections 11 and 12. The two cover sections 11 and 12 are connected so as to be able to open and close with a hinge section 13 made of an integral hinge, and are molded to cover the entire outer surface of the motor when closed.

The entire cover 11, 12, including the hinge 13, has a laminated structure including multiple fiber layers. Specifically, the cover 11, 12 is constructed by laminating a surface layer (first fiber layer) 1 made of nonwoven fabric, a sound-insulating layer 2, and a sound-absorbing layer (second fiber layer) 3 made of felt and facing the vehicle drive motor.

The material of the surface layer 1 is not particularly limited as long as it can be formed into a nonwoven fabric, and for example, general synthetic fibers such as polyamide fibers (nylon, etc.), acrylic fibers, polyester fibers (polyethylene terephthalate (PET), etc.), and polyolefin fibers can be used. The form of the nonwoven fabric is also not particularly limited, and examples include needle punch, spun lace, and spun bond. In addition, from the viewpoint of preventing water from penetrating into the interior, the material may be water repellent.

The material of the sound insulation layer 2 is not particularly limited as long as it has sound insulation properties. The sound insulation layer 2 may also be formed as a backing layer for the surface layer 1. In this case, the material of the sound insulation layer 2 may be, for example, a mass back made of a composition in which an olefin resin (polyethylene, polypropylene, etc.) or a polyvinyl chloride resin is filled with an inorganic filler (calcium carbonate, barium sulfate, etc.). The method of forming the sound insulation layer 2 in this case may be a method of applying a liquid resin composition, but is not limited to this, and a film-like material may be attached with an adhesive.

The material of the sound absorbing layer 3 is not particularly limited as long as it can be formed into felt and has sound absorbing properties. For example, general synthetic fibers such as polyamide fibers (nylon, etc.), acrylic fibers, polyester fibers (polyethylene terephthalate (PET)), polyolefin fibers, etc. can be used. In addition to sound absorbing properties, the sound absorbing layer 3 may have heat resistance. An example of such a sound absorbing layer 3 is a mixture of PET fibers (e.g., 20 to 30% by weight), low melting point PET fibers (e.g., 30 to 40% by weight), and flame retardant PET fibers (e.g., 30 to 50% by weight), with a preferred weight ratio of 30:30:40. In addition, inorganic fibers such as glass fibers and mixtures of the above-mentioned synthetic and inorganic fibers can also be used as materials for the sound absorbing layer 3 that have heat resistance.

There is no particular restriction on the molding method of the cover parts 11 and 12. For example, hot stamp molding can be used, in which a laminate of the surface layer 1, the sound-insulating layer 2, and the sound-absorbing layer 3 is heated in advance and then molded while cooling in a mold. If the sound-insulating layer 2 is backed on the surface layer 1 in advance, adhesion between the surface layer 1 and the sound-insulating layer 2 is not necessary, but otherwise, an adhesive can be applied between the surface layer 1 and the sound-insulating layer 2, and the two can be bonded when the cover parts 11 and 12 are molded. The sound-insulating layer 2 and the sound-absorbing layer 3 can also be bonded by an adhesive layer, but if a mass bag made of an olefin resin and an inorganic filler is used as the sound-insulating layer 2, the mass bag itself functions as an adhesive, so there is no need to insert an adhesive layer between the two when the cover parts 11 and 12 are molded.

In this way, in the soundproof cover 10 of this embodiment, the cover parts 11, 12 molded to cover the entire outer surface of the wheel drive motor are composed of multiple fiber layers 1, 3, so that the soundproof performance can be improved while suppressing the increase in the mass of the soundproof cover 10 as a whole. In addition, the multiple fiber layers 1, 3 are also provided in the hinge part 13 that connects the cover parts 11, 12, so the soundproof performance is not impaired by the hinge part 13. In addition, in order to attach the soundproof cover 10, it is only necessary to close and fix the integrally connected cover parts 11, 12, so that the attachment is not time-consuming and the manufacturing cost does not increase. Furthermore, the structure of the nonwoven fabric backed with resin is a structure that is generally adopted in existing carpet products. Therefore, an existing carpet product can be used as it is as the surface layer 1 backed with the soundproof layer 2, and in this respect, costs can also be reduced.

There are no particular limitations on the method for fastening the cover parts 11, 12; for example, a method of fastening using a hook-and-loop fastener or a method of providing a slit on one of the cover parts 11, 12 and a tongue on the other with a tip wider than the base end, and inserting the tongue into the slit to engage them, can be used. The method of using a slit and a tongue is preferable compared to the case of a hook-and-loop fastener, in that it reduces the labor required to attach the hook-and-loop fastener during the manufacturing process of the cover parts 11, 12.

There is no particular limit to the thickness of each layer 1 to 3 constituting the soundproof cover 10. For example, the thickness of the soundproof layer 2 and the sound absorbing layer 3 can be appropriately set according to the frequency range of the noise to be soundproofed. However, from the viewpoint of simultaneously suppressing the increase in the mass of the soundproof cover 10 as a whole and improving the soundproofing performance, it is preferable to change the thickness of the soundproof layer 2 and the sound absorbing layer 3 for each location (region) to change the soundproofing performance and the sound absorbing performance, rather than making the thickness of the soundproof layer 2 and the sound absorbing layer 3 uniform to make the soundproofing performance and the sound absorbing performance uniform. In other words, by making the soundproof layer 2 and the sound absorbing layer 3 thicker in areas where soundproofing is more necessary to improve the soundproofing performance and the sound absorbing performance, and making the soundproof layer 2 and the sound absorbing layer 3 thinner in other areas to reduce the weight, the desired soundproofing performance can be obtained while suppressing the increase in the mass of the soundproof cover 10 as a whole. Note that the thickness may be changed for each location for either the soundproof layer 2 or the sound absorbing layer 3, or for both. Also, instead of or in addition to varying the thickness from place to place, the mass per unit area (the basis weight in the sound absorbing layer 3, which is a fibrous layer) may be varied.

In addition, the soundproof cover 1 of this embodiment is composed of two cover parts 11, 12, but the number of cover parts is not limited to two and may be three or more. In addition, the cover parts 11, 12 of this embodiment are composed of three layers: a surface layer 1, a sound insulation layer 2, and a sound absorbing layer 3, but for example, if the surface layer is formed from a material having sound absorbing properties, the sound absorbing layer may be omitted.

For noise sources such as motors and compressors, it is necessary to pull out cables such as power cords and ducts and to install connecting members for fixing the noise source to the vehicle body. Therefore, soundproof covers that are attached to cover the entire outer surface of such noise sources need openings to access the noise sources. However, in conventional soundproof covers made of resin molded bodies and foam molded bodies, openings that are larger than the pull-out members and connecting members must be formed in the resin molded body, which leads to reduced soundproofing performance due to sound leakage. In addition, if a hinge portion made of an integral hinge is formed in the resin molded body to cover the entire outer surface of the noise source, it is necessary to form an opening by avoiding the hinge portion, which reduces the freedom of design.

In contrast, in the soundproof cover 10 of this embodiment, openings 14 consisting of slits are formed in the cover parts 11 and 12 to access the vehicle drive motor, which is the object of soundproofing. As a result, even if an extracting member is inserted into the opening 14 or a connecting member is placed in the opening 14, the opening 14 closes due to the restoring force of the fibers and adheres closely to the extracting member or connecting member, thereby suppressing sound leakage and suppressing deterioration of soundproofing performance. Note that such a soundproof cover 10 needs to be attached to the vehicle drive motor before the vehicle drive motor is attached to the vehicle body, because it is necessary to extract members from the vehicle drive motor and connect them to the vehicle body through the opening 14.

In the illustrated configuration, the opening 14 is formed from multiple radial slits, but the shape of the slits is not limited to this and may be, for example, an H-shaped slit. The position of the slit is also not limited to the illustrated configuration and may be, for example, formed at a position crossing the hinge portion 13. In this way, forming the opening 14 from a slit is advantageous in that it can greatly improve the degree of freedom in design. In addition, in the case of an opening 14 made of a slit, depending on the shape of the slit and the degree of the restoring force of the fiber, there is a possibility that problems such as the insertion of the pull-out member and the installation of the connection member may occur. Therefore, the opening for accessing the noise source may be an opening made of a hole carved out in a predetermined shape.

Here, we will explain the evaluation tests that were conducted to confirm the effect of the slit openings.

(Test 1)
In Test 1, a soundproof cover having the same shape as the soundproof cover shown in Fig. 1 but without any openings was prepared, and a dodecahedral speaker simulating a noise source was installed inside the cover. Then, white noise (81.3 dB) simulating noise was generated from the dodecahedral speaker, and the surrounding sound pressure level was measured. The sound pressure level was measured using microphones installed at six locations, one each on the front, back, left, right, top, and bottom of the soundproof cover (see Fig. 1(c)), and the average value was taken as the measured value.

The surface layer of the soundproof cover was made of needle-punched nonwoven fabric made of polyethylene terephthalate (PET) fibers, the sound-insulating layer was made of mass backing made of olefin resin and inorganic filler, and the sound-absorbing layer was made of molded felt made of PET fibers. Stamp molding was used to manufacture the soundproof cover. Specifically, mass backing was applied to the back side of the needle-punched nonwoven fabric to form a backing layer, which was then heated together with the molded felt, and the two were stacked and placed in a mold for clamping. The molded product was then removed, and the excess part on the outer periphery was trimmed to obtain the soundproof cover.

(Test 2)
In the second test, first, an opening made of a slit was formed in the soundproof cover used in the first test. Specifically, two openings made of radial slits were formed in the vertical direction on each of the front and rear surfaces of the soundproof cover, and two openings made of H-shaped slits were formed in the vertical direction on each of the left and right surfaces. That is, a total of eight openings were formed, two on each of the front, rear, left and right surfaces of the soundproof cover. The openings made of H-shaped slits were formed so as to cross the hinge portion and the peripheral portion of the cover portion facing the hinge portion. Then, resin cylinders simulating the pull-out member and the connecting member were inserted and fixed in the openings. Specifically, a resin cylinder was inserted and fixed in the axial direction for the openings made of radial slits, and a resin cylinder was inserted and fixed perpendicular to the axial direction (horizontally) for the openings made of H-shaped slits. Using such a soundproof cover, the sound pressure level was measured under the same conditions as in the first test.

(Test 3)
In Test 3, first, the slit portion of the soundproof cover used in Test 2 was cut out to form an opening made of a hole. Specifically, the radial slit portion formed on each of the front and rear surfaces of the soundproof cover was cut out into a square to form an opening made of a square hole, and the H-shaped slit formed on each of the left and right surfaces was cut out into a rectangle to form an opening made of a rectangular hole. Then, as in Test 2, a resin cylinder was inserted and fixed in the axial direction for the opening made of the square hole, and a resin cylinder was inserted and fixed perpendicular to the axial direction (horizontally) for the opening made of the rectangular hole. Using such a soundproof cover, the sound pressure level was measured under the same conditions as in Test 1.

Table 1 shows the sound pressure levels (measured values) and their attenuation in Tests 1 to 3. The attenuation of the sound pressure level is an index that indicates the difference between white noise (81.3 dB) that simulates noise and the sound pressure level measured around the soundproof cover, and is shown here as a relative value when the attenuation of the sound pressure level in Test 1 is set to 100.

Test 2 showed a greater attenuation of sound pressure levels and better soundproofing performance than Test 3. This is thought to be because forming the opening with a slit blocked the gap between the opening and the resin cylinder, thereby suppressing sound leakage and minimizing loss of soundproofing performance.

The soundproof cover of the present invention is suitable for use on noise sources in automobiles, including conventional gasoline vehicles, but the configuration in which the soundproof cover is attached to cover the entire outer surface of the noise source is extremely quiet compared to conventional gasoline vehicles, and is particularly suitable for use on noise sources in hybrid and electric vehicles, which require as much noise generated by the noise source as possible to be blocked.

REFERENCE SIGNS LIST 1 Surface layer 2 Sound insulation layer 3 Sound absorption layer 10 Soundproof cover 11, 12 Cover portion 13 Hinge portion 14 Opening

Claims (4)

The cover includes two cover parts connected by a hinge part formed of an integral hinge and molded to cover the entire outer surface of the noise source when closed at the hinge part ,
The soundproof cover has a laminated structure in which the two cover parts have a first fiber layer as a surface layer, a sound-insulating layer, and a second fiber layer as a sound-absorbing layer facing the noise source . 2. The soundproof cover according to claim 1 , wherein at least one of the sound-insulating layer and the second fiber layer is composed of a plurality of regions having different thicknesses and/or masses per unit area. 3. The soundproof cover of claim 1, having an opening for accessing the noise source. The soundproof cover according to claim 3 , wherein the opening comprises a slit.

Images