JP2021117287A - Design method of sound insulation member and manufacturing method of sound insulation wall using design method - Google Patents

Abstract

To install a sound insulation member in a small space and to improve weight reduction and sound insulation performance.SOLUTION: A design method for designing a sheet-like sound insulation member 10 arranged in a hollow part 13 of a hollow double wall structure 12 to posses prescribed sound insulation performance is provided. Apparent sound speed Cde-ve in the hollow part 13 of a sound wave which is made incident on the hollow double wall structure 12 is calculated as a function with an incident angle θ of the sound wave and a first interval x of a pair of lateral walls 21 and a second interval y of vertical walls as variables, and the first interval x and the second interval y are set so that the apparent sound speed Cde-ve in the hollow part 13 of the sound wave becomes a prescribed target value. Since the apparent sound speed Cde-ve in the hollow part 13 of the sound wave indicates sound insulation performance of the sound insulation member 10, the first interval x and the second interval y for achieving the apparent sound speed Cde-ve in the hollow part 13, which corresponds to required sound insulation performance, can easily be set.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to a design method for designing a sheet-shaped sound insulation member arranged in a hollow portion of a hollow double wall structure so as to have a predetermined sound insulation performance, and a method for manufacturing a sound insulation wall using this design method. ..

As a sound insulation structure for improving sound insulation while suppressing weight increase and cost increase, a mass portion having a planar shape arranged at intervals with respect to the panel and a plurality of mass portions on the side facing the panel in the mass portion are arranged. It is known that the spring portion is provided with a spring portion and a leg portion whose one end is joined to a mass portion and the other end is joined to a panel via a damping portion (Patent Document 1). The spring portion of this sound insulation structure has a hollow membrane material having airtightness and flexibility, and a gas sealed inside the membrane material. By using carbon dioxide as the gas sealed in the membrane material, the speed of sound (propagation speed of sound waves) is lower than in air, and the sound insulation performance of the sound insulation structure can be improved.

On the other hand, the sound absorbing material having a non-penetrating hole of the Helmholtz resonance structure in which the hollow portion communicates with the outside through the introduction passage faces the surface through which the non-penetrating hole of the sound absorbing material is opened, and is separated by a predetermined distance with an air layer. A soundproof structure having a sound insulating material provided in the above is known (Patent Document 2). In this soundproof structure, the thickness of the air layer, the thickness of the sound absorbing material, the size of the non-through hole, etc. are set within a predetermined range, so that the resonance transmission frequency deviates from 500 to 2000 Hz, which is unpleasant for humans. The soundproofing performance is improved by setting it to less than 500 Hz.

JP-A-2018-205419 International Publication No. 2019/008775

However, in the sound insulation structure described in Patent Document 1, in order to improve the sound insulation performance, it is necessary to increase the hollow space of the membrane material into which the gas is injected, and the thickness of the sound insulation structure becomes large. Further, the soundproof structure described in Patent Document 2 requires a predetermined thickness because it is necessary to set the thickness of the air layer and the thickness of the sound absorbing material within a predetermined range in order to adjust the resonance transmission frequency. do. As described above, these soundproof structures need to secure a predetermined space for installation, and it is difficult to install them in a small space.

In view of such a background, it is an object of the present invention to enable the sound insulation member to be installed in a small space, and to achieve both weight reduction and improvement of sound insulation performance.

In order to solve such a problem, in one embodiment of the present invention, a sheet-shaped sound insulation member (10) arranged in the hollow portion (13) of the hollow double wall structure (12) is provided with a predetermined sound insulation. A design method for designing to have performance, wherein the sound insulation member extends in the in-plane direction and is arranged to face each other with a first interval (x) in the direction perpendicular to the plane (21). And a vertical wall (22) arranged with a second interval (y) in the in-plane direction between the pair of the horizontal walls, and the hollow portion of the sound wave incident on the hollow double wall structure. The apparent sound velocity (C _de-ve ) in the above is calculated as a function with the incident angle (θ) of the sound wave, the first interval and the second interval as variables, and the sound insulation performance of the sound insulation member is shown. The first interval and the second interval are set so that the apparent speed of sound in the hollow portion of the sound wave becomes a predetermined target value.

The sound wave transmitted through the hollow double wall structure causes a time delay when passing through the vertical wall and the horizontal wall of the sound insulating member provided in the hollow portion. As a result, the inventors of the present application have found that the apparent sound velocity in the hollow portion becomes smaller, and the smaller the apparent sound velocity in the hollow portion, the higher the sound insulation performance. According to this configuration, the apparent speed of sound in the hollow portion of the sound wave incident on the hollow double wall structure is used as a function in which the incident angle of the sound wave, the first distance between the horizontal walls and the second distance between the vertical walls are variables. By calculating, the first interval and the second interval for realizing the apparent sound velocity in the hollow portion corresponding to the required sound insulation performance can be easily set. As a result, both weight reduction and sound insulation performance can be achieved with the optimum number of walls without unnecessarily increasing the number of walls.

ただし、Ｃ_{ｄｅ−ｖｅ}：入射角に応じた音波の中空部１３での見かけ音速（ｍ／ｓ）、ｘ'：中空部を音波が通過する距離（ｍ）、θ：音波の入射角（ｒａｄ）、Ｃ_ｉ：中空部での音速（ｍ／ｓ）、ｔ：壁一枚当たりの時間遅れ（ｓ）、ｘ：１対の横壁間の第１間隔（ｍ）、ｙ：面内方向に配置される縦壁同士の第２間隔（ｍ）、ａ：面直方向に配置される横壁の枚数である。 Preferably, the apparent speed of sound of the sound wave in the hollow portion is calculated as a function represented by the formula (A).

However, C _de-ve : the apparent speed of sound (m / s) of the sound wave in the hollow portion 13 according to the incident angle, x': the distance through which the sound wave passes through the hollow portion (m), θ: the incident angle of the sound wave (rad). ), _{C i:} speed of sound in the hollow portion (m / s), t: time delay per single wall (s), x: 1 pair of first spacing between the transverse walls of the (m), y: the in-plane direction Second spacing (m) between the vertically arranged vertical walls, a: The number of horizontal walls arranged in the direction perpendicular to the plane.

Preferably, the hollow double-walled structure is randomized by averaging the apparent speed of sound corresponding to the incident angle from 0 ° to the maximum value (θH) at predetermined angular intervals (θp) for the incident angle. _{The average apparent sound velocity ((C de-ve} ) ^-) of the randomly incident sound wave incident on the sound wave in the hollow portion is calculated, and the average apparent sound velocity is defined as the apparent sound velocity of the sound wave in the hollow portion.

According to this configuration, the apparent sound velocity of the randomly incident sound wave in the hollow portion can be calculated, and the first interval and the second interval for realizing the sound insulation performance for the randomly incident sound wave can be easily set. Thereby, the first interval and the second interval corresponding to the sound insulation performance for the sound in the natural world can be set accurately.

Preferably, the maximum value (θH) of the incident angle is 78 °, and the angle interval (θp) of the incident angle is 1 °.

According to this configuration, it is possible to set the first interval and the second interval corresponding to the average apparent speed of sound in the hollow portion of the randomly incident sound wave under the conditions close to the actual environment.

Preferably, the target value of the apparent speed of sound is 300 m / s or less.

According to this configuration, the sound insulation performance of the hollow double wall structure can be reliably improved.

Further, in order to solve the above problems, in one embodiment of the present invention, the first interval and the second interval are set by using the design method, and a pair of the lateral walls are arranged to face each other with the first interval. , A method of manufacturing a sound insulation wall (15) manufactured by arranging the vertical walls at the second interval, wherein the vertical walls are opened in a plan direction view and have a predetermined shape. It is composed of a body (23), and the shape of the strip-shaped body includes a spiral shape, a W-shape, and a random shape.

According to this configuration, since the vertical wall is opened and not closed in the direction perpendicular to the plane, the position of the vertical wall is suppressed from being displaced due to the thermal expansion of the gas between the pair of horizontal walls.

In one embodiment of the present invention, the first interval and the second interval are set by using the design method, a pair of the horizontal walls are arranged facing each other with the first interval, and the vertical wall is arranged with the second interval. It is a manufacturing method of a sound insulation wall (15) manufactured by arranging, and the vertical wall is composed of a large number of strip-shaped bodies (24).

According to this configuration, a vertical wall can be formed with a second interval by a large number of strips.

In one embodiment of the present invention, the first interval and the second interval are set by using the design method, a pair of the horizontal walls are arranged facing each other with the first interval, and the vertical wall is arranged with the second interval. Is a method of manufacturing a sound insulation wall (15), in which a pair of the horizontal wall and the vertical wall are made of a film material, and the vertical wall forms a closed loop in a direct view from the plane. It is composed of a large number of tubular bodies (25), and a pair of the horizontal wall and the vertical wall cooperate with each other to form a thin film closed space structure that defines a closed space.

According to this configuration, the thin film closed space defined by the membrane material can function as a spring portion. As a result, a sound insulation structure is configured in which one wall structure of the hollow double wall structure is a mass portion and the thin film closed space is a spring portion, and the sound insulation performance of the hollow double wall structure can be improved.

Preferably, in the above manufacturing method, the first panel member (4, 11) is arranged on one side of the sound insulation member in the direction perpendicular to the surface, and the second panel member (11, 11) is arranged on the other side of the sound insulation member in the direction perpendicular to the surface. 4) may be arranged so that the sound insulating member is sandwiched between the first panel member and the second panel member.

According to this configuration, the sound insulating member forms a spring portion that elastically supports the second panel member or the first panel member which is a mass portion, so that the first panel member, the second panel member, and the sound insulating member become independent. The sound insulation performance is higher than that of the case where it is provided.

Preferably, in the above manufacturing method, two resin sheets (26) are welded to each other by compression heating so that one of the pair of the lateral walls is separated from each other for each of the tubular bodies.

According to this configuration, a thin film closed space structure can be easily formed by welding two resin sheets to each other.

As described above, according to the present invention, the sound insulation member can be installed in a small space, and both weight reduction and improvement of sound insulation performance can be achieved at the same time.

Perspective view of the roof of the vehicle body provided with the sound insulating member according to the embodiment. Longitudinal sectional view of the roof shown in FIG. Enlarged sectional view of the roof shown in FIG. Explanatory drawing of sound insulation characteristic of sound insulation member shown in FIG. Graph showing the relationship between sound insulation characteristics and average apparent sound velocity Top view of a sound insulation member showing an example of a vertical wall (A) plan view, (B) cross-sectional view of the sound insulation member showing another example of the vertical wall. Top view of a sound insulation member showing an example of a vertical wall of a thin film closed space structure Cross-sectional view of a sound insulation member showing another example of a thin film closed space structure A graph showing the sound insulation characteristics of a sound insulation wall using the thin film closed space structure shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of the roof 1 of a vehicle body to which the sound insulating member 10 according to the present invention is applied as viewed from the outside of the vehicle, and FIG. 2 is a vertical sectional view of the roof 1. As shown in FIGS. 1 and 2, the roof 1 includes a roof panel 2 forming an outer shell of a vehicle body and a roof flying 3 arranged below the roof panel 2 and defining an internal space (vehicle interior) of the vehicle body. I have. The roof panel 2 includes an outer panel 4 made of a steel plate and a plurality of reinforcing frames 5 provided on the inner surface of the outer panel 4. The reinforcing frame 5 is a steel reinforcing member formed by press forming a steel plate into a channel cross-sectional shape, is arranged at intervals in the longitudinal direction of the outer panel 4, and extends in the lateral direction of the outer panel 4. There is.

A plurality of sheet-shaped sound insulating members 10 are provided on the inner surface of the outer panel 4 where the reinforcing frame 5 is not provided. The sound insulating member 10 may also be provided on the inner surface of the reinforcing frame 5. Alternatively, the sound insulating member 10 may be provided on the outer surface of the roof lining 3.

FIG. 3 is an enlarged cross-sectional view of the roof 1 shown in FIG. As shown in FIG. 3, a soundproof panel 11 is arranged below the sound insulation member 10 (inside the vehicle). The soundproof panel 11 cooperates with the outer panel 4 to form the hollow double wall structure 12. The soundproof panel 11 is preferably formed in a plate shape with a material having a higher specific gravity than the sound insulation member 10 and having high moldability, and is preferably a resin plate formed of a synthetic resin such as polypropylene (PP). It is preferable to have. The soundproof panel 11 is not limited to the one having a plate shape as a whole, and may be a member having a plate shape at least in a part thereof.

In the hollow double wall structure 12, a pair of panel members (that is, an outer panel 4 and a soundproof panel 11), which are structural walls, are arranged so as to be separated from each other so that the hollow portion 13 is between the two panel members. It is a structure that forms. The sound insulating member 10 is arranged in the hollow portion 13 of the hollow double wall structure 12. More specifically, the sound insulating member 10 is arranged in the hollow portion 13 so as to be sandwiched between the outer panel 4 and the soundproof panel 11. The sound insulation wall 15 is composed of the sound insulation member 10 and the hollow double wall structure 12 (outer panel 4 and soundproof panel 11).

The sound insulating member 10 extends in the in-plane direction and is arranged between a pair of side walls 21 and a pair of side walls 21 which are arranged so as to face each other with a first interval x in the direction perpendicular to the surface (also referred to as the out-of-plane direction). It includes a vertical wall 22 arranged inward with a second interval y. The portion of the sound insulating member 10 other than the horizontal wall 21 and the vertical wall 22 is an air layer. The pair of horizontal wall 21 and vertical wall 22 are made of a film material (thin film), and may be formed of a material having a Young's modulus lower than that of the material forming the soundproof panel 11 so as to be elastically deformed more positively than the soundproof panel 11. preferable. As a material for forming such a film material, for example, an ethylene-vinyl alcohol copolymer is preferably used. The horizontal wall 21 can be called a diaphragm, and the vertical wall 22 can be called a vertical membrane.

As a result, the soundproof panel 11 serves as a mass portion, and the sound insulation member 10 serves as a spring portion, and the vibration energy of the sound wave transmitted through the roof 1 is absorbed. The absorbed vibration energy is converted into heat energy in the spring portion. The outer panel 4, the sound insulation member 10, and the sound insulation panel 11 form a sound insulation wall 15 having a hollow double wall structure, whereby the sound insulation performance of the roof 1 is improved.

The sound insulating member 10 may or may not be adhered to the outer panel 4 or the soundproof panel 11. In the present embodiment, the sound insulation member 10 is adhered to the soundproof panel 11, and the soundproof panel 11 is attached to the outer panel 4 by an attachment member (not shown) so as to be in contact with the outer panel 4. The mounting member may be made of metal or resin and may have high rigidity, for example, may have a substantially crank shape in cross section. It is preferable that an elastic member is provided between at least one of the outer panel 4 and the soundproof panel 11 and the mounting member. As a result, the entire soundproof panel 11 can be displaced with respect to the outer panel 4. The elastic member functions as a damping portion that attenuates the vibration of the soundproof panel 11 with respect to the outer panel 4. The elastic member may be, for example, a flexible and viscous adhesive.

In addition to functioning as a spring portion as described above, the sound insulating member 10 also functions as a sound insulating material that blocks sound waves that pass through the roof 1. The inventors have found that the characteristics of the sound insulation member 10 as a sound insulation material are related to the speed of sound waves transmitted through the sound insulation member 10, that is, the speed of sound at the sound insulation member 10 (the apparent sound velocity C _{de-ve of} randomly incident sound waves, which will be described later). I found out to do. Further, the inventors have confirmed that the sound insulation performance of the sound insulation member 10 improves as the sound velocity of the sound insulation member 10 decreases. Hereinafter, a specific description will be given.

FIG. 4 is an explanatory diagram of the sound insulation characteristic of the sound insulation member 10 shown in FIG. In FIG. 4A, sound waves obliquely transmitted through the sound insulating member 10 at a predetermined incident angle θ are transmitted through the outer horizontal wall 21, the vertical wall 22, and the lower vertical wall 22 in this order, and a total of three films are formed. The case where the material is transmitted is shown. In FIG. 4B, sound waves obliquely transmitted through the sound insulating member 10 at a predetermined incident angle θ are transmitted through the outer horizontal wall 21, the three vertical walls 22, and the lower vertical wall 22 in this order, for a total of 5 The case where a sheet of film material is transmitted is shown.

ただし、ｘ'：中空部１３を音波が通過する距離（ｍ）、ｘ：１対の横壁２１間の第１間隔（ｍ）、θ：音波の入射角（ｒａｄ）である。

ただし、Ｔ：中空部１３を音波が通過するのにかかる時間（ｓ）、Ｃ_ｉ：中空部１３での音速（ここでは、３４０ｍ／ｓとする）、ｎ：膜材（壁）透過枚数、ｔ：膜材（壁）一枚当たりの時間遅れ（ここでは、０．００００３２ｓとする）である。なお、ｔ＝０．００００３２ｓは、音波が膜材を透過する際にかかる時間を計測により得た測定値である。膜材を透過する際に音波に時間遅れが生じる要因は、膜材から加振される気体の粘性抵抗や、膜材の振動が気体を加振する際の波の干渉などが考えられる。 The distance between the pair of horizontal walls 21 arranged so as to face each other in the direction perpendicular to the surface of the sound insulating member 10 is the first distance x, and the distance between the pair of horizontal walls 21 and the vertical walls 22 arranged in the in-plane direction is the second. Let the interval y be. The hollow portion 13 (see FIG. 3) filled with the adhesive, the sound insulating member 10 composed of the horizontal wall 21, the vertical wall 22, and air is regarded as uniform here, and the thickness of the adhesive, the horizontal wall 21, and the vertical wall 22 is considered to be uniform. Should not be considered. Acoustic velocity _{C i} is the speed of sound in air at the hollow portion 13 (i.e., the acoustic velocity of the incident wave) C (= 340m / s) and the same. The distance x'that the sound wave passes through the hollow portion 13 is represented by the formula (1), and the time T required at that time is represented by the formula (2).

However, x': the distance (m) through which the sound wave passes through the hollow portion 13, x: the first interval (m) between the pair of side walls 21, and θ: the incident angle (rad) of the sound wave.

However, T: the time it takes a hollow portion 13 waves passes (s), _{C i:} speed of sound (in this case, and 340m / s) in the hollow portion 13, n: film material (walls) transmitting number, t: Time delay per film material (wall) (here, 0.000032s). Note that t = 0.000032s is a measured value obtained by measuring the time required for the sound wave to pass through the membrane material. Factors that cause a time delay in sound waves when passing through the membrane material are considered to be the viscous resistance of the gas vibrated from the membrane material and the interference of waves when the vibration of the membrane material vibrates the gas.

ただし、ａ：面直方向に配置される横壁２１の枚数（本実施形態では２枚）、ｙ：面内方向に配置される縦壁２２同士の第２間隔（ｍ）である。 The number of permeated membrane materials n represented by the formula (2) is represented by the formula (3).

However, a: the number of horizontal walls 21 arranged in the direction perpendicular to the plane (two in the present embodiment), y: the second spacing (m) between the vertical walls 22 arranged in the in-plane direction.

ただし、Ｃ_ｄｅ：中空部１３を通過する音波の時間遅れによる見かけ音速（ｍ／ｓ）である。 _{Therefore, the apparent speed of sound C de} due to the time delay of the sound wave passing through the hollow portion 13 is expressed by the equation (4).

However, C _de : The apparent speed of sound (m / s) due to the time delay of the sound wave passing through the hollow portion 13.

ただし、Ｃ_ｖｅ：中空部１３での面直成分による見かけ音速（ｍ／ｓ）である。 In the hollow double wall structure 12, sound waves incident at an incident angle θ and a sound velocity C include a component that propagates radially through the hollow portion 13 and is transmitted in the shortest direction perpendicular to the plane. Thus, sound velocity C _i of a hollow portion 13 of the acoustic waves is represented by the formula (5), it increases the apparent higher incidence angle θ is large. This apparent value is defined as the apparent sound velocity _Cve due to the surface-to-plane component. The phenomenon that the apparent sound velocity _Cve increases in the hollow portion 13 occurs regardless of the material of the member provided in the hollow portion 13.

However, C _ve : is the apparent speed of sound (m / s) due to the surface-to-plane component in the hollow portion 13.

ただし、Ｃ_{ｄｅ−ｖｅ}：入射角θに応じた音波の中空部１３での見かけ音速（ｍ／ｓ）、である。 As described above, the apparent sound velocity _Cve in the hollow portion 13 increases according to the incident angle θ, so that the apparent sound velocity _Cve-ve becomes the equation (6) from the equation (5).

However, C _de-ve : the apparent speed of sound (m / s) in the hollow portion 13 of the sound wave according to the incident angle θ.

Equation (7) is obtained by substituting equation (4) into equation (6), substituting equations (2) and (1) into the equation, and further substituting equation (3).

_{As represented by this equation (7), the apparent speed of sound C de-ve in} the hollow portion 13 of the sound wave incident on the hollow double wall structure 12 is the incident angle θ of the sound wave θ, and the first of the pair of side walls 21. It can be calculated as a function with one interval x and the second interval y between vertical walls as variables. _{Then, by setting the first interval x and the second interval y so that the apparent sound velocity C de-ve in} the hollow portion 13 of the sound wave becomes a predetermined target value, the first interval corresponding to the required sound insulation performance is obtained. The x and the second interval y can be easily set. As a result, both weight reduction and sound insulation performance can be achieved with the optimum number of thin films without unnecessarily increasing the number of thin films.

ただし、（Ｃ_{ｄｅ−ｖｅ}）^―：ランダム入射音波の平均見かけ音速、θＨ：ランダム入射音波の入射角θの最大値、θｐ：積算のための入射角θの角度間隔である。 However, the sound waves in the natural world incident on the hollow double wall structure 12 are random incidents incident from various directions with a random incident angle θ. _{Therefore, by averaging the apparent sound velocity C de-ve} from 0 ° to the maximum value θH for each angle interval θp with respect to the incident angle θ, the average apparent sound velocity (C _de-ve ) ^-of the randomly incident sound wave is calculated. This is defined as the apparent speed of sound C _{de-ve in} the hollow portion 13 of the sound wave. The average apparent speed of sound (C _de-ve ) ^-of a random incident sound wave is expressed by Eq. (8). The symbol indicating the average value is written above the character in the mathematical formula, but is written as "^-" after the character in the text.

However, (C _de-ve ) ^-: average apparent sound velocity of the random incident sound wave, θH: maximum value of the incident angle θ of the random incident sound wave, θp: angular interval of the incident angle θ for integration.

By using the equation (8) in this way, the apparent sound velocity C _de-ve in the hollow portion 13 of the randomly incident sound wave is calculated, and the first interval x and the second interval for realizing the sound insulation performance for the randomly incident sound wave are achieved. y can be easily set. Thereby, the first interval x and the second interval y corresponding to the sound insulation performance for the sound in the natural world can be set accurately.

In the present embodiment, the maximum value θH = 78 ° of the incident angle θ, which is a condition close to the actual environment, is used, and the angle interval θp is set to 1 °. Therefore, the equation (8) becomes the equation (9).

Thereby, the first interval x and the second interval y corresponding to the _{average apparent speed of sound (C de-ve} ) ^-in the hollow portion 13 of the randomly incident sound wave can be set under the condition close to the actual environment.

ただし、ＴＬ（θ）：入射角θについての遮音壁１５の透過損失（ｄＢ）、τ（θ）：入射角θで入射する音波の透過率である。 Next, the sound insulation characteristics of the sound insulation wall 15 composed of the hollow double wall structure 12 and the sound insulation member 10 provided in the hollow portion 13 will be described. The transmission loss TL (θ) of the sound insulation wall 15 with respect to the incident angle θ can be expressed by the equation (10) using the transmittance τ of the sound wave incident at the incident angle θ.

However, TL (θ): the transmission loss (dB) of the sound insulation wall 15 with respect to the incident angle θ, and τ (θ): the transmittance of the sound wave incident at the incident angle θ.

ただし、τ^―：ランダム入射音波の平均透過率、θＬ：ランダム入射音波の入射角θの最小値である。ここでも、入射角θの最小値θＬ及び最大値θＨは、現実の場に近い条件とされる０°及び７８°を用いるとよい。式（１０）及び（１１）より、遮音壁１５の透過損失ＴＬは、式（１２）で表すことができる。

ただし、ＴＬ：ランダム入射音波の遮音壁１５での透過損失（ｄＢ）である。 Since the sound wave incident on the hollow double wall structure 12 is a random incident sound wave as described above, the average transmittance τ which is the average value of the transmittance of the randomly incident sound wave incident in the range of the incident angle θ of θL to θH. ^-Can be expressed by Eq. (11) using hemispherical integration.

However, τ ^ −: the average transmittance of the randomly incident sound wave, θL: the minimum value of the incident angle θ of the randomly incident sound wave. Here, too, the minimum value θL and the maximum value θH of the incident angle θ may be 0 ° and 78 °, which are conditions close to the actual field. From the formulas (10) and (11), the transmission loss TL of the sound insulation wall 15 can be expressed by the formula (12).

However, TL: transmission loss (dB) of randomly incident sound waves at the sound insulation wall 15.

The relationship between the sound insulation characteristics of the sound insulation wall 15 calculated using the equation (12) and the average apparent sound velocity (C _de-ve ) ^-and the sound insulation characteristics (actual measurement values) of the sound insulation wall 15 using the conventional porous material are as follows. As shown in FIG. From FIG. 5, when the average apparent sound velocity (C _de-ve ) ^-is about 200 m / s, the sound insulation characteristics of 500 Hz to 2000 Hz, which are easily perceived by humans as noise, are equivalent to those of the conventional porous material. You can check. It can be confirmed that when the average apparent sound velocity (C _de-ve ) ^-decreases to about 300 m / s, the sound insulation performance is clearly improved as compared with the case of 340 m / s.

When the sound insulating member 10 is applied to the vehicle body as in the present embodiment, the thickness of the sound insulating member 10 is limited due to the layout of the car. Therefore, the first interval x of the pair of lateral walls 21 is fixed to, for example, 0.010 m. Since the transmission loss TL is expressed by the equation (12), if the equation (12) is used, the target average apparent sound velocity (C _{de) is set with the second interval y, which is the interval of the vertical wall 22 in the in-plane direction, as a parameter.} The second interval y of the vertical wall 22 can be designed so as to be _{−ve) ^ −.} When the first interval x is fixed at 0.010 m, for example, the average apparent speed of sound (C _de-ve ) ^-is 200 m / s, and the second interval y between the vertical walls is 0.012 m. That is, by arranging the vertical walls 22 in the in-plane direction at intervals of 0.012 m, the average apparent speed of sound (C _de-ve ) ^-of the randomly incident sound waves in the hollow portion 13 of the hollow double wall structure 12 is 200 m. It becomes / s.

As described above, the average apparent sound velocity (C _de-ve ) ^-in the hollow portion 13 of the randomly incident sound wave is related to the sound insulation characteristic of the sound insulation member 10. Therefore, using the equations (7) and (8), the first interval x and the first interval x and so _{that the average apparent sound velocity (C de-ve) ^-in the hollow portion 13 of the randomly incident sound wave becomes a predetermined target value.} By setting the second interval y, the first interval x and the second interval y for realizing _{the average apparent sound velocity (C de-ve} ) ^-in the hollow portion 13 corresponding to the required sound insulation performance can be easily set. Can be set to.

_{For example, by setting the target value of the average apparent sound velocity (C de-ve} ) ^-in the hollow portion 13 of the randomly incident sound wave to 300 m / s or less as described above, the sound insulation performance of the hollow double wall structure 12 can be improved. It can be definitely improved. Further, by setting the maximum value θH of the incident angle θ to 78 ° and the angle interval θp of the incident angle θ to 1 °, the average apparent speed of sound (C) in the hollow portion 13 of the random incident sound wave under conditions close to the actual environment. The first interval x and the second interval y corresponding to _{de-ve) ^-can be set.}

Next, the sound insulation member 10 manufactured by using the above design method and the manufacturing method thereof will be described. FIG. 6 is a plan view of the sound insulating member 10 showing an example of the vertical wall 22. In the example shown in FIG. 6 (A), the vertical wall 22 is composed of a band-shaped body 23 having a spiral shape that is open when viewed in the direction perpendicular to the plane. Here, "opened" means that the ends of the strip 23 are not closed to each other. Since the vertical wall 22 is made of a band-shaped body 23 having a spiral shape, the vertical wall 22 can be arranged with a second interval y in all directions in the in-plane direction.

In the example shown in FIG. 6B, the vertical wall 22 is composed of a strip-shaped body 23 having a W-shape or a zigzag shape that is open when viewed in the direction perpendicular to the plane. Since the vertical wall 22 is formed of a strip-shaped body 23 having a W-shape or a zigzag shape, the vertical wall 22 can be arranged with an average value of the second interval y in one direction in the in-plane direction.

In the example shown in FIG. 6C, the vertical wall 22 is composed of a band-shaped body 23 having a random shape opened in a plane-direct view. The vertical wall 22 can be arranged with the average value of the second interval y in all the in-plane directions by arranging the strips 23 at a predetermined density.

Since the vertical wall 22 is opened and not closed in the direction perpendicular to the plane in this way, the position of the vertical wall 22 is suppressed from being displaced due to the thermal expansion of the gas between the pair of horizontal walls 21.

FIG. 7 is a plan view (A) and a cross-sectional view (B) of the sound insulating member 10 showing another example of the vertical wall 22. As shown in FIG. 7, in this example, the vertical wall 22 is composed of a large number of strips 24. By forming the vertical wall 22 from a large number of strips 24 in this way, the vertical wall 22 can be formed with a second interval y.

FIG. 8 is a plan view of the sound insulating member 10 showing an example of the vertical wall 22 having a thin film closed space structure. In the example shown in FIG. 8A, the vertical wall 22 is composed of a large number of tubular bodies 25 forming a closed loop when viewed in the direction perpendicular to the plane. The tubular bodies 25 each have a cylindrical shape, and are dispersedly arranged in a plane-directed direction so as to be separated from each other. In the illustrated example, a plurality of tubular bodies 25 are arranged in a staggered pattern. Each tubular body 25 is joined to a pair of lateral walls 21 at an upper edge and a lower edge, and is a thin film closed space that independently defines a closed space internally in cooperation with the pair of lateral walls 21. It has a structure.

In the example shown in FIG. 8B, the vertical wall 22 is also composed of a large number of tubular bodies 25 forming a closed loop when viewed in the direction perpendicular to the plane. The tubular body 25 has a polygonal shape (hexagon in the illustrated example) and is connected to each other to form a honeycomb structure. Each tubular body 25 is joined to a pair of lateral walls 21 at an upper edge and a lower edge, and is a thin film closed space that independently defines a closed space internally in cooperation with the pair of lateral walls 21. It has a structure.

In the example shown in FIG. 8, each tubular body 25 cooperates with a pair of side walls 21 to define a closed space inside, and gas is sealed inside each tubular body 25. The closed space shown in FIG. 8 may be hermetically sealed, and may allow some air to enter and exit to the extent that the thin film closed space functions as a spring portion. The gas is filled inside the hollow membrane material with a pressure equal to or higher than a preset pressure so that the membrane material does not loosen at least. As such a gas, for example, air can be used. Further, carbon dioxide or helium can be used as the gas. If carbon dioxide is used as the gas to be sealed in the membrane material, the sound velocity C can be made lower than the value in the air, thereby improving the sound insulation performance.

The sound insulating member 10 is attached to the roof panel 2 (see FIGS. 1 and 2) as follows. First, the soundproof panel 11 (see FIG. 3) is joined to one (one surface) of the sound insulation member 10 in the direction perpendicular to the surface by using an adhesive or the like. The soundproofing member 10 is arranged so that the side (the other surface) opposite to the side to which the soundproofing panel 11 is joined faces the inner surface of the outer panel 4 (see FIG. 3), and the soundproofing panel 11 is used by using the above mounting member. Is attached to the outer panel 4. With the soundproof panel 11 attached to the outer panel 4, the soundproof member 10 is sandwiched between the soundproof panel 11 and the outer panel 4.

By sandwiching the sound insulation member 10 between the sound insulation panel 11 and the outer panel 4 in this way, the sound insulation member 10 forms a spring portion that elastically supports the sound insulation panel 11 as a mass portion, so that these members become independent. The sound insulation performance is higher than when it is provided.

Further, by appropriately adjusting the mass of the soundproof panel 11 forming the mass portion and the spring constant of the sound insulating member 10 forming the spring portion, the frequency at which the sound insulating member 10 resonates with noise is adjusted, and the frequency of the target frequency range is adjusted. Noise can be suppressed efficiently.

In this way, the pair of horizontal walls 21 and the vertical wall 22 composed of the tubular body 25 cooperate with each other to form a thin film closed space structure that defines the closed space, so that the thin film closed space defined by the membrane material is formed as a spring portion. Can function as. As a result, a sound insulation structure is formed in which the soundproof panel 11 is a mass portion and the thin film closed space is a spring portion, and the sound insulation performance of the hollow double wall structure 12 can be improved.

FIG. 9 is a cross-sectional view of the sound insulating member 10 showing another example of the thin film closed space structure. As shown in FIG. 9, in this example, the sound insulating member 10 is formed by welding two resin sheets 26 to each other by compression heating. The sound insulating member 10 is manufactured by a method similar to a known method for manufacturing a bubble wrap material, and the bubble wrap material is formed so as to have a similar structure. Specifically, one resin sheet 26 forms one of a pair of lateral walls 21 and a plurality of cylindrical tubular bodies 25, and the one lateral wall 21 is separated from each other for each tubular body 25. Will be done.

In this way, the two resin sheets 26 are welded to each other by compression heating, and one of the pair of side walls 21 is separated from each other for each tubular body 25, so that a thin film closed space structure can be easily formed. ..

FIG. 10 is a graph showing the sound insulation characteristics of the sound insulation wall 15 when the _{average apparent sound velocity (C de-ve} ) ^-is 216 m / s using the thin film closed space structure shown in FIG. In the graph, the sound insulation characteristic of only the outer panel 4 (described as "panel only") and the comparative example in which the hollow portion 13 of the hollow double wall structure 12 is provided with the porous material (double). Wall structure + porous material) and measured and predicted values of the present invention (double wall structure + thin film closed space structure) are shown. The tubular body 25 forming the thin film closed space of the sound insulation wall 15 of the present invention has dimensions of 30 mm in diameter, 10 mm in height, and 100 μm in thickness, and is arranged at intervals of 4 mm. The outer panel 4 is an iron plate having a thickness of 0.8 mm. The predicted value of the transmission loss TL of the present invention is a value obtained by using the equation (12), and as can be seen from FIG. 10, it is substantially the same as the measured value. Therefore, it was confirmed that the sound insulation performance of the sound insulation member 10 _{improves as the average apparent sound velocity (C de-ve) ^-decreases.}

As shown in FIG. 10, the present invention and the comparative example show the same sound insulation performance as each other. On the other hand, the sound insulating member 10 of the present invention is 33% (0.5 kg / m ² ) lighter than the porous material of the comparative example. _{As described above, the sound insulation wall 15 according to the present invention realizes the average apparent sound velocity (C de-ve} ) ^-in the hollow portion 13 corresponding to the required sound insulation performance by using the equations (7) and (8). The first interval x and the second interval y can be easily set. As a result, both weight reduction and sound insulation performance can be achieved with an optimum number of vertical walls 22 without unnecessarily increasing the number of vertical walls 22.

Although the description of the specific embodiment is completed above, the present invention can be widely modified without being limited to the above embodiment. For example, in the above embodiment, the example in which the sound insulating member 10 is provided on the roof 1 of the vehicle body has been described, but the sound insulating member 10 may be provided on other parts such as the door, pillar, bonnet, trunk, and body panel of the vehicle body. good. Further, the sound insulating member 10 may be provided not only in an automobile but also in another structure such as a ceiling, a wall, a floor of a building, a cover of various devices, and the like. In addition, the specific configuration and arrangement of each member and portion, quantity, angle, material, procedure, and the like can be appropriately changed as long as they do not deviate from the gist of the present invention. On the other hand, not all of the components shown in the above embodiments are indispensable, and they can be appropriately selected.

1 Roof (body)
2 Roof panel 3 Roof lining 4 Outer panel (panel member)
5 Reinforcement frame 10 Sound insulation member 11 Sound insulation panel (panel member)
12 Hollow double wall structure 13 Hollow part 15 Sound insulation wall 21 Horizontal wall 22 Vertical wall 23 Band-shaped body 24 Strip-shaped body 25 Cylindrical body 26 Resin sheet a Number of horizontal walls 21 arranged in the direction perpendicular to the plane C Sound velocity in the air (m) / S)
Apparent speed of sound (m / s) due to time delay of sound waves passing through the C _{de hollow portion 13.}
Speed of sound in C _i hollow portion 13 (m / s)
Apparent speed of sound (m / s) due to the surface-to-plane component in the _{Cve hollow portion 13.}
Apparent speed of sound (m / s) in the hollow portion 13 of the sound wave according to the C _{de-ve incident angle θ}
(C _de-ve ) ^ ― Average apparent speed of sound (m / s) in the hollow portion 13 of the randomly incident sound wave
Time required for sound waves to pass through the T hollow portion 13 (s)
Transmission loss (dB) of TL random incident sound waves at the sound insulation wall 15.
TL (θ) Transmission loss (dB) of the sound insulation wall 15 with respect to the incident angle θ
t Time delay per film material (wall) (s)
n Number of membrane materials (walls) transmitted x 1st interval (interval between a pair of side walls 21)
x'Distance through which sound waves pass through the hollow portion 13 (m)
y Second interval (interval between vertical walls 22)
θ Sound wave incident angle (rad)
θH Maximum value of incident angle θ of random incident sound wave θL Minimum value of incident angle θ of random incident sound wave θp Angle interval of incident angle θ for integration τ (θ) Transmittance of sound wave incident at incident angle θ τ ^ ― Average transmittance of randomly incident sound waves

Claims (10)

It is a design method for designing a sheet-shaped sound insulation member arranged in a hollow portion of a hollow double wall structure so as to have a predetermined sound insulation performance.
The sound insulation member extends in the in-plane direction and is arranged between a pair of lateral walls and a pair of the lateral walls facing each other with a first interval in the direction perpendicular to the in-plane direction with a second interval in the in-plane direction. With vertical walls to be
The apparent sound velocity of the sound wave incident on the hollow double wall structure in the hollow portion is calculated as a function with the incident angle of the sound wave, the first interval and the second interval as variables, and the sound insulation member is said to have the same speed of sound. A method for designing a sound insulation member, which comprises setting the first interval and the second interval so that the apparent sound velocity of the sound wave in the hollow portion, which exhibits sound insulation performance, becomes a predetermined target value. The design method according to claim 1, wherein the apparent speed of sound in the hollow portion of the sound wave is calculated as a function represented by the formula (A).

However, C _de-ve : the apparent speed of sound (m / s) of the sound wave in the hollow portion according to the incident angle, x': the distance (m) through which the sound wave passes through the hollow portion, θ: the said. the incident angle of the sound wave (rad), _{C i:} speed of sound in the hollow portion (m / s), t: time delay per single wall (s), x: 1 to said first distance between the lateral wall of (M), y: The second distance (m) between the vertical walls arranged in the in-plane direction, a: the number of the horizontal walls arranged in the plane perpendicular direction. By averaging the apparent speed of sound according to the incident angle from 0 ° to the maximum value at predetermined angle intervals with respect to the incident angle, the hollow of the randomly incident sound wave randomly incident on the hollow double wall structure. The design method according to claim 2, wherein the average apparent sound velocity in the unit is calculated, and the average apparent sound velocity is set as the apparent sound velocity in the hollow portion of the sound wave. The design method according to claim 3, wherein the maximum value of the incident angle is 78 °, and the angle interval between the incident angles is 1 °. The design method according to any one of claims 1 to 4, wherein the target value of the apparent sound velocity is 300 m / s or less. The first interval and the second interval are set by using the design method according to any one of claims 1 to 5, and a pair of the lateral walls are arranged to face each other with the first interval, and the second interval is used. It is a manufacturing method of a sound insulation wall manufactured by arranging the vertical wall.
The vertical wall is composed of at least one strip-shaped body having a predetermined shape opened in a plane-direct view, and the shape of the strip-shaped body includes a spiral shape, a W-shape, and a random shape. Manufacturing method. The first interval and the second interval are set by using the design method according to any one of claims 1 to 5, and a pair of the lateral walls are arranged to face each other with the first interval, and the second interval is used. It is a manufacturing method of a sound insulation wall manufactured by arranging the vertical wall.
A manufacturing method characterized in that the vertical wall is composed of a large number of strips. The first interval and the second interval are set by using the design method according to any one of claims 1 to 5, and a pair of the lateral walls are arranged to face each other with the first interval, and the second interval is used. It is a manufacturing method of a sound insulation wall manufactured by arranging the vertical wall.
The horizontal wall and the vertical wall are composed of a film material, and the vertical wall is composed of a large number of tubular bodies forming a closed loop when viewed in the direction perpendicular to the plane. The horizontal wall and the vertical wall are paired. A manufacturing method characterized in that they cooperate with each other to form a thin film closed space structure that defines a closed space. The first panel member is arranged on one side of the sound insulation member in the direction perpendicular to the surface.
A second panel member is arranged on the other side of the sound insulation member in the direction perpendicular to the surface.
The manufacturing method according to any one of claims 6 to 8, wherein the sound insulating member is sandwiched between the first panel member and the second panel member. The manufacturing method according to claim 8, wherein one of the pair of the lateral walls is separated from each other for each of the tubular bodies by welding the two resin sheets to each other by compression heating.

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