JP2009220775A - Vehicle body structure, vehicle roof and roof inner panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing structure which converts a sound wave into vibration, and absorbs a sound by consuming sound wave energy into mechanical energy, and efficiently absorbs a sound of a low frequency such as road noise when the sound of the frequency to be absorbed by the sound absorbing structure is set to be low. <P>SOLUTION: A roof 140 of a vehicle 100 comprises a roof outer panel 120 and a roof inner panel 130. A plate sound absorbing body 10 is provided on the roof 140. An oscillating plate 13 of the sound absorbing body 10 is made to communicate with a cabin 105 through rectangular through-holes 132 formed at the roof inner panel 130. In the plate sound absorbing body 10, a sound accumulated in the cabin 105 is transmitted to the oscillating plate 13 through each through-hole 134, and oscillates the oscillating plate 13. The sound wave energy in the cabin 105 is consumed as the mechanical energy by the vibration to absorb the sound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle body structure capable of absorbing road noise having a relatively low frequency such as road noise.

  Conventionally, as a structure for absorbing sound on the roof of a vehicle, a roof in which a reflector for reflecting the particle velocity of air without being attenuated and a sound absorbing material that allows the particle velocity to pass in a high-speed state are alternately arranged on the roof panel There is a structure (Patent Document 1).

JP 2005-247267 A

  By the way, in the above-described roof structure, natural fibers such as felt and synthetic fibers such as polyethylene terephthalate (PET) are used for the sound absorbing material, and sound is absorbed by air particles passing through the fibers. Since this roof structure uses a sound absorption mechanism based on particle velocity driving, a large back air layer is required for sound in the low frequency range, and engine noise, wind noise during traveling, tires and road surfaces Therefore, it was not possible to attenuate a sound in a relatively low frequency range such as toro road noise.

  Further, when the porous sound absorbing material such as glass wool or felt inserted between the inner panel and the outer panel is disposed at a position where the acoustic particle velocity is maximized and perpendicular to the direction in which the velocity is maximized, Sound absorption efficiency is maximized. For this reason, it is necessary to have a space of about λ / 4 of the target frequency behind the room boundary (wall surface), and a large air layer (for example, 27 cm at 315 Hz) is required to absorb the low frequency range. Could not be installed in the car interior. In other words, the porous sound absorbing structure with a small back air layer cannot absorb low frequencies, and cannot dissipate low frequency acoustic energy.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a vehicle body structure, a vehicle column, and an inner panel having a sound absorbing structure that efficiently absorbs sound in a low frequency region. is there.

  In order to solve the above-described problems, a vehicle body structure employed by the present invention includes a roof supported by a vehicle column, and a sound absorbing structure that is provided on the roof and absorbs sound by sound pressure driving. It is characterized by that.

  The said structure WHEREIN: It is desirable to arrange | position the site | part driven by the sound pressure drive of the said sound absorption structure in the part with a high sound pressure in the said vehicle interior. For example, in the case of a sedan type vehicle, a portion where the sound pressure is high often becomes the roof of the vehicle. In addition, since the sound absorbing mechanism based on the sound pressure drive can absorb sound near the wall surface, it does not require a large back air layer for sound in the low frequency region. Furthermore, while the acoustic particle velocity does not take a large value at the boundary surface of the passenger compartment, the sound pressure has a high part and a low part (sound pressure distribution). In the case of a sound absorption mechanism using sound pressure drive, the sound energy absorbed is determined by the product of sound absorption efficiency and the sound energy incident on the sound absorption mechanism. Thus, the acoustic energy in the passenger compartment can be efficiently dissipated.

  In the above configuration, it is preferable that the portion driven by the sound pressure drive of the sound absorbing structure is disposed so as to be located in a portion where the sound pressure of the roof is high.

  In the above configuration, the sound absorbing structure is preferably a plate sound absorber having a diaphragm and an air layer defined behind the diaphragm.

  In the above-described configuration, the sound absorbing structure is preferably a tube sound absorber having a cavity that is a closed portion with one end closed and an opening with the other end opened.

  In the above configuration, it is desirable that a plurality of the cavities be formed.

  In the above configuration, it is desirable that a plurality of the cavities have different lengths.

  In the above configuration, the sound absorbing structure is preferably a Helmholtz sound absorber having a closed space and a tubular member communicating the closed space with the space of the vehicle compartment.

  In the above configuration, the sound absorbing structure is a plate sound absorber having a diaphragm and an air layer defined behind the diaphragm, and has a closed portion with one end closed and an opening with the other end opened. It is desirable that the sound absorber is constituted by a combination of a sound absorber and a Helmholtz sound absorber having a tube sound absorber having a cavity, a closed space, and a tubular member communicating the closed space with the outside.

  In the above configuration, it is preferable that the chassis serving as the base of the roof constitutes a part of the sound absorbing structure.

  The said structure WHEREIN: It is desirable for the said sound-absorbing structure to be attached to the chassis used as the base of the said roof.

  In the above configuration, the roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, and a roof inner panel that covers the roof outer panel from the vehicle interior side, and the sound absorbing structure includes: It is desirable to arrange between the roof outer panel and the roof inner panel.

  In the above configuration, the roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, a roof material that covers the roof outer panel from the passenger compartment side, and a surface material that covers the surface of the core material. It is preferable that the core material constitutes a part of the sound absorbing structure.

  In the above configuration, the roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, a roof material that covers the roof outer panel from the passenger compartment side, and a surface material that covers the surface of the core material. It is desirable that the sound absorbing structure is attached to the core member.

  The said structure WHEREIN: It is desirable for the said roof inner panel to have a sound pressure transmission part.

  In order to solve the above-described problems, a vehicle roof employed by the present invention is a roof supported by a vehicle column, and is provided with a core material serving as a base of the roof, the core material, and a sound pressure And a sound absorbing structure that absorbs sound by driving.

  In order to solve the above-described problems, a roof inner panel employed by the present invention is a roof inner panel that constitutes a part of a roof supported by a support of a vehicle, and a core material that forms an outer shape of the roof inner panel; And a sound absorbing structure that is provided on the core member and absorbs sound.

  According to the present invention, the sound absorbing structure converts sound waves into vibrations, consumes sound wave energy as mechanical energy, and performs sound absorption. For example, when the frequency at which the sound absorbing structure absorbs sound is set to a low value, low frequency sound such as road noise can be efficiently absorbed.

Hereinafter, the vehicle body structure including the sound absorbing structure will be described.
<First Embodiment>
The present inventors measured the sound pressure at various locations in the passenger compartment, paying attention to the noise that is trapped in the passenger compartment. As a result, it was detected that the sound pressure was relatively high at the roof. Therefore, attention was paid to providing a sound absorbing structure on the roof.

  In general, at the boundary surface of the passenger compartment, the particle velocity of sound waves does not take a large value, whereas the sound pressure is high and low (so-called sound pressure distribution). Therefore, in the sound absorbing structure having a sound absorbing mechanism driven by sound pressure as in the above configuration, the sound energy absorbed is determined by the product of the sound absorption efficiency and the sound energy incident thereon. By preferentially arranging the pressure-driven sound absorbing structure, it is possible to efficiently dissipate acoustic energy in the passenger compartment. In addition, since the sound absorbing structure based on sound pressure driving can be realized without configuring a λ / 4 back air layer, sound absorption near the wall surface is possible, and a large back air layer is also provided for sound in a low frequency region. There is an advantage that it is not necessary.

(1-1) Configuration (1-1-1) Vehicle FIG. 1 is a perspective view showing a four-door sedan type vehicle 100 according to the first embodiment of the present invention. In this vehicle 100, a bonnet 101, four doors 102, and a trunk door 103 are attached to a chassis 110 that serves as a base of a vehicle body structure so as to be opened and closed.
FIG. 2 is a diagram schematically showing the chassis 110. The chassis 110 includes a base 111, a pair of front outer panels 112, a center outer panel 113, a rear outer panel 114 extending upward from the base 111, a roof outer panel 120 supported by the outer panels 112, 113, 114, and a vehicle interior 105 in the vehicle 100. And an engine partition wall 115 divided into an engine compartment 106 and a trunk partition partition wall 116 divided into a compartment 105 and a cargo compartment 107.
Further, the roof outer panel 120 and the roof inner panel 130 constitute a roof 140.

(1-1-2) Roof The feature of this embodiment is that the box-shaped plate sound absorber 10 is provided on the roof 140 on the front seat (driver's seat / passenger seat). FIG. 3 shows only one plate sound absorber 10, but actually, as shown in FIG. 1, four plate sound absorbers 10 having different shapes are provided on the roof 140. ing.

FIG. 3 is an enlarged cross-sectional view of part a in FIG.
The roof 140 includes a roof outer panel 120 that forms a part of the chassis 110, and a roof inner panel 130 that is attached to the roof outer panel 120 by clipping or the like.
The roof outer panel 120 includes a partition wall 121 that forms the outer shape of the roof 140, and a substantially “U” -shaped beam portion 122 that extends in the vehicle width direction in order to strengthen the partition wall 121. A plurality of panel attachment holes (not shown) for attaching the roof inner panel 130 are formed on the outer peripheral side of the partition wall 121, and the sound absorber for attaching the plate sound absorber 10 to the beam portion 122. A mounting hole 123 is formed (see FIG. 3).

The roof inner panel 130 is formed of, for example, a wood fiber board, and includes a core material 131 that forms a base, and a surface material 138 that is formed of a cloth material that transmits sound pressure and covers the surface of the core material 131.
The core member 131 is provided with a rectangular insertion hole 132A at the position of the front seat (driver's seat / passenger seat), and a portion of the surface material 138 that faces the insertion hole 132A serves as a sound pressure transmitting portion 139A. The plate sound absorber 10 is opened into the passenger compartment 105 through the sound pressure transmitting portion 139A. In the present embodiment, the sound pressure transmitting portion 139A is at a position where the sound pressure increases on the front surface of the roof 140.

(1-1-3) Plate Sound Absorber Next, the structure of the plate sound absorber 10 will be described.
The plate sound absorber 10 includes a rectangular casing 11 having an opening 12, a diaphragm 13 that closes the opening 12, and an air layer 14 defined in the casing 11. The casing 11 is formed of a synthetic resin material (for example, ABS resin), and the diaphragm 13 is formed of a polymer compound (for example, a polyolefin sheet including an inorganic filler). In the present invention, the diaphragm 13 may be formed of an elastic material in a film shape.

  Further, a mounting protrusion 15 is formed on the bottom of the plate sound absorber 10 so that the tip inserted into the sound absorber mounting hole 123 becomes an umbrella-shaped retaining portion 15A. By forcibly fitting the mounting protrusion 15 into the sound absorber mounting hole 123, the retaining portion 15 </ b> A of the mounting protrusion 15 is locked to the beam portion 122 of the roof outer panel 120, so that the plate sound absorber 10 is attached to the roof outer panel 120. It is fixed in a state where it is prevented from coming off.

  The plate sound absorber 10 is set to conditions described later, so that the difference between the sound pressure on the passenger compartment 105 side transmitted to the diaphragm 13 through the sound pressure transmitting portion 139A and the sound pressure on the air layer 14 side (that is, the diaphragm 13). The diaphragm 13 is driven by the difference in sound pressure before and after. Thereby, the energy of the sound wave reaching the plate sound absorber 10 is consumed by the vibration of the diaphragm 13 and the sound is absorbed. That is, the plate sound absorber 10 exhibits a sound absorbing effect due to vibration excited by sound pressure driving.

(1-1-4) Setting Conditions for Plate Sound Absorber Here, setting conditions for the plate sound absorber 10 will be described.
In general, for a sound absorbing structure that absorbs sound by a plate-like or membrane-like vibrator and an air layer, the frequency to be attenuated depends on the resonance frequency of the spring mass system due to the mass component (mass component) of the vibrator and the spring component of the air layer. Is set. The density of air is ρ ₀ [kg / m ³ ], the speed of sound is c ₀ [m / s], the density of the vibrating body is ρ [kg / m ³ ], the thickness of the vibrating body is t [m], When the thickness is L [m], the resonance frequency of the spring mass system is expressed by the equation (1).

  In the case of the plate / membrane vibration type sound absorbing structure, when the vibrating body has elasticity and elastically vibrates, the property of a bending system due to elastic vibration is added. In the field of architectural acoustics, the shape of the vibrating body is rectangular, the length of one side is a [m], the length of the other side is b [m], the Young's modulus of the vibrating body is E [Pa], and the Poisson of the vibrating body When the ratio is σ [−] and p and q are positive integers, the resonance frequency of the plate / membrane vibration type sound absorbing structure is obtained by the following formula 2, and the obtained resonance frequency is used for acoustic design. (If the periphery is fixed support)

そして、本実施形態においては、上記数式から１６０〜３１５Ｈｚバンド（１/３オクターブ中心周波数）を吸音するよう、以下のようにパラメータが設定される。

空気の密度ρ_０ ；１．２２５[ｋｇ／ｍ³]
音速ｃ_０ ；３４０[ｍ／ｓ]
振動体の密度ρ ；１４４０[ｋｇ／ｍ³]
振動体の厚さｔ ；０．０００８５[ｍ]
空気層の厚さをＬ ；０．０３[ｍ]
筐体の長さａ ；０．３[ｍ]
筐体の長さｂ ；０．３[ｍ]
振動体のヤング率Ｅ ；０．４[ＧＰａ]
ポアソン比をσ ；０．４
モード次数 ；ｐ＝ｑ＝１

In this embodiment, parameters are set as follows so as to absorb the 160 to 315 Hz band (1/3 octave center frequency) from the above formula.

Air density ρ ₀ ; 1.225 [kg / m ³ ]
Speed of sound c ₀ ; 340 [m / s]
Density of vibrating body ρ: 1440 [kg / m ³ ]
Thickness t of vibrating body; 0.00085 [m]
The thickness of the air layer is L; 0.03 [m]
Case length a: 0.3 [m]
Case length b: 0.3 [m]
Young's modulus E of vibrating body: 0.4 [GPa]
The Poisson's ratio is σ; 0.4
Mode order; p = q = 1

On the other hand, in the above formula 2, the term of the spring mass system (ρ ₀ c ₀ ² / ρtL) and the term of the bending system (the term added in series after the term of the spring mass system) are added. For this reason, the resonance frequency obtained by the above equation is higher than the resonance frequency of the spring mass system, and it may be difficult to set the frequency at which the sound absorption peak is low.

  In such a sound absorber, the relationship between the resonance frequency of the spring mass system and the resonance frequency of the bending system due to elastic vibration due to the elasticity of the plate has not been fully elucidated, and a plate that exhibits high sound absorption in the low frequency range. The actual situation is that the structure of the sound absorber is not established.

Therefore, the inventors conducted intensive experiments, and as a result, when the value of the fundamental vibration frequency of the bending system is fa and the value of the resonance frequency of the spring mass system is fb, the above parameters are satisfied so as to satisfy the following equation (3). Set. As a result, the fundamental vibration of the bending system is coupled with the spring component of the air layer behind, and a vibration having a large amplitude is excited in the band between the resonance frequency of the spring mass system and the fundamental frequency of the bending system (the bending system). The fact that the resonance frequency fa <the sound absorption peak frequency f <the spring mass system fundamental frequency fb) and the sound absorption rate is high was verified.

このように、上記した数３，４の条件を満足するように各種パラメータを設定することにより、吸音のピークとなる周波数を低くした吸音体が構成できる。 Furthermore, when the following equation 4 is set, the frequency of the sound absorption peak is sufficiently smaller than the resonance frequency of the spring mass system. In this case, it was also verified that the fundamental frequency of the bending system is sufficiently smaller than the resonance frequency of the spring mass system due to the mode of low-order elastic vibration and is suitable as a sound absorbing structure that absorbs sound of a frequency of 300 [Hz] or less.

In this way, by setting various parameters so as to satisfy the above-described conditions of Equations 3 and 4, it is possible to configure a sound absorber that reduces the frequency at which sound absorption peaks.

(1-2) Action and Effect of First Embodiment In the plate sound absorber 10 according to the present embodiment, the sound accumulated in the passenger compartment 105 is transmitted to the diaphragm 13 through the sound pressure transmitting portion 139A. Vibrate. Due to this vibration, sound wave energy in the passenger compartment 105 is consumed as mechanical energy to absorb sound. For example, by setting the sound absorber 10 to the numerical value of the above parameter, a low-frequency sound such as road noise (a frequency at which the sound pressure corresponding to the natural vibration in the passenger compartment 105 is locally increased). (500 Hz or less)) can be efficiently absorbed.

Therefore, in the present embodiment, the box-shaped plate sound absorber 10 is provided in a position where the sound pressure is high, that is, in the roof 140, particularly in the passenger compartment 105. Road noise having a relatively low frequency transmitted from the luggage compartment through the trunk partition wall 116 into the passenger compartment 105 is efficiently absorbed by the plate sound absorber 10 provided on the roof 140.
Here, the relatively low frequency refers to the frequency of the fundamental vibration (about 80 Hz in a normal passenger compartment) which is the lowest frequency among the natural vibrations in the passenger compartment, and the passenger compartment can be regarded as a diffuse sound field. A frequency band between a frequency band (a band of about 500 Hz or more in a normal passenger compartment) and a frequency that can be regarded as having discrete modes in the passenger compartment.

FIG. 4 shows a result of an experiment in which the plate sound absorber 10 is provided on the roof 140 on the front seat (driver's seat / passenger seat). This graph is a frequency characteristic showing the sound pressure in the front seat, where the solid line indicates that there is no sound absorbing structure and the dotted line indicates that there is a sound absorbing structure.
Specifically, as shown in FIG. 1, the plate sound absorber 10 is provided with a plate sound absorber 10 having a housing 11 with a different size. The size of the casing 11 of each plate sound absorber 10 is as follows.
The housing of the plate sound absorber 10a: 300 mm × 200 mm × 30 mm
The housing of the plate sound absorber 10b: 200 mm × 200 mm × 30 mm
As shown in FIG. 4, in the frequency range of 160 to 315 Hz, the noise level was reduced by 0.3 to 1.0 dB, and a result of absorbing sound at a low frequency where noise (road noise or the like) was concentrated was obtained. .

  As a result, in the vehicle body structure in the present embodiment, the plate sound absorber 10 provided on the roof 140 can efficiently absorb, for example, road noise and the like, and the quietness in the passenger compartment 105 can be enhanced. .

In addition, since the resonance frequency of the plate sound absorber 10 varies depending on the dimensions of the casing 11, for example, the plate sound absorber 10 b having a small size and the plate sound absorber 10 a having a large size are disposed on the roof 140.
Thereby, the plate sound absorber 10 having a resonance frequency suitable for road noise such as tire noise can be disposed, the range of frequencies to be absorbed can be expanded, and sound absorption can be performed more reliably.

On the other hand, a case where the box-shaped plate sound absorber 10 is provided on the roof 140 on the rear seat will be described with reference to FIGS. 5 and 6.
The core member 131 of the roof inner panel 130 is provided with a rectangular insertion hole 132B at the position of the rear seat, and a portion of the surface material 138 that faces the insertion hole 132B serves as a sound pressure transmitting portion 139B. The plate sound absorber 10 is opened into the passenger compartment 105 through the pressure transmission part 139B.

Here, an experiment was conducted in which the plate sound absorber 10 was provided on the roof 140 on the rear seat.
The result of the experiment is as shown in FIG. 6, and this graph shows the frequency characteristics indicating the sound pressure at the rear right seat, where the solid line indicates that there is no sound absorbing structure and the dotted line indicates that there is a sound absorbing structure.
As shown in FIG. 6, as in FIG. 4, in the frequency range of 160 to 315 Hz, the noise level is reduced by 0.8 to 1.0 dB, and sound at a low frequency where noise (road noise etc.) is concentrated is absorbed. A possible result was obtained.

(1-3) Modified Example of First Embodiment The present invention is not limited to the configuration of the first embodiment described above, and various correspondences are possible. In the following modifications, the mounting structure of the plate sound absorber 10 is described. Further, in the following modified example, the mounting position of the plate sound absorber 10 on the roof 140 may be either the front seat or the rear seat, so the front seat insertion hole 132A, the sound pressure transmitting portion 139A, and the rear seat insertion hole. The insertion hole 132 and the sound pressure transmitting portion 139 are used without being distinguished from the 132B and the sound pressure transmitting portion 139B.

(1-3-1)
In the configuration according to this modification, a plurality of small-diameter communication holes 133, 133,... Are formed in the core 131 of the roof inner panel 130 in place of the rectangular insertion hole 132 as shown in FIG. Is. A portion of the surface material 138 that faces the communication holes 133 serves as a sound pressure transmitting portion 139.

(1-3-2)
The following modification shows an example in which the plate sound absorber 10 is provided on the roof inner panel 130. For this reason, only the roof inner panel 130 is illustrated.
The configuration according to this modification is an example in which the plate sound absorber 10 is provided on the roof inner panel 130. Specifically, as shown in FIG. 8, a rectangular recess 134 that opens toward the vehicle interior 105 is provided in the core 131 of the roof inner panel 130, and the plate sound absorber 10 is inserted into the recess 134. A sound absorber mounting hole 135 is formed in the bottom of the recess 134. The plate sound absorber 10 is fixed in the recess 134 by inserting the mounting protrusion 15 of the plate sound absorber 10 into the sound absorber mounting hole 135.

(1-3-3)
The configuration according to this modification is an example in which the plate sound absorber 10 is provided on the roof inner panel 130, and a part of the roof inner panel 130 is the plate sound absorber 10. Specifically, as shown in FIG. 9, the diaphragm 13 is directly fixed to the opening 134 </ b> A of the rectangular recess 134 formed in the core 131 of the roof inner panel 130, and the recess 134, the diaphragm 13, The plate sound absorber 10 </ b> A is configured by the recess 134 and the air layer 14 defined by the diaphragm 13.

(1-3-4)
The configuration according to this modification is an example in which the plate sound absorber 10 is provided on the roof inner panel 130. As shown in FIG. 10, a rectangular through-hole that opens on the core member 131 of the roof inner panel 130 toward the vehicle interior 105 side. The plate sound absorber 10 is fixed with an adhesive or the like from the roof outer panel 120 side so as to close the through hole 136.

(1-3-5)
The configuration according to this modification is an example in which the plate sound absorber 10 is provided in the roof inner panel 130. As shown in FIG. 11, a rectangular through hole 136 is formed in the core 131 of the roof inner panel 130, and A flange portion 11 </ b> A that engages with the stepped portion 136 </ b> A is formed in the casing 11 of the plate sound absorber 10. The plate sound absorber 10 is fixed to the roof inner panel 130 by forming the attachment hole 11B in the flange portion 11A, the attachment protrusion 136A in the core member 131, and inserting the attachment protrusion 136A in the attachment hole 11B.
Even if an attachment projection is formed on the flange portion 11A, an attachment hole is formed in the step portion 136A, and each portion is fixed by engagement, the flange portion 11A and the step portion 137A are bonded by an adhesive or the like. It may be fixed.

(1-3-6)
The configuration according to this modified example is an example in which the plate sound absorber 10 is provided on the roof outer panel 120, and a part of the roof outer panel 120 is the plate sound absorber 10. Specifically, as shown in FIG. 12, the diaphragm 13 is directly fixed to the opening 124 </ b> A of the rectangular recess 124 formed in the roof outer panel 120, and the recess 124, the diaphragm 13, and the recess The plate sound absorber 10 </ b> B is configured by the air layer 14 defined by 124 and the diaphragm 13.
On the other hand, the core member 131 of the roof inner panel 130 is provided with a rectangular through hole 136 that opens toward the passenger compartment 105, and a rectangular column-like shape extending toward the plate sound absorber 10 around the through hole 136. A cylindrical portion 136A is formed. The through hole 136 and the cylindrical portion 136A guide the sound pressure in the passenger compartment 105 to the plate sound absorber 10B.

(1-3-7)
The configuration according to this modification is an example in which a part of the roof outer panel 120 is the plate sound absorber 10. Specifically, as shown in FIG. 13, a rectangular recess 125 is formed in the beam portion 122 formed in the partition wall 121 of the roof 140, and the diaphragm 13 is fixed directly to the opening 125 </ b> A of the recess 125. The plate sound absorber 10 </ b> C is configured by the recess 125 serving as a housing, the diaphragm 13, and the air layer 14 defined by the recess 125 and the diaphragm 13.
On the other hand, the core member 131 of the roof inner panel 130 is provided with a rectangular through-hole 136 that opens to the passenger compartment 105 side. The through hole 136 guides the sound pressure in the passenger compartment 105 to the plate sound absorber 10C.

(1-3-8)
The configuration according to the present invention is not limited to the above embodiment and the modified examples (1-3-1) to (1-3-7), but may be any other structure as long as the plate sound absorber 10 is provided on the roof 140. There may be.
Further, in the modified examples (1-3-2) to (1-3-5), since the plate sound absorber 10 is provided in the roof inner panel 130, the plate sound absorber 10 is provided in the roof outer panel 120. Therefore, even if the vehicle 100 has already been assembled, the above effect can be obtained by replacing the roof inner panel 130.

(1-3-9)
The plate sound absorber 10 includes a rectangular casing 11, a diaphragm 13 that closes the opening 12 of the casing 11, and an air layer 14 defined in the casing 11. However, even if the shape of the casing according to the present invention is rectangular, circular, or polygonal, a concentrated mass for changing vibration conditions with respect to the diaphragm 13 is provided at the center of the diaphragm 13. You may do it.

  As described above, the plate sound absorber 10 has a sound absorbing mechanism formed of a spring mass system and a bending system. Here, the inventors conducted an experiment of the sound absorption coefficient at the resonance frequency when the surface density of the diaphragm 13 was changed.

  FIG. 14 shows that the diaphragm 13 (size: 100 mm × 100 mm, thickness: 0.85 mm) is fixed to the casing 11 having a vertical and horizontal size of 100 mm × 100 mm and a thickness of 10 mm. It is the figure which showed the simulation result of the normal incidence sound absorption coefficient of the board sound-absorbing body 10 at the time of changing the surface density of a part (a magnitude | size is 20 mm x 20 mm, thickness 0.85mm). The simulation method is based on JIS A 1405-2 (measurement of sound absorption coefficient and impedance by an acoustic tube—Part 2: transfer function method), and the sound field of the acoustic room in which the plate sound absorber 10 is arranged is a finite element method. The sound absorption characteristics were calculated from the transfer function.

Specifically, the surface density of the central part is set to (1) 399.5 [g / m ² ], (2) 799 [g / m ² ], (3) 1199 [g / m ² ], (4) 1598 [g / m ² ], (5) 2297 [g / m ² ], the surface density of the peripheral member is 799 [g / m ² ], and the average density of the diaphragm 13 is (1) 783 [g / m ² ]. m ² ], (2) 799 [g / m ² ], (3) 815 [g / m ² ], (4) 831 [g / m ² ], (5) 863 [g / m ² ] This is a simulation result.
Looking at the simulation results, the sound absorption coefficient is high between 300 to 500 [Hz] and in the vicinity of 700 [Hz].

  The high sound absorption coefficient near 700 [Hz] is due to resonance of the spring mass system formed by the mass of the diaphragm 13 and the spring component of the air layer 14. In the plate sound absorber 10, the sound is absorbed with the sound absorption coefficient at the resonance frequency of the spring mass system as a peak, and even if the surface density of the central part is increased, the mass of the entire diaphragm 13 does not change greatly. It can be seen that the resonance frequency does not change significantly.

  The reason why the sound absorption coefficient is high between 300 and 500 [Hz] is due to the resonance of the bending system formed by the bending vibration of the diaphragm 13. In the plate sound absorber 10, the sound absorption coefficient at the resonance frequency of the bending system appears as a peak on the low frequency side, and only the resonance frequency of the bending system decreases as the surface density at the center increases. I understand.

  In general, the resonance frequency of the bending system is determined by an equation of motion that governs elastic vibration of the diaphragm 13 and is inversely proportional to the density (surface density) of the diaphragm 13. The resonance frequency is greatly influenced by the density of the antinodes of natural vibration (when the amplitude is a maximum value). For this reason, in the simulation described above, the region that becomes the antinode of the 1 × 1 eigenmode is formed at different surface densities in the central portion, so that the resonance frequency of the bending system is changed.

  Thus, the simulation results show that when the surface density of the central part is made larger than the surface density of the peripheral part, the peak of the sound absorption coefficient on the low frequency side of the frequency that becomes the peak of sound absorption moves further to the low frequency side. Represents. Therefore, it is shown that by changing the surface density of the central portion, a part of the frequency at which the sound absorption is peaked can be moved (shifted) further to the low sound region side or the high sound region side.

  In the plate sound absorber 10 described above, the frequency of the sound absorption sound can be changed (shifted) simply by changing the surface density of the central portion. Therefore, the diaphragm 13 is made of the same material as the plate sound absorber 10 as a whole. Compared with the case where the sound absorbing sound is changed by increasing the mass of the plate sound absorber 10 as a whole, the sound to be absorbed can be reduced without greatly changing the mass of the plate sound absorber 10 as a whole.

  In this way, changes in the noise characteristics in the passenger compartment due to changes in the sound absorption capacity in the passenger compartment and cargo compartment (number of people and luggage, changes in shape, etc.) and changes in generated noise (changes in tires, changes in road surface conditions, etc.) It can correspond to.

  Furthermore, the sound absorption coefficient peak value may be increased by filling the air layer 14 of the plate sound absorber 10 with a porous sound absorbing material (for example, cotton-like fibers such as foamed resin, felt, polyester wool). .

Second Embodiment
Next, a second embodiment according to the present invention will be described. The feature of this embodiment is that a tube sound absorber is used for the sound absorbing structure provided on the roof. In addition, the same code | symbol shall be attached | subjected to the component same as 1st Embodiment mentioned above, and the description shall be abbreviate | omitted.

(2-1) Configuration FIG. 15 is a perspective view showing a four-door sedan type vehicle 100 according to the second embodiment. A pipe sound absorber 30 is provided on the roof 140 of the vehicle 100.

Here, the structure of the tube sound absorber used in this embodiment will be described.
As shown in FIG. 16, the pipe sound absorber 30 includes a plurality of pipes 31 (31-1 to 31-9) having different lengths arranged in a horizontal row and connected to each other or separately by a dedicated member. They are connected and integrated. Each pipe 31 is composed of a linear rigid pipe having a circular cross section made of a synthetic resin or the like having a predetermined thickness (for example, about 2 mm) and a predetermined inner diameter (for example, a diameter of 60 mm). One end of each pipe 31 is closed to become a closed portion 32, and the other end is opened to become an opening portion 33. The positions of the openings 33 are aligned in a line by the pipes 31 so that the openings 33 are adjacent to each other. In the case of the present embodiment, the pipe sound absorber 30 is attached so that the opening 33 of each pipe 31 is disposed at the overhead position of the front seat (driver seat / passenger seat) in the roof 140.

The length in each pipe 31 corresponds to a quarter wavelength of the center frequency of the sound wave absorbed by the single cavity of the pipe 31.
Here, three types of pipes having a cavity length L (= pipe length) of 0.85 m, 0.68 m, and 0.53 m are used, and these are 100 Hz, 125 Hz, and 160 Hz (that is, 1 / Sound absorption centering on (3 octave band pitch) (sound speed = 340 m).
The neck portion (opening 33 or the vicinity thereof) of the opening 33 of each pipe 31 is closed with a flow resistance material (material having flow resistance) 34 having air permeability such as glass wool, cloth, gauze and the like.

(2-2) Operation Principle of Tube Sound Absorber Next, the sound absorption principle of the tube sound absorber 30 will be described.
FIG. 17 shows two adjacent pipes 31-j and 31-k in the pipe sound absorber 30 shown in FIG. The lengths of the cavities of the pipes 31-j and 31-k are L1 and L2. Sound waves in the passenger compartment 105 are incident on the openings 33-j and 33-k into the cavity, reflected by the closed portions 32-j and 32-k at the other ends, and the openings 33-j and 33-k. Is again released into the room. At this time, while the sound waves having the wavelengths λ1, λ2 (L1 = λ1 / 4, L2 = λ2 / 4) corresponding to four times the cavity lengths L1, L2 create standing waves S1, S2, Energy is consumed by the friction on the inner wall surface of the cavity and the viscous action between the air particles at the openings 33-j and 33-k, and sound absorption is performed around the wavelengths λ1 and λ2. For example, if L1 = 1.35 m and L2 = 0.53 m, then λ1 = 5.4 m and λ2 = 2.12 m, and the center frequencies f1 and f2 of the sound waves absorbed by f1 = 63 Hz and f2 = 160 Hz.

  On the other hand, the sound wave reflected by the blocking portions 32-j and 32-k and emitted from the openings 33-j and 33-k is diffracted by the openings 33-j and 33-k and radiates energy. Part of the energy is incident into the cavity from the openings 33-k and 33-j of the other pipes 31-k and 31-j adjacent to each other. In this way, coupled vibration is generated between the adjacent pipes 31-j and 31-k, and energy is transferred. During this coupled vibration, energy is consumed and sound absorption is performed due to friction on the inner wall surface of the cavity and viscous action between the air particles at the openings 33-j and 33-k. This coupled vibration can be regarded as a both-end closed tube mode in which the pipes 31-j and 31-k are regarded as a series of pipes, and sound absorption is performed around a wavelength λ3 determined as L1 + L2 = λ3 / 2. For example, when L1 = 1.35 m and L2 = 0.53 m, λ3 = 3.76 m, and the center frequency f3 of the sound wave absorbed by the coupled vibration is f3 = 90 Hz. In the case of the arrangement of FIG. 14, the frequency of the coupled vibration between adjacent pipes is as follows.

L1 (m) L2 (m) Coupled vibration frequency (Hz)
0.85 0.68 111
0.85 0.53 123
0.68 0.53 140
According to this, the sound absorption force is obtained on the average in the range of about 100 to 160 Hz together with the sound absorption of the pipes 31-1 to 31-9 alone (centered at 100, 125, and 160 Hz).

(2-3) Action and Effect of Second Embodiment As described above, by providing the pipe sound absorber 30 on the roof 140, the tire sound or the like reflected from the rear glass 117 through the trunk partition wall 116 from the luggage compartment 107 is reflected. Road noise having a relatively low frequency is efficiently absorbed by the pipe sound absorber 30 provided on the roof 140. As a result, it is possible to enhance the quiet feeling in the passenger compartment 105.

  In addition, in 2nd Embodiment, the case where the pipe sound absorber 30 is attached so that the opening part 33 of each pipe 31 may be arrange | positioned in the overhead position of the front seat (driver's seat / passenger seat) in the roof 140 is illustrated. However, as shown in FIG. 18, you may attach so that the opening part 33 of each pipe 31 may be arrange | positioned in the overhead position of a rear seat. In this case, the core member 131 of the roof inner panel 130 is provided with a rectangular insertion hole 132B at the position of the rear seat, and a portion of the surface material 138 that faces the insertion hole 132B is connected to the sound pressure transmitting portion 139B. Become.

  Moreover, the attachment structure to the roof 140 of the pipe sound absorber 30 has various attachment structures. For example, the pipe 31 is formed in the roof outer panel 120 in advance, and only the opening 33 of the pipe 31 is opened to the vehicle interior 105 side, or the pipe 31 is formed in the core 131 of the roof inner panel 130 in advance. The pipe 31 is opened only on the side of the passenger compartment 105, the pipe 31 is disposed between the core 131 of the roof inner panel 130 and the roof outer panel 120. There is a structure.

  Furthermore, the structure of the pipe sound absorber 30 is not limited to the structure of the second embodiment, and pipes having different lengths may be provided in the roof outer panel 120 in parallel. Even in this case, a certain sound absorption effect can be obtained by vibration of the pipe. Furthermore, the pipe sound absorber 30 may be constituted by pipes (so-called open pipes) having openings 33 and 33 in which both ends of each pipe 31 are opened instead of so-called closed pipes. May be mixed and arranged.

<Third Embodiment>
Next, a third embodiment according to the present invention will be described. The feature of this embodiment is that a Helmholtz sound absorber is used as the sound absorbing structure provided on the roof 140. In addition, the same code | symbol shall be attached | subjected to the component same as 1st Embodiment mentioned above, and the description shall be abbreviate | omitted.

  FIG. 19 is a view showing a third embodiment in which the Helmholtz sound absorber 40 is provided on the core member 131 of the roof inner panel 130.

  The Helmholtz sound absorber 40 used in the present embodiment includes a rectangular parallelepiped housing 41 having a space formed therein, and tubular members inserted into insertion holes 42A and 42B drilled on the upper side of the housing 41. 43A, 43B. A sealed space 44 is defined inside the casing 41, and openings 45A and 45B that connect the sealed space 44 and the vehicle interior 105 are formed inside the tubular members 43A and 43B.

  The housing | casing 41 is formed in the rectangular parallelepiped shape, for example with FRP (fiber reinforced plastic). For the tubular members 43A and 43B, for example, a pipe made of vinyl chloride can be used, and the inner surface is roughened so that friction with air is likely to occur. The Helmholtz sound absorber 40 acts to attenuate sound generated in the passenger compartment 105 by the air in the sealed space 44, which is a small-sized cavity, acting as a spring.

  At this time, since the small openings 45A and 45B provided in the sealed space 44 communicate with the vehicle interior 105, a one-mass system spring / mass model is formed using the mass of air in the openings 45A and 45B as a mass. At the resonance frequency of this system, the air mass in the openings 45A and 45B is vibrated by the sound pressure in the passenger compartment 105, and the sound energy is heated by the friction between the peripheral walls of the openings 45A and 45B and the air mass. Converted into energy. That is, the sound is attenuated.

Now, the length of the openings 45A and 45B is L, the cross-sectional area of the openings 45A and 45B is S (total), the volume of the sealed space 44 is V, the sound velocity is C, and the effective length of the openings 45A and 45B is Le (Le≈ L + 0.8 · S ^1/2 ), the resonance frequency f0 of the Helmholtz sound absorber 40 is f0 = 1 / 2π (C ² S / Le · V) ^1/2 .
From this equation, the resonance frequency f0 can be adjusted by changing the cross-sectional area S or the effective length Le of the openings 45A and 45B, that is, the inner diameter d or the length L of the tubular members 43A and 45B. It can be seen that the sound can be reduced.

  Thus, by providing the Helmholtz sound absorber 40 on the roof 140, road noise having a relatively low frequency such as tire sound reflected from the rear glass 117 through the trunk partition wall 116 from the luggage compartment is caused by the Helmholtz sound absorber 40. Sound is absorbed efficiently.

  The mounting configuration of the Helmholtz sound absorber 40 to the roof 140 is not limited to the configuration of the third embodiment described above, and various correspondences are possible. For example, the housing 41 is provided on the roof outer panel 120, the housing 41 is integrally formed with the core member 131 of the roof inner panel 130 or the roof outer panel 120, and various assembly structures are available.

Further, the shape of the housing 41 of the Helmholtz sound absorber 40 is not limited to a rectangular parallelepiped, and may be other shapes such as a columnar shape.
Furthermore, in the Helmholtz sound absorber 40, the case where the number of the tubular members 43 is two is illustrated, but the present invention is not limited to this, and may be one or three or more. In short, the Helmholtz sound absorber 40 has a frequency for absorbing sound depending on the inner diameter d or the length L of the tubular member 43, and may be appropriately set according to the frequency.

<Fourth embodiment>
Next, a fourth embodiment according to the present invention will be described. A feature of the present embodiment is that a plate sound absorber and a tube sound absorber are used for the sound absorbing structure provided on the roof. In addition, the same code | symbol shall be attached | subjected to the component same as 1st Embodiment mentioned above, and the description shall be abbreviate | omitted.

FIG. 20 is a perspective view showing a four-door sedan vehicle 100 according to the fourth embodiment. The roof inner panel 130 of the vehicle 100 is provided with a plate sound absorber 10 and a tube sound absorber 30.
In this way, by providing the plate sound absorber 10 and the tube sound absorber 30 on the roof inner panel 130, as described in the first embodiment and the second embodiment, the plate sound absorber 10 and the tube sound absorber 30 can provide, for example, Road noise and the like can be absorbed efficiently, and a quiet feeling in the passenger compartment 105 can be enhanced.
Moreover, by using the two types of sound absorbers 10 and 30, the sound absorption efficiency can be improved as compared with the above embodiments.

  The combination of the sound absorbers is not limited to the fourth embodiment, and the plate sound absorber 10, the tube sound absorber 30 and the Helmholtz sound absorber 40, the tube sound absorber 30 and the Helmholtz sound absorber 40, the plate sound absorber 10 and the Helmholtz sound absorber. 40 may be combined.

  A modification in the case where the plate sound absorber 10 and the Helmholtz sound absorber 40 are provided on the roof 140 as a sound absorbing structure is shown in FIG. In this example, a plurality of sound absorbers 10 are arranged on a flat portion of the roof inner panel 130 of the roof 140, and a portion of the roof inner panel 130 that is inclined to the flat portion has a relatively small mounting area. The Helmholtz sound absorber 40 is disposed at the bottom. Thereby, the sound absorbers 10 and 40 can be effectively mounted on the roof 140.

  In this case, the plate sound absorber 10 changes the peak frequency of the sound to be absorbed only by changing the surface density of the central portion of the diaphragm 13 (shift) as extended in the modified example (1-3-9). Can). Therefore, if the plate sound absorber 10 in which the surface density of the diaphragm 13 is appropriately changed according to the location of the roof 140 is disposed, low-frequency road noise can be absorbed more efficiently.

<Modification>
As mentioned above, although embodiment by this invention was described, this invention is not limited to embodiment mentioned above, It can implement with other various forms.

  In each of the embodiments, a four-door sedan type is illustrated, but the present invention is not limited thereto, and can be applied to any vehicle having a roof (roof 140).

  Further, the plate sound absorber 10 may be disposed at a position where the sound pressure is high even when disposed on the entire roof inner panel 130. Also, the opening 33 of the tube sound absorber 30 may be disposed at a position where the sound pressure is high.

  In each of the embodiments described above, the configuration in which the roof inner panel 130 is attached to the roof outer panel 120 is performed by clip fastening or the like. However, the present invention is not limited to this, and each part is fixed by another fixing method such as an adhesive. You may do it.

1 is a perspective view showing a four-door sedan type vehicle according to a first embodiment of the present invention. It is a figure showing typically the chassis of vehicles. It is sectional drawing which expands and shows the a part in FIG. It is a figure which shows the experimental result which provided the board sound-absorbing body in the roof located on the head of the front seat. It is a perspective view which shows the state which provides a board sound-absorbing body in the position different from 1st Embodiment. It is a figure which shows the experimental result which provided the board sound-absorbing body in the roof located on the head of a rear seat. It is a figure which shows a modification (1-3-1). It is a figure which shows a modification (1-3-2). It is a figure which shows a modification (1-3-3). It is a figure which shows a modification (1-3-4). It is a figure which shows a modification (1-3-5). It is a figure which shows a modification (1-3-6). It is a figure which shows a modification (1-3-7). It is a figure which shows the experimental result by a modification (1-3-8). It is a perspective view which shows the 4-door sedan type vehicle which concerns on 2nd Embodiment. It is a figure which expands and shows the pipe | tube sound absorber in 2nd Embodiment. It is a schematic diagram which shows the principle of a pipe | tube sound absorber. It is a perspective view which shows the state which provides a board sound-absorbing body in the position different from 2nd Embodiment. It is sectional drawing similar to FIG. 8 in 3rd Embodiment. It is a perspective view which shows the vehicle of 4 door sedan type which concerns on 4th Embodiment. It is a figure which shows the modification of 4th Embodiment.

Explanation of symbols

10, 10a, 10b, 10A, 10B, 10C ... plate sound absorber, 11, 41 ... housing, 12 ... opening, 13 ... diaphragm, 14 ... air layer, 30. ..Pipe sound absorber, 31-1 to 31-9 ... pipe, 32 ... closed portion, 33 ... opening, 34 ... resistance material, 40 ... Helmholtz sound absorber, 43A, 43B ... Tubular member, 44 ... Sealed space, 110 ... Chassis, 120 ... Roof outer panel, 130 ... Roof inner panel, 131 ... Core material, 138 ... Surface material, 139, 139A, 139B ... Sound pressure transmitting part, 140 ... Roof.

Claims (16)

A roof supported by vehicle props,
A vehicle body structure comprising: a sound absorbing structure that is provided on the roof and absorbs sound by driving sound pressure. The vehicle body structure according to claim 1,
The vehicle body structure is characterized in that the portion driven by the sound pressure drive of the sound absorbing structure is disposed so as to be located in a portion where the sound pressure of the roof is high. The vehicle body structure according to claim 1 or 2,
The sound absorbing structure includes a diaphragm,
A vehicle body structure characterized by a plate sound absorber having an air layer defined behind the diaphragm. The vehicle body structure according to claim 1 or 2,
The sound-absorbing structure is a pipe sound-absorbing body having a cavity that is a closed portion with one end closed and an opening with the other end opened. The vehicle body structure according to claim 4,
A vehicle body structure comprising a plurality of the cavities. The vehicle body structure according to claim 4,
A plurality of the cavities having different lengths are formed. The vehicle body structure according to claim 1 or 2,
The sound-absorbing structure is a Helmholtz sound-absorbing body having a closed space and a tubular member that communicates the closed space with the space of the passenger compartment. The vehicle body structure according to claim 1 or 2,
The sound absorbing structure is
A plate sound absorber having a diaphragm and an air layer defined behind the diaphragm;
A tube sound absorber having a cavity having a closed portion with one end closed and an opening with the other open;
A Helmholtz sound absorber having a closed space and a tubular member communicating the closed space with the outside,
A vehicle body structure characterized by comprising a combination of any of the sound absorbers. The vehicle body structure according to any one of claims 1 to 8,
A chassis that serves as a base for the roof constitutes a part of the sound absorbing structure. The vehicle body structure according to any one of claims 1 to 8,
The sound absorbing structure is attached to a chassis that is a base of the roof. The vehicle body structure according to any one of claims 1 to 8,
The roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, and a roof inner panel that covers the roof outer panel from the vehicle interior side,
The sound absorbing structure is disposed between the roof outer panel and the roof inner panel. The vehicle body structure according to any one of claims 1 to 8,
The roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, a roof inner that covers the roof outer panel from the vehicle interior side, and a core material and a surface material that covers the surface of the core material. A panel, and
The vehicle body structure, wherein the core material constitutes a part of the sound absorbing structure. The vehicle body structure according to any one of claims 1 to 8,
The roof includes a roof outer panel that forms part of a chassis that serves as a base of the vehicle body structure, a roof inner that covers the roof outer panel from the passenger compartment side, and a core material and a surface material that covers the surface of the core material. A panel, and
The sound absorbing structure is attached to the core member. The vehicle body structure according to any one of claims 11 to 13,
The roof inner panel has a sound pressure transmission part. A roof supported by vehicle struts,
A core material that forms the base of the roof;
A vehicle roof, comprising: a sound absorbing structure that is provided on the core member and absorbs sound by driving sound pressure. A roof inner panel that forms part of a roof supported by a vehicle post;
A core material forming the outer shape of the roof inner panel;
A roof inner panel, comprising: a sound absorbing structure that is provided on the core member and absorbs sound.

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