JP2015136981A - Sound absorption structure of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorption structure of a vehicle, which can suppress low-frequency noises in a cabin space by a simple configuration.SOLUTION: A sound absorption structure of a vehicle includes: a closed space 7 which is provided in a recessed shape below a floor member 6 of a luggage room of the vehicle 1 and which is formed by having an upper part covered with the floor member 6; a partition wall 15 which partitions the closed space 7 into a container part 11 and a duct part 12; a communication port 14 which is provided in the partition wall 15 and which communicates the container part 11 and the duct part 12 with each other; and an opening 13 which is provided at an end, on the other side of the communication port 14, of the duct part 12 and which is opened in a cabin space.

Description

  The present invention relates to a sound absorbing structure for a vehicle that reduces noise in a passenger compartment space.

  The sound of the passenger compartment (sound inside the vehicle) is mainly composed of four elements: sound transmitted from the power plant (so-called engine sound), muffled sound, sound transmitted from the road surface (so-called road noise), and wind noise. It is known. In order to improve the quietness in the passenger compartment, it is important how to reduce these sounds, and techniques for reducing the noise in the passenger compartment have been proposed.

  For example, Patent Document 1 discloses a technique for reducing vehicle interior noise by using a spare tire house provided below a floor panel of a trunk room as a resonator. In this technique, a handle hole is provided in a tonneau board that hides the upper part of the spare tire house, and a cover is attached around the handle hole. The cover has an inner peripheral wall surface with a height dimension h, and has a hole as a resonator. With such a configuration, the spare tire house in the sealed space communicates with the trunk room through the hole, and can be used as a resonator, so that noise in a low frequency region that substantially matches the road noise region can be reduced.

Japanese Utility Model Publication No. 1-120450

However, the structure of Patent Document 1 has a problem that it is difficult to increase the height h of the hole. Of the above-mentioned sounds in the passenger compartment space, particularly loud noises may cause discomfort such as squeezing the occupant's ears with a low frequency sound lower than the road noise region (200 to 300 Hz), and are actively reduced. The sound you want to make. On the other hand, in the structure of Patent Document 1, it is difficult to set the resonance frequency of the spare tire house to a low frequency region that is lower than the road noise region.
In addition, when the connection path leading to the spare tire house is formed separately as in the third embodiment of Patent Document 1, the structure is complicated even if the height h can be increased, and the separate body An increase in cost and weight is unavoidable as long as it is provided.

  One of the objects of the present invention has been devised in view of such a problem, and provides a vehicle sound absorbing structure capable of suppressing low-frequency noise in a passenger compartment space with a simple configuration. It is. The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) A sound absorbing structure for a vehicle disclosed herein includes a closed space that is recessed below a floor member of a luggage room of the vehicle and is covered by the floor member above, and the closed space is a container portion. A partition wall that is divided into a duct part, a communication port that is provided in the partition wall, communicates the container part and the duct part, and is provided at an end opposite to the communication port of the duct part; An opening that opens into the chamber space. The vehicle compartment space means a space inside the vehicle, and the luggage room is a part of the vehicle compartment space. Moreover, the said duct part is a part which has a communicating port in one side and an opening part in the other, and connects the said vehicle interior space and the said container part. Thus, the sound absorbing structure constitutes a Helmholtz resonator.

(2) It is preferable that the said duct part is extended in the vehicle front-back direction in the vehicle width direction outer side of the said container part.
(3) The opening is preferably provided facing upward.
(4) It is preferable to provide a mesh-like cover that covers the opening.

(5) It is preferable that the closed space extends along the floor member. That is, it is preferable that the closed space is a space extending along the floor member below the floor member and having a certain height by being covered by the floor member.
(6) The closed space is preferably a storage space.

  According to the disclosed vehicle sound absorbing structure, a closed space that is recessed below the floor member of the luggage room, for example, used as a storage space, is divided into a container portion and a duct portion by a partition wall, and a communication port and an opening are provided. By providing the portion, this closed space can be used as a Helmholtz resonator. Here, in the Helmholtz resonator, the resonance frequency f is determined by the volume V of the container part, the length L of the duct part, and the area S of the opening part.

  In the present sound absorbing structure, the length L of the duct portion corresponds to the length from the opening to the communication port, so the length L of the duct portion can be increased, and the resonance frequency f can be set higher than that of the road noise region. It can be set to a lower low frequency range. Therefore, according to the present sound absorbing structure, low frequency sound such as booming noise in the passenger compartment space can be absorbed, and low frequency noise can be suppressed. In addition, a space for storing repair tools and the like is generally provided below the floor member of the luggage room. In this air intake structure, a partition wall and two openings are provided in the originally closed space. Therefore, the configuration can be simplified, and the component cost, manufacturing cost, and weight can be suppressed.

It is the perspective view which showed the sound absorption structure of the vehicle which concerns on one Embodiment except a floor member. It is the perspective view which showed the sound absorption structure of the vehicle which concerns on one Embodiment. It is a typical top view of the sound absorption structure of FIG. It is the side view which omitted the side door of the vehicle which can apply the sound absorption structure concerning one embodiment. It is a schematic diagram of a Helmholtz resonator. It is a graph for demonstrating the effect by the sound absorption structure of FIG. (A)-(c) is a typical top view of the sound-absorbing structure which concerns on a modification.

  Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment, and can be selected or combined as necessary.

[1. Sound absorption structure]
As shown in FIG. 4, the sound absorbing structure according to the present embodiment is provided below the luggage room 2 of the vehicle 1. The luggage room 2 is a space behind the rear seat 4 in the vehicle compartment space 3 and is mainly used as a storage space. The vehicle compartment space 3 here means the internal space of the vehicle 1, and the luggage room 2 is also included in the vehicle compartment space 3 (that is, the luggage room 2 is a part of the vehicle compartment space 3). The luggage room 2 can be accessed from the outside by opening the tailgate 5, and luggage can be taken in and out.

  The floor member 6 constituting the floor surface of the luggage room 2 is a non-breathable plate-like member, and a rotating shaft 6A (see FIG. 2) extending along the vehicle width direction (left-right direction) is the frontmost part. Have. The floor member 6 is turnable (openable and closable) so that the rear part moves upward about the turning shaft 6A. A storage space 7 is provided below the luggage room 2, that is, below the floor member 6, for storing tools that are not frequently used, such as repair tools.

  The storage space 7 is a space extending along the floor member 6 below the floor member 6, and is fixed by being covered by the floor member 6 (that is, when the floor member 6 is closed). It becomes a closed space having a height of. The sound absorbing structure 10 (see FIG. 1) forms a Helmholtz resonator using the storage space 7 and absorbs the sound of the vehicle interior space 3 to suppress noise.

The Helmholtz resonator is a container 90 in which a hollow portion 91 and a neck portion 92 are connected as shown in FIG. 5, and the resonance that occurs in such a container 90 is called Helmholtz resonance. As shown in FIG. 5, assuming that the volume of the hollow portion 91 of the Helmholtz resonator 90 is V ₀ , the length of the neck portion 92 is L ₀ , and the area of the opening 93 of the neck portion 92 is S ₀ , The resonance frequency f ₀ is expressed by the following formula [1]. In the following formula, a is the speed of sound.

As can be seen from this equation [1], the resonance frequency f ₀ is determined by the volume V ₀ of the cavity portion 91, the length L ₀ of the neck portion 92, and the area S _{0 of the} opening 93. When a sound wave having a frequency corresponding to the resonance frequency f ₀ is incident on such a container 90, resonance (resonance) occurs and the air in the neck portion 92 vibrates violently. At that time, sound is re-radiated from the neck portion 92, but viscous resistance works on the tube wall, and a part of the energy of the incident sound wave is converted into heat, resulting in a sound absorbing effect. That is, the Helmholtz resonator 90 can reduce sound by absorbing sound waves having a frequency close to the resonance frequency f ₀ .

  It is known that the sound of the passenger compartment 3 is mainly composed of four elements: sound transmitted from the power plant (so-called engine sound), muffled sound, sound transmitted from the road surface (road noise), and wind noise. ing. Among these, especially the booming sound may give an unpleasant feeling that presses the occupant's ear with a low frequency sound. Therefore, the sound absorbing structure 10 uses the principle of the Helmholtz resonator 90 and sets the resonance frequency f of the sound absorbing structure 10 to a low frequency so as to suppress low-frequency sound (particularly, booming sound).

  The sound absorbing structure 10 will be described with reference to FIGS. 1 and 2 are perspective views of the luggage room 2 as viewed obliquely from above with the tailgate 5 of the vehicle 1 of FIG. 4 opened, and FIG. 1 shows the sound absorbing structure 10 with the floor member 6 removed. FIG. 2 shows the sound absorbing structure 10 covered with the floor member 6. FIG. 3 is a top view schematically showing the sound absorbing structure 10 of FIG. As shown in FIG. 2, the floor member 6 that is the bottom surface of the luggage room 2 is closed except when the storage space 7 is accessed, whereby the storage space 7 becomes a closed space.

  As shown in FIGS. 1 to 3, the sound absorbing structure 10 includes a partition wall 15 that divides a closed space (that is, the storage space 7) that is covered by the floor member 6 in the horizontal direction into two spaces, The partition wall 15 includes a communication port 14 that communicates two spaces, and an opening 13 formed in the floor member 6. The partition wall 15 is a plate-like member erected on the bottom surface of the storage space 7, and is close to the lower surface of the floor member 6 when the floor member 6 is closed (that is, equivalent to the height of the closed space 7). Height). Here, the partition wall 15 extends in the vehicle front-rear direction (hereinafter simply referred to as the front-rear direction) in the storage space 7, and partitions the storage space 7 so that two large and small spaces are arranged in the vehicle width direction.

  Of the two spaces partitioned by the partition wall 15, the large space is referred to as the container portion 11, and the small space is referred to as the duct portion 12. The container portion 11 corresponds to the hollow portion 91 and the duct portion 12 corresponds to the neck portion 92. Here, the duct portion 12 extends in the front-rear direction on the outer side (left side) of the container portion 11 in the vehicle width direction. The communication port 14 corresponds to a portion connecting the hollow portion 91 and the neck portion 92 described above, and is the only opening through which the container portion 11 and the duct portion 12 communicate with each other when the floor member 6 is closed.

  The opening 13 corresponds to the opening 93 and is provided at an end (front end) opposite to a portion (here, the rear) where the communication port 14 of the duct portion 12 is provided. The opening 13 is provided facing upward and opens into the luggage room 2 (that is, the vehicle interior space 3). In the closed state of the floor member 6, the duct portion 12 and the luggage room 2 communicate with each other through the opening 13, and the air in the duct portion 12 is compressed by the air in the vehicle interior space 3 through the opening 13. That is, the sound absorbing structure 10 is configured as a Helmholtz resonator.

  As shown in FIG. 3, the volume of the container portion 11 is V, and the length in the front-rear direction from the rear end portion where the communication port 14 of the duct portion 12 is located to the front end portion of the opening portion 13 (that is, the front-rear direction of the storage space 7). The resonance frequency f of the sound absorbing structure 10 is defined by the following formula [2] where L is the total length) and S is the area of the opening 13.

  In the sound absorbing structure 10 according to the present embodiment, since the length L of the duct portion 12 can be particularly increased, the resonance frequency f can be set to a low frequency. Here, the magnitude of the vehicle interior sound (sound in the passenger compartment 3) with respect to the frequency is shown in FIG. A solid line in FIG. 6 indicates a case where the sound absorbing structure 10 is provided, and a broken line indicates a case where the sound absorbing structure 10 is not provided. The vehicle interior sound has a peak when the frequency is a predetermined value F as shown by a broken line, and this frequency F is about 30 to 100 Hz which is lower than the road noise region. In the present sound absorbing structure 10, the volume V of the container portion 11, the duct is set so that the resonance frequency f of the sound absorbing structure 10 is substantially the same as the frequency F in order to effectively reduce the sound of this frequency F (ie, the booming sound). The length L of the part 12 and the area S of the opening 13 are set. As a result, as indicated by a solid line, it is possible to absorb sound waves close to the frequency F (that is, the resonance frequency f) and to reduce the peak of the in-vehicle sound.

The length L of the duct portion 12 can be easily set according to the position and size of the opening 13 and the position of the partition wall 15. For example, as shown in FIG. 7A, the opening 13 is provided not on the floor member 6 but in a portion serving as a side wall of the storage space 7 so as to open in a space between the rear seat 4 and the storage space 7. Is also possible. By providing the opening 13 in this way, a cover 16 which will be described later is not necessary, and the possibility of dropping the luggage can be eliminated. Further, if the opening 13 is provided on the side wall, it opens perpendicularly to the length direction of the duct 12, and therefore the length L of the duct 12 corresponding to the length L ₀ of the neck portion 92 of the Helmholtz resonator 90. Can be ensured. Further, as shown in FIG. 7B, the partition wall 15 is extended in the vehicle width direction, the opening 13 is provided at one end, and the communication port 14 is provided at the other end, thereby further increasing the length L of the duct portion 12. Can be bigger.

  The length L of the duct portion 12 is preferably set in consideration of the storage performance (storage capacity), which is the original role of the storage space 7, the ease of air in and out of the passenger compartment space 3, and the like. The partition wall 15 can have a larger storage space when it is extended in the front-rear direction than when it is extended in the vehicle width direction. In addition, the opening 13 can be made easier to enter and exit the air in the passenger compartment space 3 if it is provided on the floor member 6 so as to face upward rather than being provided in a portion serving as a side wall.

  Further, in the present embodiment, as shown in FIG. 2, a mesh-like (mesh-like) cover 16 that covers the opening 13 is provided, and the load placed on the floor member 6 is stored in the storage space 7 (duct portion 12). It can be prevented from falling or tilting inside. In addition, since the cover 16 is mesh shape, air permeability is ensured.

[2. Action / Effect]
In the sound absorbing structure 10, the closed space 7 that is recessed below the floor member 6 of the luggage room 2, for example, used as a storage space, is divided into a container portion 11 and a duct portion 12 by a partition wall 15 and opened. By providing the part 13 and the communication port 14, this closed space can be used as a Helmholtz resonator. In the Helmholtz resonator, as described above, the resonance frequency f is determined by the volume V of the container part 11, the length L of the duct part 12, and the area S of the opening part 13.

  In the present sound absorbing structure 10, since the length L of the duct portion 12 corresponds to the length from the opening 13 to the communication port 14, the length L of the duct portion 12 can be increased, and the resonance frequency f can be increased. It can be set to a low frequency region that is lower than the road noise region. Therefore, according to the sound absorbing structure 10, it is possible to absorb a low frequency sound such as a booming sound in the passenger compartment space 3, and to suppress the low frequency noise. In addition, a space for storing repair tools and the like is generally provided below the floor member 6 of the luggage room 2. In the intake structure 10, the partition wall 15 and the originally provided closed space 7 are provided. Since only the two openings 13 and 14 are provided, the configuration can be simplified, and the component cost, manufacturing cost, and weight can be suppressed.

  Further, in the sound absorbing structure 10 described above, since the duct portion 12 extends in the front-rear direction on the outer side in the vehicle width direction of the container portion 11, a large volume V of the container portion 11 can be secured and the resonance frequency f can be reduced. can do. Furthermore, the storage space of the closed space 7 can be widened, and convenience can be improved.

Further, in the above sound absorbing structure 10, the opening 13 is formed in the floor member 6 and is provided facing upward, so that air in the passenger compartment space 3 can easily enter and exit from the opening 13 to the duct portion 12. . Thereby, sound absorption performance can be improved more.
The opening 13 formed in the floor member 6 is covered with a mesh-like cover 16, so that it is possible to prevent the luggage from falling from the opening 13, the inclination of the luggage, etc., and the luggage room 2. It is possible to store luggage stably.

  Further, in the above sound absorbing structure 10, the closed space 7 is a space extending along the floor member 6, so that the closed space 7 can be formed into the container portion 11 and the duct portion 12 only by erecting a partition wall 15 having a low height. And can be partitioned. Therefore, the configuration can be further simplified, and the component cost and the manufacturing cost can be reduced.

  Further, here, the closed space 7 is a storage space provided for storing repair tools and the like, and in order to utilize this space 7 as a part of the sound absorbing structure 10, a dedicated product for reducing noise is provided. Compared to the above, the component cost and the manufacturing cost can be reduced. Moreover, a space for installing a dedicated product for noise reduction is unnecessary, and space efficiency can be improved.

[3. Others]
Regardless of the embodiment described above, various modifications can be made without departing from the spirit of the invention. Each structure of this embodiment can be selected as needed, or may be combined appropriately.

  For example, the shape of the closed space 7 is not limited to the above. For example, as shown in FIG. 7 (c), depending on the shape of the luggage room 2 of the vehicle 1, a shape in which one corner of the rear end is recessed inward may be used. The portion that becomes the side wall may be a curved surface. The closed space 7 can take various shapes depending on the vehicle body shape of the vehicle 1 and the mounting position of the in-vehicle device, and at least the upper space is covered with the floor member 6 so as to be formed as a closed space. Good. Further, even when an object such as a repair tool is stored in the closed space 7, the same operation and effect as in the above embodiment can be obtained as long as a space that can function as a Helmholtz resonator remains. be able to. The closed space 7 may not be a storage space.

Further, the position and shape of the opening 13 are not limited to those described above. For example, the opening 13 may be circular or elliptical, or may be formed on a side wall as shown in FIG. Further, as shown in FIG. 7C, the duct portion 12 may be formed so as to protrude forward of the vehicle from the floor member 6, and the portion that is not covered by the floor member 6 may be the opening portion 13. The cover 16 is not essential, and may be omitted when the opening 13 does not face upward.
Moreover, the structure of said floor member 6 is an example, Comprising: What is necessary is just to be able to form the closed space 7 under the luggage room 2, The shape and rotation direction are not specifically limited.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Luggage room 3 Cabin space 4 Rear seat 5 Tailgate 6 Floor member 7 Storage space (closed space)
DESCRIPTION OF SYMBOLS 10 Sound absorption structure 11 Container part 12 Duct part 13 Opening part 14 Communication port 15 Partition wall 16 Cover

Claims (6)

A closed space that is recessed below the floor member of the luggage room of the vehicle and is covered by the floor member above;
A partition wall that partitions the closed space into a container part and a duct part;
A communication port provided in the partition wall and communicating the container portion and the duct portion;
A sound absorbing structure for a vehicle, comprising: an opening portion provided at an end portion of the duct portion opposite to the communication port and opening into a passenger compartment space. 2. The vehicle sound absorbing structure according to claim 1, wherein the duct portion extends in the vehicle front-rear direction outside the container portion in the vehicle width direction. The sound absorbing structure for a vehicle according to claim 1, wherein the opening is provided facing upward. The sound absorbing structure for a vehicle according to any one of claims 1 to 3, further comprising a mesh-like cover that covers the opening. The sound absorbing structure for a vehicle according to claim 1, wherein the closed space extends along the floor member. The vehicle sound absorbing structure according to claim 1, wherein the closed space is a storage space.

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