JP4258287B2 - Sound absorption structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sound absorbing structure that absorbs engine sound and the like to reduce noise, and more particularly to a sound absorbing structure that is suitable for installation on a hood panel of a vehicle.
[0002]
[Prior art]
Conventionally, a sound absorbing structure including a substantially flat substrate, a sound absorbing material facing the substrate, and a partition plate that divides an air layer between the substrate and the sound absorbing material into a plurality of lattice cells is known. (For example, refer to Patent Document 1). In this conventional sound absorbing structure, the thickness of the air layer behind the sound absorbing material (that is, the depth of each cell) is set to ¼ times the wavelength of the sound wave to be absorbed, so that the sound wave of the sound absorbing material is reduced. The energy is attenuated efficiently. According to this conventional sound absorbing structure, the sound absorption rate of the frequency component of the sound having a wavelength about four times the cell depth is improved.
[0003]
In addition, it has an endless (continuous ring-shaped) partition wall protruding from the back side (engine side) of the engine cover body toward the engine, and a portion with a relatively high sound pressure level (engine or There is known a sound insulation structure that closes the surface of the delivery pipe (see, for example, Patent Document 2). In this conventional sound insulation structure, the sound insulation performance can be enhanced by bringing the tip of the partition wall (engine side) into contact with the engine surface.
[0004]
In addition, as a sound insulating material attached to the surface of the vehicle hood panel on the engine room side, a sound insulating material provided with a pulverized rubber layer made of pulverized rubber of various sizes, shapes and materials, and a coating layer covering the pulverized rubber layer Materials are known (see, for example, Patent Document 3). This conventional technique aims to block and absorb noise at various frequency levels using the crushed rubber layer.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-161282 (6th page, FIG. 16)
[0006]
[Patent Document 2]
JP 2001-214752 A
[Patent Document 3]
JP-A-8-129109 (3rd page and 4th tribute)
[0008]
[Problems to be solved by the invention]
However, the conventional sound insulating material disclosed in Patent Document 2 described above includes a crushed rubber layer made of crushed rubber of various sizes, shapes, and materials so as to be able to block and absorb noise at various frequency levels. Therefore, there is a problem that the cost is increased and the weight is increased. In particular, in recent years, in order to reduce the weight of a hood panel of a vehicle, a hood inner is formed from aluminum. Therefore, it is contrary to the weight reduction of a hood panel to provide such a hood panel with a heavy weight sound-absorbing sound-insulating structure like the above-mentioned conventional sound insulating material.
[0009]
In addition, since the sound absorbing structure disclosed in Patent Document 1 described above can be configured to be relatively lightweight, it can cope with the weight reduction of the hood panel. From the viewpoint of protection, it is not an ideal configuration for installation on a hood panel. In other words, if such a highly rigid sound absorbing structure is interposed between the hood panel and the engine, a secondary peak caused by the sound absorbing structure during the deformation process of the hood panel at the time of a collision with a pedestrian (head). A load will be generated.
[0010]
Similarly, as disclosed in Patent Document 2 described above, when a partition wall (rib) is erected on the back side of the engine cover main body, the deformation load of the engine cover main body is increased, so that a pedestrian (its head) is a hood. When it collides with the panel, a secondary peak load is generated in the deformation process of the engine cover body in the latter stage of the deformation process of the hood panel. In other words, when a partition wall is erected on the back side of the engine cover body, the space between the engine cover and the hood panel (space secured for deformation of the hood panel) becomes narrow, and when an impact object collides with the hood panel. In addition, there is a problem that the partition wall prevents the shock absorption by the hood panel or the like.
[0011]
Then, even if it is a case where it installs in a food panel etc., this invention aims at provision of the sound absorption structure which can exhibit the outstanding sound absorption function, without impairing a pedestrian protection function.
[0012]
[Means for Solving the Problems]
The object is a sound absorbing structure applied in a space between a vehicle engine and a hood panel as described in claim 1 ,
A plurality of substantially cylindrical space portions that are open at one end, arranged in a lattice pattern in an adjacent manner;
A sound-absorbing material covering the openings of the plurality of spaces,
This is achieved by a sound absorbing structure characterized in that a notch is formed in the joint portion of the side wall of the adjacent space portion and a convex portion is formed on the upper edge of the side wall extending on both sides of the joint portion. .
[0017]
According to the present invention, by covering the openings of the space portions arranged in a grid with the sound absorbing material, it is possible to realize effective sound absorption with respect to the sound input into the space portions. In the present invention, in the process of deforming the hood panel, the convex portion formed on the upper edge of the side wall first contacts (contacts) the engine or the like. At this time, due to the force applied to the convex portion, a bending force acts on the side wall from both sides of the cut of the coupling portion. This causes breakage of the sound absorbing structure based on the notch formed in the coupling portion of the side wall, so that the deformation load in the compression direction of the sound absorbing structure is greatly reduced and the hood panel necessary for shock absorption is reduced. A deformation stroke is secured.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a perspective view schematically showing an embodiment of a sound absorbing structure according to the present invention. The sound absorbing structure 10 according to the present invention has a plurality of cylindrical spaces 71 (hereinafter referred to as “sound absorbing cells 71”) having one end opened. The plurality of sound absorbing cells 71 are arranged in a grid pattern, for example, and are preferably arranged vertically and horizontally in a manner adjacent to each other. The plurality of sound absorbing cells 71 are defined by erecting a plurality of partition plates 72 intersecting each other on a substantially flat bottom plate 74 (see FIG. 2). The configuration of the partition plate 72 will be described in detail later. The sound absorbing structure 10 may be formed of an aluminum plate, a steel plate, or the like, or may be integrally formed of a hard resin such as a polypropylene resin.
[0020]
The sound absorbing structure 10 of the present embodiment is provided with a sound absorbing material 76. As shown in FIG. 1, the sound absorbing material 76 is fixed to the sound absorbing structure 10 by adhesion or the like so as to cover the opening of each sound absorbing cell 71. In FIG. 1, a part of the sound absorbing material 76 is notched for the purpose of showing the inside of the sound absorbing structure 10. The sound absorbing material 76 is formed from a material having sound absorbing properties, for example, inorganic fibers such as glass wool and rock wool, metal fiber materials such as aluminum fibers, synthetic resin foams such as polystyrene resins and polyethylene resins, urethane, It may be formed from a rubber-based soft material, a porous material, or the like.
[0021]
The sound absorbing structure 10 of the present embodiment is clipped on the inner surface of the hood panel (engine hood) so that the opening (the side on which the sound absorbing material 76 is provided) of the sound absorbing cell 71 faces the sound source (that is, the engine). It is fixed with a screw or the like. However, the present invention does not specify the installation method or installation mode of the sound absorbing structure 10 (for example, the direction of the sound absorbing structure 10 within the installation surface). The sound absorbing structure 10 may not have the bottom plate 74. In this case, the sound absorbing structure 10 is installed in such a manner that the edge of the partition plate 72 is directly supported by the inner surface of the hood panel. It's okay.
[0022]
Next, the principle of sound absorption of the sound absorbing structure 10 according to the present invention will be described with reference to FIG. 2 (A) and 2 (B) show the II cross section of the sound absorbing structure 10 of FIG.
[0023]
As shown in FIG. 2A, when a sound wave having a wavelength λ is incident on the sound absorbing cell 71 substantially perpendicularly, the sound wave is reflected by the incident wave and the bottom plate 74 (or the inner surface of the hood panel). A standing wave is formed by combining with the reflected wave. On the other hand, even when a sound wave of wavelength λ is incident on the sound absorbing cell 71 from an oblique direction, the oblique incident angle of the sound wave is limited by each side surface 72 as shown in FIG. A standing wave is formed.
[0024]
This standing wave has an antinode in the sound absorbing cell 71 at a position away from the bottom plate 74 by an odd multiple of ¼ of the wavelength λ, and the particle velocity of the sound wave becomes maximum at the antinode. Therefore, if the sound absorbing material 76 is provided at a position where the particle velocity is maximum and the sound wave is passed through the sound absorbing material 76 at the position having the highest particle velocity, the sound wave can be attenuated most efficiently.
[0025]
For this reason, the depth H of the sound absorbing cell 71 (the maximum thickness of the air layer in the sound absorbing cell 71) is preferably set to 1/4 (or an odd multiple) of the wavelength λ of the sound wave to be absorbed. For example, in the case where it is desired to increase sound absorption with respect to noise having a frequency around 1 kHz, the depth H of the sound absorption cell 71 is set such that H = m × c / 4f = when the sound speed is c = 340 × 10 ³ mm / s. It is set to a value around m × 85 (m: positive odd number).
[0026]
The opening width D (see FIG. 1) of the sound absorbing cell 71 is set smaller than the wavelength λ of the sound wave in the frequency band to be absorbed in order to regulate the frequency of the sound wave incident on the sound absorbing cell 71. For example, the opening width D of the sound absorbing cell 71 is set within a range of 40 mm to 60 mm. However, the opening width D of the sound absorbing cell 71 may be different for each sound absorbing cell 71, and may be different in the depth direction and the lateral direction. Further, the sound absorbing cell 71 does not necessarily have a constant cross section in the depth direction, and may have a cross section that becomes smaller toward the opening, for example.
[0027]
FIG. 3 is a perspective view showing a main part of the partition plate 72 provided in the sound absorbing structure 10 of the present embodiment, and corresponds to an enlarged view of a portion X in FIG. 1 (intersection portion of the partition plate 72). As shown in FIG. 3, the partition plate 72 of the present embodiment is formed of a thin plate and has a bent portion 73 having a corner on the upper side (that is, the engine side in the installed state). That is, the partition plate 72 has a letter-shaped cross section in which the width increases toward the bottom plate 74. Note that the partition plate 72 may be integrally formed of a hard resin as described above.
[0028]
By the way, in this embodiment, as described above, the sound absorbing structure 10 extends in the space between the hood panel and the engine. In such a configuration, in the deformation process of the hood panel at the time of a collision with a pedestrian, the sound absorbing structure 10 is in contact with the engine (more precisely, the engine cover or the energy absorbing material placed thereon). Deformation of the sound absorbing structure 10 in the compression direction (Z direction in the figure) occurs. Therefore, in such a configuration, it is desirable that the load generated when the sound absorbing structure 10 is deformed be as small as possible from the viewpoint of pedestrian protection.
[0029]
On the other hand, according to the present embodiment, when the sound absorbing structure 10 receives a load in the compression direction on the surface, the partition plate 72 is opened in a letter-shaped cross section (that is, the angle of the bent portion 73 is large). Therefore, the deformation load of the sound absorbing structure 10 can be reduced. Further, the partition plate 72 is deformed in the direction in which the cross section is opened, so that the thickness of the sound absorbing structure 10 is reduced (that is, the angle of the bent portion 73 of the partition plate 72 is ultimately 180 °, and the partition plate 72 72), a hood panel deformation stroke necessary for shock absorption is ensured. Therefore, even if the sound absorbing structure 10 having a cell structure having a high sound absorbing effect is provided between the hood panel and the engine, the pedestrian protection function is not impaired.
[0030]
Next, referring to FIG. 3 again, some other configuration examples of the partition plate 72 will be described. In addition, these structural examples may be used independently separately from the above-mentioned structural example, or may be used in arbitrary combinations including the combination with the above-mentioned structural example.
[0031]
As shown in FIG. 3, a notch 75 may be formed in the bent portion 73 of each partition plate 72 at the intersection (joint portion) of each partition plate 72. Thereby, the rigidity of the intersection part of the partition plate 72 with especially high rigidity can be reduced. In addition to the intersections of the partition plates 72, notches 76 may be formed in the bent portions 73 of the partition plates 72. Thereby, the deformation | transformation of the opening direction of the character-shaped cross section to the above-mentioned partition plate 72 can be implement | achieved with a smaller compressive load.
[0032]
In addition, from the same viewpoint, a difference may be formed in the lower end positions of the two side surfaces 72a and 72b of the partition plate 72. For example, the lower end of one side surface 72a may be brought into contact with the bottom plate 74 (or the inner surface of the hood panel), and the lower end of the other side surface 72b may be separated from the bottom plate 74 (in the figure, a gap is indicated by Δ). In this case, in the deformation process of the hood panel when the pedestrian (its head) collides with the hood panel, the partition plate 72 first falls on the short leg side (that is, the other side surface 72b side), and then the same as described above. In other words, the two side surfaces 72a and 72b open in a direction away from each other. As a result, the deformation load in the compression direction of the sound absorbing structure 10 is reduced, and the sound absorbing structure 10 is not crushed (that is, becomes substantially flat), and the deformation stroke of the hood panel necessary for shock absorption is reduced. Secured.
[0033]
Further, as shown in FIG. 3, in order to ensure the displacement path of the side surfaces 72a and 72b of the partition plate 72 at the time of the above-described deformation, a notch 77 (by hatching in FIG. 3) is formed in the side surfaces 72a and 72b of the partition plate 72. Instructions) may be formed. As shown in FIG. 3, the notch 77 may be formed by, for example, notching a substantially triangular region that includes the intersection of the side surfaces 72 a and 72 b and the bottom edge.
[0034]
In addition, as shown in FIG. 4, a cut 78 (for example, a depth of about 2 to 5 mm) is formed in the bent portion 73 of the partition plate 72 at the intersecting portion of the partition plate 72, and other than the intersecting portion of the partition plate 72. A convex portion 79 (for example, about 2 mm in height) may be formed on the bent portion 73 of the partition plate 72. In this case, the pair of convex portions 79 are preferably formed symmetrically about the position of the notch 78. According to such a configuration, in the deformation process of the hood panel when the pedestrian (its head) collides with the hood panel, the convex portion 79 first comes into contact with the engine, and at this time, due to the force applied to the convex portion 79. Then, since the partition plate 72 is bent in the direction in which the notch 78 is torn, the partition plate 72 is separated and broken with the notch 78 as a base point. Thereby, the deformation | transformation load of the compression direction of the sound absorption structure 10 is reduced.
[0035]
The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.
[0036]
For example, in the embodiment described above, the sound absorbing structure 10 is provided on the hood panel. However, as long as the sound absorbing structure 10 according to the present invention is installed in the space between the hood panel and the engine, as described above. The same effect can be produced in the same way. Therefore, the sound absorbing structure 10 may be installed on the front surface or the back surface of the engine cover, or may be held in a space between the hood panel and the engine. In the latter case in particular, the sound absorbing structure 10 does not necessarily have to be installed so that the opening of the sound absorbing cell 71 faces the engine, but may be installed so that the opening of the sound absorbing cell 71 faces the lower surface of the hood panel. Good.
[0037]
Further, the sound absorbing structure 10 according to the present invention is not necessarily applied to the space directly above the engine. For example, the sound absorbing structure 10 may be installed in a space between auxiliary machinery (including a battery and the like) around the engine and the hood panel.
[0038]
In addition, the two side surfaces 72a and 72b of the partition plate 72 are not necessarily flat and may be configured by curved surfaces. Naturally, the bent portion 73, which is a connecting portion between the two side surfaces 72a and 72b, does not necessarily need to be sharp, and may be rounded.
In addition, in the Example mentioned above, the Example shown in FIG. 3 is a reference example which does not belong to the scope of the present invention alone.
[0039]
【The invention's effect】
Since the present invention is as described above, the following effects can be obtained. ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where it installs in a food panel etc., the sound absorption structure which exhibits the outstanding sound absorption function can be obtained, without impairing a pedestrian protection function.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing an embodiment of a sound absorbing structure according to the present invention.
FIG. 2 is an explanatory diagram of the sound absorption principle of the sound absorbing structure 10 according to the present invention.
FIG. 3 is a perspective view showing a main part of a partition plate 72 of the present embodiment.
FIG. 4 is a side view showing a main part of a partition plate 72 according to an alternative embodiment (a part defining two adjacent sound absorbing cells 71).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Sound absorption structure 71 Sound absorption cell 72 Partition plate 73 Bending part 74 Bottom plate 75 Notch 76 Sound absorption material 77 Notch 78 Notch 79 Convex part

Claims (1)

A sound absorbing structure applied in the space between the vehicle engine and the hood panel,
A plurality of substantially cylindrical space portions that are open at one end, arranged in a lattice pattern in an adjacent manner;
A sound-absorbing material covering the openings of the plurality of spaces,
A sound absorbing structure, wherein a notch is formed in a joint portion between side walls of adjacent space portions, and a convex portion is formed on an upper edge of the side wall extending on both sides of the joint portion.

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