JP2004168134A - Exterior noise reduction structure and side mudguard provided with the same - Google Patents

Abstract

An external noise structure capable of effectively reducing noise radiated from an engine room toward a side or obliquely rearward of a vehicle and a side mudguard provided with the same.
The present invention relates to a vehicle exterior noise reduction structure provided in a rocker portion (4) of a vehicle body (2), comprising a plurality of space portions (20) arranged along the vehicle front-rear direction and having an opening on the vehicle inside side; A partition plate 16 including a sound absorbing material 30 covering the openings of the plurality of space portions 20 or arranged along the vehicle front-rear direction, and only on the vehicle inner side separated from each other in the vehicle front-rear direction by the partition plate. And a plurality of spaces 72 having openings.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle exterior noise reduction structure for reducing vehicle exterior noise, and more particularly, to a vehicle exterior noise reduction structure provided near a lower end of a side portion of a vehicle body.
[0002]
[Prior art]
As a conventional structure for reducing outside noise, there is known an outside noise reduction structure in which an engine undercover that covers an engine from below has a vertically long opening in the front-rear direction (for example, see Patent Document 1). . In this conventional external noise reduction structure, the noise in the engine room is released to the centerline side opposite to the sidewalk side by reducing the noise in the sidewalk side by directing the opening direction of the vertical opening to the centerline side. It is possible to do.
[0003]
[Patent Document 1]
No. 6-72789 [0004]
[Problems to be solved by the invention]
However, in the above-mentioned conventional vehicle exterior noise reduction structure, although noise radiated outside the vehicle through the engine undercover is given an appropriate directionality, noise reduction on the nearest sidewalk side can be achieved. The noise on the sidewalk side may not be reduced, and may increase on the contrary. In addition, the engine noise is radiated outside the area where the engine undercover is installed, and the installation area of the engine undercover is also limited from the viewpoint of heat dissipation and the like, so the effect of reducing the noise outside the vehicle is very large. is not.
[0005]
By the way, as shown in FIG. 9 (A), when measuring the noise (engine sound) while the vehicle is running by fixing the measuring device at a position away from the vehicle traveling road by a certain distance, the measurement shown in FIG. 9 (B) As a result, the noise level becomes highest after the vehicle has passed through the measuring device (that is, the vehicle position I in the figure) (the horizontal axis of the measurement result in FIG. This is the vehicle position where the arrival time of the sound wave is taken into account.) This means that the sound radiated from the engine room toward the side of the vehicle or obliquely rearward has the greatest effect on the actual outside noise.
[0006]
Therefore, an object of the present invention is to provide a vehicle exterior noise reduction structure capable of effectively reducing noise radiated from an engine room toward a vehicle side or obliquely rearward and a side mudguard provided with the same.
[0007]
[Means for Solving the Problems]
An object of the present invention is to provide an external noise reduction structure provided at a lower end of a side surface of a vehicle body, as described in claim 1,
A plurality of spaces arranged along the vehicle front-rear direction and having openings only on the vehicle inner side,
And a sound absorbing material for covering the openings of the plurality of spaces.
[0008]
In the present invention, a plurality of spaces are arranged along the front-rear direction of the vehicle at the lower end of the side surface of the vehicle body. The plurality of spaces each have an opening only on the vehicle inner side. Accordingly, the sound radiated from the engine room toward the side of the vehicle or obliquely rearward is incident on each space arranged at the lower end of the side surface of the vehicle body. When sound enters a space, a standing wave is formed in the space by the combination of the incident wave and the reflected wave. Therefore, by covering the opening of the space with the sound absorbing material, sound radiated from the engine room to the vehicle side or obliquely rearward can be efficiently attenuated. In particular, since the sound radiated from the engine room toward the side of the vehicle greatly affects the actual outside noise, the effect of reducing the outside noise by effectively attenuating the sound is extremely large. Become. The opening of the space on the vehicle inner side may have various opening directions, and may be, for example, facing the engine direction or obliquely upward.
[0009]
When the maximum thickness of the air layer in the space is set to an odd multiple of 1/4 wavelength of the noise of the frequency to be reduced, the sound wave in the space is sound-absorbing at the position having the highest particle velocity. , And the energy of the sound wave can be absorbed most efficiently.
[0010]
In addition, the object is to provide an external noise reduction structure provided at a lower end portion of a side surface of a vehicle body, as described in claim 2,
Partition plates arranged along the vehicle longitudinal direction,
The present invention is also achieved by a vehicle exterior noise reduction structure comprising: a plurality of spaces that are separated from each other in the vehicle front-rear direction by the partition plate and that have openings only on the vehicle inner side.
[0011]
In the present invention, a plurality of spaces are defined at the lower end of the side surface of the vehicle body by arranging a plurality of partition plates along the vehicle front-rear direction. The plurality of spaces each have an opening only on the vehicle inner side, but the openings are not covered with the sound absorbing material. Sound radiated from the engine room toward the side of the vehicle or diagonally backward is directly output to the outside of the vehicle, and is diffracted after entering into several spaces located at the lower end of the side of the vehicle body and then diffracted outside the vehicle. It is output to the outside of the vehicle through any of the output detour routes. In particular, since a plurality of partition plates are arranged along the vehicle front-rear direction, this detour path is easily established by preventing the sound wave from traveling in the vehicle front-rear direction, and therefore, at a point where both paths merge. Sound waves passing through the respective paths interfere with each other, so that sound reduction is realized at the junction. In particular, since the sound radiated from the engine room toward the side of the vehicle greatly affects the actual noise outside the vehicle, the effect of reducing the noise outside the vehicle by canceling the sound becomes extremely large.
[0012]
When the maximum thickness of the air layer in the space is set to an odd multiple of 1/4 wavelength of the noise of the frequency to be reduced, the sound waves that have passed through the detour path and the direct path, respectively, are at the junction. Since the phases are substantially opposite (the phase difference is about 180 degrees), it is possible to realize substantially complete silencing.
[0013]
Further, the vehicle exterior noise reduction structure according to the present invention is suitable for being provided on a side mud guard mounted between wheel arches in front and rear of a vehicle body. The side mudguard includes a side skirt selectively provided to improve design and aerodynamic characteristics.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing a vehicle part to which an external noise reduction structure according to the present invention is applied. The external noise reduction structure according to the present invention is provided near the lower end of the side surface of the vehicle body 2, and is preferably provided on a side mud guard 10 extending between the front and rear wheel arches of the vehicle body 2. Hereinafter, an embodiment in which the exterior noise reduction structure according to the present invention is applied to the side mudguard 10 will be described.
[0015]
The side mudguard 10 is a long body extending between the front and rear wheel arches of the vehicle body 2, and generally protects the vehicle body 2 from muddy water, pebbles, and the like that are thrown up during running, and prevents the vehicle body 2 from being stained or damaged. It has a function to do. The side mudguard 10 extends along the rocker portion 4 forming the lower edge of the side surface of the vehicle body 2, and is securely fixed to the rocker portion 4 by a clip 6, a screw, or the like.
[0016]
FIG. 2 is a perspective view of the side mud guard 10 having the vehicle exterior noise reduction structure according to the present invention, as viewed from the inside of the vehicle. FIG. 3 is a cross-sectional view of the side mud guard 10 of FIG. .
[0017]
As shown in FIG. 3, the side mudguard 10 has a substantially L-shaped cross section when viewed from the vehicle front-rear direction, and has a side surface 12 extending in the vehicle front-rear direction and a bottom surface 14 covering the rocker portion 4 from below. And Note that a clip 6 (see FIG. 1) for attachment to the rocker unit 4 is provided inside the side surface 12 of the side mudguard 10 (in the direction IN in the figure).
[0018]
As shown in FIG. 2, a plurality of partition plates 16 are provided upright on the inner surface of the side mudguard 10 (in the direction IN in the figure) along the front-rear direction of the vehicle. The partition plate 16 may be provided over the entire length of the side mud guard 10 (vehicle longitudinal direction), but is provided only over a predetermined range (for example, a range corresponding to the front door) from the front wheel arch. You may. The partition plate 16 of the present embodiment is a substantially triangular plate member including two sides corresponding to a substantially L-shaped cross section of the side mud guard 10, and cooperates with the side surface 12 and the bottom surface 14 of the side mud guard 10, and the front and rear of the vehicle. A plurality of spaces 20 having a substantially triangular cross section when viewed from the direction (hereinafter, these spaces are referred to as “sound absorbing cells 20”) are defined.
[0019]
The partition plate 16 is formed integrally with the side mud guard 10 by resin molding. However, it is also possible to form the partition plate 16 from an aluminum plate, a steel plate or the like, and insert the partition plate 16 into a groove 10a formed on the inner surface of the side mud guard 10, as shown in the enlarged view of the portion A in FIG.
[0020]
On one edge portion 16a of each partition plate 16, a sound absorbing material 30 in a substantially sheet shape is provided so as to cover the entire surface of the opening of each sound absorbing cell 20. The sound absorbing material 30 may be fixed to the edge 16a of the partition plate 16 with an adhesive or the like. The sound absorbing material 30 is made of a material having sound absorbing performance, for example, inorganic fiber such as glass wool or rock wool, metal fiber material such as aluminum fiber, synthetic resin foam such as polystyrene resin or polyethylene resin, urethane or rubber. It may be formed from a system soft material, a porous material, or the like.
[0021]
With the above configuration, as the vehicle exterior noise reduction structure of the present invention, the openings that are arranged adjacent to each other along the vehicle front-rear direction and that are covered by the sound absorbing material 30 are located on the vehicle inner side (the IN direction side in the figure). Are formed in the side mudguard 10.
[0022]
In addition, the outside noise reduction structure of the present invention is not limited to the side mud guard 10 having an L-shaped cross-section, but can be applied to a variety of cross-sectional side mud guards according to a given side mud guard attached to a vehicle. It is possible to provide.
[0023]
For example, as shown in FIG. 4 (A), a plurality of partition surfaces 15 are erected along the vehicle front-rear direction on the inner surface of a side mud guard 10 ′ having a semi-circular cross section to form a semi-circular (or elliptical) shape. It is also possible to form a plurality of sound absorbing cells 20 having a cross section of ()).
[0024]
Further, as shown in FIG. 4B, a second partition plate 15 is provided upright on the inner surface of the side mud guard 10 ″ having an L-shaped cross section in substantially the same direction as the bottom surface 14, and the side surface 12 and the second By partitioning the space defined by the partition plate 15 and the bottom surface 14 with the plurality of partition plates 16, it is also possible to form a plurality of U-shaped cross-section sound absorbing cells 20 having openings on the vehicle inner side.
[0025]
Next, the principle of sound absorption of the vehicle exterior noise reduction structure of the present invention will be described with reference to FIG. FIGS. 5A and 5B are schematic diagrams of the sound absorbing cell 20 viewed from the Y direction in FIG.
[0026]
Referring to FIG. 5A, when a sound wave having a wavelength λ enters the sound absorbing cell 20 substantially perpendicularly, a standing wave is formed in the sound absorbing cell 20 by combining the incident wave and the reflected wave. On the other hand, even when the sound wave of the wavelength λ enters the sound absorbing cell 20 from an oblique direction, the oblique incident angle of the sound wave is restricted by each partition plate 16 as shown in FIG. A standing wave is formed inside.
[0027]
This standing wave has an antinode at a position which is an odd multiple of 1/4 of the wavelength λ in the sound absorbing cell 20, and the particle velocity of the sound wave becomes maximum at the antinode. Therefore, if the sound absorbing material 30 is provided at the position where the particle velocity is maximum, and the sound wave passes through the sound absorbing material 30 at the position having the highest particle velocity, the sound wave can be attenuated most efficiently.
[0028]
For this purpose, the depth H of the sound absorbing cell 20 (the maximum thickness of the air layer in the sound absorbing cell 20) is set to 1/4 (or an odd number thereof) the wavelength λ of the sound wave to be absorbed. Further, the opening width A of the sound absorbing cell 20 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 20.
[0029]
As is apparent from the above sound absorbing principle, according to the vehicle exterior noise reduction structure of the present invention, the opening of the sound absorbing cell 20 is covered by utilizing the fact that a standing wave is formed in the air layer in each sound absorbing cell 20. Efficient sound attenuation can be realized by the sound absorbing material 30. In addition, since the vehicle exterior noise reduction structure according to the present invention is disposed at the lower end of the side surface of the vehicle body 2, sound radiated from the engine room toward the vehicle side or obliquely rearward can be efficiently attenuated. In particular, since the sound radiated from the engine room toward the side of the vehicle greatly contributes to the actual outside noise as described above, the reduction of the outside noise by efficiently attenuating the sound is described. The effect is very large.
[0030]
Next, another embodiment of the vehicle exterior noise reduction structure of the present invention will be described. The side mudguard 10 of the present embodiment has the same configuration as the side mudguard 10 of the above-described embodiment except that the side mudguard 10 does not include the sound absorbing material 30. Accordingly, in the present embodiment, the plurality of spaces 20 arranged along the vehicle front-rear direction have openings not covered by the sound absorbing material 30 on the vehicle inner side. The space 20 corresponds to the sound absorbing cell 20 of the above-described embodiment, but is not covered with the sound absorbing material 30, and is simply referred to as “cell 20” in this embodiment.
[0031]
The external noise reduction structure of the present embodiment does not use the sound absorbing cell 20 to absorb the sound radiated from the engine room toward the side of the vehicle as in the above-described embodiment, but will be described in detail below. In addition, noise reduction outside the vehicle is realized by utilizing sound interference.
[0032]
FIG. 6 is an explanatory diagram of the sound reduction principle of the vehicle exterior noise reduction structure of the present embodiment. As shown in the figure, the engine sound radiated toward the vehicle side or obliquely rearward is directly output to the outside of the vehicle through the direct path R1 and the bottom surface of the side mudguard 10 after entering into each cell 20. The light is output to the outside of the vehicle through any one of the detour routes R2 diffracted at the edge portion 14 and output to the outside of the vehicle. Accordingly, at the junction X of these two paths, interference of the sound waves passing through the respective paths occurs, so that the sound waves passing directly through the path R1 at the junction X can be attenuated.
[0033]
In the vehicle exterior noise reduction structure of this embodiment, since each cell 20 is partitioned by the partition plate 16 in the vehicle longitudinal direction at a predetermined interval A (see FIG. 5A) as described above, Is prevented from propagating in the front-rear direction of the vehicle. This limits the range in which the route length of the detour route R2 can be set. Therefore, by appropriately setting the interval D between the cells 20, the range in which the route difference between the direct route R1 and the detour route R2 can be set. Can be defined according to the frequency band to be reduced. In this embodiment, since the interval A between the cells 20 is set to be smaller than the wavelength λ of the sound wave in the frequency band to be reduced as described above, it is possible to obtain a good reduction effect in the frequency band. It is possible.
[0034]
Further, in the vehicle exterior noise reduction structure of this embodiment, the depth H of the cell 20 is set to １ ／ times the wavelength λ of the sound having the frequency to be reduced as described above. That is, the path difference between the direct path R1 and the detour path R2 is defined to be 倍 times the wavelength λ of the sound to be reduced. Therefore, the sound wave of the frequency to be reduced passing through the bypass route R2 has an opposite phase to the sound wave of the frequency passing through the direct route R1 (the phase difference becomes 180 degrees), so that the sound wave passing through the direct route R1 is completely completed. Attenuation (that is, silencing by synthesis with a sound wave passing through the detour route R2) can be realized. Therefore, according to the vehicle exterior noise reduction structure of this embodiment, vehicle exterior noise can be significantly reduced by utilizing sound interference.
[0035]
Although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the present invention. Can be added.
[0036]
For example, in the above description, the application example of the external noise reduction structure of the present invention to the side mudguard is mentioned. However, the present invention is not particularly limited to this, and the fender provided to cover the wheel house (particularly, It is also applicable to an over fender that easily forms a thick air layer in the vehicle width direction. In addition, the term “side mudguard” used in the present specification includes so-called aero parts such as side skirts selectively provided to improve design and aerodynamic characteristics.
[0037]
Further, in the above-described embodiment, all the sound absorbing cells 20 do not necessarily have to have the same depth H (see FIG. 5), but have various depths to absorb noise in a wide frequency band. Is also good. Further, all the sound absorbing cells 20 do not necessarily have to have the same opening width A (see FIG. 5), and may have different opening widths according to the difference in the wavelength of the noise to be reduced as described above. Further, each of the sound absorbing cells 20 does not necessarily have to have openings directed in the same direction, and may have openings directed in various directions in consideration of the position of the sound source and the like.
[0038]
Further, when the lower end position of the side mudguard 10 is restricted by various conditions, and the lower end of the rocker portion 4 is located substantially at the same position as the bottom surface 14 of the side mudguard 10, as shown in FIG. It is also possible to use a slight space portion 18 formed by the rising portion of the vehicle and the bottom surface 14 of the side mudguard 10 as a vehicle exterior noise reduction structure.
[0039]
For example, as shown in FIG. 8, a separate outside noise reduction device 70 that can be accommodated in the space 18 (see FIG. 7) can be provided on the bottom surface 14 of the side mudguard 10. The external noise reduction device 70 has a space 72 having a substantially fan-shaped cross section having an opening on the vehicle inner side (in the figure, the IN direction side). A partition plate 16 is provided. The sound absorbing material 30 is provided so as to cover the opening of the space 72.
[0040]
The outside noise reduction device 70 may be fixed to the bottom surface 14 of the side mudguard 10 with an adhesive tape or the like, or may be fixed with a screw or a screw. The outside noise reduction device 70 may be provided over the entire length of the side mudguard 10 in the longitudinal direction (vehicle front-rear direction), similarly to the above-described embodiment, but may be provided in a predetermined range on the front side of the vehicle body (for example, the front door). May be provided only in the range corresponding to.
[0041]
With the above configuration, a plurality of sound absorbing cells 20 having an opening covered by the sound absorbing material 30 on the vehicle inner side (the IN direction side in the figure) are formed in the side mudguard 10 shown in FIG. In such a case, similarly to the above-described embodiment, the sound absorbing material 30 may not be provided in order to reduce the noise outside the vehicle by using the interference of sound.
[0042]
【The invention's effect】
Since the present invention is as described above, the following effects can be obtained. According to the present invention, the noise radiated from the engine room toward the vehicle side or obliquely rearward can be efficiently absorbed by the sound absorbing material having the air layer behind. In particular, since the sound radiated from the engine room toward the side of the vehicle or the like greatly affects the actual outside noise, the effect of reducing the outside noise by reducing the sound becomes very large. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a lower end of a side surface of a vehicle body provided with a vehicle exterior noise reduction structure of the present invention.
FIG. 2 is a perspective view of a side mud guard provided with the vehicle exterior noise reduction structure of the present invention.
FIG. 3 is a cross-sectional view of the side mudguard of FIG. 2 as viewed from the vehicle front-rear direction.
FIG. 4 is a view showing an alternative embodiment of the vehicle exterior noise reduction structure of the present invention.
FIG. 5 is an explanatory diagram of a sound absorbing principle of the vehicle exterior noise reduction structure of the present invention.
FIG. 6 is an explanatory diagram of the sound reduction principle of the vehicle exterior noise reduction structure of the present invention.
FIG. 7 is an explanatory diagram of an installation space of an outside noise reduction structure near a locker portion of a vehicle body.
FIG. 8 is a view showing an alternative embodiment of the vehicle exterior noise reduction structure of the present invention.
FIG. 9 is an explanatory diagram of a method of measuring noise outside the vehicle.
[Explanation of symbols]
2 Body 4 Rocker 6 Clip 10 Side mud guard 11 Groove 12 for side mud guard 12 Side 14 of side mud guard 14 Bottom 15 of side mud guard Second partition 16 Partition 16a Partition plate edge 20 Sound absorbing cell (cell)
30 Sound absorbing material R1 Direct route R2 Detour route

Claims (4)

An external noise reduction structure provided at a lower end of a side surface of a vehicle body,
A plurality of spaces arranged along the vehicle front-rear direction and having openings only on the vehicle inner side,
And a sound absorbing material covering openings of the plurality of spaces. An external noise reduction structure provided at a lower end of a side surface of a vehicle body,
Partition plates arranged along the vehicle longitudinal direction,
A vehicle exterior noise reduction structure, comprising: a plurality of spaces that are separated from each other in the vehicle front-rear direction by the partition plate and that have openings only on the vehicle inner side. 3. The external noise reduction structure according to claim 1, wherein a maximum thickness of the air layer in the space is set to an odd multiple of １ ／ wavelength of noise at a frequency to be reduced. 4. A side mud guard comprising the vehicle exterior noise reduction structure according to claim 1.

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