JPH10226283A - Cab noise reduction device of car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide CAB noise reduction device, which can be installed on a wall face of relatively small space and can reduce noise of low frequency of about 50Hz and 1kHz. SOLUTION: A cab noise reduction device comprising a muffler body 1, which can reduce noise of about 1kHz of frequency by resonant work or the like and an edge damper 2 made from an elastic member supporting the peripheral edge of the muffler body 1 is secured in an opening 8 in the side of a roof panel 5 of a cabin. The edge damper 2 has an effect to reduce the sound waves of about 50kHz by resonance. The noise in car can be substantially reduced by the resonance mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a noise reduction device for reducing noise in a passenger compartment, and more particularly to a noise reduction device capable of reducing low frequency noise of 50 Hz or less and noise of approximately 1 KHz. The present invention relates to an in-vehicle noise reduction device.

[0002]

2. Description of the Related Art Conventionally, various means have been adopted for reducing noise in a room such as a vehicle room. For example, actual Kaihei 2
JP-A-115049, JP-A-4-118839, JP-A-4-10612 and the like. Japanese Unexamined Utility Model Publication No. 2-15049 discloses a "molded ceiling" relating to a ceiling lining of a vehicle. The ceiling lining includes a base formed of a thermoplastic resin in a box shape, and a sound absorbing hole formed in a member of the base in a cabin. It has what has. The noise is resonantly absorbed by the base and the sound absorbing hole.

Japanese Unexamined Utility Model Publication No. 4-118839 discloses a "molded ceiling for a vehicle" which includes a ceiling base material in which a small hole for sound absorption is formed and a skin material is joined to the surface side thereof, and a back surface on the back side of the ceiling base material. A film is provided, and an insulator is laminated between the back film and the back side of the ceiling base material.

The "sound absorbing and insulating plate" disclosed in Japanese Utility Model Laid-Open No. 4-10612 is a sound absorbing plate formed by cutting a small piece of aluminum into a flat plate with a binder, a honeycomb-shaped flat member laminated on the sound absorbing plate, and It has a laminated structure with a metal flat plate stacked on them.

[0005]

Each of the above-mentioned known techniques is as follows.
Each has characteristics. However, Japanese Unexamined Utility Model Application Publication No. 2-15049, "molded ceiling" mainly reduces noise by a resonance effect, and cannot reduce low-frequency noise of 50 Hz or less. On the other hand, the cabin noise is 5
Those with a low frequency of 0 Hz or less have high discomfort. In addition, although the "molded ceiling for vehicles" in Japanese Utility Model Application Laid-Open No. 4-1188839 has a sound absorbing effect, it does not have a resonance function effective for reducing low-frequency noise and does not have a resonance function. Noise of about 1 KHz cannot be reduced.
Also, the “sound absorbing and insulating plate” in Japanese Utility Model Laid-Open No. 4-10612,
It has a noise reduction function due to resonance as in the above-mentioned Japanese Utility Model Application Laid-Open No. 2-15049, and it is difficult to reduce low-frequency noise of about 50 Hz. Also, its resonance function does not bring about a reliable Helmholtz resonance effect, and there is a problem that the noise reduction rate is low.

The present invention has been made in view of the above circumstances, and it is possible to reduce noise at a low frequency of about 50 Hz by resonance and also to significantly reduce noise at a frequency of about 1 KHz. It is an object of the present invention to provide an in-vehicle noise reduction device which has a relatively lightweight and simple structure and is easily mounted.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to an in-vehicle noise reduction device provided on a wall surface for reducing noise in the wall surface by resonance and resonance action. The noise reduction device constitutes an in-vehicle noise reduction device including a silencer having a sound absorbing structure, and an edge damper provided between the periphery of the silencer and the wall surface side to elastically support the silencer. Further, the muffler is characterized by comprising a number of sealed air chambers and small holes communicating with the sealed air chambers and opening. Further, the closed air chamber is arranged in a honeycomb shape,
The plate material constituting the honeycomb-shaped silencer is made of a sound absorbing material or a material having a sound absorbing material.

In the vehicle interior noise reduction device of the present invention, for example, by forming the silencer from a sound absorbing structure having a Helmholtz function, noise of about 1 KHz can be reduced by a resonance action. On the other hand, since the silencer is supported by the edge damper, low-frequency noise of 50 Hz or less can be reduced by the resonance phenomenon. By arranging the silencers in a honeycomb shape and forming the plate material with a sound absorbing material or the like, a greater noise reduction effect can be achieved.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a vehicle interior noise reduction apparatus according to the present invention. FIG. 1 shows an overall schematic structure of an in-vehicle noise reduction device of the present invention applied to a vehicle interior. The roof panel 5 holding the front window glass 4 forms one wall surface in the vehicle interior. A roof inner panel 7 is provided inside the roof panel 5 via a cavity 6. In this example, an opening 8 is formed at the center of the roof inner panel 7, and the in-vehicle noise reduction device of the present invention is mounted on the opening 8 to reduce the noise in the vehicle interior.

The in-vehicle noise reduction device of the present invention is roughly divided into a muffler 1, an edge damper 2, and a guide plate 3 for fixing the edge damper 2 to the opening 8. Also, as shown in FIG. 1, low-frequency noise (referred to as low-frequency sound) travels from various directions toward the roof panel 5 from the vehicle interior, as shown by arrows, for example, and a low-frequency sound wavefront 9. To form

FIGS. 2 and 3 show the detailed structure of each component of the in-vehicle noise reduction apparatus according to the present invention and the related state of each component. In this example, the silencer 1 includes a large number of closed air chambers 10.
Are arranged in a honeycomb shape. 3 and 4
As shown in FIG. 1, the closed air chamber 10 is composed of a closed chamber surrounded by an upper wall 11, a lower wall 12, and a partition 13. A small hole 14 is formed in the lower wall 12 so as to communicate with the inside. Further, in this example, a skin material 15 made of a resin material having air permeability is attached to the lower wall 12 in order to improve the appearance. Note that the skin material 15 may not be provided. Further, in this example, the plate material such as the upper wall 11, the lower wall 12, and the partition 13 constituting the closed air chamber 10 is formed of a resin material or a metal sheet, but the plate material itself has a known sound absorbing characteristic. It is desirable to be formed from a material.

Next, the noise reduction effect of the silencer 1 will be described. As described above, since the silencer 1 includes the closed air chamber 10 having an appropriate volume and the small hole 14 communicating with the silencer, a so-called Helmholtz sound reducing effect is generated. By forming each component of the silencer 1 so that the resonance frequency of the silencer 1 corresponds to a noise having a frequency of about 1 KHz, effective noise reduction can be achieved.

The following equation is a theoretical equation for obtaining the resonance frequency f ₀ in general Helmholtz action. f ₀ = C / 2π × [P / (t′L + PL ^2/3 )] ^1/2 (1) In the above equation (1), C is a sound velocity, P = s / S, (s
Is the area of the small hole 14, as shown in FIG. 4, s = π / 4 · d ²
And S is the area corresponding to one small hole. Also,
d is the diameter of the small hole 14. ) T '= t + 0.8d (t
Is the thickness of the lower wall 12 as shown in FIG. 4, and L is the distance between the upper wall 11 and the lower wall 12 (that is, the thickness of the back air layer).
It is.

As shown in FIGS. 1 to 3, the edge damper 2
Has one end fixed to the periphery of the silencer 1 and the other end fixed to the guide plate 3, and the intermediate portion is formed in a flexible shape. The edge damper 2 is provided so as to surround the muffling body 1. As the material, for example, resin, silicone rubber,
It is made of cloth, metal, etc., and has a shape that can be vibrated by sound waves. In the drawing, the intermediate portion has a bent shape, but is not limited to this. As shown in FIG. 1, the low-frequency sound collected on the wavefront 9 is reduced by the resonance action of the silencer 1 as described above, but hits the entire silencer 1 and flaps the edge damper 2. This causes the entire vehicle interior noise reduction device to vibrate. By adjusting the stiffness determined by the mass of the silencer 1 and the shape, material, and the like of the edge damper 2, it is possible to generate a resonance action for a low-frequency sound wave of, for example, about 50 Hz. That is, the low-frequency noise of about 50 Hz can be reduced by the resonance of the in-vehicle noise reduction device by the edge damper 2. Note that the resonance frequency f ₀ is obtained by f ₀ = ^1/2 · π · (S ₀ / m ₀ ) ^1/2 . Here, S ₀ is the stiffness of the edge damper 2 and m ₀ is the weight of the muffler 1.

As described above, the in-vehicle noise reduction device of the present invention can reduce low frequency sound waves of about 50 Hz and sound waves of about 1 KHz. Thereby, a significant noise reduction effect can be obtained. In addition, since the interior noise reduction device of the present invention is set in the opening 8 and is disposed through the cavity 6 with the roof panel 5 side, there is no adverse effect on the roof panel 5 side. In addition, even if it is arranged in the opening 8 having a relatively small area, a large noise reduction effect can be achieved.

In the above description, the silencer 1 is constituted by the honeycomb-shaped closed air chamber 10 and the small holes 14 communicating with the same. However, the honeycomb-shaped silencer 1 is made of resin, compression felt, metal or other plate material and urethane. A material obtained by combining a sound absorbing material such as glass wool and the like may be used. Further, other noise reduction means capable of absorbing a sound wave having a frequency of about 1 KHz may be used. Further, in this example, the case where the device is disposed on the inner wall of the vehicle interior on the side of the roof panel 5 has been described, but the installation location is not limited to the above. It has been demonstrated that the noise reduction device of the embodiment described above significantly reduced the noise when the engine was rotating at a rotational speed of about 1500 rpm. When the target frequency range due to the resonance silencing is expanded, a plurality of small holes 14 having different areas or a plurality of closed air chambers 10 having different volumes may be prepared and appropriately selected and arranged. Of course, both may be combined. Further, the shape of the closed air chamber 10 is not limited to the honeycomb shape.

[0017]

【The invention's effect】

1) According to the in-vehicle noise reduction device of the first aspect of the present invention, the noise of a frequency of about 1 KHz and the noise of a low frequency of about 50 Hz are resonated by the silencer having the sound absorbing structure and the edge damper supporting the same. It can be greatly reduced by the resonance action. In addition, since the edge of the muffler is supported by the edge damper, the muffler can be installed in a relatively small area. 2) According to the in-vehicle noise reduction device of the second aspect of the present invention, since the silencer is formed of the closed air chamber and the small hole communicating therewith, the noise of the frequency of about 1 KHz is surely generated by the resonance action. Can be reduced. 3) According to the in-vehicle noise reduction device of the third aspect of the present invention, since the muffler is formed from a closed air chamber arranged in a honeycomb shape, the installation space can be reduced and the space can be saved. Is raised. 4) According to the in-vehicle noise reduction device of the fourth aspect of the present invention, since the plate material of the closed air chamber of the muffler formed of the closed air chamber is formed of a sound absorbing body or the like having a noise reducing effect, Further, a significant noise reduction effect can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall structure of an embodiment of a vehicle interior noise reduction device of the present invention.

FIG. 2 is a plan view showing the overall structure of a vehicle interior noise reduction device having a honeycomb type silencer.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is an enlarged partial sectional view of the closed air chamber in FIG. 3;

[Description of Signs] 1 muffler 2 edge damper 3 guide plate 5 roof panel 6 cavity 7 roof inner panel 8 opening 9 wavefront 10 closed air chamber 11 upper wall 12 lower wall 13 partition 14 small hole 15 skin material

Claims (4)

[Claims] An in-vehicle noise reduction device provided on a wall surface for reducing noise in the wall surface by resonance and resonance action, wherein the in-vehicle noise reduction device includes a muffler having a sound absorbing structure, and a muffler having a sound absorbing structure. An in-vehicle noise reduction device comprising: an edge damper erected between a peripheral edge and the wall surface side to elastically support the muffler. 2. The muffler includes a plurality of closed air chambers,
2. The vehicle interior noise reduction device according to claim 1, further comprising a small hole communicating with the closed air chamber and opening. 3. The vehicle interior noise reduction device according to claim 2, wherein the closed air chamber is provided in a honeycomb shape. 4. The in-vehicle noise reduction device according to claim 1, wherein the plate material constituting the honeycomb-shaped muffler is made of a sound absorbing material or a material having a sound absorbing material.