JPH08260589A - Sound absorbing member - Google Patents

Abstract

PURPOSE: To reduce manufacturing man-hours and reduce the cost by concurrently generating many resonance chambers each constituted of a guide passage opened on one face of a soft porous foam body and a hollow section formed at the depth of the guide passage and having a cross sectional area larger than that of the guide passage. CONSTITUTION: A urethane foam material is injected into the cavity of a molding die to mold a urethane foam body having many resonance chambers 1 each constituted of a guide passage 11 opened on one face and a hollow section 12 having a cross sectional area larger than that of the guide passage 11 at the depth. This urethane foam body is fitted to the wall face of the engine room of a vehicle so that the opening faces of the guide passages 11 are faced to the engine. The noises generated from the engine are absorbed by this sound absorbing member itself, the noises entering into the resonance chambers 1 from the guide passages 11 are resonated and absorbed in the resonance chambers 1 tuned to the prescribed frequency. The porous foam body having many resonance chambers 1 can be simply manufactured in one molding process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing member having a resonance type sound absorbing structure for absorbing air transmitted sound.

[0002]

2. Description of the Related Art Conventionally, various types of sound absorbing members for absorbing noise have been used in vehicles equipped with an engine that generates noise. As such a sound absorbing member,
For example, in Japanese Utility Model Application Laid-Open No. 63-34775, a panel forming a vehicle interior is composed of two panels, and a honeycomb structure member is sandwiched and fixed between the two panels to form a composite panel. There is disclosed a vehicle interior forming panel having a resonance-type sound absorbing structure in which a space portion formed by a honeycomb structure member is opened to the outside by configuring the panel as a perforated plate.

Further, in Japanese Patent Laid-Open No. 4-225398, there is a panel shape in which a large number of recesses for partitioning a Hertzholm resonator having various resonance frequencies are formed on the back surface side, and each recess has a hole opening to the front surface side. Of the molded article, wherein a large number of Hertzholm resonators are formed between the molded article and the mounting wall by mounting the front surface side of the molded article on the mounting wall surface.

In such a resonance type sound absorbing structure, as shown in FIG. 6, the cross-sectional area of the introduction passage (hole, hole) 51 is S, the length of the introduction passage 51 is L, and the volume of the hollow portion 52. To V,
Resonance frequency fn in air, where C is the speed of sound in air
Is calculated by the following (Equation 1) and (Equation 2), and the target resonance frequency is tuned by this. fn = (C / 2π) · √ (μ / V) (Equation 1) μ = S / (L + 0.8√S) (Equation 2)

[0005]

However, since the resonance type sound absorbing member disclosed in the above publication is constructed by combining a plurality of parts such as a panel, the number of manufacturing steps is increased and the cost is increased. There's a problem. Further, when tuning to several different resonance frequencies, it is necessary to change the size of each resonance chamber according to each resonance frequency, which further complicates the structure and complicates the manufacturing process.

The present invention has been devised in view of the above problems, and an object of the present invention is to provide a sound absorbing member which has a small number of manufacturing steps and can be manufactured at low cost.

[0007]

The sound absorbing member of the present invention for solving the above-mentioned problems is made of a flexible porous foam formed by foam molding, and has an introduction passage opening on one surface and a depth of the introduction passage. It is characterized in that it has a large number of resonance chambers each formed by a hollow portion having a larger cross-sectional area than the introduction passage.

The porous foam in the present invention is, for example, an elastomer foam such as urethane or rubber or polyethylene,
It can be formed by using a soft resin foam such as vinyl chloride. According to a preferred aspect of the present invention, one surface of the sound absorbing member is formed in a concavo-convex shape, and the introduction passage of the resonance chamber is open to the convex portion of the one surface.

As another preferred embodiment, a portion of the wall surface of the hollow portion that is connected to the introduction passage has a tapered surface or a curved surface.

[0010]

Since the sound absorbing member of the present invention is made of a flexible porous foam body formed by foam molding, a resonance chamber having a hollow portion having a larger cross-sectional area than the introduction passage is formed in the depth of the introduction passage. By pulling out the mold from the introduction passage by utilizing the elasticity of the porous foam, a large number of resonance chambers are simultaneously formed during the molding of the porous foam. Therefore, since it can be easily manufactured by one molding step, the number of manufacturing steps and the cost are significantly reduced. Further, since the size of each resonance chamber is determined by the size of the mold forming each resonance chamber, it is easy to tune the target resonance frequency.

Further, the sound absorbing member of the present invention effectively absorbs noise by the resonance chamber formed according to the frequency for the purpose of reduction, and the porous foam itself exerts a good sound absorbing action. Then, if one surface of the sound absorbing member is formed in a concavo-convex shape and the introduction passage is opened to the convex portion of the one surface, the surface area of that surface increases and the sound absorbing effect of the sound absorbing member itself is increased. At the same time, the peripheral wall portion of the introduction passage is easily elastically deformed, and the die can be easily removed from the introduction passage. As a result, the volume of the hollow portion can be made larger, the frequency range that can be tuned is expanded, and the sound absorbing action thereof is improved.

Further, if the portion of the wall surface of the hollow portion which is connected to the introduction passage has a tapered surface or a curved surface, the hollow portion forming the medium-sized hollow portion forming the resonance chamber is smoothly moved along the tapered surface or the curved surface. Since it is guided to the introduction passage, the die cutting becomes easy.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a perspective view of a sound absorbing member according to this embodiment, and FIG. 2 is a sectional view taken along the line II-II of FIG.

As shown in FIGS. 1 and 2, the sound absorbing member of this embodiment is made of urethane foam formed into a thick plate by foaming urethane with a foaming ratio of about 10 times. It has a large number of resonance chambers 1 having different volumes opened on a surface (a surface arranged to face a sound source). Each resonance chamber 1 is composed of an introduction passage 11 that opens to one surface and a hollow portion 12 that is formed at the back of the introduction passage 11 and has a larger cross-sectional area than the introduction passage 11. A portion of the wall surface of the hollow portion 12 that is connected to the introduction passage 11 has a tapered surface 13 so that the die can be easily removed. Each resonance chamber 1 has an introduction passage 11
Based on the cross-sectional area and the length thereof and the volume of the hollow portion 12, the resonance frequencies for reduction are respectively tuned by the above-mentioned (Equation 1) and (Equation 2).

The sound absorbing member of this embodiment is manufactured as follows. First, a mold used for foam molding of the sound absorbing member is prepared. On one mold surface of this molding die, a protrusion-shaped middle die having a shape corresponding to each resonance chamber 1 to be formed and having a large cross-sectional area at the tip is provided. Next, a urethane foam material prepared by blending a predetermined amount of urethane and a foaming agent is injected into the cavity of the molding die for foam molding.
As a result, a urethane foam having a large number of resonance chambers 1 in the cavity is formed of an introduction passage 11 opening to one surface and a hollow portion 12 formed at the back of the introduction passage 11 and having a cross-sectional area larger than that of the introduction passage 11. Is formed. Then, the formed urethane foam is taken out from the molding die, and the production of the sound absorbing member is completed.

During the die-cutting, the hollow portion of the middle die forming each resonance chamber 1 is pulled out from the introduction passage 11 by utilizing the elasticity of urethane foam. At this time, since the tapered surface 13 is formed in the portion of the wall surface of the hollow portion 12 that is connected to the introduction passage 11, the medium-sized hollow portion forming portion is smoothly guided to the introduction passage 11 along the tapered surface 13. And easily extracted.

The sound absorbing member of this embodiment constructed as described above is attached to, for example, the wall surface of the engine room of the vehicle such that the open surface of the introduction passage 11 faces the engine. As a result, the noise generated from the engine is absorbed by the sound absorbing member itself, and the noise that has entered the resonance chamber 12 from the introduction passage 11 is absorbed while resonating in the resonance chamber 12 tuned to a predetermined frequency. .

As described above, according to the sound absorbing member of the present embodiment, since it is composed of the flexible porous foam having a large number of resonance chambers 1 and formed by foam molding, it can be formed by one molding step. It can be easily manufactured. As a result, the number of manufacturing steps can be reduced and the cost can be reduced. Further, the sound absorbing member of the present embodiment has the introduction passage 11 on the wall surface of the hollow portion 12.
Since the tapered surface 13 is provided at the portion connected to the resonance chamber 1,
Since the hollow portion forming portion of the middle die forming the is smoothly guided to the introduction passage 11 along the tapered surface 13, the die can be easily removed. The tapered surface 13
May be a curved surface.

Although the sound absorbing member of this embodiment is made of a porous foam alone, it can be integrally formed with a sound insulating plate such as an iron plate mounted on the back surface of the sound absorbing member. . [Embodiment 2] FIG. 3 is a perspective view of a sound absorbing member according to the present embodiment, and FIG. 4 is a sectional view taken along the line IV-IV in FIG.

The sound absorbing member of this embodiment is basically the same as that of the above-mentioned first embodiment, except that one surface (the surface facing the sound source) is formed in an uneven shape, The difference is that the two introduction passages 21 are configured to open to the convex portion on one surface thereof. That is, rectangular block-shaped convex portions 25 of various sizes are formed on one surface of the sound absorbing member at appropriate intervals, and the introduction passage 21 of each resonance chamber 2 is formed.
Has an opening on the top surface of the convex portion 25.

Since the surface area of the surface of the sound absorbing member facing the sound source is increased, the sound absorbing function of the sound absorbing member itself is increased and the sound absorbing property is improved. In addition, the introduction passage 2
Since the peripheral wall portion of No. 1 is easily elastically deformed, the die can be easily removed from the introduction passage 21. As a result, the volume of the hollow portion 22 can be increased, so that the range of tunable frequencies can be expanded and the sound absorbing action can be increased.

In the present embodiment, one surface is formed in a concavo-convex shape by providing the rectangular block-shaped convex portion 25. However, as shown in FIG. 5, for example, one surface is formed in a corrugated concavo-convex shape. Alternatively, the introduction passage 31 of the resonance chamber 3 may be opened at the top surface of the convex portion 35.

[0023]

The sound absorbing member of the present invention is made of a flexible porous foam formed by foam molding, and has an introduction passage opening to one surface and a larger passage than the introduction passage formed deep inside the introduction passage. Since it has a large number of resonance chambers each including a hollow portion having a cross-sectional area, it can be easily manufactured by one molding step, and the number of manufacturing steps can be reduced and the cost can be reduced.

Further, the sound absorbing member of the present invention can effectively absorb the noise of the target frequency in the resonance chamber, and the porous foam itself can absorb the noise satisfactorily. Excellent in. If one surface of the sound absorbing member is formed in a concavo-convex shape and the introduction passage is opened to the convex portion of the one surface, the surface area of that surface is increased, so that the sound absorbing property of the sound absorbing member itself is increased. In addition, since the peripheral wall portion of the introduction passage is easily elastically deformed, it is possible to easily remove the mold from the introduction passage.
In addition, since the volume of the hollow portion can be increased, the range of tunable frequencies can be expanded and its sound absorption can be increased.

Further, if the portion of the wall surface of the hollow portion which is connected to the introduction passage is formed into a tapered surface or a curved surface, it is possible to facilitate the die cutting of the middle die forming the resonance chamber.

[Brief description of drawings]

FIG. 1 is a perspective view of a sound absorbing member according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a perspective view of a sound absorbing member according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is a sectional view of a sound absorbing member according to a modified example of the second embodiment of the present invention.

FIG. 6 is an explanatory diagram schematically showing the structure of a resonance-type sound absorber.

[Explanation of symbols]

1, 2, 3 ... Resonance chamber 11, 21, 31, 51 ... Introducing passage 12, 22, 52 ... Hollow part 13 ... Tapered surface 2
5, 35 ... convex portion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B62D 29/04 B62D 29/04 A F16S 1/00 F16S 1/00 G10K 11/172 G10K 11/16 E

Claims (3)

[Claims] 1. An introduction passage which is made of a flexible porous foam formed by foam molding and has an introduction passage opening to one surface and a hollow portion formed at the back of the introduction passage and having a larger cross-sectional area than the introduction passage. A sound absorbing member having a large number of resonance chambers. 2. The one surface is formed in a concavo-convex shape, and the introduction passage is opened to a convex portion of the one surface.
The sound absorbing member described. 3. The sound absorbing member according to claim 1, wherein the wall surface of the hollow portion has a tapered surface or a curved surface at a portion connected to the introduction passage.