JPWO2019021480A1 - Sound absorbing member, vehicle part, automobile, and method for manufacturing sound absorbing member - Google Patents

Abstract

A sound absorbing member having a Helmholtz resonance structure consisting of an introduction passage opening to the surface and a hollow portion connected to the outside through the introduction passage, which is made of a plate material having no communication hole formed by foaming, An upper layer provided with a columnar first through hole forming a passage, a lower layer laminated on the upper layer and provided with the hollow portion, and an adhesive layer for adhering the upper layer and the lower layer, And a compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) of 0.1 to 200 MPa in a portion of the sound absorbing member where the Helmholtz resonance structure is not formed. Sound absorbing member.

Description

The present invention relates to a sound absorbing member, a vehicle part, an automobile, and a method for manufacturing the sound absorbing member.

Vehicles such as automobiles are machines that have a power source such as an engine and can be moved by human operation, and generate various vibrations and noises. The sound transmitted to the inside of the vehicle includes not only the sound generated by the power source but also the noise generated outside the vehicle such as road noise, tire pattern noise, wind noise, etc. generated when the vehicle travels. . If these sounds are transmitted to the inside of the vehicle, it will be uncomfortable for humans.Therefore, sound insulation and sound absorbing members will be used in the engine, engine room, interior, body, and exhaust pipe area. Measures are being taken.

Further, with the technical improvement of automobiles, new soundproofing measures for automobiles are needed. For example, as one of the measures for improving the fuel efficiency of an automobile, lowering the center of gravity of the automobile and the minimum ground clearance are being considered. Lowering the center of gravity of the vehicle improves the stability and operability of the vehicle, and lowering the minimum ground clearance reduces air resistance. However, the lowering of the minimum ground clearance of the automobile increases the viscosity of the air flowing between the vehicle and the road surface during traveling. Then, the noise generated from the road surface during traveling, such as tire pattern noise (in the frequency range of 500 to 3000 Hz, which is also simply referred to as pattern noise), is less likely to be reflected and diffused around the underside of the vehicle body, and the degree of sound entering the vehicle Is estimated to be high. Similar problems can occur with electric vehicles.

Therefore, when the center of gravity and the minimum ground clearance of the vehicle are lowered in order to improve the fuel efficiency of the vehicle, it is assumed that the noise that was conventionally diffused outside the vehicle will be transmitted to the person in the vehicle. .. In particular, it is considered that these noises are likely to invade from the rear part of the vehicle and the bottom part of the lower part of the luggage room (underfloor space) where the accommodation space is arranged. Since these noises also include noises in the frequency range of 500 to 2000 Hz that make people uncomfortable, countermeasures are required.

In Patent Document 1, a surface layer having fine pores formed on the surface, a communication passage communicating with the fine pores, and a deeper inside than the surface layer are formed, and are larger than the volumes of the fine pores and the communication passages. There is disclosed a sound absorbing structure having a porous layer of acoustic voids having a volume, wherein a part of the acoustic voids communicates with the fine pores through the communication passage.

International Publication No. 2012/008225

Referring to paragraph [0032] of Patent Document 1, the sound absorbing characteristic structure disclosed in Patent Document 1 is obtained by heating and foaming a composition containing a synthetic resin as a main component and a foaming agent contained therein. It is supposed to be. Further, in the same paragraph, it is said to be a urethane resin foam structure having the surface state shown in FIG. 2 and the cross section shown in FIG.

Patent Document 1 [0037] describes that fine holes and acoustic holes are formed by the decomposition gas of the foaming agent, and the passage of the decomposition gas from the acoustic holes to the fine holes serves as a communication path. ing.

In the sound absorbing characteristic structure of Patent Document 1, the material of the sound absorbing member is manufactured by the manufacturing method in which the fine holes, the acoustic holes, and the communication paths are formed by the decomposition gas of the foaming agent. When mechanical processing such as drilling was performed on these materials in order to provide an opening having a Helmholtz resonance structure, a crack was generated in the sound absorbing member. The cause of the crack was judged to be the communicating hole formed by the foaming agent.
Therefore, it is necessary to manufacture the sound absorbing member having the Helmholtz resonance structure from a plate material that is formed by foaming and does not have a communication hole.
However, it has been confirmed that the plate material having no communication hole formed by foaming causes the secondary radiation sound due to the film vibration of the sound pressure to occur at 300 Hz or less.
Further, in the method of manufacturing the sound absorbing characteristic structure of Patent Document 1, it is not possible to control the positions and shapes of the fine holes and the acoustic holes to be constant. Further, there is a portion where the communication passage and the fine hole are not connected to the acoustic hole. Therefore, it is difficult to reliably achieve the predetermined sound absorption characteristics (sound absorption frequency, sound absorption coefficient).

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sound absorbing member that prevents generation of secondary radiation sound and surely achieves a predetermined sound absorbing characteristic.

The inventors of the present invention prepared a lower layer with a hollow portion separately formed as an upper layer by forming a through hole serving as an introduction passage for a plate material having no communication hole formed by foaming, and prepared with an adhesive layer. By adhering and stacking the upper layer and the lower layer, it has been possible to manufacture a sound absorbing member having a Helmholtz resonance structure including an introduction passage and a hollow portion. The present invention has been completed by finding that such a sound absorbing member can surely achieve a predetermined sound absorbing characteristic.

That is, the sound-absorbing member of the present invention is a sound-absorbing member having a Helmholtz resonance structure consisting of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage,
Made of a plate material that does not have continuous holes formed by foaming,
An upper layer provided with a columnar first through hole forming the introduction passage,
Laminated on the upper layer, a lower layer provided with the hollow portion,
An adhesive layer that adheres the upper layer and the lower layer,
In the portion of the sound absorbing member where the Helmholtz resonance structure is not formed, the compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) is 0.1 to 200 MPa.

A columnar first through hole is provided in advance in the upper layer. Since this is a through hole provided in a predetermined shape and a predetermined position with respect to the plate material, the position and the shape are as designed before the lamination. Controlled.
Further, the lower layer is also provided with a hollow portion in advance, and since this is also a hollow portion having a predetermined shape and provided at a predetermined position, its position and shape are controlled as designed before stacking.
By bonding the upper layer and the lower layer with an adhesive layer and stacking the upper layer and the lower layer, a Helmholtz resonance structure including an introduction passage and a hollow portion can be obtained as designed. Therefore, it is possible to efficiently absorb the sound of the predetermined frequency.

In addition, if a plate material that does not have open pores due to foaming is used to improve strength, the plate material vibrates during sound absorption and a secondary radiant sound is generated. However, by bonding the upper and lower layers with an adhesive layer, the vibration damping effect Occurs, and the influence of the secondary radiation sound can be reduced.

Further, the sound absorbing member having a compressive stress of 0.1 MPa or more prevents the vibration from propagating in the horizontal direction to generate radiated sound, and the compressive stress of 200 MPa or less causes the vibration to propagate in the thickness direction. As a result, the secondary radiation sound is prevented from being generated.

In the sound absorbing member of the present invention, it is preferable that the first through hole is a through hole formed by machining.
By forming through holes in a plate material having no communication holes by machining, cracking of the plate material can be prevented. Further, since the shape and position of the introduction passage can be accurately controlled by forming the through hole, it is possible to more reliably achieve a predetermined sound absorbing characteristic.

In the sound absorbing member of the present invention, the plate material forming the upper layer is preferably made of resin.
Further, the resin is preferably a foamed resin.
When the plate material constituting the upper layer is made of resin, it is easy to reduce the weight, which is particularly desirable as a vehicle part.
Further, when the resin is a foamed resin, the weight thereof can be further reduced, which can contribute to the improvement of fuel consumption when used as a vehicle component.
In the present invention, the plate material constituting the upper layer may be a composite material of resin and fiber. As a composite method, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

In the sound absorbing member of the present invention, the lower layer is a side surface layer formed by providing a plate-like second through hole having an opening diameter larger than that of the first through hole in a plate material having no communication hole formed by foaming. ,
It is preferable that a bottom layer made of a plate material and not provided with a through hole is sequentially laminated, and the hollow portion is formed by the second through hole and the bottom layer.
With such a structure, the sound absorbing member of the present invention can be easily manufactured by sequentially stacking the upper layer, the side surface layer, and the bottom surface layer.
Further, by determining the position and shape of the second through hole, the position and shape of the hollow portion can be controlled as designed before stacking.

In the sound absorbing member of the present invention, the second through hole is preferably a through hole formed by machining.
By forming through holes in a plate material having no communication holes by machining, cracking of the plate material can be prevented. Further, by forming the through hole, the shape and position of the hollow portion can be accurately controlled, so that a predetermined sound absorbing characteristic can be achieved more reliably.

In the sound absorbing member of the present invention, it is preferable that the plate materials forming the side surface layer and the bottom surface layer are made of resin.
Further, the resin is preferably a foamed resin.
It is particularly desirable as a vehicle component when the plate material forming the side surface layer and the bottom surface layer is made of resin because weight reduction is easy.
Further, when the resin is a foamed resin, the weight thereof can be further reduced, which can contribute to the improvement of fuel consumption when used as a vehicle component.
In the present invention, the plate material forming the side surface layer and the bottom surface layer may be a composite material of resin and fiber. As a composite method, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

In the sound absorbing member of the present invention, a fiber layer is further formed on the surface of the plate material forming the upper layer on the opening forming side,
It is preferable that an opening communicating with the opening of the introduction passage is formed in the fiber layer.
When the sound absorbing member has the Helmholtz resonance structure, it can absorb sound in a predetermined frequency range, but the width of the frequency range that can be absorbed is not wide, and in particular, it is difficult to sufficiently absorb sound in a high frequency range of 2000 Hz or higher. ..
However, when the fiber layer is formed, it is possible to absorb the sound in the high frequency region of 2000 Hz or higher.

The vehicle component of the present invention is characterized by including the sound absorbing member of the present invention.
Since the sound absorbing member of the present invention has excellent soundproofing performance, it is excellent as a vehicle part.
Examples of vehicle parts provided with the sound absorbing member of the present invention include a raising member, a partition member, and a luggage box.

An automobile of the present invention is characterized in that the introduction passage of the sound absorbing member of the present invention is arranged so as to face the road surface.
By disposing the sound absorbing member of the present invention in such a direction, it is possible to absorb the noise of tire pattern noise transmitted from the road surface and prevent the noise from being transmitted to the inside of the vehicle.

One aspect of a method for manufacturing a sound absorbing member of the present invention is a method for manufacturing a sound absorbing member having a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage. ,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a lower layer which is a plate material having a hollow portion,
A step of adhering the upper layer and the lower layer with an adhesive layer,
The plate material constituting the upper layer is a plate material having no communication hole formed by foaming.

By using a plate material which does not have a communication hole formed by foaming as the plate material forming the upper layer, the strength of the plate material is sufficient, which is suitable for forming the first through hole. Further, since the influence of the secondary radiated sound can be reduced by adhering the upper layer and the lower layer as described above, the generation of the secondary radiated sound can be prevented and a predetermined sound absorbing characteristic can be achieved reliably. A sound absorbing member can be provided.

In one aspect of the method for manufacturing the sound absorbing member of the present invention, it is preferable that the upper layer is formed by forming the first through hole by machining on a plate material having no through hole.
Since the plate material having no communication hole formed by foaming is used as the upper layer material, the strength of the plate material is sufficient, and it is possible to prevent breakage when the first through hole is formed by machining.

In one aspect of the method for manufacturing a sound absorbing member of the present invention, a lower layer is produced by forming a hollow portion by machining to a plate material having no through hole up to the middle of its thickness direction. Preferably.
It is preferable to form the hollow portion by machining to control the position and shape of the hollow portion.

Another aspect of the method for manufacturing a sound absorbing member of the present invention is a method for manufacturing a sound absorbing member having a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage. ,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a side surface layer which is a plate material having a second through hole,
A step of preparing a plate material to be a bottom layer,
A plate material to be an upper layer, a plate material to be a side surface layer, and a plate material to be a bottom surface layer are laminated to form a hollow portion by the second through hole and the bottom surface layer, and a lower layer composed of the side surface layer and the bottom surface layer is formed. And a step of adhering the lower layer with an adhesive layer,
The plate material forming the upper layer and the plate material forming the side surface layer are plate materials having no communication hole formed by foaming.

The use of a plate material that does not have a communication hole formed by foaming as the plate material that constitutes the upper layer is suitable for forming the first through hole because the plate material has sufficient strength.
The use of a plate material that does not have a communication hole formed by foaming as the plate material that constitutes the side surface layer is suitable for forming the second through hole because the plate material has sufficient strength.
Further, the hollow portion can be easily formed by laminating the lower layer as two layers of the side surface layer and the bottom surface layer.
By adhering the upper layer and the lower layer to each other, the influence of the secondary radiation sound can be reduced, so that the generation of the secondary radiation sound is prevented and a sound absorbing member capable of reliably achieving a predetermined sound absorption characteristic is provided. be able to.

In another aspect of the method for manufacturing a sound absorbing member of the present invention, it is preferable that the upper layer is formed by forming the first through hole by machining on a plate material having no through hole.
Since the plate material having no communication hole formed by foaming is used as the upper layer material, the strength of the plate material is sufficient, and it is possible to prevent breakage when the first through hole is formed by machining.

In another aspect of the method for manufacturing the sound absorbing member of the present invention, it is preferable that the side surface layer is formed by forming the second through hole by machining on a plate material having no through hole.
Since the plate material having no communication hole formed by foaming is used as the material of the side surface layer, the strength of the plate material is sufficient, and it is possible to prevent the occurrence of damage at the time of forming the second through hole by machining. ..

FIG. 1 is a sectional view schematically showing an example of the sound absorbing member of the present invention. FIG. 2 is a sectional view schematically showing another example of the sound absorbing member of the present invention. FIG. 3A is an explanatory view schematically showing an example of a portion where the sound absorbing member of the present invention is arranged, and FIG. 3B is a partial enlargement of a region shown by a broken line portion in FIG. 3A. It is a figure. FIG. 4 is a perspective view schematically showing an example of the method for manufacturing the sound absorbing member of the present invention. FIG. 5: is a perspective view which shows typically another example of the manufacturing method of the sound absorbing member of this invention. FIG. 6 is an explanatory diagram schematically showing the outline of the confirmation test of the secondary radiation sound. 7(a), 7(b), 7(c), 7(d), 7(e), and 7(f) are for Example 1 and Comparative Examples 1-5, respectively. 6 is a graph showing the relationship between frequency and transmission loss.

(Detailed Description of the Invention)
Hereinafter, the present invention will be specifically described. The present invention is not limited to the following description, and can be appropriately modified and applied within the scope of the gist of the present invention.

The sound-absorbing member of the present invention is a sound-absorbing member having a Helmholtz resonance structure consisting of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage,
Made of a plate material that does not have a communication hole formed by foaming,
An upper layer provided with a columnar first through hole forming the introduction passage,
Laminated on the upper layer, a lower layer provided with the hollow portion,
An adhesive layer that adheres the upper layer and the lower layer,
In the portion of the sound absorbing member where the Helmholtz resonance structure is not formed, the compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) is 0.1 to 200 MPa.
The compressive stress σ is the maximum value of the strain amount at 10-50% when measured at 23°C.

The sound absorbing member of the present invention has a Helmholtz resonance structure including an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage.
The sound absorbing member of the present invention has a laminated structure of an upper layer and a lower layer. Since the upper layer has a first through hole serving as an introduction passage and the lower layer has a hollow portion, the upper layer and the lower layer are laminated. As a result, a Helmholtz resonance structure is formed.
Hereinafter, the structure of the sound absorbing member of the present invention will be described separately for the upper layer and the lower layer.

The upper layer is made of a plate material, and the plate material is provided with a first through hole.
The plate material forming the upper layer is a plate material having no communication hole formed by foaming.
The first through hole has a columnar shape, and is a portion having a columnar space only with air. It is preferable that the diameter of the through hole is constant from the inlet side to the outlet side in the thickness direction of the plate material.
That is, such a form that gas passes through in the thickness direction but the other side is not visible (not penetrating) in a top view in the thickness direction, such as continuous ventilation holes in a porous material, is not included.
The first through hole is preferably a through hole formed by machining a plate material having no through hole, and punching, drilling, and laser drilling are preferably used.

In the sound absorbing member of the present invention, it is preferable that the first through hole has a columnar shape, and that the cross-sectional shape in the direction perpendicular to the length direction is a perfect circle. If the first through hole has a cylindrical shape, the introduction passage has a cylindrical shape. A cylindrical introduction passage is advantageous because the sound absorption characteristics have no anisotropy.
In the sound absorbing member of the present invention, the diameter of the bottom surface when the first through hole is cylindrical is preferably 1 to 30 mm.
That is, in the sound absorbing member of the present invention, the inner diameter of the introduction passage is preferably 1 to 30 mm.
When the shape of the first through hole is not cylindrical, the diameter of the first through hole is determined as the circle equivalent diameter. The equivalent circle diameter is a diameter when the cross-sectional area of the first through hole when the first through hole is cut in a direction perpendicular to the length direction is replaced with a true circle having the same area. When the cross-sectional shape of the first through hole is a perfect circle, its diameter may be used as it is as a circle equivalent diameter.

In the sound absorbing member of the present invention, the arrangement pattern of the first through holes provided in the upper layer may be a square arrangement in which the first through holes are arranged at the vertices of the squares in a plane in which the squares are continuously arranged vertically and horizontally. It may be a staggered arrangement in which the first through holes are arranged at the vertices of the triangles on a plane in which equilateral triangles are continuously arranged vertically and horizontally.
Among these, the staggered arrangement is desirable. When the arrangement pattern of the first through holes is a zigzag arrangement, all the adjacent first through holes are likely to be at equal intervals, so that the sound absorbing effect is improved. Further, the strength as the upper layer plate material can be obtained.

In the sound absorbing member of the present invention, the plate material forming the upper layer is preferably made of resin.
The resin is preferably a foamed resin or an elastomer such as rubber.
When the plate material constituting the upper layer is made of resin, it is easy to reduce the weight, which is particularly desirable as a vehicle part.
Further, when the resin is a foamed resin, the weight thereof can be further reduced, which can contribute to the improvement of fuel consumption when used as a vehicle component.
In the sound absorbing member of the present invention, it is preferable that the resin, which is the material of the plate material that constitutes the upper layer, does not have holes serving as communication holes in the resin.
In the sound absorbing member of the present invention, the plate material constituting the upper layer may be a composite material of resin and fiber. As a composite method, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

The resin is preferably any of a foamed resin composed of foamable resin particles (beads), a foamed resin having bubbles, a thermoplastic resin, and a thermosetting resin.
The material having a resin density of 0.01 to 1 g/cm ³ is preferable, and the resin density of 0.02 to 0.1 g/cm ³ is more preferable. When the resin is a foamed resin, the density of the resin refers to the density of the foamed resin that has been foam-molded.
When the density of the resin is within the above range, it is easy to obtain the strength required for the sound absorbing member.
On the other hand, when the density of the resin is less than 0.01 g/cm ³ , the sound absorbing member may not have sufficient mechanical strength. Further, when the resin density exceeds 1 g/cm ³ , the weight of the sound absorbing member increases, which hinders weight reduction of the vehicle.
Further, the resin is more preferably a foamed resin composed of expandable resin particles (beads). When the resin is a foamed resin composed of expandable resin particles (beads), the weight of the sound absorbing member can be reduced while maintaining strength, and when used as a vehicle part, it can contribute to improvement of fuel efficiency. ..
The foamed resin is obtained by foaming and molding expandable resin particles.
The plate material, which is a foamed resin composed of expandable resin particles (beads), does not have a communication hole.

In the sound absorbing member of the present invention, the expandable resin particles (beads) used as the plate material constituting the upper layer are particles containing a foaming agent inside the resin particles, and known ones can be preferably used. ..
Examples of the resin component forming the expandable resin particles include olefin resins such as polyethylene and polypropylene, and styrene resins such as polystyrene.
Examples of the styrene resin include a styrene homopolymer, and a copolymer obtained by copolymerizing styrene and a monomer (or a derivative thereof) copolymerizable with styrene. The styrene copolymer may be any of a block copolymer, a random copolymer and a graft copolymer.
Examples of the foaming agent include hydrocarbons such as propane, butane, pentane and the like.

In the sound absorbing member of the present invention, in the expandable resin particles used as the plate material constituting the upper layer, if necessary, a flame retardant, a flame retardant aid, a processing aid, a filler, an antioxidant, a stable light resistance. Known additives such as agents, antistatic agents and colorants may be added. As an example of the use of the additive, when a black colorant is used as the colorant, the stain becomes inconspicuous.

As the flame retardant, hydrated metal flame retardants such as aluminum hydroxide and magnesium hydroxide, phosphoric acid flame retardants such as red phosphorus and ammonium phosphate, tetrabromobisphenol A (TABB), brominated polystyrene, chlorinated paraffin. And halogen-based flame retardants such as ammonium carbonate, melamine cyanurate, and other nitrogen-based flame retardants.
Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.
Examples of processing aids include stearates, liquid paraffin, olefin waxes, stearylamide compounds, epoxy compounds and the like.
Examples of the filler include silica, talc, calcium silicate and the like.
Examples of the antioxidant include alkylphenol, alkylenebisphenol, alkylphenol thioether, β,β-thiopropionic acid ester, organic phosphite ester, and phenol-nickel complex.
Examples of the light resistance stabilizer include benzotriazole-based UV absorbers and hindered amine-based stabilizers.
Examples of the antistatic agent include low molecular type antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds and aliphatic ethanolamide compounds, and high molecular type antistatic agents.
Examples of the colorant include dyes and pigments.

In the sound absorbing member of the present invention, the average particle diameter of the expandable resin particles used as the plate material constituting the upper layer is preferably 300 μm to 2400 μm, and more preferably 800 μm to 2000 μm.
The expansion ratio of the expandable resin particles is preferably 10 to 60 times.
By setting the expansion ratio in the range of 10 to 60 times, it becomes easy to adjust the density of the resin in the range of 0.02 to 0.1 g/cm ³ .
On the other hand, when the expansion ratio is less than 10 times, the sound absorbing member may become too hard or too heavy. If the expansion ratio exceeds 60 times, the strength of the sound absorbing member may be insufficient.

In the sound absorbing member of the present invention, polyurethane or the like can be used as the foamed resin used as the plate material constituting the upper layer. By mixing polyurethane as a main ingredient, a foaming agent, etc., and foaming and molding, a foamed resin having bubbles can be obtained, whereby a plate material can be manufactured.

In the sound absorbing member of the present invention, the resin used as the plate material forming the upper layer may be a thermoplastic resin or a thermosetting resin.
In the sound absorbing member of the present invention, as the thermoplastic resin used as the plate material constituting the upper layer, polypropylene resin, polyethylene resin, polyester resin (nylon 6-6, etc.), polystyrene resin or the like can be used. A sound absorbing member can be manufactured by molding a thermoplastic resin into resin pellets, heating the resin pellets, and performing molding processing such as injection molding and extrusion molding.
In the sound absorbing member of the present invention, epoxy resin, phenol resin, melamine resin, urea resin, polyurethane, polyurea, polyamide, polyacrylamide and the like can be used as the thermosetting resin used as the plate material constituting the upper layer. The sound absorbing member can be manufactured by preheating the thermosetting resin, putting it in a mold, pressurizing it, raising the mold temperature, and curing.

In the sound absorbing member of the present invention, as the plate material constituting the upper layer, a material such as an inorganic material or a metal material may be used in addition to the resin material.

In the sound absorbing member of the present invention, the plate material constituting the upper layer preferably has a compressive stress of 0.1 to 200 MPa as a material.
For example, although foamed polypropylene can be preferably used as the foamed resin, it is more preferable to prepare and use foamed polypropylene having a compressive stress of about 0.2 to 1.0 MPa by adjusting the foaming ratio and the like. ..
Further, expanded polystyrene can be preferably used as the expanded resin, but it is more preferred to prepare and use expanded polystyrene having a compressive stress of about 0.1 to 1.0 MPa by adjusting the expansion ratio and the like.
Nylon 6-6 can be preferably used as the resin, but it is more preferable to prepare and use nylon 6-6 having a compressive stress of 80 to 100 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polyethylene resin can be preferably used, but it is more preferable to prepare and use a polyethylene resin having a compressive stress of 22 to 30 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polypropylene resin can be preferably used, but it is more preferable to prepare and use a polypropylene resin having a compressive stress of 40 to 50 MPa by adjusting its molecular weight, cross-linking density and the like.
As the resin, a phenol resin can be preferably used, but it is more preferable to prepare and use a phenol resin having a compressive stress of 140 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
As the resin, an epoxy resin can be preferably used, but it is more preferable to prepare and use an epoxy resin having a compressive stress of about 110 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
The compressive stress of the plate material can be measured in the thickness direction according to JIS K 7181 (2011).

In the sound absorbing member of the present invention, the plate material forming the upper layer preferably has a thickness of 1 to 20 mm. The thickness of the plate material is the length of the first through hole, which is the length of the introduction passage. That is, the length of the first through hole is preferably 1 to 20 mm. The length of the introduction passage is also preferably 1 to 20 mm.

In the sound absorbing member of the present invention, it is preferable that a fiber layer is further formed on the surface of the plate material forming the upper layer on the side where the opening is formed, and the fiber layer is formed with an opening communicating with the opening of the introduction passage.
When the sound absorbing member has the Helmholtz resonance structure, it can absorb sound in a predetermined frequency range, but the width of the frequency range that can be absorbed is not wide, and in particular, it is difficult to sufficiently absorb sound in a high frequency range of 2000 Hz or higher. ..
However, when the fiber layer is formed, it is possible to absorb the sound in the high frequency region of 2000 Hz or higher.

The material forming the fiber layer is preferably selected from natural fibers, synthetic resin fibers, and inorganic fibers. Examples of natural fibers include plant fibers, animal fibers, and mineral fibers. Examples of synthetic resin fibers include polyamide resins (nylon, etc.), polyester resins (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), acrylic resins, polyvinyl alcohol resins, polyolefin resins (polyethylene, polypropylene, etc.), etc. Can be mentioned. Examples of the inorganic fiber include alumina fiber, silica fiber, silica-alumina fiber, glass fiber, carbon fiber, potassium titanate fiber, rock wool and the like.
The fiber layer may be formed into a felt shape or a non-woven fabric.
The thickness of the fiber layer is preferably 1 to 20 mm.
Since voids are formed between the fibers in the fiber layer, air vibrations occur in the voids, and sounds in the high frequency range can be absorbed.
The upper layer and the fiber layer may or may not be bonded with an adhesive layer.

A hollow portion is provided in the lower layer and is laminated with the upper layer.
The hollow portion of the lower layer is connected to the first through hole of the upper layer, that is, the introduction passage, so that the hollow portion is connected to the outside to form the Helmholtz resonance structure.
Further, the upper layer and the lower layer are bonded by an adhesive layer.

In the sound absorbing member of the present invention, the shape of the hollow portion provided in the lower layer is preferably cylindrical, and the cross-sectional shape in the direction perpendicular to the length direction is preferably a perfect circle.
When the hollow portion provided in the lower layer in the sound absorbing member of the present invention has a columnar shape, the height thereof is preferably 1 to 20 mm, more preferably 3 to 15 mm.
When the shape of the hollow portion is not cylindrical, the diameter of the hollow portion is determined as the equivalent circle diameter. The equivalent circle diameter is the diameter when the cross-sectional area of the hollow portion when the hollow portion is cut in the direction perpendicular to the length direction is replaced with a true circle having the same area. When the cross-sectional shape of the hollow portion is a perfect circle, its diameter may be used as the equivalent circle diameter.
In order to form the Helmholtz resonance structure by the hollow portion of the lower layer and the introduction passage of the upper layer, the circle equivalent diameter of the hollow portion is larger than the circle equivalent diameter of the introduction passage (the circle equivalent diameter of the first through hole).
The diameter of the hollow portion is preferably 4 to 171 mm, preferably 10 mm or more, and preferably 150 mm or less.

In the sound absorbing member of the present invention, the arrangement pattern of the hollow portions provided in the lower layer may be a square arrangement in which the hollow portions are arranged at the vertices of the squares in a plane in which the squares are continuously arranged vertically and horizontally. It may be a staggered arrangement in which hollow portions are arranged at the vertices of a triangle on a plane continuously arranged.
Among these, the staggered arrangement is desirable. When the arrangement pattern of the hollow portions is a zigzag arrangement, the adjacent hollow portions are likely to be all at equal intervals, so that the sound absorbing effect is improved. Further, the strength as the lower plate material can be obtained.

In the sound absorbing member of the present invention, the positional relationship between the introduction passage and the hollow portion may be such that the hollow portion is connected to the outside through the introduction passage, and the center of the introduction passage and the hollow portion (in the direction perpendicular to the thickness direction) The centers in the cross-sectional shape when cut may or may not match.
It is preferable that one hollow portion corresponds to one introduction passage to form a Helmholtz resonance structure.

The specific structure of the lower layer will be described separately for the case where the lower layer is one layer and the case where the lower layer is two layers.
As an example of the case where the lower layer is a single layer, there is a form in which a concave portion is formed in the middle of the thickness of one plate material constituting the lower layer to form a hollow portion.
In this case, the layers constituting the sound absorbing member of the present invention are the two layers of the upper layer and the lower layer excluding the adhesive layer.

As an example of the case where the lower layer is two layers, a side surface layer in which a second through hole having a columnar shape having an opening diameter larger than that of the first through hole is provided in the plate material, and a bottom surface formed of the plate material and having no through hole An example is a mode in which layers are laminated in order, and a hollow portion is formed by the second through hole and the bottom layer.
In this case, the layers constituting the sound absorbing member of the present invention are three layers, that is, an upper layer, a side surface layer and a bottom surface layer, excluding the adhesive layer.

First, the case where the lower layer is one layer will be described.
In this case, a recess is formed halfway in the thickness direction of one plate material forming the lower layer to form a hollow portion. The concave portion is a portion which becomes a columnar space which is surrounded by the bottom surface and the side surfaces and whose upper surface is open, with the material constituting the plate material as the bottom surface and the side surfaces. The recess preferably has a constant diameter from the top surface to the bottom surface. Moreover, it is preferable that the diameter of the bottom surface of the recess is larger than the diameter of the first through hole forming the upper layer.
The diameter of the bottom surface of the recess is preferably 4 to 171 mm, preferably 10 mm or more, and preferably 150 mm or less. The height of the concave portion is preferably 1 to 20 mm, more preferably 3 to 15 mm.
The recess (hollow portion) is preferably formed by machining a plate material having no through hole, and cutting by an end mill or processing by a hot wire is preferably used.
Further, when manufacturing the plate material, the plate material having the recess may be integrally molded by injection molding or press molding.
When a foamed resin made of expandable resin particles (beads) is used as the plate material, the plate material having the recessed portion can be produced by performing foam molding in a mold having protrusions corresponding to the shape of the recessed portion. it can.

When the lower layer is a single layer, the plate material constituting the lower layer is preferably made of resin.
The resin is preferably a foamed resin or an elastomer such as rubber.
Further, it is preferable that the plate material constituting the lower layer is a plate material having no communication hole formed by foaming.
In the case where the lower layer is a single layer, if the plate material forming the lower layer is made of resin, it is particularly desirable as a vehicle part because it is easy to reduce the weight.
Further, when the resin is a foamed resin, the weight thereof can be further reduced, which can contribute to the improvement of fuel consumption when used as a vehicle component.
In the sound absorbing member of the present invention, when the lower layer is one layer, the plate material constituting the lower layer may be a composite material of resin and fiber. As a composite method, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

The resin is preferably any of a foamed resin composed of foamable resin particles (beads), a foamed resin having bubbles, a thermoplastic resin, and a thermosetting resin.
The material having a resin density of 0.01 to 1 g/cm ³ is preferable, and the resin density of 0.02 to 0.1 g/cm ³ is more preferable. When the resin is a foamed resin, the density of the resin refers to the density of the foamed resin that has been foam-molded.
When the density of the resin is within the above range, it is easy to obtain the strength required for the sound absorbing member.
On the other hand, when the density of the resin is less than 0.01 g/cm ³ , the sound absorbing member may not have sufficient mechanical strength. Further, when the resin density exceeds 1 g/cm ³ , the weight of the sound absorbing member increases, which hinders weight reduction of the vehicle.
Further, the resin is more preferably a foamed resin composed of expandable resin particles (beads). When the resin is a foamed resin composed of expandable resin particles (beads), the weight of the sound absorbing member can be reduced while maintaining strength, and when used as a vehicle part, it can contribute to improvement of fuel efficiency. ..
The foamed resin is obtained by foaming and molding expandable resin particles.
The plate material, which is a foamed resin composed of expandable resin particles (beads), does not have a communication hole.

In the sound absorbing member of the present invention, when the lower layer is one layer, the expandable resin particles (beads) used as the plate material constituting the lower layer are particles containing a foaming agent inside the resin particles, and known ones are used. It can be preferably used.
Examples of the resin component forming the expandable resin particles include olefin resins such as polyethylene and polypropylene, and styrene resins such as polystyrene.
Examples of the styrene resin include a styrene homopolymer, and a copolymer obtained by copolymerizing styrene and a monomer (or a derivative thereof) copolymerizable with styrene. The styrene copolymer may be any of a block copolymer, a random copolymer and a graft copolymer.
Examples of the foaming agent include hydrocarbons such as propane, butane, pentane and the like.

In the sound absorbing member of the present invention, in the expandable resin particles used as the plate material constituting the lower layer when the lower layer is one layer, a flame retardant, a flame retardant aid, a processing aid, a filler, Known additives such as antioxidants, light resistance stabilizers, antistatic agents and colorants may be added. As an example of the use of the additive, when a black colorant is used as the colorant, the stain becomes inconspicuous.

Examples of the flame retardant include hydrated metal flame retardants such as aluminum hydroxide and magnesium hydroxide, phosphoric acid flame retardants such as red phosphorus and ammonium phosphate, tetrabromobisphenol A (TABB), brominated polystyrene, chlorinated paraffin. And halogen-based flame retardants such as ammonium carbonate, melamine cyanurate, and other nitrogen-based flame retardants.
Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.
Examples of processing aids include stearates, liquid paraffin, olefin waxes, stearylamide compounds, epoxy compounds and the like.
Examples of the filler include silica, talc, calcium silicate and the like.
Examples of the antioxidant include alkylphenol, alkylenebisphenol, alkylphenol thioether, β,β-thiopropionic acid ester, organic phosphite ester, and phenol-nickel complex.
Examples of the light resistance stabilizer include benzotriazole-based UV absorbers and hindered amine-based stabilizers.
Examples of the antistatic agent include low molecular type antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds and aliphatic ethanolamide compounds, and high molecular type antistatic agents.
Examples of the colorant include dyes and pigments.

In the sound absorbing member of the present invention, when the lower layer is one layer, the average particle diameter of the expandable resin particles used as the plate material constituting the lower layer is preferably 300 μm to 2400 μm, and more preferably 800 μm to 2000 μm. desirable.
The expansion ratio of the expandable resin particles is preferably 10 to 60 times.
By setting the expansion ratio in the range of 10 to 60 times, it becomes easy to adjust the density of the resin in the range of 0.02 to 0.1 g/cm ³ .
On the other hand, when the expansion ratio is less than 10 times, the sound absorbing member may become too hard or too heavy. If the expansion ratio exceeds 60 times, the strength of the sound absorbing member may be insufficient.

In the sound absorbing member of the present invention, when the lower layer is one layer, the resin used as the plate material forming the lower layer may be a thermoplastic resin or a thermosetting resin.
In the sound absorbing member of the present invention, when the lower layer is a single layer, as the thermoplastic resin used as the plate material constituting the lower layer, polypropylene resin, polyethylene resin, polyester resin (nylon 6-6 etc.), polystyrene resin, etc. are used. be able to. A sound absorbing member can be manufactured by molding a thermoplastic resin into resin pellets, heating the resin pellets, and performing molding processing such as injection molding and extrusion molding.
In the sound absorbing member of the present invention, when the lower layer is one layer, the thermosetting resin used as the plate material constituting the lower layer includes epoxy resin, phenol resin, melamine resin, urea resin, polyurethane, polyurea, polyamide and polyacrylamide. Etc. can be used. The sound absorbing member can be manufactured by preheating the thermosetting resin, putting it in a mold, pressurizing it, raising the mold temperature, and curing.

In the sound absorbing member of the present invention, when the lower layer is a single layer, the plate material forming the lower layer may be a material such as an inorganic material or a metal material other than resin.

In the sound absorbing member of the present invention, when the lower layer is one layer, the plate material constituting the lower layer preferably has a compressive stress of 0.1 to 200 MPa as the material.
For example, although foamed polypropylene can be preferably used as the foamed resin, it is more preferable to prepare and use foamed polypropylene having a compressive stress of about 0.2 to 1.0 MPa by adjusting the foaming ratio and the like. ..
Further, expanded polystyrene can be preferably used as the expanded resin, but it is more preferred to prepare and use expanded polystyrene having a compressive stress of about 0.1 to 1.0 MPa by adjusting the expansion ratio and the like.
Nylon 6-6 can be preferably used as the resin, but it is more preferable to prepare and use nylon 6-6 having a compressive stress of 80 to 100 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polyethylene resin can be preferably used, but it is more preferable to prepare and use a polyethylene resin having a compressive stress of 22 to 30 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polypropylene resin can be preferably used, but it is more preferable to prepare and use a polypropylene resin having a compressive stress of 40 to 50 MPa by adjusting its molecular weight, cross-linking density and the like.
As the resin, a phenol resin can be preferably used, but it is more preferable to prepare and use a phenol resin having a compressive stress of 140 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
As the resin, an epoxy resin can be preferably used, but it is more preferable to prepare and use an epoxy resin having a compressive stress of about 110 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
The compressive stress of the plate material can be measured in the thickness direction according to JIS K 7181 (2011).
The compressive stress σ is the maximum value in 10 to 50% of strain when measured at 23°C.

In the sound absorbing member of the present invention, when the lower layer is one layer, the thickness of the plate material forming the lower layer is preferably 10 to 120 mm. Further, it is more desirable that it is 20 to 100 mm.

Next, the case where the lower layer is two layers will be described.
When the lower layer is two layers, the lower layer is a plate material having no communication hole formed by foaming and a side surface layer formed by providing a columnar second through hole having an opening diameter larger than that of the first through hole, and a plate material. And a bottom layer having no through hole provided in that order. Then, the hollow portion is formed by the second through hole and the bottom layer.

The side surface layer is made of a plate material, and the plate material is provided with a second through hole.
The plate material forming the side surface layer is a plate material having no communication hole formed by foaming.
The second through hole has a columnar shape, and is a portion having a columnar space only with air. It is preferable that the diameter of the through hole is constant from the inlet side to the outlet side in the thickness direction of the plate material.
That is, such a form that gas passes through in the thickness direction but the other side is not visible (not penetrating) in a top view in the thickness direction, such as continuous ventilation holes in a porous material, is not included.
The second through hole is preferably a through hole formed by machining a plate material having no through hole, and punching, drilling, and laser drilling are preferably used.

In the sound absorbing member of the present invention, the second through hole provided in the side surface layer is preferably cylindrical, and the cross-sectional shape in the direction perpendicular to the length direction is preferably a perfect circle. If the second through hole has a cylindrical shape, the hollow portion has a cylindrical shape. The hollow portion having a cylindrical shape is advantageous because the sound absorbing property has no anisotropy.
In the sound absorbing member of the present invention, the diameter (opening diameter) of the bottom surface when the second through hole is columnar is preferably 4 to 171 mm, preferably 10 mm or more, and 150 mm or less. Is preferred.

In the sound absorbing member of the present invention, the array pattern of the second through holes provided in the side surface layer is a square array in which the second through holes are arranged at the apexes of the squares in a plane in which the squares are continuously arranged vertically and horizontally. Alternatively, a zigzag arrangement may be used in which the second through holes are arranged at the vertices of the triangles in a plane in which equilateral triangles are arranged continuously in the vertical and horizontal directions.
Among these, the staggered arrangement is desirable. When the arrangement pattern of the second through holes is a zigzag arrangement, the hollow portions formed by the adjacent second through holes are likely to be all at equal intervals, so that the sound absorbing effect is improved. Further, the strength of the side surface layer as a plate material can be obtained.

In the sound absorbing member of the present invention, the thickness of the plate material forming the side surface layer is preferably 1 to 20 mm, more preferably 3 to 15 mm. The thickness of the plate material forming the side surface layer is the length of the second through hole and is the height of the hollow portion. That is, the length of the second through hole is preferably 1 to 20 mm.

The bottom layer is made of a plate material and has no through holes.
The plate material forming the bottom layer is preferably a plate material having no communication hole formed by foaming.
By stacking the side surface layer and the bottom surface layer, a hollow portion is formed by the second through hole of the side surface layer and the bottom surface layer.
In the sound absorbing member of the present invention, the plate material forming the bottom layer preferably has a thickness of 1 to 20 mm.

In the sound absorbing member of the present invention, it is preferable that the plate materials forming the side surface layer and the bottom surface layer are made of resin.
The plate materials forming the side surface layer and the bottom surface layer are preferably the same material, but may be different materials.
The resin is preferably a foamed resin or an elastomer such as rubber.
It is particularly desirable as a vehicle component when the plate material forming the side surface layer and the bottom surface layer is made of resin because weight reduction is easy.
Further, when the resin is a foamed resin, the weight thereof can be further reduced, which can contribute to the improvement of fuel consumption when used as a vehicle component.
In the sound absorbing member of the present invention, the plate material forming the side surface layer and the bottom surface layer may be a composite material of resin and fiber. As a composite method, the resin and the fiber may be mixed, or the resin and the fiber may be combined in a block shape.

The resin is preferably any of a foamed resin composed of foamable resin particles (beads), a foamed resin having bubbles, a thermoplastic resin, and a thermosetting resin.
The material having a resin density of 0.01 to 1 g/cm ³ is preferable, and the resin density of 0.02 to 0.1 g/cm ³ is more preferable. When the resin is a foamed resin, the density of the resin refers to the density of the foamed resin that has been foam-molded.
When the density of the resin is within the above range, it is easy to obtain the strength required for the sound absorbing member.
On the other hand, when the density of the resin is less than 0.01 g/cm ³ , the sound absorbing member may not have sufficient mechanical strength. Further, when the resin density exceeds 1 g/cm ³ , the weight of the sound absorbing member increases, which hinders weight reduction of the vehicle.
Further, the resin is more preferably a foamed resin composed of expandable resin particles (beads). When the resin is a foamed resin composed of expandable resin particles (beads), the weight of the sound absorbing member can be reduced while maintaining strength, and when used as a vehicle part, it can contribute to improvement of fuel efficiency. ..
The foamed resin is obtained by foaming and molding expandable resin particles.
The plate material, which is a foamed resin composed of expandable resin particles (beads), does not have a communication hole.

In the sound absorbing member of the present invention, the expandable resin particles (beads) used as the plate material constituting the side surface layer and the bottom surface layer are particles containing a foaming agent inside the resin particles, and known materials are preferably used. can do.
Examples of the resin component forming the expandable resin particles include olefin resins such as polyethylene and polypropylene, and styrene resins such as polystyrene.
Examples of the styrene resin include a styrene homopolymer, and a copolymer obtained by copolymerizing styrene and a monomer (or a derivative thereof) copolymerizable with styrene. The styrene copolymer may be any of a block copolymer, a random copolymer and a graft copolymer.
Examples of the foaming agent include hydrocarbons such as propane, butane, pentane and the like.

In the sound absorbing member of the present invention, in the expandable resin particles used as the plate material constituting the side surface layer and the bottom surface layer, if necessary, a flame retardant, a flame retardant aid, a processing aid, a filler, an antioxidant. Known additives such as a light resistance stabilizer, an antistatic agent, and a colorant may be added. As an example of the use of the additive, when a black colorant is used as the colorant, the stain becomes inconspicuous.

As the flame retardant, hydrated metal flame retardants such as aluminum hydroxide and magnesium hydroxide, phosphoric acid flame retardants such as red phosphorus and ammonium phosphate, tetrabromobisphenol A (TABB), brominated polystyrene, chlorinated paraffin. And halogen-based flame retardants such as ammonium carbonate, melamine cyanurate, and other nitrogen-based flame retardants.
Examples of the flame retardant aid include antimony trioxide and antimony pentoxide.
Examples of processing aids include stearates, liquid paraffin, olefin waxes, stearylamide compounds, epoxy compounds and the like.
Examples of the filler include silica, talc, calcium silicate and the like.
Examples of the antioxidant include alkylphenol, alkylenebisphenol, alkylphenol thioether, β,β-thiopropionic acid ester, organic phosphite ester, and phenol-nickel complex.
Examples of the light resistance stabilizer include benzotriazole-based UV absorbers and hindered amine-based stabilizers.
Examples of the antistatic agent include low molecular type antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds and aliphatic ethanolamide compounds, and high molecular type antistatic agents.
Examples of the colorant include dyes and pigments.

In the sound absorbing member of the present invention, the average particle diameter of the expandable resin particles used as the plate material forming the side surface layer and the bottom surface layer is preferably 300 μm to 2400 μm, and more preferably 800 μm to 2000 μm.
The expansion ratio of the expandable resin particles is preferably 10 to 60 times.
By setting the expansion ratio in the range of 10 to 60 times, it becomes easy to adjust the density of the resin in the range of 0.02 to 0.1 g/cm ³ .
On the other hand, when the expansion ratio is less than 10 times, the sound absorbing member may become too hard or too heavy. If the expansion ratio exceeds 60 times, the strength of the sound absorbing member may be insufficient.

In the sound absorbing member of the present invention, polyurethane or the like can be used as the foamed resin used as the plate material forming the side surface layer and the bottom surface layer. By mixing polyurethane as a main ingredient, a foaming agent, etc., and foaming and molding, a foamed resin having bubbles can be obtained, whereby a plate material can be manufactured.

In the sound absorbing member of the present invention, the resin used as the plate material forming the side surface layer and the bottom surface layer may be a thermoplastic resin or a thermosetting resin.
In the sound absorbing member of the present invention, polypropylene resin, polyethylene resin, polyester resin (nylon 6-6 or the like), polystyrene resin or the like can be used as the thermoplastic resin used as the plate material constituting the side surface layer and the bottom surface layer. .. A sound absorbing member can be manufactured by molding a thermoplastic resin into resin pellets, heating the resin pellets, and performing molding processing such as injection molding and extrusion molding.
In the sound absorbing member of the present invention, epoxy resin, phenol resin, melamine resin, urea resin, polyurethane, polyurea, polyamide, polyacrylamide and the like are used as the thermosetting resin used as the plate material constituting the side surface layer and the bottom surface layer. be able to. The sound absorbing member can be manufactured by preheating the thermosetting resin, putting it in a mold, pressurizing it, raising the mold temperature, and curing.

In the sound absorbing member of the present invention, as the plate material forming the side surface layer and the bottom surface layer, a material such as an inorganic material or a metal material may be used in addition to the resin material.

In the sound absorbing member of the present invention, the plate material forming the side surface layer and the bottom surface layer preferably has a compressive stress of 0.1 to 200 MPa as a material.
For example, although foamed polypropylene can be preferably used as the foamed resin, it is more preferable to prepare and use foamed polypropylene having a compressive stress of about 0.2 to 1.0 MPa by adjusting the foaming ratio and the like. ..
Further, expanded polystyrene can be preferably used as the expanded resin, but it is more preferred to prepare and use expanded polystyrene having a compressive stress of about 0.1 to 1.0 MPa by adjusting the expansion ratio and the like.
Nylon 6-6 can be preferably used as the resin, but it is more preferable to prepare and use nylon 6-6 having a compressive stress of 80 to 100 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polyethylene resin can be preferably used, but it is more preferable to prepare and use a polyethylene resin having a compressive stress of 22 to 30 MPa by adjusting its molecular weight, crosslinking density and the like.
As the resin, a polypropylene resin can be preferably used, but it is more preferable to prepare and use a polypropylene resin having a compressive stress of 40 to 50 MPa by adjusting its molecular weight, cross-linking density and the like.
As the resin, a phenol resin can be preferably used, but it is more preferable to prepare and use a phenol resin having a compressive stress of 140 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
As the resin, an epoxy resin can be preferably used, but it is more preferable to prepare and use an epoxy resin having a compressive stress of about 110 to 200 MPa by adjusting its molecular weight, crosslink density and the like.
The compressive stress of the plate material can be measured in the thickness direction according to JIS K 7181 (2011).
The compressive stress σ is the maximum value in 10 to 50% of strain when measured at 23°C.

The sound absorbing member of the present invention has an upper layer and a lower layer bonded by an adhesive layer.
The adhesive layer is preferably provided on a portion of the surface of the lower layer where the hollow portion is not provided.
The thickness of the adhesive layer is preferably 10 to 500 μm. Further, it is preferably 20 to 200 μm.
Examples of the material forming the adhesive layer include a vinyl resin adhesive, a styrene resin adhesive, an epoxy resin adhesive, and a cyanoacrylate adhesive seat.
As the adhesive layer, a sheet-shaped adhesive that is hollowed out in accordance with the shape and position of the hollow portion may be used, and the adhesive is applied to the portion where the hollow portion is not provided on the surface of the lower layer. It may be one that has been created.
The upper layer and the lower layer are bonded to each other by the adhesive layer, so that the vibration damping action is generated, and the influence of the secondary radiated sound generated by the vibration of the plate material of the upper layer during sound absorption can be reduced.

In the sound absorbing member of the present invention, when the lower layer is composed of two layers of the side surface layer and the bottom surface layer, the side surface layer and the bottom surface layer may be bonded with an adhesive layer or may not be bonded with the adhesive layer. Good.
When the adhesive layer is not provided between the side surface layer and the bottom surface layer, the side surface layer and the bottom surface layer may be fixed by another method so as not to shift their positions. Further, the side surface layer and the bottom surface layer may not be fixed depending on the arrangement of the sound absorbing member.

In the sound absorbing member of the present invention, the compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) is 0.1 to 200 MPa in the portion where the Helmholtz resonance structure is not formed.
This is the compressive stress measured in the thickness direction including the upper layer, the adhesive layer and the lower layer. When the lower layer is composed of two layers, the side surface layer and the bottom surface layer, the measurement is performed including both the side surface layer and the bottom surface layer.
When the plate material forming the upper layer and the plate material forming the lower layer are made of the same material, the compressive stress of the sound absorbing member has substantially the same value as the compressive stress as the material of the plate material. In addition, when the plate material that constitutes the upper layer and the plate material that constitutes the lower layer are made of the same material, by bonding the upper layer and the lower layer, compared to the case where the upper layer and the lower layer are not bonded (for example, when the outer circumference is fixed with a jig). The compressive stress is slightly higher.
When the compressive stress of the sound absorbing member is 0.1 MPa or more, vibration is prevented from propagating in the horizontal direction and radiated sound is generated, and when the compressive stress is 200 MPa or less, vibration is propagated in the thickness direction. Generation of secondary radiation sound is prevented.

The sound absorbing member of the present invention preferably has a total thickness of 10 to 120 mm. The thickness of the sound absorbing member is more preferably 20 to 100 mm.
When the thickness of the sound absorbing member is less than 10 mm, it becomes difficult to form the Helmholtz resonance structure.
When the thickness of the sound absorbing member exceeds 120 mm, the sound absorbing member becomes too large and it is difficult to arrange the sound absorbing member in a desired space.

An example of such a sound absorbing member of the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view schematically showing an example of the sound absorbing member of the present invention.
The sound absorbing member shown in FIG. 1 is a sound absorbing member having a single lower layer.
The sound absorbing member 100 shown in FIG. 1 includes an upper layer 10, a lower layer 20, and an adhesive layer 30, and the upper layer 10 and the lower layer 20 are bonded by the adhesive layer 30.
The upper layer 10 is provided with a first through hole 110 that forms an introduction passage 110, and the lower layer 20 is provided with a hollow portion 120. The introduction passage 110 and the hollow portion 120 form a Helmholtz resonance structure.
In the sound absorbing member 100, the introduction passage 110 and the hollow portion 120 are cylindrical.

The upper layer 10 is a plate material, and the plate material is provided with a cylindrical first through hole 110.
The lower layer 20 is also a plate material, and a hollow portion 120 is provided by forming a recess in the middle of one plate material in the thickness direction.

FIG. 2 is a sectional view schematically showing another example of the sound absorbing member of the present invention.
The sound absorbing member shown in FIG. 2 is a sound absorbing member having two lower layers.
In the sound absorbing member 200 shown in FIG. 2, the lower layer 20 is composed of two layers, a side surface layer 21 and a bottom surface layer 22. The side surface layer 21 is provided with a second through hole 120, and the second through hole 120 is a hollow portion 120.
Further, the wall surface 121 that is a part of the side surface layer 21 becomes a side surface of the hollow portion 120, and the surface 122 of the bottom surface layer 22 that is a part of the bottom surface layer 22 becomes a bottom surface of the hollow portion 120.

The upper layer 10 and the lower layer 20 are bonded by an adhesive layer 30. Of the layers forming the lower layer 20, it is the side surface layer 21 that is bonded to the upper layer 10.
The adhesive layer 40 is also provided between the side surface layer 21 and the bottom surface layer 22, and the side surface layer 21 and the bottom surface layer 22 are also bonded.
The upper layer 10 is provided with a first through hole 110 that forms an introduction passage 110, and the lower layer 20 is provided with a hollow portion 120. The introduction passage 110 and the hollow portion 120 form a Helmholtz resonance structure.
In the sound absorbing member 200, the introduction passage 110 and the hollow portion 120 are cylindrical.

The upper layer 10 is a plate material, and the plate material is provided with a cylindrical first through hole 110.
The side surface layer 21 and the bottom surface layer 22 forming the lower layer 20 are also plate materials.
The plate-like material forming the side surface layer 21 is provided with a cylindrical second through hole 120.
No through hole is provided in the plate material forming the bottom layer 22.

In the sound absorbing member of the present invention, the compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) is 0.1 to 200 MPa in the portion where the Helmholtz resonance structure is not formed. 1 and 2 show an AA line as an example of a portion for measuring. The part indicated by the line AA is a part where the Helmholtz resonance structure is not formed, and the thickness direction is the direction of the line AA.

The vehicle component of the present invention is characterized by including the sound absorbing member of the present invention.
Since the sound absorbing member of the present invention has excellent soundproofing performance, it is excellent as a vehicle part.
Examples of vehicle parts provided with the sound absorbing member of the present invention include a raising member, a partition member, and a luggage box.

An automobile of the present invention is characterized in that the introduction passage of the sound absorbing member of the present invention is arranged so as to face the road surface.
By disposing the sound absorbing member of the present invention in such a direction, it is possible to absorb the noise of tire pattern noise transmitted from the road surface and prevent the noise from being transmitted to the inside of the vehicle.

An example in which the sound absorbing member of the present invention is used as a vehicle component and an example of an automobile in which the sound absorbing member of the present invention is arranged will be described with reference to FIGS. 3(a) and 3(b).
FIG. 3A is an explanatory view schematically showing an example of a portion where the sound absorbing member of the present invention is arranged, and FIG. 3B is a partially enlarged view of a region shown by a broken line portion in FIG. 3A. It is a figure.
As shown in FIG. 3A, the automobile 1 has a luggage room 3 behind the rear seat 2. A plate-shaped floor member 4 is laid under the luggage room 3, and an underfloor space 5 exists below the floor member 4.
The sound absorbing member 100 is arranged below the underfloor space 5 of the automobile 1 so that the introduction passage 110 thereof faces the road surface direction.

Next, a method for manufacturing the sound absorbing member of the present invention will be described.
One aspect of a method for manufacturing a sound absorbing member of the present invention is a method for manufacturing a sound absorbing member having a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage. ,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a lower layer which is a plate material having a hollow portion,
A step of adhering the upper layer and the lower layer with an adhesive layer,
The plate material constituting the upper layer is a plate material having no communication hole formed by foaming.
This aspect is a method of manufacturing a sound absorbing member having a single lower layer.

(Process of manufacturing upper layer)
A plate material having a predetermined thickness made of a material such as resin that can be used as the plate material is prepared.
The plate material constituting the upper layer is a plate material having no communication hole formed by foaming.
It is preferable to fabricate the upper layer by forming the first through hole by machining on a plate material having no through hole.
The upper layer can be produced by forming the first through holes in a plate material having no through holes by a mechanical processing means such as punching, drilling, or laser.
Further, when a foamed resin composed of expandable resin particles (beads) is used as the plate material, it is also possible to provide a protrusion for forming the first through hole in the mold to foam the expandable resin particles. The upper layer in which the first through hole is provided in the plate material can be manufactured. The plate material constituting the upper layer thus obtained is a plate material having no communication hole formed by foaming.

(Process of manufacturing lower layer)
A plate material having a predetermined thickness made of a material such as resin that can be used as the plate material is prepared.
It is preferable that the plate material forming the lower layer is a plate material having no communication hole formed by foaming.
The lower layer can be produced by forming a hollow portion as a hollow portion in a plate material having no through hole in the middle of its thickness direction. The diameter of the recess is made larger than the diameter of the first through hole.
The recess is preferably formed by machining, and cutting by an end mill or processing by a hot wire is preferably used.
Further, when manufacturing the plate material, the plate material having the recess may be integrally molded by injection molding or press molding.
When a foamed resin made of expandable resin particles (beads) is used as the plate material, the plate material having the recessed portion can be produced by performing foam molding in a mold having protrusions corresponding to the shape of the recessed portion. it can. The plate material constituting the lower layer thus obtained is a plate material having no communication hole formed by foaming.

(Step of adhering the upper layer and the lower layer with an adhesive layer)
Prepare a sheet-shaped adhesive that is hollowed out according to the shape and position of the recess (hollow part) of the lower layer, and sandwich it between the upper layer and the lower layer to exert the adhesive force of the adhesive, thereby separating the upper layer and the lower layer. It can be adhered by an adhesive layer.
When the upper layer, the adhesive layer, and the lower layer are laminated, the positions of the first through holes of the upper layer and the hollow portions (recesses) of the lower layer are aligned so that the Helmholtz resonance structure is formed.
By applying an adhesive according to the shape and position of the recess (hollow part) of the lower layer and stacking the upper layer and the lower layer to exert the adhesive force of the adhesive, the upper layer and the lower layer can be bonded by the adhesive layer. it can.
As a condition for exerting the adhesive force of the adhesive, a condition matched to the adhesive property of the adhesive may be used.

Another aspect of the method for manufacturing a sound absorbing member of the present invention is a method for manufacturing a sound absorbing member having a Helmholtz resonance structure composed of an introduction passage opening on the surface and a hollow portion connected to the outside through the introduction passage. ,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a side surface layer which is a plate material having a second through hole,
A step of preparing a plate material to be a bottom layer,
A plate material to be an upper layer, a plate material to be a side surface layer, and a plate material to be a bottom surface layer are laminated to form a hollow portion by the second through hole and the bottom surface layer, and a lower layer composed of the side surface layer and the bottom surface layer is formed. And a step of adhering the lower layer with an adhesive layer,
The plate material forming the upper layer and the plate material forming the side surface layer are plate materials having no communication hole formed by foaming.
This aspect is a method for manufacturing a sound absorbing member having two lower layers.

(Process of manufacturing upper layer)
The upper layer can be manufactured in the same manner as when manufacturing the sound absorbing member in which the lower layer is one layer.
A plate material having a predetermined thickness made of a material such as resin that can be used as the plate material is prepared.
The plate material constituting the upper layer is a plate material having no communication hole formed by foaming.
It is preferable to fabricate the upper layer by forming the first through hole by machining on a plate material having no through hole.
The upper layer can be produced by forming the first through holes in a plate material having no through holes by a mechanical processing means such as punching, drilling, or laser.
Further, when a foamed resin composed of expandable resin particles (beads) is used as the plate material, it is also possible to provide a protrusion for forming the first through hole in the mold to foam the expandable resin particles. The upper layer in which the first through hole is provided in the plate material can be manufactured. The plate material constituting the upper layer thus obtained is a plate material having no communication hole formed by foaming.

(Process of manufacturing side layer)
A plate material having a predetermined thickness made of a material such as resin that can be used as the plate material is prepared.
The plate material forming the side surface layer is a plate material having no communication hole formed by foaming.
It is preferable to fabricate the side surface layer by forming the second through hole by machining the plate material having no through hole.
The side surface layer can be produced by forming the second through hole in the plate material having no through hole by a mechanical processing means such as punching, drilling or laser. The diameter of the second through hole is set to be larger than that of the first through hole.
Further, when a foamed resin composed of expandable resin particles (beads) is used as the plate material, it is also possible to provide a projection for forming the second through hole in the mold to foam the expandable resin particles. The side surface layer in which the second through hole is provided in the plate material can be manufactured. The plate material constituting the side surface layer thus obtained is a plate material having no communication hole formed by foaming.

(Process of preparing a plate material to be the bottom layer)
A plate material having a predetermined thickness, which is made of a material such as resin that can be used as a plate material and has no through hole, is prepared.
The plate material forming the bottom layer is preferably a plate material having no communication hole formed by foaming.

(Step of adhering the upper layer and the lower layer with an adhesive layer)
A plate material to be an upper layer, a plate material to be a side surface layer, and a plate material to be a bottom layer are laminated. At this time, an adhesive layer is provided at least between the upper layer plate material and the side layer plate material. An adhesive layer may or may not be provided between the plate material serving as the side surface layer and the plate material serving as the bottom surface layer.
By laminating the plate material to be the side surface layer and the plate material to be the bottom surface layer, the hollow portion is formed by the second through hole and the bottom surface layer, and the lower layer is formed.
Further, a sheet-shaped adhesive is prepared by hollowing it out according to the shape and position of the second through hole, and is sandwiched between the upper layer plate material and the side layer plate material to exert the adhesive force of the adhesive. Thus, the upper layer and the side surface layer (lower layer) can be bonded by the adhesive layer.
When laminating the plate material serving as the upper layer, the adhesive layer, and the plate material serving as the side surface layer (lower layer), the positions of the first through holes of the upper layer and the second through holes of the side surface layer (hollow part) are aligned and Helmholtz Allow the resonance structure to form.
Further, an adhesive is applied in conformity with the shape and position of the second through hole (hollow portion) of the plate material to be the side surface layer, and the upper layer and the side surface layer (lower layer) are laminated to exert the adhesive force of the adhesive. Thus, the upper layer and the side surface layer (lower layer) can be bonded by the adhesive layer.
Also, when the plate material to be the side surface layer and the plate material to be the bottom surface layer are bonded by the adhesive layer, it is preferable to use a sheet-shaped adhesive that is cut out in accordance with the shape and position of the second through hole. .. Further, an adhesive may be applied in accordance with the shape and position of the second through hole of the plate material to be the side surface layer to adhere it to the bottom surface layer.
As a condition for exerting the adhesive force of the adhesive, a condition matched to the adhesive property of the adhesive may be used.
The upper layer plate material, the side layer plate material, and the bottom layer plate material may be laminated in three layers at a time, and the side layer plate material and the upper layer plate material or the bottom layer plate material may be laminated. The above two layers may be laminated first, and then the remaining one layer may be laminated.

FIG. 4 is a perspective view schematically showing an example of the method for manufacturing the sound absorbing member of the present invention.
FIG. 4 schematically shows a method of manufacturing a sound absorbing member in which the lower layer is a single layer.
In FIG. 4, the upper layer 10 and the lower layer 20 are laminated with the adhesive layer 30 interposed therebetween.
A first through hole 110 is formed in the upper layer 10, and a hollow portion 120 is formed in the lower layer 20. The adhesive layer 30 is an adhesive on a sheet and has a through hole 130 that is hollowed out according to the shape of the hollow portion.
The sound absorbing member 100 shown in FIG. 1 is obtained by laminating the upper layer 10 and the lower layer 20 via the adhesive layer 30 and adhering them. At this time, the position of the first through hole 110 and the position of the hollow portion 120 and the position of the through hole 130 of the adhesive layer are adjusted so as to match.
If the adhesive layer is formed on the upper surface of the hollow portion, the soundproof property may change, which is not preferable.

FIG. 5: is a perspective view which shows typically another example of the manufacturing method of the sound absorbing member of this invention.
FIG. 5 schematically shows a method for manufacturing a sound absorbing member having two lower layers.
In FIG. 5, the upper layer 10 and the side surface layer 21 are laminated via the adhesive layer 30. In addition, the side surface layer 21 and the bottom surface layer 22 are laminated via the adhesive layer 40.
A first through hole 110 is formed in the upper layer 10, and a second through hole 120 is formed in the side surface layer 21. The adhesive layer 30 is an adhesive on the sheet and has a through hole 130 that is hollowed out in accordance with the shape of the second through hole.
The bottom layer 22 has no through holes. The adhesive layer 40 is an adhesive on the sheet and has a through hole 140 that is hollowed out according to the shape of the second through hole.
The sound absorbing member 200 shown in FIG. 2 is obtained by laminating the upper layer 10, the side layer 21, and the bottom layer 22 with the adhesive layer 30 and the adhesive layer 40 interposed therebetween and adhering them. At this time, the positions of the first through holes 110, the positions of the through holes 130 of the adhesive layer 30, the positions of the second through holes 120, and the positions of the through holes 140 of the adhesive layer 40 are adjusted to match.
When the adhesive layer is formed on the bottom surface and/or the top surface of the hollow portion, the soundproof property may change, which is not preferable.
4 and 5, a sheet-shaped adhesive layer is used to bond the upper and lower layers, but the sound absorbing member of the present invention is manufactured by a method of applying an adhesive between the upper and lower layers. You may.

(Example)
Specific examples for explaining the present invention more specifically are shown below, but the present invention is not limited to these examples.

(Example 1)
(1) Production of plate material A primary foamed particle (made of polypropylene, an average particle size of 3.5 mm, a foaming agent: carbon dioxide) obtained by pre-expanding expandable resin particles is filled in a mold, and foamed by heating steam (143). C., 10 seconds), and after removing from the mold, it was dried at 80.degree. C. for 12 hours to produce three plate materials made of foamed resin and having a length of 100 mm.times.a width of 100 mm.times.a thickness of 10 mm. At this time, the expansion ratio of the foamed resin was 30 times. This plate material was a plate material composed of expandable resin particles (beads) and did not have a communication hole formed by foaming.

(2) Formation of through holes In one of the plate materials having a thickness of 10 mm produced in (1) above, circular through holes having a diameter of 3 mm (first through holes) are formed in a zigzag arrangement with a hole pitch of 10 mm. Was formed by a drill to prepare an upper layer.
Then, a through hole (second through hole) having a diameter of 10 mm is formed in a circle in a zigzag arrangement with a hole pitch of 10 mm in another one of the plate materials having a thickness of 10 mm produced in the above (1) by a drill. Then, the side surface layer was produced.
Another sheet of the plate material having a thickness of 10 mm produced in (1) above was not processed and used as the bottom layer.

(3) Lamination and Adhesion An adhesive (Honde G Clear made by Konishi Co., Ltd., coating thickness: 70 μm) is applied to one surface of the side surface layer to form a central position of the first through hole formed in the upper layer and the side surface layer. The upper layer and the side surface layer were adhered so that the center positions of the second through holes coincided with each other. Subsequently, the same adhesive was applied to the other surface of the side surface layer, and the bottom surface layer was adhered to obtain a sound absorbing member according to Example 1.

(Comparative Example 1)
As the plate material, a silicon rubber (made by Kyowa Kogyo Co., Ltd., silicone rubber sheet hardness 30) having no communication hole formed by foaming and having a thickness of 10 mm was prepared. The thickness of each plate and the size of the through hole were made in the same manner as in Example 1 to produce an upper layer, a side layer and a bottom layer, and the layers were adhered in the same manner as in Example 1 to obtain a sound absorbing member according to Comparative Example 1. ..

(Comparative example 2)
In addition to the foaming agent, urethane foam (Calmflex F2, manufactured by INOAC Co., Ltd.) having a communication hole that was foamed by blowing gas was prepared as a plate material having a thickness of 10 mm. The thickness of the plate material and the size of the through hole were the same as in Example 1 to produce an upper layer, a side surface layer and a bottom layer, and each layer was bonded in the same manner as in Example 1 to obtain a sound absorbing member according to Comparative Example 2.

(Comparative example 3)
A plate material, which is a polyurethane resin having communication holes formed by foaming, was produced by molding using polyisocyanate and polyether polyol as raw materials. At this time, the mold to be molded is a mold A for forming a plate material having a length of 100 mm × a width of 100 mm × a thickness of 10 mm, and a columnar shape having a diameter of 10 mm in a space for forming a plate material having a length of 100 mm × a width of 100 mm × a thickness of 20 mm. Two types of mold B having a height of 10 mm and provided with a convex portion were used. A plate material A having a communication hole having a thickness of 10 mm is obtained by the mold A, and a cylindrical recess is provided by the mold B, and a plate material B having a communication hole is obtained. A sound absorbing member according to Comparative Example 3 was obtained by applying an adhesive (Honde G Clear manufactured by Konishi Co., Ltd., coating thickness: 70 μm) to a portion of the plate material B where the recess was not provided, and by adhering the plate material A thereto.

(Comparative example 4)
As the plate material, a glass epoxy resin (107-176, manufactured by KOKUGO Co., Ltd.) having no communication hole formed by foaming and having a thickness of 10 mm was prepared. The thickness of the plate material and the size of the through hole were the same as in Example 1 to produce an upper layer, a side surface layer and a bottom layer, and the layers were bonded in the same manner as in Example 1 to obtain a sound absorbing member according to Comparative Example 4.

(Comparative example 5)
The sound absorbing member according to Comparative Example 5 was obtained in the same manner as in Example 1, except that the layers were not bonded and the outer periphery was fixed by a U-shaped cross-section fastener.

(Measurement of compressive stress)
In the portion where the Helmholtz resonance structure is not formed in the sound absorbing member manufactured in each of the examples and the comparative examples, the thickness was measured by an electromechanical universal testing machine (Instron, 5567) according to JIS K 7181 (2011). The compression stress σ was measured in the vertical direction at a compression rate of a compression test of 5 mm/min and an indoor temperature of the tester of 23° C. The compressive stress was the maximum value at 10-50% in terms of strain amount.
The results are as follows.
Example 1: 0.7 MPa
Comparative Example 1: 0.056 MPa
Comparative Example 2: 0.006 MPa
Comparative Example 3: 37 MPa
Comparative Example 4: 215 MPa
Comparative Example 5: 0.5 MPa

(Confirmation of external processing)
Regarding the sound absorbing member of each example and each comparative example, after forming 10 through holes having a diameter of 0.3 mm by drilling in the plate material (plate material A in Comparative Example 3) which is the upper layer, the presence or absence of cracks in the plate material is confirmed. did.
As a result, cracking of the plate material was not confirmed in Example 1, Comparative Example 1, Comparative Example 4, and Comparative Example 5. In Comparative Examples 2 and 3, cracking of the plate material was confirmed.

(Secondary radiation confirmation test)
The presence or absence of secondary radiation sound was measured for each of the sound absorbing members of Examples and Comparative Examples.
FIG. 6 is an explanatory diagram schematically showing the outline of the confirmation test of the secondary radiation sound.
FIG. 6 shows a secondary radiation sound measuring device 80. The secondary radiated sound measuring device 80 is a metal tube (inner diameter 30 mm, length: 50 mm), and receives sound through a sound source chamber 81 for generating sound from a speaker 83 and a sound absorbing member 100 as a test body. A chamber 82 is provided. The sound receiving chamber 82 is provided with a sound receiving chamber side microphone 85, and the sound pressure level measured by the sound receiving chamber side microphone 85 can be taken into the measuring device 86.
A sound of 120 dB was generated at 100 to 1200 Hz by the speaker, and the transmission loss was measured. At this time, it was measured whether the sound below 300 Hz was captured, and if the sound below 300 Hz was captured, it was determined that the secondary radiation sound was generated. Note that when the secondary radiation sound is generated, a drop in the transmission loss is observed. Therefore, when this drop is present, it can be determined that the secondary report sound insulation is occurring.

FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E, and FIG. 7F show Example 1 and Comparative Examples 1 to 5, respectively. It is a graph which shows the relationship between a frequency and a transmission loss.
In FIG. 7B, FIG. 7E, and FIG. 7F, a circle is drawn by a broken line at a portion where a drop in transmission loss is seen.
As a result of the measurement, in Example 1, there was no drop in the transmission loss between 100 and 1200 Hz, and no secondary radiation sound was confirmed. On the other hand, in Comparative Examples 1, 4, and 5, a drop in transmission loss was observed between 100 and 1200 Hz, and secondary radiation sound was confirmed. In Comparative Examples 2 and 3, there was no reduction in transmission loss and no secondary radiation sound was confirmed.
According to the comparison between Example 1 and Comparative Examples 1 and 4, when the constituent material of the sound absorbing member does not have the communication hole formed by foaming and the condition of the predetermined compressive strength is not satisfied, the secondary radiated sound is emitted. Is understood to occur. Further, from the comparison between Example 1 and Comparative Example 5, it is understood that the generation of the secondary radiated sound cannot be prevented unless the upper layer and the lower layer are bonded.
Further, it is understood that the sound absorbing member of Comparative Example 3 has a communication hole formed by foaming in its constituent material, and secondary radiation sound is not generated in the first place. Furthermore, from the comparison between Comparative Examples 2 and 3, it is understood that when the sound absorbing member constituent material has a communication hole due to foaming, the secondary radiation sound does not occur regardless of the compressive strength of the constituent material. That is, it can be said that the present invention solves the specific problem of preventing the secondary radiated sound that occurs when the constituent material of the sound absorbing member does not have a communication hole due to foaming.

1 Car 2 Rear Seat 3 Luggage Room 4 Floor Member 5 Underfloor Space 80 Secondary Radiation Sound Measuring Device 81 Sound Source Room 82 Sound Receiving Room 83 Speaker 85 Sound Receiving Room Microphone 86 Measuring Device 100, 200 Sound Absorbing Member 10 Upper Layer 20 Lower Layer 21 Side Layer 22 Bottom layer 30, 40 Adhesive layer 110 Introducing passage (first through hole)
120 Hollow part (second through hole)
121 Wall surface of second through hole (side surface of hollow portion)
122 Surface of bottom layer (bottom surface of hollow part)
130,140 Through hole of adhesive layer

Claims (17)

A sound absorbing member having a Helmholtz resonance structure consisting of an introduction passage opening to the surface and a hollow portion connected to the outside through the introduction passage,
Made of a plate material that does not have a communication hole formed by foaming,
An upper layer provided with a columnar first through hole forming the introduction passage,
Laminated on the upper layer, a lower layer provided with the hollow portion,
An adhesive layer for adhering the upper layer and the lower layer,
In the portion of the sound absorbing member where the Helmholtz resonance structure is not formed, the compressive stress σ measured in the thickness direction according to JIS K 7181 (2011) is 0.1 to 200 MPa. .. The sound absorbing member according to claim 1, wherein the first through hole is a through hole formed by machining. The sound absorbing member according to claim 1, wherein the plate material forming the upper layer is made of resin. The sound absorbing member according to claim 3, wherein the resin is foamed resin. The lower layer is a side surface layer formed by providing a plate-like member having no communication hole formed by foaming with a columnar second through hole having an opening diameter larger than that of the first through hole,
5. A bottom layer which is made of a plate material and is not provided with a through hole is sequentially laminated, and the hollow portion is formed by the second through hole and the bottom layer. The sound absorbing member according to item 1. The sound absorbing member according to claim 5, wherein the second through hole is a through hole formed by machining. The sound absorbing member according to claim 5 or 6, wherein the plate materials forming the side surface layer and the bottom surface layer are made of resin. The sound absorbing member according to claim 7, wherein the resin is foamed resin. On the surface of the plate material forming the upper layer on the side where the openings are formed, a fiber layer is further formed,
The sound absorbing member according to claim 1, wherein an opening communicating with the opening of the introduction passage is formed in the fiber layer. A vehicle component comprising the sound absorbing member according to any one of claims 1 to 9. An automobile, wherein the introduction passage of the sound absorbing member according to any one of claims 1 to 9 is arranged in a road surface direction. A method for manufacturing a sound absorbing member having a Helmholtz resonance structure comprising an introduction passage opening to the surface and a hollow portion connected to the outside through the introduction passage,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a lower layer which is a plate material having a hollow portion,
A step of adhering the upper layer and the lower layer with an adhesive layer,
The method for manufacturing a sound absorbing member, wherein the plate material forming the upper layer is a plate material having no communication hole formed by foaming. The method for manufacturing a sound absorbing member according to claim 12, wherein the upper layer is formed by forming the first through hole by machining on a plate material having no through hole. The method for producing a sound absorbing member according to claim 12 or 13, wherein a lower layer is produced by forming a hollow portion as a hollow portion in a plate material having no through hole in the middle of its thickness direction by machining. .. A method for manufacturing a sound absorbing member having a Helmholtz resonance structure comprising an introduction passage opening to the surface and a hollow portion connected to the outside through the introduction passage,
A step of producing an upper layer which is a plate material having a columnar first through hole which serves as an introduction passage,
A step of producing a side surface layer which is a plate material having a second through hole,
A step of preparing a plate material to be a bottom layer,
A plate material to be an upper layer, a plate material to be a side surface layer, and a plate material to be a bottom surface layer are laminated to form a hollow portion by the second through hole and the bottom surface layer, and a lower layer composed of the side surface layer and the bottom surface layer is formed. And a step of adhering the lower layer with an adhesive layer,
The method for manufacturing a sound absorbing member, wherein the plate material forming the upper layer and the plate material forming the side surface layer are plate materials formed by foaming and having no communication holes. The method for manufacturing a sound absorbing member according to claim 15, wherein the upper layer is formed by forming the first through hole by machining on a plate material having no through hole. The method for manufacturing a sound absorbing member according to claim 15 or 16, wherein a side surface layer is formed by forming a second through hole by machining on a plate material having no through hole.

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