JP2006330570A - Soundproof cover having vibration damping property and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably regulate the vibration of a sound insulating layer by a sound absorbing layer without using a vibration damping material such as a grommet and a vibration damping layer. <P>SOLUTION: The sound insulating layer 1 is laminated with the sound absorbing layer 2 formed by the foam molding using a polyol side solution containing 10-50 weight% of polyol of which average number of functional groups is 5 or more and average molecular weight is less than 1,000, in the whole polyol. The sound absorbing layer 2 has a high vibration damping property in a wide range of the temperature and a high sound absorbing property in a frequency zone which is especially important in automobiles since the tanδ is 0.3 or more at the temperature range of 0-60°C, and the degree of sound absorption is 0.5 or more in the frequency zone of 1-2 kHz. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a soundproof cover disposed in a noise source such as an intake manifold of an automobile and a method for manufacturing the same, and more particularly to a soundproof cover having a sound absorbing layer having vibration damping properties and a method for manufacturing the same.

  In the engine room of the vehicle, an engine cover, a side cover, an oil pan cover, an under cover, and the like having a sound insulating layer made of sheet metal or hard resin are arranged in order to suppress radiation sound from a noise source. In these covers, a sound absorption layer made of a molded polyurethane foam formed in a predetermined shape is interposed between a hard sound insulation layer and a noise source, and sound insulation is performed by sound absorption and sound insulation.

  Japanese Patent Application Laid-Open No. 09-134179 describes a soundproof cover in which a sound absorbing layer is formed in conformity with the surface shape of a noise source such as an intake manifold, and the sound absorbing layer is disposed in close contact with the noise source. By doing in this way, since a clearance gap does not arise between a soundproof cover and a noise source, the leakage of the noise from the clearance gap can be prevented.

  However, although the sound absorbing layer made of a conventional molded polyurethane foam is excellent in sound absorbing property, the vibration damping property is insufficient. Therefore, the sound insulation layer is fixed to a noise source via a vibration isolation member such as a rubber mount or a grommet, or the sound insulation layer is formed of a T-shaped collar member and a sound absorption layer as described in JP-A-2002-028934. However, there is a problem that the number of parts increases and the number of assembling steps increases, resulting in an increase in cost.

Japanese Patent Laid-Open No. 2003-029765 proposes a soundproof cover provided with a vibration damping layer that restricts vibration of the sound insulating layer at the interface between the sound absorbing layer and the sound insulating layer. However, in this case as well, there is an inevitable problem that the cost is increased because an extra damping layer is required.
JP 09-134179 A JP 2002-028934 JP2003-029765

  The present invention has been made in view of the above circumstances, and by making a sound absorbing layer having a sound absorbing property and a vibration damping property, the sound absorbing layer is configured to have only the sound insulating layer and the sound absorbing layer, and the sound absorbing layer vibrates the sound insulating layer. Making sure to regulate is an issue to be solved.

  A feature of the soundproof cover of the present invention that solves the above problems is a soundproof cover that is composed of a hard sound insulating layer and a sound absorbing layer made of soft urethane, and is disposed in contact with a noise source, and the sound absorbing layer has a temperature of 0 ° C to The tan δ in the range of 60 ° C is 0.3 or more, and the sound absorption coefficient in the frequency range of 1 kHz to 2 kHz is 0.5 or more.

  The sound absorbing layer preferably has a storage elastic modulus (E ′) at 0 ° C. of 5 MPa or less.

  And the characteristic of the manufacturing method of the soundproof cover of the present invention is that a polyol side liquid containing 10 to 50% by weight of a polyol having an average functional group number of 5 or more and an average molecular weight of less than 1000 in the total polyol, a polyisocyanate, a foaming agent, , To form a sound absorbing layer.

  According to the soundproof cover of the present invention, the sound absorbing layer has a characteristic that tan δ in the range of 0 ° C. to 60 ° C. is 0.3 or more and the sound absorption rate in the frequency range of 1 kHz to 2 kHz is 0.5 or more. That is, since the sound absorbing layer has a high vibration damping property in a wide temperature range, the vibration of the sound insulating layer can be surely restricted and the sound insulating layer itself can be reliably prevented from becoming a noise source. Moreover, since the sound absorbing layer has a high sound absorbing characteristic in a frequency range that is particularly problematic in automobiles, the sound absorbing characteristic equivalent to that of the conventional sound absorbing layer is exhibited.

  Therefore, the vibration of the sound insulation layer can be reliably regulated while eliminating the need for the vibration isolating member and the vibration damping layer, so that the cost can be reduced by reducing the number of parts and the number of assembly steps.

  And according to the manufacturing method of this invention, the sound-absorbing layer which has the said characteristic can be manufactured stably and reliably and easily.

  The soundproof cover of the present invention comprises a hard sound insulating layer and a sound absorbing layer made of soft urethane. As the sound insulation layer, a hard plate made of a resin plate or a metal plate can be used. Although it is necessary to have a certain large mass per unit area, the shape is determined by the shape of the sound source and the shape of the arrangement space, and is not particularly limited.

  The sound insulation layer has a mounting portion fixed to the noise source. The mounting portion is not particularly limited as long as the sound insulation layer can be directly fixed to the noise source, and the shape, bolt hole and the like are mechanically engaged with the noise source. In the soundproof cover of the present invention, even if the sound insulation layer is directly fixed to the noise source in this way, the sound insulation layer can be effectively damped by the sound absorption layer having vibration damping properties.

  The sound-absorbing layer, which is the greatest feature of the present invention, has the characteristics that tan δ in the range of 0 ° C. to 60 ° C. is 0.3 or more and the sound absorption rate in the frequency range of 1 kHz to 2 kHz is 0.5 or more. Tan δ in the range of 0 ° C. to 60 ° C. can be measured by a dynamic viscoelasticity test. If tanδ is 0.3 or more, it can be said that the sound absorbing layer is excellent in vibration damping. Therefore, the sound absorbing layer has high vibration damping at the actual use temperature ranging from 0 ° C to 60 ° C, and can regulate the vibration of the sound insulating layer. it can. It is more desirable that tan δ is 0.3 or more in the range of 0 ° C to 80 ° C.

The sound absorption layer has a sound absorption coefficient of 0.5 or more in the frequency range of 1 kHz to 2 kHz, and can well absorb noise in the frequency range of 1 kHz to 2 kHz, which is a problem in automobiles. In order to set the average sound absorption coefficient in the frequency range of 1 kHz to 2 kHz to 0.5 or more, the density of the sound absorption layer may be set to 0.1 g / cm ³ or less.

  The sound absorbing layer preferably has a storage elastic modulus (E ′) at 0 ° C. of 5 MPa or less. By doing so, it does not become hard even in a low temperature range of about 0 ° C., and vibration damping is further improved. This storage elastic modulus (E ′) can be measured by a dynamic viscoelasticity test.

  The soundproof cover of the present invention is effective for those arranged so as to come into contact with a noise source. As described above, the tanδ in the range of 0 ° C to 60 ° C is 0.3 or more, so the vibration transmitted from the noise source to the sound insulation layer is suppressed by the sound absorption layer, and secondary noise due to the vibration of the sound insulation layer is prevented. Is done. Further, if the sound absorbing layer is formed in advance so as to have a surface shape corresponding to the surface shape of the noise source, the contact area with the noise source increases, which is effective for damping the noise source itself. Further, since the sound absorbing layer itself is provided with vibration damping properties, the sound insulating layer can be attached directly to the noise source or with the sound absorbing layer interposed without using a rubber mount or grommet.

  The sound absorbing layer may be bonded to the sound insulating layer or may be simply sandwiched between the sound insulating layer and the noise source without being bonded. However, considering the assembly man-hours, it is preferable to provide a soundproof cover in which the sound insulating layer and the sound absorbing layer are integrated. Therefore, it is particularly desirable that the sound insulation layer is disposed in the foaming mold during the formation of the sound absorbing layer and integrally molded.

  This sound absorbing layer is produced by reacting a polyol side liquid containing 10 to 50% by weight of a polyol having an average number of functional groups of 5 or more and an average molecular weight of less than 1000, a polyisocyanate, and a foaming agent. The When producing a conventional sound-absorbing layer, a polyol for soft urethane having a functional group number of 4 or less and an average molecular weight of 1000 or more is common. However, as in the present invention, by using 10 to 50% by weight of a polyol having an average functional group number of 5 or more and an average molecular weight of less than 1000 in the total polyol, tan δ in the range of 0 ° C. to 60 ° C. is 0.3 or more, It has become possible to produce a sound-absorbing layer with a characteristic that the sound absorption coefficient in the frequency range of 1 kHz to 2 kHz is 0.5 or more.

  The polyol having an average functional group number of 5 or more and an average molecular weight of less than 1000 may be a single kind or a mixture of plural kinds of polyols. In the case of a mixture of a plurality of types of polyols, various combinations with polyols other than polyols having an average functional group number of 5 or more and an average molecular weight of less than 1000 can be taken, so the average functional group number and average molecular weight differ depending on the combination. However, combinations having an average number of functional groups of 5 or more and an average molecular weight of less than 1000 are limited, and even if one of the combinations is 10 to 50% by weight based on the total polyol, it is included in the scope of the present invention.

  If the amount of polyol having an average number of functional groups of 5 or more and an average molecular weight of less than 1000 is less than 10% by weight of the total polyol, tanδ in the range of 0 ° C to 60 ° C will be less than 0.3, and the sound absorbing layer will have insufficient vibration damping It becomes. If the amount of polyol having an average number of functional groups of 5 or more and an average molecular weight of less than 1000 exceeds 50% by weight of the total polyol, the storage elastic modulus (E ′) in the low temperature range becomes extremely high, and it becomes close to hard urethane, Sound absorption is reduced.

  Further, polyols other than polyols having an average number of functional groups of 5 or more and an average molecular weight of less than 1000 are used in an amount of more than 50% by weight and less than 90% by weight in all polyols. As this polyol, those having 2 to 8 functional groups in one molecule and 1000 to 10,000 molecular weights can be used. If the number of functional groups is less than 2, molding of the polyurethane foam may be difficult, and if the number of functional groups is more than 8, physical properties such as tensile elongation of the resulting polyurethane foam will be extremely lowered. On the other hand, when the molecular weight exceeds 10,000, the viscosity becomes high and foaming becomes difficult, and it becomes difficult to mold polyurethane foam.

  Polyols having an average number of functional groups of 5 or more and an average molecular weight of less than 1000, and other polyols include polyhydric hydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether ester polyols, polyether polyamines , Polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, etc. .

  The sound absorbing layer of the present invention is produced by reacting the polyol mixture, polyisocyanate, and foaming agent. Polyisocyanates include MDI polyisocyanates, aromatic polyisocyanates such as TDI (tolylene diisocyanate), TODI (tolidine diisocyanate), NDI (naphthalene diisocyanate), HDI (HMDI) (hexamethylene diisocyanate), IPDI ( Aliphatic polyisocyanates such as isophorone diisocyanate), XDI (xylylene diisocyanate), and hydrogenated XDI can be used.

  Examples of MDI polyisocyanates include pure MDI (diphenylmethane diisocyanate) and modified products thereof, polymeric MDI (polymethylene polyphenyl polyisocyanate) and modified products thereof, hydrogenated MDI (dicyclohexylmethane diisocyanate) and modified products thereof, and 4,4 ′. -MDI, 2,4'-MDI, crude MDI, carbodiimide-modified products, uretonimine-modified products, and the like can be used.

  The mixing ratio of the polyisocyanate and the polyol is preferably such that NCO / OH (index) is in the range of 0.6 to 1.0. If the index is less than 0.6, properties such as permanent distortion of the obtained sound absorbing layer are lowered and the sound absorbing property is lowered, and if it exceeds 1.0, the crosslinking reaction proceeds excessively, the moldability is lowered, the sound absorbing property is lowered and the hardness is high. Too much to suppress vibration damping.

  As the foaming agent, it is possible to use a gas that is blown or sublimated to become a gas, but it is desirable to use water as in the conventional method for producing flexible urethane.

  Moreover, in this invention, additives, such as a catalyst, a crosslinking agent, a foam stabilizer, a chain extender, and a viscosity reducing agent, can be suitably mix | blended like the conventional manufacturing method.

  As the catalyst, known amine catalysts and organometallic catalysts can be used. Specifically, bis (dimethylaminoethyl) ether, pentamethyldiethylenetriamine, N, N-dimethylcyclohexylamine, N, N-dimethylethanol. Amine, N, N, N ', N'-tetramethylhexamethylenediamine, N, N, N', N'-tetramethylpropylenediamine, N, N, N ', N'-tetramethylethylenediamine, triethylenediamine, Examples thereof include N-methyl-N ′-(dimethylamino) ethylpiperazine, N-methylmonoforin, N-ethylmonoforin, triethylamine, tin laurate, and tin octoate. The amount of the catalyst added is generally about 0.01 to 5 parts by weight per 100 parts by weight of the polyol component.

  As the crosslinking agent, those having a relatively low molecular weight are used. For example, diols, triols, polyvalent amines, those obtained by adding ethylene oxide or propylene oxide thereto, triethanolamine, diethanolamine or the like can be used. The addition amount of the crosslinking agent is generally about 0 to 20 parts by weight with respect to 100 parts by weight of the polyol component. As the foam stabilizer, a commonly used silicone foam stabilizer can be used as appropriate. In addition, according to the performance requested | required as a sound absorption layer, a flame retardant, a filler, an antistatic agent, a coloring agent, a stabilizer, etc. can be added in the range which does not deviate from the objective of this invention as needed.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Table 1 shows the compositions of the polyols (polypropylene glycols) A to G used in the examples and comparative examples. Polyol G is a mixture of three types of polyols.

Example 1
As shown in Table 1, 20 parts by weight of polyol B, 30 parts by weight of polyol C, 15 parts by weight of polyol D, 5 parts by weight of polyol E, 30 parts by weight of polyol G, and a crosslinking agent 2 parts by weight of diethylene glycol, 2.5 parts by weight of water, 1.5 parts by weight of a catalyst (such as triethylenediamine) and 1.5 parts by weight of a silicone foam stabilizer were mixed to prepare a polyol side liquid.

  On the other hand, as a polyisocyanate side liquid, a mixture of 20 parts by weight of MDI (NCO% = 29 to 33%) and 80 parts by weight of TDI (NCO% = 43%) was prepared.

The polyol side liquid and the isocyanate side liquid were mixed so that the index was 0.8, and a predetermined amount thereof was injected into a foam mold to perform foam molding. The resulting urethane foam had a density of 0.1 g / cm ³ .

  From this urethane foam, a 20 mm x 20 mm x 10 mm test piece was cut out and vibrated while the temperature was increased from -50 ° C to 80 ° C at 3 ° C / min using a "dynamic viscoelastic device" (manufactured by UBM). Dynamic viscoelasticity measurement was continuously performed at several 10 Hz and an amplitude of 10 μm. The tan δ and storage elastic modulus (E ′) at each temperature were determined, and the results are shown in FIG. In addition, the sound absorption coefficient at 20 ° C. was measured at each frequency according to the method specified in JIS-A1405, and the results are shown in FIG.

(Example 2)
As shown in Table 1, 50 parts by weight of polyol A, 20 parts by weight of polyol E, 30 parts by weight of polyol G, 2 parts by weight of diethylene glycol as a crosslinking agent, 2.5 parts by weight of water, catalyst (Triethylenediamine and the like) 1.5 parts by weight and a silicone foam stabilizer 1.5 parts by weight were mixed to prepare a polyol side liquid.

Then, using the same isocyanate side liquid as in Example 1, mixing was performed so that the index was 0.8 as in Example 1, and a predetermined amount thereof was injected into a foaming mold to perform foaming. The resulting urethane foam had a density of 0.1 g / cm ³ .

  FIG. 1 shows the results of measuring tan δ and storage elastic modulus (E ′) at each temperature in the same manner as in Example 1 using the obtained urethane foam. In addition, the sound absorption coefficient at 20 ° C. was measured at each frequency according to the method specified in JIS-A1405, and the results are shown in FIG.

(Comparative Example 1)
As shown in Table 1, 100 parts by weight of polyol C, 2 parts by weight of diethylene glycol as a crosslinking agent, 2.5 parts by weight of water, 1.5 parts by weight of a catalyst (such as triethylenediamine), and a silicone foam stabilizer 1.5 Part by weight was mixed to prepare a polyol side liquid.

Then, using the same isocyanate side liquid as in Example 1, mixing was performed so that the index was 0.8 as in Example 1, and a predetermined amount thereof was injected into a foaming mold to perform foaming. The resulting urethane foam had a density of 0.1 g / cm ³ .

  FIG. 2 shows the results of measuring tan δ and storage elastic modulus (E ′) at each temperature in the same manner as in Example 1 using the obtained urethane foam. In addition, the sound absorption coefficient at 20 ° C. was measured at each frequency according to the method specified in JIS-A1405, and the results are shown in FIG.

(Comparative Example 2)
As shown in Table 1, 100 parts by weight of polyol F, 2 parts by weight of diethylene glycol as a crosslinking agent, 2.5 parts by weight of water, 1.5 parts by weight of a catalyst (such as triethylenediamine), and a silicone foam stabilizer 1.5 Part by weight was mixed to prepare a polyol side liquid.

Then, using the same isocyanate side liquid as in Example 1, mixing was performed so that the index was 0.8 as in Example 1, and a predetermined amount thereof was injected into a foaming mold to perform foaming. The resulting urethane foam had a density of 0.1 g / cm ³ .

  FIG. 2 shows the results of measuring tan δ and storage elastic modulus (E ′) at each temperature in the same manner as in Example 1 using the obtained urethane foam.

<Evaluation>
The urethane foam of Comparative Example 1, which is a flexible urethane foam generally used in the past, has a storage elastic modulus (E ′) of 5 MPa or less over a wide temperature range, and is soft and excellent in sound absorption characteristics. However, tanδ is low over a wide temperature range, and vibration damping is extremely low.

  In addition, the urethane foam of Comparative Example 2 which is a viscoelastic urethane foam has a storage elastic modulus (E ′) that suddenly increases at 20 ° C. or less and becomes hard at low temperatures, and therefore has poor sound absorption characteristics in a low temperature range. At 0 ° C to 50 ° C, tan δ is 0.3 or more. However, when it exceeds 50 ° C, tan δ is drastically reduced and vibration damping is reduced.

  However, since the urethane foams of Examples 1 and 2 have a tan δ in the range of 0 ° C. to 60 ° C. of 0.3 or more, they exhibit high vibration damping properties in the practical temperature range. As is clear from FIG. 3, the urethane foam of Example 1 has a sound absorption coefficient of 0.5 or more in the frequency range of 1 kHz to 2 kHz, and exhibits sound absorption characteristics equivalent to the urethane foam of Comparative Example 1.

  Further, the urethane foams of Example 1 and Example 2 have a storage elastic modulus (E ′) at 0 ° C. of 5 MPa or less as in Comparative Example 1. Therefore, it is suppressed that it becomes hard in a low temperature range, and a favorable sound absorption characteristic is expressed also in a low temperature range.

  Therefore, according to the soundproof cover of the present invention formed by laminating the urethane foam of Example 1 or Example 2 and a resin plate or a metal plate, a sound absorbing layer excellent in both sound absorbing properties and vibration damping properties is provided. . This soundproof cover is shown in FIG. 4 together with a noise source such as an automobile engine.

  The soundproof cover includes a resin sound insulating layer 1 and a sound absorbing layer 2 integrally joined to the back side of the sound insulating layer 1, and the sound absorbing layer 2 is fixed in contact with the surface of the noise source 3. . The sound absorbing layer 2 is made of the urethane foam of Example 1 or Example 2, and is integrally joined to the sound insulating layer 1 by disposing the sound insulating layer 1 in a foam mold and performing foam molding. The sound insulation layer 1 is provided with a plurality of mounting holes 10 penetrating the front and back, and the sound absorbing layer 2 is not formed around the mounting holes 10. A boss 30 having a bolt hole projects from the noise source 3, and the sound insulation layer 1 is fixed to the boss 30 by a bolt 4 inserted through the mounting hole 10, so that the soundproof cover is fixed to the noise source 3. .

  Therefore, the radiated sound from the noise source 3 passes through the sound absorbing layer 2 and is repeatedly reflected by the sound insulating layer 3 and the noise source 3, while the sound energy is absorbed by changing into thermal energy due to deformation of the sound absorbing layer 2. The Further, the vibration of the noise source 3 is transmitted from the boss 30 to the sound insulation layer 1, but the vibration of the sound insulation layer 1 is suppressed by the vibration suppression action of the sound absorption layer 2, and the sound insulation layer 1 is restricted from vibrating. Therefore, the generation of secondary noise due to the vibration of the sound insulating layer 1 can be reliably prevented.

  The soundproof cover of the present invention can be used not only for transportation means such as ships, trains, airplanes, automobiles, but also for noise sources that generate noise due to vibration, such as industrial machines.

It is a graph which shows the relationship between temperature and a storage elastic modulus, and the relationship between temperature and tan-delta of the sound absorption layer used for the soundproof cover of the Example. It is a graph which shows the relationship between temperature and a storage elastic modulus, and the relationship between temperature and tan-delta of the sound absorption layer used for the soundproof cover of the comparative example. It is a graph which shows the sound absorption rate in each frequency. It is sectional drawing shown in the state which attached the soundproof cover of the Example to the noise source.

Explanation of symbols

1: Sound insulation layer 2: Sound absorption layer 3: Noise source
10: Mounting hole 30: Boss 4: Bolt

Claims (3)

A soundproof cover comprising a hard sound insulation layer and a sound absorbing layer made of soft urethane, and arranged in contact with a noise source,
The sound-absorbing layer is provided with a vibration-damping cover characterized in that tanδ in the range of 0 ° C to 60 ° C is 0.3 or more and the sound absorption coefficient in the frequency range of 1kHz to 2kHz is 0.5 or more.   2. The soundproof cover according to claim 1, wherein the sound absorbing layer has a storage elastic modulus (E ′) at 0 ° C. of 5 MPa or less. A method of manufacturing a soundproof cover having vibration damping properties according to claim 1 or claim 2,
Forming the sound-absorbing layer by reacting a polyol side liquid containing 10 to 50% by weight of a polyol having an average functional group number of 5 or more and an average molecular weight of less than 1000 in all polyols, a polyisocyanate, and a foaming agent. A method for manufacturing a soundproof cover having a characteristic vibration damping property.

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