JP3776057B2 - Production method of sound absorbing material for silencer - Google Patents
Production method of sound absorbing material for silencer Download PDFInfo
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- JP3776057B2 JP3776057B2 JP2002143681A JP2002143681A JP3776057B2 JP 3776057 B2 JP3776057 B2 JP 3776057B2 JP 2002143681 A JP2002143681 A JP 2002143681A JP 2002143681 A JP2002143681 A JP 2002143681A JP 3776057 B2 JP3776057 B2 JP 3776057B2
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Description
【0001】
【発明の属する技術分野】
本発明は、自動車等の内燃機関の排気管に設けられる消音器及びその吸音材に関するものである。
【0002】
【従来の技術】
従来のこの種の消音器は、排気管の一部に多数の通気孔を貫設し、該排気管の一部の外周にグラスウールよりなる消音層を配設し、その外周に金属よりなる外管を被せてなるものが一般的である。また、排気管と消音層との間に金属繊維よりなる飛散防止層を設け、グラスウールの熱劣化及び飛散を防止したものもある。
【0003】
【発明が解決しようとする課題】
近年、資源のリサイクルが重視されており、特に自動車の分野においてはリサイクル率の向上が至上命題とされている。従来の技術に用いられるグラスウールは、使用により劣化した際の再利用先が見当たらないため廃棄せざるを得ない。従って、これまでのグラスウール消音層を、リサイクル可能なステンレス鋼繊維等の金属繊維よりなる消音層で置き換えることを検討する必要が出てきたが、例えば、汎用のステンレス鋼よりなる繊維を綿状にしたステンレスウールには次のような問題がある。
(1)ステンレスウールは、グラスウールと比べて吸音率が低く、特に高周波(例えば1000Hz以上)の吸音率が低い。
(2)ステンレスウールは、グラスウールと比べて高温耐久性に劣り、特に平均繊維径の減少に伴い、高温環境での酸化増量が増加する傾向がある。
【0004】
上記問題(1)については、適当な解決手段がなかった。一方、上記問題(2)については、排気ガスの温度が高く、汎用のステンレス鋼繊維では酸化劣化を生ずる過酷な用途には、高Al含有フェライト系ステンレス鋼に希土類元素等を添加し耐熱特性向上を図った材料(特開平4−354850号公報、特開平6−172932号公報、特開平6−172933号公報に記載の合金や、さらに高温引張強さを改善した特開2000−273588号公報に記載の合金など)からなる繊維を用いることが考えられる。しかし、これらの合金材料は何れも高価であり、さほど高温引張強度を必要としない消音器の吸音用金属繊維としては不向きである。
【0005】
そこで、本発明者は、以前より上記の問題(1)(2)を解決し得る技術開発に取り組み、今回、ステンレスウールの平均繊維径を通常の70〜150μmから10〜40μmへと微細化し、適度な嵩密度に調整することで、グラスウール並みの吸音性能を得られる知見を得た。さらに、排気ガスの温度が高く、汎用のステンレス鋼繊維では酸化劣化を生ずる過酷な用途には、特に電熱・抵抗材料として使われる鉄・クロム・アルミニウム合金に着目し、耐高温酸化性が改善できる知見を得た。
【0006】
本発明の目的は、消音層も含めてオール金属化を図ることによりリサイクル性を高めることができるとともに、消音層の金属化にも拘わらず高い吸音率を得ることができる内燃機関の排気管用の消音器を提供することにある。
【0007】
【課題を解決するための手段】
(1)第1の発明は、平均繊維径を10〜40μmとする断面不規則形状をなし、繊維長方向に沿って延びる微小溝及び稜を有するとともに該稜に微小な欠けを有する金属繊維を用いて、嵩密度100〜700kg/m3 に調整した消音器用吸音材である。
【0008】
平均繊維径は、金属繊維の任意断面を50点測定した時の平均値とする。このように、金属繊維であっても、平均繊維径を10〜40μmとすることにより、グラスウール並みの吸音性能を付与することができる。10μm未満の微細繊維では、その加工(特に切削加工)が極めて困難で高価となり、また排気管の外周に巻き付ける時などの引張力に耐えられにくく、他方、40μmを越えるときには、嵩密度を700kg/m3 の高密度に巻き付けてもグラスウール並みの吸音性能を得ることができない。吸音材の嵩密度は、さらに好ましくは100〜550kg/m3 である。
【0009】
さらに、「断面不規則形状をなし、繊維長方向に沿って延びる微小溝及び稜を有するとともに該稜に微小な欠けを有する金属繊維」にすることで、金属繊維の空隙が歪曲やくびれを有することにより、空気の粘性摩擦抵抗が増大し、音エネルギーの一部が熱エネルギーに変換しやすくなり、吸音性能の向上により一層寄与することができる。
【0010】
金属繊維の材料は、特に限定されないが、ステンレス鋼、クロム−ニッケル系合金、高ニッケル合金、高コバルト合金、チタン合金等の耐熱合金、その他の耐熱性及び耐食性を備えた金属を例示できる。通常の排気ガス温度環境では、コストと耐久性からフェライト系ステンレス鋼からなる繊維が好ましい。また、金属繊維は極力長く連続する連続繊維であることが好ましい。
【0011】
(2)第2の発明は、前記金属連続繊維が、重量%にてC;0.10%以下、Si;1.5%以下、Mn;1.0%以下、Cr;17.0〜26.0%、Al2.0〜6.0%、Mo;0.4%以下、残部がFe及び不可避的不純物からなる成分を持ち、高温耐酸化性に優れた鉄・クロム・アルミニウム合金材料からなることを特徴とする。
【0012】
この組成は、従来から電熱・抵抗材料や耐熱金網として実施されている鉄・クロム・アルミニウム合金に、Moを0.4%まで添加することで、耐食性をも改善した材料を包括する。金属繊維は熱酸化によって、その表面に酸化皮膜が形成され、また加熱と冷却を繰り返すと、該酸化皮膜は剥離しやすくなる。前記組成の鉄・クロム・アルミニウム合金からなる繊維とすることで、過酷な高温環境下で熱酸化スケールの剥離によって縮径したり、かつ折損などによって部分欠落・飛散したりする現象を軽減する。すなわち、高温下の耐酸化性向上を図り、必要以上の酸化皮膜を抑制することができる。前記の鉄・クロム・アルミニウム合金の材料としては、フェライト系耐熱鋼の鉄クロム1種、鉄クロム2種などを例示できる。
【0013】
(3)第3の発明は、前記金属繊維が、切削加工により平均繊維径10〜40μmに繊維化されたことで、収束時の引張によるひびが誘発されて前記欠けを有したものであることを特徴とする。
前記断面不規則形状の金属繊維は、例えば線径5mm以下に冷間伸線加工した線材を、さらに例えばダイス引きにより切削加工することにより繊維として得ることができる。切削加工によって繊維化することで、例えばダイス引きした際のツールマークや収束時の引張によるひびを誘発し、平均繊維径10〜40μmの繊維の表面形態が、前記の通り、繊維長方向に沿って延びる微小溝及び稜を有するとともに該稜に微小な欠けを有する形態となる。このため、より一層吸音性能の向上に寄与できる。また、鉄・クロム・アルミニウム合金の線材は、汎用フェライト系ステンレス鋼並みの切削加工性を有しており、良好な金属連続繊維を得ることができる。
【0014】
(4)第4の発明は、平均繊維径を10〜40μmとする断面不規則形状をなし、繊維長方向に沿って延びる微小溝及び稜を有するとともに該稜に微小な欠けを有する金属繊維を、嵩密度100〜700kg/m3 に調整して吸音材とし、該吸音材を内燃機関の排気管の外周に配される消音層の少なくとも一部として設けた消音器である。
【0015】
ここで「排気管」は排気が通り消音器を構成する管であれば特に限定されず、内燃機関から延出する排気管や、該排気管に連結された消音器外筒の内部仕切板に設けられたインナーパイプ等を例示できる。消音層は、その全体が前記金属繊維の吸音材よりなるものが望ましい。また、吸音材の設け方としては、特に限定されないが、多数本の金属繊維を繊維長方向に長い帯状にまとめた吸音材を排気管の外周に巻き付ける方法を例示できる。その他の詳細は、上記第1の発明の詳細と同様である。
上記(1)〜(4)に基づき、本発明に係る消音器用吸音材の製造方法は、線径5mm以下に冷間伸線加工した金属線材を、切削加工することにより平均繊維径を10〜40μmとする断面不規則形状をなす金属繊維に繊維化することで、収束時の引張によるひびを誘発し、前記金属繊維の表面形態を、繊維長方向に沿って延びる微小溝及び稜を有するとともに該稜に微小な欠けを有する形態とし、該金属繊維を用いて嵩密度100〜700kg/m 3 に調整することを特徴とするものである。
【0016】
【発明の実施の形態】
以下、本発明を具体化した消音器の実施形態について説明する。なお、実施形態で記す材料、構成、数値等は例示であって、適宜変更できる。
【0017】
(試験1)
実施例1として、SUS434を前記ダイス引きにより切削加工して得られた平均繊維径20μ品のステンレス鋼繊維を用いて、嵩密度100〜700kg/m3 に充填・調整した吸音材を作成した。また、実施例2として、SUS434を前記ダイス引きにより切削加工して得られた平均繊維径40μ品のステンレス鋼繊維を用いて、嵩密度250〜700kg/m3 に充填・調整した吸音材を作成した。図4に表面形態を拡大して示すとおり、これらのステンレス鋼繊維10は断面不規則形状をなし、繊維長方向に沿って延びる微小溝11及び稜12を有するとともに該稜12に微小な欠け13を有している。また、比較例1として、平均繊維径9μ品のEガラス繊維を用いて、嵩密度100kg/m3 の吸音材を作成し、比較例2として、平均繊維径24μ品のアドバンテックス(オーウェンス コーニング ジャパン社の商品名:Advantex)のガラス長繊維を用いて、嵩密度200kg/m3 の吸音材を作成した。
【0018】
なお、ステンレス鋼繊維の平均繊維径は、任意断面を50点測定した時の平均値とし、その測定器としては定圧マイクロメーターを使用した。ガラス繊維の平均繊維径は、円形断面であるため、電子顕微鏡観察にて計測した。これら実施例1,2及び比較例1,2の各吸音材からJIS−A−1405に規定される厚さ10mmの円板形状の試験片を作成し、管内法による垂直入射吸音率測定法に従って各周波数における吸音率を測定した。表1にその測定結果を示す。
【0019】
【表1】
【0020】
(試験2)
次に、実施例3として、SUS434を前記ダイス引きにより切削加工して得られた平均繊維径30μ品のステンレス鋼繊維を用いて、所定の嵩密度に充填・調整した吸音材を作成した。また、実施例4として、フェライト系耐熱鋼の鉄クロム2種を前記ダイス引きにより切削加工して得られた平均繊維径40μ品の耐熱鋼繊維を用いて、所定の嵩密度に充填・調整した吸音材を作成した。これらの繊維の表面形態も、基本的に実施例1と同様である(図4参照)。次に、図1〜図3に示すように、外径φ57mm×内径φ54mm×全長310mmのSUS304製の排気管1(インナーパイプ)であって、多数の小孔2を貫通させた箇所の外周に、実施例3,4の各吸音材15を、繊維長方向に長い帯状(例えば帯幅20〜100mm、帯厚1〜10mm)にまとめて排気管1の外周に複数重にぐるぐる巻きする方法により、嵩密度100〜400kg/m3 になるように巻き付けて、全体がこれらの吸音材15からなる消音層3を構成した。その後、外径φ89×内径φ87×全長298mmのアルミメッキ鋼管(SACD80)製金属シェル4(アウターパイプ)を外挿し、排気管1と金属シェル4との当接部の隙間を溶接し、消音器を完成させた。また、前記比較例1,2の吸音材についても、実施例3,4と同様にして消音層を構成し、消音器を完成させた。
【0021】
このようにして作成した実施例3,4及び比較例1,2の消音器を、自動車用の4気筒で総排気量1.5リットルの内燃機関の排気管に連結し、該内燃機関を毎分4000回転で運転し、消音器の排気管1の出口より0.5m離れた位置で騒音レベルを測定比較した。表2にその測定結果を示す。
【0022】
【表2】
【0023】
(試験3)
次に、実施例3,2,4の吸音材と比較例1,2の吸音材について、高温酸化試験を行い、酸化による単位重量当たりの酸化重量を求めた。同試験は、大気中で700℃、800℃、900℃の条件にて、それぞれ24時間加熱し、単位重量当たりの酸化重量を算出した。表3にその測定結果を示す。
【0024】
【表3】
【0025】
(試験4)
次に、実施例5として、重量%にてMo;0.4%が添加された鉄クロム2種を前記ダイス引きにより切削加工して得られた平均繊維径40μ品の耐熱鋼繊維を用いて、所定の嵩密度に充填・調整した吸音材を作成した。そして、実施例3,4,5の吸音材と比較例1,2の吸音材について、酸による腐食試験を行い、腐食減量率を求めた。同試験は、JISO M611−92 自動車用マフラー内部腐食試験方法により、半浸漬試験条件で7日間後の腐食減量率を求めた。表4にその測定結果を示す。
【0026】
【表4】
【0027】
以上のとおり、実施例の防音材及び同防音材を用いた消音器によれば、次のような作用効果が得られる。
▲1▼ 表1及び表2に示す測定結果のとおり、実施例1〜4の吸音材は、金属繊維を用いているにも拘わらず、ガラス繊維を用いた比較例1,2の吸音材と略同等の吸音性能を有する。この点は、実施例5の吸音材も同様である。
▲2▼ 表3に示すとおり、実施例3,2の吸音材は、800℃までは良好な耐高温酸化性能を示している。さらに、実施例4の吸音材は、900℃まで極めて良好な耐高温酸化性能を示している。しかも、実施例4の吸音材に用いた鉄クロム2種は、前述した高Al含有フェライト系ステンレス鋼に希土類元素等を添加した材料と比べて、安価である。
▲3▼ 表4に示すとおり、実施例4,5の吸音材は、極めて優れた耐食性能を示している。
【0028】
なお、本発明は上記実施形態に限定されるものではなく、発明の趣旨から逸脱しない範囲で適宜変更して具体化することもできる。
【0029】
【発明の効果】
以上詳述したように、本発明に係る消音器用吸音材の製造方法によれば、リサイクルが容易で、且つガラス繊維製の吸音材と同等の吸音性能を得ることができる金属繊維を安価に提供できる。
【図面の簡単な説明】
【図1】本発明の実施形態の消音器を一部破断して示す斜視図である。
【図2】同消音器を一部破断して示す断面図である。
【図3】同消音器の消音層形成時の斜視図である。
【図4】同消音器に用いる吸音材の金属繊維を示す拡大図である。
【符号の説明】
1 排気管
2 小孔
3 消音層
4 金属シェル
10 ステンレス鋼繊維
11 微小溝
12 稜
13 欠け
15 吸音材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silencer provided in an exhaust pipe of an internal combustion engine such as an automobile and a sound absorbing material thereof.
[0002]
[Prior art]
This type of conventional silencer has a large number of ventilation holes penetrating a part of the exhaust pipe, a silencer layer made of glass wool is arranged on the outer periphery of a part of the exhaust pipe, and an outer part made of metal on the outer periphery. What is covered with a tube is common. In addition, there is a type in which a scattering prevention layer made of metal fibers is provided between the exhaust pipe and the sound deadening layer to prevent thermal degradation and scattering of the glass wool.
[0003]
[Problems to be solved by the invention]
In recent years, recycling of resources has been emphasized, and particularly in the field of automobiles, improvement of the recycling rate is regarded as the most important issue. Glass wool used in the prior art has to be discarded because there is no reuse destination when it deteriorates due to use. Therefore, it has become necessary to consider replacing the conventional glass wool sound deadening layer with a sound deadening layer made of metal fibers such as recyclable stainless steel fibers. The stainless steel wool has the following problems.
(1) Stainless steel wool has a lower sound absorption rate than glass wool, and particularly has a low sound absorption rate at a high frequency (for example, 1000 Hz or more).
(2) Stainless steel wool is inferior to glass wool in high-temperature durability, and there is a tendency that the increase in oxidation in a high-temperature environment tends to increase especially as the average fiber diameter decreases.
[0004]
Regarding the above problem (1), there was no appropriate solution. On the other hand, with regard to the above problem (2), for severe applications where the exhaust gas temperature is high and general stainless steel fibers cause oxidative degradation, the addition of rare earth elements to high Al content ferritic stainless steel improves the heat resistance characteristics. (See JP-A-4-354850, JP-A-6-172932, JP-A-6-172933, and JP-A 2000-273588 with improved high-temperature tensile strength) It is conceivable to use fibers made of the described alloys. However, all of these alloy materials are expensive and are not suitable as sound absorbing metal fibers for silencers that do not require high temperature tensile strength.
[0005]
Therefore, the present inventor has been working on technical development that can solve the above problems (1) and (2), and this time, the average fiber diameter of stainless steel wool is refined from the usual 70 to 150 μm to 10 to 40 μm, The knowledge which can obtain the sound-absorbing performance equivalent to glass wool was obtained by adjusting to an appropriate bulk density. Furthermore, high-temperature oxidation resistance can be improved by focusing on iron / chromium / aluminum alloys used as electrothermal / resistance materials for severe applications where exhaust gas temperatures are high and general-purpose stainless steel fibers cause oxidative degradation. Obtained knowledge.
[0006]
An object of the present invention is to improve the recyclability by achieving all metallization including the sound deadening layer, and for an exhaust pipe for an internal combustion engine that can obtain a high sound absorption coefficient despite the metallization of the sound deadening layer. It is to provide a silencer.
[0007]
[Means for Solving the Problems]
(1) The first invention is a metal fiber having an irregular cross-sectional shape with an average fiber diameter of 10 to 40 μm, having minute grooves and ridges extending along the fiber length direction, and having minute chips on the ridges. It is a sound-absorbing material for a silencer that is adjusted to a bulk density of 100 to 700 kg / m 3 .
[0008]
An average fiber diameter is taken as the average value when 50 arbitrary cross sections of a metal fiber are measured. Thus, even if it is a metal fiber, the sound absorption performance equivalent to glass wool can be provided by making an average fiber diameter 10-40 micrometers. With fine fibers of less than 10 μm, the processing (especially cutting) is extremely difficult and expensive, and it is difficult to withstand tensile forces such as when wound around the outer periphery of the exhaust pipe. On the other hand, when it exceeds 40 μm, the bulk density is 700 kg / Even if it is wound at a high density of m 3 , the sound absorption performance equivalent to glass wool cannot be obtained. The bulk density of the sound absorbing material is more preferably 100 to 550 kg / m 3 .
[0009]
Furthermore, the voids of the metal fiber have distortion and constriction by making “a metal fiber having an irregular cross-sectional shape and having a minute groove and a ridge extending along the fiber length direction and a minute chip on the ridge”. As a result, the viscous frictional resistance of air increases, and part of sound energy can be easily converted into heat energy, which can further contribute to the improvement of sound absorption performance.
[0010]
The material of the metal fiber is not particularly limited, and examples thereof include heat-resistant alloys such as stainless steel, chromium-nickel alloys, high nickel alloys, high cobalt alloys, titanium alloys, and other metals having heat resistance and corrosion resistance. In a normal exhaust gas temperature environment, a fiber made of ferritic stainless steel is preferable from the viewpoint of cost and durability. Moreover, it is preferable that a metal fiber is a continuous fiber which continues as long as possible.
[0011]
(2) In the second invention, the metal continuous fiber is C in weight percent: 0.10% or less, Si: 1.5% or less, Mn: 1.0% or less, Cr: 17.0 to 26 0.0%, Al 2.0-6.0%, Mo; 0.4% or less, with the balance being Fe and inevitable impurities, and made of iron / chromium / aluminum alloy material with excellent high-temperature oxidation resistance It is characterized by that.
[0012]
This composition includes materials whose corrosion resistance is also improved by adding Mo to 0.4% to an iron / chromium / aluminum alloy which has been conventionally used as an electrothermal / resistance material or a heat-resistant wire mesh. The metal fiber is thermally oxidized to form an oxide film on the surface thereof, and when the heating and cooling are repeated, the oxide film is easily peeled off. By using a fiber made of iron, chromium, and aluminum alloy having the above-described composition, the phenomenon that the diameter is reduced by peeling of the thermal oxide scale in a severe high-temperature environment, and the phenomenon of partial omission and scattering due to breakage or the like is reduced. That is, it is possible to improve the oxidation resistance at high temperatures and to suppress an unnecessary oxide film. Examples of the material of the iron / chromium / aluminum alloy include ferritic heat-resistant steel of
[0013]
(3) In the third invention, the metal fiber is made into a fiber having an average fiber diameter of 10 to 40 μm by cutting , so that cracks due to tension at the time of convergence are induced and the chip has the chip. It is characterized by.
The metal fiber having an irregular cross-sectional shape can be obtained as a fiber by, for example, further cutting a wire rod that has been cold drawn to a wire diameter of 5 mm or less, for example, by die drawing. By fiberizing by cutting, for example, a tool mark when dies are drawn and cracks due to tension at the time of convergence are induced, and the surface form of fibers having an average fiber diameter of 10 to 40 μm is along the fiber length direction as described above. It has the form which has the micro groove | channel and ridge which extend, and has a micro notch in this ridge. For this reason, it can contribute to the improvement of the sound absorption performance. Moreover, the iron / chromium / aluminum alloy wire has the same machinability as that of general-purpose ferritic stainless steel, and a good continuous metal fiber can be obtained.
[0014]
(4) The fourth invention is a metal fiber having an irregular cross-sectional shape with an average fiber diameter of 10 to 40 μm, having a minute groove and a ridge extending along the fiber length direction, and having a minute chip on the ridge. The silencer is adjusted to a bulk density of 100 to 700 kg / m 3 to obtain a sound absorbing material, and the sound absorbing material is provided as at least a part of a sound deadening layer disposed on the outer periphery of the exhaust pipe of the internal combustion engine.
[0015]
Here, the “exhaust pipe” is not particularly limited as long as exhaust passes through and constitutes a silencer, and is not limited to an exhaust pipe extending from an internal combustion engine or an inner partition plate of a silencer outer cylinder connected to the exhaust pipe. The provided inner pipe etc. can be illustrated. The sound deadening layer is preferably made entirely of the metal fiber sound absorbing material. Further, the method of providing the sound absorbing material is not particularly limited, but a method of winding a sound absorbing material in which a large number of metal fibers are combined in a strip shape long in the fiber length direction around the outer periphery of the exhaust pipe can be exemplified. Other details are the same as the details of the first invention.
Based on said (1)-(4), the manufacturing method of the sound-absorbing material for silencers which concerns on this invention sets an average fiber diameter to 10 by cutting the metal wire which cold-drawn to the wire diameter of 5 mm or less. By making it into a metal fiber having an irregular cross section of 40 μm, it induces cracks due to tension at the time of convergence, and the surface form of the metal fiber has micro grooves and ridges extending along the fiber length direction. It is characterized in that the ridge has a fine chip and is adjusted to a bulk density of 100 to 700 kg / m 3 using the metal fiber .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a silencer embodying the present invention will be described below. Note that the materials, configurations, numerical values, and the like described in the embodiments are examples and can be changed as appropriate.
[0017]
(Test 1)
As Example 1, a sound absorbing material filled and adjusted to a bulk density of 100 to 700 kg / m 3 was prepared using stainless steel fibers having an average fiber diameter of 20 μm obtained by cutting SUS434 by the above-described die drawing. In addition, as Example 2, a sound absorbing material filled and adjusted to a bulk density of 250 to 700 kg / m 3 using a stainless steel fiber having an average fiber diameter of 40 μ obtained by cutting SUS434 by the above-mentioned die drawing is prepared. did. As shown in an enlarged view of the surface form in FIG. 4, these
[0018]
The average fiber diameter of the stainless steel fibers was an average value when 50 arbitrary cross sections were measured, and a constant pressure micrometer was used as the measuring instrument. Since the average fiber diameter of the glass fiber was a circular cross section, it was measured with an electron microscope. A disk-shaped test piece having a thickness of 10 mm as defined in JIS-A-1405 is prepared from each of the sound absorbing materials of Examples 1 and 2 and Comparative Examples 1 and 2, and in accordance with a method for measuring normal incident sound absorption rate by an in-tube method. The sound absorption rate at each frequency was measured. Table 1 shows the measurement results.
[0019]
[Table 1]
[0020]
(Test 2)
Next, as Example 3, a sound-absorbing material filled and adjusted to a predetermined bulk density was prepared using stainless steel fibers having an average fiber diameter of 30 μ obtained by cutting SUS434 by the die drawing. In addition, as Example 4, a heat-resistant steel fiber having an average fiber diameter of 40 μm obtained by cutting two types of ferritic heat-resistant steel iron chromium by die drawing was filled and adjusted to a predetermined bulk density. A sound absorbing material was created. The surface form of these fibers is basically the same as in Example 1 (see FIG. 4). Next, as shown in FIG. 1 to FIG. 3, an exhaust pipe 1 (inner pipe) made of SUS304 having an outer diameter φ57 mm × inner diameter φ54 mm × total length 310 mm, and on the outer periphery of a portion through which many
[0021]
The silencers of Examples 3 and 4 and Comparative Examples 1 and 2 created in this way are connected to an exhaust pipe of an internal combustion engine having a total displacement of 1.5 liters with four cylinders for automobiles. The operation was performed at 4000 rpm, and the noise level was measured and compared at a position 0.5 m away from the outlet of the
[0022]
[Table 2]
[0023]
(Test 3)
Next, the sound absorbing materials of Examples 3, 2, and 4 and the sound absorbing materials of Comparative Examples 1 and 2 were subjected to a high-temperature oxidation test to determine the oxidized weight per unit weight due to oxidation. In this test, heating was performed in the atmosphere at 700 ° C., 800 ° C., and 900 ° C. for 24 hours, and the oxidized weight per unit weight was calculated. Table 3 shows the measurement results.
[0024]
[Table 3]
[0025]
(Test 4)
Next, as Example 5, using heat-resistant steel fibers having an average fiber diameter of 40 μm obtained by cutting two types of iron chrome added with Mo: 0.4% by weight by die drawing. Then, a sound absorbing material filled and adjusted to a predetermined bulk density was prepared. And about the sound-absorbing material of Example 3, 4, 5 and the sound-absorbing material of Comparative Examples 1 and 2, the corrosion test by an acid was done and the corrosion weight loss rate was calculated | required. In this test, the corrosion weight loss rate after 7 days was determined under the semi-immersion test condition by the JISO M611-92 automotive muffler internal corrosion test method. Table 4 shows the measurement results.
[0026]
[Table 4]
[0027]
As described above, according to the soundproofing material of the embodiment and the silencer using the soundproofing material, the following operational effects can be obtained.
(1) As the measurement results shown in Tables 1 and 2, the sound absorbing materials of Examples 1 to 4 are the same as the sound absorbing materials of Comparative Examples 1 and 2 using glass fibers, although metal fibers are used. It has almost the same sound absorption performance. This also applies to the sound absorbing material of Example 5.
(2) As shown in Table 3, the sound-absorbing materials of Examples 3 and 2 show good high-temperature oxidation resistance up to 800 ° C. Furthermore, the sound-absorbing material of Example 4 shows extremely good high-temperature oxidation resistance up to 900 ° C. Moreover, the two types of iron chromium used for the sound absorbing material of Example 4 are less expensive than the above-described material obtained by adding rare earth elements to the high Al-containing ferritic stainless steel.
(3) As shown in Table 4, the sound-absorbing materials of Examples 4 and 5 exhibit extremely excellent corrosion resistance.
[0028]
In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.
[0029]
【The invention's effect】
As described above in detail , according to the method for producing a sound absorbing material for a silencer according to the present invention, metal fiber that can be easily recycled and can obtain sound absorbing performance equivalent to a sound absorbing material made of glass fiber is provided at low cost. it can.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a muffler according to an embodiment of the present invention with a part thereof broken away.
FIG. 2 is a cross-sectional view showing the silencer partly broken away.
FIG. 3 is a perspective view of the silencer when a sound deadening layer is formed.
FIG. 4 is an enlarged view showing a metal fiber of a sound absorbing material used in the silencer.
[Explanation of symbols]
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Claims (1)
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