JPS58132293A - Sound absorbing material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound absorbing material interposed in an exhaust gas path that entrains tar and soot, such as in an exhaust silencer for an internal combustion engine.

Generally, as a sound absorbing material, glass wool, rock wool, ceramic or metal porous base materials, as well as organic base materials are used depending on the purpose and conditions of use. Among these, under high temperature conditions such as exhaust silencer KsP for internal combustion engines,
Ceramic and metallic porous substrates are used. But don't take these things as they are! When used as a sound material, it is a combustion residue such as gasoline when operating an internal combustion engine! - Since μ and soot adhere to the surface and enter the interior, causing clogging, the sound-absorbing decoration deteriorates in a relatively short period of time, and exhaust noise becomes intensified. In addition, the roughness of the surface of the sound absorbing material that comes into contact with the exhaust gas is extremely hot.
The flow resistance of the exhaust gas flow along the surface of the sound-absorbing material is large, which causes an increase in the back pressure of the internal combustion engine and causes a decrease in the efficiency of the internal combustion engine. Furthermore, the sound absorption properties of conventional sound absorbing materials in the low frequency band are drastically reduced compared to 040 in the high frequency band.
However, this is not satisfactory for use in an exhaust muffler for an internal combustion engine, where the muffling ability in the low frequency band is important.

Therefore, in order to obtain a sound absorbing material that does not have the various disadvantages mentioned above, the inventors of Jin's application found that forming a thin film on the surface of a porous base material prevents the deterioration of sound absorbing performance. It is effective in preventing the efficiency of internal combustion engines from decreasing and in educating sound absorption characteristics in the low frequency band, and in addition, forming a kind of catalyst layer on the thin film further enhances the effect. As a result, they have completed this invention.

That is, this invention forms a surface layer made by kneading a low-temperature oxidation catalyst, a solid acid catalyst, and a heat-resistant binder on a thin film formed on the surface of a porous base material.

Porous substrates that can be used in the present invention include commercially available general-purpose materials such as foamed metal, sintered metal, metal fiber, and inorganic fiber reinforced metal. 1@-Cf.

y6-NI-cr, ye-cr-mujl, 1Jl-F@
In addition to alloys such as -Cr-Mul, it is also possible to use Gofusu-mu, Loctar-mu, etc.;
) and vibrations generated during operation, it is desirable to use a metal-based material that has good impact resistance and can withstand high temperatures.

In this invention, a thin film is formed on the surface of the above-mentioned porous base material, and the surface on which the thin film is formed is the surface that comes into contact with exhaust gas. In addition to the method of forming a thin film material on a porous base material by polymerizing and heat-welding it, the method of heat-pressing the two under pressure, and the method when the porous base material is a metal material. There is a method of grinding the surface using a grinder or the like to form a film that is integrated with the base material.
There is a method of applying heat-resistant paint to the surface of a porous substrate by a spray method or the like. 9. The materials for the thin film include the constituent materials of the porous base material listed above, as well as enamel as a binder for the heat-resistant paint, glass frit, alkali metal silicate, and colloidal lv8/liquid. , Colloida/
I/Mina, metal phosphate, Ryumen) 11% &' Recon resin (Fes), sodium silicate, aluminum phosphate, methylpheniμV Recon, phosphate frit,
Calcium phosphate, water gaff containing aluminum powder, etc., and additives such as A/K, bentonite, water, silica, oxidizing power μν, carbonic power A/F, organic bentonite, magne carbonate Vium. , Magnenium silicate, and Magnenium silicate.

In this way, by forming a thin film on a porous substrate, fuel residues such as tar and soot entrained in exhaust gas can completely prevent intrusion into the porous substrate and cause clogging. However, on the other hand, the sound absorption coefficient of the porous substrate also decreases.

However, this decrease in sound absorption coefficient is caused by adjusting the thickness of the thin film.
By setting the eigenvalue of the acoustic impedance system to a low frequency band where a high sound absorption coefficient is desired, the material works advantageously as a sound absorbing material used in an exhaust muffler for an internal combustion engine.

Specifically, the appropriate film thickness is adjusted within the range of 50μm or less when using the above-mentioned heat welding, heat compression bonding, and grinding methods, and adjusted within the range of 250μm or less when using the coating method. It turns out that you can adjust it.

Next, as a low-temperature oxidation catalyst, MfiO,, cuo
.

Nio, CoO, C05Oa, CrsOmeF
e*Os*mu goo, ZnO.

pbo soto and other tD metal fluorides, MfllFesO
4 to old Cr104+MnCrm0at CuCr1O4
Other composite metal oxides, Pi, Pd, Rh, Ru,
Mug and other precious metals can be used alone or as a deposit.

All of these low-temperature oxidation catalysts are activated at a temperature of 400 to 800°C, which is the exhaust gas temperature! - It has the effect of oxidizing and decomposing combustion residues such as μ and soot (surface combustion) at a lower temperature than the original combustion temperature. Therefore, if these particle layers were formed on a thin film, they would be entrained in the exhaust gas! - After μ and soot adhere, they are quickly oxidized and decomposed and volatilized with the exhaust gas flow.

Therefore, even if the thin film or porous substrate is made of a metal material, it is protected from early high-temperature oxidation.

In addition, as solid acid catalysts, natural zeolite, synthetic zeolite, activated clay, acid clay, V Rikaji A/Niania,
Examples include V-likamagne V-a, activated alumina, V-lika fi/l, vanadium pentoxide, alumina boria, and others. All of these solid acid ropes are activated at temperatures of 400 to 800°C, which is the exhaust gas temperature. It prevents heavy metal oxide (polymerization) of the components that form soot, and also reduces the molecular weight of the components to make them easier to vaporize. Therefore, if these particle layers were formed on a thin film, they would be entrained in the exhaust gas! -~Remove the components of soot on the surface of the sound-absorbing material to which these components are attached! - Automatically vaporizes (purifies) by preventing μ from forming. Therefore, even if 1IIWI4 and porous crystal materials are composed of metal materials, they may be oxidized at high temperatures at an early stage. protected. A solid acid catalyst is a substance that has the function of releasing protons (11") or accepting pairs of electrons. In the petrochemical industry, the catalytic function described above is used in the production of heavy substances with high boiling points (high-temperature vaporized substances). This process is well known as tarazuki, which involves catalytically cracking oil and converting it into light oil with a low boiling point (low-temperature vaporized substance).

On the other hand, as heat-resistant binders, those already exemplified as materials for heat-resistant paints can be used. The additives exemplified as the materials for the above-mentioned paint are mixed.

21 describes a typical embodiment of this invention.

〔Example〕

Foamed metal (product name: SE! METS) as a porous base material, 1l
A Ni-Cr film with a thickness of 5 μm K1 was placed on the surface (one side) of this metal porous substrate.
Put this in an electric heating furnace and a! Approximately 13 in Gong gas atmosphere
Both were welded and joined by heating to 00°C. Next, the composition of the following composition example was mixed in a ball mill for about 30 minutes, and the mixture was uniformly applied onto the iris 1-Cr film by spraying. After coating, it was dried at 80°C for 30 minutes, and then
Bake at 50℃ for 30 minutes to harden the shape.

Composition Example Single oxide monoxide: Iron oxide 15 parts by weight Oxidized steel 20 parts by weight Solid acid catalyst agent: Activated clay 20 parts by weight Binding agent Niamium phosphate 9 parts by weight 8] Phosphoric acid frit 15 parts by weight Additive 60 parts by weight of μmina, silica stone, water The additives have the effect of improving the adhesion of the coating film as a fabric, improving the strength after the coating film is formed and adhesion to the underlying porous material. It has the property of increasing the performance and making the film porous.The cross-sectional layer of the nine sound-absorbing materials thus obtained was examined with an optical microscope II!
The results are shown in Figure 1. In the figure, (1) shows the skeleton of the metal porous substrate, (3) shows the welded round thin film, and (4) shows the surface layer.

Next, the foam metal porous base material alone (conventional product), the foam metal porous base material with the thin film deposited on the surface of the foam metal porous base material (comparative amount), and the foam metal porous base material obtained by the above example (comparative amount).
We conducted various performance comparison tests with the invented product).

Corrosion resistance test using an electric furnace.
The weight change rate due to corrosion was investigated when the sample was left in air at ~800°C for 72 hours. Second, the results are shown, where B shows the comparative amount and C shows the characteristic curve of the conventional product. It is clear from this that the 5% invention has the same temperature conditions as an internal combustion engine exhaust silencer, which is 400-800%.
Even at 0°C, corrosion hardly progresses even in a corrosive atmosphere containing carbon dioxide, demonstrating good corrosion resistance. On the other hand, the weight change between the conventional product and the comparative product was significant due to corrosion, and visual observation showed that a yellow-green product was attached to the surface.

It is thought that the sagging is caused by the surface layer of the thin film acting as a protective layer for the thin film and the porous material.

The normal incidence sound absorption coefficients at various frequencies were measured by the sound absorption performance test tube method (J Engineering 8m 1405), and the results are shown in FIG.

1 shows the characteristic curves of the invented product, B1 shows the comparative amount, and C1 shows the characteristic curves of the conventional product. As is clear from this, the invented product has both high-frequency characteristics and low-frequency characteristics that are superior to the comparative amounts, and especially when compared with the conventional product, its low-frequency characteristics are significantly better.

In the case of a metal porous base material with relatively large pore diameters, a thin film of an appropriate thickness is formed on the surface of the metal porous base material, and a machine formed by the thin film and the pores of the porous base material can be used. Since the eigenvalues of the acoustic impedance system are set in the low frequency range, it is thought that the sound absorption characteristics in the low frequency range are improved. Further, in the case where a surface layer is formed on the upper thin film, since this catalyst layer itself is porous, it is considered that the sound absorption characteristics in all frequency ranges are improved.

Sound-absorbing property maintenance test The three types of sound-absorbing materials mentioned above were molded into a cylindrical shape and used in commercially available domestic passenger cars (
It was installed in the same form in an exhaust silencer with a displacement of 18,008 C), and after approximately 10,000 actual runs, the silencing performance was measured using J18D 1616, and compared with the initial value before the actual run.9.
The results are shown in FIG. 3, B and Cs are the initial characteristic curves of the invention, comparison, and conventional product, respectively, and a, b, and C are characteristic curves of the invention, comparison, and conventional product after actual running, respectively.

As is clear from this, the invented product not only has good initial silencing performance, but also has no decline in initial silencing performance after 10,000 km of actual driving, whereas the conventional product has a good initial silencing performance.
The initial silencing performance was also inferior to the silencing performance of the invented product after actual running, and after 10,000 km of actual running, the silencing performance decreased significantly in all measured frequency bands. The nine comparison products are
Although there is no significant difference between the initial silencing performance and the silencing performance after actual driving, the silencing performance is still inferior to the invented product. 9. After measuring the sound-absorbing performance, we took out the sound-absorbing materials of the previous three companies and visually inspected them. The invented product maintained a clean appearance that was almost the same as the initial state, but the conventional product had the same clean appearance. A large amount of black tar-like or soot-like fuel combustion residue and yellow-green corrosion products had adhered to the entire surface, causing a lump. On the other hand, although the comparative amount was not as good as the conventional product, there was tar-like or soot-like fuel combustion residue attached that led to the thin film layer on the surface. However, the fire of Jin
Sf11 was only attached to the thin film and did not penetrate into the inside of the base material.

As mentioned above, the reason why the invented product has excellent sound absorption properties and appearance after actual running is that the invented product has low-temperature oxidation catalyst particles and solid acid catalyst particles in the surface layer formed on the thin film on the inner surface of the porous base material. is activated by the exhaust gas temperature, I-
Even if AM residues such as soot are actually burned off, they can be automatically oxidized and decomposed (surface combustion) at low temperatures, or they can undergo oxidative polymerization of the components that form tar and soot. This is thought to be due to the synergistic effect of suppressing and purifying and removing the combustion residue and preventing the combustion residue from penetrating into the porous substrate by the thin film.

As is clear from the above description, according to the present invention, a sound absorbing material with excellent sound absorbing properties, corrosion resistance, mechanical strength, etc. can be produced in a convenient and inexpensive manner, and the sound absorbing properties can be adjusted as desired. Since it is easy to perform 411F, it is possible to obtain a sound absorbing material suitable for use in automobile exhaust muffling devices, ducts in factory equipment, etc. from an economical and performance standpoint.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of the sound absorbing material, and FIGS. 2 to 4 are characteristic diagrams showing various sound absorbing performances. (1)...Skeleton, (Ri...Vacancy, (3)...Thin film, (4)...Surface layer. Agent Makoto Kuzuno (1 other person) Figure 1 4 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A sound-absorbing material in which a surface layer made by kneading a low-temperature oxidation catalyst, a solid acid catalyst, and a heat-resistant binder is formed on a circular thin film formed on the surface of a porous base material. (2) The O sound absorbing material according to claim 1, wherein the porous base material and the thin film are made of the same metal. (3) The sound absorbing material according to claim 1, wherein the thin film is made of a heat-resistant paint having a thickness of 2505 m or less.