JPS58132294A - 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, glass wool and rock wool are used as sound absorbing materials, depending on the purpose and conditions of use. In addition to porous base materials made of ceramic or metal, organic base materials are used. Among them, glass wool and rock wool are used under high temperature conditions such as in exhaust silencers for internal combustion engines. Ceramic and metallic porous substrates are used. However, when these materials are used as the tt sound absorbing material, when an internal combustion engine is operated, tar and soot, which are combustion residues of K, gasoline, etc., may adhere to the surface or penetrate into the interior, causing clogging. As a result, sound absorption performance 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 increases the flow resistance of the exhaust gas flow along the surface of the sound absorbing material.
This causes an increase in back pressure in the internal combustion engine, which reduces the efficiency of the engine. Furthermore, the sound absorption properties of conventional sound-absorbing materials in the low-frequency band drop sharply compared to those in the high-frequency band. This was not satisfactory for use as an engine exhaust silencer.

Therefore, in order to obtain a sound absorbing material that does not have the various disadvantages mentioned above, the inventors of this application have, as a result of various investigations, found that forming a thin film on the surface of a porous base material is effective in preventing the deterioration of the Kannon 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 certain kind of 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 on a thin film formed on the surface of a porous base material by kneading one or more materials selected from reducing agents or alkaline agents and a heat-resistant binder. It is.

Porous base materials that can be used in this invention include commercially available general-purpose materials such as foamed metal, sintered metal, metal fiber M, and inorganic fiber reinforced metal; , Fe-Cr, Fe-kJi
In addition to alloys such as -Cf, IP@-Cf-mu/, and Mi-Fe-Cr-mul, glasslar and rockta μ can also be used, but the exhaust gas Considering the temperature (400-800℃) and the vibrations generated during operation, it has good impact resistance and
It is desirable to use a metal material that 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. is a method of grinding the surface using a grinder or the like to form a film that is integrated with the base material, and
There is a method of applying heat-resistant paint to the surface of a porous substrate by a spray method or the like. In addition to the above-mentioned constituent materials of the porous base material, the materials for the thin film include 11 wax, glassy frit, alkali metal silicate, and colloidal silica as a binder that serves as the f material of the heat-resistant paint. , colloidal alumina, metal phosphate.

Cement, silicone resin (FESS), sodium silicate, aluminum phosphate, methylphenylene lvV
Recon, phosphoric acid frit, calcium phosphate, water glass containing aluminum powder, etc., and alumina as additives, bentonite 6 water, silica stone, oxidizing power/L/V
Um, carbonic power A/$/um.

These include organic bentonite, Magnetocarbonate V-Tsufu, thinner, and magnesium silicate (Merck).

In this way, forming a thin film on a porous substrate completely prevents fuel residues such as tar and soot entrained in exhaust gas from penetrating into the porous substrate and causing a knot. 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, etc. to lower the eigenvalue of the acoustic impedance system formed by the thin film and the pores of the porous base material to a lower value where a high sound absorption coefficient is desired. By setting it in a frequency band, it will work advantageously as a sound absorbing material used in an exhaust muffling device for an internal combustion engine. The specific appropriate film thickness is adjusted within the range of 50 μm or less when using the above-mentioned heat welding, heat compression bonding, and grinding methods, and adjusted within the range of 250 μm or less when using the coating method. It turns out that you should do it.

In addition, as a reducing agent, silver powder, sodium sulfite,
Metal powder, carbon powder/sulfite, ferrous salt, tin salt, stannous nitrate/sulfuric acid, V-oxalate, and other reducing agents can be used. Furthermore, as an alkaline agent,
Potassium silicate, sodium aluminate, sodium silicate, lithium silicate, sodium carbonate, alkali metal oxides, alkali metal silicates, hydroxides, basic oxides and other alkaline agents can be used.

On the other hand, as a heat-resistant binder, use the materials already listed as materials for heat-resistant paint! In order to improve the adhesion of such a binder onto a thin film and its film performance, the following nine additives are mixed as materials for the above-mentioned coating material.

The above-mentioned reducing agent suppresses polymerization due to oxidative polymerization of the tar generated material, and the alkaline agent inhibits the progress of the polymerization reaction by neutralizing or saponifying the substance produced by the polymerization of the tar generated material. It has the effect of preventing the formation and precipitation of Therefore, in this invention, one or more materials selected from reducing agents and alkaline agents are used, but in this case, it is also possible to use a single substance from Group 91 as the same type of material. , it is also free to use a mixture of multiple substances.

Next, typical embodiments of the invention will be described.

Example A sintered metal manufactured by Mitsubishi Metals (trade name: Diamond Fill, thickness 5 mm) was used as a porous base material, and a Ni-Cr film with a thickness of 5 μm was coated on the surface of this porous base material. Place it in an electric heating furnace and heat it for about 1 hour in an argon gas atmosphere.
Both were welded and joined by heating to 300°C. Next, the composition of the following composition example was mixed for about 30 minutes at Baum lvK, and 9 mixers were evenly sprayed onto this set-CR protective film in a circle. After drying for a minute, it was baked at 650° C. for 30 minutes to harden it.

Composition Example Reducing agent: 35 parts by weight of mug powder Alkali agent: 25 parts by weight of potassium silicate Binder: 50 parts by weight of vitreous frit Additive: Alumina. Bentonite, water 60 overlapping parts The additives have the effect of improving the adhesion and film performance of the coating material, increasing the strength after the coating film is formed and the adhesion performance to the underlying porous material. It has the property of making the film porous.

The cross-sectional layer of the sound absorbing material thus obtained was observed with an optical microscope, and the results are shown in FIG. In the figure, (1) is the skeleton of the metal porous substrate, (!) is the pores, (3) is the welded thin film,
(4) shows the surface layer, respectively.

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

Corrosion resistance test using an electric furnace, containing 40 ppm of sulfur dioxide
The weight change rate due to corrosion was investigated when the sample was left in air at 0 to 800°C for 72 hours. The results are shown in FIG. 2, where M is the characteristic curve of the invented product, B is the comparative amount, and C is the characteristic curve of the conventional product. As is clear from this, the invented product operates under the same temperature conditions as the exhaust silencer for internal combustion engines.
Even at 800°C, corrosion hardly progresses even in a corrosive atmosphere containing sulfur dioxide, demonstrating good corrosion resistance.

On the other hand, there was a significant weight change between the conventional product and the comparative product due to corrosion, and visual observation showed that yellow-green products were observed on the surface.

This is considered to be due to the rounding of the surface layer of the thin film surface acting as a protective layer for the thin film and the porous substrate.

The normal incidence sound absorption coefficient was measured at various frequencies using the sound absorption performance test tube method (J Engineering 8, 14 OS), and the results are shown in FIG.

A1 shows the characteristic curves of the invention product, B shows the comparative amount, and C shows the characteristic curves of the conventional product. As is clear from this, the invented product has better high-frequency characteristics and low-frequency characteristics than the comparative amount.
Especially when compared with conventional products, its low peripheral liquid properties are significantly better.

This is true for metal porous substrates with relatively large pore diameters.
By forming a thin film of appropriate thickness on the surface],
A machine formed by a thin film and pores in a porous base material.
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. In addition, when a surface layer is formed on the thin film, since this catalyst layer itself is porous, it is considered that the sound absorption characteristics in the gold scrap wavenumber region 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 18,000 (R), and after approximately 10,000 actual runs, the noise reduction performance was measured using a D 1616 from J and compared with the initial value before the actual run.

The results are shown in FIG. Mura, Ma, and C are the initial characteristic curves of the invented product, comparative quantity, and conventional product, respectively, and
a, b, and C show characteristic lines after actual running of the invention product, comparative product, and conventional product, respectively.

As is clear from this, the invented product not only has good initial silencing performance, but also shows almost no decline in initial silencing performance after 10,000 mm of actual punching, whereas the conventional product has good initial silencing performance. is inferior to the noise reduction performance of the invented product after actual driving,
After 10,000 km of actual driving, the silencing performance deteriorated considerably in all measured frequency bands. In addition, although there is no noticeable difference between the initial noise reduction performance and the noise reduction performance after actual driving, the comparative product is inferior in noise reduction performance compared to the invented product. After determining the sound deadening performance, the former champion's sound absorbing material was
When we came out of the XX and visually observed it, we found that the invented product maintained a clean appearance that was almost the same as the initial state, but the conventional product had black tar-like or soot-like fuel combustion residue and A large amount of yellow-green rotting products adheres to the surface.
It was causing clogging tn. On the other hand, although the comparative product is not as good as the conventional product, it has a thin layer of tar-like or soot-like fuel combustion residue attached to its surface. However, this combustion residue only adheres to the thin film and does not penetrate into the inside of the base material.

As mentioned above, the invented product has excellent sound absorption properties and appearance after actual running.In the invented product, the surface layer formed on the thin film on the surface of the porous base material is selected from a reducing agent or an alkaline agent. Rounding containing one or more materials, these materials prevent oxidative polymerization (increase in boiling point) of tar and soot forming components contained in exhaust gas, and adhere as tar. This is thought to be because the temperature of the exhaust gas automatically vaporized the gas, preventing it from occurring.

As is clear from the above description, according to the present invention, it is possible to easily and inexpensively produce a sound absorbing material with excellent sound absorbing properties, corrosion resistance, mechanical strength, etc., and the sound absorbing properties can be adjusted as desired. Since it is easy to do so, it is possible to obtain sound absorbing materials suitable for use in automobile exhaust muffling devices, ducts in factory equipment, etc. from an economical and performance standpoint.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] (1) A heat-resistant binder layer containing one or more materials selected from a reducing agent or an alkaline agent is formed on the thin film formed on the surface of the porous base material. sound absorbing material. (Sound absorbing material according to claim 1, in which the porous base material and the thin film are made of the same metal. (3) Claim 1, in which the thin film is made of a heat-resistant paint having a thickness of 250 μm or less. Sound absorbing material as described.