JPS58129491A - 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 used in an exhaust silencing device for an internal combustion engine.

Conventionally, sound absorbing materials used in exhaust silencers for internal combustion engines include glass wool, porous ceramic bodies, porous metal bodies, and the like. However, when these materials are used as sound-absorbing materials, when an internal combustion engine is operated, tar and soot, which are the combustion residues of fuel such as gasoline, adhere to the surface and cause clogging in a relatively short period of time, reducing the sound-absorbing performance. This often leads to intensified noise and adversely affects the fuel efficiency of internal combustion engines. In addition, when glass wool or porous ceramic materials are used as sound absorbing materials in exhaust silencers for internal combustion engines, the pressure of exhaust gas is high and the vibrations are large, so these sound absorbing materials may become powdered or damaged. Sometimes it becomes completely useless. and,
When a porous metal material is used, the temperature of the exhaust gas inside the silencer is as high as 400 to 800°C, and the exhaust gas contains corrosive sulfur oxides and nitrogen oxides. It is unavoidable that the corrosive deterioration caused by metal porous materials becomes significant, causing clogging due to corrosion products, and that the skeleton of the porous material corrodes and disappears, rendering it useless as a sound absorbing material. Due to its relatively large pore diameter, there were disadvantages such as the absence of any material with good sound absorption performance.

Conventional sound absorbing materials have major drawbacks as described above, and none of them can be put to practical use as an exhaust silencing device for an internal combustion engine.

This invention eliminates all the drawbacks of the above conventional ones,
The present invention provides a sound absorbing material for an exhaust silencer that has good sound absorbing performance, prevents deterioration of sound absorbing performance caused by adhesion of tar and soot, and clogging caused by these, and can withstand high temperature oxidation.

That is, the sound absorbing material of the present invention uses a porous metal material as a sound absorbing base material without fear of powdering or breakage, and is designed to suppress clogging caused by tar and soot, improve its sound absorption properties, and A heat-resistant product that contains a solid acid catalyst and a reducing agent for three main purposes: to prevent corrosion deterioration due to oxidation, and graphite fluoride to prevent soot from adhering to the surface of the sound-absorbing base material. The present invention is prepared by applying a binder to a porous metal sound-absorbing base material and curing it.The details of this invention will be explained below with reference to Examples.

[Example 1] Nippon Diacrevite Co., Ltd. as a metal porous sound absorbing material
Using milled unsintered metal (trade name Calum),
(On one side), a mixture obtained by mixing the composition of Composition Example 1 below in a ball mill for about 30 minutes was uniformly applied by spraying. Furthermore, after drying this product at 8°C for 30 minutes,
It was cured by baking at 0° C. for 30 minutes. When applying the cross-conductor, care must be taken because if the coating is applied too loosely, the sound absorption properties will deteriorate.

(Composition example 1) Solid acid catalyst: Natural zeolite 22' 1t% reduction @2mg powder 181℃% Binder Nialuminum phos 7A) 12tfi 1% Calcium phosphate 1011% Addition: Silica stone, alumina, water 32fi%Low surface energy substance: graphite fluoride 61ii1%Additives have the effect of improving the adhesion and film performance as a coating material, and improve the strength after the coating film is formed and the adhesion to the underlying porous material. It has the property of increasing performance and making the film porous.

The sound absorbing material of the present invention manufactured in this manner has a structure as shown in an enlarged cross section in Fig. 1. In other words, (1)
are metal porous particles, (2) are solid acid catalyst particles, (3)
(4) contains and disperses reducing agent particles, (4) solid acid catalyst particles (2), reducing agent particles (3), and fluorinated graphite particles (6), and penetrates into the voids between particles t1) of the porous metal body. (5J is a porous coating formed on the surface by applying a binder (3) containing solid acid catalyst particles (2) etc.). .

Composition example! Various performances were investigated while comparing with a porous metal material that was not coated with the composition at all.

FIG. 2 shows the rate of weight change due to corrosion when the material was left in air containing 51) pm of sulfur dioxide (sulfur dioxide gas) for 72 hours at a temperature of 400 to 800 DEG C. using an electric furnace. Curve a shows the superposition change rate of the sound absorbing material of the present invention manufactured by K as described above, and the curve a shows the sound absorbing material of only a metal porous body using the same material. 2nd floor
As is clear from IIJ, the sound absorbing material of the present invention has an exhaust gas temperature of 40 in an exhaust silencer for an internal combustion engine.
Even in air containing sulfur dioxide at a temperature of 0 to 800°C, corrosion hardly progresses and it has good corrosion resistance. Compared to this, the conventional metal porous material only has an A! A very drastic weight change (reduction) occurs from 600°C, which is close to the melting point of .

Although this depends on the high temperature oxidation, it is mostly due to the melting and vaporization of Muj. A white high-temperature oxidation product (SCA-A/) was observed on the surface.

Figure 3 shows the normal incidence sound absorption coefficient measured under the same conditions by the in-pipe method (JI8 M 1405).

Curve C is the characteristic of the sound absorbing material of the present invention, and curve @d is the characteristic of the sound absorbing material consisting only of metal porous bodies. It can be seen that the sound absorbing material of the invention shown in FIG. 3 has a higher sound absorption coefficient than that of the sound absorbing material made of only a metal porous body. This is because the composition of Composition Example 1 was applied and cured from the surface of the metal porous body. Therefore, the structure shown in Figure 111 is essentially porous, so air can flow through the inside. It depends on K. That is, the coated cured product of Composition Example 1 itself forms part of the sound absorber, and the sound absorption coefficient can be adjusted depending on the method of coating.

Next, the above two types of sound absorbing materials are formed into a cylindrical shape to construct an exhaust silencing device as shown in Fig. 4.
The engine was installed within a displacement of t and 5 oocc, and after about 10,000 actual runs, the noise reduction performance was measured using KJI&D I616 and compared with the initial value before the actual running. In FIG. 4, I is a casing constituting the exhaust silencing device, I is an exhaust gas inlet pipe, G is an exhaust gas passage, I is a sound absorbing material, and I is an exhaust gas outlet pipe. Figure 6 shows the frequency characteristics of the silencing performance.

In the same figure, curves 1Iilel and e2 are the initial and after-running characteristics when using the sound absorbing material of the present invention, respectively, and curves fl and fl are the characteristics when using the conventional sound absorbing material made of only porous metal bodies. These are the characteristics at the initial stage and after actual driving. As can be seen from Figure 5, the sound-absorbing material of this invention not only has good initial sound-absorbing performance, but also has almost no decline in initial performance even after 10,000 i of actual running, whereas metal After 10,000 actual runs, the sound-absorbing material using only porous materials had significantly reduced sound-dampening performance in all measured frequency bands. In addition, after measuring the silencing performance, both sound absorbing materials were taken out and visually observed, and it was found that the sound absorbing material of Jin's invention was almost as clean as the initial one, but the surface of the material with only a porous metal material was A large amount of black tar-like and soot-like combustion residue and fluttering corrosion products adhered to the entire structure, causing severe blisters. That is, as can be seen from these results, in the sound absorbing material of the present invention, the solid acid catalyst particles and the reducing agent particles dispersed and adhered to the sound absorbing base material are activated by the temperature of the exhaust gas, and the solid acid catalyst particles and the reducing agent particles dispersed in the sound absorbing base material are activated by the temperature of the exhaust gas. If the components that form the sound absorbing material scatter and adhere, oxidative polymerization (polymerization) occurs on the surface of the sound absorbing material.
In addition, by reducing the molecular weight of the components and making them easier to vaporize, they are automatically vaporized (purified) at the temperature of the exhaust gas without becoming tar. It is believed that the soot adhesion prevention function and soot adhesion decomposition function of the butted graphite particles mixed in with the catalyst particles above were fully demonstrated, and that the initial noise reduction performance was maintained for most of tX. It will be done.

A solid acid catalyst is a substance that has the function of releasing protons (H+) or accepting pairs of electrons.The above-mentioned catalytic function is used in the petrochemical industry to convert heavy oil with a high boiling point (high temperature vaporized substance). This is well known as cracking, in which oil is catalytically cracked to produce light oil with a low boiling point (low-temperature vaporized substance). On the other hand, reducing agents have the property of scavenging oxygen, as is widely known, so they have the effect of suppressing the oxidation reaction in which tar-forming components in exhaust gas are polymerized (polymerized) by heat and air (oxygen). I will do it. Therefore, both the solid acid catalyst and the reducing agent have the same effect of inhibiting the formation of tar from the combustion components in the exhaust gas, and since graphite fluoride has the function of inhibiting the adhesion of soot, etc., according to the present invention, It can be seen that by combining these, a good tar adhesion prevention effect can be obtained.

The above-mentioned fluorinated graphite and other components can effectively exhibit their respective functions at a weight of 5 to 95 weight, but both are preferably 50 weight.

[Example 2] As a metal porous sound-absorbing base material, powdered sintered metal w4 (made by gunmetal, thickness 5 mm) manufactured by Sintered Metal Industry ■ was used, and the following composition example 2 was used.
After mixing the mixtures of and 3 in the same manner as in Example 1, the mixtures were sprayed onto the sintered metal, fired and cured to obtain the sound absorbing material of the present invention.〇 (Composition Example 2) Solid acid catalyst Agent: activated clay 27fEt% return
Base agent: Sodium sulfite '51L'1P4y Ferrous sulfate 11i1!-% Binder: 'T A/7 Zirconia 18-fold silica magnesia 11tii% Reducing agent: Stannous nitrate 19iflt%
Mixture: mulch powder-containing water glass 25mm This sound absorbing material and the same porous metal material as above, but without any of the compositions of Composition Examples 2 and 3, were treated in exactly the same manner as in Example 1. Investigate various performances9. As a result, the sound absorbing materials of the present invention, in which the compositions of Composition Examples 2 and 3 were coated and cured, showed excellent results in terms of corrosion resistance, sound absorption coefficient, and silencing performance over time due to prevention of clogging during actual vehicle running. It was found that the properties were almost as good as those shown in FIGS. 2, 3, and 6 of No. 1.

By the way, the solid acid catalyst used in this invention is as follows:
In addition to those listed in Composition Examples 1 to 3, activated alumina, silica A/<, vanadium pentoxide, alumina boria,
There are Futsuishi 1 synthetic zeolites, acid clay 1, etc.

The reducing agents used in Jin's invention include metal powder, medium grain powder,
Among general substances having a reducing action, such as sulfites, ferrous salts, and tin salts, any thermally stable substance can be used.

(9) As the metal porous body used as a base material in this invention, in addition to the foamed metal and sintered metal as in the embodiments, commercially available general-purpose materials such as metal fibers and inorganic fiber reinforced metals can be used. As for the materials, in addition to Mu1 and gunmetal, there are also N1 and j'e-Or.

Alloy materials such as re-Ni-Or and Ire-Or-M1 can also be used.

The heat-resistant binders used in this invention include wax (vitreous heptads), alkali metal silicates, colloidal silica, colloidal alumina, metal phosphates,
Examples include cements, silicone resins, and mixtures thereof.

The fluorinated graphite used in this invention is a chemically very stable white to gray fine powder in which one fluorine atom is strongly bonded to each carbon atom through a covalent bond. , which is produced industrially by the electrolysis of fluoric acid anhydride, and is produced by directly reacting nine fluorine with carbon. Its properties include low surface energy and a small coefficient of friction.
It has been put into practical use as a solid lubricant. In this invention, the most suitable method for dispersing and adhering the graphite fluoride to the surface of a porous material is to apply and bake it dispersed in a resin binder or an inorganic binder, as described in the examples. When metal is used as the porous material as in the present invention, it is also effective to eutectoid plate the surface of the metal porous body with graphite fluoride, which is dispersed in a plating solution together with heat-resistant materials such as N1 and Or. there were. It was also effective to use commercially available spray sets and face-shaped products in which graphite was dispersed in a resin binder. Although it is intended to be used in equipment, depending on how it is used, it may also be used as a sound absorbing material in other equipment such as a combustor.

As explained above, this invention uses a porous metal body as a base material and contains a solid acid catalyst, a reducing agent, and graphite fluoride in a heat-resistant binder that is applied and hardened to the porous metal body. This sound-absorbing material has good sound-absorbing performance, excellent heat resistance and corrosion resistance, and when used as a sound-absorbing material for an exhaust silencer for an internal combustion engine, it effectively prevents the adhesion of tar and soot, and It is possible to prevent the deterioration of the silencing performance caused by the clogging tb and maintain the initial good silencing performance. Therefore, since it has high performance and long life, it can be widely used in exhaust silencing devices for internal combustion engines such as automobiles.

[Brief explanation of the drawing]

Figure 1 is an enlarged view showing an example of the structure of the sound absorbing material of this invention, Figures 2, 3 and 6 are characteristic diagrams showing the performance of the sound absorbing material of this invention, and Figure 4 is an application of this invention. It is a sectional view showing an example. In the figure, the same reference numerals indicate corresponding parts, fl) is the particle of the metal porous body, (2) is the solid acid catalyst particle, (3) is the reducing agent particle, (4) is the binder, and (5) is the particle of the solid acid catalyst. ) is a porous coating, (
6) is fused graphite. Agent Makoto Kuzuno (1 other person) Figure 1 Figure 2 O! L ("C) Figure 3 Cause 5 Iti CkHz)

Claims (1)

[Claims] (1) A metal porous body is used as a base material, and a heat-resistant binder applied and hardened to the metal porous body contains a solid acid catalyst, a reducing agent, and fluorinated graphite. Sound absorbing material.