JPS58129496A - Manufacture of 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 method for manufacturing a sound absorbing material that is attached to an exhaust silencer am interposed in the exhaust gas flow path of an internal combustion engine or other various types of combustion equipment.

Traditionally, the sound absorbing materials used for this spear are:
Fibrous materials made of glass wool, ceramics, metals, etc.
Foamed, particle layered porous material is Al. However, if these materials are used as sound absorbing materials as they are, components that form tar and soot contained in exhaust gas will
Soot burning residue forms pores on the surface and inside W1. It adheres to the ikl and turns into tar, which grows and clogs the sound absorbing material in a relatively short period of time, significantly reducing its initial sound absorbing performance, leading to intensified noise and reduced operating efficiency. There was a pause.

Therefore, the inventors of this application conducted extensive research into the cause of the clogging, and found the following. In other words, due to the moisture contained in the exhaust gas and the moisture retained on the wall surface of the sound absorbing material, tar-forming components and soot accompanying the exhaust gas are likely to adhere to the surface of the sound absorbing material. Due to the large roughness of the surface of the sound absorbing material, the turbulence of the exhaust gas flow in the vicinity causes the above-mentioned tar-forming components to enter the sound absorbing material together with the exhaust gas, stick to the surface of the sound absorbing material and the walls of the pores, and become attached. The tar-forming components react with the exhaust gas temperature and turn into tar, and the resulting tar-like substance further promotes the above-mentioned adhesion phenomenon, resulting in tar and soot being densely deposited on the entire surface and inside of the sound-absorbing material. adhere to.

Therefore, in order to maintain the initial characteristics of sound absorption performance over a long period of time, it is necessary to reduce the surface energy of the sound absorbing material to suppress the adhesion of tar-forming components, and to reduce the roughness of the surface of the sound absorbing material. It is effective to reduce turbulence in the exhaust gas flow.

From this point of view, we conducted further research based on the idea of solving the above problem 11h by coating the surface of the porous base material with a substance that has a low surface energy of 1.

As a result, it is possible to use organic materials such as fluororesins, which are generally considered to have low surface energy, as well as inorganic materials such as graphite and molybdenum disulfide, to coat porous substrates.
When using lubricants, the surface of the lubricant may be heated to 160 to 500°C by exhaust gas and lose its low surface energy properties, or the coating material itself may decompose. Although there are disadvantages, it has been found that the use of hydrogen fluoride (graphite fluoride), which is a compound formed by a covalent bond between fluorine and carbon, does not cause the above-mentioned disadvantages.

Therefore, in the next step, when hydrogen fluoride is used, the problem is how to apply it to the surface of the porous AH material as a coating layer. To solve this problem, it is clear that it is desirable to adopt a method that can reduce the surface roughness as much as possible in order to fully utilize its inherent low surface energy properties.

On the other hand, even when the above-mentioned abutted graphite is used, there is a limit to its low surface energy properties, so it is difficult to completely suppress the adhesion of tar-forming components.

Therefore, the inventors of this application conducted further research on a method for suppressing tar formation due to the combination of tar-forming components that inevitably adhere to the surface of the abutted graphite coating layer. As a result, it was discovered that certain substances, ie, reducing agents and alkaline agents, are effective in inhibiting tar formation.

As a result of the above, what is important in the method of manufacturing sound absorbing materials for exhaust silencing devices is how to keep the surface roughness of the graphite coating layer as low as possible, and the tar-forming components that adhere to this coating layer. There are two points to consider: in what form should the reducing agent or alkaline agent be used to keep the porous base material or its coating layer at a constant fusing level?

This invention was made in view of the above circumstances, and it is possible to satisfy the initial demand by applying a means called eutectoid plating method to form no coating on the surface of a porous base material. This makes it possible to provide a sound absorbing material that can

Hereinafter, this invention will be described in detail according to examples.

[Example 1] Sodium sulfite fine particles and crushed graphite fine particles as a reducing agent were mixed and dispersed in a t8$ liquid containing a surfactant as a dispersant, and Fe-Cr-A was positively applied to the Cu1 cathode.
Electricity was applied to the metal porous base material made of T, and the surface of the metal porous base material was plated with Cu1 sodium sulfite and graphite fluoride to form a separable coating.

On the other hand, as Comparative Example 1, on the surface of the metal porous substrate of the same polarity,
A sound-absorbing material in which powdered graphite fine particles were evenly distributed and adhered to the surface of the poukajosa was manufactured by spray coating and firing the powdered graphite kneaded with a resin as a binder. Moreover, as Comparative Example 2, the opposite porous base material itself was prepared.

Enlarged cross-sectional views of the thus obtained invented products, Comparative Part 1 and Comparative Part 2 are shown in FIGS. 1(a), 1(b), and 1(c), respectively. As is clear from this, in the invented product, the surface of the coating & (plating layer) (1) is smooth, and
The reducing agent fine particles (2) and the abutted graphite fine particles (3) are uniformly dispersed on the surface, whereas in the comparative part 1, the abutted graphite fine particles (3) have a rough surface of the porous base material (4). They are scattered and attached to the top.

Moreover, the comparison part 2 has a large surface roughness.

Next, we discussed the sound absorption coefficient of these three sound absorbing materials, their tar adhesion, and the deterioration of their sound deadening performance during pongeeing.

Figure 2 shows the sound absorption coefficients measured under the same conditions according to the in-pipe method (JIS A 1405). The curve MAA shows the characteristics of the invented product, the curved edge B shows the characteristics of the comparison part 1, and the curve C shows the characteristics of the comparison part 2.

From this kishu, the invented product has a better sound absorption coefficient than any of the comparison parts, especially in the low frequency band, and the comparison part 1
It can be seen that the sound absorption coefficient is superior to that of comparison part 2.

This may be due to the fact that Comparative Part 1, in which the atomized Kurofune fine particles were attached, has a higher porosity than Comparative Part 2, which uses the porous base material as it is as a sound absorbing material. This is considered to be because it has a high porosity.

Next, the two-pole sound absorbing material was formed into a cylindrical shape to construct an exhaust vane sound device as shown in FIG.
The noise reduction performance was measured according to JISD 1616 after being installed in a 1600cc exhaust gas engine and running approximately 10,000 times, and compared with the initial value before the actual running. In Figure ＠a, (b) is the casing that constitutes the exhaust silencer, (b) is the exhaust gas inlet pipe, the ring is the exhaust gas passage, (b) is the sound-absorbing material,
(to) is the exhaust gas outlet pipe.

Fourthly, let's look at the frequency characteristics of silencing performance. curved edges and d
are the initial and after actual running characteristics of the invented product, respectively, and curves E and el and F and f are the initial and after actual running characteristics of comparison section 1 and comparison section 2, respectively. As can be seen from Figure 4, the invented product not only has good initial silencing performance, but the initial performance has not deteriorated even after the first run.
Comparative part 2 has inferior performance during the '4IJ period, and the performance drop after actual driving is more significant than @Meisho.

After measuring the sound-absorbing performance, we took out the sound-absorbing materials from both ministries and visually observed them, and found that the invented product was almost as clean as the initial product, indicating that the fusified graphite had an unambiguous soot adhesion inhibiting effect and sodium sulfite. The synergistic effect with the tar formation inhibiting effect was demonstrated in Comparative Part 1, but in comparison part 1, only the effect of graphite alone was exerted, and some yellow-green corrosion products were observed on the surface. Also, clogging phenomenon due to black tar-like substance was observed. In addition, comparison section 2 was severely clogged.

[Example 2] In exactly the same manner as in Example 1, a sound-absorbing material was produced in which fine particles of purinated black ship and fine particles of potassium silicate were uniformly dispersed and had a layer on the surface. When this sound absorbing material was also examined in detail in the same way as in Example 1, almost the same results were obtained.

The reason why there is almost no deterioration in the appearance of the invented product after actual running, as shown in the above We, is that the surface of the porous base material is a plating layer containing homogeneously scattered graphite with low surface energy. prevents the adhesion of moisture and tar components contained in exhaust gas, and even if these adhere, the surface energy is small, so the adhering components are oxidized and fused by exhaust gas treatment. effectively blown away before,
Furthermore, this is thought to be because tar formation due to oxidation of the deposited components is prevented by the catalytic action of sodium sulfite and potassium silicate contained in the plating layer.

By the way, 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, and it is not suitable for industrial use. is produced by directly reacting fluorine generated by electrolysis of fluoric anhydride with the following system. Its properties include low surface energy and a small coefficient of friction, so it has been put into practical use as a solid lubricant.

The porous material used as the base material of the sound absorbing material of this invention is the solid metal porous material (foamed metal, sintered metal, gold 1I4-miscellaneous) used in the examples. Any material can be used as long as it has a heat resistance of 500 to 600° C. or higher.

Reducing agents include metal powders, tin salts, ferrous salts, sulfites, oxalates, and other substances that generally have a reducing effect, and alkaline agents include alkali gold silicates, water silicates, etc. Examples include those that generally have a basicity of 1, such as oxides, alkali metal oxides, and basic oxides. These reducing agents and alkaline agents respectively inhibit the reaction in which the tar-forming paper component polymerizes on the surface of the sound-absorbing material and precipitates as tar, and even if the tar-forming component turns into a single molecule, It decomposes into low molecular weight molecules, making it easier to burn or vaporize.

In this invention, the fine particles of the reducing agent and alkaline agent mentioned above do not inherently have very strong adhesion to porous substrates, but this is different from other types of particles that have strong adhesion to porous substrates. Since they are plated on the porous negative substrate together with the metal element, they are strongly polymerized to the porous substrate.

Therefore, it has excellent mechanical strength, that is, vibration resistance and impact resistance. In addition, the graphite itself has a microscopic layered structure, and the reducing agent and alkaline agent themselves are porous, so the resulting sound-absorbing material has excellent sound-absorbing performance, especially in the low frequency band. show. In this case, the content ratio of fluorinated graphite, reducing agent or alkali agent is 6 to 95.
It can be changed within a range of 1.0% depending on the application and conditions of use. The frequency band exhibiting the maximum sound absorption coefficient can be adjusted by the phoenix i11 clause and the - clause of the mating time. In addition, the weight ratio of fluorinated graphite and reducing agent or alkali agent is 6 to 95%, and each is 5%.
This is because in the following cases, the purpose of addition is not achieved in practical terms.

As explained above, the sound absorbing material of the present invention, in which fluorinated graphite fine particles and reducing agent or alkaline agent fine particles are uniformly adhered and dispersed as a sticking layer on the surface of a heat-resistant porous material, can provide good sound deadening. When used as a sound absorbing material in an exhaust silencer for an internal combustion engine, it is possible to prevent the deterioration of the silencing performance caused by soot clogging and maintain the initial good silencing performance. When using a porous body, a remarkable corrosion prevention effect can be obtained. 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 drawings]

Figures 1 (a), (b), and (c) are enlarged views showing the structure of the sound absorbing material. ! 2. Second. is a characteristic diagram showing the performance of sound absorbing material,
Figure 8 is a cross-section diagram showing an example of the application of the sound absorbing material. (1)... i at rw, (2)... reducing agent fine particles, (3)... fluorinated graphite fine particles, (4)... porous base material, αυ... exhaust silencer, Q4...Sound absorbing material. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Shin Shimano - Figure 1 (b) (C)

Claims (1)

[Claims] (1) During the dissolution process, fine particles of a reducing agent or alkaline agent are mixed in to prevent the formation of tar from the combustion residue of fluorinated graphite and fuel at the temperature of the exhaust gas discharged from the combustion engine. A method for producing a sound absorbing material, which comprises the step of plating each of the above-mentioned fine particles together with a different type of gold on the surface of a porous gold filter substrate.