JPS5869792A - Manufacture of sound absorption 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 of manufacturing a sound absorbing material for use in an exhaust silencing device for an internal combustion engine.

BACKGROUND ART Conventionally, sound-absorbing materials used in the exhaust silencer JItK for internal combustion engines include so-called porous materials in the form of fibers, foams, particles, etc., such as glass coolers, ceramic porous bodies, and metal porous bodies. However, if these materials are used as sound-absorbing materials as they are, when an internal combustion engine is operated, soot, which is the combustion residue of fuel such as gasoline, will infiltrate the surface and the inside of the porous material and become visible within a relatively short period of time. Due to clogging, the sound absorption performance becomes low F, and the test tρ・
It was an unavoidable problem that they would form into platoons and have a negative effect on the fuel efficiency of the internal combustion engine.

The inventors conducted various studies to find out why soot adheres to the surface of sound-absorbing materials, and found that the main cause was water (steam) produced by the combustion of gasoline, or a tar-like substance that was the residue of that combustion. It turned out to be. In other words, the soot discharged from the engine exhaust port has an average particle size of 1
It is a particle of about 001, but is it attached to it?
．． Or, the adhesion force (surface energy) becomes large due to water or tar adhering to the surface of the sound absorbing material.
The sound-absorbing material is adhered tightly to the entire surface and inside. Therefore, it has been found that in order to prevent soot from adhering, it is sufficient to coat the surface of the sound absorbing material with a substance having low surface energy to prevent it from adhering to the surface and from entering into the interior. Therefore, the inventors coated the surface of the sound-absorbing material with various substances having low surface energy, and when they actually used the exhaust silencer M1 for an internal combustion engine (!Niji),
It has been found that organic substances, including fluororesin, decompose and lose their low surface energy properties because the surface temperature of the sound absorbing material in the exhaust silencer reaches 150 to 500°C.

Next, a similar study was conducted after inorganic solid lubricants such as graphite and molybdenum disulfide were dispersed and adhered to the narrow surface of the sound absorbing material.
However, the surface energy increases and soot adheres to the surface, and some substances adhere to the surface, causing clogging and significantly impeding sound deadening performance, creating new drawbacks. There were some things that happened.

The present invention provides a method for manufacturing a new sound absorbing material that does not have any of the above-mentioned disadvantages and can significantly suppress the soot adhesion that conventional sound absorbing materials have. That is,
The inventors discovered that a material in which butylated graphite or butylated carbon, which is a compound of fluorine and carbon, is layered and dispersed on the surface of a sound-absorbing substrate can be used as an exhaust muffler for internal combustion engines due to its low surface energy. We have discovered that when used in this way, the adhesion of soot can be significantly suppressed, and we have already proposed a sound-absorbing material that uses this material. The present invention also relates to a method of manufacturing a sound absorbing material using fluoridated graphite, and the method of producing a sound absorbing material using fluoridated graphite,
It is grown by carbonization and subsequent fluorination of an organic polymer material applied to a porous material.

The present invention will now be described in detail according to FS Examples. [Example] A TiOz-A120B-MgO based ceramic porous body was used as the porous material. On this surface, polyacrylonitrile dissolved in a solvent and made into a paste is applied.
After volatilizing the solvent at 35°C in argon gas.
After preheating at 0°C, it was fired at soo'c. As a result, a carbonaceous coating was obtained on the surface of the base ceramic. Next, this was heat-treated at 600'C for 2 hours in fluorine gas generated by electrolysis of butic acid to fluorine the surface, resulting in the structure shown in the enlarged cross-sectional view in Figure 1. did. In FIG. 1, (1) the particles of the ceramic porous body, (2) the carbonaceous coating that has adhered and penetrated into the bottom and inside of the porous body by applying polyacrylonitrile;
3) is a fluorinated surface film. The sound absorbing material thus produced by the method of the present invention and 5iO2-A1
Regarding a conventional sound absorbing material made of a 203 series ceramic porous body, we investigated the sound absorption coefficient, soot adhesion, and the accompanying changes in sound damping performance over time.

Figure 2 shows the normal incidence sound absorption coefficient measured under the same conditions using the tube^ method (J Engineering SAI 405).

Curve (4) is the characteristic of the sound absorbing material of the present invention, and curve CB) is the characteristic of the conventional sound absorbing material made of a ceramic porous body. From FIG. 2, it can be seen that the sound absorbing material produced by the method of the present invention has a
It can be seen that it has a high sound absorption coefficient and good characteristics.

Next, the sound absorbing materials of the two buildings mentioned above are formed into a cylindrical shape to construct an exhaust silencing device as shown in Fig. 3.
Built into the engine (displacement 2000cc), approximately 10,000km17)
After actual driving, the silencing performance was measured according to JISD1616 and compared with the initial value before actual driving.

In No. 311, (4) is a casing constituting an exhaust silencing device, (5) is an exhaust gas artificial pipe, (6) is an exhaust gas passage, (7) H is a sound absorbing material produced by the method of the present invention, (8) is the exhaust gas outlet pipe. Figure 4 shows the frequency characteristics of the silencing performance. Curves (C) and (d) are the initial and actual characteristics when using the sound absorbing material according to the method of the present invention, respectively, and the curves (D) and (Il)Vi are the characteristics of the sound absorbing material made of a conventional ceramic porous body. These are the initial characteristics and the characteristics after actual driving when using As can be seen from Fig. 4, the sound absorbing material made using the method of the present invention not only has good initial sound damping performance, but also shows that the initial performance has hardly deteriorated even after 10,000 km of actual driving. On the other hand, when using a sound absorbing material made of porous ceramic material, the sound deadening performance was significantly lower in all frequency bands after actual driving.

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 materials manufactured by the manufacturing method of the present invention were almost as clean as the initial state, and the surface of the carbonaceous layer covered with the porous material was found to be almost clean. In contrast, conventional ceramic porous materials have a large amount of black soot that adheres to the entire surface and cause severe clogging. I was awake.

In addition, when the surface of the sound absorbing material produced by the manufacturing method of the present invention was analyzed by X-ray diffraction etc., it was found that due to the fluorination of the surface of the carbonaceous layer made of polyacrylonitrile, so-called fluorinated graphite (carbon fluoride, graphite fluoride) was formed. It was found that a thin film with a thickness of 5 μm or more was formed. In other words, the good soot adhesion inhibiting effect of the sound absorbing material produced by the manufacturing method of the present invention is due to the low surface energy property of this bubbly graphite, which is the main cause of soot adhesion, such as water (steam) and liquids such as tar. This makes it difficult for the combustion residue of the fuel to adhere to the surface of the sound-absorbing material, so it is thought that soot may not adhere to the surface of the sound-absorbing material, and even if it did, it would have been easily blown away by the flow of exhaust gas.

By the way, in the present invention, as the porous material used as the base material of the sound absorbing material, in addition to the ceramic porous body used in the examples, there are also metal porous bodies (foamed material, sintered metal, metal fiber, etc.), Among glass cool, inorganic fiber-reinforced metals, and the like, any material having heat resistance of 500 to 600° C. or higher can be used. In addition to the polyacrylonitrile used in the examples, examples of organic polymer materials to be coated on these porous base materials include pitch, cellulose (rayon), etc.
, polyvinyl alcohol and other resins can also be used. In order to carbonize these, they must be calcined in an inert gas at a temperature of 200-120° C. or after this, at a temperature of 700-120° C. (X)'07) temperature, it was confirmed through experiments that it becomes carbonaceous with some residual organic matter. Next, it was found that in order to fluorinate the surface of the carbon JF layer to form a fluorinated graphite layer according to the present invention, it is sufficient to sinter it at a temperature of 500° C. or higher in a fluorine atmosphere.

As explained above, the process of coating the organic polymer material on the surface of the porous material, the process of carbonizing the organic polymer material,
The method for producing a sound absorbing material of the present invention, which includes a step of reacting a carbonized substance with fluorine to produce bubbly graphite on the surface, has good power dissipation performance and is suitable for use in exhaust gas for internal combustion engines. -Extinguishing device-17) [When used as a sound material,
It is possible to produce a sound absorbing material that can prevent the deterioration of sound damping performance caused by clogging with soot and maintain the initial good sound damping performance. Therefore, the sound absorbing material produced by the method of the present invention has high performance and long life.
It can be widely applied to the production of exhaust silencing devices for internal combustion engines, such as those made by Jidoshu Higashi.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view showing the structure of the sound absorbing material produced by the method of the present invention, Fig. 2.4 is a characteristic diagram showing the performance of the sound absorbing material produced by the method of the present invention, and Fig. 3 is the sound absorbing material produced by the method of the present invention. FIG. The same reference numerals in the figures indicate the same or equivalent parts, (1) is the particle of the porous body, (2) is the carbonaceous coating layer, (3) is the fused graphite film, (4) is the casing, and (5) is the (6) is the exhaust gas passage, (7) is the sound absorbing material, and (S) is the Fi outlet pipe. Agent Shin Kuzuno - (9) Figure 1 Figure 2) EI Mantissa (KHz)

Claims (1)

[Claims] It is characterized by having the steps of applying an organic polymer material to the surface of the porous material, carbonizing the organic polymer material, and reacting the carbonized material with fluorine to generate fluorinated graphite on the surface. How to make sound absorbing material.