JPH0237105A - Muffler for combustion exhaust gas noise - Google Patents

Abstract

PURPOSE:To improve acoustic absorption effect by charging an accumulation body made of a bulk of carbon fiber in the cylindrical body of a muffler. CONSTITUTION:An inlet pipe 2 and outlet pipe 3 are connected to the cylindrical body 1 of a muffler, in which an accumulation body made of mat like material, felt like material and textiles formed of carbon fiber is charged in the cylindrical body 1. Carbon fiber consisting of crystalline structure corresponds to a spring having elasticity, and amorphous structure corresponds to a dush pot having visco-elasticity and works as viscous damping vibration system as a whole. This leads to the effective absorption of the energy of exhaust gas, and as a result, an acoustic absorption can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muffler for muffling combustion exhaust gas noise;
In particular, exhaust silencers are installed on internal combustion engines such as automobiles and bailers, jet engines, gas turbines, etc., to attenuate exhaust noise while passing the exhaust gas generated from the engine, and combustion equipment for boilers, heating, cooking, etc. This is related to the company's exhaust silencer.

(Prior art) When the combustion exhaust gas generated by the combustion of high-pressure air and fuel in a combustion engine is released into the atmosphere, it expands rapidly and generates a loud noise, which causes noise pollution. It's becoming a problem.

Therefore, a muffler is provided in the exhaust gas passage to reduce exhaust noise.

(This is a problem that the invention aims to solve!!) Conventionally, silencers for combustion exhaust gas have been made by using glass wool, rock wool, etc. Attempts have been made to fill the muffler with sound absorbing material, but a satisfactory sound absorbing effect cannot be obtained unless the density is increased, resulting in a decrease in combustion efficiency due to increased back pressure, a significant increase in the weight of the muffler, and There was a problem in that the filling deteriorated due to the high temperature gas and the partial peeling and release became a new source of secondary pollution. In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 18420/1983,
It is disclosed that a porous sound absorbing material having a desired porosity is used by heat-sealing a fibrous material, and stainless steel fibers are exemplified as the fibrous material. However, stainless steel fibers are also corroded by exhaust gas and have an unsatisfactory lifespan.

In addition, Japanese Patent Application Laid-Open No. 75521/1983 discloses that a synthetic resin having a noise damping effect is used in place of a metal material for the silencer outer cylinder, and a fiber-reinforced material reinforced with carbon fiber, glass fiber, etc. Resins are exemplified. However, synthetic resins have problems such as being unable to withstand the high temperatures of exhaust gas and being difficult to connect with the end plate.

None of the above methods is satisfactory in terms of reducing noise, which is an environmental pollution that has recently become particularly severe.

The purpose of the present invention is to solve such problems with conventional sound absorbing materials, namely, secondary pollution caused by peeling and release of sound absorbing materials due to deterioration, deterioration due to corrosion of sound absorbing materials, increase in back pressure due to high filling,
The objective is to solve the problem of weight increase and to achieve a structure that improves the heat resistance of the synthetic resin outer cylinder, which is expected to have a noise damping effect, by combining it with a sound absorbing material.

(Means for Solving the Problems) The present invention provides a combustion exhaust gas comprising a cylindrical body, an inlet pipe, and an outlet pipe, the inside of the cylindrical body being filled with or equipped with a bulky carbon fiber aggregate. Regarding noise mufflers.

The shape and structure of the cylindrical body, inlet pipe, and outlet pipe constituting the muffler of the present invention may be conventionally known ones, and if desired, partition plates, conduits, etc. may be provided, A tube, conduit, etc. with resonance holes may also be used.

Examples of the shape of the bulky carbon fiber aggregate to be filled or attached to the silencer of the present invention include mat-like materials, felt-like materials, textiles, and three-dimensional textiles.

The bulky carbon fiber aggregate used in the present invention has a bulk specific gravity of 00
It is preferable that it is 01-0.20 g/cIIr. Here, the bulk specific gravity refers to the bulk specific gravity of the carbon fiber aggregate when it is installed or filled.

When the bulk specific gravity is less than 0.001 g/cll, the silencing effect is insufficient, and when it is 0.20 g/cd or more, the silencing effect is sufficient, but the fuel consumption decreases due to pressure loss. Particularly preferred is a range of 0.02 to 0.20 g/cd.

The carbon fibers used as raw materials for the bulky carbon fiber aggregate used in the present invention may be rayon-based, polyacrylic nitrile-based, petroleum pitch-based, or coal pitch-based, but pitch-based carbon fibers are particularly effective. Further, the length of the carbon fibers may be any of short fibers, raw fibers, and long fibers. Characteristics of these carbon fibers include excellent heat resistance and acid resistance, and low thermal conductivity. What is carbon fiber here?
A general term for carbon fiber and graphite fiber.

There are no particular limitations on the method for producing the bulky carbon fiber aggregate used in the present invention (it can be produced by a commonly used method).

For example, there are methods for accumulating and needle-punching carbon fiber yarns, methods for making fibers from molten pitch by the vortex method and infusible and carbonizing the deposited pitch fiber aggregates, and methods for making paper from carbon fibers. The carbon fiber aggregate can be manufactured by a method such as needle punching. Further, it is also possible to use a carbon fiber aggregate obtained by impregnating the carbon fiber aggregate with a heat-carbonized synthetic resin and then heat-treating it to carbonize the synthetic resin. This improves strength, shape retention, prevents deterioration and radiation, and improves heat resistance.

Further, the bulky carbon fiber aggregate used in the present invention may be a mixture of carbon fiber and organic fiber or inorganic fiber.

This can also improve strength, shape retention, and the like. The inorganic fibers that can be used in combination are not particularly limited, and include, for example, boron fibers, silicon carbide fibers, alumina fibers, silicone titanium carbon oxide fibers, and amorphous fibers. When organic fibers are mixed, it is preferable to heat and carbonize them after mixing in order to improve heat resistance.

There is no particular restriction on the method of mounting or filling the bulky carbon fiber aggregate inside the cylindrical body. For example, the space of the muffler may be filled appropriately, and the mounting method may also be determined at appropriate locations, preferably at least on the inner wall of the cylindrical body, on the inner and outer surfaces of the conduit, on the surface of the partition plate, etc.
You can attach it anywhere.

Although the cylindrical body may be made of a conventionally used metal material, it is more preferable to use a heat-resistant resin from the viewpoints of lightweight and sound deadening performance. The heat-resistant resin is not particularly limited and may be either a thermoplastic resin or a thermosetting resin. Preferably, at least one selected from epoxy resins, phenol resins, silicone resins, unsaturated polyester resins, diallyl phthalate resins, melamine resins, thermosetting polycarbodiimide resins, and liquid crystal polyesters is used.

Heat-resistant resin has a viscoelastic region above its glass transition point,
It has a particularly good sound absorbing effect. Furthermore, liquid crystal polymers have extremely high heat distortion temperatures of 300° C. or higher, and are particularly excellent in heat resistance.

Furthermore, various additives may be added to the heat-resistant resin.

There are no particular restrictions on the additives, but examples include mica,
At least one of silicon oxide, talc, aluminum powder, carbon fiber, glass wool, carbon powder, etc. can be added.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of a silencer according to the present invention.

The exhaust gas passes through the inlet pipe 2, chamber 6 and exits via the outlet pipe 3 according to the arrows. The cylindrical body 1 has a cylindrical shape, an ellipse, or a rectangular tube shape, and end plates 4 are connected to both ends of the cylindrical body 1 to which an inlet pipe 2 and an outlet pipe 3 for exhaust gas are connected. The cylindrical main body 1 and end plate 4 are molded using heat-resistant resin.

In FIG. 1, the bulky carbon fiber aggregate is attached as a lining 5 to the inner surfaces of the cylindrical body 1 and the end plate 4, and is provided in a chamber 6 between the cylindrical body 1, the inlet pipe 2, and the outlet pipe 3. The bulky carbon fiber aggregate is filled. The lining 5 may be made of other heat-resistant materials.

In FIG. 2, a partition plate 7 is attached to one end of an outlet pipe 3 connected to an end plate 4 to partition a chamber 6, a compartment 8 is filled with the bulky carbon fiber aggregate, and a compartment 10 is used for exhaust gas. This is a free expansion chamber for gas. Further, a filter conduit 9 is provided on the partition plate 7 through the compartment 8 and the compartment 10.

FIG. 3 shows that in FIG. 2, the bulky carbon fiber aggregates are attached as attachments 11 to both sides of the partition plate 7, and the compartments 8 and 10 are filled with the bulky carbon wAn aggregates. Furthermore, the bulky carbon fiber aggregate is attached as a lining 5 to the inner surfaces of the cylindrical main body 1 and end plate 4.

(Examples, Comparative Examples) Test Example 1゜The inner surface of a cylindrical body 1 made of heat-resistant resin (phenolic resin) having a cross-sectional structure as shown in Fig. 1 is lined with ceramic paper 5, and a chamber 6 is filled with petroleum pitch-based carbon fiber felt with varying specific gravity.
Example No. 11 was used as an example, and an unfilled muffler and a muffler filled with rock wool were manufactured as comparative examples, and the muffling effects of these were tested. These silencers are attached to a 1.5L, 4-cylinder, water-cooled, 4-cycle gasoline engine, and the exhaust noise from the outlet pipe of the silencer is measured using a microphone for noise measurement, and an ordinary sound level meter (JIS-C-105
2). The microphone should be placed at the same height as the exit pipe and in a 45 degree direction outward from the exit pipe.
It was installed at a distance of 0 cm. FIG. 4 shows the relationship between the engine rotation speed (rp@) and the total noise level (du (A)) when the engine output is constant at 15 kW.

In Figure 4, ■ is a space and is unfilled, ■, ■,
■The bulk specific gravity of each is 0035.0053.0.07
Bulky carbon fiber with 0 (g/cIlr)! When the ik aggregate was filled, ■ indicates the result when rock wool was filled at 0.15 g/cd.

Test example 2.・FFT (fast fourier tr.
The silencing effect was investigated using an analyzer (transformation). The test method was the same as Test Example 1.

■ The same bulky carbon fiber aggregate as in Test Example 1 ■ filled with a bulk specific gravity of 0.07 g/ad, ■ Filled with rock wool at 0.15 g/cwt, and ■
Figure 5 shows the results of frequency analysis of the relationship between frequency and noise level for each muffler that is left empty without being filled with anything.

It is clear that the noise level in the case (2) of the embodiment of the present invention is lower and the silencing effect is superior to that in the conventional examples (2) and (2).

(Effects of invention) The silencer according to the present invention has the following effects.

(I) Effects of installing or filling bulky carbon fiber aggregates (al) The sound absorption effect is higher than that of conventional sound absorption materials such as rock wool.

It is not clear why bulky carbon fiber aggregates exhibit a significantly superior sound absorption effect compared to other sound absorbing materials, but it is likely that the combination of crystalline and amorphous structures of individual carbon fibers is compatible with combustion exhaust gas conditions. It is assumed that this is because there are In other words, the crystalline structure of the carbon fiber corresponds to an elastic spring, and the amorphous structure corresponds to a viscoelastic dashpot, and the whole functions as a viscous damped vibration system with the spring and dashpot, and this system acts as an engine exhaust gas. It is presumed that energy is absorbed more effectively by resonating with the frequency of combustion exhaust gas such as gas. The present invention is characterized in that it exhibits great effects particularly under the temperature conditions of combustion exhaust gas.

fbl Since it is a bulky aggregate such as felt or mat, the weight of the muffler can be reduced.

tel Does not increase back pressure at the engine or combustor outlet and does not worsen fuel consumption.

(dl) The bulky carbon fiber aggregate will not be partially degraded by exhaust gas and dissipated outside (and will not cause secondary pollution).

(n) Effects of making the cylindrical body made of heat-resistant resin (e) Since the cylindrical body has excellent acid resistance and heat resistance, it has a longer lifespan than a silencer whose cylindrical body is made of metal.

(f) Compared to a metal muffler, the weight can be reduced when heat-resistant resin is used.

(gl　Higher noise damping effect than metal silencers.

(hl The sound absorption effect is particularly exhibited in the viscoelastic region above the glass transition point.

(I) Synergistic effect +il when the cylindrical body is made of heat-resistant resin and the bulky carbon fiber aggregate is attached to the inner surface
A very lightweight silencer can be provided.

(jl　　It is possible to provide a silencer with a long life.

((trans)) It is possible to provide a muffler with a high muffling effect.

[Brief explanation of the drawing]

1 to 3 are sectional views each showing an example of a muffler according to the present invention. FIG. 4 is a graph showing the results of measurement using an ordinary sound level meter (J I 5-C-1052). FIG. 5 is a graph showing the results of FFT analysis of various silencers. 1...Tubular body, 2...Inlet pipe,
3... Outlet pipe, 4... End plate, 7... Partition plate, 10... Compartment, 5... Lining, End... Compartment, 11... ... Attachments. 6... Chamber, 9... Conduit,

Claims (7)

[Claims] (1) A silencer for combustion exhaust gas noise, comprising a cylindrical body, an inlet pipe, and an outlet pipe, the cylindrical body being filled with or fitted with a bulky carbon fiber aggregate. (2) Claim 1 characterized in that the bulky carbon fiber aggregate is at least one selected from a mat-like material, a felt-like material, a woven fabric, and a three-dimensional woven fabric formed from carbon fibers. The silencer mentioned. (3) The muffler according to claim 2, wherein the bulky carbon fiber aggregate is a mixture of carbon fiber and organic fiber or inorganic fiber. (4) The bulky carbon fiber aggregate has a bulk specific gravity of 0.02
4. A muffler according to any one of claims 1 to 3, characterized in that the muffler has a muffler of ~0.20 g/cm^2. (5) The muffler according to any one of claims 1 to 4, wherein the cylindrical body is made of a heat-resistant resin, and the bulky carbon fiber aggregate is mounted on the inner surface of the cylindrical body. (6) The heat-resistant resin is an epoxy resin, a phenol resin,
6. The sound deadener according to claim 5, characterized in that it is at least one heat-resistant resin selected from silicone resin, unsaturated polyester resin, diallyl phthalate resin, melamine resin, thermosetting polycarbodiimide resin, and liquid crystal polyester. vessel. (7) The heat-resistant resin is one to which at least one inorganic substance selected from mica, silicon oxide, talc, aluminum oxide (alumina), alumina powder, carbon fiber, glass fiber, glass wool, and carbon powder is added. 7. A muffler according to claim 6, characterized in that: