JP2548775B2 - Muffler and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention is directed to, for example, reduction of exhaust noise in an automobile, reduction of compression noise of a supercharged combustion engine in an automobile, and air compressor for a factory. The present invention relates to a muffling device that can be used for reducing compressed sound and the like, and a manufacturing method thereof.

[Prior Art] Conventionally, as a silencer for an automobile, four types of structures such as an expansion type, a resonance type, a sound absorbing type, and an interference type as shown in FIG. 4 have been known. It has the following features.

Expansion type: Sound is reduced by using the reflection of sound waves at the discontinuous portion of the passage cross section. A sound reduction effect can be obtained from high frequencies to low frequencies.

Resonance type: The acoustic energy propagating in the pipe is attenuated by the Helmholtz resonator formed by the hole provided in the pipe wall and the cavity behind it. A sound wave having a frequency corresponding to the size of the expansion chamber can be attenuated.

Sound absorption type: A sound absorbing material is lined inside the duct to absorb part of the acoustic energy toward the inner wall of the duct and attenuate the sound wave. Glass wool, ceramic wool, metal wool, etc. are used as the sound absorbing material.

Interference type: A sound propagation path is branched, the lengths of the respective paths are changed to join, and the sound is reduced by the interference of the sound from each path having a phase shift.

[Problems to be Solved by the Invention] However, the conventional vehicle silencers have the following disadvantages.

Expansion type: Since the fluid passage directly expands and contracts, the resistance of the fluid passage is large and the pressure loss of the fluid is large.

Resonance type: Since the frequency of sound reduction is proportional to 1 / square root of the size of expansion chamber, one silencer can mute only some frequencies. Further, since the volume reduction is proportional to the size of the expansion chamber, the silencing effect for high frequencies is relatively small.

Sound absorption type: Relatively effective at high frequencies, but less effective at low frequencies. Further, since the fibrous substance inside is highly likely to be sucked out along with the flow of the fluid, it cannot be used for an application (for example, for attenuating intake sound) which causes inconvenience.

An object of the present invention is to provide a novel silencer that does not cause the above-mentioned inconvenience.

[Configuration of the Invention] [Means for Solving the Problems] A sound deadening device of the present invention is a porous metal material, and a thermal expansion coefficient thereof is equal to or less than that of the porous metal material, A hollow metal member penetrating the inside of the material, an inner space of the hollow metal member, and a plurality of muffling holes radially provided so as to penetrate between at least a part of the inner space of the metal porous material, And a cover member that covers the outer periphery of the metallic porous material, wherein at least one of the size of each of the silencing holes and the size of each of the bubbles formed in the metallic porous material is a plurality of types. is there.

[Operation] Air vibration, that is, when a fluid containing acoustic energy is passed through the hollow metal member, the acoustic energy is transmitted to the sound deadening hole and is generated by the sound deadening hole and a large number of small holes (for example, bubbles) existing around the sound deadening hole. Decay. That is, the small holes and the muffling holes function as expansion chambers, and acoustic energy is attenuated and silenced while sound waves are repeatedly reflected in many expansion chambers.

According to this, since the hollow metal member does not expand and contract due to acoustic energy, the pressure loss of the fluid passing through the hollow metal member is smaller than that of the expansion silencer in which the fluid passage itself expands and contracts. In addition, the frequency characteristic of muffling is
It varies depending on the size of the sound deadening holes and the size of the small holes of the porous metal material. Since there are many muffling holes and small holes, by making them of different sizes,
A sufficient silencing effect can be obtained for various frequencies. Metal porous materials such as foam aluminum are rigid,
Since some of it does not fall out and flow out with the fluid, this type of silencer can be used for various purposes.

By the way, a metal porous material such as aluminum is generally produced by a so-called sintering method, which is produced by sintering metal powder or metal fibers. However, the porous metal material formed in this way is inflexible in bending and easily corrodes from the viewpoint of corrosion resistance because metals other than aluminum intervene, and requires a special furnace for manufacturing equipment. Therefore, there is an inconvenience that the cost becomes high. Therefore, in a preferred embodiment of the present invention, a foam molded body containing aluminum or the like as a main component is used as the metal porous material.

The foamed aluminum product has closed cells or open pores, has a small specific gravity and is ultralight, is easy to process on site, and has the advantage that it is a rigid body unlike glass wool. .

When using foamed aluminum as a muffler, it is necessary to form a composite structure of them by passing a pipe or the like forming a fluid passage through the center of the foamed aluminum. As a method for producing this kind of composite structure, the following method has been conventionally proposed.

(A) A through hole having a size corresponding to the outer diameter of a pipe to be integrated is cut with a gun drill or the like in a foam molded body formed by primary molding of a molten metal such as aluminum added with a foaming agent and cast. The holes are squeezed with a tool, and then the pipes are pressed into the insertion holes to integrate them.

(B) A preheated pipe is set in a mold in advance, and a molten foam in the process of production, that is, an added foaming agent starts foaming and bubbles are being formed inside the mold in the mold. Inject the metals and allow them to cool and solidify.

However, when using any of the above methods (a) and (b), a gap is formed at the boundary (joining portion) between the metal foam molded body and the pipe, and a sufficient joining state cannot be obtained.

FIG. 5a is an enlarged view of the cross section of the joint portion between the pipe 41 and the porous material 42 of the composite structure obtained by the method (a).
Referring to FIG. 5a, in this example, it can be seen that the pipe 41 and the porous material 42 are in contact via a number of cut air bubbles of the porous material 42. That is, the contact area between the two is small.

FIG. 5b is an enlarged cross-sectional view of the joint between the pipe 43 and the porous material 44 of the composite structure obtained by the method (b).
Referring to FIG. 5b, in this example, the surface of the porous material 44 at a portion facing the pipe 43 is wavy, that is, has an uneven shape, and an air layer 45 is formed at the boundary between the pipe 43 and the porous material 44.
You can see that exists. Therefore, the pipe 43 and the porous material
The contact area with 44 is small. This kind of air layer 45 is formed because the viscosity of the molten metal poured into the mold increases,
This is because the flow becomes worse.

In any case, in the composite structure manufactured by the conventional method, the contact area between the pipe and the porous material is small.
Therefore, when this kind of composite structure receives a force from the outside due to vibration, etc., the contact part is strongly pressed and deforms,
As a result, the joint between the pipe and the porous material is loose. That is, the durability against external force is low. Therefore,
In the preferred embodiment of the present invention, a composite structure is manufactured using the following method.

That is, by adding a molten metal such as aluminum or aluminum alloy, a thickener such as calcium, and a foaming material such as titanium hydride, the viscosity is adjusted and agitated, the bubbles of the foaming material in the molten metal expand, and During bubble growth before the formed bubbles form a thin film cell structure, a hollow metal member having a thermal expansion coefficient equal to or lower than that of the molten metal is inserted into the mold, After the foaming is completed, it is cooled and solidified to obtain a composite structure.

In the composite structure obtained by this method, the surface of the porous material is flat at the contact portion between the porous material (foamed aluminum) and the hollow metal member (for example, pipe), and bubbles of the porous material are cut off. Because it has not been
A very large contact area can be obtained.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Embodiment] FIG. 1 and FIG. 2 show an exploded perspective view and a vertical cross-sectional view, respectively, of a silencer embodying the present invention. 1 and 2
It will be described with reference to the drawings. This muffler is a muffler body 1
It comprises 0, covers 14 and 15, flanges 16 and 17.

The muffler body 10 includes a cylindrical foam aluminum 11 and
Aluminum cylindrical pipe that penetrates the center
It is a composite structure that integrates 12 and. The foamed aluminum 11 is formed by foaming molten aluminum as will be described later, and as shown in FIG.
There are innumerable bubbles 11a over the entire area. In this example, the size of the bubble 11a formed in the foamed aluminum 11 decreases as it approaches the pipe 12, and increases as it approaches the periphery.

In the muffler body 10, a large number of sound deadening holes 13 penetrating the foamed aluminum 11 and the pipe 12 are radially formed.
In this example, sound deadening holes of two types (diameters) indicated by 13a and 13b are arranged alternately. Both ends of pipe 12
12a and 12b project at both ends of the foamed aluminum 11.

The cover 14 is a cylindrical metal having an inner diameter equivalent to the outer diameter of the foamed aluminum 11, one end 14a of which is open, and the other end 14b is closed except for a hole 14c through which the pipe 12b is inserted. The cover 15 and the flanges 16 and 17 are also formed with holes 15a, 16a and 17a for passing the pipe 12, respectively. The sizes of the holes 14c, 15a, 16a and 17a are equal to the outer diameter of the pipe 12.

The covers 14 and 15 are attached to the outer periphery of the foamed aluminum 11. By welding the abutting portions of the covers 14 and 15 to each other, they are integrated to seal the foamed aluminum 11. Flanges 17 and 16 are fixed to the outer peripheries of the ends 12a and 12b of the pipe by welding, respectively. These flanges 16 and 17 are used to fix the silencer in place and to connect it to other pipes.

When air vibration, that is, a fluid containing acoustic energy (for example, exhaust gas) is passed through the pipe 12, a wave of acoustic energy is transmitted to a large number of muffling holes 13 in the muffling device and is present in and around the muffling holes. The reflection is repeated in the expansion chamber constituted by the infinite number of air bubbles 11a. During repeated reflections, the acoustic energy is attenuated and silenced.

In this example, there are two kinds of sizes of the muffling holes 13 and the sizes of the bubbles 11a are greatly different between the inner peripheral side and the outer peripheral side of the foamed aluminum 11. The distance between and differs from place to place, thus providing a silencing effect for sound waves of different frequencies.
There is no obstacle inside the pipe 12 through which the fluid passes,
Since it does not expand or contract itself, the pressure loss experienced by the fluid passing through the muffler in the pipe 12 is relatively small.

3a and 3b show modified embodiments, respectively. Referring to FIG. 3a, in this embodiment, the foam aluminum 11B is formed so that the size of the bubbles is substantially uniform over the entire area. The size of the muffling hole 13 is two kinds as in the above embodiment. Referring to FIG. 3b, in this embodiment, all the muffling holes 13C formed in the muffler body 10C have the same diameter. In this example, the bubble size of the foamed aluminum 11C is smaller on the inner peripheral side and larger on the outer peripheral side, as in the case of FIG.

That is, in any of the modified examples shown in FIGS. 3a and 3b, since the size of the expansion chamber differs depending on the location, a sound deadening effect can be obtained for sound waves of various frequencies.

Next, a method of manufacturing the composite structure of the foamed aluminum 11 and the pipe 12 which constitutes the muffler body will be described.

FIG. 6a shows an outline of an apparatus configuration for manufacturing a composite structure. This will be described with reference to FIG. 6a. The mold case 6 of the mold M is provided with a lower lid 3 formed with a concave holding hole 2 in which the lower end of the pipe 1 can be embedded and installed, and an upper lid 5 having a through hole 4 through which the pipe 1 penetrates. Provided at the top. The mold M is arranged so that the bottom thereof fits inside the bottom plate 7.

A molten metal such as aluminum or an aluminum alloy and a binder such as calcium are put in the mold M.
Then, the melting temperature of the molten metal (700 to 7 for aluminum)
The contents are sufficiently melted by heating to 20 ° C.), and the content of the binder is adjusted so that the molten metal has a predetermined viscosity while stirring with a stirrer (not shown). After a predetermined viscosity is obtained, a foaming material such as titanium hydride is added and the contents of the mold are stirred. As a result, the added foam material starts foaming.

At the stage when the blowing agent has expanded and the growth of bubbles has started, 30
The pipe 1 preheated at a temperature of 0 to 500 ° C. is passed through the through hole 4 of the upper lid 5 and the lower end is fixed in the holding hole 2 of the lower lid 3. At the lower end of the pipe 1, a sealing material (a material of the same quality as the pipe 1 or a material having a higher melting point than the pipe 1) 8 is fitted.

After a while, the foaming of the added blowing agent is completed,
The bubbles grow sufficiently, and as a result, the molten metal is melted as a foamed metal. Thereafter, when the contents of the mold M are cooled by cooling or other means, the molten metal solidifies. When the mold M is disassembled after the molten metal has solidified, a composite structure in which the foam metal (aluminum) 9 and the pipe 1 are integrated as shown in the figure is obtained.

In the example of FIG. 6a, a composite structure in which only one end of the pipe 1 protrudes from the foam metal 9 is obtained. An apparatus for obtaining a composite structure in which both ends of the pipe protrude from the foam metal is schematically shown in FIG. 6b. Referring to FIG. 6b, in this example,
A plurality of legs 3a are formed at the lower end of the lower lid 3 so that the lower lid 3 has a height sufficient to protrude one end 1b of the pipe 1. The holding hole 2 is formed in a size that allows the pipe 1 to be inserted. The other structure is the same as that of FIG. 6a.

In the apparatus shown in FIG. 6b, a composite structure of the pipe 1 and the foam metal can be obtained by the same method and under the same conditions as in the apparatus shown in FIG. 6a. In the example of FIG. 6a, the lower end of the pipe 1 is filled with the sealing material 8 in order to prevent the inflow of the foam metal, but in the example of FIG. 6b, the end 1b of the pipe 1 is the lower lid. Since it is arranged so as to pass through the holding hole 2 of No. 3, the molten metal does not flow from the end 1b of the pipe 1, and the sealing material is unnecessary.

An example of specific conditions when a composite structure is actually manufactured is shown below.

Molten metal: Aluminum with a purity of 99.7% Thickener: 2.0% by weight of calcium Foaming agent: 2.0% by weight of titanium hydride Sealant (8) Aluminum pipe (1): Aluminum ( A011-T5) 50 mmφ
Wall thickness: 1.2mm Foam mold component material: SS41 Composite structure size: Diameter: 250mm Height: 230mm That is, put 99.7% pure aluminum into mold M,
The whole mold M was heated to 700 ° C. with a heater to dissolve the aluminum, and then 2.0% by weight of calcium was added as a thickener and stirred to thicken. Then, after adjusting the viscosity of the molten metal, 2.0% by weight of titanium hydride powder was added as a foaming agent while maintaining the temperature of the molten metal at 700 ° C., and the mixture was stirred and preheated to attach the upper lid 5. Further, when the foaming agent starts foaming inside the mold M and the bubbles in the molten aluminum expand and grow, the aluminum pipe 1 is placed on the upper lid 5.
Insert the lower end 1b from the through hole 4 into the holding hole 2 of the lower lid 3 and fix it, and in that state, the mold M is heated to completely foam the foaming agent in the molten metal and make the bubbles uniform. When the thin-film cell structure was formed, the heating of the mold M was stopped and cooled at room temperature to solidify the molten metal. After solidification, the mold M was disassembled to obtain a composite structure.

The cross section of the composite structure obtained by this manufacturing method is
Shown in Figures 7a and 7b.

The composite structure shown in FIG. 7a was obtained when the cooling period of the mold M, the stirring time after adding the thickening agent, etc. were adjusted and the bubbles in the molten aluminum were sufficiently grown. 7a
Referring to the figure, in this composite structure, the size of the bubble X in the foamed aluminum 9 is
As it approaches the boundary S between the pipe 1 and the pipe 1, it becomes gradually smaller, and in the boundary S, a layer of aluminum in which no bubbles X exist is formed.

The composite structure shown in FIG. 7b was obtained when the cooling period of the mold M, the stirring time after adding the thickener, etc. were adjusted and the bubbles in the molten aluminum were not grown so much. Referring to Figure 7b, in this composite structure:
The size of the bubbles Y in the foam aluminum 9 is almost uniform as a whole. At a boundary portion S between the foamed aluminum 9 and the pipe 1, an aluminum layer without bubbles Y is formed.

In any case, in the composite structure manufactured by using the above-mentioned method, the contact portion between the pipe and the foamed aluminum has a completely independent thin film cell structure, and since there is no air layer in that portion, the pipe is The contact area between aluminum and aluminum foam is very large. Therefore, the mechanical strength is high, the backlash does not occur even when an external force is applied by vibration, etc., and the durability is high.

[Effect] As described above, the muffler of the present invention is not particularly limited in its application, can be used for muffling at various frequencies, and has a small pressure loss to the passing fluid. Further, the silencer manufactured by the method of the present invention has high durability.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a silencer embodying the present invention. FIG. 2 is a vertical sectional view of the silencer shown in FIG. FIG. 3a is a vertical sectional view showing a modification of the silencer. FIG. 3b is an exploded perspective view showing another modification of the silencer. FIG. 4 is a front view showing the outline of the internal structure of a conventional extinction device. FIG. 5a and FIG. 5b are cross-sectional views showing a composite structure of a metal foam and a pipe manufactured by a conventionally proposed method, respectively. 6a and 6b are perspective views showing the configuration of an apparatus for manufacturing a composite structure used in a silencer. 7a and 7b are cross-sectional views showing the structure of the composite structure manufactured by the method of the present invention. 1,12: Pipe (hollow metal member) 2: Recessed holding hole 3: Lower lid, 3a: Support leg 4: Through hole, 5: Upper lid 6: Mold case, 7: Bottom plate 8: Seal material, 9: Foam metal 10: Muffler body 11: Aluminum foam (porous metal material) 13,13a, 13b: Sound deadening hole 14,15: Cover, 16,17: Flange 14c, 15a, 16a, 17a: Hole 41,43: Pipe, 42,44: Porous material 45: Air layer M: Mold, S: Boundary X, Y, 11a: Bubble

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shigeru Akiyama 807 Nonoshita, Yadomachi, Tosu City, Saga Prefecture 1 Kyushu Industrial Technology Institute, Industrial Technology Institute (72) Toru Nishikawa 1 10 Nakahamacho, Amagasaki City, Hyogo Steel Wire Industry Co., Ltd. (72) Inventor Shozo Fujimoto 1-10 Nakahama-cho, Amagasaki City, Hyogo Prefecture Shinko Steel Wire Industry Co., Ltd. Kazutaka Yasuike (56) Reference JP 62-58006 (JP, A) ) JP-A-58-132294 (JP, A) Actually developed 58-42319 (JP, U)

Claims (2)

(57) [Claims] 1. A porous metal material, a hollow metal member having a thermal expansion coefficient equal to or lower than that of the porous metal material and penetrating the inside of the porous metal material, and a hollow metal member of the hollow metal member. An inner space, and a plurality of sound deadening holes radially provided in a form penetrating between at least a part of the inner space of the metal porous material, and a cover member that covers the outer periphery of the metal porous material, A silencer in which at least one of the size of each of the silencing holes and the size of each of the bubbles formed in the porous metal material is plural. 2. A foamed material in a molten metal by adding a molten metal such as aluminum or an aluminum alloy, a thickening material such as calcium and a foaming material such as titanium hydride into a mold to adjust the viscosity and agitate. When the bubbles grow before the bubbles expand and the independent bubbles form a thin film cell structure,
A hollow metal member having a thermal expansion coefficient equal to or less than that of the molten metal is inserted into the casting mold, and after the foaming in the molten metal in the mold is completed, it is cooled and solidified,
A composite silencer comprising a porous metal material and a hollow metal member is formed, and a through hole is formed through the outer periphery of the porous metal material and the inner space of the hollow metal member in the composite component. Production method.