JPH03217614A - Muffler for internal combustion engine - Google Patents

Abstract

PURPOSE:To effectively reduce noise with simple construction regardless of frequency territory of a sound wave by lining a cavity part with sheet-like sound absorbing material in which many flat and curled metallic wire bodies are mutually confounded and pressed. CONSTITUTION:A metallic wire body 4a is formed flat and curledly worked in the longitudinal direction, and cut by a prescribed length. Nextly, many metallic wire bodies 4a are mutually confounded and pressed to obtain sheet-like sound absorbing material 4. A cavity muffler 1 is formed by lining a cavity part 3 with the sheet-like sound absorbing material 4. Hereby, the sound absorbing material 4 is vibrated by sound wave entering the cavity part 3, and energy of sound wave in the territory except low frequency territory is absorbed by this vibration to reduce noise. Simultaneously, the sound wave in low frequency territory is also damped and silenced by interferential action of reflected wave in the cavity part 3. Consequently, effective noise reduction can be performed regardless of frequency territory of the sound wave, with simple construction.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a muffler for an internal combustion engine.

[Prior Art] A sound-absorbing muffler is already known, in which a heat-resistant sound-absorbing material that absorbs the energy of sound waves is inserted into a muffler that is installed in the exhaust system of an internal combustion engine to attenuate exhaust noise.

This type of muffler generally has a large number of small holes 2l, 2l drilled in the middle of the exhaust passage 20, and is parallel to the part of the exhaust passage 20 where the small holes 21 and 21 are bored, as shown in FIG. A cavity 22 is formed in the cavity 22, and this cavity 22 is filled with a sound absorbing material 23 made of glass wool, rock wool, or other materials having various sound absorbing properties.

Therefore, the sound waves entering the muffler are transmitted through the small holes 21.
21 to the sound absorbing material 23, vibrating the sound absorbing material 23,
This vibration absorbs the energy of the sound waves and muffles them.

[Problems to be Solved by the Invention] Although this type of conventional sound-absorbing muffler has the advantage of a simple structure, it is not possible to muffle sound only by vibrating the sound-absorbing material 23 and absorbing the energy of sound waves. Because of this configuration, it cannot be expected to muffle sound waves particularly in the low frequency range, and has the disadvantage that the sound muffling function is relatively low.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a muffler for an internal combustion engine that has a simple structure and can effectively muffle sound regardless of the frequency range of sound waves, and can improve the muffler function. shall be.

[Thousand Steps to Solve the Problems] In order to achieve the above object, the present invention provides a hollow section formed in the exhaust passage, which is formed flat and curled in the longitudinal direction, and is cut into a predetermined length. The inner lining is a sheet-like sound absorbing material made by intertwining and pressurizing a large number of metal filaments.

[Operation] According to the present invention, the sound absorbing material is vibrated by the sound waves entering the cavity of the muffler, and the vibration absorbs the energy key of the sound waves in a region other than the low frequency region, thereby muffling the sound.

At the same time, the sound is muffled by the interference effect of the reflected waves that reflect the sound waves within the cavity and cause them to interfere with each other, that is, the sound wave attenuation effect unique to the hollow muffler. Due to the interference effect of the reflected waves, the sound waves in the low frequency range that were not effectively muffled by the sound absorbing material are also attenuated and sound muffled.

[Example code] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a longitudinal sectional side view of a muffler for an internal combustion engine according to the present invention. In the figure, the muffler l is of a so-called hollow type in which a large-diameter cavity 3 is formed in an exhaust passage 2, and the cavity 3 is It is divided into two parts at its axial center into an upstream member 3A and a downstream member 3B, and both 3A and 3B are removably and airtightly joined together, and the upstream side in the exhaust passage 2 is connected to the inlet 3a of the upstream member 3A. The passage 2A is airtightly connected, and the downstream passage 2B in the exhaust passage 2 is airtightly connected to the outlet 3b of the downstream member 3B, and the inner surface is lined with a sheet-like sound absorbing material 4. The volume of the cavity 3 is 15 to 20 of the displacement of an internal combustion engine (not shown).
As shown in FIG. 2A, the sheet-like sound absorbing material 4, which is set to about double the size, is made by rolling a thin linear body 4A with a circular cross section made of stainless steel wire into a second B by a rolling roll.
As shown in the figure, after being formed into a flat tape-like continuum, while applying tension to this flat formed filament body 4A,
Press the corner against the appropriate member and pull it, then tighten the striated body 4.
By removing the tension from A, a naturally curled curled filament is formed, and this curled filament is cut into a predetermined length as shown in FIG. 2C to form a metal filament 4.
a, and a large number of metal filament bodies 4a are intertwined with each other and pressed together as shown in FIG.

That is, the outer diameter φ0. A 15m+m SUS304 filament body 4A (see Figure 2A) is formed into a flat tape-like continuous body with a thickness of 0.03ma+ (see Figure 2B) using a rolling roll, and then curled and rolled. A curled linear body having a diameter of 2 mm is formed, and then this curled linear body is cut into a length of about 10 mm to form a large number of metal linear bodies 4a (see FIG. 2C).

Next, a large number of metal filaments 4a are carried into the hopper 50 of the sheet-like sound absorbing material manufacturing apparatus 5 shown in FIG.
The lth roller group 52. The thickness dimension is adjusted by passing the lower surface of the needle roller 53.
．． After intertwining a large number of metal filament bodies 4a with each other by needle punching with the presser roller group 54
, 54 to further reduce the thickness dimension and carry it out from the conveying means 5l. Then, the pressure roller group 55
, 55 to a thickness of 2III1. Density 1.8 g/
Continuously form 4X cm2 sheets and roll them onto the winding drum 5.
After winding it up at step 6 and cutting it appropriately, a plurality of sheets are stacked and lined in the cavity 3.

The sheet-like sound absorbing material 4 described above is formed by intertwining a large number of cut metal filaments 4a with each other and pressurizing them, and therefore, as shown in the graph of FIG. Good sex. Therefore, it has excellent sound absorption properties. Moreover, since the sheet-like sound absorbing material 4 is made of stainless steel wire, it has excellent heat resistance, so it will not deteriorate in a short period of time even if exposed to high temperature exhaust gas. In other words, it has excellent characteristics against gas attack and contributes to extending the life of the muffler.

In the above configuration, when sound waves enter the cavity 3 from the upstream passage 2A in FIG. 1, the sheet-like sound absorbing material 4 lining the cavity 3 is vibrated.

As a result, the energy keys of sound waves in regions other than the low frequency region are absorbed, thereby muffling the sound.

At the same time, sound muffling is carried out by the interference effect 5 of the reflected waves that reflect the sound waves within the cavity 3 and cause them to interfere with each other, that is, the attenuation effect of the sound waves unique to the hollow muffler. In this way, noise is also muted by the interference effect of reflected waves, so
Even if the sound waves in the low frequency range are not effectively muffled by the sheet-like sound absorbing material 4, the sound waves in the low frequency range are attenuated and muffled similarly to the sound waves in other frequency ranges.

In the above embodiment, the sheet-like sound absorbing material 4 is formed by intertwining a large number of cut metal filament bodies 4a with each other and applying pressure. As shown in the figure, a sheet-like sound absorbing material 4 may be used in which a wire mesh 6 is placed between the sheets 4X and 4X, and the sheet-like sound absorbing material 4 is integrated by a twenty dollar punch. It can be said that this sheet-like sound-absorbing material 4 has better shape retention than the sheet-like sound-absorbing material 4 of the previous embodiment.

In addition, when maintaining the muffler l or replacing the sheet-like sound absorbing material 4, the upstream member 3A and the downstream member 3B are
All you have to do is decompose it. [Effects of the Invention] Since the present invention is configured as described above, it produces the following effects. The sound waves that enter the cavity of the muffler cause the sound absorbing material to vibrate, and this vibration absorbs the energy of the sound waves in areas other than the low frequency range, thereby muffling the sound using the unique sound absorbing action of the sound absorbing muffler. Sound muffling can be achieved by the interference effect of the reflected waves, in which sound waves are reflected within the cavity and they interfere with each other, in other words the sound wave attenuation effect unique to hollow mufflers. Furthermore, due to the interference effect of the reflected waves, it is possible to attenuate and muffle the sound waves in the low frequency range that were not effectively muffled by the sound absorbing material.

In other words, the synergistic effect of the sound absorption effect of the sheet-like sound absorbing material and the sound wave interference effect of the cavity allows effective noise reduction regardless of the frequency range of the sound waves.

In addition, the sheet-like sound absorbing material is curled in the longitudinal direction and is formed by intertwining and pressing a large number of metal filaments cut to a predetermined length, so it has excellent heat resistance. There is. Therefore, even if exposed to high temperature exhaust gas, it will not deteriorate in a short period of time. In other words, it has excellent gas attack resistance and can contribute to extending the life of the muffler. Furthermore, since the structure is simple, maintenance and replacement of the sheet-like sound absorbing material are easy, and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional side view showing one embodiment of a muffler for an internal combustion engine according to the present invention, FIGS. 2A to 2C are manufacturing process diagrams of a metal filament body cut to a predetermined length, and FIG. 3 is an enlarged perspective view showing an example of a sheet-like sound-absorbing material, FIG. 4 is a schematic explanatory diagram of a sheet-like sound-absorbing material manufacturing apparatus, and FIG. 5 is a graph showing the relationship between the compression amount and the tightening surface pressure of the sheet-like sound-absorbing material. FIG. 6 is an enlarged perspective view showing another example of a sheet-like sound absorbing material, and FIG. 7 is a schematic sectional view showing a conventional sound absorbing muffler. 1...
・Muffler 2...Exhaust passage 3...Cavity part 4...Sheet-like sound absorbing material 4a...Cut metallic linear body

Claims (1)

[Claims] (1) In a hollow muffler with a hollow part formed in the exhaust passage, a large number of metal filaments formed flat in the hollow part, curled in the longitudinal direction, and cut into predetermined lengths are entangled with each other. A muffler for an internal combustion engine characterized by being lined with a sheet-like sound absorbing material that is pressurized.