JPH0988548A - Sound absorbing type muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the scattering of a sound absorbing material accompanying its deterioration by suppressing the deterioration of the sound absorbing material due to exhaust gas when an exhaust noise is absorbed by the sound absorbing material. SOLUTION: An exhaust gas duct 2 in which many small penetrating holes are opened to a pipe wall in the vicinity of a pipe bottom, is drilled through one side bottom 1a of a sound absorbing box 1, and an exhaust gas discharge pipe 3 is drilled through the other side bottom 1b of the sound absorbing box 1. The exhaust gas duct 2 and the exhaust gas discharge pipe 3 are oppositely arranged, and also a sound absorbing material 4 consisting of a mixture of ceramic fiber and glass fiber is fixed on the inner wall surface 1c of the sound absorbing box 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle silencer, and more particularly to a sound absorbing silencer.

[0002]

2. Description of the Related Art There is a sound absorbing type silencer as shown in FIG. 3, in which a part of an exhaust pipe 11 is an inner pipe 1.
1a, and the outer pipe 12 with the inner pipe 11a closed at both ends
Is a sound-absorbing silencer in which a large number of small holes 13 are formed in the inner pipe 11a over substantially the entire length thereof, and the space between the inner pipe 11a and the outer pipe 12 is filled with a sound-absorbing material 14 such as glass wool. Yes, it is excellent in silencing in the high temperature frequency range (for example, the prior art of Japanese Utility Model Publication No. 6-27790).

[0003]

A conventional sound absorbing type silencer in which the inner tube 11a is made as long as possible and the inner tube 11a is covered with a sound absorbing material 14 made of glass wool, is a glass wool having a high temperature and high pulsation exhaust gas. When exposed to gas, the glass wool deteriorates and becomes brittle, and the starting end (front end) and end (rear end) of the row of small holes 13 formed in the inner pipe 11a due to the high temperature and high pulsating pressure of the exhaust gas. The problem that the glass wool is scattered around occurs. Therefore, the present invention has been made in order to solve the above problems, the sound absorbing material is not scattered by the high temperature of the exhaust gas flowing in the exhaust conduit, high pulsating pressure, and excellent in silencing in the high frequency range. An object is to provide a sound absorbing silencer.

[0004]

In order to solve the above problems, a sound absorbing silencer of the present invention is an exhaust pipe having a large number of small through holes formed in a pipe wall near the pipe bottom at one side bottom of the sound absorbing box. The exhaust outflow pipe through the bottom of the other side of the muffler box, the exhaust conduit and the exhaust outflow pipe are provided to face each other, and the ceramic wall and the glass fiber are provided on the inner wall surface of the muffler box. A sound absorbing material composed of a mixture of

Exhaust gas from the engine flows out from the through hole into the space between the exhaust conduit and the sound absorbing material, expands and lowers in pressure, and then contacts the sound absorbing material, so that the high frequency range of the exhaust gas is caused by the sound absorbing material. It is muted. At this time, the sound absorbing material hardly deteriorates,
The sound absorbing material does not scatter.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The sound absorbing silencer of the present invention has the sound absorbing material 4 on the inner wall surface 1c.
The sound deadening box 1 is fixed to the sound deadening box 1, the exhaust conduit 2 penetrating the one side bottom 1a of the sound deadening box 1, and the exhaust outflow pipe 3 penetrating the other side bottom 1b of the sound deadening box 1.

The sound deadening box 1 is composed of a cylindrical box body, and a sound absorbing material 4 made of a mixture of ceramic fibers and glass fibers is fixed to the inner wall surface 1c of the cylindrical shape. The sound absorbing material 4 is a cylindrical porous plate 5 And the inner wall surface 1c of the sound deadening box 1, and the perforated plate 5 and the sound absorbing material 4 are arranged concentrically with the sound deadening box 1. A cylindrical exhaust pipe 2 having a bottom and a large number of small through holes 6 formed in the wall of the sound absorbing box 1 near the bottom of the sound absorbing box 1 is provided in the sound absorbing box 1. The through hole 6 is housed in the sound absorbing box 1. The total area of the openings of the large number of through holes 6 is formed to be substantially equal to the cross-sectional area of the exhaust conduit 2. The other side bottom portion 1b of the sound deadening box 1 is provided with a cylindrical exhaust outflow pipe 3 penetrating therethrough, the exhaust conduit 2 and the exhaust outflow pipe 3 are provided facing each other, and the exhaust conduit 2, the sound deadening box 1, and the exhaust outflow pipe are provided. 3 and 3 are arranged concentrically.

Next, the operation of the sound absorbing silencer will be described. When the exhaust gas flowing out from the engine (not shown) flows through the exhaust conduit 2 and collides with the bottom of the exhaust conduit 2, the exhaust gas flows out from the through hole 6 into the space 7 between the exhaust conduit 2 and the sound absorbing material 4. After expanding and reducing the pressure, it contacts the sound absorbing material 4. When the exhaust gas comes into contact with the sound absorbing material 4, the sound pressure energy of the pressure wave mainly of the high frequency component of the sparse pressure wave generated due to the pulsating pressure of the exhaust gas is converted into heat energy inside the sound absorbing material 4, The exhaust gas with reduced sound pressure energy flows out into the atmosphere from the exhaust outflow pipe 3. At this time, since the pulsating pressure of the exhaust gas contacting the sound absorbing material 4 is low, the sound absorbing material 4 is hardly deteriorated and the sound absorbing material 4 does not scatter.

The sound pressure level of the exhaust noise of the exhaust gas flowing out into the atmosphere from the exhaust outflow pipe 3 is measured by a sound pressure meter (not shown) installed near the exhaust outlet (not shown) of the exhaust outflow pipe 3. did. The result is shown in FIG.

For comparison, the exhaust noise was measured for the prior art sound absorbing silencer shown in FIG. The sound absorbing type silencer of the prior art is filled with a large amount of the sound absorbing material 14 made of glass wool, the inner diameter of the outer tube 12 is the same as the inner diameter of the sound deadening box 1, and the length of the outer tube 12 is the same as that of the sound deadening box 1. The length was 1.8 times. The diameter of the inner pipe 11a was the same as the diameter of the exhaust conduit 3, and the diameter and distribution density of the small holes 13 were the same as the diameter and distribution density of the through holes 6 of the above-mentioned embodiment.

The noise level of the exhaust gas flowing out from the conventional sound absorbing silencer of FIG. 3 is also shown in FIG. As is clear from FIG. 2, in the sound absorbing silencer of the prior art, the sound pressure level of the present invention was measured over the entire range of the engine speed, even though the sound absorbing material 14 made of a large amount of glass wool was used. It was found that the sound pressure level of the exhaust gas flowing out of the muffler was higher than that of the muffler, and the sound absorbing muffler of the present invention had good muffling performance.

[0012]

According to the present invention, since the sound absorbing material composed of the mixture of the ceramic fiber and the glass fiber is fixed to the inner wall surface of the sound deadening box, the sound absorbing material is excellent in the sound insulating property and the sound absorbing material is not scattered and deteriorated. Absent.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a sound absorbing silencer according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between engine speed and sound pressure level of the sound absorbing silencer of the present invention.

FIG. 3 is a vertical sectional view of a conventional sound absorbing silencer.

[Explanation of symbols]

 1 sound deadening box 1a bottom part on one side 1b bottom part on the other side 1c inner wall surface 2 exhaust conduit 3 exhaust outlet pipe 4 sound absorbing material 6 through hole

Claims (1)

[Claims] 1. An exhaust pipe having a large number of small through holes formed in a pipe wall near the pipe bottom is provided at the bottom of one side of the silencer box, and an exhaust outflow pipe is provided at the bottom of the other side of the silencer box. A sound absorbing silencer characterized in that the exhaust conduit and the exhaust outflow pipe are provided so as to face each other, and a sound absorbing material made of a mixture of ceramic fibers and glass fibers is fixed to the inner wall surface of the sound deadening box.