JP2005307955A - Muffler for automobile exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a muffler which is effective against exhaust sound including a wide frequency band. <P>SOLUTION: A conical porous cylindrical member 6 wherein a large number of small holes are bored on the whole of its cylinder wall is provided in a main body case 2 of the muffler. Exhaust gas flowing from an entrance pipe 1 is made to circulate into the main body case 2 on the outside through the small holes 7 arranged in conical shapes on the cylindrical member 6. At that time, resonance sound having a wide frequency band is generated from each small hole 7, thereby canceling the exhaust sound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas silencer for a four-wheeled or two-wheeled vehicle engine, and more particularly to a structure of a silencer having a silencing effect in a wide frequency band.

  2. Description of the Related Art As a muffler for automobile exhaust gas, a compact and easy-to-manufacture structure with a high muffling effect is desired. Conventionally, a muffler having the structure shown in FIG. 2 is generally used.

In the silencer of FIG. 2, a large number of small holes 25 are formed in the extended portion of the inlet pipe 21 between the coaxial inlet pipe 21 and outlet pipe 23 to form a porous pipe 22. In the figure, the porous pipe 22 is formed in the extended portion of the inlet pipe 21 for cost reduction, but there is also a case where a separate large-diameter porous pipe 22 is joined and disposed.
Further, the outside of the porous portion of the porous pipe 22 is hermetically surrounded by a cylindrical main body case 24, and exhaust gas flowing from the inlet pipe 21 to the outlet pipe 23 as indicated by an arrow A is passed through a large number of the porous pipes 22. Since it diffuses into the main body case 24 through the small holes 25, the pressure of the exhaust gas is reduced, and the sound volume is reduced.

  For many years, the present inventor involved in the production of automobile parts has conducted research on improving the conventional silencer. As a result, in the silencer of FIG. 2, the exhaust gas passes through the small holes 25 of the perforated pipe 22 and the outer main body case. It was confirmed that a resonance sound was generated from each of the small holes 25 when returning to the inside of the gas chamber 24, and the resonance sound canceled out the exhaust sound oscillated from the engine side to reduce the volume. The silencing action that cancels out by the resonance sounds of the small holes 25 is theoretically compatible with the Helmholtz reverse whistle principle.

  In addition, in the straight cylindrical perforated pipe 22 shown in FIG. 2, the larger the pipe inner radius, the higher the frequency of the exhaust noise cancels, and the smaller the pipe inner radius, the lower the frequency of the exhaust sound. It has also been confirmed that they act to counteract each other.

  The body case 24 is filled with a glass wall 26 to absorb resonance of the perforated pipe 22, but it has also been confirmed that it does not effectively act on absorption of exhaust sound.

An example is disclosed in JP-A-2002-155723. "Silence silencer with perforated pipe"

  However, since the conventional silencer has a straight cylindrical structure, the conventional silencer works effectively for a specific frequency band corresponding to the inner diameter of the pipe, but is sufficient for exhaust sound including a wide frequency band. However, there was a problem that it was not possible to exert a sufficient silencing effect.

  The present invention aims to solve the above-mentioned problems, and provides a silencer having a structure capable of exerting a silencing effect in a wide frequency band by utilizing the action of canceling out resonance sounds generated in a perforated pipe. It is aimed at things.

In order to achieve the above object, it is necessary to make a structure in which the resonance sound generated in a large number of small holes in the perforated pipe cancels out the exhaust sound in a wide frequency band. The outlet side is composed of a small-diameter conical perforated cylinder, and a large number of small holes perforated in the cylinder wall are arranged in order from the large diameter to the small diameter, so the resonance sound generated in each small hole has a high frequency. It has a structure that works to cancel out the exhaust sound of the low frequency band from the band.
The conical cylinder 6 (FIG. 1) is a main part of the present invention.

  As a result of using the silencer of the present invention on a Toyota AE86 carola, the exhaust sound that was 70 horns when idling with the Toyota genuine silencer (engine speed 800 RPM) The engine speed was reduced to 64 horns at an engine speed of 800 RPM, and the effect of the rational structure of the present invention was demonstrated.

  The silencer of the present invention is made compact in the same way as the conventional device, and the conical cylindrical body, which is the main part of the device, is a structure that can be mass-produced, so it is easy to manufacture and contributes to prevention of automobile noise I think.

  BEST MODE FOR CARRYING OUT THE INVENTION A vehicle exhaust gas silencer of the best mode for carrying out the present invention is a conical perforated cylindrical body having a large diameter at the inlet side and a small diameter at the outlet side, a porous pipe disposed between the coaxial inlet pipe and outlet pipe. And the outside of the conical perforated cylinder is surrounded by a cylindrical main body case, and the exhaust flowing from the inlet pipe to the outlet pipe passes through the numerous small holes of the perforated pipe. -It is configured to recirculate in the exhaust so that the resonance sound generated in each small hole cancels out the exhaust sound including a wide frequency body region.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view along the axial direction of a muffler for automobile exhaust gas (hereinafter also referred to as this apparatus) of the present invention.

  In this apparatus, both side surfaces of the outer cylindrical main body case 2 are hermetically closed by the conical entrance side wall 4 and the exit side wall 5, and the opening 10 of the entrance side wall 4 is provided. The inlet pipe 1 and the outlet pipe 3 project from the peripheral edge of the opening 11 of the outlet side wall 5. The inlet pipe 1 and the outlet pipe 3 are coaxially integrated with the main body case 2. It is connected.

  In addition, the conical porous cylinder 6 which is a main part of the present invention provided in the main body case 2 has a large number of small holes 7 perforated on the entire cylinder wall, and the outer main body case 2 has a large number of holes. Are concentrically coupled with the side surface of the large-diameter opening 8 inside the outer peripheral end 12 of the inlet side wall 4 and the side surface of the small-diameter opening 9 inside the opening 11 of the outlet side wall 5. .

  Since the present apparatus is configured as described above, the exhaust gas flowing in as shown by the arrow A through the inlet pipe 1 connected to the exhaust pipe of the automobile engine passes through the small holes 7 of the conical porous cylinder 6. The exhaust passes through the outer main body case 2 and is discharged from the outlet pipe 3. At this time, the exhaust gas including a wide frequency band in which the resonance sound of a wide frequency body region generated from each small hole 7 oscillates from the engine side. Mutes the sound and cancels out the sound.

  It can also be used for noise countermeasures in fields where oil engines are used as power sources such as agricultural machinery and construction machinery.

It is a section explanatory view of the silencer for automobile exhaust gas of the present invention. It is sectional explanatory drawing of the conventional silencer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Entrance pipe 2 ... Main body case 3 ... Outlet pipe 4 ... Entrance side wall 5 ... Outlet side wall 6 ... Conical porous cylinder 7 ... Small hole 8 ... Large diameter opening 9 ... Small diameter opening 10 ... Opening of entrance side wall Part 11: Opening part 12 on the outlet side wall ... Outer peripheral edge 21 on the inlet side wall ... Entrance pipe 22 ... Perforated pipe 23 ... Outlet pipe 24 ... Main body case 25 ... Small hole 26 ... Glass wall

Claims (2)

A perforated pipe is arranged between the inlet pipe and the outlet pipe on the same axis, the outside of the perforated pipe is surrounded by a cylindrical main body case, and exhaust gas flowing from the inlet pipe to the outlet pipe is passed through the perforated pipe. In an automobile exhaust gas silencer that recirculates into the outer body case through a large number of small holes and silences, the porous pipe is composed of a conical porous cylinder with a large diameter on the inlet side and a small diameter on the outlet side Silencer for automobile exhaust gas, characterized by An outer cylindrical main body case is integrally connected to the inlet pipe through the opening on the inlet side wall and the outlet pipe through the opening on the outlet side wall. The provided conical perforated cylindrical body is constructed by connecting the large-diameter opening to the inside of the outer peripheral end of the inlet side wall and the small-diameter opening to the inside of the opening of the outlet side wall. Item 2. A muffler for automobile exhaust gas according to Item 1.

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