JPH07229415A - Silencer having sound absorbing material - Google Patents

Abstract

PURPOSE:To provide a silencing characteristic applicable to a wide range of noise frequency area by successively changing the thickness of a cylindrical sound absorbing material mounted on the inner surface of an expanded silencer in the axial direction to form the inner surface of the sound absorbing material into a tapered surface. CONSTITUTION:A cylindrical sound absorbing material 3 is stuck to the inner surface of a cylindrical vessel 2 to form a silencer 1. The thickness of the sound absorbing material 3 is axially changed to form the inner surface into a tapered surface. Since the sound absorbing material, when differed in thickness, shows silencing effect to the frequency corresponding thereto, the silencing effect can be extended to noises of a wide frequency range. Thus, a silencer having high silencing effect as the whole can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an expandable silencer mounted on, for example, an intake system, an exhaust system of an internal combustion engine.

[0002]

2. Description of the Related Art For example, there is an expansion type silencer in which a cylindrical container is provided in the middle of an air intake pipe of an internal combustion engine. In that case, there is also one in which a sound absorbing material is attached inside the side wall of the container to enhance the sound deadening effect. It is generally known that the sound deadening characteristic changes depending on the thickness of the sound absorbing material, and that when the thickness of the sound absorbing material is increased, the peak of the frequency range to be muted shifts to the low frequency side.

As shown in FIG. 3, in the conventional case, a cylindrical container 12 is attached in the middle of a gas flow pipe, for example, an air intake pipe 15 of an internal combustion engine, and a sound absorbing material 13 (thickness t) is formed on the inner surface of the side wall thereof.
Is attached to the silencer 11. The sound absorbing material 13 is, for example, a synthetic resin foam, and is attached to the inner surface of the side wall of the container 12 with an adhesive. The silencing characteristic is shown by the curve A in FIG. Further, if the thickness of the sound absorbing material is uniformly increased to 14 (thickness T) in FIG. 3, the peak of the sound deadening characteristic shifts to the low frequency side as shown by the curve B in FIG.

[0004]

When the frequency of the noise to be extinguished or attenuated by the muffler has a curved distribution having a specific frequency as a peak, the muffling characteristics of the conventional muffler are reduced. The peaks should be set so that they match the noise peaks, but if the noise frequency has no significant peaks and is distributed over a wide area, or if you want to mute over a wide frequency range, the characteristics are not compatible with the conventional ones. , The sound deadening effect is small as a whole.

[0005]

In the muffler of the present invention, a cylindrical sound absorbing material is attached to the inner surface of the side wall of a cylindrical container, and the thickness of the sound absorbing material is varied in the radial direction in the axial direction. Let
The inner surface of the sound absorbing material is formed so as to form a tapered surface.

[0006]

In this muffler, both end faces of the container are used by connecting them in the middle of gas flow pipes. The gas that has flowed in from one side of the flow pipe has its noise eliminated or attenuated in the expanded container and flows out from the flow pipe on the other side. At that time, since the inner diameter of the sound absorbing material changes and the thickness of the sound absorbing material changes in sequence, the sound absorbing material has a noise damping effect for each frequency. Therefore, the frequency range of the attenuated noise is wide.

[0007]

EXAMPLE FIG. 1 shows a muffler according to an example. The muffler 1 is a cylindrical container made of synthetic resin (which may be made of iron plate, etc.) 2 in which a sound absorbing material 3 made of synthetic resin foam is arranged.
The sound absorbing material 3 has a tubular shape and is attached to the inner surface of the side wall of the container 2 with an adhesive. The radial thickness D of the sound absorbing material 3 gradually increases according to the axial position from the one end surface to the other end surface of the container, so that the inner surface of the sound absorbing material 3 is a tapered surface.
The silencer 1 has one end face and the other end face connected to the middle of an air intake pipe 4 of an internal combustion engine, for example.

Combustion air of the internal combustion engine flows in through the air suction pipe 4, receives a sound deadening effect in the container 2, and exits to the outflow side. In this case, since the thickness of the sound absorbing material 3 is sequentially changed, the frequency range subjected to the damping action is wide and the sound deadening characteristic is as shown by the curve C in FIG. It is suitable for noise and has a great sound deadening effect as a whole.

FIG. 2 shows another embodiment. Muffler 5 in FIG.
The container 2 is the same as that shown in FIG. 1, and is installed in the middle of the air suction pipe 4. The sound absorbing material 6 is made of glass wool unlike the one shown in FIG. The upper and lower end surfaces of the support body 7 in which the wire mesh is formed into a truncated cone shape are attached to both end surfaces of the container 2 by adhesion or welding, and the sound absorbing material 6 is filled between the inner surface of the container 2 and the outer surface of the support body 7. To be done. In this way, the thickness of the sound absorbing material 6 changes in the axial direction sequentially, and the inner surface becomes a tapered surface according to the support 7.
In this case, the sound absorbing material 6 is not limited to glass wool, but may be an appropriate web made of fiber. The muffling characteristic of the muffler 5 also shows a shape without a pointed portion, which is almost the same as the curve C in FIG. These mufflers can be widely applied to the exhaust system of an internal combustion engine, other gas flow ducts, and the like, in addition to the above examples.

[0010]

According to the present invention, by making the inner surface of the sound absorbing material a taper surface, the sound deadening effect can be made large by matching the sound deadening characteristics to the frequency of the noise widely when the frequency range of the noise is wide. it can. Therefore, no noise region that is not attenuated by one conventional silencer does not remain, and it is not necessary to attach a plurality of silencers to cope with the noise.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a sectional view of another embodiment.

FIG. 3 is a sectional view of a conventional silencer.

[Fig. 4] Silent characteristic diagram of silencer

[Explanation of symbols]

 2 containers 3, 6 sound absorbing material

Claims (1)

[Claims] 1. An expansion type silencer in which a gas flow pipe is attached to both front and rear ends of a cylindrical container and a sound absorbing material is attached to an inner surface of a side wall of the container, and the radial thickness of the sound absorbing material is sequentially varied in the axial direction. , A silencer with a tapered inner surface of the sound absorbing material.