JPH0413370Y2 - - Google Patents

Description

[Detailed Description of the Invention] An object of the present invention is to easily construct a muffler that has good muffling performance over a wide band from low frequencies to high frequencies.

Silencers filled with sound-absorbing material are not very effective against low- and mid-range noise. Therefore, in order to cope with low-frequency noise, a method was developed in which a perforated sound-absorbing tube was covered with a sound-absorbing material and held by an outer tube, and a perforated sound-absorbing tube with small holes in the holding outer tube was placed inside the expansion chamber to deal with low-frequency noise. -Disclosed in Publication No. 17375. However, this configuration is still not sufficient for mid-range noise.

In view of the above points, the present invention aims to provide the perforated sound absorbing tube with a mid-range noise attenuation function.

It is known from Japanese Utility Model Publication No. 57-30401 that an insertion tube type (extended resonance type) muffler is effective for muffling mid-range sounds. The present invention is based on the above-mentioned perforated sound absorbing cylinder.
It is characterized by incorporating an insertion tube type muffler.

The embodiments shown in the drawings will be described below. Figure 1 shows a sound absorbing material-filled muffler consisting of a perforated pipe 1, a sound absorbing material 2 such as glass wool or rock wool wrapped around the perforated pipe, and a sound absorbing material holding tube 3 on the outer surface of the sound absorbing material.
A part of the outer tube 3 is provided with an opening 5 such as a small hole. The inflow-side outer tube section 3a or the outflow-side outer tube section 3b, which is not provided with the opening 5, is used as an insertion tube into the cavity 4, and performs a noise reduction effect by expansion resonance between it and the cavity wall surface.

The lengths La and Lb of the non-porous outer tube portions 3a and 3b are:
The length L of the cavity 4 is set, for example, 1/2L, 1/4L, etc. depending on the engine to which it is applied. FIG. 1 shows an example in which the outflow side outer tube part 3b is 1/2L, and FIG. 2 shows an example in which the inflow side outer tube part 3a is 1/2L. The holes in the aperture 5 of the outer tube 3 are made of a large number of small holes, and may be made of a net if necessary.

With the above configuration, the exhaust gas flowing into the ventilation pipe 1 produces noise in the low frequency range due to the contraction effect by the small hole in the ventilation pipe and the small hole 5 in the outer pipe 3, and the expansion interference effect in the cavity 4. During this period, noise in the high frequency range is absorbed by the sound absorbing material 2.

Further, from the small hole of the ventilation pipe 1, the non-porous outer pipe parts 3a, 3
b. Exhaust gas that passes through the sound absorbing material 2 and flows out from the hole 5 at the tip of the outer tube expands within the cavity, and due to the interference of the reflected waves from the tip and the wall of the cavity, the exhaust gas flows through the insertion tube. Acts as a type muffler to reduce the above-mentioned low and
It attenuates noise in the intermediate range between high frequency ranges.

It should be noted that the present invention is not limited to the single resonator type shown in FIG. 1, but can also be combined with other silencing elements. That is, FIG. 2 shows a cavity 4, an expansion chamber 6, an insertion tube type silencing chamber 8, and both chambers 4-- having ventilation holes around them.
This is an example in which the present invention is applied to a cavity 4 of a silencer consisting of a connecting pipe 9 between 7 and 7.

As mentioned above, the present invention covers a porous ventilation pipe with a sound absorbing material and holds it with an outer pipe, and a part of the holding outer pipe with an opening is placed inside the cavity to produce high and low frequency sound. The sound absorbing material retaining outer tube of the silencer is provided with a non-perforated outer tube section, and an insertion tube type silencer is constructed between the cavity and the sound absorbing material holding outer tube. This has the effect of providing good silencing performance over the band.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a muffler according to the present invention, and FIG. 2 is a vertical cross-sectional view of an embodiment in which the muffler according to the present invention is combined with another muffler. 1 is a porous ventilation pipe, 2 is a sound-absorbing material, 3 is an outer pipe holding sound-absorbing material, 3a and 3b are pipe parts without holes of the outer pipe 3, 4 is a cavity, 4a and 4b are the end plates thereof, and 5 is the outer pipe 3 aperture.

Claims (1)

[Scope of utility model registration request] The ventilation pipe 1 that penetrates the cavity 4 is a perforated pipe, and the perforated pipe is covered with a sound absorbing material 2 and held by an outer pipe 3, and non-porous outer pipe parts 3a on the exhaust gas inflow side and outflow side of the outer pipe 3, A silencer in which an opening 5 communicating with the cavity 4 is provided in the outer tube 3 except for the hole 3b, and the non-porous outer tube section is used as an insertion tube into the cavity 4 to form an extended resonance type silencer.