JPH0420968Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention consists of an inner cylinder that is open at both ends, through which fluid flows in from one end and fluid flows out from the other, and an outer cylinder that is penetrated through the inner cylinder. The present invention relates to a silencer equipped with a cylinder.

[Prior Art] For example, when fluid from a roots blower has a high sound pressure level in a specific frequency band, a combination of resonant type and expansion type mufflers is used to attenuate a plurality of different pure tone components. A sound-absorbing muffler using sound-absorbing materials or sound-absorbing materials is used.

Among these, a combination of a resonance type and an expansion type is shown in, for example, Japanese Utility Model Publication No. 62-21702. However, this type of silencer generally
It is formed by a cavity arranged in series with respect to the direction of fluid flow, and therefore requires a large amount of space in the direction of fluid flow, making it difficult to fit, for example, into the bonnet of a car or packaged equipment. There is a problem. Furthermore, there is also the problem of large pressure loss due to sudden expansion or contraction of the fluid, 180° reverse flow, etc.

Also, sound absorbing mufflers may not be used because they need to keep the fluid clean and avoid contamination with sound absorbing materials.

Further, Japanese Utility Model Publication No. 38-3478 discloses a technique in which a sound absorber is provided around the outer periphery of an air pipe and the sound absorber is divided into chambers having different volumes. however,
In this known technique, the resonant frequency band is limited because the orifice communicating with the compartment of each muffler is constant.

[Problems to be Solved] Therefore, an object of the present invention is to provide a compact muffler that can effectively attenuate a plurality of different pure tone components having high sound pressure levels in a specific frequency band.

[Means for Solving the Problems] According to the present invention, an inner cylinder having both ends opened so that fluid flows in from one side and fluid flows out from the other side;
In a silencer equipped with an outer cylinder through which the inner cylinder is penetrated, both end surfaces of the outer cylinder are closed by end plates, and the silencer is formed by the outer cylinder, the inner cylinder, and the end plate. The chamber is divided into a plurality of resonant cavities by radial partition plates parallel to the axis, and these resonant cavities are divided into two resonant cavities.
The inner cylinder and each resonant cavity communicate with each other through different numbers of holes depending on the volume of the resonant cavity.

[Description of effects] Therefore, the sound waves that flowed in together with the fluid in the inner cylinder propagate from the inner cylinder through the holes to each resonance cavity, but because the volumes of the resonance cavities are different, two or more different resonance frequencies are generated. Resonance occurs in each of the resonant cavities having a plurality of resonance cavities, and it is possible to attenuate each of a plurality of different pure tone components. Since the resonant cavity is communicated with a different number of holes depending on its volume, the resonant frequency can be set over a wide range, which is effective in muffling different pure tone components.

[Examples] Examples of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, both end surfaces of the outer cylinder 1 are closed with end plates 2, 2. An inner cylinder 6 is penetrated coaxially or eccentrically (coaxially in the case shown) with respect to the axis of the outer cylinder 1, and a large number of holes a, b, c are formed in the part of the inner cylinder 6 inside the outer cylinder 1. ,d,e,f,
It is formed in a perforated cylinder 7 with holes g and h.
A chamber 3 is formed by the inner cylinder 6, the outer cylinder 1, and the end plates 2, 2, and an inner cylinder cavity 8 is formed by the inner cylinder 6.

The chamber 3 has a plurality of (four in the illustrated example) resonance cavities 5a, 5b each having a volume of two or more types (two types in the illustrated example) by a radial partition plate 4 parallel to the axis of the outer cylinder 1. 5c and 5d.

Among these resonance cavities, 5a and 5b have the same volume, and 5c and 5d have a larger volume than 5a and 5b.

In a certain cross section shown in FIG.
b communicates with hole a and hole b, respectively.
The large resonance cavities 5c and 5d are holes c and 5d, respectively.
They communicate through holes d, e and holes f, g, and h.

During operation, a sound wave incident on the inner cylinder 6 from the direction of the arrow propagates from the inner cylinder cavity 8 through the small holes of the porous cylinder 7 to the resonance cavity 5 as shown by the arrow. At this time, resonance occurs in each resonance cavity 5, and the sound is reduced. Since the resonant cavity 5 has two volumes, it has two resonant frequencies as shown in FIG. Provides a sound reduction effect.

By selecting the number of holes, resonance suitable for a wide range of pure tone components can be obtained.
It becomes possible to design for frequencies with high sound pressure levels.

[Effects of the invention] According to the invention, the following excellent effects can be achieved by configuring as described above.

(1) Pure tone components of multiple specific frequencies can be effectively reduced.

(2) By changing the angular position of the partition plate, the volume of the resonant cavity can be changed and a design compatible with pure tone components can be achieved.

(3) By changing the number of communicating holes depending on the volume of the resonant cavity, a wide range of resonant frequencies can be selected.

(4) Therefore, for example, when a Roots blower discharges a fluid having a high sound pressure level at a specific frequency, the noise can be effectively reduced.

[Brief explanation of the drawing]

Figure 1 is a side view showing one embodiment of the present invention;
The figure is an orthogonal sectional view of FIG. 1, and FIG. 3 is a comparison diagram of sound reduction characteristics showing the effects of the present invention. 1... Outer tube, 3... Chamber, 4... Partition plate, 5a
~5d... Resonance cavity, 6... Inner tube, 7... Porous tube, 8... Inner tube cavity, a to h... Hole.

Claims (1)

[Scope of utility model registration request] In a silencer that includes an inner cylinder that is open at both ends and allows fluid to flow in from one side and flow out from the other side, and an outer cylinder through which the inner cylinder is penetrated, both end surfaces of the outer cylinder are formed by end plates. The chamber formed by the outer cylinder, the inner cylinder, and the end plate is defined into a plurality of resonant cavities by radial partition plates parallel to the axis, and the resonant cavities are divided into two. 1. A silencer characterized in that the inner cylinder and each resonance cavity communicate with each other through different numbers of holes depending on the volume of the resonance cavity.