JPH01139952A - Muffler for air conditioner - Google Patents

Abstract

PURPOSE:To reduce a noise in a low frequency range by a method wherein a sound suction structure of only two opposed surfaces, a curved port and a curved inlet part are of porous plates and a curved outlet part is of a sound shielding plate and then other opposing two surfaces are of a sound insulation material. CONSTITUTION:A muffler 1 for an air conditioner is constructed such that opposing two surface of an air passage 4 have a porous plate 5, a sound absorption material 7 and an air later 9 having more than one partition plate 8 outside them. These members may constitute a sound absorbing structure. A curved part at an inlet 2 of an aeration passage 4 is drawn into a smooth curved line form and communicated with the aeration passage. In this case, an inlet curved part is made such that a porous plate 5' is adhered to a surface of a sound absorbing material, the outlet of the aeration passage becomes a curved part which is similar to the inlet and a sound shielding plate is adhered to a surface of the sound absorption material. Other two surfaces of the opposing two surfaces constituting the sound absorbing structure are not provided with any air layer, but the sound absorbing material 7 is left as it is or the porous plate is adhered to the surface of the sound absorbing material. With this arrangement, it is possible to reduce a sound having a wide low frequency mainly around a low frequency range, resulting in that a compact device can be attained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a silencer for air conditioning.

[Conventional technology]

Silencers for air conditioning include silencers lined with sound-absorbing material on the inside, cell-type mufflers with partition plates in the muffler, elbow, and ventilation passages, and mufflers with a built-in splitter.Also, there are expansion-type mufflers with sound-absorbing material on the inside, and mufflers with a built-in splitter. There are a wide variety of silencers, including types with splitters attached to the ventilation passages, in which the length and outer diameter of the silencer itself, the thickness of the inner sound-absorbing material, etc., are changed.

[Problem that the invention seeks to solve]

The frequency band of the sound generated by an air conditioning blower and the sound generated in a duct system is wide, generally 63 to 8000 Hz, and the purpose is to muffle this noise.

However, it is particularly difficult to take measures to muffle the low frequency range of 63 to 250 Hz, and it is necessary to muffle the sound in a wide range centered on this low frequency range, and in order to save energy, the pressure loss of the muffler itself must be minimized. Less was desired. Furthermore, in duct systems, the space is small due to ceiling piping, so there has been a desire for a silencer with a small outer diameter that can be used as part of a compact duct.

However, ducts and mufflers lined with sound-absorbing materials have a low sound absorption coefficient in the low frequency range and have little sound reduction effect, and are aimed at reducing sound in the mid-range. In addition, the cell type generally reduces sound in the mid-high range, and in order to reduce sound in the low range, it is necessary to increase the width of the partition wall, which not only increases the size and weight, but also increases the pressure caused by the cell part. This increases loss and conversely causes noise generation. In addition, an expansion type muffler with a sound-absorbing material inside can reduce sound in the mid-high frequency range by increasing the area of the sound-absorbing material inside the expansion part, but the sound reduction effect in the low frequency range is mainly related to the expansion ratio. Since the larger the expansion ratio, the better, it is impossible to make it compact.

Silencers with a splitter installed inside an expansion type muffler lined with sound-absorbing material with a low expansion ratio are also relatively often used.
00-2000) TZ has a large sound reduction effect in the middle range, but shows a relatively small value in the low frequency range. In addition, since the splitters are installed at a small pitch, the cross-sectional area of the ventilation passage becomes small, the wind speed in the ventilation passage increases, which tends to increase pressure loss and self-generated noise, and the sound reduction characteristics in the low frequency range also deteriorate.

Muffler-type ducts with resonance parts on the four sides have almost no pressure loss, but cannot reduce sound in a wide frequency range, so the purpose is to reduce sound in specific frequencies.
It is possible to reduce sound in the low frequency range, which was not possible with only sound-absorbing material. However, the lower the frequency range is calculated, the larger the volume of the resonance part becomes, and the actual resonance part size is 300 ug or more, resulting in four air layers, making it impossible to fit in the ceiling space. Although a partition plate is sometimes provided in the air layer, this is generally done for structural reasons and not because of the relationship between the pitch dimension and the sound reduction effect.

[Means for solving problems]

Therefore, as a result of intensive research to provide a compact muffler that enables a wide range of sound reduction mainly in the low frequency range, has low pressure loss in ventilation conditions, and has a sound absorbing structure with only two opposing sides and a curved entrance and exit. By using a structure in which the curved part of the entrance is made of a perforated plate, the curved part of the outlet is made of a sound insulating plate, and the other two opposing surfaces are made of sound absorbing material, and a splitter is provided in the ventilation path. It is a compact design with low air resistance that enables sound reduction in a wide range of frequencies, mainly in the low frequency range, which was not possible with elbow, resonance type, expansion type silencers, or expansion type silencers with a built-in splitter. The inventors have discovered that it is possible to provide a muffler, and have arrived at the present invention.

That is, the present invention provides a silencer for air conditioning in which a sound absorbing material is lined inside the ventilation passage, and two opposing sides of the ventilation passage have a perforated plate and a sound absorbing material, and an air layer having one or more partition plates on the outside thereof. The sound absorbing structure is curved from the entrance and exit of the muffler and is narrowed to the straight part of the sound absorbing structure to communicate with the ventilation passage, and the surface of the curved part of the entrance is a perforated plate, and the surface of the curved part of the entrance is a perforated plate, A sound insulating plate is attached to each of the surfaces of the curved part, and a sound absorbing material is attached to the other two opposing surfaces. This is an air conditioning silencer installed parallel to the structure.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an embodiment of the invention set forth in claim (1), in which (a) is a plan sectional view and (b) is a front sectional view. The air conditioning silencer 1 of the present invention has a perforated plate 5 and a sound absorbing material 7 on two opposing sides (the left and right sides in FIG. 1) of the ventilation passage 4, and one or more partition plates 8 (see FIG. 1) on the outside thereof. There is an air layer 9 having two layers), which constitutes the sound absorbing structure.

The curved portion of the entrance 2 of the ventilation passage 4 is narrowed into a smooth curve and communicates with the ventilation passage. Here, a perforated plate 5' is pasted on the surface of the sound absorbing material at the curved part of the entrance, and a sound insulating board 6 is pasted on the surface of the sound absorbing material at the exit of the ventilation path, which is a curved part similar to the entrance.

The curved part of the entrance/exit may have any kind of curve, and the first
It may be a gentler curvature (R is larger) than in the case shown in the figure.

In addition, the other two opposing surfaces (upper and lower surfaces in Fig. 1) of the sound absorbing structure are not provided with an air layer, and the sound absorbing material 7 is used as it is, or only a perforated plate is attached to the surface of the sound absorbing material 7. The aim is to make it more compact.

Metal plates are used for the perforated plates, sound insulating plates, and partition plates used in the present invention, and inorganic fibers and organic fibers such as glass wool, rock wool, and asbestos can be used as the sound absorbing material, but inorganic fibers are preferable. . The sound absorbing material used preferably has a thickness of 25 to 250 fl and a density of 24 to 48 Kg/m', depending on the diameter of the ventilation passage.

Next, an embodiment of the invention according to claim 12) is shown in FIG. (,) is a plan sectional view, and (b) is a front sectional view, which is almost the same as Fig. 1, but differs in that a splitter toughness is provided in the ventilation passage 4 (Fig. 2 shows an air layer). Splitter with 1) solid). As shown in Figure 2, the splitter has a perforated plate on the outside of the sound absorbing material, which is curved at both ends and linear in the longitudinal direction, and a perforated plate is attached to the curved surface of the inlet, and a sound insulating plate is attached to the surface of the curved outlet. Furthermore, the central part may be of the type that has an air layer with a sound insulating plate in the center in the longitudinal direction and one or more partition plates orthogonal to the sound insulating plate, or may be made of round rod-shaped or flat plate-shaped sound absorbing material. A perforated plate may be attached to the surface of the plate.

The number of splitters is 1 or 2 depending on the width of the ventilation path.
It is possible to provide more than one. For example, in the silencer shown in FIG. 1, it is preferable to provide a splitter because when the width of the ventilation passage becomes 550 or more, the volume reduction decreases in all frequency ranges.

In addition, the spacing l between the partition plates (sound absorbing structure and splitter) provided in the air layer is preferably 500 to 700 mm in the low frequency range, and the spacing is more pronounced than when no partition plates are provided.
(See Figure 5).

Next, regarding the sound insulating plate at the exit curved part, the sound reduction effect in the medium and low frequency range of 63 to 500 Hz is about 20 to 30% greater than using a perforated plate.

The higher the transmission loss of this sound insulating plate, the more preferable it is.

〔Example〕

Example 1 Based on the case where the duct entrance width and height are both A in the air conditioner silencer without a splitter of the present invention shown in FIG. 1, the air conditioner with one splitter of the present invention shown in FIG. The height and inlet width of the silencer are 1.8A (the ventilation duct space is essentially the same as in Figure 1), and as a comparative example, a conventional silencer with a built-in splitter lined with sound-absorbing material (Figure 6). We also measured the relationship between frequency and volume reduction using the same entrance width and height. The results are shown in Figure 3. The silencer of the present invention of the type shown in FIG. 1 is superior to the conventional one shown in FIG.
The effect is particularly large in the low frequency range.

Example 2 FIG. 4 shows the relationship between wind speed and pressure loss for the examples shown in FIGS. 1 and 2 (invention) and FIG. 6 in Example 1. As a result, the one shown in FIG. 1 is the smallest, and the one shown in FIG. 2 is almost as good as that, but the conventional one shown in FIG. 6 is considerably inferior to that of the present invention. This allows the use of a low static pressure type of blower and helps reduce the noise generated by the blower itself.

〔Effect of the invention〕

The air conditioner silencer of the present invention makes it possible to reduce sound in a wide frequency range centered on the low frequency range, has low air resistance, and can be made compact.

[Brief explanation of the drawing]

FIG. 1 shows an air conditioning silencer of the present invention without a splitter, and FIG. 2 shows an air conditioning silencer of the invention with a splitter, in which (a) shows a plan sectional view and (b) shows a front sectional view. The third prisoner is a graph of the relationship between frequency and volume reduction in Example 1,
FIG. 4 is a graph showing the relationship between wind speed and pressure loss in Example 2, and FIG. 5 is a graph showing the relationship between frequency and volume reduction depending on the interval between partition plates. FIG. 6 shows (a) a plan sectional view and (b) a front sectional view of a conventional sound absorbing material-lined splitter internal silencer. 1... Air conditioning silencer 2... Ventilation duct population 3... Ventilation duct outlet 4... Ventilation duct 5.5C... Perforation Board 6...
・Sound insulation board 7...Sound absorbing material 8...
・Partition plate 9...Air layer 10...
... Splitter patent applicant Hishi Co., Ltd.
Engineering

Claims (4)

[Claims] (1) In an air conditioning silencer in which a sound absorbing material is lined inside the ventilation passage, two opposing sides of the ventilation passage are made of a perforated plate and a sound absorbing material, and an air layer having one or more partition plates on the outside thereof. The sound absorbing structure is curved from the entrance and exit of the muffler and narrowed to the straight part of the sound absorbing structure to communicate with the ventilation passage, and the surface of the curved part at the entrance is a perforated plate, and the curved part at the exit is a perforated plate. 1. A silencer for air conditioning, characterized in that a sound insulating plate is pasted on each surface of the part, and the other two opposing faces are made up of inner pasting of sound absorbing material. (2) The silencer for air conditioning according to claim (1), characterized in that one or more splitters are provided in the ventilation passage in parallel with the silencing structure. . (3) The silencer for air conditioning according to claim (2), wherein the splitter is a sound absorbing material in the shape of a round bar or a flat plate with a perforated plate attached to the surface thereof. (4) The splitter has a perforated plate on the outside of a sound absorbing material whose both ends are curved and whose longitudinal direction is straight, and a perforated plate is attached to the surface of the inlet curved part, and a sound insulating plate is attached to the surface of the outlet curved part,
The silencer for air conditioning according to claim (2), wherein the central portion constitutes an air layer having a sound insulating plate at the center in the longitudinal direction and one or more partition plates perpendicular to the sound insulating plate.