Silencer

Abstract

To provide a muffling device which has a large transmission loss, facilitates molding and adjustment in correspondence with a frequency, and has a wide range of frequencies in which muffling effect can be obtained.SOLUTION: A muffling device 1 inserted into a main pipe 2 through which fluid flows includes an inner pipe 3, and side branch chambers 7a-7d, 7e-7h formed between the main pipe 2 and the inner pipe 3. In the muffling device 1, inlet / outlet ports 8a-8d, 8e-8h communicating with the side branch chambers 7a-7d, 7e-7h are provided on an inner surface of the inner pipe 3. The side branch chamber is surrounded by the main pipe 2, the inner pipe 3, upstream / downstream partitioning plates 4, 5 formed on an outer surface of the inner pipe 3, and a rib plate 6 formed on the outer surface of the inner pipe 3 and extending in an axial direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a silencer that is inserted into a refrigerant pipe, an exhaust pipe, or the like of an air conditioner for a vehicle. [Background technology]

[0002] In a vehicle air conditioner, mechanical noise of the compressor and noise caused by cavitation of the refrigerant are transmitted to the evaporator through the piping, and then transmitted to the driver from the air outlet, or transmitted to the driver through the space in the engine room midway through the piping and via the vehicle body. For this reason, a muffler-type silencer or an insert-type silencer is interposed in the piping of the vehicle air conditioner. Muffler-type silencers are large and heavy, and brazing increases costs, so insert-type silencers have been widely adopted in recent years.

[0003] For example, Patent Document 1 describes a tube with spiral fins on the outer surface of the inner tube. This creates a phase difference due to the difference in the inner and outer flow paths, which causes sound interference and has a sound-deadening effect, but it is difficult to mold the tube and adjust the length of the flow paths.

[0004] Patent Document 2 describes a silencer that is inserted into a tubular body, in which a resonator chamber is provided between the silencer and the body, and the flow path of the body is connected to the resonator chamber via a connecting channel. Patent Document 3 describes a sound absorbing device in which the outer member surrounding the inner member is a bellows, a cavity is formed between the inner member and the outer member, and an opening of the inner member is open to the cavity. Both of these are of the resonance type, and the resonance frequency is determined by the shape of the resonator, so the frequency range in which the sound absorbing effect is achieved is narrow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Publication EP2138750A1 [Patent Document 2] Patent No. 5785173 specification [Patent Document 3] JP 2005-84693 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and has an object to provide a noise suppression device that has a large transmission loss, is easy to mold and adjust according to frequency, and produces a noise suppression effect over a wide frequency range. [Means for solving the problem]

[0007] As a means for solving the above problems, the present invention provides (1) A silencer to be inserted into a main pipe through which a fluid flows, the silencer comprising an inner pipe and a side branch chamber formed between the main pipe and the inner pipe, The inner surface of the inner tube has a port that communicates with the side branch chamber.

[0008] (2) The side branch chamber is The main pipe; The inner tube; an upstream side partition plate and a downstream side partition plate formed on an outer surface of the inner pipe; a rib plate formed on an outer surface of the inner tube and extending in an axial direction; It is preferable that the .lambda.

[0009] (3) It is preferable that the inner surface of the upstream end of the inner pipe is formed into a tapered surface whose diameter decreases toward the downstream side. (4) Preferably, the inner surface of the downstream end of the inner pipe is formed as a tapered surface whose diameter increases toward the downstream side.

[0010] (5) A resonance chamber is provided between the main pipe and the inner pipe, The inner surface of the inner tube is preferably provided with an opening communicating with the resonating chamber.

[0011] (6) It is preferable that the inner pipe is provided with an outer cylinder that seals the side branch chamber.

[0012] (7) It is preferable that the silencer is configured with a plurality of modules divided in the circumferential direction. (8) The silencer may be configured with a plurality of modules divided in the axial direction. (9) Alternatively, the silencer may be configured with a plurality of modules divided in the circumferential and axial directions. Effect of the Invention

[0013] According to the invention of claim 1, sound waves that enter the side branch from an inlet provided on the inner surface of the inner pipe and are reflected back are in opposite phase to the sound waves in the inner pipe, causing interference and silencing. Also, an inlet communicating with the side branch chamber is provided on the inner surface of the inner pipe, and the side branch chamber branches off from the inner pipe, which has a smaller cross-sectional area than the main pipe. Therefore, compared to when the side branch chamber branches off from the main pipe, the cross-sectional area ratio before and after the branch can be made larger, which increases the transmission loss and improves the silencing effect.

[0014] The side branch chamber of the silencer of the present invention is open to the outside air before being inserted into the main pipe, and therefore is easy to mold.

[0015] Moreover, by changing the length of the side branch chamber along the axial direction of the inner tube, the frequency at which the noise reduction effect is produced can be adjusted.

[0016] Furthermore, by forming a plurality of side branch chambers of different lengths between the main pipe and the inner pipe, the frequency range in which the noise reduction effect is achieved can be widened.

[0017] According to the invention of claim 2, the side branch chamber is surrounded by the inner surface of the main pipe, the partition plate, and the rib plate, so that the length from the entrance / exit to the inner end of the side branch chamber and the cross-sectional area are simplified, and a noise reduction effect can be obtained at a frequency close to the target frequency.

[0018] According to the inventions of claims 3 and 4, the upstream or downstream end of the inner tube is formed with a tapered surface, thereby reducing the pressure loss (hereinafter referred to as pressure loss) when a fluid flows into and out of the inner tube.

[0019] According to the invention of claim 5, the energy of the sound waves that enter the resonating chamber from the opening provided on the inner surface of the inner tube is absorbed and silenced in the resonating chamber. Therefore, a noise silencing effect is obtained that combines the noise silencing effect in a wide frequency range by the side branch chamber and the noise silencing effect in a specific frequency range by the resonating chamber. In particular, by compensating for the frequency range where it is difficult to obtain the noise silencing effect by the side branch chamber with the noise silencing effect by the resonating chamber, it is possible to obtain the noise silencing effect in a wider frequency range.

[0020] According to the invention of claim 6, since the outer cylinder seals the side branch chamber, leakage from the side branch chamber caused by bending or vibration of the main pipe is prevented, and the silencing effect can be maintained.

[0021] According to the seventh to ninth aspects of the present invention, the modules can be combined in accordance with the frequency of the sound source to provide an optimal noise reduction effect. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view of a noise suppressor according to a first embodiment of the present invention, with a portion of a main pipe cut away; [Diagram 2] FIG. 2 is a perspective view of a silencer inserted into the main pipe of FIG. 1 . [Diagram 3] 3A and 3B are a front view and a left side view of the silencer of FIG. 2. [Figure 4] Cross-sectional view (a) along line IVa-IVa and cross-sectional view (b) along line IVb-IVb in FIG. [Diagram 5] Cross-sectional view of line VV in Figure 3(b). [Figure 6] FIG. 1 is a perspective view of a conventional side branch type silencer. [Figure 7] FIG. 3 is a cross-sectional view showing a first modified example of the noise suppressor of FIG. 2. [Figure 8] FIG. 3 is a cross-sectional view showing a second modified example of the noise suppressor of FIG. 2. [Figure 9] 2. FIG. 4 is a cross-sectional view showing a third modified example of the noise suppressor of FIG. [Figure 10] 2. FIG. 4 is a cross-sectional view showing a fourth modified example of the noise suppressor of FIG. [Figure 11] 2. FIG. 9 is a cross-sectional view showing a fifth modified example of the noise suppressor of FIG. [Figure 12] FIG. 4 is a cross-sectional view showing an example of the invention and a comparative example used in an analysis of the sound deadening effect. [Figure 13] Graph showing analysis results of transmission loss for the comparative example (base), invention example (A), invention example (B), and invention example (Z). [Figure 14] 14 is a graph showing the analysis results of the transmission loss of the comparative example (base), invention example (A), invention example (B), and invention example (Z) in Figure 13, expressed as average values ​​in the low frequency range, high frequency range, and all frequency range. [Figure 15] FIG. 5 is a perspective view of a noise suppressor according to a second embodiment of the present invention. [Figure 16] FIG. 5 is a perspective view of a noise suppressor according to a third embodiment of the present invention. [Figure 17] FIG. 17 is a cross-sectional view of the silencer of FIG. 16. [Figure 18] FIG. 17 is a cross-sectional view showing a modified example of the noise suppressor of FIG. [Figure 19] FIG. 11 is a perspective view of a noise suppressor according to a fourth embodiment of the present invention. [Figure 20] FIG. 4 is a cross-sectional view showing an example of the invention and a comparative example used in an analysis of the sound deadening effect. [Figure 21] 1 is a graph showing analysis results of transmission loss for a comparative example (base), an example of the invention (refine 1), and an example of the invention (refine 2). [Figure 22] 22 is a graph superimposing the analysis results of the transmission loss of the comparative example (base), the invention example (refine 1), and the invention example (refine 2) in FIG. 21 . [Diagram 23] 22 is a graph showing the analysis results of the transmission loss of the comparative example (base), invention example (refine 1), and invention example (refine 2) in FIG. 21, as average values ​​in the low frequency range, high frequency range, and entire frequency range. [Figure 24] FIG. 13 is a perspective view of a noise suppressor according to a fifth embodiment of the present invention, with a portion of a main pipe cut away. [Diagram 25] FIG. 13 is a perspective view showing an assembled state and a divided state of a circumferentially divided type noise suppressor according to a sixth embodiment. [Figure 26] 13 is a perspective view showing an axially split type noise suppressor according to a seventh embodiment in an assembled state and in a split state. FIG. [Figure 27] FIG. 13 is a perspective view showing a state in which one module of a noise suppressor according to an eighth embodiment of a mixed type divided in the circumferential and axial directions is separated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0024] First Embodiment FIG. 1 shows a silencer 1 according to a first embodiment of the present invention. The silencer 1 is provided in a pipe through which a refrigerant of an air conditioner for a vehicle flows. Specifically, the silencer is inserted into a pipe (hereinafter referred to as a "main pipe") 2 on the outlet side of an evaporator or a compressor in an air conditioner for a vehicle, the air conditioner being composed of a compressor, a condenser, an expansion valve, and an evaporator (not shown). The main pipe 2 is formed of a material having elasticity and flexibility, such as rubber or synthetic resin, but is not limited thereto, and a material having no flexibility, such as aluminum, may also be used. In the main pipe 2, a fluid (hereinafter referred to as a "refrigerant") flows from the upstream on the left side to the downstream on the right side in FIG. 1.

[0025] As shown in Figures 2 and 3, the silencer 1 comprises an inner pipe 3, end partition plates 4 formed at the upstream end and downstream end of the inner pipe 3, a plurality of intermediate partition plates 5 formed on the outer surface of the inner pipe 3 near the upstream end in the axial middle portion, and a plurality of rib plates 6 formed at predetermined intervals around the circumferential direction of the inner pipe 3, and is integrally formed from a synthetic resin.

[0026] The silencer 1 is fixed inside the main pipe 2 by fastening either the upstream or downstream end partition plate 4 from the outside of the main pipe 2 with a fixing member (not shown). To ensure fixation by the fixing member, the thickness of the end partition plate 4 may be increased so as to increase the contact area with the fixing member.

[0027] The inner pipe 3 has an outer diameter smaller than the inner diameter of the main pipe 2. The end partition plate 4 is annular with an outer diameter almost the same as the inner diameter of the main pipe 2. The intermediate partition plate 5 is sector-shaped with an outer diameter almost the same as the inner diameter of the main pipe 2, and the four intermediate partition plates 5 are formed at the same axial position, forming an overall annular shape. Four rib plates 6 are provided in the circumferential direction, protruding radially at four equally spaced positions around the outer circumferential surface of the inner pipe 3 and extending in the axial direction. The number of rib plates 6 is arbitrary, and may be one or more. In addition, the rib plates 6 do not have to be equally spaced in the circumferential direction. The outer circumferential surface of the end partition plate 4, the outer circumferential surface of the intermediate partition plate 5, and the outer end surface of the rib plate 6 are in close contact with the inner surface of the main pipe 2 when the silencer 1 is inserted into the main pipe 2, so that the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h described later are sealed by the main pipe 2. As a substitute for the fixing member, when inserting the silencer 1 into the main pipe 2, a press-fit or a sealing material may be used.

[0028] As shown in Fig. 4(a), four side branch chambers 7a, 7b, 7c, and 7d are formed between the main pipe 2 and the inner pipe 3 and on the upstream side of the intermediate partition plate 5. Also, as shown in Fig. 4(b), four side branch chambers 7e, 7f, 7g, and 7h are formed between the main pipe 2 and the inner pipe 3 and on the downstream side of the intermediate partition plate 5. On the inner surface of the inner pipe 3, four inlets 8a, 8b, 8c, and 8d communicating with the side branch chambers 7a, 7b, 7c, and 7d, and four inlets 8e, 8f, 8g, and 8h communicating with the side branch chambers 7e, 7f, 7g, and 7h are formed.

[0029] 3 and 4(a), the side branch chambers 7a, 7b, 7c, and 7d are formed in spaces surrounded by the inner surface of the main pipe 2, the outer surface of the inner pipe 3, the upstream end partition plate 4, the intermediate partition plate 5, and a pair of rib plates 6. The inlets and outlets 8a, 8b, 8c, and 8d communicating with the side branch chambers 7a, 7b, 7c, and 7d are formed in positions upstream of and adjacent to the intermediate partition plate 5 so as to penetrate the wall of the inner pipe 3.

[0030] 3 and 4(b), the side branch chambers 7e, 7f, 7g, and 7h are formed by spaces surrounded by the inner surface of the main pipe 2, the outer surface of the inner pipe 3, the downstream end partition plate 4, the intermediate partition plate 5, and a pair of rib plates 6. The inlets and outlets 8e, 8f, 8g, and 8h communicating with the side branch chambers 7e, 7f, 7g, and 7h are formed downstream of and adjacent to the intermediate partition plate 5 so as to penetrate the wall of the inner pipe 3.

[0031] Next, the operation of the noise suppressor 1 of this embodiment will be described.

[0032] As shown in Fig. 5, the refrigerant flowing in the main pipe 2 flows into the inner pipe 3 at the upstream end of the silencer 1 and flows out of the inner pipe 3 at the downstream end. Sound (mechanical noise of the compressor and noise due to cavitation of the refrigerant) generated from a sound source (not shown) on the upstream side of the silencer 1 propagates downstream together with the refrigerant and enters the inner pipe 3 of the silencer 1. Note that the sound source may be on the downstream side, in which case the silencing effect will be generated on the upstream side.

[0033] The sound waves propagating inside the inner tube 3 enter the four side branch chambers 7a, 7b, 7c, 7d through entrances 8a, 8b, 8c, 8d provided on the inner surface of the inner tube 3, and also enter the four side branch chambers 7e, 7f, 7g, 7h through entrances 8e, 8f, 8g, 8h. They are reflected at the inner ends of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h before returning to the entrances 8a, 8b, 8c, 8d and 8e, 8f, 8g, 8h, where they become in opposite phase with the sound waves in the inner tube 3 and interfere with each other, resulting in silencing.

[0034] Here, if the cross-sectional area of ​​the inner pipe is S, the cross-sectional area of ​​the side branch chamber is Ss, the length of the side branch chamber is l, the frequency of the sound wave is f, and the sound speed is c, then the transmission loss TL in the silencer 1 is expressed by the following equation 1. The length l of the side branch chamber is the axial distance from the intermediate partition plate 5 to the end partition plate 4, as shown in Fig. 5.

number

[0035] In the silencer 1 of this embodiment, inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g, 8h communicating with the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are provided on the inner surface of the inner pipe 3, and the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h branch off from the inner pipe 3 having a smaller cross-sectional area than the main pipe 2.

[0036] Fig. 6 shows a silencer 10 of a conventional structure for comparison with the present invention. The conventional silencer 10 in Fig. 6 has an intermediate partition plate 5 provided in the middle of the inner pipe 3, tubular side branch chambers 17a, 17b formed between the main pipe 2 and the inner pipe 3, and inlets 18a, 18b of each side branch chamber 17a, 17b provided at the upstream end and downstream end of the inner pipe 3. The transmission loss TL of the silencer 10 can be found by applying Equation 1, with the cross-sectional area of ​​the main pipe 2 being S instead of the cross-sectional area of ​​the inner pipe 3.

[0037] " In the noise suppressor 1 of this embodiment shown in Fig. 5, the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h branch off from the inner pipe 3. Therefore, compared to the conventional noise suppressor 10 shown in Fig. 6 in which the side branch chambers 17a, 17b branch off from the main pipe 2, the cross-sectional area ratio Ss / S before and after the branching can be made larger, the transmission loss TL can be increased, and the noise suppression effect can be improved.

[0038] The first to fourth side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h of the noise suppressor 1 of this embodiment are open to the outside air before being inserted into the main pipe 2, and therefore are easy to mold.

[0039] Furthermore, by changing the length of each of the side branch chambers 7a, 7b, 7c, 7d, 7e, 7f, 7g, and 7h along the axial direction of the inner tube 3, it is possible to adjust the length according to the frequency of the sound source.

[0040] Furthermore, by forming a plurality of side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h of different lengths between the main pipe 2 and the inner pipe 3, the frequency range in which the sound deadening effect is produced can be widened.

[0041] In the silencer 1 of the first embodiment, the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g, 8h of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are provided adjacent to the upstream and downstream sides of the intermediate partition plate 5, but as shown in FIG. 7, the inlets 8a, 8b, 8c, 8d of the side branch chambers 7a, 7b, 7c, 7d may be provided adjacent to the upstream end partition plate 4, or as shown in FIG. 8, the inlets 8e, 8f, 8g, 8h of the side branch chambers 7e, 7f, 7g, 7h may be provided adjacent to the downstream end partition plate 4. 9, the inlets 8a, 8b, 8c, and 8d of 7a, 7b, 7c, and 7d may be provided adjacent to the upstream end partition plate 4, and the inlets 8e, 8f, 8g, and 8h of 7e, 7f, 7g, and 7h may be provided adjacent to the downstream end partition plate 4. The size of the inlets may be the same for all side branch chambers or may be different for each side branch chamber.

[0042] In the silencer 1 of the first embodiment, as shown in Fig. 10, the inner surface of the upstream end of the inner pipe 3 may be formed with a tapered surface 9a whose diameter decreases toward the downstream side. Similarly, the inner surface of the downstream end of the inner pipe 3 may be formed with a tapered surface 9b whose diameter increases toward the downstream side. This makes it possible to reduce the pressure loss of the refrigerant flowing from the main pipe 2 through the inner pipe 3 to the main pipe 2.

[0043] In the silencer 1 of the first embodiment, the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are provided on the upstream and downstream sides of the intermediate partition plate 5, but as shown in Fig. 11, two intermediate partition plates, a first and a second, 5a, 5b may be provided on the outer surface of the inner pipe 3, and the side branch chambers 7a, 7b, 7c, 7d may be provided between the first intermediate partition plate 5a and the second intermediate partition plate 5b. In this case, the upstream side of the first intermediate partition plate 5a and the downstream side of the second intermediate partition plate 5b form conventional side branch chambers 17a, 17b.

[0044] In order to confirm the noise reduction effect of the noise reduction device 1 of the first embodiment, the present inventors performed an acoustic analysis by computer simulation for four analysis models shown in FIG.

[0045] In Fig. 12, the comparative example (base) is the silencer 10 of the conventional structure shown in Fig. 6, in which the side branch chambers 17a, 17b branch off from the main pipe. In contrast, the invention examples (A), (B) and (Z) are the same as the silencer 1 of the first embodiment shown in Fig. 2, and among them, the invention example (A) has the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g and 8h of 4mm (close to the thickness of the inner pipe), the invention example (B) has the inlets 8a, 8b, 8c, 8d and 8e, 8f, 8g and 8h of 10mm (close to the cross-sectional area of ​​the side branch chamber), and the invention example (Z) has tapered surfaces 9a and 9b with a gradient of 20° at the upstream end and downstream end of the invention example (A). Each analytical model has an outer diameter of 20mm and a total length of 100mm. For each analysis model, the transmission loss was obtained by changing the inner diameter of the inner tube 3 and the frequency of the sound source.

[0046] Fig. 13 shows the transmission loss when the frequency is changed from 0 to 8000 Hz in each analysis model in which the inner diameter p of the inner tube 3 is 8 mm. From Fig. 13, it was confirmed that the analysis models (A), (B), and (Z) of the invention examples have a larger transmission loss and a larger sound deadening effect than the comparative example (base) in the frequency range of 3500 to 7000 Hz. In particular, it was confirmed that the analysis model (B) has a larger transmission loss and a larger sound deadening effect than the other analysis models at 4000 Hz or more.

[0047] Fig. 14 shows the average transmission loss at low frequencies from 0 to 4000 Hz, the average transmission loss at high frequencies from 4000 to 8000 Hz, and the average transmission loss over all frequencies for each analysis model in which the inner diameter p of the inner tube 3 is 6 mm, 8 mm, and 10 mm. Fig. 14 confirms that, in the analysis models in which the inner diameter of the inner tube 3 is the same (p=8), the transmission loss is larger and the sound deadening effect is greater in all of the invention examples (A), (B), and (Z) compared to the comparative example (base). It was also confirmed that the smaller the inner diameter p of the inner tube 3, the larger the transmission loss and the greater the sound deadening effect.

[0048] In addition, for each analysis model, the fluid pressure loss was 11.0 kPa in the comparative example (base), while it was 11.4 kPa in the invention example (A), 11.8 kPa in (B), and 6.9 kPa in (Z). It was confirmed that the invention example (Z), which had tapered surfaces 9a and 9b to reduce pressure loss, had a high pressure loss reduction effect.

[0049] <Second embodiment> FIG. 15 shows a noise suppressor 20 according to a second embodiment of the present invention.

[0050] In the silencer 20 of the second embodiment, two rib plates 6 are protruded at circumferentially equally spaced positions on the outer circumferential surface of the inner tube 3, thereby forming two side branch chambers 7a, 7b on the upstream side of the intermediate partition plate 5 and two side branch chambers 7c, 7d on the downstream side of the intermediate partition plate 5. In addition, the thickness of the intermediate partition plate 5 separating the side branch chambers 7a and 7c is made thicker than the thickness of the intermediate partition plate 5 separating the side branch chambers 7b and 7d, so that the lengths of the four side branch chambers 7a, 7b, 7c, and 7d are different. In this way, the lengths of the four side branch chambers 7a, 7b, 7c, and 7d can be adjusted according to the frequency of the sound source, thereby widening the frequency range in which the noise reduction effect is produced.

[0051] <Third embodiment> 16 and 17 show a noise suppressor 30 according to a third embodiment of the present invention.

[0052] In the silencer 30 of the third embodiment, two intermediate partition plates 5a, 5b are provided on the outer surface of the inner pipe 3, four side branch chambers 7a, 7b, 7c, 7d are formed between the upstream end partition plate 4 and the first intermediate partition plate 5a, four side branch chambers 7e, 7f, 7g, 7h are formed between the downstream end partition plate 4 and the second intermediate partition plate 5b, and four resonance chambers 31a, 31b, 31c, 31d are formed between the first intermediate partition plate 5a and the second intermediate partition plate 5b. The configurations of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h are the same as those of the first embodiment except for the length dimension, so the same reference numerals are used and the description is omitted.

[0053] Resonance chambers 31a, 31b, 31c, and 31d are formed by spaces surrounded by the inner surface of main pipe 2, the outer surface of inner pipe 3, first intermediate partition plate 5a, second intermediate partition plate 5b, and a pair of rib plates 6. Openings 32a, 32b, 32c, and 32d communicating with resonance chambers 31a, 31b, 31c, and 31d are formed to penetrate the wall of inner pipe 3 between first intermediate partition plate 5a and second intermediate partition plate 5b.

[0054] In the noise suppressor 30 of the third embodiment, in addition to the noise suppression effects of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, 7h, the noise suppression effects of the resonance chambers 31a, 31b, 31c, 31d are achieved. That is, the energy of the sound wave that has entered the inner tube 3 is absorbed and suppressed by the resonance chambers 31a, 31b, 31c, 31d.

[0055] Here, if the volume of resonance chambers 31a, 31b, 31c, and 31d is V, the cross-sectional area of ​​openings 32a, 32b, 32c, and 32d is Sr, the length of openings 32a, 32b, 32c, and 32d is l, and the sound speed is c, then the resonance frequency ωr is expressed by equation 2.

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[0056] Therefore, by matching the resonant frequencies of the resonating chambers 31a, 31b, 31c, and 31d with the frequency of the incident sound, a sound silencing effect can be achieved for a specific frequency range, and combined with the sound silencing effect of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7g, and 7h, the frequency range in which the sound silencing effect is achieved can be widened.

[0057] In the third embodiment of the sound deadening device, resonance chambers 31a, 31b, 31c, and 31d are provided between the first intermediate partition plate 5a and the second intermediate partition plate 5b, side branch chambers 7a, 7b, 7c, and 7d are provided between the end partition plate 4 and the first intermediate partition plate 5a, and side branch chambers 7e, 7f, 7g, and 7h are provided between the second intermediate partition plate 5b and the end partition plate 4. However, as shown in Figure 18, side branch chambers 7a, 7b, 7c, and 7d may be provided between the first intermediate partition plate 5a and the second intermediate partition plate 5b, resonance chambers 31a, 31b, 31c, and 31d may be provided between the end partition plate 4 and the first intermediate partition plate 5a, and resonance chambers 31e, 31f, 31g, and 31h may be provided between the second intermediate partition plate 5b and the end partition plate 4.

[0058] <Fourth embodiment> FIG. 19 shows a noise suppressor 40 according to a fourth embodiment of the present invention.

[0059] In the third embodiment of the silencer 30 in Figure 16, the four fan-shaped intermediate partition plates 5 are positioned at the same axial position to form a circular first intermediate partition plate 5a and a second intermediate partition plate 5b, but in the fourth embodiment of the silencer 40 in Figure 19, the fan-shaped intermediate partition plates 5 are formed to be offset in the axial direction, so that the resonance chambers 31a, 31b, 31c, and 31d are all different in size and position, and the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, and 7h are also different in length.

[0060] Specifically, resonance chamber 31a is formed in the axial center of inner tube 3. Resonance chamber 31b is formed in the axial center of inner tube 3 and is larger than resonance chamber 31a. Resonance chamber 31c is formed closer to end partition plate 4 on the downstream side of inner tube 3 and is smaller than resonance chamber 31a. There is no intermediate partition plate on the downstream side of resonance chamber 31c, and the downstream end partition plate 4 is also used as this. Therefore, there is no side branch chamber 7g adjacent to the downstream side of resonance chamber 31c. As a result, seven side branch chambers 7a, 7b, 7c, 7d, 7e, 7f, 7h are formed. Resonance chamber 31d is formed in the axial center of inner tube 3 and is smaller than resonance chamber 31a.

[0061] By matching the resonant frequencies of the resonating chambers 31a, 31b, 31c, and 31d with the frequency of the incident sound, a sound silencing effect can be achieved for a specific frequency range. Combined with the sound silencing effect of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, and 7h, the frequency range in which the sound silencing effect is achieved can be widened.

[0062] In order to confirm the silencing effects of the silencer 20 of the second embodiment and the silencer 40 of the fourth embodiment, the inventors performed acoustic analysis by computer simulation for three analysis models shown in FIG.

[0063] In this acoustic analysis, the medium has a temperature of 25°C, a pressure of 0.101325MPa (standard atmospheric pressure), and a density of 1.184kg / m 3 The air had a sound speed of 346.25 m / s. The target frequency range for obtaining the noise reduction effect was 0 to 4000 Hz. If the length of the side branch is l and the sound speed is c, the theoretical value of the target frequency f was calculated using Equation 3.

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[0064] 20, the comparative example (base) is the noise absorbing device 10 having the conventional structure shown in FIG. 6, in which side branch chambers 17a, 17b branch off from the main pipe 2. The lengths of the side branch chambers 17a, 17b are 22 mm and 72 mm, respectively, and the theoretical values ​​of the target frequencies for obtaining the noise absorbing effect are 3935 Hz and 1202 Hz, which are odd-number multiples of these frequencies.

[0065] The invention example (refine 1) is the same as the noise absorbing device 20 of the second embodiment shown in Fig. 15, and has a structure in which four side branch chambers 7a, 7b, 7c, and 7d branch off from the inner pipe 3. The lengths of the side branch chambers 7a, 7b, 7c, and 7d are 26 mm, 32 mm, 48 mm, and 62 mm, respectively, and the theoretical values ​​of the target frequencies for obtaining the noise absorbing effect are 3329 Hz, 2705 Hz, 1803 Hz, and 1396 Hz, which are odd-number multiples of these frequencies.

[0066] The invention example (refine 2) is the same as the noise suppressor 40 of the fourth embodiment shown in Fig. 19, and has a structure in which seven side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7h branch out from the inner tube 3, and four resonance chambers 31a, 31b, 31c, 31d are provided. The lengths of the side branch chambers 7a, 7b, 7c, 7d and 7e, 7f, 7h are, in order from largest to smallest, 87mm x 1, 43mm x 2, 29mm x 2, 22mm x 2, and the theoretical values ​​of the frequencies at which the noise suppression effect is obtained are 995Hz, 2013Hz, 2985Hz, 3935Hz, and odd multiples of these frequencies. The resonance volumes of the resonance chambers 31a, 31b, 31c, 31d are, in order from largest to smallest, 2027.7mm.3 , 1436.3mm 3 , 295.7mm 3 , 253.5mm 3 , and the theoretical values ​​of the frequencies aimed at achieving the noise reduction effect are 1159Hz, 1378Hz, 3036Hz, and 3279Hz.

[0067] Each analytical model had an outer diameter of 20 mm, a total length of 100 mm, and an inlet / outlet width of 4 mm. For each analytical model, the transmission loss was calculated by changing the frequency of the sound source.

[0068] 21(a), (b), and (c) show the change in transmission loss when the frequency is changed from 0 to 10,000 Hz in the comparative example (base), the invention example (refine 1), and the invention example (refine 2). In all of the comparative example (base), the invention example (refine 1), and the invention example (refine 2), the transmission loss is large at frequencies close to the target frequency, and it was confirmed that a sound deadening effect was obtained.

[0069] The example of the invention (refine 1) has more side branches than the comparative example (base), and each side branch is a different length, so that the noise reduction effect is obtained for many frequencies. Also, the example of the invention (refine 1) has a larger transmission loss across the entire frequency range than the comparative example (base), in which each side branch branches off from the main pipe, and has a higher overall noise reduction effect.

[0070] In the example of the invention (refine 2), in addition to the sound-absorbing effect of the seven side branch chambers, the sound-absorbing effect of the four resonant chambers is also apparent, and at some specific frequencies, the transmission loss is larger and the sound-absorbing effect is higher than in the example of the invention (refine 1).

[0071] Fig. 22 is a superimposition of the graphs of the comparative example (base), invention example (refine 1), and invention example (refine 2) in Fig. 21. This graph shows that the invention example (refine 1) and invention example (refine 2) have larger overall transmission losses and higher sound deadening effects than the comparative example (base).

[0072] 23 shows the average value of transmission loss in the low frequency range of 0 to 4000 Hz, the average value of transmission loss in the high frequency range of 4000 to 8000 Hz, and the average value of transmission loss in the entire frequency range of 0 to 8000 Hz for each of the comparative example (base), invention example (refine 1), and invention example (refine 2). It can be seen from this that the invention example (refine 1) has the same sound deadening effect in both the low and high frequency ranges, while the invention example (refine 2) has a higher sound deadening effect in the low frequency range than in the high frequency range, and also has a higher sound deadening effect than the invention example (refine 1) over the entire frequency range.

[0073] <Fifth embodiment> FIG. 24 shows a noise suppressor 50 according to a fifth embodiment of the present invention.

[0074] The noise absorbing device 50 according to the fifth embodiment is formed by pressing the noise absorbing device 40 according to the fourth embodiment shown in FIG. 19 into an outer cylinder 51 having a length equal to or greater than the spacing between the end partition plates 4 or the intermediate partition plate 5 at both ends, so that the outer cylinder 51 seals each side branch chamber and the resonating chamber.

[0075] The outer cylinder 51 is made of a synthetic resin such as nylon. The outer cylinder 51 may be made of a metal such as aluminum, but it is preferable to use a sealant or adhesive so that the outer surfaces of the end partition plates 4, the intermediate partition plate 5, and the rib plate 6 of the silencer 40 are in close contact with the inner surface of the outer cylinder 51 when the silencer 40 is inserted into the outer cylinder 51.

[0076] The silencer 50 according to the fifth embodiment is inserted into the main pipe 2 that forms a refrigerant flow path with the external cylinder 51 attached. In the silencer 50 according to the fifth embodiment, even if the main pipe 2 is bent when being laid in the engine room, the external cylinder 51 seals each side branch chamber, preventing leakage from the side branch chambers due to bending or vibration of the main pipe 2, and the silencer effect can be maintained.

[0077] <Embodiment of the split type sound silencing device> The noise absorbing devices 1, 20, 30, 40, and 50 in the above embodiments are of an integrated type, but as will be described below, they can be of a split type.

[0078] FIG. 25 shows a noise suppressor 60 according to a sixth embodiment, which is obtained by equally dividing the noise suppressor 40 according to the fourth embodiment shown in FIG. 19 in the circumferential direction. That is, the noise suppressor 60 is configured with four modules M1, M2, M3, and M4 in which the inner tube 3 and the rib plate 6 are equally divided in the circumferential direction by dividing planes S1 and S2 including the axis C. The first module M1 has a side branch chamber 7a, a resonating chamber 31a, and a side branch chamber 7e. The second module M2 has a side branch chamber 7b, a resonating chamber 31b, and a side branch chamber 7f. The third module M3 has a side branch chamber 7c and a resonating chamber 31c. The fourth module has a side branch chamber 7d, a resonating chamber 31d, and a side branch chamber 7h. The modules M1, M2, M3, and M4 are combined so that the rib plates 6 overlap, and are inserted into the main tube 2 (see FIG. 1). The modules M1, M2, M3, and M4 may be bonded to each other, or the dividing surfaces S1 and S2 may have recesses and protrusions so that they can fit together. The dividing surfaces S1 and S2 may or may not include the rib plate 6.

[0079] FIG. 26 shows a silencer 70 according to the seventh embodiment, which is divided in the axial direction. That is, the silencer 70 is composed of three modules M11, M12, and M13, in which the inner pipe 3 and the intermediate partition plate 5 are divided in the axial direction by dividing planes S11 and S12 perpendicular to the axis C. The first module M11 has four side branch chambers 7a to 7d in the circumferential direction, the second module M12 has four side branch chambers 7e to 7h in the circumferential direction, and the third module M13 has four side branch chambers 7i to 7l in the circumferential direction. The modules M11, M12, and M13 are combined so that the intermediate partition plates 5 overlap, and are inserted into the main pipe 2 (see FIG. 1). The modules M11, M12, and M13 may be bonded to each other, or may be fitted to each other by providing recesses and protrusions on the dividing planes S. 26, each of the modules M11 to M13 has a side branch chamber 7a to 7l, but the modules may have a resonance chamber and a side branch chamber. The dividing surfaces S11 and S12 may or may not include the intermediate partition plate 5.

[0080] FIG. 27 shows a silencer 80 according to an eighth embodiment, which is divided in the circumferential direction and the axial direction. That is, the silencer 80 is configured with a total of eight modules M21 to M28, in which the inner tube 3 and the rib plate 6 are equally divided in the circumferential direction by dividing planes S21 and S22 including the axis C, and the inner tube 3 and the intermediate partition plate 5 are divided in the axial direction by dividing plane S23 perpendicular to the axis C. Each of the modules M21 to M28 has a resonance chamber 31a to 31h. The modules M21 to M28 may be bonded to each other, or may have recesses and protrusions on the dividing planes S21, S22, and S23 so as to be fitted together. In FIG. 27, each of the modules M21 to M28 has the resonance chambers 31a to 31h, but may be configured with one having a resonance chamber and one having a side branch chamber. The dividing planes S21 and S22 may or may not include the rib plate 6. Moreover, the dividing surface S23 may or may not include the intermediate partition plate 5.

[0081] In this way, by preparing a plurality of side branch type modules, resonance type modules, or mixed type modules that combine the side branch type and resonance type modules, all of which have a uniform outer diameter and different sound deadening effects, and combining each module according to the frequency of the sound source, it is possible to achieve the optimal sound deadening effect.

[0082] The present invention is not limited to the above-described embodiment, and can be modified and changed within the scope of the invention as defined in the claims. For example, the number of side branch chambers is not limited to four as in the above embodiment, and the length of the side branch chambers can also be changed as appropriate. [Explanation of symbols]

[0083] 1...Silencer (first embodiment) 2…Supervisor 3…Inner tube 4...End partition plate 5, 5a, 5b...Intermediate partition plate 6…Rib board 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h…Side branch chamber 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h... Entrances and exits of side branch chambers 9a, 9b...Tapered surface 10...Sound suppressor (conventional structure for comparison) 17a, 17b...Side branch chamber (conventional structure for comparison) 18a, 18b... Entrance and exit of side branch chamber (conventional structure for comparison) 20... Silencer (second embodiment) 30... Silencer (third embodiment) 31a, 31b, 31c, 31d...Resonating chambers 32a, 32b, 32c, 32d...Openings of resonance chambers 40... Silencer (fourth embodiment) 50...silencer (fifth embodiment) 51…Outer cylinder 52…Small diameter part 60... Silencer (sixth embodiment) 70... Silencer (seventh embodiment) 80... Silencer (eighth embodiment)

Claims

1. A silencer to be inserted into a main pipe through which a fluid flows, the silencer comprising an inner pipe and a side branch chamber formed between the main pipe and the inner pipe, an inner surface of the inner tube is provided with an inlet / outlet port communicating with the side branch chamber; the side branch chamber is surrounded by the main pipe, the inner pipe, upstream and downstream partition plates formed on an outer surface of the inner pipe, and an axially extending rib plate formed on the outer surface of the inner pipe, a noise suppressor further comprising an outer cylinder for sealing the side branch chamber and for closely contacting outer surfaces of the partition plate and the rib plate.

2. 2. The silencer according to claim 1, wherein the inner surface of the upstream end of the inner pipe is formed as a tapered surface whose diameter decreases toward the downstream side.

3. 3. The silencer according to claim 1, wherein the inner surface of the downstream end of the inner pipe is formed as a tapered surface whose diameter increases toward the downstream side.

4. a resonance chamber between the main pipe and the inner pipe; 4. The silencer according to claim 1, wherein an opening is provided on the inner surface of the inner tube so as to communicate with the resonance chamber.

5. A noise absorbing device as described in any one of claims 1 to 4, characterized in that the noise absorbing device is composed of a plurality of modules divided circumferentially.

6. A noise absorbing device as described in any one of claims 1 to 4, characterized in that the noise absorbing device is composed of a plurality of modules divided in the axial direction.

7. A noise absorbing device as described in any one of claims 1 to 4, characterized in that the noise absorbing device is composed of a plurality of modules divided circumferentially and axially.

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