JP2023035173A - Muffler - Google Patents

Abstract

To provide a muffler that does not affect a muffling effect due to a state of adhesion with a main pipe, deformation or bending of the main pipe, and is easy to adjust according to frequencies, and has a wide range of frequencies having the muffling effect.SOLUTION: There is provided a muffler 1 inserted into a main pipe 2 through which fluid flows, which comprises an inner tube 3 located inside the main pipe 2 and a plurality of ribs 5 supporting the inner tube 3 on the inner surface of the main pipe 2. A fluid flow path 6 is provided on the outside of the inner tube 3, and a muffling space is provided on the inside of the inner tube 3. A plurality of muffling spaces divided by one or more partitions 4 are provided on the inner side of the inner tube. The muffling spaces may be side branch chambers 7a, 7b, resonance chambers or a combination of these.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer that is inserted into refrigerant pipes, exhaust pipes, etc. of a vehicle air conditioner.

In vehicle air conditioning systems, mechanical noise from the compressor and noise due to cavitation of the refrigerant is transmitted to the evaporator through the pipes and then transmitted to the driver from the air outlet. transmitted to For this reason, a muffler type silencer is interposed or an insertion type silencer is inserted in the piping of the vehicle air conditioner. A muffler type silencer is large and heavy, and brazing causes an increase in cost.

For example, Patent Literature 1 describes a device in which spiral fins are provided on the outer surface of an inner tube. This causes a phase difference due to the difference in channel length between the inside and outside, which causes interference of sound and produces a silencing effect. However, it is difficult to adjust.

Patent Document 2 discloses a muffler inserted into a tubular body, wherein a resonator chamber is provided between the muffler and the body, and a flow path of the body is connected to the resonator chamber through a connecting channel. A silencer is described. Further, Patent Document 3 describes a sound absorbing device in which an outer member surrounding an 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. there is All of these are of resonance type, and since the resonance frequency is determined by the shape of the resonator, the frequency at which the silencing effect is obtained is narrow.

In any of the silencers disclosed in Patent Documents 1 to 3, since the side branch chamber and the resonance chamber are formed between the silencer and the main pipe inserted inside the main pipe of the main flow path, the side branch chamber and the resonance chamber have long lengths. There is a problem that the capacity of the sheath is affected by the state of close contact with the main pipe and the deformation and bending of the main pipe, making it difficult to obtain the desired silencing effect.

European Patent Publication EP2138750A1 Patent No. 5785173 specification JP-A-2005-84693

The present invention has been made in view of the above-mentioned conventional problems. An object of the present invention is to provide a silencer with a wide range of frequencies that generate

As a means for solving the above problems, the present invention
(1) A silencer inserted into a main pipe through which a fluid flows,
an inner pipe positioned inside the main pipe;
and a plurality of ribs supporting the inner pipe on the inner surface of the main pipe,
It is characterized in that the flow path for the fluid is provided outside the inner pipe, and that a muffling space is provided inside the inner pipe.

(2) A plurality of muffling spaces partitioned by one or a plurality of partition walls are provided inside the inner tube.

(3) The muffling space is a side branch chamber, and an inlet/outlet communicating with the side branch chamber is provided at an upstream end or a downstream end of the inner pipe.

(4) The muffling space is a side branch chamber, and an inlet and outlet communicating with the side branch chamber is provided on the outer peripheral surface of the inner pipe.

(5) The muffling space is a resonance chamber, and an opening communicating with the side branch chamber is provided at an upstream end or a downstream end of the inner pipe.

(6) The muffling space is a resonance chamber, and an opening communicating with the side branch chamber is provided on the outer peripheral surface of the inner pipe.

According to claim 1, fluid entering between the main pipe and the upstream end of the inner pipe from the upstream side of the main pipe flows out from between the main pipe and the downstream end of the inner pipe to the downstream side of the main pipe. do. Sound waves entering the muffling space of the inner tube are muffled in the muffling space. Since the muffling space is provided in the inner pipe positioned inside the main pipe, the length or volume of the muffling space does not change due to the state of close contact with the main pipe, deformation or bending of the main pipe, and the muffling effect is not affected.

According to the invention of claim 2, by changing the length and volume of the plurality of silencing spaces, it is easy to adjust according to the frequency, and the frequency range in which the silencing effect is produced is widened.

According to the invention of Claims 3 and 4, the sound wave entering the side branch chamber from the upstream end or the downstream end of the inner pipe is reflected at the inner end of the side branch chamber, and is reflected at the upstream end or the downstream end. It returns to the end and interferes with the sound waves in the inner tube out of phase and is muffled. Since the side branch chamber is provided in the inner pipe located inside the main pipe, the length of the side branch chamber does not change due to the state of close contact with the main pipe, deformation or bending of the main pipe, and the noise reduction effect is not affected.

According to the inventions of claims 5 and 6, the energy of the sound wave entering the resonance chamber through the opening at the upstream end or the downstream end of the inner tube is absorbed in the resonance chamber and the sound is muffled. Since the resonance chamber is provided in the inner pipe located inside the main pipe, the volume of the resonance chamber does not change due to the state of close contact with the main pipe, deformation or bending of the main pipe, and the noise reduction effect is not affected.

1 is a perspective view of a side branch type silencer according to a first embodiment of the present invention; FIG. FIG. 2 is a longitudinal sectional view of the silencer of FIG. 1; FIG. 3 is an enlarged cross-sectional view taken along line III-III of the silencer of FIG. 2; FIG. 2 is a perspective view of a conventional side branch type silencer. FIG. 5 is a vertical cross-sectional view of the conventional silencer of FIG. 4; The graph which shows the analysis result of the transmission loss of an invention example (ext.flow) and a conventional example (base). The perspective view of the side branch 1 type|mold silencer which concerns on 2nd Embodiment of this invention. FIG. 8 is a longitudinal sectional view of the silencer of FIG. 7; The perspective view of the side branch 2 type|mold silencer which concerns on 3rd Embodiment of this invention. FIG. 10 is a longitudinal sectional view of the silencer of FIG. 9; The graph which shows the analysis result of the transmission loss of the side branch type 1 invention example (sidebranch1) and the side branch type 2 invention example (sidebranch2). FIG. 11 is a perspective view of a resonance type 1 silencer according to a fourth embodiment of the present invention; FIG. 13 is a longitudinal sectional view of the silencer of FIG. 12; FIG. 11 is a perspective view of a resonance type 2 silencer according to a fifth embodiment of the present invention; FIG. 15 is a longitudinal sectional view of the silencer of FIG. 14; 7 is a graph showing analysis results of transmission loss of a resonance type 1 invention example (resonator 1) and a resonance type 2 invention example (resonator 2). The graph which shows the analysis result of the transmission loss of the resonance type 1 invention example (resonator1) and the side branch type 1 invention example (sidebranch1). FIG. 11 is a perspective view of a hybrid silencer according to a sixth embodiment of the present invention; FIG. 19 is a longitudinal sectional view of the silencer of FIG. 18; The graph which shows the analysis result of the transmission loss of the mixed type invention example (mix).

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 shows a silencer 1 according to a first embodiment of the invention. The muffler 1 is provided in a pipe through which a refrigerant of a vehicle air conditioner flows. Specifically, the muffler is inserted into a pipe (hereinafter referred to as "main pipe") 2 on the outlet side of an evaporator or compressor in a vehicle air conditioner comprising a compressor, condenser, expansion valve and evaporator (not shown). Although the main pipe 2 is made of a material having elasticity and flexibility such as rubber or synthetic resin, the material is not limited to this, and a non-flexible material such as aluminum may be used. It is assumed that a fluid (hereinafter referred to as "refrigerant") flows through the main pipe 2 from the left upstream side to the right downstream side in FIG.

As shown in FIGS. 2 and 3 , the muffler 1 includes an inner tube 3 , partitions 4 and ribs 5 .

The inner pipe 3 has an outer diameter smaller than the inner diameter of the main pipe 2 . The thickness of the inner tube 3 is preferably as thin as possible in order to secure the flow path. The length of the inner pipe 3 is arbitrary, but it is preferably a length that does not hinder bending of the main pipe 2 at the location where the inner pipe 3 is installed. Between the main pipe 2 and the inner pipe 3, a main flow path 6 for fluid flowing through the main pipe 2 is formed. The inside of the inner tube 3 forms side branch chambers 7a, 7b.

The partition part 4 is provided inside the inner pipe 3 so as to separate the upstream side and the downstream side of the inner pipe 3 . Although the position of the partition 4 is arbitrary, the length of the side branch chambers 7a and 7b formed on the upstream side and the downstream side of the partition 4 is determined.

As shown in FIG. 3, four ribs 5 are formed on the outer surface of the inner tube 3 at equidistant positions around 4 and protrude outward in the radial direction of the inner tube 3 . The height of ribs 5 is approximately the same as the radial clearance between main pipe 2 and inner pipe 3 . The axial length of the ribs 5 is arbitrary. The ribs 5 may be formed at multiple positions in the axial direction. Although the ribs 5 are formed on the inner pipe 3 in the embodiment, they may be fixed inside the main pipe 2 . In this case, the number of ribs 5 may be other than four, and may be at least three.

The muffler 1 is fixed inside the main pipe 2 by being tightened at the position of the rib portion 5 from the outside of the main pipe 2 by a fixing member (not shown). The outer end surface of rib 5 is in close contact with the inner surface of main pipe 2 . As a substitute for the fixing member, when inserting the silencer 1 into the main pipe 2, it may be press-fitted or a sealing material may be used.

A main flow path 6 is formed between the main pipe 2 and the inner pipe 3 . A straight tubular first side branch chamber 7 a is formed from the upstream end of the inner pipe 3 to the upstream end face of the partition 4 , and from the downstream end face of the partition 4 to the downstream end of the inner pipe 3 . , a straight tubular second side branch chamber 7b is formed. The port 8a of the first side branch chamber 7a is at the upstream end of the inner tube 3 and the port 8b of the second side branch chamber 7b is at the downstream end of the inner tube 3. The main channel 6 may not have a constant cross-sectional shape, and may expand or contract in the middle of the channel.

Next, the operation of the silencer 1 of this embodiment will be described.

As shown in FIG. 2, the refrigerant flowing in the main pipe 2 flows into the main flow path 6 between the inner surface of the main pipe 2 and the outer surface of the inner pipe 3 at the upstream end of the silencer 1, and reaches the downstream end. , it flows into the main pipe 2 from between the inner surface of the main pipe 2 and the outer surface of the inner pipe 3. 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 silencer 1 . Note that the sound source may be located downstream, in which case the silencing effect will occur on the upstream side.

The sound waves entering the first side branch chamber 7a from the inlet/outlet 8a at the upstream end of the inner pipe 3 are reflected by the partition 4 of the side branch chamber 7a and return to the inlet/outlet 8a. Interfering with the opposite phase, the sound is muted. Similarly, the sound wave entering the second side branch chamber 7b from the inlet 8b at the downstream end of the inner pipe 3 is reflected by the partition 4 of the side branch chamber 7b and returns to the inlet 8b, where the inner pipe 3 interferes with the sound waves of other waves in opposite phase, and the sound is muted.

Here, if the cross-sectional area of the main pipe 2 is S, the cross-sectional area of the side branch chambers 7a and 7b is Ss, the length of the side branch chambers 7a and 7b is l, the frequency of the sound wave is f, and the speed of sound is c, then the muffler 1 The transmission loss TL at is represented by Equation (1). The length l of the side branch chambers 7a, 7b is the distance from the entrances 8a, 8b to the partition 4. As shown in FIG.

In the silencer 1 of this embodiment, the length of the first side branch chamber 7a and the length of the second side branch chamber 7b are adjusted by changing the position of the partition portion 4, and the silencing effect is achieved according to the frequency of the sound source. can be higher.

In the silencer 1 of the first embodiment, as shown in FIG. 2, the outer surface of the upstream end of the inner tube 3 may be formed with a tapered surface 9a that expands in diameter toward the downstream side. Similarly, the outer surface of the downstream end of the inner tube 3 may be formed with a tapered surface 9b that decreases in diameter toward the downstream side. Thereby, the pressure loss of the refrigerant flowing out from the main pipe 2 to the main pipe 2 via between the main pipe 2 and the inner pipe 3 can be reduced.

In order to confirm the silencing effect of the silencing device 1 of the first embodiment, the inventors performed acoustic analysis by computer simulation for two analysis models, an invention example and a comparative example.

As an invention example, the silencer 1 of the first embodiment shown in FIGS. 1 and 2 was used. As a comparative example, a conventional muffler 101 shown in FIGS. 4 and 5 was used. A conventional muffler 101 of a comparative example has an intermediate partition portion 104 provided in the intermediate portion of an inner pipe 103, and an annular first side branch chamber 107a and a second side branch chamber 107b between the main pipe 102 and the inner pipe 103. , and entrances 108a and 108b of the side branch chambers 107a and 107b are provided at the upstream end and the downstream end of the inner tube 103, respectively.

The main pipe of each analytical model had an inner diameter of 20 mm and a total length of 100 mm. The inner tube 3 of the invention example had an outer diameter of 18 mm, an inner diameter of 16 mm, and lengths of the side branches 7a and 7b of 22 mm and 72 mm, respectively. The inner tube 103 of the comparative example had an outer diameter of 12 mm, an inner diameter of 8 mm, and lengths of the side branches 107a and 107b of 22 mm and 72 mm, respectively. For each analysis model, the transmission loss was obtained by changing the frequency of the sound source.

In this acoustic analysis, the medium was air having a temperature of 25° C., a pressure of 0.101325 MPa (standard atmospheric pressure), a density of 1.184 kg/m ³ , and a sound velocity of 346.25 m/s. A target frequency for obtaining a silencing effect was set to 0 to 4000 Hz. Assuming that the length of the side branch is l and the speed of sound is c, the theoretical value of the target frequency f is obtained by Equation (2). Specifically, the target frequencies for the first side branch chamber and the second side branch chamber were 3934 Hz and 1202 Hz, respectively.

FIG. 6 shows the transmission loss when changing the frequency from 0 to 8000 Hz. From Fig. 6, it is confirmed that the invention example (ext.flow) can obtain the same transmission loss as the comparative example (base), and that the number of transmission loss peaks is large and the noise reduction effect is large as in the conventional case. was done.

<Second and third embodiments>
7 and 8 show a silencer 1A according to a second embodiment of the invention. The silencer 1A has an inner tube 3 and ribs 5 in the same manner as the silencer 1 of the first embodiment. , one side branch chamber 7 having an entrance 8 on the opening side is formed. The inlet/outlet 8 of the inner pipe 3 is oriented downstream, but may be oriented upstream.

9 and 10 show a silencer 1B according to a third embodiment of the invention. The silencer 1B has an inner tube 3 and ribs 5 like the silencer of the first embodiment. One side branch chamber 7 having four entrances 8 of is formed. Although the inlet/outlet 8 of the inner pipe 3 is provided on the upstream side, it may be provided on the downstream side.

FIG. 11 shows an analysis model (side branch type 1) of the noise suppressor 1A of the second embodiment and an analysis model (side branch type 2) of the noise suppressor 1B of the third embodiment, which was performed in the same manner as in the first embodiment. The results of acoustic analysis by computer simulation are shown.

The inner tube 3 of the side branch type 1 had an outer diameter of 18 mm, an inner diameter of 16 mm, and a length of the side branch 7 of 22 mm. The inner tube 3 of the side branch type 2 was set to have an outer diameter of 18 mm, an inner diameter of 16 mm, a length of the side branch 7 of 18 mm, and a width of the inlet/outlet 8 so as to have the same area as the inlet/outlet 8 of the side branch type 1.

From FIG. 11, it was confirmed that the side branch type 2 in which the inlet/outlet 8 is provided on the outer peripheral surface of the inner tube 3 can obtain a higher transmission loss than the side branch type 1 type.

<Fourth and fifth embodiments>
12 and 13 show a silencer 1C according to a fourth embodiment of the invention. The silencer 1C has an inner tube 3 and ribs 5 like the silencer 1 of the first embodiment, but both ends of the inner tube 3 are closed and one end of the inner tube 3 has an opening 10. A chamber 11 is formed. Although the opening 10 of the inner tube 3 is provided at the downstream end, it may be provided at the upstream end.

14 and 15 show a silencer 1D according to a fifth embodiment of the invention. The silencer 1D has an inner tube 3 and ribs 5 like the silencer 1 of the first embodiment, but both ends of the inner tube 3 are closed and an opening 10 is formed in the center of the outer peripheral surface of the inner tube 3 in the axial direction. , one resonance chamber 11 is formed.

Here, the resonance frequency ωr is expressed by Equation 3, where V is the volume of the resonance chamber 11, Sr is the cross-sectional area of the opening 10, l is the length of the opening 10, and c is the speed of sound.

FIG. 16 shows an analysis model (resonance type 1) of the silencer 1C of the fourth embodiment and an analysis model (resonance type 2) of the silencer 1D of the fifth embodiment in the same manner as in the first embodiment. The results of acoustic analysis by simulation are shown.

The inner tube 3 of the resonance type 1 had an outer diameter of 18 mm, an inner diameter of 16 mm, a length of 21 mm, and a diameter of the opening 10 of 2 mm. The inner tube 3 of the resonance type 2 had an outer diameter of 18 mm, an inner diameter of 16 mm, a length of 21 mm, and a diameter of the opening 10 of 2 mm.

From FIG. 16, it was confirmed that the resonance type 2, in which the opening 10 of the resonance chamber 11 is provided on the outer peripheral surface of the inner tube 3, can obtain a higher transmission loss than the resonance type 1.

FIG. 17 compares the silencer 1A (side branch type 1) of the second embodiment shown in FIGS. 7 and 8 with the silencer 1C (resonance type 1) of the fourth embodiment. From FIG. 17, it was found that the resonance type 1 can obtain a high transmission loss in a low frequency range, and the side branch type 1 can obtain a high transmission loss in a higher frequency range than the resonance type 1.

<Sixth Embodiment>
18 and 19 show a silencer 1E according to a sixth embodiment of the invention. The silencer 1E has an inner tube 3 and ribs 5 like the silencer 1 of the first embodiment, but two partitions 4a and 4b separated in the axial direction are formed inside the inner tube 3, A first side branch chamber 7a is formed between the upstream end of the inner tube 3 and the upstream partition 4a, a resonance chamber 11 is formed between the two partitions 4a and 4b, and a further downstream A second side branch chamber 7b is formed between the partition 4b and the downstream end. The inlet 8a of the first side branch chamber 7a is at the upstream end of the inner tube 3 and the inlet 8b of the second side branch chamber 7b is at the downstream end of the inner tube 3. An opening 10 of the resonance chamber 11 is formed on the outer peripheral surface of the inner tube 3 between the two partitions 4 .

FIG. 20 shows the results of acoustic analysis by computer simulation performed in the same manner as in the first embodiment for the analysis model (mix type) of the noise reduction device 1E of the sixth embodiment.

The mix-type inner tube 3 had an outer diameter of 18 mm and an inner diameter of 16 mm. The length of the first side branch chamber 7a was 22 mm, and the length of the second side branch chamber 7b was 57 mm. The length of the resonance chamber 11 was 19 mm, and the diameter of the opening 10 was 2 mm. The target frequencies of the first side branch chamber 7a, the second side branch chamber 7b, and the resonance chamber 11 are 3934 Hz, 1519 Hz, and 1000 Hz, respectively.

20, by providing the first side branch chamber 7a, the second side branch chamber 7b, and the resonance chamber 11 in the inner tube 3, the resonance frequency of the resonance chamber 11 is matched with the frequency of the incident sound, thereby obtaining a specific region. , and together with the silencing effects of the first side branch chamber 7a and the second side branch chamber 7b, the frequency range that produces the silencing effect can be widened between 0 and 8000 Hz. I found out.

In the silencers 1, 1A to 1E according to the above-described embodiments, the inner pipe 3 positioned inside the main pipe 2 is provided with the side branch chambers 7, 7a, 7b and the silencing space such as the resonance chamber 11. Therefore, the length or volume of the muffling space does not change due to the state of close contact with the main pipe 2, deformation or bending of the main pipe 2, and the muffling effect is not affected.

The present invention is not limited to the above embodiments, and can be modified and changed within the scope of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 1E... Silencer 2... Main pipe 3... Inner pipe 4... Partition part 5... Rib 6... Main flow path 7... Side branch chamber 7a... First side branch chamber 7b... Second side branch Chamber 8 Doorway 8a Doorway 8b Doorway 9a Tapered portion 9b Tapered portion 10 Opening 11 Resonance chamber

Claims (6)

A muffler inserted into a main pipe through which a fluid flows,
an inner pipe positioned inside the main pipe;
and a plurality of ribs supporting the inner pipe on the inner surface of the main pipe,
A muffler, wherein a flow path for the fluid is provided outside the inner pipe, and a muffling space is provided inside the inner pipe. 2. A muffler according to claim 1, wherein a plurality of muffling spaces partitioned by one or a plurality of partition walls are provided inside said inner pipe. 3. The muffling space as claimed in claim 1, wherein the silencing space is a side branch chamber, and an inlet and outlet communicating with the side branch chamber is provided at an upstream end or a downstream end of the inner pipe. silencer. 3. The muffler according to claim 1, wherein the muffling space is a side branch chamber, and an entrance and exit communicating with the side branch chamber is provided on the outer peripheral surface of the inner pipe. 3. The silencing space as claimed in claim 1, wherein the silencing space is a resonance chamber, and an opening communicating with the side branch chamber is provided at an upstream end or a downstream end of the inner pipe. Silencer. 3. A muffler according to claim 1, wherein said muffling space is a resonance chamber, and an opening communicating with said side branch chamber is provided on the outer peripheral surface of said inner pipe.

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