Silencer

Abstract

To provide a muffler which is large in a transmission loss, easy in adjustment according to a frequency, and wide in a range of the frequency which generates a muffling effect.SOLUTION: In a muffler 1 inserted into a main pipe 2 in which fluid flows, there are arranged an inner pipe 3 located inside the main pipe 2, spiral fins 4a, 4b arranged at an outer face of the inner pipe 3, and contacting with an inner face of the main pipe 2, and a partitioning part 5 for partitioning spiral grooves 6a, 6b which are formed of the fins 4a, 4b. Side branch chambers 7a, 7b surrounded by the fins 4a, 4b and the partitioning part 5 are arranged between the main pipe 2 and the inner pipe 3. Entrances 8a, 8b communicating with the side branch chambers 7a, 7b are arranged at upstream-side end parts or downstream-side end parts of the spiral grooves 6a, 6b.SELECTED DRAWING: Figure 4

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 device in which a spiral fin is provided on the outer surface of an inner tube. In this device, a phase difference occurs due to the difference in the length of the inner and outer flow passages, which causes sound interference and produces a noise-reduction effect, but the only way to adjust the frequency at which the noise-reduction effect occurs is to change the difference in the length of the inner and outer flow passages, which is difficult to adjust.

[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 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 that is inserted into a main pipe through which a fluid flows, an inner pipe located inside the main pipe; a spiral fin provided on an outer surface of the inner pipe and in contact with an inner surface of the main pipe; a partition portion that partitions the spiral groove formed by the fin, a side branch chamber surrounded by the fin and the partition portion is provided between the main pipe and the inner pipe, The spiral groove is characterized in that an inlet / outlet communicating with the side branch chamber is provided at the upstream end or downstream end of the spiral groove.

[0008] (2) The partition portion is formed in a middle portion of the spiral groove, The side branch chamber preferably comprises a first side branch chamber upstream of the partition and a second side branch chamber downstream of the partition.

[0009] (3) The partition portion is formed at an upstream end or a downstream end of the spiral groove, The side branch chamber is preferably formed upstream or downstream of the partition.

[0010] (4) The partition portion includes a first partition portion on the upstream side of the spiral groove and a second partition portion on the downstream side of the spiral groove, A resonance chamber is provided between the first partition and the second partition, The inner surface of the inner tube is preferably provided with an opening communicating with the resonating chamber.

[0011] (5) The spiral fin is composed of multiple fins, the plurality of spiral grooves formed by the plurality of fins include a first spiral groove in which the partition portion is formed and a second spiral groove in which the partition portion is not formed, It is preferable that a secondary flow passage for a fluid flowing through the main pipe is formed between the main pipe and the inner pipe along the second spiral groove.

[0012] (6) It is preferable that an outer cylinder is provided to seal the fins. Effect of the Invention

[0013] According to the inventions of claims 1 to 3, sound waves that enter the side branch chamber from the upstream end or downstream end of the spiral groove are reflected by the partition and return to the upstream end or downstream end of the spiral groove, where they interfere with the sound waves in the inner tube in opposite phase and are silenced. By changing the position of the partition, the frequency at which the sound silencing effect occurs can be adjusted.

[0014] According to the invention of claim 4, 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.

[0015] According to the invention of claim 5, among the multiple spiral grooves formed by the multiple fins, the second spiral groove without a partition section acts as a sub-channel and the main channel inside the inner tube, which causes a phase difference in sound waves due to the difference in channel between the sub-channel and the main channel, resulting in sound interference and a noise reduction effect. Therefore, a noise reduction effect is obtained that combines the noise reduction effect in a wide frequency range by the side branch chamber and the noise reduction effect due to the phase difference between the sub-channel and the main channel.

[0016] According to the invention of claim 6, since the outer cylinder seals the side branch chamber and the resonating chamber, leakage from the side branch chamber and the resonating chamber caused by bending or vibration of the main tube is prevented, and the sound deadening effect can be maintained. [Brief description of the drawings]

[0017] [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 the silencer of FIG. 1 as viewed from the upstream side. [Diagram 3] FIG. 2 is a perspective view of the silencer of FIG. 1 as viewed from the downstream side. [Figure 4] FIG. 2 is a longitudinal cross-sectional view of a main pipe with the silencer of FIG. 1 inserted. [Diagram 5] 2A and 2B are a perspective view and a front view showing a modified example of the noise suppressor of FIG. [Figure 6] FIG. 13 is a perspective view showing an example of the invention and a comparative example used in an analysis of the sound deadening effect. [Figure 7] 4 is a graph showing the analysis results of the transmission loss of a comparative example (spiral 1) and an example of the invention (spiral 2). [Figure 8] Graph showing the analysis results of transmission loss for a comparative example (spiral 1) and an example of the invention (spiral 2) in terms of average values ​​in the low frequency range, high frequency range, and all frequency ranges. [Figure 9] FIG. 5 is a perspective view of a noise suppressor according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a longitudinal cross-sectional view of a main pipe with the silencer of FIG. 9 inserted therein. [Figure 11] FIG. 10 is a perspective view showing a modified example of the noise suppressor of FIG. [Figure 12]FIG. 11 is a perspective view of a noise suppressor according to a third embodiment of the present invention, with a portion of a main pipe cut away. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] 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.

[0020] As shown in FIGS. 2 and 3, the noise suppressor 1 includes an inner pipe 3, fins 4, and a partition portion 5. The inner pipe 3 has a fin 4 and a partition portion 5. As shown in FIG.

[0021] The inner pipe 3 has an outer diameter smaller than the inner diameter of the main pipe 2. The wall thickness of the inner pipe 3 is preferably as thin as possible to ensure a flow path. The length of the inner pipe 3 is arbitrary, but a length that does not prevent the main pipe 2 from bending at the location where the main pipe 2 is installed is preferable. The inside of the inner pipe 3 forms a main flow path 10 for the fluid flowing through the main pipe 2.

[0022] The fin 4 is composed of a first fin 4a and a second fin 4b having two helical stripes. The first fin 4a is provided on the outer surface of the inner pipe 3 and extends in a helical shape with a predetermined pitch p from the upstream end of the inner pipe 3 to the downstream end. The second fin 4b extends in a helical shape with the same pitch p as the first fin 4a from a position 180 degrees out of phase with the first fin 4a at the upstream end of the inner pipe 3 to the downstream end. The second fin 4b is located in the middle between two adjacent side surfaces of the first fin 4a. The height of the fin 4 is equal to the radial dimension from the outer surface of the inner pipe 3 to the inner surface of the main pipe 2. Therefore, the outer end surface of the fin 4 is in contact with the inner surface of the main pipe 2. The thickness of the fin 4 is preferably the same as the wall thickness of the inner pipe 3, but is not limited thereto. The first fin 4a and the second fin 4b form a first groove 6a and a second groove 6b having two helical stripes between the main pipe 2 and the inner pipe 3. In this embodiment, the fins 4 have two stripes, but may have one stripe or three or more stripes.

[0023] The partition 5 is provided between the side surface of the first fin 4a of the first groove 6a and the side surface of the adjacent second fin 4b, and divides the first groove 6a into an upstream side and a downstream side. The position of the partition 5 is arbitrary, but determines the lengths of the side branch chambers 7a, 7b formed on the upstream side and downstream side of the partition 5. The height of the partition 5 is the same as the height of the fin 4. The thickness of the partition 5 is preferably the same as the thickness of the fin 4, but is not limited to this.

[0024] The silencer 1 is fixed inside the main pipe 2 by fastening a part of the fins 4 including the partition portion 5 from the outside of the main pipe 2 with a fixing member (not shown). The outer end faces of the first fin 4a and the second fin 4b and the outer end face of the partition portion 5 are in close contact with the inner surface of the main pipe 2 when the silencer 1 is inserted into the main pipe 2. This allows side branch chambers 7a and 7b, which will be described later, to be sealed by the main pipe 2. As an alternative to the fixing means, the silencer 1 may be pressed in or a sealant may be used when it is inserted into the main pipe 2.

[0025] 4, in the first spiral groove 6a formed between the main pipe 2 and the inner pipe 3 and by the first fin 4a and the second fin 4b, a first spiral side branch chamber 7a is formed on the upstream side of the partition section 5, and a second spiral side branch chamber 7b is formed on the downstream side of the partition section 5. An inlet / outlet 8a of the first side branch chamber 6a is located at the upstream end of the first groove 6a, and an inlet / outlet 8b of the second side branch chamber 7b is located at the downstream end of the second groove 6b.

[0026] In addition, the spiral second groove 6b formed between the main pipe 2 and the inner pipe 3 and by the first fin 4a and the second fin 4b forms a sub-flow passage 9 from the upstream end to the downstream end of the inner pipe 3.

[0027] Next, the operation of the noise suppressor 1 of this embodiment will be described.

[0028] As shown in Fig. 4, the refrigerant flowing through the main pipe 2 flows into a main passage 10 inside the inner pipe 3 and a spiral sub-passage 9 outside the inner pipe 3 at the upstream end of the silencer 1, and flows out from the main passage 10 inside the inner pipe 3 and the spiral sub-passage 9 outside 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 main passage 10 inside the inner pipe 3 of the silencer 1 and the sub-passage 9 outside the inner pipe 3. Note that the sound source may be on the downstream side, in which case the silencing effect will be generated on the upstream side.

[0029] The sound waves propagating through the inner pipe 3 enter the first side branch chamber 7a through the inlet / outlet 8a at the upstream end of the inner pipe 3, and enter the second side branch chamber 7b through the inlet / outlet 8b at the downstream end of the inner pipe 3. They are reflected by the partitions 5 of each side branch chamber 7a, 7b and return to the inlets 8a, 8b, where they become in opposite phase to the sound waves in the inner pipe 3 and interfere with each other, thereby being silenced.

[0030] Here, if the cross-sectional area of ​​the main pipe 2 is S, the cross-sectional area of ​​the side branch chambers 7a, 7b is Ss, the length of the side branch chambers 7a, 7b is l, the frequency of the sound wave is f, and the speed of sound 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 distance along the spiral from the entrances 8a, 8b to the partition section 5.

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[0031] In addition to the sound-dampening effect of the first side branch chamber 7a and the second side branch chamber 7b, the difference in flow path length between the main flow path 10 inside the inner tube 3 and the sub-flow path 9 outside the inner tube 3 creates a phase difference between the sound waves propagating through the main flow path 10 and the sound waves propagating through the sub-flow path 9, causing sound interference and resulting in a sound-dampening effect.

[0032] In the noise suppressor 1 of this embodiment, by changing the position of the partition portion 5, the lengths of the first side branch chamber 7a and the second side branch chamber 7b can be adjusted, and the noise suppression effect can be improved according to the frequency of the sound source.

[0033] In the silencer 1 of the first embodiment, the partition portion 5 is provided between the main pipe 2 and the inner pipe 3 and in the middle of the first spiral groove 6a formed by the first fin 4a and the second fin 4b. However, as shown in FIG. 5(a), the partition portion 5 may be provided at the upstream end of the first spiral groove 6a, or as shown in FIG. 5(b), the partition portion 5 may be provided at the downstream end.

[0034] In the silencer 1 of the first embodiment, as shown in Fig. 5(c), the inner surface of the upstream end of the inner pipe 3 may be formed with a tapered surface 11a that decreases in diameter toward the downstream side. Similarly, the inner surface of the downstream end of the inner pipe 3 may be formed with a tapered surface 11b that increases in diameter toward the downstream side. This makes it possible to reduce the pressure loss of the refrigerant that flows from the main pipe 2 through the inner pipe 3 and flows into the main pipe 2.

[0035] 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 two analysis models shown in FIG.

[0036] In Fig. 6, the comparative example (spiral 1) has two spiral fins 4a, 4b, but no partition, and has no side branch chamber. In contrast, the invention example (spiral 2) is the same as the silencer 1 of the first embodiment shown in Fig. 2, and has a structure with side branch chambers 7a, 7b. Each analytical model had an outer diameter of 20 mm, an inner diameter of 8 mm, and a total length of 100 mm. For each analytical model, the transmission loss was calculated by changing the frequency of the sound source.

[0037] 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 at which the noise reduction effect could be obtained was 0 to 4000 Hz. If the length of the side branch was l and the sound speed was c, the theoretical value of the target frequency f was calculated using Equation 2. Specifically, the target frequencies of the first side branch chamber 7a and the second side branch chamber 7b were 421 Hz and 3785 Hz, respectively.

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[0038] For the second groove 6b without a partition, the theoretical value of the target frequency f was calculated using Equation 3, where the length of the main flow path 10 is li and the length of the sub-flow path 9 is lo. Specifically, the target frequency of the second groove 6b was set to 1365 Hz.

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[0039] Fig. 7 shows the transmission loss when the frequency was changed from 0 to 8000 Hz. It was confirmed from Fig. 7 that the example of the invention (spiral 2) had a greater number of transmission loss peaks and a greater sound deadening effect than the comparative example (spiral 1) in the frequency range of 4000 to 8000 Hz.

[0040] Fig. 8 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. It was confirmed from Fig. 8 that the example of the invention (spiral 2) had a larger transmission loss and a larger sound deadening effect than the comparative example (spiral 1).

[0041] <Second embodiment> 9 and 10 show a noise suppressor 20 according to a second embodiment of the present invention.

[0042] In the silencer 20 of the second embodiment, a first partition portion 5a and a second partition portion 5b are provided on the outer surface of the inner pipe 3, a first side branch chamber 7a is formed between the first partition portion 5a on the upstream side and the upstream end of the inner pipe 3, a second side branch chamber 7b is formed between the downstream partition portion 5b and the downstream end of the inner pipe 3, and further a resonance chamber 21 is formed between the first partition portion 5a and the second partition portion 5b. The configurations of the first side branch chamber 7a and the second side branch chamber 7b are the same as those of the first embodiment except for the length dimension, so the same reference numerals are used and the description will be omitted.

[0043] Resonance chamber 21 is formed by a space surrounded by the inner surface of main tube 2, the outer surface of inner tube 3, first fin 4a, second fin 4b, first partition 5a, and second partition 5b. Opening 22 communicating with resonance chamber 21 is formed to penetrate the wall of inner tube 3 midway between first partition 5a and second partition 5b.

[0044] In the noise suppressor 20 of the second embodiment, in addition to the noise suppressing effect of the first side branch chamber 7a and the second side branch chamber 7b, a noise suppressing effect is provided by the resonance chamber 21. That is, the energy of the sound wave that has entered the inner tube 3 is absorbed by the resonance chamber 21, thereby suppressing the sound.

[0045] Here, when the volume of the resonance chamber 21 is V, the cross-sectional area of ​​the opening 22 is Sr, the length of the opening 22 is l, and the sound speed is c, the resonance frequency ωr is expressed by the following equation 4.

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[0046] Therefore, by matching the resonant frequency of the resonant chamber 21 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 effects of the first side branch chamber 7a and the second side branch chamber 7b, the frequency range over which the sound silencing effect is achieved can be widened.

[0047] In the second embodiment, the silencer 20 has a resonance chamber 21 between the first partition 5a and the second partition 5b, a first side branch chamber 7a between the first partition 5a and the upstream end of the inner pipe 3, and a second side branch chamber 7b between the second partition 5b and the downstream end of the inner pipe 3. However, as shown in FIG. 11(a), the first partition 5a may be provided at the upstream end of the inner pipe 3 and the second partition 5b may be provided downstream of the first partition 5a, so that the resonance chamber 21 is provided between the first partition 5a and the second partition 5b, and a side branch chamber 7 is provided between the second partition 5b and the downstream end of the inner pipe 3. 11(b), the second partition 5b may be provided at the downstream end of the inner pipe 3, the first partition 5a may be provided upstream of the first partition 5b, a resonance chamber 21 may be provided between the first partition 5a and the second partition 5b, and a side branch chamber 7 may be provided between the first partition 5a and the upstream end of the inner pipe 3. Also, by increasing the number of partitions, multiple resonance chambers may be provided.

[0048] <Third embodiment> FIG. 12 shows a noise suppressor 30 according to a third embodiment of the present invention.

[0049] The noise suppressor 30 according to the third embodiment is formed by press-fitting the noise suppressor 1 of the first embodiment shown in FIG. 2 into an outer cylinder 31, so that the outer cylinder 31 seals the side branch chambers 7a, 7b.

[0050] The outer cylinder 31 is made of a synthetic resin such as nylon. The outer cylinder 31 may be made of a metal such as aluminum, but it is preferable to use a sealant or adhesive so that when the silencer 1 is inserted into the outer cylinder 31, the spiral fins 4a and 4b of the silencer 1 and the outer end face of the partition portion 5 are in close contact with the inner surface of the outer cylinder 31.

[0051] The silencer 30 according to the third embodiment is inserted into the main pipe 2 that forms a refrigerant flow path with the external cylinder 31 attached. In the silencer 30 according to the third embodiment, even if the main pipe 2 is bent when being laid in the engine room, the external cylinder 31 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.

[0052] 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 fins is not limited to two as in the above embodiment, and the position of the partition, i.e., the length of the side branch chamber, can also be changed as appropriate. [Explanation of symbols]

[0053] 1...Silencer (first embodiment) 2…Supervisor 3…Inner pipe 4. Fin 4a…First fin 4b…Second fin 5…Partition 5a…First partition 5b…Second partition 6…Groove 6a…1st groove 6b…Second groove 7…Side branch chamber 7a…First side branch chamber 7b…Second side branch chamber 8…Entrance / exit 8a…1st entrance / exit 8b…Second entrance / exit 9…Sub-channel 10…Main channel 11a, 11b...Tapered surfaces 20... Silencer (second embodiment) 21…Resonating chamber 22…Aperture 30... Silencer (third embodiment) 31…Outer cylinder

Claims

1. A silencer that is inserted into a main pipe through which a fluid flows, an inner pipe located inside the main pipe; a spiral fin provided on an outer surface of the inner pipe and in contact with an inner surface of the main pipe; a partition portion that partitions the spiral groove formed by the fin, a side branch chamber surrounded by the fin and the partition portion is provided between the main pipe and the inner pipe, an inlet / outlet port communicating with the side branch chamber at an upstream end or a downstream end of the spiral groove; A silencer comprising: an outer cylinder for sealing the fin; the outer cylinder being in contact with an inner surface of the main pipe.

2. The partition portion is formed in a middle portion of the spiral groove, 2. The silencer according to claim 1, wherein the side branch chamber comprises a first side branch chamber located upstream of the partition and a second side branch chamber located downstream of the partition.

3. The partition portion is formed at an upstream end or a downstream end of the spiral groove, 2. The noise suppressor according to claim 1, wherein the side branch chamber is formed on the upstream side or the downstream side of the partition portion.

4. the partition portion includes a first partition portion on the upstream side of the spiral groove and a second partition portion on the downstream side of the spiral groove, A resonance chamber is provided between the first partition and the second partition, 2. 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. The spiral fin is composed of a plurality of fins, the plurality of spiral grooves formed by the plurality of fins include a first spiral groove in which the partition portion is formed and a second spiral groove in which the partition portion is not formed, 5. The silencer according to claim 1, wherein a secondary flow passage for a fluid flowing through the main pipe is formed between the main pipe and the inner pipe along the second spiral groove.

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