Variable interference length sound silencer

Abstract

To provide a silencer device that is easy to mold and easy to adjust according to frequency.SOLUTION: There is provided a silencer 1 inserted into a main pipe 2 through which fluid flows. In the silencer provided with an inner pipe 5 and side branch chambers 13a, 13b, 13c, 13d formed between the main pipe 2 and the inner pipe 5, a partition 6 is formed on the outer surface of the inner pipe 5, and a cap 4 made of an elastic material is attached to the outer surface of the inner pipe 5 at a position distant in the axial direction from the partition 6. The main pipe 2, inner pipe 5, partition 6, and cap 4 form the side branch chambers 13a, 13b, 13c, 13d. Gateways 9a, 9b, 9c, 9d, which communicate to side branch chamber 13, are provided on the inner surface of the inner pipe 5 at a position near the partition 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an interference length variable muffler device inserted into a refrigerant pipe, an exhaust pipe, etc. of a vehicle air conditioner.

Background Art

[0002] In a vehicle air conditioner, mechanical noise of a compressor and noise due to cavitation of a refrigerant are transmitted from a pipe to an evaporator, and are transmitted from an air outlet to a driver, or are transmitted from a pipe to a driver via a vehicle body through a space in an engine room. For this reason, a muffler type silencer is provided in the pipe of the vehicle air conditioner, or an insertion type silencer is inserted. The muffler type silencer is large and heavy, and causes an increase in cost due to brazing. Therefore, in recent years, an insertion type silencer has been widely adopted.

[0003] For example, Patent Document 1 describes a device in which a spiral fin is provided on the outer surface of an inner pipe. This causes a phase difference due to the difference between the inner and outer flow paths, causing interference of sound and resulting in a sound absorption effect, but it is difficult to form and adjust the flow path length.

[0004] Patent Document 2 describes a muffler inserted into a tubular main body, in which a resonator chamber is provided between the muffler and the main body, and the flow path of the main body is connected to the resonator chamber via a connection channel. Patent Document 3 describes a sound absorption 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. All of these are resonance types, and since the resonance frequency is determined by the shape of the resonator, it is difficult to adjust according to the frequency of the sound source.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an interference length variable type silencer that is easy to mold and easy to adjust according to frequency. [Means for Solving the Problems]

[0007] As means for solving the above problems, the present invention provides (1) A silencer 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. In the silencer, On the outer surface of the inner pipe annular that contacts the inner surface of the main pipe A partition portion is formed, At a position axially away from the partition portion on the outer surface of the inner pipe, a cylindrical Cap made of an elastic body is attached, The side branch chamber is formed by the main pipe, the inner pipe, the partition portion, and the cap, An entrance and exit communicating with the side branch chamber is provided at a position near the partition portion on the inner surface of the inner pipe.

[0008] In the present invention, sound waves that enter the side branch from the entrance and exit provided on the inner surface of the inner pipe, are reflected by the cap, and return are out of phase with the sound waves in the inner pipe and interfere with each other to be silenced. Further, an entrance and exit communicating with the side branch chamber is provided on the inner surface of the inner pipe, and the side branch chamber branches from the inner pipe having a smaller cross-sectional area than the main pipe. For this reason, compared with the case where the side branch chamber branches from the main pipe, the cross-sectional area ratio before and after the branch can be increased, the transmission loss is increased, and the silencing effect can be enhanced.

[0009] (2) Preferably, the cap is fastened from the outside of the main pipe and is in close contact with the inner surface of the main pipe and the outer surface of the inner pipe.

[0010] (3) Preferably, an outer peripheral groove is formed on the outer periphery of the inner pipe corresponding to the portion where the cap is fastened.

[0011] (4) Preferably, a plurality of ribs extending in the axial direction are formed on the outer surface of the inner pipe, and a plurality of the side branch chambers are formed by the ribs.

[0012] (5) Preferably, a plurality of insertion pieces to be inserted between the adjacent ribs are formed on the cap.

[0013] (6) Preferably, the plurality of insertion pieces have different axial lengths.

[0014] (7) Preferably, the inner surface of the upstream end portion of the inner pipe is formed with a tapered surface that tapers toward the downstream side.

[0015] (8) Preferably, an outer cylinder extending in the axial direction is provided from the outer peripheral edge of the partition portion to the cap, and the side branch chamber is sealed by the outer cylinder.

Advantages of the Invention

[0016] According to the invention of claim 1, by simply changing the length of the cap attached to the inner pipe, the length of the side branch chamber, that is, the interference length, can be adjusted so as to have a sound deadening effect on the frequency of the sound source, and adjustment according to the frequency is easy. Further, before being inserted into the main pipe, it is open to the outside air, and since the other end is attached with a cap, the inner pipe can be easily formed.

[0017] According to the invention of claim 2, by simply fastening the cap from the outside of the main pipe, the cap can be brought into close contact with the inner surface of the main pipe and the outer surface of the inner pipe, leakage of the side branch chamber can be prevented, and the sound deadening effect can be maintained.

[0018] According to the invention of claim 3, since the outer peripheral groove is formed on the outer periphery of the inner tube corresponding to the portion where the cap is tightened, the cap can be firmly adhered to the outer surface of the inner tube.

[0019] According to the invention of claim 4, since a plurality of ribs extending in the axial direction are formed on the outer surface of the inner tube, and a plurality of side branch chambers are formed by the ribs, the side branch chambers are surrounded by the inner surface of the main pipe, the partition portion, the ribs, and the cap, so that the length and cross-sectional area from the entrance and exit of the side branch chamber to the inner end are simplified, and a silencing effect can be obtained at a frequency close to the target frequency.

[0020] According to the invention of claim 5, since a plurality of insertion pieces are formed on the cap, the inner ends of the plurality of side branch chambers can be formed only by attaching one cap to the inner tube.

[0021] According to the invention of claim 6, since the axial lengths of the plurality of insertion pieces of the cap are different, the lengths of the plurality of side branch chambers can be changed only by replacing the cap with different lengths of the insertion pieces.

[0022] According to the invention of claim 7, since the upstream end portion of the inner tube is formed with a tapered surface, the pressure loss when the fluid flows into the inner tube can be reduced.

[0023] According to the invention of claim 8, since the side branch chamber is sealed by the outer cylinder, leakage of the side branch chamber due to bending or vibration of the main pipe can be prevented, and the silencing effect can be maintained.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0026] <First Embodiment> FIG. 1 shows a silencing device 1 according to the first embodiment of the present invention. The silencing device 1 is provided in a pipe through which refrigerant of a vehicle air conditioner flows. Specifically, the silencing device 1 is inserted into a pipe (hereinafter referred to as the "main pipe") 2 on the outlet side of an evaporator or a compressor in a vehicle air conditioner including 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 be used. It is assumed that fluid (hereinafter referred to as "refrigerant") flows through the main pipe 2 from the upstream on the left side to the downstream on the right side in FIG. 1, but conversely, the refrigerant may flow from the right side to the left side.

[0027] As shown in FIG. 2, the silencing device 1 is roughly divided into a main body 3 and a cap 4.

[0028] The main body 3 includes an inner pipe 5, a partition portion 6 (see FIG. 1), a plurality of ribs 7a, 7b, 7c, 7d, and an outer cylinder 8, and is integrally formed of synthetic resin.

[0029] The inner tube 5 is tubular with an outer diameter smaller than the inner diameter of the main tube 2. At the upstream end of the inner tube 5, as shown in Fig. 3(a), inlets and outlets 9a, 9b, 9c, 9d of a plurality of side branch chambers 13a, 13b, 13c, 13d described later are formed. As shown in Fig. 1, at the downstream end of the inner tube 5, a thickened portion 10 with an inner surface enlarged toward the inner diameter side is formed, and an outer peripheral groove 10a is formed on the outer periphery of this thickened portion 10. At the upstream end of the inner surface of the thickened portion 10, a tapered surface 10b that expands in diameter toward the upstream side is formed, and at the downstream end of the inner surface of the thickened portion 10, a tapered surface 10c that expands in diameter toward the downstream side is formed.

[0030] As shown in Fig. 1, the partition portion 6 is formed at the upstream end of the inner tube 5 and is annular with an inner diameter substantially the same as the inner surface of the inner tube 5 and an outer diameter substantially the same as the inner surface of the main tube 2. On the inner surface of the partition portion 6, a tapered surface 6a that contracts in diameter toward the downstream side is formed.

[0031] As shown in Fig. 3(b), a plurality of ribs 7a, 7b, 7c, 7d protrude radially at circumferentially equally spaced positions on the outer peripheral surface of the inner tube 5, are integrally connected to the outer cylinder 8, and extend axially from the partition portion 6. The number of ribs 7 is arbitrary and may be absent. Also, the ribs 7 do not have to be equally spaced in the circumferential direction.

[0032] As shown in Fig. 1, the outer cylinder 8 is tubular with an outer diameter substantially the same as the inner diameter of the main tube 2 and is spaced a predetermined distance radially outward from the inner tube 5. The outer cylinder 8 extends axially from the outer peripheral edge of the partition portion 6 toward the downstream side to the upstream end of the thickened portion 10. The downstream end of the outer cylinder 8 is open, and as shown in Fig. 2, the outer peripheral groove 10a of the inner tube 5 is exposed.

[0033] As shown in Fig. 2, the cap 4 is formed with a plurality of axially extending slits 4a at the upstream end of a cylindrical member made of an elastic material such as rubber, thereby forming a cylindrical base portion 11 and a plurality of insertion pieces 12a, 12b, 12c, 12d extending axially from the base portion 11. The slits 4a have a width into which the ribs 7a, 7b, 7c, 7d can be inserted. The base portion 11 has an inner diameter substantially the same as the outer surface of the inner tube 5 and an outer diameter substantially the same as the outer surface of the outer cylinder 8. The plurality of insertion pieces 12a, 12b, 12c, 12d have a fan-shaped cross-section and are inserted between the inner tube 5 and the outer cylinder 8 and between adjacent ribs 7a, 7b, 7c, 7d, and have an inner diameter substantially the same as the outer surface of the inner tube 5 and an outer diameter substantially the same as the inner surface of the outer cylinder 8. The plurality of insertion pieces 12a, 12b, 12c, 12d have different axial lengths respectively.

[0034] As shown in Fig. 2, the silencing device 1 attaches the cap 4 to the inner tube 5 of the device body 3. At this time, the plurality of insertion pieces 12a, 12b, 12c, 12d of the cap 4 are inserted between the inner tube 5 and the outer cylinder 8 and between adjacent ribs 7a, 7b, 7c, 7d so that the base portion 11 is positioned at the thick portion 10 of the inner tube 5. Thereby, the cap 4 is attached at a position axially away from the partition portion 6 of the device body 3. Next, as shown in Fig. 1, the silencing device 1 is inserted into the main pipe 2, and at the position corresponding to the base portion 11 of the cap 4, the main pipe 2 is tightened from the outside to press the base portion 11 of the cap 4 against the thick portion 10 of the inner tube 5. Thereby, the outer surface of the base portion 11 of the cap 4 is pressed against the main pipe 2, and the inner surface bites into the outer peripheral groove 10a of the thick portion 10 of the inner tube 5, and the silencing device 1 is fixed inside the main pipe 2.

[0035] As shown in Fig. 3(b), in the silencing device 1, four side branch chambers 13a, 13b, 13c, and 13d are formed between the inner pipe 5 and the outer cylinder 8. That is, as shown in Fig. 4, a first side branch chamber 13a with a length l1 surrounded by the partition portion 6, the adjacent ribs 7a, 7b, and the insertion piece 12a of the cap 4, a second side branch chamber 13b with a length l2 surrounded by the partition portion 6, the adjacent ribs 7b, 7c, and the insertion piece 12b of the cap 4, a third side branch chamber 13c with a length l3 surrounded by the partition portion 6, the adjacent ribs 7c, 7d, and the insertion piece 12c of the cap 4, and a fourth side branch chamber 13d with a length l4 surrounded by the partition portion 6, the adjacent ribs 7d, 7a, and the insertion piece 12d of the cap 4 are formed.

[0036] The downstream end face of the cap 4 is located upstream of the downstream end face of the inner pipe 5. For this reason, an annular side branch chamber 13s with a length shorter than that of the side branch chambers 13a, 13b, 13c, and 13d is formed between the downstream end face of the cap 4, the inner pipe 5, and the outer cylinder 8. Note that the downstream end face of the cap 4 may be at the same position as the downstream end of the inner pipe 3, so that there is no side branch chamber.

[0037] Next, the operation of the silencing device 1 of the present embodiment will be described.

[0038] As shown in Fig. 4, the refrigerant flowing in the main pipe 2 flows into the inner pipe 5 at the upstream end of the silencing device 1 and flows out of the inner pipe 5 at the downstream end. The sound (mechanical noise of the compressor and noise due to refrigerant cavitation) generated from a sound source (not shown) on the upstream side of the silencing device 1 propagates downstream together with the refrigerant and enters the inner pipe 5 of the silencing device 1. Note that the sound source may be on the downstream side, and in that case, a silencing effect will occur on the upstream side.

[0039] The sound waves that have propagated inside the inner tube 5 enter the four side branch chambers 13a, 13b, 13c, and 13d from the entrances and exits 9a, 9b, 9c, and 9d provided on the inner surface of the inner tube 5, and are reflected at the far ends of the respective side branch chambers 13a, 13b, 13c, and 13d, that is, at the tips of the insertion pieces 12a, 12b, 12c, and 12d of the cap 4, and return to the entrances and exits 9a, 9b, 9c, and 9d. Here, they interfere with the sound waves in the inner tube 5 in antiphase and are silenced.

[0040] Here, assuming that the cross-sectional area of the inner tube 5 is S, the cross-sectional area of the side branch chamber 13 is Ss, the length of the side branch chamber 13 is l, the frequency of the sound wave is f, and the speed of sound is c, the transmission loss TL in the silencer 1 is represented by Equation (1). Note that the length l of the side branch chamber 13 is the axial distance from the partition portion 6 to the insertion portion 12 of the cap 4, as shown in FIG. 4.

Equation

[0041] In the silencer 1 of the present embodiment, entrances and exits 9a, 9b, 9c, and 9d that communicate with the side branch chambers 13a, 13b, 13c, and 13d are provided on the inner surface of the inner tube 5, and the side branch chambers 13a, 13b, 13c, and 13d branch off from the inner tube 5 having a smaller cross-sectional area than the main pipe 2.

[0042] FIG. 5 shows a conventional-structured silencer 100 for comparison with the present invention. In the conventional silencer 100 of FIG. 5, an intermediate partition plate 106 is provided in the middle of the inner tube 105, and tubular side branch chambers 113a and 113b are formed between the main pipe 102 and the inner tube 105, and the entrances and exits 109a and 109b of the respective side branch chambers 113a and 113b are provided at the upstream end and the downstream end of the inner tube 105. The transmission loss TL of the silencer 100 can be obtained by applying Equation (1) with the cross-sectional area of the main pipe 102 as S instead of the cross-sectional area of the inner tube 105.

[0043] In the silencing device 1 of the present embodiment shown in FIG. 4, each of the side branch chambers 13a, 13b, 13c, 13d branches from the inner pipe 5. Therefore, compared with the conventional silencing device 100 shown in FIG. 5, in which the side branch chambers 113a, 113b branch from the main pipe 102, the cross-sectional area ratio Ss / S before and after the branch can be increased, the transmission loss TL can be increased, and the silencing effect can be enhanced.

[0044] Note that the side branch chamber 13s between the downstream end face of the cap 4 and the downstream end face of the inner pipe 5 has a conventional structure, but the silencing effect also occurs in this side branch chamber 13s. The length of the side branch chamber 13s can be adjusted only by changing the length of the base portion 11 of the cap 4.

[0045] In the silencing device 1 of the present embodiment, by simply changing the lengths of the insertion pieces 12a, 12b, 12c, 12d of the cap 4 attached to the inner pipe 5, the lengths of the side branch chambers 13a, 13b, 13c, 13d, that is, the interference lengths, can be adjusted so as to achieve a silencing effect with respect to the frequency of the sound source, and adjustment according to the frequency is easy. Further, before being inserted into the main pipe 2, it is open to the outside air, and since the other end is for attaching the cap 4, the inner pipe 5 can be easily formed.

[0046] Also, by simply tightening the cap 4 from the outside of the main pipe 2, the cap 4 can be brought into close contact with the inner surface of the main pipe 2 and the outer surface of the inner pipe 5, leakage of the side branch chambers 13a, 13b, 13c, 13d can be prevented, and the silencing effect can be maintained.

[0047] Since the outer peripheral groove 10a is formed on the outer periphery of the inner pipe 5 corresponding to the portion where the cap 4 is tightened, the cap 4 can be firmly brought into close contact with the outer surface of the inner pipe 5.

[0048] A plurality of ribs 7a, 7b, 7c, 7d extending in the axial direction are formed on the outer surface of the inner tube 5, and a plurality of side branch chambers 13a, 13b, 13c, 13d are formed by these ribs 7a, 7b, 7c, 7d. Therefore, the side branch chambers 13a, 13b, 13c, 13d are surrounded by the inner surface of the main pipe 2, the partition portion 6, the ribs 7a, 7b, 7c, 7d, and the cap 4, so that the lengths and cross-sectional areas from the entrances and exits 9a, 9b, 9c, 9d to the inner ends of the side branch chambers 13a, 13b, 13c, 13d are simplified, and a sound absorption effect can be obtained at a frequency close to the target frequency.

[0049] Since a plurality of insertion pieces 12a, 12b, 12c, 12d are formed on the cap 4, the inner ends of the plurality of side branch chambers 13a, 13b, 13c, 13d can be formed only by attaching one cap 4 to the inner tube 5.

[0050] Since the axial lengths of the plurality of insertion pieces 12a, 12b, 12c, 12d of the cap 4 are different, the lengths of the plurality of side branch chambers 13a, 13b, 13c, 13d can be changed only by replacing the cap 4 with different lengths of the insertion pieces 12a, 12b, 12c, 12d.

[0051] Since the upstream end of the inner tube 5 is formed by the tapered surface 6a, the pressure loss when the fluid flows into the inner tube 5 can be reduced.

[0052] Since the side branch chambers 13a, 13b, 13c, 13d are sealed by the outer cylinder 8, leakage of the side branch chambers 13a, 13b, 13c, 13d due to bending or vibration of the main pipe 2 can be prevented, and the sound absorption effect can be maintained.

[0053] <Second Embodiment> FIG. 6 shows a sound absorption device 20 according to the second embodiment of the present invention.

[0054] The silencing device 20 according to the second embodiment is substantially the same as the silencing device 1 of the first embodiment in FIG. 1 except that the outer cylinder 8 of the device main body 3 is absent. For corresponding parts, the same reference numerals are used and the description thereof is omitted.

[0055] Since the silencing device 20 according to the second embodiment has no outer cylinder, its structure is simple, the device main body 3 can be easily molded, and it can be easily inserted into the main pipe 2. When the silencing device 20 is inserted into the main pipe 2, it is preferable to use a sealing material or an adhesive so that the outer surfaces of the partition portion 6 and the rib 7 of the silencing device 20 are in close contact with the inner surface of the main pipe 2.

[0056] <Third Embodiment> FIG. 7 shows a silencing device 30 according to the third embodiment of the present invention.

[0057] The silencing device 30 according to the third embodiment is provided with two device main bodies 3a and 3b in the silencing device 1 of the first embodiment in FIG. 1. These two device main bodies 3a and 3b are opposed to each other on the side of the thick wall portion 10 and are connected by an adhesive, screws, or the like. The cap 4 is formed with a plurality of insertion pieces 12a, 12b, 12c, 12d and 12e, 12f, 12g, 12h having different lengths on both sides of the base portion 11. As a result, in addition to the plurality of side branch chambers 13a, 13b, 13c, 13d on the upstream side, a plurality of side branch chambers 13e, 13f, 13g, 13h on the downstream side are formed in the silencing device 30 according to the third embodiment. By adjusting the lengths of the eight side branch chambers 13a, 13b, 13c, 13d and 13e, 13f, 13g, 13h according to the frequency of the sound source, the range of frequencies that produce a silencing effect can be widened.

[0058] Note that at least one of the plurality of side branch chambers 13e, 13f, 13g, 13h on the downstream side of the silencing device 30 according to the third embodiment may be used as a resonance chamber. By making the resonance frequency of this resonance chamber coincide with the frequency of the incident sound, a silencing effect for a specific range of frequencies can be achieved, and in combination with the silencing effect of the side branch chambers 13a, 13b, 13c, 13d, the range of frequencies that produce a silencing effect can be widened.

[0059] The present invention is not limited to the above-described embodiment, and can be modified and changed within the scope of the gist of the invention described 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 appropriately changed. Further, instead of being integrally formed as in the above embodiment, the cap may be formed by being divided into a plurality in the circumferential direction.

Explanation of Signs

[0060] 1... Sound silencer (first embodiment) 2... Main pipe 3, 3a, 3b... Apparatus main body 4... Cap 5... Inner pipe 6... Partition part 7a, 7b, 7c, 7d... Ribs 8... Outer cylinder 9a, 9b, 9c, 9d... Inlet / outlet 10... Thick part 11... Base part 12a, 12b, 12c, 12d... Insertion pieces 13a, 13b, 13c, 13d, 13s... Side branch chambers 20... Sound silencer (second embodiment) 30... Sound silencer (third embodiment)

Claims

1. A silencing device inserted into a main pipe through which a fluid flows, the silencing device comprising an inner pipe and a side branch chamber formed between the main pipe and the inner pipe, An annular partition portion that contacts the inner surface of the main pipe is formed on the outer surface of the inner pipe, A cylindrical cap made of an elastic body is attached to a position axially away from the partition portion on the outer surface of the inner pipe, The side branch chamber is formed by the main pipe, the inner pipe, the partition portion, and the cap, An entrance and exit communicating with the side branch chamber is provided at a position on the inner surface of the inner pipe close to the partition portion. The silencing device is characterized by this.

2. The silencing device according to claim 1, wherein the cap is tightened from the outside of the main pipe and is in close contact with the inner surface of the main pipe and the outer surface of the inner pipe.

3. The silencing device according to claim 2, wherein an outer peripheral groove is formed on the outer periphery of the inner pipe corresponding to the position where the cap is tightened.

4. The silencing device according to any one of claims 1 to 3, wherein a plurality of ribs extending axially are formed on the outer surface of the inner pipe, and a plurality of the side branch chambers are formed by the ribs.

5. The silencing device according to claim 4, wherein a plurality of insertion pieces inserted between adjacent ribs are formed on the cap.

6. The silencing device according to claim 5, wherein the plurality of insertion pieces have different axial lengths.

7. The silencing device according to any one of claims 1 to 6, wherein the inner surface of the upstream end of the inner pipe is formed with a tapered surface that tapers toward the downstream side.

8. An outer cylinder extending in the axial direction is provided from the outer peripheral edge of the partition portion of the inner tube to the cap, and the side branch chamber is sealed by the outer cylinder. The silencing device according to any one of claims 1 to 7, characterized in that.

Images