Silencer

Abstract

To enable suppression of air column resonance sound while suppressing generation of airflow sound.SOLUTION: Muffler pipes (24, 26, 28) of a silencer 10 have: one end parts (26A, 24A) that opens into a body part 20 and constitutes an end part of an acoustic circuit; and a communication part 70 that is composed of a plurality of communication holes 72 distributed in a longitudinal direction N of the muffler pipes (24, 26, 28), is provided on a peripheral surface (26C), and allows the flow of exhaust gas G that inflows not through the one end parts (26A, 24A). The communication part 70 is arranged only in a half range on an upstream side in the flow of the exhaust gas G out of a total length L of a circulation low path 74 between the one end parts (26A, 24A) and an exhaust port 30. The position where the communication part 70 is arranged includes a position of an antinode 100B of a secondary resonant wave 100 where two antinodes 100B are formed in the circulation flow path 74.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a silencer. [Background technology]

[0002] Patent Document 1 discloses an engine muffler. The muffler discharges exhaust gas introduced into the muffler body by passing it from one end to the other end of an exhaust pipe. The exhaust gas introduced into the expansion chamber of the muffler body is introduced into the exhaust pipe through small through holes formed in the side of the exhaust pipe and then discharged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-189007 Summary of the Invention [Problem to be solved by the invention]

[0004] In the engine muffler of Patent Document 1, the small through holes in the exhaust pipe have the effect of reducing air column resonance noise generated in the exhaust pipe.

[0005] If the area where the small through holes are formed is narrow, it may not be possible to reduce the air column resonance noise as intended. On the other hand, if the area where the small through holes are formed is widened, the number of small through holes increases, which may increase the air flow noise generated inside the exhaust pipe.

[0006] The present invention has been made in consideration of the above problems, and has an object to make it possible to suppress air column resonance noise while suppressing the generation of air flow noise. [Means for solving the problem]

[0007] According to one aspect of the present invention, a silencer comprises a main body, an inlet pipe that guides exhaust gas introduced into the main body, and a muffler pipe that includes at least one pipe, discharges exhaust gas within the main body from an exhaust port that opens to the outside of the main body, and constitutes an acoustic circuit; the muffler pipe has one end that opens into the inside of the main body and constitutes an end of the acoustic circuit, and a communication portion that is composed of a plurality of communication holes that are distributed in the longitudinal direction of the muffler pipe and is provided on the circumferential surface to allow the flow of exhaust gas that flows in without passing through the one end, the communication portion being arranged only in the range of the upstream half of the total length of the flow path between the one end and the exhaust port, and the position where the communication portion is arranged includes the position of the antinode of a secondary resonance wave that forms two antinodes in the flow path. [Effects of the Invention]

[0008] In the above-described embodiment, a communication portion is provided on the circumferential surface of the muffler pipe to allow the exhaust gas to flow in. The communication portion is formed only within the upstream half of the total length of the exhaust gas flow path, and the communication portion is disposed at a location including the position of the antinode of the secondary resonance wave, which forms two antinodes in the exhaust gas flow path.

[0009] Therefore, the silencer can efficiently suppress the air column resonance sound of the secondary resonance wave generated in the flow path, compared to when the communication part is formed at a location other than the antinode position of the resonance wave generated in the flow path.

[0010] In addition, the silencer can efficiently suppress airflow noise that may occur within the muffler pipe, compared to when the range of the communication section is expanded regardless of the position of the antinode of the resonant wave generated in the flow path.

[0011] Therefore, the silencer can suppress the generation of airflow noise while suppressing air column resonance noise. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a cross-sectional view showing a silencer according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram used to explain the communication portion of the outlet pipe. [Figure 3] FIG. 3 is an explanatory diagram used to explain the relationship between the communication part of the outlet pipe and the primary resonant wave. [Figure 4] FIG. 4 is an explanatory diagram used to explain the relationship between the communicating portion of the outlet pipe and the secondary resonant wave. [Figure 5] FIG. 5 is an explanatory diagram used to explain the relationship between the communicating portion of the outlet pipe and the third-order resonance wave. [Figure 6] FIG. 6 is a view showing a main part of an outlet pipe of a silencer according to a first modified example. [Figure 7] FIG. 7 is a side view showing a main part of an outlet pipe of a silencer according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a silencer 10 according to an embodiment of the present invention will be described with reference to the drawings.

[0014] First, the overall configuration of a silencer 10 will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing a silencer 10 according to an embodiment of the present invention.

[0015] As shown in Fig. 1, the silencer 10 is a device that is provided in, for example, the exhaust path of an automobile to reduce the noise output from the engine. Note that, in this embodiment, an example will be described in which the silencer 10 is used in the exhaust path of an automobile, but the use of the silencer 10 is not limited to this. The silencer 10 may also be used by being connected to, for example, a pipe (duct) in a factory.

[0016] The silencer 10 includes a main body 20 and an inlet pipe 22 that guides exhaust gas G introduced into the main body 20. The silencer 10 also includes a muffler pipe (24, 26, 28) that includes at least one pipe (24, 26, 28) and that discharges the exhaust gas G in the main body 20 from an outlet 30 that opens to the outside of the main body 20 and that forms an acoustic circuit.

[0017] The muffler pipe (24, 26, 28) is configured by a combination of a tail pipe 28 and an outlet pipe 26, or a combination of a connecting pipe 24 and a tail pipe 28, the outlet pipe 26 communicating with the connecting pipe 24 via a fifth expansion chamber 58. The tail pipe 28 and the outlet pipe 26 may be integral with each other.

[0018] The tail pipe 28 has an exhaust port 30 that opens to the outside of the main body 20. The tail pipe 28 is connected to the outlet pipe 26 that constitutes the muffler pipe, and exhaust gas G that flows in from the outlet pipe 26 is discharged from the exhaust port 30 to the outside.

[0019] This silencer 10 has a configuration for suppressing generated air column resonance sounds. When suppressing generated air column resonance sounds, the generated air column resonance sounds are measured and the resonance waves to be reduced are narrowed down in advance. Then, the acoustic circuit in which the resonance waves to be reduced are formed is specified, and the silencer 10 is configured to reduce secondary resonance waves 100 generated in that acoustic circuit.

[0020] In this embodiment, an example will be described in which the muffler pipe that constitutes the acoustic circuit is made up of an outlet pipe 26 and a tail pipe 28.

[0021] (Main body) The main body 20 has a cylindrical portion 34 formed in a flat cylindrical shape, a one-end end plate 36 provided at one end of the cylindrical portion 34 to close an opening on the one end side, and an other-end end plate 38 provided at the other end of the cylindrical portion 34 to close an opening on the other end side. The cylindrical portion 34 of the main body 20 is connected to the inlet pipe 22 described above, and exhaust gas G discharged from the engine is introduced into the main body 20 via the inlet pipe 22.

[0022] The main body 20 is provided with a first baffle plate 40, a second baffle plate 42, a third baffle plate 44, and a fourth baffle plate 46 spaced apart in the longitudinal direction of the main body 20. A first expansion chamber 50, a second expansion chamber 52, a third expansion chamber 54, a fourth expansion chamber 56, and a fifth expansion chamber 58 are formed inside the main body 20 by the baffle plates 40, 42, 44, and 46.

[0023] The first baffle plate 40, the second baffle plate 42, and the third baffle plate 44 have through holes 60 that connect adjacent chambers (50, 52, 54, 56). The fourth baffle plate 46 does not have a through hole 60, and the fourth expansion chamber 56 and the fifth expansion chamber 58 do not communicate with each other.

[0024] As a result, the main body 20 has a plurality of chambers (50, 52, 54, 56) separated by baffle plates (40, 42, 44) having through holes 60 that allow the exhaust gas G to pass through.

[0025] The tip of the inlet pipe 22 is inserted into the third expansion chamber 54. An introduction port 64 that opens at the tip of the inlet pipe 22 opens into the third expansion chamber 54.

[0026] The aforementioned connecting pipe 24 is provided inside the main body 20. The connecting pipe 24 is fixed to each of the first baffle plate 40, the second baffle plate 42, the third baffle plate 44, and the fourth baffle plate 46 in a state where the connecting pipe 24 is inserted through each of the baffle plates 40, 42, 44, and 46.

[0027] One end opening 24A of the connecting pipe 24 opens into the first expansion chamber 50. The other end opening 24B of the connecting pipe 24 opens into the fifth expansion chamber 58.

[0028] The main body 20 is also provided with the aforementioned outlet pipe 26. The outlet pipe 26 passes through the one-end end plate 36, the first baffle plate 40, the second baffle plate 42, the third baffle plate 44, and the fourth baffle plate 46. The outlet pipe 26 is fixed to the one-end end plate 36 and each of the baffle plates 40, 42, 44, and 46.

[0029] One end 26A of the outlet pipe 26 opens into the fifth expansion chamber 58. The other end 26B of the outlet pipe 26, which is arranged outside the main body 20, is connected to the tail pipe 28.

[0030] Exhaust gas G discharged from the engine is introduced into the third expansion chamber 54 via the inlet pipe 22. The exhaust gas G introduced into the third expansion chamber 54 flows into the second expansion chamber 52 via the through-holes 60 in the second baffle plate 42. The exhaust gas G flowing into the second expansion chamber 52 flows into the first expansion chamber 50 via the through-holes 60 in the first baffle plate 40.

[0031] The exhaust gas G that has flowed into the first expansion chamber 50 flows into the connecting pipe 24 from one end opening 24A of the connecting pipe 24. The exhaust gas G that has flowed into the connecting pipe 24 flows into the fifth expansion chamber 58 from the other end opening 24B. The exhaust gas G that has flowed into the fifth expansion chamber 58 flows into the outlet pipe 26 from one end 26A of the outlet pipe 26. The exhaust gas G that has flowed into the outlet pipe 26 is discharged to the outside via the tail pipe 28.

[0032] (Outlet pipe) The outlet pipe 26 has one end 26A that opens inside the fifth expansion chamber 58 of the main body 20, the other end 26B to which the tail pipe 28 is connected, and a communication portion 70 provided on the peripheral surface 26C that allows the flow of exhaust gas G that flows in without passing through the one end 26A.

[0033] The communication part 70 is disposed only in the range of the upstream half of the total length L of the flow path 74 between the one end 26A of the outlet pipe 26 and the exhaust port 30 of the tail pipe 28 in the flow of the exhaust gas G. The position where the communication part 70 is disposed includes the position of the antinode 100B of the secondary resonant wave 100, where two antinodes are formed in the flow path 74 (see FIG. 4).

[0034] A portion of the exhaust gas G introduced from the inlet pipe 22 into the third expansion chamber 54 flows into the fourth expansion chamber 56 through the through-holes 60 in the third baffle plate 44. The exhaust gas G that has flowed into the fourth expansion chamber 56 flows into the outlet pipe 26 through the communication portion 70 provided on the circumferential surface 26C of the outlet pipe 26. The exhaust gas G that has flowed into the outlet pipe 26 merges with the exhaust gas G flowing inside the outlet pipe.

[0035] Standing waves generated within the flow path 74 have high sound pressure levels at their antinodes. If a communication hole 72 is provided in the outlet pipe 26 at a location where an antinode with a high sound pressure level is located, the sound pressure at the antinode of the standing wave will escape to the outside through the communication hole 72. This attenuates the standing wave and reduces exhaust noise.

[0036] The communication portion 70 of the outlet pipe 26 will be specifically described with reference to FIGS. 2 to 5. FIG.

[0037] Fig. 2 is an explanatory diagram used to explain the communication part 70 of the outlet pipe 26. Fig. 3 is an explanatory diagram used to explain the relationship between the communication part 70 of the outlet pipe 26 and a primary resonant wave 90. Fig. 4 is an explanatory diagram used to explain the relationship between the communication part 70 of the outlet pipe 26 and a secondary resonant wave 100. Fig. 5 is an explanatory diagram used to explain the relationship between the communication part 70 of the outlet pipe 26 and a tertiary resonant wave 110.

[0038] 2, the communication section 70 is composed of a plurality of communication holes 72 that are dispersed in the longitudinal direction N and circumferential direction C of the outlet pipe 26. The communication holes 72 are arranged spirally along the circumferential surface 26C of the outlet pipe 26.

[0039] In the spirally arranged communicating holes 72, the communicating holes 72 arranged in the circumferential direction C of the outlet pipe 26 are arranged at a constant circumferential interval SK. The communicating holes 72 arranged in the longitudinal direction N of the outlet pipe 26 are arranged at a constant longitudinal interval NK. As a result, the communicating section 70 is configured so that the arrangement interval (pitch) between adjacent communicating holes 72 is uniform. Note that the intervals (SK, NK) between the communicating holes 72 are determined by the distance between the centers of the communicating holes 72.

[0040] As shown in FIG. 1, the inlet port 64 of the inlet pipe 22 opens into the third expansion chamber 54, while the communication portion 70 formed by the communication hole 72 is disposed in the fourth expansion chamber 56.

[0041] As a result, the inlet pipe 22 has an introduction port 64 that opens into the main body 20, and the introduction port 64 is located in a position that does not face the communication portion 70. Furthermore, the introduction port 64 of the inlet pipe 22 communicates with the fourth expansion chamber 56, which is the chamber in which the communication portion 70 is located, via the through-hole 60 of the third baffle plate 44, and the introduction port 64 is located in the third expansion chamber 54, which is the chamber in which the communication portion 70 is not located.

[0042] As shown in Figures 3 to 5, the communication section 70 is provided in an upstream range 80 of one half of the total length L of the flow path 74 on the one end 26A side of the outlet pipe 26, which is the upstream side in the flow of exhaust gas G.

[0043] That is, when a standing wave is formed in the flow path 74 consisting of the outlet pipe 26 and the tail pipe 28 by the sound output from the engine, air column resonance noise occurs.

[0044] If the standing waves that generate this air column resonance sound are referred to as resonance waves, the resonance waves that affect the exhaust sound include a primary resonance wave 90, a secondary resonance wave 100, and a tertiary resonance wave 110.

[0045] 3, the primary resonant wave 90 is composed of a standing wave in which nodes 90N are formed at one end 26A of the outlet pipe 26 and the outlet 30 of the tail pipe 28, and one antinode 90B is formed in the center of the flow path 74. The antinode 90B of the primary resonant wave 90 is formed at a position approximately half the total length L of the flow path 74.

[0046] As shown in FIG. 4, the secondary resonant wave 100 is composed of a standing wave in which nodes 100N are formed at one end 26A of the outlet pipe 26, the outlet 30 of the tail pipe 28, and the center of the flow path 74, and two antinodes 100B are formed in the flow path 74.

[0047] As shown in Figure 5, the third-order resonant wave 110 is composed of a standing wave in which nodes 110N are formed at one end 26A of the outlet pipe 26, the outlet 30 of the tail pipe 28, and two locations in the flow path 74, and three antinodes 110B are formed in the flow path 74.

[0048] Here, antinodes 90B, 100B, and 110B of the standing wave indicate positions where the amplitude of the standing wave is greatest, and nodes 90N, 100N, and 110N of the standing wave indicate positions where the amplitude of the standing wave is "0."

[0049] If the total length of the flow path 74 from one end 26A of the outlet pipe 26 to the outlet port 30 of the tail pipe 28 is "L", the communication section 70 is provided in an upstream range 80 that is 1 / 2L from the one end 26A of the outlet pipe 26.

[0050] The communication section 70 provided in the upstream range 80 has a plurality of communication holes 72 that are distributed in the longitudinal direction N of the outlet pipe 26, including the position of the antinode 100B of the secondary resonant wave 100. The communication holes 72 that make up the communication section 70 have a communication hole 72(A) that is arranged at the position of the antinode 100B formed at the most upstream position of the secondary resonant wave 100 (see FIG. 4).

[0051] Furthermore, the communication holes 72 constituting the communication section 70 have a communication hole 72(B) arranged at the position of the antinode 110B formed at the most upstream position of the tertiary resonant wave 110 (see FIG. 5). As a result, the communication holes 72 are arranged so as to further include the position of the antinode 110B formed at the most upstream position of the tertiary resonant wave 110.

[0052] It is desirable that a portion of the communication hole 72 constituting the communication portion 70 is disposed in proximity to the antinode 90B of the primary resonant wave 90.

[0053] (glass wool chamber) 1, a plurality of small holes 140 are formed in the peripheral surface 26C of the outlet pipe 26 downstream of the communication portion 70. Each small hole 140 opens into a glass wool chamber 142 that surrounds the outlet pipe 26.

[0054] The glass wool chamber 142 has a surrounding wall 146 that surrounds the outlet pipe 26, and glass wool 148 provided inside the surrounding wall 146. The glass wool chamber 142 has a sound-absorbing function in which the glass wool 148 absorbs the airflow noise generated in the outlet pipe 26.

[0055] The surrounding wall 146 of the glass wool chamber 142 forms an enclosed space inside and prevents the inflow of exhaust gas G from each of the expansion chambers 50, 52, 54. As a result, the small holes 140 in the outlet pipe 26 do not allow the exhaust gas G from each of the expansion chambers 50, 52, 54 to flow into the outlet pipe 26.

[0056] In this embodiment, the muffler pipe that constitutes the acoustic circuit is configured by the outlet pipe 26 and the tail pipe 28, but the present embodiment is not limited to this.

[0057] For example, if the fifth expansion chamber 58 is sufficiently small, the muffler pipe that constitutes the acoustic circuit may be composed of the connecting pipe 24, the outlet pipe 26, and the tail pipe 28. In this case, the range from the one end opening 24A as one end of the connecting pipe 24 to the exhaust port 30 of the tail pipe 28 is defined as the flow path 74. The positions of the antinodes 90B, 100B, 110B of the resonant waves 90, 100, 110 are determined based on the total length L of the flow path 74 from the one end opening 24A of the connecting pipe 24 to the exhaust port 30 of the tail pipe 28, and the positions of the communicating portion 70 and the communicating hole 72 are also set.

[0058] (Action and effect) According to the above embodiment, the following effects are achieved.

[0059] The silencer 10 of this embodiment includes a main body 20 and an inlet pipe 22 that guides exhaust gas G introduced into the main body 20. The silencer 10 includes a muffler pipe (24, 26, 28) that includes at least one pipe (24, 26, 28) and discharges exhaust gas G from the main body 20 through an outlet 30 that opens to the outside of the main body 20 and that constitutes an acoustic circuit. The muffler pipe (24, 26, 28) has one end (26A, 24A) that opens into the inside of the main body 20 and constitutes an end of the acoustic circuit, and a communication part 70 that is provided on the circumferential surface (26C) and that is composed of a plurality of communication holes 72 that are distributed in the longitudinal direction N of the muffler pipe (24, 26, 28) and that allows the flow of exhaust gas G that flows in without passing through the one end (26A, 24A). The communication part 70 is arranged only in the range of the upstream half of the total length L of the flow path 74 between one end (26A, 24A) and the exhaust port 30 in the flow of the exhaust gas G. The position where the communication part 70 is arranged includes the position of the antinode 100B of the secondary resonant wave 100 where two antinodes 100B are formed in the flow path 74.

[0060] In this configuration, a communication section 70 that allows the inflow of exhaust gas G is provided on the peripheral surface 26C of the outlet pipe 26 that constitutes the muffler pipe. The communication section 70 is formed only in the range of the upstream half of the total length L of the flow path 74 in the flow of the exhaust gas G, and the communication section 70 is disposed in a location that includes the position of the antinode 100B of the secondary resonance wave 100 that forms two antinodes 100B in the flow path 74.

[0061] Therefore, the silencer 10 can efficiently suppress the air column resonance sound of the secondary resonance wave 100 generated in the flow path 74, compared to when the communication portion 70 is formed at a location different from the position of the antinode 100B of the resonance wave generated in the flow path 74.

[0062] Furthermore, the silencer 10 can efficiently suppress the airflow noise that may occur within the muffler pipe (26, 28) compared to when the range of the communication section 70 is expanded regardless of the position of the antinode 100B of the resonance wave generated in the flow path 74.

[0063] Therefore, the silencer 10 can suppress the generation of airflow noise while suppressing air column resonance noise.

[0064] In this embodiment, the communication section 70 is composed of a plurality of communication holes 72. Therefore, by adjusting the arrangement of the communication holes 72, it is possible to suppress not only the air column resonance sound of the secondary resonant wave 100 but also the air column resonance sound of other resonant waves.

[0065] Furthermore, in this embodiment, the communication part 70 is provided upstream of the glass wool chamber 142, which has a sound-absorbing function, in the flow direction of the exhaust gas G. Therefore, it is possible to reduce airflow noise that may be generated by the inflow of the exhaust gas G from the communication part 70 by the glass wool chamber 142 located downstream.

[0066] Furthermore, in the silencer 10 of this embodiment, the communicating portion 70 is formed in a range extending from one side to the other side in the longitudinal direction N, with the position of the antinode 100B of the secondary resonant wave 100 as the boundary, and at a position that does not include the node 100N of the secondary resonant wave 100.

[0067] According to this configuration, it is possible to reduce the secondary resonant waves 100 while restricting the area of ​​the communication portion 70.

[0068] Furthermore, the communication holes 72 that make up the communication section 70 are disposed dispersedly in the longitudinal direction N of the outlet pipe 26 that makes up the muffler pipe. Therefore, compared to a case where a large amount of exhaust gas G flows in through multiple communication holes 72 formed at the same position in the longitudinal direction N, causing a sudden change in flow velocity within the outlet pipe 26, it is possible to suppress sudden fluctuations in flow velocity, thereby suppressing the generation of turbulent vortices and reducing the generated airflow noise. Furthermore, suppressing turbulence in the flow of exhaust gas G that may occur within the outlet pipe 26 makes it possible to reduce pressure loss.

[0069] Furthermore, in the silencer 10 of this embodiment, the communication holes 72 are arranged so as to further include the position of the antinode 110B formed at the most upstream of the tertiary resonance wave 110 in which three antinodes 110B are formed in the flow path 74.

[0070] According to this configuration, the silencer 10 can efficiently suppress the air column resonance sound of the tertiary resonance wave 110 generated in the flow path 74.

[0071] Furthermore, in the silencer 10 of this embodiment, the communication holes 72 are arranged dispersedly in the circumferential direction C of the outlet pipe 26 that constitutes the muffler pipe.

[0072] With this configuration, silencer 10 can distribute the points at which exhaust gas G flows into outlet pipe 26 in circumferential direction C. This allows exhaust gas G flowing in from communication holes 72 to smoothly merge with exhaust gas G inside outlet pipe 26, thereby suppressing the generation of turbulence and reducing possible airflow noise.

[0073] In the silencer 10 of this embodiment, the communication holes 72 are arranged in a spiral shape on the circumferential surface 26C of the outlet pipe 26 that constitutes the muffler pipe.

[0074] Furthermore, in the silencer 10 of this embodiment, the spacing between adjacent communication holes 72 in the communication portion 70 is uniform.

[0075] These configurations allow the exhaust gas G flowing in from the communication hole 72 to merge smoothly with the exhaust gas G in the outlet pipe 26, thereby further suppressing the generation of turbulence and further reducing the generated airflow noise.

[0076] Furthermore, in the silencer 10 of this embodiment, the inlet pipe 22 has an introduction port 64 that opens into the main body portion 20 , and the introduction port 64 is disposed at a position that does not face the communication portion 70 .

[0077] Furthermore, in the silencer 10 of this embodiment, the main body 20 has a plurality of chambers (50, 52, 54, 56) separated by baffle plates (40, 42, 44) having through holes 60 that allow the passage of exhaust gas G. The inlet 64 is connected via the through holes 60 to the chamber (56) in which the communication portion 70 is located, and is arranged in the chamber (54) in which the communication portion 70 is not located.

[0078] These configurations make it possible to suppress the airflow noise that leaks to the outside, compared to when the airflow noise generated at the inlet 64 of the inlet pipe 22 is output to the outside without being reduced by the reduction circuit formed by each expansion chamber 50, 52, 54, 56, and 58, for example.

[0079] In the present embodiment, the communicating portion 70 is configured by the communicating holes 72 arranged in a spiral shape along the circumferential surface 26C of the outlet pipe 26, but the communicating portion 70 is not limited to this configuration. The communicating portion 70 may be configured, for example, as in the following first and second modified examples.

[0080] (First Modification) FIG. 6 is a view showing a main part of the outlet pipe 26 of a silencer 200 according to a first modified example.

[0081] 6, outlet pipes 26 constituting the muffler pipe of silencer 200 according to the first modified example are arranged, for example, in first row 210 and second row 212, offset in circumferential direction C of outlet pipe 26. Furthermore, communicating holes 72 are arranged in first row 210 and second row 212 at equal intervals in length direction N of outlet pipe 26. Note that the intervals between communicating holes 72 arranged in length direction N are determined by the intervals between the centers of communicating holes 72.

[0082] In the outlet pipe 26, the communication holes 72 arranged in a first row 210 and the communication holes 72 arranged in a second row 212 are alternately arranged in the length direction N.

[0083] As a result, the communication portion 70 is composed of a plurality of communication holes 72 that are arranged in a dispersed manner in the length direction N and the circumferential direction C of the outlet pipe 26.

[0084] The silencer 200 according to the first modification provides the same effects as the above-described embodiment with respect to the parts that are the same as or equivalent to those of the above-described embodiment.

[0085] (Second Modification) FIG. 7 is a side view showing a main part of the outlet pipe 26 of a silencer 300 according to a second modified example.

[0086] 7, in outlet pipe 26 constituting the muffler pipe of silencer 300 according to the second modified example, each of communication holes 72 constituting communication section 70 is formed randomly. Adjacent communication holes 72 are spaced apart at equal intervals in length direction N of outlet pipe 26 and are arranged at positions offset in circumferential direction C. The interval between each of communication holes 72 arranged in length direction N is determined by the distance between the centers of each of communication holes 72.

[0087] As a result, the communication portion 70 is composed of a plurality of communication holes 72 that are arranged in a dispersed manner in the length direction N and the circumferential direction C of the outlet pipe 26.

[0088] The silencer 300 according to the second modification provides the same effects as the above-described embodiment with respect to the parts that are the same as or equivalent to those of the above-described embodiment.

[0089] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0090] 10, 200, 300 silencer 20 Main body 22 Inlet pipe 24 Connecting pipe (muffler pipe) 26 Outlet pipe (muffler pipe) 26A One end 26B Other end 26C circumferential surface 28 Tail pipe (muffler pipe) 30 Outlet 40 First baffle plate 42 Second baffle plate 44 Third baffle plate 46 Fourth baffle plate 50 First Expansion Room 52 Second Expansion Room 54 Third Expansion Room 56 Fourth Expansion Chamber 58 Fifth Expansion Room 60 through holes 64 entrance 70 Communication part 72 Communication hole 74 Flow Path 80 Upstream Range 100 Secondary resonance wave 100B Belly 100N section 110 Third-order resonance wave 110B Belly Section 110N C circumferential direction G. Exhaust gas L total length N Lengthwise NK Lengthwise Spacing SK circumferential spacing

Claims

1. A silencer, a main body; an inlet pipe for guiding exhaust gas into the main body; a muffler pipe including at least one pipe, which discharges exhaust gas from the main body through an exhaust port that opens to the outside of the main body and which constitutes an acoustic circuit; Equipped with The muffler pipe is one end portion that opens into the main body and constitutes an end portion of the acoustic circuit; a communication portion formed on the circumferential surface of the muffler pipe and including a plurality of communication holes arranged in a dispersed manner in the longitudinal direction of the muffler pipe, the communication portion allowing the flow of exhaust gas that does not pass through the one end portion; and the communication portion is disposed within only a range of an upstream half of the total length of the flow path between the one end portion and the exhaust port in the flow of the exhaust gas, The position where the communication portion is arranged includes a position of an antinode of a secondary resonant wave where two antinodes are formed in the flow path. Silencer.

2. 2. The silencer of claim 1, the communicating portion is formed in a range from one side to the other side in the length direction, with the position of the antinode of the secondary resonant wave as a boundary, and at a position not including a node of the secondary resonant wave. Silencer.

3. 3. The silencer according to claim 2, the communication holes are arranged so as to further include the position of an antinode formed at the most upstream of a tertiary resonance wave in which three antinodes are formed in the flow path. Silencer.

4. The silencer according to claim 2 or 3, The communication holes are arranged in a dispersed manner in the circumferential direction of the muffler pipe. Silencer.

5. 5. The silencer according to claim 4, The communication holes are arranged spirally on the circumferential surface of the muffler pipe. Silencer.

6. 6. The silencer according to claim 5, The communication holes are arranged at uniform intervals in the communication portion. Silencer.

7. A silencer according to any one of claims 1 to 3, the inlet pipe has an inlet opening into the main body portion, The inlet is disposed at a position not facing the communication portion. Silencer.

8. 8. The silencer according to claim 7, The main body has a plurality of chambers separated by baffle plates having through holes that allow exhaust gas to pass through, the inlet communicates with the chamber in which the communication portion is located via the through hole and is disposed in a chamber in which the communication portion is not located; Silencer.

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