JP2019132266A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silencer having a double tube structure capable of supporting a plurality of frequencies. One aspect of the present disclosure is a silencer including an inner tube and an outer tube. A gap is provided between the inner pipe and the outer pipe. At the second end, the inner pipe is provided with an opening for connecting to the outer pipe, and the gap is configured to pass through the opening to the exhaust flow path. The inner pipe has a first range having a first outer peripheral surface and a second range having a second outer peripheral surface which constitutes an opening and is located inside the first outer peripheral surface. In the first range, the first outer peripheral surface and the inner peripheral surface of the outer pipe are configured to be in contact with each other, so that the space between the inner pipe and the outer pipe is closed. In the second range, a part of the gap is formed between the first outer surface and the inner surface of the outer pipe. The outer surface of the inner pipe is provided with at least one communication hole for communicating the inner pipe and the void. [Selection diagram] Fig. 2

Description

  The present disclosure relates to a silencer.

  As an exhaust system for an automobile, a system in which a sub muffler is provided between a catalyst disposed upstream of an exhaust gas passage and a main muffler disposed downstream of the exhaust gas passage is known.

  As a silencer used for this sub-muffler, there is a resonance silencer configured such that an air gap is communicated with the exhaust flow path of the inner pipe by providing an opening between the inner pipe and the outer pipe of the double pipe structure ( Patent Document 1).

Japanese Patent Application No. 2017-562822

  In the silencer of Patent Literature 1, the frequency to be silenced is limited to one type. Therefore, it is necessary to design a silencer for each frequency, and a plurality of silencers are required to cope with a plurality of frequencies.

  An object of one aspect of the present disclosure is to provide a silencer having a double tube structure that can handle a plurality of frequencies.

  One aspect of the present disclosure is a silencer including a cylindrical inner tube, and a cylindrical outer tube in which an inner tube is disposed on the inner peripheral side and forms a double tube together with the inner tube. The silencer has one end connected to the first flow path upstream in the flow direction of the exhaust gas and the other end of the first end of the double pipe and the second end of the double pipe. By connecting to the second flow path downstream in the exhaust flow direction, a first exhaust flow path connecting the first flow path and the second flow path via the inner pipe can be configured. A gap is provided between the inner tube and the outer tube. In the second end portion, an opening connected to the outer pipe is provided in the inner pipe, and the gap is configured to communicate with the first exhaust passage through the opening.

  The inner tube has a first range having a first outer peripheral surface at the second end, and a second outer surface having a second outer peripheral surface located inside the first outer peripheral surface while forming an opening. Range. In the first range, the first outer peripheral surface is configured to be in contact with the inner peripheral surface of the outer tube, or inclusions are sandwiched between the first outer peripheral surface and the inner peripheral surface of the outer tube. Thus, the space between the inner tube and the outer tube is closed. In the second range, a part of the gap is formed between the first outer peripheral surface and the inner peripheral surface of the outer tube. The outer peripheral surface of the inner tube is provided with at least one communication hole that allows the inner tube and the gap to communicate with each other.

  According to such a configuration, since the side branch type silencer is configured by the gap communicated with the first exhaust flow path by the opening and the communication hole, it is possible to mute at a plurality of frequencies by the side branch.

  In one aspect of the present disclosure, the inner tube may include a first diameter portion and a second diameter portion having an outer diameter smaller than the first diameter portion. A resonance chamber corresponding to a part of the air gap may be formed between the outer peripheral surface of the second diameter portion and the inner peripheral surface of the outer tube. The first diameter portion may include a first range and a second range. A resonance tube corresponding to a part of the gap may be formed between the second outer peripheral surface and the inner peripheral surface of the outer tube. The opening is located at one end of the resonance tube, and the resonance tube communicates with the first exhaust passage through the opening, and the resonance chamber and the resonance chamber communicate with the first exhaust passage through the resonance tube. It may be configured to function as a Helmholtz resonator. The silencer may be configured to function as a side branch type silencer by connecting the first exhaust flow path and the air gap via at least one communication hole. According to such a configuration, it is possible to achieve both the silencing by Helmholtz resonance and the silencing by the side branch.

  In one aspect of the present disclosure, the outer diameter in the range constituting the void of the outer tube may be equal to or smaller than the outer diameter at the second end portion of the outer tube. According to such a configuration, the outer diameter of the silencer can be reduced to save space.

  In one aspect of the present disclosure, when air column resonance occurs in the second exhaust flow path configured by the exhaust flow path constituent member including the silencer, a position corresponding to the abdominal portion of the standing wave generated in the second exhaust flow path An opening may be disposed on the surface. According to such a configuration, the silencing effect can be more reliably exhibited.

  In one aspect of the present disclosure, in the first range, the first outer peripheral surface may be in contact with the inner peripheral surface of the outer tube, and the inner tube and the outer tube may be joined. According to such a structure, the space | gap between an inner tube and an outer tube can be comprised easily and reliably.

  In one aspect of the present disclosure, in the vicinity of the first end portion, the space between the inner tube and the outer tube is blocked by inclusions sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. Also good. According to such a configuration, when the silencer is used (that is, the exhaust gas flows), the inner tube and the outer tube are caused by a temperature difference between the inner tube through which the exhaust gas flows and the outer tube disposed outside. When the difference in thermal expansion occurs, the outer tube can slide in the axial direction with respect to the inner tube. Therefore, stress concentration at the connecting portion between the inner tube and the outer tube is suppressed. As a result, the occurrence of cracks can be suppressed.

  In one aspect of the present disclosure, the inclusion may be a wire mesh. According to such a configuration, the outer tube can be easily and reliably slidable with respect to the inner tube while forming a gap between the inner tube and the outer tube.

  In one aspect of the present disclosure, in the vicinity of the first end portion, the first outer peripheral surface and the inner peripheral surface of the outer tube may be in contact with each other, and the inner tube and the outer tube may be joined. According to such a structure, the space | gap between an inner tube and an outer tube can be comprised easily and reliably.

  In one aspect of the present disclosure, when air column resonance occurs in the second exhaust flow path configured by the exhaust flow path constituent member including the silencer, a position corresponding to the abdominal portion of the standing wave generated in the second exhaust flow path At least one communication hole may be disposed in the first and second communication holes. According to such a configuration, the silencing effect can be more reliably exhibited.

  Another aspect of the present disclosure is a silencer including a cylindrical inner tube, and a cylindrical outer tube in which an inner tube is disposed on the inner peripheral side and forms a double tube together with the inner tube. The silencer includes a first end of the double pipe and a second end of the double pipe, one end of which is continuous with the first flow path upstream in the flow direction of the exhaust gas, and the other end is By connecting to the second flow path downstream in the exhaust flow direction, a first exhaust flow path connecting the first flow path and the second flow path via the inner pipe can be configured. A gap is provided between the inner tube and the outer tube. At the second end, the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube are configured to contact each other, or inclusions are sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. Thus, the space between the inner tube and the outer tube is closed. The outer peripheral surface of the inner tube is provided with at least one communication hole that allows the inner tube and the gap to communicate with each other.

  According to such a configuration, since the side branch type silencer is configured by the gap communicated with the inner tube by the communication hole, it is possible to mute at a plurality of frequencies by the side branch.

  In one aspect of the present disclosure, the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube may be in contact with each other and the inner tube and the outer tube may be joined at the second end portion. According to such a structure, the space | gap between an inner tube and an outer tube can be comprised easily and reliably.

  In one aspect of the present disclosure, in the vicinity of the first end portion, the space between the inner tube and the outer tube is blocked by inclusions sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. Also good. According to such a configuration, when the difference in thermal expansion between the inner tube and the outer tube occurs due to the temperature difference between the inner tube through which the exhaust gas flows and the outer tube disposed outside, the outer tube It can slide axially with respect to the inner tube. Therefore, stress concentration at the connecting portion between the inner tube and the outer tube is suppressed.

  In one aspect of the present disclosure, the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube may be in contact with each other in the vicinity of the first end, and the inner tube and the outer tube may be joined. According to such a structure, the space | gap between an inner tube and an outer tube can be comprised easily and reliably.

  In one aspect of the present disclosure, when air column resonance occurs in the second exhaust flow path configured by the exhaust flow path constituent member including the silencer, a position corresponding to the abdominal portion of the standing wave generated in the second exhaust flow path At least one communication hole may be disposed in the first and second communication holes. According to such a configuration, the silencing effect can be more reliably exhibited.

  In one aspect of the present disclosure, the cross-sectional area of the gap may be equal to or smaller than the cross-sectional area of the hollow portion of the inner tube. According to such a configuration, the outer diameter of the silencer can be reduced to save space. In addition, since the silencer can be bent, the degree of freedom in arranging the silencer is increased.

FIG. 1 is a schematic plan view illustrating an exhaust system according to an embodiment. 2A is a schematic side view of the silencer of FIG. 1A viewed from the second end side, and FIG. 2B is a schematic cross-sectional view taken along the line IIB-IIB of FIG. 2A. 3A, 3B, and 3C are schematic views for explaining the shape of the communication hole. 4A is a schematic cross-sectional view taken along line IVA-IVA in FIG. 2B, FIG. 4B is a schematic cross-sectional view taken along line IVB-IVB in FIG. 2B, and FIG. 4C is a cross-sectional view taken along line IVC-IVC. It is typical sectional drawing in. 5A and 5B are schematic views for explaining the relationship between the communication hole and the standing wave. FIG. 6 is a schematic cross-sectional view corresponding to FIG. 2B of the silencer of the embodiment different from FIG. 2A. 7A, 7B, and 7C are schematic cross-sectional views corresponding to FIG. 4A of the fixing portion of the embodiment different from FIG. 2A. FIG. 8A is a graph showing the relationship between frequency and muffled volume in Comparative Example 1, FIG. 8B is a graph showing the relationship between frequency and muffled volume in Example 1, and FIG. It is a graph which shows the relationship between a frequency and a muffling volume.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
An exhaust system 1 shown in FIG. 1 constitutes an exhaust gas flow path of an internal combustion engine. The exhaust system 1 includes a catalytic converter 2, a silencer 3 as a sub muffler, and a main muffler 4.

  The internal combustion engine to which the exhaust system 1 is applied is not particularly limited, and examples thereof include those used for driving or power generation in transportation equipment such as automobiles, railways, ships, construction machinery, power generation facilities, and the like.

  The catalytic converter 2 reforms or collects environmental pollutants in the exhaust gas. The catalytic converter 2 includes a catalyst and the like. The main muffler 4 further silences the exhaust gas that has passed through the silencer 3.

  The catalytic converter 2 and the silencer 3 are connected by a first pipe 5A. The silencer 3 and the main muffler 4 are connected by a second pipe 5B. The exhaust gas that has passed through the main muffler 4 is discharged from the third pipe 5C.

<Muffler>
As shown in FIGS. 2A and 2B, the silencer 3 includes a cylindrical inner tube 7, a cylindrical outer tube 8, and inclusions 9. The silencer 3 has a double tube structure.

(Inner pipe)
The inner pipe 7 is configured such that exhaust gas passes through the inside. Specifically, the exhaust gas that has passed through the catalytic converter 2 is introduced into the inner pipe 7 from the first end 71 or the second end 72 and discharged from the opposite end.

  The inner tube 7 has a plurality of communication holes 73A and 73B. The plurality of communication holes 73A and 73B allow the inside of the inner tube 7 to communicate with a gap 10 provided between an outer tube 8 and an inner tube 7 described later. The plurality of communication holes 73A and 73B are provided at positions separated in the axial direction (that is, the longitudinal direction) of the inner tube 7. The plurality of communication holes 73 </ b> A and 73 </ b> B are disposed between the first end 81 and the second end 82 of the outer tube 8 in the axial direction of the inner tube 7.

  The shape of each communication hole 73A, 73B is not limited to a perfect circle as long as the area where the side branch type silencer functions can be secured. Each of the communication holes 73A and 73B may have an elliptical shape (see FIG. 3A), a polygon, a shape with rounded corners of the polygon (see FIG. 3B), a star shape, or the like. Further, each of the communication holes 73A and 73B may be divided into a plurality of small holes (that is, a collection of small holes, see FIG. 3C).

  When air column resonance occurs in the second exhaust flow path (that is, the exhaust flow path in the whole exhaust system 1 in FIG. 1) configured by the exhaust flow path constituent member including the silencer 3, it occurs in the second exhaust flow path. Each communication hole 73A, 73B is arranged at a position corresponding to the abdomen of the standing wave.

  The inner diameter R2 of the second end 72 of the inner tube 7 is larger than the inner diameter R1 of the first end 71. The second end portion 72 has one fixing portion 72 </ b> A that is fixed to the inner peripheral surface of the outer tube 8. As shown in FIG. 4A, the fixing portion 72A has two concave portions 72B and 72C in which a part of the tube wall is recessed inward. The fixed portion 72 </ b> A is one of two connecting portions that connect the inner tube 7 to the inner peripheral surface of the outer tube 8.

  The two recesses 72B and 72C constitute openings 11A and 11B that allow the second end 72 of the inner tube 7 to communicate with the gap 10, respectively. The fixing portion 72A is a portion other than the two concave portions 72B and 72C and closes the space between the inner tube 7 and the outer tube 8 in the axial direction. That is, a part of the fixing portion 72 </ b> A in the circumferential direction is separated from the inner peripheral surface of the outer tube 8.

  The two concave portions 72B and 72C are disposed at positions facing each other across the central axis of the inner tube 7. Further, the radius of curvature R3 of the two recesses 72B and 72C may be substantially the same as the maximum radius R4 of the fixed portion 72A (that is, the radius of the region other than the recesses 72B and 72C) R4. Thereby, the circumferential direction length of the inner tube 7 and thus the thickness of the inner tube 7 can be maintained before and after forming the recesses 72B and 72C.

  As described above, the inner tube 7 constitutes the first range (that is, the region other than the recesses 72B and 72C) having the first outer peripheral surface and the openings 11A and 11B, and is located inside the first outer peripheral surface. It has the 2nd range (namely, crevice 72B and 72C) which has the 2nd peripheral face located.

  The inner tube 7 includes a first diameter portion (that is, the second end portion 72) including the first range and the second range, and a second diameter portion (that is, the second diameter portion) that has a smaller outer diameter than the first diameter portion. A portion other than the end portion 72).

(Outer pipe)
As shown in FIG. 4B, the outer tube 8 is disposed so as to surround the outer peripheral surface of the inner tube 7. That is, the outer tube 8 has an inner tube 7 disposed on the inner peripheral side, and forms a double tube together with the inner tube 7.

  The inner diameter of the outer tube 8 is larger than the outer diameter of the inner tube 7. The outer diameter in the range constituting the gap 10 of the outer tube 8 (that is, the region between the first end portion 81 and the second end portion 82) is equal to or smaller than the outer diameter of the second end portion 82. In the present embodiment, the outer tube 8 has a constant diameter in the longitudinal direction.

  The double pipe has one end of the first end and the second end connected to the first flow path (that is, the first pipe 5A) on the upstream side in the flow direction of the exhaust gas, and the other end. Is connected to the second flow path (that is, the second pipe 5B) on the downstream side in the flow direction of the exhaust gas, whereby the first exhaust flow path 12 connecting the first flow path and the second flow path via the inner pipe 7 is provided. Can be configured.

  The outer tube 8 has a first end portion 81 and a second end portion 82 that are respectively connected to the outer peripheral surface of the inner tube 7. The diameters of the first end 81 and the second end 82 are equal. The second end portion 82 of the outer tube 8 constitutes the end portion of the silencer 3.

  Further, a gap 10 is provided between the inner tube 7 and the outer tube 8, and openings 11A and 11B connected to the outer tube 8 are provided in the inner tube 7 at the second end portion 82, and the gap 10 is opened. It is comprised so that it may lead to the 1st exhaust flow path 12 via 11A, 11B.

  An inclusion 9 to be described later is disposed inside the first end portion 81. That is, in the vicinity of the first end portion 81, the space between the inner tube 7 and the outer tube 8 is blocked by the inclusion 9 sandwiched between the outer peripheral surface of the inner tube 7 and the inner peripheral surface of the outer tube 8. ing.

  On the other hand, the second end portion 82 is directly fixed to a portion of the outer peripheral surface of the fixing portion 72A of the inner tube 7 other than the two concave portions 72B and 72C by welding. Further, the second end portion 82 of the outer tube 8 extends outward in the axial direction from the second end portion 72 of the inner tube 7.

  That is, in the first range of the inner tube 7, the outer peripheral surface of the inner tube 7 and the inner peripheral surface of the outer tube 8 are in contact with each other, and the inner tube 7 and the outer tube 8 are joined to each other. The space between the tube 8 is closed. In the second range of the inner tube 7, a part of the gap 10 is formed between the outer peripheral surface of the inner tube 7 and the inner peripheral surface of the outer tube 8.

  A resonance chamber 10 </ b> A corresponding to a part of the gap 10 is configured between the outer peripheral surface of the second diameter portion of the inner tube 7 (that is, the portion other than the second end portion 72) and the inner peripheral surface of the outer tube 8. Has been. In addition, a resonance tube 10 </ b> B corresponding to a part of the gap 10 is formed between the second outer peripheral surface (that is, the recesses 72 </ b> B and 72 </ b> C) of the inner tube 7 and the inner peripheral surface of the outer tube 8.

  The openings 11A and 11B are located at one end of the resonance tube 10B. The resonance tube 10B communicates with the first exhaust passage 12 through the openings 11A and 11B, and the resonance chamber 10A passes through the resonance tube 10B. 12, the resonance tube 10 </ b> B and the resonance chamber 10 </ b> A are configured to function as a Helmholtz resonator.

  Furthermore, the silencer 3 is configured to function as a side branch type silencer by connecting the first exhaust flow path 12 and the gap 10 via a plurality of communication holes 73A and 73B.

  Further, when air column resonance occurs in the second exhaust flow path constituted by the exhaust flow path constituting member including the silencer 3, the openings 11A and 11A are formed at positions corresponding to the antinodes of the standing wave generated in the second exhaust flow path. 11B is arranged.

(Inclusions)
The inclusion 9 is a cushioning material sandwiched between the outer peripheral surface at the first end 71 of the inner tube 7 and the inner peripheral surface at the first end 81 of the outer tube 8. The inclusion 9 constitutes one of two connecting portions that connect the inner tube 7 to the inner peripheral surface of the outer tube 8.

  As shown in FIG. 4C, the inclusion 9 is disposed along the entire circumferential direction of the outer peripheral surface of the inner tube 7 and the inner peripheral surface of the outer tube 8. That is, the inclusion 9 is disposed so as to close the space between the inner tube 7 and the outer tube 8 in the axial direction of the inner tube 7.

  The inclusion 9 may be provided with an opening in a part in the circumferential direction as long as the function as a side branch of the gap 10 is not lost. By adjusting the size of the opening, the characteristic frequency of resonance can be adjusted.

  The inclusion 9 is not limited as long as it can form a gap 10 as a side branch described later and can slide at least with respect to the inner tube 7 or the outer tube 8. As the inclusion 9, for example, a metal wire mesh having air permeability is suitable.

(Void)
The gap 10 is a semi-enclosed space defined by the outer peripheral surface of the inner tube 7, the inner peripheral surface of the outer tube 8, the fixing portion 72 </ b> A, and the inclusions 9.

  The gap 10 communicates with the inside of the inner tube 7 through the first communication hole 73A and the second communication hole 73B, and the two recesses 72B and 72C. The air gap 10 reduces the volume of a specific frequency. The characteristic frequency of the air gap 10 can be adjusted by changing the positions of the first communication hole 73A and the second communication hole 73B.

(Relationship between inner tube, outer tube, and air gap)
As shown in FIG. 4B, the cross-sectional area S2 of the gap 10 is equal to or smaller than the cross-sectional area S1 of the hollow portion of the inner tube 7.

  Further, the average thickness of the inner tube 7 (that is, the average thickness of the plate material constituting the inner tube 7), which may be lower in strength than the outer tube 8, is the average thickness of the outer tube 8 (that is, configures the outer tube 8). The average thickness of the plate material) or less is preferable. In the present embodiment, the inner tube 7 and the outer tube 8 are arranged so that their center axes coincide with each other, but these center axes do not necessarily coincide with each other.

  The distance between the end of the gap 10 in the axial direction of the inner tube 7 and the communication hole closest to the end and the distance between the communication holes are different from each other. That is, the distance between the first end 71 of the inner tube 7 and the first communication hole 73A, the distance between the first communication hole 73A and the second communication hole 73B, the second communication hole 73B and the second of the inner tube 7. The distance to the end 72 is different from each other. In addition, the position in the circumferential direction of the inner pipe 7 of each communicating hole 73A, 73B is not specifically limited.

[1-2. effect]
According to the embodiment detailed above, the following effects can be obtained.
(1a) Since the side branch type silencer is configured by the gap 10 communicated with the first exhaust flow path 12, it is possible to mute at a plurality of frequencies.

  (1b) Since the openings 11 </ b> A and 11 </ b> B communicating with the gap 10 are provided at the second end portion 72 of the inner tube 7, it is possible to achieve both silence due to Helmholtz resonance and silence due to the side branch.

  (1c) Since the cross-sectional area of the gap 10 is equal to or smaller than the cross-sectional area of the hollow portion of the inner tube 7, and the outer diameter in the range constituting the void 10 of the outer tube 8 is equal to or smaller than the outer diameter of the second end portion 82. Thus, the outer diameter of the silencer 3 can be reduced to save space. Moreover, since the bending process of the silencer 3 becomes possible, the freedom degree of arrangement | positioning of the silencer 3 is raised.

  (1c) By providing the plurality of communication holes 73A and 73B at positions spaced apart in the axial direction of the inner tube 7, a plurality of side branches having different corresponding frequencies can be formed in the gap 10. Therefore, the silencing effect can be exhibited for more frequencies.

Here, FIG. 5A shows the configuration of the exhaust pipe 103 in which a plurality of communication holes corresponding to the communication holes 73A and 73B are not formed, and the sound pressure in the exhaust pipe 103. FIG. 5B shows the silencer 3 in which a plurality of communication holes 73 </ b> A and 73 </ b> B are formed, and the sound pressure in the silencer 3.
When air column resonance occurs in the second exhaust flow path, the second communication hole 73B is positioned at the antinode of the standing wave D1 in the primary mode generated in the exhaust system 1 in the silencer 3 of FIG. 5B, and the first communication hole 73A. Is positioned on the antinode of the standing wave D2 in the secondary mode, the sound deadening effect can be obtained more reliably.

  (1d) By disposing the inclusion 9 between the outer tube 8 and the inner tube 7 instead of joining the outer tube 8 and the inner tube 7, the difference in thermal expansion between the inner tube 7 and the outer tube 8 can be reduced. When this occurs, the outer tube 8 can slide axially relative to the inner tube 7. Therefore, stress concentration at the connecting portion between the inner tube 7 and the outer tube 8 is suppressed. As a result, the occurrence of cracks can be suppressed.

[2. Second Embodiment]
[2-1. Constitution]
A silencer 13 shown in FIG. 6 is used in the exhaust system 1 in place of the silencer 3 of FIG. The silencer 13 includes an inner tube 7, an outer tube 8, and inclusions 9. The silencer 13 has a double tube structure.

  Since the inner tube 7, the outer tube 8 and the inclusion 9 of the silencer 13 are the same as the silencer 3 of FIGS. 2A and 2B except for the points described below, a detailed description of these members will be given. Is omitted.

  In the present embodiment, the second end portion 82 of the outer tube 8 is welded to the inner tube 7 over the entire circumference. That is, the inner tube 7 does not have the recesses 72 </ b> B and 72 </ b> C at the second end portion 72. The outer shape of the second end 72 of the inner tube 7 is circular.

  Thus, unlike the silencer 3 of FIGS. 2A and 2B, the silencer 13 does not have the openings 11A and 11B. Since the silencer 13 does not include the resonance tube 10B, the silencer 13 does not function as a Helmholtz resonator and functions only as a side branch type silencer.

[2-2. effect]
According to the embodiment detailed above, the following effects can be obtained.
(2a) Since the side branch type silencer is configured by the gap 10 communicated with the first exhaust flow path 12, it is possible to mute at a plurality of frequencies.

[3. Other Embodiments]
As mentioned above, although embodiment of this indication was described, it cannot be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

  (3a) In the silencers 3 and 13 of the above embodiment, the inner tube 7 may have a single communication hole. Further, the inner tube 7 may have three or more communication holes provided at positions separated from each other in the axial direction of the inner tube 7.

  (3b) In the silencer 3 of the above-described embodiment, the fixed portion 72A may have a single opening 11B (that is, a recess 72C) as shown in FIG. 7A. In addition, the fixing portion 72A may have flat portions 72D and 72E having a chordal cross section shown in FIG. 7B or convex portions 72F and 72G protruding outward in the radial direction shown in FIG. 7C, instead of the concave portions.

  (3c) The silencers 3 and 13 of the above embodiment do not necessarily have to include the inclusion 9. That is, the two connecting portions of the inner tube 7 may be fixed portions that are fixed to the inner peripheral surface of the outer tube 8. Specifically, the first end 71 of the inner tube 7 may be directly fixed to the first end 81 instead of being connected to the first end 81 of the outer tube 8 by the inclusion 9. In this case, the gap 10 is defined by the outer peripheral surface of the inner tube 7, the inner peripheral surface of the outer tube 8, and two fixing portions.

  (3d) In the silencers 3 and 13 of the above-described embodiment, inclusions may be sandwiched between the second end 72 of the inner tube 7 and the second end 82 of the outer tube 8. In other words, the inclusions may be sandwiched between the outer peripheral surface of the inner tube 7 and the inner peripheral surface of the outer tube 8 so that the space between the inner tube 7 and the outer tube 8 may be closed.

  (3e) In the silencers 3 and 13 of the above-described embodiment, the outer diameter in the range constituting the gap 10 of the outer tube 8 is not necessarily equal to or smaller than the outer diameter at the second end portion 82. Further, the cross-sectional area of the gap 10 does not necessarily have to be equal to or smaller than the cross-sectional area of the hollow portion of the inner tube 7.

  (3f) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

[4. Example]
Next, comparison between Examples 1 and 2 and Comparative Example 1 performed to confirm the effect of the present disclosure will be described.

  In Comparative Example 1, the muffler 3 in FIG. 2B has no communication hole in the inner tube 7. In Example 1, in the silencer 3 of FIG. 2B, the number of communication holes of the inner tube 7 is one. Example 2 is the silencer 3 of FIG. 2B in which the inner tube 7 has two communication holes. 8A, 8B, and 8C show the relationship between the frequency (horizontal axis) and the silence volume (vertical axis) in Comparative Example 1 and Examples 1 and 2. FIG.

  In Comparative Example 1, the void 10 is made to function as a resonance chamber connected to the inner tube 7. Therefore, as shown in FIG. 8A, there is only one frequency to be silenced (that is, the silence peak).

  On the other hand, in Example 1, since the space | gap 10 functions as a side branch as FIG. 8B shows, the silencing effect can be exhibited with respect to several frequencies. In the lowest frequency band (at the left end in the graph) in FIG. 8B, the silencing effect by Helmholtz resonance and the silencing effect by the side branch are combined.

  Furthermore, if the number of the communication holes which the inner pipe 7 has is increased, as shown in FIG. 8C, the frequency at which the silencing effect is generated can be increased.

1 ... exhaust system, 2 ... catalytic converter, 3, 13 ... silencer, 4 ... main muffler,
5A ... 1st piping, 5B ... 2nd piping, 5C ... 3rd piping, 7 ... Inner tube, 8 ... Outer tube,
9 ... Inclusion, 10 ... Gap, 10A ... Resonance chamber, 10B ... Resonance tube, 11A, 11B ... Opening,
12 ... exhaust flow path, 71 ... first end, 72 ... second end, 72A ... fixed part,
72B, 72C ... concave portion, 72D, 72E ... flat portion, 72F, 72G ... convex portion,
73A ... 1st communicating hole, 73B ... 2nd communicating hole, 81 ... 1st edge part, 82 ... 2nd edge part.

Claims (15)

A cylindrical inner tube,
A cylindrical outer tube in which the inner tube is disposed on the inner peripheral side and forms a double tube together with the inner tube;
With
Of the first end of the double pipe and the second end of the double pipe, one end is connected to the first flow path upstream in the flow direction of the exhaust, and the other end is the exhaust. By connecting to the second flow path on the downstream side in the flow direction, a first exhaust flow path connecting the first flow path and the second flow path via the inner pipe can be configured,
A gap is provided between the inner tube and the outer tube, and an opening for connecting the outer tube to the inner tube is provided at the second end portion, and the gap is formed through the opening. 1 is configured to communicate with the exhaust passage,
The inner tube is at the second end,
A first range having a first outer peripheral surface;
A second range that constitutes the opening and has a second outer circumferential surface located inside the first outer circumferential surface;
Have
In the first range, the first outer peripheral surface is configured to be in contact with the inner peripheral surface of the outer tube, or is interposed between the first outer peripheral surface and the inner peripheral surface of the outer tube. By sandwiching an object, the space between the inner tube and the outer tube is configured to be closed,
In the second range, a part of the gap is configured between the first outer peripheral surface and the inner peripheral surface of the outer tube,
The silencer, wherein at least one communication hole for communicating the inner tube and the gap is provided on an outer peripheral surface of the inner tube. The muffler according to claim 1,
The inner tube is
A first diameter portion;
A second diameter portion having an outer diameter smaller than that of the first diameter portion;
Have
Between the outer peripheral surface of the second diameter portion and the inner peripheral surface of the outer tube, a resonance chamber corresponding to a part of the gap is configured,
The first diameter portion includes the first range and the second range,
A resonance tube corresponding to a part of the gap is configured between the second outer peripheral surface and the inner peripheral surface of the outer tube,
The opening is located at one end of the resonance tube, and the resonance tube communicates with the first exhaust passage through the opening, and the resonance chamber communicates with the first exhaust passage through the resonance tube. The resonance tube and the resonance chamber are configured to function as a Helmholtz resonator,
A silencer configured to function as a side branch silencer by connecting the first exhaust flow path and the gap through the at least one communication hole. The muffler according to claim 1 or 2,
The silencer, wherein the outer diameter of the outer tube in the range constituting the gap is equal to or smaller than the outer diameter of the second end of the outer tube. A muffler according to any one of claims 1 to 3, wherein
When air column resonance occurs in the second exhaust flow path constituted by the exhaust flow path constituting member including the silencer, the opening is arranged at a position corresponding to the abdomen of the standing wave generated in the second exhaust flow path. Muffler. The muffler according to any one of claims 1 to 4,
In the first range, the silencer in which the first outer peripheral surface and the inner peripheral surface of the outer tube are in contact with each other, and the inner tube and the outer tube are joined. The muffler according to any one of claims 1 to 5,
In the vicinity of the first end portion, the silencer is closed between the inner tube and the outer tube by inclusions sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. vessel. The muffler according to claim 6, wherein
The muffler, wherein the inclusion is a wire mesh. The muffler according to any one of claims 1 to 5,
A silencer in which the first outer peripheral surface is in contact with the inner peripheral surface of the outer tube and the inner tube and the outer tube are joined in the vicinity of the first end. A muffler according to any one of claims 1 to 8,
When air column resonance occurs in the second exhaust flow path constituted by the exhaust flow path constituting member including the silencer, the at least one is located at a position corresponding to an antinode of a standing wave generated in the second exhaust flow path. A silencer with a communication hole. A cylindrical inner tube,
A cylindrical outer tube in which the inner tube is disposed on the inner peripheral side and forms a double tube together with the inner tube;
With
Of the first end of the double pipe and the second end of the double pipe, one end is continuous with the first flow path upstream in the flow direction of the exhaust, and the other end is the exhaust. By connecting to the second flow path on the downstream side in the flow direction, a first exhaust flow path connecting the first flow path and the second flow path via the inner pipe can be configured,
A gap is provided between the inner tube and the outer tube, and at the second end, the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube are in contact with each other, or The inclusion is sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube, so that the space between the inner tube and the outer tube is closed.
The silencer, wherein at least one communication hole for communicating the inner tube and the gap is provided on an outer peripheral surface of the inner tube. The muffler according to claim 10, wherein
The silencer in which the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube are in contact with each other, and the inner tube and the outer tube are joined at the second end. A silencer according to claim 10 or claim 11,
In the vicinity of the first end portion, the silencer is closed between the inner tube and the outer tube by inclusions sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. vessel. A silencer according to claim 10 or claim 11,
A silencer in which the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube are in contact with each other and the inner tube and the outer tube are joined in the vicinity of the first end. The silencer according to any one of claims 10 to 13,
When air column resonance occurs in the second exhaust flow path constituted by the exhaust flow path constituting member including the silencer, the at least one is located at a position corresponding to an antinode of a standing wave generated in the second exhaust flow path. A silencer with a communication hole. A silencer according to any one of claims 10 to 14,
The silencer has a cross-sectional area equal to or less than a cross-sectional area of the hollow portion of the inner tube.

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