JP6730376B2 - Silencer - Google Patents

Description

The present disclosure relates to silencers.

BACKGROUND ART An exhaust system for an automobile is known in which a sub-muffler is provided between a catalyst arranged upstream of an exhaust gas passage and a main muffler arranged downstream of an exhaust gas passage.

As a silencer used for this sub-muffler, there is a resonance silencer configured such that an opening is provided between an inner pipe and an outer pipe of a double pipe structure so that a void is communicated with an exhaust passage of the inner pipe ( See Patent Document 1).

Japanese Patent Application No. 2017-562822

In the silencer of Patent Document 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 support a plurality of frequencies.

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 muffler that includes a tubular inner pipe and a tubular outer pipe that is arranged on the inner peripheral side and that forms a double pipe together with the inner pipe. In the silencer, one end of the first end of the double pipe and the second end of the double pipe is connected to the first flow path on the upstream side in the flow direction of exhaust gas, and the other end is connected to the other end. By connecting to the second flow passage on the downstream side in the flow direction of the exhaust gas, it is possible to configure the first exhaust flow passage that connects the first flow passage and the second flow passage via the inner pipe. A gap is provided between the inner pipe and the outer pipe. At the second end, the inner pipe is provided with an opening that is connected to the outer pipe, and the void is configured to communicate with the first exhaust passage through the opening.

In addition, the inner pipe constitutes a second range having a first range having a first outer peripheral surface and an opening at the second end and having a second outer peripheral surface located inside the first outer peripheral surface. And a range. In the first range, the first outer peripheral surface and the inner peripheral surface of the outer tube are configured to be in contact with each other, or inclusions are sandwiched between the first outer peripheral surface and the inner peripheral surface of the outer tube. By this, 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 peripheral surface and the inner peripheral surface of the outer tube. At least one communication hole is provided on the outer peripheral surface of the inner pipe so as to connect the inner pipe and the void.

With such a configuration, the side-branch silencer is configured by the gap that communicates with the first exhaust flow path by the opening and the communication hole, so that the side-branch silencer can muffle at a plurality of frequencies.

In one aspect of the present disclosure, the inner pipe may have 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 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, 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. It may be configured to function as a Helmholtz resonator. The muffler may be configured to function as a side-branch muffler by connecting the first exhaust passage and the void via at least one communication hole. With such a configuration, it is possible to achieve both the silencing due to Helmholtz resonance and the silencing due to the side branch.

In one aspect of the present disclosure, the outer diameter of the range forming the void of the outer tube may be equal to or less than the outer diameter of the second end portion of the outer tube. With such a configuration, it is possible to reduce the outer diameter of the silencer and save space.

According to 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 abdomen of the standing wave generated in the second exhaust flow path. An opening may be arranged in the. With such a configuration, the sound deadening effect can be exhibited more reliably.

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 pipe, and the inner pipe may be joined to the outer pipe. With such a configuration, the gap between the inner pipe and the outer pipe can be easily and reliably formed.

In one aspect of the present disclosure, in the vicinity of the first end portion, a space between the inner pipe and the outer pipe is closed by an inclusion that is sandwiched between an outer peripheral surface of the inner pipe and an inner peripheral surface of the outer pipe. Good. According to such a configuration, when the silencer is used (that is, in a state where exhaust gas flows), the temperature difference between the inner pipe through which the exhaust gas flows and the outer pipe disposed outside causes the inner pipe and the outer pipe to move. The outer pipe can slide in the axial direction with respect to the inner pipe when a difference in thermal expansion occurs between the outer pipe and the inner pipe. Therefore, stress concentration is suppressed in the connecting portion between the inner pipe and the outer pipe. As a result, the generation of cracks can be suppressed.

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

In one aspect of the present disclosure, the first outer peripheral surface may be in contact with the inner peripheral surface of the outer pipe and the inner pipe and the outer pipe may be joined in the vicinity of the first end portion. With such a configuration, the gap between the inner pipe and the outer pipe can be easily and reliably formed.

According to 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 abdomen of the standing wave generated in the second exhaust flow path. At least one communication hole may be arranged in the. With such a configuration, the sound deadening effect can be exhibited more reliably.

Another aspect of the present disclosure is a silencer that includes a tubular inner pipe and a tubular outer pipe in which the inner pipe is arranged on the inner peripheral side and forms a double pipe together with the inner pipe. In the silencer, one end of the first end of the double pipe and the second end of the double pipe is continuous with the first flow passage on the upstream side in the flow direction of exhaust gas, and the other end is By connecting to the second flow passage on the downstream side in the flow direction of the exhaust gas, it is possible to configure the first exhaust flow passage that connects the first flow passage and the second flow passage via the inner pipe. A gap is provided between the inner pipe and the outer pipe. At the second end portion, the outer peripheral surface of the inner pipe is configured to be in contact with the inner peripheral surface of the outer pipe, or an inclusion is sandwiched between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe. As a result, the space between the inner pipe and the outer pipe is closed. At least one communication hole is provided on the outer peripheral surface of the inner pipe so as to connect the inner pipe and the void.

With such a configuration, the side-branch silencer is configured by the gap that is communicated with the inner pipe by the communication hole, so that the side-branch silencer can muffle at a plurality of frequencies.

In one aspect of the present disclosure, at the second end portion, the outer peripheral surface of the inner pipe may be in contact with the inner peripheral surface of the outer pipe, and the inner pipe and the outer pipe may be joined. With such a configuration, the gap between the inner pipe and the outer pipe can be easily and reliably formed.

In one aspect of the present disclosure, in the vicinity of the first end portion, a space between the inner pipe and the outer pipe is closed by an inclusion that is sandwiched between an outer peripheral surface of the inner pipe and an inner peripheral surface of the outer pipe. Good. According to such a configuration, when the difference in thermal expansion between the inner pipe and the outer pipe occurs due to the temperature difference between the inner pipe through which the exhaust gas flows inside and the outer pipe arranged outside, the outer pipe is It can slide axially with respect to the inner tube. Therefore, stress concentration is suppressed in the connecting portion between the inner pipe and the outer pipe.

In one aspect of the present disclosure, in the vicinity of the first end portion, the outer peripheral surface of the inner pipe may contact the inner peripheral surface of the outer pipe, and the inner pipe and the outer pipe may be joined. With such a configuration, the gap between the inner pipe and the outer pipe can be easily and reliably formed.

According to 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 abdomen of the standing wave generated in the second exhaust flow path. At least one communication hole may be arranged in the. With such a configuration, the sound deadening effect can be exhibited more reliably.

In one aspect of the present disclosure, the cross-sectional area of the void may be equal to or less than the cross-sectional area of the hollow portion of the inner pipe. With such a configuration, it is possible to reduce the outer diameter of the silencer and save space. Further, since the silencer can be bent, the degree of freedom in arranging the silencer is increased.

FIG. 1 is a schematic plan view showing the exhaust system of the embodiment. 2A is a schematic side view of the silencer of FIG. 1A as viewed from the second end side, and FIG. 2B is a schematic cross-sectional view taken along line IIB-IIB of FIG. 2A. 3A, 3B, and 3C are schematic diagrams for explaining the shape of the communication hole. 4A is a schematic cross-sectional view taken along line IVA-IVA of FIG. 2B, FIG. 4B is a schematic cross-sectional view taken along line IVB-IVB of FIG. 2B, and FIG. 4C is taken along line IVC-IVC. 2 is a schematic cross-sectional view in FIG. 5A and 5B are schematic diagrams 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 a silencer of an embodiment different from that of 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. 8A is a graph showing the relationship between the frequency and the sound deadening volume in Comparative Example 1, FIG. 8B is a graph showing the relationship between the frequency and the sound deadening volume in Example 1, and FIG. It is a graph which shows the relationship between a frequency and a silence volume.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
The 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 generating electricity in transportation equipment such as automobiles, railroads, ships, construction machines, and power generation facilities.

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

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

(Inner tube)
The inner pipe 7 is configured so 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 is exhausted from the opposite end.

The inner pipe 7 has a plurality of communication holes 73A and 73B. Each of the plurality of communication holes 73A and 73B communicates the inside of the inner pipe 7 with the space 10 provided between the outer pipe 8 and the inner pipe 7, which will be 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 pipe 7. The plurality of communication holes 73A and 73B are arranged between the first end portion 81 and the second end portion 82 of the outer pipe 8 in the axial direction of the inner pipe 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 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 in which the corners of the polygon are rounded (see FIG. 3B), a star shape, or the like. Furthermore, each of the communication holes 73A and 73B may be divided into a plurality of small holes (that is, an assembly 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 entire exhaust system 1 of FIG. 1) configured by the exhaust flow path constituent member including the silencer 3, it occurs in the second exhaust flow path The communication holes 73A and 73B are arranged at positions corresponding to the abdomen of the standing wave.

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

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

The two recesses 72B and 72C are arranged at positions facing each other with the central axis of the inner pipe 7 interposed therebetween. 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. This makes it possible to maintain the circumferential length of the inner pipe 7, and hence the wall thickness of the inner pipe 7, before and after the recesses 72B and 72C are formed.

In this way, the inner pipe 7 constitutes the first range having the first outer peripheral surface (that is, the region other than the recesses 72B and 72C) and the openings 11A and 11B, and is located inside the first outer peripheral surface. The second range (that is, the recesses 72B, 72C) having the second outer peripheral surface located therein.

In addition, the inner pipe 7 includes a first diameter portion (that is, the second end portion 72) that includes the first range and the second range, and a second diameter portion (that is, the second diameter portion that has an outer diameter smaller than the first diameter portion). And a portion other than the end portion 72).

(Outer tube)
As shown in FIG. 4B, the outer pipe 8 is arranged so as to surround the outer peripheral surface of the inner pipe 7. In other words, the outer pipe 8 is arranged with the inner pipe 7 on the inner peripheral side and constitutes a double pipe together with the inner pipe 7.

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

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

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

Further, a gap 10 is provided between the inner pipe 7 and the outer pipe 8, and at the second end portion 82, the inner pipe 7 is provided with openings 11A and 11B for connecting to the outer pipe 8 and the gap 10 is opened. It is configured to communicate with the first exhaust passage 12 via 11A and 11B.

Inside the first end portion 81, an inclusion 9 described later is arranged. That is, in the vicinity of the first end portion 81, the space between the inner pipe 7 and the outer pipe 8 is closed by the inclusion 9 sandwiched between the outer peripheral surface of the inner pipe 7 and the inner peripheral surface of the outer pipe 8. ing.

On the other hand, the second end portion 82 is directly fixed to the outer peripheral surface of the fixed portion 72A of the inner pipe 7 by welding, except for the two recesses 72B and 72C. Further, the second end portion 82 of the outer pipe 8 extends axially outward from the second end portion 72 of the inner pipe 7.

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

A resonance chamber 10A corresponding to a part of the gap 10 is formed between the outer peripheral surface of the second diameter portion of the inner pipe 7 (that is, a portion other than the second end 72) and the inner peripheral surface of the outer pipe 8. Has been done. Further, between the second outer peripheral surface of the inner tube 7 (that is, the recesses 72B and 72C) and the inner peripheral surface of the outer tube 8, a resonance tube 10B corresponding to a part of the gap 10 is formed.

The openings 11A and 11B are located at one end of the resonance tube 10B, the resonance tube 10B communicates with the first exhaust flow path 12 through the openings 11A and 11B, and the resonance chamber 10A receives the first exhaust flow path through the resonance tube 10B. The resonance tube 10B and the resonance chamber 10A are configured so as to function as a Helmholtz resonator by communicating with 12.

Further, the muffler 3 is configured to function as a side-branch muffler by connecting the first exhaust passage 12 and the gap 10 via the plurality of communication holes 73A and 73B.

Further, when air column resonance occurs in the second exhaust flow passage configured by the exhaust flow passage constituent member including the silencer 3, the opening 11A is formed at a position corresponding to the abdomen of the standing wave generated in the second exhaust flow passage. 11B is arranged.

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

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

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

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

(Void)
The void 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 72A, and the inclusion 9.

The void 10 communicates with the inside of the inner pipe 7 by the first communication hole 73A and the second communication hole 73B and the two recesses 72B, 72C. The air gap 10 reduces the volume of a specific frequency. The characteristic frequency of the void 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 void)
As shown in FIG. 4B, the cross-sectional area S2 of the void 10 is less than or equal to the cross-sectional area S1 of the hollow portion of the inner pipe 7.

The average wall thickness of the inner pipe 7 (that is, the average thickness of the plate material forming the inner pipe 7), which may have lower strength than the outer pipe 8, is the average wall thickness of the outer pipe 8 (that is, the outer pipe 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 central axes coincide with each other, but these central axes do not necessarily have to coincide with each other.

The distance between the end of the void 10 and the communication hole closest to this end in the axial direction of the inner pipe 7 and the distance between the communication holes are different from each other. That is, the distance between the first end portion 71 of the inner pipe 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 pipe 7 The distance to the end 72 is different from each other. The positions of the communication holes 73A and 73B in the circumferential direction of the inner pipe 7 are not particularly limited.

[1-2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(1a) Since the side-branch silencer is configured by the gap 10 that communicates with the first exhaust passage 12, it is possible to muffle sound at a plurality of frequencies.

(1b) Since the openings 11A and 11B communicating with the space 10 are provided at the second end 72 of the inner pipe 7, both silencing due to Helmholtz resonance and silencing due to the side branch can be achieved.

(1c) Since the cross-sectional area of the void 10 is equal to or less than the cross-sectional area of the hollow portion of the inner pipe 7, and the outer diameter of the outer pipe 8 in the range forming the void 10 is equal to or less than the outer diameter of the second end portion 82. The outer diameter of the silencer 3 can be reduced to save space. Moreover, since the silencer 3 can be bent, the degree of freedom in arranging the silencer 3 is increased.

(1c) Since the plurality of communication holes 73A and 73B are provided at positions separated from each other in the axial direction of the inner pipe 7, a plurality of side branches having different corresponding frequencies can be formed in the gap 10. Therefore, the silencing effect can be exerted on 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 a muffler 3 in which a plurality of communication holes 73A and 73B are formed and the sound pressure in the muffler 3.
When air column resonance occurs in the second exhaust passage, the second communication hole 73B in the silencer 3 of FIG. 5B is located at the antinode of the standing wave D1 of the primary mode generated in the exhaust system 1 and the first communication hole 73A. Is located on the antinode of the standing wave D2 of the secondary mode, the sound deadening effect can be obtained more reliably.

(1d) By disposing the inclusion 9 between the outer pipe 8 and the inner pipe 7 instead of joining the outer pipe 8 and the inner pipe 7, the difference in thermal expansion between the inner pipe 7 and the outer pipe 8 is reduced. When generated, the outer pipe 8 can slide axially with respect to the inner pipe 7. Therefore, stress concentration is suppressed in the connecting portion between the inner pipe 7 and the outer pipe 8. As a result, the generation of cracks can be suppressed.

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

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

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

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

[2-2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(2a) Since the side-branch silencer is configured by the gap 10 that communicates with the first exhaust passage 12, it is possible to muffle sound at a plurality of frequencies.

[3. Other Embodiments]
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above embodiments and can take various forms.

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

(3b) In the muffler 3 of the above embodiment, the fixing portion 72A may have a single opening 11B (that is, the recess 72C) as shown in FIG. 7A. Further, 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, both of the two connecting portions of the inner pipe 7 may be fixed portions fixed to the inner peripheral surface of the outer pipe 8. Specifically, the first end 71 of the inner pipe 7 may be directly fixed to the first end 81 instead of being connected to the first end 81 of the outer pipe 8 by the inclusion 9. In this case, the space 10 is defined by the outer peripheral surface of the inner pipe 7, the inner peripheral surface of the outer pipe 8, and the two fixing portions.

(3d) In the silencers 3 and 13 of the above-described embodiment, an inclusion may be sandwiched between the second end 72 of the inner pipe 7 and the second end 82 of the outer pipe 8. That is, by interposing an inclusion between the outer peripheral surface of the inner pipe 7 and the inner peripheral surface of the outer pipe 8, the inner pipe 7 and the outer pipe 8 may be closed.

(3e) In the silencers 3 and 13 of the above-described embodiment, the outer diameter of the outer tube 8 in the range forming the void 10 does not necessarily have to be equal to or less than the outer diameter of the second end portion 82. The cross-sectional area of the void 10 does not necessarily have to be equal to or less than the cross-sectional area of the hollow portion of the inner pipe 7.

(3f) The functions of one constituent element in the above-described embodiment may be distributed as a plurality of constituent elements, or the functions of a plurality of constituent elements may be integrated into one constituent element. Moreover, you may omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified by the wording recited in the claims are embodiments of the present disclosure.

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

Comparative Example 1 is the silencer 3 of FIG. 2B without the communication hole of the inner pipe 7. In the first embodiment, in the muffler 3 of FIG. 2B, the number of communication holes of the inner pipe 7 is one. Example 2 is the silencer 3 of FIG. 2B in which the inner pipe 7 has two communication holes. 8A, 8B, and 8C show the relationship between the frequency (horizontal axis) and the sound deadening level (vertical axis) in Comparative Example 1 and Examples 1 and 2.

Comparative Example 1 causes the void 10 to function as a resonance chamber connected to the inner pipe 7. Therefore, as shown in FIG. 8A, the frequency to be muted (that is, the peak of muting) is only one.

On the other hand, in the first embodiment, as shown in FIG. 8B, the air gap 10 functions as a side branch, so that it is possible to exhibit a silencing effect for a plurality of frequencies. In the lowest frequency band (the left end in the graph) in FIG. 8B, the silencing effect due to Helmholtz resonance and the silencing effect due to the side branch are combined.

Further, if the number of communication holes of the inner pipe 7 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...first pipe, 5B...second pipe, 5C...third pipe, 7...inner pipe, 8...outer pipe,
9... Inclusion, 10... Void, 10A... Resonance chamber, 10B... Resonance tube, 11A, 11B... Opening,
12... Exhaust flow path, 71... First end portion, 72... Second end portion, 72A... Fixed portion,
72B, 72C... concave portion, 72D, 72E... flat portion, 72F, 72G... convex portion,
73A... 1st communicating hole, 73B... 2nd communicating hole, 81... 1st end part, 82... 2nd end part.

Claims (15)

A cylindrical inner tube,
A tubular outer tube in which the inner tube is arranged on the inner peripheral side and which constitutes a double tube together with the inner tube;
Equipped 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 on the upstream side in the exhaust flow direction, and the other end is connected to the exhaust pipe. By connecting to the second flow passage on the downstream side in the flow direction, it is possible to configure a first exhaust flow passage that connects the first flow passage and the second flow passage via the inner pipe,
A gap is provided between the inner pipe and the outer pipe, an opening is provided at the second end portion for communicating the second end portion of the inner pipe with the gap, and the gap is the opening. Is configured to communicate with the first exhaust flow path via
The inner tube has, 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 peripheral surface located inside the first outer peripheral surface;
Have
In the first range, the first outer peripheral surface and the inner peripheral surface of the outer tube are configured to be in contact with each other,
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,
On the outer peripheral surface of the inner pipe, a plurality of communication holes that communicate the inner pipe and the void are provided separately in the axial direction of the inner pipe ,
Of the plurality of communication holes, the distance between the first communication hole that is closest to the first end and the first end, and the second communication that is closest to the second end of the plurality of communication holes. The silencer in which a distance between the hole and the first communication hole and a distance between the second communication hole and the second end are different from each other . The silencer according to claim 1, wherein
The inner tube is
A first diameter portion,
A second diameter portion having an outer diameter smaller than the first diameter portion,
Have
A resonance chamber corresponding to a part of the gap is formed between the outer peripheral surface of the second diameter portion and the inner peripheral surface of the outer tube,
The first diameter portion includes the first range and the second range,
A resonance tube corresponding to a part of the gap is 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, 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. According to the configuration, 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 passage and the void via the plurality of communication holes. The silencer according to claim 1 or 2, wherein
The silencer, wherein the outer diameter of the outer tube in the range forming the void is equal to or less than the outer diameter of the outer tube at the second end portion. The silencer according to any one of claims 1 to 3,
When air column resonance occurs in the second exhaust flow path configured by the exhaust flow path constituent 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. Being a silencer. The silencer according to any one of claims 1 to 4,
A silencer in which the first outer peripheral surface and the inner peripheral surface of the outer pipe are in contact with each other and the inner pipe and the outer pipe are joined in the first range. The silencer according to any one of claims 1 to 5,
In the vicinity of the first end portion, the silencer is provided in which the space between the inner pipe and the outer pipe is closed by inclusions sandwiched between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe. vessel. The silencer according to claim 6, wherein
The silencer, wherein the inclusion is a wire mesh. The silencer according to any one of claims 1 to 5,
A silencer in which the first outer peripheral surface and the inner peripheral surface of the outer pipe are in contact with each other in the vicinity of the second end portion, and the inner pipe and the outer pipe are joined together. The silencer according to any one of claims 1 to 8,
When air column resonance occurs in the second exhaust flow path that is configured by the exhaust flow path constituent member including the silencer, the plurality of communication channels are communicated to a position corresponding to the abdomen of the standing wave generated in the second exhaust flow path. A silencer in which holes are placed. A cylindrical inner tube,
A tubular outer tube in which the inner tube is arranged on the inner peripheral side and which constitutes a double tube together with the inner tube;
Equipped with
Of the first end portion of the double pipe and the second end portion of the double pipe, one end portion is continuous with the first flow path on the upstream side in the flow direction of exhaust gas, and the other end portion is By connecting to the second flow passage on the downstream side in the flow direction, it is possible to configure a first exhaust flow passage that connects the first flow passage and the second flow passage via the inner pipe,
A space is provided between the inner pipe and the outer pipe, and at the second end portion, the outer peripheral surface of the inner pipe is in contact with the inner peripheral surface of the outer pipe, or By interposing an inclusion between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe, the inner pipe and the outer pipe are configured to be closed.
On the outer peripheral surface of the inner pipe, a plurality of communication holes that communicate the inner pipe and the void are provided apart from each other in the axial direction of the inner pipe ,
A distance between a first communication hole closest to the first end and the first end of the plurality of communication holes, and a second communication closest to the second end of the plurality of communication holes. The silencer in which the distance between the hole and the first communication hole and the distance between the second communication hole and the second end are different from each other . The silencer according to claim 10,
A silencer in which the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe are in contact with each other at the second end portion, and the inner pipe and the outer pipe are joined together. The silencer according to claim 10 or claim 11,
In the vicinity of the first end portion, the silencer is provided in which the space between the inner pipe and the outer pipe is closed by inclusions sandwiched between the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe. vessel. The silencer according to claim 10 or claim 11,
A silencer in which the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe are in contact with each other in the vicinity of the first end portion, and the inner pipe and the outer pipe are joined together. The silencer according to any one of claims 10 to 13,
When air column resonance occurs in the second exhaust flow path that is configured by the exhaust flow path constituent member including the silencer, the plurality of communication channels are communicated to a position corresponding to the abdomen of the standing wave generated in the second exhaust flow path. A silencer in which holes are placed. The silencer according to any one of claims 10 to 14, wherein
The silencer, wherein the cross-sectional area of the void is equal to or less than the cross-sectional area of the hollow portion of the inner pipe.

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