JP7502241B2 - Exhaust pipe - Google Patents

Description

This disclosure relates to an exhaust pipe.

Literature 1 discloses a double-pipe exhaust manifold in which the open end of a first inner pipe placed inside an outer pipe is inserted into the open end of a second inner pipe placed inside the outer pipe, and a buffer material is placed continuously from the inner circumference to the outer circumference of the second inner pipe so as to cover the open end of the second inner pipe. This buffer material is placed in the gap formed between the first inner pipe and the second inner pipe, and in the gap formed between the second inner pipe and the outer pipe, in order to suppress the generation of rubbing noises caused by the thermal expansion difference between the first inner pipe and the second inner pipe, and the thermal expansion difference between the second inner pipe and the outer pipe.

Patent No. 3857767

However, in the case of cushioning materials placed on components with a double-tube structure as described above, increasing the sliding ability between the inner tubes and between the second inner tube and the outer tube tends to reduce the sealing ability against exhaust gas, and increasing the sealing ability against exhaust gas tends to reduce the sliding ability between the tubes. For this reason, there was a problem in that it was difficult to achieve both sliding ability between the tubes and sealing ability against exhaust gas in the cushioning materials.

One aspect of the present disclosure aims to provide a technology that can easily reduce the effects of the difference in thermal expansion between the inner and outer tubes and improve the sealing performance of the inner tube.

One aspect of the present disclosure is an exhaust pipe with a double pipe structure, comprising an inner pipe, an outer pipe, and a retaining member. Exhaust gas passes through the inner pipe. The outer pipe is arranged to surround the outer periphery of the inner pipe. The retaining member is arranged between the outer pipe and the inner pipe. The inner pipe has a first inner pipe and a second inner pipe aligned in the flow direction of the exhaust gas, and is arranged so that the end of the first inner pipe on the second inner pipe side is inserted into the second inner pipe. The retaining member has at least a first retaining portion arranged in a gap formed between the first inner pipe and the second inner pipe, and a second retaining portion arranged in a gap formed between the first inner pipe and the outer pipe. The first retaining portion has a smaller amount of exhaust gas passing through per unit area in a plane perpendicular to the flow direction of the exhaust gas than the second retaining portion.

In this configuration, the second holding portion is disposed in the gap formed between the first inner pipe, which is located inside the second inner pipe in the radial direction of the exhaust pipe, and the outer pipe. Therefore, the second holding portion can function as a spacer that holds the gap between the first inner pipe and the outer pipe while slidably holding the first inner pipe relative to the outer pipe. Also, the first holding portion, which has a smaller exhaust gas passing amount per unit area in a plane perpendicular to the flow direction of the exhaust gas than the second holding portion, is disposed in the gap formed between the first inner pipe and the second inner pipe. Therefore, the first holding portion makes it difficult for exhaust gas to leak from the gap between the first inner pipe and the second inner pipe to the gap between the outer pipe and the inner pipe. Therefore, it is easy to reduce the influence of the thermal expansion difference between the inner pipe and the outer pipe, and the sealing property of the inner pipe can be improved.

In one aspect of the present disclosure, the first retaining portion and the second retaining portion may be connected, and the second retaining portion may be formed so that the movement of the second retaining portion toward the downstream side in the flow direction of the exhaust gas is restricted by the second inner pipe. In such a configuration, the first retaining portion disposed in the gap formed between the first inner pipe and the second inner pipe and the second retaining portion having a thickness greater than that of the first retaining portion are connected and formed as one body. Therefore, even if the first retaining portion moves along the flow direction of the exhaust gas, the movement of the first retaining portion toward the second inner pipe is restricted by the second retaining portion abutting against the second inner pipe. This makes it difficult for the retaining member to fall off into the inner pipe even if it is not fixed to the inner pipe or the outer pipe. Therefore, there is no need to fix the retaining member to the inner pipe or the outer pipe by welding or the like.

One aspect of the present disclosure may further include a connecting pipe and an outer casing member. The connecting pipe is connected to the upstream of the first inner pipe or the second inner pipe located upstream in the flow direction of the exhaust gas. The outer casing member is arranged to surround the outer periphery of the connecting pipe and is connected to the upstream of the outer pipe. There may be a space between the outer casing member and the connecting pipe. With this configuration, the air layer in the space between the outer casing member and the connecting pipe and the air layer in the space between the inner pipe and the outer pipe located downstream of the exhaust pipe can reduce radiant heat over a wide range. As a result, even if a device such as a battery, whose temperature rise is undesirable, is arranged near the outer casing member and the exhaust pipe, the heat damage to the device can be reduced, and the range in which the device can be installed is expanded. As a result, it is possible to expand the number of batteries arranged near the outer casing member and the exhaust pipe in, for example, a hybrid vehicle equipped with a battery.

In one aspect of the present disclosure, the connecting pipe may have a communication hole that connects the inside and outside of the connecting pipe. With this configuration, the communication hole provided in the connecting pipe allows the exhaust gas in the connecting pipe to spread through the communication hole into the space between the outer casing member and the connecting pipe, thereby providing a sound-deadening effect due to expansion. The communication hole also makes it possible to suppress noise caused by pulsation of the vehicle engine.

In one aspect of the present disclosure, a sound-absorbing material may be disposed in the space between the outer casing member and the connecting pipe. In such a configuration, the gap between the inner tube and the outer tube is blocked by the second retaining portion. Therefore, if the sound-absorbing material is formed of, for example, glass wool, it is possible to prevent the glass wool from scattering into the gap formed between the inner tube and the outer tube located downstream in the flow direction of the exhaust gas.

1 is a schematic cross-sectional view showing a noise suppressor having a configuration in which a muffler is connected to the upstream side of a resonating double pipe. 2 is an enlarged cross-sectional view of a connection portion between a muffler and a resonating double pipe in the silencer of FIG. 1 . A cross-sectional view showing a configuration in which the second holding portion of the holding member is arranged in the gap formed between the second straight pipe portion and the first inner pipe of the outer member of the muffler. A cross-sectional view showing a configuration in which the second retaining portion of the retaining member is arranged in the gap formed between the second straight pipe portion of the outer casing member of the muffler and the first inner pipe, and in the gap formed between the outer pipe and the first inner pipe. 1 is a cross-sectional view showing a noise suppressor in which an outer tube of a resonating double tube is inserted inside an outer member of a muffler.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. Configuration]
The silencer 100 shown in Fig. 1 is a device for reducing exhaust noise used in an exhaust system that constitutes an exhaust gas flow path of an internal combustion engine. The silencer 100 is provided, for example, in a hybrid vehicle or the like equipped with a battery 200. The silencer 100 may also be provided in a vehicle that does not have a battery 200. The silencer 100 includes a muffler 1, a resonance double pipe 2, and a holding member 3. In the example shown in Fig. 1, the resonance double pipe 2 has a bent shape that matches the shape of the battery 200 that is arranged near the silencer 100. In this embodiment, the muffler 1 is arranged upstream of the resonance double pipe 2.

The muffler 1 includes an outer casing member 11, a first inner pipe 12, a connecting pipe 13, a catalytic device 14, and an upstream cone 15. In this embodiment, the muffler 1 is a catalyst-integrated muffler formed integrally with a catalytic device 14 having a catalyst 141 that purifies exhaust gas G. The muffler 1 has a double-pipe structure including the first inner pipe 12, a connecting pipe 13 connected to the first inner pipe 12, and an outer casing member 11 arranged to surround the outer circumferential surfaces of the first inner pipe 12 and the connecting pipe 13. The muffler 1 has a first silencing space 16, which is a space for silencing formed between the outer casing member 11 and the connecting pipe 13. The muffler 1 exerts a silencing effect by the first silencing space 16.

1 and 2, the outer casing member 11 is a cylindrical metal pipe formed so that the downstream end of the outer casing member 11 is tapered toward the central axis of the muffler 1. Specifically, the outer casing member 11 has, in order from the upstream side, a first straight pipe section 111, a first truncated cone section 112, and a second straight pipe section 113. The first straight pipe section 111 and the second straight pipe section 113 each have a straight pipe-shaped portion whose diameter does not change. The diameter of the first straight pipe section 111 is larger than the diameter of the second straight pipe section 113. The first truncated cone section 112 is a truncated cone-shaped portion whose cross-sectional area gradually decreases from the downstream end of the first straight pipe section 111 toward the upstream end of the second straight pipe section 113. The catalytic device 14 is disposed inside the first straight pipe section 111. An upstream cone 15 is provided at the opening at the upstream end of the first straight pipe section 111, which connects to the exhaust pipe located upstream of the muffler 1. Exhaust gas G flowing through the exhaust pipe located upstream of the muffler 1 is introduced into the outer casing member 11 through the upstream cone 15.

The first inner pipe 12 and the connecting pipe 13 are metal pipes through which the exhaust gas G passes. The first inner pipe 12 and the connecting pipe 13 are arranged in the outer casing member 11 so as to be aligned in the flow direction of the exhaust gas G. The first inner pipe 12 is arranged downstream of the connecting pipe 13.

The first inner pipe 12 is a straight pipe whose diameter does not change, and is disposed inside the second straight pipe section 113 of the outer casing member 11. A first gap 17 that communicates with the first silencing space 16 is formed between the second straight pipe section 113 and the first inner pipe 12. The downstream end 121 of the first inner pipe 12 protrudes downstream from the downstream end 113A of the second straight pipe section 113 of the outer casing member 11. In other words, the downstream end 121 of the first inner pipe 12 is disposed so as not to be surrounded by the second straight pipe section 113.

The connecting pipe 13 has a third straight pipe section 131 and a second truncated cone section 132. The third straight pipe section 131 is a section whose diameter does not change, that is, a straight pipe section. The second truncated cone section 132 is a truncated cone section whose cross-sectional area gradually decreases from the downstream end of the third straight pipe section 131 toward the upstream end of the first inner pipe 12. The connecting pipe 13 is disposed inside the first straight pipe section 111 of the outer casing member 11 and the first truncated cone section 112 of the outer casing member 11. The upstream end of the connecting pipe 13 is connected to the separator 19. The separator 19 has a wall section 191 that is provided so as to intersect, more preferably perpendicular to, the flow direction of the exhaust gas G, and an opening section 192 formed in the center of the wall section 191. The opening section 192 protrudes with a reduced diameter as it approaches the downstream side. The downstream end of the opening section 192 is connected to the upstream end of the connecting pipe 13 described above. In addition, the catalytic converter 14 is provided upstream of the separator 19 with a space in the flow direction of the exhaust gas G. As a result, the exhaust gas G that has passed through the catalytic converter 14 passes through the separator 19, the connecting pipe 13, and the first inner pipe 12, is discharged from the muffler 1, and is introduced into the inside of the resonance double pipe 2.

The connecting pipe 13 has one or more holes, preferably multiple communication holes 133, that connect the inside and outside of the connecting pipe 13. The multiple communication holes 133 are formed in the third straight pipe section 131 of the connecting pipe 13. A sound absorbing material 18 such as glass wool is arranged in the first silencing space 16 between the outer casing member 11 and the connecting pipe 13. The sound absorbing material 18 is arranged so as to cover at least the outer circumferential surface of the third straight pipe section 131 of the connecting pipe 13 so as to cover the multiple communication holes 133. The sound absorbing material may be filled in the first silencing space 16 formed between the outer casing member 11 and the connecting pipe 13.

The resonance double pipe 2 is an exhaust pipe with a double pipe structure including a second inner pipe 21 and an outer pipe 22. The resonance double pipe 2 has a second silencing space 23, which is a space for silencing sound formed between the second inner pipe 21 and the outer pipe 22. The resonance double pipe 2 exerts a silencing effect due to the second silencing space 23. In addition, the resonance double pipe 2 can reduce the radiant heat of the exhaust gas G due to its double pipe structure.

The second inner pipe 21 is a metal pipe through which the exhaust gas G passes. Specifically, the exhaust gas G discharged from the muffler 1 is introduced into the second inner pipe 21 from the opening of the upstream end 211 of the second inner pipe 21, and is discharged from the opening of the downstream end 212 of the second inner pipe 21. The second inner pipe 21 has a shape in which the upstream end 211 and the downstream end 212 each have an enlarged diameter.

The outer pipe 22 is a metal pipe arranged to surround the outer circumferential surface of the second inner pipe 21. The downstream end 222 of the outer pipe 22 has a shape with a reduced diameter so that the inner circumferential surface of the outer pipe 22 can abut against the outer circumferential surface of the second inner pipe 21. A second gap 24 communicating with the second silencing space 23 is formed between the upstream end 211 of the second inner pipe 21 and the outer pipe 22. The outer pipe 22 has a length greater than the second inner pipe 21 in the flow direction of the exhaust gas G. The upstream end 221 of the outer pipe 22 protrudes outward from the upstream end 211 of the second inner pipe 21. In other words, the second inner pipe 21 is covered by the outer pipe 22 while being arranged inside the upstream end 221 of the outer pipe 22.

As shown in FIG. 2, the downstream end of the muffler 1 is inserted into the inside of the resonance double tube 2, thereby connecting the muffler 1 and the resonance double tube 2. Specifically, the outer casing 11 and the outer tube 22 are arranged so that the downstream end 113A of the second straight tube section 113 of the outer casing member 11 of the muffler 1 is inserted into the inside of the upstream end 221 of the outer tube 22 of the resonance double tube 2. The outer peripheral surface of the downstream end 113A of the second straight tube section 113 abuts against the inner peripheral surface of the upstream end 221 of the outer tube 22. The second straight tube section 113 of the outer casing member 11 and the outer tube 22 are fixed by welding or the like, thereby connecting the muffler 1 and the resonance double tube 2.

The first inner tube 12 and the second inner tube 21 are arranged so that the downstream end 121 of the first inner tube 12 of the muffler 1 is inserted inside the upstream end 211 of the second inner tube 21 of the resonant double tube 2. A third gap 25 is formed between the outer peripheral surface of the downstream end 121 of the first inner tube 12 and the inner peripheral surface of the upstream end 211 of the second inner tube 21. A fourth gap 26 is formed between the outer peripheral surface of the downstream end 121 of the first inner tube 12 and the inner peripheral surface of the outer tube 22. A holding member 3 is arranged in the third gap 25 and the fourth gap 26. The holding member 3 can hold the positions of the first inner tube 12 and the second inner tube 21 relative to the outer tube 22. The first inner tube 12 and the second inner tube 21 are slidably held by the holding member 3. In addition, the first inner tube 12, the second inner tube 21, and the outer tube 22 are slidably held by the holding member 3.

The retaining member 3 extends along the entire circumferential direction in the third gap 25 and the fourth gap 26. Specifically, the retaining member 3 is ring-shaped so as to reduce the ring-shaped third gap 25 formed between the first inner tube 12 and the second inner tube 21 and the ring-shaped fourth gap 26 formed between the first inner tube 12 and the outer tube 22 in the circumferential direction. In other words, the retaining member 3 is arranged to close the third gap 25 and the fourth gap 26. The shape of the retaining member is not limited to a ring shape, and for example, the retaining member may have an area in the circumferential direction where the retaining member is partially absent. The retaining member 3 is a ring member formed from a high-density material, such as stainless steel fiber, such as a wire mesh. By using stainless steel fiber as the retaining member 3, the sealing property is improved and it is possible to easily restrict the passage of the exhaust gas G.

The holding member 3 has a first holding portion 31 and a second holding portion 32. The first holding portion 31 is a portion of the holding member 3 that is disposed in the third gap 25 between the first inner tube 12 and the second inner tube 21. The second holding portion 32 is a portion of the holding member 3 that is disposed in the fourth gap 26 between the first inner tube 12 and the outer tube 22. In this embodiment, the first holding portion 31 and the second holding portion 32 are integrally formed. The first holding portion 31 of the holding member 3 has a smaller amount of exhaust gas G passing through it per unit area in a plane perpendicular to the flow direction of the exhaust gas G than the second holding portion 32. In other words, the first holding portion 31 has a higher packing density of stainless steel fibers per unit area than the second holding portion 32. As a result, the first holding portion 31 has improved sealing properties compared to the second holding portion 32, and is more likely to restrict the passage of exhaust gas G.

For example, by compressing a portion of the stainless steel fibers, the compressed portion can be made to have a higher density than the non-compressed portion, thereby forming a member in which a high-density portion and a portion with a lower density than the compressed portion are integrated. In other words, by this method, it is possible to form the holding member 3 of this embodiment in which a high-density first holding portion 31 and a low-density second holding portion 32 with a lower density than the first holding portion 31 are integrated. In this way, a step is formed between the compressed portion and the non-compressed portion by compressing a portion of the stainless steel fibers, so that the holding member 3 has a stepped shape in the thickness direction. In other words, in the holding member 3, the second holding portion 32 is thicker than the first holding portion 31. Note that the method of forming the holding member 3 in which the first holding portion 31 and the second holding portion 32 are integrally formed is not limited to the above-mentioned method, and for example, the holding member may be integrally formed by joining a separate high-density first holding portion and a low-density second holding portion together.

2. Effects
According to the embodiment described above in detail, the following effects can be obtained.
(2a) In this embodiment, the low-density second holding portion 32 is disposed in the fourth gap 26 formed between the first inner pipe 12 and the outer pipe 22. Therefore, the second holding portion 32 can function as a spacer that holds the fourth gap 26 while slidably holding the first inner pipe 12 relative to the outer pipe 22. Also, the high-density first holding portion 31, which has a smaller exhaust gas passing amount per unit area in a plane perpendicular to the flow direction of the exhaust gas G than the second holding portion 32, is disposed in the third gap 25 formed between the first inner pipe 12 and the second inner pipe 21. Therefore, the first holding portion 31 makes it difficult for the exhaust gas to leak from the third gap 25 to the gap between the second inner pipe 21 and the outer pipe 22, specifically, to the second gap 24 and the second silencing space 23. Therefore, it is easy to reduce the influence of the thermal expansion difference between the first inner pipe 12 and the second inner pipe 21 and the outer pipe 22, and the sealing property of the first inner pipe 12 and the second inner pipe 21 can be improved. As a result, it is possible to improve the function of the resonating double tube 2 as a Helmholtz resonator. Also, in the resonating double tube 2, it is possible to further reduce the radiant heat due to the exhaust gas.

(2b) In this embodiment, the first retaining portion 31, which is disposed in the third gap 25 formed between the first inner pipe 12 and the second inner pipe 21, and the second retaining portion 32, which is thicker than the first retaining portion 31, are integrally formed. For this reason, even if the first retaining portion 31 moves along the flow direction of the exhaust gas G, the second retaining portion 32 abuts against the upstream end portion 211 of the second inner pipe 21, thereby restricting the movement of the first retaining portion 31 toward the second inner pipe 21. As a result, even if the retaining member 3 is not fixed by welding or the like to any of the outer peripheral surface of the first inner pipe 12, the inner peripheral surface of the second inner pipe 21, or the outer pipe 22, the retaining member 3 is less likely to fall off into the second inner pipe 21.

In addition, in this embodiment, the downstream end 113A of the second straight pipe section 113 of the outer member 11 of the muffler 1 is inserted inside the upstream end 221 of the outer pipe 22 of the resonance double pipe 2. For this reason, even if the second holding portion 32 moves in a direction opposite to the flow direction of the exhaust gas G, the second holding portion 32 abuts against the downstream end 113A of the second straight pipe section 113, thereby restricting the movement of the second holding portion 32 toward the second straight pipe section 113. Therefore, there is no need to fix the holding member 3 by welding or the like.

(2c) In this embodiment, since both the muffler 1 and the resonance double tube 2 have a double tube structure, radiant heat can be reduced over a wide range. In addition, the first inner tube 12 is inserted into the inside of the second inner tube 21, and is arranged so as to overlap, and the first holding part 31 is arranged in the gap formed between the first inner tube 12 and the second inner tube 21. Therefore, exhaust gas is less likely to flow into the gap between the second inner tube 21 and the outer tube 22 in the double tube structure, specifically the second gap 24 and the second silencing space 23, and the radiant heat of the resonance double tube 2 can be reduced. This reduces heat damage to the battery 200, which is arranged near the muffler 1 and the resonance double tube 2 and is undesirable for a rise in temperature, and expands the range in which the battery 200 can be installed. As a result, in a hybrid vehicle, for example, in which the battery 200 is installed, it is possible to expand the battery 200 arranged near the muffler 1 and the resonance double tube 2.

(2d) In this embodiment, a plurality of communication holes 133 are provided in the connecting pipe 13. Therefore, the plurality of communication holes 133 allow the exhaust gas in the connecting pipe 13 to spread through the plurality of communication holes 133 into the space between the outer casing 11 and the connecting pipe 13, specifically into the first silencing space 16, thereby providing a silencing effect through expansion. In addition, the plurality of communication holes 133 can suppress noise caused by pulsation of the vehicle engine.

(2e) In this embodiment, the fourth gap 26 between the first inner pipe 12 and the outer pipe 22 is closed by the second retaining portion 32. This makes it possible to suppress scattering of glass wool into the gap between the second inner pipe 21 and the outer pipe 22 located downstream in the flow direction of the exhaust gas G, specifically into the second gap 24 and the second silencing space 23.

(2f) In this embodiment, the muffler 1 is a catalyst-integrated muffler formed integrally with the catalytic converter 14, so that the space required for the exhaust system under the floor of the vehicle can be reduced.
The first inner pipe 12, the second inner pipe 21 and the outer pipe 22 correspond to an example of an exhaust pipe.

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-described embodiments and can take various forms.

(3a) In the above embodiment, the second holding portion 32 of the holding member 3 is disposed in the fourth gap 26 between the first inner tube 12 and the outer tube 22, but the location where the second holding portion is disposed is not limited to this.

For example, as in the retaining member 3a shown in FIG. 3, the second retaining portion 32a may be disposed in the first gap 17 between the second straight pipe portion 113 of the outer casing member 11 and the first inner pipe 12. That is, the retaining member 3a may have a first retaining portion 31 disposed in the third gap 25 and a second retaining portion 32a disposed in the first gap 17. As with the retaining member 3 of the above embodiment, the first retaining portion 31 of the retaining member 3a has a smaller amount of exhaust gas G passing through it per unit area in a plane perpendicular to the flow direction of the exhaust gas G than the second retaining portion 32a.

In this configuration, before the muffler 1 and the resonance double tube 2 are connected, the second holding portion 32a of the holding member 3a is first press-fitted and fixed between the second straight tube portion 113 of the outer member 11 of the muffler 1 and the first inner tube 12. Therefore, when connecting the muffler 1 and the resonance double tube 2, the first holding portion 31 of the holding member 3a is easily inserted into the resonance double tube 2 without fixing the holding member 3a to the muffler 1 side by spots or the like. In addition, in this configuration, the second holding portion 32a of the holding member 3a functions as a spacer in the gap between the second straight tube portion 113 and the first inner tube 12, so that when connecting the muffler 1 and the resonance double tube 2, the first inner tube 12 can be prevented from being assembled at an angle.

For example, as in the retaining member 3b shown in FIG. 4, the second retaining portion 32b may be arranged to extend to the first gap 17 between the second straight pipe portion 113 of the outer casing member 11 and the first inner pipe 12 in addition to the fourth gap 26 between the first inner pipe 12 and the outer pipe 22. In other words, the retaining member 3b may have a first retaining portion 31 arranged in the third gap 25, and a second retaining portion 32b arranged in the fourth gap 26 and the first gap 17. The second retaining portion 32b has a third retaining portion 33 arranged in the fourth gap 26, and a fourth retaining portion 34 arranged in the first gap 17.

In this configuration, the first gap 17, the fourth gap 26, and the third gap 25 are blocked by the first holding portion 31, the third holding portion 33, and the fourth holding portion 34, so that the sealing performance of the exhaust gas is further improved. As a result, the heat insulation performance of the silencer can be further improved. In addition, in this configuration, before the muffler 1 and the resonance double tube 2 are connected, the fourth holding portion 34 of the holding member 3b is press-fitted and fixed between the second straight pipe portion 113 and the first inner pipe 12 in the outer casing member 11 of the muffler 1. Therefore, when connecting the muffler 1 and the resonance double tube 2, the first holding portion 31 and the third holding portion 33 of the holding member 3b are easily inserted into the resonance double tube 2 even if the holding member 3b is not fixed to the muffler 1 side by spots or the like. In addition, in this configuration, the third holding portion 33 functions as a spacer in the gap between the second straight pipe portion 113 and the first inner tube 12, and the fourth holding portion 34 functions as a spacer in the gap between the outer tube 22 and the first inner tube 12. This further prevents the first inner tube 12 from being assembled at an angle when connecting the muffler 1 and the resonant double tube 2.

(3b) In the above embodiment, the downstream end 113A of the second straight pipe section 113 of the outer casing member 11 of the muffler 1 is inserted into the upstream end 221 of the outer pipe 22 of the resonance double pipe 2 at the connection portion between the muffler 1 and the resonance double pipe 2. However, the method of connecting the muffler 1 and the resonance double pipe 2 is not limited to this. For example, as in the silencer 100c shown in FIG. 5, the upstream end 221 of the outer pipe 22 of the resonance double pipe 2 may be inserted into the downstream end 113C of the second straight pipe section 113c of the outer casing member 11c of the muffler 1c. In this way, since the method of connecting the muffler and the resonance double pipe is not limited, when the outer casing member and the outer pipe are fixed by welding or the like, the connection method can be changed to correspond to welding depending on the equipment held, such as a welding pattern from the muffler side or a welding pattern from the resonance double pipe side.

(3c) In the above embodiment, a configuration in which the first retaining portion 31 and the second retaining portion 32 are integrally formed is illustrated. However, the first retaining portion 31 and the second retaining portion 32 may be formed separately.
(3d) In the above embodiment, the catalyst-integrated muffler 1 formed integrally with the catalytic converter 14 is illustrated, but the configuration of the muffler is not limited to this. For example, the muffler may be formed separately from the catalytic converter 14.

(3e) In the above embodiment, a configuration in which a plurality of communication holes 133 are provided in the connecting pipe 13 is illustrated. However, the connecting pipe may be configured not to have a plurality of communication holes.
(3f) In the above embodiment, a configuration was exemplified in which sound-absorbing material 18 such as glass wool is arranged in the first sound-absorbing space 16 between the outer casing member 11 and the connecting pipe 13, but a configuration in which no sound-absorbing material is arranged in the first sound-absorbing space 16 is also possible.

(3g) The connecting pipe 13 and the first inner pipe 12 may be integral or separate.
(3h) In the above embodiment, the muffler 1 has a double pipe structure, but the muffler may have a structure other than the double pipe structure having the first silencing space 16. For example, the muffler may have a housing having a shape other than a tubular shape and an exhaust pipe, and may have a first silencing space within the housing.

(3i) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the configuration of the above embodiments may be omitted. In addition, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. All aspects included in the technical idea identified from the wording of the claims are embodiments of the present disclosure.

1, 1c... muffler, 2... resonant double tube, 3, 3a, 3b... retaining member, 11, 11c... outer shell member, 12... first inner tube, 13... connecting pipe, 14... catalytic device, 15... upstream cone, 16... first silencing space, 17... first gap, 19... separator, 24... second gap, 25... third gap, 26... fourth gap, 18... sound absorbing material, 21... second inner tube, 22... outer tube, 23... second silencing space, 31... first retaining part, 32, 3 2a, 32b...second holding portion, 33...third holding portion, 34...fourth holding portion, 100, 100c...silencer, 111...first straight pipe portion, 112...first truncated cone portion, 113, 113c...second straight pipe portion, 133...communication hole, 131...third straight pipe portion, 113A, 113C, 121, 211, 212, 221, 222...end portion, 132...second truncated cone portion, 141...catalyst, 191...wall portion, 192...opening portion, 200...battery.

Claims (5)

An exhaust pipe having a double pipe structure,
an inner pipe through which exhaust gas passes;
an outer tube arranged to surround an outer periphery of the inner tube;
a holding member disposed between the outer tube and the inner tube;
Equipped with
the inner pipe includes a first inner pipe and a second inner pipe aligned in a flow direction of exhaust gas, and an end portion of the first inner pipe on the second inner pipe side is inserted into the second inner pipe;
the holding member has at least a first holding portion disposed in a gap formed between the first inner tube and the second inner tube, and a second holding portion disposed in a gap formed between the first inner tube and the outer tube,
An exhaust pipe, wherein the first holding portion has a smaller amount of exhaust gas passing through it per unit area in a plane perpendicular to the flow direction than the second holding portion. 2. The exhaust pipe according to claim 1,
The first holding portion and the second holding portion are connected to each other,
the second holding portion is formed such that movement of the second holding portion toward a downstream side in the flow direction is restricted by the second inner pipe. The exhaust pipe according to claim 1 or 2,
a connecting pipe connected to an upstream side of the first inner pipe or the second inner pipe located on the upstream side in the flow direction, and an outer shell member arranged to surround an outer periphery of the connecting pipe and connected to the upstream side of the outer pipe,
An exhaust pipe having a space between the outer shell member and the connecting pipe. 4. The exhaust pipe according to claim 3,
The connecting pipe has a communication hole that connects the inside and outside of the connecting pipe. The exhaust pipe according to claim 3 or 4,
An exhaust pipe, wherein a sound absorbing material is disposed in a space between the outer shell member and the connecting pipe.

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