JP2021110242A - Exhaust pipe - Google Patents

Abstract

To control an inner pipe from being less likely to slide with respect to an outer pipe due to expansion in an exhaust pipe with a double pipe structure.SOLUTION: An exhaust pipe with a double pipe structure includes an inner pipe and an outer pipe. The inner pipe allows an exhaust gas to pass therethrough. The outer pipe is disposed so as to surround an outer peripheral surface of the inner pipe. The inner pipe has a slide end that is an end of the inner pipe and capable of sliding with respect to the outer pipe. The inner pipe includes a suppression part for suppressing expansion of a diameter of the inner pipe in a radial direction due to expansion of the inner pipe in the slide end.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an exhaust pipe.

In an exhaust system for an automobile, an exhaust pipe having a double pipe structure having an inner pipe and an outer pipe may be used. In an exhaust pipe having such a double pipe structure, high-temperature exhaust gas flows inside the inner pipe, so that a thermal expansion difference occurs between the inner pipe and the outer pipe.

Patent Document 1 states that in order to absorb the axial force acting on the first pipe due to thermal expansion, the first pipe is axially inserted with respect to the second pipe into which the first pipe is inserted. Disclosed is an exhaust gas treatment device that includes a slidable expansion adjusting portion at the end of the first pipe.

Japanese Unexamined Patent Publication No. 2011-127607

In the inner pipe of the exhaust pipe having a double pipe structure, in addition to the axial force due to thermal expansion, a radial force due to thermal expansion is generated. However, in the exhaust gas treatment device described above, the influence of the radial force due to thermal expansion is not taken into consideration. Therefore, when a radial force is generated in the first pipe due to thermal expansion, the gap between the first pipe and the second pipe in the expansion adjusting portion becomes narrower, and the first pipe becomes the second pipe. It may be difficult to slide against the pipe.

One aspect of the present disclosure is an object of the exhaust pipe having a double pipe structure to prevent the inner pipe from becoming difficult to slide with respect to the outer pipe due to expansion.

One aspect of the present disclosure is an exhaust pipe having a double pipe structure, which includes an inner pipe and an outer pipe. Exhaust gas passes through the inner pipe. The outer pipe is arranged so as to surround the outer peripheral surface of the inner pipe. The inner pipe is provided so that the slide end, which is the end of the inner pipe, is slidable with respect to the outer pipe. The inner pipe has a suppressing portion at the end of the slide that suppresses the radial expansion of the inner pipe due to the expansion of the inner pipe.

In such a configuration, the increase in the diameter of the inner pipe is suppressed, so that the increase in the frictional resistance between the inner pipe and the outer pipe is suppressed. Therefore, in the exhaust pipe having a double pipe structure, it is possible to prevent the inner pipe from becoming difficult to slide with respect to the outer pipe due to expansion.

In one aspect of the present disclosure, the restraint may have a notch in the end face of the slide end. In such a configuration, the radial expansion of the inner pipe due to expansion is suppressed. That is, when the high-temperature exhaust gas passes through the inside of the inner pipe, the inner pipe expands and expands in the circumferential direction. In such a case, in the configuration without a notch, the length of the inner pipe in the circumferential direction becomes large, so that the diameter of the inner pipe becomes large. In this respect, in the configuration having a notch, even if the inner pipe expands in the circumferential direction, the increased length of the inner pipe in the circumferential direction is absorbed by narrowing the gap formed by the notch. Therefore, it is possible to prevent the inner pipe from expanding in the radial direction due to the expansion in the circumferential direction. Further, even when a force is generated in the radial direction of the inner pipe due to expansion, the slide end portion of the inner pipe is easily elastically deformed by the notch. Therefore, it is possible to prevent the inner pipe from becoming difficult to slide with respect to the outer pipe due to expansion.

In one aspect of the present disclosure, the restraining portion may have a convex portion formed on the end surface of the slide end portion and projecting inward of the inner tube. In such a configuration, the radial expansion of the inner pipe due to expansion is suppressed. That is, when the high-temperature exhaust gas passes through the inside of the inner pipe, the inner pipe expands and expands in the circumferential direction. In such a case, in the configuration having no convex portion, the length of the inner pipe in the circumferential direction becomes large, so that the diameter of the inner pipe becomes large. In this respect, in the configuration having the convex portion, even if the inner pipe expands in the circumferential direction, the increased length of the inner pipe in the circumferential direction is absorbed by narrowing the space formed by the convex portion. Therefore, it is possible to prevent the inner pipe from expanding in the radial direction due to the expansion in the circumferential direction. Further, even when a force is generated in the radial direction of the inner pipe due to expansion, the slide end portion of the inner pipe is easily elastically deformed by the convex portion. Therefore, it is possible to prevent the inner pipe from becoming difficult to slide with respect to the outer pipe due to expansion.

In one aspect of the present disclosure, the inner tube may further have a contact portion at the end of the slide. The contact portion may protrude to the outside of the inner pipe and come into contact with the outer pipe. According to such a configuration, the contact portion abuts on the outer pipe to suppress the surface contact between the inner pipe and the outer pipe, so that the outer pipe can be made while reducing the contact area between the outer pipe and the inner pipe. The inner tube can be held slidably.

It is sectional drawing which shows the structure of the exhaust pipe of 1st Embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. It is a figure which shows that the diameter expansion in a radial direction of an inner pipe by thermal expansion of an exhaust pipe of 1st Embodiment is suppressed. It is sectional drawing which shows the structure of the exhaust pipe of 2nd Embodiment. It is a VV cross-sectional view of FIG. It is a figure which shows that the diameter expansion in a radial direction of an inner pipe by thermal expansion of an exhaust pipe of 2nd Embodiment is suppressed. It is sectional drawing which shows the structure of the exhaust pipe which the inner pipe can slide with respect to the fixing member fixed to the outer pipe. FIG. 6 is a cross-sectional view taken along the line VIII-VIII of FIG. 7 showing that the radial expansion of the inner pipe due to thermal expansion of the exhaust pipe in which the inner pipe can slide with respect to the fixing member is suppressed. FIG. 5 is a cross-sectional view showing the configuration of another embodiment with respect to the number and arrangement of slits and ribs. It is sectional drawing which shows the structure of the exhaust pipe which the enlarged diameter part of the inner pipe is slidable with respect to the outer pipe. 9 is a cross-sectional view taken along the line XX of FIG. It is sectional drawing which shows the structure which shows the structure which the inner pipe which is slidable with respect to the outer pipe through a holding member has a convex part at the first end part. It is sectional drawing which shows the structure which shows the structure which the inner pipe which is slidable with respect to the outer pipe through a rib has a convex part at the 1st end. FIG. 5 is a cross-sectional view showing a configuration in which an inner pipe slidable with respect to an outer pipe via a holding member has a slit and a convex portion at a first end portion. FIG. 5 is a cross-sectional view showing a configuration in which an inner pipe slidable with respect to an outer pipe via a rib has a slit and a convex portion at a first end portion. It is a figure which shows the structure of another embodiment which the slit has a semi-elliptical shape. It is a figure which shows the structure of the other embodiment which the slit is triangular shape.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
The exhaust pipe 1 shown in FIG. 1 is a silencer having a double pipe structure used in an exhaust system constituting an exhaust gas flow path of an internal combustion engine. The exhaust pipe 1 includes an inner pipe 2, an outer pipe 3, and a holding member 4. The exhaust pipe 1 exerts a sound deadening effect due to a gap formed between the inner pipe 2 and the outer pipe 3. A sound absorbing material or the like may be contained in the gap between the inner pipe 2 and the outer pipe 3.

The internal combustion engine to which the exhaust system 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, and construction machinery, and power generation facilities.

The inner pipe 2 is a metal pipe through which exhaust gas passes. Specifically, the exhaust gas is introduced into the inner pipe 2 from one of the first opening 21 and the second opening 22, and is discharged from the opening on the opposite side. In the present embodiment, the inner pipe 2 is a straight pipe having a constant diameter. That is, the inner diameter of the first end 23, which is the end on the first opening 21 side, and the inner diameter of the second end 24, which is the end on the second opening 22 side, are equal. In the present embodiment, the inner pipe 2 has a first end portion 23 fixed to the outer pipe 3 and a second end portion 24 slidable with respect to the outer pipe 3. Here, the slidable state is a state in which it is not fixed, and is held so that it can slide, in other words, slide through an object that reduces frictional resistance or the like. .. In the present embodiment, the inner pipe 2 has a slit 5 at the second end portion 24 that suppresses the radial expansion of the inner pipe 2 due to thermal expansion.

The slit 5 is a notch extending linearly from the end surface of the second end portion 24 in the direction of the central axis A of the inner pipe 2. As shown in FIG. 1, in the present embodiment, the slit 5 is formed in a rectangular shape having a long side in the central axis A direction. As shown in FIG. 2, the end surface of the second end portion 24 is formed in a circumferential shape having a gap formed by the slit 5. In the present embodiment, three slits 5 are provided at equal intervals in the circumferential direction of the inner pipe 2. As a result, in the present embodiment, the end face of the second end portion 24 is formed in a circumferential shape having three gaps.

The outer pipe 3 is a metal pipe arranged so as to surround the outer peripheral surface of the inner pipe 2. The inner diameter of the outer pipe 3 is larger than the outer diameter of the inner pipe 2. The central axis of the outer tube 3 is arranged so as to coincide with the central axis A of the inner tube 2. It should be noted that these central axes do not necessarily have to coincide. As shown in FIG. 1, in the present embodiment, the outer pipe 3 is a cylindrical pipe formed so that the ends on both sides of the outer pipe 3 are reduced in diameter toward the central axis A of the inner pipe 2. be. In other words, the outer pipe 3 is an expansion type pipe having an enlarged diameter at the center. Specifically, the outer pipe 3 has a straight pipe portion 31, a first truncated cone portion 32, a second truncated cone portion 33, a fixed portion 34, and a holding portion 35.

The straight pipe portion 31, the fixing portion 34, and the holding portion 35 each have a constant cross-sectional area, that is, are straight tubular portions. The diameter of the straight pipe portion 31 is larger than that of the fixed portion 34 and the holding portion 35, and the diameter of the holding portion 35 is formed to be larger than the diameter of the fixed portion 34. The first truncated cone portion 32 and the second truncated cone portion 33 are truncated cone-shaped portions whose cross-sectional areas gradually decrease from both ends of the straight pipe portion 31 toward the fixed portion 34 and the holding portion 35, respectively.

The fixing portion 34 is a portion for fixing the first end portion 23 of the inner pipe 2. The fixing portion 34 surrounds the first end portion 23 so that the inner peripheral surface of the fixing portion 34 and the outer peripheral surface of the first end portion 23 come into contact with each other on the entire circumference. The first end portion 23 is fixed to the inner peripheral surface of the fixing portion 34 by, for example, welding.

The holding portion 35 is a portion that slidably holds the second end portion 24 of the inner pipe 2. The holding portion 35 surrounds the second end portion 24 so as to leave a gap between the inner peripheral surface of the holding portion 35 and the outer peripheral surface of the second end portion 24. The holding portion 35 extends from the inner pipe 2 to the outside in the central axis A direction. In the present embodiment, the holding portion 35 holds the second end portion 24 via the holding member 4 described later.

As shown in FIGS. 1 and 2, the holding member 4 is a member arranged in the gap between the second end portion 24 of the inner pipe 2 and the holding portion 35 of the outer pipe 3. Specifically, the holding member 4 is sandwiched between the outer peripheral surface of the second end portion 24 and the inner peripheral surface of the holding portion 35. The holding member 4 may be fixed to the second end portion 24 of the inner pipe 2 or may be fixed to the holding portion 35 of the outer pipe 3. The holding member 4 is arranged along the entire circumferential direction of the outer peripheral surface of the second end portion 24 and the inner peripheral surface of the holding portion 35. That is, the holding member 4 is arranged so as to close the gap between the inner pipe 2 and the outer pipe 3 in the direction of the central axis A of the inner pipe 2. The holding member 4 is preferably ring-shaped so that the gap between the second end portion 24 and the holding portion 35 can be reduced. Further, the holding member 4 is formed so that the length in the central axis A direction is longer than the length in the central axis A direction of the slit 5 so as to cover the gap formed by the slit 5 in the radial direction of the inner pipe 2. The length of the holding member 4 in the central axis A direction is preferably about the same as the length of the slit 5 in the central axis A direction. By making the length of the holding member 4 in the central axis A direction longer than the length of the slit 5 in the central axis A direction or about the same as the length of the slit 5 in the central axis A direction, the holding member 4 passes through the inner tube 2. It is possible to prevent the exhaust gas from leaking from the slit 5 between the outer pipe 3 and the inner pipe 2.

The holding member 4 may be at least slidable with respect to the inner pipe 2 or the outer pipe 3. In the present embodiment, a metal wire mesh is used as the holding member 4. By using a wire mesh as the holding member 4, it is possible to reduce the contact area with respect to the inner pipe 2 and the outer pipe 3. By slidably arranging the holding member 4 in the space between the inner tube 2 and the outer tube 3, the force generated in the axial direction due to the difference in thermal expansion between the inner tube 2 and the outer tube 3 is reduced.

[1-2. effect]
According to the first embodiment described in detail above, the following effects can be obtained.
(1a) In the present embodiment, the slit 5 suppresses the radial expansion of the inner pipe 2 due to the thermal expansion of the inner pipe 2, specifically, the radial expansion of the second end portion 24. NS.

That is, when the high-temperature exhaust gas passes through the inside of the inner pipe 2, the inner pipe 2 expands and expands in the circumferential direction. In such a case, in the configuration without the slit 5, the length of the inner pipe 2 in the circumferential direction becomes large, so that the diameter of the inner pipe 2 becomes large. In this respect, in the present embodiment, the inner pipe 2 has a slit 5 at the second end portion 24. Therefore, as shown in FIG. 3, the circumferential length of the second end portion 24, which increases as the diameter of the second end portion 24 increases, is reduced by narrowing the gap formed by the slit 5. It can be absorbed. As a result, the inner pipe 2 is prevented from expanding in the radial direction due to the expansion in the circumferential direction. Further, even when a force is generated in the radial direction of the inner tube 2 due to thermal expansion, the second end portion 24 is easily elastically deformed by the slit 5.

Therefore, it is possible to prevent the inner tube 2 from being difficult to slide with respect to the outer tube 3 due to thermal expansion. As a result, it is possible to prevent the inner tube 2 from buckling or breaking.

(1b) In the present embodiment, the holding member 4 is arranged in the gap between the holding portion 35 and the second end portion 24. As a result, a force is generated in the direction of the central axis A of the inner pipe 2 due to thermal expansion, so that even when the inner pipe 2 slides with respect to the outer pipe 3, the frictional resistance can be reduced by the holding member 4. can.

That is, when the high-temperature exhaust gas passes through the inside of the inner pipe 2, the inner pipe 2 expands in the direction of the central axis A, and the length of the inner pipe 2 in the direction of the central axis A becomes longer. In such a case, in the configuration without the holding member 4, the frictional resistance when the inner pipe 2 slides with respect to the outer pipe 3 becomes large. In this respect, the present embodiment has the holding member 4. Therefore, even if the inner pipe 2 slides with respect to the outer pipe 3 due to the length of the inner pipe 2 in the central axis A direction, the frictional resistance between the inner pipe 2 and the outer pipe 3 is reduced. Will be done. Further, as described above, the slit 5 suppresses the increase in the diameter of the second end portion 24. Therefore, the holding member 4 is suppressed from being compressed by narrowing the gap between the holding portion 35 and the second end portion 24. As a result, it is possible to further suppress an increase in the frictional resistance between the inner pipe 2 and the outer pipe 3. Therefore, it is possible to prevent the inner pipe 2 from being difficult to slide with respect to the outer pipe 3 even with respect to the force generated in the direction of the central axis A of the inner pipe 2 due to thermal expansion. Further, when the thermal expansion of the inner pipe 2 is settled and the length of the inner pipe 2 in the central axis A direction and the length of the inner pipe 2 in the circumferential direction are contracted so as to return to the basic length, an abnormal noise that may occur is generated. It can also be reduced.

(1c) In the present embodiment, the slit 5 can be formed at the same time as an essential step performed at the time of forming the inner tube 2, for example, a step of forming a punch hole in a flat plate state. Therefore, a configuration that suppresses the radial expansion of the inner tube 2 due to thermal expansion can be easily provided without increasing the number of steps, as compared with the case where a new step is added to form the inner tube 2.

In the first embodiment, the second end portion 24 corresponds to the slide end portion, and the slit 5 corresponds to the suppression portion.
[2. Second Embodiment]
[2-1. Constitution]
As shown in FIGS. 4 to 6, in the second embodiment, the point that the exhaust pipe 1a does not include the holding member 4 and the point that the inner pipe 2a has the rib 6 at the second end portion 24 are first. It is different from the exhaust pipe 1 of the embodiment. In addition, since the basic configuration of the exhaust pipe 1a is the same as that of the first embodiment, the same reference numerals are used for the configurations common to the first embodiment, and the description is omitted. I will explain mainly.

As shown in FIGS. 4 and 5, the inner tube 2a has a rib 6 at the second end 24.
The rib 6 is a portion that extends linearly in the direction of the central axis A of the inner pipe 2a and protrudes to the outside of the inner pipe 2a. In the present embodiment, the rib 6 projects in a curved surface toward the outer pipe 3. A part of the outer peripheral surface of the rib 6 comes into contact with the inner peripheral surface of the outer pipe 3. As shown in FIG. 4, in the present embodiment, the rib 6 is formed in a substantially elliptical shape. The length of the rib 6 in the central axis A direction is preferably about the same as the length of the slit 5 in the central axis A direction. The ribs 6 are arranged side by side with the slit 5 in the circumferential direction of the inner pipe 2a at intervals. As shown in FIG. 5, in the present embodiment, three ribs 6 are provided at equal intervals in the circumferential direction of the inner pipe 2a so that the ribs 6 and the slits 5 are adjacent to each other in the circumferential direction of the inner pipe 2a. Are arranged alternately in. In the present embodiment, the holding portion 35 of the outer pipe 3 slideably holds the second end portion 24 of the inner pipe 2a via the rib 6.

[2-2. effect]
According to the second embodiment described in detail above, the following effects can be obtained in addition to the effects (1a) and (1c) of the first embodiment described above.

(2a) In the present embodiment, since the ribs 6 and the slits 5 are alternately arranged so as to be adjacent to each other in the circumferential direction of the inner pipe 2a, when a force in the radial direction of the inner pipe 2a is generated due to thermal expansion. In addition, the force applied to the rib 6 can be released to the slit 5. Specifically, as shown in FIG. 6, when a force is generated in the radial direction of the inner pipe 2a due to thermal expansion, the rib 6 is pressed against the outer pipe 3. However, the ribs 6 are sandwiched by the slits 5 at intervals in the circumferential direction of the inner pipe 2a. In other words, the rib 6 is sandwiched between the gaps formed by the slits 5 at intervals in the circumferential direction of the inner pipe 2a. Therefore, even when a force in the radial direction of the inner pipe 2a is generated due to thermal expansion, the rib 6 is crushed by being pressed against the outer pipe 3, and at the same time, the force applied to the rib 6 can be released to the gap. can. Therefore, it is possible to further prevent the inner tube 2a from being difficult to slide with respect to the outer tube 3 due to thermal expansion.

(2b) In the present embodiment, since the rib 6 comes into contact with the outer pipe 3 to suppress the surface contact between the inner pipe 2a and the outer pipe 3, the contact area between the outer pipe 3 and the inner pipe 2a is reduced. , The outer pipe 3 can hold the inner pipe 2a in a slidable manner. Therefore, as compared with the configuration in which the outer pipe 3 slidably holds the inner pipe 2a via the holding member 4 or the like that reduces the frictional resistance, the number of parts is reduced, so that the structure in the double pipe structure is simplified. can do. In addition, since the cost of the member and the assembly process are reduced, the cost can be reduced.

(2c) In the present embodiment, similarly to the slit 5, the rib 6 can be formed at the same time as an essential step performed at the time of forming the inner tube 2, for example, a step of forming a punch hole in a flat plate state. .. Therefore, a configuration for holding the inner tube 2a and the outer tube 3 in a slidable manner can be easily provided without increasing the number of steps, as compared with the case where a new step is added and molded.

In the second embodiment, the second end portion 24 corresponds to the slide end portion, the slit 5 corresponds to the restraining portion, and the rib 6 corresponds to the contact portion.
[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 each of the above embodiments, the holding portion 35 of the outer pipe 3, that is, the outer pipe 3 itself holds the second end portion 24 of the inner pipes 2 and 2a in a slidable manner. The structure in which the end portion 24 is slidably held is not limited to this. For example, the inner pipes 2 and 2a are slidable with respect to the member fixed to the outer pipe 3 at the end opposite to the side where the inner pipes 2 and 2a are fixed in the outer pipe 3. You may. Here, the outer pipe 3 may include a member fixed to the outer pipe 3 in addition to the outer pipe 3 itself. Specifically, as shown in FIG. 7, with respect to the fixing member 7 fixed to the outer pipe 3b at the end opposite to the side where the inner pipe 2b is fixed in the outer pipe 3b, the inner pipe 2b may have a slidable configuration.

The exhaust pipe 1b shown in FIG. 7 includes an inner pipe 2b, an outer pipe 3b, a holding member 4, and a fixing member 7.
The inner pipe 2b has the same basic configuration as the inner pipe 2 of the first embodiment, but the second end portion 24, which is the end portion on the side not fixed by the fixing portion 34 of the outer pipe 3b, has a second end portion 24. The difference is that the length of the pipe is located inside the outer pipe 3b, for example, near the center.

The outer pipe 3b has the same basic configuration as the outer pipe 3 of the first embodiment, except that it has a member fixing portion 35b instead of the holding portion 35 of the first embodiment. The member fixing portion 35b is a portion for fixing the first end portion 71 of the fixing member 7. The member fixing portion 35b surrounds the first end portion 71 so that the inner peripheral surface of the member fixing portion 35b and the outer peripheral surface of the first end portion 71 abut on the entire circumference. The first end portion 71 is fixed to the inner peripheral surface of the member fixing portion 35b by, for example, welding. That is, for example, the ends of the outer pipe 3 are welded or the like so as to prevent water or the like provided in the gap between the outer pipe 3 and the inner pipe 2b and the fixing member 7 from leaking from the outer pipe 3b. Is fixed by.

The fixing member 7 is a metal pipe through which exhaust gas passes. The central axis of the fixing member 7 is arranged so as to coincide with the central axis A of the inner tube 2b, and the outer peripheral surface is surrounded by the outer tube 3b. The fixing member 7 has a second end portion 72 so that the diameter of the second end portion 72, which is the end portion on the side not fixed by the outer pipe 3, is larger than the diameter of the first end portion 71. It is a cylindrical pipe formed so as to expand the diameter near the side. The fixing member 7 slideably holds the second end portion 24 of the inner pipe 2b at the second end portion 72. The second end portion 72 surrounds the second end portion 24 so as to leave a gap between the inner peripheral surface of the second end portion 72 and the outer peripheral surface of the second end portion 24. The second end 72 holds the second end 24 via the holding member 4.

In such a configuration, since the second end 72 of the fixing member 7 is located outside the second end 24 of the inner pipe 2b, the diameter of the second end 72 is expanded in the radial direction due to thermal expansion. Is smaller than the radial expansion due to thermal expansion of the second end 24. Therefore, a difference in thermal expansion may occur between the second end portion 72 and the second end portion 24. However, in such a configuration, since the inner tube 2b has a slit 5 at the second end portion 24, as shown in FIG. 8, the same effect as (1a) to (1c) of the first embodiment can be obtained. Obtainable. That is, it is possible to prevent the inner pipe 2b from becoming difficult to slide with respect to the outer pipe 3b, specifically, the fixing member 7 due to thermal expansion.

The exhaust pipe 1b may be configured such that the inner pipe 2b has a rib 6 as in the inner pipe 2a of the second embodiment without providing the holding member 4. According to such a configuration, the same effects as those of (1a) and (1c) of the first embodiment and (2a) to (2c) of the second embodiment can be obtained.

(3b) In each of the above embodiments, a configuration in which three slits 5 and three slits 5 and three ribs 6 are provided is illustrated, but the number of slits 5 and ribs 6 provided is not limited to this. do not have. For example, at least one slit 5 may be provided, and at least two ribs 6 may be provided. Further, the positions where the slits 5 and the ribs 6 are provided do not have to be evenly spaced in the circumferential direction of the inner pipes 2, 2a and 2b. Further, the slits 5 and the ribs 6 may not be arranged alternately so as to be adjacent to each other. For example, as shown in FIG. 9, a plurality of slits 5 and ribs 6 may be biased, for example, two slits 5 and three ribs 6 may be biased.

(3c) In each of the above embodiments, the configuration in which the exhaust pipes 1, 1a and 1b function as a silencer is illustrated. For example, the exhaust pipe is a double pipe having a double pipe for keeping the exhaust gas warm. The outer pipe covering the inner pipe may be a straight tubular double pipe.

(3d) In each of the above embodiments, the configuration in which the inner tubes 2, 2a and 2b are slidably held with respect to the outer tubes 3 and 3b via the holding member 4 or the rib 6 has been illustrated. The configuration of the inner tube that is slidably held with respect to 3b is not limited to this. For example, the entire diameter of the end portion of the inner pipe may be increased so that the inner pipe is slidably held with respect to the outer pipe.

Specifically, as shown in FIG. 10, the inner pipe 2c has a cylindrical shape in which the end portion on the side that is slidably held with respect to the outer pipe 3c is formed so as to expand in diameter toward the outer pipe 3c. It may be a pipe of.

The outer pipe 3c is a metal pipe arranged so as to cover the outer peripheral surface of the inner pipe 2c, and is a straight pipe having a constant diameter. The outer pipe 3c may be an expansion type pipe having an enlarged diameter at the center, similarly to the outer pipes 3 and 3b.

The inner pipe 2c has a straight pipe portion 25c, a truncated cone portion 26c, and a diameter-expanded portion 27c. The straight pipe portion 25c and the enlarged diameter portion 27c are portions having a constant cross-sectional area, that is, a straight tubular portion. The truncated cone portion 26c is a truncated cone-shaped portion whose cross-sectional area gradually expands from one end of the straight pipe portion 25c toward the enlarged diameter portion 27c. The enlarged diameter portion 27c is a portion that comes into contact with the outer pipe 3c. The outer peripheral surface of the enlarged diameter portion 27c and the inner peripheral surface of the outer pipe 3c are in sliding contact with each other on the entire circumference. The enlarged diameter portion 27c has a slit 5 which is a notch extending linearly from the end surface of the enlarged diameter portion 27c in the direction of the central axis A of the inner pipe 2c. The slit 5 preferably extends from one end face of the enlarged diameter portion 27c to the front of the truncated cone portion 26c. The slit 5 may extend from one end face of the enlarged diameter portion 27c to a part of the truncated cone portion 26c. In such a configuration, as shown in FIG. 11, eight slits 5 are provided at equal intervals in the circumferential direction of the inner pipe 2c in order to reduce the contact area between the inner pipe 2c and the outer pipe 3c. Although not shown, the end of the straight pipe portion 25c on the side opposite to the diameter-expanded portion 27c side is fixed to the inner peripheral surface of the outer pipe 3c by, for example, welding.

According to such a configuration, the same effect as that of (1a) of the first embodiment can be obtained. Further, according to such a configuration, a gap is unlikely to occur between the inner pipe 2c and the outer pipe 3c, and the exhaust gas passing through the inner pipe 2c is suppressed from leaking from the gap. Therefore, the influence on the flow of the exhaust gas can be reduced as compared with the configuration in which the outer peripheral surface of the inner pipe and the inner peripheral surface of the outer pipe do not come into direct contact with each other.

(3e) In each of the above embodiments, a configuration in which the diameter expansion of the inner pipes 2, 2a, 2b, and 2c due to thermal expansion is suppressed by the slit 5 in the radial direction is illustrated. It is not limited to this. For example, the inner pipes 2, 2a, 2b, 2c are formed on the end face of the second end portion 24 instead of the slit 5, and the diameters of the inner pipes 2, 2a, 2b, 2c are expanded in the radial direction by thermal expansion. It may have a convex portion that suppresses. Here, the fact that the convex portion is formed on the end face of the second end portion 24 means that the convex portion is formed in a predetermined range so as to include the end face of the second end portion 24. Specifically, as shown in FIGS. 12 and 13, the convex portion 8 extends from the end surface of the second end portion 24 in the direction of the central axis A of the inner pipes 2, 2a, 2b, and the inner pipes 2, 2a, It is a part protruding inward of 2b. Further, for example, the inner tubes 2, 2a, 2b, 2c may have both the slit 5 and the convex portion 8. As shown in FIGS. 14 and 15, for example, two slits 5 and one convex portion 8 may be provided at the second end portion 24.

According to such a configuration, the same effects as those of (1a) and (1b) of the first embodiment and (2a) and (2b) of the second embodiment can be obtained. That is, in the configuration having the convex portion 8, the convex portion is formed on the end surface of the second end portion 24 of the inner pipes 2, 2a and 2b and the end surface of the enlarged diameter portion 27c of the inner pipe 2c, as in the configuration having the slit 5. A gap is formed by 8. Therefore, even if the inner pipes 2, 2a, 2b, and 2c expand in the circumferential direction, the lengths of the enlarged second end portion 24 and the enlarged diameter portion 27c in the circumferential direction increase with the second end portion 24. It is absorbed by narrowing the gap between the end faces of the diameter portion 27c. That is, the increased circumferential lengths of the second end portion 24 and the enlarged diameter portion 27c are absorbed by narrowing the space formed by the convex portion 8. Therefore, the inner pipes 2, 2a, 2b, and 2c are suppressed from expanding in the radial direction due to the expansion in the circumferential direction.

(3f) The shape of the slit 5 is not limited to the rectangular notch. For example, as shown in FIG. 16, the slit 5a may be a semi-elliptical notch. Further, for example, as shown in FIG. 17, the slit 5b may be a triangular notch. Further, although the structure in which the slit 5, the rib 6 and the convex portion 8 extend linearly in the central axis A direction of the inner pipe 2 is illustrated, each may have a length in the circumferential direction.

(3g) The functions of one component in the above embodiment may be dispersed as a plurality of components, or the functions of the plurality of components may be integrated into one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

1,1a, 1b ... Exhaust pipe, 2,2a, 2b, 2c ... Inner pipe, 3,3b, 3c ... Outer pipe, 4 ... Holding member, 5,5a, 5b ... Slit, 6 ... Rib, 7 ... Fixing member , 8 ... Convex, 21 ... First opening, 22 ... Second opening, 23,71 ... First end, 24,72 ... Second end, 25c, 31 ... Straight pipe, 26c ... Cone base portion, 27c ... Enlarged diameter portion, 32 ... First cone base portion, 33 ... Second cone base portion, 34 ... Fixed portion, 35 ... Holding portion, 35b ... Member fixing portion, A ... Central axis.

It is sectional drawing which shows the structure of the exhaust pipe of 1st Embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. It is a figure which shows that the diameter expansion in a radial direction of an inner pipe by thermal expansion of an exhaust pipe of 1st Embodiment is suppressed. It is sectional drawing which shows the structure of the exhaust pipe of 2nd Embodiment. It is a VV cross-sectional view of FIG. It is a figure which shows that the diameter expansion in a radial direction of an inner pipe by thermal expansion of an exhaust pipe of 2nd Embodiment is suppressed. It is sectional drawing which shows the structure of the exhaust pipe which the inner pipe can slide with respect to the fixing member fixed to the outer pipe. FIG. 6 is a cross-sectional view taken along the line VIII-VIII of FIG. 7 showing that the radial expansion of the inner pipe due to thermal expansion of the exhaust pipe in which the inner pipe can slide with respect to the fixing member is suppressed. FIG. 5 is a cross-sectional view showing the configuration of another embodiment with respect to the number and arrangement of slits and ribs. It is sectional drawing which shows the structure of the exhaust pipe which the enlarged diameter part of the inner pipe is slidable with respect to the outer pipe. It is X I -X I cross-sectional view of FIG. 10. It is sectional drawing which shows the structure which shows the structure which the inner pipe which is slidable with respect to the outer pipe through a holding member has a convex part at the first end part. It is sectional drawing which shows the structure which shows the structure which the inner pipe which is slidable with respect to the outer pipe through a rib has a convex part at the 1st end. FIG. 5 is a cross-sectional view showing a configuration in which an inner pipe slidable with respect to an outer pipe via a holding member has a slit and a convex portion at a first end portion. FIG. 5 is a cross-sectional view showing a configuration in which an inner pipe slidable with respect to an outer pipe via a rib has a slit and a convex portion at a first end portion. It is a figure which shows the structure of another embodiment which the slit has a semi-elliptical shape. It is a figure which shows the structure of the other embodiment which the slit is triangular shape.

The outer pipe 3b has the same basic configuration as the outer pipe 3 of the first embodiment, except that it has a member fixing portion 35b instead of the holding portion 35 of the first embodiment. The member fixing portion 35b is a portion for fixing the first end portion 71 of the fixing member 7. The member fixing portion 35b surrounds the first end portion 71 so that the inner peripheral surface of the member fixing portion 35b and the outer peripheral surface of the first end portion 71 abut on the entire circumference. The first end portion 71 is fixed to the inner peripheral surface of the member fixing portion 35b by, for example, welding. For example, as water or the like provided in the space between the outer tube 3 b and the inner tube 2b and the fixing member 7 is prevented from leaking from the outer tube 3b, the outer tube 3 b has opposite ends It is fixed by welding or the like.

Claims (4)

It is an exhaust pipe with a double pipe structure,
The exhaust pipe includes an inner pipe through which exhaust gas passes, and an outer pipe arranged so as to surround the outer peripheral surface of the inner pipe.
The inner tube
A slide end portion, which is an end portion of the inner pipe, is provided so as to be slidable with respect to the outer pipe.
An exhaust pipe having a slide end portion having a suppressing portion that suppresses a radial expansion of the inner pipe due to expansion of the inner pipe. The exhaust pipe according to claim 1.
The restraining portion is an exhaust pipe having a notch on the end surface of the slide end portion. The exhaust pipe according to claim 1 or 2.
The restraining portion is an exhaust pipe formed on the end surface of the slide end portion and having a convex portion protruding inward of the inner pipe. The exhaust pipe according to any one of claims 1 to 3.
The inner pipe is an exhaust pipe further having a contact portion at the end of the slide, which protrudes to the outside of the inner pipe and comes into contact with the outer pipe.

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