JP2924590B2 - Double exhaust pipe for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double exhaust pipe for a vehicle, which can enhance the effect of keeping the exhaust gas warm when starting the engine and activate the catalyst.

[0002]

2. Description of the Related Art Conventional examples of exhaust pipes for vehicles include, for example, Japanese Utility Model Laid-Open No. 55-158214 and Japanese Utility Model Laid-Open No. 56-173.
Nos. 712, 58-44427 and JP-A-2-75714 are known.

[0003] Japanese Utility Model Laid-Open No. 55-158214 relates to a single pipe type exhaust pipe as shown in FIG. A folded portion 1a having a predetermined gap 2 with the surface is formed, a flange 3 is fitted to the outer peripheral surface of the folded portion 1a, and the vicinity of the tip of the folded portion 1a is welded to the flange 3 so that This is to prevent the weld 4 from being exposed to the high heat of the exhaust gas.

As shown in FIG. 9, an outer flange 12 is welded to the outer periphery of an end portion of an exhaust pipe 11, and the outer flange 12 is fastened separately from the exhaust pipe 11, as shown in FIG. The ring 13 is inserted. Then, the exhaust pipe 11 is connected to the connection target by pressing the outer flange 12 against the wall surface to be connected by pressing the outer flange 12 through the pressing plate 14 with the tightening ring 13.

[0005] Japanese Unexamined Utility Model Publication No. 58-44427 discloses a cylinder block 21 as shown in FIG.
The mounting guide member 22 is fixed to the exhaust pipe 2 of the double pipe type.
The exhaust pipe 23 is connected to the connection target portion by connecting the flange 25 fixed to the outer periphery of the outer pipe 24 to the flange 27 of the mounting guide member 22 with a spring 26.

As shown in FIG. 11, when a flange 32 formed on a single-pipe exhaust pipe 31 is fixed to a cylinder block 34 with a nut ring 33, as disclosed in Japanese Patent Application Laid-Open No. 2-75714, The gasket 35 prevents the nut ring 33 and the cylinder block 34 from contacting the exhaust pipe 31.

[0007]

In a motor vehicle, a catalyst is disposed downstream of an exhaust pipe to purify exhaust gas. In this case, when starting the engine, there is a problem in terms of purification efficiency. When the engine is started, both the catalyst and the exhaust gas are at a low temperature. Therefore, since the catalyst temperature does not reach the activation temperature, a chemical change does not occur, and a situation occurs in which the unburned components in the exhaust gas cannot react sufficiently.

Therefore, it is important to keep the exhaust gas warm when starting the engine. In order to enhance the effect of keeping the exhaust gas warm when the engine is started, the point is to quickly raise the temperature of the inner wall of the exhaust pipe. To achieve this, the first point is to reduce the heat capacity of the exhaust pipe.
As a point, it is important to reduce the escape of heat through the flange from the inner wall of the exhaust pipe.

In order to reduce the heat capacity of the exhaust pipe, it is necessary to reduce the thickness of the exhaust pipe. FIG. 12 shows a temperature change of the exhaust gas at the time of starting using the thickness of the inner pipe as a parameter when a double pipe is used. As can be seen from FIG. 12, the temperature rises faster as the wall thickness of the inner tube is reduced. In order to obtain a sufficient effect, it is necessary to make the thickness of the inner tube 0.5 mm or less. It is not particularly difficult to reduce the thickness of the inner pipe in terms of manufacturing, but if the thickness is reduced, the inner pipe may bend unless the difference in thermal expansion between the high-temperature inner pipe and the low-temperature outer pipe is sufficiently absorbed. This may cause breakage.

From the above first and second points, looking at the above-mentioned prior art, since it is a single tube type, it is impossible to reduce the heat capacity due to strength problems. Further, the gap 2 is provided inside the folded portion 1a, and the escape of heat to the flange 3 is somewhat suppressed. However, since the contact area between the flange 3 and the folded portion 1a is large, the flange 3 is still in use.
Great escape of heat to.

[0011] The holding plate 14 and the outer collar 1
Unless 2 is increased, sufficient rigidity cannot be secured, and the possibility of gas leakage increases. Therefore, when these are increased, the heat capacity increases, and the temperature raising effect deteriorates.

In addition, the fixing force of the outer tube 24 is insufficient and the possibility of gas leakage is large. To increase the fixing force, if the flange 25 attached to the outer tube 24 is enlarged, Escape becomes large. In addition, when the inner tube is greatly expanded by heat, the inner tube may come into contact with the outer tube or other parts and be damaged.

[0013] Further, since this is a single tube type, it is not possible to reduce the heat capacity due to the problem of strength.

As described above, all of the above prior arts have technical limitations in minimizing the escape of heat to the flange at the time of starting, and in reducing the heat capacity by reducing the tube thickness.

In consideration of the above circumstances, the present invention can enhance the effect of keeping the exhaust gas warm, and in particular can improve the temperature rise characteristics at the time of starting, and can reliably absorb the difference in thermal expansion between the inner pipe and the outer pipe. It is an object of the present invention to provide a double exhaust pipe for a vehicle that can be used for a vehicle.

[0016]

A double exhaust pipe for a vehicle according to the present invention is provided between an engine and a catalyst for purifying exhaust of the engine, and has a smaller diameter and a thinner wall in an outer pipe. The inner pipe has a double pipe structure in which the inner pipe is inserted and held, and the outer pipe is fixed to a cap sandwiched between connecting members such as a flange, and the cap extends into the inner pipe along a flow direction of the exhaust gas. It is characterized by having a cylindrical portion, a gap between the cap and the end of the inner tube, and overlapping by a predetermined length in the flow direction of the exhaust gas.

According to a second aspect of the present invention, there is provided the double exhaust pipe for a vehicle according to the first aspect, wherein a radial gap is provided between the cylindrical portion of the cap and the end of the inner tube when the temperature is not raised. Is secured.

According to a third aspect of the present invention, there is provided the double exhaust pipe for a vehicle according to the first aspect, wherein the cylindrical portion of the cap is inserted into the inner peripheral side of the inner pipe, and the length of the inner pipe is set at the time of thermal expansion. Also, the end of the inner tube is set to a size that does not contact the cap.

According to a fourth aspect of the present invention, there is provided the double exhaust pipe for a vehicle according to the first aspect, wherein the inner pipe is held by the outer pipe via an elastic body having heat insulation and capable of absorbing vibration. It is characterized by having.

[0020]

According to the first aspect of the present invention, the inner tube is a double tube composed of an outer tube and an inner tube. The inner tube is made thinner to reduce the heat capacity, and the temperature can be raised quickly. Also, since the inlet between the inner tube and the outer tube is covered by the cap, the inflow of exhaust gas between the inner tube and the outer tube can be suppressed, and heat loss can be minimized. Can be suppressed. Therefore,
Exhaust gas warming effect at the time of low temperature start can be enhanced.
Also, when the exhaust gas temperature and the exhaust manifold become high during normal running or high load running, the expansion of the inner pipe can be absorbed by the gap between the cap and the inner pipe, thereby preventing the inner pipe from bending or breaking. it can.

In the exhaust pipe according to the second aspect of the present invention, since a radial gap is provided between the cap and the end of the inner pipe, the inner pipe and the cap can be kept out of contact with each other.
It is possible to reliably prevent the heat of the inner tube from escaping through the cap. Further, since the radial gap is ensured, the radial expansion of the inner tube can be sufficiently absorbed.

In the exhaust pipe according to the third aspect of the present invention, since the cylindrical portion of the cap is inserted into the inner peripheral side of the inner pipe, even if the inner pipe is largely thermally expanded in the radial direction, the inner pipe and the cap are not sealed. It can avoid interference and absorb thermal expansion. Further, regarding the expansion in the flow direction of the exhaust gas, the length of the inner tube is set so that the inner tube does not come into contact with the cap even if the inner tube thermally expands.

In the exhaust pipe according to the fourth aspect of the present invention, since the inner pipe is held by an elastic body having heat insulation and vibration absorption, the amount of heat transfer from the inner pipe to the outer pipe can be reduced. It can also enhance the sound insulation effect. Further, even if the inner tube is greatly expanded by heat, it can be stably held.

[0024]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention.

The exhaust pipe 100 has a double pipe structure in which an inner pipe 104 is arranged concentrically at a predetermined interval inside an outer pipe 102. The outer pipe 102 is formed to have a large thickness so as to be a strength member of the entire exhaust pipe, and a flange 106 is fitted around the outer pipe in a non-contact manner. The inner tube 104 has a smaller thickness than the outer tube 102, for example, 0.1 mm.
It is formed with a thickness of 5 mm. Reference numeral 110 denotes a cap, and 100A denotes the inside of the exhaust pipe 100.

The cap 110 has an L-shaped cross section composed of a flange 112 and a cylindrical portion 114 as a cylindrical portion continuously formed on the inner periphery of the cap 110 via a round portion 113. It is fitted to the flange 106 via a gasket (not shown), and is bolted to an engine or another exhaust pipe via a gasket (not shown).

The outer tube 1 is attached to the flange 112 of the cap 110.
02 are fixed to each other by welding. The cap 110 and the outer tube 102 need not always be fixed at the end 102a, and need not be welded. Tip 11 of cylindrical portion 114
4 a extends toward the inside of the exhaust pipe 100 and is inserted into the inner peripheral side of the inner pipe 104. This cylindrical portion 114
And the end portion 104a of the inner tube 104 overlap with a predetermined length in the flow direction of the exhaust gas.

The length of the inner pipe 104 is shorter than the length of the outer pipe 102. The outer pipe 102, the inner pipe 104, and the flange 106 constitute the exhaust pipe 100, and the end face 110 a of the cap 110 and the inner pipe 104 are formed. A space 108 is formed between the end 104a and the end 104a. The size of the space 108 in the flow direction of the exhaust gas is set to be longer than the inner tube 104 can be thermally expanded from normal temperature to the inner tube temperature at the time of high-speed running, for example, 1000 degrees at the maximum. That is, even if the thermal expansion is sufficient, the end portion 104a of the inner tube 104 is
The length is set so as not to touch 0.

Between the outer tube 102 and the inner tube 104, an inner tube holding member 103, which is an elastic body, is interposed.
04 is held by the outer tube 102 by the inner tube holding member 103 and is not directly fixed to the outer tube 102, the flange 106, and the cap 110. The inner tube holding member 103 has a heat insulating effect, and is made of glass wool or the like that absorbs sound and vibration.

The cylindrical portion 114 of the cap 110 has a radial gap 115 between itself and the inner pipe 104 when the entire exhaust pipe 100 is kept at room temperature for a long time. A cylindrical gasket 118 is inserted into the gap 115, and the inner pipe 104 and the outer pipe 102 are inserted through the gap 115.
The exhaust gas is prevented from flowing into the space 105 as much as possible. The cap 110 is attached to the inner tube 10
4 or a material having the same or lower coefficient of thermal expansion than the inner tube 104. For example, it may be formed of ceramic. The thickness is larger than that of the inner tube 104.

In this embodiment, the space 108 and the gap 115 are connected to the cap 110 and the end 1 of the inner tube 104.
04a.

Next, the operation will be described.

First, the inner pipe 104 is connected to the inner pipe holding member 103.
Is held by the outer tube 102, and is covered by the cap 110 fixed to the outer tube 102, so that it is securely held. Therefore, even when the cap 110 is not fixed to the flange 106 in the state of the exhaust pipe alone, the transportation after the manufacturing can be easily performed without the inner pipe 104 and the inner pipe holding member 103 protruding.

Further, since the flange 106 is not fixed to the outer tube 102, the materials of the outer tube 102 and the flange 106 are optimally selected so as to achieve both cost and strength regardless of whether welding is possible or not. Can be. Further, as will be described later, since the amount of heat transfer to the flange 106 is extremely reduced, the thermal expansion of the flange 106 is reduced. Therefore, for example, as shown in FIG. 3, a structure in which a part of the flange 106 is hollowed out, and as shown in FIG. 4, a part of the flange 106 can be freely thinned, while maintaining strength. Thus, the weight can be reduced.

Next, the temperature rise of the exhaust gas at the time of starting will be described.

Except immediately after the engine is stopped, before the engine is started, the temperatures of the outer pipe 102 and the inner pipe 104 of the exhaust pipe 100 are the same as the outside air temperature. When the engine is started from this state, the inner pipe 104 is first heated by the exhaust gas flowing through the inner pipe 104. And the inner pipe 10
4 rises, and the temperature of the exhaust gas decreases by the amount of heat applied to the inner pipe 104. Since the heat capacity is reduced by reducing the thickness of the inner tube 104, the inner tube 10 is removed from the exhaust gas.
4, the amount of heat transferred to the exhaust gas 4 is small, and the temperature decrease of the exhaust gas is suppressed to a small extent.

Also, since the flange 106 is not directly fixed to the outer tube 102 or the cap 110, the outer tube 102
From the outside is less likely to be transmitted to the flange 106.

Regarding this, the case where the outer tube 102 is connected to the flange 106 having a large heat capacity,
Will be compared with a case where is fixed to the cap 110 having a small heat capacity by welding.

When the outer pipe 102 is directly welded to the flange 106, the heat from the exhaust gas passing through the inner pipe 104 and the inner pipe holding member 103 is transmitted to the outer pipe 102 and further transmitted to the flange 106. Therefore, the heat of the outer tube 102 is absorbed by the flange 106 having a large heat capacity, and the outer tube 1
02, both the inner pipe holding member 103 and the inner pipe 104 are prevented from rising in temperature, and the heat retention capacity of the exhaust gas is reduced.

On the other hand, when the outer tube 102 is welded to the cap 110, the exhaust gas heats the cap 110 and the inner tube 104, and the heat of the heated cap 110 is transmitted to the welded outer tube 102. As the outer tube 102 is warmed, a part of it escapes to the outside air surrounding the exhaust pipe. For this reason, the calorie of the exhaust gas is transmitted from the cap 110 to the outer pipe 102, and the exhaust gas is reduced. However, the surface area of the cap 110 exposed to the exhaust gas is exposed to the exhaust gas of the inner pipe 104. And the majority of the heat transferred to the outer tube 102 is smaller than the inner tube 10.
4. Depends on the inner tube holding member 103. In addition, flange 1
06 is in contact with the cap 110 and the outer pipe 102 via the gasket 116, so that heat transfer to the flange 106 is suppressed, the temperature of the outer pipe 102, the cap 110, and the inner pipe 104 is suppressed, and the exhaust gas temperature is reduced. Is prevented.

In a state where the exhaust gas and the exhaust pipe 100 are sufficiently warm after a lapse of time from the start of the engine, the inner pipe 104
The difference in heat capacity due to the difference in temperature and wall thickness between the outer tube 102 and the outer tube 102 causes a difference in thermal expansion. The outer tube 102 is not directly exposed to the exhaust gas and has a large heat capacity due to its large thickness, and the thermal expansion is smaller than that of the inner tube 104. On the other hand, inner tube 1
04 is directly exposed to high-temperature exhaust gas, and becomes hot due to its small thickness and small heat capacity, and greatly expands in the flow direction and radial direction of the exhaust gas.

FIG. 2 shows a state in which the exhaust gas and the exhaust pipe 100 are at a high temperature. The solid line shows the state at high temperature, and the dotted line shows the state at low temperature. The heated inner pipe 104 approaches the outer pipe 102 side where the thermal expansion is small due to thermal expansion in the radial direction, and the space 105 between the outer pipe 102 and the inner pipe 104 is reduced, but the inner pipe 104 having elasticity such as glass wool is used. Holding member 103
As a result, the displacement of the inner tube 104 is avoided. Further, when an elastic material such as glass wool is used as the inner tube holding member 103, it also has a vibration absorbing effect, which also contributes to improvement in sound insulation performance.

Due to the thermal expansion of the inner pipe 104 in the exhaust gas flow direction, the inner pipe 104 extends through the space 108 toward the flange 112 of the cap 110. However, the size of the space 108 is such that even if the inner tube 104 is sufficiently thermally expanded,
Since the inner tube 104 and the cap 110 do not come into contact with each other, there is no possibility that the inner tube 104 or the cap 110 will be damaged.

The thermal expansion of the cap 110 at high temperatures occurs in the radially expanding direction and in the exhaust gas flow direction in the direction toward the inside of the exhaust pipe 100.
10 has less thermal expansion than the inner tube 104,
No damage is caused by contact with 04. Also, at high temperatures, the outer tube 102 not directly exposed to the exhaust gas is
Its surface temperature is low. Therefore, heat dissipation into the engine room due to convection and radiation is prevented.

Further, even when the inner pipe 104 is heated to a high temperature and thermally expanded, the amount of heat transmitted from the inner pipe 104 to the engine is extremely small because the inner pipe 104 does not directly contact the cap 110. Further, since the outer tube 102 having a large heat capacity is separated from the inner tube 104 via the inner tube holding member 103 and the space 108, the amount of heat transmitted to the cylinder head via the outer tube 102 is small.

It should be noted that the exhaust pipe 100 of the above embodiment is provided with a flange 106 provided at an end of the outer pipe 102 and a cap 110.
Since the flange 112 is fastened to the engine or another exhaust pipe together with a bolt with the gasket 116 interposed therebetween, gas leakage can be reliably avoided.

When the temperature of the cap 110 becomes high, the amount of heat is transmitted to the outer tube 102. However, as described above, most of the heat transfer to the outer tube 102 is caused by the direct contact / non-contact between the cap 110 and the outer tube 102 because the heat is transferred via the inner tube 104 and the inner tube holding member 103. The influence of the surface temperature of the outer tube 102 is very small.
Further, the flange 106 is connected to the outer tube 102 and the cap 10.
6. Since the inner tube 104 is not in direct contact with the inner tube 104, heat from the exhaust gas is less likely to be transmitted, and the surface temperature is lower than that of the outer tube 102.

Generally, when viewed in cross section, the flange 106 extends toward the outer periphery from the exhaust pipe, and is closer to components in the engine room. In addition, the surface area in contact with the outside air flowing in the engine room is large,
As a result, heat is dissipated into the engine room due to convection and radiation, and the temperature of the atmosphere and components in the engine room rises, causing heat damage and deteriorating components.

In this regard, according to the configuration of this embodiment, the amount of heat transfer from the exhaust gas to the flange 106 is reduced,
06, the heat dissipation into the engine room is reduced, and the temperature of the atmosphere in the engine room and the temperature of parts are prevented from rising, so that heat damage and deterioration are suppressed.

Also, when viewed from the point of the heat radiation amount of the cooling water of the engine, the heat transfer amount from the exhaust pipe to the heat radiation amount of the cooling water is so large that it cannot be ignored. According to the configuration of the present embodiment, since the surface temperature of the flange 106 does not increase even during high-load operation, the amount of heat transfer from the exhaust pipe to the engine body is small. As a result, the amount of heat dissipated in the cooling water is reduced, the driving force of the fan for securing the air flow to the radiator can be reduced, and the air temperature into the engine room can be reduced.

Next, other embodiments will be described. In the following description, the same components as those in the above embodiment are denoted by the same reference numerals as in FIG. 1, and the description thereof will be omitted.

In the exhaust pipe 200 of the second embodiment shown in FIG. 5, the cap 210 is not formed as an integral product, but is formed separately into a flange 112 and a cylindrical portion 114, and is later integrated by welding.
In this case, the cylindrical portion 114 is formed to have the same thickness as the inner tube 104. According to this embodiment, since the cylindrical portion 114 and the flange 112 are formed as separate members, the amount of heat transfer from the cap 210 to the outer tube 1 can be further reduced as compared with the first embodiment. it can.

In the exhaust pipe 300 of the third embodiment shown in FIG. 6, a ring 104b is fitted around the outer circumference of the inner pipe 104,
The inner tube holding member 103 is inserted across the ring 104b. According to this embodiment, the displacement of the inner pipe 104 in the exhaust gas flow direction is prevented by the engagement of the link 104b with the inner pipe holding member 103.

In the exhaust pipe 400 of the fourth embodiment shown in FIG. 7, the positions of the inner pipe 104 and the cylindrical portion 114 of the cap 110 are reversed when viewed in the radial direction of the exhaust pipe. This example shows the rear end side of the exhaust pipe 400 in the flow direction. That is, the distal end 114 a of the cylindrical portion 114 of the cap 110 is
And overlapped in the flow direction of the exhaust gas. Then, the inner tube 104 and the tip 114 of the cylindrical portion 114
A gap 115 (gap) in the radial direction is secured between the cylindrical gasket 118 and the cylindrical gasket 118. This embodiment is effective when the flow direction of the exhaust gas is the direction of the arrow in the figure. In this case, since the gap 115 between the inner pipe 104 and the cylindrical portion 114 faces downstream in the flow direction of the exhaust gas, there is an effect that the exhaust gas is more difficult to enter from the gap 115.

[0056]

As described above, according to the double exhaust pipe for a vehicle according to the first aspect of the present invention, the outer pipe is fixed to the cap and not to the connecting member such as the flange. Because of the non-contact relationship, when connected to another exhaust pipe or engine using a flange or the like, the escape of heat through the flange is significantly reduced. Therefore, the temperature rise performance of the exhaust gas at the time of starting the engine can be improved. Further, since the shape and rigidity of the flange can be selected without considering the heat capacity, the exhaust pipe can be securely fixed without fear of gas leakage or the like. Further, since the gap between the inner tube and the outer tube is closed by the cap, the amount of heat transfer to the outer tube can be reduced, and the heat retaining effect of the exhaust gas can be enhanced. Further, since the cap and the inner tube only overlap, the thermal expansion of the inner tube can be sufficiently absorbed, and the risk of deformation and breakage of the inner tube can be reduced.

According to the double exhaust pipe for a vehicle according to the second aspect of the present invention, since a radial gap is secured between the cap and the end of the inner pipe, the inner pipe and the cap are kept in non-contact, The amount of heat transfer from the inner tube to the cap can be reduced to enhance the effect of keeping the exhaust gas warm. In addition, the thermal expansion of the inner tube in the radial direction can be sufficiently absorbed, and deformation and breakage can be more reliably prevented.

According to the double exhaust pipe for a vehicle according to the third aspect of the present invention, even if the inner pipe is largely thermally expanded in the radial direction, it can be absorbed. Further, even when the inner pipe expands greatly in the flow direction of the exhaust gas, there is no possibility that the inner pipe and the cap will interfere at all.

According to the double exhaust pipe for a vehicle according to the fourth aspect of the invention, the amount of heat transferred from the inner pipe to the outer pipe can be reduced.
The heat insulating effect of the exhaust gas can be improved, and the sound insulation effect can also be improved. Further, even if the inner tube is greatly expanded by heat, it can be stably held.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing a state at the time of temperature rise according to the first embodiment of the present invention.

3A and 3B show shapes of a flange 106 that can be used in the first embodiment of the present invention, wherein FIG. 3A is a plan view and FIG.
It is Ib-IIIb sectional drawing.

FIGS. 4A and 4B show the shape of the flange 106 that can be used in the first embodiment of the present invention, where FIG. 4A is a plan view and FIG.
It is b-IVb sectional drawing.

FIG. 5 is a sectional view of a main part of a second embodiment of the present invention.

FIG. 6 is a sectional view of a main part of a third embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram showing a conventional example.

FIG. 9 is a configuration diagram of another conventional example.

FIG. 10 is a configuration diagram of still another conventional example.

FIG. 11 is a configuration diagram of still another conventional example.

FIG. 12 is a characteristic diagram of a heat retaining effect by reducing the thickness of an inner tube (inner tube) of a double tube.

[Explanation of symbols]

 100, 200, 300, 400 Exhaust pipe 102 Outer pipe 103 Inner pipe holding member (elastic body) 104 Inner pipe 106 Flange 108 Space (gap) 110, 210 Cap 112 Flange 114 Cylindrical part (cylindrical part) 115 Gap ( Gap)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-72409 (JP, A) JP-A-7-63051 (JP, A) Japanese Utility Model 52-64205 (JP, U) Japanese Utility Model Sho 63- 98426 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F01N 7/14

Claims (4)

(57) [Claims] 1. A double-pipe structure provided between an engine and a catalyst for purifying exhaust of the engine, wherein an inner pipe having a smaller diameter and a smaller thickness is inserted and held in an outer pipe. A cap provided at an end of the inner pipe and fixed between connecting members such as a flange, the cap having a tubular portion extending toward the inner pipe along a flow direction of exhaust gas; A double exhaust pipe for a vehicle, characterized in that there is a gap between the inner pipe and an end of the inner pipe, and the pipe overlaps by a predetermined length in a flow direction of the exhaust gas. 2. The dual exhaust pipe for a vehicle according to claim 1, wherein a gap between a cylindrical portion of the cap and an end of the inner pipe is provided.
A double exhaust pipe for a vehicle, wherein a radial gap is secured when the temperature is not raised. 3. The double exhaust pipe for a vehicle according to claim 1, wherein a tubular portion of the cap is inserted into an inner peripheral side of the inner pipe, and a length of the inner pipe is equal to an end of the inner pipe even during thermal expansion. A double exhaust pipe for a vehicle, wherein a portion of the double exhaust pipe is set to a size that does not contact the cap. 4. The double exhaust pipe for a vehicle according to claim 1, wherein the inner pipe is held by the outer pipe via an elastic body having heat insulation and capable of absorbing vibration. Characteristic double exhaust pipe for vehicles.