Vehicle exhaust system

Abstract

To inhibit peeling of a fastening part between an outer pipe and an inner pipe in a vehicle exhaust system having an exhaust pipe part in which the outer pipe is provided at an outer periphery of a part of the inner pipe.SOLUTION: An exhaust system mounted on a vehicle includes: an inner pipe 30 in which exhaust gas from an internal combustion engine flows; and an outer pipe 40a provided at an outer periphery of a part of the inner pipe 30. One end 52 of the outer pipe 40a is formed to have a diameter smaller than that of other portions of the outer pipe 40a and fastened to an outer peripheral surface of the inner pipe 30. A region, ranging from an other end 54 to an area before the one end 52, of the outer pipe 40a is a free region 50 unattached to the outer peripheral surface of the inner pipe 30.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an exhaust system for a vehicle, and more particularly to a structure of an exhaust pipe section in which an outer pipe is provided around an inner pipe through which exhaust gas from an internal combustion engine flows. [Background technology]

[0002] Conventionally, a double-structure exhaust pipe is known, which includes an inner pipe through which exhaust gas discharged from an internal combustion engine of a vehicle flows, and an outer pipe provided with a gap on the outer periphery of the inner pipe. Patent Document 1 discloses a configuration in which the exhaust gas is sent to an exhaust purification device while maintaining the temperature of the exhaust gas at a high temperature by adopting a double-structure exhaust pipe. The exhaust purification device includes a catalyst that purifies the exhaust gas, and the catalyst is activated by the passage of high-temperature exhaust gas through the catalyst, improving the efficiency of purifying the exhaust gas by the catalyst.

[0003] In addition, the double-structure exhaust pipe also has the effect of making it difficult for the heat of the exhaust gas to be transmitted to structures around the exhaust pipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-144710 A Summary of the Invention [Problem to be solved by the invention]

[0005] When an outer pipe is provided on the outer periphery of a part of an inner pipe, it is possible to reduce the diameter of both ends of the outer pipe in the direction of extension and fix both ends to the outer periphery of the inner pipe in order to hold the outer pipe relative to the inner pipe. However, the inner pipe becomes hot due to the exhaust gas flowing inside, and is prone to elongation due to thermal expansion. On the other hand, the outer pipe is less likely to become hot than the inner pipe because it does not directly contact the exhaust gas, and is less likely to elongate due to thermal expansion than the inner pipe. Therefore, there is a risk that the fixed parts of both ends of the outer pipe to the inner pipe may come off due to the difference in elongation between the inner pipe and the outer pipe.

[0006] An object of the present invention is to suppress separation of the outer pipe from the inner pipe at the portion secured to the outer pipe in an exhaust system in which an outer pipe is provided on the outer periphery of part of an inner pipe. [Means for solving the problem]

[0007] The exhaust system for a vehicle according to the present invention is an exhaust system mounted on a vehicle, and includes an inner pipe through which exhaust gas from an internal combustion engine flows, and an outer pipe provided on the outer periphery of a part of the inner pipe, one end of the outer pipe is formed to have a smaller diameter than the other part of the outer pipe and is fixed to the outer periphery surface of the inner pipe, and a gas supply pipe extending from the other end of the outer pipe to the one end of The region up to this point is a free region separated from the outer circumferential surface of the inner tube, and the region is an inner surface between the one end and the front of the one end The inner pipe is formed by joining a plurality of inner pipe segments, and a double inner pipe section is provided at the joint between the two inner pipe segments, in which a portion of one inner pipe segment is overlapped with a portion of the other inner pipe segment. The above One end is fixed to the outer circumferential surface of the double inner pipe portion. The corner of the outer pipe is provided so that the position of the corner of the outer pipe in the extending direction of the inner pipe coincides with the position of the end of the inner pipe segment extending in the opposite direction to the extending direction of the free region of the outer pipe relative to the double inner pipe section. It is characterized by:

[0008] In the exhaust system for a vehicle according to the present invention, a slide mesh may be provided between an inner circumferential surface of a free region of the outer pipe and an outer circumferential surface of the inner pipe.

[0009] In the exhaust system for a vehicle according to the present invention, the outer pipe may be provided on an outer periphery of the inner pipe located on a vehicle front side of a battery pack mounted on the vehicle.

[0010] In the vehicle exhaust system of the present invention, the inner pipe may include, from upstream to downstream in the direction of exhaust gas flow, an upstream straight section, a bent section, and a downstream straight section, one end of the outer pipe is fixed to an outer peripheral surface of a downstream part of the upstream straight section of the inner pipe, and a free region of the outer pipe may extend over the bent section of the inner pipe and at least a part of the downstream straight section of the inner pipe.

[0011] In the exhaust system of the present invention, said outer tube and a joint between the two inner pipe segments, and the two inner pipe segments may be welded together. Effect of the Invention

[0012] According to the present invention, the outer tube is attached to the inner tube at only one point in the direction in which the outer tube extends, so that even if a difference in elongation occurs between the inner tube and the outer tube due to thermal expansion, peeling off of the attached portion can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] 1 is a plan view showing an exhaust device of a vehicle according to an embodiment; [Diagram 2] FIG. 4 is an enlarged plan view of an exhaust pipe portion for preventing heat damage. [Diagram 3] 2 is a cross-sectional view taken along line AA in FIG. 1. [Figure 4] FIG. 2 is a cross-sectional view of FIG. [Diagram 5] FIG. 11 is a cross-sectional view of a portion of an exhaust pipe section for preventing heat damage according to another embodiment. [Figure 6] FIG. 13 is a plan view showing an exhaust pipe portion for preventing heat damage according to a comparative technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Each embodiment of the present invention will be described below with reference to the drawings. The configurations described below are illustrative and can be modified as appropriate to suit the vehicle specifications. When multiple embodiments or modified examples are included below, it is assumed from the beginning that the characteristic parts of the embodiments or modified examples will be used in appropriate combination. The same elements in all drawings are given the same reference numerals, and duplicated descriptions will be omitted.

[0015] In each drawing, the arrow FR indicates the front of the vehicle, the arrow UP indicates the upward direction of the vehicle, and the arrow RH indicates the rightward direction of the vehicle. In the following description, upstream and downstream refer to the upstream and downstream directions of the flow of exhaust gas from the internal combustion engine.

[0016] FIG. 1 is a plan view showing an exhaust device 10 according to an embodiment. In FIG. 1, hatched arrows indicate the direction in which exhaust gas flows. The exhaust device 10 is mounted on a hybrid vehicle. A hybrid vehicle is an automobile that uses an internal combustion engine and a motor (neither shown) as drive sources. The motor is driven by power supplied from a battery pack 90.

[0017] Exhaust gas discharged from an internal combustion engine flows through an exhaust system 10 shown in Fig. 1 and is discharged outside the vehicle. The exhaust system 10 comprises, in order from upstream to downstream, a catalytic device 14, a sub-muffler 16, an exhaust pipe section 18 for preventing heat damage, and a main muffler 20. The exhaust pipe section 18 for preventing heat damage is a characteristic part of this embodiment.

[0018] Due to space limitations within the vehicle body, the battery pack 90 must be placed close to the exhaust device 10, as shown in Fig. 1. High-temperature exhaust gas flows through the exhaust device 10, so the area around the exhaust device 10 becomes hot. In order to reduce the heat flowing from the exhaust device 10 to the battery pack 90, an exhaust pipe section 18 is provided as a measure against heat damage.

[0019] 2 is an enlarged plan view of the exhaust pipe section 18 for preventing heat damage. The exhaust pipe section 18 includes an inner pipe 30 through which exhaust gas flows, and two outer pipes 40a, 40b provided on the outer periphery of the inner pipe 30. The inner pipe 30 and the outer pipes 40a, 40b are cylindrical and made of stainless steel.

[0020] The inner pipe 30 includes, from upstream to downstream, a straight portion 70a, a bent portion 72b, a straight portion 70b, a bent portion 72b, and a straight portion 70c. The outer pipes 40a and 40b have an L-shape. The outer pipe 40a is welded to the outer peripheral surface of the straight portion 70a and extends over the bent portion 72a and a part of the straight portion 70b. The outer pipe 40b is welded to the outer peripheral surface of the straight portion 70b and extends over the bent portion 72b and a part of the straight portion 70c. The outer pipe 40a and its periphery and the outer pipe 40b and its periphery have the same structure, so that the outer pipe 40a and its periphery will be described below as a representative thereof.

[0021] FIG. 3 is a cross-sectional view taken along the line AA in FIG. 1. In FIG. 3, the direction of exhaust gas flow is indicated by an outline arrow. As shown in FIG. 3, the inner pipe 30 is formed by joining a plurality of inner pipe segments 30S1, 30S2, and 30S3. The downstream end of the inner pipe segment 30S1 and the upstream end of the inner pipe segment 30S2 are welded to a joint 34C1 at which the two segments meet. The downstream end of the inner pipe segment 30S2 and the upstream end of the inner pipe segment 30S3 are welded to a joint 34C2 at which the two segments meet. The joints 34C1 and 34C2 may be connected by a method other than welding.

[0022] The outer pipe 40a comprises, in order from upstream to downstream, a narrow pipe region 42, a transition region 46, and a main body region 48. The narrow pipe region 42 is formed to have a smaller (narrower) diameter than other parts of the outer pipe 40a, and is a region that contacts the outer circumferential surface of the inner pipe 30. The transition region 46 is a region whose diameter changes from upstream to downstream. The main body region 48 is a region that extends with a constant diameter.

[0023] The narrow pipe region 42 (upstream end 52) of the outer pipe 40a is aligned with the joint 34C1 of the two inner pipe segments 30S1, 30S2 and welded to them all at once. As a result, the narrow pipe region 42 of the outer pipe 40a is fixed to the outer peripheral surface of the inner pipe 30, forming a fixed portion 60. Note that by welding the joint 34C1 of the inner pipe segment and the outer pipe 40a all at once, the number of manufacturing steps can be reduced. The transition region 46 and main body region 48 of the outer pipe 40a form a free region 50 away from the outer peripheral surface of the inner pipe 30.

[0024] A ring-shaped slide mesh 62 is provided between the inner peripheral surface of the free region 50 of the outer pipe 40a and the outer peripheral surface of the inner pipe 30. The slide mesh 62 is a member in which wire material is woven into a mesh shape. The slide mesh 62 is fixed to only one of the outer peripheral surface of the inner pipe 30 and the inner peripheral surface of the outer pipe 40a, and is slidable relative to the other. This allows the slide mesh 62 to move in the axial direction of the pipes when a difference in thermal expansion occurs between the inner pipe 30 and the outer pipe 40a. The slide mesh 62 supports the free region 50 of the outer pipe 40a to the inner pipe 30.

[0025] Fig. 4 is a cross-sectional view taken along line BB in Fig. 1. The vehicle is provided with a heat insulator 80 between the exhaust pipe portion 18 and the battery pack 90. ​​Note that the heat insulator 80 is omitted in the other figures.

[0026] Next, the effects of the exhaust device 10 of this embodiment will be described.

[0027] According to the embodiment described above, as shown in FIG. 1, outer pipes 40a, 40b are provided on the outer periphery of the inner pipe 30 in the part of the exhaust device 10 near the battery pack 90. ​​Therefore, it is possible to reduce the convection heat (heat transferred through air) and the radiant heat (heat transferred by infrared rays) from the exhaust device 10 toward the battery pack 90, and to reduce the atmospheric temperature around the battery pack 90. ​​As shown in FIG. 1, when the exhaust device 10 is located in front of the battery pack 90, the heat of the exhaust device 10 is likely to hit the battery pack 90 due to the wind generated by the vehicle running, but according to the embodiment described above, the heat can be effectively reduced. Since the outer pipes 40a, 40b cover the entire circumference of the inner pipe 30, the heat shielding performance is high and the heat damage prevention effect is large.

[0028] 3, in the embodiment described above, only the upstream end 52 of the outer pipe 40a is fixed to the outer peripheral surface of the inner pipe 30, and the region from the downstream end 54 of the outer pipe 40a to just before the upstream end 52 (the transition region 46 and the main body region 48) is a free region 50 away from the outer peripheral surface of the inner pipe 30. Therefore, when high-temperature exhaust gas flows through the inner pipe 30 and the inner pipe 30 elongates more than the outer pipe 40a due to thermal expansion (an elongation difference occurs between the inner pipe 30 and the outer pipe 40a), peeling of the fixed portion 60 of the outer pipe 40a to the inner pipe 30 can be suppressed.

[0029] In addition, according to the embodiment described above, the space between the outer pipe 40a and the inner pipe 30 is not connected to the inside of the inner pipe 30, so that water or the like that has entered the space does not flow out into the inner pipe 30. For example, as a modified structure of the exhaust pipe section 18 shown in FIG. 3, a gap is provided between the inner pipe segments 30S2 and 30S3, and the downstream end 54 of the outer pipe 40a is connected to the inner pipe segment 30S3, so that the space between the outer pipe 40a and the inner pipe 30 is connected to the inside of the inner pipe 30. However, in such a modified structure, there is a risk that water generated by the combustion of fuel by the internal combustion engine accumulates in the space between the outer pipe 40a and the inner pipe 30, and then the water in the space flows out to the downstream side of the inner pipe 30 and freezes, blocking the inside of the inner pipe 30. However, by making the space between the outer pipe 40a and the inner pipe 30 a structure independent of the inside of the inner pipe 30 as in the embodiment described above, such a risk can be eliminated.

[0030] In the above-described embodiment, as shown in FIG. 2, the outer pipe 40a is fixed to the downstream portion of the straight portion 70a of the inner pipe 30, and the outer pipe 40b is fixed to the downstream portion of the straight portion 70b of the inner pipe 30. Here, the downstream portion of the straight portion 70a refers to the downstream half of the straight portion 70a. The same applies to the direct portion 70b. With this structure, when the inner pipe 30 inside the outer pipes 40a and 40b expands due to thermal expansion, it is possible to prevent the outer peripheral surface of the bent portions 72a and 72b (inner pipe) from coming into contact with the inner peripheral surface of the outer pipes 40a and 40b. This will be described below using the outer pipe 40b as an example.

[0031] 2, the upstream end of the outer pipe 40b is fixed to the downstream portion of the straight portion 70b (upstream straight portion), and the distance L from the fixing portion 60 to the bent portion 72b is shortened. The free region of the outer pipe 40b extends over the bent portion 72b and a part of the straight portion 70c (downstream straight portion).

[0032] 6 is a plan view showing another exhaust pipe section 118 as a comparative technology. In the comparative technology, a short outer pipe 140a is provided on the upstream side, and a long outer pipe 140b (corresponding to the outer pipe 40b in FIG. 2) is provided on the downstream side. The upstream end of the outer pipe 140b is fixed to the upstream part of the straight section 70b (the upstream half of the straight section 70b), and the distance L from the fixing part 60 to the bent section 72b is long.

[0033] As shown in FIG. 6, when the distance L is long, the amount of elongation due to thermal expansion of the inner pipe 30 from the fixing portion 60 to the bending portion 72b becomes large relative to the fixing portion 60, so that the possibility that the outer peripheral surface of the inner pipe 30 will contact the inner peripheral surface of the outer pipe 140b at the location indicated by the symbol R in FIG. 6 increases. When the outer peripheral surface of the inner pipe 30 contacts the inner peripheral surface of the outer pipe 140b, shear stress is applied to the fixing portion 60 of the outer pipe 140b, and there is a risk that the fixing portion 60 will peel off. On the other hand, as shown in FIG. 2, when the distance L is short, the amount of elongation due to thermal expansion of the inner pipe 30 from the fixing portion 60 to the bending portion 72b is small relative to the fixing portion 60, so that the possibility that the outer peripheral surface of the inner pipe 30 will contact the inner peripheral surface of the outer pipe 40b at the location indicated by the symbol R in FIG. 2 can be reduced. Therefore, there is a great advantage in fixing the outer pipe 40b to the downstream portion of the straight portion 70b of the inner pipe 30 to shorten the distance L. Note that even in the configuration shown in Fig. 6, there is no problem as long as measures are taken such as ensuring a wide gap between the inner pipe 30 and the outer pipe 140b at the point indicated by the symbol R, and the configuration shown in Fig. 6 is not excluded from the scope of the claims of the present application.

[0034] Next, a modified example will be described. In the embodiment described above, as shown in Fig. 3, the upstream end 52 of the outer pipe 40a is fixed to the outer peripheral surface of the inner pipe 30, and the region from the downstream end 54 of the outer pipe 40a to just before the upstream end 52 is the free region 50. However, as shown in Fig. 5, the downstream end 54 of the outer pipe 40a may be fixed to the outer peripheral surface of the inner pipe 30, and the region from the upstream end 52 of the outer pipe 40a to just before the downstream end 54 is the free region 50 (exhaust pipe section 18A).

[0035] In the embodiment described above, the exhaust pipe section 18 for protecting against heat damage is provided for the battery pack 90. ​​However, the exhaust pipe section 18 for protecting against heat damage may be provided for other members such as a fuel tank.

[0036] In the above-described embodiment, the exhaust pipe has a double structure in which the outer pipe 40a (or 40b) is disposed on the outer periphery of the inner pipe 30. However, the exhaust pipe may have a triple or more structure in which two or more outer pipes are disposed radially spaced apart on the outer periphery of the inner pipe 30. [Explanation of symbols]

[0037] 10 exhaust device, 14 catalytic converter, 16 sub-muffler, 18, 18A exhaust pipe section for heat damage prevention, 20 main muffler, 30 inner pipe, 30S1, 30S2, 30S3 inner pipe segment, 34C1, 34C2 joint, 40a, 40b outer pipe, 42 narrow pipe region, 46 transition region, 48 main body region, 50 free region, 52 upstream end (one end), 54 downstream end (other end), 60 fixed portion, 62 slide mesh, 70a straight portion, 70b straight portion (upstream straight portion), 70c straight portion (downstream straight portion), 72a bent portion, 72b bent portion, 80 heat insulator, 90 battery pack, 118 exhaust pipe section for heat damage prevention, 140a, 140b outer pipe.

Claims

1. An exhaust system mounted on a vehicle, The exhaust gas turbine has an inner pipe through which exhaust gas from an internal combustion engine flows, and an outer pipe provided on an outer periphery of a part of the inner pipe, One end of the outer tube is formed to have a smaller diameter than the other portion of the outer tube and is fixed to an outer circumferential surface of the inner tube, a region from the other end of the outer tube to just before the one end of the outer tube is a free region separated from an outer circumferential surface of the inner tube, the outer tube has a corner on an inner surface between the one end and a portion just before the one end, The inner tube is formed by joining together a plurality of inner tube segments, a double inner pipe section is provided at a joint between the two inner pipe segments, in which a part of one inner pipe segment is overlapped with a part of the other inner pipe segment; The one end of the outer pipe is fixed to an outer circumferential surface of the double inner pipe portion, The corner of the outer pipe is provided so that the position of the corner of the outer pipe in the extension direction of the inner pipe coincides with the position of an end of the inner pipe segment extending in a direction opposite to the extension direction of the free region of the outer pipe relative to the double inner pipe section.

1. A vehicle exhaust system comprising:

2. 2. The vehicle exhaust system according to claim 1, A slide mesh is provided between the inner peripheral surface of the free region of the outer tube and the outer peripheral surface of the inner tube.

1. A vehicle exhaust system comprising:

3. 3. The exhaust system for a vehicle according to claim 1, the outer tube is provided on an outer periphery of the inner tube located on a front side of the battery pack mounted on the vehicle; 1. A vehicle exhaust system comprising:

4. In the exhaust system for a vehicle according to any one of claims 1 to 3, the inner pipe includes, in order from the upstream side to the downstream side in a flow direction of exhaust gas, an upstream straight section, a bent section, and a downstream straight section, one end of the outer pipe is fixed to an outer circumferential surface of a downstream portion of the upstream straight section of the inner pipe, The free region of the outer pipe extends over the bent portion of the inner pipe and at least a portion of the downstream straight portion of the inner pipe.

1. A vehicle exhaust system comprising:

5. The exhaust system for a vehicle according to any one of claims 1 to 4, One end of the outer pipe and a joint between the two inner pipe segments are aligned and welded together.

1. A vehicle exhaust system comprising:

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