Exhaust pipe manufacturing method

Abstract

To suppress buckling of a cover member inserted into an opening of an exhaust pipe.SOLUTION: A method of manufacturing an exhaust pipe includes inserting a cover member into a substantially circular opening disposed in a first end portion of a first exhaust pipe. The cover member has an inner peripheral portion and a holding portion. The inner peripheral portion has a ring shape having a central axis, and the outer peripheral surface confronts the inner peripheral surface of the first exhaust pipe when the cover member is inserted into the opening. The holding portion spreads from the edge portion of the inner peripheral portion to the outside, and is held by the first end portion and a second end portion of a second exhaust pipe connected to the first end portion. The longest width of the inner peripheral portion is equal to the radius of the circumference of the opening, or larger than the radius. The shortest width of the inner peripheral portion is smaller than the radius. A length in the circumferential direction of the outer peripheral surface is smaller than a length of the circumference of the opening.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an exhaust pipe. [Background technology]

[0002] Turbochargers for vehicle engines and the parts used in the vicinity thereof are required to have high-temperature oxidation resistance because they are exposed to high-temperature exhaust gases, and also to have cyclic oxidation resistance because they are repeatedly heated and cooled.In response to this, Patent Document 1 discloses a technology for improving the heat resistance of an exhaust pipe by providing a cover member at the opening of the exhaust pipe through which exhaust gas from the turbocharger flows in, and covering the area around the opening on the inner peripheral surface of the exhaust pipe.

[0003] The cover member is a perfectly circular ring-shaped member and includes an inner circumferential portion that covers the inner circumferential surface of the exhaust pipe and a clamping portion that extends outward from the end of the inner circumferential portion. The inner circumferential portion has a tightening margin around the entire circumferential direction relative to the exhaust pipe opening so that the outer diameter of the inner circumferential portion is larger than the diameter of the exhaust pipe opening, which is formed in a perfectly circular shape. The cover member is first inserted into the exhaust pipe opening so that the inner circumferential portion covers the inner circumferential surface of the exhaust pipe. Thereafter, when the upstream exhaust pipe is fastened to the exhaust pipe opening with the cover member inserted using a V-clamp or the like, the clamping portion of the cover member is clamped by the end faces that surround the exhaust pipe opening. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-181467 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with a cover member of the above-described shape, if the interference of the inner periphery of the cover member with respect to the exhaust pipe opening before insertion exceeds a certain value, the cover member inserted into the exhaust pipe opening is prone to buckling. As a result, the inner periphery of the cover member is prone to deforming toward the inside of the exhaust pipe, i.e., in a direction separating the inner periphery from the inner periphery of the exhaust pipe, which reduces the contact area between the inner periphery and the inner periphery of the exhaust pipe, making it difficult for the cover member to be held in place on the exhaust pipe.

[0006] One aspect of the present disclosure aims to suppress buckling of a cover member inserted into an opening of an exhaust pipe. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for manufacturing an exhaust pipe that forms a flow path for exhaust gas in a vehicle, the method comprising inserting a cover member into a substantially circular opening provided at a first end of a first exhaust pipe. The cover member has an inner circumferential portion and a clamping portion. The inner circumferential portion is a ring-shaped portion having a central axis, and when the cover member is inserted into the opening, its outer circumferential surface faces the inner circumferential surface of the first exhaust pipe. The clamping portion is a portion that extends outward from the end of the inner circumferential portion and is clamped between the first end and a second end of a second exhaust pipe connected to the first end. The width direction is defined as a direction along a plane perpendicular to the central axis of the inner circumferential portion. The longest width in the width direction from the central axis of the inner circumferential portion to the outer circumferential surface is equal to or greater than the radius of the circumference of the opening. The shortest width in the width direction from the central axis of the inner circumferential portion to the outer circumferential surface is smaller than the radius. The circumferential length of the outer circumferential surface is shorter than the circumferential length of the opening.

[0008] In this configuration, when the cover member is placed over the opening and viewed along the central axis of the inner periphery, a gap is formed between the portion corresponding to the shortest width of the inner periphery and the inner periphery of the opening. Because the outer periphery of the inner periphery is shorter than the circumferential length of the opening, even when the inner periphery is inserted into the opening, the longest width of the inner periphery shrinks, and the shortest width of the inner periphery expands by the same amount, the gap remains. In other words, when the inner periphery is inserted into the opening, the inner periphery is prone to deformation, and this deformation can be released into the gap. Therefore, buckling of the cover member inserted into the opening of the first exhaust pipe can be suppressed.

[0009] In one aspect of the present disclosure, the first end may have a chamfered portion. The chamfered portion is formed to surround the opening and is inclined away from the central axis of the first exhaust pipe as it approaches the first end. When inserting the cover member into the opening, when viewed along the central axis of the pipe, the portion of the inner periphery that corresponds to the widest width before insertion into the opening may be located on the chamfered portion, and the portion of the inner periphery that corresponds to the narrowest width before insertion into the opening may be located inside the chamfered portion. With this configuration, the inner periphery moves along the chamfered portion, making it easier to insert the cover member into the opening of the first exhaust pipe.

[0010] In one aspect of the present disclosure, the inner circumferential portion may have a cross-sectional shape perpendicular to the central axis that is generally elliptical. With this configuration, buckling of the cover member inserted into the opening of the first exhaust pipe can be suppressed.

[0011] In one aspect of the present disclosure, the portion of the inner periphery that corresponds to the maximum width may be located at a heat spot of the first exhaust pipe. With this configuration, the heat spot of the first exhaust pipe abuts against the inner periphery, thereby improving the heat resistance of the first exhaust pipe.

[0012] In one aspect of the present disclosure, the portion of the inner circumferential portion that corresponds to the maximum width may be located in the weakened portion of the first exhaust pipe. With this configuration, the weakened portion of the first exhaust pipe abuts against the inner circumferential portion, thereby improving the heat resistance of the first exhaust pipe.

[0013] In one aspect of the present disclosure, the first exhaust pipe may be located downstream of the second exhaust pipe in the exhaust gas flow direction. With this configuration, the exhaust gas is likely to hit a first end portion of the first exhaust pipe that is downstream in the exhaust gas flow direction, and therefore, by providing a cover member on the first end portion, damage to the first end portion due to the heat of the exhaust gas can be effectively suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] 4 is a cross-sectional view taken along the central axis of the fastened first and second exhaust pipes, including the major diameter portion of the cover member. FIG. [Figure 2] 2 is an enlarged view of the periphery of the cover member and the first edge portion in the cross-sectional view of FIG. 1. FIG. [Figure 3] 4 is a cross-sectional view taken along the central axis of the fastened first and second exhaust pipes, including the minor diameter portion of the cover member. FIG. [Figure 4] 4 is an enlarged view of the periphery of the cover member and the first edge portion in the cross-sectional view of FIG. 3. FIG. [Figure 5] FIG. [Figure 6] FIG. 4 is a front view of a first end portion of a first exhaust pipe to which a cover member is attached. [Figure 7] FIG. 4 is a front view of the first opening and the cover member before attachment to the first end portion. [Figure 8] 10A and 10B are diagrams illustrating deformation of the inner periphery of the cover member during the insertion process. [Figure 9] 10A and 10B are diagrams illustrating the position of the major diameter portion of the cover member relative to the chamfered portion in the insertion process. [Figure 10] 10A and 10B are diagrams illustrating the position of the minor diameter portion of the cover member relative to the chamfered portion in the insertion process. [Figure 11] FIG. 10 is a cross-sectional view taken along the central axis, showing the shape of a first modified example of the cover member. [Figure 12] FIG. 10 is a cross-sectional view taken along the central axis, showing the shape of a second modified example of the cover member. [Figure 13] FIG. 10 is a cross-sectional view taken along the central axis, showing the shape of a third modified example of the cover member. [Figure 14] FIG. 4 is a cross-sectional view taken along the central axis of an example of a weak portion of the first exhaust pipe. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. First exhaust pipe] 1 and 3 constitutes a flow path for exhaust gas from a vehicle engine. As an example, the first exhaust pipe 1 is fastened by a V-clamp 5 to the downstream side of a second exhaust pipe 3 that discharges exhaust gas from a turbocharger. The first exhaust pipe 1 is also configured to accommodate a purification member (for example, a catalyst or a filter) that purifies the exhaust gas.

[0016] As an example, the first exhaust pipe 1 and the second exhaust pipe 3 may be made of a heat-resistant austenitic steel material. However, the first exhaust pipe 1 and the second exhaust pipe 3 are not limited to being made of austenitic steel material, and may be made of other heat-resistant steel material. Furthermore, the second exhaust pipe 3 may be made of a material that has higher heat resistance than the material that makes up the first exhaust pipe 1.

[0017] As shown in FIGS. 1 to 4, the first exhaust pipe 1 includes a first end portion 10, a first opening 11, a first flange portion 12, and a cover member 2, which will be described later. The first opening 11 is a substantially circular opening located at the first end 10 of the first exhaust pipe 1. The first opening 11 is located upstream in the flow direction of exhaust gas in the first exhaust pipe 1, and is connected to the second exhaust pipe 3. Hereinafter, a straight line that passes through the center of the first opening 11 and is perpendicular to the first opening 11 will be referred to as the central axis 11A.

[0018] The first flange portion 12 is provided at the first end portion 10 of the first exhaust pipe 1 and is used for fastening to the second exhaust pipe 3. The first end portion 10 surrounds the first opening 11 and extends in a plane in a direction perpendicular to the central axis 11A of the first opening 11. The first end portion 10 includes a groove portion 13 and a first edge portion 14.

[0019] The first edge 14 is a portion that protrudes from the first end 10 toward the second exhaust pipe 3 along the central axis 11A, and is adjacent to and surrounds the first opening 11. A clamping surface 14A located at the top of the first edge 14 extends in a plane in a direction perpendicular to the central axis 11A. The inner circumferential surface of the first edge 14 forms the inner circumferential surface 15 of the first exhaust pipe 1.

[0020] 2 and 4, a chamfered portion 14C is formed at the boundary between the clamping surface 14A and the inner peripheral surface 15 of the first edge portion 14. The chamfered portion 14C is formed to surround the first opening 11, and is inclined so as to move away from the central axis 11A as it approaches the first end portion 10. The chamfered portion 14C is inclined at an angle of, for example, 10 to 80 degrees, more preferably 45 degrees, with respect to the central axis 11A.

[0021] Groove 13 is a groove-shaped portion provided in first end 10, and surrounds first opening 11. Groove 13 is provided adjacent to the outside of first edge 14, and outer peripheral surface 14B of first edge 14 protrudes from the bottom surface of groove 13 along central axis 11A. A ring-shaped gasket 4 is disposed in groove 13 to seal the gap between first opening 11 and second opening 31 of second exhaust pipe 3.

[0022] [2. Second exhaust pipe] As shown in FIGS. 1 to 4, the second exhaust pipe 3 includes a second end portion 30, a second opening 31, and a second flange portion 32.

[0023] The second opening 31 is located at the second end 30 of the second exhaust pipe 3. The second opening 31 is connected to the first opening 11 of the first exhaust pipe 1, and has the same shape as the first opening 11 (for example, substantially circular).

[0024] The second flange portion 32 is provided at the second end portion 30 of the second exhaust pipe 3 and is used for fastening to the second exhaust pipe 3 . The second end portion 30 surrounds the second opening 31 and extends in a plane in a direction perpendicular to the central axis 11A of the first opening 11 of the first exhaust pipe 1 connected to the second opening 31. The second end portion 30 includes a recess 33.

[0025] The recessed portion 33 is formed in the second end portion 30 adjacent to the second opening 31 and surrounding the second opening 31. As shown in FIGS. 2 and 4 , the recessed portion 33 has a bottom surface 34 and a first inner circumferential surface 35.

[0026] The bottom surface 34 is a portion that extends in a plane in a direction perpendicular to the central axis 11A of the first opening 11 connected to the second opening 31, and is provided so as to go around the inner circumferential surface of the second exhaust pipe 3. The bottom surface 34 also forms a step on the inner circumferential surface of the second exhaust pipe 3, and divides the inner circumferential surface into a first inner circumferential surface 35 and a second inner circumferential surface 36.

[0027] The first inner circumferential surface 35 is adjacent to the second opening 31 and surrounds the second opening 31. The first inner circumferential surface 35 is adjacent to the second inner circumferential surface 36 across the bottom surface 34, and the diameter of the first inner circumferential surface 35 is larger than the diameter of the second inner circumferential surface 36.

[0028] [3. Cover material] 1 to 6, the cover member 2 is provided at the first end 10 of the first exhaust pipe 1, and is clamped between the first end 10 and the second end 30 of the second exhaust pipe 3. The cover member 2 is a ring-shaped member provided so as to surround the first opening 11, and includes a clamping portion 20 and an inner peripheral portion 21, with an L-shaped cross section perpendicular to the circumferential direction.

[0029] The inner circumferential portion 21 is a flattened ring-shaped portion having a central axis 21C, and the up-down direction of the inner circumferential portion 21 roughly coincides with the direction perpendicular to the radial direction of the cover member 2. The outer circumferential surface 21B of the inner circumferential portion 21 faces the portion of the inner circumferential surface 15 of the first exhaust pipe 1 around the first opening 11. Specifically, the outer circumferential surface 21B of the inner circumferential portion 21 abuts against this portion or is disposed with a gap therebetween. The central axis 11A of the first exhaust pipe 1 and the central axis 21C of the cover member 2 coincide when the cover member 2 is attached to the first end portion 10.

[0030] The clamping portion 20 is also a flattened ring-shaped portion, and the left-right direction of the clamping portion 20 roughly coincides with the radial direction of the cover member 2. The clamping portion 20 extends outward from the top-bottom end of the inner circumferential portion 21. The clamping portion 20 is clamped between the clamping surface 14A of the first edge portion 14 of the first exhaust pipe 1 and the bottom surface 34 of the recessed portion 33 of the second exhaust pipe 3.

[0031] The cover member 2 is made of a material that has higher heat resistance than the material that makes up the first end 10 and the like of the first exhaust pipe 1. Specifically, the cover member 2 may be made of ferritic steel, as an example. Of course, the cover member 2 may be made of other materials. Furthermore, the heat resistance of the material that makes up the cover member 2 may be the same as or lower than the heat resistance of the material that makes up the first end 10 and the like of the first exhaust pipe 1.

[0032] [4. Attaching the cover] Next, a method for attaching the cover member 2 to the first end 10 of the first exhaust pipe 1, in other words, a method for manufacturing the first exhaust pipe 1 with the cover member 2 attached to the first end 10, will be described.

[0033] <Cover parts before and after installation> 5 and 7, the cover member 2 has a substantially elliptical ring shape before being attached to the first end portion 10. That is, the inner circumferential portion 21 and the clamping portion 20 have a substantially elliptical cross-sectional shape perpendicular to the central axis 21C of the cover member 2.

[0034] Specifically, as shown in FIG. 7, the major axis RL of the approximately ellipse formed by the outer surface 21B of the inner peripheral portion 21 is larger than the diameter R of the first opening 11, and the minor axis RS of the approximately ellipse is smaller than the diameter R of the first opening 11.

[0035] In other words, when the direction along a plane perpendicular to the central axis 21C is defined as the width direction, the longest distance along the width direction from the central axis 21C of the inner circumferential portion 21 to the outer peripheral surface 21B (i.e., major radius RL / 2) is greater than the radius R / 2 of the first opening 11. Furthermore, the shortest distance along the width direction from the central axis 21C of the inner circumferential portion 21 to the outer peripheral surface 21B (i.e., minor radius RS / 2) is smaller than the radius R / 2 of the first opening 11. Note that the major radius RL may be approximately the same as the diameter R of the first opening 11, and the longest width (i.e., major radius RL / 2) may be approximately the same as the radius R / 2 of the first opening 11.

[0036] The circumference of the substantially ellipse, that is, the length of the outer peripheral surface 21B in the circumferential direction, is shorter than the length of the circumference of the first opening 11. The cover member 2 is attached to the first end portion 10 by an insertion process shown in FIG. 8. The cover member 2 attached to the first end portion 10 is then arranged along the circumference of the first opening 11 in an elastically deformed state, and the shape of the cover member 2 becomes a substantially ellipse with a shortened major axis RL and an extended minor axis RS. The shape of the cover member 2 may also be a substantially circular shape. Therefore, the elastic force of the cover member 2 helps to maintain the position of the cover member 2. For ease of explanation, the clamping portion 20 of the cover member 2 is not shown in FIG. 8.

[0037] For this reason, when the cover member 2 attached to the first end portion 10 has a substantially elliptical shape, the outer peripheral surface 21B of the inner peripheral portion 21 at the long diameter portion 2A of the cover member 2 after attachment abuts against the inner peripheral surface 15 of the first exhaust pipe 1. On the other hand, the outer peripheral surface 21B of the inner peripheral portion 21 at the short diameter portion 2B of the cover member 2 is disposed with a gap S between it and the inner peripheral surface 15 of the first exhaust pipe 1.

[0038] The long diameter portion 2A refers to a portion of the cover member 2 that is located around the end of the long diameter RL before attachment to the first end portion 10. The portion of the cover member 2 that is attached to the first end portion 10 and corresponds to the long diameter portion 2A of the cover member 2 before attachment will also be referred to as the long diameter portion 2A. The short diameter portion 2B refers to a portion of the cover member 2 that is located around the end of the short diameter RS before attachment to the first end portion 10. The portion of the cover member 2 that is attached to the first end portion 10 and corresponds to the short diameter portion 2B of the cover member 2 before attachment will also be referred to as the short diameter portion 2B.

[0039] <Insertion process> The cover member 2 is brought close to the first opening 11 with the central axis 21C of the cover member 2 substantially aligned with the central axis 11A of the first exhaust pipe 1, and the cover member 2 is inserted into the first opening 11. In the present embodiment, as an example, the inner circumferential portion 21 of the cover member 2 is pressed against the first opening 11, thereby press-fitting the cover member 2 into the first opening 11.

[0040] In this embodiment, when the cover member 2 is inserted into the first opening 11, as viewed along the central axis 11A, the end of the inner circumferential portion 21 at the long diameter portion 2A is positioned on the chamfered portion 14C of the first exhaust pipe 1. The end of the inner circumferential portion 21 at the short diameter portion 2B is positioned more inward than the chamfered portion 14C of the first exhaust pipe 1.

[0041] For this reason, as shown in Fig. 9, during insertion of the cover member 2, the end of the inner circumferential portion 21 at the long diameter portion 2A of the cover member 2 collides with the chamfered portion 14C of the first exhaust pipe 1. Then, the inner circumferential portion 21 is deformed so as to be inclined inward due to the inclination of the chamfered portion 14C, and is guided toward the first opening 11. On the other hand, as shown in Fig. 10, the end of the inner circumferential portion 21 at the short diameter portion 2B does not collide with the chamfered portion 14C and enters the first opening 11.

[0042] Furthermore, in this embodiment, after inserting the cover member 2 into the first opening 11, the cover member 2 is positioned over the first opening 11 during the insertion process so that the inner circumferential portion 21 located on the major diameter portion 2A of the cover member 2 is positioned in a heat spot portion of the first exhaust pipe 1. A heat spot portion is a portion of the inner circumferential surface 15 of the first exhaust pipe 1 that is prone to damage, for example, a portion that is prone to being hit by a concentrated flow of skewed exhaust gas, and as a result, is prone to becoming locally hot. Note that, if a wastegate is provided inside the second exhaust pipe 3, the heat spot portion is a portion where the flow of exhaust gas flowing out from the wastegate is concentrated.

[0043] This encourages the inner circumferential portion 21 of the cover member 2 attached to the first opening 11 to come into contact with the heat spot portion, thereby preventing the exhaust gas from directly hitting the heat spot portion. On the other hand, the inner circumferential portion 21 located at the minor diameter portion 2B of the cover member 2 is in a state where a gap S is formed between the inner circumferential surface 15 of the first exhaust pipe 1.

[0044] Thereafter, the first end 10 of the first exhaust pipe 1, to which the cover member 2 is attached, and the second end 30 of the second exhaust pipe 3 are fastened together using, for example, a V-clamp 5 or the like. [5. Effects] According to the embodiment described above in detail, the following effects can be obtained.

[0045] (5a) In this embodiment, the first opening 11 of the first exhaust pipe 1 is substantially circular, and the cover member 2 is substantially elliptical. Therefore, when the cover member 2 is placed over the first opening 11 with the central axis 21C of the cover member 2 substantially aligned with the central axis 11A of the first exhaust pipe 1 and viewed along the central axis 21C, a gap S is formed between the inner circumferential portion 21 located at the minor diameter portion 2B of the cover member 2 and the inner circumferential surface 15 of the first opening 11. Furthermore, because the circumferential length of the outer circumferential surface 21B of the inner circumferential portion 21 is shorter than the circumferential length of the first opening 11, the gap S can remain even when the inner circumferential portion 21 is inserted into the first opening 11 and the major diameter RL of the inner circumferential portion 21 shrinks and the minor diameter RS of the inner circumferential portion 21 expands by the amount of the shrinkage. In other words, the inner circumferential portion 21 is easily deformed when inserted into the first opening 11, and this deformation can be released into the gap S. Therefore, it is possible to suppress buckling of the cover member 2 inserted into the first opening 11 of the first exhaust pipe 1. As a result, the inner circumferential portion 21 of the cover member 2 is less likely to deform toward the inside of the first exhaust pipe 1, i.e., in a direction that separates the inner circumferential portion 21 from the inner circumferential surface 15 of the first exhaust pipe 1. Therefore, it is possible to suppress the cover member 2 from becoming difficult to hold on the first exhaust pipe 1 due to the reduction in the contact area between the inner circumferential portion 21 and the first exhaust pipe 1.

[0046] (5b) In the present embodiment, when the cover member 2 is inserted into the first opening 11, the inner circumferential portion 21 located on the long diameter portion 2A of the cover member 2 is positioned on the chamfered portion 14C, and the inner circumferential portion 21 located on the short diameter portion 2B of the cover member 2 is positioned more inward than the chamfered portion 14C. This allows the inner circumferential portion 21 located on the long diameter portion 2A of the cover member 2 to move along the chamfered portion 14C, and the inner circumferential portion 21 located on the short diameter portion 2B of the cover member 2 to move without colliding with the chamfered portion 14C. This makes it easier to insert the cover member 2 into the first opening 11 of the first exhaust pipe 1.

[0047] (5c) In this embodiment, after inserting the cover member 2 into the first opening 11, the cover member 2 is positioned over the first opening 11 during the insertion process so that the inner circumferential portion 21 located on the major diameter portion 2A of the cover member 2 is positioned at the heat spot portion of the first exhaust pipe 1. Therefore, the heat spot portion of the first exhaust pipe 1 abuts against the inner circumferential portion 21, which can prevent exhaust gas from directly hitting the heat spot portion. As a result, the heat resistance of the first exhaust pipe 1 can be improved.

[0048] (5d) In this embodiment, the cover member 2 is attached to the first end 10 of the first exhaust pipe 1, which is located downstream of the second exhaust pipe 3. Because exhaust gases are likely to hit the first end 10, providing the cover member 2 at the first end 10 makes it possible to effectively prevent damage to the first end 10 caused by the heat of the exhaust gases.

[0049] In this embodiment, the first exhaust pipe 1 corresponds to an example of an exhaust pipe, the first opening 11 corresponds to an example of an opening, the central axis 21C corresponds to an example of a central axis, and the central axis 11A corresponds to an example of a pipe central axis. The radius of the major axis RL corresponds to an example of the maximum width, and the radius of the minor axis RS corresponds to an example of the minimum width. The end of the inner circumferential portion 21 at the major axis portion 2A corresponds to an example of a portion of the inner circumferential portion 21 that corresponds to the maximum width, and the end of the inner circumferential portion 21 at the minor axis portion 2B corresponds to an example of a portion of the inner circumferential portion 21 that corresponds to the minimum width.

[0050] 6. 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 on various forms.

[0051] (6a) In the above embodiment, the cover member 2 has an L-shaped cross section perpendicular to the circumferential direction, but the cross-sectional shape of the cover member is not limited to this. 11 , a tip portion 22 that bends in a direction away from the inner circumferential surface 15 of the first exhaust pipe 1 may be provided at the end of the inner circumferential portion 21 of the cover member 2a opposite to the end where the clamping portion 20 is provided. The tip portion 22 is provided around the entire circumference of the end of the inner circumferential portion 21. The tip portion 22 may extend linearly or may be curved in a cross section of the cover member 2 that is perpendicular to the circumferential direction.

[0052] The configuration of the cover member 2a makes it easy to insert the cover member 2a into the first opening 11, in other words, to attach the cover member 2a to the first edge portion 14 of the first end portion 10 of the first exhaust pipe 1. Furthermore, when attaching the cover member 2a to the first edge portion 14, damage to the cover member 2a and the first end portion 10 can be suppressed, making it easy to improve quality.

[0053] 12, the cover member 2b may have an outer peripheral portion 24 that protrudes in the same direction as the inner peripheral portion 21 from the end of the clamping portion 20 opposite the end where the inner peripheral portion 21 is provided, i.e., from the outer peripheral edge of the clamping portion 20. The outer peripheral portion 24 is a wall-like portion that is provided so as to surround the edge. In other words, the cover member 2b may be a groove-like member with the clamping portion 20 as its bottom surface, in other words, a member with a U-shaped cross section perpendicular to the circumferential direction, and may be configured to fit into the first edge portion 14 when inserted into the first opening 11. When the cover member 2b is fitted into the first edge portion 14, the clamping portion 20 covers the clamping surface 14A of the first edge portion 14, and the outer peripheral portion 24 covers the outer peripheral surface 14B of the first edge portion 14.

[0054] Furthermore, for example, as shown in FIG. 13, a cover member 2c may have an outer peripheral portion 24 similar to the cover member 2b described above, and a tip portion 22 similar to the cover member 2a described above. (6b) In the above embodiment, after the cover member 2 is inserted into the first opening 11, the cover member 2 is positioned on the first opening 11 so that the inner circumferential portion 21 located on the long diameter portion 2A of the cover member 2 is positioned in the heat spot portion of the first exhaust pipe 1. However, the position where the inner circumferential portion 21 located on the long diameter portion 2A of the cover member 2 is positioned is not limited to this. For example, the inner circumferential portion 21 located on the long diameter portion 2A of the cover member 2 may be positioned in a weak portion, which is a fragile part that is structurally weak in heat resistance. As shown in FIG. 14 , if a hole 16 is locally formed in the first end portion 10 of the first exhaust pipe 1d, the position of the inner circumferential surface 15 facing the hole 16 is an example of a weak portion of the first exhaust pipe 1d.

[0055] (6c) In the above embodiment, the first edge 14 of the first exhaust pipe 1 has the chamfered portion 14C, but, for example, the first edge may have no chamfered portion. In this case, when the cover member 2 is inserted into the first opening 11, the inner periphery 21 located on the long diameter portion 2A of the cover member 2 is positioned on the clamping surface 14A, and the inner periphery 21 located on the short diameter portion 2B of the cover member 2 is positioned inside the clamping surface 14A.

[0056] (6d) In the above embodiment, the cross-sectional shape perpendicular to the central axis 21C of the inner circumferential portion 21 is a substantially ellipse, but the shape of the cover member is not limited to this. For example, the cross-sectional shape perpendicular to the central axis of the inner circumferential portion may be a polygon (for example, a substantially triangle).

[0057] In this case, when the inner circumferential portion of the cover member and the first opening 11 are overlapped with their centers aligned, the outer circumferential surface of the inner circumferential portion of the cover member has a portion located outside or at approximately the same position as the first opening 11, and a portion located inside the first opening 11. In addition, the outer circumferential length of the inner circumferential portion of the cover member is shorter than the circumferential length of the first opening 11.

[0058] Specifically, the three vertices of the triangle are located outside the first opening 11 or at approximately the same positions, and the central portions of the three sides are located inside the first opening 11. As a result, the longest width of the cover member (i.e., the length from the center of the inner periphery to the vertices) is approximately the same as or greater than the radius of the first opening 11, and the shortest width of the cover member (i.e., the length from the center of the inner periphery to the central portion of the side) is smaller than the radius of the first opening 11.

[0059] (6e) In the above embodiment, the cover member 2 was attached to the first exhaust pipe 1 located downstream of the second exhaust pipe 3. However, for example, the cover member may be attached to the second exhaust pipe located upstream of the first exhaust pipe.

[0060] (6f) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0061] [7. Technical Ideas Disclosed in the Present Specification] [Item 1] A method for manufacturing an exhaust pipe that forms a flow path for exhaust gas of a vehicle, comprising: inserting a cover member into a substantially circular opening provided at a first end of the first exhaust pipe; Equipped with The cover member is an inner peripheral portion that is a ring-shaped portion having a central axis, and whose outer peripheral surface faces an inner peripheral surface of the first exhaust pipe when the cover member is inserted into the opening; a clamping portion that extends outward from an end of the inner circumferential portion and is clamped between the first end and a second end of a second exhaust pipe connected to the first end, The direction along the plane perpendicular to the central axis is defined as the width direction, a maximum width along the width direction from the central axis of the inner peripheral portion to the outer peripheral surface is equal to or greater than a radius of a circumference of the opening, a minimum width along the width direction from the central axis of the inner peripheral portion to the outer peripheral surface is smaller than the radius, A method for manufacturing an exhaust pipe, wherein the circumferential length of the outer circumferential surface is shorter than the circumferential length of the opening.

[0062] [Item 2] A method for manufacturing an exhaust pipe according to item 1, the first end portion has a chamfered portion that is formed to surround the opening and that is inclined so as to move away from a pipe central axis of the first exhaust pipe toward the first end portion, when inserting the cover member into the opening, when viewed along the central axis of the pipe, a portion of the inner periphery corresponding to the longest width before insertion into the opening is located on the chamfered portion, and a portion of the inner periphery corresponding to the shortest width before insertion into the opening is located more inward than the chamfered portion.

[0063] [Item 3] A method for manufacturing an exhaust pipe according to item 1 or 2, The method for manufacturing an exhaust pipe, wherein the inner peripheral portion has a cross-sectional shape perpendicular to the central axis that is substantially elliptical.

[0064] [Item 4] A method for manufacturing an exhaust pipe according to any one of items 1 to 3, A method for manufacturing an exhaust pipe, wherein the portion of the inner periphery corresponding to the maximum width is located in a heat spot portion of the first exhaust pipe.

[0065] [Item 5] A method for manufacturing an exhaust pipe according to any one of items 1 to 3, A method for manufacturing an exhaust pipe, wherein a portion of the inner periphery corresponding to the maximum width is located in a weak portion of the first exhaust pipe.

[0066] [Item 6] A method for manufacturing an exhaust pipe according to any one of items 1 to 5, A method for manufacturing an exhaust pipe, wherein the first exhaust pipe is located downstream of the second exhaust pipe in the flow direction of the exhaust gas. [Explanation of symbols]

[0067] 1, 1d...first exhaust pipe, 2...cover member, 3...second exhaust pipe, 2, 2a to 2c...cover members, 2A...long diameter portion, 2B...short diameter portion, 4...gasket, 5...clamp, 10...first end, 11...first opening, 11A, 21C...central axis, 12...first flange portion, 13...groove portion, 14...first edge portion, 14A...clamping surface, 14B, 21B...outer peripheral surface, 14C...chamfered portion, 15...inner peripheral surface, 16...hole, 20...clamping portion, 21...inner peripheral portion, 22...tip portion, 24...outer peripheral portion, 30...second end, 31...second opening, 32...second flange portion, 33...depressed portion, 34...bottom surface, 35...first inner peripheral surface, 36...second inner peripheral surface, S...gap.

Claims

1. A method for manufacturing an exhaust pipe that forms a flow path for exhaust gas of a vehicle, comprising: inserting a cover member into a substantially circular opening provided at a first end of the first exhaust pipe; Equipped with The cover member is an inner peripheral portion that is a ring-shaped portion having a central axis, and whose outer peripheral surface faces an inner peripheral surface of the first exhaust pipe when the cover member is inserted into the opening; a clamping portion that extends outward from an end of the inner circumferential portion and is clamped between the first end and a second end of a second exhaust pipe connected to the first end, The direction along the plane perpendicular to the central axis is defined as the width direction, a maximum width along the width direction from the central axis of the inner peripheral portion to the outer peripheral surface is equal to or greater than a radius of a circumference of the opening, a minimum width along the width direction from the central axis of the inner peripheral portion to the outer peripheral surface is smaller than the radius, A method for manufacturing an exhaust pipe, wherein the circumferential length of the outer circumferential surface is shorter than the circumferential length of the opening.

2. A method for manufacturing an exhaust pipe according to claim 1, the first end portion has a chamfered portion that is formed to surround the opening and that is inclined so as to move away from a pipe central axis of the first exhaust pipe toward the first end portion, when inserting the cover member into the opening, when viewed along the central axis of the pipe, a portion of the inner periphery corresponding to the longest width before insertion into the opening is located on the chamfered portion, and a portion of the inner periphery corresponding to the shortest width before insertion into the opening is located more inward than the chamfered portion.

3. A method for manufacturing an exhaust pipe according to claim 1 or 2, comprising: The method for manufacturing an exhaust pipe, wherein the inner peripheral portion has a cross-sectional shape perpendicular to the central axis that is substantially elliptical.

4. A method for manufacturing an exhaust pipe according to claim 1 or 2, comprising: A method for manufacturing an exhaust pipe, wherein a portion of the inner circumferential portion corresponding to the maximum width is located in a heat spot portion of the first exhaust pipe.

5. A method for manufacturing an exhaust pipe according to claim 1 or 2, a portion of the inner periphery corresponding to the maximum width is located in a weak portion of the first exhaust pipe.

6. A method for manufacturing an exhaust pipe according to claim 1 or 2, The method for manufacturing an exhaust pipe, wherein the first exhaust pipe is located downstream of the second exhaust pipe in the flow direction of the exhaust gas.

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