Manufacturing method of metal component

Abstract

To provide a technique of preventing a gap between both end parts of the body part in a circumferential direction from being decreased in a metal component having a body part and a flange part.SOLUTION: A metal component includes: a body part which extends in an axial direction and has an arcuate cross-section orthogonal to the axis direction; and a flange part which extends from one end part of the body part in the axial direction to an outer side in a radial direction. A manufacturing method of the metal component comprises the steps of: bending a metal plate to get a cylindrical body; bending one end part of the cylindrical body toward the outer side in the radial direction to enlarge it; and cutting out a predetermined range of the cylindrical body with the end part being enlarged in a circumferential direction when both end parts of the plate material are bended to be butted and the butted end parts are welded to obtain the cylindrical body.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a metal component. [Background technology]

[0002] For example, Patent Document 1 discloses a metal part having a main body and a flange. The main body extends in the axial direction and has an arc-shaped cross section perpendicular to the axial direction. The flange extends radially outward from one axial end of the main body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2022-181467 Summary of the Invention [Problem to be solved by the invention]

[0004] As a method for manufacturing this type of metal part, for example, the following manufacturing method is considered. First, a round hole is formed in a metal plate. Next, the periphery of the round hole in the plate is raised on one surface side of the plate by burring. Then, a predetermined range in the circumferential direction of the round hole in the plate with the raised periphery is cut away to obtain the metal part.

[0005] However, in metal components obtained by such a manufacturing method, residual stress resulting from the burring process may result in a small distance between both circumferential ends of the main body.

[0006] One aspect of the present disclosure provides a technique for preventing a reduction in the distance between both circumferential ends of a main body portion in a metal component including a main body portion and a flange portion. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for manufacturing a metal part including a main body extending in an axial direction and having a cross-sectional shape perpendicular to the axial direction that is an arc shape, and a flange extending radially outward from one axial end of the main body. The method for manufacturing the metal part includes bending a metal plate material to obtain a cylinder, and bending one end of the cylinder radially outward to expand the diameter. The method for manufacturing the metal part further includes, in the case of obtaining a cylinder by bending the plate material so that both ends of the plate material are butted together and welding the butted both ends, cutting out a predetermined range in the circumferential direction of the cylinder whose end has been expanded. With this configuration, in a metal part including a main body and a flange, it is possible to suppress the interval between both ends of the main body in the circumferential direction from becoming small.

[0008] In one embodiment of the present disclosure, the cut-out area of ​​the cylinder may include both ends of the welded portion, which allows the production of a metal part with a smaller surface roughness.

[0009] In one aspect of the present disclosure, the metal component may be an exhaust system component provided in a flow path of exhaust gas from an internal combustion engine. With this configuration, even when the metal component is exposed to high-temperature exhaust gas, it is possible to suppress a decrease in the distance between both ends of the main body in the circumferential direction. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of an exhaust system unit. [Diagram 2] FIG. 2 is a partially enlarged view of FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] Fig. 6A is a cross-sectional view for explaining U-bending in a pipe-making process, and Fig. 6B is a cross-sectional view for explaining a state subsequent to Fig. 6A in the pipe-making process. [Figure 7]Fig. 7A is a cross-sectional view showing O-bending in a pipe-making process, and Fig. 7B is a cross-sectional view for explaining a state subsequent to Fig. 7A in the pipe-making process. [Figure 8] FIG. 2 is a perspective view for explaining welding processing in a pipe making process. [Figure 9] Fig. 9A is a cross-sectional view for explaining the diameter expanding step, Fig. 9B is a cross-sectional view for explaining the state following Fig. 9A in the diameter expanding step, and Fig. 9C is a cross-sectional view for explaining the state following Fig. 9B in the diameter expanding step. [Figure 10] FIG. 11 is a plan view for explaining a cutting step. [Figure 11] Fig. 11A is a cross-sectional view taken along the line XIA-XIA in Fig. 10. Fig. 11B is a cross-sectional view for explaining a state following Fig. 11A in a cutting step. [Figure 12] Fig. 12A is a cross-sectional view taken along line XIIA-XIIA in Fig. 10. Fig. 12B is a cross-sectional view for explaining a state following Fig. 12A in a cutting step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0012] [1. Configuration] An exhaust system unit 1 shown in FIG. 1 forms a flow path of exhaust gas from an internal combustion engine of a vehicle. As an example, the exhaust system unit 1 forms a flow path of exhaust gas after passing through a turbocharger. Hereinafter, the flow path of exhaust gas from the internal combustion engine of a vehicle is referred to as an exhaust flow path. The exhaust system unit 1 includes a first exhaust pipe 2, a second exhaust pipe 3, and a cover member 4.

[0013] <First exhaust pipe> The first exhaust pipe 2 is a member that forms an exhaust flow path. The first exhaust pipe 2 is tubular. The first exhaust pipe 2 is heat resistant. The first exhaust pipe 2 is made of metal. As an example, the first exhaust pipe 2 may be made of austenitic steel. The first exhaust pipe 2 includes a first end 21, a first flange portion 22, a protruding portion 23, and a groove portion 24.

[0014] The first end 21 is the upstream end of the first exhaust pipe 2. The first end 21 is cylindrical. Of the two openings of the first exhaust pipe 2, the first end 21 forms the upstream opening. The opening formed by the first end 21 is hereinafter referred to as the first opening 20. The opening surface of the first opening 20 is circular.

[0015] An end face 25 of the first end 21 extends in a plane in a direction perpendicular to the central axis A of the first end 21. The first exhaust pipe 2 is fastened to the second exhaust pipe 3 at the first end 21. When the first exhaust pipe 2 and the second exhaust pipe 3 are fastened together, the first opening 20 is continuous with a second opening 30 of the second exhaust pipe 3, which will be described later.

[0016] The first flange portion 22 is a portion that extends radially outward from the outer circumferential surface of the first end portion 21. The radially outward referred to here can also be said to be the side opposite the first opening 20 side across the first end portion 21. The first flange portion 22 is used for fastening to the second exhaust pipe 3. The first exhaust pipe 2 and the second exhaust pipe 3 are fastened together by a fastening member 5 such as a V-clamp.

[0017] 2, the protruding portion 23 is a cylindrical portion that protrudes vertically (i.e., parallel to the central axis A of the first end portion 21) from an end face 25 of the first end portion 21. The protruding portion 23 is formed along the edge of the first end portion 21 on the side of the first opening 20. A top surface 26 located at the top of the protruding portion 23 extends in a flat shape in a direction perpendicular to the central axis A of the first end portion 21. An inner circumferential surface 28 of the protruding portion 23 constitutes a part of a first inner circumferential surface 27 of the first exhaust pipe 2.

[0018] The groove portion 24 is a groove-shaped portion formed in the end surface 25 of the first end portion 21. The groove portion 24 is adjacent to the outer circumferential surface of the protruding portion 23. The groove portion 24 is continuous so as to surround the entire circumference of the protruding portion 23. In the groove portion 24, as an example, a sealing material 6 such as a ring-shaped gasket is disposed.

[0019] <Second exhaust pipe> The second exhaust pipe 3 shown in FIG. 1 is a member that forms an exhaust flow path. The second exhaust pipe 3 is tubular. The second exhaust pipe 3 has heat resistance. For example, the second exhaust pipe 3 may have higher heat resistance than the first exhaust pipe 2. The second exhaust pipe 3 is made of metal. For example, the second exhaust pipe 3 may be made of austenitic steel. The second exhaust pipe 3 includes a second end portion 31, a second flange portion 32, and a recessed portion 33.

[0020] The second end 31 is the downstream end of the second exhaust pipe 3. The second end 31 is cylindrical. Of the two openings of the second exhaust pipe 3, the second end 31 forms the downstream opening. The opening formed by the second end 31 is hereinafter referred to as the second opening 30. The opening surface of the second opening 30 is circular. The size of the opening surface of the second opening 30 is equal to the size of the opening surface of the first opening 20 described above.

[0021] An end face 34 of the second end 31 extends in a plane in a direction perpendicular to the central axis B of the second end 31. The second exhaust pipe 3 is fastened to the first exhaust pipe 2 at the second end 31. When the first exhaust pipe 2 and the second exhaust pipe 3 are fastened to each other, the central axis A of the first end 21 and the central axis B of the second end 31 coincide with each other.

[0022] The second flange portion 32 is a portion that extends radially outward from the outer circumferential surface of the second end portion 31. The radially outward referred to here can also be said to be the side opposite to the second opening 30 side across the second end portion 31. The second flange portion 32 is used for fastening to the first exhaust pipe 2.

[0023] 2, the depressed portion 33 is a portion recessed vertically from the end face 34 of the second end portion 31 (i.e., parallel to the central axis B of the second end portion 31). Specifically, the depressed portion 33 is a portion where a corner formed between the end face 34 and the inner peripheral surface of the second end portion 31 is recessed parallel to the central axis B of the second end portion 31. The depressed portion 33 has a bottom surface 35 and a third inner peripheral surface 37.

[0024] The bottom surface 35 spreads out in a plane in a direction perpendicular to the central axis B of the second end portion 31. The bottom surface 35 forms a step on the inner circumferential surface of the second exhaust pipe 3. The inner circumferential surface of the second exhaust pipe 3 is divided by the bottom surface 35 into a second inner circumferential surface 36 and a third inner circumferential surface 37. The third inner circumferential surface 37 is located downstream of the second inner circumferential surface 36, separated by the bottom surface 35. The diameter of the third inner circumferential surface 37 is larger than the diameter of the second inner circumferential surface 36.

[0025] When the first exhaust pipe 2 and the second exhaust pipe 3 are fastened together, the protruding portion 23 fits into the recessed portion 33. In other words, the protruding portion 23 and the recessed portion 33 are used for positioning when the first exhaust pipe 2 and the second exhaust pipe 3 are connected.

[0026] <Cover material> The cover member 4 shown in Figures 3 to 5 is an exhaust system component provided in the exhaust flow path. Providing the cover member 4 in the exhaust flow path means that at least a portion of the cover member 4 is disposed within the exhaust flow path, as will be described later. The cover member 4 is used to improve the heat resistance of the exhaust pipe of a vehicle.

[0027] The cover member 4 is made of metal. As an example, the cover member 4 may be made of a ferritic steel material. The cover member 4 has heat resistance. As an example, the cover member 4 has higher heat resistance than the first exhaust pipe 2.

[0028] The cover member 4 includes a main body portion 40 and a flange portion 41. The main body portion 40 and the flange portion 41 are integrally formed.

[0029] The main body 40 extends in the axial direction, and has a cross-sectional shape perpendicular to the axial direction that is arc-shaped. The axial direction of the main body 40 can also be said to be the extension direction of the main body 40. In other words, the axial direction of the main body 40 is the direction in which the arc-shaped cross sections of the main body 40 continue. The axial direction of the main body 40 is parallel to the central axis C of a virtual cylinder that is a virtual cylinder that includes the main body 40. The radial direction and circumferential direction of the main body 40 correspond to the radial direction and circumferential direction of the virtual cylinder, respectively. Hereinafter, the outer surface and inner surface in the circumferential direction of the surface of the main body 40 are referred to as the outer surface 42 and the inner surface 43, respectively. That is, the main body 40 has the outer surface 42 and the inner surface 43. The curvature of the outer surface 42 is approximately the same as the curvature of the first inner circumferential surface 27 of the first exhaust pipe 2 (more specifically, the inner circumferential surface 28 of the protruding portion 23).

[0030] The flange portion 41 extends radially outward from one axial end of the main body portion 40. The flange portion 41 extends from the entire circumferential range of the end of the main body portion 40. The flange portion 41 extends perpendicular to the axial direction of the main body portion 40. The flange portion 41 is generally flat. That is, the first surface 44 and the second surface 45, which are both sides of the flange portion 41, are generally flat. The first surface 44 of the flange portion 41 can also be said to be a surface that continues from the outer surface 42 of the main body portion 40 in the flange portion 41. The second surface 45 of the flange portion 41 can also be said to be a surface that continues from the inner surface 43 of the main body portion 40 in the flange portion 41.

[0031] 1 and 2, the cover member 4 is attached to the first exhaust pipe 2. Specifically, the main body portion 40 is inserted (e.g., press-fitted) into the first opening 20 so that the outer surface 42 of the main body portion 40 and the inner circumferential surface 28 of the protruding portion 17 face each other, and the first surface 44 of the flange portion 41 and the top surface 26 of the protruding portion 17 face each other.

[0032] The first exhaust pipe 2 to which the cover member 4 is attached in this manner is fastened to the second exhaust pipe 3 by the fastening member 5 as described above. In a state in which the first exhaust pipe 2 and the second exhaust pipe 3 are fastened, the cover member 4 is sandwiched between the first end 21 and the second end 31. Specifically, the flange portion 41 is sandwiched between the top surface 26 of the protruding portion 23 and the bottom surface 35 of the recessed portion 33. That is, the first surface 44 of the flange portion 41 contacts the top surface 26 of the protruding portion 23, and the second surface 45 contacts the bottom surface 35 of the recessed portion 33. The main body portion 40 is disposed inside the first exhaust pipe 2, that is, in the exhaust flow path. The main body portion 40 covers the entire inner circumferential surface 28 of the protruding portion 23. The outer surface 42 of the main body portion 40 contacts the inner circumferential surface 28 of the protruding portion 23.

[0033] In this manner, the cover member 4 covers the first inner circumferential surface 27 (specifically, the inner circumferential surface 28 of the protruding portion 23), and thus the heat resistance of the first exhaust pipe 2 is improved.

[0034] [2. Manufacturing method of cover member] Next, a method for manufacturing the cover member 4 will be described. The method for manufacturing the cover member 4 includes at least a pipe-making process and a diameter-expanding process. As described below, the pipe-making process in this embodiment includes welding. In this way, when the pipe-making process includes welding, the method for manufacturing the cover member 4 further includes a cutting process.

[0035] <Pipe making process> The pipe-making process is a process in which a metal plate 50 shown in FIG. 6A is bent to obtain a cylindrical body 51 shown in FIG. 9A.

[0036] 6A, the metal plate material 50 is made of metal. The metal plate material 50 before the pipe-making process is flat. The metal plate material 50 before the pipe-making process is rectangular in plan view.

[0037] As shown in FIG. 9A, the cylinder 51 is cylindrical. The cylinder 51 obtained by the pipe making process (i.e., before the diameter expansion process is performed) extends linearly. In this embodiment, the cross-sectional shape of the cylinder 51 perpendicular to the axial direction is approximately perfect circular. The approximately perfect circular shape here includes a strict perfect circular shape as well as a perfect circular shape as distinguished from an elliptical shape. The diameter of the cylinder 51 obtained by the pipe making process is the same as or larger than the axial length of the cylinder 51. The axial length of the cylinder 51 corresponds to the short side of the metal plate material 50 before the pipe making process is performed, and the circumference of the cylinder 51 corresponds to the long side of the metal plate material 50 before the pipe making process is performed.

[0038] The pipe-making process includes U-bending and O-bending, and further includes welding.

[0039] (1) U-bending The U-bending process shown in Figures 6A and 6B is a process in which a metal plate 50 is bent into a U-shaped cross section by press forming. In the U-bending process, a first forming die 70 and a second forming die 72 made of metal are used. The first forming die 70 has a recess 71 having a U-shaped cross section. The second forming die 72 has a protrusion 73 having a U-shaped cross section. As shown in Figure 6B, the recess 71 and the protrusion 73 are sized to engage with each other.

[0040] 6A, the first molding die 70 and the second molding die 72 are disposed with a gap therebetween so that the recessed portion 71 faces the protruding portion 73. The first molding die 70 is configured to be displaceable so as to move toward or away from the second molding die 72.

[0041] In the U-bending process, first, the metal sheet material 50 is placed between a first forming die 70 and a second forming die 72, as shown in Fig. 6A. Next, as shown in Fig. 6B, the first forming die 70 is displaced so as to approach the second forming die 72. Then, the recessed portion 71 and the protruding portion 73 engage with each other while sandwiching the metal sheet material 50 therebetween. As a result, the metal sheet material 50 is bent into a U-shaped cross section.

[0042] (2) O-bending Following the U-bending process, an O-bending process is performed as shown in Figures 7A and 7B. The O-bending process is a process in which the metal plate material 50 bent into a U-shaped cross section (i.e., the metal plate material 50 after the U-bending process) is bent into an O-shaped cross section by press forming. In the O-bending process, a first forming die 80 and a second forming die 82 made of metal are used.

[0043] The first molding die 80 has a recess 81 having a C-shaped cross section. The second molding die 82 has a recess 83 having a C-shaped cross section. When the first molding die 80 and the second molding die 82 come into contact with each other as shown in FIG. 7B, the inner surface of the recess 81 and the inner surface of the recess 83 form a continuous surface. This continuous surface has a shape corresponding to the outer circumferential surface of the cylindrical body 51.

[0044] 7A, the first molding die 80 and the second molding die 82 are disposed with a gap therebetween so that the recess 81 faces the recess 83. The first molding die 80 is configured to be displaceable so as to move toward or away from the second molding die 82.

[0045] In the O-bending process, as shown in FIG. 7A, first, the metal plate material 50 bent into a U-shaped cross section is placed between the first forming die 80 and the second forming die 82. Specifically, the metal plate material 50 is placed between the first forming die 80 and the second forming die 82 so that the curved portion of the metal plate material 50 faces the recess 83 side and the open portion faces the recess 81 side. Next, as shown in FIG. 7B, the first forming die 80 is displaced so as to approach the second forming die 82. Specifically, the first forming die 80 is displaced until the surface of the first forming die 80 on which the recess 81 is formed comes into contact with the surface of the second forming die 82 on which the recess 83 is formed. As a result, the metal plate material 50 is bent so that both ends 501, 502 of the metal plate material 50 are butted against each other. That is, the metal plate material 50 is bent into an O-shaped cross section. The two ends 501, 502 of the metal plate 50 refer to two ends constituting two opposing sides of the metal plate 50. In this embodiment, the two ends 501, 502 of the metal plate 50 refer to two ends in the longitudinal direction of the metal plate 50.

[0046] (3) Welding In this embodiment, after the O-bending process, a welding process shown in FIG. 8 is performed. The welding process is a process for welding both ends 501, 502 of a metal plate material 50 that are butted together. FIG. 8 illustrates a torch T as an example of a welding machine. As shown in FIG. 8, the both ends 501, 502 of the metal plate material 50 that are butted together are welded using, for example, the torch T. The welded both ends 501, 502 of the metal plate material 50 are also referred to as, for example, a weld line, a bead portion, or the like. By performing the welding process, a cylindrical body 51 shown in FIG. 9A is obtained. That is, the cylindrical body 51 is a metal plate material 50 in which the both ends 501, 502 that are butted together are welded together.

[0047] <Diameter expansion process> Following the pipe-making process, a diameter expansion process shown in Figures 9A to 9C is performed. The diameter expansion process is a process in which one end 511 of the cylinder 51 obtained in the pipe-making process is bent radially outward by flaring to expand the diameter. More specifically, expanding the diameter of the end 511 means expanding the diameter of the circle defined by the edge of the end 511. In the diameter expansion process, a metallic holding die 90 and an insertion die 93 are used.

[0048] As shown in Fig. 9A, the holding mold 90 has a holding portion 91 and a first flange portion 92. The holding portion 91 is a cylindrical portion. The first flange portion 92 is a portion extending radially outward from one end of the holding portion 91. The first flange portion 92 extends from the entire circumference of that end of the holding portion 91. The first flange portion 92 extends perpendicular to the central axis of the holding portion 91. The first flange portion 92 is generally plate-shaped.

[0049] In this embodiment, as an example, the holding mold 90 is composed of two split molds 90a, 90b divided by a plane including the central axis of the holding portion 91. That is, the holding portion 91 and the first flange portion 92 are composed of the two split molds 90a, 90b. The two split molds 90a, 90b are configured to be displaceable in the radial direction of the holding portion 91 so as to approach or move away from each other. Therefore, when the cylindrical body 51 is placed between the two split molds 90a, 90b, the two split molds 90a, 90b can hold the cylindrical body 51 by displacing to approach each other. Specifically, the parts constituting the holding portion 91 in each of the two split molds 90a, 90b can hold the cylindrical body 51 in this way. That is, the holding portion 91 is configured to be able to hold the cylindrical body 51. The curvature of the inner peripheral surface of the holding portion 91 is approximately the same as the curvature of the outer peripheral surface of the cylindrical body 51.

[0050] The insertion mold 93 includes an insertion portion 94 , a second flange portion 95 , and a stopper 96 .

[0051] The insertion portion 94 is a cylindrical portion. The two axial ends of the insertion portion 94 are hereinafter referred to as a first end 941 and a second end 942. Specifically, the insertion portion 94 is cylindrical with a chamfered corner of the first end 941. The curvature of the outer circumferential surface of the insertion portion 94 is approximately the same as the curvature of the inner circumferential surface of the cylindrical body 51.

[0052] The second flange portion 95 is a portion extending radially outward from the second end portion 942 of the insertion portion 94. The second flange portion 95 extends from the entire circumference of the second end portion 942. The second flange portion 95 extends perpendicular to the central axis of the insertion portion 94. The second flange portion 95 is generally plate-shaped.

[0053] The stopper 96 is a cylindrical portion provided on a surface of the second flange portion 95 on the first end 941 side of the insertion portion 94. The stopper 96 surrounds the insertion portion 94. The height of the stopper 96 from the surface of the second flange portion 95 is set based on the thickness of the metal plate material 50.

[0054] The retention mold 90 and the insertion mold 93 are arranged with a gap between them so that the central axis of the retention portion 91 and the central axis of the insertion portion 94 coincide with each other. The retention mold 90 has the side of the retention portion 91 on which the first flange portion 92 is formed facing the insertion mold 93. The insertion mold 93 has the first end portion 941 of the insertion portion 94 facing the retention mold 90. With the retention mold 90 and the insertion mold 93 arranged with a gap between them, the first flange portion 92 and the second flange portion 95 face each other.

[0055] The insertion die 93 is configured to be displaceable so as to approach or move away from the retention die 90. The insertion die 93 is configured to be displaceable so as to approach the retention die 90 until the stopper 96 contacts the first flange portion 92. In other words, the stopper 96 is a portion that determines the limit of the distance by which the retention die 90 and the insertion die 93 approach each other. The limit of the distance by which the retention die 90 and the insertion die 93 approach each other coincides with the height of the stopper 96 from the surface of the second flange portion 95.

[0056] In the diameter expansion process, first, the cylindrical body 51 obtained in the pipe making process is placed between the two split dies 90a, 90b. Specifically, the cylindrical body 51 is placed between the two split dies 90a, 90b such that one end 511 of the cylindrical body 51 protrudes outward beyond the portions constituting the first flange portion 92 of the two split dies 90a, 90b.

[0057] Next, the two split dies 90a, 90b are displaced so as to approach each other. As a result, as shown in Fig. 9A, the cylindrical body 51 is sandwiched between the two split dies 90a, 90b. That is, the cylindrical body 51 is held by the holding portion 91. At this time, one end portion 511 of the cylindrical body 51 is in a state of protruding outward from the first flange portion 92 of the holding die 90 (i.e., toward the insertion die 93).

[0058] Next, as shown in Fig. 9B, the insertion die 93 is displaced so as to approach the retention die 90. The insertion die 93 is displaced until the stopper 96 comes into contact with the first flange portion 92 as shown in Fig. 9C.

[0059] When the insertion die 93 is displaced so as to approach the holding die 90, the insertion part 94 is inserted into the inside of the cylinder 51 from the end 511 side, as shown in FIG. 9B. Then, as the insertion part 94 advances while sliding on the inner surface of the cylinder 51 with the displacement of the insertion die 93, the end face of the end 511 of the cylinder 51 comes into contact with the second flange part 95. When the insertion part 94 advances further while sliding on the inner surface of the cylinder 51, as shown in FIG. 9C, the end 511 of the cylinder 51 is bent radially outward along the surface of the second flange part 95 and expanded in diameter. When the stopper 96 comes into contact with the first flange part 92 (i.e., when the insertion die 93 has finished displacing), the end 511 of the cylinder 51 is sandwiched between the first flange part 92 and the second flange part 95. Then, the end 511 of the cylinder 51 is bent radially outward to a designed angle and expanded in diameter. The designed angle in this embodiment is 90 degrees. Hereinafter, the cylinder 51 with the end 511 having the expanded diameter will be referred to as an expanded diameter cylinder 52.

[0060] <Excision process> In this embodiment, the diameter expansion step is followed by a cutting step shown in Figures 10 to 12B. The cutting step is a step of cutting out a predetermined circumferential range of the post-diameter-expanded cylinder 52 by punching. In the cutting step, a metal support die 100 and a pressing die 110 are used. Note that although the support die 100 and the pressing die 110 shown in Figures 12A and 12B are cross-sectional views, hatching has been omitted to facilitate understanding.

[0061] The support mold 100 is a metal mold for supporting the cylindrical body 52 after the diameter expansion. The support mold 100 has a recess 101 and a punch hole .

[0062] As shown in Fig. 10 and Fig. 11A, the recess 101 is a circular recess in a plan view. The recess 101 has a size corresponding to the outer shape of the expanded cylinder 52 when viewed along the axial direction. The inner diameter of the recess 101 is slightly larger than the outer diameter of the expanded end 511 of the expanded cylinder 52 (i.e., the diameter of the circle defined by the edge of the end 511). The bottom surface of the recess 101 is flat. The bottom surface of the recess 101 constitutes a placement surface for placing the expanded cylinder 52.

[0063] The punch hole 102 is a hole formed in the support die 100. As shown in Fig. 10, the punch hole 102 is formed at a position overlapping a part of the circumferential range of the expanded cylinder 52 when the expanded cylinder 52 is placed in the recess 101. The punch hole 102 has a size that allows a protrusion 111 (described later) of the pressing die 110 to be inserted. The opening surface of the punch hole 102 in this embodiment is rectangular. Moreover, the opening surface of the punch hole 102 in this embodiment is larger than both welded ends 501, 502 of the expanded cylinder 52 when viewed along the axial direction.

[0064] The pressing die 110 is a die for partially pressing the expanded cylindrical body 52 arranged in the recess 101. The pressing die 110 has a main body portion (not shown) and a protruding portion 111. The protruding portion 111 is a portion protruding from the main body portion. The protruding direction of the protruding portion 111 is a direction from the front side to the back side in FIG. 10, and a direction from the upper side to the lower side in FIGS. 11A to 12B. In this embodiment, the cross-sectional shape perpendicular to the protruding direction of the protruding portion 111 is rectangular. The cross-section perpendicular to the protruding direction of the protruding portion 111 has a constant size. The cross-section perpendicular to the protruding direction of the protruding portion 111 is formed slightly smaller than the opening surface of the punching hole 102. Note that in FIG. 10, for convenience of illustration, the protruding portion 111 is shown smaller than the actual size with respect to the punching hole 102.

[0065] 11A and 12A, the support die 100 and the pressing die 110 are disposed with a gap between them. Specifically, the support die 100 is disposed with the recess 101 facing upward. The pressing die 110 is disposed above the support die 100 so that the protruding portion 111 faces the punching hole 102. The pressing die 110 is configured to be displaceable so as to approach or move away from the support die 100. When the pressing die 110 is displaced so as to approach the support die 100, the protruding portion 111 is inserted into the punching hole 102.

[0066] 11A and 12A, in the cutting step, first, the diameter-expanded cylinder 52 is placed in the recess 101 of the support mold 100. Specifically, the diameter-expanded cylinder 52 is placed in the recess 101 so that the expanded end 511 contacts the bottom surface of the recess 101. Also, as shown in FIG. 10, the diameter-expanded cylinder 52 is placed in the recess 101 so that the welded ends 501, 502 are included in the punch hole 102 in a plan view.

[0067] 11B and 12B, the pressing die 110 is displaced so as to approach the support die 100. The pressing die 110 is displaced until the protruding portion 111 is inserted into the punched hole 102 and the end face of the protruding portion 111 reaches a position lower than the bottom surface of the recess 101. The displacement direction of the pressing die 110 is parallel to the axial direction of the expanded cylindrical body 52 arranged in the recess 101.

[0068] As the pressing die 110 is displaced so as to approach the support die 100, the protruding portion 111 comes into contact with the end face of the expanded cylinder 52 opposite to the expanded end portion 511. Then, with the displacement of the pressing die 110, the protruding portion 111 presses the range included in the punch hole 102 in a plan view of the expanded cylinder 52. The range included in the punch hole 102 in a plan view of the expanded cylinder 52 is a part of the range in the circumferential direction of the expanded cylinder 52. In this embodiment, this range includes both welded ends 501, 502 of the expanded cylinder 52.

[0069] When the protrusion 111 advances while pressing the diameter-expanded cylinder 52, a shear force is applied to the diameter-expanded cylinder 52 by the protrusion 111 and a portion of the recess 101 that forms the punch hole 102. Then, as shown in Fig. 11B and Fig. 12B, the protrusion 111 advances until the end face of the protrusion 111 reaches a position lower than the bottom surface of the recess 101, whereby the portion of the diameter-expanded cylinder 52 that is pressed by the protrusion 111 is punched out. In other words, a part of the circumferential range of the diameter-expanded cylinder 52 (in this embodiment, a range including both welded ends 501, 502 of the diameter-expanded cylinder 52) is cut out.

[0070] In other words, the expanded cylinder 52 is cut at the two cutting lines L1 and L2 shown in FIG. 12A, and the range between the two cutting lines L1 and L2 in the expanded cylinder 52 is removed. The two cutting lines L1 and L2 are imaginary lines extending from one end edge to the other end edge in the axial direction of the expanded cylinder 52. The positions of the two cutting lines L1 and L2 correspond to the surface to which the shear force is applied in the expanded cylinder 52. In this embodiment, the welded ends 501 and 502 are located between the two cutting lines L1 and L2. Therefore, as described above, the range including the welded ends 501 and 502 in the expanded cylinder 52 is cut off.

[0071] In this manner, a portion of the circumferential range of the cylindrical body 52 after diameter expansion is cut away, thereby obtaining the cover member 4 shown in Figs. 3 to 5.

[0072] [3. Effects] According to the embodiment described above in detail, the following effects can be obtained.

[0073] (3a) The cover member 4 includes a main body portion 40 and a flange portion 41. The following method, for example, can be considered as a method for manufacturing such a cover member 4. First, a round hole is formed in a metal plate. Next, the periphery of the round hole in the plate is raised on one surface side of the plate by burring. Then, a predetermined range in the circumferential direction of the round hole in the plate with the periphery raised is cut away, thereby obtaining the cover member 4.

[0074] However, the cover member 4 manufactured by such a method may have residual stress due to the burring process. In that case, if springback occurs, the main body portion 40 corresponding to the portion raised by the burring process is deformed so as to fall radially inward. As a result, the distance between both ends of the main body portion 40 in the circumferential direction becomes small.

[0075] In contrast, the manufacturing method of the cover member 4 of this embodiment includes a pipe making process and a diameter expansion process, and further includes a cutting process. With this configuration, even if residual stress occurs in the cover member 4, the expected residual stress is the residual stress caused by the pipe making process. Therefore, even if springback occurs, the main body portion 40 and the flange portion 41 corresponding to the portion bent in the pipe making process are deformed so as to expand radially outward. Therefore, it is possible to prevent the distance between both ends of the main body portion 40 in the circumferential direction from becoming small.

[0076] (3b) Furthermore, in the manufacturing method of the cover member 4 exemplified in (3a) above, scrap is generated when the round hole is formed in the metal plate material, and when a predetermined range in the circumferential direction of the round hole is cut away from the plate material with the periphery of the round hole raised. In contrast, the manufacturing method of the cover member 4 of this embodiment does not include a step of forming a round hole in the metal plate material 50. Therefore, the amount of scrap generated can be reduced. In other words, the amount of metal plate material 50 used can be reduced. As a result, the yield can be improved.

[0077] (3c) The cover member 4 is provided in the exhaust flow path. In such a configuration, if residual stress occurs in the cover member 4, the residual stress is likely to be released by exposing the cover member 4 to high-temperature exhaust gas. For this reason, in the case of a cover member 4 manufactured by the method exemplified in (3a) above, the problem that the distance between both ends in the circumferential direction of the main body portion 40 may become small is more likely to occur. Therefore, in the above configuration, it is more useful to apply the manufacturing method of the cover member 4 of this embodiment.

[0078] (3d) Particularly in this embodiment, the cover member 4 is attached to the first end 21 of the first exhaust pipe 2 by inserting the main body 40 into the first opening 20 of the first exhaust pipe 2. In this configuration, if the distance between both ends of the main body 40 in the circumferential direction becomes small, the clearance between the cover member 4 and the first exhaust pipe 2 is likely to become large. As a result, it becomes difficult for the cover member 4 to be held by the first exhaust pipe 2. In addition, it is also considered that the area of ​​the first exhaust pipe 2 covered by the cover member 4 is likely to decrease.

[0079] Therefore, it is even more useful to apply the manufacturing method of the cover member 4 of this embodiment and prevent the gap between both ends of the main body portion 40 in the circumferential direction from becoming small. This makes it possible to make it easier for the cover member 4 to be held by the first exhaust pipe 2. It also makes it possible to make it difficult for the area of ​​the first exhaust pipe 2 covered by the cover member 4 to decrease. In other words, it also makes it difficult for high-temperature exhaust gas to hit the first inner circumferential surface 27 of the first exhaust pipe 2.

[0080] (3e) In the pipe-making process of this embodiment, the metal plate 50 is bent so that both ends 501, 502 are butted together. Then, the butted ends 501, 502 are welded together to obtain the cylindrical body 51.

[0081] According to this configuration, when the end 511 of the cylinder 51 is bent and expanded in the subsequent diameter expansion step, the relative positions of the both ends 501, 502 can be made less likely to shift. Therefore, in the diameter expansion step, the cylinder 51 with the end 511 expanded in diameter, i.e., the expanded cylinder 52, can be formed with higher accuracy.

[0082] In the (3f) cutting step, both welded ends 501, 502 of the diameter-expanded cylindrical body 52 are cut off. That is, the area to be cut off in the diameter-expanded cylindrical body 52 includes both welded ends 501, 502.

[0083] In the expanded cylindrical body 52, the welded ends 501, 502 often have a larger surface roughness than other portions. According to the above-described configuration, the welded ends 501, 502 are cut off in the cutting step, so that the finished cover member 4 does not include the ends 501, 502. Therefore, a cover member 4 with a smaller surface roughness can be manufactured.

[0084] (3g) Particularly in this embodiment, the cover member 4 is attached to the first end 21 of the first exhaust pipe 2 by inserting the main body 40 into the first opening 20 of the first exhaust pipe 2. For this reason, by reducing the surface roughness of the cover member 4, it is possible to make it easier to insert the main body 40 into the first opening 20 of the first exhaust pipe 2.

[0085] (3h) The cross section perpendicular to the axial direction of the cylinder 51 is substantially circular. With this configuration, the cover member 4 can be attached to the first end 21 of the first exhaust pipe 2 at any position in the circumferential direction.

[0086] In this embodiment, the cover member 4 corresponds to an example of a metal part.

[0087] [4. Other embodiments] Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

[0088] (4a) In the above embodiment, in the pipe-making process, the metal plate material 50 is bent into a U-shaped cross section and then bent into an O-shaped cross section. However, the method of bending the metal plate material 50 into an O-shaped cross section in the pipe-making process is not particularly limited. For example, the metal plate material 50 may be bent into a V-shaped cross section and then bent into an O-shaped cross section. Also, for example, the metal plate material 50 may be bent from a flat plate shape into an O-shaped cross section by processing in one stage.

[0089] (4b) In the above embodiment, the cylindrical body 51 was obtained by welding the butted ends 501, 502 of the metal plate material 50 in the pipe-making process. That is, the cylindrical body 51 was a metal plate material 50 in which the butted ends 501, 502 were welded. However, in the pipe-making process, the butted ends 501, 502 of the metal plate material 50 do not necessarily have to be welded. In other words, the cylindrical body 51 also includes a metal plate material 50 in which the butted ends 501, 502 are not welded. In further other words, the subsequent diameter expansion process may be performed in a state in which the butted ends 501, 502 of the metal plate material 50 are not welded. In this case, the cylindrical body 51 in which one end 511 is expanded in diameter in a state in which the butted ends 501, 502 are not welded corresponds to the expanded cylindrical body 52.

[0090] (4c) For example, in the pipe-making process, when the butted ends 501, 502 of the metal plate material 50 are not welded, the cutting process may or may not be performed. For example, when the butted ends 501, 502 are not welded, even if the cutting process is not performed, the portion of the expanded cylinder 52 bent in the pipe-making process is deformed so as to spread radially outward (i.e., so that the butted ends 501, 502 are separated from each other) due to springback caused by the residual stress resulting from the pipe-making process. As a result, a cover member 4 including a main body portion 40 and a flange portion 41 can be obtained. Even in such a configuration, the residual stress that can be expected is the residual stress resulting from the pipe-making process, so that the interval between the circumferential ends of the main body portion 40 can be suppressed from becoming small.

[0091] (4d) In the above embodiment, one cylinder 51 is obtained from one metal plate 50. However, multiple cylinders 51 may be obtained from one metal plate 50. For example, multiple cylinders 51 may be obtained by bending one metal plate 50 to form a cylinder having a length corresponding to the lengths of the multiple cylinders 51, and cutting the cylinder into multiple pieces in the axial direction.

[0092] (4e) In the above embodiment, the area including the welded ends 501, 502 of the expanded cylinder 52 is cut out in the cutting step. However, the area to be cut out in the expanded cylinder 52 is not particularly limited. For example, the area not including the welded ends 501, 502 of the expanded cylinder 52 may be cut out in the cutting step. In this case, the welded ends 501, 502 are included in the cover member 4, which is a finished product.

[0093] (4f) In the above embodiment, in the cutting step, a predetermined circumferential range of the expanded cylinder 52 is cut out by punching. Specifically, the pressing die 110 is displaced in the axial direction of the expanded cylinder 52, thereby cutting out a predetermined circumferential range of the expanded cylinder 52. However, when punching is used in the cutting step, the displacement direction of the pressing die is not particularly limited. For example, the pressing die may be displaced in the radial direction of the expanded cylinder 52, thereby cutting out a predetermined circumferential range of the expanded cylinder 52.

[0094] (4g) For example, the cutting step does not necessarily require punching. For example, the diameter-expanded cylinder 52 may be cut at two cutting lines L1, L2 by laser irradiation or the like, thereby cutting off a predetermined circumferential range of the diameter-expanded cylinder 52. When cutting the diameter-expanded cylinder 52 by laser irradiation or the like, the cutting direction of the diameter-expanded cylinder 52 may be either the axial direction or the radial direction.

[0095] (4h) In the above embodiment, the cross-sectional shape perpendicular to the axial direction of the cylindrical body 51 obtained in the pipe making process is substantially circular. However, the cross-sectional shape may be, for example, elliptical.

[0096] (4i) In the above embodiment, a configuration has been described in which the cover member 4 has higher heat resistance than the first end 21 of the first exhaust pipe 2, but the heat resistance of the cover member is not particularly limited. For example, the heat resistance of the cover member may be approximately the same as that of the first end 21.

[0097] (4j) In the above embodiment, a configuration in which the main body portion 40 covers the entire inner circumferential surface 28 of the protruding portion 23 has been exemplified. However, the range of the first inner circumferential surface 27 of the first exhaust pipe 2 that is covered by the main body portion is not particularly limited. For example, in addition to covering the entire inner circumferential surface 28 of the protruding portion 23, the main body portion may cover a portion of the first inner circumferential surface 27 of the first exhaust pipe 2 that is downstream of the inner circumferential surface 28 of the protruding portion 23, or may cover only a portion of the inner circumferential surface 28 of the protruding portion 23.

[0098] (4k) In the above embodiment, a configuration has been described in which the outer surface 42 of the main body 40 is in contact with the first inner circumferential surface 27 of the first exhaust pipe 2. However, for example, a small gap may be formed between the outer surface of the main body and the first inner circumferential surface 27 of the first exhaust pipe 2.

[0099] (4l) In a metal part having a main body and a flange, the ratio of the length of the main body in the circumferential direction to the circumferential length of a virtual cylinder that is a virtual cylinder including the main body is not particularly limited. For example, the ratio may be 90% or more as in the cover member 4 of the above embodiment, about 70%, about 50%, or less than 50%. In other words, the size of the central angle specified by the main body is not particularly limited.

[0100] (4m) In the above embodiment, the cover member 4 is provided in the exhaust flow path. However, a metal part having a main body and a flange such as the cover member 4 does not necessarily have to be provided in the exhaust flow path. For example, the metal part may be provided in a flow path of a high-temperature fluid other than exhaust gas.

[0101] (4n) 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. Also, 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. [Explanation of symbols]

[0102] Reference Signs List: 1...exhaust system unit, 2...first exhaust pipe, 3...second exhaust pipe, 4...cover member, 40...main body, 41...flange portion, 50...metal plate, 501, 502...both ends, 51...cylinder, 511...end, 52...cylinder after expansion, 70...first forming die, 72...second forming die, 80...first forming die, 82...second forming die, 90...holding die, 90a, 90b...split die, 93...insertion die, 100...supporting die, 110...pressing die, T...torch.

Claims

1. A method for manufacturing a metal component including a main body portion extending in an axial direction and having an arc-shaped cross section perpendicular to the axial direction, and a flange portion extending radially outward from one end of the main body portion in the axial direction, Bending a metal plate to obtain a cylindrical body; Bending one end of the cylindrical body radially outward to expand the diameter; Including, When the cylindrical body is obtained by bending the plate material so that both ends of the plate material are butted together and welding the butted ends, the method for manufacturing a metal part further includes cutting out a predetermined circumferential range of the cylindrical body with the end with an expanded diameter.

2. The method for manufacturing a metal part according to claim 1 , wherein the areas to be cut off in the cylindrical body include both of the welded ends.

3. The method for manufacturing a metal part according to claim 1 or 2, wherein the metal part is an exhaust system part provided in a flow path of exhaust gas from an internal combustion engine.

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