METHOD FOR MANUFACTURING METAL COMPONENT ARRANGED INFLOW PATH FOR HIGH TEMPERATURE FLUID

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No. 2023-173012 filed on Oct. 4, 2023 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a method for manufacturing a metal component provided in a flow channel for high-temperature fluid, specially to a method for manufacturing a metal component for use in an exhaust pipe to form a flow channel for vehicle exhaust gas.

For example, Japanese Unexamined Patent Application Publication No. 2022-181467 discloses a metal component comprising a body portion and a flange for use in an exhaust pipe forming a flow path for vehicle exhaust gas. The body portion extends along an axial direction and has a cross section including an arc-shaped area as perpendicular to the axial direction. The flange extends toward the radial outside from one end of the body portion in the axial direction.

SUMMARY

One of the examples of methods for manufacturing this kind of metal component is as follows. First, a circular hole is formed on a metal plate material. Next, a burring process is performed to make a circumference edge of the circular hole on the plate material raised from one of surfaces of the plate material. Then a specified area of the circular hole in the circumferential direction in the plate material in which the circumference edge of the circular hole is raised is cut out, and thus a metal component is obtained.

However, in a metal component manufactured by such a method, a residual stress that occurs due to the burring process may cause reduction in a space between both ends of the body portion in the circumferential direction.

In one aspect of the present disclosure, it is desirable to provide a technique, in a metal component comprising a body portion and a flange, for curbing reduction in a space between both ends of the body portion in a circumferential direction.

One aspect of the present disclosure is a method for manufacturing a metal component that comprises a body portion and a flange. The body portion extends in an axial direction and has a cross section with an arc shape that is perpendicular to the axial direction. The flange extends toward a radial outside from one end of the body portion in the axial direction. The method for manufacturing a metal component comprises: bending a metal-made plate material to obtain a cylindrical body; and bending one end of the cylindrical body toward the radial outside to enlarge its diameter.

The method for manufacturing a metal component further comprises, when the plate material is bent such that the both ends of the plate material face each other, and the both ends facing each other are welded together to obtain the cylindrical body, cutting out a specified area of the cylindrical body in the circumferential direction, the cylindrical body having an enlarged-diameter end. Such a configuration enables, in the metal component comprising the body portion and the flange, curbing of reduction in the space between the both ends of the body portion in the circumferential direction.

In one aspect of the present disclosure, the area of the cylindrical body that is cut out may include the welded both ends. Such a configuration enables manufacturing of a metal component with smaller surface roughness.

In one aspect of the present disclosure, the metal component may be an exhaust system component that is arranged in a flow path for exhaust gas from the internal combustion engine. Such a configuration enables, even if the metal component is exposed to high-temperature exhaust gas, curbing of reduction in the space between the both ends of the body portion in the circumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an exhaust system unit;

FIG. 2 is a partial enlarged view of FIG. 1;

FIG. 3 is a perspective view of a cover member;

FIG. 4 is a front view of the cover member;

FIG. 5 is a bottom view of the cover member;

FIG. 6A is a cross-sectional view to depict a state in a U-bending step in a pipe making process;

FIG. 6B is a cross-sectional view to depict a subsequent state of the state shown in FIG. 6A in the pipe making process;

FIG. 7A is a cross-sectional view showing a state in an O-bending step in the pipe making process;

FIG. 7B is a cross-sectional view to depict a subsequent state of the state shown in FIG. 7A in the pipe making process;

FIG. 8 is a perspective view to depict a welding step in the pipe making process;

FIG. 9A is a cross-sectional view to depict a state in a diameter-enlarging process;

FIG. 9B is a cross-sectional view to depict a subsequent state of the state shown in FIG. 9A in the diameter-enlarging process;

FIG. 9C is a cross-sectional view to depict a subsequent state of the state shown in FIG. 9B in the diameter-enlarging process;

FIG. 10 is a plane view to depict a cutting process;

FIG. 11A is a cross-sectional view taken along the line XIA-XIA in FIG. 10;

FIG. 11B is a cross-sectional view to depict a subsequent state of a state shown in FIG. 11A in the cutting process;

FIG. 12A is a cross-sectional view taken along the line XIIA-XIIA in FIG. 10; and

FIG. 12B is a cross-sectional view to depict a subsequent state of a state shown in FIG. 12A in the cutting process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. Configuration

An exhaust system unit 1 shown in FIG. 1 forms a flow path for exhaust gas from an internal combustion engine of a vehicle. The exhaust system unit 1 forms, in one example, a flow path for exhaust gas after passing through a supercharger or turbocharger. Hereinafter, the flow path for exhaust gas from an internal combustion engine of a vehicle will be referred to as an exhaust flow path. The exhaust system unit 1 comprises: a first exhaust pipe 2; a second exhaust pipe; and a cover member 4.

First Exhaust Pipe

The first exhaust pipe 2 is a member to form the exhaust flow path. The first exhaust pipe 2 is pipe-shaped. The first exhaust pipe 2 has heat resistance. The first exhaust pipe 2 is made of metal. For example, the first exhaust pipe 2 may be made from austenitic stainless steel. The first exhaust pipe 2 comprises: a first end 21; a first flange 22; a projection 23; and a groove 24.

The first end 21 is an upstream end of the first exhaust pipe 2 in a state where the first exhaust pipe 2 is arranged in an exhaust channel. The first end 21 has a cylindrical shape. The first end 21 forms one opening on an upstream side out of two openings of the first exhaust pipe 2. The opening formed by the first end 21 will be hereinafter referred to as a first opening 20. An opened surface of the first opening 20 is circular in shape.

An end surface 25 of the first end 21 extends in a plane in a direction perpendicular to a central axis A of the first end 21. The first exhaust pipe 2 is joined to the second exhaust pipe 3 at the first end 21. In a state where the first exhaust pipe 2 and the second exhaust pipe 3 are joined, the first opening 20 is continuous with a later-described second opening 30 of the second exhaust pipe 3.

The first flange 22 extends toward the radial outside continuously from the first end 21. The expression “radial outside” as used herein means a side opposite to the first opening 20 across the first end 21. The first flange 22 is used for joining with the second exhaust pipe 3. A fastening member 5 such as a V clamp is used to join the first exhaust pipe 2 and the second exhaust pipe 3.

As shown in FIG. 2, the projection 23 has a cylindrical shape and protrudes perpendicularly from a plane including the end surface 25 of the first end 21 (that is, in parallel with the central axis A of the first end 21). The projection 23 is formed along the edge of the first end 21 closer to the first opening 20. A top surface 26 is situated on a top of the projection 23 and extends in a plane in the direction perpendicular to the central axis A of the first end 21. The projection 23 has a lateral surface 28 that configures a part of a first inner-circumferential surface 27 of the first exhaust pipe 2.

The groove 24 is formed in a groove shape and provided at the end surface 25 of the first end 21. The groove 24 is grooved in a direction opposite to the direction in which the projection 23 protrudes such that a lateral surface thereof and a lateral surface of the projection 23 are continuous with each other. The groove 24 is contiguous with the projection 23 over the entire circumference thereof. The groove 24 is provided with, in one example, a seal 6 such as a ring-shaped gasket.

Second Exhaust Pipe

The second exhaust pipe 3 shown in FIG. 1 forms the exhaust flow path. The second exhaust pipe 3 is formed in a pipe shape. The second exhaust pipe 3 has heat resistance. The second exhaust pipe 3 may, in one example, have a heat resistance higher than that of the first exhaust pipe 2. The second exhaust pipe 3 is made of metal. In one example, the second exhaust pipe 3 may be made of austenitic stainless steel. The second exhaust pipe 3 comprises: a second end 31; a second flange 32; and a depression 33.

The second end 31 is a downstream end of the second exhaust pipe 3 in a state where the second exhaust pipe 3 is arranged in the exhaust channel. The second end 31 has a cylindrical shape. The second end 31 forms an opening on a downstream side out of two openings of the second exhaust pipe 3. The opening formed by the second end 31 will be hereinafter referred to as the second opening 30. An opened surface of the second opening 30 is circular in shape. A size of the opened surface of the second opening 30 is equal to a size of the opened surface of the above-described the first opening 20.

An end surface 34 of the second end 31 extends in a plane in a direction perpendicular to a central axis B of the second end 31. The second exhaust pipe 3 is joined to the first exhaust pipe 2 at the second end 31. In a state where the first exhaust pipe 2 and the second exhaust pipe 3 are joined, the central axis A of the first end 21 and the central axis B of the second end 31 are coaxial (the central axes coincide).

The second flange 32 extends toward the radial outside continuously from the second end 31. The expression “radial outside” as used herein means a side opposite to the second opening 30 across the second end 31. The second flange 32 is used for joining with the first exhaust pipe 2.

As shown in FIG. 2, the depression 33 is recessed perpendicularly from a plane including the end surface 34 of the second end 31 (in other words, in parallel with the central axis B of the second end 31). Specifically, the depression 33 is recessed parallel to the central axis B of the second end 31 such that a corner portion formed by the end surface 34 and an inner-circumferential surface of the depression 33 in the second end 31 forms substantially 90 degrees. The depression 33 comprises: a bottom surface 35; and a third inner-circumferential surface 37.

The bottom surface 35 extends in a plane in the direction perpendicular to the central axis B of the second end 31. The bottom surface 35 forms a stepped portion on an inner-circumferential surface of the second exhaust pipe 3. The inner-circumferential surface of the second exhaust pipe 3 is divided into a second inner-circumferential surface 36 and the third inner-circumferential surface 37 by the bottom surface 35. The third inner-circumferential surface 37 is located on a downstream side of the second inner-circumferential surface 36 relative to the bottom surface 35. The third inner-circumferential surface 37 has a diameter (inner diameter) larger than that of the second inner-circumferential surface 36.

The projection 23 is fitted into the depression 33 to join the first exhaust pipe 2 and the second exhaust pipe 3. The projection 23 and the depression 33 are used, by way of this fitting configuration, for positioning when connecting the first exhaust pipe 2 and the second exhaust pipe 3. However, in the joining process, the cover member 4 is interposed between the first exhaust pipe 2 and the second exhaust pipe 3, which will be detailed later.

Cover Member

The cover member 4 shown in FIGS. 3 to 5 is an exhaust system component arranged in the exhaust flow path. The expression of the cover member 4 being arranged in the exhaust flow path as used herein means that at least a part of the cover member 4 is arranged in the exhaust flow path, which will be later detailed. The cover member 4 is used to enhance the heat resistance of the exhaust pipe of a vehicle.

The cover member 4 is made of metal. In one example, the cover member 4 may be made of ferritic steel material. The cover member 4 has heat resistance. In one example, the cover member 4 has a heat resistance higher than that of the first exhaust pipe 2.

The cover member 4 comprises: a main portion 40; and a flange 41. The main portion 40 and the flange 41 are integrally configured.

The main portion 40 geometrically includes an axis (central axis) and has a cross section with a circular shape as perpendicular to the axial direction. The circle (circular-shape) herein means a circle congruent with the first inner-circumferential surface 27 of the first exhaust pipe 2. So far as the circle (circular shape) is congruent with the first inner-circumferential surface 27 of the first exhaust pipe 2, it may be a perfect circle, a substantially perfect circle, or an oval. In one example, the cross-sectional shape may be interpreted as a shape including a circular (arc-shaped) area.

An axial direction of the main portion 40 is, in other words, a direction along which the main portion 40 extends. In still other words, the axial direction of the main portion 40 is a direction along which the circular cross-sections of the main portion 40 are continuous. The axial direction of the main portion 40 corresponds to an axial direction of a central axis C of a virtual pipe, which is a virtual cylindrical body including the main portion 40. The axial direction of the main portion 40 may be interpreted to be parallel to the axial direction of the central axis C.

A radial direction and a circumferential direction of the main portion 40 respectively correspond to a radial direction and a circumferential direction of the virtual pipe. Hereinafter, an outer surface and an inner surface in the circumferential direction out of the surfaces of the main portion 40 will be referred to as an outer surface 42 and an inner surface 43, respectively. That is, the main portion 40 comprises: the outer surface 42; and the inner surface 43. A curvature of the outer surface 42 is almost equal to that of the first inner-circumferential surface 27 of the first exhaust pipe 2 (in other words, the lateral surface 28 of the projection 23).

Still in other words, an outer diameter of the outer surface 42 is almost equal to an inner diameter of the first inner-circumferential surface 27 of the first exhaust pipe 2. More specifically, the outer diameter and the inner diameter as mentioned are provided by taking into consideration a manufacturing tolerance and an assembling process (for example, by press fit) to allow assembling of the cover member 4 and the first exhaust pipe 2.

The flange 41 extends toward the radial outside from one end of the axial direction of the main portion 40. The flange 41 extends from an entire area of the end of the main portion 40 in the circumferential direction. The flange 41 extends toward the radial outside perpendicularly to the axial direction of the main portion 40. The flange 41 is substantially flat. That is, a first surface 44 and a second surface 45, which are both sides of the flange 41, are substantially flat. In other words, the first surface 44 of the flange 41 is contiguous from the outer surface 42 of the main portion 40 in the flange 41. The second surface 45 of the flange 41 is, in other words, contiguous from the inner surface 43 of the main portion 40 in the flange 41.

As shown in FIGS. 1 and 2, the cover member 4 is attached to the first exhaust pipe 2. In other words, the cover member 4 and the first exhaust pipe 2 are assembled. Specifically, the main portion 40 is inserted into the first opening 20 (for example, by press fit) such that the outer surface 42 of the main portion 40 and the lateral surface 28 of a projection 17 face (abut) each other, and the first surface 44 of the flange 41 and the top surface 26 of the projection 17 face (abut) each other.

The first exhaust pipe 2 with the cover member 4 is, as described above, joined to the second exhaust pipe 3 by using the fastening member 5. In a state where the first exhaust pipe 2 and the second exhaust pipe 3 are joined together, the cover member 4 is held by the first end 21 and the second end 31 (in other words, by the projection 23 and the depression 33).

Specifically, the flange 41 is held by the top surface 26 of the projection 23 and the bottom surface 35 of the depression 33. Specifically, the first surface 44 of the flange 41 is in contact with the top surface 26 of the projection 23, and the second surface 45 is in contact with the bottom surface 35 of the depression 33. The main portion 40 is arranged inside the first exhaust pipe 2, that is, in the exhaust flow path. The main portion 40 covers the lateral surface 28 of the projection 23 entirely. The outer surface 42 of the main portion 40 is in contact with the lateral surface 28 of the projection 23.

As described above, the cover member 4 covers an inner-circumferential surface 28 of the projection 23 that configures the first inner-circumferential surface 27, and thus the heat resistance of the first exhaust pipe 2 is enhanced.

2. Method for Manufacturing Cover Member

Next, descriptions will be given of the method for manufacturing the cover member 4. The method for manufacturing the cover member 4 at least comprises: a pipe making process; and a diameter-enlarging process. As described later, the pipe making process in the present embodiment comprises a welding step. As above, in a case where the pipe making process comprises the welding step, the method for manufacturing the cover member 4 further comprises a cutting process.

Pipe Making Process

In the pipe making process, a metal plate member 50 shown in FIG. 6A is bent to obtain a cylindrical body 51 (or a cylindrical body for obtaining the cylindrical body 51) shown in FIG. 9A.

The metal plate member 50 shown in FIG. 6A is made of metal. The metal plate member 50 before subjected to the pipe making process is planar. The metal plate member 50 before subjected to the pipe making process has a rectangular shape in a plan view of the metal plate member 50.

The cylindrical body 51 shown in FIG. 9A has a cylindrical shape. The cylindrical body 51 (the cylindrical body 51 after subjected to the pipe making process but before subjected to the diameter-enlarging process) obtained through the pipe making process extends linearly in the axial direction. In this embodiment, the cylindrical body 51 has the cross-section with a substantially perfect circle shape as perpendicular to the axial direction. The expression “substantially perfect circle” as used herein includes not only an exactly perfect circle but also a perfect circle that can be differentiated from an oval.

A diameter (outer diameter) of the cylindrical body 51 obtained via the pipe making process is equal to or greater than a length of the cylindrical body 51 in the axial direction. As is understood from the description of the pipe making process below, the length of the cylindrical body 51 in the axial direction corresponds to a length of a short side of the metal plate member 50 before subjected to the pipe making process, and a circumference (circumference length) of the cylindrical body 51 corresponds to the long side (the long side length) of the metal plate member 50 before subjected to the pipe making process.

The pipe making process comprises: a U-bending step; and an O-bending step. The pipe making process in the present embodiment further comprises a welding step.

(1) U-Bending Step

FIGS. 6A and 6B each shows a status in the U-bending step. In the U-bending step, the metal plate member 50 is bent by press molding so that its cross-section is substantially U-shaped. A first shaping die 70 and a second shaping die 72 made of metal are used in the U-bending step. The first shaping die 70 comprises a recess 71 having a substantially U-shaped cross-section. The second shaping die 72 comprises a projection 73 having a substantially U-shaped cross-section. As shown in FIG. 6B, the recess 71 and the projection 73 are formed in sizes that allow them to engage with each other.

As shown in FIG. 6A, in the metal plate member 50 before being processed, the first shaping die 70 and the second shaping die 72 are spaced so that the recess 71 and the projection 73 face each other. The first shaping die 70 is configured to be displaceable toward or away from the second shaping die 72.

In the U-bending step, as shown in FIG. 6A, the metal plate member 50 is firstly arranged between the first shaping die 70 and the second shaping die 72. Next, as shown in FIG. 6B, the first shaping die 70 is displaced to get close to the second shaping die 72. Then the recess 71 and the projection 73 are engaged with each other while having the metal plate member 50 interposed therebetween. In this way, the metal plate member 50 is bent to have a substantially U-shaped cross-section.

(2) O-Bending Step

Following the U-bending step, an O-bending step shown in FIGS. 7A and 7B is performed. In the O-bending step, the metal plate member 50 that has been bent to have a substantially U-shaped cross-section (that is, the metal plate member 50 after the U-bending step) is bent by press molding to have a substantially O-shaped cross-section (a substantially circle cross-section). A first shaping die 80 and a second shaping die 82 made of metal are used in the O-bending step.

The first shaping die 80 comprises a recess 81 having a substantially C-shaped cross-section. The second shaping die 82 comprises a recess 83 having a substantially C-shaped cross-section. As shown in FIG. 7B, when the first shaping die 80 and the second shaping die 82 come into contact, an inner surface of the recess 81 and an inner surface of the recess 83 together form a continuous surface. The continuous surface has a shape corresponding to an outer-circumferential surface of the cylindrical body 51.

As shown in FIG. 7A, in the metal plate member 50 before being processed, the first shaping die 80 and the second shaping die 82 are spaced so that the recess 81 and the recess 83 face each other. The first shaping die 80 is configured to be displaceable toward or away from the second shaping die 82.

In the O-bending step, as shown in FIG. 7A, the metal plate member 50 that has been bent to have a substantially U-shaped cross-section is firstly placed between the first shaping die 80 and the second shaping die 82. Specifically, the metal plate member 50 is placed between the first shaping die 80 and the second shaping die 82 in such a manner that a curved portion of the metal plate member 50 faces the recess 83, an opened portion of the metal plate member 50 faces the recess 81. Next, as shown in FIG. 7B, the first shaping die 80 is displaced to get close to the second shaping die 82. Specifically, the first shaping die 80 keeps being displaced until the surface on which the recess 81 of the first shaping die 80 is formed comes into contact with the surface on which the recess 83 of the second shaping die 82 is formed.

In this way, the metal plate member 50 is bent such that ends 501, 502 of the metal plate member 50 face each other. In other words, the metal plate member 50 is bent such that its cross-section is substantially O-shaped. The ends 501, 502 of the metal plate member 50 configure two sides of the metal plate member 50 that face each other. In this embodiment, the ends 501, 502 of the metal plate member 50 are both ends of the metal plate member 50 in the longitudinal direction.

(3) Welding Step

In this embodiment, the O-bending step is followed by a welding step shown in FIG. 8. In the welding step, the ends 501, 502 facing each other in the metal plate member 50 are welded together. A torch T is illustrated in FIG. 8 as one example of a welder. As shown in FIG. 8, the ends 501, 502 facing each other in the metal plate member 50 are welded by using, for example, a torch T. The ends 501, 502 welded together in the metal plate member 50 are also referred to as, for example, a weld line, or a bead portion. Via the welding step, the cylindrical body 51 shown in FIG. 9A is obtained. Specifically, the cylindrical body 51 is the metal plate member 50 in which the ends 501, 502 facing each other are welded together.

Diameter-Enlarging Process

The diameter-enlarging process shown in FIGS. 9A to 9C is performed after the pipe making process. In the diameter-enlarging process, one end 511 of the cylindrical body 51, which is obtained in the pipe making process, is bent toward the radial outside via a flaring process to enlarge its diameter. To be more specific, what is meant by enlarging the diameter of the end 511 is to enlarge a diameter of a circle defined by an edge of the end 511. In the diameter-enlarging process, a holding die 90 and an insertion die 93, which are metal made, are used.

As shown in FIG. 9A, the holding die 90 comprises: a holder 91; and a first flange 92. The holder 91 has a cylindrical shape. The first flange 92 extends toward the radial outside from one end of the holder 91. The first flange 92 extends from an entire circumference of the end of the holder 91. The first flange 92 extends perpendicularly to a central axis of the holder 91. The first flange 92 is substantially flat.

In this embodiment, in one example, the holding die 90 consists of two split dies 90a, 90b that are divided by a surface including the central axis of the holder 91. Specifically, the holder 91 and the first flange 92 are configured by the two split dies 90a, 90b. The two split dies 90a, 90b are configured to be displaceable in the radial direction of the holder 91 so as to get close to or away from each other.

This makes it possible for the two split dies 90a, 90b, in a case where the cylindrical body 51 is interposed between the two split dies 90a, 90b, to be displaced to get close to each other, thereby holding the cylindrical body 51. Specifically, it is possible for a portion configuring the holder 91 of each of the two split dies 90a, 90b to hold the cylindrical body 51. That is, the holder 91 is configured to hold the cylindrical body 51. A curvature of an inner-circumferential surface of the holder 91 (an inner diameter of the holder 91) is almost equal to a curvature of the outer-circumferential surface of the cylindrical body 51 (an outer diameter of the cylindrical body 51).

The insertion die 93 comprises: an insertion portion 94; a second flange 95; and a stopper 96.

The insertion portion 94 has a cylindrical shape. Each of axial ends of the insertion portion 94 are hereinafter referred to as a first end 941 and a second end 942, respectively. The insertion portion 94 specifically has a circular cylindrical shape, and corners of the first end 941 are chamfered. A curvature of an outer-circumferential surface of the insertion portion 94 (outer diameter of the insertion portion 94) is almost equal to a curvature of an inner-circumferential surface of the cylindrical body 51 (inner diameter of the cylindrical body 51).

The second flange 95 extends toward the radial outside from the second end 942 of the insertion portion 94. The second flange 95 extends from an entire circumference of the second end 942. The second flange 95 extends perpendicularly to a central axis of the insertion portion 94. The second flange 95 is substantially flat.

The stopper 96 has a cylindrical shape and is provided on a surface of two surfaces of the second flange 95, the surface being located on the first end 941 side of the insertion portion 94. The stopper 96 surrounds the insertion portion 94. A height of the stopper 96 from the surface of the second flange 95 is determined based on a thickness of the metal plate member 50.

The holding die 90 and the insertion die 93 are spaced such that the central axis of the holder 91 and the central axis of the insertion portion 94 coincide. The holding die 90 is arranged such that a side of the holder 91 on which the first flange 92 is provided faces the insertion die 93 side. The insertion die 93 is arranged such that the first end 941 side of the insertion portion 94 faces the holding die 90 side. In a state where the holding die 90 and the insertion die 93 are spaced, the first flange 92 and the second flange 95 face each other.

The insertion die 93 is displaceable toward or away from the holding die 90. The insertion die 93 is displaceable to get close to the holding die 90 until the stopper 96 is in contact with the first flange 92. Specifically, the stopper 96 is provided to define a distance limit between the holding die 90 and the insertion die 93. The distance limit between the holding die 90 and the insertion die 93 is equivalent to the height of the stopper 96 from the surface of the second flange 95.

In the diameter-enlarging process, the cylindrical body 51 obtained via the pipe making process is firstly placed between the two split dies 90a, 90b. Specifically, the cylindrical body 51 is arranged between the two split dies 90a, 90b such that the end 511, which is one of the ends thereof, protrudes outside beyond a portion forming the first flange 92 in each of the two split dies 90a, 90b.

Next, the two split dies 90a, 90b are displaced to get close to each other. In this way, as shown in FIG. 9A, the cylindrical body 51 is held by the two split dies 90a, 90b. Specifically, the cylindrical body 51 is held by the holder 91. In the meantime, one of the end 511 of the cylindrical body 51 protrudes outside beyond the first flange 92 of the holding die 90 (that is, the insertion die 93 side).

Next, as shown in FIG. 9B, the insertion die 93 is displaced to get close to the holding die 90. The insertion die 93 keeps being displaced until the stopper 96 comes into contact with the first flange 92 as shown in FIG. 9C.

When the insertion die 93 is displaced to get close to the holding die 90, as shown in FIG. 9B, the insertion portion 94 is inserted inside the cylindrical body 51 from the end 511. As the insertion portion 94 moves forward while sliding on an inner surface of the cylindrical body 51 along with the displacement of the insertion die 93, an end surface of the end 511 of the cylindrical body 51 comes into contact with the second flange 95. As the insertion portion 94 moves further forward while sliding on the inner surface of the cylindrical body 51, as shown in FIG. 9C, the end 511 of the cylindrical body 51 is bent toward the radial outside along the surface of the second flange 95, and thus the diameter is enlarged.

When the stopper 96 is in contact with the first flange 92 (specifically, when the insertion die 93 finishes being displaced), the end 511 of the cylindrical body 51 is interposed between the first flange 92 and the second flange 95. In the meantime, the end 511 of the cylindrical body 51 is bent toward the radial outside to a designed angle so that its diameter is enlarged. In this embodiment, the designed angle is 90 degrees. Hereinafter, the cylindrical body 51 in which the diameter of the end 511 is enlarged will be referred to as a cylindrical body 52 with enlarged-diameter end.

Cutting Process

In this embodiment, the diameter-enlarging process is followed by a cutting process shown in FIGS. 10 to 12B. In the cutting process, the die-cutting step is performed to cut out a specified area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction. A support die 100 and a press die 110, which are metal made, are used in the cutting process. FIGS. 12A and 12B show the cross sections of the support die 100 and the press die 110, in which hatchings are not provided to facilitate understanding of the drawings.

The support die 100 supports the cylindrical body 52 with enlarged-diameter end. The support die 100 comprises: a recess 101; and a punched hole 102.

As shown in FIGS. 10 and 11A, the recess 101 is a circular depression as viewed in plane. The recess 101 has a size that corresponds to an outer shape of the cylindrical body 52 with enlarged-diameter end as viewed in the axial direction thereof. An inner diameter of the recess 101 is slightly greater than an outer diameter of the end 511, which is enlarged, of the cylindrical body 52 with enlarged-diameter end (that is, the diameter of the circle defined by the edge of the end 511). A bottom surface of the recess 101 is planar. The bottom surface of the recess 101 comprises a placement surface for placing the cylindrical body 52 with enlarged-diameter end thereon.

The punched hole 102 is provided in the support die 100. As shown in FIG. 10, in a case where the cylindrical body 52 with enlarged-diameter end is placed inside the recess 101, the punched hole 102 is located at an area overlapping a part of the cylindrical body 52 with enlarged-diameter end in the circumferential direction. The punched hole 102 has a size that allows a later-described projection 111 of the press die 110 to be inserted thereinto. In this embodiment, an opened surface of the punched hole 102 is rectangular in shape. Moreover, the opened surface of the punched hole 102 in this embodiment is larger than the welded ends 501, 502 of the cylindrical body 52 with enlarged-diameter end as viewed along the axial direction.

The press die 110 partially presses the cylindrical body 52 with enlarged-diameter end arranged inside the recess 101. The press die 110 comprises: a not-shown body portion; and the projection 111. The projection 111 protrudes from the body portion. The direction along which the projection 111 protrudes is a direction from a front side to a back side of a page space in FIG. 10, as well as a direction from an upper side to a lower side of FIGS. 11A to 12B. In this embodiment, the cross section of the projection 111 perpendicular to the protruding direction thereof has a rectangular shape. The cross section of the projection 111 perpendicular to the protruding direction thereof is configured to have a fixed size. The cross section of the projection 111 perpendicular to the protruding direction thereof is formed in a size slightly smaller than the opened surface of the punched hole 102. The projection 111 is depicted in FIG. 10 on a scale smaller than the real in relation to the punched hole 102 for convenience sake.

As shown in FIGS. 11A and 12A, the support die 100 and the press die 110 are spaced out from each other. Specifically, the support die 100 is arranged with the recess 101 facing upward. The press die 110 is arranged above the support die 100 so that the projection 111 faces the punched hole 102. The press die 110 is displaceable toward or away from the support die 100. When the press die 110 is displaced to get close to the support die 100, the projection 111 is inserted into the punched hole 102.

In the cutting process, as shown in FIGS. 11A and 12A, the cylindrical body 52 with enlarged-diameter end is firstly placed inside the recess 101 of the support die 100. Specifically, the cylindrical body 52 with enlarged-diameter end is placed inside the recess 101 so that the end 511 with enlarged diameter comes into contact with the bottom surface of the recess 101. Moreover, as shown in FIG. 10, the cylindrical body 52 with enlarged-diameter end is placed inside the recess 101 such that the welded ends 501, 502 is included in the punched hole 102 as viewed in plane.

Subsequently, as shown in FIGS. 11B and 12B, the press die 110 is displaced to get close to the support die 100. The press die 110 keeps being displaced until: the projection 111 is inserted into the punched hole 102; and an end surface of the projection 111 reaches a position lower than the bottom surface of the recess 101. The press die 110 is displaced in a direction parallel to the axial direction of the cylindrical body 52 with enlarged-diameter end that is arranged inside the recess 101.

As the press die 110 is displaced to get close to the support die 100, the projection 111 comes into contact with an end surface on a side opposite to the enlarged end 511 side in the cylindrical body 52 with enlarged-diameter end. Along with the displacement of the press die 110, the projection 111 presses an area of the cylindrical body 52 with enlarged-diameter end that is included by the punched hole 102 as viewed in plane. The area of the cylindrical body 52 with enlarged-diameter end included by the punched hole 102 as viewed in plane is a partial area of the cylindrical body 52 with enlarged-diameter end along the circumferential direction. In the present embodiment, such area includes the welded ends 501, 502 of the cylindrical body 52 with enlarged-diameter end.

As the projection 111 moves forward while pressing the cylindrical body 52 with enlarged-diameter end, the projection 111 and a portion forming the punched hole 102 in the recess 101 apply a shear force to the cylindrical body 52 with enlarged-diameter end. As shown in FIGS. 11B and 12B, the projection 111 moves forward until the end surface of the projection 111 reaches the position lower than the bottom surface of the recess 101, whereby the area of the cylindrical body 52 with enlarged-diameter end pressed by the projection 111 is punched out. In other words, a partial area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction (in this embodiment, the area including the welded ends 501, 502 in the cylindrical body 52 with enlarged-diameter end) is cut out.

The cylindrical body 52 with enlarged-diameter end is cut along two cutting lines L1, L2 shown in FIG. 12A, whereby an area of the cylindrical body 52 with enlarged-diameter end enclosed by the two cutting lines L1, L2 is removed. The two cutting lines L1, L2 are virtual lines extending from one edge to the other edge of the cylindrical body 52 with enlarged-diameter end in the axial direction. Positions where the two cutting lines L1, L2 are located correspond to the surface that receives the shear force in the cylindrical body 52 with enlarged-diameter end. In this embodiment, the welded ends 501, 502 are located between the two cutting lines L1, L2. Thus, as described above, the area including the welded ends 501, 502 in the cylindrical body 52 with enlarged-diameter end is cut out.

In this way, the partial area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction is cut out, whereby the cover member 4 shown in FIGS. 3 to 5 is obtained.

3. Effects

The embodiment detailed above can achieve the following effects.

(3a) The cover member 4 comprises the main portion 40 and the flange 41. The method for manufacturing the cover member 4 is, for example, as follows. First, a circular hole is formed on a metal plate material, the circular hole being an opening of the cover member 4. Next, a burring process is performed to make the circumference edge of the circular hole on the plate material raised from one of surfaces of the plate material. Then the specified area of the circular hole in the circumferential direction in the plate material in which the circumference edge of the circular hole is raised is cut out, and thus the cover member 4 is obtained.

However, in the cover member 4 manufactured using this method, there is a risk that residual stress can occur due to the burring process. If springback is caused by the residual stress, the main portion 40 corresponding to the area that is raised through the burring process is deformed so as to fall inward in the radial direction. Consequently, the space between both ends of the main portion 40 in the circumferential direction is small.

In contrast, the method for manufacturing the cover member 4 in this embodiment comprises the pipe making process, the diameter-enlarging process and, furthermore, the cutting process. In such a configuration, even if residual stress occurs in the cover member 4, the possible residual stress is resulted from the pipe making process. Thus, even if springback occurs, the main portion 40 and the flange 41 that correspond to the bent portion in the pipe making process are deformed so as to expand toward the radial outside. This limits the space between the both ends of the main portion 40 in the circumferential direction to be small.

(3b) Furthermore, in the method for manufacturing the cover member 4 described in (3a) above, scraps are produced when forming the circular hole on the metal plate material and when cutting out the specified area of the circular hole in the circumferential direction from the plate material in which the circumference edge of the circular hole is raised. In contrast, the method for manufacturing the cover member 4 in this embodiment does not include a step for forming the circular hole on the metal plate member 50. This reduces an amount of scraps produced during the process. In other words, this reduces the metal plate member 50 to be used. This results in an improvement of a yield rate.

(3c) The cover member 4 is arranged in the exhaust flow path. In such a configuration, when residual stress occurs in the cover member 4, the cover member 4 is exposed to high-temperature exhaust gas and thus the residual stress is easily released. For this reason, when the cover member 4 is manufactured by using the method described in (3a) above, there is more likely a problem that the space between the both ends of the main portion 40 in the circumferential direction is sometimes small. Therefore, it is more advantageous for the aforementioned configuration to employ the method for manufacturing the cover member 4 in this embodiment.

(3d) Especially in this embodiment, in the cover member 4, the main portion 40 is inserted into the first opening 20 of the first exhaust pipe 2, thereby being attached to the first end 21 of the first exhaust pipe 2. In such a configuration, if a space between both ends of the main portion 40 in the circumferential direction is small, a clearance between the cover member 4 and the first exhaust pipe 2 tends to be large. This makes it difficult for the cover member 4 to be held in the first exhaust pipe 2. Besides, the area of the first exhaust pipe 2 covered by the cover member 4 can be easily reduced.

Therefore, it is further advantageous to employ the method for manufacturing the cover member 4 in this embodiment to keep the space between the both ends of the main portion 40 in the circumferential direction from being small. This facilitates retention of the cover member 4 in the first exhaust pipe 2. This also makes it unlikely to decrease in an area of the first exhaust pipe 2 that is covered by the cover member 4. Specifically, such a configuration makes it unlikely for the high-temperature exhaust gas to strike the first inner-circumferential surface 27 of the first exhaust pipe 2.

(3e) In the pipe making process in this embodiment, the metal plate member 50 is bent such that the ends 501, 502 face each other. Then the ends 501, 502 facing each other are welded, and thus the cylindrical body 51 is obtained.

In such configuration, when the end 511 of the cylindrical body 51 is bent to enlarge the diameter in the subsequent diameter-enlarging process, a relative position of the ends 501, 502 is unlikely deviated. As a result, the cylindrical body 51 in which the diameter of the end 511 is enlarged, that is, the cylindrical body 52 with enlarged-diameter end is formed more accurately in the diameter-enlarging process.

(3f) In the cutting process, the welded ends 501, 502 in the cylindrical body 52 with enlarged-diameter end are cut out. Specifically, the portion cut out from the cylindrical body 52 with enlarged-diameter end includes the welded ends 501, 502.

In the cylindrical body 52 with enlarged-diameter end, the welded ends 501, 502 tend to have a larger surface roughness than any other portions. In the configuration as mentioned, the welded ends 501, 502 are cut out in the cutting process, and thus the cover member 4 as a finished product does not include the ends 501, 502. This makes it possible to produce a cover member 4 with a smaller surface roughness.

(3g) Especially in this embodiment, in the cover member 4, the main portion 40 is inserted into the first opening 20 of the first exhaust pipe 2 and thereby being attached to the first end 21 of the first exhaust pipe 2. For this reason, the cover member 4 is made to have a small surface roughness of small so as to facilitate insertion of the main portion 40 into the first opening 20 of the first exhaust pipe 2.

(3h) The cylindrical body 51 has a cross section with a substantially perfect circle as perpendicular to the axial direction. Such configuration enables an attachment of the cover member 4 to any position in the circumferential direction of the first end 21 of the first exhaust pipe 2.

In this embodiment, the cover member 4 corresponds to one example of the metal component.

4. Other Embodiments

One embodiment of the present disclosure is as explained above; nevertheless, the present disclosure should not be limited to the aforementioned embodiment and can be modified in various forms.

(4a) In the aforementioned embodiment, in the pipe making process, the metal plate member 50 is bent to have a substantially U-shaped cross-section and then bent to have a substantially O-shaped cross-section. However, in the pipe making process, the method for bending the metal plate member 50 to have a substantially O-shaped cross-section is not especially limited to this. For example, the metal plate member 50 may be bent to have a substantially O-shaped cross-section after being bent to have a substantially V-shaped cross-section. For example, the metal plate member 50 may be bent from flat to substantially O-shaped in cross-section by one-step processing.

(4b) In the aforementioned embodiment, in the pipe making process, the ends 501, 502 facing each other in the metal plate member 50 are welded together, and thus the cylindrical body 51 is obtained. Specifically, the cylindrical body 51 is the metal plate member 50 in which the ends 501, 502 facing each other are welded together. However, in the pipe making process, the ends 501, 502 facing each other in the metal plate member 50 are not necessarily welded together. In other words, the cylindrical body 51 also includes the metal plate member 50 in which the ends 501, 502 facing each other are not welded. In yet other words, the consequent diameter-enlarging process may be performed to the metal plate member 50 in which the ends 501, 502 facing each other are not welded. In such a case, the cylindrical body 51 in which the diameter of the end 511, which is one of the ends, is enlarged while the ends 501, 502 facing each other are not welded may correspond to the cylindrical body 52 with enlarged-diameter end.

(4c) For example, in the pipe making process, in a case where the ends 501, 502 facing each other in the metal plate member 50 are not welded, it is optional whether or not to perform the cutting process. For example, in a case where the ends 501, 502 facing each other are not welded, although the cutting process is not performed, springback is caused by the residual stress resulted from the pipe making process. Because of the springback, the bent portion of the cylindrical body 52 with enlarged-diameter end through the pipe making process is deformed so as to expand toward the radial outside (in other words, such that the ends 501, 502 facing each other are spaced apart). In this way, the cover member 4 comprising the main portion 40 and the flange 41 is obtained. Even in such a case, the possible residual stress is resulted from the pipe making process, and thus it is possible to keep the space between the both ends of the main portion 40 in the circumferential direction from being small.

(4d) In the aforementioned embodiment, a single cylindrical body 51 is obtained from a single metal plate member 50. However, two or more cylindrical bodies 51 may be obtained from a single metal plate member 50. For example, two or more cylindrical bodies 51 may be obtained by bending a single metal plate member 50 to form a cylindrical body with a length corresponding to lengths of two or more cylindrical bodies 51, and then cutting the cylindrical body in the axial direction into two or more pieces.

(4e) In the aforementioned embodiment, the area including the welded ends 501, 502 in the cylindrical body 52 with enlarged-diameter end is cut out in the cutting process. However, the area of the cylindrical body 52 with enlarged-diameter end that is cut out is not especially limited. For example, an area not including the welded ends 501, 502 in the cylindrical body 52 with enlarged-diameter end may be cut out in the cutting process. In such a case, the cover member 4 as a finished product includes the welded ends 501, 502.

(4f) In the aforementioned embodiment, in the cutting process, the specified area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction is cut out through the die-cutting step. Specifically, the press die 110 is displaced in the axial direction of the cylindrical body 52 with enlarged-diameter end, whereby the specified area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction is cut out. However, when the die-cutting step is employed in the cutting process, a displacement direction of the press die is not especially limited. For example, the press die may be displaced in the radial direction of the cylindrical body 52 with enlarged-diameter end so that the specified area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction is cut out.

(4g) Moreover, for example, the die-cutting step is not necessarily employed in the cutting process. For example, the cylindrical body 52 with enlarged-diameter end may be cut along the two cutting lines L1, L2 by laser irradiation or the like, whereby the specified area of the cylindrical body 52 with enlarged-diameter end in the circumferential direction is cut out. When the cylindrical body 52 with enlarged-diameter end is cut by laser irradiation or the like, the cylindrical body 52 with enlarged-diameter end may be cut along the axial direction or along the radial direction.

(4h) In the aforementioned embodiment, the cylindrical body 51 obtained through the pipe making process has a cross section with a substantially perfect circle as perpendicular to the axial direction of the cylindrical body 51. However, the shape of the cross section may be, for example, an oval.

(4i) Although the cover member 4 has the heat resistance higher than that of the first end 21 of the first exhaust pipe 2 in the aforementioned embodiment, the heat resistance of the cover member 4 is not especially limited. For example, the heat resistance of the cover member 4 may be about the same as that of the first end 21.

(4j) In the aforementioned embodiment, the main portion 40 entirely covers the lateral surface 28 of the projection 23. However, the area of the first inner-circumferential surface 27 of the first exhaust pipe 2 covered by the body portion 40 is not especially limited. For example, in addition to the entire of the lateral surface 28 of the projection 23, the body portion 40 may cover a part of the first inner-circumferential surface 27 of the first exhaust pipe 2 that is located on the downstream side relative to the lateral surface 28 of the projection 23, or may only partially cover the lateral surface 28 of the projection 23.

(4k) In the aforementioned embodiment, the outer surface 42 of the main portion 40 is in contact with the first inner-circumferential surface 27 of the first exhaust pipe 2. However, there may be a slight clearance left between the outer surface 42 of the body portion 40 and the first inner-circumferential surface 27 of the first exhaust pipe 2.

(4l) In a metal component comprising a body portion and a flange, a ratio of the length of the body portion in the circumferential direction to the circumference length of the virtual pipe, which is a virtual cylindrical body including the body portion, is not especially limited. For example, the ratio may be 90% or more as in the case of the cover member 4 in the aforementioned embodiment, about 70%, about 50%, or less than 50%. That is, a magnitude of a center angle specified by the body portion is not especially limited.

(4m) In the aforementioned embodiment, the cover member 4 is arranged in the exhaust flow path. However, a metal component like the cover member 4 that comprises the body portion and the flange is not necessarily arranged in the exhaust flow path. For example, such a metal component may be arranged in a flow path for high temperature fluid other than exhaust gas.

(4n) Functions of one component in the aforementioned embodiments may be achieved by two or more components, and functions of two or more components may be achieved by one component. Some of the components of the above embodiments may be omitted. At least part of the configurations of the aforementioned embodiments may be added to or replaced with other configurations of the aforementioned embodiments.

METHOD FOR MANUFACTURING METAL COMPONENT ARRANGED INFLOW PATH FOR HIGH TEMPERATURE FLUID

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