JP7568600B2 - Manufacturing method for exhaust system parts - Google Patents

Description

This disclosure relates to a method for manufacturing exhaust system components.

The exhaust system components that define the exhaust gas flow path are made up of multiple cylinders (i.e., pipes) that are connected by welding. Among the connected cylinders are parts with thick sections, such as joints (see Patent Document 1).

JP 2015-161308 A

When connecting the tubes that make up exhaust system components by welding, any temperature variations in the objects being welded will cause stress. Such stress may cause cracks or other damage to the exhaust system components.

Temperature variation during welding can be suppressed by heating the parts before welding. However, it is difficult to reduce temperature variation in thick parts such as the joints mentioned above, as the temperature does not increase easily when heated.

One aspect of the present disclosure aims to provide a manufacturing method for exhaust system components that can suppress breakage during welding of exhaust system components having thick portions.

One aspect of the present disclosure is a method for manufacturing an exhaust system component that constitutes an exhaust gas flow path. The method for manufacturing an exhaust system component includes a step of heating the first cylindrical body and the second cylindrical body while the first cylindrical body and the second cylindrical body are connected, and a step of welding the first cylindrical body and the second cylindrical body after the heating step. In the heating step, a thick portion of the first cylindrical body that has a larger radial thickness than other portions is heated preferentially over the other portions.

With this configuration, the first and second cylindrical bodies are welded together while reducing the temperature difference between the thick portion and other parts, which reduces the generation of stress in the first and second cylindrical bodies. As a result, damage to exhaust system components having thick portions during welding can be reduced.

In one aspect of the present disclosure, the first cylindrical body may be mainly made of ferritic stainless steel. With this configuration, the thermal expansion coefficient of the first cylindrical body is reduced, and the oxidation characteristics during cycles in which high-temperature conditions are repeated can be improved.

In one aspect of the present disclosure, the first cylinder may have a cylindrical main body and a flange having an outer diameter larger than that of the main body and provided continuously with a second end of the main body opposite the first end welded to the second cylinder. The flange may form a thick portion. With this configuration, it is possible to suppress the generation of stress in the flange used for fastening and damage to the joint caused by this stress.

In one aspect of the present disclosure, the second cylindrical body may be a catalyst case that stores a catalyst. With this configuration, damage to the catalyst case, which is made of a material with a small thermal expansion coefficient, can be suppressed.

In one aspect of the present disclosure, the heating process may use a heat source that blows hot air into the inside of the first and second cylinders, and a guide device that guides the hot air to the thick portion. With this configuration, it is relatively easy to preferentially heat the thick portion.

In one aspect of the present disclosure, in the heating process, hot air may be guided to the thick portion by colliding it with a guide tool. With this configuration, the position for guiding the hot air can be changed and adjusted relatively easily, thereby improving the production efficiency of exhaust system parts.

FIG. 1 is a schematic diagram of an exhaust system component according to an embodiment. FIG. 2 is a schematic partial cross-sectional view showing an example of a fastening state of the exhaust system components of FIG. FIG. 3 is a flow diagram of a method for manufacturing an exhaust system part according to an embodiment. FIG. 4 is a schematic diagram showing one step in the method of manufacturing the exhaust system part of FIG. FIG. 5 is a schematic diagram showing one step in the method of manufacturing the exhaust system part of FIG.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[1. First embodiment]
[1-1. Configuration]
<Exhaust system parts>
The exhaust system part 10 shown in Fig. 1 is provided in an exhaust gas flow path of an internal combustion engine. Specifically, the exhaust system part 10 constitutes a part of an exhaust gas purification device that purifies exhaust gas. The exhaust system part 10 includes a first cylindrical body 20 and a second cylindrical body 30.

(First cylindrical body)
The first cylindrical body 20 is a joint that is fastened to another pipe P by a fastening part such as a V-band clamp V shown in FIG.

The first cylindrical body 20 is mainly made of ferritic stainless steel. Specifically, the first cylindrical body 20 is formed by casting the ferritic stainless steel. As shown in FIG. 1, the first cylindrical body 20 has a main body portion 21 and a flange portion 22.

The main body 21 is a cylindrical member through which exhaust gas flows. The thickness of the main body 21 is substantially constant in the axial direction. The first end 21A of the main body 21 is welded to the second cylinder 30 at the welded portion W. A flange 22 is provided on the axially outer side of the second end 21B of the main body 21, which is opposite to the first end 21A.

The flange 22 is a ring-shaped portion with an outer diameter larger than that of the main body 21. The flange 22 protrudes radially outward from the second end 21B of the main body 21. The flange 22 constitutes a thick portion that is thicker in the radial direction than other portions of the first cylindrical body 20 (i.e., portions other than the flange 22).

In other words, the end of the first cylinder 20 opposite the second cylinder 30 is a thick portion that is thicker in the radial direction than other portions of the first cylinder 20. As shown in FIG. 2, the flange 22 has a groove 22A for arranging a gasket.

(Second cylindrical body)
1 is a catalyst case that stores a catalyst. The catalyst stored in the second cylindrical body 30 reforms or captures environmental pollutants in the exhaust gas by contacting the exhaust gas, thereby purifying the exhaust gas.

The second cylindrical body 30, like the first cylindrical body 20, is mainly made of ferritic stainless steel. Specifically, the second cylindrical body 30 is formed from a ferritic stainless steel plate. By making both the first cylindrical body 20 and the second cylindrical body 30 out of ferritic stainless steel, durability can be improved by welding the same material. In addition, ferritic stainless steel has a smaller thermal expansion coefficient (i.e., it is less susceptible to thermal expansion) than austenitic stainless steel, and has excellent oxidation properties at high temperatures (i.e., it is less susceptible to oxidation).

The thickness of the second cylindrical body 30 is substantially constant in the axial direction. One end of the second cylindrical body 30 is inserted into the first cylindrical body 20 and is connected to the first cylindrical body 20 by welding.

<Manufacturing method for exhaust system parts>
The method for manufacturing an exhaust system component shown in FIG. 3 includes a placement step S10, a heating step S20, a moving step S30, and a welding step S40.

(Placement process)
In the arrangement step S10, the unwelded first cylindrical body 20 and second cylindrical body 30 are arranged in a heating device 100 as shown in FIG.

The heating device 100 has a heat source 110, an air guide passage 120, and a guide device 130. The heat source 110 generates hot air H, for example, using a heating wire and a blower, and sends the hot air through the air guide passage 120 into the inside of the first cylinder 20 and the second cylinder 30.

The guide tool 130 guides the hot air H to the thick part of the first cylinder 20. The guide tool 130 has a collision part 131, a shaft part 132, and a support material 133.

The collision part 131 is a cone-shaped member whose diameter expands from the heat source 110 toward the inside of the first cylindrical body 20. The maximum outer diameter of the collision part 131 is smaller than the inner diameter of the first cylindrical body 20. A part of the collision part 131 is disposed inside the air guide passage 120.

The shaft portion 132 is attached to the center of the collision portion 131. The shaft portion 132 extends in the axial direction of the air guide passage 120. The support material 133 supports the shaft portion 132. The support material 133 is attached inside the air guide passage 120. The position of the collision portion 131 can be adjusted by adjusting the positions of the shaft portion 132 and the support material 133.

The internal spaces of the collision portion 131 and the shaft portion 132 may be connected to the inside of the air guide passage 120. In other words, hot air H may be supplied to the inside of each of the collision portion 131 and the shaft portion 132.

In the placement step S10, the guide tool 130 is inserted into the first cylindrical body 20 so that the collision portion 131 of the guide tool 130 overlaps with the thick portion (i.e., the flange portion 22) in the radial direction of the first cylindrical body 20. Specifically, the collision portion 131 is placed so that the side surface of the collision portion 131 faces the thick portion in the radial direction of the first cylindrical body 20.

In addition, in the placement step S10, the first cylinder 20 is placed so that the second end 21B of the first cylinder 20 is connected to the air guide passage 120. The second cylinder 30 is placed so that it is connected to the first end 21A of the first cylinder 20.

(Heating process)
In the heating step S20, the first cylindrical body 20 and the second cylindrical body 30 are heated from the inside using the heating device 100 while the first cylindrical body 20 and the second cylindrical body 30 are connected to each other.

The hot air H supplied from the air guide passage 120 into the first cylinder 20 passes through the inside of the first cylinder 20 and the second cylinder 30, and is discharged to the outside from the second cylinder 30. In addition, in the heating step S20, the hot air H is guided to the thick part of the first cylinder 20 by colliding with the collision part 131 of the guide tool 130.

In other words, by changing the course of the hot air H so that it follows the side of the collision portion 131, the hot air H is caused to collide with the inner peripheral surface of the thick portion. As a result, the first cylinder 20 is heated mainly at the thick portion, and the flange portion 22, which is a thick portion, is heated preferentially over the main body portion 21, which is another portion. In other words, the amount of heat received by the thick portion is greater than the amount of heat received by other portions of the first cylinder 20 and the second cylinder 30.

(Transfer process)
In the moving step S30, as shown in FIG. 5, after the heating step S20, the heat source 110 is removed from the air guide passage 120 and moved to a position away from the first cylindrical body 20 and the second cylindrical body 30.

This makes it possible to protect the heat source 110 from welding fumes, spatters, etc. that are generated when the first cylindrical body 20 and the second cylindrical body 30 are welded together. In addition, it is possible to suppress a decrease in weldability caused by the hot air generated from the heat source 110 disrupting the flow of welding gas during welding.

A specific example of a method for moving the heat source 110 is to swing the heat source 110 from a use position connected to the air guide 120 to a storage position protected by the protective cover 140. As a result, when the first cylinder 20 and the second cylinder 30 are welded together, the protective cover 140 is positioned between the welded portion and the heat source 110. As a result, the protective cover 140 functions as a shielding member, making it difficult for the above-mentioned welding fumes, spatter, etc. to hit the heat source 110.

(Welding process)
In the welding step S40, after the moving step S30, the first cylindrical body 20 and the second cylindrical body 30 are welded together. Specifically, the welded portion W where the first end portion 21A of the main body portion 21 of the first cylindrical body 20 and the second cylindrical body 30 overlap is welded over the entire circumferential direction.

[1-2. Effects]
According to the embodiment described above in detail, the following effects can be obtained.
(1a) Since the first cylindrical body 20 and the second cylindrical body 30 are welded together while reducing the temperature difference between the thick-walled portion and other portions, stress is suppressed from occurring in the first cylindrical body 20 and the second cylindrical body 30. As a result, damage to the exhaust system component 10 having the thick-walled portion during welding can be suppressed.

(1b) By making the first cylindrical body 20 mainly out of ferritic stainless steel, the thermal expansion coefficient of the first cylindrical body 20 is reduced, and the oxidation characteristics in a cycle in which high-temperature conditions are repeated can be improved.

(1c) By using ferritic stainless steel as the main component for both the first cylindrical body 20 and the second cylindrical body 30, the same material is welded, and the thermal expansion difference between the first cylindrical body 20 and the second cylindrical body 30 can be reduced. Furthermore, since ferritic stainless steel has a smaller thermal expansion coefficient than austenitic stainless steel, the dimensional difference between the first cylindrical body 20 and the second cylindrical body 30 when they thermally expand and contract is reduced. As a result, damage to the first cylindrical body 20 and the second cylindrical body 30 is suppressed.

(1d) Since the first cylindrical body 20 is a joint having the flange portion 22, the generation of stress in the flange portion 22 used for fastening and damage to the joint caused by this stress can be suppressed.
(1e) Since the second cylindrical body 30 is a catalyst case, damage to the catalyst case, which is made of a material with a small thermal expansion coefficient, can be suppressed.

(1f) By using the heat source 110 that blows hot air and the guiding device 130 that guides the hot air to the thick portion, it is relatively easy to heat the thick portion preferentially.
(1g) By colliding the hot air with the guide tool 130, the position for guiding the hot air can be changed and adjusted relatively easily, thereby improving the production efficiency of the exhaust system part 10.

2. 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.

(2a) In the manufacturing method of the exhaust system component of the above embodiment, the material of the first cylindrical body and the second cylindrical body is not limited to ferritic stainless steel.

(2b) In the manufacturing method of the exhaust system part of the above embodiment, the first cylindrical body is not limited to a joint having a flange portion. Moreover, the second cylindrical body is not limited to a catalyst case. Furthermore, a thick portion may be provided in both the first cylindrical body and the second cylindrical body. Moreover, the thick portion may include a portion other than the flange portion of the first cylindrical body.

(2c) In the manufacturing method of the exhaust system part of the above embodiment, the hot air may be guided to the thick portion by means other than collision with a guide tool. Also, the first cylinder and the second cylinder may be heated by means other than hot air. For example, the thick portion may be preferentially heated by attaching a heater directly to the thick portion.

(2d) 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. In addition, part of the configuration of the above embodiments may be omitted. In addition, 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. All aspects included in the technical idea identified from the wording of the claims are embodiments of the present disclosure.

DESCRIPTION OF SYMBOLS 10... Exhaust system parts, 20... First cylindrical body, 21... Main body part, 21A... First end part,
21B...second end, 22...flange, 22A...groove, 30...second cylindrical body, 100...heating device,
110: heat source, 120: air guide duct, 130: guide device, 131: collision portion, 132: shaft portion,
133...support material, 140...protective cover.

Claims (6)

A method for manufacturing an exhaust system component that configures an exhaust gas flow path, comprising the steps of:
a step of heating the first cylindrical body and the second cylindrical body in a state where the first cylindrical body and the second cylindrical body are connected to each other;
a step of welding the first cylindrical body and the second cylindrical body after the heating step;
Equipped with
In the heating step, a thick portion of the first cylindrical body, which has a radial thickness greater than other portions, is heated preferentially over other portions ;
The first cylindrical body is
A cylindrical main body;
a flange portion having an outer diameter larger than that of the main body portion and provided continuously with a second end portion of the main body portion opposite to a first end portion welded to the second cylindrical body;
having
The flange portion constitutes the thick portion,
In the welding step, the first end of the main body of the first cylindrical body and the second cylindrical body are welded to each other.
A manufacturing method for exhaust system parts. A method for manufacturing an exhaust system component that configures an exhaust gas flow path, comprising the steps of:
a step of heating the first cylindrical body and the second cylindrical body in a state where the first cylindrical body and the second cylindrical body are connected to each other;
a step of welding the first cylindrical body and the second cylindrical body after the heating step;
Equipped with
In the heating step, a thick portion of the first cylindrical body, which has a radial thickness greater than other portions, is heated preferentially over other portions ;
In the heating step, a heat source for blowing hot air into the inside of the first cylindrical body and the second cylindrical body and a guide device for guiding the hot air to the thick-walled portion are used.
A manufacturing method for exhaust system parts. A method for manufacturing an exhaust system part according to claim 2 , comprising the steps of:
The first cylindrical body is
A cylindrical main body;
a flange portion having an outer diameter larger than that of the main body portion and provided continuously with a second end portion of the main body portion opposite to a first end portion welded to the second cylindrical body;
having
The method for manufacturing an exhaust system part, wherein the flange portion constitutes the thick portion. A method for manufacturing an exhaust system part according to claim 2 or 3, comprising the steps of:
In the heating step, the hot air is guided to the thick portion by colliding with the guide tool. A method for manufacturing an exhaust system part according to any one of claims 1 to 4 , comprising the steps of:
A method for manufacturing an exhaust system part, wherein the first cylindrical body is mainly made of ferritic stainless steel. A method for manufacturing an exhaust system part according to any one of claims 1 to 5, comprising the steps of:
The second cylindrical body is a catalyst case that stores a catalyst.

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