Joint structure and manufacturing method of the joint structure

Abstract

To provide a joint structure which can inhibit reduction of joint strength even when a brass which contains bismuth (Bi) in place of lead and stainless steel are brazed with a brazing material, and to provide a manufacturing method of the joint structure.SOLUTION: A joint structure in which a stainless member and a brass member are brazed, includes a layer structure in which the stainless member, a first brazing material layer, a Bi barrier layer, a second brazing material layer, and the brass member are sequentially arranged in a laminar manner. The brass member contains Bi, and the Bi barrier layer inhibits Bi in the brass member from being moved to the first brazing material layer by brazing of the stainless member and the brass member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joint structure and a method for manufacturing a joint structure, and more particularly to a joint structure between stainless steel and brass and a method for manufacturing a joint structure. [Background technology]

[0002] Traditionally, when joining dissimilar metals, such as stainless steel and brass, brazing is used (see, for example, Patent Document 1). Recently, due to environmental regulations, the use of materials containing lead has become stricter, and there is a trend to use bismuth (hereinafter sometimes referred to as "Bi") as a substitute for lead (hereinafter sometimes referred to as "Pb"). The same applies to brass; although lead improves the machinability of brass, bismuth is used instead of lead. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-276072 [Patent Document 2] Japanese Patent Publication No. 2014-98685 [Patent Document 3] Japanese Patent Publication No. 2003-42325 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, when brass containing bismuth instead of lead is joined to stainless steel by brazing using a brazing material, the joint strength between the stainless steel and the brazing material may be lower compared to the conventional method of joining brass containing lead to stainless steel by brazing.

[0005] In view of the above problems, the present invention aims to provide a joint structure and a method for manufacturing a joint structure that can suppress a decrease in joint strength even when brass containing bismuth instead of lead and stainless steel are joined by brazing using a brazing material. [Means for solving the problem]

[0006] To solve the above problems, the joint structure of the present invention is a joint structure in which a stainless steel member and a brass member are brazed together, and the brazing provides a layered structure in which the stainless steel member, a first brazing layer, a Bi shielding layer, a second brazing layer, and the brass member are arranged in layers in order, the brass member contains Bi, and the Bi shielding layer is a layer that suppresses the movement of Bi in the brass member to the first brazing layer by brazing the stainless steel member and the brass member.

[0007] The bonding strength between the stainless steel member and the brass member is 100 N / mm². 2 That's fine too.

[0008] The brass member may be a fitting for a pressure sensor, and the stainless steel member may be a dish-shaped cover attached to the fitting for the pressure sensor.

[0009] The brass member may be a fitting for a pressure switch, and the stainless steel member may be a dish-shaped cover attached to the fitting for the pressure switch.

[0010] The brass member may be the main body of the valve, and the stainless steel member may be a lower cover material positioned around the opening of the main body.

[0011] The brass member may be the main body of the valve, and the stainless steel member may be a cylindrical member positioned in the opening of the main body.

[0012] Also, in order to solve the above problems, the manufacturing method of the joining structure of the present invention sequentially includes: a first layer structure forming step of arranging the stainless steel member, the first brazing material, the Bi shielding layer, the second brazing material, and the brass member in layers to form a first layer structure; a first brazing step of heating the first layer structure to braze the stainless steel member and the brass member; and a first cooling step of cooling the first layer structure after the first brazing step to form a joining structure having a layer structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers.

[0013] In the manufacturing method of the brazed joint of the present invention, the first brazing material and the second brazing material may be brazing materials having the same composition.

[0014] The Bi shielding layer may be in the shape of a washer.

[0015] The Bi shielding layer may be in the shape of a cylinder.

[0016] Also, in order to solve the above problems, the manufacturing method of the joining structure of the present invention sequentially includes: a second layer structure forming step of arranging the stainless steel member, the Bi shielding layer, and the brass member in layers, and arranging a brazing material between at least one of between the stainless steel member and the Bi shielding layer, between the Bi shielding layer and the brass member, or on the side surface of the Bi shielding layer to form a second layer structure; a second brazing step of heating the second layer structure to braze the stainless steel member and the brass member; and a second cooling step of cooling the second layer structure after the second brazing step to form a joining structure having a layer structure in which the stainless steel member, the first brazing material layer, the Bi shielding layer, the second brazing material layer, and the brass member are arranged in layers.

[0017] The Bi shielding layer may be in the shape of a washer.

[0018] The Bi shielding layer may be in the shape of a cylinder.

Effects of the Invention

[0019] According to the present invention, there is provided a joining structure and a method for manufacturing the joining structure capable of suppressing a decrease in joining strength even when brass containing bismuth and stainless steel are joined by brazing using a brazing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] The SEM image obtained by photographing the cross section of the joining structure in which the stainless steel member and the brass member are brazed. FIG. 1(A) shows the joining structure 200 of Comparative Example 1 using a conventional brass member containing lead, FIG. 1(B) shows the joining structure 300 of Comparative Example 1 using a brass member containing bismuth instead of lead, and FIG. 1(C) shows the joining structure 100 of Example 1 using a brass member containing bismuth instead of lead and further provided with a blocking layer between the stainless steel member and the brass member. [Figure 2] The side view of the test piece at the time of performing the joining test and the jig used for the joining test. FIG. 2(A) shows the state before assembling the jig and the test piece, FIG. 2(B) shows the state after assembling the jig and the test piece, and FIG. 2(C) is an enlarged view of a part of the joining portion of the region E surrounded by a circle of the brazed joint 200 shown in FIG. 2(A). [Figure 3] The cross-sectional view of the pressure sensor provided with the joining structure of the present invention. [Figure 4] The cross-sectional view of the pressure switch provided with the joining structure of the present invention. [Figure 5] The enlarged cross-sectional view of the region A which is a part of the joining structure in the pressure switch shown in FIG. 4. [Figure 6] The cross-sectional view of the motorized valve provided with the joining structure of the present invention. [Figure 7] The cross-sectional view of the regulating valve provided with the joining structure of the present invention. [Figure 8] The cross-sectional view of the expansion valve provided with the joining structure of the present invention. [Figure 9] The cross-sectional view of the solenoid valve provided with the joining structure of the present invention. [Figure 10] The enlarged cross-sectional view of the region C which is a part of the joining structure in the solenoid valve shown in FIG. 9. [Figure 11]This is a perspective view showing an example of the various components that make up the first layer structure. [Figure 12] This is a partial cross-sectional view of the first layer structure. [Figure 13] This is a perspective view showing an example of the various components that make up the second layer structure. [Figure 14] This is a partial cross-sectional view of the second layer structure. [Figure 15] This is a perspective view showing an example of the various components that make up the second layer structure. [Figure 16] This is a partial cross-sectional view of the second layer structure. [Figure 17] This is a partial cross-sectional view of the solenoid valve 6000. [Figure 18] This is a partial cross-sectional view of the second layer structure. [Figure 19] This is a partial cross-sectional view of the second layer structure. [Figure 20] Figure 20(A) shows a cross-sectional image of a part of the joint structure 100 taken with an SEM, and an elemental mapping of bismuth in the corresponding cross-section using EDS. Figure 20(A) is a cross-sectional image of a layered structure consisting of stainless steel 10, a first brazing layer 20, and a barrier layer 30, and Figure 20(B) is a cross-sectional image of a layered structure consisting of a barrier layer 30, a second brazing layer 40, and a brass member 50. [Figure 21] The images show a cross-sectional view of a layered structure consisting of stainless steel 10, brazing material layer 80, and brass member 50 of the joint structure 300, captured by SEM, and an elemental mapping of bismuth in the corresponding cross-section using EDS. [Modes for carrying out the invention]

[0021] The following describes one embodiment of the joining structure and the method for manufacturing the joining structure of the present invention. However, the present invention is not limited to the following example.

[0022] [Joining structure] The joint structure of the present invention is a joint structure in which a stainless steel member and a brass member are brazed together, and comprises a layered structure in which, by brazing, the stainless steel member, a first brazing layer, a Bi shielding layer, a second brazing layer, and a brass member are arranged in layers in order.

[0023] The joint structure of the present invention is not particularly limited in shape as long as it has such a layered structure, and can be used in a variety of applications as a component in which dissimilar metals such as stainless steel and brass are joined by brazing. Examples of such components include a brazed joint between a stainless steel cap and a brass fitting in a pressure switch, a brazed joint between a stainless steel cap and a brass fitting in a pressure sensor, a brazed joint between a stainless steel cap and a brass body in an electric valve, a brazed joint between a stainless steel tube and a brass body in a solenoid valve, a brazed joint between a stainless steel cap and a brass body in a control valve, and a brazed joint between a stainless steel cap and a brass body in an expansion valve. Specific examples of these components will be described later.

[0024] Figures 1(A) to 1(C) show SEM images of cross-sections of a joint structure in which a stainless steel member and a brass member are brazed together. Of these, Figure 1(C) is the joint structure 100 of Example 1 in the embodiments described later, and is an example of the joint structure of the present invention.

[0025] As shown in Figure 1(C), the joint structure 100 has a layered structure in which a stainless steel member 10, a first brazing layer 20, a Bi shielding layer 30, a second brazing layer 40, and a brass member 50 are arranged in layers in that order. That is, the stainless steel member 10 and the brass member 50 are brazed together, and in the present invention, the stainless steel member 10 and the Bi shielding layer 30 are brazed together, and the brass member 50 and the Bi shielding layer 30 are brazed together.

[0026] <Stainless steel component 10> The stainless steel component 10 is not particularly limited, and examples include stainless steel components used in the above-mentioned parts. Specifically, any of austenitic stainless steel such as SUS304, ferritic stainless steel, martensitic stainless steel, and duplex stainless steels thereof can be used as the stainless steel component 10.

[0027] <Brass component 50> The brass component 50 is not particularly limited to brass containing Bi, and examples include brass components used in the above-mentioned parts. Specifically, brass composed of components with a Cu content of 57.4 to 64.0 mass%, a Pb content of 0.1 mass or less, and a Bi content of 0.50 to 4.00 mass% can be used as the brass component 50. More specifically, C6801B, C6802B, C6803B, C6804B, etc. can be used.

[0028] In this invention, since brass containing bismuth is used instead of lead for the brass component 50, it is ideal to have as little Pb as possible. The lower limit of the Pb content is 0% by mass, and considering analytical accuracy, it is preferable that this lower limit be below the detection limit of Pb. However, there are cases where Pb is unavoidably present or where a small amount is not a problem, so it is important that the Pb content does not exceed 0.1% by mass.

[0029] <Bi shielding layer 30> The Bi shielding layer 30 is a layer that suppresses the movement of Bi in the brass member 50 to the first brazing material layer 20 by brazing the stainless steel member 10 and the brass member 50.

[0030] In the case of a conventional joint structure in which a lead-containing brass member and a stainless steel member 10 are joined by brazing, there is no problem with the joint strength. For example, the joint strength used as a guideline for the strength of the above-mentioned part is 100 N / mm². 2 It fully met the criteria of being above the standard.

[0031] However, when a brass member 50 containing bismuth instead of lead is brazed to a stainless steel member 10, the bonding strength between the stainless steel and the brazing material decreases, resulting in a bonding strength of 100 N / mm². 2 In some cases, the joint strength was less than the stated value. Upon investigating the cause of this decrease in joint strength, it was found that bismuth migrated from the brass member 50 to the brazing material layer, forming a brazing material layer containing bismuth, and that the bismuth further segregated at the stainless steel interface, resulting in a decrease in the joint strength between the brazing material layer and the stainless steel member 10. Therefore, in order to ensure sufficient joint strength, it is important that even if bismuth migrates from the brass member 50 to the brazing material layer, the bismuth does not reach the vicinity of the joint interface between the stainless steel member 10 and the brazing material layer.

[0032] Therefore, in this invention, a Bi shielding layer 30 is provided to prevent bismuth from reaching the vicinity of the bonding interface with the stainless steel member 10. Although bismuth moves from the brass member 50 to the second brazing layer 40 due to brazing, the Bi shielding layer 30 blocks the movement of bismuth, preventing the bismuth from going around the Bi shielding layer 30 and moving to the first brazing layer 20, thereby preventing a decrease in the bonding strength between the stainless steel member 10 and the first brazing layer 20. As a result, the stainless steel member 10 and the brass member 50 can be joined while maintaining sufficient strength.

[0033] For the Bi shielding layer 30 to fulfill this role, it is important that it can withstand the heating temperature during brazing and does not contain excessive amounts of lead or bismuth. Furthermore, even if the strength of the stainless steel member 10, the first brazing layer 20, the second brazing layer 40, and the brass member 50 is sufficient, if the strength of the Bi shielding layer 30 is low, there is a risk of fracture at the Bi shielding layer 30. Therefore, to prevent fracture at the shielding layer, for example, the tensile strength of the Bi shielding layer 30 itself should be 400 N / mm². 2 It is preferable that there be more than the above.

[0034] Materials that meet these conditions and can be used as the Bi shielding layer 30 include the following brass or phosphor bronze, and at least one of these can be used alone or in combination.

[0035] (Brass for Bi shielding layer 30) As the Bi shielding layer 30, brass with a Cu content of 59.0 to 71.5 mass% and a Pb content of 0.10 mass% or less can be used. In this invention, it is ideal for the Bi shielding layer 30 to contain as little Pb and Bi as possible, with the lower limits of Pb content and Bi content being 0 mass%, and it is preferable that both Pb and Bi are below the detection limit when considering analytical accuracy. However, there may be cases where Pb or Bi are unavoidably present, or where small amounts are acceptable. For example, it is important that the Pb content does not exceed 0.1 mass%.

[0036] Examples of brass that can be used include C2680 and C2801.

[0037] (Phosphor bronze for Bi shielding layer 30) As the Bi shielding layer 30, phosphor bronze can be used, having a Sn content of 5.5 to 7.0 mass%, a P content of 0.03 to 0.35 mass%, a Pb content of 0.02 mass% or less, an Fe content of 0.10 mass% or less, a Zn content of 0.20 mass% or less, and the remainder being Cu, with the total of Cu, Sn, and P being 99.5 mass% or more. In this invention, it is ideal for the Bi shielding layer 30 to contain as little Pb and Bi as possible, with the lower limits of Pb content and Bi content being 0 mass%, and considering analytical accuracy, it is preferable that both Pb and Bi are below the detection limit. However, there are cases where Pb or Bi are unavoidably present, or where small amounts are acceptable. For example, it is important that the Pb content does not exceed 0.1 mass%, and the above-mentioned phosphor bronze can be used without any problems.

[0038] For example, C5191 can be used as such a phosphor bronze.

[0039] (Shape and thickness of the Bi shielding layer 30) The Bi shielding layer 30 can be a plate or thin film of uniform thickness, a ring-shaped or cylindrical piece such as a washer or nut, or a plate or thin film of uniform thickness. When using a Bi shielding layer 30 of such shape, its dimensions can be adjusted as appropriate according to the shape of the stainless steel member 10 or the brass member 50. The thickness of the Bi shielding layer 30 may be, for example, 0.4 to 1.2 mm.

[0040] <First brazing layer 20> The brazing material constituting the first brazing layer 20 is preferably in liquid form at 680 to 800°C. By using a liquid brazing material at this temperature, the stainless steel member 10 and the brass member 50 can be joined via the Bi shielding layer 30.

[0041] The brazing material that can be used as the first brazing layer 20 is preferably one that does not contain Pb or Bi, and more preferably one that does not contain Cd, considering environmental regulations. Examples of such brazing materials include BAg-4, BAg-5, BAg-6, BAg-7, BAg-7A, BAg-7B, BAg-8, BAg-8A, BAg-8B, BAg-20, BAg-24, etc. These brazing materials can be used individually or in combination.

[0042] For example, if a stainless steel component 10 is made from processed SUS304, the first brazing layer 20 may be a brazing layer containing BAg-7.

[0043] <Second brazing layer 40> The brazing material constituting the second brazing layer 40 is preferably in liquid form at 680 to 800°C. By using a brazing material that is liquid at this temperature, the stainless steel 10 member and the brass member 50 can be joined via the Bi shielding layer 30.

[0044] The brazing material that can be used as the second brazing layer 40 is preferably one that does not contain Pb or Bi, and more preferably one that does not contain Cd, considering environmental regulations. Examples of such brazing materials include BAg-4, BAg-5, BAg-6, BAg-7, BAg-7A, BAg-7B, BAg-8, BAg-8A, BAg-8B, BAg-20, BAg-24, etc. These brazing materials can be used individually or in combination.

[0045] For example, if a stainless steel component 10 is made from processed SUS304, the second brazing layer 40 may be a brazing layer containing BAg-7.

[0046] Furthermore, the second brazing layer 40 may be formed by brazing the stainless steel member 10 and the brass member 50 using the same brazing material as the first brazing layer 20, or a different brazing material may be used. However, due to the heating required for brazing, bismuth moves from the brass member 50 to the second brazing layer 40. Therefore, the amount of bismuth in the second brazing layer 40 will be greater than in the first brazing layer 20.

[0047] <Joining strength> Pressure vessels such as pressure switches, pressure sensors, electric valves, solenoid valves, control valves, and expansion valves contain fluids such as refrigerants under high pressure. Therefore, it is important that they have pressure resistance, and to prevent fluid leakage to the outside due to damage caused by pressure, when the joint structure 100 of the present invention is used as a component of these pressure vessels, the joint strength between the stainless steel member 10 and the brass member 50 must be 100 N / mm². 2 It is preferable that the above conditions are met.

[0048] However, the bonding structure 100 of the present invention is 100 N / mm 2 For applications that do not require the above-mentioned joint strength, a joint strength of 100 N / mm² is acceptable. 2 It does not need to be more than that.

[0049] <Pressure Sensor 1000> The joint structure of the present invention can be used as a component in a pressure sensor (for example, in Patent Document 2, etc.). In this case, the brass member is the joint of the pressure sensor, and the stainless steel member is a dish-shaped cover attached to the joint of the pressure sensor. As an example of a pressure sensor, Figure 3 shows a cross-sectional view of a pressure sensor 1000 equipped with the joint structure of the present invention.

[0050] The pressure sensor 1000 has a cover 1030 connected to the end of a joint 1020, which has an introduction passage 1010 for the detected pressure fluid in the center. A metal header 1070 with an insulating member 1040 in the center is connected to the cover 1030. Furthermore, a sealing material 1110 is filled into a space formed in a resin case 1100 to prevent moisture from entering the inside of the pressure sensor.

[0051] For example, glass hermetic material is used as the insulating member 1040, and the header 1070, insulating member 1040, and diaphragm 1060 form a liquid-sealed chamber. The pressure sensing element 1050 is placed in the liquid-sealed chamber and detects the pressure acting on the diaphragm 1060 via the sealed liquid in the chamber. Multiple lead pins 1090 that input and output signals to the pressure sensing element 1050 and the stem 1080 that supports the pressure sensing element 1050 are fixed with the insulating member 1040.

[0052] In other words, in the pressure sensor 1000, the pressure acting on the diaphragm 1060 is transmitted via the sealing liquid to a pressure sensing element 1050 fixed on a stem 1080 positioned opposite the diaphragm 1060, and a detection output is obtained from a lead pin 1090 that extends through the insulating member 1040.

[0053] In such a pressure sensor 1000, the hexagonal prism-shaped joint 1020 corresponds to a brass component, and the dish-shaped cover 1030 and header 1070 are each made of stainless steel, with the cover 1030 corresponding to a stainless steel component. The joint 1020 and cover 1030 are brazed together with a brazing material, with a washer-shaped Bi shielding layer 31 in between. One example of assembling these components in the pressure sensor 1000 is to first braze the brass joint 1020 and the stainless steel cover 1030 in a reducing atmosphere furnace with the Bi shielding layer 31 sandwiched between them, then cool them in the reducing atmosphere furnace and then remove them from the reducing atmosphere furnace and allow them to cool at room temperature to form a joint structure. Finally, the header 1070 is welded to the cover 1030 of the joint structure.

[0054] In the pressure sensor 1000, the Bi shielding layer 31 acts as a layer that suppresses the movement of Bi in the joint 1020 to the first brazing material layer during the brazing of the stainless steel lid 1030 and the brass joint 1020, thereby suppressing a decrease in the joint strength between the lid 1030 and the joint 1020.

[0055] <Pressure Switch 2000> The joint structure of the present invention can be used as a component in a pressure switch. In this case, the brass member is the joint of the pressure switch, and the stainless steel member is a dish-shaped cover that is attached to the joint of the pressure switch. As an example of a pressure switch, Figure 4 shows a cross-sectional view of a pressure switch 2000 equipped with the joint structure of the present invention.

[0056] This pressure switch 2000 turns on / off by moving an operating rod in response to pressure fluctuations, causing one of a pair of contacts to move toward and away from the other. In this pressure switch 2000, a metal diaphragm 2010 made of a thin metal film is used, and the metal diaphragm 2010, the cover 2030, and the outer circumference 2130 of the stopper 2120 are welded together to form a diaphragm unit 2140, which completely blocks the permeation of the refrigerant. The pressure switch 2000 includes a dish-shaped cover 2030 that defines a pressure-sensitive chamber 2020 on one side of a metal diaphragm 2010, a coupling 2040 that is hermetically connected to the dish-shaped cover 2030 and guides a refrigerant (pressure) such as high-pressure gas or oil into the pressure-sensitive chamber 2020, and a resin case member 2090 that protects a contact section 2052 which has a movable contact 2050 and a fixed contact 2051 that are switched by an operating rod 2150 in accordance with the displacement of the metal diaphragm 2010. Connection terminal pieces 2100 and 2110 are attached to the case member 2090.

[0057] The metal holder member 2070 is a crimping material that can be plastically deformed by crimping to join and integrate two or more parts. By crimping the holder member 2070, the diaphragm unit 2140, which includes the case member 2090, the intermediate plate member 2080, the rubber O-ring 2060, the metal diaphragm 2010, the lid 2030, and the stopper 2120, can be integrated.

[0058] In this pressure switch 2000, the joint 2040 corresponds to a brass component, and the dish-shaped cover 2030 corresponds to a stainless steel component. The joint 2040 and the cover 2030 are brazed together with brazing material, with a washer-shaped Bi shielding layer 32 in between.

[0059] One example of how these components are assembled in the pressure switch 2000 is as follows: First, a brass joint 2040 and a stainless steel dish-shaped cover 2030 are brazed in a reducing atmosphere furnace with a Bi shielding layer 32 sandwiched between them. Then, the components are cooled in the reducing atmosphere furnace and then removed from the reducing atmosphere furnace and cooled at room temperature to form a joint structure. A metal diaphragm 2010 is then placed on top of the cover 2030 of the joint structure, and a stopper 2120 is placed on top of that. From this state, the stopper 2120, the metal diaphragm 2010, and the outer periphery 2130 of the cover 2030 are joined together by welding.

[0060] Figure 5 shows an enlarged cross-sectional view of region A, which is part of the joint structure 110 in the pressure switch 2000 shown in Figure 4. Although it is omitted from the illustration in Figure 4 because the brazing material layer is thin, as shown in Figure 5, the joint structure 110 has a layered structure in which, in order, a stainless steel member cover 2030, a first brazing material layer 21, a Bi shielding layer 32, a second brazing material layer 41, and a brass member joint 2040 are arranged in layers. The electric valve 3000, control valve 4000, and expansion valve 5000 shown in Figures 6 to 8, which will be described later, also have a joint structure with a similar layered structure, although it is omitted from the illustration because the brazing material layer is thin.

[0061] The SEM image of the cross-section of the joint structure 100 of Example 1 shown in Figure 1(C) is an SEM image of the cross-section of the joint structure 110 shown in Figure 5. The stainless steel member 10, first brazing layer 20, Bi shielding layer 30, second brazing layer 40, and brass member 50 in the joint structure 100 of Figure 1(C) correspond to the cover 2030, first brazing layer 21, Bi shielding layer 32, second brazing layer 41, and joint 2040 of the joint structure 110 of Figure 5, respectively.

[0062] In the pressure switch 2000, the Bi shielding layer 32 acts as a layer that suppresses the movement of Bi in the joint 2040 to the first brazing material layer 21 during the brazing of the stainless steel lid 2030 and the brass joint 2040, thereby suppressing a decrease in the joint strength between the lid 2030 and the joint 2040.

[0063] Furthermore, although the brazing material layer is thin and therefore omitted from the illustration in Figure 3, the bonding structure of the pressure sensor 1000 also has a layer structure similar to that shown in Figure 5.

[0064] <Electric valve 3000, control valve 4000, expansion valve 5000> The joint structure of the present invention can be used as a component in electric valves (e.g., Patent Document 3), regulating valves, and expansion valves. In this case, the brass member is the main body of the valve, and the stainless steel member is a lower cover material positioned around the opening of the main body. Examples of electric valves, regulating valves, and expansion valves will be described below.

[0065] (Electric valve 3000) Figure 6 shows a cross-sectional view of an electric valve 3000 equipped with the joint structure of the present invention. The electric valve 3000 has a valve body 3010, the valve body 3010 having a valve chamber 3011, a pipe connection hole 3012 opening on one inner circumferential surface of the valve chamber 3011, a pipe connection hole 3013 opening downward from the valve chamber 3011, and a valve port 3014 connecting the pipe connection hole 3013 and the valve chamber 3011. The pipe connection hole 3012 is formed as a lateral hole, and a first joint pipe 3020 is fixed to this pipe connection hole 3012 by brazing. The pipe connection hole 3013 is formed as a pilot hole, and a second joint pipe 3030 is fixed to this pipe connection hole 3013 by brazing.

[0066] A dish-shaped cover case 3050 is hermetically fixed to the upper part of the valve body 3010 by brazing, and a coil 3101 is attached to a rotor case 3110 which is hermetically fixed to the cover case 3050. The coil 3101 and magnet 3230 form a stepping motor 3100. Lead wires 3102 are wires that electrically connect the stepping motor 3100 to a power supply (not shown). Inside the rotor case 3110, a rotor 3200, which includes a fixing member 3210, a female screw member 3220, a magnet 3230, and an operating shaft 3240, is rotatably arranged. When a pulse signal is applied to the stepping motor 3100, the rotor 3200 rotates according to the number of pulses.

[0067] A stopper retaining rod 3300 is suspended and fixed inside the rotor case 3110. A helical guide 3310 is attached to the stopper retaining rod 3300, and a movable stopper 3320 is engaged with the helical guide 3310.

[0068] The valve body 3015 is integrally formed with the operating shaft 3240. When the rotor 3200 rotates due to the drive of the stepping motor 3100, the rotation of the rotor 3200 is converted into linear motion of the operating shaft 3240 by the thrust of the female threaded member 3220, which rotates together with the rotor, and the male threaded member 3040, which is fixed by the valve body 3010 and engages with the female threaded member 3220. This causes the valve body 3015 to move vertically in the direction shown in Figure 6 via the operating shaft 3240. As a result, the valve body 3015 adjusts the opening degree of the valve port 3014, controlling the flow rate of refrigerant flowing in from the first joint pipe 3020 and flowing out from the second joint pipe 3030.

[0069] In such an electric valve 3000, the valve body 3010, which is the main body of the valve, corresponds to a brass component, and the lid case 3050, which is a lower cover material positioned around the opening 3016 into which the valve element 3015 of the valve body 3010 is inserted, corresponds to a stainless steel component. The valve body 3010 and the lid case 3050 are brazed together with brazing material, with a washer-shaped Bi shielding layer 33 in between. At this time, it is also possible to braze the first joint pipe 3020, the second joint pipe 3030, and the valve body 3010 simultaneously.

[0070] One example of how these components are assembled in the electric valve 3000 is to first braze the valve body 3010, which is made of brass, and the lid case 3050, which is made of stainless steel, with a Bi shielding layer 33 sandwiched between them in a reducing atmosphere furnace, and then cool them in the reducing atmosphere furnace and then remove them from the reducing atmosphere furnace and allow them to cool at room temperature to form the joint structure.

[0071] In the electric valve 3000, the Bi shielding layer 33 acts as a layer that suppresses the movement of Bi in the valve body 3010 to the first brazing material layer by brazing the stainless steel lid case 3050 and the brass valve body 3010, and as a result, a decrease in the joint strength between the lid case 3050 and the valve body 3010 can be suppressed.

[0072] (Adjustment valve 4000) Figure 7 shows a cross-sectional view of a control valve 4000 equipped with the joint structure of the present invention. The control valve 4000 has a valve body 4010 with a substantially cylindrical outer shape. The valve body 4010 has a pipe connection hole 4020, a pipe connection hole 4030, a valve chamber 4040, a valve insertion hole 4050, a secondary port 4060, a spring chamber 4070, and a valve port 4080. The pipe connection hole 4020, the pipe connection hole 4030, the valve chamber 4040, the valve insertion hole 4050, and the secondary port 4060 are cylindrical holes.

[0073] A first fitting pipe 4100, through which fluid flows in as indicated by the arrow, is attached to the pipe connection hole 4020, and a second fitting pipe 4200, through which fluid flows out as indicated by the arrow, is attached to the pipe connection hole 4030. The first fitting pipe 4100 and the second fitting pipe 4200 are assembled integrally with the valve body 4010 by brazing.

[0074] The first joint pipe 4100 is connected to the valve chamber 4040 via the valve port 4080, and the first joint pipe 4100, the valve chamber 4040, and the valve insertion hole 4050 are located on the central axis L of the valve port 4080. The second joint pipe 4200 is connected to the valve chamber 4040 via the secondary port 4060. The valve port 4080 is a cylindrical hole centered on the central axis L.

[0075] A cylindrical valve body 4090 is disposed within the valve insertion hole 4050. The valve insertion hole 4050 is cylindrical with a central axis L, and the valve body 4090 moves within the valve insertion hole 4050 in the direction of the central axis L, that is, in the vertical direction in Figure 7. A spring chamber 4070 is formed as a ring-shaped deep groove around the valve insertion hole 4050, and a coil spring 4071 is disposed within this spring chamber 4070. A flange-shaped spring retainer 4072 is fixed to the valve body 4090, and the coil spring 4071 is compressed between the bottom 4073 of the spring chamber 4070 and the spring retainer 4072. As a result, the coil spring 4071 biases the valve body 4090 toward the diaphragm 4300 described later, pressing the valve body 4090 against the diaphragm 4300.

[0076] A ring-shaped lower cover 4400 is attached to the outer periphery of the spring chamber 4070 of the valve body 4010 by brazing via a Bi shielding layer 34. The diaphragm 4300 and the upper cover 4500 are attached to the lower cover 4400. The lower cover 4400, diaphragm 4300, and upper cover 4500 are welded together at the outer circumference B shown by the dashed-dotted ellipse in Figure 7. This creates a pressure chamber 4600 inside the lower cover 4400 that applies pressure to the diaphragm 4300.

[0077] The diaphragm 4300 is a disc-shaped component with a central axis L as its center of rotation and is made of a metal leaf spring. When the pressure in the pressure chamber 4600 exceeds the set pressure determined by the characteristics of the diaphragm 4300, the diaphragm 4300 deforms in the direction of the central axis L, and the flat portion 4310 mainly moves in the direction of the central axis L, i.e., upward in Figure 7.

[0078] In this type of control valve 4000, the valve body 4010, which is the main body of the valve, corresponds to a brass component, and the lower cover 4400, which is a lower cover material positioned around the opening 4011 of the valve body 4010, corresponds to a stainless steel component. The valve body 4010 and the lower cover 4400 are fixed together by crimping the opening 4011 of the valve body 4010 with a washer-shaped Bi shielding layer 34 in between, and then brazing with brazing material.

[0079] One example of assembling these components in the control valve 4000 is to first braze the valve body 4010, which is made of brass, and the lower cover 4400, which is made of stainless steel, with the Bi shielding layer 34 sandwiched between them in a reducing atmosphere furnace. Then, the joint structure is formed by cooling in the reducing atmosphere furnace and then cooling at room temperature after being removed from the reducing atmosphere furnace. At this time, it is also possible to braze the first joint pipe 4100, the second joint pipe 4200, and the valve body 4010 simultaneously.

[0080] In the control valve 4000, the Bi shielding layer 34 acts as a layer that suppresses the movement of Bi in the valve body 4010 to the first brazing material layer by brazing the stainless steel lower cover 4400 and the brass valve body 4010, and as a result, a decrease in the joint strength between the lower cover 4400 and the valve body 4010 can be suppressed.

[0081] (Expansion valve 5000) Figure 8 shows a cross-sectional view of an expansion valve 5000 equipped with the joint structure of the present invention. The expansion valve 5000 has a metal valve body 5010. The valve body 5010 is provided with a pipe connection hole 5020 and a pipe connection hole 5030. A first joint pipe 5040 is attached to the pipe connection hole 5020, and a second joint pipe 5050 is attached to the pipe connection hole 5030. The first joint pipe 5040 and the second joint pipe 5050 are assembled integrally with the valve body 5010 by brazing or the like.

[0082] A diaphragm device 5100 is mounted on the upper part of the valve body 5010. The diaphragm device 5100 has a case made up of a thin, disc-shaped upper cover 5110 and a lower cover 5120. The lower cover 5120 is fixed to the valve body 5010 by brazing it to the valve body 5010 via a Bi shielding layer 35. A diaphragm 5130 is provided between the upper cover 5110 and the lower cover 5120, and this diaphragm 5130 partitions the diaphragm chamber 5140 and the pressure chamber 5150. A stopper 5160 is placed inside the lower cover 5120, and the operating shaft 5200 is in contact with this stopper 5160.

[0083] The diaphragm chamber 5140 is connected to the temperature sensing cylinder 5400 by a capillary tube 5300. Note that the capillary tube 5300 is partially omitted from the illustration in Figure 8. The temperature sensing cylinder 5400 is filled with, for example, the same gas (and liquid) as the refrigerant in the refrigeration cycle, and is attached to the outlet piping of the indoor heat exchanger (evaporator) in the refrigeration cycle, as described later. The first fitting pipe 5040 is connected to the outlet piping of the condenser in the refrigeration cycle, and the second fitting pipe 5050 is connected to the inlet piping of the evaporator.

[0084] As a result, the internal pressure of the diaphragm chamber 5140 changes according to the temperature sensed by the temperature sensing cylinder 5400 at the outlet piping of the evaporator. In addition, the pressure chamber 5150 is supplied with the inlet pressure of the evaporator through the communication passage 5500.

[0085] The operating shaft 5200 is in contact with the stopper 5160 and the spring retainer 5210, and the vertical movement of the valve body 5220 opens and closes the valve port 5230. The degree of overheating is controlled by adjusting the opening of the valve port through the balance of the diaphragm chamber 5140, the pressure chamber 5150, and the spring 5240.

[0086] In such an expansion valve 5000, the valve body 5010, which is the main body of the valve, corresponds to a brass component, and the lower cover 5120, which is a lower cover material positioned around the opening 5011 of the valve body 5010, corresponds to a stainless steel component. The valve body 5010 and the lower cover 5120 are brazed together with brazing material, with a washer-shaped Bi shielding layer 35 in between. At this time, it is also possible to braze the first joint pipe 5040, the second joint pipe 5050 and the valve body 5010 simultaneously.

[0087] One example of how these components are assembled in the expansion valve 5000 is to first braze the valve body 5010, which is made of brass, and the lower cover 5120, which is made of stainless steel, with the Bi shielding layer 35 sandwiched between them in a reducing atmosphere furnace, and then cool them in the reducing atmosphere furnace and then remove them from the reducing atmosphere furnace and allow them to cool at room temperature to form the joint structure.

[0088] In the expansion valve 5000, the Bi shielding layer 35 acts as a layer that suppresses the movement of Bi in the valve body 5010 to the first brazing material layer by brazing the stainless steel lower cover 5120 and the brass valve body 5010, and as a result, a decrease in the joint strength between the lower cover 5120 and the valve body 5010 can be suppressed.

[0089] <Solenoid valve 6000> The joint structure of the present invention can be used as a component in a solenoid valve. In this case, the brass member is the main body of the valve, and the stainless steel member is a cylindrical member positioned in the opening of the main body. As an example of a solenoid valve, Figure 9 shows a cross-sectional view of a solenoid valve 6000 equipped with the joint structure of the present invention.

[0090] The solenoid valve 6000 is installed in the refrigerant circulation cycle of, for example, an air conditioning system or a refrigerator. The solenoid valve 6000 comprises a valve body 6010 that constitutes the valve body, and an electromagnetic actuation coil 6020 connected to the valve body 6010 and controlling the movement of the valve element disposed inside the valve body 6010. The valve body 6010 has a valve chamber 6030, and a first coupling pipe 6040 and a second coupling pipe 6050 are connected to this valve chamber 6030 so as to communicate with each other via a valve seat 6060.

[0091] The valve body 6060 is equipped with a valve element 6070, which is made of a ball or the like, that opens and closes the fluid passage by moving in a direction away from the seat. The valve body 6010 is also equipped with a plunger moving cylinder 6080, one end of which is connected to the valve body 6070. Within this plunger moving cylinder 6080 is a plunger 6090 which is axially movable and has one end of which is connected to the valve element 6070.

[0092] Furthermore, a suction element 6100 is fixed to the other end of the plunger movement cylinder 6080 so as to face the other end of the plunger 6090. Between the plunger 6090 and the suction element 6100, a biasing member 6110, such as a coil spring, is interposed to bias the plunger 6090 away from the suction element 6100. An electromagnetic operating coil 6020 is fixed to the upper part of the suction element 6100 via an outer casing member 6130 by fastening members 6120 such as bolts.

[0093] Furthermore, a coil member 6140 that generates magnetic flux when energized is arranged on the outer circumference of the plunger moving cylinder 6080. In Figure 9, reference numeral 6150 denotes the bobbin case and reference numeral 6160 denotes the lead wire. In the solenoid valve 6000 configured in this way, by energizing (applying voltage) the coil member 6140, a magnetic flux is generated in a direction that attracts the plunger 6090 to the attractor 6100, thereby generating an attractive force. As a result, the plunger 6090 is attracted to the attractor 6100, and the valve body 6070 moves away from the valve seat 6060, thereby opening the fluid passage, i.e., opening the valve.

[0094] On the other hand, by de-energizing the coil member 6140, the magnetic flux is eliminated, and the attractive force acting between the plunger 6090 and the suction element 6100 is also eliminated. As a result, the biasing force of the biasing member 6110 causes the plunger 6090 to move away from the suction element 6100 and move in the direction in which the valve body 6070 seats on the valve seat 6060, thereby closing the fluid passage, i.e., closing the valve.

[0095] Figure 10 shows an enlarged cross-sectional view of region C, which is the joint structure portion of the solenoid valve shown in Figure 9. Although the brazing layer is thin and therefore omitted from Figure 9, as shown in Figure 10, the joint structure 120 has a layered structure in which, in order, a plunger movement cylinder 6080 made of stainless steel, a first brazing layer 22, a Bi shielding layer 36, a second brazing layer 42, and a valve body 6010 made of brass are arranged in layers.

[0096] In this type of solenoid valve 6000, the valve body 6010, which is the main body of the valve, corresponds to a brass component, and the plunger movement cylinder 6080, which is a cylindrical component positioned in the opening 6011 of the valve body 6010, corresponds to a stainless steel component. The valve body 6010 and the plunger movement cylinder 6080 are brazed together with brazing material, with a cylindrical Bi shielding layer 36 in between.

[0097] One example of assembling these components in the solenoid valve 6000 is to first braze the valve body 6010, which is made of brass, and the plunger moving cylinder 6080, which is made of stainless steel, with a Bi shielding layer 36 sandwiched between them in a reducing atmosphere furnace. Then, the components are cooled in the reducing atmosphere furnace and then removed from the reducing atmosphere furnace and cooled at room temperature to form the joint structure 120. At this time, it is also possible to braze the first joint pipe 6040, the second joint pipe 6050, and the valve body 6010 simultaneously.

[0098] In the solenoid valve 6000, the Bi shielding layer 36 acts as a layer that suppresses the movement of Bi in the valve body 6010 to the first brazing material layer 22 by brazing the plunger movement cylinder 6080, which is made of stainless steel, and the valve body 6010, which is made of brass. As a result, a decrease in the joint strength between the plunger movement cylinder 6080 and the valve body 6010 can be suppressed.

[0099] [Method for manufacturing a joint structure 1] Next, as an example of a method for manufacturing the joint structure of the present invention, manufacturing method 1 will be described. This manufacturing method is capable of manufacturing the above-described joint structure of the present invention and includes a first layer structure formation step, a first brazing step, and a first cooling step. Hereinafter, the joint structure 100 will be described as an example, with reference to the perspective view in Figure 11 showing an example of each component constituting the first layer structure 600, and the partial cross-sectional view of the first layer structure 600 in Figure 12.

[0100] <First layer structure formation process> In this process, the stainless steel member 10, the first brazing material 25, the Bi shielding layer 30, the second brazing material 45, and the brass member 50 shown in Figure 11 are arranged in layers in order to form the first layer structure 600. The shapes of each member are as follows: for example, the stainless steel member 10 is a disc-shaped plate with an open bottom; the first brazing material 25, the Bi shielding layer 30, and the second brazing material 45 are washer-shaped; and the brass member 50 is a hexagonal prism-shaped.

[0101] The method for forming the first layer structure 600 is not particularly limited. The first layer structure 600 may be formed by stacking the second brazing material 45, the Bi shielding layer 30, the first brazing material 25, and the stainless steel member 10 in order on top of the brass member 50, or by stacking the first brazing material 25, the Bi shielding layer 30, the second brazing material 45, and the brass member 50 in order on top of the stainless steel member 10. In addition to forming the first layer structure in the vertical direction, the layer structure may also be formed in the horizontal direction.

[0102] The first layer structure may be formed manually or automatically using equipment, for example, under atmospheric pressure of around 1 atmosphere at a temperature of 0°C to 50°C. However, performing this process at temperatures above 680°C is undesirable because it may cause the first brazing material 25 and the second brazing material 45 to melt.

[0103] The stainless steel member 10, brazing material, Bi shielding layer 30, and brass member 50 that can be used in the manufacture of the joint structure are as described above, and their explanation is omitted. The first brazing material 25 and the second brazing material 45 may be brazing materials of the same composition.

[0104] <First Brazing Process> In this process, the first layer structure 600 is heated and brazed so that the temperatures of the first brazing material 25 and the second brazing material 45 reach 680-800°C.

[0105] Heating can be carried out under atmospheric pressure of around 1 atmosphere or under a reducing gas atmosphere such as hydrogen or ammonia. Specifically, this process can be carried out by placing the first layer structure 600 in a heating device such as an oven, heating furnace, or reducing atmosphere furnace. The holding time for maintaining the temperature of the first and second brazing materials at 680-800°C can be set to, for example, 5-10 minutes.

[0106] Alternatively, the stainless steel member 10 and the brass member 50 may be brazed by heating the first layer structure 600 using a burner. The holding time for maintaining the temperature of the first and second brazing materials at 680-800°C can be set to, for example, several tens of seconds.

[0107] <First cooling process> In this process, the first layer structure 600 after the first brazing process is cooled to form a joint structure 100 having a layered structure in which the stainless steel member 10, the first brazing material layer 20, the Bi shielding layer 30, the second brazing material layer 40, and the brass member 50 are arranged in layers. Upon cooling, the liquid first brazing material and the second brazing material solidify to become the first brazing material layer 20 and the second brazing material layer 40, respectively, and the joint structure 100 is manufactured.

[0108] The method for cooling the first layer structure 600 in this process is not particularly limited. For example, the first layer structure, which was installed in the heating device during the brazing process, can be removed from the heating device and allowed to cool naturally in an atmospheric atmosphere of approximately 0°C to 50°C and 1 atmosphere.

[0109] [Method for manufacturing a joint structure 2] Next, as an example of a method for manufacturing the joint structure of the present invention, manufacturing method 2 will be described. This manufacturing method is capable of manufacturing the above-described joint structure of the present invention and includes a second layer structure formation step, a second brazing step, and a second cooling step. Hereinafter, the joint structure 100 will be used as an example and explained with reference to Figures 13 to 19.

[0110] <Second layer structure formation process> In this process, the stainless steel member 10, the Bi shielding layer 30, and the brass member 50 are arranged in layers in order. At the same time, the first brazing material 25 is placed between the stainless steel member 10 and the Bi shielding layer 30 (Figure 13) to form the second layer structure 700 (Figure 14). Furthermore, the second brazing material 46 is placed between the Bi shielding layer 30 and the brass member 50 (Figure 15) to form the second layer structure 800 (Figure 16).

[0111] The shapes of each component are as follows: for example, the stainless steel component 10 is a disc-shaped plate with an open bottom, the Bi shielding layer 30 is washer-shaped, and the brass component 50 is hexagonal prism-shaped.

[0112] Figures 18 and 19 show enlarged partial cross-sectional views of a portion of the area D enclosed by the dotted line in the partial cross-sectional view of the solenoid valve 6000 shown in Figure 17. As shown in these figures, the plunger moving cylinder 6080 (corresponding to a stainless steel member), the Bi shielding layer 36, and the valve body 6010 (corresponding to a brass member) may be arranged in layers in order, and one third brazing rod 27 may be placed on the side surface of the Bi shielding layer 36 to form a second layer structure 900 (Figure 18). Alternatively, a second brazing rod 28 may be placed between the Bi shielding layer 36 and the valve body 6010, and a third brazing rod 29 may be placed on the side surface of the Bi shielding layer 36 to form a second layer structure 950 (Figure 19). Furthermore, two or more third brazing rods may be placed on the side surface of the Bi shielding layer 36.

[0113] Furthermore, from the viewpoint of simplifying the manufacturing process and managing the number of brazing material components, it is preferable to use only one brazing material, that is, the second layer structure 900 is preferable to the second layer structure 950 from the above viewpoint.

[0114] Furthermore, the third brazing material 27 may have a spring washer shape similar to the first brazing material 25 shown in Figure 11, or it may have a flat washer shape like the second brazing material 45. The same applies to the shapes of the second brazing material 46, the second brazing material 28, and the third brazing material 29.

[0115] The method for forming the second layer structures 700 and 800 is not particularly limited. The second layer structures 700 and 800 may be formed by stacking the Bi shielding layer 30 and the stainless steel member 10 on top of the brass member 50, or by stacking the Bi shielding layer 30 and the brass member 50 on top of the stainless steel member 10. In addition to forming the second layer structures in the vertical direction, the layer structure may also be formed in the horizontal direction. The same applies to the second layer structures 900 and 950, and the method of formation is not particularly limited.

[0116] The formation of the second layer structures 700, 800, 900, and 950 may be done manually or automatically using equipment, for example, by performing the process in an atmospheric pressure atmosphere of approximately 1 atmosphere at a temperature of 0°C to 50°C. However, performing the process at a temperature of 680°C or higher is undesirable because it may cause the first brazing material 25, second brazing material 46, third brazing material 27, second brazing material 28, and third brazing material 29 to melt.

[0117] The stainless steel member 10, brazing material, Bi shielding layer 30, and brass member 50 that can be used in the manufacture of the joint structure are as described above, and their explanation will be omitted.

[0118] <Second Brazing Process> In this process, the second layer structure 700 is heated and brazed so that the temperature of the first brazing material 25 reaches 680-800°C. The same procedure is followed for the second layer structures 800, 900, and 950.

[0119] Heating can be carried out under atmospheric pressure of around 1 atmosphere or under a reducing gas atmosphere such as hydrogen or ammonia. Specifically, this process can be performed by placing the second layer structure 700 inside a heating device such as an oven, heating furnace, or reducing atmosphere furnace. The holding time for maintaining the temperature of the first brazing material 25 at 680-800°C can be set to, for example, 5-10 minutes. The same applies to the second layer structures 800, 900, and 950.

[0120] Alternatively, the stainless steel member 10 and the brass member 50 may be brazed by heating the second layer structure 700 using a burner. The holding time for maintaining the temperature of the first brazing material 25 at 680-800°C can be set to, for example, several tens of seconds. The same applies to the second layer structures 800, 900, and 950.

[0121] As explained in the second layer structure formation process, there are various ways in which the first brazing material 25, second brazing material 46, third brazing material 27, second brazing material 28, and third brazing material 29 are arranged. However, in the second brazing process, the first brazing material 25, second brazing material 46, third brazing material 27, second brazing material 28, and third brazing material 29 melt, and by capillary action, the first brazing material 25, second brazing material 46, third brazing material 27, second brazing material 28, and third brazing material 29 enter between the stainless steel 10 and the barrier layer 30, between the barrier layer 30 and the brass member 50, and between the plunger moving cylinder 6080 and the Bi shielding layer 36, and between the barrier layer 36 and the valve body 6010.

[0122] <Second cooling process> In this process, the second layer structure 700 after the second brazing process is cooled to form a joint structure 100 having a layered structure in which the stainless steel member 10, the first brazing material layer 20, the Bi shielding layer 30, the second brazing material layer 40, and the brass member 50 are arranged in layers. Upon cooling, the liquid first brazing material 25 solidifies into the first brazing material layer 20 and the second brazing material layer 40, respectively, and the joint structure 100 is manufactured. The same process is followed for the second layer structures 800, 900, and 950.

[0123] The method for cooling the second layer structures 700, 800, 900, and 950 in this process is not particularly limited. For example, the second layer structures 700, 800, 900, and 950, which were installed in the heating device during the second brazing process, can be removed from the heating device and allowed to cool naturally in an atmospheric atmosphere of approximately 0°C to 50°C and 1 atmosphere.

[0124] <Other processes> The manufacturing methods 1 and 2 for the joint structure of the present invention may include methods other than those described above. For example, these may include a removal step to remove dirt, deposits, oxides, and other factors that hinder brazing from the surface of each of the stainless steel member 10, the Bi shielding layer 30, and the brass member 50 that comes into contact with the brazing material, and a step to apply flux to improve the wettability of the brazing material. The same applies to each of the plunger moving cylinder 6080, the Bi shielding layer 36, and the valve body 6010. [Examples]

[0125] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0126] [Preparation of test specimens] <Example 1> As a test specimen, a joint structure 100 (the same as the joint structure 110 shown in Figure 5) was prepared, as shown in Figure 1(C). Specifically, a hexagonal prism-shaped brass member 50 (the same as joint 2040) (C6803 Pb content 0.01 mass% or less, Bi content 0.5~4.0 mass%) with a diagonal distance of 15 mm and a height of 18 mm was stacked in the following order to form the first layer structure (first layer structure formation process). This was followed by a washer-shaped second brazing material (BAg-7) with an outer diameter of 15 mm and a thickness of 0.15 mm, a washer-shaped Bi shielding layer 30 (C2801) with an outer diameter of 15 mm and a thickness of 0.6 mm, a washer-shaped first brazing material (BAg-7) with an outer diameter of 15 mm and a thickness of 0.15 mm, and a disc-shaped stainless steel 10 (the same as lid 2030) (SUS304) with an outer diameter of 21 mm and a thickness of 0.8 mm. Then, this first layer structure was placed in a hydrogen atmosphere reduction furnace and held in the temperature range of 680°C to 720°C for 6 minutes (first brazing step). After the first brazing step, the first layer structure was cooled in the furnace, and then removed from the reduction furnace and cooled to 25°C by air cooling in a 25°C atmospheric pressure atmosphere (first cooling step) to produce the joint structure 100, which was used as the test specimen for Example 1. Multiple test specimens were prepared for use in joint strength confirmation tests and SEM observation.

[0127] <Conventional Example 1> A brass member 60 (C3604 Pb content 1.8-3.7% by mass) with the same shape and dimensions as the joint 2040 of Example 1 was used to form a layered structure by stacking a washer-shaped brazing material (BAg-7) with an outer diameter of 15 mm and a thickness of 0.15 mm, and a disc-shaped stainless steel 10 (SUS304) with an outer diameter of 21 mm and a thickness of 0.8 mm, the same as in Example 1. Then, the first brazing process and the first cooling process were performed on this layered structure in the same manner as in Example 1 to produce a joint structure 200 in which the brass member 60 and stainless steel 10 were brazed with the brazing material layer 70, and this was used as the test specimen for Conventional Example 1. Multiple test specimens were prepared for use in confirming the joint strength and for SEM observation.

[0128] <Comparative Example 1> A brass member 50 (C6803, Pb content 0.01% by mass or less, Bi content 0.5-4.0% by mass) with the same shape as in Example 1 was used to form a layered structure by stacking a washer-shaped brazing material (BAg-7) with the same outer diameter of 15 mm and thickness of 0.15 mm as in Conventional Example 1, and a disc-shaped stainless steel 10 (SUS304) with the same outer diameter of 21 mm and thickness of 0.8 mm as in Example 1. Then, the first brazing process and the first cooling process were performed on this layered structure in the same manner as in Example 1 to produce a joint structure 300 in which the brass member 50 and stainless steel 10 were brazed with the brazing material layer 80, and this was used as the test specimen for Comparative Example 1. Multiple test specimens were prepared for use in confirming the joint strength and for SEM observation.

[0129] [Confirmation of joint strength] To confirm the bonding strength between brass and stainless steel, the tensile strength of the test specimen was measured using a tensile testing machine. Figure 2 shows a side view of the test specimen and the jig used in the bonding strength confirmation test. Figure 2(A) shows the state before assembly of the jig and test specimen, and Figure 2(B) shows the state after assembly of the jig and test specimen. In Figure 2, the bonding structure 200, which is the test specimen of Conventional Example 1, is shown as an example, and the bonding strength confirmation test was performed using the upper jig 400 and the lower jig 500.

[0130] The inner surface 510 of the lower jig 500 has a shape corresponding to the outer shape of the joining structure 200. Insert the brass member 60 side of the joining structure 200 into the lower jig 500 and install it so that the brass member 60 protrudes from below the lower jig 500. Next, insert the upper jig 400 into the inner surface 510 of the lower jig 500. Here, the side surface 410 of the upper jig 400 is thread-cut so as to be a male thread, and the side surface 520 of the inner surface 510 of the lower jig 500 is thread-cut so as to have a female thread shape corresponding to the male thread shape of the side surface 410. Then, by inserting the upper jig 400 into the inner surface 510 of the lower jig 500 while rotating the upper jig 400 to the state of FIG. 2(B), it is possible to make the upper jig 400 and the lower jig 500 not come off even when pulled in the vertical direction.

[0131] After bringing it to the state of FIG. 2(B), using a tensile testing machine, grasp and fix the side (gripping part 220) around the sign 220 of the brass member 60 of the joining structure 200, and further grasp the side (gripping part 420) around the sign 420 of the upper jig 400 and pull the upper jig 400 vertically upward to measure the joining strength of the joining structure 200.

[0132] The joining strength of the joining structure 200 which is the test piece of the conventional example 1 is 100 N / mm 2 or more, and sufficient strength that can be used for the above components was exhibited.

[0133] Similarly, when the joining strength of the joining structure 100 which is the test piece of Example 1 was measured, the joining strength was 100 N / mm 2 or more, and since it was a strength sufficiently exceeding 100 N / mm 2 sufficient strength that can be used for the above components was exhibited.

[0134] Also, when the joining strength of the joining structure 300 which is the test piece of Comparative Example 1 was measured in the same manner, the joining strength was less than 100 N / mm 2 and since it was a strength far below 100 N / mm 2 sufficient strength that can be used for the above components could not be exhibited.

[0135] [SEM observation and elemental mapping] Cross-sections of the test specimens (joint structures 100, 200, and 300) of Example 1, Conventional Example 1, and Comparative Example 1 were photographed using a scanning electron microscope (SEM). These SEM images are shown in Figure 1. As shown in Figure 1(C), the first brazing layer 20 and the second brazing layer 40 are shielded by the Bi shielding layer 30, and it was confirmed that the arrangement of the Bi shielding layer 30 prevents the bismuth contained in the brass member 50 from moving to the first brazing layer 20.

[0136] Furthermore, elemental mapping of bismuth was performed on the cross-sections of the test specimens of Example 1, Conventional Example 1, and Comparative Example 1 using energy-dispersive X-ray spectroscopy (EDS). Figure 20 shows an image of the test specimen of Example 1 (joint structure 100), and Figure 21 shows an image of the test specimen of Comparative Example 1 (joint structure 300).

[0137] As a result of elemental mapping, it was confirmed that bismuth was scattered in the second brazing layer 40 of the specimen in Example 1 (Figure 20(B)), but no bismuth was present in the first brazing layer 20 (Figure 20(A)). Furthermore, the brazing layer 80 of the specimen in Comparative Example 1 contained more bismuth than the second brazing layer 40, and bismuth segregated in a planar manner was confirmed near the interface between the brazing layer 80 and the stainless steel 10. In Conventional Example 1, a brass member 60 that did not use bismuth was used, so bismuth was not detected in the brazing layer 70.

[0138] [summary] From the above, the results of Comparative Example 1 show that the joint strength is reduced because bismuth is segregated in a planar manner near the interface between the brazing material layer 80 and the stainless steel 10. Furthermore, the results of Example 1 show that by using the Bi shielding layer 30, even when using a brass member 50 containing bismuth, the bismuth migrating from the brass member 50 can be shielded by the Bi shielding layer 30, thus preventing a decrease in joint strength and providing sufficient joint strength, similar to Conventional Example 1.

[0139] Furthermore, second joint structures 700, 800, 900, and 950 were prepared using the method described in [Method for Manufacturing Joint Structure 2], and joint structure 100 was manufactured based on the test specimen preparation method described in Example 1, using the same heating and cooling processes as the same members. Then, the joint strength was confirmed, and SEM observation and elemental mapping were performed in the same manner as in Example 1.

[0140] As a result, all of the joint structures 100 exhibited a joint strength of 100 N / mm², similar to the test specimen in Example 1. 2 That's all, 100 N / mm 2 The strength was well above the limit. Furthermore, the observation results from SEM and elemental mapping were the same as those of the test specimen in Example 1.

[0141] In other words, even when the joint structure 100 is manufactured by the method described in [Method for Manufacturing Joint Structure 2], by using the Bi shielding layer 30, etc., even when using brass members 50 etc. containing bismuth, the bismuth that moves from the brass members 50 etc. can be shielded by the Bi shielding layer 30, etc., thus preventing a decrease in joint strength and ensuring sufficient joint strength.

[0142] As described above, the present invention is industrially useful because it provides a joint structure and a method for manufacturing the joint structure that can suppress a decrease in joint strength even when brass containing bismuth instead of lead and stainless steel are joined by brazing using a brazing material. [Explanation of Symbols]

[0143] 10: Stainless steel member, 20: First brazing layer, 21: First brazing layer, 22: First brazing layer, 25: First brazing material, 27: Third brazing material, 28: Second brazing material, 29: Third brazing material, 30: Bi shielding layer, 31: Bi shielding layer, 32: Bi shielding layer, 33: Bi shielding layer, 34: Bi shielding layer, 35: Bi shielding layer, 36: Bi shielding layer, 40: Second brazing layer, 41: Second brazing layer, 42: Second brazing layer, 45: Second brazing material, 46: Second brazing material, 50: Brass member, 60: Brass member, 70: Brazing layer, 80: Brazing layer, 100: Joint structure, 110: Joint structure, 120: Joint structure, 2 00: Joint structure, 220: Gripping part, 300: Joint structure, 400: Upper jig, 410: Side view, 420: Gripping part, 500: Lower jig, 510: Inner surface, 520: Side view, 600: First layer structure, 700: Second layer structure, 800: Second layer structure, 900: Second layer structure, 950: Second layer structure, 1000: Pressure sensor, 1010: Inlet passage, 1020: Joint, 1030: Cover, 1040: Insulating member, 1050: Pressure sensing element, 1060: Diaphragm, 1070: Header, 1080: Stem, 1090: Lead pin, 1100: Case, Sealing material: 1110, 2000: Pressure Force switch, 2010: Metal diaphragm, 2020: Pressure-sensitive chamber, 2030: Cover, 2040: Joint, 2050: Movable contact, 2051: Fixed contact, 2052: Contact part, 2060: O-ring, 2070: Holder member, 2080: Intermediate plate member, 2090: Case member, 2100: Connection terminal piece, 2110: Connection terminal piece, 2120: Stopper, 2130: Outer circumference, 2140: Diaphragm unit, 2150: Actuating rod, 3000: Motorized valve, 3010: Valve body, 3011: Valve chamber, 3012: Pipe connection hole, 3013: Pipe connection hole, 3014: Valve port, 3015 : Valve body, 3016: Opening, 3020: First joint pipe, 3030: Second joint pipe, 3040: Male threaded member, 3050: Cover case, 3100: Stepping motor, 3101: Coil, 3102: Lead wire, 3110: Rotor case, 3200: Rotor, 3210: Fixing member, 3220: Female threaded member, 3230: Magnet, 3240: Operating shaft, 3300: Stopper holding rod, 3310: Helical guide, 3320: Movable stopper, 4000: Adjustment valve, 4010: Valve body, 4011: Opening, 4020: Pipe connection hole, 4030: Pipe connection hole, 4040: Valve chamber,4050: Valve insertion hole, 4060: Secondary port, 4070: Spring chamber, 4071: Coil spring, 4072: Spring seat, 4073: Bottom, 4080: Valve port, 4090: Valve body, 4100: First joint tube, 4200: Second joint tube, 4300: Diaphragm, 4310: Flat section, 4400: Bottom cover, 4500: Top cover, 4600 :Pressure chamber, 5000:Expansion valve, 5010:Valve body, 5011:Opening, 5020:Pipe connection hole, 5030:Pipe connection hole, 5040:First joint pipe, 5050:Second joint pipe, 5100:Diaphragm device, 5110:Top cover, 5120:Bottom cover, 5130:Diaphragm, 5140:Diaphragm chamber, 5150:Pressure chamber, 51 60: Valve body, 5200: Actuating shaft, 5210: Spring retainer, 5220: Valve body, 5230: Valve port, 5240: Spring, 5300: Capillary tube, 5400: Temperature sensor, 5500: Communication passage, 6000: Solenoid valve, 6010: Valve body, 6011: Opening, 6020: Electromagnetic actuation coil, 6030: Valve chamber, 6040: First coupling tube , 6050: Second joint pipe, 6060: Valve seat, 6070: Valve body, 6080: Plunger moving cylinder, 6090: Plunger, 6100: Suction element, 6110: Biasing member, 6120: Fastening member, 6130: Outer casing member, 6140: Coil member, 6150: Bobbin case, 6160: Lead wire, A: Area, B: Outer periphery, C: Area,

Claims

1. A joint structure in which a stainless steel member and a brass member are brazed together, The brazing process results in a layered structure in which the stainless steel member, the first brazing layer, the Bi shielding layer, the second brazing layer, and the brass member are arranged in layers in that order. The brass member contains Bi, The Bi shielding layer is a layer that suppresses the movement of Bi in the brass member to the first brazing layer by brazing the stainless steel member and the brass member, in a joining structure.

2. The bonding strength between the stainless steel member and the brass member is 100 N / mm². ２ The joining structure described in claim 1 is as described above.

3. The joining structure according to claim 1, wherein the brass member is a joint for a pressure sensor, and the stainless steel member is a dish-shaped cover attached to the joint for the pressure sensor.

4. The joining structure according to claim 1, wherein the brass member is a joint for a pressure switch, and the stainless steel member is a dish-shaped cover attached to the joint for the pressure switch.

5. The joining structure according to claim 1, wherein the brass member is the main body of the valve, and the stainless steel member is a lower cover material positioned around the opening of the main body.

6. The joining structure according to claim 1, wherein the brass member is the main body of the valve, and the stainless steel member is a cylindrical member positioned in the opening of the main body.

7. A method for manufacturing the joint structure according to claim 1, The process involves forming a first layer structure by arranging the stainless steel member, the first brazing material, the Bi shielding layer, the second brazing material, and the brass member in layers, in that order. A first brazing step involves heating the first layer structure to braze the stainless steel member and the brass member, A first cooling step involves cooling the first layer structure after the first brazing step to form a joint structure having a layered structure in which the stainless steel member, the first brazing layer, the Bi shielding layer, the second brazing layer, and the brass member are arranged in layers, A method for manufacturing a bonded structure, including the method described above.

8. The method for manufacturing a joint structure according to claim 7, wherein the first brazing material and the second brazing material are brazing materials having the same composition.

9. The method for manufacturing the joint structure according to claim 7, wherein the Bi shielding layer is in the shape of a washer.

10. The method for manufacturing the joint structure according to claim 7, wherein the Bi shielding layer is cylindrical.

11. A method for manufacturing the joint structure according to claim 1, The process involves forming a second layer structure by arranging the stainless steel member, the Bi shielding layer, and the brass member in layers, and then placing brazing material between the stainless steel member and the Bi shielding layer, between the Bi shielding layer and the brass member, or on the side surface of the Bi shielding layer, A second brazing step involves heating the aforementioned two-layer structure to braze the stainless steel member and the brass member, A second cooling step involves cooling the second layer structure after the second brazing step to form a joint structure having a layered structure in which the stainless steel member, the first brazing layer, the Bi shielding layer, the second brazing layer, and the brass member are arranged in layers, A method for manufacturing a bonded structure, including the method described above.

12. The method for manufacturing the bonding structure according to claim 11, wherein the Bi shielding layer is in the shape of a washer.

13. The method for manufacturing the joint structure according to claim 11, wherein the Bi shielding layer is cylindrical.

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