Manufacturing method of electronic expansion valve

Abstract

According to the manufacturing method of the electronic expansion valve, materials of a valve seat and an outer cover are different, and the manufacturing method comprises the following steps that a rotor assembly, a valve needle assembly, a nut assembly and the valve seat are assembled; the rotor assembly is sleeved with the outer cover, the lower end of the outer cover is inserted into the valve seat, the welding flux is placed on the peripheral side of the outer cover and makes contact with the valve seat, and a welding assembly is formed; the welding assembly is placed in a welding furnace to be brazed; and the periphery of the brazed outer cover is sleeved with a coil assembly. According to the scheme, the valve seat and the outer cover which are made of different materials are fixed through brazing, so that cost and connection reliability are both considered.

Description

Technical Field

[0001] The invention relates to the technical field of valve processing, and in particular to a method for manufacturing an electronic expansion valve. Background Art

[0002] The electronic expansion valve includes a coil assembly, a rotor assembly, a valve needle assembly, a nut assembly and a valve seat, wherein the valve needle assembly and the nut assembly, as well as the rotor assembly, are all located in the outer cover, which abuts against the valve seat along the axial direction, and the outer cover plays a role in protecting the internal components. The outer cover and the valve seat are generally made of stainless steel, which is relatively expensive. Summary of the invention

[0003] The purpose of the present application is to provide a method for manufacturing an electronic expansion valve, which fixes a valve seat and an outer cover made of different materials by brazing, so as to take into account both cost and connection reliability.

[0004] The application provides a method for manufacturing an electronic expansion valve, the electronic expansion valve comprising a rotor assembly, a valve needle assembly, a valve seat, an outer cover and a coil assembly, the coil assembly driving the rotor assembly to rotate so as to drive the valve needle assembly to rotate, at least part of the rotor assembly is located in the inner cavity of the outer cover, and part of the valve needle assembly is located in the inner cavity of the outer cover; the valve seat and the outer cover are made of different materials, and the manufacturing method comprises the following steps:

[0005] Assembling the rotor assembly, the valve needle assembly, the nut assembly and the valve seat;

[0006] The outer cover is placed over the rotor assembly, and the lower end of the outer cover is inserted into the valve seat, and the solder is placed on the peripheral side of the outer cover and contacts the valve seat to form a welded assembly;

[0007] Placing the welding assembly into a welding furnace for brazing;

[0008] The coil assembly is sleeved on the outer circumference of the brazed outer cover.

[0009] In the present application, the material of the valve seat is different from that of the outer cover, which can achieve a combination of corrosion resistance and light weight, and can also save materials and reduce costs. At this time, in order to realize the manufacture of an electronic expansion valve of this structure, the outer cover and the valve seat are brazed together by solder. That is, the present application fixes the valve seat and the outer cover of different materials by brazing, so as to take into account both cost and connection reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the structure of the electromagnetic expansion valve in the embodiment of the present application;

[0011] Figure 2 for Figure 1A cross-sectional view of the electromagnetic expansion valve along the AA direction;

[0012] Figure 3 for Figure 1 Schematic diagram of the structure of the middle and outer covers;

[0013] Figure 4 for Figure 1 Schematic diagram of the structure of the middle valve seat;

[0014] Figure 5 for Figure 4 Axial section view of the middle valve seat;

[0015] Figure 6 for Figure 2 Schematic diagram of the assembly of the middle valve seat and the lower end of the outer cover;

[0016] Figure 7 for Figure 6 A magnified view of position B in the middle;

[0017] Figure 8 for Figure 7 Schematic diagram of the middle valve seat;

[0018] Fig. 9 for Figure 6 An enlarged view of the gap between the inner and outer covers and the valve seat;

[0019] Fig.10 This is a schematic diagram of another assembly of a valve seat and a lower end of an outer cover in an embodiment of the present application;

[0020] Fig.11 for Fig.10 Magnified view of area C in the middle.

[0021] Figure 1-11 The reference numerals in the drawings are described as follows:

[0022] 100-electronic expansion valve;

[0023] 1- Outer cover;

[0024] 2-Rotor assembly;

[0025] 3-Nut assembly;

[0026] 4-valve needle assembly;

[0027] 5-Fixed seat;

[0028] 6-valve seat; 6a-through hole portion; 61-annular boss; 62-step portion; 621-step side wall; 6211-first side wall section; 6211a-chamfered portion; 6212-second side wall section; 622-step surface; 63-upper end surface;

[0029] 7- first sealing ring;

[0030] 8- second sealing ring;

[0031] 9-bearing seat;

[0032] 10- Solder;

[0033] 11- Sealing ring;

[0034] 12-Coil assembly. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Please refer to Figures 1 to 5 , Figure 1 This is a schematic diagram of the structure of the electromagnetic expansion valve in the embodiment of the present application; Figure 2 for Figure 1 The cross-sectional view of the electromagnetic expansion valve along the AA direction is also the axial cross-sectional view of the electronic expansion valve; Figure 3 for Figure 1 Schematic diagram of the structure of the middle and outer covers; Figure 4 for Figure 1 Schematic diagram of the structure of the middle valve seat; Figure 5 for Figure 4 Axial section view of the middle valve seat.

[0037] The electronic expansion valve 100 in this embodiment includes a rotor assembly 2, a valve needle assembly 4, a nut assembly 3, a valve seat 6, an outer cover 1, and a coil assembly 12. The rotor assembly 2 is located outside the valve needle assembly 4, and part of the valve needle assembly 4 is located inside the outer cover 1. The nut assembly 3 and the rotor assembly 2 are located inside the outer cover 1. The nut assembly 3 is provided with an internal thread, and the valve needle assembly 4 has an external thread. The two threads are matched. The coil assembly 12 drives the rotor assembly 2 to rotate, so as to drive the valve needle assembly 4 to rotate. Then, the valve needle assembly 4 is threadedly driven relative to the nut assembly 3, thereby forming an axial movement of the valve needle assembly 4. In this embodiment, the electronic expansion valve 100 also includes a fixed seat 5. The annular fixed seat 5 is fixed to the valve seat 6. Part of the fixed seat 5 is located inside the valve seat 6. The nut assembly 3 is specifically fixed to the fixed seat 5. Of course, the nut assembly 3 can also be directly fixed to the valve seat 6. In addition, the electronic expansion valve 100 is also provided with a bearing seat 9, which is provided with a valve port of the electronic expansion valve 100, and is a component that forms a fluid passage and plays a throttling role. Part of the bearing seat 9 is inserted into the valve seat 6 and the fixed seat 5, and the valve needle assembly 4 can move axially in the bearing seat 9 to open and close the valve port. A first sealing ring 7 is provided on the outer periphery of the valve seat 6, and a second sealing ring 8 is provided on the outer periphery of the bearing seat 9 to play a sealing role.

[0038] The outer cover 1 of the electronic expansion valve 100 is enclosed by the rotor assembly 2, the end of the outer cover 1 away from the valve seat 6 is the upper end, and the end of the outer cover 1 close to the valve seat 6 is the lower end. The upper and lower directions are defined by this reference in the axial direction, as shown in FIG. Figure 2 The upper end of the outer cover 1 is closed, that is, the outer cover 1 has a cylindrical portion 11 and a top portion 12, and the lower end of the outer cover 1 is open. The outer cover 1 and the valve seat 6 are fixed to form a mounting cavity, and the above-mentioned rotor assembly 12, valve needle assembly 4, fixed seat 5, etc. are all installed in the mounting cavity. The coil assembly 12 of the electronic expansion valve 100 is sheathed on the outer periphery of the outer cover 1, and the coil assembly 12 can drive the rotor assembly 2 inside the outer cover 1 to rotate. A sealing ring 11 is arranged between the coil assembly 12 and the valve seat 6 to play a sealing role.

[0039] You can continue to refer to Figures 6 to 8 , Figure 6 for Figure 2 Schematic diagram of the assembly of the middle valve seat and the lower end of the outer cover; Figure 7 for Figure 6 A magnified view of position B in the middle; Figure 8 for Figure 7 Schematic diagram of the middle valve seat.

[0040] In this embodiment, the material of the valve seat 6 is different from that of the outer cover 1. For example, the valve seat 6 can be made of aluminum alloy, and the outer cover 1 can be made of stainless steel. Stainless steel and aluminum alloy are heterogeneous materials. The combination of the two has excellent corrosion resistance and light weight, and can also save materials and reduce costs. At this time, in order to realize the manufacture of the electronic expansion valve 100 of this structure, as shown in FIG. Figure 5 , 6 As shown, the valve seat 6 has a through hole portion 6a that penetrates in the axial direction. At this time, the upper end surface 63 of the valve seat 6 is an annular end surface. The upper end surface 63 of the valve seat 6 is provided with an annular boss 61. The annular boss 61 can be integrally formed with the valve seat 6, or formed by post-processing. The inner wall of the valve seat 6 is provided with an annular step portion 62. The step portion 62 includes a step side wall 621 and a step surface 622. The step side wall 621 extends in the axial direction, and the step surface 622 extends radially and is arranged upward. When assembled, as shown in FIG. Figure 7 As shown, the lower end surface of the outer cover 1 and the step surface 622 of the valve seat 6 abut axially, that is, Figure 7 From the perspective, the lower end surface of the outer cover 1 is supported on the step surface 622. At this time, the outer wall of the outer cover 1, the step surface 622 and the annular boss 61 form an annular groove.

[0041] On this basis, this embodiment provides a method for manufacturing an electronic expansion valve 100 by brazing, and the manufacturing method specifically includes the following steps:

[0042] S1, assembling the rotor assembly 2, the nut assembly 3, the valve needle assembly 4 and the valve seat 6;

[0043] It can be seen that when the fixing seat 5 is set, the fixing seat 5 can be fixed to the valve seat 6, and then the nut assembly 3 and the fixing seat 5 are fixed. The fixing method can be riveting, or other fixing connection methods such as interference fit; when the bearing seat 9 is set, the bearing seat 9 can be fixed to the valve seat 6 first, and then the fixing seat 5 is installed;

[0044] S2, put the outer cover 1 onto the rotor assembly 2, and insert the lower end of the outer cover 1 into the valve seat 6, specifically, make the lower end of the outer cover 1 abut against the step surface 622 of the valve seat 6 along the axial direction;

[0045] Solder 10 is placed on the peripheral side of the housing 1 and contacts the valve seat 5 to form a welded assembly.

[0046] An annular boss 61 can be formed on the upper end surface of the valve seat 6, and the step S2 specifically involves placing the solder 10 into the annular groove between the annular boss 61 and the outer cover 1 to form a welding assembly; it can be seen that the upper end surface of the valve seat 6 may not be provided with the annular boss 61, and the solder 10 may be directly sleeved on the outer cover 1 and contact the valve seat 6 along the axial direction. The annular boss 61 provided here can cooperate with the outer cover 1 to form an annular groove, so that the solder 10 can be better positioned to better ensure that the solder 10 is directed to the position to be welded after melting;

[0047] S3, placing the welding assembly into a welding furnace for brazing. Specifically, the welding assembly can be placed into a stainless steel sealed brazing container, and the brazing container is placed in the welding furnace as a whole. The brazing container has a support structure inside to position the welding assembly.

[0048] S4, sleeve the coil assembly 12 on the outer periphery of the brazed outer cover 1;

[0049] S5. Form the electronic expansion valve 100.

[0050] You can continue to refer to Fig. 9 , Fig. 9 for Figure 6 An enlarged view of the position of the gap a between the outer cover 1 and the valve seat 6.

[0051] In this embodiment, if Figure 8 As shown, the step side wall 621 of the valve seat 6 can be formed into a first side wall section 6211 and a second side wall section 6212, that is, the step side wall 621 includes the first side wall section 6211 and the second side wall section 6212 distributed along the axial direction. Obviously, the first side wall section 6211 and the second side wall section 6212 are also annular wall sections. Among them, the first side wall section 6211 is located above the second side wall section 6212, and the second side wall section 6212 is connected to the step surface 622, as shown in FIG. Figure 7As shown, the diameter D of the first side wall segment 6211 is greater than the diameter E of the second side wall segment 6212, and the outer wall of the outer cover 1 has an outer diameter B, which is greater than the diameter E but smaller than the diameter D. In this way, the outer cover 1 and the second side wall segment 6212 can be interference-fitted, and the interference amount is Fig. 9 The size of the interference M can be selected according to the size of the outer cover 1 and the valve seat 6, and a certain gap a can be left between the outer cover 1 and the first side wall section 6211, the gap a is annular, and the width of the gap a along the radial direction is Fig. 9 K shown. With such arrangement, when brazing is performed in a furnace, after the solder 10 is melted, in addition to being located in the annular groove to connect the outer wall of the outer cover 1 and the inner wall of the annular boss 61, the solder formed after melting can also flow into the gap a to connect the outer wall of the outer cover 1 and the first side wall section 6211, thereby increasing the welding area of ​​the valve seat 6 and the outer cover 1 and improving the welding strength. Moreover, the second side wall section 6212 and the outer cover 1 have an interference fit, so before and during brazing, the positions of the outer cover 1 and the valve seat 6 are relatively fixed. After brazing, a part of the lower end of the outer cover 1 has an interference fit with the valve seat 6, and another part located above the interference fit position has a gap a with the valve seat 6 for welding and fixing, and the connection is more reliable.

[0052] As a specific method, the welding furnace used for brazing can be a tunnel furnace. At this time, the width K of the gap a between the first side wall section 6211 and the outer cover 1 can be set to 0.05mm-0.2mm. Brazing in a tunnel furnace is to heat the workpiece as a whole, the total heat input is large, and the brazing time is relatively long, which takes several minutes. The width K of the gap a is set to a smaller 0.05mm-0.2mm, and the solder 10 has enough time to penetrate into the smaller gap a after melting to ensure the welding strength.

[0053] In addition, in this embodiment, the wall thickness of the outer cover 1 is defined as t. Fig. 9 As shown, the first side wall section 6211 has a length F in the axial direction, and the second side wall section 6212 has a length G in the axial direction. The length F of the first side wall section 6211 can satisfy: F = (2-6) t. That is, the wall thickness t of the outer cover 1 and the length F of the first side wall section 6211 with the gap a are associated and limited to further ensure the welding area of ​​the outer cover 1 and the valve seat 6 and ensure the connection reliability. The wall thickness t of the outer cover 1 can be set to be greater than or equal to 0.3 mm, which is conducive to the actual implementation of interference fit and welding. It can be seen that the length of the gap a in the axial direction is also the length F of the first side wall section 6211. The two strengths of interference fit and welding can be combined to design the length F of the first side wall section 6211 and the length G of the second side wall section 6212.

[0054] Look again Figure 7In this embodiment, the radial width of the annular groove between the annular boss 61 and the outer cover 1 is A, and the cross-section of the solder 10 is circular, that is, the solder 10 in this embodiment is a circular solder, and the solder 10 has a diameter S. The groove width A is smaller than the diameter S, and the diameter S is not smaller than the outer diameter B of the outer cover 1. In this way, the solder 10 can contact the outer wall of the outer cover 1 and the inner wall of the annular boss 61, or there can be a gap to avoid squeezing the solder 10 and causing deformation of the solder 10, so as to ensure that the solder 10 can be melted relatively evenly in the circumferential direction during the welding process to reliably connect the outer cover 1 and the valve seat 6.

[0055] The axial height of the annular boss 61 is also the depth H of the annular groove. The depth H of the annular groove may be smaller than the diameter S of the solder 10. Thus, the solder 10 can fill the annular groove after melting to ensure that enough solder is provided to ensure the welding area with the outer cover 1 and improve the welding effect.

[0056] Specifically, for brazing in a tunnel furnace, when welding is performed in the above step S4, the following operations may be performed:

[0057] The welding components are preheated in the preheating section of the tunnel furnace. The temperature of the preheating section can be set to 120℃~250℃. After slowly heating in the preheating section, the welding components enter the brazing section of the tunnel furnace for welding. The temperature of the brazing section can be set to 600℃±10℃. The welding components are transported by a mesh belt. The speed of the mesh belt can be set to 400mm / min~500mm / min.

[0058] It should be noted that during the welding process of the welding assembly in the tunnel furnace, an inert gas such as argon can be introduced into the tunnel furnace to prevent oxidation during the welding process. After brazing, the welding assembly is transported into the cooling chamber for cooling. The cooling chamber includes a water-cooled jacket chamber and an air-cooled cooling chamber. The water-cooled jacket chamber has cooling water surrounding the periphery, and the air-cooled cooling chamber is cooled by passing air. After welding, the welding assembly can be cooled to about 200°C in the water-cooled jacket chamber, and then cooled to below 100°C in the air-cooled cooling chamber before being taken out of the furnace.

[0059] As another specific method, the welding furnace used for brazing can be a vacuum furnace. Unlike the above-mentioned tunnel furnace, the tunnel furnace is protected by inert gas during the welding process, while the vacuum furnace evacuates the furnace during the welding process to maintain the welding in a vacuum environment. At this time, the width K of the gap a between the first side wall section 6211 and the outer cover 1 can be set to 0.05mm-0.15mm. Brazing in a vacuum furnace also heats the workpiece as a whole, with a large total heat input, and the brazing time is relatively long, requiring several minutes. After the solder 10 melts, it has enough time to penetrate into the gap. Compared with the tunnel furnace welding, and the vacuum furnace brazing is carried out in a vacuum environment, the capillary action will be more obvious, then the width K of the gap a can be set to 0.05mm-0.15mm, that is, compared with the width set during the tunnel furnace brazing, the width K of the gap a set during the vacuum furnace brazing can be smaller, so that the combination of the outer cover 1 and the valve seat 6 is more reliable.

[0060] Similarly, when brazing is performed in a vacuum furnace, the length F of the first side wall section 6211 along the axial direction can satisfy: F = (2-6) t. However, compared with a tunnel furnace, when brazing is performed in a vacuum furnace, as mentioned above, the capillary effect is more obvious in a vacuum environment, and a better welding effect can be achieved even if the length of the first side wall section 6211 is set relatively short. Therefore, the length F of the first side wall section 6211 forming the gap a can be set relatively smaller, and the length G of the second side wall section 6212 can be set larger, forming a longer interference fit section, thereby enhancing the reliability of the interference fit.

[0061] Specifically, for brazing in a vacuum furnace, when welding is performed in the above step S4, the following steps are performed:

[0062] After the welding assembly is placed in the vacuum furnace, the mechanical pump is started to evacuate to a preset pressure, such as 0.135 Pa, and then the diffusion pump is started to make the vacuum degree reach a preset vacuum degree, such as 6.5×10 -3 Pa, then heat for a first predetermined time, keep warm for a second predetermined time, and finally cool with the furnace.

[0063] The heating can be specifically a segmented heating method, where the first predetermined time is divided into a first segmented heating time and a second segmented heating time. For example, the first segmented heating time is 45min to 60min, and the temperature is increased to 450°C during this time period. The second segmented heating time is 30min to 45min, and the temperature is continued to be increased to 600±10°C during this time period, and then the temperature is kept warm. The second predetermined time for keeping warm is, for example, 5min to 10min. The heating and keeping warm time and specific temperature here can be set according to actual needs, and the embodiments of the present application do not impose specific restrictions.

[0064] Before brazing, the outer cover 1 and the valve seat 6 can also be cleaned with an organic solvent. The outer cover 1 and the valve seat 6 can be cleaned before assembly, or both can be cleaned at the same time after assembly. The organic solvent can be ethanol, acetone, CCl4, etc. Specifically, ultrasonic cleaning can be used to remove oil impurities. After cleaning, the outer cover 1 and the valve seat 6 are immersed in a 10% NaOH and 15% HNO3 solution to remove the oxide film, and then cleaned with anhydrous ethanol and dried, and then put into a tunnel furnace or a vacuum furnace for brazing.

[0065] It is worth noting that when brazing in a vacuum furnace, magnesium powder or magnesium blocks can be provided in the vacuum furnace. Magnesium powder or magnesium blocks are conducive to removing the oxide film of the outer cover 1 and the valve seat 6. Although the oxide film has been removed by immersion in 10% NaOH and 15% HNO3 solution, it is inevitable that a small amount of oxide film will be oxidized during the process of loading into the vacuum furnace. The provision of magnesium powder or magnesium blocks can keep the valve seat 6 and the outer cover 1 in an unoxidized state as much as possible before placing them in the vacuum furnace, so as to better perform the subsequent brazing process. In the vacuum furnace, magnesium powder or magnesium blocks can be 15g / m 3 Add in proportion.

[0066] In addition, after brazing, the hardness of the valve seat 6 may decrease to a certain extent. At this time, an aging treatment may be performed to increase the hardness, such as a quenching treatment.

[0067] Please continue to refer to Figure 10 to Figure 11 understand, Fig.10 This is a schematic diagram of another assembly of the valve seat 6 and the lower end of the outer cover 1 in the embodiment of the present application; Fig.11 for Fig.10 Magnified view of area C in the middle.

[0068] Compared to Figure 7 The valve seat 6, Fig.11 The valve seat 6 shown includes a chamfered portion 6211a, which is used to connect the first side wall section 6211 and the upper end surface 63 of the valve seat 6. Obviously, the chamfered portion 6211a is annular. Due to the provision of the chamfered portion 6211a, the melted solder 10 can penetrate into the gap a through the chamfered portion 6211a, that is, the chamfered portion 6211a plays a guiding and containing role, which can make the solder flow into the gap a more fully, avoid the solder accumulation in the annular groove, and further ensure the welding effect.

[0069] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the method and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for manufacturing an electronic expansion valve, characterized in that: The electronic expansion valve comprises a rotor assembly, a valve needle assembly, a valve seat, an outer cover and a coil assembly, wherein the coil assembly drives the rotor assembly to rotate so as to drive the valve needle assembly to rotate, at least part of the rotor assembly is located in the inner cavity of the outer cover, and part of the valve needle assembly is located in the inner cavity of the outer cover; the valve seat and the outer cover are made of different materials, and the manufacturing method comprises the following steps: Assembling the rotor assembly, the valve needle assembly, the nut assembly and the valve seat; The outer cover is placed over the rotor assembly, and the lower end of the outer cover is inserted into the valve seat, and the solder is placed on the peripheral side of the outer cover and contacts the valve seat to form a welded assembly; Placing the welding assembly into a welding furnace for brazing; The coil assembly is sleeved on the outer circumference of the brazed outer cover.

2. The method for manufacturing an electronic expansion valve according to claim 1, characterized in that: An annular boss is formed on the upper end surface of the valve seat, the outer cover is placed in the annular boss to form an annular groove, and the solder is placed in the annular groove.

3. The method for manufacturing an electronic expansion valve according to claim 2, characterized in that: A step portion is formed on an inner wall of the valve seat, and a lower end surface of the outer cover is brought into contact with a step surface of the step portion in the axial direction.

4. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: A first side wall section and a second side wall section are formed on the inner wall of the valve seat, and the outer cover is interference-fitted with the second side wall section. A gap is provided between the outer cover and the first side wall section in a radial direction so that the solder flows into the gap after melting.

5. The method for manufacturing an electronic expansion valve according to claim 4, characterized in that: The welding furnace is a tunnel furnace, the gap is 0.05 mm to 0.2 mm; and / or the wall thickness of the outer cover is t, and the length F of the first side wall section along the axial direction satisfies: F=(2-6)t.

6. The method for manufacturing an electronic expansion valve according to claim 4, characterized in that: The welding furnace is a vacuum furnace, the gap is 0.05 mm to 0.15 mm; and / or the wall thickness of the outer cover is t, and the length F of the first side wall section along the axial direction satisfies: F=(2-6)t.

7. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: The welding furnace is a tunnel furnace. The welding assembly is preheated in the preheating section of the tunnel furnace and then enters the brazing section of the tunnel furnace for welding. During the welding process, inert gas is introduced into the tunnel furnace. After brazing, the welding assembly is transported into a cooling chamber for cooling.

8. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: The welding furnace is a vacuum furnace. After the welding assembly is placed in the vacuum furnace, the pump is started to evacuate to a predetermined pressure, and then the pump is started again to make the vacuum degree reach a predetermined vacuum degree. Then, after heating for a first predetermined time, the temperature is kept for a second predetermined time, and finally the furnace is cooled.

9. The method for manufacturing an electronic expansion valve according to claim 8, characterized in that: The vacuum furnace is equipped with magnesium powder or magnesium blocks.

10. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: After brazing, the welded assembly is subjected to aging treatment.

11. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: Before brazing, the outer cover and the valve seat are cleaned with an organic solvent. After cleaning, the outer cover and the valve seat are immersed in a 10% NaOH and 15% HNO3 solution to remove the oxide film, and then cleaned with anhydrous ethanol and dried.

12. The method for manufacturing an electronic expansion valve according to any one of claims 1 to 3, characterized in that: The material of the valve seat is aluminum alloy, and the material of the outer cover is stainless steel.

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