Electronic expansion valve and machining method of base of electronic expansion valve

Abstract

The electronic expansion valve comprises a valve element assembly, a base and a valve port part, the base is provided with a first valve cavity, a first inlet channel and an outlet channel, the first inlet channel communicates with the first valve cavity, and part of the valve element assembly is located in the first valve cavity; the valve element assembly is provided with a valve component, the valve component can move relative to the valve port part, the electronic expansion valve is provided with a variable first throttling area, and the first throttling area is located between the valve component and the valve port part; the electronic expansion valve is provided with a second inlet channel, the second inlet channel is provided with a throttling hole, the second inlet channel is communicated with the outlet channel, and the second inlet channel is communicated with the first inlet channel. Due to the fact that the second inlet channel is communicated with the first inlet channel and the outlet channel, and the second inlet channel is provided with the throttling hole, small-opening-degree conduction can be reliably achieved when fluid passes through the throttling hole of the second inlet channel.

Description

Technical Field

[0001] This application relates to the technical field of fluid control components, and particularly relates to a processing method for an electronic expansion valve and its base. Background Art

[0002] In related technologies, an air-conditioning system includes an electronic expansion valve, which includes a valve component and a valve port. The valve component can move up and down to approach or move away from the valve port, so as to adjust the corresponding conduction degree. In some working conditions of the air-conditioning system, the temperature difference between the internal and external environments is small, and the required opening degree of the electronic expansion valve is small. However, due to assembly and processing errors and the special mating relationship between some components, there will be a situation where although the controller of the electronic expansion valve issues corresponding pulses, the valve core assembly does not move, resulting in it being sometimes difficult to obtain a specific small flow rate. Summary of the Invention

[0003] To solve the above technical problems, the following technical solutions are provided:

[0004] An electronic expansion valve includes a valve core assembly and a base. The valve core assembly is fixedly assembled with the base. The base has a first valve cavity, a first inlet passage, and an outlet passage. The first inlet passage is communicated with the first valve cavity, and a part of the valve core assembly is located in the first valve cavity;

[0005] The valve core assembly has a valve component, the electronic expansion valve has a valve port, the valve component can move relative to the valve port, the electronic expansion valve has a variable first throttling area, and the first throttling area is located between the valve component and the valve port; the electronic expansion valve has a second inlet passage, and the second inlet passage has a throttling hole. The second inlet passage is communicated with the outlet passage, and the second inlet passage is communicated with the first inlet passage.

[0006] Since the second inlet passage is communicated with the first inlet passage and the outlet passage respectively, and the second inlet passage has a throttling hole, in this way, the fluid can reliably achieve small-opening conduction through the throttling hole of the second inlet passage.

[0007] A processing method for the base of an electronic expansion valve is as follows: Provide a blank part, the blank part includes a first valve cavity, a first inlet passage, and an outlet passage. The first valve cavity is used to accommodate a part of the valve core assembly. The first inlet passage is communicated with the first valve cavity, and the outlet passage is communicated with the first valve cavity;

[0008] Form a first hole on the bottom wall of the first valve cavity, and then drill a hole along the axial direction of the first hole on its corresponding bottom wall to process a throttling hole communicated with the outlet passage,

[0009] Or

[0010] The outlet passage has a first opening. Along the direction of the first opening towards the first valve cavity, a first hole is formed in the corresponding wall of the outlet passage. Then, a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to machine a throttle hole communicating with the first valve cavity.

[0011] Or

[0012] The first inlet passage has a second opening. Along the direction of the second opening towards the outlet passage, a first hole is formed in the corresponding wall of the first inlet passage. Then, a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to machine a throttle hole communicating with the outlet passage.

[0013] Since the first hole is formed first and then the throttle hole is machined in the corresponding bottom wall along the axial direction of the first hole, the length of the throttle hole in its axial direction is shortened, thus facilitating the machining and forming of the throttle hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional schematic view of the present application;

[0015] Figure 2 is Figure 1 a schematic view of the middle base;

[0016] Figure 3 is Figure 1 an enlarged schematic view of area A in ;

[0017] Figure 4 is a three-dimensional schematic view of the valve core assembly in the present application;

[0018] Figure 5 is Figure 4 an enlarged schematic view of area B in ;

[0019] Figure 6 is a cross-sectional schematic view of another embodiment;

[0020] Figure 7 is Figure 6 an enlarged schematic view of area C in ;

[0021] Figure 8 is a cross-sectional schematic view of yet another embodiment;

[0022] Figure 9 is Figure 8 an enlarged schematic view of area D in.

[0023] Reference Numerals:

[0024] 1, base; 2, valve core assembly; 3, filter element;

[0025] 11. First valve cavity; 12. First inlet passage; 13. Outlet passage; 15. Second inlet passage; 17. Accommodating passage; 121. Second opening; 131. First opening; 151. First conducting section; 152. Throttle orifice; 153. Transition section;

[0026] 21. Valve seat; 22. Valve component;

[0027] 211. Second valve cavity; 212. First passage; 213. Second passage; 214. Valve port part; 215. Limiting flange part. Detailed implementation manners

[0028] The technical solutions of the detailed implementation manners will be described below with reference to the accompanying drawings.

[0029] As Figures 1-5 shown, an electronic expansion valve includes a valve core assembly 2 and a base 1. The valve core assembly 2 is fixedly assembled with the base 1. The base 1 has a first valve cavity 11, a first inlet passage 12 and an outlet passage 13. The first inlet passage 12 communicates with the first valve cavity 11. A part of the valve core assembly 2 is located in the first valve cavity 11. The electronic expansion valve has a second inlet passage 15. The valve core assembly has a valve component 22. The electronic expansion valve has a valve port part. The valve component can move relative to the valve port part. The electronic expansion valve has a variable first throttling area. The first throttling area is located between the valve component and the valve port part. The electronic expansion valve has a second inlet passage 15. The second inlet passage 15 has a throttle orifice. The second inlet passage 15 communicates with the outlet passage 131. The second inlet passage 15 communicates with the first inlet passage 12.

[0030] Since the second inlet passage communicates with the first inlet passage and the outlet passage respectively, and the second inlet passage has a throttle orifice, in this way, the fluid can reliably achieve the conduction at a small opening degree through the throttle orifice of the second inlet passage.

[0031] The second inlet passage 15 is located in the base. The second inlet passage 15 includes a first conducting section 151 and a throttle orifice 152. The first conducting section 151 communicates with the first valve cavity 11. The throttle orifice 152 communicates with the outlet passage 13. The inner diameter of the corresponding wall of the first conducting section 151 is greater than the inner diameter of the corresponding wall of the throttle orifice 152. The extension length of the throttle orifice of the second conducting section is less than the extension length of the first conducting section.

[0032] The inner diameter of the corresponding wall of the first conduction section 151 is larger than that of the corresponding wall of the throttle orifice 152. The larger inner diameter of the corresponding wall of the first conduction section 151 makes it easier to machine the first conduction section 151 compared to the throttle orifice 152. Moreover, the presence of the first conduction section 151 shortens the length of the throttle orifice 152 in its axial direction, which facilitates the machining of the throttle orifice 152, and the shortening of the length of the throttle orifice 152 in its axial direction is beneficial to ensuring the machining accuracy of the throttle orifice 152.

[0033] Along the axial direction of the first valve cavity 11, the opening of the first conduction section 151 faces the valve core assembly 2, and the central axis corresponding to the first conduction section 151 is parallel to the central axis corresponding to the first valve cavity 11. It should be noted that the error caused by machining resulting in the central axis corresponding to the first conduction section 151 being approximately parallel to the central axis corresponding to the first valve cavity 11 is also within the protection scope of this solution. The parallelism between the central axis corresponding to the first conduction section and the central axis corresponding to the first valve cavity 11 can reduce the adjustment of the position of the base during machining, and the first conduction section can be machined continuously after the first valve cavity 11 is machined.

[0034] The second inlet passage 15 further includes a transition section 153. One end of the transition section 153 is connected to the first conduction section 151, and the other end of the transition section 153 is connected to the other end of the throttle orifice 152; in the direction from the connection between the throttle orifice 152 and the transition section 153 to the connection between the first conduction section 151 and the transition section 153, the inner diameter of the corresponding wall of the transition section 153 gradually increases.

[0035] In this way, by connecting the first conduction section 151 and the throttle orifice 152 through the transition section 153, on the one hand, it is beneficial to reducing the length of the corresponding wall of the throttle orifice 152 in its axial direction (i.e., the pore channel extension length of the throttle orifice 152), which is conducive to machining the throttle orifice 152 and ensuring the accuracy of the throttle orifice 152. On the other hand, while reducing the length of the corresponding wall of the throttle orifice 152 in its axial direction, it can also ensure the strength of the corresponding wall of the second inlet passage 15 and enhance its reliability in coping with the pressure difference between the second inlet passage 15 and the outlet passage 13.

[0036] The inner diameter of the corresponding wall of the throttle orifice 152 is 0.3 - 0.6 mm, and the pore channel extension length of the throttle orifice is 0.5 - 1.5 mm. The throttle orifice is used to achieve the conduction of a specific flow rate. When the length of the throttle orifice is less than 0.5 mm, it will have an adverse impact on the machining accuracy. Whether it is machined by a drill bit or by laser drilling, it is easy to cause the aperture of the throttle orifice to be larger than the preset value. When the length of the throttle orifice is greater than 1.5 mm, the excessive wall thickness is likely to cause the drill bit to be damaged (such as breaking). If it is laser drilled, the corresponding required power will increase significantly.

[0037] The spool assembly 2 includes a valve seat 21 and a valve member 22. The valve seat 21 has a second valve cavity 211. The valve seat 21 is provided with a valve port portion 214. At least part of the valve member 22 is located in the second valve cavity 211. The valve member 22 is in sliding fit with the wall corresponding to the second valve cavity 211, and the valve member 22 can move closer to or away from the valve port portion 214 in the axial direction. The valve seat 21 further includes a first channel 212 and a second channel 213. Two ends of the first channel 212 are respectively connected to the first valve cavity 11 and the second valve cavity 211. The second channel 213 is communicated with the outlet channel 13. The valve member 22 can abut against the valve port portion 214 to block the communication between the second channel 213 and the second valve cavity 211. When the valve member 22 is separated from the valve port portion 214, the second channel 213 is communicated with the second valve cavity 211. The number of the first channels 212 is at least one. In this embodiment, the number of the first channels 212 is two. The first channels 212 are distributed along the circumferential direction of the valve seat 21 on the side wall of the valve seat 21, and the first channels 212 penetrate through the side wall of the valve seat 21.

[0038] The base 1 further includes a receiving channel 17. One port of the receiving channel 17 is located at the bottom wall of the first valve cavity 11. The receiving channel 17 communicates the first valve cavity 11 and the outlet channel 13. Part of the valve seat 21 is located in the receiving channel 17, and a seal is further provided between the wall of the valve seat 21 corresponding to the receiving channel 17 to make the wall of the valve seat 21 corresponding to the receiving channel 17 in sealing fit in the radial direction. The wall of the valve seat corresponding to the receiving channel is in sealing fit in the radial direction, so as to prevent the fluid entering the first valve cavity from flowing to the outlet channel through the space between the valve seat and the receiving channel.

[0039] The electronic expansion valve further includes a filter element 3. The filter element 3 is located in the first valve cavity 11, and the filter element 3 covers the connection between the second inlet channel 15 and the first valve cavity 11. In this embodiment, the filter element 3 is sleeved on the valve seat 21.

[0040] The filter element 3 covers the connection between the second inlet channel 15 and the first valve cavity 11, which is beneficial to filtering impurities in the fluid, thereby reducing the risk of the second inlet channel 15 being blocked by impurities.

[0041] In this embodiment, the filter element 3 covers the opening of the first conduction section 151 facing the first valve cavity 11. Since impurities will accumulate on the path through which the fluid flows, compared with the throttle orifice 152, the inner diameter of the wall corresponding to the first conduction section 151 is larger, which can reduce the risk of blockage at the connection between the second inlet channel 15 and the first valve cavity 11.

[0042] In the radial direction of the first valve cavity 11, at least part of the filter element 3 is located between the side wall of the valve seat 21 corresponding to the first valve cavity 11;

[0043] The height by which the filter element 3 protrudes above the bottom wall of the first valve chamber 11 is h, the minimum distance between the wall corresponding to the first channel 212 and the bottom wall corresponding to the first valve chamber 11 is a, the minimum distance between the wall corresponding to the connection between the first inlet channel 12 and the first valve chamber 11 and the bottom wall corresponding to the first valve chamber 11 is b, a is greater than or equal to h, and b is greater than or equal to h.

[0044] Since both a and b are greater than or equal to h, in this way, the flow path occupied by the filter element 3 between the first inlet channel 12 and the first channel 212 is reduced, thereby reducing the flow resistance. In addition, since the cross-sectional area of the first channel 212 is much larger than the cross-sectional area of the throttle hole 152, the flow rate of the fluid flowing into the first channel 212 through the upper surface of the filter element 3 is much larger than the flow rate of the fluid flowing into the second inlet channel 15 through the filter element 3, and the flow velocity of the fluid flowing into the second inlet channel 15 through the filter element 3 is also much smaller than the flow velocity of the fluid flowing into the first channel 212 through the upper surface of the filter element 3. In this way, a pressure difference is formed between the upper surface of the filter element and its interior, and under the action of the pressure difference, it is beneficial to reduce the accumulation of impurities in the filter element 3.

[0045] The valve seat 21 has a limiting flange portion 215 that protrudes from the side wall of the valve seat 21. In the axial direction of the first valve chamber 11, the limiting flange portion 215 is farther from the bottom wall of the first valve chamber 11 than the filter element 3, and in the axial direction of the first valve chamber 11, at least a part of the projection of the limiting flange portion 215 is located on the filter element 3. In this embodiment, the number of the limiting flange portions 215 is at least two, and they are evenly distributed along the circumferential direction of the valve seat 21. In this embodiment, the limiting flange portion 215 abuts against the filter element 3 to play a role in limiting the filter element 3.

[0046] In some embodiments, the side wall of the filter element 3 corresponding to the first valve chamber 11 is in interference fit to limit the movement of the filter element 3.

[0047] In this embodiment, the processing method of the base is as follows: Provide a blank part, the blank part includes a first valve chamber, a first inlet channel and an outlet channel, the first valve chamber is used to accommodate part of the valve core assembly, the first inlet channel is communicated with the first valve chamber, and the outlet channel is communicated with the first valve chamber; form a first hole on the bottom wall of the first valve chamber, and then drill a hole in the corresponding bottom wall along the axial direction of the first hole to process a throttle hole communicated with the outlet channel. The first hole has a first conduction section and a transition section. In this embodiment, the first conduction section and the transition section are simultaneously processed by a drill bit with a tapered end. In some embodiments, the first conduction section is first processed, and when drilling a hole in the corresponding bottom wall along the axial direction of the first conduction section, a transition section is processed.

[0048] Since the first hole is formed first and then the throttle hole is machined on the corresponding bottom wall along the axial direction of the first hole, the length of the throttle hole in its axial direction is shortened, which facilitates the machining and forming of the throttle hole and ensures the machining accuracy of the throttle hole.

[0049] Figures 6-7 Another embodiment is shown. In this embodiment,

[0050] The second inlet passage 15 includes a first conducting section 151 and a throttle hole 152. The first conducting section 151 communicates with the outlet passage 13, and the throttle hole 152 communicates with the first valve cavity 11; the inner diameter of the corresponding wall of the first conducting section 151 is greater than the inner diameter of the corresponding wall of the throttle hole 152.

[0051] The outlet passage 13 has a first opening 131, and the first opening 131 is located on the surface of the base 1; the opening of the first conducting section 151 faces the first opening 131, and the straight extension line of the corresponding wall of the first conducting section 151 can be within the range of the first opening 131.

[0052] Since the opening of the first conducting section 151 faces the second opening 121 and the straight extension line of the corresponding wall of the first conducting section 151 can be within the range of the first opening 131, the interference of the corresponding wall of the first opening 131 can be reduced during the machining of the first conducting section 151 (in this embodiment, the drill bit can be inserted from the first opening 131 to machine the first conducting section 151. When the drill bit is inserted from the first opening 131, the required drill bit length is relatively short and the drill bit is not easily broken).

[0053] In this embodiment, the machining method of the base is as follows: Provide a blank part, which includes a first valve cavity 11, a first inlet passage 12 and an outlet passage 13. The first valve cavity 11 is used to accommodate part of the valve core assembly. The first inlet passage communicates with the first valve cavity 11, and the outlet passage communicates with the first valve cavity 11; the outlet passage has a first opening. Along the direction of the first opening towards the first valve cavity, a first hole is formed on the corresponding wall of the outlet passage. Specifically, the drill bit can be inserted from the first opening 131 towards the first valve cavity to machine the first hole. When the drill bit is inserted from the first opening 131, the required drill bit length is relatively short and the drill bit is not easily broken. Then, a hole is drilled on the corresponding bottom wall along the axial direction of the first hole to machine a throttle hole communicating with the first valve cavity.

[0054] Figures 8-9 Another embodiment is shown. In this embodiment,

[0055] The second inlet passage 15 includes a first conducting section 151 and a throttle orifice 152. The first conducting section 151 communicates with the first inlet passage, and the throttle orifice 152 communicates with the outlet passage. The inner diameter of the corresponding wall of the first conducting section 151 is greater than the inner diameter of the corresponding wall of the throttle orifice 152. The first inlet passage has a second opening 121 facing outside the base. One port of the first conducting section 151 faces the second opening 121, and the straight extension line of the corresponding wall of the first conducting section can be within the range of the second opening. In this way, interference with the corresponding wall of the second opening can be reduced during the machining of the first conducting section 151 (in this embodiment, the drill bit can be inserted into the second opening to machine the first conducting section 151. When the drill bit is inserted into the second opening, relatively speaking, the required length of the drill bit is short and the drill bit is not easily broken).

[0056] In this embodiment, the machining method of the base is as follows: Provide a blank. The blank includes a first valve cavity 11, a first inlet passage, and an outlet passage. The first valve cavity 11 is used to accommodate part of the valve core assembly. The first inlet passage communicates with the first valve cavity 11, and the outlet passage communicates with the first valve cavity 11. The drill bit is inserted into the second opening in the direction facing the outlet passage to machine a first hole, and then a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to machine a throttle orifice communicating with the outlet passage.

[0057] It should be noted that: Although this specification has described the present application in detail with reference to the above embodiments, those of ordinary skill in the art should understand that those skilled in the art to which the present application pertains can still modify, combine, or equivalently replace the present application. All technical solutions and their improvements that do not depart from the spirit and scope of the present application should be covered within the scope of the claims of the present application.

Claims

1. An electronic expansion valve, comprising a valve core assembly (2) and a base (1), the valve core assembly (2) being assembled and fixed to the base (1), the base (1) having a first valve cavity (11), a first inlet passage (12) and an outlet passage (13), the first inlet passage (12) communicating with the first valve cavity (11), a part of the valve core assembly (2) being located in the first valve cavity (11), characterized in that, the valve core assembly has a valve member (22), the electronic expansion valve has a valve port portion, the valve member (22) is movable relative to the valve port portion, the electronic expansion valve has a variable first throttling region, and the first throttling region is located between the valve member (22) and the valve port portion; the electronic expansion valve has a second inlet passage (15), and the second inlet passage (15) has a throttling hole (152), the second inlet passage (15) communicating with the outlet passage (13), and the second inlet passage (15) communicating with the first inlet passage (12).

2. An electronic expansion valve according to claim 1, wherein, The second inlet passage (15) includes a first conduction section (151) and a throttling hole (152), the inner diameter of the corresponding wall of the first conduction section (151) being greater than the inner diameter of the corresponding wall of the throttling hole (152), and the extension length of the throttling hole being less than the extension length of the first conduction section.

3. An electronic expansion valve according to claim 2, characterized in that, The second inlet passage (15) is located in the base (1), the first conduction section (151) communicating with the first valve cavity (11), and the throttling hole (152) communicating with the outlet passage (13); the aperture of the throttling hole is 0.3 - 0.6 mm; The extension length of the passage of the throttling hole (152) is 0.5 - 1.5 mm.

4. An electronic expansion valve according to claim 3, characterized in that, Along the axial direction of the first valve cavity (11), one port of the first conduction section (151) faces the valve core assembly (2), and the central axis corresponding to the first conduction section (151) is parallel to the central axis corresponding to the first valve cavity (11).

5. An electronic expansion valve according to claim 2, characterized in that, The second inlet passage (15) is located in the base (1); the first conduction section (151) communicates with the outlet passage (13), the throttling hole (152) communicates with the first valve cavity (11), the inner diameter of the corresponding wall of the throttling hole (152) is 0.3 - 0.6 mm; the extension length of the passage of the throttling hole (152) is 0.5 - 1.5 mm.

6. An electronic expansion valve according to claim 5, wherein The outlet passage (13) has a first opening (131), one port of the first conduction section (151) faces the first opening (131), and the straight extension line of the corresponding wall of the first conduction section can be within the range of the first opening (131).

7. An electronic expansion valve according to claim 5, characterized in that, Along the axial direction of the first valve cavity (11), one port of the first conduction section (151) faces away from the valve core assembly (2), and the central axis corresponding to the first conduction section (151) is parallel to the central axis corresponding to the first valve cavity (11).

8. An electronic expansion valve according to claim 3 or 5, characterized in that The second inlet passage (15) further includes a transition section (153), one end of the transition section (153) is connected to the first conduction section (151), and the other end of the transition section (153) is connected to the other end of the throttle orifice (152); In the direction from the connection of the throttle orifice (152) and the transition section (153) to the connection of the first conduction section (151) and the transition section (153), the inner diameter of the corresponding wall of the transition section (153) gradually increases.

9. An electronic expansion valve according to any one of claims 3 to 6, characterized in that The electronic expansion valve further includes a filter element (3), the filter element (3) is located in the first valve cavity (11), and the filter element (3) covers the connection of the second inlet passage (15) and the first valve cavity (11).

10. An electronic expansion valve according to claim 9, characterized in that The valve core assembly (2) further includes a valve seat (21) and a valve member (22), and the valve member (22) can approach or move away from the valve orifice portion (214). The valve seat (21) includes a second valve cavity (211), a first passage (212) and a second passage (213), the first passage (212) is located on the side wall of the valve seat (21), the first passage (212) can communicate the first valve cavity (11) with the second valve cavity (211), and the second passage (213) can be used to communicate the first valve cavity (11) and the second valve cavity (211); In the radial direction of the first valve cavity (11), at least a part of the filter element (3) is located between the side wall of the valve seat (21) corresponding to the first valve cavity (11). The height of the filter element (3) above the bottom wall of the first valve cavity (11) is h, the minimum distance between the corresponding wall of the first passage (212) and the bottom wall of the first valve cavity (11) is a, and the minimum distance between the corresponding wall at the connection of the first inlet passage (12) and the first valve cavity (11) and the bottom wall of the first valve cavity (11) is b, a is greater than or equal to h, and b is greater than or equal to h.

11. An electronic expansion valve according to claim 10, characterized in that The filter element (3) is in interference fit with the side wall corresponding to the first valve cavity (11), or The valve seat (21) has a limiting flange portion (215), and the limiting flange portion (215) protrudes from the side wall of the valve seat (21). In the axial direction of the first valve cavity (11), the limiting flange portion (215) is farther from the bottom wall of the first valve cavity (11) than the filter element (3). And in the axial direction of the first valve cavity (11), at least a part of the projection of the limiting flange portion (215) is located on the filter element (3).

12. A processing method for the base of an electronic expansion valve, characterized in that: A blank is provided, and the blank includes a first valve cavity, a first inlet passage, and an outlet passage. The first valve cavity is used to accommodate a part of the valve core assembly. The first inlet passage communicates with the first valve cavity, and the outlet passage communicates with the first valve cavity; A first hole is formed in the bottom wall of the first valve cavity, and then a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to process a throttle hole communicating with the outlet passage. Or The outlet passage has a first opening. Along the direction of the first opening towards the first valve cavity, a first hole is formed in the corresponding wall of the outlet passage, and then a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to process a throttle hole communicating with the first valve cavity. Or The first inlet passage has a second opening. Along the direction of the second opening towards the outlet passage, a first hole is formed in the corresponding wall of the first inlet passage, and then a hole is drilled in the corresponding bottom wall along the axial direction of the first hole to process a throttle hole communicating with the outlet passage.

13. The processing method of the base of an electronic expansion valve according to claim 12, characterized in that, The first hole has a first conduction section and a transition section, and the inner diameter corresponding to the transition section gradually decreases. The first conduction section and the transition section are formed simultaneously; Or the first conduction section is formed first. When drilling a hole in the corresponding bottom wall along the axial direction of the first conduction section, a transition section is processed. The inner diameter corresponding to the transition section gradually decreases, and then the throttle hole is processed.

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