Laminar flow device structure with adjustable flow resistance and assembly method thereof

Abstract

The present invention relates to the field of mass flow measurement, and specifically to a laminar flow component structure with adjustable flow resistance and an assembly method thereof. The laminar flow component structure includes a cylindrical component and an inner plug component; the front end of the cylindrical component is a flow section, and the rear end is an inner diameter tapering section. The inner diameter of the flow section is greater than or equal to the maximum inner diameter of the inner diameter tapering section. The peripheral wall of the flow section is provided with a plurality of flow guide holes, and the flow guide holes are used to connect the inlet of a thermal flow sensor; the front end face of the inner plug component is a flow surface, and the rear end is an outer diameter tapering section. The outer diameter of the flow surface is the maximum outer diameter of the inner plug component, which is smaller than the inner diameter of the flow section; the inner plug component is inserted into the cylindrical component, and can be inserted to different depths. One of the outer peripheral wall and the inner peripheral wall of the cylindrical component is provided with a protrusion that is interference-fitted with the other, and together form a laminar flow channel; the flow surface is located in the flow section, and the outer diameter tapering section and the inner diameter tapering section overlap in the axial direction. The present invention can prepare a laminar flow component structure with a variety of flow resistances through two parts with fixed specifications, and also has a more stable pressure loss.

Description

Technical Field

[0001] The invention relates to the field of mass flow measurement, and in particular to a laminar flow component structure with adjustable flow resistance and an assembly method thereof. Background Art

[0002] A mass flow controller (MFC) is a device used to control gas flow and plays an important role in the semiconductor manufacturing process. MFC can accurately control the flow of gas, thereby ensuring stability and repeatability in the semiconductor production process. As a component of the flow metering unit of a mass flow controller, a laminar flow element (flow resistance structure) is usually configured with a laminar flow element with different flow resistances in actual application, so that the flow metering unit has different ranges to adapt to different application requirements.

[0003] Traditional laminar flow parts (flow resistance structures) generally use capillary laminar flow parts or cylindrical pin laminar flow parts. Capillary laminar flow parts change the flow resistance by controlling the number of holes on the processed parts or increasing or decreasing the number of embedded capillaries. This places high demands on actual production or assembly. The cost of opening holes in the processed parts is relatively high. In addition, due to the processing errors of the capillaries themselves and the deformation during the assembly process, the consistency of the final finished product will vary greatly. Cylindrical pin laminar flow parts usually change the flow resistance by controlling the gap between the external structure and the internal structure. The way to change the gap is to use internal structures with different outer diameters and / or external structures with different inner diameters. Therefore, it is necessary to configure external structures and internal structures of various specifications. The external structure and the internal structure themselves also have processing errors. Therefore, there is also the problem of poor consistency of the finished product.

[0004] High-precision flowmeters have very high requirements for measuring units, which requires tedious and complex debugging and calibration of finished products in the subsequent production process. In addition, considering the variety of measuring ranges, the two traditional flow resistance structures also have the problem of many inventory types, production material preparation and on-site management difficulties.

[0005] Furthermore, when the existing laminar flow component is connected in parallel with the thermal flow sensor to form a flow metering unit, when in use, when high-speed fluid flows into the laminar flow component, the pressure loss of the laminar flow component will be affected due to inertia, and the pressure at the inlet of the thermal flow sensor will be unstable, resulting in a large measurement error of the thermal flow sensor.

[0006] Therefore, it is necessary to design a laminar flow structure to solve the above problems. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a laminar flow component structure with adjustable flow resistance. It can prepare laminar flow component structures with various flow resistances through two components of fixed specifications to adapt to different product range requirements, and also has a more stable pressure loss to reduce the measurement error of the thermal flow sensor used with it.

[0008] In order to solve the above technical problems, the technical solution of the present invention is: a laminar flow structure with adjustable flow resistance, comprising:

[0009] A cylindrical member, wherein the front end is a flow section, and the rear end is a section with a gradually decreasing inner diameter, wherein the inner diameter of the flow section is greater than or equal to the maximum inner diameter of the section with a gradually decreasing inner diameter, and the peripheral wall of the flow section is provided with a plurality of flow guide holes, wherein the flow guide holes extend to the outer wall of the flow section and are used to connect to the inlet of the thermal flow sensor;

[0010] The inner plug has a front end surface as a flow-facing surface, and at least a rear end portion as a section with a tapered outer diameter, wherein the outer diameter of the flow-facing surface is the maximum outer diameter of the inner plug and is smaller than the inner diameter of the flow-facing section; wherein,

[0011] The inner plug is inserted into the cylindrical member and can be inserted to different depths. One of its outer peripheral wall and the inner peripheral wall of the cylindrical member is provided with a protrusion that is interference-fitted with the other one. The outer peripheral wall and the inner peripheral wall of the cylindrical member jointly form a laminar flow channel.

[0012] The oncoming flow surface is located in the oncoming flow section, and the outer diameter tapering section and the inner diameter tapering section overlap in the axial direction.

[0013] In order to further prevent interference with other parts during use, the rear end of the inner plug does not extend beyond the tubular member in the axial direction.

[0014] In order to further prevent the fluid from being affected by its own inertia, most of the fluid flows through the laminar flow component, and less fluid flows through the thermal flow sensor, which leads to a large error, the present invention uses a curved flow channel design, which can create a stable and effective pressure loss in a limited space. That is: the inner diameter of the incoming flow section is larger than the maximum inner diameter of the inner diameter tapering section; wherein,

[0015] The cylindrical member also has an inner diameter equal diameter section located between the incoming flow section and the inner diameter tapering section, the inner diameter of the inner diameter tapering section is smaller than the inner diameter of the incoming flow section and is equal to the maximum inner diameter of the inner diameter tapering section; the front end of the inner plug is an outer diameter equal diameter section.

[0016] In order to further make the rear end of the laminar flow channel have an equal gap in the axial direction, thereby better forming a stable laminar flow, the inner diameter tapering section and the outer diameter tapering section are both conical, and the tapering rates are equal.

[0017] A solution is further provided for gradually narrowing the inlet portion of the laminar flow channel, thereby being more conducive to the formation of laminar flow, wherein the outer diameter equal diameter section axially extends backward beyond the inner diameter equal diameter section.

[0018] Furthermore, the protrusions have two evenly distributed along the circumferential direction or have at least three arranged along the circumferential direction.

[0019] Furthermore, the protrusion extends in the axial direction.

[0020] In order to further improve the circumferential uniformity of the laminar flow channel, the cylindrical member and the inner plug member are coaxial.

[0021] The present invention also relates to an assembly method of a laminar flow component structure with adjustable flow resistance, comprising:

[0022] Press the small end of the inner plug into the tubular member from the large end of the tubular member so that the protrusions provided on one of the outer peripheral wall of the inner plug and the inner peripheral wall of the tubular member are interference-fitted with the other protrusion;

[0023] During the press-fitting process, after the frontal surface enters the frontal section, the flow resistance of the laminar flow channel is controlled by controlling the press-fitting depth of the inner plug.

[0024] In order to further achieve online measurement to ensure flow resistance accuracy and finished product consistency, the assembly method also includes:

[0025] During the press-fitting process, the flow rate of the laminar flow channel is measured; and the press-fitting is stopped when the flow rate reaches a preset flow rate value or the flow resistance corresponding to the flow rate reaches a preset flow resistance value.

[0026] After adopting the above technical solution, the present invention has the following beneficial effects:

[0027] 1. Since the cylindrical member has a portion with a gradually decreasing inner diameter, and the inner plug has a portion with a gradually decreasing outer diameter, after the inner plug is inserted into the cylindrical member, the inner plug is inserted to different depths, and the laminar flow channel formed by the inner plug and the cylindrical member has different flow resistances. In addition, after the inner plug is inserted into the cylindrical member, the two are fitted with a protrusion interference fit, that is, the inner plug is inserted to a corresponding depth, and the inner plug can be firmly fixed at its depth. Therefore, the present invention can assemble laminar flow structure with various flow resistance specifications through cylindrical members and inner plugs of fixed specifications only by adjusting the target end point during press-fitting, which greatly reduces the difficulty of production and material preparation and improves material utilization;

[0028] 2. Machined parts will always have errors, and the errors between individuals cannot be eliminated. The laminar flow structure of the present invention can also compensate for individual errors by controlling and adjusting the insertion depth of the inner plug, thereby improving the flow resistance accuracy of the laminar flow structure and the consistency of the finished product;

[0029] 3. After the multiple guide holes of the laminar flow structure of the present invention are connected to the thermal flow sensor through capillaries and put into use, when the high-speed fluid flows into the headstream section from the inlet, it will first hit the headstream surface of the inner plug, and then the fluid will disperse. A part of the fluid enters the laminar flow channel of the laminar flow structure, and the other part of the fluid enters the thermal flow sensor from the guide hole. Since the headstream surface has a large radius and directly faces the impact of the high-speed fluid, it can well offset the inertial force of the high-speed fluid and break up the fluid, further weakening the influence of the inlet high-speed fluid on the laminar flow structure. In addition, the pressure at the guide hole is more stable and less affected by the fluid flow rate, thereby reducing the measurement error of the thermal flow sensor;

[0030] 4. The rear end of the laminar flow channel of the present invention has a certain slope, and the fluid is affected by the slope of the flow channel. When the fluid flows out of the laminar flow component structure, the circumferential fluid gathers toward the axial area, collides around the fluid outflow surface, and interacts with each other, thereby effectively weakening the speed of the fluid outflow, further reducing the impact on the laminar flow component structure, and making the outlet pressure of the capillary that converges the outlet of the thermal flow sensor to the outlet of the laminar flow component structure more stable and less affected by the fluid flow rate, further reducing the measurement error of the thermal flow sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A longitudinal section of the laminar flow device structure with adjustable flow resistance according to the present invention;

[0032] Figure 2 is a cross-sectional view of the inner plug of the present invention;

[0033] Figure 3 It is a schematic diagram of the laminar flow component structure with adjustable flow resistance of the present invention used in conjunction with a thermal flow sensor;

[0034] Figure 4 A comparison diagram of the maximum flow rate of the outlet cross section of the laminar flow device structure with adjustable flow resistance of the present invention and the traditional laminar flow device;

[0035] Figure 5 A comparison diagram of the pressure loss versus flow rate curves of the laminar flow device structure with adjustable flow resistance of the present invention and the traditional laminar flow device;

[0036] Figure 6 A comparison diagram of the flow passage cross-sections of the laminar flow device structure with adjustable flow resistance of the present invention and the conventional laminar flow device under different measuring ranges;

[0037] In the figure, 1, cylindrical member; 11, inner diameter tapering section; 12, inner diameter equal diameter section; 13, flow-facing section; 2, inner plug; 2a, flow-facing surface; 21, outer diameter tapering section; 22, outer diameter equal diameter section; 3, protrusion; 4, laminar flow channel; 5, flow guide hole; 6, capillary tube; 7, thermal flow sensor. DETAILED DESCRIPTION

[0038] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0039] Embodiment 1: Figure 1 , Figure 2 and Figure 3 As shown, a laminar flow structure with adjustable flow resistance comprises:

[0040] The cylindrical member 1 has a front end portion being a flow section 13, and a rear end portion being an inner diameter tapered section 11. The inner diameter of the flow section 13 is greater than or equal to the maximum inner diameter of the inner diameter tapered section 11. The peripheral wall of the flow section 13 is provided with a plurality of flow guide holes 5. The flow guide holes 5 extend to the outer wall of the flow section 13 and are used to connect to the inlet of the thermal flow sensor.

[0041] The inner plug 2 has a front end surface as a flow-facing surface 2a, and at least a rear end portion as an outer diameter tapered section 21. The outer diameter of the flow-facing surface 2a is the maximum outer diameter of the inner plug 2 and is smaller than the inner diameter of the flow-facing section 13.

[0042] The inner plug 2 is inserted into the cylindrical member 1 and can be inserted to different depths. One of its outer peripheral wall and the inner peripheral wall of the cylindrical member 1 is provided with a protrusion 3 that is interference-fitted with the other one. The outer peripheral wall and the inner peripheral wall of the cylindrical member 1 together form a laminar flow channel 4.

[0043] The oncoming flow surface 2 a is located in the oncoming flow section 13 , and the outer diameter tapering section 21 and the inner diameter tapering section 11 overlap in the axial direction.

[0044] Specifically, since the cylindrical member 1 has a portion with a gradually decreasing inner diameter, and the inner plug 2 has a portion with a gradually decreasing outer diameter, after the inner plug 2 is inserted into the cylindrical member 1, the inner plug 2 is inserted to different depths, and the laminar flow channel 4 formed by the inner plug 2 and the cylindrical member 1 has different flow resistances. In addition, after the inner plug 2 is inserted into the cylindrical member 1, the two are interference-fitted by the protrusion 3, that is, the inner plug 2 is inserted to the corresponding depth, and the inner plug 2 can be firmly fixed at its depth. Therefore, this embodiment can assemble a laminar flow structure with various flow resistance specifications through the cylindrical member 1 and the inner plug 2 of fixed specifications only by adjusting the target end point during press-fitting, which greatly reduces the difficulty of production and material preparation and improves material utilization.

[0045] In addition, machined parts always have errors, and the errors between individuals cannot be eliminated. The laminar flow structure in this embodiment can also compensate for individual errors by adjusting the insertion depth of the inner plug 2, thereby improving the flow resistance accuracy of the laminar flow structure and the consistency of the finished product. In addition, the laminar flow structure in this embodiment allows real-time monitoring of the flow resistance or flow rate during the press-fitting process, so that the press-fitting depth can be controlled more conveniently and accurately.

[0046] And, if Figure 3 As shown, when the laminar flow structure in this embodiment is put into use, it is connected in parallel with the thermal flow sensor. The specific parallel connection method is that the flow guide hole 5 is connected to the inlet of the thermal flow sensor through the capillary 6, and the outlet of the thermal flow sensor is connected to the fluid outflow surface of the laminar flow structure through the capillary 6. The purpose is that when the fluid passes through, the laminar flow structure can generate a stable pressure loss, so that a small part of the fluid passes through the capillary 6 above. When the pressure loss generated by the laminar flow structure is stable, the ratio of the fluid flow through the capillary 6 to the fluid flow through the laminar flow structure is theoretically a constant value. At this time, it is only necessary to monitor the fluid flow through the capillary 6 to deduce the flow through the entire structure. After the laminar flow component structure in this embodiment is put into use in conjunction with the thermal flow sensor 7, when the high-speed fluid flows from the inlet into the headstream section 13, it will first hit the headstream surface 2a of the inner plug 2, and then the fluid will disperse. Part of the fluid enters the laminar flow channel 4 of the laminar flow component structure, and the other part of the fluid enters the thermal flow sensor 7 from the guide hole 5 through the capillary 6. Since the radius of the headstream surface 2a is large and it directly faces the impact of the high-speed fluid, it can well offset the inertial force of the high-speed fluid and break up the fluid, thereby reducing the influence of the inlet high-speed fluid on the laminar flow component structure, ensuring stable pressure loss, and making the pressure at the inlet of the capillary 6 more stable, which is less affected by the fluid flow rate, thereby reducing the measurement error of the thermal flow sensor 7.

[0047] In addition, the rear end of the laminar flow channel 4 has a certain slope, and the fluid is affected by the slope of the flow channel. When the fluid flows out of the laminar flow component structure, the circumferential fluid gathers toward the axial area, collides around the fluid outflow surface, and interacts with each other, thereby effectively weakening the speed of the fluid outflow, further reducing the impact on the laminar flow component structure, making the pressure loss more stable, and making the outlet pressure of the capillary 6 that converges the outlet of the thermal flow sensor 7 to the fluid outflow surface of the laminar flow component structure more stable, less affected by the fluid flow rate, and further reducing the measurement error of the thermal flow sensor 7.

[0048] It should be noted that the fluid in this embodiment is usually gas, but is not limited thereto.

[0049] In this embodiment, preferably, Figure 1 and Figure 3 As shown, the rear end of the inner plug member 2 does not extend beyond the tubular member 1 in the axial direction.

[0050] In this way, interference with other components during subsequent use can be avoided.

[0051] In addition, the flow-incoming surface 2 a may be perpendicular to the axial direction of the inner plug 2 ; and three flow-guiding holes 5 may be provided along the peripheral wall of the flow-incoming section 13 to guide the fluid into the capillary 6 .

[0052] During the processing of the parts in this embodiment, the taper angles of the inner diameter taper section 11 and the outer diameter taper section 21 are controlled to be different, so that the flow channel of the taper section presents different effects such as gradually narrowing, constant diameter, and gradually expanding. Figure 1 In the example shown, the inner diameter tapering section 11 and the outer diameter tapering section 21 are both conical, tapering at a uniform speed, and the tapering rates are equal, so the tapering section flow channel formed by the two is of equal diameter and unchanged. If the tapering angle of the outer diameter tapering section 21 is greater than the tapering angle of the inner diameter tapering section 11, that is, the tapering rate of the outer diameter tapering section 21 is greater than the tapering rate of the inner diameter tapering section 11, the tapering section flow channel formed by the two presents a trend of gradually expanding. Similarly, when the tapering rate of the outer diameter tapering section 21 is less than the tapering rate of the inner diameter tapering section 11, the tapering section flow channel formed by the two presents a trend of gradually shrinking.

[0053] In this embodiment, the cylindrical member 1 and the inner plug member 2 are kept coaxial as much as possible, so that the uniformity of the laminar flow channel 4 in the circumferential direction can be ensured.

[0054] In this embodiment, there are two protrusions 3 evenly distributed along the circumferential direction; or there are at least three protrusions 3 arranged along the circumferential direction. Each protrusion 3 can also extend along the axial direction, of course, it is also possible not to extend along the axial direction, as long as the inner plug 2 can be firmly fixed in the cylindrical member 1. Figure 2 In the example shown, the protrusions 3 are arranged on the outer peripheral wall of the inner plug 2, and there are three protrusions 3 arranged along the circumferential direction and extending along the axial direction.

[0055] Embodiment 2: Based on Embodiment 1, Figure 1 and Figure 3 As shown, the inner diameter of the incoming flow section 13 is larger than the maximum inner diameter of the inner diameter tapering section 11; wherein, the cylindrical member 1 also has an inner diameter equal diameter section 12 located between the incoming flow section 13 and the inner diameter tapering section 11, the inner diameter of the inner diameter tapering section 11 is smaller than the inner diameter of the incoming flow section 13, and is equal to the maximum inner diameter of the inner diameter tapering section 11; the front end portion of the inner plug 2 is an outer diameter equal diameter section 22, and the outer diameter of the outer diameter equal diameter section 22 is equal to the maximum outer diameter of the outer diameter tapering section 21.

[0056] In this embodiment, if Figure 1 and Figure 3 As shown, preferably, there is a smooth transition between the inner diameter constant diameter section 12 and the inner diameter tapering section 11 and between the outer diameter constant diameter section 22 and the outer diameter tapering section 21 .

[0057] In this embodiment, if Figure 1 and Figure 3As shown, preferably, the outer diameter equal diameter section 22 exceeds the inner diameter equal diameter section 12 along the fluid flow direction. In this way, the front half of the laminar flow channel 4 is gradually narrowed, which can well guide the fluid to flow in the form of laminar flow, which is conducive to generating a stable pressure loss at the head and tail of the laminar flow structure and improving the monitoring accuracy. It should be noted that the solution of making the laminar flow channel 4 have a gradually narrowing section is not limited to this, and can also be achieved through other ways as needed.

[0058] This embodiment has the following advantages:

[0059] Firstly, the formed laminar flow channel 4 has a smooth transition and gradually narrows. Such a smooth transition and extremely narrow gap are very conducive to the formation of laminar flow.

[0060] Secondly, the laminar flow channel formed by the cylindrical member 1 and the inner plug member 2 is not a simple straight channel in the direction of fluid flow, so that the bent flow channel can cause stable and effective pressure loss in a limited space.

[0061] Thirdly, the curved channel structure can effectively offset the error caused during the pressing process and the normal use later on, when high-speed fluid passes through, the fluid is affected by its own inertia and most of the fluid flows through the laminar flow component, with less fluid flowing through the thermal flow sensor 7, thereby causing errors.

[0062] The performance comparison between the solution in this embodiment and the two laminar flow parts mentioned in the background technology is as follows: Figures 3 to 5 As shown:

[0063] Figure 4 The maximum flow velocity comparison diagram of the outlet cross section shows that when the same mass flow rate of gas passes through, the maximum flow velocity of the gas in the outlet cross section of the laminar flow component in this embodiment is slightly greater than that of the cylindrical pin laminar flow component and the capillary laminar flow component, indicating that the flow state of the gas in the laminar flow channel 4 of the laminar flow component in this embodiment is closer to Poiseuille flow (i.e., ideal laminar flow state). This design achieves a laminar flow effect that is no less than that of the cylindrical pin laminar flow component and the capillary laminar flow component while reducing the difficulty of processing.

[0064] Figure 5 It is a comparison chart of pressure loss curves changing with flow rate. Compared with the cylindrical pin laminar flow component and the capillary laminar flow component, the pressure difference of the laminar flow component in this embodiment changes more linearly with the flow rate. The linear and stable pressure difference is beneficial to reducing the measurement error of the sensor (the error caused by the frontal surface 2a and the tail of the laminar flow channel 4 with a slope analyzed in Example 1, combined with the bent flow channel structure, can well offset the error caused by the passage of high-speed gas due to the influence of its own inertia, most of the gas flows through the laminar flow component, and less gas flows through the thermal flow sensor 7).

[0065] Figure 6The figure is a comparison diagram of the flow channel cross-section of the laminar flow component structure and the traditional laminar flow component under three measuring ranges. Under the same measuring range, the cross-sectional area of ​​the laminar flow component in this embodiment is larger, indicating that the laminar flow component in this embodiment achieves a greater pressure loss by means of the internal tortuous flow channel. At the same time, the cross-sectional area of ​​the cylindrical pin laminar flow component is smaller, and the smaller flow channel cross-sectional area puts higher requirements on the coaxiality of the laminar flow component; similarly, the capillary laminar flow component also puts higher requirements on the uniformity of the inner diameter of the capillary after assembly; in actual production, higher coaxiality and more uniform capillary inner diameter are more difficult to control, and the laminar flow component structure in this embodiment alleviates this problem well.

[0066] In summary, this embodiment aims to avoid the influence of airflow velocity on the entire structure, and reduces the airflow velocity everywhere. The solution in this embodiment can achieve greater pressure loss and more stable laminar flow with a larger flow channel gap.

[0067] Embodiment 3: A method for assembling the laminar flow device structure with adjustable flow resistance as described in Embodiment 1 or Embodiment 2, comprising:

[0068] The small end of the inner plug 2 is pressed into the tubular member 1 from the large end of the tubular member 1, so that the protrusion 3 provided on one of the outer peripheral wall of the inner plug 2 and the inner peripheral wall of the tubular member 1 is interference fit with the other;

[0069] During the press-fitting process, after the oncoming flow surface 2 a enters the oncoming flow section 13 , the flow resistance of the laminar flow channel 4 is controlled by controlling the press-fitting depth of the inner plug 2 .

[0070] Embodiment 4: Based on Embodiment 3, the assembly method further includes:

[0071] During the pressing process, the flow rate of the laminar flow channel 4 is measured by a pressure sensor connected in series with the laminar flow channel 4 or a thermal flow sensor 7 connected in parallel with the laminar flow channel 4; the pressing is stopped when the flow rate reaches a preset flow rate value or the flow resistance corresponding to the flow rate reaches a preset flow resistance value.

[0072] In traditional laminar flow parts, the quality of the laminar flow parts cannot be confirmed before the laminar flow parts are assembled, and there is a lot of uncertainty in the process. After assembly, they are tested to see if they are qualified. If they are unqualified, they cannot be adjusted further and can only be scrapped. However, the assembly method in this embodiment monitors the flow resistance or flow rate in real time during the press-fitting process. When the set flow rate or flow resistance is reached, the press-fitting can be stopped, which reduces costs and improves accuracy.

[0073] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A laminar flow structure with adjustable flow resistance, characterized in that: include: A cylindrical member (1), wherein the front end portion is a flow section (13), and the rear end portion is an inner diameter tapering section (11), the inner diameter of the flow section (13) is greater than the maximum inner diameter of the inner diameter tapering section (11), and the peripheral wall of the flow section (13) is provided with a plurality of flow guide holes (5), and the flow guide holes (5) extend to the outer wall of the flow section (13) and are used to connect to the inlet of a thermal flow sensor (7); The inner plug (2) has a front end surface which is a flow-facing surface (2a), a front end portion which is a section with a constant outer diameter (22), and a rear end portion which is a section with a gradually decreasing outer diameter (21); the outer diameter of the flow-facing surface (2a) is the maximum outer diameter of the inner plug (2) and is smaller than the inner diameter of the flow-facing section (13); wherein: The inner plug (2) is inserted into the cylindrical member (1) to allow insertion to different depths, and one of its outer peripheral wall and the inner peripheral wall of the cylindrical member (1) is provided with a protrusion (3) that is interference-fitted with the other, and its outer peripheral wall and the inner peripheral wall of the cylindrical member (1) together form a laminar flow channel (4); The oncoming surface (2a) is located in the oncoming section (13), and the outer diameter tapering section (21) and the inner diameter tapering section (11) overlap in the axial direction; The cylindrical member (1) further comprises an inner diameter equal diameter section (12) located between the oncoming flow section (13) and the inner diameter gradually reducing section (11); the inner diameter of the inner diameter gradually reducing section (11) is smaller than the inner diameter of the oncoming flow section (13) and is equal to the maximum inner diameter of the inner diameter gradually reducing section (11); the outer diameter equal diameter section (22) extends axially backward beyond the inner diameter equal diameter section (12); The inner diameter tapering section (11) and the outer diameter tapering section (21) are both conical and have the same tapering rate.

2. The laminar flow device structure with adjustable flow resistance according to claim 1, characterized in that: The rear end of the inner plug (2) does not extend beyond the tubular member (1) in the axial direction.

3. The laminar flow device structure with adjustable flow resistance according to claim 1, characterized in that: There is a smooth transition between the inner diameter equal section (12) and the inner diameter tapered section (11), and between the outer diameter equal section (22) and the outer diameter tapered section (21).

4. The laminar flow device structure with adjustable flow resistance according to claim 1, characterized in that: The protrusions (3) have two protrusions evenly distributed along the circumferential direction or have at least three protrusions arranged along the circumferential direction; And / or the protrusion (3) extends in the axial direction.

5. The laminar flow device structure with adjustable flow resistance according to claim 1, characterized in that: The cylindrical member (1) and the inner plug member (2) are coaxial.

6. A method for assembling a laminar flow device structure with adjustable flow resistance according to any one of claims 1 to 5, characterized in that: include: The small end of the inner plug (2) is pressed into the tubular member (1) from the large end of the tubular member (1) so that the protrusion (3) provided on one of the outer peripheral wall of the inner plug (2) and the inner peripheral wall of the tubular member (1) is interference-fitted with the other protrusion (3); During the press-fitting process, after the oncoming flow surface (2a) enters the oncoming flow section (13), the flow resistance of the laminar flow channel (4) is controlled by controlling the press-fitting depth of the inner plug (2).

7. The assembly method of the laminar flow device structure with adjustable flow resistance according to claim 6, characterized in that: Also includes: During the press-fitting process, the flow rate of the laminar flow channel (4) is measured, and the press-fitting is stopped when the flow rate reaches a preset flow rate value or the flow resistance corresponding to the flow rate reaches a preset flow resistance value.

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