Electromagnetic flowmeter and magnetic steel sheet

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By designing the coil fixing structure formed by bending the magnetic conductive sheet, the problems of electromagnetic flowmeter induction coil limit and magnetic flux guidance are solved, the measurement accuracy and stability are improved, and the manufacturing cost is reduced.

CN222393606UActive Publication Date: 2025-01-24KAIFENG HUIER INSTR CO LTD

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Patent Information

Application Number: CN202420713296.0
Authority / Receiving Office: CN · China
Patent Type: Utility models(China)
Current Assignee / Owner
Filing Date: 2024-04-08
Publication Date: 2025-01-24
Estimated Expiration: 2034-04-08

AI Technical Summary

Technical Problem

Existing electromagnetic flowmeters cannot securely limit the induction coil and cannot efficiently guide the magnetic flux generated by the induction coil into the inside of the pipe, resulting in poor measurement accuracy and stability.

Method used

Design an electromagnetic flow meter, the coil fixing structure is made of a whole magnetic conductive film, including the intermediate arc surface and the pressure connection part. Through these structures, the induction coil is firmly limited and the magnetic flux is distributed along the closed loop.

Benefits of technology

The effective guidance of the solid limit and magnetic flux of the inductive coil is realized, and the accuracy and stability of the flowmeter measurement is improved, and the manufacturing cost is reduced.

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Abstract

The electromagnetic flowmeter comprises a measuring tube, two coil fixing structures are connected end to end and wrap the circumference of the measuring tube, and an induction coil is connected in a gap between each coil fixing structure and the outer wall of the measuring tube in a pressing mode; the coil fixing structure comprises a middle cambered surface part and pressing connecting parts symmetrically arranged on the two sides of the middle cambered surface part, the middle cambered surface part is attached to and fixedly connected with the outer wall of the measuring tube, gaps formed between the pressing connecting parts and the exterior of the measuring tube limit the induction coil, and avoiding notches are formed in the pressing connecting parts; the two pressing connecting parts are fixedly connected with the other two pressing connecting parts respectively, and the two avoiding notches of one coil fixing structure are partially overlapped with the two avoiding notches of the other coil fixing structure respectively to form two measuring electrode avoiding holes. The utility model further discloses a magnetic steel sheet which can be bent into the coil fixing structure. The induction coil can be firmly limited, and magnetic flux generated by the induction coil can be efficiently guided into a pipeline.

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Description

Technical Field

[0001] The utility model relates to the technical field of flow measurement, in particular to an electromagnetic flowmeter and a magnetic steel sheet. Background Art

[0002] Electromagnetic flowmeter is a device that measures flow based on Faraday's law of electromagnetic induction. It is currently widely used in industrial processes. It calculates the flow rate of the fluid in the pipeline by measuring the induced electromotive force generated on the electrodes on both sides of the measuring tube when the fluid cuts the magnetic flux lines in the magnetic field, thereby determining the flow rate.

[0003] The magnetic flux generated by the induction coil of the traditional electromagnetic flowmeter is not well guided to the measuring position inside the pipeline, resulting in a small magnetic flux density at the measuring position. At this time, a thicker induction coil wound by copper wire needs to be set, which makes the manufacturing cost of the electromagnetic flowmeter high. In addition, the setting of a thicker induction coil also makes the induction coil cover thicker than the pipeline setting, thereby further increasing the manufacturing cost of the electromagnetic flowmeter. In addition, the induction coil of the electromagnetic flowmeter needs to be firmly limited. The displacement of the induction coil will cause the magnetic field to change, affecting the accuracy and stability of the flowmeter, making the measured value inaccurate and unstable, affecting the measurement. Therefore, it is urgent to design an electromagnetic flowmeter that can firmly limit the induction coil and can efficiently guide the magnetic flux generated by the induction coil to the inside of the pipeline. Utility Model Content

[0004] The utility model aims to provide an electromagnetic flowmeter and a magnetic steel sheet, which effectively solve the problem that the existing electromagnetic flowmeter cannot firmly limit the induction coil and cannot efficiently guide the magnetic flux generated by the induction coil into the inside of the pipeline.

[0005] In order to solve the above technical problems, the utility model provides the following technical solutions:

[0006] An electromagnetic flowmeter comprises a measuring tube and two coil fixing structures, wherein the two coil fixing structures are connected end to end and wrapped around the circumference of the measuring tube, and an induction coil is crimped in the gap between each coil fixing structure and the outer wall of the measuring tube;

[0007] The coil fixing structure is formed by bending a whole magnetic conductive sheet multiple times, and includes a middle arc surface and a compression connection portion symmetrically arranged on both sides of the middle arc surface, the middle arc surface is fitted with and fixedly connected to the outer wall of the measuring tube, the gap formed by the compression connection portion and the outside of the measuring tube limits the induction coil, and an avoidance notch is provided on the compression connection portion;

[0008] The two clamping connection parts of one coil fixing structure partially overlap and are fixedly connected with the two clamping connection parts of another coil fixing structure respectively, and the two avoidance notches of one coil fixing structure partially overlap with the two avoidance notches of another coil fixing structure respectively to form two measuring electrode avoidance holes.

[0009] In some embodiments, the coil fixing structure is formed by bending a whole magnetic steel sheet multiple times, and the middle arc surface portion is fixedly connected to the outer wall of the measuring tube through a plurality of spot welding points.

[0010] In some embodiments, the magnetic steel sheet is a silicon steel sheet.

[0011] In some embodiments, a ground electrode avoidance hole is provided in the middle of the middle arc surface portion to avoid the ground electrode.

[0012] In some embodiments, the compression connection portion includes a first plane portion, a second plane portion, a third plane portion, and a fourth plane portion, the first plane portion is connected to the middle arc portion and is bent outward relative to the middle arc portion, the second plane portion is connected to the first plane portion and is bent inward relative to the first plane portion, the third plane portion and the fourth plane portion are symmetrically connected to the second plane portion, and are both bent inward relative to the second plane portion, an avoidance gap is formed between the second plane portion, the third plane portion, and the fourth plane portion, and the gap formed by the first plane portion, the second plane portion, the third plane portion, and the fourth plane portion and the outside of the measuring tube limits the induction coil;

[0013] The third planar portion and the fourth planar portion are both provided with a first oblong hole, the two third planar portions of one coil fixing structure are respectively connected to the two third planar portions of another coil fixing structure by fasteners passing through the first oblong holes, and the two fourth planar portions of one coil fixing structure are respectively connected to the two fourth planar portions of another coil fixing structure by fasteners passing through the first oblong holes.

[0014] In some embodiments, a width covered by the third planar portion to the fourth planar portion along the axial direction of the measuring tube is equivalent to a width covered by the induction coil along the axial direction of the measuring tube.

[0015] In some embodiments, a width covered by the second planar portion along the axial direction of the measuring tube gradually increases from a side adjacent to the first planar portion to a side adjacent to the third planar portion and the fourth planar portion.

[0016] In some embodiments, the third planar portion is not coplanar with the fourth planar portion, and one end of the third planar portion adjacent to the avoidance notch is farther from the measuring tube than the other end corresponding thereto, and one end of the fourth planar portion adjacent to the avoidance notch is farther from the measuring tube than the other end corresponding thereto.

[0017] In some embodiments, the first planar portion is bent outward at an angle of 75°-135° relative to the middle curved portion, the second planar portion is bent inward at an angle of 65°-125 degrees relative to the first planar portion, the third planar portion is bent inward at an angle of 5°-25° relative to the second planar portion, and the fourth planar portion is bent inward at an angle of 5°-25° relative to the second planar portion.

[0018] The electromagnetic flowmeter provided by the utility model, by setting the coil fixing structure to the above-mentioned structural shape and making it through magnetic conductive materials, on the one hand, makes the magnetic flux be distributed along the closed loop path formed by the two coil fixing structures as much as possible, and can guide the magnetic flux generated by the induction coil well. Experiments show that after regulating the magnetic flux of the induction coil in this way, the thickness of the induction coil is reduced, and the same measurement accuracy as before can still be achieved, which is equivalent to increasing the area of the coil fixing structure made of magnetic conductive materials, but reducing the amount of copper wire used in the induction coil, which can reduce the production cost of the electromagnetic flowmeter of the present application, because the price of copper wire is high and the price of magnetic conductive materials such as silicon steel sheets is low. After the application appropriately increases the amount of magnetic conductive materials such as silicon steel sheets, the use of copper wire can be greatly reduced. At the same time, after the induction coil becomes smaller, the two supporting flanges also become shorter, and the coil cover also becomes smaller accordingly, which can save materials, and thus can further reduce the production cost of the electromagnetic flowmeter of the present application. On the other hand, by fitting and fixedly connecting the arc surface with the outer wall of the measuring tube located in the middle of the induction coil, and connecting the two coil fixing structures bent into a certain shape end to end, the induction coil can be firmly limited to a fixed position on the outer wall of the measuring tube 1. Compared with fixing the coil by filler, the compression is better, thereby improving the accuracy and stability of the flow meter measurement.

[0019] The utility model also provides a magnetic steel sheet, which can be bent into the coil fixing structure described above, including a rectangular middle sheet, a trapezoidal transition sheet and a rectangular end sheet, the two trapezoidal transition sheets are connected on both sides of the rectangular middle sheet, the two rectangular end sheets are connected one by one to the outside of the two trapezoidal transition sheets, the width of the rectangular middle sheet is smaller than the width of the rectangular end sheets, a circular hole is provided in the center of the rectangular middle sheet, a notch is provided in the middle of the outer side of the rectangular end sheet, and two second oblong holes are also provided on the rectangular end sheet at intervals, and the two second oblong holes are symmetrically arranged relative to the notch.

[0020] The effect of a magnetic steel sheet provided by the utility model after being applied to an electromagnetic flowmeter is the same as the technical effect of the above-mentioned electromagnetic flowmeter, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of the main structure of the electromagnetic flowmeter provided by an embodiment of the utility model;

[0023] Figure 2 A schematic diagram of the rear view structure of the electromagnetic flowmeter provided by an embodiment of the utility model;

[0024] Figure 3 A schematic diagram of the top view of the electromagnetic flowmeter provided by an embodiment of the utility model;

[0025] Figure 4 This is a schematic diagram of the structure of the magnetic steel sheet provided by the utility model.

[0026] The following are marked in the accompanying drawings:

[0027] 1. Measuring tube; 11. Connecting flange; 12. Support flange; 13. Insulating lining; 2. Coil fixing structure; 21. Middle arc surface; 22. First plane portion; 23. Second plane portion; 24. Third plane portion; 25. Fourth plane portion; 26. Avoidance gap; 27. First oblong hole; 28. Grounding electrode avoidance hole; 3. Induction coil; 4. Measuring electrode avoidance hole; 5. Fastener; 6. Spot welding point; 7. Grounding electrode; 8. Measuring electrode;

[0028] 101, rectangular middle piece; 102, trapezoidal transition piece; 103, rectangular end piece; 104, circular hole; 105, notch; 106, second oblong hole. DETAILED DESCRIPTION

[0029] The core of the utility model is to provide an electromagnetic flowmeter and a magnetic steel sheet, which effectively solve the problem that the existing electromagnetic flowmeter cannot firmly limit the induction coil and cannot efficiently guide the magnetic flux generated by the induction coil into the inside of the pipeline.

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] Please refer to Figures 1 to 4 In a specific embodiment, an electromagnetic flowmeter provided by the utility model includes a measuring tube 1 and two coil fixing structures 2. The two coil fixing structures 2 are connected end to end and wrapped around the circumference of the measuring tube 1. An induction coil 3 is crimped in the gap between each coil fixing structure 2 and the outer wall of the measuring tube 1. The induction coil 3 is horseshoe-shaped and can fit the outer wall of the measuring tube 1. Both ends of the measuring tube 1 are connected with connecting flanges 11. Two supporting flanges 12 are also provided on the outer wall of the measuring tube 1. The two supporting flanges 12 are fixedly connected with coil covers (not shown in the figure) outside. The coil fixing structure 2 and the induction coil 3 are both located in the cavity surrounded by the coil cover, the measuring tube 1 and the two supporting flanges 12. The inner wall of the measuring tube 1 is connected with an insulating lining 13. A grounding electrode 7 is connected to the measuring tube 1 in the middle of one of the induction coils 3. Measuring electrodes 8 are symmetrically installed on the measuring tube 1 on both sides perpendicular to the direction opposite to the two induction coils 3.

[0032] The coil fixing structure 2 is formed by bending a whole magnetic conductive sheet multiple times. The magnetic conductive sheet is made of magnetic conductive material and can guide and regulate the magnetic lines of force generated by the induction coil. The coil fixing structure 2 includes a middle arc surface 21 and a compression connection portion symmetrically arranged on both sides of the middle arc surface 21. In other words, a compression connection portion is arranged on both sides of the middle arc surface 21.

[0033] The middle arc surface 21 is fitted and fixedly connected to the outer wall of the measuring tube 1 located in the middle of the induction coil 3, so that the position of the coil fixing structure 2 relative to the measuring tube 1 can be fixed, so as to avoid the induction coil 3 crimped by the coil fixing structure 2 not being fixed and being unable to be stably and firmly limited. Optionally, the middle arc surface 21 is spot-welded or adhesively connected to the outer wall of the measuring tube 1 located in the middle of the induction coil 3. Compared with clamping the coil by welding fasteners, the spot welding connection or adhesive connection has less obstruction to the passage of magnetic flux.

[0034] The gap formed between the clamping connection part and the outside of the measuring tube 1 limits the induction coil 3, and the clamping connection part is provided with an avoidance notch 26. The two clamping connection parts of one coil fixing structure 2 partially overlap with the two clamping connection parts of another coil fixing structure 2 and are fixedly connected, and the two avoidance notches 26 of one coil fixing structure 2 partially overlap with the two avoidance notches 26 of another coil fixing structure 2 and form two measuring electrode avoidance holes 4. The above-mentioned arrangement can not only play the role of fixing the induction coil 3, but also form a closed-loop magnetic flux guiding structure.

[0035] Therefore, by setting the coil fixing structure to the above-mentioned structural shape and making it through magnetic conductive materials, on the one hand, the magnetic flux can be distributed along the closed loop path formed by the two coil fixing structures as much as possible, and the magnetic flux generated by the induction coil 3 can be well guided. Experiments show that after regulating the magnetic flux of the induction coil 3 in this way, the thickness of the induction coil 3 can still achieve the same measurement accuracy as before, which is equivalent to increasing the area of the coil fixing structure made of magnetic conductive materials, but reducing the amount of copper wire used in the induction coil 3, which can reduce the production cost of the electromagnetic flowmeter of this application, because the price of copper wire is high and the price of magnetic conductive materials such as silicon steel sheets is low. After the application appropriately increases the amount of magnetic conductive materials such as silicon steel sheets, the use of copper wire can be greatly reduced. At the same time, after the induction coil 3 becomes smaller, the two support flanges 12 also become shorter, and the coil cover also becomes smaller accordingly, which can save materials, and thus can further reduce the production cost of the electromagnetic flowmeter of this application. On the other hand, by fitting and fixedly connecting the arc surface portion to the outer wall of the measuring tube 1 located in the middle of the induction coil 3, and connecting the two coil fixing structures bent into a certain shape end to end, the induction coil 3 can be firmly limited to a fixed position on the outer wall of the measuring tube 1. Compared with fixing the coil by filler, the compression is better, thereby improving the accuracy and stability of the flow meter measurement.

[0036] In some embodiments, the coil fixing structure 2 is formed by bending a whole magnetic steel sheet multiple times, the large angle bending part can be pre-bent by a bending machine, and the small angle bending part can be formed by natural bending during the assembly process, and the middle arc surface 21 is fixedly connected to the outer wall of the measuring tube 1 through four spot welding points 6. The spot welding connection has better connection strength and is less likely to shift.

[0037] On the basis of the above specific embodiments, the magnetic steel sheet is a silicon steel sheet, which has strong magnetic conductivity and is cheap.

[0038] In some embodiments, a grounding electrode avoidance hole 28 is provided in the middle of the middle arc surface portion 21 to avoid the grounding electrode 7. For occasions where grounding is required to reduce interference, a grounding electrode needs to be provided, and a grounding electrode avoidance hole is provided in the middle of the middle arc surface portion 21 in advance for easy assembly.

[0039] On the basis of the above specific embodiment, the compression connection portion includes a first plane portion 22, a second plane portion 23, a third plane portion 24 and a fourth plane portion 25. The first plane portion 22 is connected to the middle arc portion 21 and is bent outward relative to the middle arc portion 21. The second plane portion 23 is connected to the first plane portion 22 and is bent inward relative to the first plane portion 22. The third plane portion 24 and the fourth plane portion 25 are symmetrically connected to the second plane portion 23 and are bent inward relative to the second plane portion 23. An avoidance gap 26 is formed between the second plane portion 23, the third plane portion 24 and the fourth plane portion 25. The gaps formed by the first plane portion 22, the second plane portion 23, the third plane portion 24 and the fourth plane portion 25 and the outside of the measuring tube 1 limit the induction coil 3, that is, the gaps formed by the first plane portion 22, the second plane portion 23, the third plane portion 24 and the fourth plane portion 25 on both sides of the middle arc portion 21 of the coil fixing structure 2 and the outside of the measuring tube 1 respectively limit the opposite sides of the induction coil 3. By defining the specific structural shape of the compression connection portion, the induction coil 3 can be more firmly positioned at a fixed position on the outer wall of the measuring tube 1 .

[0040] The third plane portion 24 and the fourth plane portion 25 are both provided with a first oblong hole 27, and the two third plane portions 24 of one coil fixing structure 2 are respectively connected with the two third plane portions 24 of another coil fixing structure 2 through the first oblong hole 27 by fasteners 5, and the two fourth plane portions 25 of one coil fixing structure 2 are respectively connected with the two fourth plane portions 25 of another coil fixing structure 2 through the first oblong hole 27 by fasteners 5. The connection through the fasteners 5 is convenient and reliable, and preferably, rivet connection can be selected, which is not easy to loosen and occupies little space.

[0041] In some embodiments, the width covered by the third plane portion 24 to the fourth plane portion 25 along the axial direction of the measuring tube 1 is equivalent to the width covered by the induction coil 3 along the axial direction of the measuring tube 1. Since the measuring electrode avoidance hole 4 is provided between the third plane portion 24 and the fourth plane portion 25, and the first oblong hole 27 is provided on both the third plane portion 24 and the fourth plane portion 25, the width of the coil fixing structure is widened at this position, which can increase the connection strength on the one hand, and avoid the decrease of the magnetic flux guiding ability at this position on the other hand.

[0042] Based on the above specific embodiment, the width of the second plane portion 23 along the axial direction of the measuring tube 1 gradually increases from the side adjacent to the first plane portion 22 to the side adjacent to the third plane portion 24 and the fourth plane portion 25. This can provide better wrapping and fixing of the induction coil 3 on the one hand, and can achieve a gradual change in the width of the coil fixing structure 2 from the first plane portion 22 to the third plane portion 24 and the fourth plane portion 25 on the other hand, avoiding stress caused by sudden width changes.

[0043] Based on the above specific embodiment, the third plane portion 24 and the fourth plane portion 25 are not coplanar, and the end of the third plane portion 24 adjacent to the avoidance notch 26 is farther from the measuring tube 1 than the other end corresponding thereto, and the end of the fourth plane portion 25 adjacent to the avoidance notch 26 is farther from the measuring tube 1 than the other end corresponding thereto. Thus, when the third plane portion 24 and the fourth plane portion 25 are bent relative to the second plane portion 23, they are more closely fitted to the shape of the induction coil 3, so as to provide better wrapping and fixing for the induction coil 3.

[0044] In some embodiments, the first plane portion 22 is bent outwardly at an angle of 75°-135° relative to the middle arc portion 21, the second plane portion 23 is bent inwardly at an angle of 65°-125° relative to the first plane portion 22, the third plane portion 24 is bent inwardly at 5°-25° relative to the second plane portion 23, and the fourth plane portion 25 is bent inwardly at 5°-25° relative to the second plane portion 23. Producing the coil fixing structure 2 within the specified angle range can make the coil fixing more firmly and stably, and can provide better guidance for the magnetic flux.

[0045] The utility model also provides a magnetic steel sheet, which can be bent into the coil fixing structure described above, including a rectangular middle sheet 101, a trapezoidal transition sheet 102 and a rectangular end sheet 103, wherein the two trapezoidal transition sheets 102 are connected on both sides of the rectangular middle sheet 101, and the two rectangular end sheets 103 are connected one by one to the outside of the two trapezoidal transition sheets 102, the width of the rectangular middle sheet 101 is smaller than the width of the rectangular end sheets 103, a circular hole 104 is provided in the center of the rectangular middle sheet 101, a notch 105 is provided in the middle of the outer side of the rectangular end sheet 103, and two second oblong holes 106 are also provided on the rectangular end sheet 103 at intervals, and the two second oblong holes 106 are symmetrically arranged relative to the notch 105.

[0046] The effect of a magnetic steel sheet provided by the utility model after being applied to an electromagnetic flowmeter is the same as the technical effect of the above-mentioned electromagnetic flowmeter, and will not be described in detail here.

[0047] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0048] The electromagnetic flowmeter provided by the utility model is introduced in detail above. This article uses specific examples to illustrate the principle and implementation method of the utility model. The description of the above embodiments is only used to help understand the method and core idea of the utility model. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model. Therefore, the utility model will not be limited to the embodiments shown in this article, but will conform to the widest range consistent with the principles and novel features disclosed in this article.

Claims

1. An electromagnetic flowmeter, characterized in that: It comprises a measuring tube (1) and two coil fixing structures (2), wherein the two coil fixing structures (2) are connected end to end and wrapped around the circumference of the measuring tube (1), and an induction coil (3) is crimped into a gap between each coil fixing structure (2) and the outer wall of the measuring tube (1); The coil fixing structure (2) is formed by bending a whole magnetic conductive sheet multiple times, and comprises a middle arc surface (21) and compression connection parts symmetrically arranged on both sides of the middle arc surface (21), the middle arc surface (21) is in contact with and fixedly connected to the outer wall of the measuring tube (1), the gap formed between the compression connection part and the outside of the measuring tube (1) limits the induction coil (3), and an avoidance notch (26) is provided on the compression connection part; The two clamping connection parts of one coil fixing structure (2) partially overlap with the two clamping connection parts of another coil fixing structure (2) and are fixedly connected, and the two avoidance notches of one coil fixing structure (2) partially overlap with the two avoidance notches (26) of another coil fixing structure (2) to form two measuring electrode avoidance holes (4).

2. The electromagnetic flowmeter according to claim 1, characterized in that: The coil fixing structure (2) is formed by bending a whole magnetic steel sheet multiple times, and the middle arc surface portion (21) is fixedly connected to the outer wall of the measuring tube (1) via a plurality of spot welding points (6).

3. The electromagnetic flowmeter according to claim 2, characterized in that: The magnetic steel sheet is a silicon steel sheet.

4. The electromagnetic flowmeter according to claim 1, characterized in that: A grounding electrode avoidance hole (28) is provided in the middle of the middle arc surface portion (21) to avoid the grounding electrode (7).

5. The electromagnetic flowmeter according to claim 1, characterized in that: The pressing connection portion comprises a first plane portion (22), a second plane portion (23), a third plane portion (24) and a fourth plane portion (25); the first plane portion (22) is connected to the middle curved surface portion (21) and is bent outwardly relative to the middle curved surface portion (21); the second plane portion (23) is connected to the first plane portion (22) and is bent inwardly relative to the first plane portion (22); the third plane portion (24) and the fourth plane portion (25) are symmetrically connected to the second plane portion (23) and are bent inwardly relative to the second plane portion (23); an avoidance gap (26) is formed between the second plane portion (23), the third plane portion (24) and the fourth plane portion (25); and the gap formed by the first plane portion (22), the second plane portion (23), the third plane portion (24) and the fourth plane portion (25) and the outside of the measuring tube (1) limits the induction coil (3); The third plane portion (24) and the fourth plane portion (25) are both provided with a first oblong hole (27); the two third plane portions (24) of one coil fixing structure (2) are respectively connected to the two third plane portions (24) of another coil fixing structure (2) via fasteners (5) passing through the first oblong holes (27); and the two fourth plane portions (25) of one coil fixing structure (2) are respectively connected to the two fourth plane portions (25) of another coil fixing structure (2) via fasteners passing through the first oblong holes (27).

6. The electromagnetic flowmeter according to claim 5, characterized in that: The width covered by the third plane portion (24) to the fourth plane portion (25) along the axial direction of the measuring tube (1) is equivalent to the width covered by the induction coil (3) along the axial direction of the measuring tube (1).

7. The electromagnetic flowmeter according to claim 6, characterized in that: The width of the second plane portion (23) along the axial direction of the measuring tube (1) gradually increases from the side adjacent to the first plane portion (22) to the side adjacent to the third plane portion (24) and the fourth plane portion (25).

8. The electromagnetic flowmeter according to claim 5, characterized in that: The third plane portion (24) is not coplanar with the fourth plane portion (25); an end of the third plane portion (24) adjacent to the avoidance notch (26) is farther from the measuring tube (1) than the other end corresponding thereto; and an end of the fourth plane portion (25) adjacent to the avoidance notch (26) is farther from the measuring tube (1) than the other end corresponding thereto.

9. The electromagnetic flowmeter according to claim 5, characterized in that: The first plane portion (22) is bent outwardly at an angle of 75°-135° relative to the middle curved surface portion (21), the second plane portion (23) is bent inwardly at an angle of 65°-125° relative to the first plane portion (22), the third plane portion (24) is bent inwardly at an angle of 5°-25° relative to the second plane portion (23), and the fourth plane portion (25) is bent inwardly at an angle of 5°-25° relative to the second plane portion (23).

10. A magnetic steel sheet, characterized in that: It can be bent into the coil fixing structure (2) as described in any one of claims 1 to 9, comprising a rectangular middle piece (101), a trapezoidal transition piece (102) and a rectangular end piece (103), wherein the two trapezoidal transition pieces (102) are connected to the two sides of the rectangular middle piece (101), and the two rectangular end pieces (103) are connected to the outside of the two trapezoidal transition pieces (102) in a one-to-one correspondence, the width of the rectangular middle piece (101) is smaller than the width of the rectangular end piece (103), a circular hole (104) is provided in the center of the rectangular middle piece (101), a notch (105) is provided in the middle of the outer side of the rectangular end piece (103), and two second oblong holes (106) are also provided on the rectangular end piece (103) at intervals, and the two second oblong holes (106) are symmetrically arranged relative to the notch (105).