Electromagnetic flowmeter

Abstract

To provide an electromagnetic flowmeter which achieves improved measurement accuracy.SOLUTION: An electromagnetic flowmeter 10 includes: exciting coils 3 which are installed in a measurement pipe 1 so as to generate magnetic fields in a pipe-axis vertical direction of the measurement pipe 1; a return magnetic path 6 which is installed on lateral surfaces of the exciting coils 3 in a pipe-axis peripheral direction of the measurement pipe 1 so as to integrate the magnetic fields generated by the exciting coils 3 in the inside of the measurement pipe 1; and a return magnetic path auxiliary member which is installed at least on one of outer and inner diameter sides of the exciting coils 3 in the pipe-axis vertical direction so as to assist a function of the return magnetic path 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electromagnetic flowmeter. [Background technology]

[0002] Electromagnetic flowmeters are used as measuring instruments for measuring the flow rate of conductive fluids, such as tap water, flowing through a measuring pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-172645 A [Patent Document 2] Japanese Patent Application Publication No. 9-145435 [Patent Document 3] Japanese Patent Application Publication No. 5-256674 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is difficult to improve the measurement accuracy of an electromagnetic flowmeter. For example, in a method of shielding a portion of the magnetic flux meter away from the excitation coil, the gap between the return magnetic path and the magnetic shield becomes large, making it difficult to efficiently suppress magnetic flux leakage from the excitation coil to the pipe in which the magnetic flowmeter is installed (referred to as "other pipe").

[0005] The present invention has been made in view of the above, and has an object to improve the measurement accuracy of an electromagnetic flow meter. [Means for solving the problem]

[0006] The present invention provides an electromagnetic flowmeter for measuring a flow rate of a conductive fluid flowing through a measuring tube, the electromagnetic flowmeter comprising: an excitation coil that is installed in the measuring tube and generates a magnetic field in a direction perpendicular to the tube axis of the measuring tube; a feedback magnetic path that is installed on a side of the measuring tube in the circumferential direction of the tube axis including the excitation coil and that concentrates the magnetic field generated by the excitation coil inside the measuring tube; and a feedback magnetic path auxiliary member that is installed on at least one of an outer diameter side and an inner diameter side of the excitation coil in the direction perpendicular to the tube axis and that assists the function of the feedback magnetic path. Effect of the Invention

[0007] According to the present invention, it is possible to improve the measurement accuracy of an electromagnetic flow meter. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an example of a cross-sectional view of an electromagnetic flowmeter according to an embodiment, taken along a direction perpendicular to a tube axis. [Diagram 2] FIG. 2 is a diagram showing an example of a cross-sectional view of an electromagnetic flowmeter according to an embodiment, taken along a direction parallel to a tube axis. [Diagram 3] FIG. 2 is a diagram showing a first specific example of an external view of an electromagnetic flowmeter according to an embodiment. [Figure 4] FIG. 11 is a diagram showing a second specific example of an external view of the electromagnetic flowmeter according to the embodiment. [Diagram 5] FIG. 4 is a diagram showing a specific example of an external view of a return magnetic path cover of the electromagnetic flow meter according to the embodiment. [Figure 6] FIG. 2 is a diagram showing a first specific example of an external view of a feedback magnetic path sheet of the electromagnetic flowmeter according to the embodiment. [Figure 7] FIG. 11 is a diagram showing a second specific example of an external view of a feedback magnetic path sheet of the electromagnetic flowmeter according to the embodiment. [Figure 8] FIG. 11 is a diagram showing a specific example 3 of an external view of a feedback magnetic path sheet of the electromagnetic flowmeter according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An electromagnetic flowmeter according to an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

[0010] [Embodiment] Below, an overview of the electromagnetic flowmeter 10 according to the embodiment, the configuration and functions of the electromagnetic flowmeter 10 will be described in that order, and finally, the effects of the embodiment will be described.

[0011] [1. Overview of the Electromagnetic Flowmeter 10] An overview of an electromagnetic flowmeter 10 according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing an example of a cross-sectional view of the electromagnetic flowmeter 10 according to an embodiment in a direction perpendicular to the tube axis. Figure 2 is a diagram showing an example of a cross-sectional view of the electromagnetic flowmeter 10 according to an embodiment in a direction parallel to the tube axis. An example of the basic configuration of the electromagnetic flowmeter 10 and the effects of the electromagnetic flowmeter 10 will be described below.

[0012] (1-1. Basic configuration example of electromagnetic flowmeter 10) 1 and 2, the electromagnetic flowmeter 10 has a measuring tube 1, a lining material 2, an exciting coil 3, an electrode 5, a feedback magnetic path 6, a feedback magnetic path cover 7, a feedback magnetic path sheet 8, and a fixing member 9. The electromagnetic flowmeter 10 measures the flow rate of a conductive fluid 4 flowing inside the measuring tube 1.

[0013] (1-1-1. Basic principles of electromagnetic flowmeters) The electromagnetic flowmeter 10 is a measuring device used to measure the flow rate of a conductive fluid 4 such as tap water. The measurement tube 1 is made of a non-magnetic metal having corrosion resistance such as austenitic stainless steel. The lining material 2 is an insulator that covers the inside of the measurement tube 1. A pair of excitation coils 3 (3a, 3b) are installed at positions corresponding to the top and bottom of the measurement tube 1 and perpendicular to the tube axis, and generate a magnetic field inside the measurement tube 1. A pair of electrodes 5 (5a, 5b) are installed in a position perpendicular to the tube axis of the measurement tube 1 and perpendicular to the installation position of the excitation coil 3. Here, according to Faraday's law of electromagnetic induction, when a flow velocity occurs in the conductive fluid 4 inside the measurement tube 1, an electromotive force is generated in a direction perpendicular to the magnetic field generated by the excitation coil 3 and perpendicular to the tube axis. Then, the electromagnetic flowmeter 10 detects the generated electromotive force with the electrodes 5 (5a, 5b) and converts it into a flow rate of the conductive fluid 4.

[0014] (1-1-2. Feedback magnetic path auxiliary components of the electromagnetic flowmeter 10) The feedback magnetic path 6 has a function of concentrating the magnetic field generated by the excitation coil 3 inside the measurement tube 1 including the electrodes 5, and is made of a ferromagnetic material such as a silicon steel plate. The electromagnetic flowmeter 10 has at least one of a feedback magnetic path cover 7 and a feedback magnetic path sheet 8 as a feedback magnetic path auxiliary member that assists the properties of the feedback magnetic path 6.

[0015] The return magnetic path cover 7 has a first function as a magnetic shield that contains the magnetic field generated by the excitation coil, and a second function as an electromagnet that enhances the magnetic field at the center of the excitation coil 3. The return magnetic path cover 7 is installed so as to cover the side surfaces of the excitation coil 3 and the return magnetic path 6 in the circumferential direction of the tube axis, and is shaped to penetrate (intrude) into the inside of the gap between the excitation coil 3, as shown in FIG.

[0016] The feedback magnetic path cover 7 is installed on the side surface in the circumferential direction of the tube axis, thereby performing a first function of blocking the magnetic field generated by the excitation coil 3 from leaking to the outside. The feedback magnetic path cover 7 is shaped to fit inside the gap of the excitation coil 3, thereby performing a second function of strengthening the magnetic field generated by the excitation coil 3 as an electromagnet. At this time, the feedback magnetic path cover 7 is fixed by a fixing member 9 so as to overlap with the feedback magnetic path 6 inside the gap of the excitation coil 3 in the direction perpendicular to the tube axis, and by increasing the volume of the ferromagnetic material inside the gap of the excitation coil 3, the magnetic field is further strengthened as an electromagnet.

[0017] Here, if the feedback magnetic path cover 7 is to be manufactured as a part integrated with the feedback magnetic path 6, a lot of bending work is required, which makes production technology difficult and increases manufacturing costs. Also, in the excitation coil 3, the thicker the plate thickness inside the gap of the excitation coil 3, the greater the effect as an electromagnet, and the stronger the magnetic field is. However, the plate thickness outside the excitation coil 3 is not actually required to be that thick as a magnetic shield, so this becomes a waste of material. On the other hand, by dividing the feedback magnetic path 6 and the feedback magnetic path cover 7 into two parts, the inside of the gap of the excitation coil 3 where the two parts overlap can be designed to be thick (two sheets), and conversely, the outside of the excitation coil 3 can be designed to be thin (one sheet) because there is no overlap, and a feedback magnetic path 6 with good performance can be formed with relatively inexpensive material costs.

[0018] The feedback magnetic path sheet 8 has a first function of absorbing the magnetic field generated by the excitation coil, and a second function of acting as an electromagnet to enhance the magnetic field in the center of the excitation coil 3. The feedback magnetic path sheet 8 has slits cut into it so as to avoid the area directly below the excitation coil 3, and is shaped to cover the inside of the gap at the bottom surface (ground surface) of the excitation coil 3 and the peripheral area at the bottom surface of the excitation coil 3.

[0019] The feedback magnetic path sheet 8 is disposed around the bottom surface of the excitation coil 3 to prevent the magnetic field generated by the excitation coil 3 from being attracted to the opposing pipe. In this case, the feedback magnetic path sheet 8 exhibits a first function of absorbing the magnetic flux of the magnetic field generated by the excitation coil 3. Moreover, the feedback magnetic path sheet 8 is disposed on the inner side of the gap on the bottom surface of the excitation coil 3 to exhibit a second function of enhancing the magnetic field generated by the excitation coil 3 as an electromagnet.

[0020] Furthermore, the feedback magnetic path sheet 8 has slits that avoid the area directly below the bottom surface of the excitation coil 3, and therefore does not impede the magnetic field generated by the excitation coil 3 from flowing into the flow path of the measurement tube 1. The feedback magnetic path sheet 8 only needs to be hollow directly below the bottom surface of the excitation coil 3, and the other parts, that is, the inside of the gap at the bottom surface of the excitation coil 3 and the peripheral part at the bottom surface of the excitation coil 3, be filled with a ferromagnetic material.

[0021] (1-2. Effects of the electromagnetic flowmeter 10) In the following, an overview and problems of the reference technology will be described, and then the effects of the electromagnetic flowmeter 10 according to the embodiment will be described.

[0022] (1-2-1. Overview of Reference Technology 1) First, we will explain the outline of Reference Technology 1, which realizes an inexpensive wafer-type electromagnetic flowmeter that can reduce leakage magnetic flux and the influence of the material of the mating pipe. Reference Technology 1 is a wafer-type electromagnetic flowmeter with a mini-flange, and is equipped with a blocking plate made of a magnetic material that is provided in the flange part parallel to the plane of the mini-flange and blocks leakage of magnetic flux from the excitation coil in the flow direction of the measured fluid.

[0023] (1-2-2. Overview of Reference Technology 2) Secondly, we will provide an overview of Reference Technology 2, which prevents measurement errors when two pipes made of iron, a ferromagnetic material, are connected to a measurement tube. Reference Technology 2 is an electromagnetic flowmeter that includes a coil of magnetic field generating means that generates a magnetic field perpendicular to the measurement fluid inside the measurement tube, at least a pair of electrodes that are installed facing each other on the diameter of the measurement tube so as to measure the electromotive force generated by the action of the magnetic field, and magnetic shield plates attached to the flanges on both ends of the measurement tube that are less affected by the magnetic field.

[0024] (1-2-3. Overview of Reference Technology 3) Thirdly, we will provide an overview of Reference Technology 3, which provides a magnetic circuit with high shielding properties, prevents magnetic flux leakage in the axial direction of the measurement tube, and contributes to shortening the face-to-face distance. Reference Technology 3 is an electromagnetic flowmeter detector with an integral casting structure that includes a high-permeability magnetic metal ring located at the outer end of the measurement tube, and a side magnetic path that is concentric with the measurement tube and also has high magnetic permeability.

[0025] (1-2-4. Problems with the reference technology) First, Reference Technologies 1 and 2 are technologies that shield a portion of the coil away from the excitation coil, but the gap between the return magnetic path and the magnetic shield is large, making it difficult to efficiently suppress magnetic flux leakage from the excitation coil to the opposing piping.

[0026] Secondly, in Reference Technology 3, if an iron-based ferromagnetic material is used as the material for the magnetic shield of the electromagnetic flowmeter from the viewpoint of cost, etc., the iron-based material has extremely poor corrosion resistance and cannot be directly exposed to the fluid or the external environment, and may react with the lining material such as PFA (perfluoroalkoxyalkane) that is injection molded on the inner wall of the electromagnetic flowmeter, causing severe rust. On the other hand, in Reference Technology 3, if austenitic stainless steel with high corrosion resistance is used for the detector and an iron-based material is used as the magnetic shield for part of the inside of the detector, the same problems as those in Reference Technology 1 and Reference Technology 2 described above arise.

[0027] (1-2-5. Effects) The electromagnetic flowmeter 10 according to the embodiment can improve the magnetic shielding performance without a large increase in cost by optimizing the configuration and shape of the feedback magnetic path 6 and by including at least one of the feedback magnetic path cover 7 and the feedback magnetic path sheet 8 as a feedback magnetic path auxiliary member that assists the properties of the feedback magnetic path 6. That is, the electromagnetic flowmeter 10 can improve the measurement accuracy.

[0028] 2. Configuration and Function of Electromagnetic Flowmeter 10 The configuration and function of the electromagnetic flowmeter 10 shown in FIG. 1 and FIG. 2 will be described with reference to FIG. 3 to FIG. 8. The electromagnetic flowmeter 10 measures the flow rate of the conductive fluid 4 flowing through the measurement tube 1. FIG. 3 and FIG. 4 are diagrams showing specific examples of the external view of the electromagnetic flowmeter 10 according to the embodiment. FIG. 5 is a diagram showing a specific example of the external view of the feedback magnetic path cover 7 of the electromagnetic flowmeter 10 according to the embodiment. FIG. 6 to FIG. 8 are diagrams showing specific examples of the external view of the feedback magnetic path sheet 8 of the electromagnetic flowmeter 10 according to the embodiment. Below, a detailed description will be given of an example of the configuration and function of the electromagnetic flowmeter 10 in the order of the measurement tube 1, the lining material 2, the excitation coil 3, the electrode 5, the feedback magnetic path 6, the feedback magnetic path cover 7, the feedback magnetic path sheet 8, and the fixing member 9.

[0029] (2-1. Example of the configuration and function of measuring tube 1) 3 and 4, a configuration example and a function example of the measuring tube 1 will be described. The measuring tube 1 is installed in a counterpart pipe through which the conductive fluid 4 to be measured flows, and is a cylindrical tube that forms a flow path for the conductive fluid 4. The measuring tube 1 is made of a corrosion-resistant non-magnetic metal such as austenitic stainless steel.

[0030] (2-2. Example of the composition and function of lining material 2) 3 and 4, a configuration example and a function example of the lining material 2 will be described. The lining material 2 is an insulator that covers the inside of the measuring pipe 1. For example, the lining material 2 is made of an insulator such as PFA that is injection molded onto the inner wall of the measuring pipe 1.

[0031] (2-3. Configuration and function examples of excitation coil 3) 3 and 4, a configuration example and a function example of the excitation coil 3 will be described. The excitation coil 3 is installed in the measurement tube 1, and generates a magnetic field in a direction perpendicular to the tube axis of the measurement tube 1. At this time, the excitation coil 3 is installed as a pair of excitation coils 3a and 3b facing each other on the outer diameter side in the direction perpendicular to the tube axis of the measurement tube 1, and generates a magnetic field in the measurement tube 1 between the pair of excitation coils 3a and 3b.

[0032] (2-4. Configuration and Function Examples of Electrode 5) An example of the configuration and function of the electrode 5 will be described with reference to Figures 3 and 4. The electrode 5 is installed in the measurement tube 1, and is installed in a position perpendicular to the tube axis of the measurement tube 1 and perpendicular to the installation position of the excitation coil 3, and detects an electromotive force generated by the conductive fluid 4 flowing inside the measurement tube 1. At this time, the electrodes 5 are installed as a pair of electrodes 5a and 5b facing each other on the outer diameter side in the tube axis perpendicular direction of the measurement tube 1, and detect an electromotive force signal that is generated in a direction perpendicular to the magnetic field and perpendicular to the tube axis and is proportional to the flow rate of the conductive fluid 4 flowing inside the measurement tube 1.

[0033] (2-5. Example of configuration and function of feedback magnetic path 6) An example of the configuration and function of the feedback magnetic path 6 will be described with reference to Fig. 3 and Fig. 4. The feedback magnetic path 6 is a circuit that applies a magnetic field in a direction perpendicular to the flow direction of the conductive fluid 4, and is installed on the side surface of the measuring tube 1 in the circumferential direction of the tube axis including the excitation coil 3, and concentrates the magnetic field generated by the excitation coil 3 inside the measuring tube 1. In this case, the feedback magnetic path 6 may be installed on the side surface of the measuring tube 1 in the circumferential direction of the tube axis including all of the pair of excitation coils 3 (3a, 3b) and the pair of electrodes 5 (5a, 5b). The feedback magnetic path 6 is a ferromagnetic plate. For example, the feedback magnetic path 6 is made of a silicon steel plate.

[0034] (2-6. Configuration and function examples of the feedback magnetic path cover 7) 3 to 5, a configuration example and a function example of the feedback magnetic path cover 7 will be described. The feedback magnetic path cover 7 is installed on at least one of the outer diameter side and the inner diameter side of the excitation coil 3 in the direction perpendicular to the tube axis, and is one of the feedback magnetic path auxiliary members that assists the function of the feedback magnetic path 6. For example, the feedback magnetic path cover 7 is installed on the outer diameter side of the excitation coil 3 in the direction perpendicular to the tube axis, and blocks the movement of the magnetic flux of the magnetic field to the outer diameter side. In addition, the feedback magnetic path cover 7 is installed so as to be recessed into the gap of the excitation coil 3 on the outer diameter side of the excitation coil 3 in the direction perpendicular to the tube axis, and enhances the magnetic field generated by the excitation coil. In addition, the feedback magnetic path cover 7 is a plate of a ferromagnetic material.

[0035] Here, a specific example of the feedback magnetic path cover 7 will be described with reference to FIG. 5. As shown in FIG. 5, the feedback magnetic path cover 7 has a structure that is installed on the outer diameter side of the excitation coil 3 in the direction perpendicular to the tube axis so as to be embedded in the gap between the excitation coil 3. In the example of FIG. 5, the feedback magnetic path cover 7 has a separable structure that is installed so as to cover either one of the pair of excitation coils 3a and 3b. That is, the feedback magnetic path cover 7 shown in the example of FIG. 5 is installed so as to cover both of the pair of excitation coils 3a and 3b using two sets. In addition, the feedback magnetic path cover 7 shown in the example of FIG. 5 has a separable structure to facilitate installation, but may be composed of one combined part. In addition, the feedback magnetic path cover 7 may have a structure that is installed so as to cover both of the pair of excitation coils 3a and 3b with one part.

[0036] As described above, the return magnetic path cover 7 is disposed on the side surface in the circumferential direction of the tube axis, thereby performing a first function of blocking the magnetic field generated by the exciting coil 3 from leaking to the outside. In addition, the return magnetic path cover 7 has a shape that fits inside the gap of the exciting coil 3, thereby performing a second function of enhancing the magnetic field generated by the exciting coil 3 as an electromagnet.

[0037] (2-7. Configuration and function examples of feedback magnetic path sheet 8) 3 to 8, a configuration example and a function example of the feedback magnetic path sheet 8 will be described. The feedback magnetic path sheet 8 is installed on at least one of the outer diameter side and the inner diameter side in the tube axis perpendicular direction of the excitation coil 3, and is one of the feedback magnetic path auxiliary members that assists the function of the feedback magnetic path 6. For example, the feedback magnetic path sheet 8 is installed on the inner diameter side in the tube axis perpendicular direction of the excitation coil 3, and absorbs the magnetic flux of the magnetic field toward the outer diameter side in the tube axis perpendicular direction of the excitation coil 3. In addition, the feedback magnetic path sheet 8 is installed on the inner diameter side in the tube axis perpendicular direction of the excitation coil 3, except for the part where the excitation coil 3 is installed in the measuring tube 1, and transmits the magnetic flux of the magnetic field toward the inner diameter side and enhances the magnetic field generated by the excitation coil 3. In addition, the feedback magnetic path sheet 8 is a plate of a ferromagnetic material.

[0038] Here, specific examples of the feedback magnetic path sheet 8 (8-1, 8-2, 8-3) will be described with reference to Figs. 6 to 8. As shown in Figs. 6 to 8, the feedback magnetic path sheet 8 has a structure in which it is installed on the inner diameter side in the direction perpendicular to the tube axis of the excitation coil 3. In this case, the feedback magnetic path sheet 8 has a structure that does not impede the magnetic field generated by the excitation coil 3 from flowing into the flow path of the measurement tube 1, and it is sufficient that the other parts, that is, the inside of the gap at the bottom surface of the excitation coil 3 and the peripheral part at the bottom surface of the excitation coil 3, are filled with a ferromagnetic material.

[0039] In the example of Figure 6, the feedback magnetic path sheet 8-1 has a structure separated into three parts, is shaped to avoid being installed directly below the excitation coil 3, and covers the inner gap and surrounding areas at the bottom of the excitation coil 3.

[0040] In the example of Figure 7, the feedback magnetic path sheet 8-2 has a structure with four slits formed therein, and is shaped to avoid being placed directly below the excitation coil 3 and to cover the inner gap portion and the surrounding area on the bottom surface of the excitation coil 3.

[0041] In the example of Figure 8, the feedback magnetic path sheet 8-3 has a structure in which two cavities are formed, and is shaped to avoid being installed directly below the excitation coil 3 and to cover the inner gap portion and the surrounding area at the bottom surface of the excitation coil 3.

[0042] As described above, the feedback magnetic path sheet 8 is disposed in the peripheral portion of the bottom surface of the excitation coil 3, thereby performing a first function of absorbing the magnetic flux of the magnetic field generated by the excitation coil 3. Moreover, the feedback magnetic path sheet 8 is disposed in the inner gap portion of the bottom surface of the excitation coil 3, thereby performing a second function of enhancing the magnetic field generated by the excitation coil 3 as an electromagnet.

[0043] (2-8. Configuration and Function Examples of Fixing Member 9) An example of the configuration and function of the fixing member 9 will be described with reference to Fig. 3 and Fig. 4. The fixing member 9 fixes the feedback magnetic path 6, the feedback magnetic path cover 7, and the feedback magnetic path sheet 8. In the example of Fig. 3 and Fig. 4, the fixing member 9 is composed of two parts, but the number of parts of the fixing member 9 is not particularly limited.

[0044] 3. Effects of the First Embodiment Finally, effects of the embodiment will be described below: Effects 1 to 6 corresponding to the configuration and functions of the embodiment will be described below.

[0045] (3-1. Effect 1) First, in the above-described embodiment, the electromagnetic flowmeter 10 includes the excitation coil 3 that is installed in the measurement tube 1 and generates a magnetic field in a direction perpendicular to the tube axis of the measurement tube 1, the feedback magnetic path 6 that is installed on a side surface of the measurement tube 1 in the circumferential direction of the tube axis including the excitation coil 3 and that concentrates the magnetic field generated by the excitation coil 3 inside the measurement tube 1, and a feedback magnetic path auxiliary member that is installed on at least one of the outer diameter side and the inner diameter side in the direction perpendicular to the tube axis of the excitation coil 3 and assists the function of the feedback magnetic path 6. Therefore, in the embodiment, the measurement accuracy of the electromagnetic flowmeter 10 can be improved.

[0046] (3-2. Effect 2) Secondly, in the above-described embodiment, in the electromagnetic flowmeter 10, the feedback magnetic path cover 7, which is a feedback magnetic path auxiliary member, is installed on the outer diameter side in the direction perpendicular to the tube axis of the excitation coil 3, and blocks the movement of magnetic flux of the magnetic field to the outer diameter side. Therefore, in the embodiment, the feedback magnetic path cover 7 suppresses magnetic flux leakage to the outside, thereby improving the measurement accuracy of the electromagnetic flowmeter 10.

[0047] (3-3. Effect 3) Thirdly, in the above-described embodiment, the electromagnetic flowmeter 10 is installed such that the feedback magnetic path cover 7, which is a feedback magnetic path auxiliary member, is recessed into the gap of the excitation coil 3, and enhances the magnetic field generated by the excitation coil 3. Therefore, in the embodiment, the feedback magnetic path cover 7 functions as an electromagnet to enhance the magnetic field in the central portion of the excitation coil 3, thereby improving the measurement accuracy of the electromagnetic flowmeter 10.

[0048] (3-4. Effect 4) Fourthly, in the above-described embodiment, in the electromagnetic flowmeter 10, the feedback magnetic path sheet 8, which is a feedback magnetic path auxiliary member, is installed on the inner diameter side in the direction perpendicular to the tube axis of the excitation coil 3, and absorbs the magnetic flux of the magnetic field toward the outer diameter side. Therefore, in the embodiment, the feedback magnetic path sheet 8 suppresses magnetic flux leakage to the outside, thereby improving the measurement accuracy of the electromagnetic flowmeter 10.

[0049] (3-5. Effect 5) Fifth, in the above-described embodiment, in the electromagnetic flowmeter 10, the feedback magnetic path sheet 8, which is a feedback magnetic path auxiliary member, is installed on the inner diameter side except for the portion where the excitation coil 3 is installed in the measurement tube 1, and transmits the magnetic flux of the magnetic field to the inner diameter side and enhances the magnetic field generated by the excitation coil 3. Therefore, in the embodiment, the feedback magnetic path sheet 8 enhances the magnetic field in the central portion of the excitation coil 3 as an electromagnet without impeding the magnetic field from flowing into the flow path of the measurement tube 1, thereby improving the measurement accuracy of the electromagnetic flowmeter 10.

[0050] (3-6. Effect 6) Sixth, in the above-described embodiment, at least one of the feedback magnetic path cover 7 and the feedback magnetic path sheet 8, which are the feedback magnetic path auxiliary members, is a ferromagnetic plate in the electromagnetic flowmeter 10. Therefore, in the embodiment, the feedback magnetic path auxiliary member effectively assists the function of the feedback magnetic path 6, thereby improving the measurement accuracy of the electromagnetic flowmeter 10.

[0051] 〔system〕 The information including the processing procedures, control procedures, specific names, various data and parameters shown in the above documents and drawings can be changed arbitrarily unless otherwise specified.

[0052] In addition, each component of each device shown in the figure is a functional concept, and does not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each device is not limited to that shown in the figure. In other words, all or part of them can be functionally or physically distributed and integrated in any unit according to various loads, usage conditions, etc.

[0053] 〔others〕 Some examples of combinations of the disclosed technical features are set out below.

[0054] (1) An electromagnetic flowmeter for measuring a flow rate of a conductive fluid flowing through a measuring tube, comprising: an excitation coil that is installed in the measuring tube and generates a magnetic field in a direction perpendicular to the tube axis of the measuring tube; a feedback magnetic path that is installed on a side of the measuring tube in a circumferential direction of the tube axis including the excitation coil and that concentrates the magnetic field generated by the excitation coil inside the measuring tube; and a feedback magnetic path auxiliary member that is installed on at least one of an outer diameter side and an inner diameter side of the excitation coil in the direction perpendicular to the tube axis and that assists the function of the feedback magnetic path.

[0055] (2) The electromagnetic flowmeter according to (1), wherein the return magnetic path auxiliary member is disposed on the outer diameter side of the excitation coil in a direction perpendicular to the tube axis and blocks movement of magnetic flux of the magnetic field toward the outer diameter side.

[0056] (3) The electromagnetic flowmeter according to (2), wherein the feedback magnetic path auxiliary member is disposed so as to enter a gap of the excitation coil and enhances the magnetic field generated by the excitation coil.

[0057] (4) An electromagnetic flowmeter according to any one of (1) to (3), wherein the return magnetic path auxiliary member is disposed on the inner diameter side of the excitation coil in a direction perpendicular to the tube axis and absorbs the magnetic flux of the magnetic field toward the outer diameter side.

[0058] (5) The electromagnetic flowmeter described in (4), in which the return magnetic path auxiliary member is installed on the inner diameter side excluding a portion where the excitation coil is installed on the measurement tube, and transmits magnetic flux of the magnetic field to the inner diameter side and enhances the magnetic field generated by the excitation coil.

[0059] (6) The electromagnetic flowmeter according to any one of (1) to (5), wherein the return magnetic path auxiliary member is a ferromagnetic plate. [Explanation of symbols]

[0060] 1 Measuring tube 2 Lining material 3 Excitation coil 4 Conductive fluid 5 electrodes 6. Feedback magnetic path 7 Return magnetic path cover 8. Feedback magnetic circuit sheet 9 Fixing member 10 Electromagnetic flowmeter

Claims

1. An electromagnetic flowmeter for measuring a flow rate of a conductive fluid flowing through a measurement tube, comprising: an excitation coil that is installed in the measuring tube and generates a magnetic field in a direction perpendicular to the axis of the measuring tube; a feedback magnetic path that is installed on a side surface of the measuring tube in a circumferential direction of the tube axis including the excitation coil and that concentrates the magnetic field generated by the excitation coil inside the measuring tube; a feedback magnetic path auxiliary member that is installed on at least one of an outer diameter side and an inner diameter side of the excitation coil in a direction perpendicular to the tube axis and that assists the function of the feedback magnetic path; An electromagnetic flow meter comprising:

2. The feedback magnetic path auxiliary member is The coil is disposed on the outer diameter side in a direction perpendicular to the tube axis of the excitation coil, and blocks the movement of the magnetic flux of the magnetic field to the outer diameter side.

2. The electromagnetic flowmeter of claim 1.

3. The feedback magnetic path auxiliary member is The magnetic field generating section is disposed so as to be embedded in the gap of the excitation coil and enhances the magnetic field generated by the excitation coil.

3. The electromagnetic flowmeter of claim 2.

4. The feedback magnetic path auxiliary member is The coil is disposed on the inner diameter side in a direction perpendicular to the tube axis of the excitation coil, and absorbs the magnetic flux of the magnetic field toward the outer diameter side.

2. The electromagnetic flowmeter of claim 1.

5. The feedback magnetic path auxiliary member is The excitation coil is installed on the inner diameter side excluding a portion installed on the measurement tube, and transmits the magnetic flux of the magnetic field to the inner diameter side and enhances the magnetic field generated by the excitation coil.

5. The electromagnetic flowmeter according to claim 4.

6. The feedback magnetic path auxiliary member is A plate of ferromagnetic material, 6. An electromagnetic flowmeter according to claim 1.

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