JP4216648B2 - Electromagnetic flowmeter electrode structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode structure of an electromagnetic flow meter that electrically measures a flow rate of a measurement fluid flowing in a measurement tube.
[0002]
[Prior art]
An electromagnetic flowmeter is a Faraday in which when an electrically conductive fluid flows across a magnetic field, an electromotive force proportional to the flow velocity is induced in a direction orthogonal to both the direction of fluid flow and the direction of the magnetic field. The volume flow rate of fluid is measured using the law of electromagnetic induction. For this reason, a measuring tube having a lining made of an electrically insulating material is formed on the inner peripheral surface of the tube wall, and the tube wall of this measuring tube is provided so that the axes coincide with each other and perpendicular to the measuring tube And two excitation coils that are provided on the outer peripheral surface of the tube wall of the measurement tube so as to face each other and generate a magnetic field in a direction perpendicular to the axis of the measurement tube and the electrode.
[0003]
The electrode structure in such an electromagnetic flow meter has excellent workability during electrode mounting and replacement, and the electrode mounting hole can be reliably sealed, so that the measurement fluid can be used for high water pressure. It is required not to leak from. In view of this, various electrode structures have been conventionally proposed to satisfy such requirements (see, for example, Patent Documents 1 to 4). The applicant has not been able to find prior art documents closely related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
[0004]
[Patent Document 1]
Japanese Utility Model Publication No. 3-51707 [Patent Document 2]
JP-A-7-220173 [Patent Document 3]
JP-A-7-83714 (Description of paragraphs “0003” to “0008” of the specification, FIGS. 3 and 4)
[Patent Document 4]
JP-A-7-110248 (Description of paragraphs “0012” to “0025” of the specification, FIG. 1)
[0005]
The electrode structure of the electromagnetic flow meter described in the above-mentioned Japanese Patent Application Laid-Open No. 7-83714 is an electrode having a flange 5 integrally in the electrode mounting hole 3 of the measuring tube 1 lined by the lining 2 as shown in FIG. 4 is inserted, and the flange 5 is attached to the surface of the disk-shaped lining portion 2A covering the periphery of the electrode mounting hole 3 with the outer peripheral surface of the tube wall of the measuring tube 1 via the gasket 6. The measurement fluid L flowing in the measurement tube 1 is prevented from leaking outside through the gap between the lining portion 2A and the flange portion 5 by being in close contact and being pressed by the compression coil spring 7.
[0006]
A cylindrical electrode mounting portion 8 that surrounds the electrode mounting hole 3 and accommodates the electrode 4 and the compression coil spring 7 projects from the outer peripheral surface of the tube wall of the measuring tube 1. Covered by a cap 9. The cap 9 has an electrode hole 10 for projecting the other end portion 4 b of the electrode 4 to the outside, and is screwed into the electrode mounting portion 8. The cap 9 presses the compression coil spring 7 against the electrode 4. To adjust. In addition, 11 is an insulating member that electrically insulates the electrode 4 and the compression coil spring 7, 12 is a terminal fixing screw, and 13 is a terminal.
[0007]
The electrode part structure of the electromagnetic flowmeter detector described in Japanese Patent Application Laid-Open No. 7-110248 described above uses a bush instead of a compression coil spring, and presses the bush with a holder so that the flange of the electrode is the surface of the lining. By adopting such a structure, the measurement fluid is prevented from leaking from the electrode mounting hole. The collar part of the electrode has an annular wall integrally projecting on the outer peripheral edge, and this annular wall bites into an annular recess provided on the lining surface, so that a high surface pressure against the lining, in other words, a high sealing function Like to get. The other structure is substantially the same as the electrode structure shown in FIG.
[0008]
[Problems to be solved by the invention]
The conventional electrode structure shown in FIG. 5 has the following problems.
(1) Leakage of the measuring fluid L from the gap between the boundary portion 5 of the electrode 4 and the lining 2 can be prevented by using the gasket 6, but the inner peripheral surface of the electrode mounting hole 3 is covered. The gap 15 existing at the boundary surface between the cylindrical lining portion 2B and the one end 4a of the electrode 4 cannot be sealed, and foreign matter contained in the measurement fluid L or precipitation may be contained in the gap 15. If an object or the like enters and adheres, the electromotive force generated in the measurement fluid L cannot be accurately measured. In addition, various germs, spoilage and the like may be accumulated in the gap 15, which is unsuitable for sanitary specifications.
(2) When the gasket 6 and the compression coil spring 7 are deteriorated due to aging, the sealing performance is lowered and the measurement fluid L in the measurement tube 1 leaks from the electrode mounting hole 3.
(3) When condensation occurs in the cap 9 due to a sudden drop in ambient temperature, rust is generated in the compression coil spring 7 and the terminal 13.
(4) If the cap 9 is loosened due to the vibration of the piping due to the measurement fluid L, the pressing force against the flange 5 of the compression coil spring 7 is lowered and the sealing performance is lowered. It becomes easy to do.
(5) Since parts such as the gasket 6, the compression coil spring 7, and the insulating member 11 are required, the number of parts and the number of assembling steps of the electrode 4 increase, and the manufacturing cost increases.
[0009]
According to the electrode part structure of the electromagnetic flowmeter detector described in the above-mentioned Japanese Patent Application Laid-Open No. 7-110248, the above problems (2) and (3) can be solved, but the other problems Points (1), (4), and (5) still have a problem that they cannot be solved.
[0010]
The present invention has been made to solve the above-described conventional problems. The object of the present invention is to relatively seal the electrode mounting hole with a relatively simple structure and a small number of parts. It is an object of the present invention to provide an electrode structure for an electromagnetic flow meter capable of preventing leakage.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a first invention provides an electrode mounting hole formed in a tube wall and a cylindrical electrode mounting projecting on the outer peripheral surface of the tube wall so as to surround the electrode mounting hole. A measuring tube having a portion, a lining made of a synthetic resin that is molded so as to cover at least the inner periphery of the measuring tube and the electrode mounting hole , and one end portion of the electrode mounting hole An electrode made of a corrosion-resistant metal that is inserted through the lining and faces the measurement tube, and a primer of a corrosion-resistant paint that has been applied and solidified on the peripheral surface of the electrode; The electrode and the lining are integrally formed by welding and bonding a resin coating material that is solidified and made of a resin paint made of the same material as the lining .
[0012]
In the present invention, the electrode, the lining and the punching plate are integrally formed by insert molding or the like. In molding, the resin coating material welds and joins the electrode and the lining to reliably seal the gap between these two members. Therefore, the measurement fluid does not leak from the electrode mounting hole, and foreign matter does not enter and adhere to the gap between the electrode and the lining, so that the sealing performance of the measurement tube and the measurement accuracy of the electromagnetic flow meter can be improved. it can. In addition, it is not necessary to press the electrode with a biasing means such as a compression coil spring, and the number of parts can be reduced.
[0014]
Further, according to the present invention, welding between the lining and the resin coating is reliable, excellent in adhesion and adhesion, and high sealing performance can be obtained.
[0016]
Furthermore, according to the present invention, the corrosion resistance of the electrode is further improved. The primer is applied to the electrode surface as a lower layer of the resin paint.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of an electromagnetic flowmeter according to the present invention, FIG. 2 is an enlarged sectional view taken along line II-II in FIG. 1, and FIG. 3 is an enlarged sectional view of essential parts of electrodes and linings. . In the figure, the same components as those shown in the prior art column are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In these drawings, an electromagnetic flow meter generally indicated by reference numeral 20 includes a measuring tube 1, a pair of electrodes 4 and an excitation coil 21 provided on the tube wall of the measuring tube 1, and the circumference of the measuring tube 1. The outer case 22 covers the outer case 22 and the converter 23 and the like installed above the outer case 22.
[0018]
The measuring tube 1 is composed of a tube main body 1A made of a straight tube and open at both ends, and a pair of left and right flanges 1B and 1C integrally provided at both ends of the tube main body 1A. The two electrode mounting holes 3, which are through-holes on both the left and right sides of the part and to which the respective electrodes 4 are mounted, are formed so that their axes coincide with each other and are orthogonal to the axis of the measuring tube 1. Further, a tubular electrode mounting portion 8 protrudes from the outer peripheral surface of the tube wall of the tube main body 1A so as to surround each electrode mounting hole 3.
[0019]
Such a measuring tube 1 is made of a nonmagnetic material such as SUS or ceramics, and is formed on the outer surface of each of the flanges 1B and 1C, the inner peripheral surface of each of the electrode mounting holes 3, and the outer peripheral surface of the tube wall of the tube main body 1A. The lining 2 is integrally formed on the entire inner peripheral surface of the tube main body 1A including the portion surrounded by the electrode mounting portion 8. Examples of the lining 2 include PFA (perfluoroalkoxy resin), ETFE (tetrafluoroethylene resin), PP (polypropylene resin), PE (polyethylene terephthalate resin), PTFE (polytetrafluoroethylene resin), FEP (tetrafluoroethylene resin). ) And other synthetic resins having corrosion resistance and electrical insulation. A punching plate 28 is embedded in the lining 2 in order to increase the bonding strength with the measurement tube 1. The punching plate 28 is fixed to the inside of the tube main body 1A via a fixing ring 29.
[0020]
One end 4a of the electrode 4 is inserted into the electrode mounting hole 3 so as to face the measuring tube 1, and its tip surface 30 forms a liquid contact surface with the measuring fluid L. A portion of the electrode 4 that comes into contact with the lining 2 is formed on a rough surface by blasting to ensure welding by a resin coating material 37 described later. The other end portion 4 b of the electrode 4 protrudes from the electrode mounting portion 8 into the outer case 22, and a terminal 13 is fixed to the distal end surface of the electrode 4 by a terminal fixing set screw 12. One end of a signal lead wire 33 is connected to the terminal 13, and the other end of the signal lead wire 33 is connected to the converter 23 through the outer case 22.
[0021]
Such an electrode 4 is usually made of a non-magnetic material such as stainless steel, but is made of platinum, tantalum, hastelloy, titanium, tungsten, monel, nickel, zirconium or the like when corrosion resistance is required.
[0022]
Here, in the present embodiment, as shown in FIG. 4 (a), the example in which the electrode 4 having the flange portions 5A and 5B integrally at the one end portion 4a and the intermediate portion is used has been described. As shown in (b) to (g), various shapes can be used. That is, FIG. 5B shows an example in which a straight electrode is not provided with a flange portion, and FIG. 6C shows an example in which three annular grooves 34 are formed on the outer peripheral surface of one end portion 4a of the electrode so as to be separated in the axial direction. (D) shows an example in which the electrode 4 is formed in a straight rod-like body, and two through holes 35 perpendicular to the axis are formed in the one end 4a, and (e) shows one end 4a and the other end of the electrode. FIG. 5F shows an example in which the end 4a of the electrode 4 is formed in a tapered shape, and FIG. 5G shows an example in which the end 4a of the electrode 4 is tapered. An example in which an annular groove 34 is formed in the middle portion while being tapered is shown. Among these electrodes, the electrodes other than those shown in FIGS. 4B and 4F have a high coupling strength between the electrode 4 and the lining 2 and can prevent the electrode 4 from coming off from the electrode mounting hole 3. . Reference numeral 36 denotes a screw hole into which the set screw 12 is screwed.
[0023]
The pair of exciting coils 21 is attached to the central portion in the axial direction on the outer peripheral surface of the tube body 1A of the measurement tube 1 so as to face the measurement tube 1 in the vertical direction. For this reason, the exciting coil 21 and the electrode 4 are alternately arranged with a 90 ° phase shift in the circumferential direction of the measuring tube 1. The axis of the electrode 4 is perpendicular to the axis of the measurement tube 1, in other words, the flow direction of the conductive measurement fluid L flowing in the measurement tube 1, and the axis of the measurement tube 1 generated by excitation by energization of the excitation coil 21. The magnetic flux Φ at the center is orthogonal to both the axis of the electrode 4 and the flow direction of the measurement fluid L.
[0024]
Further, a plate core 40, a center core 41, and an outer core 42 that form a magnetic circuit of each excitation coil 21 are disposed on the outer peripheral surface of the tube wall of the measurement tube 1. The plate cores 40 are respectively arranged on the outer peripheral surface of the measuring tube 1 so as to face the upper and lower sides, the center core 41 projects from the center of the surface, and the exciting coil 21 is wound around the peripheral surface. The plate core 40 and the center core 41 are formed of a material having high magnetic permeability, such as permalloy, pure iron, or the like. The outer core 42 is formed in a cylindrical shape by a yoke or the like and surrounds the measuring tube 1 and the exciting coil 21, and two upper and lower portions are respectively fixed to the surface of each center core 41 by a plurality of set screws 43. Yes.
[0025]
The lining 2, the electrode 4 and the punching plate 28 are integrally formed by insert molding, and the lining 2 and the electrode 4 are welded and joined by the resin coating material 37. The gap is completely sealed to prevent the measurement fluid L from leaking from the electrode mounting hole 3 and the entry and attachment of foreign matter into the gap.
[0026]
As shown in FIG. 3, the resin coating material 37 is composed of two layers of a resin coating 38 and a primer 39, and is applied in advance to the portion of the peripheral surface of the electrode 4 that contacts the lining 2 when the lining 2 and the electrode 4 are integrally formed. Is done. As the resin coating 38, the same material as the lining 2, for example, a synthetic resin such as PFA, ETFE, PP, PE, PTFE, FEP or the like is used. As the primer 39, a corrosion resistant material, for example, enamel coating is used.
[0027]
In such an electromagnetic flow meter 20, when the electrode 4 is assembled to the measuring tube 1, a resin coating material 37 is applied in advance to a predetermined portion of the peripheral surface of the electrode 4 and solidified. The resin coating material 37 is applied by applying a primer 39 to a predetermined portion of the peripheral surface of the electrode 4 and solidifying it, and further applying a resin paint 38 thereon to solidify it. In addition, a punching plate 28 is attached to the measuring tube 1 and loaded into a mold.
[0028]
Next, the electrode 4 coated with the resin coating material 37 is inserted into the electrode mounting hole 3 of the measuring tube 1 and held by a jig. Next, the lining 2, the electrode 4, and the punching plate 28 are integrally formed by injecting the heated and melted lining material into a mold in which the measuring tube 1 is loaded and solidifying by cooling. At this time, the resin coating material 37 is melted by the heat of the lining, and then cooled and solidified to weld and join the lining 2 and the electrode 4. Accordingly, there is no gap between the one end portion 4a of the electrode 4 and the lining 2, and foreign matter can be prevented from entering and adhering. Further, if there is no gap between the lining 2 and the electrode 4, the measurement fluid L does not leak from the electrode mounting hole 3, so that the gasket 6, the compression coil spring 7 (see FIG. 5) and the like that have been conventionally required, etc. Can be eliminated, and the electrode structure can be simplified.
[0029]
In the electromagnetic flow meter 20 having such a structure, when a pair of excitation coils 21 are excited to generate a magnetic field B in a direction perpendicular to the axis of the electrode 4 and the flow direction of the measurement fluid L inside the measurement tube 1, In the measurement fluid L, an electromotive force e proportional to the average flow velocity is generated in a direction perpendicular to both the direction of the magnetic field B and the direction of the flow, and the electromotive force e is extracted by the pair of electrodes 4 and amplified. The flow rate and average flow velocity of the measurement fluid L are measured by recording or transmitting to the indicating instrument.
[0030]
【The invention's effect】
As described above, the electrode structure of the electromagnetic flowmeter according to the present invention is formed by integrally forming the lining lined on the measuring tube and the electrode, and welding and joining between the two members via the resin coating material. Compared to the conventional electrode structure, there is no need for gaskets, springs, caps, or other parts, making the structure simple and reducing the number of parts and the number of assembly steps. can do. Also, rust is not generated by condensation, and there is no concern about the deterioration of the sealing performance due to the looseness of the cap.
[0031]
In addition, in the invention in which the resin coating material is composed of two layers of resin paint and primer and the resin material is the same material as the lining, it is excellent in adhesion and adhesion to the lining and ensures high sealing performance. it can. Moreover, the kind of material can be reduced.
[0032]
Furthermore, in the invention using a corrosion-resistant material as a primer for the resin coating material, the corrosion resistance of the electrode can be further improved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of an electromagnetic flow meter according to the present invention.
FIG. 2 is an enlarged cross-sectional view taken along the line II-II in FIG.
FIG. 3 is an enlarged sectional view of a welded portion between a lining and an electrode.
FIGS. 4A to 4F are diagrams showing electrode shapes. FIGS.
FIG. 5 is a cross-sectional view of an electrode structure in a conventional electromagnetic flow meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Measuring tube, 2 ... Lining, 3 ... Electrode attachment hole, 4 ... Electrode, 5 ... Gutter part, 7 ... Compression coil spring, 8 ... Electrode attachment part, 9 ... Cap, 37 ... Resin coating material, 38 ... Resin coating material 39, primer, L, measurement fluid.

Claims (1)

A measuring tube having an electrode mounting hole formed in the tube wall, and a cylindrical electrode mounting portion protruding from the outer peripheral surface of the tube wall so as to surround the periphery of the electrode mounting hole;
A lining made of a synthetic resin that is molded so as to cover at least the inner peripheral surface of the measurement tube and the electrode mounting hole , and has an electrical insulation property ;
One end portion is inserted into the electrode mounting hole through the lining and an electrode made of a corrosion-resistant metal facing the measurement tube,
By welding and bonding a resin coating material comprising a primer of a corrosion-resistant paint applied and solidified on the peripheral surface of the electrode, and a resin paint of the same material as the lining applied and solidified on the primer The electrode structure of the electromagnetic flowmeter , wherein the electrode and the lining are integrally formed .

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