JP2005207971A - Electromagnetic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic flowmeter with a magnetic circuit hardly affected by a flow velocity distribution, by arranging a core and an excitation coil in a feedback magnetic path, and by canceling a leaked magnetic flux generated in the feedback magnetic path. <P>SOLUTION: This electromagnetic flowmeter is provided with the pair of cores for generating a magnetic field vertical-directionally with respect to a fluid flowing in a measuring tube, a pair of detecting electrodes arranged in a tube wall of the measuring tube orthogonal to the magnetic field to detect an electromotive force generated in response to a flow rate of the fluid, a magnetic pole core coupled to the pair of cores in the feedback magnetic path other than the measuring tube, and the excitation coil wound with a coil in a periphery of the magnetic pole core. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic flow meter, and more particularly, a coil for forming a magnetic field in a measurement tube, and an electromagnetic flow meter having a circuit structure for providing a sufficient magnetic field to the center of a measurement tube by arranging a coil in a feedback magnetic path in a core. About.

  As shown in FIG. 8, the residual magnetic electromagnetic flow meter of the first example in the prior art is 101 as a flow channel pipe, and electrodes 106 and 107 are provided. The first yoke 108 and 109 and its end face are opposed to the flow channel tube 1 and are made of a soft magnetic material. 111 and 112 are cores 110 made of a semi-rigid magnetic material, and a second yoke disposed magnetically in series between the first yokes 108 and 109 and the core, respectively. Consists of materials. The core 110 and the second yokes 111 and 112 are cylindrical with the same diameter, are arranged concentrically on a straight line, and a wire ring 115 is formed on the outer periphery thereof. The second yokes 111 and 112 are inserted and coupled to the circular holes 108a and 109a provided in the first yokes 108 and 109, respectively, so as to be movable with little clearance. The length Ln of the core 110 is set shorter than the length Lm of the wire ring, and the end surface abutting portions between the core 110 and the second yokes 111 and 112 are maintained in a state where there is no gap due to surface contact.

In the second example of the electromagnetic flow meter, as shown in FIG. 9, a pole piece core 122 is disposed on the outer periphery of the measurement tube 121 and is opposed to the magnet, and an excitation coil 123 is wound around the pole piece core 122. It is configured. Detection electrodes 124a and 124b are provided at positions orthogonal to the exciting coil 123, and the detection electrodes 124a and 124b are covered with a guard case 125 filled with a gel-like resin. It has a structure in which a magnetic paint film is applied. Then, the feedback magnetic path 125 is formed by covering the outer periphery of the guard case 125 covering the excitation coil 123, the pole piece core 122, and the detection electrodes 124a and 124b disposed at the outer peripheral position of the measuring tube 121 with a magnetic material. .
Japanese Examined Patent Publication No. 6-76896 (Page 2, Fig. 1)

  However, in the electromagnetic flow meter described in the related art, the configuration of the magnetic circuit in the electromagnetic flow meter of the second conventional example is generally configured by a core, a feedback magnetic path, and an excitation coil. In this case, since the magnetic resistance between the core and the feedback magnetic path is shorter than the magnetic resistance of the measuring tube portion where the magnetic flux is to be concentrated, there is a problem that a lot of magnetic flux that does not contribute to the electromotive force is generated as leakage magnetic flux.

The configuration of the magnetic circuit in the electromagnetic flowmeter of the first example described in the prior art has the effect of arranging the coil core in a part of the feedback magnetic path to reduce the leakage magnetic flux, but the core itself has a large magnetic flux. There is a problem in that it cannot concentrate effectively on the measuring tube.
Furthermore, there is a problem that the magnetic resistance in the vicinity of the electrode is low, so that the magnetic field in the vicinity of the electrode becomes strong, and a sufficient magnetic field cannot be applied to the center of the measuring tube. This problem also causes a problem that is easily influenced by the flow velocity distribution.

  Therefore, there is a problem to be solved by a high-efficiency magnetic circuit capable of realizing a high signal level and an electromagnetic flow meter including a magnetic circuit that is not affected by the flow velocity distribution.

In order to solve the above problems, the electromagnetic flowmeter of the present invention is configured as follows.
(1) The electromagnetic flow meter is disposed on a pair of cores that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube, and on the tube wall of the measurement tube in a direction orthogonal to the magnetic field, and controls the flow rate of the fluid. A pair of detection electrodes for detecting a corresponding electromotive force, a magnetic pole core connected to the pair of cores in a feedback magnetic path other than the measurement tube, and an excitation coil in which a coil is wound around the magnetic pole core; It is equipped with.
(2) The magnetic flowmeter according to (1), wherein the length of the magnetic pole core is longer than the diameter of the measuring tube.
(3) The length of the magnetic core is longer than the diameter of the measuring tube, the pair of cores are inclined on the side connected to the magnetic core, and the pair of cores are parallel to the measuring tube. The electromagnetic flow meter according to (1), which is opposed to the electromagnetic flow meter.
(4) The length of the magnetic core is longer than the diameter of the measuring tube, the pair of cores are inclined on the side connected to the magnetic core, and the distal ends of the pair of cores are connected to the measuring tube. The electromagnetic flow meter according to (1), characterized in that it has an inclination along the diameter shape.

(5) The electromagnetic flow meter is arranged on a pair of cores that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube, and on the tube wall of the measurement tube in a direction orthogonal to the magnetic field, and adjusts the flow rate of the fluid. A pair of detection electrodes for detecting a corresponding electromotive force, a first magnetic pole core connected to one side of the pair of cores with a feedback magnetic path other than the measurement tube, and a periphery of the first magnetic pole core A first exciting coil wound around the coil, a second magnetic pole core connected to the other side of the pair of cores in a feedback magnetic path other than the measuring tube, and a coil wound around the second magnetic pole core And a second excitation coil.
(6) The electromagnetic flowmeter according to (5), wherein the length of the first and second magnetic pole cores is longer than the diameter of the measuring tube.
(7) The length of the first and second magnetic pole cores is longer than the diameter of the measuring tube, and the pair of cores are inclined on the side connected to the first and second magnetic pole cores, In addition, the electromagnetic flow meter according to (5), wherein the pair of cores are opposed to the measurement tube in parallel.

In the electromagnetic flow meter of the present invention, by arranging the magnetic pole core in the feedback magnetic path, a magnetic circuit structure with less leakage magnetic flux can be obtained, and a high efficiency and high signal level electromagnetic flow meter can be realized.
In addition, by tilting the pair of cores in the direction of the measuring tube, the magnetic resistance of the portion where the magnetic field is insufficient can be lowered, and a magnetic circuit that generates the magnetic field uniformly can be realized. An electromagnetic flow meter that is difficult to receive can be realized.

  Hereinafter, embodiments of the electromagnetic flowmeter of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the electromagnetic flow meter according to the first embodiment of the present invention includes a pair of cores 12a and 12b that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube 11, and a magnetic field. A pair of detection electrodes 13a and 13b that are disposed on the tube wall of the measurement tube 11 in a direction orthogonal to the flow tube and detect an electromotive force generated corresponding to the flow rate of the fluid, and a pair of return magnetic paths other than the measurement tube 11 A magnetic pole core 14 connected to the cores 12a and 12b and an excitation coil 15 in which a coil is wound around the magnetic pole core 14 are provided.
Since the feedback magnetic path is configured by the magnetic pole core 14 and the excitation coil 15 in this way, the magnetic field inside the coil is canceled by the magnetic field formed by the adjacent coil wire, and therefore no magnetic field exists. For this reason, there is no leakage magnetic flux between the magnetic pole core and the feedback magnetic path as in the conventional example, and the magnetic flux between the upper and lower cores 12a and 12b can be effectively created.
By doing in this way, it can be set as a magnetic circuit structure with few leakage magnetic fluxes, and a highly efficient and high signal level electromagnetic flowmeter can be realized.

Next, an electromagnetic flow meter according to a second embodiment will be described with reference to the drawings.
As shown in FIGS. 3 and 4, the electromagnetic flow meter of the second embodiment includes a pair of cores 12 a and 12 b that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube 11, and a magnetic field A pair of detection electrodes 13 a and 13 b that are arranged on the tube wall of the measurement tube 11 in the orthogonal direction and detect an electromotive force generated corresponding to the flow rate of the fluid, and a pair of cores 12 a on a feedback magnetic path other than the measurement tube 11, A magnetic pole core 14 </ b> A connected to 12 b and an excitation coil 15 </ b> A in which a coil is wound around the magnetic pole core 14 are provided.
The length of the magnetic pole core 14A is longer than the diameter of the measurement tube 11, the pair of cores 12a and 12b is inclined on the side connected to the magnetic pole core 14A, and the pair of cores 12a and 12b is It is characterized by facing in parallel.

Here, consider the magnetic field generated by the exciting coil 15A wound around the magnetic pole core 14A. If the coil radius is a, the generated magnetic field H at the center is
H = I / (2a)
I: can be represented by an excitation current.
Therefore, it can be easily understood that a large magnetic field can be generated with the same current by reducing the radius a of the magnetic pole core 14A.
Therefore, by increasing the length of the magnetic pole core 14A, a coil can be wound around the magnetic pole core 14A, thereby reducing the average radius of the coil and generating a large magnetic field.
Further, although the magnetic resistance is large, a leakage magnetic flux is generated in the space opposite to the measurement tube 11 side. Therefore, the effect of reducing the leakage magnetic flux can be obtained by making the pair of cores 12a and 12b inclined as in this embodiment and reducing the magnetic resistance on the measuring tube 11 side.

Next, an electromagnetic flow meter according to a third embodiment will be described with reference to the drawings.
As shown in FIGS. 5 and 6, the electromagnetic flow meter of the third embodiment includes a pair of cores 12a and 12b that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube 11, and a magnetic field. A pair of detection electrodes 13 a and 13 b that are arranged on the tube wall of the measurement tube 11 in the orthogonal direction and detect an electromotive force generated corresponding to the flow rate of the fluid, and a pair of cores 12 a on a feedback magnetic path other than the measurement tube 11, The magnetic pole core 14A is connected to 12b, and the exciting coil 15A is wound around the magnetic pole core 14A.
The length of the magnetic pole core 14A is longer than the diameter of the measuring tube 11, the pair of cores 12a and 12b is inclined on the side connected to the magnetic pole core 14A, and the tip ends of the pair of cores 12a and 12b are inclined. The magnetic resistance in the vicinity of the detection electrodes 13a and 13b is reduced by providing an inclination along the diameter shape of the measurement tube 11.
If the pair of cores 12a and 12b are horizontal, the magnetic resistance increases toward the end side, and there is a problem that the magnetic field cannot be uniformly generated in the measurement tube 11. The magnetic field can be generated uniformly, and the effect of reducing the influence of the flow velocity distribution can be obtained.

Next, an electromagnetic flow meter according to a fourth embodiment will be described with reference to the drawings.
As shown in FIG. 7, the electromagnetic flow meter according to the fourth embodiment includes a pair of cores 12a and 12b that generate a magnetic field in a direction perpendicular to the fluid flowing in the measurement tube 11, and a direction orthogonal to the magnetic field. One of a pair of detection electrodes 13a and 13b that are arranged on the tube wall of the measurement tube 11 and detects an electromotive force generated corresponding to the flow rate of the fluid, and a pair of cores 12a and 12b in a return magnetic path other than the measurement tube 11 The first magnetic pole core 14B connected to the side, the first exciting coil 15B wound around the first magnetic pole core 14B, and the other of the pair of cores 12a and 12b in the feedback magnetic path other than the measuring tube 11 The second magnetic pole core 14C is connected to the side, and the second magnetic excitation coil 15C is wound around the second magnetic pole core 14C.
The lengths of the first and second magnetic pole cores 14B and 14C are longer than the diameter of the measuring tube 11, and the pair of cores 12a and 12b are connected to the first and second magnetic pole cores 14B and 14C. The side is inclined and the pair of cores 12 a and 12 b are opposed to the measuring tube 11 in parallel.
As described above, the configuration in which two coils are provided makes it possible to efficiently generate a magnetic field in the measurement tube 11.

By configuring the feedback magnetic path with a magnetic pole core and an exciting coil, the magnetic field inside the coil is canceled by the magnetic field created by the adjacent coil wire, so that leakage flux can be eliminated. An electromagnetic flow meter that can be effectively manufactured is provided.

It is explanatory drawing which showed the structure of the electromagnetic flowmeter of 1st Example of this invention. It is explanatory drawing seen from the side same as the above. It is explanatory drawing which showed the structure of the electromagnetic flowmeter of 2nd Example of this invention. It is explanatory drawing seen from the side same as the above. It is explanatory drawing which showed the structure of the electromagnetic flowmeter of 3rd Example of this invention. It is explanatory drawing seen from the side same as the above. It is explanatory drawing which showed the structure of the electromagnetic flowmeter of the 4th Example of this invention. It is explanatory drawing which showed the structure of the electromagnetic flowmeter in a prior art. It is explanatory drawing which showed the structure of the electromagnetic flowmeter in a prior art.

Explanation of symbols

11 Measurement tube 12a Core 12b Core 13a Detection electrode 13b Detection electrode 14 Magnetic pole core 14A Magnetic pole core 14B First magnetic pole core 14C Second magnetic pole core 15 Excitation coil 15A Excitation coil 15B First excitation coil 15C Second excitation coil

Claims (7)

A pair of cores that generate a magnetic field in a direction perpendicular to the fluid flowing in the measuring tube;
A pair of detection electrodes disposed on the tube wall of the measurement tube in a direction orthogonal to the magnetic field and detecting an electromotive force generated corresponding to the flow rate of the fluid;
A magnetic pole core connected to the pair of cores in a feedback magnetic path other than the measurement tube;
An exciting coil in which a coil is wound around the magnetic pole core;
An electromagnetic flow meter comprising:   The electromagnetic flowmeter according to claim 1, wherein a length of the magnetic pole core is longer than a diameter of the measuring tube.   The length of the magnetic pole core is longer than the diameter of the measuring tube, the pair of cores are inclined on the side connected to the magnetic pole core, and the pair of cores are opposed to the measuring tube in parallel. The electromagnetic flow meter according to claim 1.   The length of the magnetic pole core is longer than the diameter of the measuring tube, the pair of cores are inclined on the side connected to the magnetic pole core, and the distal end side of the pair of cores is the diameter shape of the measuring tube The electromagnetic flow meter according to claim 1, wherein the electromagnetic flow meter has an inclination along the axis. A pair of cores that generate a magnetic field in a direction perpendicular to the fluid flowing in the measuring tube;
A pair of detection electrodes disposed on the tube wall of the measurement tube in a direction orthogonal to the magnetic field and detecting an electromotive force generated corresponding to the flow rate of the fluid;
A first magnetic pole core connected to one side of the pair of cores to a feedback magnetic path other than the measurement tube;
A first exciting coil in which a coil is wound around the first magnetic pole core;
A second magnetic pole core connected to the other side of the pair of cores in a feedback magnetic path other than the measurement tube;
A second exciting coil in which a coil is wound around the second magnetic pole core;
An electromagnetic flow meter comprising:   6. The electromagnetic flowmeter according to claim 5, wherein the length of the first and second magnetic pole cores is longer than the diameter of the measuring tube. The lengths of the first and second magnetic pole cores are longer than the diameter of the measuring tube, the pair of cores are inclined on the side connected to the first and second magnetic pole cores, and the pair of cores The electromagnetic flowmeter according to claim 5, wherein the core of the magnet is opposed to the measurement tube in parallel.

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