JP3335822B2 - Electromagnetic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a magnetic field in a cross direction with respect to a fluid to be measured flowing in a measuring tube, and generating an electromotive force generated in accordance with a flow rate of the fluid traversing the magnetic field with a diameter of the measuring tube. The present invention relates to an electromagnetic flowmeter that detects the above flow rate through at least a pair of electrodes provided to face each other and measures the flow rate.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the measurement principle of an electromagnetic flowmeter 50. In the figure, reference numeral 51 denotes a measuring tube whose inner surface is lined with Teflon or the like, and 52 denotes a conductive liquid flowing through the measuring tube 1. Is the fluid to be measured, and 53 is the measuring tube 5
A core 54 provided on the outer periphery of the reference numeral 1 is a coil as a magnetic field generating means wound around the core 53, and 55 is at least a pair of electrodes provided at positions facing each other on the diameter of the measuring tube 51 and intersecting the magnetic field. And 56 are converters for removing noise and the like from the electromotive force detected by the electrode 55 and converting the electromotive force into a signal corresponding to the flow rate of the fluid 52 to be measured.

FIG. 7 shows a coil 54 of a conventional electromagnetic flow meter,
FIG. 4 is a schematic diagram showing a relationship with a magnetic flux feedback outer core 57 that covers the coil 54 and is fixed to the measurement tube 51;
The coil 54 is pressed and fixed to the surface of the measurement tube 51 by an arc-shaped outer core 57 for magnetic flux feedback along the outer circumference of the measurement tube.

Next, the operation will be described. When the coil 54 is excited by power supply from a power source (not shown), the core 53
, A magnetic field φ is generated in a direction orthogonal to the axis of the measuring tube 51. When the fluid 52 to be measured is moved to the measurement tube 51 in the magnetic field, an electromotive force is generated according to Faraday's law of electromagnetic induction. In this case, if the magnetic field φ is generated at right angles to the electrically insulated measurement tube 51 and the electric conductivity of the fluid 52 to be measured is not too low, the electromotive force can be measured between the pair of electrodes 55. The electromotive force is proportional to the strength of the magnetic field φ, the average flow velocity of the fluid 52 to be measured, and the distance between the electrodes. By measuring the electromotive force, the flow rate can be measured.

That is, when the quantity symbol and unit are as follows, quantity symbol physical quantity unit B magnetic flux density TD inner diameter of measurement tube mv average axial fluid velocity m / s E electromotive force Vk constant-Q volume flow rate m ^{According to the 3} / s Faraday's law, the magnitude of the electromotive force E is represented by the following equation. E = kBDv (1) The volume flow rate is given by the following equation in the case of a circular measuring tube. ^{Q = (πD 2/4)} · v ··· (2) Because of this relationship, equation (1) is expressed by the equation (3). Q = (πD / 4 kB) · E (3) Here, assuming that the magnetic flux density B is constant, the flow rate in the measurement tube can be obtained by measuring the electromotive force E.

[0006]

Since the conventional electromagnetic flowmeter is configured as described above, the coil 54 is connected to the measuring tube 5.
Since the width W is defined by the size of the magnetic flux feedback outer core 57 along the outer circumference of 1, the performance decreases when the number of turns of the coil is limited in order to make the width W the specified size. On the other hand, if the number of windings is secured to ensure performance, the length of the coil itself (longitudinal direction) becomes longer, and as a result, the overall length of the electromagnetic flowmeter becomes longer, and there is a problem that miniaturization cannot be achieved. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an electromagnetic flowmeter capable of increasing the number of windings of a coil while reducing the overall shape, sufficiently generating magnetic flux, and improving performance. The purpose is to obtain.

[0008]

According to the present invention, there is provided an electromagnetic flowmeter, comprising: a magnetic field generating means for generating a magnetic field perpendicular to a fluid to be measured in a measuring pipe; At least a pair of electrodes provided to face each other on the diameter of the measuring tube so as to measure the electromotive force generated in the outer core for magnetic flux feedback fixed to the measuring tube covering the magnetic field generating means. It has a function of an escape part for the magnetic field generating means and is connected to the electrode.
Window machine that allows externally checking the wiring status of the lead wires
It is provided with a hole having both functions .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. 1 is a partially cutaway front view showing an electromagnetic flowmeter according to a first embodiment of the present invention, FIG. 2 is a partially cutaway side view, and FIG. 3 is a cross-sectional plane taken along line III-III in FIG. FIG. In the figure, 1 is a measuring tube, 2 is a fluid to be measured, which is a conductive liquid flowing in the measuring tube 1, 3 is a core provided on the outer periphery of the measuring tube 1, 4 is a magnetic field generating means wound around the core 3 5, at least one pair of electrodes provided at positions facing each other on the diameter of the measuring tube 1 and intersecting the magnetic field; 6, a lead wire connected to the electrode 5; An outer core for magnetic flux feedback fixed to 1, 8 is an inner core interposed between the coil 4 and the measuring tube 1 to generate a magnetic field in parallel in the diameter range of the measuring tube 1, 9 is a coil 4, and a magnetic flux feedback Is a case that covers the periphery of the outer core 7 and the inner core 8 and is fixed to the measuring tube 1 by welding.
1, an accommodation room 9-2 for the electrode 5 and the like.

The outer core 7 for magnetic flux feedback has a structure shown in FIG.
As shown in FIG. 3, holes 7a and 7b as interference escape portions of the coil 4 are provided at portions facing both sides of the surface of the coil 4, and the surface of the coil 4 is pressed against the measurement tube 1 in a state where the coil 4 is pressed against the measurement tube 1. It is attached with screws 10.

The measuring tube 1 has an inner surface and an end surface having corrosion resistance,
A lining treatment 11 for abrasion resistance is applied, and a liquid contact ring 12 for making a detection portion in the case 9 and a measurement fluid the same potential is attached to an end surface thereof. As a material of the lining treatment 11, for example, fluororesin, chloroprene rubber, polyurethane rubber, ceramics, or the like is used. As the material of the liquid contact ring 12, for example, stainless steel, platinum / indium, tantalum, titanium, Hastelloy B, Hastelloy C, Monel, conductive fluororesin, or the like is used.

The electrode 5 is measured while the flange 5b of the electrode rod 5a is in contact with the receiving seat 11a formed by the running process, and the coil spring 13 which is in contact with the other surface of the flange 5b is pressed. The cap 14 is screwed and fixed in the electrode mounting hole 1b of the tube 1. 15 is the electrode rod 3
Reference numeral 17 denotes a screw for attaching the lead wire 6 to a, and 17 denotes a lid screwed into the entrance of the electrode accommodating chamber 9-2 of the measuring tube 1.

Next, a method of assembling the electromagnetic flow meter including the above-described components will be described. First, a coil 4 having an axially symmetrical core 3 on the outer peripheral surface of the measuring tube 1, and a magnetic flux feedback outer core 7 is attached to the measuring tube 1 so that the coil 4 is pressed and fixed to the outer surface of the measuring tube 1. Then, measuring tube 1
Is inserted into the case 9 through the accommodation hole 9-1 and the joints (both ends) of the case 9 and the measuring tube 1 are welded. And case 9
The electrode 5 is attached to the measuring tube 1 in the accommodating chamber 9-2 of the electrode 5, and the coil 4 and each lead wire 4
a, 6 are taken out of the take-out chamber 9-3 of the case 9.

The electromagnetic flow meter having the above-described structure is connected and fixed to the right and left sides of the measuring pipe 1 so as to match the pipes 18a and 18b. The connecting method includes a flange connection method, a flange sandwiching method, a sanitary connection method, and the like. There are various types of screw connection methods.

Next, the operation will be described. When the coil 4 is excited by power supply from a power source (not shown) to generate a magnetic field in a direction perpendicular to the axis of the measuring tube 1, and the fluid 2 to be measured is moved to the measuring tube in the magnetic field, the Faraday electromagnetic induction An electromotive force is generated according to the law. In this case, if a magnetic field is generated at right angles to the electrically insulated measuring tube and the conductivity of the flowing liquid is not too low, the electromotive force can be measured from between the pair of electrodes 5. Since the electromotive force is proportional to the strength of the magnetic field, the average flow velocity of the fluid, and the distance between the electrodes, noise is removed from the electromotive force, and the electromotive force is converted into a signal corresponding to the fluid by the converter 56 as shown in FIG. By converting and outputting, the flow rate can be measured.

As described above, according to the first embodiment, the holes 7a, 7 with the coil 4 are provided in the outer core 7 for magnetic flux feedback which covers the coil and fixes the coil to the measuring tube 1.
Since the case b is provided, even if the size of the case 9 is reduced and the arc of the magnetic flux return outer core 7 is reduced, both side portions of the coil 4 protrude to the outside from the holes 7a and 7b and are subject to any size restrictions. Since there is no problem, there is no problem in mounting the coil 4, and the number of turns of the coil 4 can be increased to generate sufficient magnetic flux, thereby improving the performance.

Further, by using the holes 7a and 7b as windows, it is possible to externally see the lead-out state of the lead wire 6 connected to the electrode 5. As a result, as shown in FIG. 5, it is possible to reliably avoid the superposition of the 90 ° noise on the signal by the bent wiring in which the lead wire 6 crosses the magnetic flux. Here, 90 ° noise refers to the fact that when extracting an electromotive force generated by the Fleming's right-hand rule, noise is superimposed, and an accurate electromotive force and thus an accurate flow rate cannot be measured.

[0018]

As is evident from the foregoing description, according to the first aspect of the invention, the outer core flux feedback over the coil to fix the coil to the measuring tube, the machine interference relief portion of said coil
Of the internal lead wire connected to the electrode
A hole that also has a window function that allows you to check the wiring status from the outside
Since it is configured by providing the door, even if the arc dimension of the outer core for flux return is reduced, both side portions of the coil 4 is not subject to any dimensional restriction protruding outward from the interference relief portion. Therefore,
Even if the number of turns of the coil is increased, there is no problem in mounting the coil, sufficient magnetic flux can be generated, performance can be improved, and the wiring state of the lead wire can be seen from the outside. There is an effect that the superposition of 90 ° noise on the signal due to the bent wiring of the lead wire can be reliably avoided and the wiring of the lead wire itself is easy.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing an electromagnetic flow meter according to Embodiment 1 of the present invention.

FIG. 2 is a partially cut-away side view showing the electromagnetic flow meter.

FIG. 3 is a cross-sectional plan view taken along the line III-III of FIG. 2;

FIG. 4 is a side view showing a relationship between a magnetic flux feedback outer core and a coil.

FIG. 5 is a perspective view showing a state in which a lead wire is taken out of a measurement tube.

FIG. 6 is a diagram illustrating the principle of an electromagnetic flow meter.

FIG. 7 is a side view showing a relationship between a magnetic flux feedback outer core and a coil of a conventional electromagnetic flowmeter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring pipe 2 Fluid to be measured 4 Coil (magnetic field generating means) 5 Electrode 7 Outer core for magnetic flux feedback 7a, 7b Hole (interference relief part)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/58

Claims (1)

(57) [Claims] 1. A measuring pipe through which a fluid to be measured passes, a magnetic field generating means for generating a magnetic field orthogonal to the fluid to be measured in the measuring pipe, and an electromotive force generated in the fluid to be measured by the action of the magnetic field. In an electromagnetic flowmeter including at least a pair of electrodes provided to face each other on the diameter of the measurement tube so as to measure, and an outer core for magnetic flux feedback fixed to the measurement tube covering the magnetic field generating means, A function of an interference relief portion between the magnetic flux generating outer core and the magnetic flux feedback outer core
And the internal lead wires connected to the electrodes.
An electromagnetic flowmeter comprising: a hole having a function of a window part capable of confirming a line state from the outside .