JPH09138148A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light electromagnetic flowmeter of low cost by generating an uniform magnetic field at a right angle to the axis of a measuring tube, while the size of a core is limited by the size of a coil. SOLUTION: A coil 4 is energized by feeding from a power source, so that, by a core 3 and an inner core 8, a magnetic field is generated in the direction orthogonal to the axis of a measuring tube 1. When to-be-measured fluid 2 is moved into the measuring tube 1 in the magnetic field, electromotive force is generated based on Faraday's law of electromagnetic induction. At this time, the magnetic field is generated at a right angle to the measuring tube electrically insulated, and, when conductivity of the flowing fluid is not too low, the electromotive force is measured between a part of electrodes 5. A core mounting flat surface part of a magnetic field generating means is provided to the central part of inner core for constitution, so that, by fixing the core to the flat surface part, the core can be assigned in parallel to the axis of the measurement tube, so that, the magnetic field orthogonal to the axis is uniformly generated, and the effect that flow rate measurement is performed with precision is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates a magnetic field in a direction intersecting with a fluid to be measured flowing in a measuring pipe, and an electromotive force generated according to a flow rate of the fluid traversing the magnetic field is measured as a diameter of the measuring pipe. The present invention relates to an electromagnetic flow meter that measures the flow rate by detecting it through at least a pair of electrodes provided facing each other.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing the measuring principle of an electromagnetic flowmeter 50. In the figure, 51 is a measuring tube whose inner surface is lined with Teflon or the like, and 52 is a measuring tube 51.
A fluid to be measured which is a conductive liquid flowing therein, 53 is a core provided on the outer periphery of the measuring tube 51, 54 is a coil wound around the core 53 as a magnetic field generating means, and 55 is the measuring tube 51.
At least a pair of electrodes, which are provided at positions facing each other on the diameter of and intersecting the magnetic field, remove noise and the like from the electromotive force detected by the electrode 55, and according to the flow rate of the fluid 52 to be measured from this electromotive force. It is a converter for converting into a signal.

FIG. 5 shows a measuring tube 5 in a conventional electromagnetic flow meter.
1 is a schematic view showing a mounting state of a core 53 and a coil 54 with respect to No. 1 (the core 53 and the coil 54 are axially symmetrical to the measuring pipe 51, but the illustrated example shows only one side thereof), and the outer peripheral surface of the measuring pipe 51 is shown. An arc-shaped inner core 57 is provided on the axis, an arcuate paddle-shaped core 53 is provided in the center of the inner core, and a coil 54 is mounted around the core 53.

Next, the operation will be described. When the coil 54 is excited by power supply from a power source (not shown), a magnetic field is generated in a direction orthogonal to the axis of the measuring tube 51, and the measured fluid 52 is moved to the measuring tube in this magnetic field. An electromotive force is generated according to the law. In this case, the magnetic field is generated at right angles to the electrically insulated measuring tube, and the electromotive force can be measured between the pair of electrodes 55 unless the electric conductivity of the flowing measured fluid 52 is too low. Since this electromotive force is proportional to the strength of the magnetic field, the average flow velocity of the fluid to be measured 52, and the distance between the electrodes, noise is removed from this electromotive force, and this electromotive force is converted by the converter 56 into a signal corresponding to the fluid to be measured 52. Then, the flow rate can be measured.

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

[0006]

Since the conventional electromagnetic flow meter is constructed as described above, the coil is wound and fixed by using the side surface of the core, and the size of the core is determined by the size of the coil. To be For this reason, the core is required to have a size larger than the efficiency, resulting in a heavy weight and an increase in cost. Also, this core must be configured as an arcuate paddle core along the inner core attached to the peripheral surface of the measuring tube, but since the core is thick, it is troublesome to make it in an arcuate shape and to measure. The parallelism with the axis of the tube cannot be maintained and a magnetic field orthogonal to the axis of the measuring tube cannot be generated uniformly. In addition, different cores have to be prepared according to the coil size, and there has been a problem that product management is obscure.

The present invention has been made to solve the above problems, and it is possible to generate a uniform magnetic field at right angles to the axis of the measuring tube without the size of the core being restricted by the coil size. The purpose is to obtain a lightweight and inexpensive electromagnetic flowmeter that can be used.

[0008]

An electromagnetic flowmeter according to the invention described in claim 1 is characterized by a magnetic field generating means for generating a magnetic field in the measuring pipe, the magnetic field being orthogonal to the measuring pipe through which the fluid to be measured is passed, and the action of the magnetic field. 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 fluid to be measured, and an inner provided between the measuring tube and the magnetic field generating means. A core, and the core mounting plane portion of the magnetic field generating means is provided in the central portion of the inner core.

The electromagnetic flowmeter according to the second aspect of the invention is
On the diameter of the measuring tube so as to measure the electromotive force generated in the measured fluid by the action of the magnetic field, a magnetic field generating means for generating in the measuring tube a magnetic field orthogonal to the measuring tube through which the fluid to be measured is passed. A rising portion including at least a pair of electrodes provided to face each other and an inner core provided between the measuring tube and the magnetic field generating means, and positioning and fixing a coil of the magnetic field generating means to the inner core. Is provided.

[0010]

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 Embodiment 1 of the present invention, and FIG. 2 is a partially cutaway side view thereof. In FIGS. 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 circumference of the measuring tube 1, 4 is a coil wound around the core 3 as a magnetic field generating means, 5 is the measuring tube 1 At least a pair of electrodes provided at positions facing each other on the diameter of and crossing the magnetic field, 6 is a lead wire connected to the electrode 5, and 7 is an outer core for magnetic flux feedback that covers the coil 4 and is fixed to the measuring tube 1. , 8 is an inner core provided between the coil 4 and the measuring tube 1 in order to generate a magnetic field in parallel in the diameter range of the measuring tube 1, 9 is a periphery of the coil 4, the magnetic flux feedback outer core 7 and the inner core 8. With a case that covers the Ri, accommodation hole 9-1 of the measuring tube 1, has an accommodating chamber 9-2 of the electrode 5.

3A and 3B are views showing the relationship between the core 3 and the inner core 8. FIG. 3A is a front view and FIG. 3B is a plan view. The inner core 8 has a core mounting flat surface portion 8-1 of the magnetic field generating means at the center thereof, and a rising portion 8-2a for positioning and fixing the coil 4 of the magnetic field generating means around the flat surface portion 8-1. 8-2b is provided. Then, the core 3 is placed on the flat surface portion 8-1 and fixed by the screw 10, and the coil 4 is fixed by winding the rising portions 8-2a and 8-2b as winding cores.

The measuring tube 1 has corrosion resistance on the inner surface and the end surface,
A lining treatment 11 for abrasion resistance is applied, and a liquid contact ring 12 that makes the detection portion in the case 9 and the measurement fluid have the same potential is attached to the end surface thereof. As a material for the lining treatment 11, for example, fluorine resin, chloroprene rubber, polyurethane rubber, ceramics or the like is used. Further, 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 by abutting the collar seat 5b of the electrode rod 5a on the receiving seat 11a formed by the running process and pressing the coil spring 13 abutting on the other surface of the collar seat 5b. A cap 14 is screwed into and fixed to the electrode mounting hole 1b of the tube 1. 15 is an electrode rod 5
Reference numeral 17 denotes a screw for attaching the lead wire 6 to a, and 17 denotes a lid body screwed into the inlet of the electrode housing chamber 9-2 of the measuring tube 1.

Next, a method of assembling the electromagnetic flowmeter composed of the above-mentioned components will be described. First, the inner core 8 is placed axially symmetrically on the outer peripheral surface of the measuring tube 1, the core 3 is placed on the flat surface portion 8-1 of the inner core 8, and the rising portions 8-2a and 8-2b of the inner core 8 are coiled. 4 is wound, and a magnetic flux feedback outer core 7 is attached to the measuring tube 1 so as to press and fix the whole on the outer surface of the measuring tube 1. After that, the measuring tube 1 is inserted into the case 9 through the accommodation hole 9-1 and the joint portion (both ends) of the case 9 and the measuring tube 1 is welded. Then, in the electrode housing chamber 9-2 of the case 9, the electrode 5 is attached to the measuring tube 1 and the coil 4 and each lead wire 4 of the electrode 5 are attached.
The a and 6 are taken out from the take-out chamber 9-3 of the case 9.

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

Next, the operation will be described. When the coil 4 is excited by feeding power from a power source (not shown), a magnetic field is generated by the core 3 and the inner core 8 in a direction orthogonal to the axis of the measuring tube 1. Fluid to be measured 2 in the measuring tube in this magnetic field
When is moved, an electromotive force is generated by Faraday's law of electromagnetic induction. In this case, a magnetic field is generated at right angles to the electrically insulated measuring tube, and if the conductivity of the flowing liquid is not too low, the electromotive force can be measured between the pair of electrodes 5.
Since this 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 this electromotive force, and this electromotive force is converted into a signal corresponding to the fluid by the converter 56 as shown in FIG. The flow rate can be measured by converting and outputting.

As described above, according to the first embodiment, the core 3 is attached to the flat surface portion 8-1 of the inner core 8 and the rising portions 8-2a on both sides of the flat surface portion 8-1.
By winding the coil 4 around the winding core 8-2b, the core 3 can be designed to have an appropriate size without being restricted by the size of the coil 4, the core can be shared, and product management becomes easy. Further, since the core 3 can be arranged parallel to the axis of the measuring tube 1, it is possible to obtain an effect such that a magnetic field orthogonal to the axis can be generated uniformly.

[0018]

As described above, according to the first aspect of the present invention, the core mounting plane portion of the magnetic field generating means is provided in the central portion of the inner core, so that the core is attached to the plane portion. As a result, the core can be arranged in parallel with the axis of the measuring tube, the magnetic field orthogonal to the axis can be uniformly generated, and the effect of accurately measuring the flow rate can be obtained.

According to the second aspect of the present invention, since the inner core is provided with the rising portion for positioning and fixing the coil of the magnetic field generating means, the rising portion is used as the winding core to wind the coil. The core can be designed to have an appropriate size without being restricted by the size of the coil, downsizing and sharing of the core can be achieved, and product management becomes easy.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing an electromagnetic flowmeter according to an embodiment of the present invention.

FIG. 2 is a side view in which a part of the electromagnetic flow meter is cut away.

3A and 3B are views showing a relationship between a core 3 and an inner core 8, FIG. 3A being a front view and FIG. 3B being a plan view.

FIG. 4 is a schematic configuration diagram illustrating a measurement principle of an electromagnetic flow meter.

FIG. 5 is a schematic diagram showing a relationship between a coil and a core in a conventional electromagnetic flow meter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring tube 2 Fluid to be measured 4 Coil (magnetic field generating means) 5 Electrode 7 Outer core for magnetic flux feedback 8 Inner core 8-1 Plane part 8-2a, 8-2b Rising part

Claims (2)

[Claims] 1. A measuring pipe through which a fluid to be measured is passed, a magnetic field generating means for generating a magnetic field orthogonal to the fluid to be measured in the measuring pipe, and a signal generated in the fluid to be measured by the action of the magnetic field is measured. As described above, in the electromagnetic flowmeter including at least a pair of electrodes provided so as to face each other on the diameter of the measurement tube, and an inner core provided between the measurement tube and the magnetic field generating means, An electromagnetic flowmeter characterized in that a core mounting plane portion of the magnetic field generating means is provided in a central portion of the core. 2. A measuring pipe through which a fluid to be measured is passed, a magnetic field generating means for generating a magnetic field orthogonal to the fluid to be measured in the measuring pipe, and a signal generated in the fluid to be measured by the action of the magnetic field is measured. As described above, in the electromagnetic flowmeter including at least a pair of electrodes provided so as to face each other on the diameter of the measurement tube, and an inner core provided between the measurement tube and the magnetic field generating means, An electromagnetic flowmeter, wherein a rising portion for positioning and fixing the coil of the magnetic field generating means is provided on the core.