JPH08271303A - Electromagnetic flow meter - Google Patents

Abstract

(57) [Summary] [Purpose] By blocking the flow of air in the lead wire, the breathing action due to the temperature difference between the inside and outside of the electromagnetic flow meter is prevented, and the occurrence of dew condensation is prevented. [Structure] One end is connected to the electrode 17 and the other end is the converter 3
The lead wire 30 connected to 5 is made of an insulated wire, and the core wire exposed portion 42 is provided in the middle portion thereof. This exposed core wire 42
Is embedded in the potting resin 44 that closes the neck portion 34A of the case 34, thereby blocking contact with the outside air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flow meter for measuring the flow rate of a conductive fluid flowing in a measuring pipe, and more particularly to prevent the invasion of outside air and to prevent the electrical insulation deterioration between the measuring pipe and the electrode due to dew condensation. The present invention relates to an electromagnetic flow meter which is designed to prevent the above.

[0002]

2. Description of the Related Art There are various possible applications for using an electromagnetic flow meter. For example, in a case where a cooling water circulation pipe for air conditioning of a building is buried vertically and horizontally in a building, the amount of this cooling water is controlled by an electromagnetic wave. May be measured with a flow meter. In such a case, the temperature of the cooling water is lower than the temperature of the outside air in the building, so the temperature in the vicinity of the measuring pipe of the electromagnetic flow meter becomes low. On the other hand, the portion of the electromagnetic flowmeter that comes into contact with the outside air is close to the outside air temperature. Therefore, dew condensation in the electrode storage portion becomes a problem. That is, the electrode for detecting the electromotive force generated in the fluid to be measured and the converter for converting the electromotive force into a flow rate by signal processing are connected by lead wires.
This lead wire is usually an insulated wire, and its core wire,
There is a very small gap between the core wire and the coating, and the outside air on the transducer side enters the electrode housing through the gap. This is particularly remarkable when there is a pressure difference between the inside and the outside of the electromagnetic flow meter. This phenomenon is called "respiratory action". Due to this breathing action, when the outside air enters the electrode housing portion and touches the cooled measuring tube portion, the water contained in the outside air becomes supersaturated and dew condensation occurs. In particular, since the lead wire is electrically connected to the rear end of the electrode, the outside air coming out from the open end of the coating on the electrode side directly contacts the fluid to be measured and directly contacts the cold electrode. Condensation easily due to. Then, when this dew condensation is repeated and the resulting water drops adhere to the electrodes, the distance between the measuring tube and the electrodes is substantially shortened, and thus the insulation resistance between these members is reduced. Originally, since the current generated by the electromagnetic induction phenomenon is a weak current, if the insulation resistance between the electrode and the measuring tube decreases, the output decreases and it becomes impossible to accurately measure the flow rate. In the worst case, the electrode and the measuring tube may be short-circuited.

Therefore, in order to prevent the breathing action due to such a lead wire, conventionally, for example, an actual flat blade 1-701 is used.
Like the electromagnetic flowmeter disclosed in Japanese Patent No. 23, the opening portions at both ends of the coating that covers the core wire of the lead wire are covered with a colloidal adhesive. Figure 5 shows the lead wire,
Reference numeral 1 is a lead wire made of an insulated wire, 1a is a core wire, 1b is a cover, 2 is a crimp terminal connected to an end of the core wire 1a, and 3 is an exposed end of the core wire 1a exposed from the cover 1b. Colloidal adhesives such as cyanoacrylate adhesives. In such a lead wire 1, since the opening of the coating 1b is closed by the adhesive 3, it is possible to prevent air from flowing in the lead wire 1.

[0004]

However, the conventional lead wire 1 shown in FIG. 5 has a problem that it is difficult to maintain airtightness in the lead wire 1 for a long period of time. That is, connect the connection end of the lead wire 1 to the electrode and the converter at the time of maintenance, inspection and replacement of the electrode and the converter,
On the contrary, it needs to be removed. At this time, when an external force is applied by pulling or bending the connection end of the lead wire 1, a gap is created between the lead wire 1 and the adhesive 3. As a result, outside air penetrates into the lead wire 1 through this gap, and an absorption action is caused by the temperature difference between the inside and the outside of the electromagnetic flow meter. Then, when it enters the electrode accommodating portion, it is cooled by the measuring tube and the electrode, so that the moisture contained in the outside air is condensed to reduce the insulation resistance between the measuring tube and the electrode.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to cut off the flow of air in the lead wire at an intermediate portion thereof so that the electromagnetic flowmeter An object of the present invention is to provide an electromagnetic flow meter that prevents the occurrence of dew condensation by preventing the respiratory action due to the temperature difference between the inside and the outside.

[0006]

In order to achieve the above object, the present invention provides a pair of exciting coils, which are provided opposite to a peripheral wall of a measuring tube to form a magnetic flux perpendicular to the flow direction of a fluid to be measured,
A case having a pair of electrodes provided on the measuring tube so as to be orthogonal to both the magnetic flux of the exciting coil and the axis of the measuring tube, and a neck portion for taking out the lead wire of the electrode to the outside and covering the measuring tube. And a sealing member that closes the neck portion of the case, the lead wire is formed of an insulated wire and the sealing member is formed of potting resin, and the exposed core portion of the lead wire is in the potting resin. It is characterized by being buried in.

[0007]

In the present invention, the core wire exposed portion is provided by removing the coating in the middle portion of the lead wire. The sealing member is made of potting resin and hermetically closes the neck portion of the case and seals the exposed core wire of the lead wire.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 is a partially cutaway front view showing an embodiment of an electromagnetic flowmeter according to the present invention, FIG. 2 is a partially cutaway side view of the electromagnetic flowmeter, and FIG. 3 is an enlarged cross-sectional view of a neck portion of a case. 4 and 5 are perspective views of the lead wire and the positioning plate. In these figures, the electromagnetic flow meter 10 is provided with a measuring pipe 11 which is formed of a non-magnetic material such as stainless steel and has pipe connecting flanges 11a and 11b integrally at both ends. On the outer wall of the measuring pipe 11, a magnetic flux φ perpendicular to the flow direction of the fluid 12 to be measured, that is, the axis of the measuring pipe 11 is intersected.
A pair of saddle-type excitation coils 13 that form the above are arranged so as to face each other vertically. The exciting coil 13 is wound around the core 16 between the inner core 14 and the outer core 15 which form a magnetic circuit.

Further, a pair of electrodes 17 having an axis in a direction orthogonal to the magnetic flux φ generated by the exciting coil 13 are provided so as to penetrate through the center of both sides of the measuring tube 11 in the axial direction, and the inner ends thereof are measured. It faces the inside of the pipe 11 and forms a liquid contact surface. Therefore, the electrode 17 and the exciting coil 13 are connected to the measuring tube 11
90 ° out of phase with each other in the circumferential direction. In addition, the measuring tube 11
A lining material 19 such as a fluororesin or neoprene is applied to the inner peripheral surface of the electrode, the inner peripheral surface of the electrode mounting hole 18 to which the electrode 17 is mounted, and the outer end surfaces of the flange portions 11a and 11b in order to provide electrical insulation and corrosion resistance. Has been done. An earth ring 21 for grounding the measuring pipe 11 and the fluid 12 to be measured is provided on the outer surface of the flanges 11a and 11b.
Has been fixed. Further, a cylindrical electrode accommodating portion 22 accommodating the electrode 17 is integrally provided on the outer peripheral surface of the measuring tube 11. The inner bottom portion of the electrode housing portion 22 is covered with the extension portion 19A of the lining material 19 in order to enhance the sealing property of the measuring tube 11.

The electrode 17 integrally has a flange portion 17A. A front end portion of the flange portion 17A is fitted into the electrode mounting hole 18, and a cylindrical insulating cap is formed at a rear end portion of the flange portion 17A. 23 is fitted. The flange portion 17A is brought into close contact with the extension portion 19A of the lining material 19 which covers the inner bottom surface of the electrode housing portion 22 via an O-ring 24, and is pressed by a compression coil spring 25 mounted in the electrode housing portion 22. There is. The compression coil spring 25 is attached to the rear end portion of the electrode 17, and is electrically insulated from the electrode 17 by the insulating cap 23. The opening of the electrode housing portion 22 is closed by the spring receiving member 27 of the compression coil spring 25. The spring receiving member 27 is formed in a tubular body and has an external thread formed on the outer peripheral surface thereof, and the external thread portion is screwed into a female thread formed on the inner peripheral surface of the electrode housing portion 22.

The rear end of the electrode 17 has a spring receiving member 27.
A through-hole 28 provided in the terminal is projected to the outside of the electrode housing portion 22, and a crimp terminal 31 attached to one end of a signal lead wire 30 is fixed to the protruding end by a set screw 32. The other end of the lead wire 30 is guided upward together with the lead wire 33 of the exciting coil 13, and the converter 3
Connected to 5. The converter 35 is installed on the neck portion 34A of the case 34 that covers the measuring tube 11.

The case 34 is formed in a cylindrical shape and protects the measuring tube 11, the exciting coil 13, the electrode 17 and the like. The neck portion 34A is projectingly provided on the upper surface of the case 34, and a cylindrical electrode lead-out portion 36 is provided on both side surfaces of each electrode 17.
Corresponding to, it is projected integrally. The opening of the electrode lead-out portion 36 is normally airtightly closed by a lid 37,
By removing the lid 37 and the spring receiving member 27, the electrode 17 can be easily attached and detached from the outside of the case.

3 and 4, an insulated wire is used for the lead wire 30 of the electrode 17 (the same applies to the lead wire 33 of the exciting coil 13), so that the core wire 40 and the core wire 4 are formed.
It is composed of a cover 41 such as vinyl covering 0. A core wire exposed portion 42 is formed in the middle portion of the lead wire 30 by removing the coating 41. This exposed core wire 4
2 is a sealing member 4 that hermetically closes the neck portion 34A.
By being buried in 4, the contact with the outside air is blocked. The sealing member 44 is made of potting resin such as silicon. A positioning plate 45 for positioning the lead wires 30 and 33 so as not to short-circuit the lead wires 30 and 33 is provided inside the neck portion 34A. The positioning plate 45 is for each lead wire 3
It has an insertion hole 46 through which 0 and 33 are inserted, and the upper surface is covered with the potting resin 44.

When potting the exposed core wire portion 42 of the lead wire 30, the positioning plate 45 having the lead wire 30 inserted into the insertion hole 46 is inserted into the inside of the neck portion 34A so as to project from the inner peripheral surface. It is locked to the locking portion 47 and fixed by an adhesive. At this time, the core wire exposed portion 42 of the lead wire 30 is positioned slightly above the upper surface of the positioning plate 45. Next, in this state, the liquid potting resin 44 may be filled in the neck portion 34A to cover the upper surface of the positioning plate 45 and seal the core wire exposed portion 42. The potting resin 44 is hardened after filling and hermetically closes the neck portion 34A.

In the electromagnetic flow meter 20 having such a structure, when the exciting coil 13 is energized to excite it,
A magnetic field is generated across the fluid to be measured 12 flowing in the measuring tube 11 and orthogonal to the flow. When a magnetic field is generated, an electromotive force proportional to the flow velocity is generated in the fluid in a direction orthogonal to both the magnetic field direction and the flow direction due to the electromagnetic induction phenomenon, which is taken out by the pair of electrodes 17 and amplified. After signal processing, the data is recorded or transmitted to an indicating instrument to measure the flow rate and average flow velocity of the fluid 12 to be measured, or to perform constant value control of the flow rate.

Here, in the present invention, the lead wire 30
The core wire exposed portion 42 is provided in the middle portion of the
Since it is embedded in the potting resin 44, the breathing action of the lead wire 30 can be completely prevented. That is, if the core wire exposed portion 42 is provided by removing the intermediate portion of the coating 41, the air flow in the lead wire 30 can be completely blocked at the core wire exposed portion 42. Therefore, even if the warm outside air on the converter 35 side enters the inside of the lead wire 30, it cannot reach the electrode side end portion, and it is possible to prevent the occurrence of dew condensation in the electrode housing portion 45. The electromotive force can be reliably detected.

Further, in the lead wire 30 of the present invention, it is possible to prevent air from flowing for a long period of time as compared with the conventional lead wire 1 shown in FIG. That is, as described above, in the conventional lead wire 1, since the adhesive 3 is applied to the connecting end portion thereof, the connecting end portion of the lead wire 1 is used for maintenance, inspection, replacement, etc. of the electrode and the converter. When the part is detached from the electrode and the converter or reconnected, an external force is applied to the connection end each time, so that a gap is created between the lead wire 1 and the adhesive 3. Then, when the outside air enters the lead wire 1 through this gap and enters the electrode housing portion by the breathing action due to the temperature difference between the inside and the outside of the electromagnetic flow meter,
The water contained in the outside air is condensed by being cooled by the measuring tube and the electrode. On the other hand, in the present invention, since the exposed core wire portion 42 provided in the middle portion of the lead wire 30 is embedded and fixed in the potting resin 44, the connecting end portion may be removed from the electrode 17 and the converter 35. Even if the core wires are reconnected, almost no external force is applied to the exposed core wire 42, and no gap is formed between the exposed core wire 42 and the potting resin 44. Therefore, the circulation of air can be blocked for a long period of time.

Further, in the present invention, the neck portion 34A
The electrode exposed portion 4 by the potting resin 44 that closes the
Since 2 is sealed, it is not necessary to prepare an adhesive for sealing.

Here, in the present embodiment, the lead wire 33 of the exciting coil 13 is also provided with a similar core wire exposed portion 42, so that the breathing action of the lead wire 33 is prevented and the occurrence of dew condensation in the coil portion. Can be prevented. In this case, the measuring tube 11 or the core member and the exciting coil 13
It is possible to secure the insulation between and.

In the present embodiment, the exciting coil 1
3 and the example applied to the lead wire 30 of the electrode 17,
The present invention is not limited to this, and may be applied only to the lead wire 30 of the electrode 17.

[0021]

As described above, in the electromagnetic flowmeter according to the present invention, the lead wire of the electrode is composed of the insulated wire, the core wire exposed portion is formed in the middle portion thereof, and the core wire exposed portion is placed in the potting resin. Since it is buried, the air flow in the lead wire can be blocked. Therefore, the outside air does not pass through the lead wire to enter the electrode housing portion, the occurrence of dew condensation in the electrode housing portion can be prevented, and the insulation between the electrode and the measuring tube can be secured. Further, in the present invention, even if the connecting end portion of the lead wire is detached from the electrode and the converter, or reconnected, almost no external force is applied to the exposed portion of the core wire, and the circulation of air is reliably prevented for a long period of time. You can Therefore, the performance as an instrument can be maintained for a long period of time.

[Brief description of drawings]

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

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

FIG. 3 is an enlarged sectional view of a neck portion of the case.

FIG. 4 is a perspective view of a lead wire and a positioning plate.

FIG. 5 is a perspective view showing a conventional example of a lead wire.

[Explanation of symbols]

11 ... Measuring tube, 13 ... Excitation coil, 17 ... Electrode, 18 ...
Electrode mounting hole, 19 ... Lining material, 22 ... Electrode housing,
25 ... Compression coil spring, 27 ... Spring receiving member, 28 ... Through hole, 30 ... Lead wire, 34 ... Case, 40 ... Core wire, 4
DESCRIPTION OF SYMBOLS 1 ... Covering, 42 ... Core wire exposed part, 44 ... Potting resin, 45 ... Positioning plate.

Claims (1)

[Claims] 1. A pair of exciting coils, which are provided opposite to the peripheral wall of the measuring tube and form a magnetic flux orthogonal to the flow direction of the fluid to be measured,
A case having a pair of electrodes provided on the measuring tube so as to be orthogonal to both the magnetic flux of the exciting coil and the axis of the measuring tube, and a neck portion for taking out the lead wire of the electrode to the outside and covering the measuring tube. And a sealing member that closes the neck portion of the case, the lead wire is formed of an insulated wire and the sealing member is formed of potting resin, and the exposed core portion of the lead wire is in the potting resin. An electromagnetic flowmeter characterized by being buried in.