JPH01140021A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To prevent the effect of heat from a substance to be measured, by a construction wherein an exciting coil wound round a bobbin is disposed apart from a measuring tube, and free end parts of a pair of plate-shaped cores whose fixed based are fixed to the bobbin are made to face each other with the measuring tube held between. CONSTITUTION:When an exciting current is allowed to flow through an exciting coil 24, a magnetic field being effective both along the axial line of electrodes 6A and 6B and in the direction of flow of a substance to be measured is generated between free end parts of a pair of plate-shaped cores 25 and 26. A voltage generated between the electrodes 6A and 6B is expressed by the product of an inner-tube magnetic flux density caused by the coil 24, an average flow speed of the fluid to be measured and a distance between the electrodes, and therefore the average flow speed of the fluid to be measured can be measured by detecting the voltage. Since a magnetic field generating device 22 is constituted by the coil 24 and the cores 25 and 26 in a pair, the coil 24 can be disposed apart from a measuring tube 1. Accordingly, the effect of heat from the substance to be measured is prevented substantially and the accuracy in measurement is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electromagnetic flowmeter that is less susceptible to the influence of heat from a fluid to be measured. [Prior Art] Measures the flow rate of a conductive fluid flowing inside a pipe. Various types of electromagnetic flowmeters have been proposed, of which the configurations shown in FIGS. 4 and 5 are known as representative ones. To briefly explain this, 1 is formed into a cylindrical shape, connecting flanges 11L and 1b are integrally provided at the openings at both ends, and the entire inner peripheral surface is lined with an insulating lining 2 made of tetrafluoroethylene or the like. The measurement tube is made of stainless steel, and on the outer peripheral surface of this measurement t1, a pair of saddle-shaped excitation coils 4A and 4B that generate a magnetic field in a direction perpendicular to the flow direction of the fluid 3 to be measured in the tube are vertically opposed. It is arranged as follows. Further, on the wall of the measurement tube 1, the flow direction of the fluid 3 to be measured and the excitation coils 4A, 4 are located at the center in the axial direction of both sides.
A pair of electrode insertion holes (not shown) that are perpendicular to the direction of the magnetic field due to B and K are formed through the electrodes 9 so as to face each other, and electrodes 5A and 5B are attached to these insertion holes, respectively. The inner end face faces into the measurement tube 1 and forms a liquid contact surface. Furthermore, a core 6 and a case 7 (not shown in FIG. 5) are arranged around the outer circumference of the measuring tube 1, and the case 7 protects the excitation coils 4A, 4B, electrodes 5A, 5B, and the core 6. The core 6 is made of a magnetic material such as soft iron and has a cylindrical shape, and serves as a part of the excitation coils 4A and 4B (
or the whole) to form a magnetic circuit.

The measuring pipe 1 having such a configuration is interposed between the pipes 8A and 8B via gaskets 9A and 9B and an earth ring 10, and the flanges 11 and 12 of both pipes 8A and 8B are connected to a plurality of bolts 13 and nuts. 14, which holds the measuring tube 1.

[Problem that the invention seeks to solve]

Incidentally, in such a conventional electromagnetic flowmeter, the pair of saddle-shaped excitation coils 4A and 4B are closely fixed directly to the outer circumferential surface of the measuring tube 1, so that the influence of heat from the fluid 3 to be measured is reduced. However, there was a problem in that the measurement accuracy was reduced.

In general, this type of electromagnetic flowmeter is free from electrochemical noise,
A rectangular wave excitation method is adopted to make it less susceptible to electromagnetic induction noise (quadrature noise), but when the coil temperature rises due to heat from the fluid under test 3 and the coil resistance increases, this rectangular waveform rises. However, the falling characteristic deteriorates and a clean waveform is not obtained, making it impossible to obtain highly accurate flow measurement.Therefore, the excitation coil 4A is made of coil wire with excellent heat resistance, especially for high temperatures and fluids. , 4B, but such coil wire materials are expensive and have been a major obstacle to lowering the cost of the device.

Therefore, the present invention solves the above-mentioned problems,
Simple structure and less affected by heat from the fluid being measured.
The object of the present invention is to provide an electromagnetic flowmeter that enables the use of inexpensive coil wire material with low heat resistance, and that enables easy and reliable positioning of a core forming a magnetic circuit with respect to a measuring tube. It is.

[Means for solving problems]

The present invention has been made to achieve the above-mentioned object, and a first aspect of the present invention is that the electrodes provided on the side of the measuring tube are capable of controlling both the flow direction of the fluid to be measured flowing inside the tube and the electrodes provided on the measuring tube. The magnetic field generating device includes a bobbin that is orthogonal to both the measuring tube and the electrode, an excitation coil wound around the bobbin, and a magnetic field generating device that generates a magnetic field in a direction perpendicular to It is composed of a pair of plate-shaped cores formed of a magnetic material, with fixed bases fixed to both end faces of the bobbin, and free ends of the metal tubes facing each other to form a magnetic circuit.

Further, a second invention is a magnetic field generating device that is installed on the side of a measuring tube and generates a magnetic field in a direction perpendicular to both the flow direction of the fluid to be measured flowing inside the tube and the electrodes provided in the measuring tube. This magnetic field generating device includes: a bobbin that is spaced apart from the side of the measuring tube and perpendicular to both the measuring tube and the electrode; and an excitation coil wound around the bobbin. a magnetic circuit that is supported by a magnetic material and whose fixed bases are fixed to both end surfaces of the bobbin so that they face each other, and whose free ends are given elasticity in the direction of the inner surface and are pressed against the outer circumferential surface of the measuring tube; It is composed of a pair of plate-shaped cores that form a core.

[Function] In the first invention, the pair of plate-shaped cores forming the magnetic circuit extend in a direction perpendicular to the measuring tube, and the excitation coil wound around the bobbin is disposed at the fixed base thereof. , the coil can be separated from the measuring tube and is not affected by heat from the fluid to be measured.

Furthermore, in the second aspect of the invention, the free end of the plate-shaped core of the magnetic field generator is pressed against the measuring tube, so that the interval therebetween is kept constant.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of an electromagnetic flowmeter according to the present invention. In the drawings, the same components as in FIGS. 4 and 5 are designated by the same reference numerals, and their explanations will be omitted. In the figure, a pair of upper and lower chamfered grooves 20.2) are provided in the radial direction on the outer circumferential surface of the measuring tube 1 at the center in the axial direction.

Reference numeral 22 is provided on one side of the measurement tube 1, and is connected to the flow direction of the fluid to be measured (direction perpendicular to the paper surface) and a pair of electrodes 6A, 6B.
This magnetic field generating device 22 is formed in a columnar (or cylindrical) shape by a non-magnetic material, and has 7 7 in each end face.
A bobbin 23 is provided with integrally provided lunges 2) and 23b. The bobbin 23 is spaced apart from one side of the measuring tube 1 and vertically arranged so that the two flanges 23m and 23b face each other vertically, and an excitation coil 24 is wound around the bobbin 23. A pair of plate-shaped cores 25 formed of a magnetic material such as soft iron are provided on the upper and lower surfaces.
26 fixed bases 25a and zsa are each fixed by a plurality of setscrews 2T. Plate core 25.26
The free ends 25b and 26b are inserted into the chamfered grooves 2G and 2), respectively, so that they are vertically opposed in parallel with the measuring tube 1 in between. The excitation coil 24 and the measurement tube 1
A space surrounded by the pair of plate-shaped cores 25 and 26 is filled with a heat insulating material 28. The pair of plate-shaped cores 25
．． 26 fixed base zsa, 26a free end 25b, 2
Mounting parts 25c and 26c, which are bent at a substantially right angle in the vertical direction, are provided at the ends opposite to the 6b side, and these mounting parts 25c and 26c are attached to the exchanger case 3.
The measuring tube 1 and the magnetic field generator 2 are fixed to the inner wall of the exchanger case 30 with a set screw 31.
A storage section 32 for accommodating 2 is integrally formed in a protruding manner.
Replace the magnetic field generator 22 in the housing 32 of the case 30.
When the mounting parts 25c and 26c are fixed to the inner wall of the case with the set screws 31, the free end 25
b.

26b is inserted into the chamfered groove 20.2) and faces vertically. In addition, the exchanger case 30 is made of aluminum,
It is made of non-magnetic material such as plastic.

In the electromagnetic flowmeter having such a configuration, when an excitation current is passed through the excitation coil 24, the pair of plate coils 25.2
A magnetic field is generated between the free ends 25b and 26b of the electrodes 6A and 6B, which is perpendicular to both the axes of the electrodes 6A and 6B and the flow direction of the fluid to be measured. Picture electrode 6A.

The voltage (g) generated between 6B and 6B is determined by the magnetic flux density (B) in the tube due to the excitation coil 24 and the average flow velocity (V) of the fluid to be measured.
and the distance between the electrodes (d), so the voltage (g
), the average flow velocity (V) of the fluid to be measured can be measured.

Here, in the present invention, since the bobbin-shaped excitation coil 24 and the pair of plate-shaped cores 25 and 26 constitute the magnetic field generator [22], the excitation coil 24 can be placed away from the measurement tube 1. Therefore, it is less susceptible to the influence of heat from the fluid to be measured, improving measurement accuracy, and since it is possible to use an inexpensive coil wire with low heat resistance and a heat insulating material 28, the influence of heat can be further reduced. It is possible to improve accuracy and to use inexpensive coil wire material with low heat resistance, thereby reducing costs.

Further, the excitation coil 24 wound around the bobbin 23 is easier to manufacture than the conventional saddle-shaped coil shown in FIGS. 4 and 5, and the coil lead wire 33 can be easily routed.

In other words, in a saddle-shaped coil, if the coil lead wire 33 is wired at an angle to the magnetic flux in the axial direction of the measuring tube 1, it will cause electromagnetic induction noise, which will have an adverse effect on measurement accuracy and zero point stability. However, in the case of the bobbin type excitation coil 24, the coil itself is connected to the measuring tube 1.
Since it is arranged at a distance from the terminal, there is less worry about this and wiring work is easy.

FIG. 2 is a sectional view of a magnetic field generating device showing another embodiment of the present invention. In this embodiment, the free ends 25b, 26b of each of the plate-shaped cores 25, 26 are curved into an arc shape with a curvature between the outer peripheral surface of the measuring tube 1 and the path.
6b K The fixed base 25a is provided with eccentricity in the direction of approaching each other, that is, in the inward direction, and is in pressure contact with the outer circumferential surface of the measuring tube 1, and further keeps the bobbin 23 far away from the measuring tube 1.
, 25b on the side ends of the mounting portions 25c and 26c.

In such a configuration, the position of the free ends 25b, 26b of the plate core 25, 26 with respect to the measurement 1WIK is uniquely determined, eliminating the need for adjustment work during assembly, improving work efficiency, and reducing the use of heat insulating material. is also considered unnecessary.

FIG. 3 is a partially cutaway front view showing still another embodiment of the magnetic field generator. In this embodiment, a triangular bent portion 40a is provided at the boundary between the fixed base portions 25m, 26m and the free end portions 25b, 26b of the plate-shaped core 25,26.

40b to give the free ends 25b and 26b an eccentricity in the direction of approaching each other, and the chamfered groove 20 of the measuring tube 10
．． 2) and is pressed into contact with the bottom surface of the mounting portion 25c.

26c is made of a non-magnetic material and formed in an abbreviated shape separately from the plate cores 25 and 26. Note that the free end 2
The base 25a fixes the distance between 5b and 26b.

26a, this free end 25b,
Magnetic flux can be concentrated between 26b.

〔Effect of the invention〕

As described above, in the first aspect of the electromagnetic flowmeter according to the present invention, the excitation coil wound around the bobbin is arranged apart from the measuring tube, and the electromagnetic flowmeter has a pair of plate-like cores each having a fixed base fixed to the bobbin. Since the free ends of the two are opposed to each other with the measuring tube in between, it is possible to provide an electromagnetic flowmeter in which the excitation coil is less susceptible to the influence of heat from the fluid to be measured, and it is possible to improve measurement accuracy. In addition, if the influence of heat is small, it is possible to use inexpensive coil wire with low heat resistance, reducing costs.Moreover, if it can be placed away from the measurement tube, there is no need to worry about electromagnetic induction noise during assembly.

It is easy to route the lead wires.

Furthermore, in the second aspect of the present invention, the free ends of the plate-shaped cores are pressed against the outer circumferential surface of the measuring tube, so the distance between the free ends can be set constant without the need for positioning work, and assembly work can be improved. Improve your sexuality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the electromagnetic flowmeter according to the present invention, FIGS. 2 and 3 are sectional views showing other embodiments of the magnetic field generating device, and FIGS. 4 and 5 are sectional views showing other embodiments of the magnetic field generating device. FIG. 1 is a cross-sectional view and an exploded perspective view of a conventional electromagnetic flowmeter. 1... Measuring tube, 2... Insulating lining, 3...
... Fluid to be measured, 4A, 4B ... Excitation coil,
5A, 5B ・@-・i-pole, 6-・・Φ core, 22・
...Magnetic field generator, 23...Bobbin, 24...
・Exciting coil, 25.26--Plate core, 25a
, 26a...Fixed base, 25b, 26b ---
-Free end, 25c, 26c...Mounting part, 30.
...exchanger case.

Claims (2)

[Claims] (1) A magnetic field generating device is provided on the side of the measuring tube and generates a magnetic field in a direction perpendicular to both the flow direction of the fluid to be measured flowing inside the tube and the electrode provided in the measuring tube, The magnetic field generator includes a bobbin perpendicular to both the measurement tube and the electrode, an excitation coil wound around the bobbin, and fixed bases each formed of a magnetic material and fixed to both end surfaces of the bobbin. 1. An electromagnetic flowmeter characterized in that the electromagnetic flowmeter comprises a pair of plate-shaped cores whose free ends sandwich the measuring tube and face each other to form a magnetic circuit. (2) A magnetic field generating device is provided on the side of the measuring tube and generates a magnetic field in a direction perpendicular to both the flow direction of the fluid to be measured flowing inside the tube and the electrode provided on the measuring tube, The magnetic field generator includes a bobbin that is spaced apart from the measuring tube and perpendicular to both the measuring tube and the electrode, an excitation coil wound around the bobbin, and a magnetic material. a pair of magnetic circuits, the fixed bases of which are fixed to both end surfaces of the bobbin, facing each other, and whose free ends are given elasticity in the direction of the inner surface and are pressed against the outer peripheral surface of the measuring tube. An electromagnetic flowmeter characterized by comprising a plate-shaped core.