JPH067319Y2 - Electromagnetic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electromagnetic flowmeter in which a measuring tube is made of a ceramic material, and in particular, an earth used for electrically connecting a fluid to be measured to a reference potential. Regarding the improvement of the ring.

[Conventional technology]

In general, an electromagnetic flow meter uses Faraday's electromagnetic induction phenomenon to convert the flow rate of a fluid to be measured having conductivity that passes through a measuring tube into an electric signal to measure the flow rate. Many structures have been proposed. In the past, a measuring tube in this type of electromagnetic flowmeter was generally made of stainless steel or the like and the inner surface of which was covered with an insulating lining, but recently, a non-conductive material such as alumina (Al ₂ O) has been used. A ceramic material such as ₃ ) has been developed, has excellent corrosion resistance, does not deform even when used in high temperature conditions, and allows electrodes to be cast and has a good seal at the electrodes. It has been widely used because of its advantages.

In order to improve the measurement accuracy in this type of electromagnetic flow meter, it has been generally necessary to use an earth ring that electrically connects the fluid to be measured to the instrument body and the like. That is, by disposing the earth rings on both ends of the measuring tube and bringing them into contact with the fluid to be measured, the fluid to be measured and the instrument main body are kept at the same reference potential, and as a result, at the electrode portion. The electromotive force can be taken out accurately. And, such an earth ring is of course necessary even if the above-mentioned ceramic measuring tube is used. For example, as shown in JP-A-56-124823, corrosion resistance and conductivity are provided on both sides of the measuring tube. A grounding ring made of an expensive metallic material such as platinum having good conductivity is provided by vapor deposition or the like, and this is connected to the main body side with embedded terminals and lead wires so as to maintain these at the same potential, -96320, etc., a conductive material such as the platinum paste as described above is baked on the end faces of both ends of the ceramic measuring tube and brought into contact with the fluid to be measured,
Further, there has been proposed a device in which this conductive material is connected to the instrument body side with a lead wire so as to keep the fluid and the entire instrument at the same potential.

[Problems to be solved by the device]

However, according to the electromagnetic flowmeter having the above-described conventional structure, in order to electrically connect the earth ring vapor-deposited on the measuring tube or the baked conductive material to the instrument body side through the lead wire, the embedded terminal or the like is grounded. It is necessary to attach it to the side by vapor deposition, or to join a lead wire to a conductive material, and to fix the other end of the lead wire to the instrument body side by soldering, etc., from the viewpoint of structural workability and assembly workability. Was also a problem. Furthermore, if the earth ring or conductive material and the instrument body are simply connected by soldering the lead wire in this way, the connection between the lead wire and the instrument body, the embedded terminal, etc. due to vibration from the piping side, etc. There is a problem that the connection part may be loosened or broken, or the soldered part may be damaged, and the connection part may lack reliability, and it is desired to take some measures to eliminate these problems.

[Means for Solving the Problems]

In order to meet such a demand, the electromagnetic flowmeter according to the present invention is formed as an earth ring by being formed on the end faces of the ceramic measuring pipe for connecting pipes, a part of which is in contact with the fluid to be measured flowing in the measuring pipe. The liquid contact side metallized portion that functions and the connection side metallized portion formed in a strip shape on the outer peripheral side of the measuring tube in the ridge direction so as to connect between these liquid contact side metallized portions and a part of this metallized portion A coil bobbin that is disposed between the measuring instrument body and the measuring instrument body in a pressure-contacted state, and electrically connects the fluid to be measured to the measuring instrument side. A conductive sheet made of a conductive adhesive or the like is interposed between the section and the section.

[Action]

According to the present invention, the liquid contact side and the connection side metallized portions formed on both end surfaces and the outer peripheral side of the ceramic measuring tube and the coil bobbin press-contacted to the connection side metallized portion via the conductive sheet. It is possible to electrically connect the fluid to be measured and the instrument main body and hold them at the same potential, and fix the metallization portion on the connection side and the coil bobbin by inserting a conductive sheet and fixing them with adhesive or the like. As a result, the contact area between them increases and a proper and reliable conduction state can be secured.

〔Example〕

1 to 5 show an embodiment of an electromagnetic flowmeter according to the present invention. In these drawings, reference numeral 1 is made of a ceramic material such as alumina (Al ₂ O ₃ ) to have a substantially cylindrical shape. The formed measuring pipe has both end-side end faces 1a and 1b which are joined and fixed to the fluid pipe side (not shown) through which the fluid to be measured flows.

Here, an example of the configuration of the electromagnetic flowmeter detection unit using such a ceramic measuring tube 1 will be briefly described with reference to FIGS. 2 and 3, and the like. A pair of rectangular or circular electrode surfaces 1 divided into four equal parts
c, 1c and a pair of coil mounting concave portions 1d, 1d are formed so as to face each other at positions orthogonal to each other. And
A pair of electrodes 2, 2 are inserted and fixed in the electrode holes formed in the electrode mounting surfaces 1c, 1c on both sides, and the insertion ends of the electrodes are in contact with the fluid to be measured having conductivity which flows through the inner hole of the measuring tube 1. It's liquid.

Reference numeral 3 denotes a metal instrument case (instrument body) for accommodating the measuring tube 1 in the central hole 3a and fitting and fixing the outer circumferences of both ends thereof.
It is supported and fixed to a fixing portion on the process side (not shown). An annular groove 1 in which an O-ring 4 as a sealing material is inserted is provided on the outer circumference of both ends of the measuring tube 1 which is a fitting surface for the case 3.
f is formed, and the sealing property at this fitting portion is secured. Further, a pair of square tubular portions 3b, 3b are formed at positions corresponding to the recessed portions 1d, 1d of the case 3, and flange portions 3d, 3d are provided on the tip end side thereof through the cylindrical portions 3c, 3c. Are formed. A coil bobbin 5 having a tubular bobbin main body 5a having flanges provided at both ends and a disc 5b screwed to one end of the rectangular bobbin 5 is wound inside the rectangular tubular portions 3b and 3b. The coil units 7 and 7 configured with the exciting coil 6 are housed and arranged, respectively. These coil units 7 and 7 are fixed to the case 3 side by screwing the disc 5b of the coil bobbin 5 to the step portion of the case 3, and the measuring tube 1 is fixed by the pair of upper and lower coil units 7 and 7. It has a function of sandwiching from both sides and fixing the case 3 and the measuring tube 1. The lead wires 8 and 8 connected to the electrodes 2 and 2 are guided to a terminal box or a converter (not shown) through a groove portion and an inner hole in the inner end radial direction of the coil bobbin 5, and are also connected to the exciting coil 6. The lead wires 9 and 9 are connected to a power source (not shown) through the holes of the disc 5b.

Now, according to the present invention, in the electromagnetic flowmeter having the above-mentioned configuration, a part of the ceramic measuring pipe 1 is provided on the pipe connecting end faces 1a and 1b at both ends thereof, as shown in FIGS. 4 and 5. A liquid contact side metallized portion 10 composed of an annular portion and a radius portion that come into contact with the fluid to be measured flowing in the measuring pipe 1 and function as an earth ring is formed, and between these liquid contact side metallized portions 10, 10 So as to connect to each other, the connection side metallized portion 11 having a strip shape is continuously formed toward the ridge line so as to pass through the coil mounting concave portion 1d on the outer peripheral side of the measurement tube 1.
As shown in FIGS. 1 to 3, the concave portion 1d is
Part of the coil unit 7 is electrically connected to the case 3 side by direct connection through the coil bobbin 5 of the coil unit 7 which is pressed against this, and the end portion of the coil bobbin 5 on the side of the measuring tube and the recess where the pressure is pressed. It is characterized in that a conductive sheet 20 such as a conductive double-sided adhesive tape is provided so as to be interposed between the connection side metallized portion 11 in the portion 1d.

More specifically, the liquid contact side and connection side metallized portions 10 and 11 described above are formed by subjecting the ceramic surface of the ceramic measuring tube 1 to known metallization. Here, as a material of the metallized portions 10 and 11, a metallized material for electric parts such as Mo-Mn or W is plated with Ni or Au, and when corrosion resistance is required, Pt metallization or Au metallization may be applied only to the liquid contact portion.
It should be noted that a part of the metal contact portion 10 on the liquid contact side described above is formed so that a part thereof is inserted into the inner hole of the measurement tube 1, and is configured so that it can appropriately contact the fluid to be measured.

Further, the connection-side metallized portion 11 having the above-mentioned strip shape.
Is formed so as to pass through the coil mounting concave portion 1d (both sides in this embodiment) on the outer peripheral side of the measuring tube 1, and is arranged in pressure contact with the concave portion 1d by screwing or the like to the case 3 side. The coil bobbin 5 to be connected electrically connects the fluid to be measured and the case 3 to each other by short-circuiting by direct connection, so that the conventional lead wire connection is not necessary, and is reliable. The connection state can be secured.

Here, according to the present invention, the conductive sheet 20 is provided between the connection side metallized portion 11 on the outer circumference of the measuring tube 1 and the coil bobbin 5 electrically connecting the metallized portion 11 to the case 3 side. This is due to the following reasons. That is, very small protrusions of, for example, 0.1 to 0.2 mm may remain on the end face of the coil bobbin 5 that is pressed against the measuring tube side during processing, and it is difficult to find this at the manufacturing site. Is. In addition to such minute protrusions, undulations and ridges are present on the ceramic surface on the ceramic measuring tube 1 side. Further, it is difficult to control the thickness of the metallized portion 11 evenly, and the thickness often varies. Under these conditions, when the coil bobbin 5 is pressed into the concave portion 1d on the outer circumference of the measuring tube 1 and is screwed and fixed to the case 3 side, the pressing force of the coil bobbin 5 to the measuring tube 1 due to the screw tightening is reduced. When the minute projections described above are present, a concentrated load is applied to one point of the minute projections or the like, so that the measurement tube 1 may be broken due to the stress concentration. is there. Also, when the coil bobbin 5 is tilted and comes into contact with the measuring tube 1 at two points due to the presence of the above-mentioned minute protrusions, a concentrated load is similarly applied, which causes a problem. Even if there is some such a problem, it is taken into consideration so as not to cause a problem such as breakage of the measuring tube 1 side. This is because by inserting the conductive sheet 20, it is possible to absorb the minute protrusions and the like due to the thickness and bring the two members into planar contact, and to obtain the effect as a cushioning material and prevent the occurrence of the concentrated load described above. , Easy to understand. When a conductive double-sided adhesive tape is used as the conductive sheet 20, the coil bobbin 5 can be temporarily fixed,
This has the advantage that the assemblability of the electromagnetic flow meter can be improved.

Furthermore, when such a conductive sheet 20 is interposed,
A connection side metallized portion 11 in the form of a strip on the side of the measuring tube 1,
There is also an advantage that the electrical contact area with the coil bobbin 5 can be increased and a reliable conductive state can be secured.

Here, as the conductive sheet 20 described above, as illustrated in FIG. 1, a conductive double-sided adhesive tape formed by applying conductive adhesives 20b and 20c on both surfaces of an aluminum foil 20a may be used. The formed aluminum foil and the adhesive portion serve as a cushioning agent.

Further, according to the configuration of the present invention, the liquid contact side and connection side metallized portions 10 and 11 formed on both end surfaces of the ceramic measuring tube 1 and the outer peripheral side thereof, and the connection side metallized portion 11 are formed. With the coil bobbin 5 that is pressed against a part of the conductive sheet 20, the fluid to be measured and the case 3 side are appropriately and surely electrically connected and electrically connected, and it is easy to maintain the same potential. In addition, the configuration can be simplified, the reliability in operation can be improved, the number of parts and the number of assembly steps can be reduced, and the measuring tube 1 can be easily replaced. There are advantages.

It should be noted that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the electromagnetic flow meter can be appropriately modified or changed, and various modified examples can be considered. For example, in the above-described embodiment, the case where the liquid contact side metallized portion 10 including the annular portion and the radius portion is formed on the measurement pipe end surfaces 1a and 1b has been described, but the present invention is not limited to this and the entire end surface is formed. It is needless to say that they may be formed across or formed in a shape having voids at appropriate places such as a lattice shape and a mesh shape. It will be easily understood that the conductive sheet 20 may be a sheet made of conductive rubber, a conductive adhesive, or the like.

[Effect of device]

As described above, according to the electromagnetic flowmeter of the present invention,
Ceramic-made measuring pipes are formed on both ends of the pipe to form a strip shape on the outer circumference of the measuring pipe in the ridge direction so as to connect the liquid-contact side metallized parts that function as earth rings and the liquid-contact side metallized parts. And a coil bobbin for electrically connecting the fluid to be measured to the instrument body side, which is disposed between the instrument body and the connection side metallized portion under pressure contact with a part of the connection side metallized portion. Since a conductive sheet is inserted between the end portion of the measuring tube on the side of the measuring tube and the metallized portion on the connecting side to which it is pressure-welded, the metallized side on the liquid contacting side and the connecting side is formed despite the simple and inexpensive structure. It is possible to properly and surely electrically conduct the fluid to be measured to the instrument body side at the section, simplify the configuration and improve the operational reliability, etc. compared to the past, and the number of parts and assembly Steps etc. can also be reduced, also there are practically various excellent effects such as such as that performed in the easy replacement of the measuring tube. Further, according to the present invention, by inserting a conductive sheet between the connection side metallized portion on the outer circumference of the measuring tube and the coil bobbin, the contact area and the like are increased, and moreover, problems such as stress concentration due to minute protrusions are caused. There is an advantage that both members can be appropriately and surely conductively connected in the absence of the above.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential configuration showing an embodiment of an electromagnetic flowmeter according to the present invention, and FIGS. 2 and 3 are schematic cross-sectional views of an electromagnetic flowmeter to which the present invention is applied and the same. Side sectional views, FIGS. 4 and 5 are a plan view and a side view of the ceramic measuring tube. DESCRIPTION OF SYMBOLS 1 ... Measuring tube, 1a, 1b ... End surfaces on both ends, 1d ... Coil mounting recessed portion, 3 ... Instrument case (instrument body), 4 ... O-ring, 5 ... Coil bobbin, 6 ... Excitation coil, 7 ... Coil unit, 10 ... liquid contact side metallized portion, 11 ... connection side metallized portion, 20 ... conductive sheet.

Claims (1)

[Scope of utility model registration request] 1. A liquid-contact side metallized portion which is formed on both ends of a ceramic measuring pipe for connecting pipes and a part of which is in contact with a fluid to be measured flowing in the measuring pipe, and these liquid-side metallized portions are connected to each other. The connecting side metallized portion formed in the shape of a strip on the outer peripheral side of the measuring tube in the ridge direction, and the fluid to be measured is provided on the measuring instrument main body side while being pressed against a part of the connecting side metallized portion. A coil bobbin for electrically connecting the coil bobbin to the instrument body side, and a conductive sheet is interposed between the measurement tube side end of the coil bobbin and the connection side metallized portion to which the coil bobbin is pressed. Characteristic electromagnetic flow meter.