JPS6242013A - Measuring pipe for electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To execute sealing without fail and to lower cost by making a hole at the side surface of unburned or half-furned ceramic pipe, when an electrode is inserted here, forming the electrode cylindrically with the ceramic, applying the metallic paste at the inner circumferential surface while the bottom surface is closed, and burning after this is inserted into the hole. CONSTITUTION:An unburned or the half-burned ceramic is used, a measuring pipe 1 for the electromagnetic flow meter is formed, located at the central part in the shaft line direction and a hole 2 for fitting the electrode to cross over the pipe 1 is drilled. Next, an electrode 6 is inserted and fixed here, at such a time, the same ceramic is used for a cylindrical body 4 to constitute this, while the bottom surface is closed, the high melting point metal paste such as Pt and Pt.Ir alloy is applied to the inner circumferential surface and a conducting part 5 is formed. Therefore, the whole body is burned by the burning temperature of the ceramic and the electrode 6 is fixed to a pipe 3. Thus, since the shrinking allowance of the pipe 3 at the time of burning is larger than the shrinking allowance of an electrode 6, fixing is executed without fail, the sealing performance is improved and the electrode 6 can be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring tube for an electromagnetic flowmeter using a ceramic material.

[Conventional technology]

Conventionally, measuring tubes for this type of electromagnetic flowmeter have been made by inserting electrodes made of metal or conductive ceramic into the electrode mounting holes of the ceramic tube, and then firing the ceramic tube and electrode. has been done.

[Problem that the invention seeks to solve]

However, the former, that is, those that use metal for the electrodes,
The metal must be durable against the firing temperature of ceramics, and its coefficient of thermal expansion must be close to that of ceramics. For this reason, the only metals that can be used are expensive metals such as platinum. The problem was that it was limited to.

Therefore, in order to economically manufacture measuring tubes for electromagnetic flowmeters,
It is conceivable to reduce the outer diameter of the electrode, but in this case, the input impedance increases when viewed from the side of the electromagnetic flowmeter converter, which has the disadvantage of adversely affecting the performance of the meter when it is used.

On the other hand, the latter, that is, those in which conductive ceramic is used for the electrode, has a performance problem similar to the case described above because its conductivity is inferior to that of ordinary metals, although this differs somewhat depending on the composition.

[Means for solving problems]

The measurement tube for an electromagnetic flowmeter according to the present invention includes an unfired or semi-fired ceramic tube having an electrode attachment hole, and a metal tube inserted into the electrode attachment hole of the ceramic tube and provided on the inner peripheral surface and the insertion end. It is made by firing an electrode formed of a ceramic cylinder having a conductive part.

Further, a measurement tube for an electromagnetic flowmeter according to another invention of the present invention is as follows:
An unfired or semi-fired ceramic tube having an electrode mounting hole, and an electrode formed of a ceramic tube that is inserted into the electrode mounting hole of the ceramic tube and has a metal conductive part on its inner peripheral surface and insertion end. A metal conductive member is attached to the insertion side of the electrode to electrically connect to the conductive part.

The present invention was developed in view of the above circumstances, and it is possible to easily and reliably seal between an electrode and an electrode mounting hole, reduce costs, and improve performance when using a meter. To provide a measurement tube for an electromagnetic flowmeter that does not have an adverse effect on the flowmeter.

[For production]

In the present invention, the ceramic tube is made by firing an unfired or semi-fired ceramic tube having an electrode mounting hole and an electrode formed of a ceramic tube that is inserted into the electrode mounting hole of the ceramic tube. The amount of shrinkage becomes larger than the amount of shrinkage of the electrode. Further, since the electrode is formed of a ceramic cylinder having a metal conductive portion on its inner circumferential surface and insertion end, the electrode diameter can be increased even if less metal is used.

Further, in another aspect of the present invention, since a metal conductive member electrically connected to the conductive portion is attached to the insertion side of the electrode, this conductive member is exposed inside the tube.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of a measuring tube for an electromagnetic flowmeter according to the present invention. In the figure, the reference numeral 1 denotes a measuring tube for an electromagnetic flowmeter, which includes an unfired or semi-fired ceramic tube 3 having an electrode mounting hole 2 in the center in the axial direction.
An electrode 6 formed of a fired ceramic tube 4 which is fitted into the electrode mounting hole 2 of the ceramic tube 3 and has a metal conductive part 5 on its inner peripheral surface 4a and insertion end 4b is fired. It is held under pressure by connecting pipes (not shown). A signal lead wire 7 is connected to a terminal on a terminal board (not shown), and is soldered to the side of the conductive section 5 opposite to the fluid to be measured. The metal used for the conductive part 5 has a ceramic firing temperature of 1000 to 16
It is desirable to use a high melting point metal such as platinum or a platinum-iridium alloy, which has a melting point higher than 00°C.

In the measurement tube for an electromagnetic flowmeter configured in this way,
The ceramic tube is made by firing an unfired or semi-fired ceramic tube 3 having an electrode attachment hole 2 and an electrode 6 formed of a fired ceramic tube and inserted into the electrode attachment hole 2 of the ceramic tube 3. The shrinkage margin of electrode 3 is larger than that of electrode 6. Further, since the electrode 6 is formed of the ceramic tube 4 having the metal conductive portion 5 on the inner circumferential surface 4a and the insertion portion 4b, the electrode diameter can be increased even if less metal is used.

Although this embodiment shows an example in which the fired ceramic cylinder 4 is used for the electrode 6, the present invention may use a semi-fired ceramic cylinder as long as it has a relatively small shrinkage margin. That is, it is sufficient to use a combination of ceramic cylinders whose semi-firing temperature is higher than that of the ceramic tube 3.

Next, a method of manufacturing the measuring tube 1 for an electromagnetic flowmeter having the above-described configuration will be explained.

First, the inner peripheral surface 4a and the insertion end 4 of the fired ceramic tube 4
Apply platinum paste to b and heat at a temperature of 800 to 1600.
The electrode 6 is formed by baking at .degree. At this time,
The opening of the ceramic cylinder 4 on the electrode insertion side is closed with platinum. Next, after inserting this electrode 6 into the electrode mounting hole 2 of the unfired or semi-fired ceramic tube 3, the firing temperature is set to 1.
Calculate at 000-1600°C. .

In this way, the electromagnetic flowmeter measurement tube 1 equipped with the electrode 6 can be manufactured reliably.

In the method for manufacturing the measuring tube 1 for an electromagnetic flowmeter according to this embodiment, the electrode 6 is first formed, and then the electrode 6 is inserted into the electrode attachment hole 2 of the unfired or semi-fired ceramic tube 3 and then fired. However, in the present invention, after the fired ceramic tube 4 for the electrode is inserted into the electrode mounting hole 2 and fired, platinum paste is applied to the inner circumferential surface 4a and the insertion end 4b of the ceramic tube 4. The electrode 6 may be formed by baking. In this case, a material having a melting point lower than that of platinum can be selected as the metal used for the conductive part 5, and the material cost can be reduced.

Further, in another invention of the present invention, FIG.
As shown in the figure, a conductive part 10.11 is placed on the insertion side of the electrode 8.9.
Since the conductive tip 12 or the conductive cap 13 made of platinum-iridium alloy is attached to the tube, the conductive tip 12 or the conductive cap 13 is exposed inside the tube. In this case, the attachment of the conductive tip 12 or the conductive cap 13 takes place before firing the electrode 8.9 and the ceramic tube (not shown).

Further, in this embodiment, only the opening on the electrode insertion side of the ceramic cylinder 4 is closed with the conductive part 5 as the electrode 6, but the present invention is not limited to this. As shown in FIG. 5, an electrode 16 made of platinum may be used to close not only the opening of the ceramic cylinder 14 but also the inside thereof with a conductive part I5. In this case, as shown in FIG. This can be done either directly during the formation of the terminal 15 or via a platinum terminal 18 shown in FIG.

Furthermore, since the ceramic cylinder 4 of the present invention can be easily subjected to various processing, in addition to the above-mentioned embodiments, for example, as shown in FIG. The electrode 19 formed in steps and the eighth
As shown in the figure, the electrode 20 has a locking portion 20a inside to securely lock a lead wire (not shown in FIG. 8), and its shape can be freely changed. Here the seventh
In the figure, 21 is a conductive chip attached to the insertion side of the electrode 19 by brazing or press-fitting.

〔Effect of the invention〕

As explained above, according to the present invention, an unfired or semi-fired ceramic tube having an electrode mounting hole and an electrode formed of a ceramic tube fitted into the electrode mounting hole of the ceramic tube are fired. Therefore, the shrinkage margin of the ceramic tube is larger than that of the electrode, making it possible to securely fix the electrode to the ceramic tube and easily and reliably seal between the electrode and the electrode mounting hole. Moreover, since the coefficient of thermal expansion of the electrode and the coefficient of thermal expansion of the ceramic tube are approximately the same, the sealing performance will not deteriorate even if there is a temperature change. Further, since the electrode is formed of a ceramic tube having a metal conductive portion on its inner circumferential surface and insertion end, the electrode diameter can be increased even if less metal is used. Therefore, the cost can be reduced, and the performance of the meter is not adversely affected when it is used, unlike the conventional method.

Another aspect of the present invention is that a metal conductive member that is electrically connected to the conductive part is attached to the insertion side of the electrode, so this conductive member is exposed inside the tube, which reduces the wear resistance of the electrode. can be increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a measuring tube for an electromagnetic flowmeter according to the present invention, FIGS. 2, 3 and 4 are sectional views showing electrodes in other embodiments, and FIGS. FIG. 6 is a cross-sectional view and a front view for explaining the state of connection of the lead wire to the electrode, and FIGS. 7 and 8 are cross-sectional views showing electrodes in other embodiments. DESCRIPTION OF SYMBOLS 1... Measuring tube for electromagnetic flowmeter, 2... Electrode mounting hole, 3... Ceramic tube, 4... Ceramic tube, 4a... Inner peripheral surface, 4b... ...Insertion end, 5...
・Conductive part, 6...electrode. 0') (v) Taste C^

Claims (2)

[Claims] (1) An unfired or semi-fired ceramic tube that has an electrode mounting hole in the center in the axial direction, and a metal conductive part that is fitted into the electrode mounting hole of the ceramic tube and on its inner peripheral surface and insertion end. A measurement tube for an electromagnetic flowmeter made by firing an electrode formed of a ceramic tube. (2) An unfired or semi-fired ceramic tube that has an electrode mounting hole in the center in the axial direction, and a metal conductive part that is fitted into the electrode mounting hole of the ceramic tube and on its inner peripheral surface and insertion end. 1. A measuring tube for an electromagnetic flowmeter, characterized in that the electrode is formed of a ceramic tube and is fired, and a metal conductive member is attached to the insertion side of the electrode to electrically connect to the conductive part.