JPH0229170B2 - YORYOSHIKIDENJIRYURYOKEIYODOKANNOSEIZOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a conduit (hereinafter referred to as a conduit) for a capacitive electromagnetic flowmeter, and is intended to facilitate manufacturing.

FIG. 1 shows a longitudinal section of a typical conduit. Figure 2 shows its cross section. As shown in both figures, a planar measuring electrode 2 and a guard electrode 3 disposed facing the outside of the measuring electrode 2 are embedded in a pipe-shaped conduit 1 made of ceramic. . Of these, the measurement electrode 2 extracts the electromotive force generated in the fluid to be measured (not shown) flowing in the conduit 1 perpendicularly to the magnetic flux generated by the excitation coil 4 through capacitive coupling. Further, the guard electrode 3 shields the measurement electrode 2. Case 5 made of high magnetic permeability material is conduit 1
It is arranged to surround the outer periphery of the excitation coil 4, and also functions as a return magnetic path for the magnetic flux generated by the excitation coil 4, that is, it also functions as a core. Note that a pole piece 6 is provided between the conduit 1 and the case 5.

A method of manufacturing the above-mentioned conduit 1 according to the prior art will now be explained with reference to FIG. As shown in Figure 3, first the shield 7 is applied to the surface by metallization processing.
A window 8 is formed in the unfired ceramic conduit 1 which has been subjected to the process (the shaded area in the figure). Next, curved rectangular unfired ceramic pieces 9, 9a, 9b are successively fitted into the window 8 and laminated. In addition, the ceramic pieces 9, 9 were made by metallization before the lamination work.
A measurement electrode 2, a guard electrode 3, and a shield 7 were formed on the outer peripheral surfaces of the electrodes a and 9b, respectively, and then the whole was fired.

However, such conventional technology has the following drawbacks.

(1) The window punching process to form the window 8 is extremely difficult.

(2) Processing the ceramic pieces 9, 9a, 9b themselves is difficult and costly without using molding.

Further, there is a method shown in FIG. 4 as another conventional manufacturing method. In FIG. 4, first, a first pipe 10, a second pipe 10a, and a third pipe 10b made of unfired ceramic are formed. At this time, the size of the pipe 10a is such that it can fit tightly into the outer periphery of the pipe 10, and the pipe 10b is sized so that it can fit tightly into the outer periphery of the pipe 10a. Next, the measurement electrode 2 is formed on the outer peripheral surface of the pipe 10 by metallization. A shield 7a is provided on the inclined surface of the pipe 10. Thereafter, the pipe 10a having the guard electrode 3 formed on its outer circumferential surface by metallization is fitted concentrically to the outer circumference of the pipe 10. Furthermore, a pipe 10b having a shield 7b applied to its outer peripheral surface and an inclined surface is fitted concentrically to the outside of the pipe 10a. After that, the whole was fired as one piece to produce a conduit.

However, such conventional technology has the following drawbacks.

(1) It is difficult to complete levels 10, 10a, and 10b closely. (It will increase the cost) (2) 3 on the pipe insertion surface (left end in Figure 4)
The boundaries between the layers are exposed, and voids are formed at the boundaries due to differences in shrinkage rates of each layer during firing, and moisture, dust, etc. enter through these voids, causing accuracy errors.

(3) Due to the difference in shrinkage rate of each layer during firing, residual stress remains during firing and causes early failure.

The present invention relates to a method for manufacturing a conduit without the above-mentioned drawbacks, and its purpose is to provide a conduit that is easy to manufacture, has no exposed end face, and does not retain residual stress during firing.

The structure of the present invention that achieves such an object includes an unfired ceramic pipe, a first unfired ceramic sheet (hereinafter referred to as a green sheet) wound around the pipe, and an outer periphery of the first green sheet. The method is characterized in that the second green sheet is wound and then the whole is fired.

Embodiments of the present invention will be described below with reference to FIGS. 5 to 8. FIG. 5 shows a longitudinal section of the conduit, and FIG. 6 shows its cross section. In the figure, 20 is an unfired ceramic pipe (hereinafter referred to as pipe) having flanges 21, 21' at both ends and a stepped portion 22 in the middle. Measurement electrodes 23, 23' are placed at symmetrical positions on the circumference of the stepped portion 22 of the pipe 20.
is metalized. A first green sheet 24 is wound around the stepped portion 22 of the pipe 20, and guard electrodes 25, 25' are metallized on the outer surface. 26 is a second green sheet wound around the outer periphery of the first green sheet 24. A shield 27 is metallized on the slopes of the flanges 21, 21' and on the outer peripheral surface of the second green sheet 26 to shield electrical noise from the coil 4 and other electrical parts. In addition, flanges 21, 2
Ground electrodes 28, 28' are metallized on both end faces of 1'. FIG. 7 shows a developed view of the first green sheet 24, with guard electrodes 25 and
25' is metallized. Reference numerals 29 and 29' are lead wire extraction holes for the measurement electrodes 23 and 23'.
FIG. 8 shows a developed view of the second green sheet 26, in which guard electrodes 25, 25' are placed at symmetrical positions when wound around the outer periphery of the first green sheet 24.
Lead wire extraction holes 30, 30' are provided, and a shield 27 is metallized on one surface.

After shaping as described above, the entire body is fired to produce a conduit.

In the above embodiment, the measurement electrodes 23, 23' are metalized at the outer peripheral surface of the pipe 20,
The guard electrodes 25, 25' were located on the outer peripheral surface of the first green sheet 24, but the measurement electrodes 23, 23' were placed on the inner peripheral surface of the first green sheet 24, and the guard electrodes 25, 25 were placed on the outer peripheral surface of the first green sheet 24. ′ may be metalized. FIG. 9 shows a state in which the measurement electrode 23 and the guard electrode 25 are metalized in the form of through holes, and FIG. 10 is a Z view in FIG. 9. It is convenient to metalize each electrode in the form of a through-hole in this way, since the lead wire can be welded to the exposed portion when viewed from above.

As specifically explained above in conjunction with the embodiments, according to the present invention, a first green sheet is wound around the outer peripheral surface of an unfired ceramic pipe having flanges at both ends, and a second green sheet is wound around the outer peripheral surface of the first green sheet.
The green sheet is rolled up, the measurement electrode and the guard electrode are metalized between them, and then they are fired as a single piece, so manufacturing is easy and the end surface is not exposed.
A conduit with no residual stress can be manufactured, which has great industrial effects.

Note that the measurement electrode and the guard electrode are not limited to metallization, and may be coated with a paste-like conductive material.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of a capacitive electromagnetic flowmeter, where Figure 1 is a longitudinal cross-sectional view, Figure 2 is a cross-sectional view, and Figure 3 is a cross-sectional view.
The figure is a perspective view for explaining a conventional manufacturing method, FIG. 4 is a sectional view for explaining another conventional manufacturing method, and FIGS. 5 to 10 are for explaining a manufacturing method according to an embodiment of the present invention. These diagrams are for explanation purposes. FIG. 5 is a longitudinal cross-sectional view, FIG. 6 is a cross-sectional view, FIG. 7 is a developed view of the first unfired ceramic sheet, and FIG. 8 is a developed view of the second unfired ceramic sheet. The developed views, FIGS. 9 and 10, are explanatory diagrams in which the measurement electrode and the guard electrode are metalized in the form of through holes. 20...Unfired ceramic pipe, 21,2
1'...flange, 23, 23'...measuring electrode, 2
4...first unfired ceramic sheet, 25,2
5'... Guard electrode, 26... Second unfired ceramic sheet.

Claims (1)

[Claims] 1. Wrapping a first unfired ceramic sheet around the outer peripheral surface of an unfired ceramic pipe having flanges at both ends, and then wrapping a second unfired ceramic sheet around the outer peripheral surface of the first unfired ceramic sheet. and place a measurement electrode on the outer peripheral surface of the ceramic pipe or the inner peripheral surface of the first ceramic sheet.
A method of manufacturing a conduit for a capacitive electromagnetic flowmeter, characterized in that a guard electrode is provided on the outer peripheral surface of the first ceramic sheet or the inner peripheral surface of the second ceramic sheet, and then the whole is fired as one piece.