JPH034846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a measuring tube for an electromagnetic flowmeter, and is intended to facilitate manufacturing.

FIG. 1 shows a longitudinal section of a capacitive electromagnetic flowmeter transmitter, and FIG. 2 shows its cross section. As shown in both figures, a measuring electrode 2 having a planar shape and a guard electrode 3 disposed facing the outside of the measuring electrode 2 are embedded in a pipe-shaped measuring tube 1 made of ceramics. There is. Among these, the measurement electrode 2 extracts the electromotive force generated in the fluid to be measured (not shown) flowing in the measurement tube 1 orthogonally to the magnetic flux generated by the excitation coil 4 through capacitive coupling. Further, the guard electrode 3 shields the measurement electrode 2. A case 5 made of a high magnetic permeability material is arranged to surround the measuring tube 1, and also functions as a return magnetic path for the magnetic flux generated by the excitation coil 4, that is, as a core. Note that a pole bead 6 is provided between the measuring tube 1 and the case 5.

Here, a method of manufacturing the above-mentioned measuring tube 1 according to the prior art will be explained based on FIG. 3. As shown in the figure, the shield 7 is first applied to the surface by metallization processing.
(The shaded area in the figure) was applied to the measuring tube 1.
A window 8 is formed. Next, curved rectangular ceramic pieces 9, 9a, and 9b are sequentially fitted into the window 8 and laminated. Note that, before the lamination work, a measurement electrode 1, a guard electrode 3, and a shield 7 are formed on the outer peripheral surfaces of the ceramic pieces 9, 9a, and 9b, respectively, by metallization. Then the whole thing was fired.

However, this conventional technology has the following drawbacks.

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

(b) The processing of the ceramic pieces 9, 9a, and 9b themselves is as follows:
It is difficult to do so without using molding.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide a manufacturing method that facilitates manufacturing of a measuring tube.

The structure of the present invention that achieves this object is to form a planar measurement electrode by metallization on the outer peripheral surface of a first pipe made of unfired ceramics, and then to form a planar measurement electrode on the outer peripheral surface of a first pipe made of unfired ceramics. It is characterized in that it is tightly fitted concentrically around the outer periphery of the first pipe, and then the whole is fired.

Embodiments of the present invention will be described below with reference to FIG. First, the first pipe 10, the second pipe 10a, and the third pipe 10b are formed from unfired ceramics. At this time, the pipe 10a is made to have a size that can be tightly fitted to the outer circumference of the pipe 10, and the pipe 1b is made to be of a size that can be tightly fitted to the outer circumference of the pipe 10a.
A measurement electrode 2 is formed on the outer circumferential surface of 0. The shape of the measurement electrode 2 may be not only rectangular but also circular or annular, as long as it has a sufficient area to detect a required capacitance signal. Further, a shield 7a is provided on the inclined surface of the pipe 10. Thereafter, the pipe 10a, on which the guard electrode 3 is formed on the outer circumferential surface by memetalization processing, is fitted concentrically to the outer circumference of the pipe 10. Furthermore, the pipe 10b having the shield 7b applied to the outer peripheral surface and the inclined surface is concentrically connected to the pipe 10.
Fit into the outer periphery of a. Note that holes are provided in the pipes 10a, 10b, the guard electrode 3, and the shield 7 in order to draw out the leads of the measurement electrode 2. Thereafter, the measuring tube 1 is manufactured by integrally firing the whole.

The embodiment shown in FIG. 4 has a three-layer structure with a guard electrode 3, but if the guard electrode 22 is not required, a two-layer structure can be manufactured using the same method as described above. can do.

As specifically explained above in conjunction with the embodiments, according to the present invention, the second pipe is fitted concentrically around the outer periphery of the first pipe on which the measurement electrode is formed, and is then fired. The difficult work of punching is no longer necessary, and the pipe itself is easy to manufacture, making it easier to manufacture the measuring tube.

[Brief explanation of the drawing]

1 and 2 relate to a capacitive electromagnetic flowmeter transmitter, in which FIG. 1 is a longitudinal cross-sectional view, FIG. 2 is a cross-sectional view, and FIG. 3 is a perspective view for explaining a conventional manufacturing method.
FIG. 4 is a half-broken sectional view for explaining the manufacturing method according to the embodiment of the present invention. In the drawing, 1 is a measuring tube, 2 is a measuring electrode, 10,1
0a and 10b are pipes.

Claims (1)

[Claims] 1. A planar measurement electrode is formed by metallization on the outer circumferential surface of a first pipe made of unfired ceramics, and then a second pipe made of unfired ceramics is concentrically placed around the outer circumference of the first pipe. A method for manufacturing a measuring tube, characterized by tightly fitting the tube and then firing the entire measuring tube.