JPH037782Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vortex flow meter that utilizes Karman vortices.

More specifically, the alternating force acting on an object due to the Karman vortex is detected and extracted as a vortex signal.
The present invention relates to a vortex flow meter that measures flow velocity or flow rate.

[Prior art]

FIG. 1 shows a conventional example of a vortex flowmeter that has been commonly used for a pipe diameter of 2''.

In the figure, 1 is a cylindrical pipe, 11 is a pipe 1
It is a cylindrical nozzle installed at right angles to the Reference numeral 2 denotes a columnar force receiving body inserted through the nozzle 11 into the pipe line 1 at right angles, one end of which is supported by the pipe line 1 with a screw 3, and the other end fixed to the nozzle 11 by screws or welding at the flange part 21. has been done. 22
is a recess provided on the flange portion 21 side of the force receiving body 2. 4a, 4b (hereinafter collectively referred to as "4")
shall be. ) is a disk-shaped first provided in the recess 22;
The center axis of the second piezoelectric sensor coincides with the center axis of the force receiving body 2 . As shown in FIG. 2, the piezoelectric sensor 4 includes a donut plate-shaped element body 41, an electrode 42,
Consists of 43, 44, and 45. The electrodes 42 to 45 are
In this case, it is formed by paste printing.
The electrodes 42 to 45 have substantially arcuate shapes on both sides of the element body 41, and are provided symmetrically in a direction perpendicular to the direction of the conduit 1 with the center of the element body 41 in between. Electrode 4
2 to 45 have closed curved surfaces smaller than the surface of the element body 41, as shown in FIG. The element body 41 is
In this case, a piezoelectric element made of PZT is used. As shown in FIG. 3, the element main body 41 is polarized in advance so that the polarization directions are opposite to each other between the electrodes 42-44 and the electrodes 43-45. Therefore, as shown in FIG.
Electrical signal (charge in this case) generated between 3 and 45
becomes in phase. The first piezoelectric sensor 4a and the second piezoelectric sensor 4b are polarized in opposite directions. Returning to FIG. 1, 5a, 5b, and 5c (hereinafter collectively referred to as "5") are disk-shaped insulators placed on both sides of the piezoelectric sensor 4. In this case,
Ceramic is used. 6 is piezoelectric sensor 4
and a fixing body that presses and fixes the insulator 5 into the recess 22, and in this case, stainless steel material is used. One end side of the fixed body 6 is fixed to the force receiving body 2, and in this case, is welded 61.

FIG. 4 is a block diagram of the electrical circuit 7 of FIG. 1 (not shown in FIG. 1).

In the figure, 71 is a first input processing circuit that amplifies the output of the piezoelectric sensor 4a. A second input processing circuit 72 amplifies the output of the piezoelectric sensor 4b, and is configured to have a variable gain. 7
3 is an addition calculator that calculates the outputs of the first and second input processing circuits 71 and 72.

In the above configuration, when the measuring fluid flows in the pipe 1, an alternating force F as shown by the arrow in FIG. do. This alternating force F is transmitted to the piezoelectric sensor 4 via the fixed body 6. In this case, as shown in FIG. 1, stress changes occur in the force-receiving body 2 in opposite directions across the central axis of the force-receiving body 2.
An electric signal (in this case, a change in charge) corresponding to this stress change is generated between the electrodes 42 and 44 and between the electrodes 43 and 45 of the piezoelectric sensor 4. By detecting the number of times this change occurs, the vortex generation frequency can be detected. Therefore, the electrodes 42-44 and the electrodes 43-
Since the terminals 45 and 45 are polarized in opposite directions, they can be connected in parallel to obtain twice the electrical output.

However, in such conventional examples,
Since the piezoelectric sensor 4 is pressed and fixed to the force receiving body 2 together with the insulator 5 by the fixing body 6, strict mechanical dimensional accuracy is required such as the flatness of the piezoelectric sensor 4 and the insulator 5, which must be met. Otherwise, in extreme cases,
There is a possibility that cracks or the like may occur in the element body 41 of the piezoelectric sensor 4.

In this case, if the electrodes 42 to 45 cover the entire surface of the element body 41, the element body 41 will be held by these electrodes and there is no risk of the element body 41 falling apart. but,
The electrodes 42 to 45 are connected to the element body 4 for the following reasons.
It is not possible to cover the entire surface of 1.

That is, the element body 4 is made of ferroelectric ceramic.
In No. 1, in order to impart piezoelectricity, a polarization treatment must be applied in advance, that is, a strong electric field must be applied in a certain direction to align the polarization directions. To achieve such polarization, it is necessary to apply a high voltage, and if the element body 41 is thin,
If the electrodes 42 to 45 are too close to each other, electric discharge occurs and polarization cannot occur. Therefore, as shown in FIG. 2, the electrodes 42 to 45 cannot be provided at the edge portion of the element body 41, considering manufacturing errors such as sag when forming the electrodes 42 to 45. Furthermore, in order to perform reverse polarization, the polarization electrode must be divided into two parts on both the front and back surfaces.

Further, the film thickness of the electrodes 42 to 45 cannot be made thicker in order to ensure strength for the following reason. Therefore, if a crack or the like occurs in the element body 41, it cannot be held securely in terms of strength.

Since the piezoelectric sensor 4 is pressed and fixed to the force receiving body 2, in order to obtain good characteristics, the surface pressure on the piezoelectric element body 41 must be made uniform and the piezoelectric element body 41
It is necessary to make the stress distribution due to pressure as equal as possible. For this reason, the film thicknesses of the electrodes 42 to 45 need to be made thin. Therefore, the polarization electrode alone cannot prevent the element body 41 from being separated when it is dropped.

The present invention solves these problems.

[Purpose of invention]

An object of the present invention is to provide a vortex flowmeter that can maintain good characteristics even if cracks occur in the piezoelectric sensor and can be manufactured at low cost.

[Structure of the idea]

In order to achieve this object, the present invention is a vortex flowmeter that measures the flow velocity or flow rate of fluid by detecting the alternating force acting on a force receiving body due to Karman vortices, in which a piezoelectric voltage is installed in the recess of the force receiving body. In a vortex flowmeter in which a sensor is fixed by a fixed body under pressure, the piezoelectric sensor includes a plate-shaped ceramic piezoelectric element body disposed in a recess of the force receiving body;
first and second polarization electrodes each having an arcuate shape and having a closed curved surface smaller than the outer edge of the plane of the piezoelectric element body, which are provided symmetrically and separately on the upper plane of the piezoelectric element body in a direction perpendicular to the conduit direction; a third polarization electrode arranged on the lower plane of the piezoelectric element body opposite to the first polarization electrode; and a second polarization electrode arranged on the lower plane of the piezoelectric element body. a fourth arc-shaped polarization electrode disposed opposite to the polarization electrode; a first coupling electrode that covers the first and second polarization electrodes and the upper plane of the piezoelectric element body; , comprising a fourth polarization electrode and a second coupling electrode covering a lower plane of the piezoelectric element body, the first and third polarization electrodes and the second and fourth polarization electrodes. This constitutes a vortex flow meter characterized in that the piezoelectric element body is polarized in advance in opposite directions in the axial direction of the force receiving body.

〔Example〕

FIG. 5 is an explanatory view of the main part of an embodiment of the present invention, in which A is a front view and B is a plan view.

In the figure, the same symbols as in FIG. 1 indicate the same functions.

Hereinafter, only the differences from FIG. 1 will be explained.

46 is the upper surface 411 of the element body 41 and the electrode 42;
43 and covers the entire upper surface 411. 47 is the lower surface 412 of the element body 41 and the electrode 4
4 and 45, and covers the entire lower surface 412. Coupling electrodes 46 and 47 are electrodes 42 and 44,
It is formed after each of the electrodes 43 and 45 is polarized, and in this case, a Nilkel plating film is used.

The electrodes 42 and 43 and the coupling electrode 46 constitute the upper electrode of the piezoelectric sensor 4.
4, 45 and the coupling electrode 47 constitute the lower electrode of the piezoelectric sensor 4.

In the above configuration, even if a crack occurs in the element body 41 as described in the conventional example, since the coupling electrodes 46 and 47 are formed over the entire surface of both sides of the element body 41, the element body 41 but,
There is no risk of it falling apart.

Further, the electrodes 42 to 45 are also connected to the coupling electrode 4.
6 and 47, there is no fear that the electrodes 42 to 45 will be unable to prevent separation of the element body 41.

Therefore, even if cracks or the like occur in the piezoelectric element main body 41, a vortex flowmeter that can maintain good characteristics can be obtained. In addition, the dimensional accuracy of the piezoelectric sensor 4 can be relaxed, and it can be manufactured at low cost.

In addition, in the above-mentioned embodiment, the piezoelectric sensor 4
Although the explanation has been given on the case where two are provided, it goes without saying that only one may be provided.

[Function and effect of the idea]

As explained above, the present invention is a vortex flowmeter that measures the flow velocity or flow rate of a fluid by detecting the alternating force acting on a force receiving body due to Karman vortices, and in which a piezoelectric sensor is installed in a recess of the force receiving body. In the vortex flowmeter that is press-fixed by a fixed body, the piezoelectric sensor includes a plate-shaped ceramic piezoelectric element body disposed in a recess of the force receiving body;
first and second polarization electrodes each having an arcuate shape and having a closed curved surface smaller than the outer edge of the plane of the piezoelectric element body, which are provided symmetrically and separately on the upper plane of the piezoelectric element body in a direction perpendicular to the conduit direction; a third polarization electrode arranged on the lower plane of the piezoelectric element body opposite to the first polarization electrode; and a second polarization electrode arranged on the lower plane of the piezoelectric element body. a fourth arc-shaped polarization electrode disposed opposite to the polarization electrode; a first coupling electrode that covers the first and second polarization electrodes and the upper plane of the piezoelectric element body; , comprising a fourth polarization electrode and a second coupling electrode covering a lower plane of the piezoelectric element body, the first and third polarization electrodes and the second and fourth polarization electrodes. This constitutes a vortex flow meter characterized in that the piezoelectric element bodies are polarized in advance in opposite directions in the axial direction of the force receiving body.

As a result, the two coupling electrodes each cover the entire surface of one side of the piezoelectric element body, which prevents the element body from being separated due to cracks, etc., as well as reinforcing the polarization electrodes. Therefore, it is possible to realize a vortex flowmeter that can maintain good characteristics over a long period of time.

Further, since the dimensional accuracy, flatness, etc. of the piezoelectric sensor etc. can be moderated, it can be manufactured at low cost.

As explained above, according to the present invention, it is possible to realize a vortex flowmeter that can maintain good characteristics over a long period of time and can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a conventional example of a vortex flow meter that has been commonly used in the past, Fig. 2 is an explanatory diagram of the configuration of the piezoelectric sensor in Fig. 1, Fig. 3 is an explanatory diagram of the operation of Fig. 1, and Fig. 4 is an explanatory diagram of the piezoelectric sensor shown in Fig. 1. FIG. 1 is an electrical connection diagram, and FIG. 5 is an explanatory diagram of the main part configuration of an embodiment of the present invention, where A is a front view and B is a plan view. 1... Conduit, 11... Nozzle, 2... Force receiving body,
21... Flange portion, 22... Recessed portion, 3... Screw, 4a, 4b... Piezoelectric sensor, 41a, 41b
...Element body, 411...Top surface, 412...Bottom surface, 42a to 45a, 43b to 45b...Electrode,
46, 47...coupling electrode, 5a, 5b, 5c...
Insulator, 6... Fixed body, 7... Electric circuit, 71...
...first input processing circuit, 72...second input processing circuit, 73...adder.

Claims (1)

[Claims for Utility Model Registration] A vortex flowmeter that measures the flow velocity or flow rate of a fluid by detecting the alternating force acting on a force receiving body due to a Karman vortex, wherein a piezoelectric sensor is fixed in a recess of the force receiving body. In the vortex flowmeter, the piezoelectric sensor includes a plate-shaped ceramic piezoelectric element body disposed in the recess of the force receiving body, and an upper plane of the piezoelectric element body perpendicular to the pipe direction. first and second polarization electrodes each having an arcuate shape and having a closed curved surface smaller than the outer edge of the plane of the piezoelectric element body, which are provided symmetrically in each direction; a third arcuate polarization electrode arranged opposite to the first polarization electrode; and an arcuate third polarization electrode arranged opposite to the second polarization electrode on the lower plane of the piezoelectric element main body. a first coupling electrode that covers the upper plane of the first and second polarization electrodes and the piezoelectric element body; a first coupling electrode that covers the third and fourth polarization electrodes and the piezoelectric element body; a second coupling electrode that covers the lower plane, and the piezoelectric element body is caused to move in the axial direction of the force receiving body by the first and third polarization electrodes and the second and fourth polarization electrodes. A vortex flow meter characterized by being pre-polarized in opposite directions.