JP3211916B2 - Karman vortex flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection rod which receives a force based on Karman vortex and a diaphragm which generates distortion, and a piezoelectric element for detecting distortion is electrically insulated on the surface of the diaphragm. In the fixed Karman vortex flow meter, the piezoelectric element is sandwiched and fixed, especially by an insulating material integrally formed on the diaphragm surface and another insulating plate, to maintain and improve the output sensitivity of the piezoelectric element and, consequently, the measurement sensitivity. It relates to the Kalman vortex flowmeter.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIGS. 4 is a side sectional view of a conventional example, and FIG. 5 is a transverse sectional view of a hole of a vortex generator with respect to a section AA in FIG. In FIG. 4, reference numeral 1 denotes a conduit through which a measurement fluid flows. Numeral 2 denotes a vortex generator, which is inserted into the pipe 1 so as to penetrate along the diameter thereof, and the penetrating portion has an upstream columnar body 11 having a triangular cross section.
Cylindrical projections 25 and 26 for promoting the generation of Karman vortices are integrally formed at upper and lower fitting portions of the downstream columnar body 12 having a trapezoidal cross section and the pipeline 1. Line 1
O-rings without reference numerals are inserted into the upper and lower fitting portions of the above, which are used for both fluid sealing and vibration isolation.
Reference numeral 3 denotes a vortex detector, which comprises a disk-shaped diaphragm 3a, a mandrel 3b extending inward in the axial direction, and a threaded rod extending outward. The mandrel 3b has two stages. The small diameter portion on the tip side is located inside the hole 28 drilled in the columnar body 12, and the cushioning material 4 is inserted at the root of the small diameter portion for preventing resonance. You. An insulating plate 6, a piezoelectric element 8, an insulating plate 9 and a disc spring are fitted on the upper surface of the diaphragm 3a in such a manner as to fit into a threaded rod.
9 are stacked and fixed by screwing in the balance weight 10. Here, the piezoelectric element 8 detects a minute displacement of the lower bar portion of the vortex detector 3 as a displacement of the diaphragm 3a, converts the displacement into an electric signal, and outputs the electric signal. Balance weight 10
Has a function of canceling the influence of vibration factors other than the Karman vortex that the vortex detector 3 receives, for example, the vibration of the pipeline 1 and the like, in addition to the function of the nut for fixing the screw.

In FIG. 4, when a fluid flows rightward in a pipe 1, Karman vortices are generated near the column 12 by the upstream column 11 and the downstream column 12, and the generated Karman vortex is generated. The pressure change of the fluid caused by the vortex is transmitted to the mandrel 3b at the tip of the vortex detector 3. In FIG. 5, the pressure change is transmitted through a pressure guiding hole 13 penetrating through the columnar body 12 at a position corresponding to the mandrel 3b at right angles to the flow and in parallel with the sheet of FIG. Is done via Now, the minute displacement of the rod portion including the mandrel 3b of the vortex detector 3 is converted into the displacement of the diaphragm 3a,
8 to convert and output the corresponding electrical signal.

By the way, the piezoelectric element 8 and the insulating plates 6 and 7
Will be described in more detail. 2 (a) is a plan view of the conventional piezoelectric element, and FIG. 2 (b) is a rear view thereof. In FIG. 2A, an arc-shaped electrode 8a is symmetrically arranged on the lower side and an arc-shaped electrode 8b is arranged on the upper side with respect to a horizontal axis passing through the center of the piezoelectric element 8. The tongue-shaped electrode 8c shown at the right end is
This is a folded portion of the annular electrode 8c in FIG. 2 (b). The arc of each electrode 8a, 8b corresponds to the ring of electrode 8c.
In Fig. 4, the force perpendicular to the paper based on the Karman vortex is
A bending moment about a horizontal axis included in the drawing is applied to the diaphragm 3a. Due to the bending moment, bending distortion occurs in the diaphragm 3a, and a voltage signal is output from the piezoelectric element 8 in response thereto. That is, each electrode 8 in FIG.
Distortions having the same magnitude and different signs occur in a and 8b, and voltages having the same magnitude and different signs are generated between the electrodes 8a and 8c and between the electrodes 8b and 8c. Based on these voltages, a calculation circuit (not shown) calculates the flow velocity and flow rate. Note that FIG. 2 and FIG. 3 described below are common to the embodiment according to the present invention.

FIGS. 3A and 3B relate to a conventional insulating plate for a piezoelectric element. FIG. 3A is a plan view of one of them, and FIG. 3B is a plan view of the other. One insulating plate 6 is located on the back side of the piezoelectric element 8 (Fig. 2).
2 (b)), and the other insulating plate 7 contacts the upper surface side of the piezoelectric element 8 (see FIG. 2 (a)). The insulating plate 6 has no electrodes, but the insulating plate 7 has electrodes 7a, 7b, 7c.
Electrodes 7a, 7b, 7c of insulating plate 7 and electrodes 8a, 8b, 8c of piezoelectric element 8
(The tongue) overlap each other and contact each other
Voltage signals from the piezoelectric element 8 are extracted from the ends of the linear portions 7a, 7b, 7c. Note that the electrode 7c is for grounding.

[0006]

In the prior art, when a bending strain is generated in the diaphragm 3a by receiving a force based on the Karman vortex, the distortion is not transmitted to the piezoelectric element 8 exactly as it is. The cause is that between the diaphragm 3a and the insulating plate 6,
Also, a slight slippage occurs between the insulating plate 6 and the piezoelectric element 8. Due to this slip, the distortion generated in the piezoelectric element 8 is smaller than the distortion actually generated in the diaphragm 3a. In other words, the output sensitivity of the piezoelectric element 8 decreases.

An object of the present invention is to provide a Kalman vortex flowmeter which solves the above problems of the prior art and maintains and improves the output sensitivity of the piezoelectric element and hence the measurement sensitivity.

[0008]

According to a first aspect of the present invention, there is provided a Karman vortex flowmeter comprising: a detection rod receiving a force based on a Karman vortex;
In a flowmeter in which a diaphragm that generates distortion is integrally formed and a piezoelectric element for detecting strain is electrically insulated on the surface of the diaphragm, the piezoelectric element is an insulating material integrally formed on the surface of the diaphragm. And another insulating plate to be sandwiched and fixed from both sides.

According to a second aspect of the present invention, in the flow meter according to the first aspect, the integral molding of the insulating material with the diaphragm is performed by injection molding using a metal material for the detection rod and the diaphragm. A Karman vortex flowmeter according to a third aspect is the flowmeter according to the first or second aspect, wherein the insulating material is ceramics.

[0010]

In the Karman vortex flowmeter according to any one of claims 1 to 3, when the diaphragm is distorted by a force based on the Karman vortex, the distortion is integrally formed on the surface of the diaphragm. Almost accurately transmitted to the piezoelectric element via the insulating material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a Karman vortex flowmeter according to the present invention will be described below with reference to the drawings. This embodiment differs from the conventional example in the insulating structure between the piezoelectric element and the diaphragm. FIG. 1 is a side sectional view of a main part of the embodiment.
The same reference numerals are given to the same or corresponding members in the conventional example. In FIG. 1, the diaphragm
An insulating material 3c, which is a ceramic disk, is formed integrally with a portion of the upper surface of the central portion of the portion 3a where the piezoelectric element 8 is placed and in contact with the piezoelectric element 8 so that the surface is exposed and partially buried. And insulation
3c is accurately and reliably integrated with the vortex detector 3 made of stainless steel by injection molding. Since the upper insulating plate 7 of the piezoelectric element 8 is the same member as in the conventional example, the method of extracting the output signal is performed in the same manner as in the conventional example. Also, in FIG. 1, the intermediate plate 9 a is interposed for stabilization between the two disc springs 9, although it is not directly related to the subject, unlike the conventional example in FIG. 4. I add that.

Therefore, when the mandrel 3b of the vortex detector 3 receives a force based on the Karman vortex and a bending strain is generated in the diaphragm 3a, the bending strain is different from that in the conventional example, and is generated on the surface of the diaphragm 3a. Almost accurately transmitted to the piezoelectric element 8 via the integrally formed insulating material 3c. As a result, the bending strain generated in the piezoelectric element 8 becomes almost exactly equal to the bending strain actually generated in the diaphragm 3a. In other words, the output sensitivity of the piezoelectric element 8, and thus the measurement sensitivity, is maintained and improved as compared with the conventional example.

[0013]

According to the Karman vortex flowmeter according to any one of claims 1 to 3, when the diaphragm is distorted by a force based on the Karman vortex, the distortion is integrally formed on the surface of the diaphragm. Almost accurately transmitted to the piezoelectric element via the insulating material. As a result, the distortion generated in the piezoelectric element becomes almost exactly equal to the distortion actually generated in the diaphragm. In other words, the output sensitivity of the piezoelectric element and, consequently, the measurement sensitivity are maintained and improved as compared with the conventional example.

In particular, in the Kalman flowmeter according to the second aspect, since the integral molding of the insulating material with the diaphragm is performed by injection molding using a metal material for the detecting rod and the diaphragm, the production is easy, and the insulating material and the diaphragm can be easily combined. The integration is performed reliably and with high positional accuracy, and the maintenance and improvement of the output sensitivity of the piezoelectric element and, consequently, the measurement sensitivity are supported. In particular, in the Kalman flowmeter according to claim 3, since the insulating material is ceramics, the heat resistance is excellent, and the insulating property is maintained for a long time, the injection molding is facilitated, and the improvement of the reliability with respect to the measurement sensitivity is supported. .

[Brief description of the drawings]

FIG. 1 is a side sectional view of a main part of an embodiment according to the present invention.

2 (a) is a plan view and FIG. 2 (b) is a rear view of a piezoelectric element according to an embodiment and a conventional example.

FIG. 3 shows an insulating plate of a piezoelectric element according to an embodiment and a conventional example.
(a) is a plan view of one of them, (b) is a plan view of the other

FIG. 4 is a side sectional view of a conventional example.

FIG. 5 is a cross-sectional view of a hole of a vortex generator in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipeline 2 Vortex generator 3 Vortex detector 3a Diaphragm 3b Detection rod 3c Insulating material 7 Insulating plate 7a, 7b, 7c Electrode 8 Piezoelectric element 8a, 8b, 8c Electrode 9 Disc spring 9a Intermediate plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-174509 (JP, A) JP-A-3-251722 (JP, A) JP-A-1-123112 (JP, A) JP-A-59-1984 63537 (JP, A) Japanese Utility Model 4-85123 (JP, U) Japanese Utility Model 3-106424 (JP, U) Japanese Utility Model 2-118224 (JP, U) Japanese Utility Model 2-109216 (JP, U) Japanese Utility Model Application No. Sho 64-33614 (JP, U) Japanese Utility Model Application No. Sho 60-65636 (JP, U) Japanese Utility Model Application No. Sho 56-7023 (JP, U) Patent 2929731 (JP, B2) Patent 2976592 (JP, B2) Patent 3114401 (Japanese) JP, B2) Patent 3038497 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01F 1/32

Claims (3)

(57) [Claims] A detection rod receiving a force based on Karman vortex;
In a flow meter in which a diaphragm that generates distortion is integrally formed, and a piezoelectric element for strain detection is electrically insulated on the surface of the diaphragm, the piezoelectric element is an insulating material integrally formed on the surface of the diaphragm. A Karman vortex flowmeter, which is sandwiched and fixed from both sides by an insulating plate. 2. The Karman vortex flow meter according to claim 1, wherein the integral molding of the insulating material with the diaphragm is performed by injection molding using a metal material for the detection rod and the diaphragm. 3. The Karman vortex flow meter according to claim 1, wherein the insulating material is a ceramic.