JP3071997B2 - Vortex flow meter sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flowmeter sensor, and more particularly, to a vortex generator, one end of which is cantilevered and is removably mounted on the vortex generator. The present invention relates to a sensor structure of a Karman vortex flow meter that detects a vortex signal in response to a vortex signal.

[0002]

2. Description of the Related Art As is well known, a vortex flow meter utilizes the fact that the number of Karman vortices generated per unit time from a vortex generator disposed in a flow tube is constant within a predetermined Reynolds number range. It is a speculative flow meter. Thus, the vortex flowmeter has the vortex flowmeter sensor for detecting the Karman vortex generated from the vortex generator. There are two types of vortex flowmeter sensors: an integral type that is integrated into the vortex generator and a separate type that is installed at a different position from the vortex generator. Is advantageous.

The present applicant has previously proposed a vortex flowmeter sensor which can be attached to and detached from a vortex generator as described below and which can be applied to all vortex generators having different diameters, and has been put to practical use. .

FIG. 2 is a view for explaining a conventional vortex flowmeter sensor. The illustrated vortex flowmeter has both ends of a vortex generator 22 fixed in a flow tube 21 through which a fluid to be measured flows. The vortex generator 22 has an integrally formed vortex flowmeter main body.
A plurality of pressure introduction holes 25, 25 forming a pair are formed on both side surfaces of the vortex generator 31. The pressure introduction holes 25, 25 are formed in a concave measurement chamber 24 that is formed in the axial direction from one end of the vortex generator 31. Is communicated to. A mounting surface 23 is formed on the outer wall of the flow tube 21 above the measurement chamber 24, and the mounting flange 3 is provided on the mounting surface 23.
The vibrating tube 26 having one is cantilevered by a mounting flange 31.

The vibrating tube 30 has a bottomed cylindrical body 26, and a pressure receiving plate 26a is provided at the bottom of the cylindrical body 26. A plate-shaped elastic base material 27 having piezoelectric elements 28 attached to both surfaces is inserted on the inner axis of the cylindrical body 26, and is integrally fixed to the cylindrical body 26 with a highly insulating filler 29 such as glass. I have.

When the fluid to be measured flows in a direction perpendicular to the plane of the paper, Karman vortices are generated downstream of the vortex generator 21 on the back side of the paper, and pressure fluctuations occur on both sides of the vortex generator 22. This pressure fluctuation is introduced into the measurement chamber 24 from the pressure introduction holes 25, 25, and alternately displaces the pressure receiving plate 26a in the lateral direction on the paper. This alternating displacement is caused by the cantilevered vibration tube 3
A vortex signal that is transmitted to the piezoelectric element 28 that is fixed in the inside and is proportional to the flow rate corresponding to the vortex pressure fluctuation is output from the terminal 32.

As described above, in the conventional vortex flow meter, even if the vortex generator has a size determined according to the diameter, the same vibration tube 30 is used, and the measurement inside the vortex generator 22 is performed. Since a vortex flowmeter sensor having the same shape is inserted into the chamber 24 and used, the production is rationalized and an inexpensive vortex flowmeter can be provided.

[0008]

The above-mentioned conventional vortex flowmeter sensor integrated with a vortex generator is an LNG (liquefied natural gas).
Glass has been used as the filler 29 in order to be able to commonly measure the flow rates of various fluids from low-temperature fluids such as steam to high-temperature fluids such as steam. As a result, (1) there is a problem in the corrosion resistance of the vibrating tube because glass is filled in the vibrating tube at a high temperature, and the strength is deteriorated. (2) In glass sealing, it takes time to remove internal strain and to prevent air bubbles from being mixed in the glass, and it is difficult to make the glass. (3) Even if internal strain is removed, since the material of the vibrating tube and the body expansion coefficient of glass greatly differ, there is a risk that a crack or breakage may occur in the vibrating tube due to thermal fatigue due to a thermal cycle or the like. (4) Since the vortex flowmeter sensor is directly exposed to the fluid, especially when a high-temperature fluid flows, the moisture trapped in the glass gradually reaches the piezoelectric element, the insulation resistance decreases, and the usable high-temperature limit is reached. Was restricted. (5) It takes time to dry the vortex flowmeter sensor, but it is still difficult to sufficiently dehumidify. (6) Since the fluid to be measured is ejected through the pressure introducing hole 25 and the measuring chamber 24, the vortex flowmeter sensor cannot be replaced during operation. (7) As the lead wire, a parallel conductor covered with an insulating material was used, and was inserted through the metal pipe. However, noise increased due to a change in capacitance due to vibration.

[0009]

According to the present invention, in order to solve the above-mentioned problems, (1) a vortex generator has a concave measuring chamber which is formed in an axial direction from one end side of the vortex generator. In the vortex flowmeter sensor for detecting a vortex fluctuation differential pressure introduced into the measurement chamber from both side surfaces of the body, a vortex fluctuation having a bottomed tubular shape which is supported at one end of the vortex generator and is loosely inserted into the measurement chamber. A vibrating tube that is displaced in response to a differential pressure, and an elastic mother body that is displaced in response to the displacement of the vibrating tube, the column being a body supported in the vibrating tube by at least an opening and a bottom of the vibrating tube. A vibration detection element that is attached to the elastic base material and detects displacement of the elastic base material, and a lead wire that connects the vibration detection element and a terminal; The support structure of the elastic base material supported by the plate-shaped body slightly longer than the inner diameter of the vibrating tube, in the radial direction A spring plate having a notch of a few fixed concentrically to said elastic base material end face, that with a predetermined gap in the axial direction between the outer periphery and the elastic base material end face the outer periphery of the spring plate,
Further, (2) in (1), the thermal expansion coefficient of the vibrating tube and the elastic base material are made equal, and (3) in (1), the elastic base material is adhered to the elastic base material. The vibration detecting element is a plate-shaped piezoelectric element, and a lead wire between the piezoelectric element and the terminal is a stranded wire of a conductive wire having a coating of a heat-resistant insulating material.

[0010]

[Function] A vortex generating pressure acting on a vortex generator is introduced into a measurement chamber formed in the vortex generator, and the introduced fluctuating pressure is removably mounted on the vortex generator. The vibration displacement generated in the vibration tube is transmitted to the elastic base material to which the vibration detection element is attached in a non-contact manner with the vibration tube and detected by the vibration detection element. The elastic base material is supported by at least the opening and the bottom of the vibrating tube, and the support structure at the bottom is a spring plate having a radial notch concentrically fixed to the bottom of the elastic base material, and the vibration of the elastic base material In addition to facilitating the insertion and support to the tube, the sealing agent such as glass is eliminated, and the insulation of the vibration detecting element is prevented from being lowered.

[0011]

【Example】

[Embodiment 1] (corresponding to claim 1) FIG. 1 is a view for explaining an embodiment of a vortex flowmeter sensor according to the present invention, and FIG.
(B) is a sectional view taken along line BB of FIG. 1, and FIG.
1 is a vibrating tube, 2 is an elastic base material, 3a,
3b is a piezoelectric element, 4a and 4b are electrode plates, 5 is a spring plate,
6 and 7 are output terminals, 8 is a cap, 9 is a sheath pipe, 1
0 is a lead wire, 11 is a terminal block, 12 is a hermetic terminal, 13 is an external lead wire, and 14 is a terminal.

The vortex flow meter sensor shown in FIG.
The vortex sensor is mounted on a vortex flowmeter body including a cylindrical flow tube (not shown) and a vortex generator (not shown) having both ends fixed in the flow tube. The vortex generator is provided with a measurement chamber that is concave from the one end side in the axial direction, and the measurement chamber communicates with pressure introduction holes that open on both sides of the vortex generator.
A through hole coaxial with the measurement chamber is formed in the flow tube wall facing the measurement chamber, and has a sensor mounting surface perpendicular to the axis.

The vibrating tube 1 is a cylindrical body having an open end and a bottom portion 1c. A flange 1a provided on the outer periphery of one end is fixed to the sensor mounting surface in a cantilever manner with bolts or the like. The part is loosely inserted into the measurement room. A pressure receiving plate 1b is attached to an end of the vibration tube 1 loosely inserted into the measurement chamber, so that the vortex fluctuation pressure introduced into the measurement chamber from the pressure introduction hole of the vortex generator can be effectively received. I have.

The elastic base material 2 is a columnar body which is press-fitted into the vibrating tube 1 and faithfully transmits the displacement of the vibrating tube which is alternately displaced by receiving the eddy fluctuation pressure acting on the vibrating tube 1. The elastic base material 2 has an upper end press-fit portion 2a on the upper opening side of the vibrating tube 1, and an end 2d on the vibrating tube bottom 1c side is a small-diameter flat surface, for example, is cut in a tapered shape toward the lower end surface. Is flat. Since the outer diameter of the intermediate portion is slightly smaller than the inner diameter of the vibration tube 1, it is not in contact with the vibration tube.

A double chamfer 2b is formed in the upper press-fitting portion 2a, and on each surface, as shown in FIG.
Vibration detecting elements, for example, piezoelectric elements 3a and 3b are attached. The piezoelectric elements 3a and 3b are polarized in the thickness direction,
It has a piezoelectric constant d _33, the non-bonding surface electrode plate 4a made of perforated plate, 4b are attached. The piezoelectric elements 3a,
3b, the elastic base material 2 is used as one output end 7, and the electrode plate 4a
And 4b are connected to form a parallel type bimorph as another output terminal 6.

A spring plate 5 having a surface perpendicular to the axis is fixed to the end 2d of the elastic base material 2 by spot welding or the like. As shown in FIG. 1C, for example, the spring plate 5 has a disk shape whose outer diameter is slightly larger than the inner diameter of the vibrating tube 1, and is provided with a plurality of radial cutouts 5a. 5b. The support piece 5b has a spring action at the end 2d so that the outer end can be displaced in the axial direction of the elastic base material 2, and the vibrating tube 1
When it is press-fitted into the inside, it is bent in the inserting direction and is easily inserted, so that the vibration displacement of the vibration tube 1 can be faithfully transmitted to the elastic base material.

The upper opening side of the vibration tube 1 is covered with a cap 8. A sheath pipe 9 is fixed through the center of the cap 8, and a terminal block 11 having a hermetic terminal 12 is fixed through the other end of the sheath pipe 9. In the sheath pipe 9, two lead wires 10
Are inserted, and the output terminals 6, 7 and the hermetic terminals 12, 1
Connected between the two. Hermetic terminals 12, 12
External lead wires 13 having terminals 14 are connected. If a burning gas such as nitrogen gas is sealed in the terminal block 11 before the hermetic terminal 12 is fixed to the terminal block 11, the inside of the cap 8 is also replaced with the burning gas through the sheath pipe 9. Therefore, the insulation of the piezoelectric elements 3a and 3b is maintained even at high and low temperatures.

The vortex flowmeter sensor having the above-mentioned structure is fixed to the bottom without using a sealing agent such as glass in order to transmit the displacement of the vibration tube to the elastic base material to which the vibration detection element 12 is adhered. Since the force is transmitted through the spring plate having the cutout, the assembling is easy and the manufacturing time can be shortened.

[Embodiment 2] (corresponding to claim 2) If the thermal expansion coefficients of the vibrating tube 1 and the elastic base material 2 are different, thermal strain is generated in the vibrating tube 1 and the vibrating tube 1 is not used for a long time. There is a risk of cracking and breakage due to thermal fatigue. By making the thermal expansion coefficients of the vibrating tube 1 and the elastic base material 2 equal, the above danger is eliminated, and the operating temperature range is expanded.

[Embodiment 3] (corresponding to claim 3) When the vibration detecting element attached to the elastic base material 2 is a piezoelectric element, the piezoelectric elements 3a and 3b form a bimorph, and can detect displacement with high sensitivity. . However, since the piezoelectric elements 3a and 3b have a high impedance, when the lead wire 10 is vibrated, a large change in capacitance occurs between the lead wires 10, and non-negligible vibration noise is generated to lower the SN ratio.

Since the lead wire 10 is made of a heat-resistant and high-insulating ceramic felt-coated conductive wire and is made of a stranded wire, it maintains a stable position against vibrations, so that the capacitance change due to vibrations is reduced. With less vibration noise, the SN ratio can be improved.

[0022]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to the first aspect: Since the spring plate having the notch at the bottom end surface of the elastic base material is fixed with a gap at the end of the elastic base material, press-fitting into the vibration tube becomes easy. Moreover, since the vibration detecting element is attached to the elastic base material in a non-contact manner with the vibrating tube, the use range can be extended to a high temperature without lowering the insulation of the vortex flowmeter sensor. (2) Effect corresponding to claim 2: Since the thermal expansion coefficient of the vibrating tube and the elastic base material are made equal, there is no occurrence of thermal strain between the vibrating tube and the fatigue failure of the vibrating tube due to the difference in thermal expansion. Reliability is improved. (3) Effect corresponding to claim 3: By using a piezoelectric element as the detection element attached to the elastic base material, the alternating displacement can be detected with high sensitivity even at a high temperature, and the lead wire is made of a high heat-resistant and high-insulation conductive wire. , The generation of noise due to vibration is small, and the SN ratio is improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of a vortex flowmeter sensor according to the present invention.

FIG. 2 is a diagram for explaining a conventional vortex flowmeter sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vibration tube, 2 ... Elastic base material, 3a, 3b ... Piezoelectric element, 4
a, 4b: electrode plate, 5: spring plate, 6, 7 ... output terminal, 8 ...
Cap, 9 ... sheath pipe, 10 ... lead wire, 11 ...
Terminal block, 12 ... Hermetic terminal, 13 ...
External lead wires, 14 terminals.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/32

Claims (3)

(57) [Claims] 1. A vortex for detecting a vortex fluctuation differential pressure introduced into the measurement chamber from both side surfaces of the vortex generator, the measurement chamber having a concave shape formed in one axial direction from one end of the vortex generator. In the flowmeter sensor, a vibrating tube that is cantilevered at one end of the vortex generator and that is displaced in response to a vortex fluctuation differential pressure in a bottomed tubular shape loosely inserted into the measurement chamber; A columnar body supported by at least the opening and the bottom of the tube, an elastic base material which is displaced in response to the displacement of the vibrating tube, and which is adhered to the elastic base material and controls the displacement of the elastic base material. The vibration detecting element to be detected and the lead wire connecting the vibration detecting element and the terminal are integrally formed, and the support structure of the elastic base material supported at the bottom of the vibrating tube is defined by the inner diameter of the vibrating tube. It is a slightly long plate-shaped body,
A spring plate having a plurality of notches in a radial direction is fixed concentrically to the end surface of the elastic base material, and has a predetermined gap in the axial direction between the outer periphery of the spring plate and the outer periphery of the end surface of the elastic base material. Vortex flow meter sensor. 2. The vortex flowmeter sensor according to claim 1, wherein the vibrating tube and the elastic base material have the same thermal expansion coefficient. 3. The vibration detecting element attached to the elastic base material is a plate-shaped piezoelectric element, and a lead wire between the piezoelectric element and the terminal is formed of a stranded wire of a conductive wire having a coating of a heat-resistant insulating material. The vortex flowmeter sensor according to claim 1 or 2, wherein