JP2003329497A - Vortex flowmeter sensor and vortex flowmeter having this sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vortex sensor using a metallic vibrating pipe for improving the S/N ratio. <P>SOLUTION: The metallic vibrating pipe 13 has an installing flange part 11 to a vortex generator, and a pressure receiving part 13a, and has a pressure detecting element plate, a conductive base material 14 having a plate facing to the pressure receiving side in axial symmetry to the vibrating pipe 13, and a piezoelectric element 15 respectively arranged on both side surfaces of the plate of the base material 14. This pressure detecting element plate is housed by contacting a lower end contact part 14a of the base material 14 with a wall surface separating a little from a bottom part of a recessed part by fixing an upper end joining part 14b of the base material 14 to an upper end part of the recessed part formed on the vibrating pipe 13. An upper part of the recessed part is sealed by a mold material. The sensor has a structure for connecting the outside of the upper end joining part 14b of the base material 14 and an inner wall of the metallic vibrating pipe 13 only by metal contact without molding the periphery of the piezoelectric element 15 inside of the vortex sensor 10 by resin. The pressure detecting element plate is formed so that the piezoelectric element 15 is drawn up to an upper fixing part of the vibrating pipe 13. <P>COPYRIGHT: (C)2004,JPO

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 a vortex flowmeter, and more particularly to a fluctuation of a Karman vortex which is cantilevered and inserted into a vortex generator and is introduced into the vortex generator. The present invention relates to a vortex flowmeter sensor that responds to pressure and a vortex flowmeter equipped with the sensor.

[0002]

2. Description of the Related Art As is well known, in a vortex flowmeter, when a vortex generator is arranged in a fluid flow, the number of Karman vortices generated from the vortex generator within a unit time is a certain Reynolds number. It is a speculative flow meter that utilizes the fact that it is proportional to the flow rate in the range. The vortices that are generated are detected by vortex flowmeter sensors (often referred to simply as vortex sensors) as flow or pressure changes that occur around the vortex generator. These vortex sensors are fixed in the vortex generator or are detachably arranged. The flow meter is a measuring instrument that measures the flow rate of various fluids according to the purpose, but the vortex flow meter is characterized by the Reynolds number alone without being affected by the density and viscosity of the gas liquid. It has characteristics. However, since the fluctuating pressure due to the generation of Karman vortices is an amount proportional to the density of the measured fluid and the square of the flow velocity, it is necessary to increase the sensitivity in a small flow region in order to expand the measurement range. In this respect, a vortex sensor of the type that is detachably arranged in the vortex generator is advantageous.

As a detachable vortex sensor, there is a vortex flowmeter proposed by the present applicant in Japanese Patent Publication No. 63-31726, in which the same sensor can be detached regardless of the size of the vortex generator. 5 (A) and 5 (B) are views for explaining the conventional vortex flowmeter, FIG. 5 (A) is a cross-sectional view seen from the flow direction, and FIG. 5 (B) is FIG. 5 (A). It is an arrow BB sectional view. In the figure, 1 is a flow tube (tube), 2 is a vortex generator, 3 is a mounting surface, 4 is a pressure chamber, 5 is a pressure guide hole, and 30 is a vortex sensor.

The tube body 1 is provided with a vortex generator 2 on the diameter, which is interposed in a pipe through which the fluid to be measured flows. The vortex generator 2 is provided with a recess penetrating the tube body 1, and the recess serves as a pressure chamber 4, and pressure guiding holes 5 penetrate both side wall surfaces of the pressure chamber 4 to communicate with the fluid to be measured. There is. On the other hand, the vortex sensor 30 is inserted in the pressure chamber 4. Vortex sensor 30
Is a bottomed cylindrical vibrating tube 33 having a flange portion (flange) 31, and a pressure receiving plate 33a integrally formed at the bottom of the vibrating tube 33, and a base material 34 coaxially inserted into the vibrating tube 33. When,
The piezoelectric element 35 is fixed to both side surfaces of the base material 34 with a conductive adhesive, and the filler 36 and the lead wire 32 that integrally fix the base material 34 in the vibrating tube 33. In the shielded cable 32 as a lead wire, one pole of the piezoelectric element 35 is connected to its core wire 32b, and the other pole of the piezoelectric element 35 is connected to its shield wire 32a via a tinned wire soldered. .

The vortex sensor 30 is cantilevered to the tube body 1 at the mounting surface 3 formed on the tube body 1 at the flange portion 31 of the vibration tube 33. The fluctuating pressure due to the vortex is introduced into the pressure chamber 4 through the pressure guiding hole 5 and acts on the pressure receiving plate 33a. The pressure receiving plate 33a, which receives the fluctuating pressure, fluctuates around the cantilevered and fixed position, but this fluctuation is transmitted to the piezoelectric element 35 via the filler 36 filled in the concave portion 36a of the vibrating tube 33, and vibrates. Is output from the lead wire 32. Here, the filler 36 is required to have an insulating property rather than a force transmission medium. Insulation resistance generally changes with temperature and decreases at high temperatures.
An insulating material such as epoxy resin is used.

FIG. 6 is a view for explaining another vortex flowmeter sensor according to the prior art. In the figure, 40 denotes the vortex flowmeter sensor. The vortex sensor 40 includes a bottomed cylindrical vibrating tube 43 having a flange 41, and a base material 44 in which a pressure receiving plate 43a is integrally formed at the bottom of the vibrating tube 43 and is coaxially inserted into the vibrating tube 43. The piezoelectric element 45 is fixed to both side surfaces of the base material 44, and the filler 46 and the lead wire 42 (the shield wire 42a and the core wire 42b) that integrally fix the base material 44 in the vibrating tube 43. The operation of the vortex sensor 40 is as described with reference to FIG. In addition,
In the figure, 46b is a groove for positioning the base material 44, and 48 is a hole in the flange 41 for joining with the pipe body with a screw or the like. In this conventional example, the filler 46
Shows an example of using an epoxy adhesive as
Further, the electrode wire 42a is assumed to be solder-pasted on the piezoelectric element 45 at the position indicated by 45a.

Further, in contrast to the piezoelectric element which detects the stress of the alternating differential pressure due to the generation of the above-mentioned Karman vortex as a change in electric charge, a vortex which detects the vortex by a strain gauge (strain gauge) which detects the alternating differential pressure as a change in resistance. There are also sensors.
In the strain gauge type vortex sensor, the base material and the pair of strain gauges that are integrally fixed are built into the vortex generator whose only one end is supported. Strain stress is applied to the internal strain gauge by the lift force. The strain gauge constitutes two sides of the bridge circuit and detects the resistance change of the strain gauge as a voltage change. Even when the pressure is detected using the strain gauge, the basic configuration of the vibrating tube is the same, and the description thereof will be omitted.

As described above, the material of the vibrating tube in the conventional sensor for detecting the Karman vortex by the piezoelectric element or the strain gauge is resin or metal. A resin sensor is relatively simple and inexpensive to manufacture, and is useful when measuring highly corrosive fluids that cannot use metals, but it is an electromagnetic wave shield to eliminate commercial noise. The material has to be installed, which increases the number of manufacturing processes. Since the sensor is made of resin, when the durability and reliability of the sensor itself are required, the sensor made of metal is used, and it is avoided from the viewpoint of safety.

However, the metallic sensor is
Although it is reliable, the vibrating tube is shaved and becomes an expensive sensor. Further, the sensor output of the metal sensor is significantly lower than that of the resin sensor, and the S / N ratio is poor.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and does not require the application of the electromagnetic wave shield material, which is required when a resin vibrating tube is used, and is high in temperature. To provide a vortex flowmeter sensor that can improve the S / N ratio in a vortex flowmeter sensor that uses a metal vibrating tube that can withstand high pressure, and a vortex flowmeter that includes the sensor. Is its purpose.

The present invention is a vortex flowmeter sensor using a metal vibrating tube which is highly reliable and can be manufactured at a low cost without manufacturing the metal vibrating tube by an expensive shaving process, and a vortex sensor equipped with the sensor. Another purpose is to provide a flow meter.

[0012]

A first technical means is provided in a flow tube through which a fluid to be measured flows so as to face the flow, has a pressure chamber therein, and communicates with the fluid to be measured. A vortex flowmeter sensor for detecting a fluctuating pressure based on a Karman vortex introduced into the pressure chamber in the vortex generator, the vortex flowmeter sensor being disposed in the vortex generator having a pressure guiding hole for introducing fluid pressure into the chamber, A vibrating tube made of metal having a flange part for attaching to the vortex generator and a pressure receiving part, a conductive base material having a flat plate axially symmetrical to the vibrating tube and facing the pressure receiving side, and both side surfaces of the flat plate of the base material. A pressure detecting element plate having a piezoelectric element or a strain gauge respectively provided on the pressure detecting element plate, and fixing the upper end joint portion of the base material to the upper end portion of the recess formed in the vibrating tube. The base material of the base material on the wall surface slightly separated from the bottom of the recess. Housed by contacting the end contact portion, sealing the the recessed portion upper in the molding material of the insulating resin, and,
The piezoelectric element or the strain gauge is extended to the upper end joint portion of the vibrating tube.

A second technical means is the same as the first technical means, in which a lower end contact portion of the base material is provided outside a locking groove provided on a wall surface slightly separated from a bottom portion of the concave portion of the vibrating tube. It is characterized by having a disc-shaped spring portion having radial slits whose diameter is slightly larger than the inner diameter of the locking groove.

A third technical means is the same as the first or second technical means, wherein the vibrating tube is a metal powder injection molding material.

A fourth technical means is characterized in that the vortex flowmeter sensor described in any one of the first to third technical means is provided.

[0016]

1 is a diagram showing an example of the structure of a vortex flowmeter sensor according to an embodiment of the present invention. FIG. 1 (A) is a cross-sectional view seen from the flow direction, and FIG. 1 (B) is FIG. 2 is a sectional view taken along line BB of FIG. In FIG. 1, 1 is a flow tube (tubular body), 2 is a vortex generator, 3 is a mounting surface, 4 is a pressure chamber, 5 is a pressure guide hole, and 10
Indicates a vortex flowmeter sensor (hereinafter referred to as a vortex sensor), respectively. 2 is a diagram for explaining the details of the vortex flowmeter sensor of FIG. 1, FIG. 2 (A) is a vertical sectional view thereof, and FIG. 2 (B) is a horizontal sectional view thereof. 2C is a view showing another vertical cross-sectional view. In addition, in FIG.
Reference numeral 12 is a shield cable as a lead wire, 12a is a shield wire, 12b is a core wire, 13a is a pressure receiving portion, 15a is a paste position, and 18 is a hole. Further, in FIG. 2, 17 indicates a ground wire. 3 is a diagram showing an example of the pressure detection element plate of FIG. 2, FIG. 3 (A) is a plan view thereof, and FIG. 3 (B).
FIG. 4 is a diagram showing an example of a lower end contact portion of the base material of FIG. 3 (A).

The vortex sensor 10 according to the present embodiment is a sensor for detecting a fluctuating pressure based on a Karman vortex introduced into the pressure chamber 4 of the vortex generator 2 incorporated in the vortex generator 2, and is a pressure detecting element. The vibrating tube 13 having a plate accommodated therein is a main component. The vortex generator 2 is provided in the flow tube through which the fluid to be measured flows so as to face the flow, and is for generating a Karman vortex. Further, the vortex generator 2 has a pressure chamber 4 inside, and further communicates with the fluid to be measured.
It has a pressure guiding hole 5 on its side surface for introducing a fluid pressure into. The vortex flowmeter provided with the vortex generator 2 incorporating the vortex sensor 10 may be a flowmeter in which all the fluid to be measured passes through the measuring pipe (corresponding to the flow pipe 1) of the flowmeter,
Inserting a vortex flowmeter with a small diameter measuring tube (corresponding to the flow tube 1) into the flow tube so as to be suitable for measuring the flow rate in the large diameter flow tube, and obtaining the total flow rate from the partial flow velocity Although a vortex flowmeter may be used, the latter is more suitable for an embodiment in which a metal powder injection molding material (MIM material) described later is used for the vibration tube 13. Furthermore, the shape of the vortex generator 2 is also shown in FIG.
The shape shown in (B) is not limited to the triangular prism shape as long as the flow separates on both sides of the vortex generator and the Karman vortices are alternately generated.

In the present invention, the vibrating tube 13 is made of metal,
It has a flange portion 11 for attaching to the vortex generator 2 and a pressure receiving portion 13a. By using the vibration tube 13 made of metal, it is possible to improve the electric shielding property without the need to apply the electromagnetic wave shield material which was required when the vibration tube made of resin was used. Further, as the above-mentioned pressure detection element plate, a conductive base material 14 having a flat plate which is axisymmetric to the vibration tube 13 and faces the pressure receiving side, and piezoelectric elements 15 (which are provided on both side surfaces of the flat plate of the base material 14 respectively) Or strain gauge). As a main feature of the present invention, the pressure detecting element plate is a wall surface in which the upper end joint portion 14b of the base material 14 is fixed to the upper end portion of the concave portion formed in the vibration tube 13 and is slightly separated from the bottom portion of the concave portion. The lower end contact portion 14a of the base material 14 is brought into contact with and stored. Then, the vortex sensor 10 is manufactured by sealing the upper part of the concave portion with the molding material 16 of the insulating resin.
That is, the area around the piezoelectric element 15 (or strain gauge) inside the vortex sensor 10 is not molded with resin, and the base material 14 is formed as shown in FIG.
It has a T-shape as shown in (A) and its upper end joint 14
It is assumed that the outer side of b and the inner wall of the metallic vibrating tube 13 are connected by only metal contact (non-baking type structure). Further, in order to secure the fixing, it is preferable to fix with an adhesive, and the base material 14 and the vibrating tube 13 may have substantially the same thermal expansion coefficient.

As another main feature of the present invention, the pressure detecting element plate is formed so as to extend the piezoelectric element 15 (or strain gauge) to the upper fixed portion of the vibration tube 13. Here, as shown in FIG. 3A, the upper portion of the piezoelectric element 15 is connected to the upper end joint portion (corresponding to the upper fixing portion) 14 of the base material 14.
It shall have a structure extending upward to b. By using a metal vibrating tube, the output is lower than that of a resin vibrating tube.
Although the / N ratio deteriorates, the output becomes large by extending the arrangement of the piezoelectric element (or strain gauge) to the upper fixed part, and S /
It is possible to improve the N ratio.

Further, as the lower end contact portion 14a, as shown in FIG.
As shown in (B), it is preferable to have a disk-shaped spring portion having radial slits. The radial slit needs to have an outer diameter slightly larger than the inner diameter of the engaging groove provided on the wall surface slightly separated from the bottom of the concave portion of the vibrating tube 13. . Figure 3 (B)
With the lower end contact portion 14a shown in FIG. 5, it is possible to detachably lock the spring with respect to the recessed portion of the vibration tube 13, which is convenient when the pressure detection element plate is housed in the vibration tube 13, and
The piezoelectric element 15 (or strain gauge) can be detected.

FIG. 4 is a flow chart for explaining a method of manufacturing the vibration tube in the vortex flowmeter sensor according to the embodiment of the present invention. The metal vibrating tube 13 (including the flange portion 11 and the pressure receiving portion 13a) in the vortex sensor described above is
MIM (Metal Powder Injection Molding: Metal Inject)
(ionMolding) material is preferable. By using a vibrating tube formed by metal powder injection molding, it is possible to provide a highly reliable and inexpensive vibrating tube, and a vortex flowmeter sensor and a vortex flowmeter equipped therewith. First, the fine metal particle powder 22 is kneaded with the thermoplastic binder 21 (step S1). Next, this is molded using an injection generator (step S2), then debindered (degreased) (step S3), and sintered (step S4). After that, sizing (step S5) and post-treatment (step S6) are performed as necessary to form a vibrating tube (product 23) made of MIM.

In the MIM method, metal molded parts having a three-dimensionally complex shape can be mass-produced, and uniform shrinkage results in high dimensional accuracy of ± 0.5% and high relative density of 95% or more. It has excellent mechanical properties. Furthermore, since it has high extensibility, it can be pressed and bent easily and can be used for various heat treatments. Also, since fine powder is used, the surface becomes smooth and various surface treatments such as plating are easy. is there. As described above, the MIM manufacturing method is different from the conventional metal powder sintering in that both the density and the strength are improved, so that the vibration tube produced by this manufacturing method can also obtain high reliability. In terms of cost, it is actually 1
It can be manufactured at a cost of about / 10. This corresponds to a cost of about 1/4 for the whole vortex flowmeter sensor and a cost of about 2/5 for the whole vortex flowmeter.

[0023]

According to the present invention, a metal vibrating tube capable of withstanding high temperature and high pressure without using the electromagnetic wave shielding material, which is required when a resin vibrating tube is used, is used. It is possible to improve the S / N ratio in the conventional vortex flowmeter sensor.

Further, according to the present invention, the metal vibrating tube in the vortex flowmeter sensor can be manufactured with high reliability and at low cost without being manufactured by expensive shaving.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a vortex flowmeter sensor according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining details of the vortex flowmeter sensor of FIG.

FIG. 3 is a diagram showing an example of a pressure detection element plate of FIG.

FIG. 4 is a flowchart for explaining a method of manufacturing the vibration tube in the vortex flowmeter sensor according to the embodiment of the present invention.

FIG. 5 is a diagram for explaining a vortex flowmeter according to a conventional technique.

FIG. 6 is a diagram for explaining another vortex flowmeter sensor according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow tube (tubular body), 2 ... Vortex generator, 3 ... Mounting surface, 4 ... Pressure chamber, 5 ... Pressure guiding hole, 10 ... Vortex flowmeter sensor, 11 ... Flange part, 12 ... Shielded cable, 12a ... Shield wire, 12b ... Core wire, 13 ... Vibration tube, 13a ... Pressure receiving portion, 1
4 ... Base material, 14a ... Bottom contact part, 14b ... Top joint part,
15 ... Piezoelectric element, 15a ... Paste position, 16 ... Mold material, 17 ... Ground wire, 18 ... Hole, 21 ... Thermoplastic binder, 22 ... Metal fine particle powder, 23 ... Product.

Claims (4)

[Claims] 1. A pressure guide hole is provided in a flow tube through which a fluid to be measured flows so as to face the flow, has a pressure chamber therein, and further has a pressure guide hole communicating with the fluid to be measured and introducing a fluid pressure into the pressure chamber. A vortex flowmeter sensor for arranging the vortex generator, which detects a fluctuating pressure based on a Karman vortex introduced into the pressure chamber in the vortex generator, including a flange portion for attaching to the vortex generator and a pressure receiving pressure. And a vibrating tube made of metal, a conductive base material having a flat plate which is axisymmetric to the vibrating tube and faces the pressure receiving side, and piezoelectric elements or strain gauges provided on both side surfaces of the flat plate of the base material, respectively. A pressure detecting element plate having a pressure detecting element plate, the upper end joint portion of the base material is fixed to the upper end portion of the concave portion formed in the vibrating tube, and the pressure detecting element plate is slightly separated from the bottom portion of the concave portion. The bottom edge contact part of the base material is brought into contact with the Sealed the recessed portion upper in molding material of RESIN, and flowmeter sensor, characterized in that the piezoelectric element or a strain gauge was extended to the upper end joint portion of the vibrating tube. 2. A lower end contact portion of the base material is formed in a locking groove provided on a wall surface slightly separated from a bottom portion of the recessed portion of the vibrating tube and has an outer diameter slightly smaller than an inner diameter of the locking groove. The vortex flowmeter sensor according to claim 1, further comprising a disk-shaped spring portion having a large radial slit. 3. The vortex flowmeter sensor according to claim 1, wherein the vibrating tube is a metal powder injection molding material. 4. A vortex flowmeter comprising the vortex flowmeter sensor according to any one of claims 1 to 3.