JPH06323882A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To provide a vortex flowmeter, especially for gas flow, which can detect a vortex signal with high sensitivity and high SN ratio while facilitating the maintenance. CONSTITUTION:A holder 4 for vortex generator and a sensor holder 5 are secured oppositely to the wall of a measuring pipe 1. A vortex generator 6 is fixed detachably to the holder 4 while a thermal sensor unit 20 is fitted to the sensor holder 5 and secured in place by means of a converter fixing flange 13. A measuring fluid flows into the sensor unit 20 from a pressure introduction path 8 in the upstream of the vortex generator 6 and the vortex pressure forms a V-channel for feeding a laminar flow to side pressure introduction paths 9, 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flowmeter, and more particularly to a structure of a vortex flowmeter which measures a gas flow rate and has excellent small flow sensitivity and easy maintenance.

[0002]

2. Description of the Related Art A vortex flowmeter is a simple speculative flowmeter with no moving parts. As is well known, the number of Karman vortices flowing out of a vortex generator within a predetermined Reynolds number range per unit time is the flow velocity. Or, it is used in proportion to the flow rate. As described above, if the installation condition of the vortex flowmeter is constant, the instrumental error characteristic of the vortex flowmeter is determined by the Reynolds number, so that the flow velocity or flow rate can be measured with high accuracy regardless of whether the measurement fluid is gas or liquid. .

The detection of vortices can be roughly divided into a method of detecting an alternating lift force acting on the vortex generator with the generation of the vortex and a method of detecting a flow fluctuation which changes in accordance with the generation of the vortex. The former detects a signal proportional to the square of the fluid density and the square of the flow velocity, so the vortex signal is small in a small flow region and is amplified with a high gain. Sensitive to noise such as vibration SN
The ratio deteriorates. As a result, the lower limit flow rate is set to a high value, so the lift detection type vortex flowmeter is not suitable for measuring the gas flow rate such as city gas whose daily flow rate changes drastically.

On the other hand, the latter vortex flowmeter of the type that detects flow fluctuations due to vortices is suitable for measuring the flow rate of a gas whose flow rate fluctuations are severe as described above. As a typical vortex sensor of this type, there is a thermal sensor type which is arranged in a fluid and detects an eddy signal from a resistance value change of a resistor due to heat radiation which fluctuates according to a flow fluctuation.

However, when a vortex flowmeter having a heat sensor is used for measuring city gas containing dust, the characteristics may change for a long period of time due to the influence of dust adhering to the vortex generator or the heat sensor. There was a drawback to Moreover, since the detection sensitivity is lowered, it is necessary to perform regular maintenance. For this reason, it is preferable to make it easy to remove the vortex generator and the vortex sensor. However, in the conventional vortex flowmeter, the vortex generator and the vortex sensor are integrated, and it is not possible to remove the vortex generator and the vortex sensor independently. could not. In addition, the thermal sensor,
Platinum wire and thermistors were used.

However, the platinum wire is expensive, and the thermistor has a problem that the resistance value greatly changes depending on the composition and mixing ratio of the metal oxides to be mixed and the sintering conditions. The thermal sensor is usually used by incorporating it in the bridge,
Even if an inexpensive thermistor is used, it is necessary to combine thermistors with the same resistance value to form a bridge circuit, so even if the unit price is low, a large number of man-hours are required for the assembly of the sensor, which is efficient and efficient. It became expensive as a result.

Furthermore, when a thermistor is used, a protrusion surface is formed on the contact surface with the fluid, which disturbs the high frequency due to turbulence and deteriorates the SN ratio, and the fluid seal at the lead wire portion is insufficient. However, for a long period of time, a phenomenon such as an unstable fluctuation of the resistance value caused by a change in humidity occurred and reliability became poor.

[0008]

An object of the present invention is to provide a vortex flowmeter excellent in SN ratio having a structure that is easy to maintain, particularly in a vortex flowmeter for gas, in view of the above circumstances. Provides a thermal sensor unit that can reduce the thermal conductivity and heat the temperature-sensitive resistance element with a small amount of electric power, has a complete fluid seal without the temperature-sensitive element protruding in the vortex detection flow path, and has excellent mass productivity. The purpose is to do.

[0009]

In order to achieve the above object, the present invention provides (1)
A measuring tube, a vortex generator disposed on the diameter of the measuring tube and having one end removably fixed to the outer wall of the measuring tube, and an outer wall of the measuring tube opposite to the wall to which the vortex generating body is fixed. Fixed to the
A sensor holder having an upstream pressure guiding path penetrating the measurement tube tube wall and opening on the upstream side of the vortex generator and side pressure guiding paths opening in the vicinity of both sides, and detachably fixed to the sensor holder, Due to the pressure fluctuation caused by the generation of Karman's vortex, the measurement fluid introduced from the upstream pressure guiding path of the sensor holder is composed of a vortex sensor for detecting the fluid vibration that alternately flows out to the side pressure guiding path. And (2) in (1), the vortex sensor communicates with the upstream pressure guiding path and the upstream pressure guiding path, and communicates with each of the side pressure guiding paths. A flow path spacer having a V-shaped passage punched out, a temperature-sensitive resistance element spacer having a predetermined opening area punched out around the upstream pressure guiding path and the side pressure guiding path, and between the temperature sensing resistance elements. The temperature-sensitive resistor is inserted into the punched hole so that it is flush with the seat. A printed circuit board on which the temperature-sensitive resistance is connected to a predetermined circuit element, a heat-radiation-coefficient-reducing spacer having a punched out position corresponding to the temperature-sensitive resistor, and a resin-sealed spacer. And the flow path spacer, the flow path spacer, the temperature sensitive resistance spacer, the temperature sensitive resistance element mounting printed circuit board, and the heat dissipation coefficient reducing spacer through the lead wire connected to the temperature sensitive resistance terminal. And a sensor unit base that insulates the resin-sealed spacers and integrally fixes the lead wires, and heats the flow rate by a signal output from the temperature-sensitive resistive element mounted printed circuit board in proportion to the generation of Karman vortices. The heat-sensitive sensor unit that detects
(3) In (1) or (2) above, the flow rate of the side constant fluid flowing through the upstream pressure guiding path and the side pressure guiding path of the sensor holder is adjusted. It is characterized in that a flow rate adjusting nozzle and a filter for filtering a measurement fluid are detachably fitted. Hereinafter, description will be given based on examples of the present invention.

FIGS. 1A and 1B are exploded views for explaining an example of the structure of the vortex flowmeter according to the present invention.
(A) figure is an exploded side sectional view, (b) figure is an arrow BB line sectional view of (a) figure, in the figure, 1 is a measuring tube, 2 is a flange,
3 is a rectifier, 4 is a vortex generator holder, 5 is a sensor holder,
6 is a vortex generator, 7 is a vortex generator fixing flange portion, 8 is an upstream pressure guiding path, 9 and 10 are side pressure guiding paths, 11 is a flow rate adjusting nozzle, 12 is a filter, 13 is a converter mounting flange, 14
Is a converter and 20 is a thermal sensor unit.

In the vortex flowmeter shown in FIG. 1, flanges 2 and 2 are fixed to both ends of a measuring pipe 1, and a honeycomb-shaped rectifier 3 is fitted and inserted in the upstream end. A vortex generator holder 4 and a sensor holder 5 are fixed to the middle portion of the wall of the measuring tube 1 so as to face each other on the diameter of the measuring tube 1.

In the diameter direction of the vortex generator holder 4, the measuring tube 1
Has a through-hole 4a penetrating the pipe wall thereof, and the vortex generator 6 is inserted into the through-hole 4a. The vortex generator 6 is integrally formed by sealing with a sealing material 7a such as an O-ring. The vortex generator fixing flange portion 7 is airtightly fixed to the vortex generator holder 4.

The sensor holder 5 is formed with a recess 5a into which the thermosensitive sensor unit 20 is airtightly inserted, and the recess 5 has an upstream pressure guiding path 8 which is open in the measuring tube 1 and has a step 8a. Side pressure guiding paths 9 and 10 having steps 9a and 10a
Has penetrated. The upstream pressure guiding passage 8 opens upstream of the vortex generator 6, and the side pressure guiding passages 9 and 10 open near the side wall of the vortex generator 6. Further, the flow rate adjusting nozzle 11 and the filter 12 are detachably inserted into the upstream pressure guiding path 8 and the side pressure guiding paths 9 and 10.

FIG. 2 shows a flow rate adjusting nozzle 11 and a filter 1.
It is an exploded perspective view showing an example of No. 2. Flow rate adjustment nozzle 11
A nozzle port 11a having a cross-sectional diameter for adjusting the flow rate and having a taper on the inflow side penetrates on the axis of, and adjusts the inflow amount of the measurement fluid flowing into the thermal sensor unit 20 described later, and the inflow flow. Gives the effect of rectifying. The filter is for removing dust contained in the measurement fluid flowing into the flow rate adjusting nozzle 11. The mesh of the mesh is the property of the fluid to be measured and the flow rate adjusting nozzle 11.
It is determined in consideration of the flow rate flowing through.

The thermosensitive sensor unit 20 hermetically fitted in the recess 5a so that the temperature-sensitive resistance element communicates with the upstream pressure guiding path 8 and the side pressure guiding paths 9 and 10 is the mounting tube 14 of the converter 14.
The transducer mounting flange 13 attached to the other end of a is elastically pressed and fixed through an elastic ring or the like, and the electric wire and signal line of the thermal sensor unit 20 and the transducer 14 are connected.

3 (a), 3 (b) and 3 (c) are views for explaining an example of the thermal sensor unit, FIG. 3 (a) is a perspective exploded view, FIG. 3 (b) is an assembly drawing, and FIG. c) FIG. 4 is a view seen from the bottom, FIG. 4 is a view showing a mounting view of the temperature-sensitive resistance element, in which 21 is a flow path spacer, 22 is a temperature-sensitive resistance element spacer, and 23.
Is a printed circuit board on which a temperature-sensitive resistance element is mounted, 24 is a temperature-sensitive resistance element for temperature correction, 25 is a temperature-sensitive resistance element for vortex detection, 26 is a heat dissipation coefficient reducing spacer, 27 is a resin sealing spacer, and 28 is a sensor unit base. , 29 is a spacer screw, 30 is an O-ring,
31 is a lead wire.

The flow path spacer 21 is made of an insulating thin disk made of glass fiber-containing epoxy resin or the like, and introduces a fluid for measuring dynamic pressure generated upstream of the vortex generator 6 into vortex pressure generated by vortex generation. A V-shaped groove 21a serving as a flow path for guiding the following alternating flow to the vortex detecting temperature sensitive element resistance elements 25a and 25b, which will be described later, is punched out. Temperature-sensitive resistance element spacer 2
In the V-shaped groove 21a, 2 is a strip-shaped temperature sensitive resistance element 25a, 25b for detecting eddies mounted on the temperature sensitive resistance element mounting printed circuit board 23 and a convex portion of the temperature correction sensitivity resistance element 24. The temperature compensating hole 22a and the temperature sensing hole 22b so that the surface of the measuring fluid does not disturb the flow of the measuring fluid.
22c is a spacer that has been punched out.

The printed circuit board 23 on which the temperature sensitive resistance element is mounted is also a thin disk of epoxy resin containing glass fiber, and the temperature sensing temperature sensitive resistance element 24 is arranged on the upper surface at a position parallel to the flow direction.
a and 24b are provided, and vortex detection temperature-sensitive resistance elements 25a and 25b are provided on the wake side inclining symmetrically with respect to the axis of the flow direction. The temperature-correction temperature-sensitive resistance elements 24a and 24b and the vortex detection temperature-sensitive elements 25a and 25b are, for example, chip-shaped temperature-sensitive semiconductor elements of the same standard and have a thickness of about 0.5 mm (millimeter). The elements are connected by a conductor wire 23a to form a predetermined bridge circuit element. Terminal portions 23b, 23c, 23 are used as connecting portions of the bridge circuit element.
d, 23e and 23f are formed.

The heat dissipation coefficient reducing spacer 26 is a glass fiber-containing epoxy resin disk and is made of temperature-sensitive temperature-sensitive resistance elements 24a, 24.
4b and the vortex detecting temperature-sensitive resistance elements 25a, 25b, that is, punched spaces 26a, 26b, and 26c are formed at positions indicated by dotted lines. Space 26
a, 26b, and 26c are temperature-compensating temperature-sensitive resistance elements 24a, 24 that are heated by a power source applied to the bridge circuit.
b and the vortex detecting temperature sensitive resistance elements 25a and 25b are formed with an air layer for lowering the heat radiation coefficient.

The sensor unit base 28 is a disk-shaped body made of metal which serves as a substrate of the heat-sensitive sensor unit 20, and has an O-ring groove 28a in which an O-ring 30 is arranged.
On the inner surface, the terminal portions 23b to 2 of the bridge circuit element are provided.
A through hole 32 penetrates at positions corresponding to the terminal portions 23a to 23f for insulatingly inserting the lead wire 31 connected to 3f. An insulating agent such as an epoxy resin for insulating and fixing the lead wire 31 is poured into the through hole 32 and fixed.
Insulating agent flows out into the resin sealing spacers 27 and the spaces 26a to 26
It is a disc for preventing the filling of c.

The above-mentioned flow path spacer 21, temperature-sensitive resistance element spacer 22, temperature-sensitive resistance element mounting printed circuit board 23, temperature-correction temperature-sensitive resistance element 24, vortex detection temperature-sensitive resistance element 25, and heat dissipation coefficient reduction. The spacer 26 and the resin-sealed spacer 27 are sequentially stacked on the sensor unit base 28 as shown in FIG.
It is integrally fixed to the spacer screw 29, the epoxy resin is poured into the through hole 32 as described above, the lead wire 31 is insulated and fixed, and the O ring 30 is fitted into the O ring groove 28a.

The heat-sensitive sensor unit 20 thus integrally assembled has a rear surface as shown in FIG.
A temperature-sensing temperature sensing element 24 is provided at the apex of the V-shaped groove 21a.
a and 24b are arranged, and the temperature sensitive resistance element 2 for vortex detection is provided on the hypotenuse part.
It can be seen that 5a and 25b are arranged. When the V-shaped groove 21a is mounted in the recess 6a of the sensor holder 6, a flow path of alternating flow due to vortex pressure flowing from the upstream portion of the vortex generator 6 to the vicinity of both side wall portions is formed.

The thermal sensor unit 20 described above is
Although the temperature-correction temperature-sensitive resistance elements 24a and 24b and the temperature-correction temperature-sensitive resistance elements 25a and 25b are inexpensive chip-type temperature-sensitive resistance elements, they may be temperature-sensitive resistance elements such as platinum thin films or semiconductor temperature-sensitive resistance elements. You may form.

Further, the vortex signal can be detected even if other thermal detecting means for detecting the alternating flow flowing in the V-shaped groove 21a due to the vortex pressure and a pressure or strain detecting element for detecting the vortex pressure itself are provided. Becomes

[0025]

As is apparent from the above description, according to the present invention, the vortex generator and the thermal sensor unit are detachably attached to the opposite side wall surfaces of the measuring tube, so that the vortex generator and the thermal sensor unit can be easily removed, and can be easily removed. Maintenance is extremely simple in a flow meter that requires periodic maintenance due to the adherence of these foreign substances, such as gas measurement including mist such as dust and fogging oil like gas. In addition, the vortex sensor is detachably attached as a heat-sensitive sensor unit, and a V-shaped laminar flow passage for thermally detecting the AC flow due to vortex pressure is formed from the upper part to both sides of the vortex generator at the time of mounting. Therefore, the sensitivity in a small flow is improved, and the excellent detection of the SN ratio becomes possible. Further, since the flow rate adjusting nozzle and the filter for removing the dust and making the laminar flow channel an optimal flow of the SN ratio are attached, a long-term stable signal is obtained and the maintenance period is extended.

[Brief description of drawings]

FIG. 1 is an exploded view for explaining an example of the structure of a vortex flowmeter according to the present invention.

FIG. 2 is an exploded perspective view showing an example of a flow rate adjusting nozzle 11 and a filter 12.

FIG. 3 is a diagram for explaining an example of a thermal sensor unit.

FIG. 4 is a diagram showing a mounting diagram of a temperature-sensitive resistance element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Measuring tube, 2 ... Flange, 3 ... Rectifier, 4 ... Vortex generator holder, 5 ... Sensor holder, 6 ... Vortex generator, 7 ... Vortex generator fixing flange part, 8 ... Upstream pressure guiding path, 9, 10 ... Side pressure guiding passageway, 11 ... Flow rate adjusting nozzle, 12 ... Filter, 13 ...
Converter mounting flange, 14 ... Converter, 20 ... Thermal sensor unit, 21 ... Flow path spacer, 22 ... Temperature-sensitive resistance element spacer, 23 ... Temperature-sensitive resistance element mounting printed circuit board, 24 ... Temperature correction sensor Temperature resistance element, 25 ... Temperature-sensitive resistance element for vortex detection, 2
6 ... Spacer for reducing heat dissipation coefficient, 27 ... Spacer for sealing resin, 28 ... Sensor unit base, 29 ... Spacer stator screw, 30 ... O
Ring, 31 ... Lead wire.

Claims (3)

[Claims] 1. A measuring tube, a vortex generator disposed on a diameter of the measuring tube and having one end removably fixed to an outer wall portion of the measuring tube, and a tube wall opposite to the vortex generator fixed thereto. A sensor holder having an upstream pressure guiding path that is fixed to the outer wall of the measuring tube on the side and that penetrates through the measuring tube wall and opens to the upstream side of the vortex generator and side pressure guiding paths that open in the vicinity of both sides, respectively. The fluid vibration is fixed to the sensor holder in a detachable manner, and fluid vibrations in which the measurement fluid introduced from the upstream pressure guiding passage of the sensor holder alternately flows out to the side pressure guiding passage due to pressure fluctuation caused by the generation of Karman vortex is detected. A vortex flowmeter comprising a vortex sensor and measuring a flow rate based on the fluid vibration. 2. A V which communicates the vortex sensor with the upstream pressure guiding path and the upstream pressure guiding path, and communicates with each of the side pressure guiding paths.
A flow path spacer having a punched path, a temperature-sensitive resistance element spacer having a predetermined opening area punched around the upstream pressure guiding path and a side pressure guiding path, and the temperature-sensing resistance element spacer. By fixing the temperature-sensitive resistance that is inserted into the punched hole so that it becomes the same surface,
The temperature-sensitive resistance element-mounted printed circuit board in which the temperature-sensitive resistance is connected to a predetermined circuit element, a heat dissipation coefficient reducing spacer in which a position corresponding to the temperature-sensitive resistance is punched out, a resin-sealed spacer, The flow path spacer, the flow path spacer, the temperature-sensitive resistance spacer, the temperature-sensitive resistance element mounting printed circuit board, the heat dissipation coefficient reducing spacer and the resin seal are sequentially passed through the lead wire connecting to the temperature resistance terminal. The spacer comprises a sensor unit base that insulates the lead wires and integrally fixes them, and the flow rate is thermally detected by a signal output from the temperature sensitive resistance element mounted printed circuit board in proportion to the generation of a Karman vortex. The vortex flowmeter according to claim 1, wherein the vortex flowmeter is a thermosensitive sensor unit. 3. A flow rate adjusting nozzle for adjusting a flow rate of a side constant fluid flowing through the upstream pressure guiding path and the side pressure guiding path of the sensor holder, and a measurement fluid are filtered. The vortex flowmeter according to claim 1 or 2, wherein the filter is detachably fitted.