JPH06307902A - Current velocity/flow rate detector - Google Patents

Abstract

PURPOSE:To introduce the variation in the inner pressure of fluid occurring across a pressure vibration generator to a pair of diaphragms having parallel direction of displacement through a simple structure. CONSTITUTION:The current velocity/flow rate detector comprises a pair of diaphragms 17, 18 having parallel direction of displacement, a detecting section 6 equipped with pressure transmission paths 9, 34, 10, 33 for introducing chambers 13, 27 partitioned by the diaphragm 17 and chambers 14, 28 partitioned by the diaphragm 18 to the rear surfaces thereof, a pressure vibration generator, i.e., a vortex generating column 1, equipped with pressure transmission paths 37, 38 for introducing the pressure variation of fluid between the opposite sides 39, 40 to the surfaces thereof, a passage 19 provided between the detecting section 6 and the vortex generating column 1 while communicating the pressure transmission paths 9, 17, 21, and a seal member 5 provided with a passage 20 communicating the pressure transmission paths 10, 18, 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow velocity / flow rate detecting device for detecting a flow velocity or flow rate of a fluid in a flow channel, and a Karman vortex flowmeter for detecting the flow velocity or flow rate of the fluid from the wave number of pressure oscillation in the fluid. And flow velocity / flow rate detector used for fluidics flow meters.

[0002]

2. Description of the Related Art For example, in a Karman vortex flowmeter, when an object that resists the flow of a fluid is provided in the flow path of a fluid to be measured, a Karman vortex street is generated under certain conditions. The generation frequency of this Karman vortex is proportional to the flow velocity of the fluid within a certain range of Reynolds number, and therefore by detecting the number of vortex generated per unit time, the flow velocity of the fluid and further the flow rate can be measured.

As a flow velocity / flow rate detecting device of this type, there is one disclosed in Japanese Utility Model Publication No. 61-4808. Figure 4
Shows the flow velocity / flow rate detection device, (a) is a longitudinal sectional view,
(B) is an XY transverse sectional view of (a). 1 in FIG.
Is a vortex generating column fixed to the pipe 3 in which the fluid 2 to be measured flows in the A direction. The vortex generating column 1 is formed in a desired shape. The protrusion 4 from the tube 3 of the vortex generating column 1 has a recess 5,
A detection unit housing 7 having 6 is fixed, and the housing 7 and the protrusion 4 form chambers 8 and 9. The chamber 8 is bounded by a diaphragm 10 into chambers 11 and 12, and the chamber 9 is bounded by a diaphragm 13 into the chamber 1.
It is divided into 4,15.

The chamber 11 and the chamber 15 are communicated with each other by a communication passage 16. The communication passage 16 is communicated with a hole 18 having an opening 18a on one side surface 17 of the vortex generating column 1.
The chambers 12 and 14 are communicated with each other through a communication passage 19, and the communication passage 19 is communicated with a hole 21 that has an opening 21a on the other side surface 20 of the vortex generating column 1. Chamber 11, 1
The fluids 2, 14, 15 and the communication passages 16, 19 and the holes 18, 21 are filled with a fluid when the fluid 2 to be measured is a liquid.

In the above description, the first and third chambers are composed of the chambers 11 and 15, respectively, the second chamber is composed of the chambers 12 and 14 and the communication passage 19, and the first pressure transmission passage is composed of the hole 18. The pressure transmission path 2 comprises a hole 21. Note that FIG.
4 shows a modified example of the detection device of FIG. 4, and even if the diaphragms 10 and 13 are arranged vertically to the longitudinal direction of the vortex generating column 1 in order to facilitate detection of the sense of the diaphragms 10 and 13 as shown in FIG. Good. The diaphragms 10 and 13 (or their displacement directions) may be inclined with respect to the longitudinal direction of the vortex generating column 1 as long as they are parallel to each other.

When the pressure in the opening 18a becomes higher than the pressure in the opening 21a due to the vortex rows 23a, 23b generated on the side surfaces 17, 20 of the vortex generating column 1, respectively, the diaphragm 10
Is displaced in the B direction, and the diaphragm 13 is displaced in the C direction. On the other hand, due to the occurrence of the vortex rows 23a and 23b, the opening 18a
When the pressure at (1) becomes lower than the pressure at the opening 21a, the diaphragm 10 is displaced in the C direction, and the diaphragm 13 is displaced in the B direction.

In order to detect the displacement or frequency of the diaphragms 10 and 13 in the B and C directions, the diaphragms 10 and 13 are detected.
The detectors 24 and 25 are provided in the housing 7 so as to face the surface of. When the diaphragms 10 and 13 include a ferromagnetic material, the diaphragm 10 and the detection device 24 form a variable inductance 24a, and the diaphragm 13 and the detection device 25 form a variable inductance 25a. The detection devices 24 and 25 may be replaced with known detection devices such as detection of capacitance change and strain detection.

In order to differentially amplify the inductance change of the variable inductances 24a and 25a, the variable inductances 24a and 25a are arranged, for example, under the AC power supply 28 together with the coils 26 and 27 as in the electric circuit of this detection apparatus shown in FIG. It is incorporated in an operating bridge circuit 29, and the output of this circuit 29 is converted into a pulse output signal 33 having a repetition frequency proportional to the flow velocity through an amplifier circuit 30, a demodulation circuit 31, and a Schmitt circuit 32.

This flow velocity / flow rate detecting device is composed of vortex rows 23a, 2
When the diaphragm 10 is displaced in the B (C) direction and the diaphragm 13 is displaced in the C (B) direction by the pressure difference of 3b, the inductance 24a increases (decreases) and the inductance 25a decreases (increases). The period of the inductance change of the variable inductances 24a and 25a is the vortex street 2
It corresponds to the generation period of 3a and 23b and is inversely proportional to the flow velocity. Therefore, the bridge circuit 29 gives an output obtained by modulating the signal of the AC power supply 28 at a frequency proportional to the flow velocity, and the output of the bridge circuit 29 is output from the Schmitt circuit 32 as a pulse 33 having a repeating frequency proportional to the flow velocity.
The flow velocity and the flow rate can be detected by separately examining the relationship between the flow velocity distribution and the flow rate in the pipe 3.

[0010]

In the above-mentioned flow velocity / flow rate detecting device, the pressure transmitting path for guiding the pressure change generated on both sides of the vortex generating column to the pair of diaphragms arranged in parallel to each other of the detecting portion is provided. Since the branch is provided inside the vortex generating column, machining becomes complicated, which causes a cost increase. For this reason, it is conceivable to divide this vortex generating column into multiple parts in the lateral direction and machine them into layers for easier machining, but the sealing points between the divided parts and the number of assembly steps are Increase, which in turn increases costs.

An object of the present invention is to provide a flow velocity / flow rate detection device which guides a pressure change generated on both sides of a vortex generating column to a pair of diaphragms arranged in parallel to each other of a detection portion with a simple structure. It is in.

[0012]

In order to achieve the above-mentioned object, a flow velocity / flow rate detection device of the present invention comprises a pair of first and second diaphragms having displacement directions parallel to each other.
First and third chambers partitioned by the first diaphragm, second and fourth chambers partitioned by the second diaphragm, and the first to fourth chambers are respectively guided to the lower surface thereof. A detection unit having first to fourth pressure transmission paths, and first and second pressure transmission paths for guiding pressure changes in the fluid due to pressure vibrations respectively generated on one and the other side surfaces to the upper surface thereof. A pressure vibration generator provided, and arranged between the lower surface of the detection unit and the upper surface of the pressure vibration generator, and the first and fourth pressure transmission paths of the detection unit and the first of the pressure vibration generation unit. A seal member having a first communication passage communicating with the pressure transmission passage and a second communication passage communicating with the second and third pressure transmission passages of the detection unit; and the first and second sealing members. First and first detecting respective displacements of the diaphragm of the So as consisting of a displacement detector. The first and second displacement detectors each include a movable electrode made of an electret film formed on the upper surfaces of the first and second diaphragms, and a fixed electrode arranged at a predetermined distance from the movable electrode. To do so.
The electret films formed on the upper surfaces of the first and second diaphragms are each made of a polymer electret material.

[0013]

In the flow velocity / flow rate detecting device of the present invention, the detecting portion is provided with the first to fourth pressure transmission paths for guiding the first to fourth chambers to the lower surface of the detector, and the vortex generator is provided with one of them. The first and second pressure transmission paths for guiding the pressure change in the fluid due to the pressure vibration generated on the other side surface to the upper surface of the pressure vibration generator are provided, and the lower surfaces of these detectors and the upper surface of the pressure vibration generator are provided. The first and second window-shaped cuts are provided in the seal member arranged between the two, and the first and second communication paths are formed by the surfaces of these cuts and the thickness of the seal member. The first and fourth pressure transmission passages of the detection unit and the first pressure transmission passage of the pressure vibration generator are communicated with each other through the communication passage, and the second and third pressure transmissions of the detection unit are transmitted through this second communication passage. The passage and the second pressure transmission passage of the pressure vibration generator are made to communicate with each other. Therefore, simply by placing the lower surface of the detection unit on the upper surface of the pressure vibration generator via this seal member and fixing it,
Since the branching of each pressure transmission path is completed and the pressure change generated on both sides of the pressure vibration generator can be guided to the pair of diaphragms of the detection unit, the number of assembling steps is reduced. The pressure transmission paths of the detection section and the pressure vibration generator do not need to be branched inside, and the communication paths of the seal member are formed by only making cuts in the seal member, which reduces the number of machining steps. I'm sorry.

The first and second displacement detectors each have a movable electrode made of an electret film formed on the upper surfaces of the first and second diaphragms, and a fixed electrode arranged at a predetermined distance from the movable electrode. Therefore, if these electret films are both positively charged, when the first diaphragm is displaced upward and the second diaphragm is displaced downward, a positive signal voltage from the first displacement detector is detected. However, a negative signal voltage is output from the second displacement detector, and when the first diaphragm is displaced downward and the second diaphragm is displaced upward, a negative signal voltage is output from the first displacement detector. A positive signal voltage is output from the second displacement detector. Then, these signals are amplified by the differential amplifier and output as detection outputs.

Further, since the polymer electret material such as polyvinylidene fluoride, polyacrylonitrile and polyvinyl fluoride is used as the film for the electret film, it has elasticity and does not hinder the displacement of the diaphragm with high accuracy. The displacement of the diaphragm can be detected.

[0016]

1 to 3 show an embodiment in which the flow velocity / flow rate detecting device of the present invention is applied to a Karman vortex flowmeter, and FIG.
2 is a longitudinal sectional view of an essential part, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a circuit diagram of an electric circuit. In FIGS. 1 and 2, reference numeral 1 denotes a vortex generating column as a pressure vibration generator fixed to a pipe 3 in which a fluid to be measured 2 flows. The protrusion 4 of the vortex generating column 1 from the tube 3 is provided with a detection unit 6 via a seal member 5 having a predetermined thickness.
Is attached. The detection unit 6 includes a housing 7 and a lid 8.
And the housing 7 has first and second pressure transmission paths 9 and 10 each having a through hole in the center thereof.
Are provided with counterbore holes 11 and 12, and the counterbore holes 11 and 12 are provided in the first chamber 1 from below.
Insulating ring 15 for forming the third and second chambers 14
And 16, first and second diaphragms 17 and 18 having movable electrodes 19 and 20 formed of an electret film formed on the upper surfaces thereof, insulating rings 21 and 22 having a low dielectric constant and a thickness of, for example, several tens of microns, pressure Fixed electrodes 25 and 26 provided with transmission holes 23 and 24,
Insulating rings 29 and 30 for forming the third chamber 27 and the fourth chamber 28 are sequentially stacked, O-rings 31 and 32 are placed on the insulating rings 29 and 30, and the elasticity of the O-rings is used to cover the lid 8 from above. It is fixed by pressing downward with. In addition,
Due to the pressure transmission holes 23 and 24 provided in the fixed electrodes 25 and 26, the space between the fixed electrode 25 and the movable electrode 19 or the space between the fixed electrode 26 and the movable electrode 20 becomes the third chamber 27 or the fourth chamber, respectively. Configured as part of chamber 28. The electret is a dielectric that semi-permanently maintains polarization in the absence of an external electric field. In this embodiment, a polymer electret material such as polyvinylidene fluoride, polyacrylonitrile, or polyvinyl fluoride is used as a film. Therefore, it is preferable because it has elasticity and does not hinder the displacement of the diaphragm.

The third chamber 27 is the housing 7
A third pressure transmission path 34 formed of a lateral groove 34a and a vertical hole 34b is provided on the lower surface of the housing 7 near the second pressure transmission path 10, and the fourth chamber 28 has a lateral groove 33a and a vertical hole 33b. And a fourth pressure transmission line 3
3 opens in the vicinity of the first pressure transmission path 9.
Further, the seal member 5 has these pressure transmission paths 9 and 3
Window-shaped first notch 35 including openings 3 and window-shaped second notch 3 including openings of pressure transmission paths 10 and 34.
6 are provided, and the surfaces of the cuts and the thickness of the seal member 5 form first and second communication passages, respectively. When the detection unit 6 is attached to the protrusion 4 of the vortex generating column 1 via the seal member 5, the first communication passage 35 of the seal member 5 has an opening 37a on one side surface 39 of the vortex generating column 1. The second communication passage 36 communicates with the first pressure transmission passage 37, and the second communication passage 36 communicates with the second pressure transmission passage 38 having the opening 38a on the other side surface 40. It is preferable that the thickness of the seal member 5 is determined so that each communication passage formed by cutting has a cross-sectional area approximately the same as each pressure transmission passage.

The operation of this flow velocity / flow rate detecting device is as follows. When the pressure in the opening 37a becomes higher than the pressure in the opening 38a due to the vortex rows generated on the side surfaces 39 and 40 of the vortex generating column 1, the diaphragm 17 is displaced upward and the diaphragm 18 is displaced downward. On the other hand, when the pressure in the opening 37a becomes lower than the pressure in the opening 38a due to the occurrence of the vortex street, the diaphragm 17 is displaced downward and the diaphragm 18 is moved.
Is displaced upward. When each of these diaphragms is displaced in the upward direction, the distance between the movable electrode and the fixed electrode is narrowed, and when it is displaced in the downward direction, the distance between the movable electrode and the fixed electrode is expanded, so that both electret films of the movable electrode should be positively charged. When the diaphragm 17 is displaced upward and the diaphragm 18 is displaced downward, a positive signal voltage is output from the output terminal J and a negative signal voltage is output from the output terminal K, and the diaphragm 17 is downward and the diaphragm 18 is upward. When the output terminal K is displaced, the output terminal K outputs a negative signal voltage and the output terminal J outputs a positive signal voltage. That is, the fixed electrodes 25 and 26 and the movable electrodes 19 and 20 formed on the upper surfaces of the diaphragms 17 and 18 respectively have the first electrode.
And a second displacement detector. And output terminal J
The signal voltages of the first and second displacement detectors output from and K are respectively amplified by operational amplifiers 31 and 32 and input to a differential amplifier 33 as shown in the electric circuit of FIG. The difference is amplified and output as a detection signal. The reason why the difference between the signal voltages from the output terminals J and K is amplified by the differential amplifier 33 is to remove the noise of the signal. For example, if vibration is applied to the detecting device in the downward direction from the outside, the diaphragm 17 And 18
Since both are displaced upward, both terminals J and K generate a positive voltage (noise voltage). Therefore, this noise voltage can be removed by amplifying with the differential amplifier 33.

[0019]

The flow velocity / flow rate detection device of the present invention is only fixed on the upper surface of the pressure vibration generator via the seal member on the lower surface of the detecting portion, and the pressure change generated on both sides of the pressure vibration generator is paired. Since the branching of each pressure transmission path leading to the diaphragm is completed, the number of assembly steps is significantly reduced. The pressure transmission paths of the detection section and the pressure vibration generator do not need to be internally branched, and the communication path of the seal member is formed by only making a cut in the seal member, so the number of machining steps is small. Corner costs are reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of a flow velocity / flow rate detection device of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a circuit diagram of an electric circuit of the flow velocity / flow rate detection device of FIG.

FIG. 4 shows an example of a conventional flow velocity / flow rate detection device,
(A) is a vertical sectional view, (b) is an XY horizontal sectional view of (a)

5 is a longitudinal sectional view of a main part showing a modified example of the detection device of FIG.

FIG. 6 is a circuit diagram of an electric circuit of the flow velocity / flow rate detection device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vortex generating column 2 Fluid to be measured 5 Sealing member 6 Detecting section 9 First pressure transmitting path (of detecting section 6) 10 Second pressure transmitting path (of detecting section 6) 13 First chamber 14 Second chamber 17 First Diaphragm 18 Second Diaphragm 19 Movable Electrode 20 Movable Electrode 25 Fixed Electrode 26 Fixed Electrode 27 Third Chamber 28 Fourth Chamber 33 Fourth Pressure Transmission Channel (for Detection Unit 6) 34 Third Pressure Transmission path (of detection unit 6) 35 First communication path 36 Second communication path 37 First pressure transmission path (of vortex generation column 1) 38 Second pressure transmission path (of vortex generation column 1)

Claims (3)

[Claims] 1. A pair of first and second diaphragms having mutually parallel displacement directions, a first and a third chamber partitioned by the first diaphragm, and a partition by the second diaphragm. Second and fourth chambers, and first to fourth chambers for guiding the first to fourth chambers to their lower surfaces, respectively.
Pressure vibration generating device having a pressure transmitting passage and first and second pressure transmitting passages that guide pressure changes in the fluid due to pressure vibrations generated on one and the other side surfaces to the upper surface of the detecting portion. A body, a lower surface of the detection unit and an upper surface of the pressure vibration generator, and the first and fourth pressure transmission paths of the detection unit and the first of the pressure vibration generator.
A first communication passage communicating with the first pressure transmission passage, and a second communication passage communicating with the second and third pressure transmission passages of the detection unit; A flow velocity / flow rate detection device comprising: first and second displacement detectors for detecting respective displacements of the two diaphragms. 2. The movable electrode according to claim 1, wherein the first and second displacement detectors are movable electrodes made of an electret film formed on the upper surfaces of the first and second diaphragms, respectively. A flow velocity / flow rate detection device comprising a fixed electrode arranged at a predetermined interval. 3. The flow velocity / flow rate detection device according to claim 2, wherein the electret films formed on the upper surfaces of the first and second diaphragms are each made of a polymer electret material.