JPS6029694Y2 - Flow rate/flow rate detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the flow velocity of a fluid from the Karman vortex generation frequency, and particularly to a detection device applied to this type of device.

When an object that resists the flow of the fluid is provided in the passage of the fluid to be measured, a Karman vortex street is generated under certain conditions.

The generation frequency of this Karman vortex is proportional to the fluid flow rate within a certain Reynolds number range, and therefore, by detecting the number of stations occurring per unit time, the fluid flow rate and further the flow rate can be measured.

Incidentally, the occurrence of a vortex can be detected through changes in the pressure within the fluid or changes in the pressure within the fluid caused by the vortex, but in this case, it is necessary to reliably identify and detect changes in the state of the fluid due to individual vortices. .

As one such detection device, for example, a chamber formed inside a vortex generator is filled with a fluid and the liquid is sealed with two metal diaphragms, and a variable capacitance is created by an electrode embedded in the chamber and the metal diaphragms. form a capacitor,
It is known to apply, for example, a high frequency signal to this capacitor and detect the displacement of a metal diaphragm due to a pressure change in the measured fluid caused by the generation of a vortex as a frequency change due to a change in capacitance of the capacitor.

However, in the known detection device as described above, the temperature of the liquid sealed inside the chamber changes due to temperature changes in the fluid to be measured or heat generation within the device, and the volume of the liquid changes.
A displacement of the diaphragm occurs.

As a result, the detection device may malfunction or the detection sensitivity of the device may decrease.

The present invention has been devised in view of the above points, and its purpose is to provide a flow velocity/flow rate detection device regardless of the temperature of the liquid contained in the detection device.

Next, a preferred embodiment of the present invention will be explained based on the drawings.

In the figure, numeral 1 is a vortex generator disposed in the tube 2.

Recesses 3 and 4 are formed in the side surfaces of the vortex generator 1, and the recesses 3 and 4 communicate with each other through a communication hole 5 bored in the vortex generator 1.

A metal diaphragm 6.7 is provided over the recesses 3, 4, and a chamber 8 is formed by the recesses 3, 4 and the communication hole 5.

Electrodes 9, 10 are arranged in the recesses 3, 4 opposite the metal diaphragm 6.7.

A fluid 11 is sealed in the chamber 8, and a diaphragm 6
．． 7, electrodes 9 and 10, and liquid 11 form a variable capacitor as means 12 for detecting displacement of the diaphragm.

The detection means 12 does not necessarily have to be a capacitor; for example, a magnet and a detection coil may be provided opposite the diaphragm to detect the eddy current generated in the diaphragm, and furthermore, a strain gauge or the like may be used to detect the displacement of the diaphragm. You may also do so.

Alternatively, a vortex generator may be provided separately from the vortex generator, and the chamber 8 may be formed within the vortex detector.

Another chamber 13.14 is formed in the vortex generator 1,
A free piston 16 is fitted in the chambers 13 and 14, using a communicating portion 15 between the chambers 13 and 14 as a rod guide.

The piston 16 converts the chambers 13.14 into chambers 17, 1B, 1
9.20, the chamber 17 is filled with a liquid 21, and the chambers 18, 19.20 are filled with gases 22, 23.26.

25 is a seal ring. Note that the liquid 21 does not necessarily have to be the same as the liquid 11.

In the above, the amount of change in volume of liquid 11 due to temperature change of liquid 11 in chamber 8 and the amount of change in volume of liquid 21 due to temperature change of liquid 21 in chamber 17 are substantially the same.

Here, it may be provided that the volume of the chamber 17 and the amount of liquid 21 can be adjusted.

In order to match the temperature of the liquid 21 and the liquid 11, the vortex generator 1 is preferably formed of a good thermal conductor.

The chamber 8 and the chamber 19 communicate with each other through a communication hole 26 filled with the liquid 11.

The communication hole 2 is designed so that when the liquid 11 tries to flow relatively quickly inside the hole 26, a large flow path resistance occurs in the communication hole 5.
6 is preferably formed to be thin and long.

The above-mentioned chambers 13, 14, piston 16, liquid 21, gas 22, 23, 24. The hole 26 constitutes a means 27a for absorbing a volume change in the chamber 8 according to the volume change in the liquid 11 in the chamber 8, in other words, a means 27a for keeping the pressure in the chamber 8 constant.

However, both or one of the gases 22 and 24 is a high-pressure gas, and the liquid 21 is a high-pressure liquid. In the case where the holes 26 are configured to be evenly distributed, the holes 26 do not necessarily have to be formed to be elongated.

High pressure here refers to a pressure that is extremely high compared to the pressure required to displace the diaphragm 6.7.

The area of the piston portion 16 a of the piston 16 in the chamber 14 that receives pressure from the gas 23 is smaller than the area that receives pressure from the gas 24 .

In any of the above cases, the liquid 11 and the gas 2
3 is maintained at about atmospheric pressure or the static pressure experienced by the diaphragm 6.7 in the conduit 2.

Flow rate/flow rate detection device 27 of the present invention configured as described above
If the fluid 28 to be measured in the tube 2 is flowing in the direction C, the vortex generator 1 generates a line of Karman vortices 29 near the diaphragm 6.7, and the vortex line 29 displaces the diaphragm 6.7. However, the capacitance of the capacitor 12 changes, and this change in capacitance is taken out as an electrical signal by a lead wire (not shown) connected to the diaphragm 6.7 and the electrode 9.10.

In the above case, the fluid 2 due to the Karman vortex street 29
When the force in the D direction applied to the diaphragm 6 becomes larger than the force in the C direction applied to the diaphragm 7 due to the change in static pressure within the recess 8, as the diaphragm 6 is displaced in the D direction, the liquid 11 in the recess 3 A portion is sent to the recess 4 through the hole 5, and the diaphragm 7 is also displaced in the D direction.

At this time, the liquid 11 in the hole 5 also tries to flow into the hole 26, but normally the displacement speed of the diaphragm 7 due to the Karman vortex street 29 is relatively high, and in addition, the hole 26 is formed to be elongated. The flow path resistance that the fluid 11 receives at 26 is large and the fluid 11 does not substantially flow into the hole 26 .

Therefore, the hole 26 for detecting the flow rate and flow rate by the capacitor 12
is virtually occluded.

The biasing force in the C direction applied to the diaphragm 7 is greater than the biasing force in the D direction applied to the diaphragm 6, and even when the diaphragm 6.7 is displaced in the C direction, the hole 26 is substantially closed.

Even when the hole 26 is relatively thick and short, for example, the chamber 2
If the high-pressure gas 24 is sealed at 0, the piston 16 is not substantially displaced, and the diaphragm 6 or 7 is displaced in accordance with the displacement of the diaphragm 7 or 6.

Therefore, the detection sensitivity of the detection device 27 is maintained in the same way as when the hole 26 is closed.

On the other hand, when the temperature of liquids 11 and 21 increases and the volume of liquid 11.21 in chamber 8.17 increases (for the sake of simplicity, the volume of chamber 19.hole 26 is the same as the volume of chamber 18.17). (the thermal expansion of gas 23 in chamber 19 and liquid 11 in hole 26 is negligible), and as the volume of liquid 21 in chamber 17 increases, piston 16
, 24 in the A direction and is moved in the B direction.

As the piston 16 moves in the B direction, the volume of the chamber 19 increases, and the volume of the liquid 11 increases by this volume increase, and the liquid 11 is introduced into the chamber 19 through the hole 26.

The pressure of the liquid 11 in the chamber 8 is therefore kept the same as the pressure before the temperature change of the liquid 11, and there is little risk that the diaphragm 6.7 will be displaced by an increase in temperature.

When the temperature of the liquid 11.21 decreases, displacement of the diaphragm is avoided by displacing the piston in direction A.

Note that when the temperature of the liquid 11.21 changes, the liquid 11 flows through the hole 26 because the temperature change usually occurs relatively slowly and continuously for a long time, so the flow rate of the liquid 11 at the hole 26 is small. This is because the flow path resistance in the hole 26 is kept relatively small.

In the above specific example, the gas 23 is sealed in the chamber 19, but instead of the gas 23, the liquid 11 flows inside the chamber 19.
It may be filled with

Next, another specific example of the pressure holding means 27b applied to the device of the present invention will be explained.

In FIG. 3, the means 27b includes, for example, a variable volume container 33, 34 and a container 33 each having one wall surface formed of a plate 31, 32 fixed on a support plate 30 fixed to the outer wall of the tube 2.
34 and a connecting rod 35 connecting the two.

In order to make the volume of the container 33.34 variable, a portion 36.37 of the wall surface of the container 33.34 consists of a bellows or a diaphragm.

A fluid 40.41 is enclosed in chambers 38.39 within the containers 33.34.

The connecting rod 35 is connected to the outer wall 42 of the container 33, and the hole 43 of the plate 32 is connected to the outer wall 42 of the container 33.

It extends slidably through the chamber 41 in the G direction and is connected to the other wall 44 of the container 34 .

The chamber 39 and the hole 26 are communicated through a tube 45 fixed to the tube 2.

In this specific example, the change in the volume of the chamber 39 due to a change in the temperature of the fluid 40 in the chamber 38 is formed to match the change in the volume of the fluid 11 due to a change in the temperature of the fluid 11 in the chamber 8. Regardless, the pressure of the fluid 11 in the chamber 8 is kept constant, and the detector 27 can be operated with high sensitivity without this operation.

Instead of using the pressure retaining means 27a and 27b, it is also possible to configure one of the diaphragms 6.7 with a fixed wall with the upper end of the alternative waist hole 26 open to the atmosphere.

As described above, in the flow velocity/flow rate detection device of the present invention, the pressure of the liquid sealed by the diaphragm of the detection device can be kept constant regardless of the temperature, and the position of the diaphragm can be maintained at a desired position, so that the operation Detection sensitivity can be maintained high.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a flow velocity/flow rate detection device, and FIG. 2 is an explanatory diagram of a preferred specific example of a flow velocity/flow rate detection device according to the present invention.
FIG. 3 is an explanatory diagram of pressure holding means applied to another specific example of the flow velocity/flow rate detection device according to the present invention. 1... Vortex generator, 2... Tube, 6, 7.
...Diaphragm, 8...Chamber, 11...
...Liquid, 12...Detection means (capacitor), 27a, 27b...Pressure holding means, 27.
...Flow rate/flow rate detection device, 29...Karman vortex.

Claims (1)

[Scope of utility model registration request] A vortex generator, a diaphragm that is displaced by the vortex generated by the vortex generator, a chamber whose one side is defined by the diaphragm and is filled with liquid, and the volume change due to temperature change of this liquid. A flow rate/flow rate detection device comprising means for absorbing the diaphragm and means for detecting displacement of the diaphragm.