JPS6011461Y2 - Flow velocity flow measuring device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flow rate measuring device that utilizes Karman vortices.

More specifically, the present invention relates to a flow rate measuring device that detects an alternating force generated in a vortex generating body by a Karman vortex and generates a vortex signal to measure the extraction flow velocity or flow rate.

An object of the present invention is to provide a flow rate measuring device that has a simple configuration, can minimize noise caused by disturbance force, can improve the S/N ratio, has excellent earthquake resistance, and is robust.

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is a cylindrical tube, and 11 is a cylindrical nozzle provided at right angles to the tube 1.

Reference numeral 2 denotes a columnar force-receiving body inserted into the tube body 1 at right angles through the nozzle 11. One end is supported by the tube body 1 with a screw 3, and the other end is attached to the nozzle 11 by screws or welding at the flange portion 21. Fixed.

22 is a recess provided on the flange portion 21 side of the force receiving body 1.

4a*4b is a disk-shaped stress detection section provided in the recess 22, and its center axis coincides with the center axis of the force-receiving body 2.

(Hereinafter, the stress detection units 4a and 4b will be collectively referred to as the stress detection unit 4.

) In this case, the stress detection section 4 consists of a disk-shaped element body 41 and electrodes 42, 43, and 44, as shown in FIG.

The electrode 42 has a thin disk shape and is provided on one side of the element body 41.

On the other hand, the electrodes 43 and 44 have an arcuate shape, and the element body 4
They are provided symmetrically on the other surface of the device body 41 in a direction perpendicular to the flow path direction with the center of the element body 41 in between.

In this case, a piezoelectric element is used as the element body 41.

Therefore, the stress detection units 4a and 4b, as will be described in detail later,
They are arranged on both sides of a position A where the stress generated in the force receiving body 2 by the disturbance force P becomes zero.

Reference numeral 5 denotes a sealing body made of an insulating material and sealing the stress detection part 4 in the recess 22 while insulating it from the force receiving body 2. In this case, a glass material is used.

FIG. 3 is a block diagram of the electrical circuit 6 (not shown) of FIG. 1.

In the figure, 6F is a first manual processing circuit that amplifies the output of the stress detection section 4a, and 62 is a second manual processing circuit that amplifies the output of the stress detection section 4b.The gain can be varied.

63 is an adder/subtractor that adds or subtracts the outputs of the first and second human processing circuits 61 and 62; in this case, it is configured to add.

In the above configuration, when the measuring fluid flows into the tube body 1, an alternating force as shown by the arrows shown in FIG. 1 acts on the force receiving body 2 due to the Karman vortex.

This alternating force is transmitted to the stress detection section 4 via the sealed body 5.

In this case, as shown in FIG.
A stress change occurs in the opposite direction across the central axis of .

Therefore, the electrode 42-electrode 43 of the stress detection section 4, the electrode 42
An electric signal (for example, a change in charge) corresponding to this stress change is generated between the - electrodes 44.

By detecting the number of times this change occurs, the vortex generation frequency can be detected.

Thus, by differentially processing the electrical output between the electrodes 42 and 43 and between the electrodes 42 and 44, twice the electrical output can be obtained.

The outputs of the stress detectors 4a and 4b are amplified by the first and second manual processing circuits, respectively, and then added by the adder/subtractor 63.

On the other hand, the entire pipe line vibrates due to the influence of vibration noise propagating through the pipe line, for example, vibration noise caused by opening and closing of pumps, compressors, dampers, etc.

Due to this vibration, an alternating bending moment Mα based on the mass distribution of the force receiving body 2 acts on the force receiving body 2 in the direction in which the above-mentioned alternating force acts.

The stress generated in the force receiving body 2 due to this alternating bending moment Mα is detected as a nozzle in the stress detection section 4.

Figure 4 shows this bending moment Mα.
■ is the alternating bending moment caused by vortex generation.

As a conventional example, there is a method that prevents the detection of noise caused by the bending moment Mα.
There is one in which one stress detection section is placed at position A where the value is zero.

However, in such a device, the stress detection section has a thickness, so even if it is made as thin as possible, the thickness cannot be reduced to zero, and the center of the stress detection section cannot be set at position A.
In practice, it is very difficult to completely match the , and external vibration noise will inevitably be detected.

Further, at the point A where the stress due to external vibration noise is zero, the stress of the measurement signal is small, and if the position of the stress detection section is shifted, the S/N ratio of the measurement signal will deteriorate.

If the S/N ratio is poor, it will be difficult to detect small signals, so the measurable region (particularly the low flow rate region) will be limited.

Therefore, in the present invention, the stress detectors 4a and 4b are respectively arranged on both sides of the position A where the bending moment Mα becomes zero, and for example, at a certain instant, the stress detector 4a detects a positive stress due to external vibration noise. The stress detection unit 4b detects the negative stress, and the adder/subtractor 63 detects the negative stress.
I added it with , and tried to cancel it out actively.

Moreover, the gain of the second human power processing circuit 62 is configured to be variable, and the magnitude of the noise of the second human power processing circuit can be easily adjusted to the magnitude of the noise of the first human power processing circuit. It can be adjusted to

Therefore, the adder/subtractor 63 can completely cancel the noise.

As a result, the stress detection parts 4a and 4b are subjected to a bending moment Mα
It is not necessary to strictly arrange the stress detecting section 4 at each position where the positive amount and the negative amount are equal to each other, and the stress detecting section 4 can be easily placed in the recess 22, and the device can be manufactured at low cost.

As schematically shown in FIG. 5, the stress detection units 4a and 4b are located at positions C and D between a location A where the stress due to external vibration noise is zero and a location B where the stress due to vortex generation is zero. may be placed in

Further, as schematically illustrated in FIG. 6, the stress detection sections 4av4b may be arranged at positions E and F sandwiching the point B where stress due to vortex generation is zero.

However, in this case, the first and second manual processing circuits 61 and 62
The outputs of must be arranged to be subtracted by the adder/subtractor 63.

That is, if the stress due to external vibration noise detected by the stress detection units 4a and 4b has the same sign, the adder/subtractor 63 subtracts the stress.
If they have different signs, add them.

In short, it is sufficient if the configuration is such that external vibration noise is canceled.

It goes without saying that the first input processing circuit 61 may also have a variable gain.

In the above-described embodiment, one end of the force-receiving body 2' is fixed to the conduit 1 and the other end is supported, but the other end may be fixed. Of course.

As explained above, according to the present invention, noise caused by disturbance force can be extremely reduced with a simple configuration, and S/
The N ratio can be improved, and a robust flow rate measuring device with excellent earthquake resistance can be realized.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and Fig. 2 is an explanatory diagram of the configuration of an embodiment of the present invention.
3 is a block diagram of the electric circuit of FIG. 1, FIG. 4 is an explanatory diagram of the operation of FIG. 1, and FIGS. 5 and 6 are main parts of other embodiments of the present invention. It is an explanatory diagram. 1... tube body, 2... force receiving body, 22...
...Concavity, 4.4b...Stress detection part, 41
...Element body, 42, 43.44...
Electrode, 5... Sealed body, 6... Electric circuit, 61... First processing circuit, 62... Second manual processing circuit, 63. ...Adder/subtractor, L...
...Alternating force, P...Disturbance force.

Claims (1)

[Scope of utility model registration request] In a flow rate measuring device that detects flow velocity or flow rate by detecting an alternating force acting on a force receiving body due to a Karman vortex, a stress generated in the force receiving body based on the alternating force and disturbance force provided in the force receiving body. two stress detecting sections sandwiching at least one of the respective positions where It is characterized by comprising a second manual processing circuit that processes the output of the other and whose gain can be varied, and an adder/subtractor that adds or subtracts the outputs of the second manual processing circuit and the first manual processing circuit. Flow velocity flow measuring device.