JPH02293630A - Liquid level flow control mechanism - Google Patents

Abstract

PURPOSE:To enhance the measurement accuracy of a liquid level and liquid column difference by moving upward and downward plural flow control materials disposed around a float on the liquid level according to the positions in the horizontal direction of the float to restore the float to a prescribed position. CONSTITUTION:The control rods 15 are disposed at four points Y1 to Y4 at the vertexes of a square shape. The small round projecting liquid surfaces are generated at four points by the control rods 15. The float 12 is held in the prescribed position by surface tension in the static state of the liquid level. On the other hand, the float 12 deviates in position and the surface tension decreases as well when the liquid level flows. The horizontal displacement of the float 12 is detected by 4 pieces of sensors 19 and the control rods 15 are put into and out of the liquid level by the revolution of motors 16 to generate the flow in a backward direction so that the float 12 returns to the prescribed position of the liquid level. Reflected light 16 is captured from a circular reflector 13 provided at the center of the float 12 in this state and the vertical position of the float 12 is measured by an optical wave interferometer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to liquids used in transducers such as float-type precision liquid level gauges or high-precision liquid column difference gauges that detect the position of liquid levels. Regarding surface flow control mechanism.

[Conventional technology]

In the conventional standard barometer using a light wave interference type mercury liquid column differential vacuum gauge, the optical interferometer is composed of light directly reflected from the mercury liquid surface, so it is difficult to detect fluctuations in the mercury liquid level due to vibrations from the floor. As a result, the wavefront of the light reflected from the mercury liquid surface is disturbed and is considerably attenuated, making the interference fringes unclear. Therefore, the measurement limit on the low pressure side is determined by the fluctuation of the liquid level, and if the measurement resolution is about 0.7 μm and the accuracy is ±1%, Q. Low pressure ff below Q7 Torr
ll1 constant is practically difficult. Furthermore, if the fluctuation of the liquid level is large, the pressure-injected light may shift from the light detection position and the signal may disappear. Furthermore, when mercury is used as the working fluid, there is a problem in that vapor is mixed into the measurement gas at temperatures below I Torr, making measurement impossible.

Therefore, in the patent application No. 63-280954, the present applicant proposed a low-pressure pressure gauge that uses a liquid as a pressure-sensitive element and measures pressure by measuring the displacement of the liquid with a light wave interferometer. A float having multiple symmetrical planes or curved surfaces facing the wall of the pressure receiving tube containing the liquid is floated on the surface of the liquid, and the entire upper surface of the float is formed into a mirror surface, or a reflector is attached to the center of the float. We have proposed a low-pressure pressure gauge characterized by being configured to reflect incident light from a light wave interferometer.

According to this proposed low-pressure pressure gauge, due to the symmetrical shape of the float, when the reflector or mirror reflective surface deviates from the center of the liquid column and approaches the pipe wall, it is repelled by surface tension and returns to the center position. automatically returns to. In other words, since the float is held in the desired position by the combination of surface tensions, the vibrations of the hydraulic fluid surface are suppressed and smoothed, and the mirror surface of the float does not easily shift, so the optical axis of the reflected light is stabilized. , it becomes practically possible to measure pressure with high precision with a measurement resolution of 0.01 μm or less.

On the other hand, conventional float-type transducers include a float for observing the water level of a dam, as shown in Figure 6, for example.
8ppLied Optics, Vcl20 No
20.15 Oct '81, P3508: ″L
iquid LevelInterferometer
″).

In this conventional example, in order to hold the float 1 in a predetermined position, a permanent 61 stone 3
．． 4 is provided to restrain the float 1 from the top, bottom, right and left with a strong magnetic force, thereby holding the float 1 in a predetermined position and stabilizing the length measurement.

(Problem to be solved by the invention) However, the above-mentioned patent application No. 6:1-280954
In the TI device of this issue, when the liquid level is almost stationary, the float is continuously and stably maintained at the fixed position value, but when the liquid level is flowing relatively rapidly, the surface tension is reduced. Therefore, when the float deviates from its normal position, automatic return of the float to the center position of the pressure receiving tube becomes delayed or difficult, which is another problem to be solved.

On the other hand, in the case of a stabilizing mechanism for a float that is restrained by magnets as shown in Fig. 6, or in the case of a mechanism that detects the position of a float through mechanical force as shown in Figs. 7 and 8, Due to the strong restraining force on the float, it is impossible to obtain the resolution of 0.01 Atm required to detect a minute differential pressure of 10-'Torr, which is the target of the low pressure limit handled by precision low-pressure pressure gauges, for example. .

In other words, even if a differential pressure to be measured occurs where the float is restrained in its current position by strong magnetic force or mechanical force (frictional force), and the liquid level moves accordingly, the buoyancy or surface tension As long as the amount of water generated is balanced, the float will faithfully follow the new liquid level and will not move. Furthermore, if the distance between the float and the duct is narrow, the liquid level will rise due to capillary action, and this amount of rise will also add to the measurement error. Therefore, as long as the conventional mechanism measures the water level of a dam that is much deeper and longer than these errors, or the difference in the ultra-high pressure liquid column, it is a stable, practical and highly accurate liquid level recognition mechanism. However, it could not be used to detect a slight differential pressure of about 10-'Torr as described above.

In view of the above-mentioned problems, an object of the present invention is to automatically return a float to a predetermined position even when the liquid level is flowing, suppress vibrations of the liquid level, and enable high-precision measurement with stable reproducibility. The object of the present invention is to provide a liquid level flow control mechanism that can be obtained.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides floats that are disposed at symmetrical positions around a float floating on the surface of a liquid whose position in the vertical direction varies, and A plurality of elongated rod-shaped or plate-shaped flow control members, a driving means for individually raising and lowering the flow control members in at least one of the liquid, a detection means for detecting the position of the float, and a detection means. The present invention is characterized by comprising a control means for controlling the drive means in accordance with the detection signal of the float to return the float to a predetermined position in the horizontal direction.

(Function) In the present invention, with the above configuration, when the liquid level flows,
By moving a rod or plate-shaped member into and out of the liquid surface, a flow in the opposite direction is actively generated to prevent the float from drifting away due to the flow of the liquid surface. Furthermore, when the liquid level remains stationary for a long time, the value of surface tension is large, so the float is automatically returned to the predetermined position by the natural combination of surface tensions that restores the float to the predetermined position.

Therefore, according to the present invention, a pressure difference to be measured is generated while the amount of sinking of the float is kept constant without using strong magnetic force or frictional force, and if the liquid level moves along with the pressure difference, , the float faithfully follows the new center position of the liquid level without resisting it, so even when the liquid level is flowing, the flow of the liquid level is controlled and the liquid level is always stable with high resolution. Detection becomes possible, and in particular, liquid column difference measurement using minute differential pressure and high-resolution measurement of liquid level can be achieved continuously, stably, and with high precision. (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Figure 1 shows the main structure of an embodiment of the present invention in which a liquid level flow control mechanism is applied to a low-pressure pressure gauge, etc., where (A) is a schematic vertical cross-sectional view, and (B) is a line A - It is a schematic cross-sectional view cut along A'.

In FIG. 1, numeral 10 is one side of a U-shaped tube with a circular cross section (hereinafter referred to as pressure receiving tube) which is a pressure receiving tube, and its diameter is made thick as shown in the figure to avoid capillarity.

11 is a working fluid as a pressure sensing means housed in the pressure receiving tube 10, 12 is a square float floating approximately at the center of the liquid level of the working fluid 10, and 13 is a circular float attached to the upper surface of the center of the float 12. The reflector l4 is a light beam that is reflected on the surface of the reflector 13 and returns, and the vertical position of the float l2 is measured by a light wave interferometer (not shown) via the light beam l4.

In order to maintain the horizontal position of the float l2 at a predetermined position, control rods l5 are arranged around the float l2 at equal intervals on the same circumference, that is, at four positions at the vertices of a square. In the wooden example, the control rods 15 are placed at the four vertices of an outer square whose side length is the length of the diagonal of the float 12.
16 is a small reversible motor that is attached to one end of each control rod 15 and rotates the control rod, for example, using a step motor or the like. 17 is a support plate fixed to the inner wall of the pressure receiving pipe 1O at least at a predetermined position above the maximum rising position of the hydraulic fluid 11, and the control rod 15 is connected to a female thread 18 formed perpendicularly through the support plate 17. A male thread formed on the circumferential surface is fitted. Therefore, the small motor l6 rotates normally (clockwise).
Then, the control rod l5 descends and the small motor 16 reverses (
counterclockwise), the control rod l5 will rise.

A sensor 19 serves as a monitor for detecting the movement of the float l2 in the horizontal direction, and uses, for example, a reflective photo-interrupter made of a photodiode and a semiconductor transistor. The four sensors 19 detect when the float 12 is at the center of the liquid level as shown in FIG. 1(B).
In order that the emitted light (X I- are arranged at equal intervals. 20 is a through hole opened in the support plate 17 through which the light beam l4 passes. Next, the operation of the embodiment of the present invention will be explained. Hydraulic fluid container (U
Since the diameter of the tube 10 is increased to avoid capillarity, it becomes difficult to obtain the effect of natural surface tension synthesis that holds the float 12 at the center of the surface of the working fluid 11. However, since the control rods 15 are placed at the four vertices of the outer square, the control rods 15 create small round protrusions on the liquid surface at four points, and when the liquid surface is quiet, the float The combination of surface tension with 12 serves as the base of the restoring force for the displacement of float 12. Therefore, according to the wooden example, the effect of holding the float l2 at a predetermined detection position of the originally desirable liquid level that avoids capillary action is enhanced.

On the other hand, in response to the displacement of the float l2 when the liquid level is flowing, the surface tension has decreased due to the liquid level flowing, so the float l2 must be actively restored to the predetermined position. Must be. However, it must not restrict the vertical movement of float l2. Therefore, in this example,
The horizontal deviation of the float 12 is detected by four sensors 19, and the control rod 15 is moved in and out of the liquid surface to control the flow in the opposite direction so that the float 12 returns to a predetermined position on the liquid surface. In other words, when the motor 16 is rotated in the forward direction and the control rod 15 is pulled down, the surrounding hydraulic fluid 11 is pulled down due to its viscosity, as shown in Fig. 2, which shows the liquid flow situation with arrows. As it is continuously dragged in the same direction, a local flow occurs downward, and the liquid level of the working fluid 11 flows in the direction of the control rod l5, so the float l2 controls forward rotation as shown by the arrow. Approach bar 15. On the other hand, the control rod l is rotated in the reverse direction by rotating the motor l6.
5, a local upward flow occurs for the same reason as above, and the float l2 moves away from the counter-rotating control rod l5.

Therefore, when the float 12 deviates from the predetermined position, if the float 12 pulls up the approaching control rod 15 by reverse rotation, and at the same time pulls down the control rod facing the control rod by normal rotation, the hydraulic fluid 11 A local current wJ (convection) occurs simultaneously and quickly restores the float l2 to its predetermined position. Also, the rotational speed of the motor l6, that is, the control rod l5
By variably controlling the lifting and lowering speeds of the floats l2, the local flow speed of the hydraulic fluid 11 can be changed. By controlling the direction and speed of rotation, even when the hydraulic fluid l1 is flowing rapidly, the float l2
can be maintained in place.

The sensor l9 in FIG. 1 is for detecting the positional deviation of the float l2, and if the emitted light from the sensor l9 hits anything other than the reflector 13, the detection signal is in the OFF state, but the output When the emitted light hits the reflector l3, its detection signal turns ON, indicating that it has approached the correspondingly placed control rod 15.

In this way, by operating and stopping the control rod 15, the float 12 is returned to the predetermined position 1it by utilizing the flow of the liquid level and surface tension, but in any case, the acting force is
It should be noted that the effect obtained by the present invention may not be fully expected if the float is too heavy, since the original liquid level is a very small force that does not impair the action (buoyancy) exerted on the float l2. be. FIG. 3 shows a schematic circuit configuration of a control system according to an embodiment of the present invention. In FIG. 3, numeral 30 is a control circuit that controls the rotation of each small motor 16 in accordance with the detection signal from each sensor 19, and is composed of a -M type microcomputer or a logic circuit. 3l is a driver (drive circuit) that controls the rotational direction and rotation speed of the corresponding small motor 16 according to a control signal from the control circuit 30.

Figure 4 shows four sensors 1 arranged in the arrangement shown in Figure 1 (B).
9 (XI, X2. X3+ X4) (7) Detection signal and small motor 16 (Yl, Y2, Y3, Y
4) Indicates the rotation direction.

Here, "1" of the sensor 19 indicates that the emitted light hits the reflector 13, and "0" indicates that the emitted light hits something other than the reflector 13. Therefore, as shown in FIG. 1, if the values of the detection signals of all the sensors l9 are "0", the float 12
is located at a predetermined position on the liquid level, for example at the center position, so there is no need to rotate the motor l6.

On the other hand, “+1” of motor l6 indicates forward rotation;
6 is rotated forward, the control rod 15 is pulled down, and the float l
It will attract 2. Also, ″-1 of motor l6
” indicates reverse rotation, and control rod 1 is rotated due to reverse rotation of motor l6.
5 is pulled up, and the float 12 moves away.

As shown in FIG. 4, when the output signal of any sensor l9 becomes "1", the control circuit 30
By rotating the motor l6 near the motor in the opposite direction and rotating the other motor l6 facing forward in the forward direction, a plurality of control rods l5 are simultaneously lowered and raised, thereby moving the float l2 to a predetermined position. When all the output signals of the sensor l9 become "0", the driving of the motor lδ is stopped.

Note that the control circuit 30 can also be configured with a logic circuit for the control contents shown in FIG. 4, but the control contents shown in FIG. A control signal to the driver 3l can be generated.

1 plate a week Next, a modification of the above-described embodiment of the present invention will be described.

In the above embodiment (hereinafter referred to as the present example), the plurality of control rods l5 are pulled up and lowered at the same time, but the present invention is not limited to this, and the control rods l5 are pulled up and lowered simultaneously.
Alternatively, it is of course possible to restore the float 12 to the predetermined position by performing one of the lowering operations alone. In this case, for example, any control rod l5
Until the control rod 15 reaches near the liquid level, the liquid level flow is controlled only by pulling up the control rod 15, and when the tip of any control rod 15 reaches near the liquid level, the liquid level flow is controlled only by pulling down the control rod 15. , and then when the tip of the control rod 15 reaches the lowering limit position, the liquid level flow control is performed only by pulling up the control rod 15. If the operation of the control circuit 30 is repeatedly switched, it is relatively easy. short control rod 1
5, it is possible to perform continuous control for a long time. At this time, the vertical position of the tip of the control rod 15 is motor l8.
It can be easily recognized by the number of revolutions or microswitches. Further, in this example, the case where four control rods 15 and four sensors 19 are provided is illustrated, but there may be any number of these as long as they are two or more.

Further, in this example, a combination of the small motor 16 and the control rod 15 is illustrated as a means for causing local flow by raising or lowering the hydraulic fluid IT, but the present invention is not limited to this. Instead of the small rotary motor 16, drive means such as a linear motor, electromagnetic actuator, pneumatic or hydraulic actuator can be used, and instead of the threaded control rod l5, a flat round rod, a long A board etc. can be used. Also, a combination mechanism of a small endless belt and a rotating motor is also applicable. Further, the tip portion of the control rod 15 is not limited to metal, and an appropriate material such as plastic or felt may be selected depending on the properties of the hydraulic fluid 11.

Furthermore, although a square shape is shown as the shape of the float 12, the present invention is not limited to this. For example, a plurality of symmetrical flat or Any float having a curved surface may be used. Further, the reflector 13 may be a corner cube instead of a plane mirror, and the entire surface of the float 12 may be made of a mirror surface. Furthermore, although the light emitted from the sensor l9 in this example is made to hit a part other than the reflector l3 when the float l2 is in a predetermined position, the same effect can be achieved even if the light is made to hit the peripheral part of the reflector l3. It is clear that we can obtain Further, although the support plate 17 is shown fixed to the pressure receiving pipe 1O in this example, the position of the support plate 17 may be adjusted manually or automatically according to a change in the position of the liquid level. Further, the support plate 17 is not limited to a plate-like member, and may be a structure made by combining a plurality of rods, and furthermore, a guide rail for supporting and guiding the small motor 16 may be provided on the support plate 17.

Another Embodiment FIG. 5 shows a circuit configuration of a control system according to another embodiment of the present invention. Since the other configurations are almost the same as those in FIG. 1 and FIG. 2, the explanation thereof will be omitted.

In FIG. 5, 4l is an ultra-small imaging camera attached to the lower surface of the support plate l7 or directly above the float l2,
For example, a device using a COD (charge coupled device) or a device using an optical fiber such as that used in gastrocameras can be used. Float 1 imaged by camera 41
The second video signal passes through the imaging circuit 42 and is sent to the image processing circuit 43.
Then, the signal is converted into ^/0 (analog/digital), amplified to a predetermined level, and input to the contour extraction circuit 44.

The contour extraction circuit 44 extracts the contour portion of the float 12 from the input digital image signal using a conventional general method, and sends the extracted signal to the arithmetic circuit 45. In this case, the outline extraction circuit 44 suffices to extract the outline of a predetermined outline on the float 12.

The calculation circuit 45 calculates the current position and moving speed of the float l2 from the input contour data based on a predetermined calculation formula, and outputs the calculation results to the control circuit 46. The control circuit 46 calculates the correction amount for restoring the float l2 to the predetermined position and the control amount for each motor 16 based on the data input from the arithmetic circuit 45, and sends the calculation results to each driver 31 as a control signal. Output. Each driver 3l controls the rotational direction and rotational speed of the corresponding motor l6 according to the control signal, and restores the float l2 to a predetermined position. In the embodiment shown in Fig. 5, the circuit configuration is somewhat more complicated than in the embodiment shown in Fig. 3, which increases the cost. It is also suitable when you are In addition, it is possible to apply pattern recognition technology and servo control technology for temporary objects to extract the outline of a tree example, and it is easy to perform. By changing the calculation coefficients, various It is highly versatile and compatible as it can be easily applied to hydraulic fluids and pressure receiving pipes. Note that the circuit 44.
45. 48 can also be realized by software using a microcomputer and a control program.

(Effects of the Invention) As explained above, according to the present invention, the position of the float can be quickly restored to a predetermined position both when the liquid level is stationary and when it is flowing. As a result, the flow of the liquid level and floats is suppressed, making continuous, stable and high-resolution liquid level recognition possible. The effect is that resolution measurement can be easily achieved with high accuracy.

[Brief explanation of the drawing]

FIG. 1 shows the main structure of an embodiment of the present invention, and FIG.
is a longitudinal sectional view, FIG. 2 is a cross-sectional view taken along the line A-A', FIG. Figure 4 is a block diagram showing the circuit configuration of a control system according to an embodiment of the present invention, Figure 4 is an explanatory diagram showing the control contents of the control circuit shown in Figure 3, and Figure 5 is a control system according to another embodiment of the present invention. A block diagram showing the circuit configuration of FIG. 6. Figures 7 and 8 are longitudinal sectional views showing the structure of a conventional float type device, respectively. lO...Pressure tube (U
11... Hydraulic fluid, 12... Float, 13... Reflector, l4... Light beam, 15... Control rod, l6... Small motor, l7 ...Support plate, 30...Control circuit, 31...Driver, 41...Camera, 44...Contour extraction circuit, 45...Arithmetic circuit, 46...Control circuit. Figure Figure

Claims (1)

[Claims] 1) Flow control using a plurality of rod-shaped or plate-shaped rods extending into the liquid and arranged at symmetrical positions around a float floating on the liquid surface whose vertical position varies. a member; a driving means for individually raising and lowering the flow control member in the liquid; a detecting means for detecting the position of the float; A liquid level flow control mechanism comprising: control means for controlling a drive means to return the float to a predetermined position in a horizontal direction. 2) The detection means detects the position and movement speed of the float, and the control means controls the rising speed or the movement speed of the flow control member via the drive means according to the position and movement speed detected by the detection means. 2. The liquid level flow control mechanism according to claim 1, wherein the flow direction and speed of the liquid level acting on the float are adjusted and controlled by controlling the descending speed.