JP7188696B2 - Installation position calculation method of ultrasonic liquid level measuring device and ultrasonic sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic liquid level measuring device that uses ultrasonic waves to measure the liquid level in a vertically elongated tank in which liquid is stored.

As a liquid level measuring device using ultrasonic waves, for example, those disclosed in Patent Documents 1 and 2 are known.

The liquid level measuring device shown in Patent Document 1 uses an ultrasonic sensor to measure the liquid level in a pipe arranged substantially horizontally. An ultrasonic sensor is installed in the direction of It measures the liquid level at that point in time based on the speed of sound of the ultrasonic wave.

In this liquid level measuring device, it is essential that the ultrasonic waves emitted from the ultrasonic sensor enter the liquid surface perpendicularly and are reflected here, and the reflected waves are received by the ultrasonic sensor on the same route as the outward trip. Therefore, the ultrasonic sensor is placed vertically upward on the outer surface of the lowest point of the pipe, that is, at a position where the inclination angle at that position is 0 ° (a position parallel to the liquid surface) It was installed facing

Incidentally, for example, when the installation position of the ultrasonic sensor deviates in the circumferential direction from the lowest point position of the pipe, the path of the ultrasonic wave transmitted from the ultrasonic sensor deviates from the vertical direction, causing vertical reflection on the liquid surface. Therefore, the ultrasonic wave propagation time becomes longer than when the ultrasonic wave path is in the vertical direction, making it impossible to measure the liquid level with high accuracy.

In the liquid level measuring device disclosed in Patent Document 2, when an ultrasonic sensor is installed at the bottom of a pipe to measure the liquid level in the pipe, the ultrasonic sensor is installed at the lowest point of the pipe. For the purpose (in other words, for the purpose of making the ultrasonic path in the liquid vertical), the ultrasonic sensor (ultrasonic probe) and the gravity sensor are integrated, and the axis of the ultrasonic sensor is in the vertical direction The position of the ultrasonic sensor at the time when the output of the gravity sensor is maximized is configured such that the gravity sensor outputs the maximum signal when facing, and the ultrasonic sensor is moved along the outer surface of the pipe. is the lowest point of the piping, and the ultrasonic sensor is installed here.

In this way, in the liquid level measuring device using ultrasonic waves, the ultrasonic wave path in the liquid is set in the vertical direction to minimize the ultrasonic wave propagation time, thereby ensuring the accuracy of the liquid level measurement. there is

JP 2013-213717 A JP 2017-120187 A

By the way, the liquid level measurement is required not only for the pipes through which the liquid flows but also for the vertical tanks in which the liquid is stored. Therefore, as a means for measuring the liquid level of the liquid stored inside this vertically elongated tank, it is possible to measure using ultrasonic waves, as in the case of piping.

However, in this vertical tank, there are circumstances in which the methods shown in the above patent documents cannot be applied as they are due to structural reasons different from those of piping. That is, in measuring the liquid level in a pipe, an ultrasonic sensor is installed at the bottom of the pipe so that the ultrasonic wave path in the liquid is in the vertical direction. That is, since the outlet pipe for the liquid is connected to the center position of the tank bottom having a hemispherical shape, it is structurally inappropriate to install the ultrasonic sensor vertically upward at the center position of the tank bottom. It is possible.

Under these circumstances, there is a demand for the development of a liquid level measurement technique that can accurately measure the liquid level in the tank even when the ultrasonic sensor is installed at a position off the center of the bottom of the vertically elongated tank.

Therefore, the present invention provides an ultrasonic liquid level measuring device that can accurately measure the liquid level in the tank by installing an ultrasonic sensor at the bottom inclined part of the vertically long tank, and the tank of the ultrasonic sensor This was made for the purpose of proposing a method of calculating the installation position on the bottom slope.

The present invention employs the following configuration as a specific means for solving such problems.

In a first invention of the present application, an ultrasonic liquid level measuring device that measures the liquid level of a liquid stored in a tank having a substantially hemispherical bottom using ultrasonic waves emitted from an ultrasonic sensor,
The ultrasonic sensor was installed on the inclined bottom portion of the tank via a resin jig having a predetermined wedge angle, and the ultrasonic wave emitted from the ultrasonic sensor transmitted through the steel plate at the bottom of the tank and entered the liquid. After that, the ultrasonic waves that are reversed by the reflection on the liquid surface and propagate to the bottom of the tank are configured so that the path in the liquid is in the vertical direction,
The installation position of the ultrasonic sensor on the inclined part of the tank bottom is a position corresponding to the outer surface inclination angle (θ ₅ ) defined by the following formulas 1 to 5, and the outer surface inclination angle (θ ₅ ) are the inclination angle (θ ₁ ) of the tank inner surface, the underwater refraction angle (θ ₂ ), the refraction angle in the steel on the inner surface of the tank (θ ₃ ), the refraction angle in the steel on the outer surface of the tank (θ ₄ ), and the resin jig It is characterized in that it is automatically determined by determining any one of the wedge angles (θ ₆ ).

here,
Formula 1: Inclination angle of tank inner surface (θ ₁ ) = Angle of refraction in water (θ ₂ )
Equation 2: Inclination angle of tank inner surface (θ ₁ ) - Inclination angle of tank outer surface (θ ₅ )
= Angle of refraction in steel on the inner side of the tank (θ ₃ ) - Angle of refraction in steel on the outer side of the tank (θ ₄ ) = δ
Equation 3 sin δ=sin θ ₄ [(R _o /R _i ) cos θ ₄ −√(1−(R _o /R _i ) ² ·sin ² θ ₄ )
Equation 4: cos θ ₆ /ca = sin θ ₄ / _{c t}
Equation 5: sin θ ₂ / _cw = sin θ ₃ /c _t
R _i is the radius of curvature of the inner surface of the bottom of the tank
_Ro is the radius of curvature of the outer surface of the bottom of the tank θ ₆ is the wedge angle of the resin jig, which corresponds to the angle of incidence of ultrasonic waves on the bottom of the tank.
c _w is longitudinal sound velocity in water
c _a is longitudinal wave speed in resin
c _t is the shear wave speed in steel.

In the second invention of the present application, in the ultrasonic liquid level measuring device according to the first invention, the angle of inclination (θ ₅ ) of the outer surface and the angle of refraction (θ ₂ ) in water are in the range of 17° to 24°. Alternatively, the angle of refraction (θ ₄ ) in steel on the outer surface side of the tank is set to be in the range of 40° to 60°.

According to a third invention of the present application, in the ultrasonic liquid level measuring device according to the first or second invention, the ultrasonic sensor is a transverse wave oblique angle ultrasonic sensor.

In the fourth invention of the present application, when measuring the liquid level of a liquid stored in a tank having a substantially hemispherical bottom using ultrasonic waves emitted from an ultrasonic sensor installed at the bottom inclined portion of the tank, An ultrasonic sensor installation position calculation method for calculating the installation position of the ultrasonic sensor on the bottom inclined portion of the tank,
The outer surface inclination angle (θ ₅ ) calculated based on the following formulas 1 to 5, the inclination angle (θ ₁ ) of the tank inner surface, the underwater refraction angle (θ ₂ ), and the steel refraction angle on the inner surface side of the tank (θ ₃ ), the refraction angle in the steel on the tank outer surface side (θ ₄ ), and the wedge angle (θ ₆ ) of the resin jig, which is automatically determined by determining the outer surface inclination angle The position corresponding to (θ ₅ ) is calculated as the installation position of the ultrasonic sensor on the bottom inclined portion of the tank.

here,
Formula 1: Inclination angle of tank inner surface (θ ₁ ) = Angle of refraction in water (θ ₂ )
Equation 2: Inclination angle of tank inner surface (θ ₁ ) - Inclination angle of tank outer surface (θ ₅ )
= Angle of refraction in steel on the inner side of the tank (θ ₃ ) - Angle of refraction in steel on the outer side of the tank (θ ₄ ) = δ
Equation 3 sin δ=sin θ ₄ [(R _o /R _i ) cos θ ₄ −√(1−(R _o /R _i ) ² ·sin ² θ ₄ )
Equation 4: cos θ ₆ /ca = sin θ ₄ / _{c t}
Equation 5: sin θ ₂ / _cw = sin θ ₃ /c _t
R _i is the radius of curvature of the inner surface of the bottom of the tank
_Ro is the radius of curvature of the outer surface of the bottom of the tank θ ₆ is the wedge angle of the resin jig, which corresponds to the angle of incidence of ultrasonic waves on the bottom of the tank.
c _w is longitudinal sound velocity in water
c _a is longitudinal wave speed in resin
c _t is the shear wave speed in steel.

(a) First invention of the present application According to the ultrasonic liquid level measuring device according to the first invention of the present application, the ultrasonic sensor is attached to the bottom of the tank via a resin jig having a predetermined wedge angle. Installed on an inclined part, the ultrasonic wave transmitted from the ultrasonic sensor, transmitted through the steel plate at the bottom of the tank, propagated in the liquid, and further reflected by the liquid surface, propagated to the bottom side of the tank. Since the path is configured so that it is in the vertical direction, even if equipment such as an outlet pipe is installed at the center of the bottom of the tank, it is not affected by this. An ultrasonic sensor can be installed in the tank to accurately measure the liquid level in the tank, and a wave liquid level measuring device with a high degree of freedom in the installation position of the ultrasonic sensor can be provided.

In addition, since the ultrasonic sensor is installed on the inclined part of the bottom of the tank, the ultrasonic waves that are multiple-reflected in the steel plate after being incident on the steel plate are reflected each time they are reflected on the inner and outer surfaces of the steel plate. Since it gradually moves away from the ultrasonic sensor along the slope of the steel plate, this multiple reflected wave does not appear as a received waveform. , in the case where the ultrasonic sensor is installed vertically upward at the lowest position of the pipe, the ultrasonic waves are multiple-reflected at the same position in the steel plate, and this multiple-reflected wave appears as the received waveform. It is possible to improve the detection accuracy of the ultrasonic signal and provide a more highly accurate ultrasonic liquid level measuring device.

Furthermore, the installation position of the ultrasonic sensor on the inclined part of the tank bottom is set to a position corresponding to the outer surface inclination angle (θ ₅ ) defined by the following formulas 1 to 5, and the outer surface inclination angle ( θ ₅ ) is the angle of inclination (θ ₁ ) of the inner surface of the tank, the angle of refraction in water (θ ₂ ), the angle of refraction in steel on the inner surface of the tank (θ ₃ ), the angle of refraction in steel on the outer surface of the tank (θ ₄ ), and the Since it is automatically determined by determining any one of the wedge angles (θ ₆ ) of the jig, any one of these angle parameters is determined, and based on that, the above By positioning the ultrasonic sensor on the inclined part of the tank bottom, the condition of "inclination angle of the tank inner surface (θ ₁ ) = underwater refraction angle (θ ₂ )" is automatically linked, that is, the inside of the tank It is possible to provide an ultrasonic liquid level measuring device that also satisfies the condition that the ultrasonic wave path in the liquid is vertical, and as a result, the accuracy of liquid level measurement is ensured.

( b ) Second Invention of the Present Application A second invention of the present application is the ultrasonic liquid level measuring device according to the first invention, wherein the outer surface inclination angle (θ ₅ ) is replaced by the underwater refraction angle (θ ₂ ) is in the range of 17° to 24°, or the refraction angle ₍ θ ₃ ) of the transverse wave in steel is in the range of 40° to 60°. The range of 17° to 24° and the range of 40° to 60° in which the angle of refraction (θ ₃ ) of the transverse wave in the steel is 40° to 60° are ranges in which a high energy transmittance is obtained, that is, a range in which the transmission efficiency of ultrasonic waves is high. Therefore, the detection efficiency of the ultrasonic signal is high (the detection sensitivity is high), and more highly accurate liquid level measurement is ensured.

( c ) Third invention of the present application In the ultrasonic liquid level measuring device according to the third invention of the present application, since the ultrasonic sensor is configured with a transverse wave oblique ultrasonic sensor, the inside of the steel plate at the bottom of the tank The energy transmittance in is high, and more accurate liquid level measurement is ensured.

( d ) Fourth invention of the present application In the fourth invention of the present application, the liquid level of the liquid stored in the tank whose bottom is substantially hemispherical is irradiated from the ultrasonic sensor installed at the bottom inclined part of the tank. An ultrasonic sensor installation position calculation method for calculating the installation position of the ultrasonic sensor on the bottom inclined portion of the tank when measuring using ultrasonic waves, and calculating based on the following formulas 1 to 5 The outer surface inclination angle (θ ₅ ), which is the inclination angle (θ ₁ ) of the tank inner surface, the underwater refraction angle (θ ₂ ), the refraction angle (θ ₃ ) in the steel on the inner surface side of the tank, and the steel on the outer surface side of the tank The position corresponding to the outer surface inclination angle (θ ₅ ) automatically determined by determining either one of the refraction angle (θ ₄ ) and the wedge angle (θ ₆ ) of the resin jig is Since it is calculated as the installation position of the ultrasonic sensor on the bottom inclined part of the tank, the installation position of the ultrasonic sensor that satisfies the condition that the ultrasonic wave path in the liquid in the tank is vertical is calculated. , the accuracy of liquid level measurement using the ultrasonic sensor is ensured.

It is a sectional view showing the state where the liquid level measuring device concerning the embodiment of the present invention was installed in the liquid container. It is an enlarged view of the A section of FIG. FIG. 4 is a diagram of “angle of refraction in water—energy transmittance” showing ultrasonic transmission efficiency. It is an ultrasonic waveform diagram in the liquid level measuring device according to the embodiment of the present invention.

FIG. 1 shows a vertically elongated tank 1 having a hemispherical top portion 1a and a bottom portion 1b, and an outlet pipe 2 provided at the center position (lowest position) of the bottom portion 1b. At the inclined portion extending radially outward from the center position of the bottom portion 1b of the tank 1, the main part of the ultrasonic liquid level measuring device 10 according to the embodiment of the present invention is provided so as to avoid the outlet pipe 2. An ultrasonic sensor 11, which is a component, is installed. In addition to the ultrasonic sensor 11 , the liquid level measuring device 10 includes an arithmetic device 12 , sound speed data 13 and an output section 14 .

The ultrasonic sensor 11 transmits ultrasonic waves and receives reflected waves, and the time from the transmission of ultrasonic waves from the ultrasonic sensor 11 to the reception of the reflected waves at the ultrasonic sensor 11, that is, , the ultrasonic wave propagation time is input as time information to the arithmetic unit 12, and the arithmetic unit 12 calculates the liquid level based on this time information and the sound velocity information of the ultrasonic waves input from the sound velocity data 13. Output from the output unit 14 .

As described above, the ultrasonic sensor 11 acquires the ultrasonic wave propagation time, which is basic information for calculating the liquid level. 11 is installed not in the center of the bottom (i.e., the position of the inclination angle of 0) but on the inclined part around it, the ultrasonic wave emitted from the ultrasonic sensor 11 is vertically reflected on the liquid surface and travels along the same path. It is essential that the ultrasonic wave is received by the ultrasonic sensor 11 side, that is, that the ultrasonic wave path in the liquid is set in the vertical direction.

The present invention is characterized in that the installation position of the ultrasonic sensor 11 on the tank bottom 1b is set so that the ultrasonic wave path in the liquid is in the vertical direction. is accurately set by calculation as shown below. A method for setting the installation position of the ultrasonic sensor 11 will be described below with reference to FIG.

FIG. 2 is an enlarged view of the installation state of the ultrasonic sensor 11 on the inclined bottom portion of the tank 1. As shown in FIG. The ultrasonic sensor 11 is used as a transverse wave oblique ultrasonic sensor (that is, the ultrasonic wave is propagated in the steel plate 31 of the bottom portion 1b in a transverse wave mode), and the incident angle to the bottom portion 1b is For adjustment reasons, it is installed on the outer surface of the inclined portion via a wedge-shaped resin jig 4 . As the material resin of the jig 4, for example, acryl, polystyrene, or the like can be applied.

After propagating through the jig 4 in longitudinal wave mode, the ultrasonic waves emitted from the ultrasonic sensor 11 are mode-converted into transverse waves when incident on the steel plate 31 from the jig 4, and pass through the steel plate 31 in transverse wave mode. , is mode-converted into longitudinal waves when incident on the liquid from the steel plate 31, and propagates in the liquid in the longitudinal wave mode. Also, the ultrasonic waves are refracted when they enter the steel plate 31 from the jig 4 and when they enter the liquid from the steel plate 31 .

Each angular parameter in the propagation path of the ultrasonic wave shown in FIG. 2 is as follows.
“θ ₁ ”: Tilt angle of tank inner surface “θ ₂ ”: Refraction angle in water “θ ₃ ”: Refraction angle in steel on tank inner surface side “θ ₄ ”: Refraction angle in steel on tank outer surface side “θ ₅ ” … Inclination angle of tank outer surface ”θ ₆ ” … Wedge angle of jig

These angle parameters are mutually connected by the following relationships.
Inclination angle of tank inner surface (θ ₁ ) = Refraction angle in water (θ ₂ ) (Formula 1)
Inclination angle of tank inner surface (θ ₁ ) - Inclination angle of tank outer surface (θ ₅ )
= Angle of refraction in steel on the inner surface of the tank (θ ₃ ) - Angle of refraction in steel on the outer surface of the tank (θ ₄ ) = δ (Formula 2)
sin δ=sin θ ₄ [(R _o /R _i ) cos θ ₄ −√(1−(R _o /R _i ) ² ·sin ² θ ₄ ) (Formula 3)
cos θ ₆ /ca = sin θ ₄ / _{c t} (Formula 4)
sin θ ₂ / _cw = sin θ ₃ /c _t (Formula 5)
(θ ₆ ) is the wedge angle of the jig 4, (R _i ) is the radius of curvature of the inner surface of the tank bottom, and (R ₀ ) is the radius of curvature of the outer surface of the tank bottom.
In addition, when the thickness d (=R _o - R _i ) of the steel plate 31 is smaller than the radius of curvature (R _i ) (d<<R _i ), the above (Equation 3) can be expressed by the following approximation: I can use it.
δ=(d/R _i ) tan θ ₄ [rad] (Formula 3′)

The above (formula 1) to (formula 3) are based on the geometric relationship between the ultrasonic wave path and the tank 1, and (formula 4) and (formula 5) are derived from Snell's law. is. Further, each of these angle parameters has a relationship that if any one of them is determined, the other parameters are automatically determined. In addition, the above (formula 1) is a requirement for the ultrasonic path in the liquid to be in the vertical direction, and the inclination angle (θ ₅ ) of the tank outer surface in (formula 2) is the above-mentioned ultrasonic wave at the tank bottom 1b. It shows the installation position of the sonic sensor 11 (the incident position of the ultrasonic wave from the ultrasonic sensor 11 to the steel plate 31).

Here, several methods for determining the installation position of the ultrasonic sensor 11 will be described based on the above (formula 1) to (formula 5).

A: Method 1 A method in which the wedge angle “θ ₆ ” of the jig 4 is specified as an angle (for example, 45°) among the above angle parameters. In 5), the position corresponding to the inclination angle (θ ₅ ) of the outer surface of the tank is determined by assuming that the wedge angle "θ ₆ " is known. By installing the ultrasonic sensor 11 at this position, the ultrasonic wave path in the liquid in the tank 1 is always vertical, and from the time the ultrasonic wave is transmitted from the ultrasonic sensor 11, it is reflected vertically on the liquid surface. The time (ultrasonic wave propagation time) until the ultrasonic wave is received by the ultrasonic sensor 11 is always accurately measured.

Using this accurate ultrasonic wave propagation time (T), the arithmetic unit 12 calculates the liquid level (H) according to the following (Equation 6) (see FIG. 1).
(Liquid level) H = c _w {(T/2) - (L ₁ /c ₁ ) - (L ₀ /c _a )} (Equation 6)
Here, (L ₁ ) in the above (Equation 6) is a constant determined from the dimensions of the jig 4, and (L ₁ ) depends on the geometric shape of the tank bottom 1b and the refraction angle (θ ₄ ) input in the steel. , is given by the following (equation 7).
L ₁ = √{R _i ² +R _o ² ( _2cos ² θ ₄ −1)−2R _o cos θ ₄ √(R _i ² −R 0 ² sin ² θ ₄ )} (Formula 7)
In addition, in the above (Equation 7), when the thickness d (=R _o −R _i ) of the steel plate 31 is smaller than the radius of curvature (R _i ) (d<<R _i ), the following approximation is obtained. I can use it.
L ₁ = d/cos θ ₄ {1+(dtan ² θ ₄ /2R _i )} (Formula 7')

The liquid level that can be measured here is in the range from the full liquid level to the height of the installation position of the ultrasonic sensor 11 as shown in FIG. 1, and is lower than the height of the installation position of the ultrasonic sensor 11. Although the total blow liquid level cannot be measured, since the height difference between this total blow liquid level and the installation position of the ultrasonic sensor 11 is extremely small, the installation position of the ultrasonic sensor 11 can be treated as the total blow liquid level. It does not matter in practice.

B: Second method A method of specifying the installation position of the ultrasonic sensor 11, that is, the inclination angle (θ 5 ) of the outer surface of the tank.

In this case, in the above (formula 1) to (formula 5), the wedge angle (θ ₆ ) of the jig 4 is obtained by assuming that the tilt angle (θ ₅ ) is known, and the jig having this wedge angle (θ ₆ ) is obtained. 4, the ultrasonic sensor 11 is installed at a position corresponding to the inclination angle (θ ₅ ) of the outer surface of the tank. By installing the ultrasonic sensor 11 at this position, the ultrasonic wave path in the liquid of the tank 1 is always vertical, and the ultrasonic wave propagation time is always accurately measured. Then, using this accurate ultrasonic propagation time (T), the liquid level (H) is calculated by the above (Equation 6).

C: Third method A method for realizing more accurate liquid level measurement with high detection _sensitivity of ultrasonic signals. has limitations. That is, FIG. 3 shows the transmission efficiency of ultrasonic waves from the steel plate 31 through the liquid, reflected on the liquid surface, and back to the steel plate 31 again. Here, the horizontal axis is the angle of refraction in water (θ ₁ ), and the vertical axis is the energy transmittance. The closer the energy transmittance is to 100%, the less the energy loss and the higher the transmission efficiency of ultrasonic waves. do.

In FIG. 3, the dashed line indicates the energy transmittance corresponding to the angle of refraction in water when ultrasonic waves propagate in the steel plate 31 in longitudinal wave mode. The solid line indicates the energy transmittance corresponding to the refraction angle in water when the ultrasonic wave propagates in the steel plate 31 in the transverse wave mode. The numbers on each line indicate the refraction angle in steel.

From each diagram in FIG. 3, if a range with high ultrasonic transmission efficiency is selected, the refraction angle in steel (θ ₄ ) in the transverse wave mode is in the range of 40° to 60°, or the refraction angle in water (θ ₂ ) is in the range of 17° to 24°.

Therefore, when installing the ultrasonic sensor 11, the inclination angle (θ ₅ ) of the outer surface, which is the installation position of the ultrasonic sensor 11, and the angle of refraction (θ ₂ ) in water are in the range of 17° to 24°. or so that the refraction angle (θ ₄ ) in the steel of the transverse wave mode is in the range of 40° to 60°.

In this case, since the outer surface inclination angle (θ ₅ ) and the underwater refraction angle (θ ₂ ) or steel refraction angle (θ ₄ ) correspond one-to-one, for example, the outer surface inclination angle (θ ₅ ) is defined by the underwater refraction angle (θ ₂ ), the numerical value of the outer surface inclination angle (θ ₅ ) changes according to the numerical value of the underwater refraction angle (θ ₂ ), and the outer surface inclination angle ( When θ ₅ ) is defined by the refraction angle in steel (θ ₄ ), the numerical value of the outer surface inclination angle (θ ₅ ) changes according to the numerical value of the refraction angle in steel (θ ₄ ). Further, when the underwater refraction angle (θ ₂ ) or the underwater refraction angle (θ ₂ ) changes in this way, the wedge angle (θ ₆ ) of the jig ₄ also changes. ) or a jig 4 having a wedge angle (θ ₆ ) corresponding to the refraction angle (θ ₂ ) in water.

"Action and effect specific to the claimed invention"
(1) In the ultrasonic liquid level measuring device according to the present invention, the ultrasonic wave path in the liquid in the tank 1 is always vertical by installing the ultrasonic sensor 11 at the proper position as described above. Therefore, even if equipment such as the outlet pipe 2 is installed at the center of the bottom of the tank 1, the ultrasonic sensor can be installed on the slope away from the outlet pipe 2 without being affected by this. Therefore, it is possible to accurately measure the liquid level in the tank, and to provide an ultrasonic liquid level measuring device with a high degree of freedom regarding the installation position.

(2) In the ultrasonic liquid level measuring device according to the present invention, the ultrasonic sensor 11 is installed on the inclined portion of the bottom of the tank 1, so that after entering the steel plate 31, The multiple-reflected ultrasonic waves gradually move away from the ultrasonic sensor 11 along the inclination of the steel plate 31 each time they are reflected on the inner and outer surfaces of the steel plate 31, as indicated by the dashed lines in FIG. Multiple reflected waves do not appear as received waveforms. Therefore, for example, when an ultrasonic sensor is installed vertically upward at the center position of the bottom of the tank, or when an ultrasonic sensor is installed vertically upward at the lowest position of the pipe, the same position in the steel plate 31 The detection accuracy of the ultrasonic signal is improved compared to the one in which the multiple reflected waves appear as received waveforms, and a more highly accurate ultrasonic liquid level measuring device can be provided.

INDUSTRIAL APPLICABILITY The ultrasonic liquid level measuring device according to the present invention can be widely used as liquid level measuring means in tanks in various industrial fields provided with tanks.

DESCRIPTION OF SYMBOLS 1... Tank 2... Exit pipe 3... Pipe wall 4... Jig 10... Liquid level measuring device 11... Ultrasonic sensor 31... Steel plate

Claims (4)

An ultrasonic liquid level measuring device that measures the liquid level of a liquid stored in a tank having a substantially hemispherical bottom using ultrasonic waves emitted from an ultrasonic sensor,
The ultrasonic sensor was installed on the inclined bottom portion of the tank via a resin jig having a predetermined wedge angle, and the ultrasonic wave emitted from the ultrasonic sensor transmitted through the steel plate at the bottom of the tank and entered the liquid. After that, the ultrasonic waves that are reversed by the reflection on the liquid surface and propagate to the bottom of the tank are configured so that the path in the liquid is in the vertical direction,
The installation position of the ultrasonic sensor on the inclined part of the tank bottom is a position corresponding to the outer surface inclination angle (θ ₅ ) defined by the following formulas 1 to 5, and the outer surface inclination angle (θ ₅ ) is the inclination angle (θ1) of the tank inner surface, the underwater refraction angle ₍ θ2) _, the refraction angle in the steel _on the inner surface of the tank (θ3), the refraction angle in the steel on the outer surface of the tank (θ4), and the wedge of the resin jig An ultrasonic liquid level measuring device characterized in that it is automatically determined by determining any one of the angles (θ ₆ ).
here,
Formula 1: Inclination angle of tank inner surface (θ1) ₌ Angle of refraction in water (θ2)
Equation 2: Inclination angle of tank inner surface (θ1) - Inclination angle of tank outer surface ₍ θ5)
= Angle of refraction in steel on the inner side of the tank (θ ₃ ) - Angle of refraction in steel on the outer side of the tank (θ ₄ ) = δ
Equation 3 sin δ=sin θ ₄ [(R _o /R _i ) cos θ ₄ −√(1−(R _o /R _i ) ² ·sin ² θ ₄ )
Equation 4: cos θ ₆ /ca = sin θ ₄ / _{c t}
Equation 5: sin θ ₂ / _cw = sin θ ₃ /c _t
R _i is the radius of curvature of the inner surface of the bottom of the tank
_Ro is the radius of curvature of the outer surface of the bottom of the tank θ ₆ is the wedge angle of the resin jig, which corresponds to the angle of incidence of ultrasonic waves on the bottom of the tank.
c _w is longitudinal sound velocity in water
c _a is longitudinal wave speed in resin
c _t is the shear wave speed in steel. In claim 1 ,
The outer surface inclination angle (θ ₅ ) is such that the water refraction angle (θ ₂ ) is in the range of 17° to 24°, or the refraction angle (θ ₄ ) in steel on the tank outer surface side is in the range of 40° to 60°. An ultrasonic liquid level measuring device characterized by being set so as to be. In claim 1 or 2 ,
The ultrasonic liquid level measuring device, wherein the ultrasonic sensor is a transverse wave oblique angle ultrasonic sensor. When measuring the liquid level of a liquid stored in a tank having a substantially hemispherical bottom by using ultrasonic waves emitted from an ultrasonic sensor installed on the inclined bottom part of the tank, the ultrasonic sensor of the tank A method for calculating an installation position of an ultrasonic sensor for calculating an installation position on a bottom inclined portion, comprising:
The outer surface inclination angle (θ ₅ ) calculated based on the following formulas 1 to 5, the inclination angle (θ 1) of the tank inner surface, the underwater refraction angle (θ ₂ ), and the steel refraction angle on the inner surface side of the tank ( θ ₃ ), the refraction angle in the steel on the tank outer surface side (θ ₄ ), and the wedge angle (θ ₆ ) of the resin jig, which is automatically determined by determining the outer surface inclination angle ( θ ₅ ) is calculated as the installation position of the ultrasonic sensor on the inclined bottom portion of the tank.
here,
Formula 1: Inclination angle of tank inner surface (θ1) ₌ Angle of refraction in water (θ2)
Equation 2: Inclination angle of tank inner surface (θ1) - Inclination angle of tank outer surface ₍ θ5)
= Angle of refraction in steel on the inner side of the tank (θ ₃ ) - Angle of refraction in steel on the outer side of the tank (θ ₄ ) = δ
Equation 3 sin δ=sin θ ₄ [(R _o /R _i ) cos θ ₄ −√(1−(R _o /R _i ) ² ·sin ² θ ₄ )
Equation 4: cos θ ₆ /ca = sin θ ₄ / _{c t}
Equation 5: sin θ ₂ / _cw = sin θ ₃ /c _t
R _i is the radius of curvature of the inner surface of the bottom of the tank
_Ro is the radius of curvature of the outer surface of the bottom of the tank θ ₆ is the wedge angle of the resin jig, which corresponds to the angle of incidence of ultrasonic waves on the bottom of the tank.
c _w is longitudinal sound velocity in water
c _a is longitudinal wave speed in resin
c _t is the shear wave speed in steel.

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