JP2005265625A - Liquefied gas storage tank and method for detecting remaining amount of liquefied gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefied gas storage tank which enables a remaining amount of liquefied gas to be easily detected and makes its maintenance easy, even in the case the storage tank is buried in the ground. <P>SOLUTION: A reed 4 is disposed at the upper section (vicinity of a valve 3) of a gas extraction tube 2 in a tank main body 1 storing liquefied LP gas 6. The reed 4 is vibrated by a flow of gas which flows out. The vibration frequency is determined by its internal pressure and the length of air column in the gas extraction tube 2. Accordingly, the length of air column in the gas extraction tube 2 is calculated based on the vibration frequency, and the height of a liquid level 6a of the liquefied gas 6 is calculated on this basis, and the remaining amount of the liquefied LP gas is calculated based on the height of the liquid level. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in a method for detecting the remaining amount of liquefied gas from the outside in a stationary storage tank such as a bulk tank for supplying liquefied gas.

  As a method for supplying liquefied LP gas for consumer use, a conventional large-sized tank (bulk tank) is used in addition to a conventional small-sized tank, and the tank is replaced every time it is empty. In the meantime, a bulk system in which liquefied LP gas is replenished by a tank truck has come to be performed. In this bulk system, large storage tanks are often installed with most of the storage tanks buried in the ground to save installation space.

In this bulk method, it is necessary to know when to replenish the gas in the storage tank, so it is necessary to constantly or periodically measure the remaining amount of liquefied LP gas in the tank. Conventionally, as a method of measuring the remaining amount of liquefied LP gas in a tank, a float type liquid level gauge (for example, the prior art in Patent Document 1) in which a meter is rotated by a float floated on the liquefied gas in the tank is generally used. However, in recent years, as a method for electrically measuring the remaining amount, an ultrasonic wave is radiated from the bottom of the tank, and the remaining amount is measured based on the time it takes for it to be reflected back from the liquid level of the liquefied gas. A sound wave method (for example, Patent Document 2), a strain gauge method (for example, Patent Document 1) for detecting the remaining amount of liquefied gas with a strain gauge attached to the bottom of the tank, and a side surface of the tank is struck and based on the resonance frequency A method such as a striking method (for example, Patent Document 3) for detecting the remaining amount of liquefied gas has been proposed.
JP-A-11-325397 JP 2002-148093 A JP 7-333037 A

  However, the conventional float type liquid level gauge is fragile because the mechanism for moving the meter by converting the vertical movement of the float into a rotational motion is complicated, and if it breaks, the remaining amount of liquefied gas cannot be detected. There was a point.

  In addition, the ultrasonic method and strain gauge method require that an ultrasonic transducer and strain gauge be installed on the bottom surface of the storage tank. There is a problem that it is difficult to deal with failures because it must be buried in the ground, and installation is not easy, and maintenance is not possible unless it is dug. Also, the above-mentioned striking method is to strike the side of the tank to detect the tank resonance frequency and to measure the remaining amount of liquefied gas based on this, so that if the tank is buried in the ground, the striking In addition, since the tank buried in the ground hardly vibrates, it was impossible to detect the resonance frequency.

  The present invention provides a liquefied gas storage tank capable of easily detecting the remaining amount of liquefied gas even when the storage tank is buried in the ground, and a method for measuring the remaining amount of liquefied gas. For the purpose.

  (1) In the present invention, a lead that vibrates due to the outflowing gas and resonates with the length of the air column in the gas extraction pipe is provided at the upper end of the gas extraction pipe provided near the bottom surface of the tank from the upper surface of the tank. It is characterized by that.

  (2) This invention uses the liquefied gas storage tank described in (1), measures the vibration frequency of the lead from the outside of the tank, and determines the length of the air column in the gas extraction pipe based on the vibration frequency. Detecting and detecting the remaining amount of liquid gas based on the length of the air column.

  In the above inventions (1) and (2), the reed vibrates due to the gas flowing out of the tank, so that means for forcibly generating vibration such as a striking device is unnecessary. Further, since the lead is provided in the vicinity of the valve, even if the tank is buried in the ground, the vibration frequency of the lead can be measured from the surface as long as the valve is exposed on the ground surface.

  (3) The present invention is characterized in that a pipe having a small hole at the upper end is provided inside the tank, with the upper end bonded to the tank inner wall and the lower end opened.

  (4) The present invention uses the liquefied gas holding tank described in (3), and gives vibration from the outer surface of the tank to the bonded portion of the pipe, and this vibration resonates and resonates in the air column in the pipe. The frequency coming is measured outside the tank, the length of the air column in the pipe is detected based on the resonance frequency, and the remaining amount of liquid gas is detected based on the length of the air column. To do.

  In the inventions of the above (3) and (4), since the storage tank has a configuration in which only a pipe is provided inside, the structure is simple, there is no movable part, and there is no fear of failure. In addition, since the resonance frequency of the air column in the pipe inside the tank is measured, there is no effect on the resonance vibration of the air column even if the storage tank is buried in the ground, and the top of the tank is exposed to the ground surface. Measurement is possible.

  (5) The present invention is characterized in that a vibrating piece having an upper end fixed to the inner wall of the tank is provided inside the tank.

  (6) The present invention is characterized in that, in the invention described in (5), the resonator element has a tuning fork shape.

  (7) This invention, in the invention according to (6), (7), after opening a through hole on the tank upper surface, after inserting the vibrating piece through the through hole so that its upper end remains outside the tank, The vibrating piece and the upper surface of the tank are bonded and fixed so that the through hole is closed.

  (8) The present invention uses the liquefied gas storage tank described in (5), (6), (7), vibrates the vibrating piece by vibrating from the outside of the tank, and sets the vibration frequency outside the tank. Measure, detect the length of the vibrating piece immersed in the liquid gas based on the measured vibration frequency, and detect the remaining amount of the liquid gas based on the length immersed in the liquid gas It is characterized by.

  (9) The present invention is characterized in that a plurality of vibrating pieces having different lengths, each having an upper end fixed to the inner wall of the tank, are provided inside the tank.

(10) The present invention uses the liquefied gas storage tank according to (9),
The vibration pieces are vibrated by oscillating from the outside of the tank, the vibrations are detected from the outside of the tank, and which of the plurality of vibration pieces vibrate based on the measured frequency component of the vibration. And the remaining amount of liquid gas is detected based on the length of the vibrating piece.

  In the inventions of the above (5) to (10), since the storage tank has a configuration in which only the vibrating piece is provided inside, the structure is simple, there is no movable part, and there is no fear of failure. In addition, since the vibration piece inside the tank is vibrated by vibration and the vibration frequency is measured, there is no effect on the vibration of the vibration piece even if the storage tank is buried in the ground. Measurement is possible if it appears in

  (11) In the present invention, a reflector formed by superimposing a sector having a short radius and a large central angle and a sector having a long radius and a small central angle so that the vertices coincide with each other is fixed to the upper end of the tank. It is provided inside the tank.

  (12) This invention is the invention described in (11), wherein a through hole is formed in the upper surface of the tank, and after inserting the apex of the reflector into the through hole, the reflector is closed so that the through hole is closed. The tank upper surface is bonded and fixed.

  (13) This invention is characterized in that, in the invention described in (11) or (12), the reflector has an ultrasonic impedance substantially the same as that of the liquefied LP gas.

  (14) This invention uses the liquefied gas storage tank according to (11), (12) or (13), applies a pulse signal to the apex of the reflector from the outside of the tank, and the pulse signal is The reflected waves reflected by the plurality of fan-shaped arcs of the reflector are detected from the outside of the tank, and which of the plurality of arcs is in the liquefied gas based on the measured reflected wave intensity , And the remaining amount of liquid gas is detected based on this.

  In the inventions of the above (11) to (14), it is utilized that the reflectance of the boundary surface of the reflector is larger when the boundary surface is in the air than when the boundary surface is in the liquid. A multi-step boundary surface (fan-shaped arc portion) is provided, a pulse signal is emitted inside the reflector to detect the reflection intensity at each boundary surface, and which arc portion is in the air based on the reflection intensity. Determine which arc part is in the liquefied gas.

  (15) According to the present invention, a rod-like reflector extending downward from the inner wall of the tank upper surface is provided inside the tank, an ultrasonic vibrator is provided on the outer wall of the tank upper surface facing the reflector, and the transmitted ultrasonic beam is transmitted through the reflector. And a convex portion for attaching at an angle that is repeatedly reflected and returned.

  (16) The present invention is characterized in that, in the invention described in (15), the reflector has an ultrasonic impedance substantially the same as that of the liquefied LP gas.

  (17) This invention uses the liquefied gas storage tank according to (15) or (16), applies an ultrasonic signal to the reflector from an ultrasonic vibrator attached to the convex portion, and A signal obtained by repeatedly reflecting an ultrasonic wave signal from the reflector is received, and the remaining amount of liquid gas is detected based on the intensity of the received signal.

  In the inventions of the above (15) to (17), it is utilized that the reflectance of the boundary surface of the reflector is larger when the boundary surface is in the air than when the boundary surface is in the liquid. An ultrasonic signal is applied to the inside of the body, and the intensity of the signal that has been repeatedly reflected on the inner wall of the reflector is observed, and this intensity (attenuation) determines how many of the repeated reflections are reflected in the air. It is determined whether the time is reflection in the liquid, and based on this, the remaining amount of liquefied LP gas is detected.

  As described above, according to the present invention, since the remaining amount of the liquefied gas, that is, the height of the liquid level can be detected from the outside by various vibrations, the mechanism inside the tank fails and the remaining amount cannot be detected. There is nothing.

  Since it can be detected from the external upper surface by a simple operation, even when the tank is buried in the soil, it is easy to install and measure, and it is not necessary to embed the detector in the soil, so maintenance is easy.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a liquefied LP gas bulk tank and an LP gas remaining amount measuring system according to a first embodiment of the present invention.

  The LP gas bulk tank main body (hereinafter simply referred to as “tank main body”) 1 is a horizontal cylindrical steel tank for storing LP gas 6 of about 500 kg to 1 t, and is buried in the ground except for its top. ing. A valve 3 is provided at the center of the top portion appearing on the ground surface. A pipe 5 for supplying the LP gas 6 to each dwelling unit is connected to the valve 3.

  A gas extraction pipe 2 is welded to the inside of the tank (directly below) in the valve hole 1a to which the valve 3 is attached, and its end extends to the vicinity of the bottom surface inside the tank 1. Yes. A lead 4 is provided at the upper end of the gas extraction pipe 2. The lead 4 vibrates due to the airflow when the LP gas flows out of the tank body 1. The valve 3 is normally maintained in an open state, and LP gas is supplied from the inside of the tank body 1 through the gas extraction pipe 2, the valve 3, and the pipe 5 according to the use of equipment connected to the pipe 5. 6 is supplied. That is, the supply amount of gas flows to the lead 4 provided in the gas extraction pipe 2.

  The vibration frequency of the lead 4 is determined by the length of the air column in the gas extraction pipe 2, that is, the distance between the lead 4 and the liquid level 6 s of the liquefied LP gas 6. That is, in the tank, when the remaining amount of the liquefied LP gas 6 is large and the liquid level 6s is high, a high sound is produced because the distance between the lead and the liquid level is short, and the remaining amount of the liquefied LP gas 6 is small and the liquid level 6s. When is low, a low sound is produced because the distance between the lead and the liquid surface is long. Thus, since the resonance frequency has a functional relationship with the height of the liquid level 6s of the liquefied LP gas 6, the height of the liquid level 6s is determined based on this frequency by measuring the vibration frequency of the lead 4. Since the shape of the tank body 1 is known, the liquefied LP gas 6 in the tank 1 can be obtained by substituting the value of the liquid level into the remaining amount calculation formula representing the inner surface shape of the tank. The remaining amount can be calculated.

  Therefore, in this embodiment, a remaining amount measuring device 10 for detecting the vibration frequency of the lead 4 and measuring the remaining amount of the liquefied LP gas 6 based on this is externally attached. The remaining amount measuring device 10 includes a vibration sensor 11 attached near the valve 3 outside the tank, an A / D converter 12, a DSP 13, a controller 14, a communication control unit 15, and a display unit 16. Even if the A / D converter 12, the DSP 13, the controller 14, the communication control unit 15, and the display unit 16 are provided integrally with the vibration sensor 11, they are housed in a separate housing and connected to the vibration sensor 11 with a cable. You may do it.

  In the remaining amount measuring apparatus 10, the vibration sensor 11 detects the vibration of the lead 4 and converts it into an electric signal, and the A / D converter 12 samples the electric signal at a predetermined sampling frequency and converts it into a digital signal. . This digital signal is input to the DSP 13.

  The DSP 13 detects the frequency of this signal and calculates the length L of the air column based on the vibration frequency and the atmospheric pressure (gas pressure) inside the tank body 1. Then, the height of the liquid column of the liquefied LP gas is detected by subtracting the length of the air column from the inner diameter of the tank main body 1, and the remaining amount calculation formula expressing the value of the liquid level represents the inner surface shape of the tank. By substituting into and calculating, the remaining amount of the liquefied LP gas 6 is calculated. Since the internal gas pressure of the tank body 1 varies depending on the temperature, temperature correction may be performed when calculating the length of the air column in order to improve the measurement accuracy.

  The controller 14 receives the remaining amount data of the liquefied LP gas 6 from the DSP 13, displays it on the display unit 16, and notifies a predetermined notification destination via the communication control unit 15. The predetermined notification destination is, for example, a remote monitoring center.

  In this embodiment, the remaining amount measuring device 10 is always installed with respect to the tank 1. However, the remaining amount measuring device 10 is configured as a portable device, and only when measuring, You may make it install in the tank 1 and operate | move.

  In this embodiment, the lead 4 is provided at the upper end of the gas extraction pipe 2. However, the lead 4 is floated so as to float on the liquid surface 6 a of the liquefied LP gas 6 in the gas extraction pipe 2. May be.

  The lead 4 used in the above apparatus may be a plate like a harmonica or saxophone lead, or may be a so-called air lead that directly vibrates air as seen in a flute or a recorder.

Second Embodiment
FIG. 2 is a view showing a liquefied LP gas bulk tank according to a second embodiment of the present invention. This figure shows the configuration of the main part of the tank body 1. In this figure, the valve portion is not shown, but the structure near the valve 3 and the remaining amount measuring device 10 are substantially the same as those shown in FIG.

  In this embodiment, a resonance pipe 20 is provided inside the tank body 1. The resonance pipe 20 has an upper end welded and fixed to the ceiling surface of the inner wall of the tank body 1, and a lower end opened near the bottom surface inside the tank body 1. The resonance pipe 20 opens in the liquefied LP gas 6 only at the lower end and does not open in the tank at the upper end. However, the upper portion of the vaporized gas and the liquefied gas 6 are maintained at the same pressure in the resonance pipe 20 and the tank body 1. Since the liquid level antagonizes, the liquid level in the resonance pipe 20 and the liquid level in other locations of the tank body 1 are always kept the same.

  By providing the resonance pipe 20 inside the tank main body 1 as described above, by vibrating from the outside (upper part of the tank), the vaporized gas inside the tank vibrates, and this vibration resonates within the resonance pipe 20. The resonance frequency at this time is inversely proportional to the air column length L in the pipe 20 (the resonance wavelength is proportional to the air column length L in the pipe 20. This resonance in the air column is a closed tube vibration in which both become nodes. The air column length L can be determined by detecting the resonance vibration from the outside and measuring the frequency, and subtracting the air column length L from the inner diameter (2d) of the tank body 1. By substituting this liquid level height into the remaining amount calculation formula representing the inner surface shape of the tank, the remaining amount of the liquefied LP gas 6 can be calculated.

  The remaining amount measuring device for measuring the remaining amount of the liquefied LP gas 6 may have the same configuration as that shown in FIG. Further, the vibration means 21 may be one that can be automatically electrically driven, such as an electromagnetic solenoid, or may be one in which an attendant manually vibrates with a hammer or the like.

  The vibration sensor 11 is installed on the upper surface of the tank body 1, receives the resonance vibration of the air column in the resonance pipe 20 through the wall surface of the tank body 1, and converts it into an electrical signal. The A / D converter 12 converts this electric signal into a digital signal and inputs it to the DSP 13. The DSP 13 detects the frequency of this signal and calculates the length L of the air column based on this vibration frequency and the pressure inside the tank body 1. The height of the liquid column of the liquefied LP gas is detected by subtracting the length of the air column from the inner diameter of the tank body 1. The remaining amount of the liquefied LP gas 6 is calculated by substituting the height of the liquid level into the remaining amount calculation formula representing the inner surface shape of the tank. The controller 14 receives the remaining amount data of the liquefied LP gas 6 from the DSP 13, displays it on the display unit 16, and notifies a predetermined notification destination via the communication control unit 15. The predetermined notification destination is, for example, a remote monitoring center.

<Third Embodiment>
FIG. 3 is a view showing a liquefied LP gas bulk tank according to a third embodiment of the present invention. This figure shows the configuration of the main part of the tank body 1. In this figure, the valve portion is not shown, but the structure near the valve 3 and the remaining amount measuring device 10 are substantially the same as those shown in FIG.

  In this embodiment, a vibrating piece 22, which is an iron bar, is welded and fixed to the ceiling surface inside the tank body 1. The vibrating piece 22 is inserted and fixed in a small hole 1 b formed in the tank body 1, and is welded and fixed to the tank body 1 with its upper end protruding outside the tank body 1. The vibrating piece 22 is installed directly below in the tank body 1, and the tip (lower end) reaches the vicinity of the bottom surface in the tank body 1, and the tip of the vibrating piece 22 is in the tank body 1. The liquefied LP gas 6 is immersed in the liquefied LP gas 6 for a length corresponding to the height of the liquid surface 6a.

  The vibration piece 22 vibrates by being vibrated from the outside, and the vibration is complicated due to the combination of the vibration of the tip portion in the liquefied LP gas 6 and the vibration of other portions in the vaporized gas. Vibration. Therefore, by detecting this vibration waveform from the outside and analyzing the frequency component, it is possible to determine how much of the vibrating piece 22 is immersed in the liquefied LP gas 6 and liquefy based on this. The remaining amount of the liquefied LP gas 6 can be measured by calculating the height of the liquid surface 6a of the LP gas 6 and substituting it into the remaining amount calculation formula representing the inner surface shape of the tank.

  The remaining amount measuring device 10 for measuring the remaining amount of the liquefied LP gas 6 may have the same configuration as that shown in FIG. Further, the vibration means 21 may be one that can be automatically electrically driven, such as an electromagnetic solenoid, or may be one in which an attendant manually vibrates with a hammer or the like. Moreover, since the upper end portion of the vibrating piece 22 of this embodiment protrudes outside the tank, the vibration means 21 may be anything that strikes the protruding portion and vibrates the vibrating piece 22.

  The vibration sensor 11 is installed on the upper surface of the tank body 1 and receives the vibration of the vibrating piece 22 through the wall surface of the tank body 1 and converts it into an electrical signal. The A / D converter 12 converts this electric signal into a digital signal and inputs it to the DSP 13. The DSP 13 analyzes the frequency component of the signal by FFT or the like, and based on the vibration frequency component, how many of the vibrating bars 22 are immersed in the liquefied LP gas 6, that is, the length that vibrates in the air. Calculate the length of vibration in the liquid. Then, based on this, the height of the liquid level of the liquefied LP gas 6 is detected, and the height of the liquid level is substituted into the remaining amount calculation formula representing the inner surface shape of the tank. Calculate the remaining amount. The controller 14 receives the remaining amount data of the liquefied LP gas 6 from the DSP 13, displays it on the display unit 16, and notifies a predetermined notification destination via the communication control unit 15. The predetermined notification destination is, for example, a remote monitoring center.

  In this embodiment, since the end of the vibrating piece 22 protrudes outside the tank (upper part), the vibration is efficiently performed and the vibration is solid, so that the temperature change is more than the resonance vibration of the air column. Less need for temperature correction.

  If the resonator element 22 is cylindrical, it can also serve as the resonance cylinder shown in FIG. 2, and the height of the liquid level can be adjusted based on both the vibration as the resonator element and the resonance vibration of the internal air column. Can be detected.

<Fourth embodiment>
FIG. 4 is a view showing a liquefied LP gas bulk tank according to a fourth embodiment of the present invention. This embodiment is a modification of the third embodiment shown in FIG. 3, and is characterized in that the resonator element 22 has a tuning fork shape. By providing the tuning fork-shaped vibrating piece 22 'in this way, the vibration continues without being consumed by the vibration, and the waveform data can be easily captured by the vibration sensor 11. There is an advantage of becoming.

<Fifth Embodiment>
FIG. 5 is a view showing a liquefied LP gas bulk tank according to a fifth embodiment of the present invention. This embodiment is a modification of the third embodiment shown in FIG. 3, in which a plurality of vibrating pieces 22-1 to 2-n having different lengths are provided downward from the ceiling surface inside the tank body 1. is there. When the liquid level is high, the tip portions of the vibrating pieces 22-1 to 2-n are all immersed in the liquefied LP gas, but as the liquid level decreases, the vibrating pieces 22-1 are sequentially in the air (vaporization). In the gas). The vibrating piece is more likely to vibrate when the tip is immersed in the liquefied LP gas 6 and is all in the air (in the vaporized gas), and the vibration continues. Therefore, by oscillating the tank body 1 having a plurality of vibrating pieces 22-1 to 2-n having different lengths from the outside and observing the frequency of the vibrating piece vibrating inside from the outside, It is possible to detect which vibrating piece vibrates well and to determine that there is a liquid level between the longest and the next longest vibrating piece. .

  Also in this embodiment, the remaining amount measuring device 10 for measuring the remaining amount of the liquefied LP gas 6 may have the same configuration as that shown in FIG. Further, the vibration means 21 may be one that can be automatically electrically driven, such as an electromagnetic solenoid, or may be one in which an attendant manually vibrates with a hammer or the like.

  The vibration sensor 11 is installed on the upper surface of the tank body 1 and receives vibrations of the plurality of vibration pieces 22-1 to 2-n through the wall surface of the tank body 1 and converts them into electric signals. The A / D converter 12 converts this electric signal into a digital signal and inputs it to the DSP 13. The DSP 13 analyzes the frequency component of this signal by FFT or the like, and based on the vibration frequency component, up to what number of the vibration pieces 22-1 to n are in the air, and from which number of the vibration pieces Determine whether the liquefied LP gas 6 is immersed. Based on this, the liquid level of the liquefied LP gas 6 is calculated, and the liquid level of the liquefied LP gas 6 is calculated by substituting the height of the liquid level into a predetermined remaining amount calculation formula. . The controller 14 receives the remaining amount data of the liquefied LP gas 6 from the DSP 13, displays it on the display unit 16, and notifies a predetermined notification destination via the communication control unit 15. The predetermined notification destination is, for example, a remote monitoring center.

  In this embodiment, since it is only necessary to detect the sound of the vibrating piece 22 that vibrates well in the vaporized gas, there is an advantage that the sensitivity of the vibration sensor 11 can be lowered and it is resistant to external noise.

<Sixth Embodiment>
FIG. 6 is a view showing a liquefied LP gas bulk tank according to a sixth embodiment of the present invention. FIG. 7 is a diagram showing a time distribution of ultrasonic echoes in this embodiment.

  In this embodiment, a reflector 25 is provided inside the tank body 1 from the ceiling of the tank downward. The reflector 25 is for reflecting the ultrasonic wave incident from the upper end to the lower end and halfway and guiding it again to the upper end. The vertices having different radii and central angles (open angles) respectively coincide with the apexes (center of the arc). The shape is superposed. In this embodiment, five sectors 25-1 to 25-5 are overlapped. Of these, 25-1 has the longest radius and the central angle is small, and the radius gradually decreases and the central angle gradually increases as 24-2, 25-3, and 25-4. And 25-5 has the shortest radius and a large central angle. In the following description, the fan-shaped arc portion is indicated by the same number (25-1 to 5) as the fan-shape.

  The reflector 25 has a hole formed in the upper end portion of the tank body 1 and is fixed and sealed in the hole by welding. When measuring the remaining amount of the liquefied gas in the tank, a transmitting ultrasonic transducer 23 and a receiving ultrasonic transducer 24 are provided in close contact with the upper end (vertex) of the reflector 25 outside the tank body 1, An ultrasonic pulse is applied to the trusted ultrasonic transducer 23. The ultrasonic pulse is reflected by the fan-shaped arc portion and received by the receiving ultrasonic transducer 24. Since the fan-shaped radius portions (25-11 to 15) are parallel to the propagation direction of the ultrasonic wave, no reflection occurs here.

  The reflected pulse reception intensity is inversely proportional to the distance, but the reflectivity is high when the fan-shaped arc is in the air (in vaporized gas), and the reflectivity is low when the fan-shaped arc is in liquefied gas. The change in the reflection intensity due to the radius of the sector when the sectoral arc portion is in the air and in the liquefied gas is as shown by the curve in FIG.

  In the free space, the reflection intensity is inversely proportional to the square of the distance. However, since the propagation direction of the ultrasonic wave is restricted in the reflector 25, the value is different from that in the free space.

  In this embodiment, since the reflector 25 is formed by superimposing five sectors, the ultrasonic transducer receives five reflected pulses. The remaining amount of the liquefied gas is as shown in FIG. 6, and the reflector 25 has only the arc portion 25-5 in the air and the arc portions 25-1 to 25-4 are in the liquefied gas. As described above, only the reception intensity of the reflected wave of the arc portion 25-5 is strong, and the reflected waves of the arc portions 25-4 to 25-1 thereafter are weak. Therefore, the reflected wave received by the receiving ultrasonic transducer 24 is converted into a digital signal by the A / D converter 12, and the intensity is monitored by the DSP 13, thereby detecting the level of the remaining amount of the liquefied gas. can do. The receiving ultrasonic transducer 24 receives weak reflected waves from other than the fan-shaped arc portion, but this is weak and can be canceled, so it is not considered in FIG.

  In the block diagram of FIG. 6, the controller 14 drives the driver 17 to apply an ultrasonic pulse to the transmission ultrasonic transducer 23, and measures the time after applying (transmitting) this ultrasonic pulse. Yes.

  Immediately after the transmission of the ultrasonic pulse, the A / D converter 12 converts the reflected wave received by the receiving ultrasonic transducer 24 into a digital signal and inputs it to the DSP 13. The DSP 13 detects the reflected pulse from the arc portions 25-1 to 25-5 based on the level of the digital signal and the time after emitting the ultrasonic pulse. Then, based on the level, it is determined how many of the arc portions 25-1 to 25-5 are in the liquefied LP gas 6 and what number of the arc portions are in the air. Based on this, the liquid level of the liquefied LP gas 6 is calculated, and the liquid level of the liquefied LP gas 6 is calculated by substituting the height of the liquid level into a predetermined remaining amount calculation formula. . The controller 14 receives the remaining amount data of the liquefied LP gas 6 from the DSP 13, displays it on the display unit 16, and notifies a predetermined notification destination via the communication control unit 15. The predetermined notification destination is, for example, a remote monitoring center.

  The vibration piece 22 and the reflector 25 may be anything as long as they are rigid bodies, but the condition is that they are not corroded by gas. Usually, a metal, particularly the same steel as the tank body 1 is suitable.

  In this embodiment, the transmitting ultrasonic transducer 23 and the receiving ultrasonic transducer 24 may be combined with one ultrasonic transducer.

<Seventh Embodiment>
Next, a liquefied LP gas bulk tank according to a seventh embodiment of the present invention will be described with reference to FIG. In this embodiment, the reflected wave of the ultrasonic signal transmitted from the ultrasonic transducer is received as in the sixth embodiment described above, and the remaining amount of liquefied LP gas is detected based on the degree of attenuation.

  In this embodiment, a columnar reflector 26 is provided in the tank body 1 from the tank ceiling to the bottom. A convex portion 27 for attaching the transmitting ultrasonic transducer 23 ′ and the receiving ultrasonic transducer 24 ′ is formed on the opposite side (outer surface of the tank main body 1) of the tank body 1 to the reflector 26 forming surface. Yes.

  The transmitting ultrasonic transducer 23 ′ is an ultrasonic transducer that transmits a highly directional ultrasonic signal. When the ultrasonic transducer 23 ′ is attached to the convex portion 27, the transmitting ultrasonic transducer 23 ′ has a linear shape as indicated by a beam line 28 in FIG. Transmit an ultrasonic beam. The receiving ultrasonic transducer 24 ′ is an element that receives the ultrasonic beam that has been reflected back from the reflector 26. The circuit unit described later detects the remaining amount of the liquefied LP gas 6 based on the intensity of the ultrasonic beam received by the receiving ultrasonic transducer 24 ′. The receiving ultrasonic transducer 24 ′ may be directional or non-directional.

  The protruding angle of the convex portion 27 and the width and length of the reflector 26 are such that the ultrasonic beam 30 output from the transmitting ultrasonic transducer 23 ′ reaches the receiving ultrasonic transducer 24 ′ through the path shown in FIG. Has been decided to do. The number of reflections n until the ultrasonic beam emitted from the transmitting ultrasonic transducer 23 'reaches the receiving ultrasonic transducer 24' is arbitrary.

  The ultrasonic beam 30 emitted from the transmitting ultrasonic transducer 23 ′ is reflected n times as shown in the figure and reaches the receiving ultrasonic transducer 24 ′. However, depending on the remaining amount of the liquefied LP gas 6, The number of reflections m and the number of reflections in the air (nm) are determined. Although the ultrasonic beam 30 is reflected almost without attenuation in the air, the amount of attenuation of the ultrasonic beam 30 received by the reception ultrasonic transducer 24 ′ is large because leakage of the ultrasonic wave is large and the reflected wave is attenuated in the liquid. The number of reflections m in the liquid can be determined based on the above, whereby the remaining amount of the liquefied LP gas 6 can be detected.

  The driver 17 that drives the transmission ultrasonic transducer 23 'applies an ultrasonic signal having a predetermined power to the transmission ultrasonic transducer 23'. The transmitting ultrasonic transducer 23 ′ emits an ultrasonic beam 30 by applying this ultrasonic signal. The ultrasonic beam 30 reaches the reception ultrasonic transducer 24 ′ by repeating m reflections in the liquid and n−m reflections in the air within the reflector 26. The receiving ultrasonic transducer 24 ′ receives this ultrasonic beam, converts it into an electrical signal, and inputs it to the A / D converter 12. The A / D converter 12 converts the received ultrasonic signal into a digital signal and inputs it to the DSP 13. The DSP 13 determines the attenuation amount of the ultrasonic beam 30 from when it is emitted until it is received based on the amplitude change of this signal, and detects the remaining amount of the liquefied LP gas 6 based on this. The detected remaining amount is converted into a predetermined signal by the controller 14 and output to the outside by the communication control unit 15.

  In this embodiment, the reflector 26 and the convex portion 27 are formed of the same material (integral molding) as the tank main body 1, but the back side of the convex portion 27 formed separately and formed on the surface of the tank main body 1. You may adhere to. In this case, the ultrasonic impedance of the reflector 26 may be set close to that most suitable for detecting the remaining amount of liquefied LP gas. For example, if the ultrasonic impedance is close to that of the liquefied LP gas 6, the degree of attenuation is increased, and the detection accuracy when the remaining amount is reduced can be improved.

  In addition, as a material of the reflector 26, it is possible to use gel, liquid, etc. in addition to solid. When gel or liquid is used, the reflector 26 may be configured by storing this material in a flexible container in the shape of a reflector.

Structure diagram of LP gas bulk tank according to the first embodiment of the present invention Structural diagram of an LP gas bulk tank according to the second embodiment of the present invention Structural diagram of an LP gas bulk tank according to the third embodiment of the present invention Structural diagram of an LP gas bulk tank according to the fourth embodiment of the present invention Structural diagram of an LP gas bulk tank according to the fifth embodiment of the present invention Structural diagram of an LP gas bulk tank according to the sixth embodiment of the present invention The figure which shows the reflected pulse intensity | strength in the said 6th Embodiment. Structural diagram of an LP gas bulk tank according to the sixth embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... LP gas bulk tank main body, 2 ... Gas extraction pipe, 3 ... Valve, 4 ... Lead, 5 ... Piping,
DESCRIPTION OF SYMBOLS 10 ... (LP gas) residual amount measuring apparatus, 11 ... Vibration sensor, 12 ... A / D converter, 13 ... DSP, 14 ... Controller, 15 ... Communication control part, 16 ... Display part,
17 ... (ultrasonic transducer) driver,
21 ... Excitation means,
22, 22 ′, 22-1 to n ... vibrating pieces 23, 23 ′: transmitting ultrasonic transducer, 24, 24 ′: receiving ultrasonic transducer, 25, reflector, 25-1 to 5, arc portion

Claims (17)

  A liquefaction characterized in that a lead that vibrates due to the outflowing gas and resonates with the length of the air column in the gas extraction pipe is provided at the upper end of the gas extraction pipe provided near the bottom surface of the tank from the upper surface of the tank. Gas storage tank. Using the liquefied gas storage tank according to claim 1,
The vibration frequency of the lead is measured from the outside of the tank, the length of the air column in the gas extraction pipe is detected based on the vibration frequency, and the remaining amount of liquid gas is detected based on the length of the air column. A method for detecting a remaining amount of a liquefied gas.   A liquefied gas storage tank characterized in that a pipe having a small hole at its upper end is provided inside the tank, with its upper end bonded to the tank inner wall and its lower end opened. Using the liquefied gas holding tank according to claim 3,
A vibration is applied to the bonded portion of the pipe from the outer surface of the tank, and a frequency at which the vibration resonates and resonates with an air column in the pipe is measured outside the tank. Based on the resonance frequency, A method for detecting a remaining amount of liquefied gas, comprising: detecting a length of an air column and detecting a remaining amount of liquid gas based on the length of the air column.   A liquefied gas storage tank, wherein a vibrating piece having an upper end fixed to an inner wall of the tank is provided inside the tank.   The liquefied gas storage tank according to claim 5, wherein the vibrating piece has a tuning fork shape.   A through hole was opened on the tank upper surface, and the vibrating piece was inserted into the through hole so that its upper end remained outside the tank, and then the vibrating piece and the tank upper surface were bonded and fixed so as to close the through hole. The liquefied gas storage tank according to claim 5 or 6, characterized by the above. Using the liquefied gas storage tank according to claim 5, claim 6 or claim 7,
The vibrating piece is vibrated by oscillating from outside the tank, the vibration frequency is measured outside the tank, and the length of the vibrating piece immersed in liquid gas is detected based on the measured vibration frequency. A method for detecting a remaining amount of liquefied gas, wherein the remaining amount of liquid gas is detected based on a length immersed in the liquid gas.   A liquefied gas storage tank, wherein a plurality of vibrating pieces having different lengths are provided inside the tank, the upper end of which is fixed to the inner wall of the tank. Using the liquefied gas storage tank according to claim 9,
The vibration pieces are vibrated by oscillating from the outside of the tank, the vibrations are detected from the outside of the tank, and which of the plurality of vibration pieces vibrate based on the measured frequency component of the vibration. And detecting the remaining amount of the liquid gas based on the length of the vibrating piece that is vibrating.   A reflector formed by superimposing a sector with a short radius and a large central angle and a sector with a long radius and a small central angle so that the vertices coincide with each other is attached to the top of the tank, and the reflector is provided inside the tank. Characterized liquefied gas storage tank.   12. A through hole is formed in the upper surface of the tank, and after inserting the apex of the reflector into the through hole, the reflector and the upper surface of the tank are bonded and fixed so that the through hole is closed. The liquefied gas storage tank described.   The liquefied gas storage tank according to claim 11 or 12, wherein the reflector is configured with an ultrasonic impedance substantially the same as that of the liquefied LP gas. Using the liquefied gas storage tank according to claim 11, claim 12 or claim 13,
A pulse signal is applied to the apex of the reflector from the outside of the tank, and the reflected wave reflected from the plurality of fan-shaped arcs of the reflector is detected from the outside of the tank. A method for detecting a remaining amount of liquefied gas, comprising: detecting which arc portion of the plurality of arc portions is in the liquefied gas based on the intensity of the liquefied gas, and detecting the remaining amount of liquid gas based on the detected arc portion. . A rod-shaped reflector extending downward from the inner wall of the tank upper surface is provided inside the tank,
Liquefaction characterized in that a convex portion is provided on the outer wall of the upper surface of the tank facing the reflector so as to attach the ultrasonic transducer at an angle at which the transmitted ultrasonic beam is repeatedly reflected and returned within the reflector. Gas storage tank.   The liquefied gas storage tank according to claim 15, wherein the reflector is configured with an ultrasonic impedance substantially the same as that of the liquefied LP gas. Using the liquefied gas storage tank according to claim 15 or claim 16,
An ultrasonic signal is applied to the reflector from the ultrasonic transducer attached to the convex portion, and a signal returned by the ultrasonic signal being repeatedly reflected by the reflector is received. A method for detecting a remaining amount of liquefied gas, wherein the remaining amount of liquid gas is detected based on intensity.

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