JPH0763595A - Tank liquid level measuring device - Google Patents

Abstract

PURPOSE:To detect the quantity of fuel oil and the quantity of water, collected at the bottom part of a tank, by the same liquid level detecting means. CONSTITUTION:A first float having a magnet 13a with the whole specific gravity set smaller than ail, and a second float having a magnet 14a, with the whole specific gravity set smaller than water and larger than oil, are fitted with play to the outside of a coil unit with a transmitting coil 22 provided at one end of a magnetostrictive wire 20 and with a receiving coil 23 provided in a measuring area. The first float moves in line with the level of the fuel oil, and the second float moves in line with the level of water content. When the transmitting coil 22 is excited to generate ultrasonic wave in this state, electromotive force caused by the reverse magnetostrictive effect is generated in different positions where two floats are positioned. The time until the input of these two electromotive force is counted by counters 41, 53 so as to enable the measurement of the fuel oil quantity and the quantity of water in the case of water being collected therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring a liquid level and a liquid amount of a liquid contained in a tank or the like by moving a float.

[0002]

2. Description of the Related Art Liquid level measurement of a tank buried underground is
Usually, it is performed by using a measuring stick, but there is a problem that not only it is necessary to rely on human hands but also liquid level management cannot be performed online. And especially in underground tanks that always store a certain amount of fuel oil, moisture in the air is condensed and accumulated in the tank due to breathing action, and corrosion of the tank and measurement of the stored amount of fuel oil are performed. There is a problem of causing an error. In order to solve such a problem, the cylindrical electrodes are concentrically arranged and the liquid amount of the fuel oil is measured by the capacitance between the two electrodes, while the liquid detecting electrode provided below the electrode is used. A surface detection device has also been proposed, but not only does it cause a measurement error due to changes in the dielectric constant caused by oil types and minute water droplets suspended in oil, but also for fuel oil detection and water detection. The above two types of detection electrodes are required, and the water detection electrode needs to be insulated, which causes a problem such as an increase in the cost of the device.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to accurately measure the liquid amount regardless of the dielectric constant of the fuel oil. It is an object of the present invention to provide a liquid level measuring device capable of measuring the liquid level of fuel oil and detecting the amount of water accumulated at the bottom by the same liquid level detecting means.

[0004]

In order to solve such a problem, in the present invention, a coil unit having a transmitting coil at one end of a magnetostrictive wire and a receiving coil at a measurement region is sealed at the lower end. A pipe with a flameproof structure for accommodating a circuit board on the upper end of the pipe, the upper end of the pipe is hermetically sealed, and the pipe has a magnet. The first float whose specific gravity is set smaller than that of oil,
A second float, which has a magnet and whose overall specific gravity is smaller than water and larger than oil, is loosely fitted.

[0005]

The first float moves in line with the liquid surface of the fuel oil, and the second float moves in line with the liquid surface of the water accumulated under the fuel oil. When the transmitter coil is excited in this state to generate an ultrasonic wave, an electromotive force due to the inverse magnetostriction effect is generated at different positions where these two floats are located. Therefore, the excitation time and the two float positions are different at different times. By measuring the time with the generated electromotive force, the level of fuel oil and the level of water can be measured.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the liquid level detector of the present invention, which is composed of two parts, a head part 1 and a detection part 2. The head unit 1 includes the detection unit 2
A circuit board 6, 7, 8 in which a base 3 and a cover 4 for fixing are fixed as a case having an explosion-proof structure, and a signal processing circuit described later is mounted therein.
Are housed in a multi-layered structure. Circuit board 6, 7,
8 is connected to a control device described later by a cable 10 that is airtightly pulled out by a packing 9.

Reference numeral 2 denotes a detection unit, which includes a pipe 11 to be described later,
It has a flange 12 formed on the upper end side, and can be airtightly fixed to the base 3 of the head part 1 via the flange 12, and the first and second floats are axially provided outside the pipe 2. It is movably installed. The first float 13 and the second float 14 have ring-shaped permanent magnets 13 respectively.
a, 14a are provided, the first float 13 is selected so that its apparent specific gravity, ie the overall specific gravity, is smaller than the fuel oil to be measured, and the second float 14 is The specific gravity is set to be smaller than water and larger than fuel oil. The first float 13 is connected to the second float 1 by the stopper 13b.
The lower limit is set above 4 and the second float 14 is the float 14 in this embodiment.
A lower limit is set by a stopper so that the magnet 14a attached to the receiver is positioned below the lower end of the receiving coil 23, and even when the fuel oil is minimum, each float 1
The magnets 13a of the first float 13 are arranged on the upper part of the float 13 and on the first part of the float 13 so that the mutual interference of the magnetic fields by the magnets 13a and 14a provided on the magnets 3 and 14 can be prevented to reliably detect the fuel oil and water. The magnet 14 a of the two float 14 is attached to the lower portion of the float 14. A coil unit 15, which will be described later, is inserted into the pipe 11 through a filamentous material 16 which also serves as a damper member.
5 is arranged substantially on the center line of the pipe 11.

FIG. 2 is an enlarged view of the above-mentioned detecting section 2, 20 is a magnetostrictive wire made of a nickel alloy, the surface of which is covered with a synthetic resin tube 21 which also serves as an insulator, On the surface, the transmitter coil 22 is on the upper end side,
Further, the receiving coil 23 is wound over the entire length at a constant pitch from the transmitting coil 22 to the tip side. The surfaces of the coils 22 and 23 are covered with a heat-shrinkable synthetic resin tube 24 for fixing the coil, so that the coil unit 15
Are summarized in.

Reference numeral 11 in the drawing denotes the above-mentioned pipe, which is a non-magnetic metal having rigidity enough to withstand an external force,
In this embodiment, it is made of non-rust steel, and the opening 25 at one end is inserted with a metallic plug 26 and fixed with silver wax, and the other end is inserted into the through hole of the flange 12 so that the end of the pipe 11 is inserted. Is positioned so as to be substantially the same as the surface of the flange 12, and the upper end surface 12a and the lower end surface 12b of the flange 12 are integrally fixed to the pipe 11 with silver wax.

In the pipe 11 thus constructed,
The coil unit 15 is relatively thick on the surface,
In addition, a filamentous material having elasticity is wound at a coarse pitch and pulled out to such an extent that at least a part of the receiving coil 23 and the transmitting coil 22 are exposed. The inside of the pipe 11 and the external environment are cut off by dengue and sealing the tip of the coil unit 15 with a similar synthetic resin 28. The transmission coil 22 and the reception coil 23 are connected to the measurement circuits of the circuit boards 6, 7, and 8 via flexible cables C, respectively. Reference numeral 29 in the drawing denotes a ring-shaped permanent magnet for bias provided on the surface of the transmission coil 22.

FIG. 3 shows an example of a signal processing circuit housed in the head unit 1 for driving the same apparatus. Reference numeral 30 in the drawing is a measuring circuit, which is a signal processing unit 31 and a starting circuit. 32 and 32. Starting circuit 32
Receives power from the power supply means 33 through a power supply line 34 and maintains an operating state at all times, and a transmission line 35 described later.
When the start pulse is input from the power supply unit 33, the power of the power supply unit 33 is supplied to the signal processing unit 31 to start it. On the other hand, the signal processing unit 31 is always maintained in a rest state, is activated after waiting for power supply from the activation circuit 32, and is inactivated at the time when the measurement operation is completed.

The signal processor 31 will be further described.
In the figure, reference numeral 36 is a drive pulse generating circuit, which outputs an excitation pulse having a constant cycle, for example, a pulse width of 5 microseconds at a repeating cycle of 10 milliseconds, and 37 is induced in the receiving coil 23 by the inverse magnetostrictive effect. The first detection circuit detects the first electromotive force (R1 in FIG. 4), that is, the one caused by the first float 13. Reference numeral 38 denotes a first prep-flop circuit, which is set when a drive pulse is output and is reset by a signal from the first detection circuit 37. Reference numeral 39 denotes a first gate circuit, which outputs a clock signal from the clock generation circuit 40 to the first counter 41 in synchronization with the duration of the pulse output in the set state of the first flip-flop circuit 38.
Configured to output to. Reference numeral 42 denotes a first calculation means, which is a clock count number from the transmission coil 22 stored in the first data storage means 43 to a reference measurement point, for example, the lower surface 12b of the flange 12, a length per count, and the like. It is configured to calculate the liquid level or the liquid amount of the fuel oil based on the required data of 1, and output the result to the control device 57 via the interface 44.

Reference numeral 50 in the drawing denotes a second detection circuit, which is the second detection circuit when the two electromotive forces are induced in the receiving coil 23 by one drive pulse, that is, the second float 14. Is configured to detect. 5
Reference numeral 1 is a second prep-flop circuit, which is set when a drive pulse is output and is reset by a signal from the second detection circuit 50. 5
The second gate circuit 2 outputs the clock signal from the clock generation circuit 40 to the second counter 53 in agreement with the duration of the pulse output in the set state of the second flip-flop circuit 51. It is configured. 54
Is a second calculation means, and the tank is calculated based on required data such as the number of clock counts from the transmission coil 22 to the reference measurement point and the length per count stored in the second data storage means 55. Liquid level of water accumulated at the bottom,
Alternatively, the liquid volume is calculated, and the result is interface 44
It is configured to output to the control device 57 via. $ And 57 are control devices, which are connected to the measurement circuit 30 by a transmission line capable of common bidirectional communication with one or a plurality of liquid level measurement devices, for example, a transmission line 35 of RS-485, and by a switch. It is configured to output a start signal (I in FIG. 4) manually or at every preset measurement cycle T0.

Next, the operation of the apparatus thus constructed will be described. The head portion 1 is fixed to the upper end of the tank via the head portion 1 so that the pipe 11 is in the vertical state.
As a result, the coil unit 15 is arranged in a state of being positioned on the central axis of the pipe 11 by the filamentous body 16. In this state, the tip of the pipe 11 is sealed by the plug 26 so that it is kept liquid-tight, and the other end is kept airtight by the synthetic resin sealant 27 and the head 1. The combustible gas in the atmosphere is prevented from entering the pipe 11 and the head space. When the mounting of the liquid level detection means is completed, the liquid level detection means is connected to the control device 43 and the power supply means 33 by the transmission line 35 and the power supply line 34.

In the normal operating state, only the starting circuit 32 is operating, and the signal processing circuit 31 maintains the standby state. When the switch of the control device 57 is operated in such a standby state or a start signal (FIG. 4I) is output based on the measurement cycle, the start circuit 32 outputs the power supplied by the power supply line 34 as a signal. Processing circuit 31
Supply to. As a result, the drive pulse S is output from the drive pulse generation circuit 36 at a constant cycle (FIG. 4 II), a magnetic field is generated in the transmission coil 22, and mechanical strain is instantaneously generated in the magnetostrictive line 20. This strain becomes a compressional wave, that is, an ultrasonic vibration, which propagates toward the other end of the magnetostrictive line 20 at a speed of about 5 Km / s. At the same time, the first and second counters 41 and 53
Is reset to zero, and the first and second flip-flops 32 are set to output a signal to open the first and second gate circuits 39 and 52 to open the clock generation circuit 4
The clock signal from 0 is the first and second counters 41, 5
Enter in 3.

When the ultrasonic vibration reaches the float 13 which is positioned in agreement with the liquid level O of the fuel oil, it receives a magnetic field from the magnet 13a attached to the float 13 and is generated in the receiving coil 23 by the inverse magnetostrictive effect. Electricity is generated. This electromotive force is received by the first detection circuit 37 by the received signal R1 (see FIG.
III) detected as the first flip-flop 3
8 is output. As a result, the first flip-flop 3
8 is reset, the gate circuit 39 is closed, and the counting of the clock signal (V in FIG. 4) by the first counter 41 is completed.

On the other hand, the ultrasonic vibration reaching the first float 13 propagates further down the magnetostrictive line 20. In this case, there is no water at the bottom of the tank T (Fig. 5
B) Since the second float 14 is located at the lower limit and the magnet 14a thereof is located outside the detectable area of the receiving coil 23, the counter electromotive force is generated by the second float 14. Not (Fig. 4 VI).

The clock count number of the first counter 41 is the distance from the first measurement reference point to the position of the float 14 based on the basic data stored in the first data storage circuit 43, that is, the liquid level L1. , Or converted into liquid volume and transferred from the input / output interface 44 to the transmission line 35.
Is output to the control device 57 via.

On the other hand, as described above, the second float 14
Since the counter electromotive force based on is not generated, the second counter 5
3 counts up to the upper limit (FIG. 4 VI). The second calculation means 54 determines that there is substantially no water at the bottom of the tank based on this count value, and outputs the determination result to the control device 57.

When the measurement period ends, the start signal is stopped from the control device 57, the power supply by the start circuit 32 is stopped, and the power consumption in the signal processing circuit 31 is suppressed.
Thereafter, the activation signal is output from the control device 57 at a predetermined cycle T0, and the above steps are intermittently executed.

On the other hand, when water is accumulated in the tank T,
As shown in FIG. 5B, the first float 13 moves in conformity with the liquid level O of the fuel oil, and the second float 14
Moves to the boundary W between the upper surface of water and the lower surface of fuel oil. As a result, the magnet 14a of the second float 14 is positioned within the detectable area of the receiving coil 23.

In this state, the drive pulse S is output and ultrasonic vibration is generated in the magnetostrictive wire 20. When this ultrasonic vibration reaches the first float 13 located on the liquid surface of the fuel oil, the first reception signal R1 is generated, and a clock pulse corresponding to the time required to move this distance (V in FIG. 4). Is the first
The counter 41 of FIG. First float 13
The ultrasonic vibration that has passed through propagates further downward and reaches the second float 14 located on the liquid surface W of water. As a result, the electromotive force based on the inverse magnetostrictive effect is generated again in the receiving coil 23 by the magnet 14a of the second float 14. This electromotive force is applied to the second reception signal R2 by the second detection circuit 50.
(IV in FIG. 4) and resets the second flip-flop 51. Therefore, the second counter 53 has a number corresponding to the time required for the ultrasonic vibration to move from the reference point to the surface W of the water. Clocks are counted (VI).

The second computing means 54 converts the liquid level L2 of the water from the bottom of the tank T or the amount of water based on the data of the second data storage means 55 into a controller 57 via the interface 44. Output to.

Hereinafter, by repeating such an operation intermittently at a constant cycle T0, the amount of fuel oil in the tank T and the amount of water accumulated at the bottom of the tank T can be detected simultaneously with as little operating power as possible. be able to.

[0025]

As described above, in the present invention,
A coil unit having a transmitting coil at one end of the magnetostrictive wire and a receiving coil at the measurement area is housed in a pipe whose lower end is sealed, and the upper end is sealed by molding, and a circuit board is placed at the upper end of the pipe. The head part of the explosion-proof structure for housing is attached airtightly and further has a magnet,
And, having a first float whose overall specific gravity is set smaller than oil, and a magnet, and whose overall specific gravity is smaller than water,
Since the second float, which is set larger than the oil, was loosely fitted in the pipe, the position of the float indicating the liquid level of the fuel oil and the position of the float indicating the liquid level of the water accumulated at the bottom of the tank were detected by the same coil unit. Not only that, but the amount of fuel oil can be accurately measured regardless of its dielectric constant.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus showing an embodiment of a liquid level detecting means used in the present invention.

FIG. 2 is an enlarged cross-sectional view showing the above liquid level detection means.

FIG. 3 is a block diagram showing an embodiment of a liquid level measuring device using the above liquid level detecting means.

FIG. 4 is a timing chart showing the operation of the above apparatus.

5 (a) and 5 (b) are explanatory views showing the operation of the above liquid level measuring device, respectively.

[Explanation of symbols]

 1 Head Part 2 Detecting Part 3 Base 4 Cover 6, 7, 8 Circuit Board 10 Cable 11 Pipe 12 Flange 13 Float 13a Magnet 14 Float 14a Magnet 15 Coil Unit 20 Magnetostrictive Wire 22 Transmitting Coil 23 Receiving Coil 30 Measuring Circuit 31 Signal Processing Part 33 Power supply means 34 Power supply line 35 Transmission line

Claims (3)

[Claims] 1. A coil unit having a transmitting coil at one end of a magnetostrictive wire and a receiving coil at a measurement region is housed in a pipe whose lower end is sealed, and the upper end is sealed by molding, and A pressure-resistant explosion-proof structure head part for accommodating a circuit board is airtightly attached to the upper end of the pipe, and further, a magnet is attached to the pipe, and a first float having a specific gravity set smaller than that of oil and a magnet. A tank liquid level measuring device having a second float that has a specific gravity smaller than that of water and larger than that of oil. 2. The circuit board, wherein drive pulse generating means for applying a drive pulse to the transmitting coil, start timing with the drive pulse, and stop timing with the first signal from the receiving coil. 1 counter means, first
Liquid amount calculation means for converting the number of counts of the counter means into a liquid amount, and second counter means for starting timing with the drive pulse and stopping timing with a second signal from the receiving coil. 2. The tank liquid level measuring device according to claim 1, further comprising: a second liquid amount calculating unit for converting the count number of the second counter unit into a liquid amount. 3. A tank level measuring apparatus according to claim 1, wherein a magnet is provided on the upper part of the first float and on the lower part of the second float.