JP2789229B2 - Tank residual amount measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] Remaining amount measurement in a tank that can measure the remaining amount in a liquid storage tank installed in a gas station or the like of the present invention with high accuracy and in a short time. Related to the device.

[Conventional technology]

Generally, in underground tanks of gasoline filling stations,
In order to constantly monitor the remaining amount of oil, a tank remaining amount measuring device as shown in FIG. 8 is used.

In FIG. 8, 1 is a site of a gas station, 2 is a building such as an office, etc., 3A, 3B and 3C are liquid storage tanks provided in the basement of the site 1 (collectively, "liquid storage tank 3"), 4A, 4B, and 4C indicate liquid level sensors (referred to as "liquid level sensor 4") inserted into the liquid storage tanks 3A, 3B, and 3C, respectively. The liquid level sensor 4 is a single metal cylinder. A capacitance type liquid level sensor formed by forming an outer cylinder and an inner cylinder of a body in a coaxial cylindrical shape, and a static electrode between electrodes formed between the outer cylinder and the inner cylinder according to the liquid level. The liquid level is measured based on the electric capacity.

Reference numeral 5 denotes a tank monitoring device provided in the building 2. The monitoring device 5 is provided with a control unit (not shown) including a processing circuit (CPU), a storage circuit (RAM, ROM), and the like. The display 6 is provided with a numeric keypad 7 for setting the number of the liquid storage tank 3 and the like, a printer 8, a buzzer 9 for warning when the remaining amount is low, and the like. In the storage circuit of the control unit of the tank monitoring device 5, the shape, length, radius, dimensions of the mirrored portion, etc. of the liquid storage tank 3, and the liquid level height and the remaining amount corresponding to these shapes and dimensions are stored. Is stored, and the liquid level sensors 4A, 4A are stored.
The remaining amount is calculated based on the capacitance input from B and 4C.

In the tank remaining amount measuring device thus configured, the axial length of the outer cylinder and the inner cylinder of the liquid level sensor 4 is 1, the liquid level height is Δl, the inner diameter of the outer cylinder is d ₁ , and the inner cylinder is Assuming that the outer diameter is d ₂ and the dielectric constant of the test liquid is ε, the capacitance C between the electrodes formed between the inner and outer cylinders is Is known. As a result, by performing frequency conversion, voltage conversion, and the like on the detected capacitance C, the liquid level height Δl can be measured.

On the other hand, looking at the liquid storage tank, the axial length of the cylindrical body (hereinafter referred to as the body length), the radius, the presence or absence of bulge at the axial end (hereinafter referred to as the mirror), the presence or absence of a partition, etc. And a very large variety of tanks are used. Also, as shown in FIG. 8, the tank installation form is a horizontal cylindrical tank 3 without mirroring.
A, a vertical cylindrical tank 3B without a mirror, a horizontal cylindrical tank 3C with a mirror, and the like.

Then, in order to calculate the remaining amount ΔQ in the tank of various types and various types, when giving the body length as L, the radius as r, and the mirroring function as f (m), ΔQ = f [Δl, L, r, f (m)] (2) Therefore, if the liquid level height Δl in the tank can be detected, the remaining amount ΔQ can be obtained by performing the calculation of the equation (2) with the dimension value given in advance for the tank.

Thus, the tank monitoring device 5 reads the capacitance from the liquid level sensor of the liquid storage tank selected by the numeric keypad 7,
The liquid level height Δl is calculated by the equation (1), the remaining amount ΔQ is calculated by the equation (2), the remaining amount is displayed on the display 6, and the buzzer 9 is operated when refueling is required. ing.

[Problems to be solved by the invention]

However, the related art configured as described above has the following problems.

First, the capacitance C between the electrodes of the liquid level sensor 4 is (1)
As shown in the equation, it is a function of the dielectric constant ε of the test liquid, and thus the measured liquid level height Δl is also a function of the dielectric constant ε.

However, in the tank residual amount measuring device according to the prior art, for example, the dielectric constant ε of a test liquid such as gasoline or light oil is used.
It is common practice to add a nominal value, which is substantially constant depending on the type, as a constant in advance, detect the capacitance C, and calculate the liquid level.

However, the actual dielectric constant ε of the test liquid is
(Effective dielectric constant) varies depending on the crude oil producing area and each refinery, and differs from the nominal value individually. Therefore, accurate measurement cannot be performed even if liquid level detection is performed based on the nominal value. There is a point.

Second, the remaining amount ΔQ in the liquid storage tank 3 is a function of a unique dimensional value of each tank and a liquid level height Δl as shown in the equation (2). Have different complicated arithmetic expressions. Therefore, the tank monitoring device 5 must calculate the remaining amount ΔQ based on the tank type, the dimensional value, and the remaining amount calculation formula stored in the tank monitoring device 5.
In a large gas station where ten tanks are buried, there is a problem that the control unit of the tank monitoring device 5 requires a lot of time for this complicated calculation.

Third, recent gasoline filling stations have been equipped with a sales management device (hereinafter referred to as POS) and a modem horn for communication with former retailers due to the streamlining of office work, the development of communication systems, and the development of electronics. It is like
Further, a POS or an external display for outdoor installation has been provided. The tank monitoring device 5 also needs to perform data communication with the POS, modem horn, external display, and the like.

However, the tank monitoring device 5 according to the prior art, as described as the second problem, is busy with the calculation of the remaining amount ΔQ in the tank, cannot take enough time for external communication, and There is a problem that hinders the smooth operation of the project.

The present invention has been made in view of such problems of the related art, and accurately calculates the liquid level by automatically measuring the effective dielectric constant of the test liquid stored in the liquid storage tank, By giving the relationship between the liquid level and the remaining amount of the storage tank as a tank table in advance, a complicated total volume calculation is not required each time, and the tank can be used as communication time with extra time. The purpose is to provide an internal remaining amount measurement.

[Means for solving the problem]

To achieve the above object, the configuration adopted by the present invention is:
A capacitance type liquid level sensor including one outer cylinder, an upper cylinder provided in the outer cylinder, and a lower inner cylinder having a predetermined known length; and an upper inner cylinder of the liquid level sensor. After confirming that the liquid surface exists, the dielectric calculating the dielectric constant of the liquid to be measured based on the capacitance formed between the outer cylinder and the lower inner cylinder and the length dimension of the lower inner cylinder. Rate calculating means, based on a capacitance formed between the outer cylinder and the upper and lower inner cylinders of the liquid level sensor and a new dielectric constant calculated by the dielectric constant calculating means. Based on the liquid surface height calculating means for calculating the surface height and the shape of the liquid storage tank in which the type and dimensional relationship of the tank are known in advance, the relationship between the liquid surface height and the remaining amount of the liquid storage tank is determined in advance. A tank table for calculating and storing the remaining amount for each liquid level, and a liquid level calculated by the liquid level calculating means. By using the liquid level and the tank table, and a remaining amount calculating means for calculating a remaining amount of the liquid storage tank.

[Action]

With this configuration, when the liquid is newly replenished to the liquid storage tank and the liquid level rises to the upper inner cylinder, the outer cylinder and the lower inner cylinder of the liquid level sensor are calculated by the dielectric constant calculating means. A new dielectric constant is calculated for the liquid replenished this time from the capacitance formed between the above and the previously-known length of the lower inner cylinder.

Also, the liquid level height calculating means uses the capacitance formed between the outer cylinder of the liquid level sensor and the upper and lower inner cylinders and the new dielectric constant calculated by the dielectric constant calculating means. To calculate the true liquid level.

On the other hand, for a storage tank whose type and dimensional relationship are known in advance, the remaining amount for each liquid level is stored in the tank table when the storage tank is installed.

Further, when measuring the remaining amount in the liquid storage tank, the remaining amount calculating means accesses the tank table and calculates the tank level from the liquid level height obtained by the liquid level height calculating means and the data stored in the tank table. Calculate the remaining amount with high accuracy.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 7.

In the drawings, 11A, 11B, 11C,... Are storage tanks used in the present embodiment (hereinafter, referred to as “storage tank 11” as a whole).
Each of the liquid storage tanks 11 stores oil liquids 12A, 12B, 12C,... (Hereinafter, referred to as “oil liquid 12”), and 13A, 13B, 13C,. 13 ").

14A, 14B, 14C,... Are liquid level sensors of the present embodiment inserted into oil storage tanks 11A, 11B, 11C,.
14 "), and the liquid level sensor 14 is configured as a coaxial cylindrical liquid level sensor.

Here, as specifically shown in FIG. 3, the liquid level sensor 14 has an outer cylinder 15 formed of one cylindrical body, and a cylinder 16 coaxially inserted into the outer cylinder 15. , The inner cylinder 16 is an upper inner cylinder 16
A, a lower inner cylinder 16B, and a water detecting inner cylinder 16C below the lower inner cylinder 16B. The lower end of the upper inner cylinder 16A and the upper end of the lower inner cylinder 16B are insulating members. 17, the lower end of the lower inner cylinder 16B and the upper end of the water detection inner cylinder 16C are also connected via an insulating member 18. The liquid level sensor 14 has a signal line of the upper inner cylinder 16A of 19A and a lower inner cylinder 16A.
19B a signal line B, 19D ₁ a signal line of the water detection inner cylinder 16C, the signal line of the outer cylinder 15 19C, is connected to the tank monitor 20 via five signal lines 19, 19D ₂ I have.

Next, reference numeral 20 denotes a tank monitoring device provided in an office room or the like of a gas station. The casing 20A of the tank monitoring device 20 includes an arithmetic operation including a processing circuit (CPU), an input / output circuit (I / 0 circuit), and the like. 5, a circuit 21 and a tank table shown in FIG. 5, a data memory 22 comprising a RAM for storing a dielectric constant obtained by an operation to be described later, a tank shape and a dimensional relationship inputted as necessary, A program memory 23 comprising a ROM for storing various programs including the programs shown in FIGS. 6 and 7 is provided.

On the front side of the casing 20A of the tank monitoring device 20, various keys including a display 24, a numeric keypad 25, an oil key 26, and a water key 27 are provided, and a printer 28 is provided.
Moreover, a buzzer 29 is attached.

On the other hand, the arithmetic circuit 21 is connected to liquid level sensors 14A, 14B,... Provided for each of the storage tanks 11A, 11B,. ing.

In addition, 31 is an external indicator provided outside the gas station building,
32 is a modem horn for communicating with, for example, a main store,
These external display 31 and modem horn 32
It is connected to the arithmetic circuit 21 by S485. On the other hand, 33 is a POS provided in the office, and the POS 33 is also connected to the arithmetic circuit 21 by RS485.

The present embodiment is configured as described above, and its operation will be described next.

First, the tank table shown in FIG. 5 while referring to FIG.
34 is described. The tank table 34 can be created by a predetermined arithmetic expression known in advance if various conditions such as the shape, installation form, and dimensional relationship of the tank are known.
2 and can be created at the site where the liquid storage tank 11 is installed.

That is, in step 1 of FIG. 4, the tank type of the liquid storage tank 11 including the installation form and the type of the liquid level sensor 14 are set, and in step 2, these tank types are corresponded (2).
In the next step 3, the dimensional relation of the tank is set, that is, the trunk length L, the radius r, and the mirroring function f.
(M) and the like are input as constants.

Now, if the types of the liquid storage tank 11 and the liquid level sensor 14 are determined, the lower inner cylinder of the liquid level sensor 14 is
Height .DELTA.l ₀ between 16B lower end is determined as a constant value. Therefore, the following constant height .DELTA.l ₀ in step 4 by changing the liquid level .DELTA.l to 1mm each as a reference, calculates the remaining amount ΔQ at that time. This processing is repeated each time the liquid level height Δl is increased by 1 mm. When the liquid level reaches the upper limit level of the tank corresponding to the current calculation in step 5, the processing is terminated. Therefore, the tank table 34 shown in FIG. 5 can be created based on the processing of FIG. 4, and this tank table 34 is stored in the data memory 22. Needless to say, the tank table 34 is created for each of the liquid storage tanks 11A, 11B, 11C,.

Next, the operation at the time of measuring the actual remaining amount at the gas station will be described.

First, general capacitance measurement using the liquid level sensor 14 will be described.

Now, let the length of the upper inner cylinder 16A be l _a and the length of the lower inner cylinder 16B be
l _b , the capacitance formed by the outer cylinder 15 and the upper inner cylinder 16A is C _a , the capacitance formed by the outer cylinder 15 and the lower inner cylinder 16B is C _b, and the dielectric constant of air is ε _o , the dielectric constant of the liquid 12 is ε.

Now, as shown in FIG.
12 is almost fully charged and its liquid level 13 is in the upper inner cylinder
16A is in the axially intermediate position of the length of the upper inner cylinder 16A is immersed in the liquid 12 and .DELTA.l _a.

In this state, the capacitance C _a formed between the outer cylinder 15 and the upper inner cylinder 16A is changed to the upper inner cylinder signal line 19A and the outer cylinder signal line 19C.
Only the tank monitoring device 20 is electrically connected. As a result, the capacitance C _a is from _{(1), C a = K × {Δl} a × ε + (l a -Δl a) × ε o ...... (3) , and the dielectric constant of air epsilon _o Is ε _o ≒ 1, so
The expression (3) becomes the following expression (4).

C _a = K × {l _a + Δl _a (ε−1)} (4) Next, to measure the capacitance C _b formed between the outer cylinder 15 and the lower inner cylinder 16B, Only the cylinder signal line 19B and the outer cylinder signal line 19C are electrically connected to the tank monitoring device. At this time, since the lower inner cylinder 16B is immersed in the liquid 12 over its entire length l _b, the electrostatic capacitance C _b is a following equation (5).

_{C b = K × l b ×} ε ... (5) Further, to measure the total electrostatic contents C _S formed by the inner cylinder 16 and outer cylinder 15, for upper inner cylinder signal line 19A and the lower inner cylinder The signal line 19B is electrically connected to the tank monitoring device 20 as a parallel connection. This gives the total capacitance C _S
(4), can be detected as (5) from _{equation, C S = C a + C} b = K × {l a + l b + (l b + Δl a) × (ε-1)} ...... (6). Here, (l _b + Δl _a ) in the equation (6)
Is a length in which the upper inner cylinder 16A and the lower inner cylinder 16B are immersed in the liquid 2, and is a constant except for including a dielectric constant of (ε-1). Therefore, if the total capacitance C _S is obtained, the liquid surface height (l _b + Δ
l _a ) can be measured.

On the other hand, in the above description, the case where the liquid level 13 in the liquid storage tank 11 is in the state shown in FIG. 3 is described. However, when the liquid level 13 falls halfway through the lower inner cylinder 16B, the upper inner cylinder 16A Is not immersed in the liquid surface, its capacitance C _a ′, that is, the empty capacitance C _a ′
Is, C _a as with _{'= K × l a ... (} 7) , and the capacitance C _b of the lower inner tube 16B' is _{(4), C b '= K × {} l b + Δl b (ε- 1)｝ (8) Therefore, the total capacitance C _S is (7)
From equation (8), C _S = C _a ′ + C _b ′ = K × {l _a + l _b + Δl _b (ε−1)} (9), which is (l _b + Δl) in equation (6). _a) a is obtained by the Δl _b.

Kakusure In the general formula ranging total liquid level in the liquid storage tank _{11, C S = K × {(} l a + l b) + (Δl a + Δl b) × (ε-1)} ...... (10) and the upper cylinder 16A and the lower cylinder 16B are regarded as one inner cylinder 16, Thus, the liquid level can be detected in the same manner as in the case of the prior art shown in Expression (1).

By the way, the liquid stored in the liquid storage tank 11 generally has a different effective permittivity every time it is consumed and newly replenished, and it is customary that the liquid is almost completely filled when newly replenished. is there.

Therefore, in the present embodiment, it is possible to calculate the effective permittivity, which will be described below with reference to FIG.

In FIG. 6, it is monitored in step 11 whether a predetermined time, for example, 1 minute, 1 hour, 24 hours, etc., has elapsed.
Reads in the capacitance C _a of the upper cylindrical 16A calculated by the flow advances to step 12 (4) when it is determined that S ". In the next step 13, the empty capacity C _a ′ stored in the data memory 22
Is read. That is, the capacitance C _a 'when Δl _a = 0 when the upper inner cylinder 16A is not immersed in the liquid 2 does not include the dielectric constant ε as is apparent from the equation (7), and is a known value determined by a constant. Value.

Then, in the next step 14, it is determined whether or not C _a > C _a ′ (12). If “YES” is determined, the liquid level 13 is higher than the lower surface position of the upper inner cylinder 16A, 16B indicates that they are all in the position immersed in the liquid 12.

Therefore, when the liquid level is in a state satisfying the expression (12), for example, when the liquid storage tank 11 is in a full state,
Proceeds to step 15 (5) reads the capacitance C _b by an equation the effective permittivity ε at step 16, The process is completed by updating this value in the area in the data memory 22 in step 17. Therefore, in this embodiment, the liquid level can be measured by using the effective permittivity in each case, instead of using the nominal permittivity.

Further, the processing of calculating the liquid level and the remaining amount, which are the main functions of the tank monitoring device 20 according to the present embodiment, is described in FIG.
This will be described with reference to the drawings.

First, in step 21, the total capacitance C _S obtained by the equation (10) is read, and in the next step 22, the effective permittivity ε calculated in advance by the processing of FIG. 6 is read. And
In the next step 23, the liquid level height Δl is calculated from the relations of equations (10) and (11). Is calculated as In this case, K, l is a constant determined by the liquid level sensor 14, epsilon is the effective dielectric constant, the C _S is the total capacitance formed between the upper inner cylinder 16A and the lower inner tube 16B and the outer cylinder 15 Thus, the liquid level height Δl can be calculated with extremely high accuracy.

On the other hand, the current liquid level height Δl
Is calculated, the liquid level height area of the tank table 34 is accessed based on this value Δl, and the remaining amount ΔQ can be immediately calculated from the remaining amount area corresponding to the area. Specifically, if the liquid level height Δl is Δl ₄ , the remaining amount is ΔQ ₄ .

When the calculation of the remaining amount ΔQ is performed in this manner, the tank monitoring device 20 displays the remaining amount ΔQ on the display 24 by setting the tank number on the numeric keypad 25, pressing the oil key 26, or the like, and the remaining amount becomes the lower limit value. When it reaches, the buzzer 29 operates, and when the print switch is pressed, data such as the remaining amount ΔQ, the liquid level height Δl, and the amount of water are printed out from the printer 28.

In the present embodiment, since the calculation of the remaining amount ΔQ is performed based on the tank table 34 provided in advance as described above, the arithmetic circuit 21 in the tank monitoring device 20 calculates the remaining amount in a very short time. Can be performed. In contrast,
Prior art includes cubic function, trigonometric function, etc. (2)
The remaining amount calculation is performed by using the calculation formula of the formula and while reading the constant of the dimensional relation for each tank, and the present embodiment is performed at a speed of 1/5 to 1/100 as compared with the related art. The remaining amount can be measured. Therefore, even in a large gas station where ten liquid storage tanks 11 are buried, arithmetic processing can be performed with a sufficient time margin.

Further, the tank monitoring device 20 of the present embodiment is connected to the external display 31 and the modem horn 29 by RS485 communication, and it is possible to display the remaining amount outdoors and the like.
Data communication according to the demand of the original sales such as the estimated order quantity is possible, and the POS 33 is also connected to the POS 33 by the RS485 communication, so that the data communication such as the remaining amount and the sales amount is possible.

However, in the tank monitoring device 20 of the present embodiment, as described above, the remaining time calculation time for each of the liquid storage tanks 11A, 11B,... Can be shortened, so that sufficient time can be provided for these external communications. As a result, not only the function of calculating the remaining amount ΔQ and the liquid level height Δl but also the external communication function can be immediately responded to by one rank monitoring device 20, and the operation of the gas station can be smoothed.

In the embodiment, since the upper cylinder 16A and the lower cylinder 16B of the liquid level sensor 14 are connected via the insulating member 17, when the liquid level becomes higher than the position of the insulating member 17, the electrostatic theoretically occurs. There is a step between the capacity and the liquid level, but it can be practically ignored.

〔The invention's effect〕

The in-tank remaining amount measuring device according to the present invention is as described in detail above, and has the following effects.

Since the inner cylinder of the liquid level sensor is a separate type of the upper inner cylinder and the lower inner cylinder, and the length of the lower inner cylinder is known, every time oil is stored in the liquid storage tank, there is a liquid level up to the upper inner cylinder. A new dielectric constant can be measured for the replenished liquid from the capacitance formed between the outer cylinder and the lower inner cylinder and the length of the lower inner cylinder. Using this dielectric constant, the liquid level can be accurately measured.

A configuration in which the relationship between the liquid level and the remaining amount of the storage tank is calculated in advance based on the shape of the storage tank whose tank type and dimensional relationship are known in advance, and the relationship between the two is stored as a tank table. Calculated by the liquid level height calculating means, and by using the liquid level height and the data in the tank table, the remaining amount in the oil storage tank can be calculated immediately in a short time. There is no need to perform complicated calculations over a long period of time with dimensional relationships and calculation formulas according to the tank shape, and even in gas stations with a large number of buried storage tanks, residual quantity management, water quantity management, ordering It is possible to respond immediately to predictions and the like.

In connection with the above-mentioned items, since it is possible to give a margin to the processing capacity of the tank remaining amount measuring device, even when an external display, a modem horn, a POS, etc. are optionally connected, data communication with these external devices is performed. And can smoothly manage gas stations.

[Brief description of the drawings]

1 to 7 relate to an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a tank remaining amount measuring device according to the embodiment, FIG. 2 is a block diagram showing a circuit configuration, and FIG. FIG. 4 is a flow chart showing a tank table creation process, FIG. 5 is an explanatory diagram showing a tank table created by the process of FIG. 4, and FIG. 6 is a diagram showing a dielectric constant calculation process. FIG. 7 is a flowchart showing a liquid level height and remaining amount calculation process, and FIG. 8 is a configuration diagram in a case where a conventional tank remaining amount measuring device is applied to a gas station. 11 ... liquid storage tank, 12 ... oil liquid, 13 ... liquid level, 14 ... liquid level sensor, 15 ... outer cylinder, 16 ... inner cylinder, 16A ... upper inner cylinder, 16B ... lower inside Cylinder, 20 …… Tank monitoring device, 21 ……
Arithmetic circuit, 22 Data memory, 23 Program memory, 24 Display, 25 numeric keypad, 26 Oil key, 27
... water key, 28 ... printer, 29 ... buzzer, 31 ... external display, 32 ... modem horn, 33 ... POS, 34 ... tank table.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01F 23/26 G01F 23/00

Claims (1)

(57) [Claims] 1. A capacitance type liquid level sensor comprising one outer cylinder, an upper inner cylinder provided in the outer cylinder, and a lower inner cylinder having a predetermined known length, and the liquid level sensor. After confirming that the liquid surface exists up to the upper inner cylinder of the sensor, the liquid to be measured is determined based on the capacitance formed between the outer cylinder and the lower inner cylinder and the length of the lower inner cylinder. A dielectric constant calculating means for calculating a dielectric constant, a capacitance formed between the outer cylinder, the upper inner cylinder and the lower inner cylinder of the liquid level sensor, and a new dielectric constant calculated by the dielectric constant calculating means. Liquid level height calculating means for calculating the liquid level height based on the above, and the liquid level height and the remaining level of the liquid storage tank based on the shape of the liquid storage tank whose type and dimensional relationship are known in advance. A tank table for calculating the relationship with the liquid level in advance and storing the remaining amount for each liquid level, Liquid level has been calculated Te and using said tank table, the liquid storage tank amount measuring apparatus comprising consist of the remaining amount calculation means for calculating the remaining amount in the tank.