JPH0711439B2 - Liquid volume measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid amount measuring device suitable for mainly measuring the liquid amount in a container such as fuel stored in an underground tank of a gas station.

(Prior Art) In order to detect the amount of fuel remaining in a gasoline tank buried underground in a gas filling station, a bar called a scale is conventionally inserted from the upper part of the tank in accordance with the standard of the tank. The visual measurement was made. However, this is troublesome and inaccurate, so in recent years, a mechanical oil level gauge that drives the meter for capacity display in conjunction with the float floating on the fuel level in the tank Electrical oil level gauges, which convert the amount of fuel from the capacitance between the rod-shaped electrodes inserted therein, have come to be used.

On the other hand, a container that is often used as an underground tank is a horizontal type having a cylindrical shape, in which the cylinder is laid sideways. In such a tank shape, since the internal fuel liquid level position and the volume do not have a linear relationship, an error is likely to occur in the process of converting the fuel amount from the liquid level position measurement result. On the other hand, for example, in the liquid level indicator disclosed in Japanese Examined Patent Publication No. 60-35612, a conversion table is used to set a function that approximately gives the fuel amount to the liquid level position in the container. The accuracy of the display of the remaining amount in the tank is improved by eliminating the error.

(Problems to be Solved by the Invention) By the way, a mechanical oil level gauge causes a so-called mechanical error depending on frictional resistance and dimensional accuracy in a portion that supports a float and transmits its movement. It has a drawback that the float easily follows the change of the liquid level position due to the expansion and contraction of gasoline, and thus an error occurs even with the temperature change. Also in the case of the electric oil level gauge, in principle, the output changes depending on the apparent liquid level position between the electrodes, which causes an error due to the temperature. It could not be measured accurately.

On the other hand, even if a liquid level indicator that displays the remaining amount by approximate calculation according to the tank shape is used, the liquid level position measurement itself depends on the conventional liquid level measuring means using a float, etc. It is inevitable that an error will occur at the time of measurement. Also, since the liquid amount is calculated by approximate calculation with respect to the tank shape, there is a large error in the calculation process especially under usage conditions where the tank internal volume frequently increases and decreases around a specific liquid level position. Therefore, it cannot be said that the reliability of the remaining amount display finally obtained is not always sufficient.

Generally, at least five underground tanks are provided at the gas station, and it is necessary to measure the liquid amount for each tank. Therefore, not only accurate means but also inexpensive means is required. There is. Further, since such a measuring device can be installed only in a limited place in a manhole, it is also a necessary condition that it is small and easy to maintain.

The present invention has been made by paying attention to such a current situation, and an object thereof is to provide a highly accurate liquid meter which is not affected by a mechanical error or a change in fuel temperature, is small, and is easy to set and maintain. There is.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a displacer having a specific weight larger than that of a liquid to be measured contained in a container,
A load cell that has a fixed end fixed to a predetermined position on the container side and a supporting body that suspends the displacer at its displacing end and that converts the weight acting on the displacing end into an electric signal and outputs the electric signal; Liquid amount configured to measure the measured liquid amount in the container based on the detected weight of the displacer immersed in the measured liquid to the extent that it does not sink below the liquid level at the specified maximum liquid level position of the measured liquid. A measuring device is provided, and a temporary fulcrum part for temporarily fixing terminals for suspending the displacer is provided below the displacement end of the support body at a position with a predetermined interval, and the displacer is the same as the container for storing the liquid to be measured. It is made of a material having a coefficient of linear expansion and the surface thereof is treated with a fluororesin.

(Operation) Based on the above configuration, the buoyancy acting on the displacer changes according to the liquid surface position of the liquid to be measured, and the weight of the displacer corresponding to this buoyancy change is converted into an electric signal via the load cell. At this time, the buoyancy acting on the displacer is obtained by multiplying the volume of the portion of the displacer immersed in the liquid to be measured by the density of the liquid to be measured, and the liquid surface position changes as the density changes according to temperature. However, since the buoyancy, that is, the weight changes so as to compensate for this, unlike the float type that follows the liquid surface position, there are very few errors with respect to changes in density and temperature. in addition,
Since the displacer is made of a material that has the same coefficient of linear expansion as the liquid container, it is possible to reliably eliminate errors due to temperature changes. Problems such as deterioration of response and corrosion can be avoided, and therefore, these actions can be combined to measure the substantial amount of the liquid to be measured with extremely high accuracy.

On the other hand, since a temporary fulcrum part for temporarily fixing the terminal for suspending the displacer is provided below the displacement end of the support body of the load cell at a position with a predetermined interval, prior to mounting the terminal on the load cell, By temporarily installing the terminals on the temporary fulcrum, it is possible to easily set the suspending position of the displacer to be constant with reference to the bottom of the container, and therefore to accurately set the distance between the bottom of the container and the displacer, which affects the measurement accuracy. Therefore, the measurement accuracy can be improved.

In addition, since this liquid volume measuring device has no mechanically operating parts, there is no room for mechanical error due to friction, etc. and it has excellent durability, and as a device for detecting the liquid surface position etc. Are the smallest.

(Embodiment) An embodiment of the invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the first liquid amount measuring apparatus. In FIG. 1, 1 is a tank containing a liquid G to be measured such as gasoline, 2 is a rising pipe provided on the upper portion of the tank, and 3 is a rising pipe. Is a mounting flange provided horizontally at the upper end opening of the rising pipe 2, and 4 is a sensor unit fixed to the mounting flange 3 using a screw or the like not shown.

The sensor unit 4 includes a plate-shaped mounting base 5 fixed to the mounting flange 3, and a load cell 6 fixed on the mounting base 5.
And a cover 7 for covering the same. The load cell 6 is fixed on the mounting base 5 with one end of a horizontally long prismatic support 8 as a fixed end 8a, and the other end as a displacement end 8b so that it can be finely displaced vertically with respect to the mounting base 5. It is provided. The load cell 6 is configured to measure a load by applying a strain gauge. Although not shown in detail, a bridge-coupled resistor is worn on the support 8 and its input terminal is shown. The magnitude of the load is detected by the change in the resistance value and the output terminal voltage associated with the minute displacement of the support 8 when a vertical load is applied to the displacement end 8b in the state where a predetermined voltage is applied.

A suspension fulcrum portion 9 is attached to the upper surface of the support body displacement end 8b, and a stainless steel cable 10 connected to this fulcrum portion 9 penetrates through a through hole 5a of the mounting base 5 opened below. Is inserted into the tank 1. cable
A displacer 11 having a right cylindrical shape is connected to the lower end of 10 so that a part of the upper end of the liquid to be measured G is exposed even when the measured liquid G has a normal maximum liquid level.

The displacer 11 is made of, for example, a pipe material made of stainless steel, and has a hollow structure in which both ends thereof are sealed. Its specific gravity (apparent specific gravity in this case) is adjusted to be slightly larger than that of the liquid G to be measured.
The length is set according to the dimensions of the tank 1. Specifically, as described above, in a state of being suspended from the support 8 so that a part of the upper end is exposed on the specified maximum liquid level, The length is set so that the lower end portion is positioned slightly above so as not to contact the bottom surface of the tank 1. Further, the displacer 11 is made of a material having the same linear expansion coefficient as that of the tank 1 to further reduce the occurrence of errors due to temperature changes, and at the same time, has a self-lubricating fluorine resin (for example, a commercial product). (Known as “Teflon”, etc.) is applied to prevent the deterioration of responsiveness due to liquid adhesion and the occurrence of problems such as corrosion and solidification.

Next, the principle of liquid amount measurement based on the above configuration will be described with reference to FIG.

In the figure, the inner diameter of the straight cylindrical tank 1 is D, the outer diameter of the displacer 11 is d, the liquid surface position of the liquid G to be measured is h, the liquid weight at that time is W, the density is ρ, and it acts on the displacer 11. Let F be the buoyancy. However, the distance Δh between the lower end of the displacer 11 and the bottom surface of the tank 1 is so small that it can be ignored. At this time, W = (D ² −d ² ) h · ρ · π / 4 (1) F = d ² · h · ρ · π / 4 (2) From equations (1) and (2), F ^{= W · d 2 / (D} 2 -d 2) ... (3) Therefore, the buoyancy F acting on the displacer 11 is independent of the density of the liquid to be measured G, and weight W, which means that substantial amounts There is a proportional relationship. For this reason, the displacer
By measuring the weight of 11, the liquid amount can be measured extremely accurately without being affected by the expansion / contraction and the density change of the liquid to be measured due to the temperature.

By the way, since this flow rate measuring device measures the weight of the displacer 11 inserted into the liquid as described above, as shown by Δh in FIG. 2, the bottom of the tank 1 and the lower end of the displacer 11 are separated from each other. It is necessary to secure an appropriate space (hereinafter referred to as "bottom space") between the two. The amount of liquid in the space at the bottom part can be known in advance from the shape and dimensions of the tank.Therefore, if a constant interval is always provided according to the specifications of the tank, there will be no hindrance in actual liquid amount management. Does not happen. However, when suspending the displacer 11 from the sensor unit 4 attached to the tank 1, it is not possible to directly measure the space between the bottoms. Therefore, use a measuring rod or scale to measure the distance from the sensor unit 4 to the bottom surface of the tank 1. It is necessary to perform a laborious work such as determining the length of the cable 10 after measuring the depth of the cable. Therefore, in the present invention, as shown in detail in FIGS. 3 and 4, provision of a temporary fulcrum portion 15 for temporarily fixing one end of the cable 10 simplifies the above-mentioned work. , Allows you to set the bottom spacing easily and accurately.

To explain this, a circular recess 12 is formed on the upper surface of the plate-shaped fulcrum portion 9 attached to the upper surface of the support body displacement end 8b. As shown in FIG. 4, a groove 13 is cut from one side of the fulcrum 9 toward the center of the recess 12, and a cylindrical terminal 14 to which the cable 10 is fixed is formed in the groove 13.
The cable 10 is passed through and then fitted into the recess 12 to be supported by the fulcrum 9. In this state,
Displacer 11 (first
The load (see the figure) is applied to the load cell 6.

By the way, in this embodiment, a temporary fulcrum 15 in the shape of a circular recess is formed around the through hole 5a opened in the mounting base 5 so as to be located below the recess 12 and in which the terminal 14 is fitted. The distance between the temporary fulcrum portion 15 and the recess 12 is predetermined to be 30 mm, for example. Incidentally, reference numeral 16 in the drawing denotes a substrate of the signal amplifier attached to the fixed support end 8a.

In order to attach such a measuring device to the tank 1, first, the displacer 11 to which the cable 10 is attached is installed in the rising pipe 2
From the above into the tank 1, and then the mounting base 5 provided with the load cell 6 is fixed to the flange 3. Cable at this time
One end of 10 is pulled out from the through hole 5a of the mounting base 5 to the outside. Next, slide the cable 10 downward with the terminal 14 passed through the cable 10 fitted in the temporary fulcrum portion 15,
When the lower end of the displacer 11 hits the bottom surface of the tank 1, the cable 10 is fixed to the terminal 14 by caulking or welding. This means that the displacer 11 is suspended from the temporary fulcrum 15 with the bottom spacing just zero, so by pulling up the cable 10 and fitting the terminal 14 into the recess 12 of the original fulcrum 9. That is, the displacer 11 is lifted by a constant height corresponding to the distance between the recess 12 and the temporary fulcrum 15.
That is, the interval between the recess 12 and the temporary fulcrum part 15 is set as the bottom interval as it is, and therefore, it is possible to set a constant bottom interval by a simple operation as described above without using a scale or the like. You can do it.

Next, a description will be given of an embodiment in which such a measuring device is applied to easily measure and display the fuel amount in the underground tank of the gas station.

In FIG. 5, 6 is a load cell, 20 is an amplifier that amplifies and outputs the signal, 21 is a control device that processes the signal of the load cell 6 to obtain the fuel amount in the tank 1, and 22 is for measuring the fuel amount. It is an operation panel for performing various related operations and displaying the liquid amount.

As will be described in detail later, the control device 21 has a main function of measuring the fuel amount in the tank 1 based on the amplified load cell signal from the amplifier 20 and causing the operation panel 22 to display a predetermined display. Although only one tank 1, one load cell 6 and one amplifier 20 are shown in the drawing, the control device 22 sequentially outputs a plurality of load cell signals corresponding to up to about 16 underground tanks, or selectively. It is configured so that it can be processed.

The operation panel 22 has a number display section for displaying the tank number as a display device for displaying the measurement result from the control device 21.
There is provided a numerical display 23 including a quantity 23a and a quantity display section 23b for displaying the fuel quantity in the tank corresponding to the number, and an alarm device 24 for giving an upper and lower limit warning of the fuel quantity. Also,
In this embodiment, a numeric keypad portion 26a for designating a tank number and the like on the operation panel 22 and a function key portion 2 for designating a function
A keyboard 26 made up of 6b and a printer 27 for recording fuel measurement results of each tank, daily reports, etc. are also provided.

The control device 21 sequentially monitors the signals from the load cells 6 attached to the plurality of tanks 1 at a predetermined timing, and sequentially stores the fuel amount obtained from this.
Output the fuel amount measurement result for the tank 1 designated according to the command from the numerical display 23 of the operation panel 22 or the printer 27, or the fuel remaining amount in any one of the tanks 1 is set to the lower limit or the upper limit. The alarm device 25 is driven upon detection of the arrival.

In this case, the control device 21 having such a function is mainly composed of a microcomputer system as shown in FIG. Explaining this, 31 is, for example, a shunt diode type explosion-proof barrier, 32 is a first I / O device, 33 is a CPU having the functions of liquid volume search means and alarm means, 34 is storage means, and 35 is second I / O device.

The first I / O device consists of an analog switch and A / D converter, etc., and sequentially selects a plurality of load cell signals input via the explosion-proof barrier 31 according to a command from the CPU 33, and logic The level signal S is output to the CPU 33.

The storage means 34 is an RO storing a predetermined operation program and the like.
M, a RAM for temporarily storing data and the like necessary in the arithmetic processing process, and an NVRAM for holding measurement results within a predetermined period. In the ROM, in addition to the program, the data W representing the fuel amount in the tank 1 in accordance with the level of the load cell signal S has a predetermined accuracy, for example, an accuracy of every 1 mm converted into the liquid level in the tank. A plurality of types of stored tables are stored for each tank standard (shape / capacity). The standard of each of the plurality of tanks 1 is stored in advance by the initialization process.

Therefore, for example, when a plurality of tanks have different standards, when the CPU 33 measures the fuel amount in each tank, first, the load cell signal S is taken out from the tank of a predetermined number, and then the tank The operation of selecting a table according to the standard, searching the table for the fuel amount W corresponding to the signal S, and storing this is repeated for each tank. Such measurement of the fuel amount in the tank is always performed at a predetermined timing.

On the other hand, if there is an instruction from the operation panel 22 via the I / O device 35 to specify a specific tank and display the remaining amount, C
The PU 33 takes out the latest data W stored for the tank of the designated number and outputs it to the operation panel 22 via the I / O device 35. At this time, the tank number designated in the number display portion 23a shown in FIG.
The measured fuel amount corresponding to the data W is displayed in each. In addition, the data W as the measurement result is the operation panel 22
It is printed out by the printer 27 in accordance with the instruction in the above. In the case of printed output, not only the amount of fuel at a certain point,
For example, since it is possible to know the change in the amount of fuel during business hours and the relationship between the amount of arrival and the amount of shipment, a daily report can be created using this.

Thus, according to this measuring device, the amount of fuel (W) in the underground tank provided at the gas station can be met in accordance with the standard.
Of the load cell signal (S) stored in advance S-
Since the configuration is such that the remaining fuel amount is obtained by a search from the W table and is displayed, compared to the conventional one in which the remaining fuel amount is obtained by calculation processing based on the fuel level position and the tank shape. It is possible to measure the fuel amount and display the fuel amount at high speed and with high accuracy regardless of the shape and size of the tank.

By the way, in this liquid amount measuring device, since the liquid amount is measured based on the change in the buoyancy acting on the displacer 11, the measurement condition is that the liquid surface is located between the upper and lower ends of the displacer 11, in other words, When the liquid level is lower than the lower end of the displacer 11 and when the liquid level is higher than the upper end, the liquid amount cannot be measured. Normally,
Although the remaining amount in the tank of the gas station will not decrease near the lower limit or the fuel will not be injected until it exceeds the specified upper limit, if such a situation occurs, it causes management inconvenience.

Therefore, the apparatus of this embodiment is configured to issue an alarm when the upper and lower limit values of the remaining amount are reached. This function is included in the CPU 33 as described above, and is judged from the load cell signal S. That is, the upper limit value can be known in advance as the load cell signal value when the liquid surface is located at the upper end portion of the displacer 11, and the lower limit value can be known in advance as the signal value when the weight of the displacer 11 acts on the load cell. By storing this in the storage means 34 for each tank and comparing it with the actually detected load cell signal value, it can be determined that the upper limit value or the lower limit value has been reached. Since the upper and lower limit values are fixed values that are determined for each tank, it is possible to store them in the SW table so that the upper and lower limit values can be known as a result of the table search.

In this way, when it is detected that the fuel amount in a certain tank reaches the upper limit value or the lower limit value in the process of continuous measurement operation, the CPU 33 causes the operation panel 22 to pass through the I / O device 35. The alarm device 24 is driven to cause a lamp corresponding to the tank to emit light or output a buzzer sound as an alarm. Therefore, it is possible to reliably prevent a situation where the fuel in the underground tank is insufficient or the fuel is excessively injected into the tank.

It should be noted that the above-mentioned embodiment shows an example of application of the present invention to one in which the fuel in the underground tank of a gas station is measured, but the present invention is not limited to this and various liquid amounts It can be applied to measurement applications, and is particularly suitable for eliminating measurement errors due to changes in temperature and density of the liquid to be measured.

As described above, according to the present invention, the error in density and temperature change in measuring the liquid amount in a container such as a gasoline tank is very small, and in addition, the displacer has the same linear expansion coefficient as that of the liquid container. Since it is formed by, it is possible to surely eliminate the error due to the temperature change, and by applying the fluororesin processing to the surface of the displacer, it is possible to avoid problems such as deterioration of response due to liquid adhesion and corrosion, and therefore extremely high. The amount of liquid to be measured can be measured with accuracy.

On the other hand, the provisional fulcrum that temporarily fixes the terminal that suspends the displacer is placed below the displacement end of the support of the load cell at a predetermined interval. Can be accurately set, and the measurement accuracy can be further improved.

In addition, since this liquid volume measuring device has no mechanically operating parts, there is no room for mechanical error due to friction, etc. and it has excellent durability, and as a device for detecting the liquid surface position etc. Is characterized by being the cheapest and most compact.

[Brief description of drawings]

FIG. 1 is a side view showing a schematic configuration of an embodiment of a liquid amount measuring device according to the present invention, and FIG. 2 is an explanatory view of its measuring principle. FIG. 3 is a partially cutaway sectional view of an essential part of the above embodiment, FIG.
The figure is also a plan view. FIG. 5 is a schematic configuration diagram of another embodiment of the present invention, and FIG. 6 is a configuration diagram of its control device. 1 ... Tank, 4 ... Sensor part, 5 ... Mounting base, 6 ... Load cell, 8 ... Support, 8a ... Fixed end of support, 8b ... Same displacement end, 9 ... Support point, 10 …… Cable, 11 …… Displacer, 14 …… Terminal, 15 …… Temporary fulcrum, 21 …… Control device, 22 …… Operating panel, 23 …… Numerical display, 24 …… Alarm device, 26 …… Keyboard, 27 ... Printer, 32 ... First I / O device, 33 ... CPU, 34 ... Storage means, 35 ... Second I / O device.

Claims (1)

[Claims] 1. A displacer having a specific weight larger than that of a liquid to be measured contained in a container, and a fixed end fixed to a predetermined position on the container side, and a supporting body suspending the displacer at its displacing end. And a load cell that converts the weight acting on the displacement end into an electric signal and outputs the electric signal, and immerses it in the liquid to be measured to the extent that it does not sink below the liquid surface at the specified maximum liquid surface position of the liquid to be measured. A liquid amount measuring device configured to measure the amount of liquid to be measured in a container based on the detected weight of the displacer, wherein the displacer is hung at a position with a predetermined space below the displacement end of the support. In addition to providing a temporary fulcrum for temporarily fixing the terminals, the displacer is made of a material having the same linear expansion coefficient as the container for the liquid to be measured, and the surface thereof is treated with a fluororesin. Liquid measurement device according to.