JPH081456Y2 - Volume measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a volume measuring device for measuring the volume of a liquid, a powder pair, a grain pair, an irregularly-shaped object, or the like contained in a tank.

[Prior Art] As a conventional volume measuring apparatus of this type, Figs.
There are some as shown in the figure. Hereinafter, this conventional example will be specifically described.

FIG. 6 shows the initial state when the liquid level measurement is started, and FIG.
The figure is a diagram showing the state in the process of measuring the liquid level,
The piston (volume change means) 7 is a cylinder (volume change amount)
8 shows a state in which it has been moved to the deepest part of 8, that is, when it has moved by the maximum stroke.

In FIG. 6, the volume of the tank 3 is V _T , the volume V _{2 of} its hollow portion, that is, the portion not filled with the liquid 4, and the volume corresponding to the maximum volume change amount of the cylinder 8 are V ₀ (<<
V ₁ , V ₂ ), the volume of the correction chamber 9 is V ₁ , the pressure in the tank 3 is P ₀ , and the valve 10 is open, P ₀ (based on Poisson's law) V ₂ + v ₀ + V ₁ ) ^γ = nRT ₀ holds. Note that n is the number of moles of the gas in the cavity of the cylinder 8, the correction chamber 9 and the tank 3, R is the gas constant, T ₀ is the absolute temperature of the gas, and γ is the ratio of the constant pressure specific heat and the constant volume specific heat.

Here, when the piston 7 is moved by the maximum stroke while maintaining the heat insulation, v ₀ = 0 as shown in FIG. 7 and the pressure in the tank 3 increases by ΔP ₀ , and (P ₀ + ΔP ₀ ) (V ₂ + V ₁ ) ^γ = nRT ₀ holds. From this, P ₀ (V ₂ + v ₀ + V ₁ ) ^γ = (P ₀ + ΔP ₀ ) (V ₂ +
V ₁ ) ^γ (1) Equation (1) is approximately And the volume V ₂ of the hollow portion of the tank 3 is Becomes

Next, when the valve 10 is closed in FIGS. 6 and 7, the air permeability between the correction chamber 9 and the tank 3 is completely cut off,
As described above, in FIG. 7, P ₀ (v ₀ + V ₁ ) ^γ = nRT ₀ holds, and in FIG. 7, v ₀ = 0, and the pressure in the tank 3 increases by ΔP ₀ ′. (P ₀ + ΔP ₀ ′) V ₁ ^γ = nRT ₀ holds. As a result, P ₀ (v ₀ + V ₁ ) ^γ = (P ₀ + ΔP ₀ ′) V ₁ ^γ (3) Equation (3) is approximately Becomes Here, the volume v ₀ corresponding to the maximum volume change amount of the cylinder 8 and the volume V ₁ of the correction chamber 9 are known, and ΔP ₀ ′
Can be measured, so that the value of γP ₀ can be obtained. As a result, the volume V ₂ of the hollow portion of the tank 3 in the equation (2) can be calculated, and the volume V _{L of the} liquid 4 can be calculated.
Can be determined by V _T −V ₂ . The sixth
Reference numeral 3a in the drawings and FIG. 7 is a pipe for supplying a liquid 4 such as gasoline to the engine.

Next, the configuration of an example of a concrete device based on the principle of the invention described above will be described with reference to FIGS. 8 and 9. In FIG. 8, the same components as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 7 denotes a piston, which is composed of a disk-shaped permanent magnet having magnetic poles on its peripheral surface, and the magnetic fluid 7a is adsorbed on its peripheral surface.
A gap with a cylinder 8, which will be described later, is closed, ventilation is prevented, and friction when the piston 7 slides in the cylinder 8 is reduced. Note that ventilation may be prevented by attaching an O-ring to the peripheral surface of the piston 7. Reference numeral 8 denotes a cylinder, one end of which has an opening 8a communicating with the correction chamber 9 and having the other end opened. Reference numeral 9 is a correction chamber, the volume of which is V ₁
Is set to be sufficiently small with respect to the total volume V _T of the tank 3, and is set to, for example, 10 times the maximum volume change amount of the cylinder 8, that is, the maximum volume v ₀ changed by sliding of the piston 7. Once set, one reciprocation of the piston 7 causes the internal pressure change to change in a sinusoidal manner (this is due to the constant-speed rotation of the motor 16 described later). Further, the correction chamber 9 is connected near the opening edge of the liquid injection port 5 of the tank 3 via the electromagnetic valve 10 and the first pipe 11 in series,
The gas is set so as to be able to flow between the tank 3 and the correction chamber 9. In addition, the liquid injection port 5 of the first pipe 11,
A part of the space between the electromagnetic valves 10 is positioned higher than the opening edge of the liquid injection port, so that the liquid 4 does not flow into the correction chamber 9 even if the liquid 4 is injected up to the opening edge of the liquid injection port 5. Is set to. 12 is a pressure sensor, which is the reference pressure chamber
12a, the detection pressure chamber 12b, both pressure chambers 12a, 12b are partitioned, and the strain plate 12c that is distorted in proportion to the pressure difference between the both pressure chambers, and the strain gauge pressure applied to the strain plate, etc. The reference pressure chamber 12a is composed of a sensor body 12d, and the reference pressure chamber 12a is connected to the first pipe 11 which is in series with the cavity chamber 13 and the second pipe 14 of the fine tube, and the cavity chamber 13 and the second pipe 14 are connected to each other.
Composes an air pressure filter by absorbing pressure fluctuations in the tank 3. The detection pressure chamber 12b is communicated with the correction chamber 9, and the pressure sensor main body 12d receives both pressure chambers received by the strain plate 12c.
The pressure difference between 12a and 12b is detected and converted into an electric signal. Reference numeral 15 is a disk, which is provided with a through hole 15a and which has a piston 7
One end of a crank 15b for reciprocating linear movement is connected. The disk 15 is connected to a rotating shaft of a motor 16 described later via a reduction gear (not shown).

An optical sensor 17 is provided so as to face the through hole 15a at a position where the piston 7 is retracted to the maximum, and detects the through hole 15a of the disc 15. Reference numeral 18 denotes a motor drive control circuit, which receives a signal for rotating the motor 16 immediately after turning on the power from an arithmetic processing circuit 21 described later, and a disc at the position of the optical sensor 17.
A signal for matching the 15 through holes 15a is supplied to the motor 16. Further, the motor drive control circuit 18 is an arithmetic processing circuit 21 described later.
A signal different from the above signal is received from the motor 16 to drive the motor 16 at a constant angular velocity ω _0.
Supply to. Reference numeral 19 denotes a bandpass filter, which is set to extract and output only the frequency component corresponding to the angular velocity ω ₀ of the motor 16, and corresponds to the noise component generated in the pressure sensor 12 and the temperature rise in the tank 3. The drift component and the like generated in the pressure sensor 12 are removed. An amplitude detection circuit 20 receives the output of the bandpass filter 19 and detects its peak value. Reference numeral 21 denotes an arithmetic processing circuit, which is a CPU (CENTRAL PROCE
SSOR UNIT), ROM (READ ONLY MEMORY), etc., and inputs the output of the amplitude detection circuit 20 and executes the following arithmetic processing to calculate the liquid level in the tank 3 and display the calculation result. It is supplied to the part 22 and displayed.

Next, the operation of the arithmetic processing circuit 21 will be described based on the flowchart shown in FIG.

In Fig. 10, when the power is turned on, the start step
The procedure proceeds from 100 to the initial setting step 101, and when the CPU and the like which form the arithmetic processing circuit 21 are initialized, and a predetermined time has elapsed after the initial setting, the step of outputting the valve closing signal is started.
At 102, a signal for closing the valve 10 is supplied from the arithmetic processing circuit 21 to the valve 10 via a drive circuit (not shown). Next, in the coefficient estimation step 103, the coefficient γP ₀ value in the equation (4) is estimated by reciprocating the piston 7 a plurality of times. That is, the volume V ₁ of the correction chamber 9 stored in the ROM and the volume v ₀ corresponding to the maximum volume change amount of the cylinder 8 and the pressure change width ΔP ₀ ′ of the correction chamber 9 measured by the pressure sensor 12 (the piston 7 ΓP ₀ is calculated based on γP ₀ = ΔP ₀ ′ V ₁ / v ₀ of the equation (4) by the average value of the pressure change widths of a plurality of reciprocating motions. After obtaining, proceed to the step 104 of stopping the output of the valve closing signal,
In order to release the valve 10, the supply of the valve closing signal to the valve 10 is stopped, the process proceeds to the next step 105 for calculating the cavity volume in the tank, and the piston 7 in the coefficient estimating step 103
By reciprocating the piston 7 a number of times greater than the number of reciprocating motions of
03 by a factor GanmaP ₀ determined volume v ₀ corresponding to the maximum volume change in the cylinder 8 stored in the ROM, in the same manner as said volume v ₀ RO
Based on the volume V ₁ of the correction chamber 9 stored in M and the pressure ΔP ₀ (average value of the pressure change width of the reciprocating motion of the piston 7 a plurality of times) detected by the pressure sensor 12, The volume V ₂ is calculated and the next liquid level calculation step 106
Then, the volume V _{L of the} liquid 4 is calculated by subtracting the volume V _{2 of the} hollow portion in the tank 3 obtained in the immediately preceding step 105 from the total volume V _T of the tank 3 stored in the ROM.
Further, the process proceeds to the next liquid level signal generation step 107, in which the signal for displaying the liquid level on the display unit 22 is supplied from the arithmetic processing circuit 21, and then the step for starting the output of the valve closing signal is started. Return to 102. After that, the above operation is repeated periodically or aperiodically. The calculation step 105 of the cavity volume in the tank and the calculation step 106 of the liquid level
A cancel step (not shown) is provided between and when the volume of the hollow portion in the tank 3 changes significantly.

[Operation] Next, the operation of the above configuration will be described. When the power is turned on, a signal for matching the through hole 15a with the position of the optical sensor 17 is supplied from the optical sensor 17 to the motor drive control circuit 18, the motor 16 is rotated and the disc 15 is placed at the position of the optical sensor 17. Through hole 15
a is matched. This operation is completed within a predetermined time immediately after the power is turned on. Then the arithmetic processing circuit
The valve 10 is closed by supplying a valve closing signal from the valve 21 to the valve 10. Further, the arithmetic processing circuit 21 supplies a signal for instructing the motor drive control circuit 18 to start rotating the motor 16 a plurality of times. . When the signal is supplied, the motor drive control circuit 18 causes the motor 16 to rotate at a constant angular velocity ω ₀ in one direction by a designated number of rotations, and the disc 15 connected to the rotation shaft of the motor 16 is rotated. As a result, the piston 7 reciprocates in the cylinder 8 via the crank 15b, and the air in the volume V ₁ corresponding to the maximum volume change amount of the cylinder 8 is sent to the correction chamber 9 or the air in the correction chamber 9 is sucked. However, if the pressure in the correction chamber 9 is changed in a sine wave shape, the pressure in the detection pressure chamber 12b of the pressure sensor 12 becomes
The pressure in the correction chamber 9 changes in a sinusoidal manner by being transmitted, and a difference between the pressure in the tank 3 and the pressure in the reference pressure chamber 12a, which is equal to the pressure in the tank 3, is detected by the pressure sensor main body 12c and converted into a sinusoidal electric signal. The signal is supplied to the amplitude detection circuit 20 via the bandpass filter 19 and its peak value is detected. The detected peak _value is supplied to the arithmetic processing circuit 21 and averaged to calculate the coefficient γP _{0, which} is stored in a register or the like in the CPU. After that, the supply of the valve closing signal from the arithmetic processing circuit 21 to the valve 10 is stopped, the valve 10 is opened, and the motor 16 causes the coefficient γP to rise.
_The equation (2) is calculated by rotating the liquid more times than when calculating _0, and the liquid 4 in the tank 3 is rotated.
Is calculated, and the calculation result is displayed on the display unit 22. Thereafter, the above operation is repeated, and the coefficient γP ₀ is updated and stored every time the valve 10 is closed, and the liquid level is newly calculated again.

[Problems to be Solved by the Invention] However, in such a conventional volume measuring apparatus, in order to estimate the coefficient γP ₀ , the tank and the correction chamber 9
However, there is a problem in that the size of the entire apparatus becomes large due to the configuration in which the valve and the valve are connected.

Further, if a valve having a small opening cross-sectional area is used as the valve 10, the flow resistance becomes large, and when the valve 10 is opened and pressurized, the correction chamber 9 communicates with the empty space in the tank 3 into one space. As a separate space,
There is a problem that causes a measurement error, and in order to avoid this, if the drive angular frequency ω ₀ of the piston 7 is made extremely small, there is a problem that the measurement time becomes long. Therefore, it is conceivable to use a valve having a large opening cross-sectional area, but there is a problem in that cost increases. Further, in the conventional tank 3, when the material thereof is resin or metal, particularly when it is a resin or a large tank having a large capacity even if it is made of metal,
When the liquid 4 is swung in the tank 3 containing a large amount of liquid 4, the bottom surface of the tank 4 has a flat surface as shown in FIG. It resonates at a very low frequency of 10 to 30 Hz.
Therefore, there is a problem that the frequency of the signal component extracted by the filter 19 is approached and it becomes difficult to extract the signal component.

[Means for Solving the Problem] The present invention has been made in view of such conventional problems, and a plurality of tanks are connected by a pipe, and any one of the plurality of tanks is connected to the tank. A means for changing the volume is provided, and the means is driven at the same number of kinds of frequencies as the number of the tanks, the pressure fluctuation is detected by a pressure sensor, and the pressure of the plurality of tanks is detected based on the detection output. It is possible to calculate the volume of at least one in-tank containment, and to connect a desired portion of the inner bottom surface of the tank that is vibrated at the resonance frequency, between the bottom surface and the upper surface of the tank via a column. However, by shifting the resonance (deflection) frequency of the bottom of the tank by this column, that is, the low-frequency resonance frequency to a high frequency, the signal component can be easily extracted and highly accurate volume calculation can be performed. It is to provide a volume measuring device.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 5.

Reference numeral 30 denotes an irregularly shaped main tank that stores liquids, powders, particles, irregularly shaped objects, etc.
A correction tank 31 is connected to this via a connecting pipe 32. Further, a small-diameter vent hole 35 is formed in the upper portion of the irregularly shaped main tank 30. A volume changing means (mechanism) 33 such as a piston, a bellows, a diaphragm, etc. is provided above the correction tank 31, and the volume in the correction tank 31 can be changed by the operation of the volume changing mechanism 33. You can do it. Note that in FIG. 5, a gauge pressure sensor 34 for detecting the internal pressure in the correction tank 31 is provided.

The above is the configuration of the present embodiment. Next, the measurement principle of the configuration will be described.

Measurement Principle (1) Consider a connected tank system as shown in FIG. It is composed of tanks of the types V ₁ and V ₂ . The tanks 31 and 30 are connected by a pipe 32 having a flow resistance r ₁ , and the flow resistance of a ventilation hole 35, which is a gap between the liquid injection port of the tank 30 and the lid, is r ₂ . The specific heat ratio of the gas in both tanks 30 and 31 is γ, the gas constant is R, and the tank 3
Let τ be the thermal time constant of 1. A volume change mechanism 33 using a piston, a diaphragm, a bellows, etc. is attached to the tank 31, and the volume change amount actually generated by this volume change mechanism 33 is v (t).

If the tanks 30 and 31 are rigid, the tanks 30 and 31 do not distort when the tank is pressurized and depressurized, so the piston, diaphragm, and
The volume change amount v ₀ (t) of the bellows or the like is equal to the volume change amount v (t) actually generated. If the tank 30 is flexible, the tank 30 will be distorted when the tank is pressurized and depressurized.
(T) is smaller than v ₀ (t).

When v (t) = 0, the absolute pressure, temperature, and number of moles of the gas in the tank 31 are p ₀ , T ₁ , n ₁ , and the tank 30, respectively.
Let p ₀ , T ₂ and n ₂ in the gas inside. When the measurement environment does not change significantly, the gas circulates inside and outside the tanks 31 and 30 through the vent holes 35, so that the absolute pressure p ₀ is equal to the external pressure, and the change is very slow and changes to the external pressure.

When v (t) ≠ 0, the pressure, temperature and the number of moles also change to the situation of the volume change mechanism. In the tank 31, the pressure is p ₀ + Δp ₁ (t) and the temperature is T ₁ + ΔT ₁ (t), mole. The number changes as n ₁ −Δn ₁₂ (t).

In the tank 30, the pressure is p ₀ + Δp ₂ (t), the temperature is T ₂ + ΔT ₂ (t), and the number of moles is n ₂ + Δn ₁₂ (t) -Δn ₂
It changes with (t). Δn ₁₂ (t) is from tank 31 to tank
The number of moles of air that has flowed to 30 and Δn ₂ (t) is the number of moles of air that has leaked from the tank 30 to the outside through the vent holes 35.

 We now set the following assumptions for this system.

1) The gas in the tank is an ideal gas.

2) v (t) << {V ₁ , V ₂ } 3) The heat capacity of the tank 30 is large and the pressure change Δp
_The temperature change in the tank with ₂ (t) is the volume change v
It is very slow compared to the changing speed of (t) and can be ignored.

4) The rate of change of the volume change amount v (t) is such that the pressure that changes with it is equal throughout the tanks 30 and 31.

5) Even if an object to be measured is put in the tank 30, the object does not form two or more closed gas spaces, that is, hollow portions in the tank 30.

The above assumptions are not very restrictive. Δp ₁ (t), Δp with respect to the volume change amount v (t)
₂ (t), ΔT ₁ (t), ΔT ₂ (t), Δn ₁₂ (t),
The change of Δn ₂ (t) is originally expressed by a non-linear equation, but its magnitude is p ₀ , T ₁ , T ₂ , n ₁ , n according to Assumption 2).
_{It is} very small compared to ₂ , so it can be approximated by a linear equation. The gas pressure in the tanks 30 and 31 in the static state,
The relationship between temperature and the number of moles is expressed by the following algebraic equation.

p ₀ V ₁ = n ₁ RT ₁ , p ₀ V ₂ = n ₂ RT ₂ (1a) Also, from the assumptions 1), 3), 4) and 5), the gas in the tanks 30 and 31 in the dynamic state is The relationship between pressure, temperature and number of moles is
It is expressed by the following linear ordinary differential equation.

The flow resistance r, r ₁ and r ₂ in the above equation, can be obtained from the length l and the diameter d of the pipe 32 by the following equation.

This formula has a length 1 of 50 to 650 [mm] and a diameter d of 2.0 to 9.0 [m
m] was obtained experimentally using an aluminum pipe.

 The volume change v (t) is expressed as follows.

ΔV is a constant peculiar to the tank determined by the material, shape, volume, etc. of the tank, and Δv (t) is the volume change amount due to expansion and contraction of the tank due to the change in the volume change amount v ₀ (t) of the volume change mechanism 33. Is.

Laplace transform is applied to equations (1a) to (1i) and input v
The transfer function from (t) to the output Δp ₁ (t) is calculated as follows.

Becomes The coefficients r ₂ V ₂ / RT ₂ , r ₁ V ₂ / RT ₂ and r ₁ V ₁ / RT ₁ are time constants of pressure change. For example vent holes 35 of the r ₂ V ₂ / RT ₂ is the gas absolute temperature T ₂ of the hollow portion in the tank 30 flow resistance r ₂
It is a time constant of pressure decay when flowing out of the tank 30 via. The correction factor k ₂ (s, r ₁ , r ₂ , V ₁ , V ₂ ) is the main tank 30
Of the volume of V ₂ of k ₂ (s,
In the frequency characteristics of r ₁ , r ₂ , V ₁ , V ₂ ), it can be approximately regarded as a constant by selecting an appropriate frequency, for example, a frequency of 4 × 10 ⁻⁴ to 10 ⁻³ Hz in the section A.

r ₁ << r ₂ (r ₂ is the flow resistance of the air vent 35)
Then, if the thermal time constant τ and r ₂ {V ₁ + MinV ₂ } / RT ₂ are similar, the following angular frequency exists.

Under this condition, the correction coefficient k ₂ (s, r ₁ , r ₂ , V ₁ , V ₂ ) is approximated as follows.

| K ₂ (iω, r ₁ , r ₂ , V ₁ , V ₂ ) | ≈ 1 ∠k ₂ (iω, r ₁ , r ₂ , V ₁ , V ₂ ) = 0 (2d) Therefore, the formula (2c) When the condition of is satisfied, the transfer function from the input v (t) to the output Δp ₁ (t) is γp ₀ / V ₁ + V ₂ + Δ
V).

When the volume changing mechanism 33 is driven in a sine wave shape at the angular frequency ω ₀ , If is satisfied, it is considered to be equivalent to the state where the pipe is closed. It is considered to be equivalent to the state where the pipe 32 is closed.

That is Should be fine.

(2) Next, consider a single tank system as shown in FIG. This is a case where the cross-sectional area of the pipe 32 connecting between the tanks 31 and 30 in FIG. 1 is made very large, and this corresponds to the case where the value of the flow resistance r ₁ of the pipe 32 becomes very small. From this, from v (t) in FIG. 3, Δp ₂ (t)
Up to r ₁ → 0, T ₂ =
T ₁ , Δp ₂ = Δp ₁ , and V ₂ ′ = V ₁ + V ₂ are set, and are as follows.

here, Becomes Consider the following angular frequency ω.

For example, it is a frequency of 10 ⁻³ Hz or more shown by A in the frequency characteristic of FIG. By setting such a frequency, the correction coefficient k ₁ (iω, r ₂ , V ₃ ′) is approximated as follows.

| k ₁ (iω, r ₂ , V ₃ ′) ≈1, ∠k ₁ (iω, r ₂ , V ₃ ′) ≈0 (2h) At this time, the transfer function is γp ₀ / (V ₂ ′ + ΔV) Become.

Next, the above principle will be described based on a specific example of this embodiment shown in FIG.

In FIGS. 5 (a) and 5 (b), the correction tank 31 corresponds to the tank 31 in FIG.
The diaphragm of 33 has two kinds of angular frequencies ω _L and ω _{H, respectively.}
(Ω _L <ω _H ) and (v ₀ sinω _L t + v ₀ sinω _H t) at the same time,
Or alternately (v ₀ sinω _L t, v ₀ sinω _H t) drive, and pipe 3
2 shows that at a high angular frequency ω _H , the flow resistance r ₁ becomes much larger than the equation (2e), so that the pressure change is not transmitted to the main tank 30, and the correction tank 31 and the main tank 30 are substantially separated from each other. Since the pipe 32 becomes an air leak hole with an extremely large flow resistance, it is possible to measure the pressure change only in the correction tank 31.
In this case, the theory of the single tank system shown in FIG. 3 is applied.

What is important in this embodiment is that inside the main tank 30, between the bottom surface and the top surface of the main tank 30, that is, in the vibration surface generated by the resonance frequency of the main tank 30 shown in FIG. A pillar that suppresses vibration of the bottom surface between the bottom surface and the top surface other than the area corresponding to A
43 is installed. This pillar 43 is the main tank 30
Since it is difficult to mold the main tank 30 at the same time as the resin molding as a means for erection inside, there is a recess 46 at a predetermined position on the bottom surface 44, and the upper surface has a transparent portion for inserting a column. The main tank 30 having the holes 46 is molded, and then the columns 43 which are previously formed in the tank 30 through the through holes 46 are formed.
And insert the end 43 'of the column 43 into the recess
Lock in 45. Next, the tail end 43 ″ of the support column 43 is fixed to the upper surface of the tank by heat welding means or the like to support the support column.
43 is installed between the top and bottom of the tank 30,
It suppresses distortion (vibration) of 30. In addition, in FIG. 5 (a), the recess 45, which is a means for locking the tip 43 'of the support column 43, has a substantially hemispherical shape, but, for example, as shown in FIG. It may be a dent. As shown in FIG.
Can also be applied to the bottom inclined surface of the tank 30 as required.

Here, the volume of the correction tank 31 is V ₁ , the volume of the gas in the main tank 30 is V ₂ , the volume of the liquid in the main tank 30 is V _L , and the sum of the volumes of the correction tank 31 and the main tank 30 is V _T. To do.

For the pressure change Δp ₁ (t) of the correction tank 31, if the angular frequency ω _H that satisfies the equation (2h) is used, Becomes In addition, the main tank 30 is a rigid body, that is, ΔV =
0 and the angular frequency ω _L satisfies the equation (2c), Δp
₁ (t) is as follows.

At the next lowest angular frequency ω _L , the flow resistance of the pipe 32 becomes small, and the correction tank 31 and the main tank 30 are connected by a very thick pipe. The pressure change of both tanks 30 and 31 can be measured.

Also in this case, the principle of the single tank system shown in FIG. 3 is applied.

Therefore, when v (t) is driven at the angular frequency ω _L , Δ
When the amplitude of p ₁ ′ (t) is measured, Here, the amplitude of Δp ₁ (t) when driven by ω _H is A ₁ ,
Assuming that the amplitude of Δp ₁ (t) when driven by ω _L is A ₂ , the sum V ₁ + V ₂ of the gas volumes in the main tank 30 and the correction tank 31 is given by the following equations (3a) and (3b). Is asked.

The liquid volume V _L is obtained as follows.

When the main tank is flexible, the value C of the ratio of A ₁ and A ₂ is as follows.

In this case, ΔV, | k ₁ | / | k ₂ | needs to be obtained by calibration in order to obtain the liquid amount. For calibration, fill the main tank 30 with a correctly measured volume of liquid and determine V ₂ and C. This is performed twice for different volumes, and the obtained value is substituted into equation (3f) to obtain ΔV, | k ₁ |
This is a method of finding / | k ₂ |.

At this time, the liquid volume _VL is obtained as follows.

The signal processing based on the above principle is as follows.

In other words, the volume change mechanism 33 _{(v 0 sinω L t + v} 0 sin
When driven by the driving force of ω _H t (ω _L <ω _H ), the pressure change due to the driving force is detected by the gauge pressure sensor 34, and 2
The two above mentioned bandpass filters 36, 37 are supplied. One of the bandpass filters 36 extracts the signal component of the angular frequency ω _L , and the other bandpass filter 37 extracts the signal component of the angular frequency ω _H , and the respective output signals have the above-mentioned amplitudes connected to each other. The amplitudes are detected by the detectors 38 and 39, and the output γ | k ₁ | P ₀ v ₀ of the amplitude detector 38 that detects the amplitude of the signal component of the lower angular frequency ω _L is the higher angular frequency Output of the other amplitude detector 39 that detects the amplitude of the signal component of ω _H Divided by divider 40 by Is calculated.

The calculation result Is amplified by an amplification factor 42 of an amplification factor | k ₂ / k ₁ | corresponding to a correction coefficient calculated from the coefficient of the pressure transfer function. After that, the amplified signal is subtracted from the value (V ₁ + V ₂ + ΔV) set by the subtracter 41, and as a result, the volume _VL of the storage object such as the liquid stored in the main tank 30 is reduced. It is calculated. It should be noted that ΔV and | k ₂ | / | k ₁ | are previously obtained by calibration.

The greatest feature of this embodiment is that inside the main tank 30, the space between the bottom surface and the top surface of the tank 3 is formed by the resonance frequency of the main tank 30 shown in FIG. A pillar that suppresses the vibration of the bottom surface by protruding between the bottom surface and the top surface at a portion of the vibration surface of the main tank other than the portion corresponding to the node A of vibration. 43 was installed.

Therefore, according to this embodiment, since the resonance frequency generated on the bottom surface by the action of the pillar 43 is shifted to a high frequency, the resonance frequency is not approached to the frequency of the signal component, and the extraction of the signal component is performed. Of course, it is easy to improve the volume detection accuracy.
It is possible to easily and accurately construct the desired support column 43 at a predetermined position therein.

[Advantages of the Invention] As described above, the present invention provides a synthetic resin main tank for accommodating an object to be measured, a correction tank provided in communication with the main tank, and a predetermined internal pressure for each of these tanks. In a volume measuring device comprising a volume changing means for changing the frequency and a detecting means for detecting a pressure change of both tanks by the volume changing means, in the main tank, a vibration surface formed by its resonance frequency is used. Providing a pillar that bridges and connects the upper wall surface and the lower wall surface other than the portion corresponding to the node of vibration, the lower end of the pillar is fitted and held in the recess formed in the lower wall surface, and the upper end of the pillar is Since the volume measuring device is welded to the upper wall surface to prevent the distance between both wall surfaces from expanding and contracting, according to this, the resonance frequency generated at the bottom surface by the action of the pillar 43 is high. Since it is transferred, the resonance frequency does not approach the frequency of the signal component, the signal component can be easily extracted, the volume detection accuracy can be improved, and the column 43 is placed at a predetermined position in the tank. The effect that it can be easily installed in each person is obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention, and FIG. _{2 is} a change state of the coefficient k ₂ of the transfer function when the drive frequency of the volume changing mechanism 33 and the volume of the contents stored in the tank 30 in FIG. 1 are changed. FIG. 3 is a characteristic diagram showing FIG. 3, a principle explanatory diagram for explaining FIG. 1, and FIG. 4 is a diagram showing the drive frequency of the volume changing mechanism 33 and the storage volume in the tank 30 changed in FIG. characteristic diagram showing a change in state of the coefficient k ₁ of the transfer function of time, FIG. 5 (b) is a schematic view of another preferred embodiment of the present invention, FIG. 5 (b) is a partially enlarged view, FIG. 5 ( (C) is an explanatory view showing another embodiment of the present invention, and FIGS. 6 to 10 are explanatory views of a conventional example. 30 …… Main tank, 31 …… Compensation tank 32 …… Connection pipe, 33 …… Volume change mechanism 34 …… Gauge pressure sensor, 35 …… Vent hole 36,37 …… Band pass filter 38,39 …… Amplitude Detector 40 …… divider, 41 …… subtractor 42 …… amplifier, 43 …… support 44 …… bottom, 45 …… dent 46 …… through hole

Claims (1)

[Scope of utility model registration request] 1. A main tank made of synthetic resin for accommodating an object to be measured, a correction tank provided in communication with the main tank, and volume changing means for changing the internal pressure of each of these tanks at a predetermined frequency. A volume measuring device comprising a detecting means for detecting a pressure change in both tanks by the volume changing means, which corresponds to a vibration node of a vibration surface formed by the resonance frequency of the main tank. Providing a pillar that bridges and connects the upper wall surface and the lower wall surface other than the portion, the lower end of the pillar is fitted and held in the recess formed in the lower wall surface, and the upper end of the pillar is welded to the upper wall surface. The volume measuring device is characterized in that the distance between both wall surfaces is prevented from expanding and contracting.