JPH0620977Y2 - 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 contained in a tank.

[Prior Art] As a conventional volume measuring apparatus of this type, FIGS.
There is one as shown in Fig. 1. Hereinafter, this conventional example will be specifically described.

FIG. 17 shows the initial state when the liquid level measurement is started, and
FIG. 8 is a diagram showing a state in the process of measuring the liquid level, which is obtained when the piston (volume change means) 7 is moved to the deepest part of the cylinder (volume change amount) 8, that is, when the maximum stroke is moved. Indicates the status.

In FIG. 17, 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. In addition, n is the number of moles of gas in each cavity of the cylinder 8, the correction chamber 9 and the tank 3, R is a 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 keeping the heat insulation, v ₀ = 0 as shown in FIG. 18 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 (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. 17 and 18, the air permeability between the correction chamber 9 and the tank 3 is completely cut off. As described above, in FIG. 17, P ₀ (v ₀ + V ₁ ) ^{Since γ} = nRT ₀ holds, and v ₀ = 0 in FIG. 18 and the pressure in the tank 3 increases by ΔP ₀ ′, (P ₀ + ΔP ₀ ′) V ₁ ^γ = nRT ₀ holds. Thus, P ₀ (v ₀ + V ₁ ) ^γ = (P ₀ + ΔP ₀ ′) V ₁ ^γ (3) Equation (3) is approximately And from this 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 Δ
Since P ₀ ′ can be measured, 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 first
Reference numeral 3a in FIGS. 7 and 18 denotes a pipe for supplying a liquid 4 such as gasoline to the engine.

Next, the structure of an example of a concrete device based on the principle of the invention described above will be described with reference to FIGS. 19 and 20. In FIG. 19, the same components as those in FIG. 17 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 is a cylinder, one end opening 8a of which is communicated with the correction chamber 9 and the other end of which is open. 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, for example, 10 times the maximum volume change amount of the cylinder 8, that is, the maximum volume v ₀ that changes 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, and gas flows between the inside of the tank 3 and the correction chamber 9. It is set to be possible. A part of the first pipe 11 between the liquid injection port 5 and the electromagnetic valve 10 is positioned higher than the opening edge of the liquid injection port, and the liquid 4 is injected up to the opening edge of the liquid injection port 5. Is also set so that the liquid 4 does not flow into the correction chamber 9. Reference numeral 12 is a pressure sensor, which is a reference pressure chamber 12a, a detection pressure chamber 12b, and both pressure chambers.
Partitions 12a and 12b, and is composed of a strain plate 12c and a pressure sensor main body 12d such as a strain gauge attached to the strain plate in proportion to the pressure difference between the pressure chambers, and the reference pressure chamber 12a is a cavity. Chamber 13 and second pipe 14 of fine tube
Is connected in series to the first pipe 11, and the cavity 13
The second pipe 14 absorbs pressure fluctuations in the tank 3 and constitutes an air pressure filter. In addition, the detection pressure chamber 12b
Is communicated with the correction chamber 9, and the pressure sensor main body 12d detects the pressure difference between the pressure chambers 12a and 12b received by the strain plate 12c and converts it into an electric signal. Reference numeral 15 is a disk, which is provided with a through hole 15a and is connected with one end of a crank 15b for linearly reciprocating the piston 7. Also 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 for receiving a signal for rotating the motor 16 immediately after turning on the power from an arithmetic processing circuit 21 which will be described later, and for matching the position of the optical sensor 17 with the through hole 15a of the disk 15. The signal is supplied to the motor 16. Further, the motor drive control circuit 18 receives a signal other than the above signal from the arithmetic processing circuit 21 described later, and supplies the motor 16 with a drive signal for rotationally driving the motor 16 at a constant angular velocity ω ₀ . 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.
A noise component generated in the pressure sensor 12 and a drift component generated in the pressure sensor 12 in response to the temperature rise in the tank 3 are removed. An amplitude detection circuit 20 receives the output of the bandpass filter 19 and detects its peak value. Two
1 is an arithmetic processing circuit, which is a CPU (CENTRAL PROCESSOR UNIT), R
It is composed of OM (READ ONLY MEMORY) 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 supply the calculation result to the display unit 22. And display it.

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

In Fig. 21, when the power is turned on, the start step
The processing proceeds from 100 to the initialization step 101, and the arithmetic processing circuit 21
When the CPU and the like constituting the above are initialized and a predetermined time has elapsed after the initialization, in the step 102 of starting the output of the valve closing signal, a signal for closing the valve 10 is output from the arithmetic processing circuit 21 to a drive circuit (not shown). Through valve 1
Supply to 0. 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, the volume v ₀ corresponding to the maximum volume change amount of the cylinder 8 and the pressure change width ΔP ₀ ′ in the correction chamber 9 measured by the pressure sensor 12 (the piston 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 the reciprocating motions of 7). After obtaining, stop the output of the valve closing signal Step 104
Then, the supply of the valve closing signal to the valve 10 is stopped to open the valve 10, the process proceeds to the next step 105 for calculating the cavity volume in the tank, and the reciprocating motion of the piston 7 in the coefficient estimating step 103 is performed. By reciprocating the piston 7 more times than the number of times, the step piston 10
In 5, the previous coefficient GanmaP ₀ determined in step 103, the volume v ₀ corresponding to the maximum volume change in the cylinder 8, which is stored in the ROM, the volume of said volume v ₀ and the correction chamber 9 stored likewise in the ROM V ₁ and the pressure ΔP ₀ detected by the pressure sensor 12.
The volume V _{2 of the} hollow portion in the tank 3 is obtained based on (the average value of the pressure change width of the reciprocating motion of the piston 7), and then the liquid level calculation step piston 106 is executed. 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 step 1 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, and this step 1
At 07, a signal for displaying the liquid level on the display unit 22 is supplied from the arithmetic processing circuit 21, and then the process returns to the step 102 of starting the output of the valve closing signal. After that, the above operation is repeated periodically or aperiodically. A cancel step (not shown) is provided between the in-tank cavity volume calculation step 105 and the liquid level calculation step 106 when the volume of the cavity 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 disk 15 is placed at the position of the optical sensor 17. The through holes 15a are aligned with each other. This operation is completed within a predetermined time immediately after the power is turned on. afterwards,
The valve 10 is closed by the valve closing signal being supplied from the arithmetic processing circuit 21 to the valve 10. Further, the arithmetic processing circuit 21 causes the motor drive control circuit 18 to transmit the motor 16 to the valve 10.
A signal instructing the start of multiple rotations is supplied. When the signal is supplied, the motor drive control circuit 18 causes the motor 1
6 is rotated at a constant angular velocity ω ₀ in one direction by the indicated number of rotations, and the disk 15 connected to the rotation shaft of the motor 16 is rotated, whereby the piston 7 reciprocates in the cylinder 8 via the crank 15b. The air in the portion of the volume V ₁ that moves and corresponds to the maximum volume change amount of the cylinder 8 is corrected.
When the pressure in the correction chamber 9 is changed to a sine wave by sucking the air in the correction chamber 9 or sucking the air in the correction chamber 9, the pressure in the detection pressure chamber 12b of the pressure sensor 12 is sine by transmitting the pressure in the correction chamber 9. The difference between the pressure in the tank 3 and the pressure in the reference pressure chamber 12a, which changes in a wavy manner, is equal to the pressure sensor body 1
It is detected by 2c and converted into a sinusoidal electric signal. The signal is supplied to the amplitude calculation circuit 20 via the bandpass filter 19, and the peak value thereof is detected. The detected peak _value is supplied to the arithmetic processing circuit 21 and averaged, whereby the coefficient γP ₀ is calculated and stored in a register or the like in the CPU. Thereafter, 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 is rotated more times than when the coefficient γP ₀ is calculated. The calculation of 2) is performed, the volume of the liquid 4 in the tank 3 is calculated, and the calculation result is displayed on the display unit 22. After that, the above operation is repeated, and the coefficient γP ₀ is updated and stored every time the valve 10 is closed, and a new liquid level is 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 3 and the correction chamber 9 are
There is a problem that the configuration is connected via the valve 10 and the overall shape of the device becomes large.

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 and the hollow portion in the tank 3 communicate with each other to form one space. There is a problem that it is not considered and becomes a separate space, which causes a measurement error. To avoid this, if the driving angular frequency ω ₀ of the piston 7 is made extremely small, the measurement time becomes long. There was a problem. Therefore, it is conceivable to use a valve having a large opening cross-sectional area, but there is a problem in that cost increases.

[Means for Solving the Problem] The present invention has been made in view of the above-mentioned conventional problems, and a cavity is formed in a part of the tank so that the contents in the tank do not enter the cavity. A volume changing means for changing the internal volume, a tubular protective cylinder for preventing an external force load from being applied to the volume changing means due to splashing of the liquid to be measured, A volume measuring device provided with a pressure sensor for detecting a pressure change in the cavity accompanying the operation of the volume changing means, and capable of accurately measuring the volume of the contents in the tank by an output signal from the pressure sensor. To provide.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 16.

First, referring to FIGS. 1 to 6, the principle will be described.
Reference numeral 30 denotes an irregularly shaped main tank that stores liquids, powders, particles, irregularly shaped objects, and the like.
A correction tank 31 is connected to 0 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.
By the operation of the volume changing mechanism 33, the correction tank 31
The volume inside can be changed.
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. 1. This is composed of two types of tanks 31 and 30 having volumes V ₁ and V ₂ . The tanks 31 and 30 are pipes 3 having a flow resistance r ₁ .
2 and the vent hole 35 of the tank 30 has a flow resistance r ₂ . The specific heat ratio of the gas in both tanks 30 and 31 is γ, the gas constant is R, and the thermal time constant of the tank 31 is τ. 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).

When the tanks 30 and 31 are rigid, the tanks 30 and 31 do not distort when the tanks 30 and 31 are pressurized and depressurized. Therefore, the volume change amount v ₀ (t) due to the piston, the diaphragm, the bellows, etc. and the volume change amount that actually occurs. v (t) is equal. If tank 30
Is flexible, the tank 30 is distorted when the pressure inside the tank is increased or decreased, so that v (t) becomes smaller than v (t) by the amount corresponding to the volume change amount due to the expansion or contraction.

When v (t) = 0, the absolute pressure of the gas in the tank 31,
The temperature and the number of moles are p ₀ , T ₁ and n ₁ , respectively, or the absolute pressure of the gas in the tank 30, the temperature and the number of moles are p respectively.
₀ , T ₂ , and n ₂ . When the measurement environment does not change significantly, gas flows through the vent holes 35 into and out of the tanks 31 and 30, so the absolute pressure p ₀ inside the tanks 31 and 30 is equal to the atmospheric pressure, and the change is very slow. Changes equally with.

When v (t) ≠ 0, the pressure, temperature and number of moles also change according to the situation of the volume changing mechanism 33. In the tank 31, the pressure is p ₀ + Δp ₁ (t) and the temperature is T ₁ + ΔT ₁ (t ), And the number of moles changes to n ₁ −Δn ₁₂ (t).

In the tank 30, the pressure changes to p ₀ + Δp ₂ (t), the temperature changes to T ₂ + ΔT ₂ (t), and the number of moles changes to n ₂ + Δn ₁₂ (t) -Δn ₂ (t). Δn ₁₂ (t)
Is the number of moles of air flowing from tank 31 to tank 30, Δ
n ₂ (t) is the number of moles of air leaked from the tank 30 to the outside through the ventilation hole 35.

We now set the following assumptions for this system.

1) The gas inside the tanks 31 and 30 is an ideal gas.

2) v (t) << {V ₁ , V ₂ } 3) The heat capacity of the tank 30 is large, and the temperature change in the tank due to the pressure change Δp ₂ (t) is the change rate of the volume change amount v (t). It can be ignored much later than that.

4) The rate of change of the volume change amount v (t) is set so that the pressure that changes accordingly 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 ₂ (t), ΔT with respect to the volume change amount v (t)
The changes in ₁ (t), ΔT ₂ (t), Δn ₁₂ (t), and Δn ₂ (t) are originally
Although expressed by a non-linear equation, its size is very small for p ₀ , T ₁ , T ₂ , n ₁ , and n _{2 according} to Assumption 2), and therefore can be approximated by a linear equation. The relationship among the pressure, temperature, and number of moles of the gas in the tanks 30 and 31 in the static state is represented by the following algebraic equation.

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

The flow rate resistance r and r ₁ and r ₂ in the above equation are obtained from the length and diameter d of the pipe 32 by the following equation.

This formula has a length 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 tank-specific constant that is determined from the material, shape, volume, etc. of the tank, and Δv (t) is the volume change amount due to expansion or contraction of the tank due to the change in the volume change amount v ₀ (t) of the volume change mechanism 33. Is.

The transfer function from the input v (t) to the output ΔP ₁ (t) is obtained by subjecting the expressions (1a) to (1i) to the Laplace transform, and the result is 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, r ₂ V ₂ / RT ₂ is a time constant of pressure decay when the gas having the absolute temperature T ₂ of the hollow portion in the tank 30 flows to the outside of the tank 30 through the ventilation hole 35 having the flow resistance r ₁ . The correction coefficient k ₂ (s, r ₁ , r ₂ , V ₁ , V ₂ ) varies depending on the volume V ₂ of the main tank 30, but k ₂ (s, r ₁ , r ₂ , In the frequency characteristics of V ₁ and 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.

If r ₁ <<< r ₂ (r ₂ is the flow resistance of air vent 35) and thermal time constant τ and r ₂ {V ₁ + MinV ₂ } / RT ₂ are similar, There is a frequency.

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, 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 + ΔV)
Becomes

When the volume changing mechanism 33 is driven by a sine wave at an angular frequency ω ₀ , Is satisfied, it is considered that the pipe 32 is equivalent to the closed state.

I.e. If

(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. Therefore, from the input v (t) in FIG. 3, the output ΔP ₂
The transfer coefficient up to (t) is r ₁ → 0, T ₂ =
T ₁ , ΔP ₂ = ΔP ₁ , 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 (2i) At this time, the transfer function is γP ₀ / (V ₂ ′ + ΔV) Becomes

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

In FIG. 5, the correction tank 31 corresponds to the tank 31 in FIG. 1, and the diaphragm, which is the volume changing mechanism 33, has two types of angular frequencies ω _L and ω _H (ω _L <ω _H ) at the same time (v ₀ sin ω _L t + v ₀ sin ω _H t) or alternately (v ₀ sin ω _L t, v ₀ sin ω _H t) to drive the pipe 32.
At a high angular frequency ω _H , the flow resistance r ₁ becomes much larger than the equation (2e), so 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 32 becomes an air leak hole having an extremely large flow resistance, the pressure change of only the correction tank 31 can be measured, and in this case, the theory of the single tank system shown in FIG. 3 is applied.

Here, the volume of the correction tank 31 is V ₁ , the main tank 30
The volume of the gas inside is V ₂ , the volume of the liquid inside 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.

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 in 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, Δp ₁ ′ (t) when v (t) is driven at angular frequency ω _L
When you measure the amplitude of Assuming that the amplitude of Δp ₁ (t) when driven by ω _H is A ₁ and the amplitude of Δp ₁ (t) when driven by ω _L is A ₂ , the formula (3a),
From (3b), the sum V ₁ + V ₂ of the gas volumes in the main tank 30 and the correction tank 31 can be obtained as follows.

The liquid volume V _L is obtained as follows.

If the main tank 30 is flexible, A ₁ , A ₂
The value C of the ratio is as follows.

In this case, ΔV and | k ₁ | / | k ₂ | must be found by calibration to find the liquid amount. For calibration, the main tank 30 is filled with a correctly measured volume of liquid and V ₂ and C are determined. Do this twice for different volumes, substitute the obtained value into equation (3f), and
This is a method of obtaining V, | k ₁ | / | k ₂ |.

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

The signal processing for the rigid tank and the flexible tank in the above description of the principle is as follows.

(B) When the rigid tank (Figure 6) volume change mechanism 33 _{(v 0 sinω L t + v} 0 sinω H t) (ω L <
When driven by the driving force of (ω _H ), the pressure change caused by the driving force is detected by the gauge pressure sensor 34 and supplied to the two band-pass filters 36 and 37 connected in parallel.
One of the bandpass filters 36 has a central angular frequency ω
_L is set to extract only the signal component of the angular frequency ω _L , and the other band pass filter 37 is set to extract only the signal component of the angular frequency ω _H at the central angular frequency ω _H angle. ing. These bandpass filters 36,
The respective output signals of 37 are connected to each other, and the amplitudes are detected by the amplitude detectors 38 and 39 of the same gain, and one of the amplitude detectors 38 that detects the amplitude of the signal component of the lower angular frequency ω _L is detected. The output γ P ₀ v ₀ is the output of the other amplitude detector 39 that detects the amplitude of the signal component of the higher angular frequency ω _H. Is divided by the divider 40 to calculate the sum (V ₁ + V ₂ ) of the volume V ₂ of the hollow portion in the main tank 30 and the volume V ₁ of the correction tank 31.

The calculation result V ₁ + V ₂ is subtracted from the sum of the volume V _T of the main tank 30 set by the subtractor 41 and the volume V ₁ of the correction tank 31, and the result is stored in the main tank 30. The volume V _L of the stored item such as a liquid is calculated. In addition,
The gain of one bandpass filter 36 is set to V ₁ times the gain of the other bandpass filter 37.

(B) the case of a flexible tank (Figure 5) volume change mechanism 33 is driven by the driving force of _{(v 0 sinω L t + v} 0 sinω H t) (ω L <ω H), it pressure change due to gauge It is detected by the pressure sensor 34 and supplied to the two band pass filters 36 and 37. One of the bandpass filters 36 extracts the signal component of the angular frequency ω _L , the other bandpass filter 37 extracts the signal component of the angular frequency ω _H , and the output signals of the respective components are connected to the above-mentioned amplitudes. 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 for detecting the amplitude of the signal component of the lower angular frequency ω _L is the higher angular frequency ω _H
Output of the other amplitude detector 39 for detecting the amplitude of the signal component of Divided by the divider 40 by Is calculated.

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

Next, a concrete embodiment of the present invention will be described with reference to FIGS. 7 to 16.

First, referring to FIG. 7, the structure of the volume changing mechanism 33 will be described. The volume changing mechanism 33 is provided in the upper opening 33 of the tank 3.
A yoke storage housing 33s for forming a yoke storage chamber 33e is attached to the inside of a lid 33d that is airtightly attached to a via a mounting screw 33b and a backing 33c.
This yoke housing 33s is provided with a relatively large diameter ventilation hole 33t at the upper end thereof, and a hole 33g 'into which a guide rod 33f and a connecting rod 33, which will be described later, are loosely fitted, on the lower side surface thereof.
And 33g are drilled. A first yoke 33h, which is movably supported in the vertical direction by a guide rod 33f and a guide wall 33g and has a large-diameter vent hole 33r provided on the upper surface, is housed in the yoke housing chamber 33e. There is. Further, inside the first yoke 33h, a magnet 33i and a second yoke 33j which can be attached to the magnet 33i are provided, and the second yoke 33j and the first yoke 33h are provided.
A solenoid coil 33k is positioned between the and.
The solenoid coil 33k is fixed to the lid 33d via a yoke housing 33s. Second yoke 3
3j has a hole 3 provided in the yoke housing 33s.
A connecting rod 33 penetrating 3q is attached, and the tip of the connecting rod 33 is fixedly attached to the central portion of a rigid bottom plate 33m. The bottom edge of the cylindrical bellows 33n is airtightly adhered to the periphery of the bottom plate 33m, and the upper edge of the cylindrical bellows 33n is airtightly fixed to the lid 33d. In addition, in the central portion of the bottom plate 33m, there are fine holes for equalizing the static pressure between the inside of the bellows 33n and the hollow portion of the tank 3.
33p is formed, and when the cylindrical bellows 33n is stored, the pore 33
It has a function of discharging liquid such as water droplets generated when the gas in the tank 3 entering the space inside the bellows 33n is condensed via p. 33u is on the outside of the cylindrical bellows 33n,
A cylindrical protective member having a bottom which is close to the cylindrical bellows 33n so as not to come into contact with the cylindrical bellows 33n. The pore 33v is provided. Further, the base material 33x that is airtightly interposed between the upper end edge of the tubular protection member 33u and the flange portion of the yoke housing 33s is emitted from the solenoid coil 33k, and the ventilation hole 33r and
Vent holes 33w for discharging the heat that is going to be radiated through 33t to the outside of the cylindrical protection member 33u when the cylindrical bellows 33n contracts, and zero the temperature difference between the inside and outside of the cylindrical bellows 33n.
Has been drilled. The uppermost surface of the contained liquid 4 is set so that the bottom plate 33m is not immersed. In some cases, the bellows may be the one in which the cylindrical bellows 33n and the bottom plate 33m are integrated.

Next, the operation will be described based on FIGS. 8 (A) and 8 (B).

In this system, the detection signal from the pressure sensor 34 is differentiated by a differentiating circuit 43, and the differentiated output is fed back to a solenoid 33h via an amplifier 44 to resonate the bellows 33n in a vertical direction at a constant frequency.

Next, the operation of the above model is analyzed. First, in FIG. 8 (B) which is a model of FIG. 8 (A), variables and coefficients are defined as follows.

K: Composite spring constant of bellows 33n and air spring _Kb : Spring constant of bellows 33n x: Displacement of bellows 33n m: Sum of mass of first and second yokes 33h and 33j and magnet 33i d: Bellows 33n Air damper constant f: Force applied to bellows 33n G: Gain of amplifier 44 B: Magnetic flux density of solenoid 33k I: Length of solenoid 33k coil that cuts magnetic flux of magnet 33i i: Current flowing through solenoid 33k L : Inductance of solenoid 33k R: Coil resistance of solenoid 33k V ₁ : Voltage of amplifier 44 applied to solenoid 33k V: Actual voltage applied to solenoid 33k From the above definition, Fig. 8 (B) is as follows. Is shown by the equation of state.

f = bIi (7) V = V ₁ −BIx (9) V ₁ = Gx (10) In principle, this system has various conditions in the actual equipment that can be expressed by the above equation, and taking that fact into consideration, It is assumed that the following assumption holds.

In equation (8), L is a few mH and is negligible, and can be expressed by the following equation.

The spring constant K can be expressed by the bellows K _b and the air spring as follows.

Considering the maximum expansion and contraction characteristics of the bellows, K has the characteristics shown in FIG. Therefore, the term of Kx in the equation (6) can be expressed as K (x) as follows.

Therefore, equation (6) is Becomes

Since the gain G in the equation (10) is limited in the voltage obtained by the amplifier, it is assumed that the amplifier has the characteristics shown in FIG.

Taking this into consideration, the characteristics of FIG. 5 are approximated using tan ⁻¹ .

Therefore, the following equation of state holds from Eqs. (6) ′, (7), (8) ′, (9), and (10) ′.

From the above equation (13), when the resonance frequency (f) when the bellows 33n makes a single vibration is calculated: As a result, the value of V can be set low by forming the lid plate 33r in an inverted U shape as shown in FIG. 9 and setting the volume (V) of the yoke accommodating chamber large. is there.

Next, a specific example in which the volume changing means 33 is installed in the tank 3 to detect the volume of the liquid will be described with reference to FIGS. 10 to 12.

First, the case where the tank 3 is a rigid body will be described. By the volume changing mechanism 33, the volume V ₂ of the hollow portion in the tank 3 becomes V ₀ s.
It can be changed with the volume fluctuation of in ω ₀ t. The pressure accompanying the volume fluctuation is converted into an electric signal by the pressure detector 34, and is connected to the low-pass filter 45 having the amplification degree γv ₀ and the hand-pass filter 37 having the amplification factor of 1 at the central angular frequency ω _{0 which} are connected in parallel. Supplied. The static absolute pressure in the tank 3 is γ by the low-pass filter 45.
It is detected as v ₀ P ₀ , and the same frequency as the drive frequency of the volume changing mechanism 33 is set as the center frequency. However, since the drive frequency of the volume changing mechanism 33 slightly fluctuates, the drive frequency is set to the center. As volume changing means 33
Volume change V ₀ by the hand-pass filter 37 in which a band is set so as to pass the changed frequency of the drive frequency of
Pressure change equivalent to sin ω ₀ t Detected as. The maximum value of this pressure change is detected by the amplitude detector 39. Detected as. The output of the low pass filter 45 is then divided by the output of the amplitude detector 39 by the divider 40. The divided value becomes the volume V ₂ of the hollow portion of the tank 3, and when it is subtracted from the total volume V _T of the tank 3 by the subtracter 41, the result becomes the volume V _{L of the} liquid 4.

The amplitude detector 39 is formed by connecting a rectifier circuit and a smoothing circuit in series to detect the amplitude value, and noise having an angular frequency ω ₀ is supplied from the pressure sensor 34 to the bandpass filter 37. If it occurs, it may be canceled and not detected.

Further, the frequency for varying the volume V ₂ of the hollow portion in the tank 3 is 1 to 15 Hz and 20 Hz or more from the situation of the distribution of the frequency spectrum of the pressure noise caused by the vibration accompanying the driving of the vehicle as shown in FIG. Can be set as the selection range.

The bandpass filter 37 'in FIG. 10 has a cutoff characteristic by changing the gain with respect to the central angular frequency ω and the frequency characteristic, and the bandpass filter 37' is shown in FIG. ), The signal obtained from the amplifier 44 is pulsed by the waveform shaper 47, the output is converted into a voltage by the ′ -v (frequency-voltage) converter 48, and based on the converted output, the central angular frequency is changed as shown by the chain line. It changes ω ₀ . As a result, the mechanical external vibration is reduced by the bellows 33n.
When the resonance angular frequency ω ₀ fluctuates, the frequency characteristic of the bandpass filter 37 'is changed in response to the fluctuation without changing the gain, and the volume changing means 33 is surely operated.
Therefore, only the pressure change is extracted.

Further, in FIG. 12, the pressure fluctuation due to the heat of the gasoline returned from the engine to the tank is shown by a thin line (a), and the pressure fluctuation due to the vibration of the tank wall and the gasoline sloshing is shown by a thick line (b). Therefore, for example, considering the case where the spectrum for volume variation at a constant frequency is A, the frequency for varying the volume V ₂ of the hollow portion in the tank 3 can be set to 1 to 25 Hz or 30 Hz or more as a selection range. .

From the above, it is possible to obtain a signal having an S / N ratio by setting the frequency for varying the volume V ₂ of the hollow portion in the tank 3 in the range of 1 to 15 Hz and 30 Hz or higher.

Next, the case where the tank 3 is a non-rigid body, that is, flexible, will be described with reference to FIG.

Moreover, although the angular frequency ω ₀ does not satisfy the formula (2g), | k ₁ (s, r ₂ , V
_If the main tank 30 is flexible, that is, if the main tank 30 is deformed by the pressure during pressurization, the ratio of γP ₀ v and A ₁ can be calculated by the divider 40. The result is as follows.

Equation (5e) has two unknowns, ΔV and | k ₁ |. These values are obtained as experimental values by calibration. Further, the liquid volume _VL is obtained from the following equation.

V _L = V _T + ΔV-C · | k ₁ | (5f) ΔV = distortion correction amount due to pressurization C · | k ₁ |: correction amount due to drive frequency fluctuation Next, the main tank 30 is flexible as described above. The operation of the system in such a case will be described. Volume change mechanism 33
Therefore, the volume V ₂ of the hollow portion in the main tank 30 is v ₀
The volume of Sin ω ₀ t can be changed. The pressure accompanying the volume change is converted into an electric signal by the pressure detector 34, and is supplied to the low-pass filter 45 having the amplification factor γv ₀ and the hand-pass filter 37 having the amplification factor of 1 at the angular frequency ω _{0 which} are connected in parallel. To be done. The static absolute pressure in the main tank 30 is detected as γv ₀ P ₀ by the low-pass filter 45, and the same frequency as the drive frequency of the volume changing mechanism 33 is set as the center frequency, and the volume change is centered around that frequency. With the hand-pass filter 37 set to pass the fluctuation frequency of the drive frequency of the mechanism 33, the pressure change corresponding to the volume change v ₀ sin ω ₀ t. Detected as. The maximum value of this pressure change is detected by the amplitude detector 39. Detected as. The output of the low pass filter 45 is then divided by the output of the amplitude detector 39 by the divider 40. The divided value is set as the sum of the volume V ₂ of the hollow portion of the main tank 30 and the volume change ΔV when the main tank 30 is expanded by pressurization by being amplified by the amplifier 46 having the amplification degree | k |. Total volume of tank 3 V _T
When subtracted from + ΔV by the subtractor 41, the result is the volume V _{L of the} liquid 4.

In each of the embodiments of the present invention, as a result of measuring the tank internal volume when the fuel was injected into the main tank 30, as shown in FIG. High volumetric measurements were made.

Next, another embodiment of the tank structure of the present invention will be described with reference to FIGS.

That is, in the case where the tank 3'has the same shape in cross section in one direction such as a cylinder, a hole 3'having the same shape as the cross section of the same shape in one direction of the tank 3'and provided at the upper and lower ends thereof.
A partition plate 3'c having a and 3'b partitions the inside of the tank 3'to form a small measuring chamber 3'e, and the liquid volume in this measuring chamber 3'e is measured. Since the change mechanism 33 can be estimated, the overall shape of the device can be made extremely small accordingly.

However, in this case, it is necessary to measure the volume ratio between the measuring chamber 3'e and the tank 3'in advance, and the value obtained by multiplying the volume of the liquid 4 in the measuring chamber by the ratio is the liquid in the tank. Total volume.

Further, according to this embodiment, since the bellows 33n, that is, the cylindrical protection member 33u positioned around the volume changing mechanism 33 is provided, for example, the liquid 4 contained in the tank 3
When the liquid surface bounces due to mechanical rocking, or when an external liquid force generated as a large wave collides with the outer surface of the bellows, the impact force is blocked by the cylindrical protection member 33u. No external force is applied to the bellows 33n. Therefore, since the bellows is not changed by an external force, accurate volume measurement can be performed without causing a measurement error.

[Advantage of the Invention] As described above, according to the present invention, a volume changing mechanism for forming a hollow portion in which the contents in the tank do not enter in a part of the tank and changing the volume of the hollow portion, Since the pressure sensor that detects the pressure change in the cavity due to the operation of the volume changing mechanism can be provided and the volume of the contents in the tank can be measured by the output signal from the pressure sensor, the contents in the tank can be measured. The remaining amount can be detected very easily and accurately by the pressure and the electric signal, and can be detected with stable accuracy. Therefore, since the contents in the tank can be detected by the extremely simple and compact mechanism, there is an effect that the easiness of detection and the economical efficiency of the equipment are improved. Further, since the frequency characteristic of the bandpass filter can be changed, the effect of improving the mechanical vibration resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, and FIG. 2 shows a change state of the coefficient k ₂ of the transmission relationship when the drive frequency of the volume changing mechanism 33 and the volume of the stored contents in the tank in FIG. 1 are changed. FIG. 3 is a characteristic diagram, FIG. 3 is a principle explanatory diagram for explaining FIG. 1, and FIG. 4 is a diagram when the drive frequency of the volume changing mechanism 33 and the storage volume in the tank 30 are changed in FIG. FIG. 5 is a characteristic diagram showing a changing state of the coefficient k ₁ of the transfer function, FIG. 5 is an explanatory diagram of an embodiment of the present invention, FIG. 6 is an explanatory diagram of another embodiment of the present invention, and FIG. 7 is a volume changing mechanism. 33 is a detailed explanatory view of 33, FIG. 8 (A) is an operation explanatory view of the changing mechanism in FIG. 7, FIG. 8 (B) is an analysis model drawing of FIG. 8 (A), and FIG. 9 is a volume changing mechanism. FIG. 10 is an explanatory view showing another embodiment, FIG. 10 is an explanatory view of a system according to the present invention, and FIG. 11 is a pressure fluctuation due to heat of return fuel during vehicle operation. Frequency spectrum diagram, FIG. 12 is a frequency spectrum diagram of pressure fluctuation due to heat fluctuation of return fuel during operation, and pressure fluctuation due to liquid fluctuation and vibration of tank wall surface, and FIG. 13 is a system explanatory diagram according to another embodiment. FIG. 14 is a graph showing the volume measurement value of the embodiment according to FIG. 10, FIG. 15 is an explanatory view of another embodiment in which a partition plate is provided in the tank, FIG. 16 is an external view thereof, and FIG.
21 to 21 are explanatory views of a conventional example. 30 ... Main tank, 31 ... Correction tank 32 ... Connection pipe, 33 ... Volume change mechanism 34 ... Gauge sensor, 35 ... Vent hole 36, 37, 37 '... Bandpass filter 38, 39 ... … Amplitude detector 40 …… Divider, 41 …… Subtractor 42 …… Amplifier, 43 …… Differentiation circuit 44 …… Amplifier 45 …… Low-pass filter 46 …… Amplifier

Claims (1)

[Scope of utility model registration request] 1. A volume changing mechanism which is located in a tank and changes the tank internal pressure at a predetermined frequency, a pressure sensor for detecting the tank internal pressure, and a detection signal from the pressure sensor. A low-pass filter for extracting static pressure in the tank, and a band-pass filter connected in parallel to the low-pass filter for extracting a signal component of the same frequency as the frequency of the volume changing mechanism from a detection signal from the pressure sensor. A divider for dividing the output of the low-pass filter by the band-pass filter, and a volume calculating means for calculating the volume of the DUT stored in the tank based on the output from the divider, And a cylindrical protection member surrounding the volume changing mechanism and protecting the volume changing mechanism from being acted upon by an external force from the object to be measured. That volume measuring device.