JP2507655Y2 - 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 (volume) of a liquid, powder, granules, irregularly-shaped objects, etc. stored in a tank. is there.

[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. 9 shows the initial state of the measurement of the liquid level,
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. 9, 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 (V ₂ + v ₀ + V ₁ ) γ = nRT 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.

When the piston 7 is moved by the maximum stroke while keeping the heat insulation, v ₀ = 0 as shown in FIG. 10 and the pressure in the tank 3 increases by ΔP ₀ , and (P ₀ + ΔP ₀ ) (V ₂ + V ₁ ) γ = nRT ₀ holds. Therefore, 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 cavity of tank 3 is Becomes

Next, when the valve 10 is closed in FIGS. 9 and 10, the air permeability between the correction chamber 9 and the tank 3 is completely cut off,
As described above, in FIG. 9, P ₀ (v ₀ + V ₁ ) γ = nRT ₀ holds, and in FIG. 10, v ₀ = 0, and the pressure in the tank 3 increases by ΔP ₀ ′. , (P ₀ + ΔP ₀ ′) V ₁ γ = nRT ₀ holds. Therefore, P ₀ (v ₀ + V ₁ ) γ = (P ₀ + ΔP ₀ ′) V ₁ γ (3) Equation (3) is approximately And from this Becomes Since 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, 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 as V _T -V
Can be determined by ₂ . Incidentally, FIG. 9 and FIG.
Reference numeral 3a in FIG. 0 is 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. 11 and 12. In FIG. 11, the same components as those in FIG. 9 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 denotes a correction chamber, the volume V _{1 of which} is set to be sufficiently smaller than the total volume V _{T of the} tank 3, and the maximum volume change amount of the cylinder 8, that is, the maximum volume v _{0 that} changes by sliding of the piston 7. On the other hand, if the volume is set to, for example, 10 times, and one reciprocation of the piston 7, the internal pressure change changes in a sine wave shape (this is due to the constant speed rotation of the motor 16 described later). Further, the correction chamber 9 includes the tank 3 through the electromagnetic valve 10 and the first pipe 11 in series.
It is connected near the opening edge of the liquid injection port 5 and is set so that gas can flow between the tank 3 and the correction chamber 9. The liquid inlet 5 of the first pipe 11 and the electromagnetic valve
A part of the space 10 is located higher than the opening edge of the liquid injection port, and is set so that the fluid 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. Has been done. Reference numeral 12 denotes a pressure sensor, which divides the reference pressure chamber 12a, the detection pressure chamber 12b, and both pressure chambers 12a and 12b, and distorts the strain plate 12c and the strain plate in proportion to the pressure difference between the pressure chambers. It is composed of a pressure sensor body 12d such as a strain gauge attached, and its reference pressure chamber 12a is communicated with the first pipe 11 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 is the tank 3
It absorbs pressure fluctuations inside and constitutes an air pressure filter.
The detection pressure chamber 12b is communicated with the correction chamber 9, and the pressure sensor 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. 15 is a disk, through hole 15
A is provided and one end of a crank 15b for reciprocating linear movement of the piston 7 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. 13, 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 ′ in the correction chamber 9 measured by the pressure sensor 12 (the piston Γ P ₀ is calculated by the equation (4) by the average value of the pressure change width of the reciprocating motions of 7 times)
ΓP ₀ = ΔP ₀ ′ V ₁ / v ₀ . After determining, proceed to step 104 of stopping output of valve closing signal, and
Supply of the valve closing signal to the valve 10 is stopped to open the valve 10, and the process proceeds to the next step 105 for calculating the cavity volume in the tank, and the number of reciprocating motions of the piston 7 in the coefficient estimating step 103 is larger than the number of reciprocating motions. by the piston 7 reciprocates, in step 105, the volume v ₀ corresponding to the maximum volume change in the cylinder 8 which is stored before a coefficient GanmaP ₀ determined in step 103, ROM, similarly to the said volume v ₀ Based on the volume V ₁ of the correction chamber 9 stored in the ROM and the pressure ΔP ₀ detected by the pressure sensor 12 (the average value of the pressure change width of the reciprocating motion of the piston 7 a plurality of times), The volume V ₂ is obtained, and the process proceeds to the next liquid level calculation step 106, and the volume V _{2 of the} hollow portion inside the tank 3 obtained in the immediately preceding step 105.
Is calculated from the total volume V _T of the tank 3 stored in the ROM to calculate the volume V _{L of the} liquid 4. Further, the process proceeds to the next liquid level signal generation step 107, in which the display unit
A signal for displaying the liquid level on 22 is supplied from the arithmetic processing circuit 21, and then the process returns to step 102 for 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 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 sends the air in the volume V ₁ corresponding to the maximum volume change amount of the cylinder 8 to the correction chamber 9 or sucks the air in the correction chamber 9. However, when 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 changes in a sine wave shape due to the transmission of 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 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 a bandpass filter
It is supplied to the amplitude detection circuit 20 via 19 and the peak value thereof is detected. The detected peak _value is supplied to the arithmetic processing circuit 21 and averaged to calculate the coefficient γP ₀ ,
It is stored in a register 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 is rotated more times than when the coefficient γ P 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.
Thereafter, the above operation is repeated, and the coefficient γ P 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 device, in order to estimate the coefficient γ P ₀ , the tank 3 and the correction chamber 9
There is a problem in that the configuration is connected via the valve 10 and the overall shape of the device becomes large.

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 and the hollow portion in the tank 3 communicate with each other.
There is a problem that it is not regarded as one space and becomes a separate space, which causes a measurement error. To avoid this, if the drive angular frequency ω ₀ of the piston 7 is made extremely small, the measurement time becomes longer. There was a problem that it becomes longer. 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 such conventional problems. For example, the volumes of the main tank and the correction tank that are partitioned by the volume changing means such as a speaker and a bellows are controlled. The volume change means is driven to change the pressure, and the pressure fluctuation due to the change in volume is provided in the first tank provided in the main tank.
And a second microphone having a lower sensitivity than the first microphone and provided in the correction tank, and one of the detected values is divided by the other amplitude value, and the calculation is performed. It is an object of the present invention to provide a volume measuring device configured to calculate the volume of an object to be measured stored in the main tank based on the result.

[Embodiment] The principle of the present invention will be described below with reference to FIGS. 1 to 4. Reference numeral 30 denotes a main tank having a different shape for storing liquids, powders, particles, irregularly shaped objects and the like. The correction tank 31 is connected to the main tank 30 via a connecting pipe 32.
Are connected. Further, a small-diameter vent hole 35 is formed in the upper portion of the irregularly shaped main tank 30. Above the correction tank 31, there is a volume changing means (mechanism) 33 such as a piston, a speaker shape (hereinafter referred to as a speaker), or the like.
Is provided, and the volume of the correction tank 31 can be changed by the operation of the volume changing mechanism 33.

Measurement Principle (1) Consider a connected tank system as shown in FIG.
This is composed of two types of tanks 30 and 31 having volumes V ₁ and V ₂ . The tanks 31 and 30 are connected by a pipe 32 having a flow resistance r ₁ , 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. In tank 31,
A volume changing mechanism 33 using a piston, a diaphragm, a bellows, a speaker shape, etc. is attached.
Let v (t) be the amount of volume change that actually occurs.

When the tanks 30 and 31 are rigid, the tanks 30 and 31 do not distort when the internal pressure of the tanks 30 and 31 is increased or decreased.
The volume change v ₀ (t) due to the diaphragm, the bellows, etc. is equal to the volume change v (t) actually generated. If the tank 30 is flexible, the tank 30 is distorted when the internal pressure of the tank 30 or 31 is increased or decreased. Therefore, v (t) is smaller than v ₀ (t) by the amount corresponding to the volume change due to the expansion or contraction. Larger or smaller.

When v (t) = 0, the absolute pressure, temperature and number of moles of the gas in the tank 31 are P ₀ , T ₁ and n ₁ , respectively, and the absolute pressure, temperature and number of moles of the gas in the tank 30 are respectively P ₀ , T ₂ and n ₂ respectively
And When the measurement environment does not change significantly, the gas flows in and out of the tanks 31, 30 via the ventilation holes 35, so that the tank 31,
The absolute pressure p ₀ in 30 is equal to the atmospheric pressure, its change is very slow and it changes equal to the atmospheric pressure.

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 ₁₂ (t). Δ
n ₁₂ (t) is the number of moles of air flowing from the tank 31 to the tank 30, and Δn ₂ (t) is the number of moles of air leaking from the tank 30 to the outside through the vent holes 35.

 We now set the following assumptions for this system.

1) The gas inside the tanks 30 and 31 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 ₂ (t)
The temperature change in the tank due to is much slower than the change speed of the volume change amount v (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 a major constraint. Δp ₁ (t), Δp ₂ (t), ΔT _{1 with} respect to the volume change amount v (t)
The changes in (t), ΔT ₂ (t), Δn ₁₂ (t), and Δn ₂ (t) are originally represented by a non-linear equation, but their magnitudes are p ₀ , T ₁ , T _{2 according} to Assumption 2). , N ₁ and n ₂ are very small, so they can be approximated by linear equations. Tank 3 in static state
The relationship among the pressure, temperature, and number of moles of the gas in 0,31 is expressed by the following algebraic equation.

p ₀ V ₁ ＝ n ₁ RT ₁ , p ₀ V ₂ ＝ n ₂ RT ₂ (1a) Moreover, 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 rate resistance r, r ₁ and r ₂ in the above equation, is calculated from the length 1 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.

v (t) = vo (t) -Δv (t) (1h) 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 due to expansion or contraction of the tank 30 accompanying the change in the volume change amount v ₀ (t) of the volume change mechanism 33. Is the amount.

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 Coefficient r ₂ V ₂ / RT ₂ , r ₁ V ₂ / RT ₂ , r ₁ V ₁ / RT ₁ , r ₁ V ₂ / RT
₁ is the time constant of pressure change. For example r ₂ V ₂ / RT ₂ is flow gas absolute temperature T ₂ of the hollow portion in the tank 30 the resistance r ₂
Is a time constant of pressure decay when flowing out of the tank 30 through the vent hole 35 of the. 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, the angle 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, 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 + ΔV).

When the volume changing mechanism 33 is driven in a sine wave shape at the angular frequency ω ₀ , Is satisfied, 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 pipe 3 that connects the tanks 31 and 30 in FIG.
The cross-sectional area of 2 is made very large, which corresponds to the case where the value of the flow resistance r ₁ of the pipe 32 becomes very small. From this, the transfer function from v (t) to ΔP ₂ (t) in FIG. 3 is r ₁ → 0, T ₂ = T ₁ , Δp ₂ = Δ in the equation (2a).
P ₁ and V ₂ ′ = V ₁ + V ₂ are set 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 ₁ , V ₃ ′) │≈ 1, k ₁ (iω, r ₂ , V ₃ ′) = 0 (2i) At this time, the transfer function is γp ₀ / (V ₂ ′) + ΔV).

Next, an embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 33 is a speaker (volume changing means), and the volume changing means partitions the main tank 30 and the correction tank 31. Further, a condenser microphone (first microphone) 34b is provided on the main tank 30 side, and a dynamic microphone (second microphone) 34a having a lower sensitivity than the first microphone is provided on the correction tank 31 side. There is. That is, if the sensitivity of the microphone for detecting the pressure in the main tank 30 and the sensitivity of the microphone for detecting the pressure in the correction tank 31 are made equal, the pressure in the correction tank is Since it becomes larger than the pressure in the tank, the detection signal by the microphone on the correction tank 31 side may become saturated or undetectable, so in the present embodiment, as described above,
The sensitivity of the second microphone is lower than that of the first microphone. (For the second microphone, attach tape etc. to the receiving surface of the condenser microphone,
The sensitivity may be the same as that of the dynamic microphone. ) Also, the speaker 33 has a cone inside the case 50.
53 mounted upwards, case below cone 53
The correction tank 31 is formed in the inner space of 50, and the inner space of the case 50 above the cone 53 forms a part of the hollow portion of the main tank 30, and the hollow portion connects the large-diameter connecting pipe 51 and the wire mesh 52 in series. Is connected to the cavity in the main tank 30 via the connecting pipe 51 and the wire mesh 52 when the speaker 33 is driven.
The diameter of the pipe 51, the roughness of the mesh, etc. are selected so as not to be affected by the flow resistance of the pipe. A through hole 47 (flow rate resistance r ₁ ) for matching the static pressure in the main tank 30 with the static pressure in the correction tank 31 is provided in the base of the speaker 33 attached to the case 50.

The reason why the wire net 52 is provided is that liquid splash due to liquid shattering causes the connecting pipe 51 in the case 50.
It is for preventing the entry through the.

Further, the speaker 33 is driven at a predetermined angular frequency ω ₀ . 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 (V ₂ also includes the volume of the space above the cone of the speaker 33 in the case 50), the volume of gas in the main tank 30 is V ₂ , and the volume of the liquid in the main tank 30 is The volume is V _L , and the sum of the volumes of the correction tank 31 and the main tank 30 is
Let 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 equation (2c), Δp
₁ (t) is as follows.

Further, when the amplitude of Δp ₁ ′ (t) on the correction tank side when v (t) is driven at the angular frequency ω _L is measured, Here, the amplitude value of the pressure change of the correction tank 31 when the volume change mechanism 33 is driven so that the pressure change becomes a sine wave,
If A ₁ and the amplitude value of the pressure change of the main tank 30 are A ₂ ,
The ratio of these amplitude values is calculated from equations (3a) and (3b) Becomes

Than this And the volume V _L of the liquid stored in the main tank 30 is Becomes

In addition, ΔV is to be obtained in advance by an experiment.

Next, a specific embodiment according to the present invention will be described based on the above principle.

FIG. 5 (A) shows a speaker (volume change mechanism) 33 placed between the correction tank 31 and the main tank 30, and in order to make the static pressures of the main tank 30 and the correction tank 31 equal, The tanks 31 and 30 are connected by a through hole 47.

Here, the time constant of pressure transmission of this through hole 47 is
Since the time constant of the pressure change of the correction tank 31 due to 33 is sufficiently larger, the speaker 33 is driven and the volume change as shown by the function of v ₀ sin ω ₀ t is corrected by the correction tank 31 and the main tank.
Given to 30, namely the main tank 30 and the correction tank
The principle of the single tank system is applied to both 31.
(Note that the pressure loss due to the communication pipe 51 and the wire net 52 can be ignored.) Therefore, if V (t) = v ₀ sinω ₀ t (4a), the pressure change ΔP ₁ (t) in the correction tank 31 is If the angular frequency ω ₀ satisfies (2c) in the above equation, Becomes ΔP ₂ (t) is as follows.

Here, in the above formula, when the main tank 30 is a rigid body,
Similar to the correction tank 31, when the angular frequency ω ₀ satisfies the formula (2c), Becomes

In other words, the volume of each of the image tank 30 and the correction tank 31 is increased by the speaker 33 by the angular frequency ω ₀ by v ₀ sinω ₀ t.
If it fluctuates regularly in the main tank 30 and the correction tank
The respective pressure fluctuations in 31 are detected by the dynamic microphone 34a and the condenser microphone 34b attached to the respective tanks 30, 31, and the output of the condenser microphone 34b, which detects the pressure fluctuations in the main tank 30, has a gain of 1 (dB). , Bandpass filter 37b with central angular frequency ω ₀
The signal component of angular frequency ω ₀ is extracted by
Is supplied to the second amplitude detector 39b, Is detected and output. Further, the output of the dynamic microphone 34a that has detected the pressure fluctuation of the correction tank 31 is extracted by multiplying V ₁ by only the signal component of the angular frequency ω ₀ by the bandpass filter 37a having the gain V ₁ and the central angular frequency ω ₀ ,
After that, it is supplied to the first amplitude detector 39a, and γP ₀ v ₀ is detected and output. After that, the output γP ₀ v ₀ from the first amplitude detector 39a is output from the second amplitude detector 39b. The volume V ₂ of the hollow portion of the main tank 30 is calculated by dividing by the divider 40, and the calculation result is supplied to the subtractor 41 and subtracted from the set total volume V _T of the main tank 30. As a result, the volume _{VL of the} liquid or the like stored in the main tank 30 is calculated.

In the embodiment shown in FIG. 5 (c), in order to prevent the liquid in the main tank 30 from flowing into the case 50 through the communication pipe 51 when the main tank 30 is largely inclined, A ball valve 54 that can be received inside 52 is provided. Therefore, according to this embodiment, the main tank
If 30 is significantly inclined, the ball valve 54 closes the opening of the communication pipe 51, so that the liquid flow into the case 50 can be effectively prevented.

 Next, the operation will be described.

When the speaker 33 is driven by v ₀ sin ω ₀ t, the dynamic microphone 34a detects the pressure fluctuation in the correction tank 31, and the effective value of the electric signal corresponding thereto is output from the first amplitude detection circuit 38 as γP ₀ v _0. The pressure fluctuation in the main tank 30 is detected by the condenser microphone 34b, and the effective value of the electric signal corresponding thereto is detected by the second value.
From the amplitude detection circuit 39 of , The two output signals are supplied to the divider 40, the cavity inside the main tank 30 is calculated, and the subtracter 41 further calculates the reference value corresponding to the total volume of the main tank 30.
_Subtracting from V _T , the value is calculated as the volume V _L of the contents in the main tank 30.

Further, the frequency for varying the volume V ₂ of the hollow portion in the main tank 30 is 1 to 15 Hz and 20 Hz depending on the distribution of the frequency spectrum of the pressure noise caused by the vibration accompanying the driving of the vehicle as shown in FIG. The above can be set as a selection range.

Further, in FIG. 7, the pressure fluctuation due to the heat of the gasoline returned from the engine to the main tank 30 is shown by the thin line (a), and the pressure fluctuation due to the vibration of the tank wall and the gasoline sloshing is shown by the thick line (b). As shown,
For example, considering the case where the magnitude of the spectrum due to the volume variation at a constant frequency of the main tank 30 is A, the frequencies for varying the volume V ₂ of the hollow portion in the main tank 30 are selected to be 1 to 25 Hz and 30 Hz or more. Can be set as a range.

From the above, if the frequency for varying the volume V ₂ of the hollow portion in the main tank 30 is set in the range of 1 to 15 Hz and 30 Hz or higher, a signal with a good S / N ratio can be obtained.

In the above-described embodiment 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.

[Effects of the Invention] As described above, according to the present invention, the configuration is such that the opening 49 is formed at one end and the case 50 is housed in the main tank 30, and the case 50 is housed in the case 50. Volume changing means 33, which divides the inner hollow portion into a hollow portion having the opening portion and a hollow portion having no opening portion, and uses the hollow portion having no opening portion as a correction tank 31, and the volume changing means 33. Through-hole 47 for always matching the static pressures of the two cavities separated by the space, and the opening 49 formed in the case.
And the upper wall surface of the main tank 30, the static and dynamic pressure of the cavity in the case on the side communicating with the opening 49 is matched with the pressure of the cavity in the main tank 30. Communication means 51, a first microphone 34b for detecting a pressure fluctuation in the main tank 30, and a second microphone 34a having a lower sensitivity than the first microphone and detecting a pressure fluctuation in the correction tank 31. A first amplitude detection circuit 39a for detecting the amplitude value of the detection signal of the first microphone, a second amplitude detection circuit 39b for detecting the detection signal of the second microphone, and the second amplitude And a divider 40 that divides the output of the detection circuit by the output of the first amplitude detection circuit 39b, and measures the volume of the measured object stored in the main tank based on the output of the divider. Is something that can Et al., According to this invention, equal static pressure compensation tank and the main tank, receives no affected by pressure difference between the tank and out. Therefore, it is suitable for aircraft, automobile fuel gauges, high-pressure process tanks, etc. where the pressure difference between the inside and outside of the tank fluctuates greatly, and continuous measurement (simultaneous measurement) is possible. No need to drive.

Further, in the present invention, since the correction tank can be integrally formed inside the main tank, it is possible to maintain the same environmental conditions and measurement conditions with respect to the temperature (temperature) outside the tank, which enables highly accurate volume measurement. It is possible to Further, in the present invention, the sensitivity of the second microphone 34a for detecting the pressure fluctuation in the correction tank 31 is set to the sensitivity of the first microphone 34a for detecting the pressure fluctuation in the main tank 30.
Since the sensitivity is lower than that of 34b, the pressure fluctuations in the main tank 30 and the correction tank 31 can be properly detected. Furthermore, since the convex portion due to the correction tank does not occur outside the main tank, the workability of mounting the volume measuring device is improved. Further, in the present invention, since the microphone is used as the means for detecting the pressure fluctuation, there is an effect that it is possible to provide a very economical (inexpensive) volume measuring device.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention, and FIG. 2 shows a changing state of the coefficient k ₂ of the transfer function when the drive frequency of the volume changing mechanism and the volume of the stored items in the tank are changed in FIG. FIG. 3 is a characteristic diagram, FIG. 3 is an explanatory diagram of the principle for explaining the present invention, and FIG. 4 is a transfer function when the drive frequency of the volume changing mechanism and the volume of the contents stored in the tank 30 are changed in FIG. characteristic diagram showing a change in state of the coefficient k ₁ of FIG. 5 (a) is structural schematic diagram showing a first embodiment of the present invention, FIG. 5 (B) is a system diagram according to according to the exemplary embodiment, the fifth FIG. 6C is a structural explanatory view showing a second embodiment of the present invention, FIG. 6 is a frequency spectrum diagram of pressure fluctuation due to return fuel heat during vehicle operation,
FIG. 7 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. FIG. 8 is a volume measurement value of the embodiment according to FIG. 9 to 13 are explanatory views of a conventional example. 30 …… Main tank, 31 …… Compensation tank 32 …… Connection pipe 33 …… Speaker (volume change mechanism) 34a …… Second microphone 34b …… First microphone 35 …… Vent holes 36,37a, 37b ...... Band pass filter 38,39 …… Amplitude detector 40 …… Divider, 41 …… Subtractor 42 …… Amplifier, 43 …… Differentiation circuit 44 …… Amplifier, 45 …… Low pass filter 46 …… Amplifier , 47 ... Pipe 47a ... Orifice, 48 ... Wave plate 49 ... Opening, 50 ... Case 51 ... Connecting pipe, 52 ... Wire mesh 53 ... Cone, 54 ... Ball valve

Claims (1)

(57) [Scope of utility model registration request] 1. A case (50) having an opening (49) formed at one end and housed in a main tank (30), and a cavity (50) housed in the case (50). Divide into a cavity having an opening and a cavity not having an opening,
A volume changing means (33) having a cavity having no opening as a correction tank (31) and a static pressure of two cavities separated by the volume changing means (33) are always made to coincide with each other. In the case, which is formed between the through hole (47) and the opening (49) formed in the case and the upper wall surface of the main tank (30) and communicates with the opening (49). A communication means (51) for matching the static and dynamic pressures of the cavity with the pressure of the cavity in the main tank (30) and the main tank (30) provided in correspondence with the cavity.
First microphone (34b) for detecting internal pressure fluctuations
The sensitivity of the correction tank is lower than that of the first microphone, and the correction tank (31) is provided inside the correction tank.
Second microphone (34a) for detecting internal pressure fluctuations
A first amplitude detection circuit (39a) for detecting the amplitude value of the detection signal of the first microphone, and a second amplitude detection circuit (39a) for detecting the detection signal of the second microphone.
b) and a divider (40) for dividing the output of the second amplitude detection circuit by the output of the first amplitude detection circuit (39b), and the main circuit based on the output of the divider. A volume measuring device for measuring the volume of an object to be measured stored in a tank.