JPH0635140Y2 - 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 or the like as an object to be measured stored in a tank.

[Conventional technology]

As a conventional volume measuring device of this type, there is one disclosed in Japanese Patent Application No. 1-27808 as a prior art.
It will be described with reference to FIGS. 2 to 7.

First, the principle will be described with reference to FIGS. 2 to 5.
Reference numeral 30 denotes a main tank of a different shape that stores liquid, and a correction tank 31 having a smaller volume than the main tank 30 is connected to the main tank 30 via a connection pipe 32. Further, a vent hole 35 having a small diameter is formed in the upper portion of the irregularly shaped main tank 30 (note that the vent hole 35 may not be provided). A volume changing means (mechanism) 33 such as a piston and a speaker shape (hereinafter, referred to as a speaker) 33 is provided on the correction tank 31.
By the operation of the volume changing means 33, the volume in the correction tank 31 can be changed.

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. This is configured by connecting a correction tank 31 having a small volume V ₁ and a main tank 30 having a large volume V ₂ . tank
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. A volume changing means 33 using a piston, a diaphragm, a bellows, a speaker shape or the like is attached to the tank 31, and the volume change amount actually generated by the volume changing means 33 is v (t).

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, so the volume change amount v ₀ (t) actually occurs due to the piston, diaphragm, bellows, etc. The volume change amounts v (t) are equal. If the tank
When the tank 30 is flexible, the tank 30 is distorted when the internal pressure of the tank 30 or 31 is increased or decreased, so that v (t) changes by an 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, and the absolute pressure, temperature and the number of moles of the gas in the tank 30 are P ₀ , T ₂ and n ₂ , respectively.
And When the measurement environment does not change significantly, the gas flows through the air holes 35 into and out of the tanks 30 and 31.
The absolute pressure P ₀ in 31 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 the number of moles also change according to the situation of the volume changing means 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 as P ₀ + ΔP ₂ (t), the temperature changes as T ₂ + ΔT ₂ (t), and the number of moles changes as n ₂ + Δn ₁₂ (t) -Δn ₂ (t). Δn
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 temperature change in the tank due to the pressure change ΔP ₂ (t) depends on the change rate of the volume change amount v (t). It can be neglected very late in comparison.

4) The rate of change of the volume change amount v (t) is set so that the pressure changing therewith is equal throughout the tanks 30 and 31.

5) Even if a ratio measurement object is placed in the tank 30, this 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 with respect to the volume change amount v (t)
_{The change of 1} (t), ΔT ₂ (t), Δn ₁₂ (t), and Δn ₂ (t) is originally expressed by a non-linear equation, but the magnitude is P ₀ , T ₁ , T from assumption 2). _{It is} very small for ₂ , n ₁ and n ₂ , so it 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.

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

Flow resistance r, r ₁ and r ₂ in the above equation are the length l of the pipe 32.
And the diameter d can be obtained as in the following empirical formula.

This formula has a length l of 50 to 650 [mm] and a diameter d of 2.0 to 9.0 [m
[m] aluminum pipe.

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

v (t) = v ₀ (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 changing means 33. Is the amount.

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

here, The coefficients r ₂ V ₂ / RT ₂ , r ₁ V ₂ / RT ₂ , r ₁ V ₁ / RT ₁ and r ₁ V ₂ / RT ₁ are time constants of pressure change. For example, r ₂ V ₂ / RT ₂ is a gas having an absolute temperature T ₂ of the cavity of the tank 30 is a vent hole 35 having a flow resistance r _2.
It is a time constant of pressure decay when flowing out of the tank 30 via. The correction coefficient k ₂ (s, r ₁ , r ₂ , V ₁ , V ₂ ) is the main tank
It depends on the volume V ₂ of 30 but 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.

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 + Min V ₂ } / RT ₂ are similar, the following 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, 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 means 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, If

(2) Next, consider a single tank system as shown in FIG. This is the 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. 4 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, and is 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 τ P ₀ / (V ₂ ′ + ΔV) .

Next, a specific example applying the above principle will be described with reference to FIG.

In FIG. 6, 33 is a speaker (volume changing means),
By this volume changing means, the main tank 30 and the correction tank
It is configured so as to be separated from 31. Furthermore, a condenser microphone 34b is provided on the main tank 30 side,
On the correction tank 31 side, a dynamic microphone 34a having a lower sensitivity than the first microphone is provided. 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. 4 applies.

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 rigid body of the main tank 30, that is, ΔV =
0, and when the angular frequency ω _H satisfies the equation 2 (h), 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 _H is measured, Here, the amplitude value of the pressure change of the correction tank 31 when the volume changing means 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 given by equations (3a) and (3b) Becomes

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

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

Next, a specific prior art based on the above principle will be described.

FIG. 6 shows a speaker (volume changing means) 33 placed between the correction tank 31 and the main tank 30. Further, in order to equalize the static pressures of the main tank 30 and the correction tank 31, both tanks 30, Since a narrow pipe 47 having an orifice 47a is connected between 31 and the main tank 30 and the correction tank 31 are substantially completely closed so as not to be affected by the atmospheric pressure, the speaker 33 is driven. The angular frequency ω ₀ is much larger than the slow change in atmospheric pressure, and the fluid resistance in the vent hole 35 is also very large, so that the vent hole 35 acts as if the speaker 33 is being driven. Because
The atmospheric pressure in the tanks 30, 31 is not affected by the atmospheric pressure difference between the tanks 30, 31. Here, the time constant of the pressure transmission of the pipe 47 is sufficiently larger than the time constant of the pressure change in the correction tank 31 by the speaker 33, and the atmospheric pressure outside the tanks 30 and 31, that is, the time constant of the pressure change of the absolute pressure. Assuming that it is sufficiently smaller, it drives speaker 33, v ₀ s
Compensate for volume changes as shown by the function of in ω ₀ t
Given to one and the main tank 30, ie to both the main tank 30 and the correction tank 31, the principle of a single tank system applies. Therefore, assuming that V (t) = v ₀ sin ω ₀ t (4a), the pressure change ΔP ₁ (t) of the correction tank 31 is And when the angular frequency ω ₀ satisfies (2h) in the above equation, Becomes ΔP ₂ (t) is as follows.

Here, in the above equation, when the main tank 30 is rigid and the angular frequency ω ₀ satisfies the equation (2h) as in the correction tank 31, Becomes

That is, the volume of each of the main tank 30 and the correction tank 31 is increased by v ₀ sin ω ₀ by the speaker 33.
_If it is regularly fluctuated at ₀ , the respective pressure fluctuations in the main tank 30 and the compensation tank 31 will be
Condenser microphones that detect pressure fluctuations in the main tank 30 that are detected by the dynamic microphones 34a and condenser microphones 34b attached to 30, 31
From the output of 34b, a signal component having an angular frequency ω ₀ is extracted by a bandpass filter 37b having a gain of 1 and a central angular frequency ω ₀ , and then 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 stored in the main tank 30 is calculated.

[Problems to be solved by the device]

However, when such a volume measuring device is used as a fuel sensor for a vehicle, a wide range of temperature changes are forced many times a day, and therefore fuel vaporized at high temperatures is used for correction at low temperatures. Condensation may occur in the tank, dew condensation may occur, and it may accumulate in the correction tank.

[Means for Solving the Problems]

This invention was made in view of such a problem, and an air circulation hole communicating with the main tank is provided in the lowest portion of the bottom surface of the correction tank where liquid is likely to accumulate.
It is an object of the present invention to provide a volume measuring device that solves the above problems.

〔Example〕

An embodiment of the present invention will be described below in detail with reference to FIG.

The parts other than those shown in FIG. 1 are the same as those of the prior art, and therefore their explanations are omitted.

Further, in FIG. 1, the same components as those in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted. Only different portions will be described.

That is, in FIG. 1, the difference from FIG. 7 is that the pipe 47 shown in FIG. 7 is not provided in FIG. 1 and that it has the function of the pipe 47. The correction tank 31 and the main tank are attached to the mounting portion C of the speaker 33 for partitioning the main tank 30 and the correction tank 31 to the tank.
A thin air circulation hole 50 is provided for communicating the space with 30 and for equalizing the static pressures of the main tank 30 and the correction tank 31. The air circulation hole 50 is provided at the lowest position of the bottom surface of the correction tank 31,
All the condensed liquid in the correction tank 31 is collected, the speaker 33 is driven, and the atmospheric pressure in the correction tank 31 becomes the main tank.
When it becomes higher than the atmospheric pressure in 30, it is discharged into the main tank 30.

[Effect of device]

As described above, according to the present invention, the main tank for accommodating the object to be measured and the correction tank are provided with the volume changing means by separating them from each other. For calculating the volume of the object to be measured based on the pressure change, in the lowest portion of the bottom surface of the correction tank, because the air flow hole communicating with the main tank is provided, Since the liquid does not accumulate in the correction tank, the volume of the correction tank can be kept constant at all times, and thus the volume of the object to be measured can be calculated accurately.

[Brief description of drawings]

FIG. 1 is an enlarged view of an essential part of the present invention, FIG. 2 is an explanatory view of the principle of the prior art, and FIG. 3 is a view when the drive frequency of the volume changing means and the storage volume in the tank are changed in FIG. FIG. 4 is a characteristic diagram showing a changing state of the coefficient K ₂ of the transfer function of FIG. 4, FIG. 4 is a principle explanatory diagram for explaining the prior art, and FIG. 5 is a driving frequency of the volume changing means and storage in the main tank in FIG. FIG. 6 is a characteristic diagram showing a changing state of the coefficient K ₁ of the transfer function when the object volume is changed, FIG. 6 is a concrete system explanatory diagram of the prior art, and FIG. 7 is an enlarged view of a main part of FIG. . 30 ... Main tank, 31 ... Correction tank, 32 ... Connection pipe, 33 ... Speaker (volume change means), 34a ... Second microphone, 34b ... First microphone, 35 ...
… Ventilation holes, 37a, 37b …… Band pass filter, 39 …… Amplitude detector, 40 …… Divider, 41 …… Subtractor, 47 …… Pipe, 47a …… Orifice, 48 …… Wave plate , 50 …… Air circulation hole.

Claims (1)

[Scope of utility model registration request] 1. A main tank for accommodating an object to be measured and a correction tank are provided with a volume changing means by separating them from each other, and a pressure change in each tank due to the driving of the volume changing means. In the volume measuring device for calculating the volume of the object to be measured based on the bottom surface of the correction tank, an air circulation hole communicating with the inside of the main tank is provided in the lowest position portion. Volume measuring device.