JPS58105016A - Measuring device for liquid quantity in enclosed container - Google Patents

Abstract

PURPOSE:To perform a direct detection of a liquid quantity in an enclosure container, by utilizing a phenomenon in which a resonance frequency of a speaker fluctuates on a size of a space capacity in the enclosure container. CONSTITUTION:A speaker 3 is mounted to an opening in an upper wall or an upper side wall of an enclosure container 2 such as fuel tanks, in which liquid 1 at the inside is enclosed from the outside, so that it is positioned facing the inside of the container, and a resonance system consists of the speaker 3 and the enclosure container 2 or more concretely a space 4 in the enclosure container 2. A digital counter 6 is connected to the next stage of a resonating circuit 5 resonating in conformity with the resonating frequency of the speaker 3 to count the resonating frequency. The resonating frequency is converted into a capacity Vc of the space 4 in the container 2 by a computing part 9 consisting of a microcomputer connected to a next step of a latch circuit 8 to further find a liquid quantity VF.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid amount measuring device for detecting the amount of liquid contained in a closed container.

Conventionally, various liquid level detection devices for detecting the liquid level in a container are known.

Conventionally known liquid level detection devices, particularly liquid level detection devices for sealed containers in which liquid is sealed inside, are equipped with a float that changes to follow the liquid level, and the displacement of this float is measured by some method. However, this type of liquid level detection device can be used in cases where there are large fluctuations in the liquid level, such as in the case of a 7-well tank in an automobile.
Since the detection value also follows the liquid level fluctuation, the detection value fluctuates according to the liquid level fluctuation, and there is a drawback that the accurate liquid level or liquid amount cannot be detected.

Furthermore, a liquid level detection device has been proposed that detects the liquid level position based on the length of the ultrasonic reflection time and the magnitude of the reflected wave intensity, without using the above-mentioned float (Utility Model Application No. 55-81732). (see publication). However, even in such a method, the reflection time and reflected wave intensity of the ultrasonic waves are directly affected by the fluctuations in the liquid level, and therefore the There is a drawback that the liquid volume cannot be detected accurately.

The present invention has been made to solve this conventional problem. Regardless, we focused on the fact that the amount of liquid in the sealed container is accurately determined, and by detecting the volume of this internal space using a resonance phenomenon, we developed a sealed container that can directly measure the amount of liquid. The purpose is to provide a liquid volume measuring device.

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments.

As shown in the drawings, in the present invention, a mounting opening provided in a soil wall or an upper side wall of a closed container 2, such as a 7-well tank, which stores a liquid 1 inside in a sealed state from the outside, includes: A speaker 3 is mounted facing the inside of the container, and the speaker 3 and the closed container 2, more specifically, the space 4 inside the closed container 2, constitute one resonant system.

A resonant circuit 5 consisting of a negative resistance oscillation circuit having a known configuration that resonates at the resonant frequency of the speaker 3 is connected to the speaker 3, and a resonant circuit 5 that resonates in tune with the resonant frequency of the speaker 3 is connected. A digital counter 6 is connected to the next stage of the circuit 5 to count its resonance frequency.

This digital counter 6 has a count time controlled by a timer 9, counts the number of pulses output from the resonant circuit 5 for each count time, and the counted value is latched by a latch circuit 8 whose latch timing is controlled by a timer 7. Latched at each timing. The count value latched in the latch circuit 8, in other words, the resonant frequency, is determined by the calculation unit 9, which is a microcomputer connected to the next stage of the latch circuit 8, and calculates the volume V of the space 4 in the container 2.
After determining the liquid volume vp, a liquid volume instruction signal is output to the liquid volume display unit 10, and the liquid volume display unit 10 displays the instructed liquid volume VF.

In the above configuration, the relationship between the resonant frequency foc of the speaker 3 and the volume vc of the space 4 can be determined as follows.

In general, when considering a simple harmonic system with effective mass m and elastic constant, its vibration equation is given by, as is well known, and the general solution to this equation is y=A sin (ω [+θ)...・・・・・・
(2) Then, since ω=2πf, it is given by.

Now, in the vibration system composed of the above-mentioned speaker 3 and the internal space 4 of the sealed container 2, by introducing a quantity called stiffness S corresponding to the elastic modulus k, as commonly used in the field of acoustic engineering, etc. , the resonant frequency foc of the speaker 3 can be found in the same way as the simple harmonic motion.

That is, the stiffness S of the entire system is given by the sum of the inherent stiffness So of the speaker 3 and the stiffness Sc of the air (including evaporated gas) in the internal space 4.

k = S = S o + S c
-------------f41 This stay 7ness Sc is expressed as a function of the effective radius a of this vibration system (specifically, equivalent to the radius of the speaker 3) and the air volume Vc. There is a relationship (where a is a proportional constant, -αa4) Now, using equations (4) and (3), the mass of the air is the effective mass m of the speaker 3. Since it can be ignored compared to foc, the resonant frequency foc of the speaker 3 can be found by the following equation.

By the way, the resonance frequency f of the speaker 3 alone. is equivalent to setting vc to infinity, but using the relationship of the fifth equation, it becomes Sc −+o, which can be found as Sc −+o, and using equations (7) and (6), the Between the actual resonant frequency foc and the resonant frequency fo of the speaker 3 alone,
There is the following relationship.

Therefore, the volume vc of the internal space 4 of the sealed container 2 is determined as follows, and the liquid volume VF is as follows, where the volume of the sealed container 2 is V, V, -V-V, ......
... It can be found by (10).

In Equation 2 (9), So, fo, and K are known, so if the actual resonance frequency foc is detected,
The internal space Vc can be determined by equation (9), and (
10) The liquid volume VF in the sealed container 2 can be calculated from the formula number.

That is, in the calculation unit 9, the resonant frequency foc latched by the latch circuit 8 is read, and equations (9) and (1) are calculated.
0) may be used to find the liquid volume VF.

In addition, when designing the speaker 3, foc≧2
0KHz, and as is clear from the relationship in Equation 8, the stay 7ness So of the speaker 3 alone and the stiffness Sc of the air in the internal space 4 (this is the relationship in Equation 5). As is clear from the above, the ratio S c /S o is related to the effective vibration radius 3 of the speaker 3.
and the resonant frequency fO of the single speaker 3 (it is preferable to maintain an appropriate balance in order to obtain the necessary resolution).

With the above configuration, even if the level of the liquid 3 in the closed container 2 is tilted due to vibration or the like, the volume Vc of the internal space 4 remains unchanged, so the resonant frequency foc will not change. Further, when the internal liquid volume actually decreases due to liquid consumption, this causes an increase in the volume Vc of the internal space 4, changing the resonance frequency foc of the speaker 3, and from this change, the volume at that point Vc and
Therefore, the fluid volume VF can be directly determined and this fluid volume VF can be displayed.

As is clear from the above description, the present invention directly detects the amount of liquid in a sealed container by utilizing the phenomenon in which the resonant frequency of a speaker changes depending on the volume of the space inside the sealed container. The present invention provides a liquid volume measuring device for a closed container.

According to the present invention, since it is possible to directly measure the liquid volume rather than the liquid level, it is not affected by fluctuations in the liquid level due to vibrations, etc., and moreover, it is possible to always perform stable measurement without contact. It is also possible to obtain the advantage that the liquid amount can be displayed digitally if necessary.

[Brief explanation of drawings]

The drawing is a block diagram illustrating a liquid amount measuring device for a closed container according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Airtight container, 3... Speaker, 5... Resonance circuit, 6... Digital counter, 9... Arithmetic unit.

Claims (1)

[Claims] (1) A liquid amount measuring device for a closed container, which detects the amount of liquid contained in the closed container by determining the frequency of a speaker attached to the top of the container that resonates with the gas inside the container.