JP2000186953A - Floating type level gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure and display the liquid level of a liquefied gas which is filled in a prescribed container. SOLUTION: This level gauge has a permanent magnet 6 provided inside a float 5, constituted so as to move vertically in response to the fluctuation of the liquid level of a liquid material stored in a prescribed container 20, a magnetrostrictive element 7 extended toward an upper direction of the container 20, a pulse generating means for generating a pulse current flowing in the element 7 toward the extending direction, a distorted wave detecting means for detecting an elastic distorted wave generated by an Wiedemann effect in a position neghboring to a liquid surface of the element 7, which is generated by a magnetic field generated by the pulse current in the vicinity of an outer periphery of the element 7 and a parallel magnetic field by the permanent magnet 6, and a liquid level calculating means for calculating the liquid level position of the liquid material, based on the detected elastic magnetrostrictive wave. The gauge has also a volume calculating means for calculating the volume of the liquid material based on the calculated liquid level position, the magnetrostrictive element 7 is sealed inside a rigid pipe 2 which can withstand high pressure, and a material for the float 5 is a cellular material of a nitrile rubber having closed cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level gauge, for example, to a float type liquid level gauge for measuring and displaying the liquid level of a liquefied gas filled in a predetermined container.

[0002]

2. Description of the Related Art Conventionally, in order to externally know the liquid level of a liquid material such as a liquefied gas contained in a container, for example, an LPG filled in a tank mounted on a tank lorry, various liquid level gauges are used. Is used. As a typical example of such a liquid level gauge, a magnet type liquid level gauge is known.

In this magnet type liquid level gauge, a pipe is provided outside the tank and communicated with the inside of the tank, and a float is provided inside the pipe. A magnetic band is provided on the outer periphery of the float, and a display for displaying the liquid level is provided on the pipe. A plurality of magnet rotors are arranged in the display in the up-down direction, and each rotor is rotatably supported in a rotatable manner, and is color-coded such that the surface changes color when rotated. Further, each rotor has N and S magnetic poles at both ends. Then, the float floating in the pipe moves up and down from the rotor located at the lower end to the rotor closest to the magnetic band of the float from the rotor located at the lower end and rotates from the bottom in order to change the color of the surface. Is changed, and the liquid level position in the tank is displayed by the change in the color so that it can be easily determined from the outside.

[0004]

However, the above-mentioned conventional liquid level gauge has a structure in which a pipe communicated with the inside of the container is provided outside the container (tank), and a hole is formed in the container and the pipe is welded to the container. However, there is a drawback in that the structure is complicated and the production is troublesome because of the necessity of the above. For this reason, it was difficult to construct the liquid level gauge at low cost.

Further, a time lag is inevitable until the behavior of the liquid surface position of the liquid material in the container is reflected on the liquid surface position in the pipe located outside the container. For this reason, it has been very difficult to detect the liquid level quickly and with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a float type liquid level gauge which has a simple structure and can quickly and accurately measure the liquid level position.

[0007]

SUMMARY OF THE INVENTION A float type liquid level gauge according to the present invention is configured to move up and down in accordance with a change in a liquid level of a liquid material contained in a predetermined container. , A magnetostrictive element extending in the vertical direction of the container, pulse generating means for generating a pulse current flowing in the magnetostrictive element in the extending direction, and the magnetostrictive element by the pulse current Means for detecting an elastic strain wave generated from the magnetostrictive element by the Wiedemann effect from a position near the liquid surface of the magnetostrictive element by a magnetic field generated near the outer periphery of the magnetostrictive element and a parallel magnetic field generated by the permanent magnet. And liquid level calculating means for calculating a liquid level position of the liquid material based on the detected elastic strain wave.

Preferably, the float type liquid level meter of the present invention further comprises a volume calculating means for calculating the volume of the liquid material in the container based on the calculated liquid level position.

[0009] Preferably, the magnetostrictive element is sealed in a rigid pipe portion capable of withstanding high pressure.

In a preferred embodiment, the float is made of a nitrile rubber independent foam.

Further, in a preferred embodiment, the alarm setting for the liquid level fluctuation is automatically performed based on the volume of the liquid material.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid level gauge according to the present invention will be described below with reference to the accompanying drawings. 1 and 2 show a liquid level gauge according to an embodiment. This liquid level gauge includes a flange portion 1, a pipe portion 2, a guide portion 3, a spring 4, a float 5, a permanent magnet 6, a magnetostrictive element 7, a probe portion 8, a cable 9, a connector 10, a calculation portion 11, a display portion 12, and the like. It is composed of

A tank for storing a liquid material such as a liquefied gas (eg, LPG), for example, a filling opening 21 of a container 20 such as a tank installed on a tank truck,
The flange 1 is attached so as to seal the opening 21. A known packing or the like is appropriately used to seal the opening 21. The flange portion 1 is made of a member such as stainless steel in order to have pressure resistance to withstand high pressure in the container 20.

The pipe portion 2 is formed of a cylindrical stainless steel tube or the like, and the upper end of the pipe portion 2 is welded to the flange portion 1. The lower end of the pipe section 2 is hermetically sealed by a stainless steel stopper 2a or the like.

The guide section 3 is made of stainless steel or the like, and is fixed to the lower end of the pipe section 2 with bolts or the like. A spring 4 is provided on the guide portion 3. The spring 4 is made of stainless steel or the like, and is installed such that a lower end thereof contacts the upper surface of the guide portion 3 and an upper end thereof contacts the lower surface of the float 5.

The float 5 is made of a material which is inactive with respect to the liquid material in the container 20, and a member which is lighter than the liquid material is used. For example, when the liquid material is LPG, the float 5 is preferably made of an independent foam of nitrile rubber (NBR) that can withstand high-pressure liquefied gas, but it is needless to say that other materials may be used. It is preferable to form a float with this closed foam of nitrile rubber because it is lightweight and easy to obtain buoyancy, and the material does not change over time in a high-pressure liquefied gas atmosphere and the cost is low, which is preferable. In the center of the float 5, a center hole 5 through which the guide portion 3 is inserted so as to be vertically movable.
a is formed. Further, a permanent magnet 6 is integrally fixed inside the float 5.

The permanent magnet 6 is made of a known magnetic material. In the embodiment shown in FIGS.
Has a donut shape, that is, a continuous annular shape, and is embedded so that the magnet is not exposed from the surface of the float, but is provided on the outer periphery of the magnetostrictive element 7 provided in the pipe portion 2 so as to extend in the longitudinal direction. Any appropriate shape or structure can be used as long as it can provide an extremely uniform parallel magnetic field. For example, a structure in which a plurality of permanent magnet pieces are annularly arranged at predetermined intervals may be used.

An electromagnet can be used instead of the permanent magnet 6, but in this case, an electric circuit and wiring for exciting the electromagnet, and a structure for isolating the electromagnet in a liquid material are required. Become. Therefore, it is preferable to use a permanent magnet from the viewpoint of simplifying the structure.

The magnetostrictive element 7 is sealed inside the pipe part 2, that is, in a hollow part. Such encapsulation, for example,
After inserting the magnetostrictive element 7 into the inside of the pipe portion 2 from the lower opening of the pipe portion 2 with the flange portion 1 welded to the upper end, the lower end of the pipe portion 2 is sealed or sealed with the above-described plug 2a. Will be

By enclosing the magnetostrictive element 7 inside the pipe portion 2, even if the magnetostrictive element 7 is a material that is mechanically fragile or a material that is affected by a liquid material in the container, a high pressure can be easily applied. The magnetostrictive element 7 can be used in the container 20 of FIG. As the magnetostrictive element 7, for example, a magnetostrictive linear displacement sensor is used.

The probe section 8 has a high-frequency pulse generator, a distortion wave detector and a displacement calculator. The pulse generator outputs a pulse signal or a pulse current having a predetermined current value at predetermined time intervals, and includes a known pulse generator or the like. This pulse current flows through the magnetostrictive element 7 and generates a magnetic field of a constant magnitude around the magnetostrictive element 7. In addition, when the above-mentioned pulse is generated, the strain wave detector detects a pulse-like strain wave (elastic ultrasonic wave) generated from the magnetostrictive element 7 by the Wiedemann effect as described later, and converts this into an electric signal. More specifically, it is constituted by an inverse Wiedemann effect element.

The electric signal detected and converted by the probe unit 8 as described above is input to the arithmetic unit 11 via the cable 9 and the connector 10. However, the probe unit 8 calculates the distance L based on the following equation. Here, V is the sound speed (m / s) in the elastic body, T is the time (s) from the output of the pulse current or the pulse signal from the pulse generator until the distortion wave detector detects the distortion wave, and L is the distortion. The distance (m) between the wave detector and the permanent magnet. Of course, L is further converted to a distance L (m) from the lower end of the sensor to the liquid level.

[0023]

## EQU1 ## V × T = L

The calculating section 11 calculates the distance X (m) from the inner bottom surface of the container 20 to the liquid surface position of the liquid in the container based on the distance L (m) calculated above. is there.

Further, the calculating section 11 calculates the volume V (liter) of the liquid material in the container 20 based on the liquid level position calculated as described above. As a specific example of calculating such a volume, a function or a table (correspondence table) representing the relationship between the liquid level position and the volume in the container 20 is provided in the calculating unit 11 and the function corresponding to the calculated liquid level position is provided. There is a method of obtaining the volume to be calculated from these functions or tables. The display unit 12 displays, for example, digitally the liquid surface position or volume calculated or obtained as described above.

Reference numeral 22 denotes a protection cylinder which is vertically provided from the lower surface of the opening 21. The bottom is opened to communicate with the inside of the container 20 so that liquid can enter and exit. The provision of the protection tube 22 may prevent the pipe portion 2 from being damaged by temporary liquid movement caused by a sudden movement of the container 20, but the protection tube 22 is not always necessary. .

The operation of the liquid level gauge according to the embodiment of the present invention will be described below. First, the float 5 and the permanent magnet 6 integrated with the float 5 are used to change the liquid level of the liquid material in the container 20,
That is, it moves up and down in the axial direction of the pipe portion 2 according to the up and down movement. Then, when a high-frequency pulse current or pulse signal is generated from the pulse generator of the probe unit 8, a magnetic field that fluctuates at a high frequency so as to draw a circle near the circumference of the magnetostrictive element 8 as described above. Here, at the position where the magnetic field generated by the pulse current and the magnetic field generated by the permanent magnet 6 overlap, distortion of the magnetic field occurs in the magnetostrictive element 8. This distortion propagates as a distorted wave at the speed of sound to both ends of the magnetostrictive element 8.

Since the float 5 accommodates the permanent magnet 6 inside the float and does not expose it to the surface, no metal fragments floating on the surface of the float moving up and down in the liquid adhere to the float 5 and the time is reduced. Even after the passage, the weight of the float does not increase, and there is little possibility that an error occurs in the measured value. Further, since the permanent magnet 6 is provided below the center of the float 5, the stability of the float 5 as a whole can be increased.

The above-mentioned distorted wave is detected by the distorted wave detector of the probe unit 8 and converted into an electric signal. Based on this electric signal, the calculation unit 11 calculates the accurate liquid surface position or volume as described above. Are displayed on the display unit 12.

The float 5 is vertically movably inserted into a pipe portion arranged in the container 20 in a vertical direction, and the float 5 is moved up and down in response to a change in the liquid level. If an alarm is set based on the level of the liquid level, the remaining amount cannot be accurately grasped.However, since the setting is automatically performed based on the volume of the liquid, it is necessary to accurately grasp the remaining amount in the container and set an accurate alarm. It has the advantage that it can be.

According to the liquid level gauge of the first aspect of the present invention,
Since there is no need for a structure in which a pipe communicated with a container as in the related art is provided, the structure can be simplified. Also,
The liquid level can be detected based on the actual fluctuation of the liquid material in the container, and the liquid level can be detected quickly and accurately. According to the liquid level meter of the second aspect, the volume of the liquid remaining in the container can be immediately obtained. According to the liquid level gauge of the third aspect of the invention, the magnetostrictive element can be protected from the influence of the liquid in the container or the pressure in the container. According to the liquid level gauge of the invention described in claim 4, since the float is made of an independent foam of nitrile rubber, it is lightweight and easily obtains buoyancy. It does not change over time and is inexpensive and easy to use. The liquid level gauge of the invention according to claim 5 is
There is an advantage that the alarm can be set freely according to the volume of the liquid material in the container.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a liquid level gauge according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of a liquid level gauge in the embodiment of FIG.

FIG. 3 is a longitudinal sectional view of a float according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flange part 2 Pipe part 3 Guide part 4 Spring 5 Float 6 Permanent magnet 7 Magnetostrictive element 8 Probe part 11 Operation part 12 Display part 20 Container

Claims (5)

[Claims] A permanent magnet provided inside a float configured to move up and down in response to a change in the liquid level of a liquid material contained in a predetermined container; Existing magnetostrictive element, pulse generating means for generating a pulse current flowing in the magnetostrictive element in the extending direction, a magnetic field generated near the outer periphery of the magnetostrictive element by the pulse current, and a parallel magnetic field by the permanent magnet Means for detecting an elastic strain wave generated by the Wiedemann effect from a position near the liquid surface of the magnetostrictive element, and calculating the liquid surface position of the liquid based on the detected elastic strain wave. A float type liquid level meter comprising a liquid level calculating means. 2. The float type liquid according to claim 1, further comprising volume calculating means for calculating a volume of the liquid material in the container based on the calculated liquid level position. Area meter. 3. The float type liquid level gauge according to claim 1, wherein said magnetostrictive element is sealed in a rigid pipe portion capable of withstanding high pressure. 4. The float type liquid level gauge according to claim 1, wherein the float is made of a closed foam of nitrile rubber. 5. The float type liquid level gauge according to claim 1, wherein an alarm setting for the liquid level fluctuation can be automatically performed based on the volume of the liquid material.