JPS63308521A - Level sensor and compensating method of measured value thereof - Google Patents

Abstract

PURPOSE:To enable the simple compensation of inclination of a sensor by a method wherein level sensors at least of a pair or more are disposed in parallel on a supporting body so as to regard the center of fluctuation as a correct liquid level. CONSTITUTION:Level sensors 2 at least of a pair or more are disposed in parallel on a supporting body 3, which is suspended in a fuel tank 1 at a prescribed distance from the center O of fluctuation of a liquid surface set hypothetically in the tank 1 so that each level sensor 2 traverses the surface in a straight line from the center O of fluctuation. Moreover, the supporting body 3 is disposed in the direction wherein each of resistors 4A and 4B is positioned on a straight line from the center O of fluctuation and traverses the surface. By this fluctuation of the liquid surface WL, a difference is caused in output between the level sensors 2. Using this difference, a distance l1 between the sensors 2 and a distance l2 from the center O of fluctuation as elements, an inclination from the center O of fluctuation, which is an actual liquid surface, can be computed 7 as a difference in detected voltage. Thereby an actual liquid level in the state wherein it is not inclined can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a level sensor, and more particularly to a level sensor capable of compensating a measured value according to the inclination of a liquid level, and a method for compensating the measured value.

(Background of the Invention) It has been reported that a heat dissipation type resistor in which a Ni thin film is formed on a polyimide film, for example, can be used as a level sensor.

The principle for using this resistor as a level sensor is explained as follows.

Generally, the resistance value of an object increases in proportion to the temperature of the object, as shown in FIG. 1(a). This slope is determined by the material.

Then, by applying an electric current to the Ni thin film mentioned above and heating it, the resistance value is kept high, and when this resistor is immersed in a liquid, the thermal resistance of the liquid and the conductor is higher than that of the gas and the conductor. Since there is a large C, the resistance value becomes small, and as shown in Figure 1 (b
), the resistance value decreases in proportion to the immersion depth.

Therefore, the liquid level can be understood as a change in resistance value.

This relationship can be expressed by the following formula.

However, L: Total length of the resistor
: Resistance value per unit length Note that in reality, a constant current is flowing through the resistor, so
The change in resistance value due to level can be taken out as voltage (X), and can be expressed by the following equation.

By reading the voltage change, the liquid level in a liquid storage tank, etc. can be detected based on the voltage change.

(Problem that the invention seeks to solve) However, when using a sensor made of this resistor to measure the liquid level of a container that is unstable, such as a vehicle fuel tank, other level sensors may be used. Similarly, the sensor installation C
There was a problem in that the measurement level differed depending on the position of the liquid, making it impossible to measure the liquid level accurately.

In this case, the liquid level can be measured accurately by placing sensors in several places in the container and calculating the average value according to the slope of the liquid level, but the device becomes complicated and is not practical. It was not possible to convert.

By the way, when a rectangular container is filled with liquid and is rocked back and forth, left and right, or tilted, the liquid tilts relative to the container with the center of the container as the center of fluctuation.

It is easy to understand that the liquid level at this center of fluctuation is equal to the liquid level in the horizontal state within a range where the slope does not exceed a certain slope.

This invention was made based on the above assumptions,
The object is to provide a level sensor in which tilt compensation in this type of sensor can be performed by a simple principle mechanism by regarding the center of fluctuation as the correct liquid level.

(Means for Solving the Problems) In order to achieve the above object, a level sensor of the present invention is provided.
At least one pair or more of level sensors are arranged in parallel on a support, and each level sensor moves the support to the center of fluctuation in a straight line from the center of fluctuation of the liquid level, which is virtually determined in the liquid storage container. It is characterized by being vertically disposed within the liquid storage container at a predetermined distance from the container.

In addition, in this invention, based on the arrangement of each level sensor described above, the difference in the output of each level sensor caused by fluctuations in the liquid level, the distance between each level sensor, and the distance from the center of fluctuation are calculated. , calculates the slope from the center of fluctuation, which is the actual liquid level, as a detected output difference, and adds this calculation result to the actual output value to correct the liquid level at the center of fluctuation;
A method for compensating measured values is provided.

(Function) Fluctuations in the liquid level cause differences in the output between each level sensor. Using this difference, the distance between the sensors, and the distance from the center of fluctuation as specifications, the slope from the center of fluctuation, which is the actual liquid level, can be calculated as the detected voltage difference. You can know the liquid level.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

2 and 3 show a fuel tank equipped with a level sensor according to the invention.

In the figure, 1 is a fuel tank formed in a rectangular shape, and 2 is a level sensor disposed within the fuel tank 1.

The level sensor 2 is placed in the upper center of the tank 1, at an appropriate distance from J, that is, the fluctuation center ○, with a support 3 that is fitted inside and vertically installed, and is placed in parallel with the support 3, separated by a predetermined distance. A pair of heat dissipating resistors for level measurement 4A
, 4B.

The orientation of the support body 3 is set so that each of the resistors 4A and 4B is located on a straight line and crosses the center of variation O.

The resistors 4A and 4B are formed by forming a N1 thin film on a polyimide film as described above, and a constant current is applied to each resistor 4A and 4B, and the immersion depth of the liquid surface WL is A voltage measurement unit 6 is connected to the voltage measurement unit 6 for detecting an increase or decrease in the resistance value of each resistor 4A, 4B depending on the resistance.

The output end of each voltage measurement section 6 is connected to a calculation section 7, which calculates the liquid level WL in the tank 1 based on the respective voltage values, arrangement intervals, lengths of the resistors 4A, 4B, and other specifications. do.

Furthermore, a level display 8 is connected to the output end of the calculation section 7 to display the calculation results.

The configuration of the calculation unit 7 includes a multiplication unit 9 for multiplying the difference output obtained by subtracting VAe from the voltage value VBe output from each voltage measurement unit 6 by a constant G, and a value ΔV output from the multiplication unit 9.
It consists of an adding section 10 that adds eG and an output value VBe from the resistor 4B side, and the output value from this adding section 10 is displayed as a liquid level on a display section 8'c.

For convenience of explanation, the configuration of the arithmetic unit 7 is described as a dedicated arithmetic circuit such as a discrete as shown in the figure, but in practical use, arithmetic means such as a one-chip microcomputer can be adopted. Of course.

In short, the arithmetic unit 7 executes a logical operation procedure using the 1 geometric figure shown in FIG. The change in resistance value corresponding to the change in the liquid level of B is captured, and the level of the liquid level WL at the virtually determined center of fluctuation O is displayed on the display 8.

In the figure, the length of resistors 4Δ and 4B is 1-1 liquid level WL
The insertion depth from ×1 resistor/1. A, 4. The distance between B is 1. The length between the center of variation O and the resistor 48 near it is defined as 2.

When the liquid level WL is horizontal, each resistor 4A, 4
The insertion depths X of B are equal.

Furthermore, if a constant current is flowing through both, the resistances of both are equal, so the measured voltages are equal, so the value output from the multiplier 9 is 0, and the value output from the adder 10 is equal.
The output from the resistor 4B is equal to the voltage output from the resistor 4B side.

That is, in the horizontal state, only the output from the resistor 4B side is measured and displayed on the display 8.

If the tank 1 is tilted or the liquid level moves due to shaking, etc., and the actually measured liquid level WL is tilted by θ° relative to the fluctuation center O, which is the virtual true liquid level, the resistor 14A will be immersed. The depth is deeper than the immersion depth of the resistor 4B, and assuming that the respective immersion depths are (X+X+) and (X+X2), each resistor 4A and 4B has a resistance value for each immersion depth and a voltage corresponding to this. value.

That is, by tilting, the resistors 4B and 4A
The measured voltage from the horizontal state X decreases compared to the voltage value in the horizontal state.

Therefore, if you add this decrease to the horizontal value, you will get the true value.

Also, from the geometry, the ratio of the distance 1 between the resistors 4A and 48 and the length 12 between the center of variation 0 and the resistor 4B near this is constant in advance, so this value is set as a constant G and is calculated according to the slope. If the difference in depth (X+ -X2) is known, the difference x1 in depth between the resistor 4B and the fluctuation center O can be calculated.

Therefore, in reality, the detected voltage difference between the two (vBe-v
By multiplying 〇) by the above-mentioned constant G, a correction value ΔVeG can be calculated, and by adding the original detection voltage VBe to this, a compensated output can be obtained.

Note that when the liquid level WL tilts to the opposite side from that shown in the figure, the value output from the multiplier 9 becomes negative, and the adder 10 naturally outputs the subtracted value.

In either case, as long as the liquid level WL is tilted from the virtually determined center of variation O, the compensation calculation will display an accurate liquid level.

However, if the slope exceeds this limit, the center of variation O
moves.

For example, in the case of a large inclination angle where one end of the liquid level reaches the ceiling of the tank 1, as shown by the imaginary line in Fig. 5,
The center of variation deviates from the predetermined center of variation O,
This exceeds the scope of the above compensation.

However, in reality, such a large inclination angle may occur momentarily, but it is unlikely to occur under normal conditions, so it does not cause any trouble in practice.

Furthermore, in determining the virtual fluctuation center O, a rectangular tank with a relatively simple shape was used in this embodiment.

However, for other shapes (C), the center of variation when actually tilted can be easily determined by drawing or calculation (tanks with relatively simple geometry) or by experiment (tanks with complex geometry). be able to.

Therefore, the present invention is not limited to the shape of the tank, but as long as the center of fluctuation can be correctly identified and the position between the sensor and the center of fluctuation is correctly positioned, the accuracy can be improved even if the liquid level is tilted. Good measurements can be obtained.

Furthermore, in the above embodiment, a heat-dissipating resistor with relatively high detection accuracy is used as a sensor (although the results are the same even if a sensor such as Flow 1~ type is used, regardless of the type of sensor). Of course.

(Effects) As explained in detail through the embodiments above, in this invention, by utilizing the difference in output between each level sensor due to fluctuations in the liquid level, -C1 This output difference and the level The actual liquid level can be determined by calculating the slope from the fluctuation center, which is the actual liquid level, as the detected voltage difference using the distance between the sensors and the distance from the fluctuation center as specifications.

Therefore, according to the present invention, it is possible to obtain a compensation output according to the inclination of the -b liquid level without using a large number of sensors. It is suitable as a level sensor for measuring liquid level and a method for compensating the measured value thereof.

[Brief explanation of the drawing]

1<a) and (b) are graphs showing the characteristics of a heat dissipation type resistor to which the present invention is applied; FIG. 2 is an explanatory plan view showing a state in which the level sensor according to the present invention is fixed to a fuel tank; Figure 3 is a partially schematic explanatory diagram showing the section taken along the line ■-■ in Figure 2 to add arithmetic processing means; Figure 4 is an explanatory diagram of a geometric figure showing the relationship between the sensor and the center of fluctuation; 5
The figure is a schematic diagram for explaining the measurable area of the present invention. 1... Burn 1 Tank 2... Level sensor 3... Support body 4Δ, 413... Heat radiation type resistor 6... Voltage measuring section 7... Acting section 8... Level display Container 9... Multiplier 10... Adder O... Fluctuation center W [... Liquid level pattern 1... Distance between resistors Ml

Claims (2)

[Claims] (1) At least one pair or more of level sensors are arranged in parallel on a support, and each level sensor moves the support so that it crosses in a straight line from the center of fluctuation of the liquid level, which is virtually determined in the liquid storage container. A level sensor characterized by being installed vertically within a liquid storage container at a predetermined distance from the liquid storage container. (2) At least one pair or more of level sensors are arranged in parallel in a straight line across from the center of fluctuation of the liquid level determined virtually in the liquid storage container, and the output of each of the level sensors caused by the fluctuation of the liquid level is Based on the difference, the distance between each level sensor, and the distance from the center of fluctuation,
A level sensor that calculates a detected output difference with respect to an inclination from the center of fluctuation, which is the actual liquid level, and adds this calculation result to the actual output value to correct the liquid level to the center of fluctuation. Measured value compensation method.