JPH0440643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> 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 dissipating resistor in which a thin Ni film is formed on a polyimide film 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 Figure 1a. This slope is determined by the substance.

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 between the liquid and the conductor is greater than the thermal resistance between the gas and the conductor. Therefore, the resistance value becomes small, and as shown in FIG. 1b, the resistance value becomes small 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.

R(X)=Ro'・X/1-aK +Ro'・L-X/1-K where L: Total length of resistor X: Length of immersed part K: Physical quantity that influences measurement effect a: Gas and conductor Thermal resistance of / Thermal resistance of liquid and conductor Ro′: Resistance value per unit length Note that since a constant current is actually flowing through the resistor, the change in resistance value due to level can be extracted as voltage (X). can be expressed by the following formula.

V(X)=IRo′・X/1−aK +IRo′・L−X/1−K Therefore, by passing current through the above resistor and reading the voltage change, it is possible to The surface level can be detected as a voltage change.

≪Problems to be solved by the invention≫ However, when this sensor is used to measure the liquid level of a container that is unstablely installed, such as a fuel tank of a vehicle, it is similar to other level sensors; Due to the container being tilted, the measurement level would vary depending on the mounting position of the sensor, which caused the problem that accurate liquid level measurements could not be made.

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. I couldn't do it.

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.

As an idea to compensate for the measurement error of the fluctuating liquid level by using such a center of fluctuation, for example,
A device described in Japanese Patent No. 61-155731 is known.

This device is a lubricating oil amount detection device that detects the oil level at a position equidistant from the center of fluctuation on a straight line that intersects the longitudinal centerline of the vehicle at a 45 degree angle and passes through the center of fluctuation (centroid). It is configured with two sensing parts.

This invention utilizes the fact that when the liquid level is tilted, the sensing parts are displaced by the same amount in opposite directions, and by adding both displacement amounts, the liquid level at the center of the fluctuation is calculated.

However, this idea has the problem that it is large because the sensing portions are provided on both sides of the center of movement, and that the mounting position is restricted to a symmetrical position with respect to the center of movement, making it impossible to install it at a desired position.

This invention was made in order to solve the above-mentioned problems, and its purpose is to simplify the tilt compensation in this type of sensor by regarding the center of fluctuation as the correct liquid level. To provide a level sensor which is compact and can be installed at a desired position without any restrictions.

<Means for Solving the Problems> In order to achieve the above object, the level sensor of the present invention includes at least one pair of level sensors arranged in parallel on a support, and the level sensor is arranged in a virtual position within a liquid storage container. The support is placed vertically in a liquid storage container at a predetermined distance from the center of variation so that it is located on a straight line from the center of variation of the liquid level determined by and on the same side as the center of variation. By providing a voltage measuring section that detects a voltage corresponding to the liquid level of the sensor, and calculating with a comparison calculating means based on the output of each voltage measuring section and the relative positional relationship between each level sensor and the fluctuation center, the above-mentioned The present invention is characterized in that the liquid level at the virtual center of fluctuation is determined.

Further, in a measured value compensation method of another invention, at least one pair or more of level sensors are positioned on a straight line from a center of variation of a virtually determined liquid level in a liquid storage container and parallel to the same side with respect to the center of variation. At the same time, each level sensor is placed vertically in a liquid storage container at a predetermined distance from the center of fluctuation, and detects the voltage corresponding to the liquid level of each level sensor, and detects the output voltage of each level sensor caused by the fluctuation of the liquid level. Based on the difference between the two level sensors, the distance between each level sensor, and the distance from the center of fluctuation, the slope from the center of fluctuation, which is the actual liquid level, is calculated as the difference in output voltage, and this calculation result is used as the actual output voltage. It is characterized in that the liquid level is added to the value to determine the liquid level at the center of the fluctuation.

<<Function>> Fluctuations in the liquid level cause differences in output between each level sensor. Using this difference, the distance between the level 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 a detection voltage difference. You can know the surface level. Furthermore, since the plurality of level sensors are located on a straight line from the center of variation and on the same side of the center of variation, the level sensors can be installed at desired positions within the liquid storage container.

<<Example>> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

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

In the figure, reference numeral 1 indicates a fuel tank as a rectangular liquid storage container, and reference numeral 2 indicates a level sensor disposed within the fuel tank 1. As shown in FIG.

The level sensor 2 consists of a support 3 that is fitted into the liquid and vertically installed at an appropriate distance from the center of the upper part of the tank 1, that is, the center of fluctuation O, and a pair of supports 3 that are arranged parallel to each other and separated by a predetermined distance from the support 3. Heat-dissipating resistor 4 as a level sensor for level measurement
It consists of A and 4B.

The orientation of the support body 3 is set so that the resistors 4A and 4B are located on a straight line from the center of variation O and on the same side with respect to the center of variation.

The resistors 4A and 4B are formed by forming a Ni thin film on a polyimide film as described above, and a constant current is applied to each of the resistors 4A and 4B, and the immersion depth of the liquid surface WL varies. 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 terminal 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 resistors 4A, 4B, etc. 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 ΔVeG output from the multiplication unit 9 and a resistance. It consists of an adder 10 that adds the output value VBe from the body 4B side,
The output value from the adding section 10 is displayed on the display section 8 as a liquid level.

For convenience of explanation, the configuration of the arithmetic unit 7 is explained as a dedicated arithmetic circuit such as a discrete as shown in the figure. Of course, other means can be adopted.

In short, the calculation unit 7 uses the geometric figure shown in FIG. 4 below and the above-mentioned constant G calculated based on it.
Execute the logical calculation procedure using as a factor, take in the resistance value change according to the liquid level change of each resistor 4A, 4B, and display the level of the liquid level WL at the virtually determined center of fluctuation O on the display 8. do.

In the figure, the length of the resistors 4A and 4B is L, the insertion depth from the liquid level WL is X, the distance between the resistors 4A and 4B is l ₁ , and the fluctuation center O and the resistor 4B near this
Let the length between them be l ₂ .

When the liquid level WL is horizontal, the insertion depths X of the resistors 4A and 4B 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 of resistor 4B
equal to the voltage output from the side.

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

When the liquid level moves due to the tank 1 tilting or shaking, 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 4A The immersion depth of the resistor 4B is deeper than that of the resistor 4B, and the immersion depth of each is (X+
X ₁ ), (X+X ₂ ), each resistor 4A, 4B
is the resistance value for each immersion depth and the corresponding voltage value.

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

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

Also, from the geometric figure, the ratio of the distance l ₁ between the resistors 4A and 4B and the length l ₂ between the fluctuation center O and the resistor 4B near this is constant in advance, so this value is set as a constant G and the ratio is adjusted according to the slope. If the difference in depth (X ₁ −X ₂ ) is known, the difference in depth X ₁ between the resistor 4B and the fluctuation center O can be calculated.

Therefore, in practice, the correction value ΔVeG can be calculated by multiplying the detection voltage difference between the two (VBe - VAe) by the constant G mentioned above, and by adding the original detection voltage VBe to this, the compensation output can be obtained. It will be done.

Note that if 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 any case, as long as the liquid level WL is tilted from the hypothetically 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 will move.

For example, as shown by the imaginary line in Figure 5, in the case of a large inclination angle such that one end of the liquid level reaches the ceiling of tank 1, the center of variation shifts from the predetermined center of variation O, and the above It is beyond the scope of 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, even for other shapes, 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). I can do it.

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 dissipation type resistor with relatively high detection accuracy is used as a sensor, but the result is the same even if a float type sensor is used, and the type of sensor does not matter. Of course.

<<Effects>> As explained in detail using the embodiments above, the present invention utilizes the difference in output between each level sensor due to the fluctuation of the liquid level to increase the output. The actual liquid level can be determined by calculating the slope of the tilted liquid level from the center of fluctuation, which is the actual liquid level, as the detected voltage difference using the distance between the difference, the distance between the level sensors, and the distance from the center of fluctuation as specifications. can be known.

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

In addition, since a resistor is used as the sensor, it can be formed compactly, and since multiple level sensors are located on a straight line from the fluctuation center and on the same side of the fluctuation center, the level sensors can be placed in the liquid storage container. It can be installed at any desired location within.

[Brief explanation of the drawing]

1a and 1b are graphs showing the characteristics of a heat dissipation type resistor to which the present invention is applied, FIG. 2 is a plan view showing the level sensor according to the present invention fixed to a fuel tank, and FIG. In the cross section taken along the - line in Figure 2, a partially schematic explanatory diagram for adding an arithmetic processing means, Figure 4 is an explanatory diagram of a geometric figure showing the relationship between the sensor and the center of fluctuation, and Figure 5 is a diagram showing the measurement of the present invention. It is a schematic diagram for explaining a possible region. DESCRIPTION OF SYMBOLS 1...Fuel tank, 2...Level sensor, 3...Support body, 4A, 4B...Radiation type resistor, 6...Voltage measuring part, 7...Calculating part, 8...Level indicator, 9...Multiplying part, 10...Adding part , O...center of fluctuation, WL...liquid level,
l ₁ ...distance between resistors, l ₂ ...distance to center of variation.

Claims (1)

[Scope of Claims] 1. At least one pair or more of level sensors are arranged in parallel on a support, and the level sensor is located on a straight line from the center of variation of the virtually determined liquid level in the liquid storage container, and is located at the center of variation. The support body is vertically disposed within the liquid storage container at a predetermined distance from the fluctuation center so as to be disposed on the same side, and a voltage measurement unit is provided for detecting a voltage corresponding to the liquid level of each level sensor, The liquid level level at the virtual center of fluctuation is determined by calculation by a comparison calculation means based on the output of each voltage measuring section and the relative positional relationship between each level sensor and the center of fluctuation. level sensor. 2. At least one pair or more of level sensors are located on a straight line from the center of fluctuation of the virtually determined liquid level in the liquid storage container, arranged in parallel on the same side to the center of fluctuation, and at a predetermined distance from the center of fluctuation. is installed vertically in a liquid storage container, and detects the voltage corresponding to the liquid level of each level sensor, and detects the difference in output voltage of each level sensor caused by fluctuations in the liquid level and the distance between each level sensor. and the distance from the fluctuation center, calculate the slope from the fluctuation center, which is the actual liquid level, as the difference in output voltage, and add this calculation result to the actual output value to calculate the liquid level at the fluctuation center. A method for compensating measured values of a level sensor, characterized in that: