KR100219762B1 - Fuel quanity measure gauge - Google Patents

Abstract

It is a fuel level measuring device that can measure fuel amount by sensing air pressure that changes according to the liquid level, and can accurately measure the fuel amount regardless of the shape of the container.The pipe member extends vertically from the top of the fuel tank toward the bottom. A gas pressure sensor provided at an upper portion of the pipe member to sense a pressure of air proportional to a level of fuel in the pipe member, and a fuel amount signal converting unit generating an electrical signal proportional to the fuel amount from an output from the gas pressure sensor; Equipped.

Description

Fuel level meter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel level meter of an automobile, and more particularly, to a fuel level meter capable of accurately measuring fuel amount regardless of the shape of a container as well as measuring the fuel amount by sensing an air pressure that changes according to the liquid level.

Conventionally, an apparatus for measuring fuel amount has been developed and used. A representative of such a device is shown in FIG. 8. In the apparatus of FIG. 8, the portion of the contact with the resistance means 12 is changed depending on the height of the fuel with the knit 11 floating, so that the resistance value in the circuit is changed, and thus the current value flowing in the circuit is changed. The instrument panel 13 shows the current value in the circuit in terms of fuel amount. That is, the position of the guide 14 varies according to the magnitude of the current flowing. If the fuel amount is indicated in advance on the instrument panel for each position of the guide, the amount of fuel in the fuel tank can be known. Here, when the fuel tank has no change in cross-sectional area according to the fuel level, such as a rectangular parallelepiped or a cylindrical shape, the height of the knitting 11 and the current value may be proportional to each other. However, in general, since the shape of the fuel tank has a form in which the cross-sectional area changes depending on the fuel level, correction of the current value is required. As the method, a method of correcting the thickness, width, etc. of the resistance means 12 is generally used such that the resistance value per unit length of the resistance means 12 changes in accordance with the shape of the fuel tank.

However, in such a method, since the resistance value 12 and the contact point come into contact with the position of the knit 11, the resistance value varies according to the position thereof. However, there is a disadvantage in that the accurate liquid amount cannot be measured due to a change in resistance value. In particular, when the thickness or width of the resistance means is corrected according to the shape of the fuel tank, the degree of wear is different, which makes it difficult to accurately measure the amount of fuel according to the shape of the fuel tank. In addition, this type of fuel amount measuring device has a problem that it is difficult to automate because the assembly process is complicated, and the number of assembly operations, such as soldering, resistance test, it is difficult to increase the productivity.

In addition, there is a pressure fuel amount measuring device such as those disclosed in Korean Patent Laid-Open Publication Nos. 96-11392 and 97-20589. These devices are installed in the lower part of the fuel tank so as to measure the remaining fuel amount by converting the pressure by the weight of the fuel into a resistance value or a capacitance value. However, there is a problem that such a device alone cannot correct the fuel amount measurement error caused by the change in the cross-sectional area of the fuel tank.

It is an object of the present invention to provide a fuel level meter with a simple structure.

Another object of the present invention is to provide a fuel amount measuring device that solves the problems caused by wear in the conventional contact measuring apparatus for converting the liquid level into a resistance value.

Still another object of the present invention is to provide a fuel amount measuring device capable of accurately measuring fuel amount regardless of the shape of a container.

1 is a schematic view showing the configuration of a fuel amount measuring instrument according to an embodiment of the present invention,

2 is a schematic circuit diagram of an apparatus for converting a fuel level signal in a fuel level meter according to an embodiment of the present invention;

3 is a circuit diagram showing an embodiment of a cross-sectional area correction unit of the fuel amount signal conversion device of FIG.

4 is a graph showing a relationship between an input voltage and an output voltage of each OP amplifier in the cross-sectional area correction unit of FIG. 3;

5 is a graph showing the relationship between the input voltage and the output voltage of the entire cross-sectional area correction unit of FIG.

6 is a schematic block diagram showing another embodiment of the cross-sectional area correction unit of the fuel amount signal conversion device of FIG. 2;

7 is a view showing the shape of various fuel tanks,

8 is a schematic view showing a conventional fuel amount measuring device.

Explanation of symbols on the main parts of the drawings

1 Fuel tank 2 Tube

3 Gas pressure sensor 4 Fuel level signal converter

5 Connector 6 Fuel

7 Cross Section Compensation Unit 8 A / D Converter

9 Calculator 10 D / A Transducer

11 knitting 12 resistance

13 Instrument cluster 14 Instructions

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1 is a schematic diagram showing the configuration of a fuel amount measuring instrument according to an embodiment of the present invention, Figure 2 is a schematic circuit diagram of a fuel amount signal conversion apparatus in the fuel amount measuring instrument according to an embodiment of the present invention.

As can be seen in FIG. 1, the present invention provides a pipe member 2 extending vertically from an upper surface of a fuel tank 1 toward a bottom surface thereof, and provided on an upper portion of the pipe member 2. And a gas pressure sensor 3 for sensing a pressure of air proportional to the level of fuel, and a fuel amount signal converting section 4 for generating an electrical signal proportional to the amount of fuel from an output from the gas pressure sensor 3; have.

The principle of the present invention having such a configuration is as follows. The pipe member 2 extends vertically from the top of the fuel tank 1 toward the bottom. In FIG. 1, the pipe member 2 is shown to be slightly separated from the bottom surface for the entry and exit of the fuel 6, but the present invention is not limited thereto. As described above, the change in the fuel level is represented by the change in the pressure of the air trapped between the fuel in the pipe member 2 and the pressure sensor 3. This pressure change is converted into an electrical change by the pressure sensor 3 installed on the upper part of the pipe member 2. The fuel amount signal converting section 4 converts the electrical signal into a value proportional to the fuel amount and outputs it through the terminal 5. Therefore, since an electrical signal is output from the terminal 5 in proportion to the amount of fuel, the terminal 5 can be displayed on the fuel amount instrument panel of a vehicle or the like by using this. The method of displaying the instrument panel using the electrical signal from the terminal 5 may be selected from a variety of methods that are widely known, such as an analog method using a coil and a guide and a method of converting and displaying digital data.

2 shows an embodiment of the fuel amount signal converter 4 of the present invention. As the gas pressure sensor 3, a diaphragm type pressure sensor, a diffusion type semiconductor pressure sensor, or the like can be used. The diaphragm sticking pressure sensor is composed of a thin bridge diaphragm capable of elastic deformation of a small displacement due to gas pressure, and a full bridge strain gauge for measuring the deformation amount of the thin film diaphragm. Diffusion type semiconductor pressure sensors have a common feature that the diaphragm itself is formed of a semiconductor and an element is integrally formed on the surface thereof, and both of them convert a change in pressure into a change in resistance value. In order to detect such a change in resistance value, as shown in FIG. 2, when the direct current power supply is connected to the input of the pressure sensor 3 and the direct current amplifier A1 is connected to the output, the change in the gas pressure is caused by the pressure sensor 3. It is represented by the change in resistance value, and thus the voltage value to the input of the amplifier A1 is changed to be amplified by the amplifier A1 and output to the output. Such pressure sensors are widely available on the market, such as XPX / CPX from Data Instruments, 140PC series from Micro Switch, and FP101 from Yokogawa Electric. Some of them have a built-in temperature compensation circuit and an amplifier circuit. If the amplifier circuit is incorporated, the amplifier A1 in Fig. 2 may be omitted.

In FIG. 2, reference numeral 7 denotes a cross-sectional area correction unit. The cross-sectional area correction unit 7 is to compensate for the difference between the gas pressure and the fuel amount due to the change in the cross-sectional area according to the shape of the tank. That is, the output of the amplifier A1 enters the input Vi of the cross-sectional area correction unit 7, and is converted into a value Vo that compensates for the change in the cross-sectional area in the cross-sectional area correction unit 7 and is output.

First, assume that the fuel tank is divided into four equally spaced sections over the entire height, and the horizontal cross-sectional area is constant within each section, as shown in FIG. According to this assumption, when the proportional coefficient between the change amount of fuel level (Δh) and the change amount of fuel volume (ΔV) in each section is k _n (n = 1 ... 4), the fuel level in the section is The amount of change Δh can be expressed as ΔV = k _n × Δh.

Assuming that the voltage Vi input to the cross-sectional area correction unit 7 varies from 0 volts to 4 volts, it is assumed that the total height of the fuel tank is divided into four equally spaced intervals. It is divided into a first section up to, a second section from 1 volt to 2 volts, a third section from 2 volts to 3 volts, and a fourth section from 3 volts to 4 volts. In summary, in the first section, the fuel amount increases at a rate of k ₁ as the fuel level changes, in the second section, the fuel amount increases at a rate k ₂ , and in the third section, the fuel level increases. As is changed, the fuel amount increases at the rate of k ₃ , and in the fourth section, the fuel amount increases at the rate of k ₄ as the fuel level is changed. This is shown in a graph as shown in FIG.

Figure 3 shows a circuit diagram of one embodiment of the cross-sectional area correction unit of the present invention for such a fuel tank. In this circuit, the OP amplifiers A2 to A5 each constitute an amplifier circuit having a gain of 1. The Zener diodes ZD1 to ZD4 all have a Zener voltage of 1 volt.

In the amplifier circuit composed of the OP amplifier A2, since a 1 volt Zener diode is connected between the negative input terminal and the output terminal of the OP amplifier A2, when the input receives a voltage of 1 volt or less, that is, in the first section, the output However, if the input exceeds 1 volt, the voltage V ₁ is kept constant at -1 volts to exhibit the characteristics as shown in FIG.

In the amplifier circuit composed of the OP amplifier A3, a 1 volt Zener diode is connected between the negative input terminal and the output terminal of the OP amplifier A3, and an offset voltage of -1 volt is applied thereto so that an input voltage of 1 volt or less is applied to the input. When the voltage is applied, that is, the output voltage V ₂ is fixed at 0 volts in the first section, and when the input is 1 volt or 2 volts, that is, in the second section, the output is proportional to the input and the input is set to 2 volts. On the other hand, the voltage V ₂ is kept constant at -1 volts to show the characteristics as shown in FIG.

In the amplifier circuit composed of the OP amplifier A4, a 1 volt zener diode is connected between the negative input terminal and the output terminal of the OP amplifier A4, and an offset voltage of -2 volts is applied thereto so that an input voltage of 2 volts or less is applied to the input. When the voltage is applied, that is, in the first and second sections, the output voltage V ₃ is fixed at 0 volts, and when the input is between 2 and 3 volts, that is, in the third section, the output is proportional to the input, and the input is 3 Beyond the volts, the voltage V ₃ is kept constant at -1 volts to show the characteristics as shown in (c) of FIG.

In the amplifier circuit composed of the OP amplifier A5, a 1 volt zener diode is connected between the negative input terminal and the output terminal of the OP amplifier A5, and an offset voltage of -3 volts is applied thereto so that an input voltage of 3 volts or less is applied to the input. When the voltage is applied, that is, in the first to third sections, the output voltage V ₄ is fixed at 0 volts, and when the input exceeds 3 volts, that is, in the fourth section, an output proportional to the input is output. It shows the same characteristics as (d).

OP amplifier A6 is as summing the output voltage to the OP amplifier A2 to A5, with respect to V ₁ k ₁ times, with respect to the V ₂ k ₂ times, with respect to V ₃ k ₃ times, to amplify times k ₄ for V ₄ Each input resistance value was set. Therefore, the output voltage Vo is represented by Vo = k ₁ V ₁ + k ₂ V ₂ + k ₃ V ₃ + k ₄ V ₄ , and therefore, the overall characteristic becomes as shown in FIG. 5.

In the above description, it is assumed that the shape of the fuel tank is divided into four equally spaced sections over the entire height and the horizontal cross-sectional area is constant in each corner. However, when the shape of the fuel tank is changed, the offset voltage and the ratio in each section are correspondingly. It can respond by adjusting k _n . In addition, as is the case in most cases, even when the shape of the tank forms a little curved surface in each section as shown in Fig. 7B, the curved surface influences the cross-sectional area even when the cross-sectional area is not equal in each section. In the case of not exceeding, the linear proportionality can be approximated by the above method. However, as shown in FIG. 7C, when the curvature of the curved surface is severe and affects the cross-sectional area, the measurement error can be reduced by further subdividing each section.

However, when the shape of the tank is close to the circular shape as shown in Fig. 7 (d), and the section needs to be divided considerably in order to reduce the measurement error, the number of OP amplifiers required increases and the area and cost of the device are increased. There is this.

6 is a block diagram showing another embodiment of the cross-sectional area correction unit of the present invention. FIG. 6 shows the configuration of a digital cross-sectional area correction unit that can further increase the measurement accuracy compared to the method of FIG. 3 by further subdividing the fuel level section. In the cross-sectional area correction unit of Fig. 6, the input Vi from the amplifier is converted into digital data using an analog-to-digital converter 8, and then the calculation unit 9 converts the fuel tank from the digital data. Calculate the amount of fuel taking the shape into account. The calculation is performed according to the following equation.

0 Vi V ₁ If it is a bolt Vo = k ₁ Vi ,

V ₁ Vi V ₂ If it is a bolt Vo = k ₂ (Vi-V ₁ ) + k ₁ V ₁ ,

V ₂ Vi V ₃ If it is a bolt Vo = k ₃ (Vi-V ₂ ) + k ₂ (V ₂ -V ₁ ) + k ₁ V ₁ ,

...

V _n-1 Vi V _n If it is a bolt

Where n is the number of sections, and the intervals between the sections need not be equally spaced. The output value calculated by the above equation, that is, the calculated fuel amount value, is converted into an analog value again by the D / A converter 10 and then output through the terminal 5. Using the method calculated by the calculation unit 9 in this way, even if there are many sections, for example, even if n is 10 or more, the number of parts does not increase as in the method of using an OP amplifier, so that the sections can be arbitrarily adjusted as necessary. This enables accurate measurement. This is particularly effective in the case where the shape of the fuel tank is streamlined as shown in FIG.

The calculation unit 9 may use an accumulation program method using a microprocessor, which is a well-known technique, or may be implemented in hardware by a logic circuit.

Although the present invention has been described by way of example by way of example, the present invention is not limited to the specific embodiments, and a person of ordinary skill in the art to which the present invention belongs does not have to depart from the scope of the present invention. Of course, improvements and modifications are possible. For example, in the above embodiment, the fuel level signal converter and the pressure sensor are configured as separate components, but they may be integrated in one semiconductor chip. In addition, although the digital cross-sectional area correction unit 7 is configured to perform D / A conversion of the output from the calculation unit 9, when the fuel level instrument panel of the vehicle is digital, the D / A converter 10 is not directly passed. The terminal 5 may be configured to be transferred to the circuit on the fuel level instrument panel side.

As described above, according to the present invention, there is provided a liquid amount measuring device which does not have a problem of shortening of life due to wear in a conventional contact measuring device for converting and measuring a liquid level into a resistance value. In addition, a fuel amount meter is provided in which the structure is relatively simple and the measurement error is minimized. In addition, a fuel amount measuring device capable of accurately measuring fuel amount regardless of the shape of the container is provided.

Claims (4)

In the device for measuring the amount of fuel in the fuel tank, A pipe member extending vertically from the top of the fuel tank toward the bottom; A gas pressure sensor provided at an upper portion of the pipe member and detecting a pressure of air proportional to the level of fuel in the pipe member; And a fuel amount signal converter for generating an electrical signal proportional to the fuel amount from the output from the gas pressure sensor. The fuel amount measuring device according to claim 1, wherein the fuel amount signal converting unit includes a cross-sectional area correction unit for correcting the gas pressure value from the gas pressure sensor according to the shape of the fuel tank. The fuel amount measuring device according to claim 2, wherein the cross-sectional area correcting unit includes an amplifying circuit having a gain proportional to the relationship between the pressure value and the fuel amount in each section in which the tank cross-sectional area is changed. The method of claim 2, wherein the cross-sectional area correction unit calculates an A / D converter for converting the output from the gas pressure sensor into a digital signal and a formula for correcting the shape of the fuel tank from the value from the A / D converter. And a D / A converter for converting an output from the calculator to an analog signal.

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