JP2014142240A - Liquid level measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level measuring apparatus which measures a liquid level properly even when two or more kinds of liquids having different electrostatic characteristics are included.SOLUTION: A liquid level measuring apparatus includes: a liquid level detection sensor 12 arranged from a bottom surface of a tank 10 toward a top surface; and a sensor circuit part 11 which detects an amount of change in electrostatic capacitance in the liquid level detection sensor 12, to determine a liquid level in the tank 10. In the liquid level detection sensor 12, a plurality of high-sensitivity regions 17 are formed at a predetermined interval along a height direction, so that an amount of change in electrostatic capacitance with respect to an amount of change in liquid level in the tank 10 is larger than in other regions of the liquid level detection sensor 12. The sensor circuit part 11 determines the number of high-sensitivity regions 17 immersed in the liquid in the tank 10, on the basis of a detected value of the amount of change in electrostatic capacitance, determines a liquid level on the basis of the number of regions, and ignores detection of the high-sensitivity region 17 when the amount of change in electrostatic capacitance with respect to the amount of change in liquid level in the high-sensitivity region 17 is equal to or less than a predetermined threshold.

Description

  The present invention relates to a liquid level measuring device, and more particularly to a liquid level measuring device capable of accurately measuring the liquid level in a fuel tank even in a fuel non-uniform state in which different types of fuel are mixed non-uniformly.

  An insulating substrate, and a pair of electrodes disposed on the insulating substrate so as to extend from one end of the insulating substrate toward the other end, and the electrode is provided at one longitudinal end of the insulating substrate. An electrostatic device having a terminal portion, a main body portion extending linearly from the terminal portion toward the other longitudinal end portion of the insulating substrate, and a plurality of orthogonal portions provided at equal intervals so as to be orthogonal to the main body portion. There is a capacitive liquid level detection sensor (Patent Document 1).

  In this capacitance type liquid level detection sensor, when the liquid level rises or falls, the capacitance of the pair of electrodes changes linearly according to the increase or decrease of the liquid level in the main body, but in the orthogonal part. Changes much more rapidly than the straight line. Therefore, since the capacitance changes stepwise, the liquid level can be accurately measured as compared with a liquid level sensor in which the capacitance changes linearly according to the increase or decrease of the liquid level.

Japanese Patent Laid-Open No. 5-118894

  However, when fuels with significantly different characteristics, such as gasoline and ethanol, coexist in the fuel tank, in the capacitive liquid level sensor, each fuel has a sudden change in capacitance with respect to the orthogonal portion. Therefore, there is a problem that the liquid level cannot be measured accurately only by measuring the change in capacitance at the orthogonal portion.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a liquid level measuring device capable of measuring an accurate liquid level even when two or more kinds of liquids having different dielectric constants are mixed. To do.

  The first aspect of the present invention is arranged from the bottom surface of the tank toward the upper surface of the tank, and the amount of change in capacitance with respect to the change amount of the liquid level in the tank A liquid level detection sensor having a larger high sensitivity area than the area formed at a plurality of intervals along the height direction of the tank, and a change amount of capacitance in the liquid level detection sensor. The number of high-sensitivity regions immersed in the liquid in the tank is obtained based on the detected amount of change in capacitance, the liquid level in the tank is obtained based on the number, and the liquid level detection sensor When the amount of change in capacitance with respect to the change in liquid level in the high sensitivity region is equal to or less than a predetermined threshold, a sensor circuit unit that ignores detection of the high sensitivity region and obtains the liquid level; A liquid level measuring device equipped with .

  In the liquid level measuring device, the amount of change in capacitance in the liquid level detection sensor is detected by the sensor circuit unit to determine the liquid level in the tank. Here, in the liquid level detection sensor, a plurality of high sensitivity regions are formed at regular intervals, and the amount of change in capacitance detected by the sensor circuit unit is larger in the high sensitivity region. As the liquid level rises, the capacitance of the liquid level detection sensor changes stepwise. Therefore, by detecting the number of step-like changes in the sensor circuit unit, the number of liquids in the tank that have passed through the high-sensitivity region of the liquid level detection sensor can be determined, and the liquid level in the tank is obtained based on this number. be able to.

  Here, for example, when hydrocarbon fuel such as gasoline or light oil is present in the tank, if alcohol such as ethanol, methanol, propanol, or butanol is supplied to the tank, the alcohol is more specific than the hydrocarbon fuel. Therefore, the supplied alcohols are not immediately mixed with the hydrocarbon fuel in the tank, the alcohols form a lower layer, and the hydrocarbon fuel forms an upper layer.

If refueling of alcohols is continued in this state, the hydrocarbon-based fuel layer located in the upper layer is lifted upward by the lower layer made of alcohols.
Therefore, in the high sensitivity region of the liquid level detection sensor, alcohols pass after the hydrocarbon fuel layer has passed, so both the hydrocarbon solvent and alcohols are detected in each high sensitivity region. become.

  However, since the hydrocarbon fuel generally has a smaller dielectric constant than alcohols, the change in capacitance with respect to the change in liquid level in the high sensitivity region is also small. Therefore, in the liquid level measurement device, the threshold value for the capacitance with respect to the change amount of the liquid level in the high sensitivity region is larger than the change amount corresponding to the hydrocarbon fuel, and more than the change amount corresponding to the alcohols. Is also set as a small value, and if the amount of change in capacitance actually detected is less than this threshold, the detection of the high sensitivity area is ignored, in other words, the high sensitivity area is not detected. In other words, in other words, the liquid level is obtained without counting the detection of the high sensitivity region.

  Therefore, in the liquid level measurement device, detection of the hydrocarbon fuel layer in the high sensitivity region is ignored, in other words, it is considered that the detection of the hydrocarbon fuel layer was not performed in the high sensitivity region. Only the detection of alcohols is counted.

  According to a second aspect of the present invention, in the liquid level measurement device according to the first aspect, the liquid level detection sensor extends in the width direction of the liquid level detection sensor and extends in the longitudinal direction of the liquid level detection sensor. It has a group of liquid level detection electrodes arranged at regular intervals, and in the high sensitivity region, the length of the liquid level detection electrode is set longer than the region other than the high sensitivity region in the liquid level detection sensor. It is characterized by.

In a liquid level detection sensor in which a liquid level detection electrode is formed, the capacitance is detected as the total capacitance between two adjacent liquid level detection electrodes. Accordingly, the detected capacitance increases as the liquid level detection electrode becomes longer.
In the liquid level measuring device, the length of the liquid level detection electrode in the high sensitivity region is longer than the length of the liquid level detection electrode in the region other than the high sensitivity region. The amount of change in capacitance is larger than the amount of change in capacitance with respect to the change in liquid level in other regions.

  According to a third aspect of the present invention, in the liquid level measurement device according to the first aspect, the liquid level detection sensor extends in the width direction of the liquid level detection sensor and is arranged along the longitudinal direction of the liquid level detection sensor. In addition, the liquid level detection electrode has a higher density in the high sensitivity region than in a region other than the high sensitivity region in the liquid level detection sensor. And

In the liquid level detection sensor in which the liquid level detection electrode is formed, the capacitance is detected as the total capacitance between two adjacent liquid level detection electrodes. Even in the case where they are all the same, the density of the liquid level detection electrodes increases. In other words, the smaller the interval between the liquid level detection electrodes, the larger the detected capacitance.
Here, in the liquid level measurement device, the density of the liquid level detection electrode in the high sensitivity region is set to be larger and higher than that in the other regions. The amount of change in capacitance is larger than the amount of change in capacitance in other regions.

  According to a fourth aspect of the present invention, in the liquid level measurement device according to any one of the first to third aspects, the tank is provided with a hydrocarbon fuel, an alcohol, or a mixture of an alcohol and a hydrocarbon fuel. In the case where either one is refueled and alcohol or a mixture of alcohol and hydrocarbon fuel is refueled in a tank in which hydrocarbon fuel is present, the sensor circuit unit is configured to detect the liquid level in the high sensitivity region. High sensitivity when the amount of change in capacitance with respect to the amount of change is less than a predetermined threshold as a value greater than the change corresponding to the hydrocarbon-based fuel and smaller than the change corresponding to the alcohols The liquid level is obtained ignoring the detection of the region.

  In the liquid level measuring device, the tank is supplied with either hydrocarbon fuel, alcohol, or a mixture of alcohol and hydrocarbon fuel. Or mixtures of alcohols and hydrocarbon fuels are present.

  Here, when alcohol or a mixture of alcohol and hydrocarbon fuel is present in the tank, hydrocarbon fuel, alcohol, or alcohol and hydrocarbon fuel are mixed in this tank. Regardless of which mixture is supplied, the supplied fuel mixes with the fuel inside the tank substantially uniformly and does not separate into two layers, so the fuel is detected twice in each sensitive region. There is nothing to do.

  Therefore, in the sensor circuit unit, the number of high-sensitivity regions immersed in the liquid in the tank is obtained based on the detected value of the change in capacitance, and the liquid level in the tank is obtained based on this number. it can.

On the other hand, when hydrocarbon fuel is present in the tank, if the tank is supplied with alcohols or a mixture of alcohols and hydrocarbon fuel, the supplied fuel is carbonized in the tank. It does not mix with the hydrogen-based fuel immediately and moves to the lower layer. If refueling of alcohols or a mixture of alcohols and hydrocarbon fuel is continued in this state, the hydrocarbon fuel layer in the tank is pushed upward by the newly refueled fuel.
Therefore, in the high sensitivity region of the liquid level detection sensor, after the layer of hydrocarbon fuel passes, the layer of alcohol or a mixture of alcohol and hydrocarbon fuel passes. In this case, the fuel is detected twice.

  However, in the liquid level measuring device, the amount of change in capacitance with respect to the amount of change in liquid level in the high sensitivity region is larger than the amount of change corresponding to hydrocarbon fuel, and the amount of change corresponding to alcohols. When the value is smaller than a predetermined threshold as a smaller value, the detection of the high sensitivity region is ignored. In other words, the detection of the high sensitivity region is not considered. In other words, the detection of the high sensitivity region is not counted. Therefore, in the high sensitivity region, detection of the hydrocarbon fuel layer is ignored, and only the liquid level of alcohols is detected.

According to the first aspect of the present invention, for example, when alcohol is supplied into a tank in which hydrocarbon fuel is present, detection of the hydrocarbon fuel layer in the high sensitivity region is ignored, and only alcohols are present. Detected.
Therefore, an accurate liquid level can be obtained even in such a case.

  In the second aspect of the present invention, in the high sensitivity region, the liquid level detection electrode is set to be longer than the other regions. Therefore, the liquid level detection electrode in the high sensitivity region and the other regions. Can be made the same interval. Therefore, it is advantageous when the interval between the liquid level detection electrodes cannot be reduced for some reason.

  In the third aspect of the present invention, in the high sensitivity region, the density of the liquid level detection electrodes is set higher than that in other regions, in other words, the interval between the liquid level detection electrodes is set to be small. The length of the liquid level detection electrode can be the same in other regions.

  According to the fourth aspect of the present invention, in a tank in which alcohols or a mixture of alcohols and hydrocarbon fuel is present, hydrocarbon fuel, alcohols, or alcohols and hydrocarbon fuel, It is possible to obtain an accurate liquid level not only when the mixture of the fuel is fed but also when the alcohol or the mixture of the alcohol and the hydrocarbon fuel is fed into the tank in which the hydrocarbon fuel is present. .

FIG. 1 is a cross-sectional view illustrating an overall configuration of a fuel tank including the liquid level measuring device according to the first embodiment. FIG. 2 is an enlarged view showing a sub-tank provided in the fuel tank of FIG. 1 and a configuration in the vicinity thereof. FIG. 3 is a perspective view illustrating a configuration of a liquid level detection sensor provided in the liquid level measurement device according to the first embodiment. 4 is a development view of the liquid level detection sensor shown in FIG. FIG. 5 is a development view illustrating a configuration of another example of the liquid level detection sensor provided in the liquid level measuring device according to the first embodiment. FIG. 6 is a block diagram illustrating a configuration of a sensor circuit unit included in the liquid level measurement device according to the first embodiment. FIG. 7A is a schematic diagram of a fuel tank provided with the liquid level detection sensor shown in FIG. 3 or FIG. 4, and FIG. 7B shows a case where gasoline is supplied to the fuel tank of FIG. 5 is a graph showing the relationship between the fuel level and the capacitance of the liquid level detection unit in the liquid level detection sensor when ethanol and ethanol are supplied. FIG. 8 is a graph showing the relationship between the capacitance ratio between the liquid level detection unit and the reference unit provided in the liquid level detection sensor and the liquid level. FIG. 9 (A) is a schematic view showing a state where gasoline is supplied to the fuel tank in a state where ethanol is present in the fuel tank shown in FIG. 7 (A), and FIG. FIG. 10 is a graph showing the relationship between the fuel level in the fuel tank of FIG. 9A and the capacitance of the liquid level detection unit in the liquid level detection sensor. FIG. 10 (A) is a schematic view showing a state where ethanol is supplied to the fuel tank in a state where gasoline is present in the fuel tank shown in FIG. 7 (A), and FIG. 11 is a graph showing the relationship between the fuel level in the fuel tank of FIG. 10A and the capacitance of the liquid level detection unit in the liquid level detection sensor. FIG. 11 is a flowchart illustrating an example of a liquid level measurement scheme in the sensor circuit unit included in the liquid level measurement device according to the first embodiment.

1. Embodiment 1
Hereinafter, an example of the liquid level measuring device of the present invention will be described in detail with reference to the drawings.
In FIG. 1 and subsequent figures, the arrow UP indicates the upper side of the vehicle body.

  The fuel tank 10 is a container having a substantially box shape as shown in FIG. 1, and its shape is determined by the shape of a vehicle body or the like to be installed and the component arrangement. The material of the fuel tank 10 is selected in consideration of resistance to corrosion by fuel (gasoline etc.), mechanical strength, impact resistance and safety in the event of a collision.

  An attachment port 22 for a pump module or the like is provided in the ceiling surface 30 that is the upper surface of the vehicle body of the fuel tank 10, and the internal fuel does not leak outside by a lid portion 28 that closes the attachment port 22 from the outside. So that it is sealed. The mounting port 22 protruding in a cylindrical shape above the vehicle is sealed with a lid portion 28.

  Inside the fuel tank 10 is provided a sub tank 31 which is a bottomed container having an open top surface, and a pump unit 32 is accommodated in the sub tank 31. The fuel inside the fuel tank 10 is pumped out by a pump unit 32 and sent out to the outside by a fuel hose (not shown).

  Hereinafter, the configuration of the liquid level measuring device 1 provided in the fuel tank 10 will be described. As shown in FIGS. 1 and 2, the liquid level measuring device 1 is connected to the sensor circuit unit 11 fixed to the upper surface of the lid unit 28, the sensor circuit unit 11, and from the bottom surface 20 of the fuel tank 10. And a liquid level detection sensor 12 extending toward the lower surface of the lid portion 28. The liquid level detection sensor 12 and the sensor circuit unit 11 are connected by a wire harness 21.

  The liquid level detection sensor 12 is a capacitance type liquid level detection sensor that detects the liquid level of the fuel in the fuel tank 10 by a change in capacitance. As shown in FIGS. A liquid level detection unit 13 for detecting the liquid level of the internal fuel, and a reference unit 14 formed substantially perpendicular to the liquid level detection unit 13 at the lower end of the liquid level detection unit 13. The liquid level detection unit 13 and the reference unit 14 are integrally formed. The liquid level detection unit 13 is formed in a strip shape, and as shown in FIG. 2, when the sub tank 31 is attached to the fuel tank 10, the reference unit 14 contacts the bottom surface 20 of the fuel tank 10. It is attached to the side.

  As shown in FIGS. 3 to 5, the liquid level detection unit 13 and the reference unit 14 include a base film 110 made of polyimide resin, aromatic polyamide resin, aromatic polyester resin, polyether ether ketone resin, polyether sulfone resin, or the like. In the liquid level detection unit 13, a liquid level detection electrode 15 for detecting the liquid level of the fuel in the fuel tank 10 is formed on the base film 110 based on a change in electrostatic capacity. It is formed on the film 110.

  Each of the liquid level detection electrode 15 and the reference electrode 16 is formed with a comb-shaped electrode 111A formed at regular intervals in the longitudinal direction of the base film 110, and at the same interval as the comb-shaped electrode 111A, and alternately with the comb-shaped electrode 111A. A comb-shaped electrode 111B. Each of the comb-shaped electrode 111 </ b> A and the comb-shaped electrode 111 </ b> B extends in the width direction of the base film 110. In both the liquid level detection electrode 15 and the reference electrode 16, the comb-shaped electrode 111A is connected in parallel by a common lead wire 112A. On the other hand, the comb-shaped electrode 111B is connected in parallel by the common lead wire 112B in the liquid level detection electrode 15 and by the common lead wire 112C in the reference electrode 16. At the upper ends of the common lead wire 112A, the common lead wire 112B, and the common lead wire 112C, a terminal 113A, a terminal 113B, and a terminal 113C for connecting to the sensor circuit unit 11 through the wire harness 21 are formed.

  As shown in FIGS. 3 to 5, the liquid level detection electrode 15 has a high sensitivity region 17 having a higher sensitivity than other regions, in other words, a high sensitivity region 17 having a large capacitance change with respect to a unit change amount of the liquid level. A plurality of locations are formed at regular intervals along the direction, in other words, the height direction of the fuel tank 10, in this embodiment, six locations. Note that the position and number of the high-sensitivity regions 17 may be set in accordance with the fuel remaining amount segment in the fuel gauge of the meter to which the liquid level detection sensor 12 is connected via the sensor circuit unit 11.

  As shown in FIG. 3 and FIG. 4, the high sensitivity region 17 has a larger dimension in the width direction of the liquid level detection electrode 15 than the region other than the high sensitivity region 17. It is formed by setting the length of the comb-shaped electrode 111B to be long. Alternatively, as shown in FIG. 5, the density of the comb-shaped electrode 111A and the comb-shaped electrode 111B is made higher than that of the region other than the high-sensitivity region 17, in other words, the interval between the comb-shaped electrode 111A and the comb-shaped electrode 111B is increased. The high-sensitivity region 17 can also be formed by setting the region smaller than the region other than 17.

  As shown in FIG. 6, the sensor circuit unit 11 is connected to the terminals 113 </ b> A, 113 </ b> B, and 113 </ b> C of the liquid level detection sensor 12 via the harness 21, and the liquid level detection unit 13 and the reference in the liquid level detection sensor 12. Based on the impedance measurement unit 11A that measures the impedance of the unit 14, a memory unit 11C that stores various data such as a liquid level determination map and a liquid level measurement pattern, which will be described later, and the impedance measured by the impedance measurement unit 11A The capacitances of the liquid level detection unit 13 and the reference unit 14 are obtained, and necessary data is called from the memory unit 11C, and the amount of fuel in the fuel tank 10 is calculated from the obtained capacitance and the data called from the memory unit 11C. A central processing unit 11B for determining the liquid level. The central processing unit 11B is also connected to a fuel gauge in an automobile meter so that the liquid level obtained by the central processing unit 11B is displayed on the fuel gauge.

  In both cases where gasoline is supplied to the empty fuel tank 10 and ethanol is supplied, the amount of change in the capacitance Ca of the liquid level detection unit 13 with respect to the change in the liquid level is different from that in the high sensitivity region 17. Larger than the area. And the high sensitivity area | region 17 is provided in the liquid level detection electrode 15 at equal intervals. Therefore, as shown in FIG. 7B, the change amount of the capacitance with respect to the change amount of the liquid level is larger in the high sensitivity region 17 than in the other regions in both cases of gasoline and ethanol. Therefore, the graph of the fuel level relative to the capacitance Ca of the liquid level detection unit 13 detected by the sensor circuit unit 11 is stepped in both cases of gasoline and ethanol.

  However, since the dielectric constant of gasoline is as large as 24 while the dielectric constant of ethanol is as large as 24, as shown in FIG. 7B, the capacitance of the liquid level detection unit 13 with respect to the change amount of the liquid level. The amount of change in Ca is greater in ethanol than in gasoline in both the high sensitivity region 17 and other regions. However, in the reference unit 14, the area in which the reference electrode 16 is immersed in the fuel is constant regardless of the type of fuel supplied to the fuel tank 10, so that the capacitance Cb of the reference unit 14 is the fuel. Proportional only to dielectric constant.

Therefore, if the fuel in the fuel tank 10 is uniform, the ratio of the capacitance Ca of the liquid level detection unit 13 to the capacitance Cb of the reference unit 14 (capacitance ratio Ca / Cb) is It is constant regardless of the type, and simply varies depending on the liquid level as shown in FIG. For this reason, the relationship between the capacitance ratio (Ca / Cb) and the liquid level is constant regardless of the type of fuel.
In addition, since the magnitude | size of the fluctuation | variation of the electrostatic capacitance ratio Ca / Cb with respect to a liquid level becomes larger than the other area | region in the high sensitivity area | region 17, as shown in FIG. 8, electrostatic capacitance ratio (Ca / Cb) The graph of the change in the liquid level with respect to is a stepped shape in which the fluctuation of the capacitance ratio Ca / Cb becomes larger in the high sensitivity region 17. In FIG. 7B and FIG. 8, the alternate long and two short dashes line indicates the position of the high sensitivity region 17 in the height direction.

  Therefore, the relationship of the liquid level to the capacitance ratio (Ca / Cb) shown in FIG. 8 is stored as a liquid level determination map in the memory unit 11C of the sensor circuit unit 11, and the fuel in the fuel tank 10 is only gasoline. In the case of ethanol only, or when the time after refueling has elapsed and gasoline and ethanol are mixed uniformly, measurement of the electrostatic capacity in the liquid level detection unit 13 and the reference unit 14 in the liquid level detection sensor 12 The capacitance ratio (Ca / Cb) is obtained from the result, and the liquid level can be obtained from the capacitance ratio (Ca / Cb) and the liquid level determination map of FIG. Further, the liquid level may be obtained from the number of high sensitivity regions 17 detected by the sensor circuit unit 11.

  On the other hand, when ethanol is present in the fuel tank 10 and gasoline having a specific gravity lower than that of ethanol is supplied, the gasoline and ethanol are not separated into two layers, as shown in FIG. And ethanol are mixed with each other. Therefore, as shown in FIG. 9B, there are five changes in the capacitance Ca corresponding to the high sensitivity region 17 from the start of gasoline supply until the fuel tank 10 becomes full.

  Therefore, it is possible to monitor the change in the capacitance Ca of the liquid level detection unit 13 and obtain the liquid level after refueling based on how many high-sensitivity regions 17 are detected. Hereinafter, this liquid level measurement pattern is referred to as a liquid level measurement pattern 1.

  In addition, when gasoline is supplied into ethanol, the gasoline and ethanol are in a state of being dispersed with each other. Therefore, it can be said that the fuel state in the fuel tank 10 is substantially uniform. Accordingly, the electrostatic capacity Cb of the reference unit 14 is also monitored in the liquid level measurement pattern 1, the electrostatic capacity ratio (Ca / Cb) is obtained from the monitoring result, and the obtained electrostatic capacity ratio (Ca / Cb) is calculated according to FIG. The liquid level may be obtained from the liquid level determination map.

  On the other hand, when gasoline is present inside the fuel tank 10, if ethanol having a higher specific gravity than gasoline is supplied, the gasoline and ethanol are not immediately mixed as shown in FIG. The two layers are separated, with ethanol as the lower layer and gasoline as the upper layer. As the ethanol is supplied, the gasoline layer is lifted by the ethanol layer and rises. Therefore, as shown in FIG. 10B, the change in the high sensitivity region 17 of the capacitance Ca of the liquid level detection unit 13 shows a pattern in which a change due to ethanol and a change due to gasoline appear alternately.

  However, since the dielectric constant of gasoline is much lower than that of ethanol, the amount of change in capacitance due to gasoline in the high sensitivity region 17 is smaller than the amount of change in dielectric constant due to ethanol.

  Therefore, a change amount of the capacitance Ca of the liquid level detection unit 13 in the high sensitivity region 17 is set to a threshold value that is smaller than the change amount due to ethanol and larger than the change amount due to gasoline. If the change in the capacitance Ca is not counted, and only the change in the capacitance Ca that is larger than the threshold is detected, the change in the capacitance Ca in the high sensitivity region 17 due to gasoline is ignored. In other words, since the change in the capacitance Ca of the high sensitivity region 17 due to gasoline is not counted, an accurate liquid level is required. Hereinafter, this liquid level measurement pattern is referred to as a liquid level measurement pattern 2.

  The memory unit 11C in the sensor circuit unit 11 stores a measurement procedure along the liquid level measurement pattern 1 and the liquid level measurement pattern 2 in addition to the liquid level determination map of FIG.

Hereinafter, a procedure for obtaining the liquid level in the sensor circuit unit 11 will be described.
In the central processing unit 11B, the fuel level in the fuel tank 10 is obtained according to the flowchart shown in FIG. As shown in the flowchart of FIG. 11, the central processing unit 11B determines whether or not the fuel supply lid is opened in step S2. The determination as to whether or not the fueling lid has been opened can be made, for example, by connecting or disconnecting a lid switch provided on the fueling lid.

  If it is determined in step S2 that the refueling lid has been opened, the sensor circuit unit 11 is activated in step S4, and the capacitance Ca of the liquid level detection unit 13 of the liquid level detection sensor 12 and the capacitance Cb of the reference unit 14 are monitored. To start.

  When the sensor circuit unit 11 is activated, it is determined in step S6 whether the fuel remaining in the fuel tank 10 is ethanol. The determination in step S6 can be made by determining whether the capacitance Cb of the reference unit 14 is a value corresponding to ethanol or a value corresponding to gasoline.

  If it is determined in step S6 that the fuel in the fuel tank 10 is ethanol, the liquid level measurement pattern 1 is called from the memory unit 11C as the liquid level measurement pattern in step S8, and is monitored by the sensor circuit unit 11. Based on the electrostatic capacitance Ca of the liquid level detection unit 13, it is detected whether the high sensitivity region 17 of the liquid level detection unit 13 is immersed in fuel. Alternatively, instead of calling the liquid level measurement pattern 1, the liquid level determination map of FIG. 8 may be called to obtain the liquid level from the capacitance ratio (Ca / Cb) and the liquid level determination map of FIG.

  On the other hand, when it is determined in step S6 that the fuel in the fuel tank 10 is gasoline, it is determined in step S10 whether or not the refueling fuel is ethanol. The determination in step S10 is, for example, when the electrostatic capacity Cb of the reference unit 14 has not changed from the value corresponding to gasoline after the start of refueling, it is determined that gasoline is being refueled, and the electrostatic capacity Cb of the reference unit 14 is When it rises to a value corresponding to ethanol, it can be determined by determining that ethanol is being supplied.

  If it is determined in step S10 that ethanol has been supplied, the process proceeds to step S12, the liquid level measurement pattern 2 is called from the memory unit 11C as the liquid level measurement pattern, and the liquid is measured along the liquid level measurement pattern 2. Ask for rank. On the other hand, if it is determined in step S10 that gasoline is being refueled, the flow returns to step S8 to start measuring the liquid level. In addition, in step 10, when the determination item that the mixed fuel of ethanol and gasoline is refueled is added and it is determined in step 10 that the mixed fuel of ethanol and gasoline is refueled, the fuel in the tank However, the fueling fuel may move to step S12 even when the ethanol concentration is higher.

  The liquid level measuring device 1 according to the first embodiment corresponds to the case where gasoline or ethanol is supplied to the fuel tank 10, but a combination of gasoline and methanol, propanol, or butanol, or a combination of light oil and ethanol. And combinations of light oil and methanol, propanol, or butanol.

  The liquid level measuring apparatus 1 according to the first embodiment includes hydrocarbons such as gasoline and light oil when fuel of the same type is supplied to the fuel tank 10 and in the fuel tank 10 in which alcohols such as ethanol, methanol, propanol, and butanol exist. An accurate liquid level is required not only when fuel is supplied, but also when alcohol is supplied to the fuel tank 10 where hydrocarbon fuel is present.

  Further, in the liquid level detection sensor 12, the liquid level detection electrode 15 formed in the liquid level detection unit 13 is formed with high sensitivity regions 17 at regular intervals, so that the same kind of fuel is supplied to the fuel tank 10. In this case, and in the case where hydrocarbon fuel such as gasoline or light oil is supplied to the fuel tank 10 in which alcohols such as ethanol, methanol, propanol, and butanol are present, the high sensitivity region 17 is formed in the liquid level detection electrode 15. Compared with the case where it is not performed, a more accurate liquid level can be calculated | required based on the detected number of the high sensitivity area | regions 17. FIG.

DESCRIPTION OF SYMBOLS 1 Liquid level measurement apparatus 10 Fuel tank 11 Sensor circuit part 11A Impedance measurement part 11B Central processing part 11C Memory part 12 Liquid level detection sensor 13 Liquid level detection part 14 Reference part 15 Liquid level detection electrode 16 Reference electrode 17 High sensitivity area 110 Base Film 111A Comb electrode 111B Comb electrode 112A Common lead wire 112B Common lead wire 112C Common lead wire 113A terminal 113B terminal 113C terminal

Claims (4)

It is arranged from the bottom surface of the tank toward the upper surface of the tank, and the amount of change in capacitance with respect to the amount of change in liquid level in the tank is higher than that in other regions. A liquid level detection sensor in which a plurality of regions are formed at regular intervals along the height direction of the tank,
The amount of change in capacitance in the liquid level detection sensor is detected, and based on the detected amount of change in capacitance, the number of high-sensitivity regions immersed in the liquid in the tank is obtained. When the liquid level in the tank is determined and the amount of change in capacitance with respect to the amount of change in the liquid level in the high sensitivity region of the liquid level detection sensor is equal to or less than a predetermined threshold, the high sensitivity region A sensor circuit unit that determines the liquid level ignoring detection of
A liquid level measuring device. The liquid level detection sensor includes a group of liquid level detection electrodes that extend in the width direction of the liquid level detection sensor and are arranged at regular intervals along the longitudinal direction of the liquid level detection sensor.
2. The liquid level measurement device according to claim 1, wherein in the high sensitivity region, a length of the liquid level detection electrode is set longer than a region other than the high sensitivity region in the liquid level detection sensor. The liquid level detection sensor has a group of liquid level detection electrodes extending in the width direction of the liquid level detection sensor and arranged along the longitudinal direction of the liquid level detection sensor,
2. The liquid level measurement device according to claim 1, wherein in the high sensitivity region, the density of the liquid level detection electrode is set larger than that of a region other than the high sensitivity region in the liquid level detection sensor. The tank is supplied with either hydrocarbon fuel, alcohol, or a mixture of alcohol and hydrocarbon fuel,
In the case where hydrocarbon fuel is present in the tank and alcohol or a mixture of alcohol and hydrocarbon fuel is supplied to the tank, the sensor circuit unit is configured to detect the liquid level in the high sensitivity region. When the amount of change in capacitance with respect to the amount of change is greater than the amount of change corresponding to the hydrocarbon-based fuel and smaller than the amount of change corresponding to the alcohols, the value is less than a predetermined threshold value. The liquid level measuring device according to claim 1, wherein the liquid level is obtained by ignoring the detected capacitance value in the sensitivity region.

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