JP5835631B2 - Foreign matter detection device - Google Patents

Description

The present invention relates to a fueling device used in a filling station that supplies fuel oil (oil) to a vehicle or the like. More specifically, the present invention relates to a technique for detecting that foreign matters such as water are mixed in fuel oil in such a fueling device.

In a gas station, fuel oil such as gasoline stored in an underground tank of the gas station is supplied to a vehicle or the like by a fueling device.
Water may enter the fuel oil due to external factors such as damage to underground tanks, human factors such as erroneous operations, and factors such as accidents and natural disasters. If water is mixed into the fuel oil due to various factors like this, gasoline containing water will be supplied to the vehicle, causing the engine to be unable to start, and causing knocking due to poor combustion, In the worst case, there is a problem that the engine is damaged due to frequent knocking.

In order to cope with such a problem, it is conceivable to detect the property of the liquid by utilizing the property that the capacitance is different for each type of liquid.
Here, the capacitance C is C = (ε0 · εs · S) / d (where S is the area of the electrode, ε0 is the dielectric constant of the vacuum, εs is the dielectric constant of the dielectric, and d is the distance between the electrodes) It can be obtained by the following formula.
Since the influence of the disturbance can be reduced as the electrostatic capacitance C is larger, it is effective for detecting the property of the liquid.

In order to measure the capacitance and detect whether water or other foreign matter is mixed in the fuel oil, a pair of plate-like electrodes are placed in parallel to the fuel oil flow in the fuel oil supply system. It is necessary to dispose the fuel oil between the pair of plate electrodes. As described above, the larger the capacitance of the pair of plate electrodes, the better.
However, when the area of the plate electrode is increased, it is difficult to install the fuel electrode in the fuel oil supply system (supplying equipment such as piping and pump units) in the fueling device.
Further, if the interval between the plate electrodes is reduced, the fluid resistance in the region between the pair of plate electrodes is increased, and dust and other foreign matters are liable to stay, which is disadvantageous.

As another conventional technique, a technique has been proposed in which a voltage corresponding to the relative dielectric constant of alcohol-mixed gasoline is detected to detect a change in gasoline properties (see, for example, Patent Document 1).
However, in the related art, a metal box-shaped casing is necessary, and a space for installing the casing must be secured, and it is difficult to install the casing inside the fuel oil supply system in the fueling device. is there.

Japanese Patent Laid-Open No. 5-288707

The present invention has been proposed in view of the above-described problems of the prior art, and can be installed inside a fuel oil supply system to detect that foreign matters such as water are mixed in the fuel oil. The purpose is to provide a refueling device that can be used.

According to the present invention, in the foreign matter contamination detection device of the fueling device provided with the capacitance type water detection sensor (10C) in the pipe, the annular frame (11C) and the pair of conduction types not covering the insulating material And a pair of insulation-type mesh electrodes (12B) coated with an insulating material, and the annular frame (11C) has two convex shapes inwardly of the ring in its cross section. The conductive mesh electrode (12) has projections (11x, 11y), and is attached so as to sandwich the side surface of one convex projection (11x), and the insulating mesh electrode (12B) A conductive mesh electrode (12) and an insulating mesh electrode (12B) are mounted so as to sandwich the side surface of the convex protrusion (11y) and are sandwiched by these two convex protrusions (11x, 11y). ) Is insulated from the conductive mesh electrode (12). The reticulated electrode (12B) and the insulated reticulated electrode (12B) are connected to the capacitance calculating device (13). The electrostatic capacity calculation device (13) measures the electrostatic capacity with the conductive mesh electrode (12) (S1), and measures the electrostatic capacity with the insulating mesh electrode (12B) (S2). ), It is determined whether or not both measured capacitances have the same characteristics (S3). If the characteristics are similar, it is determined that water is not mixed (S4). If the characteristics are not similar, water is mixed. (S5) is provided.

In the practice of the present invention, it is preferable that the mesh electrodes (12, 12B, 12C) include not only a so-called “mesh” but also a shape having a large number of common holes.

According to the present invention having the above-described configuration, since the capacitance type water detection sensor (10C) is provided in the pipe (3, 5, 8), water (or other foreign matter) is contained in the fuel oil. Can be detected immediately by a change in capacitance or dielectric constant.
For this reason, it is possible to prevent the gasoline containing water from being supplied to the vehicle, and to prevent the engine from starting, the occurrence of knocking due to poor combustion, and the engine from being damaged.

Even if the interval between the mesh electrodes (12, 12B, 12C) is narrowed, the resistance does not increase, and the influence of noise can be reduced by increasing the capacitance.
Accordingly, the mesh electrode (12) can be easily arranged in the fuel supply system.

Here, since the mesh electrode (one or both) is insulated (12B) (if two mesh electrodes having different characteristics are used), a short circuit current (leakage current) is generated via the fuel oil flowing between the electrodes. By preventing the flow of current and cutting the leakage current, only the change in capacitance can be reliably detected with high accuracy.
And it is also prevented that the sensitivity of the sensor (10C) increases too much due to the leakage current.

It is explanatory drawing which shows the oil supply apparatus which implements this invention. It is a side view which shows the sensor which comprises the principal part of a 1st reference example. It is a perspective view of the sensor of FIG. FIG. 3 is an enlarged sectional view of a part of FIG. 2. It is a conceptual diagram which shows the general capacitor | condenser using a plate-shaped electrode. It is explanatory drawing for demonstrating the inconvenience of the capacitor | condenser of FIG. It is a conceptual diagram of the sensor of FIG. It is explanatory drawing for demonstrating the merit of the sensor of FIG. It is a characteristic view which shows an example of the relationship between the hydrolysis rate to ethanol, and an electrostatic capacitance. It is a side view which shows the sensor which comprises the principal part of the 2nd reference example of this invention. It is a conceptual diagram explaining the leakage current of the sensor used by the 1st reference example. It is a conceptual diagram explaining the effect | action of the sensor of a 2nd reference example. It is explanatory drawing which shows the influence of the frequency of an electric current, and leakage current with a chart. It is a side view which shows the sensor which comprises the principal part of 1st Embodiment of this invention. It is a characteristic view explaining the principle of water detection of the sensor of FIG. It is explanatory drawing which shows the principle of FIG. 15 as a flowchart. It is a side view which shows the sensor which comprises the principal part of 2nd Embodiment of this invention. It is a characteristic view which shows the relationship between the ratio of the ethanol included in gasoline, and an electrostatic capacitance. It is explanatory drawing which shows the state which applied embodiment of illustration to lorry piping.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, to better understand the present invention, a first reference example shown in FIGS.
FIG. 1 shows an outline of a fueling device to which the first reference example is applied.
In FIG. 1, an oil supply apparatus denoted by reference numeral 100 as a whole is a unit 3 (an oil supply unit 3) comprising an underground tank 1, an oil supply mechanism 2, an oil supply pump, and a flow meter buried underground in a gas station (gasoline station or the like). ), Underground buried pipe 4, oil supply mechanism internal pipe 5, oil supply hose 6, and oil supply nozzle 7.

The oil supply unit 3 and the oil supply mechanism internal pipe 5 are provided in the oil supply mechanism 2, and the underground buried pipe 4 connects the underground tank 1 and the oil supply unit 3.
The oil supply mechanism internal pipe 5 connects the oil supply unit 3 and the oil supply hose 6. An oil supply nozzle 7 is provided at the tip of the oil supply hose 6.
Although not clearly shown, the oil supply nozzle 7 is locked to a nozzle hook (not shown) provided on the outer peripheral panel of the oil supply mechanism 2.
The foreign matter contamination detection apparatus (hereinafter referred to as “sensor”) 10 of the first reference example is schematically shown in FIG. In FIG. 1, the sensor 10 (see FIG. 2) is interposed in any of the underground buried pipe 4, the oil supply unit 3, and the oil supply mechanism internal pipe 5.
And the sensor 10 can detect that water mixes by the change of an electrostatic capacitance. This is because the dielectric constant of fuel oil and water is greatly different, and the capacitance changes greatly even if a small amount of water is mixed into the fuel oil.

Here, since the dielectric constant of the fuel oil mixed with foreign matter is the sum of the dielectric constant of the fuel oil and the dielectric constant of the foreign matter, the presence or absence of foreign matter can be accurately detected even if the fuel oil and the foreign matter are not evenly mixed. Can be detected.
Therefore, the fuel oil is located in the underground tank 1 side of the rotating body (not shown) in the pump of the refueling unit 3, in other words, in the underground tank 1 side of the area where the fuel oil is uniformly mixed by the rotating body. Even in such a case, when foreign matter (water in the illustrated reference example) is mixed into the fuel oil, the fact and the mixing rate can be accurately determined.

The sensor 10 of the first reference example will be described with reference to FIGS.
2 to 4, the sensor 10 includes an annular frame 11, a pair of mesh electrodes 12, a capacitance calculation device 13, and a pair of cables 14. The edge of the mesh electrode 12 is supported by a frame 11 for making the interval constant. Although not shown, a spacer for making the interval constant may be disposed between the mesh electrodes 12 and 12.
As shown in FIG. 4, the cross-sectional shape of the annular frame 11 is convex, and the convex protrusion 11t faces inward in the radial direction (of the ring).
The pair of mesh electrodes 12 are disposed in contact with both side portions 11 s and the step portions 11 a of the projecting protrusion portion 11 t of the frame body 11.
Here, the term “mesh” is used to include not only a shape having a so-called “mesh” but also a shape having a large number of through holes.

If the area of the mesh electrode 12 is S, the dielectric constant of vacuum is ε0, the dielectric constant of the dielectric (mesh electrode 12) is εs, and the distance between the electrodes is d,
The capacitance C is obtained by the following formula: C = (ε0 · εs · S) / d
Here, since the influence of disturbance can be reduced as the capacitance C increases, it is effective for detecting the properties of the liquid.
The upper limit of the diameter D of the frame 11 in the sensor 10 is determined by the inner diameter of the underground buried pipe 4 if the installation location is, for example, in the underground buried pipe 4 (see FIG. 1). Therefore, in order to obtain a large capacitance C in the pair of mesh electrodes 12, the distance d between the pair of mesh electrodes 12 may be set small.
2 to 4, even if the distance d between the mesh electrodes 12 is set to be small, the fuel oil easily meshes with the mesh electrode 11 because the electrodes are mesh. Can pass through the eyes. Therefore, with the mesh electrode 12 of FIGS. 2 to 4, the passage resistance when the fuel oil as the detection target passes through the electrode 12 does not increase.

FIG. 5 shows a capacitor 10J having a general configuration constituted by a plate-shaped electrode (plate electrode) 12P without using the mesh electrode 12 of FIGS. In the general capacitor 10J in FIG. 5, electrification accumulates between the electrodes 12P, and an electric field is formed.
Here, when the capacitor 10J using the general plate electrode 12P as shown in FIG. 5 is arranged in the fuel oil supply pipe, as shown in FIG. It must be arranged in parallel to the streamline F in the supply pipe. This is because if the plate electrode 12P is arranged in a direction orthogonal to the flow line F of the fuel oil supply pipe, the plate electrode 12P blocks the flow of the fuel oil.

As described above, in the capacitor 10J, the influence of the disturbance can be reduced as the capacitance increases, which is effective for detecting the property of the liquid from the capacitance.
However, if the area of the plate-like electrode 12P of the capacitor 10J is increased, it becomes difficult to install the capacitor J inside the fuel oil supply system (supplying equipment such as a pipe and a pump unit) in the fueling device.
On the other hand, if the distance d between the plate-like electrodes 12P is reduced, the fluid resistance in the region between the pair of plate-like electrodes 12P is increased, and dust and other foreign matters are liable to stay.

Here, since the capacitance C between the electrodes 12 is determined by the atmosphere of the electric field, as shown in FIG. 7, even if the electrodes 12 are configured by a net, charges similar to those of the plate-like electrodes are stored. The That is, if it is the sensor 10 of the 1st reference example shown in FIGS. 2-4, the electrostatic capacitance similar to the capacitor | condenser 10J using the conventional plate-shaped electrode 12P will be obtained.
In addition, in the case of the sensor 10 of the first reference example shown in FIGS. 2 to 4, as shown in FIG. 8, even if the mesh electrode 12 is arranged in a direction orthogonal to the flow line F of the fuel oil in the supply pipe, Since the fuel oil can easily pass through the “mesh” (or a large number of through holes) of the mesh electrode 12, the sensor 10 of FIGS. Even if it is arranged in a direction perpendicular to the direction, it does not hinder the flow of fuel oil.
Furthermore, since the fuel oil can pass through the “mesh” (or a large number of through holes) of the mesh electrode 12 without resistance, the fuel oil can be obtained even if the distance d between the pair of mesh electrodes 12 is narrowed. The flow resistance does not increase. In other words, with the sensor 10 of the first reference example shown in FIGS. 2 to 4, the gap between the pair of mesh electrodes is reduced without increasing the resistance of the flow of fuel oil, and the electrostatic capacitance between the electrodes. The capacity can be increased.
Accordingly, in the sensor 10 according to the first reference example shown in FIGS. 2 to 4, the electrostatic capacity is increased to reduce the influence of the disturbance, and the dielectric of the fuel oil is prevented without obstructing the flow of the fuel oil. The rate can be detected accurately and effectively.

FIG. 9 is a characteristic diagram showing the relationship between the hydrolysis ratio to ethanol and the capacitance.
As shown in FIG. 9, it is possible to effectively detect that water is mixed in the first reference example for alcohol products such as ethanol.
As in the case of gasoline (dielectric constant of about 2) and water (dielectric constant 80), the dielectric constants of ethanol (dielectric constant around 20) and water (dielectric constant 80) are also very different. This is because the capacitance also changes greatly.

In FIG. 15, which shows the relationship between the water addition rate to ethanol and the capacitance, the increase in capacitance is notable until the water addition rate to ethanol becomes 0.5 or more.
However, even if the amount of water added (hydrolysis ratio) is 0.5 mol or less, if the sensitivity of the sensor (sensitivity for detecting the difference in capacitance) is increased, that water is mixed in ethanol and its It is possible to detect the mixing rate (hydrolysis rate).

Next, a second reference example will be described with reference to FIGS.
FIG. 10 shows a sensor 10B used in the second reference example.
In the sensor 10 of the first reference example shown in FIGS. 2 to 4, the mesh electrode 12 is made of a metal mesh member. On the other hand, in the sensor 10B used in the second reference example, although not clearly shown in FIG. 10, a metal mesh member constituting the mesh electrode 12B is covered with an insulating material.

The reason why the mesh electrode 12B is covered with an insulating material in the sensor 10B will be described with reference to FIGS.
Water has a property of becoming a conductor when impurities are mixed therein. Generally, the capacitance is measured by passing a current through water mixed with impurities and measuring the time during which the voltage between terminals rises (or falls). In this case (water becomes a conductor due to impurities), a short-circuit current flows between the electrodes, and the time until electrification is accumulated becomes longer, and it seems as if the capacitance has increased.
FIG. 11A schematically shows a state where no conductor exists between the electrodes 12 and no short-circuit current flows. The capacitance is measured by passing a current between the electrodes 12 in the state of FIG. 11A and measuring the time during which the voltage between the terminals rises (falls).

Here, fuel oil (including fuel oil mixed with water) is a conductor.
When there is a conductive liquid between the pair of electrodes 12, the electrodes 12 are short-circuited by the fuel oil, that is, the conductive liquid, and a short-circuit current (leakage current) flows as shown in FIG.
When the short-circuit current flows, the apparent capacitance increases (it appears as if the capacitance has increased). In other words, when the short-circuit current flows, the apparent change amount of the capacitance becomes larger than the change amount of the capacitance between the electrodes.
And since the amount of change in the apparent capacitance increases, the change in capacitance when water is mixed into the fuel oil also increases, and the sensitivity as a sensor increases.

However, there is a possibility that erroneous detection occurs due to an increase in sensitivity of the sensor. For example, even if the sensitivity of the sensor is increased and a change in capacitance is detected, the change in capacitance is “a change in capacitance due to the mixing of water?” It is impossible to distinguish between “changes” and “changes in capacitance due to other factors”. As a result, although it is “a change in capacitance due to a temperature change”, a situation may be erroneously determined as “a change in capacitance due to mixing of water”.
On the other hand, if the mesh electrode 12B is covered with an insulator and the leakage current due to the conductivity of the fuel oil is cut off and the state shown in FIG. 12 is obtained, no leakage current flows between the mesh electrodes 12B. The amount of change in apparent capacitance does not become too large. Therefore, the sensitivity of the sensor does not become too good, and the above-described erroneous detection is prevented.
For this reason, in the sensor 10B of FIG. 10, the mesh electrode 12B is covered with an insulator.

Although not explicitly shown, in the sensor 10B of FIG. 10, both of the pair of mesh electrodes 12B may be covered with an insulating material, or only one of the mesh electrodes 12B may be covered with an insulating material. .
This is because even if both of the pair of mesh electrodes 12B are covered with an insulating material or only one of the mesh electrodes 12B is covered with an insulating material, no leakage current flows between the mesh electrodes 12B.

Other configurations and operational effects of the second reference example of FIGS. 10 to 13 are the same as those of the first reference example of FIGS.

Next, with reference to FIG. 13, the cycle of charging and discharging between a pair of electrodes will be described.
In the illustrated embodiment (reference example of FIGS. 10 to 12, embodiment described later in FIG. 14 and later), the measurement frequency of the water and foreign matter detection circuit in the sensor is increased (charging and discharging between a pair of electrodes). By shortening the cycle, the leakage current can be reduced and the influence of the leakage current can be reduced.

The current is proportional to the voltage, and there is no difference in the ratio between the accumulated current and the leakage current between the pair of electrodes even if the charging and discharging cycles vary.
However, as shown in FIG. 13, if the measurement frequency of the detection circuit is increased, the time during which the leakage current flows is shortened, so the total amount of leakage current is reduced (FIG. 13B), and conversely the measurement of the detection circuit. If the frequency is slowed down, the amount of leakage current increases because the time during which the leakage current flows becomes longer (FIG. 13A).
There is an appropriate discharge and charge cycle (measurement frequency of the contamination detection circuit) corresponding to the detection target (type of fuel oil and type of foreign matter) and the purpose of detection, so the appropriate cycle (frequency) is the case.・ By determining on a case-by-case basis, the detection can be performed with higher accuracy and meeting the purpose.
13A and 13B, “leakage” means leakage current, “charging” means charging current between electrodes, and “discharge” means discharging current from between electrodes.

Next, a first embodiment of the present invention will be described with reference to FIGS.
14, the sensor according to the first embodiment generally indicated by reference numeral 10 </ b> C includes the sensor 10 of the first reference example (not coated with an insulating material: “conduction type”) illustrated in FIGS. 2 to 4, and FIG. 10. The sensor 10B of the second reference example (covered with an insulating material: “insulating type”) shown in FIG.
In FIG. 14, a sensor 10 </ b> C includes an annular frame 11 </ b> C, a pair of mesh electrodes (conductive network electrodes) 12 that do not cover an insulating material, and a pair of mesh electrodes (insulated network electrodes) that cover an insulating material. ) 12B is provided. Note that the conductive mesh electrode 12, the insulating mesh electrode 12 </ b> B, and the electrostatic capacity calculation device (not shown) are connected by a pair of cables (not shown).

The annular frame 11C has two convex protrusions 11x and 11y inward of the ring in its cross section.
A pair of conductive net electrodes 12 that do not cover the insulating material are attached so as to sandwich the side surface of one convex protrusion 11x (left convex protrusion in FIG. 14). On the other hand, the pair of insulating mesh electrodes 12B covered with an insulating material are attached so as to sandwich the side surface of the other convex protrusion 11y (right convex protrusion in FIG. 14).
The mesh electrode 12 and the mesh electrode 12B located between the two convex protrusions 11x and 11y are arranged with a gap δ at a predetermined interval. The gap δ is a distance that is not affected by the electric field of the mesh electrodes 12 and 12B.
The sensor 10C of the first embodiment is configured such that water detection can be performed quantitatively by combining a conductive mesh electrode and an insulating mesh electrode and using both in parallel.

The measurement principle of water mixing by the sensor 10C of FIG. 14 will be described with reference to FIG.
In FIG. 15, the solid line indicates the capacitance between the pair of conductive mesh electrodes 12 that do not cover the insulating material, and the dotted line indicates the capacitance between the pair of insulating mesh electrodes 12B that cover the insulating material. Yes. The solid and dotted lines in FIG. 15 are virtual representations of examples of capacitance fluctuations.
Here, the capacitance and dielectric constant of the fuel oil vary depending on the difference between gasoline manufacturers and the temperature at the time of measurement. The capacitance between the pair of conductive mesh electrodes 12 that do not cover the insulating material and the capacitance between the pair of insulating mesh electrodes 12B that cover the insulating material are measured at the time of measurement for each gasoline manufacturer. A similar behavior is exhibited at each temperature. The range of the display of “temperature fluctuation” in FIG. 15 is that the capacitance between the pair of conduction type mesh electrodes 12 and the capacitance between the pair of insulation type mesh electrodes 12B (solid line and dotted line in FIG. 15) are: Gasoline manufacturers display the same behavior even if the measured temperature is different.
Similarly, when the oil type changes due to unloading or the like, the capacitance between the pair of conductive mesh electrodes 12 that do not cover the insulating material and the pair of insulating mesh electrodes 12B that cover the insulating material The capacitance of shows similar behavior.

The range of display of “change in oil type due to unloading” in FIG. 15 is the capacitance between the pair of conductive mesh electrodes 12 and the capacitance between the pair of insulated mesh electrodes 12B (the solid line and the solid line in FIG. 15). The dotted line) indicates that the same behavior is exhibited even when the oil type changes due to unloading or the like.
The region on the right side of the wording “water detection” in FIG. 15 shows the change in capacitance when water is mixed.
As for the capacitance when water is mixed, the capacitance between the pair of conductive mesh electrodes 12 is larger than the capacitance between the pair of insulated mesh electrodes 12B coated with an insulating material. There is a tendency to change significantly. For this reason, if a combination of the conduction type and the insulation type is used in parallel and the case where the characteristics of the capacitance are different is detected, it is possible to reliably detect with high accuracy that water has been mixed into the fuel oil.
When detecting the case where water is mixed in the alcohol fuel, the alcohol is hydrophilic and the dielectric constant of the alcohol itself is large, so that the influence of fluctuation due to water is small. Therefore, a sensor that detects the capacitance between the conductive mesh electrodes 12 that reacts sensitively (a large change in capacitance) is suitable.

The detection described with reference to FIG. 15 will be described with reference to FIG.
In step S1 of FIG. 16, the capacitance is measured by the conductive mesh electrode 12 of the sensor 10C. In the next step S2, the capacitance is measured by the insulated mesh electrode 12B of the sensor 10C. Here, the order of step S1 and step S2 can be switched, and step S1 and step S2 can be performed simultaneously.
Proceeding to step S3, the electrostatic capacity calculation device 13 (see FIG. 2) determines that the electrostatic capacity measured with the conductive mesh electrode 12 and the electrostatic capacity measured with the insulated mesh electrode have similar characteristics (behavior). ) Or not.
If the capacitance measured with the conductive mesh electrode 12 and the capacitance measured with the insulated mesh electrode have similar characteristics (YES in step S3), “no water mixed” in step S4. to decide. On the other hand, if the electrostatic capacity measured with the conductive mesh electrode 12 and the electrostatic capacity measured with the insulated mesh electrode are not the same characteristic (NO in step S3), “water is mixed in” in step S4. It is judged.

Other configurations and operational effects in the first embodiment of FIGS. 14 to 16 are the same as those of the reference example of FIGS.

Next, a second embodiment will be described with reference to FIG.
In FIG. 17, the sensor denoted as a whole by 10D includes an annular frame 11D, a conductive mesh electrode 12 that does not cover the insulating material, and an insulating mesh electrode that covers the insulating material. 12B and one conductive mesh electrode 12C are provided. The mesh electrode 12C is disposed between the conductive mesh electrode 12 and the insulating mesh electrode 12B.
The mesh electrodes 12, 12C, 12B are connected to a capacitance calculation device (not shown) via cables L1, L2, L2, respectively.
In FIG. 17, the symbol α between the cables L1 and L2 means that the capacitance between the conductive mesh electrodes 12 and 12C is measured. On the other hand, the symbol β between the cables L2 and L3 means that the capacitance between the conductive mesh electrode 12C and the insulated mesh electrode 12B is measured.

The annular frame 11D has two convex protrusions 11u and 11v inward of the circular ring in its cross section.
A conductive mesh electrode 12C (shared electrode) is disposed in the groove portion 11g sandwiched between the two convex protrusions 11u and 11v.
On the side portions of the two convex protrusions 11u and 11v that are spaced apart from each other, there are a conductive mesh electrode 12 (left electrode in FIG. 17) and an insulating mesh electrode 12B (right electrode in FIG. 17). Has been placed.

As described above, the sensor 10D of the second embodiment shown in FIG. 17 includes the capacitance (α) between the conductive mesh electrodes 12 and 12C, and between the conductive mesh electrode 12C and the insulating mesh electrode 12B. Capacitance (β) can be measured simultaneously.
Here, the reason why the central shared electrode 12B is not coated with an insulating material is that if the shared electrode 12B is coated with an insulating material, the capacitance between the conductive electrodes cannot be measured. This is because, as described above with reference to the sensor 10B of FIG. 16, the capacitance between the insulating electrodes may be any one of the pair of electrodes insulated.

Other configurations and operational effects of the second embodiment of FIG. 17 are the same as those of the first embodiment of FIGS.

FIG. 18 shows the relationship between the ratio of gasoline to alcohol (ethanol ratio) and the capacitance in alcohol fuel.
Alcohol-mixed gasoline, which is a mixed fuel, is known. As the alcohol mixed gasoline, for example, E3 (containing 3% ethanol), E5 (containing 5% ethanol), E10 (containing 10% ethanol), and the like are used. In addition, E23 (containing 23% ethanol), E85 (containing 85% ethanol), and the like are also used overseas.
Since gasoline and ethanol have different dielectric constants by an order of magnitude, the ethanol ratio can be calculated by applying the illustrated embodiment. As a result, a situation (so-called “contamination”) in which different types of fuel are erroneously mixed can be prevented.

The electrostatic capacity due to the difference in the ratio of ethanol contained in regular gasoline has a proportional relationship as shown in FIG. Therefore, the ethanol ratio (%) contained in the regular gasoline can be known by measuring the capacitance.
However, since the capacitance has temperature dependence, it is necessary to correct it together with the temperature sensor in order to know the absolute value (ethanol ratio).
In FIG. 18, the solid line is a capacitance in which the arrangement of the pair of mesh electrodes in the sensor is arranged in parallel to the direction of fuel flow, and the broken line is the capacitance in the direction of the fuel flow. In contrast, the capacitance is arranged in series.

FIG. 19 shows a state in which the illustrated embodiment is applied to unloading.
In FIG. 19, a fuel oil discharge hose (lorry hose) RH of a tank lorry that is a fuel oil carrying means is indicated by a two-dot chain line.
Here, since the end portion RHe on the underground tank 1 side of the lorry hose RH is at a position lower than the tank side end portion (not shown) of the tank lorry (not shown), the refueling is finished, and the tank lorry is discharged. When the outlet valve (not shown) is closed, the fuel oil in the lorry hose RH is discharged to the underground tank 1 side by its own weight.
The inside of the pipe 8 connecting the underground hose 1 to the below-described tanker hose RH from which the fuel oil has been discharged and the tanker hose connecting part 9 is filled with air.

In FIG. 19, a sensor (not shown in FIG. 19) according to the illustrated embodiment is connected to a lorry hose RH and a lorry hose connecting part 9 on the underground tank side or a pipe 8 connecting the lorry hose connecting part 9 and the underground tank 1. It is disguised.
Since the sensor according to the illustrated embodiment is interposed in the lorry hose RH and the lorry hose connecting part 9 on the underground tank side, or the pipe 8 connecting the lorry hose connecting part 9 and the underground tank 1, the lorry hose RH is connected to the pipe 8. If the fuel oil stays in this area, the capacitance detected by the sensor according to the illustrated embodiment is a numerical value different from the capacitance in the air.
On the other hand, when fuel oil does not remain in the pipe 8 from the low hose RH, the pipe is filled with air, and the capacitance detected by the sensor according to the illustrated embodiment is The value is equivalent to the capacitance in air.

As a result, it is possible to detect whether or not oil remains in the lorry piping based on the capacitance detected by the sensor according to the illustrated embodiment.
If the electrostatic capacity detected by the sensor according to the illustrated embodiment is a numerical value different from the electrostatic capacity in the air, the fuel oil stays in the region from the lorry hose RH to the pipe 8 and unloading is performed. It turns out that it has not finished.
On the other hand, if the capacitance detected by the sensor according to the illustrated embodiment is a numerical value equivalent to the capacitance in the air, no fuel oil remains in the region from the lorry hose RH to the pipe 8. It becomes clear that unloading has been completed.

It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Underground tank 2 ... Oil supply mechanism 3 ... Oil supply unit 4 ... Underground piping 5 ... Oil supply mechanism internal pipe 6 ... Oil supply hose 7 ... Oil supply nozzle 10, 10B, 10C, 10D ... Water detection sensors 11, 11C, 11D ... Frame bodies 12, 12B, 12C ... Mesh electrode 13 ... Capacitance calculation device

Claims (1)

In the foreign matter contamination detection device of the oil supply device provided with a capacitance type water detection sensor (10C) in the pipe, an annular frame (11C) and a pair of conductive net electrodes (12) not covering the insulating material And a pair of insulating mesh electrodes (12B) coated with an insulating material, and the annular frame (11C) has two convex protrusions (11x, 11y) inwardly of the ring in its cross section. The conductive mesh electrode (12) is attached so as to sandwich the side surface of one convex protrusion (11x), and the insulating mesh electrode (12B) is attached to the other convex protrusion (11y). The gap (δ between the conductive mesh electrode (12) and the insulating mesh electrode (12B) at the position sandwiched between the two convex protrusions (11x, 11y) is attached. ) Is a conductive mesh electrode (12) and an insulating mesh electrode (1). B) is not affected by the electric field, and the conductive mesh electrode (12) and the insulated mesh electrode (12B) are connected to a capacitance calculation device (13). In the capacitance calculation device (13), the capacitance is measured with the conductive mesh electrode (12) (S1), the capacitance is measured with the insulation mesh electrode (12B) (S2), and both measured It is determined whether or not the capacitance is the same characteristic (S3). If the characteristic is the same, it is determined that water is not mixed (S4). If the characteristic is not the same, it is determined that water is mixed. (S5) A foreign matter contamination detection device for a fueling device having a function.

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