JPH0949814A - Device and method for discriminating kind of fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive gas oil discriminating device which can stably and accurately discriminate gas oil from gasoline. SOLUTION: When a switching section 203 is operated, either the vapor of gasoline or gas oil is made to flow to a sensor cell section 202 from a fuel tank 208. The output S1 of a thermal conductivity gas sensor 1 and the output S2 of a metal oxide semiconductor gas sensor 2 are outputted to a gas discriminating section 204 and a sensor sensitivity adjusting section 205 from the sensor cell section 202. The gas discriminating section 204 binarizes the outputs S1 and S2 based on a threshold read out from a memory 206 and discriminates the kind of the vapor based on the binarized data. The sensor sensitivity adjusting section 205 decides new thresholds in accordance with the deterioration of the sensors 1 and 2 based on the outputs S1 and S2 and stores the new thresholds in the memory 206.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil type discriminating apparatus for discriminating whether a test gas is a vapor of gasoline or a vapor of light oil by using a heat conduction type gas sensor and a metal oxide semiconductor type gas sensor. Regarding the method.

[0002]

2. Description of the Related Art In recent years, at gas stations and the like, a multifunctional fuel dispenser capable of refueling both gasoline for gasoline cars and light oil for diesel cars by one unit has been used. When using such a refueling machine, it is necessary to avoid the situation of refueling gasoline and light oil by mistake. As a measure to avoid such a situation, the vapor in the fuel tank of the vehicle for refueling is sucked into the oil type identification device as the test gas, and in the oil type identification device, the test gas is gasoline vapor or diesel oil. It identifies if it is steam. In the conventional oil type identification device, ultrasonic waves are applied to the gas to be inspected, and whether the gas to be inspected is vapor of gasoline or vapor of light oil is discriminated from the reflected wave. Here, the difference in the vapor component in the fuel tank between the gasoline vehicle and the diesel vehicle lies in the gas concentration. That is, gasoline having a low boiling point component as a main component generates high-concentration steam in the fuel tank, whereas diesel oil containing a large amount of components having a boiling point of 100 to 200 ° C.
At room temperature, it produces a very low concentration of steam in the fuel tank. Therefore, in order to distinguish a gasoline vehicle and a diesel vehicle from the vapor in the fuel tank at room temperature, a gas sensor having a stable sensitivity to a gas having an extremely wide range of concentration of several hundred ppm to several tens% is required. .

[0003]

However, in the above-described conventional oil type identification device, since the vapor concentration of light oil is extremely low, it is necessary to use an expensive ultrasonic transmitter / receiver which can detect it. There is a problem that the price will increase. Further, in the oil type identification device using the conventional ultrasonic transmitter / receiver, the output is the same when the test gas is air and when it is the vapor of light oil. Therefore, an abnormal situation such as failure of the test gas suction pump for sucking the vapor in the fuel tank as the test gas or clogging of the test gas suction nozzle occurs, and the air is identified. If you do, you may mistakenly identify it as a vapor of light oil. Therefore, when such an abnormal situation occurs, there is a possibility that light oil may be supplied to the fuel tank of a gasoline vehicle. Furthermore, it is desired that the detection of the test gas be performed stably and accurately for a long period of time without being affected by the change with time of the sensor.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an oil type identifying apparatus and method capable of stably identifying gasoline and light oil for a long period of time, accurately and with an inexpensive apparatus. To aim.

[0005]

In order to solve the above-mentioned problems of the prior art and to achieve the above-mentioned object, the oil type identification device of the present invention comprises a heat conduction type gas sensor for detecting a test gas, and The metal oxide semiconductor type gas sensor for detecting the test gas and the first output pattern of the heat conduction type gas sensor are binarized using a first threshold value, and the second output of the metal oxide semiconductor type gas sensor is binarized. The output pattern is binarized by using a second threshold value, and based on the binarized first output pattern or the second output pattern, the test gas is gasoline vapor and light oil vapor. And a threshold value changing unit for changing the first threshold value according to deterioration of the characteristics of the metal oxide semiconductor type gas sensor.

Further, in the oil type discriminating device of the present invention, preferably, the threshold value changing means decides a timing of changing the threshold value based on an output pattern of the heat conduction type gas sensor, and the metal oxidation. The changed threshold value is determined based on the output pattern of the semiconductor gas sensor.

Further, the oil type identifying method of the present invention binarizes the first output pattern of the heat conduction type gas sensor by using the first threshold value, and outputs the second output pattern of the metal oxide semiconductor type gas sensor. Is binarized using a second threshold value, and the test gas is either vapor of gasoline or vapor of light oil based on the binarized first output pattern or the second output pattern. Then, the first threshold value is changed according to the deterioration of the characteristics of the metal oxide semiconductor type gas sensor.

Further, in the oil type identifying method of the present invention, preferably, the timing of changing the threshold value is determined based on the output pattern of the heat conduction type gas sensor, and the output pattern of the metal oxide semiconductor type gas sensor is determined. The changed threshold value is determined based on this.

[0009]

In the oil type identification device of the present invention, the test gas is detected by the heat conduction type gas sensor. Further, the test gas is detected by the metal oxide semiconductor type gas sensor. Then, by the identifying means, the first of the heat conduction type gas sensor is provided.
Is binarized using a first threshold value, and the second output pattern of the metal oxide semiconductor gas sensor is binarized using a second threshold value. Based on the converted first output pattern and second converted output pattern, it is identified whether the test gas is vapor of gasoline or vapor of light oil. Thereafter, the detection of the test gas is repeatedly performed, and when the characteristics of the metal oxide semiconductor type gas sensor deteriorate, the first threshold value is changed by the threshold value changing means, and thereafter,
The processing in the identifying means is performed using the changed first threshold value.

Further, in the oil type identification device of the present invention, the threshold value changing means determines the timing of changing the threshold value based on the output pattern of the heat conduction type gas sensor, and the metal oxide semiconductor type The changed threshold value is determined based on the output pattern of the gas sensor.

In the oil type identifying method of the present invention, the first output pattern of the heat conduction type gas sensor is binarized by using the first threshold value and the second output pattern of the metal oxide semiconductor type gas sensor is used. Output pattern of 2 using the second threshold
Based on the binarized and binarized first output pattern and the second output pattern, it is identified whether the test gas is vapor of gasoline or vapor of light oil. Then, the detection of the test gas is repeatedly performed, and when the characteristics of the metal oxide semiconductor gas sensor deteriorate,
The first threshold value is changed, and then the identification is performed using the changed first threshold value.

Further, in the oil type identifying method of the present invention, the timing for changing the threshold value is determined based on the output pattern of the heat conduction type gas sensor, and changed based on the output pattern of the metal oxide semiconductor type gas sensor. Later thresholds are determined.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The oil type identifying apparatus and method according to the embodiments of the present invention will be described below. The oil type identification device according to the present embodiment is used, for example, in a gas station for a fueling machine that switches between gasoline and light oil to supply fuel. FIG. 1 is a configuration diagram of an oil type identification device 21 according to the present embodiment. As shown in FIG. 1, the oil type identification device 21 includes a flow rate adjusting unit 201, a sensor cell unit 202, and a switching unit 20.
3, a gas determination unit 204, a sensor sensitivity adjustment unit 205, and a memory 206. The flow rate control unit 201 applies a predetermined suction force to the flow path 20 and selectively sucks the vapor and the atmosphere in the fuel tank 208 into the sensor cell unit 202 according to the switching state of the switching unit 203. Switching unit 203
In a normal state, the flow path 20 is connected to the atmosphere side, and when a user operates a switch (not shown), for example, 1
Only for a second, the connection state is switched, the flow path 20 is connected to the fuel tank 208, and the vapor in the fuel tank 208 is caused to flow into the sensor cell unit 202.

The sensor cell section 202 shown in FIG. 1 will be described below. FIG. 2 shows the sensor cell unit 202 shown in FIG.
FIG. As shown in FIG. 2, the sensor cell unit 20
Reference numeral 2 denotes a heat conduction type inside a container 20 having an inflow port 20a formed on the left side surface in the figure for inflowing the gas to be detected and an outflow port 20b formed on the right side surface in the figure for outflowing the gas to be detected. Gas sensor 1 and metal oxide semiconductor type gas sensor 2
Are provided.

The heat conduction type gas sensor 1 shown in FIG. 2 will be described. The heat conduction type gas sensor 1 includes a reference sensor unit 5
And a gas detection sensor unit 9. The reference sensor unit 5 is configured by housing the reference heater 3 inside a sealed container 4. A power source 2 is provided at both ends of the reference heater 3.
The voltage V is applied from 2. At this time, the reference heater 3
Is located inside the sealed container 4, so that the container 20
It has a constant amount of heat radiation without being affected by the gas to be detected. In this embodiment, the container 4 is filled with air as a standard gas. Further, in this embodiment, as the voltage V of the power supply 22, for example, a voltage at which the heater applied current is 8 mA is used.

The gas detection sensor unit 9 includes a gas detection heater 6 inside a container 7 in which a gas to be detected outflow port 8 is formed.
Is stored. A voltage V is applied to both ends of the gas detection heater 6 from the power source 22 as in the reference heater 3. At this time, when the gas to be detected flows into the container 20 through the inflow port 20 a, the container 7 passes through the outflow port 8.
The gas to be detected flows in, and the gas detection heater 6 is placed in the atmosphere of the gas to be detected. Therefore, the heat radiation amount of the gas detection heater 6 changes according to the type and concentration of the inflowing gas to be detected.

In the heat conduction type gas sensor 1, it is possible to detect the difference in heat radiation amount between the reference sensor unit 5 and the gas detection sensor unit 9 and determine the presence or absence of the test gas according to the detection result. As shown in FIG. 1, the sensor output S1 ′ according to the detection result is obtained from the heat conduction type gas sensor 1 to the gas determination unit 20.
4 is output. In the present embodiment, when the test gas is gasoline, the sensor output S1 which is the binarized data of the sensor output S1 ′ has a high level (“1”) like the output 30a shown in FIG. become. When the gas to be detected is light oil, the sensor output S1 becomes a low level (“0”) like the output 30b shown in FIG. 3 (B). further,
When the test gas is air, the sensor output S1 is shown in FIG.
The output 30c shown in (C) is at a low level.

FIG. 4A shows the gas concentration of the test gas and the heat conduction type gas sensor 1 and the metal oxide semiconductor type gas sensor 2.
4B is a graph showing the relationship between the sensor outputs S1 ′ and S2 ′ of FIG. 4, and FIG. 4B is an enlarged graph showing the gas concentration around 1% in FIG. As shown in FIGS. 4A and 4B, the sensor output S1 ′ of the heat conduction type gas sensor 1
Is linearly increased in proportion to the increase in the gas concentration of the test gas. In the heat conduction type gas sensor 1, the gas to be detected is shown in FIG.
Dotted lines shown in (A) and (B), that is, gas concentration 0
In the vicinity of ˜1%, the sensor output S1 ′ is greatly affected by noise and becomes almost “0”, which makes detection impossible.
In the present embodiment, the gas determination unit 204 binarizes the sensor output S1 ′ from the heat conduction type gas sensor 1 using the threshold value A shown in FIG. 4B to generate the sensor output S1. At this time, the sensor output S1 becomes high level when the test gas is vapor of gasoline, low level when it is vapor of light oil, and low level when it is air.

The metal oxide semiconductor type gas sensor 2 shown in FIG. 2 will be described. As shown in FIG. 2, the metal oxide semiconductor type gas sensor 2 has a structure in which a counter electrode 11 formed on the surface of an insulating substrate 10 is covered with a thin film metal oxide semiconductor 12. A substrate heating heater 13 is provided on the back surface of the insulating substrate 10. In this embodiment, SnO ₂ (tin oxide) is used as the metal oxide semiconductor 12.
The operating temperature is 400 ° C. Metal oxide semiconductor 12
Alternatively, Fe ₂ O ₃ or ZnO can be used.

In the metal oxide semiconductor type gas sensor 2, when the metal oxide semiconductor 12 is placed in the test gas atmosphere,
The test gas reacts with oxygen on the surface of the metal oxide semiconductor 12 to be oxidized, and oxygen is deprived from the metal oxide semiconductor 12. At this time, electrons are exchanged between the test gas and the metal oxide semiconductor 12 along with the reaction, and as a result,
The electronic properties of the metal oxide semiconductor 12 change. Since the change in the electronic properties of the metal oxide semiconductor 12 appears as a change in the interelectrode resistance value, the metal oxide semiconductor gas sensor 2 detects the change in the interelectrode resistance value to detect the presence or absence of the test gas. to decide.

In the present embodiment, the sensor output S2 'shown in FIG. 1 according to the detected interelectrode resistance value is output from the metal oxide semiconductor type gas sensor 2 to the gas judging section 204. In the present embodiment, when the test gas is gasoline, the sensor output S2 ′ of the heat conduction type gas sensor 2 is 2
The sensor output S2, which is the binarized data, becomes a high level like the output 31a shown in FIG. Further, when the test gas is light oil, the sensor output S2 becomes a high level like the output 31b shown in FIG. 3 (B). Further, when the test gas is air, the sensor output S2 is as shown in FIG.
The output 31c shown in (C) is at a low level.

As shown in FIGS. 4A and 4B, the sensor output S2 'of the metal oxide semiconductor type gas sensor 2 increases in a curve in proportion to the increase of the gas concentration of the test gas. Due to its characteristics, the metal oxide semiconductor type gas sensor 2 can perform highly accurate gas detection even when the gas concentration is 1% or less. In the present embodiment, in the gas determination unit 204,
The sensor output S2 ′ from the metal oxide semiconductor type gas sensor 2 shown in FIGS. 4A and 4B is binarized by using the threshold value B shown in FIG. 4B to obtain the sensor output S2. To generate. The threshold value B is stored in the memory 206 and read by the gas determination unit 204. The threshold value B
Is set on the basis of the sensor output S2 before the endurance in which the characteristics of the metal oxide semiconductor type gas sensor 2 are not deteriorated. At this time, the sensor output S2 becomes high level when the test gas is gasoline vapor, high level when the test gas is light oil vapor, and low level when the test gas is air.

Next, the sensor sensitivity adjusting section 205 will be described. In the sensor sensitivity adjustment unit 205, the gas determination unit 20
In 4, the threshold value B ′ is determined by changing the threshold value B used when the sensor output S2 ′ from the metal oxide semiconductor type gas sensor 2 is binarized. That is, when the metal oxide semiconductor type gas sensor 2 is repeatedly used, its output value changes, and if the threshold value B is always used, it is necessary to accurately determine the type of the test gas. The stable sensor output S2 cannot be stably obtained in the long term.

FIG. 5 is a graph showing the relationship between the test time and the sensor output S1 'of the heat conduction type gas sensor 1 and the sensor output S2' of the metal oxide semiconductor type gas sensor 2. In the sensor output S2 ′ shown in FIG. 5, those before endurance are shown by dotted lines, and those after endurance are shown by solid lines. On the other hand, the sensor output S1 ′ of the heat conduction type gas sensor 1
Is approximately the same before and after the endurance test. The terms “before durability” and “after durability” mean that the total time during which the sensor is placed in the test gas atmosphere is relatively short and long, respectively. As shown in FIG. 5, when the test time is about 1.00 to 2.00 seconds, the sensor output S2 ′ of the metal oxide semiconductor type gas sensor 2 is longer after the endurance than before the endurance. It has fallen to about half. Therefore, in the gas determination unit 204, the required sensor output S2 can be obtained by binarizing the sensor output S2 ′ using the threshold value B shown in FIG. 5 before the endurance. If the sensor output S2 ′ is binarized using B, the sensor output S2 will always be “0”, and the required sensor output S2 cannot be obtained.

Therefore, the sensor sensitivity adjusting section 205 uses the sensor output S1 'from the heat conduction type gas sensor 1 and the sensor output S2' from the metal oxide semiconductor type gas sensor 2 and uses it after the endurance as shown below. Threshold B '
To determine. That is, when the maximum value of the sensor output S1 ′ from the heat conduction type gas sensor 1 is larger than 0.1 mV based on the level S shown in FIG. 5, the sensor sensitivity adjusting unit 205 shows the threshold value B shown in FIG. 'Is determined using the following formula (1). Threshold value B ′ = (maximum value of sensor output S2 ′) / 2 (1) On the other hand, when the maximum value of sensor output S1 ′ from the heat conduction type gas sensor 1 is 0.1 mV or less, threshold value B ′ Is used as is. In the examples shown in FIGS. 5 and 6, the maximum value of the output of the sensor output S2 ′ based on the level S ′ is 0.91V, so the threshold value B ′ is set to the value represented by the following formula (2). Become. Threshold value B ′ = 0.91V / 2 = about 0.46 mV (2) The threshold value B ′ determined by the sensor sensitivity adjusting unit 205 is output to and stored in the memory 206.

In the above-described oil type identification device 21, the gas determination unit 204 binarizes the sensor output S1 'from the heat conduction type gas sensor 1 using the threshold value A shown in FIG. 4 (B). The sensor output S1 is generated. Further, in the gas determination unit 204, the sensor output S2 ′ from the metal oxide semiconductor type gas sensor 2 is binarized by using the threshold value B shown in FIGS. Output S2 is generated, but after endurance, the above equation (1)
2 by using the threshold value B ′ shown in FIG.
The value is converted into a sensor output S2. Then, in the gas determination unit 204, the switching unit 2 is switched from the patterns shown in FIGS. 3A to 3C based on the sensor outputs S1 and S2.
It is determined whether the test gas from 03 is steam of gasoline, steam of light oil, or air.

As described above, the oil type identification device 21 according to this embodiment
According to the method and the method, even after the endurance in which the test gas is repeatedly identified, the test gas is gasoline vapor,
It is possible to accurately identify whether it is steam of light oil or air. Therefore, the test gas suction pump for sucking the vapor in the fuel tank as the test gas fails, or the test gas suction nozzle becomes clogged, which causes an abnormal situation.
Even if the identification is performed on the air, the test gas is not mistakenly identified as the vapor of light oil. As a result, even if such an abnormal situation occurs, it is possible to avoid supplying light oil to the fuel tank of the gasoline vehicle. Further, according to the oil type identification device 21 and the method thereof according to the present embodiment, it is not necessary to use an expensive ultrasonic transmitter / receiver, and the cost of the device can be reduced.

The invention is not limited to the embodiments described above. For example, the method of determining the threshold value B ′ in the sensor sensitivity adjusting unit 205 is not limited to the one represented by the above-described formula (1), and may be a constant value determined based on the data obtained in advance, for example. It may be a value. Further, in the sensor sensitivity adjusting unit 205, the reference for determining the timing for using the new threshold value B ′ is also the above-mentioned one if the sensor output S2 necessary for determining the type of the test gas can be obtained. Is not limited.

[0029]

As described above, according to the oil type identification device of the present invention,
Even after the endurance in which the test gas was repeatedly identified,
It is possible to accurately identify whether the test gas is vapor of gasoline or vapor of light oil from the output patterns of the heat conduction type gas sensor and the metal oxide semiconductor type gas sensor. Therefore, by using the oil type identifying apparatus and method of the present invention for a gas dispenser of a gas station or the like, it is possible to stably avoid supplying wrong oil to a vehicle for a long period of time. Further, according to the oil type identification device of the present invention, it is not necessary to use an expensive ultrasonic transmitter / receiver, and the cost of the device can be reduced. Further, in the oil type identification device of the present invention, in the threshold value changing means,
The timing to change the threshold value is determined based on the output pattern of the heat conduction type gas sensor, and the changed threshold value is determined based on the output pattern of the metal oxide semiconductor type gas sensor. It is possible to accurately identify whether the steam is steam of light oil or steam of light oil. Also,
According to the oil type identification method of the present invention, even after the endurance in which the test gas is repeatedly identified, the test gas is determined to be gasoline vapor or light oil from the output patterns of the heat conduction type gas sensor and the metal oxide semiconductor type gas sensor. It is possible to accurately identify which of the vapors is. Therefore, if the oil type identification method of the present invention is used for a gas station fueling machine or the like, it is possible to stably avoid supplying wrong oil to a vehicle for a long period of time. Further, in the oil type identification method of the present invention, the timing for changing the threshold value is determined based on the output pattern of the heat conduction type gas sensor, and the changed threshold value is determined based on the output pattern of the metal oxide semiconductor type gas sensor. Is determined, it is possible to accurately identify whether the test gas is the vapor of gasoline or the vapor of light oil.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an oil type identification device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a sensor unit shown in FIG.

FIG. 3 is a diagram for explaining the outputs of the heat conduction type gas sensor and the metal oxide semiconductor type gas sensor shown in FIG. 1 according to the type of the test gas, and (A) of FIG. In case (B), if the test gas is light oil vapor,
(C) is a diagram when the test gas is air.

FIG. 4A is a graph showing the relationship between the gas concentration of the test gas and the sensor outputs of the heat conduction type gas sensor and the metal oxide semiconductor type gas sensor, and FIG. 4B is an enlarged view of the gas concentration around 1% in FIG. 4A. It is a figure which shows the graph shown.

FIG. 5 is a diagram showing a graph showing the relationship between the test time and the sensor output of the heat conduction type gas sensor and the sensor output of the metal oxide semiconductor type gas sensor.

FIG. 6 is a diagram for explaining a threshold value used after endurance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermal-conduction type | mold gas sensor 2 ... Metal oxide semiconductor type gas sensor 3 ... Reference heater 4,7,20 ... Container 5 ... Reference sensor part 6 ... Gas detection heater 8 ... Outflow inlet 9 ... Gas detection sensor part 10 Insulating substrate 11 Counter electrode 12 Metal oxide semiconductor 13 Substrate heating heater 21 Oil type identification device 201 Flow rate adjusting unit 202 Sensor cell unit 203 Switching unit 204 Gas judging unit 205 Sensor sensitivity adjusting unit 206 … Memory 208… Fuel tank

Claims (4)

[Claims] 1. A heat conduction type gas sensor for detecting a test gas; a metal oxide semiconductor type gas sensor for detecting the test gas; and a first output pattern of the heat conduction type gas sensor as a first threshold value. And binarize the second output pattern of the metal oxide semiconductor gas sensor using a second threshold value, and binarize the first output pattern or the second output pattern. Identification means for identifying whether the test gas is a vapor of gasoline or a vapor of light oil based on the output pattern, and the first screen according to deterioration of characteristics of the metal oxide semiconductor gas sensor. An oil type identification device having a threshold value changing means for changing a threshold value. 2. The threshold value changing means determines the timing for changing the threshold value based on the output pattern of the heat conduction type gas sensor, and after changing the threshold value based on the output pattern of the metal oxide semiconductor type gas sensor. The oil type identification device according to claim 1, wherein the threshold value of the oil type is determined. 3. A first output pattern of the heat conduction type gas sensor is binarized by using a first threshold value, and a second output pattern of the metal oxide semiconductor type gas sensor is set by using a second threshold value. And binarize it to identify whether the test gas is a vapor of gasoline or a vapor of light oil based on the binarized first output pattern and the second output pattern. An oil type identification method for changing the first threshold value according to deterioration of the characteristics of the oxide semiconductor gas sensor. 4. The timing for changing the threshold value is determined based on the output pattern of the heat conduction type gas sensor, and the changed threshold value is determined based on the output pattern of the metal oxide semiconductor type gas sensor. Item 1. The oil type identification device according to item 1.