JP3408897B2 - Gasoline / light oil identification device and identification method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present application relates to a gasoline / light oil identification device for identifying gasoline and light oil as identification objects and a method of using the same. Such a gasoline / light oil identifying device is installed in, for example, a manned or unmanned gas station, and is used for the purpose of preventing misidentification of gasoline and light oil and eliminating explosion or engine damage.

[0002]

2. Description of the Related Art Conventionally, a gasoline / light oil discriminating device has been developed by using a sensor such as a semiconductor ceramic sensor or a catalytic combustion type sensor for the above purpose.

[0003]

First, the question of the sensor itself is presented.
From the point of view, semiconductor ceramic sensors, contact
Each combustion type sensor has the following problems.
It Semiconductor ceramic sensors compare gasoline and light oil.
Capable of highly sensitive detection with a relatively fast response speed
However, the reproducibility and stability are affected by the ambient temperature and humidity.
There is a problem. Long-term stability is also an issue. Higher concentration steam
The sensor also has a problem such as a change in sensitivity with respect to qi.
The contact combustion type sensor is not easily affected by temperature and humidity,
Long-term stability is a problem. Furthermore, for high-concentration steam
As with the semiconductor type sensor, the sensor sensitivity changes. In particular
Since it uses a precious metal catalyst, it can be used in gasoline and light oil.
Sulfur (S) compounds present (eg H₂S)
Silicone pads that are often used in industries and homes
Silicon (Si) compound volatilized from te, paint, etc.
This causes poisoning and deterioration of sensitivity. Especially with Si compounds
The poisoning that occurs on the catalyst is almost permanent SiO ₂To form
Degradation of sensitivity does not occur even if a very small amount of Si compound is present in the atmosphere.
It grows over time and eventually loses sensitivity. Si conversion
Poisoning due to compounds and S compounds also occurs in semiconductor type sensors.
Sensor sensitivity deteriorates. Therefore, it is stable and reliable.
Can't identify gasoline / light oil. Standard to supplement this
Gas inspection is performed, but it is expensive and labor-intensive.
Light Next, for a gasoline / light oil identification device equipped with both sensors
Explaining about it, gasoline using these sensors
Light oil identification device identifies gasoline / light oil relatively quickly
However, it is not enough, and it is desirable to identify it in a shorter time.
ing. The present invention has been made in view of these points,
Stable and reliable identification of gasoline and diesel oil with fast identification speed
It realizes the device.

[0004]

In order to achieve the above object, according to claim 1, a gasoline / light oil identifying device for identifying gasoline and light oil as an object to be identified is characterized in that the object to be identified is The detection unit to which one of the vapors is introduced is provided with a detection element of a heat conduction type sensor that outputs different output values according to the thermal conductivity of the ambient atmosphere, and the heat conduction is performed in response to the vapor introduced to the detection unit. It is provided with an identification means for identifying whether the identification object is the gasoline or the light oil based on the output value output by the equation sensor. Here, the heat conduction type sensor is composed of two elements, a detection element and a temperature compensation element, the detection element is exposed to the test gas, and the temperature compensation element has a structure sealed in standard gas (air). A sensor. The sensing element and the temperature compensating element are heated to a temperature higher than the ambient temperature around them, and the test gas is detected from the temperature change generated in the sensing element due to the difference in thermal conductivity between the test gas and air. is there.
The above is the configuration, structure, and detection principle of the heat conduction type sensor, but there are various shapes, and the detection unit 2 of the present invention is one of the heat conduction type sensors called the flow type. Therefore, in this device, the vapor of the identification object is guided to the detection unit,
It is sensed by a sensing element provided in the sensing section, and a heat conduction type sensor output is obtained. The output of the heat conduction sensor is different depending on whether the surrounding atmosphere is gasoline vapor or light oil vapor, as shown in FIG. Therefore, the identification means can identify the object to be identified from the relationship between the output of the heat conduction type sensor and the output value that is known in advance for gasoline vapor and light oil vapor.

The heat conduction type sensor has the following features regardless of its shape and configuration. That is, the heat conduction type sensor is stable to high-concentration vapor and poisonous substances, and is also very excellent in long-term stability. This is because the operation principle of the sensor is a physical sensor (thermometer) whose detection principle is simple: it measures the temperature change of a heated detection element caused by the difference in thermal conductivity between the detection gas and air. This is because a chemical reaction such as a catalytic action is not used unlike the type sensor and the catalytic combustion type sensor. Therefore, while the semiconductor sensitive part of the semiconductor type sensor and the catalyst and the noble metal catalyst of the catalytic combustion type sensor are exposed to high-concentration vapor and reduced to change the characteristics of the semiconductor and the oxidation activity of the catalyst, the heat conduction type sensor The Pt resistor does not change its resistance value even if it is exposed to high-concentration vapor for a long time.

Regarding poisoning, for example, in the case of Si poisoning, in a semiconductor type sensor, SiO ₂ is preferentially laminated on a catalyst having a particularly high activity in the semiconductor sensitive portion to deteriorate the semiconductor sensitive portion, and It also deteriorates activity. In the catalytic combustion type sensor, SiO ₂ is laminated on the noble metal catalyst and its catalytic activity deteriorates. However, in the heat conduction type sensor, even if SiO ₂ is formed, its characteristics are not affected. Speaking of long-term stability, the semiconductor type sensor is problematic due to the progress of sintering of the semiconductor in the sensitive part (promoted in high humidity) and the deterioration of the catalyst. It is well known that there is a downward trend. On the other hand, the Pt resistor, which is the sensitive part of the heat conduction type sensor, hardly changes with time. Therefore, the problem of the prior art described above is to be solved.

Furthermore, the characteristic structure of the gasoline / light oil identification device
The heat conduction type sensor comprises the detection element arranged in the detection section and a temperature compensation element arranged in a standard atmosphere, and the detection element has an insulating property. It is a coil made of a wire containing platinum (Pt) as a main component and covered with an inert thin film made of a heat-resistant inert material. As described above, when the sensor structure including the sensing element and the temperature compensating element is adopted, it is possible to accurately perform discrimination that does not depend on the environmental atmosphere. Furthermore, by configuring the sensing element as a coil made of a wire having an inert thin film layer on the surface, it is possible to prevent malfunction of the sensor due to contact combustion on the surface of the wire, As the detecting element, the coil portion is maintained in an appropriate temperature state, and different sensor outputs can be satisfactorily obtained due to the difference in heat conduction characteristics of gasoline vapor and light oil vapor, and responsiveness and warming-up can be accelerated.

Further, the gasoline / light oil discriminating apparatus according to claim 2 is characterized in that, in the gasoline / light oil discriminating apparatus according to claim 1 , the heat-resistant inert material is silica (SiO ₂ ), alumina (Al ₂ O ₃ ), silicon nitride (Si ₃
N ₄ ), at least one selected from aluminum nitride (AlN), and the thickness of the inert thin film is 0.01
μm to 10 μm, and the wire diameter of the wire is 5 μm to 12
μm, and the number of turns in the coil is 5 to 12
At the turn, the coil outer diameter is 50 μm to 150 μm,
The pitch between the coils is 3 times or less the wire diameter. Here, silica (SiO ₂ ), alumina (Al
₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (A
In the case of adopting 1N) or the like, an inert thin film can be easily formed on the surface of the wire because it is a material that is easily available. Further, the limitation regarding the shape of the detection coil will be described later.

Further, the characteristic configuration of the gasoline / light oil identification device according to claim 3 is that in the gasoline / light oil identification device according to claim 1 or 2 , the identification target by suction is applied to the detection section provided with the detection element. It is provided with a suction / exhaust mechanism for guiding the volatile vapor of the substance and a flow velocity relaxing mechanism for easing the flow velocity of the volatile vapor flowing through the peripheral portion of the detection element. As described above, when the suction / discharge mechanism is provided, the vapor is appropriately guided to the detection unit from the identification object stored in the tank in a liquid state, and in a state suitable for the structure of the heat conduction sensor. , Identification detection can be performed. Further, the operation / effect provided with the flow velocity alleviation mechanism will be described in the embodiment modes and effects section.

Further, the characteristic configuration of the gasoline / light oil discrimination device according to claim 4 is that in the gasoline / light oil discrimination device according to any one of claims 1 to 3 , the temperature in the tank for storing the discrimination target object. With a temperature detection means for detecting, the temperature dependence index of the output value of the heat conduction type sensor for light oil saturated vapor measured in advance, the light oil reference output of the light oil saturated vapor at the temperature detected by the temperature detection means. There is provided a reference output value derivation means for obtaining a value, and the identification means sets a value obtained by multiplying the light oil reference output value by a predetermined safety coefficient as a discrimination threshold value between gasoline and light oil. As an example, the output of the heat conduction type sensor changes with temperature as shown in FIG. Therefore, the temperature detecting means detects the temperature in the tank, the reference output value deriving means derives the output value of the sensor for the light oil vapor at this temperature from the temperature dependence index, and the identifying means determines the light oil reference output. Gasoline and light oil are discriminated using a value obtained by multiplying the value by a predetermined safety factor as a discrimination threshold. Since the output of the heat conduction type sensor is very small with respect to the light oil saturated vapor, if this method is adopted, good discrimination can be performed.

Further, the characteristic means of the discrimination method according to claim 5 is that, when the gasoline / light oil discrimination device according to claim 2 is used, the temperature of the detection element is maintained at a predetermined temperature of 200 ° C. or lower, And to identify light oil. By doing so, as will be described later, good identification can be performed on gasoline / light oil while satisfying the safety standards thereof.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a device configuration of a gasoline / light oil identification device 100 that employs a heat conduction type sensor unique to the present application, and FIGS. 2 and 3 show a detection unit 2 of the device 100.
The detailed structure of 2 is a sectional front view of the detection unit 2, and FIG. 3 is a side view. FIG. 4 shows the structure of the element 1 used in the heat conduction type sensor of the present invention. First, the device 1
The outline of 00 will be described. The gasoline / light oil identification device 100 is a detection element of a heat conduction type sensor that outputs different output values according to the thermal conductivity of the ambient atmosphere to the detection unit 2 to which either vapor of gasoline or light oil that is an identification object is introduced. 3, and a discrimination means 4 for discriminating whether the discrimination target is gasoline or light oil based on the output value of the heat conduction type sensor which is sensitive to the steam guided to the detection section 2. Has been done. Here, the sensing element 3
However, one of the major features of the present application is that the micro coil 7 is composed of a wire 6 having platinum (Pt) as a main component and covered with an inactive thin film 5 made of a heat-resistant inactive material having an insulating property.

Hereinafter, the structure of element 1 and gasoline / light oil identification
The structure of the device 100 will be described in detail in order. 1. Structure of element 1 provided in heat conduction type sensor An example of the element 1 used in the heat conduction type sensor is shown in FIGS.
It was shown to. FIG. 2 shows a minute coil that can be used as the sensing element 3.
4 shows a state in which the coil 7 is attached to the base 8, and FIG.
Shows the cross-sectional structure of the wire 6 forming the micro coil 7.
There is. When making, platinum (Pt) with a wire diameter of 10 μm
A small coil with 6 turns and a coil outer diameter of 80 μm using wire 9.
Ile 7 is produced. This micro coil 7 is connected to the Ni pin 10 etc.
Weld to the electrode. An inert thin film provided on the surface of the wire 6.
The film 5 is, for example, SiO ₂For layers, on both ends of this coil
Apply a voltage to raise the coil temperature to 500 ° C or higher and
Samethyldisiloxane (CH₃)₃SiOSi (CH₃)₃etc
By treating with steam of₂Inert thin film 5
It is formed. This SiO₂Forming an inert thin film 5
Can inactivate the element containing Pt as a main component.
I can. This inactivation treatment (inert thin film formation treatment)
Of the flammable gas that causes malfunction of the heat conduction sensor.
Contact combustion can be prevented. Thus obtained
The element 1 is replaced with the detection element 3 of the heat conduction type sensor and the temperature compensation element.
Used as child 11.

2 Structure of Gasoline / Light Oil Discrimination Device 100 Next, the configuration of the gasoline / light oil discrimination device 100 of the present application will be described. This device 100 is the same as the device 1 described above.
The heat conduction type sensor having the sensing element 3 and the temperature compensating element 11 is provided as a main device. gasoline·
The light oil identifying apparatus 100 is provided with the detection element 3 of the above-described heat conduction type sensor as a main component, and a detection unit 2 into which either vapor of gasoline or light oil is introduced, and vapor of gasoline or light oil to the detection unit 2. And a suction flow for guiding the steam to the steam introducing section 12 and the detecting section 2 for guiding the
A suction / exhaust mechanism 13 for exhausting this, and an identification unit 14 for discriminating whether the vapor sample is gasoline or light oil based on the output of the heat conduction type sensor are provided. A temperature sensor 15 as a temperature detecting means is provided at the tip of the steam introducing portion 12.

With this configuration, by connecting the tank 18 containing the identification object 17 to the suction port 16 of the steam introducing section 12, the steam of gasoline or light oil is sucked and discharged by the suction / discharge mechanism 13. And is guided to the detection unit 2. Then, the heat conduction state near the detection element 3 is determined by this vapor, and the sensor output is output by the heat conduction type sensor. At the same time, the temperature inside the tank 18 is measured by the temperature sensor 15. The outputs of the heat conduction type sensor and the temperature sensor are passed through the amplifier 19 and the A / D converter 20 and the identification unit 1
4 is input to the computer (arithmetic processing unit) 21. The software in the computer 21 mainly constitutes the identification means.
In the identification unit 14, the parameters (eg,
a, b, c), the sensor output (for example, aX ² + bX + c, X: temperature) for the saturated vapor of light oil at the temperature detected by the temperature sensor 15 is calculated. Here, the output curve of this light oil with respect to saturated steam is −
It is an index line as shown by the Δ-line. This is multiplied by a safety factor (for example, 2) to obtain the identification threshold value S. And
By the discrimination means described above, the discrimination threshold value S is compared with the sensor output value of the heat conduction type sensor to discriminate between gasoline and light oil. That is, when the sensor output value is higher than the identification threshold value S, it is determined that the steam is gasoline, and when the sensor output value is lower than 1/2 of the identification threshold value S, the steam is determined as light oil. However, the output of the heat conduction type sensor is 1 / 2S ~
If it is in S, it is treated as unidentifiable to ensure safety.
This discrimination threshold S is shown in FIG. 5 for the case where the temperature is 20 ° C. The result is output to the external output 310.

3 Detailed Structure of Detection Unit 2 Next, the detailed structure of the detection unit 2 described above will be described with reference to FIG.
It will be described with reference to FIG. 2 is a sectional front view of the detection unit 2 as seen from the steam inflow side, and FIG. 3 shows a side structure of the detection unit 2. As shown in FIG.
In addition to having a detection channel 2a through which vapor flows, a detection element disposition section 2b communicating with and connected to the detection channel 2a and a temperature compensation element disposition section 2c in which the temperature compensation element 11 is disposed are configured. Has been done. A wire mesh 23 as a flow velocity reducing mechanism is provided in the above-described detection flow path 2a. Further, air as a standard atmosphere is hermetically sealed in the temperature compensating element mounting portion 2c. Here, the wire mesh 23 reduces the influence of the flow velocity of vapor around the sensing element 3. As described above, by providing the wire mesh 23, the response speed of the heat conduction type sensor is increased, and stable and reproducible identification is possible.

The response speed of the heat conduction type sensor of the present invention is fast, and is 0.2 seconds or less in the diffusion system. However, the response speed becomes slow in the flow system. In flow systems, in general,
Since the detection element 3 of the heat conduction type sensor is a thermometer, the temperature of the detection element 3 changes until the flow state stabilizes, and therefore the output of the heat conduction type sensor also changes and it is difficult to reach a constant value. Furthermore, the operation situation from the power off state to the on state can be regarded as similar to the situation from the windless state to the flow state. Therefore, in order to speed up the response speed / warming-up time of the heat conduction type sensor, it is necessary to ensure a stable and stable flow state promptly. However, the flow velocity relaxation mechanism (wire mesh 23 in this example) of the present application is The flow velocity of the atmosphere around the detection element 3 is limited and the temperature state is stabilized, so that a quick response is possible. Therefore, in the device of the present application as a flow system, detection can be performed in less than 1 second.

4 Sensor Output of Heat Conduction Sensor The sensor output of the heat conduction sensor configured as described above will be described below. Fig. 5 Ambient temperature -20 ° C
The sensor output of the heat conduction type sensor with respect to the saturated vapor pressure of gasoline and light oil in -50 degreeC is shown. -△-shows the output of light oil,-○-shows the sensor output of regular gasoline, and -x- shows the sensor output of high-octane gasoline. As shown in the figure, the output of the heat conduction sensor for gasoline vapor at -20 ° C is larger than that for light oil vapor at 50 ° C, and the ambient temperature is -20 ° C to 50 ° C.
In, it is possible to distinguish between gasoline and light oil by a heat conduction type sensor.

5 Response Characteristics of Heat Conduction Sensor Next, the response performance of the sensor will be described. Figure 6 (a)
FIG. 6 shows a response waveform of the heat conduction type sensor using the minute coil 7 (the one in which the inert thin film 5 is provided on the surface of the Pt wire rod 6 formed as a coil) described above to 1% of gasoline. In (b), the conventional heat conduction type sensor (P
A response waveform of a heat conduction type sensor using a t-shaped wire formed in a coil shape and a ball-shaped agglomerate of a heat-resistant inert material formed around the entire coil) is shown. As described above, the heat conduction type sensor has excellent sensitivity even with about 1% of gasoline vapor, and can detect gasoline satisfactorily. Further, comparing the response speeds of the heat conduction type sensor using the micro coil 7 and the conventional type heat conduction type sensor, the response speed of the former type is within 1 second, whereas that of the conventional type is 10 seconds. It can be seen that the former one is highly practical.

6 Gasoline / Diesel Oil Discrimination Setting Gasoline / diesel oil discrimination detection will be described in more detail below. As shown in FIG. 5, in the heat conduction type sensor, since the vapor pressure of gasoline and light oil is higher in gasoline, the sensor is always highly sensitive to gasoline. And
Each vapor pressure depends on the temperature. Therefore, when the ambient temperature is -20 ° C to 50 ° C, the sensor output (gasoline 1% for gasoline 1% (resolution) at 50 ° C)
As for the output, the temperature difference between the sensor and the atmosphere is the smallest, so the case of 50 ° C is the smallest)
If it is higher than the sensor output for the saturated vapor pressure of light oil in, the discrimination between gasoline and light oil is possible. In fact, in the gasoline / light oil identification device 100 of the present application, this situation is realized, and therefore both can be identified and detected. Therefore, in the apparatus 100 of the present application, gasoline and light oil are discriminated when the output is twice the output for the saturated vapor pressure of light oil at 50 ° C. in consideration of safety. Further, assuming that the time required for the sensor output to reach an output that is twice the output for the saturated vapor pressure of light oil at 50 ° C. is the identification speed, as shown in FIG.
At ° C, this identification speed is
It will be within 0.35 seconds. This discrimination speed is sufficiently practical. The warm-up time is also greatly reduced to less than 2 seconds, and the power can be turned off when not in use, which is useful in terms of power saving and safety.

7 Structural Study of Sensing Element (Micro Coil) 3 In order to operate the heat conduction sensor, it is necessary to raise the temperature of the micro coil 7 above the ambient atmospheric temperature (in the case of the embodiment of the present invention, the former temperature). Is about 110 ° C., and the temperature of the latter is about −20 ° C. to 50 ° C.). Further, since the output of the heat conduction type sensor is proportional to the bridge voltage applied to both ends of the sensing element 3 and the temperature compensating element 11, the electric resistance values of the sensing element 3 and the temperature compensating element 11 need to be large to some extent. is there. Therefore, when the wire rod 6 having a large wire diameter is used, the outer diameter of the coil and the turn must be increased. Furthermore, while satisfying these conditions, the response time and warm-up time are fast.
Practically preferable. Here, the identification time is practically within 1 second, and the warm-up time is practically within 5 seconds. The results of examining the structure of the micro coil 7 under such conditions will be described below.

7-1 Wire Diameter of Micro Coil 7 As the wire diameter of the micro coil 7, it is necessary to adopt a wire diameter of 5 μm to 12 μm. If the wire diameter is less than 5 μm, the electric resistance value of the coil wire material increases and the heat conduction of the wire material of the coil itself deteriorates. Perhaps the response speed of the heat conduction type sensor becomes slow and the identification speed becomes slow. Further, it is difficult to obtain a wire containing Pt as a main component, which is not practical. On the other hand, when it is larger than 12 μm, in order to satisfy the above-mentioned conditions regarding the temperature, the outer diameter of the coil and the number of turns become large, the response speed becomes slow and the identification speed becomes slow, and it is difficult to satisfy these conditions. It is considered that this is because it takes time for the system to reach thermal equilibrium due to the size of the system becoming larger, and the heat distribution around the device is reconfigured to secondarily affect the temperature of the device.

7-2 Number of turns of micro coil 7 As the number of turns of the micro coil, the number of turns of 5 to 12 is adopted to satisfy the above condition. If the number of turns is less than 5 turns, the temperature of the coil part is hard to rise thermally,
The sensitivity is too low and the sensor output is too small. 1
A coil having more than 2 turns is difficult to manufacture and the manufacturing yield is poor. 7-3 Coil pitch of the minute coil 7 The coil outer diameter of the minute coil is 50 μm.
Adopting ˜150 μm satisfies the above conditions. If the outer diameter of the coil is less than 50 μm, the resistance of the coil cannot be sufficiently maintained and the temperature of the coil is unlikely to rise thermally,
The sensitivity is too low and the sensor output is too small. In addition, the production becomes difficult and the production yield deteriorates. If it is larger than 150 μm, the response speed and hence the identification speed will be slower for the same reason as described in the case of the large wire diameter.

7-4 Outer Diameter of Minute Coil 7 The above condition is satisfied when the coil pitch of the minute coil is 3 times or less the wire diameter. When the pitch of the coil is large, the system becomes large and the response speed becomes slow due to the reason described above. Also, since the resistance value of the coil hardly changes but only the system becomes large, it is difficult to raise the temperature of the coil. 7-5 Film Thickness of Inert Thin Film 5 The film thickness of the inactive thin film 5 in the wire 6 constituting the micro coil satisfies the above condition that the film thickness is 0.01 μm to 10 μm. If the thickness of the inert thin film 5 is 0.01 μm or less, it is not sufficient to prevent contact combustion with a high concentration of combustible gas. Contact combustion of combustible gas tends to develop at an accelerated rate even if locally initiated, and 0.01 μm
The following film thickness may cause catalytic combustion of flammable gas,
There is a risk of malfunction of the thermal conductivity sensor. 10 μm
The above film thickness increases the heat capacity of the coil portion and slows the response speed of the sensor. Here, in the above example, the inert thin film 5
Although a SiO ₂ film is adopted as this, other than this example, Al ₂ O ₃ ,
Even with a thin film made of at least one of Si ₃ N ₄ and AlN, the purpose of preventing catalytic combustion can be achieved.

7-6 Wire Material of Micro Coil 7 Although Pt wire is used as the wire material 6 in the examples described above, platinum rhodium wire (alloy wire of Pt and rhodium Rh), platinum zirconia wire (zirconia ZrO ₂ dispersion). Any wire rod containing Pt as a main component, such as a reinforced platinum wire, can be applied to the present invention.

8 Comparison with Conventional Heat Conduction Sensor In the present application, the distinction between gasoline and light oil is performed by the heat conduction sensor. As described above, the use of the heat conduction type sensor has various advantages over the case of using other types of sensors. However, even when the heat conduction type sensor is also used, there is a difference in the detection performance depending on the sensor structure. Therefore,
This point will be described. The conventional heat conduction type sensor for comparison is a spherical element (sphere diameter 0.7 mm to 1 mm) in which a thermistor is used as the detecting element 3 and the temperature compensating element 11, or a coil made of Pt wire is covered with alumina. Or a Pt thin film resistor formed on a 1 mm × 1 mm square alumina substrate. First, these conventional heat conduction type sensors have a response speed to the vapor of gasoline / light oil (in this text, the time required to reach 90% of the saturated output) of about 10 seconds, which is quite slow It takes 2 to 3 minutes to warm up after putting it in. Therefore, in this respect, there is room for improvement, and from a practical point of view, it is necessary to equip the main part of the gasoline / light oil identification device with the heat conduction type sensor having the micro coil type described above, It is practical in terms of responsiveness and warming-up performance.

9 A method of using the gasoline / light oil identification device 100 described above will be described.
The ignition temperature of light oil vapor is ~ 260 ° C, and when considering a safety explosion-proof structure, the temperature class T3 or higher is required, so the surface temperature of the element 1 must be 200 ° C or lower.
Further, if the surface temperature of the element 1 is kept at 135 ° C. or lower, the temperature class T4 is satisfied, and more safety is ensured, which is preferable.

[Another Embodiment] In the above embodiment, the same micro coil 7 used as the sensing element 3 was used as the temperature compensating element 11. Since air is used as the atmosphere, it is possible to use the platinum wire without the inert thin film 5 as it is as the temperature compensation element 11. further,
When the temperature inside the tank 18 is not measured, a value obtained by multiplying the output of the heat conduction type sensor for the saturated vapor of light oil at the upper limit of the operating temperature by the safety factor is input as a discrimination threshold value to the memory, and this value and the heat conduction type A structure for distinguishing gasoline and light oil by comparing the outputs of the sensors may be adopted.

[0029]

As described above, in the present application,
We have realized a stable and reliable gasoline / light oil identification device. The thermal conductivity type sensor is stable to high-concentration vapor and poisonous substances (even if SiO ₂ is formed, it does not affect the sensitivity), and has excellent long-term stability. This is because the operating principle of the sensor is a physical sensor whose sensing principle is simple, in which the temperature change of the heated sensing element caused by the difference in thermal conductivity between the sensing gas and air is measured. This is because a chemical reaction such as catalytic action is not used unlike the combustion sensor.

[Advantages over Other Types of Sensors] FIG. 5 shows the results of sensor output at a sensor temperature of 110 ° C. (ambient temperature of 25 ° C.). On the other hand, it is difficult to operate the semiconductor type sensor at such a low temperature in terms of stability and reproducibility, and it is necessary to devise such as adding a temperature pulse (400 ° C. or higher) to refresh the sensor. The catalytic combustion type sensor also has a problem in stability at such a low temperature because dirt adheres to the catalyst and the oxidation activity of the catalyst deteriorates. Further, the catalytic combustion sensor has a high sensor temperature due to catalytic combustion of high-concentration gas, and there is a risk of ignition and explosion of gasoline vapor. On the other hand, it can be seen that the heat conduction type sensor can realize a preferable situation with the sensor temperature hardly changing even with high-concentration gasoline / light oil vapor.

Further, the advantages of having each characteristic configuration are listed. [Advantages of adopting micro coil structure 1] The response speed (90% response) of the conventional heat conduction type sensor is as slow as about 10 seconds, and there is room for improvement in practical use. By adopting a micro coil structure, we have realized a gasoline / light oil identification device with a fast identification speed. The identification speed is within 0.35 seconds.
Further, when the conventional type heat conduction type sensor is used, the warming-up time, which takes 2 to 3 minutes after the power is turned on from the non-energized state, is greatly shortened within 2 seconds. For this reason, in the conventional element, it was necessary to actually use the power supply at all times, but by using this element, it is sufficient to turn on the power supply only when necessary, and electricity consumption is reduced. The risk of keeping the device at a high temperature will also be reduced. [Advantage 2 of adopting a micro coil structure] Furthermore, as an element used in a heat conduction sensor, anisotropic etching of silicon is used to construct a bridge structure or a cantilever structure on a silicon substrate. , There is a Pt minute thin film resistor formed thereon. The response speed of this element is fast. However, there are problems in thermal, mechanical and long-term stability, and various measures are required. On the other hand, the element used in the present invention is stable without any such problems. Moreover, a device manufactured by utilizing anisotropic etching of silicon has many steps in manufacturing. For example, there are processes such as a silicon substrate oxidation process, several pattern manufacturing processes, a dry etching process, an anisotropic etching process, a protective film manufacturing process, and the like, and each process consists of several small processes, which complicates manufacturing. And it's tough. Also, the equipment used for each process is expensive. On the other hand, the element used in the present invention is simple to manufacture, and the apparatus used for manufacturing can be inexpensive. Extremely speaking, it can be made by hand. Further, the element used in the present invention can be manufactured easily and inexpensively as compared with the conventional heat conduction type sensor. Therefore, the gasoline / light oil discriminating apparatus of the present invention can also be manufactured easily and inexpensively as compared with the conventional product.

[Advantage of Providing Flow Rate Relaxing Mechanism] When the measurement is a flow system, the heat conduction type sensor, which is a combination of thermometers, is affected by the flow rate. For this reason, when identification is performed by the flow system, it is necessary to devise a method to quickly bring the flow system into a constant state and mitigate the influence of the flow velocity. This is possible by installing a wire mesh, glass wool, baffle plate, etc. around the sensing element, and the wire mesh is adopted in the embodiment of the present invention.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a block diagram of a device configuration of an identification device of the present invention.

FIG. 2 is a front sectional view showing a detailed structure of a detection unit of the identification device of the present invention.

FIG. 3 is a side view showing a detailed structure of a detection unit of the identification device of the present invention.

FIG. 4 is a diagram showing a structure of a detection element of the heat conduction type sensor of the present invention.

FIG. 5 is a diagram showing an output of a sensor for a gasoline / light oil saturated vapor in the heat conduction type sensor of the present invention.

FIG. 6 is a diagram showing a response waveform of the heat conduction type sensor.

[Explanation of symbols]

2 detector 3 sensing elements 4 identification means 5 Inert thin film 6 wire rod 7 coils 11 Temperature compensation element 13 Suction and discharge mechanism 14 Identification section 15 Temperature detection means 17 Identification object 18 tanks

Continuation of front page (56) References JP-A-8-271468 (JP, A) JP-A-6-27101 (JP, A) JP-A 64-16957 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G01N 27/00-27/24 G01N 25/18

Claims (5)

(57) [Claims] 1. A gasoline / light oil identification device for identifying gasoline and light oil as an identification object, wherein a detection unit (2) to which vapor of any of the identification objects (17) is introduced has a surrounding atmosphere. Equipped with a sensing element (3) for a thermal conductivity sensor that outputs different output values according to thermal conductivity
The temperature of the heat conduction sensor in a standard atmosphere.
Compensation element (11), the sensing element (3) is an insulating
Inert thin film (5) made of heat-resistant inert material with
From the coated wire (6) whose main component is platinum (Pt)
Is a coil (7), and the discrimination target (17) is the gasoline or light oil based on the output value of the heat conduction type sensor that is sensitive to the steam guided to the detection unit (2). A gasoline / light oil identification device having an identification means (4) for identifying whether or not 2. The heat-resistant inert material is silica (Si
O ₂ ), alumina (Al ₂ O ₃ ), silicon nitride (Si
₃ N ₄ ), at least one selected from aluminum nitride (AlN), the thickness of the inert thin film (5) is 0.01 μm to 10 μm, and the wire diameter of the wire (6) is 5 μm to 12 μm. In the coil (7), the number of turns is 5 to 12 and the coil outer diameter is 50 μm.
m to 150 μm, and the pitch between the coils is 3 of the wire diameter.
The gasoline / light oil identification device according to claim 1, which is less than or equal to twice. 3. The detection unit (2) having the detection element (3) is provided with a suction / exhaust mechanism (13) for guiding volatile vapor of the identification object (17) by suction, and the detection element (3). (3) with a flow rate relief mechanism to relieve the flow rate of the volatile vapor flowing peripheral portion (23) according to claim 1 or 2
Gasoline / light oil identification device described. With 4. comprises temperature detecting means (15) for detecting the temperature in the tank for storing identification object (17) (18), the heat conduction output of the sensor to premeasured gas oil saturated steam By the temperature dependence index of the value,
Reference output value deriving means for obtaining a light oil reference output value of light oil saturated steam at the temperature detected by the temperature detecting means (15) is provided, and the identifying means is a value obtained by multiplying the light oil reference output value by a predetermined safety factor. The gasoline / light oil discrimination device according to any one of claims 1 to 3 , wherein is a threshold value (S) for discriminating between gasoline and light oil. To 5. Using gasoline and diesel identification apparatus according to claim 2, the identification method of the temperature was maintained to a predetermined temperature of 200 ° C. or less, and identifies the gasoline and light oil of the sensing element (3).