JP2020165755A - Temperature control method and temperature control device - Google Patents

Abstract

To suppress power consumption.SOLUTION: A temperature control method for measuring an electric characteristic value of a gas detection section when heated to a predetermined measured temperature and detecting target gas on the basis of the measured temperature and the electric characteristic value includes the steps of: performing pulse heating repeating heating and stopping to a first measured temperature at a predetermined cycle; and raising a temperature to a second measured temperature higher than the first measured temperature for a predetermined period when the target gas is detected at pulse heating. The first measured temperature is 200°C or more and 350°C or less, the second measured temperature is 350°C or more and 450°C or less, and the target gas detected when heated to the first measured temperature and the second measured temperature is methane.SELECTED DRAWING: Figure 2

Description

The present invention relates to a temperature control method and a temperature control device in a gas detection device that utilizes the fact that the electrical characteristic value of the gas detection unit changes upon contact with the target gas under specific conditions.

A gas detection part whose electrical characteristic value changes according to the target gas when it comes into contact with the target gas, a heater part that heats the gas detection part, a heating control part that controls heating by the heater part, and a gas. A gas detection device having a gas detection unit that measures an electrical characteristic value of a detection site and detects a target gas is known. In such a gas detection device, the heater part is controlled by the heating control unit to heat the gas detection part to an appropriate temperature according to the type of the target gas, and the electrical characteristic value (electricity) of the gas detection part. The target gas is detected based on the resistance value, voltage value, etc.).

For example, with an off state in between, high-temperature heating at 400 ° C. and low-temperature heating at 150 ° C. are repeated to detect methane as the target gas during high-temperature heating, and carbon monoxide as the target gas during low-temperature heating. Do.

Japanese Unexamined Patent Publication No. 2011-27752

However, the amount of electric power consumed increases during high-temperature heating, and in particular, many household gas detectors are battery-powered, and it is required to suppress the power consumption.

An object of the present invention is to suppress power consumption.

In order to achieve the above object, the temperature control method according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and measures the measurement temperature and the electrical. A temperature control method for detecting a target gas based on a characteristic value, which is a step of performing pulse heating in which heating and stopping to the first measurement temperature are repeated in a predetermined cycle, and during the pulse heating. When the target gas is detected, the step of raising the temperature to a second measurement temperature higher than the first measurement temperature for a predetermined time is provided, and the first measurement temperature is 200 ° C. or higher and 350 ° C. or lower. The second measurement temperature is 350 ° C. or higher and 450 ° C. or lower, and the target gas detected when heated to the first measurement temperature and the second measurement temperature is methane.

In this way, the first measurement temperature is set to the temperature selected from the range of 200 ° C. or higher and 350 ° C. or lower, and the second measurement temperature is set to the range higher than the first measurement temperature and 350 ° C. or higher and 450 ° C. or lower. The detection accuracy is higher only when the target gas is detected at the first measurement temperature, which is usually a low temperature instead of the selected temperature, and methane is detected at the first measurement temperature. The detection of methane is reconfirmed at the second measurement temperature, which is a high temperature with a high temperature and a low possibility of false detection. This makes it possible to accurately detect methane while suppressing power consumption.

Further, the temperature control method according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and is based on the measured temperature and the electrical characteristic value. A temperature control method for detecting a target gas, which is a step of performing pulse heating in which heating and stopping of heating and stopping the first measurement temperature and the second measurement temperature are performed in order, and a predetermined number of times. Each time the pulse heating is performed, the step of raising the temperature to a purge temperature higher than the measurement temperature for a predetermined time is provided, and the first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, and the temperature is raised to the first measurement temperature. The target gas detected when the temperature is increased is methane, the second measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the second measurement temperature is It is carbon monoxide, and the purge temperature is 350 ° C. or higher and 450 ° C. or lower.

In this way, by periodically raising the temperature to the purge temperature, non-target gas and the like are burned, surface adsorbed substances such as moisture and the like are removed to clean the surface, and the gas detection unit due to the surrounding environment. Fluctuations in methane detection sensitivity due to dirt on the surface of the gas are suppressed. Therefore, methane can be detected even when the measurement temperature is low, the measurement temperature can be lowered, and power consumption can be suppressed. In addition, power consumption can be suppressed by providing a heating stop period between heating to the measurement temperature. As a result, it is possible to suppress power consumption while detecting methane and carbon monoxide with high accuracy.

Further, the temperature control method according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and is based on the measured temperature and the electrical characteristic value. A temperature control method for detecting a target gas, in which heating and stopping to a first measurement temperature are performed, and then heating and stopping to a third measurement temperature lower than the first measurement temperature are performed. When the target gas is detected during the step of performing pulse heating in which the heat treatment to be performed is repeated at a predetermined cycle and the heating of the pulse heating to the first measurement temperature, the first measurement temperature is higher than the first measurement temperature. The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, the second measurement temperature is 350 ° C. or higher and 450 ° C. or lower, and the first measurement temperature includes a step of raising the temperature to the measurement temperature of 2 for a predetermined time. The target gas detected when heated to the measurement temperature and the second measurement temperature is methane, and the third measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the third measurement temperature is reached. The target gas detected when heated is carbon monoxide.

With such a configuration, it is possible to suppress power consumption while detecting methane and carbon monoxide with high accuracy.

Further, every time the pulse heating is performed a predetermined number of times, a step of raising the purge temperature to a purge temperature equal to or higher than the measurement temperature for a predetermined time is provided, and the purge temperature is preferably 350 ° C. or higher and 450 ° C. or lower.

In this way, by periodically raising the temperature to the purge temperature, non-target gas and the like are burned, surface adsorbed substances such as moisture and the like are removed to clean the surface, and the gas detection unit due to the surrounding environment. Fluctuations in the detection sensitivity of the target gas due to dirt on the surface of the gas are suppressed. As a result, the target gas can be detected even when the measurement temperature is low, the measurement temperature can be lowered, and the power consumption can be suppressed.

Further, the temperature control device according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and is based on the measured temperature and the electrical characteristic value. A temperature control device used for a gas detection device that detects a target gas, the temperature control unit includes a heater unit that heats the gas detection unit and a heating control unit that controls the heating operation of the heater unit. , The pulse heating is performed by repeating heating and stopping to the first measurement temperature at a predetermined cycle, and when the target gas is detected during the pulse heating, the second measurement temperature is higher than the first measurement temperature. The temperature is raised to the measurement temperature for a predetermined time, the first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, the second measurement temperature is 350 ° C. or higher and 450 ° C. or lower, the first measurement temperature and the first measurement temperature. The target gas detected when heated to the measurement temperature of 2 is methane.

In this way, the target gas is usually detected at the first measurement temperature, which is a low temperature instead of being inferior in detection accuracy, and the detection accuracy is higher only when it is considered that methane is detected at the first measurement temperature. , Reconfirm the detection of methane at the second measurement temperature, which is a high temperature with a low possibility of false positives. This makes it possible to accurately detect methane while suppressing power consumption.

Further, the temperature control device according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and is based on the measured temperature and the electrical characteristic value. A temperature control device used for a gas detection device that detects a target gas, the temperature control unit includes a heater unit that heats the gas detection unit and a heating control unit that controls the heating operation of the heater unit. , The first measurement temperature and the second measurement temperature are heated and stopped in order. The pulse heating is repeated, and the purge is higher than the measurement temperature every time the pulse heating is performed a predetermined number of times. The target gas detected when the temperature is raised to a temperature for a predetermined time, the first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, and the temperature is increased to the first measurement temperature is methane, and the second measurement temperature is obtained. The measurement temperature is 60 ° C. or higher and 200 ° C. or lower, the target gas detected when heated to the second measurement temperature is carbon monoxide, and the purge temperature is 350 ° C. or higher and 450 ° C. or lower. ..

In this way, by periodically raising the temperature to the purge temperature, non-target gas and the like are burned, surface adsorbed substances such as moisture and the like are removed to clean the surface, and the gas detection unit due to the surrounding environment. Fluctuations in methane detection sensitivity due to dirt on the surface of the gas are suppressed. Therefore, methane can be detected even when the measurement temperature is low, the measurement temperature can be lowered, and power consumption can be suppressed. In addition, power consumption can be suppressed by providing a heating stop period between heating to the measurement temperature. As a result, it is possible to suppress power consumption while detecting methane and carbon monoxide with high accuracy.

Further, the temperature control device according to the embodiment of the present invention measures the electrical characteristic value of the gas detection unit when heated to a predetermined measurement temperature, and is based on the measured temperature and the electrical characteristic value. A temperature control device used for a gas detection device that detects a target gas, the temperature control unit includes a heater unit that heats the gas detection unit and a heating control unit that controls the heating operation of the heater unit. After heating and stopping to the first measurement temperature, pulse heating is performed by repeating the heat treatment of heating and stopping to a third measurement temperature lower than the first measurement temperature at a predetermined cycle. At the same time, when the target gas is detected during heating of the pulse heating to the first measurement temperature, the temperature is raised to a second measurement temperature higher than the first measurement temperature for a predetermined time, and the first measurement temperature is raised. The measurement temperature of is 200 ° C. or higher and 350 ° C. or lower, the second measurement temperature is 350 ° C. or higher and 450 ° C. or lower, and is detected when heated to the first measurement temperature and the second measurement temperature. The target gas is methane, the third measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the third measurement temperature is carbon monoxide.

With such a configuration, it is possible to suppress power consumption while detecting methane and carbon monoxide with high accuracy.

Further, it is preferable that the heating control unit raises the purge temperature to a purge temperature equal to or higher than the measurement temperature for a predetermined time each time the pulse heating is performed a predetermined number of times, and the purge temperature is 350 ° C. or higher and 450 ° C. or lower.

In this way, by periodically raising the temperature to the purge temperature, non-target gas and the like are burned, surface adsorbed substances such as moisture are removed from the surface adsorbed part of the gas detection part, and the surface is cleaned. Fluctuations in the detection sensitivity of the target gas due to dirt on the surface of the gas are suppressed. As a result, the target gas can be detected even when the measurement temperature is low, the measurement temperature can be lowered, and the power consumption can be suppressed.

It is a schematic diagram which shows the outline of the gas detection device. It is a figure which illustrates the heating pattern of pulse heating. It is a figure which shows the target gas detection flow in another embodiment.

The gas detection device 100 according to the present embodiment will be described with reference to FIG. The gas detection device 100 includes a sensor element 20 (an example of a gas sensor), a heating control unit 12, a gas detection unit 13 (an example of a control unit), and a temperature detection unit 14 (an example of an environment measurement unit). The sensor element 20 has at least a gas detection layer 10 (an example of a gas detection unit), a catalyst layer 11 (an example of a catalyst unit), and a heater layer 6 (an example of a heater unit).

The gas detection device 100 heats the gas detection layer 10 to an appropriate temperature according to the type of the target gas by energizing the heater layer 6 by the heating control unit 12, and electrically the gas detection layer 10. The target gas is detected based on the characteristic values (electrical resistance value, voltage value, etc.). Such a gas detection device 100 can be used for detecting various types of target gases, but the following is an example of an embodiment in which carbon monoxide and methane are detected as target gases. First, a specific configuration of the sensor element 20 will be described.

(Sensor element)
The sensor element 20 is supported by the silicon substrate 1 to form a diaphragm. The sensor element 20 has a support layer 5, an insulating layer 7, a gas detection layer 10, and a catalyst layer 11. The support layer 5 is formed on the silicon substrate 1, and the heater layer 6 is formed on the support layer 5. The insulating layer 7 covers the entire heater layer 6 and is formed on the support layer 5. A pair of bonding layers 8 are formed on the insulating layer 7, and an electrode layer 9 is formed on the bonding layer 8. A gas detection layer 10 is formed between the pair of electrode layers 9 on the insulating layer 7. The catalyst layer 11 is formed on the insulating layer 7 so as to cover the gas detection layer 10. The sensor element 20 may have a bridge structure, and the heater layer 6 may also be used as an electrode.

Supporting layer 5, the thermal oxide film 2, and _{the Si} 3 _{N 4} film 3, and SiO ₂ film 4 is formed by stacking a. The heater layer 6 generates heat when energized to heat the gas detection layer 10 and the catalyst layer 11.

The gas detection layer 10 is a semiconductor layer containing a metal oxide as a main component. For example, the gas detection layer 10 is a mixture containing tin oxide (SnO ₂ ) as a main component. The electric resistance value of the gas detection layer 10 changes due to contact with the target gas. The gas detection layer 10 may be a thin film having a thickness of about 0.2 to 1.6 μm, or may be a film (thick film) having a thickness exceeding 1.6 μm.

The catalyst layer 11 is heated by the heater layer 6 to a high temperature, and the active (combusting) gas is burned at that temperature. Further, at that temperature, an inert flammable gas, which is the target gas, is permeated and diffused to reach the gas detection layer 10. As a result, the detection accuracy of flammable gas (for example, CH ₄ (methane), C ₃ H ₆ O (acetone), C ₃ H ₈ (propane), etc.) is improved by appropriately controlling the heating temperature. .. In other words, when detecting a flammable gas such as methane, the catalyst layer 11 does not reach the gas detection layer 10 by burning a reducing gas (non-target gas) such as hydrogen gas or alcohol gas other than the target gas. As a result, the gas detection device 100 has a function of providing gas selectivity. Therefore, the gas detection layer 10 can efficiently detect a flammable gas that is a target gas such as methane that has permeated and diffused through the catalyst layer 11. At low temperatures (160 ° C or lower), gases other than CO (carbon monoxide) do not react in the temperature range even in the gas detection layer 10 (they do not react unless the temperature is 200 ° C or higher), so it is assumed that the gas detection layer 10 has been reached. Therefore, the catalyst layer 11 is not always necessary when detecting only carbon monoxide.

The catalyst layer 11 is configured by supporting a catalyst metal on a carrier containing a metal oxide as a main component. Specifically, metal oxides supporting a catalyst metal are formed by being bonded to each other via a binder.

In detecting combustible gases such as methane, the catalytic metal, the interference gas can cause erroneous detection when the detection of the target gas (reducing gas other unclassified gases such as ethanol and H _{2 (hydrogen)),} oxidation A metal that acts as a catalyst that can be removed is used. When detecting flammable gas such as methane, palladium (Pd), platinum (Pt), rhodium (Rh), iridium (Ir) and the like can be used as the catalyst metal. For example, palladium, platinum and iridium can be used. , Rhodium containing at least one is used.

As a carrier for supporting the catalyst metal, transition metal oxide or the like is used, and for example, alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ). , Lantern oxide (La ₂ O ₃ ), titanium oxide (TIO ₂ ), hafnium oxide (HfO ₂ ), niobium oxide (Nb ₂ O ₅ ), or tantalum oxide (Ta ₂ O ₅ ) is used.

As the binder to which the carrier is bound, fine powder of metal oxide, for example, zirconium oxide, fine silica powder, silica sol, magnesia and the like is used. If a small amount is used as a binder, alumina fine powder or alumina sol can be used as long as the function of the catalyst layer 11 is not impaired. Further, the above-mentioned catalyst metal, metal oxide as a carrier, and binder may be used alone or in combination of two or more.

The amount (total content) of the catalyst metal contained in the catalyst layer 11 is preferably 0.3 to 9% by mass with respect to the total mass of the catalyst metal and the carrier, and more preferably the catalyst metal and the carrier. It is preferable that the total mass of the above is 0.5% by mass to 6% by mass.

(Heating control unit)
The heating control unit 12 controls energization of the heater layer 6 to perform a heating operation in which the heater layer 6 is energized to heat the gas detection layer 10 and a non-heating operation in which the heater layer 6 is not energized (heating of the gas detection layer 10). Non-heating operation to stop) and. Further, the heating control unit 12 can heat the heater layer 6 to an arbitrary temperature set by controlling the energizing voltage or the energizing current for the heater layer 6.

Specifically, the heating control unit 12 receives power from a power source such as a battery (not shown), energizes the heater layer 6 of the sensor element 20, and heats the sensor element 20. The heating temperature, that is, the ultimate temperature of the gas detection layer 10 and the catalyst layer 11, is controlled by, for example, changing the voltage applied to the heater layer 6.

The heating control unit 12 energizes the heater layer 6 based on the ambient temperature detected by the temperature detection unit 14. Specifically, the heating control unit 12 controls the heater drive voltage VH applied to the heater layer 6 based on the ambient temperature. For example, with an ambient temperature of 20 ° C. as a reference temperature, the heater drive voltage VH is set relatively low when the ambient temperature is high, and the heater drive voltage VH is set relatively high when the ambient temperature is low. That is, with the ambient temperature of 20 ° C as the reference temperature, the electric power for driving the heater is controlled to be relatively low when the ambient temperature is high, and the electric power for driving the heater is relatively high when the ambient temperature is low. The heating control unit 12 controls the temperature of the gas detection layer 10 to be a constant measurement temperature regardless of the ambient temperature.

(Gas detector)
The gas detection unit 13 measures the electrical characteristic value of the gas detection layer 10 to detect the target gas. For example, the gas detection unit 13 measures the resistance value of the gas detection layer 10 by measuring the electric resistance value (electrical characteristic value) between the pair of electrode layers 9, and the presence of the target gas from the change. And the concentration of the target gas are detected.

The temperature detection unit 14 detects the gas detection layer 10, or the gas detection layer 10 and the temperature around the gas detection layer 10 (hereinafter, collectively referred to as ambient temperature). Specifically, the temperature detection unit 14 is a temperature sensor such as a thermistor. Further, the temperature of the heater layer 6 (almost the same as the temperature of the gas detection layer 10) can be detected by measuring the resistance value of the heater layer 6. The temperature detected by the temperature detection unit 14 is sent to the heating control unit 12.

(Heating operation)
In the target gas detection operation, the heating control unit 12 performs pulse heating when heating the gas detection unit 13 of the sensor element 20. In the pulse heating, the temperature is repeatedly raised to a measurement temperature suitable for detecting the target gas for a predetermined time at a predetermined interval, and each time the temperature is raised to the measurement temperature a predetermined number of times, the purge temperature is reached. It is a heating operation that raises the temperature for a predetermined time. Further, only the operation of repeating raising the temperature to a measurement temperature suitable for detecting the target gas for a predetermined time at a predetermined interval is also referred to as pulse heating. The gas detection layer 10 may be configured to detect a plurality of target gases. In this case, the heating control unit 12 can heat the target gas to a measurement temperature suitable for detecting each target gas in an arbitrary order with a predetermined interval. In the following description, a case where carbon monoxide and methane are detected as target gases will be described as an example.

Pulse heating when carbon monoxide and methane are detected as the target gas is performed, for example, as shown in FIG. In this pulse heating, a heating operation for detecting carbon monoxide, which is heated to a measurement temperature for detecting carbon monoxide, and a heating operation for detecting methane, which is heated to a measurement temperature for detecting methane, are alternately performed to detect carbon monoxide. Every time the heating operation for heating and the heating operation for methane detection are repeated a predetermined number of times, the heating operation for purging, which is heated to the purge temperature, is performed. For example, the heating operation for carbon monoxide detection and the heating operation for methane detection are performed once at predetermined intervals between 30 seconds and 60 seconds, and every time this is performed three times, the heating operation for purging is performed. It is done once.

In the methane detection heating operation, the heating control unit 12 controls the energization of the heater layer 6 based on the ambient temperature to generate heat in the heater layer 6, and heats the gas detection layer 10 and the catalyst layer 11 to the methane detection temperature. It is an operation to do. The control state to the methane detection temperature is also referred to as high drive. The methane detection temperature is a predetermined temperature of 200 ° C. or higher and 350 ° C. or lower. For example, the temperature for detecting methane is 250 ° C., and the presence and concentration of methane are detected at this temperature.

Specifically, the heating control unit 12 controls the energization of the heater layer 6 to bring the gas detection layer 10 and the catalyst layer 11 to the methane detection temperature, and keeps the temperature between 0.05 seconds and 0.5 seconds. Hold. During this period, the gas detection unit 13 measures the resistance value of the gas detection layer 10 and detects the presence of methane and its concentration from the resistance value. When the presence of methane is detected, the gas detection device 100 generates an alarm sound or the like from an alarm device (not shown). The gas detection device 100 can also display the methane concentration on a display device (not shown) at the same time.

In the heating operation for methane detection, the heating control unit 12 energizes the heater layer 6 based on the ambient temperature detected by the temperature detection unit 14. Specifically, the heating control unit 12 controls the heater drive voltage VH applied to the heater layer 6 based on the ambient temperature. For example, with an ambient temperature of 20 ° C. as a reference temperature, the heater drive voltage VH is set relatively low when the ambient temperature is high, and the heater drive voltage VH is set relatively high when the ambient temperature is low. That is, with the ambient temperature of 20 ° C as the reference temperature, the electric power for driving the heater is controlled to be relatively low when the ambient temperature is high, and the electric power for driving the heater is relatively high when the ambient temperature is low. Is controlled.

In the heating operation for carbon monoxide detection, the heating control unit 12 controls the energization of the heater layer 6 based on the temperature detected by the temperature detection unit 14 to generate heat in the heater layer 6, and the gas detection layer 10 and the catalyst layer are heated. This is an operation of heating 11 to a temperature for detecting carbon monoxide. The carbon monoxide detection temperature is a predetermined temperature of 60 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 160 ° C. or lower. For example, the temperature for detecting carbon monoxide can be 150 ° C. Further, since the heating control unit 12 drives the carbon monoxide detection temperature at a lower voltage than the methane detection heating operation, the control state to the carbon monoxide detection temperature is Low drive with respect to the High drive. Also called.

Specifically, the heating control unit 12 controls the energization of the heater layer 6 to heat the gas detection layer 10 and the catalyst layer 11 to the temperature for detecting carbon monoxide, for 0.05 seconds to 10 seconds. Keep the temperature. During this period, the gas detection unit 13 measures the resistance value of the gas detection layer 10 and detects the presence of CO (carbon monoxide) and its concentration from the resistance value. When the presence of carbon monoxide is detected, the gas detection device 100 generates an alarm sound or the like from an alarm device (not shown). Further, the gas detection device 100 can also display the concentration of carbon monoxide on a display device (not shown) at the same time. The alarm sound at these times can be made different from the alarm sound when methane is detected.

In the gas detection device 100 of the present embodiment, the heating operation for detecting carbon monoxide is performed by controlling the heating by the heater layer 6 based on the ambient temperature, and the temperature is always kept constant regardless of the ambient temperature. As a result, the amount of CO adsorbed (surface coverage) on the surface of the detection layer (tin oxide) during CO detection in Low drive is kept constant, and the variation in CO sensitivity due to the variation in the amount of CO adsorption can be suppressed. it can.

In the purging heating operation, the heating control unit 12 controls the energization of the heater layer 6 based on the ambient temperature to generate heat in the heater layer 6, and the gas detection layer 10 and the catalyst layer 11 are higher than the methane detection temperature. It is an operation of heating to the purge temperature. The control state to the purge temperature is also referred to as purge drive. At the purge detection temperature, surface adsorbents (moisture, dirt, etc.) of the gas detection layer 10 that cannot be completely removed by Low drive can be removed by heating. The purging temperature is a predetermined temperature of 350 ° C. or higher and 450 ° C. or lower. For example, the purging temperature is 400 ° C., and at this temperature, hydrogen, carbon monoxide, etc. are burned to remove surface adsorbents of the gas detection layer 10 such as moisture to clean the surface, and gas detection by the surrounding environment is performed. It suppresses fluctuations in the detection sensitivity of carbon monoxide and methane due to dirt on the surface of the part.

Therefore, the sensitivity for detecting methane even at a relatively low measurement temperature can be ensured, and methane can be detected at a low temperature. In addition, the purging heating operation for cleaning the surface of the gas detection layer 10 needs to be performed a smaller number of times than the methane detection heating operation and the carbon monoxide detection heating operation. These make it possible to reduce the power consumption of the gas detection device 100. That is, the power consumption of the gas detection device 100 can be reduced by setting the methane detection temperature to a low temperature and suppressing the number of times of heating to the purge temperature to the minimum necessary.

In the present embodiment, the carbon monoxide detection heating operation and the methane detection heating operation are pulse heatings that are repeatedly performed with a pause operation (an operation of stopping the energization of the heater layer 6). The time of each operation can be set and changed as appropriate, and the pause operation can be omitted. Further, the execution frequencies of the heating operation for detecting carbon monoxide and the heating operation for detecting methane may be the same or different. For example, the gas detection device 100 is configured so that the heating operation for methane detection and the heating operation for purging are performed once each time the heating operation for carbon monoxide detection is performed five times, and the methane detection is performed according to the usage environment. -The frequency of cleaning operations may be reduced.

(Another embodiment)
<1> In the above embodiment, when methane is detected in the heating operation for methane detection, an alarm indicating that methane is detected immediately is issued, but when methane is detected in the heating operation for methane detection, the measurement temperature is set as described above. The temperature may be raised to a methane re-detection measurement temperature higher than the measurement temperature in the methane detection heating operation, and the presence and concentration of methane may be detected at this methane re-detection measurement temperature. The measurement temperature for methane re-detection at this time is a predetermined temperature of 350 ° C. or higher and 450 ° C. or lower, for example, 400 ° C. Then, even if methane is detected in the heating operation for methane detection, an alarm indicating that methane is detected is not issued, and an alarm indicating that methane is detected is issued only after methane is detected at the measurement temperature for methane re-detection. You may.

The detection sensitivity of methane is higher when the measurement temperature is 350 ° C. or higher and 450 ° C. or lower than when the measurement temperature is 200 ° C. or higher and 350 ° C. or lower. Therefore, when methane is detected in the heating operation for methane detection, methane is detected again at the measurement temperature for methane re-detection, so that methane is detected with higher accuracy. Further, since the measurement temperature that is periodically heated is lower than the measurement temperature for methane re-detection, which has high detection accuracy, it is possible to suppress power consumption while detecting the target gas with high accuracy.

Specifically, as shown in FIG. 3, when the heating operation for purging is performed every time the heating operation for methane detection and the heating operation for carbon monoxide detection are repeated in a predetermined cycle (also referred to as a normal operation). In addition, the heating control unit 12 is periodically driven to heat to the measurement temperature for methane detection (for example, heating to 250 ° C.) (step # 1), and it is confirmed whether or not methane is detected (step). # 2). When methane is detected (step # 2 = Yes), the heating control unit 12 is driven to heat to the measurement temperature for methane redetection (for example, heating to 400 ° C.) (step # 3), and methane is detected again. It is confirmed whether or not it has been done (step # 4). Again, if methane is detected (step # 4 = Yes), an alarm indicating that methane has been detected is issued (step # 5). If no methane is detected (step # 4 = No), normal operation is resumed. When methane is not detected at the measurement temperature for methane detection (step # 2 = No), the heating control unit 12 is driven to heat to the measurement temperature for carbon monoxide output (for example, heating to 150 ° C.). (Step # 6). Next, it is confirmed whether or not carbon monoxide is detected (step # 7). When carbon monoxide is detected (step # 7 = Yes), an alarm indicating that carbon monoxide has been detected is issued (step # 8). When carbon monoxide is not detected (step # 7 = No), it is confirmed whether or not the heating operation for detecting methane and the heating operation for detecting carbon monoxide are repeated in a predetermined cycle (step # 9). When the predetermined cycle is repeated (step # 9 = Yes), the heating control unit 12 is driven to heat to the purge temperature (for example, to heat to 400 ° C.) (step # 10). If the predetermined cycle is not repeated (step # 9 = No), the normal operation is returned and the process is continued.

In the example shown in FIG. 3, the purging heating operation was performed, but the purging heating operation does not necessarily have to be performed.

<2> The sensor element 20 is not limited to the above configuration, and a gas sensor having any configuration can be used.

1 Silicon substrate 2 Thermal oxide film 3 Si ₃ N ₄ film 4 SiO ₂ film 5 Support layer 6 Heater layer (heater part)
7 Insulation layer 8 Bonding layer 9 Electrode layer 10 Gas detection layer (gas detection unit)
11 Catalyst layer (catalyst part)
12 Heating control unit 13 Gas detection unit 14 Temperature detection unit 20 Sensor element (gas sensor)
100 gas detector

Claims (8)

A temperature control method for measuring an electrical characteristic value of a gas detection unit when heated to a predetermined measurement temperature and detecting a target gas based on the measured temperature and the electrical characteristic value.
A process of performing pulse heating in which heating and stopping to the first measurement temperature are repeated at a predetermined cycle, and
When the target gas is detected during the pulse heating, the step of raising the temperature to a second measurement temperature higher than the first measurement temperature for a predetermined time is provided.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower.
The second measurement temperature is 350 ° C. or higher and 450 ° C. or lower.
A temperature control method in which the target gas detected when heated to the first measurement temperature and the second measurement temperature is methane. A temperature control method for measuring an electrical characteristic value of a gas detection unit when heated to a predetermined measurement temperature and detecting a target gas based on the measured temperature and the electrical characteristic value.
A step of performing pulse heating in which the heat treatment of heating and stopping the first measurement temperature and the second measurement temperature in order is repeated, and
Each time the pulse heating is performed a predetermined number of times, a step of raising the temperature to a purge temperature higher than the measurement temperature for a predetermined time is provided.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, and the target gas detected when heated to the first measurement temperature is methane.
The second measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the second measurement temperature is carbon monoxide.
A temperature control method in which the purge temperature is 350 ° C. or higher and 450 ° C. or lower. A temperature control method for measuring an electrical characteristic value of a gas detection unit when heated to a predetermined measurement temperature and detecting a target gas based on the measured temperature and the electrical characteristic value.
A step of performing pulse heating in which a heat treatment of heating and stopping to a first measurement temperature and then heating and stopping to a third measurement temperature lower than the first measurement temperature is repeated at a predetermined cycle. When,
When the target gas is detected during heating to the first measurement temperature of the pulse heating, the step of raising the temperature to a second measurement temperature higher than the first measurement temperature for a predetermined time is provided.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower.
The second measurement temperature is 350 ° C. or higher and 450 ° C. or lower.
The target gas detected when heated to the first measurement temperature and the second measurement temperature is methane.
A temperature control method in which the third measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the third measurement temperature is carbon monoxide. Each time the pulse heating is performed a predetermined number of times, a step of raising the temperature to a purge temperature equal to or higher than the measurement temperature for a predetermined time is provided.
The temperature control method according to claim 1 or 3, wherein the purge temperature is 350 ° C. or higher and 450 ° C. or lower. A temperature control device used in a gas detection device that measures the electrical characteristic value of a gas detector when heated to a predetermined measurement temperature and detects the target gas based on the measured temperature and the electrical characteristic value. There,
A heater unit that heats the gas detection unit and
A heating control unit that controls the heating operation of the heater unit is provided.
The heating control unit performs pulse heating in which heating to the first measurement temperature and stopping are repeated at a predetermined cycle, and at the same time,
When the target gas is detected during the pulse heating, the temperature is raised to a second measurement temperature higher than the first measurement temperature for a predetermined time.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower.
The second measurement temperature is 350 ° C. or higher and 450 ° C. or lower.
A temperature control device in which the target gas detected when heated to the first measurement temperature and the second measurement temperature is methane. A temperature control device used in a gas detection device that measures the electrical characteristic value of a gas detector when heated to a predetermined measurement temperature and detects the target gas based on the measured temperature and the electrical characteristic value. There,
A heater unit that heats the gas detection unit and
A heating control unit that controls the heating operation of the heater unit is provided.
The heating control unit performs pulse heating by repeating a heat treatment of sequentially heating and stopping the first measurement temperature and the second measurement temperature, and also performing pulse heating.
Each time the pulse heating is performed a predetermined number of times, the temperature is raised to a purge temperature higher than the measurement temperature for a predetermined time.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower, and the target gas detected when heated to the first measurement temperature is methane.
The second measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the second measurement temperature is carbon monoxide.
A temperature control device in which the purge temperature is 350 ° C. or higher and 450 ° C. or lower. A temperature control device used in a gas detection device that measures the electrical characteristic value of a gas detector when heated to a predetermined measurement temperature and detects the target gas based on the measured temperature and the electrical characteristic value. There,
A heater unit that heats the gas detection unit and
A heating control unit that controls the heating operation of the heater unit is provided.
The heating control unit performs a heat treatment for heating and stopping to a first measurement temperature and then heating and stopping to a third measurement temperature lower than the first measurement temperature at a predetermined cycle. With repeated pulse heating
When the target gas is detected during the heating of the pulse heating to the first measurement temperature, the temperature is raised to a second measurement temperature higher than the first measurement temperature for a predetermined time.
The first measurement temperature is 200 ° C. or higher and 350 ° C. or lower.
The second measurement temperature is 350 ° C. or higher and 450 ° C. or lower.
The target gas detected when heated to the first measurement temperature and the second measurement temperature is methane.
A temperature control device in which the third measurement temperature is 60 ° C. or higher and 200 ° C. or lower, and the target gas detected when heated to the third measurement temperature is carbon monoxide. Each time the pulse heating is performed a predetermined number of times, the heating control unit raises the temperature to a purge temperature equal to or higher than the measurement temperature for a predetermined time.
The temperature control device according to claim 5 or 7, wherein the purge temperature is 350 ° C. or higher and 450 ° C. or lower.

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