Gas detector and gas sensor control method

Abstract

A gas detector suitable for use in harsh environments where gas sensors are likely to deteriorate, while suppressing an increase in the number of parts and an increase in the size of the device, is provided. [Solution] This gas detector 100 is a gas detector that detects a target gas, and comprises a sensor section 1 including multiple gas sensors 10 of the same type mounted on the same substrate 14, and a control section 2 that detects the target gas based on the output values ​​30 of the multiple gas sensors 10, and the control section 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of the multiple gas sensors 10.

Description

[Technical Field]

[0001] The present invention relates to a gas detector and a method for controlling a gas sensor. [Background technology]

[0002] BACKGROUND ART Gas detectors have been known in the past (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a substance detection device (gas detector) equipped with a matrix sensor having a plurality of sensor units. This gas detector is configured to determine whether the sensor units have deteriorated, and if it is determined that the sensor units have deteriorated, to use unused sensor units among the plurality of sensor units. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-025728 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the substance detection device (gas detector) described in Patent Document 1, if a sensor unit (gas sensor) is determined to be degraded, that gas sensor is not used. Therefore, if the gas detector is installed in a harsh environment where gas sensors are likely to deteriorate, the rate of deterioration of each gas sensor will increase, resulting in an earlier replacement period for the matrix sensor (sensor unit) if the same number of sensors is used as in the past. Furthermore, extending the replacement period requires increasing the number of sensors, which results in inconveniences such as an increase in the number of parts (increased costs) and an increase in the size of the device. Therefore, there is a need for a gas detector and a gas sensor control method that are suitable for use in harsh environments where gas sensors are likely to deteriorate, while suppressing the increase in the number of parts and the increase in size of the device.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a gas detector and a gas sensor control method that are suitable for use in harsh environments where gas sensors are likely to deteriorate, while suppressing an increase in the number of parts and an increase in the size of the device. [Means for solving the problem]

[0007] To achieve the above object, a gas detector according to a first aspect of the present invention is a gas detector for detecting a target gas, comprising: a sensor unit including a plurality of gas sensors of the same type mounted on a single chip; and a control unit for detecting the target gas based on output values ​​of the plurality of gas sensors, wherein the control unit is configured to perform control for correcting the output value of a deteriorated gas sensor based on the output values ​​of the plurality of gas sensors. Note that a deteriorated gas sensor refers to a gas sensor whose output value is outside a predetermined range or a gas sensor whose output value deviates by a predetermined percentage from the output values ​​of other gas sensors.

[0008] In a gas detector according to a first aspect of the present invention, the control unit is configured to perform control to correct the output value of a deteriorated gas sensor based on the output values ​​of the multiple gas sensors. This allows the deteriorated gas sensor to continue to be used to detect the target gas by correcting the output value. Therefore, the life of the gas sensors can be extended without increasing the number of gas sensors. As a result, a gas detector suitable for use in harsh environments where gas sensors are likely to deteriorate can be provided, while suppressing an increase in the number of parts and an increase in the size of the device. The life of a gas sensor has the same meaning as the remaining life, which indicates how long a gas sensor can be used in the future.

[0009] In the gas detector according to the first aspect, the control unit is preferably configured to acquire output value information corresponding to gas concentrations based on output values ​​of the plurality of gas sensors, and to correct any gas sensor among the plurality of gas sensors that outputs an output value outside a predetermined range from the output value information as a degraded gas sensor. This configuration allows the output value of a degraded gas sensor to be corrected based on the output value information acquired from the output values ​​of the plurality of gas sensors, without using a reference gas for calibration. As a result, even if the gas detector is installed in an environment where calibration is difficult, correction of a degraded gas sensor can be performed. Even if gas sensors are manufactured using the same process, the likelihood of degradation and the degree of progression of degradation may differ from one another due to manufacturing errors. Therefore, even if the plurality of gas sensors are used under the same conditions, the degree of degradation may vary. Furthermore, if dust adheres to one of the plurality of gas sensors or if the plurality of gas sensors are unevenly exposed to a degrading atmosphere, the degree of degradation may differ from one another, resulting in variation in the degree of degradation. Therefore, as described above, by correcting the output value of a gas sensor that has deteriorated based on output value information obtained based on the output values ​​of multiple gas sensors, it is possible to easily correct the sensor unit that has multiple gas sensors with varying degrees of deterioration.

[0010] In this case, the control unit is preferably configured to determine the degree of deterioration of the sensor unit based on any of the pre-correction output values, the correction state, and the output value information of the multiple gas sensors. With this configuration, the life of the sensor unit can be easily predicted based on the degree of deterioration of the sensor unit. As a result, it is possible to easily predict the time to replace the sensor unit.

[0011] In the above-described configuration in which the control unit determines the degree of deterioration of the sensor unit, the control unit is preferably configured to notify the user that the sensor unit or the gas detector needs to be replaced based on the degree of deterioration. Generally, gas sensors are set with a service life that is shorter than the period during which they can be used. Therefore, replacement becomes necessary in a shorter period than the actual lifespan of the gas sensor. Therefore, by configuring the control unit to notify the user that the sensor unit or the gas detector needs to be replaced based on the degree of deterioration of the gas sensor, the sensor unit or the gas detector can be used until the end of its actual service life, at which point it can no longer be used. As a result, the sensor unit or the gas detector can be used for a period longer than its typical service life.

[0012] In the gas detector according to the first aspect, the control unit is preferably configured to, when any of the plurality of gas sensors has deteriorated, notify the user that a deteriorated gas sensor has been detected. With this configuration, the user can easily recognize that a gas sensor has deteriorated.

[0013] In this case, the control unit is preferably configured to, when notifying the user of a deteriorated gas sensor, differentiate between the manner of notification when the corrected gas sensor can be continued and the manner of notification when the corrected gas sensor cannot be continued. This allows the user to easily determine whether the corrected gas sensor can be continued from the manner of notification. As a result, the user can easily determine when it is time to replace the gas detector.

[0014] In the gas detector according to the first aspect, the detection target gas preferably includes a first gas sensor of a predetermined type and a second gas sensor of a different type from the first gas sensor, the plurality of gas sensors including a first gas sensor for detecting the first gas sensor and a second gas sensor for detecting the second gas sensor, and the control unit is configured to correct the output value of a deteriorated first gas sensor based on output values ​​of the plurality of first gas sensors and to correct the output value of a deteriorated second gas sensor based on output values ​​of the plurality of second gas sensors. With this configuration, even if the first gas sensor and the second gas sensor deteriorate, the deteriorated first gas sensor and the deteriorated second gas sensor can continue to be used to detect their respective detection target gases by correcting the output values ​​based on the respective output values. This improves the reliability of the first gas sensor and the second gas sensor, thereby improving the reliability of the gas detector for detecting multiple types of detection target gases. As a result, a gas detector capable of detecting multiple types of detection target gases in harsh environments can be provided.

[0015] A gas sensor control method according to a second aspect of the present invention comprises the steps of: detecting a target gas based on output values ​​of a plurality of gas sensors of the same type mounted on the same chip; determining which of the plurality of gas sensors has deteriorated based on the output values ​​of the plurality of gas sensors; correcting the output value of the deteriorated gas sensor based on the output values ​​of the plurality of gas sensors; and continuing to use the corrected deteriorated gas sensor for detecting the target gas.

[0016] A gas sensor control method according to a second aspect of the present invention includes the steps of correcting an output value of a gas sensor that has deteriorated among a plurality of gas sensors based on the output values ​​of the plurality of gas sensors, and continuing to use the deteriorated gas sensor after the correction for detecting a target gas. This makes it possible to extend the life of the gas sensor, as with the gas detector according to the first aspect, and therefore provides a gas sensor control method that is suitable for use in harsh environments where gas sensors are likely to deteriorate. [Effects of the Invention]

[0017] As described above, the present invention can provide a gas detector and a gas sensor control method suitable for use in harsh environments where gas sensors are likely to deteriorate. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a block diagram showing a control configuration of the gas detector according to the embodiment. [Figure 2] 1 is a circuit diagram showing an example of the configuration of a gas sensor of a gas detector according to an embodiment; [Figure 3] 1 is a schematic plan view showing an example of the configuration of a gas sensor of a gas detector according to an embodiment; [Figure 4] 1 is a schematic cross-sectional view showing an example of the configuration of a gas sensor of a gas detector according to an embodiment; [Figure 5] 6 is a graph illustrating a configuration in which a control unit of a gas detector according to an embodiment determines whether degradation has occurred in a gas sensor. [Figure 6] 10 is a flowchart illustrating a method for controlling a gas sensor in a gas detector according to an embodiment. [Figure 7] FIG. 10 is a block diagram showing a control configuration of a gas detector according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] The configuration of a gas detector 100 according to one embodiment will be described with reference to FIGS.

[0021] (Gas detector configuration) The gas detector 100 of this embodiment is a gas detector that detects a detection target gas. When the gas detector 100 detects the detection target gas, it outputs an alarm to notify the user of a gas leak or the like. The detection target gas is a gas that the gas detector 100 is to detect. For example, the detection target gas is a fuel gas (city gas) containing methane gas as a main component.

[0022] 1, the gas detector 100 includes a sensor unit 1, a control unit 2, an alarm unit 3, a memory unit 4, multiple amplifiers 5, and a communication unit 6. The multiple gas sensors 10, the control unit 2, the alarm unit 3, and the communication unit 6 are housed within a housing of the gas detector 100. The gas detector 100 operates on power supplied from a commercial power source or on power from a battery (not shown).

[0023] The sensor unit 1 includes a plurality of gas sensors 10 of the same type. The sensor unit 1 detects a single type of target gas. In the example shown in FIG. 1, the sensor unit 1 includes gas sensors 10a to 10c. The sensor unit 1 outputs output values ​​30 of the plurality of gas sensors 10 to an amplifier 5. For convenience, FIG. 1 shows only one of the plurality of gas sensors 10 as outputting an output value 30, but the other gas sensors 10 also output output values ​​30 in the same manner.

[0024] Each of the gas sensors 10 includes a sensitive portion 11 and a heating portion 12 that heats the sensitive portion 11 to a predetermined temperature. The output values ​​30 of the gas sensors 10 are input to corresponding amplifiers 5. Each of the gas sensors 10 is a MEMS-type gas sensor. Specifically, the gas sensors 10 are fabricated using MEMS (Micro Electro Mechanical Systems) technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, each of the gas sensors 10 has a side length of approximately 0.1 mm. While FIG. 1 illustrates the sensitive portion 11 and heating portion 12 only for the gas sensor 10a for convenience, the gas sensors 10b and 10c also include the sensitive portion 11 and heating portion 12.

[0025] Each of the gas sensors 10 includes a measurement circuit as shown in Fig. 2. The measurement circuit includes sensor elements 13a to 13c, opposite-side resistors R1, R2, R4, R5, R7, and R8, and load resistors R3, R6, and R9.

[0026] A voltage is applied to the sensor element 13a, the resistors R1 and R2, and the load resistor R3 from a power source E. An output value 30 (see FIG. 1) is output from a terminal A1 connected between the sensor element 13a and the load resistor R3, and a terminal A2 connected between the resistors R1 and R2.

[0027] A voltage is applied to sensor element 13b, resistors R4 and R5, and load resistor R6 from power supply E. An output value 30 is output from terminal A3 connected between sensor element 13b and load resistor R6, and from terminal A4 connected between resistors R4 and R5.

[0028] A voltage is applied to the sensor element 13c, the resistors R7 and R8, and the load resistor R9 from a power supply E. An output value 30 is output from a terminal A5 connected between the sensor element 13c and the load resistor R9, and from a terminal A2 connected between the resistors R7 and R8.

[0029] In this embodiment, a voltage is simultaneously applied to each of the plurality of gas sensors 10 from the power source E. That is, in this embodiment, the plurality of gas sensors 10 are simultaneously driven.

[0030] The resistance value of the gas sensor 10 changes when the gas to be detected is adsorbed. Therefore, the change in the electrical resistance of the gas sensor 10 is extracted as a deviation voltage, and this is used as an output value 30, making it possible to measure the concentration of the gas to be detected.

[0031] Specifically, the sensitive part 11 of the gas sensor 10 adsorbs oxygen in the air when heated to a predetermined temperature by the heating part 12. Furthermore, when a gas to be detected (e.g., methane gas) is present, the oxygen adsorbed to the sensitive part 11 reacts with the gas, causing a change in the electrical resistance of the sensitive part 11. The gas sensors 10 measure this change in electrical resistance to detect methane gas.

[0032] As shown in FIGS. 3 and 4, each of the gas sensors 10 includes a substrate 14, an electrode pattern 15 provided on the substrate 14 via an insulating film 14a, a pair of electrodes 16 connected to a power source E (see FIG. 2), and a SnO2 sensitive layer 17 covering the electrode pattern 15. The substrate 14 is made of Si. A cavity C is formed in the substrate 14. The electrode pattern 15 is made of Pt. The electrode pattern 15 also serves as both the sensitive portion 11 and the heating portion 12. That is, the electrode pattern 15 is heated to a predetermined temperature when current is applied. When a gas to be detected is present, the electrode pattern 15 changes its resistance, thereby changing the output value 30. Note that the gas sensors 10a to 10c have the same structure, and therefore FIG. 4 illustrates only the gas sensor 10a as a representative of the gas sensors 10. The substrate 14 is an example of a "chip" as defined in the claims.

[0033] As shown in FIG. 3, the plurality of gas sensors 10 are provided on the same substrate 14. In the example shown in FIG. 3, three gas sensors 10a to 10c are provided on the same substrate 14. The number of the plurality of gas sensors 10 is not limited to three. For example, several tens to 100 gas sensors 10 may be provided. Preferably, 10 to 20 gas sensors 10 are provided. The plurality of gas sensors 10 may be arranged in an array on the same substrate 14.

[0034] The control unit 2 controls each part of the gas detector 100 (the multiple gas sensors 10, the alarm unit 3, the multiple amplifiers 5, and the communication unit 6). The control unit 2 also detects the gas to be detected based on the output values ​​30 of the multiple gas sensors 10. For example, the control unit 2 acquires the concentration of the gas to be detected based on all the output values ​​30 of the multiple gas sensors 10. The control unit 2 includes a processor such as a CPU (Central Processing Unit) and a memory such as a RAM (Random Access Memory). The control unit 2 also executes a predetermined program to perform control processing.

[0035] The control unit 2 heats the sensitive unit 11 to a predetermined temperature by pulse-driving the heating unit 12 at predetermined time intervals, and performs detection of the multiple gas sensors 10 at the predetermined temperature at the predetermined time intervals. That is, the control unit 2 pulse-heats the sensitive unit 11 to a temperature at which methane gas can be detected at the predetermined time intervals, and performs detection of methane gas at the predetermined time intervals. For example, the control unit 2 performs detection of the multiple gas sensors 10 at the predetermined temperature at approximately 60-second intervals. The control unit 2 may perform detection during the entire period of the pulse during which the sensitive unit 11 is heated in a pulsed manner, or may perform detection during a part of the period (for example, a single point in time) of the pulse during which the sensitive unit 11 is heated in a pulsed manner.

[0036] The control unit 2 is also configured to determine whether or not deterioration has occurred in the plurality of gas sensors 10. The control unit 2 is also configured to determine the degree of deterioration of the sensor unit 1. Details of the configuration by which the control unit 2 determines whether or not deterioration has occurred in the gas sensors 10 and the configuration by which the control unit 2 determines the degree of deterioration of the sensor unit 1 will be described later.

[0037] The alarm unit 3 issues an alert by sound, light, or the like when a target gas is detected. The alarm unit 3 is also configured to alert that there is a deteriorated gas sensor 10. The alarm unit 3 issues an alert in different ways depending on the degree of deterioration of the gas sensor 10 and the sensor unit 1. For example, the alarm unit 3 can issue an alert by varying the type, volume, length, etc. of the alerting sound. The alarm unit 3 can also issue an alert by varying the color of the alerting light, whether it flashes, where it emits light, etc.

[0038] The storage unit 4 stores a determination threshold value (not shown) for the concentration of the gas to be detected, various programs (not shown) executed by the control unit 2, output value information 20 (to be described later), correction count information 21 (to be described later) which is information on the number of corrections made to the gas sensor 10, and a threshold value Th (to be described later) used for determining deterioration of the gas sensor 10. The storage unit 4 includes, for example, a semiconductor storage element.

[0039] The amplifier 5 is configured to amplify the output value 30 output by the gas sensor 10. The amplifier 5 outputs the amplified output value 30 to the control unit 2. The amplifier 5 includes amplifiers 5a to 5c corresponding to the gas sensors 10a to 10c. The amplifier 5 is, for example, an operational amplifier.

[0040] The communication unit 6 is capable of communicating with the external device 7. For example, the communication unit 6 communicates with the external device 7 via a network. Alternatively, the communication unit 6 may communicate with the external device 7 by being directly connected to the external device 7 via wired or wireless communication.

[0041] The control unit 2, the notification unit 3, the storage unit 4, and the communication unit 6 may be provided on the same substrate 14 as the sensor unit 1, or may be provided on different substrates.

[0042] (Determination of Deterioration of Gas Sensor 10) In this embodiment, the control unit 2 determines whether or not the gas sensor 10 has deteriorated, based on the output values ​​30 of the multiple gas sensors 10. Specifically, the control unit 2 acquires output value information 20 corresponding to the gas concentration based on the output values ​​30 of the multiple gas sensors 10. The control unit 2 then determines that a gas sensor 10 among the multiple gas sensors 10 that outputs an output value 30 outside a predetermined range of the output value information 20 is a deteriorated gas sensor 10. The output value information 20 includes, for example, an average value 20a (see FIG. 5 ) of the output values ​​30 of the multiple gas sensors 10, a median value, and an average value of the remaining output values ​​30 excluding the maximum and minimum values.

[0043] 5, a configuration will be described in which the control unit 2 determines whether or not the gas sensor 10 has deteriorated by using an average value 20a of the output values ​​30 of a plurality of gas sensors 10 as the output value information 20. In the graph shown in FIG. 5, the vertical axis represents the output value 30 of the gas sensor 10, and the horizontal axis represents the number (No.) of the gas sensor 10.

[0044] In the example shown in FIG. 5, the first to third gas sensors 10 correspond to the gas sensors 10a to 10c.

[0045] The control unit 2 obtains an average value 20a based on the output values ​​30a to 30c of the gas sensors 10a to 10c. The control unit 2 then determines whether the output values ​​30a to 30c of each gas sensor 10 are within a predetermined range 40. The predetermined range 40 has an upper limit equal to the average value 20a plus a threshold value Th and a lower limit equal to the average value 20a minus the threshold value Th. That is, the predetermined range 40 is a range of plus ΔTh and minus ΔTh around the average value 20a. If the output value 30 of the gas sensor 10 is outside the predetermined range 40, the control unit 2 determines that the gas sensor 10 has deteriorated. The output value 30 of the deteriorated gas sensor 10 is excluded from the calculation of the average value 20a.

[0046] The threshold value Th is, for example, 1 / 10 (10%) of the 10% LEL (Lower Explosion Limit) value used to determine when reporting a gas leak. For example, if the gas to be detected is a methane-based gas, the 10% LEL is 5000 ppm. Therefore, if the gas to be detected is a methane-based gas, the threshold value Th is 500 ppm.

[0047] Furthermore, in this embodiment, when a deteriorated gas sensor 10 is present, the control unit 2 acquires the concentration of the gas to be detected, excluding the output value 30 of the deteriorated gas sensor 10. In other words, when a deteriorated gas sensor 10 is present, the control unit 2 acquires the concentration of the gas to be detected, using only the output value 30 of the gas sensor 10 that is not deteriorated.

[0048] In addition, the control unit 2 can determine that the sensor unit 1 as a whole is close to deterioration or has deteriorated when the average value 20a approaches or exceeds a predetermined value (for example, half value or full value of 10% LEL) or when a predetermined time has elapsed since the operation of the plurality of gas sensors 10.

[0049] In a harsh environment, the gas sensor 10 is prone to deterioration. If the gas sensor 10 is no longer used after deterioration occurs, the reliability of the sensor unit 1 decreases, making the gas detector unsuitable for use in the harsh environment. For example, a harsh environment includes at least one of an environment with drastic temperature changes and an environment with high temperatures.

[0050] (Gas sensor output value correction) Therefore, in this embodiment, the control unit 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of the multiple gas sensors 10. Specifically, the control unit 2 is configured to correct a gas sensor 10 that outputs an output value 30 that is outside a predetermined range based on the output value information 20, as a gas sensor 10 that has deteriorated. More specifically, the control unit 2 corrects the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of gas sensors 10 that have not deteriorated.

[0051] In this embodiment, the control unit 2 corrects the gain of the amplifier 5 corresponding to the deteriorated gas sensor 10 based on the output value 30 of the gas sensor 10 that is not deteriorated, thereby correcting the deteriorated gas sensor 10. Specifically, the control unit 2 obtains an average value 20a (see FIG. 5) from the output values ​​30 of the plurality of gas sensors 10 that are not deteriorated. The control unit 2 then obtains a predetermined range 40 (see FIG. 5) based on the average value 20a and the threshold value Th, and performs gain correction of the amplifier 5 so that the output value 30 of the deteriorated gas sensor 10 falls within the obtained predetermined range 40. Preferably, the control unit 2 performs gain correction of the amplifier 5 so that the output value 30 of the deteriorated gas sensor 10 conforms to the output value information 20 (average value 20a).

[0052] Furthermore, the control unit 2 stores the number of times that correction has been performed for each of the plurality of gas sensors 10 in the storage unit 4 as correction number information 21.

[0053] When the correction of the output values ​​30 of the plurality of gas sensors 10 is applied from the initial startup of the gas detector 100, it is possible to correct the output values ​​30 of the gas sensors 10 whose pre-correction output values ​​30 are outside the predetermined range due to an initial defect. As a result, the corrected gas sensors 10 that have an initial defect can continue to be used to detect the target gas.

[0054] (Determining the degree of deterioration of the sensor part) In this embodiment, the control unit 2 is configured to determine the degree of deterioration of the sensor unit 1 based on any of the pre-correction output values ​​30, the correction state, and the output value information 20 of the multiple gas sensors 10.

[0055] When determining the degree of deterioration of the sensor unit 1 based on the pre-correction output values ​​30 of the multiple gas sensors 10, the control unit 2 determines the degree of deterioration of the sensor unit 1, for example, based on the degree of deviation between the pre-correction output values ​​30 of the multiple gas sensors 10 and an average value 20a of the output values ​​30 excluding the output values ​​30 of the gas sensors 10 that have deteriorated. Specifically, the control unit 2 determines that the degree of deterioration of the sensor unit 1 is more advanced as the degree of deviation between the pre-correction output values ​​30 of the multiple gas sensors 10 and the average value 20a increases.

[0056] Furthermore, when determining the degree of deterioration based on the state of correction, the control unit 2 determines the degree of deterioration of the sensor unit 1, for example, based on the number of corrections made to the deteriorated gas sensor 10. Specifically, the control unit 2 acquires the number of corrections made to each gas sensor 10 based on the correction count information 21 stored in the storage unit 4, and determines that the greater the number of corrections, the more advanced the degree of deterioration of the sensor unit 1.

[0057] Furthermore, when determining the degree of deterioration based on the output value information 20, the control unit 2 may be configured to determine the degree of deterioration of the sensor unit 1 based on, for example, the number of gas sensors 10 whose pre-correction output values ​​30 fall outside a predetermined range 40 determined based on the output value information 20 (e.g., average value 20a) and a threshold value Th. In this case, the control unit 2 determines that the degree of deterioration of the sensor unit 1 is more advanced as the number of gas sensors 10 whose pre-correction output values ​​30 fall outside the predetermined range 40 increases.

[0058] (Notification of sensor or gas detector replacement) In this embodiment, the control unit 2 is configured to notify the user that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration.

[0059] Specifically, the control unit 2 notifies the user that the sensor unit 1 needs to be replaced when the degree of deterioration of the sensor unit 1 reaches a predetermined level. For example, the control unit 2 notifies the user that the sensor unit 1 needs to be replaced when the number of gas sensors 10 that cannot be used continuously after the correction exceeds a predetermined number. For example, in a sensor unit 1 having ten gas sensors 10, if three gas sensors 10 become unable to be used continuously after the correction, the control unit 2 notifies the user that the sensor unit 1 needs to be replaced. Note that if only the sensor unit 1 can be replaced, the control unit 2 may notify the user that the sensor unit 1 needs to be replaced based on the degree of deterioration of the sensor unit 1. Furthermore, if the gas detector 100 needs to be replaced along with the sensor unit 1, the control unit 2 may notify the user that the gas detector 100 needs to be replaced based on the degree of deterioration of the sensor unit 1.

[0060] (Notification of deteriorated gas sensor) The control unit 2 is configured to notify the presence of a deteriorated gas sensor 10 when any of the multiple gas sensors 10 has deteriorated. Specifically, the control unit 2 controls the notification unit 3 to notify the presence of a deteriorated gas sensor 10. In this embodiment, the control unit 2 may cause the notification unit 3 to provide notification in different notification modes depending on the degree of deterioration of the gas sensor 10. For example, when the notification unit 3 provides notification by emitting light from an LED or the like, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by lighting the LED yellow when the degree of deterioration of the gas sensor 10 is small. Furthermore, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by lighting the LED red when the degree of deterioration of the gas sensor 10 is large. Furthermore, for example, when the notification unit 3 notifies by sound, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by making the notification unit 3 emit a short "beep, beep, beep" sound when the degree of deterioration of the gas sensor 10 is small. Furthermore, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by making the notification unit 3 emit a long "beep, beep, beep" sound when the degree of deterioration of the gas sensor 10 is large.

[0061] In the present embodiment, the control unit 2 is configured to, when notifying that there is a deteriorated gas sensor 10, differentiate between the manner of notification when the corrected gas sensor 10 can be continued and the manner of notification when the corrected gas sensor 10 cannot be continued. For example, when the corrected gas sensor 10 can be continued, the control unit 2 notifies that the corrected gas sensor 10 can be continued by lighting one LED green and another LED yellow. When the corrected gas sensor 10 cannot be continued, the control unit 2 notifies that the corrected gas sensor 10 cannot be continued by lighting one LED yellow and another LED red.

[0062] (Gas detection processing) Next, the gas detection process performed by the control unit 2 will be described with reference to FIG.

[0063] In step S1 of FIG. 6, the control unit 2 detects the gas to be detected based on the output values ​​30 of a plurality of gas sensors 10 of the same type mounted on the same substrate 14.

[0064] Next, in step S2, the control unit 2 determines which of the multiple gas sensors 10 has deteriorated based on the output values ​​30 of the multiple gas sensors 10. If there is no deteriorated gas sensor 10, the process ends. If there is a deteriorated gas sensor 10, the process proceeds to step S3.

[0065] When the process proceeds from step S2 to step S3, in step S3 the control unit 2 corrects the output value 30 of the gas sensor 10 that has deteriorated among the plurality of gas sensors 10 based on the output values ​​30 of the plurality of gas sensors 10.

[0066] Next, in step S4, the control unit 2 continues to use the gas sensor 10, which has been corrected and has experienced deterioration, for detecting the gas to be detected, and then the process ends.

[0067] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0068] In this embodiment, as described above, the control unit 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of multiple gas sensors 10. This allows a gas sensor 10 that has deteriorated to continue to be used to detect the target gas by correcting the output value 30. This makes it possible to extend the life of the gas sensors 10 without increasing the number of gas sensors 10. As a result, it is possible to provide a gas detector 100 that is suitable for use in harsh environments where the gas sensors 10 are likely to deteriorate, while suppressing an increase in the number of parts and an increase in the size of the device.

[0069] In this embodiment, as described above, the control unit 2 is configured to acquire output value information 20 corresponding to gas concentrations based on the output values ​​30 of the multiple gas sensors 10, and to correct any gas sensor 10 among the multiple gas sensors 10 that outputs an output value 30 outside a predetermined range from the output value information 20 as a degraded gas sensor 10. This allows the output value 30 of a degraded gas sensor 10 to be corrected based on the output value information 20 acquired based on the output values ​​30 of the multiple gas sensors 10, without using a reference gas for calibration. As a result, even if the gas detector 100 is installed in an environment where calibration is difficult, correction of a degraded gas sensor 10 can be performed. Furthermore, even if gas sensors 10 are manufactured using the same process, the likelihood of degradation and the degree of degradation may differ from one another due to manufacturing errors. Therefore, even if multiple gas sensors 10 are used under the same conditions, the degree of degradation may vary. Furthermore, when dust adheres to any of the gas sensors 10 or when the gas sensors 10 are unevenly exposed to a degrading atmosphere, the degree of deterioration of the gas sensors 10 may differ from one another, resulting in variations in the degree of deterioration. Therefore, as described above, by correcting the output value 30 of a gas sensor 10 in which deterioration has occurred based on the output value information 20 acquired based on the output values ​​30 of the gas sensors 10, it is possible to easily correct the sensor unit 1 having the gas sensors 10 in which the degree of deterioration varies.

[0070] Furthermore, in this embodiment, as described above, the control unit 2 is configured to determine the degree of deterioration of the sensor unit 1 based on any one of the pre-correction output values ​​30, the correction state, and the output value information 20 of the multiple gas sensors 10. This makes it possible to easily predict the life of the sensor unit 1 based on the degree of deterioration of the sensor unit 1. As a result, it is possible to easily predict when to replace the sensor unit 1.

[0071] Furthermore, in this embodiment, as described above, the control unit 2 is configured to notify the user that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration. Generally, the gas sensor 10 is set to have a service life that is shorter than the period during which it can be used. Therefore, the gas sensor 10 needs to be replaced in a shorter period than the actual life of the gas sensor 10. Therefore, by configuring the control unit 2 to notify the user that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration of the gas sensor 10 as described above, the sensor unit 1 or the gas detector 100 can be used until the actual service life limit at which the sensor unit 1 or the gas detector 100 can no longer be used due to the end of its life. As a result, the sensor unit 1 or the gas detector 100 can be used for a period longer than the general service life.

[0072] Furthermore, in this embodiment, as described above, the control unit 2 is configured to notify the user that there is a deteriorated gas sensor 10 among the plurality of gas sensors 10, if any. This allows the user to easily understand that the gas sensor 10 has deteriorated.

[0073] Furthermore, in this embodiment, as described above, when notifying that there is a deteriorated gas sensor 10, the control unit 2 is configured to provide different notification modes for when the corrected gas sensor 10 can continue to be used and when the corrected gas sensor 10 cannot continue to be used. This allows the user to easily determine whether the corrected gas sensor 10 can continue to be used from the notification mode. As a result, the user can easily determine when it is time to replace the gas detector 100.

[0074] Furthermore, in this embodiment, as described above, the gas sensor control method includes the steps of correcting the output value 30 of a gas sensor 10 that has deteriorated among the plurality of gas sensors 10 based on the output values ​​30 of the plurality of gas sensors 10, and continuing to use the deteriorated gas sensor 10 after the correction for detecting the target gas. This makes it possible to extend the life of the gas sensor 10, similar to the gas detector 100, and therefore provides a gas sensor control method that is suitable for use in harsh environments where the gas sensor 10 is likely to deteriorate.

[0075] (Variation) The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the above description of the embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0076] For example, in the above embodiment, an example was shown in which gas detector 100 detects a single type of target gas, but the present invention is not limited to this. In the present invention, the target gas may include a first target gas of a predetermined type and a second target gas of a different type from the first target gas. The first target gas is, for example, methane gas. The second target gas is, for example, hydrogen sulfide gas generated from sewage or the like.

[0077] As in the modified example shown in FIG. 7, a gas detector 200 may include a sensor section 201, a control section 202, a notification section 3, a storage section 4, an amplifier 5, and a communication section 6.

[0078] The plurality of gas sensors included in the sensor unit 201 according to the modified example include a plurality of first gas sensors 203 for detecting a first gas to be detected, and a plurality of second gas sensors 204 for detecting a second gas to be detected.

[0079] The first gas sensor 203 is a semiconductor gas sensor capable of detecting, for example, methane gas. The first gas sensor 203 includes three gas sensors, namely, first gas sensors 203a to 203c. The first gas sensor 203 has the same configuration as the gas sensor 10 according to the above embodiment, and therefore a detailed description thereof will be omitted.

[0080] The second gas sensor 204 is, for example, a semiconductor gas sensor capable of detecting hydrogen sulfide gas. The second gas sensor 204 is formed by MEMS technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, the second gas sensor 204 has a size of about 0.1 mm on one side. The second gas sensor 204 also includes a substrate, an electrode pattern provided on the substrate, and a ZnO sensitive layer covering the electrode pattern. The ZnO sensitive layer also contains gallium. The second gas sensor 204 detects gas by heating the ZnO sensitive layer to a predetermined temperature by pulse driving. The second gas sensor 204 includes second gas sensors 204a to 204c.

[0081] In the gas detector 200 according to the modified example, the amplifier 5 includes amplifiers 5a to 5c corresponding to the first gas sensors 203a to 203c, and amplifiers 5d to 5f corresponding to the second gas sensors 204a to 204c.

[0082] The control unit 202 is configured to correct the output value 30 of the deteriorated first gas sensor based on the output values ​​30 of the multiple first gas sensors 203, and to correct the output value 30 of the deteriorated second gas sensor based on the output values ​​30 of the multiple second gas sensors 204. The configuration in which the control unit 202 corrects the deteriorated first gas sensor 203 is similar to the configuration in which the control unit 2 according to the above embodiment corrects the deteriorated gas sensor 10, except that a first threshold value Th1 is used instead of the threshold value Th, and therefore a detailed description thereof will be omitted. Furthermore, the configuration in which the control unit 202 corrects the deteriorated second gas sensor 204 is similar to the configuration in which the control unit 2 according to the above embodiment corrects the deteriorated gas sensor 10, except that a second threshold value Th2 is used instead of the threshold value Th, and therefore a detailed description thereof will be omitted.

[0083] The first threshold value Th1 and the second threshold value Th2 may be set to 10% of the 10% LEL of the first detection target gas and the second detection target gas, respectively.

[0084] As described above, in the gas detector 200 according to the modified example, the control unit 202 is configured to correct the output value 30 of a deteriorated first gas sensor 203 based on the output values ​​30 of the multiple first gas sensors 203, and to correct the output value 30 of a deteriorated second gas sensor 204 based on the output values ​​30 of the multiple second gas sensors 204. This allows the deteriorated first gas sensor 203 and the deteriorated second gas sensor 204 to continue being used to detect their respective target gases, even if the first gas sensor 203 and the second gas sensor 204 are deteriorated, by performing correction based on their respective output values ​​30. This improves the reliability of the first gas sensor 203 and the second gas sensor 204, thereby improving the reliability of the gas detector 200 that detects multiple target gases. As a result, a gas detector 200 that can detect multiple target gases even in harsh environments can be provided.

[0085] In the above embodiment, the control unit 2 corrects a gas sensor 10 that outputs an output value 30 outside a predetermined range from the output value information 20 among the plurality of gas sensors 10 as a degraded gas sensor 10. However, the present invention is not limited to this. The control unit may be configured to determine whether a gas sensor has degraded based on the output value of the gas sensor without using the output value information. For example, the control unit may be configured to determine that a gas sensor has degraded when the difference between the output value of the gas sensor and that of another gas sensor is equal to or greater than a predetermined difference.

[0086] In the above embodiment, the control unit 2 determines the degree of deterioration of the sensor unit 1, but the present invention is not limited to this. For example, the control unit does not have to determine the degree of deterioration of the sensor unit.

[0087] In the above embodiment, the control unit 2 notifies the user that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration, but the present invention is not limited to this. For example, the control unit does not need to notify the user that the sensor unit or the gas detector needs to be replaced.

[0088] In the above embodiment, the control unit 2 notifies the user that a deteriorated gas sensor 10 is present among the plurality of gas sensors 10. However, the present invention is not limited to this. For example, the control unit may not notify the user that a deteriorated gas sensor 10 is present, even if such a gas sensor is present.

[0089] In the above embodiment, the control unit 2 provides different notification modes for when the corrected gas sensor 10 can be continuously used and when the corrected gas sensor 10 cannot be continuously used, but the present invention is not limited to this. For example, the control unit does not need to provide different notification modes for when the corrected gas sensor can be continuously used and when the corrected gas sensor cannot be continuously used.

[0090] In the above embodiment, the threshold value Th is set to 10% of the 10% LEL of the gas to be detected, but the present invention is not limited to this. For example, the threshold value may be set to 1σ of the variance of the output values ​​of multiple gas sensors, or may be set to a value 20% from the average value.

[0091] In the above embodiment, an example of a configuration in which all of the plurality of gas sensors 10 are used to detect the target gas is shown, but the present invention is not limited to this. It is not necessary to use all of the plurality of gas sensors when detecting the target gas. Even if not all of the plurality of gas sensors are used when detecting the target gas, all of the plurality of gas sensors must be driven.

[0092] In the above embodiment, the control unit 2 acquires the concentration of the gas to be detected based on the output values ​​30 of the plurality of gas sensors 10. However, the present invention is not limited to this. For example, the control unit may be configured to determine the presence or absence of the gas to be detected based on the output values ​​of the plurality of gas sensors.

[0093] In the above embodiment, gas detection at a predetermined temperature is performed at predetermined time intervals of approximately 60 seconds, but the present invention is not limited to this. In the present invention, gas detection at a predetermined temperature may be performed at predetermined time intervals other than 60 seconds.

[0094] In the above embodiment, the multiple gas sensors 10 are semiconductor-type gas sensors, but the present invention is not limited to this. For example, the multiple gas sensors may be electrochemical sensors (potential electrolysis type, diaphragm galvanic cell type), catalytic combustion type gas sensors, or gas thermal conduction type gas sensors. When the multiple gas sensors are configured as gas sensors other than semiconductor-type gas sensors, the gas sensors must be arranged within a predetermined range (for example, several centimeters) so that they can detect the same target gas.

[0095] In the above embodiment, the gas to be detected is methane, but the present invention is not limited to this. For example, the gas to be detected may be hydrogen gas, ethane gas, propane gas, or carbon monoxide gas.

[0096] Furthermore, in the above embodiment, an example of a configuration in which the gas detector 100 includes the alarm unit 3 and the communication unit 6 has been shown, but the present invention is not limited to this. In the present invention, the gas detector may be provided with only one of the alarm unit and the communication unit. For example, the gas detector may not be provided with a communication unit. Furthermore, the gas detector may not be provided with an alarm unit. In this case, the alarm unit may be provided separately from the gas detector. Furthermore, even if the gas detector is provided with an alarm unit, the alarm may be performed by a device external to the gas detector.

[0097] In the above embodiment, for convenience of explanation, an example has been shown in which the control processing is explained using a flow-driven flowchart in which processing is performed sequentially according to a processing flow, but the present invention is not limited to this. In the present invention, the control processing may be performed by event-driven processing in which processing is performed on an event-by-event basis. In this case, the control processing may be performed completely event-driven, or may be performed by combining event-driven and flow-driven processing. [Explanation of symbols]

[0098] 1, 201 Sensor unit 2, 202 control section 10, 10a to 10c Gas sensors 20 Output value information 30 Output Values 100, 200 Gas Detector 203, 203a to 203c First gas sensor 204, 204a to 204c second gas sensors

Claims

1. A gas detector for detecting a gas to be detected, a sensor unit including a plurality of gas sensors of the same type provided on the same chip; a control unit that detects the detection target gas based on output values ​​of the plurality of gas sensors, The gas detector is configured so that the control unit performs control to correct the output value of a deteriorated gas sensor based on the output values ​​of the plurality of gas sensors.

2. 2. The gas detector according to claim 1, wherein the control unit is configured to acquire output value information corresponding to a gas concentration based on output values ​​of the plurality of gas sensors, and to perform the correction by treating a gas sensor among the plurality of gas sensors that outputs an output value outside a predetermined range based on the output value information as the gas sensor that has deteriorated.

3. 3. The gas detector according to claim 2, wherein the control unit is configured to determine a degree of deterioration of the sensor unit based on any of the pre-correction output values ​​of the plurality of gas sensors, the state of the correction, and the output value information.

4. 4. The gas detector according to claim 3, wherein the control unit is configured to notify a user that the sensor unit or the gas detector needs to be replaced based on the degree of deterioration.

5. 2. The gas detector according to claim 1, wherein, when the deteriorated gas sensor is present among the plurality of gas sensors, the control unit notifies the user that the deteriorated gas sensor is present.

6. 6. The gas detector according to claim 5, wherein the control unit is configured to, when notifying that there is a deteriorated gas sensor, differentiate between the manner of notification when the gas sensor can continue to be used after the correction and the manner of notification when the gas sensor cannot continue to be used after the correction.

7. the detection target gas includes a first detection target gas of a predetermined type and a second detection target gas of a different type from the first detection target gas, the plurality of gas sensors include a plurality of first gas sensors that detect the first detection target gas and a plurality of second gas sensors that detect the second detection target gas; 2. The gas detector according to claim 1, wherein the control unit is configured to correct an output value of a first gas sensor that has deteriorated based on output values ​​of the plurality of first gas sensors, and to correct an output value of a second gas sensor that has deteriorated based on output values ​​of the plurality of second gas sensors.

8. detecting a gas to be detected based on output values ​​of a plurality of gas sensors of the same type mounted on the same chip; determining a gas sensor that has deteriorated among the plurality of gas sensors based on output values ​​of the plurality of gas sensors; correcting an output value of the deteriorated gas sensor among the plurality of gas sensors based on the output values ​​of the plurality of gas sensors; and continuing to use the deteriorated gas sensor after the correction for detecting the gas to be detected.

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