Control method for gas detectors and gas sensors

Abstract

This invention provides a gas detector with an extended lifespan by increasing the lifespan of the gas sensor itself. [Solution] This gas detector 100 is a gas detector 100 that detects a target gas, and comprises a first gas sensor 1 that detects the target gas, a second gas sensor 2 that detects the target gas, and a control unit 3 that controls the first gas sensor 1 and the second gas sensor 2. The control unit 3 controls whether or not to drive the second gas sensor 2 based on a first detection result 30 of the first gas sensor 1, and when the second gas sensor 2 is driven, it determines the concentration of the target gas based on a second detection result 31 of the second gas sensor 2.

Description

Technical Field

[0005]

[0001] This invention relates to a gas detector and a method for controlling a gas sensor.

Background Art

[0002] Conventionally, gas detectors have been known (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a gas detector including a first gas detection unit, a second gas detection unit, and control means. In this gas detector, power is supplied to the first gas detection unit and the second gas detection unit to start detecting the detected gas. Further, when the concentration of the detected gas detected by the first gas detection unit exceeds a preset threshold value, the control means stops supplying power to the second gas detection unit to perform control for protecting the second gas detection unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the gas detector described in Patent Document 1, when detecting the gas to be detected, both the first gas detection unit (first gas sensor) and the second gas detection unit (gas sensor) are energized. As a result, the first gas sensor deteriorates due to the energization. Furthermore, even when the second gas sensor is stopped based on the detection result of the first gas sensor, the second gas sensor is still energized, causing it to deteriorate. Moreover, as the deterioration of the first gas sensor progresses, the accuracy of the first gas sensor in determining the concentration of the gas to be detected decreases, preventing proper control of the second gas sensor from stopping, thus shortening the overall lifespan of the gas detector. Therefore, there is a need for a gas detector and a gas sensor control method that can extend the lifespan by extending the lifespan of the gas sensor itself.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a gas detector and a gas sensor control method that can extend the lifespan of the gas sensor itself. [Means for solving the problem]

[0007] To achieve the above objective, the gas detector according to the first aspect of this invention is a gas detector for detecting a target gas, comprising a first gas sensor for detecting the target gas, a second gas sensor for detecting the target gas, and a control unit for controlling the first gas sensor and the second gas sensor, wherein the control unit controls whether or not to drive the second gas sensor based on a first detection result of the first gas sensor, and, when driving the second gas sensor, determines the concentration of the target gas based on a second detection result of the second gas sensor.

[0008] In the gas detector according to the first aspect of this invention, the control unit controls whether or not to drive the second gas sensor based on the first detection result of the first gas sensor, and, when driving the second gas sensor, determines the concentration of the target gas based on the second detection result of the second gas sensor. As a result, the second gas sensor is driven only when it is determined that driving is necessary based on the first detection result of the first gas sensor, so the rate of deterioration of the second gas sensor can be slowed compared to a configuration in which the second gas sensor is driven without being based on the first detection result of the first gas sensor. Therefore, the lifespan of the second gas sensor can be extended. As a result, the lifespan of the gas detector can be extended by extending the lifespan of the gas sensor itself. In addition, since the concentration of the target gas is determined based on the second detection result of the second gas sensor, rather than using the first detection result to determine the concentration of the target gas, even if the first gas sensor deteriorates, it is possible to suppress a decrease in the accuracy of determining the concentration of the target gas in the gas detector. The term "lifespan" for a gas sensor refers to the remaining period of use, similar to the term "lifetime." Similarly, the term "lifespan" for a gas detector refers to the remaining period of use, similar to the term "lifetime."

[0009] In the gas detector according to the first aspect described above, preferably, the first gas sensor and the second gas sensor are of the same type. This configuration helps to suppress the complexity of the device configuration compared to the case where the first gas sensor and the second gas sensor are of different types. Note that "same type of gas sensor" means that they have the same structure. Therefore, gas sensors that have the same structure but differ in detection sensitivity for the gas to be detected may be included in the category of "same type of gas sensor".

[0010] In this case, preferably, the control unit either controls the first gas sensor to operate continuously or intermittently, and controls the second gas sensor to operate when the first detection result indicates the presence of the target gas. With this configuration, the second gas sensor is operated only when the target gas is present, so the rate of deterioration of the second gas sensor can be easily slowed compared to a configuration in which the second gas sensor is operated regardless of the presence of the target gas. Therefore, the lifespan of the second gas sensor can be easily extended. Furthermore, since the first detection result only needs to ensure an accuracy sufficient to determine whether or not the target gas is present, the first gas sensor can continue to be used even if its detection accuracy decreases. Therefore, the actual service life of the first gas sensor can be extended. As a result, the actual service life of the first gas sensor and the lifespan of the second gas sensor can be extended, thus further extending the lifespan of the gas detector. Note that the control that operates the gas sensor continuously means the control that operates the gas sensor continuously. Furthermore, intermittent operation of the gas sensor refers to control that pulses the gas sensor at predetermined time intervals.

[0011] In the gas detector according to the first aspect described above, preferably, the control unit uses the first detection result to determine the presence or absence of the target gas, and uses the second detection result to determine the concentration of the target gas. With this configuration, the first gas sensor only needs to be able to determine the presence or absence of the target gas, so it does not need to determine the concentration of the target gas based on the first detection result. Therefore, the first gas sensor can be used even if the accuracy of determining the concentration of the target gas decreases, thus extending the actual service life of the first gas sensor compared to a gas sensor that determines the concentration of the target gas. Furthermore, since the concentration of the target gas is determined based on the second detection result of the second gas sensor, even if the accuracy of determining the concentration of the target gas in the first detection result of the first gas sensor decreases, it does not affect the accuracy of determining the concentration of the target gas as a gas detector. Therefore, even if the accuracy of determining the concentration of the target gas in the first gas sensor decreases, it is possible to suppress a decrease in the accuracy of determining the concentration of the target gas in the gas detector itself, thereby suppressing a decrease in the reliability of the gas detector. As a result, it is possible to provide a gas detector that can achieve a longer lifespan while suppressing a decline in reliability.

[0012] In the gas detector according to the first aspect described above, preferably, the first gas sensor and the second gas sensor are provided on the same chip. With this configuration, the first gas sensor and the second gas sensor can be formed by MEMS (Micro Electro Mechanical Systems) technology, which forms mechanical structures in a semiconductor substrate using a semiconductor manufacturing process. As a result, the lifespan of the semiconductor gas sensor can be extended.

[0013] In the gas detector according to the first aspect described above, preferably, the control unit is configured to notify which of the first gas sensor and the second gas sensor is being driven in an identifiable manner. With this configuration, the user can easily understand whether the gas detector is detecting the presence of the target gas or determining the concentration of the target gas. As a result, user convenience (usability) can be improved.

[0014] In the gas detector according to the first aspect described above, preferably, the control unit controls the second gas sensor to be driven at predetermined time intervals, regardless of the first detection result. With this configuration, for example, if the second gas sensor is a type of gas sensor such as a semiconductor gas sensor that deteriorates by being poisoned with siloxane when not being driven, the deterioration of the second gas sensor can be reduced. As a result, the lifespan of the gas detector can be extended even for gas sensors that deteriorate if not driven.

[0015] A gas sensor control method according to the second aspect of this invention comprises the steps of: obtaining a first detection result of the gas to be detected using a first gas sensor; determining whether or not to drive a second gas sensor that detects the gas to be detected based on the first detection result; obtaining a second detection result of the gas to be detected using the second gas sensor if the second gas sensor is driven; and determining the concentration of the gas to be detected based on the second detection result.

[0016] In the second aspect of this invention, the gas sensor control method includes the steps of: obtaining a second detection result of the gas to be detected using the second gas sensor when driving the second gas sensor; and determining the concentration of the gas to be detected based on the second detection result. This makes it possible to provide a gas sensor control method that extends the lifespan of the gas detector by extending the lifespan of the gas sensor itself, similar to the gas detector in the first aspect described above. [Effects of the Invention]

[0017] According to the present invention, as described above, by extending the life of the gas sensor itself, it is possible to provide a gas detector and a method for controlling a gas sensor that can achieve a longer life.

Brief Description of the Drawings

[0018] [Figure 1] It is a block diagram showing a control configuration of a gas detector according to the first embodiment. [Figure 2] It is a circuit diagram (A) showing a configuration example of a first gas sensor and a circuit diagram (B) showing a configuration example of a second gas sensor of the gas detector according to the first embodiment. [Figure 3] It is a schematic plan view showing a configuration example of a gas sensor of a gas detector according to the first embodiment. [Figure 4] It is a schematic cross-sectional view showing a configuration example of a gas sensor of a gas detector according to the first embodiment. [Figure 5] It is a schematic diagram for explaining a configuration in which a control unit of a gas detector according to the first embodiment drives a second gas sensor based on a first detection result. [Figure 6] It is a flowchart for explaining a method for controlling a gas sensor by a gas detector according to the first embodiment. [Figure 7] It is a block diagram showing a control configuration of a gas detector according to the second embodiment. [Figure 8] It is a flowchart for explaining a method for controlling a gas sensor by a gas detector according to the second embodiment. [Figure 9] It is a block diagram showing a control configuration of a gas detector according to a modification. [Figure 10] It is a flowchart for explaining a method for controlling a gas sensor by a gas detector according to a modification.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] [First Embodiment] The configuration of the gas detector 100 according to the first embodiment will be described with reference to Figures 1 to 6.

[0021] (Gas detector configuration) The gas detector 100 of the first embodiment is a gas detector that detects a target gas. Furthermore, when the gas detector 100 detects the target gas, it outputs an alarm to notify the user of gas leaks or other issues. The target gas is the gas that the gas detector 100 should detect. For example, the target gas is fuel gas (city gas) that mainly contains methane.

[0022] As shown in Figure 1, the gas detector 100 comprises a first gas sensor 1, a second gas sensor 2, a control unit 3, a notification unit 4, a storage unit 5, a plurality of amplifiers 6, and a communication unit 7. The first gas sensor 1, the control unit 3, the notification unit 4, and the communication unit 7 are housed within the casing of the gas detector 100. The gas detector 100 operates on power supplied from a commercial power source or from a battery (not shown).

[0023] The first gas sensor 1 detects the target gas. The first gas sensor 1 includes a sensing element 1a and a heating element 1b that heats the sensing element 1a to a predetermined temperature. The first detection result 30 of the first gas sensor 1 is input to the corresponding amplifier 6. The first gas sensor 1 is a MEMS-type gas sensor. In other words, the first gas sensor 1 is formed using MEMS (Micro Electro Mechanical Systems) technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, the first gas sensor 1 has a size of about 0.1 mm on each side.

[0024] The first gas sensor 1 includes a measurement circuit as shown in Figure 2(A). The measurement circuit of the first gas sensor 1 comprises a sensor element 10a, opposite-side resistors R1 and R2, and a load resistor R3.

[0025] Voltage is applied from power supply E to the sensor element 10a, the opposite side resistors R1 and R2, and the load resistor R3. In addition, the first detection result 30 (see Figure 1) is output from terminal A1 connected between the sensor element 10a and the load resistor R3, and terminal A2 connected between the opposite side resistors R1 and R2.

[0026] The second gas sensor 2 detects the target gas. The second gas sensor 2 includes a sensing element 2a and a heating element 2b that heats the sensing element 2a to a predetermined temperature. The second detection result 31 of the second gas sensor 2 is input to the corresponding amplifier 6. The second gas sensor 2 is a MEMS-type gas sensor. In other words, the second gas sensor 2 is formed using MEMS technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, the second gas sensor 2 has a size of about 0.1 mm on each side.

[0027] Furthermore, the second gas sensor 2 includes a measurement circuit as shown in Figure 2(B). The measurement circuit of the second gas sensor 2 comprises a sensor element 10b, opposite-side resistors R4 and R5, and a load resistor R6.

[0028] Voltage is applied from power supply E to the sensor element 10b, the opposite side resistors R4 and R5, and the load resistor R6. In addition, a second detection result 31 (see Figure 1) is output from terminal A3 connected between the sensor element 10b and the load resistor R6, and from terminal A4 connected between the opposite side resistors R4 and R5.

[0029] In the first embodiment, the first gas sensor 1 and the second gas sensor 2 are gas sensors of the same type. However, the timing at which voltage is applied from the power supply E to the first gas sensor 1 and the timing at which voltage is applied from the power supply E to the second gas sensor 2 are different.

[0030] The resistance values ​​of the first gas sensor 1 and the second gas sensor 2 change when the target gas is adsorbed. Therefore, the first gas sensor 1 is configured to detect the target gas by extracting the change in electrical resistance as a deviation voltage and using this as the first detection result 30.

[0031] Furthermore, the second gas sensor 2 is configured to measure the concentration of the target gas by extracting the change in electrical resistance as a deviation voltage and using this as the second detection result 31.

[0032] Specifically, the sensing element 1a of the first gas sensor 1 is heated to a predetermined temperature by the heating element 1b, thereby adsorbing oxygen from the air. Furthermore, if the target gas (for example, methane gas) is present, the oxygen adsorbed on the sensing element 1a reacts, causing a change in the electrical resistance of the sensing element 1a. The first gas sensor 1 detects methane gas by measuring this change in electrical resistance.

[0033] Furthermore, the sensing element 2a of the second gas sensor 2 is heated to a predetermined temperature by the heating element 2b, thereby adsorbing oxygen from the air. When the oxygen adsorbed on the sensing element 2a is present, it reacts with the target gas (for example, methane gas), causing a change in the electrical resistance of the sensing element 2a. The second gas sensor 2 determines the concentration of methane gas by measuring this change in electrical resistance.

[0034] Each of the first gas sensor 1 and the second gas sensor 2, as shown in Figures 3 and 4, includes a substrate 11, an electrode pattern 12 provided on the substrate 11 via an insulating film 11a, a pair of electrode parts 13 connected to a power supply E (see Figure 2), and a SnO2 sensitive layer 14 covering the electrode pattern 12. The substrate 11 is made of Si. A cavity C is formed in the substrate 11. The electrode pattern 12 is made of Pt. The electrode pattern 12 also serves as both the sensitive part 1a and the heating part 1b. In other words, the electrode pattern 12 is heated to a predetermined temperature when current is passed through it. Furthermore, when the gas to be detected is present, the resistance value of the electrode pattern 12 changes, thereby changing the first detection result 30. Note that the structures of the first gas sensor 1 and the second gas sensor 2 are identical, so only the first gas sensor 1 is shown in Figure 4. The substrate 11 is an example of a "chip" as defined in the claims.

[0035] Furthermore, as shown in Figure 3, the first gas sensor 1 and the second gas sensor 2 are mounted on the same substrate 11.

[0036] The control unit 3 controls each part of the gas detector 100 (first gas sensor 1, second gas sensor 2, notification unit 4, multiple amplifiers 6, and communication unit 7). The control unit 3 also detects the presence or absence of the target gas based on the first detection result 30 of the first gas sensor 1. The control unit 3 also determines the concentration of the target gas based on the second detection result 31 of the second gas sensor 2. The control unit 3 includes a processor such as a CPU (Central Processing Unit) and memory such as RAM (Random Access Memory). The control unit 3 also performs control processing by executing a predetermined program.

[0037] The notification unit 4 provides notification by sound, light, etc., when the target gas is detected. For example, the notification unit 4 can provide notification by varying the type, volume, and length of the sound it emits. The notification unit 4 can also provide notification by varying the color, whether or not the light flashes, and the location where the light is emitted.

[0038] The memory unit 5 stores various programs (not shown) executed by the control unit 3, and threshold values ​​Th used to determine the presence or absence of the gas to be detected, as described later. The memory unit 5 includes, for example, semiconductor memory elements.

[0039] Amplifier 6 is configured to amplify the first detection result 30 output by the first gas sensor 1. Amplifier 6 is also configured to amplify the second detection result 31 output by the second gas sensor 2. Amplifier 6 outputs the amplified first detection result 30 and the amplified second detection result 31 to the control unit 3. Amplifier 6 includes amplifiers 6a and 6b corresponding to the first gas sensor 1 and the second gas sensor 2. Amplifier 6 is, for example, an operational amplifier.

[0040] The communication unit 7 can communicate with an external device 8. For example, the communication unit 7 communicates with the external device 8 via a network. Alternatively, the communication unit 7 may communicate by directly connecting to the external device 8 via wired or wireless connection.

[0041] The control unit 3, notification unit 4, storage unit 5, and communication unit 7 may be provided on the same substrate 11 as the first gas sensor 1 and the second gas sensor 2, or they may be provided on different substrates.

[0042] (Drive control of the first gas sensor) In the first embodiment, the control unit 3 controls the first gas sensor 1 to be driven continuously. Specifically, the control unit 3 controls the first gas sensor 1 to be driven continuously.

[0043] (Drive control of the second gas sensor) In the first embodiment, the control unit 3 heats the sensing unit 2a to a predetermined temperature by driving the heating unit 2b, thereby detecting the second gas sensor 2 at a predetermined temperature. If the second gas sensor 2 is controlled to be driven continuously, similar to the first gas sensor 1, the second gas sensor 2 will be driven continuously, which will accelerate the deterioration of the second gas sensor 2. However, if the gas detector 100 is not present in the atmosphere of the gas to be detected, there is no need to drive the second gas sensor 2.

[0044] Therefore, in this embodiment, the control unit 3 controls whether or not to drive the second gas sensor 2 based on the first detection result 30 of the first gas sensor 1. Specifically, as shown in Figure 5, the control unit 3 acquires the first detection result 30 from the first gas sensor 1. Then, if the first detection result 30 indicates the presence of the target gas, the control unit 3 controls the second gas sensor 2 to drive by sending a drive signal 40 to the heating unit 2b of the second gas sensor 2, which is in a stopped state. When the control unit 3 drives the second gas sensor, it controls it to drive continuously. Furthermore, even after driving the second gas sensor 2, the control unit 3 continues to drive the first gas sensor 1 without stopping it.

[0045] In the first embodiment, the control unit 3 uses the first detection result 30 to determine the presence or absence of the gas to be detected. The control unit 3 determines that the gas to be detected is present if the first detection result 30 is equal to or greater than the threshold Th. The threshold Th is, for example, 1 / 100 (1%) 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 Th is 50 ppm.

[0046] The control unit 3 then determines the concentration of the target gas based on the second detection result 31 of the second gas sensor 2 when driving the second gas sensor 2. In other words, the control unit 3 uses the second detection result 31 to determine the concentration of the target gas. The control unit 3 also controls the second gas sensor to stop when the concentration of the target gas detected by the second gas sensor 2 falls below a threshold Th. In this case, the control unit 3 stops the second gas sensor 2 when the concentration of the target gas falls below the threshold Th once, or a predetermined number of times.

[0047] Furthermore, increasing the number of times the second gas sensor 2 is driven and stopped may accelerate its deterioration. Therefore, it is preferable to set the number of times the second gas sensor 2 is driven and stopped, as well as the driving time, in a manner that minimizes deterioration, depending on the environment in which the gas detector 100 is installed and the type of gas being detected.

[0048] (Notification from a working gas sensor) In the first embodiment, the control unit 3 is configured to provide an identifiable notification of which of the first gas sensor 1 and the second gas sensor 2 is active. For example, when the notification unit 4 provides notification by emitting light such as an LED, the control unit 3 provides notification that the first gas sensor 1 is active by lighting up the LED in blue. The control unit 3 also provides notification that the second gas sensor 2 is active by lighting up the LED in yellow. Furthermore, for example, when the notification unit 4 provides notification by sound, the control unit 3 provides notification that the first gas sensor 1 is active by causing the notification unit 4 to emit a short beep, beep, beep sound. The control unit 3 also provides notification that the second gas sensor 2 is active by causing the notification unit 4 to emit a long beep, beep, beep sound.

[0049] (Gas sensor control processing) Next, with reference to Figure 6, the control process of the gas sensor by the control unit 3 will be described.

[0050] In step S1 of Figure 6, the control unit 3 uses the first gas sensor 1 to acquire a first detection result 30 of the gas to be detected.

[0051] Next, in step S2, the control unit 3 determines whether or not to activate the second gas sensor 2, which detects the target gas, based on the first detection result 30. Specifically, if the first detection result 30 indicates the presence of the target gas, the control unit 3 determines to activate the second gas sensor 2. If the second gas sensor 2 is activated, the process proceeds to step S3. If the second gas sensor 2 is not activated, the process ends.

[0052] When the process proceeds from step S2 to step S3, that is, when the second gas sensor 2 is driven, in step S3, the control unit 3 uses the second gas sensor 2 to acquire a second detection result 31 of the gas to be detected.

[0053] Next, in step S4, the control unit 3 determines the concentration of the gas to be detected based on the second detection result 31.

[0054] Next, in step S5, the control unit 3 determines whether the concentration of the gas to be detected, determined based on the second detection result 31, is below the threshold Th. If the concentration of the gas to be detected is below the threshold Th, the process proceeds to step S6. If the concentration of the gas to be detected is greater than the threshold Th, the process proceeds to step S3.

[0055] If the process proceeds from step S5 to step S6, in step S6, the control unit 3 stops the second gas sensor 2. After that, the process ends.

[0056] The control unit 3 controls the first gas sensor 1 to operate continuously by performing the processes in steps S1 to S4 at predetermined time intervals.

[0057] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0058] In the first embodiment, as described above, the control unit 3 controls whether or not to drive the second gas sensor 2 based on the first detection result 30 of the first gas sensor 1, and when driving the second gas sensor 2, it determines the concentration of the gas to be detected based on the second detection result 31 of the second gas sensor 2. As a result, the second gas sensor 2 is driven only when it is determined that driving is necessary based on the first detection result 30 of the first gas sensor 1, so the rate of deterioration of the second gas sensor 2 can be slowed down compared to a configuration in which the second gas sensor 2 is driven without being based on the first detection result 30 of the first gas sensor 1. Therefore, the lifespan of the second gas sensor 2 can be extended. As a result, the lifespan of the gas detector 100 can be extended by extending the lifespan of the gas sensor itself. Furthermore, since the first detection result 30 is not used to determine the concentration of the target gas, and the concentration of the target gas is determined based on the second detection result 31 of the second gas sensor 2, even if the first gas sensor 1 deteriorates, it is possible to suppress a decrease in the accuracy of determining the concentration of the target gas in the gas detector 100.

[0059] Furthermore, in the first embodiment, as described above, the first gas sensor 1 and the second gas sensor 2 are of the same type. This makes it possible to suppress the complexity of the device configuration compared to the case where the first gas sensor 1 and the second gas sensor 2 are of different types.

[0060] Furthermore, in the first embodiment, as described above, the control unit 3 either controls the first gas sensor 1 to drive continuously or controls it to drive intermittently, and controls the second gas sensor 2 to drive when the first detection result 30 indicates that the target gas is present. As a result, the second gas sensor 2 is driven only when the target gas is present, so the rate of deterioration of the second gas sensor 2 can be easily slowed compared to a configuration in which the second gas sensor 2 is driven regardless of the presence of the target gas. Therefore, the lifespan of the second gas sensor 2 can be easily extended. Also, since the first detection result 30 only needs to have enough accuracy to determine whether or not the target gas is present, the first gas sensor 1 can continue to be used even if the detection accuracy of the first gas sensor 1 decreases. Therefore, the actual service life of the first gas sensor 1 can be extended. As a result, the actual service life of the first gas sensor 1 and the lifespan of the second gas sensor 2 can be extended, so the gas detector 100 can have an even longer lifespan.

[0061] Furthermore, in the first embodiment, as described above, the control unit 3 uses the first detection result 30 to determine the presence or absence of the target gas, and the second detection result 31 to determine the concentration of the target gas. As a result, the first gas sensor 1 only needs to be able to determine the presence or absence of the target gas, and does not need to determine the concentration of the target gas based on the first detection result 30. Therefore, the first gas sensor 1 can be used even if the accuracy of determining the concentration of the target gas decreases, thus extending the actual usage period of the first gas sensor 1 compared to a gas sensor that determines the concentration of the target gas. Also, since the concentration of the target gas is determined based on the second detection result 31 of the second gas sensor 2, even if the accuracy of determining the concentration of the target gas in the first detection result 30 of the first gas sensor 1 decreases, it does not affect the accuracy of determining the concentration of the target gas as a gas detector 100. Therefore, even if the accuracy of determining the concentration of the target gas in the first gas sensor 1 decreases, it is possible to suppress a decrease in the accuracy of determining the concentration of the target gas in the gas detector 100 itself, thereby suppressing a decrease in the reliability of the gas detector 100. As a result, it is possible to provide a gas detector 100 that can achieve a longer lifespan while suppressing a decrease in reliability.

[0062] Furthermore, in the first embodiment, as described above, the first gas sensor 1 and the second gas sensor 2 are provided on the same substrate 11. This allows the first gas sensor 1 and the second gas sensor 2 to be formed by MEMS technology, which forms mechanical structures in a semiconductor substrate using a semiconductor manufacturing process. As a result, the lifespan of the semiconductor gas sensor can be extended.

[0063] Furthermore, in the first embodiment, as described above, the control unit 3 is configured to notify which of the first gas sensor 1 and the second gas sensor 2 is being driven, making it possible to identify which gas sensor is being driven. This allows the user to easily understand whether the gas detector 100 is detecting the presence of the target gas or determining the concentration of the target gas. As a result, user convenience (usability) can be improved.

[0064] Furthermore, in the first embodiment, as described above, the gas sensor control method includes a step of determining the concentration of the gas to be detected based on the second detection result 31. This makes it possible to provide a gas sensor control method that extends the lifespan of the gas detector 100 by extending the lifespan of the gas sensor itself, similar to the gas detector 100.

[0065] [Second Embodiment] Next, a second embodiment will be described with reference to Figures 7 and 8.

[0066] The gas detector 200 according to the second embodiment comprises a first gas sensor 1, a second gas sensor 2, a control unit 201, a notification unit 4, a storage unit 5, an amplifier 6, and a communication unit 7. The configurations of the first gas sensor 1, the second gas sensor 2, the notification unit 4, the storage unit 5, the amplifier 6, and the communication unit 7 are the same as those of the first embodiment, so a detailed explanation is omitted.

[0067] Furthermore, the storage unit 5 in the second embodiment stores first drive information 50 used for controlling the second gas sensor 2, which will be described later. The first drive information 50 is information about a predetermined time interval for driving the second gas sensor 2, and information about the drive time when driving the second gas sensor 2. The predetermined time interval and predetermined time for driving the second gas sensor 2 are set in advance according to the gas to be detected and are stored in the storage unit 5 as the first drive information 50.

[0068] Here, for example, if the second gas sensor 2 is a semiconductor type gas sensor, if it is poisoned with siloxane while not in operation, silicon oxide may be generated on the element of the gas sensor, and the deterioration of the gas sensor may progress.

[0069] Therefore, in the second embodiment, the control unit 201 controls the second gas sensor 2 to be driven at predetermined time intervals regardless of the first detection result 30. That is, the control unit 201 intermittently drives the second gas sensor 2 regardless of the presence or absence of the gas to be detected. Specifically, the control unit 201 drives the second gas sensor 2 for a predetermined time at predetermined time intervals based on the first drive information 50. The predetermined time interval at which the control unit 201 drives the second gas sensor 2 is longer than the time interval at which the control unit 201 drives the first gas sensor 1.

[0070] (Driving process for the second gas sensor) Next, referring to Figure 8, we will explain the process by which the control unit 201 drives the second gas sensor 2 regardless of the first detection result 30.

[0071] In step S10 of Figure 8, the control unit 201 acquires the first drive information 50 from the storage unit 5.

[0072] Next, in step S11, the control unit 201 determines whether or not to drive the second gas sensor 2. Specifically, the control unit 201 determines, based on the first drive information 50, whether or not it is time to drive the second gas sensor 2. If the second gas sensor 2 is to be driven, the process proceeds to step S12. If the second gas sensor 2 is not to be driven, the process ends.

[0073] If the process proceeds from step S11 to step S12, in step S12, the control unit 201 drives the second gas sensor 2.

[0074] Next, in step S13, the control unit 201 determines whether a predetermined time has elapsed since the second gas sensor 2 was activated. If the predetermined time has elapsed since the second gas sensor 2 was activated, the process proceeds to step S14. If the predetermined time has not elapsed since the second gas sensor 2 was activated, the process in step S13 is repeated.

[0075] If the process proceeds from step S13 to step S14, in step S14, the control unit 201 stops the second gas sensor 2. After that, the process ends.

[0076] The other configurations of the second embodiment are the same as those of the first embodiment described above.

[0077] (Effects of the second embodiment) In the second embodiment, the following effects can be obtained.

[0078] In the second embodiment, as described above, the control unit 201 controls the second gas sensor 2 to be driven at predetermined time intervals regardless of the first detection result 30. This reduces the progression of deterioration of the second gas sensor 2, for example, in the case of a type of gas sensor such as a semiconductor gas sensor, which deteriorates when poisoned with siloxane while not being driven. As a result, the lifespan of the gas detector 200 can be extended even in the case of a type of gas sensor that deteriorates when not driven.

[0079] Other effects of the second embodiment are the same as those of the first embodiment described above.

[0080] (modified version) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims.

[0081] For example, the above embodiment shows an example configuration in which the control unit 3 controls the first gas sensor 1 to operate continuously, but the present invention is not limited to this. In the present invention, the control unit does not have to operate the first gas sensor continuously.

[0082] For example, as shown in the modified example in Figure 9, the gas detector 300 may include a first gas sensor 1, a second gas sensor 2, a control unit 301, a notification unit 4, a storage unit 5, an amplifier 6, and a communication unit 7. The configurations of the first gas sensor 1, the second gas sensor 2, the notification unit 4, the storage unit 5, the amplifier 6, and the communication unit 7 are the same as those of the first embodiment described above, so a detailed explanation is omitted.

[0083] In this modified version, the storage unit 5 stores second drive information 51, which is used to control the intermittent operation of the first gas sensor 1, as described later. The second drive information 51 is information about predetermined time intervals for intermittently operating the first gas sensor 1. The predetermined time intervals for intermittently operating the first gas sensor 1 are set in advance and stored in the storage unit 5 as second drive information 51.

[0084] In this modified configuration, the control unit 301 controls the intermittent operation of the first gas sensor 1. Specifically, the control unit 301 heats the sensing unit 1a to a predetermined temperature by pulse-driving the heating unit 1b at predetermined time intervals, thereby performing detection at the predetermined temperature of the first gas sensor 1 at predetermined time intervals. In other words, the control unit 301 pulse-heats the sensing unit 1a to a temperature at which methane gas can be detected at predetermined time intervals, thereby performing detection of methane gas at predetermined time intervals. For example, the control unit 301 performs detection of the first gas sensor 1 at a predetermined temperature with a period of approximately 60 seconds. The control unit 301 may also perform detection for the entire duration of the pulse in which the sensing unit 1a is pulse-heated, or it may perform detection for a portion of the duration of the pulse in which the sensing unit 1a is pulse-heated (for example, for the duration of one point). The control unit 301 then controls the operation of the second gas sensor 2 when the first detection result 30 indicates the presence of the target gas.

[0085] (Gas sensor control processing) Next, with reference to Figure 10, the control process of the gas sensor by the control unit 301 will be described. Note that processes similar to those performed by the control unit 3 in the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0086] In step S20 of Figure 10, the control unit 301 acquires the second drive information 51 from the storage unit 5.

[0087] Next, in step S21, the control unit 301 determines whether or not to drive the first gas sensor 1. Specifically, the control unit 301 determines, based on the second drive information 51, whether or not it is time to drive the first gas sensor 1. If the first gas sensor 1 is to be driven, the process proceeds to step S1. If the first gas sensor 1 is not to be driven, the process in step S21 is repeated.

[0088] If the process proceeds from step S21 to step S1, in step S1, the control unit 301 acquires the first detection result 30. Then, in step S2, the control unit 301 determines, based on the first detection result 30, whether or not to activate the second gas sensor 2, which detects the target gas. If the second gas sensor 2 is not activated, the process ends. If the second gas sensor 2 is activated, the process proceeds to steps S3 and S4, where the concentration of the target gas is determined. After that, if the process proceeds from step S5 to step S6, the second gas sensor 2 is stopped, and then the process ends.

[0089] In the modified gas detector 300, as described above, the control unit 301 controls the first gas sensor 1 to drive intermittently, and when the first detection result 30 indicates the presence of the target gas, it controls the second gas sensor 2 to drive. This makes it possible to extend the lifespan of the gas detector 300 even further, similar to the gas detector 100 according to the first embodiment.

[0090] Furthermore, while the first and second embodiments described above show examples of configurations in which the first gas sensor 1 and the second gas sensor 2 are of the same type, the present invention is not limited thereto. The first gas sensor and the second gas sensor may be of different types, as long as it is possible to determine the presence or absence of the target gas using the first gas sensor and the concentration of the target gas using the second gas sensor.

[0091] Furthermore, while the first and second embodiments described above show examples of configurations in which the first gas sensor 1 and the second gas sensor 2 are provided on the same substrate 11, the present invention is not limited thereto. The first gas sensor and the second gas sensor do not have to be arranged on the same substrate. In this case, in order to have multiple gas sensors detect the same target gas, it is necessary to arrange each gas sensor within a predetermined range (for example, a few centimeters).

[0092] Furthermore, while the first and second embodiments described above show an example configuration in which the control unit 3 (control unit 201) identifies and notifies which of the first gas sensor 1 and the second gas sensor 2 is being driven, the present invention is not limited thereto. For example, depending on the degree of deterioration of the first gas sensor, the detection sensitivity of the first gas sensor may become too sharp. In this case, the degree of danger of the gas to be detected cannot be determined until the concentration of the gas to be detected is determined based on the second detection result from the second gas sensor. Therefore, the control unit does not need to identify and notify which of the first and second gas sensors is being driven. In this case, the control unit only needs to notify that at least the second gas sensor is being driven.

[0093] Furthermore, while the first and second embodiments described above show an example configuration in which the gas detector 100 (gas detector 200) comprises one first gas sensor and one second gas sensor 2, the present invention is not limited thereto. The gas detector may comprise a plurality of first gas sensors and a plurality of second gas sensors. In addition, if the gas detector comprises a plurality of second gas sensors, it may be configured to use the next second gas sensor (an unused second gas sensor) when the second gas sensor currently in use reaches the end of its lifespan and can no longer be used to determine the concentration of the gas to be detected. That is, if the gas detector comprises a plurality of second gas sensors, it may be configured to use each second gas sensor one at a time. Also, if the gas detector comprises a plurality of second gas sensors, it may be used as a first gas sensor when the second gas sensor currently in use reaches the end of its lifespan and can no longer be used to determine the concentration of the gas to be detected. In other words, multiple second gas sensors can be used one by one, and any second gas sensor that can no longer be used to determine the concentration of the target gas can be used as a first gas sensor to determine the presence or absence of the target gas.

[0094] Furthermore, while the first and second embodiments described above show an example where the threshold value Th is 1 / 100 (1%) of the 10% LEL of the gas to be detected, the present invention is not limited thereto. For example, the threshold value can be any value as long as it is possible to detect the presence or absence of the gas to be detected.

[0095] Furthermore, while the first and second embodiments described above show an example configuration in which the control unit 3 (control unit 201) detects the gas at a predetermined temperature at predetermined time intervals of approximately 60 seconds using the first gas sensor 1, the present invention is not limited to this. In the present invention, the gas at a predetermined temperature may be detected at predetermined time intervals other than 60 seconds.

[0096] Furthermore, while the first and second embodiments described above show examples where the first gas sensor 1 and the second gas sensor 2 are semiconductor-type gas sensors, the present invention is not limited thereto. For example, the first gas sensor and the second gas sensor may be catalytic combustion type gas sensors or gas heat conduction type gas sensors. Also, at least one of the first gas sensor and the second gas sensor may be a gas sensor having a filter covering the top of the sensor element. When the first gas sensor and the second gas sensor are configured as gas sensors other than semiconductor-type, it is necessary to place each gas sensor within a predetermined range (for example, a few centimeters) in order for the first gas sensor and the second gas sensor to detect the same target gas. Also, when at least one of the first gas sensor and the second gas sensor is equipped with a filter, the first gas sensor and the second gas sensor must be placed on different substrates.

[0097] Furthermore, in the above embodiment, an example was shown in which the control unit 3 drives the second gas sensor 2 continuously, but the present invention is not limited to this. For example, the control unit may be configured to drive the second gas sensor intermittently by pulse drive.

[0098] Furthermore, in the above embodiment, an example was shown in which the control unit 3 continues to drive the first gas sensor 1 even after the second gas sensor 2 has been driven, but the present invention is not limited to this. For example, the control unit may be configured to stop the first gas sensor when the second gas sensor is driven. In this case, the control unit should be configured to drive the first gas sensor when the second gas sensor is stopped.

[0099] Furthermore, in the above embodiment, an example was shown in which the control unit 3 stops the second gas sensor when the concentration of the gas to be detected falls below a threshold Th used to determine the presence or absence of the gas to be detected. However, the present invention is not limited to this. For example, the control unit may be configured to stop the second gas sensor when the concentration of the gas to be detected falls below a threshold different from the threshold used to determine the presence or absence of the gas to be detected.

[0100] Furthermore, although the above embodiment showed methane as the gas to be detected, the present invention is not limited to this. For example, the gas to be detected may be hydrogen gas, ethane gas, propane gas, carbon monoxide gas, or hydrogen sulfide gas.

[0101] Furthermore, while the first and second embodiments described above show examples of configurations in which the gas detector 100 (gas detector 200) includes a notification unit 4 and a communication unit 7, the present invention is not limited thereto. In the present invention, the gas detector may be provided with only one of the notification unit and the communication unit. For example, the gas detector may not be provided with a communication unit. Also, the gas detector may not be provided with a notification unit. In this case, the notification unit may be provided separately from the gas detector. Furthermore, even if the gas detector is provided with a notification unit, notification may be performed by an external device to the gas detector.

[0102] Furthermore, in the above embodiment, for the sake of explanation, an example was shown in which the control process was explained using a flow-driven flowchart that processes sequentially according to the processing flow, but the present invention is not limited to this. In the present invention, the control process may be performed by an event-driven process that executes processing on an event-by-event basis. In this case, it may be performed as a completely event-driven process, or a combination of event-driven and flow-driven processes may be used. [Explanation of Symbols]

[0103] 1. First gas sensor 2. Second gas sensor 3, 201, 301 Control Unit 11. Circuit board (chip) 30. First detection result 31. Second detection result 100, 200, 300 Gas Detectors

Claims

1. A gas detector that detects the target gas, A first gas sensor for detecting the target gas, A second gas sensor for detecting the target gas, The system comprises a control unit that controls the first gas sensor and the second gas sensor, The control unit controls whether or not to drive the second gas sensor based on the first detection result of the first gas sensor, and when the second gas sensor is driven, determines the concentration of the gas to be detected based on the second detection result of the second gas sensor, in a gas detector.

2. The gas detector according to claim 1, wherein the first gas sensor and the second gas sensor are gas sensors of the same type.

3. The control unit, Either control the first gas sensor to operate continuously, or control it to operate intermittently. The gas detector according to claim 1, wherein control is performed to drive the second gas sensor when the first detection result indicates the presence of the gas to be detected.

4. The gas detector according to claim 1, wherein the control unit uses the first detection result to determine the presence or absence of the gas to be detected, and uses the second detection result to determine the concentration of the gas to be detected.

5. The gas detector according to claim 1, wherein the first gas sensor and the second gas sensor are provided on the same chip.

6. The gas detector according to claim 1, wherein the control unit is configured to notify which of the first gas sensor and the second gas sensor is being driven in an identifiable manner.

7. The gas detector according to claim 1, wherein the control unit controls the second gas sensor to be driven at predetermined time intervals regardless of the first detection result.

8. A step of obtaining a first detection result of the gas to be detected using a first gas sensor, Based on the first detection result, a step is to determine whether or not to activate the second gas sensor that detects the target gas, When the second gas sensor is driven, the second gas sensor is used to obtain a second detection result of the gas to be detected. A method for controlling a gas sensor, comprising the step of determining the concentration of the gas to be detected based on the second detection result.

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