Sensor module, gas sensor, control device, control method and control program

Abstract

To provide a technology that can identify a kind of gas serving as a base of mixed gas in a sensor module detecting a content rate of at least one kind of specific gas included in mixed gas.SOLUTION: A sensor module, which identifies a content rate of specific gas in mixed gas, comprises: at least one thermal conductivity heater that heats in response to supplied power; at least one element that is heated by the at least one heater; and a control device. The at least one element incudes: a first element that is exposed to the mixed gas; and a second element that is not exposed to the mixed gas. The control device is configured to acquire a first detection value corresponding to a temperature of the first element, and a second detection value corresponding to a temperature of the second element; and identify a kind of based gas on the basis of a first change rate of the first detection value and a second change rate of the second detection value when driving the at least one heater over a prescribed period.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to a sensor module, a gas sensor, a control device, a control method, and a control program for specifying the content rate of a specific gas in a mixed gas containing a base gas and a specific gas.

Background Art

[0002] Conventionally, sensors for detecting the content rate of at least one type of gas contained in a mixed gas are known. For example, Japanese Unexamined Patent Application Publication No. 2022-183481 (Patent Document 1) discloses a thermal conductivity type gas sensor that specifies the content rate of a gas in a mixed gas by utilizing the fact that the thermal conductivity of a gas differs for each type of gas. The gas sensor of Patent Document 1 has a metal layer exposed in the mixed gas.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] The mixed gas includes a specific gas such as hydrogen, which is the target of content rate detection, and a base gas such as air other than the specific gas. When the type of the base gas is different, even if the content rate of the specific gas in the mixed gas is the same, a difference occurs in the amount of heat transferred from the metal layer to the mixed gas, so the temperature change of the metal layer differs depending on the type of the base gas. Due to such a difference in the temperature change of the metal layer depending on the type of the base gas, when calculating the content rate of the specific gas without considering the type of the base gas, an error may occur in the calculation result of the content rate of the specific gas depending on the type of the base gas. For this reason, it has been desired to specify the type of the base gas before the detection process of the content rate of the specific gas.

[0005] The present disclosure has been made in view of the problems of the prior art as described above. More specifically, the present disclosure provides a technique capable of identifying the type of the base gas of the mixed gas in a sensor module that detects the content rate of at least one specific gas contained in the mixed gas.

[0006] The sensor module of the present disclosure is a sensor module that identifies the content rate of a specific gas in a mixed gas, and includes at least one heat conduction type heater that generates heat in response to supplied power, at least one element heated by the at least one heater, and a control device. The at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas. The control device acquires a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and identifies the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving the at least one heater over a predetermined period.

[0007] The control device of the present disclosure is a control device that controls a gas sensor that identifies the content rate of a specific gas in a mixed gas including a base gas and a specific gas. The gas sensor includes at least one heat conduction type heater that generates heat in response to supplied power and at least one element heated by the at least one heater. The at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas. The control device includes a gas sensor interface that acquires a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and an arithmetic device that identifies the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving the at least one heater over a predetermined period.

[0008] The control method of the present disclosure is a control method for controlling a gas sensor that specifies the content rate of a specific gas in a mixed gas containing a base gas and a specific gas. The gas sensor includes at least one heat conduction type heater that generates heat in response to supplied power, and at least one element heated by the at least one heater. The at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas. The control method includes, as a process executed by a computer, a step of obtaining a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step of specifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period.

[0009] The control program of the present disclosure is a control program for controlling a gas sensor that specifies the content rate of a specific gas in a mixed gas containing a base gas and a specific gas. The gas sensor includes at least one heat conduction type heater that generates heat in response to supplied power, and at least one element heated by the at least one heater. The at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas. The control program causes a computer to execute a step of obtaining a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step of specifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

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Figure 8

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Figure 10

Figure 11

[0011] [Detailed Description] [Embodiment 1] Embodiment 1 of the present disclosure will be described in detail with reference to the drawings. For the same or corresponding parts in the drawings, the same reference numerals are given and the description thereof will not be repeated.

[0012] [Configuration of Sensor Module] With reference to FIGS. 1 to 5, the configuration of the sensor module 1 according to Embodiment 1 will be described. FIG. 1 is a diagram for explaining the configuration of the sensor module 1 according to Embodiment 1. As shown in FIG. 1, the sensor module 1 according to Embodiment 1 includes a gas sensor 2 and a control device 100. The gas sensor 2 includes a sensor unit 10 and a sensor unit 20. Note that the sensor unit 10 may correspond to the "first sensor unit" in the present disclosure. The sensor unit 20 may correspond to the "second sensor unit" in the present disclosure.

[0013] Each of the sensor unit 10 and the sensor unit 20 is a chip-type gas sensor that has a micro heater using MEMS (Micro Electro Mechanical Systems) technology and detects a gas to be detected such as hydrogen. The sensor units 10 and 20 are installed in the same air-fuel mixture. Hereinafter, the space in which the sensor units 10 and 20 are installed may be referred to as an "atmosphere". In the first embodiment, the substrate of the sensor unit 10 and the substrate of the sensor unit 20 are separate substrates.

[0014] Hereinafter, the sensor unit 10 will be described with reference to FIG. 2. FIG. 2 is a diagram for explaining the configuration of the sensor unit 10 having the element E1 exposed in the air-fuel mixture according to the first embodiment. A cross-sectional view of the sensor unit 10 is shown in FIG. 2. As shown in FIG. 2, the sensor unit 10 includes a silicon substrate Sb1, thin film layers 11 and 19, at least one element E1, and at least one heater unit H1. Note that the element E1 may correspond to the "first element" in the present disclosure. The heater unit H1 may correspond to the "first heater" in the present disclosure.

[0015] An open cavity Cv1 is formed on the back surface of the silicon substrate Sb1. The thin film layer 19 is provided on the silicon substrate Sb1. The thin film layer 11 is provided on the thin film layer 19. The thickness D0 of the thin film layer 19 and the thin film layer 11 is, for example, about 2.4 μm. Each base material of the thin film layers 11 and 19 contains silicon dioxide (SiO2).

[0016] At least one heater section H1 is provided in the thin film layer 11. The heater section H1 has a metal oxide M2 and a metal P2. The metal P2 is configured to include platinum. An element E1 is provided on the thin film layer 11. The element E1 has a metal oxide M1 and a metal P1 provided on the metal oxide M1. The metal P1 is configured to include platinum. The metal oxide M1 functions as a barrier film between the thin film layer 11 and the metal P1, and includes at least one of titanium oxide (TiO2), chromium oxide (Cr2O3), tantalum pentoxide (Ta2O5), and a metal oxide with oxygen deficiency.

[0017] In the heat conduction type sensor section 10 configured as described above, the heater section H1 generates heat according to the electric power supplied from the control device 100 (hereinafter also referred to as "heater power"), and the thin film layer 11 is heated. In the sensor section 10, the element E1 provided on the thin film layer 11 is exposed to the mixed gas. Direct heat exchange occurs between the element E1 and the mixed gas. The temperature of the thin film layer 11 changes according to the thermal conductivity of the gas present in the mixed gas in which the sensor section 10 is disposed.

[0018] Here, with reference to FIGS. 3 and 4, the thermal conductivity of each of a plurality of types of gases will be described. Hydrogen, air, and nitrogen have different thermal conductivities from each other. FIG. 3 is a diagram showing an example of the thermal conductivity of each of a plurality of types of gases. As shown in FIG. 3, when the temperature in the mixed gas containing each gas is 0 °C, the thermal conductivity of hydrogen is the highest, and then, in descending order of thermal conductivity, air and nitrogen are listed. Air is standard air, for example, the air at the time of shipment of the sensor sections 10 and 20.

[0019] Furthermore, for each of the gases hydrogen, air, and nitrogen, the thermal conductivity of each gas changes according to the temperature change of the mixed gas. FIG. 4 is a diagram showing an example of the thermal conductivity with respect to temperature for each of a plurality of types of gases. In the graph shown in FIG. 4, for simplicity of illustration, the thermal conductivity of hydrogen is converted to 1 / 10.

[0020] As shown in FIG. 4, as the temperature in the mixed gas changes between 200K and 800K, the thermal conductivity of each gas changes. Specifically, the higher the temperature in the mixed gas, the higher the thermal conductivity of each gas. Further, the thermal conductivity with respect to the temperature in the mixed gas is the largest for hydrogen, followed by air and nitrogen in that order. Thus, since the thermal conductivity varies depending on the type of gas present in the mixed gas in which the sensor unit 10 is disposed, the heat generation amount of the thin film layer 11 varies depending on the type (thermal conductivity) of gas present in the mixed gas.

[0021] For example, the thermal conductivity of hydrogen is greater than the thermal conductivity of each of air and nitrogen. For this reason, if the atmosphere around the sensor unit 10 is only hydrogen, the heat of the thin film layer 11 more easily escapes into the mixed gas than when the atmosphere contains only air or when the atmosphere contains only nitrogen, and the temperature of the thin film layer 11 (hereinafter, also referred to as "heater temperature") becomes lower.

[0022] Also, the thermal conductivity of each of air and nitrogen is smaller than the thermal conductivity of hydrogen. For this reason, when the atmosphere contains only air, the heat of the thin film layer 11 is less likely to escape into the mixed gas than when the atmosphere is composed only of hydrogen, and the heater temperature becomes higher. Similarly, when the atmosphere contains only nitrogen, the heat of the thin film layer 11 is less likely to escape into the mixed gas than when the atmosphere contains only hydrogen, and the heater temperature becomes higher.

[0023] That is, the heater temperature changes according to the type (thermal conductivity) of gas present in the mixed gas in which the sensor unit 10 is disposed, and the resistance value of the platinum contained in the element E1 changes according to the heater temperature. By utilizing such a phenomenon, the control device 100 can acquire the resistance value of the platinum of the element E1 as a detection value, and based on the acquired detection value, detect the content rate of a specific gas present in the mixed gas.

[0024] In the present embodiment, the control device 100 specifies the heater temperature based on the detected resistance value of platinum, and detects the content rate of a specific gas based on the specified heater temperature. Hereinafter, the resistance value of platinum in the element may be simply referred to as the "resistance value of the element". Note that the control device 100 may directly detect the heater temperature of the thin film layer 11 as a detection value instead of acquiring the resistance value of platinum.

[0025] Referring to FIG. 1, the control device 100 in the example of the present embodiment acquires the detection value (the resistance value of platinum of the element E1) acquired from the sensor unit 10, and specifies at least the content rate of hydrogen present in the atmosphere in which the sensor units 10 and 20 are disposed. The control device 100 is an information processing device such as, for example, a notebook or desktop PC, a smartphone, a tablet terminal, an in-vehicle ECU (Engine Control Unit), or a PLC (Programmable Logic Controller) of production equipment.

[0026] The main components of the control device 100 include an arithmetic unit 101, a memory 102, a storage device 103, a communication device 104, a display interface 105, a peripheral device interface 106, a storage medium interface 107, and a gas sensor interface 108.

[0027] The arithmetic unit 101 is an arithmetic entity (computer) that executes various processes by executing various programs. The arithmetic unit 101 is configured by a processor such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), for example. Note that a processor, which is an example of the arithmetic unit 101, has a function of executing various processes by executing a program, but some or all of these functions may be implemented using a dedicated hardware circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0028] The "processor" is not limited to a narrow - sense processor that executes processing in a stored - program manner like a CPU or MPU, and may include hard - wired circuits such as an ASIC or an FPGA. Therefore, the "processor", which is an example of the arithmetic unit 101, can also be read as a processing circuitry whose processing is defined in advance by computer - readable code and / or hard - wired circuits. Note that the arithmetic unit 101 may be composed of one chip or a plurality of chips. Furthermore, some functions of the arithmetic unit 101 may be provided in a server device (for example, a cloud - type server device) not shown in the figure.

[0029] The memory 102 includes a volatile storage area (for example, a working area) that temporarily stores program codes, work memories, etc. when the arithmetic unit 101 executes various programs. Examples of the memory 102 include volatile memories such as DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory), or non - volatile memories such as ROM (Read Only Memory) and flash memory.

[0030] The storage device 103 stores various programs or various data executed by the arithmetic unit 101. The storage device 103 may be one or more non - transitory computer - readable media or one or more computer - readable storage media. Examples of the storage device 103 include HDD (Hard Disk Drive) and SSD (Solid State Drive). In the control device 100 according to Embodiment 1, the storage device 103 stores the control program 120 and the thermal conductivity data 130.

[0031] As described above, the control program 120 defines at least a process of identifying the type of the base gas contained in the mixed gas in which the sensor unit 10 is installed, and a process for detecting the hydrogen content present in the mixed gas, based on the detection values acquired by the arithmetic unit 101 from the sensor unit 10. In Embodiment 1, the mixed gas in which the sensor unit 10 is installed is a mixed gas composed of a plurality of types of gases including at least hydrogen. The thermal conductivity data 130 is data regarding the thermal conductivity of each of the plurality of types of gases contained in the mixed gas, and includes data indicating the thermal conductivity with respect to the temperature in each gas as shown in FIG. 4.

[0032] The communication device 104 transmits and receives data to and from an external device (not shown) via wired communication or wireless communication.

[0033] The display interface 105 is an interface for connecting the display 51. The display interface 105 realizes input / output of data between the control device 100 and the display 51. For example, the display interface 105 outputs various image data to the display 51 according to the control of the arithmetic unit 101. The display 51 displays the image data acquired from the display interface 105.

[0034] The peripheral device interface 106 is an interface for connecting peripheral devices 60 such as a keyboard or a mouse. The peripheral device interface 106 realizes input / output of data between the control device 100 and the peripheral device 60. For example, the peripheral device interface 106 acquires various data such as the control program 120 or the thermal conductivity data 130 input by the user using the peripheral device 60.

[0035] The memory medium interface 107 is an interface for connecting a memory medium 70 such as a removable disk or a USB (Universal Serial Bus) memory. The memory medium interface 107 reads various data such as programs or data stored in the memory medium 70, and writes various data to the memory medium 70. For example, the memory medium interface 107 reads various data such as the control program 120 or the thermal conductivity data 130 stored in the memory medium 70 from the memory medium 70, or writes various data such as the control program 120 or the thermal conductivity data 130 stored in the storage device 103 to the memory medium 70.

[0036] The gas sensor interface 108 is an interface for connecting the gas sensor 2. The gas sensor interface 108 detects a detection value corresponding to the heater temperature and acquires the detection value. In addition, the gas sensor interface 108 supplies heater power to the sensor units 10 and 20 according to the control of the arithmetic unit 101. Note that the gas sensor interface 108 may be divided into different configurations as an interface for acquiring a detection value from the gas sensor 2 and an interface for supplying heater power to the gas sensor 2.

[0037] The air-fuel mixture around the sensor units 10 and 20 contains a specific gas and a base gas. The specific gas is the type of gas whose content rate in the air-fuel mixture is to be detected, and is hydrogen in the first embodiment. The base gas is the gas when the specific gas is removed from the air-fuel mixture. For example, when detecting the content rate of hydrogen contained in the air, hydrogen corresponds to the specific gas and air corresponds to the base gas. The sensor module 1 is used to detect the content rate of hydrogen, but it is assumed to be installed in various environments. For example, it may be installed in an air-fuel mixture having another gas such as nitrogen as the base gas other than in the air.

[0038] However, as described with reference to FIGS. 3 and 4, there is a difference between the thermal conductivity of air and the thermal conductivity of nitrogen. Therefore, depending on whether the base gas is air or nitrogen, an error may occur in the detected hydrogen content. Thus, in addition to the sensor unit 10 having the element E1 exposed to the mixed gas, the sensor module 1 of the present embodiment further includes a sensor unit 20, which will be described later.

[0039] FIG. 5 is a diagram for explaining the configuration of the sensor unit 20 having the passivation layer 22 according to the first embodiment. The sensor unit 20 has a similar configuration to the sensor unit 10, except that the sensor unit 20 further includes a passivation layer 22. That is, the silicon substrate Sb2, the thin film layer 21, the thin film layer 29, the heater unit H2, the element E2, and the cavity Cv2 in FIG. 5 respectively correspond to the silicon substrate Sb1, the thin film layer 11, the thin film layer 19, the heater unit H1, the element E1, and the cavity Cv1 in FIG. 2.

[0040] As shown in FIG. 5, the sensor unit 20 further includes a passivation layer 22 provided on the thin film layer 21. In the sensor unit 20, the element E2 is provided in the passivation layer 22. That is, in the sensor unit 20, the element E2 is covered by the passivation layer 22 without being exposed to the mixed gas. The base material of the passivation layer 22 is, for example, silicon dioxide (SiO2), aluminum oxide (Al2O3), or silicon nitride (SiN). Note that the base material of the passivation layer 22 may be other materials as long as they do not allow oxygen gas to permeate.

[0041] In the sensor unit 20, the thickness D1 of the thin film layer 21 is greater than the thickness D2 of the passivation layer 22. Note that the element E2 may correspond to the "second element" in the present disclosure. The heater unit H1 may correspond to the "second heater" in the present disclosure. The silicon substrate Sb2 may correspond to the "support substrate" in the present disclosure. The thin film layer 21 may correspond to the "first layer" in the present disclosure. The passivation layer 22 may correspond to the "second layer" in the present disclosure. Hereinafter, a method for identifying the type of base gas will be described using the sensor unit 10 having the element E1 exposed to the mixed gas and the sensor unit 20 having the element E2 covered by the passivation layer 22.

[0042] [Difference in Resistance Change Rate Depending on the Presence or Absence of Oxygen] FIG. 6 is a graph showing the resistance change rate of the element E1 when the base gas does not contain oxygen and the hydrogen content of the mixed gas. In the example of FIG. 6, the mixed gas contains hydrogen as the specific gas and nitrogen as the base gas. That is, the mixed gas in FIG. 6 is composed of only nitrogen and hydrogen and does not contain oxygen.

[0043] In FIG. 6, the horizontal axis represents the hydrogen content. The vertical axis represents the resistance change rate of the element E1. The resistance change rate of the element E1 is a value obtained by dividing the resistance value of the element E1 when heater power is supplied to the heater unit H1 and the heater unit H1 is generating sufficient heat by the resistance value of the element E1 when heater power is not supplied to the heater unit H1 and the heater unit H1 is not generating heat.

[0044] In FIG. 6, lines Ln1 to Ln6 are shown. In FIG. 6, for illustrative convenience, lines Ln1, Ln3, and Ln5 are shown as solid lines, and lines Ln2, Ln4, and Ln6 are shown as dashed lines.

[0045] Line Ln1 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 560°C. Line Ln2 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 440°C. Line Ln3 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 325°C. Line Ln4 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 210°C. Line Ln5 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 120°C. Line Ln6 represents the resistance change rate of element E1 with respect to the hydrogen content when the heater unit H1 is raised to 50°C.

[0046] As shown in FIG. 6, the higher the temperature of the heater unit H1, the smaller the resistance change rate of the element E1. That is, when the temperature of the heater unit H1 is high, the resistance value of the element E1 heated by the heater unit H1 is likely to decrease significantly. When the temperature of the heater unit H1 is increased, the resolution of the gas sensor 2 is improved, and the gas sensor 2 can detect the hydrogen content more accurately.

[0047] FIG. 7 is a graph showing the resistance change rate of the element E1 when the base gas contains oxygen and the hydrogen content of the mixed gas. In the example of FIG. 7, the mixed gas contains hydrogen as a specific gas and air as a base gas. Here, air is the general atmosphere on the earth, containing 78% nitrogen, 21% oxygen, and 1% such as carbon dioxide. The mixed gas in FIG. 6 contains oxygen. In FIG. 7, similar to FIG. 6, the vertical axis represents the resistance change rate of the element E1, and the horizontal axis represents the hydrogen content. Lines Ln1A to Ln5A are shown in FIG. 7. In FIG. 7, for the sake of illustration, lines Ln1A, Ln3A, and Ln5A are shown as solid lines, and lines Ln2A and Ln4A are shown as dashed lines.

[0048] Line Ln1A represents the resistance change rate of element E1 with respect to the hydrogen content when the heater section H1 is raised to 500°C. Line Ln2A represents the resistance change rate of element E1 with respect to the hydrogen content when the heater section H1 is raised to 360°C. Line Ln3A represents the resistance change rate of element E1 with respect to the hydrogen content when the heater section H1 is raised to 230°C. Line Ln4A represents the resistance change rate of element E1 with respect to the hydrogen content when the heater section H1 is raised to 120°C. Line Ln5A represents the resistance change rate of element E1 with respect to the hydrogen content when the heater section H1 is raised to 50°C.

[0049] As shown in FIGS. 6 and 7, the graph of FIG. 6 when the base gas does not contain oxygen is different from the graph of FIG. 7 when the base gas contains oxygen. Specifically, in FIG. 6, the resistance change rate of element E1 decreases, while in FIG. 7, the resistance change rate of element E1 increases around 0.5%. This is because oxygen reacts with hydrogen using platinum as a catalyst, causing the heater temperature to rise. As shown by line Ln1A in FIG. 7, when the temperature of the heater section H1 is raised to 500°C for a mixed gas with a hydrogen content of 0.6% and an air content of 99.4%, the resistance value change rate of element E1 increases significantly to around 1.04. Similarly, as shown by line Ln2A, when the temperature of the heater section H1 is raised to 360°C for a mixed gas with a hydrogen content of 0.6% and an air content of 99.4%, the resistance value change rate of element E1 increases to around 1.005. Thus, the resistance change rate of element E1 with respect to the hydrogen content when the atmosphere contains oxygen and when the atmosphere does not contain oxygen increases as the temperature of the heater section H1 is raised. The resistance change rate of element E1 is affected by the surface area and volume of element E1. However, for example, when the heater temperature is raised to 230°C or higher, it increases to a level recognizable by the control device 100.

[0050] As described above, in the sensor unit 10 having the exposed element E1, it has been explained that the relationship between the change rate of the resistance value of the element E1 and the hydrogen content varies depending on whether oxygen is contained in the base gas. The inventor of the present invention has noted that even when the sensor unit 20 in which the element E2 is covered by the passivation layer 22 is installed in an atmosphere containing oxygen, the relationship between the resistance change rate of the element E2 and the hydrogen content is the same as the relationship shown in the graph of FIG. 6 in which the sensor unit 10 is installed in an oxygen-free atmosphere. Even when the sensor unit 20 is installed in a mixed gas containing oxygen, since the element E2 is not exposed to the mixed gas, no catalytic reaction occurs. Therefore, the resistance change rate of the element E2 will exhibit the same change rate as the resistance change rate when the element E1 is exposed to a mixed gas containing no oxygen.

[0051] That is, when the base gas does not contain oxygen, no catalytic reaction occurs in both of the elements E1 and E2, and the resistance change rate of the element E1 in the sensor unit 10 and the resistance change rate of the element E2 in the sensor unit 20 will be the same change rate. On the other hand, when the base gas contains oxygen, a catalytic reaction occurs only in the element E1, and the difference between the resistance change rate of the element E1 in the sensor unit 10 and the resistance change rate of the element E2 in the sensor unit 20 becomes large. Hereinafter, a processing procedure for determining whether oxygen is contained in the base gas will be described using this phenomenon.

[0052] [Processing Procedure] FIG. 8 is a flowchart showing a processing procedure for determining the hydrogen content after determining whether the base gas contains oxygen. The processing in FIG. 8 is realized by the control program 120 being executed by the arithmetic unit 101.

[0053] The arithmetic unit 101 starts the execution of the flowchart shown in FIG. 8, for example, based on a command from the user. When the heater unit H1 or the heater unit H2 is being driven at the start of the execution of the flowchart shown in FIG. 8, the arithmetic unit 101 stops the driving of the heater unit H1 and the heater unit H2, and after a predetermined period has elapsed, executes the processing of step S101.

[0054] The arithmetic unit 101 acquires the resistance value T1 of the element E1 (step S101). The resistance value T1 may correspond to the "first detection value" in the present disclosure. The arithmetic unit 101 acquires the resistance value T2 of the element E2 (step S102). The resistance value T2 may correspond to the "second detection value" in the present disclosure. That is, in steps S101 and S102, the arithmetic unit 101 acquires the resistance values of the elements E1 and E2 when they are not heated by the heater units H1 and H2.

[0055] Subsequently, the arithmetic unit 101 drives the heater units H1 and H2 at a temperature equal to or higher than a predetermined temperature (step S103). In Embodiment 1, the predetermined temperature is 230°C. As described above, when the temperatures of the heater units H1 and H2 are raised to 230°C or higher, the difference between the resistance change rate of the element E1 and the resistance change rate of the element E2 when the base gas contains oxygen becomes large. The arithmetic unit 101 determines whether or not a predetermined period has elapsed (step S104). That is, after starting the drive of the heater units H1 and H2, in order to sufficiently raise the heater temperature, the arithmetic unit 101 waits for a predetermined period. If the predetermined period has not elapsed (NO in step S104), the arithmetic unit 101 repeats the process of step S104.

[0056] When the predetermined period has elapsed (YES in step S104), the arithmetic unit 101 acquires the resistance value T1A of the element E1 (step S105). The resistance value T1A may correspond to the "first detection value" in the present disclosure. Also, the arithmetic unit 101 acquires the resistance value T2A of the element E2 (step S106). The resistance value T2A may correspond to the "second detection value" in the present disclosure. That is, the resistance value T1A is the resistance value of the element E1 when the heater unit H1 heats the element E1. The resistance value T2A is the resistance value of the element E2 when the heater unit H2 heats the element E2.

[0057] The arithmetic unit 101 calculates the resistance change rate (T1A / T1) of the element E1 (step S107). The resistance change rate (T1A / T1) may correspond to the "first change rate" in the present disclosure. The arithmetic unit 101 calculates the resistance change rate (T2A / T2) of the element E2 (step S108). The resistance change rate (T2A / T2) may correspond to the "second change rate" in the present disclosure. Here, the arithmetic unit 101 compares the resistance value change rate (T1A / T1) of the element E1 with the resistance value change rate (T2A / T2) of the element E2.

[0058] Specifically, the arithmetic unit 101 determines whether the difference between the resistance value change rate (T1A / T1) of the element E1 and the resistance value change rate (T2A / T2) of the element E2 is within a predetermined range (step S109). If it is within the predetermined range (YES in step S109), the arithmetic unit 101 determines that no catalytic reaction has occurred in the element E1 and determines that the base gas is not air containing oxygen (step S110). In Embodiment 1, the arithmetic unit 101 determines that the base gas is nitrogen when the base gas does not contain air (oxygen).

[0059] The arithmetic unit 101 specifies the hydrogen content using a first table showing the relationship between the hydrogen content and the resistance change rate of the element E1 when the base gas is nitrogen, which is stored in advance in the storage device 103 (step S111).

[0060] On the other hand, if it is outside the predetermined range (NO in step S109), the arithmetic unit 101 determines that a catalytic reaction has occurred in the element E1 and determines that the base gas is air containing oxygen (step S112).

[0061] The arithmetic unit 101 specifies the hydrogen content using a second table showing the relationship between the hydrogen content and the resistance change rate of the element E1 when the base gas is air, which is stored in advance in the storage device 103 (step S113).

[0062] As described above, in this embodiment, the types of the base gas can be specified using the two sensor units 10 and 20. After specifying the base gas, the control device 100 specifies the hydrogen content using the table corresponding to the specified base gas. Thus, in the sensor module 1 of this embodiment, even though the base gas is nitrogen, the hydrogen content can be specified using the second table corresponding to air, and an error in the specified hydrogen content can be suppressed. Similarly, in the sensor module 1 of this embodiment, even though the base gas is air, the hydrogen content can be specified using the first table corresponding to nitrogen, and an error in the specified hydrogen content can be suppressed.

[0063] In the example of FIG. 8, an example of specifying the heater temperature using the resistance values of the elements E1 and E2 has been described. However, the heater temperature may be specified using a separate temperature sensor. That is, in the example of FIG. 8, the resistance change rate of the element E1 corresponds to the "first change rate" in the present disclosure, and the resistance change rate of the element E2 corresponds to the "second change rate" in the present disclosure.

[0064] [Embodiment 2] In Embodiment 1, an example in which the thickness D2 of the passivation layer 22 in the sensor unit 20 is configured to be thinner than the thickness D1 of the thin film layer 21 has been described. In Embodiment 2, an example in which the relationship between the thickness of the passivation layer 22 and the thickness of the thin film layer 21 in the sensor unit 20 is reversed will be described. In addition, in Embodiment 2, the description of the configuration overlapping with that of Embodiment 1 will not be repeated.

[0065] FIG. 9 is a diagram for explaining the configuration of the sensor unit 20A having the passivation layer 22A according to Embodiment 2. In Embodiment 2, the thickness D2A of the passivation layer 22A is thicker than the thickness D1A of the thin film layer 21A.

[0066] As shown in FIG. 9, in Embodiment 2, compared with Embodiment 1, the distance between the surface Sf1 of the passivation layer 22 and the element E2 becomes larger. As a result, in Embodiment 2, the element E2 in the passivation layer 22 is less likely to be affected by the external air-fuel mixture, and it is possible to suppress the occurrence of an unintentional catalytic reaction when oxygen is contained in the base gas.

[0067] [Embodiment 3] In Embodiment 1, an example in which the thin film layers 21 and 29 and the passivation layer 22 are provided on the upper part of the silicon substrate Sb2 has been described. In Embodiment 3, an example in which the sensor unit 20B further has insulating layers Z1 and Z2 will be described. Note that in Embodiment 3, the description of the configuration overlapping with that of Embodiment 1 will not be repeated.

[0068] FIG. 10 is a diagram for explaining the configuration of the sensor unit 20B having the passivation layer 22 according to Embodiment 3. As shown in FIG. 10, in the sensor unit 20B, an insulating layer Z1 is provided between the thin film layer 29 and the silicon substrate Sb2. Further, in the sensor unit 20B, an insulating layer Z2 is provided between the passivation layer 22 and the thin film layer 21.

[0069] Each base material of the insulating layers Z1 and Z2 contains, for example, aluminum oxide (Al2O3) or silicon nitride (SiN). Each of the insulating layers Z1 and Z2 prevents the permeation of oxygen gas. As a result, in Embodiment 3, it is possible to suppress oxygen contained in the external air-fuel mixture of the sensor unit 20B from reaching the heater unit H2.

[0070] [Embodiment 4] In Embodiment 1, the configuration in which the silicon substrate Sb2 in the sensor unit 20A has the cavity Cv2 has been described. In Embodiment 4, an example in which the cavity Cv2A is provided as a closed space will be described. Note that in Embodiment 4, the description of the configuration overlapping with that of Embodiment 1 will not be repeated.

[0071] FIG. 11 is a diagram for explaining the configuration of the sensor unit 20C having the passivation layer 22 according to the fourth embodiment. As shown in FIG. 11, the cavity Cv2A of the fourth embodiment is provided as a closed space. The cavity Cv2A is provided in a region that overlaps with the heater H2 when the silicon substrate Sb2 is viewed in plan. By providing the cavity Cv2A as a closed space, the external air-fuel mixture is prevented from directly entering the cavity Cv2A. Thereby, in the fourth embodiment, it is possible to suppress oxygen contained in the external air-fuel mixture from reaching the heater unit H2 from the cavity Cv2A.

[0072] [Modification Example] In the above example, in the sensor module 1, an example in which each of the sensor unit 10 and the sensor unit 20 is provided as a separate substrate has been described. However, the sensor unit 10 and the sensor unit 20 may be integrally provided in the same substrate. Specifically, the sensor module 1 may include both the element E1 on which the sensor unit 10 is exposed and the element E2 that is not exposed without having the sensor unit 20. In this case, the number of heater units for heating the elements E1 and E2 may be one. Thereby, the number of heater units can be reduced, and an increase in cost can be suppressed. Furthermore, since only one heater unit is provided in the sensor module 1, it is not necessary to consider the variation in temperature rise between the heater unit H1 and the heater unit H2, and the resistance changes of the elements E1 and E2 can be compared more accurately.

[0073] In the above example, an example in which the predetermined temperature in step S103 of FIG. 8 is 230°C has been described, but the predetermined temperature is not limited to 230°C. For example, the predetermined temperature may be a value such as 100°C, 150°C, 200°C, 300°C, etc.

[0074] In the above example, in step S110 of FIG. 8, since the base gas does not contain oxygen, an example in which it is determined that the base gas is nitrogen has been described. However, the arithmetic unit 101 may determine that the base gas is a gas other than nitrogen that does not contain oxygen. The arithmetic unit 101 can determine the type of the base gas according to the usage and installation location of the sensor module 1.

[0075] [Appendix] (Item 1, FIGS. 1 to 8) The sensor module (1) of the present disclosure is a sensor module that specifies the content rate of a specific gas in a mixed gas containing a base gas and a specific gas. (1) It includes at least one heat conduction type heater (H1, H2) that generates heat according to the supplied power, at least one element (E1, E2) heated by at least one heater, and a control device (100). The at least one element includes a first element (E1) exposed in the mixed gas and a second element (E2) not exposed in the mixed gas. The control device (100) acquires a first detection value corresponding to the temperature of the first element (E1) and a second detection value corresponding to the temperature of the second element (E2) (S101, S102, S105, S106), and based on a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period, specifies the type of the base gas (S109).

[0076] (Item 2, FIG. 8) The sensor module (1) according to Item 1, wherein the control device (100) determines whether the base gas is air based on the first change rate and the second change rate (S109).

[0077] (Item 3, FIG. 8) The sensor module (1) according to Item 1 or 2, wherein the specific gas contains hydrogen.

[0078] (Item 4, FIG. 8) The sensor module (1) according to any one of Items 1 to 3, wherein the control device (100) specifies the type of the base gas based on the difference between the first change rate and the second change rate (S109).

[0079] (Item 5, Figure 8) The sensor module 1 according to Item 4, wherein when the difference between the first change rate and the second change rate is within a predetermined range (NO in S109), the control device (100) determines that the base gas is a gas other than air (S110), and when the difference between the first change rate and the second change rate is not within the predetermined range (YES in S109), the control device determines that the base gas is air (S112). (Item 6, Figure 8) The sensor module (1) according to Item 5, wherein the gas other than air contains nitrogen.

[0080] (Item 7, Figure 8) The sensor module (1) according to Item 5 or Item 6, wherein the control device (100) drives at least one heater at a temperature equal to or higher than a predetermined temperature at which the difference between the first change rate and the second change rate is not within the predetermined range when the base gas is air (S103).

[0081] (Item 8, Figure 8) The sensor module 1 according to Item 7, wherein the predetermined temperature is 230°C.

[0082] (Item 9, Figure 8) The sensor module (1) according to any one of Items 1 to 8, wherein at least one heater includes a first heater (H1) that heats the first element (E1) and a second heater (H2) that heats the second element. The sensor module (1) further includes a first sensor unit (10) including the first element (E1) and the first heater (H1), and a second sensor unit (20) including the second element (E2) and the second heater (H2).

[0083] (Item 10, Figure 5) The sensor module (1) according to Item 9, wherein the second sensor unit (20) further includes a support substrate (Sb2), a first layer (21) disposed above the support substrate, and a second layer (22) disposed above the first layer. The first layer (21) includes the second heater (H2), and the second layer (22) includes the second element (E2).

[0084] (Item 11, Figure 9) The sensor module (1) according to Item 10, wherein the thickness (D2A) of the second layer (22A) is greater than the thickness (D1A) of the first layer (21A).

[0085] (Item 12, Figure 5) The sensor module (1) according to Item 10 or 11, ~.

[0086] (Item 13, Figure 10) The sensor module (1) according to any one of Items 10 to 12, further comprising an insulating layer (Z1) disposed between the first layer (21) and the support substrate (Sb2). The insulating layer (Z1) is formed of at least one of aluminum oxide, silicon nitride, or silicon dioxide.

[0087] (Item 14, Figure 11) The sensor module (1) according to any one of Items 10 to 13, wherein a cavity (Cv2A) for providing a closed space is formed in the support substrate (Sb2) in a region where the support substrate (Sb2) and the second heater (H2) overlap when the support substrate (Sb2) is viewed in plan.

[0088] (Item 15, Figure 8) The sensor module (1) according to any one of Items 10 to 14, wherein the control device (100) specifies the content rate of the specific gas based on whether the base gas is air or not (S111, S113).

[0089] (Item 16, Figures 1 to 8) The gas sensor (2) of the present disclosure is a gas sensor (2) that specifies the content rate of a specific gas in a mixed gas containing a base gas and a specific gas. The gas sensor (2) includes at least one heat conduction type heater (H1, H2) that generates heat in response to supplied power, and at least one element (E1, E2) heated by at least one heater (H1, H2). The at least one element (E1, E2) includes a first element (E1) exposed in the mixed gas and a second element (E2) not exposed in the mixed gas. The gas sensor (2) is configured to be able to specify the type of the base gas based on a first change rate of a first detection value corresponding to the temperature of the first element and a second change rate of a second detection value corresponding to the temperature of the second element when at least one heater is driven over a predetermined period.

[0090] (Item 17, FIGS. 1 to 8) The control device (100) of the present disclosure is a control device (100) that controls a gas sensor (2) that specifies the content rate of a specific gas in a mixed gas including a base gas and a specific gas. The gas sensor (2) includes at least one heater (H1, H2) of a heat conduction type that generates heat in response to supplied power, and at least one element (E1, E2) heated by the at least one heater. The at least one element includes a first element (E1) exposed to the mixed gas and a second element (E2) not exposed to the mixed gas. The control device (100) includes a gas sensor interface (108) that acquires a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period, and specifies the type of the base gas (S109), and an arithmetic device (101).

[0091] (Item 18, FIGS. 1 to 8) The control method of the present disclosure is a control method that controls a gas sensor that specifies the content rate of a specific gas in a mixed gas including a base gas and a specific gas. The gas sensor (2) includes at least one heater (H1, H2) of a heat conduction type that generates heat in response to supplied power, and at least one element (E1, E2) heated by the at least one heater. The at least one element includes a first element (E1) exposed to the mixed gas and a second element (E2) not exposed to the mixed gas. The control method includes, as processes executed by a computer, steps (S101, S102, S105, S106) of acquiring a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step (S109) of specifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period.

[0092] (Item 19, FIGS. 1 to 8) The program (120) of the present disclosure is a control program (120) for controlling a gas sensor (2) that specifies the content rate of a specific gas in a mixed gas including a base gas and a specific gas. The gas sensor includes at least one heat conduction type heater (H1, H2) that generates heat in response to supplied power, and at least one element (E1, E2) that is heated by the at least one heater. The at least one element includes a first element (E1) exposed to the mixed gas and a second element (E2) not exposed to the mixed gas. The control program (120) causes a computer to execute steps (S101, S102, S105, S106) of obtaining a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step (S109) of specifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when driving at least one heater over a predetermined period.

[0093] As described above, the embodiments of the present disclosure have been described, but it is also possible to variously modify the above-described embodiments. Further, the scope of the present invention is not limited to the above-described embodiments. The scope of the present invention is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0094] 1 Sensor module, 2 Gas sensor, 10, 20, 20A to 20C Sensor units, 11, 19, 21, 21A, 29 Thin film layers, 22, 22A Passivation layers, 51 Display, 60 Peripheral device, 70 Storage medium, 100 Control device, 101 Arithmetic device 102 Memory, 103 Storage device, 104 Communication device, 105 Display interface, 106 Peripheral device interface, 107 Storage medium interface, 108 Gas sensor interface, 120 Control program, H1, H2 Heater section, 130 Thermal conductivity data, Cv1, Cv2, Cv2A Cavity, D0, D1A, D1, D2A, D2 Thickness, E1, E2 Element, Ln1~Ln6, Ln1A~Ln5A Line, M1 Metal oxide, P1, P2 Metal, Sb1, Sb2 Silicon substrate, Sf1 Surface, T1, T1A, T2A, T2 Resistance value, Z1, Z2 Insulating layer.

Claims

1. A sensor module for specifying the content rate of a specific gas in a mixed gas containing a base gas and a specific gas, at least one heat conduction type heater that generates heat in response to supplied power, at least one element heated by the at least one heater, and a control device, wherein the at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas, and the control device, acquires a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and specifies the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when the at least one heater is driven over a predetermined period. A sensor module.

2. The sensor module according to claim 1, wherein the control device determines whether the base gas is air based on the first change rate and the second change rate.

3. The sensor module according to claim 1 or claim 2, wherein the specific gas includes hydrogen.

4. The sensor module according to claim 1 or claim 2, wherein the control device specifies the type of the base gas based on a difference between the first change rate and the second change rate.

5. The control device, when the difference between the first change rate and the second change rate is within a predetermined range, determines that the base gas is a gas other than air, and when the difference between the first change rate and the second change rate is not within the predetermined range, determines that the base gas is air. The sensor module according to claim 4.

6. The sensor module according to claim 5, wherein the gas other than air includes nitrogen.

7. The sensor module according to claim 5, wherein the control device drives the at least one heater at a temperature equal to or higher than a predetermined temperature at which the difference between the first change rate and the second change rate is not within the predetermined range when the base gas is air.

8. The sensor module according to claim 7, wherein the predetermined temperature is 230°C.

9. The at least one heater includes a first heater that heats the first element and a second heater that heats the second element, and the sensor module, a first sensor unit including the first element and the first heater, The sensor module according to claim 1 or claim 2, further comprising a second sensor unit including the second element and the second heater.

10. The second sensor unit includes a support substrate, a first layer disposed above the support substrate, and a second layer disposed above the first layer, wherein the first layer includes the second heater, and the second layer includes the second element, the sensor module according to claim 9.

11. The sensor module according to claim 10, wherein the thickness of the second layer is greater than the thickness of the first layer.

12. The sensor module according to claim 10, wherein the second layer is formed of at least one of aluminum oxide, silicon nitride, or silicon dioxide.

13. The sensor module according to claim 10, further comprising an insulating layer disposed between the first layer and the support substrate, wherein the insulating layer is formed of at least one of aluminum oxide, silicon nitride, or silicon dioxide.

14. The sensor module according to claim 10, wherein a cavity for providing a closed space is formed in the support substrate in a region where the support substrate and the second heater overlap when the support substrate is viewed in plan.

15. The sensor module according to claim 1 or claim 2, wherein the control device specifies the content rate of the specific gas based on whether the base gas is air or not.

16. A gas sensor for specifying the content rate of a specific gas in a mixed gas containing a base gas and a specific gas, at least one heat conductive heater that generates heat in response to supplied power, and at least one element heated by the at least one heater, wherein the at least one element includes a first element exposed in the mixed gas and a second element not exposed in the mixed gas, and the gas sensor is configured to be able to specify the type of the base gas based on a first change rate of a first detection value corresponding to the temperature of the first element and a second change rate of a second detection value corresponding to the temperature of the second element when the at least one heater is driven for a predetermined period.

17. A control device for controlling a gas sensor that specifies the content rate of a specific gas in a mixed gas containing a base gas and a specific gas, wherein the gas sensor has at least one heat conductive heater that generates heat in response to supplied power, At least one element heated by the at least one heater, and the at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas, the control device includes a gas sensor interface that obtains a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and an arithmetic unit that identifies the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when the at least one heater is driven over a predetermined period. A control device

18. A control method for controlling a gas sensor that identifies the content rate of a specific gas in a mixed gas including a base gas and the specific gas, the gas sensor includes at least one heat conduction type heater that generates heat according to supplied power, and at least one element heated by the at least one heater, and the at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas, the control method includes, as a process executed by a computer, a step of obtaining a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step of identifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when the at least one heater is driven over a predetermined period. A control method

19. A control program for controlling a gas sensor that identifies the content rate of a specific gas in a mixed gas including a base gas and the specific gas, the gas sensor includes at least one heat conduction type heater that generates heat according to supplied power, and at least one element heated by the at least one heater, and the at least one element includes a first element exposed to the mixed gas and a second element not exposed to the mixed gas, the control program causes a computer to execute a step of obtaining a first detection value corresponding to the temperature of the first element and a second detection value corresponding to the temperature of the second element, and a step of identifying the type of the base gas based on a first change rate of the first detection value and a second change rate of the second detection value when the at least one heater is driven over a predetermined period. A control program

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