JP6339479B2 - Combustible gas detector - Google Patents

Description

  The present invention relates to a flammable gas detection device that detects a gas concentration of a flammable gas present in an atmosphere to be detected.

  2. Description of the Related Art In recent years, research on fuel cells has been actively conducted as an energy source having high efficiency and a low environmental load in response to social demands such as environmental protection and nature protection. Among fuel cells, a polymer electrolyte fuel cell (PEFC) has attracted attention as an energy source for home use or an on-vehicle energy source because of its advantages such as low operating temperature and high output density. Solid polymer fuel cells use hydrogen as a fuel, which is more likely to leak than other fuels. Therefore, in order to put the polymer electrolyte fuel cell into practical use, it is considered that a gas detection device that detects hydrogen leakage is required.

  As a flammable gas detection device that detects the concentration of flammable gas in the atmosphere to be detected, the gas detection element placed in the atmosphere to be detected has a heating resistor whose resistance value changes according to its own temperature change, and the object to be detected A device in which a resistance temperature detector whose resistance value changes according to a change in the environmental temperature of the atmosphere is known.

  And in such a combustible gas detection device, an environmental temperature is detected using a temperature detection circuit that outputs a temperature voltage indicating a voltage value corresponding to the environmental temperature based on the resistance value of the resistance temperature detector. (For example, refer to Patent Document 1).

JP 2014-41055 A

  However, in the combustible gas detection device described in Patent Document 1, when the disconnection failure occurs in the temperature detection circuit, the value of the temperature voltage output from the temperature detection circuit is a value that can be taken in a normal state. There is a fear that it cannot be determined whether the temperature detection circuit is normal or abnormal.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique that makes it possible to determine whether a circuit that detects the environmental temperature of a detected atmosphere is normal or abnormal.

  The present invention made to achieve the above object is a combustible gas detection device comprising a heating resistor, an energization control means, a resistance temperature detector, and a temperature voltage output circuit, and comprises an abnormality determination means. .

  The heating resistor is provided on the base and is disposed in the atmosphere to be detected, and its resistance value changes due to its own temperature change. The energization control means performs control to switch the energization state of the heating resistor at a preset energization cycle, thereby changing the temperature of the heating resistor from the preset first set temperature and the first set temperature. It switches alternately with the 2nd preset temperature set so that it may become low.

  The resistance temperature detector is provided on the same base as the heating resistor, and the resistance value changes according to a change in the environmental temperature that is the temperature of the atmosphere to be detected. The temperature voltage output circuit outputs a temperature voltage indicating a voltage value corresponding to the environmental temperature using a resistance temperature detector.

  The abnormality determination means controls the first temperature voltage, which is a temperature voltage when the temperature of the heating resistor is controlled to be the first set temperature, and the temperature of the heating resistor to be the second set temperature. If the relationship with the second temperature voltage, which is the temperature voltage at the time of being set, satisfies a preset temperature voltage abnormality determination condition, it is determined that an abnormality has occurred in the temperature voltage output circuit.

  In the combustible gas detection device of the present invention configured as described above, the first temperature voltage and the second temperature voltage output from the temperature voltage output circuit when the temperature voltage output circuit is abnormal are values that can be taken at the normal time. Even if it exists, when the relationship between the first temperature voltage and the second temperature voltage satisfies the temperature voltage abnormality determination condition, it can be determined that an abnormality has occurred in the temperature voltage output circuit. That is, the combustible gas detection device of the present invention utilizes the fact that the difference between the first temperature voltage and the second temperature voltage is different between when the temperature voltage output circuit is normal and when it is abnormal, A determination is made as to whether the circuit is normal or abnormal.

  Furthermore, the combustible gas detection device of the present invention does not need to newly add means for detecting an abnormality in the temperature voltage output circuit in order to determine that an abnormality has occurred in the temperature voltage output circuit. .

  In the combustible gas detection device of the present invention, the temperature voltage abnormality determination condition may be that a difference between the first temperature voltage and the second temperature voltage is smaller than a preset abnormality determination voltage difference. Good.

  Thus, the combustible gas detection device according to the present invention is a simple method of comparing the difference between the first temperature voltage and the second temperature voltage with the abnormality determination voltage difference, and whether the temperature voltage output circuit is normal. It can be determined whether it is abnormal, and the calculation load of the combustible gas detection device can be reduced.

  In the combustible gas detection device of the present invention, the temperature voltage abnormality determination condition may be that a ratio of the second temperature voltage to the first temperature voltage is larger than a preset abnormality determination voltage ratio. .

  Thus, the combustible gas detection device of the present invention has a normal temperature voltage output circuit with a simple method of determining whether or not the ratio of the second temperature voltage to the first temperature voltage is larger than the abnormality determination voltage ratio. It is possible to determine whether or not it is abnormal, and the calculation load of the combustible gas detection device can be reduced.

  Further, in the combustible gas detection device of the present invention, a state in which the temperature voltage abnormality determination condition is smaller than the abnormality determination voltage difference in which the difference between the first temperature voltage and the second temperature voltage is set in advance is a preset abnormality. The fixed time may be continued.

  Further, in the combustible gas detection device of the present invention, the state in which the temperature voltage abnormality determination condition is larger than the abnormality determination voltage ratio in the ratio of the second temperature voltage to the first temperature voltage continues for a preset abnormality determination time. You may make it be.

  Thus, the combustible gas detection device of the present invention suppresses the occurrence of a situation in which the abnormality determination unit erroneously determines due to the temperature voltage output from the temperature voltage output circuit fluctuating due to noise, and the abnormality determination unit The determination accuracy by can be improved.

  The combustible gas detection device of the present invention further includes a first average value calculation unit and a second average value calculation unit, and the abnormality determination unit calculates the first temperature voltage average value calculated by the first average value calculation unit. The first temperature voltage may be used, and the second temperature voltage average value calculated by the second average value calculating unit may be used as the second temperature voltage to determine whether or not the temperature voltage abnormality determination condition is satisfied.

  The first average value calculating means acquires the temperature voltage from the temperature voltage output circuit a plurality of times in the first energization control period, which is a period in which the temperature of the heating resistor is controlled to become the first set temperature, A first temperature voltage average value that is an average value of a plurality of temperature voltages acquired during the energization control period is calculated.

  The second average value calculating means acquires the temperature voltage from the temperature voltage output circuit a plurality of times in the second energization control period, which is a period in which the temperature of the heating resistor is controlled to become the second set temperature, A second temperature voltage average value that is an average value of a plurality of temperature voltages acquired during the energization control period is calculated.

  As a result, the combustible gas detection device of the present invention uses the first temperature voltage or the average value of the plurality of temperature voltages even when noise is included in some of the acquired plurality of temperature voltages. By adopting it as the second temperature voltage, the influence of noise can be reduced, and the determination accuracy by the abnormality determination means can be improved.

  In the combustible gas detection device of the present invention, the gas concentration calculation means controls the terminal voltage of the heating resistor when the temperature of the heating resistor is controlled to be the first set temperature, and the heating resistor Using the voltage between the terminals of the heating resistor and the temperature voltage when the temperature is controlled to be the second set temperature, an operation for calculating the concentration of the combustible gas contained in the detected atmosphere is performed. You may make it perform.

1 is a circuit diagram showing a configuration of a combustible gas detection device 1. FIG. 3 is a plan view of a gas detection element 2. FIG. It is a figure which shows the AA cross section of FIG. It is a flowchart which shows the first half part of a calculation data acquisition process. It is a flowchart which shows the latter half part of a calculation data acquisition process. It is a flowchart which shows a gas concentration calculation process. It is a flowchart which shows a circuit abnormality detection process.

Embodiments of the present invention will be described below with reference to the drawings.
The combustible gas detection device 1 of the embodiment to which the present invention is applied is a heat conduction type gas detector, for example, installed in a passenger room of a fuel cell vehicle and used for the purpose of detecting hydrogen leakage or the like. It is done.

As shown in FIG. 1, the combustible gas detection device 1 includes a gas detection element 2, a control unit 3, a calculation unit 4, and a DC power source 5.
The gas detection element 2 detects the concentration of hydrogen gas. The control unit 3 controls the operation of the gas detection element 2. The calculation unit 4 executes a process for calculating the hydrogen gas concentration based on the output signal from the gas detection element 2. The DC power supply 5 supplies power to the control unit 3 and the calculation unit 4.

As shown in FIG. 2, the gas detection element 2 includes a base 11, a heating resistor 12, electrodes 13 and 14, and wirings 15 and 16.
The base 11 constitutes the main body of the gas detection element 2 and is a member formed in a rectangular plate shape mainly using silicon. The base 11 is formed to have a size of about several mm in both vertical and horizontal directions (in this embodiment, a size of about 3 mm × 3 mm).

As shown in FIG. 3, the base 11 includes a silicon substrate 21 and an insulating layer 22 formed on the surface of the silicon substrate 21. The insulating layer 22 is made of an insulating material such as silicon dioxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ).

  In the center of the silicon substrate 21, a cavity 23 that is formed in a square shape in plan view and penetrates the silicon substrate 21 is formed. Thereby, the base 11 has a diaphragm structure in which the silicon substrate 21 is a frame and the insulating layer 22 is a thin film.

  The heating resistor 12 is linearly formed of a conductive material (platinum (Pt) in the present embodiment) whose resistance value changes with its own temperature change and has a large temperature resistance coefficient. The linear heating resistor 12 is spirally embedded in a region of the insulating layer 22 that faces the cavity 23.

  The electrodes 13 and 14 are made of, for example, aluminum (Al) or gold (Au), and are installed on the surface of the base 11. As shown in FIG. 2, the electrode 13 and the electrode 14 are connected to one end and the other end of the linear heating resistor 12 via wirings 15 and 16, respectively.

  A resistance temperature detector 17 is provided inside the insulating layer 22. The resistance temperature detector 17 is formed in a rectangular plate shape with a conductive material whose electric resistance changes in proportion to the temperature. In the present embodiment, the resistance temperature detector 17 is formed of a conductive material (in this embodiment, platinum (Pt)) whose resistance value increases as the temperature rises.

  Furthermore, electrodes 18 and 19 are provided on the surface of the base 11. The electrode 18 and the electrode 19 are respectively connected to one end and the other end in the longitudinal direction of the temperature measuring resistor 17 formed in a rectangular shape.

As shown in FIG. 1, the control unit 3 includes an energization control circuit 31 and a temperature adjustment circuit 32.
First, the energization control circuit 31 is a circuit that keeps the temperature of the heating resistor 12 constant, and includes a bridge circuit 41, an amplifier circuit 42, and a current adjustment circuit 43.

The bridge circuit 41 is a Wheatstone bridge circuit including the heating resistor 12, the variable resistance unit 51, and fixed resistors 52 and 53.
The heating resistor 12 has one end connected to the fixed resistor 52 and the other end connected to the variable resistor unit 51. Hereinafter, a connection point between the heating resistor 12 and the fixed resistor 52 is referred to as a connection point P1 +. A connection point between the heating resistor 12 and the variable resistance unit 51 is referred to as a connection point PG. The connection point PG is grounded.

The variable resistor unit 51 includes a changeover switch 61 and fixed resistors 62 and 63.
The changeover switch 61 includes connection terminals 71, 72, and 73. The connection terminal 71 is connected to the fixed resistor 53, the connection terminal 72 is connected to the fixed resistor 62, and the connection terminal 73 is connected to the fixed resistor 63. The changeover switch 61 is either in a state in which the connection terminal 71 and the connection terminal 72 are connected or in a state in which the connection terminal 71 and the connection terminal 73 are connected according to the switching signal CG1 output from the calculation unit 4. Switch to one side. Hereinafter, a connection point between the connection terminal 71 and the fixed resistor 53 is referred to as a connection point P1-.

  The fixed resistor 62 has an end on the side not connected to the connection terminal 71 connected to the connection point PG. The fixed resistor 63 has an end on the side not connected to the connection terminal 72 connected to the connection point PG.

  The fixed resistor 52 is connected at its end on the side not connected to the heating resistor 12 to the end on the side of the fixed resistor 53 not connected to the variable resistor 51. Hereinafter, a connection point between the fixed resistor 52 and the fixed resistor 53 is referred to as a connection point PV.

  The bridge circuit 41 is applied with a control voltage from the current adjustment circuit 43 so that the potential difference generated between the connection point P1 + and the connection point P1- is zero. Accordingly, the resistance value of the heating resistor 12, that is, the temperature of the heating resistor 12 is controlled to be constant.

  The fixed resistor 62 has a resistance value that is controlled so that the heating resistor 12 reaches a first set temperature (for example, 400 ° C.). The fixed resistor 63 has a resistance value controlled so that the heating resistor 12 has a second set temperature (for example, 300 ° C.) set lower than the first set temperature.

The amplifier circuit 42 is a differential amplifier circuit, and includes an operational amplifier 81, fixed resistors 82, 83, and 84, and a capacitor 85.
The fixed resistor 82 is connected between the non-inverting input terminal of the operational amplifier 81 and the connection point P1 +. Fixed resistor 83 is connected between the inverting input terminal of operational amplifier 81 and connection point P1-. The fixed resistor 84 and the capacitor 85 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 81.

  When the input voltage at the non-inverting input terminal is higher than the input voltage at the inverting input terminal, the value of the adjustment signal C output from the amplifier circuit 42 is increased. On the other hand, when the input voltage at the non-inverting input terminal is smaller than the input voltage at the inverting input terminal, the value of the adjustment signal C becomes small.

  The current adjustment circuit 43 is a PNP transistor, and has an emitter, a collector, and a base. The emitter of the current adjustment circuit 43 is connected to a power supply line that supplies a DC power supply Vcc. The collector of the current adjustment circuit 43 is connected to the connection point PV. The base of the current adjustment circuit 43 is connected to the output terminal of the operational amplifier 81.

  For this reason, when the value of the adjustment signal C increases, the on-resistance of the transistors constituting the current adjustment circuit 43 increases, and the current flowing from the DC power supply Vcc to the bridge circuit 41 via the current adjustment circuit 43 decreases. On the other hand, when the value of the adjustment signal C decreases, the on-resistance decreases, and the current flowing from the DC power supply Vcc to the bridge circuit 41 increases.

  In the energization control circuit 31 configured as described above, when energization from the DC power supply 5 to the bridge circuit 41 is started, the amplifier circuit 42 and the current adjustment circuit 43 are connected between the connection point P1 + and the connection point P1-. Feedback control is performed to adjust the current flowing through the bridge circuit 41 so that the generated potential difference becomes zero. As a result, the resistance value of the heating resistor 12, that is, the temperature of the heating resistor 12 is controlled to a constant value determined by the variable resistance portion 51 (that is, the first set temperature or the second set temperature).

  Specifically, when the amount of heat deprived by the combustible gas from the heating resistor 12 is greater than the amount of heat generated in the heating resistor 12 due to a change in the concentration of the combustible gas in the atmosphere to be detected. The temperature of the heating resistor 12 is lowered, and the resistance value of the heating resistor 12 is reduced. Conversely, when the amount of heat taken away from the heat generating resistor 12 by the combustible gas is smaller than the amount of heat generated in the heat generating resistor 12, the temperature of the heat generating resistor 12 rises and the resistance of the heat generating resistor 12 increases. The value increases.

  When the resistance value of the heating resistor 12 decreases as described above, the amplifier circuit 42 and the current adjustment circuit 43 increase the current flowing through the bridge circuit 41, in other words, the amount of heat generated in the heating resistor 12. Conversely, when the resistance value of the heating resistor 12 increases, the current flowing through the bridge circuit 41, in other words, the amount of heat generated in the heating resistor 12 is reduced. In this way, the amplifier circuit 42 and the current adjustment circuit 43 perform feedback control that brings the resistance value of the heating resistor 12, in other words, the temperature of the heating resistor 12 close to a constant value.

  The magnitude of the current flowing through the heating resistor 12 can be detected by measuring the voltage V1 at the connection point P1 +. The magnitude of this current corresponds to the amount of heat necessary to keep the temperature of the heating resistor 12 (in other words, the resistance value) constant, that is, the amount of heat taken from the heating resistor 12 to the combustible gas. The amount of heat taken from the heating resistor 12 to the combustible gas depends on the concentration of the combustible gas. For this reason, the concentration of the combustible gas can be detected by measuring the voltage V1.

  The voltage V1 when the heating resistor 12 is controlled to be at the first set temperature (400 ° C. in the present embodiment) is referred to as a high temperature voltage VH. The voltage V1 when the heating resistor 12 is controlled to be at the second set temperature (300 ° C. in the present embodiment) is referred to as a low temperature voltage VL.

Next, the temperature adjustment circuit 32 includes a bridge circuit 91 and an amplifier circuit 92.
The bridge circuit 91 is a Wheatstone bridge circuit including the resistance temperature detector 17 and fixed resistors 101, 102, and 103.

The resistance temperature detector 17 has one end connected to the fixed resistor 103 and the other end grounded. Hereinafter, a connection point between the resistance temperature detector 17 and the fixed resistor 101 is referred to as a connection point P2-.
The fixed resistor 101 has one end connected to the fixed resistor 102 and the other end grounded. Hereinafter, a connection point between the fixed resistor 101 and the fixed resistor 102 is referred to as a connection point P2 +.

Fixed resistor 102 is connected to a power supply line that supplies DC power supply Vcc at the end not connected to fixed resistor 101.
The fixed resistor 103 is connected at its end on the side not connected to the resistance temperature detector 17 to a power supply line that supplies the DC power supply Vcc.

The amplifier circuit 92 is a differential amplifier circuit, and includes an operational amplifier 111, fixed resistors 112, 113, and 114, and a capacitor 115.
The fixed resistor 112 is connected between the non-inverting input terminal of the operational amplifier 111 and the connection point P2 +. Fixed resistor 113 is connected between the inverting input terminal of operational amplifier 111 and connection point P2-. The fixed resistor 114 and the capacitor 115 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 111.

  The amplifier circuit 92 amplifies the voltage difference between the connection point P2 + and the connection point P2- and outputs the amplified voltage difference VT to the calculation unit 4. Hereinafter, the amplified voltage difference VT is referred to as a temperature voltage VT. The temperature voltage VT when the heating resistor 12 is controlled to be at the first set temperature (400 ° C. in this embodiment) is referred to as a high temperature voltage VTH. Further, the temperature voltage VT when the heating resistor 12 is controlled to be at the second set temperature (300 ° C. in the present embodiment) is referred to as a low temperature voltage VTL.

The arithmetic unit 4 includes a known microcomputer including an arithmetic processing device (CPU and the like), a storage unit (RAM and ROM and the like), an input / output unit, and the like.
The storage unit of the calculation unit 4 stores temperature conversion data, humidity conversion data, and concentration conversion data.

  The temperature conversion data indicates the correlation between the environmental temperature T of the atmosphere to be detected and the temperature voltage VT. The humidity conversion data indicates the correlation among the humidity H in the atmosphere to be detected, the high-temperature voltage VH, the low-temperature voltage VL, and the temperature voltage VT. The concentration conversion data indicates a correlation between the high temperature voltage VH or the low temperature voltage VL and the gas concentration X of the combustible gas. Each conversion data includes conversion map data, a conversion calculation formula, and the like, and is created in advance based on data obtained through experiments or the like.

  The humidity conversion data includes voltage ratio conversion map data and humidity conversion map data. The voltage ratio conversion map data indicates a correlation between the environmental temperature T (and thus the temperature voltage VT) and a voltage ratio VC (0) described later. The humidity conversion map data indicates a correlation between a voltage ratio difference ΔVC described later and the humidity H.

  The concentration conversion data includes high temperature voltage conversion map data, humidity voltage change conversion map data, and gas sensitivity conversion map data. The high-temperature voltage conversion map data indicates a correlation between the temperature voltage VT and a high-temperature voltage VH (0) described later. The humidity voltage change conversion map data shows a correlation between the high temperature voltage VH and the humidity H and a high temperature voltage change ΔVH (H) described later. The map data for gas sensitivity conversion indicates a correlation between the temperature voltage VT and the high temperature voltage VH and a gas sensitivity G (VT) described later.

  The calculation unit 4 is activated when power supply from the DC power supply 5 is started, and after initializing each unit of the calculation unit 4, starts calculation data acquisition processing, gas concentration calculation processing, and circuit abnormality detection processing described later.

First, the calculation data acquisition process will be described.
When the calculation data acquisition process is started, as shown in FIG. 4, the calculation processing device of the calculation unit 4 first performs control for holding the heating resistor 12 at the first set temperature and a resistance temperature detector in S10. Control to energize 17 is started. The control for maintaining the heating resistor 12 at the first set temperature is started by outputting a switching signal CG1 instructing connection between the connection terminal 71 and the connection terminal 72 and energizing the heating resistor 12. .

  Further, in S20, the acquisition determination timer is incremented. This acquisition determination timer is a timer that increments (adds 1) every 1 ms, for example. If the value is set to 0 at a certain time, it is incremented from 0 again at that time. Hereinafter, the value of the acquisition determination timer is referred to as timer value T1.

In S30, the acquisition number counter is reset. Thereby, the value of the acquisition number counter is set to 0. Hereinafter, the value of the acquisition number counter is referred to as an acquisition number N.
Next, in S40, it is determined whether or not the timer value T1 is equal to or greater than a preset acquisition determination value (in this embodiment, for example, a value corresponding to 10 ms). Here, if the timer value T1 is less than the acquisition determination value (S40: NO), the process of S40 is repeated to wait until the timer value T1 becomes equal to or greater than the acquisition determination value. If the timer value T1 is equal to or greater than the acquisition determination value (S40: YES), the acquisition determination timer is reset (set to 0) and the acquisition number counter is incremented (added by 1) in S50.

  Thereafter, in S60, it is determined whether or not the acquisition number N is equal to or higher than a preset high-temperature data acquisition determination value (11 in the present embodiment). If the acquisition number N is less than the high temperature data acquisition determination value (S60: NO), the temperature voltage VT (that is, the high temperature temperature voltage VTH) is acquired from the temperature adjustment circuit 32 in S70, and the calculation is performed. Store in the storage unit of unit 4.

  In S80, it is determined whether or not the acquisition number N is equal to (high temperature data acquisition determination value -1). Here, when the acquisition number N is not equal to (high temperature data acquisition determination value-1) (S80: NO), the process proceeds to S40 and the above-described processing is repeated.

  On the other hand, when the acquisition number N is equal to (high temperature data acquisition determination value-1) (S80: YES), after the acquisition number N becomes 1 (high temperature data acquisition determination value-1) in S90. The average value of the temperature voltage VT (that is, the high temperature temperature voltage VTH) acquired so far is calculated, and this average value is stored in the storage unit of the calculation unit 4 as the temperature voltage average value VTHav. When the process of S90 ends, the process proceeds to S40 and the above process is repeated.

  If the acquisition number N is equal to or higher than the high temperature data acquisition determination value in S60 (S60: YES), the voltage V1 (that is, the high temperature voltage VH) is acquired from the energization control circuit 31 in S100, and the calculation is performed. Store in the storage unit of unit 4.

  In S110, it is determined whether or not the acquisition number N is equal to a preset low temperature switching determination value (20 in the present embodiment). Here, when the acquisition number N is not equal to the low temperature switching determination value (S110: NO), the process proceeds to S40 and the above process is repeated.

  On the other hand, if the acquisition number N is equal to the low temperature switching determination value (S110: YES), the low temperature switching determination value (in this embodiment, 11) after the acquisition number N becomes the high temperature data acquisition determination value (11 in this embodiment). In this embodiment, the average value of the high-temperature voltage VH acquired until 20) is calculated, and this average value is stored in the storage unit of the calculation unit 4 as the high-temperature voltage average value VHav.

  Thereafter, in S130, the acquisition number counter is reset. In S140, the control for holding the heating resistor 12 at the first set temperature is terminated, and the control for holding the heating resistor 12 at the second set temperature is started. The control for maintaining the heating resistor 12 at the second set temperature is started by outputting a switching signal CG1 instructing connection between the connection terminal 71 and the connection terminal 73.

  Then, as shown in FIG. 5, in S150, it is determined whether or not the timer value T1 is equal to or greater than a preset acquisition determination value. Here, when the timer value T1 is less than the acquisition determination value (S150: NO), the process of S150 is repeated to wait until the timer value T1 becomes equal to or greater than the acquisition determination value. If the timer value T1 is greater than or equal to the acquisition determination value (S150: YES), the acquisition determination timer is reset and the acquisition number counter is incremented in S160.

  Next, in S170, it is determined whether or not the acquisition number N is equal to or higher than a preset low-temperature data acquisition determination value (11 in the present embodiment). If the acquisition number N is less than the low-temperature data acquisition determination value (S170: NO), the temperature voltage VT (that is, the low-temperature temperature voltage VTL) is acquired from the temperature adjustment circuit 32 in S180, and the calculation is performed. Store in the storage unit of unit 4.

  In S190, it is determined whether or not the acquisition number N is equal to (low temperature data acquisition determination value -1). If the acquisition number N is not equal to (low-temperature data acquisition determination value-1) (S190: NO), the process proceeds to S150 and the above-described process is repeated.

  On the other hand, when the acquisition number N is equal to (low temperature data acquisition determination value-1) (S190: YES), after the acquisition number N becomes 1 (low temperature data acquisition determination value-1) in S200. The average value of the temperature voltage VT acquired so far is calculated, and this average value is stored in the storage unit of the calculation unit 4 as the temperature voltage average value VTLav. When the process of S200 is completed, the process proceeds to S150 and the above process is repeated.

  If the acquisition number N is equal to or higher than the low-temperature data acquisition determination value in S170 (S170: YES), the voltage V1 (that is, the low-temperature voltage VL) is acquired from the energization control circuit 31 in S210, and the calculation Store in the storage unit of unit 4.

  In S220, it is determined whether or not the acquisition number N is equal to a preset high-temperature switching determination value (20 in this embodiment). Here, when the acquisition number N is not equal to the high temperature switching determination value (S220: NO), the process proceeds to S150 and the above process is repeated.

  On the other hand, when the acquisition number N is equal to the high temperature switching determination value (S220: YES), in S230, after the acquisition number N becomes the low temperature data acquisition determination value (11 in this embodiment), the high temperature switching determination value ( In this embodiment, the average value of the low-temperature voltage VL acquired until 20) is calculated, and this average value is stored in the storage unit of the calculation unit 4 as the low-temperature voltage average value VLav.

  Thereafter, in S240, the acquisition number counter is reset. In S250, the control for holding the heating resistor 12 at the second set temperature is terminated, and the control for holding the heating resistor 12 at the first set temperature is started. The control for maintaining the heating resistor 12 at the first set temperature is started by outputting a switching signal CG1 instructing the connection between the connection terminal 71 and the connection terminal 72.

When the process of S250 is completed, the process proceeds to S40 and the above process is repeated.
Next, the procedure of the gas concentration calculation process will be described.
When the gas concentration calculation process is started, as shown in FIG. 6, the calculation processing device of the calculation unit 4 first stores the latest high-temperature voltage average value VHav, low-temperature value from the storage unit of the calculation unit 4 in S310. The voltage average value VLav and the temperature voltage average value VTLav are acquired.

In S320, the voltage ratio VC is calculated by the following equation (1).
VC = VHav / VLav (1)
In S330, based on the temperature voltage average value VTLav and the voltage ratio conversion map data, the gas concentration X is zero and the humidity H is zero at the temperature voltage average value VTLav (that is, the environmental temperature T). The voltage ratio VC (0) is calculated.

  Further, in S340, voltage ratio difference ΔVC in temperature voltage average value VTlav is calculated by the following equation (2) using voltage ratio VC calculated in S320 and voltage ratio VC (0) calculated in S330.

ΔVC = VC−VC (0) (2)
In S350, the humidity H at the voltage ratio difference ΔVC is calculated based on the voltage ratio difference ΔVC calculated in S340 and the humidity conversion map data.

  In S360, based on the high-temperature voltage average value VHav, the high-temperature voltage average value VTLav, and the high-temperature voltage conversion map data, the gas concentration X is zero at the temperature-voltage average value VTLav (that is, the environmental temperature T). A high-temperature voltage VH (0) when the humidity H is zero is calculated.

  Further, in S370, based on the high-temperature voltage average value VHav obtained in S310, the humidity H calculated in S350, and the humidity voltage change conversion map data, it is caused by the humidity H of the high-temperature voltage average value VHav. A high temperature voltage change ΔVH (H) indicating the voltage change to be calculated is calculated.

  Next, in S380, the high-temperature voltage average value VHav acquired in S310, the high-temperature voltage VH (0) calculated in S360, and the high-temperature voltage change ΔVH (H) calculated in S370 are From (3), the high temperature voltage change ΔVH (G) indicating the voltage change caused by the combustible gas in the high temperature voltage average value VHav is calculated.

ΔVH (G) = VHav−VH (0) −ΔVH (H) (3)
In S390, the high-temperature voltage average value VHav is previously determined for each temperature-voltage average value VTLav based on the high-temperature voltage average value VHav and the temperature-voltage average value VTLav acquired in S410 and the gas sensitivity conversion map data. A gas sensitivity G (VT) indicating sensitivity (unit is reciprocal of gas concentration X) for the set combustible gas is calculated.

  In S400, the gas concentration of the combustible gas (hydrogen) is calculated by the following equation (4) using the high-temperature voltage change ΔVH (G) calculated in S380 and the gas sensitivity G (VT) calculated in S390. X is calculated.

X = ΔVH (G) / G (VT) (4)
When the process of S400 is completed, the process proceeds to S310 and the above-described process is repeated.
Next, the procedure of the circuit abnormality detection process will be described.

  When the circuit abnormality detection process is started, the arithmetic processing unit of the arithmetic unit 4 first starts incrementing the abnormality determination timer in S510 as shown in FIG. This abnormality determination timer is a timer that is incremented, for example, every 1 ms. When the value is set to 0 at a certain time, the abnormality determination timer is incremented from 0 again at that time. Hereinafter, the value of the abnormality determination timer is referred to as timer value T2.

In S520, the abnormality detection flag is cleared. In S530, the latest temperature voltage average values VTHav and VTLav are acquired from the storage unit of the calculation unit 4.
Thereafter, in S540, it is determined whether or not a preset abnormality detection condition is satisfied. The abnormality detection condition of the present embodiment is that the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than a preset abnormality determination voltage (for example, 0.1 V in this embodiment).

  If the abnormality detection condition is not satisfied (S540: NO), the abnormality determination timer is reset in S550, and the process proceeds to S530. On the other hand, if the abnormality detection condition is satisfied (S540: YES), whether or not the timer value T2 is equal to or greater than a preset abnormality confirmation value (a value corresponding to, for example, 2 s) in S560. Judging. Here, when the timer value T2 is less than the abnormality determined value (S560: NO), the process proceeds to S530.

On the other hand, if the timer value T2 is equal to or greater than the abnormality confirmed value (S560: YES), an abnormality detection flag is set in S570, and the circuit abnormality detection process is terminated.
The combustible gas detection device 1 configured as described above performs control for switching the energization state of the heating resistor 12 in 100 ms, thereby setting the temperature of the heating resistor 12 to a first preset temperature set in advance. It switches alternately with the 2nd preset temperature set so that it may become lower than the 1st preset temperature (S10, S140, S250). The temperature adjustment circuit 32 uses the resistance temperature detector 17 to output a temperature voltage VT indicating a voltage value corresponding to the environmental temperature.

  The combustible gas detection device 1 uses the high-temperature voltage average value VHav, the low-temperature voltage average value VLav, and the temperature-voltage average value VTLav to calculate the concentration of hydrogen contained in the detected atmosphere. (S310 to S400).

  The combustible gas detection device 1 determines that an abnormality has occurred in the temperature adjustment circuit 32 when the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than a preset abnormality determination voltage. (S510 to S570).

  As described above, the combustible gas detection device 1 assumes that the high-temperature temperature voltage VTH and the low-temperature temperature voltage VTL output from the temperature adjustment circuit 32 when the temperature adjustment circuit 32 is abnormal are values that can be taken at normal times. Also, it can be determined that an abnormality has occurred in the temperature adjustment circuit 32 based on the above-described abnormality detection condition indicating that the difference between the high temperature temperature voltage VTH and the low temperature temperature voltage VTL is small. In other words, the combustible gas detection device 1 uses the difference between the high temperature temperature voltage VTH and the low temperature temperature voltage VTL between the normal time and the abnormal time of the temperature adjustment circuit 32 to make use of the temperature adjustment circuit 32. To determine whether is normal or abnormal.

Further, the combustible gas detection device 1 does not need to newly add means for detecting an abnormality of the temperature adjustment circuit 32 in order to determine that an abnormality has occurred in the temperature adjustment circuit 32.
In the combustible gas detection device 1, the abnormality detection condition is that the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than a preset abnormality determination voltage. As a result, the combustible gas detection device 1 uses the simple method of comparing the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav with the abnormality determination voltage, so that the temperature adjustment circuit 32 is normal or abnormal. Therefore, it is possible to reduce the calculation load of the combustible gas detection device 1.

  Further, in the combustible gas detection device 1, the state where the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than the preset abnormality determination voltage continues for a time corresponding to the preset abnormality confirmation value. In this case (S560: YES), it is determined that an abnormality has occurred in the temperature adjustment circuit 32. Thereby, the combustible gas detection apparatus 1 can suppress the occurrence of an erroneous determination due to the fluctuation of the temperature voltage VT output from the temperature adjustment circuit 32 due to noise, and can improve the determination accuracy.

  Further, the combustible gas detection device 1 supplies the temperature voltage VT from the temperature adjustment circuit 32 to 10 during the period in which the temperature of the heating resistor 12 is controlled to be the first set temperature (hereinafter referred to as the first energization control period). The temperature voltage average value VTHav, which is the average value of the ten temperature voltages VT acquired in the first energization control period, is calculated (S40 to S90).

  Further, the combustible gas detection device 1 supplies the temperature voltage VT from the temperature adjustment circuit 32 to 10 during the period in which the temperature of the heating resistor 12 is controlled to be the second set temperature (hereinafter referred to as the second energization control period). The temperature voltage average value VTLav, which is the average value of the ten temperature voltages VT acquired in the second energization control period, is calculated (S150 to S200).

  The combustible gas detection device 1 determines that the abnormality detection condition is satisfied when the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than a preset abnormality determination voltage.

  Thereby, even if combustible gas detection apparatus 1 is a case where noise is contained in some acquired 10 temperature voltage VT, abnormality detection conditions are used using the average value of 10 temperature voltage VT. By determining whether or not is established, the influence of noise can be reduced and the determination accuracy can be improved.

  In the embodiment described above, the base 11 is the base in the present invention, the processes in S10, S140, and S250 are the energization control means in the present invention, the temperature adjustment circuit 32 is the temperature voltage output circuit in the present invention, and the processes in S510 to S570 are the present. It is an abnormality determination means in the invention.

Moreover, the process of S40-S90 is the 1st average value calculation means in this invention, and the process of S150-S200 is the 2nd average value calculation means in this invention.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

  For example, in the above-described embodiment, the abnormality detection condition is that the difference between the temperature voltage average value VTHav and the temperature voltage average value VTLav is less than a preset abnormality determination voltage. However, the abnormality detection condition is not limited to this as long as it indicates that the difference between the high temperature voltage VTH and the low temperature voltage VTL is small. For example, the abnormality detection condition may be that the ratio of the low temperature temperature voltage VTL to the temperature voltage average value VTHav is a value near 1. For example, the abnormality detection condition may be that the ratio of the low temperature temperature voltage VTL to the temperature voltage average value VTHav is larger than a preset abnormality determination voltage ratio (for example, 0.9).

  DESCRIPTION OF SYMBOLS 1 ... Combustible gas detection apparatus, 2 ... Gas detection element, 3 ... Control part, 4 ... Calculation part, 5 ... DC power supply, 11 ... Base, 12 ... Heating resistor, 17 ... Resistance temperature detector, 31 ... Current supply control Circuit, 32 ... Temperature adjustment circuit, 41 ... Bridge circuit, 42 ... Amplification circuit, 43 ... Current adjustment circuit, 91 ... Bridge circuit, 92 ... Amplification circuit

Claims (6)

A heating resistor which is provided on the substrate and is arranged in the atmosphere to be detected and whose resistance value changes due to its own temperature change;
By performing control to switch the energization state to the heating resistor at a preset energization cycle, the temperature of the heating resistor becomes lower than the preset first set temperature and the first set temperature. Energization control means for switching alternately between the second set temperature set as described above,
A resistance temperature detector provided on the same base as the heating resistor, the resistance value of which varies with a change in environmental temperature that is the temperature of the atmosphere to be detected;
A combustible gas detection device comprising a temperature voltage output circuit that outputs a temperature voltage indicating a voltage value corresponding to the environmental temperature using the resistance temperature detector,
Control is performed so that the temperature of the heating resistor is the first set temperature and the first temperature voltage, which is the temperature voltage when the temperature is controlled to be the first set temperature, and the temperature of the heating resistor is the second set temperature. An abnormality determining means for determining that an abnormality has occurred in the temperature voltage output circuit when a relationship with the second temperature voltage that is the temperature voltage when the condition is satisfied satisfies a preset temperature voltage abnormality determination condition; A combustible gas detection device. The temperature voltage abnormality determination condition is:
The combustible gas detection device according to claim 1, wherein a difference between the first temperature voltage and the second temperature voltage is smaller than a preset abnormality determination voltage difference. The temperature voltage abnormality determination condition is:
The state in which the difference between the first temperature voltage and the second temperature voltage is smaller than a preset abnormality determination voltage difference is that a preset abnormality determination time continues. The combustible gas detection apparatus as described. The temperature voltage abnormality determination condition is:
The combustible gas detection device according to claim 1, wherein a ratio of the second temperature voltage to the first temperature voltage is larger than a preset abnormality determination voltage ratio. The temperature voltage abnormality determination condition is:
The combustibility according to claim 4, wherein a state in which a ratio of the second temperature voltage to the first temperature voltage is larger than the abnormality determination voltage ratio is continued for a preset abnormality confirmation time. Gas detection device. In the first energization control period in which the temperature of the heating resistor is controlled to become the first set temperature, the temperature voltage is acquired a plurality of times from the temperature voltage output circuit, and the first energization control period A first average value calculating means for calculating a first temperature voltage average value that is an average value of the plurality of temperature voltages acquired in
In the second energization control period in which the temperature of the heating resistor is controlled to be the second set temperature, the temperature voltage is acquired a plurality of times from the temperature voltage output circuit, and the second energization control period A second average value calculating means for calculating a second temperature voltage average value which is an average value of the plurality of temperature voltages acquired in
The abnormality determining means uses the first temperature voltage average value calculated by the first average value calculating means as the first temperature voltage, and uses the second temperature voltage average value calculated by the second average value calculating means as the first temperature voltage. The combustible gas detection device according to any one of claims 1 to 5, wherein whether or not the temperature voltage abnormality determination condition is satisfied is determined as the second temperature voltage.

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