JP5065332B2 - Carbon monoxide gas measuring device and alarm - Google Patents

Description

  The present invention relates to a carbon monoxide gas measuring device and an alarm device that self-diagnose whether or not there is a failure in an electrochemical gas sensor that detects a target gas concentration by an electrochemical reaction of the target gas.

  As a device for measuring the CO concentration in the ambient atmosphere, such as a CO alarm device that detects and alarms CO gas due to incomplete combustion of combustion equipment, etc., a device that has conventionally incorporated an electrochemical CO sensor (= gas sensor) Are known.

  As shown in a cross-sectional view in FIG. 6, this electrochemical CO sensor 1 has a proton conductor film 3 installed in an upper opening 4 of a metal can 2 (= water container) in which water 5 is accommodated. The counter electrode 32 is exposed in the metal can 2, and the metal cap 8 including the gas adsorption filter 8 c is overlapped on the opposite detection electrode 31 and is caulked and fixed to the upper opening 4 of the metal can 2.

In the electrochemical CO sensor 1 having the above-described configuration, CO (= target gas) in the ambient atmosphere is introduced into the inside through the introduction hole 8a of the metal cap 8, and the gas adsorption filter 8c made of activated carbon, silica gel, zeolite, or the like. And through the diffusion control hole 7a of the metal diffusion control plate 7 interposed between the metal cap 8 and the proton conductor film 3, and reaches the detection electrode 31, where the counter electrode Oxidation reaction using the water 5 in the metal can 2 supplied to the proton conductor film 3 from the 32 side is caused to generate protons (2H ⁺ ) and electrons (2e ⁻ ) at the detection electrode 31.

The electrons (2e ⁻ ) generated in the detection electrode 31 cannot pass through the proton conductor film 3 and therefore stay in the detection electrode 31, while the proton (2H ⁺ ) passes through the proton conductor film 3. It moves to the counter electrode 32, where it causes a reduction reaction with oxygen in the metal can 2 to generate water (H ₂ O) at the counter electrode 32.

Accordingly, a metal cap 8 that is electrically connected to the detection electrode 31 via the diffusion control plate 7 and functions as its terminal, and a metal can that is electrically connected to the counter electrode 32 and the washer 9 and functions as its terminal. When a current / voltage conversion circuit (not shown) is connected between the current and voltage, a flow of electrons (2e ⁻ ) staying in the detection electrode 31 toward the counter electrode 32 is generated in the input resistance of the current / voltage conversion circuit. Since a current flows from the counter electrode 32 to the detection electrode 31 through the input resistance, the current / voltage conversion circuit converts this current into current / voltage so that a voltage value corresponding to the CO concentration in the ambient atmosphere can be obtained. A CO concentration signal is obtained (for example, Patent Documents 1 and 2).

  Further, as described above, as a gas sensor that utilizes the reaction between water vapor from a water container and a target gas, an ion conductive solid electrolytic membrane is provided between two electrodes, and a constant relative humidity is maintained in the ion conductive solid electrolytic membrane. There is a gas sensor including a water container filled with water (for example, Patent Document 3).

  The CO sensor 1 itself does not require an external power supply in order to generate a CO concentration signal having a voltage value corresponding to the CO concentration in the ambient atmosphere. Suitable for use with certain CO alarms.

  By the way, the above-mentioned CO alarm device has conventionally performed self-diagnosis for detecting failures such as “no water”, “disconnection”, and “short circuit” in which water in the metal can 2 is reduced (for example, Patent Document 3). . The self-diagnosis of the CO sensor 1 regards this CO sensor 1 as a kind of capacitor, and uses the fact that the current waveform at the time of discharge differs from the normal state due to failures such as “no water”, “disconnection”, and “short circuit”. Is going.

JP 2004-170101 A JP 2004-279293 A JP 2000-146908 A

  In the conventional alarm device using the electrochemical gas sensor, the sensitivity of the electrochemical gas sensor is adjusted when the alarm device is built. However, it has been found that the sensitivity of the gas sensor may decrease thereafter. As described above, the gas sensor was considered to be a large capacitor. However, when a misalignment occurs between the conductive hydrophobic film and the electrolyte due to vibration or impact of the alarm, a series resistance is generated by the misalignment. I understood that. And depending on the magnitude | size of DC resistance of a gas sensor, since it will lead to the sensitivity fall of a gas sensor, the quick response was calculated | required.

  However, since the conventional sensitivity adjustment is an adjustment including variations in the series resistance of each gas sensor, there is a possibility that the sensitivity of the gas sensor may be lowered depending on the magnitude of the series resistance. However, as described above, in the method of charging the gas sensor to store the charge and then discharging the charge to check the charge / discharge characteristics, the gas sensor can operate as a capacitor, that is, disconnection, short circuit, and water depletion. Although it could be detected, it was not possible to detect the occurrence of a stacking deviation different from that.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a carbon monoxide gas measuring device and an alarm device that can detect the occurrence of stacking misalignment in an electrochemical gas sensor.

  The invention according to claim 1, which has been made to solve the above-described problem, sequentially stacks a detection electrode, an electrolyte membrane, and a counter electrode, and generates a current corresponding to the concentration of the target gas by a reaction between the solid or liquid electrolyte and the target gas. An electrochemical gas sensor generated between the detection electrode and the counter electrode; a current / voltage conversion circuit that converts the current flowing through the electrochemical gas sensor into a voltage; and a charging current supplied to the electrochemical gas sensor A power source for charging the electrochemical gas sensor, an equivalent circuit provided between the supply path from the power source to the electrochemical gas sensor and the input terminal of the current / voltage conversion circuit, and at the start of charging of the electrochemical gas sensor A resistance set to a resistance value at which a current flowing from the power source changes in accordance with a change in the resistance value of the series internal resistance component of the A resistance value of the series internal resistance component is calculated based on an output voltage from the current / voltage conversion circuit and a resistance value of the resistor at the start of charging, and the electrical resistance is calculated based on the resistance value of the series internal resistance component. And self-diagnosis means for detecting a stacking deviation of the chemical gas sensor.

  According to the first aspect of the present invention, when supply of the charging current from the power source to the electrochemical gas sensor is started, the equivalent of the electrochemical gas sensor is determined based on the output voltage output from the current / voltage conversion circuit and the resistance value of the resistance. Since the resistance value of the series internal resistance component in the circuit can be calculated, the self-diagnosis means can detect the stacking deviation of the electrochemical gas sensor based on the change in the resistance value.

  The invention according to claim 2, which has been made to solve the above-described problem, notifies the stacking misalignment between the carbon monoxide gas measuring device according to claim 1 and the electrochemical gas sensor detected by the carbon monoxide gas measuring device. And notifying means.

  According to the present invention of claim 2, when the carbon monoxide gas stacking deviation is detected by the carbon monoxide gas measuring device, it can be notified by the notification means.

  As described above, according to the present invention, the electrochemical gas sensor is based on the output voltage output from the current / voltage conversion circuit in response to the start of supply of the charging current from the power source to the electrochemical gas sensor. When the internal displacement of the electrochemical gas sensor occurs due to vibration, impact, etc. after adjustment and shipment, because the internal internal resistance component in the equivalent circuit is calculated and the stacking displacement is detected based on the internal resistance component. In addition, since the occurrence of the stacking deviation can be detected from the output voltage output from the current / voltage conversion circuit in response to the start of charging, it is possible to contribute to prevention of a decrease in accuracy of the measured target gas concentration. Further, since only the stacking misalignment is detected based on the output voltage, self-diagnosis can be performed periodically, and the stacking misalignment can be detected quickly, so that the maintainability can be improved. Therefore, an electrochemical gas sensor with an internal resistance value in a range that does not cause a problem in use is no longer determined as a failure, so it can be distinguished from conventional failures such as disconnection, short circuit, water depletion, etc. Can be done.

  As described above, according to the second aspect of the present invention, when the carbon monoxide gas measuring device detects the stacking misalignment of the carbon monoxide gas, the notification means notifies it. Since the occurrence can be promptly notified to the user, the worker, etc., it is possible to prevent the electrochemical gas sensor from being continuously used in a state where a failure has occurred. In addition, since the carbon monoxide gas measuring device can periodically perform self-diagnosis, an alarm can be given for the target gas concentration measured in a normal state. Accordingly, it is possible to prevent a decrease in measurement accuracy, thereby contributing to an improvement in safety.

It is a circuit diagram showing one embodiment of a gas alarm as an alarm according to an embodiment of the present invention. It is an equivalent circuit schematic of the electrochemical gas sensor in the gas alarm device shown in FIG. FIG. 3 is an equivalent circuit diagram at the moment when the electrochemical gas sensor shown in FIG. 2 is charged. It is a graph which shows the relationship between a voltage value and time in an electrochemical gas sensor. It is a flowchart which shows an example of the self-diagnosis process which CPU of FIG. 1 performs. It is sectional drawing which shows an example of the electrochemical CO sensor which concerns on this invention.

  Hereinafter, an example of an alarm device having a carbon monoxide gas measuring device according to the present invention will be described with reference to the drawings of FIGS. In addition, the same code | symbol is attached | subjected to the part which is the same as that of what was demonstrated in the prior art, or the detailed description is abbreviate | omitted.

  In FIG. 1, a gas alarm device 100 includes an electrochemical gas sensor (hereinafter referred to as a CO sensor) 1, a microcomputer (hereinafter referred to as a microcomputer) 10, a self-diagnosis circuit 30, a current / voltage conversion circuit 40, and a resistor R1. And a sound alarm output unit 50 and a battery 60 that supplies power to each unit of the gas alarm device.

  The CO sensor 1 is, for example, the electrochemical CO sensor 1 shown in FIG. The CO sensor 1 generates a current I corresponding to the target gas concentration by a reaction between water vapor from a water container containing water or water vapor in the atmosphere and the target gas, and outputs the current I to the current / voltage conversion circuit 40. To do. A resistor R1 is provided between the detection electrode 31 of the CO sensor 1 and the negative input terminal of the operational amplifier 41.

  The current / voltage conversion circuit 40 includes an operational amplifier 41 having a detection electrode 31 and a first switch SW1 of the CO sensor 1 connected to a negative input terminal and a counter electrode 32 and a current source 33 connected to a positive input terminal via a resistor R1. And a feedback resistor R2 provided between the negative input terminal and the output terminal of the operational amplifier 41, and outputs a voltage signal corresponding to the current I to the microcomputer 10.

  The microcomputer 10 includes a CPU 10a that performs various processes according to a processing program, a ROM 10b that stores a program for processing performed by the CPU 10a, a work area that is used in various processes in the CPU 10a, a data storage area that stores various data, and the like. The RAM 10c has a timer 10d for measuring the time set in a predetermined register or the date, time, etc., and these elements are connected by a bus line. The microcomputer 10 samples the voltage signal output from the current / voltage conversion circuit 40 at a predetermined sampling period and measures the CO gas concentration. When the gas concentration reaches or exceeds the alarm set point, a sound alarm is issued. An alarm is issued from the output unit 50, and the alarm is stopped when the alarm is below the alarm release set point.

  Note that CO is known to be generated even when the combustion utensil is used in a normal state. In particular, when boiling hot water using a cooking utensil such as a pan or a kettle, the cold cooking utensil is warmed up. Since CO occurs during this period, even if the CO concentration (gas concentration) exceeds the alarm set point, an alarm is not generated immediately, and the alarm set point is exceeded even after a predetermined delay time has elapsed. If it continues, an alarm may be generated.

  The self-diagnosis circuit 30 is a circuit that executes a self-diagnosis of the CO sensor 1 in accordance with an instruction from the microcomputer 10. The self-diagnosis circuit 30 is provided between the current source 33 and the CO sensor 1 as a power source for charging the CO sensor 1 by supplying a charging current to the CO sensor 1 and the CO sensor 1. 1 and a first switch SW1 for switching between charging and discharging.

  When the CO sensor 1 is charged from the current source 33, the equivalent circuit shown in FIG. The equivalent circuit of the CO sensor 1 includes a series resistor (corresponding to a series internal resistance component) Rs electrically connected to the current source 33 and the resistor R1, a resistor Rp connected in series to the series resistor Rs, and a resistor Rp. And a capacitor C connected in parallel. The relationship between the series resistance Rs and the resistance Rp is resistance Rp >> series resistance Rs. The resistance value of the resistor R1 is 1 kΩ, and the resistance value of the feedback resistor R2 is 100 kΩ.

  FIG. 4 shows the relationship between the voltage value of the CO sensor 1 and time corresponding to charging and discharging. In FIG. 4, the vertical axis indicates the voltage value, and the horizontal axis indicates time. Then, at the start of charging ST of the CO sensor 1, the capacitance component of the CO sensor 1 can be ignored transiently, and the impedance can be regarded as 0Ω. Then, the CO sensor 1 can be considered as an equivalent circuit shown in FIG.

  The charging current I in FIG. 3 is divided into a current Ia flowing through the series resistor Rs of the CO sensor 1 and a current Ib flowing through the resistor R1. Therefore, the larger the resistance value of the series resistor Rs, the larger the current flowing to the 1 kΩ resistor R1 side. Since the current Ib is converted into a voltage output by the current / voltage conversion circuit 40, the resistance value of the DC resistance Rs of the CO sensor 1 can be calculated based on the voltage value.

  For example, in the configuration described above, the DC resistance Rs is 500Ω and the charging current I is 1 μA. At this time, the ratio of the current flowing through the DC resistor Rs and the resistor R1 is changed from 500Ω: 1 kΩ = 1: 2 to the current on the series resistor Rs side: current on the resistor R1 = 2: 1. When the output voltage is obtained by setting the value of the current flowing through the resistor R1 to X, 1: 2 = X: (1 μA−X), and X = 1/3 μA.

  Therefore, the output voltage of the current / voltage conversion circuit 40 is 1/3 μA * 100 kΩ = 100/3 mV≈33.3 mV. That is, the resistance value of the series resistor Rs can be obtained by performing the reverse calculation described above.

  For example, if the output voltage of the current / voltage conversion circuit 40 is 25 mV, 25 mV / 100 kΩ = 0.25 μA, and 0.25 μA: (1-0.25) μA = 1: 3. Therefore, from 1: 3 = series resistance Rs: 1 kΩ, it can be determined that series resistance Rs = 1000 / 3Ω = 333.3Ω.

  In this way, the series resistance Rs is calculated based on the output voltage of the current / voltage conversion circuit 40. Depending on the magnitude of the series resistance Rs, the ROM 10b or the like has a range, threshold value, etc. that are not problematic in use as a stacking deviation determination condition. By storing in advance, the stacking deviation of the CO sensor 1 can be detected. Therefore, in the present invention, when the CO sensor 1 is charged, it is not regarded as a kind of capacitor, but by focusing on the series resistance Rs of the equivalent circuit, the stacking deviation in the CO sensor 1 can be detected. .

  The resistor R1 is an input resistor of the current / voltage conversion circuit 40. The resistor R1 is once electrically connected to the supply path from the current source 33 (power supply) to the CO sensor 1, and the other end is electrically connected to the negative input terminal of the operational amplifier 41 described above. The resistance R1 is set to a resistance value at which the current Ib flowing from the current source 33 increases (changes) in accordance with the increase (change) in the resistance value of the series resistance Rs in the equivalent circuit of the CO sensor 1 described above.

  The voice alarm output unit 50 corresponds to a notification unit in the claims, and is electrically connected to the microcomputer 10. The voice alarm output unit 50 is configured to be capable of various outputs such as voice, display, etc. in response to a request from the CPU 10a. In this embodiment, the case where the voice alarm output unit 50 performs voice notification and warning by the voice output circuit will be described. However, the present invention is not limited to this, and various implementations such as notification only by display are provided. It can be in the form.

  Next, an example of the self-diagnosis process according to the present invention executed by the CPU 10a of the gas alarm device 100 will be described below with reference to the flowchart shown in FIG.

  When the self-diagnosis processing program stored in the ROM 10b is executed by the CPU 10a, it is determined in step S11 whether or not it is a predetermined diagnosis timing (for example, every 24 hours, every week, etc.). . When it is determined that it is not the diagnosis timing (N in S11), this determination process is repeated to wait for the diagnosis timing. On the other hand, when it is determined that it is the diagnosis timing (Y in S11), the process proceeds to step S12.

  In step S12, the first switch SW1 is turned on. In step S13, a voltage signal is taken from the operational amplifier 41, and the voltage value is stored in the RAM 10c. In step S14, the CO sensor is based on the voltage value as described above. The resistance value of the first series resistor Rs is calculated and stored in the RAM 10c. In step S15, the first switch SW1 is turned off after a predetermined time elapses after the first switch SW1 is turned on based on the timer 10d. Thereafter, the process proceeds to step S16.

  In step S16, based on the resistance value of the RAM 10c and the stacking shift determination condition (for example, determination threshold, determination range, etc.) stored in advance in the ROM 10b, whether or not stacking shift has occurred in the CO sensor 1 is determined. Determined. When it is determined that no stacking error has occurred (N in S15), the process returns to step S11 and a series of processes is repeated.

  If it is determined in step S16 that stacking misalignment has occurred (Y in S16), in step S17, notification information for notifying the user, worker, etc. of the occurrence of stacking misalignment is created in the RAM 10c. After the discharge of the capacitor C is completed, the notification information is output to the audio alarm output unit 50, so that the audio alarm output unit 50 notifies the occurrence of the stacking deviation by audio, and then ends the processing.

  As is clear from the above description, the CPU 10a functions as the self-diagnosis unit in the claims by executing the self-diagnosis processing program. In this embodiment, the CPU 10a corresponds to the self-diagnosis unit. .

  Next, an example of the operation (action) of the gas alarm device 100 described above during self-diagnosis according to the present invention will be described below.

  The gas alarm device 100 charges the CO sensor 1 by turning on the first switch SW1 and supplying a charging current from the current source 33 to the CO sensor 1 at the diagnosis timing. The current shunted from the current source 33 is input to the current / voltage conversion circuit 40 via the resistor R1, converted into a voltage by the current / voltage conversion circuit 40, and output.

  Then, the gas alarm device 100 calculates the resistance value of the series resistance Rs at the moment when the CO sensor 1 starts to be charged based on the voltage value from the current / voltage conversion circuit 40 and the resistance R1. Based on the comparison result between the resistance value of Rs and the stacking shift determination condition, it is determined whether or not stacking shift has occurred in the CO sensor 1.

  If the gas alarm device 100 determines that the stacking error has not occurred, the gas alarm device 100 turns off the first switch SW1 and returns to the normal state. Thereafter, the above-described inspection process is periodically performed. In addition, when the gas alarm device 100 determines that the stacking error has occurred, the gas alarm device 100 outputs notification information to the sound alarm output unit 50 to notify the occurrence of the stacking error in the CO sensor 1. Therefore, since the operator can recognize the occurrence of the stacking deviation by the notification, it can cope with the sensitivity adjustment.

  According to the gas alarm device 100 described above, the equivalent of the CO sensor 1 based on the output voltage output from the current / voltage conversion circuit 40 in response to the start of supply of the charging current from the current source 33 to the CO sensor 1. Since the series resistance (series internal resistance component) Rs in the circuit is calculated and the stacking deviation is detected based on the series resistance Rs, the stacking deviation of the CO sensor 1 occurs due to vibration, impact, etc. after adjustment and shipment. In this case, the occurrence of the stacking deviation can be detected from the output voltage output from the current / voltage conversion circuit 40 in response to the start of charging, which can contribute to prevention of a decrease in accuracy of the measured target gas concentration. Further, since only the stacking misalignment is detected based on the output voltage, self-diagnosis can be performed periodically, and the stacking misalignment can be detected quickly, so that the maintainability can be improved. Therefore, the electrochemical gas sensor having a resistance value of the series resistance Rs in a range where there is no problem in use is not determined as a failure, so that it can be distinguished from conventional failures such as disconnection, short circuit, water depletion, Maintenance can be performed appropriately.

  In addition, according to the gas alarm device 100, when the stacking deviation of the CO sensor 1 is detected, it is notified by the voice alarm output unit 50 which is a notification means. Since it is possible to notify an operator or the like, it is possible to prevent the CO sensor 1 from being continuously used in a state where a failure has occurred. Moreover, since the gas alarm device 100 can perform a self-diagnosis periodically, an alarm can be given to the target gas concentration measured in a normal state. Accordingly, it is possible to prevent a decrease in measurement accuracy, thereby contributing to an improvement in safety.

  In the embodiment described above, the gas alarm device 100 has been described as a condition for determining whether or not the stacking deviation determination condition is normal. However, the present invention is not limited to this, and the stacking shift determination condition is not limited to this. Various embodiments can be made, such as setting in stages and performing notifications and alarms in stages.

  In the above-described embodiment, the case where the carbon monoxide gas measuring device of the present invention is applied to the alarm device 100 has been described. However, the present invention is not limited to this, and for example, the carbon monoxide gas measuring device is Various embodiments can be made such as incorporating a carbon monoxide gas measuring apparatus as a single measuring instrument incorporated in various devices such as a combustion instrument and a fire alarm.

  Further, in the self-diagnosis method described above, water vapor from a water container containing water or water vapor in the atmosphere is used as an electrolyte, and the CO sensor 1 generates a current corresponding to the target gas concentration by the reaction between the water vapor and the target gas. The case where it occurs is explained. Instead, it can be applied to an electrochemical sensor composed of two or three electrodes using sulfuric acid as an electrolyte. For example, the detection target gas includes a pair of electrodes in contact with a solid or liquid electrolyte, and the detection target gas based on a current flowing between the detection electrode to which the detection target gas reacts and the other electrode or a voltage corresponding to the current. The present invention can also be applied to an electrochemical gas sensor that detects the concentration of the gas.

  As described above, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

1 CO sensor (electrochemical gas sensor)
2 Metal can (water container)
10a CPU (self-diagnosis means)
31 Detection electrode 32 Counter electrode 33 Current source (power supply)
40 Current / voltage conversion circuit 50 Voice alarm output section (notification means)
R1 resistance Rs series resistance (series internal resistance component)
SW1 1st switch

Claims (2)

An electrochemical gas sensor in which a detection electrode, an electrolyte membrane, and a counter electrode are sequentially stacked, and a current corresponding to a target gas concentration is generated between the detection electrode and the counter electrode by a reaction between a solid or liquid electrolyte and the target gas; ,
A current / voltage conversion circuit for converting the current flowing through the electrochemical gas sensor into a voltage;
A power source for charging the electrochemical gas sensor by supplying a charging current to the electrochemical gas sensor;
A resistance value of a series internal resistance component that is provided between the supply path from the power source to the electrochemical gas sensor and the input terminal of the current / voltage conversion circuit and that the equivalent circuit at the start of charging of the electrochemical gas sensor has A resistance set to a resistance value at which the current flowing from the power source changes according to the change of
The resistance value of the series internal resistance component is calculated based on the output voltage from the current / voltage conversion circuit and the resistance value of the resistor at the start of charging of the electrochemical gas sensor, and based on the resistance value of the series internal resistance component Self-diagnostic means for detecting stacking misalignment of the electrochemical gas sensor;
A carbon monoxide gas measuring device comprising: A carbon monoxide gas measuring device according to claim 1;
A notification means for notifying a stacking deviation of the electrochemical gas sensor detected by the carbon monoxide gas measuring device;
An alarm device comprising:

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