JP5566420B2 - Gas alarm - Google Patents

Description

  The present invention relates to a gas alarm including an electrochemical gas sensor that detects a target gas concentration in an atmosphere by a reaction using water content stored in a water container, such as an electrochemical gas sensor using a proton conductor film. .

  2. Description of the Related Art Conventionally, devices that incorporate an electrochemical CO sensor have been known as devices for measuring the CO concentration in the surrounding atmosphere, such as a CO alarm device that detects and alarms CO gas due to incomplete combustion or the like of combustion equipment. .

  As shown in a cross-sectional view in FIG. 4, this electrochemical CO sensor 1 has a proton conductor film 3 installed in an upper opening 4 of a metal can 2 in which water 5 is accommodated, and a counter electrode 32 as a metal can. The metal cap 8 having the gas adsorption filter 8 c built in is overlapped with the detection electrode 31 on the opposite side 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 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 and the discharge hole 8b made of activated carbon, silica gel, zeolite, and the like, and Then, it passes through the diffusion control hole 7a of the metal diffusion prevention plate 7 interposed between the metal cap 8 and the proton conductor film 3, and reaches the detection electrode 31, where the proton conductor from the counter electrode 32 side. An oxidation reaction using the water of the water 5 in the metal can 2 supplied to the membrane 3 is caused, and protons (2H +
) And electrons (2e-).

Electrons (2e−) generated at the sensing electrode 31 cannot pass through the proton conductor film 3 and thus stay at the sensing electrode 31, while protons (2H +)
) Passes through the proton conductor film 3 and moves to the counter electrode 32, where it undergoes a reduction reaction with oxygen in the container 2 to generate water (H 2 O) at the counter electrode 32.

  Therefore, between the metal cap 8 that is electrically connected to the detection electrode 31 and functions as its terminal, and the metal can 2 that is electrically connected to the counter electrode 32 via the diffusion prevention plate 7 and functions as its terminal. When a load (not shown) is connected, a flow of electrons (2e−) staying at the detection electrode 31 toward the counter electrode 32 is generated in the load, whereby a short-circuit current flows from the counter electrode 32 to the detection electrode 31 through the load. Therefore, a CO concentration signal having a voltage value corresponding to the CO concentration in the ambient atmosphere can be obtained by current-voltage conversion of the short-circuit current flowing through the load (for example, Patent Documents 1 and 2).

  Also, as described above, as a gas sensor that utilizes the water content of water stored in a water container, an ion conductive solid electrolytic membrane is provided between two electrodes, and water is supplied to the ion conductive solid electrolytic membrane so as to maintain a constant relative humidity. There is a gas sensor provided with a filled water container (for example, Patent Document 3).

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

  Since the electrochemical CO sensor itself does not require an external power supply to generate a CO concentration signal having a voltage value corresponding to the CO concentration in the surrounding atmosphere, it needs to be driven by a battery for a long period of time. Suitable for use with CO alarms with On the other hand, since the CO sensor 1 detects the CO concentration using the water 5, if the water 5 decreases due to evaporation or the like, the water 5 cannot be sufficiently supplied to the detection electrode 32a, and the CO concentration cannot be detected accurately. There's a problem. Therefore, there is a conventional self-diagnosis that detects a decrease in water using the charge / discharge characteristics of the CO sensor 1.

  However, particularly in a cryogenic environment, the water that has entered the caulking portion of the upper opening 4 of the metal can 2 solidifies and expands, and the contact between the electrode and the conductor film may be separated, resulting in a phenomenon similar to disconnection. . Even if such a phenomenon occurs, the sensor returns to normal when the temperature returns from low temperature to room temperature. That is, an error may occur in self-diagnosis even though there is sufficient water. The error due to this self-diagnosis is to detect the depletion of water, that is, to judge the deterioration of the alarm device. Therefore, in many alarm devices, if this error occurs, there will be no inconvenience since it will not be restored. Arise.

  An object of the present invention is to provide a gas alarm device that is easy to manage by preventing the occurrence of unintentional errors due to self-diagnosis, focusing on the above problems.

  The gas alarm device according to claim 1 includes an electrochemical gas sensor that detects a target gas concentration in an atmosphere by a reaction using water moisture stored in a water container, and has a self-diagnosis function that detects an abnormality of the gas sensor. A function of selectively executing execution of the self-diagnosis function and prohibition of the self-diagnosis function by determining a temperature of the gas sensor, and determining that the temperature of the gas sensor is not lower than a freezing point; When the execution of the function is selected and it is determined that the temperature of the gas sensor is below the freezing point, the gas alarm is selected to prohibit the self-diagnosis function, and whether or not the temperature of the gas sensor is below the freezing point The determination is made by detecting the temperature of the atmosphere of the gas sensor in the main body case of the gas alarm device.

  According to the gas alarm device of claim 1, since the self-diagnosis function is prohibited when the water in the gas sensor is solidified, an error does not occur even in a disconnection state due to the solidification of the water. In the unsolvable state, the self-diagnosis function can detect the depletion of water in the water container, and an appropriate self-diagnosis can be performed.

  When the self-diagnosis function is prohibited, if temperature judgment and execution of self-diagnosis and selection of prohibition are performed at a short processing timing, when the temperature reaches room temperature, the temperature change immediately follows and normal Return to the state to execute the self-diagnosis function.

It is a principal part block diagram of the gas alarm which concerns on embodiment of this invention. It is a flowchart of the alarm monitoring process in embodiment of this invention. It is a flowchart of the self-diagnosis process in the embodiment of the present invention. It is sectional drawing which shows an example of the electrochemical CO sensor which concerns on this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a principal block diagram of a gas alarm device according to an embodiment of the present invention. As shown in the figure, the gas alarm device includes a CO sensor 1 as a gas sensor, a microcomputer 10 (hereinafter referred to as a microcomputer), a temperature sensor 20 such as a thermistor, a self-diagnosis circuit 30, an amplifier circuit 40, an audio alarm output circuit 50, and A battery 60 for supplying power to each part of the gas alarm is provided. The CO sensor 1 is, for example, the electrochemical sensor 1 shown in FIG. 4 described above, converts a current generated according to the CO concentration into a voltage, and outputs the voltage to the microcomputer 10 via the amplifier circuit 40. The temperature sensor 20 detects a temperature in a main body case (not shown) of the gas alarm device, and outputs a temperature detection signal 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 and time, and the like, and these elements are connected by a bus line. Then, the microcomputer 10 measures the CO gas concentration by the voltage signal output from the CO sensor 1 via the amplifier circuit 40 at a predetermined sampling period, and when the gas concentration becomes equal to or higher than the alarm set point, a sound alarm is issued. An alarm is issued from the output circuit 50, and the alarm is stopped when the alarm becomes 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 of the CO sensor 1 by the self-diagnosis circuit 30 uses the fact that the CO sensor 1 is regarded as a kind of capacitor and its charge / discharge characteristics differ depending on the amount of water. The self-diagnosis circuit 30 includes a charging circuit that charges the CO sensor 1 and a transistor switch that performs switching operation between charging and discharging. The self-diagnosis circuit 30 charges the CO sensor 1 through a resistor in accordance with an instruction from the microcomputer 10, discharges it, converts the discharge current into a voltage, and outputs the voltage to the microcomputer 10 via the amplifier circuit 40. Then, the microcomputer 10 detects the discharge curve. This discharge curve is different between when the gas sensor 1 is in a normal state where water is not decreasing and when the water sensor is deteriorated. Therefore, the microcomputer 10 compares the detected discharge curve with the normal discharge curve to detect the presence or absence of water reduction. If the detection result is not within the normal range, it is determined that the deterioration has occurred, and if the deterioration has occurred, the fact is notified using a display means (not shown).

  2 and 3 are main part flowcharts of the control program of the CPU 10a in the gas alarm device of the embodiment, and the operation will be described based on the same figure. FIG. 2 is a flowchart of the alarm monitoring process, and this alarm monitoring process is started at a predetermined sampling cycle every 30 seconds, for example. First, the CPU 10a measures the temperature based on the detection signal of the temperature sensor 20 in step S1, measures the gas concentration based on the output of the CO sensor 1 in step S2, and performs predetermined arithmetic processing in step S3. In step S4, it is determined whether or not an alarm is required. If necessary, an alarm is output in step S5, and one process is completed. If an alarm is not necessary, the alarm is canceled if the alarm is in step S6, and one process is terminated.

  FIG. 3 is a flowchart of the self-diagnosis process. The self-diagnosis process of FIG. 3 is started with a set time set in the timer 10d as a cycle. In the initial state, the set time is set to 50 hours. First, in step S11, it is determined whether or not the latest measured temperature measured in step S1 is 0 ° C. or less. The measured temperature is a temperature measured by the temperature sensor 20 in the predetermined sampling period, and is determined by the latest measured temperature. If the measured temperature is not 0 ° C. or less, it is determined that the temperature of the CO sensor 1 is not below the freezing point, and in step S12, an instruction is output to the self-diagnosis circuit 30 to perform self-diagnosis. In step S13, the set time of the timer 10d is set to 50 hours, and one process is completed. In step S11, if the measured temperature is 0 ° C. or less, it is determined that the temperature of the CO sensor 1 is below the freezing point. In step S14, the set time of the timer 10d is set to 1 hour, and one process is completed. .

  As described above, when it is determined that the temperature of the CO sensor 1 is not below the freezing point, the self-diagnosis process is repeated every 50 hours, and if it is not below the freezing point, the self-diagnosis is executed. On the other hand, when it is determined that the temperature of the CO sensor 1 is below the freezing point, self-diagnosis is prohibited and the self-diagnosis process (that is, temperature determination) is repeated every hour. When the temperature of the CO sensor 1 exceeds the freezing point, the self-diagnosis is executed, and thereafter, the self-diagnosis process is set to be repeated every 50 hours.

  Accordingly, when the water 5 in the CO sensor 1 is solidified at a caulking portion or the like, self-diagnosis is prohibited, so that an inadvertent error due to a disconnection state does not occur. Even if water coagulation occurs in the CO sensor 1 and the gas concentration cannot be detected by the CO sensor 1 itself, the generation of CO gas is not considered at such a temperature below the freezing point. No problem. Moreover, if the temperature exceeds the freezing point, the coagulation of the water in the CO sensor 1 can be solved, so that the CO sensor 1 returns to normal and a normal alarm and self-diagnosis can be performed.

  Although the self-diagnosis process is normally performed every 50 hours, the initial failure check is performed immediately after the release of the gas alarm device in the shipping mode, immediately after resetting, or immediately after the power is turned on. I am doing so. In this case, if it is determined that the temperature of the CO sensor 1 is below the freezing point, the self-diagnosis is prohibited. However, even if the self-diagnosis is prohibited during the initial failure check, the initial failure check itself is normally completed. Treat as you did.

  In the above embodiment, the electrochemical sensor 1 shown in FIG. 4 has been described as an example of the gas sensor. However, for example, a sensor such as the sensor described in Patent Document 3 may be used to react the atmosphere using water stored in a water container. Needless to say, the present invention can be applied to an electrochemical gas sensor for detecting a target gas concentration.

1 Electrochemical CO Sensor 2 Metal Can 5 Water 10 Microcomputer 10a CPU
10b ROM
10c RAM
10d timer 20 temperature sensor 30 self-diagnosis circuit 50 voice alarm output circuit 60 battery

Claims (1)

Equipped with an electrochemical gas sensor that detects the target gas concentration in the atmosphere by a reaction using the water content of the water stored in the water container,
While having a self-diagnosis function to detect abnormality of the gas sensor,
A function of selectively executing execution of the self-diagnosis function and prohibition of the self-diagnosis function by determining the temperature of the gas sensor;
When it is determined that the temperature of the gas sensor is not below the freezing point, the execution of the self-diagnosis function is selected. When it is determined that the temperature of the gas sensor is below the freezing point, the gas alarm is selected to prohibit the self-diagnosis function. A vessel,
A gas alarm device characterized by determining whether the temperature of the gas sensor is below the freezing point by detecting the temperature of the atmosphere of the gas sensor in the main body case of the gas alarm device.

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