JP5198403B2 - Alarm - Google Patents

Description

  The present invention relates to an alarm device, and more particularly, to an alarm device that self-diagnose whether there is a failure in an electrochemical gas sensor that detects a target gas concentration by a reaction between water vapor from a water container that contains water and the target gas. .

  2. Description of the Related Art Conventionally, devices that incorporate an electrochemical CO sensor (gas sensor) are 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 of combustion equipment. ing. FIG. 8 is a cross-sectional view showing an example of an electrochemical CO sensor. This electrochemical CO sensor 1 has a proton conductor film 3 in the upper opening 4 of a metal can 2 (water container) containing water 5 therein. Installed, the counter electrode 32 is exposed in the metal can 2, and the metal cap 8 containing the gas adsorption filter 8 c is overlapped on the opposite detection electrode 31 and caulked and fixed to the upper opening 4 of the metal can 2. Has been.

In this electrochemical CO sensor 1, CO gas (target gas) in the ambient atmosphere is introduced into the inside through the introduction hole 8 a of the metal cap 8, and the gas adsorption filter 8 c and the lead-out hole made of activated carbon, silica gel, zeolite, or the like. 8b, and 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 An oxidation reaction is performed using the moisture of the water 5 in the metal can 2 supplied to the proton conductor film 3 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. 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 ⁻ ) accumulated in the detection electrode 31 toward the counter electrode 32 is generated in the load, and thereby a short-circuit current flows from the counter electrode 32 through the load to the detection electrode 31. As a result, 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.

  By the way, in the CO alarm device using the above-described CO sensor, a self-diagnosis for detecting a failure such as “no water”, “disconnection”, and “short circuit” in which water in the metal can 2 decreases has been conventionally performed ( For example, Patent Documents 1 and 2). This self-diagnosis of the CO sensor 1 regards the CO sensor 1 as a kind of capacitor, and utilizes the fact that the current waveform at the time of discharge differs from that in the normal state due to failures such as “no water”, “disconnection”, and “short circuit” It is done.

  If CO gas is present around the CO sensor (CO alarm device) during the above-described self-diagnosis of the CO sensor, the charge / discharge current flowing through the CO sensor varies depending on the CO concentration. For this reason, in the actual installation environment, when the shipping mode is canceled while the CO gas is present, there is a problem that the CO gas is detected and erroneously detected as a failure. In order to solve this problem, in Japanese Patent Application Laid-Open No. 2003-228561, when the presence of CO gas is detected when the shipping mode is canceled, the shipping mode cancellation is stopped and a notification is made.

JP 2008-309711 A JP 2008-309713 A JP 2008-309712 A

  In the above-described conventional alarm device, when the CO sensor is in the initial normal state and the CO gas is present, it is erroneously detected as a failure and the release of the shipping mode is stopped, and the CO sensor is normal. Regardless, there is a problem of being returned as a complaint.

  Therefore, the present invention pays attention to the above-mentioned problems, and prevents false detection of CO sensor failure even in the presence of CO gas in an alarm device that self-diagnose whether or not the CO sensor has a failure. The task is to do.

  In the alarm device according to claim 1, the current flowing between the detection electrode and the counter electrode sandwiching the proton conductor film is changed according to the gas concentration of the target gas due to the reaction between the water vapor from the water container containing water and the target gas. An electrochemical gas sensor, a discharge resistor connected to the gas sensor, a power source for charging the gas sensor by supplying a current to a detection electrode and a counter electrode of the gas sensor, and a power source provided between the gas sensor and the gas sensor. A changeover switch for switching between charging and discharging of the gas sensor; switch control means for turning off the changeover switch and discharging the gas sensor after charging the gas sensor by turning on the changeover switch; and converting a current flowing through the gas sensor into a voltage Current / voltage conversion circuit that performs charging and discharging of the gas sensor by the switch control means, and the current / voltage A self-diagnosis unit that diagnoses a failure of the gas sensor based on the output voltage of the conversion circuit, wherein the self-diagnosis unit includes a first diagnosis function that performs a failure diagnosis at a first point during charging of the gas sensor; A second diagnostic function for performing a fault diagnosis at a second point at a constant voltage immediately after the start of discharge of the gas sensor, and a third diagnostic function for performing a fault diagnosis at a third point after the discharge of the gas sensor, When the target gas concentration detected by the gas sensor is less than a predetermined level, the self-diagnosis means uses the second diagnostic function and the first diagnostic function or the third diagnostic function, or the second diagnostic function and the The first diagnostic function and the third diagnostic function perform failure diagnosis of the gas sensor, and when the target gas concentration detected by the gas sensor is equal to or higher than a predetermined level, the second diagnostic machine Only by and performing failure diagnosis of the gas sensor.

  The alarm device according to claim 2 is the alarm device according to claim 1, wherein the self-diagnosis unit is configured to use only the second diagnosis function when the target gas concentration detected by the gas sensor is equal to or higher than a predetermined level. After the failure diagnosis of the gas sensor, the failure diagnosis of the gas sensor is performed at least by the first diagnosis function or the third diagnosis function after a predetermined time has elapsed. In addition, after performing the failure diagnosis of the gas sensor only by the second diagnosis function, the failure diagnosis of the gas sensor may be performed by the first diagnosis function and the third diagnosis function after a predetermined time has elapsed. That is, the first and third diagnostic functions can be freely combined depending on the purpose of determining whether or not the failure content is to be determined.

  FIG. 3 is a diagram showing the characteristics of the voltage signal corresponding to the charge / discharge current when the CO sensor is normal, short-circuited, disconnected, or without water. In the normal state shown in FIG. 3A, the waveform of the voltage signal differs between the case where the CO gas indicated by the thick solid line does not exist and the case where the CO gas indicated by the thick broken line exists. P1, P2, and P3 shown in the figure are candidate points for performing failure detection. The first point P1 is a point during charging, the second point P2 is a point at a constant voltage immediately after the start of discharging, and the third point P3 is a point after discharging. Among these, at the first point P1 and the third point P3, the voltage value differs depending on whether or not the CO gas is present, and the voltage value decreases as the gas concentration of the CO gas increases. However, at the second point, the voltage value is the same when no CO gas is present and when it is present. Therefore, when the gas concentration is less than the predetermined level, the gas sensor is diagnosed for failure by each of the first diagnostic function based on the first point P1, the second diagnostic function based on the second point P2, and the third diagnostic function based on the third point P3. However, if the gas concentration is equal to or higher than the predetermined level and the gas sensor is diagnosed only by the second diagnostic function based on the second point P2, it is possible to prevent malfunctions even if CO gas is present. Detection can be prevented.

  According to the alarm device of claim 1, since the failure diagnosis is performed at the second point that does not depend on the CO gas even if the CO gas exists, the CO gas is detected at the time of the failure diagnosis in the shipping mode release or the normal mode, for example. It is possible to detect an actual failure while preventing erroneous detection of the failure due to the presence of.

  According to the alarm device of claim 2, in addition to the effect of claim 1, for example, when the CO gas is present at the beginning, such as when the shipping mode is released, when the CO gas is no longer present after a predetermined time has elapsed, Failure diagnosis can be performed at least by the first point and the third point to improve failure detection accuracy.

It is a principal part block diagram of the gas alarm device of embodiment of this invention. It is an equivalent circuit schematic of the gas alarm device shown in FIG. It is a figure which shows the characteristic of the voltage signal corresponding to the charging / discharging electric current at the time of the normal time of the CO sensor which concerns on this invention, a short circuit failure, a disconnection, and a waterless failure. It is a principal part flowchart of the control program of the self-diagnosis process at the time of cancellation | release of the shipping mode of 1st Example which the microcomputer in embodiment performs. It is a principal part flowchart which shows the control program at the time of the normal mode of 1st Example which the microcomputer in embodiment performs. It is a principal part flowchart which shows the control program of the self-diagnosis process at the time of the shipping mode cancellation | release of 2nd Example which the microcomputer in embodiment performs. It is a principal part flowchart which shows the control program at the time of the normal mode of 2nd Example which the microcomputer in embodiment performs. 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 circuit diagram showing an embodiment of a gas alarm as an alarm according to an embodiment of the present invention. As shown in the figure, this gas alarm device includes a CO sensor 1 as a gas sensor, a microcomputer (hereinafter referred to as a microcomputer) 10, a self-diagnosis circuit 30, a current / voltage conversion circuit 40, an audio alarm output circuit 50, and the gas. A battery 60 for supplying power to each part of the alarm device is provided. The CO sensor 1 is, for example, the electrochemical CO sensor 1 shown in FIG. 8 described above, and outputs a short circuit current I corresponding to the CO concentration (gas concentration) of the CO gas as the target gas to the current / voltage conversion circuit 40. The processing of the microcomputer 10 differs depending on the following embodiments, but the block diagram is the same.

  The current / voltage conversion circuit 40 is provided between the operational amplifier 41 having the detection electrode 31 of the CO sensor 1 connected to the negative input terminal and the counter electrode 32 connected to the positive input terminal, and between the negative input terminal and the output terminal of the operational amplifier 41. A voltage signal corresponding to the short-circuit current I is output to the microcomputer 10. A resistor Rs is provided between the detection electrode 31 of the CO sensor 1 and the negative input terminal of the operational amplifier 41. A switch SW2 is provided in parallel with the resistor Rs. The switch SW2 is turned on / off by 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. Then, the microcomputer 10 samples the voltage signal output from the current / voltage conversion circuit 40 at a predetermined sampling period to measure the CO concentration of the CO gas. When the CO concentration becomes equal to or higher than the alarm set point, the microcomputer 10 An alarm is issued from the alarm output circuit 50, and the alarm is stopped when the alarm output set point or lower is reached.

  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 is performed by regarding the CO sensor 1 as a kind of capacitor. The self-diagnosis circuit 30 will be described with reference to FIG. FIG. 2 is an equivalent circuit diagram of the gas alarm shown in FIG.

  In FIG. 2, Rd is the input resistance Rd of the current / voltage conversion circuit 40. The input resistance Rd is connected to both ends of the CO sensor 1 and functions as a discharge resistance. The self-diagnosis circuit 30 is provided between the current source 33 and the CO sensor 1 as a power source for supplying current to the CO sensor 1 to charge the CO sensor 1 and charging the CO sensor 1. And a changeover switch SW1 for switching between discharges. On / off of the changeover switch SW1 is controlled by the microcomputer 10.

  Next, the operation at the time of self-diagnosis using the self-diagnosis circuit 30 of the gas alarm will be described. When the changeover switch SW1 is turned on and the switch SW2 is turned off according to an instruction from the microcomputer 10, the CO sensor 1 is charged from the current source 33. Thereafter, when the changeover switch SW1 is turned off and the switch SW2 is turned on, the charging from the current source 33 to the CO sensor 1 is interrupted, and the electric charge accumulated in the CO sensor 1 is discharged via the input resistor Rd.

  The current / voltage conversion circuit 40 outputs a predetermined reference voltage when the current flowing through the input resistor Rd (that is, the current flowing through the current / voltage conversion circuit 40) is 0, and becomes smaller as the current flowing through the input resistor Rd increases. Outputs a voltage signal. For this reason, the voltage signal of the current / voltage conversion circuit 40 (input resistance Rd) during charging and discharging has a waveform as shown by the thick solid line in FIG. That is, it gradually decreases from the reference voltage in response to the start of charging, and immediately after switching from charging to discharging, it sticks to 0 V for a certain period of time, increases due to the transient phenomenon of the discharge current, and becomes the reference voltage again.

  The voltage signal output from the current / voltage conversion circuit 40 at the time of a short circuit failure is as shown in FIG. When the CO sensor 1 is short-circuited, the current from the current source 33 flows only to the short-circuited CO sensor 1 and hardly flows to the current / voltage conversion circuit 40. Therefore, since no electric charge is accumulated in the CO sensor 1 at the time of a short circuit failure, no current flows through the current / voltage conversion circuit 40 even if the changeover switch SW2 is turned on to start discharging. Therefore, the voltage signal has a waveform that keeps approximately the vicinity of the reference voltage during charging and discharging.

  Further, the voltage signal output from the current / voltage conversion circuit 40 at the time of disconnection or failure without water is as shown in FIG. In the case of a disconnection or waterless failure, both have no capacitor component of the CO sensor 1 and are in an open state. Therefore, even if the switch SW1 is turned on and charging is started, the current from the current source 33 is supplied to the CO sensor 1. All flow through the current / voltage conversion circuit 40. In the case of a disconnection failure or a failure without water, no electric charge is accumulated in the CO sensor 1, so that no current flows through the current / voltage conversion circuit 40 even when the changeover switch SW1 is turned on to start discharging. Therefore, the voltage signal is constant at a voltage lower than the reference voltage during charging, and has a waveform that returns to the reference voltage when switching from charging to discharging.

  When performing the fault diagnosis, the microcomputer 10 controls the change-over switches SW1 and SW2 to control the charge / discharge, and samples the voltage signal output from the current / voltage conversion circuit 40 at that time. Further, as shown in FIG. 3, threshold values A to E of voltages are set for the first point P1, the second point P2, and the third point P3, and the threshold values A to E and the voltage values at the respective points are set. To make a fault diagnosis. The diagnosis at the first point P1 is the first diagnosis function, the diagnosis at the second point P2 is the second diagnosis function, and the diagnosis at the third point P3 is the third diagnosis function.

  In the first diagnosis function, if the voltage value of the first point P1 is within the range between the threshold value D and the threshold value E, it is determined as normal, and if it is outside the range between the threshold value D and the threshold value E, it is determined as a failure. In the second diagnosis function, if the voltage value of the second point P2 is less than the threshold value C, it is determined to be normal, and if it is equal to or greater than the threshold value C, it is determined to be a failure. In the third diagnosis function, if the voltage value of the third point P3 is within the range between the threshold A and the threshold B, it is determined as normal, and if it is outside the range between the threshold A and the threshold B, it is determined as a failure. When a failure is detected by the first diagnostic function, the reason for the failure is determined based on the voltage value. That is, as shown in FIGS. 3B and 3C, the voltage value differs between a short-circuit fault and a disconnection or waterless fault. Therefore, when the voltage value at the first point P1 is greater than or equal to the threshold value D, it is determined that there is a short circuit failure, and when the voltage value at the first point P1 is less than the threshold value E, it is determined that there is a disconnection or no water failure.

  As shown in FIG. 3A, at the second point P2, there is no change in the voltage value in the presence of CO gas or in the absence of CO gas. Switch the diagnostic function. That is, if the CO concentration is equal to or higher than a predetermined level (for example, 50 ppm), failure diagnosis is performed using only the second diagnosis function. If the CO concentration of the CO gas is less than a predetermined level, failure diagnosis is performed using the first to third diagnosis functions.

(First Embodiment) FIG. 4 is a flow chart of the main part of a control program for self-diagnosis processing at the time of canceling the shipping mode of the first embodiment executed by the microcomputer 10, and FIG. 5 is a normal mode of the first embodiment executed by the microcomputer 10. It is a principal part flowchart of a control program at the time. First, when the shipping mode is canceled, it is determined in step S1 in FIG. 4 whether the CO concentration detected by the CO sensor 1 is equal to or higher than a predetermined level (for example, 50 ppm). If it is less than the predetermined level, failure diagnosis is performed in step S2 using the voltage signals at the first point P1, the second point P2, and the third point P3 (diagnosis of the first diagnosis function, the second diagnosis function, and the third diagnosis function). . If a failure is detected in step S3, a failure alarm is started in step S4 and the process is terminated. If the CO concentration is equal to or higher than the predetermined level in step S1, failure diagnosis is performed with a voltage signal of only the second point P2 in step S5 (diagnosis using only the second diagnosis function). If a failure is detected in step S6, a failure alarm is started in step S7 and the process ends.

  In the normal mode of FIG. 5, it is determined in step S11 whether 50 hours have passed since the previous failure diagnosis, and if 50 hours have not passed, CO gas monitoring (and alarm) in step S12, or other The process returns to step S11. If 50 hours have elapsed, failure diagnosis is performed in step S13 and subsequent steps. That is, in this normal mode, failure diagnosis is performed every 50 hours.

  In step S13, it is determined whether the CO concentration detected by the CO sensor 1 is equal to or higher than a predetermined level (for example, 50 ppm). If it is less than the predetermined level, the process after step S14 is performed. If the CO concentration is equal to or higher than the predetermined level, the process after step S18 is performed. Steps S14 to S16 are the same as steps S2 to S4 in FIG. 4, and steps S18 to S20 are the same as steps S5 to 7 in FIG. In the failure diagnosis in the normal mode, since a failure alarm that has been determined as a failure may have started before this, if it is determined in step S15 and step S19 that no failure has been detected, step The failure alarm is canceled in S17 and S21, respectively.

(Second Embodiment) FIG. 6 is a main part flowchart of a control program for self-diagnosis processing at the time of canceling the shipping mode of the second embodiment executed by the microcomputer 10, and FIG. 7 is a normal mode of the second embodiment executed by the microcomputer 10. It is a principal part flowchart of a control program at the time. In the second embodiment, when the CO concentration detected by the CO sensor 1 is equal to or higher than a predetermined level (50 ppm), as in the first embodiment, only the second point P2 (only the second diagnostic function) is used. Perform fault diagnosis. Then, after a predetermined time (for example, a predetermined time such as 1 hour) has elapsed, a failure diagnosis of the CO sensor 1 is performed by the first to third diagnosis functions of the first point P1, the second point P2, and the third point P3. In the following description, the correspondence with the first embodiment is described, and a detailed description of the same processing is omitted.

  That is, Steps S31 to S37 in FIG. 6 are the same as Steps S1 to S7 in the first embodiment (FIG. 4), and after performing failure diagnosis based only on the second point P2 in Steps S35 to S37, constant in Step S38. The process waits until the time elapses, and returns to step S31 when a predetermined time elapses. Further, steps S41 to S51 in FIG. 7 are the same as steps 11 to S21 in the first embodiment (FIG. 5), and after performing failure diagnosis based only on the second point P2 in steps S48 to S51, constant in step S52. The system waits until the time elapses, and returns to step S43 when a predetermined time elapses.

  In the second embodiment, when the CO concentration of the CO gas is equal to or higher than a predetermined level, that is, even when the CO gas is present, the CO gas does not exist after a certain period of time. Since fault diagnosis is performed, the fault detection accuracy is increased. In the failure diagnosis in this case, the diagnosis based on the second point may not be performed.

  As described above, when the CO concentration of the CO gas is equal to or higher than a predetermined level when the shipping mode is canceled and during the normal mode (when CO gas is present), the failure diagnosis based on the first point P1 and the third point P3 is not performed ( Since the process is skipped), erroneous determination can be prevented. In addition, failure diagnosis can be performed at a point that does not depend on CO gas (second point), so there is no need to stop the release of the shipping mode, and the function is deteriorated and the CO concentration is not notified without being notified. It is possible to avoid such a situation.

  Also, as in the second embodiment, when CO gas is present, after performing failure diagnosis at the second point, for example, by performing re-diagnosis when the CO concentration decreases after 1 hour, a failure state Can be avoided, and the accuracy of failure detection is increased.

1 CO sensor (gas sensor)
10a CPU (switch control means, self-diagnosis means)
33 Current source (power supply)
40 Current / voltage conversion circuit SW1 selector switch

Claims (2)

An electrochemical gas sensor in which a current flowing between a detection electrode and a counter electrode sandwiching a proton conductor film due to a reaction between water vapor from a water container containing water and the target gas changes according to the gas concentration of the target gas, and the gas sensor A discharge resistor connected to the gas sensor, a power source for charging the gas sensor by supplying a current to a detection electrode and a counter electrode of the gas sensor, and a switch provided between the power source and the gas sensor to switch charging and discharging of the gas sensor A switch, a switch control unit that turns on the changeover switch and charges the gas sensor and then turns off the changeover switch to discharge the gas sensor; a current / voltage conversion circuit that converts a current flowing through the gas sensor into a voltage; The gas sensor is charged and discharged by the switch control means to obtain an output voltage of the current / voltage conversion circuit. In alarm with a self-diagnosis means for performing a fault diagnosis of the gas sensor Zui,
The self-diagnosis means includes a first diagnosis function for performing a failure diagnosis at a first point during charging of the gas sensor, and a second diagnosis function for performing a failure diagnosis at a second point at a constant voltage immediately after the discharge of the gas sensor. A third diagnostic function for performing a fault diagnosis at a third point after the gas sensor discharges,
The self-diagnosis means includes
When the target gas concentration detected by the gas sensor is less than a predetermined level, the second diagnostic function and the first diagnostic function or the third diagnostic function, or the second diagnostic function and the first diagnostic function and The third diagnosis function performs failure diagnosis of the gas sensor,
When the target gas concentration detected by the gas sensor is equal to or higher than a predetermined level, a failure diagnosis of the gas sensor is performed only by the second diagnosis function.   When the target gas concentration detected by the gas sensor is equal to or higher than a predetermined level, the self-diagnosis unit performs at least the first diagnostic function after a predetermined time has elapsed after performing a fault diagnosis of the gas sensor only by the second diagnostic function. The alarm device according to claim 1, wherein a failure diagnosis of the gas sensor is performed by a third diagnosis function.

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