JP6594704B2 - Gas alarm - Google Patents

Description

  The present invention relates to a gas alarm device including a gas sensor having a capacitor-type sensor body and alarm means for generating an alarm.

  2. Description of the Related Art Conventionally, a battery-driven gas alarm device having a mode setting unit capable of switching power consumption has been proposed (see, for example, Patent Document 1). In such a gas alarm device, when it is not used, it is switched to the power saving mode, and when it is used, it is switched to the power consumption mode, thereby reducing power consumption.

JP 2006-31451 A

  However, the gas alarm device described in Patent Document 1 consumes a small amount of power even in the power saving mode. Therefore, a configuration in which the power supply unit and the gas sensor are completely cut off to suppress power consumption is also conceivable. By the way, an amplification means (for example, an operational amplifier) for amplifying an output may be connected to a gas sensor (for example, an electrochemical gas sensor) having a capacitor type sensor body. There is a possibility that an offset voltage is generated between the two input terminals of the amplifying means. In this case, it takes time until the output is stabilized by charging the sensor body with the offset voltage after the power is turned on. Such an offset voltage varies depending on the amplification means, and it is difficult to predict the time required for stabilization. Accordingly, during the installation work of the gas alarm device, if it is attempted to perform the initial inspection after the output is stabilized, the work time becomes long.

  The objective of this invention is providing the gas alarm device which can shorten the time which installation requires, reducing power consumption.

In order to solve the above-mentioned problems and achieve the object, the invention described in claim 1 is a gas alarm device comprising a gas sensor having a capacitor-type sensor body, and alarm means for generating an alarm, The gas sensor can be inspected by at least a power supply unit that supplies power to the gas sensor, a switch unit that can switch between electrical connection and disconnection between the power supply unit and the gas sensor, and a charging unit that charges the sensor body. Inspection means; at least control means for controlling the inspection means; and amplification means for amplifying the output of the gas sensor , wherein the gas sensor is separated from the power supply part by the switch part. A charging prevention switch that forms a closed circuit connecting both ends of the sensor body by being connected to the case, and the control means When the gas sensor and the power supply unit are connected by the switch unit , the charge prevention switch is disconnected, and within a predetermined stable time after the power supply unit and the gas sensor are electrically connected by the switch unit. Moreover, when the output of the gas sensor becomes lower than a first threshold, the control means causes the inspection means to start an initial inspection of the gas sensor.

  According to a second aspect of the present invention, in the first aspect of the present invention, the control unit is configured to control the alarm unit, and the power supply unit and the gas sensor are electrically connected. When the output of the gas sensor does not become lower than the first threshold value within the stable time, the control means causes the alarm means to generate an alarm instead of the initial inspection. .

  The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the inspection means is configured to detect a failure of an electric circuit of the gas sensor in the initial inspection. To do.

  According to a fourth aspect of the present invention, in the invention according to the third aspect, the charging means is configured such that the charging time is variable in the initial inspection and the normal inspection after the initial inspection. It is a feature.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, when the output of the gas sensor becomes equal to or higher than the first threshold after the completion of the initial inspection, The control means causes the alarm means to generate an alarm.

  According to the first aspect of the present invention, since the switch unit capable of switching between electrical connection and disconnection between the power source unit and the gas sensor is provided, power is not supplied to the gas sensor when the gas alarm is not used. As a result, power consumption can be reduced when the gas alarm device is stored before shipment or during transportation. Compared with the configuration in which the initial inspection is started after the gas sensor output is stabilized by starting the initial inspection of the gas sensor when the output of the gas sensor becomes lower than the first threshold value within the stable time. Thus, the initial inspection can be started early, and the time required for installing the gas alarm can be shortened.

  At this time, even if the initial inspection is started before the output of the gas sensor stabilizes and the sensor body is charged by the charging means or charged after stabilization, the potential difference between the electrode plates of the sensor body after charging is charged. It becomes equal to the voltage, and the potential difference between the electrode plates after completion of charging is constant regardless of before and after stabilization of the output of the gas sensor. Therefore, if the potential difference between the electrode plates at the start of charging is measured as the starting voltage, the gas sensor can be inspected based on the change in the potential difference between the electrode plates between the starting voltage and the charging voltage.

  According to the second aspect of the present invention, when the output of the gas sensor does not become lower than the first threshold value within a stable time after the power supply unit and the gas sensor are electrically connected, that is, an abnormality occurs in the gas sensor. If the capacitor is not normally charged due to the offset voltage, or if a gas leak has occurred, the alarm means will generate an alarm to allow the operator or user to recognize the gas sensor failure or gas leak. it can.

  According to the invention described in claim 3, since the failure of the electric circuit of the gas sensor is detected in the initial inspection, that is, the short circuit or the disconnection of the electric circuit is detected, the output of the gas sensor at the time of charging the sensor main body is used. And determine the failure. Specifically, when the electrode plates of the sensor body and the electric wires connected to the electrode plates are short-circuited, the potential difference (gas sensor output) between the electrode plates hardly changes even if the sensor body is charged. . On the other hand, when the wire around the sensor body is disconnected and the sensor body is disconnected from the circuit, the capacitor is not charged, and the voltage applied to the sensor body by the charging means may be the output of the gas sensor. The voltage changes instantaneously. In this way, when the electrical circuit is short-circuited or disconnected, the gas sensor output changes little or instantaneously, so failure can be detected in a short time and the charging time during initial inspection is shortened. can do. Therefore, the time required for the initial inspection can be shortened, and the time required for installing the gas alarm can be further shortened. Also, when transporting the gas alarm, the electrical circuit may be damaged due to vibration or shock, and other failures are unlikely to occur. Therefore, the entire gas alarm is inspected and installed before shipping. If the electric circuit is inspected as described above by the initial inspection later, the inspection can be made more efficient.

  According to the invention described in claim 4, during the initial inspection, the charging time is shortened as described above to shorten the time required for the initial inspection, and during the normal inspection after the initial inspection, the charging time is increased to increase the detection accuracy. Can be improved. That is, by increasing the charging time, the change in potential difference between the electrode plates of the sensor body can be increased, and the change in output can be detected more accurately.

  According to the fifth aspect of the present invention, when the output of the gas sensor becomes equal to or higher than the first threshold after completion of the initial inspection, the alarm means generates an alarm, that is, the alarm threshold and the initial inspection start. The control can be simplified by making the thresholds coincide with each other.

It is a block diagram which shows typically the gas alarm device which concerns on embodiment of this invention. It is a circuit diagram which shows the electric circuit of the gas alarm device of FIG. It is a timing chart which shows the output change at the time of the initial inspection of the gas alarm device of FIG. It is a timing chart which shows an output change when the gas sensor of the gas alarm device of Drawing 1 carries out (A) disconnection and (B) short circuit.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the gas alarm device 1 of the present embodiment includes a gas sensor 2, a speaker 3 as an alarm means, a battery 4 as a power supply unit that supplies power to at least the gas sensor 2, a battery 4, and a gas sensor 2. A battery-type gas comprising a switch unit 5 that can be switched between electrical connection and disconnection, an inspection unit 6 that can inspect the gas sensor 2, and a control unit 7 that controls the speaker 3 and the inspection unit 6. It is an alarm. In addition, the gas alarm device 1 may not be battery-powered, and may operate with, for example, a household AC100V power source.

  The gas sensor 2 is, for example, an electrochemical gas sensor, and as shown in FIG. 2, a sensor main body 21 and a first operational amplifier as an amplifying means that amplifies an output by amplifying a current generated by the sensor main body 21 as will be described later. 22, a second operational amplifier 23, first to fourth resistors R1 to R4, and a charge prevention switch SW1. As for the resistance value of each resistor, for example, the first resistor is 1 kΩ, the second resistor is 68 kΩ, the third resistor is 300 kΩ, and the fourth resistor is 20 kΩ.

  The sensor body 21 includes a capacitor C composed of a detection electrode (lower electrode in FIG. 2) and a counter electrode (upper electrode in FIG. 2), and a parallel resistor Rp connected in parallel to the capacitor C. And a capacitor type sensor having a series resistance Rs connected in series to the capacitor C, for example, carbon monoxide is used as a detection target gas. When the detection target gas exists between the detection electrode and the counter electrode, an oxidation-reduction reaction occurs in each electrode, and current tends to flow. Due to this current and each resistance, a potential difference (voltage) is generated between the point a and the point b, and this voltage becomes the output of the gas sensor 2. The output of the gas sensor 2 is transmitted to the control means 7 as a signal S1. In addition, the density | concentration of detection object gas and the output of the gas sensor 2 shall be substantially proportional.

  The charge prevention switch SW <b> 1 is connected when the gas sensor 2 and the battery 4 are disconnected by the switch unit 5, thereby forming a closed circuit that connects both ends of the sensor body 21. When a gas to be detected is present when the gas alarm is not operating, a current flows through the closed circuit due to a potential difference between the electrode plates of the capacitor C, so that no charge is accumulated in the capacitor C.

  In the first operational amplifier 22, an offset voltage can be generated between the input terminals In1 and In2. The offset voltage generated by the operational amplifier varies and is difficult to predict. Further, although an offset voltage may be generated in the second operational amplifier 23, the contribution ratio to the charging of the capacitor C is sufficiently small as compared with the offset voltage of the first operational amplifier 22.

  The speaker 3 is configured to generate an alarm sound by receiving the alarm generation signal S2 transmitted from the control means 7. In addition, as a warning means, it may replace with the speaker 3 and the display means which has display parts, such as a lamp | ramp, may be used, and the speaker 3 and a display means may be combined.

  The battery 4 may be a dry battery or a secondary battery, and may be configured to supply power not only to the gas sensor 2 but also to the speaker 3, the inspection means 6, the control means 7, and the like. And the power supply part which supplies electric power to these structures may be provided separately. When the battery 4 supplies power to a configuration other than the gas sensor 2, for example, the switch unit 5 is used as a main power switch, and the switch unit 5 is connected so that power is supplied to the configuration other than the gas sensor 2. May be.

  The checking means 6 has a charging means 61. The charging unit 61 includes a voltage application unit (not shown) that is connected to the gas sensor 2 and applies a voltage between the points a and d, and a charging switch 611 that switches connection and disconnection between the points c and d. Have.

  The voltage application unit is configured to apply a voltage of 0.2 V between point a and point d by setting the potential at point a to 2.2 V and the potential at point d to 2.4 V, for example. Has been.

  The charging switch 611 applies a voltage to the sensor main body 21 by connecting the point c and the point d with a resistor interposed therebetween. The charging means 61 is configured to vary the charging time by adjusting the connection time of the charging switch 611. A voltage equal to the potential difference between the points a and d is held between both electrodes of the capacitor C when charging is completed.

  Hereinafter, the procedure for installing the gas alarm device 1 and performing the initial inspection and the output of the gas sensor 2 at that time will be described with reference to the timing chart of FIG. In FIG. 3, the vertical axis corresponding to the magnitude of the output of the gas sensor 2 indicates that the value increases as it goes downward. In the following, the level of the output of the gas sensor 2 corresponds to the level of the gas concentration. That is, high output means that the gas concentration is high, and low output means that the gas concentration is low.

  First, the gas alarm device 1 is subjected to an initial inspection for shipping (for example, an inspection of whether the gas sensor 2 and the speaker 3 operate normally) before shipping at the factory, and then the switch unit 5 is disconnected to detect the gas sensor. 2 is shipped with no power supplied. As will be described later, when the capacitor C is charged by the offset voltage of the first operational amplifier 22 and the output is stabilized, this output corresponds to 0 ppm, and the output corresponding to 0 ppm is measured in advance at the factory. When installing the gas alarm device 1 thus shipped, when the installation operator puts the switch unit 5 into a connected state (switch ON), the control means 7 disconnects the charge prevention switch SW1. As a result, the points a and c are not equipotential, and the capacitor C is charged by the offset voltage of the first operational amplifier 22. The time constant at this time is determined by each resistance value and the capacitance of the capacitor C. Table 1 shows an example of the maximum time required until the potential difference between the electrode plates of the capacitor C becomes equal to the offset voltage and the charging is completed. Moreover, the change of the output (gas concentration conversion value) of the gas sensor 2 in the conditions 2 and 4 is shown in the timing chart of FIG. In the example of FIG. 4, an example is shown in which an offset voltage is generated such that the input terminal In1 has a higher voltage than the input terminal In2, but this positive / negative may be reversed.

  When a stable time (for example, 30 seconds) has elapsed since the charging prevention switch SW1 was disconnected, the control means 7 determines whether or not the output of the gas sensor 2 is lower than the first threshold value. The gas concentration converted value of the first threshold is, for example, 200 ppm. When the output of the gas sensor 2 is lower than the first threshold, the control means 7 starts an initial inspection. That is, the control unit 7 transmits a charging signal S4 to the charging unit 61, connects the charging switch 611, and starts charging the capacitor C. As the capacitor C is charged and the potential difference between the electrode plates increases (the output of the gas sensor 2 increases), it becomes difficult for current to flow to the sensor body 21 side. Therefore, if charging is continued, the capacitor C is saturated and the output of the gas sensor 2 becomes a constant value. When a predetermined time (for example, 1 second) elapses after the start of charging, the control unit 7 disconnects the charging switch 611. That is, the charging time at the initial inspection is, for example, 1 second.

  In the initial inspection, the following determination is performed when the capacitor C is charged. That is, as shown in FIG. 4, the control means 7 determines whether or not the output of the gas sensor 2 is equal to or less than the first determination value P1 after a predetermined time (for example, 10 ms) has elapsed from the start of charging, and further time has elapsed. After that (for example, after 0.1 second elapses), it is determined whether or not the output of the gas sensor 2 becomes a value not less than the second determination value P2 and not more than the third determination value P3. The second determination value is higher than the first determination value. When the electric circuit of the gas sensor 2 is normal, as indicated by a two-dot chain line in FIG. 4, the output increases with time and becomes equal to or higher than the second determination value P2 and third after the first determination value P1 or less. The value is equal to or less than the determination value P3. On the other hand, for example, when the sensor main body 21 is disconnected between the point a and the point c, the capacitor C is disconnected from the electric circuit and is not charged, and the point a and the point b that are the outputs of the gas sensor 2 are not charged. The potential difference between them is substantially equal to the amplified potential difference between the points a and c, and rapidly increases after the connection of the charge switch 611 as shown by the solid line in FIG. Therefore, the output of the gas sensor 2 becomes larger than the first determination value P1 and the third determination value P3.

  In addition, when both electrodes of the capacitor C are short-circuited (impedance is 0), no electric charge is accumulated in the capacitor C. Therefore, the potential difference between the point a and the point b which is the output of the gas sensor 2 is As shown by the solid line in FIG. Therefore, the output of the gas sensor 2 does not become the second determination value P2 or more and the third determination value P3 or less after the first determination value P1 or less.

  The determination values P1 to P3 are set to appropriate values according to the output corresponding to 0 ppm, the output at the start of charging, the charging voltage, and the time constant at the time of charging the sensor body 21. Good.

  When 33 seconds elapse after the sensor body 21 is charged, the control means 7 finishes the initial inspection. After completion of the initial inspection, the control means 7 repeatedly determines whether or not the output of the gas sensor 2 is equal to or higher than the first threshold value. When the output of the gas sensor 2 is equal to or higher than the first threshold value, an alarm signal S2 is sent to the speaker 3. Send and generate an alarm. Further, after the completion of the initial inspection, the control means 7 performs a failure inspection (normal inspection) periodically (for example, every 24 hours). In addition, what is necessary is just to set the charge time at the time of a normal inspection to 5 second, for example. In this way, by increasing the charging time during normal inspection, the change in potential difference between the electrode plates of the sensor body 21 can be increased, the change in output can be detected more accurately, and the detection accuracy can be improved. .

  On the other hand, if the output of the gas sensor 2 does not become lower than the first threshold even after the stabilization time has elapsed since the sensor body 21 first started discharging (after the switch was turned on), the control means 7 generates an alarm on the speaker 3. The signal S2 is transmitted to generate an alarm and the initial inspection is finished. At this time, the control means 7 carries out the first periodic inspection of the failure early (for example, after one hour).

  According to this embodiment, there are the following effects. That is, since the gas alarm device 1 is shipped in a state in which the switch unit 5 is cut and no power is supplied to the gas sensor 2, power consumption during transportation or the like can be reduced. Moreover, when the output of the gas sensor 2 becomes lower than the first threshold value within the stable time, the initial inspection of the gas sensor 2 is started, so that the initial inspection is started after the output of the gas sensor 2 is stabilized. Thus, the initial inspection can be started early, and the time required for installing the gas alarm device 1 can be shortened.

  Further, by causing the speaker 3 to issue an alarm when the output of the gas sensor 2 does not become lower than the first threshold value within a stable time after the switch unit 5 is connected and charging of the sensor body 21 is started, the gas sensor When an abnormality occurs in the capacitor 2 and the capacitor C is not normally charged due to the offset voltage, or when a gas leak occurs, an alarm is generated and the installation worker or user is made aware of the failure of the gas sensor 2 or the gas leak. be able to.

  Further, in the initial inspection, the output and the determination values P1 to P3 are compared at two different timings to detect a disconnection and a short circuit in the gas sensor 2, so that the output of the gas sensor 2 changes instantaneously at the time of the disconnection or the short circuit. The failure can be detected in a short time because it changes little or no. Accordingly, the charging time can be shortened, the time required for the initial inspection can be shortened, and the time required for installing the gas alarm can be further shortened.

  Furthermore, when the output of the gas sensor 2 becomes equal to or higher than the first threshold after the end of the initial inspection, an alarm is generated in the speaker 3, that is, by matching the threshold for alarm and the threshold for starting the initial inspection, Control can be simplified.

  In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.

  For example, in the above embodiment, an alarm is issued to the speaker 3 when the output of the gas sensor 2 does not become lower than the first threshold value within a stable time after the switch unit 5 is connected and charging of the sensor body 21 is started. However, the alarm generated at this time may be different from the alarm when the gas concentration is high in the gas alarm device 1 during normal use. A message may be generated, or a message indicating the possibility of failure of the gas sensor 2 and the possibility of gas leakage may be generated.

  In the above-described embodiment, the disconnection and the short circuit in the gas sensor 2 are detected in the initial inspection. However, in the initial inspection, the operation inspection of the gas sensor 2 (whether the output exceeds the alarm threshold) or the speaker 3 An operation check (whether or not an alarm sound can be generated) may be performed.

  In the above embodiment, the charging time by the charging means 61 is shorter at the initial inspection than at the normal inspection, but the charging time at each inspection is appropriately set according to the required detection accuracy. For example, the charging time may be equal between the initial inspection and the normal inspection. When the charging time is the same during the initial inspection and during the normal inspection, the charging unit 61 may not be configured to have a variable charging time.

  Moreover, in the said embodiment, when the output of the gas sensor 2 became more than a 1st threshold value after completion | finish of an initial inspection, it was set as the alarm for the speaker 3, but the 1st threshold value which is a threshold value for an initial inspection, The alarm threshold value may be set to a value different from each other.

  In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations. Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such is included in this invention.

1 Gas alarm device 2 Gas sensor 3 Speaker (alarm means)
4 batteries (power supply)
5 Switch part 6 Inspection means 7 Control means 21 Sensor body 61 Charging means

Claims (5)

A gas alarm device comprising a gas sensor having a capacitor-type sensor body and an alarm means for generating an alarm,
A power supply unit for supplying power to at least the gas sensor;
A switch unit capable of switching between electrical connection and disconnection between the power supply unit and the gas sensor;
Inspection means capable of inspecting the gas sensor by charging means for charging the sensor main body, control means for controlling at least the inspection means,
Amplifying means for amplifying the output of the gas sensor;
The gas sensor has a charge prevention switch that forms a closed circuit that connects both ends of the sensor body by being connected when the gas sensor and the power supply unit are disconnected by the switch unit,
When the gas sensor and the power supply unit are connected by the switch unit, the control unit disconnects the charge prevention switch,
When the output of the gas sensor becomes lower than the first threshold value within a predetermined stable time after the power supply unit and the gas sensor are electrically connected by the switch unit, the control unit is configured to check the inspection unit. The gas alarm device starts an initial check of the gas sensor. The control means is also configured to control the alarm means;
When the output of the gas sensor does not become lower than the first threshold value within the stable time after the power supply unit and the gas sensor are electrically connected, the control means replaces the initial inspection, The gas alarm according to claim 1, wherein an alarm is generated in the alarm means.   The gas alarm device according to claim 1, wherein the inspection unit is configured to be able to detect a failure of an electric circuit of the gas sensor in the initial inspection.   4. The gas alarm device according to claim 3, wherein the charging means is configured such that a charging time is variable between the initial check and a normal check after the initial check.   The control means causes the alarm means to generate an alarm when the output of the gas sensor becomes equal to or higher than the first threshold after completion of the initial inspection. Gas alarm device as described in.

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