JP2003302369A - Co sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a CO sensor whose detection accuracy is improved and power is reduced. <P>SOLUTION: The CO of a CO detection section 20 is intermittently detected, a detection period is changed by an external signal inputted from an external signal generation means 33, a detection interval is reduced when it is necessary to improve the detection accuracy, and the detection interval is extended normally to reduce power consumption. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO sensor for detecting carbon monoxide.

[0002]

2. Description of the Related Art Conventional gas sensors of various types and shapes such as a semiconductor type, a hot wire semiconductor type, and a solid electrolyte type have been proposed. As an example, the solid electrolyte type has a pair of platinum electrodes 2 and 3 on both surfaces of a plate-shaped solid electrolyte 1 as shown in FIG.
And cover both sides with plate-shaped gas selective permeators 4 and 5,
A heater 6 is formed on the surface of one of the gas selective permeators 4 and an oxidation catalyst layer 7 is placed on the heater 6.

[0003]

Generally, gas sensors are selectively sensitive to carbon monoxide, methane, propane, hydrogen, etc., and are used for gas leak alarms, CO alarms and the like. Therefore, the final safety device is required to have high sensitivity, fast response, high reliability, high selectivity, and low power consumption.

However, in the conventional gas sensor shown in FIG. 12, the solid electrolyte 1, the gas selective permeation body 4, and the oxidation catalyst layer 7 have large heat capacities of plate-shaped chips, and therefore a large amount of electric power is required to keep the sensor at the operating temperature. Therefore, a commercial power supply was necessary for that. Therefore, the power outlet is always occupied, and it is usually installed in a very limited place such as a kitchen in a general household. However, considering the current situation where unfortunate accidents due to poor combustion of indoor combustors such as heaters and water heaters are still present, and the spread of central heating due to high airtightness and insulation of houses, CO alarms need to be spread. There is. However, it is very inconvenient to occupy a power outlet in a home where electric appliances are overflowing, and it is desired to improve the installability.

In order to solve such a problem, a thin film gas sensor having the structure shown in FIG. 13 has been proposed (Japanese Patent Laid-Open No. 2001).
-194329). This thin film gas sensor has a substrate 8
A solid electrolyte thin film 11 having oxygen ion conductivity formed on the upper surface of the heater 9 formed above via an electric insulating layer 10, and a pair of electrodes 12 and electrodes 12 ′ formed on the solid electrolyte thin film 11. , The oxidation catalyst layer 13 provided on one electrode 12 ′ of the pair of electrodes 12. It has been shown that with this configuration, the heat capacity can be reduced to enable pulse driving, and as a result, significant power saving can be achieved and battery driving can be performed. However, since the semiconductor type, the hot wire semiconductor type, the solid electrolyte type, etc. are all heated by a heater to a predetermined temperature, it is necessary to set a large pulse interval in order to maintain the battery capacity for a long time. However, if the pulse interval is large, C in an emergency such as a fire
When O suddenly occurs, CO detection may be delayed. In order to solve this, a driving method of a heater as shown in FIG. 14 is shown (Japanese Patent Laid-Open No. 2001-1).
94329). This is because the heating means operates intermittently, and by making the pulse interval when the output is lower than the first set value longer than the pulse interval when the output is higher than the first set value, the CO can be accelerated in an emergency. It is something to detect.

[0006]

However, even in this method, since the pulse interval is usually long, the operation is
CO detection may be delayed in the initial stage of CO generation.

The present invention solves the above-mentioned conventional problems. The detection interval of the CO sensor is changed by an external signal, and in an emergency, the detection interval is shortened to improve the detection accuracy, and in the normal state, the detection interval is increased. By reducing the power consumption in this way, it is intended to improve the detection accuracy and reduce the power consumption at the same time.

[0008]

In order to solve the above conventional problems, carbon monoxide detection is performed intermittently, and the application interval of a pulse signal for detecting carbon monoxide is changed by a control signal from the outside. It is a thing.

Thus, in an emergency, the detection interval can be shortened and an early warning can be given.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, carbon monoxide detection is performed intermittently, and an application interval of a pulse signal for detecting carbon monoxide is changed by an external control signal. It is possible to output an early warning in an emergency.

The invention according to claim 2 is to change an external control signal by an external switch, and when the early warning is judged to be necessary, the alarm interval is determined by setting the external switch. You can

Further, according to the third aspect of the invention, the control signal from the outside is changed by the remote operation via the communication means, and the detection cycle can be set by the remote operation.

Further, the invention according to claim 4 is to connect to a sensor device by a communication means and change a detection cycle of a CO sensor upon receiving a signal from an external sensor device, which is interlocked with another sensor device. Then, it is possible to issue an early warning.

The invention according to claim 5 is the second C
When the CO concentration detected by the O sensor is equal to or higher than a predetermined level, a control signal for shortening the pulse interval of the CO sensor connected by the communication means is transmitted.
When an abnormality in the concentration is detected, the detection interval for early detection by other CO sensors is shortened, and the CO sensors can cooperate to issue an early warning.

The invention according to claim 6 is the second C
When the CO concentration detected by the O sensor is equal to or lower than a predetermined level, a control signal for increasing the pulse interval of the CO sensor connected by the communication means or for setting the pulse interval to a predetermined value is transmitted. When the value falls below a predetermined value, the initial detection interval is restored, and when the dangerous state is exited, the detection interval is returned to save power.

In the invention according to claim 7, when the detected CO concentration is equal to or higher than a predetermined level, the pulse interval of the CO sensor is shortened and a control signal for shortening the pulse interval is set to a specific CO sensor. The information is transmitted to the surrounding CO sensor, and the peripheral CO sensor is instructed to enter the emergency warning system.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a CO sensor in Embodiment 1 of the present invention. The CO detection unit 20 is configured to be intermittently heated by the heater 21. Reference numeral 22 is a pulse signal control means, which is a microcomputer 23 as a signal control means.
The pulse output voltage output from is input to the + terminal of the operational amplifier 24, and the fixed resistor 25 and the capacitor 2 are output from the output terminal.
It becomes the input of the + terminal of the operational amplifier 27 via the filter composed of 6. The PNP transistor 28, the NPN transistor 29, and the DC power supply 30 constitute power supply means 31 to the heater 21. In this configuration, current flows from the DC power supply 30 to the emitter of the PNP transistor 28.
It flows through the collector and flows into the heater 21. The magnitude of the current depends on the base current of the PNP transistor 28. The base current of the PNP transistor 28 is controlled by the base voltage of the NPN transistor 29, that is, the output voltage of the operational amplifier 27. Since the operational amplifier 27 operates so that the − terminal and the + terminal have the same potential, the current flowing into the heater 21 is determined, the variation of the resistance value due to heat generation reaches an equilibrium state, and the voltage applied to the heater 21 is determined. The temperature balance of the heater 21 is also achieved, and the CO detection unit 20 is heated.

When the temperature rises, the resistance value of the heater 21 increases and the voltage at the negative terminal of the operational amplifier 27 increases. When the voltage difference from the + terminal becomes small, the base current of the NPN transistor 29 is narrowed. Therefore, the PNP transistor 28
Is also throttled, the current flowing into the heater 21 is also throttled, the equilibrium state is reached, and a voltage corresponding to the pulse output voltage is applied to the heater 21. And heater 2
The temperature of 1 is controlled to a constant value. The CO detection unit 20 heated to a constant temperature outputs a voltage according to the concentration of carbon monoxide gas, and the output signal is input to the signal processing unit 32. Inside the microcomputer 23, the CO concentration is determined based on the signal from the signal processing unit 32, and a notification signal is output to the notification means 34. The output signal from the external signal generating means 33 enters the microcomputer 23 and changes the pulse output cycle.

FIG. 2 is a perspective view of the CO detector 20 in the first embodiment of the present invention.

In FIG. 2, reference numeral 40 is a sensor element.
41 is a heat-resistant and low-thermal-conductivity substrate, here about 2 mm
Quartz glass of x2 mm x 0.3 mm is used. 42
The resistance of the platinum heater is set so as to reach a predetermined temperature by a sputtering method, an electron beam evaporation method or the like. 43
Is an insulating film formed of an insulating material such as alumina, silica, or silicon nitride so as to cover the heater 21 by a sputtering method, an electron beam evaporation method, or the like. Reference numeral 44 denotes a solid electrolyte film formed on the insulating film 43 in an area smaller than that of the insulating film 43. A solid electrolyte having oxygen ion conductivity (8% yttria-stabilized zirconia) is about 0.4 mm formed by a sputtering method.
It is formed to have a size of 0.6 mm. As the solid electrolyte, all solid electrolytes having oxygen ion conductivity can be used, but yttria-stabilized zirconia (YS) obtained by mixing a small amount of yttria with zirconia and firing the mixture.
Z) is relatively inexpensive and easy to obtain. 45a, 45b
Is an electrode, and platinum is formed on the solid electrolyte membrane 44 by a sputtering method. Platinum may be partially mixed with a noble metal such as palladium, ruthenium or rhodium. In addition, all electrode materials generally used for solid electrolyte type sensors can be used. Reference numeral 46 denotes a catalyst set on one electrode 45a, and the catalyst 46 may be any one as long as it can oxidize and decompose the gas to be measured. A mixture obtained by supporting the mixture on alumina or the like is formed by a screen printing method.

In the above structure, electric power is supplied to the heater 21 from a power source (not shown) to heat the solid electrolyte membrane 44 to a predetermined temperature (400 ° C. to 500 ° C.). Solid electrolyte membrane 44
Reaches a predetermined temperature, electrons are exchanged at the interfaces between the electrodes 45a and 45b, the solid electrolyte membrane 44 and the air, and oxygen ions are generated. Here, if CO is present in the air,
At the electrode 45a covered with the catalyst 46, CO is oxidized by the catalyst 46 and does not reach the surface of the electrode 45a. At the other electrode 45b, CO reaches the electrode surface and is oxidized into CO ₂ . Oxygen ions in the solid electrolyte membrane 44 are used for this oxidation reaction, and as a result, a difference occurs in the electrode reaction between the two electrodes, the equilibrium of oxygen ions in the solid electrolyte membrane 44 is disrupted, and a potential difference occurs between both electrodes. To do. The CO concentration can be detected by detecting this potential difference.

The quartz glass used for the substrate 41 has a thermal conductivity of 1.5 W / mK and an insulating film 43 (35 to 45 W / m).
K) and the solid electrolyte membrane 44 (6 W / mK), which is small when heated by the heater 21.
It is possible to raise the temperature only in the region of the solid electrolyte membrane 44 directly above the heater 21 and in the vicinity thereof with almost no rise in the temperature. Therefore, the power consumption for heating can be significantly reduced. Further, since the thermal shock strength is high, it is possible to raise the temperature to a predetermined temperature in a short time. With the above configuration, 450 m with an electric power of 15 mWsec.
It was possible to raise the temperature to ° C. Therefore, the heater 21
Since it can be driven in a pulsed manner to significantly reduce power consumption, it can be driven by a battery power supply.

With the above construction, carbon monoxide is detected intermittently, and the detection interval is changed by a signal from the outside. In an emergency, the detection interval is shortened when it is necessary to detect carbon monoxide quickly. Then, the frequency of detection can be increased, and in the normal time, the detection interval can be widened to save power.

(Embodiment 2) FIG. 3 is a configuration diagram of a CO sensor according to Embodiment 2 of the present invention. Contact information of the external switch 47 is input to the microcomputer 23.

With this configuration, by turning on the external switch 47, when the generation of CO is predicted or when the detection accuracy is required, the external switch 4 is previously set.
7 can be turned on to instruct the microcomputer 23 to shorten the pulse interval, and it is possible to improve detection accuracy and save power. Further, the pulse interval may be returned to the original value or increased by operating the external switch 47.

(Third Embodiment) FIG. 4 is a block diagram of a CO sensor according to a third embodiment of the present invention. A command from the telephone line is input to the microcomputer 23 via the internal bus 48 and the communication adapter 49, and it is possible to instruct the indoor CO sensor to change the pulse output interval from the outside. With the above configuration, the CO sensor can be controlled from a remote place. The communication adapter may be a telephone line, a wireless communication, a wired communication, the Internet, or ISDN communication.

(Embodiment 4) FIG. 5 is a block diagram of a CO sensor in Embodiment 4 of the present invention. Other sensors (here, the fire alarm 5
The signal from 0) is input.

When the fire alarm 50 senses an increase in the ambient heat and sends a signal to the CO sensor microcomputer 23 via the internal bus 48, the microcomputer 23 shortens the interval of the detection pulse and abruptly. Accurately detect an increase in CO. By thus catching the sign of a fire and quickly responding to the detection of an increase in carbon monoxide, it is possible to reduce the possibility of losing a person's life due to a rapid increase in CO accompanying a fire.

The fire alarm may be one that detects the generation of smoke. Alternatively, the other sensor may be, for example, a gas leak sensor or a gas meter, and outputs a signal for shortening the interval of the detection pulse of the CO sensor to the CO sensor when these sensors detect an abnormality. Further, the other sensor may be an in-room detection sensor, and the interval of the detection pulse of the CO sensor may be shortened when there is a person in the room. Alternatively, the other sensor may be a clock, and the interval between the detection pulses of the CO sensor may be shortened at bedtime.

(Embodiment 5) FIG. 6 is a configuration diagram of a CO sensor according to Embodiment 5 of the present invention. A signal from the external CO sensor 51 is input to the microcomputer 23 via the internal bus 48, the communication adapter 49, and the external network 50.

FIG. 7 shows the external CO sensor 51 to the microcomputer 2
3 is a signal transition diagram showing a signal transmission state in FIG. External CO
The transmission signal A (201) is sent from the sensor 51 to the network 5
When it is transmitted to the communication adapter 49 via 0, the communication adapter 49 receives this and returns a response signal A (202). If the communication adapter 49 cannot receive the transmission signal A (201), it does not return the response signal A (202). External C
The O sensor 51 receives the response signal A (202), and the communication between the external CO sensor 51 and the communication adapter 49 is completed.

Next, the communication adapter 49 transmits to the microcomputer 23 a transmission signal A '(203) obtained by converting the received transmission signal A (201) into a communication form with the microcomputer 23. The microcomputer 23 receives this and returns a response signal A ′ (204). If the microcomputer 23 cannot receive the transmission signal A '(203), it does not return the response signal A' (204).
The communication adapter 49 receives this response signal A '(204), and the communication between the communication adapter 49 and the microcomputer 23 is completed.

As described above, the external CO sensor transmits to the microcomputer 23.

Here, FIG. 8 shows the communication adapter 4 with the above configuration.
9 is a flowchart showing the operation of FIG.
6 is a schematic diagram of a communication path between the sensor 51 and the microcomputer 23. FIG.

The operation of the communication adapter 49 will be described with reference to FIGS. Communication means 11 via network 50
This is a case where 0 is received and transmitted to the device connection means 114. As shown in FIG. 9, the determination means 11 determines whether or not the content received by the communication means 110 needs to be communicated to the microcomputer 23.
It judges by 1 (S101). The determination method is to determine whether or not the destination of the received content is the microcomputer 23, whether the received content is related to the microcomputer 23, the received content and the past content stored in the storage unit 112, and change. It is determined whether or not there is, and communication is performed when the destination of the received content is the microcomputer 23, the received content is related to the microcomputer 23, and there is a change from the past content stored in the storage unit 112. It is judged necessary. That is, it is determined whether the predetermined CO level is exceeded or the detection pulse interval should be shortened.

Next, the communication control means 114 selects and sets the communication partner / communication content. The communication partner is the microcomputer 23
Is an identification code for communication designating (S102).
As for the communication content, necessary parts are extracted from the content received by the communication means 110 from the network 50, or the communication adapter 4 is used.
This is a new content required for communication between the CPU 9 and the microcomputer 23. It may also include code conversion for communication and encryption for security.

After selecting and setting the communication partner / content, the device connecting means 114 transmits the information to the microcomputer 23 (S103). When the communication adapter 49 and the microcomputer 23 are transmitting and receiving at the communication timing, the transmission is performed at the communication timing.

After the transmission, if the response signal is to be returned from the microcomputer 3, the response signal is waited for a fixed time (S104). Whether the response signal is to be returned from the microcomputer 23 includes, for example, designation of whether to respond to the communication content transmitted from the communication adapter 49 (S103), or the communication adapter 49 and the microcomputer 23. There are various methods such as the arrangement of the response signal in advance.

When the response signal is to be returned from the microcomputer 23, the device connection means 114 receives the response signal (S105), and if the content is normal (S10).
6) The communication is finished. If the response signal cannot be received, or if the content is abnormal even if it is received, retransmit the transmitted content.If communication is still not possible, notify or display the communication abnormality to the user or display it externally. Notify (S107).

In the above, the case where the communication means 110 receives via the network 50 and transmits to the equipment connecting means 104 has been described, but the case where the equipment connecting means 104 receives and transmits to the communication means 110 is also in accordance with this. . Further, the operation thus performed by the communication adapter 49 may be performed by the communication control means 115 of the microcomputer 23 or the communication control means 116 of the external CO sensor device 51. The communication is not limited to the above-mentioned embodiment, and any communication can be used as long as the communication can be performed between the external CO sensor 51 and the microcomputer 23 via the communication adapter 49.

With this configuration, one CO sensor 51 is provided.
When C captures the increase in carbon monoxide, the associated C
By sending a signal to the microcomputer 23 of the O sensor, it is possible to detect the spread of carbon monoxide expected due to a fire or the like at an early stage by shortening the detection cycle of neighboring sensors. The above-mentioned association is, for example, a CO sensor which is installed on a passage of smoke or a cold and which is considered to sequentially detect signals when a fire or the like occurs. Alternatively, it may be associated with a CO sensor closest to its own CO sensor or a CO sensor within a predetermined distance (not limited to one).

(Sixth Embodiment) FIG. 10 is a flow chart showing the communication operation of the CO sensors in the sixth embodiment of the present invention. In the communication procedure, it is determined whether the CO level is less than or equal to a predetermined value (S201), and if not, communication is required, and a signal is set to return the pulse period to a predetermined value (S202). Perform the procedure as described in. By this procedure, the set pulse interval can be returned to a predetermined state, and recovery from an emergency can be performed.

(Embodiment 7) FIG. 11 is a flow chart showing the communication operation between CO sensors according to Embodiment 7 of the present invention. First, it is determined whether the CO level is below a predetermined value (S3
01), and if so, first, the pulse interval of itself is shortened (S302), and the signal for shortening the pulse interval is set (S302).
303) Then, when it is determined by this procedure that the CO concentration exceeds the predetermined value, a short pulse is set and the procedure as described in the fifth embodiment is executed. When it is determined by this procedure that the concentration of CO exceeds the predetermined value, the detection pulse period of its own sensor can be shortened and the detection period of another CO sensor connected by communication can be set short. You can quickly deal with emergencies.

Although the pulse interval of the CO sensor has been described in two steps, it may be three steps or more. In that case, the pulse interval may be gradually shortened or lengthened with time, or the pulse interval may be gradually shortened or lengthened according to the content of a control signal from the outside such as a fire sensor output or a CO sensor output. It may be.

[0046]

As described above, according to the present invention, since the detection cycle of the CO sensor can be changed by an external signal, when the urgency is increased and the detection interval is shortened, CO can be detected quickly. Therefore, it is possible to prevent an accident before it occurs and to extend the detection interval to save power when an emergency is not required, and it is possible to realize a CO sensor that achieves both power saving and high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CO sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a CO detection unit according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a CO sensor according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a CO sensor according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a CO sensor according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a CO sensor according to a fifth embodiment of the present invention.

FIG. 7 is a signal transition diagram showing a signal transmission state according to the fifth embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the communication adapter according to the fifth embodiment of the present invention.

FIG. 9 is a schematic diagram of a communication path between an external CO sensor and a microcomputer according to a fifth embodiment of the present invention.

FIG. 10 is a flowchart showing a communication operation between CO sensors according to the sixth embodiment of the present invention.

FIG. 11 is a flowchart showing a communication operation between CO sensors according to the seventh embodiment of the present invention.

FIG. 12 is a perspective view showing a configuration of a conventional CO sensor detection unit.

FIG. 13 is a perspective view showing the configuration of another conventional CO sensor detection unit.

FIG. 14 is a schematic diagram showing heater driving of another conventional CO sensor.

[Explanation of symbols]

20 CO detector 21 heater 22 Pulse signal control means 23 Microcomputer 32 signal processor 33 External signal generating means 40 sensor elements 47 External switch 48 internal buses 49 Communication adapter 50 network 51 External CO sensor 53 Fire alarm

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhiko Uno             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kunihiro Tsuruta             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takahiro Umeda             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kazunari Nishii             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yasuo Yoshimura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2G004 BB04 BC02 BD04 BG13 BJ03                       BL07 BL14 BL19 BM04

Claims (7)

[Claims] 1. A CO sensor in which a pulse signal application interval for intermittently detecting carbon monoxide is changed by a control signal from the outside. 2. The CO sensor according to claim 1, wherein a control signal from the outside is input by an external switch. 3. The CO sensor according to claim 1, wherein a control signal from the outside is input via the communication means. 4. A sensor device is connected by communication means,
The CO sensor according to claim 1, wherein the control signal from the outside is a transmission signal from the sensor device. 5. The sensor device is a second CO sensor,
The CO sensor according to claim 4, wherein when the CO concentration detected by the second CO sensor is equal to or higher than a predetermined level, a control signal for shortening the pulse interval of the CO sensor connected by the communication means is transmitted. 6. The sensor device is a second CO sensor,
5. When the CO concentration detected by the second CO sensor is equal to or lower than a predetermined level, the pulse interval of the CO sensor connected by the communication means is lengthened or a control signal for setting the pulse interval to a predetermined value is transmitted. The described CO sensor. 7. When the CO concentration detected by the communication means is equal to or higher than a predetermined level, the pulse interval of the CO sensor is shortened and a control signal for shortening the pulse interval is transmitted to another CO sensor. The CO sensor according to claim 4.