JP2004069534A - Co sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a CO sensor achieving both of improvement in detection accuracy and reduction in power consumption. <P>SOLUTION: CO is detected intermittently, and an installation condition of the CO sensor is detected by a installation place detection means. According to the installation condition of the CO sensor, an output period of a CO detection pulse is changed. If increase of detection precision is necessary, a detection interval is shortened. Usually, the detection interval is increased for lowering power consumption. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a CO sensor for detecting carbon monoxide.
[0002]
[Prior 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, in the solid electrolyte type, as shown in FIG. 11, a pair of platinum electrodes 2 and 3 are formed on both sides of a plate-shaped solid electrolyte 1, and both sides are covered with plate-shaped gas selective permeators 4 and 5. The heater 6 is formed on the surface of the permselective body 4, and the oxidation catalyst layer 7 is provided thereon.
[0003]
[Problems to be solved by the invention]
Generally, gas sensors are selectively sensitive to carbon monoxide, methane, propane, hydrogen, and the like, and are used for applications such as gas leak alarms and CO alarms. Therefore, the final safety device is required to have high sensitivity, fast response, high reliability, high selectivity, and low power consumption.
[0004]
However, in the conventional gas sensor shown in FIG. 11, the solid electrolyte 1, the gas selective permeator 4, and the oxidation catalyst layer 7 have a large heat capacity of a plate-shaped chip, so that large power is required to keep the sensor at an operating temperature. Therefore, a commercial power supply was required. Therefore, the power outlet is always occupied and usually installed in a very limited place such as a kitchen in a general home. However, considering the current situation where unfortunate accidents due to poor combustion of indoor combustors such as heaters and water heaters continue to occur, and the spread of central heating due to high airtightness and high insulation of houses, it is necessary to spread CO alarms There is. However, it is very inconvenient to occupy a power outlet in a home where electrical appliances are overflowing, and it is desired to improve installation.
[0005]
In order to solve such a problem, a thin film gas sensor having a configuration shown in FIG. 12 has been proposed (Japanese Patent Application Laid-Open No. 2001-194329). This thin film gas sensor includes a solid electrolyte thin film 11 having oxygen ion conductivity formed on an upper surface of a heater 9 formed on a substrate 8 via an electric insulating layer 10, and a pair of solid electrolyte thin films formed on the solid electrolyte thin film 11. The electrode 12 and the electrode 12 ′ and the oxidation catalyst layer 13 provided on one of the electrodes 12 ′ of the pair of electrodes 12. It has been shown that pulse driving can be performed with a small heat capacity by this configuration, and as a result, significant power saving is possible and battery driving is possible. However, the semiconductor type, the hot-wire semiconductor type, the solid electrolyte type, and the like all require heating at a predetermined temperature by a heater, so that a long pulse interval is required to maintain the battery capacity for a long time. However, when the pulse interval is large, when CO is rapidly generated in an emergency such as a fire, detection of CO may be delayed. In order to solve this, a method of driving a heater as shown in FIG. 13 is disclosed (Japanese Patent Application Laid-Open No. 2001-194329). This is because the heating means operates intermittently, and the pulse interval when the output is lower than the first set value is longer than the pulse interval when the output is higher than the first set value, so that the CO can be quickly set in an emergency. It is to detect.
[0006]
[Problems to be solved by the invention]
However, even in this method, since the operation is usually performed with a longer pulse interval, the detection of CO may be delayed in the initial stage of CO generation.
[0007]
The present invention solves the above-mentioned conventional problems, and uses an installed CO sensor in an emergency to search for an evacuation site with a low CO concentration by making it portable. At this time, the detection interval of the CO sensor is changed according to the place where the CO sensor is installed. For example, when the CO sensor is carried around, the detection interval is shortened to improve the detection accuracy and fixed. At times, the detection interval is increased to reduce the power consumption, thereby aiming at both the improvement of the detection accuracy and the reduction of the power consumption.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned conventional problems, a CO sensor for intermittently detecting carbon monoxide has a detecting means for detecting a change in an installation location, and a pulse for detecting carbon monoxide in response to a signal from the detecting means. This is for setting the interval.
[0009]
This shortens the detection interval when urgency is required and enables early warning, and increases the detection interval when less urgency is required to reduce power consumption.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, there is provided a CO sensor for intermittently detecting carbon monoxide, comprising a detecting means for detecting a change in an installation location and outputting an installation location change signal. It sets the pulse interval of carbon oxide detection, shortening the detection interval when urgent is needed, enabling early warning, and increasing the detection interval when less urgent is needed, to reduce power consumption. It is.
[0011]
Further, the invention according to claim 2 further comprises a detecting means for detecting a change in the installation location and outputting an installation location change signal, and setting a pulse interval for carbon monoxide detection by the installation location change signal, and Has a notification means for notifying that the pulse interval has been set short, and has an effect of calling attention by notifying that the pulse interval has become short.
[0012]
Further, the invention according to claim 3 detects that the driving power of the CO sensor changes from the AC power to the DC power or from the DC power to the AC power, and shortens the pulse interval of the CO sensor when driving the DC power. Is what you do. When driven by a DC power supply, the CO sensor is carried around or it is determined that the CO sensor is installed in a place requiring special caution, so that the pulse interval is shortened to increase the detection sensitivity.
[0013]
Further, the invention according to claim 4 detects that the driving power supply of the CO sensor changes from the AC power supply to the DC power supply or from the DC power supply to the AC power supply, and shortens the pulse interval of the CO sensor when driving the AC power supply. Is what you do. In the case of driving with a DC power supply, the pulse interval is set long to maintain the battery life long.
[0014]
Further, the invention according to claim 5 detects whether the CO sensor is fixed or moving, and shortens the pulse interval of the CO sensor when the CO sensor is moving. Is determined to be necessary, and the pulse interval is shortened.
[0015]
According to a sixth aspect of the present invention, the detecting means for detecting whether the CO sensor is fixed or moving is constituted by a vibration sensor, and the pulse interval is set by detecting the movement during the movement from the shaking. I do.
[0016]
Further, according to the invention described in claim 7, the pulse interval is shortened after detecting that the vibration sensor is moving, and the pulse interval is short even if the signal of the vibration sensor is stopped within a predetermined time. The pulse signal during movement is set without fail.
[0017]
The invention according to claim 8 determines whether the CO sensor is fixed or moving by contact detection means with a fixture for fixing the CO sensor, and it is determined that the CO sensor is removed by the contact detection. It is possible to determine whether the vehicle is moving and to set a pulse interval.
[0018]
According to the ninth aspect of the present invention, the detecting means for detecting whether the CO sensor is fixed or moving is constituted by an external switch, and the pulse interval can be reliably set by a switch input. .
[0019]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
(Example 1)
FIG. 1 is a configuration diagram of a CO sensor according to Embodiment 1 of the present invention. The CO detection unit 20 is configured to be intermittently heated by the heater 21. Reference numeral 22 denotes a pulse signal control unit. The pulse output voltage output from the microcomputer 23 as a signal control unit is input to the + terminal of the operational amplifier 24, and is output from the output terminal via a filter including a fixed resistor 25 and a capacitor 26 to the operational amplifier. It becomes the input of 27 + terminal. The PNP transistor 28, the NPN transistor 29, and the DC power supply 30 constitute a power supply unit 31 to the heater 21. In this configuration, current flows from the DC power supply 30 through the emitter-collector of the PNP transistor 28 and flows into the heater 21. The magnitude of the current is determined by 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 negative terminal and the positive terminal have the same potential, the current flowing into the heater 21 is determined, the variation in the resistance value due to heat generation reaches an equilibrium state, and the voltage applied to the heater 21 is determined. The balance of the temperature of the heater 21 is also achieved, and the CO detection unit 20 is heated.
[0021]
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 with the + terminal is reduced, the base current of NPN transistor 29 is reduced. Accordingly, the base current of the PNP transistor 28 is also reduced, the current flowing into the heater 21 is also reduced, and a voltage corresponding to the pulse output voltage is applied to the heater 21 after reaching the equilibrium state. Then, the temperature of the heater 21 is controlled to a constant value. The CO detector 20 heated to a constant temperature outputs a voltage corresponding to the concentration of the CO gas, and an output signal is input to the signal processor 32. Inside the microcomputer 23, the CO concentration is determined based on a signal from the signal processing unit 32, and a notification signal is output to the notification unit 34. The output signal from the installation location detection means 33 enters the microcomputer 23 and changes the cycle of the pulse output.
[0022]
FIG. 2 is a perspective view of the CO detection unit 20 according to the first embodiment of the present invention.
[0023]
In FIG. 2, reference numeral 40 denotes a sensor element. Reference numeral 41 denotes a heat-resistant and low-thermal-conductivity substrate, which is made of quartz glass of about 2 mm × 2 mm × 0.3 mm. Reference numeral 42 denotes a platinum heater whose resistance is set to a predetermined temperature by a sputtering method, an electron beam evaporation method, or the like. Reference numeral 43 denotes an insulating film formed of a thin film 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 to have a smaller area than the insulating film 43. A solid electrolyte having oxygen ion conductivity (8% yttria-stabilized zirconia) is sputtered to about 0.4 mm × 0.4 mm. It is formed in a size of 6 mm. As the solid electrolyte, any solid electrolyte having oxygen ion conductivity can be used, but yttria-stabilized zirconia (YSZ) obtained by mixing zirconia with a small amount of yttria and firing is relatively inexpensive and easily available. Electrodes 45a and 45b are formed on the solid electrolyte membrane 44 by sputtering platinum. Precious metals such as palladium, ruthenium, and rhodium may be partially mixed with platinum. 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. The catalyst 46 may be any as long as it oxidizes and decomposes the gas to be measured. However, noble metals such as platinum, palladium, ruthenium, and rhodium, and oxides such as vanadium and manganese or oxides thereof. Formed on alumina or the like to form a mixture by screen printing.
[0024]
In the above configuration, power is supplied from a power supply (not shown) to the heater 21 to heat the solid electrolyte membrane 44 to a predetermined temperature (400 ° C. to 500 ° C.). When the temperature of the solid electrolyte membrane 44 reaches a predetermined temperature, electrons are transferred at the interface between the electrodes 45a and 45b, the solid electrolyte membrane 44, and air, and oxygen ions are generated. Here, if CO exists in the air, the CO is oxidized by the catalyst 46 at the electrode 45a covered with the catalyst 46, and does not reach the surface of the electrode 45a. In other electrode 45b CO reaches the electrode surface becomes oxidized CO _2. In this oxidation reaction, oxygen ions in the solid electrolyte membrane 44 are used. As a result, a difference occurs between the electrode reactions at the two electrodes, and the equilibrium of the oxygen ions in the solid electrolyte membrane 44 is disrupted, thereby generating a potential difference between the two electrodes. I do. By detecting this potential difference, the CO concentration can be detected.
[0025]
The quartz glass used for the substrate 41 has a thermal conductivity of 1.5 W / mK, which is smaller than that of the insulating film 43 (35 to 45 W / mK) and the solid electrolyte film 44 (6 W / mK). In this case, the temperature of the region of the solid electrolyte membrane 44 immediately above the heater 21 and the vicinity thereof can be increased without substantially increasing the temperature of the substrate 41. Therefore, 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, it was possible to raise the temperature to 450 ° C. with a power amount of 15 mWsec. Therefore, since the heater 21 can be driven in a pulsed manner and the power consumption can be greatly reduced, it is possible to drive with a battery power supply.
[0026]
With the above configuration, the detection of carbon monoxide is performed intermittently, and the detection interval is changed by a signal from the installation location detecting means 33, and the detection interval is set at a position away from the original installation location or carried around. When it is necessary to quickly detect carbon monoxide, it is possible to shorten the detection interval and increase the detection frequency, and when it is installed in the original place, it is possible to extend the detection interval and save power. .
[0027]
(Example 2)
FIG. 3 is a configuration diagram of the CO sensor according to the second embodiment of the present invention. The same elements as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted. According to the signal from the microcomputer 23, if the pulse interval signal from the installation location detecting means 33 is "short", it is displayed on the display unit 35 that "short" is output. When the pulse interval is "short", the power consumption is large, so that it is possible to promptly return to the original installation location immediately after the end of the mission, thereby saving power. It should be noted that the pulse interval is not limited to the display of “short”, but may be any other information that notifies the user such as sound.
[0028]
(Example 3)
FIG. 4 is an electric circuit diagram for determining the power supply of the CO sensor according to the third embodiment of the present invention.
[0029]
In FIG. 4, the power source is determined by inputting that the power source is an AC power source to the installation location detecting means 33. The AC 100 V is stepped down by the transformer 50 and is half-wave rectified by passing through the diode 51. The half-wave rectified voltage charges the capacitor 52, and keeps the base voltage of the NPN transistor 53 high. When the base voltage of the NPN transistor 53 becomes High, the NPN transistor 53 conducts, a current flows from the collector to the emitter, the collector potential becomes Low, and a Low signal is input to the installation location detecting means 33. On the other hand, when the supply of the AC voltage is interrupted due to disconnection of the outlet or the like, the charge stored in the capacitor 52 is discharged through the resistor 54, and the base voltage of the NPN transistor 53 becomes low. When the signal goes low, the NPN transistor 53 stops conducting, the collector potential goes high, and a high signal is input to the installation location detecting means 33. The installation location detecting means 33 detects whether the input signal is High or Low, determines the pulse interval, and sends a command to the microcomputer 23. With such a configuration, whether the power supply is an AC power supply or not is detected, the pulse interval is determined, the installation state is determined, and the optimal pulse interval is determined.
[0030]
FIG. 5 is a flowchart of the pulse interval setting.
[0031]
First, it is determined whether or not the input signal of the installation location detecting means 33 is High (ST101). If High, it is determined that the power supply is a DC power supply, and the pulse interval of the CO sensor is set to “short” (ST102). If it is not High, the pulse interval of the CO sensor is set to “long” (ST103). In this way, the installation state of the CO sensor is determined based on the state of the input signal of the installation location detecting means 33, and the fact that the CO sensor is driven by the DC power supply means that the vehicle is being carried by a person or where monitoring is required. It is determined that it is one of the cases where it is installed, the pulse interval is shortened, the CO gas detection accuracy is increased, and if not, the pulse interval is lengthened, and power saving can be achieved. .
[0032]
(Example 4)
FIG. 6 is a flowchart for setting a pulse interval according to the fourth embodiment of the present invention.
First, it is determined whether or not the input signal of the installation location detecting means 33 is High (L101). If High, the power source is determined to be a DC power source, and the pulse interval of the CO sensor is set to “long” (L102). If it is not High, the pulse interval of the CO sensor is set to “short” (L103). As described above, the installation state of the CO sensor is determined based on the state of the input signal of the installation location detection unit 33, and when the CO sensor is driven by the DC power supply, it is determined that it is necessary to save power. If it is longer, otherwise, the pulse interval is shorter, and the detection accuracy can be improved.
[0033]
(Example 5)
FIG. 7 is a flowchart for setting a pulse interval according to the fifth embodiment of the present invention.
[0034]
It is assumed that the signal from the sensor for detecting the movement of the input of the installation location detecting means 33 is High during the movement, and Low during the stop. First, it is determined whether or not the input signal of the installation location detecting means 33 is High (S101). If it is High, it is determined that the movement has occurred, and the pulse interval of the CO sensor is set to “short” (S102). If it is not High, the pulse interval of the CO sensor is set to “long” (S103). As described above, the state of the CO sensor is determined based on the state of the input signal of the installation location detecting means 33, and it is considered that a person moving is likely to be wearing the CO sensor. It is determined that it is necessary to increase the power, otherwise it is determined that it is necessary to save power, and the interval between pulses is lengthened.
[0035]
(Example 6)
FIG. 8 is a configuration diagram of a CO sensor according to Embodiments 6 and 7 of the present invention.
[0036]
A signal from a vibration sensor 57 formed by a structure in which a main part of the vibration detection is suspended from a weight 55 by a spring 56 is supplied with a High signal when the vibration is detected. 33 outputs a signal for shortening the pulse interval to the microcomputer 23. Thus, it is possible to detect that the CO sensor is moving, and to improve the detection accuracy. In addition, since it is vibration detection, it is possible to detect an earthquake instead of a movement. Since there is a risk of fire after an earthquake, the detection accuracy of the CO sensor is increased.
[0037]
(Example 7)
In FIG. 8, the signal of the switch 58 is input to the installation location detecting means 33. This means that even if the signal from the vibration sensor 57 stops, it is prohibited to return the pulse interval from the installation location detecting means 33 to the original state unless a signal from the switch 58 is input. Accordingly, even when the vibration sensor 57 does not detect the vibration even though the CO sensor is moving, the pulse interval can be kept “short” and the detection accuracy can be kept high. Further, even when the state is changed from moving to fixed, the state can be reliably transmitted to the installation location detecting means 33 by the switch 58.
[0038]
Also, using a timer provided in the microcomputer 23, after detecting that the vibration sensor is moving, the pulse interval is shortened, and if the signal from the vibration sensor is stopped within a certain time, the pulse interval is maintained. Keep short. This makes it possible to reliably set the moving pulse signal.
[0039]
(Example 8)
FIG. 9 is a configuration diagram of a CO sensor according to Embodiment 8 of the present invention. The casing 58 of the CO sensor is placed in a box 59 also serving as a charger. A microswitch 60 is provided at a lower portion of the housing 58, and is in an OFF state when the housing 58 is taken out of the box 59. When the casing 58 comes into contact with the casing 58, the casing is turned on. The contact information of the microswitch 60 is input to the installation location detecting means 33.
[0040]
With such a configuration, the installation location detecting means 33 can know whether the housing 58 is moving or fixed from the contact information of the microswitch 60, and instruct the microcomputer 23 of a pulse interval signal according to the state. Can be.
[0041]
Note that the contact detection means may be electromagnetic detection in addition to mechanical detection. For example, an external power supply circuit for charging a rechargeable battery in the CO sensor, a magnetic switch using a magnet, and the like can be considered.
[0042]
(Example 9)
FIG. 10 is an external view of a CO sensor according to Embodiment 9 of the present invention. The external switch 61 is provided for directly inputting contact information to the installation location detecting means 33. When carrying around the CO sensor or changing the installation location, the external switch 61 directly instructs to change the pulse interval setting. In this way, an appropriate pulse interval can be set by human intention.
[0043]
Note that the pulse interval may be set by detecting a change in the state of the power supply regardless of a change in the installation location. That is, in a CO sensor that intermittently performs carbon monoxide detection, the CO sensor includes a power supply state detection unit that detects a change in the state of supply power and outputs a change signal. May be set as the CO sensor. For example, when a power failure occurs, the pulse interval is lengthened to operate in a low power consumption mode. After a power failure due to an earthquake, there is a risk of fire occurring. Therefore, the pulse interval is shortened to increase the detection accuracy of the CO sensor.
[0044]
【The invention's effect】
As described above, according to the present invention, the detection cycle of the CO sensor is detected by the installation location detection means, and the interval of the pulse for detecting the CO is changed, so that a person can move or be installed at a dangerous location. In such a highly urgent use, CO is quickly detected to prevent accidents before it occurs, and when emergency is not required, the detection interval is extended to reduce power consumption. It becomes possible to realize a sensor.
[Brief description of the drawings]
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 a 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 an electric circuit diagram for determining a power supply of a CO sensor according to a third embodiment of the present invention. FIG. 5 is a flowchart of setting a pulse interval of the CO sensor according to the third embodiment of the present invention. FIG. 7 is a flowchart of setting the pulse interval of the sensor according to the fifth embodiment of the present invention. FIG. 8 is a configuration diagram of the CO sensor according to the sixth and seventh embodiments of the present invention. FIG. 10 is a configuration diagram of a CO sensor according to an eighth embodiment of the present invention. FIG. 10 is an external view of a CO sensor according to a ninth embodiment of the present invention. FIG. 11 is a perspective view illustrating a configuration of a conventional CO sensor detecting unit. Schematically shows a perspective view [13] heater driving of another conventional CO sensors showing the configuration of another CO sensor detection unit [Description of symbols]
Reference Signs List 20 CO detection unit 21 Heater 22 Pulse signal control unit 23 Microcomputer 32 Signal processing unit 33 Installation location detection unit 35 Display unit (notification unit)
50 Transformer 51 Diode 53 NPN transistor 54 Resistance 57 Vibration sensor 58 Switch 60 Micro switch (contact detection means)
61 External switch

Claims (9)

In a CO sensor that intermittently performs carbon monoxide detection, the CO sensor includes an installation location detecting unit that detects a change in the installation location and outputs an installation location change signal, and determines a pulse interval of the carbon monoxide detection by the installation location change signal. CO sensor to set. In a CO sensor for intermittently detecting carbon monoxide, the CO sensor is provided with a detecting means for detecting a change in the installation location and outputting an installation location change signal, and setting a pulse interval of the carbon monoxide detection based on the installation location change signal. In addition, a CO sensor having a notifying unit for notifying that the pulse interval is set short. The detection means for detecting a change in the installation location detects that the driving power of the CO sensor changes from AC power to DC power or from DC power to AC power, and shortens the pulse interval of the CO sensor when driving with DC power. The CO sensor according to claim 1, wherein The detecting means for detecting a change in the installation location detects that the driving power of the CO sensor changes from AC power to DC power or from DC power to AC power, and shortens the pulse interval of the CO sensor when driving with AC power. The CO sensor according to claim 1, wherein 2. The CO sensor according to claim 1, wherein the detecting means for detecting a change in the installation location detects whether the CO sensor is fixed or moving, and shortens the pulse interval of the CO sensor when the CO sensor is moving. The CO sensor according to claim 5, wherein the detecting means for detecting whether the CO sensor is stationary or moving is a vibration sensor. 6. The CO sensor according to claim 5, wherein a pulse interval is shortened after detecting that the vibration sensor is moving, and the pulse interval is set to be short even if the signal of the vibration sensor is stopped within a certain period of time. . 6. The CO sensor according to claim 5, wherein the detecting means for detecting whether the CO sensor is fixed or moving is a contact detecting means with a fixture for fixing the CO sensor. 2. The CO sensor according to claim 1, wherein the detecting means for detecting whether the CO sensor is fixed or moving is an external switch.

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