JP3700378B2 - Gas detection alarm - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature control device for a battery-driven thin film gas sensor used for a home gas leak alarm, a fire alarm or the like.
[0002]
[Prior art]
The present applicant has already filed a Japanese Patent Application No. 9-248629 for a battery-driven thin film gas sensor used for a home gas leak alarm, a fire alarm or the like. This is because, as a gas detection element, a thin film of a metal oxide semiconductor such as tin oxide capable of detecting a reducing gas is formed on a silicon chip, and at the same time, a heater resistance wire for heating the gas detection element is provided. The sensor body is laminated with a thin film, and the gas detection element is intermittently heated to the operating temperature by applying a pulsed voltage to the heater resistance wire at regular intervals, and the temperature is raised to the operating temperature. By measuring the resistance of the gas detection element during measurement, the presence or absence of the detection gas and the concentration thereof are measured.
[0003]
In this thin film gas sensor, the gas detection element and the heater part are formed as small as possible on a silicon chip by using a silicon microfabrication technique, so that their heat capacities are made minute values. As a result, it is possible to intermittently apply a pulse voltage and heat it, hold it at the operating temperature for a very short time to operate the gas detection, significantly reduce power consumption, and drive the battery for a long time. Realized.
As a result, when this thin film gas sensor was used for a battery-driven gas leak alarm or fire alarm, the battery replacement life could be extended to 5 years.
[0004]
[Problems to be solved by the invention]
By the way, the thin film gas sensor described above applies a pulsed voltage to the heater wire in order to raise the temperature of the gas detection element to a predetermined operating temperature. However, the electrical energy supplied to the gas detection element and the heater wire is If the applied voltage is constant, it is proportional to the pulse width (application time) as is well known. Therefore, an optimum pulse width is set in advance by calculation or experiment according to the heat capacity of the thin film gas sensor, the installation environment, and the like.
[0005]
However, if the pulse width is constant and the same amount of electric energy is supplied to the gas detection element and the heater part each time, the gas detection element correspondingly changes when the ambient temperature at the installation location fluctuates. In some cases, the temperature of the temperature rises too much and exceeds the temperature range of the operating range. Similarly, when the ambient temperature fluctuates and becomes low, a rise in the temperature of the gas detection element is suppressed accordingly, and the temperature range of the operating range may not be reached. As described above, in the above-described thin film gas sensor, the installation condition may be limited because it may not be able to follow a large temperature fluctuation of the installation atmosphere.
[0006]
Furthermore, when the applied voltage changes due to battery consumption or a decrease in ambient temperature, the amount of supplied electric energy also decreases, and the heating capacity of the gas detection element decreases. Although it is possible to solve this problem by installing a constant voltage circuit in the power supply circuit, the loss of power occurs when the constant voltage circuit is installed, which is preferable in terms of efficient use of battery energy. It is not a thing.
[0007]
[Means for solving the problem]
  In order to solve the above problem, the invention of claim 1,
  ShiOn the recon chip, heater resistance wire andBigSensor detectors are stacked to form a sensor body,The battery voltage ofA fixed interval between the heater resistance wiresMarkIn addition, in the gas detection alarm device that detects the gas and outputs an alarm by heating the gas detection element to a predetermined operating temperature with the applied voltage and taking out the resistance value of the gas detection element at that time,
  SEA temperature sensing element formed on the sensor body,
  ElectricPond voltageMeasure battery voltage detectionCircuit and,
  markA temperature measuring circuit for measuring the ambient temperature of the sensor body from the output of the temperature sensing element during the idle period when the applied voltage is not applied to the heater resistance wire;,
  ForecastThe application time of the set application voltage was measured immediately beforebatteryMeans for correcting the application time of the optimum applied voltage to heat the gas detecting element to a predetermined operating temperature based on the voltage and the ambient temperature;,
  TheIt is characterized by having.
[0008]
  The invention of claim 2 is the invention of claim 1,,
  ElectricA booster circuit connected via a switching circuit between the source circuit and the heater resistance wire;,
  The battery voltage detection circuitMonitor the measurements ofbatteryWhen the voltage drops below a predetermined value, the switching circuit is operated tobatteryMeans for boosting the voltage by a booster circuit and then applying the voltage to the resistance wire for the heater;,
  TheIt is characterized by having.
[0009]
  The invention of claim 3 is the invention of claim 2.,
  HiThe application time of the voltage applied to the data resistor wire is monitored, and when the application time increases beyond a predetermined value, the switching circuit is operated tobatteryMeans for boosting the voltage by a booster circuit and then applying the voltage to the resistance wire for the heater;,
  TheIt is characterized by having.
[0010]
  The invention of claim 4 is the invention of claim 1 or claim 2 or claim 3.,
  markElectrificationPressure,Ambient temperatureDegreeAnd each value of applied voltage application time are monitoredMeans to
  Applied voltage and ambient temperatureIs within the range set for each value,Battery voltage value measurement operation by battery voltage detection circuit and ambient temperature value by temperature measurement circuitStop the measurement operation for a certain periodAnd means for holding the applied voltage application time,
  Means for applying the applied voltage at the applied voltage application time held for a certain period of time to be stopped;
  TheIt is characterized by having.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, a waveform described as a pulse is not necessarily a step-like waveform, and includes various waveforms other than a step waveform for the purpose of reducing thermal stress.
FIG. 1 is a diagram showing a configuration of an embodiment of a battery type gas leak alarm to which the present invention is applied. This kind of gas leak alarm is installed in the home and has the function of detecting the gas leak of fuel gas and the generation of CO gas generated during incomplete combustion and notifying that it is in a dangerous situation with a buzzer or sound. Device.
Generally, a conventional gas leak alarm is operated using a commercial power source or a DC power source supplied from the outside. However, the gas leak alarm device according to the present invention uses a battery 7 as a power source as shown in FIG. 1 and realizes a function capable of operating for about 6 years if used in a standard state. .
[0012]
The gas leak alarm is centrally controlled by a CPU (microcomputer) 1.
The gas sensor 2 which is a gas detection element is an extremely small sensor having a small heat capacity formed on a silicon chip by using a silicon film forming technique. Similarly, a heater resistance wire (hereinafter abbreviated as “heater”) 3 is formed in the vicinity of the gas sensor 2 on the silicon chip. If energized for a period of 10 ms, the gas sensor 2 is heated to a predetermined operating temperature. In general, if the gas leak can be detected within 20 seconds, it is sufficient in terms of capability. Therefore, it is sufficient to energize for several tens of milliseconds at a rate of once every 10 seconds.
Therefore, the energized period is an extremely small ratio compared to the non-energized period, and the actual energy consumption is extremely small, which is suitable for battery driving.
[0013]
Since the gas sensor 2 has a temperature at which it easily reacts depending on the type of target gas, a thin film temperature sensor 4 is provided near the gas sensor 2 to measure the temperature of the gas sensor 2. Since this temperature sensor 4 which is a temperature detecting element is made of platinum, it can measure a stable temperature. The heater 3 is heated by being supplied with electric energy for a certain period of time under the control of the CPU 1 and rises in temperature. In order to detect this temperature change, a bridge is constituted by the temperature sensor 4 and the resistors R2 to R4, a change in the resistance value of the temperature sensor 4 is detected, amplified by the amplifier Amp1, and input to the comparator Cp1.
[0014]
An analog output terminal having a DA conversion function of the CPU 1 is connected to the other input terminal of the comparator Cp1, and it can be determined whether or not the output from the temperature sensor 4 has reached a predetermined level. These constitute a temperature measurement circuit. Moreover, ambient temperature is also measured by measuring temperature in the state in which the gas sensor 2 fell to ambient temperature. Since the level detection function in this temperature measurement circuit is a general method, detailed description of the operation is omitted. These configurations constitute a methane sensor circuit.
[0015]
Further, a constant voltage circuit 5 having an output voltage of 1 V is connected to the + side power supply unit of the entire circuit, and this constant voltage circuit 5 is driven by a battery voltage. The circuit voltage of 1V is also applied to the gas sensor 2 via the resistor R1. In a state where the gas concentration is low, the resistance value of the gas sensor 2 maintains a high value, but the resistance value decreases as the gas concentration increases. The terminal voltage of the gas sensor 2 is connected to one input terminal of the comparator Cp2 that detects the gas concentration. The comparator Cp2 can also detect the level of the signal from the gas sensor 2 by using the DA conversion function of the CPU 1 in the same manner as the temperature sensor comparator Cp1. This gas sensor 2 detects methane gas which is the main component of fuel gas.
[0016]
Separately from this, a CO sensor circuit 6 having substantially the same circuit configuration is also connected, but the functional configuration is the same, and thus the description thereof is omitted. The CO sensor circuit 6 is connected to a terminal for absorbing variations in the gas sensor, which is also provided on the methane sensor circuit side. In other words, if there is a variation in the gas sensor production and there is a large difference in the gas reaction capacity, in the case of the gas sensor 2, the value of the resistor R1 is changed equivalently depending on the operating state of the output port of the CPU 1 It is a circuit to control.
[0017]
When the CPU 1 detects a gas having a concentration higher than the set concentration by software operation, the CPU 1 instructs the sound LSI 13 to generate sound. Upon receiving the instruction, the audio LSI 13 sends a predetermined audio signal to the speaker 15 via the amplifier 14 to output an audio alarm.
The voice LSI 13 is a commercially available LSI, and since it is used in many electronic devices, a detailed description of its function is omitted. Further, the generated audio content differs depending on which gas sensor detects the gas. The reason is that the countermeasures after detection differ depending on the nature of the target gas.
[0018]
Further, although the detection level does not reach the alarm level, it may be desirable to take an initial measure according to the pre-alarm if it can be notified. In such a case, a function may be provided in which, for example, only a display such as an LED is used without generating a sound. A display for that purpose is not shown, but may be added as necessary. If the current applied to the LED is about 2 to 10 mA, a sufficiently recognizable display can be obtained. On the other hand, when sound is generated, a current of 100 mA or more is required. Therefore, even if a part of the current consumption of the sound alarm is used for this pre-alarm, the battery life is not greatly affected. .
[0019]
In FIG. 1, an audio power supply circuit 12 having a voltage stabilizing function is provided in order to absorb battery voltage fluctuation due to audio generation. Moreover, the battery voltage detection circuit 8 is provided in CPU1, and the condition of a battery voltage is detected. This is because if the battery voltage falls below a predetermined value, the gas sensor may have insufficient detection capability or the level of the sound alarm that is generated may be insufficient.
The electromagnetic latches 9 and 10 are provided for switching the display plate 11 or the like for displaying the detection result. When a gas leakage state is detected, the electromagnetic coil is energized for a short time to cause the display plate 11 or the like to gas. It switches to the detection display.
[0020]
For example, when there is no gas leak, the display board is displayed in green or blue, and when the gas leak state is detected, the display board is displayed using a mechanical mechanism so that red, orange, etc., which are colors close to the danger image. 11 is switched. There are various methods for realizing this function, but a description thereof will be omitted.
The EEPROM 16 is an electrically rewritable memory. The memory 16 incorporates heater heating control conditions for the gas sensor 2, sensor level setting values for detecting gas, and the like, which are read out by the CPU 1 and used for controlling the sensor circuit.
[0021]
FIG. 2 is a diagram showing a configuration model of the gas sensor unit. Sensors used in battery-powered gas leak alarms must first be of low power consumption type. Therefore, by using a silicon microfabrication technique, a heater 3 is formed on a silicon with a resistor such as tungsten using a thin film technique, and a SnO2 thin film is formed in the vicinity or on an insulated upper layer portion to form the gas sensor 2 To do. The heater 3 is connected to terminals h1 and h2 via lead wires, and the gas sensor 2 is connected to terminals gs1 and gs2 via lead wires.
[0022]
In these manufacturing processes, a catalyst technology for facilitating reaction with gas is also used. Further, a temperature sensor 4 is formed of a platinum resistor near the gas sensor 2, and is connected to the terminals t1 and t2 via lead wires. These constitute the elements of the gas sensor 2, the heater 3 and the temperature sensor 4 of FIG. These elements are extremely small, the heating time constant of the heater 3 is several tens of ms, and can be heated to a predetermined temperature in a short time, so that the battery can be used for a long time even as a power source.
[0023]
FIG. 3 is an explanatory diagram showing the relationship between the voltage applied to the gas sensor section shown in FIG. 2 and the temperature change. The pulse is a voltage pulse having a width of several tens of ms from the battery power supply to the heater 3. As shown in the figure, application of a voltage pulse to the heater 3 heats the heater 3 and transmits the heat to raise the temperature of the gas sensor 2. As described above, since the heat capacity of the entire sensor unit is extremely small, the temperature increase starts in a short time. At first, the temperature rises at the rising edge of the straight line l, and heat dissipation to the surroundings starts with the temperature rise, and the rising curve becomes gentle. When application by the pulse is lost, the temperature of the gas sensor 2 is lowered after a time delay of a young thousand and returns to a normal temperature state before heating.
[0024]
Since the gas sensor 2 has a temperature at which it easily reacts depending on the type of gas to be detected, the pulse width is selected so that the voltage application to the heater 3 is heated to its optimum operating temperature. Since the reaction of the detection target gas has a time delay of 1000, the measurement timing of the gas sensor 2 is set in accordance with the actual sensor temperature rise and gas reactivity. In general, the timing is set according to a comparison with the pulse timing.
[0025]
Since the actual temperature of the gas sensor 2 itself cannot be measured as it is, it is indirectly detected by inputting a signal from the temperature sensor 4 provided in the vicinity of the gas sensor 2 to the temperature detection circuit shown in FIG. There is an error due to a time delay in the temperature 2 and the output of the measured temperature sensor 4. For this reason, the setting of actual measurement timing is determined by simulating thermal behavior using a computer. In addition, refer to the results of gas reaction time characteristics and the measurement data of the above temperature sensor to determine the timing of measurement in advance for stable gas detection. Decide in consideration.
[0026]
The temperature of the gas sensor 2 can be changed by changing the pulse width or changing the magnitude of the applied voltage.
FIG. 4 is an explanatory diagram showing another example of a voltage pulse applied to the heater 2. FIG. 2A shows the temperature of the gas sensor 2 with a solid line, and the output of the temperature sensor 4 with a broken line. Here, in order to widen the measurement timing of gas detection, an applied pulse having a pattern as shown in FIGS. In the pattern of FIG. 2B, the peak of the sensor temperature is widened by intermittently applying a pulse between t1 and t2 in the latter half.
[0027]
That is, the application of this pattern extends the stable period of temperature suitable for gas detection of the gas sensor 2 by continuously supplying the same amount of electric energy as the thermal energy dissipated from the gas sensor 2. In the pattern of FIG. (C), the level change between the start part 0 and t1 and the end part t2 to t3 is controlled in an analog manner to reduce the heat shock to the gas sensor 2, and the sensor temperature. The control is performed so as to increase the stability of measurement. The pattern of FIG. (D) is obtained by replacing the intermittent pulse portion from t1 to t2 of FIG. (B) with analog level control.
[0028]
FIG. 5 is a diagram showing the relationship between the ambient temperature of the gas sensor unit and the energy required to heat the gas sensor unit to the target temperature. When a voltage is applied by a pulse having a fixed width as shown in FIG. 3, the sensor temperature actually reached changes due to the influence of the ambient temperature. FIG. 5 shows this relationship. In general, the reaction characteristic of a methane sensor is preferably about 400 ° C. On the other hand, the reaction characteristic of the CO gas sensor is preferably around 150 ° C.
[0029]
In order to obtain such a target temperature, it is possible to always measure the output of the temperature sensor and control it to be within a certain temperature range. However, for that purpose, it is necessary to measure the sensor output in several ms, and a high-speed measurement circuit is required. Moreover, if the measurement process is always performed, the power consumption in the circuit increases, and the battery is consumed greatly. In particular, a high-speed measurement circuit consumes a large amount of power, which is not practical in terms of both the cost for realizing the circuit and the power consumption.
[0030]
Therefore, in the present invention, in order to control heating with a low-cost and low power consumption circuit, the energy relationship corresponding to the difference between the target sensor temperature and the ambient temperature shown in FIG. The target sensor temperature can be obtained with relatively simple control by measuring and measuring and injecting electric energy corresponding to the measured value. As can be seen from FIG. 5, the amount of energy required to heat the gas sensor portion to the target temperature varies greatly with the ambient temperature.
[0031]
In particular, if the target temperature is a low temperature of 150 ° C., the influence of the ambient temperature becomes greater. Therefore, by measuring the ambient temperature, calculating the difference from the target, and applying a pulse with a time width proportional to the value, the target sensor temperature can be obtained with high accuracy. Specifically, the heater application time t1 in FIG. 3 is set in accordance with the difference between the target temperature and the ambient temperature. Alternatively, a reference application time is set in accordance with the difference from the standard ambient temperature to the target temperature and stored in the CPU 1, and the reference application time is increased according to the difference between the measured ambient temperature and the standard ambient temperature. You may make it correct | amend.
[0032]
  However, in the heating control according to the above temperature difference, various conditions such as heat dissipation conditions, thermal capacity, and time delay are not considered. Therefore, simple temperature difference proportionalSekiIn order to improve accuracy, it is necessary to incorporate a specific correction coefficient in addition to the clerk. In addition, a battery voltage change is a major variation factor in the heating conditions of the heater. The battery voltage varies depending on the remaining capacity of the battery and the ambient temperature. In general, the battery voltage decreases as the remaining capacity decreases, and the battery voltage increases as the ambient temperature increases. In FIG. 1, the voltage of the battery 7 is measured by the battery voltage detection circuit 8 and input to the CPU 1.
[0033]
The relationship between the battery voltage and the heating energy is proportional to the square of the voltage value applied to the heater if the heater resistance value is constant. This relationship is shown in FIG. Actually, when a metal heater material is used, the value of the heater resistance also changes as the temperature rises. Therefore, it is desirable to control the heating by correcting the influence of these temperature characteristics, but in actual control there are various fluctuation factors such as variations in heater manufacturing and surrounding mounting conditions in addition to these influences. It is easier to determine control parameters from actual measured values than to determine control parameters by.
[0034]
Therefore, it is necessary to correct the pulse width t1 of the heater application as shown in FIG. 3 in consideration of the influence of the battery voltage and the influence of the ambient temperature. For this purpose, various parameters are measured to create correction parameters, and a correction method using them is provided in the software of the CPU 1 shown in FIG. In many cases, this correction parameter is determined experimentally. Here, the heater temperature control is performed by open control using the battery voltage and the ambient temperature as parameters.
[0035]
If the temperature sensor is always used and the heater is controlled using an automatic feedback control means, the influence of the battery voltage and the ambient temperature, which are fluctuation factors, are automatically absorbed and stable temperature control can be realized. . However, as described above, this method has a problem in terms of price and power consumption, and cannot be used at present for a device that is small and inexpensive, such as a home gas leak alarm.
[0036]
In order to reduce the power consumption, in FIG. 1, the + side power source from the battery 7 is directly connected to the heater 3, and the driver circuit D 1 that is controlled to open and close by a command from the CPU 1 is connected to the − side. By doing so, energy is directly supplied from the battery 7. Since the voltage fluctuation of the battery 7 is large, the stability of control can be easily realized by providing a constant voltage circuit to absorb the fluctuation. However, considering the efficiency, it is not preferable because the energy loss in the constant voltage circuit is large.
[0037]
Another problem is that the battery voltage is as low as 3 V for lithium batteries. In other words, since the voltage of the battery itself is low, the efficiency of the constant voltage circuit is poor and the energy loss is increased. In addition, it is conceivable to increase the voltage by connecting batteries in series, but this increases the power consumption of the entire circuit and is contrary to the method of using the battery, which requires stable and low risk. Series connections should be avoided.
[0038]
Therefore, as a countermeasure against a decrease in battery voltage, a constant voltage circuit 20 with a boosting function is provided as shown in FIG. In this figure, the heater driving circuit portion comprising the CPU 1, battery 7 and heater 3 having the configuration shown in FIG. 1 is taken out and a new constant voltage circuit 20 with a boosting function is connected together with transistors T10 to T12 for circuit switching. is there. That is, in order to use the battery 7 efficiently, the constant voltage circuit 20 is connected to the heater 3 via the transistors T10 and T11, and the CPU 1 switches the transistors T11 and T12 so that the heater 3 is energized. do.
[0039]
Energization when the voltage of the battery 7 is directly applied to the heater 3 is controlled by the CPU 1 turning on / off the base current of T12. While the normal battery voltage is maintained, energy is supplied directly from the battery 7. When the battery voltage detection circuit 8 detects that the voltage of the battery 7 has decreased to a level lower than the predetermined voltage, the transistor T10 is turned on to operate the constant voltage circuit 20 with a boosting function, and the output is output to the transistor T11. The energization to the heater 3 is controlled by turning on / off the base current. Here, the voltage drop of the battery 7 is detected by the battery voltage detection circuit 8, but the CPU 1 monitors the application time of the pulse, and if it exceeds a predetermined length, it is similarly regarded as a voltage drop, and the constant voltage The circuit 20 can also be activated.
[0040]
As described above, by configuring the constant voltage circuit 20 to operate when the voltage of the battery 7 drops, most of the battery energy is used directly from the battery, and the most energy efficient circuit Configuration can be realized. As a result, the battery life can be greatly extended.
In addition, although the voltage detection of the battery 7 by the battery voltage detection circuit 8 mentioned above and the measurement of the ambient temperature by the temperature sensor 4 are normally performed in the cycle of voltage application, those values are not changed so much. In this case, each measurement and correction of the pulse application time results in wasteful power consumption.
[0041]
Therefore, the CPU 1 monitors the pulse application voltage and the ambient temperature value measured each time, and when the changes are within a predetermined range, the subsequent operation of the battery voltage detection circuit 8 and the temperature measurement circuit is performed for a certain period. While stopping, the value of the pulse application time output immediately before is held, and during the stop period, a voltage pulse is output using the pulse application time of that value. After the stop period, the measurement is restarted. If there is a large change in the measured value, the pulse application time is newly corrected. If there is no large change, the measurement operation is stopped again. By providing these energy saving operations in the CPU 1, it is possible to greatly extend the battery life at the installation place where the change in the ambient temperature is small.
[0042]
As described above, according to the embodiment of the present invention, the heating condition is determined according to the heater characteristics of the gas sensor, and the gas sensor is periodically heated only for a short time according to the condition and heated to the detection operation temperature. Measure ambient temperature and battery voltage at regular intervals, change the heating condition if the measurement result is outside the predetermined range, and stop the temperature sensor and battery voltage measurement process if the result is within the range As a result, the battery power is not consumed excessively, and the battery life can be extended accordingly.
[0043]
Further, since the sensor for measuring the ambient temperature is integrally provided in the gas sensor unit, the configuration is simplified and the sensor can be manufactured at low cost.
Furthermore, normally, the heater is directly heated from the battery, and the voltage is boosted by the booster circuit only when the battery voltage is lowered, so that the battery energy usage efficiency can be increased. Battery life can be extended.
Needless to say, the present invention can be used not only for gas leak alarms but also for various alarms using batteries as a power source.
[0044]
【The invention's effect】
As described above, according to the first aspect of the present invention, the sensor body is provided with the temperature detecting element to measure the ambient temperature of the sensor body, and the battery voltage or the heater terminal voltage applied to the heater resistance wire is measured. By correcting the pulse application time to the optimum value based on these measured values, it can be installed in an environment where the ambient temperature fluctuates, and stable even if the battery voltage drops after installation. The operation can be kept.
[0045]
According to the second or third aspect of the present invention, the booster circuit is connected via the switching circuit between the power battery circuit and the heater resistance wire, and the measured value of the voltage measuring circuit and the application time of the pulse are determined. When the voltage applied to the heater resistance wire drops below a predetermined value or when the application time increases above a predetermined value, the switching circuit is switched and the booster circuit is operated to A decrease in the battery life is prevented and the battery power is effectively consumed, thereby extending the battery life.
[0046]
According to the invention of claim 4, the pulse application voltage, the application time, and the ambient temperature that are measured each time are monitored, and when these changes are within a predetermined range, these measurement operations are temporarily suspended. As a result, useless power is not consumed, and the battery life can be extended accordingly.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a battery-type gas leak alarm which is an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration model of the gas sensor unit of FIG. 1;
FIG. 3 is an explanatory diagram showing a relationship between a voltage applied to a gas sensor unit and a temperature change.
FIG. 4 is an explanatory diagram showing another example of voltage pulses applied to the heater of the gas sensor unit.
FIG. 5 is a diagram showing the relationship between the ambient temperature of the gas sensor unit and the energy required for heating to the target temperature.
FIG. 6 is a diagram showing a relationship between battery voltage and heating energy to a gas sensor unit.
7 is a diagram showing a case where a constant voltage circuit with a boosting function is provided in the circuit configuration of FIG.
[Explanation of symbols]
1 CPU
2 Gas sensor
3. Heater (resistance wire for heater)
4 Temperature sensor
5 Constant voltage circuit
6 CO sensor circuit
7 batteries
8 Battery voltage detection circuit
9,10 Electromagnetic latch
11 Display board
12 Audio power circuit
13 Voice LSI
14 Amplifier
15 Speaker
16 EEPROM
20 Voltage regulator with boost function
Amp1 amplifier
Cp1, Cp2 comparator
D1 driver circuit
R1-R4 resistance
T10 to T12 transistors

Claims (4)

On a silicon chip by stacking a beauty gas sensing element Oyo resistance wire heater previously formed the sensor body, at regular intervals to the resistance wire for the heater to convert the battery voltage from the power supply battery voltage by pulse and indicia pressurized, the gas detection alarm device outputs an alarm by detecting the gas by removing the resistance value of the gas sensing element at that time to heat the gas sensing element in the applied voltage up to a predetermined operating temperature,
A temperature sensing element formed on the sensor body,
A battery voltage detection circuit that measures the batteries voltage,
A temperature measuring circuit for measuring the ambient temperature of the sensor body from the output of the temperature sensing element during the rest period in which the applied voltage is not applied to the heater resistance wire;
Means for correcting a preset application voltage application time to an optimum application voltage application time for heating the gas detection element to a predetermined operating temperature based on the battery voltage and ambient temperature measured immediately before When,
A gas detection alarm device comprising: The gas detection alarm device according to claim 1, wherein
A booster circuit connected via a switching circuit between the power supply circuit and the heater resistance wire;
The measured value of the battery voltage detection circuit is monitored, and when the battery voltage falls below a predetermined value, the switching circuit is activated to boost the battery voltage of the power supply circuit by the booster circuit and then applied to the heater resistance wire Means to
A gas detection alarm device comprising: The gas detection alarm device according to claim 2,
The application time of the voltage applied to the heater resistance wire is monitored, and when the application time increases to a predetermined value or more, the battery voltage of the power supply circuit is boosted by the booster circuit by operating the switching circuit, and then the heater Means for applying to the resistance wire;
A gas detection alarm device comprising: In the gas detection alarm according to claim 1 or claim 2 or claim 3,
Mark pressurization voltage, and means for monitoring the value of the ambient temperature Contact and applied voltage application time,
When the change in applied voltage and ambient temperature is within the range set for each value, the measurement operation of the battery voltage value by the battery voltage detection circuit and the measurement operation of the ambient temperature value by the temperature measurement circuit are constant. Means for stopping the period and holding the applied voltage application time;
Means for applying the applied voltage at the applied voltage application time held for a certain period of time to be stopped;
Gas detection alarm, characterized in that it comprises a.

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