JPH02114164A - Gas detector - Google Patents

Abstract

PURPOSE:To enable self-correction according to a degrading in performance of a gas sensor with an automatic self-diagnosis of the degree of the degrading in the performance thereof by arranging a temperature sensor, a multiplexer and a microcomputer. CONSTITUTION:As a natural resistance value of a gas sensing section lowers, a voltage of a resistance 902 rises. Then, an atmospheric temperature in the perimeter of a gas sensor 1 is detected depending on a voltage change across the resistance 905 resulted from a resistance change according to a temperature of a temperature sensor 903. Then, output voltages of the gas sensor and the sensor 903 are switched sequentially with a multiplexer 906 and fed to an A/D converter 907 to be sent to a microcomputer 1,001 after digitized. The microcomputer 1,001 compares an output voltage of the gas sensor with a gas leak detection level predetermined. At this point, when the output voltage of the gas sensor exceeds the gas leak detection level for a specified time, a light emitting diode 1,101 is lighted or flashed for reporting a gas leak to sound an alarm buzzer 1,103.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas detection device for detecting a reducing gas,
In particular, the present invention relates to a gas detection device suitable for performing gas detection with high reliability and high quality over a long period of time.

[Conventional technology]

Various gas detection devices for flammable gases have been proposed in the past, but they tend to malfunction or cause false alarms due to miscellaneous gases such as alcohol other than the detected gas, and furthermore, the specific resistance value of the gas sensor decreases during long-term operation. Therefore, if the predetermined alarm level remains unchanged.

Gradually, an alarm will be issued even if the gas concentration is lower than the setting. This appears to be equivalent to the sensitivity of the gas sensor becoming more sensitive, and this poses problems in terms of long-term stability and reliability.

As a solution to these problems,
, a method using a filter for miscellaneous gas oxidation as shown in Japanese Patent Publication No. 5B-47665,
551, using a plurality of gas sensors (secondly, a method of canceling out changes in gas sensors over time is used).

[Problem that the invention seeks to solve]

Although the initial characteristics have been improved by using the above-mentioned subordinate column, the alarm is issued at almost the same gas concentration as the initial setting.
No consideration was given to the signal output for controlling other devices, as well as the end-of-life notification, and there was a problem with long-term reliability.

The purpose of the present invention is to detect changes in the characteristics of the gas sensor itself (characteristic deterioration), and to raise the alarm level so that the gas concentration remains almost the same as the initial setting over a long period of time, or to output a signal for controlling other devices. Or to provide a highly reliable gas detection device that is equipped with a function to self-correct settings such as operating levels, notify the end of the gas sensor's lifespan when correction becomes impossible, and prevent loss of correction data due to power outages, etc. There is a particular thing.

[Means for solving problems]

In order to achieve the above objective, we conducted various studies on the aging of gas sensors, and as a result, we discovered the following new phenomenon. It has been found that as the performance of the gas sensor deteriorates, the ratio of the specific resistance value of the gas sensor when operating at the rated operating temperature and when operating at varying temperatures changes. I would like to congratulate you on this phenomenon below.

RT is the specific resistance value at the rated operating temperature U (To) of the gas sensor in a normal air atmosphere without reducing gases.
. , the operating temperature is T from the rated operating temperature.

Let RT1 be the specific resistance value when the temperature is changed to (T, <T.), and the ratio of the specific resistance of the gas sensor when the operating temperature is changed: P = RT, /R,. (hereinafter referred to as deterioration determination index). As the gas sensor performance deteriorates due to long-term use, the ratio of the gas sensor's specific resistance value to the deterioration determination index P decreases. P is the deterioration determination index P at the initial stage of use of the gas sensor.

The deterioration determination index P of the gas sensor after use is Pn.
Then, the rate of change in the deterioration judgment index P from the initial stage of use: Qn=
When Pn/Po is calculated, the rate of change of this deterioration judgment index P is:
Qn==p/PO is related to the degree of performance deterioration due to change over time of the gas sensor, and the value of Qn=Pn/Po becomes small for gas sensors with large performance deterioration.

In other words, the degree of performance deterioration of the gas sensor and the rate of change of the deterioration determination index P of the gas sensor in the air atmosphere: Pn
It was newly discovered that there is a correlation between /Po.

Utilizing the above new phenomenon, the above-mentioned problem can be solved by a gas detection device using a half-body type gas sensor having a gas sensing part for detecting 1° reducing gas and a heater part for heating the gas sensing part. , a heater control section that controls the operating temperature of the gas sensing section, a signal detection section of the gas sensor, an ambient temperature detection section, and a detection level control section that can change the signal detection level.
A comparison section that compares the signal level and the detection level corresponding to a predetermined gas concentration of a predetermined gas, a notification section that displays and/or reports a gas leak, and a gas cutoff valve etc. that uses information from the gas detection device. It consists of an external output section for controlling other devices, a main control section for overall control of these, and a power supply section for driving these, and using a microcomputer having a part of a timer as the main control section, the gas sensor As a self-detection means for deterioration over time, the operating temperature of the gas sensor is adjusted to a rated operating temperature: To and a lower predetermined operating temperature: T, each time a predetermined aging deterioration detection condition is satisfied. A temperature control signal for changing the operating temperature T of the gas sensing section is sent from the timer section to the heater control section. and resistance 1 of the gas sensor at T1
[RT. and R,! , deterioration judgment index: P =
R,,/R,. is calculated and stored, and the change in the deterioration judgment index since the initial use of the gas sensor: Qn=Pn/P
o, and furthermore, as a means for self-correcting the aging deterioration of the nitrogen gas sensor, the detection level control section sets a detection level commensurate with the change in the deterioration determination index: Qn, and the change in the deterioration determination index This problem can be solved by using Qn to notify the lifespan of the gas sensor, and by configuring it using a non-volatile memory: ggpRou or CMOSRAM with battery backup means to hold the detection level and control signal for self-correction of the detection level. be done.

The above-mentioned problems are caused by the gas-sensitive part for detecting two reducing gases and the
A gas detection device using a semiconductor gas sensor having a heater section that heats the gas sensing section, comprising: a heater control section that controls the operating temperature of the gas sensing section; and a gas signal detection section;
a detection level control unit that can change a plurality of signal detection levels; a comparison unit that compares a degree of change of the detection signal from the base 111 with a plurality of changeable detection levels corresponding to a predetermined degree of air pollution; , a display section for displaying the degree of air pollution, and/or an external output section for device control for controlling equipment for improving air pollution, and overall control of these by the signal from this comparison section. A microcomputer having a part of a timer is used as the main control section, and as a means for self-detecting aging deterioration of the gas sensor, it satisfies predetermined aging deterioration detection conditions. Each time a point in time is reached, the operating temperature of the gas sensor is adjusted to the rated operating temperature: To and a lower predetermined operating temperature: T.
, a heater control signal is sent from the timer section to the heater control section to change the operating temperature T of the gas sensing section.

and T, the resistance value RT of the gas sensor. and R
Calculating and storing a deterioration determination index: P''RTl/RT from T1, and calculating a change in the deterioration determination index from the initial use of the gas sensor: Qn=Pn/Po, and further as a self-correction means for deterioration over time of the gas sensor. , a plurality of detection levels commensurate with the change in the deterioration determination index: Qn are set by the detection level control unit, and when the change in the deterioration determination index: Qn reaches a predetermined value, a display and has a gas sensor life notification means that issues an alarm,
Furthermore, a non-volatile memory for holding the detection level and detection level self-correction control signal: CMOSRA equipped with backup means using EERROM or battery.
This can be solved by configuring using M etc.

[Effect]

Gas concentration remains almost the same as at initial setting over a long period of time (for example, hydrogen gas: 2000 ppm...absolute 11i)
In order to issue an alarm, the operating temperature of the gas sensor must be set to the rated operating temperature T in order to find out how much the gas sensor has deteriorated. The deterioration determination index: P = RT, /RTo is determined from the resistance value of the gas sensor at each operating temperature by changing the operating temperature T to a lower operating temperature T, and the change from the deterioration determination index Po at the initial use of the gas sensor: Q
By calculating n=Pn/Po, the degree of deterioration of the gas is determined from Qn, the detection level is controlled according to the degree of deterioration, and the characteristic deterioration of the gas sensor is self-corrected.

This operation is repeated every time a predetermined aging deterioration detection condition is satisfied until self-correction is no longer possible. The result of self-correction (detection level) is stored in a nonvolatile memory (for example, IJPROM) attached to the main control section. When self-correction finally becomes impossible, a message is displayed to notify that the gas sensor has reached the end of its service life.

In addition, over a long period of time, air purifiers can
In order to output an external output for controlling a device for improving contaminated atmosphere such as a ventilation fan or an air p4 device, similarly to the above, the deterioration of the characteristics of the gas sensor is self-corrected, and finally the life of the gas sensor is notified.

Furthermore, even if a gas leak or air pollution occurs during self-detection of deterioration over time, the detection level is changed to the second level for self-detection of deterioration over time. When the signal exceeds the second level, the system immediately returns to the gas leak detection operation or the air pollution detection operation to prevent detection errors.

Further, since the detection level, deterioration determination index: Po, etc. are stored in a non-volatile memory, malfunctions will not occur even if a power outage or the like occurs. Due to the above-described effects, the gas sensor can be used with high reliability.

〔Example〕

Before entering into the description of the embodiments, basic matters related to the present invention will be explained.

The inventors of the present invention have thoroughly investigated changes in the performance of gas sensors over time, and have found that when performance deterioration occurs in a gas sensor, the operating temperature of the gas sensor is set to the rated operating temperature (degrees: To) and a lower operating temperature: T. From the resistance values RT0 and RT1 of the gas sensor at operating temperatures T0 and T, R'H/RT. The ratio of resistance values for each operating temperature is P=RT1/RT. It has been newly discovered that the value of gas sensor decreases compared to when it was first used. Regarding this phenomenon, Fig. 3, Fig. 4, Fig. 5, Fig. 6,
This will be explained below with reference to FIG.

Figure 3 shows the state of a semiconductor gas sensor, which has a gas sensing section for detecting a reducing gas and a heater section that heats the gas sensing section, at various points in time from the beginning of use to when deterioration over time is progressing due to use. FIG. 2 is a characteristic diagram showing resistance values in a normal air atmosphere at a rated operating temperature: T0 and a lower operating temperature: T1. In the figure, characteristic 31 is a characteristic at the initial stage of use of the gas sensor, and C characteristics 32, 33, 34, and 35 are characteristics when the performance deteriorates over time due to long-term use. Ratio of the resistances of the gas sensor at each operating temperature of To, T: P=RT, /RT. decreases as performance deteriorates over time. Therefore, P is referred to as a deterioration determination index. Figure 4 shows the detection of a constant gas concentration (for example, hydrogen gas: 2000
2 is a characteristic diagram showing a change in resistance value of a gas sensor (ppm). Constant gas at 1 bar due to deterioration of the gas sensor over time! 1
The resistance value of the gas sensor during temperature detection has decreased compared to the initial value, which indicates that the sensitivity of the gas sensor has apparently become more sensitive. In other words, when using the resistance of a gas sensor or the absolute value of the output voltage correlated with the resistance as the gas leak detection level, such as in a gas leak alarm system, the performance deteriorates over time and the Nevertheless, as the resistance of the gas sensor decreases, it detects that the gas concentration in the atmosphere is gradually increasing, and initially, hydrogen gas: 2000pp
Gas leakage was detected at 1000ppm, then 400ppm as performance deterioration progressed.

Gas leaks are detected at concentrations as low as 1100pp, causing malfunctions.

Figure 5 shows the change (relative value) in the resistance of the gas sensor from the beginning of use due to aging deterioration when detecting a constant gas concentration, and the deterioration judgment index when the operating temperature is changed: P = RT, /R
T. Changes from the beginning of use: This shows the relationship Qn=Pn/Po (relative value), and it was found that there is a good correlation.

Next, Figure 6 shows that unlike the gas leak alarm shown above, which needs to detect the absolute value of gas concentration, it is only necessary to detect changes in the air atmosphere due to contamination, such as air purifiers. This shows the aging deterioration characteristics of the detection performance of the gas detection device used in ventilation, etc. 10 cigarettes at
This graph shows the change in contamination detection sensitivity due to deterioration over time, when the contamination detection sensitivity of the gas sensor is set to the ratio of resistance of the gas sensor at a contaminated atmosphere concentration equivalent to 15 pipes of smoke (=RA1R/RE2). , the sensitivity becomes higher as it deteriorates over time. FIG. 7 is a characteristic diagram showing the relationship between the contamination detection feeling K: K = RAIR/R[I2 and the change in deterioration determination index: Qn=Pn/Po due to performance deterioration of the gas sensor. A good correlation is shown except when there is little performance deterioration.

The deterioration determination index P of the performance of the gas sensor and the change in the deterioration determination index: Qn=Pn/Po are the gas sensor's rated operating temperature: T(1(C), lower operating temperature: T,
(C) The temperature at this time is 2T.

However, the rated operating temperature: 1/2 or more of the 77
A temperature of 8F or higher is desirable.

If T, < 1/2 To, set the operating temperature to 'I'
, (C) Stable gas sensor characteristics after changing l2 (
R, , ) is not practical as it takes a lot of time to obtain it. In addition, in the case of T, >7/8 To, the deterioration judgment index: P
= Rt+ / R2O becomes small, and the accuracy of deterioration detection performance decreases, which is undesirable.

In addition, operation @ degree T is 1/2 To≦T, ≦7/8 T
In the range o, good self-deterioration detection results of sensor performance similar to those shown in FIGS. 5, 5, and 7 were obtained.

The present invention has been made based on the newly discovered basic matter shown above, and will be explained below with reference to Examples.

FIG. 1 is a block diagram showing a gas detection device according to a first embodiment of the invention, FIG. 2 is a block diagram showing the configuration of a gas detection device according to another embodiment of the invention, and FIG. 1st
FIG. 13 is a circuit diagram showing a specific circuit configuration of the gas detection device according to FIG.

The outline of this gas detection device will be explained using FIG.
4 is an output resistor for measuring the gas-sensitive characteristics of the gas sensor 1; 5 is a heater control for controlling the operating temperature of the heater section 3 of the gas sensor 1; 6 is the gas sensor 1
A timer section 7 is a timer section for sending a control signal to cause the heater control section 5 to change the operating temperature of the heater section 6 to a predetermined temperature for a fixed period of time every time a fixed period of time has elapsed since the start of use of the gas sensor 1; Rated operating temperature T. (C) Specific resistance value RTO and operating temperature T, (C) (1/2T,
Ratio to specific resistance value RT1 when ≦T, ≦7/8 To):
P=RT1/RT. : a deterioration determination index measurement unit for measuring a deterioration determination index; 8 is an arithmetic record lji unit for calculating and storing the change in the deterioration determination index: P: Qn=Pn/Po from the initial use of the gas sensor 1; , 9 is a change in the deterioration determination index: The detection level of the reducing gas is reset to one of the predetermined first detection levels according to the degree of the signal in the calculation storage unit 8 corresponding to Qn. At the same time, during the deterioration determination index measurement operation, a detection level control section for setting a predetermined second detection level; 10 a signal detection section for detecting the output signal of the gas sensor 1; 11 a signal detection section for detecting the output signal of the gas sensor 1; A temperature detection unit for detecting the temperature of the surrounding atmosphere; 12 a correction calculation unit for temperature-correcting the output signal of the gas sensor of the signal detection unit 10 based on the signal from the temperature detection unit 11; and 13 a signal after the temperature correction. and a detection level newly set by the detection level control section 9, and a comparison section 14 outputs a signal when the signal level exceeds the detection level. A gas leak alarm unit 15 is configured to display the gas leakage of the gas and the life of the gas sensor and to notify the gas leakage by issuing an alarm. This is an external output unit for device control to control other devices such as.

An example of the circuit configuration embodying this gas detection device is shown in the eighth section.
This will be explained using figures. In FIG. 8, 1 is a semiconductor type gas sensor, 2 is a gas sensing section, 3 is a heater section for heating the gas sensing section 2, and 800 is a heater control section. In this embodiment, the heater section 3 of the gas sensor 1 A switching regulator is used to supply power to the 801 to 803 are resistors, 804 is a light receiving transistor, and together with the light emitting diode 804, a photocoupler is formed. 805 is a driving circuit for the switching transistor 806, and the light receiving transistor 8
The transistor 806 is controlled by the 0N-OFF state of the transistor 804, and a predetermined bias current is applied to the transistor 806. Note that, as a simple method, the transistor 806 may be conductive during rated operation and non-conductive when the temperature is low, and the resistor 807 may be selected to have an appropriate value.

Reference numeral 900 denotes a signal detection unit of the gas sensor 1, which detects signals for detecting gas leakage and performance deterioration of the gas sensor. 9
01 and 902 are resistors connected in series with the gas sensor 1, and the specific resistance fluctuation (impedance fluctuation) of the gas sensor appears at both ends of the resistor.

Reference numeral 903 denotes a temperature sensor (for example, a thermistor) for measuring the ambient ambient temperature of the gas sensor 1, and 904 and 905 denote resistors, from which a voltage output signal proportional to the temperature signal detected by the temperature sensor 903 is obtained at both ends. 906 is a multiplexer,
9'07 is an A/D converter, and multiplexer 906
switches the output signal of the gas sensor 1 and the voltage signal corresponding to the ambient temperature, sends it to the A/D converter 907, and
/D conversion.

Reference numeral 1100 denotes a gas leak notification unit that notifies the gas leak and the life of the gas sensor by display or alarm.

1101 and 1102 are display devices such as light emitting diodes, and 1103 is an alarm buzzer.

Reference numeral 1200 denotes an external output unit for device control, which uses information from the gas detection device to close a cutoff valve in a gas pipe or operate a device that transmits the information to the outside.

Reference numeral 1000 denotes a system unit that collectively controls the heater control unit 800, signal detection unit 900, gas leak notification unit 1100, and device control external output unit 1100 as described above. This is mainly a microcomputer (hereinafter referred to as microcomputer)
1001 and timer section 1 built into the microcomputer 1001
002, a ROM 1003 that stores constants that are safe for the operation of the microcomputer 1001, and operating procedures of the gas detection device described later, and a RAM 1004 that stores calculation results when the microcomputer operates. It is also possible to store the sensor deterioration determination index calculated during operation, the gas leakage detection level reset by deterioration self-correction, and the like. Non-volatile memory EE
FROM or CMO3RAM 1005 backed up by a battery.

Reference numeral 1500 denotes an 'i power supply section that drives the above-mentioned circuit.

1301 is an AC source, 1302, 1303 and 130
4 is a computation transformer; 1305 and 1306 are rectifying diode stacks; 1507, 1508 and 1609 are smoothing capacitors; and 1310 is a stabilizing power supply circuit.

Gas leak detection is performed with the gas sensing part 6 heated to the rated operating temperature by the heater part 3 of the gas sensor 1, and when the gas sensing part comes into contact with gas, the decrease in its specific resistance value is caused by a voltage change across the resistor 902. It is something to detect. When the specific resistance value of the gas sensing portion decreases, the voltage across resistor 902 increases. - 10,000, resistance change according to the temperature of temperature sensor 903 consisting of a thermistor etc. is measured by resistor 9.
It is detected by the voltage change across 05. The output voltages of gas sensor 1 and temperature sensor 903 are sequentially switched by multiplexer 906 and sent to A/D i converter 907, digitized, and sent to microcomputer 1001. microcomputer 100
1, a predetermined gas leak detection level is compared with the output voltage of the gas sensor 1. When the output voltage of the gas sensor 1 exceeds the gas leak detection level for a predetermined period of time, the light emitting diode 1101 is turned on or flashed and the alarm buzzer 1103 is sounded to notify the gas leak.

Detection of gas sensor performance deterioration is determined by the ratio of the degree of performance deterioration of the gas sensor to the specific resistance value of the gas sensor when the operating temperature changes in the air atmosphere: P = RT, /R
,. (Since there is a two-way relationship, the aforementioned heater control section 800 sets the operating temperature of the gas sensing section 2 to the rated operating temperature of 2T.

Operating temperature lower than this: T+(1/2To≦T,≦
7/8 T. ), and from the specific resistance value of the gas sensor at that time: R1°, R1, the deterioration judgment index: P=RT
, /R1° and monitor the change in deterioration determination index from the initial use of the gas sensor: Qn=Pn/Po (initial deterioration determination index for Po22 side, Pn: deterioration determination index during use). It becomes possible.

Additionally, as shown in Figure 4, as the performance of the gas sensor deteriorates, the resistance value of the gas sensor decreases even when detecting a constant gas concentration, so if the detection level for gas leak detection remains constant, malfunctions are likely to occur. Become.

Therefore, the degree of performance deterioration of the gas sensor is known from the change in the deterioration judgment index when the operating temperature of the gas sensor changes: Qn, and the detection level control unit 11 resetting the detection level of
OM or battery backed CMOSR
Hold on AM 1005.

Therefore, even if the power is cut off due to a power outage, etc.

After the power is restored, the microcomputer first reads the self-corrected detection level and the initial value of the deterioration judgment index: Po from the non-volatile memory, thereby avoiding negative effects caused by power outages, etc.

Furthermore, if the performance of the gas sensor deteriorates due to long-term use and self-correction by changing the detection level becomes impossible, the light emitting diode 1102 is turned on or blinks to notify the life of the gas sensor, and the alarm buzzer 1103 is activated. Give an alarm.

Next, the operation of this embodiment will be explained.

9, 10, 11, and 12 are flowcharts showing the operation of the gas detection device according to the present invention, which is equipped with self-correction of gas sensor performance deterioration and gas sensor life detection functions. Fig. 9 shows the main routine of the gas detection device, Fig. 10 shows the subroutine for gas leak detection, Fig. 11 shows the subroutine for detecting deterioration of gas sensor performance, and Fig. 12 shows self-correction of gas sensor performance deterioration. This shows a subroutine.

The flowchart will be explained below. First, when the gas detection device is powered on, the main controller 1000's Miko/10
01 performs reset, initialization, etc. (1), and then reads the set value of the gas detection level (2). This operation uses the gas sensor for a long period of time, and when the power is restored, the data that self-corrects for the performance deterioration of the gas sensor, which will be described later, is read from the non-volatile memory: EEPI (OM) or CMOS RAM 1005 backed up by a battery, and the gas sensor is This is to increase reliability.The gas detection level Ln set in step (2) is newly set as L.(3).(4) and (5) maintain the temperature of the gas sensing part at the rated temperature. However, the determination value S is provided to select between the steady operation mode for gas leak detection and the self-correction mode for sensor performance deterioration, and the determination value S is used to determine the cycle of the self-correction mode.

Now, if N is smaller than S in (5), set the heater control section to the rated operating temperature: T = To (8), enter gas leak detection mode (9), and perform gas leak detection as shown in Figure 10. If there is no gas leak, return to (4) again.
Add J to N and proceed to the next step. If N becomes larger than S in (5), N is set to 0 in (6). Next, the process moves to the subroutine (7) of the gas sensor deterioration detection mode (FIG. 11). After detecting the deterioration and completing the sensor deterioration self-correction process (subroutine in Figure 12), return to (8).
Set the rated operating temperature and continue gas leak detection (9) operation.

The details of this (9) gas leak detection will be explained with reference to the flowchart of FIG. First, the gas sensor output is selected by the multiplexer 906, A/Df is converted by the A/D converter 907, and the gas sensor output V? α1 to measure
Next, the multiplexer 906 selects the ambient temperature output, and the A/D converter 9071 performs A/D conversion.
The ambient temperature T is measured αυ, and the gas sensor output V is corrected by this Ta.

This corrected value v? 25 and the gas leak detection level L. If v, 25 is less than L, it is determined that no gas leak has occurred, and t' is initialized (t'=o) (21
) L, Cancels gas leak notifications such as gas leak display and alarm 22), Cancels external output for device control 25),
Return to (9), where the subroutine was called, and perform normal operation thereafter. But v? 25 is greater than or equal to L, it is determined that a gas leak has occurred, and the gas leak duration time t' is integrated, and if the α east gas leak continues for more than tMl (for example, 10 seconds), the light emitting diode 1101 is activated to detect the gas leak. is displayed and the alarm buzzer 1103 is sounded to notify the gas leak (g). In addition, if the gas leak continues for more than 30 seconds (for M211J or 30 seconds), the external output for equipment control will be activated to close the gas piping cutoff valve or activate the device that transmits the gas leak to the outside. Output to the section (G). Next, a call is made to determine whether or not gas leak countermeasures have been taken based on the gas leak alarm.

For example, if it is determined that a person has pressed an alarm stop switch (not shown), the time integration, t' and N are set to 0 and 1)
, returns to (9) where the subroutine was called, and thereafter performs steady operation.

Next, a mode for detecting deterioration of the gas sensor will be described. In FIG. 11 (24), the initial I of the deterioration determination index P
I * Read PO. Then, the time integration t' is initialized (25). Then, the operating temperature T is changed to the rated operating temperature f.
T. 26), set the gas leak detection level to L (27), and execute the gas leak detection (28) subroutine for tB4 hours (for example, 10 minutes) (3. This t81
If no gas leak occurs during the time, the gas sensor output voltage v after temperature correction of @, ! From 25, the resistance is calculated (31). Next, set the operating temperature to T, which is lower than the rated operating temperature (32), set it to M, which is the gas leak detection level (&), measure the sensor output (34), and set the ambient temperature to T.
, elbow measurement (35), temperature correction (Akira) of the 7/s output,
The output v at that time? 25 and the gas leak detection level M. 37), v? If 25 is M or more, it is determined that a gas leak has occurred and a subroutine is immediately called (7
), set the rated operating temperature (8), shift to the regular gas leak detection mode (9), and perform gas leak detection.

However, the sensor output v after temperature correction? If 25 is less than M, the sensor output v? Calculate the resistance Ryt from 25), deterioration judgment index: Pn=RT+/RT. 39) and determines whether the initial l1fPo of the degraded foot index read in (24) is O (40).

When Po is 0, the calculated deterioration determination index P is set to the initial stage of the deterioration determination index P. 45), the subroutine is called (7) (=return, and the steady operation is performed thereafter. If P. is not 0 in (413) and the box is read, the deterioration judgment index changes: Qn=P, /Po
41), and this Qn and the predetermined deterioration it
42) If it is below K5, it is determined that the gas sensor has deteriorated extremely and is at the end of its lifespan, and the lifespan of the gas sensor is evaluated (m). However, Qn crab 5
If it is not below, then go to the deterioration level of C/S.
(K, >K, ) 43), if Qn is not less than or equal to 43), it is determined that the performance of the gas sensor has not deteriorated yet, and returns to step (7), where the length blue routine call is made.
Perform steady operation. Qn, in the following cases, the performance of the gas sensor has deteriorated and it is determined that self-correction is necessary.
Move to sensor deterioration self-correction (44) mode.

In Fig. 12, (47), first, the change in the deterioration judgment index: Q
o, and then to the deterioration level.

Compared with K2 and 3, the gas detection level should be reset to L2 and above (L2>L,) depending on the degree of deterioration of each.48) , (49) , (50) , (
51) After that, the main nochin returns to the steady operation of (8) and (9) and performs the gas leak detection operation.

A second embodiment of the present invention is shown in FIGS. 2, 13, 14, 15, and 16. FIG. 2 shows the configuration of a gas detection device. A block diagram, FIG. 13 is a circuit diagram showing an example of a specific circuit configuration of the gas detection device according to FIG. 2, and FIG. 14 is a block diagram.

15 and 16 are flowcharts showing the operation of the gas detection device according to FIG. 2, respectively. This shows a subroutine.

The outline of this gas detection device will be explained using FIG. 2. 1 is a semiconductor type gas sensor having a gas sensing part 2 and a heater part 3; 4 is an output resistor for measuring the gas sensing characteristics of the gas sensor. , 5 is a heater control unit for controlling the operating temperature of the heater unit 3, 6 is a timer unit for sending control signals at predetermined time intervals, and 7 is a deterioration determination unit for measuring the deterioration of the performance of the gas sensor 1 over time. Index measurement section, 8 is gas sensor 1
Changes in the deterioration judgment finger from the initial stage of use: Q, = Pn/
An arithmetic storage unit 9 for calculating and storing Po determines the detection level of air pollution caused by reducing gas according to the level of the signal from the arithmetic unit tt unit 8, which is a combination of first detection levels that is predetermined. (2. During the deterioration determination index measurement operation, a detection level control unit for setting a predetermined second detection level (2); 10 is a signal detection unit for detecting the output signal of the gas sensor 1; A reference value setting section 16 sets the output signal of the gas sensor 1 at that time as a reference value: V every time the signal from the timer section 6 is received, and a reference value setting section 17 sets the output signal of the gas sensor 1: vl and the corresponding Reference value:
vo and the air pollution degree: [1= A calculation unit for calculating Vi/V0, 73 is the air pollution degree: U, and the detection level control unit 9 (2) A comparison section 18 outputs a signal when the signal level exceeds the detection level; 18 is an air pollution display section for displaying the degree of air pollution and the lifespan of the gas sensor based on the output signal of the comparison section 13; 15 is an air pollution display section; This is an external output unit for equipment control for outputting a plurality of control signals for controlling other equipment such as an air cleaner, a ventilation fan, and a 22-control machine for removing and purifying contamination.

An example of the circuit configuration of this gas detection device will be explained using FIG. 13. Circuit configuration according to the first embodiment (Fig. 8)
Circuit components that are the same as those shown in the figure are numbered the same. Only the parts that are different from the circuit configuration according to the first embodiment will be explained below.

Reference numeral 900 denotes a signal detection unit of the gas sensor 1, which detects an output signal of the gas sensor due to air pollution and performance deterioration. Fluctuations in the specific resistance value of the gas sensor are measured by the output voltage across the resistor 902, converted into an A/D V, and then sent to the microcomputer 1001i of the main control section. At the beginning of use, the microcomputer 1001 calculates the air pollution degree (U: V, /V0) and compares it with the predetermined air pollution detection level.Gas sensor output an air purifier for removing and purifying air pollution by lighting or blinking a light emitting diode 1101 to notify air pollution when the air pollution degree U determined from the voltage exceeds the air pollution detection level for a predetermined time; In order to control other devices such as ventilation fans and air conditioners, a plurality of control signals are output to the device control external output unit 1202.

The method for detecting performance deterioration of the gas sensor is the same as in the first embodiment, so it will be omitted. However, if the performance deterioration of the gas sensor progresses due to long-term use and self-correction by changing the air pollution detection level is no longer possible, the gas sensor The light emitting diode 1102 is turned on or blinked to notify the end of its life.

Next, the operation of the second embodiment will be explained in FIGS. 14, 15, and 1.
This will be explained using the operation flowchart shown in FIG. 14th
The figure shows the main routine of gas detection to detect air pollution. First, when the gas detection device is turned on, the main control unit 10
The microcomputer 1001 of 00 performs resent and initialization (151), then reads the air pollution detection level set value (152), and sets the read air pollution detection level Ln as a new detection level L (153). (15
4) In (155), a steady operation mode for detecting air pollution and a mode for detecting deterioration of the gas sensor are selected. Judgment It's is for determining the cycle of the deterioration detection mode, and if N is smaller than S at (155), the heater control unit changes the operating temperature of the gas sensor to the rated operating temperature:
Set 'I'=To(C) (158), enter the air pollution detection mode (159), perform the air pollution detection shown in Figure 15, and if the degree of air pollution is below the detection level, return (154). ), add J to N, and proceed to the next step. When N becomes larger than S in (155), after initializing N to 0 (156), the gas sensor deterioration detection mode (1
The process moves to the subroutine 57) (FIG. 16). Deterioration was detected, and if the deterioration was progressing, deterioration self-correction processing (not shown because it is the same as the subroutine in FIG. 12 shown in the first embodiment) according to the degree of deterioration was performed. After that, the normal operation of setting the rated operating temperature and detecting air pollution in (158) and (159) is continued again.

7 in Figure 15 for the details of the air pollution detection of
0-chart (explained starting from 2). At (160) it is determined whether the reference value for detecting air pollution has been set. At the start of use after turning on the m source, the initial setting operation at (151) is performed. Since F'=0 is set, time t is set to O161), the gas sensor output vi after A/D conversion in a normal electric atmosphere is measured162), and set as a standard value (163). . Next, the time integration t until the next reference value setting is started (164), and the sensor output v1 for detecting air pollution is measured (165), and this gas sensor output V and the reference +1 iV are measured.

Calculate the ratio: U=V, /V0 as the air pollution degree (166) and compare it with the air pollution detection level L (167)
). When the air pollution degree is low and U (L), it is necessary to judge whether the cumulative time has reached the reference value update time t0.16B
), if the reference value has been reached, F=O is set to update the reference value, and if it has not been reached, F=i is set so that the reference value is not updated, and the process returns to (159) and (154) of the main routine. However, if the air pollution degree U is higher than the set level L, it is determined whether this condition continues for 1 = 1M and time (for example, 1SθC) in (171) and (172),
If the process does not continue, the standard value is not updated, but it is assumed that there is no air pollution and the process returns to the normal operation of (159) and (154).

tM.

If it continues for more than a time (for example, i5ea), it is assumed that air pollution has occurred, and after setting t and N (condition setting 1+1 for entering deterioration detection mode) to 0, air pollution is removed.
In order to control the air purifier, ventilation fan, air conditioner, etc. that are to be cleaned, a plurality of control outputs are outputted to the dual-use external output section on the one equipment side in accordance with the degree of the air 115 stain U.

Next, a mode for detecting deterioration of the gas sensor will be described. In FIG. 16 (176), the initial first shift: Po of the deterioration determination index P is read, and the operating temperature is set to the rated operating temperature T. (177), then set it to L (17B), which is the air pollution detection level, and the gas sensor output crab v? . Measure L (1
79) To determine whether air pollution has occurred (180), if it is determined that air pollution has occurred, immediately return to main routine (i57) and perform air pollution detection mode with (15B) and (159). (i8n) determines that there is no air pollution, the sensor output v? o to the sensor's specific resistance RT. is calculated (181). Next, the operating temperature; 1 is the operating temperature for deterioration detection: T, (C) (1/2 T
o≦T, ≦7/8'r. ) (After setting 2 (1s2),
Again, the air pollution detection level 2 M corresponding to the operating temperature T
Please set it to 183), gas sensor output V, (1
84) and determine the presence or absence of re-entering air contamination.1ss
), If it is determined that there is a possibility of air contamination due to VH≧M, immediately remove the main routine (157), (158)
, Return to (159) and perform the air pollution detection mode. V
,, (If we judge that there is no possibility of air contamination with M, ■?
After calculating the specific resistance value R71 of the sensor from (1B6), calculate the deterioration judgment index: Pn=RT1''RHl.
87), above (176) 'c Initial value P of the read deterioration judgment index.

It is determined whether or not is 0 (iss). When Po is 0, the calculated Chika publication index P is the first 19 of the deterioration judgment index.
1+ip. After setting (190), the process returns to the main routine (157) and the steady operation is performed thereafter. If Po is not 0 and a value has been read, calculate the change in deterioration judgment index: Qn-Pn/Po189), and compare this Qn with the predetermined deterioration degree judgment level of 3.191
), K.

If the gas sensor is below, it is determined that the gas sensor has deteriorated to an extreme extent and its lifespan is reached, and a gas sensor lifespan notification is performed (192). If the deterioration, Q, is not below, then the deterioration level is compared with (K, >K, )193), Qn
However, if it is not below, it is determined that no performance deterioration has occurred, and the routine returns to step (157) of the main routine to perform steady operation. Qn, in the following cases, the performance of the gas sensor has deteriorated, and it is determined that self-correction is safe, and the process shifts to sensor deterioration self-correction (194) mode. Since the self-correction mode operates exactly the same as the first embodiment (FIG. 12), its explanation will be omitted.

〔Effect of the invention〕

According to the present invention, it is possible to automatically self-diagnose the degree of performance deterioration of a gas sensor and perform self-correction according to the deterioration. Since the correction contents are held in a non-volatile memory, they will not be adversely affected by a power outage or the like.

Furthermore, since the life of the gas sensor can be notified, it is possible to provide a gas detection device that maintains high reliability and high accuracy over a long period of time and does not cause malfunctions.

[Brief explanation of drawings]

1 and 2 are block diagrams showing the configuration of gas detection devices according to the first and second embodiments of the present invention, and FIG. 3 shows the elapsed time from the start of use of the gas sensor. 4 and 6 are characteristic diagrams showing the relationship between the gas sensor's specific resistance value and the gas sensor's operating temperature when the gas sensor's operating temperature is changed.
The figure is a characteristic diagram showing the performance deterioration over time of the gas sensor according to the first example and the second implementation row, and FIGS. 5 and 7 are
Characteristic diagrams illustrating the relationship between performance deterioration and deterioration determination index of gas sensors according to the first and second embodiments, FIGS. 8 and 13, show specific examples of the gas detection devices according to the first and second embodiments Circuit diagrams showing one example of the circuit configuration, Figures 9, 10, and 11
Figures 14 and 12 are flowcharts showing an overview of the operation of the gas detection device according to the first embodiment], Figures 14 and 15,
FIG. 16 is a flowchart showing an overview of the operation of the gas detection device according to the second embodiment. 1... Gas sensor 2... Gas sensing section 3... Heater section 5.800... Heater control section 6.1002... Timer section 7... Deterioration judgment index measurement section... Act 34H Wide section...Detection level control section 0...FG detection section 1...Temperature detection section 2...Correction calculation section 3...Comparison section 4...Gas leak alarm section 5... External output section for equipment control 6...Reference value setting section 7...Calculation section 8...Air pollution display section. Figure 5 Ashi Figure 4 Ivy 5 [21 Ka6 Figure Ivy 7121 ;qhζ#missing0Dlf;, (Omeme 1i), qth
Ko No. 102 Nu 1? Figure 1/2, Noka 13F71 r-'-1'jf114 Figure 5L2]

Claims (10)

[Claims] 1. A gas detection device using a semiconductor gas sensor having a gas sensing section for detecting a reducing gas and a heater section heating the gas sensing section, at least a heater control section controlling the operating temperature of the gas sensing section; A signal detection section of the gas sensor, an ambient temperature detection section, a detection level control section that can change the detection level, a comparison section that compares the detection signal level of the signal detection section and the detection level, and the comparison section. an alarm section that displays gas leaks and issues alarms based on signals from the gas detection device; an external output section for device control that controls other devices using information from the gas detection device; a main control section that comprehensively controls these; As a self-detection means for aging deterioration of the gas sensor, the operating temperature of the gas sensor is set to the rated operating temperature: T_0 and from this every time a predetermined aging deterioration detection condition is reached. Low predetermined set operating temperature: T_1, and the resistance value R of the gas sensor at operating temperatures T_0 and T_1.
From _T_0 and R_T_1, deterioration judgment index: P=R
_T_1/R_T_0 is calculated and stored, and the change in the deterioration determination index from the initial use of the gas sensor: Q_n=
Calculating P_n/P_0, and furthermore, as a means for self-correcting the aging deterioration of the gas sensor, setting a detection level commensurate with the change in the deterioration determination index Q_n in the detection level control section, or Change: Q
A gas detection device characterized by performing self-correction of performance deterioration of a gas sensor, displaying a lifespan, and issuing an alarm based on __n. 2. A gas detection device using a semiconductor gas sensor having a gas sensing section for detecting a reducing gas and a heater section heating the gas sensing section, at least a heater control section controlling the operating temperature of the gas sensing section; a signal detection section of the gas sensor, a detection level control section that can change a plurality of detection levels, and a plurality of detection level control sections that correspond to the degree of change from a reference value of the detection signal of the signal detection section and a predetermined degree of air pollution. a comparison section that compares the changeable detection level of the
A display section for displaying the degree of air pollution based on the signal from the comparison section, and/or an external output section for device control for controlling equipment for improving air pollution, and a main control section for overall control of these. and a power supply unit that drives these, and as a self-detection means for aging deterioration of the gas sensor, the operating temperature of the gas sensor is adjusted to the rated operating temperature K:
T_0 and lower predetermined operating temperature: T_
1, and from the resistance values R_T_0 and R_T_1 of the gas sensor at operating temperatures T_0 and T_1, a deterioration determination index: P=R_T_1/R_T_0 is calculated and stored, and a change in the deterioration determination index from the initial use of the gas sensor: Q_n= Calculating P_n/P_0; and furthermore, setting a plurality of detection levels commensurate with the change in the deterioration determination index Q_n in the detection level control section as a self-correcting means for self-correcting the aging deterioration of the gas sensor; A gas detection device characterized by performing self-correction of performance deterioration of a gas sensor, displaying a life span, and issuing an alarm based on a change in index: Q_n. 3. In a gas detection device using a semiconductor type gas sensor having a gas sensing section for detecting a reducing gas and a heater section for heating the gas sensing section, at every predetermined elapsed time, the rated operating temperature of the gas sensor: T_0, From the specific resistance value: R_T_0 and the specific resistance value at the operating temperature: T_1 lower than the rated operating temperature: T_0,
The deterioration determination index: P=R_T_1/R_T_0 is calculated, and the change in the deterioration determination index from the initial use of the gas sensor: Q
__n=P_n/P_0 is determined, and the gas sensor is used as a means for detecting deterioration over time of the performance of the gas sensor, and the gas sensor comprises a deterioration self-correction means and a life notification means commensurate with the deterioration detection result obtained by the deterioration detection means over time. Detection device. 4. As a means for storing the deterioration determination index: P, the change in the deterioration determination index: Q_n, and the detection level after self-correction of the detection level control section when the gas sensor is used, a non-volatile memory: EEPROM or battery backup means is maintained. The gas detection device according to claims 1 and 2, characterized in that a CMOS RAM or the like is used. 5. While changing the operating temperature of the gas sensing part of the gas sensor from the rated operating temperature: T_0 to the set operating temperature, and executing the aging deterioration self-detection means for measuring the deterioration determination index: P, the above-mentioned detection level is changed. 2. The gas detection device according to claim 1, wherein the detection level is set to a predetermined second detection level. 6. The predetermined aging deterioration detection condition for the gas sensor is that the fluctuation of the detection signal (or the resistance value of the gas sensor) during the rated operation of the gas sensor continues at a predetermined value or less for a predetermined period of time. A gas detection device according to claims 1 and 2. 7. The gas according to claim 1, wherein the detection level is initialized in advance by the resistance value of the gas sensor at a predetermined gas concentration or the absolute value of the output signal of the signal detection section of the gas sensor. Detection device. 8. The gas detection according to claim 2, wherein the detection level is initialized in advance by a change amount (ratio) to a resistance value or an output signal (reference value) of the gas sensor in a normal air atmosphere. Device. 9. The above reference value is first set as the resistance value or output signal of the gas sensor at the beginning of use, and the set reference value is determined for a predetermined period of time when the output signal from the signal detection section remains below the above detection level. 9. The gas detection device according to claim 8, wherein if the gas detection device continues, the reference value is updated using the current output signal or the resistance value of the gas sensor as the new reference value. 10. Operating temperature of the gas sensing part of the above gas sensor: T_1(
The gas detection according to claims 1, 2, and 3, characterized in that C) is a temperature within the range of 1/2 to 7/8 of the rated operating temperature: T_0(C). Device.