JP2001165890A - Gas leak alarm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas leak alarm capable of lengthening life. SOLUTION: This gas leak alarm involves a gas sensor 1, a computing means 2 for computing gas concentration based on the detected output of the gas sensor 1, and an alarm means 5 for issuing an alarm when gas concentration A determined by the computing means 2 reaches a prescribed alarm concentration A0. The gas leak alarm is provided with a storing means 3 for storing an alarm concentration aging variation computing expression about gas types to be detected, and an aging time counting means 4 for counting the cumulative lapsed time of the gas sensor. The computing means 2 computes an alarm concentration aging variation K based on the alarm concentration aging variation computing expression stored in the storing means 3 and a counted value from the aging time counting means 4, and compensates the aging of alarm sensitivity using the computed alarm concentration aging variation K at the time of computing the gas concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas leak alarm used for general households and commercial kitchens and living rooms, and more particularly, to a gas sensor using a contact-combustion gas sensor having a long-term stable sensor output. It relates to a gas leak alarm.

[0002]

2. Description of the Related Art As a gas leak alarm used in general homes and commercial kitchens and living rooms, semiconductor gas sensors and catalytic combustion gas sensors mainly composed of SnO ₂ have been used for a long time.

In a semiconductor gas sensor, when used for a long period of time, the neck portion of SnO ₂ grows (reduction in internal resistance) due to the heating temperature of the sensor, the ambient temperature and humidity, and the staying gas, etc. Pd), platinum (P
t), a change in gas sensitivity occurs due to agglomeration of a noble metal such as rhodium (Rh) or the like, and an increase in sensitivity particularly to hydrogen gas and ethanol gas, which are miscellaneous gases, occurs.

Further, regarding a contact combustion type gas sensor,
Generally, aluminum (Al), silicon (S
Using a metal oxide such as i), Pd, Pt, Rh and the like are supported, and are configured to have sensitivity to the detection gas.

[0005]

The contact combustion type gas sensor is used as a gas sensor that can withstand the accumulation of miscellaneous gas or a commercial kitchen or the like where the ambient temperature and humidity are severe. As in the case of the gas sensor, activity deterioration occurs due to aggregation of Pd, Pt, Rh and the like due to the sensor heating temperature, ambient temperature and humidity, and stagnant gas, resulting in sensitivity deterioration.

From the above, at present, the life of a gas leak alarm is determined to be 5 years. Therefore, in order to extend the life of the gas leak alarm, it is necessary to develop a sensor material. However, at present, no sensor material capable of extending the life has been developed.

It is an object of the present invention to solve the above-mentioned problems and to provide a gas leak alarm capable of extending the life.

[0008]

SUMMARY OF THE INVENTION In view of the above objects, a gas leak alarm according to the first aspect of the present invention has a gas sensor 1 and a detection output of the gas sensor 1 as shown in FIG. Calculating means 2 for calculating the gas concentration based on
And the gas concentration A obtained by the arithmetic means 2 is the predetermined alarm concentration A
A gas leak alarm having alarm means 5 for issuing an alarm when it reaches ₀ , a storage means 3 for storing an alarm concentration aging calculation formula for a gas type to be detected, and a cumulative process of the gas sensor 1. Aging time counting means 4 for counting time is provided, and the arithmetic means 2 is based on the alarm concentration aging change calculation formula stored in the storage means 3 and the count value from the aging time counting means 4. The method is characterized in that the alarm concentration aging amount K is calculated, and the calculated alarm concentration aging amount K is used to compensate for the aging of the alarm sensitivity when calculating the gas concentration.

According to the first aspect of the present invention, a gas leak alarm includes a gas sensor 1, a calculating means 2 for calculating a gas concentration based on a detection output of the gas sensor 1, and a gas detected by the calculating means 2. and a warning means 5 for issuing an alarm when the concentration a reaches a predetermined alarm concentration a _0. The gas leak alarm includes a storage unit 3 for storing an equation for calculating an alarm concentration aging change amount relating to a gas type to be detected, and an aging time counting unit 4 for counting the accumulated elapsed time of the gas sensor 1. The calculating means 2 calculates the alarm concentration aging amount K based on the alarm concentration aging amount calculation formula stored in the storage means 3 and the count value from the aging time counting means 4, and calculates the gas concentration. The calculated alarm concentration aging amount K is used to compensate for the aging of the alarm sensitivity. As a result, the aging of the alarm sensitivity of the gas leak alarm is compensated, and an alarm is issued at a constant alarm concentration regardless of the passage of time, so that the life of the gas leak alarm can be extended.

[0010] The gas leak alarm according to the second aspect of the present invention,
A gas sensor 1, the calculating means 2 for calculating a gas concentration based on the detection output of the gas sensor 1, the warning means gas concentration A calculated in the calculation means 2 emits an alarm when it reaches a predetermined alarm concentration A ₀ 5 And a storage means 3 for storing a formula for calculating an alarm concentration aging change relating to a gas type to be detected, and an aging time counting means 4 for counting the accumulated elapsed time of the gas sensor 1. The arithmetic means 2 calculates and calculates the alarm density aging amount K based on the alarm density aging calculation formula stored in the storage means 3 and the count value from the aging time counting means 4. subtracting the alarm concentration secular change amount K from the gas concentration F, if the result a has reached the predetermined alarm concentration a _0, and drives the alarm unit.

According to the second aspect of the present invention, a gas leak alarm includes a gas sensor 1, a calculating means 2 for calculating a gas concentration based on a detection output of the gas sensor 1, and a gas sensor calculated by the calculating means 2. and a warning means 5 for issuing an alarm when the concentration a reaches a predetermined alarm concentration a _0. The gas leak alarm includes a storage unit 3 for storing an equation for calculating an alarm concentration aging change amount relating to a gas type to be detected, and an aging time counting unit 4 for counting the accumulated elapsed time of the gas sensor 1. The calculating means 2 calculates the alarm concentration aging amount K based on the alarm concentration aging change calculation formula stored in the storage means 3 and the count value from the aging time counting means 4 and calculates the alarm concentration aging change K from the calculated gas concentration F. subtracting the alarm concentration secular change amount K, if the result a has reached a predetermined alarm concentration a _0, and drives the alarm unit. Thus, the alarm concentration aging amount K is calculated based on the alarm concentration aging calculation formula and the count value from the aging time counting means 4, and the alarm concentration aging amount K is subtracted from the calculated gas concentration F. As a result, the aging of the alarm sensitivity of the gas leak alarm is compensated, so that an alarm is issued at a constant alarm concentration regardless of the passage of time, and the life of the gas leak alarm can be extended.

The invention described in claim 3 is the first or second invention.
In the gas leak alarm described above, the alarm concentration aging calculation formula is a logarithmic function of the number of days elapsed since the installation of the gas leak alarm.

According to the third aspect of the present invention, the equation for calculating the alarm concentration aging is a logarithmic function of the number of days that have elapsed since the gas leak alarm was installed. Thus, by substituting the number of days elapsed into the logarithmic function, the alarm concentration aging amount can be obtained.

According to a fourth aspect of the present invention, in the gas leak alarm according to any one of the first to third aspects, the gas sensor 1 is a contact combustion type gas sensor.

According to the fourth aspect of the invention, the gas sensor 1 is a contact combustion type gas sensor. As a result, the aging of the alarm sensitivity of the gas leak alarm using the contact combustion type gas sensor is compensated, so that an alarm is issued at a constant alarm concentration regardless of the elapse of time and the life of the gas leak alarm is extended. It can be carried out.

According to a fifth aspect of the invention, in the gas leak alarm according to any one of the first to fourth aspects, the alarm means 5 includes an alarm sound circuit 5A and an alarm display circuit 5B. And

According to the invention described in claim 5, the alarm means 5
Includes an alarm sound circuit 5A and an alarm display circuit 5B. Thus, an audible and visual alarm can be issued.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a gas leak alarm according to the present invention will be described below with reference to the drawings. FIG.
1 shows an example of an electric circuit diagram of a gas leak alarm according to the present invention.

In FIG. 2, a gas leak alarm comprises a gas sensor 1 and a microcomputer 2 as a calculating means.
And an EEPROM (Electric
all Erasable Programmable
e Read Only Memory) 3, a counter 4 as aging time counting means, an alarm sound circuit 5A and an alarm display circuit 5B as alarm means.

In this gas leak alarm device, the gas concentration of the detected gas is equal to or higher than a predetermined alarm concentration A ₀ (for example, a concentration at which there is a risk of adversely affecting the human body such as gas poisoning, or 1/4 of the lower explosion limit). In the case of, an alarm indicating that the gas concentration has become abnormal can be notified by an alarm sound by the alarm sound circuit 5A and an alarm display by the alarm display circuit 5B.
The predetermined alarm concentration A ₀ is individually set based on the type of gas to be detected. Here, the types of detected gas are, for example, methane gas (CH ₄ ), hydrogen gas (H ₂ ), and isobutane gas (i-C ₄ H ₁₀ ).

The gas sensor 1 is, for example, a contact combustion type gas sensor, and includes a power supply 11, resistors 12 and 13 connected in series to the power supply 11, and a power supply 11 connected in series with each other and in parallel with the resistances 12 and 13. Connected sensing element 1
4 and a comparison element 15 and an amplifier 16. The resistors 12, 13 and the detection element 14 and the comparison element 15 form a bridge circuit, and the voltage at the connection point between the resistance 12 and the resistance 13 and the voltage at the connection point between the detection element 14 and the comparison element 15 are supplied to the amplifier 16, An output signal corresponding to the concentration of the detected gas can be obtained from the output of the amplifier 16.

As shown in FIG. 3A, the sensing element 14 includes a stem 14a, a pin 14b, and a net cap 14c.
And a detection member 14d.

The detecting member 14d is manufactured as follows.
First, 5 to 15 wt% of Pd is added to the fired γ-alumina.
Rh is supported in a high dispersion, crushed to about 1 to 10 μm,
It is used as a sensing element catalyst. An alumina-based binder is added to this catalyst, and an appropriate amount of water is added to form a paste. Next, 50
The above-mentioned paste is applied to a platinum wire of about μm, dried and baked, and formed into a particle shape of about φ1.5 mm.
d.

As shown in FIG. 3B, the comparison element 15 includes a stem 15a, a pin 15b, and a seal cap 15c.
And a comparison member 15d.

The comparison member 15d is manufactured as follows.
First, the calcined γ-alumina is pulverized to about 1 to 10 μm to obtain a comparative element catalyst. An alumina-based binder is added to this catalyst, and an appropriate amount of water is added to form a paste. next,
The above-mentioned paste is applied to a platinum wire of about 50 μm, dried and baked, and shaped into a grain of about φ1.5 mm to obtain a comparative member 15d.

When the gas sensor 1 having the above configuration is placed in the atmosphere of the gas to be detected, the combustible gas passes through the net cap 14c of the detecting element 14 and the detecting member 15
Touching d causes an oxidation reaction to occur due to the action of the catalyst, and the heat generated during the oxidation reaction raises the temperature of the detection member 14d. Thereby, the temperature of the platinum wire in the detection member 14d also increases, and the electric resistance value of the detection element 14 increases.

The change in the electric resistance value of the sensing element 14 is
A change in voltage is extracted by a bridge circuit of the comparison element 15 and the resistors 12 and 13, amplified by the amplifier 16, and
An output signal corresponding to the concentration of the detected gas is obtained from 6 and supplied to the input port P1 of the microcomputer 2.

On the other hand, the EEPROM 3 previously stores alarm concentration aging calculation formula data relating to the gas to be detected.
It is supplied to the input port P2 of the microcomputer 2.

The counter 4 counts the accumulated elapsed time from the installation of the gas leak alarm, and this count data is supplied to the input port P3 of the microcomputer 2 as aging time count data.

The alarm density aging calculation formula data stored in the EEPROM 3 in advance is obtained as follows.

In the gas leak alarm having the above-described configuration, the sensitivity of the gas sensor 1 deteriorates as described above due to the lapse of time from the time of installation. The degree of this sensitivity degradation is
As shown in FIG. 4, a correlation is obtained between the logarithm of the number of elapsed days and the gas concentration for operating the alarm sound circuit 5A and the alarm display circuit 5B in the gas leak alarm, that is, the alarm concentration (percent). Has a linear characteristic that increases with time.

In FIG. 4, while the alarm was issued at the predetermined alarm density _A0 % at the time of installation,
Due to the sensitivity degradation of the gas sensor 1, will X1_nichinokeikajitendewakeihogaokonawarerukeihonodowa A ₁ percent,
It increases by ΔA ₁ from the predetermined alarm density A. Similarly, X2_nichikeikashitajitendewa from the installation point, the alarm concentration alarm is performed becomes A ₂ percent, .DELTA.A than a predetermined alarm concentration A
Increase by _two .

As shown in FIG. 5, the change in the alarm concentration is caused by the fact that the detection output of the gas sensor 1 for the same gas concentration is
This occurs because the sensitivity decreases with the passage of days due to deterioration in sensitivity. That is, in FIG. 5, the sensor detection output V corresponding to the predetermined alarm concentration A ₀ at the time of installation of the gas leak alarm is V ₁ at the time of the X1 day due to the sensitivity deterioration.
And decreases by ΔV ₁ . Similarly, X
When two days have elapsed, the sensor detection output becomes V ₂ ,
It decreases by ΔV ₂ .

This will be described with reference to the relationship between the gas concentration to be detected and the sensor detection power shown in FIG. As shown in FIG. 6, the sensor detection output increases in proportion to the increase in the gas concentration. For example, the characteristic curve C1 after one day has passed the characteristic curve C1 after 100 days due to the sensitivity deterioration. The curve C2 is located below the characteristic curve C1, and the characteristic curve C3 after 1000 days, for example, is located further below the characteristic curve C2. Therefore, in the change in the sensor detection output shown in FIG. 6, the sensor detection output V corresponding to the predetermined alarm density A ₀ in the characteristic curve C1 after one day has passed, the alarm density higher than the predetermined alarm density A ₀ after 100 days has passed. is achieved by a _1, also, it will be achieved at a higher alarm concentration a ₂ than the alarm concentration a ₁ at the elapsed time 1000 days.

Therefore, before installing the gas leak alarm, a long
Alarm concentration over the period, i.e., the actual alarm
By measuring the gas concentration, the alarm concentration shown in FIG.
Long term aging data is obtained. In FIG. 7, as an example,
Methane gas (C) against log of elapsed days (DAY)
H_Four), Hydrogen gas (H_Two) And isobutane gas (i-
C _FourH_Ten) Indicates the characteristics of the alarm concentration (%). FIG.
As can be seen from the characteristic diagram of FIG.
Alarm concentration A₀To rise over time
(And thus the sensitivity is degraded)
Gas, especially methane gas (CH_Four) Markedly deteriorated sensitivity
ing.

The degree of aging of the sensitivity of the alarm concentration for each gas can be correlated between the logarithm of the aging days and the alarm concentration from the characteristic diagram of FIG. 8 in which the scale of the alarm concentration is enlarged in the characteristic diagram of FIG. And the alarm density aging K
Can be derived.

Aging amount of alarm concentration of methane gas (CH ₄ ) K1 K1 (%) = 4.51 × 10 ⁻² lnY−0.137 Correlation coefficient R ² = 0. 932 (1)

Alarm concentration aging of hydrogen gas (H ₂ ) K 2 K 2 (%) = 2.35 × 10 ⁻² InY−0.093 Correlation coefficient R ² = 0. 9 (2)

Aging concentration of alarm concentration of isobutane gas (iC ₄ H ₁₀ ) K3 K3 (%) = 1.59 × 10 ⁻² lnY−0.068 Correlation coefficient R ² = 0. 913 (3)

In each of the above equations, ln is the natural logarithm, Y
Is the number of elapsed days (DAY).

As described above, the alarm concentration aging amount K (that is, K1, K2, K3) of each gas is derived as a logarithmic function of the number of elapsed days, so that the corrected alarm concentration A is obtained by the following equation. A (%) = F−K (4) where F is the actual alarm density, K is the alarm density aging (K ≧ 0), and A is the corrected alarm density.

The calculated alarm density A after correction has the same value as the predetermined alarm density A ₀ , has a characteristic shown by a dotted line in FIG. 4, and is constant regardless of the number of days. That is, in FIG. 4, the alarm concentration A _{1 at} the lapse of the X1 day is ΔA corresponding to the alarm concentration aging amount K calculated at that time.
Only ₁ is subtracted, it will be identical values and the predetermined alarm concentration A _0,
Similarly, X2_nichikeikajitendenokeihonodo A _2, only .DELTA.A ₂ corresponding to the alarm concentration secular change amount K calculated at that time is subtracted, the same value as the predetermined alarm concentration A _0.

Therefore, the above-mentioned equation (1), (2) and (3) for calculating the alarm concentration over time are stored in advance in the EEPROM 3, and the microcomputer 2 detects the gas concentration of a specific gas type with the gas sensor 1. At this time, the aging count data representing the accumulated elapsed time of the gas sensor 1 at that time, which is supplied from the counter 4, is substituted into the alarm concentration aging calculation formula for the specific gas type stored in the EEPROM 3, and the alarm at that time is obtained. The concentration aging amount K (for example, K1, K2 or K3) is calculated.

Next, the microcomputer 2 subtracts the alarm concentration aging amount K calculated as described above from the gas concentration corresponding to the sensor detection output from the gas sensor 1 at that time, and obtains the result.

Next, when the above result reaches the predetermined alarm density A ₀ , the microcomputer 2 outputs the output port P
4 outputs a drive signal to an alarm sound circuit 5A and an alarm display circuit 5B. As a result, the transistor 51 of the alarm sound circuit 5A is turned on and current flows through the buzzer 52, and an alarm sound is generated. At the same time, the transistor 61 of the alarm display circuit 5B is turned on and current flows through the LED (light emitting diode) 62.
The LED 62 emits light (for example, emits red light), and an alarm is displayed.

In this way, the aging of the alarm sensitivity from the point of installation of the gas leak alarm is compensated, and the alarm is issued at a constant alarm concentration regardless of the elapse of time. It can be performed. In addition, since the alarm is given audibly and visually, it is easy for the user to recognize.

As described above, the embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications and applications are possible.

For example, the counter 4 may use a built-in counter of the microcomputer 2.

[0049]

According to the first aspect of the present invention, the aging of the alarm sensitivity of the gas leak alarm is compensated, and an alarm is issued at a constant alarm concentration regardless of the passage of time. Life can be extended.

According to the second aspect of the present invention, the alarm concentration aging amount K is calculated based on the alarm concentration aging amount calculation formula and the count value from the aging time counting means 4, and the calculated gas concentration F is calculated from the calculated gas concentration F. By subtracting the alarm concentration aging K, the aging of the alarm sensitivity of the gas leak alarm is compensated, so that an alarm is issued at a constant alarm concentration regardless of the passage of time, and the life of the gas leak alarm is reduced. Extensions can be made.

According to the third aspect of the present invention, it is possible to obtain the alarm concentration secular change by substituting the elapsed days into the logarithmic function.

According to the fourth aspect of the present invention, since the aging of the alarm sensitivity of the gas leak alarm using the contact combustion type gas sensor is compensated, the alarm is issued at a constant alarm concentration regardless of the lapse of time. Thus, the life of the gas leak alarm can be extended.

According to the fifth aspect of the present invention, an audible and visual alarm can be issued.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a gas leak alarm according to the present invention.

FIG. 2 is an electric circuit diagram showing a gas leak alarm according to the present invention.

FIG. 3 is a schematic view showing a structure of a detection element and a comparison element of the gas sensor in FIG. 2;

FIG. 4 is a characteristic diagram of an alarm density with respect to a logarithm of elapsed days.

FIG. 5 is a characteristic diagram of a sensor detection output with respect to the logarithm of the elapsed days.

FIG. 6 is a characteristic diagram of a sensor detection output with respect to a gas concentration to be detected.

FIG. 7 is an example of actually measured data of an alarm density with respect to a logarithm of elapsed days.

FIG. 8 is a characteristic diagram obtained by enlarging the scale of the alarm density in the characteristic diagram of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Operation means 3 Storage means 4 Aging time counting means 5 Alarm means 5A Alarm sound circuit 5B Alarm display circuit

Claims (5)

[Claims] 1. A gas sensor and a calculating means for calculating a gas concentration based on the detection output of the gas sensor, alarm means for gas concentration A calculated in the computing means issues an alarm when it reaches a predetermined alarm concentration A ₀ A gas leak alarm device comprising: storage means for storing an alarm concentration aging change calculation formula for a gas type to be detected; and aging time counting means for counting the accumulated elapsed time of the gas sensor; The means calculates the alarm concentration aging amount K based on the alarm concentration aging amount calculation formula stored in the storage unit and the count value from the aging time counting unit, and calculates the alarm concentration aging amount when calculating the gas concentration. A gas leak alarm which compensates for the aging of the alarm sensitivity using the alarm concentration aging amount K. 2. A gas sensor and a calculating means for calculating a gas concentration based on the detection output of the gas sensor, alarm means for gas concentration A calculated in the computing means issues an alarm when it reaches a predetermined alarm concentration A ₀ A gas leak alarm device comprising: storage means for storing an alarm concentration aging change calculation formula for a gas type to be detected; and aging time counting means for counting the accumulated elapsed time of the gas sensor; The means calculates the alarm concentration aging amount K based on the alarm concentration aging amount calculation formula stored in the storage unit and the count value from the aging time counting unit, and calculates the alarm concentration aging amount from the calculated gas concentration F. subtracting the secular change amount K, as a result when a reaches the predetermined alarm concentration a _0, gas leakage alarm, characterized in that for driving the alarm means. 3. The gas leak alarm device according to claim 1, wherein the alarm concentration aging change calculation formula is a logarithmic function of the number of days that have elapsed since the gas leak alarm device was installed. 4. The gas sensor according to claim 1, wherein the gas sensor is a catalytic combustion type gas sensor.
Gas leak alarm according to the paragraph. 5. The gas leak alarm according to claim 1, wherein the alarm unit includes an alarm sound circuit and an alarm display circuit.