JPH0843342A - Carbonic aid gas sensor and carbonic acid gas concentration adjusting equipment and air ventilation equipment using it - Google Patents

Abstract

PURPOSE:To obtain a small-sized carbonic acid sensor with its high sensitivity and high response speed and improve the performance of carbonic acid gas concentration adjusting equipment, etc., by constituting a sintered disk by plural oxides in which a carbonic acid salt forming reaction reversible to a carbonic acid gas is generated and detecting the variation of the electrostatic capacitance or electric resistance valve due to the adsorbed carbon acid gas. CONSTITUTION:A sintered disk is formed by adding oxides in which no carbonic aid forming reaction is generated to two or more oxides. Out of oxides of alkali earth metals Fe, Co, Ni, Cu, Zn, etc., in which the carbonic acid salt forming reaction reversible to carbonic acid gas is generated. And, the variation in current due to the adsorption of carbonic acid gas is fetched by means of an electrode and a lead wire provided on both surfaces of the disk. This carbonic acid gas sensor is installed in a gas sensing part 5, the carbonic acid gas concentration in a box 4 is measured, for example, when volume % is more than 10, a carbonic acid gas detection circuit 7 is actuated, a control part 11 opens an air flow-in valve 12, the carbonic acid gas concentration in the box 4 is maintained constant. This small-sized, high-performance sensor is inexpensive and maintenance is easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide sensor for measuring and controlling carbon dioxide concentration used in environmental hygiene, horticulture, disaster prevention equipment, and production equipment, and carbon dioxide concentration adjusting equipment and ventilation equipment using the same. Is.

[0002]

2. Description of the Related Art In recent years, as a carbon dioxide sensor, a detection method using infrared rays, a method using an electrolytic solution, a method using heat conduction, a method using NaCO ₃ as an electrode and an alkali ion conductive solid electrolyte such as NASICON, K ₂ CO
_There are a method of using a CO ₃ ^2- ion conductor such as ₃ and a method of using a resistance value of hydroxyapatite, a method of using a resistance value of a perovskite compound or a method of utilizing a change in capacitance by mixing with another oxide.

Further, a growing facility for flowers, vegetables, fruits and the like using a carbon dioxide detecting device by infrared rays has been put into practical use.

[0004]

However, the conventional carbon dioxide gas sensor is difficult to maintain.
There is a problem that the detection sensitivity of carbon dioxide concentration is low and the response speed at the time of carbon dioxide detection is slow.

Further, in the equipment using the conventional carbon dioxide gas sensor, the equipment is large due to the large size of the carbon dioxide gas sensor, the manufacturing cost is high, the carbon dioxide gas sensor itself has a poor detection sensitivity of the carbon dioxide gas concentration, and the response speed is slow. That is, since the carbon dioxide gas sensor is large in size, it is impossible to install a plurality of carbon dioxide gas sensors in the equipment, so that the carbon dioxide concentration in the equipment cannot be accurately controlled.

The present invention solves the above-mentioned conventional problems, and is a small-sized carbon dioxide sensor having high detection sensitivity of carbon dioxide, high response speed, and easy maintenance, and carbon dioxide concentration adjusting equipment using the same. , For the purpose of providing ventilation equipment.

[0007]

[Means for Solving the Problems] To achieve this object
The carbon dioxide sensor according to claim 1 of the present invention is
Disk, electrodes formed on both sides of the sintered disk,
A carbon dioxide gas sensor having a terminal portion fixed to the electrode
The sintered disk is carbon dioxide and reversible charcoal.
Formed from a composition of two or more oxides that undergo an acid salt formation reaction
It has a configuration that is configured. Carbon dioxide according to claim 2
The sensor consists of a sintered disc and both sides of the sintered disc.
The formed electrode and the terminal portion fixed to the electrode,
A carbon dioxide sensor having, wherein the sintered disk is charcoal.
Two or more oxidations that cause a reversible carbonate formation reaction with acid gas
And a composition of a non-reactive oxide.
It has a structure. Carbon dioxide gas according to claim 3.
The sensor is in any one of claim 1 or claim 2.
Acid that causes a reversible carbonate formation reaction with the carbon dioxide gas.
Oxides of alkaline earth metals, such as Fe, Co, Ni,
Oxide of Cu, Zn, Oxidation of Y, Zr, Pb, Bi
Oxides of lanthanide elements with atomic numbers 57 to 72
It has a configuration that is a little off. Carbon dioxide according to claim 4.
The scan sensor is any one of claims 1 to 3.
And the electrode is one of Au, Pt, and RuO, or
It has a composition that is a mixture of these. Claim 5
The carbon dioxide sensor of is a carbonate form reversible with the carbon dioxide.
Al oxide is the oxide that does not cause the reaction₂ O ₃ , SiO₂ Either
It has a constitution which is one kind or a mixture thereof. Contract
Carbon dioxide using the carbon dioxide sensor of the present invention according to claim 6
The concentration adjusting facility detects the carbon dioxide concentration.
Carbon dioxide provided with the carbon dioxide sensor according to any one of 5
Gas sensing unit and carbon dioxide gas for adjusting the flow rate of carbon dioxide
Inlet valve and an air inlet valve that regulates the flow rate of air
And the carbon dioxide detection times for detecting the upper and lower limits of the carbon dioxide concentration.
Of the passage and the carbon dioxide gas inflow valve and the air inflow valve
A control unit having a control unit for controlling each opening and closing
And has a configuration including. The present invention according to claim 7
The ventilation equipment using the carbon dioxide sensor of
The method according to any one of claims 1 to 5 for detecting
The carbon dioxide sensing unit equipped with the carbon dioxide sensor of
Carbon dioxide that detects the upper limit of carbon dioxide concentration with a fan
Rotation or ON / OF of the detection circuit and the ventilation fan
And a control unit having a control circuit for controlling F.
It has the above configuration. As the carbon dioxide concentration adjusting equipment
, Plant growing equipment, storage equipment for fresh food, fresh food
There are transportation facilities such as.

The carbon dioxide gas sensing section surrounds the carbon dioxide gas sensor with a heater and is heated to a temperature at which an oxide of the carbon dioxide gas sensor causes a reversible carbonate formation reaction with carbon dioxide gas.

[0009]

With this configuration, the carbon dioxide gas is detected by detecting the carbon dioxide gas adsorbed at the interface between the oxide and another oxide that causes a reversible carbonate formation reaction with the carbon dioxide gas of the sintered disk. Occurs, and the electron density and the ion density involved in the electric conduction at the interface are changed, and the electrostatic capacitance value and the electric resistance value of the entire sintered disk are changed.

In order to optimize this change, an oxide that does not cause a reversible carbonate formation reaction with carbon dioxide gas is added to the sintered disk to optimize the impedance, thereby obtaining the capacitance value, the electric The resistance value can be optimized to detect carbon dioxide.

With this configuration, the carbon dioxide gas concentration adjusting equipment using the carbon dioxide gas sensor of the present invention can accurately detect the carbon dioxide gas concentration in the box by the carbon dioxide gas sensor of the present invention, and the carbon dioxide gas inflow is immediately supplied by the signal of the control unit. By adjusting the valve and the air inflow valve, the carbon dioxide concentration in the box can be precisely controlled.

With this configuration, the ventilation equipment of the present invention is
With the carbon dioxide sensor of the present invention, the concentration of carbon dioxide in the box can be accurately detected, and the ventilation fan can be operated by the signal of the control unit to ventilate the carbon dioxide in the box.

[0013]

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

(Examples 1 to 8 Comparative Examples 1 and 2) FIG. 1 is a perspective view of a carbon dioxide sensor according to an example of the present invention.

In FIG. 1, 1 is a sintered disk, 2 is an electrode, and 3 is a terminal portion. The materials 1 and 2 described in (Table 1) were mixed in the same molar ratio to form a disk shape (diameter 10 mm,
After being formed into a thickness of 0.4 mm), it was fired at 500 ° C. to 800 ° C. in an electric furnace to obtain a sintered disk 1. After the electrodes 2 were formed of Ag on both sides of the sintered disk 1, the terminal portion 3 was formed by using Pt that withstands an operating temperature and has a low electric resistance.

The carbon dioxide gas sensor is heated to 200 ° C.
The electrical resistance value and the capacitance were measured by a two-terminal method using an impedance analyzer 4192A manufactured by YHP Co. while being heated to 800 ° C. The frequency at this time is 0.1
The range was 1000 Hz, and dry air and carbon dioxide gas diluted with dry air were used as the sample gas. The capacitance value measured with the dry air introduced is used as a reference, and the ratio of the capacitance value measured with the dry air adjusted to a carbonic acid concentration of 2% and the reference is taken as the sensitivity, The results of capacitance sensitivity are shown in (Table 1). The electric resistance value was also measured for sensitivity by the same method as described above, and the results are shown in (Table 1).

[0017]

[Table 1]

In this example, when the carbon dioxide concentration was 2%, the response time to reach 80% when the equilibrium was reached to 100% was 20 seconds for both capacitance and electric resistance. The recovery response time when the carbon dioxide atmosphere was changed to dry air was about 3 minutes.

As is clear from (Table 1), the carbon dioxide sensor according to the present embodiment has an excellent effect that the sensitivity to carbon dioxide is very high and the response sensitivity is sufficiently fast.

In Comparative Examples 1 and 2 containing only one kind of carbonate-forming oxide, the measured values did not change even when carbon dioxide gas was introduced.

(Examples 9, 10 and 11) Materials 1, 2, and 3 described in (Table 2) were molded into a sintered disk so that the molar ratio was 60: 5: 35, and thereafter, performed. A carbon dioxide sensor was molded in the same manner as in Example 1, and the capacitance sensitivity and resistance value sensitivity were measured.

[0022]

[Table 2]

In order to increase the capacitance sensitivity and the electric resistance value sensitivity, it is necessary that the impedance values are appropriate, and the electric resistance value and the phase angle must be optimized.

Even when SiO ₂ was used instead of Al ₂ O _3, the same results as in (Table 2) were obtained. As is clear from this (Table 2), it was found that the carbon dioxide sensor according to the present example has an excellent effect that the sensitivity to carbon dioxide is very high and the response sensitivity is sufficiently fast.

(Example 12) (Table 3) shows the carbonate decomposition temperature and the sensitivity development temperature of the samples described in Examples 1 and 9. Example 12 is a carbonate decomposition temperature and a sensitivity expression temperature of a carbon dioxide sensor prepared in the same manner as in Example 9 except that PbO, BaO and Al ₂ O ₃ are used as raw materials.

[0026]

[Table 3]

The carbonate decomposition temperature was determined from the graph of measured temperature and sensitivity from the intersection of the extension line of the sensitivity curve and the measured temperature axis.

As is clear from this (Table 3), the decomposition temperature of the carbonate and the temperature at which the sensitivity develops are the same, and the sensitivity does not appear in the metal oxide having no carbonate. The formation of carbonate by the reaction with various carbon dioxides plays an important role in the appearance of sensitivity. According to the gravimetric analysis, desorption of carbon dioxide occurs even at a temperature below the decomposition temperature of carbonate, and some sensitivity is shown in the measurement of capacitance value and electric resistance value.

From the above, it can be said that the carbon dioxide gas sensor of this embodiment is effective when used at a carbonate decomposition temperature or higher.

(Examples 13 to 15 Comparative Example 3) Example 1
The sample of CuO and CaO described in 1.
A carbon dioxide gas sensor was molded in the same manner as in Example 1 except that t and RuO were used. As electrode materials, Ag paste, Au paste, Pt manufactured by Tanaka Kikinzoku International Co., Ltd.
Using paste and RuO paste, each paste was applied to both surfaces of each sintered disk in a circular shape having a diameter of 6 mm, and then heat-treated to form electrodes.

A carbon dioxide sensor was placed in a heater at 600 ° C.
It was left for 30 days while flowing 500 cc / min of air. The rate of change in capacitance sensitivity after leaving the carbon dioxide sensor is shown in (Table 4).

[0032]

[Table 4]

As is apparent from this (Table 4), Au, Pt, and RuO are suitable as the electrode material, and Ag is not suitable.

(Embodiment 16) FIG. 2 is a structural diagram of ventilation equipment in an embodiment of the present invention.

In FIG. 2, 4 is a box and 5 is 2 mm ×
A carbon dioxide sensing part in which a 1 mm × 0.4 mm carbon dioxide sensor is covered with a heater, 6 is a ventilation fan, 7 is a carbon dioxide detection circuit that generates a signal at a carbon dioxide concentration of 2%, and 8 is for ventilation. A control circuit of the fan 6, 9 is a carbon dioxide gas inflow valve for adjusting the flow rate of carbon dioxide, and 10 is an infrared gas measuring instrument for measuring the carbon dioxide concentration. The operation of the ventilation equipment configured as described above will be described with reference to FIG. First, when the carbon dioxide gas inflow valve 9 is opened and closed to increase the carbon dioxide gas concentration in the box 4, the carbon dioxide gas sensing unit 5 detects the carbon dioxide gas concentration, and when the carbon dioxide gas concentration becomes 2%, the carbon dioxide gas detection circuit 7 is activated. Operate.
When this signal is generated, the control circuit 8 generates a signal, the ventilation fan 6 is operated, and the carbon dioxide concentration in the box 4 is lowered. When the carbon dioxide gas concentration in the box 4 was measured by the infrared gas measuring device 10, it was found that the carbon dioxide gas concentration in the box 4 was around 2%. The carbon dioxide concentration at which the carbon dioxide detection circuit 7 operates can be easily changed by changing the capacitance value or the electric resistance value of the carbon dioxide sensor.

(Embodiment 17) FIG. 3 is a block diagram of a plant growing facility in an embodiment of the present invention.

In FIG. 3, 5 is a carbon dioxide sensing unit, 7 is a carbon dioxide detection circuit, 9 is a carbon dioxide inflow valve for adjusting the flow rate of carbon dioxide, and 11 is a carbon dioxide inflow valve 9.
And a control unit for controlling the air inflow valve 12,
Is an air inflow valve for adjusting the flow rate of air, and 13 is a greenhouse.

The operation of the plant growing facility constructed as described above will be described with reference to FIG. First, the carbon dioxide gas concentration in the greenhouse 13 is measured by the carbon dioxide gas sensing unit 5, and when it is 750 ppm or more, the carbon dioxide gas detection circuit 7 is activated and the control unit 11 opens the air inflow valve 12. When the carbon dioxide gas concentration in the vinyl house 13 is 750 ppm or less, the carbon dioxide gas detection circuit 7 does not operate, and the control unit 11 opens the carbon dioxide gas inflow valve 9.

Spinach was grown in the vinyl house 13. The average weight of the cultivated spinach was 40 g, and the average weight of the cultivated spinach was 25 g. The amount of spinach grown in the plant growing equipment of this example increased by 60% or more as compared with the spinach grown by the conventional growing method.

(Embodiment 18) FIG. 4 is a block diagram of storage equipment in an embodiment of the present invention.

In FIG. 4, 5 is a carbon dioxide sensing unit, 7 is a carbon dioxide detection circuit, 9 is a carbon dioxide inflow valve for adjusting the flow rate of carbon dioxide, and 11 is a carbon dioxide inflow valve 9.
And an air inflow valve 12 for controlling the opening and closing of the air inflow valve 12, 12 for adjusting the flow rate of air, and 4 a box.

The operation of the storage facility constructed as above will be described with reference to FIG. First, the carbon dioxide gas concentration in the box 4 is measured by the carbon dioxide gas sensing unit 5, and when it is 10% by volume or more, the carbon dioxide gas detection circuit 7 is activated and the air inlet valve 12 is opened by the control unit 11. When the carbon dioxide concentration in the box 4 is 10% by volume or less, the carbon dioxide detection circuit 7 does not operate, and the control unit 11 opens the carbon dioxide inflow valve 9.

Broccoli was stored in Box 4. The broccoli stored in the storage facility of this example did not discolor for 8 days, but the broccoli stored in the conventional storage facility did not discolor for only 2 days.

The storage facility of this embodiment can be used for storing fresh foods such as plants and fish other than broccoli.
The storage equipment of this embodiment can also be used as the above-mentioned transportation equipment for fresh food.

[0045]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, by using two or more oxides which cause a reversible carbonate formation reaction with carbon dioxide in the sintered disk, the size is extremely small and the sensitivity to carbon dioxide is high. The response speed to carbon dioxide is fast,
An excellent carbon dioxide sensor that is easy to maintain can be realized.

The carbon dioxide concentration adjusting facility and the ventilation facility using the carbon dioxide sensor having the excellent characteristics of the present invention are small in size, the carbon dioxide concentration in the facility can be controlled with high accuracy, and the maintenance is easy. Also, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a carbon dioxide sensor according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of ventilation equipment according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a plant growing facility according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a storage facility according to an embodiment of the present invention.

[Explanation of symbols]

 1 Sintered disc 2 Electrode 3 Terminal part 4 Box 5 Carbon dioxide sensing part 6 Ventilation fan 7 Carbon dioxide detection circuit 8 Control circuit 9 Carbon dioxide inflow valve 10 Infrared gas measuring instrument 11 Control part 12 Air inflow valve 13 Vinyl house

Claims (7)

[Claims] 1. A sintered disk, electrodes formed on both surfaces of the sintered disk, and a terminal portion fixed to the electrode.
2. A carbon dioxide gas sensor having: a carbon dioxide gas sensor, wherein the sintered disk is formed of a composition of two or more oxides that cause a reversible carbonate formation reaction with carbon dioxide. 2. A sintered disk, electrodes formed on both sides of the sintered disk, and terminal portions fixed to the electrodes.
A carbon dioxide gas sensor having: a sintered disc formed from a composition of two or more oxides that cause a reversible carbonate formation reaction with carbon dioxide and an oxide that does not react. Carbon dioxide sensor characterized by. 3. The oxide that causes a reversible carbonate formation reaction with carbon dioxide is an oxide of an alkaline earth metal, Fe or C.
O, Ni, Cu, Zn, oxides, Y, Zr, Pb, B
3. The carbon dioxide sensor according to claim 1, wherein the carbon dioxide sensor is any one of an oxide of i and an oxide of a lanthanide element having an atomic number of 57 to 72. 4. The electrode is any one of Au, Pt, and RuO.
2. A seed or a mixture thereof.
The carbon dioxide sensor according to any one of claims 1 to 3. 5. A method for reversible carbonate formation reaction with carbon dioxide
The oxide that does not occur is Al ₂ O₃ , SiO₂ Any one or
Is a mixture thereof.
Carbon dioxide sensor. 6. A carbon dioxide gas sensing unit equipped with the carbon dioxide gas sensor according to claim 1, which detects a carbon dioxide gas concentration, and a carbon dioxide gas inflow valve for adjusting the flow rate of carbon dioxide gas. A control unit including an air inflow valve for adjusting the flow rate of air, a carbon dioxide detection circuit for detecting upper and lower limits of carbon dioxide concentration, and a control unit for controlling opening / closing of each of the carbon dioxide inflow valve and the air inflow valve. And a carbon dioxide concentration adjusting facility. 7. A carbon dioxide sensing part equipped with the carbon dioxide sensor according to claim 1, which detects the carbon dioxide concentration, a ventilation fan, and an upper limit of the carbon dioxide concentration. A ventilation facility comprising: a carbon dioxide detection circuit; and a control unit having a control circuit for controlling rotation or ON / OFF of the ventilation fan.