JPH08182914A - Controller for air purifier - Google Patents

Abstract

PURPOSE: To perform operation control suitable for property of human sense of smell in a controller by which an air purifier is controlled based on the value of output of a gas sensor by using, as a gas sensor, the one whose sensibility represented by the rate of change in resistance values in air and in gaseous ammonia is specified. CONSTITUTION: In a controller for an air purifier performing the startup and shutdown control of an air purifier based on the value of an output of a gas sensor S, a gas sensor S whose sensibility represented by the rate of change in resistance values in air and in 500ppm gaseous ammonia during operation of the air purifier shows >=5 is used. For such a gas sensor S, a catalytic sensitizing semiconductor gas sensor comprising a gas sensitive body consisting essentially of an oxidizing gas or indium oxide and a platinum catalyst to which molybdenum or its compound is added is used. As the gas sensitive body, oxidizing gas or indium oxide sintered or formed into a film or the like is exemplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an air purifier using a gas sensor, and more particularly to a control device for an air purifier using a gas sensor capable of detecting ammonia with high sensitivity.

[0002]

2. Description of the Related Art In recent years, with the increasing interest in clean and comfortable living spaces, for example, air purifiers for cleaning dirt in the air in the passenger compartment or in the passenger compartment caused by cigarette smoke have begun to spread rapidly. Accordingly, various proposals have been made for a control device for automating the start and stop of the air cleaner. As an example, an air purifier is equipped with a catalyst-sensitized semiconductor gas sensor that is compact, easy to maintain, and has a long life, and a device that automatically controls the start and stop of the cleaning function based on the output of this gas sensor is used. is there.

Originally, in this type of apparatus, among substances contained in cigarette smoke, substances which can be purified by an air purifier, for example, malodorous substances such as ammonia, are detected by a gas sensor, and the human sense of smell is detected. It is desired to perform rational control that matches the characteristics. However, this control method has not been put to practical use because there is no catalyst-sensitized semiconductor gas sensor that has sufficient sensitivity to ammonia. In addition to ammonia, acetaldehyde exists as a substance that can be purified by an air purifier among the foul-smelling substances contained in cigarette smoke, and a method of detecting this acetaldehyde with a gas sensor and controlling the air purifier is also available. Conceivable. However, since acetaldehyde exists in an extremely small amount as compared with ammonia, this method is not practical either.

Therefore, at present, a catalyst-sensitized semiconductor gas sensor having sensitivity to other coexisting gases contained in cigarette smoke, such as carbon monoxide and hydrogen, is used, and the air purifier is based on the output value of the gas sensor. Control the start and stop. However, in such a device, since the air purifier can hardly purify gas components such as carbon monoxide and hydrogen, the output of the gas sensor does not decrease unless the gas components are forcibly removed by a ventilation fan or the like,
There is a drawback that stop control is very difficult.

As a solution to such a problem,
For example, Japanese Examined Patent Publication No. 6-7897 discloses that saturation detection means for detecting that the change width of the gas sensor output is less than or equal to a predetermined value, and that the output of the gas sensor has decreased during the operation of the air cleaner. Disclosed is a control device for an air purifier, which is provided with an output drop detecting means for detecting, and which is configured to stop the air purifier at the output of either the saturation detecting means or the output drop detecting means. FIG. 5 is a control flowchart of the microcomputer shown in the embodiment of the above publication. As can be seen from this, after the saturation is detected, timer means for continuing the operation of the air cleaner for a predetermined time is provided to control the air cleaner.

[0006]

However, in such a control device, the airtightness of the room in which the air cleaner is used, the difference in the cleaning capacity depending on the model of the air cleaner, the deterioration of the cleaning capacity due to the deterioration of the filter, etc. However, there was a problem of insufficient purification or excessive purification because it was not possible to deal with the changes due to time. Further, there is also a problem that the cost is increased because the control is very complicated and requires a high-performance microcomputer.

The present invention has been made on the basis of the above points, and an object thereof is to use a gas sensor capable of detecting ammonia with high sensitivity.
An object of the present invention is to provide a control device of an air purifier capable of rationally performing start control and stop control of the air purifier in accordance with human olfactory characteristics.

[0008]

In order to achieve the above object, a control device for an air purifier according to the present invention controls an air purifier based on the output value of a gas sensor for starting and stopping the air purifier. In the apparatus, as the gas sensor, a gas sensor having a sensitivity of 5 or more represented by a change rate of a resistance value in air and in an atmosphere of 500 ppm of ammonia when the air cleaner is operating is used. .

When a gas sensor having a sensitivity of less than 5 expressed by the rate of change of resistance value in air and in the atmosphere of 500 ppm ammonia during operation of the air cleaner has a small change in resistance value, it is used in a detection circuit. In addition, the voltage change obtained as the output becomes minute. For this reason, the resistance value of the gas sensor is easily affected by environmental changes such as temperature and humidity, and the air cleaner may malfunction. Further, an amplifier circuit or the like may be added to obtain a large change in the output voltage of the detection circuit, but the circuit becomes complicated and the cost increases.

A gas sensor having tin oxide or indium oxide as a main component is used as a gas sensor having a sensitivity of 5 or more, which is represented by the rate of change of resistance value in air and in the atmosphere of 500 ppm of ammonia when the air cleaner is operating. A catalyst-sensitized semiconductor gas sensor composed of a body and a platinum catalyst may have molybdenum or a molybdenum compound added thereto. At this time, the mode of the gas sensitizer is not particularly limited, and examples thereof include those obtained by sintering tin oxide or indium oxide, and those obtained by forming tin oxide or indium oxide into a film shape (thick film or thin film). To be When the tin oxide thin film or the indium oxide thin film is used as the gas sensitive material, a gas sensor having high sensitivity to ammonia can be obtained.

As a method for forming the gas sensitive body, any conventionally known means may be used as it is without any particular limitation. For example, when forming a thin-film gas sensitive body, a method such as a vacuum vapor deposition method or a sputtering method can be used. At this time, the tin oxide thin film or the indium oxide thin film is preferably formed so that the mass film thickness is 5000 Å or less. If the mass film thickness exceeds 5000 Å, the resistance value of the sensor element decreases and the sensitivity decreases.

The method of adding the platinum catalyst may be any known method, and is not particularly limited. For example, when the platinum catalyst is added to the thin film gas sensor, a method such as a vacuum vapor deposition method or a sputtering method can be used. The addition amount at this time is
It is preferable to form it so that the mass film thickness is 100 Å or less. If the mass film thickness exceeds 100Å, the gas sensitive body itself cannot maintain the properties of semiconductor and the sensitivity is lowered.

By adding molybdenum or a molybdenum compound to the catalyst-sensitized semiconductor gas sensor having the above structure, a gas sensor having high sensitivity to ammonia can be obtained. As the molybdenum compound, oxides (MoO ₃ , MoO _2, etc.), halides, sulfides (Mo ₂ S ₃ , MoS _2, etc.), nitrides, silicides (Mo).
₅ Si ₃ , MoSi ₂ , Mo ₃ Si, etc.) and the like. The method of adding these is not particularly limited, but when the gas sensitizer constituting the catalyst-sensitized semiconductor gas sensor is a thin film, a method such as a vacuum deposition method or a sputtering method can be used.

At this time, the amount of molybdenum or a molybdenum compound added is arbitrary as long as it does not affect the improvement of the sensitivity to ammonia, but the mass film thickness is preferably 10,000 Å or less, more preferably 2000 Å or less. It is desirable to do. Mass film thickness is 10
If it exceeds 000Å, the responsiveness to ammonia is lowered, and the material cost and the addition time are lengthened, resulting in an increase in manufacturing cost. If the mass film thickness exceeds 2000Å, the manufacturing cost will increase.

[0015]

The controller of the air purifier of the present invention uses a gas sensor capable of highly sensitively detecting ammonia, which is a typical malodorous substance contained in cigarette smoke, to start and stop the air purifier. Is to control. Ammonia is a substance that is more easily purified by an air purifier than carbon monoxide or hydrogen, so its odor is also removed together with the purification by the air purifier. Therefore, if it is configured to detect this ammonia and control the air purifier,
It is possible to perform rational control that matches human olfactory characteristics without using a special component such as a timer.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a detection circuit diagram of a control device for an air cleaner according to this embodiment. In the figure, reference symbol S is a gas sensor, reference symbol H is a heater, reference symbol Vc is a circuit voltage, and reference symbol Vr is a load resistance, which are connected in series with the gas sensor S. The potential difference across the load resistance Vr is taken out as the output voltage Vout, and the output voltage Vout can be expressed by the following equation, where Rs is the resistance value of the gas sensor S. Vout = Vc · Vr / (Rs + Vr)

Here, in FIG. 1, the resistance value of Vc = 5V and Vr is 1.3 when the value of Vout when the cigarette is not burned.
It is sealed with a detection circuit adjusted to V.
3 cigarettes in a tatami room [made by Japan Tobacco Inc.,
Commodity name: Mild Seven] were sequentially burned, and then the air purifier was operated. FIG. 2 is a diagram showing the time-output characteristic of the value detected by the gas sensor at this time. (1) in the figure
Shows the present example, and (2) shows the comparative example.

In this embodiment, as the gas sensor S, a catalyst-sensitized semiconductor gas sensor consisting of a gas sensitizer made of a tin oxide thin film having a mass film thickness of 150 Å and a platinum catalyst having a mass film thickness of 20 Å is used. A structure having molybdenum oxide added was used. In addition, when the air cleaner of this gas sensor is operating, 500 pp of ammonia in the air and ammonia
The sensitivity represented by the rate of change of resistance value in m was about 10.

In the comparative example, as the gas sensor S, a catalyst-sensitized semiconductor gas sensor [manufactured by Figaro Giken Co., Ltd., trade name: TGS 800] mounted on a commercially available air cleaner was used. The sensitivity of this gas sensor, which is represented by the rate of change in resistance value in air and in the atmosphere of 500 ppm of ammonia, was only about 3 when the air cleaner was operating.

According to the time-output characteristic diagram shown in FIG.
In both the present example (1) and the comparative example (2), the output of the gas sensor increased with the combustion of the cigarette, and almost no change was observed. However, when the cigarette burns and the air purifier operates, the output of this example (1) decreases with time, whereas the output of the comparative example (2) almost decreases after 30 minutes. I haven't.

Next, an example of the control operation of the air cleaner using the output value Vout detected from the detection circuit shown in FIG. 1 will be described with reference to FIGS. 3 and 4. FIG. 3 is a control flowchart showing an example of the control operation of the air purifier. FIG. 4A is a graph showing the change in the output value of Vout when the concentration of cigarette smoke is changed so that it can be confirmed that the flowchart shown in FIG. 3 all works. 4) is an operation diagram showing an operation change of Fan of the air purifier controlled by the flowchart of FIG. 3 according to the change of FIG. 4 (a).

[0023] Here, in the drawing _{V L,} is V M, _{V H} in weak, for adjusting the operation of the air purifier Fan, a predetermined value corresponding to the intensity, set in the output range of the output Vout Is the value to do. This predetermined value is preferably set as equal difference or equal ratio. Further, the coefficients of a, b and c are empirically determined constants.

First, the minimum value of the output Vout in a predetermined period is stored as the reference value M, and the contamination detection is determined by comparing the output Vout with the reference value M. Output Vout is
If it is larger than the reference value M, it is detected as contamination and the output Vou
The t is compared with the predetermined value V _L, and in other cases, the loop is rotated again. When the output Vout is larger than the predetermined value V _L , the air purifier is made to operate weakly, and in other cases, the loop is turned again. Output V during weak driving
When out is larger than the predetermined value V _M , the air cleaner is operated in the middle. Otherwise, perform the comparison of the output Vout and a predetermined value aV _L, the output Vout is, when a predetermined value aV _L smaller than back to reading the reference values M by off the fan of the air cleaner, in other cases back to the comparison of the output Vout and a predetermined value V _M. During mid-running operation, the output Vout is, when greater than the predetermined value V _H is strongly operated air purifier. Otherwise, perform the comparison of the output Vout and a predetermined value bV _M, the output Vout may perform a comparison with a predetermined value bV _M smaller case again a predetermined value V _H, In other cases Output V
Returning to the comparison between out and the predetermined value V _H. When the output Vout is smaller than the predetermined value cV _H during the strong driving operation, the fan of the air purifier is returned to the middle operation,
In other cases back to the comparison between the output Vout and a predetermined value cR _H.

In the above embodiment, the gas sensor used was a tin oxide thin film as a gas sensor, but a tin oxide sintered body was used as a gas sensor, or an indium oxide thin film or indium oxide burned. The unit may be a gas sensitive body.

[0026]

As described in detail above, according to the present invention, in a control device for an air cleaner using a gas sensor, ammonia, which is a typical malodorous substance contained in cigarette smoke, is used as a gas sensor forming a detection circuit. By using a material that can be detected with high sensitivity, rational control that matches human olfactory characteristics has become possible. Further, this eliminates the need for the conventional control using a special component such as a timer, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a detection circuit diagram of a control device for an air cleaner according to the present embodiment.

FIG. 2 is a time-output characteristic diagram of gas sensors in the present example and the comparative example.

FIG. 3 is a control flowchart showing an example of a control operation of an air cleaner using the gas sensor according to the present embodiment.

FIG. 4 is a graph showing the changes in the output value of Vout when the concentration of cigarette smoke is changed, so that it can be confirmed that the flow chart shown in FIG. 3 all works. , (B) are operation diagrams showing the operation change of Fan of the air purifier controlled with the change of (a).

FIG. 5 is a control flowchart of a microcomputer in a control circuit of a conventional air cleaner.

[Explanation of symbols]

 S ... Gas sensor Rs ... Gas sensor resistance value H ... Heater Vc ... Circuit voltage Vr ... Load resistance Vout ... Output voltage

Claims (2)

[Claims] 1. A controller for an air purifier that performs start control and stop control of the air purifier based on an output value of a gas sensor, wherein the gas sensor is air and ammonia 500 ppm in air during operation of the air purifier. A control device for an air purifier, which uses a gas sensor having a sensitivity of 5 or more represented by the rate of change of resistance value in 1. 2. The air cleaner control device according to claim 1, wherein the gas sensor is a catalyst-sensitized semiconductor gas sensor including a gas sensor containing tin oxide or indium oxide as a main component and a platinum catalyst. An air purifier control device comprising molybdenum or a molybdenum compound added thereto.