JPH0729021B2 - Air purifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air cleaner, and more particularly to an air cleaner having a smoke (gas) detection circuit suitable for automatic operation.

[Conventional technology]

Conventionally, a semiconductor gas sensor has been used as a smoke detector for cigarettes and the like, and is discussed, for example, in Practical Manual for Detectors, pages 638 to 644, published by the New Technology Development Center on September 20, 1976. That is, the gas sensor is a sintered body containing semiconductor SnO ₂ as a main component, and has a heating heater coil that also serves as an electrode and is incorporated inside.
In a clean atmosphere, a constant resistance value is maintained, so a constant current flows in the circuit.

When a reducing gas such as hydrogen or carbon monoxide comes into contact with the sensor, the resistance value of the sensor decreases in accordance with the gas concentration, so that the change appears as a voltage change across the load resistance R _L. Is shown in. By the way, since the above-mentioned sensor is generally affected by temperature, a temperature compensating circuit is added as disclosed in, for example, Japanese Patent Laid-Open No. 60-236054.

However, when such a sensor is used in an air purifying device for an automobile, it is necessary to have a stable device that adapts not only to the influence of only the temperature but also to various environmental conditions described later and does not malfunction.

[Problems to be solved by the invention]

The commonly used gas sensor as a smoke detector described above has a detection sensitivity that changes with changes in temperature and humidity. Specifically, the resistance value of the gas sensor itself changes according to temperature and humidity, and the resistance value is small at high temperature and high humidity, and becomes large at low temperature and low humidity.

In order to solve this problem, for example, a temperature compensating circuit is added to stabilize the detection sensitivity.

When such a sensor is applied to an air cleaning apparatus for an automobile, (1) fluctuation in detection sensitivity immediately after starting energization after being left unenergized for a long time (temporarily large resistance value of gas sensor).

(2) Malfunction due to the particles filling the interior of the vehicle when using an air freshener or deodorant.

(3) There is a problem that the detection sensitivity changes (gas sensor resistance value change) due to a sudden change in the vehicle interior atmosphere temperature due to opening and closing of the door.

An object of the present invention is to solve the above problems and to provide an air purifying device with high operational reliability.

[Means for solving problems]

To achieve the above object, the present invention provides a gas detection element for detecting a gas concentration in air, a reference signal circuit for outputting a reference signal for gas detection, a detection signal for the gas detection element, and the reference signal. The present invention is directed to an air purifying device that includes a comparison circuit that compares a reference signal of the circuit with the output signal of the comparison circuit.

Then, the detection signal of the gas detection element is input to one input end of the comparison circuit via a voltage dividing circuit, and the detection signal of the gas detection element is delayed by a time delay composed of a series circuit of a first resistor and a capacitor. A circuit and a series circuit of a second resistor and a diode are configured to be input to the other input end of the comparison circuit via a rapid charging circuit in which the first resistor is connected in parallel to the first resistor. Is.

[Action]

As described above, according to the present invention, the sensitivity of the comparison circuit can be appropriately set by the voltage dividing circuit. Further, since the quick charging circuit is provided, the detection sensitivity of the gas detection element can be quickly returned to the original sensitive state even when the atmosphere suddenly changes by temporarily opening a window or a door. Furthermore, by providing a time delay circuit, it is possible to eliminate the effects of changes in temperature, humidity, etc. and the effects of the use of fragrances and the like. As a result, an air purifier with high operational reliability can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Reference numeral 10 denotes a constant voltage power supply, which is a circuit that receives power supply from the battery of the vehicle through the key switch, for example, from the accessory position, and supplies a stabilized constant voltage (= V _C ) to the output side. 11
Is a semiconductor gas sensor, which is composed of a heater 11a and an electrode 11a, the heater 11a receives power from a constant voltage power source 10 to generate heat, one of the electrodes 11b is connected to Vc, the other is connected to a resistor 12, and a resistor 12 The other end is grounded. Assuming that the middle point of the electrode 11b of the gas sensor 11 and the resistor 12 is P, an impedance matching circuit (commonly called voltage follower) composed of an operational amplifier from the P point.
13 is provided, and from the voltage follower output, one is a time delay circuit connected to the constant voltage power source 10 with a resistor 15 and a capacitor 14, the other is a quick charge circuit connected to the capacitor 14 via a resistor 17 and a diode 16, and the other one. Is connected to a voltage divider circuit which is grounded via resistors 18 and 19. Next capacitor
If the connection point between 14 and the resistor 15 is Q and the connection point between the resistors 18 and 19 is R, a voltage comparator 20 having two inputs at the Q point and the R point is provided,
The output of the comparator 20 is connected to the input of the monostable multivibrator 22.

When the multivibrator 22 receives a trigger, for example, the resistance 2
4. Output a single pulse for the pulse length determined by the capacitor 23. Reference numeral 28 is a blower motor of the air purifier, which receives power supply from the battery voltage V _B and is grounded via the limiting resistor 27. The transistor 26 connected in parallel with the resistor 27 is controlled by the output of the multivibrator 22, whereby the blower motor 28 is controlled in rotation.

The operation of the apparatus having the above configuration will be described below.

This device is installed on the ceiling or Riyashi Elf in the passenger compartment and operates mainly during engine operation.When the heater 11a of the gas sensor 11 is energized, the electrode 11b is activated, and the gas sensor 11 emits a combustible gas such as hydrogen or hydrogen. When carbon oxide, propane, alcohol-based, benzol-based, or the like comes into contact, it reacts with them, and the resistance value of the electrode 11b decreases.
By the way, it is known that cigarette smoke contains carbon monoxide, and the gas sensor 11 reacts with combustible gas such as carbon monoxide in the cigarette smoke. The second example of actual measurement of point P in Fig. 1 when a smoking test was conducted in the passenger compartment of the automobile
Shown in the figure. That is, V _P when not smoking is a constant potential balanced in the vehicle interior atmosphere.
Since the resistance value of 11b decreases, V _P has a characteristic of increasing with the concentration. Smoking detection using the Supporting go-between gas sensor, V _P
It can be seen that it can be obtained by detecting the potential change of. In the present invention, smoking detection is performed by impedance conversion of the gas sensor output V _P by the voltage follower 13, and then one of the resistances is resistance.
The voltage dividing point R of the voltage dividing circuit of 18, 19 is input, and the other one is input by inputting two to the voltage comparator 20 which receives the output point Q of the time delay circuit of the resistor 15 and the capacitor 14. .

During non-smoking during stable operation, V _P and V _Q are almost equal, and R
Since the voltage V _{R at the} point is determined by the product of the output voltage V _P of the gas sensor 11 and the voltage division ratio of the resistors 18 and 19, the two inputs of the comparator 20 are kept at a substantially constant value at the voltage division value. Become. After smoking started
As V _P rises, a potential proportional to this rise is applied to point R without any time delay. On the other hand, when the time constant is set to a large value, the time delay circuit keeps the potential at the point Q without much change with respect to the increase in V _P during smoking. Therefore, V _Q −V _R is positive when non-smoking and goes from zero to negative during the rise of V _P after the start of smoking. Eventually, V _Q −V _R returns to positive during the period when smoking ends and V _P falls. The time delay circuit can be regarded as the reference value circuit of the comparator 20. Further, the voltage dividing circuit of the resistors 18 and 19 is the comparator 20.
With the function to set the sensitivity of.

Here, the gas sensor 11 has a temperature, a temperature affected by humidity,
There is a characteristic that the resistance value decreases when the humidity is high, and the resistance value increases when both are low, and it varies depending on the date and season. FIG. 3 is a characteristic diagram showing an example thereof. In addition, this gas sensor 11 is used when an air freshener or deodorant is used inside the vehicle.
Since these gases fill the inside of the vehicle, they are erroneously detected by the gas components. Furthermore, when the gas sensor 11 is left unenergized for a long period of time and then started to operate, the sensor is slightly
If the resistance of 11 increases and the resistance becomes stable, the above-mentioned characteristics will change the detection sensitivity if it is a normal circuit, and if it changes in the direction of decreasing sensitivity, it cannot be detected even if smoking. On the contrary, if the sensitivity fluctuates in the sensitive direction, the detection output may be output without smoking, which is a great obstacle to practical use. According to the present invention, the above-mentioned various characteristics are obviated by the time delay circuit.

That is, the output voltage of the gas sensor 11 due to the above-mentioned various obstacle characteristics
The rate of change in V _P changes very gently in comparison with smoking, so it is a time delay circuit with a time constant that follows changes in various obstacle characteristics and does not react to changes during smoking. The time delay circuit absorbs the fault characteristic at the beginning of energization or during energization.

Description will be given with reference to FIG. The gas sensor 11 has a very high resistance value immediately after the start of energization, and the heater 11a starts heating after a few seconds, so that the gas sensor 11 temporarily approaches zero, and eventually (for example, after 2 minutes) equilibrates to the set stable value. Therefore, the output of the electrode 11b of the gas sensor 11, that is, V _P follows the characteristic as shown in FIG. 4 (a). In this case, the output V _Q of only the time delay circuit of the resistor 15 and the capacitor 14 is as shown in FIG. 4 (b).
Since the change in V _P is abrupt, the capacitor 14 is hardly charged and passes. So diode 16 and low value resistor
If a quick charging circuit with 17 is installed as shown in Fig. 1, the power source from the constant voltage power source 10 is a capacitor when V _P drops sharply at the beginning of energization.
It is grounded through the circuit of 14, diode 16, resistor 17, and voltage follower 13, and the capacitor 14 is rapidly charged. Therefore, the characteristic of V _Q follows the characteristic as shown in FIG. 4 (c), reaches the stable range relatively quickly, and thereafter balances at a setting value slightly higher than V _P. The stable value of V _P is affected by the above-mentioned various obstacle characteristics and balances. Therefore, when these are included, the characteristics become as shown in FIG. 4 (d). In other words, V _Q at equilibrium in this case is balanced with the potential that has absorbed the disturbance factor, and V _{P of} comparator 20
Will serve as a reference value for. Next, during operation after reaching equilibrium, the temperature inside the vehicle may gradually rise due to the heater, etc., and the time delay circuit sets this kind of temperature change to a specific number that can be followed, and _Made it possible to follow V _Q.

Further, while the vehicle is in operation, the vehicle window may be temporarily opened or the door may be temporarily stopped to open the door, which may cause a sudden change in temperature, humidity, fragrance concentration, etc. in the vehicle compartment. For example, when the outside temperature is low and the door is opened, the gas sensor 11 is temporarily cooled, so that the resistance value of the sensor itself increases. In a vehicle filled with fragrance, the inside of the vehicle is ventilated, which is noticeable. Therefore, the sensor potential V _P decreases, but the decrease rate of V _{Q of the} time delay circuit is slow.
The potential difference between the two becomes large, and the potential difference between P and R also becomes large. This means that the detection sensitivity of the sensor is temporarily lowered, and after that, even if the user smokes for a certain period of time after closing the vehicle window or door, there is a problem that it cannot be detected. Therefore, even when the atmosphere changes suddenly due to the opening and closing of the door, the quick charging circuit has a function of returning the detection sensitivity to the original sharp detection sensitivity at an early stage.

As described above, the air purifier control circuit when smoking with the smoking detection circuit with the function of compensating various atmospheric factors
It will be described below with reference to FIG.

When the engine is running and you are not smoking, the purifier has transistor 26
Turn it off, operate the resistor 27 as a limiting resistor of the blower 28, and operate the blower 28 at a low speed. When smoking starts in the passenger compartment, the gas sensor 11 detects this, and the potential of V _P begins to rise as shown in Fig. 5b, and eventually coincides with the potential V _R of the reference value circuit (Fig. 5a). Then, the comparator 20 outputs a coincidence pulse as shown in FIG. The monostable multi 22 is triggered by the first match signal of the comparator 20 and outputs a pulse for its own set time, for example 8 minutes (Fig. 5d). When the monostable multi 22 outputs a pulse, the transistor 26 is turned on to make the resistor 27 conductive, and the blower 28 of the air purifier is operated at high speed. As described above, the air in the passenger compartment can be efficiently cleaned during smoking.

According to the present embodiment, the temperature and humidity peculiar to the gas sensor in the automobile air cleaner using the gas sensor 11 as a smoke detector, the fluctuation in the initial stage of energization, and the cigarette with a constant sensitivity without being affected by the fragrance and the deodorant. There is an effect that an air purifier that operates by detecting the smoke of is obtained.

〔The invention's effect〕

As described above, according to the present invention, the sensitivity of the comparison circuit can be appropriately set by the voltage dividing circuit. Further, since the quick charging circuit is provided, the detection sensitivity of the gas detection element can be quickly returned to the original sensitive state even when the atmosphere suddenly changes by temporarily opening a window or a door. Furthermore, by providing a time delay circuit, it is possible to eliminate the effects of changes in temperature, humidity, etc. and the effects of the use of fragrances and the like. As a result, an air purifier with high operational reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit connection of an embodiment of the present invention, FIG. 2 is a diagram showing detection characteristics of a gas sensor during smoking, FIG. 3 is a diagram showing temperature and humidity characteristics of the gas sensor, and FIG. FIG. 5 is a diagram showing the characteristics of the gas sensor circuit at the initial stage of power-on, and FIG. 5 is a diagram showing the operation in one embodiment of the present invention. 10 …… Constant voltage power supply circuit 11 …… Gas sensor 13 …… Voltage follower 14 …… Capacitor 15 …… Resistance 20 …… Voltage comparator 22 …… Monostable multivibrator 28 …… Air purifier blower

Claims (1)

[Claims] 1. A gas detection element for detecting a gas concentration in air, a reference signal circuit for outputting a reference signal for gas detection, a detection signal for the gas detection element and a reference signal for the reference signal circuit. In an air cleaning device comprising a comparison circuit for comparing and controlling the operation of the air cleaner by an output signal of the comparison circuit, the detection signal of the gas detection element is supplied to one of the comparison circuits via a voltage dividing circuit. A time delay circuit consisting of a series circuit of a first resistor and a capacitor and a series circuit of a second resistor and a diode are input in parallel to the first resistor while being input to the input terminal. An air purifier characterized in that it is configured to input to the other input end of the comparison circuit via a connected rapid charging circuit.