JPH084706B2 - Air cleaner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air purifier used in a general home or an automobile, which detects air pollution using a sensor and purifies the air according to the dirt.

2. Description of the Related Art In recent years, air cleaners that use sensors to detect air pollution and control operation have become mainstream.

Conventionally, this type of air cleaner uses a gas sensor whose resistance value changes according to the gas concentration as a sensor, detects the degree of contamination of air from the amount of change in the resistance value of this gas sensor, and detects the air level according to this detection level. It was purifying. In addition, the degree of change of the resistance value with respect to the gas concentration of the gas sensor is
First, the resistance value at a certain gas concentration (air that seems to be clean) was set as a reference resistance value R0, and the degree of air pollution was judged from the amount of change in the resistance value R at the current gas concentration with respect to this value.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In such a conventional air purifier, the resistance value at the gas concentration that is the reference of the gas sensor varies from several kΩ to several 100 kΩ, so the resistance value must be accurately taken over a wide range. There was a drawback that it had to be. Therefore, in order to detect the gas concentration with a certain degree of accuracy or higher, it has to be detected with a considerably high accuracy. For example, if a reference resistance value of several kΩ requires a resolution of 8 bits, 7 bits are required to capture several 100 kΩ with the same resolution, which requires 15 bits in total, resulting in high cost. Was there. Further, if 15 bits is reduced to 10 bits, it becomes 3 bits at several kΩ, and there is a problem that the gas concentration detection accuracy deteriorates. Further, there have been cases where a process of selecting and using the sensor so that the reference resistance value falls within a certain value range, or manually adjusting the sensor is added.

The present invention is to solve the conventional problems described above, the output level at a certain reference resistance value is constant, by detecting the relative change amount with respect to this value, to detect the change amount of the gas,
It is an object of the present invention to provide an inexpensive and highly reliable air purifier that always determines the degree of contamination of air with a constant resolution (for example, 8 bits) regardless of variations in the reference resistance value.

Means for Solving the Problems The present invention, in order to achieve the above object, a sensor for detecting air pollution, a detection means for detecting the output level of the sensor, and a switch for switching the output destination of the detection means, Depending on the reference value input means that is one output destination of this switch, the switch switching means that switches the output destination of the switch according to the value input by this reference value input means, and the value input by the reference value input means. Level adjusting means for adjusting the detection level of the detecting means, the comparison value input means which is the other output destination of the switch, the reference value input means and the comparison value input means, and compares the values by taking in signals from the comparison value input means. Means and an output means for outputting according to the comparison result of the comparison means, wherein the reference input means inputs the output of the detection means to the reference value input means. The problem solving means is that the output of the detecting means is adjusted and held via the level adjusting means so that the output of the detecting means becomes a constant value in that state, and then the output of the detecting means is input to the comparison value input means.

Operation According to the present invention, the present invention first adjusts the detection level of the resistance value at the gas concentration to be the reference so that the detection level becomes a certain value, and then uses that value as the reference value from the values detected thereafter. The gas concentration can be detected, and the output can be changed according to this value.

Embodiments Before describing the embodiments of the present invention, the relationship between the gas concentration and the change amount of the gas sensor resistance value will be described.

Assuming that the reference resistance value (clean air) is R0, the resistance value of the air to be detected is R, and the change amount of the resistance value of air containing 1000 ppm of isobutane is 1, the relationship between each gas concentration and the change amount of the resistance value Is as shown in FIG. As is clear from this figure, the content that can be detected by the gas sensor is in contrast to how much the gas concentration changes with respect to a certain reference gas concentration. Therefore, even if the reference gas resistance value R0 varies, it can always be derived from the relationship of R / R0 with respect to the amount of change in gas concentration. Therefore, it is not necessary to detect the resistance value of the gas sensor as an absolute value, and the change amount of the gas concentration can be detected from the change amount with respect to the reference gas concentration level. as a result,
If the detection level at the reference gas concentration can be made constant, the amount of change in gas concentration can always be detected with the same accuracy.

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

As shown in the figure, the gas sensor 1 inputs to the detection means 2, and this detection means detects the output level of the gas sensor 1. The switch 3 switches the output destination of the detection means 2, and the reference value input means 4 is one output destination of the switch 3. The switch switching means 5 switches the output destination of the switch 3 according to the value input by the reference value input means 4. The level adjusting means 6 adjusts the detection level of the detecting means 2 according to the value input by the reference value inputting means 4. The comparison value input means 7 is the other output destination of the switch 3, and the comparison means 8 takes in signals from the reference value input means 4 and the comparison value input means 7 and compares the values. Output means 9
Performs output according to the result of comparison by the comparison means 8.

To explain the operation in the above configuration, first, the switch 3 is switched to the reference value input means 4 side in order to set the reference resistance value. Then, the value of the gas sensor 1 input to the reference value input means 4 is sent from the reference value input means 4 to the detection means 2 via the level adjusting means 6 so as to be a constant value. This is repeated until the value output from the detecting means 2 becomes a constant value. When the reference value input means 4 confirms that this value has reached a certain value, the reference value input means 4 outputs a signal for holding the level adjustment value as it is to the level adjustment means 6, and switches the signal for switching the switch 3. Output to the switching means 5. Gas sensor 1 receiving these signals
The reference level is determined, and the switch 3 is switched to the comparison value input means 7 side to detect the gas concentration. Next, the comparison means 8 compares the reference resistance value R0 held by the reference value input means 4 with the resistance value R of the gas sensor 1 fetched by the comparison value input means 7 this time, and outputs according to the value. The output content of the means 9 is changed.

Next, the second method using the electronic polymium 10 as the detecting means 2
The above operation will be described more specifically with reference to the drawings. The resistance value R0 of the gas sensor 1 is taken out as a partial pressure value by resistance division with the resistance value of the electronic volume 10. First, in order to set the reference value, the switch 3 is switched to the reference value input means 4 side. Then, if the voltage value input to the reference value input means 4 is high, the resistance value of the electronic polysilicon 10 is decreased, and if the voltage value is low, the resistance value of the electronic polysilicon 10 is increased. The value is sent from the reference value input means 4 to the detection means 2 via the level adjusting means 6 so that it becomes a certain constant value. Then, this is repeated until the voltage value becomes a constant value. When the reference value input means 4 confirms that the voltage value has reached a certain value, the reference value input means 4 outputs the voltage value to the level adjusting means 6 so as to keep the voltage value as it is, and switches the signal for switching the switch 3. Output to the means 5. Receiving these signals, the reference level of the gas sensor 1 is determined, and the switch 3 is switched to the comparison value input means 7 side in order to detect the gas concentration. Next, the reference value V0 (R0) held by the reference value input means 4 and the comparison value V (R) of the gas sensor 1 fetched by the comparison value input means 7 this time.
Is compared by the comparison means 8, and the output means 9 is used according to the value.
Is changing the output content of.

Next, another embodiment of the present invention will be described with reference to FIG. The same components as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in the figure, the threshold voltage setting means 11
Is for setting the threshold level. The electric charge output from the DC power supply 12 is stored in the capacitor 13. The switch 14 switches the connection destination of the gas sensor 1 between the DC power supply 12 and the ground, and is controlled by the control means 15. The counter 16 inputs the voltage value output from the threshold voltage setting means 11 and the charging voltage value of the capacitor 13, and the time from when the capacitor 13 starts charging until the charging voltage value becomes larger than the threshold voltage value. Is counted at a certain sampling period.

To explain the operation of the above configuration, first, the switch
By switching 14 to the ground side, the electric charge stored in the capacitor 13 is discharged. When discharging is completed, the switch 14 is switched to the DC power source 12 side to start charging. As shown in FIG. 4 (b), the charging curve at this time is the resistance value R of the gas sensor 1.
And the capacitance value C of the capacitor 13 depends on the product CR. Then, the counter 16 starts counting at a certain sampling period from the moment the switch 14 is switched to the DC power supply 12 side. Then, the counting is continued until the charging voltage value rises to the threshold level. The gas concentration is detected from this count value. Therefore, when the gas concentration changes, the resistance value of the gas sensor 1 changes and the charging time of the capacitor 13 changes. As a result, the value counted by the counter 16 also changes, and the change amount T / T0 of the gas concentration can be detected.

At this time, as shown in FIG. 5B, when the reference resistance value is different, the reference value is changed to, and when the gas concentration is changed to, the reference value is changed to. At this time, by changing the sampling period from t1 to t2 so that the count number of the charging voltage time at the reference gas concentration is constant T, the amount of change in gas concentration is T / T0 with constant accuracy. Can be detected.

In the above embodiment, the resistance value of the gas sensor 1 is converted into a voltage value or time for detection, but the point is that even if the reference value of the gas sensor 1 varies about 100 times, the change of the gas concentration with respect to the reference gas concentration. Any method that can detect the amount with the same accuracy may be used.

EFFECTS OF THE INVENTION As is apparent from the above embodiments, according to the present invention, the output level at a certain reference resistance value of the gas sensor is made constant, and the change amount of gas is detected by detecting the relative change amount with respect to this value. As a result, it is possible to always determine the degree of air contamination with a constant resolution (for example, 8 bits) regardless of the variation in the reference resistance value.

[Brief description of drawings]

FIG. 1 is a block diagram of an air cleaner according to an embodiment of the present invention,
FIG. 2 is a block diagram of the air purifier with some specific circuits added, and FIG. 3 is a block diagram of another embodiment of the present invention.
FIGS. 5A to 5C are operation timing diagrams when the reference resistance value of the air cleaner is small, and FIGS.
(C) is an operation timing diagram when the reference resistance value of the air cleaner is large, and FIG. 6 is a gas concentration-change amount characteristic diagram showing a change amount of resistance with respect to each gas concentration of the gas sensor. 1 ... Gas sensor (sensor), 2 ... Detection means, 3 ...
Switches, 4 ... Reference value input means, 5 ... Switch switching means, 6 ... Level adjusting means, 7 ... Comparison value input means, 8 ... Comparison means, 9 ... Output means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01N 27/12

Claims (1)

[Claims] 1. A sensor for detecting contamination of air, a detecting means for detecting an output level of the sensor, a switch for switching an output destination of the detecting means, and a reference value inputting means which is one output destination of the switch. And a switch switching means for switching the output destination of the switch according to the value input by the reference value input means, and a level adjusting means for adjusting the detection level of the detection means according to the value input by the reference value input means. And a comparison value input means which is the other output destination of the switch, a comparison means for taking in signals from the reference value input means and the comparison value input means and comparing the values, and a comparison result obtained by the comparison means. Output means for outputting, and the reference value input means sets a level so that the output of the detection means becomes a constant value while the output of the detection means is being input to the reference value input means. Adjusted and held via the adjusting means,
After that, the air purifier in which the output of the detection means is input to the comparison value input means.