JP2002195929A - Dust sensor and air cleaner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust sensor small in size and low in cost capable of measuring the diameter of particle of dust and discriminating the dust from smoke. SOLUTION: The dust sensor optically detects the amount of dust by emitting light from a light source 1 and detecting the scattered light using a photodetector 2. The diameter of particle of the dust is detected on the basis of a period during which the photodetector 2 outputs continuously. The continuous period of the output is varied due to the difference between the particles in diameter, thereby measures the diameter of particle of the dust from the continuous period of the output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust sensor for optically detecting dust in indoor air and an air cleaner using the same.

[0002]

2. Description of the Related Art Dust (allergen substances) and smoke (tobacco) are mixed in the indoor air, and when an air purifier or a smoke detector is operated according to the output of a dust sensor,
If dust and smoke can be distinguished, a more favorable operation can be performed.

Here, the particle diameter of the allergen substance is concentrated in the range of 3 to 100 μm (particularly 3 to 50 μm), and the smoke particle of cigarette is 1 μm or less. You can deal with it by making it possible.

On the other hand, when it is desired to optically know the particle size of the detected dust, the inside diameter of the dust passage portion is narrowed down like a particle counter, and the scattered light is reduced by using light having a short wavelength such as laser light as a light source. Detection is performed by a light receiving element, and the particle diameter is measured based on its characteristics.

[0005]

However, in the above-mentioned particle counter, there is a problem that the size of the apparatus cannot be reduced and the apparatus becomes expensive, and cannot be applied to an air purifier, a smoke detector, and the like. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a small and inexpensive dust sensor capable of measuring the particle diameter of dust and distinguishing between dust and smoke. Another object of the present invention is to provide an air purifier that can operate according to dust and smoke by including the dust sensor.

[0007]

According to the present invention, there is provided an optical dust sensor for detecting the amount of dust by irradiating light from a light source and detecting the scattered light with the light receiving element. It is characterized in that the particle diameter of the dust is detected based on the continuous time. Since the continuous output time varies depending on the particle size, the particle size of the dust is measured from the continuous output time. When it is only necessary to distinguish between dust and smoke, dust having a continuous output time within a predetermined time may be regarded as dust, and smoke having a continuous output time equal to or longer than a predetermined time may be regarded as smoke.

Further, in an optical dust sensor for detecting the amount of dust by irradiating light from a pulse-driven light source and detecting the scattered light with a light receiving element in synchronization with the pulse generation timing, It is sufficient to detect the particle size of the dust based on the number of continuous outputs.In this case, if it is sufficient to distinguish between dust and smoke, it is assumed that the number of continuous outputs is constant and the number of continuous outputs is constant. What is necessary is just to make smoke more than the number of pulses.

In any case, it is desirable to change the criterion value according to the wind speed to be induced.

Also, an optical dust sensor for irradiating light from a light source and detecting the amount of dust by detecting the scattered light with a light receiving element, or irradiating light from a pulse-driven light source to obtain the scattered light In the optical dust sensor that detects the amount of dust by detecting the amount of dust by synchronizing with the pulse generation timing, the difference between the maximum value and the average value of the photodetector output within a certain period is more than
Those below a certain level may be distinguished from smoke.

Further, after the presence of smoke is identified from the continuous output time or the number of continuous outputs of the light receiving element, the presence of dust is identified from the difference between the maximum value and the average value of the output of the light receiving element within a certain period. Good.

In addition, the dust concentration may be determined from the output of the light receiving element output after rectification and amplification, and the dust and smoke may be distinguished from the output of the light receiving element output before rectification.
At this time, if the output before rectification cannot be detected, the smoke may be identified from the dust generation density by the output after rectification and amplification.

[0013] It is also preferable to optimize the displayed dust concentration value according to the type of dust.

An air purifier according to the present invention is characterized in that the air purifier includes the above-described dust sensor and a switching unit that switches the operation in accordance with the output of the dust sensor.

The dust sensor is preferably provided in the bypass of the filter flow path, but is not limited to this.

As the switching unit, a switching unit that switches a filter flow path to be passed according to the result of discrimination between dust and smoke by the dust sensor can be suitably used. In particular, it is possible to obtain a preferable result if the filter passage that is passed when dust is distinguished is a low pressure loss type dust collector that is different from the dust filter that passes when smoke is distinguished.

The switching unit may switch the air flow control pattern in accordance with the result of dust and smoke discrimination by the dust sensor.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an example of an embodiment. As shown in FIG. 1, this dust sensor includes a light source 1 and an illumination from the light source 1 when dust passes. A light receiving element for receiving scattered light; and a processing circuit for processing the output of the light receiving element.
The light source 1 may be driven by a direct current. However, since the detection sensitivity needs to be improved in measuring the particle diameter and distinguishing dust and smoke as described below, the oscillation circuit 3 is used. Pulse driving. In the case where the light source 1 is pulse-driven, the current used in the light source 1 can be increased as compared with the case of direct-current driving, so that the detection sensitivity can be improved. In addition, the pulse interval when the pulse is driven,
If the current value is the same, the detection sensitivity can be further improved by shortening the current value. For example, if the pulse interval is 20 m
By changing from s to 5 ms, the detection sensitivity to dust can be approximately quadrupled.

The processing circuit C comprises a rectifier circuit 4 and an amplifier 5 for obtaining a dust concentration, and an identification circuit C1 for measuring a particle diameter and distinguishing between dust and smoke. The output of the light receiving element 2 is rectified by using the rectifier circuit 4, the signal is amplified by using the amplifier 5, and the output is obtained from the signal level. In the figure, reference numeral 6 denotes a display 6, which includes a concentration display section 6a and a dust type display section 6b.

On the other hand, the identification circuit C1 performs the measurement and the identification by processing the output of the light receiving element 2 before entering the rectifier circuit 4. The output continuation time of the light receiving element 2 when dust passes therethrough. (Pulse width) is proportional to the particle diameter of the passed dust (when the light emitting element 1 is pulse-driven, the number of continuous pulses is proportional to the particle diameter of the dust).

That is, the relationship between the particle diameter of the dust and the output continuous time (pulse width) or the number of continuous pulses is as shown in FIG. 2, and the slope β of the correlation line decreases as the flow velocity of the dust passing through the dust sensor increases. There are characteristics. For this reason, by determining the passing velocity of the dust, the particle diameter of the passing dust can be measured from the output continuous time (number of continuous pulses) of the light receiving element 2.

[0022] Of the dust, the particle size of dust containing a large amount of allergen substance is 3 to 100 µm (particularly 3 to 100 µm).
50 μm), the amount of dust (allergen substance) can be measured by counting particles having a measured particle diameter within the above range.

In addition, dust due to smoke (tobacco) also exists in the air, whereas dust has a particle diameter of 1 μm or more as described above, whereas dust due to smoke is 1 μm.
Many have the following particle diameters. For this reason, smoke can be identified from the difference in particle diameter.

Further, comparing the dust generation density between dust and smoke, the amount of smoke is overwhelmingly large, and the output of the light receiving element 2 is as shown in FIG. The result is as shown in FIG. Therefore, the output continuous time (the number of continuous pulses) is short as shown in FIG. 3B, for example, 150 ms (30 if the pulse interval is 5 ms).
4) Smoke that has a continuous output time (number of continuous pulses) longer than that shown in Fig. 4 (b), for example, 400ms (80 if the pulse interval is 5ms) or more. Alternatively, dust and smoke may be distinguished.

Further, the maximum value and the average value of the output of the light receiving element 2 per unit time are obtained, and the difference between the two is shown in FIG.
As shown in FIG. 4 (c), dust having a large difference, for example, 0.5V or more, and dust having a small difference as shown in FIG. And smoke may be identified.

As described above, the output continuous time (number of continuous pulses) of the light receiving element 2 when the dust passes through the dust sensor varies depending on the flow velocity of the dust in the dust sensor. The accuracy of identification can be improved by changing the criterion value for identifying dust and smoke based on the flow velocity.

[0027]

[Table 1]

By the way, as the flow velocity of dust increases,
The reference value (output continuous time t _da, T_db, T_dcif
Or the number of continuous pulses t_sa, T_sb, T_sc) Is shortened. You
That is, t_da> T_db> T_dc t_sa> T_sb> T_sc And Note that t_da<< t_sa, T_db<< t_sb, T_dc<<<
t_scIt is.

By the way, when dust and smoke are distinguished by the output continuous time of the light receiving element 2 (the number of continuous pulses), when dust and smoke are mixed, the dust output is masked by the smoke output and the dust output is detected. It becomes difficult to do.
In the discrimination based on the difference between the maximum value and the average value, discrimination is possible even if dust and smoke are mixed, but the sensitivity is low. For this purpose, as shown in FIG. 5, after discrimination between dust and smoke is performed based on the output continuous time (number of continuous pulses), dust is further detected at the time of smoke discrimination by the difference between the maximum value and the average value. Thus, detection accuracy and detection sensitivity can be improved.

As shown in FIG. 6, when the output of the light receiving element 2 is rectified and amplified to obtain the dust concentration, the detection sensitivity is increased and the target dust concentration display output having a low dust concentration, for example, 0 to 2 mg. / m with respect to ³ target, dust and smoke output signal of the previous dust concentration higher rectification of interest to capture the output characteristics to be used to identify, for example 0～12Mg /
With m ³ target, output dust concentration display has been detected may be rectified before the output can not be detected. In this case, from the output feature that the dust is sporadic and the dust concentration display is not performed when the dust concentration cannot be identified, the dust concentration display output may be detected, but when the output before rectification cannot be detected, it may be identified as smoke.

Further, when the dust concentration is obtained by rectifying and amplifying the output of the light receiving element 2, the displayed value may differ from a human sense because the displayed dust concentration varies depending on the particle diameter of the dust. In this regard, the value of the dust concentration display may be optimized based on the result of discriminating between dust and smoke, for example, matching with a human sensory value.

FIG. 8 schematically shows an air cleaner equipped with the above dust sensor. The dust sensor 7 is, for example,
It is provided in a bypass flow path or the like that bypasses a flow path to the dust collection filter 9 in the air purifier 8 so that dust and smoke in room air can be detected. In this air purifier, the filter flow path is switched based on the result of the dust sensor 7 discriminating dust and smoke. For example, when it is identified as dust, only the dust filter 9 is passed as shown in FIG. 2B, and when it is identified as smoke, both dust filter 9 and the deodorizing filter 10 are passed as shown in FIG. This can improve the dust removal efficiency.

As shown in FIG. 9, a filter may be prepared according to the particle size of each dust. When it is identified as dust, it passes through a dust collection filter 11 with a low pressure loss for dust having a large particle diameter as shown in (b) in the figure, and when it is identified as smoke, as shown in (a) in the figure. 9 and through the deodorizing filter 10.

In addition to the above-mentioned switching of the filter channel,
The air volume may be controlled according to dust and smoke. FIG. 10 shows an example of the air volume control pattern. It is desirable to remove the dust before the dust settles naturally, but if the operation is performed too quickly, the dust is further rolled up. Therefore, as shown in FIG. As for smoke, both dust collection and deodorization first remove rough ones, and over time, a large air volume is obtained as shown in FIG. Switch to the control pattern to be reduced.

[0035]

As described above, according to the first aspect of the present invention, in a scattered light type dust sensor, the particle diameter is measured from the continuous output time of the light receiving element. It is capable of measuring dust and distinguishing between dust and smoke.

The above-mentioned dust and smoke can be easily distinguished by using dust whose output continuous time is within a predetermined time as dust and smoke whose output continuous time is longer than a predetermined time as smoke.

In the case where light is emitted from a pulse-driven light source and the scattered light is detected by a light-receiving element in synchronization with the pulse generation timing to achieve high sensitivity, the light output is based on the number of continuous outputs of the light-receiving element. By detecting the particle size of the dust, it is possible to measure the particle size of the dust and distinguish between dust and smoke while being small and inexpensive. In this case as well, regarding the discrimination between dust and smoke, dust having a constant number of output pulses is dust, and smoke having a continuous output number of more than a certain number of pulses is smoke.

By changing the criterion value according to the induced wind speed, it is possible to measure and identify the particle diameter with higher accuracy.

Even if the difference between the maximum value and the average value of the output of the light receiving element within a certain period is more than a certain value, and the difference is less than a certain value, the difference between the dust and the smoke is accurately determined. be able to.

Further, after the presence of smoke is identified from the continuous output time or the number of continuous outputs of the light receiving element, the presence of dust is identified from the difference between the maximum value and the average value of the output of the light receiving element within a certain period. Good. Even when dust and smoke coexist, the presence of both can be detected.

When the dust concentration is determined from the output of the light receiving element output after rectification and amplification, and dust and smoke are identified from the output of the light receiving element output before rectification, identification and display of the dust concentration can be performed.

When the output before rectification cannot be detected, smoke can be identified from the dust generation density by the output after rectification and amplification, so that smoke can be identified even if the output before rectification cannot be detected.

By optimizing the dust concentration values to be displayed according to the type of dust, it is possible to display the dust concentration at the optimum value for each.

The air purifier according to the present invention is provided with the dust sensor and the switching unit for switching the operation in accordance with the output of the dust sensor. Suitable operation can be performed.

In this case, when the switching unit switches the filter flow path to be passed according to the result of discrimination between dust and smoke by the dust sensor, dust and smoke can be efficiently removed.

In particular, by using a low pressure loss type dust collecting filter that is different from the dust collecting filter that allows the filter to pass when discriminating dust, the dust can be efficiently removed with a large air flow. .

When the switching unit switches the air volume control pattern in accordance with the result of the dust sensor discriminating dust and smoke, dust and smoke can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the correlation between the output continuous time (pulse width), the number of continuous pulses, and the particle diameter.

3A is a time chart of the output of the light receiving element when dust is dust, FIG. 3B is an enlarged view of the output of the same, and FIG. 3C is an explanatory diagram of the maximum value and the minimum value of the same.

4A is a time chart of the output of the light receiving element when the dust is smoke, FIG. 4B is an enlarged view of the output, and FIG. 4C is an explanatory diagram of a maximum value and a minimum value of the output.

FIG. 5 is a flowchart of another example of the above.

FIG. 6 is a block diagram of still another example of the above.

FIG. 7 is a block diagram of another example of the above.

FIG. 8 is a block diagram of an example of an air purifier according to the present invention.

FIG. 9 is a block diagram of another example of the above.

10A is an explanatory diagram of an air volume control pattern at the time of dust identification, and FIG. 10B is an explanatory diagram of an air volume control pattern at the time of smoke identification.

[Explanation of symbols]

 1 light source 2 light receiving element C1 identification circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiro Araki 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. F-term (reference) 4D058 NA02

Claims (16)

[Claims] An optical dust sensor for irradiating light from a light source and detecting scattered light with a light receiving element to detect the amount of dust, wherein the particle diameter of the dust is determined based on the output continuous time of the light receiving element. A dust sensor characterized by detecting. 2. The dust sensor according to claim 1, wherein the continuous output time within a predetermined time is regarded as dust, and the continuous output time exceeding a predetermined time is identified as smoke. 3. An optical dust sensor for detecting the amount of dust by irradiating light from a pulse-driven light source and detecting the scattered light with a light-receiving element in synchronization with the pulse generation timing. A dust sensor which detects a particle diameter of dust based on a continuous number. 4. The dust sensor according to claim 3, wherein the number of continuous output pulses is a certain number of pulses, and the number of continuous output pulses is equal to or more than the predetermined number of pulses is identified as smoke. 5. The dust sensor according to claim 1, wherein the criterion value is changed according to the wind speed to be induced. 6. An optical dust sensor for detecting the amount of dust by irradiating light from a light source and detecting the scattered light with a light receiving element, the maximum value and the average value of the output of the light receiving element within a certain period. A dust sensor characterized in that the difference between dust is greater than a certain value and dust is less than a certain value as smoke. 7. An optical dust sensor for detecting the amount of dust by irradiating light from a pulse-driven light source and detecting the scattered light with a light-receiving element in synchronization with a pulse generation timing. A dust sensor characterized in that a difference between a maximum value and an average value in a period is equal to or greater than a certain value, and that the difference is equal to or less than a certain value. 8. After the presence of smoke is identified from the continuous output time or the number of continuous outputs of the light receiving element, the presence of dust is identified from the difference between the maximum value and the average value of the light receiving element output within a certain period. The dust sensor according to claim 2 or 4, wherein 9. The method according to claim 1, wherein a dust concentration is determined from an output of the light receiving element output after rectification and amplification, and dust and smoke are distinguished from an output of the light receiving element output before rectification. A dust sensor according to any of the above items. 10. The dust sensor according to claim 9, wherein when the output before rectification cannot be detected, smoke is identified based on the dust generation density by the output after rectification and amplification. 11. The dust concentration value displayed according to the type of dust is optimized.
Dust sensor as described. 12. An air purifier comprising: the dust sensor according to claim 1; and a switching unit that switches operation according to an output of the dust sensor. Machine. 13. The dust sensor according to claim 12, wherein the dust sensor is provided in a bypass of the filter flow path.
Air purifier. 14. The switching unit according to claim 12, wherein the switching unit switches a filter channel to be passed according to a result of discrimination between dust and smoke by the dust sensor.
An air purifier as described. 15. The air purifier according to claim 14, wherein the filter passage that passes when identifying dust is a low pressure loss type dust collecting filter that is different from the dust collecting filter that passes when identifying smoke. 16. The air purifier according to claim 12, wherein the switching unit switches the air volume control pattern in accordance with a result of discrimination between dust and smoke by the dust sensor.