JPH10170435A - Method and device for dust detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect dust with high precision by performing corrective process accurately in a short time. SOLUTION: The dust detecting device comprises a dispersion detecting means 13 which detects dispersion in dust detection output, a comparison means 14 which compares a detected dispersion to a pre-set threshold value, a offset value assuming means 15 which, in response to judgement that dispersion is smaller than threshold value, takes the correct dust detection output as an offset value of dust detection output, and concentration detecting means 16 and 17 which detect dust concentration by correcting the dust detection output with the offset value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust detection device and a dust detection method, and more particularly, to a dust detection device and a dust detection method for detecting the concentration of dust by receiving scattered light caused by dust particles. .

[0002]

2. Description of the Related Art Conventionally, as a dust detection device for detecting the concentration of dust in the air, there has been proposed a dust detection device for detecting the concentration of dust by receiving scattered light caused by dust particles. When this dust detection device is adopted, a detection signal that changes in a pulse shape as the dust particles pass through the detection area is output, so that the appearance frequency and the height of the pulse-like detection output are detected. This makes it possible to detect the number and size of dust particles.

However, in practice, the output of the dust sensor included in the dust detection device fluctuates due to the attachment of dirt in the optical system of the dust detection device. Therefore, some correction must be made to the output of the dust sensor. If the dust concentration cannot be accurately detected. Considering these points,
There has been proposed a smoke sensor in which a correction process for setting the minimum value of the detection output for several days to a zero level is performed (Japanese Patent Application Laid-Open No. Hei 5 (1993)).
No. 325058).

If the smoke sensor having this configuration is adopted, the correction process for setting the minimum value of the detection output for several days to the zero level is performed, so that the output of the smoke sensor caused by adhesion of dirt on the optical system of the smoke sensor is obtained. Can be eliminated or reduced to increase the smoke detection accuracy.

[0005]

However, dust particles are significantly larger than smoke particles to be detected by the smoke sensor, and even if only one dust particle adheres to the optical system, the detection output becomes smaller. Levels can fluctuate dramatically. In such a case, although the correction processing needs to be performed immediately, when the method described in JP-A-5-325058 is applied to the dust sensor, an accurate correction processing is performed. Up to several days are required before the dust can be applied, during which time only inadequate correction processing can be performed, and the dust detection accuracy may be significantly reduced. There is.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a dust detection device capable of performing accurate correction processing in a short time and capable of detecting dust with high accuracy. It is intended to provide a dust detection method.

[0007]

According to a first aspect of the present invention, there is provided a dust detecting apparatus for detecting the concentration of dust by receiving scattered light caused by dust particles. Means, comparing means for comparing the detected variation with a preset threshold value, and adopting a corresponding dust detection output as an offset value of the dust detection output in response to the determination that the variation is smaller than the threshold value. An offset value adopting means and a density detecting means for correcting the dust detection output with the offset value and detecting the dust density are included. Here, as the corresponding dust detection output, any of the dust detection outputs used for detecting the variation may be employed, but an average value of the dust detection outputs used for detecting the variation may be employed. Is also good.

According to a second aspect of the present invention, there is provided a dust detecting apparatus which employs a means for quantifying a variation in dust detection output as a variation detecting means, and compares the quantified variation with a preset threshold value as a comparing means. Is adopted. here,
Methods for quantifying the variation of the dust detection output include a method of obtaining a variance, a method of obtaining a standard deviation, a method of obtaining a sum of differences between individual data and their average values, and a method of obtaining a sum of individual data and their average values. A method of obtaining an average value of the differences can be exemplified.

The dust detecting device according to a third aspect of the present invention further includes a prohibiting means for prohibiting the use of a new offset value until a predetermined time has elapsed after detecting the dust. Here, as the predetermined time, for example, a time required for the dust once floating to settle to some extent can be exemplified. A dust detection device according to a fourth aspect is a dust detection device that is incorporated in a device that needs to control its operation in accordance with the concentration of dust and receives scattered light caused by dust particles to detect the concentration of dust. Means for preventing the outside air from being guided to the dust sensor for a predetermined time when the dust sensor included in the apparatus or the dust detection device is activated, and a period during which the outside air is prevented from being guided to the dust sensor. And an offset value adopting means for employing the dust detection output of the dust sensor as an offset value of the dust detection output, and a density detecting means for correcting the dust detection output with the offset value and detecting the density of the dust.

According to a fifth aspect of the present invention, there is provided a dust detection device, wherein the dust detection output is output as a result of receiving the scattered light caused by the dust particles, or the dust detection output is output in time series. A dust detection output that is obtained by accumulatively adding a difference between outputs that are output in response to receiving light is adopted. The dust detection method according to claim 6 is a dust detection method for detecting the concentration of dust by receiving scattered light caused by dust particles, wherein the variation in dust detection output is detected, and the detected variation is set in advance. In response to the determination that the variation is smaller than the threshold value, the corresponding dust detection output is adopted as an offset value of the dust detection output, and the dust detection output is corrected by the offset value to correct the dust detection output. This is a method for detecting the concentration.

According to a seventh aspect of the present invention, there is provided a dust detection method, wherein the dust detection output is output when the scattered light caused by the dust particles is received, or the dust detection output is output in time series. This method employs a dust detection output that is cumulatively added to a difference between outputs that are output in response to receiving light.

[0012]

According to the first aspect of the present invention, in detecting dust concentration by receiving scattered light caused by dust particles,
The variation in the dust detection output is detected by the variation detection means, and the detected variation is compared with a threshold value set in advance by the comparison means. In response to the determination that the variation is smaller than the threshold value, the corresponding dust detection output Is adopted as an offset value of the dust detection output by the offset value adopting means, and the density of the dust can be detected by correcting the dust detection output with the offset value by the density detecting means. Therefore, if a variation in the dust detection output can be detected, and if the detected variation is smaller than a preset threshold, the dust detection output is immediately adopted as an offset value, thereby achieving highly accurate dust detection. be able to.
In other words, it is possible to achieve both quickness in adopting an appropriate offset value and high accuracy in dust detection.

According to a second aspect of the present invention, there is provided a dust detecting apparatus which employs a variation detecting means for quantifying a variation in dust detection output, and as a comparing means, compares the quantified variation with a preset threshold value. Therefore, the same operation as the first aspect can be achieved. The dust detection device according to claim 3 further includes a prohibition unit that prohibits the adoption of a new offset value until a predetermined time elapses after detecting the dust, so that the amount of dust is large and the dust detection output is high. Is smaller than the threshold,
The inconvenience that the offset value is changed can be greatly reduced.

According to a fourth aspect of the present invention, there is provided a dust detecting device incorporated in a device whose operation needs to be controlled in accordance with the concentration of dust. In detecting the concentration, when the dust sensor included in the device or the dust detection device is activated, the blocking unit prevents the outside air from being guided to the dust sensor for a predetermined time, and prevents the outside air from being guided to the dust sensor. The dust detection output of the dust sensor during the period during which the dust detection output is adopted as the offset value of the dust detection output by the offset value adopting means, and the density detection means corrects the dust detection output with this offset value to detect the dust density. it can. Therefore, the offset value can be obtained by keeping the dust detection area of the dust sensor in a clean state, the dust detection can be made highly sensitive, and the process for obtaining the offset value is performed by the original operation of the device and the original operation of the dust sensor. Almost no inconvenience of hindering operation can be eliminated.

In the dust detection device according to the present invention, the dust detection output is output as a result of receiving the scattered light caused by the dust particles, or the dust detection output is caused by the dust particles in a time series. Since the dust detection output that is output by cumulatively adding the difference between the outputs that are output in response to receiving the scattered light that is output is adopted, even when any of the dust detection outputs is adopted. The same operation as any of claims 1 to 4 can be achieved.

According to the dust detecting method of the present invention, when detecting the concentration of dust by receiving the scattered light caused by the dust particles, a variation in the dust detection output is detected, and the detected variation is set in advance. In response to the determination that the variation is smaller than the threshold value, the corresponding dust detection output is adopted as an offset value of the dust detection output, and the dust detection output is corrected by the offset value to correct the dust detection output. Since the density is detected, a variation in the dust detection output can be detected, and if the detected variation is smaller than a preset threshold value, it is immediately adopted as an offset value, thereby achieving highly accurate dust detection. Can be. In other words, it is possible to achieve both quickness in adopting an appropriate offset value and high accuracy in dust detection.

According to the seventh aspect of the present invention, as the dust detection output, the dust detection output output in response to receiving the scattered light caused by the dust particles, or the dust detection output caused by the dust particles in time series. Since the dust detection output that is output by cumulatively adding the difference between the outputs that are output in response to receiving the scattered light that is output is adopted, even when any of the dust detection outputs is adopted. Thus, the same function as that of claim 6 can be achieved.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an internal mechanism of an example of a dust sensor included in the dust detection device of the present invention, and FIG. 2 is a schematic front view. The dust sensor includes a substrate 1 on which a light emitting unit 1a formed of a light emitting diode and the like and a light receiving unit 1b formed of a photodiode and the like are mounted, and a dark box (case body) 2. Here, as the substrate 1, for example, a printed wiring board made of glass epoxy can be exemplified, and as the dark box 2, for example, an acrylonitrile butadiene styrene copolymer (hereinafter, ABS)
) Can be exemplified.

The dark box 2 is a rectangular parallelepiped box. A wall member extending upward is formed inside the dark box 2 to form a light-emitting portion accommodating space 2a and a light-receiving portion accommodating space 2b. Lens systems 2c and 2d are provided in the housing space 2a and the light receiving unit housing space 2b, respectively. The two lens systems 2c and 2d are arranged so that the optical axes of the two lens systems 2c and 2d form a predetermined angle. In addition, a hole is formed on the optical axis of the lens system 2c and in the inner part of the light emitting unit housing space 2a to allow the light emitting unit 1a to enter. Note that the lens system 2c can be omitted.

The light emitted from the light emitting portion 1a through the lens system 2c is prevented from being guided directly to the light receiving portion 1b through the lens system 2d in the intermediate portion between the light emitting portion housing space 2a and the light receiving portion housing space 2b. A light shielding member 2e is provided. Further, a noise light shielding member 2f for preventing light possibly acting as noise light from being guided to the light receiving portion 1b through the lens system 2d is substantially the same as the light emitting portion housing space 2a, the light receiving portion housing space 2b, and the light shielding member 2e. It is provided at a position facing directly. A plurality of noise light shielding members 2f are provided, and the noise light shielding members 2f adjacent to each other constitute a noise light attenuation chamber. The light introduced into the noise light attenuating chamber is reflected a plurality of times on the inner wall surface of the chamber where the absorbance is high, so that its intensity is sufficiently attenuated. In addition, a hole 2j for allowing direct light to pass therethrough is formed at a predetermined position of the noise light shielding member 2f to which the direct light from the light emitting unit 1a is radiated, and the noise light shielding member 2f and the light receiving unit housing space are formed. The light trap 2k is composed of the plate member defining the second box 2b and the outer wall member of the dark box 2. Further, an opening 2i for introducing a fluid is provided at a predetermined position near the tip of the light shielding member 2e. Needless to say, an opening (not shown) for introducing a fluid is also provided at a corresponding portion of the substrate 1.

FIG. 3 is a block diagram showing one embodiment of the dust detection device of the present invention. The dust detection device includes a dust detection output holding unit 12 that takes in a dust detection output from a dust sensor 11 at predetermined sampling times and temporarily and chronologically holds a predetermined number of the dust detection outputs. A variation calculator for calculating a variation in the dust detection output based on a predetermined number of dust detection outputs held in time series by the controller; a variation calculated by the variation calculator and a preset threshold; And a corresponding dust detection output in response to a comparison result signal from the comparison unit 14 indicating that the variation calculated by the variation calculation unit 13 is smaller than the threshold value. An offset value holding unit 15 that holds an offset value for correcting the offset, and a dust detection output from the dust sensor 11 and an offset value held by the offset value holding unit 15. And a correction unit 16 that calculates a difference between the two by using the input value as an input and outputs the corrected dust detection output as a corrected dust detection output, and outputs a dust concentration and the like using the corrected dust detection output output from the correction unit 16 as an input. And an output unit 17.

As the dust detection output, the dust detection output from the dust sensor 11 may be used as it is, but the difference between the dust detection outputs from the dust sensor 11 obtained in time series is calculated and obtained. The sum of the differences may be used as the dust detection output. Here, the inventor of the present application has empirically found that the latter dust detection output corresponds to the concentration of dust in the air.

The variation calculator 13 calculates the variance, the standard deviation, the sum of the differences between individual data and their average values, the average value of the differences between individual data and their average values, and the like. Is to be numerically expressed. The threshold value is empirically determined based on, for example, a variation in the dust detection output when there is almost no dust.

The corresponding dust detection output may be, for example, any of the dust detection outputs used for detecting variation, but may be an average value of the dust detection outputs used for detecting variation. Is also good. The output unit 17 converts the dust detection output into a density of dust and the like based on the amplitude and frequency of the dust detection output after the correction, and outputs the same. Detailed description is omitted. However, when outputting the output signal from the output unit 17 as a control signal for controlling the operation of the air purifier or the like, it is not necessary to output a signal that accurately indicates the concentration of dust or the like. It is enough to output a signal indicating whether the density is higher than the set dust concentration. In this case, by setting a preset dust concentration to a plurality of concentrations,
For example, the operation of the air purifier can be controlled in a plurality of stages such as strong, weak, and stopped.

The operation of the dust detecting device having the above configuration is as follows. When the atmosphere to be measured does not contain any dust, the light emitted from the light emitting unit 1a through the lens system 2c propagates straight as it is, and is not irradiated at all to the lens system 2d due to the presence of the light shielding member 2e. As a result, the dust detection output output from the light receiving section 1b remains small. At least a part of the light propagating linearly is introduced into the optical trap 2k through the hole 2j and is almost completely attenuated by being confined. The remainder of the light propagating linearly is a noise light blocking member 2f having a hole 2j, a noise light blocking member 2f facing the noise light blocking member 2f, and a noise light formed by the outer wall member of the dark box 2. It is sufficiently attenuated by multiple reflection in the attenuation chamber. Therefore, noise light caused by direct light from the light emitting unit 1a hardly affects the light receiving unit 1b.

Conversely, when the atmosphere to be measured contains dust, the fluid containing dust enters the interior of the dark box 2 through the fluid introduction opening 2i, and is emitted from the light emitting section 1a through the lens system 2c. Light is scattered and reflected by the dust particles, and a part of the scattered reflected light is guided to the light receiving unit 1b through the lens system 2d. As a result, the dust detection output output from the light receiving section 1b increases according to the intensity of the scattered reflected light received. In addition, since the light propagating linearly is sufficiently attenuated by the noise light attenuation chamber and the optical trap 2k, it hardly affects the light receiving portion 1b.

The above description corresponds to an ideal state. In an actual use state, for example, even if the atmosphere to be measured does not contain any dust, the lens system 2
c, if the dust particles adhere to the light shielding member 2e, the noise light shielding member 2f, etc., the scattered reflected light caused by such dust particles affects the light receiving portion 1b, and the dust detection output is measured. The state does not exactly correspond to the amount of dust in the atmosphere. Conventionally, it is considered that it is impossible to accurately grasp the amount of dust particles attached to the lens system 2c, the light shielding member 2e, the noise light shielding member 2f, and the like. Therefore, it has conventionally been considered that it is impossible to accurately correct the dust detection output.

However, when the dust detection device of the present invention is adopted, the lens system 2c and the light shielding member 2
e. The dust detection output can be accurately corrected by eliminating the influence of dust particles attached to the noise light shielding member 2f and the like. That is, the dust detection output holding unit 12 takes in the dust detection output from the dust sensor 11 every predetermined sampling time, and temporarily and chronologically holds a predetermined number of the dust detection outputs. Based on the predetermined number of dust detection outputs held in series, the variation calculation unit 13 calculates the variation in the dust detection output, and the comparison unit 14 sets the variation calculated by the variation calculation unit 13 in advance. In response to a comparison result signal from the comparison unit 14 indicating that the variation calculated by the variation calculation unit 13 is smaller than the threshold value, the offset value holding unit 15 The detection output is held as an offset value for correcting the dust detection output, and the correction unit 16 offsets the dust detection output from the dust sensor 11 from the dust detection output. The difference between the two is calculated by using the offset value held in the value holding unit 15 as an input and output as a corrected dust detection output. The output unit 17 outputs the corrected dust detection output output from the correction unit 16. Can be used as an input to output the concentration of dust and the like.

In the above description, the variation in the dust detection output is caused not only by the change in the amount of dust contained in the measurement target atmosphere introduced into the dark box 2 but also by the measurement target atmosphere introduced into the dark box 2. Even when the amount of dust contained in the image hardly changes, it is also caused by a quantization error, electric noise, or the like. However, the former variation has a characteristic that if measured within a certain period of time, it will be quite large, whereas the latter variation will not become too large if measured within a certain period. Therefore, by comparing the magnitude of the variation calculated by the variation calculation unit 13 with a preset threshold value, it is possible to determine which variation is quite accurate.

Therefore, when it is determined that the variation is the latter, the corresponding dust detection output is held as an offset value, and thereafter, the dust detection output is corrected using this offset value, so that the lens system etc. It is possible to detect the density of dust and the like with high accuracy while eliminating the influence of errors caused by dirt and the like. FIG. 4 is a block diagram showing another embodiment of the dust detection device of the present invention.

This dust detection device causes the operation of an air cleaner or the like based on the output from the output unit 17 indicating that dust has been detected, and then responds to the stop of the operation of the air cleaner or the like. Then, a predetermined time (for example, 2
Timer 18 for measuring the time of a predetermined time of about 30 minutes to 30 minutes)
And a prohibition unit 19 that receives a non-time-up signal output from the timer 18 and outputs a prohibition signal for prohibiting the offset value holding unit 15 from holding a new offset value.
3 is different from the dust detection device of FIG. The configuration of the other parts is the same as that of the dust detection device of FIG. 3, and thus the detailed description is omitted.

In the case where this dust detection device is adopted,
When the operation of the air purifier or the like is performed based on the output from the output unit 17 indicating that the dust has been detected, when the operation of the air purifier or the like is stopped, the timer 18 counts a predetermined time. Until the timer 18 outputs a time-up signal, the prohibition unit 19 outputs a prohibition signal to prohibit the offset value holding unit 15 from holding a new offset value.

Therefore, during this period, even if the variation in the dust detection output is smaller than the threshold value, the updating of the offset value is prohibited, and the inconvenience of using an incorrect offset value is prevented. Can be prevented. This disadvantage will be described in more detail. When the operation of an air purifier or the like is performed by detecting dust and then the operation of the air purifier or the like is stopped, the variation in the dust detection output is larger than the threshold value despite the large amount of dust. May be smaller. If the offset value is updated in such a state, the offset value becomes extremely large, and thereafter, it becomes impossible to perform normal dust detection. In connection with this point, the present inventor considered the behavior of dust, the amount of dust is large,
In addition, it has been found that when a state in which the variation in the dust detection output becomes smaller than the threshold value is accidentally continued, the duration is at most several tens of seconds. They also found that the dust that once floated generally settled out within 30 minutes. Based on these findings, the time to prohibit updating of the offset value is set to 2
It is enough to secure about 30 minutes, and if this time is set to 30 minutes, the offset value can be updated after the dust has substantially settled, so that the accuracy of the offset value and, consequently, the accuracy of dust detection can be improved. it can.

FIG. 5 is a block diagram showing still another embodiment of the dust detection device of the present invention. This dust detection device,
A device (for example, an air cleaner) that operates based on an output signal from the dust detection device, or a predetermined time (for example, 10 to 10) in response to activation of the dust sensor 11.
The outside air introduction preventing unit 20 for preventing the outside air from being introduced into the dark box 2 of the dust sensor 11 for 30 seconds), and the outside air being introduced into the dark box 2 of the dust sensor 11 by the outside air introduction preventing unit 20. Value holding unit 21 that holds the dust detection output from dust sensor 11 as an offset value for correcting the dust detection output in response to preventing dust detection.
And input of the dust detection output from the dust sensor 11 and the offset value held in the offset value holding unit 21 in response to the introduction of the outside air into the dark box 2 of the dust sensor 11. A correction unit 22 that calculates the difference between the two and outputs the result as a corrected dust detection output, and an output unit 23 that receives the corrected dust detection output output from the correction unit 22 and outputs dust density and the like. Have.

Examples of the outside air introduction preventing section 20 include a mechanism for closing an entrance of the dust sensor 11, a mechanism for closing a part of a ventilation path to the dust sensor 11, a mechanism for stopping a fan for sucking outside air, and the like. . The offset value holding unit 21 may be, for example, one that holds an arbitrary dust detection output as an offset value among dust detection outputs sampled at a predetermined cycle, and one that holds a dust detection output sampled at a predetermined cycle. Examples include a device that holds the minimum dust detection output as an offset value, a device that calculates an average value of dust detection outputs sampled at a predetermined cycle, and stores the average value as an offset value.

When the dust detection device of this embodiment is employed, a device which operates based on an output signal from the dust detection device, or a device which prevents the introduction of outside air in response to the activation of the dust sensor 11. The unit 20 prevents the outside air from being introduced into the dark box 2 of the dust sensor 11 for a predetermined time. During this time, the offset value holding unit 21 obtains and holds an offset value.
The dust detection output from the dust sensor 11 is corrected by the offset value to obtain a corrected dust detection output, and the output unit 23 can output a proud density or the like. That is, the dust sensor 1
In a state where dust is not introduced into the inside of the first dark box 2, an accurate offset value is obtained by obtaining an offset value based on the dust detection output of the dust sensor 11, and the dust detection output is corrected based on this offset value. Thereby, the dust detection accuracy can be improved. Also, the outside air introduction prevention time is set to 10 to 30 seconds because, for example, when the power is turned on to operate an air purifier or the like, a time of 30 seconds or more is required before the actual operation. If this is the case, there is a sense problem for the user. If a time shorter than 10 seconds is set, an accurate offset value may not always be obtained due to the influence of electric noise or the like. Because there is.

FIGS. 6 and 7 are flow charts for explaining one embodiment of the dust detecting method according to the present invention. The processing based on this flowchart is performed for dust detection for controlling the operation of the air purifier. Step SP
In step 1, sampling of the dust detection output is performed at a predetermined cycle (for example, 0.01 second cycle). At step SP2, until it is determined at step SP2 that sampling for a predetermined period (for example, one second) is completed. Is repeated. If it is determined in step SP2 that sampling for a predetermined period has been completed, step SP3
In step SP4, a cumulative value of the dust detection output sampled during a predetermined period is calculated, and in step SP4, the calculated cumulative value is stored in a first memory (for example, a first FIFO memory).
To be stored. Here, the first memory stores a preset number (for example, 5) of cumulative values (the cumulative value of the latest predetermined period,
The accumulated value of the preceding predetermined period, the accumulated value of the preceding predetermined period, and so on can be stored. 8 and 9 are diagrams showing an example of a transition of the sum (V) of the accumulated value for one second for 5 seconds, and FIG.
FIG. 9 corresponds to a state with little dust. Note that the sum of the accumulated value for one second for five seconds corresponds to a numerical value level described later.

In step SP5, it is determined whether or not a preset number of accumulated values are stored in the first memory, and it is determined that the number of stored accumulated values is smaller than the preset number. If not, step SP again
1 is performed. If it is determined in step SP5 that a predetermined number of accumulated values are stored in the first memory, a numerical value level indicating the magnitude of the accumulated value is calculated in step SP6. Where the numerical value leave
The calculation of 1 is performed, for example, by subtracting the offset value offset used at that time from the average value of a preset number of accumulated values stored in the first memory. Next, in step SP7, a flag flg_dust indicating whether or not the pulse appears once or not is set. Here, the flag flg_dust is set to 1 when the number of cumulative values exceeding a preset threshold value “border” is equal to or more than a predetermined number among the preset number of cumulative values, and is set to 0 otherwise. You. That is, the flag flg_dust is for preventing a malfunction due to a sudden dust detection in a state where the dust is small. Next, in step SP8, it is determined whether or not the condition of strong driving is satisfied. That is, level> WIN_PWR
(WIN_PWR is a threshold value for strong driving) and flg_du
It is determined whether st = 1 or not, and if the condition of strong driving is not satisfied, in step SP10, it is determined whether the condition of weak driving is satisfied, ie, level> WI.
N_WK (WIN_WK is the threshold value for weak driving) and flg
It is determined whether _dust = 1 or not.

If it is determined in step SP8 that the conditions for strong driving are satisfied, the process proceeds to step S8.
In P9, the timer value of the strong operation timer is set to CYCLE_
Set to P and start strong operation timer. Step SP1
When it is determined that the condition of the weak operation is satisfied at 0, the strong operation timer is set to 1 at step SP11.
Advance in seconds. That is, the timer value of the strong operation timer is decremented by one. If it is determined in step SP10 that the condition of the weak operation is not satisfied, the strong operation timer and the weak operation timer are advanced by one second in step SP13. That is, the timer values of the strong operation timer and the weak operation timer are decremented by one.

Processing in step SP9 or step S
When the process of P11 has been performed, in step SP12, the timer value of the weak operation timer is set to CYCLE_W, and the weak operation timer is started. Here, both timer values C
YCLE_P and CYCLE_W are preset seconds, and when any of the timer values is positive, the air purifier is operated. Also, the timer value CYCLE_ of the strong operation timer
When P is positive, the air purifier is strongly operated, and when the timer value CYCLE_P of the strong operation timer is 0 and the timer value CYCLE_W of the weak operation timer is positive, the air cleaner is weakly operated. Of course, both timer values CYCLE_P, CYC
When LE_W is 0, the air purifier stops.

When the processing in step SP12 or the processing in step SP13 is performed, the processing in step SP14
In step SP15, the variance ss of all the accumulated values stored in the first memory is calculated. In step SP15, the calculated variance ss is smaller than a preset threshold value border_ss, and the air purifier is in an operation stop state. It is determined whether or not. In step SP15, when it is determined that the calculated variance ss is smaller than the preset threshold value border_ss and the air purifier is in the operation stop state, in step SP16, all the values stored in the first memory are determined. The average of the cumulative value of
It is stored in a memory (for example, a second FIFO memory). Here, the reason why the operation stop state of the air purifier is determined is to provide a period during which updating of the offset is prohibited. That is, one of the CYCLE_P and CYCLE_W matches the prohibited section. The second memory is configured to be able to store a predetermined number (for example, 10) of average values. Next, in step SP17, it is determined whether or not an average value of a preset number is stored in the second memory.

If it is determined in step SP17 that the predetermined number of average values are stored in the second memory, then in step SP18, the average value off_ave of all the average values stored in the second memory is determined. Is calculated, and in step SP19, a new offset value o
ffset is calculated. This new offset value off
The calculation of the set is, for example, (offset × K + off
_Ave) / (K + 1). Here, K is a constant that gives a weight between the average value off_ave and the offset value offset before that, and is determined empirically, for example.

If it is determined in step SP15 that the calculated variance ss is equal to or greater than the preset threshold value border_ss or that the air purifier is in the operating state, the data in the second memory is read in step SP20. Clear all. If it is determined in step SP17 that only an average value smaller than the preset number is stored in the second memory, if the processing of step SP19 is performed, or if the processing of step SP20 is performed. Performs the process of step SP1 again.

When the above-described series of processing is performed, instead of using each dust detection output of the dust sensor 11 as it is,
The average value of the cumulative value of the dust detection outputs obtained within the predetermined period is used as the dust detection output. If the number of cumulative values exceeding the preset threshold value “border” is small, it is regarded as a sudden dust detection, and the operation of the air purifier based on the dust detection output and the offset value “offset” adopted at the time is determined. Not reflected in control. As a result, accurate control of the operation of the air purifier can be achieved by eliminating the influence of sudden dust detection.

Further, the variance ss of all the accumulated values stored in the first memory is obtained, and each time the accumulated value stored in the first memory is updated after a predetermined period of time, the first variance ss is obtained. The variance ss of all the accumulated values stored in the memory is obtained, and when the number of variances s thus obtained reaches a preset number, a new ss based on all the obtained variance ss is obtained. After that, the dust detection output is corrected based on the new offset value offset, and the accurate control of the operation of the air purifier can be achieved based on the corrected dust detection output. . However, all the variances ss used as the basis for calculating the new offset value offset are equal to the preset threshold b
Since it is smaller than order_ss and obtained continuously, it is possible to prevent the inconvenience that the variance ss becomes too large, and eventually the offset value offset becomes too large.

In each of the above embodiments, the variation may be evaluated based on the history of the dust detection output output from the dust sensor 11, or the dust sensor 11 may be evaluated in chronological order.
The variation may be evaluated based on the history of the result (dust detection output) obtained by cumulatively adding the difference between the dust detection outputs output from the. In these cases, an offset value for correcting the dust detection output output from the dust sensor 11 may be set, or the dust sensor 1 may be set in time series.
An offset value for correcting the result (dust detection output) obtained by cumulatively adding the difference between the dust detection outputs output from 1 may be set.

By adopting a configuration for setting an offset value for correcting the dust detection output output from the dust sensor 11, not only the variation but also the level of the dust detection output is high or low. Can be determined. Therefore, when it is determined that the level of the dust detection output is high and the variation is small, it can be determined that tobacco smoke is present. Further, when it is determined that the cigarette smoke is present, the smoke density of the cigarette is sufficiently low to prevent a significantly large offset value from being set due to the cigarette smoke. It is preferable to prohibit the holding of the new offset value for several hours (2 to 3 hours or more) until the value is attenuated.

[0048]

According to the first aspect of the present invention, it is possible to achieve both a quick adoption of an appropriate offset value and a high accuracy of dust detection. The invention of claim 2 has the same effect as that of claim 1. The invention according to claim 3 has a unique effect that when the amount of dust is large and the variation of the dust detection output is smaller than the threshold value, the disadvantage that the offset value is changed can be significantly reduced. .

According to the fourth aspect of the invention, the offset value can be obtained by keeping the dust detection area of the dust sensor in a clean state, the sensitivity of the dust detection can be increased, and the processing for obtaining the offset value is originally performed by the apparatus. And the inherent effect that the original operation of the dust sensor is obstructed can be almost completely eliminated. The invention of claim 5 is the invention of claim 1
Accordingly, the same effect as any one of the fourth aspect is obtained.

The sixth aspect of the invention has a unique effect that both the speed of adopting an appropriate offset value and the high accuracy of dust detection can be achieved. The invention of claim 7 has the same effect as that of claim 6.

[Brief description of the drawings]

FIG. 1 is a plan view showing an internal mechanism of an example of a dust sensor included in a dust detection device of the present invention.

FIG. 2 is a schematic front view of the same.

FIG. 3 is a block diagram showing one embodiment of the dust detection device of the present invention.

FIG. 4 is a block diagram showing another embodiment of the dust detection device of the present invention.

FIG. 5 is a block diagram showing still another embodiment of the dust detection device of the present invention.

FIG. 6 is a diagram showing a part of a flowchart illustrating an embodiment of a dust detection method according to the present invention.

FIG. 7 is a diagram showing the remaining part of the flowchart illustrating one embodiment of the dust detection method of the present invention.

FIG. 8 is a diagram showing an example of a transition of the total value of the accumulated value for one second for five seconds.

FIG. 9 is a diagram illustrating an example of a transition of the total value of the accumulated value for one second for five seconds.

[Explanation of symbols]

11 Dust Sensor 12 Dust Detection Output Holder 13
Variation calculation unit 14 Comparison unit 15 Offset value holding unit 16 Correction unit 17 Output unit 18 Timer 19 Prohibition unit 20 Outside air introduction prevention unit 21 Offset value holding unit 22 Correction unit 23 Output unit

Claims (7)

[Claims] A dust detection device for detecting scattered light caused by dust particles and detecting the concentration of dust, wherein the variation detection means (1) detects variation in dust detection output.
(3) comparing means (14) for comparing the detected variation with a preset threshold; and offsetting the corresponding dust detection output in response to the determination that the variation is smaller than the threshold to the dust detection output. Offset value adopting means (15) adopted as a value, and density detecting means (16) for correcting dust detection output with this offset value and detecting dust density
(17) A dust detection device comprising: 2. A variation detecting means (13) for quantifying a variation in a dust detection output, the comparing means (1).
The dust detection device according to claim 1, wherein 4) compares the quantified variation with a preset threshold value. 3. A prohibiting means (1) for prohibiting the adoption of a new offset value until a predetermined time has elapsed after detecting dust.
8) The dust detection device according to claim 1 or 2, further comprising (19). 4. A dust detection device that is incorporated in a device that needs to control its operation in accordance with the concentration of dust and receives scattered light caused by dust particles to detect the concentration of dust. Including a blocking means (20) for preventing outside air from being guided to the dust sensor (11) for a predetermined time when the dust sensor (11) included in the dust detection device is activated,
Offset value adopting means (21) for adopting a dust detection output of the dust detection sensor as an offset value of the dust detection output during a period in which outside air is prevented from being guided to the dust sensor.
And a density detecting means (22) and (23) for detecting the density of dust by correcting the dust detection output with the offset value. 5. The dust detection output includes a dust detection output output in response to receiving scattered light caused by dust particles, or a dust detection output output in response to scattered light caused by dust particles in time series. 5. The dust detection device according to claim 1, wherein the dust detection device is a dust detection output that is output by accumulatively adding a difference between outputs output from the dust detection device. 6. A dust detection method for detecting the concentration of dust by receiving scattered light caused by dust particles, detecting a variation in dust detection output, and comparing the detected variation with a preset threshold. Then, in response to the determination that the variation is smaller than the threshold value, the corresponding dust detection output is adopted as an offset value of the dust detection output, and the dust detection output is corrected with this offset value to detect the dust concentration. A dust detection method, comprising: 7. The dust detection output is a dust detection output that is output in response to receiving scattered light caused by dust particles, or a chronologically-acquired scattered light that is caused by dust particles. The dust detection method according to claim 6, wherein the dust detection output is a dust detection output that is output by accumulatively adding a difference between outputs that are output through the dust detection.