KR20180048117A - Air purifying apparatus - Google Patents

Abstract

The present invention relates to an air purification apparatus to adjust an air volume of discharged air with respect to surrounding environment and a change in pollution levels of the air purification apparatus. According to the present invention, the apparatus comprises: a fan driving unit to operate a fan; a pollution detection unit to detect pollution of air; and a control unit acquiring a pollution detection value from the pollution detection unit to determine a pollution level and controlling the fan driving unit with an air volume corresponding to the determined pollution level. The control unit compares the previously determined pollution level with the current determined pollution level to determine whether the pollution level is increased or decreased, and controls the fan driving unit by performing air volume addition reinforcement with respect to the air volume corresponding to the current determined pollution level when the pollution level is increased, or by adding a holding time to a standard time with the air volume corresponding to the previously determined pollution level when the pollution level is decreased.

Description

{AIR PURIFYING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an air cleaning apparatus, and more particularly to an air cleaning apparatus that adjusts the air volume of discharged air on the basis of changes in environmental conditions and pollution degree steps of the air cleaning apparatus.

Recently, modern people are living 80% of the day in the indoor space of houses, offices and underground spaces. For modern people, who spend most of their time indoors, pleasant indoor environment can increase work efficiency, It is becoming a very important factor in maintaining good health. Particularly, as human living standards are improved, there is a growing demand for more pleasant indoor environment.

However, in general, the air in the enclosed space increases the content of odor and harmful gas over time due to respiration or smoking of the innocent person, which interferes with breathing of the innocent person, and various dusts It will cause unpleasantness to the person who is confused.

In order to solve such discomfort, there have been developed various types of air purifying apparatuses capable of removing dust, odors, and noxious gases from indoor air.

The conventional air cleaning apparatus includes a cabinet having an air inlet and an air outlet formed therein, a blower installed in the cabinet for forcibly blowing air into and out of the cabinet, and an air cleaner installed in the cabinet for blowing air blown into the cabinet through the air inlet And a controller for controlling the operation of the air cleaning apparatus and informing the current operating state of the air cleaning apparatus when the operating condition of the air cleaning apparatus is inputted.

The controller largely detects the degree of contamination of the air cleaning device in the operating condition of the air cleaning device, that is, in the manual mode in which the air flow rate is set, and in the place where the air cleaning device is installed through the gas sensor and the dust sensor, An automatic mode in which the air volume as the operation condition of the air cleaning apparatus is set or a turbo mode in which the air volume is set as the maximum air volume.

However, since air convection is weak in a general indoor space, when the air amount is adjusted according to the degree of contamination at a place where the conventional air purifying apparatus is installed in the automatic mode, only the air around the air purifying apparatus is cleaned or the cleaning time is considerably long And particularly when the air cleaning device is installed in a large space, the problem becomes more serious. Further, in the case of the turbo mode, although a wide range of air can be cleaned, noise (for example, 50 dB or more) is generated, which causes inconvenience to the user.

The air purifying apparatus of the present invention adjusts the intensity of the air flow rate and the holding time of the air purifying apparatus on the basis of changes in the surrounding environment and the degree of pollution, thereby smoothly convecting the air, And an object thereof is to provide an air cleaning apparatus.

The air cleaning apparatus according to the present invention includes a fan driving unit for driving a fan, a pollution sensing unit for sensing air contamination, a pollution sensing unit for determining a pollution level by acquiring a pollution sensing value from the pollution sensing unit, Wherein the control unit controls the fan driving unit to perform air cleaning by comparing a previously determined pollution degree step with a currently determined pollution degree step to determine whether the pollution degree step is rising or falling, And a control unit for controlling the fan driving unit by adding a holding time to the basic time with an air volume corresponding to the previously determined pollution degree step when the pollution degree step is lowered.

Preferably, the control unit controls the fan driving unit to increase the air flow rate by an air flow rate exceeding the air flow rate corresponding to the currently determined pollution level at the rising of the pollution degree step.

In addition, when the air volume corresponding to the currently determined pollution degree step is the maximum air volume of the fan driving unit, the controller preferably controls the fan driving unit with the air volume corresponding to the currently determined pollution degree step.

Preferably, the control unit adds the holding time to the base time when the previously determined pollution degree step is included in the high pollution degree step area when the pollution degree step is lowered.

Preferably, the control unit determines the holding time according to the surrounding environment and adds the determined holding time to the basic time.

When the previously determined pollution degree step is included in the low pollution degree step region when the pollution degree step is lowered, the control unit controls the fan driving unit during the basic time with the air amount corresponding to the previously determined pollution degree step desirable.

Preferably, the control unit determines the surrounding environment by using the contamination detection value from the pollution detection unit while performing the air cleaning.

Preferably, the controller determines the surrounding environment by calculating an elapsed time at which the contamination detection value is reduced from the start detection value to the end detection value of the determination detection range.

Preferably, the controller compares the calculated elapsed time with at least one determination reference time to determine the surrounding environment.

The present invention has the effect of facilitating the convection of the air with an air volume exceeding the air volume corresponding to the degree of pollution step at the time of rising of the pollution degree step, thereby promptly cleaning the entire air at the installation place.

The present invention also relates to a method for controlling air convection by maintaining the air volume of the previous pollution level step by adding the holding time determined by the surrounding environment of the air cleaning apparatus at the basic time when the previous pollution degree step is high when the pollution degree step is lowered So that the air can be uniformly cleaned in the entire space.

In addition, the present invention can accurately and quickly (for example, smoothly, normally, stagnant) the environment in which the air cleaning apparatus is installed based on the elapsed time during which the contamination detection value is reduced within the judgment detection range while performing the air cleaning And performing air cleaning according to the determined surrounding environment, there is an effect that the air is uniformly cleaned in the entire space.

1 is a control block diagram of an air cleaning apparatus according to the present invention.
FIG. 2 is a control flowchart of the air cleaning apparatus of FIG. 1; FIG.
FIG. 3 is a flow chart of a process of determining the ambient environment performed by the air cleaning apparatus of FIG. 1;
FIG. 4 is graphs of reduction of the contamination detection value according to the surrounding environment.

Hereinafter, the present invention will be described through embodiments and drawings.

The air cleaning apparatus of the present invention comprises a cabinet having an air inlet and an air outlet formed therein, a fan installed in the cabinet for sucking air through the air inlet and forcedly blowing air to be discharged through the air outlet, And a mechanical device having at least one filter that cleans air blown into the interior of the cabinet.

1 is a control block diagram of an air cleaning apparatus according to the present invention. The air cleaning apparatus includes an input unit 1 for acquiring an operation mode (manual mode, automatic mode, room care mode, and the like) from the user, and a control unit for visually and / or audibly A fan driving unit 5 for driving the fan to perform forced air circulation, a contamination detecting unit 7 for detecting contamination of the air inside and outside the air cleaning apparatus, 7 and performs the air cleaning by controlling the fan driving unit 5 in accordance with the operation mode from the input unit 1 or the pre-stored operation mode. In particular, in performing the room care mode, (Fan speed) of the air discharged on the basis of the change in the degree of contamination of the surrounding environment and / or the surrounding environment. However, the power supply unit (not shown), the input unit 1, the display unit 3, and the fan driving unit 5 are merely technical skills that a person of ordinary skill in the art perceives, A detailed description is omitted.

The pollution sensing unit 7 senses the concentration of a pollution source (for example, dust, gas, etc.) contained in the air inside and outside the air cleaning apparatus and applies the pollution detection value to the control unit 10. The pollution sensing unit 7 may include a dust sensor and / or a gas sensor which are installed separately from each other. The dust sensor detects the amount of scattered light by measuring the scattered light pattern according to the size of particles included in the air when the light is irradiated to the air, and measures the contamination detection value, which is the number of dusts contained in the air, For example, it may be constituted of a first dust sensor for measuring a dust concentration of 1.0 mu m and a second dust sensor for measuring a dust concentration of 0.7 mu m in size and spaced apart from the first dust sensor. The gas sensor measures the pollution detection value, which is the gas pollution degree, by the kind or composition ratio of the gas.

The control unit 10 receives the contamination detection values for at least one of the pollutants (for example, 1.0 mu m dust, 0.7 mu m dust, gas, etc.) from the pollution sensing unit 7. [ The control unit 10 stores pollution degree data indicating a pollution degree step corresponding to the contamination detection value of each pollution source (for example, from the cleanest first step to the sixth polluted step) Each pollution degree step corresponding to the pollution detection value is determined using the pollution degree step data, and finally, the pollution degree step of the present air is determined by taking all or consideration of all the determined pollution degree steps all together. For example, when determining the pollution level of the present air, the controller 10 determines the highest pollution level among the pollution levels corresponding to the plurality of pollution detection values applied from the pollution detection unit 7 as the pollution level of the present air Or, if they are the same, determine the same step as the current pollution level of the air. Table 1 below are examples of pollution degree steps determined by the control unit 10.

Occation The first dust sensor The second dust sensor Gas sensor Determined contamination level In the first case Stage 1 Stage 1 Stage 1 Stage 1 In the second case Stage 1 Step 3 Stage 1 Step 3 Third case Stage 1 Step 4 Step 4 Step 4

In Table 1, the pollution level determined in the first case is the same as the pollution level in step 1, and in the second case, the third pollution level is determined as the pollution level in the third case, Of the three steps, the two steps are the highest and the same, so step 4 is determined as the pollution level. Generally, the first and second dust sensors and gas sensors measure the degree of contamination to the air around the sensor. Therefore, when the degree of air pollution is unbalanced or the degree of contamination changes due to the air flow around the sensor, only one sensor The controller 10 may use the contamination detection values from the plurality of sensors because the pollution degree determined by the sensor 10 may not accurately indicate the pollution degree of the air. When the air changes from a clean state (from the first stage) to a contaminated state (for example, three stages) as in the second case, the control unit 10 does not control according to the first stage of pollution degree, The air cleaning function can be performed by performing the control immediately. Also, while the air is determined to be in a contaminated state (step 4) and the air cleaning is performed, the controller 10, even if the pollution degree step corresponding to the contamination detection value from the first dust sensor is one step as in the third case The air cleaning corresponding to the four highest steps is performed so that the degree of contamination can be lowered uniformly throughout the air.

In addition, the controller 10 performs air cleaning according to an operation mode or a pre-stored operation mode from the input unit 1, and the operation mode includes a manual mode, an automatic mode, a room care mode, and the like.

In the manual mode, the control unit 10 controls the fan driving unit 5 with the air volume or air volume level selected by the user, and the controller 10 determines a pollution degree step corresponding to the contamination detection value from the pollution detection unit 7 , The determined degree of contamination level is displayed only on the display unit 3, and is not referred to in the control process of the fan driving unit 5. [

In the automatic mode, the control unit 10 determines a pollution degree step corresponding to the pollution detection value from the pollution detection unit 7, and controls the fan driving unit 5 to drive the fan with the air amount corresponding to the determined pollution degree step. Table 2 below shows the airflow level (airflow intensity), fan speed, noise and power consumption at each pollution level.

Pollution level step Airflow stage Fan speed (rpm) Noise (dB) Power consumption (W) Stage 1 Stage 1 400 26 4 Step 2 Step 2 500 30 5 Step 3 Step 4 Step 3 620 34.3 7 Step 5 Step 6 Step 4 830 43.9 13

The pollution degree step described above is made up of six steps, and each pollution degree step is an example corresponding to the air amount step of four steps, and the fan speed, noise and power consumption in each air amount step are confirmed. For example, in the automatic mode, the pollution degree steps 2 and 3 have the same air amount step, but they are displayed differently on the display part 3. In addition, the fourth stage of the airflow provides a high airflow, but the power consumption is considerably large, and it is extremely noisy, which may give the user discomfort.

Further, the contamination degree step described above may be carried out from an intermediate pollution degree step (for example, from step 4) to a highest pollution degree step (for example, from step 6) to a high pollution degree step area and from a lowest pollution degree step Up to intermediate pollution levels (for example, three stages) can be distinguished into low pollution stage areas.

In the room care mode, initially, as in the automatic mode, the control unit 10 determines a pollution degree step corresponding to the pollution detection value from the pollution detection unit 7, and controls the fan driving unit 5 with the air amount corresponding to the determined pollution degree step. And adjusts the air flow rate of the fan driving unit 5 in consideration of the change of the pollution degree step and / or the surrounding environment, completely different from the automatic mode when there is a change (rising or falling) of the pollution degree step. The room care mode is described in more detail in FIG. 2 below.

In addition, the ambient environment used in the room care mode means a degree of smooth air convection, and can be classified into, for example, smooth convection, normal, and congestion. In a place where the air convection is smooth, the air pollution degree of the whole space can be lowered even with a weak air volume. However, if the air cleaning is performed for a predetermined time with a specific air volume in a place where the air convection stagnates, There is a case where the air pollution degree in the space far from the air cleaning apparatus is unevenly distributed, which is a phenomenon that the air pollution degree is lowered more slowly. In order to prevent the unevenness of the air pollution, the controller 10 may receive the surrounding environment selected by the user through the input unit 1, or may independently determine the surrounding environment by performing the surrounding environment determination process independently. The control unit 10 controls the fan driving unit 5 by adding a holding time of the air flow rate to the basic time so that convection of air can be smoothly performed using the inputted or determined surrounding environment. .

FIG. 2 is a control flowchart of the air cleaning apparatus of FIG. 1; FIG. In the initial stage, the air cleaning apparatus is in a state of being able to operate by receiving power, and the control unit 10 receives the room care mode selection and starts the room care mode or starts the execution of the stored room care mode.

In step S1, the control unit 10 determines the surrounding environment for the place where the air cleaning apparatus is installed. In this determination, the control unit 10 receives the surrounding environment selected by the user through the input unit 1, determines the inputted surrounding environment as the surrounding environment of the air cleaning apparatus, As shown in FIG. Also, the controller 10 may determine the surrounding environment by performing the surrounding environment determination process in FIG. Step S1 may be performed only before proceeding from step S17 to step S19. In the present embodiment, it is described that the determination step of the surrounding environment of step S1 is preferentially performed for the sake of convenience.

In step S3, the control unit 10 obtains a plurality of contamination detection values from the contamination detection unit 7 and determines the pollution degree step of the present air. The process of determining the contamination level step has already been described in detail in Table 1 and the description above. Also, step S3 is shown and described before step S5 for convenience, but should be understood to be performed continuously in the entire control sequence.

In step S5, the control unit 10 controls the fan driving unit 5 to start the air cleaning with the air volume according to the determined pollution level.

In step S7, the control unit 10 determines whether there is a change in the contamination level determined as a result of the step S3 being continuously performed. Here, the change in the pollution degree step includes an increase in pollution degree (for example, a change from step 1 to step 2), or a decrease in pollution degree (for example, a change from step 2 to step 1). If there is a change in the pollution degree step, the process proceeds to step S9; otherwise, step S7 is repeated.

In step S9, the control unit 10 determines whether the pollution degree step has been raised. If the pollution degree step has been raised, the process proceeds to step S11. Otherwise, if the pollution degree step has been lowered, the process proceeds to step S17.

In step S11, the control unit 10 determines whether it is possible to further enhance the air flow rate. For example, when the pollution degree step rises from the first stage to the second stage, in the automatic mode, the control unit 10 controls the air amount in the first stage corresponding to the pollution level 1, There are three levels of airflow higher than the airflow level 2, so it is judged that the airflow can be further strengthened. In addition, even if the pollution degree step rises from the second stage to the third stage, since there are three stages of air flow rate higher than the second stage, it is judged that the air flow rate can be further strengthened. However, in the case where the pollution degree is increased from the third stage to the fourth stage or the fourth stage is increased to the fifth stage, there is a higher air flow rate in the fourth stage (the highest air flow stage) than in the third air flow rate, , Noise and power consumption are considerably large. Due to this excessive noise and power consumption, it is possible to control the air volume in four steps instead of the air volume three steps, but it is considered impossible to further enhance the air volume. That is, if the air volume exceeding the air volume corresponding to the increased pollution level is in the highest air volume stage, it is determined that the air volume can not be further strengthened. If it is possible to further enhance the air flow rate, the flow proceeds to step S13, and if not, the flow proceeds to step S15.

In step S13, the control unit 10 controls the fan driving unit 5 with an air flow amount exceeding the air flow amount corresponding to the pollution degree step. In this embodiment, the contamination degree step rises from the first step to the second step, and the control unit 10 controls the air amount of the fan driving unit 5 in three steps.

In step S15, the control unit 10 controls the fan driving unit 5 with the air volume corresponding to the pollution degree step.

In step S17, the control unit 10 determines whether it is necessary to add the holding time of the air volume by the fan driving unit 5 during the descent of the pollution degree. For example, in the case where the degree of contamination is lowered to a level lower than the degree of contamination, the degree of contamination of the air may be uneven as described above. Therefore, It is necessary to carry out by adding the holding time. In this regard, the controller 10 determines that it is necessary to add the holding time of the air amount when the previous pollution degree step is included in the steps with high pollution degree. For example, when the degree of pollution in the high pollution degree step region falls, or when the degree of pollution degree in the low pollution degree step region falls in the pollution degree step in the high pollution degree step region, it is necessary to add the air amount retention time . For example, if the previous contamination level is in the 6 level (included in the high pollution level zone) and the current pollution level is in the 5 level (included in the high pollution level zone) or the previous pollution level is in the 4 level , And the current pollution level is in the third level (included in the low pollution level zone). If it is necessary to add the holding time, the process proceeds to step S19. Otherwise, the process proceeds to step S21 if the pollution level is lowered in the lower steps.

In step S19, the control unit 10 controls the fan driving unit 5 by adding the holding time according to the surrounding environment to the basic time with the air volume corresponding to the previous pollution degree step. Here, the basic time is, for example, 2 minutes, and the holding time is variable depending on the surrounding environment. For example, 1 minute for smooth environment, 2 minutes for normal condition, and 3 minutes for congestion And a more detailed description is made in Figs. 3 and 4. Fig. The control unit 10 determines the holding time according to the surrounding environment and adds the holding time determined in the basic time to perform the air cleaning with the air volume corresponding to the previous pollution degree step to quickly remove the contamination degree Can be lowered.

In step S21, the control unit 10 controls the fan driving unit 5 only for the basic time with the air volume corresponding to the previous pollution degree step. Since the pollution level falls from the third stage to the second stage or from the second stage to the first stage, the pollution degree is low (for example, It is determined that the unevenness of air pollution degree is also low and the fan driving unit 5 is controlled with the air volume corresponding to the previous pollution degree stage only during the basic time.

In step S23, the control unit 10 controls the fan driving unit 5 with the air volume corresponding to the current pollution degree step.

The controller 10 proceeds to step S7 in the above described step S5 or step S13 or step S15 or step S23 and if there is no change in the contamination degree step in step S7, The fan driving unit 5 is controlled by the air volume in the step S5 or the step S13 or the step S15 or the step S23.

The flowchart of FIG. 2 relates to the room care mode, and is continuously performed until power-off, an operation interruption or standby command, or a mode change to the air cleaner is input.

FIG. 3 is a flow chart of a process of determining the ambient environment performed by the air cleaning apparatus of FIG. 1; 3 is performed independently while the control according to the control flow chart of FIG. 2 is performed, and is performed using the contamination detection value from the contamination detection unit 7. FIG.

In step S31, the control unit 10 initializes the elapsed time for determining the surrounding environment. This elapsed time is a time during which the contamination detection value is reduced in the judgment detection range (range between the start detection value and the end detection value), and the control unit 10 initializes the previously calculated elapsed time to zero, The process starts.

  In step S33, the air pollution degree is lowered because the control unit 10 performs the air cleaning according to the control flowchart in Fig. 2, and the contamination detection value from the pollution detection unit 7 is equal to or lower than the start detection value . If the contamination detection value is equal to or lower than the start detection value, the process proceeds to step S35; otherwise, the process repeats step S33.

In step S35, the control unit 10 calculates and stores the elapsed time.

In step S37, the control unit 10 determines whether the contamination detection value from the contamination detection unit 7 is equal to or lower than the end detection value. If the contamination detection value is equal to or lower than the end detection value, the process proceeds to step S39; otherwise, the elapsed time is calculated and stored while repeating step S37.

In step S39, the control unit 10 determines the surrounding environment based on the elapsed time, which is the time during which the contamination detection value is reduced from the start detection value to the end detection value. For example, when the surrounding environment is smooth, the pollution degree will be quickly lowered and the elapsed time will be short. If the surrounding environment is stagnant, the pollution degree will be gradually lowered and the elapsed time will be calculated to be longer. Using this point, the control unit 10 can determine the surrounding environment using the elapsed time. This point will be described in detail in Fig. 4 below.

FIG. 4 is graphs of reduction of the contamination detection value according to the surrounding environment.

The pollution detection values included in the graphs of the first to third cases, which are the decrease graphs, are the same as the pollution detection values detected in the case where the air cleaning is performed with the same air volume for air having the same pollution degree in a space having different surrounding environments admit. The contamination detection value has a linear characteristic in the judgment detection range (range between the start detection value and the end detection value), and the change of the pollution detection value with time increases to distinguish the first to third cases , And when the contamination detection value is larger than the start detection value and when the pollution detection value is lower than the end detection value, the change of the pollution detection value is considerably small with time, and the first to third cases It is difficult to distinguish each. Because of this phenomenon, the controller 10 distinguishes the first to third cases using the elapsed time when the contamination detection value is reduced within the determination detection range, without using the contamination detection value that deviates from the judgment detection range .

The elapsed time in the first case is time t2-t1, the elapsed time in the second case is time t3-t1, and the elapsed time in the third case is time t4-t1. The first case is a case where the air convection is smooth and the contamination detection value is relatively quickly reduced. In the third case, the air pollution is stagnated and the contamination detection value is gradually decreased. In the second case, And the third case. In step S39, the control unit 10 compares the calculated elapsed time with the determination reference times to determine the current surrounding environment. . The determination reference times include a first determination reference time that is at least two determination reference times for distinguishing, for example, three surrounding environments (e.g., smooth, normal, If the elapsed time is equal to or less than the first determination reference time, the surrounding environment is smooth. If the elapsed time is between the first determination reference time and the second determination reference time, If the elapsed time exceeds the second determination reference time, it is determined that the surrounding environment is stagnant. In the graphs, the first case is a smooth surrounding environment, the second case is a normal surrounding environment, and the third case is a congested environment. In addition, the number of judgment reference times increases corresponding to the number of distinctions of surrounding environments to be distinguished. In this embodiment, two determination reference times are used to distinguish the three kinds of surrounding environments.

The above-described determination reference times and the determination sensing range can be variably set in accordance with the air flow rate of the fan of the air cleaning apparatus, the structure of the fan, the suction amount of the air cleaning apparatus, and the like.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims. It is to be understood that modifications are possible and that such modifications are within the scope of the claims.

1: input unit 3: display unit
5: Fan drive unit 7: Pollution detection unit
10:

Claims (12)

A fan driving unit for driving the fan;
A pollution sensing unit for sensing pollution of the air;
A pollution detection step is performed to obtain a pollution detection value from the pollution detection unit, and a pollution degree step is determined, and the fan driving unit is controlled with the air amount corresponding to the determined pollution degree step to perform air cleaning. The air pollution level is increased or decreased, and when the pollution level is increased, the air pollution level is further strengthened with respect to the air volume corresponding to the currently determined pollution level, or when the pollution level is lowered, And a control unit for controlling the fan driving unit by adding a holding time to the basic time with the air volume corresponding to the fan unit. The method according to claim 1,
Wherein the control unit controls the fan driving unit to increase the air flow rate by an air flow rate exceeding the air flow rate corresponding to the currently determined pollution degree step when the pollution degree step rises. 3. The method of claim 2,
Wherein the air amount exceeding the air amount corresponding to the currently determined pollution degree step is less than a maximum air amount of the fan driving unit. 3. The method of claim 2,
Wherein when the air volume corresponding to the currently determined pollution degree step is the maximum air volume of the fan driving unit, the controller controls the fan driving unit with the air volume corresponding to the currently determined pollution degree step. The method according to claim 1,
Wherein the control unit adds the holding time to the base time when the previously determined pollution degree step is included in the high pollution degree step area when the pollution degree step is lowered. 6. The method of claim 5,
Wherein the control unit determines the holding time according to the surrounding environment and adds the determined holding time to the basic time. The method according to claim 1,
When the previously determined pollution degree step is included in the low pollution degree step region when the pollution degree step is lowered, the control unit controls the fan driving unit during the basic time with the air amount corresponding to the previously determined pollution degree step An air cleaning device. The method according to claim 1,
Wherein the control unit determines the surrounding environment by using the contamination detection value from the pollution detection unit while performing the air cleaning. 9. The method of claim 8,
Wherein the controller determines the surrounding environment by calculating an elapsed time at which the contamination detection value is reduced from the start detection value to the end detection value of the determination detection range. 9. The method of claim 8,
Wherein the ambient environment is a degree of smoothness of convection of the air. 10. The method of claim 9,
Wherein the controller compares the calculated elapsed time with at least one or more determination reference times to determine the surrounding environment. 9. The method of claim 8,
Wherein the control unit determines the holding time according to the determined surrounding environment and adds the determined holding time to the basic time.

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