JP2015141045A - suspended particulate matter sensor unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suspended particulate matter sensor unit capable of maintaining excellent detection accuracy for a long period of time.SOLUTION: A suspended particulate matter sensor unit includes: an air flow channel 11; filters 15, 16 provided in the flow channel 11; detection means 14 for detecting suspended particulate matter in a space between the filters 15, 16; and air supply means 17, 18, 19 for supplying air from the outside of the flow channel 11 to the space between the filters 15, 16. A direction of the air flowing in the flow channel 11 can be changed by the air supply means 17, 18, 19.

Description

  The present invention relates to a suspended particulate matter sensor unit.

  Recently, there has been concern about human health damage due to suspended particulate matter in the air environment, and attention to suspended particulate matter is increasing. Under such circumstances, there is an increasing trend to measure and monitor the concentration change of suspended particulate matter around the living environment. As a method for measuring and monitoring the concentration of suspended particulate matter, there is a method of installing a suspended particulate matter sensor unit in a target environment.

  The suspended particulate matter sensor unit takes ambient air into the interior, and a sensor provided inside detects the suspended particulate matter in the air. However, a large substance that easily settles may be contained in the air, and when such a substance is taken into the suspended particulate matter sensor unit, it may settle inside. And when such a substance accumulates inside, detection accuracy may fall. Also, detection itself may not be possible.

  The above problem can be avoided by providing a filter at the air inlet so that substances that tend to settle out do not enter. However, when a filter is provided at the air inlet, pressure loss increases due to clogging of the filter and air suction amount decreases. If the filter is initialized (initialized), clogging of the filter can be avoided. Conventionally, filter replacement and filter drop-out have been performed for filter initialization.

  However, maintenance such as filter initialization is complicated. In particular, when a plurality of suspended particulate matter sensor units are used, the maintenance becomes extremely complicated. In addition, the suspended particulate matter sensor unit may be installed in a place where it is difficult for humans to go. In this case, maintenance is not easy.

Special table 2010-523967 JP 2011-59013 A JP2013-530399A

  An object of the present invention is to provide a suspended particulate matter sensor unit capable of maintaining good detection accuracy over a long period of time.

  One aspect of the suspended particulate matter sensor unit includes an air flow path, a first filter and a second filter provided in the flow path, and a space between the first filter and the second filter. Detection means for detecting suspended particulate matter in the space, and air supply means for supplying air from outside the flow path to the space between the first filter and the second filter. Yes. The direction of the air flowing through the flow path can be switched by the air supply means.

  According to the above suspended particulate matter sensor unit, good detection accuracy can be maintained over a long period of time by a combination of the first filter, the second filter, and the air supply means.

It is a figure which shows the structure of the suspended particulate matter sensor unit which concerns on embodiment. It is a figure which shows the structure of the suspended particulate matter sensor unit which concerns on embodiment. It is a figure which shows the example of the change of the density | concentration of a suspended particulate matter. It is a figure which shows operation | movement of the suspended particulate matter sensor unit which concerns on embodiment. It is a figure which shows the effect of the suspended particulate matter sensor unit which concerns on embodiment. It is a figure which shows the modification of the suspended particulate matter sensor unit which concerns on embodiment. It is a figure which shows the other modification of the suspended particulate matter sensor unit which concerns on embodiment.

  Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 1A and 1B are diagrams illustrating a configuration of a suspended particulate matter sensor unit according to an embodiment.

  In this suspended particulate matter sensor unit 10, as shown in FIG. 1, a filter 15 and a filter 16 are provided in an air flow path 11. Further, a detector 14 for detecting suspended particulate matter in the space between the filter 15 and the filter 16 is provided. The detector 14 includes, for example, a sensor 12 and a light source 13. For example, the sensor 12 detects scattered light emitted from the light source 13 and scattered by the suspended particulate matter. Further, fans 17 and 18 for supplying air from outside the flow path 11 are provided in the space between the filter 15 and the filter 16. The fans 17 and 18 are fans that can be switched between forward rotation and reverse rotation. Here, rotation in the direction of taking air from outside the flow path 11 through the fan is referred to as forward rotation, and rotation in the opposite direction is referred to as reverse rotation. Moreover, the control apparatus 19 which controls operation | movement of the detector 14, the fan 17, and the fan 18 and the cable 20 which outputs the detection result by the detector 14 outside are provided. Furthermore, an indicator 21 that is lit when the fan 17 is rotating forward and an indicator 22 that is lit when the fan 18 is rotating forward are provided. For example, the meshes of the filter 15 and the filter 16 are large enough to pass through the suspended particulate matter to be detected, but not to pass through substances that are larger than that and settle into the flow path 11. The suspended particulate matter to be detected is a fine particulate matter called PM2.5 having a particle size of 2.5 μm or less, for example. The detector 14 is an example of detection means, and the fan 17, the fan 18, and the control device 19 are examples of air supply means. Indicator 21 and indicator 22 are examples of display means.

  Next, the operation of the suspended particulate matter sensor unit 10 will be described. In the present embodiment, the control device 19 controls the operations of the detector 14, the fan 17, and the fan 18. The control device 19 compares, for example, an arbitrary set value predetermined for the concentration of suspended particulate matter (SPM) with the concentration of SPM detected by the sensor 12, and according to the result, The direction of rotation of the fan 17 and the fan 18 is controlled.

  For example, if the SPM concentration detected by the sensor 12 is equal to or higher than a set value, the control device 19 rotates the fan 17 forward and reverses the fan 18. As a result, air flows into the flow path 11 through the filter 15, and air is discharged from the flow path 11 through the filter 16. For example, if the SPM concentration detected by the sensor 12 is less than the set value, the control device 19 reverses the fan 17 and causes the fan 18 to rotate forward. As a result, air flows into the flow path 11 through the filter 16, and air is discharged from the flow path 11 through the filter 15. Since the concentration of SPM in the air naturally changes, when such control is performed, the direction of rotation of the fan 17 and the fan 18 is reversed in accordance with the change in the concentration of SPM in the air. For example, as shown in FIG. 2, when the concentration of the suspended particulate matter is changing, in the period A, the fan 17 rotates in the forward direction and the fan 18 rotates in the reverse direction. In period B, fan 17 rotates reversely and fan 18 rotates forward. The set value is, for example, an average value of the maximum value and the minimum value of the assumed concentration of suspended particulate matter in the air.

  In period A, as shown in FIG. 3A, the substance 51 that settles in the flow path 11 adheres to the outside of the filter 15 and hardly enters the flow path 11. On the other hand, the substance 52 to be detected, for example PM2.5, passes through the filter 15, passes through the detection range of the detector 14, and is discharged through the filter 16. In the period B, as shown in FIG. 3B, the substance 51 that settles in the flow path 11 adheres to the outside of the filter 16 and does not easily enter the flow path 11. On the other hand, the substance 52 to be detected, for example PM2.5, passes through the filter 16, passes through the detection range of the detector 14, and is discharged through the filter 15. Therefore, it is possible to suppress a decrease in detection accuracy due to the inflow of the substance 52. In the period A, the amount of the substance 51 adhering to the outside of the filter 15 increases as time passes. After that, in the period B, the fan 17 is reversed, and when the fan 18 is rotated forward, it adheres to the filter 15. The material 51 that has been discharged is discharged into the air. That is, the filter 15 is initialized. In the period B, the amount of the substance 51 adhering to the outside of the filter 16 increases with time, but when the fan 17 rotates forward and the fan 18 reverses thereafter, the substance 51 attached to the filter 16. Is discharged into the air. That is, the filter 15 is initialized. Such an operation is repeated.

  As described above, according to the present embodiment, it is possible to suppress the inflow of the substance that reduces the detection accuracy into the flow path 11. Moreover, clogging of the filter 15 and the filter 16 can be suppressed. Therefore, even if the frequency of complicated maintenance is significantly reduced, good detection accuracy can be maintained over a long period of time.

For example, as shown in FIG. 4, in the present embodiment, the rotation direction of the fan 17 and the fan 18 is reversed at time t _n (n = 1, 2, 3,...), And accordingly the filter 15 or The material adhering to the filter 16 is removed. For this reason, as shown in FIG. 4A, the pressure loss is kept low, and as shown in FIG. 4B, the air intake amount is kept high. On the other hand, in the reference example in which the direction of the air flowing in the flow path is one direction, the amount of the substance adhering to the filter increases with time, and the pressure loss increases as shown in FIG. . Further, when the amount of the substance adhering to the filter exceeds a certain criticality, the air suction amount rapidly decreases as shown in FIG.

  In the present embodiment, in the period A, the indicator 21 is lit as shown in FIG. 3A, and in the period B, the indicator 22 is lit as shown in FIG. For this reason, the operation state of the suspended particulate matter sensor unit 10 can be grasped even from the outside.

  The distance from the detector 14 to the air inlet / outlet on the filter 15 side and the distance from the detector 14 to the air inlet / outlet on the filter 16 side are preferably substantially equal. This is because the detection conditions substantially match between the case where the fan 17 is rotating forward and the fan 18 is rotating backward and the case where the fan 17 is rotating backward and the fan 18 is rotating forward. The greater the difference in the detection conditions, the higher the possibility that the data output from the detector 14 will differ despite the fact that the concentration of suspended particulate matter in the atmosphere has not changed. Centering on the detector 14, the structure of the flow path 11 including the filter 15 and the fan 17 on the filter 15 side and the structure of the flow path 11 including the filter 16 and the fan 18 on the filter 16 side are the filter characteristics of the filter 15 and It is even more preferable that the filter 16 is symmetric including the filter characteristics. However, the structure on the filter 15 side and the structure on the filter 16 side do not necessarily match.

  Filter 15 and filter 16 are preferably removable and replaceable as shown in FIG. This is because by making the filter 15 and the filter 16 exchangeable, it becomes easy to appropriately change the size of the mesh according to the measurement environment and the detection target.

  In the above embodiment, the rotation direction of the fan 17 and the fan 18 is controlled according to the detected SPM concentration, but the rotation direction of the fan 17 and the fan 18 is controlled based on other criteria. Also good. For example, as shown in FIG. 6 (a), a pressure sensor 31 is provided between the filter 15 and the detector 14, and a pressure sensor 32 is provided between the filter 16 and the detector 14. It may be switched accordingly. Specifically, when the output of the pressure sensor 31 reaches a certain threshold during the period when the filter 15 is rotating forward, and when the output of the pressure sensor 32 reaches a certain threshold during the period when the filter 16 is rotating forward, the fan 17 and the fan 18. The direction of rotation may be switched. Since the outputs of the pressure sensor 31 and the pressure sensor 32 reflect the pressure loss, that is, the degree of clogging of the filter 15 and the filter 16, it is possible to change the rotation direction before adversely affecting the clogging accuracy. It becomes. As the threshold value, for example, a pressure corresponding to a pressure loss twice as large as the pressure loss immediately after switching the rotation direction can be used.

  As shown in FIG. 6B, a vibration mechanism 41 that vibrates the filter 15 and a vibration mechanism 42 that vibrates the filter 16 may be provided. For example, the vibration mechanism 41 vibrates the filter 15 during a period when the fan 17 is reverse, and the vibration mechanism 42 vibrates the filter 16 during a period when the fan 18 is reverse. Such vibration promotes the removal of the substance attached to the filter 15 or the filter 16. As the vibration mechanism 41 and the vibration mechanism 42, for example, a vibrator or the like used in a mobile phone can be used. The operation period of the vibration mechanism 41 may be a fixed period from the start of reverse rotation of the fan 17, and the operation period of the vibration mechanism 42 may be a fixed period from the start of reverse rotation of the fan 18. The vibration mechanism 41 and the vibration mechanism 42 are examples of vibration means.

  The rotational speeds of the fan 17 and the fan 18 are preferably higher in a certain period from the start of reverse rotation than in the subsequent period. This is because the substances adhering to the filter 15 and the filter 16 are more quickly removed.

  Instead of the detector 14, a suspended particulate matter sensor having another structure may be used. For example, a QCM sensor or a TEOM sensor may be used. The QCM sensor detects suspended particulate matter by a quartz crystal microbalance (QCM) method. The TEOM sensor detects suspended particulate matter by a vibrating element type micro balance (TEOM) method.

  In the above embodiment, the fan 18 is rotated while the fan 17 is rotating forward, and the fan 17 is rotated while the fan 18 is rotating forward. However, while the fan 17 is rotating forward, the fan 18 is The fan 17 may be stopped while the fan 18 is rotating forward. Even in this case, the direction of the air flowing in the flow path 11 can be switched. Alternatively, the fan 17 may be reversed while the fan 18 is stopped, and the fan 18 may be reversed while the fan 17 is stopped. Even in this case, the direction of the air flowing in the flow path 11 can be switched. In these cases, fan 17 and fan 18 that can rotate in only one direction can be used. Furthermore, although symmetry about the detector 14 cannot be obtained, the direction of the air flowing in the flow path 11 can be switched even if only one fan capable of switching between forward rotation and reverse rotation is provided. is there. Three or more fans may be provided.

  As described above, it is preferable that the detection conditions substantially match before and after the direction of the air flowing in the flow path 11 is switched. If these detection conditions match, for example, the detection result during the period when the substance adhering to the filter 15 is removed and the detection result during the period when the substance adhering to the filter 16 is removed have the same accuracy. It is because it shows.

  The interval for measuring the concentration of the suspended particulate matter is not particularly limited. For example, the concentration may be measured every hour or may be measured every minute. This interval can be set in the control device 19, for example.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
An air flow path;
A first filter and a second filter provided in the flow path;
Detection means for detecting suspended particulate matter in the space between the first filter and the second filter;
Air supply means for supplying air from the outside of the flow path to a space between the first filter and the second filter;
Have
The suspended particulate matter sensor unit, wherein the direction of the air flowing through the flow path can be switched by the air supply means.

(Appendix 2)
The suspended particulate matter sensor unit according to appendix 1, wherein the air supply means includes a fan that can be switched between forward rotation and reverse rotation.

(Appendix 3)
The air supply means includes
A first fan rotatable in at least a first direction;
A second fan rotatable at least in a second direction opposite to the first direction;
The suspended particulate matter sensor unit according to supplementary note 1, characterized by comprising:

(Appendix 4)
The first fan is also rotatable in the second direction;
The suspended particulate matter sensor unit according to appendix 3, wherein the second fan is rotatable also in the first direction.

(Appendix 5)
The distance from the detection means to the air inlet / outlet on the first filter side and the distance from the detection means to the air inlet / outlet on the second filter side are substantially equal. The suspended particulate matter sensor unit according to any one of 1 to 4.

(Appendix 6)
Any one of appendices 1 to 5, wherein the air supply means compares the detection result by the detection means with a predetermined threshold value, and switches the direction of the air flowing through the flow path based on the result. The suspended particulate matter sensor unit according to claim 1.

(Appendix 7)
A first pressure sensor provided between the detection means and the first filter;
A second pressure sensor provided between the detection means and the second filter;
The suspended particulate matter sensor unit according to any one of appendices 1 to 6, characterized by comprising:

(Appendix 8)
First excitation means for applying vibration to the first filter;
Second excitation means for applying vibration to the second filter;
The suspended particulate matter sensor unit according to any one of appendices 1 to 7, characterized by comprising:

(Appendix 9)
The suspended particulate matter sensor unit according to any one of appendices 1 to 8, further comprising display means for indicating a direction of air flowing in the flow path.

11: Flow path 12: Sensor 13: Light source 14: Detector 15, 16: Filter 17, 18: Fan 19: Control device 20: Cable 21, 22: Indicator 31, 32: Pressure sensor 41, 42: Excitation mechanism

Claims (5)

An air flow path;
A first filter and a second filter provided in the flow path;
Detection means for detecting suspended particulate matter in the space between the first filter and the second filter;
Air supply means for supplying air from the outside of the flow path to a space between the first filter and the second filter;
Have
The suspended particulate matter sensor unit, wherein the direction of the air flowing through the flow path can be switched by the air supply means.   2. The suspended particulate matter sensor unit according to claim 1, wherein the air supply unit includes a fan capable of switching between forward rotation and reverse rotation. The air supply means includes
A first fan rotatable in at least a first direction;
A second fan rotatable at least in a second direction opposite to the first direction;
The suspended particulate matter sensor unit according to claim 1, comprising: The first fan is also rotatable in the second direction;
The suspended particulate matter sensor unit according to claim 3, wherein the second fan is rotatable in the first direction.   The distance from the detecting means to the air inlet / outlet on the first filter side is substantially equal to the distance from the detecting means to the air inlet / outlet on the second filter side. Item 5. The suspended particulate matter sensor unit according to any one of Items 1 to 4.

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