JP2012127773A - Particulate number measuring device - Google Patents

Abstract

In a particle number measuring apparatus, problems caused by a clogging of a throttle for measurement are eliminated.
SOLUTION: Particle counters 18 and 40 and sample gas introduction nozzles 17 and 44 for introducing a sample gas containing fine particles into the optical path of the particle counters 18 and 40 are provided. The sample gas introduction nozzles 17, 44 or the measurement throttle unit 4 is subjected to normal measurement when the sample gas introduction nozzles 17, 44 or the measurement throttle unit 4 are closed. The sample gas introduction nozzles 17 and 44 or the measurement gas introduction nozzles 17 and 44 or the measurement gas supply nozzles 17 and 44 or the measurement throttle unit 4 by making the upstream side high pressure or the downstream side low pressure. A closed state releasing mechanism for releasing the closed state of the throttle unit 4 is provided.
[Selection] Figure 1

Description

  The present invention relates to a particle number measuring apparatus that measures the concentration of fine particles contained in the atmosphere, automobile exhaust gas, and the like.

  As the particle number measuring device, an aerosol particle number measuring device called CPC (condensing particle counter) that counts the number of particles in aerosol containing nanometer-sized fine particles of several nm to several tens of nm, particles of 300 nm to several micrometers There is a particle counter (dust meter) that measures the particle diameter and particle number concentration.

  The aerosol particle number measuring device increases the particle size by condensing working fluid vapor such as water or butanol around the fine particle as a nucleus, and then irradiates the increased particle with light, and the specific scattering angle The particle number concentration is measured by detecting the number of scattered light pulses. The aerosol is in a state where solid or liquid fine particles are present in a relatively stable floating state in the gas, and is contained in the exhaust gas of an automobile, the exhaust gas from a factory, or the like.

  The particle counter measures the particle diameter and the particle number concentration by irradiating the fine particles with light and detecting the number of scattered light pulses, scattered light intensity or transmitted light intensity at the specific scattering angle.

  In addition, a classifier such as a differential electric mobility classifier or an impactor is installed in front of these particle number measuring apparatuses, and particle size-particle concentration measurement is also performed.

Japanese Patent No. 3435015

Ultrafine Condensation Particle Counter [online], 2005, TSI Incorporated, [Search July 25, 2008], Internet (URL: www.tsi.com/documents/3776.pdf)

  Both the aerosol particle number measuring apparatus and the particle counter are provided with a sample gas introduction nozzle for guiding particles to the measurement optical path without leakage. Further, the aerosol particle number measuring apparatus is provided with a measurement throttle unit in front of the sample gas introduction nozzle in order to limit the number of particles introduced into the sample gas introduction nozzle. Many commercially available aerosol particle number measuring devices and particle counters have a flow rate measurement restrictor in the sample gas flow path in order to measure the sample gas flow rate. The flow rate measuring throttle unit is configured to determine the flow rate by detecting the differential pressure before and after that portion.

  In the particle number measuring device, the sampling sample gas cannot be filtered for the purpose of measuring the particle concentration. As a result, solid or liquid particles are placed in the sample gas introduction nozzle or the throttle for measurement with a narrow channel. Ingredients are introduced. In addition, the adhesion of particles to the channel side wall due to the diffusion of particles at those sites cannot be avoided. As a result, after a long time measurement, the sample gas introduction nozzle or the throttle for measurement closes, and the predetermined sample gas flow rate cannot be obtained, causing an error in the concentration calculation, or sampling itself becomes impossible. A malfunction occurs.

  An object of the present invention is to eliminate problems caused by the clogging of a sample gas introduction nozzle or a measurement throttle in a particle number measuring apparatus.

  In the present invention, the number of particles or the number of particles is determined based on an analog change in the amount of scattered light or the amount of transmitted light that is emitted from the microscopic particle through the optical path, or the pulse count value of a signal digitized by a threshold value. A particle number measuring device provided with a particle counting unit (18, 40) for measuring the concentration and a sample gas introduction nozzle (17, 44) for reducing the diameter of an air flow for carrying particles into the optical path of the particle counting unit (18, 40). It is intended for.

  Then, when the sample gas introduction nozzle (17, 44) is in a closed state, a larger amount of gas is allowed to flow to the sample gas introduction nozzle (17, 44) than for normal measurement, or from the normal measurement time. Further, it is characterized in that a closed state releasing mechanism for releasing the closed state of the sample gas introduction nozzle (17, 44) by setting the upstream side to a high pressure or the downstream side to a low pressure is provided.

  The aerosol particle number measuring apparatus includes a measurement throttle (4) in addition to the sample gas introduction nozzle (17) as a portion that may be blocked. Therefore, the aerosol particle number measuring apparatus is provided with a closed state releasing mechanism that releases not only the sample gas introduction nozzle (17) but also the measurement throttle part (4).

  Here, the “closed state” of the sample gas introduction nozzle (17, 44) or the measurement throttle (4) means the flow rate of the sample gas flowing through the sample gas introduction nozzle (17, 44) or the measurement throttle (4). Is not meant to be zero, but the sample gas introduction nozzle (17, 44) or the measurement restriction is caused by particles or moisture adhering to the sample gas introduction nozzle (17, 44) or the measurement restriction (4). It means a state in which the flow rate of the sample gas flowing through the section (4) is reduced to an extent that affects the measurement accuracy. For example, in order to maintain the measurement accuracy, it is specified that the variation rate of the sample gas flow rate flowing through the sample gas introduction nozzle (17, 44) or the measurement throttle (4) is ± 10% or less with respect to the specified value. In this case, the “closed state” means that the flow rate of the sample gas flowing through the sample gas introduction nozzle (17, 44) or the measurement throttle (4) is close to 10%, for example, a value between 7 and 9%. , That means it has decreased. Therefore, for example, in order to detect the flow rate of the sample gas, a flowmeter is provided in which the throttle portion is provided in the sample gas flow path and the flow rate is detected by the pressure sensor using the pressure difference between the upstream side and the downstream side. In this case, the threshold value of the differential pressure by the pressure sensor for releasing the closed state is such that the rate of decrease in the flow rate of the sample gas flowing through the sample gas introduction nozzle (17, 44) or the measurement throttle (4) Is set to the differential pressure value by the pressure sensor corresponding to the reduction rate set as “,” in the above example, the reduction rate between 7% and 9% with respect to the specified value.

  An example of the particle number measuring device is an aerosol particle number measuring device. The aerosol particle number measuring apparatus uses a particle in order to avoid overlapping of particles in the optical path of the sample gas inlet (2) for inhaling aerosol containing nanometer-sized fine particles as a sample gas and the particle counter (18). An aerosol flow capillary (4) for flowing a part of the sample gas as an aerosol flow as a throttle for measurement to reduce the number of particles supplied to the counting unit (18), and provided at the tip of the sample gas inlet (2) A splitter (6) that separates the sample gas into a gas flowing through the aerosol flow capillary (4) and a remaining gas, and a filter (10) disposed downstream of the splitter (6) to remove particles in the sample gas. ) And a sheath gas flow path (8) having an adjustment valve (12) for adjusting the flow rate, and the gas from the sheath gas flow path (8) in a saturated vapor state. A saturator (14) that joins the aerosol flow that flows out of the aerosol flow capillary 4 in a sflow and cools the combined gas of the aerosol flow from the aerosol flow capillary (4) and the sheath flow from the saturator (14) Then, a cooling condenser (16) for growing fine particles in the aerosol flow by the steam of the sheath flow, and the sample gas introduction nozzle for supplying the sample gas from the cooling condenser (16) to the particle counter (18) (17), an exhaust pump (22) provided downstream of the particle counter (18) and controlled to exhaust at a predetermined flow rate, the particle counter (18) and the exhaust pump (22) And a flow meter (20) provided between the two.

  Another example of the particle number measuring apparatus is a particle counter. The particle counter includes a sample gas inlet (2) that sucks in as a sample gas containing fine particles, and the sample gas that guides the sample gas from the sample gas inlet (2) into the optical path of the particle counter (40). An introduction nozzle (44), an exhaust pump (22) provided downstream of the particle counter (40) and controlled to exhaust at a predetermined flow rate, the particle counter (40) and the exhaust pump ( 22) and a flow meter (20) provided between

  The closed state release mechanism can be variously configured. As a closed state release mechanism for the sample gas introduction nozzles (17, 44), for example, an open / close valve (21) may be provided between the flow meter (20) and the exhaust pump (22). The on-off valve (21) is normally opened at the time of measurement, and when the closed state of the sample gas introduction nozzle (17, 44) is released, it is once closed and then opened to open the sample gas introduction nozzle ( 17, 44).

  In this closed state release mechanism, the output of the exhaust pump (22) is increased from that during normal measurement before the on-off valve (21) is temporarily closed, and the on-off valve (21) is opened. If it is made to return to the thing at the time of a normal measurement after being opened, an obstruction | occlusion state can be cancelled | released more effectively.

  As an occlusion state release mechanism for the aerosol flow capillary (4), for example, an on-off valve (7) provided in the sheath gas flow path (8) may be provided. The on-off valve (7) is released at the time of normal measurement, and is closed when the closed state of the aerosol flow capillary (4) is released, so that a larger amount of sample gas is supplied to the aerosol flow capillary (4) than at the time of normal measurement. It is a flow.

  The blockage release operation by the blockage state release mechanism may be started by a manual switch, may be automatically started by a timer, or the sample gas introduction nozzle (17, 44) or the measurement throttle unit (4) is blocked. Means for detecting the state may be provided, and the state may be automatically started when the closed state is detected. The following can be mentioned as forms for automatically starting the closing release operation.

  In order to automatically release the closed state of the sample gas introduction nozzles (17, 44), for example, the flow meter (20) includes a throttle portion with a narrow flow path, and an upstream portion and a downstream portion of the throttle portion. And a pressure sensor for detecting the differential pressure between them, and the flow rate is detected by the differential pressure. The control unit (26, 46) further includes a control unit (26, 46), and the control unit (26, 46) is configured so that the on-off valve (21) is provided when the differential pressure in the throttle unit is lower than a preset threshold value or a predetermined ratio. The sample gas introduction nozzle (17, 44) is automatically released from the closed state by controlling the opening / closing operation so that the sample gas introduction nozzle (17, 44) is opened.

  The controller (26, 46) normally outputs the output of the exhaust pump (22) before temporarily closing the on-off valve (21) in order to release the closed state of the sample gas introduction nozzle (17, 44). It is assumed that the exhaust pump (22) is also controlled so as to return the output of the exhaust pump (22) to that at the time of normal measurement after opening the on-off valve (21). Thus, the blocked state of the sample gas introduction nozzle (17, 44) can be released more effectively.

  In order to automatically release the blockage of the aerosol flow capillary (4), for example, by the adjustment valve (12) between the upstream side and the downstream side of the adjustment valve (12) of the sheath gas flow path (8). A pressure sensor (24) for detecting the differential pressure is provided. Then, when the differential pressure by the pressure sensor (24) exceeds a preset threshold value or a certain ratio during normal measurement, the on-off valve (7) is temporarily closed to block the aerosol flow capillary (4). A control unit (26) for canceling is provided.

  In another preferred embodiment, the sample gas inlet (2) is connected to the classification particle discharge port of the classification device (30), and the control units (26, 46) perform measurement by the classification operation of the classification device (30). During the acquisition of data, the closed state release operation by the closed state release mechanism is not performed. If a block release action is inserted in the middle of a series of classification operations, some classification data will be missing. Furthermore, for example, when the classifier is a differential electric mobility classifier (DMA), and thereby performing a voltage scanning type classification operation, not only missing data of some classification data but also whole classification data. Becomes invalid. Therefore, the start threshold value of the occlusion release is set in a range that suggests the start of the occlusion but does not affect the measurement accuracy, and the start of the occlusion release is determined to be after the end of the classification operation. In other words, the start threshold value of the occlusion release is set so that the occlusion state that affects the measurement accuracy is not reached until the end of the classifying operation of that measurement. By controlling the operation of the closed state releasing mechanism in this way, it is possible to prevent the start operation of releasing the closed state from interfering with the acquisition of measurement data.

  Furthermore, instead of simply synchronizing the start of the occlusion release operation with the end of the classification operation, the sample flow rate, the classification unit flow rate, the classification unit size, and the voltage scanning speed and pipe length in the DMA voltage scanning type classification operation Taking into account the delay time taking into account, further missing of classification data can be avoided. Specifically, in the case of the classification device (30) in which measurement data acquisition is repeatedly performed, the period during which measurement data is being acquired for avoiding the blocking release operation can be set as follows. The delay time until the classified particles reach the particle counter (18) from the voltage application time for classification in the classifier (30) is Td, and the classification operation start time of the classifier (30) is Ts. Assuming that the classification operation end time is Te, a period from the (Ts + Td) time to the (Te + Td) time is during acquisition of measurement data. When performing the blocking release operation, control is performed so as to avoid a period during acquisition of any measurement data.

In the present invention, when the sample gas introduction nozzle (17, 44) of the particle number measuring apparatus having the sample gas introduction nozzle (17, 44) is in the closed state, the closed state of the sample gas introduction nozzle (17, 44) is set. Since the closed state releasing mechanism for releasing is provided, the number of particles can be measured stably for a long period of time.
In the case of CPC, when the measurement throttle section (4) is in the closed state, the closed state of the measurement throttle section (4) is also released, and the number of particles can be measured stably for a long period of time.

It is a schematic block diagram which shows one Example which applied this invention to the aerosol particle number measuring apparatus. It is a schematic block diagram which shows one Example which applied this invention to the particle counter. It is a schematic sectional drawing which shows the particle | grain count part in the Example. It is a schematic sectional drawing which shows an example of the classification apparatus connected to the aerosol particle number measuring apparatus of the Example. It is a wave form diagram which shows an example of the applied voltage which operates the classification device.

  An embodiment in which the present invention is applied to an aerosol particle number measuring apparatus is schematically shown in FIG.

  The sample gas inlet 2 sucks in a sample gas in an atmospheric pressure state including an aerosol composed of nanometer-sized fine particles. A splitter 6 is provided at the tip of the sample gas inlet 2. The splitter 6 separates the sample gas into a gas flowing through the aerosol flow capillary 4 and a remaining gas. The aerosol flow capillary 4 allows a part of the sample gas separated by the splitter 6 to flow as an aerosol flow.

  A sheath gas flow path 8 is connected to the downstream of the splitter 6 via the on-off valve 7, and the remaining portion of the sample gas separated by the splitter 6 flows to the sheath gas flow path 8. The sheath gas flow path 8 is provided with an adjustment valve 12 for adjusting the flow rate, and a filter 10 such as a HEPA (High Efficiency Particulate Air Filter) filter for removing particles in the sample gas.

  The on-off valve 7 of the sheath gas flow path 8 is released during normal measurement, and is closed when the closed state of the aerosol flow capillary 4 is released, so that a larger amount of sample gas flows through the aerosol flow capillary 4 than during normal measurement. It is.

  Since the sample gas supplied to the sample gas inlet 2 is divided into the aerosol flow capillary 4 and the sheath gas channel 8, the sample gas flow rate that flows through the aerosol flow capillary 4 by detecting the sample gas flow rate that flows through the sheath gas channel 8. Can be detected indirectly. In order to detect the flow rate of the sample gas flowing through the sheath gas channel 8, a pressure sensor 24 is provided to detect the differential pressure due to the adjustment valve 12 between the upstream side and the downstream side of the adjustment valve 12 in the sheath gas channel 8. ing. The differential pressure at the adjusting valve 12 corresponds to the flow rate of the sample gas flowing through the adjusting valve 12, and the differential pressure increases as the flow rate increases. When the aerosol flow capillary 4 is closed, the flow rate of the sample gas flowing through the aerosol flow capillary 4 decreases and the flow rate of the sample gas flowing through the adjustment valve 12 increases, so that the detection pressure of the pressure sensor 24 increases. It can be detected that the aerosol flow capillary 4 is closed due to the increase in pressure.

  A saturator 14 is provided to make the gas from the sheath gas flow path into a saturated vapor state sheath flow and merge with the aerosol flow flowing out of the aerosol flow capillary 4. The saturator 14 heats butyl alcohol to about 40 ° C. to form a vapor, and the sheath gas flows in the alcohol vapor so that the sheath gas is saturated with the alcohol vapor.

  A cooling condenser 16 is provided to cool the combined gas of the aerosol flow from the aerosol flow capillary 4 and the sheath flow from the saturator 14 to grow the fine particles in the aerosol flow by the steam of the sheath flow. When the combined gas is guided to the cooling condenser 16 and cooled to about 10 ° C., the surroundings of the aeroflow are cooled with the sheath gas saturated with the alcohol vapor, and the alcohol vapor is absorbed into the fine particles in the aerosol. It grows so that it adheres and condenses and the particle size increases.

  The tip of the cooling condenser 16 is squeezed into a sample gas introduction nozzle 17. A particle counter 18 is provided to count the number of particles in the gas that has passed through the sample gas introduction nozzle 17. An example of the particle counting unit 18 is to count the number of particles in the aerosol passing through the particle counting unit 18 by irradiating a laser beam from a direction perpendicular to the aerosol flow and detecting the scattered light. At this time, the fine particles in the aerosol grow and grow in size due to the condensation of the alcohol, and the counting accuracy increases.

  An exhaust pump 22 whose drive is controlled to exhaust at a predetermined flow rate is provided downstream of the particle counting unit 18 through a filter 19 such as a HEPA filter that removes particles in the exhaust gas. The flow rate of the exhaust pump 22 is controlled by the control unit 26. In this embodiment, a flow meter 20 and an on-off valve 21 are provided between the filter 19 and the exhaust pump 22. An example of the flow meter 20 measures the flow rate by detecting the pressure difference between the upstream side and the downstream side of the critical orifice. The on-off valve 21 is normally opened during measurement.

The operation of this embodiment will be described.
The aerosol of the sample gas sucked from the sample gas inlet 2 is separated by the splitter 6, a part thereof is guided to the aerosol flow capillary 4 to become an aerosol flow, and the remaining part is guided to the sheath gas flow path 8 to become a sheath gas. .

  The sample gas flow rate that is led to the aerosol flow capillary 4 and becomes the aerosol flow is a small part of the sample gas flow rate sucked from the sample gas introduction port 2, and most of the sample gas is led to the sheath gas flow path 8 and the sheath gas. It becomes. Thus, the reason why the sample gas flows at a large flow rate before the aerosol flow capillary 4 is to prevent the loss of fine particles due to the diffusion of the aerosol in the sample gas.

  The flow rate of the sample gas flowing through the sheath gas flow path 8 is adjusted by the adjustment valve 12 to become a constant flow rate. In the sheath gas flow path 8, the sample gas becomes a sheath gas by removing particles in the sample gas by the filter 10.

  The sheath gas is made into a sheath flow in a saturated vapor state by the saturator 14, merged with the aerosol flow flowing out from the aerosol flow capillary 4, and then cooled by the cooling condenser 16, whereby the fine particles in the aerosol flow are caused by the steam of the sheath flow. The particles are counted, and the particle count unit 18 counts the number of particles. The flow rate of the sample gas sucked from the sample gas introduction port 2 is measured by a flow meter 20 provided downstream of the particle counting unit 18, and the drive of the exhaust pump 22 is controlled so that the flow rate becomes a predetermined flow rate.

  In order to accurately measure the number of fine particles in the sample gas, the flow rate of the aerosol flow flowing through the aerosol flow capillary 4 must be accurately controlled. The flow rate of the aerosol flow is indirectly monitored by the pressure sensor 24 detecting the pressure drop caused by the regulating valve 12 as a differential pressure.

  In the first embodiment, the closed state of the aerosol flow capillary 4 is manually released. In this embodiment, the operator who is measuring with this measuring device monitors the differential pressure by the pressure sensor 24 during normal measurement, and the differential pressure is determined in advance to correspond to the closed state of the aerosol flow capillary 4. When it increases to a certain value, the on-off valve 7 is closed by a manual switch for a certain time. The time for closing the on-off valve 7 is necessary to remove the particles and moisture adhering to the aerosol flow capillary 4 by flowing a large amount of sample gas through the aerosol flow capillary 4 to release the closed state of the aerosol flow capillary 4. It is a long time, and is set to several seconds to several tens of seconds.

  In the second embodiment, the closed state of the sample gas introduction nozzle 17 is manually released. In this embodiment, the operator who is measuring with this measuring device monitors the flow rate by the flow meter 20 during normal measurement, and the flow rate is a predetermined constant that corresponds to the closed state of the sample gas introduction nozzle 17. When the value falls to the value, the on-off valve 21 is once closed by a manual switch and then opened to allow the sample gas to flow into the sample gas introduction nozzle 17 rushingly.

  At this time, if the output of the exhaust pump 22 is increased from that during normal measurement before the on-off valve 21 is temporarily closed and is returned to that during normal measurement after the on-off valve 21 is opened, the sample gas introduction nozzle 17 As a result, the flow rate of the sample gas flowing suddenly increases, and the closed state of the sample gas introduction nozzle 17 is more reliably released.

  In the third embodiment, the closed state of the aerosol flow capillary 4 is automatically released. In this embodiment, the control unit 26 monitors the closed state of the aerosol flow capillary 4, and when it is determined to be in the closed state, the on-off valve 7 is automatically closed for a predetermined time. For this purpose, the control unit 26 is also connected to the pressure sensor 24 and the opening / closing valve 7, and receives a detection signal from the pressure sensor 24 to control the opening / closing operation of the opening / closing valve 7. The control unit 26 performs an operation of closing the on-off valve 7 for a certain period of time when the differential pressure by the pressure sensor 24 exceeds a preset threshold during normal measurement.

  The control unit 26 may be provided as a dedicated unit for controlling the opening / closing operation of the on-off valve 7. However, as in this embodiment, the flow rate detection value by the flow meter 20 is input, and the detected flow rate is a predetermined constant value. You may make it also serve as the control part for controlling operation | movement of the pump 22 so that it may become a value.

  In the fourth embodiment, the closed state of the sample gas introduction nozzle 17 is automatically released. In this embodiment, the control unit 26 is connected to the flow meter 20 and the on-off valve 21, and the control unit 26 monitors the closed state of the sample gas introduction nozzle 17 with the flow rate of the flow meter 20. When the flow rate decreases to a predetermined value that corresponds to the closed state of the sample gas introduction nozzle 17, the control unit 26 closes the open / close valve 21 once and then opens the sample gas introduction nozzle 17. Flow sample gas.

  In this case as well, the control unit 26 may increase the output of the exhaust pump 22 from that during normal measurement before temporarily closing the on-off valve 21 and return it to that during normal measurement after opening the on-off valve 21. Good.

  The control unit 26 can be realized as a microcomputer dedicated to the aerosol particle number measuring apparatus or a general-purpose personal computer.

  The aerosol particle number measuring apparatus of this embodiment can be used as a single measuring apparatus that takes and measures automobile exhaust gas and environmental air into the sample gas inlet 2.

  Another embodiment in which the particle number measuring apparatus of the present invention is applied to a particle counter is schematically shown in FIGS.

  A sample gas introduction nozzle 44 is provided in order to guide the sample gas from the sample gas introduction port 2 to be sucked in as a sample gas containing fine particles into the optical path of the particle counting unit 40 by narrowing its flux. An exhaust pump 22 whose drive is controlled to exhaust at a predetermined flow rate through a filter 19 such as a HEPA filter that removes particles in the exhaust gas is provided downstream of the particle counting unit 40. The flow rate of the exhaust pump 22 is controlled by the control unit 46. Also in this embodiment, a flow meter 20 and an on-off valve 21 are provided between the filter 19 and the exhaust pump 22. An example of the flow meter 20 measures the flow rate by detecting the pressure difference between the upstream side and the downstream side of the critical orifice. The on-off valve 21 is normally opened during measurement.

  As shown in FIG. 3, the particle counter 40 is configured such that the sample gas whose flux is narrowed by the sample gas introduction nozzle 44 is led to the sample gas discharge port 45, and the sample gas led to the sample gas discharge port 45 is The gas is discharged by an exhaust pump 22 through a filter 19, a flow meter 20 and an on-off valve 21.

  A measurement light beam 48 in a direction orthogonal to the direction of the sample gas flux is irradiated on the sample gas flux from the sample gas introduction nozzle 44 toward the sample gas outlet 45. A laser diode is provided as the light source 50 for the measurement light beam 48, and the laser light from the light source 50 becomes a measurement light beam in a direction orthogonal to the direction of the sample gas flux by the aspherical lens 52 and the cylindrical lens 54. This measurement light beam is condensed at a position intersecting with the sample gas flux, and extends in the direction perpendicular to the paper surface so that the condensed portion has a width wider than the sample gas flux. In order to detect the scattered light beam generated by the particles included in the sample gas flux, a light detection comprising a lens 56 that collects the scattered light beam and a photodiode that detects the scattered light collected by the lens 56. A container 58 is provided.

  The optical system that guides the measurement light transmitted through the sample gas flux to the photodetector 58 may be transmitted light instead of scattered light.

  In this embodiment, the sample gas sucked from the sample gas introduction port 2 is guided by the sample gas introduction nozzle 44 to the particle counter 40 with the flux narrowed, and the transmitted light of the measurement light beam irradiated on the sample gas flux. Alternatively, the number of fine particles in the sample gas is counted from the scattered light.

  The first mode in this embodiment is to manually release the closed state of the sample gas introduction nozzle 44. In this embodiment, an operator who is measuring with this measuring device monitors the flow rate by the flow meter 20 during normal measurement, and the flow rate is a predetermined constant that corresponds to the closed state of the sample gas introduction nozzle 44. When the value drops to the value, the on-off valve 21 is once closed by a manual switch, and then opened to allow the sample gas to flow into the sample gas introduction nozzle 44 rushingly.

  At this time, if the output of the exhaust pump 22 is increased more than that during normal measurement before the on-off valve 21 is temporarily closed, and then returned to that during normal measurement after the on-off valve 21 is opened, the sample gas introduction nozzle 44 is provided. As a result, the flow rate of the sample gas flowing suddenly increases, and the closed state of the sample gas introduction nozzle 44 is more reliably released.

  The second mode in this embodiment is to automatically release the closed state of the sample gas introduction nozzle 44. In this embodiment, the control unit 46 is also connected to the flow meter 20 and the on-off valve 21, and the control unit 46 monitors the closed state of the sample gas introduction nozzle 44 by the flow rate of the flow meter 20. When the flow rate decreases to a predetermined value that corresponds to the closed state of the sample gas introduction nozzle 44, the control unit 46 closes the open / close valve 21 and then opens it to enter the sample gas introduction nozzle 44 suddenly. Flow sample gas.

  In this case as well, the control unit 46 may increase the output of the exhaust pump 22 from that during normal measurement before temporarily closing the on-off valve 21, and return it to that at the time of normal measurement after opening the on-off valve 21. Good.

  The control unit 46 can be realized as a microcomputer dedicated to the particle counter or a general-purpose personal computer.

  The particle counter of this embodiment can also be used as a single measuring device for taking in and measuring automobile exhaust gas and environmental air into the sample gas inlet 2.

  The particle number measuring apparatus shown as an embodiment in FIG. 1 or 2 can be used alone, but as schematically shown in FIG. 1 and FIG. It can also be used as a particle number detection device for classified particles. As a specific example of the classification device 30 used in such a usage pattern, an example of a differential electric mobility classifier (DMA) is shown in FIG. 4 (see Patent Document 1). The differential electric mobility classifier classifies and takes out charged fine particles for each particle size using the difference in electric mobility. The differential electric mobility classifier shown in FIG. 4 is an example of a classifying device 30, and other types of classifying devices 30 can be similarly applied to the present invention.

  A cylindrical center electrode 103 is provided inside the cylindrical casing 101 of the classification device 30 so as to coincide with the central axis of the casing 101. The casing 101 is made of a conductive material, and the inner surface thereof is an outer electrode 104. The housing 101 is disposed on an insulating base 102. The center electrode 103 is disposed on the insulating base 119, and the center electrode 103 is insulated from the housing 101 by the base 119 and the base 102. The counter electrode is constituted by the center electrode 103 and the outer electrode 104 to generate an electric field for classifying charged fine particles according to electric mobility. The electrode 104 is grounded, the electrode 103 is connected to the power supply device 131, and the power supply device 131 is connected to the control unit 133. The power supply device 131 that applies a voltage between the electrodes 103 and 104 is controlled by the control unit 133. The control unit 133 is connected to the control unit 26 of the aerosol particle number measuring apparatus of the embodiment of FIG. 1 or the control unit 46 of the particle counter of the embodiment of FIG.

  A sheath gas supply unit 107 for introducing an uncharged gas as a sheath gas at a constant flow rate is provided on the upper portion of the housing 101. An insulating commutator 109 for laminating the sheath gas is provided at the upper end of the classification region 105, and the sheath gas that has passed through the commutator 109 is supplied to the classification region 105.

  In the classification region 105, a slit-like introduction port 111 is provided on the outer electrode 104 side, and charged aerosol is supplied from the introduction port 111 at a constant flow rate. In order to supply charged aerosol to the inlet 111, a charging device (not shown) is provided outside the classifier 30. Charged aerosol charged by the charging device is supplied to the inlet 111.

  An annular exit slit 120 for discharging the classified fine particles is formed below the center electrode 103. The space from the sample gas inlet 111 to the outlet slit 120 in the space formed between the electrodes 103 and 104 is a classification region 105.

  The exit slit 120 is connected to the classified particle outlet 122, and the classified particle outlet 122 is connected to the sample gas inlet 2 of the aerosol particle number measuring device.

  The casing 101 is supplied with sheath gas and charged aerosol at a constant flow rate. A part of the gases supplied to the casing 101 is led to the aerosol particle number measuring device through the classified particle discharge port 122 from the outlet slit 120 together with the classified charged particles, and the remaining gas is placed in the lower part of the casing 101. It is discharged from the provided outlet 124.

  The charged aerosol charged by the charging device to the classifying device 30 is supplied to the classification region 105 through the introduction port 111, moves downward in the axial direction together with the sheath gas supplied from the sheath gas supply unit 107, and is formed in the classification region 105. Under the influence of an electric field, the particles are attracted in the direction of the central axis at a speed corresponding to the electric mobility of fine particles of individual particle sizes in the charged aerosol. As a result, only the fine particles 112 that reach the exit slit 120 while drawing a predetermined trajectory corresponding to the electric field at that time are guided from the classified particle outlet 122 to the sample gas inlet 2 of the aerosol particle number measuring device and counted. .

  The voltage applied between the electrodes 103 and 104 from the power supply device 131 is changed by the control unit 133, and fine particles having a particle size corresponding to the voltage are classified and guided to the aerosol particle number measuring device.

  The aerosol flow capillary 4 or sample gas introduction nozzle 17 in the aerosol particle number measuring apparatus of the embodiment of FIG. 1 and the sample gas introduction nozzle 44 of the particle counter of the embodiment of FIG. Therefore, the on-off valve 7 or 21 is closed for a certain time. When the on-off valve 7 or 21 is closed, the measurement operation of the aerosol particle number measuring device or the particle counter is interrupted, so the control units 26 and 46 take in a signal for controlling the power supply device 131 from the control unit 133 of the classification device 30, Control is performed so as not to perform the operation of closing the on-off valve 7 or 21 during the acquisition of the measurement data by the classification operation of the classification device 30.

  Whether or not measurement data is being acquired by the classification operation of the classification device 30 is determined as follows. The voltage applied between the electrodes 103 and 104 is changed as shown in FIG. 5, for example. The voltage is raised stepwise (a) or ramped (b). When the voltage is raised stepwise, the voltage is held for a certain time so that the voltage of the classification region 105 is stabilized at each step of the staircase, and fine particles having a particle size corresponding to the voltage for the certain time, or particles are classified. Fine particles having a particle size corresponding to the integral voltage received while in the unit are classified and guided from the classified particle outlet 122 to the sample gas inlet 2 of the aerosol particle number measuring device or particle counter. The applied voltage is not limited to a stepwise increase as shown in FIG. 5, but may be a stepwise decrease, an appropriate combination of voltage increase and decrease, or a ramp shape. It may be raised, lowered, or a combination of rising and falling.

  The classification operation by a series of voltage changes is repeated with a time interval to. There is a delay time Td from when the charged aerosol is supplied to the classification region 105 and classified by the applied voltage until it reaches the particle counter 18 of the aerosol particle number measuring device. This delay time Td is affected by the type of classification device 30, operating conditions, the piping volume of the aerosol particle number measuring device, the sample gas flow rate, and the like. Assuming that the classification operation start time of the classification device 30 for one measurement data acquisition is Ts and the classification operation end time is Te, the measurement data acquisition is from (Ts + Td) to (Te + Td) time. It becomes a period. The first measurement data acquisition time is t1, and the second measurement data acquisition time is t2, and the time Tn between the period t1 and t2 is a time during which no measurement data is acquired. When the measurement is repeated, there is a time Tn during which the measurement data is not acquired between the measurements, so that the aerosol flow capillary 4 or the sample gas introduction nozzles 17 and 44 are closed and the closed state is released. When it becomes necessary to close the on-off valve 7 or 21, the on-off valve 7 or 21 is closed at any time Tn.

  Based on the signal from the control unit 133 of the classification device 30, the control units 26 and 46 do not take the time during which the on-off valve 7 or 21 is closed to acquire any measurement data. The opening / closing operation of the opening / closing valve 7 or 21 is controlled so as to close the opening / closing valve 7 or 21.

  The present invention can be used for environmental measurement for automobile exhaust gas, factory exhaust gas, and the like.

2 Sample gas introduction port 6 Splitter 4 Aerosol flow capillary 8 Sheath gas flow path 10 Filter 12 Variable orifice 14 Saturator 16 Cooling condenser 17 Sample gas introduction nozzle 18 Particle counter 20 Flow meter 21 On-off valve 22 Exhaust pumps 26, 46, 133 Control unit 30 DMA
104 Outer electrode 103 Center electrode 105 Classification area 122 Classification particle outlet

Claims (11)

The particle number itself or the particle number concentration is measured based on analog changes in the amount of scattered light or transmitted light emitted from the light path, or the pulse count value of the signal digitized by a threshold value. In the particle counting device including a particle counting unit (18, 40) and a sample gas introduction nozzle (17, 44) for narrowing an airflow diameter for transporting particles into the optical path of the particle counting unit (18, 40),
When the sample gas introduction nozzle (17, 44) is closed, a larger amount of gas is supplied to the sample gas introduction nozzle (17, 44) than when it is used for normal measurement, or from the time of normal measurement. A particle number measuring apparatus comprising a closed state releasing mechanism for releasing the closed state of the sample gas introduction nozzle (17, 44) by setting the upstream side to a high pressure or the downstream side to a low pressure. The particle number measuring device is an aerosol particle number measuring device,
A sample gas inlet (2) for inhaling aerosol containing nanometer-sized fine particles as a sample gas;
An aerosol flow in which a part of the sample gas is flowed as an aerosol flow as a measurement throttle unit that reduces the number of particles supplied to the particle counting unit (18) in order to avoid overlapping of particles in the optical path of the particle counting unit (18). Capillary (4);
A splitter (6) provided at the tip of the sample gas introduction port (2) and separating the sample gas into a gas flowing into the aerosol flow capillary (4) and a remaining gas;
A sheath gas flow path (8) provided downstream of the splitter (6) and provided with a filter (10) for removing particles in the sample gas and an adjustment valve (12) for adjusting the flow rate;
A saturator (14) for converting the gas from the sheath gas flow path (8) into a sheath flow in a saturated vapor state and joining the aerosol flow flowing out from the aerosol flow capillary 4;
A cooling condenser (16) that cools the combined gas of the aerosol flow from the aerosol flow capillary (4) and the sheath flow from the saturator (14) to grow the fine particles in the aerosol flow by the steam of the sheath flow;
The sample gas introduction nozzle (17) for supplying the sample gas from the cooling condenser (16) to the particle counter (18);
An exhaust pump (22) provided downstream of the particle counter (18) and controlled to be exhausted at a predetermined flow rate;
A flow meter (20) provided between the particle counter (18) and the exhaust pump (22);
The particle number measuring apparatus according to claim 1, comprising: The particle number measuring device is a particle counter,
A sample gas inlet (2) for inhaling a sample gas containing fine particles;
The sample gas introduction nozzle (44) for introducing the sample gas from the sample gas introduction port (2) into the optical path of the particle counter (40);
An exhaust pump (22) provided downstream of the particle counter (40) and controlled to be exhausted at a predetermined flow rate;
A flow meter (20) provided between the particle counter (40) and the exhaust pump (22);
The particle number measuring apparatus according to claim 1, comprising: As the closed state release mechanism for the sample gas introduction nozzle (17, 44), an on-off valve (21) is provided between the flow meter (20) and the exhaust pump (22),
The on-off valve (21) is normally opened during measurement, and when the sample gas introduction nozzle (17, 44) is released from the closed state, it is once closed and then opened to open the sample gas introduction nozzle ( The particle number measuring apparatus according to claim 2 or 3, wherein the sample gas is allowed to flow in a rushing manner to (17, 44).   The exhaust pump (22) has its output increased more than during normal measurement before the on-off valve (21) is temporarily closed, and after the on-off valve (21) is opened, during normal measurement. The particle number measuring apparatus according to claim 4, wherein the apparatus is returned to the object. The flow meter (20) includes a throttle part with a narrow flow path and a pressure sensor for detecting a differential pressure between the upstream and downstream of the throttle part, and detects the flow rate by the differential pressure. Is what
The sample gas introduction is performed by controlling the opening / closing operation so that the opening / closing valve 21 is opened after the opening / closing valve 21 is temporarily closed when the differential pressure at the throttle portion falls below a preset threshold value or a certain ratio. The particle number measuring device according to claim 4, further comprising a control unit (26, 46) for automatically releasing the closed state of the nozzle (17, 44).   The controller (26, 46) normally outputs the output of the exhaust pump (22) before temporarily closing the on-off valve (21) in order to release the closed state of the sample gas introduction nozzle (17, 44). The exhaust pump (22) is also controlled so as to return the output of the exhaust pump (22) to that at the time of normal measurement after opening the on-off valve (21). Item 7. The particle number measuring apparatus according to Item 6. As the closed state release mechanism for the aerosol flow capillary (4), comprising an on-off valve (7) provided in the sheath gas flow path (8),
The on-off valve (7) is released during normal measurement and closed when the closed state of the aerosol flow capillary (4) is released, so that a larger amount of sample gas is supplied to the aerosol flow capillary (4) than during normal measurement. The particle number measuring device according to claim 2, wherein the particle number is measured. A pressure sensor (24) for detecting a differential pressure by the adjustment valve (12) between the upstream side and the downstream side of the adjustment valve (12) of the sheath gas flow path (8);
When the differential pressure by the pressure sensor (24) exceeds a preset threshold value or a fixed ratio during normal measurement, the on-off valve (7) is temporarily closed to automatically close the aerosol flow capillary (4). The particle number measuring apparatus according to claim 8, further comprising a control unit (26) that is automatically released. The sample gas introduction port (2) is connected to a classification particle discharge port of the classifier (30),
The control unit (26, 46) is configured not to perform the closed state release operation by the closed state release mechanism during acquisition of measurement data by the classification operation of the classification device (30). The particle number measuring apparatus described in 1. The delay time from the time of voltage application for classification in the classifier (30) until the classified particles reach the particle counter (18) is Td,
When the classification operation start time of the classification device (30) is Ts and the classification operation end time is Te,
The particle number measuring apparatus according to claim 10, wherein the acquisition of the measurement data is a period from a (Ts + Td) time point to a (Te + Td) time point.

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