WO2018163661A1

WO2018163661A1 - Microparrticle number detector

Info

Publication number: WO2018163661A1
Application number: PCT/JP2018/002891
Authority: WO
Inventors: 京一菅野; 和幸水野; 英正奥村
Original assignee: 日本碍子株式会社
Priority date: 2017-03-10
Filing date: 2018-01-30
Publication date: 2018-09-13
Also published as: JPWO2018163661A1

Abstract

This microparticle number detector 10 is provided with an electric charge generating element 20, a collecting device 40, and a number detecting device 50. The electric charge generating element 20 adds, to microparticles 16 in a gas, electric charges generated by electrical discharge to thereby convert the microparticles into charged microparticles P. The collecting device 40 collects, in a collecting electrode 42, the charged microparticles P that pass through between the collecting electrode 42 and a counter electrode 44 while performing Brownian motion. The number detecting device 50 detects the number of the microparticles 16 on the basis of a current varying according to the number of charged microparticles P collected by the collecting electrode 42. When the microparticles 16 or the like are deposited on the collecting electrode 42, a heater 60 burns and eliminates the deposits by heating the collecting electrode 42.

Description

Particle count detector

The present invention relates to a particle number detector.

The particle number detector adds charge to the particles in the gas, collects the charged particles with the electrode plate of the diffusion separator, and measures the number of particles based on the amount of charges of the collected particles Is known (see, for example, Patent Document 1).

JP 2014-59314 A

However, in the particle number detector of Patent Document 1, since particles accumulate on the surface of the electrode plate of the diffusion separator, it is necessary to remove the deposit by removing the electrode plate and cleaning it at appropriate times.

The present invention has been made to solve such a problem, and its main object is to facilitate the maintenance of the collecting electrode.

The particle number detector of the present invention is
A charge generation unit that adds charged charges generated by discharge to the fine particles in the gas introduced into the vent pipe to form charged fine particles;
Provided on the downstream side of the gas flow with respect to the charge generation unit, and has a collecting electrode and a counter electrode facing the collecting electrode, and the distance between the collecting electrode and the counter electrode is 0.01 mm. Less than 0.2 mm, a charged particle collection unit that collects the charged particles passing through the Browning motion between the collection electrode and the counter electrode on the collection electrode;
A number detection unit that detects the number of the fine particles based on a physical quantity that changes according to the number of the charged fine particles collected by the collection electrode;
A heating unit for heating the collecting electrode;
It is equipped with.

In this particle number detector, the charge generated by the discharge is added to the particles in the gas introduced into the vent tube to form charged particles. The charged fine particles that pass through the Brownian motion between the collecting electrode and the counter electrode having an interval of 0.01 mm or more and less than 0.2 mm are collected by the collecting electrode. The number detection unit detects the number of fine particles in the gas based on a physical quantity that changes according to the number of charged fine particles collected by the collection electrode. This fine particle number detector includes a heating unit. Therefore, when fine particles or the like are deposited on the collection electrode, the collection electrode can be refreshed by heating the collection electrode in the heating unit and burning the deposit. Therefore, it is not necessary to remove the collection electrode and clean it to remove the deposit, and the maintenance of the collection electrode is facilitated.

In this specification, “charge” includes positive charges and negative charges as well as ions. “Detecting the number of fine particles” determines whether or not the number of fine particles falls within a predetermined numerical range (for example, whether or not a predetermined threshold value is exceeded) in addition to measuring the number of fine particles. Including cases. The “physical quantity” may be a parameter that changes based on the number of charged fine particles (charge quantity), and examples thereof include current. The interval between the collection electrode and the counter electrode is set to 0.01 mm or more in order to avoid excessive pressure loss, and the interval between the collection electrode and the counter electrode is set to less than 0.2 mm. This is to make it easier to collect the charged fine particles in Brownian motion on the collecting electrode.

In the fine particle number detector of the present invention, it is preferable that the collection electrode and the counter electrode are arranged with a predetermined distance set in a range of 0.01 mm or more and less than 0.1 mm. If this distance is less than 0.1 mm, it becomes easier to collect charged fine particles that are in Brownian motion between the collecting electrode and the counter electrode.

In the particle number detector of the present invention, the counter electrode is a partition electrode plate that bisects the passage, the collection electrode is provided to face each of the front and back surfaces of the partition electrode plate, and the heating unit includes: , Each of the collecting electrodes may be provided. In this case, the total area of the collecting electrode is increased as compared with the case where one collecting electrode is provided, so that the frequency of refreshing the collecting electrode by the heating unit can be reduced.

In the particle number detector of the present invention, the charged particle collection unit can apply a voltage between the collection electrode and the counter electrode, and a voltage set in advance for each particle size range of the particles. You may make it apply between the said collection electrode and the said counter electrode. Even if no voltage is applied between the collecting electrode and the counter electrode, the charged fine particles passing through the two electrodes while moving in brown can be collected by the collecting electrode. On the other hand, when a voltage is applied between the collecting electrode and the counter electrode, the particle size range of the collected fine particles varies depending on the applied voltage. Therefore, the number of particles in a desired particle size range can be detected by applying a voltage preset for each particle size range between the collecting electrode and the counter electrode.

In the particle number detector of the present invention, a plurality of the collecting electrodes may be provided at intervals from the upstream side to the downstream side of the gas flow. In terms of fluid dynamics, the smaller charged fine particles are collected on the upstream collecting electrode, and the larger charged fine particles are collected on the downstream collecting electrode. Therefore, the charged fine particles can be easily classified.

The particle number detector of the present invention is provided between the charge generation unit and the charged particle collection unit, a removal electrode is disposed between a pair of removal electric field generation electrodes, and the pair of removal electric field generation electrodes There may be provided a surplus charge removing unit that removes surplus charges that have not been added to the fine particles when the removal voltage is applied therebetween. By so doing, excess charge is removed by the removal electrode, so that it is not collected by the collection electrode of the collection device and counted as the number of fine particles.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of the particle number detector 10. The graph showing the relationship between the particle size of fine particles and the transmittance. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a particle number detector 110. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a particle number detector 210. The graph showing the relationship between the particle size of fine particles and the transmittance. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a particle number detector 310. FIG. 4 is a cross-sectional view illustrating a schematic configuration of a residual particle number detection device 70. Sectional drawing at the time of dividing the hollow part 12c into n steps and providing the collection apparatus 40 in each step.

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of the fine particle number detector 10, and FIG. 2 is a graph showing the relationship between the particle size and transmittance of the fine particles.

The fine particle number detector 10 measures the number of fine particles contained in a gas (for example, exhaust gas from an automobile). As shown in FIG. 1, the particle number detector 10 includes a vent tube 12, a charge generation element 20, a surplus charge removal device 30, a collection device 40, a number detection device 50, and a heater 60. The vent pipe 12 is made of ceramic, and has a gas inlet 12a for introducing gas into the vent pipe 12 and a gas outlet 12b for discharging the gas that has passed through the vent pipe 12.

The charge generation element 20 includes a needle electrode 22 and a counter electrode 24 provided so as to be exposed on a wall facing the needle electrode 22, provided on the side of the vent pipe 12 close to the gas inlet 12 a. is doing. The needle electrode 22 and the counter electrode 24 are connected to a discharge power source 26 that applies a voltage Vp (for example, a pulse voltage). The charge generating element 20 generates an air discharge due to a potential difference between the two electrodes when a voltage Vp is applied between the needle-like electrode 22 and the counter electrode 24. As the gas passes through the air discharge, the fine particles 16 in the gas are added with charges 18 (here, positive charges) to become charged fine particles P.

The surplus charge removing device 30 includes a pair of removal electric field generating electrodes (an application electrode 32 and a ground electrode 34) and a removal electrode 36. The application electrode 32 and the ground electrode 34 are embedded in positions facing each other on the wall of the vent pipe 12. The application electrode 32 is a minute positive potential V2 electrode. The ground electrode 34 is an electrode connected to the ground. The removal electrode 36 is disposed between the application electrode 32 and the ground electrode 34, and is exposed on the wall of the hollow portion 12 c in which the ground electrode 34 is embedded. As a result, a weak electric field is generated between the application electrode 32 and the ground electrode 34 of the surplus charge removing device 30. Therefore, of the electric charges 18 generated by the electric charge generating element 20, the excessive electric charges 18 that have not been added to the fine particles 16 are attracted to the ground electrode 34 by this weak electric field, captured by the removal electrode 36, and then discarded to the ground. . Therefore, surplus charges 18 are not collected by the collection electrode 42 of the collection device 40 and counted as the number of fine particles 16.

The collection device 40 is a device that collects the charged fine particles P, and is provided in the hollow portion 12 c in the vent pipe 12. The collection device 40 includes a collection electrode 42 and a counter electrode 44 that faces the collection electrode 42. The collecting electrode 42 and the counter electrode 44 are exposed at positions facing each other on the wall of the vent pipe 12. Both

electrodes

42 and 44 are arranged with a predetermined distance set within a range of 0.01 mm or more and less than 0.2 mm (preferably 0.01 mm or more and 0.1 mm or less). The distance between the

electrodes

42 and 44 is also referred to as a channel thickness. The counter electrode 44 is an electrode to which the voltage V1 can be applied. In the present embodiment, the voltage V1 is zero. The collecting electrode 42 is connected to the ground via an ammeter 52. The charged fine particles P (positively charged) enter the hollow portion 12 c while performing the Brownian motion, and pass between the collection electrode 42 and the counter electrode 44 after passing through the surplus charge removing device 30. At this time, the channel thickness is the above-mentioned predetermined distance (minute distance). For this reason, the charged fine particles P having a small particle size with a sharp Brownian motion collide with the collecting electrode 42 and are collected even if no electric field is generated in both the

electrodes

42 and 44. Note that the electrical wiring connecting the collecting electrode 42 and the ammeter 52 penetrates the heater 60 in a state where it is electrically insulated from the heater 60.

Here, the relationship between the particle size of the fine particles and the transmittance is shown in the graph of FIG. When the voltage application to the counter electrode 44 is zero, when the channel thickness is 4 mm, almost all the fine particles having a particle diameter of 10 to 100 nm are transmitted without being collected by the collecting electrode. It can be seen that when the channel thickness is 0.1 mm, the smaller the particle size, the lower the transmittance and the easier it is to be collected by the collecting electrode 42. There are two peaks in the particle size distribution of the fine particles, one is a peak of 10 to 20 nm (condensed nucleus mode) and the other is a peak of 50 to 100 nm (accumulation mode). Therefore, when the voltage application to the counter electrode 44 is zero and the channel thickness is 0.1 mm, the charged fine particles P collected by the collecting electrode 42 are estimated to have a particle diameter of 10 to 20 nm.

The number detection device 50 includes an ammeter 52 and a number measurement device 54. The ammeter 52 has one terminal connected to the collecting electrode 42 and the other terminal connected to the ground. The ammeter 52 measures the current based on the charge 18 of the charged fine particles P collected by the collecting electrode 42. The number measuring device 54 calculates the number of fine particles 16 based on the current of the ammeter 52.

The heater 60 is embedded in the wall of the vent pipe 12 at a position in the vicinity of the collecting electrode 42. The heater 60 is connected to a power supply device (not shown), and generates heat when the power supply device is energized to heat the collecting electrode 42.

Next, a usage example of the particle number detector 10 will be described. When measuring particulates contained in the exhaust gas of an automobile, the particulate number detector 10 is attached in the exhaust pipe of the engine. At this time, the particulate matter detector 10 is attached so that the exhaust gas is introduced into the vent pipe 12 from the gas inlet 12a of the particulate detector 10 and discharged from the gas outlet 12b.

The fine particles 16 contained in the exhaust gas introduced into the ventilation pipe 12 from the gas introduction port 12a are charged with the charge 18 (positive charge in this case) generated by the discharge of the charge generation element 20 and become the charged fine particles P and then the hollow portion. Enter 12c. Among the charged fine particles P entering the hollow portion 12c, those having a particle diameter of 10 to 20 nm have a low transmittance as shown in FIG. 2, and therefore when passing between the collecting electrode 42 and the counter electrode 44, both electrodes Even if no electric field is generated at 42 and 44, they are collected by the collecting electrode 42. On the other hand, the charged fine particles P having a particle diameter of 50 to 100 nm pass through without being collected by the collecting electrode 42 because the transmittance exceeds 0.9 as shown in FIG.

The current based on the charge 18 of the charged fine particles P attached to the collecting electrode 42 is measured by an ammeter 52, and the number measuring device 54 calculates the number of the fine particles 16 based on the current. The relationship between the current I and the charge amount q is I = dq / (dt), q = ∫Idt. The number measuring device 54 integrates (accumulates) the current value over a predetermined period to obtain the integrated value (accumulated charge amount), and divides the accumulated charge amount by the elementary charge to obtain the total number of charges (collected charge number). The number Nt of fine particles 16 having a particle diameter of 10 to 20 nm attached to the collecting electrode 42 is obtained by dividing the number of collected charges by the average value of the number of charges added to one fine particle 16. However, as shown in FIG. 2, some of the fine particles 16 having a particle diameter of 10 to 20 nm pass through without being collected by the collecting electrode. Therefore, it is necessary to obtain the total number Na of fine particles having a particle diameter of 10 to 20 nm by correcting the obtained number Nt. For example, the average value of the collection rate of the fine particles 16 having a particle size of 10 to 20 nm is obtained by subtracting the average value of the transmittance of the fine particles 16 having a particle size of 10 to 20 nm from 1, and the number Nt is the average value of the collection rates. The value divided by may be the total number Na.

When a large number of fine particles 16 and the like are deposited on the collecting electrode 42, the charged fine particles P may not be newly collected on the collecting electrode 42. Therefore, the collection electrode 42 is heated and incinerated by heating the collection electrode 42 with the heater 60 periodically or at the timing when the accumulation amount reaches a predetermined amount. Refresh the face.

Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The charge generation element 20 of the present embodiment corresponds to a charge generation unit of the present invention, the collection device 40 corresponds to a charged particle collection unit, the number detection device 50 corresponds to a number detection unit, and the heater 60 serves as a heating unit. It corresponds to.

In the fine particle number detector 10 of the present embodiment described in detail above, the charged fine particles P having a predetermined particle size range (particle size of 10 to 20 nm) passing between the collecting electrode 42 and the counter electrode 44 while performing Brownian motion are as follows. And collected by the collecting electrode 42. Then, the number of fine particles 16 in the gas is detected based on a current that changes according to the number of charged fine particles P collected by the collecting electrode 42. The particle number detector 10 includes a heater 60. Therefore, when the fine particles 16 or the like are deposited on the collecting electrode 42, the collecting electrode 42 can be refreshed by heating the collecting electrode 42 with the heater 60 and burning the deposit. Therefore, it is not necessary to remove the collection electrode 42 and clean it to remove the deposit, and the maintenance of the collection electrode 42 is facilitated.

In addition, since the collection electrode 42 and the counter electrode 44 are arranged with a predetermined distance set within a range of 0.01 mm or more and less than 0.2 mm, the collection electrode 42 and the counter electrode 44 are disposed between the collection electrode 42 and the counter electrode 44. It is easy to collect the charged fine particles P that are in a Brownian motion, and the pressure loss does not become too high. In addition, if this distance is 0.1 mm or less, it becomes easier to collect.

Furthermore, since the surplus charges 18 that have not been added to the fine particles 16 among the charges 18 generated by the charge generation element 20 are removed by the removal electrode 36, they are collected by the collection electrode 42 of the collection device 40. It is not counted as a number of 16.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

For example, in the above-described embodiment, the heater 60 is embedded in the wall of the vent pipe 12, but the heater 160 may be provided on the outer peripheral surface of the vent pipe 12 as in the particle number detector 110 shown in FIG. In FIG. 3, the same components as those in the above-described embodiment are denoted by the same reference numerals. Also in this case, the same effect as the above-described embodiment can be obtained. However, since the heater 60 of the embodiment described above can be installed near the collecting electrode 42, the collecting electrode 42 can be efficiently heated.

In the above-described embodiment, the collection device 40 including the collection electrode 42 and the counter electrode 44 is employed. However, like the particle number detector 210 illustrated in FIG. 4, the

collection electrodes

241 and 242 and the counter electrode 244 are used. You may employ | adopt the collection apparatus 240 provided with these. In FIG. 4, the same components as those in the above-described embodiment are denoted by the same reference numerals. In the collection device 240, the counter electrode 244 is a partition electrode plate that divides the hollow portion 12 c into two, and the

collection electrodes

241 and 242 are provided to face the front and back of the counter electrode 244, respectively. The

heaters

261 and 262 are provided in the vicinity of the collecting

electrodes

241 and 242. The

number detection devices

251 and 252 are also connected to the

respective collecting electrodes

241 and 242. In this case, since the total area of the

collection electrodes

241 and 242 is larger than that in the embodiment described above, the frequency with which the

collection electrodes

241 and 242 are refreshed by the

heaters

261 and 262 can be reduced. Instead of the counter electrode 244, members supporting the counter electrode may be arranged on both the upper and lower surfaces of the ceramic plate so that the voltage V1 can be applied to both counter substrates. In this case, the counter electrode on the lower surface of the ceramic plate faces the collecting electrode 241, and the counter electrode on the upper surface of the ceramic plate faces the collecting electrode 242.

In the above-described embodiment, the voltage V1 applied to the counter electrode 44 is zero, but a voltage set in advance for each particle size range of the charged fine particles P may be applied to the counter electrode 44. For example, FIG. 5 is a graph showing the relationship between the particle size of the fine particles and the transmittance when the voltage is changed with a flow channel thickness of 0.1 mm. When the voltage V1 is zero, the fine particles 16 having a particle diameter of 10 to 20 nm hardly pass through the flow path (that is, are easily collected). In contrast, when the voltage V1 is the predetermined voltage Va (> 0), fine particles having a particle size of 10 to 50 nm are unlikely to pass through the flow path (that is, are easily collected), and the voltage V1 is equal to the predetermined voltage Vb (> 0). In the case of Va), fine particles having a particle size of 10 to 100 nm hardly pass through the flow path (that is, are easily collected). Therefore, when it is desired to detect the number of fine particles having a particle size of 10 to 20 nm, the voltage V1 is set to zero, and when it is desired to detect the number of fine particles having a particle size of 10 to 50 nm, the voltage V1 is set to a predetermined voltage Va. When it is desired to detect the number of fine particles of 10 to 100 nm, the voltage V1 may be set to the predetermined voltage Vb. That is, by applying a preset voltage between the collection electrode 42 and the counter electrode 44 for each particle size range of the charged fine particles P, the number of particles in a desired particle size range can be detected. Further, by switching the set value of the voltage V1 stepwise with time, the number of particles in different particle size ranges can be grasped, and the particle size distribution can be obtained.

In the embodiment described above, the collecting electrode 42 is provided as a single electrode, but a plurality of gaps may be provided from the upstream side to the downstream side of the gas flow. An example is shown in FIG. The fine particle number detector 310 of FIG. 6 includes three

collection electrodes

421, 422, and 423. The

collection electrodes

421, 422, and 423 are connected to

ammeters

521, 522, and 523, respectively, and the

ammeters

521, 522, and 523 are connected to the

number measuring devices

541, 542, and 543, respectively. In FIG. 6, the same components as those in the above-described embodiment are denoted by the same reference numerals. In this way, in terms of fluid dynamics, the smaller charged fine particle P is collected by the upstream collecting electrode 421, and the larger charged fine particle P is collected by the downstream collecting electrode 423. Therefore, the charged fine particles P can be classified. Further, since the

collection electrodes

421, 422, and 423 are provided with the

number measuring devices

541, 542, and 543, the number of the small-sized fine particles 16, the number of the medium-sized fine particles 16, and the large-sized fine particles 16, respectively. Each number can be measured.

In the embodiment described above, as shown in FIG. 7, the number of charged fine particles P that have not been collected by the collection device 40 are collected before the gas discharge port 12b (upstream side of the gas flow). You may provide the residual particle number detection apparatus 70 to detect. The residual particle number detection device 70 has a pair of electric

field generating electrodes

72 and 74 and a recovery electrode 76. The pair of electric

field generating electrodes

72 and 74 are embedded at positions facing each other on the wall of the vent pipe 12, and a voltage is applied so that a potential difference is generated between the

electrodes

72 and 74. As a result, an electric field is generated between the

electrodes

72 and 74. The collection electrode 76 is disposed between the

electrodes

72 and 74 and is exposed to the wall of the vent pipe 12. The charged fine particles P that have passed through the collecting device 40 (see FIG. 1) and have reached between the

electrodes

72 and 74 are attracted to the electrode 74 by the electric field generated between the

electrodes

72 and 74, and in the middle It is recovered by a recovery electrode 76 installed in A number detection device 78 similar to the number detection device 50 (see FIG. 1) is connected to the collection electrode 76. The number detection device 78 detects the number of charged fine particles P that have not been collected by the collection device 40. Therefore, the total number of particles contained in the gas can be known by adding the number of particles calculated by the two

number detection devices

50 and 78. Further, the ratio of the number of fine particles having a particle diameter of 10 to 20 nm detected by the number detection device 50 to the total number of fine particles can be obtained.

The residual particle number detection device 70 may be configured by a mesh having an opening smaller than the interval between the collection electrode 42 and the counter electrode 44. In this case, since the charged fine particles P reach the mesh by Brownian motion, the particles can be collected without applying a voltage. Furthermore, if a voltage having a polarity opposite to that of the charged fine particles P is applied to the mesh, the charged fine particles P can be collected more reliably.

In the above-described embodiment, the case of measuring the number of positively charged fine particles P has been described, but the number of fine particles 16 can be measured in the same manner even for negatively charged charged fine particles P.

In the embodiment described above, one collecting device 40 is provided in the hollow portion 12c. However, as shown in FIG. 8, the height of the hollow portion 12c is set to n stages (n is an integer equal to or larger than 2, n = in FIG. 3), and a collecting device 40 (collecting electrode 42 and counter electrode 44) may be provided at each stage. In this way, the length of the hollow portion 12c in the gas flow direction can be reduced to 1 / n that of the above-described embodiment in order to obtain the same effect as that of the above-described embodiment, so that the particle number detector can be made compact. .

This application is based on Japanese Patent Application No. 2017-45632 filed on Mar. 10, 2017, the contents of which are incorporated herein by reference.

The present invention can be used to detect the number of fine particles in exhaust gas from a power machine such as an automobile.

10, 110, 210, 310 Fine particle number detector, 12 vent tube, 12a gas inlet, 12b gas outlet, 12c hollow part, 16 fine particles, 18 charges, 22 needle electrodes, 24 counter electrode, 26 discharge power supply, 30 surplus charge removal device, 32 applied electrode, 34 ground electrode, 36 removal electrode, 40,240 collection device, 42,242,421-423 collection electrode, 44,244 counter electrode, 50,251,252

number detection device

52, 521 to 523 ammeter, 54, 541 to 543 number measuring device, 60, 160, 261, 262 heater, 70 remaining particle number detecting device, 72, 74 electric field generating electrode, 76 collecting electrode, 78 number detecting device, P Charged fine particles.

Claims

A charge generation unit that adds charged charges generated by discharge to the fine particles in the gas introduced into the vent pipe to form charged fine particles;
Provided on the downstream side of the gas flow with respect to the charge generation unit, and has a collecting electrode and a counter electrode facing the collecting electrode, and the distance between the collecting electrode and the counter electrode is 0.01 mm. Less than 0.2 mm, a charged particle collection unit that collects the charged particles passing through the Browning motion between the collection electrode and the counter electrode on the collection electrode;
A number detection unit that detects the number of the fine particles based on a physical quantity that changes according to the number of the charged fine particles collected by the collection electrode;
A heating unit for heating the collecting electrode;
Particle number detector equipped with.
The collection electrode and the counter electrode are arranged with a predetermined distance set in a range of 0.01 mm or more and 0.1 mm or less,
The fine particle number detector according to claim 1.
The counter electrode is a partition electrode plate that bisects the passage, the collection electrode is provided to face each of the front and back sides of the partition electrode plate, and the heater is provided to each of the collection electrodes. ing,
The fine particle number detector according to claim 1 or 2.
The charged particulate collection unit is capable of applying a voltage between the collection electrode and the counter electrode, and a preset voltage for each particle size range of the particulate is between the collection electrode and the counter electrode. Applied during
The fine particle number detector according to any one of claims 1 to 3.
A plurality of the collecting electrodes are provided at intervals from the upstream side to the downstream side of the gas flow,
The fine particle number detector according to any one of claims 1 to 4.
The fine particle number detector according to any one of claims 1 to 5,
When the removal electrode is disposed between the charge generation unit and the charged particulate collection unit, the removal electrode is disposed between the pair of removal electric field generation electrodes, and the removal voltage is applied between the pair of removal electric field generation electrodes. A fine particle number detector comprising a surplus charge removing unit that removes surplus charges not added to the fine particles by the removal electrode.