WO2021060105A1 - Élément de détection de microparticules et détecteur de microparticules - Google Patents

Élément de détection de microparticules et détecteur de microparticules Download PDF

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Publication number
WO2021060105A1
WO2021060105A1 PCT/JP2020/035078 JP2020035078W WO2021060105A1 WO 2021060105 A1 WO2021060105 A1 WO 2021060105A1 JP 2020035078 W JP2020035078 W JP 2020035078W WO 2021060105 A1 WO2021060105 A1 WO 2021060105A1
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Prior art keywords
electrode
fine particles
collecting
flow path
detection element
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PCT/JP2020/035078
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English (en)
Japanese (ja)
Inventor
英正 奥村
晃暢 織部
和幸 水野
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日本碍子株式会社
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Publication of WO2021060105A1 publication Critical patent/WO2021060105A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/60—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing

Definitions

  • the present invention relates to a fine particle detection element and a fine particle detector.
  • the fine particle detector includes a ceramic housing having a gas flow path, a charge generating part that adds an electric charge generated by electric discharge to the fine particles in the gas introduced into the gas flow path to form charged fine particles. It is provided with a collecting unit that collects charged fine particles on the downstream side of the electric field generating unit in the gas flow path, and a number measuring unit that measures the number of fine particles based on the amount of electric charge of the collected charged fine particles. Things are known.
  • the collecting portion has a collecting electrode exposed to the gas flow path and a counter electrode facing the collecting electrode across the gas flow path. The collecting electrode collects charged fine particles by utilizing the electric field generated between the collecting electrode and the counter electrode in the gas flow path by the voltage applied between the collecting electrode and the counter electrode.
  • Patent Document 1 discloses a detector provided with a partition wall for partitioning a gas flow path into a plurality of branch flow paths. A pair of collection electrode and counter electrode are provided in each of the branch flow paths.
  • cracks may occur in the partition wall.
  • cracks may occur in the wall provided with the collecting electrode and the wall provided with the counter electrode regardless of the presence or absence of the partition wall.
  • the present invention has been made to solve such a problem, and an object of the present invention is to prevent cracks from occurring on the wall of the gas flow path.
  • the first fine particle detection element of the present invention is A fine particle detection element used to detect fine particles in a gas.
  • a gas flow path provided on one end side of the housing in the longitudinal direction so as to penetrate the housing,
  • a charge generating part that adds an electric charge generated by electric discharge to the fine particles in the gas introduced into the gas flow path to form charged fine particles.
  • a partition wall that divides the gas flow path into a plurality of branch flow paths,
  • a collection electrode provided for each branch flow path and collecting an object to be collected, which is either the charged fine particles or the electric charge not added to the fine particles.
  • An electric field generating electrode which is provided at a position facing the collecting electrode for each branch flow path and generates a collecting electric field for moving the collecting target toward the collecting electrode, For each branch flow path, a support column provided so as to bridge the wall provided with the collecting electrode and the wall provided with the electric field generating electrode, and It is equipped with.
  • the charge generating part generates an electric charge to turn the fine particles in the gas into charged fine particles, which are then moved to the collecting electrode by a collecting electric field (charges not added to the charged fine particles and the fine particles).
  • a collecting electric field charges not added to the charged fine particles and the fine particles.
  • One of the above) is collected by the collection electrode. Since the physical quantity changes according to the collection target collected by the collection electrode, fine particles in the gas can be detected by using this fine particle detection element.
  • the gas flow path is divided into a plurality of branch flow paths by a partition wall. Since the collection electrode is provided for each branch flow path, the total area of the collection electrode becomes large, and the collection target can be reliably collected. Since the columns are provided so as to bridge the wall provided with the collecting electrode and the wall provided with the electric field generating electrode for each branch flow path, both walls are reinforced. This makes it possible to prevent cracks from occurring on the wall of the gas flow path.
  • one end of the support column may be arranged on the electrode surface of the collecting electrode, and the other end may be arranged on the electrode surface of the electric field generating electrode.
  • the collecting electrode and the electric field generating electrode are not separated by the columns. Therefore, the number of lead wires of the collecting electrode and the number of lead wires of the electric field generating electrode do not increase due to the provision of the support column.
  • the partition wall is one, and one section of the gas flow path separated by the support column and the partition wall is the section with respect to the width of the section.
  • the height ratio of the particles may be 0.9 or more and 3.5 or less.
  • the second fine particle detection element of the present invention is A fine particle detection element used to detect fine particles in a gas.
  • a gas flow path provided on one end side of the housing in the longitudinal direction so as to penetrate the housing, A charge generating part that adds an electric charge generated by electric discharge to the fine particles in the gas introduced into the gas flow path to form charged fine particles.
  • a collection electrode for collecting an object to be collected, which is either the charged fine particles or the electric charge not added to the fine particles.
  • An electric field generating electrode provided at a position facing the collecting electrode and generating a collecting electric field for moving the collecting target toward the collecting electrode, and an electric field generating electrode.
  • a strut provided so as to bridge the wall provided with the collecting electrode and the wall provided with the electric field generating electrode, and It is equipped with.
  • the charge generating part generates an electric charge to turn the fine particles in the gas into charged fine particles, which are then moved to the collecting electrode by a collecting electric field (charges not added to the charged fine particles and the fine particles).
  • a collecting electric field charges not added to the charged fine particles and the fine particles.
  • One of the above) is collected by the collection electrode. Since the physical quantity changes according to the collection target collected by the collection electrode, fine particles in the gas can be detected by using this fine particle detection element. Since the columns are provided so as to bridge the wall provided with the collecting electrode and the wall provided with the electric field generating electrode, both walls are reinforced. This makes it possible to prevent cracks from occurring on the wall of the gas flow path.
  • one end of the support column may be arranged on the electrode surface of the collecting electrode, and the other end may be arranged on the electrode surface of the electric field generating electrode.
  • the collecting electrode and the electric field generating electrode are not separated by the columns. Therefore, the number of lead wires of the collecting electrode and the number of lead wires of the electric field generating electrode do not increase due to the provision of the support column.
  • the ratio of the height of the section to the width of the section is 0.3 or more and 1.5 or less. It may be formed so as to be. In this way, the gas flowing through each section tends to have a uniform flow due to the rectifying effect, so that the collection rate at the collection electrode tends to be stable.
  • the fine particle detector of the present invention includes a fine particle detection element of any of the above-described embodiments, and a detection unit that detects the fine particles based on a physical quantity that changes according to the collection target collected by the collection electrode. , Is provided. Therefore, this fine particle detector can obtain the same effect as the fine particle detection element of the present invention described above, for example, the effect of preventing cracks from being generated on the wall of the gas flow path.
  • the detection unit may detect the amount of the fine particles based on the physical quantity.
  • the "amount of fine particles" may be, for example, at least one of the number, mass, and surface area of fine particles.
  • the detection unit uses the physical quantity and the electric charge generated by the charge generating unit (for example, the number of electric charges or the electric charge).
  • the fine particles may be detected based on the amount).
  • charge includes ions in addition to positive and negative charges.
  • Detecting the amount of fine particles means not only measuring the amount of fine particles, but also determining whether or not the amount of fine particles falls within a predetermined numerical range (for example, whether or not it exceeds a predetermined threshold value). Including cases.
  • the "physical quantity” may be a parameter that changes based on the number of objects to be collected (charge amount), and examples thereof include an electric current.
  • FIG. 3A is a cross-sectional view taken along the line AA of FIG.
  • FIG. 1 is an explanatory view of the fine particle detector 10 of the present embodiment
  • FIG. 2 is a perspective view of the fine particle detection element 20
  • FIG. 3 is a perspective view of a main part of the fine particle detection element 20
  • FIG. 4 is a cross section taken along the line AA of FIG.
  • FIGS. 5, 5 and 6 are exploded perspective views of the fine particle detecting element 20.
  • the vertical direction, the horizontal direction, and the front-rear direction are as shown in FIGS. 1, 2, 5, and 6.
  • the fine particle detector 10 detects the number of fine particles 26 (see FIG. 4) contained in the exhaust gas flowing through the exhaust pipe 12 of the engine.
  • the fine particle detector 10 includes a fine particle detection element 20, and an accessory unit 80 including various power supplies 36 and 56 and a number detection unit 70.
  • the fine particle detection element 20 is attached to a ring-shaped pedestal 16 fixed to an exhaust pipe 12 in a state of being inserted into a columnar support 14.
  • the fine particle detection element 20 is protected by a protective cover 18.
  • the protective cover 18 is provided with a hole (not shown), and the exhaust gas flowing through the exhaust pipe 12 passes through the gas flow path 24 provided at the lower end 22a of the fine particle detection element 20.
  • the fine particle detecting element 20 includes a charge generating unit 30, a collecting unit 50, 150, and guard electrodes 60, 160 in a housing 22.
  • the housing 22 is a long rectangular parallelepiped that is long in a direction intersecting the axial direction of the exhaust pipe 12 (here, a direction substantially orthogonal to each other).
  • the housing 22 is made of ceramic such as alumina.
  • the lower end 22a of the housing 22 is arranged inside the exhaust pipe 12, and the upper end 22b is arranged outside the exhaust pipe 12.
  • a gas flow path 24 is provided at the lower end 22a of the housing 22.
  • the axial direction of the gas flow path 24 coincides with the axial direction of the exhaust pipe 12.
  • the housing 22 includes a short portion 221 having a short length in the longitudinal direction and a long portion 222 having a long length in the longitudinal direction.
  • the short portion 221 and the long portion 222 are aligned.
  • the short portion 221 does not reach the long portion 222 and has a step, and the step surface 22s of the long portion 222 is exposed to the outside.
  • the gas flow path 24 has a rectangular gas exhaust port 24a provided on the front surface of the housing 22 and a rectangular gas exhaust port provided on the rear surface of the housing 22. It is a rectangular parallelepiped space that extends to the exit 24b.
  • the housing 22 includes a left wall 22c and a right wall 22d constituting the gas flow path 24, and also includes a partition wall 22e parallel to these walls 22c and 22d.
  • the partition wall 22e is a wall that reaches the gas discharge port 24b from a position slightly deeper than the gas introduction port 24a, and divides the gas flow path 24 into the first branch flow path 241 and the second branch flow path 242 substantially equally. are doing.
  • the housing 22 further includes a first support column 22f in the first branch flow path 241 and a second support column 22g in the second branch flow path 242.
  • the first and second columns 22f and 22g are plate members orthogonal to the partition wall 22e, and have the same length in the front-rear direction as the partition wall 22e.
  • the first support column 22f is provided so as to bridge the left wall 22c and the partition wall 22e.
  • the second support column 22g is a plate member, and is provided so as to bridge the right side wall 22d and the partition wall 22e.
  • the electric charge generation unit 30 generates an electric charge in the vicinity of the gas introduction port 24a in the gas flow path 24 (between the gas introduction port 24a and the front end surface 22e1 of the partition wall 22e). As described above, it is provided on the left wall 22c.
  • the charge generation unit 30 has a discharge electrode 32 and two ground electrodes 34 and 34.
  • the discharge electrode 32 is provided along the inner surface of the left wall 22c and has a plurality of fine protrusions around the rectangle.
  • the two ground electrodes 34 and 34 are rectangular electrodes and are embedded in the left wall 22c at intervals so as to be parallel to the discharge electrode 32.
  • a pulse voltage of several kV of the discharge power supply 36 (one of the accessory units 80) is applied between the discharge electrode 32 and the two ground electrodes 34 and 34.
  • an aerial discharge occurs due to the potential difference between the two electrodes.
  • the portion of the housing 22 between the discharge electrode 32 and the ground electrodes 34, 34 serves as a dielectric layer.
  • the discharge electrode 32 is connected to a discharge electrode terminal 33 (see FIG. 2) provided on the upper left side surface of the long portion 222 of the housing 22, and is connected to the discharge power supply 36 via the terminal 33.
  • the two ground electrodes 34, 34 are connected to a ground electrode terminal 35 (see FIG. 2) provided on the upper left surface of the long portion 222 of the housing 22, and the discharge power supply 36 is connected via the terminal 35. It is connected to the.
  • the fine particles 26 contained in the gas enter the gas flow path 24 from the gas introduction port 24a, and when passing through the charge generation unit 30, the electric charge 28 generated by the aerial discharge of the charge generation unit 30 Is added to form charged fine particles P, and then the particles move to either the first or second branch flow paths 241,242. Further, among the generated charges 28, those not added to the fine particles 26 move to either the first or second branch flow paths 241,242 with the charges 28 as surplus charges.
  • the collecting units 50 and 150 collect the charged fine particles P, and are provided downstream of the charge generating unit 30 as shown in FIG.
  • the collecting unit 50 has a counter electrode (electric field generating electrode) 52 and a collecting electrode 54.
  • the counter electrode 52 is provided on the left wall 22c and is exposed to the first branch flow path 241.
  • the collection electrode 54 is provided on the left surface of the partition wall 22e and is exposed to the first branch flow path 241.
  • the counter electrode 52 and the collection electrode 54 are arranged at positions facing each other.
  • a DC voltage V1 positive potential, for example, about 2 kV
  • V1 positive potential, for example, about 2 kV
  • the charged fine particles P flowing through the first branch flow path 241 are attracted to the collection electrode 54 by this relatively strong electric field and collected.
  • One end of the first support column 22f is arranged on the electrode surface of the collecting electrode 54, and the other end is arranged on the electrode surface of the counter electrode 52.
  • the first support column 22f is provided at a position half the height of the first branch flow path 241. Therefore, the first branch flow path 241 is equally divided by the first support column 22f.
  • the collecting unit 150 has a counter electrode (electric field generating electrode) 152 and a collecting electrode 154.
  • the counter electrode 152 is provided on the right wall 22d and is exposed to the second branch flow path 242.
  • the collection electrode 154 is provided on the right surface of the partition wall 22e and is exposed to the second branch flow path 242.
  • the counter electrode 152 and the collection electrode 154 are arranged at positions facing each other.
  • a DC voltage V1 is applied to the counter electrode 152 via the counter electrode terminal 153 (see FIG. 2) by the collection power supply 56.
  • a relatively strong electric field is generated between the counter electrode 152 of the collecting unit 150 and the collecting electrode 154 to move the charged fine particles P toward the collecting electrode 154.
  • the charged fine particles P flowing through the second branch flow path 242 are attracted to the collection electrode 154 by this relatively strong electric field and collected.
  • One end of the second support column 22g is arranged on the electrode surface of the collection electrode 154, and the other end is arranged on the electrode surface of the counter electrode 152.
  • the second support column 22g is provided at a position half the height of the second branch flow path 242. Therefore, the second branch flow path 242 is equally divided by the second support column 22g.
  • the guard electrode 60 is a leakage current absorbing electrode that absorbs the leakage current flowing from the counter electrode 52 to the collecting electrode 54 via the housing 22.
  • the guard electrode 60 includes a first guard electrode 62 and a second guard electrode 64.
  • the first guard electrode 62 is provided in a layered manner between the counter electrode 52 and the collection electrode 54.
  • the second guard electrode 64 is provided so as to surround the collection electrode 54.
  • the first and second guard electrodes 62 and 64 are electrically connected to each other and are connected to the ground.
  • the portion 64b exposed to the gas flow path 24 and located downstream of the charge generating portion 30 and upstream of the collecting portion 50 plays a role of removing excess charge.
  • the guard electrode 160 is a leakage current absorption electrode that absorbs the leakage current flowing from the counter electrode 152 to the collection electrode 154 via the housing 22.
  • the guard electrode 160 includes a first guard electrode 162 and a second guard electrode 164.
  • the first guard electrode 162 is provided in a layered manner between the counter electrode 152 and the collection electrode 154.
  • the second guard electrode 164 is provided so as to surround the collection electrode 154.
  • the first and second guard electrodes 162 and 164 are electrically connected to each other and are connected to the ground.
  • the portion 164b of the second guard electrode 164 which is exposed to the gas flow path 24 and is located downstream of the charge generating portion 30 and upstream of the collecting portion 150, serves to remove excess charge.
  • the number detection unit 70 is one of the accessory units 80, and includes an ammeter 72 and a number measuring device 74 as shown in FIG.
  • the ammeter 72 measures the current based on the charge 28 of the charged fine particles P collected on the collection electrodes 54 and 154.
  • the number measuring device 74 includes a microprocessor provided with a well-known CPU or the like, and calculates the number of fine particles 26 based on the current of the ammeter 72.
  • the fine particle detection element 20 is composed of eight sheets S1 to S8.
  • Each sheet S1 to S8 is made of the same material as the housing 22. For convenience of explanation, they are referred to as first sheet S1, second sheet S2, ... From left to right.
  • Ground electrodes 34, 34 are provided below the right surface of the first sheet S1.
  • the ground electrodes 34, 34 are connected to one lead wire 34a extending in the vertical direction.
  • the upper end of the lead wire 34a is located above the right surface of the first sheet S1 and is connected to a ground electrode terminal 35 provided above the left surface of the first sheet S1 via a through hole of the first sheet S1. ..
  • a discharge electrode 32 and a counter electrode 52 are provided below the right surface of the second sheet S2.
  • the discharge electrode 32 is connected to a lead wire 32a extending in the vertical direction.
  • the upper end of the lead wire 32a is located above the right surface of the second sheet S2, and is provided above the left surface of the first sheet S1 through the through holes of the second sheet S2 and the first sheet S1. It is connected to the.
  • the counter electrode 52 is connected to a lead wire 52a extending in the vertical direction.
  • the upper end of the lead wire 52a is located above the right surface of the second sheet S2, and is provided above the left surface of the first sheet S1 through the through holes of the second sheet S2 and the first sheet S1. It is connected to the.
  • a rectangular parallelepiped space E1 is provided below the third sheet S3.
  • the third sheet S3 includes an upper seat portion S3a arranged on the upper side of the space E1, a lower seat portion S3b arranged on the lower side of the space E1, and an intermediate seat portion S3c arranged in the center of the space E1. I have.
  • a rectangular parallelepiped space E2 is provided below the fourth sheet S4.
  • the fourth sheet S4 has an upper sheet portion S4a arranged on the upper side of the space E2, a lower sheet portion S4b arranged on the lower side of the space E2, and an intermediate sheet portion S3c arranged in the center of the space E2. I have.
  • the two intermediate sheet portions S3c and S4c form the first support column 22f.
  • the two spaces E1 and E2 mainly form the first divided flow path 241 of the gas flow path 24.
  • a first guard electrode 62 is provided on the entire left surface of the upper sheet portion S4a.
  • the fifth sheet S5 is a member that serves as a partition wall 22e, and is provided with a rectangular notch at the lower front end. The portion of the notch extending in the vertical direction becomes the front end surface 22e1 of the partition wall 22e.
  • a collection electrode 54 and a second guard electrode 64 are provided on the left surface of the fifth sheet S5.
  • a collection electrode 154 and a second guard electrode 164 are provided on the right surface of the fifth sheet S5.
  • the collection electrode 54 and the collection electrode 154 are arranged so as to be plane-symmetric with the fifth sheet S5 as the plane of symmetry, and the second guard electrode 64 and the second guard electrode 164 are planes with the fifth sheet S5 as the plane of symmetry. They are arranged symmetrically.
  • the collection electrode 154 on the right side of the fifth sheet S5 is connected to a lead wire 154a extending in the vertical direction.
  • the upper end of the lead wire 154a is a collecting electrode terminal 55, and is arranged on a stepped surface 22s (see FIG. 2) exposed to the outside on the right surface of the fifth sheet S5.
  • the collection electrode 54 on the left surface has a short lead wire 54a, and the lead wire 54a is connected to the lead wire 154a on the right surface via a through hole in the fifth sheet S5.
  • the second guard electrode 64 on the left surface of the fifth sheet S5 is formed in a substantially U shape so as to surround the collection electrode 54 with a clearance that can maintain electrical insulation with the collection electrode 54.
  • the lower portion 64a of the second guard electrode 64 extending in the front-rear direction is a quadrangle (lower side of the third sheet S3) surrounded by the vertical side and the front-rear side of the lower sheet portion S4b of the fourth sheet S4. It is provided so as to coincide with the quadrangle surrounded by the vertical side and the front-back side of the sheet portion S3b).
  • the lower portion 64a may be provided so as to be slightly larger than the quadrangle (for example, to protrude upward).
  • the lateral portions 64b and 64c extending in the vertical direction before and after the second guard electrode 64 extend from the lower portion 64a to the collection electrode 54 side after passing the upper portion of the collection electrode 54 at each of the front and rear portions of the collection electrode 54. It has a short and bent shape.
  • One side portion 64b is provided so as to be in contact with the vertical side (front end surface 22e1) forming the notch of the fifth sheet S5, and the other side portion 64c is in contact with the rear side of the fifth sheet S5. It is provided as follows. Since the second guard electrode 164 on the right surface of the fifth sheet S5 is formed symmetrically with the second guard electrode 64 and the fifth sheet S5 as symmetrical planes, the lower portion 164a and the side thereof are similar to the second guard electrode 64. Although the square portions 164b and 164c are provided, the description thereof will be omitted.
  • a guard electrode terminal 65 is provided above the right surface of the fifth sheet S5.
  • the guard electrode terminal 65 is arranged on the stepped surface 22s (see FIG. 2) exposed to the outside on the right surface of the fifth sheet S5.
  • the upper portion of the first guard electrode 62 of the fourth sheet S4 is connected to the guard electrode terminal 65 via the through holes of the fourth sheet S4 and the fifth sheet S5.
  • a rectangular parallelepiped space E3 is provided below the sixth sheet S6.
  • the sixth sheet S6 includes an upper seat portion S6a arranged on the upper side of the space E3, a lower seat portion S6b arranged on the lower side of the space E3, and an intermediate seat portion S6c arranged in the center of the space E3. I have.
  • a first guard electrode 162 is provided on the entire right surface of the upper sheet portion S6a. The first guard electrode 162 is connected to the second guard electrode 164 of the fifth sheet S5 via the through hole of the sixth sheet S6, and the second guard electrode 164 is connected to the second guard electrode 164 through the through hole of the fifth sheet S5.
  • both the first guard electrodes 62 and 64 and the second guard electrodes 162 and 164 are connected to the guard electrode terminal 65.
  • the guard electrode 60 including the first and second guard electrodes 62 and 64 leaks from the counter electrode 52 including the lead wire 52a to the collection electrode 54 including the lead wire 54a via the third and fourth sheets S3 and S4. Cut off the current. Further, the guard electrode 160 including the first and second guard electrodes 162 and 164 is transferred from the counter electrode 152 including the lead wire 152a to the collection electrode 154 including the lead wire 154a via the seventh and sixth sheets S7 and S6. Cut off the flowing leakage current.
  • the seventh sheet S7 includes an upper seat portion S7a arranged on the upper side of the space E4, a lower seat portion S7b arranged on the lower side of the space E4, and an intermediate seat portion S7c arranged in the center of the space E4. I have.
  • the lower portion 164a of the second guard electrode 164 is a quadrangle surrounded by the vertical side and the front-rear side of the lower sheet portion S6b of the sixth sheet S6 (lower sheet portion S7b of the seventh sheet S7). It is provided so as to coincide with the quadrangle surrounded by the vertical side and the front-back side of.
  • a counter electrode 152 is provided below the left surface of the eighth sheet S8.
  • the counter electrode 152 is connected to a lead wire 152a extending in the vertical direction.
  • the upper end of the lead wire 152a is located above the left surface of the eighth sheet S8 and is connected to the counter electrode terminal 153 provided above the right surface of the eighth sheet S8 via a through hole of the eighth sheet S8. ..
  • the first to fifth sheets S1 to S5 form the long portion 222 of the housing 22, and the sixth to eighth sheets S6 to S8 form the short portion 221.
  • the fine particle detection element 20 can be manufactured by using a plurality of ceramic green sheets. Specifically, for each of the plurality of ceramic green sheets, notches, through holes and grooves are provided as necessary, electrodes and wiring patterns are screen-printed, and then they are laminated and fired. The notches, through holes, and grooves may be filled with a material (for example, an organic material) that burns out during firing. In this way, the fine particle detection element 20 is obtained. Subsequently, the discharge electrode terminal 33 and the counter electrode terminals 53 and 153 of the fine particle detection element 20 are connected to the discharge power supply 36 and the collection power supply 56 of the accessory unit, respectively. Further, the ground electrode terminal 35 and the guard electrode terminal 65 are connected to the ground. Further, the collection electrode terminal 55 is connected to the number measuring device 74 via the ammeter 72. By doing so, the fine particle detector 10 can be manufactured.
  • a material for example, an organic material
  • the fine particles detection element 20 When measuring the fine particles 26 contained in the exhaust gas of an automobile, the fine particles detection element 20 is attached to the exhaust pipe 12 of the engine as described above (see FIG. 1). As shown in FIG. 4, the fine particles 26 contained in the exhaust gas introduced into the gas flow path 24 from the gas introduction port 24a are charged with a charge 28 (here, a positive charge) generated by the discharge of the charge generation unit 30. It becomes fine particles P. The charged fine particles P pass through the upstream portions of the collecting portions 50 and 150 of the guard electrodes 60 and 160 as they are, and reach the collecting portions 50 and 150.
  • a charge 28 here, a positive charge
  • the electric charge 28 not added to the fine particles 26 is attracted to the upstream portion of the collecting portions 50 and 150 of the guard electrodes 60 and 160 and discarded to the ground. As a result, the unnecessary electric charge 28 not added to the fine particles 26 hardly reaches the collecting portions 50 and 150.
  • the charged fine particles P that have reached the collection portions 50 and 150 are collected by the collection electrodes 54 and 154 by the collection electric field generated by the counter electrodes 52 and 152.
  • a current based on the charge 28 of the collected charged fine particles P flows through the collection electrodes 54 and 154.
  • a current based on the charge 28 of the charged fine particles P collected by the collection electrodes 54 and 154 flows through the ammeter 72. Then, the current is measured by the ammeter 72, and the number measuring device 74 calculates the number of fine particles 26 based on the current.
  • the number measuring device 74 integrates (accumulates) the current values over a predetermined period to obtain the integrated value (accumulated charge amount), divides the accumulated charge amount by the elementary charge, and obtains the total number of charges (collected charge number).
  • the number Nt of the fine particles 26 collected on the collection electrodes 54 and 154 is obtained by dividing the number of collected charges by the average value (average number of charges) of the number of charges added to one fine particle 26. (See equation (1) below).
  • the gas flow path 24 is partitioned into first and second branch flow paths 241,242 by a partition wall 22e. Since the collection electrode 54 is provided in the branch flow path 241 and the collection electrode 154 is provided in the branch flow path 242, the total area of the collection electrode becomes large and the charged fine particles P can be reliably collected. .. Further, the first support column 22f provided in the first branch flow path 241 is provided so as to bridge the partition wall 22e provided with the collecting electrode 54 and the left wall 22c provided with the counter electrode 52. There is.
  • the second support column 22g provided in the second branch flow path 242 is provided so as to bridge the partition wall 22e provided with the collecting electrode 154 and the right wall 22d provided with the counter electrode 152. Therefore, the walls of the gas flow path 24 (partition wall 22e, left wall 22c and right wall 22d) are reinforced by the first and second columns 22f and 22g. This makes it possible to prevent cracks from occurring in the wall of the gas flow path 24.
  • first support column 22f is arranged on the electrode surface of the collecting electrode 54, and the other end is arranged on the electrode surface of the counter electrode 52.
  • One end of the second support column 22g is arranged on the electrode surface of the collection electrode 154, and the other end is arranged on the electrode surface of the counter electrode 152. Therefore, the collection electrode 54 and the counter electrode 52 are not separated by the first support column 22f, and the collection electrode 154 and the counter electrode 152 are not separated by the second support column 22g. Therefore, the number of lead wires of the collection electrodes 54 and 154 and the number of lead wires of the counter electrodes 52 and 152 do not increase by providing the first and second columns 22f and 22g.
  • the compartment C separated by the first and second columns 22f, 22g and the partition wall 22e is the height Y of the compartment C with respect to the width X of the compartment C. It is preferable that the ratio Y / X (hereinafter referred to as aspect ratio) is formed so as to be 0.9 or more and 3.5 or less. In this way, the gas flowing through each compartment C tends to have a uniform flow due to the rectifying effect, so that the collection rate at the collection electrodes 54 and 154 tends to be stable.
  • FIG. 8 (a) to 8 (h) are explanatory views when one partition wall is provided in the gas flow path 24 and zero to seven columns are provided.
  • the aspect ratios (Y / X) of FIGS. 8A to 8H are 6.4.3.14, 2.05, 1.5, 1.17, 0.93, 0.8, 0, respectively. It was set to 68.
  • turbulence such as vortex generation was observed in FIG. 8 (a), and in FIGS. 8 (g) and 8 (h), the compartments were too fine to allow gas to enter.
  • FIGS. 8 (c) to 8 (f) the gas flowed in a state close to laminar flow and at an appropriate flow velocity.
  • the number of fine particles is determined by setting the collection target as the charged fine particles P, but the number of fine particles may be obtained by using the collection target as the surplus charge.
  • the side portions 64b and 164b of the second guard electrodes 64 and 164 are omitted, and the voltage applied by the collection power supply 56 to the counter electrodes 52 and 152 is set lower than the voltage V1.
  • the excess charge may be collected by the collection electrodes 54 and 154, and the charged fine particles P may be discharged from the gas discharge port 24b without being collected by the collection electrodes 54 and 154.
  • the total number of charges 28 generated by the charge generating unit 30 is measured, and then, when a gas containing fine particles 26 is passed through the gas flow path 24, a surplus is generated from the current flowing through the collection electrodes 54 and 154.
  • the number of charges is measured, and the number of fine particles is obtained by subtracting the number of surplus charges from the total number of charges 28. Even in this way, since the guard electrodes 60 and 160 completely or almost completely block the leakage current path, the detection accuracy of the fine particles can be improved.
  • the gas flow path 24 is partitioned into the first and second branch flow paths 241,242 by the partition wall 22e, but the partition wall 22e is provided as in the particle detection element 120 shown in FIGS. 9 and 10. It may not be.
  • the fine particle detection element 120 the sixth to eighth sheets S6 to S8 of the fine particle detection element 20 are omitted, and the second guard electrode 164 and the collection electrode provided on the right surface of the fifth sheet S5 are provided. Fine particle detection except that the lead wire 154a and the lead wire 154a are omitted and the lead wire 54a provided on the left surface of the fifth sheet S5 is extended to the upper part and connected to the collection electrode terminal 55 via the through hole of the fifth sheet S5.
  • the intermediate sheet portions S3c and S4c form the support column 22h of FIG. 9, and the spaces E1 and E2 form the gas flow path 24.
  • the support column 22h is provided so as to bridge the left wall 22c and the right wall 22d constituting the gas flow path 24.
  • One end of the support column 22h is arranged on the electrode surface of the collecting electrode 54, and the other end is arranged on the electrode surface of the counter electrode 52. This makes it possible to prevent cracks from occurring in the walls 22c and 22d of the gas flow path 24.
  • the number of lead wires of the collection electrode 54 and the number of lead wires of the counter electrode 52 are increased by providing the support column 22h. There is no. Further, the compartments of the gas flow path 24 separated by the columns 22h are formed so that the ratio (aspect ratio) of the height of the compartments to the width of the compartments is 0.3 or more and 1.5 or less. preferable. In this way, the gas flowing through each section tends to have a uniform flow due to the rectifying effect, so that the collection rate at the collection electrode 54 tends to be stable.
  • the numerical range of the aspect ratio was determined by examining the distribution of the gas flow velocity when the number of columns was changed, as in the above-described embodiment.
  • one partition wall 22e is provided in the gas flow path 24, but two or more partition walls may be provided.
  • the charge generation unit 30 is provided on the left wall 22c of the housing 22, but instead or in addition, a charge generation unit may be provided on the right wall 22d.
  • the counter electrodes 52 and 152 are exposed in the gas flow path 24, but the present invention is not limited to this, and the counter electrodes 52 and 152 may be embedded in the housing 22.
  • the present invention is not particularly limited to the exhaust pipe 12 of the engine, and any pipe through which a gas containing fine particles flows can be used. It may be such a tube.
  • the fine particle detecting element 20 detects the number of fine particles, but it may also detect the mass, surface area, or the like of the fine particles.
  • the mass of the fine particles can be obtained, for example, by multiplying the number of fine particles by the average mass of the fine particles, and the relationship between the accumulated charge amount and the mass of the collected fine particles is stored in the storage device as a map in advance. , It is also possible to obtain the mass of fine particles from the amount of accumulated charge using this map.
  • the surface area of the fine particles can also be determined by the same method as the mass of the fine particles.
  • the present invention can be used when detecting fine particles contained in a gas.

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Abstract

La présente invention concerne un élément de détection de microparticules (20) comprenant : un générateur de charge (30) qui ajoute, à des microparticules (26), une charge (28) générée par une décharge électrique dans un gaz afin de créer des microparticules fines chargées (P) ; un diviseur (22e) permettant de diviser un trajet d'écoulement de gaz en une pluralité de trajets d'écoulement de ramification ; des électrodes collectrices (54, 154) permettant de collecter les microparticules fines chargées (P) ; des électrodes opposées (52, 152) permettant de générer un champ électrique de collecte permettant de déplacer un matériau à collecter vers les électrodes collectrices (54, 154) ; et, dans chaque trajet d'écoulement de ramification, des dispositifs de soutien (22f, 22g) de part et d'autre desquels sont agencées une paroi sur laquelle les électrodes collectrices (54, 154) sont disposées et une paroi sur laquelle les électrodes opposées (52, 152) sont disposées.
PCT/JP2020/035078 2019-09-26 2020-09-16 Élément de détection de microparticules et détecteur de microparticules WO2021060105A1 (fr)

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JP2019175708 2019-09-26

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018163467A1 (fr) * 2017-03-10 2018-09-13 日本碍子株式会社 Élément de détection de microparticules et détecteur de microparticules
WO2018212156A1 (fr) * 2017-05-15 2018-11-22 日本碍子株式会社 Détecteur de comptage de particules fines
JP2019027853A (ja) * 2017-07-27 2019-02-21 株式会社デンソー 粒子状物質検出センサ
WO2019049566A1 (fr) * 2017-09-06 2019-03-14 日本碍子株式会社 Élément de détection de microparticules et détecteur de microparticules

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018163467A1 (fr) * 2017-03-10 2018-09-13 日本碍子株式会社 Élément de détection de microparticules et détecteur de microparticules
WO2018212156A1 (fr) * 2017-05-15 2018-11-22 日本碍子株式会社 Détecteur de comptage de particules fines
JP2019027853A (ja) * 2017-07-27 2019-02-21 株式会社デンソー 粒子状物質検出センサ
WO2019049566A1 (fr) * 2017-09-06 2019-03-14 日本碍子株式会社 Élément de détection de microparticules et détecteur de microparticules

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