WO2022093367A1

WO2022093367A1 - Collection device with collection electrode

Info

Publication number: WO2022093367A1
Application number: PCT/US2021/046618
Authority: WO
Inventors: Takashi Nakazawa; Takuya Ito; Yuji Aoshima
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-27
Filing date: 2021-08-19
Publication date: 2022-05-05
Also published as: JP2022070508A

Abstract

A collection device includes a passage to direct air in an airflow direction, a discharge electrode disposed in the passage, a counter electrode that is disposed in the passage to cause a discharge between the counter electrode and the discharge electrode to charge particles in the air, and to collect the particles charged, and a collection electrode that is disposed in the passage to collect the particles charged by the discharge electrode.

Description

COLLECTION DEVICE WITH COLLECTION ELECTRODE

BACKGROUND

[0001] An imaging system may include a collection device that collects fine particles inside a housing. Such a collection device includes an ion generator that generates ions to charge the particles, and an electret filter that collects the particles charged.

BRIEF DESCRIPTION OF DRAWINGS

[0002] FIG. 1 is a schematic diagram of an example imaging apparatus.

[0003] FIG. 2 is a cross-sectional view illustrating a collection device according to an example.

[0004] FIG. 3 is a perspective view of the example collection device, as viewed from a downstream side in an airflow direction.

[0005] FIG. 4 is a perspective view of the example collection device, as viewed from an upstream side in the airflow direction.

[0006] FIG. 5 is a cross-sectional view illustrating a collection device according to another example.

[0007] FIG. 6 is a cross-sectional view illustrating a collection device of another example.

[0008] FIG. 7 is a cross-sectional view illustrating a collection device of another example.

[0009] FIG. 8 is a partial enlarged view of a collection device according to yet another example, illustrating a positional relationship between a collection electrode and a discharge electrode when viewed in the airflow direction.

DETAILED DESCRIPTION

[0010] Some collection devices include an electret filter that is charged with a polarity opposite to a polarity of particles that are charged, to collect the particles by electrostatic attraction. When the static electricity of the electret filter weakens after some time has elapsed, for example, the particle collection rate decreases, and the filter may then be replaced. Other collection devices include a discharge electrode that applies a high voltage, and a counter electrode that faces the discharge electrode to collect particles that are charged. Since the collection device does not include an electret filter, there is no need to replace the filter. However, performance for collecting the particles may not be sufficient.

[0011] An example collection device may include a passage that directs air in an airflow direction, a discharge electrode disposed in the passage, a counter electrode that is disposed in the passage to cause a discharge between the counter electrode and the discharge electrode that charges particles in the air, and to collect the particles charged, and a collection electrode that is disposed in the passage to collect the particles charged by the discharge electrode.

[0012] Another example collection device may include a passage that directs air in an airflow direction, a discharge electrode disposed in the passage, a counter electrode that is disposed in the passage to cause a discharge between the counter electrode and the discharge electrode that charges particles in the air, and to collect the particles charged, and a collection electrode that is disposed downstream of the discharge electrode, in the airflow direction, and that forms a plurality of columnar cells extending substantially in the airflow direction.

[0013] In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. Hereinafter, a collection device according to various examples will be described with reference to the drawings. The collection device may be included in an imaging system or imaging device, according to some examples. The imaging system may be an imaging apparatus (or imaging device) such as a printer or may be a device used in the imaging apparatus or the like.

[0014] With reference to FIG. 1 , an example imaging apparatus 1 may form a color image by using four colors such as magenta, yellow, cyan, and black, which are represented by the characters "M", "Y", "C", "K", respectively, in the reference symbols. The example imaging apparatus 1 includes a conveying device 10 that conveys a recording medium, such as a paper (e.g., a sheet of paper) 3, image carriers 20M, 20Y, 20C, and 20K having respective surfaces (peripheral surfaces) that may form electrostatic latent images, developing devices 30M, 30Y, 30C, and 30K that develop the respective electrostatic latent images to form toner images, a transfer device 40 that transfers the toner images onto the paper 3, a fixing device 50 that fixes the toner images to the paper 3, an output device 60 that outputs the paper 3, and a control unit (or controller) 70.

[0015] The conveying device 10 conveys the paper 3 on which an image is to be formed, along a conveyance path 11. The papers 3 are stacked and contained in a cassette 12, and are picked up from the cassette 12 and conveyed by a paper feeding roller 13 to the conveyance path 11 .

[0016] The image carriers 20M, 20Y, 20C, and 20K may also be referred to as electrostatic latent image carriers, photoconductor drums, or the like. The image carriers 20M, 20Y, 20C, and 20K form electrostatic latent images to generate a magenta toner image, a yellow toner image, a cyan toner image and a black toner image, respectively. The image carriers 20M, 20Y, 20C, and 20K have similar configurations. Accordingly, the image carrier 20M will be described as a representative one of the image carriers 20M, 20Y, 20C, and 20K, unless otherwise described.

[0017] The developing device 30M, a charging roller 22M, an exposure unit 23, and a cleaning unit 24M are provided adjacent the image carrier 20M. Similarly to the image carrier 20M, the respective developing devices 30Y, 30C, and 30K, respective charging rollers, the exposure unit 23, and respective cleaning units are also provided adjacent the respective image carriers 20Y, 20C, and 20K.

[0018] The charging roller 22Mcharges the surface of the image carrier 20M to a predetermined potential. The charging roller 22M rotates to follow a rotation of the image carrier 20M. The exposure unit 23 exposes the surface of the image carrier 20M to light according to the image to be formed on the paper 3, after the surface has been charged by the charging roller 22M. Accordingly, the potential of a portion of the surface of the image carrier 20M that is exposed to the light by the exposure unit 23, is changed, so that an electrostatic latent image is formed. The cleaning unit 24M recovers a toner remaining on the image carrier 20M.

[0019] The developing device 30M develops an electrostatic latent image formed on the image carrier 20M, with a toner supplied from a toner tank 21 M that contains a magenta toner and a carrier, to form a magenta toner image based on the electrostatic latent image of the image carrier 20M. The developing device 30Y develops an electrostatic latent image formed on the image carrier 20Y, with a toner supplied from a toner tank 21 Y that contains a yellow toner and a carrier, to form a yellow toner image based on the electrostatic latent image of the image carrier 20Y. The developing device 30C develops an electrostatic latent image formed on the image carrier 20C, with a toner supplied from a toner tank 21 C that contains a cyan toner and a carrier, to form a cyan toner image based on the electrostatic latent image of the image carrier 20C. The developing device 30K develops an electrostatic latent image formed on the image carrier 20K with a toner supplied from a toner tank 21 K that contains a black toner and a carrier, to form a black toner image based on the electrostatic latent image of the image carrier 20K. The developing devices 30M, 30Y, 30C, and 30K have similar configurations. Accordingly, the developing device 30M will be described as a representative one among the developing devices 30M, 30Y, 30C, and 30K, unless otherwise described.

[0020] The developing device 30M includes a developing roller 31 M that carries the toner to the image carrier 20M. The developing device 30M uses a two-component developer containing a toner and a carrier as a developer. Namely, in the developing device 30M, the toner and the carrier are adjusted to achieve a targeted mixing ratio and are further mixed and stirred to disperse the toner, so as to adjust the developer to have an optimal charge amount. In the developing device 30M, the developer is carried on the developing roller 31 M. Then, when the developer is conveyed to a region facing the image carrier 20M by the rotation of the developing roller 31 M, the toner of the developer carried on the developing roller 31 M transfers to the electrostatic latent image formed on a peripheral surface of the image carrier 20M, so that the electrostatic latent image is developed, thereby forming the toner image. [0021] The transfer device 40 conveys respective the toner images, which have been formed by the developing devices 30M, 30Y, 30C, and 30K, and transfers the toner images onto the paper 3. The transfer device 40 includes a transfer belt 41 onto which the respective toner images are primarily transferred from the image carriers 20M, 20Y, 20C, and 20K in a layered manner so as to form a single composite toner image on the transfer belt 41 , suspension rollers 44, 45, 46, and 47 that support (suspend) the transfer belt 41 , primary transfer rollers 42M, 42Y, 42C, and 42K that are positioned to interpose the transfer belt 41 between the primary transfer rollers 42M, 42Y, 42C, and 42K and the image carriers 20M, 20Y, 20C, and 20K in order to primarily transfer the respective toner images from the image carriers 20M, 20Y, 20C, and 20K onto the transfer belt 41 , and a secondary transfer roller 43 that is positioned to interpose the transfer belt 41 between the secondary transfer roller 43 and the suspension roller 47 in order to secondarily transfer the toner images, as the composite toner image, from the transfer belt 41 onto the paper 3.

[0022] The transfer belt 41 is an endless belt which is rotated by the suspension rollers 44, 45, 46, and 47. Each of the suspension rollers 44, 45, 46, and 47 is a roller rotatable around an axis thereof. The suspension roller 47 is a drive roller that rotates around its axis, and the suspension rollers 44, 45, and 46 are driven rollers that are driven to rotate by the rotation of the suspension roller 47. The primary transfer rollers 42M, 42Y, 42C, and 42K are pressed against the image carriers 20M, 20Y, 20C, and 20K, respectively, from an inner peripheral side of the transfer belt 41 . The secondary transfer roller 43 is disposed parallel to the suspension roller 47 with the transfer belt 41 interposed between the secondary transfer roller 43 and the suspension roller 47, and pressed against the suspension roller 47 from an outer peripheral side of the transfer belt 41. Accordingly, a transfer nip region 14 where the toner images are transferred from the transfer belt 41 onto the paper 3, is formed between the secondary transfer roller 43 and the transfer belt 41 .

[0023] The fixing device 50 is positioned to convey the paper 3 on which the composite toner image has been transferred, to pass through a fixing nip region where the paper 3 is subjected to heat and pressure, so as to attach and fix the composite toner image to the paper 3. The fixing device 50 includes a heating roller 52 that heats the paper 3, and a pressure roller 54 that is pressed against the heating roller 52 to drive the heating roller 52 to rotate. The heating roller 52 and the pressure roller 54 are formed in a cylindrical shape, and the heating roller 52 includes a heat source such as a halogen lamp thereinside. The fixing nip region which is a contact region is provided between the heating roller 52 and the pressure roller 54, and when the paper 3 passes through the fixing nip region, the composite toner image is melted to be fixed to the paper 3.

[0024] The output device 60 includes output rollers 62 and 64 that output the paper 3, to which the composite toner image has been fixed, to the outside of the apparatus.

[0025] The control unit (or controller) 70 may be an electronic control unit including a central processing unit (CPU), a read-only memory (ROM), a randomaccess memory (RAM), and the like. In the control unit 70, a program which is stored in the ROM in the form of data and instructions, may be loaded onto the RAM to be executed by the CPU to execute various control operations. The control unit 70 may be formed of a plurality of electronic control units (electronic control devices) or may be formed of a single electronic control unit (single electronic control device). The control unit 70 performs various control operation in the imaging apparatus 1.

[0026] The example imaging apparatus 1 includes a collection device 100 in a housing space 4 defined by a housing 2. The collection device 100 collects particles floating in the housing space 4. The particles collected by the collection device 100 may be, for example, ultrafine particles (UFP), having a particle size of approximately 5 nm to 300 nm. The particles may be generated from the toner heated by the fixing device 50, the paper, the components of the fixing device 50, and/or other peripheral components or devices, depending on examples. The collection device 100 is disposed adjacent to the fixing device 50 at a position where the amount of generation of the particles is relatively large, so that the collection device 100 can more effectively collect the particles.

[0027] FIG. 2 schematically illustrates a cross section of the example collection device 100 when taken along an airflow direction 103. In FIG. 2, the airflow direction 103 is illustrated by a white arrow. The airflow direction is also illustrated in other drawings by a white arrow. The example collection device 100 includes a passage 110, a discharge electrode 120, a counter electrode 130, and a collection electrode 140. The passage 110 is a space in the housing space 4 in which air is directed in the airflow direction 103. Particles 105A contained in the air can move along the airflow direction 103. A frame 113 having a cylindrical shape forms the passage 110, and includes an upstream end portion 110a and a downstream end portion 110b that are open in the airflow direction 103. The the frame 113 that defines the passage 110, may be made of, for example, resin having insulating properties. The frame 113 may have any suitable shape that forms a space through which air flows. For example, the frame 113 may have a shape to position the discharge electrode 120, the counter electrode 130, and the collection electrode 140 within the frame 113. The frame 113 of the illustrated example has a rectangular frame shape having a pair of long sides and a pair of short sides when viewed in the airflow direction 103. In the following description of the collection device, a direction in which the short sides of the frame 113 extend may be described as a short-side direction, and a direction in which the long sides extend may be described as a long-side direction.

[0028] FIGS. 3 and 4 illustrate the example collection device as viewed from a downstream side and from an upstream side, respectively, in the airflow direction. In FIGS. 3 and 4, the frame 113 forming the passage 110 is omitted for simplification. The discharge electrode 120 and the counter electrode 130 are disposed in the passage 110 to charge the particles 105A that are contained in air in the passage 110, so that the particles 105A become charged particles 105B (cf. FIG. 2). The discharge electrode 120 is connected to a power source that applies a high voltage to the discharge electrode 120. In the illustrated example, a high positive voltage is applied to the discharge electrode 120, by the power source.

[0029] The example discharge electrode 120 includes a proximal end portion 121 extending in a direction intersecting (for example, orthogonal to) the airflow direction 103, and a plurality of needle electrodes 122 protruding from the proximal end portion 121. The proximal end portion 121 of the illustrated example is positioned at the center in the short-side direction of the frame 113 and extends to opposite ends in the long-side direction of the frame 113 as viewed from the airflow direction 103. According to examples, the plurality of needle electrodes 122 are arranged in an extending direction of the proximal end portion 121 (e.g., the long-side direction), and are spaced apart by equal space intervals. In some examples, the needle electrode 122 is formed to protrude in a needle shape or a saw blade shape. The plurality of needle electrodes 122 are disposed such that distal ends thereof are pointed upstream in the airflow direction 103.

[0030] The counter electrode 130 causes a discharge between the counter electrode 130 and the discharge electrode 120 to charge the particles 105A in the air and to collect the charged particles 105B. The example counter electrode 130 is disposed at least in a region of the passage 110, and overlap the discharge electrode 120 disposed within the region, in the airflow direction 103. The example collection device 100 includes a pair of the counter electrodes 130. The discharge electrode 120 is disposed between the pair of counter electrodes 130, and the pair of counter electrodes 130 are disposed parallel to each other in a state where the pair of counter electrodes 130 are spaced apart from each other in the short-side direction. In some examples, the counter electrode 130 has a plate shape extending along the airflow direction 103. In addition, the counter electrode 130 of the illustrated example extends to opposite ends in the long-side direction of the frame 113 as viewed from the airflow direction 103. The pair of counter electrodes 130 are grounded. In some examples, the discharge electrode 120 and the counter electrode 130 may be made of stainless steel.

[0031] The collection electrode 140 is disposed in the passage 110, and collects the charged particles 105B charged by the discharge electrode 120. The collection electrode 140 is disposed downstream of the discharge electrode 120, in the airflow direction 103. With reference to FIG. 2, in a cross-sectional view taken along the airflow direction 103, a plurality of the collection electrodes 140 are provided, and are spaced apart from each other by a distance that is less than a distance between the pair of counter electrodes 130. Accordingly, the collection electrode 140 can form an area (e.g., surface area) per unit length along the passage 110, in the airflow direction 103, that is greater than an area (e.g., surface area) per unit length of the counter electrode 130 in the airflow direction 103. The areas of the collection electrode 140 and the counter electrode 130 may refer to the respective areas of the surfaces of the collection electrode 140 and the counter electrode 130, that face the passage 110.

[0032] With reference to FIGS. 3 and 4, the example collection electrodes 140 includes a plurality of columnar cells 143 that are electrically connected to each other. The plurality of columnar cells 143 extending substantially in the airflow direction 103, for example such that an axial direction defined by each one of the columnar cells 143 extends substantially along the airflow direction 103. For example, when the columnar cell 143 is viewed from the upstream side in the airflow direction 103, in a case where a downstream side of the columnar cell 143 can be observed through an internal space of the columnar cell 143, the axial direction of the columnar cell 143 can be considered to be along the airflow direction 103.

[0033] The plurality of columnar cells 143 are disposed between the pair of counter electrodes 130 when viewed in the airflow direction 103 (e.g., in a transverse cross-section along a plane that is orthogonal to the airflow direction 103). The counter electrode 130 and the collection electrode 140 may be integrally formed. In a case where the counter electrode 130 and the collection electrode 140 are integrally formed, when the counter electrode 130 is grounded, the collection electrode 140 is also grounded. The example collection electrode 140 includes a pair of plate-shaped portions 141 that form the pair of counter electrodes 130 and that extend downstream in the airflow direction 103, and the plurality of columnar cells 143 that are located between the pair of plate-shaped portions 141 and that are physically and electrically connected to the pair of plateshaped portions 141 . The plurality of columnar cells 143 have a hexagonal shape when viewed in the airflow direction 103 (e.g., in a transverse cross-section), and are arranged along the short-side direction and along the long-side direction of the frame 113. Namely, the plurality of columnar cells 143 form a honeycomb structure.

[0034] With reference to FIG. 2, according to examples, a first region 130R of the passage 110 is surrounded by wall surfaces forming the passage 110 and includes the counter electrodes 130. In addition, a second region OR of the passage 110 is surrounded by wall surfaces forming the passage 110, and includes the collection electrodes 140. In this case, the second region OR is a region of the passage 110 that is defined by one of the columnar cells M3. Accordingly, a transverse cross-sectional area of the second region MOR, that is orthogonal to the airflow direction 103, is less than a transverse cross-sectional area of the first region 130R, that is orthogonal to the airflow direction 103. In addition, the electrodes face each other inside each of the columnar cells M3. A shortest distance MOD between the electrodes facing each other inside the columnar cell M3 is less than a shortest distance 130D between the discharge electrode 120 and the counter electrode 130.

[0035] In the example collection device 100, an insulator 129 is disposed between the discharge electrode 120 and the collection electrodes 140 in the airflow direction 103. The insulator 129 may be made of a resin material such as polycarbonate/acrylonitrile butadiene styrene (PC/ABS) having electrical insulating properties. According to examples, similar to the discharge electrode 120, the insulator 129 has a substantially plate shape extending along the long- side direction intersecting the airflow direction 103. The insulator 129 is disposed between the proximal end portion 121 of the discharge electrode 120 and an upstream end portion of the columnar cell 143, in the axial direction. The example insulator 129 is located adjacent to the discharge electrode 120 and the columnar cells 143.

[0036] The example insulator 129 has a groove 129a that extends along the extending direction of the proximal end portion 121 of the discharge electrode 120. In addition, the groove 129a is open upstream in the airflow direction 103, so as to position the proximal end portion 121 of the discharge electrode 120 in the groove 129a. Namely, the proximal end portion 121 may be disposed within the groove, so as to be interposed between side walls of the groove 129a. According to example, the insulator 129 may be integrally formed with the frame 113. The insulator 129 insulates between the collection electrodes 140 (columnar cells 143) and the proximal end portion 121. The lower limit of a thickness 129d of the insulator 129 in the airflow direction 103 is determined according to a voltage applied to the discharge electrode 120, and may be 3 mm or more, according to examples. The thickness 129d corresponds to a thickness excluding the portion forming the groove 129a, and is defined by a distance between the proximal end portion 121 of the discharge electrode 120 and the upstream end portion of the columnar cell 143.

[0037] In the example collection device 100, when a voltage applied to the discharge electrode 120 is less than a predetermined value, no current flows between the discharge electrode 120 and the pair of counter electrodes 130. However, when a voltage applied to the discharge electrode 120 corresponds to the predetermined value or more, a discharge phenomenon occurs due to an electric field 106 formed between the discharge electrode 120 and the pair of counter electrodes 130, so that current flows between the discharge electrode 120 and the pair of counter electrodes 130. The current causes the plurality of needle electrodes 122 to release ions. The greater a voltage applied to the discharge electrode 120 is, the greater the amount of current (amount of energization) flowing between the discharge electrode 120 and the pair of counter electrodes 130 is, so that the amount (or number) of ions released from the plurality of needle electrodes 122 is increased. In FIG. 2, the electric field 106 is schematically represented in FIG. 2 by a broken line. The electric field 106 is also formed between the discharge electrode 120 and the collection electrodes 140.

[0038] The columnar cells 143 are positioned so as to not enter the region of the electric field 106, which is schematically represented in FIG. 2 by a circle drawn in a broken line, centered around a distal end 123 of the discharge electrode 120 and having a radius corresponding to the shortest distance 130D from the distal end 123 to the counter electrode 130. Namely, a shortest distance 142D from the distal end 123 of the discharge electrode 120 to the columnar cell 143 is greater than the shortest distance 130D from the distal end 123 of the discharge electrode 120 to the counter electrode 130. Consequently, a discharge is more likely to be generated between the distal end 123 of the discharge electrode 120 and the counter electrode 130, than between the distal end 123 of the discharge electrode 120 and the columnar cell 143. Accordingly, ions are more likely to be released upstream from the needle electrodes 122, in the airflow direction 103.

[0039] When ions are released from the plurality of needle electrodes 122, the particles 105A in the air are charged to form the charged particles 105B. In the illustrated example, the charged particles 105B are positively charged with the ions released upstream from the needle electrodes 122. The charged particles 105B are carried by the air, to move downstream in the airflow direction 103. The charged particles 105B moving downstream are attracted to the collection electrodes 140 due to application of an electric field, so as to be collected by the collection electrodes 140. The charged particles 105B collected are adsorbed to the collection electrodes 140 by electrostatic attraction.

[0040] A portion of the charged particles 105B can be also collected by the counter electrodes 130 due to application of the electric field 106 generated between the discharge electrode 120 and the counter electrodes 130. Accordingly, the boundary between the collection electrode 140 and the counter electrode 130 may be defined by features other than whether or not the charged particles 105B are collected. In some examples, among electrodes forming an electric field between the electrodes and the discharge electrode 120, electrodes having the shortest space distance to the distal end 123 may be defined as the counter electrodes 130, and electrodes which are other than the counter electrodes 130 and collect the charged particles 105B may be defined as the collection electrodes 140. In this case, electrodes which are located downstream of the region 106 indicated by the circle having a radius corresponding to the shortest distance 130D between the distal end 123 and the counter electrode 130, may be defined as the collection electrodes 140. In other examples, electrodes which are positioned to overlap at least a portion of the discharge electrode 120 in the airflow direction 103 and which are positioned to have the shortest distance with the distal end 123 may be defined as the counter electrodes 130, while electrodes which are located downstream of the counter electrodes 130 may be defined as the collection electrodes 140. In that case, electrodes which overlap the position of the distal end 123 of the discharge electrode 120 in the airflow direction may be defined as the counter electrodes. In other examples, electrodes which are located upstream from the position of the distal end 123 of the discharge electrode 120 in the airflow direction may be defined as the counter electrodes. In other examples, electrodes which are located upstream from the position of the proximal end portion 121 of the discharge electrode 120 in the airflow direction may be defined as the counter electrodes. In some examples, when electrodes which are located to overlap the discharge electrode 120 in the airflow direction 103 are not provided, electrodes having the shortest space distance to the distal end 123 are considered to form the counter electrodes. In some examples, when the counter electrode and the collection electrode are integrally formed, portions of electrodes having the shortest space distance to the distal end 123 may be considered to form counter electrodes.

[0041] As described above, the example collection device 100 illustrated in FIGS. 2 to 4 includes the passage 110 that directs air in the airflow direction 103, the discharge electrode 120 disposed in the passage 110, the counter electrodes 130 that are disposed in the passage 110 to cause a discharge between the counter electrodes 130 and the discharge electrode 120 that charges the particles 105A in the air, and to collect the charged particles 105B, and the collection electrodes 140 that are disposed in the passage 110 to collect the charged particles 105B charged by the discharge electrode 120.

[0042] In the collection device 100 described above, the particles 105A in the air are charged by the discharge electrode 120 and the counter electrodes 130, and the charged particles 105B are collected by the counter electrodes 130 and the collection electrodes 140, so as to improve a performance for collecting the charged particles 105B, namely in comparison to a collection device including the discharge electrode and the counter electrode, without any collection electrode 140.

[0043] In addition, the collection device 100 includes the passage 110 that directs air in the airflow direction 103, the discharge electrode 120 disposed in the passage 110, the counter electrodes 130 that are disposed in the passage 110 to cause a discharge between the counter electrodes 130 and the discharge electrode 120 that charges the particles 105A in the air, and to collect the charged particles 105B, and the collection electrodes 140 that are disposed downstream of the discharge electrode 120 in the airflow direction 103 to form the plurality of columnar cells 143 extending substantially in the airflow direction 103.

[0044] In this configuration, the collection electrode 140 has an area per unit length larger than the area per unit length of the counter electrode 130 in the airflow direction in the passage. Namely, the area of the collection electrode 140 which collects the charged particles 105B can be increased, so as to improve the performance for collecting the charged particles 105B.

[0045] In the example collection device, the counter electrode 130 and the collection electrode 140 are integrally formed. Accordingly, either one of the counter electrode 130 and the collection electrode 140, may be grounded, so as to ground both of the counter electrode 130 and the collection electrode 140. In addition, the number of components is reduced, so that the assembly cost can be reduced.

[0046] In the example collection device, when viewed in the airflow direction 103, the first region 130R surrounded by the wall surfaces and including the counter electrodes 130, and the second region OR surrounded by the wall surfaces and including the collection electrodes 140 are formed in the passage 110, and the transverse cross-sectional area of the second region OR, that is orthogonal to the airflow direction 103, is less than the transverse cross-sectional area of the first region 130R, that is orthogonal to the airflow direction 103. Accordingly, the charged particle 105B passing between the collection electrodes 140 are relatively close to the collection electrodes 140, so that the charged particles 105B are more easily collected by the collection electrodes 140.

[0047] The example collection device includes the collection electrodes 140 facing each other, in which the shortest distance MOD between the collection electrodes 140 facing each other is less than the shortest distance 130D between the discharge electrode 120 and the counter electrode 130, in the cross section illustrated in FIG. 2. Accordingly, the charged particle 105B passing between the collection electrodes 140 are relatively close to the collection electrodes 140, so that the charged particles 105B are more easily collected by the collection electrodes 140.

[0048] The example discharge electrode 120 includes the plurality of needle electrodes 122 that are pointed upstream in the airflow direction 103. Accordingly, ions are released upstream in the airflow direction 103, from the needle electrodes 122, so as to charge the particles 105A located upstream in the airflow direction 103. In this case, the distance by which the charged particles 105B travel in the passage 110 is increased, thereby increasing the duration for which the electric field is applied to the charged particles 105B, so that the charged particles 105B can be more easily collected by the collection electrodes 140.

[0049] The example collection device includes the pair of counter electrodes 130 which extend along the airflow direction 103 and are spaced apart from each other in a cross-sectional view along the airflow direction 103 and the plurality of collection electrodes 140 which are spaced apart from each other by a distance that is less than the distance between the pair of counter electrodes 130. Accordingly, the distance between the charged particle 105B passing between the collection electrodes 140 and the collection electrodes 140 is reduced, so that the charged particles 105B are more easily collected by the collection electrodes 140.

[0050] The example collection electrodes 140 are grounded. For example, when a voltage having a polarity opposite to that of a voltage applied to the discharge electrode 120 is applied to the collection electrodes 140, the collection electrodes 140 can more easily attract the charged particles 105B. However, in this case, a power source is to separately apply a voltage to the collection electrodes 140. In addition, the distances between the discharge electrode 120 and the collection electrodes 140 are to be increased to prevent a current from flowing between the discharge electrode 120 and the collection electrodes 140. Meanwhile, when the collection electrodes 140 are grounded, the distance between the collection electrode 140 and the discharge electrode 120 can be reduced, to form a strong electric field between the discharge electrode 120 and the collection electrodes 140, so that the charged particles 105B are more easily collected by the collection electrodes 140.

[0051] Further, in the example collection device, the insulator 129 is disposed between the discharge electrode 120 and the collection electrodes 140 in the airflow direction 103, in order to provide electrical insulation between the discharge electrode 120 and the collection electrodes 140, without increasing the distance from the proximal end portion 121 of the discharge electrode 120 to the collection electrodes 140. Accordingly, the insulator 129 is disposed, so that the distances between the discharge electrode 120 and the collection electrodes 140 can be reduced.

[0052] According to examples, each of the plurality of columnar cells 143 has a hexagonal shape when viewed in the airflow direction 103, and in some examples, the collection electrodes 140 can be formed in a honeycomb structure. In this case, the area per unit length of the collection electrode 140 in the airflow direction 103 can be easily increased without disrupting the flow of air. In addition, the strength of the collection electrodes 140 can be improved. Further, the collection electrodes 140 can be manufactured at a lower cost.

[0053] The example collection device is provided with the pair of counter electrodes 130, and the plurality of columnar cells 143 are disposed between the pair of counter electrodes 130 when viewed in the airflow direction 103. Accordingly, the charged particle 105B passing between the collection electrodes 140 are close to the collection electrodes 140, so that the charged particles 105B are more easily collected by the collection electrodes 140. According to examples, the number of the plurality of columnar cells 143 may be increased, so that a distance between the charged particle 105B and the collection electrodes 140 may be further reduced.

[0054] Although an example of the collection device has been described above, the collection device may be suitably modified.

[0055] FIG. 5 illustrates a collection device according to another example. FIG. 5 schematically illustrates a cross section of an example collection device 200 when taken along the airflow direction 103. The collection device 200 includes a discharge electrode 120, a counter electrode 130, and a collection electrode 140 that are similar to the corresponding features described with respect to the example collection device 100. A passage 210 of the collection device 200 can be formed by a frame 213 having a cylindrical shape and having an upstream end portion 210a and a downstream end portion 210b in the airflow direction 103, that are open. The passage 210 can be defined by the frame 213 which may be made of, for example, resin having insulating properties. According to examples, the position of the upstream end portion 210a may be aligned with an end portion of the counter electrode 130 in the airflow direction. The position of the downstream end portion 210b is located downstream of the position of the collection electrodes 140 in the airflow direction. An airflow generation device 220 is disposed in the downstream end portion 210b of the passage 210. The airflow generation device 220 may be a fan that generates an airflow from the downstream end portion 210b toward the outside of the passage 210 to generate an airflow in the airflow direction 103 in the passage 210. In such a case, the airflow generation device 220 is disposed on a downstream side of the collection device 200, so that an airflow along the airflow direction 103 can be generated without causing disturbance to (or interference with) an airflow upstream of the collection device 200.

[0056] FIG. 6 illustrates a collection device according to yet another example. FIG. 6 schematically illustrates a cross section of an example collection device 300 when taken along the airflow direction 103. The collection device 300 includes a passage 210, a discharge electrode 120, a counter electrode 130, a collection electrode 140, and a airflow generation device 220. In the collection device 300, a plurality of the discharge electrodes 120 are provided, and a plurality of the counter electrodes 130 are disposed to correspond to the plurality of discharge electrodes 120. In the illustrated cross-sectional view, two sets are provided, in which each of the two sets includes a discharge electrode 120 disposed between a pair of the counter electrodes 130 in an overlapping manner so as to face each other. In FIG. 6, the direction in which the pair of counter electrodes 130 face each other is illustrated as an upward and downward direction. Given a set including a pair of the counter electrodes 130 and one of the discharge electrodes 120 to form a charging device, a first charging device 301 A and a second charging device 301 B that is adjacent, share a counter electrode 130A located therebetween. When a plurality of the charging devices 301 A and 301 B overlap each other, the cross-sectional area of the passage 210 may be increased, so as to improve a performance for collecting particles.

[0057] FIG. 7 illustrates a collection device according to yet another example. FIG. 7 schematically illustrates a cross section of an example collection device 400 when taken along the airflow direction 103. The example collection device 400 includes the passage 210, the discharge electrode 120, the counter electrode 130, the collection electrode 140, and the airflow generation device 220. The collection device 400 includes a plurality of charging devices 401 A and 401 B similar to the charging devices 301 A and 301 B of the example collection device 300 illustrated in FIG. 6. Each of the charging devices 401 A and 401 B includes a plurality of adjustment plates 410 that adjust the direction of the particles 105A and 105B moving along the airflow direction 103. The adjustment plate (or adjustment plate arrangement) 410 includes first adjustment plates 410A and 410B and second adjustment plates 411 A and 411 B that extend in the passage 210 to direct the airflow direction 103.

[0058] The first adjustment plates 410A and 410B are located upstream of the distal end 123 of the discharge electrode 120. In the illustrated example, an airflow upstream of the distal end 123 of the discharge electrode 120 is adjusted by the first adjustment plates 410A and 410B. The first adjustment plate 410A and the first adjustment plate 410B are disposed on opposite sides of the discharge electrode 120, in a direction in which a pair of the counter electrodes 130 face each other. The first adjustment plates 410A and 410B have, for example, a curved plate shape. The first adjustment plate 410A and the first adjustment plate 410B have convexly curved surfaces that face each other. In addition, the first adjustment plates 410A and 410B are disposed closer to each other toward the downstream direction of the passage 210 (e.g., curved to slant toward the distal end of the discharge electrode 120 in the airflow direction 103). Accordingly, each of the first adjustment plates 410A and 410B is disposed in a slanted position to extend downstream in the air flow direction and toward the discharge electrode in a direction orthogonal to the airflow direction.

[0059] The second adjustment plates 411 A and 411 B are located downstream of the distal end 123 of the discharge electrode 120, so as to adjust an airflow downstream of the distal end 123 of the discharge electrode 120. The second adjustment plate 411 A and the second adjustment plate 411 B are disposed on opposite sides of the discharge electrode 120, in the direction in which the pair of counter electrodes 130 face each other. The second adjustment plates 411 A and 411 B have, for example, a curved plate shape. The second adjustment plate 411 A and the second adjustment plate 411 B have convexly curved surfaces that face each other. In addition, the second adjustment plates 411 A and 411 B are spaced farther apart from to each other toward the downstream direction of the passage 210 (e.g., curved to slant downstream from the position of the discharge electrode 120 in a direction away from the discharge electrode 120). Accordingly, each of the second adjustment plates 411 A and 411 B is disposed in a slanted position to extend downstream in the air flow direction and away from the discharge electrode in a direction orthogonal to the airflow direction.

[0060] The adjustment plate 410 is disposed outside of the region of the electric field 106 that is defined by a circle having a radius corresponding to the shortest distance 130D from the distal end 123 of the discharge electrode 120 to the counter electrode 130 in a cross-sectional view taken along the airflow direction. In some examples, the first adjustment plates 410A and 410B may extend along respective circular arcs along which the second adjustment plates 411 A and 411 B respectively extend. For example, imaginary lines drawn when the first adjustment plates 410A and 410B extend downstream may coincide with imaginary lines drawn when the second adjustment plates 411 A and 411 B extend upstream. Although the illustrated example includes the adjustment plates that are curved, the shape of the adjustment plate(s) may be modified so as to suitably adjust the direction of an airflow. For example, the adjustment plate having a flat plate shape may be disposed in a slanted position to slant with respect to the airflow direction.

[0061] The adjustment plate 410 is disposed to direct the particles moving in the airflow direction 103 to move toward the distal end 123 of the discharge electrode 120, so as to more efficiently charge the particles. . In addition, adjustment plate 410 is disposed to promote an even diffusion of the charged particles away from the distal end 123 downstream of the discharge electrode 120, so that the charged particles can be more uniformly collected by the collection electrodes 140. [0062] FIG. 8 is a view illustrating another example of a positional relationship between a collection electrode 140 and a needle electrode 122, in another example collection device, when viewed in the airflow direction. With reference to FIG. 8, a plurality of the needle electrodes 122 may be positioned to correspond to a plurality of the columnar cells 143 forming a plurality of the collection electrodes 140. When viewed in the airflow direction, the needle electrode 122 may be disposed at a center of the columnar cell 143 according to some examples, or may be disposed in a position deviated from the center of the columnar cell 143 in other examples.

[0063] In addition, although an example where the columnar cell 143 forming the collection electrode has a hexagonal shape when viewed in the airflow direction has been illustrated, the columnar cell may have any suitable shape. The columnar cell, when viewed in the airflow direction, may have a polygonal shape having five vertices or less such as a triangular shape or a quadrangular shape, in some examples, or may have a polygonal shape having seven vertices or more, in other examples. In addition, the columnar cell may have a circular shape when viewed in the airflow direction. In addition, although the collection electrode illustrated includes the plurality of columnar cells 143, so that the area per unit length in the airflow direction is increased, the collection electrode may have a different configuration in other examples. For example, a plurality of electrodes that have a plate shape, may be disposed parallel to each other and spaced apart from each other.

[0064] In addition, although an example in which the counter electrode 130 and the plate-shaped portion 141 of the collection electrode 140 are integrally formed has been illustrated, the counter electrode 130 and the plate-shaped portion 141 of the collection electrode 140 may be separate members in some examples. When the counter electrode 130 and the plate-shaped portion 141 are formed as separate members, the counter electrode 130 and the plate-shaped portion 141 of the collection electrode 140 each may be grounded. In addition, when the counter electrode 130 and the plate-shaped portion 141 are formed as separate members, the counter electrode 130 may be selectively grounded. In this case, a voltage having a polarity opposite to that of a voltage applied to the discharge electrode 120 may be applied to the plate-shaped portion 141 , namely, the collection electrode 140.

[0065] In addition, the adjustment plate 410 provided in the collection device 400 may be applied to any of the collection devices 100, 200, and 300.

[0066] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.

Claims

22 CLAIMS

1 . A collection device comprising: a passage to direct air in an airflow direction; a discharge electrode disposed in the passage; a counter electrode that is disposed in the passage to cause a discharge between the counter electrode and the discharge electrode to charge particles in the air, and to collect the particles charged; and a collection electrode that is disposed in the passage to collect the particles charged by the discharge electrode.

2. The collection device according to claim 1 , wherein the collection electrode forms a surface facing the passage, that has an area per unit length in the airflow direction, that is greater than an area per unit length in the airflow direction, of a surface of the counter electrode that faces the passage.

3. The collection device according to claim 1 , wherein the passage includes a first region surrounded by wall surfaces and including the counter electrode, and a second region surrounded by wall surfaces and including the collection electrode, and wherein a transverse cross-sectional area of the second region, that is orthogonal to the airflow direction, is less than a transverse cross-sectional area of the first region, that is orthogonal to the airflow direction.

4. The collection device according to claim 1 , wherein the counter electrode and the collection electrode are integrally formed.

5. The collection device according to claim 1 , wherein the discharge electrode includes a plurality of needle electrodes, and each of the plurality of needle electrodes is disposed to point upstream in the airflow direction.

6. The collection device according to claim 1 , wherein an adjustment plate is disposed upstream of the discharge electrode in the airflow direction and in a slanted position to extend downstream in the air flow direction and toward the discharge electrode in a direction orthogonal to the airflow direction.

7. The collection device according to claim 1 , wherein an adjustment plate is disposed downstream of the discharge electrode in the airflow direction and in a slanted position to extend downstream in the air flow direction and away from the discharge electrode in a direction orthogonal to the airflow direction.

8. The collection device according to claim 1 , wherein an insulator is disposed between the discharge electrode and the collection electrode in the airflow direction.

9. The collection device according to claim 1 , wherein the collection electrode is grounded.

10. A collection device comprising: a passage to direct air in an airflow direction; a discharge electrode disposed in the passage; a counter electrode that is disposed in the passage to cause a discharge between the counter electrode and the discharge electrode to charge particles in the air, and to collect the particles charged; and a collection electrode that is disposed downstream of the discharge electrode in the airflow direction to form a plurality of columnar cells extending substantially in the airflow direction.

11 . The collection device according to claim 10, wherein each of the plurality of columnar cells has a hexagonal shape when viewed in the airflow direction.

12. The collection device according to claim 10, comprising: a pair of counter electrodes that include the counter electrode, wherein the plurality of columnar cells is disposed between the pair of counter electrodes.

13. The collection device according to claim 10, wherein the counter electrode and the collection electrode are integrally formed.

14. The collection device according to claim 10, wherein the collection electrode is grounded.

15. The collection device according to claim 14, wherein an insulator is disposed between the discharge electrode and the collection electrode in the airflow direction.