WO2022093369A1 - Charging device with target area for electrical discharge - Google Patents

Charging device with target area for electrical discharge Download PDF

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Publication number
WO2022093369A1
WO2022093369A1 PCT/US2021/046828 US2021046828W WO2022093369A1 WO 2022093369 A1 WO2022093369 A1 WO 2022093369A1 US 2021046828 W US2021046828 W US 2021046828W WO 2022093369 A1 WO2022093369 A1 WO 2022093369A1
Authority
WO
WIPO (PCT)
Prior art keywords
image carrier
charging
electrical discharge
target area
charging device
Prior art date
Application number
PCT/US2021/046828
Other languages
French (fr)
Inventor
Yasuyuki Ishii
Koichiro Takashima
Yoichi Yoshida
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Publication of WO2022093369A1 publication Critical patent/WO2022093369A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0208—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices by contact, friction or induction, e.g. liquid charging apparatus
    • G03G15/025—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices by contact, friction or induction, e.g. liquid charging apparatus by bringing a charging member in the vicinity with the member to be charged, e.g. proximity charging, forming microgap
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0275—Arrangements for controlling the area of the photoconductor to be charged

Definitions

  • An imaging apparatus to form an image on a print medium may include a photoconductor that forms an electrostatic latent image, a charging device that charges the photoconductor, and a developing device that develops the electrostatic latent image formed on the photoconductor, by transferring a toner thereto.
  • the charging device may be spaced apart from the photoconductor. In this case, the charging device charges the photoconductor in a non-contact state.
  • a gap formed between the photoconductor and the charging device is not constant and a charging bias to be applied by the charging device is set based on the maximum value of the gap.
  • FIG. 1 is a schematic diagram of an example imaging apparatus.
  • FIG. 2 is a diagram schematically illustrating an image carrier and a charging member in the example imaging apparatus.
  • FIG. 3 is a graph of an alternating current (AC) flowing from the charging member to the image carrier, and of an electrical discharge current generated between the charging member and the image carrier, in relation to an AC voltage applied to the charging member in the example imaging apparatus.
  • AC alternating current
  • FIG. 4 is a graph of the electrical discharge current generated and of the AC voltage applied, in the example imaging apparatus and in another example apparatus.
  • FIG. 5 is a graph illustrating a wear rate of the example image carrier, relative to the electrical discharge current generated.
  • FIG. 6 is a graph of a surface potential of the image carrier, and of the electrical discharge current generated, relative to a width of a slit of a discharge target area regulating member adjacent the example charging member.
  • FIG. 7 is a graph of a surface potential of the image carrier, and of the electrical discharge current generated, relative to a number of alternations.
  • FIG. 8 is a graph illustrating a relationship between a width of a target area delimited by the discharge target area regulating member for an electrical discharge, and a deviation of a surface potential of the image carrier.
  • FIG. 9 is a graph illustrating a relationship between the number of alternations and the width of the target area.
  • FIG. 10 is a graph showing a relationship between the number of alternations and the deviation of a surface potential of the image carrier.
  • FIG. 11 is a diagram schematically illustrating a charging member and an image carrier in another example imaging apparatus.
  • FIG. 12 is a graph showing a relationship between an outer diameter of the image carrier and an outer diameter of the charging member, according to various examples of the imaging apparatus.
  • An example imaging apparatus includes a plurality of stations. Each of the stations includes an image carrier on which an electrostatic latent image may be formed, a developing device which supplies a toner to the image carrier to form a toner image according to electrostatic latent image, and a charging device which charges the image carrier.
  • the image carrier indicates a component that carries a toner image, such as a photoconductor, for example.
  • the charging device includes a charging member that charges the image carrier by an electrical discharge. In the example charging member, a target area for an electrical discharge on the surface of the image carrier is restricted. Since the target area for the electrical discharge by the charging member is restricted, it is possible to reduce an electrical discharge current and suppress the wear of the image carrier.
  • FIG. 1 illustrates an example imaging apparatus 1.
  • the imaging apparatus 1 may form a color image by using respective colors of yellow, magenta, cyan, and black (respectively represented by the characters "Y", “M”, “C” and "K” in the reference symbols).
  • the imaging apparatus 1 includes a print medium conveying device 10, a transfer device 30, a fixing device 50, and four stations including a first station 2A, a second station 2B, a third station 2C, and a fourth station 2D.
  • the first station 2A, the second station 2B, the third station 2C, and the fourth station 2D respectively supply yellow toner, magenta toner, cyan toner, and black toner.
  • the first station 2A includes a developing device 20Y and an image carrier 40Y
  • the second station 2B includes a developing device 20M and an image carrier 40M
  • the third station 2C includes a developing device 20C and an image carrier 40C
  • the fourth station 2D includes a developing device 20K and an image carrier 40K.
  • the image carrier 40Y, the image carrier 40M, the image carrier 40C, and the image carrier 40K are, for example, photoconductors (as an example, photoconductor drums).
  • the print medium conveying device 10 includes a paper feeding roller 11 which conveys, along a conveyance route R1 , a print medium P on which an image is to be formed.
  • the print medium P is stored in a cassette C in a stacked state and is picked up and conveyed by the paper feeding roller 11.
  • the print medium conveying device 10 allows the print medium P to reach a secondary transfer area R2 along the conveyance route R1 , at a timing at which a toner image to be transferred, reaches the secondary transfer area R2.
  • the transfer device 30 receives, for example, a toner from each of the stations 2A to 2D and forms a toner image (layered toner image or composite toner image).
  • the transfer device 30 includes a transfer belt 31 , suspension rollers 32a, 32b, 32c, and 32d, primary transfer rollers 33a, 33b, 33c, and 33d, and a secondary transfer roller 34.
  • the transfer belt 31 extends between the secondary transfer roller 34 and the suspension roller 32d.
  • the secondary transfer roller 34 and the suspension roller 32d form the secondary transfer area R2 to perform a secondary transfer operation that transfers the composite toner image from the transfer belt 31 onto the print medium P.
  • the fixing device 50 fixes the composite toner image to the print medium P.
  • the fixing device 50 includes a heating belt 51 which heats the print medium P and fixes the toner image to the print medium P and a pressing roller 52 which presses the heating belt 51 .
  • a nip portion forms a fixing area between the heating belt 51 and the pressing roller 52.
  • the imaging apparatus 1 may additionally include discharge rollers 55 and 56 which are provided downstream the fixing device 50 in the conveyance route R1 of the print medium P, so as to discharge the print medium P with the fixed toner image to the outside of the imaging apparatus 1 .
  • the station 2A, the station 2B, the station 2C, and the station 2D are process cartridges 2 that each integrally includes a corresponding one of the developing devices 20Y, 20M, 20C, and 20K, a corresponding one of the image carriers 40Y, 40M, 40C, and 40K, and a corresponding one of the charging devices 41 Y, 41 M, 41 C, and 41 K.
  • the imaging apparatus 1 includes a housing 3 to which the stations 2A, 2B, 2C, and 2D may be attached.
  • each of the stations 2A, 2B, 2C, and 2D is attachable to and detachable from the housing 3 by being inserted into and removed from the housing 3 after opening the door of the housing 3.
  • the image carriers 40Y, 40M, 40C, and 40K form the respective electrostatic latent images and the developing devices 20Y, 20M, 20C, and 20K develop respective the electrostatic latent images formed on the image carriers 40Y, 40M, 40C, and 40K.
  • the charging devices 41 Y, 41 M, 41 C, and 41 K respectively face the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K, and an exposure unit (exposure device) 42 is positioned adjacent the stations 2A, 2B, 2C, and 2D.
  • the charging devices 41 Y, 41 M, 41 C, and 41 K charges the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K to a predetermined potential.
  • the exposure unit 42 exposes the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K that have been previously charged .according to the image to be formed on the print medium P.
  • a potential of a portion exposed by the exposure unit 42 in the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K changes so that the respective electrostatic latent images are formed on the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K.
  • the stations 2A, 2B, 2C, and 2D may be arranged so as to substantially align with the respective toner tanks 25Y, 25M, 25C, and 25K.
  • the yellow, magenta, cyan and black toners are supplied from the respective toner tanks 25Y, 25M, 25C, and 25K to the developing devices 20Y, 20M, 20C, and 20K, respectively.
  • the developing devices 20Y, 20M, 20C, and 20K supply the toners to the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K in order to develop the electrostatic latent images, such that the respective toner images are formed.
  • the toner images formed on the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K are primarily transferred to the transfer belt 31 .
  • the paper feeding roller 11 rotates, the print medium P is picked up, and the print medium P is conveyed along the conveyance route R1.
  • the charging devices 41 Y, 41 M, 41 C, and 41 K uniformly charge the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K to a predetermined potential.
  • the exposure unit 42 irradiates the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K with a laser beam based on the image signal so that the electrostatic latent images are formed on the outer circumferential surfaces of the respective image carriers 40Y, 40M, 40C, and 40K.
  • the developing devices 20Y, 20M, 20C, and 20K perform a developing process to form the respective toner images on the electrostatic latent images of the image carriers 40Y, 40M, 40C, and 40K.
  • a primary transfer is carried out, for example, in areas where the image carriers 40Y, 40M, 40C, and 40K respectively face the transfer belt 31 so as to transfer and layer the respective toner images onto the transfer belt 31 .
  • the layered toner image (or composite toner image) is formed on the transfer belt 31 , and the layered toner image is secondarily transferred to the print medium P that is conveyed to the secondary transfer area R2.
  • the print medium P having been subjected to the secondary transfer is conveyed from the secondary transfer area R2 to the fixing device 50 so that the layered toner image is melted and fixed.
  • the print medium P with the fixed toner image may be discharged via the discharge rollers 55 and 56, to the outside of the imaging apparatus 1 .
  • the charging device 41 will be described as a representative one of the charging devices 41 Y, 41 M, 41 C, and 41 K
  • the image carrier 40 will be described as a representative one of the image carriers 40Y, 40M, 40C, and 40K.
  • the charging device 41 uniformly charges the outer circumferential surface of the image carrier 40 to a predetermined potential.
  • the charging device 41 of the example imaging apparatus 1 may be a noncontact charging device 41 .
  • the charging device 41 is disposed so as not to contact the image carrier 40.
  • a surface 40b of the image carrier 40 is uniformly charged by applying a voltage obtained by superimposing an alternating current voltage component on a direct current voltage component to the charging device 41 .
  • the charging device 41 generates, for example, an electrical discharge for applying the electrostatic charge to the surface 40b of the image carrier 40 for forming the electrostatic latent image.
  • the imaging apparatus 1 further includes, for example, a power supply 71 and a control device 72.
  • the control device 72 may be, for example, a control unit (or control device, or controller) which controls the operation of the imaging apparatus 1 .
  • the surface 40b of the image carrier 40 is rotatable in a rotational direction D1 .
  • the image carrier 40 is, for example, a rotatable organic photo conductor (OPC).
  • OPC organic photo conductor
  • the image carrier 40 includes a substrate and a photosensitive layer disposed over the substrate so as to form the surface 40b of the image carrier 40.
  • the photosensitive layer may include a charge generation layer formed over the substrate and a charge transport layer formed over the charge generation layer.
  • the charge transport layer of the image carrier 40 may contain filler particles.
  • the filler particles may be formed of a material that is less susceptible to the electrical discharge than organic compounds, so as to suppress the wear of the image carrier 40 due to the electrical discharge generated between the image carrier 40 and the charging device 41 .
  • the average particle diameter of the filler particle may be 50 nm to 500 nm, so as to more effectively suppress the wear of the image carrier 40.
  • the example charging device 41 may uniformly charges the surface 40b of the image carrier 40 to form a charging surface on the surface 40b, and the electrostatic latent image is formed on the surface 40b when the exposure unit 42 irradiates the charging surface with light.
  • Opposite end portions of the image carrier 40 in the axial direction are rotatably supported by support members, and a drive source such as a motor drives the image carrier 40 into rotation.
  • the image carrier 40 rotates, for example, at the rotation speed which is the process speed of the imaging apparatus 1.
  • the process speed of the imaging apparatus 1 matches the tangential speed (linear speed) of the surface 40b of the image carrier 40.
  • the example charging device 41 includes a charging member 45 and a discharge target area regulating member (or a target positioning member) 46.
  • the charging member 45 is positioned to be spaced apart (e.g., to be separated) from the image carrier 40.
  • the charging member 45 has a substantially cylindrical shape.
  • the example charging member 45 includes a conductive support body 45b and a conductive elastic layer 45c which is formed over the outer circumferential surface of the conductive support body 45b.
  • the outer circumferential surface of the conductive support body 45b may be plated, so as to improve the rust prevention performance and the scratch resistance performance of the conductive support body 45b.
  • the conductive elastic layer 45c may be formed of a resin containing a conductive material, for example.
  • the charging member 45 is a charging roller which rotates in a rotational direction D2 around an axis extending parallel to the axial direction of the image carrier 40.
  • a ratio (linear speed ratio) of the rotation speed of the image carrier 40 with respect to the rotation speed of the charging member 45 which is the charging roller may be, for example, 0.5 to 1.0.
  • the resistance of the charging member 45 may be, for example, 10 5 to 10 8 .
  • an aluminum roller having a diameter of 30 mm is brought into contact with the entire area of the charging member 45 at a contact load of 1.67 N (170 gF) in the axial direction (the longitudinal direction) and the aluminum roller is rotated at 30 rpm (0.5 rps). Then, a direct current voltage of - 400 V is applied from the power supply 71 to the charging member 45, a resistor of 100 k is disposed on the ground side, a voltage at opposite ends of the charging member 45 in the axial direction is measured, a current is calculated, and a resistance of the charging member 45 is measured.
  • the length of the charging member 45 in the axial direction is 320 mm.
  • a gap G is formed between the charging device 41 and the image carrier 40.
  • the power supply 71 is electrically connected to the charging device 41 .
  • the power supply 71 applies, for example, a voltage for charging the image carrier 40 to the conductive support body 45b of the charging member 45.
  • the voltage applied from the power supply 71 to the conductive support body 45b is, for example, a voltage obtained by superimposing the direct current (DC) voltage on the alternating current (AC) voltage.
  • a gap L (distance) formed between the charging member 45 and the image carrier 40 varies depending on the position along the circumference of the image carrier 40, due to the curvatures of the charging member 45 and the image carrier 40.
  • the control device 72 may set a bias supplied from the power supply 71 to the charging member 45 in accordance with the maximum value (maximum gap) of the gap L. In this case, an excess of electrical discharge current flows to a portion having a gap L that is less than the maximum gap, which may wear the image carrier 40.
  • a current (AC current) increases as the set alternating current voltage (AC voltage) increases.
  • the example imaging apparatus 1 includes the discharge target area regulating member (or target positioning member) 46 that restricts the target area for the electrical discharge on the surface 40b of the image carrier 40.
  • the discharge target area regulating member 46 is disposed between the image carrier 40 and the charging member 45.
  • the discharge target area regulating member 46 may have a sheet shape, for example.
  • a thickness T of the discharge target area regulating member 46 is, for example, 30 pm to 100 pm.
  • the discharge target area regulating member 46 includes, for example, a slit 47 which extends in the axial direction of the image carrier 40 (the direction orthogonal to the view of FIG. 2).
  • the charging member 45 applies the electrostatic charge to the surface 40b of the image carrier 40 through, for example, the slit 47 formed in the discharge target area regulating member 46.
  • the gap L between the charging member 45 and the image carrier 40 may be 8 pm or more.
  • An upper limit for the gap L may be, for example, 100 pm.
  • the charging device 41 including the discharge target area regulating member 46 with the slit 47 for example, provides the surface 40b of the image carrier 40 with a target area A to receive the electrical discharge.
  • the target area A has the closest contact portion P (the portion having the shortest distance) between the charging member 45 and the image carrier 40.
  • the width W of the surface 40b of the target area A satisfies the following relationship:
  • the value of the width W of the target area A may be, for example, 0.475 mm or more.
  • PS tangential speed of the surface 40b of the image carrier 40and the frequency F (Hz) of the electrical discharge voltage generated by the charging member 45
  • the discharge target area regulating member (or target positioning member) 46 may be formed by a resinous film. According to examples, the discharge target area regulating member 46 may contain one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), polyamide (PA), and urethane.
  • PET polyethylene terephthalate
  • PI polyimide
  • PA polyamide
  • urethane urethane
  • the discharge target area regulating member 46 includes, for example, an insulator.
  • the resistance of the discharge target area regulating member 46 is, for example, 10 10 Q cm or more.
  • the example imaging apparatus 1 and the example charging device 41 include the discharge target area regulating member 46 that is disposed between the image carrier 40 and the charging member 45 and restricts or limits the target area A for the electrical discharge in the surface 40b of the image carrier 40.
  • the target area A for the electrical discharge by the charging member 45 is restricted, so as to reduce the electrical discharge current and suppress the wear of the image carrier 40.
  • the graph of FIG. 4 illustrates a relationship between the AC voltage (Vpp) and the electrical discharge current (mA) described above.
  • the electrical discharge current is 0.44 mA when the AC voltage is 2500 Vpp and the gap L is 50 pm to 100 pm.
  • the electrical discharge current can be set to 0.23 mA.
  • the width W of the target area A may be set to 0.475 mm.
  • the graph in FIG. 5 illustrates the wear rate (nm/kc) of the image carrier 40 relative to the electrical discharge current (mA).
  • the wear rate of the image carrier 40 was approximately 23 nm/kc.
  • the OPC wear rate was approximately 12 nm/kc. Accordingly, in the example including the discharge target area regulating member 46 to restrict the target area A for the electrical discharge, it was found that the OPC wear rate could be reduced by approximately 48% as compared with the example without the discharge target area regulating member.
  • the image carrier 40 includes the rotatable surface 40b, the rotatable surface 40b forms the target area A receiving the electrical discharge, and, as described above, the width W of the target area A may satisfy the following relationship:
  • the above-described numerical values "4" and "20" may indicate the number of alternations.
  • the effect of suppressing the electrical discharge current can be more reliably exhibited when the width W is 20 x (PS/4) or less. Additionally, when the width W is equal to or greater than the value of 4 x (PS/F), the number of alternations reaches 4 or more, so as to suppress uneven charging of the surface 40b of the image carrier 40 and improve charging uniformity.
  • the width W may be 0.475 mm or more. Namely, when the tangential speed PS of the image carrier 40 is 285 mm/sec and the frequency of the electrical discharge voltage is 2400 Hz, the width W may satisfy the following relationship;
  • the graph in FIG. 6 illustrates a relationship between the width W which corresponds to a width of the slit 47 (slit width), and the potential (surface potential) of the surface 40b of the image carrier 40.
  • the graph in FIG. 7 illustrates a relationship between the number of alternations and the surface potential. Based on FIG. 6, the potential of the surface 40b can be stabilized when the width W is 0.475 mm or more. Based on FIG. 7, the potential of the surface 40b can be stabilized when the number of alternations is 4 or more.
  • the graph in FIG. 8 illustrates a relationship between the width W which is a slit width and the deviation of the surface potential in the surface 40b of the image carrier 40. Based on FIG. 8, when the width W is 0.475 mm or more, the deviation of the surface potential in the surface 40b can be suppressed. Additionally, the graph in FIG. 9 illustrates a relationship between the number of alternations and the width W. As shown in FIG. 9, it is considered that the number of alternations and the width W have a proportional relationship. Accordingly, with reference to the graph of FIG. 10, when the number of alternations is 4 or more, the deviation of the surface potential in the surface 40b can be suppressed.
  • width W may satisfy the following relationship:
  • the width W may be 2.375 mm or less, so as to suppress the excessive electrical discharge current.
  • the discharge target area regulating member (or target positioning member) 46 includes the slit 47 and the charging member 45 may apply the electrostatic charge to the surface 40b of the image carrier 40 through the slit 47 of the discharge target area regulating member 46.
  • the shape of the discharge target area regulating member 46 restricting the target area A for the electrical discharge can be simplified.
  • the gap L between the charging member 45 and the image carrier 40 may be 8 pm or more, so as to form a sufficient distance between the charging member 45 and the image carrier 40.
  • the resistance of the charging member 45 may be 10 5 to 10 8 to apply a suitable resistance of the charging member 45.
  • the thickness T of the discharge target area regulating member (or target positioning member) 46 may be 30 pm to 100 pm. Further, the discharge target area regulating member 46 may be formed by a resinous film and the discharge target area regulating member 46 may contain at least one of polyethylene terephthalate (PET), polyimide (PI), polyamide (PA), and urethane, so as to set a suitable thickness T and obtain a suitable material for the discharge target area regulating member 46. Further, the resistance of the discharge target area regulating member 46 may be 10 1 ° cm or more to obtain a suitable resistance for the discharge target area regulating member 46.
  • PET polyethylene terephthalate
  • PI polyimide
  • PA polyamide
  • urethane urethane
  • the charging member 45 may be a rotating charging roller and a ratio of the circumferential speed of the image carrier 40 with respect to the circumferential speed of the charging roller may be 0.5 to 1.0, so as to increase the charging uniformity of the image carrier 40 by the charging member 45.
  • a charging device 81 including a charging member 85 according to a another example.
  • the charging device 81 is different from the charging device 41 in that the charging member 85 is narrower and non- rotatable (namely, fixed). Since a configuration of a part of the charging device 81 may be the same as or similar to a corresponding configuration of the charging device 41 described above, overlapping description thereof will be omitted.
  • the charging device 81 includes the non-rotatable narrow and fixed charging member 85.
  • the term "non-rotatable narrow and fixed type" may refer to a usage in a fixed state without rotating in a narrow range.
  • the charging device 81 does not include the discharge target area regulating member (or target positioning member) 46.
  • the charging member 85 has, for example, an elongated shape extending in parallel to the axial direction of the image carrier 40 (in the direction orthogonal to the view of FIG. 11 ) along with the image carrier 40.
  • the resistance of the charging member 85 is, for example, 10 5 to 10 8 .
  • an aluminum roller having a diameter of 30 mm is brought into contact with the entire area of the charging member 85 at a contact load of 1 .67 N (170 gF) in the axial direction (longitudinal direction), a voltage at both ends of the resistor on the ground side is measured after 3 seconds after applying a voltage from the power supply 71 to the charging member 85, a current is calculated from the measured voltage, and a resistance of the charging member 85 is measured.
  • the length of the charging member 85 in the axial direction is 320 mm
  • the gap L between the charging member 85 and the image carrier 40 may be 50 pm to 100 pm.
  • the charging member 85 is a non- rotatable narrow and fixed charging member. Accordingly, the target area A for the electrical discharge in the surface 40b of the image carrier 40 is restricted by the narrow and fixed charging member 85, so as to suppress the wear of the image carrier 40 by reducing the electrical discharge current similarly to the charging device 41 described above.
  • the charging device 81 is modified from the example charging device 41 previously described. Accordingly, the configuration of the charging device and the shape of the charging member are not particularly limited.
  • the charging device may be a roller-shaped charging member similar to the charging member 45 described above and can achieve the same or similar effects as described above by adjusting the diameter (outer diameter) of the image carrier and the diameter of the charging member.
  • the graph in FIG. 12 illustrates a relationship between the outer diameter of the image carrier and the outer diameter of the charging member when the number of alternations described above, is four. Based on FIG. 10, when the outer diameter of the image carrier is 30 mm and the outer diameter of the charging member is 1 .4 mm, and when the outer diameter of the image carrier is 10 mm and the outer diameter of the charging member is 1.4 mm, the same or similar effects as described above can be obtained.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)

Abstract

A charging device includes a charging member to generate an electrical discharge for applying an electrostatic charge to a surface of an image carrier of a developing device, and a target positioning member disposed between the image carrier and the charging member to restrict a target area for the electrical discharge on the surface of the image carrier.

Description

CHARGING DEVICE WITH TARGET AREA FOR ELECTRICAL DISCHARGE BACKGROUND
[0001] An imaging apparatus to form an image on a print medium may include a photoconductor that forms an electrostatic latent image, a charging device that charges the photoconductor, and a developing device that develops the electrostatic latent image formed on the photoconductor, by transferring a toner thereto. The charging device may be spaced apart from the photoconductor. In this case, the charging device charges the photoconductor in a non-contact state. A gap formed between the photoconductor and the charging device is not constant and a charging bias to be applied by the charging device is set based on the maximum value of the gap.
BRIEF DESCRIPTION OF DRAWINGS
[0002] FIG. 1 is a schematic diagram of an example imaging apparatus.
[0003] FIG. 2 is a diagram schematically illustrating an image carrier and a charging member in the example imaging apparatus.
[0004] FIG. 3 is a graph of an alternating current (AC) flowing from the charging member to the image carrier, and of an electrical discharge current generated between the charging member and the image carrier, in relation to an AC voltage applied to the charging member in the example imaging apparatus.
[0005] FIG. 4 is a graph of the electrical discharge current generated and of the AC voltage applied, in the example imaging apparatus and in another example apparatus.
[0006] FIG. 5 is a graph illustrating a wear rate of the example image carrier, relative to the electrical discharge current generated.
[0007] FIG. 6 is a graph of a surface potential of the image carrier, and of the electrical discharge current generated, relative to a width of a slit of a discharge target area regulating member adjacent the example charging member. [0008] FIG. 7 is a graph of a surface potential of the image carrier, and of the electrical discharge current generated, relative to a number of alternations.
[0009] FIG. 8 is a graph illustrating a relationship between a width of a target area delimited by the discharge target area regulating member for an electrical discharge, and a deviation of a surface potential of the image carrier.
[0010] FIG. 9 is a graph illustrating a relationship between the number of alternations and the width of the target area.
[0011] FIG. 10 is a graph showing a relationship between the number of alternations and the deviation of a surface potential of the image carrier.
[0012] FIG. 11 is a diagram schematically illustrating a charging member and an image carrier in another example imaging apparatus.
[0013] FIG. 12 is a graph showing a relationship between an outer diameter of the image carrier and an outer diameter of the charging member, according to various examples of the imaging apparatus.
DETAILED DESCRIPTION
[0014] 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.
[0015] An example imaging apparatus includes a plurality of stations. Each of the stations includes an image carrier on which an electrostatic latent image may be formed, a developing device which supplies a toner to the image carrier to form a toner image according to electrostatic latent image, and a charging device which charges the image carrier. The image carrier indicates a component that carries a toner image, such as a photoconductor, for example. The charging device includes a charging member that charges the image carrier by an electrical discharge. In the example charging member, a target area for an electrical discharge on the surface of the image carrier is restricted. Since the target area for the electrical discharge by the charging member is restricted, it is possible to reduce an electrical discharge current and suppress the wear of the image carrier.
[0016] FIG. 1 illustrates an example imaging apparatus 1. The imaging apparatus 1 may form a color image by using respective colors of yellow, magenta, cyan, and black (respectively represented by the characters "Y", "M", "C" and "K" in the reference symbols). The imaging apparatus 1 includes a print medium conveying device 10, a transfer device 30, a fixing device 50, and four stations including a first station 2A, a second station 2B, a third station 2C, and a fourth station 2D.
[0017] The first station 2A, the second station 2B, the third station 2C, and the fourth station 2D respectively supply yellow toner, magenta toner, cyan toner, and black toner. The first station 2A includes a developing device 20Y and an image carrier 40Y, the second station 2B includes a developing device 20M and an image carrier 40M, the third station 2C includes a developing device 20C and an image carrier 40C, and the fourth station 2D includes a developing device 20K and an image carrier 40K. The image carrier 40Y, the image carrier 40M, the image carrier 40C, and the image carrier 40K are, for example, photoconductors (as an example, photoconductor drums).
[0018] As an example, the print medium conveying device 10 includes a paper feeding roller 11 which conveys, along a conveyance route R1 , a print medium P on which an image is to be formed. The print medium P is stored in a cassette C in a stacked state and is picked up and conveyed by the paper feeding roller 11. The print medium conveying device 10 allows the print medium P to reach a secondary transfer area R2 along the conveyance route R1 , at a timing at which a toner image to be transferred, reaches the secondary transfer area R2. [0019] The transfer device 30 receives, for example, a toner from each of the stations 2A to 2D and forms a toner image (layered toner image or composite toner image). As an example, the transfer device 30 includes a transfer belt 31 , suspension rollers 32a, 32b, 32c, and 32d, primary transfer rollers 33a, 33b, 33c, and 33d, and a secondary transfer roller 34. The transfer belt 31 extends between the secondary transfer roller 34 and the suspension roller 32d. The secondary transfer roller 34 and the suspension roller 32d form the secondary transfer area R2 to perform a secondary transfer operation that transfers the composite toner image from the transfer belt 31 onto the print medium P.
[0020] The fixing device 50 fixes the composite toner image to the print medium P. As an example, the fixing device 50 includes a heating belt 51 which heats the print medium P and fixes the toner image to the print medium P and a pressing roller 52 which presses the heating belt 51 . A nip portion forms a fixing area between the heating belt 51 and the pressing roller 52.
[0021] The imaging apparatus 1 may additionally include discharge rollers 55 and 56 which are provided downstream the fixing device 50 in the conveyance route R1 of the print medium P, so as to discharge the print medium P with the fixed toner image to the outside of the imaging apparatus 1 .
[0022] According to examples, the station 2A, the station 2B, the station 2C, and the station 2D are process cartridges 2 that each integrally includes a corresponding one of the developing devices 20Y, 20M, 20C, and 20K, a corresponding one of the image carriers 40Y, 40M, 40C, and 40K, and a corresponding one of the charging devices 41 Y, 41 M, 41 C, and 41 K.
[0023] As an example, the imaging apparatus 1 includes a housing 3 to which the stations 2A, 2B, 2C, and 2D may be attached. For example, each of the stations 2A, 2B, 2C, and 2D is attachable to and detachable from the housing 3 by being inserted into and removed from the housing 3 after opening the door of the housing 3.
[0024] In the stations 2A, 2B, 2C, and 2D, the image carriers 40Y, 40M, 40C, and 40K form the respective electrostatic latent images and the developing devices 20Y, 20M, 20C, and 20K develop respective the electrostatic latent images formed on the image carriers 40Y, 40M, 40C, and 40K. The charging devices 41 Y, 41 M, 41 C, and 41 K respectively face the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K, and an exposure unit (exposure device) 42 is positioned adjacent the stations 2A, 2B, 2C, and 2D.
[0025] The charging devices 41 Y, 41 M, 41 C, and 41 K charges the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K to a predetermined potential. The exposure unit 42 exposes the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K that have been previously charged .according to the image to be formed on the print medium P. A potential of a portion exposed by the exposure unit 42 in the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K changes so that the respective electrostatic latent images are formed on the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K.
[0026] The stations 2A, 2B, 2C, and 2D may be arranged so as to substantially align with the respective toner tanks 25Y, 25M, 25C, and 25K. The yellow, magenta, cyan and black toners are supplied from the respective toner tanks 25Y, 25M, 25C, and 25K to the developing devices 20Y, 20M, 20C, and 20K, respectively. The developing devices 20Y, 20M, 20C, and 20K supply the toners to the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K in order to develop the electrostatic latent images, such that the respective toner images are formed. The toner images formed on the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K are primarily transferred to the transfer belt 31 .
[0027] In operation, when an image signal of a recording target image is input to the imaging apparatus 1 , the paper feeding roller 11 rotates, the print medium P is picked up, and the print medium P is conveyed along the conveyance route R1. In addition, the charging devices 41 Y, 41 M, 41 C, and 41 K uniformly charge the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K to a predetermined potential. The exposure unit 42 irradiates the outer circumferential surfaces of the image carriers 40Y, 40M, 40C, and 40K with a laser beam based on the image signal so that the electrostatic latent images are formed on the outer circumferential surfaces of the respective image carriers 40Y, 40M, 40C, and 40K.
[0028] The developing devices 20Y, 20M, 20C, and 20K perform a developing process to form the respective toner images on the electrostatic latent images of the image carriers 40Y, 40M, 40C, and 40K. A primary transfer is carried out, for example, in areas where the image carriers 40Y, 40M, 40C, and 40K respectively face the transfer belt 31 so as to transfer and layer the respective toner images onto the transfer belt 31 . Accordingly, the layered toner image (or composite toner image) is formed on the transfer belt 31 , and the layered toner image is secondarily transferred to the print medium P that is conveyed to the secondary transfer area R2. The print medium P having been subjected to the secondary transfer, is conveyed from the secondary transfer area R2 to the fixing device 50 so that the layered toner image is melted and fixed. The print medium P with the fixed toner image may be discharged via the discharge rollers 55 and 56, to the outside of the imaging apparatus 1 .
[0029] With reference to FIG. 2, examples of the charging devices 41 Y, 41 M, 41 C, and 41 K will be described. Hereinafter, the charging device 41 will be described as a representative one of the charging devices 41 Y, 41 M, 41 C, and 41 K, and the image carrier 40 will be described as a representative one of the image carriers 40Y, 40M, 40C, and 40K.
[0030] The charging device 41 uniformly charges the outer circumferential surface of the image carrier 40 to a predetermined potential. As illustrated in FIG. 2, the charging device 41 of the example imaging apparatus 1 may be a noncontact charging device 41 . The charging device 41 is disposed so as not to contact the image carrier 40. In the imaging apparatus 1 , for example, a surface 40b of the image carrier 40 is uniformly charged by applying a voltage obtained by superimposing an alternating current voltage component on a direct current voltage component to the charging device 41 . The charging device 41 generates, for example, an electrical discharge for applying the electrostatic charge to the surface 40b of the image carrier 40 for forming the electrostatic latent image.
[0031] The imaging apparatus 1 further includes, for example, a power supply 71 and a control device 72. The control device 72 may be, for example, a control unit (or control device, or controller) which controls the operation of the imaging apparatus 1 . The surface 40b of the image carrier 40 is rotatable in a rotational direction D1 . The image carrier 40 is, for example, a rotatable organic photo conductor (OPC). As an example, the image carrier 40 includes a substrate and a photosensitive layer disposed over the substrate so as to form the surface 40b of the image carrier 40. The photosensitive layer may include a charge generation layer formed over the substrate and a charge transport layer formed over the charge generation layer.
[0032] As an example, the charge transport layer of the image carrier 40 may contain filler particles. The filler particles may be formed of a material that is less susceptible to the electrical discharge than organic compounds, so as to suppress the wear of the image carrier 40 due to the electrical discharge generated between the image carrier 40 and the charging device 41 . As an example, the average particle diameter of the filler particle may be 50 nm to 500 nm, so as to more effectively suppress the wear of the image carrier 40.
[0033] The example charging device 41 may uniformly charges the surface 40b of the image carrier 40 to form a charging surface on the surface 40b, and the electrostatic latent image is formed on the surface 40b when the exposure unit 42 irradiates the charging surface with light. Opposite end portions of the image carrier 40 in the axial direction (the direction orthogonal to the view of FIG. 2) are rotatably supported by support members, and a drive source such as a motor drives the image carrier 40 into rotation. The image carrier 40 rotates, for example, at the rotation speed which is the process speed of the imaging apparatus 1. As an example, the process speed of the imaging apparatus 1 matches the tangential speed (linear speed) of the surface 40b of the image carrier 40.
[0034] The example charging device 41 includes a charging member 45 and a discharge target area regulating member (or a target positioning member) 46. The charging member 45 is positioned to be spaced apart (e.g., to be separated) from the image carrier 40. As an example, the charging member 45 has a substantially cylindrical shape. The example charging member 45 includes a conductive support body 45b and a conductive elastic layer 45c which is formed over the outer circumferential surface of the conductive support body 45b. In some examples, the outer circumferential surface of the conductive support body 45b may be plated, so as to improve the rust prevention performance and the scratch resistance performance of the conductive support body 45b. The conductive elastic layer 45c may be formed of a resin containing a conductive material, for example.
[0035] According to examples, the charging member 45 is a charging roller which rotates in a rotational direction D2 around an axis extending parallel to the axial direction of the image carrier 40. A ratio (linear speed ratio) of the rotation speed of the image carrier 40 with respect to the rotation speed of the charging member 45 which is the charging roller may be, for example, 0.5 to 1.0. The resistance of the charging member 45 may be, for example, 105 to 108 . [0036] In an example of a method of measuring the resistance of the rollershaped charging member 45, an aluminum roller having a diameter of 30 mm is brought into contact with the entire area of the charging member 45 at a contact load of 1.67 N (170 gF) in the axial direction (the longitudinal direction) and the aluminum roller is rotated at 30 rpm (0.5 rps). Then, a direct current voltage of - 400 V is applied from the power supply 71 to the charging member 45, a resistor of 100 k is disposed on the ground side, a voltage at opposite ends of the charging member 45 in the axial direction is measured, a current is calculated, and a resistance of the charging member 45 is measured. As an example, the length of the charging member 45 in the axial direction is 320 mm.
[0037] A gap G is formed between the charging device 41 and the image carrier 40. The power supply 71 is electrically connected to the charging device 41 . The power supply 71 applies, for example, a voltage for charging the image carrier 40 to the conductive support body 45b of the charging member 45. The voltage applied from the power supply 71 to the conductive support body 45b is, for example, a voltage obtained by superimposing the direct current (DC) voltage on the alternating current (AC) voltage.
[0038] When a voltage is applied to the charging member 45, an electrical discharge is generated between the charging member 45 and the image carrier 40. An alternating current flows from the charging member 45 to the image carrier 40 due to the electrical discharge and a portion the surface 40b of the image carrier 40, that faces the charging member 45 is charged. By the rotation of the image carrier 40, for example, the surface 40b of the image carrier 40 is uniformly charged along the entire circumference.
[0039] A gap L (distance) formed between the charging member 45 and the image carrier 40 varies depending on the position along the circumference of the image carrier 40, due to the curvatures of the charging member 45 and the image carrier 40. The control device 72 may set a bias supplied from the power supply 71 to the charging member 45 in accordance with the maximum value (maximum gap) of the gap L. In this case, an excess of electrical discharge current flows to a portion having a gap L that is less than the maximum gap, which may wear the image carrier 40. [0040] With reference to FIGS. 2 and 3, a current (AC current) increases as the set alternating current voltage (AC voltage) increases. Accordingly, when the alternating current voltage exceeds a constant value (as an example, 2000 Vpp), an electrical discharge current may be generated to flow to the image carrier 40, such that the image carrier 40 may be worn due to the electrical discharge current. Accordingly, the example imaging apparatus 1 includes the discharge target area regulating member (or target positioning member) 46 that restricts the target area for the electrical discharge on the surface 40b of the image carrier 40. [0041] The discharge target area regulating member 46 is disposed between the image carrier 40 and the charging member 45. The discharge target area regulating member 46 may have a sheet shape, for example. A thickness T of the discharge target area regulating member 46 is, for example, 30 pm to 100 pm. The discharge target area regulating member 46 includes, for example, a slit 47 which extends in the axial direction of the image carrier 40 (the direction orthogonal to the view of FIG. 2). The charging member 45 applies the electrostatic charge to the surface 40b of the image carrier 40 through, for example, the slit 47 formed in the discharge target area regulating member 46.
[0042] As an example, the gap L between the charging member 45 and the image carrier 40 may be 8 pm or more. An upper limit for the gap L may be, for example, 100 pm. The charging device 41 including the discharge target area regulating member 46 with the slit 47, for example, provides the surface 40b of the image carrier 40 with a target area A to receive the electrical discharge. The target area A has the closest contact portion P (the portion having the shortest distance) between the charging member 45 and the image carrier 40.
[0043] According to examples, given a width W (mm) of the target area A of the surface 40b of the image carrier 40 in the rotational direction D1 , a frequency F (Hz) of the electrical discharge voltage generated by the charging member 45, and a tangential speed PS (mm/sec) of the surface 40b of the image carrier 40 (e.g., the speed of the surface 40b in the rotational direction D1 ), the width W of the surface 40b of the target area A satisfies the following relationship:
4 x (PS/F) < W < 20 x (PS/F) [0044] The value of the width W of the target area A may be, for example, 0.475 mm or more. In addition, given the tangential speed PS (mm/sec) of the surface 40b of the image carrier 40and the frequency F (Hz) of the electrical discharge voltage generated by the charging member 45, the following relationship may be satisfied:
(PS/F) < 0.125 mm
[0045] In this case, it is possible to improve the charging uniformity of the charging member 45 and to improve the image quality of the image formed by the imaging apparatus 1 .
[0046] The discharge target area regulating member (or target positioning member) 46 may be formed by a resinous film. According to examples, the discharge target area regulating member 46 may contain one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), polyamide (PA), and urethane. The discharge target area regulating member 46 includes, for example, an insulator. The resistance of the discharge target area regulating member 46 is, for example, 1010 Q cm or more.
[0047] As described above, the example imaging apparatus 1 and the example charging device 41 include the discharge target area regulating member 46 that is disposed between the image carrier 40 and the charging member 45 and restricts or limits the target area A for the electrical discharge in the surface 40b of the image carrier 40. The target area A for the electrical discharge by the charging member 45 is restricted, so as to reduce the electrical discharge current and suppress the wear of the image carrier 40.
[0048] The graph of FIG. 4 illustrates a relationship between the AC voltage (Vpp) and the electrical discharge current (mA) described above. In an example without any discharge target area regulating member (without target positioning member) between the charging device and the image carrier, the electrical discharge current is 0.44 mA when the AC voltage is 2500 Vpp and the gap L is 50 pm to 100 pm. On the other hand, in an example with the discharge target area regulating member (target positioning member) 46, the electrical discharge current can be set to 0.23 mA. Additionally, the width W of the target area A may be set to 0.475 mm.
[0049] The graph in FIG. 5 illustrates the wear rate (nm/kc) of the image carrier 40 relative to the electrical discharge current (mA). As described above, when the electrical discharge current was 0.44 mA in the above-mentioned example without any discharge target area regulating member, the wear rate of the image carrier 40 was approximately 23 nm/kc. In the example with the discharge target area regulating member 46, when the electrical discharge current was 0.23 mA, the OPC wear rate was approximately 12 nm/kc. Accordingly, in the example including the discharge target area regulating member 46 to restrict the target area A for the electrical discharge, it was found that the OPC wear rate could be reduced by approximately 48% as compared with the example without the discharge target area regulating member.
[0050] The image carrier 40 includes the rotatable surface 40b, the rotatable surface 40b forms the target area A receiving the electrical discharge, and, as described above, the width W of the target area A may satisfy the following relationship:
4 x (PS/F) < W < 20 x (PS/F)
[0051] The above-described numerical values "4" and "20" may indicate the number of alternations. The effect of suppressing the electrical discharge current can be more reliably exhibited when the width W is 20 x (PS/4) or less. Additionally, when the width W is equal to or greater than the value of 4 x (PS/F), the number of alternations reaches 4 or more, so as to suppress uneven charging of the surface 40b of the image carrier 40 and improve charging uniformity.
[0052] The width W may be 0.475 mm or more. Namely, when the tangential speed PS of the image carrier 40 is 285 mm/sec and the frequency of the electrical discharge voltage is 2400 Hz, the width W may satisfy the following relationship;
W > 4 x (PS/F) = 4 x (285/2400) = 0.475 [0053] In this case, as described above, the charging uniformity can be improved.
[0054] The graph in FIG. 6 illustrates a relationship between the width W which corresponds to a width of the slit 47 (slit width), and the potential (surface potential) of the surface 40b of the image carrier 40. The graph in FIG. 7 illustrates a relationship between the number of alternations and the surface potential. Based on FIG. 6, the potential of the surface 40b can be stabilized when the width W is 0.475 mm or more. Based on FIG. 7, the potential of the surface 40b can be stabilized when the number of alternations is 4 or more.
[0055] The graph in FIG. 8 illustrates a relationship between the width W which is a slit width and the deviation of the surface potential in the surface 40b of the image carrier 40. Based on FIG. 8, when the width W is 0.475 mm or more, the deviation of the surface potential in the surface 40b can be suppressed. Additionally, the graph in FIG. 9 illustrates a relationship between the number of alternations and the width W. As shown in FIG. 9, it is considered that the number of alternations and the width W have a proportional relationship. Accordingly, with reference to the graph of FIG. 10, when the number of alternations is 4 or more, the deviation of the surface potential in the surface 40b can be suppressed.
[0056] Further, the width W may satisfy the following relationship:
W < 20 x (PS/F) = 20 x (285/2400) = 2.375
[0057] Namely, the width W may be 2.375 mm or less, so as to suppress the excessive electrical discharge current.
[0058] With reference to FIG. 2, the discharge target area regulating member (or target positioning member) 46 includes the slit 47 and the charging member 45 may apply the electrostatic charge to the surface 40b of the image carrier 40 through the slit 47 of the discharge target area regulating member 46. In this case, the shape of the discharge target area regulating member 46 restricting the target area A for the electrical discharge can be simplified. Additionally, the gap L between the charging member 45 and the image carrier 40 may be 8 pm or more, so as to form a sufficient distance between the charging member 45 and the image carrier 40.
[0059] When the tangential speed of the surface 40b of the image carrier 40 is PS (mm/sec) and the frequency of the electrical discharge voltage generated by the charging member 45 is F (Hz), the following relationship may be satisfied:
(PS/F) < 0.125 mm
[0060] In this case, it is possible to increase the charging uniformity by the charging member 45 and increase the image quality of the image formed by the imaging apparatus 1. The resistance of the charging member 45 may be 105 to 108 to apply a suitable resistance of the charging member 45.
[0061] The thickness T of the discharge target area regulating member (or target positioning member) 46 may be 30 pm to 100 pm. Further, the discharge target area regulating member 46 may be formed by a resinous film and the discharge target area regulating member 46 may contain at least one of polyethylene terephthalate (PET), polyimide (PI), polyamide (PA), and urethane, so as to set a suitable thickness T and obtain a suitable material for the discharge target area regulating member 46. Further, the resistance of the discharge target area regulating member 46 may be 101° cm or more to obtain a suitable resistance for the discharge target area regulating member 46.
[0062] Further, the charging member 45 may be a rotating charging roller and a ratio of the circumferential speed of the image carrier 40 with respect to the circumferential speed of the charging roller may be 0.5 to 1.0, so as to increase the charging uniformity of the image carrier 40 by the charging member 45.
[0063] With reference to FIG. 11 , a charging device 81 including a charging member 85 according to a another example. The charging device 81 is different from the charging device 41 in that the charging member 85 is narrower and non- rotatable (namely, fixed). Since a configuration of a part of the charging device 81 may be the same as or similar to a corresponding configuration of the charging device 41 described above, overlapping description thereof will be omitted.
[0064] The charging device 81 includes the non-rotatable narrow and fixed charging member 85. The term "non-rotatable narrow and fixed type" may refer to a usage in a fixed state without rotating in a narrow range. The charging device 81 does not include the discharge target area regulating member (or target positioning member) 46. The charging member 85 has, for example, an elongated shape extending in parallel to the axial direction of the image carrier 40 (in the direction orthogonal to the view of FIG. 11 ) along with the image carrier 40.
[0065] The resistance of the charging member 85 is, for example, 105 to 108 . As an example method of measuring the resistance of the fixed charging member 85, an aluminum roller having a diameter of 30 mm is brought into contact with the entire area of the charging member 85 at a contact load of 1 .67 N (170 gF) in the axial direction (longitudinal direction), a voltage at both ends of the resistor on the ground side is measured after 3 seconds after applying a voltage from the power supply 71 to the charging member 85, a current is calculated from the measured voltage, and a resistance of the charging member 85 is measured. As an example, the length of the charging member 85 in the axial direction is 320 mm, and the gap L between the charging member 85 and the image carrier 40 may be 50 pm to 100 pm.
[0066] In the charging device 81 , the charging member 85 is a non- rotatable narrow and fixed charging member. Accordingly, the target area A for the electrical discharge in the surface 40b of the image carrier 40 is restricted by the narrow and fixed charging member 85, so as to suppress the wear of the image carrier 40 by reducing the electrical discharge current similarly to the charging device 41 described above.
[0067] As described above, the charging device 81 is modified from the example charging device 41 previously described. Accordingly, the configuration of the charging device and the shape of the charging member are not particularly limited. For example, the charging device may be a roller-shaped charging member similar to the charging member 45 described above and can achieve the same or similar effects as described above by adjusting the diameter (outer diameter) of the image carrier and the diameter of the charging member.
[0068] The graph in FIG. 12 illustrates a relationship between the outer diameter of the image carrier and the outer diameter of the charging member when the number of alternations described above, is four. Based on FIG. 10, when the outer diameter of the image carrier is 30 mm and the outer diameter of the charging member is 1 .4 mm, and when the outer diameter of the image carrier is 10 mm and the outer diameter of the charging member is 1.4 mm, the same or similar effects as described above can be obtained.
[0069] 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

1 . A charging device comprising: a charging member to generate an electrical discharge for applying an electrostatic charge to a surface of an image carrier of a developing device; and a target positioning member disposed between the image carrier and the charging member to restrict a target area for the electrical discharge on the surface of the image carrier.
2. The charging device according to claim 1 , wherein the image carrier includes a rotatable surface that forms a target area to receive the electrical discharge, and wherein a width of the target area in a rotational direction of the surface satisfies 4 x (PS/F) < W < 20 x (PS/F) wherein W represents a width of the target area in the rotational direction of the surface of the image carrier, F represents a frequency of an electrical discharge voltage generated by the charging member, and PS represents a tangential speed of the surface of the image carrier.
3. The charging device according to claim 2, wherein the width W is 0.475 mm or more.
4. The charging device according to claim 1 , wherein the target setting member includes a slit, and wherein the charging member applies the electrostatic charge to the surface of the image carrier through the slit of the target setting member.
5. The charging device according to claim 1 , wherein a gap between the charging member and the image carrier is 8 pm or more.
6. The charging device according to claim 1 , the image carrier to rotate according to a tangential speed PS of the surface of the image carrier, and the charging member to generate an electrical discharge voltage at a frequency F, wherein a relationship of (PS/F) < 0.125 mm is satisfied.
7. The charging device according to claim 1 , wherein a resistance of the charging member is approximately 105 to 108 .
8. The charging device according to claim 1 , wherein a thickness of the target setting member is approximately 30 pm to 100 pm.
9. The charging device according to claim 1 , wherein the target setting member is formed of a resinous film.
10. The charging device according to claim 1 , wherein the target setting member contains at least one of polyethylene terephthalate (PET), polyimide (PI), polyamide (PA), and urethane.
11 . The charging device according to claim 1 , wherein a resistance of the target setting member is 101° Q cm or more.
12. The charging device according to claim 1 , wherein the charging member is a rotating charging roller, and wherein a ratio of a circumferential speed of the image carrier with respect to a circumferential speed of the charging roller is 0.5 to 1 .0.
13. A charging device comprising: a charging member to generate an electrical discharge for an image carrier having a rotatable surface to form an electrostatic latent image, wherein the rotatable surface includes a target area to receive the electrical discharge, and 18 wherein a width of the target area in a rotational direction of the surface satisfies 4 x (PS/F) < W < 20 x (PS/F) wherein W represents a width of the target area in the rotational direction of the surface of the image carrier, F represents a frequency of an electrical discharge voltage generated by the charging member, and PS represents a tangential speed of the surface of the image carrier.
14. The charging device according to claim 13, wherein the charging member is a non-rotatable narrow and fixed charging member.
15. An imaging apparatus comprising: a developing device including an image carrier having a surface to form an electrostatic latent image; and a charging device including: a charging member to generate an electrical discharge for applying an electrostatic charge to the surface of the image carrier of the developing device; and a target positioning member disposed between the image carrier and the charging member to restrict a target area for the electrical discharge on the surface of the image carrier.
PCT/US2021/046828 2020-10-29 2021-08-20 Charging device with target area for electrical discharge WO2022093369A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0579499B1 (en) * 1992-07-16 1999-03-10 Canon Kabushiki Kaisha An image forming apparatus comprising a charging member
US6785494B2 (en) * 2001-07-12 2004-08-31 Fuji Xerox Co., Ltd. Image formation apparatus and charger used therewith
US7634202B2 (en) * 2006-10-06 2009-12-15 Seiko Epson Corporation Image forming apparatus and abnormality determination method for such an apparatus
US8131185B2 (en) * 2008-06-30 2012-03-06 Oki Data Corporation Charging device, development device, and image forming apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0579499B1 (en) * 1992-07-16 1999-03-10 Canon Kabushiki Kaisha An image forming apparatus comprising a charging member
US6785494B2 (en) * 2001-07-12 2004-08-31 Fuji Xerox Co., Ltd. Image formation apparatus and charger used therewith
US7634202B2 (en) * 2006-10-06 2009-12-15 Seiko Epson Corporation Image forming apparatus and abnormality determination method for such an apparatus
US8131185B2 (en) * 2008-06-30 2012-03-06 Oki Data Corporation Charging device, development device, and image forming apparatus

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