EP0501151A2 - Bilderzeugungsgerät - Google Patents

Bilderzeugungsgerät Download PDF

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Publication number
EP0501151A2
EP0501151A2 EP19920101337 EP92101337A EP0501151A2 EP 0501151 A2 EP0501151 A2 EP 0501151A2 EP 19920101337 EP19920101337 EP 19920101337 EP 92101337 A EP92101337 A EP 92101337A EP 0501151 A2 EP0501151 A2 EP 0501151A2
Authority
EP
European Patent Office
Prior art keywords
brush
image
image carrier
section
developing agent
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP19920101337
Other languages
English (en)
French (fr)
Inventor
Kazuhiko C/O Intellectual Property Div. Kikuchi
Naruhito C/O Intellectual Property Div. Yoshida
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Original Assignee
Toshiba Corp
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 Toshiba Corp filed Critical Toshiba Corp
Publication of EP0501151A2 publication Critical patent/EP0501151A2/de
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
    • G03G21/0005—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge for removing solid developer or debris from the electrographic recording medium
    • G03G21/0064—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge for removing solid developer or debris from the electrographic recording medium using the developing unit, e.g. cleanerless or multi-cycle apparatus
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
    • G03G21/0005—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge for removing solid developer or debris from the electrographic recording medium
    • G03G21/0035—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge for removing solid developer or debris from the electrographic recording medium using a brush; Details of cleaning brushes, e.g. fibre density
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2221/00—Processes not provided for by group G03G2215/00, e.g. cleaning or residual charge elimination
    • G03G2221/0005—Cleaning of residual toner

Definitions

  • the present invention relates to an image forming apparatus, such as an electrophotographic apparatus, electrostatic printer, etc., and more particularly, to an image forming apparatus which forms a developing agent image on an image carrier, such as a photoconductive drum, and transfer the developing agent image to a paper sheet or other transfer medium, and which is provided with an image distributing member adapted to come into sliding contact with the image carrier on the downstream side of a transfer region for the transferred material so that a developing agent remaining on the image carrier after passage through the transfer region is made nonpatterned.
  • an image forming apparatus which forms a developing agent image on an image carrier, such as a photoconductive drum, and transfer the developing agent image to a paper sheet or other transfer medium, and which is provided with an image distributing member adapted to come into sliding contact with the image carrier on the downstream side of a transfer region for the transferred material so that a developing agent remaining on the image carrier after passage through the transfer region is made nonpatterned.
  • the above problem is liable to arise particularly when a solid portion (region where the developing agent covers a wide area) of a latent image is superposed on a residual image, such as characters, formed in the preceding process. It is often impossible to fully remove the developing agent as well as the latent image in the preceding process, so that a developing agent image also remains a memory image on the photoconductive drum and is transferred directly to a paper sheet. Thus, the conventional image forming apparatuses cannot provide satisfactory reliability, and often cannot produce clear images.
  • an improved image forming apparatus has been developed and started to be practically used to bring a solution to these problems.
  • This apparatus comprises an image distributing member which is arranged in sliding contact with an image carrier, on the downstream side of a transfer region where a developing agent image is transferred to a paper sheet, and is used to make a residual developing agent, remaining on the image carrier after passage through the transfer region, nonpatterned.
  • a brush-shaped structure is generally used as the image distributing member.
  • the brush-type image distributing member is formed in the following manner. First, a brush member composed of two overlapping brush materials is folded double so that the respective distal ends of the materials are trued up. Then, the bent end portion of the brush member is fitted into a doubled aluminum plate, and the aluminum plate is caulked. The brush is located so that the distal end side of its flank is in sliding contact with the circumferential surface of the photoconductive drum. The developing agent remaining on the drum is temporarily attracted to the brush and discharged therefrom so that the developing agent image remaining after the passage through the transfer region is distributed or made non-patterned.
  • the diameter of the photoconductive drum is as small as 40 mm or less, however, it is difficult to bring the brush fully into contact with the outer circumferential surface of the drum, and a satisfactory distributing effect cannot be obtained with use of one brush alone. If a plurality of independent brushes are arranged around the drum, as disclosed in Published Unexamined Japanese Patent Application No. 2-211487, in order to avoid this problem, the manufacturing cost increases, and a wide setting space is required. This constitutes a substantial hindrance to the miniaturization of the apparatus.
  • the present invention has been contrived in consideration of these circumstances, and its object is to provide an image forming apparatus in which a single image distributing member can provide the same distributing effect as the conventional combination of two independent distributing members produces, and which enjoys simpler construction and lower cost.
  • an image forming apparatus comprises means for forming a developing agent image on an image carrier by using a developing agent, means for transferring the developing agent image to a transfer medium, and an image distributing member arranged in sliding contact with the image carrier on the downstream side of the transferring means, for making a residual developing agent, remaining on the image carrier after passage through the transferring means, nonpatterned.
  • the image distributing member includes a holding member and a brush extending from the holding member.
  • the brush includes a first brush section, which has a distal end portion in contact with the image carrier, and a second brush section which has a distal end portion extending beyond that of the first brush section and in contact with the image carrier.
  • the brush of the image distributing member is arranged so that the positions of the respective distal ends of the first and second brush sections are offset to form a stepped portion at the distal end of the brush.
  • the stepped portion defines a cavity in the contact region between the image carrier and the brush. This cavity serves substantially as a buffer for storing some of the developing agent.
  • Figs. 1 to 7 show an image forming apparatus according to an embodiment of the present invention, in which:
  • Fig. 1 shows an image forming apparatus according to the present embodiment.
  • a photoconductive drum 2 for use as an image carrier is arranged substantially in the central portion of a body 1 of the apparatus so as to be rotatable in the direction of arrow A.
  • the drum 2 which is formed of a photoconductive material based on an organic photoconductor (OPC), has a recording area smaller than the area of an image to be recorded. In this embodiment, the drum diameter is as small as 40 mm.
  • OPC organic photoconductor
  • the photoconductive drum 2 is surrounded by a discharger 3 having the function mentioned later, developer distributing device 4, charger 5, electrostatic latent image forming device 6, developing/cleaning device 7, and transfer device 8, which are arranged successively in the rotating direction A of the drum.
  • developer distributing device 4 having the function mentioned later
  • charger 5 electrostatic latent image forming device 6, developing/cleaning device 7, and transfer device 8, which are arranged successively in the rotating direction A of the drum.
  • These elements constitute an image forming process unit 9 which forms a toner image T' as a developing agent image on the circumferential surface of the drum 2 and transfers the image to a paper sheet.
  • a paper conveying path 13 which guides a paper sheet P as a transferred material taken out from a paper cassette 10, which is disposed in the lower right-hand portion of the body 1, to a receiving tray 12 on the left-hand side of the body 1, via an image transfer section 11 between the photoconductive drum 2 and the transfer device 8 of the process unit 9.
  • Aligning rollers 15 are arranged on the upstream side of the image transfer section 11 with respect to the paper conveying path 13.
  • the rollers 15 serve to align the leading end of the paper sheet P delivered thereto from the paper cassette 10 by means of a paper-supply roller 14, and then feed the sheet to the transfer section 11 with predetermined timing.
  • a fixing device 16 and a discharge roller pair 17 are arranged on the downstream side of the image transfer section 11.
  • the fixing device 16 fixes the toner image T' transferred to the paper sheet P.
  • the roller pair 17 discharges the sheet P, having the image fixed thereon, onto the receiving tray 12.
  • a gate 19 is arranged between the fixing device 16 and the exit roller pair 17. It guides the paper sheet P, fixed by means of the fixing device 16, to a reverse conveying path 18 as required.
  • the sheet P guided to the transportation path 18 is discharged, with its image forming surface downward, into a recessed paper receiving portion 21, which is formed on the top side of the body 1, by means of an exit roller pair 20.
  • the circumferential surface of the drum 2 is electrically charged to about -500 to -800V by means of the charger 5, which is formed of a Scorotoron charger. Then, a light beam 25 from the electrostatic latent image forming device, formed of an edge emitter array (EL), is applied to the charged region of the drum 2, in accordance with image information, to expose the same, thereby forming an electrostatic latent image on the drum surface.
  • the charger 5 is formed of a Scorotoron charger.
  • a light beam 25 from the electrostatic latent image forming device formed of an edge emitter array (EL)
  • EL edge emitter array
  • the electrostatic latent image is then transported to a developing/cleaning position opposite to the developing/cleaning device 7.
  • the device 7 comprises a hopper 26 which contains a toner T for use as a so-called one-component developing agent having frictional chargeability.
  • a developing roller 27 Arranged in the hopper 26 is a developing roller 27, which transports the toner T to a position opposite to the photoconductive drum 2, and returns the toner T remaining on the drum 2 to the hopper 26.
  • the developing roller 27 includes an electrically conductive surface layer 28, having electric resistance of 102 to 108 ⁇ , and an elastic layer 29 of urethane foam, silicone rubber, or EPDM located inside the layer 28.
  • the roller 27 is an elastic roller as a whole.
  • An elastic blade 30 is pressed against the roller 27.
  • the blade 30, which is formed of phosphor bronze or urethane or silicone resin, serves to form a thin toner layer on the roller 27 while frictionally charging the toner T.
  • the toner T transported past the blade 30 is frictionally charged for negative polarity, the same polarity of the photoconductive drum 2, thereby forming one to three toner layers on the circumferential surface of the drum.
  • the surface layer 28 is formed by applying a mixture of urethane resin and 10 to 30% by weight of conductive carbon, for example.
  • the developing roller 27 is connected with a bias power source (not shown) so that the surface layer 28 conducts.
  • a predetermined developing bias is applied to the roller 27 during developing and cleaning operations.
  • the toner T supplied from developing roller 27 is brought elastically into contact with the photoconductive drum 2 with a nip attributable to deformation, so that it is adhered to the electrostatic latent image, thereby forming the toner image T'.
  • the toner T adheres to the exposed region of the drum 2, thereby effecting the so-called reversal development.
  • the toner T is charged to about -5 to -30 ⁇ c/g (micro-coulomb/gram) by friction between the blade 30 and the surface layer 28 of the developing roller 27, and a voltage of about -150 to -450V is applied to the roller 27.
  • the toner image T' is transported to a region where it faces the transfer device 8 including a transfer roller 22, that is, the image transfer section 11, as the drum 2 rotates.
  • the image transfer section 11 is supplied with a paper sheet P which is delivered from the paper cassette 10 as the paper-supply roller 14 rotates.
  • a positive bias is applied to the reverse side of the paper sheet P by means of the transfer roller 22, so that the toner image T' on the circumferential surface of the photoconductive drum 2 is electrostatically attracted to the paper sheet P to be transferred thereto.
  • a positive AC bias from a power source (not shown) is applied to the rotational shaft of the transfer roller 22, and a voltage is applied through a conducting portion to a conductive surface portion of electrical resistance 105 to 109 ⁇ cm on the surface of the roller 22.
  • the conducting portion which is provided on either end portion of the roller 22, is formed of a mixture of silicone resin and 5 to 0% by weight of conductive carbon.
  • the surface of the transfer roller 22 should be formed from a low-friction material having surface smoothness, in order to facilitate the removal of contaminants, such as the adhering toner T, paper dust, etc.
  • conductive polyfluoride resin or conductive polyester is used as the material of the surface of the roller 22.
  • the surface of the roller 22 is satisfactorily cleaned by means of a cleaning blade 32. A high degree of allowance for the force of pressure on the photoconductive drum 2 was able to be obtained when soft rubber having general hardness of 25 to 50° (based on the JIS (Japanese Industrial Standard) relative measurement method) was used for the transfer roller 22.
  • the paper sheet P is delivered to the fixing device 16, whereupon the toner image T' is fused and fixed on the sheet P. Thereafter, the sheet P is alternatively discharged to the receiving tray 12 or the paper receiving portion 21.
  • the device 4 comprises a brush-type image distributing member 40.
  • the member 40 slides on the circumferential surface of the drum, so that the residual toner T on the drum surface is fully distributed and made nonpatterned by the member 40.
  • the photoconductive drum 2 is charged again to a predetermined potential by means of the charger 5. In doing this, the scattered nonpatterned toner T on the drum 2 is also negatively charged, and is removed in the developing/cleaning device 7. Thereafter, desired images can be formed by repeating the above-described processes.
  • the image distributing member 40 comprises a brush 41, which is twice-folded with a stepped portion at the distal end, and a holding member 42 for holding the brush.
  • a power source 48 (see Fig. 2) is connected to the brush 41 so that a predetermined voltage is applied to the brush.
  • the brush 41 includes first and second brush sections 41a and 41b extending from the holding member 42.
  • the respective proximal end portions of these brush sections are clamped on both sides by means of the holding member 42 so that the brush sections are intimately in contact with each other.
  • the distal end potion of the second brush section 41b extends longer by a length e than that of the first brush section 41a.
  • the width of the brush 41 is equal to or greater than that of the effective image forming area of the photoconductive drum 2.
  • the holding member 42 is fixedly fitted with a backup plate 45 which serves to press the brush 41 against the drum 2 and shield the brush from the charger 5.
  • the backup plate 5, which is opposed to that lateral face of the second brush section 41b on the opposite side to the first brush section 41a is formed of an insulating elastic material, e.g., polyethylene phthalate and urethane.
  • the image distributing member 40 is manufactured in the following manner.
  • a brush material 41' formed of a bundle of electrically conductive fibers (trademark: TORAYKA) having electric resistance of 103 to 109 ⁇ cm (preferably 104 to 105 ⁇ cm) is folded double to form the first and second brush sections 41a and 41b, as shown in Fig. 5.
  • the material 41' is doubled so that the distal end portion of the second brush section 41b extends beyond that of the first brush section 41a by the length e .
  • the bent portion of the brush material 41' is inserted into an aluminum plate 42', which is previously bent V-shaped and used as the holding member 42, as indicated by two-dot chain line in Fig. 5.
  • the aluminum plate 42' is caulked inward so as to hold the bent portion of the material 41', that is, the respective proximal end portions of the brush sections 41a and 41b, from both sides, as shown in Fig. 6, thus forming the image distributing member 40.
  • the image distributing member 40 is arranged so that the first brush section 41a faces the outer circumferential surface of the photoconductive drum 2 and that a lateral face or flank portion of the distal end portion of the each brush section is in contact with the outer circumferential surface of the drum. Further, the distributing member 40 is arranged so that a certain spot on the circumferential surface of the drum 2 is brought into contact with the second brush section 41b after it is brought into contact with the first brush section 41a. The respective distal end portions of the brush sections 41a and 41b are pressed against the circumferential surface of the drum 2 under a desired pressure by the agency of its own elasticity and the backup plate 45.
  • a cavity 46 is defined by the respective distal end portions of the first and second brush sections and the outer circumferential surface of the drum.
  • the cavity 46 serves substantially as a buffer for storing some of the toner T.
  • the untransferred toner is temporarily stored in the cavity 46 as it is leveled by means of the brush 41 of the image distributing member 40, and is gradually discharged from the cavity as the drum rotates. Even if plenty of untransferred toner remains on the drum 2, therefore, the drum can be cleaned satisfactorily.
  • the image distributing member 40 which makes the residual developing agent on the photoconductive drum 2 nonpatterned after the transfer section 11 is passed, is provided with the brush 41 whose distal end portion contacting the drum is stepped.
  • the cavity 46 is formed substantially having the function of a buffer capable of temporarily storing some of the toner T.
  • the single image distributing member 40 can provide the same distributing effect as the conventional combination of two independent distributing members produces, and can adequately cope with the situation after solid printing or removal of a jam. Since the image distributing means is composed of the single distributing member 40 only, moreover, it does not require a wide setting space, thus ensuring simple construction and low-cost production of the apparatus, as well as reduced apparatus size.
  • the holding member 42 may be doubled so that a second plate section 42b in contact with the second brush section 41b is longer than a first plate section 42a in contact with the first brush section 41a.
  • the first and second brush sections 41a and 41b can be satisfactorily pressed against the photoconductive drum 2 through the medium of the plate section 42b.
  • first and second brush sections 41a and 41b may be formed individually of two fiber bundles with different lengths.
EP19920101337 1991-02-27 1992-01-28 Bilderzeugungsgerät Withdrawn EP0501151A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP33046/91 1991-02-27
JP3304691A JPH04271381A (ja) 1991-02-27 1991-02-27 画像形成装置

Publications (1)

Publication Number Publication Date
EP0501151A2 true EP0501151A2 (de) 1992-09-02

Family

ID=12375842

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920101337 Withdrawn EP0501151A2 (de) 1991-02-27 1992-01-28 Bilderzeugungsgerät

Country Status (2)

Country Link
EP (1) EP0501151A2 (de)
JP (1) JPH04271381A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2700399A1 (fr) * 1993-01-13 1994-07-13 Murata Machinery Ltd Appareil de formation d'une image sans nettoyeur.
EP0649073A2 (de) * 1993-10-15 1995-04-19 Fujitsu Limited Bilderzeugungsgerät
US5421261A (en) * 1993-04-27 1995-06-06 Gerber Scientific Products, Inc. Printing apparatus having web-cleaning members for removing particles affecting print quality

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2700399A1 (fr) * 1993-01-13 1994-07-13 Murata Machinery Ltd Appareil de formation d'une image sans nettoyeur.
US5421261A (en) * 1993-04-27 1995-06-06 Gerber Scientific Products, Inc. Printing apparatus having web-cleaning members for removing particles affecting print quality
EP0649073A2 (de) * 1993-10-15 1995-04-19 Fujitsu Limited Bilderzeugungsgerät
US5678143A (en) * 1993-10-15 1997-10-14 Fujitsu Limited Image forming apparatus for collecting residual toner from a drum using an AC voltage
EP0649073A3 (de) * 1993-10-15 1997-11-19 Fujitsu Limited Bilderzeugungsgerät
US5778285A (en) * 1993-10-15 1998-07-07 Fujitsu Limited Image forming apparatus for collecting residual toner from a drum using an AC voltage

Also Published As

Publication number Publication date
JPH04271381A (ja) 1992-09-28

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