WO2016017115A1 - Dispositif de développement, cartouche de traitement et appareil de formation d'image - Google Patents

Dispositif de développement, cartouche de traitement et appareil de formation d'image Download PDF

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Publication number
WO2016017115A1
WO2016017115A1 PCT/JP2015/003673 JP2015003673W WO2016017115A1 WO 2016017115 A1 WO2016017115 A1 WO 2016017115A1 JP 2015003673 W JP2015003673 W JP 2015003673W WO 2016017115 A1 WO2016017115 A1 WO 2016017115A1
Authority
WO
WIPO (PCT)
Prior art keywords
toner
developer
developing
chamber
circulation
Prior art date
Application number
PCT/JP2015/003673
Other languages
English (en)
Inventor
Daisuke Baba
Bunro Noguchi
Nobuyoshi Yoshida
Naoki Fukushima
Shunsuke Matsushita
Original Assignee
Canon Kabushiki Kaisha
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
Priority claimed from JP2015135911A external-priority patent/JP2016066056A/ja
Application filed by Canon Kabushiki Kaisha filed Critical Canon Kabushiki Kaisha
Publication of WO2016017115A1 publication Critical patent/WO2016017115A1/fr

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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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
    • G03G15/0921—Details concerning the magnetic brush roller structure, e.g. magnet configuration
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
    • G03G15/0815—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer handling means after the developing zone and before the supply, e.g. developer recovering roller
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0896—Arrangements or disposition of the complete developer unit or parts thereof not provided for by groups G03G15/08 - G03G15/0894
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
    • G03G15/0812—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer regulating means, e.g. structure of doctor blade
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
    • G03G15/0877—Arrangements for metering and dispensing developer from a developer cartridge into the development unit
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
    • G03G15/0887—Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity
    • G03G15/0889—Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity for agitation or stirring

Definitions

  • the present invention relates to a developing device, a process cartridge, and an image forming apparatus.
  • the present invention relates to a developing device or the like used for an electrophotographic image forming apparatus.
  • the electrophotographic image forming apparatus forms an image on a recording medium by using an electrophotographic image forming process.
  • the electrophotographic image forming apparatus include, for example, an electrophotographic copier, electrophotographic printers (an LED printer, a laser beam printer, and the like), an electrophotographic facsimile machine, and an electrophotographic word processor.
  • the developing device refers to a device that includes a developer bearing member that bears developer.
  • the process cartridge refers to a cartridge into which at least an image bearing member that bears a developer image (toner image) and a process unit are integrated and which is detachably attached to a main body of the electrophotographic image forming apparatus.
  • An electrophotographic image forming apparatus forms an electrostatic image (latent image) by radiating light corresponding to image data to a electrophotographic photosensitive member (photosensitive member).
  • Toner as developer is supplied from a developing device to this electrostatic image so as to form a visualized toner image.
  • the toner image is transferred from the photosensitive member to a recording material such as recording paper by using a transfer device. This toner image is fixed onto the recording material by a fixing device, thereby forming a recording image.
  • a variety of types of developing devices that use two-component development have been proposed.
  • An example of which is as follows: that is, a two-component developer that includes a toner and carrier is contained in a developing chamber of the developing device.
  • a developing sleeve serving as a developer bearing member is disposed in the developing chamber.
  • the developing sleeve surrounds a magnetic roller and is rotatably secured.
  • the developer is borne on the developing sleeve by a magnetic force of the magnetic roller.
  • a layer thickness regulating unit is used to form a magnetic brush layer made of the developer on the developing sleeve.
  • the magnetic brush layer on the developing sleeve is moved close to or brought into contact with the photosensitive member, and a developing bias voltage including an alternating current component and a direct current component is applied to the developing sleeve.
  • a developing bias voltage including an alternating current component and a direct current component is applied to the developing sleeve.
  • This generates a potential difference between the electrostatic image on the photosensitive member and the developing sleeve.
  • the toner in the developer is moved to the electrostatic image so as to develop the electrostatic image.
  • the toner concentration in the developing chamber having been reduced by development is controlled to a specified range by supplying the toner from a toner chamber to the developing chamber. In many cases, the toner concentration is detected by a toner concentration detector, and when the amount of the toner is low, the toner is supplied.
  • PTL1 proposes a developing device that automatically controls the toner concentration to a specified range by filling a developing chamber with developer.
  • the toner is introduced into a narrow toner supply channel by using a partitioning member in order to prevent the toner from being excessively pushed into the developing chamber.
  • a sufficient amount of the toner is not necessarily supplied to the developer in time. This may reduce image density or produce other effects on the image.
  • a first aspect of the present invention provides a developing device that includes a developing sleeve, a magnetic member, a toner chamber, and a developing chamber.
  • the developing sleeve bears developer including a magnetic particle and toner which is supplied through a first opening.
  • the magnetic member is surrounded by the developing sleeve.
  • the toner chamber has a second opening and contains the toner.
  • the toner is supplied from the toner chamber to the developing chamber through the first opening.
  • the developing chamber contains the developer.
  • the developing chamber has a space that contains the developer below the first opening in a direction of gravity.
  • the developing sleeve is rotated so as to convey the developer to a lower side in the direction of the gravity on a second opening side.
  • a magnetic pole of the magnetic member generates a magnetic field that contributes to rotational circulation of the magnetic particle below the first opening.
  • a regulating member is provided so as to regulate a size of the rotational circulation of the magnetic particle.
  • a second aspect of the present invention provides a developing device that includes a developing sleeve, a magnetic member, a toner chamber, a developing chamber, and a regulating member.
  • the developing sleeve bears developer including a magnetic particle and toner which is supplied through a first opening.
  • the magnetic member has an adding pole generating a magnetic field for adding the toner to the developer.
  • the magnetic member is surrounded by the developing sleeve.
  • the toner chamber has a second opening and contains the toner.
  • the toner is supplied from the toner chamber to the developing chamber through the first opening.
  • the developing chamber contains the developer.
  • the regulating member regulates a movement of the magnetic particle. A boundary surface exists between the toner and the developer.
  • the developing chamber has a space that contains the developer below the first opening in a direction of gravity.
  • the developing sleeve is rotated so as to convey the developer to a lower side in the direction of the gravity on a second opening side.
  • a lower end of the regulating member is positioned at a level identical to or below a level of an upper end of the boundary surface and at a level identical to or above a level of the adding pole in the direction of the gravity.
  • the upper end of the boundary surface is positioned at a level identical to or below a level of an upper end of the developing sleeve.
  • a third aspect of the present invention provides a developing device that includes a developing sleeve, a magnetic member, a toner chamber, a developing chamber, and a regulating member.
  • the developing sleeve bears developer including a magnetic particle and toner.
  • the magnetic member is surrounded by the developing sleeve.
  • the toner chamber has an opening and contains the toner.
  • the toner is supplied from the toner chamber to the developing chamber through the opening.
  • the the developing chamber contains the developer.
  • the regulating member is provided in the developing chamber and regulates flying of the toner.
  • the developing chamber has a space that contains the developer below the opening in a direction of gravity.
  • the developing sleeve is rotated so as to convey the developer to a lower side in the direction of the gravity on the opening side. In an initial use, at least part of a boundary surface between the toner and the developer is positioned above a lower end of the regulating member.
  • a fourth aspect of the present invention provides a developing device that includes a developing sleeve, a magnetic member, a toner chamber, and a developing chamber.
  • the developing sleeve bears developer including a magnetic particle and toner.
  • the magnetic member is surrounded by the developing sleeve.
  • the toner chamber has an opening and contains the toner.
  • the toner is supplied from the toner chamber to the developing chamber through the opening.
  • the developing chamber contains the developer. In a direction of gravity, the opening is positioned above a toner surface formed by the toner contained in the toner chamber.
  • the present invention provides a process cartridge and an image forming apparatus.
  • the toner concentration in the developing chamber can be set in a specified range. This can suppress reduction in image density caused by a situation in which the toner is not sufficiently supplied in time.
  • Fig. 1 is an explanatory view of a toner concentration automatic control mechanism according to a first embodiment.
  • Fig. 2 is an explanatory view of an image forming apparatus according to the first embodiment.
  • Fig. 3 is an explanatory view of a developing device according to the first embodiment.
  • Fig. 4 is an explanatory view of toner concentration automatic control according to the first embodiment.
  • Fig. 5 is a graph illustrating a progression of the toner concentration according to the first embodiment and a first comparative example.
  • Fig. 6 is an explanatory view of a developing chamber according to the first comparative example.
  • Fig. 7 is an explanatory view of a change in the toner concentration according to the first comparative example.
  • Fig. 1 is an explanatory view of a toner concentration automatic control mechanism according to a first embodiment.
  • Fig. 2 is an explanatory view of an image forming apparatus according to the first embodiment.
  • Fig. 3 is an explanatory view of a developing device according
  • Fig. 8 is an explanatory view of a developing chamber according to a second embodiment.
  • Fig. 9 is a graph illustrating a progression of the image density according to the first embodiment and the second embodiment.
  • Fig. 10 is a graph illustrating a progression of the toner concentration according to the first embodiment and the second embodiment.
  • Fig. 11 is a graph illustrating a progression of the toner concentration according to the second embodiment.
  • Fig. 12A is an explanatory view of another embodiment to which the present invention can be implemented.
  • Fig. 12B is an explanatory view of yet another embodiment to which the present invention can be implemented.
  • Fig. 13 is an explanatory view of a position of a regulating member according to the first embodiment.
  • Fig. 14 is an explanatory view illustrating a boundary between toner and developer according to the first embodiment.
  • Fig. 15 is an explanatory view of a toner flying prevention mechanism according to the third embodiment.
  • Fig. 16 is an explanatory view illustrating toner flying according to a second comparative example.
  • Fig. 17 is a flowchart illustrating an example of a toner discharge process according to a fourth embodiment.
  • Fig. 18 is a graph illustrating a progression of the T/D ratio according to the fourth embodiment.
  • Fig. 19 is an explanatory view of a developing device according to a fifth embodiment.
  • Fig. 20 is an explanatory view of an image forming apparatus according to the fifth embodiment.
  • Fig. 21 is an explanatory view of a developing device according to a fourth comparative example.
  • Fig. 22 is an explanatory view of a developing device according to a fifth comparative example.
  • Fig. 23 is an explanatory view of a developing device according to a seventh embodiment.
  • Fig. 24 is an explanatory view of a toner concentration automatic control mechanism according to the seventh embodiment.
  • Fig. 25 is an explanatory view of a developing device according to a sixth comparative example.
  • Fig. 26 is an explanatory view of positions of elements of the developing device according to the fifth embodiment.
  • Fig. 27 is a sectional view of a developing device illustrating a movement of the developer when a developing sleeve is rotated according to an eighth embodiment.
  • FIG. 28A is a schematic view illustrating a movement of the toner in a structure having the circulation return angle ⁇ according to the eighth embodiment.
  • Fig. 28B is a schematic view illustrating the movement of the developer in a structure of a seventh comparative example having no circulation return angle ⁇ .
  • Fig. 29 is a graph in which the difference in image density with the structure of the eighth embodiment having the circulation return angle ⁇ and the difference in image density with the structure of the seventh comparative example without the circulation return angle ⁇ related to the number of printed sheets are compared.
  • Fig. 30 is a sectional view of the developing device according to a variant of the eighth embodiment.
  • Fig. 31 is a sectional view of a developing device according to a ninth embodiment.
  • Fig. 33A is a schematic view of the structure of an agitating member in the structure according to the seventh comparative example.
  • Fig. 33B is a schematic view of the structure of an agitating member in the structure according to the ninth embodiment.
  • Fig. 34 illustrates a variant of a developing chamber according to the ninth embodiment.
  • FIG. 2 illustrates a state of the typically installed image forming apparatus. In this state, the up-down direction in Fig. 2 is the direction of the gravity and the left-right direction in Fig. 2 is the horizontal direction.
  • a drum-shaped image bearing member 1 (referred to as a "photosensitive drum” hereafter) serving as a member to be charged is disposed at the center of an image forming apparatus main body 50 (referred to as an "apparatus main body” hereafter).
  • the photosensitive drum 1 includes a conductive drum substrate formed of aluminum or the like and an organic photoconductive layer (OPC layer) formed on the conductive drum substrate.
  • OPC layer organic photoconductive layer
  • the photosensitive drum 1 is rotated at a specified process speed in an arrow R1 direction. According to the present embodiment, the photosensitive drum 1 is rotated at (a circumferential speed of) 240 mm/s.
  • a surface (circumferential surface) of the above-described photosensitive drum 1 is uniformly charged to a specified polarity and a potential by a charging roller 2 serving as a charging unit.
  • a latent image is formed on the surface of the charged photosensitive drum 1 by a laser beam output from a laser beam scanner 3 serving as a light exposure unit.
  • the surface of the photosensitive drum 1 is exposed to the scanning laser beam modulated corresponding to time-series electric digital pixel signals of target image information, so that the latent image is formed on the surface of the photosensitive drum 1.
  • Toner is attracted to the latent image formed as described above by using a developing device 4 serving as a developing unit so as to develop the latent image into a toner image on the photosensitive drum 1.
  • a recording material 5 is fed by a sheet feed roller and conveyed to a transfer nip formed between the photosensitive drum 1 and a transfer roller 6 in synchronization with the toner image written on the photosensitive drum 1, so that the toner image is transferred onto a surface of the recording material 5.
  • a transfer bias for the transfer is applied from a transfer bias applying power source 6a to the transfer roller 6.
  • the recording material 5 onto which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and conveyed to a fixing device 7 serving as a fixing unit.
  • the recording material 5 is subjected to heat and pressure by the fixing device 7, so that the toner image is fixed onto the surface of the recording material 5, and the recording material 5 is output from the apparatus main body 50.
  • the printing speed of the apparatus main body 50 according to the present embodiment is 40 sheets per minute. Meanwhile, the toner not having been transferred onto the recording material 5 and remaining on the surface of the photosensitive drum 1 after the toner image has been transferred is removed by a cleaning member 8 serving as a cleaning unit and supplied for forming the next image.
  • process devices that is, the photosensitive drum 1, the charging roller 2, the developing device 4, and the cleaning member 8 are integrally assembled into a process cartridge, which is detachably attached to the apparatus main body 50 so as to be replaceable according to the present embodiment.
  • the process devices other than the photosensitive drum 1, which serves as the image bearing member, are also referred to as process units. It is sufficient that at least one of the charging unit, developing unit, and cleaning unit be provided as a process unit.
  • Fig. 3 is a sectional view of the developing device 4 in a position assumed when a process cartridge 51 is attached to the apparatus main body 50.
  • a direction indicated by an arrow Y is the direction of the gravity (referred to as a "downward direction” hereafter).
  • a direction spaced apart from the downward direction by 180° is an upward direction of the direction of the gravity and referred to as an "upward direction”.
  • An arrow X direction spaced apart from the downward direction by 90° is referred to as a "rightward direction”
  • a direction spaced apart from the rightward direction by 180° is referred to as a "leftward direction”.
  • the developing device 4 includes a developing chamber 9 and a toner chamber 10, which are connected to each other through a toner supply opening (second opening) 11.
  • the developing chamber 9 has a space that contains a developer 14 including a toner and magnetic carrier (or magnetic particles). This space is provided below the toner supply opening 11 in the direction of the gravity. This space is filled with the developer during use.
  • the developing chamber 9 includes a developing sleeve 16 that surrounds a magnetic roller 15 serving as a magnetic member.
  • the magnetic roller 15 is secured to the developing chamber 9.
  • the developing sleeve 16 is rotatably provided. The developing sleeve 16 bears the developer 14 by using the magnetic force of the magnetic roller 15 and is rotated in an arrow R2 direction.
  • a developing blade 17 formed of non-magnetic stainless steel is spaced apart from the developing sleeve 16 by a gap of 250 ⁇ m.
  • the developer 14 on the developing sleeve 16 is physically regulated by the developing blade 17.
  • a magnetic brush layer is formed of the developer 14.
  • This magnetic brush layer formed of the developer is conveyed to a developing region.
  • a developing bias voltage which is a superposed voltage formed by superposing a direct current and an alternating current on each other, is applied to the developing sleeve 16, and the magnetic brush and the photosensitive drum 1 are in contact with each other in the developing region.
  • the electrostatic latent image on the photosensitive drum 1 is developed into a toner image with the toner in the magnetic brush.
  • the developing sleeve 16 has an outer diameter of ⁇ 14.
  • the concentration of the toner in the developing chamber 9 is reduced by development.
  • toner 12 contained in the toner chamber 10 is supplied to the developing chamber 9 through the toner supply opening 11 of the toner chamber 10 by a toner conveying unit 18.
  • the toner 12 having been supplied is added to the developer, so that the toner concentration in the developing chamber 9 is set to a specified range.
  • the toner conveying unit 18 includes a polyethylene terephthalate (PET) sheet 19 and a rotational shaft 20.
  • PET polyethylene terephthalate
  • One end of the PET sheet 19 is secured to the rotational shaft 20 so as to allow the PET sheet 19 to be rotated about the rotational shaft 20 in the toner chamber 10.
  • the PET sheet 19 is bent by a projection 21 provided on an inner wall of the toner chamber 10.
  • the toner 12 is pushed up and supplied to the developing chamber 9 through the toner supply opening 11 of the toner chamber 10.
  • a boundary surface 22 is formed between the toner 12 and the developer 14 including the toner and the magnetic carrier (magnetic particles) in the developing chamber 9.
  • a space below the boundary surface 22 in the direction of the gravity is filled with the developer 14.
  • the boundary surface 22 between the developer 14 and the toner 12 is referred to as an "adding surface 22".
  • the toner 12 on the adding surface 22 is supplied through a adding opening 26 (first opening).
  • the toner supplied from the toner chamber 10 by the toner conveying unit 18 to the developing chamber 9 through the toner supply opening 11 of the toner chamber 10 and the adding opening 26 is added to the developer at the adding surface 22.
  • the space of the developing chamber 9 at the same level as or below the level of the adding surface 22 in the direction of the gravity is filled with the developer 14.
  • the volume of the developer 14 is maintained at a fixed value by maintaining the position of the adding surface 22 at a fixed position. This also means as follows: when the amount of the magnetic carrier (magnetic particles) is fixed, the volume of the developer 14 and the toner concentration are in a one-to-one relationship, and accordingly, the toner concentration is automatically controlled to be a fixed value.
  • the magnetic roller 15 serving as the magnetic member has an S2 pole (referred to as a "adding pole 23" hereafter) positioned on the toner chamber 10 side and a circulation determining member 24 side opposite to the image bearing member side.
  • the adding pole 23 as a magnetic pole generates a magnetic field that contributes to adding of the toner and rotational circulation of the magnetic carrier.
  • the position of the adding pole 23 is also on the toner supply opening 11 side and a side toward which the developer on the developing sleeve 16 moves downward in the direction of the gravity.
  • the adding pole 23 is disposed such that a peak position of the magnetic flux density on the developing sleeve 16 is positioned 1 mm above the rotational center of the developing sleeve 16 in the direction of the gravity.
  • the adding pole 23 is a point where the surface of the magnetic roller 15 intersects a line connecting the peak position of the magnetic flux density on the developing sleeve 16 to the rotational center of the magnetic roller 15.
  • the magnetic roller 15 according to the present embodiment has a quadrupole structure.
  • the peak value of the magnetic flux density of the adding pole 23 on the developing sleeve 16 is 70 mT.
  • the circulation determining member 24 is provided as a regulating member that regulates a movement of the magnetic carrier. Since the regulating member according to the present embodiment also has the function of determining the size of the circulation of the developer, the regulating member is also referred to as the "circulation determining member".
  • a lower end of the circulation regulating member is positioned above the adding pole 23 by 3 mm in the direction of the gravity. Also, the circulation regulating member is positioned to the left of an end portion of the developing sleeve 16 on the left side (the left side end portion) by 0.5 mm in the horizontal direction.
  • the developing chamber 9 is filled with the developer illustrated in Fig. 4 such that the position of the adding surface 22 in the direction of the gravity is above the adding pole 23 and at the same level as or below the level of the circulation determining member 24.
  • FIG. 1 A movement of the developer when the developing sleeve 16 is rotated in the above-described structure is illustrated in Fig. 1.
  • the developer 14 on the left side of the developing sleeve 16 in the developing chamber 9 receives a force that conveys the developer 14 in the downward direction (arrow A direction).
  • the developing chamber 9 is filled with the developer 14.
  • the developer having been conveyed collides with the developer that originally fills the developing chamber 9 but cannot move into the originally filling developer in the downward direction.
  • the conveyed developer flows in an arrow B direction.
  • the developer flowing in the arrow B direction collides with a circulation return portion (changing portion) 25 formed by part of a wall of the developing chamber 9.
  • the developer having collided with the wall attempts to change a movement direction thereof so as to move in the downward direction and the upward direction along a wall surface of the circulation return portion 25.
  • the developer having been collided is unlikely to move in the downward direction due to existence of the developer filling the developing chamber 9 below.
  • most of the developer flowing in the arrow B direction is pushed upward in an arrow C direction along the wall surface of the circulation return portion 25.
  • the wall surface of the circulation return portion 25 Since the wall surface of the circulation return portion 25 according to the present embodiment is perpendicular to the horizontal direction, the distance between an upper end of the circulation return portion 25 and the center of the developing sleeve 16 in the horizontal direction is the same as the distance between a lower end of the circulation return portion 25 and the center of the developing sleeve 16.
  • the developer 14 having been pushed upward in the arrow C direction is drawn back in an arrow D direction by the magnetic force of the adding pole 23.
  • rotational circulation of the developer 14 as indicated by the arrows A, B, C, and D is generated.
  • This rotational circulation is also referred to as "adding circulation" hereafter.
  • the adding opening 26 (first opening) is defined between the circulation return portion 25 where the adding circulation is generated and the circulation determining member 24 that faces the circulation return portion 25.
  • the width of the adding opening 26 (a minimum distance between the circulation return portion 25 and the circulation determining member 24) is 5 mm.
  • the width of the adding opening 26 (first opening) of this structure is preferably more than 1.5 mm and equal to or less than 10 mm.
  • the width of the opening is increased, the magnetic force and the peak value of the magnetic flux density are required to be increased to circulate the developer.
  • the width of the opening is excessively small, the supply of the toner 12 may be delayed.
  • it is more preferable that the width of the opening is more than 1.5 mm and equal to or less than 6 mm.
  • the width of the adding opening (first opening) 26 can be freely set in the design as described above, and accordingly, unlike the related art, it is not required to set a small opening width with which a sufficient amount of the toner cannot be supplied in time.
  • the developer sequentially moves in the arrow A, the arrow B, the arrow C, and the arrow D directions in this order.
  • the amount of the toner 12 included in the developer varies.
  • the amount of the toner 12 included in the developer is small while the developer moves in the arrow A and arrow B directions.
  • the developer includes little toner 12 and, in effect, only the magnetic particles move.
  • the toner 12 is added to the developer, and consequently, the amount of the toner 12 in the developer increases.
  • the toner 12 is added to the developer 14 through the above-described adding circulation, thereby increasing the toner concentration and also increasing the volume of the developer 14. Since the developing chamber 9 is filled with the developer 14, the adding surface 22 moves in the upward direction by the increase in the volume of the developer 14, and the flow of the adding circulation indicated by the arrow D collides with the circulation determining member 24 when the volume of the developer 14 increases to a certain value. Due to the collision of the adding circulation with the circulation determining member 24, the adding circulation is blocked and stopped.
  • a point where the adding surface 22 in a stopped state and the circulation determining member 24 are adjacent to each other is defined as a boundary 22a.
  • the boundary 22a is disposed on a side surface on the opening side of the circulation determining member 24.
  • the adding surface 22 moves upward in the direction of the gravity, and the boundary 22a of the adding surface 22 reaches a position above the lower end of the circulation determining member 24 as illustrated in Fig. 14.
  • the boundary 22a is also a contact point and in contact with the side surface of the circulation regulating member not on the developing sleeve 16 side but on the toner supply opening 11 side.
  • the movement of the adding surface 22 is stopped, and the adding of the toner 12 to the developer 14 is stopped. This movement is regulated due to a collision of the magnetic carrier in the developer with the circulation determining member 24 serving as the regulating member.
  • the toner is not added to the magnetic carrier when the movement of the magnetic carrier is stopped.
  • the toner concentration at the time when the adding of the toner is stopped is a stabilized point of the toner concentration with the structure according to the present embodiment.
  • the toner concentration is automatically controlled to this value by rotating the developing sleeve 16 for a certain period of time even after the printing operation has been performed.
  • the toner concentration is automatically controlled to a fixed value in accordance with whether or not the adding circulation, which is started by a slight change in the volume, is generated. Furthermore, in accordance with the above-described mechanism of the automatic control of the toner concentration, the position of the adding surface 22 near the circulation determining member 24 (for example, the boundary 22a) according to the present invention is at the same position as or slightly above the lower end of the circulation determining member 24 in many cases. Fig. 14 clearly illustrates the case in which the boundary 22a is positioned above the lower end of the circulation determining member 24.
  • FIG. 13 the positional relationships of the circulation determining member 24 according to the first embodiment are described.
  • the positions of a lower end 11a of the toner supply opening 11 and an upper end of the developing sleeve 16 are the same in the direction of the gravity. Since the toner 12 is supplied from the toner chamber 10 through the toner supply opening 11, the toner 12 accumulates and forms a toner surface below the lower end 11a of the toner supply opening 11.
  • the lower end of the circulation determining member (regulating member) 24 that determines the size of the circulation movement of the magnetic particles is disposed at the same level as or below the level of the upper end of the developing sleeve 16. This is to suppress passage and resulting leakage of the developer above the developing sleeve 16.
  • the lower end of the circulation determining member 24 is disposed at the same level as or above the level of the toner adding pole 23 in the direction of the gravity. According to the present embodiment, the circulation determining member 24 is disposed at the same level as or above the level of a lower end of the developing sleeve 16 and also at the same level as or above the level of the rotational center of the developing sleeve 16.
  • the adding pole 23 is positioned at the same level as or above the level of the rotational center of the developing sleeve 16 in the direction of the gravity. Also, the adding pole 23 is positioned at the same level as or below the level of the lower end of the circulation determining member 24. Also, the adding pole 23 is disposed closer to the rotational center of the developing sleeve 16 than the lower end of the circulation determining member 24 in the direction of the gravity. According to the present embodiment, the magnetic field that contributes to the rotational circulation of the magnetic particles can efficiently act on the magnetic carrier (magnetic particles).
  • the adding surface which is the boundary surface 22 between the toner 12 and the developer, is illustrated as a curve in Fig. 13. Both end sides of the adding surface are positioned below the lower end of the circulation determining member 24. An upper end of the adding surface is at the same level as the level of the lower end of the circulation determining member 24. The upper end of the adding surface is not necessarily near the center illustrated in Fig. 13. The uppermost end may be positioned at a boundary part in contact with the circulation determining member 24.
  • the size of the rotational circulation of the magnetic particles can be regulated, and the toner concentration in the developing chamber 9 can be set to a specified range.
  • the structure of the present embodiment illustrated in Fig. 1 and the structure of a first comparative example illustrated in Fig. 6 are compared.
  • the circulation determining member 24 illustrated in Figs. 1 and 4 is provided.
  • the circulation determining member 24 is not provided according to the first comparative example as illustrated in Fig. 6.
  • the conditions for the comparison are as follows: a solid white image that does not consume the toner 12 is continuously printed on 15 sheets, and then, a halftone image of a printing ratio of 50% (referred to as the "halftone image" hereafter) is continuously printed on 15 sheets. Changes in the toner concentration are illustrated in Fig. 5.
  • the horizontal axis represents the number of printed sheets and the vertical axis represents the toner concentration in the developing chamber 9.
  • the toner concentration is substantially fixed to 7 weight % even when the halftone image is printed on 15 sheets after the solid white image that does not consume the toner 12 has been continuously printed on 15 sheets.
  • the adding circulation is in the stopped state because the structure according to the present embodiment includes the circulation determining member 24, and accordingly, the adding of the toner 12 can be stopped.
  • the results also indicate that, when printing the halftone image, the adding circulation is generated, so that the same amount of the toner 12 as that consumed by printing the halftone image can be added from the adding surface 22 to the developer.
  • the position of the adding surface 22 is determined by the position of the circulation determining member 24, the position of the adding surface 22 is substantially unchanged in both the case of printing the solid white image and the case of printing the halftone image. That is, the volume of the developer 14 is substantially unchanged.
  • the toner concentration increases when the solid white image is printed and reduces when the halftone image is printed with the first comparative example.
  • the adding circulation is not stopped and adding of the toner 12 to the developer continues because the circulation determining member 24 is not provided. Consequently, the toner concentration increases and, as illustrated in Fig. 7, the volume of the developer also increases at the same time. As can be understood from Fig. 7, since the toner 12 is constantly added with this structure, the adding surface 22 moves upward as the solid white image is printed.
  • the amount of toner 12 added from the adding surface 22 to the developer is insufficient relative to the amount of toner 12 consumed by printing the halftone image, and accordingly, the toner concentration is being reduced with the first comparative example.
  • the structure of the present embodiment is applied. This allows the volume of the developer to be substantially unchanged and the adding of the toner to be determined in accordance with whether or not the adding circulation is generated. Thus, even when an image of a very low printing ratio is continuously printed, the toner 12 is not excessively added, and the increase in the toner concentration can be suppressed. Furthermore, the toner 12 can be sufficiently added when an image of high printing ratio of about 50% is continuously printed. Thus, it is understood that the toner concentration can be automatically controlled to a substantially fixed value.
  • a second embodiment is described with reference to Fig. 8.
  • the wall surface of the circulation return portion 25 according to the present embodiment is not perpendicular to the horizontal direction but inclined so as to increase the distance from the rotational center of the developing sleeve 16 in the horizontal direction toward the upper side.
  • ⁇ inclination relative to the horizontal direction
  • ⁇ 75°. That is, the distance between the rotational center of the developing sleeve 16 and an upper end 25a of the return portion 25 is larger than the distance between a lower end 25b of the return portion 25 and the rotational center of the developing sleeve 16 in the horizontal direction.
  • Elements other than these are the same as those of the first embodiment.
  • the flow of the adding circulation indicated by the arrow B receives a reactive force including an upward component from the circulation return portion 25 when colliding with the circulation return portion 25.
  • the smoothness of the flow indicated by the arrow C is further increased, thereby further increasing the rotational speed of the adding circulation.
  • FIG. 9 illustrates values obtained with the present embodiment and the first embodiment.
  • the horizontal axis represents the number of printed sheets of the solid image
  • the vertical axis represents the density of the solid image.
  • Fig. 10 illustrates values obtained with the present embodiment and the first embodiment.
  • the horizontal axis represents the number of printed sheets of the solid image
  • the vertical axis represents the toner concentration in the developing chamber 9. From Figs. 9 and 10, with the present embodiment, reduction in the density of the solid image and the toner concentration is not observed even when the solid image is continuously printed on five sheets. In contrast, with the first embodiment, it can be understood that reduction in the density of the solid image and the toner concentration is observed when the solid image is continuously printed on about four sheets.
  • the horizontal axis represents the number of sheets on which the solid white image is printed
  • the vertical axis represents the toner concentration value in the developing chamber 9 according to the present embodiment. It is understood from the results illustrated in Fig. 11 that, also with the structure according to the present embodiment, the toner concentration is substantially fixed when the solid white image that does not consume the toner 12 is continuously printed on 15 sheets.
  • the toner 12 can be sufficiently added for continuously printing the solid image, and even when an image of a very low printing ratio is continuously printed, the toner concentration can be automatically controlled to a substantially fixed value without adding excessive amount of the toner 12.
  • the inclination angle ⁇ is set to 75° according to the present embodiment, the inclination angle ⁇ is preferably set to an angle less than 90° and equal to or more than the angle of repose of the toner 12.
  • the image forming apparatus of the first and second embodiments is of a monochrome type, the image forming apparatus is not limited to this.
  • a configuration of plurality of process cartridges for, for example, a full-color image forming apparatus is also possible (Fig. 12A).
  • the process cartridge into which the developing chamber 9 and the toner chamber 10 are integrated is used.
  • the developing device 4 and a cleaning device 1a can be prepared as separate attachable and detachable devices (Fig. 12B).
  • the toner chamber 10 of the developing device 4 can be made to be a toner cartridge 10a that is an attachable and detachable cartridge separated from the process cartridge (Fig. 12B).
  • a desirable initial state in use is described according to a third embodiment.
  • the toner may fly to the outside of the developing device 4. Although flying of a very small amount of the toner 12 does not affect an image, it is desirable that the toner 12 do not fly. Thus, a desirable state at an initial stage of use according to the present embodiment is described.
  • a mechanism of flying when the toner 12 is supplied at the initial stage of use of the process cartridge is specifically described.
  • an agent surface (boundary surface) of an initial developer 14N contained in the developing chamber 9 is positioned below the lower end of the circulation determining member 24 in the direction of the gravity according to a second comparative example.
  • the circulation determining member 24 also functions as a flying prevention member.
  • the toner 12 passes through this gap and a space above the developing sleeve 16 and flies to the outside of the developing device 4 (arrows h, i, and j).
  • a structure as illustrated in Fig. 15 is adopted for the present embodiment.
  • at least part of the agent surface (boundary surface) of the initial developer 14N contained in the developing chamber 9 is positioned above the lower end of the circulation determining member 24 in the direction of the gravity.
  • the toner concentration of the toner 12 added to the developer is increased compared to that when an image is formed while the mass of the carrier is fixed.
  • the toner concentration of the developer is referred to as a "T/D ratio" hereafter.
  • T/D ratio the weight of the toner/(the weight of the toner + the weight of the carrier).
  • the toner in the developer is consumed as the image is formed, thereby reducing the toner concentration.
  • the toner concentration is reduced to a T/D ratio which is a stabilized point of the toner concentration of the present embodiment, the automatic control of the concentration is started. That is, the toner having accumulated on the boundary surface between the initial developer and the toner is added to the developer so as to prevent reduction of concentration to a certain value or less.
  • the range of the T/D ratio at which the toner concentration is automatically controlled according to the present embodiment is 3 to 20%. A T/D ratio of more than 20% is not appropriate because uncharged toner is likely to fly due to rotation of the developing sleeve 16.
  • Toner flying occurring when the toner is supplied at the initial stage of use of the process cartridge was evaluated with the structures of the present embodiment and the second comparative example.
  • the stabilized point of the toner concentration is attained when the mass of the magnetic carrier, the mass of the toner, and the T/D ratio of the initial developer 14N contained in the developing chamber 9 are respectively 45 g, 3.4 g, and 7.0%.
  • the agent surface of the initial developer 14N of the second comparative example is positioned below the lower end of the circulation determining member 24 in the direction of the gravity.
  • the mass of the magnetic carrier, the mass of the toner, and the T/D ratio of the initial developer 14N contained in the developing chamber 9 are respectively 45 g, 2.4 g, and 5.1%.
  • the agent surface of the initial developer 14N of the present embodiment is positioned above the lower end of the circulation determining member 24 in the direction of the gravity.
  • the mass of the magnetic carrier, the mass of the toner, and the T/D ratio of the initial developer 14N contained in the developing chamber 9 are respectively 45 g, 5 g, and 10%.
  • the evaluation was made under the following conditions: that is, the image forming apparatus had been left to stand for one day before the evaluation was performed in an evaluation environment of a temperature of 25.0°C and a relative humidity of 50%Rh so as to fit the image forming apparatus to the evaluation environment.
  • the flying was evaluated by measuring the mass of the toner that flied after the solid white image had been continuously printed on 400 sheets.
  • the amount of the toner that flied is 1 mg or less after continuously printing 400 sheets. That is, substantially no toner flied.
  • the reason for this is that the T/D ratio of the initial developer 14N is set to be higher than the T/D ratio observed while the toner concentration is automatically controlled.
  • the volume of the developer contained in the developing chamber 9 is more than that contained while the toner concentration is automatically controlled, and consequently, the lower end of the circulation determining member 24 in the direction of the gravity and the agent surface of the initial developer 14N are brought into contact with each other.
  • the toner does not fly.
  • the amount of toner that flied is 200 mg after continuously printing 400 sheets.
  • This flying of the toner 12 is the result of flying of the toner through the gap between the initial developer 14N and the circulation determining member 24 indicated by the arrows (h, i, and j) of Fig. 16 occurring when the toner 12 is supplied to the developing chamber 9 during initial rotation because of the low T/D ratio.
  • flying of the toner 12 can be suppressed with the structure in which the agent surface of the initial developer 14N is positioned above (on the upper side of) the lower end of the circulation determining member 24 in the direction of the gravity.
  • the T/D ratio of the initial developer 14N is 10%.
  • a lower limit of the T/D ratio of developer usable as the initial developer is determined in accordance with an upper limit of the T/D ratio at which the toner concentration is automatically controlled.
  • An upper limit of the T/D ratio for developer usable as the initial developer is 20% which is the upper limit of the T/D ratio at which the toner concentration can be automatically controlled.
  • the upper limit of the T/D ratio may be changed depending on the structure of the device.
  • a method of using a process cartridge with an increased T/D ratio in the structure according to the third embodiment is described.
  • the T/D ratio is increased in consideration of the case where a main body of the process cartridge 51 is inclined.
  • the T/D ratio is largely increased so that the agent surface of the initial developer 14N is positioned above the lower end of the circulation determining member 24 in the direction of the gravity throughout a range in a direction perpendicular to the direction of the gravity even when the process cartridge is inclined.
  • so called "fogging" that is, toner is attracted to a non-image region may occur.
  • the T/D ratio is set to be a very high value compared to that of the third embodiment so that the agent surface of the initial developer 14N is positioned above the lower end of the circulation determining member 24 in the direction of the gravity throughout a range in a direction perpendicular to the direction of the gravity even when the main body of the process cartridge 51 is inclined.
  • the toner 12 cannot be sufficiently charged when an image is formed. This causes the fogging.
  • a toner discharge process is performed when the process cartridge is new before a printing preparation operation.
  • a new component detection is performed on the photosensitive drum 1 and the cleaning member 8 by determining whether the photosensitive drum 1 and the cleaning member 8 are new with an identification member such as, for example, a non-volatile memory that is capable of storing information and provided in the process cartridge. That is, when the process cartridge is new, new component information is stored in the memory.
  • the information in the memory is read through a main body electrical contact provided in the main body. When the information of the memory indicates that the cartridge is new, it is determined that the cartridge is new.
  • the identification member may be a fuse provided in the cartridge. That is, when it is detected that the fuse in not burned by a new component detection unit, the cartridge is determined to be new. After that, the fuse is burned so as to prevent the cartridge from being identified as new.
  • This new component detection operation for the cartridge is performed upon turning on of the power of the main body or upon opening and closing of the door of the main body.
  • the toner discharge process of the fourth embodiment is performed by continuously printing a solid black image without passing sheets so as to discharge the toner to the photosensitive drum 1 and by cleaning the photosensitive drum 1 with the cleaning member 8.
  • Fig. 17 illustrates the toner discharge process.
  • Whether or not the cartridge is new is determined (S3) upon turning on of the power or opening and closing of the door of the main body (S2).
  • the printing preparation operation S16
  • a drive motor is driven (S4) so as to rotate the developing sleeve 16 and the photosensitive drum 1 (S5).
  • the developing bias is applied to the developing sleeve 16 (S6), and then the charging bias is applied to the charging roller 2 (S7) so as to uniformly charge the surface of the photosensitive drum 1.
  • the photosensitive drum 1 is exposed to the laser beam output from the laser beam scanner 3 serving as the light exposure unit, thereby forming an electrostatic latent image corresponding to the solid black image on the photosensitive drum 1 (S8).
  • the toner on the developing sleeve 16 is caused to be attracted onto the electrostatic latent image having been formed so as to develop the electrostatic latent image into a toner image corresponding to the solid black image (S9).
  • the toner image attracted onto the photosensitive drum 1 is cleaned by the cleaning member 8 (S10).
  • the exposure of the photosensitive drum 1 to the light is stopped (S11).
  • the specified number of sheets here means the number of sheets of the solid black image corresponding to the amount of the discharged toner. Then, after development into the toner image corresponding to the solid black image has been performed the number of times corresponding to the specified number of sheets, application of the charging bias and the developing bias is stopped in this order (S12 and S13). After that, the drive motor is stopped (S14). After that, new component historical information is erased (S15), and the printing preparation operation is started (S16).
  • Fogging that occurs at the initial stage of use of the process cartridge was evaluated with the structures of the fourth embodiment and the third comparative example.
  • the structures of developing of the fourth embodiment and the third comparative example are the same. That is, the stabilized point of the toner concentration is attained when the mass of the magnetic carrier, the mass of the toner, and the T/D ratio of the initial developer 14N contained in the developing chamber 9 are respectively 45 g, 5 g, and 10%.
  • the mass of the magnetic carrier, the mass of the toner, and the T/D ratio of the initial developer 14N according to the present embodiment are respectively 45 g, 7 g, and 13.5%.
  • FIG. 17 A sequence at the initial stage of use of the process cartridge of the fourth embodiment is illustrated in Fig. 17.
  • the toner is discharged in a procedure illustrated in Fig. 17.
  • the specified number of sheets on which the electrostatic latent image and the toner image are formed is seven.
  • the toner is discharged when a new cartridge is attached.
  • the toner is not discharged when a new cartridge is attached according to the third example.
  • the specified number of sheets on which the electrostatic latent image and the toner image corresponding to the solid black image are formed according to the present embodiment indicates a time period required to obtain the T/D ratio of about 10% at which the fogging is suppressed.
  • FIG. 18 is a graph illustrating a progression of the T/D ratio for the number of sheets on which the electrostatic latent image and the toner image corresponding to the solid black image are formed when the toner is discharged.
  • the T/D ratio of the initial developer is 13.5%
  • the T/D ratio is reduced to less than 10% when the electrostatic latent image and the toner image corresponding to the solid black image are formed the number of times corresponding to seven sheets.
  • the evaluation was made under the following conditions: that is, the image forming apparatus had been left to stand for one day before the evaluation was performed in an evaluation environment of a temperature of 25.0°C and a relative humidity of 50%Rh so as to fit the image forming apparatus to the evaluation environment.
  • the solid white image was continuously printed on a hundred sheets at the initial printing, and after that, the solid white image on the first, fiftieth, and hundredth sheets was evaluated.
  • reflection density was measured by photovoltaic reflection densitometer (TC-6DS/A, manufactured by Tokyo Denshoku Co., Ltd.) at five points including an upper left end, an upper right end, the center, a lower left end, and a lower right end of the solid white image on each of the sheets, and the measurements were averaged for evaluation.
  • the results are listed in Table 2.
  • the reflection density is low from the first sheet and remains substantially unchanged to the hundredth sheet.
  • the electrostatic latent image and the toner image corresponding to the solid white image are formed the number of times corresponding to seven sheets and collected by the cleaning member 8 before the initial printing (before image forming). This discharges 2.1 g of the toner (toner used to print the solid black image is 0.3 g per sheet), and consequently, the T/D ratio at the initial printing becomes about 10%.
  • the reflection density is high from the first sheet and remains high even in the printing of the hundredth sheet.
  • the solid white image is printed at a higher T/D ratio than that for image forming by not discharging the toner before the initial printing.
  • the T/D ratio is higher than that for image forming, the toner is not sufficiently charged, thereby generating fogging, the reflection density of which is high.
  • the electrostatic latent image and the toner image corresponding to the solid black image are formed the number of times corresponding to seven sheets without transferring to recording materials (before image forming) and collected by the cleaning member 8.
  • the toner discharge process is performed as described above, the T/D ratio of the initial developer is determined in accordance with the amount of the developer or the T/D ratio at which the toner is in good state. Accordingly, an image pattern formed in the toner discharge process and the number of sheets in the toner discharge process are not limited to the above description.
  • the developing device according to a fifth embodiment is described, which has a structure with which the toner is scooped up to the developing sleeve.
  • Fig. 20 illustrates a state of the typically installed image forming apparatus. In this state, the up-down direction in Fig. 20 is the direction of the gravity and the left-right direction in Fig. 20 is the horizontal direction.
  • the drum-shaped image bearing member 1 (referred to as the "photosensitive drum” hereafter) serving as the member to be charged is disposed at the center of the apparatus main body 50.
  • the four process devices that is, the photosensitive drum 1, the charging roller 2, the developing device 4, and the cleaning member 8, are integrally assembled into the process cartridge, which is detachably attached to the apparatus main body 50 of the present embodiment so as to be replaceable.
  • Fig. 19 is a sectional view of the developing device 4 in a position assumed when the process cartridge 51 is attached to the apparatus main body.
  • a direction indicated by an arrow Y is the direction of the gravity which is referred to as the "downward direction” hereafter.
  • a direction spaced apart from the downward direction by 180° is referred to as an "upward direction”
  • an arrow X direction spaced apart from the downward direction by 90° is referred to as a "rightward direction”
  • a direction spaced apart from the rightward direction by 180° is referred to as a "leftward direction”.
  • the developing device 4 includes the developing chamber 9 and the toner chamber 10, which are connected to each other through the toner supply opening (second opening) 11 of the toner chamber 10.
  • the adding opening 26 (first opening) is provided at the same position as that of the toner supply opening 11 of the present embodiment.
  • the developing chamber 9 has a space containing the developer that is filled with the developer 14 including the toner and the magnetic carrier (magnetic particles).
  • a toner buffer portion 13 which will be described later, and a space formed around the developing sleeve 16 and surrounded by a frame of the developing device 4 are included in the developing chamber 9 herein.
  • the toner agent surface (or, first toner surface) is positioned below the lower end of the toner supply opening 11 in the direction of the gravity.
  • the amount of the toner in the new developing device 4 is adjusted so that the above-described positional relationship is satisfied.
  • the developing sleeve 16 that surrounds the magnetic roller 15 serving as the magnetic member is provided.
  • the magnetic roller 15 is secured to the developing chamber 9, and the developing sleeve 16 is rotatably provided.
  • the developing sleeve 16 bears the developer 14 by using the magnetic force of the magnetic roller 15 and is rotated in an arrow R2 direction.
  • a regulating member 17 formed of non-magnetic stainless steel is spaced apart from the developing sleeve 16 by a gap of 250 ⁇ m.
  • the developer 14 on the developing sleeve 16 is physically regulated by the developing blade 17.
  • the magnetic brush layer is formed of the developer 14 and conveyed to the developing region.
  • the developing bias voltage which is a superposed voltage formed by superposing a direct current and an alternating current on each other, is applied to the developing sleeve 16, and the magnetic brush formed of the magnetic particles and the photosensitive drum 1 are in contact with each other in the developing region. In this contact state, an electrostatic latent image on the photosensitive drum 1 is developed into a toner image with the toner in the magnetic brush.
  • the developing sleeve 16 of the present embodiment has an outer diameter of ⁇ 14.
  • the toner 12 is consumed and the toner concentration in developing chamber 9 is reduced.
  • the toner concentration in the developing chamber 9 having been reduced is controlled to a specified range by supplying the toner 12 from the toner chamber 10 to the developing chamber 9 by the toner conveying unit 18.
  • the toner buffer portion 13 is provided adjacent to the toner supply opening 11.
  • the toner buffer portion 13 holds the toner 12 out of the toner 12 in the toner chamber 10 so that a minimum amount of the toner 12 for toner supply can be immediately used. That is, even by scooping up a large amount of toner 12 to the toner buffer portion 13 of the developing chamber 9, the toner 12 cannot be easily moved to the developer side of the interface 22 with the developer. For this reason, the toner accumulates in a space between the toner supply opening 11 and the interface 22 between the toner 12 and the developer. However, when a large amount of the toner 12 is scooped up, the toner fills a recess formed by a bottom portion of the toner buffer portion 13 and the interface 22 and overflows.
  • the toner buffer portion 13 holds the toner 12 in the amount corresponding to ten sheets of the solid black image printed over an entire region of each of the sheets.
  • the length of the toner buffer portion 13 (the length from the toner supply opening 11 to a region filled with the developer (interface 22)) is set to 10 mm.
  • the toner conveying unit 18 includes the PET sheet 19 and the rotational shaft 20.
  • One end of the PET sheet 19 is secured to the rotational shaft 20 so as to allow the PET sheet 19 to be rotated about the rotational shaft 20 in the toner chamber 10.
  • the PET sheet 19 is bent by the projection 21 provided on the inner wall of the toner chamber 10.
  • the free end of the PET sheet 19 is released after the PET sheet 19 has passed through the projection 21, the toner 12 is pushed up by the PET sheet 19 and supplied to the developing chamber 9 through the toner supply opening 11 of the toner chamber 10.
  • the toner concentration of the developer 14 in the developing chamber 9 can also be automatically controlled to a specified range.
  • the automatic control of the toner concentration is described.
  • the toner concentration in the developing chamber 9 is reduced, and the volume of the developer 14 in the developing chamber 9 is reduced.
  • the toner 12 supplied to the toner buffer portion 13 by the toner conveying unit 18 is added to the developing chamber 9 by the amount corresponding to the reduction in the developer 14 in the developing chamber 9.
  • the toner 12 is supplied by the amount of the toner 12 used for the development and reduced, the toner concentration can be automatically controlled to a specified range.
  • the developing device 4 does not circulate the developer in the longitudinal direction in the developing chamber 9.
  • density unevenness vertical bands
  • the structure of the present embodiment in which the toner 12 is supplied by pushing up the toner 12 by the toner conveying unit 18 from the toner chamber 10 is useful.
  • the structure of the present embodiment is useful.
  • the toner 12 can be stably supplied in the entirety of the longitudinal direction. This can reduce the occurrence of the density unevenness (vertical bands) in the longitudinal direction.
  • the structure according to a fourth comparative example is described with reference to Fig. 21.
  • the toner 12 conveyed by being pushed up by the toner conveying unit 18 is used as supply toner.
  • the toner agent surface (toner surface) in the toner chamber 10 is positioned above the toner supply opening 11.
  • the toner buffer portion 13 and a portion of the toner chamber 10 around the toner buffer portion 13 are constantly filled with the toner 12.
  • the weight due to the self-weight of the toner 12 is likely to be applied to the toner buffer portion 13.
  • the toner 12 having a low flowability as it is is used as the supply toner.
  • the density unevenness did not occur with the fifth embodiment independently of the installation environment. Furthermore, the density unevenness did not occur with the fourth comparative example installed in one of the environment (temperature 23°C/humidity 50%), either, but occurred with the fourth comparative example installed in the other environment (temperature 15°C/humidity 10%). The reason for this is that the toner clump was formed in part of the toner buffer portion 13 in the longitudinal direction, and consequently, the toner supply was obstructed and the toner concentration in the developing chamber 9 became non-uniform in the longitudinal direction.
  • the reason for formation of the toner clump is that the amount of charge of the toner 12 initially increases in the low-temperature low-humidity environment, thereby increasing electrostatic clumping forces between toner particles and reducing the flowability of the toner 12.
  • the toner 12 is pushed up by the toner conveying unit 18 so as to be supplied.
  • the toner 12 having a low flowability is supplied as it is.
  • the toner clump is likely to be formed.
  • the weight of the toner 12 in the toner chamber 10 is applied to the toner buffer portion 13.
  • the toner 12 is not likely to move in the toner buffer portion 13. This facilitates formation of the toner clump.
  • the toner used in the present embodiment has properties with which the toner clump tends to be formed in a low-temperature low-humidity environment, the results as listed in Table 3 are obtained.
  • the toner clump may be formed also in a high-temperature high-humidity environment depending on the type (difference in production method, difference in the type of external additive, and so forth) of the toner in use. Even in such a situation, the toner clump is unlikely to be formed by using the structure of the fifth embodiment.
  • the fifth embodiment is a useful structure.
  • the first toner surface (G2) is positioned below a toner surface (second toner surface G6) formed by the toner 12 that accumulates in the toner buffer portion 13 of the developing chamber 9 in the direction of the gravity.
  • second toner surface G6 formed by the toner 12 that accumulates in the toner buffer portion 13 of the developing chamber 9 in the direction of the gravity.
  • the upper end of the boundary surface 22 between the developer and the toner 12 is positioned below the second toner surface (G6) in the direction of the gravity.
  • the second toner surface is positioned between the upper end (G7) and the lower end (G4) of the developing sleeve 16.
  • the reason for this is to dispose the boundary surface 22 and the rotational center of the developing sleeve 16 in a single horizontal plane in order to efficiently supply the toner 12 to the developer borne by the developing sleeve 16. That is, the second toner surface is formed near the boundary surface 22, and the position of the second toner surface is determined when the position of the boundary surface 22 is determined.
  • a lower end of the boundary surface 22 (G5) is positioned above the first toner surface and the lower end of the developing sleeve 16.
  • a bottom portion of the developing chamber 9 (G3) is positioned above the first toner surface (G2) formed of the toner 12 in the toner chamber 10 in the direction of the gravity.
  • the reason for this is that the developing chamber 9 is also required to be provided in an upper portion when the position where development is performed on the photosensitive member or the like is positioned in an upper portion.
  • a bottom portion of the toner chamber 10 (G1) is positioned below the bottom portion of the developing chamber 9 (G3) in the direction of the gravity.
  • a sixth embodiment is described with reference to Fig. 3.
  • the structure near the toner buffer portion 13 of the developing chamber 9 is different from that of the fifth embodiment, and the mechanism that automatically controls the toner concentration of the developer in the developing chamber 9 is also different from that of the fifth embodiment.
  • Other elements are the same as those of the fifth embodiment, and description thereof is omitted.
  • formation of the toner clump can be prevented, and accordingly, the occurrence of the density unevenness (vertical bands) due to uneven toner supply can be suppressed by pushing up the toner 12 with the toner conveying unit 18 to supply the toner 12 in the same way as or similarly to the fifth embodiment.
  • Fig. 3 is a sectional view of the developing device 4 in the position assumed when the process cartridge 51 is attached to the apparatus main body 50.
  • the developing device 4 includes the developing chamber 9 and the toner chamber 10, which are connected to each other through the toner supply opening 11.
  • the developing chamber 9 has the space that contains the developer 14 including the toner and the magnetic carrier (or the magnetic particles). This space is provided below the toner supply opening 11 in the direction of the gravity. This space is filled with the developer during use.
  • toner 12 contained in the toner chamber 10 is supplied to the developing chamber 9 through the toner supply opening 11 of the toner chamber 10 by the toner conveying unit 18.
  • the toner 12 having been supplied is added to the developer, so that the toner concentration in the developing chamber 9 is set to the specified range.
  • the structure according to a fifth comparative example is described with reference to Fig. 22.
  • the toner agent surface in the toner chamber 10 is positioned above the toner supply opening 11. Accordingly, the toner buffer portion 13 and a portion of the toner chamber 10 around the toner buffer portion 13 are constantly filled with the toner 12. As a result, the weight due to the self-weight of the toner 12 is likely to be applied to the toner buffer portion 13. Furthermore, even when the flowability of the toner 12 is reduced by a low-temperature low-humidity environment, the toner 12 having a low flowability as it is is used as the supply toner.
  • the density unevenness did not occur with the sixth embodiment independently of the installation environment. Furthermore, the density unevenness did not occur with the fifth comparative example installed in one of the environment (temperature 23°C/humidity 50%), either, but occurred with the fifth comparative example installed in the other environment (temperature 15°C/humidity 10%). The reason for this is that the toner clump was formed in part of the toner buffer portion 13 in the longitudinal direction, and consequently, the toner supply was obstructed and the toner concentration in the developing chamber 9 became non-uniform in the longitudinal direction.
  • the reason for formation of the toner clump is that the amount of charge of the toner 12 initially increases in the low-temperature low-humidity environment, thereby increasing the electrostatic clumping forces between toner particles and reducing the flowability of the toner 12.
  • the toner 12 is pushed up by the toner conveying unit 18 so as to be supplied.
  • the flowability of the toner 12 can be improved.
  • the toner 12 having a low flowability is supplied as it is.
  • the toner clump is likely to be formed.
  • the weight of the toner 12 in the toner chamber 10 is applied to the toner buffer portion 13.
  • the toner 12 is not likely to move in the toner buffer portion 13. This facilitates formation of the toner clump.
  • the toner used in the present embodiment has properties with which the toner clump tends to be formed in a low-temperature low-humidity environment.
  • the toner clump may be formed also in a high-temperature high-humidity environment depending on the type of the toner. Even in such a situation, the toner clump is unlikely to be formed by using the structure of the sixth embodiment.
  • the sixth embodiment is a useful structure.
  • a seventh embodiment is described with reference to Fig. 23.
  • a developer agitating member 28 is added to the developing chamber 9 of the sixth embodiment.
  • adding circulation of the toner 12 toward the developing chamber 9 is formed.
  • the magnetic force is not used for the adding circulation.
  • Other elements are the same as those of the sixth embodiment.
  • toner clump near the toner supply portion can be prevented, and accordingly, the occurrence of the density unevenness (vertical bands) due to uneven toner supply can be prevented by pushing up the toner 12 with the toner conveying unit 18 to supply the toner 12 in the same way or similarly to the fifth and sixth embodiments.
  • the space of the developing chamber 9 at the same level as or below the level of the boundary surface 22 between the developer and the toner 12 is filled with the developer 14.
  • a boundary surface between a region affected by the conveying force of the developer agitating member 28 and a region not affected by the conveying force of the developer agitating member 28 is referred to as the "adding surface 22".
  • the toner 12 supplied from the toner chamber 10 to the developing chamber 9 through the toner supply opening 11 by the toner conveying unit 18 the toner 12 supplied to the space at the same level as or below the level of the adding surface 22 is added to the developer by a rotating conveying force of the developer agitating member 28 in an arrow A direction.
  • the space of the developing chamber 9 at the same level as or below the level of the adding surface 22 is filled with the developer 14, and the position of the adding surface 22 is maintained at a fixed position.
  • the volume of the developer 14 is controlled to a fixed value. This also means as follows: when the amount of the magnetic carrier is fixed, the volume of the developer 14 and the toner concentration are in a one-to-one relationship, and accordingly, the toner concentration is automatically controlled to be a fixed value.
  • the developer agitating member 28 has a crisscross shape.
  • An outer diameter a and an inner diameter b of the developer agitating member 28 are respectively 12 mm and 6 mm, and the developer agitating member 28 is rotated at 200 rpm.
  • the distance between an outermost surface of the developer agitating member 28 and the developing sleeve 16 and the distance between the outermost surface of the developer agitating member 28 and an inner surface of the developing chamber 9 are 1 mm.
  • the lower end of the circulation determining member 24 is positioned above and on the toner supply opening 11 side of the rotational center of the developer agitating member 28 and below the upper end of the developing sleeve 16.
  • the toner concentration of the developer 14 in the initial state is 7%, and the developer 14 fills the developing chamber 9 so that the adding surface 22 is positioned at a lower end t (Fig. 24) of the circulation determining member 24.
  • Fig. 24 illustrates a movement of the developer 14 when the developing sleeve 16 and the developer agitating member 28 are rotated in the above-described structure.
  • the developer in the developing chamber 9 is circulated as indicated by arrows A, B, C, and D.
  • the toner 12 is disposed above a region of the arrow A.
  • the toner 12 is supplied to a region at the same level as or below the level of the adding surface 22 where the developer is circulated by the gravity, the toner 12 is added to the developer 14 by the conveying force of the developer agitating member 28 in the arrow A direction.
  • the toner 12 having been added to the developer 14 is mixed with the the magnetic carrier and agitated in a region indicated by the arrows B and C, obtains sufficient charge, and supplied to the developing sleeve 16 as the developer 14. Furthermore, the developer 14 having returned to the developing chamber 9 after development is removed from the developing sleeve 16 by circulation indicated by the arrow D by the developer agitating member 28 and conveyed again to the arrow A region.
  • the toner 12 is added to the developer 14 through the above-described adding circulation, thereby increasing the toner concentration and also increasing the volume of the developer 14. Since the developing chamber 9 is filled with the developer 14, the space of the developing chamber 9 up to the adding surface 22 is filled with the developer 14 by the increase in the volume of the developer 14.
  • the circulation determining member 24 is disposed above the developer agitating member 28.
  • the circulation of the developer 14 by the developer agitating member 28 is regulated at the lower end t of the circulation determining member 24. That is, with the circulation determining member 24, a space above the lower end t of the circulation determining member 24 is not affected by the conveying force of the developer agitating member 28.
  • the circulation determining member 24 is provided, the toner 12 is not directly supplied to the developing sleeve 16. Accordingly, when the space up to the adding surface 22 is filled with the developer 14, the space at the same level as or above the level of the adding surface 22 is not affected by the circulation caused by the developer agitating member 28. Thus, adding of the toner 12 to the developer 14 is stopped.
  • the lower end t of the circulation determining member 24 is disposed to the left (on the toner supply opening 11 side) of a vertical line v passing through the rotational center of the developer agitating member 28.
  • the developer 14 in the adding surface 22 receives a force toward the lower left side such as a force in the arrow A direction.
  • the developer 14 does not receive a force in a direction opposite to the direction of the gravity in the adding surface 22.
  • the adding surface 22 is stabilized.
  • the toner concentration is likely to be stabilized.
  • the developer in the developing chamber 9 is not circulated in the longitudinal direction.
  • the density unevenness vertical bands
  • the structure of the present embodiment in which the toner 12 is supplied by pushing up the toner 12 by the toner conveying unit 18 from the toner chamber 10 is useful.
  • this increases the number of components.
  • a screw or the like that circulates the developer in the longitudinal direction may be provided together with the toner conveying unit 18.
  • the structure according to a sixth comparative example is described with reference to Fig. 25.
  • the toner agent surface in the toner chamber 10 is positioned above the toner supply opening 11. Accordingly, the toner buffer portion 13 and a portion of the toner chamber 10 around the toner buffer portion 13 are constantly filled with the toner 12. As a result, the weight due to the self-weight of the toner 12 is likely to be applied to the toner buffer portion 13. Furthermore, even when the flowability of the toner 12 is reduced by a low-temperature low-humidity environment, the toner 12 having a low flowability as it is is used as the supply toner.
  • the density unevenness did not occur with the seventh embodiment independently of the installation environment. Furthermore, the vertical bands were not formed with the sixth comparative example installed in one of the environment (temperature 23°C/humidity 50%), either, but the density unevenness occurred with the sixth comparative example installed in the other environment (temperature 15°C/humidity 10%). The reason for this is that the toner clump was formed in part of the toner buffer portion 13 in the longitudinal direction, and consequently, the toner supply was obstructed and the toner concentration in the developing chamber 9 became uneven in the longitudinal direction.
  • the reason for formation of the toner clump is that the amount of charge of the toner 12 initially increases in the low-temperature low-humidity environment, thereby increasing the electrostatic clumping forces between toner particles and reducing the flowability of the toner 12.
  • the toner 12 is pushed up by the toner conveying unit 18 so as to be supplied.
  • the flowability of the toner 12 can be improved.
  • the toner 12 having a low flowability is supplied as it is.
  • the toner clump is likely to be formed.
  • the weight of the toner 12 in the toner chamber 10 is applied to the toner buffer portion 13.
  • the toner 12 is not likely to move in the toner buffer portion 13. This facilitates formation of the toner clump.
  • An eighth embodiment is a variant of the second embodiment with which the toner adding circulation is stabilized. Initially, stabilization of the toner adding circulation is described.
  • a circulation return portion 27 that extends from a lower end portion of the opening 11 is angled at a circulation return angle ⁇ so that the distance between the circulation return portion 27 and the center of the developing sleeve 16 reduces from a steep inclination portion 27b toward a circulation guide portion 27a.
  • the circulation return angle ⁇ formed between the circulation guide portion 27a and the steep inclination portion 27b is less than 90°, a flow of the adding circulation from the arrow B direction to toward the arrow C direction is obstructed, and when the circulation return angle ⁇ is 180° or more, no effect is produced. For this reason, the circulation return angle ⁇ as a "first angle" formed between the circulation guide portion 27a and the steep inclination portion 27b is set in a range between 90° and less than 180°.
  • the circulation return angle ⁇ formed between the circulation guide portion 27a and the steep inclination portion 27b is more desirably set so that an upper limit of the angle ⁇ of the circulation guide portion 27a, which will be described later, relative to the horizontal direction is equal to or less than the angle of repose of the developer.
  • the developer 14 is easily moved in the arrow B direction of the adding circulation, and accordingly, the toner adding circulation is desirably performed.
  • the angle ⁇ is set to 115°.
  • a contact point where the circulation guide portion 27a and the steep inclination portion 27b are in contact with each other is disposed above the lower end portion of the circulation determining member 24 in the direction of the gravity, a flow of the toner adding circulation in the arrow C direction is generated on the circulation guide portion 27a. Consequently, the adding circulation is not stabilized.
  • the contact point where the circulation guide portion 27a and the steep inclination portion 27b are in contact with each other is disposed below the lower end portion of the developing sleeve 16, a reversing flow is not generated on the circulation guide portion 27a.
  • the contact point where the circulation guide portion 27a and the steep inclination portion 27b are in contact with each other is required to be disposed below a lower end 24z of the circulation determining member 24 and above a lower end 16z1 of the developing sleeve 16 in the direction of the gravity.
  • the contact point where the circulation guide portion 27a and the steep inclination portion 27b are in contact with each other is disposed below the lower end 24z of the circulation determining member 24 by a distance of 4 mm in the direction of the gravity.
  • the angle ⁇ of the circulation guide portion 27a relative to the horizontal direction is set to 4°.
  • a direction of the brush of the developer 14 matches with a direction of the circulation guide portion 27a.
  • the smallest distance between the circulation guide portion 27a and the developing sleeve 16 needs to be at least 250 ⁇ m or more which is a size of a gap between the developing sleeve 16 and the regulating member 17 and set to be 2.0 mm in the structure according to the present embodiment.
  • the width of the circulation guide portion 27a is 4 mm or more, the magnetic attractive force of the magnetic roller 15 is reduced because of an increase in distance from the developing sleeve 16, and consequently, the flow of the toner adding circulation in the arrow D direction is not generated.
  • the width of the circulation guide portion 27a is set to be 2.0 mm according to the present embodiment.
  • the adding pole S2 is disposed 5° upstream of a line connecting the position of the circulation guide portion 27a closest to the developing sleeve 16 and the center 16x of the developing sleeve 16 in the rotational direction of the developing sleeve 16.
  • Fig. 28A is a schematic view illustrating a movement of the toner 12 in a structure having the circulation return angle ⁇ according to the present embodiment.
  • Fig. 28B is a schematic view illustrating the movement of the developer in a structure of a seventh comparative example having no circulation return angle ⁇ . The seventh comparative example will be described later. Referring to Figs. 28A and 28B, the movement of the developer in the arrow B direction of the toner adding circulation is described.
  • an arbitrary particle P1 circulating in the arrow B direction on the circulation guide portion 27a receives a force in the same direction as the direction of the adding circulation in the arrow B direction. Since the directions of the forces received by particles of the developer circulating in the arrow B direction are uniform, the force in the arrow B direction is unlikely to be dispersed. Thus, circulation in the arrow B direction can be formed. Furthermore, since the force in the arrow B direction is unlikely to be dispersed, the flow velocity in the arrow B direction is unlikely to be affected by the flowability of the developer.
  • an arbitrary particle P2 receives a force the vector of which is different from that of the arrow B direction.
  • the velocity of the particle P2 in the toner adding circulation B direction is reduced compared to that of the particle P1.
  • the force of the adding circulation B is dispersed.
  • Fig. 29 illustrates a graph in which the difference in image density with the structure of the eighth embodiment having the circulation return angle ⁇ and the difference in image density with the structure of the seventh comparative example without the circulation return angle ⁇ related to the number of printed sheets are compared.
  • the horizontal axis represents the number of printed sheets on which a horizontal line image of a printing ratio of 1% is printed, and the vertical axis represents the difference in image density. Each time the horizontal line image is printed on 1000 sheets, the difference in image density is measured by printing the following image.
  • the difference in image density is the difference in density between the left and light of a halftone image of a printing ratio of 50% printed after an image the printing ratio of which is 0% on the left side of the center of the image and 100% on the right side of the center of the image has been printed on three sheets.
  • the difference in image density gradually increases, and the difference in image density reaches 0.1 or more when 3000 sheets have passed through.
  • the image density is stable independently of the number of printed sheets with the present embodiment.
  • the flowability of the developer 14 is degraded after 3000 sheets have passed through by the effects of an external additive of the toner 12 being embedded and a fine powder component and the external additive of the toner 12 attracted to the surface of the carrier, and so forth.
  • the angle ⁇ is set to 4° according to the present embodiment
  • Fig. 30 is a sectional view of the developing device according to a variant of the eighth embodiment.
  • the circulation guide portion 27a and the steep inclination portion 27b of the circulation return portion 27 may be continuous with each other so as to form a curved shape convex toward the toner chamber 10 side.
  • a dotted line in contact with the circulation return portion 27 is the shapes of the circulation guide portion 27a and the steep inclination portion 27b according to the eighth embodiment.
  • Fig. 31 is a sectional view of the developing device according to a ninth embodiment.
  • An agitating member 29 and a direction changing portion 30 are provided in the developing chamber 9.
  • the agitating member 29 agitates the developer 14.
  • the direction changing portion 30 that has a uniform width of 1.5 mm in the longitudinal direction extends from the steep inclination portion 27b toward the circulation determining member 24. Elements other than these are the same as those of the eighth embodiment.
  • the agitating member 29 has a rhombus shape in a section perpendicular to the axial direction and is uniformly formed in the longitudinal direction.
  • the agitating member 29 is rotated in a counter direction (an arrow R3 direction in Fig. 31) relative to a surface facing the developing sleeve 16.
  • the lengths of symmetric shafts for agitation are 8 mm and 6 mm and the circumferential speed for agitation is 400 rpm.
  • the direction changing portion 30 is disposed at a destination toward which the developer 14 is pushed up in the arrow C direction. This direction changing portion 30 extends from an upper portion of the steep inclination portion 27b on the upper side of the circulation guide portion 27a to a position near the developing sleeve 16 and changes the direction of the flow of the magnetic carrier.
  • a second angle ⁇ of the direction changing portion 30 relative to the horizontal plane is set to be more than 0° and less than 90° relative to the horizontal plane.
  • the second angle ⁇ is set to be 15°.
  • the density unevenness does not occur even when the flowability of the developer 14 is changed by degradation of the developer 14.
  • image density unevenness may occur due to reduction of the adding speed of the toner 12 caused by clumping of the toner 12 and the developer 14.
  • the agitating member 29 that agitates the magnetic carrier in a developer space 9J is disposed under the developing sleeve 16 (in the developer space 9J) in the developing chamber 9.
  • the developer in the developing chamber 9 is agitated.
  • part of the developer 14 in the developing chamber 9 is pushed up onto the circulation guide portion 27a. This causes the developer 14 in the developing chamber 9 and the developer 14 on the circulation guide portion 27a to be partially interchanged, thereby releasing the clumped state of the developer 14.
  • the circulation velocity of the developer 14 in a region of the toner adding circulation from the arrow A to the arrow B is not changed depending on a time period for which the developer 14 is left to stand.
  • Fig. 32 illustrates the results of the difference in image density before and after leaving to stand for six hours after a horizontal line image of a printing ratio of 1% has been printed on 3000 sheets with the structures according to the eighth and ninth embodiments.
  • the difference in image density here is the difference in density between the left and light of a halftone image of a printing ratio of 50% printed after an image the printing ratio of which is 0% on the left side of the center of the image and 100% on the right side of the center of the image has been printed on three sheets.
  • the image density unevenness occurred with the eighth embodiment and does not occur with the ninth embodiment after leaving to stand for six hours.
  • the developer 14 in the developing chamber 9 having been left to stand for a long time clumps and is unlikely to move.
  • a force that is received by the developer in the adding circulation from the developer in the developing chamber 9 is increased at the position of the toner adding circulation from the arrow A to the arrow B that serves as the connecting portion where the developing chamber 9 and the adding circulation are connected to each other, thereby reducing the circulation velocity.
  • a sufficient amount of the toner is not added in time.
  • the adding circulation becomes non-uniform in the longitudinal direction by the effects of the toner clump. This causes the image density unevenness.
  • the circulation velocity of the developer 14 in the region of the toner adding circulation from the arrow A to the arrow B is not changed depending on a time period for which the developer 14 is left to stand. Furthermore, since the direction changing portion 30 is provided, the toner adding circulation is uniform in the longitudinal direction. Thus, the image density unevenness does not occur even when the developer 14 is left to stand for a long time.
  • the agitating member 29 In order to agitate the developer 14 while the developing chamber 9 is filled with the developer 14, the agitating member 29 has the rhombus shape. In a state in which the developing chamber 9 is filled with the developer 14, the developer 14 existing in a region away from the agitating radius may be unlikely to move even when the agitating member 29 is rotated.
  • Fig. 33A illustrates a flat plate-shaped agitating structure uniformly formed in the longitudinal direction.
  • a force Fa received by the developer 14 is in the same direction as that of a dotted arrow ga indicating the rotational direction of an agitating member.
  • the developer 14 within the agitating radius is constantly moved so as to follow the agitation, and accordingly, the developer 14 outside the agitating radius cannot be agitated.
  • Fig. 33B is a schematic view of the structure of the agitating member 29 in the structure according to the ninth embodiment.
  • the agitating member 29 has a central axis 29a and an agitating portion 29b.
  • the central axis 29a is parallel to the rotational axis of the developing sleeve 16.
  • the agitating portion 29b has inclined surfaces 29X that connect first positions 291 separated from the central axis 29a by a first specified distance and second positions 292 separated from the central axis 29a by a second distance y greater than the first specified distance x to one another on the arrow R3 side.
  • the arrow R3 indicates a rotational direction.
  • the agitating member 29 is rotated in the same direction as that of the developing sleeve 16.
  • the agitating member 29 has the rhombus shape.
  • the developer 14 that is brought into contact with the agitating member 29 receives a force Fb which is directed at an angle ⁇ relative to the dotted arrow gb indicating the rotational direction of agitation at a contact position where the developer 14 is brought into contact with the agitating member 29.
  • the developer 14 agitated by the agitating member 29 is conveyed to the outside of the radius of rotation of the agitating member 29.
  • the developer 14 having been conveyed can convey the developer 14 outside the agitating radius.
  • the developer 14 in the developing chamber 9 can be agitated.
  • the agitating member 29 that agitates the developer 14 in the developing chamber 9 and the direction changing portion 30 the toner 12 can be stably added even after the toner 12 is left to stand for a long time, and accordingly, the occurrence of the image density unevenness can be prevented.
  • Fig. 34 illustrates a variant of the developing chamber 9 according to the ninth embodiment.
  • the circulation guide portion 27a, the steep inclination portion 27b, and the direction changing portion 30 may be continuous with one another so as to form a curved shape convex toward the toner chamber 10 side.
  • the dotted line in contact with the steep inclination portion 27b and the direction changing portion 30 represents the shapes of the steep inclination portion 27b and the direction changing portion 30 according to the ninth embodiment.
  • the effects that is the same as or similar to those obtained with the structure of the ninth embodiment can also be obtained with the structure as illustrated in Fig. 34.
  • the toner concentration in the developer can be automatically controlled to a specified range.
  • the cartridge in which the developing chamber and the toner chamber are integrated with each other is used for the eighth and ninth embodiments, this is not limiting.
  • the toner chamber can be made to be a toner cartridge that is an attachable and detachable cartridge separated from the cartridge.
  • the structure of the agitating member 29 according to the ninth embodiment can also be applied to the structure according to the eighth embodiment.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)

Abstract

L'invention vise à supprimer la réduction de densité d'image se produisant lorsqu'une image d'un rapport d'impression élevé est imprimée sur de nombreuses feuilles. Une concentration de toner dans une chambre de développement modifiée en ajoutant du toner à un développeur par la circulation en rotation d'une particule magnétique peut être ajustée à une plage spécifiée à l'aide d'un élément de régulation qui régule le mouvement de la particule magnétique.
PCT/JP2015/003673 2014-07-29 2015-07-22 Dispositif de développement, cartouche de traitement et appareil de formation d'image WO2016017115A1 (fr)

Applications Claiming Priority (10)

Application Number Priority Date Filing Date Title
JP2014154305 2014-07-29
JP2014-154305 2014-07-29
JP2014-167557 2014-08-20
JP2014167557 2014-08-20
JP2014190118 2014-09-18
JP2014-190118 2014-09-18
JP2014-196307 2014-09-26
JP2014196307 2014-09-26
JP2015135911A JP2016066056A (ja) 2014-07-29 2015-07-07 現像装置、プロセスカートリッジ及び画像形成装置
JP2015-135911 2015-07-07

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WO2016017115A1 true WO2016017115A1 (fr) 2016-02-04

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02114284A (ja) * 1988-10-24 1990-04-26 Konica Corp 現像装置
JPH02135474A (ja) * 1988-11-17 1990-05-24 Canon Inc 現像装置
JP2002062719A (ja) * 2000-08-16 2002-02-28 Canon Inc 現像装置、プロセスカートリッジ及び画像形成装置
JP2006018210A (ja) * 2004-06-04 2006-01-19 Ricoh Co Ltd 現像装置、プロセスカートリッジ、及び画像形成装置
JP2011257693A (ja) * 2010-06-11 2011-12-22 Sharp Corp 画像形成装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02114284A (ja) * 1988-10-24 1990-04-26 Konica Corp 現像装置
JPH02135474A (ja) * 1988-11-17 1990-05-24 Canon Inc 現像装置
JP2002062719A (ja) * 2000-08-16 2002-02-28 Canon Inc 現像装置、プロセスカートリッジ及び画像形成装置
JP2006018210A (ja) * 2004-06-04 2006-01-19 Ricoh Co Ltd 現像装置、プロセスカートリッジ、及び画像形成装置
JP2011257693A (ja) * 2010-06-11 2011-12-22 Sharp Corp 画像形成装置

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