JP2013025231A - Development device, process cartridge, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fastening of a toner to a seal member caused by an electric field generated between a developing roller and the seal member and thereby prevent an abnormal image and in-machine contamination due to toner fall.SOLUTION: In a development device, a seal member 70 that is attached to a developer container and extends to the vicinity of a development nip portion between a developing roller 61 and a photoreceptor includes: an insulator sheet 71 positioned on the developer container side; and a conductor sheet 72 positioned on the developing roller 61 side. The conductor sheet 72 and the developing roller 61 are connected by a conductor so as to have equal electric potentials, or electric potentials of the conductor sheet 72 and the developing roller 61 are set so that a scattered tonner is drawn to the developing roller 61 side by an electric field generated between the conductor sheet 72 and the developing roller 61.

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, a process cartridge provided with the developing device, and these image forming apparatuses.

  2. Description of the Related Art Conventionally, various toner scattering prevention measures have been taken in an electrophotographic image forming apparatus using a developer having powdered toner and a carrier. In particular, there are various measures for preventing toner scattering around the developing roller in the developing device. In order to prevent the toner released from the developing roller from scattering outside the developing device, an insulator seal around the developing roller is provided. Measures such as providing a member or generating an airflow are known.

  Of such measures for preventing toner scattering, a configuration is widely used in which the developing roller is covered with a seal member in the longitudinal direction and the seal member is abutted against a photoconductor disposed to face the developing roller. In such a configuration, generally, the portion of the developing roller exposed from the developing container is covered with an arc-shaped member of the developing container, and an insulating seal member such as a urethane sheet is attached to the tip thereof, and this is attached to the photosensitive member. The approaching method is used.

  However, the arc-shaped member and the urethane sheet are charged by friction with the toner, and the toner adheres to them. The adhered toner may suddenly fall due to its own weight or impact, resulting in a toner drop image or internal contamination.

  With respect to such a problem, in Patent Document 1, a seal member is provided on an arc-shaped member of a developing container that covers the developing roller, the developing roller side of the sealing member is formed of a conductive member, and this is grounded to cause friction. Charge accumulation on the seal member is prevented, and adhesion of toner to the seal member is suppressed.

  However, if a ground plane is provided in the vicinity of the developing roller, an electric field is generated due to a potential difference between the ground plane and the developing roller. Therefore, even if there is no charge accumulation on the ground plane, toner adheres to the ground plane due to the influence of the electric field. The problem arises.

This will be described more specifically with reference to schematic perspective views of the developing device shown in FIGS.
For example, as shown in FIG. 5, the exposed portion of the developing roller 61 from the developer container that holds the developer is covered with side seals 62 and 63 at the front and back portions in the drawing, and the upper portion in the drawing is sealed. A support member 64 and a seal 65 located below the support member 64 are covered. In the lower part of the seal 65, the developing roller 61 is exposed from the developing container.

  In FIG. 6, the developing roller facing surface 80 of the seal 65 positioned below the seal support member 64 is grounded. On the other hand, when negatively charged toner is used, since the developing roller 61 is generally set at a negative potential, an electric field is generated near the developing roller 61 from the ground surface 80 toward the developing roller 61 as indicated by an arrow in the figure. As a result, the negatively charged toner receives a force from the developing roller 61 toward the ground surface 80 and adheres to the ground surface 80. Therefore, there still remains a problem that the adhered toner suddenly falls due to its own weight, impact, or the like, and a toner drop image or in-machine contamination occurs.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a developing device and a process cartridge that can prevent toner from adhering to the seal member due to an electric field generated between the developing roller and the seal member, and thus prevent abnormal images and in-machine contamination due to toner dropping. An object of the present invention is to provide an image forming apparatus.

  In order to achieve this object, the developing device of the present invention includes a developer container that holds a developer, a developer transport member that transports the developer, a developer supported on the surface, and rotates so as to face each other. A developer carrier for supplying toner to the image carrier, and a seal member attached to the developer container and extending to the vicinity of the developing nip portion between the developer carrier and the image carrier. The seal member includes an insulating member located on the developer container side and a conductive member located on the developer carrier, so that the conductive member and the developer carrier are at the same potential. The electric potential of the conductive member and the developer carrier is such that the scattered toner is attracted to the developer carrier by the electric field generated between the conductive member and the developer carrier. It is characterized by being set.

  According to the present invention, since the seal member and the developer carrying member are at the same potential, an electric field that attracts scattered toner to the seal member is not generated between the seal member and the developer carrying member, and the toner seal member is thus formed. Abnormal images and internal contamination due to toner sticking and toner drop associated therewith are suppressed. Alternatively, the scattered toner is attracted to the developer carrier side by an electric field generated between the seal member and the developer carrier.

1 is a schematic view of a color image forming apparatus according to the present invention. 1 is a schematic perspective view of a developing device according to the present invention. 1 is a schematic cross-sectional view of a developing device according to the present invention. It is an expanded sectional view of the vicinity of a developing roller and a seal support member. It is a schematic perspective view of the conventional developing device. It is an expanded sectional view of the vicinity of a conventional developing roller and a seal support member.

FIG. 1 schematically shows an example of a color image forming apparatus 1. First, the image forming apparatus 1 will be described.
In the color image forming apparatus 1, the apparatus main body 100 is placed on a paper feed table 200 as illustrated. A scanner 300 is mounted on the apparatus main body 100, and an automatic document feeder (ADF) 400 is mounted thereon. In the apparatus main body 100, a transfer device having an intermediate transfer belt 10 which is a belt-like endless moving member is provided in the approximate center, and the intermediate transfer belt 10 is provided between a driving roller 14 and two driven rollers 15 and 16. 1 so as to rotate clockwise in FIG.

  The intermediate transfer belt 10 is configured so that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15. Yellow (Y), magenta (M), and cyan along the direction of movement of the intermediate transfer belt 10 above the linear portion spanned between the driving roller 14 and the driven roller 15 of the intermediate transfer belt 10. (D) Four drum-shaped photoconductors 40Y, 40M, 40C, and 40Bk (hereinafter simply referred to as photoconductors 40 if not specified) of black (Bk) are arranged at predetermined intervals. . Four primary transfer rollers 58 are provided inside the intermediate transfer belt 10 so as to sandwich the intermediate transfer belt 10 so as to face the respective photoreceptors 40.

Each of the four photoconductors 40 as image carriers can be rotated counterclockwise in FIG. 1, and around each photoconductor 40 is a charging device, a developing device 60, and the above-described primary transfer. A roller 58, a photoconductor cleaning device, and a charge eliminating device are provided, and each constitutes an image forming unit 18. A common exposure device 21 is provided above the four image forming units 18.
Each image (toner image) formed on each photoconductor is successively transferred onto the intermediate transfer belt 10 in a superimposed manner.

  On the other hand, on the lower side of the intermediate transfer belt 10, a secondary transfer device 22 including a transfer unit that transfers an image on the intermediate transfer belt 10 to a sheet as recording paper is provided. The secondary transfer device 22 has a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, 23, and the secondary transfer belt 24 is driven by the driven roller 16 via the intermediate transfer belt 10. It comes to be pressed against.

The secondary transfer device 22 collectively transfers the toner images on the intermediate transfer belt 10 onto a sheet fed between the secondary transfer belt 24 and the intermediate transfer belt 10.
A fixing device 25 that fixes the toner image on the sheet P is disposed downstream of the secondary transfer device 22 in the sheet conveying direction. A pressure roller 27 is pressed against the fixing belt 26 that is an endless belt. Yes.

  The secondary transfer device 22 also functions to convey the sheet after image transfer to the fixing device 25. Further, the secondary transfer device 22 may be a transfer device using a transfer roller or a non-contact charger. A sheet reversing device 28 is provided below the secondary transfer device 22 for reversing the sheet when images are formed on both sides of the sheet.

As described above, the apparatus main body 100 constitutes an indirect transfer tandem color image forming apparatus 1.
When color copying is performed by the color image forming apparatus 1, a document is set on the document table 30 of the automatic document feeder 400. When the document is manually set, the automatic document feeder 400 is opened, the document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.

  When a start key (not shown) is pressed, when the document is set on the automatic document feeder 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner 3 is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

  Further, when the start key is pressed, the intermediate transfer belt 10 starts to rotate. At the same time, the photoconductors 40Y, 40M, 40C, and 40K start rotating, and yellow (Y), magenta (M), cyan (C), and black (Bk) single color toners are formed on the photoconductors. The operation for forming an image is started. The toner images of the respective colors formed on the respective photoreceptors are sequentially transferred while being superimposed on the intermediate transfer belt 10 that rotates clockwise in FIG. 1, and a full-color composite color image is formed there. Is done.

  On the other hand, when the start key is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the sheet is fed out from one selected paper feed cassette 44 in the paper bank 43. Then, it is separated into one sheet by the separation roller 45 and conveyed to the sheet feed path 46. The sheet is conveyed by a conveying roller 47 to a sheet feeding path 48 in the apparatus main body 1, hits a registration roller 49 and temporarily stops.

  In the case of manual sheet feeding, the sheet set on the manual tray 51 is fed by the rotation of the sheet feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual sheet feeding path 53. Then, it hits the registration roller 49 and temporarily stops.

  The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 10, and feeds the temporarily stopped sheet between the intermediate transfer belt 10 and the secondary transfer device 22. . Then, a color image is transferred onto the sheet by the secondary transfer device 22.

  The sheet on which the color image has been transferred is conveyed to a fixing device 25 by a secondary transfer device 22 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. Thereafter, the sheet is guided to the discharge side by the switching claw 55, is discharged onto the discharge tray 57 by the discharge roller 56, and is stacked there.

  When the double-sided copy mode is selected, the sheet on which an image is formed on one side is conveyed to the sheet reversing device 28 side by the switching claw 55, reversed there and led to the transfer position again, and this time the image is formed on the back side. After that, the paper is discharged onto the paper discharge tray 57 by the discharge roller 56.

FIG. 2 is a schematic perspective view of the developing device 60 in the present invention.
On the side facing the photoconductor 40, the exposed portion of the developing roller 61 from the developing container is covered with the side seals 62 and 63 in the front portion and the back portion in the figure, and the upper portion in the figure is the seal support member 64 and below it It is covered with the sealing member 70 located in the. In the lower part of the seal member 70, the developing roller 61 is exposed from the developing container and faces the photoconductor 40.

FIG. 3 is a schematic sectional view of the developing device 60 according to the present invention.
As shown in FIG. 1, four developing devices 60 are arranged to face each photoconductor corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk). All developing devices have the same structure. The developer is a two-component developer having toner and a magnetic carrier, and is contained in a developing container of the developing device 60 (not shown).

Here, the flow of the developer and the developer regulating member 73 in the developing device 60 will be described with reference to FIG.
The developing device 60 includes a developing roller 61 as a developer carrying member. The developing roller 61 moves on the surface of the photosensitive member 40 facing the developing roller 61 while moving in the rotational direction I by a driving unit (not shown). It has a function of supplying toner to the latent image on the surface and developing it. Further, a supply screw 68 as a developer conveying member is provided. The supply screw 68 includes a rotation shaft and a wing portion provided on the rotation shaft, and is rotated in the rotation direction J by a driving unit (not shown). The developer is supplied to the developing roller 61 while conveying the developer in the direction, that is, the front side in FIG. A supply conveyance path 90 for supplying the developer to the developing roller 61 including the area of the supply screw 68 is disposed beside the developing roller 61.

  Further, a recovery screw 66 is provided further downstream in the rotation direction I of the developing roller 61 when viewed from the developing nip portion, which is the facing portion between the developing roller 61 and the photoreceptor 40. The recovery screw 66 is a developer conveying member that is rotated in a rotation direction K by a driving unit (not shown), collects the developed residual developer that has dropped through the developing nip portion, and supplies the collected recovered developer. The paper is conveyed from the back side of the paper in the same direction as the screw 68 to the near side. A recovery conveyance path 91 for the recovered developer including the area of the recovery screw 66 is disposed below the developing roller 61.

  Further, a stirring screw 67 is disposed on the left side of the recovery screw 66 in the drawing and below the supply screw 68. The stirring screw 67 is a developer conveying member that is rotated in the rotation direction L by a driving unit (not shown). While stirring the developer conveyed from the collecting screw 66, the stirring screw 67 is a paper surface that is in the opposite direction to the collecting screw 66. Transport from the near side to the far side. An agitation conveyance path 92 for agitating the developer including the area of the agitation screw 67 is provided on the left side of the collection conveyance path 91 in the drawing and below the supply conveyance path 90. When the developer is transported to the back side of the paper surface through the stirring transport path 92, the developer is transported upward and reaches the supply transport path 90. The developer that has not been supplied to the developing roller 61 is normally returned to the region of the stirring screw 67 when conveyed to the end of the supply screw. However, when the amount of the developer exceeds the capacity of the developing device 60, the excess developer is transferred to the developer discarding screw 69 and discharged outside the developing device.

  The supply conveyance path 90 and the agitation conveyance path 92 are partitioned by a first partition wall 93, but the first partition wall 93 is not provided at both ends of the front side and the back side in the figure, and thus openings are provided. The supply conveyance path 90 and the agitation conveyance path 92 communicate with each other, and the developer is conveyed through the supply conveyance path 90 and the agitation conveyance path 92. In addition, although the supply conveyance path 90 and the collection | recovery conveyance path 91 are also partitioned off by the 1st partition wall 93, the opening part is not provided.

  Further, the two conveyance paths of the agitation conveyance path 92 and the collection conveyance path 91 are partitioned by a second partition wall 94. The second partition wall 94 has an opening on the front side in the figure, and the agitation transport path 92 and the recovery transport path 91 are in communication.

  Residual developer after development is collected by the collection conveyance path 91, conveyed to the front side in the figure, and transferred to the agitation conveyance path 92 through the opening of the first partition wall 94 provided in the non-image area portion. Is done. In the vicinity of the opening of the first partition wall 94 on the upstream side of the developer conveyance direction in the agitating / conveying path 92, toner is replenished to the agitating / conveying path 92 from a toner replenishing port provided on the upper side of the agitating / conveying path 92. .

  Further, as viewed from the facing portion between the developing roller 61 and the supply screw 68, on the downstream side in the rotation direction I of the developing roller 61, the developer supplied from the supply screw 68 to the developing roller 61 has a thickness suitable for development. A developer regulating member 73 is provided for regulating the developer. The thickness of the developer on the developing roller 61 after passing the developer regulating member 73 is regulated and becomes a constant thickness.

  The developer regulating member 73 that is a doctor blade is mainly composed of a non-magnetic plate made of a long, substantially rectangular plate-like member, and a substantially rectangular plate-like member that is longer in size and smaller than the non-magnetic plate. And a magnetic plate. As the material of the nonmagnetic plate, for example, stainless steel SUS304, SUS316, or the like can be used. As a material of the magnetic plate, for example, a material such as SUS430 can be used. The magnetic plate is thinner than the non-magnetic plate. The non-magnetic plate has a thickness of, for example, 1 to 3 mm, and the magnetic plate has a thickness of, for example, 0.1 to 0.3 mm.

  The developer thinned by the stainless steel developer regulating member 73 on the developing roller 61 is conveyed to a developing region (developing nip portion) that is a portion facing the photosensitive member, and development is performed.

  The supply screw 68, the recovery screw 66, and the stirring screw 67, which are developer conveying members, are made of resin or metal screws, each screw diameter is φ22 mm, and the screw pitch is a double winding with a supply screw of 50 mm. The recovery screw 66 and the agitation screw 67 are a single winding of 25 mm, and the number of rotations is all set to about 700 rpm.

  Further, the seal support member 64 constituting the developing container of the developing device 60 extends from the outer periphery of the cylindrical developing roller 61 to the vicinity of the developing nip portion between the developing roller 61 and the photoconductor 40 at a certain interval. doing. A seal member 70 for preventing toner scattering before and after development is attached to a seal support member 64 of the developing container. The seal member 70 is supported on the inner side of the seal support member 64 and extends from the outer periphery of the developing roller 61 to the vicinity of the developing nip portion between the developing roller 61 and the photoconductor 40 at a certain interval. .

FIG. 4 is an enlarged cross-sectional view of the vicinity of the developing roller 61 and the seal support member 64.
Here, the seal member 70 has a two-layer structure of an insulator sheet 71 as an insulating member and a conductor sheet 72 as a conductive member. By imparting conductivity (charge) to the seal member on the developing roller 61 side, toner adhesion to the seal member is suppressed, and by making the seal member on the photoconductor 40 side non-conductive, the surface of the photoconductor Can be prevented from affecting the latent image. It is desirable to use a urethane sheet as the insulator sheet 71. Further, as the conductor sheet 72, it is desirable to use polyethylene terephthalate (PET) or conductive urethane sheet in which aluminum is deposited with the conductive surface facing the developing roller 61 side.

  By using aluminum vapor-deposited PET that can be easily installed along a curved surface, a potential can be applied to the opposing surface of the developing roller 61 easily and inexpensively. Further, by using a conductive member made of a urethane sheet that is difficult to adhere to or deteriorate, it is possible to prevent toner adhesion to the seal member more stably.

  The insulating sheet 71 is bonded to the whole or a part of the surface of the seal support member 64 facing the developing roller 61 with a double-sided tape or the like. The conductor sheet 72 is bonded on the insulator sheet 71 or on a part of the surface of the seal support member 64 facing the developing roller 61 with a double-sided tape or the like. Therefore, the insulator sheet 71 is located on the seal support member 64 side, and the conductor sheet 72 is located on the developing roller 61 side. At this time, one end of the conductor sheet 72 may be sandwiched between the developer regulating member 73 and the seal support member 64.

  The tip of the insulator sheet 71 is in contact with the photoreceptor 40, but the conductor sheet 72 is shorter than the insulator sheet 71 and the tip is not in contact with the photoreceptor 40. By abutting the insulator sheet 71 against the photoreceptor, it is possible to more effectively prevent toner scattering and toner dropping from the developing roller. Further, it is preferable that the conductor sheet 72 provided in a cylindrical shape is longer than the seal support member 64 and shorter than the insulator sheet 71 in the direction along the outer periphery of the developing roller 61.

  Here, one end of the conductor sheet 72 is in contact with the developer regulating member 73. On the other hand, the developer regulating member 73 is connected to the developing roller 61 by a conductor such as a heat sink 74 and a sheet metal member (not shown), and has the same potential as the developing roller 61. Therefore, the conductor sheet 72 is at the same potential as the developing roller 61. As a result, there is no potential difference between the developing roller 61 and the conductive sheet 72, and no electric field is generated, so that a force that attracts toner to the conductive sheet 72 side does not work. The developing roller 61 is connected to a bias circuit (not shown) provided in the main body of the image forming apparatus, and is supplied with power and given a potential.

  In this case, since the space between the conductor sheet 72 and the developing roller 61 has the same potential and no electric field is generated in the range where the conductor sheet 72 extends, the extension range of the conductor sheet 72 should be made as wide as possible. Is advantageous for preventing toner scattering.

  Instead, the potentials of the conductor sheet 72 and the developing roller 61 may be set so that the scattered toner is attracted to the developing roller 61 side by an electric field generated between the conductor sheet 72 and the developing roller 61. For example, in the case of negatively charged toner, if the developing roller 61 is set to −600 V and the conductive sheet 72 is set to −800 V or the like, an electric field from the developing roller 61 toward the conductive sheet 72 is generated. Since the negatively charged toner receives a force from the conductive sheet 72 toward the developing roller 61, the scattered toner is suppressed from adhering to the conductive sheet 72, the insulating sheet 71, and the seal support member 64, and is thus fixed. It is also possible to prevent the toner from dropping suddenly due to its own weight, impact, etc., and causing a toner drop image and in-machine contamination.

  In this case, the conductive sheet 72 and the developing roller 61 are not connected to each other by a conductor and set to the same potential, but the conductive sheet 72 and the developing roller 61 are provided in a separate bias circuit (not shown) provided in the image forming apparatus main body. And a desired potential may be applied to each.

  Further, in the present invention, the photosensitive member 40, the charging device disposed around each photosensitive member 40, the developing device 60, and the photosensitive member cleaning device may be unitized and housed in a case to form a process cartridge. . Each process cartridge is detachably attached to the image forming apparatus main body. By unitizing these devices as process cartridges, replacement and maintenance work can be facilitated, and the positional accuracy between the members can be maintained with high accuracy, thereby improving the quality of the formed image. be able to. In addition, the unitized process cartridge can suppress toner contamination and occurrence of abnormal images.

  There are various process cartridge configurations. For example, at least one of the charging device, the developing device 60, and the photoconductor cleaning device and the photoconductor 40 may be housed in a case to form a unit.

40 photoconductor (image carrier)
60 Developing Device 61 Developing Roller (Developer Carrier)
66 Recovery screw (developer transport member)
67 Stir screw (developer transport member)
68 Supply screw (developer transport member)
70 Seal member 71 Insulator sheet (insulation member)
72 Conductor sheet (conductive member)

Japanese Patent No. 4351542

Claims (7)

A developer container for holding the developer, a developer carrying member for carrying the developer, a developer carrying member that carries the developer on the surface, rotates, and supplies toner to the image carrier arranged oppositely; A developing device including a seal member attached to the developer container and extending to the vicinity of a developing nip portion between the developer carrier and the image carrier.
The seal member has an insulating member located on the developer container side and a conductive member located on the developer carrier side,
The conductive member and the developer carrier are connected by a conductor so as to have the same potential, or the scattered toner is attracted to the developer carrier by an electric field generated between the conductive member and the developer carrier. The developing device is characterized in that the electric potential of the conductive member and the developer carrying member is set.   The developing device according to claim 1, wherein the conductive member is made of polyethylene terephthalate deposited with aluminum.   The developing device according to claim 1, wherein the conductive member is made of a conductive urethane sheet.   The developing device according to claim 1, wherein the insulating member of the seal member is in contact with the image carrier. The insulating member is bonded to a seal support member constituting the developer container,
5. The development according to claim 1, wherein the conductive member is longer than the seal support member and shorter than the insulating member in a direction along an outer periphery of the developer carrying member. apparatus.   A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the developing device according to claim 1.

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