JP2010190987A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of extending its service life without any image defects. <P>SOLUTION: A multipolar permanent magnet 45 is rotatably arranged such that a developer conveying magnetic pole S2 of a developer carrier 44 passes through a regulation member 46 when an image is not formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic system, and more particularly, to an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine having a plurality of these functions.

  Conventionally, as shown in FIG. 6, an image forming apparatus using an electrophotographic system uniformly charges a surface of a photoreceptor 1 generally in the form of a drum as an image carrier with a charger 2 and charges the surface. The exposed photoreceptor 1 is exposed according to image information by the exposure device 3 to form an electrostatic latent image on the photoreceptor 1.

  The electrostatic latent image formed on the photosensitive member 1 is visualized with a toner in the developer using the developing device 4. The visualized image is transferred to the sheet by the transfer device 5. Thereafter, the toner image transferred onto the sheet is fused and fixed onto the sheet by heat and pressure by the fixing device 6.

  After the transfer process, the toner remaining on the photosensitive member 1 is removed by the cleaning device 7, and the charge remaining on the photosensitive drum 1 is removed by the charge eliminating device 8, whereby the photosensitive member 1 is ready for the next image forming process.

  As the developing device 4, for example, there is a device using a two-component developer including non-magnetic toner particles (toner) and magnetic carrier particles (carrier) as a developer as in Patent Document 1. In particular, in color image forming apparatuses, it is not necessary to include a magnetic substance in the toner, so that it is widely used for reasons such as good color.

  For example, as shown in FIGS. 7 and 8, the developing device 4 that uses a two-component developer has a developing container 41 that contains the developer, and the developing container 41 is separated from the developing chamber by a partition wall 41c that extends in the vertical direction. It is divided into 41a and stirring chamber 41b. A first developer transport stirring member 42 and a second developer transport stirring member 43 are provided in the developing chamber 41a and the stirring chamber 41b, respectively.

  Further, developer conveying paths 41d and 41e for delivering the developer between the developing chamber 41a and the stirring chamber 41b are provided at the longitudinal end of the partition wall 41c. The first and second developer conveying and stirring members 42 and 43 circulate the developer in the developing container 41 while stirring the developer.

  A developing sleeve 44 as a developer carrying member is rotatably disposed at a position facing the photosensitive drum 1 of the developing container 41. The developing sleeve 44 incorporates a magnet as magnetic field generating means.

  The magnet of the developing device 4 has a configuration with three or more poles. The developer stirred by the first developer transport stirring member 42 is restrained by the magnetic force of the transport magnetic pole (pumping pole) N2 for pumping, and transported to the developer reservoir 48 by the rotation of the developing sleeve 44. .

  The amount of the developer is restricted by the developer return member 47, and is sufficiently restrained by the transport magnetic pole (cut pole) S2 having a magnetic flux density of a certain level or more in order to restrain the stable developer, and magnetically. It is conveyed while forming a brush.

  Next, the amount of the developer is optimized by cutting off the magnetic spikes by the regulating blade 46, conveyed by the conveying magnetic pole N1, conveyed to the portion facing the photoreceptor 1, and developed by the developing pole S1. To be served.

  In the opposed portion, only the toner is transferred to the electrostatic latent image formed on the surface of the photosensitive member 1 by the developing bias applied to the developing sleeve 44, and the toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive member 1. Is formed.

JP 2001-83784 A

  However, in the conventional example, the developer reservoir 48 has a portion where the flow of the developer is blocked by the regulating blade 46, and a portion where the developer is conveyed at a substantially equal speed following the rotation speed of the developing sleeve 44. And a shear plane occurs at the boundary.

  Due to the difference in flow on the shear plane, the toner is liberated and a soft toner layer is generated. When this toner layer grows, the gap between the regulating blade 46 and the developing sleeve 44 is obstructed.

  As a result, when the toner layer grows, the coating amount of the developer on the developing sleeve 44 is smaller than in other places, and the density of the image is reduced. In view of this, there is a situation in which the long life of the image forming apparatus cannot be achieved because the change is made by changing the developer or the developing device.

  The technical problem of the present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus that is free from image defects and can achieve a long life.

  In order to achieve the above object, a typical configuration according to the present invention includes an image carrier, a rotatable developer carrier that carries a developer and develops a latent image formed on the image carrier, and In an image forming apparatus, comprising: a magnetic member provided in a developer carrying member, wherein a plurality of magnetic poles are rotatably arranged; and a regulating member that regulates the amount of the developer carried on the developer carrying member. A driving means for rotating the magnetic member; and at the time of image formation, the magnetic member is stopped so as to be at a predetermined rotational position, and at the time of non-image formation, at least the regulating member is opposed to the plurality of magnetic poles. And a controller for controlling the driving of the driving means so that one of the magnetic poles adjacent to the opposing position passes through the regulating member.

  According to the present invention, it is possible to obtain an image forming apparatus having a long lifetime in which image defects such as low density and overflow of developer do not occur.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment of the present invention. It is explanatory drawing of the image development apparatus of the image forming apparatus shown in FIG. It is a timing chart of magnet rotation of a 1st embodiment. It is sectional drawing which shows magnetic pole arrangement | positioning when rotating the magnet of 1st Embodiment. It is a timing chart of magnet rotation of a 2nd embodiment. It is sectional drawing of the conventional image forming apparatus. It is explanatory drawing of the image development apparatus of the image forming apparatus shown in FIG. It is explanatory drawing of the other conventional developing apparatus.

[Embodiment 1]
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of the image forming apparatus.

  The image forming apparatus shown in FIG. 1 generates four-color full-color images of yellow (Y), magenta (M), cyan (C), and black (K) according to image information from a document reading device or a host device such as a personal computer. It forms on a sheet | seat using an electrophotographic system.

  The image forming apparatus also includes first, second, third, and fourth image forming units PY, PM, PC, and PBk that form yellow, magenta, cyan, and black images, respectively, as a plurality of image forming units. Have.

  Here, the configurations of the image forming units PY, PM, PC, and PBk are substantially the same except that the development colors are different. Therefore, in the following, when there is no particular need to distinguish, the subscripts Y, M, C, and Bk given to the reference numerals to indicate that they belong to any of the image forming units PY, PM, PC, and PBk are omitted. And will be described in a comprehensive manner.

  The image forming unit P includes a drum-shaped photoreceptor 1 as an image carrier. Around the outer periphery of the photoreceptor 1, there are a charger 2 as a charging means, a laser exposure optical system 3 as an exposure means, a developing device 4 as a developing means, a transfer device 5 as a transferring means, and a cleaning device 7 as a cleaning means. A static elimination device 8 is provided as a static elimination means.

  The transfer device 5 has an intermediate transfer belt 51 as an intermediate transfer member. The intermediate transfer belt 51 is wound around a plurality of rollers and rotates (circulates) in the direction of the arrow in the drawing. A primary transfer member 52 is disposed at a position facing each photoconductor 1 via the intermediate transfer belt 51. A secondary transfer member 53 is provided at a position facing one of the rollers around which the intermediate transfer belt 51 is wound.

  While the intermediate transfer belt 51 moves in the direction indicated by the arrow and passes through the image forming portion P, the images of the respective colors of the image forming portions P are superimposed on the intermediate transfer belt 51. A recorded image is obtained by transferring the multiple toner images superimposed on the intermediate transfer member 51 onto a sheet.

  That is, at the time of image formation, the charger 2 uniformly charges the surface of the rotating photoreceptor 1. Next, an electrostatic image (latent image) is formed on the photosensitive member 1 by scanning and exposing the surface of the charged photosensitive member 1 according to an image information signal by the laser exposure optical system 3.

  The electrostatic image formed on the photosensitive member 1 is visualized as a toner image with the developer toner using the developing device 4. At that time, the replenisher is supplied from the hopper 20 to the developing device 4 in accordance with the amount of consumed toner.

  The toner image formed on the photoreceptor 1 is intermediated by the action of the primary transfer bias applied to the primary transfer member 52 in the primary transfer portion (primary transfer nip) where the intermediate transfer belt 51 and the photoreceptor 1 abut. Transfer (primary transfer) is performed on the transfer belt 51.

  For example, when a four-color full-color image is formed, a toner image is sequentially transferred from each photoconductor 1 onto the intermediate transfer belt 51 from the image forming unit PY, and the four-color toner images are superimposed on the intermediate transfer belt 51. A toner image is formed.

  The toner image on the intermediate transfer belt 51 is transferred to the secondary transfer portion (nip portion) where the intermediate transfer belt 51 and the secondary transfer member 53 come into contact with each other. It is transported in synchronization.

  Then, the multiple toner images on the intermediate transfer belt 51 are transferred onto the sheet by the action of the secondary transfer bias applied to the secondary transfer member 53 in the secondary transfer portion.

  Thereafter, the sheet separated from the intermediate transfer belt 51 is conveyed to the fixing device 6. The toner image transferred onto the sheet is melted and mixed by being heated and pressed by the fixing device 6 and fixed on the sheet.

  Thereafter, the sheet is discharged out of the machine. Deposits such as toner remaining on the photoreceptor 1 after the primary transfer step are collected by the cleaning device 7. Further, the electrostatic image remaining on the photosensitive member 1 is erased by the static eliminator 8.

  Thus, the photoreceptor 1 is ready for the next image forming process. Further, deposits such as toner remaining on the intermediate transfer belt 51 after the secondary transfer step are removed by the intermediate transfer body cleaner 54.

  Next, the two-component developer will be described. The toner includes colored resin particles containing a binder resin, a colorant, and other additives as necessary, and colored particles to which an external additive such as colloidal silica fine powder is externally added. The toner is a negatively chargeable polyester resin, and the volume average particle diameter is preferably 5 μm or more and 8 μm or less. In this embodiment, it was 7.0 μm.

  As the carrier, for example, surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium, rare earth and other metals, alloys thereof, oxide ferrite, etc. are preferably usable. The method for producing magnetic particles is not particularly limited.

The carrier has a volume average particle size of 20 to 50 μm, preferably 30 to 40 μm, and a resistivity of 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm or more. In this embodiment, a carrier having a volume average particle diameter of 40 μm, a resistivity of 5 × 10 ⁷ Ωcm, and a magnetization amount of 260 emu / cc is used. For the toner, the volume average particle diameter was measured by the following apparatus and method.

  As a measuring apparatus, a Coulter counter TA-2 type (manufactured by Coulter), an interface for outputting number average distribution and volume average distribution (manufactured by Nikka) and a CX-I personal computer (manufactured by Canon) were used. A 1% NaCl aqueous solution prepared using primary sodium chloride was used as the electric field aqueous solution.

  The measuring method is as follows. That is, 0.1 ml of a surfactant, preferably alkyl benzene sulfonate, is added as a dispersant to 100 to 150 ml of the above electric field aqueous solution, and 0.5 to 50 mg of a measurement sample is added.

  The electric field aqueous solution in which the sample is suspended is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the particle size distribution of 2 to 40 μm particles is measured using the above-mentioned Coulter counter TA-2 type with an aperture of 100 μm. To obtain a volume average distribution. The volume average particle diameter is obtained from the volume average distribution thus obtained.

  The carrier resistivity is measured by applying a voltage E (V / cm) between the two electrodes under a pressure of 1 kg using one sandwich electrode with a measuring electrode area of 4 cm and a distance between electrodes of 0.4 cm. Then, the measurement was performed by a method of obtaining the carrier resistivity from the current flowing in the circuit.

  Next, FIG. 2 shows an explanatory view of the vicinity of the developer reservoir of the developing device. In FIG. 2, a developing sleeve 44, which is a developer carrier, is provided with a multi-pole permanent magnet magnet 45, which is a rotatable magnetic member having a plurality of magnetic poles. The developer conveying speed in the vicinity of the developing sleeve 44 and the developer conveying speed in the developer reservoir 48 near the regulating blade (regulating member) 46 that regulates the amount of developer carried on the developing sleeve 44 are significantly different. A shear plane is formed.

  Due to the difference in flow on the shear plane, the toner is liberated and a soft toner layer is generated. When this toner layer grows, the gap between the regulating blade 46 and the developing sleeve 44 is obstructed. As a result, when the toner layer grows, the coating amount of the developer on the developing sleeve 44 is smaller than in other places, and the density of the image is reduced.

  Therefore, the magnet 45 is rotated so that the conveying magnetic pole (cut pole) S2 passes through the regulating blade 46. The toner layer is passed between the regulating blade 46 and the developing sleeve 44 by the magnet 45, and the toner layer is loosened by physical contact of the portion. Thereby, a decrease in the coating amount of the developer can be prevented.

  Further, the portion where the magnetic brush of the developer stands perpendicular to the developing sleeve 44, that is, the toner that comes into contact most when the peak position of the magnetic flux density of the conveying magnetic pole S2 passes through the regulating blade 46 through the magnet 45. Easy to loosen layers. Therefore, it is preferable to rotate the magnet 45 until the half value on the upstream side in the rotation direction of the developing sleeve 44 of the magnetic flux density of the conveying magnetic pole S2 passes through the regulating blade 46.

  Next, the rotation timing of the magnet 45 is shown in the timing chart of FIG. Further, FIG. 4 shows the magnetic pole arrangement during rotation of the magnet. After the image formation is finished, after the application of the development bias AC and the development bias DC is stopped, the magnet rotation signal for turning the magnet 45 is turned on while the development sleeve 44 is rotated, and the magnet 45 is turned until the next development bias DC is applied. Turn off the rotation signal. As a result, the toner layer generated on the back of the regulating blade 46 can be discharged.

  Here, when rotating the magnet 45, a clutch mechanism (not shown) controlled by a controller was used. This clutch mechanism is a so-called one-way clutch mechanism, and when the clutch gear is rotated in a certain direction (forward rotation direction) by the drive gear (output gear), a driving force is transmitted from the clutch gear according to the pressing contact to the mechanical clutch.

  As a result, the clutch spring is tightened and the rotating shaft (transmission shaft) rotates. And the magnet 45 attached to the rotating shaft rotates. When the protrusion provided on the outer peripheral surface of the mechanical clutch is locked by the solenoid switching claw (lever), the rotation of the clutch is stopped and the force for tightening the clutch spring is lost.

  As a result, the clutch spring is loosened and the rotation of the rotating shaft is stopped. In the present embodiment, the angle between the regulating blade 46 and the conveying magnetic pole S2 is 10 °, the rotation angle is 15 °, and the magnet 45 is rotated.

  Thus, in the present embodiment, the magnet 45 is stopped so as to be at a predetermined rotational position during image formation. Then, at the time of non-image formation, the magnet 45 is rotated so that one of the magnetic poles adjacent to the facing position facing the regulating blade 46 passes through the regulating blade 46, thereby loosening the toner layer. As a result, the long-life developing device 4 in which image defects such as low density and overflow of the agent do not occur can be obtained.

[Embodiment 2]
In this embodiment, a developing device that rotates only the magnet 45 to loosen the toner layer will be described. Note that the developing device and the developer in the present embodiment have the same configurations as those in the first embodiment.

  In the image forming apparatus according to the first embodiment, when the magnet 45 and the developing sleeve 44 are rotated in synchronization, the load applied between the regulating blade 46 and the developing sleeve 44 is reduced as the conveying magnetic pole S2 approaches the regulating blade 46. . If the gap between the regulating blade 46 and the developing sleeve 44 is the same, the developer coating amount on the developing sleeve 44 may increase.

  In such a case, the developer transport amount increases and the amount of coating on the developing sleeve 44 increases, so that the developer rushes into the vicinity of the photoreceptor 1 and the developing sleeve 44 one after another. There is a possibility that the developer is clogged and the developer overflows.

  Therefore, in the present embodiment, after the image formation is completed, the development bias AC application is stopped, the development sleeve 44 is stopped, the development bias DC application is stopped, and then the magnet rotation signal for turning the magnet 45 is turned ON. Then, the magnet rotation signal for turning the magnet 45 is turned off until the next development bias DC is applied. The timing chart is shown in FIG.

  Although the magnet 45 is rotated after the development sleeve 44 is stopped, the developer moves only by the rotation angle of the magnet 45 by rotating only the magnet 45. Further, the developer does not enter one after another in the vicinity of the photosensitive member 1 and the developing sleeve 44, so that the overflow of the developer can be prevented.

  As described above, in the present embodiment, when the developing sleeve 44 is stopped, the magnet 45 is rotated to loosen the toner layer, thereby obtaining a long-life image forming apparatus in which image defects such as low density and overflow of the developer do not occur.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to description of the said embodiment, In the range which does not deviate from the mind of the invention described in the claim of this invention Various changes can be made.

  For example, the material of the photoreceptor 1, the developer, the configuration of the image forming apparatus, and the like are not limited to these, and it is needless to say that the present invention can be applied to various developers and image forming apparatuses.

  Specifically, the color and number of toners, the order in which toner development of each color is performed, the rotation method of the magnet 45, the rotation angle, the number of rotations, the number of developing sleeves 44, etc. are not limited to the present embodiment.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Laser exposure optical system 4 Developing apparatus
20 hopper
41 Developer container
41a Development chamber
41b Mixing chamber
41c Bulkhead
41d, 41e Developer transport path
42 First developer transport stirring member
43 Second developer transport stirring member
44 Development sleeve
45 Magnet
46 Regulatory blade
48 Developer reservoir

Claims (5)

An image carrier, a rotatable developer carrier that carries a developer and develops a latent image formed on the image carrier, and a plurality of magnetic poles that are provided in the developer carrier and are rotatable. In an image forming apparatus comprising: a magnetic member disposed; and a regulating member that regulates the amount of the developer carried on the developer carrying member.
Driving means for rotating the magnetic member, and at the time of image formation, the magnetic member is stopped so as to be at a predetermined rotation position, and at the time of non-image formation, at least the opposing of the plurality of magnetic poles facing the regulating member An image forming apparatus comprising: a controller that controls driving of the driving unit so that one of magnetic poles adjacent to the position passes through the regulating member. 2. The image according to claim 1, wherein the magnetic member is rotated until at least a peak position of a magnetic flux density formed by an upstream magnetic pole in a rotation direction of the developer carrier passes through the regulating member. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the rotation timing of the magnetic member is when the developer carrying member is not driven. The image forming apparatus according to claim 1, wherein the rotation timing of the magnetic member is when application of a developing bias is stopped. The image forming apparatus according to claim 1, wherein the image carrier is not rotated when the magnetic member is rotated.

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