JP2006259013A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that can collect toner particles from on an electrostatic carrying member moving the toner particles with a phase shifting electric field and uniformly supply toner, and also to provide a process cartridge, and an image forming apparatus. <P>SOLUTION: The developing device 41 is equipped with: an electrostatic carrying roller 42 which moves toner particles as powder with the phase shifting electric field to develop an electrostatic latent image on an image carrier 21; a storage section 43 which stores the toner particles etc.; a supply roller 44 constituting a supply means of supplying toner particles from the storage section 43 to the electrostatic carrying roller 42; and a collecting means 45 of collecting toner moved by the electrostatic carrying roller 42. The collecting means 45 is equipped with a metal plate 451 which is applied with a bias voltage VB1 by a bias power source 452 with the opposite polarity from the toner particles within a range from a development region of the electrostatic carrying roller 42 to a toner supply region to which the toner is supplied by the supply roller 44 and then electrostatically attracts the toner particles to collect them before they are supplied to the development region again. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus, and more particularly, to a developing device, a process cartridge, and an image forming apparatus that transfer powder by a traveling wave electric field.

  As various image forming apparatuses such as printers, facsimiles, copying machines, plotters, printer / fax / copier multifunction machines, etc., the image carrier is charged to form an electrostatic latent image, and the electrostatic latent image is colored. There is known an image forming apparatus using an electrophotographic process in which a powder (hereinafter referred to as “toner particles”) is applied and developed, and a toner image is transferred to a recording medium.

In such an image forming apparatus, as a developing device for developing a latent image, as described in Patent Document 1, the energy of a phase-shifting electric field is applied to toner particles that are powders, so that A developing device that moves toner particles horizontally and vertically on the surface is known. In such a developing device, the toner particles are transferred to a developing area which is a facing portion between the image carrier and the developing device by a phase-shift electric field, and adhere to an image portion of a latent image on the image carrier in the developing area.
Japanese Patent No. 3530124

In addition, as described in Patent Document 2, the present applicant is a phenomenon including horizontal movement (conveyance) and vertical movement (hopping) of powder due to electrostatic force. We have proposed a development system that utilizes the phenomenon that the surface jumps with a component in the traveling direction due to a phase-shifting electric field.
JP 2004-198675 A

  Here, for example, in the developing device of Patent Document 1, the developer is conveyed by forming a traveling wave electric field by applying a multiphase voltage to a plurality of electrodes arranged at predetermined intervals. A developer conveying unit configured to arrange a plurality of electrodes in an endless loop, the plurality of electrodes being divided into a plurality of units and controlling voltage application for each unit. And a multi-phase voltage can be applied to each unit.

  Unlike the developing sleeve in two-component development, the electrostatic conveying member itself does not move in a developing device that moves toner particles by a phase-shift electric field (traveling wave electric field) as described above. If it is not uniformly transported over the entire development area of the transport member, it becomes difficult to perform development without unevenness.

  Further, in a developing device that moves toner particles by a phase-shifting electric field, the toner particles move so as to jump off the surface of the electrostatic conveyance member. Contact. Therefore, in a state where the toner particles are moved by the phase-shift electric field, the force that electrostatically adheres the toner particles and the electrostatic transport member is weak. For this reason, even if the developing electric field is set weak (for example, even if the developing potential is 100 V or less), there is an advantage that the developing ability can be easily secured. On the other hand, if the developing electric field is set to be weak, the amount of toner particles transported is small, so that even a slight variation in toner amount causes development unevenness. Therefore, particularly in a low potential process with a development potential of 100 V or less, there is a problem that it is difficult to uniformly convey toner particles.

  If variations occur in the amount of toner particles supplied on the electrostatic conveyance member, the phase-shift electric field is disturbed, which adversely affects the conveyance performance and development performance.

  As described above, in a developing device that moves toner particles by a phase-shift electric field, it is important to uniformly supply the toner particle amount to the electrostatic conveyance member.

  Here, even if the supply of toner particles onto the electrostatic transport member is made uniform, if the electrostatic transport member has an endless loop shape as described in Patent Document 1, it does not contribute to development. Since the toner particles that have passed through return to the toner supply unit again, the supply is not uniform, and there is a risk of uneven toner conveyance. In this case, the apparatus described in Patent Document 1 is provided with toner recovery means, but this is not sufficient to suppress variations in toner amount.

  As described above, when a developing device that moves toner particles by a phase-shifting electric field is put to practical use, there is a problem that the toner must be completely recovered from the electrostatic conveyance member and supplied uniformly. is there.

  The present invention has been made in view of the above problems, and a developing device and a process capable of collecting toner particles from an electrostatic transport member that moves the toner particles by a phase-shift electric field and supplying the toner uniformly. An object is to provide a cartridge and an image forming apparatus.

  In order to solve the above problems, a developing device according to the present invention includes an electrostatic transport member, a supply unit that supplies powder to the electrostatic transport member from a powder container that stores powder, and an electrostatic transport member In the developing device including the collecting means for collecting the powder moved in the step, the collecting means is configured to apply a bias before the powder that has not been developed reaches the developing area again. It was set as the structure provided with the collection | recovery member which collect | recovers.

  Here, it is preferable that the collecting means is not in contact with the electrostatic transfer surface of the electrostatic transfer member. The recovery means preferably has a separation means for separating the powder recovered by the recovery member from the recovery means. In these cases, the recovery member of the recovery means is preferably an electrostatic roller that is not in contact with the electrostatic transfer surface of the electrostatic transfer member and to which a bias is applied.

  Further, the recovery member of the recovery means is a rotating body that rotates in contact with the electrostatic transfer surface of the electrostatic transfer member, the recovery member of the recovery means is formed of a magnetic carrier particle and a brush is formed on the peripheral surface, A magnetic brush roller that rotates to face the electrostatic transfer surface of the electrostatic transfer member is preferable.

  When the collection member of these collection means is a rotating body or a roller, it is preferable that the circumferential speed of the collection member of the collection means is faster than the traveling speed of the phase shift electric field of the electrostatic transfer member.

  The developing device according to the present invention includes an electrostatic transfer member that moves powder by a phase-shift electric field to develop an electrostatic latent image on an image carrier, and an electrostatic transfer from a powder storage unit that stores the powder. In a developing device including a supply unit for supplying powder to a member and a recovery unit for recovering powder moved by the electrostatic transport member, the recovery unit is disposed on the electrostatic transport surface side of the electrostatic transport member. It was set as the structure provided with the magnet roller arrange | positioned at the back surface side of the electrostatic conveyance surface which forms the brush formed with the magnetic body carrier particle.

  The developing device according to the present invention includes an electrostatic transfer member that moves powder by a phase-shift electric field to develop an electrostatic latent image on an image carrier, and an electrostatic transfer from a powder storage unit that stores the powder. In a developing device comprising a supply means for supplying powder to a member and a recovery means for recovering the powder moved by the electrostatic transfer member, the recovery means is not on the electrostatic transfer surface of the electrostatic transfer member. It was set as the structure provided with the electrostatic conveyance member which opposed by contact.

  The developing device according to the present invention includes an electrostatic transfer member that moves powder by a phase-shift electric field to develop an electrostatic latent image on an image carrier, and an electrostatic transfer from a powder storage unit that stores the powder. In a developing device including a supply unit for supplying powder to a member and a recovery unit for recovering powder moved by the electrostatic transport member, the recovery unit is configured to remove the powder from the electrostatic transport surface of the electrostatic transport member. It was set as the structure provided with the nozzle which attracts | sucks a body.

  The developing device according to the present invention includes an electrostatic transfer member that moves powder by a phase-shift electric field to develop an electrostatic latent image on an image carrier, and an electrostatic transfer from a powder storage unit that stores the powder. In the developing apparatus including a supply unit that supplies powder to the member and a recovery unit that recovers the powder that is moved by the electrostatic conveyance member, the supply unit also serves as the recovery unit.

  Here, it is preferable that the rotation direction of the supply unit is opposite to the traveling direction of the phase-shift electric field on the electrostatic transfer surface of the electrostatic transfer member. Moreover, it is preferable to provide the some conveyance roller which conveys powder. Furthermore, a one-component developer can be used, or a two-component developer can be used.

  The process cartridge according to the present invention is configured to include at least one of charging, cleaning, and image carrier in an electrophotographic image forming process, and the developing device according to the present invention as developing means.

  The image forming apparatus according to the present invention includes a developing device according to the present invention or a process cartridge according to the present invention.

  The image forming apparatus according to the present invention is configured to include a plurality of process cartridges according to the present invention in an image forming apparatus for forming a color image.

  According to the developing device book of the present invention, the collecting means includes the collecting member that collects the powder by applying a bias before the powder that has not been subjected to the development reaches the developing region again. Since it is configured, toner particles are collected from the electrostatic conveyance surface after being developed on the image carrier by the electrostatic conveyance member, so that uneven toner conveyance due to the toner remaining on the electrostatic conveyance surface is eliminated and the toner supply is made uniform. Image quality is improved.

  According to the developing device of the present invention, the collecting unit includes the magnet roller disposed on the back surface side of the electrostatic transport surface that forms the brush formed of the magnetic carrier particles on the electrostatic transport surface side of the electrostatic transport member. Therefore, the toner particles can be mechanically separated and recovered from the electrostatic transport surface, the recovery means can be included in the electrostatic transport member, and the toner remaining on the electrostatic transport surface As a result, the unevenness of conveyance due to the toner can be eliminated, and the toner supply can be made uniform, improving the image quality and reducing the size.

  According to the developing device of the present invention, since the collecting unit includes the electrostatic conveyance member that faces the electrostatic conveyance surface of the electrostatic conveyance member in a non-contact manner, the toner remaining on the electrostatic conveyance surface As a result, the unevenness of conveyance due to the toner can be eliminated, and the toner supply can be made uniform, improving the image quality and reducing the size.

  According to the developing device of the present invention, since the collecting unit includes the nozzle that sucks the powder from the electrostatic conveyance surface of the electrostatic conveyance member, uneven conveyance due to the toner remaining on the electrostatic conveyance surface. Is eliminated, the toner supply can be made uniform, the image quality can be improved, and the toner particles can be easily separated from the electrostatic conveyance surface in a non-contact manner and collected at an arbitrary place.

  According to the developing device of the present invention, since the supply unit also serves as the recovery unit, the unevenness of conveyance due to the toner remaining on the electrostatic conveyance surface can be eliminated, and the toner supply can be made uniform. The quality is improved and the size can be reduced.

  According to the process cartridge according to the present invention, since at least one of charging, cleaning, and image carrier in an electrophotographic image forming process and the developing device according to the present invention are provided as developing means, The unevenness of transport due to the toner remaining on the electrostatic transport surface is eliminated, the toner supply can be made uniform, and the image quality is improved.

  According to the image forming apparatus according to the present invention, since the developing device according to the present invention or the process cartridge according to the present invention is provided, the unevenness in transport due to the toner remaining on the electrostatic transport surface is eliminated, and the toner is supplied. Can be made uniform, and the image quality is improved.

  According to the image forming apparatus of the present invention, the image forming apparatus for forming a color image is configured to include a plurality of process cartridges according to the present invention, so that uneven transport due to toner remaining on the electrostatic transport surface is eliminated. Thus, the toner supply can be made uniform, and the image quality of the color image is improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram illustrating an example of an image forming apparatus capable of forming a color image including the developing device according to the first embodiment of the present invention.
The image forming apparatus includes an image carrier, a charging unit, a developing unit according to the present invention as a developing unit, and an image forming unit including a cleaning unit, black (K), magenta (M), cyan (C), and yellow. (Y) image forming units 1K, 1M, 1C, and 1Y (hereinafter simply referred to as “image forming unit 1” when not distinguished), optical writing devices 2K, 2M, 2C, and 2Y, and transfer A transfer belt 3B, 3Bm, 3Bc, and 3By that are opposed to the conveyance belt 3A that conveys the material 6 and the image forming units 1K, 1M, 1C, and 1Y with the conveyance belt 3A interposed therebetween, the fixing device 4, and the transfer material 6 are accommodated. And a paper feeding device 5.

  Here, the optical writing devices 2K, 2M, 2C, and 2Y are for writing latent images on the charged image carriers of the image forming units 1K, 1M, 1C, and 1Y according to image information. Various devices such as a scanning device and an LED array can be used.

  The conveyor belt 3 </ b> A is stretched between the conveyor roller 11, the driven roller 12, and the tension rollers 13 and 14, and moves around in the direction of the arrow as the conveyor roller 11 rotates. Then, an adsorption roller 15 for adsorbing the transfer material 6 onto the conveyance belt 3A is arranged opposite to the conveyance roller 11, and a toner image is formed on the conveyance belt 3A at the exit side of the conveyance belt 3A. A P sensor 16 for detecting a pattern is arranged.

The transfer rollers 3Bk, 3Bm, 3Bc, 3By have at least a core metal and a conductive elastic layer covering the core metal, and the conductive elastic layer is an elastic material such as polyurethane rubber, ethylene-propylene-diene polyethylene (EPDM), or the like. In addition, an elastic roller in which a conductivity imparting agent such as carbon black, zinc oxide or tin oxide is blended and dispersed to adjust the electric resistance value (volume resistivity) to a medium resistance of 10 ⁶ to 10 ¹⁰ Ω · cm.

  The fixing device 4 includes a heating roller 4a and a pressure roller 4b facing the heating roller 4a.

  In this image forming apparatus, in a normal image forming operation, the transfer material 6 such as a recording sheet supplied from the paper supply device 5 is a transfer material that is a transfer body when a predetermined voltage is applied to the suction roller 15. It is adsorbed to the conveyor belt 3A. The transfer material 6 moves together with the transfer material conveyance belt 3A while being carried on the transfer material conveyance belt 3A. During the movement, toner images are transferred from the image forming units 1K, 1M, 1C, and 1Y, and are transferred onto the transfer material 6. A color toner image is formed. When the transfer material 6 passes through the conveying belt 3A and reaches the fixing device 4, the toner image on the transfer material 6 is heated while being sandwiched between the heating roller 4a and the pressure roller 4b to be fixed on the transfer material 6. As a result, a visible image is fixedly formed on the transfer material 6. Thereafter, the transfer material 6 on which the color image is formed is discharged to a paper discharge unit 7 at the top of the apparatus main body 10.

  In a mode in which the color misregistration and toner density of each color toner image are adjusted, a toner image having a predetermined pattern is directly formed on the transfer material conveying belt 3A from the image forming units 1K, 1M, 1C, and 1Y. The toner pattern is detected, and the write timing and development bias are changed based on the detection result, so that an optimum color image can be obtained. The toner pattern on the transfer material conveying belt 3A is adjusted in charge polarity by a bias applied to the suction roller 15, and then the image forming units 1K, 1M, and 1C by voltages applied to the transfer rollers 3Bk, 3Bm, 3Bc, and 3By. 1Y is collected.

Next, the image forming unit 1 according to the present invention will be described with reference to FIG. FIG. 2 is an enlarged explanatory view of the image forming unit.
The image forming unit 1 includes an image carrier 21, a contact charging member 31, a developing device 41, and a cleaning device 51.

  The image carrier 21 is a negatively charged organic photoreceptor, and is provided so as to be rotated in an arrow direction (counterclockwise direction in the drawing) by a rotation driving mechanism (not shown).

  The contact charging member 31 is a flexible charging in which a medium-resistance urethane foam layer 33 formulated with urethane resin, carbon black as a conductive particle, a sulfurizing agent, a foaming agent, etc. is formed in a roller shape on a core metal 32. Laura. The intermediate resistance layer formed on the cored bar 32 of the contact charging member (charging roller) 31 is not limited to the urethane foam layer 33 described above, but urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene. A rubber material in which a conductive substance such as carbon black or a metal oxide is dispersed for resistance adjustment in acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, or the like, or a foamed material thereof can be used.

  The developing device 41 is an electrostatic transport member (electrostatic transport roller) that constitutes an electrostatic transport member that moves toner particles that are powder by a phase-shifting electric field to develop an electrostatic latent image on the image carrier 21. 42, a storage unit 43 that stores toner particles and the like, a supply roller 44 that constitutes a supply unit that supplies toner particles in the storage unit 43 to the electrostatic transport roller 42, and a toner that is moved by the electrostatic transport roller 42 is collected. And a recovery means 45 and the like.

  The cleaning device 51 includes a cleaning blade 52 that is brought into contact with the rotation direction of the image carrier 21 in a counter direction, a waste toner storage unit 53 that stores the cleaned toner particles as waste toner, and the like.

Next, details of the developing device 41 will be described with reference to FIG.
As described above, the developing device 41 is a roller-shaped electrostatic transport member (hereinafter referred to as “electrostatic transport roller”) having a plurality of electrodes for generating an electric field for transporting, developing, and collecting powder toner particles. 42). The electrostatic transport roller 42 is opposed to the image carrier 21 in a non-contact manner with a gap of 50 to 1000 μm, preferably 150 to 400 μm, at the time of image formation.

  The configuration of the electrostatic transport roller 42 will be described in detail with reference to FIG. FIG. 3 is an enlarged cross-sectional view of the surface of the electrostatic transport roller 42 on the image carrier 21 side. The electrostatic transport roller 42 includes a plurality of electrodes 102, 102, 102... On the support substrate 101 as a set, arranged at a predetermined interval along the toner moving direction, and electrostatic transport thereon. A surface protective layer 103 made of an inorganic or organic insulating material, which becomes an insulating electrostatic transfer surface forming member for forming the surface 103a and serves as a protective film covering the surface of the electrode 102, is laminated.

  As the support substrate 101 in this embodiment, a substrate made of an insulating material such as a glass substrate, a resin substrate or a ceramic substrate, or a substrate made of a conductive material such as SUS, and an insulating film such as SiO 2 is formed, A substrate made of a flexibly deformable material such as a polyimide film can be used.

  The electrode 102 is formed by depositing a conductive material such as Al or Ni—Cr on the support substrate 101 with a thickness of 0.1 to 10 μm, preferably 0.5 to 2.0 μm, and using a photolithography technique or the like. It is formed by patterning into the required electrode shape. The width L of the plurality of electrodes 102 in the powder traveling direction is 1 to 20 times the average particle diameter of the powder to be moved, and the distance R in the powder traveling direction of the electrodes 102 and 12 is also moved. The average particle size of the body is 1 to 20 times.

As the surface protective layer 103, for example, SiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5 and the} like are formed to a thickness of 0.5 to 10 μm, preferably 0.5 to 3 μm. Formed.

  In FIG. 3, lines extending from the respective electrodes 102 represent conductive lines for applying a voltage to the respective electrodes 102, and only the portions indicated by black circles in the overlapping portions of the respective lines are electrically connected. This part is electrically insulated. Different drive voltages V11 to V13 and V21 to V23 having different n phases are applied to the respective electrodes 102 from the power source 104 on the main body side. In this embodiment, a case where a three-phase driving voltage is applied (n = 3) will be described. However, the present invention can be applied to any natural number n satisfying n> 2 as long as toner particles are transported. It is.

  In the present embodiment, each electrode 102 is connected to one of the contacts S11, S12, S13, S21, S22, and S23 on the developing device 41 side, and each of the contacts S11, S12, S13, S21, S22, and S23 is In a state where the developing device 41 is mounted on the image forming apparatus main body 10, it is connected to a main body side power source 104 that provides drive waveforms V11, V12, V13, V21, V22, and V23, respectively.

  The electrostatic transport roller 42 transports toner particles to the vicinity of the image carrier 21, and transports toner particles to the latent image of the image carrier 21 for transporting toner particles that have not contributed to development after passing through the development region. It is divided into a developing region for forming particles by adhering particles.

  The development area exists only in the area close to the image carrier 21, and the conveyance area exists on the circumference of the electrostatic conveyance roller 42 and in the entire area other than the development area. In the present invention, an area in which toner particles can be moved by a phase-shift electric field is referred to as an “electrostatic transfer surface”. In this embodiment, the entire surface of the electrostatic transport roller 42 is an electrostatic transport surface.

  In the transport region, the drive waveforms V11, V12, and V13 are applied to the electrodes 102 by the power source 104, and in the development region, the drive waveforms V21, V22, and V23 are applied to the electrodes 102 by the power source 104.

  Therefore, the principle of electrostatic conveyance of toner by the electrostatic conveyance roller 42 will be described. By applying an n-phase driving waveform to the plurality of electrodes 102 of the electrostatic conveyance roller 42, a phase shift electric field (traveling wave electric field) is generated by the plurality of electrodes 102, and the electrostatic conveyance roller 42 is charged. The toner particles move in the transport direction in response to a repulsive force and / or suction force.

  For example, as shown in FIG. 4 with respect to the plurality of electrodes 102 of the electrostatic conveyance roller 42, three phases of A phase, B phase, and C phase that change between the ground G (0 V) and the positive voltage + are obtained. A pulse-like drive waveform is applied at different timings. At this time, as shown in FIG. 5, the negatively charged toner T is present on the electrostatic transport roller 42, and “G”, “G”, “+”, Assuming that “G” and “G” are applied (FIG. 5A), the negatively charged toner T is positioned on the “+” electrode 102. At the next timing, “+”, “G”, “G”, “+”, and “G” are respectively applied to the plurality of electrodes 102 ((b) in the figure). Since a repulsive force acts between the “G” electrode 102 and an attractive force acts between the “+” electrode 102 on the right side, the negatively charged toner T moves to the “+” electrode 102 side. Further, as shown in FIG. 5C, “G”, “+”, “G”, “G”, and “+” are applied to the plurality of electrodes 102 at the next timing, respectively, and negatively charged toner Similarly, the repulsive force and the attractive force act on T, so the negatively charged toner T further moves to the “+” electrode 102 side.

  In this way, by applying a multi-phase driving waveform whose voltage changes to the plurality of electrodes 102, a traveling wave electric field is generated on the electrostatic conveyance roller 42, and the negatively charged toner moves in the traveling direction of the traveling wave electric field. Moving. In the case of positively charged toner, the drive waveform changes in the same direction by reversing the drive waveform change pattern.

  Here, in this embodiment, in the transport region of the electrostatic transport roller 42, the application time ta of +100 V for each phase is 1/3 of the repetition period tf for each electrode 102 as shown in FIG. Three-phase drive waveforms (drive pulses) V11, V12, and V13, which are set to about 33% (this is referred to as “carrier voltage pattern”), are applied. It has been found from the applicant's research that this drive waveform is a waveform suitable for high-speed conveyance of toner particles in the conveyance region.

  Further, in the development region, as shown in FIG. 7, for each electrode 102, the application time ta of + 100V or 0V of each phase is set to about 67%, which is 2/3 of the repetition period tf (this is referred to as “ Three-phase drive waveforms (drive pulses) V21, V22, and V23 are applied. In the development region, it is preferable that toner particles are positively launched toward the image carrier, and it has been found from the applicant's research that the drive waveform in FIG. 7 is suitable for launching toner particles.

  Even when a drive waveform of the development voltage pattern is applied, since the toner is also subjected to a lateral force other than the toner positioned at the center of the 0V electrode, not all the toners are launched at the same time, but move in the horizontal direction. Conversely, even when a drive waveform of a carrier voltage pattern is applied, depending on the position of the toner, there is a toner whose ascending distance is larger than that of being obliquely launched at a large angle and moving horizontally.

  Therefore, the drive waveform pattern applied to each electrode 102 in the transport region is not limited to the transport voltage pattern shown in FIG. 6 described above, and the drive waveform pattern applied to each electrode 102 in the development region 12 is also described above. The development voltage pattern shown in FIG.

  Up to this point, the drive waveform has been described for the case of three phases. When this is generalized to the n phase, the drive waveform is as follows. That is, when an n-phase (n is an integer of 3 or more) pulsed voltage (driving waveform) is applied to each electrode to generate a traveling wave electric field, the voltage application time per phase {repetition period time × By setting the voltage application duty to be less than (n−1) / n}, it is possible to increase the efficiency of conveyance and development. For example, when a three-phase drive waveform is used, the voltage application time ta of each phase is set to less than about 67%, which is 2/3 of the repetitive cycle time tf, and when a four-phase drive waveform is used, It is preferable to set the voltage application time of each phase to less than 75%, which is 3/4 of the repetition cycle time.

  On the other hand, the voltage application duty is preferably set to {repetition cycle time / n} or more. For example, when a three-phase driving waveform is used, it is preferable to set the voltage application time ta of each phase to about 33% or more, which is 1/3 of the repetition cycle time tf.

  That is, between the voltage applied to the target electrode and each voltage applied to the upstream adjacent electrode and the downstream adjacent electrode in the traveling direction, a time is set for the upstream adjacent electrode to repel and the downstream adjacent electrode to be sucked. The efficiency can be improved. In particular, when the driving frequency is high, the initial speed for the toner on the electrode of interest is set by setting it within the range of {repeat cycle time / n} or more and less than {repeat cycle time × (n−1) / n}. It becomes easy to obtain.

  Note that the above description of the electrostatic transfer member has described what is considered to be the best mode. However, if the desired transfer / development performance can be obtained, the distance between the electrodes 102 in the development region and the transfer region is set to be the same. The direction of the electric field may be adjusted to be different, or the distance between the electrodes and the drive waveform may be the same in the development area and the conveyance area.

  Returning to FIG. 2, the developing device 41 includes a supply roller 44 for supplying toner particles to the electrostatic transport roller 42, and a magnetic brush is formed at a portion where the supply roller 45 and the electrostatic transport roller 42 face each other. Yes. On the surface of the supply roller 44, a nonmagnetic sleeve 44a formed of a nonmagnetic material such as aluminum, brass, stainless steel or conductive resin in a cylindrical shape is provided in the direction indicated by the arrow (clockwise in FIG. 2) by a rotation drive mechanism (not shown). ) To be rotated.

  A doctor blade 46 for regulating the height of the developer chain spike, that is, the amount of developer on the sleeve 44a, is provided on the upstream side of the developing region in the developer transport direction of the supply roller 44. The doctor gap, which is the distance between the doctor blade 46 and the sleeve 44a of the supply roller 44, is set to 0.4 mm. Further, in the region opposite to the image carrier 21 of the supply roller 44, two screws 48 for pumping up the container 43 developer in the developing casing 47 to the supply roller 44 while being stirred are rotatably provided. .

  As shown in FIG. 8, the supply roller 44 includes a plurality of magnetic poles (magnets) 44 c that form a magnetic field so as to cause developer spikes on the peripheral surface of the sleeve 44 a, and a magnet roller body (magnet roller). 44b is provided in a fixed state. The developer carrier rises in a chain shape on the sleeve 44a so as to follow the normal magnetic field lines emitted from the magnet roller body 44b, and the charged toner adheres to the carrier that has the chain shape. Thus, a magnetic brush is configured. The magnetic brush is transferred in the same direction as the sleeve 44a by the rotation of the sleeve 44a.

  Specifically, as shown in FIG. 8, the main developing magnetic pole P1 that causes the rising of the developer in the developing region, the magnetic poles P4 and P5 for pumping the developer onto the sleeve 44a, and the pumped developer are supplied. A magnetic pole P6 for transporting to the region, a magnetic pole P2 for transporting the developer in the region after the supply, and a agent separating magnetic pole P3 are provided. Here, the magnet roller body 44b is configured by a 6-pole magnet, but may be configured by 8 or 12 poles. In FIG. 8, the curve drawn on the surface of the supply roller 44 shows the outline of the normal magnetic force pattern, and the symbols “N” and “S” indicate that the polarity of each magnetic pole on the surface of the supply roller is N poles, respectively. , S pole.

  Although not shown, toner particles and a magnetic carrier are stored in the accommodating portion 43 of the developing device 41. In carrying out the present invention, it is not necessary to specifically limit the carrier particles and the toner particles, but an example of the aspect in the present embodiment will be described.

  In this example, the toner particles are radically polymerized with a styrene or acrylic polymerizable monomer dispersed in water together with a polymerization initiator as a binder resin, or a polyester resin is dispersed in water. Non-magnetic toner particles having a weight average particle diameter of about 5 μm obtained by granulating using a polymer obtained by polyaddition reaction and adding a colorant, a charge control agent and the like thereto.

The magnetic carrier is first magnetization amount of the magnetic field in kOe is 30 emu / cm ³ or more, the carrier in the range of 200 emu / cm ³ or less preferred. If the magnetization amount is 200 emu / cm ³ or less, preferably 140 emu / cm ³ or less, the magnetic interaction between adjacent magnetic brushes becomes small, and the ears of the formed magnetic brush become dense and short. . As a result, uniform toner particles can be supplied to the electrostatic transport roller 42. On the other hand, when the magnetization amount of the magnetic carrier is less than ³⁰ emu / cm ³ , the developer transport performance is poor. Therefore, the magnetization of the magnetic carrier is 30 emu / cm ³ or more, preferably 80 emu / cm ³ or more.

As this magnetic carrier, a resin magnetic carrier in which a magnetic material produced by a polymerization method composed of at least a binder resin and a magnetic metal oxide and a nonmagnetic metal oxide is dispersed is used. Specifically, magnetite (Fe ₃ O ₄ ) is used as the magnetic metal oxide, and a vinyl monomer such as styrene or ethyl acrylate is polymerized as the binder resin for dispersing and binding the metal oxide. The resulting resin is used. A carrier in which a magnetic material is dispersed in a binder resin may be used as it is. However, it may be used as a carrier core, and an insulating resin may be used as a coating agent, and the carrier core surface may be used as a coated magnetic carrier. The amount of magnetization is determined by placing a magnetic carrier packed in a cylindrical container in an external magnetic field of 1 kilo-Oersted with an oscillating magnetic field type magnetic property automatic recording device manufactured by Riken Denshi Co., Ltd. It can be calculated by multiplying the true specific gravity of the carrier by the magnetization strength obtained by the measurement.

Next, the operation of the image forming unit 1 configured as described above will be described.
This image forming apparatus is a multifunction machine that can function as a copying machine and a printer. When the image forming apparatus functions as a copying machine, image information read from the scanner is subjected to various processes such as A / D conversion, MTF correction, and gradation processing. The image processing is performed and converted into write data. When functioning as a printer, image information in a format such as a page description language or a bitmap transferred from a computer or the like is subjected to image processing and converted into write data.

  Prior to image formation, the image carrier 21 starts rotating in the direction of the arrow in FIG. 2, that is, in the counterclockwise direction so that the moving speed of the surface becomes a predetermined speed. The charging roller 31 is rotated with respect to the image carrier 21. At this time, a DC voltage of −100 V and an AC voltage with an amplitude of 1200 V and a frequency of 2 kHz are applied to the core metal 32 of the charging roller 31 from the charging bias application power source, whereby the surface of the image carrier 21 is charged to about −100 V.

  The optical writing device 2 irradiates the charged image carrier 21 with a laser beam 2a in accordance with the writing data. That is, by changing the potential of the image portion by light irradiation, a difference from the potential of the non-image portion not irradiated with light is generated, and an electrostatic latent image is formed by this potential contrast.

  The electrostatic latent image formed on the image carrier 21 by the optical writing device 2 is developed by the developing device 41, and the toner particles adhere to the image portion to be visualized on the image carrier 21 as a toner image. In the development by the phase-shift electric field, the toner particles move while jumping off the surface of the electrostatic conveyance roller 42, and are attached so as to be attracted to the image portion when the toner particles approach the image carrier 21 for development. In this embodiment, a voltage of −50 V is applied to the electrostatic conveyance roller 42 and −250 V is applied to the supply roller 44, so that the electrostatic conveyance roller 42 is supplied from the supply roller 45 and the electrostatic conveyance roller 42 is applied to the image carrier 21. An electric field is formed that guides the toner particles to the image area.

  The transfer material is transported from the sheet feeding device 5 in synchronization with the timing at which the toner image formed on the image carrier 21 reaches the transfer portion which is the opposite portion between the transfer roller 3B and the image carrier 21. The toner image on the carrier 21 is transferred to the transfer material 6 by the voltage applied to the transfer roller 3B. The transfer material 6 onto which the toner image has been transferred is fixed by the fixing device 4 and a color image is output on the transfer material 6.

  On the other hand, the toner remaining on the image carrier 21 without being transferred (transfer residual toner) is cleaned by the cleaning device 51, and the surface of the image carrier 21 after cleaning is used for the next image formation.

Accordingly, a first example of the collecting means 45 in the developing device 41 will be described with reference to FIG.
Here, toner particles in which a bias voltage VB1 is applied by a bias power source 452 to a polarity opposite to that of the toner particles within a range from the development area of the electrostatic conveyance roller 42 to the toner supply area to which the toner is supplied by the supply roller 44. A metal plate 451 is disposed as a recovery member that electrostatically attracts and recovers.

  Accordingly, toner particles that have not contributed to development among the toner particles conveyed by the electrostatic conveyance roller 42 pass through the development region of the electrostatic conveyance roller 42 and then are applied to the metal plate 451 to which the bias voltage VB1 is applied. It is electrostatically attracted and separated from the electrostatic transport roller 42. The bias voltage VB1 applied to the metal plate 451 is applied with a reverse polarity to the bias voltage applied to the electrostatic transport roller.

  In the present embodiment, the bias voltage VB is applied to the metal plate 451 within the range of 0V to + 100V. The metal plate 451 is installed slightly spaced from the electrostatic transport roller 42. The gap between the metal plate 451 and the electrostatic transport roller 42 is 50 to 1000 μm, preferably 150 to 400 μm, and is preferably smaller than the height at which the toner particles hop when moved by the phase-shifting electric field. In this example, they are installed approximately 400 μm apart.

  The toner particles adsorbed on the metal plate 451 are electrostatically repelled from the metal plate 451 by applying a voltage having a polarity opposite to the bias voltage VB1 at the time of adsorption at a timing when the toner is not conveyed by the electrostatic conveyance roller 42. Alternatively, the charge is removed by grounding and dropped from the metal plate 451 by gravity and collected in the casing 47 of the developing device 41.

  In this case, the metal plate 451 is attached with an inclination in the vertical direction so that the toner particles can easily fall. At this time, in order to make it easy to separate and drop the toner particles from the metal plate 451, a vibration means 453 such as a piezoelectric element can be provided to vibrate the metal plate 451 by ultrasonic vibration or high-frequency vibration.

  The toner particles dropped and recovered from the metal plate 451 in this manner are again captured by the developer on the supply roller 44 and are transported to the supply region, where they are supplied to the electrostatic transport roller 42.

  As described above, the electrostatic conveying member is provided as a collecting unit including a collecting member that collects the powder by applying a bias before the powder that has not been developed again reaches the developing region. Since toner particles can be collected from the electrostatic conveyance surface after development on the image carrier, uneven conveyance due to toner remaining on the electrostatic conveyance surface is eliminated, and toner supply can be made uniform. Quality can be improved.

  In this case, since the recovery member of the recovery means is not in contact with the electrostatic transfer surface of the electrostatic transfer member, the toner particles can be electrostatically separated and recovered from the electrostatic transfer surface with a simple configuration. And downsizing. further. The collecting means has a separating means for separating the powder collected by the collecting member from the collecting means, so that the toner particles can be reliably separated and collected from the collecting member.

Next, a second example of the collecting means 45 in the developing device 41 will be described with reference to FIG.
Here, within the range from the development area to the toner supply area of the electrostatic transport roller 42, the bias voltage VB1 is applied by the bias power source 452 to the opposite polarity to the toner particles, and the toner particles are electrostatically adsorbed and collected. A metal roller 455 constituting an electrostatic roller is disposed.

  Accordingly, toner particles that have not contributed to development among the toner particles conveyed by the electrostatic conveyance roller 42 pass through the development region of the electrostatic conveyance roller 42 and then are applied to the metal roller 455 to which the bias voltage VB1 is applied. It is electrostatically attracted and separated from the electrostatic transport roller 42. The bias voltage VB1 applied to the metal roller 455 is applied with a reverse polarity to the bias voltage applied to the electrostatic transport roller.

  In the present embodiment, the bias voltage VB is applied to the metal roller 455 within the range of 0V to + 100V. The electrostatic roller 455 is installed slightly separated from the electrostatic transport roller 42. The gap between the metal roller 455 and the electrostatic transport roller 42 is 50 to 1000 μm, preferably 150 to 400 μm, and is preferably smaller than the height at which the toner particles hop when moved by the phase-shifting electric field. In this example, they are installed approximately 400 μm apart.

  The toner particles adsorbed on the metal roller 455 are scraped off by the blade 456 brought into contact with the roller surface by rotating the metal roller 455 and are collected in the casing 47 of the developing device 41 by gravity. Although the rotation direction of the metal roller 455 is not particularly limited, the same direction as the toner conveyance direction of the electrostatic conveyance roller 42 is preferable.

  The toner particles dropped and collected from the metal roller 455 in this way are captured again by the developer on the supply roller 44 and are transported to the supply region, where they are supplied to the electrostatic transport roller 42.

  In this way, by configuring the recovery member of the recovery means with an electrostatic roller to which a bias that is not in contact with the electrostatic transfer surface is applied, toner particles from the electrostatic transfer surface after development on the image carrier by the electrostatic transfer member Therefore, unevenness in transport due to the toner remaining on the electrostatic transport surface is eliminated, toner supply can be made uniform, and image quality can be improved.

Next, a third example of the collecting means 45 of the developing device 41 will be described with reference to FIG.
Here, a brush roller 457 serving as a rotating member that constitutes a recovery member having a brush 457a in which fine fibers are planted on the outer peripheral surface is installed in a range from the developing region to the toner supply region of the electrostatic transport roller 42. The brush roller 457 is rotated at a high speed to be frictionally charged, or as shown in the figure, a bias voltage VB1 is applied in a polarity opposite to that of the toner particles to attach the toner to the hair tips of the brush 457a, and mechanically the toner Remove. The bias voltage VB1 applied to the brush roller 457 is applied with a reverse polarity to the bias voltage applied to the electrostatic transport roller. Here, the bias voltage VB1 is applied to the brush roller 457 within the range of 0V to + 100V.

  Further, a flip cover 458 that contacts the tip of the brush 457 a of the brush roller 457 is provided. The toner particles adhering to the bristles of the brush 457a of the brush roller 457 collide with the flip cover 458 brought into contact with the tip of the brush by rotating the brush roller 457 and are detached. Instead of the flip cover 458, a bias roller may be brought into contact with the brush tip to electrostatically collect.

  The toner scraped off by the flip cover 458 is collected in the casing 47 of the developing device 41. Although the rotation direction of the brush roller 457 is not particularly limited, the direction opposite to the toner conveyance direction of the electrostatic conveyance roller 42 is preferable.

  The toner particles dropped and collected from the brush roller 457 in this manner are again captured by the developer on the supply roller 44 and are transported to the supply region, where they are supplied to the electrostatic transport roller 42.

  As described above, by providing the rotating member that rotates in contact with the electrostatic transport surface as the recovery member, the toner particles can be easily and mechanically separated and recovered from the electrostatic transport surface.

Next, a fourth example of the collecting means 45 of the developing device 41 will be described with reference to FIG.
Here, a magnetic brush roller 461 which is a rotating recovery member in which a brush is formed with magnetic carrier particles by a magnetic force line of a magnet included in a sleeve is provided in a range from the developing area to the toner supply area of the electrostatic conveyance roller 42. Yes. The carrier particles for the magnetic brush roller 461 are supplied from a portion adjacent to the supply roller 44 and also used as the carrier used by the supply roller 44. A bias voltage having a reverse polarity to the toner is applied to the sleeve of the magnetic brush roller 461 by a bias power source (not shown).

  Further, the tip of the magnetic brush roller 461 is regulated by the doctor blade 462 so as to uniformly contact the surface of the electrostatic transport roller 42. Further, a collection roller 463 to which a bias voltage is applied from a bias power source (not shown) that separates and collects toner from the magnetic brush of the magnetic brush roller 461 is provided.

  As a result, the toner particles that have not contributed to the development pass through the development region of the electrostatic transport roller 42 and are captured by the carrier particles of the magnetic brush roller 461, and further collected by the recovery roller 462 to which a bias voltage is applied. Then, it is collected in the casing 47 of the developing device 41.

  The toner particles collected by the magnetic brush roller 461 in this manner are again captured by the developer of the supply roller 44 and are transported to the supply region and supplied to the electrostatic transport roller 42.

  As described above, the toner particles are electrostatically collected from the electrostatic conveyance surface by including the magnetic brush roller that rotates opposite to the electrostatic conveyance surface in which the brush is formed of the magnetic carrier particles as the collection member of the collection unit. can do.

  The rotational speeds of the metal roller 455, the brush roller 457, and the magnetic brush roller 461 in the second to fourth examples are more likely to capture toner as the contact or proximity probability with the surface of the electrostatic transport roller 42 increases. By setting the peripheral speed faster than the toner conveyance speed of the electrostatic conveyance roller 42, the toner can be efficiently collected.

Next, a fifth example of the collecting means 45 of the developing device 41 will be described with reference to FIG.
Here, as a collecting means having a plurality of electrodes for generating an electric field for moving toner particles within the range from the development area to the toner supply area of the electrostatic conveyance roller 42, similar to the electrostatic conveyance roller 42. A collection electrostatic transfer substrate 471 is provided to face the electrostatic transfer roller 42.

  If the average value of the transport pulse (drive pulse) of the electrostatic transport roller 42 is −100V, the average value of the transport pulse of the recovery electrostatic transport substrate 471 is set to 0V and the electrostatic transport for recovery from the electrostatic transport roller 42. The toner is moved to the substrate 461. The toner particles that have not contributed to the development are captured by the phase-shift electric field of the recovery electrostatic transfer substrate 461 that passes through the development region of the electrostatic transfer roller 42 and are transported by the recovery electrostatic transfer substrate 461. It is collected in the casing 47 of the developing device 41. Note that the pulses of the phase-shift electric field of the electrostatic transfer roller 42 and the recovery electrostatic transfer substrate 104 are synchronized.

  The toner particles recovered from the recovery electrostatic transport substrate 471 in this manner are again captured by the developer on the supply roller 44 and are transported to the supply region, where they are supplied to the electrostatic transport roller 42.

  As described above, the recovery means can be reduced in size by moving the toner particles from the electrostatic transfer surface to the opposite electrostatic transfer member for recovery.

Next, a sixth example of the collecting means 45 of the developing device 41 will be described with reference to FIG.
Here, in the range from the development area of the electrostatic conveyance roller 42 to the toner supply area, the magnetic force lines of the magnet roller (mag roller) 473 included in the endless electrostatic conveyance roller 42 cause the outer circumferential surface of the electrostatic conveyance roller 42 to move. A magnetic spike 472 is formed as a collecting means formed by forming a brush with magnetic carrier particles. The carrier particles are also used as a carrier used in the supply roller 44 and are supplied from a portion adjacent to the supply roller 44.

  As a result, the toner particles that have not contributed to the development pass through the development region of the electrostatic transport roller 42 and are captured by the carrier particles of the magnetic spike 472 on the surface of the electrostatic transport roller 42. The magnetic roller contained in the electrostatic transport roller 42 rotates counterclockwise so that the magnetic force on the surface of the electrostatic transport roller 42 disappears and falls together with the toner particles captured by the carrier particles and is collected in the casing 47 of the developing device 41. Is done.

  The toner particles collected in this way are captured again by the developer on the supply roller 44 and are transported to the supply region, where they are supplied to the electrostatic transport roller 42.

  In this way, the toner particles are separated mechanically from the electrostatic transfer surface by using the magnet roller installed on the back side of the electrostatic transfer surface as a collecting means with the brush formed of the magnetic carrier particles on the electrostatic transfer surface side. Thus, the collecting means can be included in the electrostatic conveyance member, and the size can be reduced.

Next, a seventh example of the collecting means 45 of the developing device 41 will be described with reference to FIG.
Here, a suction nozzle 474 as a collecting means is provided in the range from the development area to the toner supply area of the electrostatic conveyance roller 42 so as to face the electrostatic conveyance roller 42. The gap between the opening of the suction nozzle 474 and the surface of the electrostatic transport roller 42 is preferably 150 to 400 μm, and is preferably about the height at which the toner particles hop when moved by the phase-shifting electric field. In this example, the distance is approximately 500 μm.

  Further, a seal member 475 is provided at one end of the opening of the suction nozzle 474 so that the toner to be conveyed does not pass through the suction nozzle, so that the toner is damped and easily sucked. Further, a suction pump 476 is connected to the suction nozzle 474 through a duct 477, and the toner sucked into the casing 47 of the developing device 41 is discharged from the suction pump 476 through the discharge port 478a of the duct 478. . The suction pump 476 uses a pump capable of conveying powder such as toner, such as a diaphragm pump or a Mono pump. The flow velocity at the opening of the suction nozzle 474 is preferably equal to or higher than the toner conveyance speed. In this example, the suction nozzle flow velocity is set to 2 m / sec with respect to the toner conveyance speed of 1 m / sec.

  As a result, the toner particles that have not contributed to the development pass through the development area of the electrostatic transport roller 42 and are sucked by the opposing suction nozzle 474 and are transported through the ducts 477 and 478 by the suction pump 476 to be stored in the storage portion. (Stirring unit) Collected on the 43 side. The toner particles collected in the stirring unit 43 are stirred together with the developer and supplied to the supply roller 44.

  Thus, by providing a nozzle for sucking toner particles in the vicinity of the electrostatic conveyance surface as a collecting means, the toner particles can be separated from the electrostatic conveyance surface in a non-contact manner and collected at an arbitrary location. Easy to do.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 16 is a block diagram showing an example of an image forming apparatus capable of forming a color image provided with the developing device according to the second embodiment of the present invention. Note that elements having the same functions as the image forming elements described in the first embodiment are denoted by the same reference numerals, and description of the configuration is omitted unless particularly necessary.

  The image forming apparatus includes a belt-like image carrier 61 in which a negatively charged organic photoconductor is configured in a belt shape. The belt-like image carrier 61 is interposed between a driving roller 62, a driven roller 63, and a transfer counter roller 64. It is bridged and moved around in the direction of the arrow by a rotary drive mechanism (not shown).

  The belt-like image carrier 61 includes charging devices 65K, 65M, 65C, and 65Y for charging the belt-like image carrier 61, and development according to the present invention for developing an electrostatic latent image on the belt-like image carrier 61. The developing cartridges 66K, 66M, 66C, and 66Y, which are apparatuses, face each color, and are configured to sequentially superimpose toner images on the image carrier 61 as the image carrier 21 moves. Yes (1 pass color).

  Further, opposed rollers 67K, 67M, 67C, and 67Y are arranged at positions facing the electrostatic conveyance rollers 42 of the developing cartridges 66K, 66M, 66C, and 66Y with the belt-shaped image carrier 61 interposed therebetween. Further, a transfer roller 68 is disposed at a position facing the transfer counter roller 64 with the belt-shaped image carrier 61 interposed therebetween.

  In this image forming apparatus, at the time of image formation, the transfer material 6 sent from the sheet feeding device 5 is conveyed to a contact portion between the image carrier 61 and the transfer roller 68, and is placed on the image carrier 61 at the contact portion. The formed full color image is transferred onto the transfer material 6 by the voltage applied to the transfer roller 68. Thereafter, when the transfer material 6 reaches the fixing device 4, the toner image on the transfer material 6 is heated while being sandwiched between the heating roller 4 a and the pressure roller 4 b to be fixed on the transfer material 6. A full color visible image is formed on top.

  Here, the developing cartridges 66K, 66M, 66C, and 66Y for developing the black, magenta, cyan, and yellow toner images are opened and retracted from the apparatus main body 10 as shown in FIG. It is removable from the open space and can be replaced by the user.

Next, each part of charging and developing in this image forming apparatus will be described with reference to FIG. For the developing cartridge 66, the same parts as those in the first embodiment described above are denoted by the same reference numerals, and the description will be simplified.
The charging device 65 is for uniformly charging the surface of the image carrier 61. In this embodiment, a corona charging method is adopted. If non-contact charging means such as corona charging is used, the image carrier 61 can be charged without disturbing the toner image formed by the upstream developing cartridge 66.

  The developing cartridge 66 is a developing device according to the present invention, and is the same as the developing device 41 described in the first embodiment, although the shape is slightly changed.

An operation for forming a toner image on the image carrier 61 will be described.
First, the surface of the image carrier 61 is uniformly charged by the charging device 65. Even when a toner image is already formed on the image carrier 61, the surface of the image carrier 61 including the toner image is uniformly charged. Next, a light beam corresponding to the image information is emitted from the optical writing device 2. Since the light beam passes between the charging device 65 and the developing cartridge 66, the light beam is applied to the image carrier 61 that has already been uniformly charged, and the image carrier, which is a negatively chargeable photoconductor. On the surface of the body 61, a region corresponding to the image portion is neutralized to form a latent image.

  As in the first embodiment, the developing cartridge 66 attaches toner particles to the image portion of the latent image formed on the image carrier 61 and visualizes the latent image as a toner image. The charging, light beam irradiation, and development processes described above are repeated at the portion facing each developing cartridge as described above, and a full color image in which four color toner images are superimposed on the image carrier 61 is formed.

  Note that the image forming apparatus according to the present embodiment does not include a cleaning member for collecting the transfer residual toner particles on the surface of the image carrier 61. The transfer residual toner particles remain on the surface of the image carrier 61, but are charged by the four charging devices 65 and eventually transferred to a transfer material and removed from the image carrier 61. When the transfer residual toner particles are transferred to the transfer material, some image disturbance occurs, but if the transfer residual toner particles are slightly disturbed, they are not visually recognized.

Accordingly, a first example of the collecting means provided in the developing cartridge 66 will be described with reference to FIG.
Here, the developing device 66 is provided with a supply roller 44 for supplying toner particles to the electrostatic transport roller 42, and a magnetic brush is formed at a portion where the supply roller 44 and the electrostatic transport roller 42 face each other. Yes. On the surface of the supply roller 44, a nonmagnetic sleeve formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape is rotated in the direction indicated by an arrow (clockwise in the figure) by a rotation drive mechanism (not shown). It is designed to be rotated.

  A doctor blade 46 that regulates the height of the developer chain spike, that is, the amount of developer on the sleeve, is provided on the upstream side portion of the development area in the developer transport direction. The doctor gap, which is the distance between the doctor blade 46 and the sleeve of the supply roller 44, is set to 0.4 mm. Further, two screws 48 for pumping up the developer in the developing casing 47 to the supply roller 44 while stirring the developer are installed in a region opposite to the image carrier 61 of the supply roller 44.

  In the supply roller 44, a magnet roller body (magnet roller) that forms a magnetic field is provided in a fixed state so as to cause the rising of the developer on the peripheral surface of the sleeve. Along the normal magnetic field lines emitted from the magnet roller body, the developer carrier is spiked in a chain shape on the sleeve, and the charged toner is attached to the carrier that has the chain shape on the sleeve, A magnetic brush is constructed. The magnetic brush is transferred in the same direction as the sleeve by the rotation of the sleeve. The magnet roller body includes a plurality of magnetic poles (magnets). Specifically, as shown in FIG. 8 described above, the supply main magnetic pole P1 that causes the rising of the developer in the supply region, the magnetic poles P4 and P5 for pumping up the developer on the sleeve, and the pumped-up developer. A magnetic pole P6 that conveys to the supply area, a magnetic pole P2 that collects the developer in the area after development, and an agent separation magnetic pole P3 are provided.

  Here, the electrostatic transport roller 42 has a plurality of electrodes for generating an electric field for supplying, transporting, developing, and collecting toner particles that are powder. In this embodiment, a case where a three-phase driving voltage is applied (n = 3) will be described. However, the present invention can be applied to any natural number n satisfying n> 2 as long as toner particles are conveyed. . In the present embodiment, as shown in FIG. 19, each electrode 102 is connected to any one of the contacts S11, S12, S13, S21, S22, and S23 of the developing cartridge 66. When mounted on the forming apparatus main body 10, it is connected to a main body side power supply 104 that provides drive waveforms V 11, V 12, V 13, V 21, V 22, V 23, respectively.

  The electrostatic conveyance roller 42 forms a toner image by attaching toner particles to a supply area where the toner particles are supplied from the supply roller 44, a conveyance area where the toner particles are transferred to the vicinity of the image carrier 61, and a latent image on the image carrier 61. A development area for collecting toner particles that have not contributed to development after passing through the development area. The supply area is an area close to the supply main magnetic pole P <b> 1 of the supply roller 44, the transport area exists from the supply area to the development area, and the development area exists only in the area close to the image carrier 61. On the other hand, the recovery area is an area in the vicinity of the recovery magnetic pole P <b> 2 of the supply roller 44.

  The drive waveforms V11, V12, and V13 are applied to the electrodes 102 in the supply, conveyance, and development areas, and the drive waveforms V21, V22, and V23 are applied to the electrodes 102 in the recovery area. Here, when the bias of the supply roller 44 is −400 V, the charging voltage is −140 V, and the post-exposure voltage is −40 V, a driving pulse signal having an average value of −100 V and ± 100 V is applied to the driving waveforms V11, V12, and V13. Toner is supplied, conveyed, and developed, and a drive pulse signal having an average value of −500 V and ± 100 V is applied to the drive waveforms V21, V22, and V23 to collect the toner.

  Here, the rotation direction of the supply roller 44 is the same as the toner conveyance direction of the electrostatic conveyance roller 42 so that toner particles that have not contributed to development after passing through the development region are mixed with toner in the supply region and density unevenness does not occur. The reverse direction is preferred. Thus, by rotating in the reverse direction, the toner can be reliably supplied to the electrostatic conveyance surface without being affected by the toner recovery from the electrostatic conveyance surface.

  In this example, the magnet roller body is composed of 6-pole magnets, but it may be composed of 8-poles or 12-poles.

  In this way, the supply means also serves as the collection means, so that the size can be reduced.

Next, a second example of the collecting means provided in the developing cartridge 66 will be described with reference to FIG.
Here, a plurality of supply rollers 44A and 44B are provided as supply means. The supply roller 44A mainly collects toner particles that have not contributed to development from the electrostatic conveyance roller 42, and the supply roller 44B supplies toner to the electrostatic conveyance roller 42, thereby preventing toner mixing. .

  In each of the above-described examples, the supply roller 44 has been described as being configured to carry a two-component developer composed of magnetic carrier particles and toner particles. However, as shown in FIG. 21, the supply roller 44C is a conductive sponge roller. A configuration in which only the particles are supported, that is, a one-component developer can be used.

Next, a third embodiment in which the image forming unit of the first embodiment described above is a process cartridge will be described with reference to FIG.
That is, in this embodiment, the image forming units 4K, 4M, 4C, and 4Y are process cartridges 71K, 71M, 71C, and 71Y for forming black, magenta, cyan, and yellow toner images, respectively. In the present embodiment, the “process cartridge” is a cartridge that is integrated with at least the developing device and is detachable from the image forming apparatus main body 10.

  In this image forming apparatus, the process cartridges 71K, 71M, 71C, and 71Y are removable from the open space by the transfer material conveyance belt 3A being opened and retracted from the apparatus body 10, and can be replaced by the user. It has become. At the time of image formation, writing devices 2K, 2M, 2C, and 2Y irradiate process cartridges 71K, 71M, 71C, and 71Y with writing light corresponding to the image information of black, magenta, cyan, and yellow, respectively. The process cartridge 71 forms a toner image corresponding to the writing light and transfers it to the transfer material 6.

  Needless to say, the present invention is also applicable to a color image forming apparatus, a monochrome image forming apparatus, and the like using an intermediate transfer belt, a transfer drum, an intermediate transfer drum, and the like.

1 is a configuration diagram illustrating an example of an image forming apparatus capable of forming a color image including a developing device according to the first embodiment of the present invention. It is explanatory drawing explaining the developing device. FIG. 3 is an enlarged explanatory view of a main part for explaining an electrostatic conveyance roller of the developing device. It is explanatory drawing which shows an example of the drive waveform with which it uses for description of the conveyance principle of the electrostatic conveyance member. FIG. 6 is an explanatory diagram for explaining an example of toner conveyance. It is explanatory drawing which shows an example of the drive waveform applied to the conveyance area | region of the electrostatic conveyance roller. It is explanatory drawing which shows an example of the drive waveform applied to the image development area | region of the electrostatic conveyance roller. It is explanatory drawing with which it uses for description of the supply roller of the developing device. It is explanatory drawing with which it uses for description of the 1st example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 2nd example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 3rd example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 4th example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 5th example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 6th example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the 7th example of the collection | recovery means in the developing device. It is a block diagram which shows an example of the image forming apparatus which can form the color image provided with the developing device which concerns on 2nd Embodiment of this invention. FIG. 3 is an explanatory diagram for explaining the attachment / detachment of the developing cartridge of the image forming apparatus. FIG. 3 is an explanatory diagram for explaining a first example of a collecting unit in the developing device of the image forming apparatus. It is explanatory drawing with which it uses for description of the electrostatic conveyance roller in the developing device. It is explanatory drawing with which it uses for description of the 2nd example of the collection | recovery means in the developing device. It is explanatory drawing with which it uses for description of the image development apparatus in the case of using a one-component developer. It is explanatory drawing with which it uses for description of the process cartridge which concerns on this invention.

Explanation of symbols

1K, 1M, 1C, 1Y ... Image forming unit 2K, 2M, 2C, 2Y ... Optical writing device 3A ... Transfer material conveying belt 3Bk, 3Bm, 3Bc, 3By ... Transfer roller 4 ... Fixing device 5 ... Paper feed device 6 ... Transfer Material 7 ... Paper discharge unit 21 ... Image carrier 31 ... Charging device 41 ... Developing device 42 ... Electrostatic conveying roller 44 ... Supply roller 45 ... Recovery means 51 ... Cleaning device 61 ... Image carrier 65K, 65M, 65C, 65Y ... Charging device 66K, 66M, 66C, 66Y ... Developing cartridge 71K, 71M, 71C, 71Y ... Process cartridge 451 ... Metal plate 455 ... Metal roller 457 ... Brush roller 461 ... Magnetic brush roller 471 ... Electrostatic conveying member for collection 473 ... Mag roller 474 ... Suction nozzle

Claims (18)

  An electrostatic transfer member for moving powder by a phase-shifting electric field to develop an electrostatic latent image on the image bearing member; and a powder receiving unit for storing the powder to the electrostatic transfer member In a developing device comprising a supply means for supplying a body and a collecting means for collecting the powder moved by the electrostatic conveying member, the collecting means develops the powder that has not been used for the development again. A developing device, comprising: a collecting member that collects the powder by applying a bias before reaching the region.   2. The developing device according to claim 1, wherein the collecting unit is not in contact with the electrostatic transfer surface of the electrostatic transfer member.   3. The developing device according to claim 2, wherein the collecting unit includes a separating unit that separates the powder collected by the collecting member from the collecting unit.   4. The developing device according to claim 2, wherein the collecting member of the collecting unit is an electrostatic roller to which the bias is applied without being in contact with the electrostatic carrying surface of the electrostatic carrying member. Developing device.   2. The developing device according to claim 1, wherein the collecting member of the collecting means is a rotating body that rotates in contact with the electrostatic carrying surface of the electrostatic carrying member.   2. The developing device according to claim 1, wherein the collecting member of the collecting means is a magnetic brush roller having a magnetic carrier particle and a brush formed on a peripheral surface thereof and rotating opposite to the electrostatic carrying surface of the electrostatic carrying member. A developing device characterized by the above.   7. The developing device according to claim 4, wherein a circumferential speed of the collecting member of the collecting unit is faster than a traveling speed of the phase-shifting electric field of the electrostatic conveying member.   An electrostatic transport member that moves powder by a phase-shifting electric field to develop an electrostatic latent image on an image carrier, and a powder container that stores the powder from the powder container to the electrostatic transport member. In the developing device including a supply unit for supplying and a recovery unit for recovering the powder moved by the electrostatic transfer member, the recovery unit has a magnetic body on the electrostatic transfer surface side of the electrostatic transfer member. A developing device comprising a magnet roller disposed on a back surface side of the electrostatic conveyance surface for forming a brush formed of carrier particles.   An electrostatic transport member that moves powder by a phase-shifting electric field to develop an electrostatic latent image on an image carrier, and a powder container that stores the powder from the powder container to the electrostatic transport member. In a developing device comprising a supply means for supplying and a recovery means for recovering powder moved by the electrostatic transfer member, the recovery means is in non-contact with the electrostatic transfer surface of the electrostatic transfer member A developing device comprising an electrostatic transfer member facing each other.   An electrostatic transport member that moves powder by a phase-shifting electric field to develop an electrostatic latent image on an image carrier, and a powder container that stores the powder from the powder container to the electrostatic transport member. In a developing device comprising a supply means for supplying and a recovery means for recovering the powder moved by the electrostatic transfer member, the recovery means is configured to remove the powder from the electrostatic transfer surface of the electrostatic transfer member. A developing device comprising a nozzle for sucking the water.   An electrostatic transport member that moves powder by a phase-shifting electric field to develop an electrostatic latent image on an image carrier, and a powder container that stores the powder from the powder container to the electrostatic transport member. A developing apparatus comprising: a supplying means for supplying; and a collecting means for collecting powder moved by the electrostatic conveying member. The developing apparatus, wherein the supplying means also serves as the collecting means.   12. The developing device according to claim 11, wherein a rotation direction of the supply unit is opposite to a traveling direction of a phase-shift electric field on the electrostatic transfer surface of the electrostatic transfer member.   12. The developing device according to claim 11, further comprising a plurality of conveying rollers for conveying the powder.   14. The developing device according to claim 11, wherein a single-component developer is used.   14. The developing device according to claim 11, wherein a two-component developer is used.   16. The developing device according to claim 1, wherein the developing device includes at least one of charging, cleaning, and an image carrier in an electrophotographic image forming process, and a developing unit. To process cartridge.   An image forming apparatus comprising: an image carrier; a charging unit that applies an electric charge to form an electrostatic latent image on the image carrier; and a developing unit that develops powder by attaching the powder to the electrostatic latent image An image forming apparatus comprising the developing device according to claim 1 or the process cartridge according to claim 16. An image forming apparatus for forming a color image, comprising: a plurality of process cartridges according to claim 16.

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