JP2008134357A - Image forming apparatus, process cartridge and auxiliary electrifying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleanerless image forming apparatus capable of stably and sufficiently removing and recovering residual toner left after transfer over a long period while simultaneously developing and cleaning. <P>SOLUTION: A toner electrification control member 6 disposed on the upstream side of an electrifying roller 2 is configured to electrify the residual toner left after transfer while reciprocating in the axial direction of a photoreceptor drum 1 and rubbing the surface of the photoreceptor drum 1 with the conductive bristles thereof. A flicker member 200 whose projection is deeply inserted in the bristles of the toner electrification control member 6 is arranged in parallel to the toner electrification control member 6 and reciprocatively moved. During the image formation period, the toner electrification control member 6 and the flicker member 200 are reciprocatively driven with the same phase and the same amplitude. A recovery mode where an image forming operation is stopped for three seconds is performed for every printing operation of 100 sheets. In the recovery mode, the electrification bias voltage of the electrifying roller 2 is set as 0V, and the toner electrification control member 6 and the flicker member 200 are reciprocatively driven with the reverse phase and the same amplitude. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleanerless image forming apparatus that collects transfer residual toner with a developing device, and more particularly, to an auxiliary charging method that charges a transfer residual toner by sliding a brush member on an image carrier upstream of a charging unit. .

  A tandem type image forming apparatus in which a plurality of photosensitive drums having different development colors are arranged along a recording material conveyance belt or the like has been put into practical use. An intermediate transfer type image forming apparatus that primarily transfers a plurality of toner images with different development colors to an intermediate transfer belt and superimposes them to form a full color toner image, and then secondary transfer them onto a recording material has been put into practical use. Yes. A cleanerless type image forming apparatus that efficiently performs simultaneous development cleaning with a developing device by auxiliary charging that charges the transfer residual toner remaining on the surface of the photosensitive drum after transfer to a normal polarity has been put into practical use. A cleanerless process cartridge in which a photosensitive drum, a developing device, a charging roller, and the like for each development color are integrated and housed in a detachable housing has been put into practical use.

  Patent Document 1 discloses a tandem-type full-color image forming apparatus in which yellow, magenta, cyan, and black cleanerless process cartridges are arranged in an upward linear section of an intermediate transfer belt. Here, the auxiliary charging unit charges the residual toner to the same polarity as the charging voltage by rubbing the surface of the photosensitive drum with a brush member on the upstream side of the charging roller that applies a charging voltage to uniformly charge the surface of the photosensitive drum. A charging device is arranged. A pair of brush members are disposed on a moving table that reciprocates in the axial direction of the photosensitive drum, with a spacing in the rotational direction of the photosensitive drum. The upstream brush member is applied with an AC voltage to align the charged state of the residual toner. The brush member on the downstream side is applied with a DC voltage having the same polarity as the DC component of the charging voltage to charge the transfer residual toner to a normal polarity. Thus, efficient simultaneous development cleaning by the developing device is enabled.

  Patent Document 2 discloses an image forming apparatus in which a pair of brush members disposed upstream of a charging roller is reciprocally moved in the axial direction of a photosensitive drum to charge transfer residual toner to a normal polarity. Here, the brush member on the upstream side is applied with a DC voltage of 350 V to take in the transfer residual toner, and returns the toner to the photosensitive drum little by little so that the charged state of the toner is made positive. The brush member on the downstream side is charged with a negative voltage with discharge by applying a DC voltage of −800 V higher than the charging voltage to the transfer residual toner on the surface of the photosensitive drum. A brush recovery period is provided at the initial operation between paper and when the power is turned on or at the end of the printing operation, and the toner accumulated in the brush member is collectively moved to the surface of the photosensitive drum to clean the brush member. is doing.

  Here, during the brush recovery period, a large amount of toner charged to a reverse polarity (positive polarity) or uncharged toner is discharged from the brush member to the surface of the photosensitive drum. For this reason, if a charging voltage (negative polarity) is left applied to the charging roller, the toner is transferred to the charging roller to form an insulating layer, causing uneven charging. Therefore, during the brush recovery period, application of the charging voltage to the charging roller is stopped to prevent contamination of the charging roller. Further, a reverse polarity (negative polarity) voltage is applied to the transfer roller to transfer the toner charged with the reverse polarity to an intermediate transfer belt or the like and collected by a belt cleaning device.

  Patent Document 3 discloses an image forming apparatus in which a pair of brush members arranged upstream of a charging roller are independently reciprocated in the axial direction of a photosensitive drum.

  Patent Document 4 discloses an electrostatic fur brush type drum cleaning device that electrostatically attracts transfer residual toner on the surface of a photosensitive drum using a conductive roll brush. Here, a flicker member in which a large number of protrusions are inserted into the gaps of the hairs of the conductive roll brush is arranged in parallel with the conductive roll brush. Then, during the brush recovery period without image formation, the reciprocating drive mechanism reciprocally moves the flicker member in the axial direction of the photosensitive drum, and the toner accumulated in the back of the brush of the conductive roll brush is sprinkled to the surface of the photosensitive drum. Sweep out. Thereby, the cleaning performance of the conductive roll brush is refreshed.

JP 2003-167477 A JP 2003-316202 A JP 2005-208322 A Japanese Patent Laid-Open No. 5-53489

  The auxiliary charging devices disclosed in Patent Document 2 and Patent Document 3 reciprocate a fixed conductive brush to which a DC voltage is applied in the axial direction of the photosensitive drum so that the transfer residual toner on the surface of the photosensitive drum has a normal polarity. It is charged. However, the fixed conductive brush gradually accumulates the toner charged in the opposite polarity at the interval between the hairs as the image is formed, and discharges the toner charged in the opposite polarity during the image formation. Cleaning does not work well.

  Therefore, in the auxiliary charging device disclosed in Patent Document 2, the toner is electrically discharged from the conductive brush to the surface of the photosensitive drum during non-image formation. However, the toner moves to the back side of the brush by rubbing with reciprocating movement and accumulates. On the other hand, even when a high voltage is applied, the toner is transferred to the photosensitive drum only at the hair portion close to the surface of the photosensitive drum. It is not possible to form a sufficient electric field to urge the surface. Therefore, the discharge effect is limited for the toner accumulated slightly in the back of the brush, and a sufficient refresh effect cannot be obtained by an electric method in a fixed brush with reciprocating movement. If the reciprocating movement is continued while applying the discharge voltage, the toner gradually moves from the back side of the brush to the tip side due to the density diffusion and is swept out, but it takes a long time to obtain a sufficient refresh effect.

  In view of this, an auxiliary charging device has been proposed in which the electrical method disclosed in Patent Document 2 is replaced with the flicker member disclosed in Patent Document 4 and the toner is mechanically sprinkled from the back side of the stationary brush.

  However, only the method of reciprocating in the axial direction the flicker member in which the protrusion is deeply inserted into the stationary brush has caused some of the following problems.

  First, if the protrusion of the flicker member and the brush interfere too much during image formation, the contact area with the image carrier decreases due to the falling of the brush, and the charged state of the transfer residual toner on the image carrier is uniform. Lost control.

  Next, the polarity reversal toner or uncharged toner held by the brush is dropped on the image carrier during image formation, and these toners having no normal polarity cannot be collected by the developing device, and are not collected on the image carrier. Came to go around. The toner that was carried around reversed the polarity at the transfer portion and contaminated the charging roller during image formation, which caused charging defects and fogging. In addition, there is a problem that the brush is deformed into a fallen state due to excessive excessive interference between the protrusion and the brush.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a cleanerless type image forming apparatus that can remove and collect transfer residual toner stably and favorably for a long period of time by simultaneous cleaning of development without causing the above disadvantages. Yes.

  The image forming apparatus of the present invention includes an image carrier on which a toner image is formed on a moving surface, charging means for applying a charging voltage to charge the surface, and applying a transfer voltage to the toner image from the surface. A transfer means for transferring the toner, a brush member for charging the transfer residual toner by rubbing a conductive hair on the surface between the transfer means and the charging means, and the brush member along the surface. And a brush drive mechanism that periodically moves. A flicker member arranged with a large number of protrusions inserted into the hairs, a flicker drive mechanism for periodically moving the flicker member, the brush drive mechanism and the flicker drive mechanism to control the brush member, Control means for moving the flicker member. The control means moves the brush member and the flicker member relative to each other with a larger amplitude than during image formation during a brush recovery period without image formation.

  The process cartridge of the present invention includes a developing unit that develops an electrostatic latent image formed on the surface of an image carrier to form a toner image, a charging unit that uniformly contacts and charges the surface, The cleaner-less type includes a brush member that reciprocates in the direction intersecting the moving direction of the surface on the upstream side and rubs the surface. A flicker member that reciprocates in parallel with the brush member in a state in which a large number of protrusions are inserted into the hairs of the brush member. The flicker member and the brush member can be controlled from the outside to switch between the reciprocating movement and the relative movement of the isotope homologous amplitude.

  The auxiliary charging method of the present invention is a method in which the transfer residual toner on the surface of the photosensitive drum is charged with the same polarity as the charging voltage applied to the charging roller. In a state where the charging voltage is applied to the charging roller, the brush member to which an auxiliary charging voltage of the same polarity is applied is reciprocated integrally with a flicker member in which a large number of protrusions are inserted into the hair member spacing. A first step and a second step of relatively moving the flicker member and the brush member in the reciprocating direction without applying the charging voltage to the charging roller.

  In the image forming apparatus of the present invention, the control unit sets a brush recovery period without image formation, and cleans the brush member with the flicker member. The flicker member moves relative to the brush member during the brush recovery period with a larger amplitude than that at the time of image formation, and causes the protrusions to more strongly interfere with the hair of the brush member. Toner is swept away. Therefore, when an image is formed over an overwhelmingly long time compared to the brush recovery period, the effects of the protrusions on the hair of the brush member are reduced, and the negative effects such as hair fall, poor charging, and discharge of uncharged toner are caused. Can be reduced.

  In addition, since the protrusions of the flicker members are held at the intervals between the hairs of the brush members even during image formation, there is no need to insert and remove the protrusions at the intervals between the hairs before and after the brush recovery period. Relative movement can be started. Therefore, the auxiliary charging device can be made smaller and lighter than the structure in which the protrusions are inserted and removed between the hairs before and after the brush recovery period. Since there are no difficulties associated with insertion and removal, the reliability of the mechanism is also increased. Further, since the transition to the brush recovery period is completed in a short time, the necessary cleaning can be completed in a short time, and the image formation can be restored in a short time, so that the productivity of image formation is not hindered.

  The process cartridge of the present invention is mounted on the image forming apparatus of the present invention, and the image forming apparatus and the brush recovery period are controlled by the control means on the image forming apparatus side. The control means relatively moves the flicker member and the brush member during the brush recovery period, and causes the flicker member and the brush member to reciprocate with the same homologous amplitude during image formation.

  In the auxiliary charging method of the present invention, the second step (brush recovery period) is executed to discharge the staying toner from the brush member, so that hair fall in the first step (during image formation), charging failure, uncharged toner The harmful effect of releasing can be reduced.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. The image forming apparatus of the present invention is not limited to the configuration of the embodiment described below. As long as the image bearing member is rubbed with reciprocation to charge the transfer residual toner, another embodiment in which part or all of the configuration of each embodiment is replaced with the alternative configuration can be realized. is there.

  In this embodiment, an image forming apparatus that performs full color image formation using four process cartridges that form toner images of different separation colors will be described. However, the present invention may be implemented in an image forming apparatus in which one or more photosensitive drums are arranged, an image forming apparatus that does not use a process cartridge, an image forming apparatus that uses an image carrier other than the photosensitive drum, and the like. The intermediate transfer belt, the recording material conveyance belt, the intermediate transfer drum, and the recording material conveyance drum can be replaced with each other, and can be used for various applications such as printers, various printing machines, copiers, FAX machines, multifunction machines, etc. Can also be implemented.

  It should be noted that the configuration of the general image forming apparatus disclosed in Patent Documents 1 to 4, details of the brush reciprocating mechanism, the power supply configuration of the auxiliary charging device, the control content, etc. are not shown and detailed description is also omitted. To do.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of a configuration in which a main part of the image forming apparatus of the present embodiment is shown in cross section, and FIG. 2 is an enlarged view of a part including a process cartridge. As shown in FIG. 1, the image forming apparatus 100 is a color laser printer that uses an intermediate transfer type electrophotographic process, a contact charging method, and a reverse development method and has a maximum sheet passing size of A3 size. The image forming apparatus 100 is equipped with four process cartridges 8Y, 8M, 8C, and 8K having different development colors that can be individually replaced, and forms a full-color image on a recording material such as paper, an OHP sheet, or a cloth. Since the process cartridges 8Y, 8M, 8C, and 8K are substantially the same except that different developers are used, the subscripts Y, M, C, and K representing the different colors are omitted in FIG. Overall configuration is shown.

  The image forming apparatus 100 arranges image forming units PY, PM, PC, and PK in the order of yellow (Y), magenta (M), cyan (C), and black (K) in the moving direction of the intermediate transfer belt 91. Yes. Process cartridges 8Y, 8M, 8C, and 8K are mounted on the image forming units PY, PM, PC, and PK, respectively. When a four-color full-color image is formed, a color-separated image signal is generated in accordance with a signal from an external host device that is communicably connected to the image forming apparatus 100. In response to this signal, toner images of the respective colors are formed in the process cartridges 8Y, 8M, 8C, and 8K of the image forming units PY, PM, PC, and PK.

  The toner images of the respective colors formed on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially superimposed and transferred onto the circulating intermediate transfer belt 91. The full-color toner image formed on the intermediate transfer belt 91 is collectively transferred onto the recording material P conveyed to the secondary transfer portion where the intermediate transfer belt 91 and the secondary transfer roller 10 face each other. Next, the recording material P is conveyed to the fixing device 12 where the toner image is fixed by heating and pressurization, and then discharged outside the apparatus.

  As shown in FIG. 2, in the process cartridge 8, the exposure device 3 scans and exposes the surface of the photosensitive drum 1 charged by the charging roller 2 to form an electrostatic latent image, and the developing device 4 converts the electrostatic latent image into an electrostatic latent image. Toner is supplied and developed into a toner image. Around the rotating photosensitive drum 1, a charging roller 2, a developing device 4, a primary transfer roller 92, a toner charge amount control member 6, and a residual toner image equalizing member 7 are arranged.

  The photosensitive drum 1 is a rotating drum type electrophotographic photosensitive member formed with an organic photoconductor (OPC) surface layer, and has an outer diameter of 30 mm and a process speed (circumferential speed) of 195 mm / sec centering on a central support shaft. Is rotated in the direction indicated by the arrow in the figure.

  The photosensitive drum 1 has an undercoat layer for improving the adhesion of the upper layer by suppressing light interference, a photocharge generation layer, and a charge transport layer (thickness 20 μm) on the surface of an aluminum cylinder (conductive drum base). The three layers are coated in order from the bottom.

The charging roller 2 is a roller-shaped contact charger that charges the surface of the photosensitive drum 1 with a uniform negative polarity while rotating in accordance with the rotation of the photosensitive drum 1. The charging roller 2 has a three-layer structure in which a lower layer 2b, an intermediate layer 2c, and a surface layer 2d are sequentially laminated from the bottom centering on a core metal 2a. The roller outer diameter is 14 mm, the longitudinal length is 320 mm, and the roller resistance is 10 ⁴ Ω to 10 ⁷ Ω. The lower layer 2b is a foamed sponge layer for reducing charging noise, and the intermediate layer 2c is a resistance layer for obtaining uniform resistance as a whole of the charging roller 2. The surface layer 2d is a protective layer that is made of a fluorocarbon resin in which carbon is dispersed and prevents leakage even if there are defects such as pinholes on the photosensitive drum 1. The cored bar 2a is a stainless steel round bar having a diameter of 6 mm. Both ends of the cored bar 2a are rotatably held by a bearing member and are urged by a pressing spring to be pressed against the surface of the photosensitive drum 1 with a predetermined pressing force. ing.

  A charging bias voltage Vdc + Vac obtained by superimposing an AC voltage Vac having a predetermined frequency on the DC voltage Vdc is applied from the charging power source 20 to the charging roller 2 via the cored bar 2a. A contact portion between the charging roller 2 and the photosensitive drum 1 is a charging portion a. In this embodiment, the charging bias voltage applied to the charging roller 2 is an oscillating voltage in which a DC voltage of −500 V, a frequency = 1985 Hz, a peak-to-peak voltage Vpp = 1400 V, and a sinusoidal AC voltage are superimposed. As a result, the peripheral surface of the photosensitive drum 1 is uniformly charged to −500 V (dark portion potential Vd).

  A charging roller cleaning member 2 f is provided in contact with the charging roller 2. The charging roller cleaning member 2f is a flexible cleaning film. The charging roller cleaning member 2f is disposed in parallel with the charging roller 2 and fixed at one end to a support member 2g that reciprocates in the longitudinal direction of the charging roller 2, and forms a contact nip with the charging roller 2 on the surface near the free end side. To do. The support member 2g is driven by a drive motor of the image forming apparatus 100 through a gear train to reciprocate, whereby the surface layer 2d of the charging roller 2 is slid by the charging roller cleaning member 2f. As a result, adhering contaminants (fine toner, external additives, etc.) on the surface layer 2d of the charging roller 2 are removed.

  The exposure device 3 is a laser scanner that outputs an image exposure L to the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 and writes an electrostatic latent image. The exposure apparatus 3 includes a laser light source using a semiconductor laser, an imaging exposure optical system, and a scanning optical system using a rotating mirror. The exposure device 3 outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of color separation / image information of a color original image sent from a host device such as an image reading device (not shown) to perform scanning exposure. To do. As a result, on the uniformly charged surface of the rotating photosensitive drum 1, the potential of the portion irradiated by the image exposure L is reduced, and an electrostatic latent image for each color component corresponding to the scanned and exposed image information is formed. The In this embodiment, the exposed portion potential Vl is set to −150V. The irradiation position of the image exposure L on the photosensitive drum 1 is the exposure part b.

  The developing device 4 is a two-component contact developing device (two-component magnetic brush developing device) that develops the toner by electrically attaching the toner to the electrostatic latent image formed on the photosensitive drum 1. The developing device 4 stores a two-component developer 46, which is mainly a mixture of resin toner particles (toner) and magnetic carrier particles (carrier), in a developing container 40, and a developer carrier in an opening on the photosensitive drum 1 side. The developing sleeve 41 is arranged. A developer regulating blade 42 as a developer regulating member is disposed opposite to the developing sleeve 41 with a predetermined gap.

  The developing sleeve 41 has a magnet roller fixed therein and is driven to rotate in a direction opposite to the traveling direction of the surface of the opposing photosensitive drum 1. As the developing sleeve 41 rotates, a thin developer layer regulated by the developer regulating blade 42 is formed on the developing sleeve 41. In the present embodiment, the developing sleeve 41 is disposed to face the photosensitive drum 1 with the closest distance (S-Dgap) to the photosensitive drum 1 maintained at 350 μm. A facing portion between the photosensitive drum 1 and the developing sleeve 41 is a developing portion c. The developer thin layer carried on the developing sleeve 41 comes into contact with the surface of the photosensitive drum 1 and rubs appropriately at the developing portion c.

  A predetermined developing bias voltage is applied to the developing sleeve 41 from a developing power source (not shown). In this embodiment, the developing bias voltage applied to the developing sleeve 41 is an oscillating voltage obtained by superimposing a DC voltage (Vdc) of −350 V and an AC voltage (Vac) of 1800 Vpp and frequency = 2300 Hz. Accordingly, the toner in the developer 46 conveyed to the developing portion c as a developer thin layer by the rotating developing sleeve 41 is selectively attached to the electrostatic latent image on the photosensitive drum 1 by the electric field due to the developing bias voltage. The toner image is developed. In the present embodiment, toner adheres to the exposed bright portion (potential drop portion) of the photosensitive drum 1 and the electrostatic latent image is reversely developed.

  The developer thin layer carried on the developing sleeve 41 passes through the developing portion c as the developing sleeve 41 rotates, and is returned to the developer reservoir in the developing container 40. In the developing device 4, stirring screws 43 and 44 as developer stirring members are provided. The agitation screws 43 and 44 rotate in synchronization with the rotation of the developing sleeve 41, agitate and mix the toner replenished to the developer 46 with the carrier, and give a predetermined charged charge to the toner. The agitating screws 43 and 44 respectively convey the developer 46 in the opposite direction in the longitudinal direction, supply the developer 46 to the developing sleeve 41, and develop the toner density (ratio of toner in the developer) decreased by development. The agent 46 is conveyed, stirred, and circulated in the developing container 40.

  A sensor 45 is provided on the upstream side wall surface of the screw 44 of the developing device 4 to detect a change in the magnetic permeability of the developer 46 and detect the toner concentration in the developer 46. A toner replenishing opening 47 is provided on the downstream side of the sensor 45 in the circulation direction of the developer 46. The screw 51 is driven according to the detection result of the toner density detected by the sensor 45, and toner is supplied from the toner supply unit 5 through the toner supply opening 47, so that the toner density in the developer 46 is recovered. The replenished toner is conveyed by the agitating screws 44 and 43 and mixed with the carrier. After being given an appropriate charge, it is supplied to the developing sleeve 41 to form a thin layer again on the developing sleeve 41 for development. Provided.

In this embodiment, a negatively charged toner having an average particle diameter of 5.5 μm is used as the toner, and a magnetic carrier having a saturation magnetization of 205 emu / cm ³ and an average particle diameter of 35 μm is used as the carrier. Toner and carrier were mixed at a weight ratio of 6:94 to obtain developer 46. The toner charge amount measured on the photosensitive drum 1 was −25 μC / g.

  As shown in FIG. 1, an intermediate transfer unit 9 is provided so as to face image forming portions PY, PM, PC, and PK. The intermediate transfer unit 9 uses an endless intermediate transfer belt 91 as a photosensitive drum 1Y, 1M, 1C. 1K. The intermediate transfer belt 91 is wound around the driving roller 94, the tension roller 95, and the secondary transfer counter roller 96 with a predetermined tension, and circulates in the direction of the arrow in the figure. In the image forming units PY, PM, PC, and PK, the primary transfer rollers 92Y, 92M, 92C, and 92K are controlled to primarily transfer the toner image to the intermediate transfer belt 91. First, a yellow toner image formed on the photosensitive drum 1Y by the above-described operation is transferred to the intermediate transfer belt 91 by the first color (yellow) image forming unit PY. Next, magenta, cyan, and black toner images are sequentially transferred in multiple from the photosensitive drums 1M, 1C, and 1K corresponding to the respective colors that have undergone the same process.

  As shown in FIG. 2, a primary transfer roller 92 is disposed on the back side of the intermediate transfer belt 91 facing the photosensitive drum 1. The primary transfer roller 92 urges the bearing portion by a pressing spring and presses the bearing portion against the intermediate transfer belt 92 to form a transfer portion (primary transfer nip portion) d between the intermediate transfer belt 91 and the photosensitive drum 1. The toner image formed on the photosensitive drum 1 enters the transfer portion d and is transferred to the intermediate transfer belt 91.

  In the transfer section d, an independent primary transfer bias voltage adjusted for each of the image forming sections PY, PM, PC, and PK is applied to the primary transfer roller 92 from each primary transfer bias power supply 93. In this embodiment, the primary transfer bias voltage is set to +350 V for all of the first to fourth colors in consideration of the transfer efficiency of toner to the surface of the exposed portion potential Vl (−150 V).

As a material for the intermediate transfer belt 91, a material that expands and contracts is not desirable in order to improve registration in the image forming portions PY, PM, PC, and PK. From a resin system or a rubber belt with a metal core, resin, and rubber. A belt is desirable. In this embodiment, a resin belt in which carbon is dispersed in PI (polyimide) and the volume resistivity is controlled to the order of 10 ⁸ Ωcm is used. The thickness is 80 μm, the longitudinal direction is 320 mm, and the entire circumference is 900 mm. The primary transfer roller 92 is made of a conductive sponge and has a resistance of 10 ⁶ Ω or less, an outer diameter of 16 mm, and a longitudinal length of 315 mm.

  As shown in FIG. 1, the four-color full-color toner image formed on the intermediate transfer belt 91 is transferred between the secondary transfer roller 10 and the intermediate transfer belt 91 that are pressed against the secondary transfer counter roller 96 via the intermediate transfer belt 91. To the secondary transfer nip. A recording material P is supplied from a recording material feeding mechanism (not shown) to the secondary transfer nip portion in time with a four-color full-color toner image, and a secondary transfer roller 10 to which a secondary transfer bias voltage is applied, A four-color full-color toner image is secondarily transferred onto the recording material P at once.

  The recording material P onto which the four-color full-color toner image has been secondarily transferred is then conveyed to a fixing device (roller fixing device) 12 where the toner image is melted into the recording material P by being heated and pressed by the fixing device 12. It is fixed. Thereafter, the recording material P is discharged out of the apparatus and a color print image is obtained. The secondary transfer residual toner that passes through the secondary transfer nip portion and remains on the intermediate transfer belt 91 is cleaned by a cleaning blade 11a included in the intermediate transfer belt cleaner 11 to prepare for the next image forming process.

  In the cleanerless type image forming apparatus 100 that simultaneously cleans the transfer residual toner with the developing device 4, toner charged to a polarity opposite to the normal polarity adheres to the charging roller 2 and causes charging failure. When the transfer residual toner on the photosensitive drum 1 passes through the nip between the photosensitive drum 1 and the charging roller 2, the toner in which the charging polarity in the transfer residual toner is reversed to a polarity opposite to the normal polarity is charged to the charging roller 2. The toner adheres to the charging roller 2 and causes the toner to be contaminated more than allowable.

  This is because the toner as a developer contains a toner whose charge polarity is originally reversed to a polarity opposite to the normal polarity although it is small in quantity. Furthermore, even when the toner has a normal charge polarity, there are toners whose charge polarity is reversed by being affected by the primary transfer bias voltage, peeling discharge, and others, and those whose charge amount is reduced due to charge removal.

  That is, the transfer residual toner includes a mixture of a normal polarity charge toner, a reverse polarity reversal toner, and a low charge amount, and the reversal toner and the low charge amount toner are charged with the photosensitive drum 1. It easily adheres to the charging roller 2 when passing through the nip with the roller 2.

  Further, in order to remove and collect the transfer residual toner on the photosensitive drum 1 by the simultaneous development cleaning of the developing device 4, the charged polarity of the transfer residual toner on the photosensitive drum 1 carried by the developing device 4 is just the normal polarity. Is not enough. The charge amount needs to be a toner charge amount that allows the developing device 4 to develop the electrostatic latent image on the photosensitive drum 1. Reversal toner and toner with an inappropriate charge amount cannot be removed and collected from the photosensitive drum 1 to the developing device 4 and cause a defective image.

<Auxiliary charging device>
As shown in FIG. 2, the image forming portions PY, PM, PC, and PK are provided with a toner charge amount control member 6 and a residual toner image equalizing member 7, respectively. The residual toner image equalizing member 7 is located downstream of the transfer portion d of the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 and upstream of the charging portion a and sequentially from the upstream side of the rotation direction of the photosensitive drum 1. A toner charge amount control member 6 is disposed. As a result, a contact portion e between the residual toner image equalizing member 7 and the photosensitive drum 1 and a contact portion f between the toner charge amount control member 6 and the photosensitive drum 1 are formed.

  The photosensitive drum 1, the charging roller 2, the charging roller cleaning member 2 f, the developing device 4, the residual toner image equalizing member 7, the toner charge amount control member 6, and the like are integrally formed by a charging unit frame 111 and a developing frame 112. The process cartridge 8 is configured. The process cartridge 8 is detachably mounted on a mounting frame 110a provided in the apparatus main body of the image forming apparatus (100: FIG. 1). The toner replenishing unit 5 is detachably mounted on the developing device 4 while being supported by a mounting frame 110b of the apparatus main body.

  With the process cartridge 8 mounted on the apparatus main body, the drive transmission mechanism on the apparatus main body side and the drive transmission mechanism on the process cartridge 8 side are connected, and the photosensitive drum 1, the developing device 4, the charging roller 2, and the toner charge amount. The control member 6 and the like can be driven. Further, in a state where the process cartridge 8 is mounted on the apparatus main body, the contact on the process cartridge 8 side and the contact on the apparatus main body side communicate with each other, and voltage is applied from the apparatus main body side to each voltage applying member in the process cartridge 8. Supply is possible. The charging power source 20 and the power sources 21 and 22 are electrically connected to the charging roller 2, the toner charge amount control member 6, and the residual toner image equalizing member 7, and the voltage can be supplied to the developing sleeve 41.

  In this embodiment, the toner charge amount control member 6 and the residual toner image uniformizing member 7 are both brush members made of conductive fibers. The toner charge amount control member 6 includes a horizontally long electrode plate 62 and a brush portion 61. Similarly, the residual toner image equalizing member 7 includes a brush portion 71 on the electrode plate 72. The brush portions 61 and 71 are disposed substantially in parallel with an interval in the axial direction of the photosensitive drum 1 (a direction substantially orthogonal to the moving direction of the surface), and are in contact with the surface of the photosensitive drum 1.

The brush parts 61 and 71 are formed by adding carbon or metal powder to fibers such as rayon, acrylic, and polyester to control the resistance value. The brush portions 61 and 71 preferably have a thickness of 30 denier or less and a density of 1 to 500,000 / inch ² or more so that the surface of the photosensitive drum 1 and the transfer residual toner can be uniformly contacted. In this embodiment, the brush portions 61 and 71 are both 6 denier, 100,000 pieces / inch ² , the length of the bristle is 5 mm, and the volume resistivity of the brush is 6 × 10 ³ Ω · cm.

  The toner charge amount control member 6 and the residual toner image equalizing member 7 are arranged such that the brush portions 61 and 71 are in contact with the surface of the photosensitive drum 1 with an intrusion amount of 1 mm, and are in contact with the photosensitive drum 1. The length in the rotation direction of the parts f and e was 5 mm.

  A predetermined voltage is applied from the power source 22 to the residual toner image equalizing member 7 and from the power source 21 to the toner charge amount control member 6. The charging power source 20 and the power sources 21 and 22 are installed in the apparatus main body of the image forming apparatus (100: FIG. 1), and are controlled by a control circuit 130 that performs overall control of the operation of the apparatus main body.

  Transfer residual toner adheres to the surface of the photosensitive drum 1 that has passed through the transfer portion d. The transfer residual toner includes negative toner in the image portion, positive toner in the non-image portion, and reversal toner whose polarity is reversed to positive polarity due to the positive transfer bias voltage at the time of transfer. .

  In the present embodiment, as a voltage condition for improving the toner recoverability with respect to the toner having the normal polarity and the reverse polarity, an AC voltage on which a DC voltage is superimposed is applied to the residual toner image equalizing member 7 at the time of image formation. Applied. By applying an AC voltage to the residual toner image equalizing member 7, the ability to electrostatically collect the transfer residual toner on the photosensitive drum 1 is improved. Further, the electrostatic latent image on the photosensitive drum 1 is applied to the residual toner image equalizing member 7 by applying a DC voltage having a polarity (positive polarity) opposite to the normal polarity of the toner superimposed on the AC voltage. Prevents positive ghosts by applying electricity.

  Here, the positive ghost is a surface potential unevenness of the photosensitive drum 1 that is too large to be uniformed by the charging roller 2 formed when passing through the transfer portion d. When the portion where the toner layer is present and the portion where the toner layer is not present pass through the transfer portion d, a large difference occurs in the transfer current flowing into the photosensitive drum 1 between the portion where the toner layer is present and the portion where the toner layer is not present. A step in surface potential is formed. If this surface potential step is too large to be smoothed by the charging roller 2, the step affects the image, which is called positive ghost. The residual toner image uniformizing member 7 is effective in eliminating the potential difference at the transfer portion d.

  On the other hand, a negative DC voltage having the same polarity as the normal polarity of the toner is applied from the power source 21 to the toner charge amount control member 6 during image formation. This is to prevent the toner slightly slipping from the residual toner image uniformizing member 7 from contaminating the charging roller 2. In order to avoid this, in the present embodiment, a DC voltage of −700 V or higher, which is equal to or higher than the discharge start voltage, is applied to expose the transfer residual toner passing through the toner charge amount control member 6 to have sufficient discharge to have a negative polarity ( Normal polarity) is charged. Thereafter, the charging unit a charges the surface of the photosensitive drum 1 from above the transfer residual toner. Since the polarity of the transfer residual toner is made negative by the toner charge amount control member 6, the charging of the toner is performed. There is no adhesion to the roller 2. The charged charge of the transfer residual toner is appropriately neutralized by the AC voltage applied to the charging roller 2.

  Subsequently, the exposure unit b irradiates the image exposure L on the transfer residual toner. However, since the amount of the transfer residual toner is small, the substantial exposure amount is not affected.

  Subsequently, in the developing portion c, the negative transfer residual toner adhering to the unexposed portion (non-image portion) that should not be developed moves to the developing sleeve 41 that is relatively charged to the positive polarity side. And removed from the surface of the photosensitive drum 1. The untransferred toner in the unexposed area is completely negative and is appropriately neutralized by the charging roller 2 to reduce the mirror power with the photosensitive drum 1. For this reason, the untransferred residual toner in the unexposed portion is surely determined by the relationship (fogging removal potential difference Vback) between the surface potential of the photosensitive drum 1 (unexposed portion potential: −500 V) and the DC component (−350 V) of the developing bias. It is collected in the developing device 4.

  In this embodiment, the developing sleeve 41 is a contact two-component counter developing system in which the developing portion c rotates in a direction opposite to the moving direction of the surface of the photosensitive drum 1 and rubs the photosensitive drum 1 with the developer layer. . This is advantageous for collecting the transfer residual toner on the photosensitive drum 1.

  According to the simultaneous development cleaning, the transfer residual toner is collected by the developing device 4 and reused for developing the electrostatic latent image in the subsequent process. Therefore, waste toner is eliminated and maintenance is less troublesome. Become. The absence of the waste toner container is advantageous in reducing the size of the image forming apparatus (100: FIG. 1).

<Flicker member drive mechanism>
3 is a schematic view of the driving mechanism of the flicker member and the toner charge amount control member as viewed from the photosensitive drum side, and FIG. 4 is a schematic view of the drive mechanism of the flicker member and the toner charge amount control member as viewed from the residual toner image equalizing member side. FIG. FIG. 5 is a flowchart of the control of the flicker member and the toner charge amount control member. 3 and 4, in order to simplify the illustration, the dimensions, number, density, and the like of the protrusion 202d and the shapes of the reciprocating cams 203 and 204 of the reciprocating drive mechanism are exaggerated and conceptually expressed. is doing. Further, the drive transmission mechanism described above is omitted, and motors 207 and 208 are directly connected to the reciprocating cam shafts 205 and 206, respectively. In actuality, these members are optimally designed differently from those in FIGS. 3 and 4 in accordance with the description of the configuration.

  As shown in FIG. 2, a flicker member 200 having a large number of protrusions arranged in the axial direction of the image carrier is provided in the vicinity of the toner charge amount control member 6. As shown in FIG. 3, the toner charge amount control member 6 and the flicker member 200 are each provided with a reciprocating drive mechanism so as to be able to reciprocate independently in the axial direction of the photosensitive drum 1.

As shown in FIG. 4, the protrusion 212 of the flicker member 200 is formed and arranged so as to penetrate deeply into the brush portion 61 of the toner charge amount control member 6. The density of the protrusions 212 is 100 / cm ² , and the height of the protrusions 212 is applicable to about 2 to 5 mm, preferably about 3 to 4 mm. The protrusion 212 can be applied with a diameter of about 0.5 to 2 mm, preferably about 1 mm in diameter.

  The protrusion 212 has a circular cross section, but there is no problem as long as it has a certain degree of rigidity, such as a square, a diamond, or a star. Further, when a 4 mm protrusion is used, the intrusion amount is 3 mm, and the clearance where the protrusion 212 does not enter the brush is preferably about 1 mm.

  As shown in FIG. 3, the reciprocating cam 203 is fixed to the reciprocating cam shaft 205. The reciprocating cam 203 is restrained in the axial direction of the reciprocating cam shaft 205 by the groove 201 a of the reciprocating cam receiver 201. The reciprocating cam 203 is formed with a guide surface for driving the reciprocating cam receiver 201 in the axial direction. When the motor 207 rotates the reciprocating cam shaft 205 under the control of the control circuit 130, the reciprocating cam 203 rotates synchronously, and the reciprocating cam receiver 201 and the reciprocating cam 203 interfere with each other. As a result, the flicker member 200 connected to the reciprocating cam receiver 201 reciprocates in the axial direction of the photosensitive drum (1: FIG. 2).

  Similarly, the groove 202 a of the reciprocating cam receiver 202 restrains the reciprocating cam 204 in the axial direction of the reciprocating cam shaft 206. The reciprocating cam 204 is formed with a guide surface that drives the reciprocating cam receiver 202 in the axial direction of the reciprocating cam shaft 206. When the motor 208 rotates the reciprocating cam shaft 206 under the control of the control circuit 130, the reciprocating cam 204 rotates synchronously, and the reciprocating cam receiver 202 and the reciprocating cam 204 interfere with each other. As a result, the toner charge amount control member 6 connected to the reciprocating cam receiver 202 reciprocates in the axial direction of the photosensitive drum (1: FIG. 2).

  A control circuit 130 that comprehensively controls the operation of the apparatus main body of the image forming apparatus (100: FIG. 1) controls the rotation timing and rotation / stop of the motors 207 and 208. As a result, the toner charge amount control member 6 and the flicker member 200 are reciprocally driven independently or in synchronization with a predetermined phase difference.

  As shown in FIG. 5 with reference to FIG. 2, the control circuit 130 controls the image forming apparatus (100: FIG. 1) to print 100 sheets (YES in S <b> 11) and return as the brush recovery period. The mode operation is interrupted (S12). In the return mode, image formation is prohibited and a post-rotation process is forcibly performed for 3 seconds. At this time, relative movement is performed between the toner charge amount control member 6 and the flicker member 200. Thus, the toner is discharged from the brush portion (61: FIG. 4) of the toner charge amount control member 6 to the surface of the rotating drum (1: FIG. 2).

  During the return mode, the charging bias voltage was not applied to the charging roller 2, and the normal bias voltage was applied only to the primary transfer roller 92. However, in Example 2, which will be described later, a reverse polarity bias voltage was set.

  On the other hand, a normal print operation is executed (S13) until 100 sheets are reached (No in S11) or after the return mode operation (S12) is completed. In the normal printing operation (S13), the toner charge amount control member 6 and the flicker member 200 are reciprocally driven in synchronization so that relative movement does not occur between the toner charge amount control member 6 and the flicker member 200. Thereby, the charge control effect by the toner charge amount control member 6 without variation in the axial direction of the photosensitive drum 1 can be obtained.

  Thereafter, when the job is completed (Yes in S14), the normal post-rotation is executed to stop the image forming apparatus 100. If there is a remaining job, the processes in S11 to S14 are repeated.

  In this way, the image forming apparatus (100: FIG. 1) conducts a real-shooting test in which 50,000 sheets of print output with an image coverage of 10% are intermittently executed continuously at 50,000 sheets in a normal temperature and humidity environment. The printed image obtained on the tenth sheet was visually evaluated. In other words, output jobs with 2 sheets were performed until the total number of output jobs reached 50,000.

  Then, the same experiment was repeated under the conditions of Examples 1 to 7 in which the setting of the relative movement between the toner charge amount control member 6 and the flicker member 200 in the return mode was repeated, and the effects of the return mode were compared. The same experiment was repeated and compared with Examples 1 to 7 under the conditions of Comparative Examples 1 to 4 in which the setting of relative movement between the toner charge amount control member 6 and the flicker member 200 during image formation or in the return mode was changed. .

  As shown in Table 1, the toner charge amount control member 6 and the flicker member 200 are prohibited from relative movement during image formation, and the toner charge amount control member 6 and the flicker member 200 are relatively moved in the return mode. In ˜7, a good 50,000th image was obtained. However, in Comparative Example 1 in which the relative movement between the toner charge amount control member 6 and the flicker member 200 is prohibited even in the return mode, a good image cannot be obtained at the 20,000th sheet. In Comparative Examples 2 to 4 in which the toner charge amount control member 6 and the flicker member 200 are relatively moved during image formation, a good image cannot be obtained with a smaller number of sheets.

<Example 1>
6 is an explanatory view of the arrangement of the toner charge amount control member and the flicker member in the first embodiment, and FIG. 7 is an explanatory view of the relative movement of the toner charge amount control member and the flicker member.

  As shown in FIG. 6, in Example 1, a fixed brush portion 61 having a reciprocating drive mechanism was used as the toner charge amount control member 6. During normal image formation, the toner charge amount control member 6 and the flicker member 200 have the same reciprocating drive phase, and in the return mode, as shown in FIG. 7, the toner charge amount control member 6 and the flicker member. 200, the reciprocal drive with the phase shifted by 180 degrees was performed.

  In the first exemplary embodiment, the reciprocating drive is set so that the brush portion 61 and the protrusion 212 of the flicker member 200 do not interfere so much during image formation. Therefore, the charging roller 2 is contaminated with the toner discharged from the brush portion 61. No fogging occurred. In the return mode, the brush portion 61 and the protrusion 212 of the flicker member are largely interfered with each other at a timing other than image formation, and toner clogging to the brush portion 61 can be prevented. For this reason, the toner charging capability of the brush portion 61 did not decrease for a long time, and the cleanerless system could be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

  That is, in the image forming apparatus 100, since the brush member and the flicker member are each independently provided with a reciprocating drive mechanism, it is possible to change the phase of each reciprocating motion. When forming an image in which the toner accumulated on the brush member should not be discharged to the image carrier, the phase of the reciprocating drive is not changed, and the brush member's hair and the flicker member's protrusion are kept in the same direction. Reciprocating drive so as not to cause large interference. On the contrary, in the return mode without image formation, reciprocal driving is performed by changing the phase so that the hair of the brush member and the protrusion of the flicker member greatly interfere with each other. As a result, the transfer residual toner that has deeply entered and accumulated in the hair of the brush member is neatly discharged onto the image carrier.

  Therefore, the brush member is completely refreshed to be free of toner clogging in the return mode, and the toner charging ability of the brush member can be maintained for a long time.

  Further, only in the return mode, as shown in FIG. 7, the bristle of the brush portion 61 and the protrusion 212 of the flicker member 200 are largely interfered with each other, and only in the return mode, there is no polarity or the polarity is reversed. The toner is discharged to the photosensitive drum (1: FIG. 2). For this reason, the charging roller 2 is not contaminated with toner during image formation and the image is not affected.

<Example 2>
In the second embodiment, similarly to the first embodiment, the phase of the reciprocating drive of the toner charge amount control member 6 and the flicker member 200 is made the same during normal image formation using the fixed brush portion 61. Also in the return mode, the toner charge amount control member 6 and the flicker member 200 are reciprocally driven with a phase difference of 180 degrees as in the first embodiment. However, in the second embodiment, control is performed so that a bias voltage opposite to the normal bias voltage is applied to the primary transfer roller.

  The effect of applying a reverse bias voltage to the primary transfer roller will be described. As described above, since the bias voltage applied to the toner charge amount control member 6 has the same polarity (negative polarity) as the charge polarity of the toner, the toner that clogs the brush portion 61 of the toner charge amount control member 6. The polarity is opposite to the normal charging polarity of the toner (positive polarity). Therefore, when such clogged toner of reverse polarity is discharged onto the surface of the photosensitive drum 1 by the flicker member 200, in order to transfer it to the intermediate transfer belt (91: FIG. 2) for recovery, This is not possible with a positive transfer bias voltage. For this reason, it is necessary to effectively recover using a reverse polarity bias voltage.

  Also in the second embodiment, since the reciprocating drive is set so that the brush portion 61 and the protrusion 212 of the flicker member 200 do not interfere so much during image formation, the charging roller 2 is contaminated with the toner discharged from the brush portion 61. No fogging occurred. In the return mode, the brush portion 61 and the protrusion 212 of the flicker member are largely interfered with each other at a timing other than image formation, and toner clogging to the brush portion 61 can be prevented. For this reason, the toner charging capability of the brush portion 61 did not decrease for a long time, and the cleanerless system could be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

  In other words, in the image forming apparatus 100, the toner discharged on the image carrier in the return mode often has little polarity or is a toner having a slightly reversed polarity opposite to normal. Therefore, the toner has a polarity opposite to the polarity of the charging voltage of the charging unit, and the toner discharged on the image carrier in the state where the charging voltage is applied to the charging unit If it passes through the nip portion, the charging means is contaminated, the charging failure of the image carrier occurs, and the developer is fogged. Therefore, it is desirable that the charging voltage is not applied to the charging means at the timing when the toner discharged in the return mode passes through the charging nip. Further, since the toner discharged in the return mode is often a toner having a polarity opposite to the normal polarity as described above, it is difficult for the developing unit to collect the toner even in the cleanerless system.

  Accordingly, it is desirable that a voltage is applied to the transfer means so that the discharged toner does not travel on the image carrier. Furthermore, it is desirable that the voltage applied to the transfer unit is a voltage having a polarity opposite to the transfer voltage of the normal transfer unit. Accordingly, the reversal toner discharged on the image carrier can be transferred to the intermediate transfer member, the recording material transport member, or directly to the recording material by the transfer means, and can be removed by the respective cleaning members.

<Example 3>
In the third embodiment, similarly to the first embodiment, the phase of the reciprocating drive of the toner charge amount control member 6 and the flicker member 200 is made the same during normal image formation using the fixed brush portion 61. In the return mode, control was performed such that a normal bias voltage was applied to the primary transfer roller. However, the relative movement between the toner charge amount control member 6 and the flicker member 200 in the return mode is slightly different from that in the first embodiment, and the reciprocating drive is performed with a phase difference of 90 degrees.

  In the third embodiment as well, since the reciprocating drive is set so that the brush portion 61 and the protrusion 212 of the flicker member 200 do not interfere so much during image formation, the toner discharged from the brush portion 61 contaminates the charging roller 2. No fogging occurred. In the return mode, the brush portion 61 and the protrusion 212 of the flicker member are largely interfered with each other at a timing other than image formation, and toner clogging to the brush portion 61 can be prevented. For this reason, the toner charging capability of the brush portion 61 did not decrease for a long time, and the cleanerless system could be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

<Example 4>
FIG. 8 is an explanatory diagram of relative movement between the toner charge amount control member and the flicker member in the fourth embodiment. In the fourth embodiment, similarly to the first embodiment, the phase of the reciprocating drive of the toner charge amount control member 6 and the flicker member 200 is made the same during normal image formation using the fixed brush portion 61. In the return mode, control was performed such that a normal bias voltage was applied to the primary transfer roller. However, the relative movement between the toner charge amount control member 6 and the flicker member 200 in the return mode is slightly different from that in the first embodiment, and as shown in FIG. 8, the reciprocating drive of the flicker member 200 is stopped and the toner charge amount control is performed. Only the member 6 was driven reciprocally.

  In the fourth embodiment as well, since the reciprocating drive is set so that the brush portion 61 and the protrusion 212 of the flicker member 200 do not interfere so much during image formation, the toner discharged from the brush portion 61 contaminates the charging roller 2. No fogging occurred.

  Further, in the return mode, at a timing other than image formation, as shown in FIG. 8, the brush portion 61 and the flicker member projection 212 are largely interfered to prevent clogging of toner into the brush portion 61. did it. For this reason, the toner charging capability of the brush portion 61 did not decrease for a long time, and the cleanerless system could be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

<Example 5>
FIG. 9 is an explanatory diagram of relative movement between the toner charge amount control member and the flicker member in the fifth embodiment. In the fifth embodiment, similarly to the first embodiment, the phase of the reciprocating drive of the toner charge amount control member 6 and the flicker member 200 is made the same during normal image formation using the fixed brush portion 61. In the return mode, control was performed such that a normal bias voltage was applied to the primary transfer roller. However, the relative movement between the toner charge amount control member 6 and the flicker member 200 in the return mode is slightly different from that in the first embodiment, and the reciprocating drive of the toner charge amount control member 6 is stopped as shown in FIG. Only the member 200 was driven reciprocally.

  Also in the fifth embodiment, since the reciprocating drive is set so that the brush portion 61 and the protrusion 212 of the flicker member 200 do not interfere so much during image formation, the charging roller 2 is contaminated with the toner discharged from the brush portion 61. No fogging occurred.

  Further, in the return mode, at a timing other than image formation, as shown in FIG. 9, the brush portion 61 and the protrusion 212 of the flicker member greatly interfere to prevent the toner from clogging the brush portion 61. did it. For this reason, the toner charging capability of the brush portion 61 did not decrease for a long time, and the cleanerless system could be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

  That is, in the image forming apparatus 100, since the brush member and the flicker member are each independently provided with a reciprocating drive mechanism, it is possible to independently change the timing of operation and stop of each reciprocating drive. Therefore, when forming an image in which the toner accumulated on the brush member should not be discharged to the image carrier, the reciprocating drive operation and stop timing are not changed, and the reciprocating drive is performed while following the same direction.

  On the other hand, in the return mode without image formation, the flicker member is stopped and only the brush member is reciprocally driven, so that the toner that has penetrated deeply into the brush member and discharged is neatly discharged onto the image carrier. Therefore, the brush member is completely refreshed to be free of toner clogging in the return mode, and the toner charging ability of the brush member can be maintained for a long time. Also, only in the return mode, the brush member and the flicker member greatly interfere with each other, and only in the return mode, the toner having no polarity or reversed is discharged onto the image carrier. The means is not contaminated with toner and does not affect the image.

<Example 6>
FIG. 10 is an explanatory view of the arrangement of the toner charge amount control member and the flicker member in Embodiment 6, and FIG. 11 is an explanatory view of the relative movement of the toner charge amount control member and the flicker member.

  As shown in FIG. 10, in Example 6, a rotating roll brush having a reciprocating / rotating drive mechanism was used as the toner charge amount control member 300. During normal image formation, the toner charge amount control member 300 and the flicker member 200 have the same reciprocating drive phase, and in the return mode, as shown in FIG. 11, the toner charge amount control member 300 and the flicker member. 200, the reciprocal drive with the phase shifted by 180 degrees was performed. Similarly to Example 1, in the return mode, the bias voltage was not applied to the charging roller 2 and control was performed so that the normal bias voltage was applied only to the primary transfer roller (92: FIG. 2).

The toner charge amount control member 300 has an outer diameter in which a fiber length of the brush portion 361 is adjusted to 3 mm by winding and bonding a rayon as a conductive fiber raised with a conductive adhesive on a metal round bar 362 having a diameter of 3 mm. 9 mm conductive fur brush roller. The volume resistivity is adjusted to 10 ⁸ Ωcm. A metal round bar 362 is connected to the power source 121, and a negative bias voltage is supplied during image formation. The toner charge amount control member 300 is constantly rotated by distributing power from the drive system of the photosensitive drum 1, and plays a role of charging the toner on the surface of the photosensitive drum 1 to a negative polarity. The crossing angle between the protrusion 212 of the flicker member 200 and the brush part 361 is 0 degree, and the intrusion amount of the protrusion 212 with respect to the brush part 361 is set to 1.0 mm.

  Also in the sixth embodiment, since the brush portion 361 and the protrusion 212 of the flicker member 200 are reciprocally driven so as not to interfere so much during image formation, the charging roller 2 is contaminated with the toner discharged from the brush portion 361. There was no occurrence of fog. In the return mode, the brush portion 361 and the protrusion 212 are largely interfered with each other at a timing other than image formation, so that the toner can be prevented from being clogged. For this reason, the toner charging capability of the brush part 361 has not been lowered for a long time, and the cleanerless system can be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

  In the image forming apparatus 100, the brush member is not limited to a fixed conductive brush composed of artificial fibers in which a conductive substance is dispersed, but is a roll-shaped member that rotates in one direction while contacting the image carrier. The same effect can be exhibited for the conductive brush.

<Example 7>
In Example 7, the same configuration as in Example 6 was used, and the same voltage application control as in Example 6 and reciprocating drive during image formation were performed. However, the relative movement between the toner charge amount control member 300 and the flicker member 200 in the return mode is slightly different, the reciprocal drive of the flicker member 200 is stopped, and only the toner charge amount control member 300 is reciprocally driven.

  Also in the seventh embodiment, during the image formation, the brush portion 361 and the protrusion 212 of the flicker member 200 are reciprocally driven so as not to interfere so much, so the charging roller 2 is contaminated with the toner discharged from the brush portion 361. There was no occurrence of fog. In the return mode, the brush portion 361 and the protrusion 212 are largely interfered with each other at a timing other than image formation, so that the toner can be prevented from being clogged. For this reason, the toner charging capability of the brush part 361 has not been lowered for a long time, and the cleanerless system can be satisfactorily functioned. Therefore, it was possible to continue obtaining good images up to the 50,000th sheet.

<Comparative Example 1>
In Comparative Example 1, as shown in FIG. 6, the same voltage application control as in Example 1 and reciprocal driving during image formation were performed using the same configuration as in Example 1. However, the toner charge amount control member 6 and the flicker member 200 continued to be reciprocally driven at the same phase from start to finish without interposing the return mode.

  In Comparative Example 1, as shown in FIG. 6, during image formation, reciprocating driving was performed so that the brush portion 61 and the protrusion 212 of the flicker member 200 did not interfere so much. For this reason, the toner discharged from the brush portion 61 does not contaminate the charging roller 2 and fog does not occur. However, since the return mode of the brush portion 61 was not particularly provided, toner clogging into the brush portion 61 began to become serious, and the toner charging capability of the brush portion 61 was significantly reduced. Therefore, the cleanerless system could not function well, and fogging occurred at the approximately 20,000th sheet.

  That is, when the toner charging capability of the brush unit 61 is reduced, a toner having a polarity opposite to that of a normal toner, or a toner that does not have a sufficient charge rotates around the photosensitive drum 1, and the toner reaches the charging roller 2. Then, the charging roller is contaminated to cause charging failure. Therefore, the charging potential becomes smaller than the set counter potential, and the fog removal potential difference Vback necessary for the simultaneous development cleaning is reduced. As a result, development fogging occurs.

<Comparative example 2>
In Comparative Example 2, using the same configuration as in Comparative Example 1, the toner charge amount control member 6 and the flicker member 200 were continuously reciprocated with a phase difference of 180 degrees from start to finish. In other words, the toner charge amount control member 6 and the flicker member 200 are moved relative to each other in the same manner as in the return mode in the first embodiment without providing the return mode.

  In Comparative Example 2, the toner discharged from the brush unit 61 during image formation is applied with a bias voltage because the brush unit 61 and the protrusion 212 of the flicker member 200 interfere too much during image formation. It continues to adhere to the charging roller 2. For this reason, the charging roller 2 was quickly contaminated to cause a charging failure, and fogging occurred on the approximately 5,000th sheet.

<Comparative Example 3>
In Comparative Example 3, using the same configuration as that of Comparative Example 1, the toner charge amount control member 6 was continuously reciprocally driven, while the flicker member 200 was continuously stopped. In other words, the toner charge amount control member 6 and the flicker member 200 are moved relative to each other in the same manner as in the return mode in the fifth embodiment without providing the return mode.

  Also in the comparative example 3, the toner discharged from the brush unit 61 during image formation is applied with a bias voltage because the brush unit 61 and the protrusion 212 of the flicker member 200 interfere too much during image formation. It continues to adhere to the charging roller 2. For this reason, the charging roller 2 was quickly contaminated and a charging failure occurred, and fogging occurred on the approximately 7000th sheet.

<Comparative Example 4>
In Comparative Example 4, as shown in FIG. 10, the same voltage application control as in Example 6 was performed using the same configuration as in Example 6. However, the toner charge amount control member 300 continues to be reciprocally driven from start to finish without interposing the return mode, while the flicker member 200 continues to stop reciprocating drive from end to end.

  In Comparative Example 4, as shown in FIG. 11, the brush portion (roll brush) 361 of the toner charge amount control member 300 and the protrusion 212 of the flicker member 200 interfere too much during image formation. As a result, toner discharged from the brush portion (roll brush) 361 during image formation continues to adhere to the charging roller 2 to which a bias voltage is applied, and the charging roller 2 is quickly contaminated, resulting in poor charging. As a result, fogging occurred on the 10,000th sheet.

<Effect of Example>
Conventionally, in a cleanerless type image forming apparatus, it has been very important that the reverse toner remaining on the photosensitive drum is returned to a normal polarity by a toner charging means such as a brush member and collected by the developing device. Then, since toner accumulates on the brush member and the resistance of the brush member increases, current does not easily flow, and there is a problem that the toner cannot be sufficiently charged. In this embodiment, a flicker member having a structure that has penetrated deeply into the brush member is brought into contact with the brush member, and the brush member and the flicker member are caused to interfere by utilizing the reciprocal drive of the brush member and the reciprocal drive of the flicker member. Scratch off. As a result, the toner accumulated deeply into the brush member can be completely discharged. At that time, a return mode without image formation is specially provided. In the return mode, interference between the brush member and the flicker member is made stronger than that during image formation, and the brush member is further disturbed. This makes it possible to cleanly remove the toner clogged in the brush member while preventing the brush member from falling down and causing fog.

  In the image forming apparatus 100, since the electrical method is replaced with the flicker member 200, the toner charge amount control member 6 can be efficiently cleaned by inserting a return mode of only 3 seconds every time 100 sheets are printed. Since the time for which the hair of the toner charge amount control member 6 interferes with the protrusion of the flicker member 200 is stopped for only 3 seconds, the toner charge amount control member 6 does not fall down for a long time. The toner is not discharged from the toner charge amount control member 6 during image formation.

  Also, during the image formation, the protrusion of the flicker member 200 is kept inserted into the hair of the toner charge amount control member 6, and the image formation and return mode are controlled by the phase and amplitude of both. Therefore, it is not necessary to insert and remove the elongated protrusions in the space between the soft and closely-fitted hairs. An amount of hair that is equal to the interval between the protrusions is ensured, and the density of the hair in the direction along the toner charge amount control member 6 does not vary. Relative movement can be started immediately without interposing a preparation period such as insertion and removal. In other words, the control for cleaning the toner charge amount control member 6 that is reciprocally driven by the flicker member 200 provides better results than the control for removing and inserting the fixed flicker member into the toner charge amount control member 6.

  Further, by providing the residual toner image equalizing member 7, even if there is a large amount of pattern-like transfer residual toner image on the photosensitive drum 1 that is carried to the toner charge amount control member 6, the transfer residual toner image is transferred to the photosensitive drum. 1 is distributed and non-patterned on one surface. For this reason, the transfer residual toner does not concentrate on a part of the toner charge amount control member 6, and the entire charge process of the transfer residual toner by the toner charge amount control member 6 is always sufficiently performed. The adhesion to the charging roller 2 is effectively prevented. Generation of a ghost image of the residual current toner image pattern is also strictly prevented.

  The toner charge amount control member 6 controls the charge amount of the transfer residual toner to an appropriate charge amount by which the electrostatic latent image on the photosensitive drum 1 can be developed by the developing device 4. Recovery was efficient. Further, since the toner charge amount control member 6 avoids contamination of the charging roller 2, the charging roller 2 can stably charge the photosensitive drum 1 uniformly to a predetermined potential over a long period of time. As a result, a good image free from ghosts and poor charging was obtained.

<Correspondence with Invention>
The image forming apparatus 100 includes a photosensitive drum 1 on which a toner image is formed on a moving surface, a charging roller 2 that charges the surface by applying a charging voltage, and a toner image transferred from the surface by applying a transfer voltage. A primary transfer roller 92, a toner charge amount control member 6 for charging the transfer residual toner by rubbing a conductive hair on the surface between the primary transfer roller 92 and the charging roller 2, and a toner charge amount control. And a motor 208 that periodically moves the member 6 along the surface. A flicker member 200 having a large number of protrusions inserted into the hairs, a motor 207 that periodically moves the flicker member 200, a motor 208, and a motor 207 to control the toner charge amount control member 6. And a control circuit 130 for moving the flicker member 200. The control circuit 130 moves the toner charge amount control member 6 and the flicker member 200 relative to each other with a larger amplitude than during image formation during a brush recovery period without image formation.

  The motor 208 reciprocates the toner charge amount control member 6 arranged in the direction intersecting the moving direction of the surface, and the motor 207 moves the flicker member in the direction along the toner charge amount control member 6. 200 is reciprocated. The control circuit 130 reciprocally moves the toner charge amount control member 6 and the flicker member 200 with the same homologous amplitude while the charging voltage is applied to the charging roller 2 during image formation.

  When the predetermined total image forming amount is reached, the control circuit 130 interrupts image formation and starts the brush recovery period, and with the toner charging amount control member 6 in a state where the charging voltage is not applied to the charging roller 2. The flicker member 200 is relatively moved. The total image formation amount is not limited to the number of image formation output sheets after the end of the previous brush recovery period, but may be an operation time after the end of the previous brush recovery period or a toner consumption amount.

  The toner charge amount control member 6 may be a roll brush that rubs the surface and rotates in one direction. At this time, it is desirable that the protrusions be arranged in parallel with the rotation direction of the roll brush.

  The control circuit 130 applies a voltage having a polarity opposite to the transfer voltage to the primary transfer roller 92 during the brush recovery period.

  The process cartridge 8 includes a developing unit 4 that develops an electrostatic latent image formed on the surface of the photosensitive drum 1 to form a toner image, a charging roller 2 that uniformly contacts and charges the surface, and a charging roller 2. And a toner charge amount control member 6 that reciprocates in the direction crossing the moving direction of the surface on the upstream side and rubs the surface. A flicker member 200 that reciprocates in parallel with the toner charge amount control member 6 in a state where a large number of protrusions are inserted into the hairs of the toner charge amount control member 6 is provided. The flicker member 200 and the toner charge amount control member 6 can be controlled from the outside to switch between the reciprocating movement and the relative movement of the isotope homologous amplitude.

  The image forming apparatus 100 charges the transfer residual toner on the surface of the photosensitive drum 1 with the same polarity as the charging voltage applied to the charging roller 2. At the time of image formation, in the state where the charging voltage is applied to the charging roller 2, the toner charge amount control member 6 to which the auxiliary charge voltage of the same polarity is applied is connected to the protrusions of the toner charge amount control member 6 with a large number of protrusions. Is reciprocated integrally with the flicker member 200 inserted. In the return mode, the flicker member 200 and the toner charge amount control member 6 are relatively moved in the reciprocating direction without applying the charging voltage to the charging roller 2.

1 is an explanatory diagram of a configuration in which a main part of an image forming apparatus according to an exemplary embodiment is illustrated in cross section. FIG. 4 is an enlarged view of a portion including a process cartridge. FIG. 4 is a schematic view of a driving mechanism of a flicker member and a toner charge amount control member as viewed from the photosensitive drum side. FIG. 6 is a schematic view of a driving mechanism of a flicker member and a toner charge amount control member as viewed from a residual toner image equalizing member side. 6 is a flowchart of control of a flicker member and a toner charge amount control member. 3 is an explanatory diagram of an arrangement of a toner charge amount control member and a flicker member in Embodiment 1. FIG. FIG. 6 is an explanatory diagram of relative movement between a toner charge amount control member and a flicker member. FIG. 10 is an explanatory diagram of relative movement between a toner charge amount control member and a flicker member in Embodiment 4. FIG. 10 is an explanatory diagram of relative movement between a toner charge amount control member and a flicker member in Embodiment 5. FIG. 10 is an explanatory diagram of an arrangement of a toner charge amount control member and a flicker member in Embodiment 6. FIG. 6 is an explanatory diagram of relative movement between a toner charge amount control member and a flicker member.

Explanation of symbols

1 Image carrier (photosensitive drum)
2 Charging means (charging roller)
3 Exposure device 4 Developing means (developer)
6 Brush member (toner charge amount control member)
7 Residual toner image equalizing member 8 Process cartridge 61, 71 Brush section 62, 72 Electrode plate 91 Intermediate transfer belt 92 Transfer means (primary transfer roller)
100 Image forming apparatus 130 Control circuit 200 Flicker member 207 Flicker drive mechanism (motor)
208 Brush drive mechanism (motor)
212 Protrusions PY, PM, PC, PK Image forming portion P Recording material

Claims (8)

An image carrier on which a toner image is formed on a moving surface;
Charging means for applying a charging voltage to charge the surface;
Transfer means for applying a transfer voltage to transfer the toner image from the surface;
A brush member for charging a transfer residual toner by rubbing a conductive hair on the surface between the transfer unit and the charging unit;
A brush drive mechanism that periodically moves the brush member along the surface; and an image forming apparatus comprising:
A flicker member arranged by inserting a large number of protrusions into the hairs;
A flicker driving mechanism for periodically moving the flicker member;
Control means for controlling the brush drive mechanism and the flicker drive mechanism to move the brush member and the flicker member;
The image forming apparatus according to claim 1, wherein the control unit relatively moves the brush member and the flicker member with a larger amplitude than during image formation during a brush recovery period without image formation. The brush drive mechanism reciprocates the brush member arranged in a direction intersecting the moving direction of the surface in the intersecting direction,
The flicker driving mechanism reciprocates the flicker member in a direction along the brush member,
2. The image according to claim 1, wherein the control unit reciprocates the brush member and the flicker member with the same homologous amplitude in a state in which the charging voltage is applied to the charging unit during the image formation. Forming equipment.   When the control unit reaches a predetermined total image forming amount, the image forming is interrupted to start the brush recovery period, and the brush member and the flicker member are not applied with the charging voltage applied to the charging unit. The image forming apparatus according to claim 2, wherein the two are moved relative to each other.   The image forming apparatus according to claim 3, wherein the total image forming amount is an image forming output number, an operation time, or a toner consumption amount after the end of the previous brush recovery period. The brush member is a roll brush that rubs the surface and rotates in one direction,
5. The image forming apparatus according to claim 1, wherein the protrusion is disposed in parallel with a rotation direction of the roll brush.   The image forming apparatus according to claim 1, wherein the control unit applies a voltage having a polarity opposite to the transfer voltage to the transfer unit during the brush recovery period. Developing means for developing the electrostatic latent image formed on the surface of the image carrier to form a toner image;
Charging means for uniformly contacting and charging the surface;
In a cleanerless process cartridge comprising: a brush member that reciprocates in a direction intersecting the moving direction of the surface on the upstream side of the charging means and rubs the surface.
A flicker member that reciprocates in parallel with the brush member in a state in which a large number of protrusions are inserted into the hair members of the brush member,
The process cartridge according to claim 1, wherein the flicker member and the brush member can be switched from reciprocal movement and relative movement of the same homologous amplitude by being controlled from the outside. In the auxiliary charging method for charging the transfer residual toner on the surface of the photosensitive drum to the same polarity as the charging voltage applied to the charging roller,
In a state where the charging voltage is applied to the charging roller, the brush member to which an auxiliary charging voltage of the same polarity is applied is reciprocated integrally with a flicker member in which a large number of protrusions are inserted into the hair member spacing. The first step;
And a second step of relatively moving the flicker member and the brush member in the reciprocating direction without applying the charging voltage to the charging roller.

Images