JP2008122464A - Image forming apparatus and image forming method using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technique to perform satisfactory cleaning by removing residual toner accumulated at a cleaning position in an image forming apparatus adopting a wet developing system using liquid developer where electrified toner is dispersed in liquid carrier. <P>SOLUTION: Low-toner developer is obtained by separating the toner from the liquid developer carried on the surface of a developing roller at a position on an upstream side in the rotating direction of the developing roller with respect to the cleaning position while rotating the developing roller in the rotating direction of the developing roller, and blade washing operation that the low-toner developer is supplied to the cleaning position is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using a developer in which toner is dispersed in a liquid carrier, and an image forming method using the apparatus.

  In this type of image forming apparatus, toner is attached to an electrostatic latent image formed on the surface of a latent image carrier such as a photoconductor to develop the electrostatic latent image and execute an image forming operation. Patent Document 1 describes an apparatus that employs a wet development system that uses a developer in which toner charged in a liquid carrier is dispersed as such a development system. In the apparatus described in the patent document, a developing solution is supplied to the surface of the photosensitive member using a developing roller facing the photosensitive member at the developing position. That is, the developing roller rotates in a predetermined rotation direction while carrying the developer on the surface thereof and conveys the developer to the developing position, thereby supplying the developer to the surface of the photosensitive member. Then, the toner in the developer supplied to the developing position is attached to the electrostatic latent image on the surface of the photoreceptor, and the electrostatic latent image is developed with toner.

JP 2005-70184 A

  In order to improve the development, there is a technique for aggregating (compacting) toner on the surface of the developing roller before the developing position (that is, upstream of the developing position in the rotation direction of the developing roller). That is, in the case of the wet development method using the developer as described above, at the development position, the toner is electrophoresed in the carrier from the surface of the developing roller to the surface of the photosensitive member and adheres to the electrostatic latent image. At this time, the toner migrates in the carrier while receiving resistance from the carrier. However, toner with a small particle size is susceptible to resistance from the carrier, and its migration speed is low. Therefore, after the toner is once aggregated on the surface of the developing roller before the development position, it is migrated as a lump having a certain size at the development position, thereby improving the migration speed and realizing good development. There is technology to do.

  The surface of the developing roller that has finished toner development at the development position is cleaned by a cleaner blade in order to remove toner remaining on the surface. The cleaner blade is disposed downstream of the developing position in the rotation direction of the developing roller, and contacts the developing roller surface at the cleaning position to scrape and remove (clean) residual toner on the developing roller surface. However, such residual toner is toner aggregated on the surface of the developing roller and exists as a lump. As a result, even after the residual toner is scraped off by the cleaner blade, it may remain in the vicinity of the cleaning position as a lump and further accumulate. As a result of an increase in the amount of accumulated residual toner, there are cases where the residual toner cannot be removed (cleaned) satisfactorily.

  The present invention has been made in view of the above problems, and performs development using a developer that has been compacted in front of the development position, and a cleaner blade is brought into contact with the surface of the development roller to thereby develop the surface of the development roller. In an image forming apparatus or an image forming method for removing residual toner from an object, it is an object to provide a technique for removing residual toner accumulated at a cleaning position and enabling good cleaning.

  The image forming method according to the present invention includes a developing roller for transporting a developing solution to a developing position facing a latent image carrier by rotating in a predetermined direction while carrying a developing solution in which toner is dispersed in a liquid carrier on the surface thereof. And a cleaning blade that contacts the surface of the developing roller at a cleaning position downstream of the developing position in the rotational direction of the developing roller and removes residual toner from the surface of the developing roller. In contrast, the toner contained in the developer is aggregated on the surface of the developing roller at the aggregation position upstream of the developing roller in the rotation direction, and the aggregated aggregated toner is statically carried on the surface of the latent image carrier at the development position. An image forming method in which toner is developed by being attached to an electrostatic latent image, and in order to achieve the above object, the developing roller is rotated in the rotating direction of the developing roller. A blade that separates the toner from the developer carried on the surface of the developing roller at a position upstream of the cleaning roller in the rotation direction of the developing roller to obtain a low toner developer, and supplies the low toner developer to the cleaning position It is characterized by performing a cleaning operation.

  According to a first aspect of the image forming apparatus of the present invention, in order to achieve the above object, a latent image carrier capable of carrying an electrostatic latent image on its surface, and an electrostatic surface on the surface of the latent image carrier. A latent image forming means for forming a latent image and a developer in which toner is dispersed in a liquid carrier are conveyed to a developing position facing the latent image carrier by rotating in a predetermined rotation direction while being carried on the surface. A developing roller which is brought into contact with the latent image carrier at the developing position and is supplied to the surface of the latent image carrier, and a surface thereof is opposed to the developing roller at an aggregation position upstream of the developing position in the rotation direction of the developing roller. The surface of the developing roller is brought into contact with the developing solution carried on the surface of the developing roller, and a voltage is applied to the surface to electrically discharge the toner contained in the developing solution to the surface side of the developing roller. Can be agglomerated A voltage applying roller, a cleaner blade that contacts the surface of the developing roller at a cleaning position downstream of the developing position in the rotational direction of the developing roller, and removes residual toner from the surface of the developing roller, the developing roller, and the voltage applying roller And control means for executing the following image forming operation and blade cleaning operation. Here, the image forming operation is an operation of forming the aggregated toner by the voltage application roller and attaching the aggregated toner to the electrostatic latent image carried on the surface of the latent image carrier at the development position. The blade cleaning operation is included in the developer carried on the surface of the developing roller at the aggregation position by applying a voltage to the surface of the voltage application roller at the aggregation position while rotating the developing roller in the rotation direction of the developing roller. In this operation, a low toner developer obtained by electrically attracting toner to the surface of the voltage application roller and separating the toner from the developer carried on the surface of the developing roller is supplied to the cleaning position.

  According to a second aspect of the image forming apparatus of the present invention, in order to achieve the above object, a latent image carrier capable of carrying an electrostatic latent image on its surface, and an electrostatic surface on the surface of the latent image carrier. A latent image forming means for forming a latent image and a developer in which toner is dispersed in a liquid carrier are conveyed to a developing position facing the latent image carrier by rotating in a predetermined rotation direction while being carried on the surface. A developing roller which is brought into contact with the latent image carrier at the developing position and is supplied to the surface of the latent image carrier, and a surface thereof is opposed to the developing roller at an aggregation position upstream of the developing position in the rotation direction of the developing roller. The surface of the developing roller is brought into contact with the developing solution carried on the surface of the developing roller, and a voltage is applied to the surface to electrically discharge the toner contained in the developing solution to the surface side of the developing roller. Can be agglomerated A voltage application roller, a cleaner blade that contacts the surface of the developing roller at a cleaning position downstream of the developing position in the rotational direction of the developing roller and removes residual toner from the surface of the developing roller, a latent image forming unit, and development And control means for controlling the roller to execute the following blade cleaning operation. Here, in the blade cleaning operation, a solid latent image is formed on the surface of the latent image carrier by the latent image forming unit, while the aggregated toner is formed by the voltage application roller and the aggregated toner is attached to the solid latent image at the development position. Thus, the low toner developer obtained by separating the toner from the developer carried on the surface of the developing roller is supplied to the cleaning position.

  In the present invention (image forming apparatus and image forming method) configured as described above, the toner contained in the developer is electrically applied to the surface side of the developing roller at a position upstream of the developing position in the rotation direction of the developing roller. And is condensed (compacted) on the surface of the developing roller. In particular, in the invention relating to the image forming apparatus, the compaction is performed by the voltage application roller facing the developing roller at the upstream aggregation position in the rotation direction of the developing roller with respect to the developing position. Then, the toner is developed by causing the aggregated aggregated toner to migrate at the development position and attaching the toner to the electrostatic latent image on the surface of the latent image carrier. Further, a cleaner blade is brought into contact with the surface of the developing roller after the development at the developing position to remove (clean) residual toner on the surface of the developing roller. Therefore, there is a case where the residual toner which is compacted and exists as a lump is accumulated near the cleaning position where the cleaner blade and the developing roller abut. As a result of an increase in the accumulated amount of residual toner that exists as a lump in this way, there are cases where the residual toner cannot be removed (cleaned) satisfactorily.

  To solve this problem, the present invention rotates the developing roller in a predetermined rotation direction, and separates the toner from the developer carried on the surface of the developing roller upstream of the cleaning position in the rotation direction of the developing roller. Thus, an operation for obtaining a low toner developer can be executed. By executing this operation, the low toner developer is supplied to the cleaning position while being carried on the surface of the developing roller. Therefore, in the present invention, the toner deposited in the vicinity of the cleaning position can be washed away by the low toner developer. More specifically, as described above, since the accumulated toner is once compacted, it exists as a lump. However, the supply of the low toner developer relaxes the state of the accumulated toner as a lump. Further, when the low toner developer is supplied, the accumulated toner is washed away from the vicinity of the cleaning position. Therefore, it is possible to improve the subsequent cleaning, which is preferable.

  In other words, in the first aspect of the image forming apparatus according to the present invention, the developer is carried on the surface of the developing roller with the surface facing the developing roller at the upstream aggregation position in the rotation direction of the developing roller with respect to the cleaning position. In addition, the above-described problem of toner accumulation in the vicinity of the cleaning position is solved by performing the following blade cleaning operation to supply a low toner developer to the cleaning position. More specifically, in the blade cleaning operation in the first aspect, a voltage is applied to the surface of the voltage application roller at the aggregation position, and the toner contained in the developer carried on the surface of the developing roller is applied to the voltage at the aggregation position. The toner is electrically attracted to the surface of the roller to separate the toner from the developer carried on the surface of the developing roller to obtain a low toner developer. In other words, in the invention, the toner is separated from the developer carried on the surface of the developing roller at the aggregation position upstream of the cleaning position in the rotation direction of the developing roller to obtain a low toner developer. The low toner developer thus obtained is supplied to the cleaning position downstream in the rotation direction of the developing roller with respect to the aggregation position while being carried on the surface of the developing roller rotating in the predetermined rotation direction. Therefore, even when residual toner is accumulated in the vicinity of the cleaning position, the residual toner can be washed away with the low toner developer. Therefore, it is possible to improve the subsequent cleaning.

  Further, the second aspect of the image forming apparatus according to the present invention performs the following blade cleaning operation to supply the low toner developer to the cleaning position, thereby causing the problem of toner accumulation in the vicinity of the cleaning position described above. It has been solved. More specifically, in the blade cleaning operation in the second aspect, a solid latent image is formed on the surface of the latent image carrier, and the toner contained in the developer that is carried on the surface of the developing roller and supplied to the developing position. Is attached to the solid latent image. In other words, this invention develops a solid latent image to separate the toner from the developer carried on the surface of the developing roller at the developing position upstream in the rotation direction of the developing roller with respect to the cleaning position. Obtain a liquid. The low toner developer thus obtained is supplied to the cleaning position downstream in the developing roller rotation direction with respect to the developing position while being carried on the surface of the developing roller rotating in the predetermined rotating direction. . Therefore, even when residual toner is accumulated in the vicinity of the cleaning position, the residual toner can be washed away with the low toner developer. Therefore, it is possible to improve the subsequent cleaning.

  As described above, since the toner accumulated at the cleaning position is removed by executing the blade cleaning operation, the subsequent cleaning can be improved, which is preferable.

  The present invention can also be said to be suitable in that it is possible to remove such accumulated toner very simply. In other words, conventionally, when the accumulated toner near the cleaning position is to be removed, for example, a serviceman disassembles the apparatus and cleans the vicinity of the cleaning position where the cleaner blade and the developing roller abut, thereby cleaning the accumulated toner. Needed to be removed. That is, in order to suppress the cleaning failure due to toner accumulation and realize good cleaning, it is necessary to disassemble the apparatus. However, according to the present invention, it is possible to realize good cleaning only by executing the blade cleaning operation without disassembling the apparatus. Therefore, it is possible to execute the removal of the accumulated toner very simply, which is preferable.

  By the way, in the first aspect described above, there is a case where the separated toner adheres to the surface of the voltage application roller by separating the toner from the developer using the voltage application roller. However, when the adhesion amount becomes excessive, there is a possibility that the toner cannot be efficiently separated from the developer (toner separation). Therefore, an image forming apparatus in which the voltage application roller rotates in a predetermined rotation direction may be configured as follows. That is, a toner removing unit that removes toner from the surface of the voltage application roller may be further provided on the downstream side in the rotation direction of the voltage application roller with respect to the aggregation position.

  The image forming apparatus configured as described above can remove the toner on the surface of the voltage application roller by the toner removing unit. Accordingly, it is possible to suppress excessive adhesion of toner on the surface of the voltage application roller, which is preferable because efficient toner separation can be performed.

  In the second aspect of the present invention, the solid latent image may be formed over a time longer than the rotation period of the developing roller. Such a configuration is preferable because the low toner developer can be supplied to the cleaning position over a time longer than the rotation period of the developing roller, and the residual toner can be washed away more reliably.

  FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus uses a color mode in which four color toners of yellow (Y), magenta (M), cyan (C) and black (K) are superimposed to form a color image, and only black (K) toner. Thus, the image forming apparatus can selectively execute a monochrome mode for forming a monochrome image. In this image forming apparatus, when an image forming command is given from an external device such as a host computer to a main controller MC having a CPU, a memory and the like, the main controller MC gives a control signal to the CPU of the engine controller EC, and based on this. The CPU of the engine controller EC controls each part of the apparatus such as the engine unit EG to execute a predetermined image forming operation, and forms an image corresponding to the image forming command on a sheet as a recording material. As will be apparent from the following description, in this embodiment, the CPU of the engine controller EC functions as the “control unit” in the present invention.

  As shown in FIG. 1, the image forming apparatus according to the present embodiment includes an image forming unit 2, a transfer belt unit 3, a secondary transfer unit 4, and a registration roller pair 5. Below, each structure and operation | movement are demonstrated.

  The image forming unit 2 includes four image forming stations 2Y (for yellow), 2M (for magenta), 2C (for cyan), and 2K (for black) that form a plurality of different color images. As shown in FIG. 1, these four image forming stations 2Y, 2M, 2C, and 2K are arranged side by side in the conveyance direction D31 of the transfer belt 31 of the transfer belt unit 3 below the transfer belt unit 3 in the gravity direction. Has been. As described above, the image forming apparatus according to the present embodiment is a so-called tandem type image forming apparatus. In FIG. 1, the image forming stations of the image forming unit 2 have the same configuration. Therefore, for convenience of illustration, only some of the image forming stations are denoted by reference numerals, and other image forming stations are denoted by reference numerals. Omitted.

  FIG. 3 is an enlarged view of the configuration around the image forming station. The subsequent description will be made with reference to FIGS. Each of the image forming stations 2Y, 2M, 2C, and 2K is provided with a photosensitive drum 21 (latent image carrier) on which a corresponding color toner image is formed. Each photosensitive drum 21 has a photosensitive layer made of amorphous silicon, and is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of arrow D21 in the figure. Further, around the photosensitive drum 21, along the rotation direction, a charging unit 22, an exposure unit 23 (not shown in FIGS. 1 and 3), a developing unit 24, a photosensitive member squeeze unit 25, a charge eliminating unit 26, and a photosensitive member. A cleaner 27 is provided. Then, a charging operation, a latent image forming operation, a toner developing operation, and the like are executed by these functional units. When the color mode is executed, the toner images formed by all the image forming stations 2Y, 2M, 2C, and 2K are superimposed on the surface of the transfer belt 31 to form a color image. When the monochrome mode is executed, only the image forming station 2K is operated to form a black monochrome image.

  The charging unit 22 includes a charging roller 221 in which an elastic member such as conductive urethane rubber and a fluororesin surface layer are arranged on the surface of a metal core. The charging roller 221 is configured to rotate in contact with the surface of the photosensitive drum 21 at a charging position, and is driven to rotate as the photosensitive drum 21 rotates. The charging roller 221 is connected to a charging unit drive control circuit, and receives the power from the charging unit drive control circuit. The charging roller 221 is a charging position where the charging roller 221 and the photosensitive drum 21 come into contact with each other. Is charged to a predetermined surface potential (+550 V) having the same polarity as that of the toner.

  The exposure unit 23 is driven by the exposure unit drive control circuit and irradiates the surface of the photosensitive drum 21 charged to a predetermined potential with a laser beam LB (arrow in the figure). As a result, an electrostatic latent image corresponding to the image formation command is formed on the surface of the photosensitive drum 21. In the present embodiment, the potential of the region where the electrostatic latent image is formed is about + 50V. As a specific configuration of the exposure unit 23, for example, a technique related to a line head in which a plurality of light emitting elements such as LEDs are arranged in an array in the axial direction of the photosensitive drum 21, or a light beam emitted from a single light source. It is possible to employ a known exposure technique such as an optical scanning technique for scanning the image with a polygon mirror or the like. Thus, in the present embodiment, the charging unit 22 and the exposure unit 23 function as “latent image forming means” in the present invention.

  The developing unit 24 includes a developing roller 240 and brings the surface of the developing roller 240 into contact with the surface of the photosensitive drum 21 at the developing position DP. Then, at the development position DP, the electrostatic latent image carried on the surface of the photosensitive drum 21 is developed with toner, and a toner image is formed on the surface of the photosensitive drum 21. The detailed configuration and operation of the developing unit 24 will be described later.

  The photoreceptor squeeze unit 25 includes a photoreceptor squeeze roller 251, a carrier collection blade 252, and a carrier collection container 253. The photoreceptor squeeze roller 251 has a diameter of 14 mm, and has a urethane rubber layer having a thickness of 2 mm and a hardness of JIS-A 30 ° on the surface layer. The surface of the urethane rubber layer is subjected to PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tubing having a thickness of 20 μm.

  The photoconductor squeeze roller 251 is in contact with the photoconductor drum 21 to peel off the liquid carrier from the developer DM carried on the surface of the photoconductor drum 21, and the liquid carrier contained in the developer DM on the surface of the photoconductor drum. Adjust the amount. That is, the photosensitive member squeeze roller 251 is biased to a predetermined potential (+150 V) by the photosensitive member squeeze unit drive control circuit. Therefore, the toner in the developer DM is discharged to the electrostatic latent image side, while a part of the liquid carrier in the developer DM is peeled off by the photosensitive member squeeze roller 251. The carrier thus peeled off is carried on the surface of the photosensitive member squeeze roller 251, conveyed to the downstream side in the rotation direction of the photosensitive member squeeze roller 251 (arrow in the figure), and scraped off by the carrier recovery blade 252. It is recovered in the carrier recovery container 253. The carrier recovery blade 252 is made of urethane rubber having a thickness of 2.0 mm.

  The primary transfer roller 32 is in contact with the photosensitive drum 21 with the transfer belt 31 in between at the primary transfer position TR1. The primary transfer roller 32 electrically transfers the toner image carried on the surface of the photosensitive drum 21 at the primary transfer position TR1 to the surface of the transfer belt 31 by the primary transfer bias applied from the primary transfer roller drive control circuit. Attract to and transcribe.

  After the primary transfer, the surface of the photoconductor drum 21 is cleaned by a photoconductor cleaner 27 after the electric potential is uniformly removed by the charge eliminating unit 26. The static elimination unit 26 is driven by the static elimination unit drive control circuit, and removes the surface potential of the photosensitive drum 21 by irradiating the surface of the photosensitive drum 21 with light.

  The belt squeeze unit 33 includes a belt squeeze roller 331, a squeeze backup roller 332, and a carrier recovery blade 333. The belt squeeze roller 331 and the squeeze backup roller 332 are in contact with each other with the transfer belt 31 in between, and can rotate in a direction according to the conveyance direction D31 of the transfer belt 31, respectively. The belt squeeze roller 331 has a diameter of 14 mm and a urethane rubber layer having a thickness of 2 mm and a hardness of JIS-A 30 ° on the surface layer. Further, the surface of the urethane rubber layer is subjected to PFA tubing having a thickness of 20 μm.

  The belt squeeze roller 331 abuts on the surface of the transfer belt 31 and peels off the liquid carrier from the developer DM carried on the surface of the transfer belt 31, so that the amount of the liquid carrier contained in the developer DM on the surface of the transfer belt 31. Adjust. That is, the belt squeeze roller 331 is biased to a predetermined potential (+150 V) by the belt squeeze unit drive control circuit with respect to the squeeze backup roller 332. Accordingly, the toner in the developer DM is discharged to the surface side of the transfer belt 31, while a part of the liquid carrier in the developer DM is peeled off by the belt squeeze roller 331. The carrier thus peeled off is conveyed on the downstream side in the rotation direction of the belt squeeze roller 331 (arrow in the figure) while being carried on the surface of the belt squeeze roller 331, and after being scraped off by the carrier recovery blade 333, the carrier is recovered. It is collected in the container 253. The carrier recovery blade 333 is made of urethane rubber having a thickness of 2.0 mm.

  The transfer belt 31 has a three-layer structure having a base material layer, an elastic layer, and a coat layer from the inside. The base material layer is polyimide having a thickness of 100 μm. The elastic layer is a urethane rubber having a thickness of 200 μm and a hardness of JIS-A 30 °. The coat layer is a fluororesin coat having a thickness of 10 μm. The volume resistance value of all layers of the transfer belt 31 is about Log 10 Ωcm.

  The transfer belt 31 is stretched around the driving roller 34 and the driven roller 35 and is transported by the rollers in the transport direction D31 at a process speed of 210 mm / s. During color image formation, the toner images formed by the image forming stations 2Y, 2M, 2C, and 2K are superimposed on the surface of the transfer belt 31 to form a color image. In addition, when forming a monochrome image, only the toner image formed by the image forming station 2K is transferred to the surface of the transfer belt 31 to form a monochrome image. The image thus formed on the surface of the transfer belt 31 is conveyed by the transfer belt 31 to the secondary transfer position TR2. Then, the surface of the transfer belt 31 that has finished the secondary transfer at the secondary transfer position TR2 is cleaned by the belt cleaner 36.

  The secondary transfer unit 4 includes a secondary transfer roller 41 and a transfer roller cleaner 42 that cleans the surface of the secondary transfer roller 41. The secondary transfer roller 41 faces the drive roller 34 at the secondary transfer position TR2, and the sheet is conveyed by the registration roller pair 5 to the secondary transfer position TR2. At this time, the registration roller pair 5 conveys the sheet to the secondary transfer position TR2 in accordance with the conveyance timing of the image to the secondary transfer position TR2 by the transfer belt 31. Then, the secondary transfer roller 41 electrically transfers the image carried on the surface of the transfer belt 31 at the secondary transfer position TR2 to the surface of the sheet by the secondary transfer bias applied by the secondary transfer unit drive control circuit. Attract to and transcribe. Then, the sheet having the image transferred on its surface is conveyed in the direction of the arrow in FIG. Although not shown in FIG. 1, the image on the sheet surface is fixed on the sheet surface by the fixing unit existing in the direction of the arrow.

  The developing unit 24 includes a developing roller 240, a developer container 241, a scooping roller 242, a coating roller 243, a regulating blade 244, a cleaner blade 245, a voltage application roller 246 and an application roller blade 247.

  The developer storage unit 241 stores a liquid developer DM (developer) for developing the electrostatic latent image formed on the photosensitive drum 21 with toner. The developer DM accommodated in the developer accommodating portion 241 has a low concentration (about 1 to 2 wt%) and a low viscosity with a generally used Isoper (trademark: exon) as a liquid carrier. It is not a volatile liquid developer having volatility, but a non-volatile liquid developer having a high concentration and high viscosity and having non-volatility at room temperature. That is, the liquid developer DM according to the present embodiment has a high concentration of toner particles (resin, pigment, etc.) having an average particle size of about 0.1 to 5 μm in a non-volatile and insulating liquid carrier such as silicone oil ( It is a developer having a high viscosity (about 100 to 10,000 mPa · s) dispersed in about 5 to 40 wt%.

  The scooping roller 242 pumps up the liquid developer DM accommodated in the developer accommodating portion 241 and conveys it to the application roller 243. At least the lower part of the drawing roller 242 is immersed in the liquid developer DM accommodated in the developer accommodating portion 241, and is separated from the application roller 243 with a width of about 1 mm.

  Further, the drawing roller 242 can rotate around its central axis, and the central axis is below the rotational central axis of the application roller 243. Further, the drawing roller 242 rotates in the same direction (clockwise in the figure) as the rotation direction of the application roller 243 (clockwise in FIG. 3). The scooping roller 242 has a function of scooping up the developer DM stored in the developer storage unit 241 and transporting it to the application roller 243, and also has a function of stirring the developer DM.

  The application roller 243 supplies the developer DM conveyed from the developer container 241 by the scooping roller 242 to the developing roller 240. The application roller 243 is a roller made of a metal such as iron and has a groove formed in a uniform and spiral shape and nickel-plated, and has a diameter of about 20 mm. The application roller 243 is biased to the same potential as the bias potential of the developing roller 240 described later.

  Further, the surface of the application roller 243 is in pressure contact with a later-described elastic layer of the development roller 240 in order to appropriately supply the developer DM on the application roller 243 to the development roller 240. The application roller 243 can rotate around its central axis, and the central axis is below the rotation central axis of the developing roller 240. The application roller 243 rotates in a direction (clockwise in FIG. 3) opposite to the rotation direction of the developing roller 240 (counterclockwise in FIG. 3).

  The regulating blade 244 is disposed on the left shoulder of the application roller 243 in FIG. 3 and abuts on the surface of the application roller 243 to regulate the amount of developer DM on the surface of the application roller 243. That is, the regulation blade 244 plays a role of scraping off the excess developer on the surface of the application roller 243 and adjusting the amount of the developer DM on the surface of the application roller 243 supplied to the development roller 240. The restriction blade 244 is made of urethane rubber, which is an elastic body, and is supported by a restriction blade support member 2441 made of metal such as iron.

  Further, the edge of the regulation blade 244 is in contact with the surface of the application roller 243. Further, as shown in FIG. 3, the regulation blade 244 is arranged so that the tip thereof faces the upstream side in the rotation direction of the application roller 243, and performs so-called counter regulation. However, the mode of regulation by the regulation blade 244 is not limited to this, and so-called trail regulation may be performed.

  The developing roller 240 is rotatable about its central axis, and the central axis is below the rotational central axis of the photosensitive drum 21, and the rotation direction is counterclockwise in FIG. 3 as described above. The developing roller 240 rotates with the developer DM held on the surface of the photosensitive drum 21 in order to develop the electrostatic latent image carried on the surface of the photosensitive drum 21 with the developer DM. It is transported to the developing position DP that faces it. The developing roller 240 has a conductive elastic layer on the outer periphery of an inner core made of metal such as iron and has a diameter of about 24 mm. The elastic layer is formed by forming a urethane resin coat having a thickness of 100 μm on the outside of a urethane rubber having a thickness of 4 mm and a hardness of JIS-A 30 °. The developing roller 240 is in contact with both the application roller 243 and the photosensitive drum 21 with the elastic layer deformed. Note that when the electrostatic latent image formed on the surface of the photosensitive drum 21 is developed with toner, the developing roller 240 is biased to a predetermined developing bias potential (+400 V) by the developing unit drive control circuit.

  The voltage application roller 246 can rotate around its central axis, and the direction of rotation is opposite to the direction of rotation of the developing roller 240 (clockwise in FIG. 3). This voltage application roller 246 has a conductive elastic layer on the outer periphery of an inner core made of metal such as iron and has a diameter of about 20 mm. The elastic layer is formed by forming a urethane resin coat having a thickness of 100 μm on the outside of a urethane rubber having a thickness of 4 mm and a hardness of JIS-A 30 °. The voltage application roller 246 contacts the developing roller 240 at the aggregation position CPP on the upstream side in the rotation direction of the developing roller 240 with respect to the developing position DP, and is applied to the developer DM carried on the surface of the developing roller 240. In contact. An application roller blade 247 is disposed on the downstream side of the rotation direction D246 of the voltage application roller 246 with respect to the aggregation position CPP so as to contact the surface of the voltage application roller 246. The operation of the application roller blade 247 will be described later.

  The voltage application roller 246 causes the toner contained in the developer DM held on the surface of the developing roller 240 to aggregate (compact) on the surface of the developing roller 240 at the aggregation position CPP. The reason for performing such compaction is as follows.

  As described above, when the electrostatic latent image is developed with toner by the developing roller 240, a developing bias is applied to the developing roller 240 by the developing unit drive control circuit. That is, at the development position DP where the developing roller 240 and the photosensitive drum 21 abut, the toner in the liquid carrier migrates from the surface of the developing roller 240 toward the electrostatic latent image carried on the surface of the photosensitive drum 21. In order to do so, an electric field is generated. In this case, the toner migration speed is preferably high from the viewpoint of improving the development speed. However, toner with a small particle size is susceptible to the resistance of the liquid carrier and its migration speed is low. In particular, when a high-viscosity developer in which toner particles are dispersed at a high concentration in a non-volatile and insulating liquid carrier is used as in the present embodiment, such a decrease in migration speed becomes significant.

  Therefore, the voltage application roller 246 electrically discharges the toner contained in the developer DM to the surface of the developing roller 240 at the aggregation position CPP before the development position DP, and aggregates (compacts) the surface of the developing roller 240. Let That is, upon application of a predetermined compaction bias voltage (+800 V) from the development unit drive control circuit, the voltage application roller 246 performs toner compaction prior to toner development at the development position DP.

  FIG. 4 is a diagram showing compaction by the voltage application roller. As shown in the figure, the toner contained in the developer DM before compaction on the upstream side in the rotation direction of the developing roller 240 (or the voltage application roller 246) with respect to the aggregation position CPP was dispersed in the liquid carrier. Is in a state. On the other hand, the toner contained in the developer CDM after compaction on the downstream side in the rotation direction of the developing roller 240 (or the voltage application roller 246) with respect to the aggregation position CPP is in a state of being aggregated on the surface of the developing roller 240. . Hereinafter, the aggregated toner is simply referred to as “aggregated toner”. Further, the developer after compaction is particularly referred to as “aggregated developer CDM”.

  It can be seen that a part of the carrier contained in the aggregated developer CDM after compaction is peeled off on the surface of the voltage application roller 246. Such compaction causes the toner to aggregate prior to toner development at the development position DP, so that the toner involved in toner development migrates in the liquid carrier as a lump having a certain size at the development position DP. Thus, the migration speed is improved. Therefore, the development speed is improved, and good development can be realized.

  FIG. 5 is a diagram illustrating a state of toner development at the development position. As shown in the drawing, the toner in the aggregated developer CDM aggregates on the surface of the developing roller 240 and aggregates on the upstream side of the developing position DP in the rotational direction D240 (developing roller rotational direction) of the developing roller 240. A toner layer is formed. In addition, a carrier layer is formed outside the aggregated toner layer.

  In the nip portion formed at the development position DP, a part of the aggregated toner layer is electrophoresed from the surface of the developing roller 240 to the surface of the photosensitive drum 21, and adheres to the electrostatic latent image on the surface of the photosensitive drum 21. To do. Thereby, the electrostatic latent image is developed with toner. Then, after passing through the developing position DP, the liquid carrier adheres to the respective surfaces of the photosensitive drum 21 and the developing roller 240 and is conveyed while being carried on the respective surfaces. In addition, aggregated toner that has not been involved in toner development remains on the surface of the developing roller 240 that has passed the developing position DP.

  Returning to FIG. 3, the description will be continued. A cleaner blade 245 is provided at a cleaning position CLP that is downstream of the developing position DP in the rotation direction D240 of the developing roller. The cleaner blade 245 is disposed such that the tip thereof faces the upstream side in the rotation direction D240 of the developing roller 240, and is in contact with the surface of the developing roller 240 at the cleaning position CLP. The cleaner blade 245 scrapes and removes (cleans) the aggregated toner remaining on the surface of the developing roller 240 at the cleaning position CLP.

  Incidentally, the toner scraped off by the cleaner blade 245 at the cleaning position CLP is agglomerated toner as described above. Such agglomerated toner exists as a lump having a certain size. As a result, even after the aggregated toner remaining on the surface of the developing roller 240 is scraped off by the cleaner blade 245, it may remain in the vicinity of the cleaning position CLP as a lump and further accumulate. As a result of an increase in the amount of accumulated residual toner, there are cases where the residual toner cannot be removed (cleaned) satisfactorily. In particular, when a high-viscosity developer in which toner particles are dispersed at a high concentration in a non-volatile and insulating liquid carrier is used as in the present embodiment, such a cleaning defect becomes remarkable.

  In order to cope with such a problem, the image forming apparatus according to the present embodiment is configured to be able to perform a blade cleaning operation. In other words, the blade cleaning operation can be executed at an appropriate timing, such as at the initial setting immediately after the apparatus power is turned on, at the end operation before the apparatus power is turned off, or after the image forming operation is executed for a certain cumulative time. Has been. This blade cleaning operation is performed by rotating toner from the developer DM carried on the surface of the developing roller 240 at a position upstream of the cleaning position CLP in the developing roller rotating direction D240 while rotating the developing roller 240 in the rotating direction D240. To obtain a low toner developer LDM (low toner developer) and to supply the low toner developer LDM to the cleaning position CLP. An example will be described.

  FIG. 6 is a diagram illustrating an example of the blade cleaning operation. The blade cleaning operation is executed at a timing when the image forming operation is not executed at the time of initial setting or the like. In such a blade cleaning operation, voltage application is performed so that an electric field in a direction opposite to that at the time of image formation is generated between the development roller 240 and the voltage application roller 246 while rotating the development roller 240 in the rotation direction D240. A voltage is applied to the roller 246. That is, when the image forming operation is performed, a voltage that electrically discharges toner to the surface side of the developing roller 240 is applied to the voltage applying roller 246, but when the cleaning operation is performed, the voltage is applied to the surface side of the voltage applying roller 246. A voltage that electrically attracts the toner is applied to the voltage application roller 246. Specifically, a voltage of −300 V is applied to the voltage application roller 246 by the development unit drive control circuit. At this time, the same developing bias (+400 V) as that when the image forming operation is executed is applied to the developing roller 240. As a result, the toner contained in the liquid developer DM behaves as shown in FIG.

  On the upstream side of the rotation direction D240 of the developing roller 240 with respect to the aggregation position CPP, the toner in the developer DM exists in a dispersed state in the carrier. Next, in the nip portion formed at the aggregation position CPP, the toner in the developer DM is attracted to the surface side of the voltage application roller 246. On the other hand, in such a nip portion, only the carrier exists on the surface side of the developing roller 240. Then, on the downstream side in the rotation direction D240 of the aggregation position CPP, most of the toner contained in the developer DM is attracted to the surface of the voltage application roller 246. Therefore, most of the toner is separated from the developer DM carried on the surface of the developing roller 240, and as a result, a low toner developer LDM (low toner developer) is obtained. At this time, the toner adhering to the surface of the voltage application roller 246 is conveyed in the rotation direction D246 of the voltage application roller 246 and scraped off from the surface of the voltage application roller by the application roller blade 247 (FIG. 3).

  The description will be continued with reference to FIG. The low toner developer LDM from which the toner has been separated at the aggregation position CPP is conveyed in the rotational direction D240 while being carried on the surface of the developing roller 240, and is supplied to the cleaning position CLP. Accordingly, it is possible to wash away the accumulated toner near the cleaning position CLP. In other words, as described above, such accumulated toner exists as a lump because it is once aggregated by compaction. However, when the low toner developer LDM is supplied, the state as a lump of accumulated toner is relaxed. Further, when the low toner developer LDM is supplied, the accumulated toner is washed away from the vicinity of the cleaning position CLP.

  As described above, in the above-described embodiment, by performing the blade cleaning operation, the toner from the developer DM carried on the surface of the developing roller 240 at the aggregation position CPP on the upstream side in the rotation direction D240 with respect to the cleaning position CLP. To obtain a low toner developer LDM. The low toner developer LDM is supplied to the cleaning position CLP. Therefore, the accumulated toner is washed away from the vicinity of the cleaning position CLP, and it is possible to improve the subsequent cleaning, which is preferable.

  Further, in the above-described embodiment, the application roller blade 247 (toner removal unit) for removing the toner from the surface of the voltage application roller 246 is provided on the downstream side in the rotation direction D246 of the voltage application roller 246 with respect to the aggregation position CPP. Yes. Therefore, the toner on the surface of the voltage application roller 246 can be removed by the application roller blade 247. Therefore, excessive adhesion of toner on the surface of the voltage application roller can be suppressed, and efficient toner separation can be performed, which is preferable.

  By the way, in the above embodiment, the blade cleaning operation is performed using the voltage application roller 246. However, the blade cleaning operation can also be executed using the photosensitive drum 21. The blade cleaning operation will be described.

  The blade cleaning operation using the photosensitive drum 21 is also executed at a timing when a normal image forming operation such as initial setting is not executed. In such blade cleaning operation, a solid latent image is formed on the surface of the photosensitive drum 21. Here, the solid latent image refers to an electrostatic latent image formed to the full width in the axial direction of the developing roller 240 with respect to an area where the electrostatic latent image can be carried on the surface of the photosensitive drum 21. .

  Then, while rotating the developing roller 240 in the rotation direction D240, the same developing bias (+ 400V) as that at the time of executing the normal image forming operation is applied to the developing roller 240. Therefore, at the development position DP, the solid latent image formed on the surface of the photosensitive drum 21 is developed by the toner in the developer DM carried on the surface of the developing roller 240. Here, the electrostatic latent image developed at the development position DP is a solid latent image. Therefore, most of the toner in the developer DM adheres to the surface of the photosensitive drum 21 during the development process. That is, in this blade cleaning operation, the toner is separated from the developer DM at the development position DP to obtain the low toner developer LDM. Therefore, the low toner developer LDM is carried on the surface of the developing roller 240 on the downstream side in the rotation direction D240 of the developing roller 240 with respect to the developing position DP. At this time, the toner adhered to the photosensitive drum 21 is scraped off from the photosensitive drum 21 by the photosensitive cleaner 27 without being transferred to the transfer belt 31.

  The low toner developer LDM is transported in the rotational direction D240 while being carried on the surface of the developing roller 240, and is supplied to the cleaning position CLP. Accordingly, it is possible to wash away the accumulated toner near the cleaning position CLP.

  In this blade cleaning operation, the solid latent image may be formed over a time longer than the rotation period of the developing roller 240. Such a configuration is preferable because the low toner developer LDM can be supplied to the cleaning position CLP over a time longer than the rotation period of the developing roller 240, and the residual toner can be more reliably washed away. is there.

  In addition, it is preferable that the toner contained in the developer DM is compacted before the solid latent image is developed at the development position DP. That is, by developing the toner related to the development of the solid latent image, it is possible to improve the development of the solid latent image. As a result, more toner can be separated from the developer DM (aggregated developer CDM) at the development position DP. As a result, the amount of toner contained in the low toner developer LDM can be reduced. Therefore, it is preferable because the toner deposited on the cleaning position CLP can be more reliably washed away.

  Thus, both the blade cleaning operation using the voltage application roller 246 and the blade cleaning operation using the photosensitive drum 21 are developed at a position upstream of the cleaning position CLP in the developing roller rotation direction D240. By separating the toner from the developer DM carried on the surface of the roller 240, the low toner developer LDM is supplied to the cleaning position CLP. Therefore, it is possible to wash away the accumulated toner from the vicinity of the cleaning position CLP and improve the subsequent cleaning.

  In addition, it can be said that the above-described embodiment is preferable in that the removal of the accumulated toner can be performed very simply. In other words, conventionally, when the toner accumulated near the cleaning position CLP is to be removed, for example, a serviceman disassembles the image forming apparatus and the vicinity of the cleaning position CLP where the cleaner blade 245 and the developing roller 240 abut. It was necessary to remove the accumulated toner by cleaning the toner. That is, in order to suppress the cleaning failure due to toner accumulation and realize good cleaning, it is necessary to disassemble the apparatus. However, in the above embodiment, it is possible to realize good cleaning only by executing the blade cleaning operation without disassembling the apparatus. Therefore, it is possible to execute the removal of the accumulated toner very simply, which is preferable.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. That is, in the above-described blade cleaning operation, most of the toner is separated from the developer DM to obtain the low toner developer LDM. For example, in the blade cleaning operation using the voltage application roller 246 shown in FIG. 6, although some toner remains in the low toner developer LDM, most of the toner is attracted to the surface side of the voltage application roller 246. However, in obtaining the low toner developer LDM, separating most of the toner from the developer DM is not an essential requirement of the present invention. However, from the viewpoint of more favorably washing away the accumulated toner near the cleaning position CLP from the accumulation, it is preferable that the low toner developer LDM supplied to the cleaning position CLP has as little toner as possible.

  Therefore, in particular, in the blade cleaning operation using the voltage application roller 246, as shown in FIG. 6, the toner in the developer DM is attracted to the surface to such an extent that the toner aggregates on the surface of the voltage application roller 246. Is preferred. If this is the case, it is possible to more reliably attract the toner contained in the developer DM to the voltage application roller 246 side, and as a result, more toner remaining in the low toner developer LDM can be obtained. This is because it can be reduced.

  In the above-described embodiment, the blade cleaning operation is performed using the voltage application roller 246 or using the photosensitive drum 21. However, the embodiment of the blade cleaning operation is not limited to this. That is, as described above, the blade cleaning operation is a low toner obtained by separating toner from the developer DM carried on the surface of the developing roller 240 at a position upstream of the cleaning position CLP in the developing roller rotation direction D240. The essence is to supply the developer LDM to the cleaning position CLP. Therefore, a blade cleaning operation may be performed by separately providing a configuration for separating the toner from the developer DM to obtain the low toner developer LDM on the upstream side of the cleaning position CLP. However, the blade cleaning operation using the voltage application roller 246 is preferable in the following points.

  In the blade cleaning operation using the voltage application roller 246, toner is attracted to the surface side of the voltage application roller 246. The toner attracted in this way is scraped off from the surface of the voltage application roller by the application roller blade 247. Therefore, toner may accumulate at a position where the voltage application roller 246 and the application roller blade 247 come into contact (that is, a position where the application roller blade 247 scrapes off the toner). In particular, when a blade cleaning operation is performed by attracting toner in the developer DM to such a degree that the toner aggregates on the surface of the voltage application roller 246, the aggregated toner accumulates at the contact position. May occur.

  However, the voltage application roller 246 performs compaction when the image forming operation is performed. That is, as described with reference to FIG. 4, when the image forming operation is performed, the toner contained in the developer DM is electrically discharged to the surface of the developing roller 240 at the aggregation position CPP and the surface of the developing roller 240 is discharged. Aggregate. At this time, almost no toner is present in the developer DM carried on the surface of the voltage application roller 246 on the downstream side in the rotation direction D246 of the voltage application roller 246. The developer DM substantially free of toner is supplied to the application roller blade 247 on the downstream side in the rotation direction D246. That is, when the image forming operation is performed, the low toner developer LDM is supplied to the application roller blade 247. Therefore, even when the aggregated toner is accumulated at the contact position between the voltage application roller 246 and the application roller blade 247 by the blade cleaning operation, the accumulated toner is washed away during the image forming operation. Therefore, there is no need to separately provide a configuration or operation for washing away the accumulated toner at the contact position, which is preferable.

  In the above-described blade cleaning operation using the photoconductor drum 21, the toner adhering to the photoconductor drum 21 due to the development of the solid latent image is not transferred to the transfer belt 31, but is transferred to the photoconductor drum 27 by the photoconductor cleaner 27. 21 is scraped off. However, for example, the toner may be scraped by the belt cleaner 36 after the primary transfer to the transfer belt 31 and without performing the secondary transfer. However, in consideration of the possibility that the toner is scattered in the process of transporting the toner inside the apparatus and contaminates the inside of the apparatus, it is preferable to scrape off with the photoreceptor cleaner 27.

  Further, in the above-described embodiment, as the liquid developer DM, toner particles made of a resin, pigment, or the like having an average particle diameter of about 0.1 to 5 μm in a non-volatile and insulating liquid carrier such as silicone oil have a high concentration ( A high viscosity (about 100 to 10000 mPa · s) developer dispersed in about 5 to 40 wt% was used. However, the developer that can be used in the present invention is not limited to such a developer. However, when image formation is performed using a high-viscosity developer as in the above-described embodiment, the problem of toner accumulation near the cleaning position CLP becomes significant. Therefore, it is extremely preferable to apply the present invention to image formation using a high viscosity developer.

  In the above embodiment, the application roller 243 rotates in a direction (clockwise in FIG. 3) opposite to the rotation direction of the developing roller 240 (counterclockwise in FIG. 3). However, the rotation direction of the application roller 243 is not limited to this, and may be the same direction as the rotation direction of the developing roller 240 (counterclockwise in FIG. 3).

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. FIG. 3 is an enlarged view of a configuration around an image forming station. The figure which shows the compaction by a voltage application roller. FIG. 6 is a diagram illustrating a state of toner development at a development position. The figure which shows an example of a blade washing | cleaning operation | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Photosensitive drum (latent image carrier), 22 ... Charging unit (latent image forming means), 23 ... Exposure unit (latent image forming means), 24 ... Developing unit, 240 ... Developing roller, 245 ... Cleaner blade, 246 ... Voltage application roller, 247 ... Application roller blade (toner removing means), 27 ... Photoconductor cleaner, D240 ... Development roller rotation direction, DM ... Liquid developer (developer), LDM ... Low toner developer (low toner development) Liquid), CDM: Aggregated developer, DP: Development position, CPP: Aggregation position, CLP: Cleaning position, EC: Engine controller

Claims (5)

A developing roller that conveys the developing solution to a developing position facing the latent image carrier by rotating the developer in a predetermined direction while supporting the developing solution in which the toner is dispersed on the liquid carrier, with respect to the developing position An image forming apparatus comprising: a cleaner blade that contacts a surface of the developing roller at a cleaning position downstream in the rotation direction of the developing roller and removes residual toner from the surface of the developing roller. The toner contained in the developer is aggregated on the surface of the developing roller at the aggregation position upstream of the rotation direction of the roller, and the aggregated aggregated toner is carried on the surface of the latent image carrier at the development position. An image forming method in which toner development is performed by attaching to an electrostatic latent image,
While rotating the developing roller in the rotation direction of the developing roller, the toner is separated from the developer carried on the surface of the developing roller at a position upstream of the cleaning position in the rotation direction of the developing roller. An image forming method comprising: performing a blade cleaning operation for obtaining a developer and supplying the low toner developer to the cleaning position. A latent image carrier capable of carrying an electrostatic latent image on its surface;
Latent image forming means for forming the electrostatic latent image on the surface of the latent image carrier;
The developer in which the toner is dispersed in the liquid carrier is rotated in a predetermined rotation direction while being carried on the surface thereof, so that the developer is conveyed to a development position facing the latent image carrier, and the latent image carrier is developed at the development position. A developing roller that is brought into contact with and supplied to the surface of the latent image carrier,
At the aggregation position upstream of the developing position in the rotation direction of the developing roller, the surface thereof faces the developing roller and contacts the developer carried on the surface of the developing roller, and a voltage is applied to the surface. A voltage application roller that is capable of electrically discharging the toner contained in the developer to the surface side of the developing roller by being applied and aggregating the toner on the surface of the developing roller;
A cleaner blade that contacts the surface of the developing roller at a cleaning position downstream of the developing position in the rotational direction of the developing roller and removes residual toner from the surface of the developing roller;
An image forming apparatus comprising: control means for controlling the developing roller and the voltage application roller to execute the following image forming operation and blade cleaning operation.
The image forming operation is an operation of forming aggregated toner by the voltage application roller and attaching the aggregated toner to the electrostatic latent image carried on the surface of the latent image carrier at the development position.
The blade cleaning operation applies a voltage to the surface of the voltage application roller at the aggregation position while rotating the development roller in the rotation direction of the development roller, and is carried on the surface of the development roller at the aggregation position. A low toner developer obtained by electrically attracting toner contained in the developer to the surface of the voltage application roller and separating the toner from the developer carried on the surface of the developer roller is provided at the cleaning position. This is a supply operation. The image forming apparatus according to claim 2, wherein the voltage application roller rotates in a predetermined rotation direction.
An image forming apparatus further comprising a toner removing unit that removes toner from the surface of the voltage application roller on the downstream side in the rotation direction of the voltage application roller with respect to the aggregation position. A latent image carrier capable of carrying an electrostatic latent image on its surface;
Latent image forming means for forming the electrostatic latent image on the surface of the latent image carrier;
The developer in which the toner is dispersed in the liquid carrier is rotated in a predetermined rotation direction while being carried on the surface thereof, so that the developer is conveyed to a development position facing the latent image carrier, and the latent image carrier is developed at the development position. A developing roller that is brought into contact with and supplied to the surface of the latent image carrier,
At the aggregation position upstream of the developing position in the rotation direction of the developing roller, the surface thereof faces the developing roller and contacts the developer carried on the surface of the developing roller, and a voltage is applied to the surface. A voltage application roller that is capable of electrically discharging the toner contained in the developer to the surface side of the developing roller by being applied and aggregating the toner on the surface of the developing roller;
A cleaner blade that contacts the surface of the developing roller at a cleaning position downstream of the developing position in the rotational direction of the developing roller and removes residual toner from the surface of the developing roller;
An image forming apparatus comprising: control means for controlling the latent image forming means and the developing roller to execute the following blade cleaning operation.
In the blade cleaning operation, a solid latent image is formed on the surface of the latent image carrier by the latent image forming unit, while aggregating toner is formed by the voltage application roller, and the agglomerated toner is removed from the solid latent image at the development position. And a low toner developer obtained by separating the toner from the developer carried on the surface of the developing roller and supplying the toner to the cleaning position. The image forming apparatus according to claim 4, wherein the solid latent image is formed over a time longer than a rotation period of the developing roller.

Images