JP6921547B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copier, a printer, and a facsimile.

In an image forming apparatus such as a printer using an electrophotographic image forming method (electrophotographic process), an electrophotographic photosensitive member (hereinafter, "photoreceptor") is uniformly charged, and the charged photosensitive member is selectively exposed. As a result, an electrostatic image is formed on the photoconductor. The electrostatic image formed on the photoconductor is visualized as a toner image by the toner of the developing agent. Then, the toner image formed on the photoconductor is transferred to a recording material such as recording paper or a plastic sheet, and heat or pressure is applied to the toner image transferred on the recording material to convert the toner image into a recording material. Image recording is performed by fixing.

Such an image forming apparatus generally requires replenishment of a developer and maintenance of various process means. In order to facilitate the replenishment work of the developer and the maintenance of various process means, the photoconductor, charging means, developing means, cleaning means, etc. are collectively made into a cartridge in the frame and can be attached to and detached from the main body of the image forming apparatus. Cartridge method has been put into practical use. According to the cartridge method, it is possible to provide an image forming apparatus having excellent usability.

Conventionally, in a developing device used for an image forming device, a coating agent is applied to a developing roller (developer carrier) for the purpose of suppressing turning of a developing blade (developer layer thickness regulating member) and reducing driving torque. The method is widely used. Patent Document 1 uses a powder having the same polarity as toner as a coating agent for a developing roller. When the coating agent is rubbed against the developing blade or the developing agent supply member, it has a high potential and adheres to the surface layer of the developing roller with a strong force. If image formation is performed in this state, there is a risk that image defects such as uneven density and white spots may occur. As a means for solving this problem, it is conceivable to carry out a developing roller cleaning sequence in which the coating agent on the developing roller is developed on the photoconductor together with the toner.

Further, in recent years, colorization in image forming apparatus has progressed, and an intermediate transfer type image forming apparatus has been put into practical use as an apparatus for forming a color image. In the intermediate transfer type image forming apparatus, after the toner image is transferred from the intermediate transfer body to the recording material, the transfer residual toner remains on the intermediate transfer body. The transfer residual toner (secondary transfer residual toner) on the intermediate transfer body is removed from the intermediate transfer body by the intermediate transfer body cleaning means and recovered.

Patent Document 2 proposes as an intermediate transfer body cleaning means to provide a toner charging means for charging the secondary transfer residual toner on the intermediate transfer body with a polarity opposite to the normal charging polarity of the toner. In this case, the secondary transfer residual toner is charged in a polarity opposite to the normal charging polarity of the toner, so that the toner is reverse-transferred from the intermediate transfer body to the photoconductor in the primary transfer portion of the subsequent image forming portion. NS. The reverse-transferred toner is collected and removed by a cleaning member (photoreceptor cleaning blade) on the photoconductor.

Japanese Unexamined Patent Publication No. 2-298971 Japanese Patent No. 3267507 JP-A-2007-248547

In recent years, against the background of the expansion of the market for image forming apparatus, it has been required to deal with paper dust and paper containing a large amount of filler. At the same time, it is required to extend the service life in order to reduce the frequency of process cartridge replacement. As a result, in the image forming apparatus that reverse-transfers the secondary transfer residual toner to the photoconductor and collects it, the paper dust generated in the secondary transfer portion is collected together with the secondary transfer residual toner by the photoconductor cleaning blade more than before. Will be done. Most of the collected paper dust and toner are scraped off from the surface of the photoconductor by a cleaning blade and collected, but some paper dust bites into the photoconductor cleaning blade and reduces the cleaning ability of the surface of the photoconductor. If the developing roller cleaning sequence is executed in this state, the photoconductor cleaning blade cannot withstand the load of toner recovery for one round of the developing roller, and there is a problem that image adverse effects due to poor cleaning occur.

In Patent Document 3, by transferring a part of the toner developed on the photoconductor to the intermediate transfer belt, the amount of toner supplied to the cleaning blade per unit area is reduced, and the recovery load of the photoconductor cleaning blade is reduced. ing. However, in this case, the downtime becomes large.

Accordingly, the present invention is an image forming apparatus capable of executing an image forming mode for forming an image on a recording material, carries a rolling possible image bearing member rotating, the developer, the developer charged to the regular polarity A rotatable developer carrier that develops an electrostatic latent image formed on the surface of the image carrier into a developer image, and a developer supply member that supplies the developer to the surface of the developer carrier. a regulating member for regulating an amount of the developer carried on the surface of the developer carrying member, a cleaning member for removing the developer from the surface of the image bearing member, is formed on the surface of the image bearing member An intermediate transfer body to which the developer image is transferred, and a transfer member that contacts the intermediate transfer body to form a transfer portion and transfers the developer image from the intermediate transfer body to a recording material at the transfer portion. the said developer image formed on the intermediate transfer member after passing through the transfer portion, a developer charging member, wherein the said regular polarity the developer remaining on the intermediate transfer member is charged to a reverse polarity, the developing A developing voltage applying section that applies a developing voltage to the agent carrier, a supply voltage applying section that applies a supply voltage to the developing agent supply member, a regulated voltage applying section that applies a regulating voltage to the regulating member, and the developing voltage. and applying unit, the supply voltage applying unit, and a control unit for controlling, and the regulating voltage application unit, in the picture image formation mode, the intermediate transfer member the developer charged to the opposite polarity The developer is supplied from the developer carrier to the image carrier in a non-image forming mode in which the image carrier is moved from the developer to the image carrier and removed from the image carrier by the cleaning member, and the image forming mode is not executed. An image forming apparatus capable of executing a cleaning mode in which the developer supplied to the image carrier is removed by the cleaning member, and the developer carrier does not have a coating agent charged to the normal polarity. are applied to the surface in use, the coating agent is the same charge polarity as the developer, and the large average charge amount of the developing agent, prior Symbol controller, the developer on the image carrier In the cleaning mode in which the coating agent is supplied to the image carrier while supplying the image-bearing body, one circumference of the developer-supporting body in the rotation direction of the developer-supporting body is divided into a plurality of regions in the rotation direction. When divided, the developer and the coating agent are supplied to the image carrier from a part of the plurality of regions while the developer carrier makes one revolution, and after the developer carrier makes one revolution. Before a region other than a part of the plurality of regions during multiple rotations The developer and the coating agent are controlled to be supplied to the image carrier, and the first voltage difference between the supply voltage and the development voltage is the second voltage difference between the development voltage and the regulation voltage. Provided is an image forming apparatus that controls the absolute value of the supply voltage and the absolute value of the regulated voltage to be larger than the absolute value of the developing voltage.

According to the present invention, it is possible to reduce the occurrence of cleaning defects.

It is a figure explaining the belt cleaning composition in the Example of this invention. It is sectional drawing explaining the image forming apparatus of this invention. It is a figure explaining the operation of the developing roller cleaning mode. It is a figure explaining the operation of the development roller cleaning mode of Example 1. FIG. It is a figure explaining the photosensitive drum and the photoconductor cleaning blade setting angle. It is a figure explaining the operation of the development roller cleaning mode of Example 2. FIG.

[Example 1]
(1) Image Forming Device The overall configuration of the image forming device according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 2 is a schematic cross-sectional view of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 of this embodiment is an in-line type and intermediate transfer type full-color printer using an electrophotographic method. In this embodiment, the image forming apparatus 100 has process cartridges 1a, 1b, 1c, and 1d which are first, second, third, and fourth image forming units as a plurality of image forming means. The process cartridges 1a, 1b, 1c, and 1d form images of each color of yellow, magenta, cyan, and black, respectively. These four process cartridges 1a, 1b, 1c, and 1d are arranged in a row at regular intervals. In this embodiment, the configurations and operations of the process cartridges 1a, 1b, 1c, and 1d for each color are substantially the same except for the type (color) of the developing agent contained therein. Therefore, in the description of the process cartridge configuration, the process cartridge 1a will be taken as a representative. In addition to the explanation of the configuration of the process cartridge, when individual explanations are not required for a to d, each configuration is generalized and the subscripts a to d are omitted.

1a of FIG. 1 is a cross-sectional view of a process cartridge more detailed than that of FIG. 2 cut along a plane perpendicular to the rotation axis direction (longitudinal direction) of the photosensitive drum 2a.

The process cartridge 1a includes a photoconductor unit 6a including a photosensitive drum 2a or the like as an image carrier, and a developing unit (developer) 4a including a developing roller 8a or the like as a developing agent carrier.

A photosensitive drum 2a is rotatably attached to the photoconductor unit 6a via a bearing. The photosensitive drum 2a is rotationally driven in the direction of arrow R1 according to the image forming operation by receiving the driving force of the driving motor. In this embodiment, it is driven to rotate at 190 mm / sec.

Further, in the photoconductor unit 6a, a drum charging roller 3a and a drum cleaning member 61a are arranged so as to come into contact with the peripheral surface of the photosensitive drum 2a which is an image carrier. A charging bias is applied to the drum charging roller 3a from the charging bias power supply. In this embodiment, the bias applied so that the potential (charging potential: Vd) on the surface of the photosensitive drum 2a is −500 V is set. The charging member may be a non-contact corona charging instead of a charging roller that is charged by contact.

Then, a laser beam is irradiated from the exposure apparatus 7a based on the image information to form an electrostatic latent image on the photosensitive drum 2a. In this example, the amount of laser light ^{was set to 0.2 μJ / cm 2} at the time of image formation, and the latent image potential was set to −150 V.

On the other hand, the developing apparatus 4a has a developing chamber 4a1 and a developing agent accommodating chamber 4a2, and the developing agent accommodating chamber 4a2 is arranged below the developing chamber 4a1. Toner 99a (developer) is housed inside the developer storage chamber 4a2. In this embodiment, the normal charging polarity of the toner 99a is negative, and the case where a negatively charged toner is used will be described below, but it is also possible to use a positively charged toner.

Further, the developer accommodating chamber 4a2 is provided with a developer conveying member 11a for conveying the toner 99a to the developing chamber 4a1, and the toner is conveyed to the developing chamber 4a1 by rotating in the direction of the arrow R6. doing.

At the time of shipment of the cartridge, a toner seal is attached to the opening of the developer storage chamber 4a2. This is to prevent the toner 99a from moving from the developer accommodating chamber 4a2 to the developing chamber 4a1 before the process cartridge 1a starts to be used. This toner seal is broken by the developer transport member 11a at the start of use of the process cartridge 1a.

The developing chamber 4a1 is provided with a developing roller 8a that comes into contact with the photosensitive drum 2a and rotates in the direction of arrow R4 by receiving the driving force of the driving motor. The developing roller 8a and the photosensitive drum 2a rotate so that their surfaces move in the same direction at the facing portion (contact portion). Further, a bias (voltage) sufficient to develop and visualize the electrostatic latent image on the photosensitive drum 2a as a toner image is applied to the developing roller 8a from the developing bias power supply.

Inside the developing chamber 4a1, a toner supply roller 9a (developer material supply member) for supplying the toner conveyed from the developer accommodating chamber 4a2 to the developing roller 8a is arranged. Further, a developing blade, which is a layer thickness regulating member 10a that regulates the coating amount (layer thickness) of toner on the developing roller 8a and applies electric charges, is arranged.

The outer diameters of the developing roller 8a and the toner supply roller 9a are both 12 mm, and both are installed so as to form a predetermined contact portion. The toner supply roller 9a is an elastic spousy roller having a foam layer formed on the outer periphery of the conductive core metal. The toner supply roller 9a rotates in the direction of arrow R5 by receiving the driving force of the driving motor. In this embodiment, the developing roller 8a is driven to rotate at a peripheral speed of 230 mm / sec, and the toner supply roller 9a is driven to rotate at a peripheral speed of 460 mm / sec.

Further, a bias (voltage) is applied to the toner supply roller 9a from the toner supply roller bias power supply. As a result, the toner is supplied from the toner supply roller 9a to the developing roller 8a which is the developer carrier. In this embodiment, the bias applied to the toner supply roller 9a is controlled to be −500 V, and the bias applied to the developing roller 8a is controlled to be −400 V.

The toner supplied to the developing roller 8a by the toner supply roller 9a enters the contact contact portion between the layer thickness regulating member 10a and the developing roller 8a by the rotation of the developing roller 8a in the direction of the arrow R4. Therefore, the toner is triboelectrically charged by rubbing between the surface of the developing roller 8a and the layer thickness regulating member 10a, and at the same time the charge is applied, the layer thickness is regulated. A bias (voltage) is applied to the layer thickness regulating member 10a from the regulating member power supply to stabilize the toner layer thickness regulation. In this embodiment, −500 V is applied.

The toner on the developing roller 8a whose layer thickness is regulated is conveyed to the portion facing the photosensitive drum 2a by the rotation of the developing roller 8a, and the electrostatic latent image on the photosensitive drum 2a is developed and visualized as a toner image. ..

In this embodiment, the process cartridge 1 including the photoconductor unit 6 and the developing unit 4 is detachable from the apparatus main body of the image forming apparatus 100, but the developing apparatus 4 which is the developing unit independently forms an image. The configuration may be such that it can be attached to and detached from the main body of the device 100.

Further, an intermediate transfer belt 20 which is an endless belt-shaped intermediate transfer body as a second image carrier is arranged so as to face all of the photosensitive drums 2a to 2d of the process cartridges 1a to 1d. The intermediate transfer belt 20 is hung around a drive roller 21, a cleaning opposed roller 22, and a secondary transfer opposed roller 23 as a plurality of support members, and rotates in the direction of arrow R7. On the inner peripheral surface side of the intermediate transfer belt 20, primary transfer rollers 5a to 5d are arranged corresponding to the photosensitive drums 2a to 2d of the process cartridges 1a to 1d. Further, on the outer peripheral surface side of the intermediate transfer belt 20, a secondary transfer roller 24, which is a secondary transfer member as a secondary transfer means, is arranged at a position facing the secondary transfer opposed roller 23. A portion composed of a secondary transfer roller which is a secondary transfer member and a portion of an intermediate transfer belt facing the secondary transfer roller is referred to as a secondary transfer unit. If toner does not intervene, the part that becomes the contact part between the secondary transfer roller and the intermediate transfer belt becomes the secondary transfer part.

In this example, PEN (polyethylene naphthalate) resin was used as the intermediate transfer belt 20 as the second image carrier that supports the toner image which is the developer image. The total length of the intermediate transfer belt 20 is 700 mm, the surface resistivity is 5.0 × 10 ¹¹ Ω / □, and the volume resistivity is 8.0 × 10 ¹¹ Ωcm.

In addition, as the intermediate transfer belt 20, resins such as PVDF (polyvinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene terephthalate), and polycarbonate can be used. Further, as the intermediate transfer belt 20, for example, a rubber base layer such as EPDM (ethylene, propylene, diene rubber) coated with urethane rubber in which a fluororesin such as PTFE (polytetrafluoroethylene) is dispersed is used. Can be done.

By rotationally driving the drive roller 21 in the direction of arrow R2 (counterclockwise) in the drawing, the intermediate transfer belt 20 is driven in the direction of arrow R3 (counterclockwise) in the drawing, which is substantially equal to the peripheral speed of the photosensitive drum 2. , Moves (rotates) orbits at a predetermined process speed. In this embodiment, the surface moving speed is driven to orbit at 190 mm / sec.

The primary transfer roller 5 is made of an elastic member such as sponge rubber. Further, the primary transfer roller 5 abuts on the photosensitive drum 2 via the intermediate transfer belt 20 to form a primary transfer nip portion (primary transfer portion) at the contact portion between the intermediate transfer belt 20 and the photosensitive drum 2. .. Then, the primary transfer roller 5 rotates in accordance with the movement of the intermediate transfer belt 20.

The primary transfer roller 5 is connected to a primary transfer bias power source as a means for applying the primary transfer voltage, and the primary transfer bias is applied to the primary transfer roller 5 from the primary transfer bias power source. The toner image formed on the photosensitive drum 2 is transferred onto the rotating intermediate transfer belt 20 by the primary transfer roller 5 to which the primary transfer bias having the polarity opposite to the normal charging polarity of the toner is applied. (Primary transcription).

The secondary transfer roller 24 is made of an elastic member such as sponge rubber. In this example, as the secondary transfer roller, a nickel-plated steel rod having a diameter of 6 mm coated with NBR hydrin rubber having a wall thickness of 6 mm was used. The electrical resistance of the secondary transfer roller 24 is such that the secondary transfer roller is pressed onto an aluminum cylinder with a force of 9.8 N and rotated at 50 mm / sec in an environment of a temperature of 23 ° C. and a relative humidity of 50%. it is 3.0 × 10 ⁷ Ω in case of applying 1000V.

The secondary transfer roller 24 comes into contact with the secondary transfer opposed roller 23 via the intermediate transfer belt 20 to form a secondary transfer nip portion (secondary transfer portion) at the contact portion. Then, the secondary transfer roller rotates in accordance with the movement of the intermediate transfer belt, or the intermediate transfer belt and the recording material P.

A secondary transfer bias power source is connected to the secondary transfer roller 24 as a means for applying the secondary transfer bias, and the secondary transfer bias is applied to the secondary transfer roller from the secondary transfer bias power source. The secondary transfer bias power supply can select and apply a bias of positive or negative polarity.

The toner image formed on the intermediate transfer belt 20 is recorded as being conveyed to the secondary transfer nip portion by the secondary transfer roller 24 to which the secondary transfer bias having a polarity opposite to the normal charging polarity of the toner is applied. It is transferred (secondary transfer) onto the material P.

A belt cleaning device 30 as an intermediate transfer body cleaning means is installed outside the intermediate transfer belt 20 and downstream of the secondary transfer unit. Details of the configuration and operation of the belt cleaning device 30 will be described later.

A resist roller 13 constituting the recording material supply means is installed on the upstream side in the transport direction of the recording material P from the secondary transfer unit.

Further, a fixing device 12 as a fixing means is installed on the downstream side of the secondary transfer unit in the transport direction of the recording material P. The fixing device 12 includes a fixing roller 12A provided with a heat source and a pressure roller 12B that press-contacts the fixing roller 12A.

(2) Image forming operation Next, the image forming operation by the image forming apparatus 100 of this embodiment will be described by taking a full-color image forming mode as an example.

First, toner images of each color are formed on the photosensitive drums 2a to 2d of the image forming portions 1a to 1d by an electrophotographic process.

That is, when the image formation operation start signal is generated, the photosensitive drums 2a to 2d rotationally driven at a predetermined process speed are uniformly charged by the drum charging rollers 3a to 3d, respectively.

Then, each of the exposure devices 7a to 7d converts the input color-separated color image signal into an optical signal at the laser output unit. Then, each of the exposure devices 7a to 7d scans and exposes each of the uniformly charged photosensitive drums 2a to 2d with a laser beam which is a converted optical signal, and electrostatically performs static electricity on the photosensitive drums 2a to 2d. Form a latent image.

Then, in the process cartridge 1a, which is the first image forming unit, the yellow-colored toner is electrostatically adsorbed according to the potential on the surface of the photosensitive drum 2a, so that it is developed as a toner image which is a developer image. At this time, a development bias having the same polarity as the charging polarity (negative electrode property in this embodiment) of the photosensitive drum 2a is applied to the developing roller 8a of the developing unit 4a.

The yellow toner image on the photosensitive drum 2a is a primary transfer roller 5a to which a primary transfer bias having a polarity opposite to the normal charging polarity of the toner (positive electrode property in this embodiment) is applied to the primary transfer nip portion. Is primarily transferred onto the rotating intermediate transfer belt 20. The intermediate transfer belt 20 on which the yellow toner image is transferred moves to the process cartridge 1b side, which is the second image forming portion.

In the process cartridge 1b, which is the second image forming unit, a magenta toner image is formed on the photosensitive drum 2b in the same manner as in the process cartridge 1a. Then, the magenta toner image is superimposed on the yellow toner image on the intermediate transfer belt 20 at the primary transfer nip portion and the primary transfer is performed.

The same applies to the third and fourth process cartridges 1c and 1d. The toner images of each color of cyan and black are sequentially superposed on the toner images of each color of yellow and magenta that are superimposed on the intermediate transfer belt 20 and transferred first, and the toner images of each color of cyan and black are sequentially transferred in the primary transfer portion.

In this way, a multi-color toner image composed of a plurality of color toner images is formed on the intermediate transfer belt 20 by sequentially superimposing and primary transferring toner images of each color at each primary transfer nip portion.

The recording material P is conveyed to the secondary transfer section by the resist roller 13 at the timing when the tip of the toner image on the intermediate transfer belt 20 moves to the secondary transfer section. Then, in the secondary transfer section, the multiple toner on the intermediate transfer belt 20 is provided by the secondary transfer roller 24 to which the secondary transfer bias having a polarity opposite to the normal charging polarity of the toner (positive electrode property in this embodiment) is applied. The images are collectively secondarily transferred to the recording material P.

After that, the recording material P to which the toner image is transferred is conveyed to the fixing device 12. The recording material P carrying the toner image is heated and pressurized at the fixing nip portion between the fixing roller 12A and the pressure roller 12B installed in the fixing device 12. As a result, the toner image is heat-fixed (melt-fixed) on the surface of the recording material P, and a full-color image (or multicolor image) is formed on the recording material P. After that, the recording material P is discharged to the outside of the image forming apparatus 100, and a series of image forming operations is completed.

The toner remaining on the photosensitive drum 2 after the primary transfer step (primary transfer residual toner) is removed from the photosensitive drum 2 by the photosensitive member cleaning blade 61, which is a cleaning member formed of an elastic body, and is recovered. NS.

Further, the toner remaining on the intermediate transfer belt 20 after the secondary transfer step (secondary transfer residual toner) is moved from the intermediate transfer belt 20 to the photosensitive drum by the belt cleaning mechanism 30 as described in detail below. It will be recovered.

(3) Belt Cleaning Mechanism Next, the belt cleaning mechanism in this embodiment will be described with reference to FIG.

Reference numeral 30 in FIG. 1 is a schematic view showing the configuration of the belt cleaning mechanism. In this embodiment, a conductive brush 31 (first charging member) and a charging roller 32 (second charging member) are provided as charging portions for charging the secondary transfer residual toner. The charging portion having the conductive brush 31 and the charging roller 32 is located on the downstream side in the moving direction (rotational direction) of the intermediate transfer belt 20 from the secondary transfer portion and on the upstream side of the primary transfer portion. Further, the conductive brush 31 is located on the upstream side with respect to the charging roller 32.

The conductive brush 31 in this embodiment uses nylon having conductivity imparted to the material, has a fineness of 7 decitex, a pile length of 5 mm, and a brush width of 5 mm. Electrical resistance of the conductive brush, the conductive brush on an aluminum cylinder, and pressed with a force of 9.8 N, at 1.0 × 10 ⁶ Ω in the case of applying 500V while being rotated at 50 mm / sec be.

Instead of the conductive brush 31, a fixedly arranged foam sponge-like member (for example, one formed of urethane rubber or NBR hydrin rubber) or a rotatable fur brush roller may be used. Further, a rotatable foam sponge roller or the like may be used.

Further, as the charging roller 32 in this embodiment, a nickel-plated steel rod having a diameter of 6 mm coated with a solid elastic body made of EPDM rubber in which carbon was dispersed with a wall thickness of 5 mm was used. Electrical resistance of the charging roller 32, the charging roller on an aluminum cylinder, and pressed with a force of 9.8 N, which is 5.0 × 10 ⁷ Ω in the case of applying 500V while being rotated at 50 mm / sec .. The charging roller 32 is in contact with the intermediate transfer belt 20 and is pressed against the cleaning opposing roller 22 with a total pressure of 9.8 N.

The conductive brush 31 is electrically connected to a high-voltage power source so that positive and negative biases (voltages) can be selectively applied. Similarly, the charging roller 32 is also electrically connected to the high-voltage power supply so that positive and negative biases (voltages) can be selectively applied.

The belt cleaning operation is controlled by the control unit 33. During the belt cleaning operation, a positive DC voltage is output from the high-voltage power supply to the conductive brush 31 and the charging roller 32, respectively. The output value of the DC voltage is controlled based on the current detected by the current detecting means, and is constantly controlled so that the current value becomes a preset target current value. A value has been selected as the target current value that does not overcharge the secondary transfer residual toner and does not cause cleaning defects due to insufficient charging. The target current value of the conductive brush in this embodiment is 20 μA. The target current value of the charging roller is 30 μA.

The toner on the intermediate transfer belt 20 before the secondary transfer step is charged with a negative electrode property having the same polarity as the charge charge on the surface of the photosensitive drum 2 and in a state where the variation in the charge distribution is small. On the other hand, in the secondary transfer residual toner on the intermediate transfer belt after the secondary transfer step, the charge distribution becomes broad and the peak moves to the positive electrode side, which is the opposite polarity to the normal charge polarity of the toner. Form a distributed distribution. As a result, the secondary transfer residual toner is a mixture of negatively charged toner, almost uncharged toner, and positively charged toner, and many of them are relatively positively charged. ..

By applying a positive bias to the conductive brush 31 during the belt cleaning operation, a positive electric field is formed from the conductive brush 31 toward the intermediate transfer belt, and the negatively charged toner of the secondary transfer residual toner is discharged. The conductive brush collects electrostatically. As a result, the amount of toner that passes through the charging roller 32 on the downstream side during the cleaning operation can be reduced. In addition, there is also an action of charging (pre-charging) the toner on the positive electrode side by discharging the conductive brush 31 and the secondary transfer residual toner. In this embodiment, the amount of toner electrostatically recovered by the charged brush 31 is about 10% of the residual transfer toner, and most of the toner passes through the conductive brush 31.

In the charging roller 32 on the downstream side, the secondary transfer residual toner that has passed through the conductive brush 31 is uniformly positively charged by the discharge due to the potential difference with the intermediate transfer belt 20.

Next, a step of collecting the secondary transfer residual toner to the image forming unit 1a will be described. The toner charged positively by the charging roller proceeds to the primary transfer nip portion of the process cartridge 1a, which is the first image forming portion. Then, by the action of the positive primary transfer bias applied to the primary transfer roller 5a, the intermediate transfer belt 20 is reverse-transferred to the photosensitive drum 2a of the process cartridge 1a. The toner reverse-transferred to the photosensitive drum 2a is then recovered by the photoconductor cleaning blade 61a of the photoconductor unit 6a. At this time, the process cartridge 1a simultaneously forms an image, and the negatively charged toner is transferred from the photosensitive drum 2a to the intermediate transfer belt 20 by the developing roller 8a.

In this way, the conductive brush 31 temporarily collects the residual transfer toner and precharges the toner, and the charging roller 32 further downstream charges the toner uniformly, and then collects the toner at the primary transfer nip portion. This makes it possible to form an image while removing the secondary transfer residual toner from the intermediate transfer belt.

Further, in this cleaning configuration, the fibrous paper dust of the recording material P generated in the secondary transfer portion is also collected in the photosensitive drum 2a through the same process as the toner.

In the belt cleaning device 30 of this embodiment, the secondary transfer residual toner is not collected and removed by the device itself, but the secondary transfer residual toner is transferred to the photosensitive drum and removed by the photoconductor cleaning blade. Therefore, 80% or more of the total amount of the secondary transfer residual toner remaining after the secondary transfer (after passing through the secondary transfer portion) is moved to the photosensitive drum and collected by the photoconductor cleaning blade which is a cleaning member. However, the present invention is not limited to this, and a belt cleaning device may be configured to collect a part of the total amount of the secondary transfer residual toner. In that case, 50% or more of the total amount of the secondary transfer residual toner remaining after the secondary transfer (after passing through the secondary transfer portion) is moved to the photosensitive drum and collected by the photoconductor cleaning blade which is a cleaning member. ..

(4) Coating Agent for Developing Roller Here, the coating agent applied to the developing roller 8 which is the developing agent carrier at the time of shipping the cartridge (or when not in use) will be described.

The developing roller 8 of this embodiment protects the developing roller 8 from manufacturing to the start of use (when not in use), and between the layer thickness regulating member 10 and the developing roller at the start of use. A powder different from the toner is used as a coating agent for the purpose of improving the lubrication performance of the roller.

In this example, silicone resin particles (trade name: Tospearl 120, manufactured by GE Toshiba Silicone Co., Ltd., average particle size: 2 μm) are used as a coating agent, and about 10 to 150 mg is applied to the developing roller 8. .. Tospearl 120 has a negative electrode property, which is a negative electrode property, and has a negative electrode property which is stronger than that of toner. Specifically, in a temperature / humidity environment of 23 ° C. and 40%, the average charge per unit mass of toner was about 50 μC / g, while the average charge per unit mass of tospar was 90 μC / g.

If a substance that is positively charged on the positive side is used as the coating agent, the coating agent may adhere to the layer thickness regulating member 10 to which −500 V is applied, which may cause poor layer thickness regulation. , This is not adopted.

However, the type of the coating agent is not limited to the above-mentioned silicone resin particles as long as it is a material that is negatively charged on the negative side.

(5) Development Roller Cleaning Mode The toner and the coating agent of this embodiment have the same electrical polarity, but the amount of electric charge is different, so that the coating agent tends to stay on the developing roller during normal printing operation. When the amount of the coating agent on the developing roller increases, the coating agent is developed together with the printed image, and white streaks appear as image defects. Therefore, in this embodiment, the cleaning operation of the developing roller 8 is periodically performed.

In the developing roller cleaning mode, a command is issued from the control unit 33 of the image forming apparatus, the drive motor is driven, and the cleaning operation is started / executed. Since this cleaning mode is performed during non-image formation, it is executed with the intermediate transfer belt and the photosensitive drum separated from each other, or the intermediate transfer belt and the photosensitive drum are in contact with each other, but toner is applied to the primary transfer member. It is performed by applying a voltage that does not transfer to the belt.

The coating agent applied to the developing roller 8 at the initial stage of using the developing unit 4 is mostly on the surface of the toner supply roller 9 and the inside of the developing unit due to the rotary rubbing between the developing roller 8 and the toner supply roller 9. Will be collected.

Further, since the coating agent of this embodiment has a higher charge than the toner, it is necessary to control (cleaning mode) to discharge the coating agent at a potential setting different from that at the time of normal image formation. That is, the potential difference is opposite to the charging polarity of the coating agent charged by the layer thickness regulating member 10, and the magnitude of the absolute value forms a potential difference larger than the potential difference during the image forming operation. .. Specifically, the toner supply roller 9 is supplied with a toner supply roller bias power supply so that the potential difference between the potential of the toner supply roller 9 and the potential of the development roller 8 is V = + 300V and V = -700V. DC bias is applied. Further, a DC bias is applied to the developing roller 8 from the developing roller bias power supply so that V = −400V. Since tospearl as the coating agent used in this embodiment has higher charging characteristics than the toner in the developing agent storage chamber 4a2, the coating agent is electrostatically supplied to the developing roller 8 having an apparent potential on the positive side. That is, the absolute value of the voltage applied to the toner supply roller is made larger in the cleaning mode than in the image formation. Since the voltage applied to the developing roller is the same during image formation and in the cleaning mode, the coating agent can easily move to the developing roller side in the cleaning mode. By setting the potential based on the electrical characteristics of the coating agent in this way, the coating agent remaining in the toner supply roller 9 can be positively supplied to the developing roller 8.

In this way, the coating agent accumulated in the developing roller 8 moves to the photosensitive drum 2 together with the toner by performing the solid black image forming operation for one round of the developing roller 8 and is removed by the photoconductor cleaning blade 61. .. By periodically performing this work at the time of non-image formation, the amount of the coating agent remaining in the developing chamber 4a1 can be surely reduced. Further, the cleaning mode also serves to supply a lubricant to the photoconductor cleaning blade 61. At this time, the intermediate transfer belt 20 is separated from the photosensitive drum 2, and all the toner that has moved from the developing unit 4 to the photosensitive drum 2 is collected by the photoconductor cleaning blade 61. When the intermediate transfer belt 20 and the photosensitive drum 2 are brought into contact with each other to transfer the toner to the intermediate transfer belt 20, the toner goes around the intermediate transfer belt 20 once and finally returns to the photoconductor cleaning blade 61 to be collected. .. If the toner is transferred to the intermediate transfer belt 20 in this way, the downtime (the time during which the apparatus cannot be used for the image forming operation) becomes longer by one round of the intermediate transfer belt. The drum 2 is not brought into contact with the drum 2. Of course, even if the intermediate transfer belt 20 and the photosensitive drum 2 are brought into contact with each other, a voltage that does not transfer the toner to the belt is applied to the primary transfer roller.

This cleaning mode is performed every time 100 sheets of A4 size recording material P are passed in total.

In this embodiment, since a coating agent having a higher charging characteristic than the toner was used, the potential was set as described above, but the potential is not limited to this, and the coating agent can be efficiently discharged according to the electrical characteristics of the coating agent. It may be the potential setting to be performed.

(6) Problem In the belt cleaning of this embodiment, when the toner is removed by the photoconductor cleaning blade 61a, the fibrous paper dust that should be removed together with the toner is between the photoconductor cleaning blade 61a and the photosensitive drum 2a. It may get in. The entry of paper dust may reduce the cleaning ability of the photoconductor cleaning blade 61a. If the developing roller cleaning mode is performed in this state, the solid black image toner for one round of the developing roller may not be completely removed by the photoconductor cleaning blade 61a. Therefore, there is a problem that cleaning failure occurs.

Table 1 shows the cleaning evaluation results when the developing roller cleaning mode is executed when the solid black image toner for one round of the developing roller is supplied as the amount of toner supplied in the cleaning mode. As the process cartridge used, a paper dust was bitten into the photoconductor cleaning blade 61a by carrying out a paper passing durability test with a recording material P: RED LABEL (OCE, trade name). The cleanability evaluation was carried out in a developing roller cleaning mode in an environment of a temperature of 15 ° C. and a relative humidity of 10%. Immediately after that, the recording material P: GFC-081 (Canon Marketing Japan, trade name) dried by leaving it in the same environment for 48 hours was used to perform the following output. As for the output, a solid black image (maximum density level image), a halftone image, and a thin line image were output three by each in each color of cyan, magenta, yellow, black, red, blue, and green. For the sampled evaluation image, it was judged whether or not an image defect due to a cleaning defect occurred.

As shown in Table 1, when the solid black image toner for one round of the developing roller is moved to the photoconductor and removed by the photoconductor cleaning blade 61 in the cleaning mode, it cannot be completely removed by the photoconductor cleaning blade 61 and has a streak shape. Image defect occurred. The streak image is mainly generated in the process cartridge 1a in which the secondary transfer residual toner and paper dust are most recovered. At this time, the amount of toner developed on the photosensitive drum 2a per unit area was 0.30 mg / cm ² .

As a method of avoiding this cleaning defect, there is a method of suppressing the cleaning defect by lowering the peripheral speed of the developing roller 8 and reducing the amount of toner developed on the photosensitive drum 2 per unit area. This will be described with reference to FIG. The circles at the top of FIGS. 3A, 3B, and 3C represent the rotation of the developing roller 8, and the shaded areas in the circles are the developments developed on the photosensitive drum 2 while rotating. The area of the roller 8 is shown. A short thick line is marked inside the circle so that the state of rotation can be easily understood. The rectangle under the developing roller represents the developing state on the photosensitive drum 2, and the time series advances from left to right. FIG. 3A shows the state of Comparative Example 1, and the numbers in the rectangle indicate the amount of toner per unit area.

3 (b) and 3 (c) are explanatory views of Comparative Examples 2 and 3, FIG. 3 (b) sets the peripheral speed of the developing roller to 154 mm / sec, which is 2/3, and FIG. 3 (c) shows the developing roller. It is a figure when the peripheral speed is set to 115 mm / sec which is 1/2. Since the peripheral speed of the developing roller is lowered, the amount of developing toner per unit area in FIG. 3 (b) is reduced to 0.20 mg / cm ^{2 as} compared with Comparative Example 1, and in FIG. 3 (c), it is 0.15 mg / cm. It has dropped to ^{cm 2.} By reducing the peripheral speed (surface moving speed) of the developing roller in this way, the amount of toner removed by the photoconductor cleaning blade 61 can be reduced per unit area, and cleaning defects can be suppressed.

The cleaning evaluation results when the peripheral speed of the developing roller 8 is 154 mm / sec in Comparative Example 2 of Table 2 and the cleaning evaluation when the peripheral speed of the developing roller 8 is 115 mm / sec in Comparative Example 3 of Table 1 are obtained. The result of was specified. The evaluation method was the same as in Table 1.

In Comparative Example 2, a minute streak image due to poor cleaning was found. Although it is better than Comparative Example 1, cleaning failure has occurred in this evaluation. In Comparative Example 3, the cleaning could not be evaluated. This is because the peripheral speed of the developing roller 8 was lowered too much, so that the peripheral speed difference between the photosensitive drum 2, the toner supply roller 9, and the developing roller 8 widened, and the torque increased, causing the drive motor of the developing roller to step out. It depends on what has been done.

As described above, in Comparative Example 3, the suppression effect is limited due to the torque limitation of the drive motor.

As described above, in the comparative example, it is difficult to develop the toner on the entire circumference of the developing roller and suppress the image defect caused by the coating agent without being limited by the torque and causing the cleaning defect.

(7) Features In order to solve the above problems, in the developing roller cleaning mode, in the developing roller cleaning mode, first, one circumference of the developing roller, which is a developer carrier, is divided into a plurality of regions in the rotational direction, and the developing rollers are divided from the regions. Selects a region to supply toner to the photosensitive drum during one revolution. Then, by rotating the developing roller a plurality of times, toner is supplied to the drum from all the plurality of regions of the developing roller.

The features of the main development roller cleaning mode will be described with reference to FIG. FIG. 4 shows how the developing roller 8 makes two rounds, and the circled numbers in the developing roller 8 indicate each quadrant when the developing roller 8 is divided into four quadrants (four regions). The basic view of the figure is the same as in FIG. 3, but the black-painted part in the rectangle represents the area where the developing roller 8 is developing the solid black image toner on the photosensitive drum 2, and the white-painted part is being developed. Represents no area. The area A is the area of the first lap of the developing roller, and the area B shows the second lap of the developing roller. The developing roller cleaning mode of this embodiment goes around the developing roller 8 twice. In the first lap, solid black image toner is developed in the fourth quadrant (fourth region) and the second quadrant (second region), and in the second lap, the first quadrant (first region) and the third quadrant (third region) are developed. Develop a solid black image toner in 3 areas). The quadrant where the solid black image toner has been developed once corresponds to the shaded area in the round schematic diagram on FIG.

The method of dividing the developing roller into four quadrants and developing the photosensitive drum 2 is performed by adjusting the laser exposure timing by the exposure apparatus 7. In this embodiment, the outer diameter of the developing roller is 12 mm and the peripheral speed is 230 mm / s. Therefore, in order to divide the peripheral length into four parts for exposure, the laser beam is emitted every 41 ms during the orbit. The division development to the drum 2 is carried out.

When the developing roller cleaning mode of this embodiment is carried out, the solid black image toner for one round of the developing roller is developed while the developing roller 8 makes two rounds, so that the coating agent on the developing roller can be reliably removed. Is. Further, since the amount of toner per unit area developed on the photosensitive drum 2 is reduced, the load on the photosensitive member cleaning blade 61a can be reduced.

Table 3 shows the evaluation results of the comparative examples and this example so far. The evaluation method was the same as the method in Table 1.

As shown in Table 3, cleaning defects can be suppressed by carrying out the developing roller cleaning mode of this embodiment. Since the peripheral speeds of the developing roller 8 and the photosensitive drum 2 are not changed, the driving torque is not limited.

Since this control does not change the peripheral speed of the developing roller 8, the amount of developing toner per unit area is strictly the same as that of Comparative Example 1 when only the black-painted portion in FIG. 4 is considered. Locally, the following can be considered as a mechanism in which cleaning failure does not occur even with the same amount of toner as in Comparative Example 1. The toner removing mechanism of the cleaning blade 61 is said to dampen and remove the toner by the presence of lumps of fine particles externally attached to the toner on the cleaning blade 61. The lumps of particles that are damming the toner are destroyed when the toner exceeds the permissible amount, and the toner slips through the cleaning blade 61, resulting in poor cleaning. On the other hand, in the case of toner that does not exceed the allowable amount, the toner is blocked by a mass of particles, and the toner is removed from the photosensitive drum 2 by the streamlines and gravity of the toner generated in the vicinity of the blade. In Comparative Example 1, before the toner is removed from the photosensitive drum 2, the toner is pushed one after another and the particle agglomerates are destroyed. In this embodiment, even if a large amount of toner comes to the blade part momentarily, it is removed from the photosensitive drum 2 while the toner is not developed, so that cleaning is possible even if the next toner group comes to the blade. Become. Even if the local amount of toner is the same as that of Comparative Example 1, it is considered that cleaning failure does not occur because it is intermittent.

As described above, by performing the developing roller cleaning mode in which the surface for one rotation of the developing roller is divided and the toner for one rotation of the developing roller is developed while making a plurality of turns, cleaning defects do not occur.

Since the secondary transfer residual toner, paper dust, and filler may be collected by a device other than the process cartridge 1a after the image formation is completed, the developing roller cleaning sequence shown in this embodiment is not limited to the process cartridge 1a.

Further, in addition to the same belt cleaning configuration as in this embodiment, there is an image forming apparatus in which the belt cleaning blade is installed upstream of the belt cleaning mechanism 30. In this case, most of the secondary transfer residual toner and paper dust are removed by the belt cleaning blade, and the belt cleaning mechanism 30 plays an auxiliary role. In this configuration, most of the secondary transfer residual toner is removed by the belt cleaning blade, so that the paper dust is hardly collected by the photosensitive drum 2. Therefore, due to the belt cleaning mechanism 30, even if the developing toner for one round of continuous developing rollers is supplied to the photosensitive drum, it does not lead to poor cleaning. Even with a belt cleaning blade with poor recoverability, 70% or more of the secondary transfer residual toner is recovered. Therefore, it is premised that 50% or more of the secondary transfer residual toner is recovered by the photoconductor unit 6 with respect to the total amount of the secondary transfer residual toner.

[Example 2]
In the second embodiment, a case where the cleaning property of the photoconductor cleaning blade 61 is further lowered will be described.

When the secondary transfer residual toner and paper dust are collected on the photosensitive drum 2a, the paper filler (calcium carbonate) is also collected at the same time. If a large amount of the filler is collected on the photosensitive drum 2a, the filler may stick to the surface layer of the photosensitive drum 2a, and the friction coefficient between the photosensitive drum 2a and the cleaning blade 61a may increase. Along with this, the drive torque of the photosensitive drum 2a increases, and the drive motor of the photosensitive drum 2a is out of step. Therefore, the set angles of the photosensitive drum 2 and the cleaning blade 61 are adjusted in order to reduce the driving torque. FIG. 5 shows an explanatory diagram of the set angles of the photosensitive drum 2 and the cleaning blade 61. The angle α between the tangent of the photosensitive drum 2 and the cleaning blade 61 and the cleaning blade 61 was set as the set angle, which was 25 ° in Example 1 and 22 ° in Example 2. As a result, the vertical effect of the photosensitive drum 2 given by the cleaning blade 61 is reduced, so that the driving torque of the photosensitive drum 2 is reduced. However, as the vertical effectiveness decreases, the toner cleaning ability decreases, and in the developing roller cleaning sequence, the method of Example 1 causes cleaning defects. The results are shown in Table 4. The cleaning evaluation method is the same as in Example 1.

On the other hand, in this embodiment, the developing roller is divided into six parts, and the toner for one round of the developing roller is developed on the photosensitive drum while making three rounds in the developing roller cleaning mode. A diagram showing the situation is specified in FIG. The view of the figure is the same as that of FIG. 4, and the area A shows the area of the first lap of the developing roller, the area B shows the area of the second lap of the developing roller, and the area C shows the third lap of the developing roller. In the first lap of the developing roller, the regions 3 and 6 indicated by the circled numbers are developed, and in the second lap, the regions 2 and 5, and in the third lap, the regions 1 and 4 are developed, respectively.

The evaluation results of cleanability in this example are specified in Table 5 together with the results in Table 4.

As shown in Table 5, cleaning defects can be suppressed by carrying out the developing roller cleaning mode of this embodiment. Since the drive torque is not limited, the number of laps and the number of divisions can be changed according to the cleaning ability of the image forming apparatus, and the developing roller cleaning mode can be executed without being limited by the motor.

In this embodiment, the developing roller 8 is divided into integers, but the area ratio of the divided areas is not limited. Further, since it is sufficient that the developing roller is rotated a plurality of times in the developing roller cleaning mode and the toner for one round of the developing roller is finally developed on the photosensitive drum, for example, the toner is developed in the first and second rounds. The case where the areas to be processed overlap is also the scope of reference in this patent.

Needless to say, by combining not only the operation of the developing roller cleaning mode of this embodiment but also the operation of lowering the peripheral speed of the developing roller and the photosensitive drum, the amount of toner per unit area is reduced and the cleaning ability is further improved.

In this embodiment, the number of rotations of the developing roller in the developing roller cleaning mode is preferably 2 to 4 rotations. Further, it is preferable that the region divided into a plurality of regions is 2 to 8 regions.

Further, in this embodiment, the angle α between the tangent of the photosensitive drum 2 and the cleaning blade 61 and the cleaning blade 61 is preferably 20 ° to 30 °.

1 Process cartridge 2 Photosensitive drum 4 Development unit 6 Photoreceptor unit 8 Development roller 10 Layer thickness control member 20 Intermediate transfer belt 30 Belt cleaning mechanism 31 Conductive brush 32 Charging roller 61 Photoreceptor cleaning blade

Claims (12)

An image forming apparatus capable of executing an image forming mode for forming an image on a recording material.
Times and the rolling possible image bearing member,
A rotatable developer carrier that carries a developer and develops an electrostatic latent image formed on the surface of the image carrier by the developer charged to a normal polarity into a developer image.
A developer supply member that supplies the developer to the surface of the developer carrier, and
A regulatory member that regulates the amount of the developer supported on the surface of the developer carrier, and
A cleaning member that removes the developer from the surface of the image carrier, and
An intermediate transfer body to which the developer image formed on the surface of the image carrier is transferred, and
A transfer member that forms a transfer portion in contact with the intermediate transfer body and transfers the developer image from the intermediate transfer body to the recording material at the transfer portion.
A developer charging member that charges the developer remaining in the intermediate transfer body with a polarity opposite to the normal polarity after the developer image formed on the intermediate transfer body passes through the transfer unit.
A developing voltage application unit that applies a developing voltage to the developer carrier,
A supply voltage application unit that applies a supply voltage to the developer supply member,
A regulated voltage applying portion that applies a regulated voltage to the regulating member,
It has a control unit that controls the development voltage application unit, the supply voltage application unit, and the regulation voltage application unit.
In the picture image formation mode, removing the developer charged to the opposite polarity from said image bearing member by said cleaning member is moved to said image bearing member from said intermediate transfer member,
In the non-image forming mode without executing the image forming mode, cleaning said from the developer carrying member to said image bearing member a developer supplying, removing the developer supplied to the image bearing member by said cleaning member An image forming device capable of executing a mode
The developer carrier is coated on the surface when the coating agent charged to the normal polarity is not used, the coating agent has the same charging polarity as the developing agent, and the average charge amount is higher than that of the developing agent. Is big,
Before SL control unit supplies the developer to the image bearing member, in the supplying the coating agent to the image carrier cleaning mode,
When the region for one round of the developer carrier in the rotation direction of the developer carrier is divided into a plurality of regions in the rotation direction, one of the plurality of regions is used during one rotation of the developer carrier. The developer and the coating agent are supplied from the unit to the image carrier, and the image carrier is rotated from a region other than a part of the plurality of regions while the developer carrier is rotated a plurality of times after the one rotation. Controlled to supply the developer and the coating agent to
The first voltage difference between the supply voltage and the development voltage is larger than the second voltage difference between the development voltage and the regulation voltage, and the absolute value of the supply voltage and the absolute value of the regulation voltage , Is controlled so as to be larger than the absolute value of the development voltage . The image forming apparatus according to claim 1, wherein the plurality of regions are 2 to 8 regions. The image forming apparatus according to claim 1 or 2, wherein the plurality of rotations is 2 to 4 rotations. Wherein the control unit, characterized that you control the developing voltage and the same size as composed as the developing voltage applying unit that the developing voltage applied have you to the cleaning mode is applied have you to the image forming mode The image forming apparatus according to any one of claims 1 to 3. Wherein the control unit, the supply voltage applied have you to the cleaning mode, the said supply voltage and polarity applied in the image formation mode is the same, and the absolute value of the supply voltage, the image forming mode the image forming apparatus according to claim 1, any one of 4, wherein the controller controls the supply voltage applied portion on the size Kunar so than the absolute value of the supply voltage at. The image forming apparatus according to any one of claims 1 to 5, wherein the developer charging member includes a brush-shaped first charging member and a roller-shaped second charging member. The image forming apparatus according to any one of claims 1 to 6, wherein the control unit can be controlled to perform cleaning of the developer charging member. A developing device having the developer carrier and
A photoconductor unit having the image carrier and the cleaning member is provided.
The image forming apparatus according to any one of claims 1 to 7, wherein the developing apparatus is removable from the image forming apparatus. A process cartridge having the image carrier, the cleaning member, and the developer carrier is provided.
The image forming apparatus according to any one of claims 1 to 7, wherein the process cartridge is detachable from the image forming apparatus. In the image forming mode, the amount of the developer moving from the intermediate transfer body to the image carrier is 50% or more of the amount of the developer remaining in the intermediate transfer body after passing through the transfer unit. The image forming apparatus according to any one of claims 1 to 9 . Any of claims 1 to 10, wherein the control unit controls the regulation voltage application unit so that the regulation voltage applied in the cleaning mode becomes the same magnitude as the regulation voltage applied in the image formation mode. The image forming apparatus according to item 1 . When the average charge amount of the developer is C1, the average charge amount of the coating agent is C2, the first voltage difference in the image forming mode is V1, and the first voltage difference in the cleaning mode is V2. The image forming apparatus according to any one of claims 1 to 11, wherein the control unit controls so that V2 / V1 is larger than C2 / C1 .

Images