JP2018189899A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that reduces movement of a carrier from a developing unit to an image holding body caused by an increase in electrification potential of the image carrier due to cleaning of the transfer unit.SOLUTION: An image forming apparatus comprises: an electrifier 11 that electrifies an image holding body 10: a transfer unit 14 that transfers a toner image on the image holding body 10 onto a sheet; a cleaning unit 15 that removes toner remaining on the image holding body 10; a control part 51 that applies a transfer bias to the transfer unit 14 to cause the transfer unit to transfer the toner image on the image holding body 10 onto the sheet, and applies a cleaning bias including a reverse transfer bias having a polarity opposite to that of the transfer bias to the transfer unit 14 in a transfer unit cleaning period T in a period during which the sheet is not present to move toner attached to the transfer unit 14 to the image holding body 10; and carrier movement prevention means that prevents movement of the carrier from a developing unit 13 to the image holding body 10 in the transfer unit cleaning period T without including static eliminating means that eliminates static electricity on the image holding body 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses a technique for cleaning a transfer device by applying a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer device, and transferring toner adhered to the transfer device to an image holding member. Has been.

JP 2002-207373 A

  If the image carrier is not equipped with a neutralization unit that neutralizes the image carrier until the portion opposite the transfer unit is charged next, the charge potential of the image carrier rises due to the application of the reverse transfer bias. Then, the next charging is performed.

  An object of the present invention is to provide an image forming apparatus in which the movement of the carrier from the developing device to the image holding member due to the increase in the charging potential of the image holding member due to the cleaning of the transfer device is suppressed.

Claim 1
An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
From the developing unit during the transfer unit cleaning period without providing a neutralizing unit for neutralizing the image holding unit after the image holding unit passes through a portion facing the transfer unit and is charged next. An image forming apparatus comprising: carrier movement suppressing means for suppressing carrier movement to the image holding member.

Claim 2
An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
A charging bias controller that applies the charging bias to the charger to charge the image carrier and applies a low charging bias lower than the charging bias to the charger during the cleaning period of the transfer device; An image forming apparatus including the image forming apparatus.

Claim 3
An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
An exposure device that irradiates the image carrier with exposure light carrying image information to form an electrostatic latent image on the image carrier;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
The exposure device is controlled to irradiate the exposure light onto the image carrier to form an electrostatic latent image on the image carrier and to charge the image carrier during the transfer device cleaning period. An image forming apparatus comprising: an exposure control unit configured to irradiate the image holding member with charging potential adjusting light for lowering a potential.

Claim 4
An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A developing unit that receives a developing bias and develops the electrostatic latent image on the image holding member with toner in the developer;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
The developing bias is applied to the developing unit to develop the electrostatic latent image on the image carrier with toner in the developer, and the developing unit is subjected to the developing unit during the cleaning period of the transfer unit. An image forming apparatus comprising: a developing bias control unit that applies a carrier movement suppression bias that suppresses carrier movement from the developing unit to the image holding member to the developing unit.

  According to a fifth aspect of the present invention, the transfer bias control unit applies a static elimination bias having the same polarity as the transfer bias and neutralizing the image carrier after the transfer unit cleaning period. The image forming apparatus according to any one of the above.

  6. The image according to any one of claims 1 to 5, wherein the charger is a plurality of charging rolls provided along a rotation direction of the image carrier. Forming device.

  Here, in the present invention, the level of the bias or the potential means the level of the absolute value of the bias or the potential.

  According to the image forming apparatus of the first aspect, the movement of the carrier from the developing unit to the image holding member during the cleaning period of the transfer unit is suppressed without providing the neutralizing unit.

  According to the image forming apparatus of the second aspect, the movement of the carrier from the developing unit to the image carrier during the transfer unit cleaning period is suppressed by controlling the charging bias.

  According to the image forming apparatus of the third aspect, the movement of the carrier from the developing unit to the image holding member during the transfer unit cleaning period is suppressed by controlling the exposure.

  According to the image forming apparatus of the fourth aspect, the movement of the carrier from the developing unit to the image holding member during the cleaning period of the transfer unit is suppressed by controlling the developing bias.

  According to the image forming apparatus of the fifth aspect, after the end of the transfer unit cleaning period, special control for suppressing the movement of the carrier from the developing unit to the image carrier that is performed during the transfer unit cleaning period is unnecessary. Become.

  According to the image forming apparatus of the present invention, the movement of the carrier from the developing device to the image carrier is suppressed even in the case of claim 6 in which the amount of increase in the charged potential is likely to be larger than when there is a single charging roll. .

1 is a schematic configuration diagram of a printer which is an embodiment of an image forming apparatus of the present invention. FIG. 2 is an enlarged view showing a structure around an image carrier of the printer shown in FIG. 1. It is explanatory drawing of a transfer device cleaning sequence (A) and the operation | movement (B) of a control part and power supply part accompanying it.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic configuration diagram of a printer which is an embodiment of the image forming apparatus of the present invention.

  FIG. 2 is an enlarged view showing the structure around the image carrier of the printer shown in FIG.

  A printer 1 shown in FIG. 1 is a printer that prints an image on paper P by an electrophotographic method, and the left side surface in FIG. 1 is the front surface of the apparatus.

  The printer 1 is provided with an image carrier 10. The image carrier 10 holds an electrostatic latent image formed through charging and exposure processes while rotating in the direction of arrow A, and further formed through a development process using toner in a developer containing toner and carrier. The toner image is held.

  Further, in the present embodiment, the charger 11 receives a negative (−) potential charging bias to charge the surface of the image carrier 10 to a negative (−) potential. In this charging, the surface of the image carrier 10 is charged aiming at a predetermined charging target potential. The charger 11 according to the present embodiment includes two charging rolls 11 a and 11 b provided along the rotation direction of the image carrier 10. These two charging rolls 11a and 11b are connected to one common power source, and the same charging bias is applied to both of these two charging rolls 11a and 11b. The reason why the two charging rolls 11a and 11b are provided in the present embodiment is to increase the charging ability, and thereby, a high process speed (a high rotation speed of the image carrier 10, that is, a sheet P described later). Even at a high conveyance speed, the surface of the image carrier 10 can be charged to the charging target potential.

  Further, the exposure device 12 irradiates the image carrier 10 with exposure light carrying image information to form an electrostatic latent image on the surface of the image carrier 10. The exposure device 12 of the present embodiment is composed of a number of LED light sources arranged in the main scanning direction (direction perpendicular to the paper surface of FIGS. 1 and 2).

  Further, the developer 13 contains a developer (not shown) containing a carrier and toner. The developer in the developing device 13 is transported to the developing position facing the image carrier 10 by the developing roll 131. A developing bias is applied to the developing roller 131, and the electrostatic latent image on the image carrier 10 is developed by the toner in the developer by the action of the developing bias, and the toner on the image carrier 10 is developed. An image is formed.

  The printer 1 includes a detachable toner cartridge 19 in which replenishment toner is accommodated. When the toner in the developing device 13 decreases, toner corresponding to the decrease is supplied from the toner cartridge 19 to the developing device 13.

  Further, a transfer bias is applied to the transfer device 14. The transfer unit 14 receives a transfer bias and transfers the toner image formed on the image carrier 10 onto the paper P that has been conveyed as described later.

  The toner image transferred onto the paper P is fixed on the paper P by being heated and pressurized by the fixing device 20.

  The cleaning device 15 scrapes off the residual toner after transfer on the image carrier 10 from the image carrier 10 and stores it in the waste toner tank 18.

  In the printer 1, in order to reduce costs, an intermediate path from the rotation of the image carrier 10 to the opposing portion of the image carrier 10 to the transfer device 14 is opposed to the charger 11 by the rotation of the image carrier 10. There is no neutralization means such as a neutralization lamp for neutralizing the image carrier 10 above.

  A paper cartridge 30 is attached to the lower part of the printer 1 so that it can be pulled out to the left in FIG. In the paper cartridge 30, a plurality of sheets P before printing are stored in a stacked state. In printing, the uppermost stacked paper P among the papers P accommodated in the paper cartridge 30 is taken out by the take-out roll 41, and a plurality of papers P are taken out while being overlapped. Even so, the sheet is reliably separated into only one sheet by the separating roll 42 and conveyed on the conveyance path d1 to reach the registration roll 43. The registration roll 43 plays a role of correcting the posture of the conveyed sheet and adjusting the subsequent conveyance timing to send the sheet further downstream. From the registration roll 43, the paper P is sent out in time with the transfer timing of the toner image on the image carrier 10, and the toner image on the image carrier 10 is transferred onto the paper P. The sheet P that has received the transfer of the toner image is further transported on the transport path d2 and passed through the fixing device 20 to receive the toner image, and is ejected by a paper ejection roll 44 on the upper portion of the printer 1. It is discharged onto the table 17.

  When printing on both sides of the paper, the paper P printed on one side in the same manner as described above is sent out halfway by the paper discharge roll 44, and then the paper discharge roll 44 rotates in the reverse direction. It is conveyed on d3 and reaches the registration roll 43 again. After that, the above printing operation is repeated again, and the paper printed on both sides is discharged onto the paper discharge tray 17 by the paper discharge roll 44.

  Further, the printer 1 includes a control unit 51 and a power supply unit 52. The control unit 51 controls the entire printing operation of the printer 1 and the power source unit 52. The power supply unit 52 is responsible for power supply of the entire printer 1 including the charging bias of the charger 11, the developing bias of the developing roll 131, the transfer bias of the transfer device 14, and the like under the control of the control unit 51. .

  FIG. 3 is an explanatory diagram of the transfer device cleaning sequence (A) and the operation (B) of the control unit and the power supply unit associated therewith. In the following description, unless otherwise specified, the level of the bias and the potential is described as the level of the absolute value of the bias and the potential.

  Toner spilled from both sides of the transferred paper P or toner attached to the image holding body 10 when the paper P is not present between the image holding body 10 and the like adheres to the transfer device 14. 14 may become dirty. Therefore, in this embodiment, in order to remove the contamination of the transfer unit 14, the transfer unit cleaning is performed in a period in which the sheet P is not conveyed, that is, in a period in which the sheet P does not exist between the transfer unit 14 and the image carrier 10. In the period T, the transfer device cleaning sequence is executed. In this transfer unit cleaning sequence, a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias applied to the transfer unit 14 when the toner image on the image carrier 10 is transferred onto the paper P is transferred to the transfer unit 14. Apply. Then, dirt such as toner adhering to the transfer device 14 is transferred to the image holding member. The dirt such as toner transferred to the image carrier 10 is scraped off from the image carrier 10 by the cleaner 15 and is stored in the waste toner tank 18.

  The horizontal axis in FIG. 3A represents the time axis t, and the vertical axis represents the bias applied to the transfer unit 14.

  When the toner image on the image carrier 10 is transferred onto the paper P, a plus (+) transfer bias is applied to the transfer unit 14. This plus (+) transfer bias acts to draw the toner image on the image carrier 10 toward the transfer unit 14. At the time of transfer, since the paper P exists between the image carrier 10 and the transfer device 14, the toner image on the image carrier 10 is attracted to the transfer device 14 and transferred onto the paper P. On the other hand, in the transfer unit cleaning sequence, a cleaning bias including a negative (−) reverse transfer bias having a reverse polarity to the transfer bias is applied. As shown in FIG. 3A, the cleaning bias in the present embodiment is a bias that alternately repeats a negative (−) reverse transfer bias and a positive (+) bias that is the same as the transfer bias. The duration of one reverse transfer bias or one plus (+) bias is set to a time equal to or less than one round of the image carrier 10.

  When a negative (−) reverse transfer bias is applied to the transfer device 14, the toner or the like adhering to the transfer device 14 moves to the image carrier 10. However, some toners on the transfer unit 14 are charged with opposite polarity. The reverse polarity toner or the like is transferred to the image carrier 10 by applying a plus (+) bias to the transfer unit 14. In this embodiment, the transfer device cleaning sequence in which the cleaning bias is continuously applied as shown in FIG. 3A is executed over the transfer device cleaning period T shown in FIG.

  Here, in a normal transfer process, a plus (+) transfer bias is applied to the transfer device 14. Since the surface of the image carrier 10 is negatively charged (−), the potential of the surface of the image carrier 10 is neutralized to some extent by this plus (+) transfer bias, and then the normal charging is performed again by the charger 11. Charged to potential.

  However, when the transfer device cleaning sequence as shown in FIG. 3 is executed, there is a period during which a negative (−) reverse transfer bias is applied, and the image carrier 10 is not neutralized during that period. When the image carrier 10 that has not been neutralized and remains charged on the minus (−) side is charged again by the charger 14, the image carrier 10 has an allowable range on the minus (−) side. Beyond this, there is a risk of being strongly charged. In particular, in the case of this embodiment, the charging ability is improved by configuring the charger 14 with two charging rolls 131 so as to correspond to a high process speed. There is a strong fear. If the charge of the image carrier 10 is too strong, there arises a problem that the carrier in the developer conveyed to the development position by the developing roller 131 moves to the image carrier 10. Therefore, in the present embodiment, the following measures are taken.

  First, as shown in FIG. 3A, when the transfer device cleaning period T ends, a neutralization bias Vre having the same polarity as the plus (+) transfer bias is applied to the transfer device 14. The image carrier 10 is neutralized by a neutralizing current that flows by applying the neutralizing bias Vre.

  In this manner, the transfer bias, the cleaning bias including the reverse transfer bias, and the charge eliminating bias are applied to the transfer device 14. The application of the bias to the transfer unit 14 is executed by the power supply unit 52 under the control unit 51 shown in FIG. The controller 51 corresponds to an example of a transfer bias controller according to the present invention.

  However, the neutralization bias is applied to the transfer unit 14 as a countermeasure after the end of the transfer unit cleaning period T. For the transfer device cleaning period T, one or more of the measures described below with reference to FIG.

  (B1) of FIG. 3B shows a bias control sequence of the charger 11. FIG. Also, (b2) and (b3) in FIG. 3B show an exposure control sequence in the exposure unit 12 and a bias control sequence in the developing unit 13, respectively. Here, the time T <b> 1 is a time required for the portion of the image carrier 10 facing the transfer device 14 to move to a position facing the charger 11 due to the rotation of the image carrier 10. The time T2 is a time required for the portion of the image carrier 10 facing the transfer unit 14 to move to a position facing the exposure unit 12 by the rotation of the image carrier 10. Further, the time T3 is a time required for the portion of the image carrier 10 facing the transfer device 14 to move to a position facing the developing roller 131 by the rotation of the image carrier 10. For the charger 11, the exposure device 12, and the developing device 13, the influence of the transfer device cleaning sequence in the transfer device 14 appears with a delay of time T1, time T2, and time T3, respectively. Here, the period in which the influence of the transfer unit cleaning sequence on the charger 11, the exposure unit 12, and the developing unit 13 is referred to as the transfer unit cleaning period T.

  As shown in FIG. 3B, (b1), in the normal image forming process, for example, a charging bias of −1000 V is applied to the charger 11 to charge the image carrier 10, whereas the transfer device cleaning is performed. During the period T, as shown in (b1) of FIG. 3B, a low charging bias of −970 V, for example, lower than the charging bias (−1000 V) is applied. As a result, the charged potential of the image carrier 10 within the transfer device cleaning period T is suppressed within an allowable range, and the movement of the carrier from the developing roller 131 to the image carrier 10 is suppressed. The application of the bias to the charger 11 is performed by the power supply unit 52 under the control of the control unit 51. That is, the control unit 51 in the present embodiment corresponds to an example of the charging bias control unit referred to in the present invention.

  Further, the exposure device 12 forms an electrostatic latent image on the image carrier 10 by irradiating the image carrier 10 with exposure light carrying image information in a normal image forming process. On the other hand, during the transfer device cleaning period T, the exposure device 12 reduces the charging potential of the image carrier 10 under the control of the control unit 51 as shown in (b2) of FIG. Is applied to the image carrier 10. As a result, even if the image carrier 10 within the transfer device cleaning period T is charged by the charger 11 to a charged potential that exceeds the allowable range, the image holding member 10 is irradiated with the potential adjustment light and falls within the allowable range. From the carrier to the image carrier 10 is suppressed.

  In addition, a predetermined developing bias is applied to the developing roll 131 in a normal image forming process. This development bias is such that when the charge of the image carrier 10 is within an allowable range and an electrostatic latent image is formed thereon, the toner in the developer on the developing roller 131 is transferred to the image carrier 10 to be static. The bias is adjusted to a level at which the electrostatic latent image is developed and the carrier does not move to the image carrier 10. Here, during the transfer device cleaning period T, image formation is not performed, and there is no need to consider normal development with toner. Therefore, during the transfer device cleaning period T, the developing roller 131 is charged by the power supply unit 52 under the control of the control unit 51 even when the image carrier 10 is charged to a potential exceeding the allowable range. A carrier movement suppression bias having a voltage for suppressing the carrier from moving to the image carrier 10 is applied. This action of the control unit 51 corresponds to an example of the developing bias control unit referred to in the present invention.

  Here, as a means for suppressing the movement of the carrier from the developing roller 131 to the image carrier 10 within the transfer device cleaning period T, a low charging bias is applied to the charger 11 ((b1 in FIG. 3B)). )), Irradiation of charging potential adjusting light to the image carrier 10 by the exposure device 12 ((b2) in FIG. 3B), and application of a carrier movement suppression bias to the developing roll 131 (FIG. 3B). The three types of means (b3)) have been described, but only one of these means may be executed, or two or three means may be combined and executed. Regardless of which of these three means is executed, the movement of the carrier from the developing roller 131 to the image carrier 10 within the transfer device cleaning period T is suppressed.

DESCRIPTION OF SYMBOLS 1 Printer 10 Image holding body 11 Charging device 11a, 11b Charging roll 12 Exposure device 13 Developing device 131 Developing device 14 Developing device 14 Transfer device 15 Cleaning device 17 Discharge stand 18 Waste toner tank 19 Toner cartridge 20 Fixing device 30 Paper cartridge 41 Take-out roll 42 Separating roll 43 Registration roll 44 Paper discharge roll 51 Control section 52 Power supply section

Claims (6)

An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
From the developing device during the cleaning period of the transfer device, without providing a discharging means for discharging the image holding member until the image holding member passes through a portion facing the transfer device and is next charged. An image forming apparatus comprising: carrier movement suppressing means for suppressing carrier movement to the image holding member. An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
A charging bias controller that applies the charging bias to the charger to charge the image carrier and applies a low charging bias lower than the charging bias to the charger during the cleaning period of the transfer device; An image forming apparatus comprising the image forming apparatus. An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
An exposure device that irradiates the image carrier with exposure light carrying image information to form an electrostatic latent image on the image carrier;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
The exposure device is controlled to irradiate the exposure light onto the image carrier to form an electrostatic latent image on the image carrier and to charge the image carrier during the transfer device cleaning period. An image forming apparatus comprising: an exposure control unit configured to irradiate the image holding member with charged potential adjusting light for lowering a potential. An image carrier that holds an electrostatic latent image formed through charging and exposure processes while rotating, and further holds a toner image formed through a development process using toner in a developer containing toner and carrier. When,
A charger for charging the image carrier by receiving a charging bias;
A developing unit that receives a developing bias and develops the electrostatic latent image on the image holding member with toner in the developer;
A transfer unit that receives a transfer bias and transfers the toner image on the image carrier onto the conveyed paper;
A cleaner for removing residual toner after transfer on the image carrier from the image carrier;
The transfer bias is applied to the transfer device to transfer the toner image on the image carrier onto the paper, and in the transfer device cleaning period when there is no paper between the transfer device and the image carrier. A transfer bias control unit that applies a cleaning bias including a reverse transfer bias having a reverse polarity to the transfer bias to the transfer unit, and moves the toner attached to the transfer unit to the image holding member to be cleaned by the cleaning unit;
The developing bias is applied to the developing unit to develop the electrostatic latent image on the image holding member with toner in the developer, and the developing unit removes the developing bias from the developing unit during the cleaning period of the transfer unit. An image forming apparatus comprising: a developing bias control unit that applies a carrier movement suppression bias that suppresses carrier movement to the image carrier to the developing device.   5. The charge transfer controller according to claim 1, wherein the transfer bias controller applies a discharge bias having the same polarity as the transfer bias and discharging the image carrier after the cleaning period of the transfer device. The image forming apparatus described in the item.   The image forming apparatus according to claim 1, wherein the charger is a plurality of charging rolls provided along a rotation direction of the image carrier.

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