JP2010091754A - Transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device which allows an increase in the manufacturing cost thereof to be suppressed and is made compact by collecting toner sticking to an image carrier after conveying the toner to an endless belt. <P>SOLUTION: An intermediate transfer belt unit 6 and a secondary transfer unit 200 include the intermediate transfer belt 61, the secondary transfer belt 201, a transfer roller 10, an adsorption roller 205, an intermediate transfer belt cleaning unit 65, power switches 50 to 52 and a control part 60. The adsorption roller 205 is configured to collect the toner from the secondary transfer belt 201 in a non-contact position with a paper. The power switch 50 is configured to form a first electric field to make the toner go from intermediate transfer belt 61 to the second transfer belt 201, or a second electric field with polarity inverse to that of the first electric field. The power switch 51, 52 are configured to form a third electric field to make the toner go from the secondary transfer belt 201 to the adsorption roller 205, and a fourth electric field with polarity inverse to that of the third electric field. The control part 60 is configured to switch the first electric field and the third electric field during the transfer processing, and after the transfer processing, switch the first electric field to the second electric field, and also, switch the third electric field to the fourth electric field. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile. In particular, the present invention relates to a transfer device of an image forming apparatus provided with an intermediate transfer belt.

  With the colorization of office documents, electrophotographic color image forming apparatuses capable of forming color images, such as color copying machines and color printers, are becoming mainstream. For example, the color image forming apparatus forms toner images by image forming units of four colors, for example, yellow, magenta, cyan, and black, and superimposes the toner images on a sheet to perform transfer processing to form a toner image on the sheet.

  In recent years, image forming apparatuses that employ borderless printing are also increasing. In borderless printing, the transfer process is performed using a toner image having a width wider than the paper width, so that the toner protruding from the paper adheres to the secondary transfer belt. The toner adhering to the secondary transfer belt adheres to the sheet to be transferred next, adheres to the back surface of the sheet, and causes dirt.

In some of such transfer devices, as the secondary transfer process ends, the secondary transfer roller is separated from the intermediate transfer member, and the cleaning unit is also separated from the secondary transfer roller (for example, patents). Reference 1).
JP 2008-40129 A

  However, in the transfer processing apparatus disclosed in Patent Document 1, it is necessary to provide a blade that collects toner from the peripheral surface of the transfer roller and a toner collection container (housing) that collects toner scraped off by the blade. Further, it is necessary to provide a mechanism for separating the secondary transfer roller from the intermediate transfer member, which is a problem in reducing the size of the apparatus.

  Accordingly, the present invention provides a transfer apparatus that can reduce the size of the apparatus while suppressing an increase in manufacturing cost by transporting the toner adhering to the image carrier to an endless belt and then collecting the toner. With the goal.

  The transfer device of the present invention includes an image carrier, an endless belt, a pressure contact member, a recovery member, a cleaning unit, a first power source unit, a second power source unit, and a control unit. The image carrier carries a toner image and rotates in a predetermined direction. The endless belt is looped around a plurality of rollers in a transfer region close to the image carrier, moves in the circumferential direction of the image carrier, and abuts on the paper in a predetermined paper contact range including the transfer region. The pressure contact member presses the endless belt to the image carrier with the sheet sandwiched in the transfer region. The collection member contacts the outer peripheral surface of the endless belt outside the sheet contact range. The cleaning unit collects the toner attached to the image carrier. The first power supply means forms a first electric field for directing the toner from the image carrier to the endless belt or a second electric field for directing the toner from the endless belt to the image carrier. The second power supply unit forms a third electric field for directing the toner from the endless belt to the collecting member or a fourth electric field for directing the toner from the collecting member to the endless belt. A control part switches the polarity of the voltage of a 1st power supply means and a 2nd power supply means. The controller causes the first power supply means to form a first electric field and the second power supply means to form a third electric field when the toner image is transferred from the image carrier to the paper, and after the paper has passed through the transfer region, A second electric field is formed in one power supply means, and a fourth electric field is formed in the second power supply means.

  In this configuration, when the toner image is transferred to the paper, a first electric field is formed to direct the toner from the image carrier to the endless belt, and a third electric field is formed from the endless belt to the recovery member. For this reason, the toner adhering to the endless belt in the transfer region can be collected by the collecting member.

  On the other hand, after the sheet passes through the transfer region, a second electric field is formed to direct the toner from the endless belt to the image carrier, and a fourth electric field is formed from the collection member to the endless belt. For this reason, the toner attached to the image carrier can be collected by the cleaning means for collecting the toner attached to the image carrier.

  According to the present invention, the toner adhering to the endless belt can be collected only by the cleaning unit that wipes off the toner adhering to the image carrier. For this reason, it is not necessary to provide a cleaning unit around the endless belt, and space saving can be achieved while suppressing an increase in manufacturing cost.

  An image forming apparatus 100 according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically illustrating the overall configuration of the image forming apparatus 100.

  The image forming apparatus 100 is a multifunction machine that mainly includes an image forming unit 110 and an automatic document feeder 120 and performs multicolor and single color printing processing on the paper P in accordance with image data.

  The automatic document feeder 120 has a reading unit 90 disposed above the image forming unit 110, and reads a document image while automatically conveying the document.

  The reading unit 90 has a document table 92 made of transparent glass on the upper surface, and reads a document when sequentially conveyed documents pass through a reading area Z of the document table 92.

  The image forming unit 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit (transfer device) 6, a fixing unit 7, a paper feed cassette 81, and a paper discharge tray 91. The control unit 60 is included. The image forming unit 110 performs a printing process on the paper P.

  The developing device 2, the photosensitive drum 3, the charger 5, and the cleaner unit 4 are arranged in four image stations corresponding to color images of black (K), cyan (C), magenta (M), and yellow (Y). Each is arranged. Each station forms four types of latent images corresponding to each color.

  The cleaner unit 4 collects and discharges the toner remaining on the circumferential surface of the photosensitive drum 3.

  The charger 5 is a charger-type charger that uniformly charges the surface of the photosensitive drum 3 to a predetermined potential.

  The exposure unit 1 is a laser scanning unit (LSU) provided with a laser emitting portion, a reflection mirror, and the like. The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toner of four colors (YMCK).

  The intermediate transfer belt unit 6 is disposed above the photosensitive drum 3 and has an intermediate transfer belt (image carrier) 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt. A cleaning unit 65 and a driving roller 66 are provided. Four intermediate transfer rollers 64 are provided corresponding to each color for YMCK. A positive polarity transfer bias of about several hundred volts is applied to the intermediate transfer roller 64. On the other hand, the toner image carried on the photosensitive drum 3 is charged with a negative polarity. For this reason, the toner image can be carried on the intermediate transfer belt 61.

  The paper feed cassette 81 stores a plurality of sheets P used for printing processing, and is provided below the exposure unit 1 of the image forming unit 110. The paper P used for image formation can also be placed on the manual feed tray 82 provided on the side surface of the image forming apparatus 100. A paper discharge tray 91 provided above the image forming unit 110 is a tray for collecting the sheets P on which image forming processing has been performed by the image forming unit 110.

  The image forming unit 110 is provided with a paper conveyance path Q for sending the paper P from the paper feed cassette 81 or the manual feed tray 82 to the paper discharge tray 91 via the secondary transfer unit (transfer device) 200 or the fixing unit 7. Yes. The paper transport path Q is a transport path from the paper feed cassette 81 to the manual feed tray 82 to the paper discharge tray 91. In the paper conveyance path Q, the pickup rollers 11A and 11B, the conveyance roller pair 12A, the registration roller pair 13, the secondary transfer unit 200, the fixing unit 7, and the conveyance roller pair 12B are arranged in this order from the upstream side to the downstream side. ing.

  The pickup roller 11 </ b> A is provided in the vicinity of the end of the paper feed cassette 81, feeds paper P from the paper feed cassette 81 one by one, and supplies it to the paper transport path Q. The pickup roller 11 </ b> B is provided near the end of the manual feed tray 82, picks up the paper P one by one from the manual feed tray 82, and supplies it to the paper transport path Q.

  The registration roller pair 13 temporarily holds the paper P being transported along the paper transport path Q. Then, the toner image carried on the intermediate transfer belt 61 is conveyed between the upstream intermediate transfer belt 61 and the secondary transfer unit 200 at the timing when the printing position of the paper P is adjusted.

  FIG. 2 is a schematic diagram illustrating a configuration around the nip region of the intermediate transfer belt 61 and the secondary transfer unit 200.

  The secondary transfer unit 200 includes a transfer roller (pressure contact member) 10, a paper guide 206, a secondary transfer belt (endless belt) 201, a holding roller 202, idle rollers 203 and 204, and a suction roller (collecting member) 205. Yes.

  The secondary transfer belt 201 is stretched around the holding roller 202, the idle roller 203, and the idle roller 204 so as to be movable in the direction along the conveyance path Q. Note that the transfer process with the paper P sandwiched between the intermediate transfer belt 61 and the secondary transfer belt 201 is more effective than the transfer process with the paper P sandwiched between the transfer roller and the transfer belt. P can be transported smoothly and the occurrence of paper jams during the transfer process can be alleviated.

  The paper guide 206 is a guide member that guides the paper P sent out from the registration roller pair 13. As a result, the paper P can be smoothly conveyed to the secondary transfer belt 201.

  The roller pair composed of the intermediate transfer belt driving roller 62 and the transfer roller 10 is a roller pair that sandwiches and conveys the paper P and transfers the toner image carried on the intermediate transfer belt 61 onto the printing surface of the paper P.

  The intermediate transfer belt drive roller 62 is a hard roller made of metal. On the other hand, the transfer roller 10 is a soft roller made of a resin material. The intermediate transfer belt driving roller 62 may be a soft roller made of a resin material, and the transfer roller 10 may be a hard roller made of metal.

Intermediate transfer belt driving roller 62 presses intermediate transfer belt 61 and secondary transfer belt 201 against transfer roller 10 to form a predetermined nip region (hereinafter referred to as a nip region for simplicity). As the intermediate transfer belt driving roller 62 rotates, the intermediate transfer belt 61 and the secondary transfer belt 201 rotate in a direction along the paper transport path Q. The paper P sent out from the registration roller pair 13 is transported along the paper transport path Q to the fixing unit 7 via the nip region. The resistance value of the secondary transfer belt 201 is 10 ¹¹ Ω · cm. As the secondary transfer belt 201, for example, a material in which an appropriate amount of a conductive material such as carbon black is contained in polyimide, polycarbonate, NBR coated with fluorine coating, or the like is used. The predetermined nip region corresponds to the transfer region of the present invention.

  The fixing unit 7 is disposed immediately above the transfer roller 10, has a roller pair including a heat roller 71 and a pressure roller 72, and heats and pressurizes the sheet P on which the toner image is transferred to thereby surface the sheet P The toner image is fixed to the toner image.

  FIG. 3 is a diagram illustrating an electrical configuration of the transfer roller 10, the holding roller 202, and the suction roller 205 controlled by the control unit 60.

  The controller 60 controls driving of the pickup rollers 11A and 11B, the transport roller pair 12A, the registration roller pair 13, the secondary transfer unit 200, the fixing unit 7, the transport roller pair 12B, and the like. The control unit 60 controls switching of the power switch (first power supply means) 50, the power switch (second power supply means) 51, and the power switch (second power supply means) 52.

  The power switch 50 is connected to the transfer roller 10 and switches the voltage polarity applied to the transfer roller 10. Thus, the electric field in the vicinity of the transfer roller 10 can be selectively switched between the first electric field that attracts toner to the transfer roller 10 side and the second electric field that attracts toner to the intermediate transfer belt drive roller 62 side. The power switch 50 applies a positive polarity voltage to the transfer roller 10 when the first electric field is formed. The power switch 50 applies a negative polarity voltage to the transfer roller 10 when the second electric field is formed.

The power switch 52 applies a voltage to the suction roller 205 and switches the polarity of the voltage applied to the suction roller 205. More specifically, the power switch 52 has a third electric field for attracting the toner adhering to the secondary transfer belt 201 to the adsorption roller 205 and a fourth electric field for adsorbing the toner adsorbed to the adsorption roller 205 to the secondary transfer belt 201. Switch the polarity of the voltage to the electric field. The power switch 52 applies a positive polarity voltage to the suction roller 205 when the third electric field is formed. The power switch 52 applies a negative polarity voltage to the suction roller 205 when the fourth electric field is formed.

  The power switch 51 applies a voltage to the holding roller 202 to form an electric field, and switches the polarity of the voltage applied to the holding roller 202. The power switch 51 applies a negative polarity voltage to the holding roller 202 when the third electric field is formed. The power switch 51 applies a positive polarity voltage to the holding roller 202 when the fourth electric field is formed. The power switch 51 may apply a voltage to the holding roller 202 only when either the third electric field or the fourth electric field is formed. In this embodiment, an example in which a voltage is applied to the holding roller 202 is described. However, a voltage may not be applied to the holding roller 202 according to the specification of the secondary transfer unit 200.

  The suction roller 205 has a large number of bristles extending in the radial direction from the shaft center, and the peripheral surface in the axial direction has a brush shape. Thus, more toner can be held when a positive polarity voltage is applied from the power switch 52. The suction roller 205 does not have to be in a brush shape as long as the toner can be sufficiently collected from the secondary transfer belt 201. The suction roller 205 is disposed at a position separated from the paper transport path Q with the holding roller 202 interposed therebetween. Thereby, it is possible to prevent the suction roller 205 from coming into contact with the paper P transported along the paper transport path Q.

  The control unit 60 has a normal print mode in which a toner image is transferred while leaving a margin at the edge of the paper P, and a borderless print mode in which the toner image is transferred without leaving a margin at both ends of the paper P. is doing.

  FIG. 4 is a diagram illustrating a configuration around the nip region when the control unit 60 performs the transfer process in the normal printing mode.

  When executing the printing process in the normal printing mode, the controller 60 applies a positive polarity voltage only to the transfer roller 10 via the power switch 50 to form the first electric field. In the present embodiment, the power switch 50 applies a voltage of +2 kV to the transfer roller 10. The control unit 60 drives the intermediate transfer belt driving roller 62 and the registration roller pair 13 so that the timing at which the toner image reaches the nip region and the timing at which the paper P reaches the nip region are aligned. Thus, the sheet P is pressed between the transfer roller 10 and the intermediate transfer belt driving roller 62 while the toner image is attracted to the secondary transfer belt 201 side in the nip region, and the transfer process is executed. Note that the voltage applied to the transfer roller 10 may be a voltage at which the transfer process to the sheet in the nip region is appropriately executed.

  The controller 60 executes a cleaning operation for wiping off the toner transferred to the secondary transfer belt 201 when performing borderless printing.

  FIG. 5 is a flowchart showing a flow of control of the cleaning operation by the control unit 60. In this embodiment, an example is given in which the cleaning operation is performed only when performing borderless printing. However, for example, the cleaning process may always be performed when performing the transfer process.

  When the borderless printing is selected (S1), the control unit 60 starts the transfer process of the toner image carried on the intermediate transfer belt 61 onto the paper P supplied from the registration roller pair 13 in the nip region. (S2), a positive polarity voltage is applied to the suction roller 205. At the same time, the controller 60 applies a negative polarity voltage to the holding roller 202 and causes the suction roller 205 to attract toner (S3).

  FIG. 6 is a diagram illustrating a configuration of voltage polarities applied to the transfer roller 10, the holding roller 202, and the suction roller 205 when the control unit 60 executes processing in step S <b> 3.

  In step S <b> 3, the control unit 60 applies a positive polarity voltage to the transfer roller 10 to form a first electric field. Accordingly, the toner image carried on the intermediate transfer belt 61 can be transferred to the paper P. The controller 60 applies a negative polarity voltage to the holding roller 202 and applies a positive polarity voltage to the suction roller 205 to form a third electric field. Thereby, the toner can be smoothly adsorbed to the adsorption roller 205. In the present embodiment, a voltage of −1.5 kV is applied to the holding roller 202, and a voltage of +1.5 kV is applied to the suction roller 205.

  Here, in order to transfer the toner image carried on the intermediate transfer belt 61 across the paper P onto the printing surface of the paper P, the control unit 60 is applied to the holding roller 202 and the suction roller 205 to the transfer roller 10. A voltage larger than the absolute value of the voltage is applied. Note that the absolute value of the voltage applied to the holding roller 202 and the suction roller 205 is smaller than the voltage applied to the transfer roller 10 that attracts the toner image to the secondary transfer belt 201 across the paper P. Just do it. Thereby, power consumption can be suppressed.

  FIG. 7 is a diagram illustrating a state immediately after the sheet P passes through the nip region in step S3.

  The toner that protrudes from the end of the paper P in the nip region is attracted to the secondary transfer belt 201. The toner is carried on the secondary transfer belt 201 and conveyed by the secondary transfer belt 201 to the vicinity of the suction roller 205 facing the holding roller 202 with the secondary transfer belt 201 interposed therebetween. The toner conveyed by the secondary transfer belt 201 to the vicinity of the adsorption roller 205 is adsorbed by the adsorption roller 205. Accordingly, it is possible to prevent the toner carried on the secondary transfer belt 201 from being conveyed to the nip region and adhering to the paper.

  Further, since a negative polarity voltage is applied to the holding roller 202 located immediately upstream of the suction roller 205, the toner can be smoothly sucked from the secondary transfer belt 201 to the suction roller 205 by the suction roller 205. Can do.

  When the transfer process to the paper P ends, that is, when the paper P passes through the nip region (S4), the control unit 60 switches the polarity of the voltages of the suction roller 205 and the transfer roller 10 to a negative polarity and Switch voltage polarity to positive polarity. As a result, the toner adsorbed on the adsorbing roller 205 can be conveyed from the secondary transfer belt 201 onto the intermediate transfer belt 61 via the nip region. The toner adsorbed on the intermediate transfer belt 61 is collected from the intermediate transfer belt 61 by the intermediate transfer belt cleaning unit 65. Therefore, the toner attached to the suction roller 205 can be collected only by the intermediate transfer belt cleaning unit 65. As a result, it is not necessary to separately provide a cleaning unit for collecting toner from the secondary transfer belt 201, and the image forming apparatus 100 can be reduced in size while suppressing an increase in manufacturing cost.

  FIG. 8 shows the result of examining the toner image transfer result (transfer image quality) when the resistance characteristic of the secondary transfer belt 201 is changed, and the toner adsorption property of the adsorption roller 205.

It was found that when the resistance value of the secondary transfer belt 201 is 10 ¹⁰ Ω · cm to 10 ¹¹ Ω · cm, good results can be obtained for both the transfer image quality and the toner adsorbability of the suction roller 205.

On the other hand, it was found that when the resistance value of the secondary transfer belt 201 is 10 ⁹ Ω · cm, the transfer image quality is not good, and a higher voltage is required for the suction roller 205 to suck the toner. . It has been found that when the resistance value of the secondary transfer belt 201 is 10 ¹² Ω · cm, the toner is scattered and the transfer image quality is lowered.

For this reason, by setting the resistance value of the secondary transfer belt 201 to 10 ¹⁰ Ω · cm to 10 ¹¹ Ω · cm, good transfer image quality and toner adsorbability can be obtained. However, the present invention is not limited to this. For example, a secondary transfer belt having a resistance value other than the range of 10 ¹⁰ Ω · cm to 10 ¹¹ Ω · cm according to the specifications of the image forming apparatus can be obtained as long as good transfer image quality and toner adsorbability can be obtained. May be used.

  In the above embodiment, the peripheral speed of the secondary transfer belt 201 and the peripheral speed of the suction roller 205 are 350 mm / sec. Here, the peripheral speed of the secondary transfer belt 201 is the rotational movement speed of the secondary transfer belt 201, and the peripheral speed of the suction roller 205 is the rotational speed of the suction roller 205.

  FIG. 9 shows the result of examining the toner adsorptivity to the suction roller 205, that is, the toner recoverability when the peripheral speed of the secondary transfer belt 201 is fixed and the peripheral speed of the suction roller 205 is changed. is there.

  As shown in FIG. 9, it has been found that the higher the peripheral speed ratio, that is, the higher the peripheral speed of the suction roller 205, the better the toner recoverability.

  On the other hand, when the peripheral speed ratio is set to 1.5, the toner transferability is good, but the secondary transfer belt 201 is scratched. For this reason, it was found that the peripheral speed ratio is optimally around 1.2.

  In the above embodiment, a secondary transfer type transfer device that performs transfer processing on a sheet in the nip region between the intermediate transfer belt unit 6 and the secondary transfer unit 200 is described as an example. The transfer process may be performed on the sheet in the nip region with the transfer belt. In this case, the same effect as that of the secondary transfer unit 200 according to the above embodiment can be obtained.

  In the above-described embodiment, an example in which the suction roller 205 is constantly in contact with the secondary transfer belt 201 is described. However, the contact / contact state in which the suction roller 205 is brought into contact with the secondary transfer belt 201 only when the cleaning operation is performed. A mechanism may be further provided. In this case, since the suction roller 205 contacts the secondary transfer belt 201 only during the cleaning operation, it is possible to prevent the suction roller 205 and the secondary transfer belt 201 from contacting each other and being worn. . For this reason, the effect that the use period of the adsorption | suction roller 205 and the secondary transfer belt 201 is extended can be acquired.

  1 to 9, the cross-sectional notation is omitted as appropriate. The black circles shown in FIGS. 4, 6, and 7 indicate toner.

  In addition, it should be thought that description of the above-mentioned embodiment is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention when viewed from the front. FIG. FIG. 3 is a diagram illustrating a configuration around a secondary transfer unit. It is a figure which shows the electrical structure in a transfer roller, a holding roller, and a suction roller. FIG. 6 is a view around a nip region partially showing a configuration of a positive polarity voltage applied to a transfer roller in a normal printing mode. It is a flowchart which shows the flow of the control processing in cleaning operation. FIG. 6 is a view around the nip area showing a state when a sheet is sent to the upstream side of the nip area when performing borderless printing. FIG. 6 is a view around the nip showing a state after the sheet has passed through the nip area when performing borderless printing. FIG. 6 is a diagram illustrating a result of investigation of transfer image quality and toner collection performance of a suction roller when resistance characteristics of a secondary transfer belt are changed. It is a figure which shows the result of investigating the toner collection | recovery property of an adsorption roller when changing the rotational speed of an adsorption roller.

Explanation of symbols

6 Intermediate transfer belt unit (transfer device)
10 Transfer roller (pressure contact member)
50 Power switch (first power supply means)
51 Power switch (second power supply means)
52 Power switch (second power supply means)
60 Controller 61 Intermediate transfer belt (image carrier)
65 Intermediate transfer belt cleaning unit (cleaning means)
200 Secondary transfer unit (transfer device)
201 Secondary transfer belt (endless belt)
202 Holding roller 205 Suction roller (collecting member)

Claims (8)

An image carrier that carries a toner image and rotates in a predetermined direction;
An endless belt that is stretched in a loop on a plurality of rollers in a transfer region adjacent to the image carrier, moves in the circumferential direction of the image carrier, and contacts a sheet within a predetermined sheet contact range including the transfer region When,
A pressure-contact member that press-contacts the endless belt to the image carrier with a sheet sandwiched in the transfer region;
A recovery member that contacts the outer peripheral surface of the endless belt outside the sheet contact range;
Cleaning means for recovering toner adhering to the image carrier;
First power supply means for forming a first electric field for directing toner from the image carrier to the endless belt or a second electric field for directing toner from the endless belt to the image carrier;
Second power supply means for forming a third electric field for directing toner from the endless belt to the collecting member or a fourth electric field for directing toner from the collecting member to the endless belt;
A control section for switching the polarity of the voltage of the first power supply means and the second power supply means;
With
The controller causes the first power supply means to form the first electric field and the second power supply means to form the third electric field when the toner image is transferred from the image carrier to the paper, and the paper is Causing the first power source means to form the second electric field after passing through the transfer region and causing the second power source means to form the fourth electric field;
Transfer device. The image carrier is an intermediate transfer belt stretched in a loop on a plurality of rollers.
The transfer device according to claim 1. The control unit has a borderless printing mode for transferring a toner image over the entire width of the paper,
The control unit causes the first power supply unit to form the second electric field and causes the second power supply unit to generate the fourth electric field only after executing the borderless printing mode after the sheet passes through the transfer region. Form,
The transfer device according to claim 1. The second power supply means applies a voltage to the recovery member and the roller disposed at a position facing the recovery member across the endless belt to form a third electric field or a fourth electric field,
The transfer device according to claim 1. The voltage applied by the second power supply means is set to have an absolute value smaller than the voltage applied by the first power supply means.
The transfer device according to claim 4. The endless belt has a resistance value ranging from 10 ¹⁰ Ω · cm to 10 ¹¹ Ω · cm.
The transfer device according to claim 1. The circumferential speed of the collection member is greater than the circumferential speed of the endless belt,
The transfer device according to claim 1. The collection member has a brush shape,
The transfer device according to claim 1.

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