JP2011232573A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can reduce manufacturing costs while preventing smear on the back of a recording medium.SOLUTION: The image forming apparatus comprises: an image forming section (6) that has an image carrier (7) and develops a latent image on the image carrier with toner with the drive of the image carrier to form a toner image; a transfer belt (14) that is stretched between the rollers, travels between the image carrier and a transfer roller (12) with a recording medium placed on its conveyance surface (14a) and directly transfers the toner image to the recording medium by application of voltage of the reverse polarity to that of the toner adhering to the latent image on the transfer roller; bias cleaning means (30) that recovers the remaining toner adhering to the conveyance surface using electrostatic force; and auxiliary cleaning means (40) that is located downstream of the bias cleaning means as seen from the travelling direction of the transfer belt and adjusts the uncollected remaining toner to the same polarity as that of the toner adhering to the latent image using the bias screening means.

Description

  The present invention relates to an image forming apparatus that forms an image using a transfer belt.

  In this type of image forming apparatus, an electrophotographic method is used. When a charger precharges an image carrier (for example, a photosensitive drum) and the exposure unit irradiates light on the surface of the photosensitive drum, the photosensitive member is used. An electrostatic latent image is formed on the surface of the drum. Further, the developing device carries toner, and when a developing bias voltage is applied, the toner charged in advance adheres to the electrostatic latent image, and a toner image is formed.

Then, the paper is conveyed to the transfer nip by a pair of rollers arranged on the upstream side of the transfer nip, and the visualized toner image is transferred to the paper on the transfer belt.
Here, when the toner image is transferred onto the paper, the toner that moves from the photosensitive drum toward the paper may also adhere to the conveyance surface of the transfer belt (for example, fog toner between papers) ), The residual toner adhering to the conveying surface causes the back side of the paper to become dirty. Therefore, a technique for removing the residual toner from the conveyance surface is disclosed (for example, see Patent Document 1).

Japanese Patent No. 2954812

  By the way, the residual toner adhering to the transfer surface of the transfer belt includes a reverse charge toner, that is, a toner having a charge polarity opposite to that of the regular charged toner adhered to the electrostatic latent image, and the regular charged toner. Even if they have the same charging polarity, the toner is often a very large charge amount. The former reverse charge toner is caused by an increase in the surface potential of the image carrier, and causes image defects such as fogging. On the other hand, the latter toner having an extremely large charge amount is generated by gradually charging up the toner that continues to adhere to the conveying surface due to the circular running of the transfer belt.

  In order to remove both the reversely charged toner and the toner of the extremely large charge amount having the same charging polarity from the conveying surface, it is conceivable to use a two-stage bias cleaning means. In other words, in the first stage, a voltage having a polarity opposite to that of the regular charged toner is applied to remove the latter toner, and in the second stage, a voltage having the same polarity as that of the regular charged toner is applied. Reverse charge toner can be removed.

However, when the two-stage bias cleaning means is provided, there is a problem that the apparatus becomes complicated and the manufacturing cost of the apparatus cannot be reduced.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of solving the above-described problems and achieving reduction in manufacturing cost while preventing backside contamination of paper.

  According to a first aspect of the present invention for achieving the above object, an image carrier is provided, and a latent image on the image carrier is developed with toner by driving the image carrier. The recording medium is placed on the conveying surface and travels between the image carrier and the transfer roller. By applying a voltage having a polarity opposite to that of the toner attached to the latent image on the transfer roller, the toner is A transfer belt that directly transfers an image to a recording medium, a bias cleaning unit that collects residual toner adhering to the conveyance surface using electrostatic force, and a downstream side of the bias cleaning unit as viewed in the running direction of the transfer belt. And a cleaning auxiliary means for adjusting the unrecovered residual toner to the same polarity as the toner adhering to the latent image by the bias cleaning means.

According to the first invention, the transfer belt is a belt that electrostatically conveys the recording medium. On the other hand, the toner adheres to the electrostatic latent image on the image carrier, and a toner image is formed on the image carrier. When a voltage having a polarity opposite to that of the toner adhering to the latent image is applied to the transfer roller, the toner image is transferred to the recording medium.
When the toner image is transferred to the recording medium, the toner that moves from the image carrier toward the recording medium may adhere to the conveyance surface of the transfer belt in addition to the recording medium.

  By the way, in the transfer belt described above, it is not necessary to form an image on the conveying surface. In other words, unlike a color machine using an intermediate transfer member, there is no need to perform primary transfer of the toner image and secondary transfer to the recording medium, so there is some residual toner on this transport surface. However, if the charge polarity of the residual toner is the same as that of the regular charged toner that adheres to the latent image, the residual toner does not stain the back side of the recording medium when the toner image is transferred to the recording medium. .

That is, in view of collecting the remaining toner, although this corresponds to a slight cleaning failure, the cleaning failure is not a major problem as long as the recording medium does not become dirty.
Therefore, in the present invention, the bias cleaning unit uses the electrostatic force to collect the residual toner adhering to the transport surface, but the downstream side thereof is not a separate bias cleaning unit, but a regular charge adhering to the latent image. A cleaning auxiliary means for adjusting the same charging polarity as that of the toner is arranged, and the bias voltage is not applied by the cleaning auxiliary means. If the charging polarity of the unrecovered residual toner is adjusted to the same charging polarity as the regular charged toner by the upstream bias cleaning means, the unrecovered residual toner is transported when a reverse polarity voltage is applied by the transfer roller. This is because it remains on the surface and does not move to the back side of the recording medium.

As a result, the back contamination of the recording medium can be prevented in the same manner as when the two-stage bias cleaning means is provided while the one-stage bias cleaning means is provided. As a result, a significant reduction in device manufacturing costs can be achieved.
According to a second aspect of the invention, in the configuration of the first aspect of the invention, the cleaning assisting means adjusts the residual toner to the same polarity as the toner that adheres to the latent image by friction with the residual toner that has not been collected by the bias cleaning means. The triboelectric charging characteristic of the toner adhering to the latent image and the triboelectric charging characteristic of the conveying surface are in a reverse polarity relationship.

  According to the second aspect of the invention, in addition to the action of the first aspect, the triboelectric charge characteristic of the toner adhering to the latent image and the triboelectric charge characteristic of the material of the conveying surface are in a reverse polarity relationship. When the auxiliary unit recharges the remaining toner that has not been collected by the bias cleaning unit due to friction, the remaining toner is quickly adjusted to the same polarity as that of the regular charged toner. Therefore, the back contamination of the recording medium can be surely prevented while simplifying the structure by the one-stage bias cleaning means.

According to a third aspect of the invention, in the configuration of the second aspect of the invention, the cleaning assisting means is a friction blade member that abuts on the conveying surface, and the friction charging characteristics of the toner adhering to the latent image and the friction charging characteristics of the friction blade member Is characterized by a reverse polarity relationship.
According to a fourth aspect of the invention, in the configuration of the second aspect of the invention, the cleaning auxiliary means is a friction brush member that rotates in contact with the conveying surface, and the friction charging characteristics of the toner adhering to the latent image and the friction of the friction brush member The charging characteristic is characterized by having a reverse polarity relationship.

According to the third and fourth aspects of the invention, in addition to the action of the second aspect, the friction blade member or the friction brush member is in contact with the conveying surface, and residual toner that has not been collected by the bias cleaning means can be easily obtained. The remaining toner can be adjusted more quickly with the same polarity as that of the regular charged toner.
According to a fifth aspect of the present invention, in the configuration of the first to fourth aspects, the bias cleaning means is in contact with the conveyance surface in the trail direction, a metal collection roller that collects residual toner attached to the conveyance surface, and a collection A cleaning blade that contacts the roller in the counter direction and scrapes the residual toner collected by the collecting roller, and a voltage having a polarity opposite to that of the toner adhering to the latent image is applied to collect the residual toner adhering to the conveying surface. And voltage control means for generating an electric field from the transport surface toward the collecting roller.

  According to the fifth invention, in addition to the actions of the first to fourth inventions, the voltage control means applies a voltage having a charging polarity opposite to that of the toner adhering to the latent image and applies the recovery roller from the conveying surface. The toner having the same charging polarity as the regular charged toner out of the remaining toner adhering to the conveying surface is moved toward the collecting roller.

  The collection roller rotates at a slight speed difference along the running direction of the transfer belt, and comes into contact with the transfer belt in the trail direction that presses the conveying surface. As a result, the remaining toner having the same charging polarity as that of the regular charged toner is recovered by electrostatic force. Since the cleaning blade contacts the collecting roller in the counter direction facing each other, the remaining toner collected by the collecting roller can be easily scraped off. As a result, toner having the same charging polarity as the regular charged toner can be quickly removed from the remaining toner adhering to the conveying surface.

  According to the present invention, an image forming apparatus that can prevent backside contamination of a recording medium and achieve a reduction in manufacturing cost can be achieved as in the case of including a two-stage bias cleaning unit while including a one-stage bias cleaning unit. Is to provide.

1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 2 is an enlarged view of the periphery of the transfer belt in FIG. 1. FIG. 3 is an explanatory diagram of toner around the photosensitive drum of FIG. 2. FIG. 3 is an explanatory diagram of toner around a bias cleaning unit in FIG. 2. FIG. 3 is an explanatory diagram of toner around a friction brush member in FIG. 2. FIG. 3 is a diagram illustrating a state of toner that has passed through the bias cleaning unit and the friction brush member of FIG. 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a tandem color printer according to the present embodiment, in which the right side corresponds to the front of the printer 1 and the left side corresponds to the back.
As shown in the figure, a sheet (recording medium) cassette 3 is disposed at the bottom of the apparatus main body 2, and sheets P before image formation are accommodated in the cassette 3 in a stacked state. The sheets P are separated one by one from the cassette 3 and conveyed from the front of the printer 1 toward the back of the printer 1.

Inside the apparatus main body 2, the registration roller 5, the image forming unit 6, and the fixing unit 18 are arranged in this order when viewed from the paper transporting path 4 in the transporting direction of the paper P, and the paper P delivered from the fixing unit 18. Is discharged to the paper discharge tray 22 through the paper transport path 20.
The image forming unit 6 according to the present exemplary embodiment includes four image forming units 6C, 6M, 6Y, and 6B.

  These image forming units 6C, 6M, 6Y, and 6B are arranged in order from the front side to the back side of the printer 1, and are provided corresponding to images of four different colors (cyan, magenta, yellow, and black). Cyan, magenta, yellow, and black images are sequentially formed through charging, exposure, development, and transfer processes.

Specifically, each of the image forming units 6C, 6M, 6Y, and 6B is provided with a photosensitive drum (image carrier) 7 that carries a visible image (toner image) of a corresponding color. Each photosensitive drum 7 is rotatably installed with respect to the apparatus main body 2 and is driven clockwise by a driving motor (not shown).
A corresponding charger 8, exposure unit (LED print head unit or the like) 9, developing unit 10, transfer roller 12, and rubbing roller 13 are provided around each photosensitive drum 7.

The charger 8 is disposed on the opposite side of the transfer roller 12 and uniformly charges the surface of each corresponding photosensitive drum 7. The exposure unit 9 is disposed on the downstream side of the charger 8 as viewed in the rotation direction of the photosensitive drum 7, and irradiates laser light toward the surface of each corresponding photosensitive drum 7.
The developing device 10 is arranged on the downstream side of the exposure unit 9 when viewed in the rotation direction of the photosensitive drum 7, and cyan, magenta, yellow, and black toners are supplied from the toner containers 11C, 11M, 11Y, and 11B, respectively. The toner of each color is electrostatically attached to the surface of the photosensitive drum 7.

As a result, a toner image corresponding to the electrostatic latent image by the exposure unit 9 is developed on the surface of each photosensitive drum 7. The toner images formed on the photosensitive drums 7 are transferred onto the paper P that is transported on the transfer belt 14.
Specifically, the transfer belt 14 is an endless belt in which both end portions of a resin sheet material are overlapped and joined, or a seamless belt without a joint, and includes a driving roller 15 and a driven roller 16. And run counterclockwise in the figure by a drive motor (not shown).

  As the resin sheet material, for example, polyvinylidene fluoride (PVDF), polyimide (PI), polyamideimide (PAI) or the like is used, and the frictional charging characteristics of the material of the transfer belt 14 are electrostatic latent images. It has a relationship of reverse polarity (reverse charge polarity) with respect to the frictional charging characteristics of the toner adhering to the toner. In the case of a monochrome machine instead of the tandem color machine, acrylonitrile butadiene rubber (NBR) having a fluorine-based (for example, PTFE) coating on its surface can be used.

  The transfer belt 14 travels between the photosensitive drum 7 and the transfer roller 12 with the paper P placed thereon. As a result, the toner images formed on the respective photoconductive drums 7 are directly transferred one after another to the paper P delivered from the registration roller 5, and the paper P is conveyed toward the fixing unit 18 by the transfer belt 14. .

  The rubbing roller 13 is disposed on the upstream side of the charger 8 when viewed in the rotation direction of the photosensitive drum 7. The rubbing roller 13 is configured to be able to come into contact with the surface of each corresponding photosensitive drum 7, and is driven by the drive motor with a slight speed difference from the photosensitive drum 7 in the counterclockwise direction of FIG. Thus, this surface is polished. The toner remaining on each photosensitive drum 7 is removed by a cleaning device (not shown).

On the other hand, toner (residual toner) remaining on the transfer belt 14 is removed by a bias cleaning unit (bias cleaning means) 30 and a friction brush member (cleaning auxiliary means) 40.
Specifically, first, as shown in FIG. 2, the bias cleaning unit 30 is disposed in the vicinity of the downstream side of the driving roller 15 when viewed in the traveling direction of the transfer belt 14, and the conveyance surface 14a on which the paper P is placed. The residual toner adhering to the toner is collected by using electrostatic force and removed from the conveying surface 14a.

  2 and FIGS. 3 to 6 described below show only the pair of photosensitive drums 7 and the transfer roller 12 in order to help understanding the structure of the bias cleaning unit 30 and the friction brush member 40. However, as described above, a total of four pairs of photosensitive drums 7 and transfer rollers 12 are arranged between the driving roller 15 and the driven roller 16 in FIG.

The bias cleaning unit 30 of this embodiment includes a collection roller 32, a cleaning blade 34, a collection container 36, and a voltage control unit (voltage control means) 39 (FIG. 2).
The collection roller 32 is made of metal (for example, made of SUS430), extends in the width direction of the transfer belt 14, and has a higher speed (linear speed ratio: 1.2 to 2.0) than the transfer belt 14. It rotates around and abuts on the conveying surface 14a in the trail direction.

The cleaning blade 34 extends in the width direction of the transfer belt 14 and contacts the collection roller 32 in the counter direction on the side opposite to the conveyance surface 14a. Further, the collection container 36 is disposed below the contact position between the collection roller 32 and the cleaning blade 34.
The drive roller 15 described above is grounded, and a voltage having a polarity opposite to that of the toner adhering to the electrostatic latent image on each photosensitive drum 7 is provided between the recovery roller 32 and the drive roller 15. 39, an electric field is generated from the conveyance surface 14a of the transfer belt 14 toward the collection roller 32.

Note that a voltage having a polarity opposite to that of the toner attached to the electrostatic latent image on each photosensitive drum 7 is also applied between the transfer roller 12 and the photosensitive drum 7 described above from the voltage control unit 38.
That is, if the toner used in this embodiment is a positively chargeable toner (regularly charged toner), when the voltage control unit 38 applies a voltage having a polarity opposite to that of the toner to the transfer roller 12, FIG. As shown in FIG. 4, the positively chargeable toner 80 on the photosensitive drum 7 is separated from the photosensitive drum 7 and basically goes to the paper P on the conveying surface 14a.

  Here, on the transport surface 14a, a positively charged toner 80 that is separated from the photosensitive drum 7, and a negatively charged toner 81 that is generated due to an increase in the surface potential of the photosensitive drum 7 are left as residual toner. It may adhere (FIG. 4). Further, in the positively chargeable toner 80, there may be the same positively chargeable residual toner that is gradually charged up by the rotation of the transfer belt 14.

However, in this embodiment, the voltage control unit 39 of the bias cleaning unit 30 applies a reverse polarity voltage between the recovery roller 32 and the drive roller 15, for example, about 10 μA (1 μA = 1 × 10 ⁻⁶ A). The electric field from the transport surface 14a toward the collection roller 32 is generated. As a result, as shown in FIG. 4, the positively chargeable toner 80 adhering to the conveyance surface 14 a is collected from the conveyance surface 14 a and adhered to the collection roller 32.

Residual toner adhering to the collection roller 32 is scraped off by a cleaning blade 34 and collected in a collection container 36.
However, the negatively chargeable toner 81 adhering to the transport surface 14a cannot be removed from the remaining toner as it is, but the negatively chargeable toner 81 is adjusted to the same charging polarity as the regular charged toner by the friction brush member 40. .

  Specifically, as shown in FIG. 2, the friction brush member 40 is disposed in the vicinity of the upstream side of the driven roller 16 when viewed in the traveling direction of the transfer belt 14, and extends in the width direction of the transfer belt 14. Further, the friction brush member 40 rotates counterclockwise in FIG. 2 at the same speed (linear speed ratio: 1.0) as that of the transfer belt 14, and comes into contact with the conveyance surface 14a in the counter direction.

The friction brush member 40 of this example is a brush having a fineness of 6D of insulating PET resin, and has 100 kF / inch ² , that is, 100,000 filaments per square inch on the base fabric. The frictional charging characteristics of the material are configured so as to have a reverse polarity (negative chargeability in this embodiment) to that of a regular charged toner.

  That is, as shown in FIG. 5, the negatively chargeable toner 81 adhering to the transport surface 14 a is disturbed by the friction brush member 40 even after passing through the collection roller 32, and is added to the positively chargeable toner 80. To be prepared. Next, the conveyance surface 14 a on which the positively chargeable toner 80 is adhered is placed on the sheet P in the vicinity of the registration roller 5 and heads toward the photosensitive drum 7.

  Subsequently, when the voltage controller 38 applies a voltage having a polarity opposite to that of the toner to the transfer roller 12, the thickness of the belt 14 is partially thinned in order to clarify the presence of toner on the front and back surfaces of the paper P. As shown in FIG. 6, the positively chargeable toner 80 on the photosensitive drum 7 moves away from the photosensitive drum 7 toward the paper P, but the positively chargeable toner 80 adhering to the transport surface 14a is It does not face the back surface of the paper P, and continues to adhere to the transport surface 14a.

  In the collection roller 32, an electric field from the conveyance surface 14a toward the collection roller 32 is generated by the voltage control unit 39. Therefore, the positively chargeable toner 80 that continues to adhere to the conveyance surface 14a can be collected from the conveyance surface 14a. (FIG. 4), scraped off by the cleaning blade 34 and collected in the collection container 36. This makes it difficult for residual toner to accumulate on the subsequent conveyance surface 14a.

  Returning to FIG. 1 again, in the printer 1 described above, the paper P is separated from the cassette 3 and sent out one by one, and the paper P reaches the registration roller 5. The registration roller 5 feeds the paper P toward the transfer belt 14 while correcting the oblique feeding of the paper P and measuring the timing of the image transfer operation by each of the photosensitive drums 7 and the transfer rollers 12.

  In the printer 1, the laser beam irradiation by the exposure unit 9 is controlled. As a result, an electrostatic latent image of the original image is formed on each photoconductive drum 7 in the image forming unit 6, and then a toner image is formed on each photoconductive drum 7 from this latent image and is conveyed by the transfer belt 14. The toner images for each color are transferred one after another to the sheet P to be printed. The sheet P is fed toward the fixing unit 18 with an unfixed toner image carried thereon, and after a color image or a monochrome image is formed, the sheet P is discharged to the sheet discharge tray 22 through the sheet conveyance path 20.

  As described above, according to the present embodiment, the transfer belt 14 is a belt that electrostatically conveys the paper P. On the other hand, for example, the positively charged toner 80 adheres to the electrostatic latent image on the photosensitive drum 7, and a toner image is formed on the photosensitive drum 7. When a negative polarity voltage is applied to the transfer roller 12, the toner image is transferred to the paper P.

When the toner image is transferred onto the paper P, the toner moving from the photosensitive drum 7 toward the paper P may adhere to the transport surface 14 a of the transfer belt 14 in addition to the paper P.
Here, in this embodiment, the bias cleaning unit 30 uses the electrostatic force to collect the residual toner adhering to the transport surface 14a. However, on the downstream side of the bias cleaning unit 30, a positively charging property is used instead of another bias cleaning unit. A negatively chargeable friction brush member 40 for arranging the toner 80 is disposed, and no bias voltage is applied to the friction brush member 40.

  The transfer belt 14 does not need to primarily transfer the toner image to the paper P and transfer it to the paper P. Therefore, even if some residual toner is present on the transport surface 14a, the upstream bias cleaning unit 30 can perform the transfer. If the charging polarity of the unrecovered residual toner is adjusted to the positively chargeable toner 80, when the transfer roller 12 applies a negative polarity voltage, the unrecovered residual toner remains on the transport surface 14a and remains on the sheet P. This is because it does not move to the back side.

  As a result, the first-stage bias cleaning unit 30 for applying a negative polarity voltage is applied, but the first-stage voltage for applying a reverse polarity voltage to the regular charged toner, and the same polarity as for the regular charged toner. Similarly to the case where a two-stage bias cleaning unit composed of the second stage for applying toner is provided, it is possible to prevent contamination of the back of the paper P and in-machine contamination due to development of reverse charge toner. As a result, a significant reduction in the manufacturing cost of the printer 1 can be achieved.

The voltage control unit 39 applies a negative polarity voltage between the collection roller 32 and the driving roller 15 to generate an electric field from the conveyance surface 14a toward the collection roller 32, and is attached to the conveyance surface 14a. Of the remaining toner, the positively chargeable toner 80 is moved toward the collection roller 32.
The collection roller 32 rotates along the traveling direction of the transfer belt 14 (preferably a slight speed difference with respect to the belt), and contacts the transfer belt in a trail direction that presses the conveying surface 14a. As a result, the positively charged toner 80 is recovered by electrostatic force.

  Since the cleaning blade 34 contacts the collection roller 32 in the counter direction facing each other, the positively chargeable toner 80 collected by the collection roller 32 can be easily scraped off. As a result, the remaining toner having an extremely large charge amount can be quickly removed from the positively chargeable toner 80 adhering to the transport surface 14a.

  Further, the conveyance surface 14a has a characteristic that the material is negatively charged by friction, whereas the toner has a characteristic that the toner is positively charged by friction, and the frictional charging characteristic between the conveyance surface 14a and the toner is low. Because of the reverse polarity relationship, when the friction brush member 40 recharges the remaining toner that has not been collected by the bias cleaning unit 30 due to friction, the reversely charged toner out of the remaining toner quickly becomes the positively charged toner 80. To be arranged. Therefore, while the structure is simplified by the one-stage bias cleaning unit 30, it is possible to reliably prevent the back side of the paper P from being contaminated and the contamination inside the apparatus due to the development of the reverse charge toner.

Furthermore, the friction brush member 40 is in contact with the conveying surface 14a in the counter direction, and the remaining toner that has not been collected is easily agitated by the bias cleaning unit 30, and the remaining toner is more quickly absorbed by the positively charged toner 80. Can be arranged.
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims.

For example, in the above-described embodiment, the friction brush member 40 is used, and the negatively chargeable toner 81 adhering to the transport surface 14a is adjusted to the positively chargeable toner 80. A positively chargeable toner 80 may be prepared using a chargeable friction blade member (cleaning auxiliary means).
The friction brush member 40 (or the friction blade member) of the above embodiment is in contact with the transport surface 14a in the counter direction, but may be in contact with the transport surface 14a in the trail direction. This is because the function is achieved if there is a relative speed difference between the friction brush member 40 (or the friction blade member) and the conveying surface 14a.
In the above embodiment, the positively charged toner 80 is described as a regular charged toner. However, the present invention can also be applied to a case where a negatively charged toner 81 is used as a regular charged toner.

Furthermore, the image carrier of the present invention is not limited to four photosensitive drums. Further, in the above embodiment, an example in which the image forming apparatus is embodied in a printer is shown. Naturally, it can also be applied to multifunction machines, copiers and facsimiles.
In any of these cases, similarly to the above, it is possible to achieve a reduction in manufacturing cost while preventing the recording medium from being stained.

1 Printer (image forming device)
6 Image forming unit 7 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 12 Transfer roller 14 Transfer belt 14a Conveyance surface 15 Drive roller 16 Driven roller 30 Bias cleaning unit (bias cleaning means)
32 Collection roller 34 Cleaning blade 39 Voltage control unit (voltage control means)
40 Friction brush member (cleaning auxiliary means)

Claims (5)

An image carrier having an image carrier and developing a latent image on the image carrier with toner by driving to form a toner image;
A voltage having a polarity opposite to that of the toner adhering to the latent image with respect to the transfer roller is run between the image carrier and the transfer roller by placing a recording medium on the conveyance surface thereof. A transfer belt that directly transfers the toner image to the recording medium by application;
Bias cleaning means for recovering residual toner adhering to the conveying surface using electrostatic force;
A cleaning auxiliary means arranged downstream of the bias cleaning means as viewed in the running direction of the transfer belt, and for adjusting unrecovered residual toner to the same polarity as the toner adhering to the latent image by the bias cleaning means. An image forming apparatus comprising: The image forming apparatus according to claim 1,
The cleaning auxiliary means adjusts the residual toner to the same polarity as the toner attached to the latent image by friction with the residual toner that has not been collected by the bias cleaning means,
2. An image forming apparatus according to claim 1, wherein the triboelectric charging characteristic of the toner adhering to the latent image and the triboelectric charging characteristic of the conveying surface have a reverse polarity relationship. The image forming apparatus according to claim 2,
The cleaning auxiliary means is a friction blade member that comes into contact with the transport surface,
2. An image forming apparatus according to claim 1, wherein the frictional charging characteristic of the toner adhering to the latent image and the frictional charging characteristic of the friction blade member are in a reverse polarity relationship. The image forming apparatus according to claim 2,
The cleaning auxiliary means is a friction brush member that rotates in contact with the transport surface,
2. An image forming apparatus according to claim 1, wherein the frictional charging characteristic of the toner adhering to the latent image and the frictional charging characteristic of the friction brush member have a reverse polarity relationship. An image forming apparatus according to any one of claims 1 to 4,
The bias cleaning means includes
A metal recovery roller that abuts the transport surface in the trail direction and collects residual toner adhering to the transport surface;
A cleaning blade that comes into contact with the collecting roller in the counter direction and scrapes the remaining toner collected by the collecting roller;
In order to collect the residual toner adhering to the conveying surface, voltage control means is provided that applies a voltage having a polarity opposite to that of the toner adhering to the latent image and generates an electric field from the conveying surface toward the collecting roller. An image forming apparatus.

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