JP2010002533A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that stabilizes drive of an intermediate transfer belt and prevents image failure and transfer failure. <P>SOLUTION: The image forming apparatus includes: image forming sections (6)having image carriers (7) that develop latent images on the image carriers with toner by driving the image carriers (7), thereby forming toner images; a belt member (14) that is extended around a drive roller (15) and a follower roller (16), runs between the image carriers and intermediate rollers (12), and transfers the toner images to a transfer surface (14a) by its drive, thereby transferring the toner images to paper via the transfer surface; a cleaning member (30) disposed downstream of the intermediate transfer roller but upstream of the drive roller in the running direction of the belt member and abutting on a non-transfer surface (14b) opposite the transfer surface; and a voltage control means (54) for generating an electric field from the non-transfer surface to the cleaning member during image formation in order to recover toner deposited on the non-transfer surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

This type of image forming apparatus has an image carrier (for example, a photosensitive drum), and toner is supplied to the surface of the drum from a developing device to develop the toner image. The toner image is transferred onto a sheet via an intermediate transfer belt.
Specifically, the transfer belt is looped between a driving roller and a driven roller and travels between a drum and an intermediate transfer roller, and the toner image is primarily transferred onto the transfer surface by the driving. Secondary transfer is performed from the transfer surface to the paper.

  Here, the transfer surface is cleaned by a cleaning member, and a technique for cleaning a non-transfer surface opposite to the transfer surface is disclosed (for example, see Patent Document 1). The life of the transfer roller and the drive roller is extended.

JP 2007-187844 A

By the way, in the above conventional technique, after the non-transfer surface is secondarily transferred, in other words, the cleaning member is disposed on the downstream side of the driving roller and on the upstream side of the driven roller in the traveling direction of the transfer belt. In this case, there is a problem that the driving force of the driving roller is reduced and an image defect or a transfer defect occurs.
This is because the toner can scatter from the developing unit and adhere to the non-transfer surface.

  More specifically, when the non-transfer surface to which the toner is attached reaches the drive roller, the toner reduces the frictional force between the non-transfer surface and the drive roller, destabilizes the speed of the transfer belt, and The non-transfer surface is damaged, and the effect appears on the transfer surface like a streak-like image defect or local transfer defect. This instability of the speed also causes deterioration of the color resist property in the case of an apparatus capable of color printing.

As described above, some measures are required to prevent the driving force of the driving roller from being lowered. However, the conventional technique still has a problem in this respect.
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, stabilizing the intermediate transfer belt drive, and preventing image defects and transfer defects.

  A first invention for achieving the above object has an image carrier, and an image forming unit for developing a latent image on the image carrier with toner by driving the image carrier, and a driving roller And a belt member that is wound around the driven roller and travels between the image carrier and the intermediate transfer roller, and transfers the toner image onto the transfer surface by the drive, and transfers the toner image onto the sheet via the transfer surface; A cleaning member that is disposed on the downstream side of the intermediate transfer roller and the upstream side of the driving roller as viewed in the traveling direction of the member, and that contacts the non-transfer surface opposite to the transfer surface, and the toner attached to the non-transfer surface Voltage control means for generating an electric field from the non-transfer surface toward the cleaning member at the time of image formation so as to collect the toner.

According to the first invention, the belt member is looped between the driving roller and the driven roller, and runs between the image carrier and the intermediate transfer roller. And transferred to the paper.
Here, the cleaning member comes into contact with the non-transfer surface opposite to the transfer surface and cleans the non-transfer surface, but this cleaning member is located on the downstream side of the intermediate transfer roller in the running direction of the belt member. And disposed upstream of the drive roller. Accordingly, since the toner adhering to the non-transfer surface is cleaned immediately before the driving roller, it is possible to prevent the driving force of the driving roller from being lowered and to prevent image defects and transfer defects as compared with the conventional case.

In addition, the voltage control means generates an electric field from the non-transfer surface to the cleaning member, and at the time of image formation, the toner adhering to the non-transfer surface is actively collected by the cleaning member. The driving force of the driving roller does not decrease during the next transfer.
As a result, it contributes to improving the reliability of the image forming apparatus.

According to a second aspect of the present invention, in the configuration of the first aspect, the voltage control means applies a voltage having the same polarity as the toner to the intermediate transfer roller during image formation, while the cleaning member has a polarity opposite to that of the toner. By applying a voltage, an electric field from the non-transfer surface toward the cleaning member is generated.
According to the second invention, in addition to the operation of the first invention, a voltage having the same polarity as the toner is applied to the intermediate transfer roller, and a voltage having a polarity opposite to that of the toner is applied to the cleaning member. Therefore, current flows from the intermediate transfer roller to the cleaning member via the belt member, and the toner adhering to the non-transfer surface is promptly collected by the cleaning member, and the opposite of the cleaning member across the belt member. There is no need to provide a counter electrode on the side.

According to a third invention, in the configuration of the second invention, the voltage control means applies a voltage for moving the toner adhering to the surface of the intermediate transfer roller to the non-transfer surface to the intermediate transfer roller. And
According to the third invention, in addition to the action of the second invention, the intermediate transfer roller is applied with a voltage for moving the toner adhering to the surface to the non-transfer surface. The toner adhering to the surface is also quickly collected by the cleaning member. Therefore, the surface of the intermediate transfer roller as well as the non-transfer surface of the belt member can be simultaneously cleaned.

  According to the present invention, the toner adhering to the non-transfer surface is cleaned immediately before the drive roller, so that it is possible to provide an image forming apparatus capable of stabilizing the intermediate transfer belt drive and preventing image defects and transfer defects. .

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 direction corresponds to the front of the printer 1 and the left direction corresponds to the back.
As shown in the figure, a sheet cassette 3 is arranged at the lower part of the apparatus main body 2, and sheets P before image formation are accommodated in the cassette 3 in a stacked state. It is separated and sent from the cassette 3 in the right direction.

The paper P sent out from the cassette 3 is transported toward the left of the main body 2 through the paper transport path 4. Inside the main body 2, a registration roller 5, an image forming unit 6, a transfer unit 17, and a fixing unit 18 are sequentially arranged on the downstream side when viewed in the paper transport direction, and the paper P discharged from the fixing unit 18. Is discharged to the paper discharge tray 22 through the paper transport path 20.
Here, the image forming unit 6 of the present embodiment includes four image forming units 6M, 6C, 6Y, and 6B.

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

Specifically, each unit 6M, 6C, 6Y, 6B is provided with a photosensitive drum (image carrier) 7 that carries a visible image (toner image) of each corresponding color. Each drum 7 is rotatably installed with respect to the main body 2 and is driven counterclockwise in the figure by a drive motor (not shown).
Further, at appropriate positions around each drum 7, a corresponding charger 8, exposure device (LED print head unit or the like) 9, developing device 10, primary transfer roller (intermediate transfer roller) 12, and rubbing roller 13. Is provided.

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

Thereby, a toner image corresponding to the electrostatic latent image by the exposure device 9 is developed on the surface of each drum 7. The toner images formed on the drums 7 are transferred to a sheet via an intermediate transfer belt (belt member) 14.
Specifically, the belt 14 is an endless belt in which both ends of a dielectric resin sheet material are overlapped and joined, or a seamless belt without a seam, as shown in FIG. Further, the belt is wound between the driving roller 15 and the driven roller 16 and runs clockwise in FIG.

In addition, as a sheet material made of dielectric resin, for example, a high resistance polymer dielectric resin sheet such as a sheet made of polyethylene terephthalate resin (PET sheet) or a sheet made of polyvinylidene fluoride resin (PVDF sheet) can be used. The volume resistivity is 10 ⁹ Ωcm, and the surface resistivity of the back surface (non-transfer surface) 14b opposite to the front surface (transfer surface) 14a is 10 ¹¹ Ωcm.

  Further, the belt 14 runs between the drum 7 and the primary transfer roller 12, whereby the toner images formed on the drums 7 are sequentially transferred onto the surface 14a, and one page of toner is transferred. Synthesized as an image. Thereafter, the toner image on the front surface 14 a is secondarily transferred to the paper P sent from the registration roller 5 by the transfer unit 17 and transferred toward the fixing unit 18.

  On the other hand, the rubbing roller 13 is disposed on the upstream side of the charger 8 when viewed in the rotation direction of the drum 7. The roller 13 is configured so as to be able to contact the surface of each corresponding drum 7, and this surface is polished by being driven counterclockwise in the figure by a drive motor. The toner remaining on each drum 7 is removed by a cleaning device (not shown).

  Next, the above-described image forming unit 6 and the like are electrically connected to a controller (main ECU) 50 (FIG. 3). The controller 50 is an element that functions as a computer, and has hardware resources such as a CPU and a memory. The input port 40 is configured so that image data to be printed can be received from the outside, and this image data is obtained by converting various images such as characters, signs, figures, symbols, diagrams, and patterns into data. is there. Based on this data, the controller 50 executes a predetermined program using hardware resources. Thereby, an electrostatic latent image is formed on the surface of the drum 7 through charging and exposure, and the toner image is developed.

By the way, in this embodiment, the back surface 14 b of the belt 14 is cleaned in the vicinity of the drive roller 15.
More specifically, as shown in FIG. 2, when viewed in the running direction of the belt 14, a rear surface cleaning roller (cleaning member) is disposed downstream of the primary transfer roller 12 and upstream of the drive roller 15 of the unit 6B. ) 30 is arranged.

The front surface of the cleaning roller 30 is in contact with the back surface 14b. When a driving motor (not shown) is driven by a signal from the roller driving unit 52 in FIG. 3, the cleaning roller 30 is driven clockwise to clean the back surface 14b. Execute.
Specifically, the roller driving unit 52 outputs a driving signal to the motor during the above-described image formation, in other words, before the toner image on the drum 7 is primarily transferred to the surface 14a. A voltage control unit (voltage control means) 54 generates a toner recovery electric field from the back surface 14b toward the cleaning roller 30.

  More specifically, for example, when each of the drums 7 having a diameter of 30 mm is used, the interval between them is 100 mm, the peripheral speed V1 is 200 mm / sec, the dark potential of the drum 10 is +350 V, and positively charged toner is used. Is assumed. In addition, a φ10 mm metal core is used for the cleaning roller 30, the distance from the primary transfer roller 12 of the unit 6 </ b> B is 20 mm, and the peripheral speeds V <b> 2 of the roller 30 and the driving roller 15 are 200.2 mm / sec.

Then, before the primary transfer is started, the voltage control unit 54 applies a voltage of +800 V to the primary transfer roller 12 having the same polarity as the toner and larger than the dark potential of the drum 10. When a voltage of −200 to −300 V, which is opposite to the toner, is applied to the belt 30, a current of about −2 to −3 μA (1 μA = 1.0 × 10 ⁻⁶ A) is applied to the belt 30 toward the roller 30. It flows via 14.

Accordingly, even if the toner leaks from the developing device 10 and adheres to the back surface 14b of the belt 14, the toner is collected from the back surface 14b to the cleaning roller 30.
Even if toner adheres to the surface of the primary transfer roller 12, the toner moves to the back surface 14b and is then collected by the cleaning roller 30 through the back surface 14b. The toner on the surface 14 a is collected by the drum 7 due to the potential difference between the transfer roller 12 and the drum 7 described above.

Returning again to FIG. 2, the blade 32 polishes the surface of the roller 30, and the toner scraped off from this surface is collected in a collection container 34.
Thereafter, during primary transfer, a negative voltage is applied to the primary transfer roller 12, and the cleaning roller 30 is grounded.
In the printer 1 described above, the paper P is separated and sent from the cassette 3 one by one, and the paper P reaches the registration roller 5. The roller 5 feeds the paper P toward the transfer unit 17 while correcting the oblique feeding of the paper P and measuring the timing of the image transfer operation by each drum 7, the transfer roller 12, and the like.

In the printer 1, the laser beam irradiation by the exposure device 9 is controlled. As a result, an electrostatic latent image of the original image is formed on each drum 7 in the image forming unit 6, and then a toner image is formed on each drum 7 from this latent image. At this time, the back surface 14 b of the belt 14 is formed. Is cleaned.
Subsequently, the toner image on the drum 7 is transferred onto the paper P via the belt 14. The sheet P is fed toward the fixing unit 18 with an unfixed toner image carried thereon, and after a desired image is formed, the sheet P is discharged to the tray 22 through the conveyance path 20.

As described above, according to this embodiment, the intermediate transfer belt 14 is wound between the driving roller 15 and the driven roller 16 and travels between the drum 7 and the primary transfer roller 12. The toner image is transferred to the paper through the surface 14a by the driving.
Here, the back surface cleaning roller 30 abuts on the back surface 14b and cleans the back surface 14b. This roller 30 is downstream of the transfer roller 12 of the unit 6B in the traveling direction of the belt 14 and is connected to the drive roller 15. Arranged upstream. Therefore, since the toner adhering to the back surface 14b is cleaned immediately before the driving roller 15, the back surface 14b does not slip with respect to the driving roller 15, and the driving roller 15 is compared with the conventional cleaning in the secondary transfer position. It is possible to prevent a decrease in driving force and to prevent image defects and transfer defects.

  In addition, the voltage control unit 54 generates a toner recovery electric field from the back surface 14b toward the cleaning roller 30, and at the time of image formation, the toner attached to the back surface 14b is actively collected by the cleaning roller 30. The driving force of the driving roller 15 does not decrease even during the subsequent primary transfer. As a result, the reliability of the printer 1 is improved.

  Further, a voltage having the same polarity as the toner is applied to the primary transfer roller 12, and a voltage having a polarity opposite to that of the toner is applied to the cleaning roller 30. Therefore, current flows from the transfer roller 12 to the cleaning roller 30 via the belt 14, and the toner attached to the back surface 14 b is quickly collected by the roller 30. In addition, since it is not necessary to provide a counter electrode on the opposite side of the cleaning roller 30 with the belt 14 in between, the load on the belt 14 does not fluctuate.

Furthermore, since the primary transfer roller 12 is applied with a voltage that moves the toner adhering to the surface to the back surface 14b, the toner adhering to the surface of the transfer roller 12 is also quickly collected by the cleaning roller 30, In addition to the back surface 14b, the surface of the primary transfer roller 12 can be simultaneously cleaned.
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, a part of the configurations of the above embodiments can be omitted or arbitrarily combined so as to be different from the above.

  For example, the voltage control unit 54 of the present embodiment generates a toner recovery electric field at the time of image formation, but may generate an electric field when the printer 1 is started up. Further, although the cleaning roller 30 of the present embodiment is configured to be drivable, it may be driven with respect to the belt 14 as long as the frictional force with the back surface 14b is sufficient. Further, a resistance layer such as alumite or a resin layer may be formed on the surface of the roller 30 to improve the toner collecting ability.

  Further, the image carrier of the present invention is not limited to four photosensitive drums, and the transfer belt of the present invention can be applied to a printer capable of only monochrome printing. Further, in the above embodiment, an example in which the image forming apparatus is embodied in a printer is shown. However, the image forming apparatus of the present invention is naturally applicable to a multifunction machine, a copier, a facsimile machine, and the like.

1 is a schematic configuration diagram of an image forming apparatus of an embodiment. It is a principal part enlarged view of the apparatus of FIG. It is a control block diagram of the apparatus of FIG.

Explanation of symbols

1 Printer (image forming device)
6 Image forming unit 7 Photosensitive drum (image carrier)
12 Primary transfer roller (intermediate transfer roller)
14 Intermediate transfer belt (belt member)
14a Surface (transfer surface)
14b Back side (non-transfer side)
15 Driving roller 16 Driven roller 30 Back surface cleaning roller (cleaning member)
50 controller 54 voltage control unit (voltage control means)

Claims (3)

An image carrier that has an image carrier and develops a latent image on the image carrier with toner by driving to form a toner image;
Driven by a driving roller and a driven roller and running between the image carrier and the intermediate transfer roller, the toner image is transferred to a transfer surface by the drive, and transferred to a sheet through the transfer surface. A belt member;
A cleaning member disposed on the downstream side of the intermediate transfer roller and the upstream side of the driving roller as viewed in the traveling direction of the belt member, and abutting against a non-transfer surface opposite to the transfer surface;
An image forming apparatus comprising: a voltage control unit that generates an electric field from the non-transfer surface toward the cleaning member during image formation so as to collect the toner attached to the non-transfer surface. The image forming apparatus according to claim 1,
The voltage control unit applies a voltage having the same polarity as that of the toner to the intermediate transfer roller during the image formation, and applies a voltage having a polarity opposite to that of the toner to the cleaning member. An image forming apparatus that generates an electric field from a non-transfer surface toward the cleaning member. The image forming apparatus according to claim 2,
The image forming apparatus according to claim 1, wherein the voltage control unit applies a voltage to the intermediate transfer roller to move the toner attached to the surface of the intermediate transfer roller to the non-transfer surface.

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