JP2005084158A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus adopting an intermediate transfer system, which can shorten the time for applying a bias voltage and which can reduce the electric power consumption, without deteriorating the cleaning performance for a secondary transfer roller. <P>SOLUTION: The image forming apparatus adopting the intermediate transfer system includes a photoreceptor 1, an intermediate transfer belt 7, the secondary transfer roller 9, and a secondary transfer roller cleaning device 10. The secondary transfer roller cleaning device 10 includes a secondary transfer roller cleaning brush 11 and a secondary transfer bias voltage apply power supply 13. The secondary transfer roller cleaning brush 11 is freely separatable from the secondary transfer roller 9, and the bias voltage, having the same polarity as toner, is applied to the secondary transfer roller 9 by the secondary transfer bias voltage apply power supply 13. The secondary transfer roller cleaning brush 11 is separated from the secondary transfer roller 9, and the bias voltage having the same polarity as that of the toner is applied to the secondary transfer roller 9 for a period of time, equal to or larger than the period of time required for the secondary transfer roller 9 to rotate by one turn. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that employs an electrophotographic system such as a laser printer or an electrophotographic copying machine, and more particularly, a toner image formed on a photoconductor is primarily transferred to an intermediate transfer body and then secondarily transferred to a sheet. The present invention relates to an image forming apparatus employing an intermediate transfer system for forming an image.

Conventionally, in an image forming apparatus employing an electrophotographic method, a toner image formed on a photoconductor is not directly transferred onto a sheet, but a toner image formed on the photoconductor is temporarily transferred to an intermediate transfer body, and thereafter There is known an image forming apparatus that employs an intermediate transfer method in which a toner image formed on an intermediate transfer member is secondarily transferred onto a sheet to form an image on the sheet.
By adopting such an intermediate transfer method, it is possible to transfer a plurality of color toner images to an intermediate transfer body in order and then transfer the plurality of color toner images to a sheet at once. Compared with the method of transferring directly to a sheet sequentially, a toner image of a plurality of colors can be stably transferred to a sheet, which is suitable for a color printer and a color copying machine.

Therefore, a case where the intermediate transfer method is applied to a color printer will be specifically described with reference to FIG.
First, the surface of the photoconductor 1 is charged to a predetermined potential by the charging device 2, and then the surface of the photoconductor 1 is exposed by an exposure device 3 such as a leather unit, and a predetermined electrostatic latent image is formed on the surface of the photoconductor 1. Is done. Then, magenta toner is attached to the electrostatic latent image and developed by the magenta developing device 4M mounted on the rotary developing unit 4.
The magenta toner image formed on the photoconductor 1 is applied with a primary transfer bias voltage having a polarity opposite to that of the toner when the photoconductor 1 rotates and reaches the position of the primary transfer roller 8. Then, it is transferred to the intermediate transfer belt 7.
The magenta toner remaining on the surface of the photoconductor 1 without being transferred to the intermediate transfer belt 7 is removed from the surface of the photoconductor 1 by the photoconductor cleaning device 6 having the photoconductor cleaning brush 6a and the photoconductor cleaning blade 6b. Is done.

Again, the surface of the photoconductor 1 is charged to a predetermined potential by the charging device 2 and then exposed by the exposure device 3 to form a predetermined electrostatic latent image on the surface of the photoconductor 1. Then, cyan toner is attached to the electrostatic latent image and developed by the cyan developing device 4C mounted on the rotary developing unit 4.
When the photoreceptor 1 rotates and reaches the position of the primary transfer roller 8, the primary transfer bias voltage is applied to the primary transfer roller 8 and the cyan toner image formed on the photoreceptor 1 is transferred to the intermediate transfer belt 7. Transcribed.
The cyan toner remaining on the surface of the photoconductor 1 is removed from the surface of the photoconductor 1 by the photoconductor cleaning device 6.
Thereafter, similarly, a yellow toner image and a black toner image are sequentially formed on the surface of the photoreceptor 1 and transferred to the intermediate transfer belt 7. Incidentally, 4Y is a yellow developing device mounted on the rotary developing unit 4, and 5 is a black developing device.

On the other hand, the paper is supplied from the paper feed cassette 15 and conveyed to the secondary transfer roller 9 position by a conveying roller or the like.
As described above, the magenta, cyan, yellow and black toner images formed on the intermediate transfer belt 7 are transferred to the secondary transfer roller 9 when the intermediate transfer belt 7 moves and reaches the position of the secondary transfer roller 9. Since a secondary transfer bias voltage having a polarity opposite to that of the toner is applied, the toner image is transferred onto the conveyed paper.
Thereafter, the sheet on which the toner image has been transferred is pressurized and heated in the fixing device 16, the toner image is fixed on the sheet, a color image is formed, and the sheet is discharged out of the color printer.
The toner remaining on the surface of the intermediate transfer belt 7 is removed from the surface of the intermediate transfer belt 7 by the intermediate transfer belt cleaning device 14 having the intermediate transfer belt cleaning blade 14a.

Here, the transfer device of the color printer includes an intermediate transfer belt 7, a primary transfer roller 8, and a secondary transfer roller 9, and in order to prevent the back side of the paper from being stained with toner, generally, a secondary transfer belt is used. A secondary transfer roller cleaning device 10 having a transfer roller cleaning brush 11, a brush wiping member 12, and a secondary transfer bias voltage application power supply 13 is provided.
Then, the toner that unexpectedly adheres to the surface of the secondary transfer roller 9 by the surface of the intermediate transfer belt 7 coming into contact with the surface of the secondary transfer roller 9 or the surface of the paper jammed when a paper jam occurs. Is removed from the surface of the secondary transfer roller 9 by the secondary transfer roller cleaning device 10.

As described above, in an image forming apparatus employing the intermediate transfer method, a cleaning device 10 having a secondary transfer roller cleaning brush 11, a brush wiping member 12, and a secondary transfer bias voltage application power source 13 is generally provided. However, in the conventional image forming apparatus, the secondary transfer roller cleaning brush 11 is always in contact with the secondary transfer roller 9 and rotated, and the secondary transfer roller 9 has the same polarity as that of the toner. The toner was removed from the surface of the secondary transfer roller 9 by alternately applying a secondary transfer bias voltage having a reverse polarity.
The image forming apparatus is configured to efficiently remove the toner from the surface of the secondary transfer roller 9 by appropriately setting the outer diameter, peripheral speed, and the like of the secondary transfer roller 9 and the secondary transfer roller cleaning brush 11. Has also been proposed (see Patent Document 1).

  Although the target is an intermediate transfer member, the rotary fur brush is selectively brought into contact with the intermediate transfer roller, and the toner remaining on the surface of the intermediate transfer roller is disturbed and dispersed by the rotary fur brush to which a bias voltage is applied. After that, an image forming apparatus has also been proposed in which a bias voltage is applied to the intermediate transfer roller to efficiently remove the toner from the surface of the intermediate transfer member (see Patent Document 2).

JP 2002-91191 A JP 2001-249549 A

  However, when the secondary transfer roller cleaning brush 11 is always in contact with the secondary transfer roller 9 and rotated as in the prior art, the toner image formed on the intermediate transfer belt 7 is secondarily transferred to a sheet. Alternatively, if a paper jam occurs before that, the toner image is directly transferred from the intermediate transfer belt 7 to the secondary transfer roller 9, so that a large amount of toner easily adheres to the secondary transfer roller cleaning brush 11. Further, even if a large amount of toner adhering to the secondary transfer roller cleaning brush 11 is wiped off by the brush wiping member 12 or a bias voltage is applied to the secondary transfer roller cleaning brush 11, it is extremely difficult to completely remove the toner. As a result, the cleaning performance of the secondary transfer roller 9 was lowered.

  In addition, when the secondary transfer bias voltage having the same polarity and reverse polarity as the toner is alternately applied to the secondary transfer roller 9 as in the prior art, it is necessary to generate a secondary transfer bias voltage of both polarities. The cost of the secondary transfer bias voltage application power source 13 is increased accordingly, and in order to apply the bipolar secondary transfer bias voltage, the time for applying the bias voltage is also increased, and the power consumption is increased. It became a thing.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to apply a large amount of toner to the secondary transfer roller cleaning brush even when a paper jam occurs. Does not wear, does not degrade the cleaning performance of the secondary transfer roller, reduces the cost of the secondary transfer bias voltage application power supply, shortens the time for applying the bias voltage, and reduces power consumption. An object of the present invention is to provide an image forming apparatus that employs an intermediate transfer method.

  In order to achieve the above object, an image forming apparatus employing the intermediate transfer method of the present invention includes a photoconductor on which a toner image is formed, an intermediate transfer belt on which the toner image is primarily transferred from the photoconductor, and an intermediate transfer belt. Image forming comprising: a secondary transfer roller that sandwiches a sheet with a transfer belt and secondarily transfers a toner image from the intermediate transfer belt to the sheet; and a secondary transfer roller cleaning device that cleans the surface of the secondary transfer roller The secondary transfer roller cleaning device comprises: a secondary transfer roller cleaning brush that rubs the surface of the secondary transfer roller; a secondary transfer bias voltage application power source that applies a bias voltage to the secondary transfer roller; The secondary transfer roller cleaning brush is separable from the secondary transfer roller, and the secondary transfer bias voltage By applying power, characterized in that so as to apply only bias voltage of the same polarity as the toner to the secondary transfer roller.

  In order to efficiently remove the toner adhering to the surface of the secondary transfer roller, the secondary transfer roller cleaning brush is separated from the secondary transfer roller, and the secondary transfer bias voltage application power source supplies toner to the secondary transfer roller. A bias voltage having the same polarity as that of the secondary transfer roller is applied for a time required for one rotation of the secondary transfer roller.

  In order to remove the toner mechanically adhered to the surface of the secondary transfer roller, a bias voltage having the same polarity as the toner is applied to the secondary transfer roller, and then the secondary transfer roller cleaning brush is applied to the surface of the secondary transfer roller. Abut and rotate.

The image forming apparatus employing the intermediate transfer system of the present invention also includes a photoconductor on which a toner image is formed, an intermediate transfer belt on which the toner image is primarily transferred from the photoconductor, and a sheet sandwiched with the intermediate transfer belt. An image forming apparatus comprising: a secondary transfer roller that secondarily transfers a toner image onto a sheet from an intermediate transfer belt; and a secondary transfer roller cleaning device that cleans the surface of the secondary transfer roller, The secondary transfer roller cleaning device comprises: a secondary transfer roller cleaning brush that rubs the surface of the secondary transfer roller; and a secondary transfer bias voltage application power source that applies a bias voltage to the secondary transfer roller. It is necessary for the secondary transfer roller to make one rotation of a bias voltage having the same polarity as the toner to the secondary transfer roller by the secondary transfer bias voltage application power source. Applied above while, then, a secondary transfer roller bias voltage having a polarity opposite to that of toner to the secondary transfer roller is applied less than time required for one rotation, and repeating the steps of.

  In order to efficiently pull the toner adhering to the secondary transfer roller cleaning brush back to the surface of the secondary transfer roller, the secondary transfer roller rotates once when a bias voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller. In the meantime, it is preferable that the secondary transfer roller cleaning brush is set so as to make one rotation or more.

  Furthermore, it is more preferable to dispose the brush wiping member that contacts the secondary transfer roller cleaning brush because the toner attached to the secondary transfer roller cleaning brush can be removed by the brush wiping member.

  Hereinafter, an embodiment of an image forming apparatus employing the intermediate transfer method of the present invention will be specifically described with reference to the drawings.

As shown in FIG. 1, an image forming apparatus 31 according to an embodiment of the present invention also includes a photosensitive member 1, a charging device 2, an exposure device 3, developing devices 4 and 5, a photosensitive member cleaning device 6, an intermediate transfer belt 7, and a primary. The image forming apparatus includes a transfer roller 8, a secondary transfer roller 9, a paper feed cassette 15, a fixing device 16, and the like.
In the same manner as described above, toner images of a plurality of colors are sequentially formed on the surface of the photoreceptor 1. When the photoreceptor 1 reaches the position of the primary transfer roller 8, the toner images of the plurality of colors are sequentially transferred to the intermediate transfer belt 7. Is done. The toner images of a plurality of colors formed on the intermediate transfer belt 7 are transferred onto the conveyed paper when the intermediate transfer belt 7 reaches the secondary transfer roller 9 position. Thereafter, the sheet on which the toner image has been transferred is fixed by the fixing device 16 and discharged out of the image forming device 31.

In the image forming apparatus 31 of the present embodiment, in order to prevent the back side of the paper from being stained with toner, as shown in FIG. 2, the secondary transfer roller cleaning brush 11, the brush wiping member 12, and the secondary transfer bias voltage application. A secondary transfer roller cleaning device 32 having a power source 33 is provided so that the toner adhering to the surface of the secondary transfer roller 9 is removed from the surface of the secondary transfer roller 9 by the secondary transfer roller cleaning device 32. It has become.
Here, unlike the conventional case, the secondary transfer roller cleaning brush 11 is separable from the secondary transfer roller 9. Here, the secondary transfer roller cleaning brush 11 is preferably separated from the secondary transfer roller 9 by about 2 to 3 mm.

In the image forming apparatus 31 of the present embodiment, after the toner image formed on the intermediate transfer belt 7 is secondarily transferred to the paper, first, the secondary transfer roller cleaning brush 11 is separated from the surface of the secondary transfer roller 9. Then, a bias voltage having the same polarity as the toner is applied to the secondary transfer roller 9 by the secondary transfer bias voltage application power source 33. As shown in FIG. 3, the time for applying the bias voltage having the same polarity as the toner to the secondary transfer roller 9 is at least longer than the time required for the secondary transfer roller 9 to make one rotation. It is preferable that the time is not less than the time required for one rotation of the next transfer roller 9 and not more than the time required for three rotations.
The time for applying the bias voltage is defined in this way, as shown in FIG. 4, the time required for the secondary transfer roller 9 to make one rotation, and the bias voltage having the same polarity as the toner is applied to the secondary transfer roller 9. This is because if applied, about 90% of the toner adhering to the surface of the secondary transfer roller 9 is removed. Here, the charge amount of the toner used in the experiment is about −25 μC / g, the surface resistance of the intermediate transfer belt 7 is 10 ⁺¹³ Ω / cm ² or more, the volume resistance is 1.0 × 10 ⁺¹¹ Ωcm, and the secondary transfer roller 9. The resistance was 10 ⁺⁸ Ω.
By applying a bias voltage having the same polarity as the toner to the secondary transfer roller 9, the toner adhering to the surface of the secondary transfer roller 9 is pulled back to the surface of the intermediate transfer belt 7 and removed by the intermediate transfer belt cleaning device 14. Is done.

As shown in FIG. 4, about 10% of the toner remaining on the surface of the secondary transfer roller 9 is hardly removed even when a bias voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 9. 9 It is thought that there are many that are mechanically attached to the surface.
Therefore, the secondary transfer roller cleaning brush 11 is then brought into contact with the surface of the secondary transfer roller 9 and rotated to mechanically scrape and remove the toner remaining on the surface of the secondary transfer roller 9.

  In the image forming apparatus 31 of this embodiment, a bias voltage having the same polarity as the toner is applied to the secondary transfer roller 9 in a state where the secondary transfer roller cleaning brush 11 is separated from the surface of the secondary transfer roller 9. Therefore, the toner does not adhere so much to the secondary transfer roller cleaning brush 11, and the toner attached to the secondary transfer roller cleaning brush 11 is transferred by the brush wiping member 12 in contact with the secondary transfer roller cleaning brush 11. Can be fully paid off.

As shown in FIG. 1, an image forming apparatus 51 according to an embodiment of the present invention also includes a photoreceptor 1, a charging device 2, an exposure device 3, developing devices 4 and 5, a photoreceptor cleaning device 6, an intermediate transfer belt 7, and a primary. The image forming apparatus includes a transfer roller 8, a secondary transfer roller 9, a paper feed cassette 15, a fixing device 16, and the like.
In the image forming apparatus 51, the method for forming an image on a sheet is the same as that in the image forming apparatus 31.

Also in the image forming apparatus 51 of the present embodiment, in order to prevent the back side of the sheet from being stained with toner, as shown in FIG. 5, the secondary transfer roller cleaning brush 11, the brush wiping member 12, and the secondary transfer bias voltage application. A secondary transfer roller cleaning device 52 having a power source 13 is provided so that toner adhering to the surface of the secondary transfer roller 9 is removed from the surface of the secondary transfer roller 9 by the secondary transfer roller cleaning device 52. It has become.
Here, the secondary transfer roller cleaning brush 11 is always in contact with the secondary transfer roller 9 as in the prior art.

In the image forming apparatus 51 of the present embodiment, after the toner image formed on the intermediate transfer belt 7 is secondarily transferred to a sheet, first, the toner and the toner are transferred to the secondary transfer roller 9 by the secondary transfer bias voltage application power source 13. Apply a bias voltage of the same polarity. As shown in FIG. 6, the time for applying the bias voltage having the same polarity as the toner to the secondary transfer roller 9 is at least longer than the time required for the secondary transfer roller 9 to make one rotation. It is preferable that the time is not less than the time required for one rotation of the next transfer roller 9 and not more than the time required for three rotations.
The reason why the time for applying the bias voltage is defined in this way is the same as in the first embodiment.
By applying a bias voltage having the same polarity as the toner to the secondary transfer roller 9, the toner adhering to the surface of the secondary transfer roller 9 is pulled back to the surface of the intermediate transfer belt 7 and removed by the intermediate transfer belt cleaning device 14. Is done.

Next, a bias voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 9 by the secondary transfer bias voltage application power source 13. As shown in FIG. 6, the time for applying a bias voltage having a polarity opposite to that of the toner to the secondary transfer roller 9 is less than the time for which the secondary transfer roller 9 rotates once.
However, it is preferable that the secondary transfer roller cleaning brush 11 be rotated once or more while the secondary transfer roller 9 is rotated once. In particular, as shown in FIG. 7, the secondary transfer roller cleaning brush 11 is rotated three times. It is preferable to set the speed ratio and the roller diameter ratio between the secondary transfer roller 9 and the secondary transfer roller cleaning brush 11 within a region indicated by hatching so that the secondary transfer roller 9 is less than one rotation.
By applying a bias voltage having a polarity opposite to that of the toner to the secondary transfer roller 9, the toner attached to the secondary transfer roller cleaning brush 11 is pulled back to the surface of the secondary transfer roller 9.

As described above, according to the image forming apparatus 51 of the present embodiment, the secondary transfer roller 9 and the secondary transfer roller are alternately applied to the secondary transfer roller 9 by applying a bias voltage having the same polarity and reverse polarity as the toner. The toner can be efficiently removed from the cleaning brush 11.
Furthermore, since the toner adhering to the secondary transfer roller cleaning brush 11 can be wiped off by the brush wiping member 12, the toner adhering to the secondary transfer roller cleaning brush 11 can be minimized.

As described above, in the image forming apparatus of the present invention, when the secondary transfer roller cleaning brush 11 is separable from the secondary transfer roller 9, a large amount of toner is applied to the secondary transfer roller cleaning brush 11. The cleaning performance of the secondary transfer roller 9 is not deteriorated, and only the bias voltage having the same polarity as the toner is applied to the secondary transfer roller 9, so that the cost of the secondary transfer bias voltage application power source 33 is greatly increased. The time for applying the bias voltage can be greatly shortened, and the power consumption can be reduced.
Further, even when the secondary transfer roller cleaning brush 11 is always in contact with the secondary transfer roller 9, a bias voltage having the same polarity and reverse polarity as the toner is alternately applied to the secondary transfer roller 9 for an appropriate time. As a result, the toner adhering to the secondary transfer roller cleaning brush 11 can be sufficiently removed, the cleaning performance of the secondary transfer roller 9 is not deteriorated, and the time for applying the bias voltage can be shortened. The amount of power can be reduced.

1 is a schematic configuration diagram of an image forming apparatus of the present invention. FIG. 3 is a schematic cross-sectional view of the vicinity of a secondary transfer roller in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing the polarity and application time of a bias voltage applied to a secondary transfer roller in the image forming apparatus shown in FIG. 2. 3 is a graph showing toner removal efficiency from the surface of the secondary transfer roller when a bias voltage having the same polarity and reverse polarity as that of toner is alternately applied to the secondary transfer roller in the image forming apparatus shown in FIG. It is a schematic sectional drawing of the secondary transfer roller vicinity in the image forming apparatus of the other Example of this invention. FIG. 6 is a diagram illustrating the polarity and application time of a bias voltage applied to a secondary transfer roller in the image forming apparatus illustrated in FIG. 5. 6 is a graph showing a region for setting a speed ratio and a roller diameter ratio between a secondary transfer roller and a secondary transfer roller cleaning brush in the image forming apparatus shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 7 Intermediate transfer belt 9 Secondary transfer roller 11 Secondary transfer roller cleaning brush 12 Brush wiping member 13 Secondary transfer bias voltage application power source 31 Image forming device 32 Secondary transfer roller cleaning device 33 Secondary transfer bias voltage application power source 51 Image forming device 52 Secondary transfer roller cleaning device

Claims (6)

  A photoconductor on which a toner image is formed, an intermediate transfer belt on which the toner image is primarily transferred from the photoconductor, and a sheet sandwiched between the intermediate transfer belt and the toner image is secondarily transferred from the intermediate transfer belt to the sheet. An image forming apparatus that employs an intermediate transfer system that includes a secondary transfer roller and a secondary transfer roller cleaning device that cleans the surface of the secondary transfer roller, wherein the secondary transfer roller cleaning device includes the secondary transfer roller cleaning device. A secondary transfer roller cleaning brush for rubbing the surface of the secondary transfer roller; and a secondary transfer bias voltage application power source for applying a bias voltage to the secondary transfer roller. The secondary transfer roller can be separated from the transfer roller, and the secondary transfer bias voltage application power source has the same polarity as the toner on the secondary transfer roller. An image forming apparatus of intermediate transfer system employed, characterized in that so as to apply a bias voltage.   The secondary transfer roller cleaning brush is separated from the secondary transfer roller, and the secondary transfer roller is rotated once by applying a bias voltage having the same polarity as the toner to the secondary transfer roller by the secondary transfer bias voltage application power source. 2. The image forming apparatus employing the intermediate transfer system according to claim 1, wherein the image is applied for a time or more.   3. The intermediate according to claim 2, wherein after applying a bias voltage having the same polarity as the toner to the secondary transfer roller, the secondary transfer roller cleaning brush is brought into contact with the surface of the secondary transfer roller and rotated. An image forming apparatus employing a transfer method.   A photoconductor on which a toner image is formed, an intermediate transfer belt on which the toner image is primarily transferred from the photoconductor, and a sheet sandwiched between the intermediate transfer belt and the toner image is secondarily transferred from the intermediate transfer belt to the sheet. An image forming apparatus that employs an intermediate transfer system that includes a secondary transfer roller and a secondary transfer roller cleaning device that cleans the surface of the secondary transfer roller, wherein the secondary transfer roller cleaning device includes the secondary transfer roller cleaning device. A secondary transfer roller cleaning brush for rubbing the surface of the secondary transfer roller; and a secondary transfer bias voltage application power source for applying a bias voltage to the secondary transfer roller. A bias voltage having the same polarity as the toner is applied to the secondary transfer roller for a time required for one rotation of the secondary transfer roller, A secondary transfer roller bias voltage having a polarity opposite to that of toner to the next transfer roller is applied less than time required for one rotation, the image forming apparatus of intermediate transfer system employed, wherein repeating the steps of. The secondary transfer roller cleaning brush is set to make one rotation or more while the secondary transfer roller makes one rotation when a bias voltage having a polarity opposite to that of toner is applied to the secondary transfer roller. Item 5. An image forming apparatus employing the intermediate transfer method according to Item 4.   6. An image forming apparatus employing an intermediate transfer system according to claim 1, further comprising a brush wiping member that contacts the secondary transfer roller cleaning brush.

Images