JP2000321881A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image with less color slippage by restraining the circumferential speed change of an intermediate transfer body as a result of attaching and detaching of a cleaning roller. SOLUTION: This image forming device, as a typical structure is provided with the image carrier 1 carrying the electrostatic latent image, developing means (applying roller, sleeve and blade) for developing this latent image by toner, an intermediate transfer belt transferring the developed toner image by overlapping one over the other, the secondary transfer roller 11a transferring the toner image on the intermediate transfer to a sheet, and the cleaning roller 21a removing the residual toner on the intermediate transfer belt. Meanwhile, the cleaning roller 21a, imparting the electric charge in polarity opposite to the secondary transfer roller 11a, applies the rotary drive at circumferential speed approximately same as the intermediate transfer belt 5a to the cleaning roller 21a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type image forming apparatus such as a color copying machine or a color printer using an intermediate transfer member. The present invention relates to an image forming apparatus in which the image quality is reduced.

[0002]

2. Description of the Related Art An example of a conventional image forming apparatus will be described with reference to the drawings. FIG. 4 is a cross-sectional view illustrating a transfer section of a conventional image forming apparatus, FIG. 5 is a view illustrating a state in which a secondary transfer unit is in contact with an intermediate transfer member, and FIG. 6 is a diagram in which a cleaning roller is in contact with an intermediate transfer member. FIG. 7 is a view for explaining the movement of the toner.

In FIG. 4, electrostatic latent images of respective colors formed on the image carrier 101 are developed by developing means (not shown). The image carrier 101 is an intermediate transfer belt 102 of the intermediate transfer body 102.
a is pressed by the primary transfer roller 103, and the formed toner image is transferred in a superimposed manner. Intermediate transfer belt 10
2a is stretched by a driving roller 104, rollers 105 and 106.

As shown in FIG. 5, a secondary transfer unit 107 is disposed near the intermediate transfer member 102,
As a result, the secondary transfer roller 107a is pressed against the intermediate transfer belt 102a. The toner image primarily transferred onto the intermediate transfer belt 102a is transferred from the registration roller pair 110 to the intermediate transfer belt 102a and the secondary transfer roller 107.
The transfer is collectively secondary-transferred to the transfer material sent to the nip portion with the portion a.

Thereafter, as shown in FIG. 6, the cleaning roller 108a is pressed against the intermediate transfer belt 102a by rotating the cleaning unit 108 by the separation / contact cam 108b. Here, a DC bias having a polarity opposite to that of the secondary transfer roller 107a and an AC bias superimposed on the DC bias are applied to the cleaning roller 108a, and a charge having a polarity opposite to that of the secondary transfer is applied to the toner. The toner having the opposite polarity charge is electrostatically attached to the image carrier 101, and thereafter is collected by the cleaning device 109 of the image carrier 101 as shown in FIG.

[0006]

However, in the above-described conventional example, the cleaning roller 108a is connected to the intermediate transfer belt
The rotation resistance of the intermediate transfer belt 102a when the cleaning roller 108a is in contact with the cleaning roller 108a is different from that when the cleaning roller 108a is in contact with the cleaning roller 108a. In the case where image formation is continuously performed, the driving roller 104 and the cleaning roller 108 perform the primary transfer of the first color for the next image formation while performing secondary transfer and cleaning.
The belt tension between the first and second colors changes during the first and second colors, and the transfer state of the primary transfer roller 103 fluctuates, causing color misregistration.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of suppressing a change in the peripheral speed of an intermediate transfer member due to separation and contact of a cleaning roller and obtaining a high-quality image with little color shift.

[0008]

In order to solve the above-mentioned problems, a typical configuration of an image forming apparatus according to the present invention comprises an image carrier for carrying an electrostatic latent image, and the latent image formed by toner. Developing means for developing, an intermediate transfer member for transferring the developed toner image in a superimposed manner, secondary transfer means for transferring the toner image on the intermediate transfer member to a sheet, and residual toner on the intermediate transfer member An image forming apparatus having a cleaning unit that removes toner, wherein the cleaning unit is a rotatable cleaning roller that applies a charge opposite to that of the secondary transfer unit, and that the cleaning roller is The present invention is characterized in that a rotational drive having a peripheral speed substantially equal to that of the intermediate transfer member is given.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment, and FIG. 2 is a partially enlarged view illustrating a transfer unit of the image forming apparatus. In the present embodiment, a four-color full-color laser beam printer employing an electrophotographic method will be described as an image forming apparatus.

(Overall Configuration) Image forming apparatus A shown in FIG.
Forms an electrostatic latent image by uniformly charging the image carrier 1 with the primary charging device 1a and then exposing the image carrier 1 with the optical unit 3. The optical unit 3 reflects light output from an oscillator (not shown) according to image information by a polygon mirror 3a and irradiates the image carrier 1 via a lens 3b and a mirror 3c. The electrostatic latent image formed on the image carrier 1 is developed by the developing device switching device 2 to generate a toner image.

The developing means switching device 2 has developing means 4 for each color of yellow 4Y, magenta 4M, cyan 4C, and black 4Bk. The developing means 4 is rotated about a shaft 2a to attach the developing means 4 to the image carrier 1. Can be switched to a position opposite to. The developing means 4 applies the toner of each color stored inside to the sleeve 4b by the application roller 4a and the blade 4c.
A thin film is applied to the outer periphery of the image carrier, and a developing bias is applied to perform toner development on the image carrier 1 according to the latent image on the image carrier 1. The toner images of the respective colors formed on the image carrier 1 are primarily transferred in a superimposed manner onto an intermediate transfer belt 5a of an intermediate transfer unit 5 described later. The toner remaining on the image carrier 1 is removed by the cleaning blade 6a and stored in the cleaning cassette 6.

A feed cassette 7 for stacking sheets S is mounted below the image forming apparatus A, and is fed while being separated one by one by a feed roller 7a and a separation roller 7b. The fed sheet is guided to a conveying path 7d by a pair of conveying rollers 7c, and skew is corrected by abutting against a pair of registration rollers 7e.
The conveyance is restarted in synchronization with the operation a.

The toner image primarily transferred to the intermediate transfer belt 5a is transferred to a sheet S by a secondary transfer roller 11a, and then the sheet S is conveyed to a fixing unit 8 by a conveying unit 12. The sheet S is fixed with a toner image by applying heat and pressure by a heating roller 8a and a pressure roller 8b in a fixing unit 8, is conveyed by a conveying path 15 by conveying rollers 13 and 16, and is a device by a discharge roller pair 9. The sheet is discharged to the outside discharge tray 10 and loaded. The transport roller 16 is connected to the discharge roller pair 9 and shares a drive source.

(Intermediate Transfer Unit) Intermediate Transfer Unit 5
Drives the intermediate transfer belt 5a with a driving roller 17, a driven roller 18,
19, it is detachable from the apparatus main body, and rotates in the direction of arrow B in FIG. Then, the intermediate transfer belt 5a is connected to a primary transfer roller.
The toner image of each color formed on the image carrier 1 is superimposed and primary-transferred by applying a voltage having a polarity opposite to that of the toner while bringing the toner image into contact with the image carrier 1 by 20.

During this time, the secondary transfer unit 11 is separated from the intermediate transfer belt 5a, and the secondary transfer roller 11a is not in contact with the intermediate transfer belt 5a. When all toner images have been transferred onto the intermediate transfer belt 5a, the separation / contact cam 11b
Rotates to rotate the secondary transfer unit 11, and the secondary transfer roller 11a is pressed against the intermediate transfer belt 5a.

The secondary transfer roller 11a is driven to rotate at a peripheral speed slightly higher than that of the intermediate transfer belt 5a by a drive motor (not shown). Further, a voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 11a.
a, the toner image primarily transferred onto the pair of registration rollers 7
e, the secondary transfer is collectively performed on the transfer material sent to the nip portion between the intermediate transfer belt 5a and the secondary transfer roller 11a.

In the vicinity of the intermediate transfer unit 5, there is provided a cleaning unit 21 for removing the toner remaining on the intermediate transfer belt 5a. The cleaning unit 21, like the secondary transfer unit 11, is separated from the intermediate transfer belt 5a during the primary transfer.

The cleaning unit 21 has a cleaning roller 21a at one end, is rotatable around a rotation shaft 21b, and has a swing plate 21c at the other end. The driving force of the cleaning roller 21a is transmitted from the pulley 17a of the driving roller 17 via the belt 23, the pulley 21e, the gears 21f and 21g, and is configured to rotate at a peripheral speed substantially equal to that of the intermediate transfer belt 5a. . The peripheral speed here means
This is the average peripheral speed of the nip.

A tension spring 21d is provided near the cleaning roller 21a.
a to the intermediate transfer belt 5a. On the other hand, the separation / contact cam 22 is provided in the apparatus main body, and the intermediate transfer unit 5 is provided.
When the cleaning roller 21a is inserted into the apparatus main body, the swinging plate 21c abuts on the separation / contact cam 22 to keep the cleaning roller 21a separated from the intermediate transfer belt 5a.

When performing the secondary transfer, the secondary transfer unit 11
Similarly to the separation cam 11b, the separation cam 22 of the cleaning unit 21 also rotates to release the swing plate 21c. Then, the cleaning unit 21 rotates by the urging force of the spring 21d,
The cleaning roller 21a is pressed against the intermediate transfer belt 5a with a predetermined pressure. At this time, a DC bias having a polarity opposite to that of the secondary transfer roller 11a and an AC bias superimposed on the DC bias are applied to the cleaning roller 21a, and a charge having a polarity opposite to that of the secondary transfer is applied to the toner. The toner having the opposite polarity charge is electrostatically attached to the image carrier 1 and thereafter collected by the cleaning cassette 6 of the image carrier 1.

As described above, since the cleaning roller 21a is configured to be driven at a peripheral speed substantially equal to that of the intermediate transfer belt 5a, the intermediate transfer is performed when the cleaning roller 21a is in contact with the cleaning roller 21a and when the cleaning roller 21a is in the separated state. There is no difference in the rotational resistance of the belt 5a. Therefore, a change in the peripheral speed of the intermediate transfer belt 5a due to separation and contact of the cleaning roller 21a can be suppressed, and a high-quality image with little color shift can be obtained.

In addition to the image forming apparatus shown in this embodiment, for example, an image carrier for carrying four electrostatic latent images, a developing means for developing the latent images individually with toner of each color, and
An intermediate transfer member for transferring the toner images developed on the plurality of image carriers in a superimposed manner, a secondary transfer means for transferring the toner image on the intermediate transfer member to a sheet, and removing the toner remaining on the intermediate transfer member An image forming apparatus including a cleaning unit that performs cleaning may be used.

[Other Embodiments] In the above embodiment, the cleaning roller 21a is configured to rotate at a peripheral speed substantially equal to that of the intermediate transfer belt 5a, but the secondary transfer roller 11a is rotated by the intermediate transfer belt 5a. If the rotation is performed at a slightly higher peripheral speed, the cleaning roller 21a
Is desirably rotationally driven to be slightly slower than the intermediate transfer belt 5a. This is to cancel the contraction in the circumferential direction of the intermediate transfer belt 5a that has passed the secondary transfer portion, or to cancel the torque fluctuation at the position of the drive roller 17, and drive the belt stably.

In the case where the secondary transfer means is constituted by, for example, a blade and has a resistance to the intermediate transfer belt 5a, the cleaning roller 21a is rotationally driven so as to be slightly faster than the intermediate transfer belt 5a. It is desirable to do. This is the intermediate transfer belt 5 that has passed the secondary transfer section.
This is to cancel the elongation of “a” or cancel the torque fluctuation at the position of the drive roller 17 to stably drive the belt.

In the above embodiment, the cleaning roller 21a is configured to be driven so as to transmit the drive from the drive roller 17 of the intermediate transfer unit 5. However, the drive source may be shared with the secondary transfer unit 11. . FIG.
Is a partially enlarged view illustrating another configuration of the transfer unit of the image forming apparatus, and the same parts as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

In FIG. 3, the secondary transfer unit 11 has a drive gear 24 connected to a drive motor (not shown).
The drive is transmitted to the secondary transfer roller 11a via the. Further, the cleaning roller 21a is rotated by a rotating shaft 21 via gears 27 and 28 from a gear 26 coaxial with a driving gear 24 of the secondary transfer unit 11.
The drive is transmitted to a gear 29 coaxial with b, and the drive is transmitted from a gear 30 having a different diameter to a gear 31 coaxial with the cleaning roller 21a.

[0027]

As described above, in the image forming apparatus according to the present invention, the cleaning roller is provided with a driving rotation having a peripheral speed substantially equal to that of the intermediate transfer member.
There is no difference in the rotational resistance of the intermediate transfer member between when the cleaning roller is in contact and when it is separated.
Therefore, a change in the peripheral speed of the intermediate transfer member due to the separation and contact of the cleaning roller can be suppressed, and a high-quality image with little color shift can be obtained.

Further, when the cleaning roller is rotated so as to be slightly slower than the intermediate transfer member, it is possible to absorb the influence of the frictional force between the intermediate transfer member and the sheet during the secondary transfer on the intermediate transfer member. As a result, a high-quality image with little color shift can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to an embodiment.

FIG. 2 is a partially enlarged view illustrating a transfer unit of the image forming apparatus.

FIG. 3 is a partially enlarged view illustrating another configuration of the transfer unit of the image forming apparatus.

FIG. 4 is a cross-sectional view illustrating a transfer unit of a conventional image forming apparatus.

FIG. 5 is a diagram illustrating a state in which a secondary transfer unit is in contact with an intermediate transfer member.

FIG. 6 is a diagram illustrating a state where a cleaning roller is in contact with an intermediate transfer member.

FIG. 7 is a diagram illustrating movement of toner.

[Explanation of symbols]

 A: Image forming apparatus S: Sheet 1: Image carrier 1a: Primary charging device 2: Developing means switching device 2a: Shaft 3: Optical means 3a: Polygon mirror 3b: Lens 3c: Mirror 4: Developing means 4a: Coating roller 4b ... Sleeve 4c ... Blade 5 ... Intermediate transfer unit 5a ... Intermediate transfer belt 6 ... Cleaning cassette 6a ... Cleaning blade 7 ... Supply cassette 7a ... Supply roller 7b ... Separation roller 7c ... Transport roller pair 7d ... Conveyance path 7e ... Register roller Pair 8: Fixing means 8a: Heating roller 8b: Pressure roller 9: Discharge roller pair 10: Discharge tray 11: Secondary transfer unit 11a: Secondary transfer roller 11b: Separation cam 12: Transport means 13, 16: Transport roller 15… Conveying path 17… Drive roller 17a… Pulley 18, 19… Driving roller 20… Primary transfer roller 21… Leaning unit 21a ... cleaning roller 21b ... rotating shaft 21c ... oscillation plate 21d ... spring 21e ... pulley 21f, 21g ... gear 22 ... disjunction cam 23 ... belt 24 ... driving gear 25 to 31 ... gear

Claims (3)

[Claims] 1. An image carrier for carrying an electrostatic latent image, developing means for developing the latent image with toner, an intermediate transfer body for superimposedly transferring the developed toner image, and the intermediate transfer An image forming apparatus comprising: a secondary transfer unit that transfers a toner image on a body to a sheet; and a cleaning unit that removes toner remaining on the intermediate transfer body, wherein the cleaning unit is a rotatable cleaning roller. An image forming apparatus for applying a charge opposite to that of the secondary transfer means, and for applying a rotational drive to the cleaning roller at a peripheral speed substantially equal to that of the intermediate transfer body. 2. The cleaning device according to claim 1, wherein the secondary transfer unit is a roller that is driven to rotate at a peripheral speed slightly higher than the intermediate transfer member, and applies a rotational drive to the cleaning roller at a peripheral speed that is slightly lower than the intermediate transfer member. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as described above. 3. The image forming apparatus according to claim 2, wherein the secondary transfer unit is configured to provide resistance to the intermediate transfer body, and to provide the cleaning roller with a rotational drive at a peripheral speed slightly higher than that of the intermediate transfer body. The image forming apparatus according to claim 1.