JP2005062642A - Transfer unit and image forming apparatus - Google Patents

Abstract

Provided is a low-cost transfer unit having a small separation mechanism capable of reducing the influence of a nip of a Bk transfer roller due to contact and separation of a color frame and the effect of bending and vibration of a transfer belt. Another object of the present invention is to provide an image forming apparatus including the transfer unit.
A transfer mechanism for a YMC color transfer roller 1 uses a shaft of a backup roller 12 having a function of stabilizing the nip of the transfer roller 1 as a rotation axis, and the backup roller 12 is a Bk transfer roller of a color transfer roller. It is characterized in that it is installed on the side opposite to the Bk transfer roller of the color transfer roller. Further, the link member 12 is attached to the color frame, and the link member 12 rotates around the backup roller shaft.
[Selection] Figure 1

Description

The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine.

Today, the demand for full-color output increases in image forming apparatuses, and an output speed comparable to that of a monochrome image is desired. Therefore, tandem type color image forming apparatuses are attracting attention. The tandem type electrophotographic apparatus includes a direct transfer system in which images on each photoconductor are sequentially transferred to a sheet conveyed by a sheet conveying belt by a transfer device, and an image on each photoconductor by a primary transfer device. There is an indirect transfer type in which images are sequentially transferred to an intermediate transfer member and then transferred onto a sheet by a secondary transfer device.
These tandem image diameter apparatuses have a mechanism for separating the color transfer rollers when outputting a monochrome image, as described in Patent Document 1, in order to extend the life of the photoreceptor and the transfer belt. There is something.

  Next, one example of a conventional separation mechanism is shown in FIGS. The transfer belt unit includes a driving roller 2 for driving the belt, a tension roller 3 for applying tension to the belt, a driven roller 4, a color backup roller 5 for eliminating the influence of fluctuation of the tension roller, and a latent image on the photosensitive member. 4, a color backup roller 11 and a color frame 6 that holds a transfer roller for yellow (Y), cyan (S), and magenta (M). The color frame 6 is biased in the direction in which the transfer roller 11 is separated from the photosensitive member by a spring. When outputting a color image, the photosensitive member and the color transfer roller 11 are transferred by a cam as shown in FIG. As shown in FIG. 10, when the monochrome image is output, the photosensitive member 1 is separated from the Y, S, and M color transfer rollers 11 by eliminating the restriction by the cam 9, as shown in FIG. .

  However, in the case of the transfer unit described above, the orbit of the transfer belt 8 changes due to the contact and separation of the color transfer roller, the nip of the black (Bk) transfer roller changes, and the color transfer roller is separated. Since the transfer belt is easily affected by bending or vibration of the transfer belt, it causes a decrease in the transfer rate of the Bk transfer roller and a transfer failure such as worm-eaten. As a countermeasure against this problem, means for adding a back roller before and after the transfer roller has been proposed, but there are problems such as an increase in cost and difficulty in downsizing the unit.

JP 2003-043770 A

  In view of the above problems, the present invention includes a low-cost and small-sized separation mechanism that can reduce the influence of the nip of the Bk transfer roller due to the contact and separation of the color frame and the influence of the deflection and vibration of the transfer belt. It is an object of the present invention to provide a transfer unit and to provide an image forming apparatus including the transfer unit.

  In order to solve the above-described problems, the invention described in claim 1 eliminates the influence of fluctuations in the transfer belt, the driving roller for driving the transfer belt, the tension roller for applying tension to the transfer belt, the driven roller, and the tension roller. A color backup roller, four color transfer rollers for transferring a latent image on the photosensitive member, and a color frame for holding a color backup roller and three color transfer rollers for yellow, cyan, and magenta In a transfer unit having a mechanism in which three color transfer rollers for yellow, cyan, and magenta are separated from the photosensitive member during monochrome output, the contact / separation mechanism of the color transfer roller stabilizes the nip of the transfer roller. A transfer unit characterized in that the axis of a backup roller having a function is a rotation axis. Tsu is a door.

The invention according to claim 2 is characterized in that the color frame rotates around a backup roller shaft, and the backup roller is installed on the Bk transfer roller side of the color transfer roller. This is a transfer unit.
According to a third aspect of the present invention, the color frame rotates about a backup roller shaft, and the backup roller is disposed on the opposite side of the color transfer roller from the Bk transfer roller. The transfer unit described in 1.
The invention according to claim 4 is the transfer unit according to claim 1, wherein a link member is attached to the color frame, and the link member rotates about a backup roller shaft.

The invention according to claim 5, D ₁ the diameter of the driving _roller, when the diameter of the backup roller as a rotation center of the separation mechanism of the color for the transfer roller and _{D 2 D 2 = n × D} 1 or D ₁ = n × D ₂ (n is an arbitrary integer)
The transfer unit according to any one of claims 1 to 4, wherein the transfer unit has the following relationship.
According to the sixth aspect of the present invention, the image primarily transferred from the photosensitive member disposed along the outer peripheral surface of the transfer belt is secondarily transferred to a recording medium supplied toward the outer peripheral surface of the transfer belt. 6. The transfer unit according to claim 1, wherein the transfer unit is an intermediate transfer belt unit.
According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising the intermediate transfer belt unit according to the sixth aspect.
The invention according to claim 8 is a transfer and conveyance belt unit that conveys a recording medium on which an image is recorded and transfers an image on a photoconductor disposed along the outer peripheral surface of the belt to the recording medium. The transfer unit according to any one of claims 1 to 5.
According to a ninth aspect of the present invention, there is provided an image forming apparatus comprising the transfer / conveying belt unit according to the eighth aspect.

  As described above, by adopting the contact / separation mechanism including the backup roller, it is possible to reduce the influence of the nip change of the Bk transfer roller due to the contact / separation of the color frame, the bending or vibration of the transfer belt, Further, by using the axis of the backup roller as the rotating shaft of the contact / separation mechanism, it is possible to provide a transfer unit that is low in cost and easy to downsize, and an image forming apparatus including the transfer unit. .

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the positions of the backup roller and the color frame when outputting a color image. FIG. 2 is a diagram showing the positions of the backup roller and the color frame when outputting a monochrome image. As shown in FIGS. 1 and 2, the backup roller is positioned between the Bk (black) transfer roller and M (magenta), and the color frame rotates about the axis of the backup roller. At this time, if the diameter of the driving roller is D _a and the diameter of the backup roller is D _b ,
D _a = 2 × D _b
When is established, the phase of the drive roller and the phase of the backup roller for Bk can be made uniform.
When outputting a color image, the color frame is fixed by a cam so that the YMC color transfer roller can be transferred. When outputting a monochrome image, the cam is no longer restricted and the color frame is rotated by a spring. The photoreceptor and the YMC color transfer roller are separated from each other.

FIG. 3 is a diagram showing a color image output with the backup roller attached at the Y (yellow) side opposite to the Bk transfer roller.
FIG. 4 is a diagram showing a monochrome roller output when the backup roller is attached in the same position as in FIG. The color frame holds a transfer roller for Y (yellow), M (magenta), and C (cyan), and can rotate around the color backup roller. At the time of outputting a color image, the color frame is fixed by a cam in a state where the YMC color transfer roller can be transferred. When a monochrome image is output, the cam is no longer restricted, and the color frame is rotated by the spring, so that the photoreceptor and the YMC color transfer roller are separated.

FIG. 5 is a diagram showing a color image output with a link member attached to the color frame.
FIG. 6 is a diagram showing a monochrome image output with a link member attached to the color frame. The link member rotates about the axis of the backup roller and is connected to the color frame. At the time of color image output, the link member is fixed in a state where the YMC color transfer roller can be transferred by the cam. At the time of monochrome image output, the link member is rotated by the spring because the cam restriction is removed. The YMC color transfer roller is separated from the photoreceptor.
FIG. 7 is a diagram showing an embodiment of the present invention applied to an intermediate transfer type image forming apparatus.
The latent image on the photosensitive member is transferred to the intermediate transfer belt by the transfer roller, and transferred to the transfer paper by the secondary transfer roller.
FIG. 8 is a diagram similarly showing an example applied to a direct transfer type image forming apparatus. The latent image on the photosensitive member is transferred onto a transfer sheet conveyed on a transfer conveyance belt by a transfer roller.
FIG. 9 is a diagram showing one example of a conventional separation mechanism at the time of outputting a color image.
FIG. 10 is a diagram showing one example of a conventional separation mechanism at the time of outputting a monochrome image.

It is a figure which shows the position of the backup roller at the time of color image output, and a color frame. It is a figure which shows the position of the backup roller and color frame at the time of monochrome image output. FIG. 6 is a diagram showing a color image output with the backup roller attached at a Y (yellow) side opposite to the Bk transfer roller. FIG. 4 is a diagram showing a monochrome roller output when the backup roller is attached in the same position as in FIG. 3. It is a figure which shows the time of a color image output by attaching a link member to a color frame. It is a figure which shows the time of monochrome image output, attaching a link member to a color frame. 1 is a diagram illustrating an embodiment of the present invention applied to an intermediate transfer type image forming apparatus. 1 is a diagram illustrating an embodiment of the present invention applied to a direct transfer type image forming apparatus. It is a figure which shows one of the Examples of the conventional separation mechanism at the time of a color image output. It is a figure which shows one of the Examples of the conventional separation mechanism at the time of a monochrome image output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Driving roller 3 Tension roller 4 Driven roller 5 Color backup roller 6 Color frame 7 Color frame rotation mechanism 8 Transfer belt 9 Cam 10 Spring 11 Transfer roller 12 Link member 13 Secondary transfer roller 14 Transfer paper 15 Color frame rotation shaft

Claims (9)

Transfer belt, drive roller for driving the transfer belt, tension roller for applying tension to the transfer belt, driven roller, color backup roller for eliminating the influence of fluctuation of the tension roller, and transferring the latent image on the photosensitive member A color frame for holding four color transfer rollers and a color backup roller and three color transfer rollers for yellow, cyan and magenta;
During monochrome output,
In a transfer unit having a mechanism in which three color transfer rollers for yellow, cyan, and magenta are separated from the photosensitive member,
The contact mechanism of the color transfer roller is
A transfer unit comprising a shaft of a backup roller having a function of stabilizing the nip of the transfer roller as a rotating shaft. The color frame rotates around the backup roller shaft,
The transfer unit according to claim 1, wherein the backup roller is installed on the Bk transfer roller side of the color transfer roller. The color frame rotates around the backup roller shaft,
The transfer unit according to claim 1, wherein the backup roller is installed on the opposite side of the color transfer roller from the Bk transfer roller. A link member is attached to the color frame,
The transfer unit according to claim 1, wherein the link member rotates about a backup roller shaft. The diameter of the driving roller _D 1,
The diameter of the backup roller as a rotation center of the contact and separation mechanism for color transfer roller When _{D 2 D 2 = n × D} 1 or _{D 1 = n × D 2 (} n is an arbitrary integer)
The transfer unit according to claim 1, wherein the transfer unit has the following relationship. It is an intermediate transfer belt unit that secondarily transfers an image primarily transferred from a photoreceptor arranged along the outer peripheral surface of the transfer belt to a recording medium supplied toward the outer peripheral surface of the transfer belt. The transfer unit according to any one of claims 1 to 5. An image forming apparatus comprising the intermediate transfer belt unit according to claim 6. 6. A transfer / conveying belt unit that conveys a recording medium on which an image is recorded and transfers an image on a photoconductor disposed along the outer peripheral surface of the belt to the recording medium. The transcription unit described in 1. An image forming apparatus comprising the transfer conveyance belt unit according to claim 8.

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