Image forming apparatus that can selectively switch between two transfer rollers

Patent metadata

Field	Value
Publication number	US-11474457-B2
Application number	US-202217578308-A
Country	US
Kind code	B2
Filing date	Jan 18, 2022
Priority date	Jan 22, 2021
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

An image forming apparatus includes an image forming portion, an image input portion, a transfer unit, a transfer voltage power supply, and a control portion. The transfer unit includes a transfer roller having a metal shaft and an elastic layer laid around an outer circumferential face of the metal shaft to form a transfer nip by keeping the elastic layer in pressed contact with an image carrying member, and transfers a toner image formed on the image carrying member to a recording medium as it passes through the transfer nip. The transfer unit includes, as the transfer roller, a first roller, and a second roller having a larger axial-size elastic layer compared to the first roller. The control portion arranges the first or second roller opposite the image carrying member according to width-direction sizes of the recording medium and image data fed to the image input portion.

First claim

What is claimed is:

1. An image forming apparatus, comprising:
an image forming portion that forms a toner image on an image carrying member;
an image input portion that receives image data of the toner image formed by the image forming portion;
a transfer unit that includes a transfer roller having a metal shaft and an elastic layer laid around an outer circumferential face of the metal shaft to form a transfer nip by keeping the elastic layer in pressed contact with the image carrying member, the transfer unit transferring the toner image formed on the image carrying member to a recording medium as the recording medium passes through the transfer nip;
a transfer voltage power supply that applies a voltage to the transfer roller; and
a control portion that controls the image forming portion, the transfer unit, and the transfer voltage power supply,
wherein
the transfer unit includes, as the transfer roller, a first roller and a second roller, the elastic layer of the second roller being larger in an axial direction than the elastic layer of the first roller, and
the control portion arranges one of the first and second rollers at a reference position at which the first or second roller is in pressed contact with the image carrying member and forms the transfer nip in accordance with a width-direction size of the image data that has been fed to the image input portion and a width-direction size of the recording medium.

2. The image forming apparatus according to claim 1 ,
wherein
the image input portion is an image reading portion that reads a document image to convert the document image to the image data, and
the control portion arranges one of the first and second rollers at the reference position in accordance with a width-direction size of the document image that is read in the image reading portion.

3. The image forming apparatus according to claim 2 , further comprising a size sensing portion that senses the width-direction size of the recording medium that is conveyed to the image forming portion,
wherein
when an axial-direction length of the elastic layer of the first or second roller arranged at the reference position is not compatible with the width-direction size of the image data and the width-direction size of the recording medium sensed by the size sensing portion, the control portion stops conveyance of the recording medium and arranges at the reference position the first or second roller having the elastic layer compatible with the width-direction size of the image data and the recording medium.

4. The image forming apparatus according to claim 3 ,
wherein
the size sensing portion includes
a contact image sensor having a large number of sensing portions comprising photoelectric conversion elements arranged in a width direction of the recording medium, and
a light emitting portion that emits light to the contact image sensor, and

the size sensing portion senses a width-direction edge part of the recording medium in the width direction based on a difference in light intensity between in a part of the size sensing portion directly struck by the light emitted from the light emitting portion and a part of the size sensing portion shielded from the light by the recording medium.

5. The image forming apparatus according to claim 2 ,
wherein
if the axial-direction length of the elastic layer of the first or second roller arranged at the reference position is larger than the width-direction size of the image data, even when the width of the recording medium changes during continuous printing, the control portion does not switch the first or second roller arranged at the reference position.

6. The image forming apparatus according to claim 1 ,
wherein
the control portion arranges the first or second roller arranged opposite the image carrying member selectively either at the reference position or at a released position at which the first or second roller lies away from the image carrying member.

7. The image forming apparatus according to claim 6 ,
wherein
the transfer unit includes
a first bearing member that rotatably supports the first roller,
a second bearing member that rotatably supports the second roller,
a roller holder having a first bearing holding portion and a second bearing holding portion that hold the first bearing member and the second bearing member respectively so as to be slidable in directions toward and away from the image carrying member,
a first urging member that is arranged between the first bearing holding portion and the first bearing member and urges the first bearing member in the direction toward the image carrying member,
a second urging member that is arranged between the second bearing holding portion and the second bearing member and urges the second bearing member in the direction toward the image carrying member,
a switching cam that has a guide hole with which a first engaging portion formed on the first bearing member and a second engaging portion formed on the second bearing member engage, and
a driving mechanism that drives the roller holder and the switching cam to rotate,

wherein
by rotating the roller holder, one of the first and second rollers is arranged opposite the image carrying member, and
by rotating the switching cam to change positions at which the first and second engaging portions engage with the guide hole, the first or second roller that is arranged opposite the image carrying member is arranged selectively either at the reference position or at the released position.

8. The image forming apparatus according to claim 7 ,
wherein
the driving mechanism includes
a shaft that is fixed to a rotation center of the switching cam, and
a roller switching motor for rotating the shaft, and

the roller holder is rotatably supported on the shaft and, by rotating the shaft with the roller switching motor, rotates the switching cam and the roller holder.

9. The image forming apparatus according to claim 7 , further comprising a plurality of position sensors that sense positions of the roller holder and the switching cam in a rotation direction,
wherein
by controlling the driving mechanism based on a result of sensing by the plurality of position sensors, the control portion arranges one of the first and second rollers opposite the image carrying member and arranges the first or second roller arranged opposite the image carrying member selectively either at the reference position or at the released position.

10. The image forming apparatus according to claim 1 , further comprising:
a plurality of image forming portions that form toner images of different colors;
an endless intermediate transfer belt as the image carrying member that moves along the plurality of image forming portions;
a plurality of primary transfer members that are arranged, across the intermediate transfer belt, opposite photosensitive drums arranged respectively in the plurality of image forming portions and that primarily transfer the toner images formed on the photosensitive drums to the intermediate transfer belt; and
a secondary transfer unit as the transfer unit that secondarily transfers the toner images primarily transferred to the intermediate transfer belt to the recording medium.

Assignees

• Kyocera Document Solutions Inc

Inventors

• Shimohora Yuya
• Yamada Masayuki
• Takagi Masaru
• Sato Takehiro

Classifications

• G03G15/5029 Primary

  by measuring the copy material characteristics, e.g. weight, thickness · CPC title

• G03G15/5025

  by measuring the original characteristics, e.g. contrast, density · CPC title

• G03G15/1685

  Structure, details of the transfer member, e.g. chemical composition · CPC title

• G03G15/1605

  using at least one intermediate support (G03G15/1625 takes precedence) · CPC title

• G03G15/1615

  relating to the driving mechanism for the intermediate support, e.g. gears, couplings, belt tensioning · CPC title