Image forming apparatus

Patent metadata

Field	Value
Publication number	US-12411435-B2
Application number	US-202418806744-A
Country	US
Kind code	B2
Filing date	Aug 16, 2024
Priority date	Dec 16, 2021
Publication date	Sep 9, 2025
Grant date	Sep 9, 2025

Abstract

An image forming apparatus includes a photosensitive member, a charging member, an exposing device, a developing device, a transfer member, a brush, a voltage applying portion, and a control portion controlling a surface potential of the photosensitive member at the brush contacting position. When a value of subtracting a value of the surface potential of the photosensitive member in the brush contacting position from a value of the brush voltage is defined as a contacting position potential difference, the control portion controls the surface potential of the photosensitive member in the brush contacting position so that the contacting position potential difference is changed from a first potential difference to a second potential difference in a predetermined direction which is either one of an increasing direction or a decreasing direction, and then the contacting position potential difference is changed from the second potential difference to a third potential difference in the predetermined direction.

First claim

What is claimed is:

1. An image forming apparatus comprising:
a photosensitive drum;
a charging member configured to electrically charge a surface of the photosensitive drum at a charging portion;
an exposing unit configured to expose a surface of the photosensitive drum to light to form an electrostatic latent image on the surface of the photosensitive drum electrically charged by the charging member;
a developing member configured to develop the electrostatic latent image formed on the surface of the photosensitive drum with a developer and to form a developer image at a developing portion;
a transfer member configured to transfer the developer image formed by the developing member to a recording material at a transfer portion;
a contacting member provided upstream of the charging portion and downstream of the transfer position with respect to a rotational direction of the photosensitive drum and contacting the surface of the photosensitive drum at a contacting portion;
a first applying portion configured to apply a charging voltage to the charging member;
a second applying portion configured to apply a developing voltage to the developing member; and
a controller configured to control the first applying portion and the second applying portion to perform (1) an image formation operation for forming an image on the recording material and (2) a non-image formation operation which is different from the image formation operation and which does not form the image on the recording material, and to collect the toner remaining on the photosensitive drum without being transferred to the recording material by the transfer member,
wherein when an area of the photosensitive drum in the developing portion is defined as a first area and an area of the photosensitive drum in the charging portion is defined as a second area, the controller controls so as to execute following operations in the non-image formation operation,
i) a first operation in which the controller controls the second applying portion so as to form a first potential difference, between the photosensitive drum and the developing member, by which the toner charged with a normal polarity is moved from the photosensitive drum to the developing member in the first area in a state in which a surface potential of the photosensitive drum formed between the charging portion and the developing portion in a rotational direction of the photosensitive drum is smaller in an absolute value than the surface potential of the photosensitive drum charged in the charging portion in the image formation operation, and
ii) a second operation in which after executing the first operation, when the second area is charged by applying the charging voltage to the charging member by the first applying portion and the second area is moved to the developing portion by rotation of the photosensitive drum, the controller controls the first applying portion and the second applying portion so as to form a second potential difference, between the photosensitive drum and the developing member, by which the toner charged with the normal polarity in the developing portion is moved from the photosensitive drum to the developing member, and before the second area passing through the developing portion reaches the contacting area, to form a third potential difference, between the photosensitive drum and the contacting member, by which the toner charged with the normal polarity in the contacting portion is moved from the contacting member to the photosensitive drum.

2. An image forming apparatus according to claim 1 , wherein when the developing voltage is applied by the second applying portion, the contacting voltage is applied to the contacting member.

3. An image forming apparatus according to claim 1 , wherein a collection of the developer is executed before the image formation operation to the recording material and after the image formation operation to the recording material, or from when the image formation operation to the first recording material has been terminated until the image formation operation to a second recording material to be conveyed following the first recording material is started in a case in which continuous image formation operation is performed.

4. An image forming apparatus according to claim 3 , wherein the controller executes the collection of the developer for each image formation operation of a predetermined number of recording materials in the case in which the continuous image formation operation is performed.

5. An image forming apparatus according to claim 1 , wherein a length of the transfer member in a longitudinal direction perpendicular to the rotational direction is shorter than a width of a recoding material of which the width in the longitudinal direction is longest of recording materials to which the image forming apparatus is capable of performing the image formation operation.

6. An image forming apparatus according to claim 1 , wherein the developing member is in contact with the photosensitive drum during the image formation operation and the non-image formation operation.

7. An image forming apparatus according to claim 1 , wherein the controller controls the surface potential of the photosensitive drum at the contacting portion of a section to a predetermined potential by controlling at least one of (1) the charging voltage of the first applying portion, (2) the developing voltage of the second applying portion, and (3) a light quantity of the exposing unit during the section.

8. An image forming apparatus according to claim 7 , further comprising a pre-exposing unit configured to expose the surface of the photosensitive drum downstream of the contacting portion and upstream of the charging portion,
wherein the controller controls the surface potential of the photosensitive drum in the contacting portion of a section to a predetermined potential by controlling at least one of (1) the charging voltage of the first applying portion, (2) the developing voltage of the second applying portion, (3) a light quantity of the pre-exposing unit, and (4) a light quantity of the exposing unit during the section.

9. An image forming apparatus according to claim 1 , wherein the charging member electrically charges the surface of the photosensitive drum by contacting the surface of the photosensitive drum.

10. An image forming apparatus according to claim 1 , wherein the contacting member includes a brush collecting a paper powder deposited on the surface of the photosensitive drum,
wherein the brush is provided with base materials contacting the surface of the photosensitive drum, and
wherein a density of the base materials of the brush is 120 kF/inch 2 or more.

11. The image forming apparatus according to claim 1 , wherein, in an axial direction of the developing member, (1) the length of the contacting member is longer than the length of the developing member, and (2) the first end of the contacting member is located outside the first end of the developing member.

12. The image forming apparatus according to claim 1 , wherein in the first operation, the surface of the photosensitive drum formed between the charging portion and the developing portion is not charged by the charging member.

13. An image forming apparatus according to claim 2 , wherein the developing voltage is the same voltage in magnitude as the contacting voltage.

Assignees

• Canon Kk

Inventors

• Hara Jun
• Hamada Mikihiko
• Tetsuno Shuichi
• Takayama Toshihiko
• Kobayashi Shinsuke

Classifications

• G03G15/5004

  Power supply control, e.g. power-saving mode, automatic power turn-off · CPC title

• G03G15/5037

  the characteristics being an electrical parameter, e.g. voltage · CPC title

• G03G2221/0015

  Width of cleaning device related to other parts of the apparatus, e.g. transfer belt width · CPC title

• G03G21/0064

  using the developing unit, e.g. cleanerless or multi-cycle apparatus · CPC title

• G03G21/0082

  Separate cleaning member for toner and debris · CPC title