CN-114967393-B - Image forming apparatus

CN114967393BCN 114967393 BCN114967393 BCN 114967393BCN-114967393-B

Abstract

An image forming apparatus. The driving unit is controlled such that a driving state in which the image bearing member is driven in the case where a first potential difference is formed between the brush member and the image bearing member at a contact portion where the image bearing member is in contact with the brush member is converted into a stopped state in which the image bearing member is stopped being driven in the case where a second potential difference is formed, the absolute value of the second potential difference being smaller than the absolute value of the first potential difference.

Inventors

TAKAYAMA TOSHIHIKO
Kobayashi introduction
TETSUNO SHUUICHI
FUNATANI KAZUHIRO
YUAN CHUN

Assignees

佳能株式会社

Dates

Publication Date: 20260512
Application Date: 20220222
Priority Date: 20210224

Claims (10)

1. An image forming apparatus comprising: a rotatable image bearing member; a driving unit configured to drive the image bearing member to rotate; A charging member configured to charge a surface of the image bearing member at a charging portion of the charging member opposite to the image bearing member; An exposure unit configured to expose a surface of the image bearing member charged by the charging member to form an electrostatic latent image on the surface of the image bearing member; a developing member configured to develop the electrostatic latent image into a developer image by supplying a developer charged to a normal polarity to a surface of the image bearing member; A transfer member configured to contact the image bearing member to form a transfer portion and transfer the developer image from a surface of the image bearing member to a transfer material at the transfer portion; a brush member configured to form a contact portion downstream of the transfer portion and upstream of the charging portion in a rotation direction of the image bearing member and to be in contact with a surface of the image bearing member at the contact portion, and A control unit configured to control the driving unit, Wherein the developing member is configured to collect the developer remaining on the surface of the image bearing member after the developer image formed on the surface of the image bearing member is transferred to the transfer material at the transfer portion, Wherein the control unit is configured to control the driving unit such that a driving state in which the image bearing member is driven in a case where a first potential difference is formed at the contact portion between the brush member and the image bearing member is converted into a stopping state in which the image bearing member stops being driven in a case where a second potential difference is formed at the contact portion, the second potential difference having the same polarity as the first potential difference and an absolute value of the second potential difference being smaller than an absolute value of the first potential difference, and Wherein the control unit is configured to control a potential difference formed at the contact portion to change from the first potential difference to a fourth potential difference having the same polarity as the first potential difference and from the fourth potential difference to the second potential difference, an absolute value of the fourth potential difference being a potential difference larger than an absolute value of the second potential difference, and an absolute value of the fourth potential difference being a potential difference larger than an absolute value of the first potential difference.
2. The imaging apparatus according to claim 1, wherein the control unit is configured to control the potential difference formed at the contact portion to change from a first potential difference to a third potential difference having the same polarity and from the third potential difference to a second potential difference, an absolute value of the third potential difference being smaller than an absolute value of the first potential difference and larger than an absolute value of the second potential difference.
3. The imaging apparatus according to claim 1, wherein the control unit is configured to control the potential difference formed at the contact portion to stepwise change it from a first potential difference to a second potential difference.
4. The imaging apparatus according to claim 1, wherein the control unit is configured to control the potential difference formed at the contact portion to continuously change from the first potential difference to the second potential difference.
5. The image forming apparatus according to claim 1, further comprising a brush voltage applying unit configured to apply a brush voltage to the brush member, Wherein the control unit is configured to control the formation of the first potential difference and the second potential difference by controlling the brush voltage applied by the brush voltage applying unit.
6. The image forming apparatus according to claim 1, further comprising a charging voltage applying unit configured to apply a charging voltage to the charging member, Wherein the control unit is configured to control the charging voltage applying unit to form the first potential difference and the second potential difference at the contact portion by controlling the surface potential of the image bearing member.
7. The image forming apparatus according to claim 1, further comprising a transfer voltage applying unit configured to apply a transfer voltage to the transfer member, Wherein the control unit is configured to control the transfer voltage applying unit to form the first potential difference and the second potential difference at the contact portion by controlling the surface potential of the image bearing member.
8. The image forming apparatus according to claim 1, wherein the control unit is configured to control the exposure unit to form the first potential difference and the second potential difference at the contact portion by controlling a surface potential of the image bearing member.
9. The image forming apparatus as claimed in claim 1, wherein the brush member is a paper dust removing member.
10. The image forming apparatus according to claim 1, Wherein the developer is a one-component developer.

Description

Image forming apparatus Technical Field The present disclosure relates to an image forming apparatus, such as a laser printer, a copier, and a facsimile machine, that obtains a recorded image by transferring a toner image formed on an image bearing member in an electrophotographic method to a recording material. Background As an image recording method used in image forming apparatuses such as printers and copiers, there is known an electrophotographic method. An electrophotographic method uses an electrophotographic process of forming an electrostatic latent image on a photosensitive drum (hereinafter, may be referred to as a drum) with a laser beam, developing the electrostatic latent image with a charged coloring material (hereinafter, referred to as toner) to form a developer image, and then transferring and fixing the developer image to a recording material to form an image. In recent years, in order to miniaturize an image forming apparatus, a cleanerless method has been proposed. A cleanerless method refers to a method in which a developing unit removes residual toner or developer from the surface of a drum while developing after a transfer step to remove and collect the residual toner from the drum and reuse it. Since the cleanerless method does not use a cleaning unit that is generally disposed with respect to the drum, paper dust on the drum may cause image defects during the transfer step to the recording material. Japanese patent application laid-open No.2007-65580 discusses a configuration in which a fixed brush for collecting paper dust on a drum in a transfer step is rotatably disposed downstream of a transfer portion and upstream of a charging portion with respect to the drum. However, with the configuration in which the brush is in contact with the drum, paper dust collected and held in the brush may fall on the surface of the drum due to a speed change at the start and stop of the rotational drive of the drum, and partly pass downstream of the brush, which may cause image defects. Disclosure of Invention The present disclosure provides an image forming apparatus that can stably hold paper dust that has accumulated in a brush due to sheet passage and can help reduce image defects caused by the paper dust. According to an aspect of the present disclosure, an image forming apparatus includes a rotatable image bearing member, a driving unit configured to drive the image bearing member to rotate, a charging member configured to charge a surface of the image bearing member at a charging portion of the charging member opposite to the image bearing member, an exposing unit configured to expose the surface of the image bearing member charged by the charging member to form an electrostatic latent image on the surface of the image bearing member, a developing member configured to develop the electrostatic latent image into a developer image by supplying a developer charged with a normal polarity to the surface of the image bearing member, a transfer member configured to contact the surface of the image bearing member to form a transfer portion and transfer the developer image from the surface of the image bearing member to a transfer material at the transfer portion, a brush member configured to form a contact portion downstream of the transfer portion and upstream of the charging portion and to contact the surface of the image bearing member at the contact portion, and a control unit configured to control the driving unit. The developing member is configured to collect the developer remaining on the surface of the image bearing member after the developer image formed on the surface of the image bearing member is transferred to the transfer material at the transfer portion. The control unit is configured to control the driving unit such that a driving state in which the image bearing member is driven in a case where a first potential difference is formed between the brush member and the image bearing member at the contact portion is shifted to a stopping state in which the image bearing member stops being driven in a case where a second potential difference is formed at the contact portion, the second potential difference having the same polarity as the first potential difference and an absolute value of the second potential difference being smaller than an absolute value of the first potential difference. Other features of the present disclosure will become apparent from the following description of exemplary embodiments, which refers to the accompanying drawings. Drawings Fig. 1 is an explanatory diagram showing an image forming apparatus according to a first exemplary embodiment. Fig. 2A and 2B are schematic views showing a brush member according to the first exemplary embodiment. Fig. 3 is a control block diagram according to the first exemplary embodiment. Fig. 4 is a diagram for describing control according to the first comparative example. Fig. 5 is a diagram for describing control according to