Image forming apparatus

Patent metadata

Field	Value
Publication number	US-10001719-B2
Application number	US-201615281397-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Oct 5, 2015
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

An image forming apparatus includes: an acquisition portion that acquires, based on a current value detected by a detection unit, a discharge start voltage value between a photosensitive body and a charging member, in a voltage value of a voltage applied to the charging member, the discharge start voltage value being acquired from at least one of a plurality of measurement regions set by dividing an image forming region of the photosensitive body, in which an electrostatic image is formed, into a plurality of regions in a longitudinal direction orthogonal to a recording material conveyance direction; and a control portion that performs unevenness suppression control to reduce unevenness, in the longitudinal direction, of density of a developer image transferred onto the recording material based on the discharge start voltage value.

First claim

What is claimed is:

1. An image forming apparatus comprising:
a photosensitive body on which an electrostatic image used to form a developer image to be transferred onto a recording material is formed;
a charging member that is arranged close to or in contact with the photosensitive body and charges the photosensitive body with a voltage applied thereto;
a voltage application unit that applies the voltage to the charging member;
an exposure unit that exposes the photosensitive body;
a detection unit that detects a current value of a current flowing to the charging member;
an acquisition portion that acquires, based on the current value detected by the detection unit, a discharge start voltage value, at which a discharge starts between the photosensitive body and the charging member, in a voltage value of the voltage applied to the charging member, the discharge start voltage value being acquired from at least one of a plurality of measurement regions set by dividing an image forming region of the photosensitive body, in which the electrostatic image is formed, into a plurality of regions in a longitudinal direction orthogonal to a conveyance direction of the recording material; and
a control portion that performs unevenness suppression control to reduce unevenness, in the longitudinal direction, of density of the developer image transferred onto the recording material based on an unevenness of film thickness of a photosensitive layer the discharge start voltage value acquired by the acquisition portion,
wherein
the acquisition portion acquires a first discharge start voltage value based on the current value detected by the detection unit when, after the voltage application unit applies a voltage of a first voltage value to the charging member, the exposure unit exposes only one measurement region, from which the discharge start voltage value is to be acquired, among the plurality of measurement regions to be set at a prescribed exposure potential and thereafter the voltage application unit applies, to the charging member, a voltage of a second voltage value having an absolute value closer to the first voltage value than the prescribed exposure potential,
acquires a second discharge start voltage value based on the current value detected by the detection unit when, after the voltage application unit applies the voltage of the first voltage value to the charging member, the exposure unit exposes only measurement regions other than the one measurement region among the plurality of measurement regions to be set at the prescribed exposure potential and thereafter the voltage application unit applies, to the charging member, a voltage of a third voltage value having an absolute value closer to the prescribed exposure potential than the first voltage value,
acquires an exposure potential in the one measurement region after the exposure by the exposure unit based on the first discharge start voltage value and the second discharge start voltage value, and
acquires film thickness of a photosensitive layer in the one measurement region based on the exposure potential.

2. The image forming apparatus according to claim 1 , wherein
the second voltage value has an absolute value greater than an absolute value of the first voltage value.

3. The image forming apparatus according to claim 1 , wherein
the third voltage value has an absolute value smaller than an absolute value of the prescribed exposure potential.

4. The image forming apparatus according to claim 1 , wherein, when the exposure potential of the one measurement region D(i) is indicated by Vl(i), the first discharge start voltage value is indicated by Vth1(i), the second discharge start voltage value is indicated by Vth2(i), and the first voltage value is indicated by Vd, the acquisition portion acquires the exposure potential based on a relationship of Vl(i)=−(Vth1(i)+Vth2(i))−Vd.

5. The image forming apparatus according to claim 1 , wherein,
as the unevenness suppression control, the control portion performs control to scrape a photosensitive layer based on the discharge start voltage value in each of the plurality of measurement regions such that a difference in film thickness of the photosensitive layer between the plurality of measurement regions becomes small.

6. The image forming apparatus according to claim 5 , wherein,
as the control to scrape the photosensitive layer, the control portion controls the voltage application unit and the exposure unit such that
the voltage application unit applies the voltage to the charging member to charge the photosensitive body,
the exposure unit thereafter exposes only a measurement region having relatively large film thickness among the plurality of measurement regions, and
the voltage application unit thereafter applies the voltage to the charging member to generate the discharge between the charging member and the photosensitive body.

7. The image forming apparatus according to claim 5 , wherein
the control portion performs the unevenness suppression control when the difference in the film thickness between a measurement region having relatively large film thickness and a measurement region having relatively small film thickness becomes greater than or equal to a second threshold in regions having film thickness less than or equal to a first threshold among the plurality of measurement regions.

8. The image forming apparatus according to claim 1 , wherein,
as the unevenness suppression control, the control portion performs control to adjust an exposure amount of the exposure unit based on the discharge start voltage value in each of the plurality of measurement regions such that a difference in exposure potential between the plurality of measurement regions after the exposure by the exposure unit becomes small.

9. The image forming apparatus according to claim 8 , wherein,
as the control to adjust the exposure amount, the control portion controls the exposure unit such that the exposure amount is increased as film thickness is smaller.

10. The image forming apparatus according to claim 1 , further comprising:
a notification unit that issues a notification to urge an exchange of the photosensitive body when, after the control portion performs the unevenness suppression control, a difference in film thickness between a measurement region having relatively large film thickness and a measurement region having relatively small film thickness among the plurality of measurement regions exceeds a prescribed service life threshold.

11. The image forming apparatus according to claim 1 , wherein
the charging member is a charging member used to charge the photosensitive body at a prescribed potential before the exposure unit performs an exposure to form the electrostatic image on the photosensitive body in an image forming step of forming an image on the recording material.

12. The image forming apparatus according to claim 1 , wherein
the voltage applied to the charging member by the voltage application unit is a direct current voltage.

13. The image forming apparatus according to claim 1 , wherein
at least the photosensitive body is configured to be attachable/detachable to/from an apparatus body of the image forming apparatus as a process cartridge provided with a non-volatile memory.

14. The image forming apparatus according to claim 1 , wherein
the control portion performs the unevenness suppression control based on unevenness, in the longitudinal direction, of film thickness of a photosensitive layer of the photosensitive body acquired based on the discharge start voltage value acquired by the acquisition portion.

Assignees

• Canon Kk

Inventors

• Kihara Takayoshi
• Ikada Kosuke
• Mochizuki Masataka
• Naito Norihito

Classifications

• G03G15/55

  Self-diagnostics; Malfunction or lifetime display · CPC title

• G03G2215/00071

  by measuring the photoconductor or its environmental characteristics · CPC title

• G03G15/0266 Primary

  Arrangements for controlling the amount of charge · CPC title

• G03G15/0275

  Arrangements for controlling the area of the photoconductor to be charged · CPC title