Image forming apparatus acquiring a duration of overcharge

Patent metadata

Field	Value
Publication number	US-9753395-B2
Application number	US-201615222338-A
Country	US
Kind code	B2
Filing date	Jul 28, 2016
Priority date	Jul 31, 2015
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

An image forming apparatus includes an acquiring portion that acquires a duration of an overcharged state occurring in an area of an image bearing body charged by a charging member after the image bearing body is exposed by a preliminary exposing portion. Adjustment is made to an interval between a first timing when the preliminary exposing portion starts exposing the image bearing body before execution of an adjustment operation for setting a transfer voltage value and a second timing when a voltage applying portion starts, during the subsequent adjustment operation, applying a voltage with an adjustment voltage value to a transfer member such that the second timing is later than a third timing when the duration acquired by the acquiring portion ends.

First claim

What is claimed is:

1. An image forming apparatus comprising:
an image bearing body that bears a developer image to be transferred to a recording material;
a charging member that charges the image bearing body;
a transfer member that transfers a developer image formed by development, using a developer, of an electrostatic image formed by exposure of the charged image bearing body, from the image bearing body to a transferred body;
a voltage applying portion that applies a voltage to each of the charging member and the transfer member;
a current detecting portion that detects a current flowing through the transfer member;
a preliminary exposing portion that exposes the image bearing body after the developer image is transferred and before the image bearing body is charged by the charging member;
a setting portion that sets a value of a transfer voltage applied to the transfer member by the voltage applying portion during image formation; and
an acquiring portion is provided which acquires a duration of an overcharged state occurring in an area of the image bearing body charged by the charging member after the image bearing body is exposed by the preliminary exposing portion,
wherein an adjustment operation being performed before image formation is started and after the charging member charges the image bearing body, the adjustment operation involving the voltage applying portion applying a voltage with a predetermined adjustment voltage value to the transfer member and the setting portion setting the transfer voltage value based on a current value detected by the current detecting portion when the voltage applying portion applies the voltage, and
wherein adjustment is made to an interval between a first timing when the preliminary exposing portion starts exposing the image bearing body before execution of the adjustment operation and a second timing when the voltage applying portion starts, during the subsequent adjustment operation, applying the voltage with the adjustment voltage value to the transfer member such that the second timing is later than a third timing when the duration acquired by the acquiring portion ends.

2. The image forming apparatus according to claim 1 , wherein the interval is adjusted so as to decrease consistently with the acquired duration.

3. The image forming apparatus according to claim 1 , wherein the interval is adjusted by varying the first timing.

4. The image forming apparatus according to claim 1 , wherein the interval is adjusted by varying the second timing.

5. The image forming apparatus according to claim 1 , wherein the acquiring portion acquires the duration based on at least one of information on a film thickness of a photosensitive layer in the image bearing body and information on a use environment of the image forming apparatus.

6. The image forming apparatus according to claim 1 , wherein the acquiring portion acquires the duration based on at least one of information on a film thickness of a photosensitive layer in the image bearing body, information on a use environment of the image forming apparatus, and information on a charging capability of the charging member.

7. The image forming apparatus according to claim 6 , wherein the information on the charging capability is acquired based on at least one of a resistance value of the charging member, a time for which a voltage is applied to the charging member, and an integrated value of a current flowing through the charging member.

8. The image forming apparatus according to claim 5 , wherein the information on the film thickness is acquired based on one of pieces of information including a number of recording materials on which image formation has been performed, a rotation speed of the image bearing body as a rotating body, a number of recording materials having passed through the image forming apparatus, and a time for which the image bearing body has been charged by the charging member.

9. The image forming apparatus according to claim 5 , wherein the information on the use environment is a temperature and a humidity sensed by a temperature and humidity sensor.

10. The image forming apparatus according to claim 9 , wherein the interval is adjusted to decrease with an increasing absolute moisture content acquired based on the temperature and the humidity sensed by the temperature and humidity sensor.

11. The image forming apparatus according to claim 5 , wherein the interval is adjusted to decrease consistently with the film thickness of the photosensitive layer.

12. The image forming apparatus according to claim 1 , wherein the acquiring portion acquires the duration based on the current value detected by the current detecting portion.

13. The image forming apparatus according to claim 12 , wherein based on the current value detected by the current detecting portion, the acquiring portion acquires the duration by determining a period from a fourth timing when a position on the image bearing body where the preliminary exposing portion starts exposure arrives at a position where the developer image is transferred by the transfer member until a fifth timing when the current value detected by the current detecting portion falls within a predetermined threshold range.

14. The image forming apparatus according to claim 12 , wherein the acquiring portion acquires the duration when a temperature and a humidity sensed by a temperature and humidity sensor exceed predetermined thresholds or when a number of recording materials on which image formation has been performed is equal to a predetermined number.

15. The image forming apparatus according to claim 1 , wherein the acquiring portion acquires the duration based on the current value detected by the current detecting portion when the voltage applying portion applies the voltage with the adjustment voltage value to the transfer member during the adjustment operation.

16. The image forming apparatus according to claim 15 , wherein during the adjustment operation, the voltage applying portion first applies a voltage with a first adjustment voltage value of a first magnitude and then a voltage with a second adjustment voltage value of a second magnitude, and the acquiring portion acquires an average value of current values detected by the current detecting portion between a sixth timing when the voltage applying portion applies the voltage with the first adjustment voltage value and a seventh timing when the voltage value of the voltage applied by the voltage applying portion is switched from the first adjustment voltage value to the second adjustment voltage value, and determines the average value to be a normal transfer current value obtained while no overcharged state is occurring.

17. The image forming apparatus according to claim 16 , wherein based on the current value detected by the current detecting portion, the acquiring portion acquires the duration by determining a period from a fourth timing when a position on the image bearing body where the preliminary exposing portion starts exposure arrives at a position where the developer image is transferred by the transfer member until a fifth timing when the current value detected by the current detecting portion falls within a predetermined current value range with respect to the normal transfer current value.

18. The image forming apparatus according to claim 1 , wherein the voltage applying portion applies to the charging member, during the adjustment operation, a voltage with the same voltage value as that of a voltage applied during image formation.

Assignees

• Canon Kk

Inventors

• Ikada Kosuke
• Agata Shinichi

Classifications

• G03G15/0266 Primary

  Arrangements for controlling the amount of charge · CPC title

• G03G15/1675

  with means for controlling the bias applied in the transfer nip · CPC title

• G03G21/203

  Humidity · CPC title

• G03G21/08

  using optical radiation · CPC title