Image forming apparatus and image forming method for controlling a secondary transfer bias according to recording sheet type

Patent metadata

Field	Value
Publication number	US-10185255-B2
Application number	US-201715432392-A
Country	US
Kind code	B2
Filing date	Feb 14, 2017
Priority date	Feb 15, 2016
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

An image forming apparatus includes an image bearer to bear a toner image, a nip forming member contacting the image bearer to form a transfer nip, and a transfer power source. The transfer bias has a transfer peak value to electrostatically move toner from the image bearer to the recording sheet and an opposite-peak value to electrostatically move less toner from the image bearer to the recording sheet than the transfer peak value. An opposite-peak duty of the transfer bias is less than 50%. The opposite-peak duty is tr/T×100% where T is one cycle of the transfer bias and tr is a time period during which the transfer bias is on a side of the opposite-peak value relative to an offset voltage of the transfer bias in the one cycle T.

First claim

What is claimed is:

1. An image forming apparatus comprising:
an image bearer to bear a toner image, the image bearer having a micro-rubber hardness of less than 100;
a nip forming member contacting the image bearer to form a transfer nip;
a transfer power source to output a transfer bias including a superimposed voltage, in which an alternating current (AC) voltage is superimposed on a direct current (DC) voltage to transfer the toner image borne on the image bearer onto a recording sheet disposed between the image bearer and the nip forming member; and
a controller to switch a transfer mode between a first mode to transfer the toner image onto a first type sheet having a surface smoothness higher than a surface smoothness of a second type sheet and a second mode to transfer the toner image onto the second type sheet,
the transfer bias having a transfer peak value to electrostatically move toner from the image bearer to the recording sheet and an opposite-peak value to electrostatically move less toner from the image bearer to the recording sheet than the transfer peak value,
an opposite-peak duty on a side of the opposite-peak value in the second mode being less than 50%,
the opposite-peak duty on the side of the opposite-peak value in the first mode being greater than 50%, and
the opposite-peak duty being tr/T×100%,
where
T is one cycle of the transfer bias, and
tr is a time period during which the transfer bias is on the side of the opposite-peak value relative to an offset voltage of the transfer bias in T.

2. The image forming apparatus according claim 1 ,
wherein the image bearer has a micro-rubber hardness of less than or equal to 82.

3. The image forming apparatus according to claim 2 ,
wherein the image bearer has a micro-rubber hardness of greater than or equal to 36.

4. The image forming apparatus according to claim 1 ,
wherein the image bearer has a multi-layer structure including a base layer and an elastic layer disposed on the base layer.

5. The image forming apparatus according to claim 4 ,
wherein the image bearer has a Martens hardness of less than 240.

6. The image forming apparatus according to claim 5 ,
wherein the image bearer has a Martens hardness of less than or equal to 1.1.

7. The image forming apparatus according to claim 6 ,
wherein the image bearer has a Martens hardness of greater than or equal to 0.3.

8. The image forming apparatus according to claim 4 ,
wherein the image bearer includes a surface layer disposed on the elastic layer.

9. The image forming apparatus according to claim 4 ,
wherein the elastic layer has a thickness of greater than or equal to 240 μm.

10. The image forming apparatus according to claim 9 ,
wherein the elastic layer has a thickness of less than or equal to 390 μm.

11. The image forming apparatus according to claim 1 , further comprising:
circuitry configured to acquire information regarding surface smoothness of the recording sheet that is a transfer target of the toner image; wherein
the controller switches the transfer mode between the first mode and the second mode based on the information acquired by the circuitry,
the controller to control the transfer power source to output the transfer bias having the opposite-peak duty of less than 50% in the second mode.

12. The image forming apparatus according to claim 11 ,
wherein the controller controls the transfer power source to output the transfer bias that reverses a polarity during one cycle voltage in the second mode.

13. The image forming apparatus according to claim 12 ,
wherein the controller controls the transfer power source to output the transfer bias having the opposite-peak duty that exceeds 50% in the first mode.

14. The image forming apparatus according to claim 13 ,
wherein the controller controls the transfer power source to output the transfer bias that does not reverse the polarity during the one cycle in the first mode.

15. The image forming apparatus according to claim 1 , further comprising:
another image bearer to bear a toner image, which is to be transferred onto the image bearer, on a surface of said another image bearer; and
a charger to supply charges having a same polarity as a normal charge polarity of toner to the toner on said another image bearer.

16. The image forming apparatus according to claim 15 , further comprising:
circuitry configured to acquire information regarding surface smoothness of the recording sheet that is a transfer target of the toner image, wherein
the controller is further configured to control a voltage applied to the charger based on the information acquired by the circuitry.

17. The image forming apparatus according to claim 16 ,
wherein the controller switches the voltage applied to the charger between the first mode and the second mode based on the information acquired by the circuitry, and
wherein the controller increases an absolute value of the voltage applied to the charger in the first mode to be greater than an absolute value of the voltage applied to the charger in the second mode.

18. The image forming apparatus according to claim 15 , further comprising:
a plurality of color image bearers disposed in contact with the image bearer, side by side in a direction of movement on a surface of the image bearer, to bear toner images of different colors,
wherein each of the plurality of color image bearers is constituted by said another image bearer, and
wherein the charger supplies the charges to only one of the plurality of color image bearers to bear a black toner image.

19. An image forming method comprising:
transferring a toner image from an image bearer having a micro-rubber hardness of less than 100 onto a recording sheet by a transfer bias; and
switching a transfer mode between a first mode to transfer the toner image onto a first type sheet having a surface smoothness higher than a surface smoothness of a second type sheet and a second mode to transfer the toner image onto the second type sheet,
the transfer bias having a transfer peak value to electrostatically move toner from the image bearer to the recording sheet and an opposite-peak value to electrostatically move less toner from the image bearer to the recording sheet than the transfer peak value,
an opposite-peak duty of the opposite-peak value in the second mode being less than 50%,
the opposite-peak duty on a side of the opposite-peak value in the first mode being greater than 50%, and
the opposite-peak duty being tr/T×100%,
where
T is one cycle of the transfer bias, and
tr is a time period during which the transfer bias is on the side of the opposite-peak value relative to an offset voltage of the transfer bias in T.

Assignees

• Ricoh Co Ltd

Inventors

• Kochi Naoto
• Ishii Hirokazu
• Kogure Seiichi
• Kumagai Naohiro
• Sugiura Kenji
• Tanaka Shinya
• Nakamatsu Hiroki
• Wada Yuuji
• Fujita Junpei
• Suzuki Takahiro
• Yogosawa Kazuki
• Nagata Atsushi

Classifications

• G03G5/147

  Cover layers · CPC title

• G03G15/1675 Primary

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

• G03G5/005

  Materials for treating the recording members, e.g. for cleaning, reactivating, polishing · CPC title