Image forming apparatus

Patent metadata

Field	Value
Publication number	US-10073386-B2
Application number	US-201715482837-A
Country	US
Kind code	B2
Filing date	Apr 10, 2017
Priority date	Apr 14, 2016
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

An image forming apparatus including an image bearer; a nip forming member, a nip width changing device, a power source; and a controller. The controller switches between a first mode and a second mode according to a predetermined condition. In the first mode, a duty of the transfer bias is a first duty and a width of a transfer nip is a first width. In the second mode, the duty of the transfer bias is a second duty lower than the first duty and the width of the transfer nip is a second width greater than the first width. The duty is (T−Tt)/T×100% where T denotes one cycle of the transfer bias, and Tt denotes a time period, in which the transfer bias is on a transfer-directional side relative to a time-averaged value of the transfer bias, in the one cycle.

First claim

What is claimed is:

1. An image forming apparatus comprising:
an image bearer;
a nip forming member to form a transfer nip between the image bearer and the nip forming member;
a nip width changing device to change a width of the transfer nip;
a power source to output a transfer bias including an alternating-current (AC) component to transfer a toner image from the image bearer to a recording sheet in the transfer nip; and
a controller to switch between a first mode and a second mode according to a predetermined condition,
a duty of the transfer bias being a first duty and a width of the transfer nip being a first width in the first mode,
the duty of the transfer bias being a second duty lower than the first duty and the width of the transfer nip being a second width greater than the first width in the second mode,
the duty being (T−Tt)/T×100%
where
T denotes one cycle of the transfer bias, and
Tt denotes a time period, in which the transfer bias is on a transfer-directional side to move the toner image from the image bearer to the recording sheet relative to a time-averaged value of the transfer bias, in the one cycle.

2. The image forming apparatus according to claim 1 ,
wherein the first duty is greater than 50% and the second duty is less than 50%.

3. The image forming apparatus according to claim 1 ,
wherein the predetermined condition is a type of the recording sheet.

4. The image forming apparatus according to claim 3 ,
wherein the controller executes the first mode when the type of the recording sheet is a smooth sheet, and
wherein the controller executes the second mode when the type of the recording sheet is an uneven-surface sheet having a greater surface unevenness than a surface unevenness of the smooth sheet.

5. The image forming apparatus according to claim 4 ,
wherein the first duty is greater than 50% and the second duty is less than 50%.

6. The image forming apparatus according to claim 4 ,
wherein the controller controls the power source to output the transfer bias having the duty of from 8% to 35% when the recording sheet is the uneven-surface sheet.

7. The image forming apparatus according to claim 6 ,
wherein the controller controls the power source to output the transfer bias having the duty of less than or equal to 17% when the recording sheet is the uneven-surface sheet.

8. The image forming apparatus according to claim 4 ,
wherein the controller controls the power source to output the transfer bias having the duty of from 70% to 90% when the recording sheet is the smooth sheet.

9. The image forming apparatus according to claim 4 ,
wherein the controller controls the power source to output the transfer bias that alternately changes a polarity of the transfer bias when the recording sheet is the uneven-surface sheet.

10. The image forming apparatus according to claim 4 ,
wherein the controller controls the power source to output the transfer bias having a constant polarity when the recording sheet is the smooth sheet.

11. The image forming apparatus according to claim 1 , further comprising a mode selector that selects between a halftone-image priority mode to give a higher priority to image quality of a halftone image than to image quality of a solid image and a solid-image priority mode to give a higher priority to the image quality of the solid image than to the image quality of the halftone image,
wherein the controller executes the first mode according to the halftone-image priority mode selected by the mode selector, and
wherein the controller executes the second mode according to the solid-image priority mode selected by the mode selector.

12. The image forming apparatus according to claim 1 , further comprising a mode selector that selects between the first mode and the second mode,
wherein the controller executes one of the first mode and the second mode according to a selection result of the mode selector.

13. The image forming apparatus according to claim 1 ,
wherein a frequency of the transfer bias in the first mode is higher than a frequency of the transfer bias in the second mode.

14. The image forming apparatus according to claim 1 ,
wherein a peak-to-peak value of the AC component of the transfer bias in the first mode is smaller than the peak-to-peak value of the AC component of the transfer bias in the second mode.

15. The image forming apparatus according to claim 1 ,
wherein the transfer bias has a transfer-peak value, which is on the transfer-directional side relative to the time-average value, and an opposite-peak value that is different from the transfer-peak value, and
wherein the opposite-peak value in the first mode is on the transfer-directional side relative to the opposite-peak value in the second mode.

16. A transfer method comprising:
transferring a toner image from an image bearer to a recording sheet by a transfer bias having a duty of greater than 50% in the transfer nip, to which a first pressure is applied, when the recording sheet is a plain sheet, and
transferring the toner image from the image bearer to the recording sheet by the transfer bias having the duty of less than 50% in the transfer nip, to which a second pressure greater than the first pressure is applied, when the recording sheet is an uneven sheet having a greater unevenness than the plain sheet, the duty being (T−Tt)/T×100% where T denotes one cycle of the transfer bias, and Tt denotes a time period, in which the transfer bias is on a transfer-directional side to move the toner image from the image bearer to the recording sheet relative to a time-averaged value of the transfer bias, in the one cycle.

17. An image forming apparatus comprising:
an image bearer;
a drive source to drive the image bearer;
a nip forming member to form a transfer nip between the image bearer and the nip forming member;
a power source to output a transfer bias including an alternating-current (AC) component to transfer a toner image from the image bearer to a recording sheet in the transfer nip; and
a controller to switch a mode between a first mode and a second mode according to a predetermined condition,
a duty of the transfer bias being a first duty and a linear velocity of the image bearer being a first linear velocity in the first mode,
the duty of the transfer bias being a second duty lower than the first duty and the linear velocity of the image bearer being a second linear velocity lower than the first linear velocity in the second mode,
the duty being (T−Tt)/T×100%
where
T denotes one cycle of the transfer bias, and
Tt denotes a time period, in which the transfer bias is on a transfer-directional side to move the toner image from the image bearer to the recording sheet relative to a time-averaged value of the transfer bias, in the one cycle.

18. The image forming apparatus according to claim 17 ,
wherein the predetermined condition is a type of the recording sheet.

19. The image forming apparatus according to claim 18 ,
wherein the controller executes the first mode when the type of the recording sheet is a smooth sheet, and
wherein the controller executes the second mode when the type of the recording sheet is an uneven-surface sheet having a greater surface unevenness than a surface unevenness of the smooth sheet.

20. The image forming apparatus according to claim 19 ,
wherein the first duty is greater than 50% and the second duty is less than 50%.

Assignees

• Sugimoto Naomi
• Ishii Hirokazu
• Sugiura Kenji
• Nagata Atsushi
• Mizutani Takehide
• Nakamura Keigo
• Wada Yuuji
• Kochi Naoto
• Tanaka Shinya
• Ricoh Co Ltd

Inventors

• Sugimoto Naomi
• Ishii Hirokazu
• Sugiura Kenji
• Nagata Atsushi
• Mizutani Takehide
• Nakamura Keigo
• Wada Yuuji
• Kochi Naoto
• Tanaka Shinya

Classifications

• G03G15/1665 Primary

  by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat · CPC title

• G03G15/1605 Primary

  using at least one intermediate support (G03G15/1625 takes precedence) · CPC title

• G03G15/6591

  characterised by the recording material, e.g. plastic material, OHP, ceramics, tiles, textiles (details transferring the toner pattern onto particular materials G03G15/1625) · CPC title

• G03G15/5016

  User-machine interface; Display panels; Control console · CPC title

• G03G2215/00751

  of sheet type, e.g. OHP · CPC title