Image formation apparatus

Patent metadata

Field	Value
Publication number	US-11556077-B2
Application number	US-202217589640-A
Country	US
Kind code	B2
Filing date	Jan 31, 2022
Priority date	Feb 12, 2021
Publication date	Jan 17, 2023
Grant date	Jan 17, 2023

Abstract

An image formation apparatus includes an image-bearing member, an exposure device, an electro-conductive member, a bias application unit and a development device having a development roller and a toner supply roller. The bias application unit configured to apply biases to the toner supply roller, the development roller, and the electro-conductive member during image formation so that a first potential difference between the toner supply roller and the development roller and a second potential difference between the electro-conductive member and the development roller cause normally charged toner to travel respectively from the toner supply roller and the electro-conductive member to the development roller, and a third potential difference between the electro-conductive member and the toner supply roller causes normally charged toner to travel from the electro-conductive member to the toner supply roller. The second potential difference is larger than the first potential difference and is larger than the third potential difference.

First claim

What is claimed is:

1. An image formation apparatus comprising:
an image-bearing member;
an exposure device configured to expose the image-bearing member to form an electrostatic latent image on the image-bearing member;
a development device including first and second chambers, first and second conveyance screws, a rotatable development roller, and a rotatable toner supply roller,
wherein the first chamber is configured to accommodate a developer containing toner and a carrier,
wherein the second chamber is divided from the first chamber by a partition wall and configured to form a circulation path of the developer between the second chamber and the first chamber,
wherein the first conveyance screw is arranged in the first chamber and configured to convey the developer in a first direction,
wherein the second conveyance screw is arranged in the second chamber and configured to convey the developer in a second direction opposite to the first direction,
wherein the development roller is arranged facing the image-bearing member and configured to carry and convey the toner to a development position where the electrostatic latent image formed on the image-bearing member is developed, and
wherein the toner supply roller is arranged facing the development roller and configured to carry and convey the developer supplied from the first chamber and supply only the toner to the development roller, where a rotation direction of the toner supply roller is opposite to a rotation direction of the development roller at a position where the toner supply roller and the development roller face each other;
an electro-conductive member arranged facing the toner supply roller and the development roller, downstream of the development position and upstream of a position where the toner supply roller is positioned closest to the development roller in the rotation direction of the development roller; and
a bias application unit configured to apply biases to the toner supply roller, the development roller, and the electro-conductive member during an image formation operation so that (i) a first potential difference is formed between the toner supply roller and the development roller to cause normally charged toner to travel from the toner supply roller to the development roller, (ii) a second potential difference is formed between the electro-conductive member and the development roller to cause normally charged toner to travel from the electro-conductive member to the development roller, and (iii) a third potential difference is formed between the electro-conductive member and the toner supply roller to cause normally charged toner to travel from the electro-conductive member to the toner supply roller,
wherein the second potential difference is larger than the first potential difference and is larger than the third potential difference.

2. The image formation apparatus according to claim 1 ,
wherein a bias having a direct-current component and an alternating-current component superimposed on each other is applied to the toner supply roller,
wherein the bias having the direct-current component and the alternating-current component superimposed on each other is applied to the development roller, and
wherein the bias having the direct-current component and the alternating-current component superimposed on each other is applied to the electro-conductive member.

3. The image formation apparatus according to claim 2 ,
wherein a polarity of the direct-current component of the bias applied to the toner supply roller, a polarity of the direct-current component of the bias applied to the development roller, and a polarity of the direct-current component of the bias applied to the electro-conductive member are the same as a polarity of normally charged toner, and
wherein an absolute value of the direct-current component of the bias applied to the electro-conductive member is larger than an absolute value of the direct-current component of the bias applied to the toner supply roller, and is larger than an absolute value of the direct-current component of the bias applied to the development roller.

4. The image formation apparatus according to claim 2 , wherein the alternating-current component of the bias applied to the electro-conductive member is the same as the alternating-current component of the bias applied to the toner supply roller.

5. The image formation apparatus according to claim 2 , wherein the alternating-current component of the bias applied to the electro-conductive member is the same as the alternating-current component of the bias applied to the development roller.

6. The image formation apparatus according to claim 1 ,
wherein a bias having a direct-current component and an alternating-current component superimposed on each other is applied to the toner supply roller,
wherein the bias having the direct-current component and the alternating-current component superimposed on each other is applied to the development roller, and
wherein a bias having a direct-current component alone is applied to the electro-conductive member.

7. The image formation apparatus according to claim 6 ,
wherein a polarity of the direct-current component of the bias applied to the toner supply roller, a polarity of the direct-current component of the bias applied to the development roller, and a polarity of the direct-current component of the bias applied to the electro-conductive member are the same as a polarity of normally charged toner, and
wherein an absolute value of the direct-current component of the bias applied to the electro-conductive member is larger than an absolute value of the direct-current component of the bias applied to the toner supply roller, and is larger than an absolute value of the direct-current component of the bias applied to the development roller.

8. The image formation apparatus according to claim 6 , wherein an absolute value of a potential of the direct-current component of the bias applied to the electro-conductive member is smaller than an absolute value of a peak potential on the same polarity side as a polarity of normally charged toner out of the alternating-current component of the bias applied to the toner supply roller.

9. The image formation apparatus according to claim 6 , wherein an absolute value of a potential of the direct-current component of the bias applied to the electro-conductive member is smaller than an absolute value of a peak potential on the same polarity side as a polarity of normally charged toner out of the alternating-current component of the bias applied to the development roller.

10. The image formation apparatus according to claim 1 , wherein a power source configured to supply electric power for applying the bias to the toner supply roller by the bias application unit during the image formation operation and a power source configured to supply electric power for applying the bias to the electro-conductive member by the bias application unit during the image formation operation are used in common with each other.

11. The image formation apparatus according to claim 1 , wherein a power source configured to supply electric power for applying the bias to the development roller by the bias application unit during the image formation operation and a power source configured to supply electric power for applying the bias to the electro-conductive member by the bias application unit during the image formation operation are used in common with each other.

12. The image formation apparatus according to claim 1 ,
wherein the toner supply roller includes a first magnet having a plurality of magnetic poles including a first magnetic pole, where the fi

Assignees

• Canon Kk

Inventors

• Sakamaki Tomoyuki
• Fujita Hideki
• Ariizumi Osamu
• Wakisaka Masashi
• Tanaka Chihiro
• Abe Masashi

Classifications

• G03G15/0893

  in a closed loop within the sump of the developing device · CPC title

• G03G15/0896

  Arrangements or disposition of the complete developer unit or parts thereof not provided for by groups G03G15/08 - G03G15/0894 · CPC title

• G03G15/065 Primary

  Arrangements for controlling the potential of the developing electrode · CPC title

• G03G15/0887 Primary

  Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity · CPC title

• G03G15/0808 Primary

  characterised by the developer supplying means, e.g. structure of developer supply roller · CPC title