Development apparatus and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9268263-B2
Application number	US-201514702011-A
Country	US
Kind code	B2
Filing date	May 1, 2015
Priority date	May 13, 2014
Publication date	Feb 23, 2016
Grant date	Feb 23, 2016

Abstract

A development device wherein a magnetic force distribution of a developer bearing member in a longitudinal direction at positions at which a magnetic flux density of a low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less.

First claim

What is claimed is:

1. A development device comprising:
a developing container which houses two-component developer including toner and a magnetic carrier;
a developer bearing member which bears the two-component developer; and
a magnetic field generation member which includes a plurality of magnetic poles including first and second magnetic poles having the same polarity and being adjacent to each other in a peripheral direction of the developer bearing member, the magnetic field generation member being arranged inside the developer bearing member,
wherein the magnetic field generation member, between the first magnetic pole and the second magnetic pole, includes a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less, and
wherein, in a space between the developing container and the developer bearing member, an electric field formation member which is arranged in a peripheral area of an end portion of the developer bearing member and can form an electric field repelling normal charged polarity of the toner is included.

2. The development device according to claim 1 , wherein the electric field formation member is a sealing member having a charged series of the same polarity as that of the toner and is arranged in the developing container at a position facing the end portion of the developer bearing member.

3. The development device according to claim 2 , wherein the sealing member is arranged in the developing container at a position facing the low magnetic field area.

4. The development device according to claim 1 , wherein the electric field formation member is a sealing member having a charged series of the same polarity as that of the toner and is arranged in the end portion of the developer bearing member.

5. The development device according to claim 1 , wherein the electric field formation member is an electrode to which a voltage is applied by a voltage power supply and is arranged in the developing container at a position facing the end portion of the developer bearing member.

6. The development device according to claim 5 , wherein the voltage power supply applies a voltage to the electrode such that an electric potential difference between a voltage applied to the developer bearing member and the voltage applied to the electrode has the same polarity as charged polarity of the toner.

7. The development device according to claim 5 ,
wherein the electrode has a plurality of sub-electrodes, and the sub-electrodes are arranged in the developing container at positions facing both end portions of the developer bearing member, and
wherein the sub-electrodes are connected together by using a longitudinal electrode disposed to extend in the longitudinal direction of the developer bearing member.

8. An image forming apparatus comprising:
an image bearing member; and
the development device according to claim 1 which supplies toner to the image bearing member.

9. A development device comprising:
a developer bearing member which bears and conveys two-component developer including toner and a carrier and supplies the developer to a developing area;
a magnetic field generation member which is fixedly arranged inside the developer bearing member;
a layer-thickness regulation member which is arranged to face the developer bearing member and regulates a developer layer thickness of the developer bearing member;
a first chamber which includes a first opening portion disposed to face a peripheral face of the developer bearing member and supplies the developer to the developer bearing member through the first opening portion;
a first stirring member which is arranged inside the first chamber;
a second chamber which includes a second opening portion disposed to face the peripheral face of the developer bearing member, collects the developer from the developer bearing member through the second opening portion, and circulates the developer between the first chamber and the second chamber; and
a second stirring member which is arranged inside the second chamber;
wherein the magnetic field generation member includes magnetic poles of the same polarity adjacent to each other in a peripheral direction of the developer bearing member, and between the magnetic poles is a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less.

10. The development device according to claim 9 , wherein a guide member conveying the developer peeled off from the developer bearing member to the second chamber is included.

11. The development device according to claim 10 , wherein, in a portion at which the developer bearing member and the guide member are closest to each other, a position of a longitudinal-direction end portion of the guide member is located on a further inner side than a position of an end portion of a developer bearing area of the developer bearing member in the longitudinal direction of the developer bearing member.

12. The development device according to claim 10 , wherein, in a portion at which the developer bearing member and the guide member are closest to each other, a lateral slip preventing member for preventing movement of the developer to a longitudinal-direction outer side is provided at a position of a longitudinal-direction end portion of the guide member.

13. The development device according to claim 9 , wherein the developer bearing member is arranged above the first stirring member in the gravity direction.

14. An image forming apparatus comprising:
an image bearing member; and
the development device according to claim 9 which supplies toner to the image bearing member.

15. A development device comprising:
a developing container which houses two-component developer including toner and a carrier;
a developer bearing member which bears the two-component developer; and
a magnetic

Assignees

• Canon Kk

Inventors

• Ariizumi Osamu
• Iida Takanori
• Suzuki Shinya
• Terada Ryohei
• Katsuie Ichiro
• Naruge Shoji
• Ootsuka Masahiro

Classifications

• G03G15/0907

  with bias voltage (G03G15/065 takes precedence) · CPC title

• G03G15/0942 Primary

  with means for preventing toner scattering from the magnetic brush, e.g. magnetic seals · CPC title

• G03G15/0889

  for agitation or stirring · CPC title

• G03G15/0921

  Details concerning the magnetic brush roller structure, e.g. magnet configuration · CPC title