Development apparatus, image forming apparatus and development method

Abstract

In a development apparatus of the hybrid method using a component developer, a development apparatus and a development method that prevent the reduction of density or the occurrence of residual images (ghost images) and can carry out good image forming over a long period. A development apparatus having the feature that the surfaces of the toner supporting member and the developer supporting member move in a mutually opposite direction at the part that they are opposite to each other, and the electric field in the closest part applied in a direction to recover the toner from the toner supporting member to the developer supporting member is in the range from 2.5×106 V/m to 5×106 V/m, and the share (PD) of the developer in the space of the closest part of the opposing portion satisfies the following relationship.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an outline configuration diagram of the essential part of an image forming apparatus according to a preferred embodiment of the present invention.

FIG. 2 shows an outline configuration diagram of the essential part of a conventional image forming apparatus.

FIG. 3 shows an outline configuration diagram of a charge amount measurement apparatus.

FIGS. 4( a) and 4(b) show sample images for evaluating occurrence of memory.

FIGS. 5( a) and 5(b) show schematically the state of application of voltage in examples of experiments.

FIG. 6 shows the relationship between the ratio of presence and clogging of the developer between the toner supporting member and the developer supporting member.

FIG. 7 shows the relationship between the separation electric field strength of the opposite polarity particles and the amount of separation.

Claims

1. A development apparatus, comprising: a developer supporting member which supports developer containing toner and carrier on the surface thereof to convey the developer;a toner supporting member which is disposed facing the developer supporting member to receive the toner transferred from the developer supporting member onto the surface thereof, to convey the toner to a development area, and to cause the developer supporting member to collect the toner having passed through the development area, wherein the surface of the toner supporting member travels to an opposite direction of a traveling direction of the surface of the developer supporting member at an opposing portion between the toner supporting member and the developer supporting member; andan electric field forming mechanism which is adapted to form an alternating electric field between the developer supporting member and the toner supporting member, wherein a strength of an electric field in a direction in which the toner is collected from the toner supporting member onto the developer supporting member is in a range from 2.5×106 V/m to 5×106 V/m at the closest portion between the developer supporting member and the toner supporting member, and a share PD of the developer in a space at the closest portion between the developer supporting member and the toner supporting member satisfies the following relationship, 0.09≦PD≦650×Dss

2. The development apparatus of claim 1, wherein a strength of an electric field in a direction in which the toner is supplied from the developer supporting member onto the toner supporting member is in a range from 2.5×106 V/m to 6×106 V/m at the closest portion between the developer supporting member and the toner supporting member.

3. The development apparatus of claim 1, wherein the developer contains opposite polarity particles which are different from the toner and the carrier and are charged in an opposite polarity to a polarity of electrostatic charge of the toner.

4. The development apparatus of claim 3, wherein a strength of an electric field in a direction in which the toner is supplied from the developer supporting member onto the toner supporting member is in a range from 2.5×106 V/m to 6×106 V/m at the closest portion between the developer supporting member and the toner supporting member.

5. The development apparatus of claim 3, wherein a number average particle diameter of the toner is from 3 to 15 μm, and a number average particle diameter of the opposite polarity particles is from 100 to 1000 nm.

6. The development apparatus of claim 1, wherein the carrier has magnetism, and the developer supporting member comprises a fixedly arranged magnet body and a rotatable sleeve in which the magnet body is mounted.

7. The development apparatus of claim 6, wherein the developer forms a magnetic brush on the developer supporting member to collect the toner from the toner supporting member while supplying new toner onto the toner supporting member by rubbing the toner supporting member.

8. An image forming apparatus, comprising: an image carrier;an electrostatic latent image forming mechanism which is adapted to form an electrostatic latent image on the image carrier;a development apparatus which is adapted to develop the electrostatic latent image on the image carrier to form a toner image, the development apparatus including:a developer supporting member which supports developer containing toner and carrier on the surface thereof to convey the developer;a toner supporting member which is disposed facing the developer supporting member to receive the toner transferred from the developer supporting member onto the surface thereof, to convey the toner to a development area, and to cause the developer supporting member to collect the toner having passed through the development area, wherein the surface of the toner supporting member travels to an opposite direction of a traveling direction of the surface of the developer supporting member at an opposing portion between the toner supporting member and the developer supporting member;an electric field forming mechanism which is adapted to form an alternating electric field between the developer supporting member and the toner supporting member, wherein a strength of an electric field in a direction in which the toner is collected from the toner supporting member onto the developer supporting member is in a range from 2.5×106 V/m to 5×106 V/m at the closest portion between the developer supporting member and the toner supporting member; andan image transfer mechanism which is adapted to transfer the toner image formed on the image carrier onto a recording media;wherein a share PD of the developer in a space at the closest portion between the developer supporting member and the toner supporting member satisfies the following relationship, 0.09≦PD≦650×Dss

9. A developing method, comprising the steps of: causing a developer supporting member to support developer containing toner and carrier;causing a surface of a toner supporting member, which is disposed facing the developer supporting member, to travel in a direction opposite to a traveling direction of the surface of the developer supporting member at an opposing portion between the toner supporting member and the developer supporting member;forming an alternating electric field between the developer supporting member and the toner supporting member so that the strength of the electric field in a direction in which the toner is collected from the toner supporting member onto the developer supporting member is in a range from 2.5×106 V/m to 5×106 V/m at the closest portion between the developer supporting member and the toner supporting member; andsetting a share PD of the developer in a space at the closest portion between the developer supporting member and the toner supporting member so as to satisfy the following relationship, 0.09≦PD≦650×Dss

10. The developing method of claim 9, wherein the alternating electric field is formed so that a strength of an electric field in a direction in which the toner is supplied from the developer supporting member onto the toner supporting member is in a range from 2.5×106 V/m to 6×106 V/m at the closest portion between the developer supporting member and the toner supporting member.

11. The developing method of claim 9, wherein the developer contains opposite polarity particles which are different from the toner and the carrier and are charged in an opposite polarity to a polarity of electrostatic charge of the toner.

12. The developing method of claim 9, wherein the alternating electric field is formed so that a strength of an electric field in a direction in which the toner is supplied from the developer supporting member onto the developer toner member is in a range from 2.5×106 V/m to 6×106 V/m at the closest portion between the developer supporting member and the toner supporting member.