DEVELOPING DEVICE USING ELECTROSTATIC TRANSPORT & HOPPING (ETH)

Abstract

A developing device, process cartridge, and image forming apparatus that use ETH development, and are capable of forming good multi-color images with a simple construction, and are capable of preventing the dispersal of powder. The developing device is for developing latent images on a latent image carrying member by applying powder to the latent image carrying member, and comprises: a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate a progressive wave electric field to move the powder; a voltage supply device for applying a multi-phase voltage to the transport electrodes; and a transport member surface potential determination device for determining the surface potential of the transport member. The voltage supply device in the developing device according to the present invention applies a multi-phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:

FIG. 1 is a diagram showing the schematic structure of a developing device according to an embodiment of the present invention;

FIG. 2 is a plan view showing the structure of the transport substrate of the developing device;

FIG. 3 is a sectional view on the line A-A′ in FIG. 2;

FIG. 4 is a sectional view on the line B-B′ in FIG. 2;

FIG. 5 is a sectional view on the line C-C′ in FIG. 2;

FIG. 6 is a sectional view on the line D-D′ in FIG. 2;

FIG. 7 is a wave form diagram showing an example of a drive wave form applied to the transport substrate;

FIG. 8 is a diagram showing the carrying and hopping of powder;

FIG. 9A through 9D are diagrams showing specific examples of carrying and hopping;

FIG. 10 a block diagram showing an example of the structure of the drive circuit of FIG. 1;

FIG. 11 is a time chart showing an example of the drive wave form of the transport voltage pattern and the collecting and transport voltage pattern;

FIG. 12 is a time chart showing an example of the drive wave form of the hopping voltage pattern;

FIG. 13 is a time chart showing an example of another drive wave form of the hopping voltage pattern;

FIG. 14 is a diagram showing the electrode width and electrode spacing of the transport substrate of the developing device;

FIG. 15 is a characteristic diagram showing an example of the relationship between electrode width and the electric field (X direction) at the 0 V electrode end;

FIG. 16 is a characteristic diagram showing an example of the relationship between electrode width and the electric field (Y direction) at the 0 V electrode end;

FIG. 17 is a diagram showing the potential of toner adhering to the photosensitive member;

FIGS. 18A and 18B are diagrams showing the relationship between the hopping voltage and the potential of the image portions, and the potential of the non-image portions, between a plurality of developing operations;

FIG. 19 is a circuit diagram showing an example of the structure of the wave form amplifier of FIG. 10;

FIG. 20A through 20C are diagrams showing the signal wave form from the pulse signal generation circuit of FIG. 10;

FIG. 21 is a circuit diagram showing an example of the structure of the wave form amplifier of FIG. 10;

FIGS. 22A through 22C are diagrams showing the signal wave form from the pulse signal generation circuit of FIG. 10;

FIG. 23 is a diagram showing an example of the structure of an image forming apparatus that uses the developing device;

FIG. 24 is a diagram showing an example of the schematic structure of the developing device;

FIG. 25 is a flowchart showing an example of the procedure for setting the process conditions;

FIG. 26 is a diagram showing the schematic structure of an image forming apparatus provided with a process cartridge according to a separate invention; and

FIG. 27 is a diagram showing the schematic structure of the process cartridge in FIG. 26.

Claims

1. A developing device for applying powder to a latent image carrying member to develop latent images on the latent image carrying member, comprising: a transport member disposed in opposition to the latent image carrying member, and having a plurality of transport electrodes for generating electric fields to transport powder;voltage supply means for applying n phase (where n is a positive integer equal to or greater than 2) voltage to the transport electrodes; andtransport member surface potential determination means for determining the surface potential of the transport member, whereinthe voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member.

2. The developing device as claimed in claim 1, wherein when latent image forming and developing are repeated to successively develop powder in different colors on the same latent image carrying member, the voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member in respect of the powder of each color.

3. The developing device as claimed in claim 1, wherein when developing the powder for the second and subsequent colors, the voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions that has been reduced by the charge of the previously developed powder and the potential of the non-image portions of the latent image carrying member.

4. The developing device as claimed in claim 1, wherein when developing the powder for the second and subsequent colors, the voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions, for which the charge on the previously developed powder has been increased by charging that is carried out prior to writing the latent image, and the potential of the non-image portions, of the latent image carrying member.

5. The developing device as claimed in claim 1, wherein when developing the powder for the second and subsequent colors, the voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions that has been reduced by the charge of the previously developed powder and the charge on the powder that has been increased by charging that is carried out prior to writing the latent image, and the potential of the non-image portions of the latent image carrying member.

6. The developing device as claimed in claim 1, wherein the electric field that moves the powder is a progressive wave electric field.

7. The developing device as claimed in claim 1, wherein the wave form of the voltage applied to the electrodes of the transport member is a wave form obtained by superimposing a direct current bias onto a pulse voltage.

8. The developing device as claimed in claim 1, wherein surface potential V on the transport member, when the surface potential V on the mth time (where m is a positive integer) in an order that powder is applied to the latent image carrying member is Vm, satisfies Vm>Vm+1.

9. A process cartridge which has at least a developing device for developing latent images on a latent image carrying member by applying powder to the latent image carrying member, and which can be freely inserted into and removed from a main body of an image forming apparatus, the process cartridge comprising: a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate electric fields to transport powder;voltage supply means for applying n phase (where n is a positive integer equal to or greater than 2) voltage to the transport electrodes; andtransport member surface potential determination means for determining the surface potential of the transport member, whereinthe voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member.

10. An image forming apparatus comprising either a developing device that applies powder to a latent image carrying member to develop latent images on the latent image carrying member, or a process cartridge, wherein the developing device comprises:a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate electric fields to transport powder;voltage supply means for applying n phase (where n is a positive integer equal to or greater than 2) voltage to the transport electrodes; andtransport member surface potential determination means for detetermining the surface potential of the transport member, whereinthe voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member, andthe process cartridge comprises at least the developing device, and can be freely inserted into and removed from the main body of the image forming apparatus.

11. The image forming apparatus as claimed in claim 10, further comprising potential control means for controlling the surface potential on the transport member of the developing device so that the surface potential is a value between the potential of the image portions and the potential of the non-image portions of the latent image carrying member.

12. The image forming apparatus as claimed in claim 10, wherein the transport voltage applied to the transport member of the developing device is a wave form in which a pulse voltage and a direct current bias are superimposed, and the transport voltage is controlled by adjusting the value of the direct current bias.

13. A color image forming apparatus which comprises a plurality of process cartridges including at least a developing device for developing latent images on a latent image carrying member by applying powder to the latent image carrying member, and which can be freely inserted into and removed from the main body of the image forming apparatus, wherein the developing device comprises:a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate electric fields to transport powder;voltage supply means for applying n phase (where n is a positive integer equal to or greater than 2) voltage to the transport electrodes; andtransport member surface potential determination means for determining the surface potential of the transport member, whereinthe voltage supply means applies the n phase voltage to the transport electrodes so that the surface potential on the transport member is between the potential of the image portions and the potential of the non-image portions of the latent image carrying member.