Developing device and image forming apparatus

Abstract

An developing device comprising a developing roller for developing an electrostatic latent image on a photo conductor; a developing roller driving unit for rotating the developing roller in a forward direction and in a backward direction respectively while development is performed and not performed; a thickness regulating member, which is pressed against a surface of the developing roller, for regulating a thickness of developer adhered to the surface of the developing roller; and a suppression unit for suppressing a pressing force of the thickness regulating member when the developing roller is rotated in the backward direction.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view showing the essential structure of an image forming apparatus comprising a developing device according to the present invention;

FIG. 2 is a block diagram showing the structure of an image forming apparatus according to the present invention;

FIG. 3 is an explanatory view showing an example of rotation control of a developing roller;

FIG. 4 is an explanatory view showing an example of the amount of backward rotation in a case where the developing roller is rotated backward;

FIG. 5 is an explanatory view showing an example of the frequency of backward rotation in a case where the developing roller is rotated backward;

FIG. 6 is an explanatory view showing another example of the frequency of backward rotation in a case where the developing roller is rotated backward;

FIG. 7 is a schematic view of a case where the developing roller is rotated forward;

FIG. 8 is a schematic view of a case where the developing roller is rotated backward;

FIGS. 9A and 9B are explanatory views showing the state of toner which piles up between a second doctor blade and the surface of the developing roller;

FIG. 10 is a flow chart showing the process procedure of a control unit;

FIG. 11 is a flow chart showing the process procedure of a control unit; and

FIG. 12 is a flow chart showing the procedure of a backward rotation driving process.

Claims

1. A developing device comprising: a developing roller for developing an electrostatic latent image on a photo conductor;a developing roller driving unit for rotating the developing roller in a forward direction and in a backward direction respectively while development is performed and not performed;a thickness regulating member, which is pressed against a surface of the developing roller, for regulating a thickness of developer adhered to the surface of the developing roller; anda suppression unit for suppressing a pressing force of the thickness regulating member when the developing roller is rotated in the backward direction.

2. The developing device according to claim 1, wherein the suppression unit separates the thickness regulating member from the surface of the developing roller.

3. The developing device according to claim 1, wherein the suppression unit comprises a cam-like rotor plate to be in contact with the thickness regulating member, andthe thickness regulating member is driven by rotation of the cam-like rotor plate.

4. The developing device according to claim 1, wherein the thickness regulating member comprises a first thickness regulating plate and a second thickness regulating plate separated from the first thickness regulating plate in said order upstream of a development position, where the electrostatic latent image is developed, in the forward direction anda pressing force of the first thickness regulating plate is larger than a pressing force of the second thickness regulating plate.

5. The developing device according to claim 4, further comprising a splash preventing plate, which is provided upstream of the development position in the forward direction to be in contact with the photo conductor, for preventing splash of developer, wherein the developing roller driving unit rotates the developing roller in the backward direction within a range of a perimeter of the developing roller corresponding to a distance between the development position and a contact position of the splash preventing plate.

6. The developing device according to claim 1, wherein the developing roller is rotatable at a plurality of different rotational speeds, andthe developing roller driving unit rotates the developing roller in the backward direction at a lowest speed of the rotational speeds.

7. An image forming apparatus comprising: a photo conductor for forming an electrostatic latent image;a developing device described in claim 1 for developing the electrostatic latent image formed on the photo conductor; andan image forming unit for transferring the electrostatic latent image developed by the developing device onto a sheet for completing an image formation.

8. An image forming apparatus comprising: a photo conductor for forming an electrostatic latent image;a developing device described in claim 4 for developing the electrostatic latent image formed on the photo conductor; andan image forming unit for transferring the electrostatic latent image developed by the developing device onto a sheet for completing an image formation.

9. An image forming apparatus comprising: a photo conductor for forming an electrostatic latent image;a developing device described in claim 5 for developing the electrostatic latent image formed on the photo conductor; andan image forming unit for transferring the electrostatic latent image developed by the developing device onto a sheet for completing an image formation.

10. An image forming apparatus comprising: a photo conductor for forming an electrostatic latent image;a developing device described in claim 6 for developing the electrostatic latent image formed on the photo conductor; andan image forming unit for transferring the electrostatic latent image developed by the developing device onto a sheet for completing an image formation.

11. The image forming apparatus according to claim 7, further comprising: an information obtaining unit for obtaining information relating to usage of the developing roller; anda control unit for controlling an amount of rotation of the developing roller in the backward direction based on the information obtained by the information obtaining unit when the developing roller is rotated in the backward direction.

12. The image forming apparatus according to claim 11, further comprising a density information obtaining unit for obtaining information relating to an image formation density, wherein the control unit controls an amount of rotation of the developing roller in the backward direction based on the information obtained by the density information obtaining unit.

13. The image forming apparatus according to claim 7, further comprising: an information obtaining unit for obtaining information relating to usage of the developing roller; anda control unit for controlling a frequency of rotation of the developing roller in the backward direction based on the information obtained by the information obtaining unit when the developing roller is rotated in the backward direction.

14. The image forming apparatus according to claim 13, further comprising a density information obtaining unit for obtaining information relating to an image formation density, wherein the control unit controls a frequency of rotation of the developing roller in the backward direction based on the information obtained by the density information obtaining unit.