IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD

Abstract

An image forming apparatus includes a developing contrast voltage controller to control a developing contrast voltage so as to obtain a desired image density, a transfer condition controller to control transfer conditions for transferring a toner image, an environment sensor to detect an environment, and a correcting coefficient setting unit to refer to a database for pre-registering correcting coefficients to correct the transfer conditions corresponding to the developing contrast voltage and environment and set the correcting coefficients on the basis of the developing contrast voltage controlled by the developing contrast voltage controller and the environment detected by the environment sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the mechanical constitution of the schematic section of the image forming apparatus to which the present invention is applied;

FIG. 2 is a block diagram showing the schematic and functional constitution of the control system inside the image forming apparatus shown in FIG. 1;

FIG. 3 is a schematic view for explaining the developing contrast voltage;

FIG. 4 is a drawing for explaining the mutual relation between the developing contrast voltage VC calculated by the image quality maintaining control process and the charge amount of toner;

FIG. 5 is a drawing for explaining the method for correcting the transfer voltage according to the charge amount of toner;

FIG. 6 is a flow chart for explaining the image quality maintaining control process of the image forming apparatus shown in FIG. 2;

FIG. 7 is graphs for explaining the relationship between the non-exposing portion potential of the photosensitive drum for the absolute value of the grid bias voltage, the exposing portion potential of the photosensitive drum, and the developing bias voltage;

FIG. 8 is a drawing for explaining the high density pattern area and low density pattern area which are formed on the photosensitive drum;

FIG. 9 is a flow chart for explaining the primary transfer control processing of the image forming apparatus shown in FIG. 2;

FIGS. 10A and 10B are drawings showing constitution examples of the database managed by the correcting coefficient database shown in FIG. 2;

FIG. 11 is a flow chart for explaining the secondary transfer control processing of the image forming apparatus shown in FIG. 2;

FIG. 12 is a block diagram showing the mechanical constitution of another schematic section of the image forming apparatus to which the present invention is applied;

FIG. 13 is a block diagram showing the internal schematic and mechanical constitution of the process cartridge shown in FIG. 12; and

FIG. 14 is a perspective view showing the appearance constitution of the process cartridge shown in FIG. 12.

Claims

1. An image forming apparatus comprising: control means for controlling a developing contrast voltage so as to obtain a desired image density;transfer condition control means for controlling transfer conditions for transferring a toner image;environment detecting means for detecting an environment; andcorrecting coefficient setting means for referring to a database for pre-registering correcting coefficients for correcting the transfer conditions corresponding to the developing contrast voltage and environment and setting the correcting coefficients on the basis of the developing contrast voltage controlled by the control means and the environment detected by the environment detecting means.

2. The apparatus according to claim 1, wherein the developing contrast voltage is a difference voltage between a potential of a surface of an image carrier on which an image is formed and a developing bias potential.

3. The apparatus according to claim 1, wherein the transfer condition control means corrects the transfer conditions on the basis of the correcting coefficients set by the correcting coefficient setting means.

4. The apparatus according to claim 1, wherein the environment detecting means detects at least relative humidity.

5. The apparatus according to claim 1, wherein the correcting coefficients pre-registered in the database are different from each other between a plurality of sections divided beforehand according to the developing contrast voltage.

6. The apparatus according to claim 5, wherein the plurality of sections divided according to the developing contrast voltage are any one of a low charging area in which a toner charge amount is small, an appropriate charging area in which the toner charge amount is within a predetermined standard value range, and a high charging area in which the toner charge amount is large, and the correcting coefficients pre-registered in the database are respectively a value smaller than 1, a value of 1, and a value larger than 1 in the low charging area, the appropriate charging area, and the high charging area.

7. The apparatus according to claim 1, wherein the correcting coefficients pre-registered in the database are values according to the environment.

8. An image forming method comprising: controlling a developing contrast voltage so as to obtain a desired image density;controlling transfer conditions for transferring a toner image;detecting an environment; andreferring to a database for pre-registering correcting coefficients for correcting the transfer conditions corresponding to the developing contrast voltage and the environment and setting the correcting coefficients on the basis of the developing contrast voltage controlled and the environment detected.

9. The method according to claim 8, wherein the developing contrast voltage is a difference voltage between a potential of a surface of an image carrier on which an image is formed and a developing bias potential.

10. The method according to claim 8, wherein on the basis of the set correcting coefficients, the transfer conditions are corrected.

11. The method according to claim 8, wherein the environment detected is at least relative humidity.

12. The method according to claim 8, wherein the correcting coefficients pre-registered in the database are different from each other between a plurality of sections divided beforehand according to the developing contrast voltage.

13. The method according to claim 12, wherein the plurality of sections divided according to the developing contrast voltage are any one of a low charging area in which a toner charge amount is small, an appropriate charging area in which the toner charge amount is within a predetermined standard value range, and a high charging area in which the toner charge amount is large, and the correcting coefficients pre-registered in the database are respectively a value smaller than 1, a value of 1, and a value larger than 1 in the low charging area, the appropriate charging area, and the high charging area.

14. The method according to claim 8, wherein the correcting coefficients pre-registered in the database are values according to the environment.

15. An image forming apparatus comprising: a developing contrast voltage controller to control a developing contrast voltage so as to obtain a desired image density;a transfer condition controller to control transfer conditions for transferring a toner image;an environment sensor to detect an environment; anda correcting coefficient setting unit to refer to a database for pre-registering correcting coefficients to correct the transfer conditions corresponding to the developing contrast voltage and environment and set the correcting coefficients on the basis of the developing contrast voltage controlled by the developing contrast voltage controller and the environment detected by the environment sensor.

16. The apparatus according to claim 15, wherein the developing contrast voltage is a difference voltage between a potential of a surface of an image carrier on which an image is formed and a developing bias potential.

17. The apparatus according to claim 15, wherein the transfer condition controller corrects the transfer conditions on the basis of the correcting coefficients set by the correcting coefficient setting unit.

18. The apparatus according to claim 15, wherein the correcting coefficients pre-registered in the database are different from each other between a plurality of sections divided beforehand according to the developing contrast voltage.

19. The apparatus according to claim 18, wherein the plurality of sections divided according to the developing contrast voltage are any one of a low charging area in which a toner charge amount is small, an appropriate charging area in which the toner charge amount is within a predetermined standard value range, and a high charging area in which the toner charge amount is large, and the correcting coefficients pre-registered in the database are respectively a value smaller than 1, a value of 1, and a value larger than 1 in the low charging area, the appropriate charging area, and the high charging area.

20. The apparatus according to claim 15, wherein the correcting coefficients pre-registered in the database are values according to the environment.