Color image forming apparatus

Abstract

A color image forming apparatus includes: a plurality of image carriers each on which a toner image having a color different from each other is formed; an intermediate transfer member to which each of the image carriers is transferred; a plurality of a primary transfer units each which transfers a toner image formed on each of the plurality of image carriers onto the intermediate transfer member; a discharging unit provided between two adjoining image carriers in a moving direction of the intermediate transfer member, which discharges an electrical charge of a toner image transferred on the intermediate transfer member; and a secondary transfer unit which transfers a plurality colors of toner images which have been superimposed on the intermediate transfer member onto a transfer material.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a cross sectional view of a total configuration of a color image forming apparatus;

FIG. 2 illustrates a cross sectional view of a main portion of the color image forming apparatus;

FIG. 3 illustrates a schematic diagram of the main portion of an example 1 of the color image forming apparatus;

FIG. 4 illustrates a schematic diagram of the main portion of an example 2 of the color image forming apparatus;

FIG. 5 illustrates a schematic diagram of the main portion of an example 3 of the color image forming apparatus;

FIG. 6 illustrates a schematic diagram of the main portion of a comparison example of the color image forming apparatus; and

FIGS. 7( a)-7(n) illustrate schematic diagrams of various disposal examples of discharging units.

Claims

1. A color image forming apparatus comprising: (a) a plurality of image carriers each on which a toner image having a color different from each other is formed;(b) an intermediate transfer member;(c) a plurality of a primary transfer units each transferring a toner image formed on each of the plurality of image carriers onto the intermediate transfer member;(d) a discharging unit provided between two adjoining image carriers in a moving direction of the intermediate transfer member, which discharges an electrical charge of a toner image transferred on the intermediate transfer member; and(e) a secondary transfer unit transferring a plurality colors of toner images which have been superimposed on the intermediate transfer member onto a transfer material.

2. The color image forming apparatus of claim 1, further comprising a second discharging unit provided downstream of a most-downstream primary transfer unit and upstream of the secondary transfer unit with respect to the moving direction of the intermediate transfer member.

3. A color image forming apparatus comprising: (a) n units of image carriers;(b) an intermediate transfer member;(c) n units of primary transfer units which transfers toner images of n colors formed on the image carriers onto the intermediate transfer member;(d) a discharging unit which discharges an electric charge of a toner image transferred on the intermediate transfer member, the discharging unit being disposed at a position just after a first transfer process by any one of the primary transfer units for a first to (n−1)th color; and(e) a secondary transfer unit which transfers a plurality colors of toner images which have been superimposed on the intermediate transfer member onto a transfer material.

4. The color image forming apparatus of claim 3, wherein the discharging unit is disposed upstream of the primary transfer unit at least for an n-th color.

5. The color image forming apparatus of claim 3, further comprising a second discharging unit provided downstream of the first transfer unit for an n-th color.

6. The color image forming apparatus of claim 1, wherein the discharging unit discharges an electric charge of the toner image corresponding to a lower layer of a plurality of layers which have been superimposed on the intermediate transfer member.

7. The color image forming apparatus of claim 3, wherein the discharging unit discharges an electric charge of the toner image corresponding to a lower layer of a plurality of layers which have been superimposed on the intermediate transfer member.

8. The color image forming apparatus of claim 1, wherein the discharging unit is a scorotron discharger.

9. The color image forming apparatus of claim 3, wherein the discharging unit is a scorotron discharger.

10. The color image forming apparatus of claim 8, wherein the scorotron discharger comprises a discharging electrode to which a voltage having a polarity reverse to an electric charge of the toner image that has been carried on the intermediate transfer member, is applied, and a grid electrode to which a voltage having the same polarity as that of the electric charge of the toner image, is applied.

11. The color image forming apparatus of claim 9, wherein the scorotron discharger comprises a discharging electrode to which a voltage having a polarity reverse to an electric charge of the toner image that has been carried on the intermediate transfer member, is applied, and a grid electrode to which a voltage having the same polarity as that of the electric charge of the toner image, is applied.