Charging apparatus and image forming apparatus

Abstract

There is provided a charging apparatus which has high durability and suffers from no rust etc. and of which controllability of charged potential of a photoreceptor is hardly impaired even with a some amount of contaminants such as a toner so that control of charged potential of a photoreceptor can be stably carried out to fall in an appropriate range over a long period of time, and moreover which is inexpensive. A charging apparatus includes a needle electrode, a holding member, two cleaner members, a support member, a moving member, a shield case, and a grid electrode. A length in minor axis of a secondary aggregate of polytetrafluoroethylene contained in a polytetrafluoroethylene-containing nickel layer formed on a surface of the needle electrode is twice or less than a layer thickness of the nickel layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein:

1 is a sectional view schematically showing a configuration of an image forming apparatus according to one embodiment of the invention;

FIG. 2 is a perspective view schematically showing a basic configuration of a charging apparatus used in the image forming apparatus according to the one embodiment of the invention;

FIG. 3 is a front view of the charging apparatus shown in FIG. 2;

FIG. 4 is a sectional view schematically showing a configuration of a discharging electrode used in the charging apparatus according to a first embodiment of the invention;

FIG. 5 is a sectional view schematically showing a configuration of a grid electrode used in the charging apparatus according to a second embodiment of the invention;

FIG. 6 is a graph showing a relationship between unevenness in charged potential (V) of a photoreceptor surface and the number of printed sheets; and

FIG. 7 is a graph showing a relationship between unevenness in charged potential (V) of a photoreceptor surface and the number of printed sheets.

Claims

1. A charging apparatus mounted in an electrophotographic image forming apparatus including a photoreceptor to be opposite to a surface of the photoreceptor, the charging apparatus comprising: a discharging electrode having a plurality of pointed protrusions, that applies voltage to the surface of the photoreceptor to charge the surface of the photoreceptor; anda grid electrode disposed between the discharging electrode and the photoreceptor, that controls a charged potential of the surface of the photoreceptor,wherein at least one of surfaces of the discharging electrode is provided with a polytetrafluoroethylene-containing nickel layer which contains a secondary aggregate of polytetrafluoroethylene, and a length in minor axis of the secondary aggregate of polytetrafluoroethylene contained in the polytetrafluoroethylene-containing nickel layer is twice or less than a layer thickness of the polytetrafluoroethylene-containing nickel layer.

2. The charging apparatus of claim 1, wherein the polytetrafluoroethylene-containing nickel layer is formed on the discharging electrode or a surface of the nickel layer formed on the surface of the discharging electrode, and a length in minor axis of a defect part in the discharging electrode or surface of the nickel layer coated with the polytetrafluoroethylene-containing nickel layer is twice or less than the layer thickness of the polytetrafluoroethylene-containing nickel layer.

3. The charging apparatus of claim 1, wherein the polytetrafluoroethylene-containing nickel layer is formed by an electroless plating method.

4. The charging apparatus of claim 1, wherein a diameter of primary particle of polytetrafluoroethylene contained in the polytetrafluoroethylene-containing nickel layer is 0.7 μm or more.

5. The charging apparatus of claim 1, wherein a layer thickness of the polytetrafluoroethylene-containing nickel layer is larger than the diameter of primary particle of polytetrafluoroethylene.

6. The charging apparatus of claim 1, wherein a nickel plated layer is further formed between the discharging electrode and the polytetrafluoroethylene-containing nickel layer.

7. The charging apparatus of claim 1, wherein the polytetrafluoroethylene-containing nickel layer contains phosphorus together with nickel.

8. An image forming apparatus comprising: a photoreceptor on a surface of which an electrostatic latent image is formed;a charging section for charging the surface of the photoreceptor;an exposure section that irradiates a charged surface of the photoreceptor with signal light which is based on image information to thereby form the electrostatic latent image;a developing section that supplies a toner to the electrostatic latent image on the surface of the photoreceptor to thereby form a toner image;a transfer section that transfers the toner image onto a recording material; anda fixing section that fixes the toner image transferred on the recording material,wherein the charging section is the charging apparatus of claim 1.

9. The image forming apparatus of claim 8, wherein a toner contains hydrophobic silica as an external additive.

10. The image forming apparatus of claim 8, further comprising a cleaning section that removes a toner remaining on the surface of the photoreceptor after the toner image has been transferred onto the recording material, wherein the charging section is disposed vertically below the developing section or the cleaning section.

11. A charging apparatus mounted in an electrophotographic image forming apparatus including a photoreceptor to be opposite to a surface of the photoreceptor, the charging apparatus comprising: a discharging electrode having a plurality of pointed protrusions, that applies voltage to the surface of the photoreceptor to charge the surface; anda grid electrode disposed between the discharging electrode and the photoreceptor, which is provided with a porous plate substrate and a polytetrafluoroethylene-containing nickel layer formed on an entirety or part of a surface of the porous plate substrate,wherein a length in minor axis of a secondary aggregate of polytetrafluoroethylene contained in the polytetrafluoroethylene-containing nickel layer is twice or less than a layer thickness of the polytetrafluoroethylene-containing nickel layer.

12. The charging apparatus of claim 11, wherein the polytetrafluoroethylene-containing nickel layer is formed on the grid electrode or a surface of the nickel layer formed on a surface of the grid electrode, and a length in minor axis of a defect part in the grid electrode or surface of the nickel layer coated with the polytetrafluoroethylene-containing nickel layer is twice or less than the layer thickness of the polytetrafluoroethylene-containing nickel layer.

13. The charging apparatus of claim 11, wherein the polytetrafluoroethylene-containing nickel layer is formed by an electroless plating method.

14. The charging apparatus of claim 11, wherein a diameter of primary particle of polytetrafluoroethylene contained in the polytetrafluoroethylene-containing nickel layer is 0.7 μm or more.

15. The charging apparatus of claim 11, wherein a layer thickness of the polytetrafluoroethylene-containing nickel layer is larger than the diameter of primary particle of polytetrafluoroethylene.

16. The charging apparatus of claim 11, wherein a nickel plated layer is further formed between the porous plate substrate and the polytetrafluoroethylene-containing nickel layer.

17. The charging apparatus of claim 11, wherein the polytetrafluoroethylene-containing nickel layer contains phosphorus together with nickel.

18. The charging apparatus of claim 11, wherein the porous plate substrate is a porous stainless steel plate or a porous copper plate.

19. An image forming apparatus comprising: a photoreceptor on a surface of which an electrostatic latent image is formed;a charging section for charging the surface of the photoreceptor;an exposure section that irradiates a charged surface of the photoreceptor with signal light which is based on image information to thereby form the electrostatic latent image;a developing section that supplies a toner to the electrostatic latent image on the surface of the photoreceptor to thereby form a toner image;a transfer section that transfers the toner image onto a recording material; anda fixing section that fixes the toner image transferred on the recording material,wherein the charging section is the charging apparatus of claim 11.

20. The image forming apparatus of claim 19, wherein a toner contains hydrophobic silica as an external additive.

21. The image forming apparatus of claim 19, further comprising a cleaning section that removes a toner remaining on the surface of the photoreceptor after the toner image has been transferred onto the recording material, wherein the charging section is disposed vertically below the developing section or the cleaning section.