Image Forming Apparatus

Abstract

The present invention relates to an image forming apparatus including an electrophotographic photosensitive member provided with a substantially cylindrical body having outer circumference on which a photosensitive layer with a latent image forming area is formed, and a contact electrification means positioned substantially parallel to the axial direction of the electrophotographic photosensitive member. A nip width of a contact area between the photosensitive layer and the electrification means is larger at a middle portion than at end portions of the latent image forming area. Preferably, the nip width becomes larger gradually or stepwise as proceeding from the end portions to the middle portion of the latent image forming area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an example of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of the principal portions illustrating the relationship between an electrophotographic photosensitive member and an electrification mechanism of the image forming apparatus shown in FIG. 1.

FIG. 3 is a sectional view and an enlarged view of the principal portions illustrating an example of the electrophotographic photosensitive member of the image forming apparatus shown in FIG. 1.

FIGS. 4A and 4B are sectional views illustrating other examples of the electrophotographic photosensitive member of the image forming apparatus shown in FIG. 1.

FIG. 5 is an overall perspective view illustrating a heater provided at the electrophotographic photosensitive member shown in FIG. 3 or 4.

FIG. 6 is an exploded perspective view illustrating the heater of FIG. 5.

FIG. 7 is a sectional view illustrating a CVD apparatus for forming a photosensitive layer of the electrophotographic photosensitive member shown in FIG. 3 or 4.

FIG. 8 is a schematic view corresponding to FIG. 1, illustrating another example of the image forming apparatus according to the present invention.

FIGS. 9A through 9C are plan views illustrating nip width between the electrophotographic photosensitive member and the electrification roller.

Claims

1. An image forming apparatus comprising: an electrophotographic photosensitive member including a substantially cylindrical body having outer circumference on which a photosensitive layer with a latent image forming area is formed; anda contact electrification unit positioned substantially parallel to axial direction of the body;wherein a nip width of a contact area between the photosensitive layer and the electrification unit is larger at a middle portion than at end portions of the latent image forming area.

2. The image forming apparatus according to claim 1, wherein the nip width gradually becomes larger as proceeding from the end portions to the middle portion of the latent image forming area.

3. The image forming apparatus according to claim 2, wherein the outer diameter of the body gradually becomes larger as proceeding from the end portions to the middle portion of the latent image forming area.

4. The image forming apparatus according to claim 1, wherein the nip width becomes larger stepwise as proceeding from the end portions to the middle portion of the latent image forming area.

5. The image forming apparatus according to claim 4, wherein the outer diameter of the body becomes larger stepwise as proceeding from the end portions to the middle portion of the latent image forming area.

6. The image forming apparatus according to claim 1, further comprising a heating member for heating the latent image forming area of the photosensitive layer.

7. The image forming apparatus according to claim 1, wherein during operation, temperature of the latent image forming area is higher at the middle portion than at the end portions of the latent image forming area.

8. The image forming apparatus according to claim 1, wherein the photosensitive layer comprises a photoconductive layer made of inorganic material and a surface layer made of inorganic material and laminated on the photoconductive layer.

9. An image forming apparatus comprising: an electrophotographic photosensitive member including a substantially cylindrical body having outer circumference on which a photosensitive layer with a latent image forming area is formed; anda contact electrification unit positioned substantially parallel to axial direction of the body;wherein a nip width at a portion including a reference point on the latent image forming area of the electrophotographic photosensitive member is adjusted according to temperature at the reference point.

10. The image forming apparatus according to claim 9, wherein the electrophotographic photosensitive member further comprises a heating member for heating the latent image forming area of the photosensitive layer.

11. The image forming apparatus according to claim 9, wherein the photosensitive layer comprises a photoconductive layer made of inorganic material and a surface layer made of inorganic material and laminated on the photoconductive layer.