Developing device, and image forming apparatus provided with the same

A developing device for supplying a developer to a photosensitive drum, which has a cylindrical shape, and is rotatable around an axis thereof for forming an electrostatic latent image on a circumferential surface thereof, comprising:

• a developing roller disposed to face the photosensitive drum, the developing roller having a cylindrical shape, and being rotatable around an axis thereof for carrying a developer on a circumferential surface thereof, the developing roller including a cylindrical base member and a flange portion to be mounted in an axial end of the base member, the flange portion has a press-fitting portion to be pressed in an inner periphery of the base member, wherein
• the developing roller is provided with a small diameter portion, the small diameter portion being a part of the circumferential surface of the developing roller, the small diameter portion extending from an axial end of the developing roller axially inward by a predetermined length, the small diameter portion having an outer diameter smaller than an axially middle portion of the developing roller,
• the developing roller is provided with a surface layer to be formed by an immersion process of immersing the base member in such a manner that an axial direction of the developing roller is aligned with a vertical direction, and
• the small diameter portion is formed in advance on a lower end of the base member before the immersion process is applied.

A developing device for supplying a developer to a photosensitive drum, which has a cylindrical shape, and is rotatable around an axis thereof for forming an electrostatic latent image on a circumferential surface thereof, comprising:

• a developing roller disposed to face the photosensitive drum, the developing roller having a cylindrical shape, and being rotatable around an axis thereof for carrying a developer on a circumferential surface thereof, the developing roller including a cylindrical base member and a flange portion to be mounted in an axial end of the base member, the flange portion has a press-fitting portion to be pressed in an inner periphery of the base member, wherein
• the developing roller is provided with a small diameter portion, the small diameter portion being a part of the circumferential surface of the developing roller, the small diameter portion extending from an axial end of the developing roller axially inward by a predetermined length, the small diameter portion having an outer diameter smaller than an axially middle portion of the developing roller,
• the developing roller is provided with a surface layer to be formed by an immersion process of immersing the base member in such a manner that an axial direction of the developing roller is aligned with a vertical direction,
• an outer diameter of the press-fitting portion is set to be equal to or larger than an inner diameter of an axial end of the base member, and
• a thickness of the surface layer is set to be larger than one-half of a difference between the outer diameter of the press-fitting portion and the inner diameter of the axial end of the base member.