Image forming apparatus capable of changing the surface potential of a photosensitive member

An image forming apparatus comprising:

• a photosensitive member;
• charger means for charging the surface of the photosensitive member while regulating the surface potential of the photosensitive member, said charger means including:
• corona ion generator means for charging the surface of the photosensitive member, and
• grid electrode means provided between the photosensitive member and the corona ion generator means for regulating the surface potential of the photosensitive member;
• current supply means connected to the corona ion generator means for supplying to the corona ion generator means:
• a first current not lower than a specified level for charging the surface of the photosensitive member at a first stabilized voltage at which an image of high contrast can be formed, and
• a second current lower than the specified level for charging the surface of the photosensitive member at a second stabilized voltage at which an image having an intermediate gradation thereof can be formed, the second stabilized voltage being lower than the first stabilized voltage;
• and
• current switch means for switching the level of the current to be supplied by said current supply means to the corona ion generator means between said first current when an image of high contrast is to be formed, and said second current when an image having an intermediate gradation thereof is to be formed.