Image forming apparatus capable of suppressing toner fusion on a photosensitive member

An image forming apparatus comprising:

• a rotatable photosensitive member;
• an image forming portion configured to form a toner image on said photosensitive member;
• a cleaning device configured to clean said photosensitive member,
• wherein said cleaning device comprises:
• a blade contacting said photosensitive member at a first contact portion and configured to clean said photosensitive member;
• a rotatable brush contacting said photosensitive member at a second contact portion upstream of the first contact portion with respect to a rotational direction of said photosensitive member and configured to collect toner remaining on said photosensitive member;
• and
• an applying portion configured to apply a bias to said brush;
• and
• a controller configured to control said applying portion,
• wherein said controller controls said applying portion so as to apply the bias to said brush so that a potential of said brush has a polarity opposite to a normal charge polarity of the toner when an image forming region of a surface of said photosensitive member passes through the second contact portion, and
• when a tensile strength of said brush is A (cn/dtex), a thickness of said brush is B (denier), a bristle density of said brush is C (kF/inch2), a length of said brush is D (mm), and an elastic deformation rate of the surface of said photosensitive member is E (%), the following relationships are satisfied:
• 48(%)≤E≤60(%), and
• 400≤{A×B2×C/D2}≤20408.