Image forming apparatus including developing unit

An image forming apparatus comprising:

• an image bearing member on the surface of which an electrostatic latent image is formed;
• an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the image bearing member;
• a developer accommodating unit that accommodates developer containing at least toner;
• a developing unit that supplies toner to the image bearing member and develops the electrostatic latent image as toner image;
• a developer supply unit that supplies the developer accommodated in the developer accommodating unit to the developing unit;
• a toner density detecting unit that detects toner density in the developing unit;
• a mode setting unit that when toner density detected by the toner density detecting unit is less than a first standard value and a second standard value that is lower than the first standard value or more, sets a first developer supply mode as a mode for supplying developer to the developing unit and when the toner density detected by the toner density detecting unit is less than the second standard value, sets a second developer supply mode as a mode for supplying developer to the developing unit;
• a first supply control unit that when the first developer supply mode is set by the mode setting unit, controls the developer supply unit to supply developer accommodated in the developer accommodating unit to the developing unit;
• a second supply control unit that when the second developer supply mode is set by the mode setting unit, interrupts development of the electrostatic latent image by the developing unit and controls the developer supply unit to supply the developer accommodated in the developer accommodating unit to the developing unit;
• and
• a second standard value setting unit that calculates toner consumption speed in the developing unit, sets the second standard value to be a lower value as the toner consumption speed increases, and sets the second standard value to be a higher value as the toner consumption speed decreases.