Patent ID: 7228085

Claim:
A color image forming apparatus which, in a sequential order for each of plural colors of a composite color image, charges plural photosensitive bodies, exposes electrostatic latent images on the plural photosensitive bodies, develops latent images on the photosensitive bodies into color images, and transfers the color images to sequentially form images of each of the plural colors one on another to form the composite color image and transcribing the composite color image onto a printing medium, the color image forming apparatus comprising: plural charging units which perform the charging process for each of the plural colors; plural exposing units which perform the exposing process for each of the plural colors; plural developing units which perform the developing process for each of the plural colors; plural transfer units which perform the transfer process for each of the plural colors; and a power supply unit which supplies power to the plural charging units, the plural developing units, and the plural transfer units, the power supply unit outputting the same reference voltage toward each of the charging units, developing units and transfer units, the outputted reference voltage varying in accordance with changes in an environment of the color image forming apparatus, wherein voltages are applied to each of the plural charging units, the plural developing units, and the plural transfer units based on at least the reference voltage output toward each of the charging units, developing units and transfer units.