Image forming apparatus

An image forming apparatus which forms an image on an image-forming medium by use of a developer comprising:

• an image input section which inputs image data,
• an optical unit which applies light to an image carrier to expose the image carrier to light according to image data input by said image input section,
• a transferring section which transfers a developer image corresponding to an electrostatic latent image formed on the image carrier by applying light thereto by use of said optical unit onto the image-forming medium,
• a fixing device including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters,
• an image area determining section which determines whether a fixing process is necessary or not for each of areas corresponding to the portions of the heat roller respectively heated by the heaters based on image data input by said image input section,
• a heater control section which supplies preset electric power only to the heater corresponding to the area which is determined to require the fixing process by said image area determining section to set the corresponding portion of the heat roller to a fixing temperature, and
• a printing control section which feeds the image-forming medium having the developer image transferred thereon by said transferring section to the fixing device and fixes the to-be-fixed agent on the image-forming medium by use of the heat roller when the portion of the heat roller corresponding to the heater supplied with the electric power by said heater control section has reached a preset fixing temperature.

An image forming apparatus which forms an image on an image-forming medium by use of a developer comprising:

• image input means for inputting image data,
• optical control means for applying light to an image carrier to expose the image carrier to light according to image data input by said image input means,
• transferring means for transferring a developer image corresponding to an electrostatic latent image formed on the image carrier by applying light thereto by said optical control means onto the image-forming medium,
• fixing means including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters,
• image area determining means for determining whether a fixing process is necessary or not for each of areas corresponding to the portions of the heat roller which are selectively heated by the heaters based on image data input by said image input means,
• heater control means for supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by said image area determining means to set the corresponding portion of the heat roller to a fixing temperature, and
• printing control means for feeding the image-forming medium having the developer image transferred thereon by said transferring means to the fixing means and fixing the to-be-fixed agent on the image-forming medium by use of the heat roller when the portion of the heat roller corresponding to the heater supplied with the electric power by said heater control means has reached a preset fixing temperature.

An image forming method used in an image forming apparatus using a fixing device including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters comprising:

• inputting image data,
• applying laser light to an image carrier to expose the image carrier to light according to the input image data,
• transferring a developer image corresponding to an electrostatic latent image formed on the image carrier onto the image-forming medium,
• determining whether a fixing process is necessary or not for each of areas corresponding to the portions of the heat roller respectively heated by the heaters based on the input image data,
• supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by said determining step to set the corresponding portion of the heat roller to a fixing temperature, and
• feeding the image-forming medium having the developer image transferred thereon and fixing the to-be-fixed agent on the image-forming medium when the portion of the heat roller corresponding to the heater supplied with electric power has reached a preset fixing temperature.