Abstract: An image forming apparatus includes an image-forming unit having a charging section and a developing section that are rotated together with a photoconductor in an idling manner. The charging section and developing section receive voltages while rotating. The apparatus includes a toner sensor and a controller. The toner sensor outputs a detection signal indicating that the toner has been replenished in the image-forming unit. In accordance with the detection signal, the controller changes the voltages, a time length during which the photoconductor, charging section, and developing section are rotated, or speeds at which the photoconductor, charging section, and developing section are rotated. The time length is extended or speeds are increased when the image-forming unit has been replaced.

Abstract: An image forming apparatus includes an image-forming unit having a charging section and a developing section that are rotated together with a photoconductor in an idling manner. The charging section and developing section receive voltages while rotating. The apparatus includes a toner sensor and a controller. The toner sensor outputs a detection signal indicating that the toner has been replenished in the image-forming unit. In accordance with the detection signal, the controller changes the voltages, a time length during which the photoconductor, charging section, and developing section are rotated, or speeds at which the photoconductor, charging section, and developing section are rotated. The time length is extended or speeds are increased when the image-forming unit has been replaced.

Abstract: A color image forming apparatus includes a carrier belt which runs along a transport path of a recording medium to transport the recording medium. A number of image-forming sections are aligned in the transport path. Each of the plurality of image-forming sections forms a toner image of a corresponding color included in an image signal. A plurality of transfer units are provided, with each being disposed to oppose a corresponding one of the number of image-forming sections. Each of the number of transfer units transferring the toner image of the corresponding color to the recording medium. A fixing unit is provided that fixes the toner image to the recording medium. A controller is provided that detects a number of colors in the image signal. The controller sets one set of speeds from a plurality of different sets of speeds in accordance with the number of colors.

Abstract: A fixing unit has a heat roller with a heater element built therein, a pressure roller disposed to oppose the heat roller and holds and advances a print medium therebetween in sandwiched relation. A thermistor is in contact with the heat roller and detects the temperature of the heat roller. Another thermistor detects the temperature of the pressure roller. A control circuit controls energization of the heater element so as to maintain the temperature of the heat roller to a target temperature. The heater element is energized to maintain a constant value of Tc given by an equation Tc=Th+k.multidot.Tp where Th is a surface temperature of the heat roller, Tp is a surface temperature of the pressure roller, and k is a coefficient having the range of 0<k<1.

Abstract: A color image forming apparatus provides the prolonged life of the photosensitive drums, carrier belt, and toner of the respective colors and improves the quality of the printed color image. A carrier belt transports a recording medium placed thereon so that the recording medium passes through a plurality of printing mechanisms which print images of different colors on the recording medium in superposition. Each printing mechanism prints an image of a corresponding color. The printing mechanism is adapted to be moved into its operative position where the photosensitive drum of the printing mechanism is in contact with the carrier belt to print the image on the recording medium, and into its non-operative position where the photosensitive drum of the printing mechanism is not in contact with the carrier belt.