Abstract: A rotational shaft of a photosensitive drum is connected to a rotational shaft of a stepping motor by a coupling, so that the stepping motor directly drives the photosensitive drum. Here, &thgr; (°) indicating a step angle of the stepping motor, p (mm) indicating a distance between scanning lines on the photosensitive drum, &pgr; indicating the circular constant, and d (mm) indicating a diameter of the photosensitive drum are set so as to satisfy an equation n·&thgr;=(360·p)/(&pgr;·d) to make an optical unit scan the photosensitive drum by one scanning line every time the photosensitive drum is made to rotate n steps, n being a positive integer.

Abstract: In an image forming apparatus which forms images by transferring to a transfer drum a toner image formed on the surface of the photosensitive member directly driven by a stepping motor, the relationship between the stepping angle ".theta." (.degree.) of the stepping motor and the rotational speed "N" (rpm) of the photosensitive drum is expressed by the equation .theta..ltoreq.(360.times.N)/(60.times.a.times.b). Where "a" is a natural number, optimally 10, which is less than the initial predetermined tolerance value when the harmonic content of rotational variation generated by the step period of the stepping motor is "1/a", and "b" is the target frequency (Hz) of 100.

Abstract: An apparatus and method for eliminating position deviations of a photosensitive drum which is rotated by a stepping motor driven by full step and half step drive pulses. The apparatus includes a photosensitive drum, a stepping motor which rotates the photosensitive drum; and a controller which controls the stepping motor to be driven with half step drive pulses when the photosensitive drum is being scanned. In the apparatus and method, a scanning starting control is performed by driving the stepping motor by full step drive pulses so that salient poles of the rotor are aligned with salient poles of the stator such that the rotor is in a stable position. The full step drive pulses are switched to half step drive pulses before scanning is started, and the scanning of the photosensitive drum is started on an even numbered half step drive pulse.

Abstract: An electrical device for controlling heater has a power supply connected in parallel with a heater or the like. A reducer such as a resistor is provided for reducing electrical current flowing into the heater. A switch can be operated by a controller to connect the heater to the electrical power supply or to connect the heater and the reducer in series to the electrical power supply. The controller operates the switch to disconnect the heater from the electrical power supply after operating the switch to connect the heater and the reducer in series to the power supply. Thus, even at a timing when the load of the power supply is the maximum and the capacitor charging current to the power supply increases, the change in the current through the heater becomes gradual, and the harmonic components in the current do not increase by using the reducer even if the timing of the maximum load overlaps with the timing of the stop of power supply to the heater.

Abstract: Copying apparatus is provided in which outline copying for only a designated area of an original image can be easily selected. An area for the outline copying can be designated and images inside and outside the designated area can be copied in different colors. The arrangement includes a plurality of keys for designating an area of an original image to be copied and a scorotron charger for causing a potential in areas other than the outline portions of an electrostatic latent image, formed on a photoreceptor drum, to be substantially equal to a potential in an area containing the image. An eraser unit is provided for erasing the charge in an area where development is not required and a developing device develops the electrostatic latent image. A transfer charger is provided for transferring the image developed by the developing device onto copying paper.

Abstract: A copying apparatus in which after a single scan multicolor copy mode and a region to be copied are specified to carry out the single scan multicolor copy, when the specified mode is cancelled, a developing unit which has been selected in the single scan multicolor copy mode is automatically selected again and thus, a copy operation can be continued.