Patent ID: 9256168
Filing Date: 2016-02-09
CPC Classification: G03G

Claim Text:
1. An image forming apparatus, comprising: an image bearer to bear a toner image on a surface thereof; a transfer device to contact the image bearer to form a transfer nip; a power source to output a voltage to transfer the toner image from the image bearer onto a recording medium interposed in the transfer nip, the voltage including a first voltage in a transfer direction in which the toner image is transferred from the image bearer to the recording medium and a second voltage having a polarity opposite that of the first voltage, and the first voltage and the second voltage alternating upon transfer of the toner image from the image bearer to the recording medium; and a controller operatively connected to the power source to control the power source; wherein a time-averaged value (Vave) of the voltage has a polarity in the transfer direction, and an absolute value of the time-averaged value (Vave) is greater than a midpoint value (Voff) of the voltage intermediate between a maximum value and a minimum value of the voltage, wherein with an increase in a difference (Vpp) between the maximum value and the minimum value of the voltage, the controller controls the power source to increase a duty ratio (Duty) expressed by B/(A+B), where B is an application time in one cycle at a return direction side opposite a transfer direction side relative to the midpoint value (Voff) and A is an application time at the transfer direction side relative to the midpoint value (Voff), and with a decrease in the difference (Vpp), the controller controls the power source to reduce the duty ratio (Duty).