Method and apparatus for controlling transfer voltage in image forming device

A method of controlling a transfer voltage in an image forming apparatus, the method comprising:

• applying a constant voltage to a transfer roller in a state where a photosensitive drum and the transfer roller form a transfer nip and detecting a transfer roller resistance between the transfer roller and the photosensitive drum;
• applying the constant voltage to the transfer roller when paper approaches the transfer nip of the transfer roller and detecting a paper resistance among the transfer roller, the paper, and the photosensitive drum;
• determining a type of paper based on the transfer roller resistance and the paper resistance;
• and
• applying the transfer voltage to the transfer roller to perform a transferring operation based on the determined type paper.

A method of controlling a transfer voltage applied to a transfer roller in an image forming apparatus having a photosensitive drum, the method comprising:

• determining an expected current flow between the transfer roller and the photosensitive drum in response to a predetermined voltage applied to the transfer roller prior to entry of a printing paper into a nip between the transfer roller and the photosensitive drum, wherein the expected current flow is based on an environmental condition in which the image forming apparatus is operating or an expected life cycle of the transfer roller;
• forming a transfer table including entries correlating the transfer voltage, a paper type, a plurality of the expected current flows, and corresponding environmental conditions or the transfer voltage, the paper type, the plurality of expected current flows and predetermined intervals along the expected lifecycle of the transfer roller;
• determining an actual current flow between the transfer roller and the photosensitive drum in response to the predetermined voltage applied to the transfer roller prior to the entry of the printing paper into the nip between the transfer roller and the photosensitive drum;
• and
• selecting the transfer voltage to be applied based on an entry in the transfer table correlating the expected current flow and the paper type and the actual current flow and the paper type.