Method of and apparatus for controlling transfer voltage based on specific resistance of paper in laser beam printer

A method of controlling a transfer voltage in a laser beam printer, comprising the steps of:

• detecting a resistance of feed rollers as a first resistance before a printing medium passes between the feed rollers;
• detecting a resistance of the printing medium and the feed rollers as a second resistance when the printing medium passes between the feed rollers;
• obtaining a specific resistance of the printing medium as a third resistance by determining the difference between the first resistance and a second resistance;
• detecting a resistance between a transfer roller and a photosensitive drum as a fourth resistance before the printing medium passes between the transfer roller and the photosensitive drum;
• obtaining a composite resistance as a fifth resistance by adding the third resistance to the fourth resistance;
• and
• printing on the printing medium by applying a transfer voltage to the transfer roller based on the fifth resistance.

An apparatus for controlling a transfer voltage in a laser beam printer, comprising:

• a controller controlling the recording of an image on a printing medium, the controller generating a first control signal to control a feed roller voltage to be applied to feed rollers of the laser beam printer and generating a second control signal to control a transfer voltage to be applied to a transfer roller of the laser beam printer, the controller determining a specific resistance of the printing medium as a difference between a first detected resistance of the feed rollers without being in contact with the printing medium and a second detected resistance of the feed rollers and the printing medium in contact with the feed rollers, the controller determining a composite resistance by adding said specific resistance of the printing medium to a third detected resistance, the third detected resistance being a resistance between the transfer roller and a photosensitive drum of the laser beam printer without being in contact with the printing medium, and the controller generating a said second control signal to apply a transfer voltage to the transfer roller for printing on the printing medium based upon said composite resistance;
• and
• a high voltage supply circuit coupled to said controller, said high voltage supply circuit generating said feed roller voltage to be applied to the feed rollers corresponding to a said first control signal from said controller, generating said transfer voltage to be applied to the transfer roller corresponding to a said second control signal from said controller, and detecting said first detected resistance, said second detected resistance and said third detected resistance and providing said first detected resistance, said second detected resistance and said third detected resistance to said controller.

An apparatus for controlling a transfer voltage in a laser beam printer, comprising:

• means for detecting a resistance of feed rollers as a first resistance before a paper sheet passes between the feed rollers;
• means for detecting a resistance of the paper sheet and the feed rollers as a second resistance when the paper sheet passes between the feed rollers;
• means for obtaining a specific resistance of the paper sheet as a third resistance by determining the difference between the first resistance and the second resistance;
• means for detecting a resistance between a transfer roller and a photosensitive drum as a fourth resistance before the paper sheet passes between the transfer roller and the photosensitive drum;
• means for obtaining a composite resistance as a fifth resistance by adding the third resistance to the fourth resistance;
• and
• means for applying a transfer voltage to the transfer roller based on the fifth resistance for printing on the paper sheet.