Patent ID: 8190046
Filing Date: 2012-05-29
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: a controller; a database to register information on a plurality of types of recording media in the controller; an image carrier to carry a toner image; an exposure unit to expose the image carrier; a transfer unit to transfer the toner image from the image carrier to a recording medium; a fixing device to fix the toner image transferred on the recording medium at the transfer unit using heat and pressure, the fixing device comprising a temperature detector to detect a temperature of the fixing device and a first drive device to change a fixing nip angle of the fixing device, the fixing nip angle being an angle of departure of the recording medium from the fixing device; a speed changer disposed at an upstream side of the fixing device in a feed direction of the recording medium to change a feed speed of the recording medium; and an electric-current detector disposed at an upstream side of the transfer unit in the feed direction of the recording medium to measure an electric current flowing through the recording medium, wherein the controller calculates a toner adhesion amount of toner adhering to the toner image on the recording medium from an exposure amount of the exposure unit, identifies a type of the recording medium based on the information on the plurality of types of recording media registered in the database when the recording medium is selected from the plurality of recording media by a user, detects a temperature of the fixing device with the temperature detector, determines a moisture content of the recording medium from the electric current flowing through the recording medium measured with the electric-current detector, calculates a reaction force of the recording medium arising when the recording medium is fed out of the fixing device, calculates from the toner adhesion amount a toner adhesion force generated by the toner image fused with the heat of the fixing device, compares the reaction force and the toner adhesion force, determines the fixing nip angle when the controller determines that the reaction force exceeds the toner adhesion force, drives the first drive device to set the fixing device to the fixing nip angle, determines a target speed of the feed speed of the recording medium, and drives the speed changer to change the feed speed of the recording medium to match the target speed.