Patent ID: 7885568

Claim:
An image forming device for achieving image formation by transporting a recording sheet with an unfixed image formed thereon to pass a fixing nip so that thereby the unfixed image is thermally fixed onto the recording sheet, the fixing nip being formed between two rotation members located closely to each other as a pair, at least one of the two rotation members having been heated by a heater, the image forming device comprising: a non-contact infrared sensor located at a position more downstream than the fixing nip in a recording sheet transport direction, and operable to detect a surface temperature of one of the rotation members which is located across a recording sheet transport route from the non-contact infrared sensor; a judging part operable to judge whether or not the recording sheet after the fixing is passing between the non-contact infrared sensor and the one of the rotation members; a controller operable to control the heater using a first threshold value and a temperature detected by the non-contact infrared sensor when the judging part has judged that the recording sheet is not passing, and to control the heater using a second threshold value, which is different from the first threshold value, and the temperature detected by the non-contact infrared sensor when the judging part has judged that the recording sheet is passing; and a storage storing a first conversion table and a second conversion table, the first conversion table being used to convert an output voltage of the non-contact infrared sensor into a temperature value based on a heat radiation rate of the one of the pair of rotation members, the second conversion table being used to convert the output voltage of the non-contact infrared sensor into a temperature value based on a heat radiation rate of the recording sheet, wherein when the judging part has judged that the recording sheet is not passing, the controller controls the heater based on the temperature value converted via the first conversion table from the output voltage of the non-contact infrared sensor, and based on a temperature value corresponding to the first threshold value, and when the judging part has judged that the recording sheet is passing, the controller controls the heater based on the temperature value converted via the second conversion table from the output voltage of the non-contact infrared sensor, and based on a temperature value corresponding to the second threshold value.