Image forming apparatus that can predict a life of the fixing roller

An image forming apparatus comprising:

• an image forming portion forming a toner image on a recording medium;
• a fixing device including
• a fixing belt that is endless,
• a fixing roller disposed inside the fixing belt, the fixing roller having a metal base and an elastic layer laid on an outer circumferential surface of the metal base,
• a pressing roller disposed in pressed contact with the fixing roller across the fixing belt to form a fixing nip portion, and
• an induction heating portion heating the fixing belt,
• the fixing device heating and pressing the recording medium passing through the fixing nip portion to perform fixing whereby the toner image is fixed to the recording medium;
• a fixing voltage power supply applying a voltage to the induction heating portion;
• and
• a control portion controlling the image forming portion, the fixing device, and the fixing voltage power supply,
• wherein
• the control portion
• calculates, as a cumulative electric power supply time, a cumulative value of electric power supply time for which a predetermined supplied electric power is supplied to the induction heating portion,
• takes, as a lifetime of the fixing roller, a failure time y [min] of the elastic layer calculated with the supplied electric power substituted in a damage electric power x [W] in lifetime prediction formula (1) below, and
• compares the lifetime of the fixing roller with the cumulative electric power supply time to determine a remaining lifetime of the fixing roller:
• y
• =
• 2
• .57
• E
• +
• 08
• ⁢
• e
• -
• 7
• .27
• E
• -
• 0.3
• x
• .
• (
• 1
• )