Image heating device and image forming apparatus

An image heating device configured to heat an image formed on a recording material, the image heating device comprising:

• a tubular rotary member including a conductive layer;
• a magnetic core material installed inside the rotary member and forming an open magnetic path in a longitudinal direction;
• an excitation coil wound around the magnetic core material such that a spiral axis extends in the longitudinal direction of the magnetic core material;
• an inverter configured to cause an alternating current to flow through the excitation coil;
• a control unit configured to control the inverter to cause the alternating current to flow through the excitation coil and generate an alternating magnetic flux in the magnetic core material to perform electromagnetic induction heating of the rotary member;
• and
• a power cutoff unit configured to cut off supply of power from the inverter to the excitation coil regardless of a control state of the inverter by the control unit in a case where the power input from the inverter to the excitation coil exceeds a threshold, wherein
• the control unit is configured to change a driving frequency of the inverter, and
• the power cutoff unit is configured to change a value of the threshold based on a value of the driving frequency of the inverter.