Heating device and image forming apparatus

A heating device comprising:

• a magnetic-field generating unit that generates an alternating-current magnetic field;
• an endless belt that includes a first region in which heat is generated by electromagnetic induction caused by an effect of the alternating-current magnetic field, the endless belt heating and transporting a medium that contacts an outer peripheral surface of the endless belt;
• and
• a heat transfer unit that transmits heat to the belt by contacting and sliding along an inner peripheral surface of the belt,
• wherein the heat transfer unit includes
• a heat storage layer that stores heat,
• a thermosensitive layer that is positioned closer to the belt than the heat storage layer is and that extends so as to separate the magnetic-field generating unit and the heat storage layer from each other, the thermosensitive layer forming a magnetic path that allows a magnetic flux of the alternating-current magnetic field to pass through the thermosensitive layer in a direction in which the thermosensitive layer extends at a temperature below a Curie temperature and forming a magnetic path that allows the magnetic flux of the alternating-current magnetic field to extend through the thermosensitive layer and reach the heat storage layer at a temperature higher than or equal to the Curie temperature, and
• a diffusion layer that has a higher thermal conductivity than thermal conductivities of the thermosensitive layer and the heat storage layer, the diffusion layer diffusing heat of the belt along an axial direction of the belt.