Heating device capable of accurately determining change in state, and image forming apparatus

摘要

A heating device capable of accurately determining a change in the state of a to-be-heated member, caused in a narrow area. An induction heating coil generates magnetic flux by flow of electric current therethrough. The fixing belt generates heat by the action of the magnetic flux generated by the induction heating coil. A first antenna is disposed at a location where the magnetic flux generated by the induction heating coil can be detected assuming that there is no fixing belt. A second antenna is disposed such that at least some area of the second antenna overlaps the first antenna. A control circuit determines whether or not a state of the fixing belt has changed, based on a result of detection by the first antenna and a result of detection by the second antenna.

主权项

1. A heating device comprising:
a coil that generates magnetic flux by flow of electric current therethrough; a to-be-heated member configured to generate heat by action of the magnetic flux generated by said coil; a first magnetic flux-detecting unit disposed at a location where said first magnetic flux-detecting unit is capable of detecting the magnetic flux generated by said coil assuming that said to-be-heated member does not exist; a second magnetic flux-detecting unit disposed such that at least some area of said second magnetic flux-detecting unit overlaps said first magnetic flux-detecting unit; and a control unit configured to determine whether or not a state of said to-be-heated member has changed, based on a result of detection by said first magnetic flux-detecting unit and a result of detection by said second magnetic flux-detecting unit, wherein said first magnetic flux-detecting unit includes at least one polarity inverting portion as a boundary on opposite sides of which a polarity of output is inverted therebetween, and wherein said second magnetic flux-detecting unit includes a polarity inverting portion as a boundary at which on opposite sides of which a polarity of output is inverted therebetween, provided at a position that is not coincident with a position of said polarity inverting portion of said first magnetic flux-detecting unit.