Fixing apparatus having an enhanced planar heat generating body, and image forming apparatus including the same

A fixing apparatus, comprising:

• a fixing member which is rotatable;
• a heating member which is curved and includes a planar heat-generating body;
• and
• a fixing belt which is endless and moves while getting in contact with the fixing member and the heating member,
• the fixing member and the heating member being arranged such that a concave curved surface of the heating member faces the fixing member,
• the planar heat-generating body, including:
• a resistive heat-generating body which extends in a direction perpendicular to a direction in which the fixing belt moves;
• a plurality of small electrodes, provided on one side surface of the resistive heat-generating body in a direction in which the resistive heat-generating body extends, which are electrically separated from each other and cause current to flow through the resistive heat-generating body in a direction parallel to the direction in which the fixing belt moves;
• an electrode, provided on the other side surface of the resistive heat-generating body, which is grounded;
• and
• (i) positive temperature coefficient elements connected in series with whole of or some of the plurality of small electrodes in a power supply path from a power source or (ii) a single positive temperature coefficient element connected in series with some of the plurality of small electrodes in a power supply path from the power source, in an area corresponding to a non-sheet passing area of the fixing belt, the non-sheet passing area being an area where a smallest-size sheet does not pass, the smallest-size sheet being smallest among sheets that the fixing apparatus deals with, the positive temperature coefficient element(s) having a resistance value increasing at a predetermined temperature or higher.