Induction-heating fusion device

An induction-heating fusion device comprising:

• an electrically conductive hollow member;
• an iron core forming a closed loop and having a portion inserted into a hollow portion of the electrically conductive member;
• a main coil spirally wound around the inserted portion of the iron core along an internal wall of the electrically conductive member;
• and
• a first sub-coil continuously wound around the inserted portion of the iron core along the internal wall of the electrically conductive member, wherein the main coil and the sub-coil cause the electrically conductive member to generate induction heat when applied with alternating current.

A fusion device comprising:

• a sheet conveying mechanism for conveying a sheet to be subjected to fusion processing along a first direction;
• a hollow electrically conductive member extending along a second direction perpendicular to the first direction of sheet conveyance so as to directly or indirectly come in contact with the sheet being conveyed;
• an iron core arranged within a hollow space of the electrically conductive member, the iron core extending along the same direction as the second direction;
• a main coil wound around the iron core to cover a predetermined range of the iron core in the second direction;
• a sub-coil wound around the iron core to cover only opposed ends of the iron core and vicinity in the second direction;
• and
• a current applying circuit for applying current to the main coil and sub-coil so as to generate a magnetic flux which causes the electrically conductive member to generate an induction current circumferentially thereof.

A fusion device for generating heat by applying current to a coil to cause an electrically conductive member to generate induction current, comprising:

• an iron core extending across a sheet transport direction;
• an electrically conductive member having an endless configuration in section and covering the iron core;
• a main coil wound around the iron core within the endless configuration of the electrically conductive member for generating a magnetic flux which causes the electrically conductive member to generate an induction current circumferentially thereof,
• the main coil being wound for a first length substantially equal to an extending dimension of a first side of a first standardized sheet;
• and
• a sub-coil wound around the iron core within the endless configuration of the electrically conductive member main coil for generating a magnetic flux which causes the electrically conductive member to generate induction current circumferentially thereof, the sub-coil being wound around the iron core at the opposing ends of the main coil so that a sum of the length of the main coil and the sub-coil is substantially equal to an extending dimension of a first side of a second standardized sheet, greater than the extending dimension of the first side of the first standardized sheet, the first sides of the first and second standardizes sheets being the sides of the respective sheets that first encounter the fusion device.