Fixing device and image forming apparatus including the same

An image forming apparatus comprising:

• an image forming section configured to form a toner image on a transfer material;
• and
• a feed/discharge section configured to supply the transfer material to the image forming section and configured to discharge the transfer material on which the toner image is formed,
• wherein the image forming section includes an image carrying member where an electrostatic latent image is formed, a developing device configured to develop the electrostatic latent image to form the toner image, a transfer device configured to transfer the toner image to the transfer material, and a fixing device configured to fix the toner image transferred to the transfer material to the transfer material, and
• wherein the fixing device includes
• a heating rotating member configured to generate heat by induction heating;
• a pressing rotating member that is disposed so as to oppose the heating rotating member;
• a fixing nip section that is formed by the heating rotating member and the pressing rotating member, the fixing nip section nipping and transporting a transfer material;
• an induction coil disposed apart from and along an outer surface of the heating rotating member, the induction coil being operable for generating magnetic flux for causing the heating rotating member to generate the heat;
• and
• a magnetic member core section forming a magnetic path extending along an inner side of an inner peripheral edge of the induction coil and an outer side of an outer peripheral edge of the induction coil, the magnetic path surrounding the induction coil,
• wherein the magnetic member core section includes a first core section, a second core section, a magnetic flux shielding member, and a plurality of third core sections, the first core section opposing the outer surface of the heating rotating member with the induction coil being disposed therebetween, the second core section being disposed beside the first core section and near the inner peripheral edge of the induction coil in a direction in which the magnetic path surrounds the induction coil, the second core section opposing the outer surface of the heating rotating member without the induction coil being disposed therebetween, the magnetic flux shielding member being disposed at a side of an end portion of the first core section opposite to the second core section and separated from the end portion near the outer peripheral edge of the induction coil, the magnetic flux shielding member opposing the outer surface of the heating rotating member without the induction coil being disposed therebetween, the magnetic flux shielding member reducing or blocking the magnetic flux, the plurality of third core sections being disposed at a side of the magnetic flux shielding member facing the end portion of the first core section, the plurality of third core sections opposing the outer surface of the heating rotating member without the induction coil being disposed therebetween, and
• wherein at least one of the third core sections is movable to a first position and to a second position, the first position being where an end portion of the at least one of the third core sections that faces the heating rotating member is separated from the outer surface of the heating rotating member by a first distance and opposes the outer surface of the heating rotating member, the second position being where the end portion of the at least one of the third core sections that faces the heating rotating member is separated from the outer surface of the heating rotating member by a second distance and opposes the outer surface of the heating rotating member, the second distance being greater than the first distance.