Belt unit and image heating apparatus having a belt unit that includes an insulating holder portion that provides insulation between an exposed portion of a leaf spring and a stay

A belt unit for forming a heating nip in cooperation with an opposing rotatable member, said belt unit comprising:

• an endless belt including a metal layer;
• a nip forming member having a heater that includes a heat generating element generating heat by energization and configured to heat said endless belt while being in contact with an inner peripheral surface of said endless belt, said nip forming member being configured to sandwich said endless belt in cooperation with said rotatable member so as to form the heating nip;
• a metal stay configured to press said nip forming member toward said rotatable member;
• a temperature detecting element configured to detect a temperature of said endless belt;
• a metal leaf spring configured to urge said temperature detecting element, configured to detect the temperature of said endless belt, toward the inner peripheral surface of said endless belt;
• an insulating supporting member positioned inside said stay and configured to support said leaf spring;
• a cord configured to electrically connect with said temperature detecting element through said leaf spring;
• and
• an insulating holder portion including an interposed portion interposed between an exposed portion of said leaf spring and said stay, so as to provide insulation therebetween, and being configured to hold said supporting member,
• wherein, when said leaf spring is bent against elasticity thereof, bending of said leaf spring is prevented by contact of the exposed portion of the leaf spring with said interposed portion.

An image heating apparatus comprising:

• an endless belt including a metal layer;
• a rotatable member configured to form a heating nip, in which a toner image on a sheet is heated, in cooperation with said endless belt;
• a nip forming member having a heater that includes a heat generating element generating heat by energization and configured to heat said endless belt while being in contact with an inner peripheral surface of said endless belt, said nip forming member being configured to sandwich said endless belt in cooperation with said rotatable member so as to form the heating nip;
• a metal stay configured to press said nip forming member toward said rotatable member;
• a temperature detecting element configured to detect a temperature of said endless belt;
• a metal leaf spring configured to urge said temperature detecting element, configured to detect the temperature of said endless belt, toward the inner peripheral surface of said endless belt;
• an insulating supporting member positioned inside said stay and configured to support said leaf spring;
• a cord configured to electrically connect with said temperature detecting element through said leaf spring;
• and
• an insulating holder portion including an interposed portion interposed between an exposed portion of said leaf spring and said stay, so as to provide insulation therebetween, and being configured to hold said supporting member,
• wherein a creepage distance from said heat generating element to the exposed portion of said leaf spring through said stay and said interposed portion is 2.5 mm or more.

An image heating apparatus comprising:

• an endless belt including a metal layer;
• a rotatable member configured to form a heating nip, in which a toner image on a sheet is heated, in cooperation with said endless belt;
• a nip forming member having a heater that includes a heat generating element generating heat by energization and configured to heat said endless belt while being in contact with an inner peripheral surface of said endless belt, said nip forming member being configured to sandwich said endless belt in cooperation with said rotatable member so as to form the heating nip;
• a metal stay configured to press said nip forming member toward said rotatable member;
• a temperature detecting element configured to detect a temperature of said endless belt;
• a metal leaf spring configured to urge said temperature detecting element, configured to detect the temperature of said endless belt, toward the inner peripheral surface of said endless belt;
• an insulating supporting member positioned inside said stay and configured to support said leaf spring;
• a cord configured to electrically connect with said temperature detecting element through said leaf spring;
• and
• an insulating holder portion including an interposed portion interposed between an exposed portion of said leaf spring and said stay, so as to provide insulation therebetween, and being configured to hold said supporting member,
• wherein, when said leaf spring is bent against elasticity thereof, bending of said leaf spring is prevented by contact of the exposed portion of the leaf spring with said interposed portion.