HEATER, FIXING DEVICE, AND IMAGE FORMING APPARATUS
A heater includes a heat generating element and a protective layer. The protective layer covers the heat generating element, and at least part of a surface thereof has a convex surface that is convex toward the heat generating element.
1 . A heater comprising:
a heat generating element; and
a protective layer configured to cover the heat generating element, at least part of a surface of the protective layer having a convex surface that is convex toward the heat generating element.
2 . The heater according to claim 1 , wherein one of ends of the protective layer in a shorter-side direction of the heat generating element protrudes in a stacking direction of the heat generating element and the protective layer and has a curved top surface.
3 . The heater according to claim 2 , wherein the other one of the ends of the protective layer in the shorter-side direction protrudes in the stacking direction and has a curved top surface.
4 . The heater according to claim 3 , wherein a curvature of the one end and a curvature of the other end differ from each other.
5 . A fixing device comprising:
an endless belt;
a heater; and
a pressure element placed at a position to face the heater via the endless belt and configured to form, together with the endless belt, a nip to interpose a sheet being conveyed,
the heater comprising:
a heat generating element; and
a protective layer configured to cover the heat generating element and to be in contact with the endless belt, a surface of the protective layer that faces the pressure element having a concave surface that is concave with respect to the pressure element.
6 . The fixing device according to claim 5 , wherein a curvature of the concave surface is smaller than a curvature of a surface of the pressure element.
7 . The fixing device according to claim 5 , wherein an upstream end of the protective layer in a conveyance direction of the sheet protrudes in a stacking direction of the heat generating element and the protective layer and has a curved top surface.
8 . The fixing device according to claim 7 , wherein a downstream end of the protective layer in the conveyance direction protrudes in the stacking direction and has a curved top surface.
9 . The fixing device according to claim 8 , wherein a curvature of the curved surface of the upstream end is smaller than a curvature of the curved surface of the downstream end.
10 . An image forming apparatus comprising:
an image forming unit configured to form a toner image on a sheet; and
a fixing device configured to heat the sheet and thereby fix the toner image onto the sheet, the fixing device comprising:
an endless belt;
a heater; and
a pressure element placed at a position to face the heater via the endless belt and configured to form, together with the endless belt, a nip to interpose a sheet being conveyed,
the heater comprising:
a heat generating element; and
a protective layer configured to cover the heat generating element and to be in contact with the endless belt, a surface of the protective layer that faces the pressure element having a concave surface that is concave with respect to the pressure element.