A fixing belt including a base layer, an elastic layer and a surface layer, wherein the elastic layer has a total thickness of 200 to 3,000 m, has a thermal conductivity of 0.4 W/(m.Math.K) or more in a total thickness direction thereof, and contains fillers in a content of 40 to 60 vol % with respect to the total volume of the elastic layer. The fillers in a region A of the elastic layer have a practical sphericity SA of 0.75 or more, and a content ratio of the fillers in the region A is 60 vol % or less with respect to the region A. The fillers in a region B have a practical sphericity SB of less than 0.75, and a content ratio of the fillers in the region B is 40 vol % or more with respect to the region B.

A fixing device according to the present disclosure includes a rotatable endless belt and an end portion holder. The end portion holder supports each of end portions of the fixing belt rotatably, and has a cylindrical part along which an inner circumferential surface of the fixing belt slides and an end wall part which faces an end surface of the fixing belt. The end wall part has a restraint part which faces an outer circumferential surface of the fixing belt with a predetermined interval and restrains the fixing belt from turning up.

A fixing device including an endless belt, a heat source, a rotatable member forming a nip together with a belt, a nip forming member, a contact member contacting an inner peripheral surface of the belt, a reflecting portion reflecting radiation heat from the heat source toward the nip forming member, a heat conducting portion, and a heat insulating member. The nip forming member includes a first member having a U-shape made of metal and open on a side opposite from the rotatable member and a second member provided inside the first member. The heat conducting portion conducts heat of the reflecting portion to the contact member. The heat insulating member is provided between the first member and the second member. A thickness t (m) and thermal conductivity (W/m.Math.K) of the heat insulating member satisfy:
t100 (m)
0.02 (W/m.Math.K)0.05 (W/m.Math.K).

A fixing device including a fixing belt having a maximum curvature in a rotational direction of the fixing belt. The number of times the fixing belt is bent when a temperature of the fixing belt is equal to or lower than a glass transition temperature of the fixing belt surface material is controlled to operate within a specified range.

Provided is a fixing member having excellent heat resistance and durability. The fixing member includes a substrate and an elastic layer on the substrate, wherein the elastic layer includes: rubber, thermally conductive particles dispersed in the rubber, and iron oxide particles dispersed in the rubber, a content of the thermally conductive particles in the elastic layer is 30% by volume or more and 50% by volume or less, a content of the iron oxide particles in the elastic layer is 0.01% by volume or more and 1.0% by volume or less, the thermally conductive particles are at least one selected from the group consisting of aluminum oxide, metal silicon, magnesium oxide, zinc oxide, and silicon carbide, and the iron oxide particles have a localization index M of 0.2 or more and less than 0.8, wherein the localization index M is determined by specific steps.

An image fixing device for fixing an image on a sheet includes a rotatable fixing film, a heater, a rotatable pressing member, a holding member, and a metal sheet. The heater is provided on an inner surface of the fixing belt. The rotatable pressing member is provided in contact with an outer peripheral surface of the film to press against the heater through the film, thus forming a nip configured to nip and feed the sheet. The holding member includes a guide portion configured to guide the rotation of the fixing film and to hold the heater. The metal sheet covers the heater and an area of guide portion slidable relative to an inner surface of the fixing film. The metal sheet has a thermal conductivity 10W/(m.Math. C.) and has a thickness more than 0 m and not more than 50 m.

An electrophotographic fixing member having an elastic layer that is high in thermal conductivity in the thickness direction, resists causing fracture or plastic deformation even by repeated compression in a high temperature state, and is low in hardness. The electrophotographic fixing member has a substrate, and an elastic layer provided on the substrate, wherein the elastic layer contains a filler containing an inorganic oxide and is provided on an outer circumference of the substrate, wherein (1) in a binarized image on a first cross-section in a thickness-circumferential direction of the elastic layer and a binarized image on a second cross-section in a thickness-axial direction of the elastic layer, 1.0(A/B)2.0 and 0.40(A+B)0.50 are satisfied; and (2) 50.sub.Ave90 is satisfied.

Provided is a fixing member having excellent heat resistance and durability. The fixing member includes a substrate and an elastic layer on the substrate, wherein the elastic layer includes: rubber, thermally conductive particles dispersed in the rubber, and iron oxide particles dispersed in the rubber, a content of the thermally conductive particles in the elastic layer is 30% by volume or more and 50% by volume or less, a content of the iron oxide particles in the elastic layer is 0.01% by volume or more and 1.0% by volume or less, the thermally conductive particles are at least one selected from the group consisting of aluminum oxide, metal silicon, magnesium oxide, zinc oxide, and silicon carbide, and the iron oxide particles have a localization index M of 0.2 or more and less than 0.8, wherein the localization index M is determined by specific steps.

An image forming apparatus includes a resistive heat generator, a temperature detector, and a power controller that detects a temperature-resistance property of the resistive heat generator before the resistive heat generator is used when the resistive heat generator is removably installed. The power controller obtains power supplied to the resistive heat generator and a change in a temperature of the resistive heat generator, that is detected by the temperature detector, while the power controller supplies the power at a predetermined power duty cycle for adjustment to the resistive heat generator. The power controller calculates the temperature-resistance property of the resistive heat generator based on the power and the change in the temperature that are obtained. The power controller adjusts a power duty cycle at which the power is supplied to the resistive heat generator in use of the resistive heat generator, based on the temperature-resistance property.

A fixing member includes: a substrate layer including a resin; a first metal layer that is provided on an outer peripheral surface of the substrate layer and includes Cu; a second metal layer that is provided on an outer peripheral surface of the first metal layer so as to be in contact with the first metal layer, includes Ni, and has an average crystal grain size of 0.15 m to 0.19 m; and an elastic layer that is provided on an outer peripheral surface of the second metal layer.