Abstract: A fixation device according to an embodiment may include: an annular belt including an elastic layer with a thickness of more than 300 ?m; and a counter member opposed to an outer peripheral surface of the annular belt to form a nip region with the annular belt. A ratio (A/B) of a first hardness value (A) to a second hardness value (B) of the outer peripheral surface of the annular belt is 0.566 or more, where the first hardness value is measured, in hardness measurement using a hardness meter, at a time when a passage time, which is a time it takes for a certain point of the outer peripheral surface to pass through the nip region, has just passed from the start of the hardness measurement, and the second hardness value is measured at a time when the measured value of the hardness meter has just been saturated.

Abstract: A fixing device includes an annular belt, a heating member disposed to face an inner circumferential surface of the annular belt; and a heat storage member disposed to face a surface of the heating member on a side opposite to the annular belt. A thermal diffusivity of the heat storage member is lower than a thermal diffusivity of the annular belt.

Abstract: A fixation device according to an embodiment may include: an annular belt including an elastic layer with a thickness of more than 300 ?m; and a counter member opposed to an outer peripheral surface of the annular belt to form a nip region with the annular belt. A ratio (A/B) of a first hardness value (A) to a second hardness value (B) of the outer peripheral surface of the annular belt is 0.566 or more, where the first hardness value is measured, in hardness measurement using a hardness meter, at a time when a passage time, which is a time it takes for a certain point of the outer peripheral surface to pass through the nip region, has just passed from the start of the hardness measurement, and the second hardness value is measured at a time when the measured value of the hardness meter has just been saturated.

Abstract: A fixing device includes an annular belt, a heating member disposed to face an inner circumferential surface of the annular belt; and a heat storage member disposed to face a surface of the heating member on a side opposite to the annular belt. A thermal diffusivity of the heat storage member is lower than a thermal diffusivity of the annular belt.

Abstract: A fusing device includes an annular belt, a heat generation member arranged inside the annular belt, and a heat transmission member that has first and second faces, wherein the first face opposes the heat generation member and the second face opposes the annular belt, and the heat transmission member transmits heat to the annular belt, wherein the heat transmission member satisfies the following Conditional Expression (1): D/L?0.18×S?28??(1) where D means a thermal diffusivity [×10?6 m2/s] that is determined along the first face of the heat transmission member, L means a half of an interval [×10?3 m] between two of the heat generation parts adjacent to one another, and S: the carrying speed [×10?3 m/s] at which the medium is carried.

Abstract: A fusing device includes an annular belt, a heat generation member arranged inside the annular belt, and a heat transmission member that has first and second faces, wherein the first face opposes the heat generation member and the second face opposes the annular belt, and the heat transmission member transmits heat to the annular belt, wherein the heat transmission member satisfies the following Conditional Expression (1): D/L?0.18×S?28??(1) where D means a thermal diffusivity [×10?6 m2/s] that is determined along the first face of the heat transmission member, L means a half of an interval [×10?3 m] between two of the heat generation parts adjacent to one another, and S: the carrying speed [×10?3 m/s] at which the medium is carried.