A heating device includes a first rotator, a second rotator, a heater, and a first, second and third temperature sensors. The second rotator contacts an outer circumferential surface of the first rotator to form a nip through which a recording medium passes. The heater heats the first rotator. The first temperature sensor is disposed outside a space extending from a first region through which a minimum recording medium passes and detects the temperature of the first rotator. The second temperature sensor is disposed outside the space extending from the first region and detects the temperature of the heater. The third temperature sensor is disposed outside the space extending from the first region and detects the temperature of the second rotator. At least one of the second temperature sensor or the third temperature sensor is disposed outside a space extending from a second region through which a maximum sheet passes.

A heating device includes a heater, a rotator, and a pressure rotator. The heater includes resistive heat generators forming a heat generation area and has a separation area formed by the resistive heat generators. The pressure rotator includes a first region and a second region. The first region faces the heater in a range of 20 mm from a center position of the heat generation area toward an end thereof in the arrangement direction. The second region faces the heater in at least a part of a range of 30 mm from a center position of the separation area toward the center position of the heat generation area. An outer diameter of the pressure rotator increases from the center toward the end. The outer diameter of the second region increases at an increasing rate larger than an increasing rate of the outer diameter of the first region.

An image forming apparatus includes an image forming device, a heater, and a controller. The image forming device is configured to generate a laser scanning beam based on the image data to form a toner image on a sheet. The heater is configured to heat the sheet. The heater includes heater elements arranged in a direction corresponding to the main scanning direction of the laser scanning. The controller is configured to selectively control the heater elements to be energized at an energization start timing based on the image data and a signal from the image forming device indicating a start of scanning by the laser scanning beam in the main scanning direction.

The heating apparatus including a plurality of heat generation members including first, second and third generation members, the second heat generation member and the third heat generation member having lengths in a longitudinal direction shorter than a length of the first heat generation member, the heating apparatus including first, second, third, and fourth contacts, and a first switching unit configured to bring an electric path between the second contact and the fourth contact into one of a connecting state and an open state.

According to one embodiment, a fixing device, includes a fixing member having a first surface configured to be pressed against a recording medium and a heater on a second surface of the fixing member. A first heat conducting member contacts aback surface side of the heater, and a second heat conducting member is provided to be moveable between a first state, in which the second heat conducting member is in contact with the first heat conducting member and the second surface of the fixing member, and a second state, in which the second heat conducting member is contacting the first heat conducting member, but separated from the second surface of the fixing member.

In an image heating apparatus, a plurality of heat-generating members that a heater has include a first heat-generating member group and a second heat-generating member group, symmetrically laid out with a conveyance reference position of a recording material. A control portion supplies electric power via first and second common circuits to the first heat-generating member group and the second heat-generating member group. A temperature-detecting portion includes a first temperature-detecting element for detecting a temperature of one of the heat-generating members included in the first heat-generating member group, and a second temperature-detecting element for detecting the temperature of one of the heat-generating members included in the second heat-generating member group. The first temperature-detecting element is placed on one side as to the conveyance reference position in the width direction, and the second temperature-detecting element is placed on other side as to the conveyance reference position in the width direction.

A heater includes a heat generating member in a first layer, a sensor that is in a second layer different from the first layer and configured to detect a temperature of the heat generating member, and a wiring pattern in one or more third layers between the first and second layers to supply power to the heat generating member.

The fixing device includes a fixing member, a heat source, a pressure member, a nip forming member, and a heat equalizing member. The heat equalizing member covers a face of the nip forming member, the face facing the fixing member, and transfers heat in an axial direction of the fixing member. The fixing member includes at least a tubular base made of metal and a sliding layer made of heat resistant resin on an inner circumferential surface of the base. The heat equalizing member made of aluminum or an aluminum alloy includes an alumite layer on a surface facing an inner circumferential surface of the fixing member. A plurality of micropores in the alumite layer is filled with a solid lubricant having a coefficient of friction lower than that of the alumite layer. The alumite layer has a thickness smaller than that of the sliding layer of the fixing member.

A heating device includes a heating roller having a resistance heat-generating layer that generates heat by passage of a current through the resistance heat-generating layer, a pressure rotating body that rotates in such a manner as to press a sheet-shaped heating target that is an object to be subjected to a heating treatment against an outer peripheral surface of the heating roller and in such a manner as to cause the heating target to pass through the outer peripheral surface of the heating roller, and an auxiliary heating unit that supplementarily heats at least an axial end region included in a heat-generating region in which heat is generated by the resistance heat-generating layer of the heating roller.

An image forming apparatus is operable in a first small-sheet printing in which power is supplied to the first heat generating element and the second heat generating element and in a second small-sheet printing in which power is supplied to the first heat generating element and the third heat generating element. A first power ratio, which is a proportion of power supplied to the first heat generating element to power supplied to the second heat generating element in the first small-sheet printing, is higher than a second power ratio, which is a proportion of power supplied to the first heat generating element to power supplied to the third heat generating element in the second small-sheet printing.