A control unit controls power to be supplied to a common power supply path in a first period, using a selected first temperature detection member, and controls power to be supplied to the common power supply path in a second period, using a selected second temperature detection member. The first temperature detection member has a higher detected temperature than that of the second temperature detection member, and in the second period, the first detected temperature and the second detected temperature fall within a temperature range between a first temperature and a second temperature lower than the first temperature.

An image heating device heats up an image formed on a recording material, the device having: a heating member provided with a heater having a plurality of heating elements juxtaposed in a direction perpendicular to a conveyance direction of the recording material; a roller, such that the circumference of the roller increases from a central portion towards ends portions, in a direction perpendicular to the conveyance direction; and a control portion that controls individually the power supplied to the plurality of heating elements. The control portion sets a control target temperature, being set in order to supply power to a heating element corresponding to a non-sheet passing area, from among the plurality of heating elements, to be higher than a lowest control target temperature from among control target temperatures that are set in order to supply power to a heating element corresponding to a sheet passing area.

A fixing device includes a tubular body in a tubular shape that forms a nip with a pressurizing member. The heater, disposed inside the tubular body, faces a part of the tubular body in a circumferential direction. The heat equalizing member is disposed on an opposite side of a side where the heater faces the tubular body. The heat equalizing member transfers heat from a place having a high temperature to a place having a low temperature in a second direction along an axial direction of the tubular body. The heat conductive member, disposed between the heater and the heat equalizing member, can conduct the heat in each of the second direction and a first direction in which the heater and the heat equalizing member face each other. A side portion of the heat conductive member in the second direction is divided into three or more portions.

A thermopile sensor that is a temperature measuring device of a fusing device is held on a substrate. The substrate is provided with a cylindrical member extending in front of the thermopile sensor and an aperture disposed at an end of the cylindrical member.

A calculation system includes an obtaining unit and a calculation unit. The obtaining unit obtains information of a sheet. The calculation unit calculates an amount of change in length of the sheet in a conveyance direction of the sheet heated by a heating device to fix a toner image to the sheet based on the information of the sheet obtained by the obtaining unit and an elapsed time from a time when the sheet passes through the heating device.

An image forming apparatus includes plural image forming units and a controller. The plural image forming units are configured to form images of colors using colorants, respectively. The controller is configured to perform control such that the plural images formed by the plural image forming units are output as one image onto a recording medium. At least two of the image forming units are configured to form images using colorants of special colors, respectively and are arranged in succession.

A belt device includes a heater and a belt. The heater includes a substrate and a heat generator on the substrate. The heater has a first heater surface and a second heater surface opposite the first heater surface. The first heater surface is adjacent to the heat generator. The belt is rotatable, has an endless shape, and slides on the second heater surface. The belt includes an inner portion having an inner circumferential surface to slide on the second heater surface. The inner portion has an elastic power of 52% or more.

According to one embodiment, a temperature control device includes a temperature estimation unit and a frequency generation unit. The temperature estimation unit is configured to estimate a temperature of an object being heated by an induction heating coil, the temperature being estimated based on a frequency of a drive signal supplied to an inverter connected to the induction heating coil. The frequency generation unit is configured to set the frequency of the drive signal based on the temperature estimated by the temperature estimation unit, a detected temperature of the object from a temperature sensor, and a target temperature for the object.

According to one embodiment, the information processing apparatus includes an acquisition unit, a derivation unit, and a determination unit. The acquisition unit acquires voltage information indicating a voltage applied to a heat generation unit that heats a sheet in an image forming apparatus. The derivation unit derives a fluctuation range in the voltage indicated by the voltage information acquired by the acquisition unit. The determination unit determines whether or not there is an indication of a malfunction in the heat generation unit using the fluctuation range derived by the derivation unit and a reference fluctuation range.

An image processing apparatus includes an image forming unit configured to form an image on a sheet, a heating device including a belt that contacts the sheet and a plurality of heating elements for heating the belt, a pressure roller configured to press the sheet against the belt, a voltage detection circuit configured to measure a voltage applied to the heating elements, and a controller configured to determine whether at least one of the heating elements is abnormal according to a voltage drop value that is based on voltages measured by the voltage detection unit before and after the plurality of heating elements is energized.