A fuser is described including a heater, a belt, a rotating member, and a pad. A nip portion is formed between the belt and the rotating member as the pad presses the belt toward the rotating member. The pad is biased toward a restricting member. The biasing may be performed by one or more springs. The spring may be a compression spring, a tension spring, and/or a plate spring among other types of springs.

According to one embodiment, an image forming apparatus includes a fixing member, a pressurizing member, a movable member, and a controller. The fixing member heats a sheet. The pressurizing member has first heat capacity and faces the fixing member. The movable member is provided to be movable between a contact position to contact with the pressurizing member and a separation position to be separated from the pressurizing member, and has second heat capacity smaller than the first heat capacity. The controller is configured to move the movable member to one of the contact position and the separation position based on a change of a control temperature of the fixing member or the pressurizing member.

According to one embodiment, a heating device, a cooling device, a temperature sensor, and a control device are provided. A heating device operates in a first operation mode in which a first toner transferred to a medium at a predetermined first temperature is heated, or in a second operation mode in which an image formed in the medium by the first toner is heated at a second temperature higher than the first temperature. The cooling device reduces the temperature of the heating device from an operation range in the second operation mode to an operation range in the first operation mode. The temperature sensor detects the temperature of the heating device. The control device controls the cooling device to reduce the temperature of the heating device. After the temperature of the heating device detected by the temperature sensor reaches the operation range in the first operation mode, the control device further cools down the heating device based on a cooling time taken until the temperature reaches the operation range in the first operation mode from the operation range in the second operation mode.

A pressure-applying device includes a pressure-applying portion that applies pressure to a pressure-receiving object and a pressing portion that presses the pressure-applying portion toward the pressure-receiving object, the pressing portion having a hardness higher than a hardness of the pressure-applying portion. The pressure-applying portion includes plural projections that project from a back surface of the pressure-applying portion that faces the pressing portion toward a pressing surface of the pressing portion that faces the pressure-applying portion.

A fuser is described including a heater, a belt, a rotating member, and a pad. A nip portion is formed between the belt and the rotating member as the pad presses the belt toward the rotating member. The pad is biased toward a restricting member. The biasing may be performed by one or more springs. The spring may be a compression spring, a tension spring, and/or a plate spring among other types of springs.

A pressure-applying device includes a pressure-applying portion that applies pressure to a pressure-receiving object and a pressing portion that presses the pressure-applying portion toward the pressure-receiving object, the pressing portion having a hardness higher than a hardness of the pressure-applying portion. The pressure-applying portion includes plural projections that project from a back surface of the pressure-applying portion that faces the pressing portion toward a pressing surface of the pressing portion that faces the pressure-applying portion.

According to one embodiment, an image forming apparatus includes a fixing member, a pressurizing member, a movable member, and a controller. The fixing member heats a sheet. The pressurizing member has first heat capacity and faces the fixing member. The movable member is provided to be movable between a contact position to contact with the pressurizing member and a separation position to be separated from the pressurizing member, and has second heat capacity smaller than the first heat capacity. The controller is configured to move the movable member to one of the contact position and the separation position based on a change of a control temperature of the fixing member or the pressurizing member.

A maximum curvature in a rotational direction of a fixing belt and the number of times of bendings when a temperature of the fixing belt is equal to or lower than a glass transition temperature of the fixing belt surface material are specified, and the fixing belt controlled to operate within the specified range.

A fixing device includes an endless belt; a pressing unit that is in contact with an outer peripheral surface of the belt and that rotates the belt; a first unit that is provided on an inner peripheral surface of the belt and that retains the belt in contact with the pressing unit; a second unit provided on the inner peripheral surface of the belt and located downstream of the first unit in a rotation direction of the belt, the second unit applying tension to the belt and including a portion that is in contact with a central portion of the belt in a width direction of the belt and that is farther in a direction toward the outer peripheral surface of the belt than both ends of the belt in the width direction of the belt; and a third unit provided on the inner peripheral surface of the belt and located downstream of the second unit in the rotation direction of the belt, the third unit applying tension to the belt and including a portion that is in contact with the central portion of the belt in the width direction of the belt and that is farther in the direction toward the outer peripheral surface of the belt than both ends of the belt in the width direction of the belt.

A fixing device includes an endless belt, multiple stretchers that stretch the belt, a heater that heats the belt including sections, section by section, sectioned in a direction crossing a rotation direction of the belt, and a switch that switches the sections heated by the heater from one to another in accordance with a position of an edge portion of the belt in the direction crossing the rotation direction of the belt.