According to one embodiment, a fuser includes a heat roller, an endless belt, a first press roller and a second press roller. The heat roller rotates and contacts a toner surface side of a sheet, and heats the sheet. The endless belt contacts a part of an outer peripheral surface of the heat roller. The first press roller contacts a part of an inner peripheral surface of the endless belt, and is provided at an insertion part of the sheet in a nip portion where the heat roller contacts the endless belt. The second press roller contacts a part of the inner peripheral surface of the endless belt, is provided at an exit part of the sheet in the nip portion, and has a lower rotational resistance than the first press roller.

A nip former that forms a nip between an endless belt and a pressure rotator includes a base that is made of aluminum and has a nip forming face disposed opposite the nip. An anodic oxidation coating is treated with sealing and coats at least the nip forming face. The anodic oxidation coating has a thickness that is not smaller than 22 μm and is not greater than 45 μm and a variation in thickness that is not greater than 20 percent. The base and the anodic oxidation coating define a nip forming portion that is disposed opposite the nip. The nip forming portion has a thickness that is not smaller than 0.40 mm and is not greater than 1.20 mm.

A pressure and pressure relief device includes a rotator, a pressure body, a first pressure lever, and a biasing mechanism. The biasing mechanism includes a first elastic body, a second pressure lever, a cam, and a cam follower. A relations of L1>L3, L2>L4, and L3<L4 are satisfied. L1 represents a length between a first fulcrum of the first pressure lever and a point of load of the first pressure lever. L2 represents a length between the point of load of the first pressure lever and a hook portion of the first pressure lever. L3 represents a length between a pivot of the second pressure lever and a second fulcrum of the second pressure lever. L4 represents a length between the second fulcrum of the second pressure lever and a fastened portion of the second pressure lever.

A fixing device including an endless belt, a rotary body positioned outside of the endless belt, the rotary body having an axis extending in an axial direction, an elastic member positioned at an inner space of the endless belt and configured to nip the endless belt in cooperation with the rotary body, and an adhering member having rigidity higher than rigidity of the elastic member. The elastic member has a contact surface in contact with the endless belt. The adhering member has an adhered portion adhered to an opposite surface opposite to the contact surface. The adhering portion has a length in the axial direction smaller than the length of the elastic member in the axial direction.

A fixing member for a fixing device, the fixing member includes a cylindrical base layer; and a plurality of heat generating resistors extending in a longitudinal direction of the fixing member on the base layer and arranged with intervals in a circumferential direction of the base layer, wherein heat generating resistors have volume resistivities lower than that of the base layer, the heat generating resistors include a first heat generating resistor and a second heat generating resistor adjacent to each other in the circumferential direction, and the first heat generating resistor and the second heat generating resistor are at least partly overlapped in the circumferential direction.

A fixing device includes a fixing roller heated to a predetermined temperature by a heater; a pressure belt in pressure contact with the fixing roller; and a pressing part which presses the pressure belt toward the fixing roller. The fixing device adopts a belt-nip system and fixes a toner image formed on a recording medium to the recording medium by heat and pressure while the recording medium is nipped and conveyed through a nip part. The nip part is formed by the fixing roller and the pressure belt and includes an adhesion nip and a separation nip. The pressing part includes a pressing member, a sheet member which covers the pressing surface of the pressing member along a conveying direction of the recording medium, and a pressing fluid which is filled at the adhesion nip between the pressing member and the sheet member.

An image forming apparatus includes an endless belt, a roller configured to rotate the endless belt by rotating in a state in which the roller is in contact with an outer circumferential surface of the endless belt, a heater, a pressure pad configured to nip the endless belt between the pressure pad and the roller to form a nip portion, a sliding sheet interposed between an inner circumferential surface of the endless belt and the pressure pad. The image forming apparatus is configured to execute a fixing operation in which a developer image on a sheet is fixed in a state in which the sheet is nipped between the roller and the endless belt. A nip pressure at the nip portion P [MPa] and a peripheral velocity of the endless belt V [mm/sec] satisfies V/P≥200 when the image forming apparatus executes the fixing operation.

An image forming apparatus includes a photoconductive drum, a developing roller, a sheet supplier, a fixing unit, and a controller. The fixing unit includes a heating roller, a first heater, a second heater, a first temperature sensor, and a second temperature sensor. The controller is configured to control the first heater so that a first detected-temperature becomes a target temperature at a central area, and control the second heater so that a second detected-temperature becomes a target temperature at an end area, and in accordance with a heat storage amount of the fixing unit stored by the heating of the second heater, change (i) a timing when supply of the sheet is started or (ii) the target temperature at the end area.

A fixing device includes a first fixing member, a second fixing member, a pressing member, and a heating device. The first fixing member is in an ungrounded state and comes into contact with a toner image on a sheet. The second fixing member is arranged opposite the first fixing member. The pressing member presses the first fixing member against the second fixing member so as to form, at the contact portion between the first fixing member and the second fixing member, a nip portion through which the sheet passes. The heating device heats the first fixing member.

A fixing apparatus includes an endless first rotary member, a heating element, a second rotary member configured to form a nip portion, and a nip member configured to receive radiant heat from the heating element and heat the nip portion. The nip member includes a main-body portion that contains aluminum or aluminum alloy and a protective layer that includes an oxide film formed on a surface of the main-body portion. The main-body portion contains a heat receiving surface that faces the heating element and receives radiant heat from the heating element, and a rubbed surface that is rubbed against the inner circumferential surface of the first rotary member. The protective layer contains coloring agent that causes an emissivity of the heat receiving surface and the rubbed surface to be higher than an emissivity of a natural color oxide film.