According to one embodiment, an image forming apparatus includes a sheet supply unit, a printer, a fixing device, and a controller. The sheet supply unit supplies a sheet from a sheet container. The printer forms a toner image to the sheet conveyed from the sheet supply unit. The fixing device includes a heater, a fixing belt, and a pressure roller. The heater includes a heat generating member including a plurality of heating elements arranged in a first direction orthogonal to a sheet conveyance direction and in which a heating element group selected in response to a printing request from the heat generating member generates heat. The fixing belt fixes the toner image heated by the heater to the sheet. The pressure roller presses the fixing belt.

An electric circuit includes a power supply circuit that supplies electric power, a load, a power supply line that supplies the power from the power supply circuit to the load, a signal line located along and adjacent to the power supply line, a detector that detects whether the power is being supplied to the signal line, and a controller including a processor, and configured to, when the processor executes a control program, cause the power supply circuit to supply the power to the power supply line, in a case where the detector detects the power supply to the signal line when a signal is outputted to the signal line, and restrict the power supply circuit from supplying the power to the power supply line, in a case where the detector does not detect the power supply to the signal line.

According to an embodiment, a heater unit includes a substrate. A first heating element is on a first side of the substrate. A second heating element is on a second side of the substrate. A first wiring is on the first side of the substrate and connected to the first heating element. A first electrode is on the first side of the substrate and connected to the first heating element. A second wiring is on the second side of the substrate and connected to the second heating element. A second electrode is on the second side of the substrate and connected to the second heating element via the second wiring. A portion of the second heating element overlaps a first portion of the first heating element.

A fixing unit includes a first heater, a first switch, a second heater, and a second switch. In an image forming mode, a controller controls the first switch and the second switch to keep a temperature of the fixing unit at a fixing temperature serving as a target temperature for fixing the image on the sheet. In a standby mode, the controller controls the first and second switches to keep the temperature of the fixing unit at a standby temperature, and controls the first and second switches such that a period in which a first current is supplied to the first heater and a period in which a second current is supplied to the second heater do not overlap.

A controller obtains a first duty cycle of a first current to be supplied to a first heater and a second duty cycle of a second current to be supplied to a second heater and controls the first switch and the second switch after the reduction control period, such that the temperature of a fixing unit maintains a target temperature for fixing the image by the fixing unit.

In a caser where a first current is supplied to a first heater, a controller gradually increases the first current in a first period, supplies the first current based on a first duty cycle in a second period, and gradually reduces the first current to stop supplying the first current in a third period. In a case where a second current is supplied to a second heater, the controller gradually increases the second current in a fourth period, supply the second current based on a second duty cycle in a fifth period, and gradually reduces the second current to stop supplying the second current in a sixth period. The controller controls the supply of the second current such that part of the fourth period overlaps with the third period.

An image forming apparatus is disclosed. A fixing device includes a heating rotary member and a pressing rotary member. The fixing device further includes an acquisition means that acquires information about a printing medium for a predetermined number of sheets beforehand, and a temperature control means that controls a temperature of the heating rotary member based on the information about a basis weight acquired by the acquisition means. A job in which different basis weights are mixed is a mixed job. In a case where the mixed job is executed and the temperature of the heating rotary member is changed while the mixed job is executed, a change amount of the temperature of the heating rotary member is reduced based on the information about the basis weight of the printing medium acquired by the acquisition means.

According to one embodiment, a temperature control device stores a fixing device temperature estimation value and a storage time obtained by WAE control in a memory at any time during operation. After an electric power supply to the temperature control device is stopped, the next time the electric power supply is started, an electric power supply stop period until the electric power supply is started is calculated. If the electric power supply stop period is shorter than a set time, the WAE control is started by using the stored fixing device temperature estimation value, and if the electric power supply stop period exceeds the set time, the WAE control is started based on an initial set value.

According to one embodiment, a temperature control device stores a fixing device temperature estimation value and a storage time obtained by WAE control in a memory at any time during operation. After an electric power supply to the temperature control device is stopped, the next time the electric power supply is started, an electric power supply stop period until the electric power supply is started is calculated. If the electric power supply stop period is shorter than a set time, the WAE control is started by using the stored fixing device temperature estimation value, and if the electric power supply stop period exceeds the set time, the WAE control is started based on an initial set value.

An image forming apparatus for forming a toner image on a recording material includes a fixing unit and a blower unit to blow air around a roller. The fixing unit includes a tubular shape film, a heating member disposed in a space surrounded by the film, and the roller forming a nip portion with the heating member. The fixing unit heats and fixes the toner image onto the recording material at the nip portion. For printing that forms toner images on continuously conveyed recording materials where a roller surface temperature is lower than a predetermined temperature, fan stop and operation periods are set. During the fan stop period, the blower unit is stopped and an interval between preceding and subsequent recording materials is widened. During the fan operation period, the blower unit is in operation and the interval is narrower than the interval during the fan stop period.