An image formation system includes an image carrier that rotates; an opposed member that is opposed to the image carrier and is connected to the image carrier by an adjuster that adjusts a distance to the image carrier; and a temperature detector that is provided on any two or more components among the opposed member, the adjuster, and components other than the adjustor that are interposed between the opposed member and the image carrier.

A fuser detachably attachable to an image forming apparatus includes a heating rotatable body to heat a sheet, a heater to heat the heating rotatable body, a pressing rotatable body to nip the sheet in cooperation with the heating rotatable body, a detection sensor to detect a status of the fuser, a fuser connector, through which the fuser is connected with the image forming apparatus when the fuser is attached to the image forming apparatus and which includes a fuser common terminal, and a relay board including a common terminal connected to the fuser common terminal, and a memory. The relay board is connected with the detection sensor and is configured to relay a detection signal from the detection sensor to the image forming apparatus and a memory signal between the memory and the image forming apparatus via the common terminal and the fuser common terminal.

An image forming apparatus includes an image forming portion, an exposure device, an image density sensor, and a control portion. The control portion can, by adjusting the development voltage based on the image density of a reference image and the amount of exposure from the exposure device, perform image density correction to adjust the image density. The control portion predicts the toner charge amount based on a formation condition of the reference image and the image density of the reference image and determines the timing of performing the image density correction next time based on the rate of change of the toner charge amount calculated using a first toner charge amount predicted when the image density correction was performed last time, a second toner charge amount predicted when the image density correction is performed this time, and the interval between the image density correction performed last time and this time.