Patent ID: 8503896

Claim:
An image formation device for forming an image on a print medium by an electrophotographic process, comprising: a photosensitive body on which a developer image to be transferred to the print medium is formed by the electrophotographic process including charging of the photosensitive body; a charging unit which includes a charging wire and a grid and thereby electrically charges the photosensitive body; a charging power unit which applies a wire potential to the charging wire; a wire potential measuring unit which measures the wire potential; a charging control unit which controls the amount of electric charge supplied from the charging unit to the photosensitive body by controlling the wire potential based on the wire potential measured by the wire potential measurement unit, wherein the charging control unit includes a control range restricting unit which restricts a control range of the wire potential within a prescribed electric potential; and a grid output measuring unit which measures at least one selected from a grid potential as electric potential of the grid and a grid current as electric current passing through the grid, wherein: the charging control unit executes the control in a grid output control mode in which at least one selected from the grid potential and the grid current is controlled to be at a constant level by controlling the wire potential in order to control the amount of the electric charge supplied from the charging unit to the photosensitive body, and the grid output control mode is a control mode in which the control range of the wire potential is restricted further so that potential difference between the wire potential and the grid potential is kept less than or equal to a preset second threshold value when the wire potential has exceeded a preset first threshold value.