IMAGE FORMING APPARATUS

To provide an image forming apparatus that can estimate the state of deterioration of toner.SOLUTION: An image forming apparatus 100 comprises: an image carrier 65; a developing device that has a developer carrier 641; a voltage application unit 121; a first measuring unit 101; a second measuring unit 102; and an estimation unit 103. The voltage application unit 121 applies a bias voltage to the developer carrier 641 to move toner from the developer carrier 641 to the image carrier 65. The first measuring unit 101 measures a toner development amount M indicating the weight per unit area of the toner moved from the developer carrier 641 to the image carrier 65. The second measuring unit 102 measures a developing current Id flowing between the developer carrier 641 and the image carrier 65. The estimation unit 103 calculates the value of a determination coefficient R2 indicating a value obtained by dividing dispersion of estimates in a regression model between the toner development amount M and the developing current Id by dispersion of sample values, and estimates the state of deterioration of toner according to the value of the determination coefficient R2.SELECTED DRAWING: Figure 3 【課題】トナーの劣化状態を推定することができる画像形成装置を提供する。【解決手段】画像形成装置１００は、像担持体６５と、現像剤担持体６４１を有する現像装置と、電圧印加部１２１と、第１測定部１０１と、第２測定部１０２と、推定部１０３とを備える。電圧印加部１２１は、現像剤担持体６４１から像担持体６５へトナーを移動させるように現像剤担持体６４１にバイアス電圧を印加する。第１測定部１０１は、現像剤担持体６４１から像担持体６５へ移動したトナーの単位面積当たりの重量を示すトナー現像量Ｍを測定する。第２測定部１０２は、現像剤担持体６４１と像担持体６５との間に流れる現像電流Ｉｄを測定する。推定部１０３は、トナー現像量Ｍと現像電流Ｉｄとの間の回帰モデルにおける推定値の分散を標本値の分散で割った値を示す決定係数Ｒ2の値を算出し、決定係数Ｒ2の値に応じてトナーの劣化状態を推定する。【選択図】図３