A device includes a charge roller and a control portion. The charge roller is removably insertable to be in charge-transferring relation to, and spaced apart by a first air gap from, a photoconductive imaging portion of an electrophotographic printer. The control portion is to determine a size of the first air gap based on determination of a charging threshold voltage associated with the charge roller.

A binary ink developer (BID) may include a power supply electrically coupled to an electrode, a developer roller, and a cleaner roller. The BID may also include a controller to determine a level of image ghosting based on a sum of currents at the electrode, the developer roller and the cleaner roller, and instruct the power supply to provide an adjusted voltage to the cleaner roller in response to a determination of the level of image ghosting.

An image forming apparatus includes a motor configured to rotationally drive an image bearing roller and a developer bearing roller at a first peripheral velocity ratio and a second peripheral velocity ratio which is larger than the first peripheral velocity ratio. A development contrast formed between a developing bias to the developer bearing roller and a light-part potential formed on the image bearing roller in a case where a development operation is performed at the second peripheral velocity ratio is larger than a development contrast formed between the developing bias to the developer bearing roller and the light-part potential formed on the image bearing roller in a case where the development operation is performed at the first peripheral velocity ratio.

A device includes a charge roller and a control portion. The charge roller is removably insertable to be in charge-transferring relation to, and spaced apart by a first air gap from, a photoconductive imaging portion of an electrophotographic printer. The control portion is to determine a size of the first air gap based on determination of a charging threshold voltage associated with the charge roller.

An image forming apparatus that executes an image forming operation for forming a toner image on a recording material and an application operation of applying a metal soap to a surface of an image bearing member by supplying a toner stored in a toner storing unit to the surface of the image bearing member from the developing member. A surficial moving speed of the image bearing member during the application operation is lower than the surficial moving speed of the image bearing member during the image forming operation, and a speed difference between the surficial moving speed of the developing member and the surficial moving speed of the image bearing member during the application operation is larger than that during the image forming operation.

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.

An image forming apparatus includes an image bearing member, a transfer member, a voltage source, a current detecting portion, and a controller. When the recording material passes through the transfer portion, the controller is capable of changing the predetermined voltage on the basis of a detection result of said current detecting portion so that the detection result of the current detecting portion falls within a predetermined range. A maximum changeable amount per once of the predetermined voltage is larger when a leading end portion of the recording material with respect to a recording material feeding direction passes through the transfer portion than when a central portion of the recording material with respect to the recording material feeding direction passes through the transfer portion.

An image forming apparatus includes an image forming portion, a high-voltage generation circuit, a current detection portion and a control portion. The image forming portion includes an image carrying member, a charging device, an exposure device and a developing device which includes a developer carrying member for carrying a two-component developer. The control portion can perform a transfer memory prediction mode that includes a step of estimating, when a first reference image is formed, the level of occurrence of transfer memory based on the direct-current component of a development current flowing through the developer carrying member and a step of measuring, when the measured direct-current component of the development current is larger than a predetermined value, the amount of charge of the toner within the developing device and estimating the cause of occurrence of the transfer memory based on the measured amount of charge of the toner.

An image forming apparatus includes: a development device which develops an electrostatic latent image formed on a photosensitive drum into a toner image; a charger which charges the photosensitive drum; a development power supply which applies a prescribed bias voltage to the development device; and a calculating section which calculates a surface potential of the photosensitive drum based on a development current flowing in the development device. The calculating section calculates, as the surface potential, a bias voltage at which a non-charging development current that flows in the development device in an uncharged state in which the charger has not charged the photosensitive drum is equal to a charging development current that flows in the development device in a charged state in which the charger has charged the photosensitive drum.

An image forming apparatus includes: a development device which develops an electrostatic latent image formed on a photosensitive drum into a toner image; a charger which charges the photosensitive drum; a development power supply which applies a bias voltage to the development device; a calculating section which calculates a surface potential of the photosensitive drum based on a development current flowing in the development device; and an estimating section which estimates a fogging toner amount. The fogging toner amount is an amount of toner moved due to fogging. When the fogging toner amount estimated by the estimating section is less than a prescribed threshold, the calculating section calculates a value of the bias voltage at which the development current stops flowing as the surface potential.