An image forming apparatus includes a replaceable roller member, an applying unit that applies voltage to the roller member, a current detecting unit that detects a current flowing in the roller member to which the voltage is applied, and a controlling unit. The controlling unit calculates a value of a slope of a current-voltage characteristic of the roller member on the basis of a first current detected when a first voltage is applied to the roller member and a second current that is detected when a second voltage is applied, and determines whether or not the roller member has been replaced on the basis of an amount of change from a value of a first slope calculated at a first timing and a value of a second slope calculated at a second timing later than the first timing.

An image forming apparatus includes an image bearing member, a charging member, a development member, a transfer member, a charging voltage application unit, a development voltage application unit, and a control unit. The development member collects toner that remains on a surface of the image bearing member after a toner image is transferred from the image bearing member surface to transfer material. The control unit controls application of a development voltage to apply, to the development member in a cleaning operation, a development voltage having a polarity that is opposite to a normal polarity, and controls application of a charging voltage to apply, to the charging member, a charging voltage having the normal polarity such that a potential difference formed at a charging portion between the applied charging voltage and a surface potential formed at the image bearing member surface is lower than or equal to a discharge start voltage.

A control unit of an image forming apparatus can perform a density correction mode to correct toner density, based on detection results of toner density of a plurality of reference images formed with density gradations changed sequentially in a plurality of steps, detects presence or absence of a change in the voltage in each density gradation, based on the toner density detection value detected in the density correction mode, and if the density gradation has a specific density gradation in which a change in the voltage is detected, it corrects the toner density of the specific density gradation, using the detection values of density gradations before and after the specific density gradation.

An image forming apparatus includes a developing device that is mountable and dismountable and has a sealing member for sealing to be removed at a time of start using the developing device. The image forming apparatus further includes a winding shaft, a drive source, a detector, and a controller. The winding shaft rotates for removal processing for removing the sealing member. The drive source drives the winding shaft. The detector detects a value corresponding to a load torque applied to the drive source. The controller notifies of an error in a case where the value detected by the detector has become smaller than a predetermined value before a predetermined period of time elapses from start of the drive by the drive source.

A sheet characteristic detection device includes: a detector that is disposed on a sheet ejection path through which a sheet is ejected and that detects an electrical resistance value of the sheet; and a charge neutralizer that is disposed on a downstream side of the detector on the sheet ejection path and that neutralizes electric charge on the sheet.

According to one embodiment, an image forming system includes a photoreceptor system, first and second detection system, a controller, and a determination system. The photoreceptor system having a rotational shaft in a longitudinal direction. The first detection system detects whether there is an abnormality on a surface of the cylindrical photoreceptor system at a first position. The second detection system detects whether there is the abnormality on the surface of the cylindrical photoreceptor system at a second position. The controller causes the second detection system to start detecting of the abnormality at a point in time after a waiting time. The determination system determines damage occurred at a surface position of the surface of the cylindrical photoreceptor system if the second detection system detects the abnormality at the surface position at which the first detection system detected the abnormality.

The control unit of an image forming apparatus applies, with a voltage application unit, a collection voltage to a cleaning roller when an image is formed, estimates a surface potential of an image carrying member based on a current flowing between the image carrying member and the cleaning roller which is detected by a current detection unit when the collection voltage is applied and changes the collection voltage and the rotation speed of the cleaning roller when the surface potential of the image carrying member is lowered.

A control portion can perform printing operation and to determine a transfer voltage for performing it, transfer voltage setting operation. When performing adjusting operation, the control portion estimates the amount of static charge of toner in a development device to determine the transfer voltage based on the estimated amount of static charge of the toner and the resistance value of a transferring member previously stored in a memory.

A charge eliminating apparatus configured to remove charges from a sheet on which an image is formed by a printing apparatus, includes a charge eliminating roller pair including a first charge eliminating roller and a second charge eliminating roller configured to form a nip portion together with the first charge eliminating roller, the charge eliminating roller pair being configured to remove the charges from the sheet in a state of contacting the sheet at the nip portion, a first setting unit configured to set a value of a voltage applied to the charge eliminating roller pair, and a second setting unit configured to set whether to apply the voltage to the charge eliminating roller pair, wherein the second setting unit is configured to set whether to apply the voltage to the charge eliminating roller pair without changing the value of the voltage set by the first setting unit.

An image forming apparatus includes a photosensitive member, a charging member, an exposing device, a developing device, a transfer member, a brush, a voltage applying portion, and a control portion controlling a surface potential of the photosensitive member at the brush contacting position. When a value of subtracting a value of the surface potential of the photosensitive member in the brush contacting position from a value of the brush voltage is defined as a contacting position potential difference, the control portion controls the surface potential of the photosensitive member in the brush contacting position so that the contacting position potential difference is changed from a first potential difference to a second potential difference in a predetermined direction which is either one of an increasing direction or a decreasing direction, and then the contacting position potential difference is changed from the second potential difference to a third potential difference in the predetermined direction.