A control unit controls a transfer power source in such a manner that a current value detected by a detection unit is a predetermined value while a transfer medium is not held in a transfer portion, and the control unit sets a transfer voltage based on a voltage value applied from the transfer power source to a transfer member. Then, the transfer voltage is applied from the transfer power source to a transfer roller after the leading edge of the transfer medium in the conveyance direction for the transfer medium is held in the transfer portion and before the leading edge is held in a fixing portion. While the transfer voltage is applied, the control unit sets a voltage to be applied from the transfer power source to the transfer member based on the value of current detected by the detection unit.

An image forming apparatus includes a photoconductor, a charging roller for charging the photoconductor, a current sensor for detecting a value of current flowing through the photoconductor or the charging roller as a result of application of voltage to the charging roller, an acquisition sensor for acquiring an environment value representing an environment state inside the image forming apparatus, and a processor configured to estimate a film thickness of the photoconductor, based on a value of current detected by the current sensor when a state in which the environment value falls within a predetermined range continues for a predetermined time or longer.

An adsorbing member includes a plurality of adsorbing sheets and a plurality of spacers. The plurality of adsorbing sheets adsorb a floating matter. The plurality of spacers are each provided between the adsorbing sheets to form a laminate that the plurality of adsorbing sheets are overlapped via a gap.

An image forming apparatus includes a movable photosensitive member, a charging roller, an electrostatic image forming portion, a developing sleeve, a charging voltage source, a charging voltage conducting path, a developing voltage source, a developing voltage conducting path, and a capacitor electrically connected between an output terminal of the charging voltage source and a ground potential or between the charging voltage conducting path and the ground potential. The capacitor satisfies the following relationship: {C1/(C1+C2)}Vpp5 (V), where C1 (pF) is electrostatic capacity formed by the first and second conducting paths, C2 (pF) is electrostatic capacity of the capacitor, and Vpp (V) is a peak-to-peak voltage of the AC component of the developing voltage.

An image forming apparatus includes a transfer belt, a cleaning device that sweeps off toner remaining on a transfer surface of the transfer belt by using a rotary brush, electrically adsorbs the toner swept by a recovery roller, and removes the toner, a pre-cleaning brush that slidably contacts with the transfer surface of the transfer belt at an upstream side in a belt rotation direction from the cleaning device, and a support member that supports the pre-cleaning brush. A support wall of the support member is formed with openings that liberate foreign matters such as toner and paper powder deposited onto the pre-cleaning brush.

A charging device includes: a housing having a U-shaped cross-section, disposed such that an opening thereof faces a surface of a rotating image carrier, and extending in an axial direction of the image carrier; a discharge electrode configured to charge the surface, the discharge electrode being attached to the housing, inside the housing, and extending in the axial direction; and a cleaner having a protrusion that comes into contact with a bottom plate of the housing and configured to move in the axial direction to clean the discharge electrode in a state in which the protrusion is in contact with the bottom plate, regardless of whether the opening in the housing faces upward or downward.

A first high-voltage power supply includes a first transformer configured to generate a voltage to be supplied to a first wire of a charger, and a second high-voltage power supply includes a second transformer configured to generate a voltage to be supplied to a second wire of the charger. The first and second high-voltage power supplies respectively drive the first and second transformers in accordance with pulse signals that are supplied from a CPU and that have the same frequency and phase. The first and second high-voltage power supplies respectively supply, to the first and second wires of the charger, voltages generated by driving the first and second transformers.

An image forming apparatus includes an image bearing member and a charging member that electrostatically charges a surface of the image bearing member. Control is performed for increasing a voltage to be applied to the charging member in a stepwise manner so that the voltage becomes higher than when the image bearing member passes through a region where the image bearing member faces the charging member in a previous rotation, the control being performed as the image bearing member rotates while a single image region worth of image is being formed in an image region that is longer than a length equivalent to one rotation of the image bearing member in a rotational direction of the image bearing member.

An image forming apparatus includes a photosensitive member, a corona charger including a discharging electrode and a grid electrode having a surface layer containing carbon atoms as a main component and configured to electrically charge the photosensitive member under application of a voltage to the discharging electrode and the grid electrode, and an output portion configured to output information on a lifetime of the grid electrode. The output portion outputs the information on the basis of an index value of an amount of use of the grid electrode correlating with a product of a value of a grid current flowing through the grid electrode and a time of flowing of the grid current through the grid electrode.

An image forming apparatus includes a control unit configured to execute a first mode and a second mode of forming images on first through third image bearing members. In the first mode, a toner image is formed on a third image bearing member without having toner images formed on the first and second image bearing members in a state where the first through third image bearing members are abutted against an intermediate transfer body. In the first mode, the control unit controls at least a first charging device such that a primary transfer contrast in a first primary transfer portion is set to be equal to or greater than a discharge starting voltage, and applies an AC voltage to a second charging device such that a discharge current having a current quantity smaller than that in the second mode is supplied.