An image forming apparatus includes a photoconductor, a charging roller configured to charge the photoconductor, and a self-excited oscillation circuit. The image forming apparatus includes a transformer including a primary coil and a secondary coil, the transformer being configured to produce, at the secondary coil, a voltage applied to the charging roller, in accordance with the primary coil being driven by the self-excited oscillation circuit. The image forming apparatus includes a controller configured to control, at start-up of the self-excited oscillation circuit, the self-excited oscillation circuit to allow an amount of a current flowing through the primary coil to be larger than an amount of a current flowing from the photoconductor through the secondary coil, via the charging roller.

An image forming apparatus includes: an image carrier in which a latent image is formed; a developing device that transfers toner to the latent image from a developing member opposed to the image carrier, and develops the latent image; a development power supply that applies a development voltage across the image carrier and the developing member; a period detector that detects periodic information on the developing member and the image carrier in a circumferential direction; and a corrector that corrects the development voltage or an exposure amount of the latent image based on the periodic information detected by the period detector. At least one of the developing device and the development power supply is set so that a supply rate of charge of the toner to the latent image in a solid area of an image reaches 80% or higher.

Let V1 be a potential difference between a photosensitive member charged by a charging member to which a second charging voltage is applied in a preparation process and a developing member to which a developing voltage is applied. Let V2 be a potential difference between the photosensitive member charged by the charging member to which a first charging voltage is applied in an image forming process and the developing member. Given this definition, a relation of |V1|<|V2| is satisfied.

An image forming apparatus includes a storage unit and a charging amount acquisition unit. The charging amount acquisition unit performs a charging amount acquisition operation for forming a measurement toner image on the image carrier while changing the frequency of the alternating current voltage of the development bias with a potential difference in a direct current voltage between the developing roller and the image carrier being kept constant, acquiring a tilt of a measurement straight line representing a relationship between the change amount of the frequency and a density change amount of the measurement toner image, and acquiring the charging amount of the toner based on the acquired tilt of the measurement straight line and the reference information in the storage unit.

An image forming apparatus includes a developing section, storage, a first calculation section, a comparing section, and an executing section. The developing section develops an electrostatic latent image with toner. The storage stores coverage rates. The first calculation section calculates a first coverage rate and a second coverage rate. The comparing section compares the first coverage rate with the second coverage rate. The first coverage rate includes one or more coverage rates stored earlier in the storage than the second coverage rate. The second coverage rate includes coverage rates of a specified number of latest images individually formed on the specified number of sheets. The running-in operation is driving the developing section. The executing section executes the running-in operation.

An image forming apparatus includes an image former and a hardware processor. The image former includes, an image carrier; a developer; a conductive rotating member; and a voltage applier which applies voltage to the rotating member. The hardware processor executes an attached material detection mode which detects material attached to a surface of the rotating member. In such mode, the hardware processor controls the voltage so that the developing bias is a value between a surface potential in a region of the image carrier in contact with a portion in which attached material exists on a surface of the rotating member if a reference voltage is applied by the voltage applier, and a surface potential in a region of the image carrier in contact with a portion in which the attached material does not exist on the surface of the rotating member if the reference voltage is applied.

An image formation apparatus includes a first electrode portion including a contact electrode and a counter electrode, a second electrode portion arranged as not being in contact with a recording medium, a first sensing unit configured to sense a first current which flows to the first electrode portion as a result of application of a voltage across the contact electrode and the counter electrode while the recording medium lies between the contact electrode and the counter electrode, a second sensing unit configured to sense a second current which flows from the charged recording medium to the second electrode portion, and a control unit. The control unit sets a transfer condition for transferring a toner image to the recording medium based on the first current sensed by the first sensing unit and the second current sensed by the second sensing unit.

An image forming apparatus includes a plurality of image forming portions, an intermediate transfer belt, a belt displacement detector, an attraction force changer, and a controller. The intermediate transfer belt is an endless belt wound around drive and driven rollers. The belt displacement detector detects displacement of the intermediate transfer belt in a rotation axis direction of the driven roller. The attraction force changer is operable to change electrostatic attraction force of the driven roller with respect to the intermediate transfer belt exerted on each of opposite end sides of the driven roller in the rotation axis direction thereof. When the belt displacement detector detects displacement of the intermediate transfer belt, the controller makes the attraction force changer increase the electrostatic attraction force of the driven roller with respect to the intermediate transfer belt exerted on a side opposite to a side toward which the displacement has taken place.

An image forming apparatus includes a rotatable photoconductor, a charging device, a voltage applying device, a current detection device, and control circuitry. The control circuitry is configured to determine a film thickness of the photoconductor based on a charging current detected with the current detection device; determine an estimated film thickness of the film thickness, based on a previous film thickness and travel information of the photoconductor after determination of the previous film thickness; determine a discharging start voltage that the voltage applying device applies to start discharging from the charging device to the photoconductor; determine, from the estimated film thickness and the discharging start voltage, a film thickness determining voltage that the voltage applying device applies to pass a film thickness determining current being a charging current used for determining the film thickness; and apply the film thickness determining voltage to the charging device to determine the film thickness.

An image forming apparatus detects a current flowing between a developer carrying member and a cleaning member is detected for each of a plurality of toner images when a region on the developer carrying member passes through the cleaning member, and a potential difference to be used during image formation between the developing voltage and an image portion potential is set on the basis of a value of the detected current for each of the plurality of toner images. An absolute value of the potential difference to be used during image formation is larger than the potential difference between the developing voltage and the image portion potential whose absolute value is smallest among potential differences between the developing voltage and the image portion potential to be used for developing a toner image of which the value of the current detected is in a predetermined range among the plurality of toner images.