An image forming apparatus includes: an image carrier; an exposing device; a developing device with a developing roller; a development current detector that detects development current between the image carrier and the developing roller; and a hardware processor. Under an image forming condition, the hardware processor causes the exposing device to draw, on the image carrier, a development current-detection pattern that includes a solid image and a halftone image that follows the solid image in an image-conveying direction of the image carrier, causes the developing device to develop the development current-detection pattern, obtains information on a chronological change of the detected development current from the development current detector, and determines whether or not a ghost image due to the solid image occurs based on a temporary drop of the detected development current during development of the halftone image.

An image forming portion applies a bias voltage in which an AC component is superimposed on a DC component between a first carrying member and a second carrying member, and transfers toner from the first carrying member to the second carrying member to form an image on the second carrying member. An AC setting processing portion performs AC calibration to set a magnitude of the AC component of the bias voltage. A potential measurement processing portion measures a surface potential of the first carrying member or the second carrying member based on a target current flowing between the first carrying member and the second carrying member. A drive processing portion executes the AC calibration before measurement of the surface potential in a case where, when measuring the surface potential, an activation condition is satisfied.

An image forming apparatus includes a rotatable image bearing member, a charging member, a developing member, a transfer member, an exposure unit, and a controller. The controller executes a preparatory operation in which before an image forming operation, rotation of the image bearing member is started and a charging voltage and a developing voltage are increased stepwise. In the preparatory operation, the controller carries out control so as to start application of the charging voltage at a voltage value not less than a discharge start voltage of the charging member before a surface region of the image bearing member positioned in a developing portion at a time of a start of the rotation of the image bearing member reaches a charging portion in a state which a surface of the image bearing member is exposed to light by the exposure unit.

An image forming apparatus is capable of performing a second image forming operation in which a peripheral velocity ratio of a developer bearing member to an image bearing member becomes greater than that in a first image forming operation, and in which a potential difference between a developing bias applied to the developer bearing member and a supply bias applied to a supply member becomes a potential difference at which a urging force causing a developer at the contact portion between the developer bearing member and the supply member to move from the supply member to the developer bearing member becomes smaller than that in the first image forming operation, or becomes a potential difference at which a urging force causing the developer to move from the developer bearing member to the supply member is generated.

A developing device is detachably supported by an image forming apparatus. The developing device includes a housing that can store developer inside the housing, at least one rotating member rotatably provided for the housing, a first support shaft composed of a conductive member and disposed at an axial end of the rotating member, and a support member including a first bearing portion that supports the first support shaft and constituting a side face of the housing in an axial direction of the rotating member. The first bearing portion includes a first guide portion. The first guide portion protrudes outward from an outer surface of the support member and configured to be guided to an installation position of the developing device during installation of the developing device in the image forming apparatus.

In a cartridge, a housing has a developer accommodating portion and includes a first side wall and a second side wall. A coupling member is disposed at a position opposite to the developer accommodating portion with respect to the first side wall. A detection body is disposed at a position opposite to the developer accommodating portion with respect to the second side wall. A first driving force transmission member is positioned at the same side with the coupling member with respect to the first side wall, and transmits driving force from the coupling member to a rotating member. A second driving force transmission member is positioned at the same side with the detection body with respect to the second side wall, and transmits driving force from the rotating member to the detection body.

An image forming apparatus includes image forming units. A controller includes an execution section, a measurement section, and a prediction section. The execution section controls execution of a developer refresh operation in which toner is ejected from a developer bearing member to an image bearing member so that a specific image forming unit replenishes a development device with the toner from the developer bearing member. The measurement section measures respective surface potentials of the image bearing members included in other image forming units while the specific image forming unit is executing the developer refresh operation. The prediction section uses measurement results of the respective surface potentials of the image bearing members included in the other image forming units for a prediction on the surface potential of the image bearing member included in the specific image forming unit.

An image forming apparatus includes an image bearing member, a developing member that supplies a developer of a regular polarity, a developer supply member that supplies developer to the developing member, and a control unit that applies a first voltage to the developing member and a second voltage to the developer supply member. The control unit executes an image forming operation, and a rotational operation in which the developer supply member rotates in a state in which the first voltage of a regular polarity is applied thereto. The rotational operation includes a first rotational operation in which a potential difference is a first potential difference and a second rotational operation in which the developing member and the developer supply member rotate in a state in which the second voltage having the same polarity as the regular polarity and having a greater absolute value is applied.

An image forming apparatus includes: an image forming unit comprising: a photosensitive member configured to rotate; a charging unit configured to charge the photosensitive member based on a charging bias; an exposure unit configured to expose the photosensitive member charged by the charging unit with laser light to form an electrostatic latent image on the photosensitive member; and a developing device configured to develop the electrostatic latent image based on a development bias to form an image on the photosensitive member, a reading unit configured to read a test image formed by the image forming unit, and a controller configured to: control the image forming unit to form the test image; control the reading unit to read the test image.

An image forming device including an image carrier, a charge device, a developer device, power supply circuitry that applies a charge bias and a developer bias to the charge device and the developer device, respectively, a detector, and a hardware processor that operates as: a control unit that changes a fogging margin, which is a difference between charge bias and developer bias, and controls the power supply circuitry to set the charge bias and developer bias accordingly; a calculation unit that calculates amounts of change between detected values; and a determination unit that obtains differences between amounts of change, determines whether each difference is less than a defined value, and determines a position of a boundary between a first range greater than or equal to the defined value and a second range less than the defined value as a fogging margin to be used in forming a print image.