An image forming apparatus that forms an image on a sheet includes: a rotating body that forms the image; a motor that rotationally drives the rotating body; a current measurer that measures a motor current flowing through a current supply path including a winding of the motor at a measurement timing that is a timing after the motor is started; a torque acquisitor that acquires a torque value of the motor, based on a measured value of the motor current; and a corrector that performs correction to cancel a current change amount based on a characteristic change depending on a temperature state of the motor at the measurement timing, in acquisition of the torque value by the torque acquisitor.

An apparatus to control a motor includes a detector that detects a driving current flowing through a motor winding, phase determiner that determines a motor rotor rotation phase based on the detected driving current, generator that generates an instructed phase, and controller. The controller includes a first mode where controlling the driving current flowing through the motor winding controls the motor based on a torque current component value such that a deviation between the generated instructed phase and the determined rotation phase is reduced, and a second mode in which a current of a predetermined magnitude controls the motor. The torque current component is expressed in a rotating coordinate system based on determined rotation phase. The generator generates, based on the rotation phase determined while executing second mode, the instructed phase in the first mode when a controlling driving current mode is switched from the second to the first mode.

An image forming apparatus that is capable of executing image forming operation includes an image bearing member, a developer carrying member that faces the image bearing member in a state of keeping a predetermined gap therefrom and develops a latent image on the image bearing member using developer, a frame that supports the developer carrying member, and applying unit that apply developing voltage, in which DC voltage and AC voltage are superimposed, to the developer carrying member. A conductive member is disposed in the frame, a detecting unit detects AC current induced in the conductive member by applying the developing voltage to the developer carrying member, and a control portion controls the applying unit. The control portion controls the developing voltage in the image forming operation, based on the AC current which the detecting unit detects in a case where the voltage is applied by the applying unit.

Devices include electrically conductive elements contacting a vacuum belt, and a voltage source connected to the electrically conductive elements. The electrically conductive elements form an electrical circuit from the voltage source, through the belt, and back to the voltage source. The electrically conductive elements are positioned so that they are separated from the belt when the belt moves the sheets of media between the electrically conductive elements and the belt. A processor is capable of identifying leading edges of the sheets of media on the belt (when voltage of the electrical circuit changes from a relatively higher voltage to a relatively lower voltage) and identifying trailing edges of the sheets of media on the belt (when the voltage of the electrical circuit changes from the relatively lower voltage back to the relatively higher voltage).

An imaging device has a developer roll to provide toner to a photoconductive drum to develop a latent image on the drum for direct transfer to media or an intermediate transfer member. A power supply in communication with a controller sets relative voltages on the developer roll and drum. During transfer of the toner, the imaging device determines a current between the developer roll and drum. In turn, the controller determines a charge and mass of the toner for setting with the power supply an operating voltage on the drum or developer roll. Preventing and reporting toners with insufficient charge are other embodiments.

An image forming apparatus includes a controller configured to execute a mode for correcting a command value of the transfer voltage during a continuous image forming job of forming an image to a plurality of recording materials. The controller is configured to correct the command value of the transfer voltage on the basis of detection results which are detected by a voltage detection unit and a current detection unit during a predetermined time.

After a predetermined period elapses since the start of use of a photosensitive member, if a calculated value calculated from a detection current between a charging unit and a photosensitive member is out of a predetermined range, a determining unit does not perform determination using a currently calculated value and, if the calculated value is within the predetermined range, the determining unit performs determination using the currently calculated value.

An image forming apparatus includes an image carrying member, an intermediate transfer belt, a primary transfer roller, a first belt support roller, a secondary transfer roller, a second belt support roller, a current feeder, a controller, a current sensor, and a rectifier. The current sensor has a lead member. The rectifier shuts off a current passing from the second belt support roller to the ground if the voltage on the second belt support roller is less than a predetermined reference voltage. The controller controls the output current such that the secondary transfer current has a current value resulting from subtracting a leak current from the output current and, when the lead member is in a conducting state, keeps the voltage on the second belt support roller less than the reference voltage.

In post-rotation control of removing an electric charge from a surface of an image bearing member in a state that the image bearing member and a developing member rotate while in contact with each other, in a case that the post-rotation control is started in a state that a recording medium is being conveyed by the image bearing member and a transfer member, i) a control portion controls a transfer voltage applying portion so as to apply a first transfer voltage in a case that the recording medium is being sandwiched between the image bearing member and the transfer member, and ii) the control portion controls the transfer voltage applying portion so as to apply a second transfer voltage that is lower than the first transfer voltage after the recording medium passes through a sandwiching portion.

A method of controlling a printing system including a printing apparatus that prints an image on a sheet and a charge eliminating apparatus that performs a charge eliminating process on the sheet on which the image is printed includes measuring an amount of charge on the sheet that has undergone the charge eliminating process performed by the charge eliminating apparatus, and displaying a message prompting a user to change a setting for charge elimination to be performed by the charge eliminating apparatus in a case where the amount of charge on the sheet measured in the measuring does not fall within a predetermined range.