A developing device includes a developing roller and a conveyor roller. The developing roller includes a first magnet. The conveyor roller includes a second magnet. The first magnet includes a first magnetic pole and a second magnetic pole. The second magnet includes a third magnetic pole and a fourth magnetic pole. The first and fourth magnetic poles are magnetic poles having the same polarity. One of the second and third magnetic poles is a magnetic pole having the same polarity as the first magnetic pole. The other of the second and third magnetic poles is a magnetic pole having a polarity different from the first magnetic pole. The developer is transferred from the conveyor roller to the developing roller by the third and second magnetic poles. The developer is transferred from the developing roller to the conveyor roller by the first and fourth magnetic poles.

A developing device includes a developing roller, a conveyor roller, a developer stirring unit and a development bias applying unit. The developing roller is arranged to face a photoconductive drum at a predetermined developing position and supplies the toner. The conveyor roller is arranged to face the developing roller at a predetermined facing position and supplies the developer to the developing roller. The development bias applying unit applies development biases to the first sleeve of the developing roller and the second sleeve of the conveyor roller during a developing operation of developing the electrostatic latent image on the photoconductive drum with the toner. The development bias applying unit applies the development biases such that a shifting electric field to move the toner on the first sleeve of the developing roller toward the second sleeve of the conveyor roller is formed at the facing position during the developing operation.

An image forming apparatus includes a developing device that forms a toner image, by developing an electrostatic latent image formed on a photoconductor drum, a charging device that electrically charges the photoconductor drum, a developing power source that applies a predetermined developing bias voltage to the developing device, and a calculation device that calculates a surface potential of the photoconductor drum, on a basis of the developing current flowing in the developing device. The developing power source applies the developing bias voltage in a plurality of levels, to the developing device. A current measurement device measures a developing current, with respect to the developing bias voltage of each level. The calculation device calculates the surface potential, on the basis of each developing current.

An image forming apparatus incudes a first conveyance guide portion having a first roller, a first engagement portion, and a second engagement portion, and includes a second conveyance guide portion having a second roller, a first engaged portion, and a second engaged portion. The first and second conveyance guide portions form a conveyance path where the first and second rollers convey a sheet. The second conveyance guide portion moves so that engagement between the second engagement portion and the second engaged portion is released and relative positioning between the second and first conveyance guide portions is released. When the first engagement portion and the first engaged portion engage each other and the relative positioning between the second and first conveyance guide portions is released, the second conveyance guide portion pivots in an opening direction relative to the first conveyance guide portion so that the conveyance path is opened.

An image forming apparatus includes an image carrier, a developing device, a voltage applier, a current detector, a cleaning blade, and a control device. The control device acts as a measurer and an estimator. The measurer changes the DC bias to a first value and a second value, and acquires a first magnitude of the developing current corresponding to the first value, and a second magnitude of the developing current corresponding to the second value, from the current detector. The estimator calculates a current ratio between the first magnitude and the second magnitude, and estimates deterioration status of the cleaning blade, according to the value of the current ratio.

An image forming apparatus includes an image carrier, an exposure device to expose the image carrier to form an electrostatic latent image on the image carrier, a conductive member, and a developing device having a rotatable developing roller and a rotatable toner supply roller. Polarity of direct-current components of biases applied during an image forming operation to the conductive member, the developing roller, and the toner supply roller are the same as a polarity of normally charged toner. An absolute value of the bias applied to the developing roller during the image forming operation is smaller than an absolute value of the bias applied to the toner supply roller during the image forming operation. The absolute value of the bias applied to the toner supply roller during the image forming operation is smaller than an absolute value of the bias applied to the conductive member during the image forming operation.

In an image forming apparatus, a fixing member has a surface layer having conductivity. A developer is a toner having a toner particle including a binder resin, a reactant of a polyhydric acid and a compound containing a group 4 element is present on a surface of the toner particle, and Tv/Fv>100 is satisfied where Tv represents a volume resistivity upon being unfixed, and Fv represents a volume resistivity after fixing. A bias applying unit can selectively apply a bias of a positive polarity and a bias of a negative polarity, and applies a bias of the same polarity as the charged polarity of a filler included in a recording material when the recording material passes through a fixing nip portion, and when the recording material does not pass through the fixing nip portion, respectively.

An image forming apparatus includes an image carrier, an exposure device to expose the image carrier to form an electrostatic latent image on the image carrier, a conductive member, and a developing device having a rotatable developing roller and a rotatable toner supply roller. Polarity of direct-current components of biases applied during image forming operation to the conductive member, the developing roller, and the toner supply roller are the same as a polarity of normally charged toner. An absolute value of the bias applied to the developing roller during the image forming operation is smaller than an absolute value of the bias applied to the toner supply roller during the image forming operation. The absolute value of the bias applied to the toner supply roller during the image forming operation is smaller than an absolute value of the bias applied to the conductive member during the image forming operation.

In an image forming apparatus, in a case in which a second toner image to be transferred to a same recording material as a first toner image is to be transferred is formed on the photosensitive member after the first toner image is formed on the photosensitive member and the first toner image is formed on an area of the photosensitive member including at least a part of a position of the second toner image one cycle before with respect to a movement direction of the surface of the photosensitive member, a control unit changes a value of a transfer current at a time of transferring the first toner image to a transfer-receiving member between a first value and a second value of which an absolute value is greater than an absolute value of the first value, based on image information regarding the second toner image.

An image forming apparatus includes an image carrier, a developing device, a voltage applier, a current detector, a cleaning blade, and a control device. The control device acts as a measurer and an estimator. The measurer changes the DC bias to a first value and a second value, and acquires a first magnitude of the developing current corresponding to the first value, and a second magnitude of the developing current corresponding to the second value, from the current detector. The estimator calculates a current ratio between the first magnitude and the second magnitude, and estimates deterioration status of the cleaning blade, according to the value of the current ratio.