A power supply apparatus includes a transformer, an electrolytic capacitor provided in primary circuitry of the transformer, a board, and a heat sink having a protruding portion and a cover portion. The electrolytic capacitor includes an explosion-proof valve that opens to cause an electrolytic solution to be jetted from the electrolytic capacitor. The electrolytic capacitor is placed on the board so that a surface of the electrolytic capacitor opposite to a surface on which the explosion-proof valve is provided faces the board. The cover portion has a hole formed in the cover portion and, when the cover portion is viewed in a direction vertical to the surface of the electrolytic capacitor on which the explosion-proof valve is provided, at least the explosion-proof valve and the hole formed in the cover portion do not overlap each other and the cover portion encompasses the explosion-proof valve.

A control unit performs control to make a direction of an electric field generated in a first area of an image carrier forming a transfer portion during image forming operation, relative to a voltage applied to a brush member in a state where the first area passes through a contact portion, different from a direction of an electric field generated in a second area of the image carrier forming the contact portion, relative to the voltage applied to the brush member during a period when operation is shifted from first operation in which the image carrier is rotated at a first speed to second operation in which the image carrier is rotated at a second speed different from the first speed, during non-image forming operation different from the image forming operation.

A conveyance device includes a conveyance roller, a registration roller, a sensor, a mode setting part, a storage, a conveyance state determination part and a drive control part. The mode setting part sets the mode to either a plain paper mode or a tab paper mode. The storage stores threshold information corresponding to the mode. The conveyance state determination part determines, when the plain paper mode is set, whether the conveyance state of the recording medium is a skew conveyance state or a tab paper conveyance state, based on the detection result of the sensor and the plain paper mode threshold information. The conveyance state determination part determines, when the tab paper mode is set, whether the conveyance state of the recording medium is the skew conveyance state or the tab paper conveyance state, based on the detection result of the sensor and the tab paper mode threshold information.

In an image forming apparatus, a cleaning blade, disposed on a downstream side of a transfer roller in a rotation direction of an image carrier, removes toner remaining on the image carrier after transfer of a toner image to an intermediate transfer member. After completion of an image forming operation, a controller causes the transfer roller to separate from the intermediate transfer member, cause the developing device to form on the image carrier a toner band to be supplied to the cleaning blade, and cause rotation of the image carrier to stop such that at least a part of the toner band formed on the image carrier stops within a section from a first position facing the transfer roller to a second position facing the cleaning blade in the rotation direction.

In an image forming apparatus, a calibration controller controls an exposure device to form a toner patch image for calibration in a non-printable area outside a printable area in a main scanning direction, and executes at least one of density adjustment and gradation adjustment based on a density measurement value of the toner patch image. A toner refresh controller controls the exposure device to form a toner band for toner refresh in accordance with a coverage rate. Further, when the length of the toner band to be formed in the non-printable area exceeds a predetermined threshold value, the toner refresh controller forms at least a part of the toner band to be formed in the non-printable area in parallel with a subsequent page image.

An image forming apparatus includes a developing roller, a photoconductor drum, a density detector, a current detector, and a controller. The developing roller carries a toner. The photoconductor drum carries a toner patch. The density detector detects toner density of the toner patch. The current detector detects developing current flowing to the toner patch. The controller calculates an inclination of an approximate straight line approximating a relation between the toner density and the developing current. The developing roller develops three or more toner patches, different in toner density and different in developing current from one another, on the photoconductor drum. The controller calculates the inclination, using different mathematical expressions depending on whether three toner patches or four toner patches are provided.

A sheet cutting apparatus includes: a cutting unit that includes a plurality of cutting blades for cutting a sheet along a conveyance direction of the sheet, the plurality of cutting blades configured to be able to move to a cutting position and a retracted position; and a control unit. The plurality of cutting blades are provided at different positions in a widthwise direction that is perpendicular to the conveyance direction and a perpendicular direction perpendicular to a surface of the sheet. The control unit is configured to set a first cutting blade to the cutting position or the retracted position by changing a position in the perpendicular direction of the first cutting blade and set a second cutting blade to the cutting position or the retracted position by changing a position in the widthwise direction of the second cutting blade.

A toner supply device for supplying toner to a developing device includes a toner container containing toner to be supplied to the developing device and a remaining amount sensor for detecting the remaining amount of toner in the toner container. The toner container includes a cylindrical rotating container having a spiral conveying rib formed on the inner peripheral surface thereof and a paddle provided so as to be slidable on the inner peripheral surface of the rotating container. The remaining amount sensor detects the remaining amount of toner on the upstream side on or before the contact position of the paddle in the toner conveying direction.

A detection device includes: a transport unit that stops transportation of a medium on which a first image is formed, the transport unit restarting the transportation of the medium toward an image forming unit after the medium has been in a stopped state, the image forming unit forming a second image on the medium; and a detection unit that detects an edge portion of the medium while the medium is in the stopped state.

A gear unit for transmitting a rotational force to a rotatable member carrying developer and to which a coupling member is mountable. The gear unit includes a hole portion which opens outwardly in a direction along a rotational axis of the cylinder gear and which has an opening capable of accommodating the spherical portion, a groove portion which continues from the hole portion and which is capable of accommodating the projected portion, and a limiting portion for limiting inward movement of the spherical portion in the direction along the rotational axis of the gear. A closing member is provided for partially covering the opening of the hole portion and mounted to the gear to limit outward movement of the spherical portion in the direction along the rotational axis of the gear. The closing member is constituted by a plurality of independent pieces.