A developing device includes a developing container, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including a second magnetic pole and a third magnetic pole, a regulating member provided opposed to the third magnetic pole. During non-image formation, an operation in a mode in which the supplying roller is rotated in a direction opposite to a rotational direction of the supplying roller during image formation is executable. With respect to the rotational direction of the supplying roller during the image formation, a position where a magnet flux density of the third magnetic pole in a tangential direction to an outer peripheral surface of the supplying roller is zero is positioned downstream of an upstream end of the regulating member and upstream of the second magnetic pole.

An image-forming apparatus includes first and second photosensitive drums, first and second image-forming portion including first and second development rollers configured to bear developers composed of first and second toner particles and organosilicon protrusions formed on surfaces of the first and second toner particles, an intermediate transfer member to which a developer image is to be transferred in first and second contact portions in contact with the first and second photosensitive drums, and a transfer member configured to transfer the developer image to a recording material in a transfer portion. The first contact portion is formed downstream of the transfer portion and upstream of the second contact portion in a movement direction of the surface of the intermediate transfer member. A protrusion formed on the second developer has a lower height than a protrusion formed on the first developer.

A cartridge including: a first unit including an image bearing member and a first portion, and configured to take a removal posture when the cartridge is to be removed from a main body; a second unit including a developer bearing member and a second portion, the second unit being movable between a first position where the developer bearing member is in contact with the image bearing member and a second position where the developer bearing member is separated from the image bearing member and where the second portion is in contact with the first portion, wherein when the first unit takes the removal posture, the second unit is located at the second position, and when the second unit is located at the second position, movement of the second unit in a direction, in which the developer bearing member is separated from the image bearing member, is restricted.

A conductive roller includes a support member, an elastic layer disposed on an outer peripheral surface of the support member, and a surface layer disposed on an outer peripheral surface of the elastic layer. The elastic layer includes a cylindrical elastic foam and a conductive covering layer covering an exposed surface of the elastic foam and has a volume resistance value of 10.sup.5Ω or less at an applied voltage of 10 V. The elastic foam has a conductive particle content of 1% by mass or less based on the total mass of the elastic foam.

A developing device includes a developer container configured to contain a developer, a developing carrying member configured to carry and feed the developer to a developing position, and a regulating member configured to regulate an amount of the developer carried by the developer carrying member, wherein the developer carrying member includes a magnet provided non-rotatably and stationarily inside the developer carrying member, and wherein the developer carrying member is provided with information regarding magnetic flux density of the magnet.

A developing roll has a metal core, an elastic layer, and a surface layer, A value X is 65.6 N/mm.sup.3 or more and a value Y is 229 μm or more. The value X is P.sub.1/(D.sub.2×A) P.sub.2/(D.sub.2× A). P.sub.1 is the load to displace the roll by 100 μm when a metal probe is pressed against the roll. D.sub.1 is the displacement of the roll caused by the probe under the load P.sub.1. A is the area of the probe. P.sub.2 is the load to displace a material roll by 100 μm when the probe is pressed against the material roll with the core and the elastic layer and without the surface layer. D.sub.2 is the displacement of the material roll caused by the probe under the load P.sub.2. The value Y is the displacement of the developing roll when the probe pierces the surface layer.

An image forming apparatus comprising an image bearing member, a developer bearing member, a drive unit for driving the image bearing member and the developer bearing member in varied peripheral speeds, a control unit, a developing voltage application unit, a supply member for supplying a developer to the developer bearing member, and, a supply member voltage application unit, wherein the control unit executes a first image forming mode in which a rotational peripheral speed ratio between surface movement speeds of the developer bearing member and the image bearing member is not more than 1 and a second image forming mode in which the rotational peripheral speed ratio is larger than 1, and, the control unit controls the drive unit so that a difference between developing voltage and supply voltage becomes larger in the second image forming mode than in the first image forming mode.

An image forming apparatus includes a development cartridge having a developing roller. The developing roller includes a roller body, and a shaft to pass through a central axis of the roller body. A coupling structure is disposed at an end part of the shaft, is movable from a first position to a second position, and includes a first coupling piece and a second coupling piece. Positions of the first coupling piece and the second coupling piece are maintained with respect to one another by a static frictional force between surfaces of the first coupling piece and the second coupling piece to hold the coupling structure in the first position. When a predetermined force overcomes the static frictional force, the first coupling piece and the second coupling piece disengage from one another to allow the coupling structure to move from the first position to the second position.

The present invention provides a process cartridge and an electronic imaging device. The process cartridge includes a cartridge body having an accommodating cavity; a developing roller rotatably installed in the accommodating cavity; a photosensitive drum rotatably installed in the cartridge body; a charging roller that is in contact with a peripheral surface of the photosensitive drum and is spaced from the developing roller; and a cleaning member that is located in the accommodating cavity and installed in the cartridge body, extends in a direction parallel to the charging roller, and is in contact with a peripheral surface of the charging roller. The developing roller is in contact with the peripheral surface of the photosensitive drum. The electronic imaging device includes a machine body, and the foregoing process cartridge is detachably installed thereon. The present invention can increase the utilization rate of toner and reduce abrasion of the photosensitive drum.

A power supply apparatus generates an output voltage. A boost circuit boosts a voltage supplied from a reference voltage source and generates a first power supply voltage. A processor controls switching the boost circuit on and off. A first transistor is connected to the first power supply voltage. A second transistor is connected to a collector of the first transistor. A resistance element is connected to a collector of the second transistor. A voltage source is connected to the resistance element and generates a second power supply voltage. A collector voltage, which is an output voltage, of the second transistor is controlled by controlling an amount of base current of the first transistor.