A charging device includes a charging roller and a cleaning roller that includes a core and a foamed elastic layer disposed on an outer circumferential surface of the core and that rotates in contact with a surface of the charging roller. The number of ends of a cell skeleton that protrude from a surface of the foamed elastic layer is 25 ends/mm.sup.2 or more and 50 ends/mm.sup.2 or less. The cleaning roller is disposed in contact with the charging roller such that the compression ratio of the foamed elastic layer is 30% or less. The compression ratio is represented by Equation (1):
compression ratio (%)=(r1/2+r2/2d)/t1100Equation (1):
where r1 is the outer diameter (mm) of the cleaning roller, r2 is the outer diameter (mm) of the charging roller, d is the interaxial distance (mm) between the charging roller and the cleaning roller, and t1 is the thickness (mm) of the foamed elastic layer of the cleaning roller.

A bearing component for rotatably receiving a rotating shaft on an end of a rotating unit includes a component body, an inner protrusion, and one or more outer protrusions. The component body has a recess into which the rotating shaft is rotatably inserted. The inner protrusion protrudes from a wall portion of the recess facing an end surface of the rotating shaft. The inner protrusion receives an axial load by the rotating shaft. The outer protrusions protrude from an outer surface of the component body opposite to the recess. The one or more outer protrusions are in contact with a holding unit. A contact portion between the outer protrusions and the holding unit is offset from a contact portion position between the inner protrusion and the end surface. The contact portion between at least one of the outer protrusions and the holding unit has a non-planar shape.

A cleaning device that cleans a surface of an image holding unit capable of holding an image formed using an image forming material includes: a cleaning tool that is movable along an intersecting direction intersecting with a moving direction of the image holding unit and cleans the surface of the image holding unit when placed in a contact position where the cleaning tool is in contact with the surface of the image holding unit; and a guiding unit that guides the cleaning tool so that the cleaning tool moves from a non-contact position where the cleaning tool is not in contact with the image holding unit to the contact position for cleaning the surface of the image holding unit, wherein when the image holding unit is moved, the cleaning tool placed in the contact position cleans the surface of the image holding unit.

A charging device includes a charging member and a cleaning member. The charging member electrically charges a surface of a charging target member and is rotatable while being in contact with the surface of the charging target member. The cleaning member is in contact with a surface of the charging member and removes a foreign object attached to the surface of the charging member. Surface free energy of the surface of the charging member is 5.00 dynes per centimeter or more. A dynamic friction coefficient of the surface of the charging member and a surface of the cleaning member falls within a range from 0.48 to 0.88 both inclusive. The surface free energy and the dynamic friction coefficient satisfy a relation represented by the following expression (1).
E63+69(1) E is the surface free energy in dynes per centimeter, and is the dynamic friction coefficient.

A charging device includes: a charging member that charges an image holding member according to a contact charging method, and includes a conductive substrate and a surface layer provided on the conductive substrate; and a clean member that cleans the charging member while contacting the charging member, and includes a shaft and a foamed elastic layer provided on the shaft, wherein a ratio of a distance between irregularities in an axial direction of the surface layer in the charging member (Sm) to a width of a nodal section of a foam cell wall surface protruding from a surface of the foamed elastic layer in the clean member (W) satisfies 2.4Sm/W5.9.

A charging member includes a conductive substrate, an elastic layer disposed on the conductive substrate, and a surface layer disposed on the elastic layer. Regarding the surface of the surface layer, in the axial direction, the ratio of the mean spacing of profile irregularities Sm to the ten-point mean roughness Rz and the reduced peak height Spk respectively satisfy 15Sm/Rz35 and Spk5 m.

A charging device includes: a charging member that is rotatable and has a peripheral surface to be in contact with a charging target and to which a voltage is to be applied for charging the charging target; a removing member that includes a core and a removing material spirally wound one to less than two times around the core and rotates and comes into contact with the charging member to remove an unnecessary material from the peripheral surface of the charging member; and a detecting unit that detects a current flowing between the charging member and the removing member.

A charging device includes: a charging member that charges an image holding member according to a contact charging method, and includes a conductive substrate and a surface layer provided on the conductive substrate; and a clean member that cleans the charging member while contacting the charging member, and includes a shaft and a foamed elastic layer provided on the shaft, wherein a ratio of a distance between irregularities in an axial direction of the surface layer in the charging member (Sm) to a width of a nodal section of a foam cell wall surface protruding from a surface of the foamed elastic layer in the clean member (W) satisfies 2.4Sm/W5.9.

A charging member which is driven so that the surface of the charging member has a speed difference from the surface of an image bearing member. In a cleaning operation for cleaning the charging member by transferring toner adhering to the surface of the charging member from the charging member to the image bearing member and collecting the transferred toner with a developing member, a first charging voltage forming a potential difference between the charging member and the image bearing member is applied to the charging member, and then a second charging voltage having the same polarity as that of the first charging voltage and an absolute value greater than that of the first charging voltage is applied. The potential difference is in a direction in which electrostatic force directed from the charging member to the image bearing member acts on the toner charged to normal polarity.

A charging device includes a charging member that includes a conductive elastic layer and a conductive surface layer disposed on an outer circumferential surface of the conductive elastic layer and a cleaning member that includes a support and a foamed elastic layer disposed on an outer circumferential surface of the support and having a higher surface free energy than the conductive surface layer of the charging member and that rotates in contact with the conductive surface layer of the charging member.