Abstract: A developing roller configured to carry developer and extending in an axial direction includes: a hollow cylindrical rubber portion; and a shaft. The hollow cylindrical rubber portion has axial end faces. The shaft extends through the hollow cylindrical rubber portion and has a shaft portion positioned inward of the axial end faces of the hollow cylindrical rubber portion in the axial direction. The shaft portion has an axially middle portion and axial end portions positioned outward of the axially middle portion in the axial direction. The axially middle portion has an outer diameter smaller than that of each of the axial end portions.

Abstract: There is provided an image forming apparatus including: a forming section having an image holding member and an developing portion, and configured to apply a developing bias voltage to the developing portion to develop an electrostatic latent image on the image holding member; a sensor configured to detect a mark formed by the forming section; a storage; and a controller configured to perform: forming first and second marks, obtaining the densities of the first and second marks, obtaining a slope, and determining a target bias voltage value, and storing the target bias voltage value in the storage.

Abstract: In a developing device, a developing roller has an outer peripheral surface movable in a moving direction upon rotation of the developing roller to transfer developing agent to a developing region having a width in an axial direction of the developing roller. A thickness regulation blade includes a rubber portion. The rubber portion provides a contact region in contact with the outer peripheral surface to provide a nip region relative to the developing roller. The contact region includes a first region; and a second region. The first region and the second region each extends in the axial direction by a length at least equal to or greater than the width of the developing region. The first region has a first surface roughness. The second region is positioned downstream of the first region in the moving direction and has a second surface roughness finer than the first surface roughness.

Abstract: A developing roller configured to carry developer and extending in an axial direction includes: a first rotation shaft; a second rotation shaft; a rubber body portion; a first cylindrical rubber portion; and a second cylindrical rubber portion. The body portion has a first side and a second side opposite to the first side in the axial direction. The first cylindrical rubber portion is disposed on the first side. The first rotation shaft is configured to be fitted with the first cylindrical rubber portion. The second cylindrical rubber portion is disposed on the second side. The second rotation shaft is configured to be fitted with the second cylindrical rubber portion. The rubber body portion is configured to be deformable more than the first cylindrical rubber portion and the second cylindrical rubber portion.

Abstract: In a developing device, a developing roller has an outer peripheral surface movable in a moving direction upon rotation of the developing roller to transfer developing agent to a developing region having a width in an axial direction of the developing roller. A thickness regulation blade includes a rubber portion. The rubber portion provides a contact region in contact with the outer peripheral surface to provide a nip region relative to the developing roller. The contact region includes a first region; and a second region. The first region and the second region each extends in the axial direction by a length at least equal to or greater than the width of the developing region. The first region has a first surface roughness. The second region is positioned downstream of the first region in the moving direction and has a second surface roughness finer than the first surface roughness.

Abstract: There is provided an image forming apparatus including: a forming section having an image holding member and an developing portion, and configured to apply a developing bias voltage to the developing portion to develop an electrostatic latent image on the image holding member; a sensor configured to detect a mark formed by the forming section; a storage; and a controller configured to perform: forming first and second marks, obtaining the densities of the first and second marks, obtaining a slope, and determining a target bias voltage value, and storing the target bias voltage value in the storage.

Abstract: A developing device includes: a casing; a developing roller rotatably supported to the casing; a resiliently deformable blade supported to the casing; a regulation portion; and a covering portion. The developing roller is rotatable in a rotational direction and carries a layer of developer thereon. The blade extends in an axial direction of the developing roller and has one axial end portion formed with a through-hole, the blade having a first surface facing the developing roller and a second surface opposite to the first surface. The regulation portion is configured to be in contact with the developing roller to regulate a thickness of the layer of the developer carried on the developing roller. The covering portion is provided on the second surface and positioned to cover the through-hole.

Abstract: A developing device includes: a casing; a developing roller rotatably supported to the casing; a resiliently deformable blade supported to the casing and extending in an axial direction of the developing roller; and a regulation portion. The developing roller is rotatable in a rotational direction and to carry a layer of developer thereon. The blade has a first surface facing the developing roller. The regulation portion is configured to be in contact with the developing roller to regulate a thickness of the layer of the developer. The blade is formed with a through-hole to allow a material of the regulation portion to pass therethrough to form the regulation portion, the through-hole being exclusively formed in a central area in the axial direction assuming that the blade were divided into three areas each having an identical length in the axial direction with each other.

Abstract: A developing roller configured to carry developer and extending in an axial direction includes: a hollow cylindrical rubber portion; and a shaft. The hollow cylindrical rubber portion has axial end faces. The shaft extends through the hollow cylindrical rubber portion and has a shaft portion positioned inward of the axial end faces of the hollow cylindrical rubber portion in the axial direction. The shaft portion has an axially middle portion and axial end portions positioned outward of the axially middle portion in the axial direction. The axially middle portion has an outer diameter smaller than that of each of the axial end portions.

Abstract: A developing roller configured to carry developer and extending in an axial direction includes: a first rotation shaft; a second rotation shaft; a rubber body portion; a first cylindrical rubber portion; and a second cylindrical rubber portion. The body portion has a first side and a second side opposite to the first side in the axial direction. The first cylindrical rubber portion is disposed on the first side. The first rotation shaft is configured to be fitted with the first cylindrical rubber portion. The second cylindrical rubber portion is disposed on the second side. The second rotation shaft is configured to be fitted with the second cylindrical rubber portion. The rubber body portion is configured to be deformable more than the first cylindrical rubber portion and the second cylindrical rubber portion.

Abstract: A developing device includes: a casing; a developing roller rotatably supported to the casing; a resiliently deformable blade supported to the casing; a regulation portion; and a covering portion. The developing roller is rotatable in a rotational direction and carries a layer of developer thereon. The blade extends in an axial direction of the developing roller and has one axial end portion formed with a through-hole, the blade having a first surface facing the developing roller and a second surface opposite to the first surface. The regulation portion is configured to be in contact with the developing roller to regulate a thickness of the layer of the developer carried on the developing roller. The covering portion is provided on the second surface and positioned to cover the through-hole.

Abstract: A developing device includes: a casing; a developing roller rotatably supported to the casing; a resiliently deformable blade supported to the casing and extending in an axial direction of the developing roller; and a regulation portion. The developing roller is rotatable in a rotational direction and to carry a layer of developer thereon. The blade has a first surface facing the developing roller. The regulation portion is configured to be in contact with the developing roller to regulate a thickness of the layer of the developer. The blade is formed with a through-hole to allow a material of the regulation portion to pass therethrough to form the regulation portion, the through-hole being exclusively formed in a central area in the axial direction assuming that the blade were divided into three areas each having an identical length in the axial direction with each other.

Abstract: An image forming apparatus includes: photosensitive members; an endless belt facing the photosensitive members; developing rollers respectively supplying, to the photosensitive members, developer of different colors which is charged to a first polarity; cleaning rollers adjacent to the photosensitive members; a separating mechanism separating the developing roller from the photosensitive member in a single color printing. If in a multi color printing, a control unit applies a cleaning bias whose polarity is a second polarity opposite to the first polarity and which holds a first electric potential to each cleaning roller. If in the single color printing, the control unit executes a bias reduction control in which a cleaning bias applied to the cleaning roller not used in the single color printing is given the second polarity and is made to hold a second electric potential whose absolute value is smaller than that of the first electric potential.

Abstract: An image forming apparatus includes: photosensitive members; an endless belt facing the photosensitive members; developing rollers respectively supplying, to the photosensitive members, developer of different colors which is charged to a first polarity; cleaning rollers adjacent to the photosensitive members; a separating mechanism separating the developing roller from the photosensitive member in a single color printing. If in a multi color printing, a control unit applies a cleaning bias whose polarity is a second polarity opposite to the first polarity and which holds a first electric potential to each cleaning roller. If in the single color printing, the control unit executes a bias reduction control in which a cleaning bias applied to the cleaning roller not used in the single color printing is given the second polarity and is made to hold a second electric potential whose absolute value is smaller than that of the first electric potential.