An image forming apparatus includes a rotatable photosensitive member (drum), a first corona charger, a second corona charger, an image forming portion, a voltage applying portion, a surface potential detecting portion, a controller. The controller determines a condition of voltages applied to the first and second corona chargers during image formation, by setting a first voltage condition for the first corona charger so that the surface potential of the drum is a second potential lower in absolute value than the first potential in a state in which the first corona charger operates, and the second corona charger does not operates, and then by setting a second voltage condition for the second corona charger so that the surface potential of the drum is the first potential in a state in which the first corona charger operates under the first voltage condition, and the second corona charger operates.

In an image forming apparatus, a charging process of a photosensitive member is performed by forming a combined surface potential Vd(U+L) by superimposing, on a first charge potential Vd(U) formed on a surface of the photosensitive member by a first corona charger, a second charge potential Vd(L) provided by a second corona charger. The apparatus includes a controller for executing an adjusting operation in which a superimposition start voltage Vg(L)A, which is the second voltage Vg(L) at which formation of the combined surface potential Vd(U+L) is started, is acquired by changing the second voltage Vg(L) applied to a grid electrode of the second corona charger in a state that the first charge potential Vd(U) is formed on the surface of the photosensitive member and in which setting of the second voltage Vg(L) during the charging process is adjusted on the basis of the superimposition start voltage Vg(L).

Disclosed is an image forming apparatus wherein a controller performs a first adjusting operation and thereafter the controller performs a second adjusting operation. In the first adjusting operation, a voltage applied to a first grid electrode by a first voltage applying portion is set so that a surface potential of an image bearing member charged by a first corona charger becomes a first target value. In the second adjusting operation, a voltage applied to a second grid electrode by a second voltage applying portion is set so that a surface potential of the image bearing member charged by the first corona charger and a second corona charger becomes a second target value whose absolute value is larger than the first target value.

An image forming apparatus includes a photosensitive member, a corona charger including a discharging electrode and a grid electrode having a surface layer containing carbon atoms as a main component and configured to electrically charge the photosensitive member under application of a voltage to the discharging electrode and the grid electrode, and an output portion configured to output information on a lifetime of the grid electrode. The output portion outputs the information on the basis of an index value of an amount of use of the grid electrode correlating with a product of a value of a grid current flowing through the grid electrode and a time of flowing of the grid current through the grid electrode.

An image forming apparatus 100 in which a charging process of a photosensitive member 1 is performed by forming a combined surface potential Vd(U+L) by superimposing, on a first charge potential Vd(U) formed on a surface of the photosensitive member 1 by a first corona charger 31, a second charge potential Vd(L) provided by the second corona charger 32 has a constitution including a control means 200 for executing an adjusting operation in which a superimposition start voltage Vg(L)A which is the second voltage Vg(L) at which formation of the combined surface potential Vd(U+L) is started is acquired by changing the second voltage Vg(L) applied to a grid electrode of the second corona charger in a state that the first charge potential Vd(U) is formed on the surface of said photosensitive member 1 and in which setting of the second voltage Vg(L) during the charging process is adjusted on the basis of the superimposition start voltage Vg(L).

An image forming apparatus includes a photosensitive member, a corona charger including a discharging electrode and a grid electrode having a surface layer containing a carbon atom as a main component and configured to electrically charge the photosensitive member under application of a voltage to the discharging electrode and the grid electrode, and an output portion configured to output information on a lifetime of the grid electrode. The output portion outputs the information on the basis of an index value of an amount of use of the grid electrode correlating with a product of a value of a grid current flowing through the grid electrode and a time of flowing of the grid current through the grid electrode.

A resin particle contains a resin B containing a component derived from at least one of polyethylene terephthalate or polybutylene terephthalate and a biomass-derived resin C containing a linear aliphatic alcohol with 2 to 4 carbon atoms and a linear aliphatic acid with 10 to 12 carbon atoms, wherein the resin particle has a core shell structure of a core resin and a shell resin, the core resin contains a crystalline resin, and the proportion of the sum of the resin B and the resin C to 100 percent by mass of the resin particle is 30 or greater percent by mass.

An image forming apparatus includes a controller that performs a first adjusting operation and thereafter performs a second adjusting operation. In the first adjusting operation, a voltage applied to a first grid electrode by a first voltage applying portion is set so that a surface potential of an image bearing member charged by a first corona charger becomes a first target value. In the second adjusting operation, a voltage applied to a second grid electrode by a second voltage applying portion is set so that a surface potential of the image bearing member charged by the first corona charger and a second corona charger becomes a second target value whose absolute value is greater than the first target value.

In an image forming mode, in which a first image forming portion forms a toner image on a first image bearing member and a second image forming portion does not form a toner image on a second image bearing member, thereby forming an image on a recording material, a first voltage lower than a minimum value of absolute values of a plurality of voltages applied to a plurality of grid electrodes of the first image forming portion and higher than an absolute value of a target potential of a surface of the second image bearing member in the image forming mode is applied to one of a plurality of grid electrodes of the second image forming portion, and no voltage is applied to the other grid electrodes except the grid electrode to which the first voltage is applied among the plurality of grid electrodes of the second image forming portion.

An electrophotographic roller comprising a substrate having a conductive outer surface and a resin layer on a side of the outer surface of the substrate, in which the volume resistivity of the outer surface of the electrophotographic roller is 1.010.sup.6 .Math.cm or higher, when a corona discharger having a grid part is relatively moved along the axial direction of the electrophotographic roller to charge the electrophotographic roller, and the potentials of the outer surface after 0.06 seconds from passage of the grid part are measured, a maximum value of the potentials is lower than 20.0 V, the ionization potential of the outer surface of the electrophotographic roller is 5.0 to 5.6 eV, and an elastic modulus E1 in a region from the outer surface of the electrophotographic roller to a depth of 0.1 m is 200 MPa or higher.