Image forming device, charging device and cleaning device

A charging device comprising:

• a charging roller that abuts an image carrier on which a toner image is to be formed, and charges the image carrier, the charging roller including a shaft that is rotatably supported;
• and
• a cleaning roller that abuts and cleans the charging roller, the cleaning roller including a shaft that is rotatably supported, and a porous elastic layer being provided around the shaft
• wherein the image forming device satisfies the relation
• T×β/100>(R1+R2)−L>B>0
• where L [mm] is a separation distance of axial centers of both end portions of the shaft of the cleaning roller and the shaft of the charging roller, R1[mm] is a radius of the charging roller, T [mm] is a thickness of the porous elastic layer, R2[mm] is a radius of the cleaning roller, B [mm] is a flexure amount of an axial direction central portion of the shaft of the cleaning roller, and α [%] is a maximum allowable compression rate in accordance with a stress-flexure curve when compressing the porous elastic layer with an applied stress which is 200% of an average stress P [kPa], the average stress P [kPa] being an average value of stresses at compression rates of the porous elastic layer of 10% to 40%.

A cleaning device for cleaning a rotatable body having a shaft that is rotatably supported, the cleaning device comprising:

• a cleaning roller that abuts and cleans the rotatable body, the cleaning roller including a shaft which is rotatably supported, and a porous elastic layer being provided around the shaft,
• wherein the cleaning device satisfies the relation
• T×α/100>(R1+R2)−L>B>0
• where L [mm] is a separation distance of axial centers of both end portions of the shaft of the cleaning roller and the shaft of the rotatable body, R1 [mm] is a radius of the rotatable body, T [mm] is a thickness of the porous elastic layer, R2[mm] is a radius of the cleaning roller, B [mm] is a flexure amount of an axial direction central portion of the shaft of the cleaning roller, and α [%] is a maximum allowable compression rate in accordance with a stress-flexure curve when compressing the porous elastic layer with an applied stress which is 200% of an average stress P [kPa], the average stress P [kPa] being an average value of stresses at compression rates of the porous elastic layer of 10% to 40%.