Patent ID: 6453142
Filing Date: 2002-09-17
Classification: G03G

Abstract:
A developing apparatus for developing an electrostatic latent image into a toner image, comprising:a developing roller including a conductive substrate, and a resistance layer and a dielectric layer which are formed on a surface of the conductive substrate, the developing apparatus developing at a developing portion where the developing roller contacts a photosensitive body including a conductive substrate and a photosensitive layer formed on a surface of the conductive substrate, by a predetermined nip width, an electrostatic latent image formed on the photosensitive layer into a toner image by layered toner carried on a peripheral surface of the developing roller, wherein a relation expressed by the following Equation (1) is established: Cc&gE;&rgr;tÂ·dtÂ·k/Vvâ€ƒâ€ƒ(1) wherein Vv=âˆ’(Vbp+Vpr)âˆ’Vco+VtÂ·k Cc=1/{1/Cp+2/Ct+rr/k+1/(Cr3Â·k)}k=vr/vp rr=&rgr;rÂ·d2Cp=âˆˆp/dp Ct=2Â·âˆˆt/dt Cr1=âˆˆ1/d1Cr2=âˆˆ2/d2C1=1/{1/Cp+2/Ct+1/(Cr1Â·k)}â€ƒC2=kÂ·Cr2Ex=(W/vp)/{rrÂ·(C1+C2)}Cr3=Cr1Â·{1âˆ’C1/(C1+C2)}Â·exp(âˆ’Ex) &rgr;t=(qpm+qr)Â·m/dt Vco=âˆ’qpmÂ·m/Cr1Vpr=âˆ’qrÂ·mÂ·k/Cp Vt=&rgr;tÂ·dt/Ct, â€ƒwherein dp (m) and âˆˆp (F/m) are thickness and dielectric constant of the photosensitive layer of the photosensitive body, respectively, dt (m), âˆˆt (F/m) and m (kg/m2) are thickness, dielectric constant and amount of adhesion per unit area of a toner layer formed on the photosensitive body, respectively, d1 (m) and âˆˆ1 (F/m) are thickness and dielectric constant of the dielectric layer of the developing roller, respectively, d2 (m), âˆˆ2 (F/m) and &rgr;r (&OHgr;Â·m) are thickness, dielectric constant, and specific constant of the resistance layer of the developing roller, respectively, Vbp (=Vsâˆ’Vb) (V) is potential difference between photosensitive body surface potential Vs (V) in a saturation image density region on the photosensitive body before entering into the developing portion and developing bias Vb (V), qpm (C/kg) is specific charge of toner before entering into the developing portion, Vco. (V) is voltage of the dielectric layer of the developing roller before entering into the developing portion, qr (C/kg) is amount of change in specific charge of the toner caused by passing through the developing portion, W (m) is nip width of the developing portion, vp (m/s) is peripheral speed of the photosensitive body, and vr (m/s) is peripheral speed of the developing roller.