Developing unit and image forming device
A developing unit includes a developing roller which rotates about a rotational axis to supply toner to a photoreceptor, and a magnetic roller which forms a magnetic brush with a two-component developing agent having carrier and the toner and thereby forms a toner layer on the developing roller, the developing roller including: a cylindrical core portion which includes an electric conductor; a first resistive layer which covers a cylindrical surface of the core portion; a second resistive layer which covers the first resistive layer, and has electric-resistivity lower than that of the first resistive layer; and a current leakage control member which prevents leakage of electric current from the core portion toward the second resistive layer through an end of the developing roller along a direction of the rotational axis.
1. A developing unit comprising a developing roller which rotates about a rotational axis to supply toner to a photoreceptor, and a magnetic roller which forms a magnetic brush with a two-component developing agent having carrier and the toner and thereby forms a toner layer on the developing roller,
the developing roller including:
a cylindrical core portion which includes an electric conductor;
a first resistive layer which covers a cylindrical surface of the core portion;
a second resistive layer which covers the first resistive layer, and has electric-resistivity lower than that of the first resistive layer; and
a current leakage control member which prevents leakage of electric current from the core portion toward the second resistive layer through an end of the developing roller along a direction of the rotational axis.
2. A developing unit according to claim 1 ,
wherein the current leakage control member is an end of the second resistive layer which is arranged so as to maintain a first distance along the direction of the rotational axis from an end of the first resistive layer.
3. A developing unit according to claim 2 ,
wherein the first distance is longer than a second distance between the surface of the second resistive layer and the photoreceptor.
4. A developing unit according to claim 1 ,
wherein the current leakage control member is a current leakage control layer provided between an end of the first resistive layer and an end of the second resistive layer along the direction of the rotational axis.
5. A developing unit according to claim 1 ,
wherein the current leakage control member is a current leakage control layer provided at an end of the core portion along the direction of the rotational axis.
6. A developing unit according to claim 1 ,
wherein the first resistive layer contains alumite and the second resistive layer contains silicone-modified urethane.
7. An image forming device, comprising the developing unit according to claim 1 , wherein the developing unit develops an electrostatic latent image formed on a photoreceptor with toner supplied to the photoreceptor.