US 6,601,946 B1Granted

Image forming apparatus in which toner is removed by changing electric field between opposing electrode and control electrode

AssigneeSharp Kabushiki Kaisha

InventorsShirou Wakahara, Yukihito Nishio, Yasuhiro Takai, Hirokazu Fujita

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Abstract

An image forming apparatus capable of forming an image with a uniform density includes a toner carrier, an opposing electrode, a high voltage power source for supplying a voltage to generate potential difference between the toner carrier and the opposing electrode, a control electrode arranged between the toner carrier and the opposing electrode and having a plurality of electrodes, and a control power source unit for implementing a plurality of potential states to each of the electrodes of the control electrode. The control electrode includes an insulating substrate, the plurality of electrodes provided on the insulating substrate and having passage portions for the toner, and a dielectric layer formed on a side facing the opposing electrode such that attracting force Fc attracting the toner adhered on the surface of the control electrode facing the opposing electrode is made smaller than attracting force Fb attracting the toner adhered on the opposing electrode. The control power supply unit includes an image forming unit for forming an image on a surface of a recording medium conveyed on the opposing electrode by applying prescribed potentials to respective ones of the plurality of electrodes and an electric field applying unit for applying an electric field of which electric field direction changes between the opposing electrode and the control electrode and which ensures that an electric force FE received by the toner adhered on the control electrode is greater than the attracting force Fc and that the force FE is smaller than the attracting force Fb.

Claims9

Dependent claims

An image forming apparatus, comprising:

carrier means for carrying a developer;
an opposing electrode arranged opposing to said carrier means;
power supply means for supplying a voltage to generate a potential difference between said carrier means and said opposing electrode;
a control electrode including a plurality of electrodes, arranged between said carrier means and said opposing electrode;
and
control means for implementing a plurality of potential states to each of the electrodes of said control electrode;
wherein
said control electrode includes
an insulating substrate,
a plurality of said electrodes provided on said insulating substrate and each having a passage portion for said developer, and
a dielectric layer formed on a side facing said opposing electrode to ensure that an attracting force Fc attracting said developer adhered on that side of said control electrode which faces said opposing electrode is smaller than an attracting force Fb attracting said developer adhered on said opposing electrode;
and
said control means includes
image forming means for applying a prescribed potential to each of said plurality of electrodes, controlling passage of said developer through said passage portion, and for forming an image on a surface of a recording medium conveyed on said opposing electrode, and
electric field applying means for applying an electric field of which electric field direction changes between said opposing electrode and said control electrode, and which ensures that an electric force FE received by said developer adhered on said control electrode is greater than said attracting force Fc and that said electric force FE is smaller than said attracting force Fb.

12 more elements

Dependencies are inferred from the claim text.