Image forming apparatus
AssigneeMinolta Co., Ltd.
InventorMakoto Takase
Life of this patent
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Abstract
An object of the present invention is to provide an image forming apparatus which prevents transfer memory from occurring and achieves a desired potential of an image carrier (photosensitive body) when forming an image in next cycle, thereby to obtain a high-quality output image. In order to achieve the object described above, the image forming apparatus of the invention has a belt grounding device 21 which makes contact with a transfer belt 5 and is capable of switching between grounded state and ungrounded state according to the size of copy paper P. With this configuration, because only a portion not covered by the copy paper P can be grounded according the size of the copy paper P, excessive current can be prevented from flowing into a photosensitive drum 1 at this portion, thereby preventing transfer memory from occurring.
Claims23
An image forming apparatus comprising:
- an image carrier which holds a toner image;
- a transfer material carrier which carries a transfer material to a transferring position;
- an image transfer electric field forming means which forms, at said transferring position, an image transfer electric field for transferring the toner image held on said imager carrier onto said transfer material;
- an electrically conductive member which makes contact with said transfer material carrier and is capable of switching between grounded state and ungrounded state, said electrically conductive member comprising a plurality of pieces divided in the direction of width of said transfer material carrier;
- and
- a switching device which switches between grounded state and ungrounded state of the electrically conductive member.
A transfer device for transferring a toner image held by an image carrier onto a transfer material comprising:
- an image transfer electric field forming device which forms an electric field for attracting the toner image held by the image carrier onto the transfer material;
- an electrically conductive member which is in contact with said transfer material carrier and is capable of switching between grounded state and ungrounded state, said electrically conductive member comprising a plurality of pieces divided in the direction of width of the transfer material carrier;
- and
- a switching device for switching the electrically conductive member between grounded state and ungrounded state.
An image forming apparatus comprising:
- an image carrier which holds a toner image;
- a transfer material carrier which carries a transfer material to a transferring position;
- an image transfer electric field forming device which forms, at said transferring position, an image transfer electric field for transferring the toner image held on said imager carrier onto said transfer material;
- an electrically conductive member which makes contact with said transfer material carrier and is capable of switching between grounded state and ungrounded state, the electrically conductive member comprising a plurality of pieces divided in the direction of width of the transfer material carrier;
- a detecting device for detecting the size of the transfer material;
- and
- a switching device which switches the electrically conductive member between grounded state and ungrounded state.
An image forming method comprising:
- a step of holding a toner image on an image carrier;
- a step of carrying a transfer material to a transferring position;
- a step of forming an image transfer electric field at said transferring position for transferring the toner image held on said image carrier onto said transfer material;
- a step for detecting the size of the transfer material;
- and
- a step of switching the electrically conductive member between grounded state and ungrounded state according to the result of detection by the detecting device,
- wherein the electrically conductive member comprises a plurality of pieces divided in the direction of width of the transfer material carrier.
Dependencies are inferred from the claim text.