US 2011/0255892 A1Published application

Image forming apparatus capable of minimizing reverse toner transfer

AssigneeRicoh Company, Ltd.

InventorShinji Aoki

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Abstract

In an image forming apparatus, a determiner determines a target amount of transfer current based on first and second algorithms each representing a relation between an image area rate of a latent image bearer in the vicinity of an exit of a transfer nip and a target amount of transfer current to be provided to a nip creating member. The first algorithm is utilized in a second transfer step when the image area rate falls within a typical range from the lower limit (a %) to the upper limit (b %). The first algorithm decreases the target amount as the image area rate increases within that range.

Claims8

Dependent claims

An image forming apparatus comprising:

a latent image bearer to bear a latent image;
a developing device to develop a latent image on the latent image bearer with toner;
a nip creating member contacting the latent image bearer to create a transfer nip therebetween;
a transfer current providing device to provide a prescribed target amount of transfer current to the nip creating member, said transfer current transferring the toner image from the latent image bearer onto one of the nip creating member and a recording sheet conveyed by the nip creating member,
an image area rate detecting device to detect an image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip;
a determiner to determine a prescribed target amount of transfer current to be provided to the nip creating member based on one of at least two first and second algorithms, each of said at least two first and second algorithms representing a relation between the image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip and a prescribed target amount of transfer current;
and
a process controller to execute a first transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet for the first time, and a second transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet already bearing a prescribed toner image thereon,
wherein said first algorithm is utilized in the second transfer step when the image area rate falls within a typical range from the lower limit (a %) to the upper limit (b %), said first algorithm decreasing the prescribed target amount as the image area rate increases within the typical range, and
wherein said second algorithm is utilized in the second transfer step when the image area rate is less than the lower limit (a %) of the typical range, said second algorithm decreasing the target amount to be less than that obtained by the first algorithm when the image area rates is the lower limit (a %), and wherein said lower limit (a %) is more than zero and said higher limit (b %) is greater than the lower limit (a %).

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Dependencies are inferred from the claim text.

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Abstract

An image forming apparatus comprising:

a latent image bearer to bear a latent image;
a developing device to develop a latent image on the latent image bearer with toner;
a nip creating member contacting the latent image bearer to create a transfer nip therebetween;
a transfer current providing device to provide a prescribed target amount of transfer current to the nip creating member, said transfer current transferring the toner image from the latent image bearer onto one of the nip creating member and a recording sheet conveyed by the nip creating member,
an image area rate detecting device to detect an image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip;
a determiner to determine a prescribed target amount of transfer current to be provided to the nip creating member based on one of at least two first and second algorithms, each of said at least two first and second algorithms representing a relation between the image area rate of the latent image borne on the image bearer in the vicinity of an exit of the transfer nip and a prescribed target amount of transfer current;
and
a process controller to execute a first transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet for the first time, and a second transfer step, in which the toner image on the latent image bearer is transferred onto one of the nip creating member and the recording sheet already bearing a prescribed toner image thereon,
wherein said first algorithm is utilized in the second transfer step when the image area rate falls within a typical range from the lower limit (a %) to the upper limit (b %), said first algorithm decreasing the prescribed target amount as the image area rate increases within the typical range, and
wherein said second algorithm is utilized in the second transfer step when the image area rate is less than the lower limit (a %) of the typical range, said second algorithm decreasing the target amount to be less than that obtained by the first algorithm when the image area rates is the lower limit (a %), and wherein said lower limit (a %) is more than zero and said higher limit (b %) is greater than the lower limit (a %).

7 more elements