US 2005/0031384 A1 · Image forming apparatus for recording on two sides in a single pass

Abstract

An image forming apparatus for recording on two sides in a single pass, with which the transfer of a toner image onto one side of a recording medium and the transfer of a toner image onto the other side can both be performed under optimal conditions, which results in an increase in image quality. Contact-type transfer rollers are used as secondary and tertiary transfer means, so unlike with a transfer charger (a non-contact type of transfer means), there is no discharge product. A toner image that has been once transferred from an image support onto a recording medium is prevented from being retransferred back onto the image support, and a toner image that has been transferred onto the recording medium by the action of a first transfer member is prevented from being retransferred to the image support when a toner image is transferred onto the recording medium by the action of a second transfer member.

Claims63

Dependent claims

A transfer method, comprising the steps of:

moving a first image support for supporting a toner image and a second image support for supporting a toner image in the same direction and at the same speed within a contact region in which the image support sides of the two image supports come into contact;
conveying a recording medium sandwiched between the two image supports within the contact region;
using a first transfer member disposed upstream in the movement direction of the image supports within the contact region to transfer a toner image supported on one of the image supports to one side of the recording medium conveyed within the contact region;
and
using a second transfer member disposed downstream in the movement direction of the image supports within the contact region to transfer a toner image supported on the other image support to the other side of the recording medium conveyed within the contact region.

2 more elements

An image forming apparatus, comprising:

a first image support that moves while supporting a toner image on an image support side;
a second image support that moves while supporting a toner image on an image support side;
a contact region in which the image support side of the first image support and the image support side of the second image support come into contact and a recording medium having toner images transferred onto both sides thereof is conveyed in between these image support sides;
two electroconductive rollers disposed upstream and downstream in the movement direction of the first image support and in contact with the side of the first image support opposite the image support side within the contact region;
and
two electroconductive rollers disposed upstream and downstream in the movement direction of the second image support and in contact with the side of the second image support opposite the image support side within the contact region,
the two electroconductive rollers on the first image support side and the two electroconductive rollers on the second image support side sandwiching the first image support and the second image support and thereby forming an upstream nip and a downstream nip,
in the pair of electroconductive rollers forming the upstream nip and the pair of electroconductive rollers forming the downstream nip, one electroconductive roller in each pair serving as an application roller to which transfer current is applied, and the other electroconductive roller serving as a ground roller, and
the absolute value of the transfer current applied to the application roller located in the upstream nip being set to be equal to or greater than the absolute value of the transfer current applied to the application roller located in the downstream nip.

6 more elements

An image forming apparatus, comprising:

a first image support that moves while supporting a toner image on an image support side;
a second image support that moves while supporting a toner image on an image support side;
a contact region in which the image support side of the first image support and the image support side of the second image support come into contact and a recording medium having toner images transferred onto both sides thereof is conveyed in between these image support sides;
two electroconductive rollers disposed upstream and downstream in the movement direction of the first image support and in contact with the side of the first image support opposite the image support side within the contact region;
and
two electroconductive rollers disposed upstream and downstream in the movement direction of the second image support and in contact with the side of the second image support opposite the image support side within the contact region,
the two electroconductive rollers on the first image support side and the two electroconductive rollers on the second image support side sandwiching the first image support and the second image support and thereby forming an upstream nip and a downstream nip,
in the pair of electroconductive rollers forming the upstream nip and the pair of electroconductive rollers forming the downstream nip, one electroconductive roller in each pair serving as an application roller to which transfer current is applied, and the other electroconductive roller serving as a ground roller, and
the hardness of the pair of electroconductive rollers that form the upstream nip being set to be equal to or greater than the hardness of the pair of electroconductive rollers that form the downstream nip.

6 more elements

An image forming apparatus, comprising:

a first image support that moves while supporting a toner image on an image support side;
a second image support that moves while supporting a toner image on an image support side;
a contact region in which the image support side of the first image support and the image support side of the second image support come into contact and a recording medium having toner images transferred onto both sides thereof is conveyed in between these image support sides;
two electroconductive rollers disposed upstream and downstream in the movement direction of the first image support and in contact with the side of the first image support opposite the image support side within the contact region;
and
two electroconductive rollers disposed upstream and downstream in the movement direction of the second image support and in contact with the side of the second image support opposite the image support side within the contact region,
the two electroconductive rollers on the first image support side and the two electroconductive rollers on the second image support side sandwiching the first image support and the second image support and thereby forming an upstream nip and a downstream nip,
in the pair of electroconductive rollers forming the upstream nip and the pair of electroconductive rollers forming the downstream nip, one electroconductive roller in each pair serving as an application roller to which transfer current is applied, and the other electroconductive roller serving as a ground roller, and
the timing at which the transfer current is applied to the two upstream and downstream application rollers is either when or before the front end of the recording medium reaches the upstream nip.

6 more elements

An image forming apparatus, comprising:

a first image support that moves while supporting a toner image on an image support side;
a second image support that moves while supporting a toner image on an image support side;
a contact region in which the image support side of the first image support and the image support side of the second image support come into contact and a recording medium having toner images transferred onto both sides thereof is conveyed in between these image support sides;
two electroconductive rollers disposed upstream and downstream in the movement direction of the first image support and in contact with the side of the first image support opposite the image support side within the contact region;
and
two electroconductive rollers disposed upstream and downstream in the movement direction of the second image support and in contact with the side of the second image support opposite the image support side within the contact region,
the two electroconductive rollers on the first image support side and the two electroconductive rollers on the second image support side sandwiching the first image support and the second image support and thereby forming an upstream nip and a downstream nip,
in the pair of electroconductive rollers forming the upstream nip and the pair of electroconductive rollers forming the downstream nip, one electroconductive roller in each pair serving as an application roller to which transfer current is applied, and the other electroconductive roller serving as a ground roller, and
the timing at which application of the transfer current to the two upstream and downstream application rollers is stopped is after the rear end of the recording medium has passed through the downstream nip.

6 more elements

An image forming apparatus for recording images on both sides of a recording medium, comprising:

first and second image supports on the surfaces of which are formed toner images, the toner image formed on each of said first and second image supports being transferred to one side or the other of a recording medium;
and
first and second transfer members disposed along a contact component in contact with the first and second image supports,
said first transfer member being located further upstream in the movement direction of the first and second image supports than the second transfer member, the toner image formed on the surface of the first image support being transferred by the action of one of the first and second transfer members onto one side of a recording medium fed in between the first and second image supports in contact with each other, and the toner image formed on the surface of the second image support being transferred by the action of the other of the first and second transfer members onto the other side of the recording medium fed in between the first and second image supports in contact with each other, and
the toner image transfer conditions being set such that if we let E(U) be the transfer electric field formed by the first transfer member, q1 be the amount of toner charge per unit of volume of the toner image transferred by the action of the first transfer member, E(D) be the transfer electric field formed by the second transfer member, and q2 be the amount of toner charge per unit of volume of the toner image transferred by the action of the second transfer member, the absolute values of the forces at which the toner images are transferred onto the recording medium, which are expressed by F(U)=q1×E(U) and F(D)=q2×E(D), are such that F(U)≧F(D).

2 more elements

An image forming apparatus for recording images on both sides of a recording medium, comprising:

an image support;
and
first and second intermediate transfer members,
a visualized image temporarily transferred from the image support via the first intermediate transfer member onto the second intermediate transfer member being transferred from the second intermediate transfer member onto one side of a recording medium, and a visualized image transferred from the image support onto the first intermediate transfer member being transferred from the first intermediate transfer member onto the other side of the recording medium,
a first transfer roller for transferring the visualized image on the first intermediate transfer member onto one side of the recording medium or the second intermediate transfer member being disposed inside the first intermediate transfer member or second intermediate transfer member, and a second transfer roller for transferring the visualized image on the second intermediate transfer member onto the other side of the recording medium being disposed inside the first intermediate transfer member or second intermediate transfer member,
first and second opposing rollers being disposed sandwiching the first and second intermediate transfer members and in pressure contact facing the respective transfer rollers, and
an elastic layer with a thickness of 5 mm or less being provided on the top layer of each of the transfer rollers, the hardness of said transfer rollers being no more than 50 degrees as JIS hardness, and the hardness of said transfer rollers being lower than the hardness of the opposing rollers.

4 more elements

Dependencies are inferred from the claim text.

Image forming apparatus for recording on two sides in a single pass

Life of this patent

Image forming apparatus for recording on two sides in a single pass

Life of this patent

Abstract

Claims63