Image forming apparatus

Patent metadata

Field	Value
Publication number	US-10322893-B2
Application number	US-201715458318-A
Country	US
Kind code	B2
Filing date	Mar 14, 2017
Priority date	Mar 25, 2016
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

An image forming apparatus includes an image forming portion, an endless belt and a plurality of stretching rollers. The stretching rollers includes a tiltable steering roller, a sliding member, a first stretching roller having a smallest diameter, and a second stretching roller having a largest diameter of the diameters. With respect to rotational axis directions of the stretching rollers, lengths of contact portions of the stretching rollers with the belt are shorter than a width of the belt, the length of the contact portion of the first stretching roller with the belt is a first length, the length of the contact portion of the second stretching roller with the belt is a second length shorter than the first length, and end positions of the contact portions of the first and second stretching rollers with respect to the rotational axis direction are different from each other.

First claim

What is claimed is:

1. An image forming apparatus comprising:
an endless belt;
a primary transfer roller contacting an inner surface of said endless belt and configured to transfer a toner image onto said endless belt at a primary transfer portion;
a secondary transfer roller contacting an outer surface of said endless belt and configured to transfer the toner image from said endless belt onto a recording material at a secondary transfer portion;
a steering unit configured to adjust a position of said endless belt with respect to a widthwise direction of said endless belt, said steering unit including: (a) a steering roller (i) being rotatable about a first rotational axis, (ii) being tiltable about a steering axis crossing the first rotational axis, and (iii) having a first end and a second end with respect to the first rotational axis; (b) a first sliding member adjacent to said first end of said steering roller; and (c) a second sliding member adjacent to said second end of said steering roller, wherein said first and second sliding members are slidable with an inner surface of said endless belt;
a first stretching roller contacting the inner surface of said endless belt and configured to stretch said endless belt, said first stretching roller being located upstream of the primary transfer portion and downstream of a contact portion between said steering roller and said endless belt with respect to a rotational direction of said endless belt, said first stretching roller (i) being rotatable about a second rotational axis, (ii) having a first play with respect to the second rotational axis, and (iii) having a first outer diameter, a contact portion between said first stretching roller and said endless belt with respect to the widthwise direction of said endless belt being a first contact portion having a first contact length; and
a second stretching roller contacting the inner surface of said endless belt and configured to stretch said endless belt, said second stretching roller being upstream of the first contact portion and downstream of the primary transfer portion with respect to the rotational direction of said endless belt, said second stretching roller (i) being rotatable about a third rotational axis, (ii) having a second play with respect to the third rotational axis, and (iii) having a second outer diameter larger than the first outer diameter, a contact portion between said second stretching roller and said endless belt with respect to the widthwise direction of said endless belt being a second contact portion having a second contact length, which is smaller than the first contact length,
wherein, with respect to the widthwise direction of said endless belt, end portions of the first contact portion within the first play are outside end portions of the second contact portion within the second play.

2. An image forming apparatus according to claim 1 , further comprising a third stretching roller configured to stretch said endless belt, said third stretching roller forming the secondary transfer portion between itself and said secondary transfer roller with said endless belt therebetween, said third stretching roller (i) being rotatable about a fourth rotational axis, (ii) having a third play with respect to the fourth rotational axis, and (iii) having a third outer diameter, larger than the first outer diameter, a contact portion between the third stretching roller and said endless belt with respect to the widthwise direction of said endless belt being a third contact portion having a third contact length, which is smaller than the first contact length,
wherein, with respect to the widthwise direction of said endless belt, end portions of the third contact portion within the third play are outside end portions of the first contact portion within the first play, and
wherein, with respect to the widthwise direction of said endless belt, end portions of the third contact portion within the third play are outside end portions of the second contact portion within the second play.

3. An image forming apparatus according to claim 2 , wherein the second outer diameter and the third outer diameter are substantially equal to each other, and
wherein each of said second stretching roller and said third stretching roller has a winding angle of said endless belt, the one of said second stretching roller and said third stretching roller with a larger winding angle having a smaller contact width with said endless belt, with respect to the widthwise direction of said endless belt, than the other stretching roller.

4. An image forming apparatus according to claim 2 , wherein the one of said second stretching roller and said third stretching roller having a larger outer diameter has a smaller contact length with said endless belt, with respect to the widthwise direction of said endless belt, than the other stretching roller.

5. An image forming apparatus according to claim 1 , further comprising a plurality of stretching rollers including said first stretching roller and said second stretching roller,
wherein each stretching roller of the plurality of stretching rollers has (i) an outer diameter of Dn and (ii) a contact length of the respective stretching roller with said endless belt with respect to the widthwise direction of said endless belt of Ln, n being an integer indicating the n-th stretching roller,
wherein, as n increases, Ln increases and Dn decreases,
wherein each stretching roller of the plurality of stretching rollers has an n-th play with respect to a rotational axis direction of a rotation axis of the corresponding stretching roller, and
wherein each stretching roller of the plurality of stretching rollers is disposed so that end portions of said stretching rollers are nonoverlapping with each other within the respective amounts of play of said stretching rollers.

6. An image forming apparatus according to claim 1 , wherein said second stretching roller is upstream of the secondary transfer portion and downstream of the primary transfer portion with respect to the rotational direction of said endless belt.

7. An image forming apparatus according to claim 1 , wherein said second stretching roller is a driving roller configured to drive said endless belt.

8. An image forming apparatus according to claim 1 , wherein said second stretching roller forms the secondary transfer portion.

9. An image forming apparatus comprising:
an endless belt;
a primary transfer roller contacting an inner surface of said endless belt and configured to transfer a toner image onto said endless belt at a primary transfer portion;
a secondary transfer roller contacting an outer surface of said endless belt and configured to transfer the toner image from said endless belt onto a recording material at a secondary transfer portion;
a first stretching roller contacting the inner surface of said endless belt and configured to stretch said endless belt, said first stretching roller being located upstream of the primary transfer portion and downstream of the secondary transfer portion with respect to a rotational direction of said endless belt, said first stretching roller (i) being rotatable about a first rotational axis, (ii) having a first play with respect to the first rotational axis, and (iii) having a first outer diameter, a contact portion between said first stretching roller and said endless belt with respect to the widthwise direction of said endless belt being a first contact portion having a first contact length; and
a second stretching roller contacting the inner surface of said endless belt and configured to stretch said endless belt, said second stretching roller being upstream of the secondary transfer portion and downstream of the primary

Assignees

• Canon Kk

Inventors

• Nakajima Takao

Classifications

• B65H2404/253

  Relative position of driving and idler rollers · CPC title

• G03G15/16 Primary

  of a toner pattern, e.g. a powder pattern {, e.g. magnetic transfer} · CPC title

• B65H5/021 Primary

  by belts · CPC title

• G03G15/0879

  for dispensing developer from a developer cartridge not directly attached to the development unit · CPC title

• B65H2404/2511

  Arrangement for varying outer diameter, e.g. for adjusting speed or belts · CPC title