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A transfer belt is driven by a plurality of supporting rollers. A unit frame supports the supporting rollers in a rotatable manner. At least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof. Each end portion of the c

A transfer belt is driven by a plurality of supporting rollers. A unit frame supports the supporting rollers in a rotatable manner. At least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof. Each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner.

대표청구항 ▼

What is claimed is: 1. A transfer unit comprising: a plurality of supporting rollers; a transfer belt that is driven by the supporting rollers; a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member havin

What is claimed is: 1. A transfer unit comprising: a plurality of supporting rollers; a transfer belt that is driven by the supporting rollers; a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof, each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner, and the unit frame includes a through hole communicating with the inside of the cylindrical member. 2. The transfer unit according to claim 1, wherein the cylindrical member includes a driven member that is engaged with a driving member provided on a main body of an image forming apparatus and driven by the driving member in a rotatable manner. 3. The transfer unit according to claim 1, wherein the through hole and the inside of the cylindrical member form an airflow path. 4. The transfer unit according to claim 3, wherein the cylindrical member includes a heat-dissipating member, said heat dissipating member includes a plurality of elongated members fixed to an inside surface of the cylindrical member. 5. The transfer unit according to claim 3, wherein the cylindrical member includes a plurality of arcuate blades that form a fan. 6. The transfer unit according to claim 1, wherein the cylindrical member is made of aluminum. 7. A transfer unit comprising: a plurality of supporting rollers; a transfer belt that is driven by the supporting rollers; a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof, each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner, and the unit frame includes a through hole communicating with the inside of the cylindrical member, wherein a harness extends along the through hole and the inside of the cylindrical member. 8. A transfer unit comprising: a plurality of supporting rollers; a transfer belt that is driven by the supporting rollers; a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof, each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner, wherein the cylindrical member includes a rotation detecting unit that detects number of rotations of the cylindrical member per unit time, and the rotation detection unit includes a photosensor mounted on a bracket projecting from the unit frame. 9. An image forming apparatus comprising: a transfer unit that includes a plurality of supporting rollers, a transfer belt that is driven by the supporting rollers, a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof, each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner, the unit frame includes a through hole communicating with the inside of the cylindrical member; and an image carrier on which a toner image is formed, wherein the toner image formed on the image carrier is transferred onto the transfer belt of the transfer unit for a primary transfer, and the toner image on the transfer belt is transferred onto a recording medium for a secondary transfer to obtain a recorded image. 10. An image forming apparatus comprising: a transfer unit that includes a plurality of supporting rollers, a transfer belt that is driven by the supporting rollers, a unit frame that supports the supporting rollers in a rotatable manner, wherein at least one of the supporting rollers includes a cylindrical member having a substantially same outer diameter over an entire length thereof, each end portion of the cylindrical member in a longitudinal direction is supported by the unit frame via a bearing in a rotatable manner, the unit frame includes a through hole communicating with the inside of the cylindrical member; and an image carrier on which a toner image is formed, wherein the toner image formed on the image carrier is transferred onto a recording medium carried by the transfer belt to obtain a recorded image.