TRANSFER UNIT AND IMAGE FORMING APPARATUS

Abstract

Latent images of different colors are superimposed on an intermediate transfer belt of an endless type from image carriers, to form a full color toner image. A tension roller maintains a tension of the intermediate transfer belt. A driving roller drives the intermediate transfer belt. A biasing unit applies the tension to the tension roller. A holding unit holds the tension roller. An image reading sensor detects the toner image formed on the intermediate transfer belt. The image reading sensor is disposed in the holding unit, in an opposite position to the tension roller with respect to the intermediate transfer belt.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention;

FIG. 2 is a schematic diagram of a transfer unit according to a first embodiment of the present invention;

FIG. 3 is a schematic diagram of a transfer unit according to a second embodiment of the present invention;

FIG. 4 is a schematic diagram of a transfer unit according to a third embodiment of the present invention; and

FIG. 5 is a schematic diagram of a conventional transfer unit.

Claims

1. A transfer unit comprising: a plurality of image carriers on which latent images of different colors are formed, respectively;an intermediate transfer belt of an endless type, on which the latent images are superimposed to form a full color toner image;a tension roller that maintains a tension of the intermediate transfer belt;a driving roller that drives the intermediate transfer belt;a biasing unit that applies the tension to the tension roller;a holding unit that holds the tension roller; andan image reading sensor that detects the toner image formed on the intermediate transfer belt, whereinthe image reading sensor is disposed in the holding unit, in an opposite position to the tension roller with respect to the intermediate transfer belt.

2. The transfer unit according to claim 1, wherein the intermediate transfer belt is tightly supported by the tension roller and the driving roller, anda diameter of the driving roller is the same as a diameter of the tension roller.

3. The transfer unit according to claim 1, wherein the diameter of the tension roller is equal to or longer than 14 millimeters.

4. The transfer unit according to claim 1, wherein the image reading sensor is disposed above the tension roller in a vertical direction.

5. The transfer unit according to claim 1, further comprising: a chassis that encloses the intermediate transfer belt, the tension roller, the driving roller, the biasing unit, and the holding unit, whereina relative position between the image reading sensor and the intermediate transfer belt is ensured to be constant.

6. The transfer unit according to claim 1, further comprising: a secondary transfer roller that is disposed in an opposite position to the driving roller with respect to the intermediate transfer belt, whereinthe secondary transfer roller is constantly making a contact with the intermediate transfer belt.

7. An image forming apparatus comprising: a transfer unit that includes a plurality of image carriers on which latent images of different colors are formed, respectively;an intermediate transfer belt of an endless type, on which the latent images are superimposed to form a full color toner image;a tension roller that maintains a tension of the intermediate transfer belt;a driving roller that drives the intermediate transfer belt;a biasing unit that applies the tension to the tension roller;a holding unit that holds the tension roller; andan image reading sensor that detects the toner image formed on the intermediate transfer belt, whereinthe image reading sensor is disposed in the holding unit, in an opposite position to the tension roller with respect to the intermediate transfer belt.