1. Field of the Invention
The present invention relates to an automatic document conveying device that conveys a document to a reading position automatically, and an image forming apparatus including the automatic document conveying device.
2. Description of Related Art
As an automatic document conveying device used in a copier, a scanner, a facsimile, etc., there are well-known automatic document conveying devices in a form capable of inverting front and back surfaces of a document so as to read both surfaces of the document. In recent years, along with the downsizing of an image forming apparatus, there is also a demand for the downsizing of the automatic document conveying device as well as an image forming portion of the image forming apparatus.
FIG. 13 illustrates a related technology of such an automatic document conveying device. The related technology of the automatic document conveying device includes a document stacking tray (101), a pickup roller (102), a sheet feeding roller (103), a conveying drum (104), a front reading roller (105) and a back reading roller (106) disposed so as to be in contact with the conveying drum (104), a branching member (107), a lower inversion roller (108), an upper discharge roller (109), an inversion guide (110), and a discharge tray (111) in this order in a conveying direction (direction of an arrow “a”) of a document (D). Further, a document reading position (R) is located below the conveying drum (104) between the front reading roller (105) and the back reading roller (106). For convenience of the description, an upper surface of the document placed on the document stacking tray (101) is referred to as an A-surface and a lower surface thereof is referred to as a B-surface.
When only the A-surface of the document is read, the A-surface of the document (D) supplied by the pickup roller (102) from the document stacking tray (101) is read at the document reading position (R). The branching member (107) is supported so as to be swingable about an axis at its back end. When only the A-surface of the document (D) is read, the branching member (107) is placed at a position indicated by a solid line illustrated in the figure, and the document (D) is discharged to the discharge tray (111).
When both the surfaces (A-surface and B-surface) of the document are read, after the A-surface of the document (D) conveyed from the document stacking tray (101) is read at the document reading position (R), the document (D) is inverted by the lower inversion roller (108), the upper discharge roller (109), and the inversion guide (110) due to the presence of the branching member (107) at a position indicated by a dotted line illustrated in the figure. Then, the document (D) is conveyed to the document reading position (R) and the B-surface is read. The document (D) is further inverted again due to the similar operation and discharged to the discharge tray (111).
In the above-mentioned related technology, the number of members such as a conveying roller for use in the automatic document conveying device is reduced by configuring the automatic document conveying device as described above. However, drive sources of the branching member (107) and the lower inversion roller (108) are provided separately, and hence there is a problem in that spaces are required for setting the respective drive sources. Further, in a case of using an inexpensive solenoid as a drive source, the noise from the drive source increases, which requires countermeasures against the noise. Consequently, there is also a problem in that the number of parts increases to increase the number of assembly steps, leading to an increase in production cost.