Image reading apparatus and document transport method used therefor

A document transport method used for an image reading apparatus that transports a document stacked on a document placing table on the document transport path and reads an image on the document,

• wherein the image reading apparatus comprises:
• a transport roller pair that includes a separation roller and a retard roller, and that transport the document interposed between the separation roller and the retard roller;
• an image reader that is disposed at a downstream side of the transport roller pair in the transport direction of the document, and that reads the image on the document;
• a double feeding detector that is disposed between the transport roller pair and the image reader in the transport direction, and that detects double feeding of documents;
• and
• a controller that controls rotation of the separation roller and rotation of the retard roller,
• the method comprising:
• when double feeding of the documents is detected by the double feeding detector, transporting, by the controller, the documents in a direction reverse to the transport direction at least until the leading edges of the double-fed documents are positioned at the upstream side of the transport roller pair by rotating the separation roller and the retard roller so as to transport the documents in the reverse direction, and then transporting the documents in the transport direction by rotating only the separation roller, of the transport roller pair, so as to transport the documents in the transport direction, and
• when the documents are transported in the reverse direction, setting, by the controller, a second rotation speed of the retard roller to be faster than a first rotation speed of the separation roller.

An image reading apparatus that transports a document stacked on a document placing table on the document transport path and reads an image on the document, comprising:

• a transport roller pair that includes a separation roller and a retard roller, and that transport the document interposed between the separation roller and the retard roller;
• an image reader that is disposed at a downstream side of the transport roller pair in the transport direction of the document, and that reads the image on the document;
• a double feeding detector that is disposed between the transport roller pair and the image reader in the transport direction, and that detects double feeding of documents;
• and
• a controller that controls rotation of the separation roller and rotation of the retard roller,
• wherein, when double feeding of documents is detected by the double feeding detector, the controller transports the documents in a direction reverse to the transport direction at least until the leading edges of the double-fed documents are positioned at the upstream side of the transport roller pair by rotating the separation roller and the retard roller so as to transport the documents in the reverse direction, and then transports the documents in the transport direction by rotating the separation roller so as to transport the documents in the transport direction, and
• wherein, when the documents are transported in the reverse direction, the controller sets a second rotation speed of the retard roller to be variably faster than a first rotation speed of the separation roller.