Patent ID: 8038144

Claim:
An image forming apparatus comprising: a circulating transfer path configured to form a path for circulatingly transferring print sheets, the path including a switchback reverse path for reversing print sheets; a plurality of transfer mechanisms provided on the circulating transfer path and configured to transfer print sheets; an image forming unit configured to perform image formation on print sheets being transferred on the circulating transfer path; a sheet reversing mechanism provided on the switchback reverse path, the sheet reversing mechanism configured to take over and transfer, at a transfer speed Vr, a print sheet with an image already formed on one side being transferred at the transfer speed Vr from a first transfer mechanism, to stop the print sheet once, then to start transfer of the print sheet in an opposite direction, and to pass the print sheet to a second transfer mechanism at the transfer speed Vr, the first transfer mechanism being located on an upstream of the switchback reverse path, the second transfer mechanism being located on a downstream of the switchback reverse path; a print sheet detection unit provided on the upstream of the switchback reverse path and configured to detect presence or absence of a print sheet; and a transfer control unit configured to control the sheet reversing mechanism, wherein upon lapse of a time T 1 after detection of the print sheet by the print sheet detection unit, the transfer control unit drives the sheet reversing mechanism to start acceleration from a stopped state to the transfer speed Vr, the time T 1 calculated based on the transfer speed Vr, and wherein the time T 1 is calculated shorter, as the transfer speed Vr becomes greater.