Image forming apparatus

An image forming apparatus, comprising:

• a sheet cassette configured to support a sheet;
• an image former configured to form an image on the sheet;
• a fixer disposed above the sheet cassette and configured to thermally fix the image formed on the sheet;
• a discharge tray configured to support the sheet on which the image has been thermally fixed by the fixer;
• a conveyor configured to convey the sheet along a conveyance passage extending from the sheet cassette to the discharge tray via the image former and the fixer;
• a return conveyor configured to convey the sheet from a branch position, located between the fixer and the discharge tray in the conveyance passage, to a merge position, located between the sheet cassette and the image former, along a return passage which branches from the conveyance passage at the branch position, passes below the sheet cassette, and merges with the conveyance passage at the merge position;
• a switchback roller disposed between the branch position and the discharge tray in the conveyance passage and configured to convey the sheet to the discharge tray when the switchback roller rotates forwardly and to convey the sheet to the return passage when the switchback roller rotates backwardly;
• an intermediate conveyance roller disposed in the return passage at a height level intermediate between the fixer and the sheet cassette, an upper end of the intermediate conveyance roller being disposed at a height level lower than a lower end of the fixer, a lower end of the intermediate conveyance roller being disposed at a height level higher than an upper end of the sheet cassette;
• and
• an intermediate discharge roller disposed upstream of the intermediate conveyance roller in a conveyance direction of the sheet in the return passage,
• wherein an intermediate-part of the return passage is a part of the return passage, the intermediate-part of the return passage extending from the intermediate discharge roller to the intermediate conveyance roller, and
• wherein a downstream side of the intermediate-part of the return passage inclines frontwardly as the downstream side of the intermediate-part approaches the intermediate conveyance roller.

An image forming apparatus, comprising:

• a sheet cassette configured to support a sheet;
• an image former configured to form an image on the sheet;
• a fixer disposed above the sheet cassette and configured to thermally fix the image formed on the sheet;
• a discharge tray configured to support the sheet on which the image has been thermally fixed by the fixer;
• a conveyor configured to convey the sheet along a conveyance passage extending from the sheet cassette to the discharge tray via the image former and the fixer;
• a return conveyor configured to convey the sheet from a branch position, located between the fixer and the discharge tray in the conveyance passage, to a merge position, located between the sheet cassette and the image former, along a return passage which branches from the conveyance passage at the branch position, passes below the sheet cassette, and merges with the conveyance passage at the merge position;
• a switchback roller disposed between the branch position and the discharge tray in the conveyance passage and configured to convey the sheet to the discharge tray when the switchback roller rotates forwardly and to convey the sheet to the return passage when the switchback roller rotates backwardly;
• an intermediate conveyance roller disposed in the return passage at a height level intermediate between the fixer and the sheet cassette;
• a first conveyance roller disposed downstream of the intermediate conveyance roller in a conveyance direction of the sheet in the return passage;
• a second conveyance roller disposed downstream of the first conveyance roller in the conveyance direction of the sheet in the return passage,
• a first rotation shaft which is a rotation shaft of the first conveyance roller;
• a second rotation shaft which is a rotation shaft of the second conveyance roller;
• a drive source configured to provide a drive force to the first rotation shaft and the second rotation shaft;
• and
• a connector which is connected to the first rotation shaft so as to be freely rotatable relative to the first rotation shaft by a predetermined play angle and to which the drive force is inputted from the drive source,
• wherein a conveying speed of the second conveyance roller is higher than a conveyance speed of the first conveyance roller, and
• wherein a free rotational amount, by which the first conveyance roller is freely rotatable relative to the connector by the predetermined play angle, is not smaller than a slip amount of the sheet on the first conveyance roller determined based on a difference between the conveyance speed of the second conveyance roller and the conveyance speed of the first conveyance roller.