Medium conveying apparatus and image forming apparatus

A medium conveying apparatus, comprising:

• a drive roller which rotates by being driven;
• a driven roller which conveys a medium nipped by the drive roller and the driven roller while rotating in a state where the driven roller is driven by the drive roller;
• and
• a supporting portion which supports the driven roller such that the driven roller is movable between a non-conveying position at which the driven roller comes into contact with the drive roller and a conveying position at which the driven roller is set apart from the drive roller, wherein
• the driven roller moves from the non-conveying position to the conveying position when the medium is conveyed between the drive roller and the driven roller,
• the drive roller includes
• a drive body portion having a cylindrical shape, and
• a drive contact portion having a cylindrical shape, which is formed of a material having a smaller friction coefficient or a higher surface hardness than the drive body portion, is arranged coaxially with the drive body portion, and is formed with a groove portion along a circumferential direction,
• the driven roller includes
• a driven contact portion having a disk shape, which comes into contact with a portion of the drive contact portion excluding the groove portion at the non-conveying position, and
• a plurality of protrusion portions which are arranged in a circumferential direction of the driven contact portion with intervals provided therebetween, protrude outwardly in a radial direction, and are arranged in the groove portion while being set apart from a bottom surface of the groove portion at the non-conveying position,
• the drive contact portion is formed with a pair of guide portions which guide, to the groove portion, the protrusion portions of the driven roller moving from the conveying position to the non-conveying position,
• the pair of guide portions are formed by chamfering a pair of edge portions of the groove portion on an outer circumferential surface side, and
• the drive contact portion is formed to have a smaller diameter than the drive body portion, and forms a step portion that is concave with respect to the drive body portion.