Holding device of recording medium, image forming apparatus, and conveying method of recording medium

An image forming apparatus comprising:

• an endless device which includes a circumferential surface which holds the recording medium, a plurality of suction holes which is formed on the circumferential surface, and a negative pressure chamber which communicates with the suction holes;
• a rotation mechanism which rotates the endless device in a predetermined direction;
• a suction mechanism which discharges air in the negative pressure chamber;
• a opening and closing mechanism which has a switching blade which is provided in the endless device, and moves between a first position at which the suction holes are closed and a second position at which the suction holes are opened;
• a driving mechanism which moves the switching blade to the first position and the second position;
• a recording head unit which is arranged to face a circumferential surface of the endless device, and forms images on the recording medium;
• a supplying mechanism which supplies the recording medium to the circumferential surface of the endless device;
• and
• a controller which drives the opening and closing mechanism according to a size of the recording medium.

A conveying method of a recording medium comprising:

• generating a negative pressure in a negative pressure chamber of an endless device including a plurality of suction holes on a circumferential surface;
• opening suction holes in a position which corresponds to a size of the recording medium, among the plurality of suction holes;
• closing at least a part of the suction holes in a position which is not covered by the recording medium, among, the plurality of suction holes;
• adsorbing the recording medium to the circumferential surface of the endless device, by allowing the negative pressure to act on the recording medium through the opened suction holes;
• and
• conveying the recording medium to the recording head unit by rotating the endless device.