Sheet folding device, sheet post-processor provided with the same, and image forming system

A sheet folding device that performs a folding process with respect to a sheet, comprising:

• a sheet conveyance path on which the sheet is conveyed in a conveyance direction;
• a first side plate and a second side plate that are disposed to be opposed to each other in a width direction orthogonal to the conveyance direction;
• a first folding roller pair that forms a first folding nip, folds in two the sheet passing through the first folding nip, and conveys the folded sheet to a first folding conveyance path branching and extending from the sheet conveyance path;
• a first folding guide that is reciprocatable between a folding position for guiding a to-be-folded part of the sheet that is conveyed on the sheet conveyance path to the first folding nip and a retracted position away from the first folding nip;
• and
• a guide drive mechanism that causes the first folding guide to reciprocate between the folding position and the retracted position,
• wherein
• the first folding guide includes:
• a guide main body that extends in the width direction;
• and
• a first arm and a second arm that are provided respectively at both ends of the guide main body in the width direction and are swingably supported to the first side plate and the second side plate, and
• the guide drive mechanism includes:
• a drive source that is disposed on the first side plate;
• a first drive transmission portion that is disposed on the first side plate and transmits a drive force of the drive source to the first arm;
• a second drive transmission portion that is disposed on the second side plate and transmits the drive force of the drive source to the second arm;
• and
• a drive coupling portion that couples the first drive transmission portion to the second drive transmission portion and transmits the drive force of the drive source from the first drive transmission portion to the second drive transmission portion, wherein
• the drive source is formed of a guide drive motor,
• the first folding guide includes:
• a first arm gear that is secured to a pivot fulcrum of the first arm;
• and
• a second arm gear that is secured to a pivot fulcrum of the second arm,
• the drive coupling portion includes:
• a coupling shaft that extends in the width direction and has one end rotatably supported to the first side plate and the other end rotatably supported to the second side plate;
• a coupling input gear that is secured to the one end of the coupling shaft;
• and
• a coupling output gear that is secured to the other end of the coupling shaft,
• the first drive transmission portion includes:
• at least one first transmission gear that couples a drive output gear of the guide drive motor to the first arm gear and couples the drive output gear to the coupling input gear, and
• the second drive transmission portion includes:
• at least one second transmission gear that couples the second arm gear to the coupling output gear.