Drive joint mechanism and image forming apparatus using the same

An image forming apparatus comprising:

• an apparatus main body including an image forming section operable to form an image on a sheet;
• a mounted unit detachably mounted in the apparatus main body;
• a drive joint mechanism operable to transmit a driving force generated in the apparatus main body to the mounted unit;
• the drive joint mechanism including:
• a drive shaft provided in the apparatus main body;
• a driven shaft provided in the mounted unit and arranged to be coupled to the drive shaft in coaxial relation thereto;
• a coupling provided on one of the drive shaft and the driven shaft, and having a plurality of pin-engaging grooves formed in a circumferential direction of the coupling and at least one pyramid-shaped pin-guiding portion formed between the adjacent pin-engaging grooves;
• an engagement pin provided on the remaining one of the drive shaft and the driven shaft and engageable with the pin-engaging groove;
• wherein each of the coupling and the engagement pin is fixed at a given position in an axially non-displaceable manner relative to the respective one of the drive shaft and the driven shaft;
• and
• wherein when the engagement pin is brought into contact with the pin-guiding portion during an operation of coupling the drive shaft and the driven shaft the drive shaft is rotated by a pressing force exerted in the axial direction by the driven shaft so as to allow the engagement pin to be guided into the pin-engaging groove by the pin-guiding portion.