Driving transmission device, driving device and image forming apparatus

A driving transmission device comprising:

• a storage part housing a gear and having a through hole formed corresponding to the gear;
• a fixing pin which rotatably supports the gear;
• and
• a supporting part to which the fixing pin is fixed in a state where a tip end portion of the fixing pin is inserted into the through hole, wherein
• a hole side chamfered portion in which a corner is notched is formed at an outside opening edge portion of the through hole,
• a shaft side chamfered portion in which a corner is notched is formed at the tip end portion of the fixing pin,
• in the state where the fixing pin is inserted into the through hole, a lubricant is applied to a contact area between the fixing pin and the through hole,
• a hole side boundary portion which is a boundary between an inner circumferential surface of the through hole and the hole side chamfered portion is in contact with an outer circumferential surface of the fixing pin, and
• a shaft side boundary portion which is a boundary between the outer circumferential surface of the fixing pin and the shaft side chamfered portion faces the hole side chamfered portion with a gap,
• the hole side chamfered portion is notched in an arc shape, and
• in the state where the fixing pin is inserted into the through hole, a distance between the hole side boundary portion and the shaft side boundary portion is set in a range of not less than a half a radius of the hole side chamfer portion and not more than the radius.