Insertion device, rotating tubular member, and driving unit

An insertion device comprising:

• an insertion section extended along a longitudinal axis;
• a rotating tubular member which is attached to the insertion section so that the insertion section is inserted through the rotating tubular member, and which is rotatable relative to the insertion section in directions around the longitudinal axis;
• a driving motor which is configured to cause a driving force to rotate the rotating tubular member;
• a driving shaft, one end of which is connected to the driving motor and which is extended inside the insertion section, the driving shaft being configured to transmit the driving force caused in the driving motor;
• a driving gear to which an other end of the driving shaft is coupled and which is configured to rotate when the driving force is transmitted through the driving shaft, the driving gear being configured to rotate so as to rotate the rotating tubular member;
• a connection member which connects the driving shaft to the driving gear and which is configured to transmit the driving force from the driving shaft to the driving gear;
• a ring member which is provided on an outer peripheral portion of the connection member and which is rotatable relative to the connection member;
• a channel defining portion which defines a channel inside the insertion section, the driving gear, the connection member with the ring member and the driving shaft being configured to be disposed in the channel in this order from a distal direction side;
• and
• a first channel diameter setting portion which is provided to the channel defining portion and in which an inner peripheral surface of the channel defining portion is protruded, the first channel diameter setting portion being configured to hold an outer peripheral surface of the ring member so as to support the connection member.