Inserting device

1. An inserting device comprising:

an inserting section which is extended along a longitudinal axis from a proximal side toward a distal side;

a rotor which is attached to the inserting section, and which is configured to rotate around the longitudinal axis when a driving force is transmitted thereto;

a shape-variable tube which forms a part of the inserting section, and which has a flexibility, the shape-variable tube being extended along the longitudinal axis with the longitudinal axis serving as a central axis, the shape-variable tube being elastically returnable to a tube straight extended shape, in which the shape-variable tube is extended straight, in a case where the shape-variable tube bends at a tube bending radius of a tube radius boundary value or greater from the tube straight extended shape;

at least one of an imaging cable and a light guide which has a member axis as a central axis and is disposed inside the shape-variable tube from the proximal side toward the distal side along the member axis;

a shaft which has a shaft axis as a central axis, and which is disposed inside the shape-variable tube from the proximal side toward the distal side along the shaft axis,

the shaft being disposed outside the at least one imaging cable and the light guide in an inner space of the shape-variable tube,

the shaft being configured to rotate around the shaft axis by an action of a rotational torque so that the shaft transmits the driving force to rotate the rotor from the proximal side toward the distal side,

a sectional area of the inner space of the shape-variable tube perpendicular to the longitudinal axis being larger than a sum of a sectional area of the at least one of the imaging cable and the light guide perpendicular to the member axis and a sectional area of the shaft perpendicular to the shaft axis,

the shaft being elastically returnable to a shaft straight extended shape, in which the shaft is extended straight, in a case where the shaft bends at a shaft bending radius of a shaft radius boundary value or greater,

the shaft being bendable at the shaft bending radius smaller than the tube bending radius in the inner space of the shape-variable tube when the tube bends at the tube bending radius of the tube radius boundary value or greater,

the shaft bending radius being constantly maintained at the shaft radius boundary value or greater in the inner space of the shape-variable tube when the shaft rotates and the tube bending radius is constantly maintained at the tube radius boundary value or greater,

wherein the shape-variable tube includes a tube inner peripheral surface which is configured to exert a pressing force on the shaft toward the longitudinal axis so that the tube inner peripheral surface maintains the shaft bending radius at the shaft radius boundary value or greater in the inner space of the shape-variable tube; and

a cylindrical spiral unit which includes a fin portion spirally extended from the proximal side toward the distal side, and which is attached to an outer peripheral side of the inserting section, the spiral unit being configured to rotate in a periaxial direction of the longitudinal axis when the driving force is transmitted thereto by the rotation of the rotor, the spiral unit being configured to rotate in a state where the fin portion is pressed toward an inner peripheral side so as to exert an impulsive force onto the inserting section in the distal side or the proximal side.

2. The inserting device according to claim 1 ,

wherein the shaft radius boundary value of the shaft bending radius of the shaft changes in accordance with an amount of the rotational torque to rotate the shaft, and

wherein the shaft bending radius is constantly maintained at the shaft radius boundary value or greater in the inner space of the shape-variable tube when the shaft rotates and the tube bending radius is constantly maintained at the tube radius boundary value or greater, irrespective of the amount of the rotational torque.

3. The inserting device according to claim 1 ,

wherein in the shaft, a rigidity is lower and transmitting properties of the driving force are lower in a first rotating state to rotate toward a first rotating direction that is one side of a periaxial direction of the shaft axis than in a second rotating state to rotate toward a second rotating direction that is a direction opposite to the first rotating direction, and

wherein the shaft bending radius is constantly maintained at the shaft radius boundary value or greater in the inner space of the shape-variable tube when the shaft rotates toward the first rotating direction in the first rotating state and the tube bending radius is constantly maintained at the tube radius boundary value or greater.

4. The inserting device according to claim 1 , further comprising:

a driving source which is configured to generate the driving force to rotate the rotor, and configured to transmit the generated driving force to the shaft from the proximal side so as to exert the rotational torque onto the shaft.

5. The inserting device according to claim 1 , further comprising:

an amplifying unit configured to amplify the driving force transmitted from the shaft toward the distal side.

6. The inserting device according to claim 5 ,

wherein the amplifying unit includes a first gear which is configured to rotate when the driving force is transmitted thereto via the shaft, and a second gear which meshes with the first gear and which is configured to rotate at a rotational angular velocity smaller than that of the first gear when the driving force is transmitted from the first gear thereto.

7. The inserting device according to claim 1 , further comprising:

a guide tube which is disposed outside the at least one of the imaging cable and the light guide in the inner space of the shape-variable tube from the proximal side toward the distal side along the shaft, and through which the shaft is inserted, the guide tube covering an outer peripheral portion of the shaft.