Treatment tool insertion channel of endoscope

1. A treatment tool insertion channel of an endoscope, which is arranged through an inside of an insertion part of an endoscope, the insertion part including a flexible tube and a bendable part linked with a distal end of the flexible tube, the treatment tool insertion channel comprising:

a flexible inner tube;

a spiral groove formed around the flexible inner tube, in an outer circumferential surface of the flexible inner tube, over an entire length of the bendable part and the flexible tube;

at least one coil wound along a bottom of the spiral groove around the flexible inner tube; and

a first filler and a second filler with which the spiral groove is filled, and wherein the flexible inner tube includes a first portion that includes a part inside the bendable part and a second portion at a proximal end side of the first portion, and a border portion connecting the first portion and the second portion, the first portion being configured more flexible than the second portion, wherein the second filler is harder than the first filler, the portion of the spiral groove extending the first portion being filled with the first filler, the portion of the spiral groove extending the second portion being filled with the second filler, and the portion of the spiral groove extending the border portion being filled with mixed filler which is a mixture of the first filler and the second filler, the mixed filler being a filler in which constituents of the first filler and second filler are blended together, the first filler and the second filler being made of a same type of material, between which a blending ratio is gradually changed such that a part of the border portion that is closer to the first portion is more flexible, and

wherein the at least one coil is doubly wound along a bottom of the portion of the spiral groove extending the border portion, and

wherein the border portion is located within a range of several millimeters to several centimeters between the first portion and the second portion, and flexibility thereof gradually varies at the border portion.

2. The treatment tool insertion channel according to claim 1 ,

wherein the at least one coil includes an all-range coil and a border coil,

wherein the all-range coil is wound along the bottom of the spiral groove around the flexible inner tube over the entire length of the bendable part and the flexible tube, and

wherein the border coil is wound along the bottom of the portion of the spiral groove extending the border portion.

3. The treatment tool insertion channel according to claim 1 ,

wherein the at least one coil includes a front coil and a rear coil,

wherein the front coil is wound along the bottom of the spiral groove of the first portion,

wherein the rear coil is wound along the bottom of the spiral groove of the second portion, and

wherein both of the front coil and the rear coil are wound along the bottom of the spiral groove of the border portion between the first portion and the second portion.

4. The treatment tool insertion channel according to claim 1 , wherein the at least one coil is formed from a stainless steel wire.

5. The treatment tool insertion channel according to claim 1 , wherein one of the first filler and the second filler includes at least one of silicon filler, polyurethane filler, fluorocarbon filler, and polyester filler.

6. The treatment tool insertion channel according to claim 1 , wherein the first portion is configured more flexible than the second portion with at least one of a depth and a pitch of the spiral groove being changed between the first portion and the second portion.

7. The treatment tool insertion channel according to claim 6 , wherein the at least one of the depth and the pitch of the spiral groove is gradually changed around a border portion between the first portion and the second portion.

8. The treatment tool insertion channel according to claim 6 , wherein the at least one coil is formed from a stainless steel wire.

9. The treatment tool insertion channel according to claim 6 , wherein the at least one type of filler includes silicon adhesive material.

10. The treatment tool insertion channel according to claim 1 , wherein the border portion is defined by a plurality of adjacent spiral turns of the spiral groove, and the mixture of the first and second fillers extending the entire range of the adjacent spiral turns of the border portion.

11. The treatment tool insertion channel according to claim 10 , further comprising the at least one coil including an all-range coil and a border portion coil, the border portion coil having spring characteristics which are different from the all-range coil, and the border portion coil being wound along the bottom of the spiral groove around the flexible inner tube in parallel with the all-range coil over a range of the border portion, wherein an inside diameter of the all-range coil is the same as an inside diameter of the border portion coil.