Bending operation apparatus for endoscope and endoscope including the bending operation apparatus

1. A bending operation apparatus for an endoscope, the apparatus comprising:

a bending operation knob that is pivotable with a pivoting shaft and performs a bending operation of a bending portion of the endoscope;

a first movable disk that is provided inside the bending operation knob;

a second movable disk that is movable between a first position in which the second movable disk is separated from the first movable disk by a first gap in an axial direction and a second position in which the second movable disk is separated from the first movable disk by a second gap that is shorter than the first gap in the axial direction;

a cam member that is disposed in a position where the cam member contacts the second movable disk, the cam member causing an inclined surface formed on a cam groove to come into contact with the second movable disk as the cam member is pivoted in one direction, to move the second movable disk from the first position to the second position;

a fixed disk that is disposed to be in contact with an inner circumferential surface of the bending operation knob, the fixed disk being sandwiched by the first movable disk and the second movable disk in the second position to apply a frictional force to pivoting of the bending operation knob;

an annular member that is provided integrally with the second movable disk and is movable along with the second movable disk in the axial direction; and

a step portion that is provided at the annular member, the step portion coming into contact with a base portion of the cam member as the cam member is pivoted in another direction opposite to the one direction, to cause the second movable disk to move from the second position to the first position.

2. The bending operation apparatus for the endoscope according to claim 1 , wherein

the first movable disk and the second movable disk each include a slit that penetrates in the axial direction, and

the annular member further includes a penetrating portion that penetrates through the slit.

3. The bending operation apparatus for the endoscope according to claim 2 , wherein the annular member further includes a projecting portion that is provided at an end portion of the penetrating portion in a pivoting direction to fix the second movable disk to the annular member.

4. The bending operation apparatus for the endoscope according to claim 3 , wherein the first movable disk and the second movable disk each further include an escape portion that is provided at an end portion of the slit in the pivoting direction and is protruded inward in a radial direction, the escape portion being configured to cause the end portion of the penetrating portion in the pivoting direction to escape inward in the radial direction.

5. The bending operation apparatus for the endoscope according to claim 1 , wherein the annular member is provided coaxially with the first movable disk and the second movable disk, and is disposed on an inside in the radial direction with respect to the cam member.

6. The bending operation apparatus for the endoscope according to claim 1 , wherein the step portion is not in contact with the base portion by fitting in a cutout formed at the base portion of the cam member when the second movable disk is disposed in the second position.

7. The bending operation apparatus for the endoscope according to claim 1 , wherein the cam member causes the first movable disk to move from the first position to the second position.

8. An endoscope comprising the bending operation apparatus for the endoscope according to claim 1 .