Variable stiffness device, endoscope, and method of varying stiffness of variable stiffness device
A variable stiffness device includes a first elongated member including high-bending stiffness portions and a low-bending stiffness portion between adjacent high-bending stiffness portions, a second elongated member arranged along the first elongated member and including shape-memory members and a connecting member between adjacent shape-memory members, a heater to heat a shape-memory member in the low-bending stiffness portion to increase the bending stiffness, and a moving mechanism to move the second elongated member relative to the first elongated member. When the heater heats a first shape-memory member in the low-bending stiffness portion, a second shape-memory member next to the first shape-memory member is arranged in a high-bending stiffness portion.
1. A variable stiffness device comprising:
a first elongated member including high-bending stiffness portions spaced apart from each other, and at least one low-bending stiffness portion arranged between adjacent high-bending stiffness portions and having a bending stiffness lower than a bending stiffness of the high-bending stiffness portions;
a second elongated member arranged along the first elongated member and including shape-memory members spaced apart from each other, and at least one connecting member arranged between adjacent shape-memory members;
at least one heater configured to heat at least one of the shape-memory members that is located in the at least one low-bending stiffness portion to increase the bending stiffness of the shape-memory member; and
an actuator configured to move the second elongated member relative to the first elongated member,
when the heater heats a first shape-memory member of the shape-memory members that is arranged in the low-bending stiffness portion to vary stiffness of the first shape-memory member, a second shape-memory member of the shape-memory members that is arranged next to the first shape-memory member to be varied in stiffness being arranged in a high-bending stiffness portion.
2. The variable stiffness device according to claim 1 , wherein, when the first shape-memory member in a low-stiffness state and arranged in the low-bending stiffness portion is varied to a high-stiffness state, the second shape-memory member in a high-stiffness state is arranged in the high-bending stiffness portion.
3. The variable stiffness device according to claim 2 , wherein
the high-bending stiffness portions are tubular, and
the second shape-memory member in the high-stiffness state is arranged inside the high-bending stiffness portion.
4. The variable stiffness device according to claim 3 , wherein
the low-bending stiffness portion is tubular, and
the first shape-memory member to be varied from the low-stiffness state to the high-stiffness state is arranged inside the low-bending stiffness portion.
5. The variable stiffness device according to claim 4 , wherein the second shape-memory member in the high-stiffness state is cooled and varied from the high-stiffness state to the low-stiffness state.
6. The variable stiffness device according to claim 1 , wherein
the first shape-memory member has a property of transitioning from the low-stiffness state to the high-stiffness state by heat generated from the heater.
7. The variable stiffness device according to claim 6 , wherein the high-bending stiffness portion receives the heat released from the first shape-memory member that has been varied to the high-stiffness state by the heat and then is arranged in the high-bending stiffness portion, and releases the received heat to outside the variable stiffness device.
8. The variable stiffness device according to claim 1 , wherein the second elongated member includes an inner supporting member arranged on an outer peripheral side of the shape-memory members and the connecting member, and supporting the shape-memory members and the connecting member.
9. The variable stiffness device according to claim 1 , wherein the first elongated member includes an outer supporting member arranged inside the high-bending stiffness portions and the low-bending stiffness portion, and supporting the high-bending stiffness portions and the low-bending stiffness portion.
10. The variable stiffness device according to claim 1 , wherein a length of one of the high-bending stiffness portions is longer than a length of the low-bending stiffness portion.
11. The variable stiffness device according to claim 1 , wherein a length of one of the high-bending stiffness portions is longer than a length of one of the shape-memory members.
12. The variable stiffness device according to claim 1 , wherein a sum of a length of one of the high-bending stiffness portions and a length of the low-bending stiffness portion is longer than twice a length of one of the shape-memory members.
13. The variable stiffness device according to claim 1 , wherein a thermal conductivity of the connecting member is lower than a thermal conductivity of the shape-memory members.
14. The variable stiffness device according to claim 1 , wherein the low-bending stiffness portion comprises the heater.
15. The variable stiffness device according to claim 1 , wherein the low-bending stiffness portion is separate from the heater.
16. The variable stiffness device according to claim 1 , wherein
the high-bending stiffness portions are tubular,
the low-bending stiffness portion is tubular, and
when the heater heats the first shape-memory member arranged inside the tubular low-bending stiffness portion to vary stiffness of the first shape-memory member, the second shape-memory member arranged next to the first shape-memory member to be varied in stiffness is arranged inside a tubular high-bending stiffness portion.
17. An endoscope comprising:
a flexible member; and
the variable stiffness device according to claim 1 , installed in the flexible member, and configured to provide the flexible member with different degrees of stiffness.
18. The variable stiffness device according to claim 1 , wherein the actuator is a motor.
19. A method of varying stiffness of a variable stiffness device,
the variable stiffness device including:
a first elongated member including high-bending stiffness portions spaced apart from each other, and at least one low-bending stiffness portion arranged between adjacent high-bending stiffness portions and having a bending stiffness lower than a bending stiffness of the high-bending stiffness portions;
a second elongated member arranged along the first elongated member, and including shape-memory members spaced apart from each other, and at least one connecting member arranged between shape-memory members, the shape-memory members varying from a first phase to a second phase through being heated, and varying from the second phase to the first phase through being cooled, the shape-memory members having a higher stiffness in the second phase than in the first phase; and
an actuator configured to move the second elongated member relative to the first elongated member,
the method comprising:
heating a first shape-memory member arranged in the low-bending stiffness portion to cause the first shape-memory member to transition to the second phase; and
performing at least one of: maintaining a second shape-memory member arranged next to the first shape-memory member in the first phase, and cooling the second shape-memory member in the second phase.
20. The method of varying the stiffness of the variable stiffness device according to claim 19 , further comprising:
after causing the first shape-memory member to transition to the second phase, causing the actuator to move the second shape-memory member in the low-bending stiffness portion, and then causing the second shape-memory member to transition to the second phase by heating; and
causing the actuator to move the first shape-memory member next to the second shape-memory member that has been moved in the low-bending stiffness portion, so as to cool the first shape-memory member.