Motion assist device
Provided is a motion assist device that can minimize the number of actuators that are required for assisting a certain mode of motion of the user while allowing a greater freedom of motion beside from the motion which the motion assist device is designed to assist. A power transmission mechanism for the device includes a belt drive mechanism which is incorporated with a differential mechanism.
1. A motion assist device for assisting a motion of a body part of a user, comprising:
a support member extending in a prescribed direction, and configured to be worn by a first body part of the user;
a first link member connected to a first end of the support member so as to be rotatable around a first axial line and configured to be worn by a second body part of the user;
a second link member connected to a second end of the support member so as to be rotatable around a second axial line and configured to be worn by a third body part of the user;
a drive source mounted on the support member; and
a power transmission mechanism for transmitting a power of the drive source to the first link member and the second link member;
wherein the power transmission mechanism includes:
a rotary arm rotatably supported by the support member at an intermediate point of the rotary arm and driven to rotate by the drive source;
a first drive pulley and a second drive pulley supported by one end of the rotary arm so as to be rotatable around a common axial line or mutually parallel axial lines;
a third drive pulley and a fourth drive pulley supported by another end of the rotary arm so as to be rotatable around a common axial line or mutually parallel axial lines;
a first driven pulley fixedly secured to the first link member in a coaxial relationship to the first axial line;
a second driven pulley fixedly secured to the second link member in a coaxial relationship to the second axial line;
a first drive belt passed around the first driven pulley, the first drive pulley, the third drive pulley and the second driven pulley in that order; and
a second drive belt passed around the second driven pulley, the second drive pulley, the fourth drive pulley and the first driven pulley in that order;
wherein the first drive belt is passed around the first drive pulley and the third drive pulley in a cross belt drive, and the second drive belt is passed around the second drive pulley and the fourth drive pulley in the cross belt drive.
2. The motion assist device according to claim 1 , wherein the rotary arm is positioned centrally between the first and second drive pulleys, and is provided with a neutral position where a lengthwise direction of the rotary arm is substantially orthogonal to a line connecting the first and second drive pulleys to each other.
3. The motion assist device according to claim 1 , wherein the first drive belt and the second drive belt are passed around both the first driven pulley and the second driven pulley in an open belt drive.
4. The motion assist device according to claim 1 , wherein the first drive belt and the second drive belt are passed around the first driven pulley in a cross belt drive and the second driven pulley in an open belt drive.
5. The motion assist device according to claim 1 , further comprising idler pulleys for preventing a slacking of the first drive belt and the second drive belt.
6. The motion assist device according to claim 5 , wherein the rotary arm is positioned centrally between the first and second drive pulleys, and is provided with a neutral position where a lengthwise direction of the rotary arm is substantially orthogonal to a line connecting the first and second drive pulleys to each other,
and wherein the idler pulleys include a pair of idler pulleys located on either lateral side of the one end of the rotary arm in the neutral position and another pair of idler pulleys located on either lateral side of the other end of the rotary arm in the neutral position, such that the idler pulleys push the drive belts outward.
7. The motion assist device according to claim 1 , wherein the first drive belt and the second drive belt consist of a single endless drive belt.
8. The motion assist device according to claim 1 , wherein the first body part is a pelvic part of the user, and the second and third body parts are right and left upper legs of the user.
9. The motion assist device according to claim 1 , wherein the first body part is an upper leg of the user, the second body part is a pelvic part of the user, and the third body part is a lower leg of the user.
10. The motion assist device according to claim 1 , wherein the first driven pulley and the second driven pulley have a same diameter.
11. The motion assist device according to claim 1 , wherein the first driven pulley and the second driven pulley have different diameters.