Motion assistance apparatus
A motion assistance apparatus includes a first link, a second link coupled to the first link via a rotary shaft so as to rotate, a duct fixed to the first link, an electromagnet disposed so as to cover at least part of the duct, a first movable portion connected to a first end of the duct, a second movable portion connected to a second end of the duct, magnetic fluid filled in a hermetically sealed space defined by the duct, the first movable portion, and the second movable portion, a transmitting portion configured to convert relative rotation between the first link and the second link to a relative position change between the first movable portion and the second movable portion, and a control unit configured to control the electromagnet.
1. A motion assistance apparatus configured to be worn on a joint of a user, the motion assistance apparatus comprising:
a first link;
a second link coupled to the first link via a rotary shaft so as to rotate;
a duct fixed to the first link;
an electromagnet disposed so as to cover at least part of the duct;
a first movable portion connected to a first end of the duct so as to communicate with the duct and configured to contain magnetic fluid;
a second movable portion connected to a second end of the duct so as to communicate with the duct and configured to contain the magnetic fluid;
the magnetic fluid filled in a hermetically sealed space defined by the duct, the first movable portion, and the second movable portion;
a transmitting portion configured to convert relative rotation between the first link and the second link to a relative position change between the first movable portion and the second movable portion; and
a control unit configured to control the electromagnet.
2. The motion assistance apparatus according to claim 1 , wherein the at least part of the duct, covered with the electromagnet, is made of a magnetically permeable material.
3. The motion assistance apparatus according to claim 1 , wherein:
the duct includes a crank part; and
the electromagnet is disposed so as to cover at least part of the crank part.
4. The motion assistance apparatus according to claim 1 , further comprising:
a bypass passage connected in parallel with the duct; and
a check valve provided in the bypass passage.
5. The motion assistance apparatus according to claim 1 , wherein:
the transmitting portion includes
a closed-end cylindrical first storage portion connected to the first link so as to slide on the first link,
a closed-end cylindrical second storage portion connected to the first link so as to slide on the first link,
a pinion fixed to the rotary shaft, and
a first rack meshing with the pinion and fixed to the first storage portion;
in a state where the first movable portion is accommodated in the first storage portion, a distal end of the first movable portion is connected to a bottom of the first storage portion; and
in a state where the second movable portion is accommodated in the second storage portion, a distal end of the second movable portion is connected to a bottom of the second storage portion.
6. The motion assistance apparatus according to claim 5 , further comprising a second rack meshing with the pinion and fixed to the second storage portion.
7. The motion assistance apparatus according to claim 5 , further comprising:
a first lid portion fitted to an opening of the first storage portion so as to be displaceable relative to the first storage portion and disposed between the first end of the duct and the first movable portion; and
a second lid portion fitted to an opening of the second storage portion so as to be displaceable relative to the second storage portion and disposed between the second end of the duct and the second movable portion, wherein:
the first lid portion includes a through portion configured to communicate the duct with the first movable portion; and
the second lid portion includes a through portion configured to communicate the duct with the second movable portion.
8. The motion assistance apparatus according to claim 5 , wherein:
the first storage portion is connected to the first link via a slider so as to slide on the first link; and
the second storage portion is connected to the first link via a slider so as to slide on the first link.
9. The motion assistance apparatus according to claim 1 , wherein:
the transmitting portion includes
a closed-end cylindrical first storage portion connected to the first link so as to slide on the first link,
a closed-end cylindrical second storage portion connected to the first link so as to slide on the first link,
an arm fixed to the second link,
a first rod connecting a first end of the arm and the first storage portion, and
a second rod connecting a second end of the arm and the second storage portion;
in a state where the first movable portion is accommodated in the first storage portion, a distal end of the first movable portion is connected to a bottom of the first storage portion; and
in a state where the second movable portion is accommodated in the second storage portion, a distal end of the second movable portion is connected to a bottom of the second storage portion.
10. The motion assistance apparatus according to claim 1 , wherein:
the first movable portion is configured so as to extend and contract; and
the second movable portion is configured so as to extend and contract.
11. The motion assistance apparatus according to claim 10 , wherein:
the first movable portion includes a bellows; and
the second movable portion includes a bellows.
12. The motion assistance apparatus according to claim 1 , wherein:
the first movable portion is in a closed-end cylindrical shape; and
the second movable portion is in a closed-end cylindrical shape.
13. The motion assistance apparatus according to claim 1 , wherein the control unit is configured to control a voltage applied to the electromagnet.
14. The motion assistance apparatus according to claim 13 , wherein the control unit is configured to control start and stop of application of the voltage to the electromagnet.