Rotor and electric motor including the same

1. A rotor comprising:

a plurality of main magnets that are disposed spaced apart from each other along a circumferential direction with respect to a rotation axis of the rotor, and have a magnetizing direction that is a direction of the rotation axis;

a plurality of auxiliary magnetic units that are disposed on opposite sides of each of the main magnets in the direction of the rotation axis, and have a magnetizing direction in the circumferential direction, so as to concentrate magnetic flux in each of the main magnets;

a plurality of webs that are disposed between the auxiliary magnetic units so as to generate a reluctance torque; and

a plurality of pole pieces disposed on front and rear surfaces of each of the main magnets with respect to the rotation axis,

wherein a length of a single rectangular main magnet of the plurality of main magnets in the direction of the rotation axis is greater than a gap between two auxiliary magnets of the plurality of auxiliary magnetic units in the direction of the rotation axis and less than a sum of the gap and a length of the two auxiliary magnets in the direction of the rotation axis, the single rectangular main magnet being in contact with a pair of non-magnetic substances and a pair of the plurality of pole pieces, and the length of the single rectangular main magnet being constant in the circumferential direction,

wherein a plane surface of each of the plurality of pole pieces is disposed to overlap with the plurality of auxiliary magnetic units,

wherein the overlapped plane surface of at least one of the plurality of pole pieces is disposed below an edge of a surface of the plurality of auxiliary magnetic units, the edge being in contact with the overlapped plane surface of the plurality of auxiliary magnetic units.

2. The rotor according to claim 1 , further comprising:

another non-magnetic substance which has a surface in contact with one of the auxiliary magnets and another surface exposed to an air gap of the rotor.

3. The rotor according to claim 1 , wherein each of the webs is made of a material having a magnetic reluctance that is lower than a magnetic reluctance of each of the pole pieces.

4. The rotor according to claim 1 , wherein the length of the plurality of main magnets in the direction of the rotation axis is less than a length of the plurality of webs in the direction of the rotation axis.

5. The rotor according to claim 1 , further comprising a frame that supports the main magnets, the auxiliary magnets, the webs, and the pole pieces, wherein the frame comprises:

an outer rim that is formed along outer peripheries of the pole pieces and the webs, and supports the pole pieces and the webs so as to wrap around outer portions of the pole pieces and the webs,

an inner rim that is formed along inner peripheries of the pole pieces and the webs, and supports the pole pieces and the webs so as to wrap around inner portions of the pole pieces and the webs, and

a plurality of spokes that are disposed between the auxiliary magnets, each of the spokes including an end connected to the outer rim and another end connected to the inner rim.

6. An electric motor comprising:

a rotor comprising:

a plurality of main magnets that are disposed spaced apart from each other along a circumferential direction with respect to a rotation axis of the rotor, and have a magnetizing direction that is a direction of the rotation axis;

a plurality of auxiliary magnetic units that are disposed on both sides of each of the main magnets in the direction of the rotation axis, and have a magnetizing direction that is the circumferential direction, so as to concentrate magnetic flux in each of the main magnets;

a plurality of webs that are disposed between the auxiliary magnetic units so as to generate a reluctance torque; and

a plurality of pole pieces that are disposed on front and rear surfaces of each of the main magnets with respect to the rotation axis, and

a plurality of stators that are disposed so that there is an air gap between each of the stators and front and rear sides of the rotor in the direction of the rotation axis,

wherein a length of a single rectangular main magnet of the plurality of main magnets in the direction of the rotation axis is greater than a gap between two auxiliary magnets of the plurality of auxiliary magnetic units in the direction of the rotation axis and less than a sum of the gap and a length of the two auxiliary magnets in the direction of the rotation axis, the single rectangular main magnet being in contact with a pair of non-magnetic substances and a pair of the plurality of pole pieces, and the length of the single rectangular main magnet being constant in the circumferential direction,

wherein a plane surface of each of the plurality of pole pieces is disposed to overlap with the plurality of auxiliary magnetic units, and

wherein the overlapped plane surface of at least one of the plurality of pole pieces is disposed below an edge of a surface of the plurality of auxiliary magnetic units, the edge being in contact with the overlapped plane surface of the plurality of auxiliary magnetic units.

7. The electric motor according to claim 6 , further comprising:

another non-magnetic substance which has a surface in contact with one of the auxiliary magnets and another surface exposed to the air gap.

8. The electric motor according to claim 6 , wherein each of the webs is made of a material having a magnetic reluctance that is lower than a magnetic reluctance of each of the pole pieces.

9. The electric motor according to claim 6 , wherein the length of the plurality of main magnets in the direction of the rotation axis is less than a length of the plurality of webs in the direction of the rotation axis.

10. The electric motor according to claim 6 , further comprising a frame that supports the main magnets, the auxiliary magnets, the webs, and the pole pieces, wherein the frame comprises:

an outer rim that is formed along outer peripheries of the pole pieces and the webs, and supports the pole pieces and the webs so as to wrap around outer portions of the pole pieces and the webs,

an inner rim that is formed along inner peripheries of the pole pieces and the webs, and supports the pole pieces and the webs so as to wrap around inner portions of the pole pieces and the webs, and

a plurality of spokes that are disposed between the auxiliary magnets, each of the spokes including an end connected to the outer rim and another end connected to the inner rim.

11. The rotor according to claim 1 , wherein the plurality of main magnets comprise odd-numbered main magnets and even-numbered main magnets,

wherein a magnetizing direction of the odd-numbered main magnets is opposite to a magnetizing direction of the even-numbered main magnets.