Rotor core, rotor, and rotating electric machine

1. A rotor core comprising:

a plurality of pairs of magnet openings formed in juxtaposition with each other in a circumferential direction, the pair respectively disposed such that a space therebetween widens toward an outer peripheral side and in which a pair of permanent magnets having a magnetic pole direction relative to a radial direction identical to each other are inserted; and

cavity portions, each being formed relative to an area sandwiched between two magnet openings, out of the magnet openings, in which the permanent magnets that are mutually adjacent and that have magnetic pole directions relative to the radial direction opposite to each other are inserted, wherein

the magnet openings each have a shape that connects together a first opening portion formed along a profile of the corresponding permanent magnet and a second opening portion that, when the permanent magnet is inserted in the first opening portion, covers, out of corner portions of the permanent magnet, a corner portion closest to the other permanent magnet with an air gap defined therebetween,

the second opening portion forms a bridge portion between the second opening portion and the second opening portion of the other magnet opening, and

the area is defined by a virtual line that connects together points in the two magnet openings disposed at extreme ends on an outer peripheral side, a virtual line that connects together points in the two magnet openings disposed at extreme ends on a rotation center side, and the two magnet openings.

2. The rotor core according to claim 1 , wherein the air gap makes demagnetization caused by an opposing magnetic field hard to occur.

3. The rotor core according to claim 1 , wherein the second opening portion is formed in size that generates magnetic saturation in the bridge portion.

4. The rotor core according to claim 1 , wherein both second opening portions are each formed such that side surfaces thereof that face each other extend in parallel with each other or are spaced farther away from each other toward the outer peripheral side.

5. The rotor core according to claim 1 , wherein the second opening portion is farmed such that a distance from a side surface of the permanent magnet on the outer peripheral side becomes greater toward the bridge portion.

6. The rotor core according to claim 1 , wherein the cavity portions are each formed in, of the area, an area formed on the rotation center side of a virtual line that connects together points of the two magnet openings closest to each other.

7. The rotor core according to claim 6 , wherein the cavity portions are each formed on the outer peripheral side of a virtual line that divides the area radially into two.

8. The rotor core according to claim 1 , wherein

the magnet openings are each formed into a substantially rectangular shape; and

the cavity portions are each formed such that at least part of side surfaces thereof facing the magnet openings extends in parallel with a side surface of the magnet openings.

9. The rotor core according to claim 1 , wherein a minimum space between the cavity portions and the magnet openings is equal to or less than a minimum space between the magnet openings and an outer periphery of the rotor core.

10. The rotor core according to claim 1 , wherein the area is sandwiched between one magnet opening out of the pair of magnet openings and the other magnet opening out of the pair of magnet openings, being adjacent to the one magnet opening.

11. A rotor comprising:

a rotor core accord to claim 1 ; and

a permanent magnet inserted in the magnet openings the rotor core has.

12. A rotating electric machine comprising

the rotor according to claim 11 ; and

a stator disposed so as to face an outer peripheral surface of the rotor with an air gap defined therebetween.