Synchronous reluctance rotary electric machine

1. A synchronous reluctance rotary electric machine comprising:

a shaft rotating around a rotation axis; and

a rotor core fixed to the shaft, including four layers of hollow parts having a convex shape toward a radially inner side formed for each pole in cross section, and including bridges between the respective hollow parts and an outer circumferential surface thereof, wherein,

in each pole, when a center in a circumferential direction is a pole center, both ends in the circumferential direction are pole ends, and the plurality of bridges are a first layer bridge, a second layer bridge, a third layer bridge, and a fourth layer bridge in order from the pole center toward each of the pole ends, a circumferential width between the second layer bridge and the third layer bridge is set to be greater than a circumferential width between the first layer bridge and the second layer bridge and a circumferential width between the third layer bridge and the fourth layer bridge.

2. The synchronous reluctance rotary electric machine according to claim 1 , wherein, when the four layers of the hollow parts are a first layer hollow part, a second layer hollow part, a third layer hollow part, and a fourth layer hollow part in order from a hollow part farthest from the shaft toward the shaft, a width between the second layer hollow part and the third layer hollow part is set to be greater than a width between the first layer hollow part and the second layer hollow part and a width between the third layer hollow part and the fourth layer hollow part.

3. The synchronous reluctance rotary electric machine according to claim 1 , wherein,

when the circumferential width between the first layer bridge and the second layer bridge, the circumferential width between the second layer bridge and the third layer bridge, and the circumferential width between the third layer bridge and the fourth layer bridge are at regular intervals, and

when positions of the first layer bridge, the second layer bridge, the third layer bridge, and the fourth layer bridge are a first reference bridge position, a second reference bridge position, a third reference bridge position, and a fourth reference bridge position, respectively,

the first layer bridge is formed at the first reference bridge position,

the fourth layer bridge is formed at the fourth reference bridge position,

the second layer bridge is formed at a position displaced from the second reference bridge position toward the first reference bridge position, and

the third layer bridge is formed at a position displaced from the third reference bridge position toward the fourth reference bridge position.

4. The synchronous reluctance rotary electric machine according to claim 1 , further comprising a stator core formed in a cylindrical shape to surround the rotor core and including 36 slots through which windings are inserted, wherein

an edge portion on the bridge side of each of the hollow parts includes:

an inflection point that changes from a curve protruding radially inward to a curve protruding radially outward toward the outer circumferential surface; and

a curvature change point at which a magnitude of a radius of curvature changes rapidly, and

when an angle between a first straight line passing through the rotation axis and the inflection point of the first layer bridge and the pole end is θ 1 ,

an angle between a second straight line passing through the rotation axis and the curvature change point of the first layer bridge and the pole end is θ 2 ,

an angle between a third straight line passing through the rotation axis and the inflection point of the second layer bridge and the pole end is θ 3 ,

an angle between a fourth straight line passing through the rotation axis and the curvature change point of the second layer bridge and the pole end is θ 4 ,

an angle between a fifth straight line passing through the rotation axis and the inflection point of the third layer bridge and the pole end is θ 5 ,

an angle between a sixth straight line passing through the rotation axis and the curvature change point of the third layer bridge and the pole end is θ 6 ,

an angle between a seventh straight line passing through the rotation axis and the inflection point of the fourth layer bridge and the pole end is θ 7 , and

an angle between an eighth straight line passing through the rotation axis and the curvature change point of the fourth layer bridge and the pole end is θ 8 ,

each of the angles is set to satisfy

θ 1 =36.6°,

θ 2 =31°,

θ 3 =23.3°,

θ 4 =20°,

θ 5 =12.8°,

θ 6 =9.4°,

θ 7 =5.5°, and

θ 8 =3.2°.