Motor rotor, and compressor motor and compressor incorporated with the motor rotor

1. A motor rotor comprising

a rotor core formed of electromagnetic steel plates stacked in an axial direction of the rotor core, the rotor core having a plurality of magnet insertion holes in each of which a permanent magnet is inserted, a flow path formed on a radially inner side of the plurality of magnet insertion holes to allow a fluid to flow through, and a shaft insertion hole located on a radially inner side of the flow path in which a rotary shaft is inserted, the flow path circumferentially extends around the shaft insertion hole, wherein

the rotor core having an inlet opening and an outlet opening of the flow path, which are each located on in a corresponding one of end faces of the rotor core in the axial direction, and

the electromagnetic steel plates include slotted electromagnetic steel plates and perforated electromagnetic steel plates,

the slotted electromagnetic steel plates include communication holes that extend circumferentially inside the rotor core and communicate with the inlet opening and the outlet opening of the flow path,

the communication holes are formed to satisfy an expression of 360/N×M A≤360/N×(M+1) where N denotes the number of magnetic poles, M denotes the number of the communication holes (M<N), and A denotes a total of formation angles of the communication holes about the rotary shaft, the total of formation angles of the communication holes being a total arc length of the communication holes in degrees, and

the rotor core includes the plurality of slotted electromagnetic steel plates of (N/M) layers, phase-shifted from each other by (360/N) degrees×M degrees in the circumferential direction to form a flow path that extends circumferentially around the shaft insertion hole.

2. The motor rotor of claim 1 , wherein the slotted electromagnetic steel plates have the same shape, and are stacked by a phase difference of the communication holes in a circumferential direction about the rotary shaft, and the communication holes are shifted in the circumferential direction and communicating with each other.

3. The motor rotor of claim 1 , wherein

the number of the communication holes M satisfies M (N/2)−1, and

the rotor core includes a plurality of the flow paths independent from each other.

4. The motor rotor of claim 1 , wherein the rotor core includes the flow path having the communication holes of the plurality of slotted electromagnetic steel plates stacked on each other, the communication holes communicating with each other.

5. The motor rotor of claim 1 , wherein

the perforated electromagnetic steel plates each include the plurality of magnet insertion holes and a plurality of through holes opened on the radially inner side of the plurality of magnet insertion holes to open in the axial direction, and

the perforated electromagnetic steel plates are stacked so that the plurality of through holes of the perforated electromagnetic steel plates communicate with the communication holes of the plurality of slotted electromagnetic steel plates.

6. The motor rotor of claim 5 , wherein

the perforated electromagnetic steel plates are each provided on a corresponding one of the end faces in the axial direction, and

all of the plurality of through holes of the perforated electromagnetic steel plates provided on the end faces each communicate with the communication holes of the plurality of slotted electromagnetic steel plates.

7. A compressor motor comprising:

the motor rotor of claim 1 ; and

a stator located along an outer circumference of the motor rotor and including a coil.

8. A compressor comprising:

the compressor motor of claim 7 ;

a crank shaft connected to the compressor motor and configured to be driven by the compressor motor to rotate; and

a compression element connected to the crank shaft and configured to compress a fluid.

9. A compressor motor comprising:

the motor rotor of claim 1 ; and

a stator located along an outer circumference of the motor rotor and including a coil.

10. A compressor comprising:

the compressor motor of claim 9 ;

a crank shaft connected to the compressor motor and configured to be driven by the compressor motor to rotate; and

a compression element connected to the crank shaft and configured to compress a fluid.

11. The motor rotor according to claim 1 , wherein

each of the slotted electromagnetic steel plates includes through holes that each extend in a straight line parallel to the axial direction of the rotor core between the inlet opening and the outlet opening of the flow path, and

the communication holes of the slotted electromagnetic steel plates extend circumferentially between two adjacent through holes to communicate the inlet opening and the outlet opening.