Rotating electric machine and rotor therefor

1. A rotor for a rotating electric machine, comprising:

a rotor main body including:

a rotor core having a cylindrical shape with a shaft hole formed at a center of the rotor core; and

a plurality of permanent magnets fixed to the rotor core,

the rotor main body having a plurality of magnetic poles formed apart from each other in a circumferential direction of the rotor core; and

a shaft which is inserted into the shaft hole, and is fixed to the rotor core,

wherein a key groove is provided at an outer periphery of the shaft,

wherein a key portion, a first stress relaxation groove, a second stress relaxation groove, and a protruding portion are provided at an inner periphery of the rotor core,

wherein the key portion is fitted into the key groove,

wherein the first stress relaxation groove is formed to be adjacent to the key portion in the circumferential direction of the rotor core,

wherein a bottom surface of the first stress relaxation groove in a cross section perpendicular to an axial direction of the rotor core includes one or more first arcs including a first largest arc being an arc having a largest radius,

wherein a bottom surface of the second stress relaxation groove in the cross section perpendicular to the axial direction of the rotor core includes one or more second arcs including a second largest arc being an arc having a largest radius,

wherein the protruding portion is formed between the first stress relaxation groove and the second stress relaxation groove, and is in contact with the outer periphery of the shaft, and

wherein the protruding portion is arranged between two d-axes adjacent to each other in the cross section perpendicular to the axial direction of the rotor core.

2. The rotor for a rotating electric machine according to claim 1 , wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a center of a circle along the second largest arc is located at a position apart from a center of the key portion by 90° in the circumferential direction of the rotor core.

3. The rotor for a rotating electric machine according to claim 2 ,

wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a center of the protruding portion is located on a straight line bisecting an angle formed by a key straight line and a second groove straight line,

wherein the key straight line is a straight line passing through the center of the rotor core and the center of the key portion, and

wherein the second groove straight line is a straight line passing through the center of the rotor core and the center of the circle along the second largest arc.

4. The rotor for a rotating electric machine according to claim 3 , wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a relationship of d2≤3×d1×(R2/R1) is satisfied, where d1 a largest distance between the bottom surface of the first stress relaxation groove and the outer periphery of the shaft in a radial direction of the rotor core, d2 is a largest distance between the bottom surface of the second stress relaxation groove and the outer periphery of the shaft in the radial direction of the rotor core, R1 is a radius of a circle along the first largest arc, and R2 is a radius of the circle along the second largest arc.

5. The rotor for a rotating electric machine according to claim 2 , wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a relationship of d2≤3×d1×(R2/R1) is satisfied, where d1 is a largest distance between the bottom surface of the first stress relaxation groove and the outer periphery of the shaft in a radial direction of the rotor core, d2 is a largest distance between the bottom surface of the second stress relaxation groove and the outer periphery of the shaft in the radial direction of the rotor core, R1 is a radius of a circle along the first largest arc, and R2 is a radius of the circle along the second largest arc.

6. The rotor for a rotating electric machine according to claim 1 ,

wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a center of the protruding portion is located on a straight line bisecting an angle formed by a key straight line and a second groove straight line,

wherein the key straight line is a straight line passing through the center of the rotor core and a center of the key portion, and

wherein the second groove straight line is a straight line passing through the center of the rotor core and a center of a circle along the second largest arc.

7. The rotor for a rotating electric machine according to claim 6 , wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a relationship of d2≤3×d1×(R2/R1) is satisfied, where d1 a largest distance between the bottom surface of the first stress relaxation groove and the outer periphery of the shaft in a radial direction of the rotor core, d2 is a largest distance between the bottom surface of the second stress relaxation groove and the outer periphery of the shaft in the radial direction of the rotor core, R1 is a radius of a circle along the first largest arc, and R2 is a radius of the circle along the second largest arc.

8. The rotor for a rotating electric machine according to claim 1 , wherein, when the cross section perpendicular to the axial direction of the rotor core is viewed, a relationship of d2≤3×d1×(R2/R1) is satisfied, where d1 is a largest distance between the bottom surface of the first stress relaxation groove and the outer periphery of the shaft in a radial direction of the rotor core, d2 is a largest distance between the bottom surface of the second stress relaxation groove and the outer periphery of the shaft in the radial direction of the rotor core, R1 is a radius of a circle along the first largest arc, and R2 is a radius of a circle along the second largest arc.

9. A rotating electric machine, comprising the rotor of claim 1 .