CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of foreign priority to Japanese Patent Application No. JP2018-198871, filed Oct. 23, 2018, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a rotary electric machine which can achieve highly efficient operation, and a vehicle equipped with the rotary electric machine.

BACKGROUND ART

In an effort to realize low carbon society, various types of vehicles equipped with a rotary electric machine have become widespread in recent years; such vehicles (i.e., hybrid electric vehicles and electric vehicles) are equipped with a rotary electric machine as a prime mover, in addition to or in place of a conventional internal combustion engine.

The rotary electric machine includes an annular stator and an annular rotor. The stator includes a stator core having a plurality of slots, and stator coils respectively provided in the corresponding slots. The rotor is rotatably provided in the stator opposite to an inner circumferential wall of the stator with a slight gap present therebetween. A plurality of permanent magnets are disposed in a rotor core of the rotor at fixed intervals in the circumferential direction.

In the rotary electric machine, when a motor current flows through a stator coil, a revolving field is generated in the stator. The revolving field thus generated in the stator and magnetic fields generated in the rotor by the permanent magnets disposed in the rotor core interact to cause the rotor to rotate. To address lower power consumption, it is strongly desired that the rotary electric machine be operated highly efficiently (at high output) with appropriate rotation speed and torque in accordance with the operating conditions.

JP2017-158282A discloses a rotary electric machine, which comprises a stator having a hollow portion, and a rotor rotatably provided in the hollow portion of the stator. The rotor has a plurality of insertion holes for magnets, and magnets are received in the corresponding insertion holes. The inner wall of each insertion hole has a center-side wall surface portion located closer to the radially center of the rotor, and a periphery-side wall surface portion remote opposite to the center-side wall surface and located far from the radially center of the rotor. A pair of lugs jut out from the center-side wall surface portion toward the magnet to engage with a pair of grooves formed in the magnet. Further, a pair of recess portions are formed in the center-side wall surface portion at positions continuous to root portions of the lugs, so that gaps are formed between the magnet and the center-side wall portion at the recess portions. In this rotary electric machine disclosed in JP2017-158282A, the magnets are held in the insertion holes by the lugs, while being spaced apart from the periphery-side wall surface portions. This configuration makes it possible to improve the degree of flexibility in designing the shape of the outer peripheral side wall of the rotor and to efficiently improve the usability of magnetic flux of the magnets without deteriorating the durability of the rotor.

SUMMARY

The rotary electric machine disclosed in JP2017-158282A includes the lugs for holding and positioning the permanent magnets. However, a permanent magnet expands in a direction orthogonal to the magnetization direction due to decreased temperature of the permanent magnet, so that the pair of lugs disposed outside the permanent magnet are subjected to stress. For this reason, to disperse the stress applied to the lugs, a pair of cold thermal stress relieving portions each having a large radius of curvature are formed in the center-side wall surface portion at positions where the lugs contact the permanent magnet.

However, providing the cold thermal stress relieving portions having a large radius of curvature requires large gaps in the center-side wall surface portion. Further, provision of the gaps prevents magnetic flux paths from passing through the gaps, and this will disadvantageously cause a decrease in torque.

In view of the above, the present invention seeks to provide a rotary electric machine, which can prevent the lugs from damaging and which can enhance torque density and demagnetization resistance, while ensuring the magnetic flux paths. The present invention also seeks to provide a vehicle equipped with such a rotary electric machine.

The present invention proposed to attain the above object provides a rotary electric machine comprising: an annular stator including a stator core and coils disposed in the stator core; and an annular rotor disposed inside the stator and opposite to an inner circumferential wall of the stator with a gap present therebetween, the rotor including a rotor core having a plurality of receiving holes for magnetic material members, which receiving holes extend in an axial direction of a drive shaft and are arranged in a circumferential direction of the rotor core, wherein the rotor includes a plurality of protrusions provided in each of the plurality of receiving holes, the protrusions jutting out from an inner wall of the receiving hole to hold a corresponding magnetic material member, wherein each of the magnetic material members comprises a hard magnetic material member and a soft magnetic material member, which are stacked one on another in a magnetization direction, and wherein the soft magnetic material member is disposed to border the inner wall of the receiving hole at positions where the protrusions are provided.

