PERMANENTLY EXCITED ELECTRIC MACHINE

Abstract

A permanently excited electric machine including a stator, a rotor rotatable within the stator on a shaft about a rotation axis, an air gap is arranged between a radially outer circumferential surface of the rotor and a radially inner circumferential surface of the stator, recesses formed in a rotor body of the rotor, and permanent magnets received in at least two of the recesses. The at least two recesses that receive the permanent magnets are open towards the air gap.

Claims

1. A permanently excited electric machine, comprising: a stator; a rotor rotatable within the stator on a shaft about a rotation axis; an air gap is arranged between a radially outer circumferential surface of the rotor and a radially inner circumferential surface of the stator; recesses formed in a rotor body of the rotor; and permanent magnets received in at least two of the recesses, wherein the at least two recesses that receive the permanent magnets are open towards the air gap.

2. The permanently excited electric machine according to claim 1, wherein openings are formed in the radially outer circumferential surface of the rotor body, and wherein the openings lead on a first side into the at least two recesses and on a second side into the air gap.

3. The permanently excited electric machine according to claim 2, wherein a rim of the openings respectively protrudes in a radial direction of the openings so that the permanent magnets received in the at least two recesses are each respectively partially overlapped by the rim.

4. The permanently excited electric machine according to claim 1, wherein the permanent magnets are arranged like spokes about the rotation axis of the rotor.

5. The permanently excited electric machine according to claim 1, wherein the rotor body includes segments made from at least one type of metal, and wherein the segments are arranged like spokes about the rotation axis of the rotor and arranged between the permanent magnets viewed in a circumferential direction in the rotor.

6. The permanently excited electric machine according to claim 5, wherein the segments are separate segments.

7. The permanently excited electric machine according to claim 5, wherein the segments are respectively made from plural lamellas that are stacked in a direction of the rotation axis to form lamella packets.

8. The permanently excited electric machine according to claim 5, wherein the segments are made from steel or include steel.

9. The permanently excited electric machine according to claim 5, wherein the segments are connected at radially inner circumferential surfaces of the segments with a hub body that is connected with the shaft at least torque proof.

10. The permanently excited electric machine according to claim 9, wherein the segments are connected with the hub body by positive form locking, friction locking or bonding.

11. The permanently excited electric machine according to claim 10, wherein the hub body includes radially outer hooks that cooperate with complementary hook-shaped recesses at the radially inner circumferential surfaces of the segments so that positive form locking with an undercut cross section is respectively provided between the radially outer hooks and the complementary hook shaped recesses.

12. The permanently excited electric machine according to claim 9, wherein the hub body is made from a diamagnetic or paramagnetic material.

13. The permanently excited electric machine according to claim 12, wherein the hub body is made from aluminum.

14. The permanently excited electric machine according to claim 1 implemented as a brushless direct current motor (BLDC).

15. The permanently excited electric machine according to claim 1, implemented as a permanent magnet synchronous motor (PMSM).

16. A vehicle, comprising: the permanently excited electric machine according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] An advantageous embodiment of the invention is subsequently described with reference to drawing figures, wherein:

[0023] FIG. 1 illustrates a prior art embodiment;

[0024] FIG. 2 illustrates a prior art embodiment;

[0025] FIG. 3 illustrates a schematic cross-sectional view of a rotor of the permanently excited electric machine according to the invention;

[0026] FIG. 4 illustrates a detail of FIG. 3, showing a permanent magnet received in a recess of a rotor body of a rotor and magnetic flux lines of the magnetic field of the permanent magnet; and

[0027] FIG. 5 illustrates a diagram comparing a torque generated by the electric machine according to the invention at a particular angular position of the rotor with a prior art electric machine.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The permanently excited electric machine 301 that is partially shown in FIG. 3, is implemented e.g. as a permanently excited electric motor that is configured e.g. as a brushless DC motor (BLDC) or as a permanent magnet synchronous motor (PMSM).

[0029] The electric machine 301 includes a shaft 305 that rotates about a rotation axis 314. A hub body 308 is connected torque proof with the shaft 305 that is e.g. made from steel wherein segments 309 of a rotor body 310 and permanent magnets 315 are supported at the hub body 308. The segments 309 are made e.g. from steel or include steel and are arranged with respect to the rotation axis 314 in a spoke shape or in a radial direction. Advantageously the rotor body 310 is exclusively made from the e.g. separate segments 309.

[0030] The advantageously separate segments 309 can be formed in particular by lamellas 316 arranged or stacked on top of each other in the axial direction of the rotation axis 314 to form a lamella packet. The rotor body 310 or the lamellas 316 or the lamella packet include radial recesses 313 in which permanent magnets 315 are arranged. The hub body 308 is connected with the shaft 305 at least torque proof and supports the rotor body 310 torque proof. The hub body 308 can be made from a diamagnetic and/or paramagnetic material, such as from aluminum. A rotor 304 of the electric machine 301 thus includes the shaft 305, the permanent magnets 315, the rotor body 310 thus configured in particular from segments 309 made from lamellas 316, and the hub body 308.

[0031] The shaft 305 is supported in bearings at a housing of the electric machine 301. The housing supports a stator 317 with electric magnets 318, wherein the stator is only partially shown. An air gap 321 is formed between the stator 317 and the rotor 304.

[0032] Openings 324 are advantageously formed at a radially outer circumferential surface of the rotor body 310 wherein the openings 324 lead on one side into the recesses 313 and on another side into the air gap 321. No magnetically conductive elements are arranged or provided in the openings 324. The openings 324 are therefore formed at or in a radially outer circumferential surface of the rotor body 310 of the rotor 304.

[0033] As shown in FIG. 4, an advantageously circumferential rim 325 of the openings 324 respectively protrudes in a radial direction so that the permanent magnets 315 received in the recesses 313 are respectively partially overlapped, in particular with the respective rim 325 leaving the respective opening 324 uncovered. The rims 325 of the openings 324 therefore positively form lock or interlock the permanent magnets 315 at radial outer ends of the permanent magnets 315 in the recesses 313. Radially inner ends of the permanent magnets 315 may protrude from the recesses 313 of the rotor body 310 in a radially inward direction and contact the hub body 308. Then the permanent magnets 315 are fixed on a radial outside by the rims 325 of the openings 324 and are fixed on a radial inside by the hub body 308. The recesses 313 in the rotor body 310 can extend as illustrated in FIG. 3 e.g. from the hub body 308 to the openings 324 in the rotor body 310. Furthermore, the permanent magnets 315 and the recesses 313 are arranged in the rotor body e.g. like spokes about the rotation axis 314 of the rotor 304.

[0034] The segments 309 of the rotor body 310 are made from at least one type of metal, advantageously steel and are arranged in a circumferential direction of the rotor 304 respectively between two permanent magnets 315. Furthermore, the permanent magnets 315 are respectively arranged between two adjacent segments viewed in the circumferential direction of the rotor 304.

[0035] As evident from FIG. 3 the segments 309 can be connected with the hub body 308 at their radially inner circumferential surfaces. In particular the segments 309 can be connected with the hub body 308 by positive form locking and/or friction locking e.g. by a threaded connection or clamping and/or bonding e.g. by gluing.

[0036] In order to form a positive form locking connection between the hub body 308 and the segments 309 the hub body 308 can include hooks 326 on a radial outside as illustrated in FIG. 3, wherein the hooks cooperate with hook shaped recesses 327 at a radially inner circumferential surface of the segment 309 so that a respective positive form locking with an undercut cross section is provided between the hooks 326 and the recesses 327. The hooks 326 protrude in particular in a radially outward direction from the hub body 308.

[0037] FIG. 4 illustrates magnetic flux lines 323 of the magnetic field of the permanent magnet 315 received in the recess 313. FIG. 4 illustrates that the magnetic flux lines 323 cannot connect amongst each other and are not interrupted at least on a radial outside due to a lack of the bridge described supra which is provided in the portion indicated by the dashed circle in the prior art and due to the radially outer opening 324 in the rotor body 310 or in the recess 313 that is oriented towards the air gap 321. This reduces magnetic leakage flux and improves efficiency of the permanently excited electric motor 302.

[0038] FIG. 5 presents a diagram showing a functional relationship between a torque M generated by the permanently excited electric motor 302 according to the invention and an angular position φ of the rotor 304 by a line 328 that is unfilled on an inside. A solid line 329 represents the same functional relationship for a permanently excited prior art electric motor 2 which includes the bridges 22 in the rotor body according to FIGS. 1 and 2. The torque M of the permanently excited electric motor 302 according to the invention is greater than the torque M of the prior art electric motor 2 for all angular positions φ of the rotor 4.

REFERENCE NUMERALS AND DESIGNATIONS

[0039] 1 electric machine

[0040] 2 electric motor

[0041] 3 generator

[0042] 4 rotor

[0043] 5 shaft

[0044] 6 balancing disc

[0045] 7 recess

[0046] 11 first end section

[0047] 12 second end section

[0048] 13 recess

[0049] 14 rotation axis

[0050] 15 permanent magnet

[0051] 16 lamella

[0052] 17 stator

[0053] 18 electromagnet

[0054] 19 roller bearing

[0055] 20 housing

[0056] 21 air gap

[0057] 22 bridge

[0058] 23 magnetic flux line

[0059] 301 electric machine

[0060] 302 electric motor

[0061] 304 rotor

[0062] 305 shaft

[0063] 308 hub body

[0064] 309 segment

[0065] 310 rotor body

[0066] 313 recess

[0067] 314 rotation axis

[0068] 315 permanent magnet

[0069] 316 lamella

[0070] 317 stator

[0071] 318 electromagnet

[0072] 321 air gap

[0073] 323 magnetic flux line

[0074] 324 opening

[0075] 325 rim

[0076] 326 hook

[0077] 327 recess

[0078] 328 unfilled line

[0079] 329 solid line

[0080] 330 radially outer circumferential surface

[0081] M torque

[0082] φ angular position of rotor