Electric motor having an asymmetric stator

Patent metadata

Field	Value
Publication number	US-9859760-B2
Application number	US-201314390386-A
Country	US
Kind code	B2
Filing date	Apr 3, 2013
Priority date	Apr 3, 2012
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

An electric motor may have a rotor and a stator. An external part and an internal part may be arranged concentrically to a rotation axis and may be adjustable rotationally relative to each other about the rotation axis. The electric motor may be one of an external rotor motor and an internal rotor motor. The external part may have at least two permanent magnets. The internal part may have at least two pole arms and at least one electric coil. The rotor may be formed symmetrically and the stator may be formed asymmetrically.

First claim

The invention claimed is:

1. An electric motor, comprising:
a symmetric rotor and an asymmetric stator;
an external part and an internal part arranged concentrically to a rotation axis and adjustable rotationally relative to each other about the rotation axis;
wherein the external part defines one of the rotor and the stator, and the internal part defines the other of the rotor and the stator;
the external part including at least two permanent magnets;
the internal part including at least two pole arms and at least one electric coil, the at least two pole arms including a first pole arm having a pole shoe and a second pole arm without a pole shoe, wherein the at least one coil is arranged on the second pole arm without the pole shoe; and
wherein an asymmetry of the stator is provided by an asymmetry of the second pole arm without the pole shoe that bears the at least one coil.

2. The electric motor according to claim 1 , wherein the asymmetry of the stator is selected such that, when the electric motor is supplied with current in order to start the electric motor in a starting relative position that is automatically produced between the stator and the rotor when the electric motor is not supplied with current, a magnetic field is produced, which drives the electric motor in a predefined rotation direction.

3. The electric motor according to claim 1 , wherein the pole shoe is disposed on a radial outside of the first pole arm relative to the rotation axis and extends from the first pole arm in a circumferential direction of the rotation axis, the pole shoe having a radially outer side;
an air gap is disposed radially between the outer side of the pole shoe and an inner side of a respective one of the at least two magnets that faces the pole shoe; and
the asymmetry of the stator is further provided by an asymmetrical profile of the outer side of the pole shoe in such a manner that the air gap is asymmetrical in the circumferential direction.

4. The electric motor according to claim 3 , wherein the asymmetrical profile of the outer side of the pole shoe varies a radial dimension of the air gap along the circumferential direction.

5. The electric motor according to claim 1 , wherein the pole shoe is disposed on a radial outside of the first pole arm relative to the rotation axis, the pole shoe having two pole shoe sections arranged on circumferentially opposite sides of the first pole arm extending away from each other in a circumferential direction; and
the asymmetry of the stator is further provided by an asymmetry of the two pole shoe sections.

6. The electric motor according to claim 5 , wherein one pole shoe section is larger than the other pole shoe section.

7. The electric motor according to claim 1 , wherein the asymmetry of the stator provided by the asymmetry of the second pole arm includes an asymmetrical arrangement of the second pole arm bearing the at least one coil, the asymmetrical arrangement defined by the second pole arm arranged offset eccentrically to the rotation axis.

8. The electric motor according to claim 1 , wherein the at least two pole arms include a third pole arm bearing another electric coil; and
wherein the asymmetry of the stator is further provided by at least one of asymmetrically formed coils and asymmetrically arranged coils.

9. The electric motor according to claim 1 , wherein the at least one coil is a prefabricated component placed onto the second pole arm without the pole shoe.

10. The electric motor according to claim 1 , wherein the at least two pole arms include four pole arms; and
the at least one coil includes two coils respectively disposed on opposite pole arms.

11. The electric motor according to claim 10 , wherein at least one of:
the two coils are formed by one of separate windings and a common winding, and
the at least two permanent magnets includes four permanent magnets arranged distributed along the external part with alternating polarity in a circumferential direction.

12. The electric motor according to claim 1 , wherein a number of pole arms is twice as high as a number of coils and equal to a number of permanent magnets alternating in polarity along a circumferential direction, the coils being assigned to every other pole arm in the circumferential direction.

13. The electric motor according to claim 3 , wherein the pole shoe of the first pole arm includes a radial step in the respective outer side to vary a radial dimension of the air gap along the circumferential direction, the radial step defining the asymmetrical profile of the outer side of the pole shoe.

14. The electric motor according to claim 13 , wherein the at least two pole arms further include a third pole arm, the third pole arm having a pole shoe defining an outer side provided with another step, and wherein the step of the first pole arm and the step of the third pole arm lie diametrically opposite each other in relation to the rotation axis.

15. The electric motor according to claim 1 , wherein the first pole arm having the pole shoe is without an electric coil.

16. The electric motor according to claim 1 , wherein the second pole arm has an end section at a distance radially from the rotation axis, and wherein the end section tapers radially outwards with increasing distance from the rotation axis.

17. The electric motor according to claim 1 , wherein the at least two permanent magnets form at least two plus poles and at least two minus poles alternately in a circumferential direction, an extent of the plus poles and of the minus poles being unequal in the circumferential direction.

18. The electric motor according to claim 17 , wherein:
the plus poles extend over a larger circumferential section in the circumferential direction than the minus poles, and
the minus poles extend over a larger circumferential section in the circumferential direction than the plus poles.

19. A hydraulic pump for conveying a hydraulic medium, comprising:
a conveying device;
an electric motor for driving the conveying device, the electric motor including:
a rotor and a stator;
an external part and an internal part arranged concentrically to a rotation axis of the electric motor and adjustable rotationally relative to each other about the rotation axis;
wherein the electric motor is one of (i) an external rotor motor where the external part is the rotor and the internal part is the stator, and (ii) an internal rotor motor where the external part is the stator and the internal part is the rotor;
the external part including at least two permanent magnets;
the internal part including at least two pole arms and at least one electric coil, the at least two pole arms including at least one pole arm having an end section disposed at a distance from the rotation axis that tapers with increasing distance from the rotation axis, wherein the end section tapers asymmetrically in relation to a circumferential direction of the rotation axis; and
wherein the rotor is formed symmetrically and the stator is formed asymmetrically.

20. The electric motor according to claim 1 , wherein the asymmetry of the stator is provided via an asymmetric distribution of electromagnetic forces in a circumferential direction effective for driving the rotor.

21. The electric motor according to claim 1 , wherein the external part defines the rotor and the internal part defines the stator.

22. An electric motor, comprising:
a rotor and a stator;
an external part and an internal part a

Assignees

• Mahle Int Gmbh

Inventors

• Helmis Martin
• Krappel Michael

Classifications

• H02K2201/03

  Machines characterised by aspects of the air-gap between rotor and stator · CPC title

• H02K1/14 Primary

  Stator cores with salient poles · CPC title

• H02K21/222 Primary

  Flywheel magnetos · CPC title

• H02K29/03

  with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems · CPC title