Brushless motor
View Patent ↗The motor ( 10 ) has a rotor ( 2 ) which can rotate around a rotation axis (A), and a specific number (N 1 ) of magnetic poles ( 12 ). Furthermore, the motor ( 10 ) has a stator ( 4 ) which is arranged coaxially with respect to the rotor ( 2 ) and has three stator teeth ( 5 ) for each two magnetic poles ( 12 ), which stator teeth ( 5 ) are distributed uniformly around the rotation axis, with center points of mutually adjacent stator teeth ( 5 ) being separated from one another by one slot pitch (Pc). The stator teeth ( 5 ) have free surfaces (Ss′) which are opposite the magnetic poles ( 12 ). Each stator tooth ( 5 ) is provided with one, and only one, projecting element ( 14 ), which extends radially from the respective free surface (Ss′) in the direction of the rotor ( 2 ).
1. A brushless motor,
having a rotor which can rotate about a rotation axis and has a specific number of magnetic poles which are distributed uniformly around the rotation axis and each extend along a slot pitch;
having a stator which is arranged coaxially with respect to the rotor and has three stator teeth for each two magnetic poles, which stator teeth are distributed uniformly around the rotation axis, with center points of mutually adjacent stator teeth being separated from one another by one slot pitch;
wherein the stator teeth have free surfaces which are opposite the magnetic poles, and
wherein each stator tooth is provided with a single projecting element which extends radially from the respective free surface in the direction of the rotor and wherein each projecting element essentially being in the form of an equilateral trapezoid, with the smaller base surface facing the rotor and the circumferential size being measured on the center line between the smaller and the larger base surface.
2. The motor as claimed in claim 1 , with each projecting element being in the form of a profiled tooth, having an extent in the circumferential direction of the stator which corresponds essentially to the distance between two stator teeth, and having a radial size such that the cogging torque is as low as possible.
3. The motor as claimed in claim 1 , with the projecting element being arranged in the center of the associated free surface.
4. The motor as claimed in claim 1 , which is designed such that said motor has a sinusoidal electromotive force with a fifth harmonic whose phase is in antiphase to the fundamental of the electromotive force and whose amplitude is less than 10% of the amplitude of the fundamental.
5. The motor as claimed in claim 4 , with the amplitude of the fifth harmonic being approximately 6% of the amplitude of the fundamental.
6. The motor as claimed in claim 1 , with the rotor being located inside the stator.
7. The motor as claimed in claim 6 , wherein the magnetic poles are bounded radially by a cylindrical rotor surface whose radius of curvature is smaller than the radius of curvature of a cylindrical surface which encloses the rotor.
8. The motor as claimed in claim 1 , which contains a large number of laminations which are bundled together axially and form corresponding sectors as magnetic poles, two of which in each case form a seat for a permanent magnet.
9. A brushless motor,
having a rotor which can rotate about a rotation axis and has a specific number of magnetic poles which are distributed uniformly around the rotation axis and each extend along a slot pitch;
having a stator which is arranged coaxially with respect to the rotor and has three stator teeth for each two magnetic poles, which stator teeth are distributed uniformly around the rotation axis, with center points of mutually adjacent stator teeth being separated from one another by one slot pitch;
wherein the stator teeth have free surfaces which are opposite the magnetic poles, and
wherein each stator tooth is provided with a single projecting element which extends radially from the respective free surface in the direction of the rotor; and
the projecting elements defining a cylindrical stator surface which is interrupted between the stator teeth and describes a directrix essentially having a cosine shape, with the directrix oscillating about a reference circle which runs concentrically around the rotation axis.
10. A brushless motor,
having a rotor which can rotate about a rotation axis and has a specific number of magnetic poles which are distributed uniformly around the rotation axis and each extend along a slot pitch;
containing a large number of laminations which are bundled together axially and form corresponding sectors as magnetic poles, two of which in each case form a seat for a permanent magnet;
having a stator which is arranged coaxially with respect to the rotor and has three stator teeth for each two magnetic poles, which stator teeth are distributed uniformly around the rotation axis, with center points of mutually adjacent stator teeth being separated from one another by one slot pitch;
wherein the stator teeth have free surfaces which are opposite the magnetic poles, and
wherein each stator tooth is provided with a single projecting element which extends radially from the respective free surface in the direction of the rotor;
whereby the projecting elements defining a cylindrical stator surface which is interrupted between the stator teeth and describes a directrix essentially having a cosine shape, with the directrix oscillating about a reference circle which runs concentrically around the rotation axis.
11. A brushless motor,
having a rotor which can rotate about a rotation axis and has a specific number of magnetic poles which are distributed uniformly around the rotation axis and each extend along a slot pitch;
containing a large number of laminations which are bundled together axially and form corresponding sectors as magnetic poles, two of which in each case form a seat for a permanent magnet;
having a stator which is arranged coaxially with respect to the rotor and has three stator teeth for each two magnetic poles, which stator teeth are distributed uniformly around the rotation axis, with center points of mutually adjacent stator teeth being separated from one another by one slot pitch;
wherein the stator teeth have free surfaces which are opposite the magnetic poles, and
wherein each stator tooth is provided with a single projecting element which extends radially from the respective free surface in the direction of the rotor;
whereby each projecting element essentially being in the form of an equilateral trapezoid, with the smaller base surface facing the rotor and the circumferential size being measured on the center line between the smaller and the larger base surface.
12. The motor as claimed in claim 11 , with each projecting element being in the form of a profiled tooth, having an extent in the circumferential direction of the stator which corresponds essentially to the distance between two stator teeth, and having a radial size such that the cogging torque is as low as possible.
13. The motor as claimed in claim 11 , with the projecting element being arranged in the center of the associated free surface.
14. The motor as claimed in claim 11 , which is designed such that said motor has a sinusoidal electromotive force with a fifth harmonic whose phase is in antiphase to the fundamental of the electromotive force and whose amplitude is less than 10% of the amplitude of the fundamental.
15. The motor as claimed in claim 14 , with the amplitude of the fifth harmonic being approximately 6% of the amplitude of the fundamental.
16. The motor as claimed in claim 11 , with the rotor being located inside the stator.
17. The motor as claimed in claim 16 , wherein the magnetic poles are bounded radially by a cylindrical rotor surface whose radius of curvature is smaller than the radius of curvature of a cylindrical surface which encloses the rotor.