Patent Description:
In the related art, a stator core <NUM>' of an active radial magnetic levitation bearing has a structure symmetrically arranged from top to bottom and from left to right. In general, the active radial magnetic levitation bearing has N poles (i.e., N teeth and N slots), the number N of the poles is: N=<NUM>, <NUM>, <NUM>, etc. The radial winding coils <NUM>' are evenly distributed on and wound on the pole pillars <NUM>' of the stator core <NUM>' of the radial bearing, respectively, and coil turns thereof are the same. In the radial magnetic levitation bearing, each magnetic pole generates an electromagnetic force on each freedom degree by means of the coil current. The generated electromagnetic force is mainly used to overcome the gravity of the rotor <NUM>' and adjust the radial displacement of the rotor <NUM>'. The output force of the upper-half magnetic pole of the radial magnetic levitation bearing is greater than that of the lower-half magnetic pole, and the excess electromagnetic forces offset against each other, so that the radial winding coil <NUM>' needs to generate a greater unilateral magnetic force by means of a greater current to overcome the rotor gravity, thus resulting in a relatively large volume and a relatively large power consumption thereof. Specifically, it is mainly the electromagnetic attraction force of the upper-half part of the bearing that overcomes the gravity of the radial magnetic levitation bearing, and the resultant force of the upper-half part is greater than the resultant electromagnetic force of the lower-half part. In the case of a symmetrical structure, it is necessary to increase the coil turn or increase the current to increase the output force, which causes the volume and the power consumption of the magnetic levitation bearing to be greater. Document <CIT> discloses a reluctance motor, in which a rotor support force is increased.

Therefore, the technical problem to be solved by the present invention is to provide a stator core, a magnetic levitation bearing, and a motor. The stator core has a non-centrosymmetric structure, so that a cross-sectional area of a magnetic path in some region of the stator core is increased, which is beneficial to an improvement of an output force of the magnetic levitation bearing.

In order to solve the problems above, the present invention provides a stator core for a magnetic levitation bearing and including an annular yoke. The annular yoke has an inner circumferential wall and an outer circumferential wall, a plurality of pole pillars are disposed on the inner circumferential wall, and each of the plurality of pole pillars extends towards an axis of the inner circumferential wall, and there is a distance D between an axis of the outer circumferential wall and the axis of the inner circumferential wall, and D≠<NUM> is satisfied.

In a projection of the annular yoke projected on any radial plane of the annular yoke, the inner circumferential wall has a circle center O, the outer circumferential wall has a circle center S, the distance D is a distance between the circle center O and the circle center S, and the stator core is symmetrical with respect to a straight line OS connecting the circle center O and the circle center S.

A straight line passing through the circle center O and perpendicular to the straight line OS is a first straight line, the first straight line divides the annular yoke into a first yoke part and a second yoke part, and an area A<NUM> of the first yoke part is greater than an area A<NUM> of the second yoke part.

A circumferential width W<NUM> of each of pole pillars on the first yoke part is greater than a circumferential width W<NUM> of each of pole pillars on the second yoke part.

In some embodiments, <NUM>. 2A<NUM>≤A<NUM>≤6A<NUM> is satisfied.

In some embodiments, in the projection of the annular yoke projected on any radial plane of the annular yoke, <MAT> is satisfied, where R denotes a radius of the outer circumferential wall, and r denotes a radius of the inner circumferential wall.

In some embodiments, <NUM>. 2W<NUM>≤W<NUM>≤6W<NUM> is satisfied.

In some embodiments, the pole pillars on the first yoke part are symmetrical with respect to a straight line OS; H<NUM> denotes a distance between an intersection of the straight line OS and the inner circumferential wall and an intersection of the straight line OS and the outer circumferential wall; the distance H<NUM> and the pole pillars on the first yoke part are located at the same side of the first straight line, and W<NUM>=H<NUM> is satisfied; and/or the pole pillars on the second yoke part are symmetrical with respect to the straight line OS, and H<NUM> denotes a distance between an intersection of the straight line OS and the outer circumferential wall and an intersection of the straight line OS and the inner circumferential wall, and the distance H<NUM> and the pole pillars on the second yoke part are located at the same side of the first straight line, and W<NUM>=H<NUM> is satisfied.

The present invention further discloses a magnetic levitation bearing, including the stator core above.

The present invention further discloses a motor, including the magnetic levitation bearing above.

According to the stator core, the magnetic levitation bearing, and the motor of the present invention, the stator core has the non-centrosymmetric structure, so that the output force of the magnetic levitation bearing corresponding to the region whose magnetic path with the relatively large cross-sectional area is increased. Moreover, the stator core meets the requirement that the working current is relatively small while the bearing provides the output force, thereby greatly improving the reliability and stability of the magnetic levitation bearing during operation, greatly reducing the loss of silicon steel sheets, reducing the cost, and reducing the weight of the bearing, and the reliability of the magnetic levitation bearing system may also be improved.

Reference numerals are indicated as:
<NUM>. annular yoke; <NUM>. inner circumferential wall; <NUM>. outer circumferential wall; <NUM>. first straight line; <NUM>. first yoke part; <NUM>. second yoke part; <NUM>. pole pillar; <NUM>. winding coil; <NUM>. rotor; <NUM>'. stator core; <NUM>'. winding coil; <NUM>'. pole pillar; <NUM>'.

Referring to <FIG>, an embodiment of the present invention provides a stator core used in a radial magnetic levitation bearing. The stator core includes an annular yoke <NUM>. The annular yoke <NUM> has an inner circumferential wall <NUM> and an outer circumferential wall <NUM>. A plurality of pole pillars <NUM> are disposed on the inner circumferential wall <NUM>, and each of the pole pillars extends towards the axis of the inner circumferential wall <NUM>. There is a distance D between the axis of the outer circumferential wall <NUM> and the axis of the inner circumferential wall <NUM>, where D ≠ <NUM>, that is, the axis of the outer circumferential wall <NUM> and the axis of the inner circumferential wall <NUM> do not coincide, and there is an offset distance therebetween. In this case, it will objectively lead to a difference between radial thicknesses of the annular yoke in the related art. That is, the radial thickness of some part of the annular yoke <NUM> is relatively thick, while the radial thickness of some part of the annular yoke <NUM> is relatively thin. Specifically, the stator core with two similar pole pillars <NUM> is shown in <FIG>, and the radial thickness of the upper yoke part is greater than the radial thickness of the lower yoke part, such that the cross-sectional area of the magnetic path in one region of the stator core is greater than that of the magnetic path in another region of the stator core. That is, compared with the stator core with a symmetrical structure in the related art, the stator core of the present invention has a non-centrosymmetric structure, and the output force of the magnetic levitation bearing corresponding to the region with a greater cross-sectional area of the magnetic path is increased. Moreover, the stator core of the present invention meets the requirement for the relatively small working current while meeting the requirement for the output force of the bearing, thereby greatly improving the reliability and stability of the magnetic levitation bearing during operation, greatly reducing the loss of silicon steel sheets, reducing the cost, and reducing the weight of the bearing, and the reliability of the magnetic levitation bearing system may also be improved.

In some embodiments, in a projection of the annular yoke <NUM> projected on any radial plane thereof, the inner circumferential wall <NUM> has a circle center O, the outer circumferential wall <NUM> has a circle center S, and the distance D is a distance between the circle center O and the circle center S. The stator core is symmetrical with reference to the straight line OS connecting the circle center O and the circle center S, and in this case, the stator core is of mirror symmetry with reference to the straight line OS, which ensures that while the output force of some region of the magnetic levitation bearing is increased, the control difficulty of the magnetic levitation bearing is reduced as well.

In some embodiments, a straight line passing through the circle center O and perpendicular to the straight line OS is a first straight line <NUM>, and the first straight line <NUM> divides the annular yoke <NUM> into a first yoke part <NUM> and a second yoke part <NUM>. An area A<NUM> of the first yoke part <NUM> is greater than an area A<NUM> of the second yoke part <NUM>. In the projection of the annular yoke <NUM> projected on any radial plane thereof, R denotes a radius of the outer circumferential wall <NUM>, and r denotes a radius of the inner circumferential wall <NUM>. An optimal range for A<NUM> and A<NUM> is obtained based on theoretical foundations as follows.

The electromagnetic force generated by the radial magnetic levitation bearing is: <MAT>.

µ<NUM> denotes air permeability, N denotes the coil turn, A denotes the cross-sectional area of the magnetic path of the stator core, i denotes a current of the coil, x denotes a length of an air gap. A depends on a cross-sectional area of an outer ring (namely, the annular yoke) of the stator core and cross-sectional areas of the pole pillars. When the coil turn is constant, the electromagnetic force is directly proportional to the coil current and the cross-sectional area of the magnetic path, and is inversely proportional to a square of the length of the air gap. The electromagnetic force of the bearing is mainly used to overcome the gravity and adjust a radial displacement of the rotor. Supposing that F<NUM> denotes an upwards vertical resultant force of the electromagnetic forces of the bearing, and F<NUM> denotes a downwards vertical resultant force, and an adjustment force is a times of the gravity and mainly includes a possible disturbance force and a centrifugal force generated due to a disequilibrium of the rotor itself during a rotation of the rotor, and a is in a range of <NUM> to <NUM>, then <MAT>.

The relationship among the cross-sectional area A<NUM> of an upper magnetic path, the cross-sectional area A<NUM> of a lower magnetic path, and the electromagnetic forces F<NUM> and F<NUM> is: <MAT>.

As shown in <FIG> and <FIG>, in the solutions of the present invention, the cross-sectional area of the magnetic path is changed by adjusting the structure of the annular yoke <NUM> and the pole pillars <NUM> of the stator core of the radial bearing, thereby changing the electromagnetic force generated by the stator of the bearing. The annular yoke <NUM> of the stator core is shown in <FIG>. The width of each part of the annular yoke <NUM> may be changed by changing the distance D (wherein <NUM><D<R-r) between the circle centers of the inner circumferential wall <NUM> and the outer circumferential wall <NUM> of the annular yoke <NUM>, wherein the width of the upper-half part of the outer ring of the stator core is approximate L=R-r+D, and the width of the lower-half part is approximate l=R-r-D, so that the cross-sectional area of the magnetic path of the stator core is changed, which may be realized when the formula (<NUM>) is satisfied.

Considering coil winding and the output force of the bearing, when the adjustment force is <NUM> to <NUM> times of the gravity, namely <NUM>≤a≤<NUM>, the bearing structure is optimum and the performance is optimal, and the area of the upper-half part of the outer ring of the stator core is <NUM> to <NUM> times of the area of the lower-half part, namely <NUM>. 2A<NUM>≤A<NUM>≤6A<NUM>.

When the distance D between the two circle centers is within a range of the formula (<NUM>), the bearing has an optimal structure.

The circumferential width of the pole pillar <NUM> at each position is consistent with a corresponding radial thickness of the annular yoke <NUM>. When the performance is optimal, a width of the pole pillar of the upper-half part of the stator core is <NUM> to <NUM> times of a width of the pole pillar of the lower-half part. That is, a circumferential width W<NUM> of the pole pillar <NUM> on the first yoke part <NUM> is greater than a circumferential width W<NUM> of the pole pillar <NUM> on the second yoke part <NUM>, and <NUM>. 2W<NUM>≤W<NUM>≤6W<NUM> is satisfied.

In some embodiments, the pole pillars <NUM> on the first yoke part <NUM> are symmetrical with respect to the straight line OS, and H<NUM> denotes a distance between an intersection of the straight line OS and the inner circumferential wall <NUM> and an intersection of the straight line OS and the outer circumferential wall <NUM>, and the distance H<NUM> and the pole pillar <NUM> on the first yoke part <NUM> are located at the same side of the first straight line <NUM>, and W<NUM>=H<NUM>. And/or, the pole pillars <NUM> on the second yoke part <NUM> are symmetrical with respect to the straight line OS, and H<NUM> denotes a distance between the intersection of the straight line OS and the outer circumferential wall <NUM> and the intersection of the straight line OS and the inner circumferential wall <NUM>, and the distance H<NUM> and the pole pillar <NUM> on the second yoke part <NUM> are located at the same side of the first straight line <NUM>, and W<NUM>=H<NUM>. That is, the circumferential width of the pole pillar <NUM> is the same as a radial thickness of the yoke part at the corresponding position, so as to ensure better performance of the formed magnetic levitation bearing.

As shown in <FIG>, the present invention further provides a magnetic levitation bearing, including the stator core above, winding coils <NUM> wound around the pole pillars <NUM> respectively, and a rotor <NUM> located in an inner hole of the stator core.

Claim 1:
A stator core, for a magnetic levitation bearing, comprising an annular yoke (<NUM>),
wherein:
the annular yoke (<NUM>) has an inner circumferential wall (<NUM>) and an outer circumferential wall (<NUM>);
a plurality of pole pillars (<NUM>) are disposed on the inner circumferential wall (<NUM>), and each of the plurality of pole pillars (<NUM>) extends towards an axis of the inner circumferential wall (<NUM>); and
there is a distance D between an axis of the outer circumferential wall (<NUM>) and the axis of the inner circumferential wall (<NUM>), and D≠<NUM> is satisfied;
wherein, in a projection of the annular yoke (<NUM>) projected on any radial plane of the annular yoke (<NUM>), the inner circumferential wall (<NUM>) has a circle center O, the outer circumferential wall (<NUM>) has a circle center S, the distance D is a distance between the circle center O and the circle center S, and the stator core is symmetrical with respect to a straight line OS connecting the circle center O and the circle center S;
a straight line passing through the circle center O and perpendicular to the straight line OS is a first straight line (<NUM>), the first straight line (<NUM>) divides the annular yoke (<NUM>) into a first yoke part (<NUM>) and a second yoke part (<NUM>), and an area A<NUM> of the first yoke part (<NUM>) is greater than an area A<NUM> of the second yoke part (<NUM>); characterized in that
a circumferential width W<NUM> of each of pole pillars (<NUM>) on the first yoke part (<NUM>) is greater than a circumferential width W<NUM> of each of pole pillars (<NUM>) on the second yoke part (<NUM>).