CROSS REFERENCE TO RELATED APPLICATION

This application claims priority and benefits of Chinese Patent Application No. 201310175369.1, filed with State Intellectual Property Office, P. R. C . on May 13 , 2013 , the entire content of which is incorporated herein by reference.

FIELD

Embodiments of the present disclosure generally relate to a rotor for a permanent magnet motor, more particularly, to a rotor for a permanent magnet motor of a washing machine.

BACKGROUND

Most of the roller washing machines adopt a series excited brushless motor or an external rotor brushless motor. Chinese patent CN201048338Y describes a series excited motor with a complex structure, and the rotor current is commutated via the commutator and the electric brush. During the anhydration of the washing machine, the motor operates at a high speed and a high speed friction between the electric brush and the commutator occurs, thus causing large mechanical wear, loud noise, great electromagnetic interference and electric sparks.

Chinese application CN101069335 A describes an external rotor motor which is assembled via a cantilever beam and causes a loud noise due to the imbalance of the external rotor.

Furthermore, Chinese patent CN201877987U discloses an interior permanent magnet motor, in which a groove is formed at the end of the permanent magnet on the rotor, has a gap communicating the groove with the exterior of the rotor, and is filled with polyesters. However, the permanent magnet has a complex process, low mechanical strength and a low rated rotating speed.

SUMMARY

Embodiments of the present disclosure seek to provide a rotor for a permanent magnet motor with a high performance and a high mechanical strength.

Embodiments of the present invention provide a rotor for the permanent magnet motor, including a rotor core having a central hole, including: a plurality of mounting recesses, an outer surface having a plurality of circular arc segments, and a plurality of magnetic bridges each connected between adjacent circular arc segments, an outer surface of the magnetic bridge being closer to the central hole than the circular arc segments; and a plurality of permanent magnets mounted in the mounting recesses, wherein an outer end surface of the mounting recess is recessed outwards so as to form a blank recess in the magnetic bridge.

In some embodiments, each of the magnetic bridges includes a narrow portion, wide portions wider than the narrow portion and located at two sides of the narrow portion, and connecting portions connecting the narrow portion with the wide portions respectively.

In some embodiments, a length of the narrow portion is LI, a total length of the narrow portion and the connecting portions is L2, and a total length of the magnetic bridge is L3, in which 0.5<L1/L2<0.9, and 0.4<L2/L3<0.8.

In some embodiments, a transition surface is connected between the circular arc outer segment and the magnetic bridge, and the transition surface is closer to the central hole than the circular arc outer segment.

In some embodiments, the transition surface is tangent to the circular arc outer segment, and the outer surface of the magnetic bridge is closer to the central hole than the transition surface.

In some embodiments, the transition surface is circular arc-shaped, a radius of the transition surface is smaller than that of the circular arc outer segment, a distance between a circle center of the transition surface and a center of the central hole is H and a radius of the circular arc segment is D, in which 0.2<H/D<0.8.

In some embodiments, the outer surface of the magnetic bridge is circular arc-shaped.

In some embodiments, the outer surface of the magnetic bridge includes a plurality of straight segments.

In some embodiments, a central angle of the circular arc segment is Θ, and PI is the number of pole pairs of the rotor, in which 0°<Θ<90/Ρ1, and Pl>2.

In some embodiments, a length of the magnetic bridge is equal to a width of the mounting recess.

In some embodiments, an outer end of the permanent magnet facing the magnetic bridge is a non-magnetic end.

Compared with the motor in the related art, the permanent magnet motor having the rotor according to embodiments of the present invention, may obtain a low cogging torque, a substantially sinusoidal back-electromotive force and a low-load torque ripple via the magnetic bridge and the blank recess. With the outer surface of the magnetic bridge being circular arc-shaped or including a plurality of straight segments, the rotor according to embodiments of the present invention has a simple manufacture process, a high mechanical strength, a low noise and a high resistance to demagnetization, so as to be used in the roller washing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a rotor for a permanent magnet motor according to an embodiment of the invention;

Fig. 2 is a partial enlarged view of the rotor in Fig. 1.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure.

In the specification, unless specified or limited otherwise, relative terms such as "central", "longitudinal", "lateral", "front", "rear", "right", "left", "inner", "outer", "lower", "upper", "horizontal", "vertical", "above", "below", "up", "top", "bottom" as well as derivative thereof (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present disclosure be constructed or operated in a particular orientation, and the relative terms also do not limit the present invention.

In the description of the present disclosure, unless specified or limited otherwise, it should be noted that, terms "mounted," "connected" and "coupled" may be understood broadly, such as electronic connection or mechanical connection, inner communication between two elements, direct connection or indirect connection via intermediary. These having ordinary skills in the art should understand the specific meanings in the present disclosure according to specific situations.

It should be particularly noted that, in the description of the present invention, "inner" indicates a direction towards to a center of the rotor, and "outer" indicates a direction away from a center of the rotor. As shown in Fig. 1 and Fig. 2, a rotor 100 for a permanent magnet motor according to embodiments of the present invention includes a rotor core 1 having a plurality of mounting recesses 3 and a plurality of permanent magnets 2 mounted in the mounting recesses 3 respectively. The permanent magnet 2 may be a ferrite structure and be tangentially magnetized, and the magnetizing directions of adjacent permanent magnets 2 are opposite to each other.

The number of the mounting recesses 3 may be eight (as shown in the embodiment in Fig. 1), also may be six, ten, twelve or others.

As shown in Fig. 1, an outer surface of the rotor core 1 is manufactured to have a plurality of circular arc segments 11, and the rotor core 1 has a central hole 10.

As shown in Fig. 2, a central angle of each circular arc segment 11 is Θ. In other words, the central angle whose vertex is a center P of the central hole 10 and whose sides pass through a pair of ends of the circular arc segment 11 is Θ, and PI is the number of pole pairs of the rotor 100, in which 0°<Θ<90/Ρ1, and Pl>2.

Transition surfaces 12 are disposed at two sides of the circular arc segment 11 and tangent to the circular arc segment 11. The transition surface 12 may be an arc-shaped or straight segment. When the transition surface 12 is arc-shaped, the transition surface 12 may be circular arc-shaped or irregular arc-shaped and the transition surface 12 is recessed toward the central hole 10 with respect to the circular arc segment 11. When the transition surface 12 is a straight segment, the transition surface 12 is inclined toward the central hole 10 with respect to the circular arc segment 11. Thus, the transition surface 12 is closer to the central hole 10 than the circular arc segment 11.

In the embodiment shown in Fig. 1, the transition surface 12 is circular arc-shaped and the radius of the transition surface 12 is smaller than that of the circular arc segment 11 of the rotor core 1.

As shown in Fig. 2, a ratio of a distance H from the circle center Q of the transition surface 12 to the center P of the central hole 10 to the radius D of the circular arc segment 11 ranges from 0.2 to 0.8.

As shown in Fig. 1 and Fig. 2, a magnetic bridge 13 is connected between the adjacent transition surfaces 12. An outer end of the permanent magnet 2 facing the magnetic bridge 13 is a non-magnetic end, and an end surface of the non-magnetic end is a side edge connecting the N pole and the S pole of the permanent magnet 2.

An outer surface of the magnetic bridge 13 may be of a shape of a circular arc whose circle center coincides with the circle center of the circular arc segment 11. The outer surface of the magnetic bridge 13 may include a plurality of segments or a straight segment located between adjacent transition surfaces 12. The outer surface of the magnetic bridge 13 is closer to the central hole 10 than the circular arc segment 11 and the transition surface 12. In order to improve the performance of the rotor 100, a width of the magnetic bridge 13 is equal to that of the mounting recess 3.

In some embodiments, the rotor 100 for the permanent magnet motor may not include the transition surface 12, and the magnetic bridge 13 is directly connected between the adjacent circular arc segments 11.

The outer end surface of the mounting recess 3 is recessed outwards so as to form a blank recess 14 in the magnetic bridge 13, and the blank recess 14 is not filled with any filler. The blank recess 14 is isolated from the exterior of the rotor 100 via the magnetic bridge 13 and has a width smaller than that of the mounting recess 3.

Each of the magnetic bridges 13 includes a narrow portion 131 located in a middle of the magnetic bridge 13, wide portions 132 wider than the narrow portion 131 and located at two sides of the narrow portion 131, and connecting portions 133 connecting the narrow portion 131 with the wide portions 132 respectively.

A width of the narrow portion 131 is LI, a total length of the narrow portion 131 and the connecting portions 133 is L2, and a total length of the magnetic bridge 13 is L3. In order to increase the resistance to demagnetization, reduce the load torque ripple in a state of high speed and weak magnetic field, and improve the load voltage wave form, LI, L2 and L3 satisfy following relationships: 0.5<L1/L2<0.9, and 0.4<L2/L3<0.8.

The permanent magnet motor having the rotor according to embodiments of the present invention, may obtain a low cogging torque, a substantially sinusoidal back-electromotive force and a low-load torque ripple via the magnetic bridge 13 and the blank recess 14. With the outer surface of the magnetic bridge being circular arc-shaped or including a plurality of straight segments, the rotor according to embodiments of the present invention has a simple manufacture process, a high mechanical strength, a low noise and a high resistance to demagnetization, so as to be used in the roller washing machine.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "another example," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment", "in an embodiment", "in another example," "in an example," "in a specific example," or "in some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.