SEGMENTED INNER STATOR AND BRUSHLESS PERMANENT MAGNET MOTOR WITH THE SAME

Abstract

A segmented inner stator comprises a stator core and a stator winding. The stator core includes a plurality of core segments which are retained together in a circular arrangement by at least one retaining ring and are mated with each other. At least some of the core segments are provided with slots on the radial side surfaces. The at least one retaining ring comprises a radial extension portion extending along the axial side surface of the core segment. A plurality of corresponding axial projections are provided on the radial extension portion of the at least one retaining ring along the circumferential direction to be inserted into the slot on one of the core segments so that the core segments are not free to move axially and radially relative to each other or relative to the retaining rings.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1b are front views showing prior art outer stator and inner stator, respectively, for a brushless permanent magnet motor;

FIG. 2 is a front view showing a prior art segmented outer stator configuration for a brushless permanent magnet motor;

FIG. 3 is a front view showing a segmented inner stator configuration according to a first embodiment of the invention for a brushless permanent magnet motor;

FIG. 4 is a perspective view showing the segmented inner stator;

FIG. 5 is a front view showing retaining rings of the segmented inner stator of FIG. 4;

FIG. 6 is a side view showing the retaining ring of FIG. 5;

FIG. 7 is a front view showing stator core segments of the segmented inner stator; and

FIG. 8 is a perspective view showing the segmented inner stator in an assembled configuration.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exemplary embodiment of a segmented inner stator configuration according to the present invention will be explained with reference to the accompanying drawings, wherein identical parts are represented with identical reference numerals.

In the present description, the term “circumferential” indicates the peripheral direction of the circular retaining ring (or stator core); the term “axial” indicates the direction along the central line of the retaining ring; and the term “radial” indicates the direction vertical to the central line of the circular retaining ring and through the center of circle of the retaining ring.

As shown in FIGS. 3 and 4, a segmented inner stator configuration according to a first embodiment of this invention comprises an inner stator 1 including a stator core 1′, a stator winding, and two circular retaining rings 2, 3.

As shown in FIG. 7, the stator core 1′ comprises a plurality of generally T-shaped core segments 7. One of the two side surfaces of each core segment 7, which are contacted with another core segment during assembling is provided with a projection 8, and the other side surface is provided with a convex cutout 9 adapted to be mated with the projection 8 on an adjacent core segment for locating the core segments 7 during assembling and for assembly itself. A long slot 10 with a hole 11 is provided approximately in the center of the two axial side surfaces of the core segments 7 near the radial inner end.

Referring to FIGS. 4, 5, and 6, the retaining rings 2, 3 are made of steel and comprise a radial extension portion extending along the axial side surfaces of the core segments and an axial extension portion inserted into the inner hole of the stator core. The radial extension portion is a flange 12 formed on the circumference of the retaining rings 2, 3 and extending along the radial direction, and a plurality of axial projections 13, which are designed to be mated with the long slots 10 with hole 11 in the segments 7, are provided on the flange along the circumferential direction for engagement with every other core segment. In the present embodiment, which has twenty-four (24) segments 7, there are twelve (12) axial projections 13. During assembling, the projections 13 are inserted into the long slot 10 with hole 11 in every other core segment 7, thereby to assemble a plurality of core segments together to form the stator core 1′ as a whole. The axial extension portion of each of the illustrated retaining rings 2, 3 has a dentate configuration for engaging with the opposing retaining ring when the retaining rings are assembled. It is to be understood that such dentate configurations are dispensable.

When all of the core segments 7 are assembled together, as shown in FIGS. 6 and 7, the maximum distance B between the two long slots 10 with hole 11 along the diameter direction of the core segments 7 is slightly greater than the maximum distance A between the two projections 13 along the diameter direction of the retaining rings 2, 3 inserted thereinto, to thereby pull all of the core segments 7 together along the radius direction.

As shown in FIGS. 5 and 7, the through hole 11, which passes through the core segment 7, is provided at the center of the long slot 10 with the hole of the core segment 7 and a hole 14 corresponding to the through hole 11 is provided on the flange 12 of the retaining rings 2, 3 on every other projection 13. Thus, after the retaining rings 2, 3 are assembled on to the stator core 1′, the core segment 7 and the two retaining rings 2, 3 located before and after the core segment are secured together along the axial direction every other long slot 10 with hole (i.e. every other projection 13) by a fastener such as a screw (or bolt) 4 and a nut 5. It is understood that more or fewer holes and fasteners can be provided to secure the core segments to the retaining rings. For example, as shown in FIG. 8, a screw is disposed on every three projections. As a result, six screws and nuts are used.

Besides the above configurations, a hub 6 can be assembled into the inner hole of the circular retaining rings 2, 3. The hub 6 can be mated with the inner hole of the retaining rings 2, 3 to thereby strengthen the entire segmented stator configuration. The hub 6 can support the rotation of the outer rotor of the brushless permanent magnet motor so as to drive the electric bicycle or washing machine to rotate. Of course, the hub 6 may be provided with a plurality of lugs with holes, through which the screw can pass for securing the retaining rings 2, 3 and the core segments 7 to thereby secure the hub 6 with the retaining rings and the core segments.

In one embodiment of this invention, the number of core segments 7 is equal to the number of stator slots, e.g. the stator core 1′ comprises 24 core segments and 24 stator slots, and it may be wound alone, thus it is particularly convenient to wrap wires.

It is intended that the above descriptions to the embodiments of this invention in conjunction with the drawings be merely interpreted as illustrative and not in a limiting sense, and many variants and modifications would be made to this invention.

For example, a mounting ring may be used to replace the above two retaining rings, and flanges extending along the radial direction are provided on the circumference of the two axial side surfaces of the mounting ring respectively, just like the retaining rings as described above. The two flanges clamp a core segment and the distance therebetween corresponds to the thickness of the core segment. A plurality of through holes, the number of which corresponds to the number of the core segments, are provided on the two flanges regularly along the circumferential direction. When assembling, each core segment is assembled with the mounting ring by the screw which passes through each core segment and the through hole. Here, the long slot with hole on the core segment is unnecessary.

Besides, a plurality of through holes, the number of which corresponds to the number of core segments, are provided regularly on the body portion of the mounting ring, and a threaded hole corresponding to the through hole is provided at the midpoint of one end of the core segment facing the mounting ring. It shall be noted that the through holes on the core segments are designed such that the head of the screw is embedded into the inner surface of the mounting ring after each core segment is secured on the mounting ring from the inner surface of the mounting ring by the screw which passes through the through hole, that is, the through hole is designed as a counter bore, thereby not to disturb the mounting of the hub.

When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes could be made in the above constructions, products and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A segmented inner stator for a brushless permanent magnet motor, the segmented inner stator comprising a stator core and a stator winding, said stator core including a plurality of core segments which are retained together in a circular arrangement by at least one retaining ring and are mated with each other, wherein at least some of the core segments are provided with slots on the radial side surfaces; the at least one retaining ring comprises a radial extension portion extending along the axial side surface of the core segment; and a plurality of corresponding axial projections are provided on the radial extension portion of the retaining rings along the circumferential direction to be inserted into said slots, so that the core segments are not free to move axially and radially relative to each other and relative to the at least one retaining ring.

2. The segmented inner stator for a brushless permanent magnet motor according to claim 1 wherein at least some of the core segments are provided with first holes on the radial side surfaces, a plurality of second holes corresponding to the first holes on the core segments are disposed on the radial extension portion of the at least one retaining ring along the circumferential direction, and a fastener is mounted by passing through said first and second holes respectively.

3. The segmented inner stator for a brushless permanent magnet motor according to claim 1, further comprising two retaining rings which are assembled from the two axial sides of the core segments to retain the plurality of core segments.

4. The segmented inner stator for a brushless permanent magnet motor according to claim 2, wherein the radial side surfaces of the core segments are provided with slots and first holes, the first holes are located in the slots to form slots with holes.

5. The segmented inner stator for a brushless permanent magnet motor according to claim 4, wherein all of the core segments are designed as a configuration having a slot with a hole on at least one radial side, and the plurality of axial projections on the radial extension portion of the at least one retaining ring are disposed alternately with said plurality of second holes.

6. The segmented inner stator for a brushless permanent magnet motor according to claim 3, wherein the inner stator is provided with a hub onto which the core segments and two retaining rings are secured by the fastener.

7. The segmented inner stator for a brushless permanent magnet motor according to claim 1, wherein each of the core segments comprises a projection and a convex cutout on the two side surfaces along the circumferential direction respectively for engaging with the adjacent core segments.

8. The segmented inner stator for a brushless permanent magnet motor according to claim 3, wherein each of the retaining rings comprises an axial extension portion extending along the radial inner surface of the core segments, said axial extension portions being engaged with each other.

9. The segmented inner stator for a brushless permanent magnet motor according to claim 3, wherein the maximum distance between the two slots of the core segments is slightly greater than the maximum distance between the two axial projections of the two retaining rings.

10. The segmented inner stator for a brushless permanent magnet motor according to claim 1, wherein the number of core segments is equal to the number of stator slots.

11. The segmented inner stator for a brushless permanent magnet motor according to claim 10, wherein the number of the core segments is 24.

12. A brushless permanent magnet motor equipped with the segmented inner stator according to claim 1.