STATOR TOOTH WITH STATOR-TOOTH ARC-CUTTING STRUCTURE

Abstract

A stator tooth includes an arc-shaped stator yoke portion and a stator tooth portion. The arc-shaped stator yoke portion extends along an arc having an axis as a center. The stator tooth portion includes a tooth body segment and two shoe-shaped structures. The tooth body segment, protruding along a centripetal axis from the arc-shaped stator yoke portion, has a first inner arc-shaped edge defined with a first center and a first radius. The centripetal axis passes through a center point of first inner arc-shaped edge, the first center and the axis. The two shoe-shaped structures extend oppositely, but symmetrically, from the tooth body segment, and each the shoe-shaped structure has a second inner arc-shaped edge and an inner-edge end point. The second inner arc-shaped edge, extending from the first inner arc-shaped edge to the inner-edge end point, has a second radius larger than the first radius.

Claims

1. A stator tooth with a stator-tooth arc-cutting structure, comprising: an arc-shaped stator yoke portion, extended along an arc of a circle having an axis as a center of the circle; and a stator tooth portion, including: a tooth body segment, formed by protruding along a centripetal axis from the arc-shaped stator yoke portion as a unique piece, having a first inner arc-shaped edge defined with a first center of curvature and a first radius of curvature, the centripetal axis passing through a center point of first inner arc-shaped edge, the first center of curvature and the axis; and two shoe-shaped structures, extended oppositely and symmetrically with respect to the centripetal axis from the tooth body segment, each of the two shoe-shaped structures having a second inner arc-shaped edge and an inner-edge end point, the second inner arc-shaped edge extending from a corresponding end of the first inner arc-shaped edge to the inner-edge end point, the second inner arc-shaped edge having a second radius of curvature larger than the first radius of curvature; wherein the first center of curvature is spaced from the inner-edge end point of the corresponding shoe-shaped structure by a first distance, and the first distance is larger than the first radius of curvature.

2. The stator tooth with a stator-tooth arc-cutting structure of claim 1, wherein each of the two shoe-shaped structures further has a root of protrusion, the first center of curvature is spaced from the root of protrusion by a second distance, and the second distance is larger than the first distance.

3. The stator tooth with a stator-tooth arc-cutting structure of claim 1, wherein the two second inner arc-shaped edges are both overlapped by a reference arc line, the reference arc line intersects the centripetal axis at a center point of the second inner arc-shaped edge, the center point of the second inner arc-shaped edge is spaced from the center point of the first inner arc-shaped edge by a concave depth, the center point of the second inner arc-shaped edge is spaced from the first center of curvature by a radial spacing, and a sum of the radial spacing and the concave depth is equal to the first radius of curvature.

4. The stator tooth with a stator-tooth arc-cutting structure of claim 3, wherein the reference arc line and the arc have the same center of circle.

5. The stator tooth with a stator-tooth arc-cutting structure of claim 3, wherein the radial spacing is larger than the concave depth.

6. The stator tooth with a stator-tooth arc-cutting structure of claim 1, wherein the first inner arc-shaped edge further has two end points, and the second inner arc-shaped edge of the corresponding shoe-shaped structure is extended from a corresponding one of the two end points to the inner-edge end point of the corresponding shoe-shaped structure.

7. The stator tooth with a stator-tooth arc-cutting structure of claim 6, wherein the two end points of the first inner arc-shaped edge forms an angle ranged from 80° to 120° with respect to the first center of curvature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which:

[0020] FIG. 1 is a schematic view of a conventional stator of a permanent magnet motor;

[0021] FIG. 2 demonstrates schematically the stator tooth of FIG. 1;

[0022] FIG. 3 is a schematic view of an embodiment of the stator tooth with a stator-tooth arc-cutting structure in accordance with the present invention;

[0023] FIG. 4 is a schematic view of a stator composed of a plurality of the stator teeth of FIG. 3;

[0024] FIG. 5 is another view of FIG. 3 with different labels; and

[0025] FIG. 6 illustrates schematically variations of operation torque with respect to time for a permanent magnet motor having the stator teeth with individual stator-tooth arc-cutting structures in accordance with the present invention and another permanent magnet motor having the conventional stator teeth.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] The invention disclosed herein is directed to a stator tooth with a stator-tooth arc-cutting structure. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention.

[0027] Referring to FIG. 3, an embodiment of the stator tooth with a stator-tooth arc-cutting structure in accordance with the present invention is schematically shown. In this embodiment, the stator tooth with a stator-tooth arc-cutting structure 100 includes an arc-shaped stator yoke portion 1 and a stator tooth portion 2.

[0028] The arc-shaped stator yoke portion 1 is extended along an arc AL1. The stator tooth portion 2 includes a tooth body segment 21 and two shoe-shaped structures 22 and 23. The tooth body segment 21 is formed by protruding along a centripetal axis X from the arc-shaped stator yoke portion 1 as a unique piece, and has a first inner arc-shaped edge 211 defined with a first center of curvature CC and a first radius of curvature R. The centripetal axis X is to penetrate through a center point of first inner arc-shaped edge 2111 and the first center of curvature CC of the first inner arc-shaped edge 211. In addition, the first inner arc-shaped edge 211 further has thereof two opposite end points 2112, 2113 and a center point 2111 disposed at a center of the two end points 2112 and 2113.

[0029] Referring to FIG. 4, a stator composed of a plurality of the stator teeth of FIG. 3 is schematically shown. As shown in FIG. 3 and FIG. 4, a plurality of the stator teeth 100 with individual stator-tooth arc-cutting structures are assembled side by side to form a stator 100a. The aforesaid centripetal axis X penetrates through an axis XC of the stator 100a; i.e., the arc AL1 is a part of a circle having the axis XC as the center of circle.

[0030] Referring to FIG. 5, another view of FIG. 3 with different labels is provided for a concise explanation purpose. As shown in FIG. 3 and FIG. 5, the two shoe-shaped structures 22, 23 are extended oppositely, but symmetrically with respect to the centripetal axis X, from the same tooth body segment 21. In other words, the two shoe-shaped structures 22 and 23 are two sides of mirror-symmetry with respect to the centripetal axis X.

[0031] By having the shoe-shaped structure 22 as an example, the shoe-shaped structure 22 has a second inner arc-shaped edge 221, an inner-edge end point 222 and a root of protrusion 223. The second inner arc-shaped edge 221 is a portion of an arc AL2 extended from the end point 2113 of the first inner arc-shaped edge 211 to the inner-edge end point 222, and the root of protrusion 223 is disposed at the junction of the shoe-shaped structure 22 and the tooth body segment 21. Similarly, the shoe-shaped structure 23 has a second inner arc-shaped edge 231, an inner-edge end point 232 and a root of protrusion 233. The second inner arc-shaped edge 231 is another portion of the arc AL2 extended from the end point 2112 of the first inner arc-shaped edge 211 to the inner-edge end point 232, and the root of protrusion 2323 is disposed at the junction of the shoe-shaped structure 23 and the tooth body segment 21.

[0032] In addition, though each of the second inner arc-shaped edges 221 and 231 of the corresponding shoe-shaped structures 22 and 23 is defined by having the axis XC as the center of curvature, yet, in some other embodiments, each of the second inner arc-shaped edges 221 and 231 of the corresponding shoe-shaped structures 22 and 23 may be defined by another center of curvature (not shown in the figure).

[0033] As shown in FIG. 3 and FIG. 5, the two second inner arc-shaped edges 221, 231 are both overlapped by the same reference arc line (i.e., the arc AL2), and the reference arc line AL2 is intersected with the centripetal axis X at a center point AL2C of the two second inner arc-shaped edges 221 and 231. The center point AL2C of the two second inner arc-shaped edges 221 and 231 is spaced from another center point 2111 of the first inner arc-shaped edge 211 by a concave depth d3, and from the first center of curvature CC by a radial spacing d4. The sum of the radial spacing d4 and the concave depth d3 is equal to the first radius of curvature R. In addition, in this embodiment, the reference arc line AL2 and the arc AL1 have the same center of circle at XC.

[0034] As described above, the first center of curvature CC is spaced from each of the two inner-edge end points 222 and 232 of the corresponding shoe-shaped structures 22 and 23 by a first distance d1 (only one labeled in the figure) larger than the first radius of curvature R. In addition, the first center of curvature CC is spaced from each of the two roots of protrusion 223 and 233 of the corresponding shoe-shaped structures 22 and 23 by a second distance d2 (only one labeled in the figure) larger than the first distance d1.

[0035] Referring to FIG. 6, variations of operation torque with respect to time for a permanent magnet motor having the stator teeth with individual stator-tooth arc-cutting structures in accordance with the present invention and another permanent magnet motor having the conventional stator teeth are schematically provided.

[0036] As shown from FIG. 1 to FIG. 6, the conventional stator PA100 is formed by integrating the conventional stator teeth PA1, and then the conventional stator PA100 is used to produce a conventional permanent magnet motor (not shown in the figure). A variation of operation torque for this conventional permanent magnet motor is illustrated by Curve TC in FIG. 6. On the other hand, the stator 100a is formed by integrating the stator teeth 100 with individual stator-tooth arc-cutting structures provided by this invention, and then this stator 100a is used to produce another permanent magnet motor (not shown in the figure) in accordance with the present invention. A variation of operation torque for this permanent magnet motor of the present invention is illustrated by Curve IC in FIG. 6.

[0037] By comparing Curve TC with Curve IC, it is found that the operation torques of the permanent magnet motor having the stator 100a furnished with the stator teeth 100 with individual stator-tooth arc-cutting structures provided by the present invention are fluctuated in smaller amplitudes than that of the conventional permanent magnet motor having the stator PA100 furnished with the conventional stator teeth PAL Logically, it can be concluded as well that the effects of the cogging torque and the torque ripples at the permanent magnet motor having the stator 100a furnished with the stator teeth 100 with individual stator-tooth arc-cutting structures provided by the present invention can be substantially reduced.

[0038] In summary, the stator tooth with the stator-tooth arc-cutting structure provided by this invention is mainly to provide the stator tooth portion with a first inner arc-shaped edge and two second inner arc-shaped edges. In addition, since the radius of curvature of the first inner arc-shaped edge is smaller than that of any of the two second inner arc-shaped edges, thus the concave arc-cutting structure can be formed at the stator tooth portion by producing the first inner arc-shaped edge in the middle of the two second inner arc-shaped edges. Thereupon, through the two second inner arc-shaped edges to keep closer to the rotor, the magnetic flux between the rotor and the stator can be maintained at a high level. Simultaneously, with the existence of the first inner arc-shaped edge, the rotational resistance caused by the magnetic forcing between poles of the rotor and the stator can be substantially reduced, and thus the cogging torque and the torque ripples can be effectively inhibited.

[0039] While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.