Motor rotor core plug-in

Abstract

A rotor core for an electric motor comprises: a core stack including a plurality of laminates, each laminate including a plurality of holes formed therein, the plurality of holes of each laminate being axially aligned and defining a plurality of axial magnet slots, the axial magnet slots extending through the core stack and adapted to support a plurality of permanent magnets therein; and at least one insert extending axially through the core stack and adapted to provide radial structural stability to the plurality of laminates to prevent bending of portions of the plurality of laminates adjacent to the plurality of magnet slots due to radial forces applied to the plurality of laminates during operation of the electric motor.

Description

Technical Field

[0001] The present disclosure relates to a rotor core for an electric motor inside an automobile. Background Art

[0002] An electric machine functions as a motor by using electrical energy to produce mechanical torque through the interaction of a rotor magnetic field generated by current-carrying conductors and a stator magnetic field. Some electric motors can also act as generators, using torque to produce electrical energy. Electric machines such as interior permanent magnet motors or synchronous motors have a rotor assembly including a rotor core with magnets of alternating polarity spaced around the rotor core. Some rotor cores define slots that act as magnetic field barriers. Some of the slots may contain magnets.

[0003] Due to centrifugal forces, the stress level in the rotor core is usually at the highest point of the web or bridge of the rotor core. Increasing the thickness of the web or bridge or increasing the arc radius of the slot that partially defines the web or bridge can reduce this stress, but not without reducing torque due to increased leakage flux. Selective heat treatment of parts of the stainless steel laminate that make up the rotor core can provide additional strength without the corresponding reduction in torque due to reduced leakage flux and permeability. This means increasing torque or strength by increasing the cross-section, but without increasing torque / leakage flux because they are now impermeable. However, this approach is expensive and significantly increases the cost of the rotor.

[0004] Therefore, while the current rotor core achieves its intended purpose, there is still a need for a new and improved rotor core that is structurally complete enough to withstand the centrifugal force during the use of the motor and does not reduce torque due to increased magnetic leakage. Summary of the invention

[0005] According to several aspects of the present disclosure, a rotor core for an automotive motor includes: a core stack comprising a plurality of nearly identical laminates, each laminate including a plurality of holes formed therein, the plurality of holes of each laminate being axially aligned and defining a plurality of axial magnet slots, the axial magnet slots extending through the core stack and being suitable for supporting a plurality of permanent magnets therein; and at least one insert extending axially through the core stack and being suitable for providing radial structural stability to the plurality of laminates to prevent bending of portions of the plurality of laminates adjacent to the plurality of magnet slots due to radial forces applied to the plurality of laminates during operation of the motor.

[0006] According to another aspect, each of the at least one insert comprises a single beam extending axially along the entire length of the core stack.

[0007] According to another aspect, each of the at least one insert includes a plurality of beam segments axially aligned and extending axially along the entire length of the core stack, each beam segment extending through a portion of the plurality of laminate sheets.

[0008] According to another aspect, each of the at least one insert includes a plurality of beam sheets axially aligned and extending axially along the entire length of the core stack, the beam sheets of each of the at least one insert being positioned in each of the plurality of laminate sheets.

[0009] According to another aspect, each of the at least one insert is made entirely of ferrous material.

[0010] According to another aspect, each of the at least one insert comprises a portion of a ferrous material and a portion of an austenitic material.

[0011] According to another aspect, the austenitic portion of each of the at least one insert is located between adjacent magnet slots within the core stack.

[0012] According to another aspect, each of the at least one insert is made entirely of non-ferrous material.

[0013] According to another aspect, each of the at least one insert extends radially between an inner diameter of the core stack and an outer diameter of the core stack, and each of the plurality of laminate sheets includes a plurality of pie-shaped radial segments located between adjacent pairs of the at least one insert.

[0014] According to another aspect, each of the plurality of laminate sheets is a single piece and includes at least one radial slot, one of the at least one insert being positioned in each of the at least one radial slot.

[0015] According to another aspect, each of the at least one insert is adapted to provide a compressive preload to the core stack to counteract radial forces experienced by portions of the plurality of lamination sheets adjacent the plurality of magnet slots during operation of the rotor.

[0016] According to another aspect, each of the at least one insert is press-fit or shrink-fit within the plurality of laminates.

[0017] According to another aspect, each of the at least one insert extends radially inwardly and engages a rotor shaft extending axially through the core stack.

[0018] According to another aspect, each of the at least one insert includes a feature adapted to engage radially outward portions of the plurality of laminates adjacent the plurality of magnet slots to radially support portions of the plurality of laminates adjacent the plurality of magnet slots during operation of the rotor.

[0019] Further areas of applicability will become apparent from the description provided herein.It should be understood that the foregoing description and specific examples are for illustration purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0021] Figure 1 is a perspective view of a core stack of a rotor core according to an exemplary embodiment of the present disclosure;

[0022] Figure 2A Yes Figure 1 An end view of the core stack without the insert is shown;

[0023] Figure 2B Yes Figure 1 An end view of the core stack with inserts shown;

[0024] Figure 2C yes Figure 2B A magnified view of a portion of it;

[0025] Figure 3A is an end view of a plug-in according to an exemplary embodiment of the present disclosure;

[0026] Figure 3B is a perspective view of a one-piece insert according to an exemplary embodiment;

[0027] Figure 4 is a perspective view of an insert including a beam segment according to another exemplary embodiment;

[0028] Figure 5 is a perspective view of a stacked rotor having a laminate partially removed and including a beam sheet of an insert according to another exemplary embodiment;

[0029] Fig. 6A is an end view of a rotor core having an insert extending from an inner diameter of the core stack to an outer diameter of the core stack according to another exemplary embodiment;

[0030] Figure 6B is an end view of a rotor core having an insert extending inwardly from an outer diameter of the core stack and engaging a slot formed in a rotor shaft;

[0031] Figure 7 is a cross-sectional view of an insert having a ferrous portion and an austenitic portion according to another exemplary embodiment; and

[0032] Figure 8 Is such as Figure 7 An enlarged view of a portion of the core stack of the insert is shown. DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0034] refer to Figure 1 A rotor core 10 for an automotive motor includes a core stack 12 comprising a plurality of identical laminates 14. The rotor core 12 is from an electric motor inside an automobile, such as, but not limited to, a starter, an alternator, a starter / generator, or other electric motor. Each laminate 14 is made of a ferrous material, such as, but not limited to, steel or non-oriented electrical steel. The laminates 14 are disposed adjacent to each other along a central axis 16 to define the core stack 12.

[0035] refer to Figure 2A , each lamination plate 14 includes a plurality of holes 17 formed therein. The lamination plates 14 are aligned relative to each other along the central axis 16 such that the holes 17 of each lamination plate 14 are axially aligned with corresponding holes 17 in adjacent lamination plates 14 to define a plurality of magnet slots 18. The magnet slots 18 extend axially through the core stack 12 parallel to the central axis 16. The magnet slots 18 are adapted to support a plurality of permanent magnets therein.

[0036] In such Figure 1 and Figure 2A In the exemplary embodiment shown, the core stack 12 includes eight symmetrical groups of magnet slots 18 evenly spaced circumferentially around the core stack 12. Each group of magnet slots 18 includes four magnet slots 18 oriented in a V-shape. Each group of magnet slots 18 also defines an outer flux guide 20, an intermediate flux guide 22, and an inner flux guide 24. The outer, intermediate, and inner flux guides 20, 22, 24 provide paths for electromagnetic flux currents during operation of the rotor core 10.

[0037] refer to Figure 1 and Figure 2B , the core stack 12 includes at least one insert 26 extending axially through the core stack 12. The at least one insert 26 is adapted to provide radial structural stability to the plurality of laminations 14 to prevent bending of portions of the plurality of laminations 14 adjacent to the plurality of magnet slots 18 due to radial forces exerted on the plurality of laminations 14 during operation of the rotor core 10. More specifically, an insert 26 is associated with each group of magnet slots 18. As shown, the core stack 12 includes eight inserts 26. The inserts 26 are adapted to provide support for the outer flux guide 20, the intermediate flux guide 22, and the inner flux guide 24 to prevent the outer flux guide, the intermediate flux guide, and the inner flux guide 20, 22, 24 from bending outwardly due to centrifugal forces when the rotor core 10 rotates during operation.

[0038] refer to Figure 2C and Figure 3A, each of the at least one insert 26 includes a feature adapted to engage a radially outward portion of the plurality of laminates 14 adjacent to the plurality of magnet slots 18. In the exemplary embodiment shown, each insert 26 includes a first distal end 28, a second distal end 30, and a body portion 32 extending between the first distal end 28 and the second distal end 30. The first and second distal ends 28, 30 each include an outwardly flared flange portion 34, 36 and a tab 38 extending from a side 40 of the body portion 32. The flange portion 34 of the first distal end 28 includes a radially inward surface 42 that engages a radially outward portion 44 of the outer magnetic flux guide 20. The flange portion 36 of the second distal end 30 includes a radially outward surface 46 that engages a radially inward portion 48 of the laminate 14 near the inner diameter 50 of the core stack 12. The tab 38 extends circumferentially outward from the body portion 32 of the insert 26 and engages a radially outward surface 52 of the intermediate magnetic flux guide 22.

[0039] refer to Figure 3B In an exemplary embodiment, each insert 26 comprises a single beam 26' extending axially along the entire length 54 of the core stack 12. Figure 4 In another exemplary embodiment, each insert 26 includes a plurality of beam segments 26" that are axially aligned and extend axially along the entire length 54 of the core stack 12. As shown, the insert 26 includes three beam segments 26". Each beam segment 26" extends through a portion of the plurality of laminate sheets 14 and, when inserted into the core stack 12, extends axially end-to-end through the entire length 54 of the core stack 12. Figure 5 , where one laminate 14 is shown as being partially removed from the core stack 12. In another exemplary embodiment, each plug-in 26 includes a plurality of beam sheets 26'" that are axially aligned and extend axially along the entire length 54 of the core stack 12. Each individual beam sheet 26'" is approximately the same thickness as one laminate 14. One beam sheet 26'" of each plug-in 26 is positioned within each laminate 14. When the laminates 14 are axially aligned along the central axis 16 of the core stack 12, each beam sheet 26'" is aligned in a row to form the plug-in 26. As shown, each laminate 14 includes eight beam sheets 26'" positioned therein. When the laminates 14 are axially aligned along the central axis 16 of the core stack 12, each beam sheet 26'" is aligned in a row to form eight plug-ins 26.

[0040] Reference again Figure 1 , Figure 2B and Figure 2CIn an exemplary embodiment, each laminate 14 is a single piece and includes at least one radial slot 56. As shown, each laminate 14 includes eight radial slots 56. The laminates 14 are aligned relative to each other along the central axis 16 so that the radial slots 56 of each laminate 14 are axially aligned with corresponding radial slots 56 in adjacent laminates 14 and the inserts 26 are positioned therein.

[0041] like Figure 1 , Figure 2B and Figure 2C As shown, the inserts 26 extend radially between the outer diameter 58 of the core stack 12 and the inner diameter 50 of the core stack 12. The first distal end 28 of each insert 26 does not extend all the way outward to the outer diameter 58 of the core stack 12, and the second distal end 30 of each insert 26 does not extend all the way inward to the inner diameter 50 of the core stack 12.

[0042] refer to Fig. 6A In another exemplary embodiment, each insert 26 extends radially between the inner diameter 50 of the core stack 12 and the outer diameter 58 of the core stack 12. The first distal end 28 of each insert 26 extends outwardly to the outer diameter 58 of the core stack 12, and the second distal end 30 of each insert 26 extends inwardly to the inner diameter 50 of the core stack 12. Each laminate 14 includes a plurality of pie-shaped radial segments 60 positioned between adjacent pairs of inserts 26.

[0043] refer to Figure 6B In another exemplary embodiment, each insert 26 extends radially between the inner diameter 50 of the core stack 12 and the outer diameter 58 of the core stack 12. The first distal end 28 of each insert 26 extends all the way to the outer diameter 58 of the core stack 12, and the second distal end 30 of each insert 26 extends inboard of the inner diameter 50 of the core stack 12. The flange portion 36 of the second distal end 30 of each insert 26 is received in a groove 68 formed in the rotor shaft 70, which extends axially through the core stack 12. The flange portion 36 of the second distal end 30 includes a radially outward surface 46 that engages the radially inward portion 49 of the rotor shaft 70. Each laminate 14 includes a plurality of pie-shaped radial segments 60 located between adjacent pairs of inserts 26.

[0044] In another exemplary embodiment, each insert 26 is adapted to provide a compressive preload on the core stack 12 to counteract radial forces experienced by portions of the plurality of laminations adjacent to the plurality of magnet slots during operation of the rotor. The compressive preload generates a compressive force on the core stack 12, such as Figure 2CAs shown by arrows 62 in FIG. 1 . In one example, each insert 26 is press-fit into a plurality of laminates 14. Each insert 26 is sized such that, when the insert 26 is positioned within the laminates 14 of the core stack 12, the radially inward surface 42 of the first distal end 28 has little interference fit with the radially outward portion 44 of the outer flux guide 20. Similarly, the radially outward surface 46 of the second distal end 30 has little interference fit with the radially inward portion 48 of the laminate 14 near the inner diameter 50 of the core stack 12. When the insert 26 is pressed into the core stack 12, or when the beam piece 26″′ of the insert 26 is pressed into the laminate 14, the engagement of these interference fits causes the insert 26 to apply a compressive preload to the laminate 14, as shown in FIG. Figure 2C As shown by arrow 62 in FIG.

[0045] In another example, each insert 26 is shrink fit within a plurality of laminates 14. Each insert 26 is sized such that when the insert 26 is positioned within the laminates 14 of the core stack 12, the radially inward surface 42 of the first distal end 28 has a minimal interference fit with the radially outward portion 44 of the outer magnetic flux guide 20. Similarly, the radially outward surface 46 of the second distal end 30 has a minimal interference fit with the radially inward portion 48 of the laminates 14 near the inner diameter 50 of the core stack 12. The insert 26 and core stack 12 or beam piece 26'' and laminate 14 are heated to a controlled temperature. The thermal expansion characteristics of the insert 26 and laminate 14 result in the insert 26 being easily positioned within the core stack 12 as the core stack 12 and insert 26 are strategically heated and cooled. Likewise, the thermal expansion characteristics of the beam piece 26'' and laminate 14 result in the beam piece 26'' being easily positioned within the laminate 14 as the laminate 14 and beam piece 26'' are strategically heated and cooled. As the material cools, the interference fit engagement between the insert 26 and laminate 14 results in the insert 26 applying a compressive preload to the laminate 14 and core stack 12, as shown in FIG. Figure 2C As shown by arrow 62 in FIG.

[0046] refer to Figure 3A and 3B In an exemplary embodiment, each insert 26 is made entirely of austenite or non-magnetic material. When ferrous or magnetic material interconnects two adjacent permanent magnets, the efficiency of the flux current within the rotor core 10 is lost. Inserts made entirely of non-magnetic material prevent this loss and allow the rotor core 10 to be designed with smaller magnets, thereby reducing costs. In another exemplary embodiment, each insert 26 is made entirely of high-strength ferrous material. In this case, the rotor assembly can rotate at a higher speed without increasing leakage flux.

[0047] refer to Figure 7 and Figure 8In another exemplary embodiment, each insert 26 is made of a dual phase material. Each insert 26 includes a portion 64 made of a ferrous or magnetic material and a portion 66 made of an austenitic or non-magnetic material. The austenitic portion 66 of each insert 26 is located between adjacent magnet slots 18 within the core stack 12 to avoid efficiency loss.

[0048] The rotor core disclosed herein has the following advantages: providing a rotor core having structural integrity and sufficient to withstand the centrifugal force during the use of the motor without reducing the torque due to the increase of leakage flux caused by the traditional rotor core strengthening method. The motor using the rotor core disclosed herein can use smaller permanent magnets to provide the same motor torque as the rotor core using larger permanent magnets, thereby improving the cost and packaging characteristics of the rotor core, or alternatively, the motor using the rotor core disclosed herein will bring an increase in motor torque, power and operating speed.

[0049] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are within the scope of the present disclosure. These variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A rotor core for an automotive motor, comprising: a core stack comprising a plurality of laminates; each lamination plate including a plurality of apertures formed therein, the plurality of apertures of each lamination plate being axially aligned and defining a plurality of axial magnet slots extending through the core stack and adapted to support a plurality of permanent magnets therein; as well as At least one insert extending axially through the core stack and adapted to provide radial structural stability to the plurality of laminates to prevent bending of portions of the plurality of laminates adjacent to the plurality of magnet slots due to radial forces applied to the plurality of laminates during operation of the motor, each of the at least one insert comprising a portion made of a ferrous material and a portion made of a non-ferrous material.

2. The rotor core according to claim 1, wherein: Each of the at least one insert comprises a single beam extending axially along the entire length of the core stack.

3. The rotor core according to claim 1, wherein: Each of the at least one insert includes a plurality of beam segments axially aligned and extending axially along the entire length of the core stack, each beam segment extending through a portion of the plurality of laminate sheets.

4. The rotor core according to claim 1, wherein: Each of the at least one insert includes a plurality of beam sheets axially aligned and extending axially along the entire length of the core stack, one beam sheet of each of the at least one insert being positioned in each of the plurality of laminate sheets.

5. The rotor core according to claim 1, wherein: The austenitic portion of each of the at least one insert is located between adjacent magnet slots within the core stack.

6. The rotor core according to claim 1, wherein: Each of the at least one insert is made entirely of ferrous material.

7. The rotor core according to claim 1, wherein: Each of the at least one insert is made entirely of non-ferrous material.

8. The rotor core according to claim 1, wherein: Each of the at least one insert extends radially between an inner diameter of the core stack and an outer diameter of the core stack, and each of the plurality of laminate sheets includes a plurality of pie-shaped radial segments located between adjacent pairs of the at least one insert.

9. The rotor core according to claim 8, wherein: Each of the at least one insert extends radially inwardly and engages a rotor shaft extending axially through the core stack.

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