Machine with internal permanent magnets, featuring a rotor with a mixture of rare-earth magnets and ferrite magnets

Abstract

Machine (20) with internal permanent magnets (38, 66), comprising: a wound stator (22); a rotor core (28) comprising a ferrite pole (30) defining several first pole cavities (36) and a rare-earth pole (32) defining several second pole cavities (64), wherein the rotor core (28) interacts magnetically with the wound stator (22) for rotation about a central axis of rotation (26) and wherein the ferrite pole (30) and the rare-earth pole (32) are arranged in an alternating circumferential relationship about the central axis of rotation (26); several ferrite magnets (38), wherein one of the several ferrite magnets (38) is arranged in each of the first pole cavities (36) of the ferrite pole (30); and several rare-earth magnets (66), wherein one of the several rare-earth magnets (66) is arranged in each of the second pole cavities (64) of the rare-earth pole (32).

Description

TECHNICAL AREA

[0001] The invention relates generally to a machine with internal permanent magnets and in particular to a rotor arrangement for the machine with internal permanent magnets. BACKGROUND

[0002] Internal permanent magnet (IPM) machines contain a rotor with multiple magnets of alternating polarity arranged around an outer circumference. The rotor rotates within a stator containing multiple windings. The rotor interacts magnetically with the stator to generate rotation around an axis of rotation. An IPM machine can use either ferrite magnets or rare-earth magnets, such as NdFeB, in the rotor. Compared to rare-earth magnets, ferrite magnets are less expensive but produce lower power when used in identically designed IPM machines.

[0003] German patent application DE 103 08 282 A1 discloses a rotor with internal permanent magnets, wherein the permanent magnets comprise high-energy and low-energy magnetic materials. To enable remagnetization of the permanent magnets, the permanent magnets with high-energy magnetic material are arranged close to a surface of the rotor, and the permanent magnets with low-energy magnetic material are arranged in the central and inner regions. SUMMARY

[0004] A machine with internal permanent magnets contains a wound stator and a rotor core. The rotor core contains a ferrite pole and a rare-earth pole. The ferrite pole defines several first pole cavities, and the rare-earth pole defines several second pole cavities. For rotation around a central axis of rotation, the rotor core interacts magnetically with the wound stator. The machine with internal permanent magnets further contains several ferrite magnets and several rare-earth magnets. One of the several ferrite magnets is located in each of the first pole cavities of the ferrite pole, and one of the several rare-earth magnets is located in each of the second pole cavities of the rare-earth pole.

[0005] A rotor assembly for a machine with internal permanent magnets is also provided. The rotor assembly includes a rotor core arranged concentrically around a central axis of rotation. The rotor core contains multiple ferrite poles and multiple rare-earth poles. Each of the multiple ferrite poles defines multiple first pole cavities, and each of the multiple rare-earth poles defines multiple second pole cavities. The rotor assembly further includes multiple ferrite magnets and multiple rare-earth magnets. One of the multiple ferrite magnets is located in each of the first pole cavities of the ferrite pole, and one of the multiple rare-earth magnets is located in each of the second pole cavities of the rare-earth pole. The multiple ferrite magnets of the ferrite pole are arranged in multiple rows, radially spaced from one another relative to the central axis of rotation.Each of the multiple first pole cavities and each of the multiple ferrite magnets in the ferrite pole contains a cross-section perpendicular to the central axis of rotation, defining a curved shape with an arc center. The arc centers of each of the multiple ferrite magnets of the ferrite pole are arranged concentrically relative to each other. Each of the multiple rare-earth magnets of the rare-earth pole contains a cross-section perpendicular to the central axis of rotation, defining a rectangular shape. The multiple rare-earth magnets of the rare-earth pole are arranged in multiple layers. Each layer of the rare-earth magnets of the rare-earth pole defines a concave V-shape perpendicular to the central axis of rotation.

[0006] Consequently, the rotor assembly incorporates both ferrite magnets and rare-earth magnets arranged in alternating poles in a configuration specifically designed to minimize the volume of the rare-earth magnets while essentially maintaining the performance of an equivalent rotor assembly consisting solely of rare-earth magnets. Minimizing the volume of the rare-earth magnets used in the rotor assembly reduces its manufacturing cost compared to one using only rare-earth magnets, without any significant loss of performance.

[0007] The foregoing features and advantages and other features and advantages of the present invention will be readily apparent from the following detailed description of the best ways of carrying out the invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic cross-sectional view of a machine with internal permanent magnets. Fig. Figure 2 is an enlarged schematic partial cross-sectional view of the machine with internal permanent magnets. DETAILED DESCRIPTION

[0008] The person skilled in the art will recognize that terms such as "above", "below", "upwards", "downwards", "top", "bottom", etc. are used to describe the figures and do not represent any limitations on the scope of the invention as defined by the attached claims.

[0009] With reference to the figures, where the same reference numerals denote the same parts in the multiple views, a machine with internal permanent magnets is generally shown at 20. The IPM machine 20 may include an electric motor or other similar device, but is not limited to this.

[0010] With reference to Fig. In Figure 1, the IPM machine 20 comprises a wound stator 22 and a rotor assembly 24. The rotor assembly 24 interacts magnetically with the wound stator 22 to rotate relative to the wound stator 22 about a central axis of rotation 26. The rotor assembly 24 includes a rotor core 28. The central axis of rotation 26 is located at the center point of the rotor core 28. The rotor core 28 includes at least one ferrite pole 30 and at least one rare-earth pole 32. Preferably, the rotor assembly 24 includes multiple ferrite poles 30 and multiple rare-earth poles 32. The number of ferrite poles 30 is equal to the number of rare-earth poles 32. The ferrite poles 30 and the rare-earth poles 32 are arranged radially around the central axis of rotation 26 in an alternating relationship.If the rotor arrangement 24 contains several ferrite poles 30 and several rare-earth poles 32, each ferrite pole 30 is arranged circumferentially between two rare-earth poles 32, and each rare-earth pole 32 is arranged circumferentially between two ferrite poles 30. Fig. Figure 1 represents an IPM machine 20, which has a total of 12 poles, comprising 6 ferrite poles 30 and 6 rare-earth poles 32. However, it should be noted that the total number of poles of the IPM machine 20 differs from that shown in Figure 1. Fig. The exemplary embodiment shown in 1 may differ.

[0011] With reference to Fig. 2 Each of the ferrite poles 30 contains a first pole axis 34, which extends radially outwards from the central axis of rotation 26 through the center of each respective ferrite pole 30. Each of the ferrite poles 30 defines several first pole cavities 36.

[0012] Each ferrite pole 30 contains an equal number of first pole cavities 36 arranged in an identical orientation. The first pole cavities 36 extend three-dimensionally into the rotor core 28. The first pole cavities 36 may include recesses, grooves, etc. The rotor assembly 24 further contains several ferrite magnets 38, with one of the several ferrite magnets 38 being arranged in each of the first pole cavities 36. It can be noted that the ferrite magnets 38 and the first pole cavities 36 have substantially corresponding cross-sectional shapes perpendicular to the central axis of rotation 26. The ferrite magnets 38 may completely fill the first pole cavities 36, or they may leave one or more air gaps between each of the ferrite magnets 38 and its respective first pole cavities.The wound stator 22 contains several windings 40 which interact magnetically with the ferrite magnets 38 which are arranged in the first pole cavities 36 of the ferrite poles 30 in order to generate torque and to cause a rotation of the rotor core 28 around the central axis of rotation 26 relative to the wound stator 22.

[0013] The shape and orientation of the ferrite magnets 38 and the first pole cavities 36 are described below with reference to Fig. 2 described in detail. Although the description provided here refers to only a single ferrite pole 30, which is in Fig. As shown in Figure 2, which is limited, it can be observed that the shape and orientation of the ferrite magnets 38 and their respective first pole cavities 36 are identical to the orientation shown here with reference to the single ferrite pole 30, which is in Fig. 2 is shown, described.

[0014] Each of the first pole cavities 36 and their respective ferrite magnets 38 arranged therein has a cross-section perpendicular to the central axis of rotation 26, defining a curved shape with an arc center. The magnets of each ferrite pole 30 are preferably arranged symmetrically around their respective first pole axis 34, such that the arc centers of each of the ferrite magnets 38 of each ferrite pole 30 are concentric with each other, i.e., all arc centers of all ferrite magnets 38 of each ferrite pole 30 use a common radial center point 42.

[0015] The first pole cavities 36 of each ferrite pole 30 are arranged in one or more rows, spaced radially apart from each other relative to the central axis of rotation 26. Each row is radially spaced from the other rows. As shown in the figures, the first pole cavities 36 of each ferrite pole 30 define three rows: a first row 44, or the outermost row relative to the central axis of rotation 26; a second row 46, or the radially middle row; and a third row 48, or the innermost row relative to the axis of rotation 26. Consequently, the third row 48 is closer to the central axis of rotation 26 than the second row 46, and the second row 46 is closer to the central axis of rotation 26 than the first row 44. It should be noted that the first pole cavities 36 of each ferrite pole 30 can define only a single row, or they can define more than the three rows shown.Furthermore, each row can contain any number of first pole cavities 36. As shown, the first row 44 contains two first pole cavities 36, the second row 46 contains three first pole cavities 36, and the third row 48 contains three first pole cavities 36. However, the number of first pole cavities 36 in each row can differ from the exemplary embodiment shown.

[0016] Each ferrite magnet 38 of the first row 44 has a first radius 50, each ferrite magnet 38 of the second row 46 has a second radius 52, and each ferrite magnet 38 of the third row 48 has a third radius 54. The third radius 54 is larger than the second radius 52, and the second radius 52 is larger than the first radius 50. Preferably, the first radius 50, the second radius 52, and the third radius 54 each have a value in the range of 8 mm to 25 mm. However, it should be noted that the value of the first radius 50, the second radius 52, and the third radius 54 may deviate from the exemplary range provided here.

[0017] Each layer of the ferrite magnets 38 of each ferrite pole 30 comprises a thickness. As in Fig. As shown in Figure 2, the first row 44 of ferrite magnets 38 has a first thickness 56, the second row 46 of ferrite magnets 38 has a second thickness 58, and the third row 48 of ferrite magnets 38 has a third thickness 60. Consequently, each ferrite magnet 38 in each row has the same thickness, but the thickness of the ferrite magnets 38 in all other rows can differ. As shown, the thickness of the ferrite magnets 38 in each row decreases with increasing radial distance from the central axis of rotation 26. Consequently, the first thickness 56 of the first row 44 of ferrite magnets 38 is smaller than the second thickness 58 of the second row 46 of ferrite magnets 38, and the second thickness 58 of the second row 46 of ferrite magnets 38 is smaller than the third thickness 60 of the third row 48 of ferrite magnets 38.Preferably, the first thickness 56 for the first row 44 of the ferrite magnets 38, the second thickness 58 for the second row 46 of the ferrite magnets 38, and the third thickness 60 for the third row 48 of the ferrite magnets 38 are in the range of 2 mm to 5 mm. However, it should be noted that the values ​​of the first thickness 56, the second thickness 58, and the third thickness 60 may deviate from the exemplary range provided here.

[0018] Each of the rare-earth poles 32 contains a second polar axis 62, which extends radially outward from the central rotation axis 26 through the center of each respective rare-earth pole 32. Each of the rare-earth poles 32 defines several second polar cavities 64.

[0019] Each rare-earth pole 32 contains an equal number of second pole cavities 64 arranged in an identical orientation. The second pole cavities 64 extend three-dimensionally into the rotor core 28. The second pole cavities 64 may include recesses, grooves, etc. The rotor assembly 24 further contains several rare-earth magnets 66, with one of the rare-earth magnets 66 arranged in each of the second pole cavities 64. It can be noted that the rare-earth magnets 66 and the second pole cavities 64 have substantially corresponding cross-sectional shapes perpendicular to the central axis of rotation 26. The rare-earth magnets 66 may completely fill the second pole cavities 64, or they may leave one or more air gaps between the rare-earth magnets 66 and the respective second pole cavities 64.The windings 40 of the wound stator 22 interact magnetically with the rare-earth magnets 66, which are arranged in the second pole cavities 64 of the rare-earth poles 32, to generate torque and to cause a rotation of the rotor core 28 around the central axis of rotation 26 relative to the wound stator 22.

[0020] The rare-earth magnets 66 can contain any type of rare-earth magnetic material suitable for use in the IPM machine 20. For example, each of the rare-earth magnets 66 can be made of and contain neodymium-iron-boron (NdFeB), but is not limited to this. The flux of the strong rare-earth magnets 66 from one of the rare-earth poles 32 enhances the flux of the ferrite magnets 38 of the circumferentially adjacent ferrite poles 30, thereby lowering the demagnetization potential of the ferrite magnets 38 in the adjacent ferrite poles 30.

[0021] The shape and orientation of the rare-earth magnets 66 and the second pole cavities 64 are described below with reference to Fig. 2 described in detail. Although the description provided here refers to only a single rare-earth pole 32, which is in Fig. As shown in Figure 2, which is limited, it can be observed that the shape and orientation of the rare-earth magnets 66 and their respective second pole cavities 64 are identical to the orientation shown here with reference to the single rare-earth pole 32, which is in Fig. 2 is shown, described.

[0022] With reference to Fig. 2 All second pole cavities 64 and their respective rare-earth magnets 66 arranged therein contain a cross-section perpendicular to the central axis of rotation 26, defining a rectangular shape. The rare-earth magnets 66 of all rare-earth poles 32 are arranged in at least one layer that defines a concave V-shape perpendicular to the central axis of rotation 26, with a vertex 68 of the concave V-shape located on the second pole axis 62.

[0023] The rare-earth magnets 66 of each of the rare-earth poles 32 are preferably arranged symmetrically around the second pole axis 62 of each respective rare-earth pole 32. The rare-earth magnets 66 of each rare-earth pole 32 are arranged to define a first group 70 of the rare-earth magnets 66 and a second group 72 of the rare-earth magnets 66. The first group 70 of the rare-earth magnets 66 is arranged on a first side 74 of the second pole axis 62, and the second group 72 of the rare-earth magnets 66 is arranged on a second side 76 of the second pole axis 62. The first group 70 of rare-earth magnets 66 and the second group 72 of rare-earth magnets 66 are preferably mirror images of each other along the second polar axis 62. All rare-earth magnets 66 of the first group 70 are arranged completely on the first side 74 of the second polar axis 62.Similarly, all rare-earth magnets 66 of the second group 72 are arranged completely on the second side 76 of the second polar axis 62.

[0024] As mentioned above, the second polar cavities 64 of the rare-earth poles 32 are arranged in one or more layers. If the second polar cavities 64 of each rare-earth pole 32 are arranged in multiple layers, then the layers are radially spaced apart relative to the central axis of rotation 26. As shown in the figures, the second polar cavities 64 of each rare-earth pole 32 are arranged to define two layers: a first layer 78, or an outermost layer radially relative to the central axis of rotation 26, and a second layer 80, or an innermost layer radially relative to the central axis of rotation 26. Consequently, the first layer 78 is arranged radially farther from the central axis of rotation 26 than the second layer 80. It should be noted that the second polar cavities 64 can define only a single layer, or they can define more than the two layers shown.Furthermore, each layer therein can contain any number of second pole cavities 64. As shown, the first layer 78 contains two second pole cavities 64 and the second layer 80 contains two second pole cavities 64. However, the number of second pole cavities 64 in each layer of each rare-earth pole 32 can differ from the exemplary embodiment shown.

[0025] Each layer of the rare-earth magnets 66 of each rare-earth pole 32 has a thickness. As in Fig.As shown in Figure 2, the first layer 78 has a first thickness 82, and the second layer 80 has a second thickness 84. Consequently, each magnet in each layer has the same thickness. The thickness of the magnets in each layer is different. As shown, the thickness of the magnets in each layer decreases with increasing radial distance from the central axis of rotation 26. Consequently, the first thickness 82 of the first layer 78 of magnets is less than the second thickness 84 of the second layer 80 of magnets. Preferably, the first thickness 82 for layer 78 of the rare-earth magnets 66 and the second thickness 84 of the second layer 80 of the rare-earth magnets 66 are in the range of 2 mm to 5 mm. However, it should be noted that the value of the first thickness 82 and the second thickness 84 of the rare-earth magnets 66 can deviate from the exemplary range provided here.

[0026] The detailed description and the drawings or figures support and describe the invention, but the scope of the invention is defined only by the claims. Although some of the best ways and other embodiments for carrying out the claimed invention have been described in detail, there are various alternative designs and embodiments for putting the invention defined in the accompanying claims into practice.

Claims

[1] Machine (20) with internal permanent magnets (38, 66), comprising: a wound stator (22); a rotor core (28) including a ferrite pole (30) defining a plurality of first pole cavities (36) and a rare earth pole (32) defining a plurality of second pole cavities (64), wherein the rotor core (28) magnetically interacts with the wound stator (22) for rotation about a central axis of rotation (26), and wherein the ferrite pole (30) and the rare earth pole (32) are arranged in an alternating relationship circumferentially about the central axis of rotation (26); a plurality of ferrite magnets (38), wherein one of the plurality of ferrite magnets (38) is arranged in each of the first pole cavities (36) of the ferrite pole (30); and a plurality of rare earth magnets (66), wherein one of the plurality of rare earth magnets (66) is arranged in each of the second pole cavities (64) of the rare earth pole (32). [2] Machine (20) with internal permanent magnets (38, 66) according to claim 1, wherein each of the plurality of ferrite magnets (38) in the ferrite pole (30) includes a cross-section perpendicular to the central axis of rotation (26) defining a curved shape with an arc center. [3] Machine (20) with internal permanent magnets (38, 66) according to claim 2, wherein the arc centers of each of the plurality of ferrite magnets (38) of the ferrite pole (30) are concentric with each other. [4] Machine (20) with internal permanent magnets (38, 66) according to claim 3, wherein the plurality of ferrite magnets (38) of the ferrite pole (30) are arranged in a plurality of rows (44, 46, 48) which are radially spaced from one another relative to the central axis of rotation (26). [5] Machine (20) with internal permanent magnets (38, 66) according to claim 4, wherein the plurality of rows (44, 46, 48) of ferrite magnets (38) comprise a first row (44), a second row (46) and a third row (48), the third row (48) being closer to the central axis of rotation (26) than the second row (46) and the second row (46) being closer to the central axis of rotation (26) than the first row (44). [6] Machine (20) with internal permanent magnets (38, 66) according to claim 5, wherein the first row (44), the second row (46) and the third row (48) of ferrite magnets (38) in the ferrite pole (30) each define a different thickness (56, 58, 60). [7] Machine (20) with internal permanent magnets (38, 66) according to claim 6, wherein the thickness (56, 58, 60) of the ferrite magnets (38) in the first row (44), the second row (46) and the third row (48) of ferrite magnets (38) each decreases with an increase in the radial distance from the central axis of rotation (26). [8] Machine (20) with internal permanent magnets (38, 66) according to claim 1, wherein each of the plurality of rare earth magnets (66) of the rare earth pole (32) includes a cross-section perpendicular to the central axis of rotation (26) defining a rectangular shape. [9] Machine (20) with internal permanent magnets (38, 66) according to claim 8, wherein the rare earth magnets (66) of the rare earth pole (32) are arranged around a second pole axis (62) to define a first group (70) of the rare earth magnets (66) arranged on a first side (74) of the second pole axis (62) and a second group (72) of the rare earth magnets (66) arranged on a second side (76) of the second pole axis (62). [10] Machine (20) with internal permanent magnets (38, 66) according to claim 9, wherein the first group (70) of rare earth magnets (66) and the second group (72) of rare earth magnets (66) are mirror images of each other along the second pole axis (62). [11] Machine (20) with internal permanent magnets (38, 66) according to claim 10, wherein the plurality of rare earth magnets (66) of the rare earth pole (32) are arranged in at least one layer (78, 80) defining a concave V-shape perpendicular to the central rotation axis (26), an apex (68) of the concave V-shape being arranged on the second pole axis (62).

Images