rotor

Abstract

The present application relates to a rotor. The rotor includes: a rotor core formed by stacking electromagnetic steel sheets having anisotropy, the anisotropy meaning that magnetic characteristics of the electromagnetic steel sheets in a first direction along a rolling direction are different from magnetic characteristics of the electromagnetic steel sheets in a second direction obtained by rotating the first direction by 90°, the rotor core having 4n magnetic pole portions formed in a circumferential direction; and magnets installed in the rotor core in each of the magnetic pole portions. The 4n magnetic pole portions include first magnetic pole portions formed in a region including the first direction and second magnetic pole portions formed in a region including the second direction, and a total magnetic flux of the magnets per pole in the second magnetic pole portions is greater than a total magnetic flux of the magnets per pole in the first magnetic pole portions.

Description

Technical Field

[0001] This disclosure relates to a rotor. Background Technology

[0002] Traditionally, a rotor for a rotating electric motor is known, which includes a rotor core formed by stacking multiple electromagnetic steel plates, as disclosed in Japanese Patent Application Publication No. 2015-033167 (Patent Document 1). Summary of the Invention

[0003] Meanwhile, the electromagnetic steel sheet used for the rotor core is rolled during its manufacturing process and can be anisotropic, meaning its magnetic properties vary depending on its orientation relative to the rolling direction. This anisotropy also affects the rotor core formed by stacking electromagnetic steel sheets. In the rotor core, multiple magnetic pole portions are formed along the circumferential direction, and due to the anisotropy of the electromagnetic steel sheet, these pole portions have different magnetic properties. That is, in a rotor core using electromagnetic steel sheets, magnetic pole portions with different magnetic properties are arranged along the rotation direction. Therefore, when the rotor core rotates, torque pulsations, which indicate the amount of torque fluctuation, may increase.

[0004] Therefore, one object of this disclosure is to reduce torque pulsation in a rotor having a rotor core formed by stacking electromagnetic steel plates.

[0005] In one aspect of this disclosure, a rotor is provided, comprising: a rotor core formed by stacking anisotropic electromagnetic steel sheets, the anisotropy meaning that the magnetic properties of each of the electromagnetic steel sheets in a first direction along a rolling direction are different from the magnetic properties of each of the electromagnetic steel sheets in a second direction obtained by rotating the first direction by 90°, the rotor core having 4n (n is a natural number) magnetic pole portions formed along a circumferential direction; and a magnet, wherein the magnet is mounted in the rotor core in each of the magnetic pole portions, wherein the 4n magnetic pole portions include a first magnetic pole portion and a second magnetic pole portion, the first magnetic pole portion being formed in a region including the first direction, the second magnetic pole portion being formed in a region including the second direction, and wherein the total magnetic flux of the magnet in each pole of the second magnetic pole portion is greater than the total magnetic flux of the magnet in each pole of the first magnetic pole portion.

[0006] In the aforementioned rotor, in a cross-section orthogonal to the stacking direction of the electromagnetic steel plates, the total cross-sectional area of ​​the magnets of each pole in the second magnetic pole section can be greater than the total cross-sectional area of ​​the magnets of each pole in the first magnetic pole section.

[0007] In the rotor described above, the number of magnets in each pole of the first magnetic pole portion can be equal to the number of magnets in each pole of the second magnetic pole portion. Each of the magnets can be a cuboid. In a cross-section orthogonal to the stacking direction of the electromagnet plates, each of the magnets can have a first side extending in the direction along the magnetic pole surface and a second side extending in the direction along the easy magnetization direction. The first side in the second magnetic pole portion can be longer than the first side in the first magnetic pole portion.

[0008] In the rotor described above, the first magnetic pole portion may include a first central bridging portion formed between adjacent magnet mounting holes separated by d-axis extending in the radial direction, and the second magnetic pole portion may include a second central bridging portion formed between adjacent magnet mounting holes separated by d-axis extending in the radial direction, and the width of the first central bridging portion in the circumferential direction may be wider than the width of the second central bridging portion in the circumferential direction.

[0009] In the rotor described above, the magnetic flux density of the magnet installed in the second magnetic pole section can be higher than that of the magnet installed in the first magnetic pole section. Attached Figure Description

[0010] Figure 1A This is a cross-sectional view of the rotor of the first embodiment, taken along a direction orthogonal to the stacking direction of the electromagnetic steel sheets, and Figure 1B This is a side view of the rotor core in the first embodiment;

[0011] Figure 2A This is a plan view of an electromagnetic steel sheet blank, from which a punched electromagnetic steel sheet is formed to create the rotor core of the first embodiment. Figure 2B It is a perspective view schematically showing how an electromagnetic steel sheet blank is punched into a punched electromagnetic steel sheet.

[0012] Figure 3 This is an illustrative view schematically showing a rotary stack in which the punched electromagnetic steel plates forming the rotor core in the first embodiment are rotated 180° one by one and stacked.

[0013] Figure 4 This is an enlarged cross-sectional view showing a portion of the rotor of the first embodiment;

[0014] Figure 5A It is a perspective view of the first permanent magnet included in the rotor of the first embodiment, and Figure 5B This is a perspective view of the second permanent magnet included in the rotor of the first embodiment;

[0015] Figure 6It is an illustrative diagram showing a comparison between the length of the first side of the first permanent magnet and the length of the first side of the second permanent magnet;

[0016] Figure 7 This is a cross-sectional view of the rotor of the second embodiment, taken along a direction orthogonal to the stacking direction of the electromagnetic steel sheets;

[0017] Figure 8 This is an enlarged cross-sectional view showing a portion of the rotor of the second embodiment;

[0018] Figure 9 This is an enlarged cross-sectional view showing a portion of the rotor of the third embodiment;

[0019] Figure 10 This is a cross-sectional view of the rotor of the fourth embodiment, taken along a direction orthogonal to the stacking direction of the electromagnetic steel sheets; and

[0020] Figure 11A This is a perspective view of the sixth permanent magnet included in the rotor of the fourth embodiment, and Figure 11B This is a perspective view of the seventh permanent magnet included in the rotor of the fourth embodiment. Detailed Implementation

[0021] In the following description, embodiments of the present disclosure will be illustrated with reference to the accompanying drawings. However, in the drawings, the dimensions, proportions, etc., of each part may not be shown to ensure a perfect match with the actual parts. Furthermore, details may be omitted in some of the drawings.

[0022] First Embodiment

[0023] [Rotor Structure]

[0024] First, refer to Figure 1A and Figure 1B An overview of the rotor 5 according to the first embodiment is described. The rotor 5 includes a rotor core 20, a first permanent magnet 22 attached to the rotor core 20, and a second permanent magnet 23 attached to the rotor core 20. The rotor core 20 is concentrically disposed inside a stator 10 having a generally cylindrical shape and is rotatably disposed relative to the stator 10. The rotor 5 together with the stator 10 forms an internal permanent magnet (IPM) type rotary motor. The rotary motor is used as, for example, an electric motor, a generator, or an electric generator having both the functions of an electric motor and a generator. In this embodiment, the stator 10 consists of three phases: U phase, V phase, and W phase, and includes stator coils, but in Figure 1A The stator coils are not shown. Rotary electrical machines can be of the IPM type or the surface permanent magnet (SPM) type.

[0025] In the following description, "axial direction", "radial direction" and "circumferential direction" refer to the axial direction, radial direction and circumferential direction of the rotor core, respectively.

[0026] like Figure 1A As shown, the rotor core 20 has a rotating shaft mounting hole 21 at its center. Figure 1B As shown, the rotating shaft component 11 is attached to the rotating shaft mounting hole 21. The rotating shaft mounting hole 21 is provided with an inwardly protruding key protrusion 21a. The key protrusion 21a is located at two positions 180° apart. The key protrusion 21a and... Figure 3 The corresponding keyway 11a of the rotating shaft component 11 shown is engaged.

[0027] The rotor core 20 includes four magnetic pole portions arranged circumferentially. Specifically, the rotor core 20 includes two first magnetic pole portions 5a and two second magnetic pole portions 5b arranged circumferentially. The two first magnetic pole portions 5a are positioned 180° apart. The two second magnetic pole portions 5b are positioned 180° apart. The first magnetic pole portions 5a and the second magnetic pole portions 5b are arranged alternately in the circumferential direction. The adjacent first magnetic pole portions 5a and second magnetic pole portions 5b have a certain positional relationship in which the position of one of them is obtained by rotating the other by 90°. The polarities of the first magnetic pole portions 5a and the second magnetic pole portions 5b are alternately reversed in the circumferential direction. For example, when the polarities of both first magnetic pole portions 5a are both south poles, the polarities of both second magnetic pole portions 5b are both north poles.

[0028] Each of the magnetic pole portions has a fan-shaped form, with the q-axis positioned at both ends. In each magnetic pole portion, the d-axis passes radially through the central portion of the fan-shaped form. When the direction in which the d-axis extends in the first magnetic pole portion 5a is defined as the first direction and the direction in which the d-axis extends in the second magnetic pole portion 5b is defined as the second direction, the second direction is obtained by rotating the first direction by 90°. The first and second directions are related to the rolling direction of the electromagnetic steel sheet forming the rotor core 20. The rolling direction of the electromagnetic steel sheet will be described later. Therefore, the first and second directions will also be described in detail later along with the rolling direction of the electromagnetic steel sheet.

[0029] Although four magnetic pole portions are formed in this embodiment, the number of magnetic pole portions can be 4n (n is a natural number). For example, the number of magnetic pole portions can be eight, twelve, or more.

[0030] [Rolling direction, L direction, and C direction]

[0031] Rotor core 20 is produced by stacking from Figure 2A and Figure 2B A plurality of electromagnetic steel sheets (hereinafter referred to as "punched electromagnetic steel sheets") 2001 punched out of an electromagnetic steel sheet blank ES are formed. In this case, as Figure 1B As illustrated, the axial direction in which the axis AX extends is the stacking direction of the punched electromagnetic steel sheets 2001. Figure 1B The state in which the punched electromagnetic steel sheets 2001 are stacked is schematically illustrated. Thus, Figure 1B The actual number of stacked layers is not illustrated. The number of the punched electromagnetic steel sheets 2001 stacked is appropriately set according to the specifications of the rotor core 20.

[0032] As Figure 2B illustrated, the punched electromagnetic steel sheets 2001 are formed by punching out one sheet at a time from the electromagnetic steel sheet blank ES. Here, the electromagnetic steel sheet blank ES undergoes a rolling process in its manufacturing process. As Figure 2A indicated by an arrow 1a therein, the rolling direction in the rolling process is the same as the longitudinal direction (left-right direction in Figure 2A ) of the electromagnetic steel sheet blank ES. As indicated by an arrow 1b, the punched electromagnetic steel sheets 2001 are punched by lowering a punch 2 with respect to such an electromagnetic steel sheet blank ES. Here, a direction indicated by an arrow 1c therein is referred to as an L direction, which is the same as the rolling direction in the punched electromagnetic steel sheets 2001. A direction obtained by rotating the L direction by 90° and indicated by an arrow 1d is referred to as a C direction. Figure 2A

[0033] In the present embodiment, the L direction is defined as a first direction. The C direction is defined as a second direction. Thus, as Figure 1A illustrated, the direction in which the d-axis extends in the first magnetic pole portion 5a is the L direction. The direction in which the d-axis extends in the second magnetic pole portion 5b is the C direction. Thus, the first magnetic pole portion 5a is formed in a region including the L direction (i.e., the first direction). The second magnetic pole portion 5b is formed in a region including the C direction (i.e., the second direction).

[0034] [Anisotropy of electromagnetic steel sheet]

[0035] Here, the anisotropy of the electromagnetic steel sheet will be described. It is well known that electromagnetic steel sheets exhibit various anisotropies depending on the material and the rolling process. The electromagnetic steel sheet blank ES used in the present embodiment exhibits anisotropies in magnetic properties and mechanical strength properties. The magnetic properties are the easy flowability of magnetic flux flowing in the magnetic circuit of the material, and can be referred to as magnetic saturation properties or magnetic flux density properties. The mechanical strength properties are properties evaluated in the field of material mechanics and material strength, such as tensile strength, compressive strength, and shear strength.

[0036] ​The magnetic properties of the electromagnetic steel sheet blank ES of the present embodiment exhibit the order of magnetic properties in the C direction < magnetic properties in the L direction. That is, the magnetic properties in the C direction are lower than the magnetic properties in the L direction, and the likelihood of the magnetic flux flowing in the C direction is smaller than the likelihood of the magnetic flux flowing in the L direction.

[0037] On the other hand, the mechanical strength properties of the electromagnetic steel sheet blank ES of the present embodiment exhibit the order of strength in the C direction > strength in the L direction. That is, the strength in the C direction is higher than the strength in the L direction.

[0038] [Rotational stacking structure]

[0039] As Figure 3 indicated, the punched electromagnetic steel sheets 2001 punched out of the electromagnetic steel sheet blank ES in the manner indicated in Figure 2B are stacked while being rotated 180° one after another as indicated in Figure 3 . As a result, in the rotor core 20 in which the punched electromagnetic steel sheets 2001 are stacked, two positions at which the L directions are in agreement with each other are formed at intervals of 180°. Each of the magnetic pole portions formed at the two positions is the first magnetic pole portion 5a. Further, by stacking the punched electromagnetic steel sheets 2001 while rotating the punched electromagnetic steel sheets 2001 180° one after another, two positions at which the C directions are in agreement with each other are formed in the rotor core 20 at intervals of 180°. Each of the magnetic pole portions formed at the two positions is the second magnetic pole portion 5b.

[0040] Rotational stacking is also performed in conventional rotor cores. Rotational stacking eliminates the shape properties of the respective punched electromagnetic steel sheets 2001, and allows the punched electromagnetic steel sheets to be stacked in a stable state. As Figure 2B indicated, the punched electromagnetic steel sheets 2001 are formed by punching. At this time, the effects of processing, such as a slightly rounded or slightly warped peripheral portion, remain on the punched electromagnetic steel sheets 2001. The punched electromagnetic steel sheets 2001 to be stacked are all affected by the processing. For this reason, when the punched electromagnetic steel sheets 2001 are stacked in the same direction, there is a possibility that stable stacking cannot be performed due to, for example, inclination in a certain direction. Therefore, in order to stack the punched electromagnetic steel sheets 2001 in a stable state, rotational stacking is performed.

[0041] Here, the rotation of 180° is for manufacturing reasons. In the present embodiment, by fitting the key groove 11a of the rotation shaft member 11 to the key protrusion 21a (see Figure 1AIn this embodiment, the rotating shaft member 11 is attached to the rotor core 20. Therefore, in this embodiment, for example, it is not possible to use a method of stacking the punched electromagnetic steel sheet 2001 while rotating it by 90° or other angles, and a method of rotating the punched electromagnetic steel sheet by 180° is used instead. Here, it is conceivable to change the rotation angle by increasing the number of key protrusions. However, in this case, the number of keyways formed in the rotating shaft member increases. As a result, the number of machining steps for the rotating shaft member increases, and the manufacturing cost also increases. Given the above, it is difficult to increase the number of key protrusions.

[0042] Note that, for example, when the accuracy of the punching operation is high, or when stable stacking can be ensured, such as when the number of stacked sheets is small, it is conceivable to stack the punched electromagnetic steel sheets 2001 without rotating them. Similarly, in this case, a rotor core 20 is obtained that is similar to the stacking condition with 180° rotation.

[0043] [Permanent magnet]

[0044] The first magnetic pole portion 5a has two first magnet mounting holes 22a. The two first magnet mounting holes 22a are arranged linearly symmetrically with respect to the d-axis. A first permanent magnet 22 is mounted in each of the two first magnet mounting holes 22a. The second magnetic pole portion 5b has two second magnet mounting holes 23a. The two second magnet mounting holes 23a are arranged linearly symmetrically with respect to the d-axis. A second permanent magnet 23 is mounted in each of the two second magnet mounting holes 23a. In this embodiment, the first permanent magnet 22 and the second permanent magnet 23 are formed of the same type of material.

[0045] Here, the total magnetic flux Φ1 of each pole in the first magnetic pole portion 5a is compared with the total magnetic flux Φ2 of each pole in the second magnetic pole portion 5b. The total magnetic flux Φ2 of each pole in the second magnetic pole portion 5b is greater than the total magnetic flux Φ1 of each pole in the first magnetic pole portion 5a. Total magnetic flux refers to all the magnetic flux flowing through the entire permanent magnet disposed in each magnetic pole. The greater the total magnetic flux, the stronger the magnetic force of the magnet. In this embodiment, each pole of the first magnetic pole portion 5a is provided with two first permanent magnets 22. Therefore, the sum of the magnetic flux flowing through the two first permanent magnets 22 is the total magnetic flux Φ1 of each pole in the first magnetic pole portion 5a. Similarly, in this embodiment, each pole of the second magnetic pole portion 5b is provided with two second permanent magnets 23. Therefore, the sum of the magnetic flux flowing through the two second permanent magnets 23 is the total magnetic flux Φ2 of each pole in the second magnetic pole portion 5b.

[0046] In this embodiment, the total magnetic flux Φ1 per pole in the first magnetic pole portion 5a and the total magnetic flux Φ2 per pole in the second magnetic pole portion 5b are set to have the aforementioned relationship for the following reasons. The rotor core 20 of this embodiment is formed by stacking anisotropic punched electromagnetic steel plates 2001 as described above. Therefore, in the rotor core 20 without the first permanent magnet 22 and the second permanent magnet 23 installed, the probability of magnetic flux flowing in the second magnetic pole portion 5b is less than the probability of it flowing in the first magnetic pole portion 5a.

[0047] Therefore, in this embodiment, the total magnetic flux Φ2 of each pole of the magnet in the second magnetic pole portion 5b is set to be greater than the total magnetic flux Φ1 of each pole of the magnet in the first magnetic pole portion 5a, so as to eliminate the influence of anisotropy on the magnetic properties of the punched electromagnetic steel plate 2001.

[0048] In this embodiment, the relationship between the total magnetic flux Φ1 and the total magnetic flux Φ2 is defined by the relationship between the total cross-sectional areas of the magnets of each pole in the pole portion of a cross-section orthogonal to the stacking direction of the punched electromagnetic steel plates 2001 in the rotor core 20. Specifically, by Figure 4 The sum of the cross-sectional areas of the second permanent magnet 23 indicated by the shading in the second magnetic pole portion 5b shown is greater than the sum of the cross-sectional areas of the first permanent magnet 22 indicated by the shading in the first magnetic pole portion 5a.

[0049] With this configuration, when the permanent magnets are installed in each of the magnetic pole sections, the magnetic properties of the magnetic pole sections become closer to each other, and the magnetic properties are leveled. As a result, torque ripple is reduced, and smooth rotation of rotor 5 is achieved.

[0050] In this embodiment, the number of first permanent magnets 22 and the number of second permanent magnets 23 are the same, and the first permanent magnets 22 and the second permanent magnets 23 are made of the same type of material. Each of the first permanent magnets 22 and the second permanent magnets 23 has a cuboid shape. However, as... Figure 5A and Figure 5B As shown, the first permanent magnet 22 and the second permanent magnet 23 have different dimensions. Therefore, when comparing the first permanent magnet 22 and the second permanent magnet 23, not only are their cross-sectional areas different, but their volumes and weights are also different. Therefore, when the magnets installed in the first magnetic pole portion 5a and the magnets installed in the second magnetic pole portion 5b are made of the same type of material, the total magnetic flux can be evaluated based on the volume or weight of these magnets. For example, by making the weight of the permanent magnet installed in the second magnetic pole portion 5b greater than the weight of the permanent magnet installed in the first magnetic pole portion 5a, the relationship between the total magnetic flux Φ2 and the total magnetic flux Φ1 can be adjusted to a desired relationship.

[0051] The magnetic flux of a magnet is affected by various elements of the magnet. For example, the length of the side of a permanent magnet along the direction of its pole face affects the amount of magnetic flux. (See reference...) Figure 6 When viewed in a cross-section orthogonal to the stacking direction of the punched electromagnetic steel sheet 2001, each of the first permanent magnet 22 and the second permanent magnet 23 has a rectangular shape and has a first side and a second side. The first side is a long side extending in the direction along the magnetic pole plane, and the second side is a short side extending in the direction along the easy magnetization direction. A north (N) pole and a south (S) pole are formed in each permanent magnet along the short side direction. The direction in which magnetic flux flows between the N and S poles in each permanent magnet is the easy magnetization direction. The direction perpendicular to the easy magnetization direction is along the magnetic pole plane. In the permanent magnet, the amount of magnetic flux increases as the first side becomes longer. Therefore, in this embodiment, the first side of the second permanent magnet 23 is longer than the first side of the first permanent magnet 22. Therefore, the relationship between the total magnetic flux Φ2 and the total magnetic flux Φ1 becomes the desired relationship.

[0052] In this embodiment, the number of first permanent magnets 22 installed in the first magnetic pole portion 5a is the same as the number of second permanent magnets 23 installed in the second magnetic pole portion 5b. For this reason, by making the sizes of the first permanent magnets 22 and the second permanent magnets 23 different, a difference in total magnetic flux is provided. Alternatively, the number of permanent magnets can be different between the first magnetic pole portion 5a and the second magnetic pole portion 5b to provide a difference in total magnetic flux. In this case, permanent magnets having the same material, size, and shape are used as the magnets to be installed in the first magnetic pole portion 5a and the second magnetic pole portion 5b.

[0053] In short, it only requires that the total magnetic flux Φ2 of each pole of the magnet in the second magnetic pole section 5b is greater than the total magnetic flux Φ1 of each pole of the magnet in the first magnetic pole section 5a.

[0054] [Central Bridging Section]

[0055] Reference Figure 4The rotor 5 has a first magnetic pole portion 5a having first magnet mounting holes 22a adjacent to each other across a d-axis extending in the radial direction. A first central bridging portion 24 is formed between adjacent first magnet mounting holes 22a. The rotor 5 has a second magnetic pole portion 5b having second magnet mounting holes 23a adjacent to each other across a d-axis extending in the radial direction. A second central bridging portion 25 is formed between adjacent second magnet mounting holes 23a. The circumferential width W1 of the first central bridging portion 24 is wider than the circumferential width W2 of the second central bridging portion 25. Here, the circumferential width W1 of the first central bridging portion 24 is the shortest distance between the first magnet mounting holes 22a adjacent to each other across a d-axis. The circumferential width W2 of the second central bridging portion 25 is the shortest distance between the second magnet mounting holes 23a adjacent to each other across a d-axis.

[0056] The radial direction of the first central bridging portion 24 is aligned with the L direction, while the radial direction of the second central bridging portion 25 is aligned with the C direction. In the rotor core 20 of this embodiment, the mechanical strength characteristics in the C direction are higher than those in the L direction. Therefore, the circumferential width W1 of the first central bridging portion 24, which extends along the L direction where the mechanical strength characteristics are lower, is set to be wider than the circumferential width W2 of the second central bridging portion 25, which extends along the C direction where the mechanical strength characteristics are higher. Therefore, the strength of the first central bridging portion 24 can be ensured.

[0057] When the first permanent magnet 22 is viewed in a plan view of the rotor 5, that is, when viewed along the direction of axis AX, gaps are provided on both sides of the first permanent magnet 22 along the longitudinal direction of the first magnet mounting hole 22a. Similarly, gaps are provided on both sides of the second permanent magnet 23 along the longitudinal direction of the second magnet mounting hole 23a. Each of these gaps is a magnetic flux barrier. The rotor 5 may not have magnetic flux barriers.

[0058] In the rotor 5 of this embodiment, the total magnetic flux Φ2 of each pole in the second pole portion 5b is greater than the total magnetic flux Φ1 of each pole in the first pole portion 5a. As a result, the magnetic characteristics between the pole portions are leveled, torque pulsation is reduced, and smooth rotation of the rotor 5 is achieved.

[0059] Second Embodiment

[0060] Next, we will refer to Figure 7 and Figure 8 The rotor 105 according to the second embodiment is described. The rotor 105 of the second embodiment includes a first magnetic pole portion 105a and a second magnetic pole portion 105b, instead of the first magnetic pole portion 5a and the second magnetic pole portion 5b of the first embodiment.

[0061] The first magnetic pole portion 105a has a third magnet mounting hole 122a and a fourth magnet mounting hole 122b. Compared with the third magnet mounting hole 122a, the fourth magnet mounting hole 122b is located further radially inward. The third magnet mounting hole 122a is symmetrically arranged with respect to the d-axis extending along the L direction, and the fourth magnet mounting hole 122b is symmetrically arranged with respect to the d-axis extending along the L direction.

[0062] A third permanent magnet 122 is installed in each of the third magnet mounting holes 122a. Two third permanent magnets 122 are installed in each of the fourth magnet mounting holes 122b. Therefore, the number of third permanent magnets 122 per pole in the first magnetic pole portion 105a is six.

[0063] The second magnetic pole portion 105b has two fifth magnet mounting holes 123a and two sixth magnet mounting holes 123b. The sixth magnet mounting holes 123b are located further radially inward than the fifth magnet mounting holes 123a. The two fifth magnet mounting holes 123a are symmetrically arranged with respect to the d-axis extending along the C direction. Similarly, the two sixth magnet mounting holes 123b are symmetrically arranged with respect to the d-axis extending along the C direction.

[0064] A fourth permanent magnet 123 is installed in each of the fifth magnet mounting holes 123a. Two fourth permanent magnets 123 are installed in each of the sixth magnet mounting holes 123b. Therefore, the number of fourth permanent magnets 123 per pole in the second pole portion 105b is six.

[0065] In this embodiment, the third permanent magnet 122 and the fourth permanent magnet 123 are made of the same type of material. However, in the cross-section of the rotor 105 orthogonal to the stacking direction of the punched electromagnetic steel plates, the third permanent magnet 122 and the fourth permanent magnet 123 have similar shapes but different cross-sectional areas.

[0066] The rotor core 120 in the second embodiment has an anisotropy similar to that of the rotor core 20 in the first embodiment. That is, the magnetic properties in the C direction are lower than those in the L direction, and the probability of magnetic flux flowing in the C direction is less than the probability of it flowing in the L direction.

[0067] Therefore, in the second embodiment, in Figure 8 The sum of the cross-sectional areas of the fourth permanent magnet 123 (indicated by shaded areas) in the second magnetic pole portion 105b is set to be greater than the sum of the cross-sectional areas of the third permanent magnet 122 (indicated by shaded areas) in the first magnetic pole portion 105a. Therefore, the total magnetic flux Φ2 of each pole in the second magnetic pole portion 105b is greater than the total magnetic flux Φ1 of each pole in the first magnetic pole portion 105a.

[0068] As described above, even when the number of permanent magnets in each magnetic pole section increases, the total magnetic flux of the magnets can be adjusted by the size of the cross-sectional area.

[0069] Therefore, with the permanent magnet attached to each of the magnetic pole portions, the magnetic properties of the magnetic pole portions become closer to each other, and the magnetic properties are leveled. As a result, torque ripple is reduced, and smooth rotation of the rotor 105 is achieved.

[0070] In the second embodiment, as in the first embodiment, the width of the first central bridging portion formed in the first magnetic pole portion 105a in the circumferential direction is set to be wider than the width of the second central bridging portion formed in the second magnetic pole portion 105b in the circumferential direction.

[0071] Third Embodiment

[0072] Next, we will refer to Figure 9 The rotor 205 of the third embodiment is described. The rotor 205 of the third embodiment includes a first magnetic pole portion 205a and a second magnetic pole portion 205b, instead of the first magnetic pole portion 105a and the second magnetic pole portion 105b of the second embodiment.

[0073] The first magnetic pole portion 205a has two seventh magnet mounting holes 222a. The two seventh magnet mounting holes 222a are arranged symmetrically with respect to the d-axis extending along the L direction.

[0074] Two fifth permanent magnets 222 are installed in each of the seventh magnet mounting holes 222a. Therefore, the number of fifth permanent magnets 222 in each pole of the first magnetic pole portion 205a is four.

[0075] The second magnetic pole portion 205b has two eighth magnet mounting holes 223a and two ninth magnet mounting holes 223b. Compared to the eighth magnet mounting holes 223a, the ninth magnet mounting holes 223b are located further radially inward. The two eighth magnet mounting holes 223a are symmetrically arranged with respect to the d-axis extending along the C direction. Similarly, the two ninth magnet mounting holes 223b are symmetrically arranged with respect to the d-axis extending along the C direction.

[0076] A fifth permanent magnet 222 is installed in each of the eighth magnet mounting holes 223a. Two fifth permanent magnets 222 are installed in each of the ninth magnet mounting holes 223b. Therefore, the number of fifth permanent magnets 222 per pole in the second pole portion 205b is six.

[0077] In this embodiment, the magnets installed in each magnetic pole section are all fifth permanent magnets. That is, all permanent magnets are made of the same type of material. Furthermore, the cross-sectional area of ​​the rotor 205 in a cross-section orthogonal to the stacking direction of the punched electromagnetic steel plates is the same.

[0078] The rotor core 220 in the third embodiment has an anisotropy similar to that of the rotor core 20 in the first embodiment and the rotor core 120 in the second embodiment. That is, the magnetic properties in the C direction are lower than those in the L direction, and the probability of magnetic flux flowing in the C direction is less than that in the L direction.

[0079] Therefore, in the third embodiment, in Figure 9 The sum of the cross-sectional areas of the fifth permanent magnets 222 (indicated by shading) in the second magnetic pole portion 205b is set to be greater than the sum of the cross-sectional areas of the fifth permanent magnets 222 (indicated by shading) in the first magnetic pole portion 205a. Therefore, the total magnetic flux Φ2 of each pole in the second magnetic pole portion 205b is greater than the total magnetic flux Φ1 of each pole in the first magnetic pole portion 205a.

[0080] Using this configuration, with the permanent magnets installed in each of the magnetic pole sections, the magnetic properties of the pole sections become closer to each other, and the magnetic properties are leveled. As a result, torque ripple is reduced, and smooth rotation of the rotor 205 is achieved.

[0081] Here, when comparing the third embodiment with the first and second embodiments, the following differences exist. In the first and second embodiments, the number of permanent magnets per pole in the magnetic pole portion is the same between the first and second magnetic pole portions. However, the cross-sectional area of ​​each permanent magnet disposed in the first magnetic pole portion is different from the cross-sectional area of ​​each permanent magnet disposed in the second magnetic pole portion. On the other hand, in the third embodiment, the number of permanent magnets per pole in the magnetic pole portion is different between the first and second magnetic pole portions. Therefore, the total cross-sectional area of ​​each pole in the second magnetic pole portion 205b is set to be greater than the total cross-sectional area of ​​each pole in the first magnetic pole portion 205a.

[0082] The total area of ​​each pole in the magnetic pole section can be set differently by combining the cross-sectional areas of individual permanent magnets and the number of permanent magnets. Therefore, the individual cross-sectional areas of the permanent magnets and the number of permanent magnets can be appropriately combined so that the total cross-sectional area of ​​each pole in the second magnetic pole section is greater than the total cross-sectional area of ​​each pole in the first magnetic pole section.

[0083] Fourth embodiment

[0084] Next, we will refer to Figures 10 to 11BThe rotor 305 according to the fourth embodiment is described. The rotor 305 of the fourth embodiment includes a first magnetic pole portion 305a and a second magnetic pole portion 305b, instead of the first magnetic pole portion 5a and the second magnetic pole portion 5b of the first embodiment.

[0085] The first magnetic pole portion 305a has a tenth magnet mounting hole 322a. The tenth magnet mounting hole 322a is arranged symmetrically with respect to the d-axis extending along the L direction. A sixth permanent magnet 322 is mounted in each of the tenth magnet mounting holes 322a.

[0086] The second magnetic pole portion 305b has an eleventh magnet mounting hole 323a. The eleventh magnet mounting hole 323a is arranged symmetrically with respect to the d-axis extending along the C direction. A seventh permanent magnet 323 is mounted in each of the eleventh magnet mounting holes 323a.

[0087] In this embodiment, the sixth permanent magnet 322 and the seventh permanent magnet 323 have the same dimensions. Therefore, in the cross-section of the rotor 305 orthogonal to the stacking direction of the punched electromagnetic steel plate, the cross-sectional area of ​​the sixth permanent magnet 322 and the cross-sectional area of ​​the seventh permanent magnet 323 are the same.

[0088] The rotor core 320 in the fourth embodiment has an anisotropy similar to that of the rotor core 20 in the first embodiment. That is, the magnetic properties in the C direction are lower than those in the L direction, and the probability of magnetic flux flowing in the C direction is less than the probability of it flowing in the L direction.

[0089] Therefore, in the fourth embodiment, Figure 11B The magnetic flux density B2 of the seventh permanent magnet 323 shown is set to be higher than Figure 11A The magnetic flux density B1 of the sixth permanent magnet 322 is shown. With this configuration, the total magnetic flux Φ2 per pole in the second pole portion 305b is greater than the total magnetic flux Φ1 per pole in the first pole portion 305a. Magnetic flux density indicates the strength of the magnetic force and is the amount of magnetic flux flowing per unit area. In this embodiment, the sixth permanent magnet 322 and the seventh permanent magnet 323 have the same dimensions. Therefore, the seventh permanent magnet 323, with its higher magnetic flux density, has a stronger magnetic force than the sixth permanent magnet 322.

[0090] Therefore, with the permanent magnets installed in each of the magnetic pole sections, the magnetic properties of the magnetic pole sections become closer to each other, and the magnetic properties are leveled. As a result, torque ripple is reduced, and smooth rotation of the rotor 305 is achieved.

[0091] As described above, even when the number and size of permanent magnets set in the corresponding magnetic pole sections are the same, the total magnetic flux of each pole in the magnetic pole section can be adjusted by selecting permanent magnets with different magnetic flux densities.

[0092] This embodiment includes a sixth permanent magnet 322 and a seventh permanent magnet 323 having the same dimensions. The number of sixth permanent magnets 322 is the same as the number of seventh permanent magnets 323. Here, the dimensions and number of permanent magnets are not necessarily the same. When permanent magnets with different magnetic flux densities are selected, the dimensions and number of permanent magnets can be appropriately set according to the magnetic flux density.

[0093] Although some embodiments of the invention have been described in detail, the invention is not limited to the specific embodiments, but may be varied or modified within the scope of the claimed invention.

Claims

1. A rotor, comprising: The rotor core is formed by stacking anisotropic electromagnetic steel plates, the anisotropy meaning that the magnetic properties of each electromagnetic steel plate in a first direction along the rolling direction are different from the magnetic properties of each electromagnetic steel plate in a second direction, wherein the second direction is obtained by rotating the first direction by 90°, and the rotor core has 4n magnetic pole portions formed along the circumferential direction, wherein n is a natural number; as well as A magnet is mounted in the rotor core in each of the magnetic pole portions. The 4n magnetic pole portions include a first magnetic pole portion and a second magnetic pole portion, wherein the first magnetic pole portion is formed in a region including the first direction, and the second magnetic pole portion is formed in a region including the second direction. Wherein, the total magnetic flux of the magnet in each pole of the second magnetic pole portion is greater than the total magnetic flux of the magnet in each pole of the first magnetic pole portion.

2. The rotor according to claim 1, wherein, In a cross section orthogonal to the stacking direction of the electromagnetic steel plates, the total cross-sectional area of ​​the magnets in each pole of the second magnetic pole portion is greater than the total cross-sectional area of ​​the magnets in each pole of the first magnetic pole portion.

3. The rotor according to claim 1 or 2, in, The number of magnets in each pole of the first magnetic pole portion is equal to the number of magnets in each pole of the second magnetic pole portion. Each of the magnets is a cuboid. In a cross-section orthogonal to the stacking direction of the electromagnetic steel plates, each magnet has a first side extending along the direction of the magnetic pole face and a second side extending along the direction of easy magnetization. Wherein, the first side of the second magnetic pole portion is longer than the first side of the first magnetic pole portion.

4. The rotor according to claim 1, in, The first magnetic pole portion includes a first central bridging portion formed between adjacent magnet mounting holes that extend radially along the d-axis. The second magnetic pole portion includes a second central bridging portion, which is formed between adjacent magnet mounting holes spaced apart by a radially extending d-axis. The width of the first central bridging portion in the circumferential direction is wider than the width of the second central bridging portion in the circumferential direction.

5. The rotor according to claim 1, wherein, The magnetic flux density of the magnet installed in the second magnetic pole portion is higher than that of the magnet installed in the first magnetic pole portion.

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