Rotor core, rotor, and rotating electric machine

Abstract

This rotor core has a plurality of holes including holes in which permanent magnets are installed, and is provided with a high magnetic permeability portion, and a low magnetic permeability portion having a relative magnetic permeability that is lower than the relative magnetic permeability of the high magnetic permeability portion and higher than the relative magnetic permeability of a vacuum, wherein the whole of an inner circumferential side bridge portion, of which at least a partial region is disposed further toward the rotor core inner circumferential surface side than at least one of the regions in which the permanent magnets are arranged, is the low magnetic permeability portion.

Description

Technical Field

[0001] The present disclosure relates to a rotor core, a rotor, and a rotating electrical machine.

Background Art

[0002] In a permanent magnet embedded type rotating electrical machine such as an IPMSM (Interior Permanent Magnet Synchronous Motor), permanent magnets are embedded in a rotor core, and a flux barrier is formed in the vicinity of the permanent magnets. The flux barrier is for controlling the flow of magnetic flux in the rotating electrical machine and improving the characteristics of the rotating electrical machine. When such a flux barrier is formed, a bridge portion is formed between two flux barriers or between the flux barrier and the end face of the rotor core. If the bridge portion is formed of a soft magnetic body portion (such as an electromagnetic steel sheet) constituting the rotor core, there is a possibility that the magnetic flux generated by the permanent magnet does not go toward the stator core but flows back in the rotor core through the bridge portion.

[0003] Therefore, International Publication No. 2019 / 065112 describes providing a plurality of magnetic resistance portions, which are arranged at intervals at a plurality of positions in the suspension direction and have a reduced magnetic permeability compared to other portions of the steel sheet, in the bridge portion.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technology described in International Publication No. 2019 / 065112, a plurality of magnetoresistive parts are formed inside the corner part of the flux barrier sandwiching the magnetoresistive part. Therefore, it becomes easier for magnetic flux to enter the bridge part. Further, in the technology described in International Publication No. 2019 / 065112, it is said that there is almost no magnetoresistance in the region between the plurality of magnetoresistive parts in the bridge part. Therefore, there is a possibility that the magnetic flux entering from one end in the suspension direction of the bridge part reaches the other end via the region. Therefore, there is a possibility that it is impossible to reduce the reflux of the magnetic flux generated by the permanent magnet through the bridge part instead of going toward the stator core and within the rotor core. For example, when the region between the plurality of magnetoresistive parts is short (for example, when the bridge part is short), it becomes difficult to reduce the magnetic flux refluxing within the rotor core. Therefore, there is a possibility that the torque of the rotating electrical machine cannot be increased. The present disclosure has been made in view of the above problems, and an object thereof is to increase the torque of a rotating electrical machine.

Means for Solving the Problems

[0005] The rotor core according to one aspect of the present disclosure is a rotor core having a plurality of holes including holes in which permanent magnets are installed, and includes a high magnetic permeability part and a low magnetic permeability part having a relative magnetic permeability smaller than that of the high magnetic permeability part and larger than that of vacuum. The entire inner peripheral side bridge part, at least a part of the region of which is arranged closer to the inner peripheral surface side of the rotor core than at least one of the regions where the permanent magnets are installed, is the low magnetic permeability part. The rotor core according to another aspect of the present disclosure is a rotor core having a plurality of holes including holes in which permanent magnets are installed, and includes a high magnetic permeability part and a low magnetic permeability part having a relative magnetic permeability smaller than that of the high magnetic permeability part and larger than that of vacuum. A part of the first outer peripheral side bridge part, which is arranged on the leading side in the rotation direction rather than the center in the circumferential direction of the region in the region constituting one pole of the rotor core and at least a part of the region of which is arranged closer to the outer peripheral surface side of the rotor core than at least one of the regions where the permanent magnets are installed, is the low magnetic permeability part.

Advantages of the Invention

[0006] According to the present disclosure, the torque of the rotating electrical machine can be increased.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In addition, for comparisons of length, position, size, interval, etc., the objects to be compared being the same means not only being exactly the same, but also including those that are different within the scope not departing from the gist of the present disclosure (for example, those that are different within the tolerance range determined during design). Also, in each figure, the x-y-z coordinates indicate the directional relationship in each figure. In the x-y-z coordinates, the symbol with ● inside 〇 indicates that the direction from the back side to the front side of the paper surface is the positive direction.

[0009] (First Embodiment) First, the first embodiment will be described. In this embodiment, the case where the rotating electrical machine is an IPMSM will be exemplified. FIG. 1 is a diagram showing an example of the configuration of an IPMSM 100. FIG. 1 is a cross-sectional view of the IPMSM 100 when cut perpendicularly to the center line 0 (the rotation axis of the rotor 110) of the IPMSM 100. In FIG. 1, the IPMSM 100 includes a rotor 110 and a stator 120.

[0010] The stator 120 includes a stator core 121 and a stator coil (not shown), and is for generating a rotating magnetic field. Since the notation becomes complicated, in FIG. 1, the illustration of the stator coil included in the stator 120 is omitted, but the stator coil is arranged in the slots 122 of the stator core 121 (since the notation becomes complicated, only one of the 48 slots is labeled in FIG. 1).

[0011] The rotor 110 rotates about the center line 0 of the IPMSM 100 as the rotation axis. In this embodiment, the case where the rotor 110 rotates in the direction of the arrow line shown in FIG. 1 (i.e., counterclockwise direction toward the paper surface) is exemplified. However, in this embodiment, the rotation direction of the rotor 110 is not limited to the direction of the arrow line shown in FIG. 1. The rotor 110 may rotate in a direction opposite to the direction of the arrow line shown in FIG. 1 (i.e., clockwise direction toward the paper surface), or may rotate in both directions, the direction of the arrow line shown in FIG. 1 and the opposite direction thereof. FIG. 2 is a diagram showing an example of the configuration of the rotor 110. Similar to FIG. 1, FIG. 2 is also a cross-sectional view of the rotor 110 when cut perpendicular to the center line 0 of the rotor 110 (in the following description, the cross-section of the rotor 110 when cut perpendicular to the center line 0 of the rotor 110 is also referred to as the rotor cross-section). Note that the center line 0 of the rotor 110 coincides with the center line 0 of the IPMSM 100.

[0012] As shown in FIG. 2, the rotor 110 includes a rotor core 111 and a plurality of permanent magnets 112 (here, three permanent magnets 112a to 112c per pole). The rotor core 111 is made of a soft magnetic material having high magnetic permeability characteristics. The rotor core 111 is manufactured, for example, using a plurality of electromagnetic steel sheets laminated along the center line 0 of the rotor 110. However, it is not necessarily required to configure the rotor core 111 using a plurality of laminated electromagnetic steel sheets. The rotor core 111 may be, for example, a powder core, an amorphous core, or a nanocrystalline core. Note that when the rotor core 111 is a powder core, an amorphous core, or a nanocrystalline core, the soft magnetic materials constituting the rotor core 111 are each made of insulated soft magnetic particles, an amorphous alloy, or a nanocrystalline alloy.

[0013] A plurality of holes are formed in the rotor core 111 in a direction parallel to the center line 0 of the rotor core 111 (hereinafter referred to as the z-axis direction). In this embodiment, the case where the holes are through holes penetrating in the z-axis direction is exemplified.

[0014] A plurality of permanent magnets 112 are each inserted into a hole formed in the rotor core 111, thereby being installed (or embedded) in the rotor core 111. In FIG. 2, a case where magnetic flux flows in and out from the magnetic pole surfaces 201 (201a to 201f) of the permanent magnets 112 (112a to 112c) is illustrated. The direction orthogonal to the magnetic pole surface 201 (the direction of the double arrow line shown across the permanent magnets 112a to 112c in FIG. 2) is the magnetization direction of the permanent magnets 112. In the hole where the permanent magnet 112 is installed, the region where the permanent magnet 112 does not exist becomes the flux barrier 113 (113a to 113f). Also, for the hole where the permanent magnet 112 is not installed, the entire hole becomes the flux barrier 113 (113g to 113j). There is no physical object in the flux barrier 113, and the flux barrier 113 is a void portion (an air region). The flux barrier 113 is a region where magnetic flux does not pass or is more difficult to pass through than the surrounding region. However, the flux barrier 113 may be constituted by installing a non-magnetic body. Also, in the rotor core 111, holes 114 are formed in addition to the flux barrier 113. A shaft or the like (not shown) is installed in the hole 114.

[0015] Note that, in the present embodiment, a case where the shape of the rotor cross-section is the shape shown in FIG. 2 at any position in the z-axis direction of the rotor 110 is illustrated, but it is not necessarily required to be like this.

[0016] Also, in FIGS. 1 and 2, the case where the number of poles of the IPMSM 100 is 8 poles is illustrated. In FIGS. 1 and 2, the range of the double arrow lines indicated as "one pole" constitutes one pole of the IPMSM 100. There are three permanent magnets 112a to 112c embedded per pole, and a total of 24 permanent magnets are embedded in the rotor core 111. The number of poles, the number and arrangement of the permanent magnets 112 per pole are merely examples and can be arbitrarily determined. In FIGS. 1 and 2, since the notation becomes complicated, only the portion constituting one pole of the rotor 110 is labeled, and the notations for the other seven poles of the rotor 110 are omitted. Incidentally, when the number of poles of the IPMSM 100 is n poles (n is an integer of 2 or more, n = 8 in the examples shown in FIGS. 1 and 2), the IPMSM 100 generally has a rotational symmetry relationship of n-fold symmetry with the center line 0 of the IPMSM 100 as the axis of rotational symmetry.

[0017] FIG. 3 is a diagram showing an example of the configuration of the rotor core 111. FIG. 4 is a diagram showing an enlarged view of a part of the rotor core 111 shown in FIG. 3. Similar to FIGS. 1 and 2, FIG. 3 is also a cross-sectional view of the rotor core 111 when cut perpendicular to the center line 0 of the rotor core 111 (in the following description, the cross-section of the rotor core 111 when cut perpendicular to the center line 0 of the rotor core 111 is also referred to as the rotor core cross-section). Incidentally, the center line 0 of the rotor core 111 coincides with the center line 0 of the IPMSM 100 and the center line 0 of the rotor 110. Also, similar to FIG. 2, in FIG. 3, only the portion constituting one pole of the rotor core 111 is labeled, and the notations for the other seven poles of the rotor core 111 are omitted.

[0018] In FIG. 3, the rotor core 111 includes holes 301a to 301c in which the permanent magnets 112 (112a to 112c) are installed, and holes 301d to 301g in which the permanent magnets 112 are not installed.

[0019] The holes 301a to 301b in which the permanent magnets 112a to 112b are installed are arranged such that the magnetic pole surfaces 201a to 201d (see FIG. 2) of the permanent magnets 112a to 112b installed in the holes 301a to 301b are inclined with respect to the outer peripheral surface which is the end surface facing the stator 120 of the rotor core 111. In other words, the magnetic pole surfaces 201a to 201d of the permanent magnets 112a to 112b are arranged so as to be inclined with respect to the radial direction of the rotor core 111. In FIG. 3, an example is illustrated in which the circumferential interval of the holes 301a to 301b (the permanent magnets 112a to 112b installed in the holes 301a to 301b) in which the permanent magnets 112a to 112b are installed is made wider as it is closer to the outer peripheral surface of the rotor core 111. As shown in FIG. 2 in this way, an example is illustrated in which the permanent magnets 112a to 112b are arranged in a so-called V shape (an upside-down V shape). On the other hand, the hole 301c in which the permanent magnet 112c is installed is made such that the magnetic pole surfaces 201e to 201f (see FIG. 2) of the permanent magnet 112c installed in the hole 301c face the outer peripheral surface of the rotor core 111 via the high magnetic permeability portion 311 (so as to be in a so-called flat arrangement).

[0020] In FIG. 1, an inner rotor type IPMSM 100 is illustrated. Therefore, as shown in FIG. 1, the outer peripheral surface of the rotor 110 (rotor core 111) becomes an end surface facing the stator 120 with a gap therebetween. Also, in FIG. 2, the side surfaces 202 (202a to 202c), 203 (203a to 203c) of the permanent magnets 112 (112a to 112c) are the end surfaces located on the end side in the direction parallel to the magnetic pole surfaces 201 (201a to 201f) (hereinafter referred to as the length direction) (in the example shown in FIG. 2, the end surfaces located at the ends in the length direction of the magnetic pole surfaces 201 (201a to 201f) of the permanent magnets 112 (112a to 112c)).

[0021] As described above, in this embodiment, a case is exemplified in which three holes per pole, namely, holes 301a to 301c in which permanent magnets 112a to 112c are installed, are formed in the rotor core 111. However, the number of holes per pole in which the permanent magnets are installed may be three or more or two or less. For example, a permanent magnet may be installed in hole 301d, or the permanent magnet 112c may not be installed in hole 301c.

[0022] In FIG. 4, among the regions of holes 301a to 301c where permanent magnets 112a to 112c are installed, regions other than regions 401a to 401c where permanent magnets 112a to 112c are installed (that is, regions where permanent magnets 112a to 112c are not installed) become flux barriers 113a to 113f shown in FIG. 2. Also, all regions of holes 301d to 301g where no permanent magnet is installed become flux barriers 113g to 113j shown in FIG. 2.

[0023] The rotor core 111 includes a high magnetic permeability portion 311 and low magnetic permeability portions 321a to 321b in regions other than holes 301a to 301g. The high magnetic permeability portion 311 is made of a soft magnetic material (such as an electromagnetic steel sheet) having the above-described high magnetic permeability characteristics, which constitutes the rotor core 111.

[0024] The relative permeability of the low magnetic permeability portions 321a to 321b is lower than that of the high magnetic permeability portion 311 and higher than the relative permeability of vacuum or air (≈1) (the relative permeability of vacuum or air < the relative permeability of the low magnetic permeability portions 321a to 321b < the relative permeability of the high magnetic permeability portion 311). In this embodiment, as an example, the low magnetic permeability portions 321a to 321b and the high magnetic permeability portion 311 are integrally formed of the same material. Specifically, the high magnetic permeability portion 311 is a portion constituted by the soft magnetic material (such as an electromagnetic steel sheet) as described above, and the low magnetic permeability portions 321a to 321b are portions where the soft magnetic material has been made to have a lower magnetic permeability. In this way, by integrally forming the low magnetic permeability portions 321a to 321b and the high magnetic permeability portion 311 of the same material, the mechanical strength can be increased compared to inserting and bonding a low magnetic permeability material (or non-magnetic material) different from the high magnetic permeability portion 311 into the low magnetic permeability portions 321a to 321b. The method of making the soft magnetic material have a lower magnetic permeability, that is, the method of manufacturing the low magnetic permeability portions 321a to 321b, will be described below. The method of manufacturing the low magnetic permeability portions 321a to 321b is not particularly limited as long as the relative permeability of the low magnetic permeability portions 321a to 321b is smaller than the relative permeability of the high magnetic permeability portion.

[0025] For example, by pressing the regions constituting the low magnetic permeability portions 321a to 321b among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 to make the thickness of the regions constituting the low magnetic permeability portions 321a to 321b thinner than the thickness of the regions constituting the high magnetic permeability portion 311, a part of the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 (in this embodiment, the low magnetic permeability portions 321a to 321b) may be made to have a lower magnetic permeability.

[0026] Also, as described in Japanese Patent Application Laid-Open No. 2011-114927, the thickness of the regions constituting the low magnetic permeability portions 321a to 321b among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 may be thinned by etching.

[0027] Also, as described in Japanese Patent Application Laid-Open No. 2001-93717, by irradiating a beam with high energy density while adding a modifying material to the region constituting the low magnetic permeability portions 321a to 321b among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111, a part of the region of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 may be made to have a low magnetic permeability.

[0028] Also, as described in Japanese Patent Application Laid-Open No. 11-18324, by welding the region constituting the low magnetic permeability portions 321a to 321b among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111, or causing strain or transformation in the region, a part of the region of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 may be made to have a low magnetic permeability.

[0029] Also, the low magnetic permeability portions 321a to 321b may be produced without making a part of the region of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 have a low magnetic permeability. For example, as described in Japanese Patent Application Laid-Open No. 2010-029514, holes (such as through holes) are made in the region constituting the low magnetic permeability portions 321a to 321b among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 111 in the z-axis direction of the IPMSM100, and the low magnetic permeability members are filled in the holes, whereby the low magnetic permeability portions 321a to 321b may be produced.

[0030] The low magnetic permeability portions 321a to 321b produced as described above are bridge portions that are disposed on the entire inner peripheral side bridge portion disposed closer to the inner peripheral surface side of the rotor core 111 than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c are installed, at least in part. FIG. 5 is a diagram showing an example of the configuration of the inner peripheral side bridge portions 501a to 501b. Note that, since the notation becomes complicated, the illustration of the low magnetic permeability portions 321a to 321b is omitted in FIG. 5.

[0031] In FIGS. 3 to 5, an example is illustrated in which the inner peripheral side bridge portions 501a and 501b are disposed between the holes 301a and 301b where the permanent magnets 112a and 112b are installed and the hole 301d where no permanent magnet is installed. In this specification, the region between holes refers to the region from the surface forming one hole to the surface forming the other hole, the region between a hole and an end face refers to the region from the surface forming the hole to the end face, and the region between end faces refers to the region from one end face to the other end face. Further, the inner peripheral side bridge portions 501a and 501b are not limited to being disposed between the holes 301a and 301b where the permanent magnets 112a and 112b are installed and the hole 301d where no permanent magnet is installed. The inner peripheral side bridge portion may be disposed between two holes as long as it is sandwiched between the two holes. For example, the inner peripheral side bridge portion may be disposed between two holes where permanent magnets are installed by being sandwiched between the two holes, or may be disposed between two holes where no permanent magnets are installed by being sandwiched between the two holes. Further, the inner peripheral side bridge portions 501a and 501b are not limited to the case of being disposed between two holes (in the examples shown in FIGS. 3 to 5, two holes 301a, 301d and two holes 301b, 301d). For example, when the distance between one hole (for example, hole 301d) formed in the rotor core 111 and the inner peripheral surface of the rotor core 111 is short and the region between the one hole and the inner peripheral surface of the rotor core 111 becomes a bridge portion, the bridge portion may be regarded as an inner peripheral side bridge portion. Thus, the inner peripheral side bridge portion may be disposed between the hole and the inner peripheral surface of the rotor core by being sandwiched between the one hole and the inner peripheral surface of the rotor core.

[0032] As described above, at least a part of the inner peripheral side bridge portions 501a to 501b is disposed closer to the inner peripheral surface side of the rotor core 111 than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c are installed. As described above, in the present embodiment, the outer peripheral surface of the rotor 110 (rotor core 111) becomes an end surface facing the stator 120 of the rotor core 111 with a gap therebetween. Therefore, the inner peripheral surface side (i.e., the center line 0 side) of the rotor 110 (rotor core 111) is on the side opposite to the end surface side facing the stator 120 of the rotor core 111. In FIG. 5, in each pole, a case is illustrated where at least a part of the inner peripheral side bridge portions 501a to 501b is disposed closer to the inner peripheral surface side (center line 0 side) of the rotor 110 (rotor core 111) than the regions 401a to 401c where the three permanent magnets 112a to 112c are installed. As shown in FIG. 4, since the regions 401a to 401b where the permanent magnets 112a to 112b are installed are disposed closer to the inner peripheral surface side (center line 0 side) of the rotor 110 (rotor core 111) than the region 401c where the permanent magnet 112c is installed, all regions of the inner peripheral side bridge portions 501a to 501b are disposed closer to the inner peripheral surface side (center line 0 side) of the rotor 110 (rotor core 111) than the region 401c where the permanent magnet 112c is installed.

[0033] In FIG. 5, a case is illustrated where the inner peripheral side bridge portions 501a to 501b are disposed between the ends 504a to 504b on the side where the circumferential interval of the regions 401a to 401c where the permanent magnets 112a to 112c are installed becomes shorter (i.e., the ends on the inner peripheral surface side of the rotor core 111) among the longitudinal ends of the holes 301a to 301b.

[0034] The region of the inner peripheral side bridge portion 501a will be described more specifically. In the cross-section of the rotor core, the inner peripheral side bridge portion 501a is a region between the holes 301a and 301d partitioned by two lines connecting the corner portions of the holes 301a and 301d that sandwich the inner peripheral side bridge portion 501a (in other words, in the cross-section of the rotor core, the connection portion between the sides forming the holes including the portions that will be representative points described later). As will be described later, the larger the ratio of the area of the low magnetic permeability portion in the inner peripheral side bridge portion to the area of the inner peripheral side bridge portion, the better. Therefore, these two lines are, for example, straight lines connecting the representative points of the corner portions selected from the regions forming the corner portions such that the straight line does not pass through the inside of the holes 301a and 301d and the size of the inner peripheral side bridge portion 501a is maximized.

[0035] For example, in the cross-section of the rotor core, when the corner portion appears as a single vertex, the vertex is selected as the representative point of the corner portion. On the other hand, when the corner portions of the holes 301a and 301d have curvature or the like and the corner portion is not determined by a single vertex, the representative point of the corner portion of the holes 301a and 301d is selected from the regions forming the corner portions of the holes 301a and 301d, such as the regions having the curvature. The representative point of the corner portion is selected, for example, such that the size of the inner peripheral side bridge portion 501a is maximized. However, it is not always necessary to select the representative point of the corner portion in this way. For example, the center position of the region forming the corner portion may be selected as the representative point of the corner portion.

[0036] In the example shown in FIG. 5, among the corner portions of the hole 301a, since the two corner portions located at the ends facing the hole 301d each have a curvature, points 502a to 502b are selected from the region forming the corner portion of the hole 301a to be the representative points of the corner portion of the hole 301a. Also, among the corner portions of the hole 301d, since the two corner portions located at the ends facing the hole 301a each have a curvature, points 502c to 502d are selected from the region forming the corner portion of the hole 301d to be the representative points of the corner portion of the hole 301d. Then, a straight line 503a connecting the representative point 502a of the corner portion of the hole 301a and the representative point 502c of the corner portion of the hole 301d, a straight line 503b connecting the representative point 502b of the corner portion of the hole 301a and the representative point 502d of the corner portion of the hole 301d, and the holes 301a and 301d define a region between the holes 301a and 301d as the inner peripheral side bridge portion 501a.

[0037] Similarly, representative points 502e to 502f of the corner portion of the hole 301b and representative points 502g to 502h of the corner portion of the hole 301d are selected. Then, a straight line 503c connecting the representative point 502e of the corner portion of the hole 301b and the representative point 502g of the corner portion of the hole 301d, a straight line 503d connecting the representative point 502f of the corner portion of the hole 301b and the representative point 502h of the corner portion of the hole 301d, and the holes 301b and 301d define a region between the holes 301b and 301d as the inner peripheral side bridge portion 501b. In the present embodiment, the inner peripheral side bridge portions 501a to 501b are determined as described above.

[0038] As described above, since the entire inner peripheral side bridge portions 501a to 501b are the low magnetic permeability portions 321a to 321b, the inner peripheral side bridge portions 501a to 501b shown in FIG. 5 coincide with the low magnetic permeability portions 321a to 321b shown in FIGS. 3 and 4. In FIG. 4, the symbols 321a(501a) and 321b(501b) indicate this fact.

[0039] As described above, the rotor core 111 of the present embodiment includes two inner peripheral side bridge portions 501a to 501b per pole, and an example where the entire inner peripheral side bridge portions 501a to 501b are low magnetic permeability portions 321a to 321b is illustrated. However, the number of inner peripheral side bridge portions per pole may be two or more, or may be one. For example, the hole 301d may be divided into two, and the regions between the two holes may be used as inner peripheral side bridge portions, respectively, and the entire inner peripheral side bridge portions may be used as low magnetic permeability portions. In this case, the inner peripheral side bridge portions will be arranged between two holes where no permanent magnet is installed. Also, without forming the hole 301d, the region between the holes 301a to 301b may be used as an inner peripheral side bridge portion, and the entire inner peripheral side bridge portion may be used as a low magnetic permeability portion. In this case, the inner peripheral side bridge portion will be arranged between two holes where permanent magnets are installed. Also, in this case, it is preferable to change the size and shape of the holes 301a to 301b so that the region between the holes 301a to 301b becomes narrower.

[0040] The present inventors have found that by making the entire inner peripheral side bridge portions 501a to 501b into low magnetic permeability portions 321a to 321b, the torque of the rotating electrical machine increases more than when only a part of the inner peripheral side bridge portions 501a to 501b is made into a low magnetic permeability portion. This will be described below. Here, as shown in FIGS. 3 and 4, what makes the entire inner peripheral side bridge portions 501a to 501b into low magnetic permeability portions 321a to 321b will be referred to as Example 1 of the present disclosure.

[0041] FIGS. 6, 7, and 8 are diagrams showing the configurations of Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the rotor core. FIGS. 6 to 8 are diagrams corresponding to FIG. 4.

[0042] As shown in FIG. 6, Comparative Example 1 is obtained by changing the low magnetic permeability portions 321a to 321b in Example 1 to high magnetic permeability portions 311 (that is, without the low magnetic permeability portions 321a to 321b), and the others are the same as those in Example 1. In Comparative Example 1, in the rotor core cross section, the value representing the ratio of the area of the low magnetic permeability portion in the inner peripheral side bridge portions 501a to 501b to the area of the inner peripheral side bridge portions 501a to 501b is 0% in percentage.

[0043] As shown in FIG. 7, Comparative Example 2 is obtained by changing the low magnetic permeability portions 321a to 321b in Example 1 to low magnetic permeability portions 721a to 721b, and the others are the same as those in Example 1. In Comparative Example 2, a part of the inner peripheral side bridge portions 501a to 501b is made into the low magnetic permeability portions 721a to 721b. In Comparative Example 2, in the rotor core cross section, the value representing the ratio of the area of the low magnetic permeability portions 721a to 721b in the inner peripheral side bridge portions 501a to 501b to the area of the inner peripheral side bridge portions 501a to 501b is 40% in percentage.

[0044] As shown in FIG. 8, Comparative Example 3 is obtained by changing the low magnetic permeability portions 321a to 321b in Example 1 to low magnetic permeability portions 821a to 821f, and the others are the same as those in Example 1. Also in Comparative Example 3, as in Comparative Example 2, a part of the inner peripheral side bridge portions 501a to 501b is made into the low magnetic permeability portions 821a to 821f. However, in Comparative Example 3, in the rotor core cross section, the value representing the ratio of the area of the low magnetic permeability portions 821a to 821f in the inner peripheral side bridge portions 501a to 501b to the area of the inner peripheral side bridge portions 501a to 501b is 60% in percentage.

[0045] The high magnetic permeability portions 311 in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 have the same magnetization characteristics. Also, the low magnetic permeability portions 321a to 321b in Example 1, Comparative Example 2, and Comparative Example 3 721a to 721b, 821a to 821f only differ in the area ratio they occupy in the inner peripheral side bridge portions 501a to 501b and have the same magnetization characteristics. Here, when evaluating the torque of the IPMSM by electromagnetic field analysis, a sample was fabricated by pressing an electromagnetic steel sheet of the same type as the high magnetic permeability portion 311 to a thickness that is half of the thickness of the electromagnetic steel sheet, and the magnetization characteristics of the sample were measured. The measured magnetization characteristics were used as the magnetization characteristics of the low magnetic permeability portions 321a to 321b, 721a to 721b, 821a to 821f. Note that the magnetization characteristics of the high magnetic permeability portion 311 are the magnetization characteristics of the electromagnetic steel sheet that constitutes the high magnetic permeability portion 311.

[0046] Under the operating conditions of rotational speed = 3000 rpm, exciting current (effective value of exciting current) = 20 A, and advance angle = 30 deg, the electromagnetic field analysis of the IPMSM equipped with the rotor cores of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was performed by the finite element method using the magnetization characteristics of the high magnetic permeability portion 311 and the magnetization characteristics of the low magnetic permeability portions 321a to 321b, 721a to 721b, 821a to 821f. Here, a two-dimensional electromagnetic field analysis in the x-y plane was performed. Then, based on the magnetic flux density vector obtained as a result of the electromagnetic field analysis, Maxwell's stress tensor was calculated, and the torque of the IPMSM was calculated from Maxwell's stress tensor.

[0047] As a result, in Comparative Example 1 shown in FIG. 6, the torque T of the IPMSM was 15.00 Nm, in Comparative Example 2 shown in FIG. 7, the torque of the IPMSM was 15.08 Nm, in Comparative Example 3 shown in FIG. 8, the torque T of the IPMSM was 15.10 Nm, and in Example 1 shown in FIG. 4, the torque T of the IPMSM was 15.14 Nm. Therefore, the larger the ratio of the area of the low magnetic permeability portion to the area of the inner peripheral side bridge portions 501a to 501b in the order of 321a to 321b, 721a to 721b, and 821a to 821f, the larger the torque of the IPMSM. Compared with Comparative Example 1 shown in FIG. 6, in Example 1 shown in FIG. 4, the torque of the IPMSM increased by 1.0%. Also, the maximum magnetic flux density within the inner peripheral side bridge portions 501a to 501b was 1.7 T in Comparative Example 1 shown in FIG. 6, whereas it was 1.4 T in Example 1 shown in FIG. 4. These results correspond to the fact that the larger the ratio of the area of the low magnetic permeability portion to the area of the inner peripheral side bridge portions 501a to 501b in the order of 321a to 321b, 721a to 721b, and 821a to 821f, the less the magnetic flux that refluxes through the inner peripheral side bridge portions 501a to 501b within the rotor core 111, and this contributes to an increase in the torque of the IPMSM100.

[0048] As described above, in the present embodiment, the entire inner peripheral side bridge portions 501a to 501b, which are disposed at least partially on the inner peripheral surface side of the rotor core 111 rather than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c are installed, are made into low magnetic permeability portions 321a to 321b. Therefore, the magnetic flux that refluxes through the inner peripheral side bridge portions 501a to 501b within the rotor core 111 can be reduced. Thus, the torque of the IPMSM100 can be increased. Also, making low magnetic permeability portions can increase the mechanical strength of the core more than making non-magnetic portions (relative magnetic permeability is the same as that of vacuum (=1)) as voids. Therefore, even when the outer dimensions of the rotor core 111 are the same, it is possible to produce a rotor core 111 that can increase the torque of the IPMSM100 and achieve higher rotational speeds, that is, achieve higher output.

[0049] In this embodiment, the rotating electrical machine is exemplified by an inner rotor type IPMSM 100. However, the rotating electrical machine is not limited to the inner rotor type IPMSM 100. For example, a low magnetic permeability portion may be formed in the rotor of an outer rotor type IPMSM motor in the same manner as described in this embodiment. In this case, the inner peripheral surface of the rotor core becomes the end surface facing the stator with a gap, and the outer peripheral surface of the rotor core becomes the end surface on the side opposite to the end surface facing the stator with a gap. Therefore, when forming a low magnetic permeability portion in the rotor of an outer rotor type IPMSM motor in the same manner as described in this embodiment, for example, in the description of this embodiment, the inner rotor may be replaced with an outer rotor, the outer periphery may be replaced with the inner periphery, and the inner periphery may be replaced with the outer periphery. As the rotating electrical machine, a low magnetic permeability portion may be formed in the rotor of a permanent magnet embedded type generator in the same manner as described in this embodiment, instead of a permanent magnet embedded type motor.

[0050] (Second Embodiment) Next, the second embodiment will be described. In the first embodiment, the case where the entire inner peripheral side bridge portions 501a to 501b are made into the low magnetic permeability portions 321a to 321b is exemplified. In this embodiment, the case where bridge portions other than the inner peripheral side bridge portions 501a to 501b are also made into low magnetic permeability portions will be described. Thus, this embodiment increases the locations where the low magnetic permeability portions are formed compared to the first embodiment. Therefore, in the description of this embodiment, for the same parts as in the first embodiment, the same reference numerals as those in FIGS. 1 to 8 are used and detailed descriptions are omitted.

[0051] In this embodiment, the rotor 110 shown in FIG. 2 is modified as follows. FIG. 9 is a diagram showing an example of the configuration of the rotor 910. FIG. 9 is a cross-sectional view of the rotor 910 (a diagram showing the rotor cross-section) when cut perpendicular to the center line 0 of the rotor 910, and is a diagram corresponding to FIG. 2. Also in this embodiment, similar to the first embodiment, the case where the rotor 910 rotates in the direction of the arrow line shown in FIG. 9 (counterclockwise direction toward the paper surface) and does not rotate in the direction opposite to the direction of the arrow line shown in FIG. 9 (clockwise direction toward the paper surface) is exemplified.

[0052] The rotor 910 includes a rotor core 911 and a plurality of permanent magnets 112 (three permanent magnets 112a to 112c per pole). The rotor core 911 is formed, for example, by laminating a plurality of electromagnetic steel sheets along the center line 0 of the rotor 910. However, it is not always necessary to form the rotor core 911 by laminating a plurality of electromagnetic steel sheets. As exemplified in the first embodiment, the rotor core 911 may be formed of other soft magnetic materials.

[0053] The holes formed in the rotor core 911 are the same as the holes formed in the rotor core 111 of the first embodiment. Also, the plurality of permanent magnets 112 are the same as the plurality of permanent magnets 112 of the first embodiment. Therefore, in the rotor 910 of this embodiment as well, the same flux barriers 113 (113a to 113j) and holes 114 as those of the rotor 110 of the first embodiment are formed.

[0054] Also, in this embodiment as well as in the first embodiment, an example is illustrated in which the shape of the rotor cross-section becomes the shape shown in FIG. 9 at any position in the z-axis direction of the rotor. Also, in FIG. 9, as in the first embodiment, a case where the number of poles of the IPMSM is 8 poles is illustrated. Also in FIG. 9, as in FIG. 2, since the notation becomes complicated, only the portions constituting one pole of the rotor 910 are labeled, and the notations for the portions constituting the other seven poles of the rotor 910 are omitted. 910

[0055] FIG. 10 is a diagram showing an example of the configuration of the rotor core 911. FIG. 10 is a cross-sectional view of the rotor core 911 when cut perpendicular to the center line 0 of the rotor core 911 (that is, a diagram showing the rotor core cross-section), and is a diagram corresponding to FIG. 3. Note that, as in FIG. 3, in FIG. 10 as well, only the portions constituting one pole of the rotor core 911 are labeled, and the notations for the portions constituting the other seven poles of the rotor core 911 are omitted. FIG. 11 is a diagram showing an enlarged view of a part of the rotor core 911 shown in FIG. 10, and is a diagram corresponding to FIG. 4.

[0056] ​In FIGS. 10 and 11, the rotor core 911 is obtained by making a part of the high magnetic permeability portion 311 of the rotor core 111 of the first embodiment into low magnetic permeability portions 1021a to 1021c and 1022a to 1022c. The relative magnetic permeability of the low magnetic permeability portions 321a to 321b, 1021a to 1021c, and 1022a to 1022c is smaller than the relative magnetic permeability of the high magnetic permeability portion 1011 and is larger than the relative magnetic permeability of vacuum (= 1) (relative magnetic permeability of vacuum < relative magnetic permeability of low magnetic permeability portions 321a to 321b, 1021a to 1021c, and 1022a to 1022c < relative magnetic permeability of high magnetic permeability portion 1011).

[0057] The low magnetic permeability portions 1021a to 1021c and 1022a to 1022c are manufactured by adopting, for example, one of the manufacturing methods of the low magnetic permeability portions 321a to 321b described in the first embodiment. From the viewpoint of reducing the workload, it is preferable to manufacture the low magnetic permeability portions 321a to 321b and the low magnetic permeability portions 1021a to 1021c and 1022a to 1022c by the same method. For example, by pressing the regions constituting the low magnetic permeability portions 321a to 321b, 1021a to 1021c, and 1022a to 1022c among the regions of the soft magnetic material (such as an electromagnetic steel sheet) constituting the rotor core 911, the low magnetic permeability portions 321a to 321b, 1021a to 1021c, and 1022a to 1022c can be manufactured, and the regions of the low magnetic permeability portions 321a to 321b, 1021a to 1021c, and 1022a to 1022c in one electromagnetic steel sheet can be manufactured by a single press.

[0058] The low magnetic permeability portions 1021a to 1021c and 1022a to 1022c are manufactured as part of a first outer peripheral side bridge portion or part of a second outer peripheral side bridge portion, which are bridge portions arranged on the outer peripheral side of the rotor core 911 rather than the inner peripheral side bridge portions 501a to 501b described in the first embodiment. The first outer peripheral side bridge portion is arranged on the leading side in the rotation direction of the rotor core 911 rather than the center in the circumferential direction of the region constituting one pole of the rotor core 911. On the other hand, the second outer peripheral side bridge portion is arranged on the trailing side in the rotation direction of the rotor core 911 rather than the center in the circumferential direction of the region constituting one pole of the rotor core 911.

[0059] In the examples shown in FIGS. 10 and 11, the low magnetic permeability portions 1021a to 1021c are formed in a part of the first outer peripheral side bridge portion. On the other hand, the low magnetic permeability portions 1022a to 1022c are formed in the entire second outer peripheral side bridge portion. FIG. 12 is a diagram showing an example of the first outer peripheral side bridge portions 1211a to 1211c and the second outer peripheral side bridge portions 1221a to 1221c. Note that, since the notation becomes complicated, the illustration of the low magnetic permeability portions 1021a to 1021c and 1022a to 1022c is omitted in FIG. 12.

[0060] In FIGS. 10 to 12, the first outer peripheral side bridge portions 1211a to 1211c and the second outer peripheral side bridge portions 1221a to 1221 c are bridge portions in which at least a part of the plurality of holes 301a to 301g formed in the rotor core 911 are arranged on the outer peripheral surface side of the rotor core 911 with respect to the inner peripheral side bridge portions 501a to 501b. The first outer peripheral side bridge portion and the second outer peripheral side bridge portion include a bridge portion disposed between two holes by being sandwiched between the two holes, or a bridge portion disposed between the hole and the outer peripheral surface of the rotor core by being sandwiched between one hole and the outer peripheral surface of the rotor core.

[0061] Specifically, the first outer peripheral side bridge portion 1211a is a bridge portion disposed between the hole 301a formed in the rotor core 911 and the outer peripheral surface of the rotor core 911. Further, the second outer peripheral side bridge portion 1221a is a bridge portion disposed between the hole 301b formed in the rotor core 911 and the outer peripheral surface of the rotor core 911.

[0062] As described above, in FIG. 12, the first outer peripheral side bridge portion 1211a (all regions of the first outer peripheral side bridge portion 1211a) is disposed on the leading side in the rotation direction of the rotor core 911 rather than at the center in the circumferential direction of the region that constitutes one pole of the rotor core 911. The second outer peripheral side bridge portion 1221a (all regions of the second outer peripheral side bridge portion 1221a) is disposed on the trailing side in the rotation direction of the rotor core 911 rather than at the center in the circumferential direction of the region that constitutes one pole of the rotor core 911. The leading side in the rotation direction of the rotor core 911 is the opposite side of the trailing side in the rotation direction of the rotor core 911. Hereinafter, the leading side in the rotation direction of the rotor core 911 will also be simply referred to as the leading side, and the trailing side in the rotation direction of the rotor core 911 will also be simply referred to as the trailing side.

[0063] In the example shown in FIG. 9, the region that constitutes one pole of the rotor core 911 is the range of the double arrow line indicated as "1 pole". In FIGS. 11 and 12, it is indicated by a virtual line 1101 connecting the position at the center in the circumferential direction of the region that constitutes one pole of the rotor core 911 and the center line 0. The position indicated by the virtual line 1101 is the position at the center in the circumferential direction of the region that constitutes one pole of the rotor core 911. The first outer peripheral side bridge portion 1211a (all regions of the first outer peripheral side bridge portion 1211a) is disposed on the leading side of the virtual line 1101, and the second outer peripheral side bridge portion 1221a (all regions of the second outer peripheral side bridge portion 1221a) is disposed on the trailing side of the virtual line 1101.

[0064] The leading side in the rotation direction of the rotor core 911 is the position side of the leading end of the permanent magnet 112 when viewed in the rotation direction of the rotor 910, and the trailing side in the rotation direction of the rotor core 911 is the position side of the trailing end of the permanent magnet 112. Specifically, in the example shown in FIG. 9, when viewed in the rotation direction of the rotor 910, the position of the leading end of the permanent magnet 112 is on the side surface 202 of the permanent magnet 112, and the position of the trailing end of the permanent magnet 112 is on the side surface 203 of the permanent magnet 112. Therefore, the rotor core 911 is disposed on the rotor 910 such that the leading side in the rotation direction of the rotor core 911 is on the side surface 202 side of the permanent magnet 112 and the trailing side in the rotation direction of the rotor core 911 is on the side surface 203 side of the permanent magnet 112.

[0065] Further, at least a part of the first outer peripheral side bridge portion 1211a is disposed on the outer peripheral surface side of the rotor core 911 rather than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c shown in FIG. 11 are installed. Similarly, at least a part of the second outer peripheral side bridge portion 1221a is disposed on the outer peripheral surface side of the rotor core 911 rather than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c shown in FIG. 11 are installed. In this embodiment as well, an inner rotor type IPMSM is exemplified. Therefore, also in this embodiment, as in the first embodiment, a case is exemplified in which the outer peripheral surface of the rotor 910 (rotor core 911) becomes an end surface facing the stator 120 of the rotor core 911 with a gap therebetween.

[0066] FIG. 12 exemplifies a case where all of the first outer peripheral side bridge portion 1211a and the second outer peripheral side bridge portion 1221a are disposed on the outer peripheral surface side of the rotor 910 (rotor core 911) rather than the regions 401a to 401c where the three permanent magnets 112a to 112c are installed (note that, as shown in FIG. 11, the region 401c where the permanent magnet 112c is installed is disposed on the outer peripheral surface side of the rotor 910 (rotor core 911) rather than the regions 401a to 401c where the permanent magnets 112a to 112c are installed). More specifically, in FIG. 12, a case is exemplified in which the first outer peripheral side bridge portion 1211a and the second outer peripheral side bridge portion 1221a are disposed between the holes 301a and 301b and the outer peripheral surface of the rotor 910 (rotor core 911).

[0067] Using FIG. 12, the region of the first outer peripheral side bridge portion 1211a will be described in more detail. The first outer peripheral side bridge portion 1211a is, in the rotor core cross-section, the region between the hole 301a and the outer peripheral surface of the rotor core 911, which is defined by two perpendicular lines drawn from the representative points of the two corner portions of the hole 301a adjacent to the first outer peripheral side bridge portion 1211a to the outer peripheral surface of the rotor core 911 (so as to be perpendicular to the tangent of the outer peripheral surface of the rotor core 911), the hole 301a, and the outer peripheral surface of the rotor core 911. The representative points of the two corner portions of the hole 301a are selected, for example, such that the perpendicular line does not pass through the inside of the hole 301a and the size of the first outer peripheral side bridge portion 1211a is maximized. In the rotor core cross-section, the perpendicular line drawn from the representative point of the corner portion to the outer peripheral surface of the rotor core 911 coincides with the straight line connecting the representative point of the corner portion and the center line 0.

[0068] For example, in the rotor core cross-section, when the corner portion appears as one vertex, the vertex is selected as the representative point of the corner portion. On the other hand, when the corner portion of the hole 301a has a curvature or the like and the corner portion is not determined by one vertex, the representative point of the corner portion of the hole 301a is taken as the corner portion from the region forming the corner portion such as the region having the curvature. The representative point of the corner portion is selected, for example, such that the size of the first outer peripheral side bridge portion 1211a is maximized. However, it is not necessarily required to select the representative point of the corner portion in this way. For example, the center position of the region forming the corner portion may be selected as the representative point.

[0069] In the example shown in FIG. 12, among the corner portions of the hole 301a, since two corner portions located at positions facing the outer peripheral surface of the rotor core 911 each have a curvature, points 1201a to 1201b are selected from the region forming the corner portion of the hole 301a to serve as the corner portion of the hole 301a. Then, a perpendicular line 1202a dropped from the representative point 1201a of the hole 301a to the outer peripheral surface of the rotor core 911, a perpendicular line 1202b dropped from the representative point 1201b of the hole 301a to the outer peripheral surface of the rotor core 911, the hole 301a, and the outer peripheral surface of the rotor core 911 define a region between the hole 301a and the outer peripheral surface of the rotor core 911 as the first outer peripheral side bridge portion 1211a.

[0070] Similarly, representative points 1201c to 1201d of the corner portion of the hole 301b are selected. Then, a perpendicular line 1202c dropped from the representative point 1201c of the hole 301b to the outer peripheral surface of the rotor core 911, a perpendicular line 1202d dropped from the representative point 1201d of the hole 301b to the outer peripheral surface of the rotor core 911, the hole 301b, and the outer peripheral surface of the rotor core 911 define a region between the hole 301b and the outer peripheral surface of the rotor core 911 as the second outer peripheral side bridge portion 1221a.

[0071] In FIG. 12, the first outer peripheral side bridge portion 1211b is a bridge portion disposed between the hole 301e formed in the rotor core 911 and the outer peripheral surface of the rotor core 911. The first outer peripheral side bridge portion 1211c is a bridge portion disposed between the holes 301c and 301e formed in the rotor core 911. The second outer peripheral side bridge portion 1221b is a bridge portion disposed between the hole 301f formed in the rotor core 911 and the outer peripheral surface of the rotor core 911. The second outer peripheral side bridge portion 1221c is a bridge portion disposed between the holes 301c and 301f formed in the rotor core 911.

[0072] Similar to the first outer peripheral side bridge portion 1211a, the first outer peripheral side bridge portions 1211b to 1211c (all regions of the first outer peripheral side bridge portions 1211b to 1211c) are arranged on the head side of the center in the circumferential direction of the region (in other words, the virtual line 1101) of the region constituting one pole of the rotor core 911. Similar to the second outer peripheral side bridge portion 1221a, the second outer peripheral side bridge portions 1221b to 1221c (all regions of the second outer peripheral side bridge portions 1221b to 1221c) are arranged on the tail side of the center in the circumferential direction of the region (virtual line 1101) of the region constituting one pole of the rotor core 911.

[0073] Also, similar to the first outer peripheral side bridge portion 1211a, at least a part of the first outer peripheral side bridge portions 1211b to 1211c is arranged on the outer peripheral surface side of the rotor core 911 rather than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c shown in FIG. 11 are installed. Also, similar to the second outer peripheral side bridge portion 1221a, at least a part of the second outer peripheral side bridge portions 1221b to 1221c is arranged on the outer peripheral surface side of the rotor core 911 rather than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c shown in FIG. 11 are installed.

[0074] In FIG. 12, an example is illustrated in which all of the first outer peripheral side bridge portion 1211b and the second outer peripheral side bridge portion 1221b are arranged on the outer peripheral surface side of the rotor 910 (rotor core 911) rather than the regions 401a to 401c where the permanent magnets 112a to 112c are installed. More specifically, in FIG. 12, an example is illustrated in which the first outer peripheral side bridge portion 1211b and the second outer peripheral side bridge portion 1221b are arranged between the holes 301e and 301f and the outer peripheral surface of the rotor 910 (rotor core 911). In this way, the first outer peripheral side bridge portion 1211b and the second outer peripheral side bridge portion 1221b are bridge portions between the outer peripheral surface of the rotor 910 (rotor core 911) and the holes, similar to the first outer peripheral side bridge portion 1211a and the second outer peripheral side bridge portion 1221a, and thus are defined in the same manner as the first outer peripheral side bridge portion 1211a and the second outer peripheral side bridge portion 1221a.

[0075] Specifically, in the example shown in FIG. 12, representative points 1201e to 1201f at the corner portions of the hole 301e are selected. Then, a perpendicular line 1202e dropped from the representative point 1201e of the hole 301e to the outer peripheral surface of the rotor core 911, a perpendicular line 1202f dropped from the representative point 1201f of the hole 301e to the outer peripheral surface of the rotor core 911, the hole 301e, and the outer peripheral surface of the rotor core 911 define a region between the hole 301e and the outer peripheral surface of the rotor core 911 as the first outer peripheral side bridge portion 1211b.

[0076] Similarly, representative points 1201h to 1201i at the corner portions of the hole 301f are selected. Then, a perpendicular line 1202g dropped from the representative point 1201h of the hole 301f to the outer peripheral surface of the rotor core 911, a perpendicular line 1202h dropped from the representative point 1201i of the hole 301f to the outer peripheral surface of the rotor core 911, the hole 301f, and the outer peripheral surface of the rotor core 911 define a region between the hole 301f and the outer peripheral surface of the rotor core 911 as the second outer peripheral side bridge portion 1221b.

[0077] Also, in FIG. 12, a case is illustrated where the first outer peripheral side bridge portion 1211c is disposed between the hole 301c and the hole 301e, and the second outer peripheral side bridge portion 1221c is disposed between the hole 301c and the hole 301f. At least a part of the first outer peripheral side bridge portion 1211c and the second outer peripheral side bridge portion 1221c is disposed closer to the outer peripheral surface side of the rotor 910 (rotor core 911) than at least one of the regions 401a to 401c where the permanent magnets 112a to 112c are installed. A case is illustrated where a part of the first outer peripheral side bridge portion 1211c and the second outer peripheral side bridge portion 1221c is disposed closer to the outer peripheral surface side of the rotor 910 (rotor core 911) than the region 401c where the permanent magnet 112c is installed.

[0078] Thus, the first outer peripheral side bridge portion 1211c and the second outer peripheral side bridge portion 1221c are bridge portions between two holes, similar to the inner peripheral side bridge portions 501a to 501b of the first embodiment, and are defined in the same manner as the inner peripheral side bridge portions 501a to 501b of the first embodiment.

[0079] Specifically, in the example shown in FIG. 12, representative points 1201f to 1201g at the corner of hole 301e are selected, and representative points 1201k to 1201l at the corner of hole 301c are selected. Then, a straight line 1202i connecting the representative point 1201f at the corner of hole 301e and the representative point 1201k at the corner of hole 301c, a straight line 1202j connecting the representative point 1201g at the corner of hole 301e and the representative point 1201l at the corner of hole 301c, and holes 301c and 301e define a region between holes 301c and 301e as the first outer peripheral side bridge portion 1211c.

[0080] Similarly, representative points 1201i to 1201j at the corner of hole 301f are selected, and representative points 1201m to 1201n at the corner of hole 301c are selected. Then, a straight line 1202k connecting the representative point 1201i at the corner of hole 301f and the representative point 1201m at the corner of hole 301c, a straight line 1202l connecting the representative point 1201j at the corner of hole 301f and the representative point 1201n at the corner of hole 301c, and holes 301c and 301f define a region between holes 301c and 301f as the second outer peripheral side bridge portion 1221c. In this embodiment, the first outer peripheral side bridge portions 1211a to 1211c and the second outer peripheral side bridge portions 1221a to 1221c are defined as described above.

[0081] As described above, since a part of the first outer peripheral side bridge portions 1211a to 1211c is the low magnetic permeability portions 1021a to 1021c, a part of the first outer peripheral side bridge portions 1211a to 1211c shown in FIG. 12 becomes the low magnetic permeability portions 1021a to 1021c, and the rest of the first outer peripheral side bridge portions 1211a to 1211c becomes the high magnetic permeability portion 1011. On the other hand, since the entire second outer peripheral side bridge portions 1221a to 1221c are the low magnetic permeability portions 1022a to 1022c, the second outer peripheral side bridge portions 1221a to 1221c shown in FIG. 12 coincide with the low magnetic permeability portions 1022a to 1022c shown in FIGS. 10 and 11. In FIG. 11, the notations 1021a (1221a), 1021b (1221b), and 1021c (1221c) mean this. In FIG. 11 as well, similar to FIG. 4, the notations 321a (501a) and 321b (501b) are given to indicate that the inner peripheral side bridge portions 501a to 501b coincide with the low magnetic permeability portions 321a to 321b.

[0082] The present inventors have found that by making a part of the first outer peripheral side bridge portions 1211a to 1211c, which are arranged on the leading side rather than the circumferential center of the region constituting one pole of the rotor core 911, the low magnetic permeability portions 1021a to 1021c, the torque of the rotating electrical machine increases more than when the entire first outer peripheral side bridge portions 1211a to 1211c are made the low magnetic permeability portions. This will be described below.

[0083] FIG. 13 is a diagram showing the configuration of Comparative Example 4 of the rotor core. FIG. 13 is a diagram corresponding to FIG. 11. Here, as shown in FIGS. 10 and 11, what makes a part of the first outer peripheral side bridge portions 1211a to 1211c the low magnetic permeability portions 1021a to 1021c will be referred to as Example 2 of the present disclosure. Here, for the sake of comparison with Example 2, the rotor core shown in FIG. 13 will be referred to as Comparative Example 4. However, Comparative Example 4 also makes the entire inner peripheral side bridge portions 501a to 501b the low magnetic permeability portions 321a to 321b, similar to Example 1 shown in FIGS. 3 and 4 described above, so it can also be called an example.

[0084] As shown in Fig. 13, Comparative Example 4 is obtained by changing the low magnetic permeability portions 1021a to 1021c in Example 2 to low magnetic permeability portions 1321a to 1321c (that is, the entire first outer peripheral side bridge portions 1211a to 1211c are made into low magnetic permeability portions), and the rest is the same as in Example 2. Therefore, in Comparative Example 4, in the rotor core cross-section, the value representing the ratio of the area of the low magnetic permeability portions in the first outer peripheral side bridge portions 1211a to 1211c to the area of the first outer peripheral side bridge portions 1211a to 1211c in percentage is 100%. On the other hand, in Example 2, in the rotor core cross-section, the value representing the ratio of the area of the low magnetic permeability portions in the first outer peripheral side bridge portions 1211a to 1211c to the area of the first outer peripheral side bridge portions 1211a to 1211c in percentage is 50%. Incidentally, in the rotor core cross-section, the value representing the ratio of the area of the low magnetic permeability portions in the first outer peripheral side bridge portions 1211a to 1211c to the area of the first outer peripheral side bridge portions 1211a to 1211c in percentage is preferably more than 0% and 90% or less, and more preferably more than 40% and 60% or less. Also, the number of low magnetic permeability portions formed in one of the first outer peripheral side bridge portions 1211a to 1211c may be one or more than one.

[0085] The low magnetic permeability portions 1021a to 1021c and 1321a to 1321c in Example 2 and Comparative Example 4 only have different area ratios in the first outer peripheral side bridge portions 1211a to 1211c and have the same magnetization characteristics. Here, when evaluating the torque of the IPMSM by electromagnetic field analysis, a sample is prepared by pressing an electromagnetic steel sheet of the same type as the high magnetic permeability portion 1011 to a thickness that is half of the thickness of the electromagnetic steel sheet, and the magnetization characteristics of the sample are measured. The measured magnetization characteristics are regarded as the magnetization characteristics of the low magnetic permeability portions 1021a to 1021c and 1321a to 1321c. Incidentally, the magnetization characteristics of the high magnetic permeability portion 1011 are the magnetization characteristics of the electromagnetic steel sheet constituting the high magnetic permeability portion 1011.

[0086] An electromagnetic field analysis of an IPMSM including rotor cores according to Example 2 and Comparative Example 4 was performed using the finite element method (FEM) with the magnetization characteristics of high permeability portion 1011 and the magnetization characteristics of low permeability portions 1021a-1021c and 1321a-1321c under the operating conditions of a rotation speed of 3000 rpm, an excitation current (effective value of the excitation current) of 20 A, and an advance angle of 30 degrees. Here, a two-dimensional electromagnetic field analysis was performed on the xy plane. Then, a Maxwell's stress tensor was calculated based on the magnetic flux density vector obtained as a result of the electromagnetic field analysis, and the torque of the IPMSM was calculated from the Maxwell's stress tensor.

[0087] As a result, the torque T of the IPMSM was 15.75 Nm in Comparative Example 4 shown in Fig. 13, whereas the torque T of the IPMSM was 15.76 Nm in Example 2 shown in Fig. 11. Therefore, the torque T of the IPMSM is greater when part of the first outer periphery bridge portions 1211a-1211c are made up of low permeability portions 1021a-1021c than when the entire first outer periphery bridge portions 1211a-1211c are made up of low permeability portions 1321a-1321c. In this example, the torque T of the IPMSM is increased by 0.1% in Example 2 shown in Fig. 11 compared to Comparative Example 4 shown in Fig. 13.

[0088] As described above, in this embodiment, at least a part of the rotor core is closer to the rotor core than at least one of the regions 401a to 401c in which the permanent magnets 112a to 112c are disposed. 911 In a region that is disposed on the outer peripheral surface side of the rotor core 911 and that constitutes one pole of the rotor core 911, a part of the first outer peripheral bridge portions 1211a to 1211c that is disposed on the leading side in the rotation direction from the circumferential center of the region is set as the low magnetic permeability portions 1021a to 1021c. Therefore, the torque of the IPMSM 100 can be further increased.

[0089] In this embodiment, at least a portion of the rotor core is closer to at least one of the regions 401a to 401c in which the permanent magnets 112a to 112c are disposed. 911In a region that constitutes one pole of rotor core 911, second outer periphery side bridge portions 1221a to 1221c that are arranged on the outer periphery side of rotor core 911 and are arranged further rearward in the direction of rotation than the circumferential center of that region are made into low permeability portions 1022a to 1022c. Therefore, the torque of IPMSM 100 can be further increased.

[0090] In this embodiment, as in the first embodiment, the entire inner bridge portions 501a-501b are formed as low permeability portions 321a-321b. However, a configuration in which the entire inner bridge portions 501a-501b are not formed as low permeability portions 321a-321b may be employed. In other words, a rotor core may be employed that does not include low permeability portions 321a-321b, but includes low permeability portions 1021a-1021c and 1022a-1022c.

[0091] Although it is preferable to make a portion of the first outer periphery bridge portions 1211a-1211c the low permeability portions 1021a-1021c, the entire first outer periphery bridge portions 1211a-1211c may be made low permeability portions. In this case, the entire bridge portions of the rotor core become low permeability portions. Also, a portion of the second outer periphery bridge portions 1221a-1221c may be made low permeability portions.

[0092] It should be noted that the above-described embodiments of the present disclosure are merely examples of specific embodiments for carrying out the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be embodied in various forms without departing from its technical concept or main features.

[0093] The following additional notes are provided regarding the above-described embodiments.

[0094] (Appendix 1) A rotor core having a plurality of holes including holes in which permanent magnets are installed, A high permeability part, a low-permeability portion having a relative permeability smaller than that of the high-permeability portion and larger than that of air, A rotor core in which the entire inner bridge portion, at least a portion of which is located closer to the inner surface of the rotor core than at least one of the areas in which the permanent magnets are installed, is the low magnetic permeability portion.

[0095] (Appendix 2) Each pole has two or more of the inner bridge portions, 2. The rotor core of claim 1, wherein the entirety of two or more of the inner bridge portions is the low magnetic permeability portion.

[0096] (Appendix 3) 3. The rotor core of claim 1, wherein the inner bridge portion is located between the two holes in which the permanent magnets are installed.

[0097] (Appendix 4) The plurality of holes further include holes in which no permanent magnets are installed, A rotor core according to any one of appendixes 1 to 3, wherein the inner bridge portion is located at least either between a hole in which the permanent magnet is installed and a hole in which the permanent magnet is not installed, or between two holes in which the permanent magnet is not installed.

[0098] (Appendix 5) A rotor core according to any one of appendices 1 to 4, wherein the inner bridge portion is located between the inner end portions of two holes, among the holes in which the permanent magnets are installed, that are arranged so that the pole faces of the installed permanent magnets are inclined with respect to the outer surface of the rotor core.

[0099] (Appendix 6) A rotor core according to any one of appendices 1 to 5, wherein the low magnetic permeability portion is a portion of a first outer bridge portion that is positioned toward the front of the rotational direction relative to the circumferential center of a region that constitutes one pole of the rotor core, and at least a portion of which is positioned closer to the outer surface of the rotor core than at least one of the regions in which the permanent magnets are installed.

[0100] (Appendix 7) In a region constituting one pole of the rotor core, the entire second outer peripheral side bridge portion is disposed on the trailing side in the rotational direction from the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core rather than at least one of the regions where the permanent magnet is installed, and the entire second outer peripheral side bridge portion is the low magnetic permeability portion, the rotor core of Appendix 6.

[0101] (Appendix 8) A rotor core including a plurality of holes including holes where permanent magnets are installed, a high magnetic permeability portion, a low magnetic permeability portion having a relative magnetic permeability smaller than that of the high magnetic permeability portion and larger than that of air, and In a region constituting one pole of the rotor core, a part of the first outer peripheral side bridge portion is disposed on the leading side in the rotational direction from the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core rather than at least one of the regions where the permanent magnet is installed, and the part of the first outer peripheral side bridge portion is the low magnetic permeability portion, the rotor core.

[0102] (Appendix 9) In a region constituting one pole of the rotor core, the rotor core of Appendix 8 is disposed on the trailing side in the rotational direction from the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core rather than at least one of the regions where the permanent magnet is installed.

[0103] (Appendix 10) The first outer peripheral side bridge portion is disposed in at least one of between the hole and the outer peripheral surface and between two holes including the hole where at least a part of the hole is disposed on the outer peripheral surface side rather than at least one of the regions where the permanent magnet is installed, the rotor core according to any one of Appendices 6 to 9.

[0104] (Appendix 11) The rotor core according to any one of Appendices 1 to 10, the permanent magnet, and a rotor including the same.

[0105] (Appendix 12) A rotor according to Appendix 11; a stator; A rotating electric machine comprising:

[0106] (Appendix 13) A rotor core having a plurality of holes including holes in which permanent magnets are installed, A high permeability part, a low-permeability portion having a relative magnetic permeability smaller than that of the high-permeability portion and larger than that of a vacuum, A rotor core in which the entire inner bridge portion, at least a portion of which is located closer to the inner surface of the rotor core than at least one of the areas in which the permanent magnets are installed, is the low magnetic permeability portion.

[0107] (Appendix 14) 14. The rotor core of claim 13, wherein the low permeability portion and the high permeability portion are integrally formed from the same material.

[0108] (Appendix 15) the high magnetic permeability portion is a portion made of a soft magnetic material, 15. The rotor core of claim 14, wherein the low magnetic permeability portion is a portion of the soft magnetic material whose magnetic permeability has been reduced.

[0109] (Appendix 16) Each pole has two or more of the inner bridge portions, 16. The rotor core according to any one of appendix 13 to appendix 15, wherein two or more of the inner periphery side bridge portions are entirely the low magnetic permeability portions.

[0110] (Appendix 17) 17. The rotor core according to any one of claims 13 to 16, wherein the inner bridge portion is located between the two holes in which the permanent magnets are installed.

[0111] (Appendix 18) The plurality of holes further include holes in which no permanent magnets are installed, The inner peripheral side bridge portion is a rotor core according to any one of Appendices 13 to 17, which is located in at least one of the spaces between the holes where the permanent magnets are installed and the holes where the permanent magnets are not installed, or between two holes where the permanent magnets are not installed.

[0112] (Appendix 19) The inner peripheral side bridge portion is a rotor core according to any one of Appendices 13 to 18, and there is at least one between the inner peripheral surface side ends of two holes arranged such that the magnetic pole surfaces of the permanent magnets to be installed are inclined with respect to the outer peripheral surface of the rotor core among the holes where the permanent magnets are installed.

[0113] (Appendix 20) A part of the first outer peripheral side bridge portion, which is arranged on the leading side in the rotation direction rather than the center in the circumferential direction of the region constituting one pole of the rotor core and at least a part of the region is arranged on the outer peripheral surface side of the rotor core rather than at least one of the regions where the permanent magnets are installed, is the low magnetic permeability portion, and it is a rotor core according to any one of Appendices 13 to 19.

[0114] (Appendix 21) The entire second outer peripheral side bridge portion, which is arranged on the trailing side in the rotation direction rather than the center in the circumferential direction of the region constituting one pole of the rotor core and at least a part of the region is arranged on the outer peripheral surface side of the rotor core rather than at least one of the regions where the permanent magnets are installed, is the low magnetic permeability portion, and it is a rotor core according to Appendix 20.

[0115] (Appendix 22) A rotor core including a plurality of holes including holes where permanent magnets are installed, A high magnetic permeability portion, A low magnetic permeability portion having a relative magnetic permeability smaller than that of the high magnetic permeability portion and larger than the relative magnetic permeability of vacuum, In a region constituting one pole of the rotor core, a part of the first outer peripheral side bridge portion is disposed on the leading side in the rotation direction from the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core with respect to at least one of the regions where the permanent magnet is installed. The rotor core, wherein the part is the low magnetic permeability portion.

[0116] (Appendix 23) The rotor core according to Appendix 22, wherein the low magnetic permeability portion and the high magnetic permeability portion are integrally formed of the same material.

[0117] (Appendix 24) The high magnetic permeability portion is a portion constituted by a soft magnetic material. The rotor core according to Appendix 23, wherein the low magnetic permeability portion is a portion obtained by reducing the magnetic permeability of the soft magnetic material.

[0118] (Appendix 25) In a region constituting one pole of the rotor core, the entire second outer peripheral side bridge portion is disposed on the trailing side in the rotation direction from the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core with respect to at least one of the regions where the permanent magnet is installed. The rotor core according to any one of Appendices 22 to 24, wherein the entire portion is the low magnetic permeability portion.

[0119] (Appendix 26) The rotor core according to any one of Appendices 20 to 25, wherein the first outer peripheral side bridge portion is disposed on at least one of between the hole and the outer peripheral surface and between two holes including the hole where at least a part is disposed on the outer peripheral surface side with respect to at least one of the regions where the permanent magnet is installed.

[0120] (Appendix 27) The rotor core according to any one of Appendices 13 to 26, and The permanent magnet, and A rotor comprising the same.

[0121] (Appendix 28) The rotor according to Appendix 27, and A stator, An electric rotating machine comprising

[0122] The disclosure of Japanese Patent Application No. 2021-060471 filed on March 31, 2021 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A rotor core having a plurality of holes including holes in which permanent magnets are installed, a high magnetic permeability portion, and a low magnetic permeability portion having a relative magnetic permeability smaller than that of the high magnetic permeability portion and larger than that of vacuum, In a region constituting one pole of the rotor core, a part of a first outer peripheral side bridge portion is disposed on the leading side in the rotational direction with respect to the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core with respect to at least one of the regions where the permanent magnet is installed, and the part is the low magnetic permeability portion, In a region constituting one pole of the rotor core, the entire second outer peripheral side bridge portion is disposed on the trailing side in the rotational direction with respect to the center in the circumferential direction of the region, and at least a part of the region is disposed on the outer peripheral surface side of the rotor core with respect to at least one of the regions where the permanent magnet is installed, and the entire portion is the low magnetic permeability portion, the rotor core.

2. The rotor core according to claim 1, wherein the low magnetic permeability portion and the high magnetic permeability portion are integrally formed of the same material.

3. The high magnetic permeability portion is a portion constituted by a soft magnetic material, The rotor core according to claim 2, wherein the low magnetic permeability portion is a portion obtained by reducing the magnetic permeability of the soft magnetic material.

4. The rotor core according to any one of claims 1 to 3, wherein the entire inner peripheral side bridge portion, at least a part of which is disposed on the inner peripheral surface side of the rotor core with respect to at least one of the regions where the permanent magnet is installed, is the low magnetic permeability portion.

5. Having two or more of the inner peripheral side bridge portions per pole, The rotor core according to claim 4, wherein the entire two or more of the inner peripheral side bridge portions are the low magnetic permeability portion.

6. The rotor core according to claim 4 or claim 5, wherein the inner peripheral side bridge portion is between the two holes in which the permanent magnets are installed.

7. The plurality of holes further includes holes in which permanent magnets are not installed, The rotor core according to any one of claims 4 to 6, wherein the inner peripheral side bridge portion is at least one of between the hole in which the permanent magnet is installed and the hole in which the permanent magnet is not installed, or between two holes in which the permanent magnet is not installed.

8. The inner peripheral side bridge portion is provided between the ends on the inner peripheral surface side of two holes among the holes in which the permanent magnet is installed, and the magnetic pole surface of the installed permanent magnet is inclined with respect to the outer peripheral surface of the rotor core. The rotor core according to any one of claims 4 to 7, wherein there is at least one.

9. The first outer peripheral side bridge portion is disposed on at least one of the regions between the hole and the outer peripheral surface and between two holes including the hole in which at least a part of the region where the permanent magnet is installed is disposed on the outer peripheral surface side. The rotor core according to any one of claims 1 to 8.

10. A rotor core according to any one of claims 1 to 9, The permanent magnet, A rotor comprising.

11. A rotor according to claim 10, A stator, An electric rotating machine comprising.

Images