Rotor core, rotor, and rotating electric machine

Abstract

The invention relates to a rotor comprising a number of holes in which permanent magnets are installed, such that: in a cross-section of the rotor core perpendicular to the axis of rotation, at least one of the holes comprises a first end positioned on the front face in the direction of rotation in the left and right directions, which is the direction on both the left and right sides with respect to the magnetization direction of the permanent magnet, and a second end positioned on the rear face in the direction of rotation in the left and right directions; the first end opens to the outer peripheral surface of the rotor core, and the circumferential length of the opening is longer than the circumferential length of the second end; in a cross-section, the hole to which the first end opens has an inner space whose length in the direction of width is equal to the length of the permanent magnet in the direction of magnetization, and the first outer space communicates with the inner space, whose first end is the end of the hole in the direction of rotation in the left and right directions, and is wider than the inner space;and the first head is positioned eccentrically at the rear in the direction of rotation relative to the center in the circumferential direction of the interior space at the point where the interior space connects with the first exterior space.

Description

Rotor core, rotor, and rotating electric machine

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

[0002] In an interior permanent magnet synchronous motor (IPMSM) or other rotating electrical machines with embedded permanent magnets, permanent magnets are embedded in the rotor core, and a flux barrier is formed near the permanent magnets. The flux barrier controls the flow of magnetic flux within the rotating electrical machine and improves the characteristics of the rotating electrical machine.

[0003] Japanese Patent Application Laid-Open Publication No. 2013-99047 discloses that by connecting the magnet insertion holes provided in the rotor core to the outer periphery of the rotor core, it is possible to prevent magnetic flux from the permanent magnet from circling around the permanent magnet within the rotor core and causing a short circuit.

[0004] However, the technology described in JP 2013-99047 A only considers magnetic short-circuiting of magnetic flux within the rotor core when connecting the magnet insertion holes provided in the rotor core to the outer periphery of the rotor core. Therefore, it is not possible to sufficiently increase the torque of the rotating electric machine. The present disclosure has been made in consideration of the above-mentioned problems, and aims to increase the torque of a rotating electric machine.

[0005] A rotor core according to one aspect of the present disclosure includes a plurality of holes in which permanent magnets are installed, and in a cross section perpendicular to a rotation axis that is the center of rotation, at least one of the plurality of holes includes a first end located at the leading end of the rotation direction in the left-right direction, which are directions on both the left and right sides of the magnetization direction of the permanent magnet, and a second end located at the trailing end of the rotation direction in the left-right direction, the first end opening to the outer peripheral surface, and the circumferential length of the opening being longer than the circumferential length of the second end, and in the cross section, the hole into which the first end opens has an inner space whose widthwise length is equal to the length corresponding to the length of the magnetization direction of the permanent magnet, and a first outer space that communicates with the inner space, has the first end as one of the left-right ends of the hole, and is wider than the inner space, and the first end is positioned so as to be biased towards the trailing end of the rotation direction with respect to the circumferential center position of the inner space at the position where it communicates with the first outer space.

[0006] According to one aspect of the present disclosure, the torque of a rotating electric machine can be increased.

[0007] 1 is a diagram illustrating an example of the configuration of an IPMSM. FIG. 1 is a diagram illustrating a first example of a rotor configuration, corresponding to the rotor of FIG. 1. FIG. 2 is a diagram illustrating a first example of a rotor core configuration, corresponding to the rotor core of FIG. 2. FIG. 3 is a diagram illustrating a first example of an inner space and a first outer space. FIG. 4 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a first end of a hole. FIG. 5 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a first end of a hole. FIG. 6 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a first end of a hole. FIG. 7 is a diagram illustrating an example of an inner space, a first outer space, and a second outer space. FIG. 8 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a second end of a hole. FIG. 9 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a second end of a hole. FIG. 10 is a diagram illustrating an example of a difference in magnetic flux flow due to a difference in a second end of a hole.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The term "comparison objects" as being the same in terms of length, position, size, spacing, etc., includes not only cases where they are exactly the same, but also cases where they differ within the scope of the gist of the present disclosure (for example, differences within the tolerance range determined at the time of design). In each figure, the x-y-z coordinates indicate the relationship of the orientations in each figure. In the x-y-z coordinates, a circle with a black circle indicates that the direction from the back of the page to the front is the positive direction.

[0009] First Embodiment First, a first embodiment will be described. In this embodiment, a rotating electric machine is illustrated as an IPMSM. 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 taken perpendicular to a center line O (the rotation axis of a 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 used to generate a rotating magnetic field. The stator coil included in the stator 120 is not shown in Fig. 1 to avoid complicating the notation, but the stator coil is disposed in a slot 122 of the stator core 121 (only one of the six slots is marked in Fig. 1).

[0011] The rotor 110 rotates around the center line O of the rotor 110 as the rotation axis. In this embodiment, a case is illustrated in which the rotor 110 rotates in the direction of the arrow shown in FIG. 1 (i.e., counterclockwise as viewed on the page) and does not rotate in the direction opposite to the direction of the arrow shown in FIG. 1 (i.e., clockwise as viewed on the page). FIG. 2 is a diagram showing an example of the configuration of the rotor 110. Like FIG. 1, FIG. 2 is a cross-sectional view of the rotor 110 taken perpendicular to the center line O of the rotor 110. Note that the center line O of the rotor 110 coincides with the center line O 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, one permanent magnet per pole). The rotor core 111 includes a soft magnetic portion, which is a portion of the rotor core 111 made of a soft magnetic material, and a plurality of holes. The soft magnetic portion is formed, for example, by stacking a plurality of electromagnetic steel plates along the center line O of the rotor 110. However, the soft magnetic portion does not necessarily have to be formed by stacking a plurality of electromagnetic steel plates. The rotor core 111 may be, for example, a powder magnetic core, an amorphous core, or a nanocrystalline core. Note that when the rotor core 111 is a powder magnetic core, an amorphous core, or a nanocrystalline core, the soft magnetic portion included in the rotor core 111 is formed using insulating-coated soft magnetic particles, an amorphous alloy, or a nanocrystalline alloy, respectively.

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

[0014] The multiple permanent magnets 112 are installed (embedded) in the rotor core 111 by being inserted into holes formed in the rotor core 111. Figure 2 illustrates an example in which magnetic flux flows in and out of magnetic pole faces 201 (201a, 201b) of the permanent magnets 112. The direction perpendicular to the magnetic pole faces 201 (the direction of the double-headed arrows in Figure 2 that cross the permanent magnets 112 in the radial direction of the rotor core 111) is the magnetization direction Dm of the permanent magnets 112. The radial direction is the direction extending radially on the xy plane from the center line O (the rotational axis of the rotor 110).

[0015] In the holes where the permanent magnets 112 are installed, the areas where the permanent magnets 112 are not present become flux barriers 113 (113a to 113b). The flux barriers 113 are voids (i.e., air regions) with no tangible material. The flux barriers 113 are regions through which magnetic flux does not pass or passes more difficultly than the surrounding regions. However, non-magnetic materials may be installed in the flux barriers 113. In addition to the flux barriers 113, the rotor core 111 also has holes 114 (114a to 114d) formed therein. The holes 114a to 114c are formed to function as flux barriers or to accommodate rivets (not shown). The rivets are used, for example, to secure the rotor 110 to end plates (not shown) located at both ends of the rotor 110 in the z-axis direction. A hole 114d penetrating the rotor core 111 in the z-axis direction is also formed on the inner periphery of the rotor core 111. A shaft or the like (not shown) is placed in the hole 114d.

[0016] In this embodiment, an example is given in which the shape of the cross section of the rotor 110 when cut perpendicular to the center line O of the rotor 110 (hereinafter referred to as the rotor cross section) is the shape shown in Figure 2 at any position in the z-axis direction of the rotor 110.

[0017] 1 and 2 illustrate an example in which the IPMSM 100 has four poles. In FIG. 2, the area indicated by the double-headed arrow labeled "1 pole" corresponds to the portion constituting one pole of the IPMSM 100. One permanent magnet 112 is embedded per pole, and a total of four permanent magnets are embedded in the holes of the rotor core 111. The number of poles and the number and arrangement of the permanent magnets 112 per pole are merely examples and can be determined arbitrarily. In FIG. 2, to avoid complicating the notation, only the portion constituting one pole of the rotor 110 is labeled with a reference numeral, and the reference numerals for the other three poles of the rotor 110 are omitted. Note that when the IPMSM 100 has n poles (where n is an integer greater than or equal to 2; in the example shown in FIGS. 1 and 2, n = 4), the IPMSM 100 generally has n-fold rotational symmetry with the center line O of the IPMSM 100 as the axis of rotational symmetry.

[0018] Fig. 3 is a diagram showing an example of the configuration of the rotor core 111. Like Figs. 1 and 2, Fig. 3 is a cross-sectional view of the rotor core 111 taken perpendicularly to the center line O of the rotor core 111. Note that the center line O of the rotor core 111 coincides with the center line O of the IPMSM 100 and the center line O of the rotor 110. Also, in Fig. 3, as in Fig. 2, reference numerals are assigned only to portions that constitute one pole of the rotor core 111, and reference numerals are omitted for portions that constitute the other three poles of the rotor core 111.

[0019] In FIG. 3 , rotor core 111 is formed with holes 310 that include an area occupied by permanent magnets 112 (hereinafter referred to as a magnet-occupied area) and an area that serves as a flux barrier 113. In a cross section of rotor core 111 taken perpendicular to center line O of rotor core 111 (hereinafter referred to as a rotor core cross section), at least one hole 310 (all four holes 310 in FIG. 3 ) is open at a first end 311 located at the leading end in the rotation direction of rotor core 111, among the ends in the left-right direction Ds, which are directions on both the left and right sides of magnetization direction Dm of permanent magnet 112 at the center of permanent magnet 112. In the example shown in FIG. 3 , the left-right direction Ds of hole 310 is the longitudinal direction of hole 310. In FIG. 3 , the left-right direction Ds of hole 310 is indicated by a double-arrowed line next to hole 310. On the other hand, in the cross section of the rotor core, the hole 310 does not open at a second end 312 on the opposite side of the first end 311 (in other words, the rear side in the rotation direction of the rotor core 111). Hereinafter, the leading side in the rotation direction of the rotor core 111 will also be simply referred to as the leading side, and the rear side in the rotation direction of the rotor core 111 will also be simply referred to as the rear side.

[0020] As described above, this embodiment illustrates a case where the IPMSM 100 has four poles. As shown in FIG. 3 , this embodiment illustrates a case where all four holes 310 in which permanent magnets 112 are installed are open at the first end 311. However, it is sufficient that at least one of the four holes 310 in which permanent magnets 112 are installed is open at the first end 311 of the hole 310. Also, this embodiment illustrates a case where not all of the four holes 310 in which permanent magnets 112 are installed are open at the second end 312. However, it is sufficient that at least one of the four holes 310 in which permanent magnets 112 are installed is not open at the second end 312.

[0021] 1 illustrates an example of an inner rotor type IPMSM 100. As shown in FIG. 1, the area of ​​the outer peripheral surface of the rotor 110 (rotor core 111) other than the hole 310 becomes an end face that faces the stator 120 of the rotor 110 (rotor core 111) with a gap therebetween.

[0022] Furthermore, the leading side of the rotor core 111 in the rotational direction is the leading side of the permanent magnet 112 when viewed in the rotational direction of the rotor 110, and the trailing side of the rotor core 111 in the rotational direction is the trailing side of the permanent magnet 112. Specifically, in the example shown in Figure 2, when viewed in the rotational direction of the rotor 110, the leading position of the permanent magnet 112 is on side surface 202 of the permanent magnet 112, and the trailing position of the permanent magnet 112 is on side surface 203 of the permanent magnet 112. Therefore, the rotor core 111 is arranged in the rotor 110 so that the leading side of the rotor core 111 in the rotational direction is on the side surface 202 of the permanent magnet 112, and the trailing side of the rotor core 111 in the rotational direction is on the side surface 203 of the permanent magnet 112. In the example shown in Figure 2, the side surfaces 202 and 203 of the permanent magnet 112 are end surfaces of the magnetic pole surfaces 201 (201a, 201b) of the permanent magnet 112 that are located at the ends in a direction perpendicular to the magnetization direction Dm of the permanent magnet 112.

[0023] In FIG. 3 , the hole 310 has an inner space 310a and a first outer space 310b. FIG. 4 is a diagram illustrating an example of the inner space 310a and the first outer space 310b. In the cross section of the rotor core, the inner space 310a is a space constituting the hole 310, whose widthwise length, which is along the magnetization direction Dm of the permanent magnet 112, is approximately constant and equal to the length L1 corresponding to the length of the magnetization direction Dm of the permanent magnet 112. As is clear from comparing FIG. 2 with FIGS. 3 and 4 , the permanent magnet 112 is installed in the inner space 310a. Therefore, the widthwise length of the magnet-occupied region of the hole 310 is the same as the widthwise length L1 of the inner space 310a. The widthwise length L1 of the inner space 310a may be the same as the length in the magnetization direction Dm of the permanent magnet 112, or may be (slightly) longer than the length in the magnetization direction Dm of the permanent magnet 112 to facilitate installation of the permanent magnet 112 in the hole 310. In this embodiment, the case where the length of the magnetization direction Dm of the permanent magnet 112 is constant is exemplified. However, the length of the magnetization direction Dm of the permanent magnet 112 does not necessarily have to be constant. If the length of the magnetization direction Dm of the permanent magnet 112 is not constant, the length in the width direction of the inner space 310a does not have to be constant and may be made equal to the length corresponding to the length of the magnetization direction Dm of the permanent magnet 112.

[0024] The width direction of the hole 310 is a direction perpendicular to both the left-right direction Ds of the hole 310 (the direction indicated by the double-headed arrows beside the hole 310 in FIGS. 3 and 4 ) and the depth direction of the hole 310 (the z-axis direction of the rotor core 111). As described above, the magnetization direction Dm of the permanent magnet 112 is the direction indicated by the double-headed arrows crossing the permanent magnet 112 in FIG. 2 , and the width direction of the inner space 310a coincides with the magnetization direction Dm of the permanent magnet 112. As shown in FIG. 3 , in a typical IPMSM 100, the length of the hole 310 in the left-right direction Ds, in which the permanent magnet 112 is installed, in the rotor core 111 is longer than the length of the hole 310 in the width direction. However, the length of the hole 310 in the left-right direction Ds may be the same as or shorter than the length of the hole 310 in the width direction.

[0025] The first outer space 310b is a space that communicates with the inner space 310a and the outside of the rotor core 111 among the spaces that constitute the hole 310. The first outer space 310b is a space that communicates with the inner space 310a among the spaces that constitute the hole 310 and has the first end 311 of the hole 310 as one of its ends in the left-right direction Ds. Therefore, the outer peripheral end of the first outer space 310b (in other words, the end opposite to the side that communicates with the inner space 310a) coincides with the first end 311 of the hole 310. There is no outer space aft of the inner space 310a, and the aft end of the inner space 310a coincides with the second end 312 of the hole 310. In other words, the second end 312 of the hole 310 is not open in the cross section of the rotor core. Meanwhile, the circumferential length of the first end 311 of the hole 310 is L2.

[0026] The circumferential length L2 of the first end 311 of the hole 310 is the circumferential length in the direction from the end point 401 on the leading side of the first end 311 of the hole 310 to the end point 402 on the trailing side of the first end 311 of the hole 310. The circumferential length L2 of the first end 311 of the hole 310 may be approximated to the widthwise length of the first end 311 of the hole 310. The widthwise length of the first end 311 of the hole 310 is the linear distance between the end point 401 on the leading side of the first end 311 of the hole 310 and the end point 402 on the trailing side of the first end 311 of the hole 310.

[0027] As shown in Fig. 4, in this embodiment, the circumferential length L2 of the first end 311 of the hole 310 is longer than the widthwise length L1 of the inner space 310a. The reason for this is explained below. Figs. 5A, 5B, and 5C are diagrams illustrating differences in magnetic flux flow depending on the first end 311 of the hole 310. Note that the magnetic flux indicated by the arrows in Figs. 5A, 5B, and 5C is a conceptual representation, and for example, the length and number of the arrows do not necessarily correspond to the magnitude and density of the magnetic flux.

[0028] 5A , 5B, and 5C show enlarged views of the vicinity of first end 311 of hole 310 when IPMSM 100 is operating. FIG. 5A shows the flow of magnetic flux assuming that first end 311 of hole 310 is not connected to the outer circumferential surface of rotor core 111. As shown in FIG. 5A , if first end 311 of hole 310 is not open, the region outside first end 311 of hole 310 is a soft magnetic material portion such as an electromagnetic steel plate. While the region inside first end 311 of hole 310 functions as a flux barrier, the soft magnetic material portion acts as a bridge portion, generating magnetic flux 501 that circulates within rotor core 111 rather than flowing toward stator core 121. As a result, the torque of IPMSM 100 cannot be sufficiently increased.

[0029] 5B shows the flow of magnetic flux when the circumferential length L2 of the first end 311 of the hole 310 is approximately the same as the widthwise length L1 of the inner space 310a of the hole 310. As shown in FIG. 5B , when the first end 311 of the hole 310 is open, the return of magnetic flux via the bridge portion as shown in FIG. 5A hardly occurs. Therefore, the return of magnetic flux is directed toward the stator core 121 at an angle relative to the radial direction of the IPMSM 100, thereby increasing the torque of the IPMSM 100. However, because the circumferential length L2 of the first end 311 of the hole 310 is short, there is a possibility that magnetic flux may pass through the flux barrier 113a.

[0030] 1 to 4, Fig. 5C shows the flow of magnetic flux when the circumferential length L2 of first end 311 of hole 310 is longer than the widthwise length L1 of inner space 310a of hole 310. As shown in Fig. 5C, by making the circumferential length L2 of first end 311 of hole 310 longer than the widthwise length L1 of inner space 310a, it is possible to more reliably reduce the generation of magnetic flux that passes through flux barrier 113a.

[0031] Furthermore, it is preferable to make the circumferential length L2 of the first end 311 of the hole 310 longer than the widthwise length L1 of the inner space 310a by making the circumferential length of the rearward region of the first end 311 of the hole 310 longer. This makes it possible to generate a large amount of magnetic flux in the region of the soft magnetic material portion rearward of the flux barrier 113a, which has an increased angle from the radial direction of the IPMSM 100 (i.e., the direction extending radially from the center line O on the xy plane) toward the leading edge in the circumferential direction (this corresponds to the fact that the directions of the magnetic fluxes 504 and 505 shown in FIG. 5C are inclined toward the leading edge in the circumferential direction more than the directions of the magnetic fluxes 502 and 503 shown in FIG. 5B). That is, when the magnetic flux density vectors representing the magnetic fluxes 504 and 505 shown in FIG. 5C are expressed in an r-θ coordinate system (two-dimensional polar coordinate system) with the center line O as the origin, the θ component B of the magnetic flux density vector due to the magnetic fluxes 504 and 505 is expressed as follows: θ This has the effect of increasing the reluctance torque of the IPMSM 100, and contributes to increasing the torque of the IPMSM 100.

[0032] This can also be seen from the following: When the formula for calculating torque T from Maxwell's stress tensor described in "Design and Application of AC / DC Electromagnets by Finite Element Method, by Takayoshi Nakata, Akiyoshi Ito, and Junhiro Kawase, August 1991, Morikita Publishing Co., Ltd." is converted to the r-θ coordinate system, torque T is expressed by the following formula (1).

[0033]

[0034] Here, L is the height of the rotor core (length in the z-axis direction). When the rotor core (specifically, the soft magnetic material portion of the rotor core) is made of electromagnetic steel sheets, L is the lamination thickness of the electromagnetic steel sheets. R is the radius of the rotor core. μ0 is the magnetic permeability of a vacuum. B r is the r component (i.e., the radial component) of the magnetic flux density vector. θ is the θ component (i.e., the deflection angle component) of the magnetic flux density vector. Here, the θ direction is the positive direction counterclockwise when facing the paper of FIGS. 5A, 5B, and 5C, and coincides with the rotation direction in this embodiment. Therefore, as shown in equation (1), the θ component B of the magnetic flux density vector θIt can be seen that as the value of is increased, the torque T is increased.

[0035] Therefore, it is preferable to configure the first end 311 of the hole 310 as follows. First, in FIG. 4 , the first outer space 310b of the hole 310 is a region wider than the inner space 310a of the hole 310. Furthermore, it is preferable that the first end 311 of the hole 310 is biased rearward in the circumferential direction relative to the center position 403 of the inner space 310a at the position (boundary) where the first end 311 communicates with the first outer space 310b. That is, it is preferable that the circumferential center position 404 of the first end 311 of the hole 310 is positioned rearward in the circumferential direction relative to the circumferential center position 403 of the inner space 310a at the position where the first end 311 communicates with the first outer space 310b. This corresponds to the circumferential center position 404 of the first end 311 of the hole 310 being positioned rearward in the circumferential direction relative to the extrapolated center position 406 of the inner space 310a of the hole 310 in FIG. 4 . The extrapolated center position 406 of the inner space 310a of the hole 310 is the position of the intersection between a straight line (dashed line extending from the center position 403 in FIG. 4 ) extending along the radial direction of the rotor core 111 from a center position 403 of the inner space 310a at the position (boundary) where the inner space 310a communicates with the first outer space 310b, and the first end 311 of the hole 310. In this way, a space recessed toward the center line O from the outer peripheral surface of the other regions of the rotor core 111 can be formed rearward of the end point 405 on the rear side of the inner space 310a. Therefore, it is possible to increase the magnetic flux density vector with a large positive θ component in the soft magnetic material portion rearward of the first outer space 310b. FIG. 4 illustrates such a case.

[0036] Furthermore, in this case, it is more preferable that the circumferential length L3 in the direction toward the rear, from the extrapolated center position 406 of the inner space 310a of the hole 310 to the end point 402 on the rear side of the first end 311 of the hole 310, be equal to or greater than the widthwise length L1 of the inner space 310a (L3≧L1). This makes it possible to increase the space recessed toward the center line O from the outer peripheral surface of other regions of the rotor core 111, rearward of the end point 405 on the rear side of the inner space 310a. Therefore, it is possible to further increase the magnetic flux density vector with a large θ component rearward of the flux barrier 113a (first outer space 310b). Figure 4 illustrates this case.

[0037] Furthermore, it is even more preferable that the circumferential length L4 in the direction toward the rear from the extrapolated position 407 of the rear end point of the inner space 310a of the hole 310 to the end point 402 on the rear side of the first end 311 of the hole 310 be equal to or greater than the widthwise length L1 of the inner space 310a (L4≧L1). The extrapolated position 407 of the rear end point of the inner space 310a of the hole 310 is the position of the intersection of a straight line extending from an end point 405 on the rear side of the inner space 310a at a position where the inner space 310a communicates with the first outer space 310b along the radial direction of the rotor core 111 (the dashed line extending from the end point 405 in FIG. 4 ), and the first end 311 of the hole 310. In this way, the space recessed toward the center line O from the outer circumferential surface of the rotor core 111 in other regions can be made even larger on the rear side of the end point 405 on the rear side of the inner space 310a. Therefore, the magnetic flux density vector with a large θ component can be further increased on the rear side of the flux barrier 113a (first outer space 310b). FIG. 4 illustrates such a case.

[0038] As shown in FIG. 4 , the hole wall surface 310W of the hole 310 includes a rear wall surface 310W1 that forms the rear side of the first outer space 310b in the rotational direction and is inclined relative to a direction perpendicular to the center line O (radial direction). Specifically, as shown in FIGS. 4 and 6 , the rear wall surface 310W1 is formed so that the length of the hole 310 in the width direction gradually increases toward the outer periphery. The rear wall surface 310W1 is also concavely curved. The concavely curved portion formed on the rear wall surface 310W1 may be present on at least a portion of the rear wall surface 310W1. Specifically, the rear wall surface 310W1 is formed in a stepped shape that is concavely curved relative to an imaginary line connecting the end points 402 and 405. For example, the stepped shape may include a portion that intersects with the imaginary line, but the portion on the rear side and / or radially inward of the imaginary line may be longer than the portion on the opposite side. Note that the present disclosure is not limited to this configuration, and the rear wall surface 310W1 may be linear (aligned with an imaginary straight line) or curved (a curved surface that curves in an arc relative to an imaginary straight line). Here, tilting the rear wall surface 310W1 relative to a direction perpendicular to the center line O (radial direction) can increase the magnetic resistance of the soft magnetic material portion located rearward of the first outer space 310b, thereby increasing the number of magnetic flux density vectors with a large positive θ component. This can further increase the reluctance torque. Furthermore, curving the rear wall surface 310W1 in a concave shape can further increase the magnetic resistance of the soft magnetic material portion, thereby further increasing the number of magnetic flux density vectors with a large positive θ component.

[0039] The shape and radial length of first outer space 310b are not limited to those shown in Fig. 3 and Fig. 4. For example, the shape and radial length of first outer space 310b may be determined based on the results of an electromagnetic field analysis of IPMSM 100 so that the torque T of IPMSM 100 is greater when first outer space 310b is formed as described above compared to when first outer space 310b is not formed.

[0040] On the other hand, as described above, the second end 312 of the hole 310 does not communicate with the outer peripheral surface of the rotor core 111 (in other words, the end surface facing the stator 120 with a gap therebetween). Therefore, as shown in FIG. 4 , the rear end of the inner space 310a in the left-right direction Ds coincides with the second end 312 of the hole 310. In the rotor core 111 shown in FIG. 3 , if the second end 312 of the hole 310 were open, the region of the rotor core 111 on the outer peripheral side of the hole 310 would be isolated, and the rotor core 111 would have a shape in which this region appears to be floating in midair. This would reduce the mechanical strength of the rotor core 111. In such a case, a measure would be required, such as placing a nonmagnetic material in the second end 312 of the hole 310 to connect the outer peripheral region and the inner peripheral region of the rotor core 111. However, due to manufacturing difficulties, such an arrangement may not be directly adopted. Therefore, in this embodiment, the second end 312 of the hole 310 is not open.

[0041] Here, the reason why the first end 311 of the hole 310 is opened instead of the second end 312 of the hole 310 is that the magnetic flux density vector B in the θ direction is smaller in this way than when the second end 312 of the hole 310 is opened instead of the first end 311 of the hole 310. θ This is because the positive component of can be increased. This will be explained below.

[0042] FIG. 6 is a diagram illustrating an example of the inner space 310a, the first outer space 310b, and the second outer space 310c, and corresponds to FIG. 4. FIGS. 7A, 7B, and 7C are diagrams illustrating differences in magnetic flux flow depending on the second end 312 of the hole 310. FIGS. 7A, 7B, and 7C correspond to FIGS. 5A, 5B, and 5C, respectively. That is, FIG. 7A illustrates the magnetic flux flow when the second end 312 of the hole 310 is not open, as shown in FIGS. 3 and 4. FIG. 7B illustrates the magnetic flux flow when the second end 312 of the hole 310 is open and the circumferential length L12 of the second end 312 of the hole 310 is substantially the same as the widthwise length L1 of the inner space 310a of the hole 310. 7C shows the flow of magnetic flux when second end 312 of hole 310 is open and the circumferential length L12 of second end 312 of hole 310 is longer than the widthwise length L1 of inner space 310a of hole 310. Note that in Figures 7A, 7B, and 7C, as in Figures 5A, 5B, and 5C, the magnetic flux indicated by arrows is a conceptual representation, and for example, the length and number of arrows do not necessarily correspond to the magnitude and density of the magnetic flux.

[0043] 7A , if second end 312 of hole 310 is not opened, the region outside second end 312 of hole 310 becomes a soft magnetic material portion such as an electromagnetic steel plate, and the region inside first end 311 of hole 310 functions as a flux barrier. However, the soft magnetic material portion becomes a bridge portion, generating magnetic flux 701 that circulates within rotor core 111 rather than flowing toward stator core 121. This makes it difficult to increase the torque of IPMSM 100. However, as described above, in order to prevent the region on the outer periphery of rotor core 111 from appearing suspended in air, second end 312 of hole 310 is not opened in this embodiment.

[0044] 6 , it is assumed that a second outer space 310c similar to the first outer space 310b of the first end 311 of the hole 310 is also formed at the second end 312 of the hole 310, and that the circumferential length L12 of the second end 312 of the hole 310 is longer than the widthwise length L1 of the inner space 310a. Note that the circumferential length L12 of the end 312 at the rear side of the rotor core 111 is the circumferential length in the direction toward the leading end, from an end point 411 at the rear side of the second end 312 of the hole 310 to an end point 412 at the leading end of the second end 312 of the hole 310. The circumferential length L12 of the end 312 at the rear side of the rotor core 111 may be approximated to the widthwise length of the end 312 at the rear side of the rotor core 111 (the linear distance between the end points 411 and 412).

[0045] Under this assumption, it is preferable that the second end 312 of the hole 310 be biased toward the leading edge in the circumferential direction relative to the center position 413 of the inner space 310a at the position where the second end 312 communicates with the second outer space 310c. In other words, it is preferable that the circumferential center position 414 of the second end 312 of the hole 310 be positioned toward the leading edge in the circumferential direction relative to the circumferential center position 413 of the inner space 310a at the position where the second end 312 communicates with the second outer space 310c. This corresponds to the fact that, in Figure 6, the circumferential center position 414 of the second end 312 of the hole 310 is positioned toward the leading edge in the circumferential direction relative to the extrapolated center position 416 of the inner space 310a of the hole 310. The extrapolated center position 416 of the inner space 310a of the hole 310 is the position of the intersection of a straight line (dashed line extending from the center position 413 in Figure 6) extending along the radial direction of the rotor core 111 from the center position 413 of the inner space 310a at the position (boundary) where it communicates with the second outer space 310c, and the second end 312 of the hole 310.

[0046] In this case, it is more preferable that the circumferential length L13 in the direction toward the leading edge, from the extrapolated center position 416 of the inner space 310a of the hole 310 to the leading end point 412 of the second end 312 of the hole 310, be equal to or greater than the widthwise length L1 of the inner space 310a (L13≧L1). Furthermore, it is even more preferable that the circumferential length L14 in the direction toward the leading edge, from the leading end point extrapolated position 417 of the inner space 310a of the hole 310 to the leading end point 412 of the second end 312 of the hole 310, be equal to or greater than the widthwise length L1 of the inner space 310a (L14≧L1). The leading end point extrapolation position 417 of the inner space 310a of the hole 310 is the position of the intersection of a straight line (dashed line extending from the end point 415 in Figure 4) extending along the radial direction of the rotor core 111 from the end point 415 at the leading side of the inner space 310a at the position where it communicates with the second outer space 310c, and the second end 312 of the hole 310.

[0047] 4 and 6 , the rearward region of the first outer space 310b is expanded. Therefore, as shown in FIG. 5B , the magnetic flux at a position near the end point 402 on the rearward side of the first outer space 310b travels from the rearward side (i.e., rearward with respect to the direction of rotation of the rotor core 111) toward the stator core 121, compared to when the circumferential length L2 of the first end 311 of the hole 310 is substantially equal to the widthwise length L1 of the magnet-occupied region of the hole 310 (i.e., the widthwise length of the inner space 310a) (see magnetic fluxes 502 and 503 shown in FIG. 5B and magnetic fluxes 504 and 505 shown in FIG. 5C ). Because the rotor core 111 is rotating toward the forward side, the direction of travel of the magnetic fluxes 504 and 505 is significantly inclined relative to the direction of travel of the magnetic fluxes 502 and 503, and the positive component in the θ direction of the magnetic flux density vector represented by the magnetic fluxes 504 and 505 becomes large.

[0048] On the other hand, by forming second outer space 310c as shown in Fig. 6, the region on the leading side of second outer space 310c is expanded. Therefore, magnetic flux at a position near end point 412 on the leading side of second outer space 310c travels from the leading side (i.e., forward with respect to the direction of rotation of rotor core 111) toward stator core 121, compared to when circumferential length L12 of second end 312 of hole 310 is substantially the same as widthwise length L1 of the magnet-occupied region of hole 310 (i.e., widthwise length L1 of inner space 310a), as shown in Fig. 7B (see magnetic fluxes 702 and 703 shown in Fig. 7B and magnetic fluxes 704 and 705 shown in Fig. 7C). However, because rotor core 111 rotates toward the front, the direction of travel of magnetic fluxes 704, 705 is not inclined as much as magnetic fluxes 504, 505 shown in Fig. 5C, and the increase in the positive component in the θ direction of the magnetic flux density vector represented by magnetic fluxes 704, 705 is smaller than the θ component of the magnetic flux density vector represented by magnetic fluxes 504, 505 shown in Fig. 5C. Furthermore, if second outer space 310c is formed so that L12 > L1 as shown in Fig. 6, the mechanical strength of rotor core 111 will be significantly reduced, and manufacturing will also be more difficult.

[0049] As described above, because rotor core 111 rotates toward the leading end, directing the magnetic flux return via the bridge portion as shown in Fig. 5A toward stator core 121 as shown in Fig. 5C can make the direction of magnetic flux more inclined with respect to the radial direction of IPMSM 100 than directing the magnetic flux return via the bridge portion as shown in Fig. 7A toward stator core 121 as shown in Fig. 7C, thereby making it possible to increase the positive component of the magnetic flux density vector in the θ direction. For the reasons described above, in this embodiment, first end 311 of hole 310 is opened, rather than second end 312 of hole 310.

[0050] As described above, in this embodiment, at least one of the holes 310 in which the permanent magnets 112 are installed is open at the first end 311 in the cross section of the rotor core. Furthermore, the circumferential length L2 of the first end 311 of the hole 310 (i.e., the circumferential length of the opening of the first end 311) is longer than the circumferential length of the opening of the second end 312. Therefore, the magnetic flux 501 circulating within the rotor core 111 on the first end 311 side of the hole 310 can be suppressed, and the reluctance torque can be increased. This allows the torque T of the IPMSM 100 to be increased.

[0051] Furthermore, in this embodiment, by preventing the second end 312 of the hole 310 from opening in the cross section of the rotor core, the circumferential length L2 of the first end 311 of the hole 310 (i.e., the circumferential length of the opening of the first end 311) is made longer than the circumferential length of the opening of the second end 312. Therefore, the torque T of the IPMSM 100 and the mechanical strength of the rotor core 111 can be increased without using a non-magnetic material or the like.

[0052] Furthermore, in this embodiment, in the cross section of the rotor core, the circumferential length L2 of the first end 311 of the hole 310 is longer than the length L1 in the magnetization direction Dm of the permanent magnet 112 (i.e., the widthwise length L1 of the magnet-occupied area of ​​the hole 310 (the widthwise length of the inner space 310a)). Therefore, on the first end 311 side of the hole 310 in the left-right direction Ds, it is possible to reliably suppress the magnetic flux 501 circulating within the rotor core 111 and reliably increase the reluctance torque.

[0053] Furthermore, in this embodiment, first ends 311 of all holes 310 are open in the cross section of the rotor core. Therefore, magnetic flux 501 circulating within rotor core 111 can be more reliably suppressed on the side of first end 311 of each hole 310, and reluctance torque can be more reliably increased.

[0054] In addition, in the present embodiment, in the cross section of the rotor core, the first end 311 of the hole 310 is biased rearward in the circumferential direction with respect to the center position 403 of the inner space 310a at the position where the inner space 310a communicates with the first outer space 310b. Therefore, the reluctance torque can be made larger on the side of the first end 311 of the hole 310.

[0055] Furthermore, in the present embodiment, in the cross section of the rotor core, a circumferential length L4 in the direction toward the aft side from an extrapolated position 407 of the aft end point of the inner space 310a of the hole 310 to an end point 402 on the aft side of the first end 311 of the hole 310 is equal to or greater than the widthwise length L1 of the inner space 310a (L4≧L1). Therefore, the reluctance torque can be further increased on the side of the first end 311 of the hole 310.

[0056] Second Embodiment Next, a second embodiment will be described. In the first embodiment, a case was illustrated in which, in the cross section of the rotor core, the second ends 312 of the holes 310 in which the permanent magnets 112 are installed are not open. In contrast, in the present embodiment, a case will be described in which, in the cross section of the rotor core, the second ends of the holes in which the permanent magnets 112 are installed are open. As such, the main difference between this embodiment and the first embodiment is the second ends 312 of the holes 310. Therefore, in the description of this embodiment, the same parts as those in the first embodiment will be denoted by the same reference numerals as those used in FIGS. 1 to 7C, and detailed description thereof will be omitted.

[0057] In this embodiment, the rotor 110 shown in Fig. 2 is modified as follows. Fig. 8 is a diagram showing an example of the configuration of a rotor 810. Fig. 8 is a cross-sectional view of the rotor 810 taken perpendicular to the center line O of the rotor 810, and corresponds to Fig. 2. In this embodiment, as in the first embodiment, an example is shown in which the rotor 810 rotates in the direction of the arrow shown in Fig. 8 (i.e., counterclockwise as viewed on the paper), but does not rotate in the direction opposite to the direction of the arrow shown in Fig. 8 (i.e., clockwise as viewed on the paper).

[0058] The rotor 810 includes a rotor core 811 and a plurality of permanent magnets 112. The rotor core 811 includes a soft magnetic material portion and a plurality of holes. The soft magnetic material portion is formed, for example, by stacking a plurality of electromagnetic steel sheets along the center line O of the rotor 810. However, the soft magnetic material portion does not necessarily have to be formed by stacking a plurality of electromagnetic steel sheets. As exemplified in the first embodiment, the soft magnetic material portion may be formed from another soft magnetic material.

[0059] In the holes where the permanent magnets 112 are installed, the regions where the permanent magnets 112 are not present become flux barriers 813 (813a to 813b). The rotor 110 shown in FIG. 2 differs from the rotor 810 shown in FIG. 8 in the shape and size of the flux barriers 813b. The flux barrier 113a shown in FIG. 2 is the same as the flux barrier 813a shown in FIG. 8. As described in the first embodiment, the flux barriers 813a to 813b may be gaps (i.e., air regions) or may be provided with non-magnetic material. However, to prevent the region of the rotor core 811 outer circumferentially of the flux barrier 813 from being isolated and appearing to be floating in the air, it is preferable to install a non-magnetic material in, for example, part or all of the flux barrier 813b.

[0060] In this embodiment, as in the first embodiment, the cross-sectional shape of the rotor is the shape shown in FIG. 8 at any position in the z-axis direction of the rotor 810.

[0061] 8 illustrates an example in which the number of poles of the IPMSM is four, similar to the first embodiment. In FIG. 8, similar to FIG. 2, to avoid complicating the notation, reference numerals are assigned only to the portion constituting one pole of the rotor 810, and reference numerals are omitted for the portions constituting the other three poles of the rotor 810.

[0062] Fig. 9 is a diagram showing an example of the configuration of rotor core 811. Fig. 9 is a cross-sectional view of rotor core 811 cut perpendicularly to the center line O of rotor core 811, and corresponds to Fig. 3. In Fig. 9, as in Fig. 3, reference numerals are assigned only to the parts that constitute one pole of rotor core 811, and reference numerals are omitted for the parts that constitute the other three poles of rotor core 811.

[0063] 9 , a rotor core 811 has a hole 910 formed therein, the hole 910 including a magnet-occupied region and a region that serves as a flux barrier 813. In the cross section of the rotor core, a first end 911 of the hole 910 is open. In addition, a second end 912 of the hole 910 is also open in the cross section of the rotor core.

[0064] As in the first embodiment, this embodiment also illustrates a case in which, in the cross section of the rotor core, all of the four holes 910 in which the permanent magnets 112 are installed are open at the first end 911 of the hole 910. However, it is sufficient that the first end 911 of at least one of the four holes 910 in which the permanent magnets 112 are installed is open. Similarly, this embodiment illustrates a case in which the second end 912 of the hole 910 is open at all of the four holes 910 in which the permanent magnets 112 are installed. However, it is sufficient that the second end 912 of the hole 910 is open at least one of the four holes 910 in which the permanent magnets 112 are installed.

[0065] In Fig. 9, the hole 910 has an inner space 910a and a first outer space 910b. Fig. 10 is a diagram illustrating the inner space 910a and the first outer space 910b, and corresponds to Fig. 4. In Fig. 10, the first outer space 910b is the same as the first outer space 310b shown in Fig. 4.

[0066] In the cross section of the rotor core, the inner space 910a is a space constituting the hole 910, whose widthwise length is substantially constant and equal to the length L1 corresponding to the length of the magnetization direction Dm of the permanent magnet 112. As in the first embodiment, the leading end of the inner space 910a coincides with the trailing end of the first outer space 910b. Furthermore, the trailing end of the inner space 910a (i.e., the end opposite the side communicating with the first outer space 910b) coincides with the second end 912 of the hole 910. Therefore, the circumferential length of the second end 912 of the hole 910 is substantially the same as the widthwise length L1 of the inner space 910a. Meanwhile, the circumferential length L2 of the first end 911 of the hole 910 is longer than the circumferential length L1 of the second end 912 of the hole 910. As described above, the circumferential lengths L2, L1 of the open ends 911, 912 of the hole 910 in the left-right direction Ds are such that the leading end 911 is longer than the trailing end 912 (L2 > L1). Therefore, the torque T of the IPMSM can be increased while preventing the magnetic flux 701 from circumferentially flowing within the rotor core 111 shown in FIG. 7A . On the other hand, if the rotor core is formed solely from soft magnetic material portions, the mechanical strength of the rotor core 811 is reduced compared to the rotor core 111 of the first embodiment. Therefore, to prevent the mechanical strength of the rotor core 811 from decreasing, it is preferable to provide a non-magnetic material in, for example, part or all of the flux barrier 813b. Therefore, for example, the second embodiment may be adopted when it is important to prevent the magnetic flux 701 from circumferentially flowing within the rotor core, whereas the first embodiment may be adopted when it is important to prevent the mechanical strength of the rotor core from decreasing. Note that the various modifications described in the first embodiment may also be adopted in this embodiment.

[0067] (Calculation Example) In this calculation example, an electromagnetic field analysis of each IPMSM was performed using the finite element method when the IPMSM was operated under the following operating conditions: rotation speed = 3000 rpm, excitation current (effective value) = 5.5 A, and advance angle = 20 deg. Then, 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 T of the IPMSM was calculated from the Maxwell's stress tensor. Hereinafter, the rotor 110 of the first embodiment will be referred to as the rotor of Example 1, and the rotor 810 of the second embodiment will be referred to as the rotor of Example 2.

[0068] FIG. 11 is a diagram illustrating the configuration of a rotor 1100 of Comparative Example 1. FIG. 11 is a cross-sectional view of the rotor 1100 taken perpendicular to the center line O of the rotor 1100, and corresponds to FIG. 2 . The rotor cross-sectional shape is the shape shown in FIG. 11 at any position in the z-axis direction of the rotor 1100. Similar to Examples 1 and 2, Comparative Example 1 also illustrates a case in which the IPMSM has four poles. Also, similar to FIG. 2 , in FIG. 11 , to avoid complicating the notation, only the portion constituting one pole of the rotor 1100 is labeled with a reference numeral, and the portions constituting the other three poles of the rotor 1100 are omitted. As shown in FIG. 11 , in the rotor 1100 of Comparative Example 1, neither the first end 1111 of the hole in which the permanent magnet 112 is installed nor the second end 1112 of the hole in which the permanent magnet 112 is installed is open in the rotor core cross-section.

[0069] FIG. 12 is a diagram illustrating the configuration of a rotor 1200 of Comparative Example 2. FIG. 12 is a cross-sectional view of the rotor 1200 taken perpendicular to the center line O of the rotor 1200, and corresponds to FIG. 2 . The rotor cross-sectional shape is the shape shown in FIG. 12 at any position in the z-axis direction of the rotor 1200. Similar to Examples 1 and 2, Comparative Example 2 also illustrates a case in which the IPMSM has four poles. Also, similar to FIG. 2 , in FIG. 12 , to avoid complicating the notation, only the portion constituting one pole of the rotor 1200 is labeled with a reference numeral, and the portions constituting the other three poles of the rotor 1200 are omitted. As shown in FIG. 12 , in the rotor 1200 of Comparative Example 1, both a first end 1211 of the hole in which the permanent magnet 112 is installed and a second end 1212 of the hole in which the permanent magnet 112 is installed are open in the rotor core cross-section. However, the circumferential length of the first end 1211 of the hole in which the permanent magnet 112 is installed is the same as the circumferential length of the second end 1212 of the hole in which the permanent magnet 112 is installed (almost the same as the length L1 corresponding to the length of the magnetization direction Dm of the permanent magnet 112).

[0070] When rotor 1100 of Comparative Example 1 shown in Fig. 11 was used, torque T of the IPMSM was 0.800 Nm. In contrast, when rotor 110 of Example 1 shown in Fig. 2 was used, torque T of the IPMSM was 1.199 Nm. As described above, torque T of the IPMSM in Example 1 increased by 49.9% compared to Comparative Example 1. Therefore, it can be seen that torque T of the IPMSM can be increased by forming first outer space 310b on the leading side of hole 310 in the left-right direction Ds, as shown in Fig. 3.

[0071] Furthermore, when rotor 1200 of Comparative Example 2 shown in FIG. 12 was used, the torque T of the IPMSM was 0.956 Nm. In contrast, when rotor 810 of Example 2 shown in FIG. 8 was used, the torque T of the IPMSM was 1.251 Nm. As such, the torque T of the IPMSM in Example 2 increased by 30.8% compared to Comparative Example 2. Therefore, it can be seen that the torque T of the IPMSM can be increased by forming first outer space 910b on the leading side of hole 910 in the left-right direction Ds, as shown in FIG. 9.

[0072] Furthermore, comparing Example 1 with Comparative Example 1, the increase in torque due to the formation of first outer space 310b on the leading side of hole 310 in the left-right direction Ds is 0.399 (=1.199-0.800) Nm. Furthermore, comparing Example 1 with Example 2, the increase in torque due to the communication of second end 912 of hole 910 with the outer peripheral surface of rotor core 811 is 0.052 (1.251-1.199) Nm. Therefore, it can be seen that the torque T of the IPMSM can be effectively increased by forming first outer space 310b on the leading side of hole 310 in the left-right direction Ds.

[0073] (Modifications) In the first and second embodiments, the cross-sectional shape of the rotor core is the shape shown in FIGS. 2 and 8 at all positions in the z-axis direction of the rotor 110, 810. However, this is not necessarily required. For example, the cross-sectional shape of the rotor 110, 810 does not have to be the shape shown in FIGS. 2 and 8 at some positions in the z-axis direction of the rotor 110, 810, as long as the overall torque of the IPMSM is increased compared to when the rotor 110, 810 does not have the shape shown in FIGS. 2 and 8 at all positions in the z-axis direction. For example, the cross-sectional shape of the rotor 110, 810 may be the shape shown in FIG. 11 or 12 at some positions in the z-axis direction of the rotor 110.

[0074] In addition, although the first and second embodiments have been described with reference to an example in which one pole is formed by one permanent magnet 112, the present disclosure is not limited to this. One pole may be formed by a plurality of permanent magnets 112.

[0075] In addition, in the first and second embodiments, the case where the IPMSM 100 is an inner rotor type has been exemplified. However, the first and second ends of the holes in which the permanent magnets 112 are installed may be formed in the rotor of an outer rotor type IPMSM motor as described in the first and second embodiments. In this case, the inner circumferential surface of the rotor core becomes the end face that faces the stator with a gap therebetween. Furthermore, the first and second ends of the holes in which the permanent magnets 112 are installed may be formed in the rotor of an embedded permanent magnet generator, rather than an embedded permanent magnet motor, as described in the first and second embodiments.

[0076] Furthermore, in one rotor core cross section, the second end of the hole in which the permanent magnet is installed may include both an end that is not open, as in the first embodiment, and an end that has a circumferential length that is shorter than the circumferential length of the open end of the first end of the hole, as in the second embodiment.

[0077] 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.

[0078] The following additional notes are provided regarding the above-described embodiments.

[0079] (Supplementary Note 1) A rotor core having a plurality of holes in which permanent magnets are installed, wherein in a cross section perpendicular to a rotation axis that is the center of rotation, at least one of the plurality of holes includes a first end located at the leading end of the rotation direction in a left-right direction that is a direction on both the left and right sides of the magnetization direction of the permanent magnet, and a second end located at the trailing end of the rotation direction in the left-right direction, wherein the first end is open, and in the cross section, the circumferential length of the opening is longer than the circumferential length of the second end.

[0080] (Supplementary Note 2) The rotor core according to Supplementary Note 1, wherein in the cross section, the circumferential length of the opening is longer than the length of the region of the hole occupied by the permanent magnet in the magnetization direction of the permanent magnet.

[0081] (Supplementary Note 3) The rotor core according to Supplementary Note 1 or Supplementary Note 2, wherein the first ends of all of the holes are open in the cross section.

[0082] (Supplementary Note 4) The rotor core according to any one of Supplementary Note 1 to Supplementary Note 3, wherein in the cross section, the second end of at least one of the holes is not open.

[0083] (Supplementary Note 5) The rotor core according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the second ends of all the holes are not open in the cross section.

[0084] (Supplementary Note 6) A rotor core according to any one of Supplementary Notes 1 to 5, wherein, in the cross section, the hole into which the first end is open has: an inner space whose length in a width direction is equal to a length corresponding to a length in the magnetization direction of the permanent magnet; and a first outer space that communicates with the inner space, has the first end as one of the left-right ends of the hole, and is wider than the inner space, and the first end is arranged so as to be biased rearward in the direction of rotation with respect to a circumferential center position of the inner space at a position where it communicates with the first outer space.

[0085] (Supplementary Note 7) A rotor core according to Supplementary Note 6, wherein, in the cross section, a circumferential length in a direction toward the aft side in the direction of rotation from an extrapolated position of a rear end point of the inner space to an end point of the first end portion that is on the aft side in the direction of rotation is equal to or greater than a widthwise length of the inner space, and the extrapolated position of the aft end point of the inner space is a position of an intersection of a straight line extending along the radial direction of the rotor core from the end point on the aft side of the inner space at a position communicating with the first outer space in the cross section and the first end portion.

[0086] (Supplementary Note 8) A rotor comprising: the rotor core according to any one of Supplementary Notes 1 to 7; and the permanent magnet.

[0087] (Supplementary Note 9) A rotating electric machine comprising: the rotor of Supplementary Note 8; and a stator.

[0088] (Supplementary Note 10) A rotor core comprising a plurality of holes in which permanent magnets are installed, wherein in a cross section perpendicular to a rotation axis that is the center of rotation, at least one of the plurality of holes includes a first end located at the leading end of the rotation direction in a left-right direction that is a direction on both the left and right sides of a magnetization direction of the permanent magnet, and a second end located at the trailing end of the rotation direction in the left-right direction, wherein the first end opens to an outer peripheral surface, and the circumferential length of the opening is longer than the circumferential length of the second end, wherein in the cross section, the hole into which the first end opens has an inner space whose widthwise length is equal to a length corresponding to the length of the magnetization direction of the permanent magnet, and a first outer space that communicates with the inner space, has the first end as one of the left-right ends of the hole, and is wider than the inner space, wherein the first end is arranged so as to be biased towards the trailing end of the rotation direction with respect to a circumferential center position of the inner space at a position where it communicates with the first outer space.

[0089] (Supplementary Note 11) A rotor core according to Supplementary Note 10, wherein, in the cross section, a circumferential length in a direction toward the aft side in the direction of rotation from an extrapolated position of a rear end point of the inner space to an end point of the first end portion that is on the aft side in the direction of rotation is equal to or greater than a widthwise length of the inner space, and the extrapolated position of the aft end point of the inner space is a position of an intersection of a straight line extending along the radial direction of the rotor core from the end point on the aft side of the inner space at a position communicating with the first outer space in the cross section and the first end portion.

[0090] (Supplementary Note 12) The rotor core according to Supplementary Note 10 or Supplementary Note 11, wherein, in a hole wall surface constituting the hole, a rear wall surface forming a rear side of the first outer space in the rotation direction is inclined with respect to a direction perpendicular to the rotation axis.

[0091] (Supplementary Note 13) The rotor core according to Supplementary Note 11 or Supplementary Note 12, wherein at least a portion of the aft-side wall surface is concavely curved.

[0092] (Supplementary Note 14) The rotor core according to any one of Supplementary Note 10 to Supplementary Note 13, wherein, in the cross section, a circumferential length of the opening is longer than a length of a region of the hole occupied by the permanent magnet in a magnetization direction of the permanent magnet.

[0093] (Supplementary Note 15) The rotor core according to any one of Supplementary Note 10 to Supplementary Note 14, wherein the first ends of all of the holes are open in the cross section.

[0094] (Supplementary Note 16) The rotor core according to any one of Supplementary Notes 10 to 15, wherein, in the cross section, the second end of at least one of the holes is not open. (Supplementary Note 17) The rotor core according to any one of Supplementary Notes 10 to 16, wherein, in the cross section, the second end of all of the holes is not open.

[0095] (Supplementary Note 18) A rotor comprising: the rotor core according to any one of Supplementary Notes 10 to 17; and the permanent magnet.

[0096] (Supplementary Note 19) A rotating electric machine comprising: the rotor of Supplementary Note 18; and a stator.

[0097] The disclosure of Japanese Patent Application No. 2021-060596, filed on March 31, 2021, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein 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 in which permanent magnets are installed, wherein in a cross section perpendicular to a rotation axis which is the center of rotation, at least one of the plurality of holes includes a first end located at the leading end of the rotation direction in a left-right direction which is a direction on both the left and right sides of the magnetization direction of the permanent magnet, and a second end located at the trailing end of the rotation direction in the left-right direction, wherein the first end opens onto the outer peripheral surface, and the circumferential length of the opening is longer than the circumferential length of the second end, wherein in the cross section, the hole into which the first end opens has an inner space whose widthwise length is equal to a length corresponding to the length of the magnetization direction of the permanent magnet, and a first outer space which communicates with the inner space, has the first end as one of the left-right ends of the hole and is wider than the inner space, wherein the first end is positioned so as to be biased toward the trailing end of the rotation direction with respect to the circumferential center position of the inner space at the position where it communicates with the first outer space.

2. A rotor core according to claim 1, wherein, in said cross section, a circumferential length in a direction toward the rear side in the direction of rotation from an extrapolated position of a rear end point of said inner space to an end point of said first end point that is on the rear side in the direction of rotation is equal to or greater than a widthwise length of said inner space, and said extrapolated position of said rear end point of said inner space is a position of an intersection between said first end and a straight line extending in the radial direction of said rotor core from an end point on the rear side of said inner space at a position communicating with said first outer space in said cross section.

3. A rotor core as described in claim 1 or claim 2, wherein in the hole wall surface constituting the hole, a rear wall surface forming the rear side in the rotational direction of the first outer space is inclined with respect to a direction perpendicular to the rotation axis.

4. A rotor core according to claim 3, wherein at least a portion of said rear wall surface is concavely curved.

5. A rotor core according to any one of claims 1 to 4, wherein, in the cross section, the circumferential length of the opening is longer than the length of the area of ​​the hole occupied by the permanent magnet in the magnetization direction of the permanent magnet.

6. A rotor core according to any one of claims 1 to 5, wherein the first ends of all of the holes are open in the cross section.

7. A rotor core according to any one of claims 1 to 6, wherein in the cross section, at least one of the holes does not open at the second end.

8. A rotor core according to any one of claims 1 to 7, wherein in the cross section, the second ends of all of the holes are not open.

9. A rotor comprising: a rotor core according to any one of claims 1 to 8; and the permanent magnet.

10. A rotating electric machine comprising: a rotor according to claim 9; and a stator.

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