Rotor, motor, compressor and refrigeration cycle device

Abstract

The rotor (1) has a rotor core (10) and permanent magnets (20). The outer periphery of the rotor core (10) has an elliptical arc portion (15) including an intersection with the d-axis and an arc portion (16) including an intersection with the q-axis. The elliptical arc portion (15) is line-symmetric with respect to the d-axis, the arc portion (16) is line-symmetric with respect to the q-axis, and they are connected to each other. If the distance on the d-axis from the central axis (Ax) to the elliptical arc portion (15) is r1, the elliptical arc portion (15) touches a circle with a radius r1 centered on the central axis (Ax) at a point on the d-axis. The arc portion (16) forms a part of a circle with a radius r2 (< r1) centered on the central axis (Ax) of the rotor core (10) and is provided at at least two locations symmetric with respect to the central axis (Ax). The elliptical arc portion (15) has a second axis which is the minor axis or the major axis on the d-axis. If the length of the second axis is 2b and the distance from the central axis (Ax) to the center of the elliptical arc portion (15) is k, then k = r1 - b holds.

Description

[Technical Field]

[0001] The present disclosure relates to a rotor, a motor, a compressor, and a refrigeration cycle device. [Background technology]

[0002] The motor has a rotor with a permanent magnet and a stator surrounding the rotor via an air gap. A motor has been proposed in which the width of the air gap is continuously varied so that it is minimum on the rotor's d-axis and maximum on the q-axis (see, for example, Patent Document 1). This configuration reduces the harmonic components of the induced voltage, thereby reducing vibration and noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-86955 A (see abstract) Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional designs, the air gap width increases with increasing distance from the d-axis in the circumferential direction. However, if the air gap width increases rapidly, the effective value of the induced voltage decreases, resulting in reduced motor efficiency. While it is possible to change the air gap width by configuring the rotor's outer periphery as an elliptical arc, this makes it difficult to control the rotor's outer diameter and complicates the manufacturing process. Therefore, there is a need to suppress the decrease in the effective value of the induced voltage and improve the efficiency of the manufacturing process.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to suppress a decrease in the effective value of the induced voltage and to simplify the manufacturing process. [Means for solving the problem]

[0006] The rotor of the present disclosure has an outer periphery extending circumferentially around a central axis, a rotor core having magnet insertion holes along the outer periphery, and permanent magnets arranged in the magnet insertion holes to form magnetic poles. A gap is formed at an end of the magnet insertion hole in the circumferential direction, and a bridge portion extending in the circumferential direction is formed between the gap and the outer periphery of the rotor core. If a line passing through the central axis and the circumferential center of the magnet insertion hole is defined as a d-axis, and a line passing through the central axis and an inter-pole portion spaced circumferentially from the magnet insertion hole is defined as a q-axis, the outer periphery of the rotor core has an elliptical arc portion at a portion including an intersection with the d-axis and a circular arc portion at a portion including an intersection with the q-axis. The elliptical arc portion is line-symmetric with respect to the d-axis, and the circular arc portion is line-symmetric with respect to the q-axis, and the elliptical arc portion and the circular arc portion are connected. If the distance on the d-axis from the central axis to the outer periphery is defined as r1, the elliptical arc portion is tangent to a circle of radius r1 centered on the central axis at a single point on the d-axis. The circular arc portions form part of a circle centered on the central axis and having a radius r2 smaller than r1, and are provided at at least two locations symmetrical with respect to the central axis. The elliptical arc portions have a first axis perpendicular to the d-axis and a second axis on the d-axis. The first axis is either the major axis or the minor axis, and the second axis is the other of the major axis or the minor axis. If the length of the second axis is 2b and the distance from the central axis to the center of the elliptical arc portion is k, then k = r1 - b holds. The bridge portion has a minimum width t in the radial direction of the rotor core. At least a part of the outer periphery of the rotor core that constitutes the bridge portion is formed by the arc portion, and the edge of the bridge portion on the gap side forms part of a circle whose radius is r2-t, which is the radius r2 minus the minimum width t of the bridge portion. [Effects of the Invention]

[0007] According to the present disclosure, since the outer periphery of the rotor core has the above-described elliptical arc portion, a rapid expansion of the air gap around the d-axis can be suppressed, thereby suppressing a decrease in the effective value of the induced voltage. Furthermore, since the outer periphery of the rotor core has a circular arc portion, it is easy to control the outer diameter of the rotor core, and the manufacturing process can be simplified. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a motor according to a first embodiment. [Figure 2] 1 is a plan view showing a rotor according to a first embodiment. [Figure 3]1A is a diagram showing a portion corresponding to one magnetic pole of the rotor of the first embodiment together with teeth, and FIG. 1B is a diagram showing a portion including the outer periphery of the rotor core and magnet insertion holes. [Figure 4] 2 is an enlarged view showing an inter-pole portion of the rotor according to the first embodiment. FIG. [Figure 5] 6A to 6C are diagrams showing examples of a connecting portion between an elliptical arc portion and a circular arc portion of the rotor core according to the first embodiment. [Figure 6] 3A and 3B are diagrams for illustrating the shapes of an elliptical arc portion and a circular arc portion of the rotor core according to the first embodiment. [Figure 7] 4 is a graph showing the relationship between a / r1 and the torque constant in the rotor of the first embodiment. [Figure 8] 4 is a graph showing the relationship between a / r1 and the harmonic content rate in the rotor of the first embodiment. [Figure 9] 4 is a graph showing the relationship between b / r1 and the torque constant in the rotor of the first embodiment. [Figure 10] 4 is a graph showing the relationship between b / r1 and the harmonic content rate in the rotor according to the first embodiment. [Figure 11] 4 is a graph showing the relationship between the rate of change of the torque constant and the rate of change of the motor efficiency in the rotor of the first embodiment. [Figure 12] 10 is a plan view showing a portion corresponding to one magnetic pole of a rotor according to a second embodiment. FIG. [Figure 13] 10 is a plan view showing another example of a portion corresponding to one magnetic pole of the rotor according to the second embodiment. FIG. [Figure 14] 10 is a graph showing the relationship between angle V and torque constant in the rotor of the second embodiment. [Figure 15] 10 is a graph showing the relationship between angle V and maximum torque in the rotor of the second embodiment. [Figure 16] 10 is a graph showing the relationship between angle V and iron loss in the rotor of the second embodiment. [Figure 17] 10 is a graph showing the relationship between angle V and harmonic content in the rotor of the second embodiment. [Figure 18]10 is a schematic diagram for illustrating a distance D from the d-axis to an end face of a permanent magnet in a rotor according to a second embodiment. FIG. [Figure 19] 10 is a graph showing the relationship between angle V and distance D in the rotor of the second embodiment. [Figure 20] FIG. 10 is a vertical cross-sectional view showing a compressor according to a third embodiment. [Figure 21] FIG. 10 is a diagram showing a refrigeration cycle device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiment 1 <Motor configuration> First, a description will be given of motor 5 according to embodiment 1. Fig. 1 is a cross-sectional view showing motor 5 according to embodiment 1. Motor 5 shown in Fig. 1 is a permanent magnet embedded synchronous motor, and is used in, for example, compressor 8 (Fig. 20).

[0010] The motor 5 has a shaft 90 which is a rotating shaft, a rotor 1 fixed to the shaft 90, and a stator 3 provided to surround the rotor 1. An air gap is formed between the stator 3 and the rotor 1. The radial width of the air gap is, for example, 0.3 mm to 1.0 mm. The stator 3 is incorporated inside a cylindrical frame 81 of a compressor 8 (FIG. 20) which will be described later.

[0011] In the following, the direction of the center axis Ax, which is the center axis of the shaft 90, that is, the center of rotation of the rotor 1, will be referred to as the "axial direction." The radial direction centered on the central axis Ax will be referred to as the "radial direction." The circumferential direction centered on the central axis Ax will be referred to as the "circumferential direction."

[0012] <Stator configuration> As shown in Fig. 1, the stator 3 has a stator core 30 that surrounds the rotor core 10 from the radial outside, and a winding 40 wound around the stator core 30. The stator core 30 has a plurality of laminated elements that are laminated in the axial direction. The laminated elements are, for example, electromagnetic steel sheets. The plate thickness of the laminated elements is 0.1 mm to 0.7 mm.

[0013] The stator core 30 has an annular core back 31 centered on the central axis Ax, and M (M is an integer of 2 or more) teeth 32 extending radially inward from the core back 31. The teeth 32 are arranged at regular intervals in the circumferential direction. The number M of the teeth 32 is 9 in this example, but may be any number equal to or greater than 2.

[0014] The teeth 32 have tooth tip surfaces 32a at their radially inner tips. The circumferential width of the tooth tip surfaces 32a is greater than the circumferential width of other portions of the teeth 32. The tooth tip surfaces 32a face the rotor 1.

[0015] Slots 33 are formed between circumferentially adjacent teeth 32. The slots 33 are spaces that house the windings 40. The number of slots 33 is M, the same as the number of teeth 32, and is nine in this example.

[0016] The windings 40 are made of magnet wire and are wound around each tooth 32. The windings 40 are wound by concentrated winding, but may also be wound by distributed winding. A current having a frequency corresponding to the rotational speed of the motor 5 flows through the windings 40, generating a rotating magnetic field that rotates the rotor 1.

[0017] The wire diameter of the winding 40 and the number of turns around one tooth 32 are determined by the required specifications such as rotational speed and torque, the supply voltage, and the cross-sectional area of ​​the slot 33. The wire diameter of the winding 40 is, for example, 1.0 mm, and the number of turns is, for example, 80 turns. An insulating portion is provided between the stator core 30 and the winding 40. The insulating portion can be formed, for example, by an insulator 34 (see FIG. 20) or an insulating film.

[0018] The stator core 30 is divided into M split cores 35 at dividing surfaces 31b formed on the core back 31. Each split core 35 includes one tooth 32. The portion of the core back 31 included in each split core 35 is also referred to as a core back portion 31a. Circumferentially adjacent split cores 35 are connected by crimping portions 31c provided on the outer periphery of the dividing surfaces 31b or by welding at the dividing surfaces 31b.

[0019] When manufacturing the stator 3, the M split cores 35 of the stator core 30 are spread out linearly, and a winding nozzle is used to wind the windings 40 around the teeth 32. After the windings 40 are wound around the teeth 32, the M split cores 35 are bent into an annular shape, and the split cores 35 at both ends are fixed by welding or the like to form the annular stator core 30.

[0020] The stator core 30 is not limited to an annular combination of M split cores 35, but may be, for example, an integral core formed by stacking annular laminated elements (for example, electromagnetic steel sheets) in the axial direction.

[0021] Grooves 31d may be formed on the outer peripheral surface of the core back 31. A refrigerant passage through which the refrigerant of the compressor 8 passes is formed between the grooves 31d and the frame 81. The grooves 31d are located radially outward of the teeth 32, but are not limited to this location.

[0022] Furthermore, a step portion 36 may be formed at each axial end of the core back 31 and the teeth 32 so as to face the slot 33 .

[0023] <Rotor configuration> 2 is a cross-sectional view showing the rotor 1. The rotor 1 has an annular rotor core 10 centered on a central axis Ax, and permanent magnets 20 attached to the rotor core 10. The rotor core 10 has a plurality of laminated elements laminated in the axial direction. The laminated elements are, for example, electromagnetic steel sheets. The plate thickness of the laminated elements is 0.1 mm to 0.7 mm.

[0024] A center hole 18 is formed in the radial center of the rotor core 10. A shaft 90 (FIG. 1) is fixed in the center hole 18 of the rotor core 10 by shrink fitting, press fitting, or the like.

[0025] N magnet insertion holes 11 (N is an integer of 2 or greater) are formed along the outer periphery of the rotor core 10. One permanent magnet 20 is placed in each magnet insertion hole 11, constituting one magnetic pole. Because the rotor core 10 has six magnet insertion holes 11, the number of poles (N) of the rotor 1 is 6. However, the number of poles of the rotor 1 is not limited to 6; it may be 2 or greater, and is preferably an even number of 2 or greater.

[0026] The permanent magnets 20 have a width in the circumferential direction of the rotor core 10 and a thickness in the radial direction. Each permanent magnet 20 is magnetized in the thickness direction. The permanent magnets 20 are made of a rare earth magnet containing, for example, neodymium (Nd), iron (Fe), and boron (B).

[0027] Dysprosium (Dy) may be added to rare earth magnets to improve coercivity. However, adding Dy increases manufacturing costs and reduces remanence, so it is desirable to keep the Dy content below 4% by weight, or to add no Dy at all. In other words, the Dy content is preferably between 0 and 4% by weight.

[0028] The circumferential center of the magnet insertion hole 11 is the pole center. The d-axis is defined by the circumferential center of the magnet insertion hole 11, i.e., the pole center. The d-axis is a straight line that passes through the circumferential center of the magnet insertion hole 11 and the central axis Ax.

[0029] An inter-pole space is formed between adjacent magnetic poles. The q-axis is defined in the inter-pole space. The q-axis is a straight line that passes through the inter-pole space and the central axis Ax. The q-axis is also an axis that is 90 electrical degrees away from the d-axis.

[0030] Here, the magnet insertion holes 11 extend linearly in a direction perpendicular to the d-axis. However, the magnet insertion holes 11 are not limited to extending linearly, and may extend in a V-shape (see FIG. 12). Two or more permanent magnets 20 may be placed in each magnet insertion hole 11. Flux barriers 12, which are air gaps, are formed on both circumferential sides of the magnet insertion holes 11.

[0031] Through holes 19a and 19b are formed radially inward of the magnet insertion holes 11 in the rotor core 10. The circumferential position of through hole 19a coincides with the pole center, and the circumferential position of through hole 19b coincides with the inter-pole portion. Through holes 19a and 19b penetrate rotor core 10 in the axial direction and are used as refrigerant passages. Note that the positions of through holes 19a and 19b are not limited to the positions described here. Furthermore, it is not necessary to provide through holes 19a and 19b in rotor core 10.

[0032] <Outer periphery shape of rotor core> Next, we will explain the shape of the outer periphery of rotor core 10. In Fig. 2, the point where the outer periphery of rotor core 10 intersects with the d-axis is designated as point P. The point where the outer periphery of rotor core 10 intersects with the q-axis is designated as point Q.

[0033] An elliptical arc portion 15 is formed on the outer periphery of rotor core 10 in a portion including point P (i.e., the intersection with the d-axis), and a circular arc portion 16 is formed on a portion including point Q (i.e., the intersection with the q-axis). If the number of poles is N, then N elliptical arc portions 15 and N circular arc portions 16 are formed on the outer periphery of rotor core 10.

[0034] The elliptical arc portion 15 is formed to be line-symmetrical with respect to the d-axis. The circular arc portion 16 is formed to be line-symmetrical with respect to the q-axis. The elliptical arc portion 15 and the circular arc portion 16 are connected to each other.

[0035] More specifically, the elliptical arc portion 15 corresponds to a portion of an imaginary ellipse E1 having a center C1 on the d-axis. The ellipse E1 has a first axis perpendicular to the d-axis and a second axis on the d-axis. The first axis is one of the major axis and the minor axis, and the second axis is the other of the major axis and the minor axis. In the example shown in FIG. 2, the first axis is the major axis and the second axis is the minor axis.

[0036] The length of the first axis of the ellipse E1 is 2a, and the length of the second axis of the ellipse E1 is 2b. In the example shown in Figure 2, the length of the major axis of the ellipse E1 is 2a, and the length of the minor axis is 2b.

[0037] Hereinafter, the center C1 of the ellipse E1 that forms the elliptical arc portion 15 will be referred to as the "center C1 of the elliptical arc portion 15." Furthermore, the length 2a of the first axis (e.g., the major axis) of the ellipse E1 will be referred to as the "length 2a of the first axis of the elliptical arc portion 15," and the length 2b of the second axis (e.g., the minor axis) of the ellipse E1 will be referred to as the "length 2b of the second axis of the elliptical arc portion 15."

[0038] Furthermore, half of the length 2a of the first axis (e.g., the major axis) of the ellipse E1 is referred to as the "first axis radius (e.g., the major axis radius) a of the elliptical arc portion 15," and half of the length 2b of the second axis (e.g., the minor axis) of the ellipse E1 is referred to as the "second axis radius (e.g., the minor axis radius) b of the elliptical arc portion 15."

[0039] The distance from the central axis Ax of rotor core 10 to elliptical arc portion 15 is maximum at point P and minimum at the connection point with circular arc portion 16 (connection point R shown in FIG. 4, described later). The distance from central axis Ax of rotor core 10 to point P is defined as r1. r1 can also be said to be the distance from central axis Ax to the outer periphery of rotor core 10 on the d-axis, or can also be said to be the maximum radius of rotor core 10.

[0040] Circle A1 is an imaginary circle having a radius r1 and centered on central axis Ax of rotor core 10. Elliptical arc portion 15 of rotor core 10 and circle A1 are in contact with each other at only one point (namely, point P).

[0041] Furthermore, the distance k from the central axis Ax of rotor core 10 to the center C1 of elliptical arc portion 15 is expressed as k = r1 - b. The second axis radius b of elliptical arc portion 15 (i.e., 1 / 2 the second axis length 2b) is shorter than the maximum radius r1 of rotor core 10, and therefore r1 - b > 0.

[0042] Arc portion 16 corresponds to a part of an imaginary circle A2 (FIG. 3(B)) having a radius r2 and centered on central axis Ax. r2 is the distance from central axis Ax of rotor core 10 to point Q. r2 can also be said to be the distance from central axis Ax to the outer periphery of rotor core 10 on the q axis. The radii r1 and r2 of circles A1 and A2 satisfy r1>r2.

[0043] The number of elliptical arc portions 15 and the number of circular arc portions 16 are preferably the same as the number of poles, i.e., N, but are not limited to N. From the viewpoint of enabling high-precision dimensional control, which will be described later, it is desirable that the circular arc portions 16 are provided in at least two locations symmetrical with respect to the central axis Ax (i.e., 180 degrees apart from the central axis Ax). It is also desirable that the elliptical arc portions 15 are provided in at least two locations symmetrical with respect to the central axis Ax.

[0044] Fig. 3(A) is a diagram showing a portion corresponding to one magnetic pole of the rotor 1 and the opposing tooth 32. Fig. 3(B) is a diagram showing a portion including the outer periphery of the rotor core 10 (the elliptical arc portion 15 and the circular arc portion 16) and the magnet insertion hole 11.

[0045] 3(B), the magnet insertion hole 11 has a first edge 11a on the radially outer side and a second edge 11b on the radially inner side. Flux barriers 12, which are gaps, are formed at both circumferential ends of the magnet insertion hole 11.

[0046] A bridge portion 13, which is a thin portion, is formed between the flux barrier 12 and the outer periphery of the rotor core 10. In order to reduce leakage flux between adjacent magnetic poles, the radial width of the bridge portion 13 is set to be the same as the plate thickness of the laminated element, for example.

[0047] In the rotor core 10, positioning protrusions 14 are formed radially inside each flux barrier 12. The positioning protrusions 14 face the circumferential end faces (side end faces 23 to be described next) of the permanent magnets 20 and position the permanent magnets 20 in the circumferential direction.

[0048] As shown in FIG. 3(A), the permanent magnet 20 has a first magnetic pole face 21 on the radially outer side, a second magnetic pole face 22 on the radially inner side, and side end faces 23 on both sides in the circumferential direction. The first magnetic pole face 21 faces the first edge 11a of the magnet insertion hole 11, and the second magnetic pole face 22 faces the second edge 11b of the magnet insertion hole 11. The side end faces 23 of the permanent magnet 20 face the positioning protrusions 14 (FIG. 3(B)).

[0049] Here, the magnet insertion hole 11 is located radially outside the center C1 of the ellipse E1 of the elliptical arc portion 15. However, the magnet insertion hole 11 may be located on the center C1 of the ellipse E1 or may be located radially inside the center C1 of the ellipse E1.

[0050] An air gap is formed between the outer circumference of the rotor core 10 and the inner circumference of the stator core 30. The inner circumference of the stator core 30 is the tooth tip surface 32a of the teeth 32. The tooth tip surface 32a of the teeth 32 extends on a virtual circle centered on the central axis Ax (FIG. 2). The width of the air gap is the minimum width Gmin on the d-axis.

[0051] The elliptical arc portion 15 is a part of an ellipse E1 that touches a circle A1 (FIG. 3(B)) with a radius r1 centered on the central axis Ax at a point P. On the other hand, the arc portion 16 is a part of a circle A2 (FIG. 3(B)) with a radius r2 (<r1) centered on the central axis Ax. The elliptical arc portion 15 and the arc portion 16 are connected at a connection point located between the d-axis and the q-axis.

[0052] <Effective value of induced voltage and reduction effect of harmonic components> Reducing the harmonic components contained in the induced voltage is effective for reducing vibration and noise of the motor 5. The reduction of the harmonic components contained in the induced voltage is achieved by smoothing the circumferential magnetic flux density distribution of the magnetic flux flowing from the rotor 1 to the stator 3. To achieve this, it is desirable for the width of the air gap between the rotor core 10 and the stator core 30 to continuously change so that it is minimum on the d-axis and maximum on the q-axis.

[0053] For example, Patent Document 1 discloses a rotor core whose outer periphery is made up of two or more arcs for each magnetic pole (see FIG. 2 of Patent Document 1). However, when the outer periphery of rotor core 10 is made up of two or more arcs for each magnetic pole, the width of the air gap increases rapidly around the d-axis, which may reduce the effective value of the induced voltage.

[0054] In contrast, in the first embodiment, as shown in Fig. 3(A), the outer periphery of rotor core 10 is composed of elliptical arc portion 15 and circular arc portion 16. Elliptical arc portion 15 is formed in a portion including point P (the intersection of the outer periphery of rotor core 10 and the d axis), and is line-symmetrical with respect to the d axis.

[0055] Additionally, elliptical arc portion 15 is tangent at one point (point P) to a circle A1 of radius r1 centered on central axis Ax. In other words, elliptical arc portion 15 is located on circle A1 or on the inner periphery side of circle A1 in the range from the d-axis to the q-axis. Furthermore, if the length of the second axis (i.e., the minor axis) of elliptical arc portion 15 is 2b, then the distance k from central axis Ax of rotor core 10 to center C1 of elliptical arc portion 15 is k = r1 - b (FIG. 2).

[0056] With this configuration, the width of the air gap between rotor core 10 and stator core 30 is at its minimum width (Gmin) on the d-axis and gradually increases with increasing circumferential distance from the d-axis. Because a sudden increase in the width of the air gap is suppressed, it is possible to suppress a decrease in the effective value of the induced voltage while reducing the harmonic components of the induced voltage.

[0057] Generally, rotor core 10 is formed by laminating electromagnetic steel plates punched out with a press die, and as the press die wears, the outer diameter of rotor core 10 changes. Dimensional inspection is required to confirm whether the finished outer diameter of rotor core 10 is within an acceptable range during mass production. However, if the outer diameter of rotor core 10 is formed as an elliptical arc portion, the curvature of the elliptical arc portion changes depending on the circumferential position. This means that a three-dimensional measuring device is required to accurately measure the outer diameter of rotor core 10, making dimensional control difficult.

[0058] In contrast, in the first embodiment, elliptical arc portion 15 of rotor core 10 touches circle A1 at point P, so the outer diameter of rotor core 10 on the d axis (i.e., r1 × 2) can be measured with a simple dimension measuring tool such as a vernier caliper, thereby making it possible to grasp the wear state of rotor core 10. Therefore, the difficulty of dimensional control caused by rotor core 10 having elliptical arc portion 15 on its outer periphery can be alleviated.

[0059] Arc portion 16 of rotor core 10 is a part of a circle centered on central axis Ax, is formed in a portion including point Q (the intersection of the outer periphery of rotor core 10 and the q axis), and is line-symmetric with respect to the q axis. Arc portion 16 is formed in at least two locations symmetric with respect to central axis Ax.

[0060] Therefore, the outer diameter of the rotor core 10 on the q axis (i.e., r2 × 2) can be measured with a simple measuring tool such as a vernier caliper. It is also possible to measure the coaxiality or circularity of the arc portion 16 relative to the central axis Ax. This enables highly accurate dimensional control of the rotor core 10, thereby improving the reliability of the motor 5.

[0061] The curvature of the elliptical arc portion 15 can be flexibly set by adjusting the lengths 2a and 2b of the first and second axes of the elliptical arc portion 15. By appropriately setting the curvature of the elliptical arc portion 15, it is possible to reduce the harmonic components of the induced voltage and suppress a decrease in the effective value of the induced voltage, as described above, without offsetting the center of the arc portion 16 from the central axis Ax.

[0062] Fig. 4 is an enlarged view of the inter-pole portion of the rotor 1. As shown in Fig. 4, the portion of the rotor core 10 located on the outer periphery side of the magnet insertion holes 11 is referred to as the outer core portion 10a, and the portion located on the inner periphery side of the magnet insertion holes 11 is referred to as the inner core portion 10b. The bridge portion 13 connects the outer core portion 10a and the inner core portion 10b of the rotor core 10. The bridge portion 13 has a width t in the radial direction.

[0063] When the rotor 1 rotates at high speed, centrifugal force acts on the bridge portions 13 from the outer core portion 10a of the rotor core 10 and the permanent magnets 20, causing stress concentration. If the bridge portions 13 are deformed toward the outer periphery by centrifugal force, noise and vibration will occur, and the reliability of the motor 5 may be reduced.

[0064] In rotor 1 of embodiment 1, the outer periphery of rotor core 10 is composed of elliptical arc portion 15 and circular arc portion 16. Therefore, compared to when the outer periphery of rotor core 10 is composed only of elliptical arc portions, the radius of curvature of the terminal end portion on the q-axis side of elliptical arc portion 15 (i.e., the portion including connection point R with circular arc portion 16) can be made larger and the curvature can be made smaller, so the outer periphery of rotor core 10 can be made into a smooth shape. As a result, stress concentration caused by centrifugal force when rotor 1 rotates can be suppressed.

[0065] The inner peripheral edge 13a of the bridge portion 13, which is the edge on the flux barrier 12 side, is desirably an arc shape centered on the central axis Ax. More specifically, the inner peripheral edge 13a of the bridge portion 13 is desirably an arc shape centered on the central axis Ax and having a radius equal to the radius r2 of the arc portion 16 minus the width t of the bridge portion 13 (r2-t).

[0066] When the outer periphery of the bridge portion 13 is the arc portion 16, if the inner peripheral edge 13a of the bridge portion 13 is also arc-shaped, the width t of the bridge portion 13 becomes constant in the circumferential direction, making it easier to control the width t of the bridge portion 13. Since the width t of the bridge portion 13 has the greatest effect on the centrifugal force acting on the bridge portion 13, controlling the width t of the bridge portion 13 with high precision leads to improved reliability of the motor 5.

[0067] It is desirable that the width t of the bridge portion 13 is constant in the circumferential direction, but it does not necessarily have to be constant. The inner peripheral edge 13a of the bridge portion 13 may be an arc shape with a radius (r2-t) obtained by subtracting the width t, which is the minimum width of the bridge portion 13, from the radius r2 of the arc portion 16.

[0068] 5(A), (B), and (C) are schematic diagrams showing changes in stress concentration with respect to the position of connection point R between elliptical arc portion 15 and circular arc portion 16. In Figures 5(A) to 5(C), the boundary between elliptical arc portion 15 and circular arc portion 16 on the outer periphery of rotor core 10 is defined as connection point R. The boundary L between outer periphery core portion 10a of rotor core 10 and bridge portion 13 is defined as boundary L.

[0069] In the example shown in Fig. 5(A), the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed in the bridge portion 13. In the example shown in Fig. 5(B), the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed on the boundary L. In the example shown in Fig. 5(C), the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed in the outer core portion 10a.

[0070] Since stress tends to concentrate at connection point R between elliptical arc portion 15 and circular arc portion 16 when rotor 1 rotates, it is desirable to locate this point at a position where stress can be reduced as much as possible. Figures 5(A) to 5(C) show the degree of stress concentration, determined by analysis, when rotor 1 is rotated at a rotational speed of 9,600 rpm, represented by spots indicated by the symbol Z. The greater the spread of the spots, the greater the stress concentration.

[0071] 5(A) to 5(C), when the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed in the outer core portion 10a (FIG. 5(C)), the stress concentration is greatest in the region including the connection point R. When the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed on the boundary L (FIG. 5(B)), the stress concentration is second greatest in the region including the connection point R.

[0072] In contrast, when the connection point R between the elliptical arc portion 15 and the circular arc portion 16 is formed in the bridge portion 13 (FIG. 5(A)), stress concentration is smallest in the region including the connection point R. This is because part of the outer periphery of the bridge portion 13 is formed by the elliptical arc portion 15, and therefore the width of the bridge portion 13 expands on the elliptical arc portion 15 side.

[0073] From the results shown in FIGS. 5(A) to 5(C), it is most desirable that the connection point R between the elliptical arc portion 15 and the circular arc portion 16 be formed in the bridge portion 13.

[0074] As shown in Figure 3(A), it is desirable that the first axis radius a, which is 1 / 2 of the first axis length 2a of the elliptical arc portion 15, and the second axis radius b, which is 1 / 2 of the second axis length 2b, satisfy a>b in order to reduce the curvature of the portion of the elliptical arc portion 15 that includes the d axis.

[0075] On the other hand, in order to limit the position where the air gap is minimum (Gmin) to point P (the intersection of the elliptical arc portion 15 and the d-axis), it is necessary that the elliptical arc portion 15 does not protrude outward from the circle A1 of radius r1.

[0076] Fig. 6 is a diagram showing a portion corresponding to one magnetic pole of rotor 1. In Fig. 6, the distance between points P and Q in the direction of the d axis is defined as distance c. Fig. 6 shows both an elliptical arc portion 15 (referred to as elliptical arc portion 151) that satisfies b = c and an elliptical arc portion 15 (referred to as elliptical arc portion 152) that satisfies b > c.

[0077] In the region close to the d-axis, elliptical arc portion 151 and elliptical arc portion 152 describe similar arcs. On the other hand, in the region close to the q-axis, the change in curvature of elliptical arc portion 152 (b>c) is smaller than the change in curvature of elliptical arc portion 151 (b=c). Therefore, in the region close to the d-axis, the expansion of the air gap is more gradual for elliptical arc portion 152 (b>c) than for elliptical arc portion 151.

[0078] That is, the elliptical arc portion 152 (b>c) is advantageous in suppressing a decrease in the effective value of the induced voltage and increasing motor efficiency.

[0079] Although not shown in Fig. 6, when the elliptical arc portion 15 is formed such that b < c, the change in curvature in the region near the q-axis becomes even larger than that of the elliptical arc portion 151 (b = c), and the air gap expands rapidly.

[0080] Therefore, it is desirable that the elliptical arc portion 15 be formed so as to satisfy b ≥ c, and more preferably so as to satisfy b > c.

[0081] That is, it is desirable that the first axis radius (for example, the major axis radius) a and the second axis radius (for example, the minor axis radius) b of the elliptical arc portion 15, and the distance c in the d-axis direction from point P to point Q satisfy a > b and b ≥ c (more preferably b > c).

[0082] Next, the relationship between the first axis radius a and the second axis radius b of the elliptical arc portion 15, and the harmonic content of the torque constant and the induced voltage will be described.

[0083] The torque constant is a value indicating the ratio of the torque [Nm] generated with respect to the current [A] flowing through the winding 40. The larger the torque constant, the more torque can be generated with less current. As described above, when the effective value of the induced voltage is improved, the torque constant increases.

[0084] The harmonic content of the induced voltage is the content [%] of the harmonic components in the induced voltage. The smaller the harmonic content, the lower the vibration and noise of the motor 5. Although there are orders in the harmonic components, here, the total content of the harmonic components of all orders is used.

[0085] With the maximum radius r1 of the rotor core 10 being 27.5075 [mm], the width of the permanent magnet 20 being 11.15 [mm], a / r1 was changed under the conditions of a > b and b > c, and the changes in the torque constant and the harmonic content of the induced voltage were examined.

[0086] Figure 7 is a graph showing the relationship between a / r1 and the torque constant. The horizontal axis represents a / r1, and the vertical axis represents the torque constant [Nm / Arms]. Figure 8 is a graph showing the relationship between a / r1 and the harmonic content of the induced voltage. The horizontal axis represents a / r1, and the vertical axis represents the harmonic content (THD) [%].

[0087] As shown in Fig. 7, the torque constant reaches a maximum (peak) when a / r1 is 0.439 (a = 12.1 mm). Also, as shown in Fig. 8, the harmonic content decreases as a / r1 increases, but remains flat in the range where a / r1 is 0.471 (a = 12.95 mm) or more.

[0088] Therefore, if the elliptical arc portion 15 is formed so that a / r1 satisfies 0.439≦a / r1≦0.471, it is possible to reduce the content of higher harmonics while improving the torque constant.

[0089] Fig. 9 is a graph showing the relationship between b / r1 and the torque constant. The horizontal axis shows b / r1, and the vertical axis shows the torque constant [Nm / Arms]. Fig. 10 is a graph showing the relationship between b / r1 and the harmonic content of the induced voltage. The horizontal axis shows b / r1, and the vertical axis shows the harmonic content (THD) [%].

[0090] As shown in Fig. 9, the relationship between b / r1 and the torque constant shows no peaks or bottoms, and the torque constant increases as b / r1 decreases. On the other hand, as shown in Fig. 10, the relationship between b / r1 and the harmonic content is similar to that between a / r1 and the harmonic content, with the harmonic content decreasing as b / r1 increases, but remaining flat in the range where b / r1 is 0.270 or greater.

[0091] Based on these results, the ranges of a / r1 and b / r1 can be selected depending on whether priority is given to improving the torque constant or reducing the harmonic content.

[0092] That is, the above-mentioned range of a / r1, 0.439≦a / r1≦0.471, can be divided into the range of 0.439≦a / r1<0.451 (FIG. 7), where there is a significant improvement in the torque constant, and the range of 0.451≦a / r1≦0.471 (FIG. 8), where there is a significant reduction in the harmonic content.

[0093] The value of "0.451", which is the boundary between the two ranges of a / r1 mentioned above, is the value of a / r1 when the torque constant drops by 0.2% on the side where a / r1 increases relative to the peak (a / r1 = 0.439) of the curve in Figure 7. The reason for using the value when the torque constant drops by 0.2% from the peak as the standard is as follows.

[0094] Generally, when the torque constant decreases, the operating current of the motor 5 increases, which increases the motor's copper loss and circuit loss and reduces motor efficiency. On the other hand, iron loss, which is a motor loss similar to copper loss, can decrease when the torque constant decreases as the magnetic saturation of the stator 3 is alleviated.

[0095] Here, we prepared Motor A, which has a large iron loss ratio out of iron loss and copper loss, and Motor B, which has a large copper loss ratio, and conducted tests to measure the change in motor efficiency when the torque constant was reduced by 0.1%. In the tests, the current value was increased according to the reduction rate of the torque constant, and the iron loss was reduced according to the reduction rate of the torque constant. The configurations of Motors A and B were the same as Motor 5 described with reference to Figures 1 to 3.

[0096] Figure 11 is a graph showing the relationship between the rate of change in torque constant and the rate of change in motor efficiency, measured for each of motors A and B. The horizontal axis shows the rate of change in torque constant, and the vertical axis shows the rate of change in motor efficiency. The relationship between the rate of change in torque constant and the rate of change in motor efficiency is also shown in Table 1 below. The rate of change in each motor efficiency is rounded to two decimal places. The difference in the rate of change, shown in the rightmost column of Table 1, is the value obtained by subtracting the rate of change in motor efficiency of motor B from the rate of change in motor efficiency of motor A.

[0097] [Table 1]

[0098] As shown in Table 1, the difference in the rate of change of motor efficiency between motors A and B is -0.001% (rounded to -0.00%) when the rate of change of the torque constant is -0.1%, -0.004% (rounded to -0.00%) when the rate of change of the torque constant is -0.2%, and -0.007% (rounded to -0.01%) when the rate of change of the torque constant is -0.3%.

[0099] In motor efficiency tests, it is difficult to measure changes in motor efficiency of less than 0.01%. Therefore, when the rate of change in the torque constant is in the range of 0 to -0.2% (in other words, when the rate of decrease in the torque constant is 0.2% or less), it can be considered that there is no significant difference in the rate of change in motor efficiency between Motors A and B.

[0100] In other words, if the rate of decrease in the torque constant is 0.2% or less, even if the torque constant is reduced to prioritize quietness (i.e., reducing the harmonic content), the impact of differences in the models of motors A and B (i.e., which is greater, iron loss or copper loss) can be ignored. In this case, a / r1 should be set in a range that is advantageous for reducing the harmonic content (0.451≦a / r1≦0.471).

[0101] On the other hand, if the rate of decrease in the torque constant exceeds 0.2%, there will be a significant difference in the motor efficiency between Motors A and B. In this case, it will be necessary to take into account the model differences between Motors A and B, but if Motor B has a large rate of change in motor efficiency (i.e., a motor with a high copper loss ratio), then a / r1 should be set in a range that is advantageous for improving the torque constant (0.439≦a / r1<0.451).

[0102] To summarize the above, if priority is given to improving the torque constant, it is desirable to set a / r1 within the range of 0.439≦a / r1<0.451 (FIG. 7) and also set b / r1 within the range of b / r1<0.244 (FIG. 9).

[0103] Also, when prioritizing the reduction of the harmonic content, it is desirable to set a / r1 within the range of 0.451 ≦ a / r1 ≦ 0.471 (Fig. 8), and further, to set b / r1 within the range of b / r1 ≧ 0.244 (Fig. 10).

[0104] Note that the value "0.244", which is the boundary of the above two ranges of b / r1, is the value of b / r1 when the torque constant decreases by 0.2 [%] from the peak (b / r1 = 0.218) of the curve in Fig. 8, similar to the boundary of the above two ranges of a / r1.

[0105] <Effect of Embodiment 1> As described above, the rotor 1 of Embodiment 1 includes a rotor core 10 having magnet insertion holes 11 and permanent magnets 20 arranged in the magnet insertion holes 11 to form magnetic poles. When a straight line passing through the central axis Ax of the rotor core 10 and the circumferential center of the magnet insertion hole 11 is defined as the d-axis, and a straight line passing through the central axis Ax and the interpolar portion spaced apart in the circumferential direction from the magnet insertion hole 11 is defined as the q-axis, the outer periphery of the rotor core 10 has an elliptical arc portion 15 at a portion including a point P intersecting the d-axis and an arc portion 16 at a portion including a point Q intersecting the q-axis. The elliptical arc portion 15 is line-symmetric with respect to the d-axis, the arc portion 16 is line-symmetric with respect to the q-axis, and the elliptical arc portion 15 and the arc portion 16 are connected. When the distance from the central axis Ax to the elliptical arc portion 15 on the d-axis is r1, the elliptical arc portion 15 is tangent to a circle A1 with a radius r1 centered on the central axis Ax at a point (P) on the d-axis. The arc portion 16 forms a part of a circle A2 having a radius r2 (< r1) centered on the central axis Ax and is provided at at least two locations symmetric with respect to the central axis Ax. The elliptical arc portion 15 has a first axis in a direction orthogonal to the d-axis and a second axis on the d-axis. The first axis is one of the major axis or the minor axis, and the second axis is the other of the major axis or the minor axis. When the length of the second axis is 2b and the distance from the central axis Ax to the center C1 of the elliptical arc portion 15 is k, k = r1 - b holds.

[0106] This configuration minimizes the width of the air gap between the rotor core 10 and the stator core 30 on the d-axis, and also suppresses a rapid expansion of the air gap width around the d-axis. This reduces the harmonic components contained in the induced voltage while suppressing a decrease in the effective value of the induced voltage. Furthermore, because the outer periphery of the rotor core 10 has the arc portion 16, dimensional control of the rotor core 10 is easy, and the manufacturing process of the rotor 1 can be simplified. In addition, compared to when the outer periphery of the rotor core 10 is formed only with an elliptical arc portion, the outer periphery of the rotor core 10 can be made smoother, thereby suppressing stress concentration during rotation of the rotor 1.

[0107] Furthermore, flux barriers 12 are formed at the circumferential ends of magnet insertion holes 11, and bridge portions 13 are formed between the flux barriers 12 and arc portions 16. If the radial width of bridge portion 13 is t, the edge (inner peripheral edge 13a) of bridge portion 13 on the flux barrier 12 side is an arc of radius r2-t centered on central axis Ax, so the width t of bridge portion 13 can be made nearly constant in the circumferential direction. This makes it easier to manage the dimensions of bridge portion 13, where stress concentration is likely to occur when rotor 1 rotates, and improves the reliability of motor 5.

[0108] Furthermore, the first axis radius (e.g., major axis radius) a and the second radius (e.g., minor axis radius) b of the elliptical arc portion 15, and the distance c in the d-axis direction from the intersection (point P) between the d-axis and the outer periphery of the rotor core 10 to the intersection (point Q) between the q-axis and the outer periphery of the rotor core 10 satisfy a>b and b>c, thereby suppressing a sudden change in the width of the air gap and enhancing the effect of suppressing a decrease in the effective value of the induced voltage.

[0109] Furthermore, since the first axis radius a of the elliptical arc portion 15 and the maximum radius r1 of the rotor core 10 satisfy 0.439≦a / r1≦0.471, the effect of improving the torque constant and the effect of reducing the harmonic content can be enhanced.

[0110] Furthermore, since the first axis radius a of the elliptical arc portion 15, the second axis radius b of the elliptical arc portion 15, and the maximum radius r1 of the rotor core 10 satisfy 0.439≦a / r1<0.451 and b / r<0.244, the torque constant can be particularly improved.

[0111] Furthermore, since the first axis radius a of the elliptical arc portion 15, the second axis radius b of the elliptical arc portion 15, and the maximum radius r1 of the rotor core 10 satisfy 0.451≦a / r1≦0.471 and b / r≧0.244, the harmonic content can be particularly reduced.

[0112] Embodiment 2 12 is a plan view showing a portion corresponding to one magnetic pole of rotor 1A of embodiment 2. Rotor 1A of embodiment 2 differs from rotor 1 of embodiment 1 in the shape of magnet insertion holes 101 of rotor core 10 and the number of permanent magnets 20.

[0113] The magnet insertion holes 101 of the rotor core 10 according to the second embodiment are formed in a V shape with the circumferential center protruding toward the central axis Ax (i.e., radially inward). One magnet insertion hole 101 corresponds to one magnetic pole.

[0114] The magnet insertion hole 101 has a first edge 101a on the radially outer side and a second edge 101b on the radially inner side. Both the first edge 101a and the second edge 101b extend in a V-shape with their circumferential centers projecting toward the central axis Ax. A protrusion 102 that protrudes into the magnet insertion hole 101 is formed at the center of the second edge 101b of the magnet insertion hole 101 in the X direction.

[0115] Furthermore, flux barriers 12, which are gaps, are formed at both circumferential ends of the magnet insertion hole 101. Bridge portions 13 are formed between the flux barriers 12 and the outer periphery of the rotor core 10. The shapes of the flux barriers 12 and bridge portions 13 are as described in the first embodiment.

[0116] Two permanent magnets 20 are placed in the magnet insertion hole 101. That is, two permanent magnets 20 are provided per magnetic pole. The circumferential center of the magnet insertion hole 101 is the pole center. A line passing through the pole center (the circumferential center of the magnet insertion hole 101) and the central axis Ax defines the d-axis. The permanent magnets 20 are housed in the magnet insertion hole 101 on both sides of the d-axis.

[0117] The permanent magnet 20 has a first magnetic pole face 21 on the radially outer side, a second magnetic pole face 22 on the radially inner side, and side end faces 23 on both circumferential sides. The first magnetic pole face 21 faces a first end edge 101a of the magnet insertion hole 101, and the second magnetic pole face 22 faces a second end edge 101b of the magnet insertion hole 101. The side end face 23 of each permanent magnet 20 closer to the d axis faces a protrusion 102 of the magnet insertion hole 101.

[0118] The outer periphery of rotor core 10 has elliptical arc portion 15 and circular arc portion 16 described in embodiment 1. The shapes of elliptical arc portion 15 and circular arc portion 16 are as described in embodiment 1.

[0119] In a plane perpendicular to the central axis Ax, the angle between the magnet insertion hole 101 and the q axis is defined as angle V [degrees]. More specifically, the angle between a straight line H extending from the first edge 101a of the magnet insertion hole 101 and the q axis is defined as angle V. It can also be said that angle V is the angle between the straight line H extending from the first pole face 21 of the permanent magnet 20 and the q axis.

[0120] In Fig. 12, the angle V between the magnet insertion hole 101 and the q axis is 135 degrees. Fig. 13 shows an example in which the angle V between the magnet insertion hole 101 and the q axis is 140 degrees in a rotor 1A having the same configuration as Fig. 12.

[0121] When elliptical arc portion 15 and circular arc portion 16 are formed on the outer periphery of rotor core 10, the area in which permanent magnets 20 can be arranged is narrower than when the outer periphery of rotor core 10 is a perfect circle. In the second embodiment, magnet insertion holes 101 of rotor core 10 are V-shaped, thereby ensuring storage space for permanent magnets 20 while achieving the effects of elliptical arc portion 15 and circular arc portion 16 described in the first embodiment.

[0122] Here, angle V between magnet insertion hole 101 and the q axis affects the characteristics of motor 5, so it is desirable to set angle V to an optimal angle. Below, we will explain how the torque constant, maximum torque, iron loss, and harmonic content change when angle V is changed.

[0123] In the analysis, as shown in Figures 12 and 13, the position of the end point (i.e., corner) U closest to the q axis of the first pole face 21 of the permanent magnet 20 was kept constant, and the size (width, thickness, etc.) of the permanent magnet 20 was also kept constant, while the angle V of the magnet insertion hole 101 relative to the q axis was changed.

[0124] The larger the angle V, the longer the distance of the permanent magnets 20 from the outer periphery of the rotor core 10 (in other words, the deeper the embedding depth of the permanent magnets 20). Conversely, the smaller the angle V, the shorter the distance of the permanent magnets 20 from the outer periphery of the rotor core 10 (in other words, the shallower the embedding depth of the permanent magnets 20).

[0125] 14 is a graph showing the relationship between angle V and torque constant. The horizontal axis represents angle V [degrees], and the vertical axis represents torque constant [Nm / Arms]. The definition of the torque constant is as explained in the first embodiment.

[0126] Figure 15 is a graph showing the relationship between angle V and maximum torque. The horizontal axis represents angle V [degrees], and the vertical axis represents maximum torque [Nm]. Maximum torque is the maximum torque value that can be generated when a specified voltage value is applied and the motor rotates at a specified rotation speed.

[0127] 16 is a graph showing the relationship between angle V and iron loss. The horizontal axis represents angle V [degrees], and the vertical axis represents iron loss [W]. Iron loss is loss that occurs when magnetic flux flows through rotor core 10.

[0128] 17 is a graph showing the relationship between angle V and harmonic content. The horizontal axis represents angle V [degrees], and the vertical axis represents harmonic content [%]. The definition of harmonic content is as explained in the first embodiment.

[0129] As shown in FIG. 14, the torque constant increases as the angle V decreases. In the range of V≤138 [degrees], compared with the range of 138 [degrees]<V≤140 [degrees], the increase rate of the torque constant with respect to the decrease of the angle V (or equivalently, the decrease rate of the torque constant with respect to the increase of the angle V) is large. On the other hand, as shown in FIG. 15, the maximum torque increases linearly with respect to the decrease of the angle V.

[0130] As is clear from FIGS. 14 and 15, the torque constant and the maximum torque improve as the angle V decreases. The reason for the improvement of the torque constant and the maximum torque is considered to be that as the angle V is smaller, the embedding depth of the permanent magnet 20 becomes shallower, and the magnetic flux of the permanent magnet 20 becomes easier to flow into the stator 3, as described above.

[0131] As shown in FIG. 14, the decrease rate of the torque constant with respect to the increase of the angle V is blunted in the range of 138 [degrees]<V≤140 [degrees] compared with the range of V≤138 [degrees]. The reason for the blunting is that as the angle V is larger, the embedding depth of the permanent magnet 20 becomes deeper, so the magnetic flux of the permanent magnet 20 becomes more difficult to flow into the stator 3. On the other hand, since the distance between the two permanent magnets 20 in the magnet insertion hole 101 increases, the leakage magnetic flux between them decreases.

[0132] On the other hand, as shown in FIG. 15, the decrease rate of the maximum torque with respect to the increase of the angle V (i.e., the increase rate of the maximum torque with respect to the decrease of the angle V) is constant. The reason why the blunting of the decrease rate as seen in the above-described torque constant is not observed is that the maximum torque is inversely proportional to the increase of the d-axis inductance, and as the angle V is larger (i.e., as the embedding depth of the permanent magnet 20 becomes deeper), the volume of the core portion on the outer peripheral side rather than the permanent magnet 20 increases, so the d-axis inductance increases.

[0133] Also, as shown in FIG. 16, the iron loss increases as the angle V decreases. The increase rate of the iron loss with respect to the decrease of the angle V becomes larger in the range of V<136.5 [degrees] compared with the range of 136.5 [degrees]≤V<140 [degrees].

[0134] <Iron loss generally increases as the torque constant increases, and the torque constant increases as the angle V decreases (see FIG. 14). However, in the range of 136.5 degrees≦V<140 degrees, the rate of increase in iron loss relative to a decrease in angle V is small. This is thought to be because the volume of the core portion of rotor core 10 on the outer periphery of permanent magnet 20 decreases as angle V decreases (i.e., the embedding depth of permanent magnet 20 becomes shallower).

[0135] On the other hand, in the range of V<136.5 degrees, the rate of increase in iron loss with respect to the decrease in angle V is large. This is thought to be because, in the range of V<136.5 degrees, the increase in iron loss caused by the increase in torque constant due to the decrease in angle V exceeds the decrease in volume of the core portion of rotor core 10 on the outer periphery side of permanent magnet 20 caused by the decrease in angle V.

[0136] Therefore, it is desirable that the angle V be set in a range that allows for securing an area for arranging the permanent magnets 20 without increasing iron loss as much as possible, and therefore it is desirable to set the angle V in the range of 136.5 degrees≦V.

[0137] 17, the harmonic content reaches a minimum (bottom) when the angle V is 138 degrees. That is, whether the angle V increases or decreases from 138 degrees, the harmonic content increases.

[0138] It is believed that when angle V decreases (i.e., the embedding depth of permanent magnet 20 becomes shallower), the magnetic flux flowing from permanent magnet 20 into stator 3 increases, resulting in an uneven circumferential magnetic flux density distribution of the magnetic flux flowing into stator 3.

[0139] Furthermore, as the angle V increases (i.e., the embedding depth of the permanent magnets 20 increases), the distance between the two permanent magnets 20 in the magnet insertion holes 101 increases, resulting in variations in density of the magnetic flux flowing from the rotor 1 to the stator 3, and it is thought that the circumferential magnetic flux density distribution of the magnetic flux flowing into the stator 3 becomes uneven.

[0140] If the angle V is in the range of 136.5 degrees≦V<140 degrees, the harmonic content can be kept relatively small (FIG. 17), and iron loss can also be reduced (FIG. 16).

[0141] When two permanent magnets 20 are arranged in a V-shape, both permanent magnets 20 are urged toward the q-axis by magnetic repulsion. Each permanent magnet 20 is positioned by contacting the positioning protrusion 14 on the q-axis side. Therefore, even if the central protrusion 102 of the magnet insertion hole 101 is not provided, a gap is created between the two permanent magnets 20.

[0142] 18 is a schematic diagram for explaining the distance D from the d-axis to the permanent magnet 20. More specifically, as shown in FIG. 18, the distance D is the shortest distance from a point 103 at the circumferential center of the first edge 101a of the magnet insertion hole 101 to the side end face 23 of the permanent magnet 20.

[0143] The distance D from the d-axis to the permanent magnet 20 defines the distance between two permanent magnets 20 placed in one magnet insertion hole 101. The distance between the two permanent magnets 20 in the magnet insertion hole 101 affects the flow of magnetic flux emitted from each permanent magnet 20.

[0144] Fig. 19 is a graph showing the relationship between angle V and distance D. As described above, if the position of point U (Figs. 12 and 13) of permanent magnet 20 is constant and the size of permanent magnet 20 is also constant, determining angle V determines distance D from the d-axis to permanent magnet 20. Fig. 19 shows the value of distance D when angle V is changed from 136 degrees to 140 degrees.

[0145] The above-mentioned range of angle V, 136.5 degrees ≦ V < 140 degrees, corresponds to the range of distance D, 0.109 mm ≦ D < 0.338 mm. Therefore, it is desirable that distance D from the d-axis to permanent magnet 20 be in the range of 0.109 mm ≦ D < 0.338 mm.

[0146] As described above, in the rotor 1A of embodiment 2, the magnet insertion hole 101 is formed in a V shape with its circumferential center projecting toward the central axis Ax, two permanent magnets 20 are disposed in the magnet insertion hole 101, and the angle V formed between the magnet insertion hole 101 and the q axis satisfies 136.5 degrees ≦ V. This configuration increases the torque constant and maximum torque and reduces iron loss.

[0147] Furthermore, when the angle V between the magnet insertion hole 101 and the q axis is in the range of 136.5 degrees≦V<140 degrees, the torque constant and maximum torque can be increased, iron loss can be reduced, and the harmonic content can be reduced.

[0148] Furthermore, even when the distance D from the d-axis to the permanent magnet 20 is in the range of 0.109 [mm]≦D<0.338 [mm], the torque constant and maximum torque can be increased, iron loss can be reduced, and the harmonic content can be reduced.

[0149] Here, an example has been described in which two permanent magnets 20 are arranged in the magnet insertion hole 101, but three or more permanent magnets 20 may be arranged in the magnet insertion hole 101. In other words, it is sufficient that two or more permanent magnets 20 are arranged in the magnet insertion hole 101 to form a magnetic pole.

[0150] Embodiment 3 Next, a compressor 8 according to a third embodiment will be described. Fig. 20 is a cross-sectional view showing the compressor 8 according to the third embodiment. The compressor 8 is a rotary compressor in this case, and has a sealed container 80, a compression mechanism 9 disposed in the sealed container 80, a motor 5 that drives the compression mechanism 9, and a shaft 90 that connects the motor 5 and the compression mechanism 9 so as to be capable of transmitting power. The shaft 90 is the shaft 90 shown in Fig. 1 and other figures, and is fitted into the central hole 18 (Fig. 1) of the rotor 1 of the motor 5. The motor 5 has the configuration described in the first embodiment.

[0151] The sealed container 80 is a sealed container formed, for example, from a steel plate, and covers the motor 5 and the compression mechanism 9. The sealed container 80 has an upper frame 82 and a lower frame 81. Attached to the upper frame 82 are a glass terminal 83 serving as a terminal portion for supplying power to the motor 5, and a discharge pipe 85 for discharging the refrigerant compressed in the compressor 8 to the outside. The motor 5 and the compression mechanism 9 are housed in the frame 81.

[0152] The compression mechanism 9 has an annular first cylinder 91 and a second cylinder 92 arranged along the shaft 90. The first cylinder 91 and the second cylinder 92 are fixed to the inside of the frame 81. An annular first piston 93 is arranged on the inner circumferential side of the first cylinder 91, and an annular second piston 94 is arranged on the inner circumferential side of the second cylinder 92. The first piston 93 and the second piston 94 are rotary pistons that rotate together with the shaft 90.

[0153] A partition plate 97 is provided between the first cylinder 91 and the second cylinder 92. The partition plate 97 is a disk-shaped member with a through-hole in the center. The cylinder chambers of the first cylinder 91 and the second cylinder 92 are provided with vanes (not shown) that divide the cylinder chambers into an intake side and a compression side. The first cylinder 91, the second cylinder 92, and the partition plate 97 are fixed together with bolts 98.

[0154] An upper frame 95 is disposed above the first cylinder 91 so as to close the upper side of the cylinder chamber of the first cylinder 91. A lower frame 96 is disposed below the second cylinder 92 so as to close the lower side of the cylinder chamber of the second cylinder 92. The upper frame 95 and the lower frame 96 rotatably support the shaft 90.

[0155] Refrigeration oil (not shown) for lubricating each sliding part of compression mechanism 9 is stored in the bottom of frame 81 of sealed container 80. The refrigeration oil rises through hole 90a formed in the axial direction inside shaft 90, and is supplied to each sliding part from oil supply holes 90b formed at multiple locations on shaft 90.

[0156] The stator 3 of the motor 5 is attached to the inside of a frame 81 by shrink fitting. Electric power is supplied to the windings 40 of the stator 3 from a glass terminal 83 attached to an upper frame 82. A shaft 90 is fixed in the center hole 18 of the rotor 1 (FIG. 1).

[0157] An accumulator 87 that stores refrigerant gas is attached to the frame 81. The accumulator 87 is held by, for example, a holder 86 provided on the outside of the frame 81. A pair of suction pipes 88, 89 are attached to the frame 81, and refrigerant gas is supplied from the accumulator 87 to cylinders 91, 92 via the suction pipes 88, 89.

[0158] As the refrigerant, for example, R410A, R407C, or R22 may be used, but from the viewpoint of preventing global warming, it is desirable to use a refrigerant with a low GWP (global warming potential). For example, the following refrigerants can be used as the low GWP refrigerant.

[0159] (1) First, halogenated hydrocarbons with carbon double bonds in their composition, such as HFO (Hydro-Fluoro-Orefin)-1234yf (CFCF=CH), can be used. HFO-1234yf has a GWP of 4. (2) Hydrocarbons containing carbon double bonds in their composition, such as R1270 (propylene), may also be used. R1270 has a GWP of 3, which is lower than HFO-1234yf, but is more flammable than HFO-1234yf. (3) Alternatively, a mixture containing at least one of a halogenated hydrocarbon having a carbon-carbon double bond in its composition or a hydrocarbon having a carbon-carbon double bond in its composition, such as a mixture of HFO-1234yf and R32, may be used. Because HFO-1234yf is a low-pressure refrigerant, it tends to have a large pressure loss, which may lead to a decrease in the performance of the refrigeration cycle (especially the evaporator). Therefore, it is practically desirable to use a mixture of HFO-1234yf with R32 or R41, which are higher-pressure refrigerants than HFO-1234yf.

[0160] The basic operation of compressor 8 is as follows. Refrigerant gas supplied from accumulator 87 is supplied to each cylinder chamber of first cylinder 91 and second cylinder 92 through suction pipes 88 and 89. When motor 5 is driven and rotor 1 rotates, shaft 90 rotates together with rotor 1. Then, first piston 93 and second piston 94 fitted to shaft 90 rotate eccentrically within each cylinder chamber, compressing the refrigerant within each cylinder chamber. The compressed refrigerant passes through groove 31d (FIG. 1) of stator 3 and through holes 19a and 19b (FIG. 2) of rotor 1, rises within sealed container 80, and is discharged to the outside through discharge pipe 85.

[0161] The compressor in which the motor 5 is used is not limited to a rotary compressor, but may be, for example, a scroll compressor.

[0162] As described in the first and second embodiments, the motor 5 can suppress a decrease in the effective value of the induced voltage while reducing the harmonic components of the induced voltage, thereby improving the operating efficiency of the compressor 8 and enhancing quietness.

[0163] Embodiment 4 Next, a refrigeration cycle apparatus 200 according to embodiment 4 will be described. Fig. 21 is a diagram showing the refrigeration cycle apparatus 200 according to embodiment 4. The refrigeration cycle apparatus 200 is, for example, an air conditioner, but is not limited to this and may be, for example, a refrigerator.

[0164] 21 includes a compressor 201, a condenser 202 that condenses a refrigerant, a pressure reducing device 203 that reduces the pressure of the refrigerant, and an evaporator 204 that evaporates the refrigerant. The compressor 201, the condenser 202, and the pressure reducing device 203 are provided in an outdoor unit 210, and the evaporator 204 is provided in an indoor unit 220.

[0165] Compressor 201, condenser 202, pressure reducing device 203, and evaporator 204 are connected by refrigerant piping 207 to form a refrigerant circuit. Compressor 201 is configured as compressor 8 described in embodiment 3. Refrigeration cycle apparatus 200 also includes outdoor fan 205 facing condenser 202 and indoor fan 206 facing evaporator 204.

[0166] The operation of the refrigeration cycle apparatus 200 is as follows. The compressor 201 compresses the refrigerant it has drawn in and sends it out as a high-temperature, high-pressure refrigerant gas. The condenser 202 exchanges heat between the refrigerant sent out from the compressor 201 and the outdoor air sent by the outdoor blower 205, condenses the refrigerant, and sends it out as a liquid refrigerant. The pressure reducing device 203 expands the liquid refrigerant sent out from the condenser 202 and sends it out as a low-temperature, low-pressure liquid refrigerant.

[0167] The evaporator 204 exchanges heat between the low-temperature, low-pressure liquid refrigerant sent from the pressure reducing device 203 and the indoor air, evaporating the refrigerant and sending it out as refrigerant gas. The air from which heat has been removed by the evaporator 204 is blown into the room by the indoor fan 206.

[0168] The compressor 201 of the refrigeration cycle apparatus 200 has high operating efficiency and quietness, and therefore the operating efficiency and quietness of the refrigeration cycle apparatus 200 can be improved.

[0169] Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various improvements and modifications can be made. [Explanation of symbols]

[0170] DESCRIPTION OF SYMBOLS 1, 1A rotor, 3 stator, 5 motor, 8 compressor, 9 compression mechanism, 10 rotor core, 11, 101 magnet insertion hole, 12 flux barrier (gap), 13 bridge portion, 13a inner peripheral edge (edge), 14 positioning protrusion, 15 elliptical arc portion, 16 circular arc portion, 18 center hole, 20 permanent magnet, 21 first magnetic pole face, 22 second magnetic pole face, 23 side end face, 30 stator core, 31 core back, 32 teeth, 33 slot, 40 winding, 101 magnet insertion hole, 101a first edge, 101b second edge, 102 protrusion, 200 refrigeration cycle device, 201 compressor, 202 condenser 203 Pressure reducing device, 204 Evaporator.

Claims

1. a rotor core having an outer periphery extending in a circumferential direction around a central axis and having magnet insertion holes along the outer periphery; a permanent magnet that is disposed in the magnet insertion hole and forms a magnetic pole; and A gap is formed at an end of the magnet insertion hole in the circumferential direction, a bridge portion extending in the circumferential direction is formed between the gap and the outer periphery of the rotor core, If a line passing through the central axis and the center of the magnet insertion hole in the circumferential direction is defined as a d-axis, and a line passing through the central axis and an inter-pole portion spaced apart from the magnet insertion hole in the circumferential direction is defined as a q-axis, the outer periphery of the rotor core has an elliptical arc portion at a portion including an intersection with the d axis and a circular arc portion at a portion including an intersection with the q axis, the elliptical arc portion is line-symmetric with respect to the d-axis, the circular arc portion is line-symmetric with respect to the q-axis, and the elliptical arc portion and the circular arc portion are connected to each other; When the distance on the d-axis from the central axis to the outer periphery is r1, the elliptical arc portion is tangent to a circle having a radius r1 and centered on the central axis at one point on the d-axis, the arc portions form parts of a circle having a radius r2 smaller than the radius r1 and centered on the central axis, and are provided at at least two locations symmetrical with respect to the central axis, the elliptical arc portion has a first axis in a direction perpendicular to the d axis and a second axis on the d axis, the first axis being one of a major axis and a minor axis, and the second axis being the other of the major axis and the minor axis; When the length of the second axis is 2b and the distance from the central axis to the center of the elliptical arc portion is k, k=r1−b holds true, the bridge portion has a minimum width t in a radial direction of the rotor core, At least a part of the outer periphery of the rotor core that constitutes the bridge portion is formed by the arc portion, The edge of the bridge portion on the gap side forms a part of a circle having a radius r2-t, which is the radius r2 minus the minimum width t of the bridge portion. Rotor.

2. When the length of the first axis of the elliptical arc portion is 2a, a>b 2. The rotor according to claim 1, wherein:

3. If the distance in a direction parallel to the d-axis between the intersection point of the elliptical arc portion and the d-axis and the intersection point of the circular arc portion and the q-axis is c, then b ≧ c 3. The rotor according to claim 2, wherein the following holds true:

4. When the length of the first axis of the elliptical arc portion is 2a, 0.439≦a / r1≦0.471 4. A rotor according to claim 1, wherein the following holds true:

5. When the length of the first axis of the elliptical arc portion is 2a and the length of the second axis of the elliptical arc portion is 2b, 0.439≦a / r1<0.451, b / r<0.244 4. A rotor according to claim 1, wherein the following holds true:

6. When the length of the first axis of the elliptical arc portion is 2a and the length of the second axis of the elliptical arc portion is 2b, 0.451≦a / r1≦0.471, b / r≧0.244 4. A rotor according to claim 1, wherein the following holds true:

7. The magnet insertion hole extends in a V-shape with the circumferential center protruding toward the central axis, Two or more permanent magnets are arranged in the magnet insertion holes to form magnetic poles, The angle V between the magnet insertion hole and the q axis is 136.5 [degrees]≦V 4. The rotor according to claim 1, wherein the following is satisfied:

8. The angle V between the magnet insertion hole and the q axis is 136.5[degrees]≦V<140[degrees] 8. The rotor according to claim 7, wherein the following is satisfied:

9. The magnet insertion hole extends in a V-shape with the circumferential center protruding toward the central axis, Two or more permanent magnets are arranged in the magnet insertion holes to form magnetic poles, The shortest distance D from the d axis to each permanent magnet is 0.109 [mm]≦D<0.338 [mm] 4. The rotor according to claim 1, wherein the following is satisfied:

10. A rotor according to any one of claims 1 to 3; a stator surrounding the rotor via an air gap; A motor equipped with

11. a motor according to claim 10; a compression mechanism driven by the motor; A compressor equipped with

12. A compressor comprising the compressor according to claim 11, a condenser, a pressure reducing device, and an evaporator. Refrigeration cycle equipment.

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