Rotor, motor, compressor, and refrigeration cycle device

Abstract

This rotor comprises: a rotor core that has an outer circumference extending in a circumferential direction centered on a central axis, and magnet insertion holes along the outer circumference; and permanent magnets that are disposed in the magnet insertion holes and constitute magnetic poles. When a straight line passing through the central axis and the center of a magnet insertion hole in the circumferential direction is defined as a d-axis, and a straight line passing through the central axis and an inter-pole section spaced apart from the magnet insertion hole in the circumferential direction is defined as a q-axis, at least one portion of the section from the d-axis to the q-axis in the outer circumference of the rotor core is formed as an elliptical arc section centered on the d-axis, and the elliptical arc portion has line symmetry with the d-axis. When the distance on the d-axis from the central axis to the outer circumference is defined as r, the elliptical arc section is tangent to a circle having the radius r centered on the central axis at one point on the d-axis. The elliptical arc section has a first axis in a direction orthogonal to the d-axis, and has a second axis on the d-axis. The first axis is one among a major axis and a minor axis, and the second axis is the other among the major axis and the minor axis. When the length of the second axis is defined as 2b and the distance from the central axis to the center of the elliptical arc section is defined as k, the expression k = r-b is established.

Description

Rotor, motor, compressor, and refrigeration cycle device

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

[0002] The motor has a rotor having permanent magnets and a stator surrounding the rotor via an air gap. Conventionally, a motor has been proposed in which the width of the air gap is continuously changed so as to be minimum on the d-axis of the rotor and maximum on the q-axis (see, for example, Patent Document 1). This configuration has the effect of reducing the harmonic components of the induced voltage and reducing vibration and noise.

[0003] Japanese Patent Application Laid-Open No. 2003-116236 (see the abstract)

[0004] In the conventional configuration, the width of the air gap increases as it moves away from the d-axis in the circumferential direction. However, if the width of the air gap increases abruptly, the effective value of the induced voltage decreases, leading to a decrease in the motor output. Therefore, it is required to suppress a decrease in the effective value of the induced voltage while reducing the harmonic components of the induced voltage.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to suppress a decrease in the effective value of the induced voltage while reducing the harmonic components of the induced voltage.

[0006] The rotor of the present disclosure has a rotor core having an outer periphery extending in the circumferential direction centered on a central axis and magnet insertion holes along the outer periphery, and permanent magnets arranged in the magnet insertion holes to form magnetic poles. When a straight line passing through the central axis and the circumferential center of the magnet insertion hole is defined as the d-axis, and a straight line passing through the central axis and the interpolar part spaced apart from the magnet insertion hole in the circumferential direction is defined as the q-axis, at least a part of the section from the d-axis to the q-axis of the outer periphery of the rotor core is formed by an elliptical arc portion having a center on the d-axis, and the elliptical arc portion is line-symmetric with respect to the d-axis. When the distance from the central axis to the outer periphery on the d-axis is r, the elliptical arc portion is tangent to a circle with a radius r centered on the central axis at a point on the d-axis. The elliptical arc portion 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 to the center of the elliptical arc portion is k, k = r - b holds.

[0007] According to this disclosure, since at least a portion of the section from the d-axis to the q-axis on the outer circumference of the rotor core is formed by the elliptical arc described above, the rapid expansion of the air gap around the d-axis is suppressed. Therefore, it is possible to reduce the harmonic components of the induced voltage while suppressing the decrease in the effective value of the induced voltage.

[0008] This is a cross-sectional view showing the motor of Embodiment 1. This is a plan view showing the rotor of Embodiment 1. This is a plan view showing the rotor of Embodiment 1. This is a diagram showing the part corresponding to one magnetic pole and the teeth of the rotor of Embodiment 1. These are Figures (A) to (D) showing examples of the shape of the elliptical arc portion of the rotor core of Embodiment 1. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the harmonic content in the induced voltage. This is a diagram for explaining the shape of the elliptical arc portion of the rotor core of Embodiment 1. This is a graph showing the relationship between b / r and a / b in the rotor core of Embodiment 1. These are Figures (A) to (H) showing examples of the shape of the elliptical arc portion of the rotor core of Embodiment 1. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the effective value of the induced voltage. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the rate of change of iron loss. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the rate of change of copper loss. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the rate of change of total loss. This is a graph showing the relationship between a / b in the rotor core of Embodiment 1 and the harmonic content in the induced voltage. This is a plan view (A) of the rotor of the comparative example, and a magnified view (B) of a part of the rotor. This is a plan view (A) of the rotor of the comparative example, and a magnified view (B) of a part of the rotor. This is a diagram showing the area around the flux barrier of the rotor of the comparative example. This is a plan view (A) of the rotor of Embodiment 1, and a magnified view (B) of a part of the rotor. These are diagrams (A) and (B) to explain the dimensions used in the analysis of the motor of the comparative example. These are diagrams (A) and (B) to explain the dimensions used in the analysis of the motor of Embodiment 1. This is a graph comparing the relationship between the width W of the permanent magnet and the effective value of the induced voltage for the motors of Embodiment 1 and the comparative example. This is a graph comparing the relationship between the volume of the permanent magnet and the effective value of the induced voltage for the motors of Embodiment 1 and the comparative example. This is a diagram showing a magnified view of a part of the rotor of a modified example. This is a longitudinal cross-sectional view showing the compressor of Embodiment 2. This is a diagram showing the refrigeration cycle device of Embodiment 3.

[0009] Embodiment 1. <Motor Configuration> First, the motor 5 of Embodiment 1 will be described. Figure 1 is a cross-sectional view showing the motor 5 of Embodiment 1. The motor 5 shown in Figure 1 is a permanent magnet embedded type synchronous motor and is used, for example, in a compressor 8 (Figure 24).

[0010] The motor 5 has a shaft 90 which is the axis of rotation, a rotor 1 fixed to the shaft 90, and a stator 3 provided so as 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 the cylindrical frame 81 of the compressor 8 (Figure 24), which will be described later.

[0011] In the following, the direction of the central axis Ax, which is the center of rotation of the rotor 1 and the central axis of the shaft 90, 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 Figure 1, the stator 3 has a stator core 30 that surrounds the rotor core 10 from the radially outer side, and windings 40 wound around the stator core 30. The stator core 30 has a plurality of laminated elements stacked in the axial direction. The laminated elements are, for example, electrical steel sheets. The 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 teeth 32 (where M is an integer of 2 or more) extending radially inward from the core back 31. The teeth 32 are arranged at regular intervals in the circumferential direction. The number of teeth 32, M, is 9 here, but it can be 2 or more.

[0014] Each tooth 32 has a tooth tip surface 32a at its radially inward tip. The circumferential width of the tooth tip surface 32a is wider than the circumferential width of the rest of the tooth 32. The tooth tip surface 32a faces the rotor 1.

[0015] Slots 33 are formed between adjacent teeth 32 in the circumferential direction. The slots 33 are regions in which the windings 40 are accommodated. The number of slots 33 is M, which is the same as the number of teeth 32, and in this case there are 9 slots.

[0016] The winding 40 (Figure 1) is made of magnet wire and is wound around each tooth 32. The winding method for the winding 40 is concentrated winding, but it may also be distributed winding. A current with a frequency corresponding to the rotational speed of the motor 5 is passed through the winding 40, generating a rotating magnetic field that rotates the rotor 1.

[0017] The wire diameter of the winding 40 and the number of turns on 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. For example, the wire diameter of the winding 40 is 1.0 mm and the number of turns is 80. An insulating section is provided between the stator core 30 and the winding 40. The insulating section can be made of, for example, an insulator 34 (see Figure 24), an insulating film, or the like.

[0018] The stator core 30 is divided into M segmented cores 35 by a dividing surface 31b formed on the core back 31. Each segmented core 35 contains one tooth 32. The portion of the core back 31 included in each segmented core 35 is also referred to as the core back portion 31a. Adjacent segmented cores 35 in the circumferential direction are connected by crimping portions 31c provided on the outer circumference of the dividing surface 31b, or by welding.

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

[0020] The stator core 30 is not limited to a combination of M segmented cores 35 arranged in a ring shape; for example, it may be an integrated core formed by stacking annular electromagnetic steel sheets in the axial direction.

[0021] A groove 31d is formed on the outer circumferential surface of the core back 31. A refrigerant passage for the refrigerant of the compressor 8 is formed between the groove 31d and the frame 81. The groove 31d is located radially outward of the teeth 32, but is not limited to this position.

[0022] Furthermore, stepped portions 36 may be formed at the axial ends of the core back 31 and teeth 32 so as to face the slot 33.

[0023] <Rotor Configuration> Figure 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 stacked in the axial direction. The laminated elements are, for example, electrical steel sheets. The thickness of the laminated elements is 0.1 [mm] to 0.7 [mm].

[0024] A central hole 16 is formed at the radial center of the rotor core 10. The shaft 90 (Figure 1) is fixed to the central hole 16 of the rotor core 10 by shrink fitting or press fitting.

[0025] N magnet insertion holes 11 (where N is an integer of 2 or more) are formed along the outer circumference of the rotor core 10. One permanent magnet 20 is placed in each magnet insertion hole 11. Each magnet insertion hole 11 corresponds to one magnetic pole. Since 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 can be 2 or more.

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

[0027] Dysprosium (Dy) may be added to rare earth magnets to improve their coercivity. However, the addition of Dy increases manufacturing costs and reduces residual magnetic flux density, so it is desirable to limit the Dy content to 4% by weight or to omit Dy altogether. In other words, the Dy content should ideally be 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 passing through the circumferential center of the magnet insertion hole 11 and the central axis Ax.

[0029] An interpole region is formed between adjacent magnetic poles. A q-axis is defined within this interpole region. The q-axis is a straight line passing through the interpole region and the central axis Ax. The q-axis is also an axis that is 90 degrees away in electrical angle from the d-axis.

[0030] The magnet insertion holes 11 here extend linearly in a direction perpendicular to the d-axis. However, the magnet insertion holes 11 are not limited to a linear shape; they may also extend in a V-shape. Furthermore, two or more permanent magnets 20 may be placed in each magnet insertion hole 11.

[0031] Flux barriers 12, which are air gaps, are formed on both sides of the magnet insertion hole 11 in the circumferential direction. A bridge portion 13 (see Figure 4) is formed between the flux barriers 12 and the outer circumference 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, for example, the thickness of the laminated element.

[0032] A positioning projection 14 is formed on the radially inward side of each flux barrier 12. The positioning projection 14 faces the circumferential end face (side end face 23 shown in Figure 4) of the permanent magnet 20 and positions the permanent magnet 20 in the circumferential direction.

[0033] Through holes 18a and 18b are formed radially inside the magnet insertion hole 11. The circumferential position of through hole 18a coincides with the pole center, and the circumferential position of through hole 18b coincides with the inter-pole portion. The through holes 18a and 18b penetrate the rotor core 10 axially and are used as coolant passages. Note that the positions of the through holes 18a and 18b are not limited to those described here. Also, the rotor core 10 does not necessarily have to have through holes 18a and 18b.

[0034] <Outer circumference shape of the rotor core> Figure 3 is a diagram illustrating the outer circumference shape of the rotor core 10. Point P is the point where the outer circumference of the rotor core 10 intersects the d-axis. Point Q is the point where the outer circumference of the rotor core 10 intersects the q-axis.

[0035] At least a portion of the outer circumference of the rotor core 10, from the d-axis to the q-axis (i.e., at least a portion of the section from point P to point Q), is formed by an elliptical arc portion 15. More preferably, the entire outer circumference of the rotor core 10, from the d-axis to the q-axis (i.e., the entire section from point P to point Q), is formed by an elliptical arc portion 15. The rotor core 10 has the same number of elliptical arc portions 15 as the number of poles N.

[0036] The elliptical arc 15 corresponds to a part of a hypothetical ellipse E1 having its center C1 on the d-axis. Ellipse E1 has a first axis perpendicular to the d-axis and a second axis on the d-axis. The first axis is either a major axis or a minor axis, and the second axis is the other of the major axis or minor axis. In the example shown in Figure 3, the first axis is the major axis and the second axis is the minor axis.

[0037] The length of the first axis of ellipse E1 is 2a, and the length of the second axis of ellipse E1 is 2b. In the example shown in Figure 3, the length of the major axis of ellipse E1 is 2a, and the length of the minor axis is 2b. Furthermore, the elliptical arc 15 is formed symmetrically with respect to the d-axis.

[0038] Hereafter, the center C1 of the ellipse E1 that forms the elliptical arc portion 15 will be referred to as "center C1 of the elliptical arc portion 15". Also, the length 2a of the first axis (e.g., the major axis) of the ellipse E1 will be referred to as "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 "length 2b of the second axis of the elliptical arc portion 15".

[0039] The distance from the central axis Ax of the rotor core 10 to the elliptical arc portion 15 is maximum at point P and minimum at point Q. Let the distance from the central axis Ax of the rotor core 10 to point P be r. r can also be said to be the distance from the central axis Ax on the d-axis to the outer periphery of the rotor core 10. r is also referred to as the maximum radius of the rotor core 10.

[0040] Let the virtual circle with radius r centered on the central axis Ax of the rotor core 10 be circle A1. The elliptical arc portion 15 of the rotor core 10 and circle A1 are tangent at only one point (i.e., point P).

[0041] Also, the distance k from the central axis Ax of the rotor core 10 to the center C1 of the elliptical arc portion 15 is expressed as k = r - b. Note that b, which is half of the length 2b of the second axis (for example, the minor axis) of the elliptical arc portion 15, is shorter than the maximum radius r of the rotor core 10, and r - b > 0.

[0042] FIG. 4 is a diagram showing a portion corresponding to one magnetic pole of the rotor 1 and the teeth 32 facing it. 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. At both circumferential ends of the magnet insertion hole 11, flux barriers 12, which are void portions, are formed. A bridge portion 13 is formed between the flux barrier 12 and the outer periphery of the rotor core 10.

[0043] The permanent magnet 20 has a first magnetic pole surface 21 on the radially outer side, a second magnetic pole surface 22 on the radially inner side, and side end surfaces 23 on both circumferential sides. The first magnetic pole surface 21 faces the first edge 11a of the magnet insertion hole 11, and the second magnetic pole surface 22 faces the second edge 11b of the magnet insertion hole 11. The side end surface 23 of the permanent magnet 20 faces the positioning convex portion 14.

[0044] In FIG. 4, 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.

[0045] 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 A2 centered on the central axis Ax (Figure 3). The width of the air gap is the minimum width Gmin on the d axis.

[0046] <Effect of reducing the effective value and harmonic components of the induced voltage> In order to reduce the vibration and noise of the motor 5, it is effective to reduce the harmonic components contained in the induced voltage. The reduction of harmonic components contained in the induced voltage is achieved by smoothly changing the magnetic flux of the magnets flowing from the rotor 1 to the stator 3. To this end, it is desirable that the width of the air gap between the rotor core 10 and the stator core 30 changes continuously so that it is the minimum on the d axis and the maximum on the q axis.

[0047] For example, Patent Document 1 discloses a rotor core in which the outer circumference is composed of two or more arcs for each magnetic pole (see Figure 3 of Patent Document 1). However, when the outer circumference of the rotor core 10 is composed of two or more arcs for each magnetic pole, the width of the air gap expands rapidly around the d-axis, which may reduce the effective value of the induced voltage.

[0048] In contrast, in Embodiment 1, as shown in Figure 3, the outer circumference of the rotor core 10 is composed of elliptical arcs 15 for each magnetic pole. The center C1 of the elliptical arc 15 is located on the d-axis, and the elliptical arc 15 is symmetric with respect to the d-axis.

[0049] Furthermore, if r is the distance from the central axis Ax on the d-axis to the outer circumference of the rotor core 10, then the elliptical arc portion 15 is tangent to a circle A1 with radius r centered on the central axis Ax at one point (point P). In other words, the elliptical arc portion 15 is located on the inner side of circle A1 in the range from the d-axis to the q-axis. Also, if the length of the second axis (for example, the minor axis) of the elliptical arc portion 15 is 2b, then the distance k from the central axis Ax of the rotor core 10 to the center C1 of the elliptical arc portion 15 is k = r - b.

[0050] Because of this configuration, the width of the air gap between the rotor core 10 and the stator core 30 is the minimum width (Gmin) on the d-axis, and gradually increases as it moves away from the d-axis in the circumferential direction. Since a rapid expansion of the air gap width is suppressed, it is possible to reduce the harmonic components of the induced voltage while suppressing the decrease in the effective value of the induced voltage.

[0051] <Relationship between the shape of the elliptical arc portion and the harmonic content and effective value of the induced voltage> Here, we will explain the relationship between the shape of the elliptical arc portion 15 of the rotor core 10 and the effect of reducing the harmonic content (hereinafter also referred to as harmonic content) in the induced voltage. Figures 5(A) to (D) show examples of the shape of the elliptical arc portion 15 when the ratio a / b of the lengths of the first axis and second axis of the elliptical arc portion 15 is changed.

[0052] In the rotor core 10 shown in Figure 5(A), a circular arc portion 17 satisfying a / b = 1.0 is formed instead of the elliptical arc portion 15. In the rotor core 10 shown in Figure 5(B), the elliptical arc portion 15 has a shape where a / b = 0.96.

[0053] The elliptical arc portion 15 of the rotor core 10 shown in Figure 5(C) has a shape where a / b = 0.93. The elliptical arc portion 15 of the rotor core 10 shown in Figure 5(D) has a shape where a / b = 0.89.

[0054] Figure 6 is a graph showing the relationship between the ratio a / b of the lengths of the first and second axes of the elliptical arc 15 and the harmonic content in the induced voltage. The horizontal axis represents the ratio a / b of the lengths of the first and second axes, as explained with reference to Figures 5(A) to (D). The vertical axis represents the harmonic content in the induced voltage. Although harmonic components have orders, the harmonic content in Figure 6 is the sum of the harmonic components of all orders.

[0055] As shown in Figure 6, when the outer circumference of the rotor core 10 is formed with an elliptical arc 15 (i.e., when a / b < 1), the harmonic content in the induced voltage is reduced compared to when the outer circumference of the rotor core 10 is formed with an arc 17 (i.e., when a / b = 1).

[0056] Next, we will explain the relationship between the ratio a / b of the lengths of the first and second axes of the elliptical arc portion 15 and the maximum radius r of the rotor core 10.

[0057] In order to increase the effective value of the induced voltage, it is necessary to reduce the average width of the air gap between the rotor core 10 and the stator core 30, to the extent that the effect of reducing the harmonic content is not impaired.

[0058] To reduce the harmonic components in the induced voltage, the width of the air gap must be minimized on the d-axis. On the other hand, to suppress the decrease in the effective value of the induced voltage, the average width of the air gap must be as small as possible.

[0059] The following describes a configuration that minimizes the width of the air gap on the d-axis and also minimizes the average width of the air gap.

[0060] Figure 7 shows two ellipses E1 and E2 with different a / b values ​​as examples of ellipses that make up the elliptical arc 15. Figure 7 also shows a circle A1 centered on the central axis Ax. Both ellipses E1 and E2 satisfy a / b > 1, but the a / b of ellipse E2 is greater than the a / b of ellipse E1.

[0061] Ellipse E1 is tangent to circle A1 only at point P on the d-axis. In contrast, ellipse E2 intersects circle A1 not only at point P on the d-axis but also at point F, which is off the d-axis. Therefore, the section of ellipse E2 from point P to point F protrudes outward from circle A1. If the elliptical arc 15 is composed of a part of such ellipse E2, it is difficult to minimize the width of the air gap on the d-axis.

[0062] Whether the elliptical arc portion 15 is tangent to circle A1 only at point P on the d-axis (i.e., whether the width of the air gap is minimized on the d-axis) depends not only on a / b but also on the maximum radius r of the rotor core 10.

[0063] Therefore, through analysis, the value of b / r was varied, and the value of a / b was determined when the elliptical arc 15 is tangent to circle A1 only at point P on the d-axis and the average width of the air gap is minimized. Figure 8 is a graph showing the relationship between b / r and a / b. In Figure 8, the horizontal axis represents b / r, and the vertical axis represents a / b.

[0064] As shown in Figure 10, which will be described later, the larger the value of a / b, the smaller the average width of the air gap can be and the larger the effective value of the induced voltage can be. From Figure 8, if b / r ≤ 0.67, then in the range of a / b > 1 shown by the shaded area, the elliptical arc portion 15 can be made to touch the circle A1 only at point P on the d axis (i.e., the width of the air gap is minimized on the d axis).

[0065] Next, we will explain the relationship between the shape of the elliptical arc portion 15 of the rotor core 10 and the effect of improving the effective value of the induced voltage. Figures 9(A) to 9(H) show examples of the shape of the elliptical arc portion 15 when the ratio a / b of the lengths of the first axis and second axis of the elliptical arc portion 15 is changed.

[0066] The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(A) has a shape where a / b = 0.86. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(B) has a shape where a / b = 0.98. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(C) has a shape where a / b = 1.18. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(D) has a shape where a / b = 1.34.

[0067] The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(E) has a shape where a / b = 1.58. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(F) has a shape where a / b = 2.01. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(G) has a shape where a / b = 2.13. The elliptical arc portion 15 of the rotor core 10 shown in Figure 9(H) has a shape where a / b = 2.27.

[0068] Figure 10 is a graph showing the relationship between the ratio a / b of the lengths of the first and second axes of the elliptical arc 15 and the effective value of the induced voltage. The horizontal axis represents the ratio a / b of the lengths of the first and second axes, as explained with reference to Figures 9(A) to (H). The vertical axis represents the effective value of the induced voltage obtained by analysis.

[0069] In the analysis, the maximum radius r of the rotor core 10 was fixed at 27.5075 [mm], and the a / b ratio was changed by varying the values ​​of a and b.

[0070] As shown in Figure 10, the larger a / b ratio, the larger the effective value of the induced voltage. This is because a larger a / b ratio increases the radius of curvature of the elliptical arc portion 15 around the d-axis, thereby suppressing the rapid expansion of the air gap width.

[0071] These results suggest that, in order to achieve both a reduction in the harmonic components of the induced voltage and a suppression of the decrease in the effective value of the induced voltage, it is desirable that b / r ≤ 0.67 and a / b > 1 hold true.

[0072] In the analysis described with reference to Figures 6, 8, and 10, the maximum radius r of the rotor core 10 and the ratio a / b of the lengths of the first and second axes of the elliptical arc portion 15 were changed, but the shape and dimensions of the flux barrier 12 remained the same.

[0073] <Effects on Iron Loss and Copper Loss> Next, we will explain the relationship between the shape of the elliptical arc 15 and the iron loss and copper loss. As described above, in order to increase the effective value of the induced voltage, it is desirable that the ratio a / b of the lengths of the first axis and the second axis of the elliptical arc 15 be large, but a / b also affects the iron loss and copper loss.

[0074] Figure 11 is a graph showing the relationship between a / b and the rate of change in iron loss. The horizontal axis represents a / b, and the vertical axis represents the rate of change in iron loss. The rate of change in iron loss is the rate of change in iron loss based on the case where a / b = 0.85 and b = r. The iron loss is a value analyzed from the torque of the motor 5 when a peak current of 1 [A] is passed through the winding 40 of the stator 3.

[0075] As shown in Figure 11, the larger a / b ratio, the greater the iron loss. This is because, as a / b increases, the magnetic flux flowing from the permanent magnet 20 to the stator core 30 increases, causing magnetic saturation in the stator core 30.

[0076] Figure 12 is a graph showing the relationship between a / b and the copper loss change rate. The horizontal axis represents a / b, and the vertical axis represents the copper loss change rate. The copper loss change rate is the rate of change in copper loss based on the case where a / b = 0.85 and b = r. The copper loss is a value analyzed from the torque of the motor 5 when a peak current of 1 [A] is passed through the winding 40 of the stator 3.

[0077] As shown in Figure 12, copper loss decreases as the a / b ratio increases. This is because as a / b increases, the magnetic flux flowing from the permanent magnet 20 to the stator core 30 increases, and the current value required to generate the desired torque decreases.

[0078] By summing the iron loss and copper loss, the total loss (also called the total loss) of the motor 5 can be evaluated. Figure 13 is a graph showing the relationship between a / b and the rate of change of the total loss of iron loss and copper loss. The horizontal axis shows a / b, and the vertical axis shows the rate of change of the total loss of iron loss and copper loss.

[0079] As shown in Figure 13, the total loss of iron loss and copper loss decreases with increasing a / b in the range a / b < 1.3, reaches a minimum when a / b = 1.3, and increases with increasing a / b in the range a / b > 1.3.

[0080] This is because, when a / b = 1.3, the reduction in copper loss due to the decrease in current value (Figure 12) is obtained at a stage where the increase in iron loss due to magnetic saturation in the stator core 30 is relatively small (Figure 11).

[0081] Figure 14 is a graph showing the relationship between a / b and the harmonic content in the induced voltage. The horizontal axis represents a / b, and the vertical axis represents the harmonic content in the induced voltage.

[0082] As shown in Figure 14, the harmonic content in the induced voltage decreases with increasing a / b in the range a / b < 1.85, reaches a minimum when a / b = 1.85, and increases with increasing a / b in the range a / b > 1.85.

[0083] This is because when a / b is small, the change in air gap width is large around the d-axis, and when a / b is large, the change in air gap width is large around the q-axis.

[0084] When the total loss (Figure 13) is minimized, a / b = 1.3, the harmonic content is 2.4%. The harmonic content can be kept below 2.4% when a / b is in the range of 1.3 to 2.4, as shown by the dashed line in Figure 14.

[0085] When the motor 5 is driven, losses also occur in the motor 5's drive circuit. The losses in the drive circuit depend on the current flowing through the winding 40 (also called the motor current), and the lower the motor current, the lower the circuit losses.

[0086] As described above, the total loss is minimized when a / b = 1.3 (see Figure 13), and as shown in Figure 14, when a / b satisfies 1.3 ≤ a / b ≤ 2.4, the harmonic content is equal to or less than that when a / b = 1.3 (2.4% or less). Therefore, when a / b satisfies 1.3 ≤ a / b ≤ 2.4, the total loss of iron loss and copper loss can be reduced to the greatest extent, the motor current can be lowered, and circuit losses can also be reduced.

[0087] <Maximum width of permanent magnets> Up to this point, we have described the effect of the rotor core 10 having an elliptical arc portion 15 on its outer circumference and the radius of the rotor core 10 being smaller on the q axis than on the d axis. However, reducing the radius of the rotor core 10 on the q axis reduces the width of the permanent magnets 20 that can be placed in the magnet insertion holes 11 compared to the case where the outer circumference of the rotor core 10 is a perfect circle. A narrower width of the permanent magnets 2 may reduce the motor output.

[0088] Therefore, we will examine the maximum width (Wmax) of the permanent magnet 20 that can be placed in the magnet insertion hole 11 when the rotor core 10 has an elliptical arc portion 15 on its outer circumference.

[0089] First, let's describe the comparative example rotor 1A. Figure 15(A) is a plan view showing the comparative example rotor 1A. The comparative example rotor 1A shown in Figure 15(A) differs from the rotor 1 of Embodiment 1 in that the outer circumference of the rotor core 10 is composed of a circle (i.e., a perfect circle) centered on the central axis Ax.

[0090] As shown in Figure 15(A), the radius r of the rotor core 10 in Comparative Example 1A is constant in the circumferential direction. Let W be the width of the permanent magnet 20 in the direction perpendicular to the d-axis.

[0091] Figure 15(B) is a plan view showing an enlarged portion of the rotor 1A shown in Figure 15(A). As shown in Figure 15(B), the magnet insertion hole 11 is located at a distance h from the outer circumference of the rotor core 10 on the d-axis.

[0092] A positioning projection 14 is formed on the q-axis side of the second end edge 11b of the magnet insertion hole 11, which abuts against the side end face 23 of the permanent magnet 20. The distance from the d-axis to the positioning projection 14 is shorter than the distance from the d-axis to the bridge portion 13. The width W of the permanent magnet 20 is defined by the position of the positioning projection 14. The distance from the d-axis to the positioning projection 14 is W / 2.

[0093] Figure 16(A) is a plan view showing an example in which the width W of the permanent magnet 20 is widened in the comparative example rotor 1A. Figure 16(B) is a plan view showing an enlarged portion of the rotor 1A shown in Figure 16(A).

[0094] The positioning projection 14 is formed in a position where the permanent magnet 20 does not come into contact with the bridge portion 13. Therefore, as shown in Figure 16(B), the maximum width Wmax of the permanent magnet 20 is obtained when the distance from the d-axis to the positioning projection 14 is the same as the distance from the d-axis to the bridge portion 13.

[0095] Here, let V be the point where the extension of the first edge 11a of the magnet insertion hole 11 intersects with the outer circumference of the rotor core 10. The distance S from the d-axis to point V is given by the radius r of the rotor core 10 and the distance h from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d-axis, so S = √(r ２ - (r-h) ２ It is represented as follows:

[0096] Figure 17 is a plan view showing an enlarged portion of the rotor 1A shown in Figure 16(B). The thickness (i.e., radial dimension) of the bridge portion 13 is denoted as t. The thickness t of the bridge portion 13 is set to be approximately the same as the thickness of the laminated element (specifically, the electromagnetic steel sheet) in order to suppress magnetic flux leakage between adjacent magnetic poles. Specifically, a range of 0.25 [mm] ≤ t ≤ 0.5 [mm] is desirable.

[0097] Furthermore, let θ be the angle between the extension direction of the bridge portion 13 and the direction perpendicular to the d-axis. The distance U from the d-axis end of the bridge portion 13 to point V is given by the thickness t of the bridge portion 13 and the angle θ, and is expressed as U = t / sinθ.

[0098] The maximum width Wmax of the permanent magnet 20 (Figure 16(B)) is given by Wmax = 2 × (S - U). Therefore, based on the radius r of the rotor core 10, the distance h from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d axis, and the thickness t and angle θ of the bridge portion 13, the maximum width Wmax of the permanent magnet 20 in the comparative example can be expressed by the following equation (1).

[0099]

[0100] For example, if r = 27.5075 [mm], h = 3.5 [mm], t = 0.4 [mm], and t / sinθ = 0.8397 (i.e., θ = 27.93 [degrees]), then from equation (1) above, Wmax = 25.176 [mm].

[0101] Note that while Wmax is the theoretical maximum width of the permanent magnet 20, the actual width of the permanent magnet 20 is set to be slightly smaller than the maximum width Wmax, taking into consideration ease of insertion into the magnet insertion hole 11.

[0102] Figure 18(A) is a plan view showing the rotor 1 of Embodiment 1. Figure 18(B) is an enlarged view showing a part of the rotor 1 shown in Figure 18(A). As described above, the lengths 2a and 2b of the first and second axes of the elliptical arc portion 15 are set so that the air gap is minimized on the d axis and the average width of the air gap is made as small as possible.

[0103] Let c be the distance in the d-axis direction between point P, which is the intersection of the elliptical arc 15 and the d-axis, and point Q, which is the intersection of the elliptical arc 15 and the q-axis. The distance c and b, which is half the length of the second axis (e.g., the minor axis) of the elliptical arc 15, satisfy the condition b > c. In other words, point Q is located on the outer circumference of the rotor core 10 in the d-axis direction, relative to the center C1 of the elliptical arc 15.

[0104] Furthermore, the distance h from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d-axis is less than or equal to the distance c (i.e., c ≥ h). That is, b > c ≥ h holds true.

[0105] Similar to the comparative example, point V is defined as the intersection of the extension of the first edge 11a of the magnet insertion hole 11 and the outer circumference of the rotor core 10. In Embodiment 1, since point V is located on the elliptical arc portion 15, the equation of the ellipse can be used.

[0106] From the equation of the ellipse, a and b are 1 / 2 of the lengths of the first axis (e.g., major axis) and the second axis (e.g., minor axis) of the elliptical arc portion 15, respectively, and between the distance S from the d axis to point V and the distance h from the outer circumference of the rotor core 10 on the d axis to the magnet insertion hole 11, S ２ / a ２ + (b - h) ２ / b ２ The relationship = 1 holds true.

[0107] From this equation, the distance S from the d-axis to point V is expressed by the following equation (2).

[0108] Similar to the comparative example, since Wmax = 2 × (S - U) holds true, the maximum width Wmax of the permanent magnet 20 is expressed by the following equation (3), using the thickness t and angle θ of the bridge portion 13 (Figure 17).

[0109]

[0110] For example, if a = 12.8 [mm], b = 6.0075 [mm], h = 3.5 [mm], t = 0.4 [mm], and t / sinθ = 0.5804 (i.e., θ = 43.58 [degrees]), then from equation (3) above, Wmax = 22.10 [mm].

[0111] The width W of the permanent magnet 20 is set to be slightly smaller than the maximum width Wmax, taking into consideration ease of insertion into the magnet insertion hole 11. That is, the width W of the permanent magnet 20 in Embodiment 1 is expressed by the following equation (4).

[0112]

[0113] Thus, when b, which is half the length 2b of the second axis (for example, the minor axis) of the elliptical arc portion 15, c, the distance in the d-axis direction between the elliptical arc portion 15 and points P and Q, which are the intersections of the d-axis and q-axis, and h, the distance from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d-axis, satisfies b > c ≥ h, and the width W of the permanent magnet 20 satisfies the above equation (4), a wide permanent magnet 20 can be placed in the rotor core 10, thereby improving the motor output.

[0114] To verify the effect of the width W of the permanent magnet 20 on the induced voltage, analyses were performed for both the comparative example rotor 1A and the rotor 1 of embodiment 1, by varying the width W of the permanent magnet 20.

[0115] Figure 19(A) is a diagram illustrating the dimensions used in the analysis of motor 5A, a comparative example. Figure 19(B) is a magnified view of a portion of motor 5A in Figure 19(A).

[0116] As shown in Figure 19(A), for the comparative example motor 5A, the radius r of the rotor core 10 is 27.5075 [mm], and the distance h from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d axis is 3.5 [mm]. Also, the air gap G between the rotor 1A and the stator 3 shown in Figure 19(B) is 0.555 [mm].

[0117] Figure 20(A) is a diagram illustrating the dimensions used in the analysis of the motor 5 of Embodiment 1. Figure 20(B) is a magnified view of a part of the motor 5 in Figure 20(A).

[0118] As shown in Figure 20(A), in the motor 5 of Embodiment 1, the maximum radius r of the rotor core 10 is 27.5075 [mm], and the distance h from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d axis is 3.5 [mm].

[0119] Furthermore, the length 2a of the first axis (in this case, the major axis) of the elliptical arc portion 15 of the rotor core 10 is set to 25.6 [mm], and the length 2b of the second axis (in this case, the minor axis) is set to 12.015 [mm]. Also, the minimum width Gmin between the rotor 1 and the stator 3 shown in Figure 20(B) is set to 0.555 [mm].

[0120] Furthermore, in the analysis, both the rotor 1A of the comparative example and the rotor 1 of embodiment 1 had an axial length of 45 mm.

[0121] Figure 21 is a graph showing the relationship between the width W of the permanent magnet 20 and the effective value of the induced voltage for the motor 5 of Embodiment 1 and the motor 5A of the comparative example. The horizontal axis represents the width W of the permanent magnet 20, and the vertical axis represents the effective value of the induced voltage.

[0122] In Figure 21, the width W of the permanent magnet 20 in the comparative example is varied from 20.000 [mm] to 25.176 [mm] (= Wmax). In Embodiment 1, the width W of the permanent magnet 20 is varied from 21.40 [mm] to 22.10 [mm] (= Wmax).

[0123] As shown in Figure 21, when comparing with the same width W of the permanent magnet 20, the effective value of the induced voltage in the motor 5 of Embodiment 1 is higher than that of the motor 5A of the comparative example. In other words, the motor 5 of Embodiment 1 makes more effective use of the magnetic flux of the permanent magnet 20 compared to the motor 5A of the comparative example. This is because, in the motor 5 of Embodiment 1, the outer circumference of the rotor core 10 is recessed on the q-axis, which suppresses magnetic flux leakage between adjacent magnetic poles.

[0124] On the other hand, in the motor 5 of Embodiment 1, the maximum width Wmax of the permanent magnets 20 that can be arranged on the rotor core 10 is smaller compared to the motor 5A of the comparative example. Therefore, in the range where the width W of the permanent magnets 20 of the motor 5A of the comparative example exceeds the maximum width Wmax of the permanent magnets 20 of the motor 5 of Embodiment 1, the effective value of the induced voltage of the motor 5A of the comparative example is larger.

[0125] To increase the effective value of the induced voltage, it is conceivable to increase the axial length (also called the stacking thickness) of the rotor 1. Note that increasing the axial length of the rotor 1 means increasing the axial length of both the rotor core 10 and the permanent magnets 20 arranged thereon.

[0126] Here, from Figure 21, the maximum effective value of the induced voltage of motor 5A in the comparative example is 81.45 [Vrms / krpm], and the maximum effective value of the induced voltage of motor 5 in Embodiment 1 is 77.13 [Vrms / krpm].

[0127] It is known that increasing the axial length of rotor 1 increases the induced voltage at the same rate as the axial length of rotor 1. Since the ratio of the effective values ​​of the induced voltages is 81.45 / 77.13 = 1.0560, the effective values ​​of the induced voltages can be made equivalent by making the axial length of rotor 1 in embodiment 1 5.60% longer than that of rotor 1A in comparative example.

[0128] Figure 22 is a graph showing the relationship between the volume of the permanent magnet 20 and the effective value of the induced voltage for the motor 5 of Embodiment 1 and the motor 5A of the comparative example. For the data of Embodiment 1, data is shown for the case where the axial length of the rotor 1 is the same as that of the rotor 1A of the comparative example, and for the case where the axial length of the rotor 1 is 5.60% longer than that of the rotor 1A of the comparative example.

[0129] As shown in Figure 22, increasing the axial length of the rotor 1 in Embodiment 1 increases the effective value of the induced voltage, obtaining a value equivalent to that of the comparative example. Furthermore, when comparing with the same effective value of the induced voltage, increasing the axial length of the rotor 1 in Embodiment 1 allows for a smaller volume of the permanent magnet 20 compared to the comparative example.

[0130] In the plots of Embodiment 1 shown in Figure 21, the plots for permanent magnets 20 with a width W of 20.8 [mm] to 22.1 [mm] are distributed on the straight line L1, but the plots for permanent magnets 20 with a width W of less than 20.8 [mm] are deviated downward from the straight line L1.

[0131] This is because as the width W of the permanent magnet 20 decreases, the distance between the bridge portion 13 and the side end face 23 of the permanent magnet 20 increases, and the leakage path increases.

[0132] From this, it can be considered that if the width W of the permanent magnet 20 is in the range of 20.8 [mm] ≤ W ≤ 22.1 [mm], there will be no effect from leakage flux, and the magnetic flux of the permanent magnet 20 can be effectively utilized. Since 20.8 / 22.1 = 0.941, if the width W of the permanent magnet 20 is in the range of 0.94 × Wmax ≤ W ≤ Wmax with respect to Wmax in equation (3), the magnetic flux of the permanent magnet 20 can be effectively utilized.

[0133] Therefore, from equation (3) above, it is desirable that the width W of the permanent magnet 20 be within the range of equation (5) below. Note that the value 1.882 on the left side of equation (5) is 0.941 × 2.

[0134] Furthermore, if the motor 5A of the comparative example is replaced with the motor 5 of the first embodiment, the design will be easier if the width W of the permanent magnet 20 of the first embodiment can be estimated based on the width W of the permanent magnet 20 of the comparative example.

[0135] As explained with reference to Figure 22, by increasing the axial length of the motor 5 of Embodiment 1, an effective value of induced voltage equivalent to that of the motor 5A of the comparative example can be obtained. In the motor 5A of the comparative example, as explained with reference to equation (1), the maximum width Wmax of the permanent magnet 20 is 25.176 [mm].

[0136] As stated above, the desirable range for the width W of the permanent magnet 20 is 20.8 [mm] ≤ W ≤ 22.1 [mm]. Dividing the lower limit of 20.8 [mm] by the maximum width Wmax (25.176 [mm]) of the comparative example permanent magnet 20 gives 20.8 / 25.176 = 0.826. Dividing the upper limit of 22.1 [mm] by the maximum width Wmax (25.176 [mm]) of the comparative example permanent magnet 20 gives 22.1 / 25.176 = 0.878.

[0137] Therefore, it is desirable that the width W of the permanent magnet 20 be within the range of the following equation (6) with respect to the width Wmax of the comparative example permanent magnet 20 obtained by equation (1). Note that the value 1.652 on the left side of equation (6) is 0.826 × 2, and the value 1.756 on the right side is 0.878 × 2.

[0138] Furthermore, as shown in Figure 21, in the comparative example motor 5A, the plots for permanent magnet 20 width W in the range of 21.4 [mm] to 23.8 [mm] are arranged along the straight line L2, but when the width W exceeds 23.8 [mm], they deviate from the straight line. In other words, as the width W of the permanent magnet 20 increases, the increase in the effective value of the induced voltage slows down.

[0139] This is because even if the width W of the permanent magnet 20 is increased until the side end face 23 of the permanent magnet 20 is close to the bridge portion 13, not all of the magnetic flux emitted from the permanent magnet 20 flows to the stator 3; a portion of the magnetic flux short-circuits within the rotor core 10.

[0140] As in Embodiment 1, by configuring the outer circumference of the rotor core 10 with an elliptical arc portion 15, the magnetic flux can be effectively utilized without making the width W of the permanent magnet 20 too large. This reduces the component cost of the permanent magnet 20.

[0141] <Effects of Embodiment 1> As described above, in the rotor 1 of Embodiment 1, at least a portion of the outer circumference of the rotor core 10, from the d-axis to the q-axis, is formed by an elliptical arc portion 15 having its center on the d-axis, and the elliptical arc portion 15 is symmetric with respect to the d-axis. Furthermore, if the distance from the central axis Ax on the d-axis to the outer circumference of the rotor core 10 is r, then the elliptical arc portion 15 and a circle A1 with radius r centered on the central axis Ax coincide at a single point. In addition, the elliptical arc portion 15 has a first axis (e.g., a major axis) in a direction perpendicular to the d-axis, and a second axis (e.g., a minor axis) on the d-axis. If the length of the second axis of the elliptical arc portion 15 is 2b, and the distance from the central axis Ax to the center C1 of the elliptical arc portion 15 is k, then k = r - b holds true.

[0142] With this configuration, the width of the air gap between the rotor core 10 and the stator core 30 is minimized on the d-axis, and a rapid expansion of the air gap width around the d-axis is suppressed. As a result, the decrease in the effective value of the induced voltage can be suppressed while reducing the harmonic components contained in the induced voltage.

[0143] In particular, since the ratio a / b of the lengths of the first and second axes of the elliptical arc portion 15 satisfies a / b > 1, the average width of the air gap can be reduced, and the effect of suppressing the decrease in the effective value of the induced voltage can be enhanced.

[0144] Furthermore, since b, which is half the length 2b of the second axis, and r, the maximum radius of the rotor core 10, satisfy b / r ≤ 0.67, the average width of the air gap can be reduced while minimizing the width of the air gap on the d axis. This enhances the effect of reducing harmonic components and suppressing the decrease in the effective value of the induced voltage.

[0145] Furthermore, since the ratio a / b of the lengths of the first and second axes of the elliptical arc portion 15 satisfies 1.3 ≤ a / b ≤ 2.4, iron loss and copper loss in the motor 5 can be reduced.

[0146] Furthermore, since b, which is half the length 2b of the second axis (for example, the minor axis) of the elliptical arc portion 15, c, the distance in the d-axis direction between the elliptical arc portion 15 and points P and Q, which are intersections of the d-axis and q-axis, and h, the distance from the outer circumference of the rotor core 10 to the magnet insertion hole 11 on the d-axis, satisfies b > c ≥ h, the width W of the permanent magnets 20 that can be placed in the rotor core 10 can be increased, thereby improving the motor output.

[0147] In the example described here, the elliptical arc portion 15 of the rotor core 10 extended from point P to point Q, but this embodiment is not limited to this example. The elliptical arc portion 15 only needs to be formed in at least a part of the section from point P to point Q (more preferably the portion including point P).

[0148] For example, in the modified example shown in Figure 23, an intermediate point T is defined between point P and point Q, the elliptical arc portion 15a of the rotor core 10 extends from point P to intermediate point T, and the circular arc portion 15b extends from intermediate point T to point Q. In this case as well, since the rapid increase in the air gap around point P is suppressed, it is possible to reduce the harmonic components included in the induced voltage while suppressing the decrease in the effective value of the induced voltage.

[0149] Embodiment 2. Next, the compressor 8 of Embodiment 2 will be described. Figure 24 is a cross-sectional view showing the configuration of the compressor 8 of Embodiment 2. The compressor 8 is a rotary compressor and comprises a sealed container 80, a compression mechanism 9 disposed inside 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 in a way that allows power transmission. The shaft 90 is the shaft 90 shown in Figure 1, etc., and fits into the central hole 16 (Figure 1) of the rotor 1 of the motor 5. The motor 5 has the configuration described in Embodiment 1.

[0150] The sealed container 80 is a sealed container made of, for example, steel plate, and encloses the motor 5 and the compression mechanism 9. The sealed container 80 has an upper frame 82 and a lower frame 81. The upper frame 82 is fitted with glass terminals 83 as terminals 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 frame 81 houses the motor 5 and the compression mechanism 9.

[0151] The compression mechanism 9 has annular first cylinder 91 and second cylinder 92 along the shaft 90. The first cylinder 91 and second cylinder 92 are fixed inside the frame 81. An annular first piston 93 is positioned on the inner circumference of the first cylinder 91, and an annular second piston 94 is positioned on the inner circumference of the second cylinder 92. The first piston 93 and second piston 94 are rotary pistons that rotate together with the shaft 90.

[0152] A partition plate 97 is provided between the first cylinder 91 and the second cylinder 92. The partition plate 97 is a disc-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 by bolts 98.

[0153] An upper frame 95 is positioned above the first cylinder 91 so as to close the upper part of the cylinder chamber of the first cylinder 91. A lower frame 96 is positioned below the second cylinder 92 so as to close the lower part of the cylinder chamber of the second cylinder 92. The upper frame 95 and the lower frame 96 rotatably support the shaft 90.

[0154] At the bottom of the frame 81 of the sealed container 80, refrigerant oil (not shown) is stored to lubricate each sliding part of the compression mechanism 9. The refrigerant oil rises through holes 90a formed axially inside the shaft 90 and is supplied to each sliding part through oil supply holes 90b formed at multiple locations on the shaft 90.

[0155] The stator 3 of the motor 5 is attached to the inside of the frame 81 by shrink-fitting. Power is supplied to the windings 40 of the stator 3 from glass terminals 83 attached to the upper frame 82. The shaft 90 is fixed to the central hole 16 (Figure 1) of the rotor 1.

[0156] An accumulator 87 for storing refrigerant gas is attached to the frame 81. The accumulator 87 is held, for example, by a retaining part 86 provided on the outside of the frame 81. A pair of suction pipes 88 and 89 are attached to the frame 81, and refrigerant gas is supplied from the accumulator 87 to the cylinders 91 and 92 via these suction pipes 88 and 89.

[0157] As refrigerants, for example, R410A, R407C, or R22 may be used, but from the viewpoint of preventing global warming, it is desirable to use refrigerants with a low GWP (Global Warming Potential). Examples of low GWP refrigerants that can be used include the following:

[0158] (1) First, halogenated hydrocarbons having a carbon double bond in their composition, for example, HFO(Hydro-Fluoro-Orefin)-1234yf(CF ３ CF=CH ２) can be used. The GWP of HFO-1234yf is 4. (2) Alternatively, a hydrocarbon having a carbon double bond in its composition, such as R1270 (propylene), may be used. The GWP of R1270 is 3, which is lower than that of HFO-1234yf, but its flammability is higher than that of HFO-1234yf. (3) Alternatively, a mixture containing at least one halogenated hydrocarbon having a carbon double bond in its composition or a hydrocarbon having a carbon double bond in its composition, such as a mixture of HFO-1234yf and R32, may be used. As mentioned above, HFO-1234yf is a low-pressure refrigerant and tends to cause a large pressure drop, which can lead to a decrease in the performance of the refrigeration cycle (especially the evaporator). For this reason, it is practically desirable to use a mixture with R32 or R41, which are higher-pressure refrigerants than HFO-1234yf.

[0159] The basic operation of the compressor 8 is as follows: The refrigerant gas supplied from the accumulator 87 is supplied to the cylinder chambers of the first cylinder 91 and the second cylinder 92 through the suction pipes 88 and 89. When the motor 5 is driven and the rotor 1 rotates, the shaft 90 rotates together with the rotor 1. Then, the first piston 93 and the second piston 94, which are fitted onto the shaft 90, rotate eccentrically within each cylinder chamber, compressing the refrigerant within each cylinder chamber. The compressed refrigerant rises through the groove 31d of the stator 3 (Figure 1) and the through holes 18a and 18b of the rotor 1 (Figure 2) within the sealed container 80 and is discharged to the outside through the discharge pipe 85.

[0160] Furthermore, the compressor using motor 5 is not limited to a rotary compressor; for example, a scroll compressor or the like may also be used.

[0161] As described in Embodiment 1, the motor 5 can reduce the harmonic components of the induced voltage while suppressing the decrease in the effective value of the induced voltage. Therefore, the operating efficiency of the compressor 8 can be improved and the quietness can be enhanced.

[0162] Embodiment 3. Next, the refrigeration cycle device 100 of Embodiment 3 will be described. Figure 25 shows the refrigeration cycle device 100 of Embodiment 3. The refrigeration cycle device 100 is, for example, an air conditioner, but is not limited to this, and may be, for example, a refrigerator.

[0163] The refrigeration cycle device 100 shown in Figure 25 comprises a compressor 101, a condenser 102 for condensing the refrigerant, a pressure reducing device 103 for reducing the pressure of the refrigerant, and an evaporator 104 for evaporating the refrigerant. The compressor 101, condenser 102, and pressure reducing device 103 are installed in the outdoor unit 110, and the evaporator 104 is installed in the indoor unit 120.

[0164] The compressor 101, condenser 102, pressure reducing device 103, and evaporator 104 are connected by refrigerant piping 307 to form a refrigerant circuit. The compressor 101 is composed of the compressor 8 described in Embodiment 2. The refrigeration cycle device 100 also includes an outdoor fan 105 facing the condenser 102 and an indoor fan 106 facing the evaporator 104.

[0165] The operation of the refrigeration cycle device 100 is as follows: The compressor 101 compresses the inhaled refrigerant and sends it out as a high-temperature, high-pressure refrigerant gas. The condenser 102 exchanges heat between the refrigerant sent out from the compressor 101 and the outdoor air sent out by the outdoor fan 105, condensing the refrigerant and sending it out as liquid refrigerant. The depressurizing device 103 expands the liquid refrigerant sent out from the condenser 102 and sends it out as a low-temperature, low-pressure liquid refrigerant.

[0166] The evaporator 104 exchanges heat between the low-temperature, low-pressure liquid refrigerant sent from the pressure reducing device 103 and the room air, evaporating the refrigerant and sending it out as refrigerant gas. The air from which heat has been removed in the evaporator 104 is blown into the room by the room blower 106.

[0167] The compressor 101 of the refrigeration cycle device 100 has high operating efficiency and quietness, thus improving the operating efficiency and quietness of the refrigeration cycle device 100.

[0168] Although preferred embodiments have been described in detail above, this disclosure is not limited to the embodiments described above, and various improvements or modifications can be made.

[0169] 1 Rotor, 3 Stator, 5 Motor, 8 Compressor, 9 Compression mechanism, 10 Rotor core, 11 Magnet insertion hole, 12 Flux barrier (air gap), 13 Bridge section (thin-walled section), 14 Positioning protrusion, 15 Elliptical arc section, 16 Center hole, 20 Permanent magnet, 30 Stator core, 31 Core back, 32 Teeth, 33 Slot, 34 Insulator (insulating section), 40 Winding, 80 Sealed container, 81 Frame, 90 Shaft, 100 Refrigeration cycle device, 101 Compressor, 102 Condenser, 103 Pressure reducing device, 104 Evaporator, A1 Circle (virtual circle), a 1 / 2 of the length of the first axis of the elliptical arc section, b 1 / 2 of the length of the second axis of the elliptical arc section, C1 E1, E2 are the centers of the elliptical arc, h is the distance from the outer circumference of the rotor core to the magnet insertion hole on the d axis, G is the width of the air gap, Gmin is the minimum width of the air gap, P is the intersection of the outer circumference of the rotor core and the d axis, Q is the intersection of the outer circumference of the rotor core and the q axis, r is the radius of the rotor core on the d axis (maximum radius), W is the width of the permanent magnet, and Wmax is the maximum width of the permanent magnet.

Claims

1. A rotor core having an outer circumference extending in the circumferential direction with respect to a central axis, and having magnet insertion holes along the outer circumference; and permanent magnets disposed in the magnet insertion holes to form magnetic poles, wherein the line passing through the central axis and the circumferential center of the magnet insertion holes is defined as the d-axis, and the line passing through the central axis and the inter-pole portion spaced circumferentially from the magnet insertion holes is defined as the q-axis, wherein at least one portion of the outer circumference of the rotor core from the d-axis to the q-axis is formed as an elliptical arc having its center on the d-axis, the elliptical arc is symmetrical with respect to the d-axis, and if the distance from the central axis to the outer circumference on the d-axis is r, the elliptical arc is tangent to a circle of radius r centered on the central axis at one point on the d-axis, the elliptical arc has a first axis in a direction perpendicular to the d-axis, and a second axis on the d-axis, the first axis being either a major axis or a minor axis, and the second axis being the other of the major axis or minor axis, A rotor in which, if the length of the second axis is 2b and the distance from the central axis to the center of the elliptical arc is k, then k = r - b holds true.

2. The rotor according to claim 1, wherein the length of the first axis of the elliptical arc portion is 2a, and a / b > 1 holds true.

3. The rotor according to claim 2, wherein b / r ≤ 0.67 is further satisfied.

4. The rotor according to claim 2 or 3, wherein 1.3 ≤ a / b ≤ 2.4 holds true.

5. Let c be the distance from the intersection of the outer circumference and the d-axis to the intersection of the outer circumference and the q-axis, and let h be the distance on the d-axis from the outer circumference to the magnet insertion hole, then b > c ≥ h, and the rotor according to any one of claims 1 to 4.

6. A bridge portion is formed between the circumferential end of the magnet insertion hole and the outer circumference, the bridge portion has a thickness t in the radial direction centered on the central axis and extends at an angle θ with respect to the direction perpendicular to the d axis, and if the length of the first axis of the elliptical arc portion is 2a, the length of the permanent magnet in the direction perpendicular to the d axis is W, and the distance on the d axis from the outer circumference to the magnet insertion hole is h, then the following equation (1) holds true. The rotor according to any one of claims 1 to 5.

7. A bridge portion is formed between the circumferential end of the magnet insertion hole and the outer circumference, the bridge portion has a thickness t in the radial direction centered on the central axis and extends at an angle θ with respect to the direction perpendicular to the d axis, and if the length of the first axis of the elliptical arc portion is 2a, the length of the permanent magnet in the direction perpendicular to the d axis is W, and the distance on the d axis from the outer circumference to the magnet insertion hole is h, then the following equation (2) holds true. The rotor according to any one of claims 1 to 6.

8. A bridge portion is formed between the circumferential end of the magnet insertion hole and the outer circumference, the bridge portion has a thickness t in the radial direction centered on the central axis and extends at an angle θ with respect to the direction perpendicular to the d axis, and if the length of the permanent magnet in the direction perpendicular to the d axis is W, then the following equation (3) holds true. The rotor according to any one of claims 1 to 7.

9. A motor comprising a rotor according to any one of claims 1 to 8, and a stator surrounding the rotor with an air gap.

10. A compressor comprising the motor described in claim 9 and a compression mechanism driven by the motor.

11. A refrigeration cycle apparatus comprising the compressor, condenser, depressurization device, and evaporator described in claim 10.

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