Permanent magnet synchronous motor

Abstract

A permanent magnet synchronous motor includes a stator, a rotor, and a plurality of permanent magnets. In the circumferential direction, each of the plurality of permanent magnets has a first magnet end and a second magnet end. In the circumferential direction, each recess of the plurality of permanent magnets has a first recess end and a second recess end. When the distance between the first magnet end and the first recess end is set as L1, and the distance between the second magnet end and the second recess end is set as L2, L1 is not equal to L2.

Description

Technical Field

[0001] The present disclosure relates to permanent magnet synchronous motors. Background Art

[0002] Conventionally, permanent magnet synchronous motors have been used for industrial applications such as machine tools, vehicle-related applications such as electric vehicles, and compressor applications such as air conditioners. It is known that in a permanent magnet synchronous motor, in order for the motor to output torque, the terminal voltage generated by the motor needs to be set to be less than the input voltage. For example, the terminal voltage Vt generated by the permanent magnet synchronous motor is expressed as follows using the dq axis theory.

[0003] Vd=R|d+ωLqIq Vq=R|q+ωLdId+ωΦm

[0004] Among them, Vd is the d-axis voltage. Vq is the q-axis voltage. Ld is the d-axis inductance. Lq is the q-axis inductance. R is the resistance. Id is the d-axis current. Iq is the q-axis current. ω is the angular velocity. φm is the magnet flux. ωφm is the induced voltage. ωLd, ωLq, ωφm increase in proportion to the rotation speed or speed. Therefore, in the state where the motor rotates at high speed or the motor is driven at high speed, the terminal voltage Vt increases.

[0005] As a control technique for making the terminal voltage Vt lower than the input voltage Vi, a known control technique is to input a negative d-axis current Id to the motor through a weak magnetic field control. According to such a weak magnetic field control, the terminal voltage Vt can be controlled to be lower than the input voltage Vi even when the motor is rotating at high speed or when the motor is driven at high speed. In such a field weakening control, a negative d-axis current Id is supplied to the motor, thereby reducing the amount of induced voltage ωφm generated and preventing the terminal voltage Vt from being saturated during high-speed rotation.

[0006] However, when the d-axis inductance Ld is small, the function of suppressing the terminal voltage Vt cannot be effectively obtained by the field weakening control. Therefore, it is necessary to supply a d-axis current Id larger than necessary to energize the motor. For example, there is the following relationship between the d-axis current Id, the q-axis current Iq and the input current Ia.

[0007]

[0008] Therefore, the increase in the d-axis current Id causes the q-axis current Iq to decrease.

[0009] Generally speaking, the torque T generated by a surface magnet type permanent magnet synchronous motor is expressed as follows, assuming that the number of pole pairs is pn.

[0010] T=pnφmIq

[0011] The q-axis current Iq is required to generate the torque T. Therefore, the reduction of the q-axis current Iq reduces the torque of the motor. Therefore, in order to output a large torque during high-speed rotation or high-speed driving, it is necessary to perform effective field weakening control with a small d-axis current Id. In order to perform such a field weakening control, Patent Document 1 discloses increasing the d-axis inductance Ld and effectively performing the field weakening control with a small d-axis current Id.

[0012] In Patent Document 1, a protrusion protruding radially from the rotor core is formed in such a manner as to fit with a plurality of permanent magnets arranged on the surface of the rotor core, thereby increasing the d-axis inductance Ld, effectively exerting the function of field weakening control, and improving the torque output of the motor during high-speed rotation. Prior art literature Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2009-131070 Summary of the invention Technical problem to be solved by the invention

[0014] However, in the above-mentioned prior art document, the convex portion of the rotor core for increasing the d-axis inductance Ld is located at the magnetic pole center in the circumferential direction. In addition, the shape of the convex portion is mirror-symmetrical with respect to the magnetic pole center.

[0015] In a structure having such a convex portion, when a segmented skewed pole structure for reducing torque ripple is applied to a rotor, a deviation occurs in the d-axis position of each segment, and therefore it is difficult to effectively increase the d-axis inductance Ld.

[0016] The present disclosure is made to solve the above-mentioned problems, and its object is to provide a permanent magnet synchronous motor capable of increasing the d-axis inductance Ld and performing effective field weakening control. Technical solutions to technical problems

[0017] The permanent magnet synchronous motor involved in the present disclosure includes a stator, a rotor and a plurality of permanent magnets. The rotor includes a rotor core body made of electromagnetic steel plates and having one or more convex parts protruding in the radial direction toward the stator, and a rotating shaft fixed to the rotor core body. The rotor is configured to rotate freely relative to the stator. The plurality of permanent magnets respectively have a stator opposing surface in an arc shape that is opposite to the stator across a gap, a rotor core fixing surface that is located on the side opposite to the stator opposing surface and fixed to the outer peripheral surface of the rotor core body, and a recessed portion connected to a part of the rotor core fixing surface and engaged with the convex part. The plurality of permanent magnets are arranged along the circumferential direction of the rotor. In the circumferential direction, the polarities of the stator opposing surfaces of two permanent magnets adjacent to each other among the plurality of permanent magnets are different from each other, and in the circumferential direction, the plurality of permanent magnets respectively have a first magnet end connected to the rotor core fixing surface, and a second magnet end connected to the rotor core fixing surface and located on the side opposite to the first magnet end. In the circumferential direction, the recess of each of the plurality of permanent magnets has a first recess end connected to the rotor core fixed surface, and a second recess end connected to the rotor core fixed surface and located on the opposite side of the first recess end. The rotor core fixed surface has a first region located between the first magnet end and the first recess end, and a second region located between the second magnet end and the second recess end. The recess is located between the first region and the second region. When the distance between the first magnet end and the first recess end in the first region is set to L1, and the distance between the second magnet end and the second recess end in the second region is set to L2, L1≠L2 is satisfied. Effects of the Invention

[0018] According to the permanent magnet synchronous motor disclosed in the present invention, the d-axis inductance Ld can be increased to perform effective field weakening control, thereby improving the torque output of the permanent magnet synchronous motor when rotating at high speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A It is a diagram showing the permanent magnet synchronous motor according to the first embodiment, and is a cross-sectional view viewed along the axial direction. Figure 1B It is a diagram showing the permanent magnet synchronous motor according to the first embodiment, and is a cross-sectional view viewed along the axial direction. Figure 2A This is a diagram showing an enlarged view of a region near a permanent magnet constituting the permanent magnet synchronous motor according to the first embodiment, and is a cross-sectional view as viewed along the axial direction. Figure 2B In the two-stage skewed pole structure constituting the permanent magnet synchronous motor according to the first embodiment, when viewed along the axial direction Figure 1A The permanent magnet shown is Figure 1BA partial cross-sectional view of the overlapping state of the permanent magnets shown. Figure 3 This is an enlarged view showing a region near a permanent magnet constituting a conventional permanent magnet synchronous motor, and is a cross-sectional view viewed along the axial direction. Figure 4 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the first embodiment and a conventional permanent magnet synchronous motor with respect to the d-axis inductance Ld. Figure 5 This is a diagram showing an enlarged view of a region near a permanent magnet constituting a modified example of the permanent magnet synchronous motor according to the first embodiment, and is a cross-sectional view as viewed along the axial direction. Figure 6 This is a diagram showing an enlarged view of a region near a permanent magnet constituting a modified example of the permanent magnet synchronous motor according to the first embodiment, and is a cross-sectional view as viewed along the axial direction. Fig. 7A This is a diagram showing an enlarged view of a region near a permanent magnet constituting the permanent magnet synchronous motor according to the second embodiment, and is a cross-sectional view as viewed along the axial direction. Figure 7B This is a diagram showing an enlarged view of a region near a permanent magnet constituting a modified example of the permanent magnet synchronous motor according to the second embodiment, and is a cross-sectional view as viewed along the axial direction. Figure 8 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the first embodiment and a conventional permanent magnet synchronous motor with respect to the d-axis inductance Ld and the induced voltage reduction rate after demagnetization. Fig.9A It is a diagram showing the demagnetization rate distribution of a conventional permanent magnet synchronous motor. Fig. 9B It is a diagram showing the demagnetization rate distribution of the permanent magnet synchronous motor according to the first embodiment. Fig.10 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the first embodiment, the permanent magnet synchronous motor according to the second embodiment, and the permanent magnet synchronous motor according to the modification of the second embodiment, regarding the induced voltage reduction rate after demagnetization. Fig.11A It is a diagram showing the demagnetization rate distribution of the permanent magnet synchronous motor according to the first embodiment. Fig. 11B It is a diagram showing the demagnetization rate distribution of the permanent magnet synchronous motor according to the second embodiment. Fig. 11C It is a diagram showing the demagnetization rate distribution of the permanent magnet synchronous motor according to the modification of the second embodiment. Fig. 12AThis is a diagram showing an enlarged view of a region near a permanent magnet constituting a modified example of the permanent magnet synchronous motor according to the second embodiment, and is a cross-sectional view as viewed along the axial direction. Fig. 12B This is a diagram showing an enlarged view of a region near a permanent magnet constituting a modified example of the permanent magnet synchronous motor according to the second embodiment, and is a cross-sectional view as viewed along the axial direction. Fig.13 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the first embodiment and a modification of the permanent magnet synchronous motor according to the second embodiment with respect to the induced voltage reduction rate after demagnetization. Fig.14A It is a diagram showing the demagnetization rate distribution of a modified example of the permanent magnet synchronous motor according to the first embodiment. Fig. 14B It is a diagram showing the demagnetization rate distribution of a modified example of the permanent magnet synchronous motor according to the second embodiment. Fig. 14C It is a diagram showing the demagnetization rate distribution of a modified example of the permanent magnet synchronous motor according to the second embodiment. Fig.15 It is a perspective view showing a rotor constituting the permanent magnet synchronous motor according to the third embodiment. Fig.16 It is a perspective view showing a rotor core constituting the permanent magnet synchronous motor according to the third embodiment. Fig.17 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the third embodiment and a conventional permanent magnet synchronous motor with respect to torque ripple. Fig.18 It is a perspective view showing a rotor constituting the permanent magnet synchronous motor according to the fourth embodiment. Fig.19 It is a perspective view showing a rotor core constituting the permanent magnet synchronous motor according to the fourth embodiment. Fig. 20 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the fourth embodiment and a conventional permanent magnet synchronous motor with respect to torque ripple. Fig.21 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the fourth embodiment and a conventional permanent magnet synchronous motor with respect to the d-axis inductance Ld. DETAILED DESCRIPTION

[0020] Reference Figure 1A to Figure 21 A permanent magnet synchronous motor according to an embodiment will be described. In the description of the embodiments, the permanent magnet synchronous motor may be simply referred to as a motor. In Figure 1~ Fig.21 In the drawings, the same reference numerals are given to the same or corresponding structural parts. The drawings schematically or conceptually illustrate the embodiments. The relationship between the thickness and width of each part, the ratio of the size between parts, etc. shown in the drawings are not necessarily the same as the actual components. Illustration of structures not related to the features of the present disclosure is sometimes omitted.

[0021] In the drawings used to illustrate the embodiments, the X direction, Y direction and Z direction (labeled X, Y, Z) corresponding to the three-dimensional orthogonal coordinate system are shown. The Z direction is consistent with the axial direction of the permanent magnet synchronous motor. In other words, the Z direction is consistent with the axial direction of the rotation axis located at the axis of the rotor. The Z direction can also be called the up and down direction in the two-stage oblique pole structure. The X direction and the Y direction intersect with the Z direction (for example, orthogonal). The X direction and the Y direction intersect with each other (for example, orthogonal).

[0022] The terms “circumferential direction” and “radial direction” used in the following description correspond to the “circumferential direction” and the “radial direction”, respectively, in a stator or a rotor constituting the permanent magnet synchronous motor. The term "circumferential direction" corresponds to the rotation direction of the rotor. In other words, in a cross-sectional view viewed in the axial direction, the circumferential direction centered on the rotation axis of the rotor is the circumferential direction. The term "radial" refers to the radial direction of the rotor. For example, the term "radially outer" refers to the direction from the center of the rotor toward the outer periphery in the radial direction. The term "radially inner" refers to the direction from the outer periphery of the rotor toward the center in the radial direction.

[0023] Implementation method 1. The electric motor according to the first embodiment will be described. Figure 1A and Figure 1B 1 is a cross-sectional view showing a permanent magnet synchronous motor 100 according to Embodiment 1. The permanent magnet synchronous motor 100 has a two-stage skew pole structure. Figure 1A A cross section of one of the two-segment slanted pole structures is shown. Figure 1B The cross section of another segmented structure in the two-segment oblique pole structure is shown. Figure 1A Indicates the structure of the upper segment of the two-segment oblique pole structure. Figure 1B Represents the structure of the lower section of the two-section oblique pole structure.

[0024] exist Figure 1A and Figure 1B In FIG. 1 , reference numeral CL indicates the center line of the permanent magnet synchronous motor 100. Reference numeral O indicates the axis center of the rotating shaft 23 described later. The positions of the center line CL and the axis center O are Figure 1A and Figure 1BIn other words, the center line CL is equivalent to the d-axis of the permanent magnet synchronous motor 100. In the following description, the position of the d-axis is sometimes referred to as the d-axis position d1. The reference numeral S is a magnet center line extending radially outward from the axis center O and passing through the circumferential center point of the permanent magnet 22 described later. That is, the magnet center line S passes through the circumferential center point C of the stator opposing surface 26 described later.

[0025] In the structure of the permanent magnet synchronous motor 100 according to the first embodiment, the skewed pole structure on the upper stage side and the skewed pole structure on the lower stage side are offset by a skew angle θ in the circumferential direction. Figure 1A The shape of the tilted pole structure shown is similar to Figure 1B The shape of the slanted pole structure shown is the same. Therefore, using Figure 1A The structure of the permanent magnet synchronous motor 100 will be described. The skew angle θ will be described later.

[0026] <Permanent magnet synchronous motor> like Figure 1A As shown, the permanent magnet synchronous motor 100 includes a stator 10 and a rotor 20. In the two-stage skewed pole structure, with respect to the circumferential center of the magnets in the segments arranged in the Z direction, the rotating shaft 23 of the rotor 20 is offset from the center to the circumference by a skew angle θ. Thus, the permanent magnet synchronous motor 100 has a so-called segmented skewed pole structure. Each of the multiple segments constituting the segmented skewed pole structure is sometimes referred to as "each segment". In a structure with two segments, that is, in the description of the two-stage skewed pole structure, the skewed pole structure on the upper segment side is sometimes referred to as the "upper segment", and the skewed pole structure on the lower segment side is sometimes referred to as the "lower segment".

[0027] In addition, in this specification, the terms "upper section" and "lower section" are used to simplify the description, and do not specify the upper and lower directions of the permanent magnet synchronous motor 100. For example, the oblique pole structure on the upper section side may be referred to as a first oblique pole structure, and the oblique pole structure on the lower section side may be referred to as a second oblique pole structure. In this case, the first oblique pole structure and the second oblique pole structure are arranged along the Z direction.

[0028] <Stator> The stator 10 is configured to surround the outer circumference of the rotor 20 via a gap 15 that serves as a magnetic gap. The stator 10 includes a stator core 11 and a winding 14. The stator core 11 includes a core back 12 that is formed in a circular ring shape in the circumferential direction and a plurality of teeth 13 that protrude radially inward from the core back 12. The winding 14 is wound around each of the plurality of teeth 13. In the following description, the winding 14 wound around the teeth 13 is sometimes referred to as a coil portion. Figure 1A In the example shown, one coil portion is provided on one tooth 13 .

[0029] exist Figure 1AIn the illustrated structure, the number of teeth 13 is 12. The number of teeth 13 is not limited to 12, but is appropriately determined according to the design of the permanent magnet synchronous motor 100. In the first embodiment, the core back 12 is formed by connecting a plurality of core blocks each formed in an arc shape into a circular ring. The structure of the core back 12 is not limited to Figure 1A The structure shown. The core back 12 can be formed by integrally forming a plurality of core blocks. In addition, the core back 12 and the teeth 13 can be separated.

[0030] <Rotor> The rotor 20 includes a rotor core 21 , a rotating shaft 23 , and a plurality of permanent magnets 22 . The rotor core 21 is formed, for example, by stacking a plurality of electromagnetic steel plates in the Z direction. For example, the electromagnetic steel plates may also be referred to as core plates. The rotating shaft 23 is fixed to the rotor core 21 so as to penetrate the rotor core 21 in the Z direction. The rotating shaft 23 may also be referred to as an axis. Such a rotor 20 is configured to rotate freely relative to the stator 10 inside the permanent magnet synchronous motor 100.

[0031] The rotor core 21 has a convex portion 24 protruding in the radial direction. The convex portion 24 protrudes radially outward toward the stator 10. In Embodiment 1, the convex portion 24 has a rectangular shape. In Embodiment 1, the number of the convex portions 24 corresponds to the number of the plurality of permanent magnets 22, which is eight. The number of the convex portions 24 may be one or more.

[0032] <Permanent magnet> A plurality of permanent magnets 22 are arranged along the circumferential direction on the outer peripheral surface 28 of the rotor core 21. The permanent magnet synchronous motor 100 including such a plurality of permanent magnets 22 is an example of a surface magnet type motor (SPM).

[0033] Each of the plurality of permanent magnets 22 has a stator opposing surface 26 and a rotor core fixing surface 27. The stator opposing surface 26 is opposed to the stator 10 via the gap 15. The stator opposing surface 26 has an arc shape. The rotor core fixing surface 27 is located on the side opposite to the stator opposing surface 26. The rotor core fixing surface 27 is fixed to the outer peripheral surface 28 of the rotor core 21. The recess 25 is provided on a portion of the rotor core fixing surface 27. In other words, the recess 25 is connected to a portion of the rotor core fixing surface 27. The recess 25 is engaged with the protrusion 24. In embodiment 1, the shape of the recess 25 is the same as that of the protrusion 24, which is a rectangle.

[0034] As described later, the rotor core fixing surface 27 has a first region 27F and a second region 27S. The first region 27F and the second region 27S are fixed to the outer peripheral surface 28 of the rotor core 21. The recessed portion 25 is located between the first region 27F and the second region 27S.

[0035] The plurality of permanent magnets 22 are arranged along the circumferential direction of the rotor 20. In the circumferential direction, the polarities of the stator facing surfaces 26 of two permanent magnets 22 adjacent to each other among the plurality of permanent magnets 22 are different from each other. For example, when the polarity of the stator facing surface 26 of one of the two permanent magnets 22 adjacent to each other in the circumferential direction is an N pole, the plurality of permanent magnets 22 are arranged in a state where the magnetization directions are different so that the other stator facing surface 26 is an S pole.

[0036] exist Figure 1A In the permanent magnet synchronous motor 100 shown, the number of teeth 13 is 12, the number of coil parts composed of windings 14 is 12, and the number of permanent magnets is 8. Figure 1A The so-called 8-pole 12-slot permanent magnet synchronous motor is shown. The combination of the plurality of permanent magnets 22, the teeth 13, and the number of coil parts is not limited to this. Figure 1A In the example shown, the number of teeth 13 is the same as the number of coil parts, but the number of teeth 13 and the number of coil parts may be different.

[0037] like Figure 1A As shown, the center positions of the plurality of permanent magnets 22 in the circumferential direction are shifted in the circumferential direction as they advance in the axial direction. When the skew angle between the permanent magnets 22 in the upper section and the permanent magnets 22 in the lower section in the segmented skew pole structure is set to θ, the recess 25 is shifted in a direction different from the offset amount θ of the permanent magnets 22 shown in the same cross-sectional view.

[0038] In the segmented skew-pole structure, the plurality of permanent magnets 22 include a first magnet group 41 and a second magnet group 42 that are adjacent in the Z direction. Figure 1A The first magnet group 41 is shown. Figure 1B denoted by the second magnet group 42. Between the first magnet group 41 and the second magnet group 42, the rotor 20 has a segmented skewed pole structure. In the following description, each of the plurality of permanent magnets 22 constituting the first magnet group 41 may be referred to as a first permanent magnet 22A. Each of the plurality of permanent magnets 22 constituting the second magnet group 42 may be referred to as a second permanent magnet 22B.

[0039] In other words, the first permanent magnets 22A constituting the first magnet group 41 are arranged to be offset from the center line CL by an offset of θ / 2 in the counterclockwise direction in the circumferential direction. Figure 1A The magnet center line S is shown offset from the center line CL by an offset of θ / 2. That is, the first permanent magnets 22A constituting the first magnet group 41 are offset by θ / 2 in the counterclockwise direction in the circumferential direction with respect to the d-axis of the permanent magnet synchronous motor 100 .

[0040] The second permanent magnets 22B constituting the second magnet group 42 are arranged to be offset from the center line CL by an offset of θ / 2 in the clockwise direction in the circumferential direction. That is, in the clockwise direction, Figure 1B The magnet center line S is shown offset from the center line CL by an offset of θ / 2. That is, the second permanent magnets 22B constituting the second magnet group 42 are offset by θ / 2 in the clockwise direction in the circumferential direction with respect to the d-axis of the permanent magnet synchronous motor 100 . When focusing on the second magnet group 42 and the first magnet group 41 , the second permanent magnets 22B constituting the second magnet group 42 are offset by an offset amount θ (skew polar angle θ) in the circumferential direction with respect to the first permanent magnets 22A constituting the first magnet group 41 .

[0041] Reference Figure 1A , Figure 1B , Figure 2A and Figure 2B , the plurality of first permanent magnets 22A constituting the first magnet group 41 and the plurality of second permanent magnets 22B constituting the second magnet group 42 are described in detail. Figure 2A The permanent magnet 22 shown corresponds to the first permanent magnet 22A shown in FIG. Figure 2A The permanent magnet shown is reversed in the left-right direction, then Figure 2A The permanent magnet 22 shown in FIG. 2 is the second permanent magnet 22B. Figure 2A In the figure, the description of the second permanent magnet 22B is omitted.

[0042] Reference Figure 2A , the recessed portion 25 engaged with the convex portion 24 will be described in detail. Figure 2A It is a diagram showing an enlarged area near the permanent magnet 22 and is a cross-sectional view viewed along the axial direction. Figure 2A It means by Figure 1A An enlarged view of the portion surrounded by the dotted line A. like Figure 2A As shown, the magnet center line S is defined as the circumferential center position CP of the permanent magnet 22, and the magnet center line S extends radially outward from the axial center O of the rotating shaft 23 and passes through the circumferential center point C of the permanent magnet 22. Here, the center point C is located at the circumferential center of the stator opposing surface 26 of the permanent magnet 22. The center point C is located in the part of the stator opposing surface 26 having an arc shape that is closest to the tooth 13. A line passing through the center of the convex portion 24 and parallel to the magnet center line S is defined as the convex portion center position TP. The convex portion center position TP can also be referred to as the center of the convex portion 24. The convex portion center position TP is located at the center between the first concave end 35 and the second concave end 36.

[0043] Each of the plurality of permanent magnets 22 has a first magnet end 31 connected to the rotor core fixing surface 27 and a second magnet end 32 connected to the rotor core fixing surface 27 in the circumferential direction. The second magnet end 32 is located on the opposite side of the first magnet end 31 relative to the circumferential center position CP. The permanent magnet 22 has a first side surface 33 and a second side surface 34 located on opposite sides to each other in the circumferential direction. The first magnet end 31 is equivalent to the portion where the first side surface 33 is connected to the rotor core fixing surface 27. The second magnet end 32 is equivalent to the portion where the second side surface 34 is connected to the rotor core fixing surface 27.

[0044] Each recess 25 of the plurality of permanent magnets 22 has a first recess end 35 connected to the rotor core fixing surface 27 and a second recess end 36 connected to the rotor core fixing surface 27 and located on the opposite side to the first recess end 35 in the circumferential direction. The first region 27F of the rotor core fixing surface 27 is located between the first magnet end 31 and the first recess end 35. The second region 27S of the rotor core fixing surface 27 is located between the second magnet end 32 and the second recess end 36.

[0045] In other words, the first region 27F is a surface formed between the first magnet end 31 and the first recess end 35. The second region 27S is a surface formed between the second magnet end 32 and the second recess end 36. In other words, the first region 27F and the second region 27S are located on both sides of the recess 25. When the distance between the first magnet end 31 and the first recess end 35 in the first region 27F is set to L1, and the distance between the second magnet end 32 and the second recess end 36 in the second region 27S is set to L2, L1≠L2 is satisfied. In the segmented skew pole structure, each of the plurality of permanent magnets 22 satisfies L1≠L2, and L1>L2 is satisfied.

[0046] Furthermore, the magnet center line S intersects the first region 27F. In other words, the magnet center line S intersects a line connecting the first magnet end 31 and the first recess end 35 . Specifically, in Figure 1A In the upper skewed pole structure shown, the magnet center line S, which is offset from the center line CL by an offset amount of θ / 2 in the counterclockwise direction, intersects the first region 27F of the permanent magnet 22 . exist Figure 1B In the oblique pole structure on the lower side shown, the magnet center line S, which is offset from the center line CL by an offset amount of θ / 2 in the clockwise direction, intersects the first region 27F of the permanent magnet 22 .

[0047] Next, refer to Figure 2B , in the two-stage skew-pole structure constituting the permanent magnet synchronous motor, the arrangement of the first permanent magnet 22A and the second permanent magnet 22B is described. Figure 2B1 is a partial cross-sectional view showing a state where the first permanent magnet 22A and the second permanent magnet 22B overlap each other when viewed in the Z direction. exist Figure 2B In FIG. 1 , the first permanent magnet 22A is indicated by a solid line, and the second permanent magnet 22B is indicated by a dotted line.

[0048] The first permanent magnet 22A has a first rotor core fixing surface 27A fixed to the outer peripheral surface 28 of the rotor core 21. The first rotor core fixing surface 27A is a surface corresponding to the rotor core fixing surface 27. Figure 2A As shown, the first rotor core fixing surface 27A has a first region 27F having a distance L1 and having a first recess end 35 , and a second region 27S having a distance L2 and having a second recess end 36 .

[0049] The second permanent magnet 22B has a second rotor core fixing surface 27B fixed to the outer peripheral surface 28 of the rotor core 21. The second rotor core fixing surface 27B is a surface corresponding to the rotor core fixing surface 27. Figure 2A As shown, the second rotor core fixing surface 27B has a first region 27F having a distance L1 and having a first recess end 35 , and a second region 27S having a distance L2 and having a second recess end 36 .

[0050] The center point of the first permanent magnet 22A in the circumferential direction is defined as a first center point C1. In other words, the first center point C1 corresponds to the center point of the stator facing surface 26 of the first permanent magnet 22A in the circumferential direction. The center point of the second permanent magnet 22B in the circumferential direction is defined as a second center point C2. In other words, the second center point C2 corresponds to the center point of the stator facing surface 26 of the second permanent magnet 22B in the circumferential direction. A line extending radially outward from the axial center O of the rotating shaft 23 , passing through the first central point C1 , and intersecting the first region 27F of the first permanent magnet 22A is defined as a first magnet central line S1 . A line extending radially outward from the axial center O of the rotating shaft 23 , passing through the second central point C2 , and intersecting the first region 27F of the first permanent magnet 22B is defined as a second magnet central line S2 . In the direction 27AD parallel to the first rotor core fixing surface 27A, a midpoint between the first recess end 35 and the second recess end 36 of the first permanent magnet 22A is defined as a first midpoint 37A. In the direction 27BD parallel to the second rotor core fixing surface 27B, a midpoint between the first recess end 35 and the second recess end 36 of the second permanent magnet 22B is defined as a second midpoint 37B. A line extending radially outward from the shaft center O of the rotating shaft 23 and passing through the first midpoint 37A is defined as a first recessed portion center line N1. A line extending radially outward from the shaft center O of the rotating shaft 23 and passing through the second midpoint 37B is defined as a second recessed portion center line N2.

[0051] In the above definition, the angle between the first magnet center line S1 and the second magnet center line S2 is the oblique polar angle θ. In addition, the angle between the first recess center line N1 and the second recess center line N2 is the recess center angle M. In this case, the recess center angle M is smaller than the oblique polar angle θ. In addition, L1≠L2 is satisfied, and L1>L2 is satisfied. The value of L1 divided by L2, that is, the value of L1 / L2 is in the range of 1.0<L1 / L2<1.6.

[0052] <Effect> Next, the effects obtained by the first embodiment will be described while comparing a conventional permanent magnet synchronous motor with the permanent magnet synchronous motor 100 according to the first embodiment.

[0053] <Existing permanent magnet synchronous motor> First, a conventional permanent magnet synchronous motor will be described. Figure 3 This is an enlarged view showing the vicinity of a permanent magnet constituting a conventional permanent magnet synchronous motor, and is a cross-sectional view viewed along the axial direction. Figure 3 In the figure, the stator is omitted. Figure 3 In the unspecified structure and Figure 1A same.

[0054] like Figure 3 As shown, the existing permanent magnet synchronous motor has a permanent magnet 122 fixed on the stator. The convex portion 124 of the stator of the existing permanent magnet synchronous motor is engaged with the concave portion 125 of the permanent magnet 122. The shape of the concave portion 125 has a mirror-symmetrical shape relative to the circumferential center of the permanent magnet 122. That is, in the permanent magnet 122, when the distance between the first magnet end 31 and the first concave portion end 35 is set to L1, and the distance between the second magnet end 32 and the second concave portion end 36 is set to L2, L1=L2 is satisfied. In addition, the magnet center line S intersects with the concave portion 125, but does not intersect with the first region 27F.

[0055] Next, the effects of the first embodiment will be described. In a permanent magnet synchronous motor, it is impossible to generate a terminal voltage Vt exceeding the input voltage Vi to output a torque T. Generally, when the rotation speed of the motor increases, the terminal voltage Vt increases as shown in the following equation.

[0056] Vd=R|d+ωLqIq…(2) Vq=R|q+ωΦm+ωdLdId…(3) ω=2πf=2π(N / 60)pn…(4)

[0057] Where Vd is the d-axis voltage. Vq is the q-axis voltage. R is the phase resistance. Id is the d-axis current. Iq is the q-axis current. φm is the magnet flux. Ld is the d-axis inductance. Lq is the q-axis inductance. ω is the angular velocity. f is the frequency. N is the revolutions per minute. pn is the number of pole pairs.

[0058] As a control method for a permanent magnet synchronous motor, so-called field weakening control is known as a control method for increasing torque output during high-speed rotation, which suppresses an increase in terminal voltage. This field weakening control is a control method for passing a d-axis current Id in a direction that weakens the magnetic flux Φm. In this control method, when the d-axis inductance Ld is small, a large d-axis current Id needs to flow through the motor. However, there is an upper limit to the current that can be supplied to the motor. If the current supplied from the inverter to the motor is Iinv, the following equation is obtained.

[0059]

[0060] The torque T output by an SPM permanent magnet synchronous motor is generally expressed by the following formula.

[0061] T=PnφmIq…(6)

[0062] Therefore, when the d-axis current Id increases, the q-axis current Iq for outputting the torque T decreases, and the torque output decreases. Therefore, in order to increase the torque T during high-speed rotation, it is necessary to effectively obtain the weak magnetic field control with a small d-axis current Id, and it is necessary to increase the d-axis inductance Ld. Therefore, by adopting Figure 3 The structure shown can increase the d-axis inductance Ld.

[0063] When the permanent magnet flux contains harmonic components, the torque T generated by equation (6) contains pulsation of harmonics, which is called torque ripple. Since torque ripple causes vibration or noise, measures to reduce it are usually taken.

[0064] As one of the countermeasures, a method of applying a segmented skewed pole structure as a rotor structure is known. This structure is composed of two or more rotors, and there is an angle difference when comparing the circumferential center positions of the permanent magnets of each segment. This angle difference is called the skew angle. By adjusting this angle difference, the torque ripple of the motor as a whole can be reduced.

[0065] However, if Figure 2A As shown, in the entire motor, a deviation (angle difference) of Pn×θ / 2 occurs in electrical angle between the d-axis position d1 and the circumferential center position CP of the permanent magnet 22 in each stage of the rotor 20 .

[0066] In contrast, Figure 3 The structure shown can effectively increase the d-axis inductance Ld when the d-axis position d1 is consistent with the circumferential center position CP. However, when a segmented slanted pole structure with a slanted pole angle θ is applied, Figure 3 In the structure shown, there is an angle difference between the circumferential center position CP of each stage of the convex portion 124 and the d-axis position d1. Therefore, it is difficult to effectively increase the d-axis inductance Ld.

[0067] Embodiment 1 solves the problems of the conventional permanent magnet synchronous motor. Specifically, if Figure 2A As shown, by shifting the protrusion 24 from the circumferential center position CP of the magnet in the direction opposite to the oblique polarity direction, a structure satisfying L1≠L2 is obtained. Figure 4 This is a diagram showing a comparison result of the d-axis inductance Ld between the condition L1 = L2 of the conventional motor and the condition L1 ≠ L2 of the first embodiment.

[0068] exist Figure 4 In the figure, the vertical axis represents the d-axis inductance Ld, and the horizontal axis represents the shape of the concave portion. Figure 2A and Figure 3 The shape of the concave portion shown. "Sawtooth" means the shape of one tooth constituting a saw having a plurality of teeth. "Arc" means a substantially U-shape or a substantially C-shape. exist Figure 4 In the case of L1 = L2, the d-axis inductance Ld is normalized to 1.0. The "sawtooth shape" corresponds to the shape shown in Modification 1A described later. The "arc" corresponds to the shape shown in Modification 1B described later.

[0069] like Figure 4 As shown in the first embodiment, by setting L1≠L2, the d-axis inductance Ld can be further increased compared with the conventional permanent magnet synchronous motor. Furthermore, the permanent magnet synchronous motor 100 includes the first magnet group 41 and the second magnet group 42 adjacent to each other in the Z direction, and the rotor 20 has a segmented skewed pole structure between the first magnet group 41 and the second magnet group 42. Therefore, the d-axis inductance Ld can be effectively increased.

[0070] Moreover, different from the existing permanent magnet synchronous motor, in Embodiment 1, the angle M between the centers of the recesses is smaller than the skew angle θ. In addition, L1≠L2 is satisfied, and L1>L2 is satisfied. Furthermore, the value of L1 / L2 is in the range of 1.0<L1 / L2<1.6. Therefore, the d-axis inductance Ld can be more effectively increased.

[0071] <Modification Example 1A of Embodiment 1> Next, Modification Examples 1A and 1B of the permanent magnet synchronous motor according to Embodiment 1 will be described. In the description of Modification Examples 1A and 1B, the description of the parts common to the above-mentioned Embodiment 1 is omitted.

[0072] <Modification Example 1A> Figure 5 FIG. is an enlarged view showing a region near the permanent magnet constituting Modification Example 1A, and is a cross-sectional view taken along the axial direction. As Figure 5 shown, the recess 25 has a first bottom end 51 and a second bottom end 52. The first bottom end 51 and the second bottom end 52 respectively form the bottom 50 of the recess 25. The second bottom end 52 is spaced apart from the first bottom end 51. When the distance between the first recess end 35 in the radial direction and the first bottom end 51 is set as H1, and the distance between the second recess end 36 in the radial direction and the second bottom end 52 is set as H2, H1≠H2 is satisfied. In this modification example, H1<H2 is satisfied. And, this modification example satisfies L1≠L2.

[0073] According to Modification Example 1A, as Figure 4 shown by the results of "L1≠L2" and "zigzag", compared with the existing permanent magnet synchronous motor, the d-axis inductance Ld can be further increased.

[0074] <Modification Example 1B> Figure 6 FIG. is an enlarged view showing a region near the permanent magnet constituting Modification Example 1B, and is a cross-sectional view taken along the axial direction. As Figure 6 shown, the surface 53 forming the bottom 50 of the recess 25 has an arc shape. And, this modification example satisfies L1≠L2.

[0075] According to Modification Example 1B, as Figure 4 shown by the results of "L1≠L2" and "arc", compared with the existing permanent magnet synchronous motor, the d-axis inductance Ld can be further increased.

[0076] Embodiment 2. The permanent magnet synchronous motor according to Embodiment 2 will be described. In Embodiment 2, the same reference numerals are assigned to the same components as those in the above-mentioned embodiments and modification examples, and the description thereof is omitted or simplified.

[0077] Reference Fig. 7A , the recessed portion 25 engaged with the convex portion 24 will be described in detail. Fig. 7A It is a diagram showing an enlarged area near the permanent magnet 22 and is a cross-sectional view viewed along the axial direction. Fig. 7A Corresponds to Figure 2A , which means that Figure 1A This is an enlarged view of the portion surrounded by the dotted line A. Fig. 7A Although not shown, the permanent magnet synchronous motor according to the second embodiment is constituted by a stator 10 and a rotor 20 in the same manner as in FIG. 1 .

[0078] like Fig. 7A As shown, the permanent magnet synchronous motor according to the second embodiment is different from the permanent magnet synchronous motor according to the first embodiment in that the inclined surface connected to the second bottom end 52 is formed inside the recess 25 .

[0079] Specifically, the recess 25 has a first bottom end 51 and a second bottom end 52. The first bottom end 51 and the second bottom end 52 respectively form the bottom 50 of the recess 25. The second bottom end 52 is spaced apart from the first bottom end 51. The recess 25 has a first inner wall 61 and a second inner wall 62. The first inner wall 61 is formed between the first recess end 35 and the first bottom end 51 and extends in the radial direction. The second inner wall 62 is formed between the second recess end 36 and the second bottom end 52. The second inner wall 62 has a vertical surface 63 and an inclined surface 64. The vertical surface 63 is connected to the second recess end 36 and extends in the radial direction. The inclined surface 64 is connected to the vertical surface 63 and the second bottom end 52, and is inclined relative to the vertical surface 63 and extends in a straight line.

[0080] Furthermore, in the second embodiment, L1≠L2 is satisfied, and L1>L2 is satisfied. The value of L1 divided by L2, that is, the value of L1 / L2 is within the range of 1.0<L1 / L2<1.6.

[0081] <Variation 2A of Embodiment 2> Next, Modification 2A of the permanent magnet synchronous motor according to the second embodiment will be described. In the description of modification 2A, description of parts common to the above-mentioned first and second embodiments will be omitted.

[0082] Reference Figure 7B , the recessed portion 25 engaged with the convex portion 24 will be described in detail. Figure 7B It is a diagram showing an enlarged area near the permanent magnet 22 and is a cross-sectional view viewed along the axial direction. Figure 7B Corresponds to Figure 2A , which means that Figure 1A This is an enlarged view of the portion surrounded by the dotted line A. Figure 7BAlthough not shown, the permanent magnet synchronous motor according to the modification 2A is constituted by a stator 10 and a rotor 20 in the same manner as in FIG. 1 .

[0083] like Figure 7B As shown, the permanent magnet synchronous motor according to Modification 2A is different from the permanent magnet synchronous motor according to Embodiment 1 in that a curved surface connected to the second bottom end 52 is formed inside the recess 25 .

[0084] Specifically, the recess 25 has a first bottom end 51 and a second bottom end 52. The first bottom end 51 and the second bottom end 52 respectively form the bottom 50 of the recess 25. The second bottom end 52 is spaced apart from the first bottom end 51. The recess 25 has a first inner wall 61 and a second inner wall 62. The first inner wall 61 is formed between the first recess end 35 and the first bottom end 51 and extends in the radial direction. The second inner wall 62 is formed between the second recess end 36 and the second bottom end 52. The second inner wall 62 has a curved surface 65 connected to the second bottom end 52.

[0085] Furthermore, in the modification 2A, L1≠L2 is satisfied, and L1>L2 is satisfied. The value of L1 divided by L2, that is, the value of L1 / L2 is within the range of 1.0<L1 / L2<1.6.

[0086] <Effect> Next, the effects obtained by the second embodiment will be described after explaining the irreversible demagnetization phenomenon related to the change in magnetic force and the reduction in magnetic flux of the magnet due to the demagnetization.

[0087] For example, in the structure described in Embodiment 1, the shape of the protrusion 24 of the rotor core 21 is rectangular, and the protrusion center position TP of the protrusion 24 is offset from the circumferential center of the permanent magnet 22. In addition, in this structure, the outer shape of the stator facing surface 26 is an arc. At this time, at the position of the corner of the protrusion 24, in other words, at the second bottom end 52 of the recess 25, the distance between the stator facing surface 26 and the second bottom end 52 becomes extremely short.

[0088] In permanent magnets, a phenomenon called irreversible demagnetization occurs in which the residual magnetic flux density Br of the permanent magnet decreases due to the effect of the temperature rise of the permanent magnet or the effect of the anti-magnetic field applied to the permanent magnet by the magnetic field from the stator in the direction opposite to the magnetization direction. The ease with which this irreversible demagnetization phenomenon occurs is related to the coercive force of the permanent magnet and the permeance coefficient Pc determined by the magnetic circuit. The permeance coefficient Pc depends on the thickness and magnetic resistance of the magnet in the magnetization direction. In a magnetic circuit with a narrow magnetic gap between the stator and the rotor, such as a permanent magnet synchronous motor, the permeance coefficient Pc can be approximately calculated by the following formula.

[0089]

[0090] Here, Hm is the thickness of the permanent magnet in the magnetization direction. gm is the magnetic gap between the stator and the rotor. According to equation (7), as the thickness Hm of the permanent magnet in the magnetization direction decreases, Pc decreases. The decrease in Pc affects the ease with which the irreversible demagnetization phenomenon occurs.

[0091] Figure 8 This is a diagram showing a comparison result of the permanent magnet synchronous motor according to the first embodiment and a conventional permanent magnet synchronous motor with respect to the d-axis inductance Ld and the induced voltage reduction rate after demagnetization. Figure 8 The d-axis inductance Ld and the induced voltage reduction rate due to demagnetization are shown relative to L1 / L2 when the condition of the permanent magnet 22 is L1>L2. The d-axis inductance Ld and the induced voltage reduction rate when L1=L2 are normalized to 1.0.

[0092] Depend on Figure 8 It can be seen that as L1 / L2 increases, the d-axis inductance Ld increases, but the induced voltage reduction rate also increases.

[0093] Furthermore, if attention is paid to the increasing trend of the d-axis inductance Ld, the increasing amount of the d-axis inductance Ld is saturated. On the other hand, if attention is paid to the increasing trend of the induced voltage reduction rate, it is found that the increasing amount of the induced voltage reduction rate is not saturated.

[0094] Therefore, the d-axis inductance Ld can be effectively increased within the range where L1 / L2 satisfies 1.0<L1 / L2<1.6, but demagnetization significantly proceeds within the range where L1 / L2>1.6 is satisfied.

[0095] Fig.9A and Fig. 9B It is the result obtained by calculating the demagnetization rate distribution of the demagnetization state through magnetic field analysis. Fig.9A Graph showing the demagnetization rate distribution of a conventional permanent magnet synchronous motor. Fig.9A As a condition of the permanent magnet, L1=L2 is satisfied. Fig. 9B : is a diagram showing the demagnetization rate distribution of the permanent magnet synchronous motor according to the first embodiment. Fig. 9B In the example, as the conditions for the permanent magnet, L1≠L2 and L1 / L2>1.6 are satisfied.

[0096] exist Fig.9A and Fig. 9B In the figure, the regions indicated by the reference numerals 70, 71, and 72 represent the progress of demagnetization. The region indicated by the reference numeral 70 represents the least progress of demagnetization. The region indicated by the reference numeral 72 represents the most progress of demagnetization. The region indicated by the reference numeral 71 represents the progress of demagnetization greater than that of the region indicated by the reference numeral 70, and the progress of demagnetization less than that of the region indicated by the reference numeral 72. Fig.9A and Fig. 9B The results shown show that region 72 is generated at a portion where the distance between second bottom end 52 of recess 25 and stator facing surface 26 is short. In other words, it is found that the range of demagnetization is expanded as the distance between the corner of projection 24 and stator facing surface 26 becomes shorter.

[0097] The reduction in residual magnetic flux density Br due to demagnetization leads to a reduction in magnetic flux Φm. Therefore, according to the calculation result based on equation (6), the torque T is reduced. Therefore, the output of the permanent magnet synchronous motor is reduced.

[0098] Implementation method 2 solves the above-mentioned problems. Fig.10 : is a graph showing the comparison results of the permanent magnet synchronous motor according to the first embodiment, the permanent magnet synchronous motor according to the second embodiment, and the permanent magnet synchronous motor according to the modification 2A with respect to the induced voltage reduction rate after demagnetization. Fig.10 In the figure, the induced voltage reduction rate of the permanent magnet 22 of Embodiment 1 is normalized to 1.0. Specifically, "no inclined surface, no curved surface" corresponds to Embodiment 1. Also, "with an inclined surface" corresponds to Embodiment 2. Also, "with a curved surface" corresponds to Modification 2A.

[0099] like Fig.10 As shown, Embodiment 2 using permanent magnets 22 having inclined surfaces 64 can reduce the induced voltage reduction rate compared to Embodiment 1. Similarly, Modification 2A using permanent magnets 22 having curved surfaces 65 can reduce the induced voltage reduction rate compared to Embodiment 1.

[0100] Figures 11A to 11C It is the result obtained by calculating the demagnetization rate distribution of the demagnetization state through magnetic field analysis. Fig.11A This is a diagram showing the demagnetization rate distribution of the permanent magnet 22 according to the first embodiment. Fig. 11B This is a diagram showing the demagnetization rate distribution of the permanent magnet 22 according to the second embodiment. Fig. 11C It is a diagram showing the demagnetization rate distribution of the permanent magnet 22 according to the modification 2A.

[0101] exist Figures 11A to 11C In the figure, the regions indicated by reference numerals 70, 71, and 72 indicate the progress of demagnetization. The region indicated by reference numeral 70 indicates that the progress of demagnetization is the least. The region indicated by reference numeral 72 indicates that the progress of demagnetization is the greatest. The region indicated by reference numeral 71 indicates that the progress of demagnetization is greater than that of the region indicated by reference numeral 70, and the progress of demagnetization is less than that of the region indicated by reference numeral 72.

[0102] Compare Figures 11A to 11CAs can be seen from the results shown, in the case of Embodiment 2 having an inclined surface and in the case of Modification 2A having a curved surface, the total area generated in Regions 71 and 2 is smaller than that in Embodiment 1 having no inclined surface or curved surface. In other words, by forming an inclined surface or a curved surface, the distance between the point on the stator opposing surface 26 closest to the second bottom end 52 and the second bottom end 52 can be extended. From this, it can be understood that in Embodiment 2 and Modification 2A, compared with Embodiment 1, the progress of magnetic flux weakening can be suppressed.

[0103] Therefore, according to Embodiment 2 and Modification 2A, even when performing magnetic flux weakening control, high output of the motor can be achieved. In addition, since L1 / L2 is within the range of satisfying 1.0 < L1 / L2 < 1.6, the magnetic flux weakening tolerance can be improved. That is, high output of the motor and improvement of the magnetic flux weakening tolerance can be achieved concurrently.

[0104] <Modifications 2B and 2C of Embodiment 2> Next, Modifications 2B and 2C of the permanent magnet synchronous motor according to Embodiment 2 will be described. In the description of Modifications 2B and 2C, the description of the parts common to the above-described Embodiment 1 and Embodiment 2 will be omitted.

[0105] <Modification 2B> Fig. 12A It is a diagram showing an enlarged view of a region near the permanent magnet constituting Modification 2B, and is a cross-sectional view taken along the axial direction. As Fig. 12A shown, the recess 25 has a first bottom end 51 and a second bottom end 52. The first bottom end 51 and the second bottom end 52 respectively form the bottom 50 of the recess 25. The second bottom end 52 is spaced apart from the first bottom end 51. When the distance between the first recess end 35 and the first bottom end 51 in the radial direction is set as H1, and the distance between the second recess end 36 and the second bottom end 52 in the radial direction is set as H2, H1 ≠ H2 is satisfied. In this modification, H1 < H2 is satisfied. And, in this modification, L1 ≠ L2 is satisfied. In addition, the value of L1 / L2 is within the range of 1.0 < L1 / L2 < 1.6.

[0106] Moreover, in this modification, the recess 25 has a first inner wall 61 and a second inner wall 62. The first inner wall 61 is formed between the first recess end 35 and the first bottom end 51 and extends in the radial direction. The second inner wall 62 is formed between the second recess end 36 and the second bottom end 52. The second inner wall 62 has a vertical surface 63 and an inclined surface 64. The vertical surface 63 is connected to the second recess end 36 and extends in the radial direction. The inclined surface 64 is connected to the vertical surface 63 and the second bottom end 52, and extends linearly while being inclined with respect to the vertical surface 63.

[0107] <Modification 2C> Fig. 12B It is a view that enlarges and shows a region near the permanent magnet that constitutes the modified example 2C, and is a cross-sectional view observed along the axial direction. Fig. 12B Same as Fig. 12A , satisfying H1≠H2, satisfying H1<H2, satisfying L1≠L2. The value of L1 / L2 is within the range of 1.0<L1 / L2<1.6.

[0108] Moreover, in this modified example, the recess 25 has a first inner wall 61 and a second inner wall 62. The first inner wall 61 is formed between the first recess end 35 and the first bottom end 51 and extends in the radial direction. The second inner wall 62 is formed between the second recess end 36 and the second bottom end 52. The second inner wall 62 has a curved surface 65 connected to the second bottom end 52.

[0109] <Effect> Fig.13 It is a view showing the comparison result obtained by comparing the permanent magnet synchronous motor related to the modified example 1A, the permanent magnet synchronous motor related to the modified example 2B, and the permanent magnet synchronous motor related to the modified example 2C with respect to the reduction rate of the induced voltage after demagnetization. In Fig.13 , the reduction rate of the induced voltage of the permanent magnet 22 in the modified example 1A is standardized to 1.0. Specifically, "no inclined surface, no curved surface" corresponds to the embodiment 1A. In other words, in the modified example 1A, as described above, H1<H2 is satisfied, but no inclined surface or curved surface is formed in the recess 25. In addition, "having an inclined surface" corresponds to the modified example 2B. In addition, "having a curved surface" corresponds to the modified example 2C.

[0110] As Fig.13 shown, it can be seen that the reduction rate of the induced voltage of the modified example 2B using the permanent magnet 22 having the inclined surface 64 is reduced compared with the modified example 1A. Similarly, it can be seen that the reduction rate of the induced voltage of the modified example 2C using the permanent magnet 22 having the curved surface 65 is reduced compared with the modified example 1A.

[0111] Figures 14A to 14C It is the result obtained by calculating the demagnetization rate distribution in the demagnetized state through magnetic field analysis. Fig.14A It is a view showing the demagnetization rate distribution of the permanent magnet 22 related to the modified example 1A. Fig. 14B It is a view showing the demagnetization rate distribution of the permanent magnet 22 related to the modified example 2B. Fig. 14C It is a view showing the demagnetization rate distribution of the permanent magnet 22 related to the modified example 2C.

[0112] In Figures 14A to 14CIn the figure, the regions indicated by reference numerals 70, 71, and 72 indicate the progress of demagnetization. The region indicated by reference numeral 70 indicates that the progress of demagnetization is the least. The region indicated by reference numeral 72 indicates that the progress of demagnetization is the greatest. The region indicated by reference numeral 71 indicates that the progress of demagnetization is greater than that of the region indicated by reference numeral 70, and the progress of demagnetization is less than that of the region indicated by reference numeral 72.

[0113] Compare Figures 14A to 14C The results shown show that in the case of modification 2B having an inclined surface and modification 2C having a curved surface, the total area generated by the regions 71 and 72 is smaller than that of modification 1A having neither an inclined surface nor a curved surface. In other words, by forming an inclined surface or a curved surface, the distance between the point on the stator facing surface 26 closest to the second bottom end 52 and the second bottom end 52 can be increased. As can be seen from this, in Modifications 2B and 2C, the progress of demagnetization can be suppressed compared to Modification 1A.

[0114] Therefore, according to Modification 2B and Modification 2C, even when performing field weakening control, the motor can achieve high output. In addition, since L1 / L2 is within the range of 1.0<L1 / L2<1.6, the demagnetization resistance can be improved. In other words, it is possible to achieve both high output of the motor and improvement of the demagnetization resistance.

[0115] Implementation method 3. A permanent magnet synchronous motor according to a third embodiment will be described. In the third embodiment, the same reference numerals are used to denote the same components as those in the above-described embodiment and modification examples, and descriptions thereof will be omitted or simplified.

[0116] Fig.15 It is a perspective view showing a permanent magnet synchronous motor according to the third embodiment. Fig.16 2 is a perspective view showing only the rotor core 21 including the protrusion 24. In other words, Fig.16 The figure shows a state where the plurality of permanent magnets 22 are removed from the permanent magnet synchronous motor.

[0117] like Fig.15 and Fig.16 As shown, the permanent magnet synchronous motor according to the third embodiment is different from the permanent magnet synchronous motor according to the first embodiment in that the circumferential center positions CP of the permanent magnets 22 coincide with each other in the upper and lower stages.

[0118] Specifically, among the plurality of permanent magnets 22, the stator facing surfaces 26 of the permanent magnets 22 arranged in the Z direction in which the rotating shaft 23 extends are aligned with each other in the Z direction. No pole tilting is performed between the permanent magnets 22 arranged in the Z direction. Only the concave portions 25 of each of the plurality of permanent magnets 22 and the convex portions of the rotor core 21 are tilted.

[0119] The permanent magnet synchronous motor according to the third embodiment will be described in more detail. The permanent magnet synchronous motor according to the third embodiment includes an upper stage portion 100U and a lower stage portion 100L adjacent to the upper stage portion 100U in the Z direction. The upper stage portion 100U is an example of a first rotor portion, and the lower stage portion 100L is an example of a second rotor portion.

[0120] The plurality of permanent magnets 22 include a first magnet group 41 disposed in the upper section 100U and a second magnet group 42 disposed in the upper section 100U. Each of the plurality of permanent magnets 22 constituting the first magnet group 41 is the first permanent magnet described above. Each of the plurality of permanent magnets 22 constituting the second magnet group 42 is the second permanent magnet described above. The stator facing surface 26 of the first permanent magnet constituting the first magnet group 41 coincides with the stator facing surface 26 of the second permanent magnet constituting the second magnet group 42 in the Z direction. In other words, the position of the circumferential center point C of the stator facing surface 26 of the first permanent magnet coincides with the position of the circumferential center point C of the stator facing surface 26 of the second permanent magnet in the axial direction. The circumferential center point C of the stator facing surface 26 is referred to as Figure 2A Provide explanation.

[0121] The protrusion 24 of the rotor core 21 includes a first protrusion 24U disposed in the upper portion 100U and a second protrusion 24L disposed in the lower portion 100L. The first protrusion 24U fits in the recess 25 of the first permanent magnet constituting the first magnet group 41. The second protrusion 24L fits in the recess 25 of the second permanent magnet constituting the second magnet group 42. In the circumferential direction, the second protrusion 24L is offset at an oblique polar angle relative to the first protrusion 24U.

[0122] That is, Fig.16 As shown, the position of the first convex portion 24U (24) in the circumferential direction of the upper section 100U and the position of the second convex portion 24L (24) in the circumferential direction of the lower section 100L are as shown in FIG. Figure 2A As shown, the permanent magnet 22 is offset from the circumferential center position CP. The position of the first convex portion 24U of the upper portion 100U and the position of the second convex portion 24L of the lower portion 100L are mirror-symmetrical with respect to the circumferential center position CP of the permanent magnet 22.

[0123] <Effect> Next, a rotor manufacturing process of the permanent magnet synchronous motor will be described, and effects obtained by the third embodiment will be described. The rotor manufacturing process of the permanent magnet synchronous motor includes a magnetization process of mounting the permanent magnet 22 on the rotor core 21 .

[0124] In the magnetization process of the permanent magnet, a method of magnetizing the permanent magnet 22 by bonding it to the rotor core 21 using a magnetizer is widely used. However, when a segmented skewed pole structure is applied as the structure of the rotor 20, since the magnetization directions of the permanent magnets of the upper and lower segments differ by a skewed pole angle θ, it is difficult to magnetize the permanent magnets of each segment at the same time, and thus magnetize in each segment. Therefore, as the number of magnetization times increases, the life of the magnetizer is shortened or the tact time in rotor manufacturing is deteriorated.

[0125] Implementation method 3 solves the above-mentioned problems. like Fig.16 As shown in FIG. 1 , the position of the first convex portion 24U (24) on the circumferential direction of the upper section 100U and the position of the second convex portion 24L (24) on the circumferential direction of the lower section 100L are mirror-symmetrical with respect to the circumferential center position CP. Due to the influence of the position of the convex portion 24, the higher harmonic components of the permanent magnet flux in the upper section 100U and the lower section 100L have a phase difference.

[0126] Therefore, by setting the circumferential position of the protrusion 24 to an appropriate position, the harmonic components of the permanent magnet fluxes of each stage are canceled out, thereby reducing the torque ripple of the entire motor.

[0127] Fig.17 : is a diagram showing the comparison results of the case where the condition L1=L2 of the conventional motor is compared with the case where the condition L1≠L2 of the third embodiment with respect to the torque ripple. Fig.17 In the example, the torque pulse when L1=L2 is standardized to 1.0.

[0128] like Fig.17 As shown in FIG. 1 , it can be seen that when the condition L1≠L2 in the third embodiment is satisfied, the torque ripple is reduced.

[0129] Therefore, according to Embodiment 3, the number of man-hours required for the magnetization process can be reduced. Furthermore, even when the field weakening control is performed as in the related art, the output of the motor can be increased or the torque ripple can be reduced.

[0130] Implementation method 4. A permanent magnet synchronous motor according to a fourth embodiment will be described. In the fourth embodiment, the same reference numerals are given to the same components as those in the above-mentioned embodiment and modification examples, and the description thereof will be omitted or simplified.

[0131] Fig.18 It is a perspective view showing a permanent magnet synchronous motor according to a fourth embodiment. Fig.19 2 is a perspective view showing only the rotor core 21 including the protrusion 24. In other words, Fig.19 The figure shows a state where the plurality of permanent magnets 22 are removed from the permanent magnet synchronous motor.

[0132] like Fig.18 and Fig.19 As shown in FIG. 1 , the permanent magnet synchronous motor according to the fourth embodiment is different from the permanent magnet synchronous motor according to the first embodiment in that the circumferential positions of the protrusions 24 of the rotor core coincide with each other in the upper and lower stages.

[0133] Specifically, the positions of the convex portions 24 of the rotor core 21 are aligned in the Z direction, and only the concave portions 25 of the permanent magnets 22 are skewed. Fig.18 As shown, in each of the upper and lower stages, the position of the recessed portion 25 of the permanent magnet 22 in the circumferential direction is offset from the circumferential center position CP of the permanent magnet 22 , satisfying L1 ≠ L2 .

[0134] The permanent magnet synchronous motor according to the fourth embodiment will be described in more detail. The permanent magnet synchronous motor according to the fourth embodiment includes an upper stage portion 100U and a lower stage portion 100L adjacent to the upper stage portion 100U in the Z direction. The plurality of permanent magnets 22 include a first magnet group 41 disposed in the upper portion 100U and a second magnet group 42 disposed in the upper portion 100U. Each of the plurality of permanent magnets 22 constituting the first magnet group 41 is a first permanent magnet. Each of the plurality of permanent magnets 22 constituting the second magnet group 42 is a second permanent magnet.

[0135] The stator facing surface 26 of the first permanent magnet constituting the first magnet group 41 coincides with the stator facing surface 26 of the second permanent magnet constituting the second magnet group 42 in the Z direction. In other words, the position of the circumferential center point C of the stator facing surface 26 of the first permanent magnet and the position of the circumferential center point C of the stator facing surface 26 of the second permanent magnet do not coincide in the axial direction. The circumferential center point C of the stator facing surface 26 is referred to as Figure 2A Provide explanation. The protrusions 24 of the rotor core 21 extend continuously from the upper stage 100U to the lower stage 100L. The protrusions 24 fit into the recesses 25 of the first permanent magnets constituting the first magnet group 41 and the recesses 25 of the second permanent magnets constituting the second magnet group 42 .

[0136] In the circumferential direction, the stator-opposing surfaces 26 of the first permanent magnets constituting the first magnet group 41 are offset at an oblique polar angle relative to the stator-opposing surfaces 26 of the second permanent magnets constituting the second magnet group 42 .

[0137] The position of the convex portion 24 in the circumferential direction of the upper portion 100U and the position of the convex portion 24 in the circumferential direction of the lower portion 100L are mirror-symmetrical with respect to the circumferential center position CP of the permanent magnet 22 .

[0138] <Effect> Next, a rotor manufacturing process of the permanent magnet synchronous motor will be described, and effects obtained by the fourth embodiment will be described.

[0139] When segmented skewed poles are applied to the rotor, in the rotor core manufacturing process of the permanent magnet synchronous motor, after the rotor core of each segment is formed, the rotating shaft is fitted into the rotor core so as to produce a skewed pole angle.

[0140] Therefore, time and effort are required to realize the skew angle with high accuracy, and the manufacturing cost of the rotor becomes higher than the manufacturing process of a rotor that does not use segmented skew.

[0141] Implementation method 4 solves the above-mentioned problems. like Fig.19 As shown, the convex portions 24 of the upper section 100U and the lower section 100L of the rotor core 21 are identical in the circumferential direction. Therefore, the rotor core 21 does not need to be manufactured so as to have the convex portions 24 divided to correspond to the upper section 100U and the lower section 100L, respectively.

[0142] The position of the recess 25 of the permanent magnet 22 satisfies L1≠L2, and the circumferential center position CP of each of the permanent magnets 22 in the upper and lower stages is mirror-symmetrical with respect to the position of the recess 25, resulting in an angular difference.

[0143] Due to the angular difference between the circumferential center positions CP of the permanent magnets 22 , a phase difference occurs in the harmonic components of the permanent magnet magnetic fluxes in the upper and lower stages.

[0144] Therefore, by setting the recess 25 at an appropriate position, the harmonic components of the permanent magnet flux of each stage are canceled, thereby reducing the overall torque pulsation of the motor. In addition, since the rotor core 21 can be integrally formed, the number of man-hours required to manufacture the rotor core 21 can be reduced.

[0145] Fig. 20 : is a diagram showing the comparison results of the case where the condition L1=L2 of the conventional motor is compared with the case where the condition L1≠L2 of the fourth embodiment with respect to the torque ripple. Fig. 20 In the example, the torque pulse when L1=L2 is standardized to 1.0.

[0146] like Fig. 20 As shown in FIG. 1 , it can be seen that when the condition L1≠L2 in the fourth embodiment is satisfied, the torque ripple is reduced.

[0147] Fig.21 : is a diagram showing the comparison results of the condition L1=L2 of the conventional motor and the condition L1≠L2 of the fourth embodiment with respect to the d-axis inductance Ld. Fig.21In the example, the d-axis inductance Ld when L1=L2 is standardized to 1.0.

[0148] like Fig.21 As shown, in the case of the condition L1≠L2 in the fourth embodiment, the d-axis inductance Ld can be increased more effectively. Therefore, according to Embodiment 4, it is possible to reduce the number of man-hours required for manufacturing the rotor core 21. Furthermore, even when the flux weakening control is performed as in the related art, it is possible to achieve higher output of the motor or reduce torque ripple compared to the conventional configuration. Description of symbols

[0149] 10… stator, 11… stator core, 12… core back, 13… teeth, 14… winding (coil portion), 15… gap, 20… rotor, 21… rotor core, 22… permanent magnet, 22A… first permanent magnet (permanent magnet), 22B… second permanent magnet (permanent magnet), 23… rotating shaft, 24… convex portion, 24L… second convex portion (convex portion), 24U… first convex portion (convex portion), 25… concave portion, 26… stator Opposite surface, 27…rotor core fixing surface, 27A…first rotor core fixing surface (rotor core fixing surface), 27B…second rotor core fixing surface (rotor core fixing surface), 27F…first region, 27S…second region, 28…outer peripheral surface, 31…first magnet end, 32…second magnet end, 33…first side surface, 34…second side surface, 35…first recessed portion end, 36…second recessed portion end, 37A…first midpoint , 37B…second midpoint, 41…first magnet group, 42…second magnet group, 50…bottom, 51…first bottom end, 52…second bottom end, 53…surface, 61…first inner wall, 62…second inner wall, 63…vertical surface, 64…inclined surface, 65…curved surface, 100…permanent magnet synchronous motor, 100L…lower section (second rotor section), 100U…upper section (first rotor section), 122…permanent magnet, 12 4…convex part, 125…concave part, C…central point, C1…first central point, C2…second central point, CL…center line, CP…circumferential center position, L1, L2…distance, M…angle between centers of concave parts, N1…center line of first concave part, N2…center line of second concave part, O…axis center, S…center line of magnet, S1…center line of first magnet, S2…center line of second magnet, TP…center position of convex part, θ…slant polar angle.

Claims

1. A permanent magnet synchronous motor, characterized in that: include: stator; a rotor rotatably arranged relative to the stator, comprising a rotor core formed of an electromagnetic steel sheet and having one or more convex portions protruding in a radial direction toward the stator, and a rotating shaft fixed to the rotor core; as well as a plurality of permanent magnets, the plurality of permanent magnets being arranged along the circumferential direction of the rotor, and each having an arc-shaped stator-opposing surface opposing the stator across a gap, a rotor core-fixing surface located on the side opposite to the stator-opposing surface and fixed to the outer circumferential surface of the rotor core, and a recessed portion connected to a portion of the rotor core-fixing surface and engaged with the protruding portion, In the circumferential direction, the polarities of the stator facing surfaces of two adjacent permanent magnets among the plurality of permanent magnets are different from each other, In the circumferential direction, the plurality of permanent magnets respectively have a first magnet end connected to the rotor core fixed surface, and a second magnet end connected to the rotor core fixed surface and located on a side opposite to the first magnet end. In the circumferential direction, the recess of each of the plurality of permanent magnets has a first recess end connected to the rotor core fixing surface, and a second recess end connected to the rotor core fixing surface and located on the side opposite to the first recess end. The rotor core fixing surface has a first region between the first magnet end and the first recess end and a second region between the second magnet end and the second recess end, The recess is located between the first region and the second region, When the distance between the first magnet end and the first recess end in the first region is set to L1, and the distance between the second magnet end and the second recess end in the second region is set to L2, Satisfies L1≠L2.

2. The permanent magnet synchronous motor according to claim 1, characterized in that: The plurality of permanent magnets include a first magnet group and a second magnet group adjacent to each other in the axial direction of the rotation shaft. The plurality of permanent magnets constituting the first magnet group are respectively first permanent magnets, The plurality of permanent magnets constituting the second magnet group are respectively second permanent magnets, The oblique polar angle is called θ, The first permanent magnet is offset by θ / 2 in the counterclockwise direction in the circumferential direction relative to the d-axis of the permanent magnet synchronous motor. The second permanent magnet is offset by θ / 2 in the clockwise direction in the circumferential direction relative to the d-axis of the permanent magnet synchronous motor. A magnet center line extending radially outward from the axis center of the rotating shaft and passing through the circumferential center points of each of the plurality of permanent magnets intersects the first region. L1≠L2 and L1>L2 are satisfied.

3. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that: The recess has: a first bottom end, the first bottom end forming a bottom of the recess; and a second bottom end, the second bottom end forming the bottom of the recess and spaced apart from the first bottom end; When the distance between the first recessed portion end and the first bottom end in the radial direction is set to H1, and the distance between the second recessed portion end and the second bottom end in the radial direction is set to H2, Satisfies H1≠H2.

4. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that: A surface forming the bottom of the recess has an arc shape.

5. The permanent magnet synchronous motor according to claim 2, characterized in that: The first permanent magnet has a first rotor core fixing surface fixed on the outer peripheral surface of the rotor core. The first rotor core fixing surface is a surface corresponding to the rotor core fixing surface, and has the first region and the second region, the first region has the distance L1 and has the first recessed end, and the second region has the distance L2 and has the second recessed end. The second permanent magnet has a second rotor core fixing surface fixed on the outer peripheral surface of the rotor core. The second rotor core fixing surface is a surface corresponding to the rotor core fixing surface, and has the first region and the second region, the first region has the distance L1 and has the first recessed end, and the second region has the distance L2 and has the second recessed end. The central point of the circumference of the first permanent magnet is defined as a first central point, The central point of the circumference of the second permanent magnet is defined as a second central point, A line extending radially outward from the axis center of the rotating shaft, passing through the first center point, and intersecting the first region of the first permanent magnet is defined as a first magnet center line. A line extending radially outward from the axis center of the rotating shaft, passing through the second center point, and intersecting the first region of the second permanent magnet is defined as a second magnet center line. A midpoint between the first recessed end and the second recessed end of the first permanent magnet in a direction parallel to the first rotor core fixing surface is defined as a first midpoint, A midpoint between the first recessed end and the second recessed end of the second permanent magnet in a direction parallel to the second rotor core fixing surface is defined as a second midpoint, A line extending radially outward from the axis center of the rotation axis and passing through the first midpoint is defined as a first recessed portion center line. A line extending radially outward from the axis center of the rotation axis and passing through the second midpoint is defined as a second recessed portion center line. The angle between the center line of the first magnet and the center line of the second magnet is the oblique polar angle θ, The angle between the center line of the first concave portion and the center line of the second concave portion is the center-to-center angle of the concave portions. The angle between the centers of the concave portions is smaller than the oblique polar angle θ, When L1>L2, The value of L1 / L2 is in the range of 1.0<L1 / L2<1.

6.

6. The permanent magnet synchronous motor according to claim 2, characterized in that: The recess has: a first bottom end, the first bottom end forming a bottom of the recess; a second bottom end, the second bottom end forming the bottom of the recess and spaced apart from the first bottom end; a first inner wall formed between the first recess end and the first bottom end and extending in the radial direction; as well as a second inner wall formed between the second recess end and the second bottom end, The second inner wall has: a vertical surface connected to the second recess end and extending along the radial direction; as well as An inclined surface is connected to the vertical surface and the second bottom end and is inclined relative to the vertical surface and extends linearly.

7. The permanent magnet synchronous motor according to claim 2, characterized in that: The recess has: a first bottom end, the first bottom end forming a bottom of the recess; a second bottom end, the second bottom end forming the bottom of the recess and spaced apart from the first bottom end; a first inner wall formed between the first recess end and the first bottom end and extending in the radial direction, a second inner wall formed between the second recess end and the second bottom end, The second inner wall has a curved surface connected to the second bottom end.

8. The permanent magnet synchronous motor according to claim 3, characterized in that: The recess has: a first inner wall formed between the first recess end and the first bottom end and extending in the radial direction; and a second inner wall formed between the second recess end and the second bottom end, The second inner wall has: a vertical surface connected to the second recess end and extending along the radial direction; as well as An inclined surface is connected to the vertical surface and the second bottom end and is inclined relative to the vertical surface and extends linearly.

9. The permanent magnet synchronous motor according to claim 3, characterized in that: The recess has: a first inner wall formed between the first recess end and the first bottom end and extending in the radial direction; and a second inner wall formed between the second recess end and the second bottom end, The second inner wall has a curved surface connected to the second bottom end.

10. The permanent magnet synchronous motor according to claim 1, characterized in that: The rotor includes a first rotor portion and a second rotor portion adjacent to the first rotor portion in an axial direction in which the rotation shaft extends. The plurality of permanent magnets include a first magnet group disposed on the first rotor portion and a second magnet group disposed on the second rotor portion, The plurality of permanent magnets constituting the first magnet group are respectively first permanent magnets, The plurality of permanent magnets constituting the second magnet group are respectively second permanent magnets, The center position of the stator-facing surface of the first permanent magnet in the circumferential direction coincides with the center position of the stator-facing surface of the second permanent magnet in the circumferential direction in the axial direction. The protrusion of the rotor core has a first protrusion arranged on the first rotor part and a second protrusion arranged on the second rotor part. The first convex portion is engaged with the concave portion of the first permanent magnet, The second convex portion is engaged with the concave portion of the second permanent magnet, In the circumferential direction, the second protrusion is offset from the first protrusion at an oblique polar angle.

11. The permanent magnet synchronous motor according to claim 1, characterized in that: The rotor includes a first rotor portion and a second rotor portion adjacent to the first rotor portion in an axial direction in which the rotation shaft extends. The plurality of permanent magnets include a first magnet group disposed on the first rotor portion and a second magnet group disposed on the second rotor portion, The plurality of permanent magnets constituting the first magnet group are respectively first permanent magnets, The plurality of permanent magnets constituting the second magnet group are respectively second permanent magnets, The center position of the stator-facing surface of the first permanent magnet in the circumferential direction does not coincide with the center position of the stator-facing surface of the second permanent magnet in the circumferential direction in the axial direction. The protrusion of the rotor core extends continuously from the first rotor part to the second rotor part, The convex portion is engaged with the concave portion of the first permanent magnet and the concave portion of the second permanent magnet, In the circumferential direction, a central position of the stator-facing surface of the first permanent magnet in the circumferential direction is offset from a central position of the stator-facing surface of the second permanent magnet in the circumferential direction by an oblique polar angle.

Images