Permanent magnet motor

Abstract

A technique capable of preventing demagnetization of a permanent magnet and reducing the thickness of the permanent magnet in a 6-pole 36-slot permanent magnet motor is disclosed. The motor is composed of a stator having 36 teeth (slots) and a rotor having 6 main magnetic poles. The motor is configured to satisfy [83 mm ≤ L ≤ 101 mm] (L: diameter of the rotor), [0.5 mm ≤ G ≤ 0.6 mm] (G: distance of a gap between a first outer peripheral surface portion and an inner peripheral surface of the stator), [0.36 × (L + 2 × G) × π / 36 < Wt < 0.42 × (L + 2 × G) × π / 36] (Wt: width of the teeth), [14.9 degrees ≤ K1 ≤ 15.7 degrees] (K1: opening angle (mechanical angle) of the first outer peripheral surface portion), [0.6 mm ≤ H ≤ 0.96 mm] (H: interval along the radial direction between the first outer peripheral surface portion and a second outer peripheral surface portion). The thickness (Wp) of the permanent magnet is set to [2 × G × 1.3 < Wp < 2 × G × 2.0].

Description

Technical Field

[0001] This application relates to a permanent magnet motor in which permanent magnets are inserted into magnet insertion holes formed in the rotor, and particularly to a technique for reducing the thickness of the permanent magnets. Background Technology

[0002] Permanent magnet motors, used as compressor drive motors, vehicle drive motors, and on-board equipment drive motors, employ a stator and a rotor equipped with permanent magnets. The stator has a yoke extending circumferentially and multiple teeth extending radially inward from the yoke. These teeth are arranged circumferentially apart. Additionally, the stator has multiple slots formed by two adjacent circumferentially arranged teeth. The rotor is rotatably disposed within the inner space of the stator. In the rotor, main magnetic poles and auxiliary magnetic poles are arranged alternately circumferentially. Magnet insertion holes are formed in the main magnetic poles, and permanent magnets are inserted into these holes.

[0003] Ferrite magnets and rare-earth magnets are used as permanent magnets. Rare-earth magnets are more expensive than ferrite magnets, but they have higher remanent flux density and coercivity. For example, neodymium magnets containing neodymium (Nd) and iron (Fe) are used as rare-earth magnets. The coercivity of neodymium magnets decreases with increasing ambient temperature. Therefore, neodymium magnets containing dysprosium (Dy) and terbium (Tb) diffused from the outer surface (grain boundary diffusion) are also used.

[0004] As a permanent magnet motor, a 6-pole, 36-slot permanent magnet motor is used. The 6-pole, 36-slot permanent magnet motor consists of a rotor with 6 main magnetic poles (a rotor with 6 poles or 3 pole pairs (= pole number / 2)) and a stator with 36 teeth (or 36 slots). For example, a 6-pole, 36-slot permanent magnet motor is disclosed in Patent Document 1 (Japanese Patent Application Publication No. 2021-164325).

[0005] The torque Tr of such a permanent magnet motor is expressed by the following formula when the magnetic flux generated by the permanent magnet is set as Φ, the q-axis current is set as Iq, the d-axis current is set as Id, the q-axis inductance is set as Lq, the d-axis inductance is set as Ld, and the number of pole pairs of the rotor is set as P (=number of poles / 2).

[0006] Tr=P[Φ×Iq+(Ld-Lq)×Id×Iq]

[0007] The first term on the right side of the above equation represents the magnetic torque generated by the magnetic flux Φ of the permanent magnet, and the second term represents the reluctance torque generated by the salient polarity (Ld-Lq) of the rotor.

[0008] Typically, the q-axis inductance Lq is greater than the d-axis inductance Ld. That is, (Ld - Lq) is negative. In this case, when a negative d-axis current Id flows, the reluctance torque becomes positive. Therefore, as a method to increase the sum of the magnetic torque and the reluctance torque, i.e., the torque Tr, the d-axis current Id is controlled to be negative. As a method to control the d-axis current to be negative, a method of advancing the phase angle of the current flowing through the stator winding is usually used (called "lead angle control" or "field weakening control").

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2021-164325 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In the permanent magnet motor disclosed in Patent Document 1, the torque Tr can be increased by performing lead angle control.

[0014] On the other hand, permanent magnets can sometimes demagnetize due to the magnetic flux flowing into the rotor through the stator teeth. When permanent magnets demagnetize, the magnetic flux density of the permanent magnets decreases, and the characteristics of the permanent magnet motor change (e.g., torque decreases).

[0015] Therefore, it is necessary to prevent demagnetization of permanent magnets ("improving demagnetization resistance"). In existing permanent magnet motors, the following methods are used to prevent demagnetization of permanent magnets. The first method is to increase the thickness of the permanent magnet (using a thicker permanent magnet). By increasing the thickness of the permanent magnet, the coercivity increases, and thus the demagnetization resistance increases. The second method is to use a permanent magnet with higher coercivity. For example, in the case of using neodymium magnets, neodymium magnets with dysprosium (Dy) and terbium (Tb) diffused from the outer peripheral surface (grain boundary diffusion) are used. The third method is to use a high-speed current cut-off switch that can quickly cut off the current when it is necessary to allow a current that is highly likely to cause demagnetization of the permanent magnet to flow.

[0016] However, in the first method, the amount of permanent magnets used increases, thus raising the cost of permanent magnets. Furthermore, the second method requires expensive permanent magnets. Additionally, the third method requires expensive high-speed current-cutting switches. Therefore, using methods one through three increases the cost of the permanent magnet motor.

[0017] Therefore, the inventors of this invention have researched a technique that can prevent permanent magnets from demagnetizing without increasing the thickness of the permanent magnet.

[0018] exist Figure 14 , Figure 15The image shows a permanent magnet motor 400 disclosed in Patent Document 1. The permanent magnet motor 400 consists of a stator 410 and a rotor 420.

[0019] The stator 410 has a magnetic yoke 411 and 36 teeth 412. The teeth 412 have a tooth base 413 and a tooth tip 414. The tooth base 413 has a tooth tip face 415 on the tip side (radially inward).

[0020] In the rotor 420, six main magnetic poles and auxiliary magnetic poles are arranged alternately in the circumferential direction. Magnet insertion holes 431 and 432 are formed on the main magnetic poles for inserting permanent magnets 441 and 442. The outer circumferential surface of the rotor 420 is formed by a first outer circumferential surface portion 420a, a second outer circumferential surface portion 420b, a connecting portion 420c, and a connecting portion 420d. The first outer circumferential surface portion 420a intersects the d-axis and is formed as an arc with a radius R1 centered on the rotation center. The second outer circumferential surface portion 420b intersects the q-axis and is formed as an arc with a radius R2 (R2 < R1) centered on the rotation center and a radius smaller than R1. The connecting portion 420c connects the connecting part M1 on the other side (counterclockwise) of the first outer circumferential surface portion 420a to the second outer circumferential surface portion 420b. The connecting portion 420d connects the connecting portion M2 on the circumferential side (clockwise direction) of the first outer peripheral surface portion 420a to the second outer peripheral surface portion 420b. The second outer peripheral surface portion 420b, the connecting portion 420c, and the connecting portion 420d form a notch formed by cutting off the outer periphery of a circle with a diameter L.

[0021] exist Figure 14 In the configuration shown, teeth J2 to J4 of teeth J1 to J6 are positioned opposite the first outer peripheral surface portion 420a of the main magnetic pole [A]. Figure 14 In the middle, the connecting part M1 (the line m1 passing through the center point and the connecting part M1) is located on the circumferential side (clockwise direction) of the gear J2, on the other circumferential side (counterclockwise direction). Additionally, the connecting part M2 (the line m2 passing through the center point and the connecting part M2) is located on the circumferential side (clockwise direction) of the gear J4, on the other circumferential side (counterclockwise direction), on the other circumferential side (clockwise direction).

[0022] exist Figure 14 In the illustrated state, magnetic flux flows from the N-pole teeth J3 and J4 through the first outer peripheral surface portion 420a toward the S-pole of the permanent magnet 442. This magnetic flux is more abundant due to the gap g between the first outer peripheral surface portion 420a and the tooth tip surface 415. Conversely, magnetic flux flows from the N-pole teeth J5 and J6 through the second outer peripheral surface portion 420b toward the S-pole of the permanent magnet 442. This magnetic flux is less abundant due to the gap g and the notch.

[0023] Figure 15 Indicates from Figure 14 The state shown is a state in which the body has rotated 5 degrees (=[360 degrees / 36] / 2) to one side of the circumference (clockwise).

[0024] exist Figure 15 In the shown configuration, teeth J2 to J5 of teeth J1 to J6 are positioned opposite the first outer peripheral surface portion 420a of the main magnetic pole [A]. Figure 15 In the middle, the connecting part M1 (the line m1 passing through the center point and the connecting part M1) is located on the other side of the circumferential direction (counterclockwise) of the gear J3, on the side wall JA (the extension line ja of the side wall JA), on the other side of the circumferential direction (counterclockwise). Additionally, the connecting part M2 (the line m2 passing through the center point and the connecting part M2) is located on the other side of the circumferential direction (clockwise) of the gear J4, on the side wall JB (the extension line jb of the side wall JB), on the other side of the circumferential direction (clockwise).

[0025] exist Figure 15 In the illustrated state, magnetic flux flows from the teeth J3, J4, and J5 of the N pole towards the S pole of the permanent magnet 442 via the first outer peripheral surface portion 420a. This magnetic flux is increased due to passing through the gap g. Conversely, magnetic flux flows from the tooth J6 of the N pole towards the S pole of the permanent magnet 442 via the second outer peripheral surface portion 420b. This magnetic flux is reduced due to passing through the gap g and the notch.

[0026] like Figure 14 , Figure 15 As shown, in the existing permanent magnet motor 400, three teeth 412 and two teeth 412 are alternately arranged at positions opposite to the first outer peripheral surface portion 420a of the rotor 420.

[0027] Moreover, for Figure 14 , Figure 15 The analysis of the observed state revealed that, in existing permanent magnet motors, the increased magnetic flux density due to a large influx of magnetic flux into the rotor's permanent magnets from multiple teeth is one of the causes of permanent magnet demagnetization. In other words, it was discovered that preventing a large influx of magnetic flux into the rotor's permanent magnets from the teeth can prevent permanent magnet demagnetization.

[0028] The purpose of this invention is to provide a technique that can prevent demagnetization of permanent magnets and reduce the thickness of permanent magnets in a 6-pole 36-slot permanent magnet motor.

[0029] Solution for solving the problem

[0030] The first invention relates to a permanent magnet motor having a stator and a rotor.

[0031] The stator has a plurality of teeth arranged circumferentially, a plurality of slots formed by teeth adjacent to each other in the circumferential direction, stator windings wound around the teeth, and an inner circumferential surface of the stator forming the inner space of the stator.

[0032] The rotor is rotatably arranged within the space inside the stator. In the rotor, main magnetic poles and auxiliary magnetic poles are arranged alternately along the circumference, and permanent magnets are inserted into the magnet insertion holes formed in the main magnetic poles.

[0033] In this invention, the stator winding is wound around multiple teeth in a distributed winding manner. Furthermore, there are 6 main magnetic poles and 36 teeth. That is, it is configured as a 6-pole, 36-slot permanent magnet motor.

[0034] The outer circumferential surface of the rotor is formed by multiple first outer circumferential surface portions, multiple second outer circumferential surface portions, and multiple connecting portions. The first outer circumferential surface portions intersect the d-axis, forming an arc shape with radius R1 centered at the rotation center. The second outer circumferential surface portions intersect the q-axis, forming an arc shape with radius R2 centered at the rotation center. Radius R2 is set to be smaller than radius R1 (R2 < R1). The connecting portions connect the first and second outer circumferential surface portions.

[0035] Furthermore, the rotor diameter L is set to satisfy [83mm ≤ L ≤ 101mm]. Additionally, the distance G of the gap g between the first outer circumferential surface and the stator inner circumferential surface is set to satisfy [0.5mm ≤ G ≤ 0.6mm]. Furthermore, the tooth width Wt is set to satisfy [0.36 × (L + 2 × G) × π / 36 < Wt < 0.42 × (L + 2 × G) × π / 36]. Furthermore, the opening angle K1 (mechanical angle) of the first outer circumferential surface relative to the rotation center is set to satisfy [14.9 degrees ≤ K1 ≤ 15.7 degrees]. Furthermore, the radial spacing H between the first and second outer circumferential surface portions is set to satisfy [0.6mm ≤ H ≤ 0.96mm].

[0036] In this invention, teeth are used to limit the inflow of magnetic flux into the permanent magnet that could cause it to demagnetize. Therefore, the thickness of the permanent magnet can be reduced.

[0037] In the first invention, it is possible to prevent the permanent magnet from demagnetizing and to reduce the thickness of the permanent magnet.

[0038] In different technical solutions of the first invention, a permanent magnet with a residual magnetic flux density in the range of 1.34 Tesla to 1.52 Tesla and a coercivity in the range of 1550 kA / m to 2100 kA / m is used as the permanent magnet.

[0039] In different technical solutions of the first invention, the stator and rotor are made of electromagnetic steel plates whose magnetic flux density changes from the linear region to the nonlinear region in the range of 1.75 Tesla to 1.9 Tesla.

[0040] The second invention relates to a compressor. The compressor of the second invention includes a compression mechanism and an electric motor for driving the compression mechanism. Moreover, any of the aforementioned permanent magnet electric motors is used as the electric motor.

[0041] The second invention has the same effect as the permanent magnet motor described above.

[0042] The effects of the invention

[0043] By using the permanent magnet motor of the present invention, it is possible to prevent demagnetization of the permanent magnet in a 6-pole 36-slot permanent magnet motor and to reduce the thickness of the permanent magnet. Attached Figure Description

[0044] Figure 1 This is a cross-sectional view of the permanent magnet motor according to the first embodiment.

[0045] Figure 2 yes Figure 1 Enlarged view of the main parts.

[0046] Figure 3 It is a graph showing the relationship between the magnet thickness Wp and the magnetic flux density of the permanent magnet, analyzed by changing the current lead angle under the first current flow state.

[0047] Figure 4 It is represented in different ways Figure 3 The graph shows the relationship between the magnet thickness Wp and the magnetic flux density of the permanent magnet.

[0048] Figure 5 It is a graph showing the relationship between the magnet thickness Wp and the magnetic flux density of the permanent magnet, analyzed by changing the current lead angle under the second current flow state.

[0049] Figure 6 It is represented in different ways Figure 5 The graph shows the relationship between the magnet thickness Wp and the magnetic flux density of the permanent magnet.

[0050] Figure 7 It is a graph showing the relationship between the opening angle K1 of the first outer circumferential surface and the cogging torque.

[0051] Figure 8 This is a graph showing the relationship between the distance G between the first outer circumferential surface and the inner circumferential surface of the stator and the efficiency.

[0052] Figure 9 It is a graph showing the relationship between the depth of the notch (the interval between the first outer peripheral surface portion and the second outer peripheral surface portion) H and the magnetic flux density of the magnetic flux flowing through the tooth.

[0053] Figure 10 This is a diagram illustrating the magnetic flux of the permanent magnet motor according to the first embodiment.

[0054] Figure 11 This is a diagram illustrating the magnetic flux of the permanent magnet motor according to the first embodiment.

[0055] Figure 12 This is a cross-sectional view of the rotor of the permanent magnet motor constituting the second embodiment.

[0056] Figure 13 This is a cross-sectional view of the rotor of the permanent magnet motor constituting the third embodiment.

[0057] Figure 14 This is a diagram illustrating the magnetic flux of an existing permanent magnet motor.

[0058] Figure 15 This is a diagram illustrating the magnetic flux of an existing permanent magnet motor.

[0059] Explanation of reference numerals in the attached figures

[0060] 100, 400, Permanent magnet motor; 110, 410, Stator; 111, 411, Yoke; 112, 412, Tooth; 113, 413, Tooth base; 114, 414, Tooth tip; 115, 415, Tooth tip face (stator inner circumferential surface); 116, 416, Slot; 120, 220, 320, 420, Rotor; 120a, 220a, 320a, 420a, First outer circumferential surface portion; 120b, 220b, 320b, 420b, Second outer circumferential surface portion; 120c, 120d, 220c, 220d, 320c, 320d, 420c, 420d, Connecting portion; 121, 221, 321, 421, Inner circumferential surface; 122, 222, 32 2. Inner space; 125. Central bridge section; 126, 127. Outer peripheral bridge section; 131, 132, 231, 331, 332, 333, 431, 432. Magnet insertion holes; 131a, 132a. Inner peripheral sidewall section; 131b, 132b. Outer peripheral sidewall section; 131c, 132c. Inner peripheral endwall section; 131d, 132d 131e, 132e, end wall portion; 141, 142, 241, 341, 342, 342, 441, 442, permanent magnet; 141a, 142a, inner peripheral outer wall surface; 141b, 142b, outer peripheral outer wall surface; 141c, 142c, inner peripheral end wall surface; 141d, 142d, outer peripheral end wall surface. Detailed Implementation

[0061] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0062] Furthermore, in this specification, the term "axial" refers to the direction of rotation of the rotor through its rotation center O (refer to...) when the rotor is configured to rotate relative to the stator. Figure 1 The direction of extension of the rotation center line. One side along the axis is called the "axial side" or "axial first side", and the other side along the axis is called the "axial second side" or "axial third side".

[0063] Furthermore, the term "circumferential direction" refers to the circumferential direction centered on the rotor's rotation center O when viewed from one axial side (or the other axial side) with the rotor configured to rotate relative to the stator. Moreover, when viewed from one axial side (refer to...) Figure 1 The clockwise direction (arrow Z direction) is called the "circumferential side" or "circumferential first side", and the counterclockwise direction (the side opposite to arrow Z direction) is called the "circumferential other side" or "circumferential second side".

[0064] Furthermore, the term "radial" refers to the direction of extension of a line passing through the rotor's rotation center O when viewed from one axial side (or the other axial side) with the rotor configured to rotate relative to the stator. The side opposite to the rotation center O is called the "radial inner side," and the side opposite to the rotation center O is called the "radial outer side."

[0065] Reference Figure 1 , Figure 2 The first embodiment 100 of the permanent magnet motor of the present invention will be described. Figure 1 This is a cross-sectional view of the permanent magnet motor 100 according to the first embodiment. Figure 2 yes Figure 1 Enlarged view of the main parts.

[0066] The permanent magnet motor 100 consists of a stator 110 and a rotor 120.

[0067] The stator 110 is composed of a cylindrical stator core formed by stacking multiple plate-shaped electromagnetic steel plates.

[0068] The stator 110 has a circumferentially extending yoke 111 and a plurality of teeth 112 extending radially inward from the yoke 111. The plurality of teeth 112 are arranged separately in the circumferential direction.

[0069] The tooth 112 has a tooth base 113 and a tooth tip 114. The tooth base 113 extends radially inward from the yoke 111. The tooth tip 114 is connected to the radially inward side of the tooth base 113 and extends circumferentially. A tooth tip surface 115 is formed on the radially inward side of the tooth tip 114. The tooth tip surface 115 is formed in an arc shape centered at the rotation center O. The tooth tip surface 115 of each tooth 112 forms a stator inner space inside the stator 110.

[0070] The tooth tip surface 115 corresponds to the "stator inner circumferential surface" of the present invention.

[0071] A groove 116 is formed by two adjacent teeth 112 in the circumferential direction.

[0072] The permanent magnet motor 100 of this embodiment has 36 teeth 112 (36 slots 116). That is, the permanent magnet motor 100 has a stator 110 with 36 slots.

[0073] Furthermore, the stator winding (not shown) is wound in a distributed winding manner on each tooth 112 (more specifically, the tooth base 113).

[0074] Various methods can be used as a method of winding stator windings in a distributed winding manner.

[0075] Compared to winding the stator winding in a concentrated manner, winding the stator winding in a distributed manner results in more copper losses, but can achieve higher output and reduce vibration and noise.

[0076] The rotor 120 is composed of a rotor core formed by stacking multiple plate-shaped electromagnetic steel plates.

[0077] The rotor 120 is rotatably disposed within the stator inner space formed by the stator inner circumferential surface (tooth tip surface 115). In this embodiment, the rotor 120 is disposed such that a gap (air gap) g is maintained between the first outer circumferential surface portion 120a (see below) and the tooth tip surface 115 (stator inner circumferential surface).

[0078] The rotor 120 has an inner space 122 formed by the inner circumferential surface 121 of the rotor. A rotating shaft is inserted, for example, pressed into the inner space 122 of the rotor.

[0079] The rotor 120 has main magnetic poles [A] to [F] and auxiliary magnetic poles [AB] to [FA]. The main magnetic poles [A] to [F] and the auxiliary magnetic poles [AB] to [FA] are arranged alternately along the circumferential direction.

[0080] The permanent magnet motor 100 of this embodiment has a rotor 120, which has 6 main magnetic poles. That is, the permanent magnet motor 100 has a 6-pole rotor 120. In addition, the number of poles of the rotor is sometimes expressed as the number of pole pairs P (=number of poles / 2).

[0081] The permanent magnet motor 100 with a stator 110 having 36 slots and a rotor 120 having 6 poles (pole pairs P = 3) is called a 6-pole 36-slot permanent magnet motor 100.

[0082] One or more magnet insertion holes are formed at each of the main magnetic poles [A] to [F]. Furthermore, a permanent magnet is inserted into each magnet insertion hole.

[0083] The regions of the main magnetic poles [A] to [F] and the d-axis of the main magnetic poles [A] to [F] are defined by permanent magnets inserted into the insertion holes of each magnet, and the regions of the auxiliary magnetic poles [AB] to [FA] and the q-axis of the auxiliary magnetic poles [AB] to [FA] are also defined.

[0084] Furthermore, the d-axis is defined as the line connecting the rotation center O with the circumferential center of the region of the main magnetic poles [A] to [F]. Additionally, the q-axis is defined as the line connecting the rotation center O with the circumferential center of the region of the auxiliary magnetic poles [AB] to [FA].

[0085] In this embodiment, a first magnet insertion hole 131 and a second magnet insertion hole 132 are formed on each of the main magnetic poles [A] to [F]. Furthermore, the first magnet insertion hole 131 and the second magnet insertion hole 132 are arranged on both sides of the d-axis in a letter V shape, protruding on the side of the rotation center O (opening on the side opposite to the side where the rotation center O is located).

[0086] The first magnet insertion hole 131 is formed by an inner peripheral side wall portion 131a, an outer peripheral side wall portion 131b, an inner peripheral side end wall portion 131c, an outer peripheral side end wall portion 131d, and an end wall portion 131e.

[0087] The second magnet insertion hole 132 is formed by an inner peripheral sidewall portion 132a, an outer peripheral sidewall portion 132b, an inner peripheral endwall portion 132c, an outer peripheral endwall portion 132d, and an endwall portion 132e.

[0088] A central bridge portion 125 extending parallel to (including "generally parallel") the d-axis is formed between the inner peripheral end wall portion 131c of the first magnet insertion hole 131 and the inner peripheral end wall portion 132c of the second magnet insertion hole 132. An outer peripheral bridge portion 126 extending circumferentially is formed between the outer peripheral end wall portion 131d of the first magnet insertion hole 131 and the outer peripheral surface of the rotor 120 (the second outer peripheral surface portion 120b described later). An outer peripheral bridge portion 127 extending circumferentially is formed between the outer peripheral end wall portion 132d of the second magnet insertion hole 132 and the outer peripheral surface of the rotor 120 (the second outer peripheral surface portion 120b described later).

[0089] In addition, a magnetic flux path extending parallel to (including "generally parallel") the q-axis is formed between the end wall portion 131e of the first magnet insertion hole 131 of one main magnetic pole and the end wall portion 132e of the second magnet insertion hole 132 of the other main magnetic pole.

[0090] Permanent magnets are inserted into the first magnet insertion hole 131 and the second magnet insertion hole 132. In this embodiment, a first permanent magnet 141 extending in a straight line is inserted into the first magnet insertion hole 131, and a second permanent magnet 142 extending in a straight line is inserted into the second magnet insertion hole 132.

[0091] The first permanent magnet 141 has a rectangular cross-section formed by the inner peripheral outer wall surface 141a, the outer peripheral outer wall surface 141b, the inner peripheral end wall surface 141c, and the outer peripheral end wall surface 141d.

[0092] The second permanent magnet 142 has a rectangular cross-section formed by the inner peripheral outer wall surface 142a, the outer peripheral outer wall surface 142b, the inner peripheral end wall surface 142c, and the outer peripheral end wall surface 142d.

[0093] With the first permanent magnet 141 (the second permanent magnet 142) inserted into the first magnet insertion hole 131 (the second magnet insertion hole 132), the configuration is such that gaps are formed on the side walls at both ends.

[0094] Various permanent magnets can be used as the first permanent magnet 141 and the second permanent magnet 142. In this embodiment, neodymium magnets are used. In addition, neodymium magnets with dysprosium (Dy) and terbium (Tb) diffused (grain boundary diffused) are sometimes used.

[0095] The outer peripheral surface of the rotor 120 (rotor outer peripheral surface) is formed by a plurality of first outer peripheral surface portions 120a, a plurality of second outer peripheral surface portions 120b, a plurality of connecting portions 120c and a plurality of connecting portions 120d.

[0096] The first outer peripheral surface portion 120a intersects the d-axis. The second outer peripheral surface portion 120b intersects the q-axis and is formed at a position radially inward compared to the first outer peripheral surface portion 120a. Connecting portions 120c and 120d connect the first outer peripheral surface portion 120a and the second outer peripheral surface portion 120b. The first outer peripheral surface portion 120a has a connecting portion M1 on the other side of the circumference that connects to the connecting portion 120c, and a connecting portion M2 on one side of the circumference that connects to the connecting portion 120d.

[0097] The second outer peripheral surface portion 120b, the connecting portion 120c, and the connecting portion 120d form a notch, which is formed by removing the outer periphery of a circle (radius R1) having an outer peripheral surface that extends from the first outer peripheral surface portion 120a. The second outer peripheral surface portion 120b, the connecting portion 120c, and the connecting portion 120d form the bottom surface, one circumferential side (clockwise side), and the other circumferential side (counterclockwise side) of the notch.

[0098] In this embodiment, the first outer peripheral surface portion 120a has an arc shape with a radius R1 (in mm) centered at the rotation center O. The radius R1 is (1 / 2) of the diameter (outer diameter) L of the rotor 120. The second outer peripheral surface portion 120b has an arc shape with a radius R2 (in mm) centered at the rotation center O, which is smaller than the radius R1 (R2 < R1). Furthermore, the connecting portions 120c and 120d extend in a straight line parallel to (including "generally parallel") the d-axis. The shapes of the connecting portions 120c and 120d can also be formed to extend parallel to (including "generally parallel") a line passing through the rotation center O and extending radially. However, the shapes of the first outer peripheral surface portion 120a, the second outer peripheral surface portion 120b, the connecting portion 120c, and the connecting portion 120d are not limited to these.

[0099] Next, the structure of the permanent magnet motor 100 of this embodiment that prevents the permanent magnets 141 and 142 from demagnetizing and reduces the thickness of the permanent magnets 141 and 142 will be described.

[0100] Furthermore, in this embodiment, as described above, the stator 110 has 36 slots 116 (teeth 112), and the rotor 120 has 6 main magnetic poles A to F. That is, the permanent magnet motor 100 is configured as a 6-pole, 36-slot permanent magnet motor.

[0101] like Figure 2 As shown, the d-axis flux and the q-axis flux flow in the rotor 120.

[0102] The d-axis flux is the flux flowing between adjacent main magnetic poles. For example, it flows into rotor 120 from the d-axis side of main magnetic pole A, and from the circumferential side relative to main magnetic pole A. Figure 2 The magnetic flux flowing out from the d-axis side of the adjacent main magnetic pole B (clockwise direction) is the d-axis inductance Ld, which is determined by the d-axis magnetic flux.

[0103] The q-axis flux is the flux flowing between adjacent auxiliary magnetic poles. For example, from the main magnetic pole A and on the other side circumferentially relative to the main magnetic pole A (in... Figure 2 The auxiliary magnetic pole FA side between adjacent main magnetic poles F (in the counterclockwise direction) flows into the rotor 120 and flows out from the auxiliary magnetic pole AB side between the main magnetic pole A and the main magnetic pole B adjacent to the main magnetic pole A on the circumferential side.

[0104] The q-axis inductance Lq is determined by the q-axis magnetic flux.

[0105] Next, the following describes the structure used to prevent demagnetization of the permanent magnet and to reduce the thickness of the permanent magnet.

[0106] In existing permanent magnet motors, the d-axis magnetic flux flowing through the teeth is set to be unsaturated, thus exhibiting a current characteristic where the d-axis inductance Ld remains approximately unchanged even as the current increases or decreases.

[0107] In contrast, in this embodiment, the d-axis magnetic flux flowing through the teeth is set to saturation, thereby having a current characteristic in which the d-axis inductance Ld decreases in regions with large currents.

[0108] Furthermore, as the current increases, the magnetic flux density of the tooth saturates (magnetic saturation), thus reducing the q-axis inductance Lq.

[0109] That is, even if the d-axis inductance Ld decreases, the absolute value of [Ld-Lq] will not decrease. Therefore, the reluctance torque can be guaranteed.

[0110] The diameter (outer diameter) L of rotor 120 is set in the range of 83mm to 101mm (83mm≤L≤101mm).

[0111] The first outer peripheral surface portion 120a is the portion of the outer peripheral surface obtained by removing the notch formed by the second outer peripheral surface portion 120b, the connecting portion 120c, and the connecting portion 120d from a circle with a diameter L. When the diameter L of the rotor 120 is less than 83 mm, the circumferential length of the first outer peripheral surface portion 120a becomes shorter, making it impossible to ensure a sufficient path for magnetic flux. When a sufficient path for magnetic flux cannot be ensured, the magnetic flux decreases, and copper losses increase. Moreover, with the increase in copper losses, efficiency decreases.

[0112] Reference Figure 7 The opening angle K1 (mechanical angle) of the first outer peripheral surface portion 120a relative to the rotation center O will be explained.

[0113] Figure 7 The results obtained by measuring the opening angle K1 of the first outer circumferential surface portion 120a and the cogging torque are presented as a curve. Figure 7 In the diagram, the horizontal axis represents the opening angle K1 (degrees), and the vertical axis represents the cogging torque (N·m).

[0114] exist Figure 7 In the curve diagram shown, the cogging torque is larger in the regions where the opening angle K1 is less than 14.9 degrees and greater than 15.7 degrees.

[0115] Depend on Figure 7 As shown in the graph, setting the opening angle K1 within the range of 14.9 degrees to 15.7 degrees (14.9 degrees ≤ K1 ≤ 15.7 degrees) can reduce the cogging torque.

[0116] By reducing cogging torque, the generation of noise and vibration can be suppressed. Furthermore, by reducing cogging torque, the inflow and outflow of magnetic flux that does not contribute to torque generation can be reduced. In this case, iron losses caused by the inflow and outflow of magnetic flux that does not contribute to torque can be reduced.

[0117] Reference Figure 8 The distance G of the gap g between the first outer peripheral surface portion 120a of the rotor 120 and the inner peripheral surface (tooth tip surface 115) of the stator will be explained.

[0118] Figure 8 The results are presented as a graph showing the relationship between the distance G of the measured gap g and the efficiency of the permanent magnet motor 100. Figure 8 In the figure, the horizontal axis represents the distance G (mm) of the gap g, and the vertical axis represents the efficiency (%).

[0119] exist Figure 8 In the curve shown, efficiency decreases in regions where the distance from G is less than 0.5 mm and greater than 0.6 mm.

[0120] When the distance G is less than 0.5 mm, the higher harmonic components in the electromotive force (induced electromotive force) increase. Furthermore, with the increase in higher harmonic components in the electromotive force, higher harmonic iron losses increase, and efficiency decreases. Additionally, when the distance G is less than 0.5 mm, noise and vibration increase.

[0121] When the distance G is greater than 0.6 mm, the fundamental component in the electromotive force decreases. Moreover, when the fundamental component in the electromotive force decreases, copper losses increase and efficiency decreases.

[0122] Depend on Figure 8 As shown in the graph, efficiency can be improved by setting the distance G of the gap g within the range of 0.5mm to 0.6mm (0.5mm≤G≤0.6mm).

[0123] Reference Figure 9 The radial spacing (depth of the notch) H between the first outer peripheral surface portion 120a and the second outer peripheral surface portion 120b will be explained.

[0124] Figure 9 The results are presented as graphs showing the relationship between the depth H of the notch and the magnetic flux density of tooth 112, as well as the relationship between the depth H of the notch and the fundamental component of the electromotive force. Figure 9 In the diagram, the horizontal axis represents the depth H (mm) of the notch, the left vertical axis represents the magnetic flux density (Tesla: T) of tooth 112, and the right vertical axis represents the fundamental component of the electromotive force (Volt: V). Additionally, in... Figure 9 In the figure, the solid line represents the curve of the fundamental component of the electromotive force, and the dashed line represents the curve of the magnetic flux density of the tooth.

[0125] from Figure 9 As shown in the graph, when the depth H of the notch is less than 0.6 mm, the magnetic flux density of tooth 112 decreases. Furthermore, when the depth H of the notch is greater than 0.96 mm, the fundamental component of the electromotive force decreases.

[0126] from Figure 9 As shown in the graph, by setting the depth H of the notch in the range of 0.6 mm to 0.96 mm (0.6 mm ≤ H ≤ 0.96 mm), the magnetic flux density of tooth 112 can be increased, and the fundamental component contained in the electromotive force can be increased.

[0127] In this embodiment, by configuring the tooth 112 to saturate the magnetic flux density (magnetic saturation) when a large current exceeding the operating current flows through it, excessive magnetic flux is prevented from flowing into the permanent magnet.

[0128] With the rotor diameter L, the distance G of the gap g, the opening angle K1 of the first outer peripheral surface portion 120a, and the depth H of the notch set within the aforementioned range, in order to saturate the magnetic flux density of the tooth 112 when an excessive current exceeding the operating current flows through it, the width of the tooth 112 (specifically, the width of the tooth base 113) Wt needs to be set within the range of [0.36×(L+2×G)×π / 36] to [0.42×(L+2×G)×π / 36]. That is, it needs to be set to satisfy [0.36×(L+2×G)×π / 36<Wt<0.42×(L+2×G)×π / 36].

[0129] In this case, the magnet thickness Wp of permanent magnets 141 and 142 can be set in the range of [2×G×1.3] to [2×G×2.0] (2×G×1.3<Wp<2×G×2.0).

[0130] Furthermore, in the existing permanent magnet motor 400, when the diameter L of the rotor 420, the distance G of the gap g, and the depth H of the notch are set in the same way as in the permanent magnet motor 100 of this embodiment, in order to prevent demagnetization, the thickness Wp of the permanent magnets 441 and 442 needs to be set in the range of [2×G×1.8] to [2×G×2.8] (2×G×1.8<Wp<2×G×2.8).

[0131] Next, refer to Figures 3-6 The relationship between the thickness (magnet thickness) of permanent magnets 141 and 142 and the magnetic flux density of tooth 112 is explained.

[0132] Figures 3-6The results of the analysis of the relationship between the magnet thickness (mm) and the magnetic flux density (Tesla) of permanent magnets 141 and 142 by changing the energizing lead angle under the condition that a predetermined current flows through the stator winding are presented as a curve.

[0133] The magnetic flux density of the permanent magnet is set to the average magnetic flux density obtained by averaging the magnetic flux densities measured at multiple points along the length of the permanent magnet.

[0134] Furthermore, the magnet thickness can be deduced by analogy from the width of the magnet insertion hole in the thickness direction. Typically, the width of the magnet insertion hole in the thickness direction is set to be approximately 0.03mm to 0.16mm larger than the magnet thickness. Therefore, by analyzing the width of the magnet insertion hole in the thickness direction, the magnet thickness can be deduced from that width.

[0135] exist Figure 3 , Figure 5 In the diagram, the horizontal axis represents the magnet thickness Wp (mm), and the vertical axis represents the magnetic flux density (Tesla). Additionally, in... Figure 4 , Figure 6 In the figure, the horizontal axis represents the magnet thickness Wp (mm), and the vertical axis represents the magnetic flux density (%).

[0136] Figure 3 , Figure 4 It is a graph showing a current value of 2A.

[0137] in addition, Figure 5 , Figure 6 It is a graph showing a current value of 4A.

[0138] In addition, Figure 3 , Figure 5 In this context, magnetic flux density is expressed as an analytical value. Additionally, in... Figure 4 , Figure 6 In this context, the magnetic flux density is represented by the standardized value after setting the flux density at a current-lead angle of 0 degrees to 100%.

[0139] according to Figures 3-6 When the magnet thickness Wp is less than 1.7 mm, the curve bends non-linearly.

[0140] For example, in Figure 4 In the experiment, with a magnet thickness Wp of 1.7 mm, the magnetic flux density (%) at a current-carrying lead angle of 20 degrees decreased to 98.5%. As the magnetic flux density decreases, the magnetic flux quantity decreases. When the magnetic flux quantity decreases, a higher rotational speed can be achieved. That is, the rotational speed with a magnet thickness Wp of 1.7 mm and a current-carrying lead angle of 20 degrees is approximately equal to the rotational speed with a magnet thickness Wp of 2.5 mm and a current-carrying lead angle of 30 degrees.

[0141] In this case, operation can be performed with a smaller energizing lead angle. When operating with a smaller energizing lead angle, the reluctance torque decreases. As a result, iron losses caused by reluctance torque can be reduced, and efficiency is improved. Furthermore, the thickness of the permanent magnet can be reduced, thus reducing the cost of the permanent magnet.

[0142] The width of tooth 112 (specifically, the minimum width of tooth base 113) Wt is set to satisfy [0.36 × (stator inner circumference / 36) < Wt < 0.42 × (stator inner circumference / 36)]. The stator inner circumference (mm) is represented by [stator inner circumference = (rotor 120 diameter L + distance 2G) × π].

[0143] When the width Wt of tooth 112 is less than [0.36 × (stator inner circumference / 36)], there is not enough magnetic flux flowing from tooth 112 to rotor 120. As a result, copper losses increase and efficiency decreases.

[0144] When the width Wt of tooth 112 is greater than [0.42 × (stator inner circumference / 36)], sufficient magnetic flux flows between tooth 112 and rotor 120, and the d-axis magnetic flux is not saturated. In this case, the d-axis inductance Ld exhibits the same current characteristics as existing permanent magnet motors.

[0145] Figure 10 , Figure 11 This indicates the flow of magnetic flux in the permanent magnet motor 100 of this embodiment.

[0146] exist Figure 10 In the illustrated configuration, tooth J2 of teeth J1 to J5 is positioned opposite the first outer peripheral surface portion 120a of the main magnetic pole [A]. Figure 10 In the middle, the connecting part M1 (the line m1 passing through the center point O and the connecting part M1) is located on the circumferential side (clockwise direction) of the gear J1, on the side wall JB (the extension line jb of the side wall JB), on the circumferential side (clockwise direction). Meanwhile, the connecting part M2 (the line m2 passing through the center point O and the connecting part M2) is located on the other circumferential side (counterclockwise direction) of the gear J3, on the other circumferential side (counterclockwise direction), on the side wall JA (the extension line ja of the side wall JA), on the other circumferential side (counterclockwise direction).

[0147] exist Figure 10 In the illustrated state, magnetic flux flows from the N-pole tooth J2 through the first outer peripheral surface portion 120a toward the S-pole of the permanent magnet 142. This magnetic flux is more abundant because it passes through the gap g between the first outer peripheral surface portion 120a and the tooth tip surface 115. Conversely, magnetic flux flows from the N-pole teeth J3 to J5 through the second outer peripheral surface portion 120b toward the S-pole of the permanent magnet 142. This magnetic flux is less abundant because it passes through the gap g and the notch.

[0148] Figure 11 Indicates from Figure 10The state shown is rotated 5 degrees (=[360 degrees / 36] / 2) to one side of the circumference (clockwise).

[0149] exist Figure 11 In the shown configuration, teeth J2 and J3 of teeth J1 to J5 are positioned opposite to the first outer peripheral surface portion 120a of the main magnetic pole [A]. Figure 11 In the middle, the connecting part M1 (the line m1 passing through the center point O and the connecting part M1) is located on the other side of the circumference of the gear J2 (counterclockwise direction), on the side wall JA (the extension line ja of the side wall JA) near the other side of the circumference (counterclockwise direction). Additionally, the connecting part M2 (the line m2 passing through the center point O and the connecting part M2) is located on the other side of the circumference of the gear J3 (clockwise direction), on the side wall JB (the extension line jb of the side wall JB) near the other side of the circumference (clockwise direction).

[0150] exist Figure 11 In the illustrated state, magnetic flux flows from the N-pole teeth J2 and J3 through the first outer peripheral surface portion 120a toward the S-pole of the permanent magnet 142. This magnetic flux is more abundant because it passes through the gap between the first outer peripheral surface portion 120a and the tooth tip surface 115. Conversely, magnetic flux flows from the N-pole teeth J4 and J5 through the second outer peripheral surface portion 120b toward the S-pole of the permanent magnet 142. This magnetic flux is less abundant because it passes through the gap g and the notch.

[0151] In this embodiment, Figure 11 In the state shown, magnetic flux flows from the two teeth J2 and J3 into the rotor 120 via the first outer peripheral surface portion 120a.

[0152] In this embodiment, the magnetic flux density of teeth J2 and J3 is saturated (magnetic saturation). Therefore, teeth J2 and J3 function as magnetic flux limiters to prevent further magnetic flux flow.

[0153] This prevents demagnetization of permanent magnets 141 and 142 and reduces their thickness. Furthermore, the reduced magnetic flux flowing through the yoke 111 decreases iron losses. It also allows for a reduction in the size of the yoke 111 (and thus the size of the stator 110). Alternatively, it enables the formation of a refrigerant passage with a larger opening area in the stator 110.

[0154] In the existing permanent magnet motor 400, such as Figure 14 , Figure 15 As shown, the configuration is such that four teeth 412 and three teeth 412 are alternately arranged at positions opposite to the first outer peripheral surface portion 420a of the rotor 420.

[0155] In contrast, in the permanent magnet motor 100 of this embodiment, such as Figure 10 , Figure 11As shown, the rotor is configured such that two teeth 112 and one tooth 112 are alternately arranged at a position opposite to the first outer peripheral surface portion 120a of the rotor 120.

[0156] Furthermore, the length of the magnet insertion hole formed on the main magnetic pole is set to maintain the magnetic flux flowing through the tooth 113 when the tooth 112 is saturated.

[0157] For example, the total length of the magnet insertion holes formed on the main magnetic pole is set to be more than 5 times the width Wt of the tooth 112.

[0158] In this embodiment, the length of the magnet insertion holes 131 and 132 formed on the main magnetic pole is Y (refer to...). Figure 2 Therefore, (Y+Y) is set to more than 5 times Wt. For example, Wt is set to 3.1mm and Y is set to 19mm. In this case, it becomes [38mm (=2×19mm) / 3.1mm=12.25 times].

[0159] As permanent magnets 141 and 142, it is preferable to use permanent magnets with a residual magnetic flux density in the range of 1.34 Tesla to 1.52 Tesla and a coercivity in the range of 1550 kA / m to 2100 kA / m.

[0160] Furthermore, as for the electromagnetic steel plates constituting the stator 110 (stator core) and the rotor 120 (rotor core), it is preferable to use electromagnetic steel plates whose magnetic flux density changes from the linear region to the nonlinear region in the range of 1.75 Tesla to 1.9 Tesla.

[0161] In the permanent magnet motor 100 of the first embodiment, a rotor 120 with a letter V-shaped arrangement of a first magnet insertion hole 131 and a second magnet insertion hole 132 extending in a straight line and protruding from the rotation center O side is used. However, rotors with different shapes, numbers, and arrangement positions of the magnet insertion holes can also be used.

[0162] exist Figure 12 The rotor 220 of the permanent magnet motor according to the second embodiment is shown.

[0163] exist Figure 12 In the rotor 220 shown, each of the six main magnetic poles (pole pairs P = 3) has a magnet insertion hole 231 extending in a straight line. The magnet insertion holes 231 are configured such that, in the direction intersecting the d-axis (in... Figure 12 The middle part extends in the direction orthogonal to the d-axis. Furthermore, a permanent magnet 241 extending in a straight line is inserted into the magnet insertion hole 231.

[0164] The outer peripheral surface of the rotor 220 is similar to that of the rotor 120 constituting the permanent magnet motor 100 of the first embodiment, and is formed by a first outer peripheral surface portion 220a intersecting the d-axis, a second outer peripheral surface portion 220b intersecting the q-axis, a connecting portion 220c, and a connecting portion 220d.

[0165] exist Figure 13 The rotor 320 of the permanent magnet motor according to the third embodiment is shown.

[0166] exist Figure 13 In the rotor 320 shown, each of the six main magnetic poles (pole pairs P=3) has a first magnet insertion hole 331, a second magnet insertion hole 332, and a third magnet insertion hole 333 extending in a straight line. The magnet insertion holes 331-333 are arranged in a trapezoidal shape, intersecting the d-axis and protruding towards the rotation center O (opening on the side opposite to the rotation center O). That is, the magnet insertion holes 331-333 are arranged in a trapezoidal shape. Figure 13 In the trapezoid, magnet insertion hole 332 is located at the upper base, and magnet insertion holes 331 and 333 are located at the waist of the trapezoid. Furthermore, permanent magnets 341 and 343 extending in a straight line are inserted into magnet insertion holes 331 to 333 respectively.

[0167] The outer peripheral surface of the rotor 320 is similar to that of the rotor 120 constituting the permanent magnet motor 100 of the first embodiment, and is formed by a first outer peripheral surface portion 320a intersecting the d-axis, a second outer peripheral surface portion 320b intersecting the q-axis, a connecting portion 320c, and a connecting portion 320d.

[0168] Furthermore, trapezoidal magnet insertion holes protruding toward the rotation center O can also be formed at each main magnetic pole. In this case, the first to third permanent magnets, which extend in a straight line, are inserted into the trapezoidal magnet insertion holes.

[0169] This invention is not limited to the structure described in the embodiments, but can be modified, added to, or deleted in various ways.

[0170] While a permanent magnet motor has been described, the present invention can be configured to use a permanent magnet motor as a drive motor in various devices. For example, it can be configured to drive a compressor with a compression mechanism using a permanent magnet motor.

[0171] The shape, number, and arrangement of the magnet insertion holes formed on each main magnetic pole of the rotor, as well as the shape, number, and insertion position of the permanent magnets inserted into the magnet insertion holes, can be appropriately changed.

[0172] The structures described in the implementation can be used individually or in combination with a suitable selection of multiple structures.

Claims

1. A permanent magnet motor comprising a stator and a rotor, the stator having a plurality of teeth arranged circumferentially, a plurality of slots formed by circumferentially adjacent teeth, stator windings wound around the teeth, and an inner circumferential surface forming an inner space of the stator, the rotor being rotatably disposed within the inner space of the stator, further comprising main magnetic poles and auxiliary magnetic poles alternately arranged circumferentially in the rotor, and permanent magnets inserted into magnet insertion holes formed in the main magnetic poles. The permanent magnet motor is characterized by, The stator windings are wound in a distributed winding manner on the plurality of teeth. The main magnetic poles are provided with 6. The tooth has 36 teeth. The outer peripheral surface of the rotor has: a first outer peripheral surface portion that intersects the d-axis of the main magnetic pole and forms an arc shape with radius R1 centered at the rotation center; a second outer peripheral surface portion that intersects the q-axis of the auxiliary magnetic pole and forms an arc shape with radius R2 (R2 < R1) centered at the rotation center and having a radius smaller than radius R1; and a connecting portion that connects the first outer peripheral surface portion and the second outer peripheral surface portion. The diameter L of the rotor is set to satisfy 83mm≤L≤101mm. The distance G between the first outer peripheral surface portion and the inner peripheral surface of the stator is set to satisfy 0.5mm ≤ G ≤ 0.6mm. The width Wt of the tooth is set to satisfy 0.36×(L+2×G)×π / 36<Wt<0.42×(L+2×G)×π / 36. The opening angle K1 of the first outer peripheral surface portion relative to the rotation center is set to satisfy 14.9 degrees ≤ K1 ≤ 15.7 degrees, where the opening angle K1 is a mechanical angle. The radial spacing H between the first outer peripheral surface portion and the second outer peripheral surface portion is set to satisfy 0.6mm≤H≤0.96mm.

2. The permanent magnet motor according to claim 1, characterized in that, The permanent magnet used is a permanent magnet with a residual magnetic flux density in the range of 1.34 Tesla to 1.52 Tesla and a coercivity in the range of 1550 kA / m to 2100 kA / m.

3. The permanent magnet motor according to claim 1 or 2, characterized in that, The stator and the rotor are made of electromagnetic steel plates with magnetic flux density ranging from 1.75 Tesla to 1.9 Tesla, which transition from a linear region to a nonlinear region.

4. A compressor comprising a compression mechanism and an electric motor for driving the compression mechanism. The compressor is characterized by, The permanent magnet motor according to any one of claims 1 to 3 is used as the motor.

Images