Permanent magnet electric motor

Abstract

To provide a technique that can reduce the thickness of a permanent magnet while preventing demagnetization of the permanent magnet in a 4-pole, 24-slot permanent magnet motor.SOLUTION: An electric motor 100 includes a stator 110 with 24 slots and a rotor 120 with 4 poles. The diameter L of the rotor 120 is set to [55 mm≤L≤67 mm]. The distance G of the gap g between a first outer peripheral surface portion 120a and a stator inner peripheral surface 115 is set to [0.5 mm≤G≤0.6 mm]. The width Wt of the teeth 112 is set to [0.36×(L+2×G)×π / 24<Wt<0.42×(L+2×G)×π / 24]. The opening angle K1 (mechanical angle) of the first outer peripheral surface portion 120a is set to [22.5 degrees≤K1≤23.5 degrees]. The distance H along the radial direction between the first outer peripheral surface portion 120a and the second outer peripheral surface portion 120b is set to [0.6≤H≤0.96]. The thickness Wp of the permanent magnets 141 and 142 is set to [2×G×1.4<Wp<2×G×2.0].SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a compressor drive motor, a vehicle drive motor, an in-vehicle device drive motor, etc., a permanent magnet motor having a stator and a rotor in which permanent magnets are arranged is used. The stator has a yoke extending along the circumferential direction and a plurality of teeth extending radially inward from the yoke. The plurality of teeth are arranged at intervals in the circumferential direction. Further, the stator has a plurality of slots formed by two adjacent teeth in the circumferential direction. The rotor is rotatably arranged in the inner space of the stator. In the rotor, main poles and auxiliary poles are alternately arranged in the circumferential direction. In the main poles, magnet insertion holes are formed, and permanent magnets are inserted into the magnet insertion holes. The shape, number, arrangement position, etc. of the magnet insertion holes and the permanent magnets are appropriately set. As the permanent magnet, a ferrite magnet, a rare earth magnet, etc. are used. Rare earth magnets are more expensive than ferrite magnets, but have a large residual magnetic flux density and Coercivity For example, a neodymium magnet containing neodymium (Nd) and iron (Fe) is used as the rare earth magnet. The neodymium magnet Coercivity decreases as the ambient temperature rises. Therefore, neodymium magnets in which dysprosium (Dy) or terbium (Tb) is diffused (grain boundary diffusion) from the outer peripheral surface are also used. As a permanent magnet motor, a permanent magnet motor (hereinafter referred to as a "4-pole 24-slot permanent magnet motor") composed of a stator having 4 main poles (a stator having 4 poles or 2 pole pairs) and a rotor having 24 teeth (or 24 slots) is used. The 4-pole 24-slot permanent magnet motor is disclosed in, for example, Patent Document 1. The torque Tr of such a permanent magnet motor can be expressed by the following formula, where Φ is the magnetic flux due to the permanent magnet, Iq is the q-axis current, Id is the d-axis current, Lq is the q-axis inductance, Ld is the d-axis inductance, and P is the number of pole pairs of the rotor (= number of poles / 2). Tr = P[Φ × Iq ​​+ (Ld - Lq) × Id × Iq] The first term on the right-hand side of the above equation represents the magnetic torque due to the magnetic flux Φ of the permanent magnet, and the second term represents the reluctance torque due to the salient polarity (Ld-Lq) of the rotor. Typically, the q-axis inductance Lq is greater than the d-axis inductance Ld. That is, (Ld-Lq) is negative. In this case, if a negative d-axis current Id flows, the reluctance torque becomes positive. Therefore, a method of controlling the d-axis current Id to be negative is used to increase the torque Tr, which is the sum of the magnet torque and the reluctance torque. A common method of controlling the d-axis current to be negative is to advance the phase angle of the current flowing through the stator winding (called "advance angle control" or "field weakening control"). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-164324 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the permanent magnet motor disclosed in Patent Document 1, the torque Tr can be increased by performing advance angle control, which controls the advance angle of the energization. On the other hand, permanent magnets can be demagnetized by the magnetic flux flowing into the rotor through the stator teeth. When permanent magnets are demagnetized, the magnetic flux density of the permanent magnets decreases, and the characteristics of the permanent magnet motor change (for example, the torque decreases). Therefore, it is necessary to prevent the demagnetization of the permanent magnet ("increase the demagnetization resistance"). In conventional permanent magnet motors, the following methods are used to prevent the demagnetization of the permanent magnet. The first method is to use the same permanent magnet and increase its thickness. By increasing the thickness of the permanent magnet, Coercivity The demagnetizing resistance increases as the thickness increases. The second method does not increase the thickness. Coercivity One method involves using a permanent magnet with high magnetism. For example, when using a neodymium magnet, a neodymium magnet is used in which dysprosium (Dy) or terbium (Tb) is diffused from the outer surface (grain boundary diffusion). The third method involves using a high-speed current interruption switch that can quickly interrupt the current when it is necessary to pass a current that is likely to demagnetize the permanent magnet. However, the first method increases the cost of permanent magnets because it requires a larger quantity of them. The second method requires the use of expensive permanent magnets. The third method requires the use of expensive high-speed current cutoff switches. Thus, using the first to third methods increases the cost of the permanent magnet motor.

[0005] Therefore, the inventors investigated a technique that can prevent demagnetization of a permanent magnet without increasing its thickness. Figures 14 and 15 show the permanent magnet motor 400 disclosed in Patent Document 1. The permanent magnet motor 400 consists of a stator 410 and a rotor 420. The stator 410 has a yoke 411 and 24 teeth 412. Each tooth 412 has a tooth base 413 and a tooth tip 414. The tooth base 413 has a tooth tip surface 415 on the tip side (radially inward). The rotor 420 has four main poles and auxiliary poles alternately arranged in the circumferential direction. Magnet insertion holes 431 and 432 for inserting permanent magnets 441 and 442 are formed in the main poles. The outer peripheral surface of the rotor 420 is formed by a first outer peripheral surface portion 420a, a second outer peripheral surface portion 420b, connection portions 420c and 420d. The first outer peripheral surface portion 420a intersects the d-axis and is formed in an arc shape with a radius R1 centered on the rotation center. The second outer peripheral surface portion 420b intersects the q-axis and is formed in an arc shape with a radius R2 (R2 < R1) smaller than the radius R1 centered on the rotation center. The connection portion 420c connects the connection portion M1 on the other circumferential side (counterclockwise) of the first outer peripheral surface portion 420a and the second outer peripheral surface portion 420b. The connection portion 420d connects the connection portion M2 on one circumferential side (clockwise) of the first outer peripheral surface portion 420a and the second outer peripheral surface portion 420b. The second outer peripheral surface portion 420b and the connection portions 420c and 420d form a notch portion obtained by cutting out a circular outer periphery with a diameter L.

[0006] In the state shown in FIG. 14, teeth J2 to J4 among teeth J1 to J6 are arranged at positions facing the first outer peripheral surface portion 420a of the main pole [A]. In FIG. 14, the connection portion M1 (line m1 passing through the center point and the connection portion M1) is located on the other circumferential side (counterclockwise) than the side wall JB (extension line jb of the side wall JB) on one circumferential side (clockwise) of the tooth J2. Also, the connection portion M2 (line m2 passing through the center point and the connection portion M2) is located on one circumferential side (clockwise) than the side wall JA (extension line ja of the side wall JA) on the other circumferential side (counterclockwise) of the tooth J4. In the state shown in FIG. 14, magnetic flux flows from the teeth J3 and J4 of the N pole toward the S pole of the permanent magnet 442 through the first outer peripheral surface portion 420a. Since this magnetic flux passes through the gap g between the first outer peripheral surface portion 420a and the tooth tip surface 415, it is large. Also, magnetic flux flows from the teeth J5 and J6 of the N pole toward the S pole of the permanent magnet 442 through the second outer peripheral surface portion 420b. Since this magnetic flux passes through the gap g and the notch portion, it is small.

[0007] Figure 15 shows the state after rotating 7.5 degrees (= 1 / 2 of 360 degrees / 24) in one direction (clockwise) from the state shown in Figure 14. In the state shown in Figure 15, 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]. In Figure 15, the connection portion M1 (the line m1 passing through the center point and the connection portion M1) is located on the other side (counterclockwise) of the side wall JA (extension line ja of side wall JA) on the other side (counterclockwise) of tooth J3. Also, the connection portion M2 (the line m2 passing through the center point and the connection portion M2) is located on the one side (clockwise) of the side wall JB (extension line jb of side wall JB) on the one side (clockwise) of tooth J4. In the state shown in Figure 15, magnetic flux flows from the N pole teeth J3, J4, and J5 toward the S pole of the permanent magnet 442 via the first outer peripheral surface portion 420a. This magnetic flux is large because it passes through the air gap g. Also, magnetic flux flows from the N pole tooth J6 toward the S pole of the permanent magnet 442 via the second outer peripheral surface portion 420b. This magnetic flux is small because it passes through the air gap g and the notch. As shown in Figures 14 and 15, in the conventional permanent magnet motor 400, four teeth 412 and three teeth 412 are alternately arranged at positions facing the first outer peripheral surface portion 420a of the rotor 420.

[0008] Furthermore, from the analysis results shown in Figures 14 and 15, it was found that in conventional permanent magnet motors, a large amount of magnetic flux flows from multiple teeth into the rotor's permanent magnets, increasing the magnetic flux density, which is one of the causes of permanent magnet demagnetization. In other words, it was found that demagnetization of the permanent magnets can be prevented by preventing a large amount of magnetic flux from flowing from the teeth into the rotor's permanent magnets. This invention relates to a 4-pole 24-slot system permanent magnet electric motor The objective is to provide a technology that can reduce the thickness of a permanent magnet while preventing its demagnetization. [Means for solving the problem]

[0009] The first invention relates to a permanent magnet motor including a stator and a rotor. The stator has a plurality of teeth arranged at intervals along the circumferential direction, a plurality of slots formed by the teeth adjacent to each other in the circumferential direction, a stator winding wound around each tooth, and a stator inner peripheral surface forming an inner space of the stator. The rotor is rotatably disposed within the inner space of the stator. The rotor has main poles and auxiliary poles alternately arranged along the circumferential direction, and permanent magnets are inserted into magnet insertion holes formed in the main poles. In the present invention, the stator winding is wound around the plurality of teeth in a distributed winding manner. Also, four main poles are provided, and 24 teeth are provided. That is, it is configured as a 4-pole 24-slot permanent magnet motor. The outer peripheral surface of the rotor is formed by a plurality of first outer peripheral surface portions, a plurality of second outer peripheral surface portions, and a plurality of connecting portions. The first outer peripheral surface portion intersects the d-axis and is formed in an arc shape with a radius R1 centered on the rotation center. The second outer peripheral surface portion intersects the q-axis and is formed in an arc shape with a radius R2 centered on the rotation center. The radius R2 is set to be smaller than the radius R1 (R2 < R1). The connecting portion connects the first outer peripheral surface portion and the second outer peripheral surface portion. And the diameter L of the rotor is set to satisfy [55 mm ≤ L ≤ 67 mm]. Also, the first outer peripheral surface portion and Stator inner circumferential surface The distance G of the gap g between them is set to satisfy [0.5 mm ≤ G ≤ 0.6 mm]. Also, the width Wt of the teeth is set to satisfy [0.36×(L + 2×G)×π / 24 < Wt < 0.42×(L + 2×G)×π / 24]. Also, the opening angle K1 (mechanical angle) of the first outer peripheral surface portion with respect to the rotation center is set to satisfy [22.5 degrees ≤ K1 ≤ 23.5 degrees]. Also, the interval H along the radial direction between the first outer peripheral surface portion and the second outer peripheral surface portion is set to satisfy [0.6 mm ≤ H ≤ 0.96 mm]. In the present invention, the teeth regulate the flow of magnetic flux that may demagnetize the permanent magnet into the permanent magnet. Therefore, Permanent magnetsThe thickness can be reduced. In the first invention, while preventing demagnetization of the permanent magnet, the thickness of the permanent magnet can be reduced. In a different form of the first invention, as the permanent magnet, the residual magnetic flux density is within the range of 1.34 tesla to 1.52 tesla, Coercivity and a permanent magnet within the range of 1550 kA / m to 2100 kA / m is used. In a different form of the first invention, the stator and the rotor are composed of electromagnetic steel sheets in which the magnetic flux density transitions from the linear region to the non-linear region within the range of 1.75 tesla to 1.9 tesla. The second invention relates to a compressor. The compressor of the second invention includes a compression mechanism section and an electric motor that drives the compression mechanism section. And any of the permanent magnet motors described above is used as the electric motor. The second invention has the same effect as the permanent magnet motor described above.

Advantages of the Invention

[0010] By using the permanent magnet motor of the present invention, in a 4-pole 24-slot permanent magnet motor at while preventing demagnetization of the permanent magnet, the thickness of the permanent magnet can be reduced.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view of the permanent magnet motor of the first embodiment. [Figure 2] It is an enlarged view of the main part of FIG. 1. [Figure 3] It is a graph showing the relationship between the magnet thickness Wp and the magnetic flux density in the permanent magnet, analyzed by changing the energization advance angle in the state where the first current is flowing. [Figure 4] It is a graph showing the relationship between the magnet thickness Wp and the magnetic flux density in the permanent magnet, shown in a different way from that shown in FIG. 3. [Figure 5] It is a graph showing the relationship between the magnet thickness Wp and the magnetic flux density in the permanent magnet, analyzed by changing the energization advance angle in the state where the second current is flowing. [Figure 6]Figure 5 shows a graph illustrating the relationship between magnet thickness Wp and magnetic flux density in a permanent magnet, using different methods. [Figure 7] This graph shows the relationship between the opening angle K1 of the first outer surface portion and the cogging torque. [Figure 8] This figure shows the relationship between the distance G between the first outer peripheral surface and the inner peripheral surface of the stator and the efficiency. [Figure 9] This graph shows the relationship between the notch depth (the distance between the first and second outer surface portions) H and the magnetic flux density of the magnetic flux flowing through the teeth. [Figure 10] This is a diagram illustrating the magnetic flux in a permanent magnet motor according to the first embodiment. [Figure 11] This is a diagram illustrating the magnetic flux in a permanent magnet motor according to the first embodiment. [Figure 12] This is a cross-sectional view of the rotor constituting the permanent magnet motor of the second embodiment. [Figure 13] This is a cross-sectional view of the rotor constituting the permanent magnet motor of the third embodiment. [Figure 14] This diagram illustrates the magnetic flux in a conventional permanent magnet motor. [Figure 15] This diagram illustrates the magnetic flux in a conventional permanent magnet motor. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. In this specification, the term "axial direction" refers to the direction of the extension of the rotational centerline passing through the rotor's rotational center O (see Figure 1) when the rotor is rotatably positioned relative to the stator. One side along the axial direction is referred to as the "axial first side" or "axial first side," and the other side along the axial direction is referred to as the "axial other side" or "axial second side." Furthermore, the term "circumferential direction" refers to the circular direction centered on the rotor's rotation center O, as viewed from one axial side (or the other axial side) when the rotor is rotatably positioned relative to the stator. When viewed from one axial side (see Figure 1), the clockwise direction (arrow Y direction) is called the "circumferential direction one side" or "circumferential direction first side," and the counterclockwise direction (opposite to the arrow Y direction) is called the "circumferential direction other side" or "circumferential direction second side." Furthermore, the term "radial direction" refers to the direction in which a line passing through the rotor's center of rotation O extends, as viewed from one axial side (or the other axial side) when the rotor is rotatably positioned relative to the stator. The side of the rotor towards the center of rotation O is called the "radial inner side," and the side opposite the center of rotation O is called the "radial outer side."

[0013] A permanent magnet motor 100 according to the first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the permanent magnet motor 100 according to the first embodiment, and Figure 2 is an enlarged view of the main part of Figure 1. The permanent magnet motor 100 consists of a stator 110 and a rotor 120.

[0014] The stator 110 is composed of a cylindrical stator core formed by laminating multiple sheets of plate-shaped electromagnetic steel. The stator 110 has a yoke 111 extending in the circumferential direction and a plurality of teeth 112 extending radially inward from the yoke 111. The plurality of teeth 112 are spaced apart in the circumferential direction. Each 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 with the rotation center O as its center point. The tooth tip surface 115 of each tooth 112 forms an inner stator space inside the stator 110. The tooth tip surface 115 corresponds to the "inner circumferential surface of the stator" in this invention.

[0015] A slot 116 is formed by two teeth 112 that are adjacent to each other in the circumferential direction. The permanent magnet motor 100 of this embodiment has 24 teeth 112 (24 slots 116). That is, the permanent magnet motor 100 has a stator 110 with 24 slots. The stator windings (not shown) are wound around each tooth 112 (more specifically, the tooth base 113) using a distributed winding method. Various methods can be used to wind the stator windings using a distributed winding method. By winding the stator wires using a distributed winding method, copper loss is higher compared to winding using a concentrated winding method, but high output can be obtained, and vibration and noise can be reduced.

[0016] The rotor 120 is composed of a rotor core formed by stacking multiple sheets of plate-shaped electromagnetic steel. The rotor 120 is rotatably positioned within the stator's inner space, which is formed by the stator's inner circumferential surface (tooth tip surface 115). In this embodiment, the rotor 120 is positioned such that an air gap g is maintained between the first outer circumferential surface portion 120a (described later) and the tooth tip surface 114a (stator's inner circumferential surface). The rotor 120 has an inner rotor space 122 formed by the inner rotor circumferential surface 121. The rotating shaft is inserted, for example, press-fitted, into the inner rotor space 122.

[0017] The rotor 120 has main magnetic poles [A] to [D] and auxiliary magnetic poles [AB] to [DA]. The main magnetic poles [A] to [D] and auxiliary magnetic poles [AB] to [DA] are arranged alternately along the circumferential direction. The permanent magnet motor 100 of this embodiment has a rotor 120 having four main magnetic poles. That is, the permanent magnet motor 100 has a rotor 120 with four poles. The number of poles of the rotor is sometimes expressed as the number of pole pairs P (= number of poles / 2). A permanent magnet motor 100 having a 24-slot stator 110 and a 4-pole rotor 120 (with a pole-to-pole ratio P of 2) is called a 4-pole 24-slot permanent magnet motor 100. Each of the main magnetic poles [A] to [D] has one or more magnet insertion holes. A permanent magnet is inserted into each of these magnet insertion holes. The permanent magnets inserted into each magnet insertion hole define the region of the main magnetic poles [A] to [D] and the d-axis of the main magnetic poles [A] to [D], as well as the region of the auxiliary magnetic poles [AB] to [DA] and the q-axis of the auxiliary magnetic poles [AB] to [DA]. The d-axis is defined as the line connecting the rotation center O and the circumferential centers of the main magnetic pole regions [A] to [D]. The q-axis is defined as the line connecting the rotation center O and the circumferential centers of the auxiliary magnetic pole regions [AB] to [DA].

[0018] In this embodiment, the main magnetic poles [A] to [D] each have a first magnet insertion hole 131 and a second magnet insertion hole 132. The first magnet insertion hole 131 and the second magnet insertion hole 132 are arranged in a V-shape on both sides of the d-axis, with the side facing the rotation center O protruding (the side opposite the rotation center O being open). The first magnet insertion hole 131 is formed by an inner circumferential side wall portion 131a, an outer circumferential side wall portion 131b, an inner circumferential end wall portion 131c, an outer circumferential end wall portion 131d, and an end wall portion 131e. The second magnet insertion hole 132 is formed by an inner circumferential side wall portion 132a, an outer circumferential side wall portion 132b, an inner circumferential end wall portion 132c, an outer circumferential end wall portion 132d, and an end wall portion 132e. A central bridge portion 125 is formed between the inner circumferential end wall portion 131c of the first magnet insertion hole 131 and the inner circumferential end wall portion 132c of the second magnet insertion hole 132, extending parallel to the d-axis (including "approximately parallel"). An outer circumferential bridge portion 126 is formed between the outer circumferential end wall portion 131d of the first magnet insertion hole 131 and the outer circumferential surface of the rotor 120 (the second outer circumferential surface portion 120b, described later). An outer circumferential bridge portion 127 is formed between the outer circumferential end wall portion 132d of the second magnet insertion hole 132 and the outer circumferential surface of the rotor 120 (the second outer circumferential surface portion 120b, described later). Furthermore, a magnetic flux passage is formed between the end wall portion 131e of the first magnet insertion hole 131 of one of the two adjacent main magnetic poles and the end wall portion 132e of the second magnet insertion hole 132 of the other main magnetic pole, extending parallel to the q-axis (including "approximately parallel").

[0019] 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 and a second permanent magnet 142, which extend in a straight line, are inserted into the first magnet insertion hole 131 and the second magnet insertion hole 132. The first permanent magnet 141 has a rectangular cross-section formed by an inner circumferential outer wall surface 141a, an outer circumferential outer wall surface 141b, an inner circumferential end wall surface 141c, and an outer circumferential end wall surface 141d. The second permanent magnet 142 has a rectangular cross-section formed by the inner circumferential outer wall surface 142a, the outer circumferential outer wall surface 142b, the inner circumferential end wall surface 142c, and the outer circumferential end wall surface 142d. When the first permanent magnet 141 (second permanent magnet 142) is inserted into the first magnet insertion hole 131 (second magnet insertion hole 132), a gap is formed on both end wall surfaces. Various permanent magnets can be used as the first permanent magnet 141 and the second permanent magnet 142. In this embodiment, Neodymium magnet This is used. Additionally, neodymium magnets with dysprosium (Dy) or terbium (Tb) diffused (grain boundary diffusion) are sometimes used.

[0020] The outer circumferential surface of the rotor 120 (rotor outer circumferential surface) is formed by a plurality of first outer circumferential surface portions 120a, a plurality of second outer circumferential surface portions 120b, and a plurality of connecting portions 120c and 120d. 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 radially inward of the first outer peripheral surface portion 120a. The 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 connected to the connecting portion 120c on the other side in the circumferential direction and a connecting portion M2 connected to the connecting portion 120d on one side in the circumferential direction. The second outer peripheral surface portion 120b, the connecting portions 120c and 120d form a notch portion that cuts out the outer periphery of a circle (radius R1) having an outer periphery extending the first outer peripheral surface portion 120a. The second outer peripheral surface portion 120b, the connecting portions 120c and 120d form the bottom surface of the notch portion, the side surface on one side in the circumferential direction (clockwise side), and the side surface on the other side in the circumferential direction (counterclockwise side). In the present embodiment, the first outer peripheral surface portion 120a has an arc shape with a radius of R1 mm centered on 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 of R2 mm (R2 < R1) smaller than the radius R1 centered on the rotation center O. Further, the connecting portions 120c and 120d extend linearly in parallel with the d-axis (including "substantially parallel"). The shapes of the connecting portions 120c and 120d can also be formed so as to extend in parallel (including "substantially parallel") to a line passing through the rotation center O and extending in the radial direction. Note that the shapes of the first outer peripheral surface portion 120a, the second outer peripheral surface portion 120b, the connecting portions 120c and 120d are not limited to this.

[0021] Next, a configuration for reducing the thickness of the permanent magnets 141 and 142 while preventing demagnetization of the permanent magnets 141 and 142 in the permanent magnet motor 100 of the present embodiment will be described. In the present embodiment, as described above, the stator 110 has 24 slots 116 (teeths) and the rotor 120 has four main poles A to D. That is, the permanent magnet motor 100 is configured as a four-pole 24-slot permanent magnet motor.

[0022] As shown in Figure 2, d-axis magnetic flux and q-axis magnetic flux flow through the rotor 120. The d-axis magnetic flux is the magnetic flux flowing between adjacent principal magnetic poles. For example, it is the magnetic flux that flows from the d-axis side of principal magnetic pole A into the rotor 120 and flows out from the d-axis side of principal magnetic pole B, which is adjacent to principal magnetic pole A on one side in the circumferential direction (clockwise in Figure 2). The d-axis inductance Ld is determined by the d-axis magnetic flux. The q-axis magnetic flux is the magnetic flux flowing between adjacent auxiliary magnetic poles. For example, it flows into the rotor 120 from the auxiliary magnetic pole DA side between the main magnetic pole A and the main magnetic pole D adjacent to the main magnetic pole A on the other circumferential side (counterclockwise in Figure 2), 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 one circumferential side. The q-axis inductance Lq is determined by the q-axis magnetic flux.

[0023] Next, the following describes a configuration for reducing the thickness of a permanent magnet while preventing its demagnetization. In conventional permanent magnet motors, the d-axis magnetic flux flowing through the teeth is set to not saturate, so the d-axis inductance Ld has a current characteristic that remains almost unchanged even when the current increases or decreases. In contrast, in this embodiment, the d-axis magnetic flux flowing through the teeth is set to saturate, thereby configuring the device to have a current characteristic in which the d-axis inductance Ld becomes small in the region of large current. Furthermore, as the current increases, the magnetic flux density of the teeth saturates, causing the q-axis inductance Lq to decrease. In other words, even if the d-axis inductance Ld decreases, the absolute value of [Ld-Lq] does not decrease. Therefore, reluctance torque can be ensured.

[0024] The diameter (outer diameter) L of the rotor 120 is set within the range of 55 mm and 67 mm ([55 mm ≤ L ≤ 67 mm]). The first outer peripheral surface portion 120a is the outer peripheral surface portion obtained by removing the notches formed by the second outer peripheral surface portion 120b and the connecting portions 120c and 120d from a circle with diameter L. If the diameter L of the rotor 120 is less than 55 mm, the length of the first outer peripheral surface portion 120a along the circumferential direction becomes shorter, making it impossible to secure a passage through which sufficient magnetic flux can pass. When sufficient magnetic surface area cannot be secured, the amount of magnetic flux decreases, and copper loss increases. And with the increase in copper loss, the efficiency decreases.

[0025] The opening angle K1 (mechanical angle) of the first outer peripheral surface portion 120a with respect to the rotation center O will be explained with reference to Figure 7. Figure 7 is a graph showing the relationship between the opening angle K1 of the first outer surface portion 120a and the cogging torque. In Figure 7, the horizontal axis represents the opening angle K1 (degrees), and the vertical axis represents the cogging torque (N·m). In the graph shown in Figure 7, the cogging torque is large in the region where the opening angle K1 is less than 14.9 degrees and greater than 15.7 degrees. From the graph shown in Figure 7, it can be seen that cogging torque can be reduced by setting the opening angle K1 within the range of 22.5 degrees and 23.5 degrees ([14.9 degrees ≤ K1 ≤ 15.7 degrees]). Reducing cogging torque can suppress the generation of noise and vibration. Furthermore, reducing cogging torque reduces the inflow and outflow of magnetic flux that does not contribute to torque generation. In this case, iron loss due to the inflow and outflow of magnetic flux that does not contribute to torque can be reduced.

[0026] 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 with reference to Figure 8. Figure 8 is a graph showing the relationship between the distance G of the air gap and the efficiency of the permanent magnet motor 100. In Figure 8, the horizontal axis represents the distance G mm of the air gap, and the vertical axis represents the efficiency (%). In the graph shown in Figure 8, efficiency decreases in the region where the distance G is less than 0.5 mm and greater than 0.6 mm. When the distance G is less than 0.5 mm, the harmonic components in the electromotive force (induced electromotive force) increase. As the harmonic components in the electromotive force increase, the harmonic iron loss increases, and the efficiency decreases. Also, when the distance G is From 0.5mm If it's small, the noise and vibration will be greater. When the distance G is greater than 0.6 mm, the fundamental wave component included in the electromotive force decreases. The fundamental wave component contained within As the amount decreases, copper loss increases, and efficiency decreases. From the graph shown in Figure 8, it can be seen that efficiency can be improved by setting the distance G of the void g within the range of 0.5 mm and 0.6 mm ([0.5 mm ≤ G ≤ 0.6 mm]).

[0027] 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 with reference to Figure 9. Figure 9 shows graphs of the relationship between the notch depth H and the magnetic flux density of teeth 112, and the relationship between the notch depth H and the fundamental wave component of the electromotive force. In Figure 9, the horizontal axis represents the notch depth H mm, the left vertical axis represents the magnetic flux density of teeth 112 (Tesla), and the right vertical axis represents the fundamental wave component of the electromotive force (V volts). In Figure 9, the graph of the fundamental wave component of the electromotive force is shown as a solid line, and the graph of the magnetic flux density of the teeth is shown as a dashed line. As shown in the graph in Figure 9, when the depth H of the notch is less than 0.6 mm, the magnetic flux density of teeth 112 decreases. Also, when the depth H of the notch is greater than 0.96 mm, the fundamental wave component of the electromotive force decreases. As shown in the graph in Figure 9, by setting the depth H of the notch to within the range of 0.6 mm and 0.96 mm ([0.6 mm ≤ H ≤ 0.96 mm]), the magnetic flux density of teeth 112 can be increased, and the fundamental wave component included in the electromotive force can also be increased.

[0028] In this embodiment, when a large current exceeding the operating current flows, the magnetic flux density of the teeth 112 is configured to saturate, thereby preventing an excessive magnetic flux from flowing into the permanent magnet. With the diameter L of the rotor, the distance G of the air gap g, the opening angle K1 of the first outer peripheral surface portion 120a, and the depth H of the notch being set within the aforementioned ranges, when an excessive current exceeding the operating current flows, in order to saturate the magnetic flux density of the teeth 112, the width of the teeth 112 (specifically, the width of the tooth base 113) Wt needs to be set within the range of [0.36×(L + 2×G)×π / 24] to [0.42×(L + 2×G)×π / 24]. That is, it needs to be set so as to satisfy [0.36×(L + 2×G)×π / 24 < Wt < 0.42×(L + 2×G)×π / 24]. In this case, the permanent magnet 141 , the magnet thickness Wp (mm) of 142 can be set within the range of [2×G×1.4] to [2×G×2.0] ([2×G×1.4 < Wp < 2×G×2.0]). In the conventional permanent magnet motor 400, when the diameter L of the rotor 420, the distance G of the air gap g, and the depth H of the notch are set in the same manner as in the permanent magnet motor 100 of this embodiment, the thickness Wp of the permanent magnets 441 and 442 needs to be set within the range of [2×G×2.0] to [2×G×2.8] ([2×G×2.0 < Wp < 2×G×2.8]) in order to prevent demagnetization.

[0029] Next, the relationship between the thickness (magnet thickness) of the permanent magnets 141 and 142 and the magnetic flux density of the teeth 112 will be described with reference to FIGS. 3 to 6. FIGS. 3 to 6 are graphs showing the results of analyzing the relationship between the magnet thickness (mm) and the magnetic flux density (Tesla) of the permanent magnets 141 and 142 with the energization advance angle changed in a state where a predetermined current is flowing through the stator winding. The magnetic flux density of the permanent magnet was taken as the average magnetic flux density obtained by averaging the magnetic flux densities measured at a plurality of locations along the length direction of the permanent magnet. Also, the magnet thickness is the In the thickness directionIt can be inferred from the width. Typically, the width in the thickness direction of the magnet insertion hole is set to be about 0.03 mm to 0.16 mm larger than the magnet thickness. Therefore, the analysis was performed using the width in the thickness direction of the magnet insertion hole, and the magnet thickness was inferred from the width in the thickness direction of the magnet insertion hole. In Figures 3 and 5, the horizontal axis represents the magnet thickness Wp (mm), and the vertical axis represents the magnetic flux density (tesla). In Figures 4 and 6, the horizontal axis represents the magnet thickness Wp (mm), and the vertical axis represents the magnetic flux density (%).

[0030] Figures 3 and 4 are graphs for a current value of 2A. Figures 5 and 6 are graphs for a current value of 4A. Note that in Figures 3 and 5, the magnetic flux density is shown as an analytical value. In addition, in Figures 4 and 6, the magnetic flux density is shown as a normalized value with the magnetic flux density at an energization lead angle of 0 degrees set to 100%.

[0031] Figures 3 to 6 show that the graph curves non-linearly when the magnet thickness Wp is 1.7 mm or less. For example, in Figure 4, when the magnet thickness Wp is 1.7 mm, the magnetic flux density (%) at an energized lead angle of 20 degrees decreases to 98.5%. When the magnetic flux density decreases, the amount of magnetic flux decreases. When the amount of magnetic flux decreases, it becomes possible to operate at higher rotational speeds. In other words, the rotational speed when the magnet thickness Wp is 1.7 mm and the energized lead angle is 20 degrees is almost equivalent to the rotational speed when the magnet thickness Wp is 2.5 mm and the energized lead angle is 30 degrees. In this case, it becomes possible to operate with a small lead angle of current application. Operating with a small lead angle of current application reduces reluctance torque. As a result, iron losses due to reluctance torque can be reduced, and efficiency can be improved. Furthermore, the thickness of the permanent magnet can be reduced, thus lowering the cost of the permanent magnet.

[0032] The width of the teeth 112 (specifically, the minimum width of the tooth base 113) Wt is set to satisfy [0.36×(stator inner circumference / 24) < Wt < 0.42×(stator inner circumference / 24)]. The stator inner circumference (mm) is represented by [stator inner circumference = (diameter L of the rotor 120 + distance 2G) × π]. If the width Wt of the teeth 112 is less than [0.36×(stator inner circumference / 24)], sufficient magnetic flux does not flow from the teeth 112 to the rotor 120. As a result, the copper loss increases and the efficiency decreases. If the Wt of the teeth 112 is greater than [0.42×(stator inner circumference / 24)], sufficient magnetic flux flows between the teeth 112 and the rotor 120, and the d-axis magnetic flux does not saturate. In this case, the d-axis inductance Ld exhibits the same current characteristics as a conventional permanent magnet motor.

[0033] In FIGS. 10 and 11, the flow of magnetic flux in the permanent magnet motor 100 of the present embodiment is shown. In the state shown in FIG. 10, the tooth J2 among the teeth J1 to J5 is arranged at a position facing the first outer peripheral surface portion 120a of the main pole [A]. In FIG. 10, the connection portion M1 (the line m1 passing through the center point O and the connection portion M1) is on the one circumferential side (clockwise) of the side wall JB (the extension line jb of the side wall JB) of the tooth J1 in the circumferential direction ( Clockwise ) and is located on the one circumferential side (clockwise). Also, the connection portion M2 (the line m2 passing through the center point O and the connection portion M2) is on the other circumferential side (counterclockwise) of the side wall JA (the extension line ja of the side wall JA) of the tooth J3 in the circumferential direction (counterclockwise) and is located on the other circumferential side (counterclockwise). In the state shown in FIG. 10, magnetic flux flows from the tooth J2 of the N pole through the first outer peripheral surface portion 120a toward the S pole of the permanent magnet 142. Since this magnetic flux passes through the gap g between the first outer peripheral surface portion 120a and the tooth tip surface 115, it is large. Also, magnetic flux flows from the teeth J3 to J5 of the N pole through the second outer peripheral surface portion 120b toward the S pole of the permanent magnet 142. Since this magnetic flux passes through the gap g and the notch portion, it is small.

[0034] Figure 11 shows the state after rotating 7.5 degrees (= 1 / 2 of 360 degrees / 24) in one direction (clockwise) from the state shown in Figure 10. In the state shown in Figure 11, teeth J2 and J3 of teeth J1 to J5 are positioned opposite the first outer peripheral surface portion 120a of the main magnetic pole [A]. In Figure 11, the connection portion M1 (the line m1 passing through the center point O and the connection portion M1) is located on the other side (counterclockwise) of the circumferential side (counterclockwise) of tooth J2's side wall JA (the extension line ja of side wall JA). Also, the connection portion M2 (the line m2 passing through the center point O and the connection portion M2) is located on the one side (clockwise) of the circumferential side (clockwise) of tooth J3's side wall JB (the extension line jb of side wall JB). In the state shown in Figure 11, magnetic flux flows from the N-pole teeth J2 and J3 towards the S-pole of the permanent magnet 142 via the first outer peripheral surface portion 120a. This magnetic flux is abundant because it passes through the air gap g between the first outer peripheral surface portion 120a and the tooth tip surface 115. Also, magnetic flux flows from the N-pole teeth J4 and J5 towards the S-pole of the permanent magnet 142 via the second outer peripheral surface portion 120b. This magnetic flux is less abundant because it passes through the air gap g and the notch.

[0035] In this embodiment, in the state shown in Figure 11, magnetic flux flows into the rotor 120 from the two teeth J2 and J3 via the first outer peripheral surface portion 120a. In this embodiment, the magnetic flux density of teeth J2 and J3 is configured to saturate. Therefore, teeth J2 and J3 function as magnetic flux limiters, preventing any further magnetic flux from flowing. This prevents demagnetization of the permanent magnets 141 and 142 while reducing the thickness of the permanent magnets 141 and 142. Furthermore, the reduced magnetic flux flowing through the yoke 111 reduces iron loss. Additionally, the dimensions of the yoke 111 (and thus the stator 110) can be reduced. Alternatively, a larger refrigerant passage can be formed in the stator 110.

[0036] In the conventional permanent magnet motor 400, as shown in Figures 14 and 15, four teeth 412 and three teeth 412 are arranged alternately at positions facing the first outer peripheral surface portion 420a of the rotor 420. In contrast, in the permanent magnet motor 100 of this embodiment, as shown in Figures 10 and 11, two teeth 112 and one tooth 112 are arranged alternately at positions facing the first outer peripheral surface portion 120a of the rotor 120.

[0037] Furthermore, the length of the magnet insertion holes formed in the main magnetic poles is set so as to be maintained by the magnetic flux flowing through teeth 113 when teeth 112 are saturated. For example, the total length of the magnet insertion holes formed in the main magnetic poles is set to be five times or more the width Wt of the teeth 112. In this embodiment, the magnet insertion holes 131 and 132 formed in the main magnetic pole length Since Y is (see Figure 2), (Y+Y) is set to 5 times or more Wt. For example, if Wt is set to 3.1 mm and Y is set to 19 mm, then [38 mm (= 2 × 19 mm) / 3.1 mm = 12.25 times].

[0038] The permanent magnets 141 and 142 are preferably: Residual magnetic flux density Permanent magnets with a power rating between 1.34 Tesla and 1.52 Tesla are used. Furthermore, preferably, the electromagnetic steel sheets constituting the stator 110 (stator core) and rotor 120 (rotor core) have a magnetic flux density within the range of 1.75 Tesla and 1.9 Tesla from the linear region. Nonlinear domain Electrical steel sheets that transition to this type are used.

[0039] In the first embodiment of the permanent magnet motor 100, a rotor 120 was used in which the first magnet insertion holes 131 and the second magnet insertion holes 132, which extend in a straight line, are arranged in a V-shape with the rotation center O side protruding. However, rotors with different shapes, numbers, and arrangement positions of magnet insertion holes can also be used.

[0040] The rotor 220 of the permanent magnet motor according to the second embodiment is shown in Figure 12. The rotor 220 shown in Figure 12 has one linearly extending magnet insertion hole 231 formed at each of the four main magnetic poles (number of pole pairs P=2). The magnet insertion holes 231 are positioned to extend in a direction intersecting the d-axis (in Figure 12, in a direction perpendicular to the d-axis). A linearly extending permanent magnet 241 is inserted into the magnet insertion hole 231. The outer circumferential surface of the rotor 220 is formed by a first outer circumferential surface portion 220a intersecting the d-axis, a second outer circumferential surface portion 220b intersecting the q-axis, and connecting portions 220c and 220d, similar to the rotor 120 constituting the permanent magnet motor 100 of the first embodiment.

[0041] The rotor 320 of the permanent magnet motor according to the third embodiment is shown in Figure 13. The rotor 320 shown in Figure 13 has four main magnetic poles (number of pole pairs P=2), each of which has a first magnet insertion hole 331, a second magnet insertion hole 332, and a third magnet insertion hole 333 that extend linearly. The magnet insertion holes 331 to 333 are arranged along a trapezoid that intersects the d-axis and has a protruding side on the side of the rotation center O (the side opposite the rotation center O is open). In other words, the magnet insertion holes 331 to 333 are arranged in a trapezoidal shape. In Figure 13, the magnet insertion hole 332 is located at the top base of the trapezoid, and the magnet insertion holes 331 and 333 are located at the legs of the trapezoid. Then, linearly extending permanent magnets 341 to 343 are inserted into each of the magnet insertion holes 331 to 333. The outer circumferential surface of the rotor 320 is formed by a first outer circumferential surface portion 320a intersecting the d-axis, a second outer circumferential surface portion 320b intersecting the q-axis, and connecting portions 320c and 320d, similar to the rotor 120 constituting the permanent magnet motor 100 of the first embodiment. Furthermore, trapezoidal magnet insertion holes can be formed in each main magnetic pole, protruding toward the rotation center O. In this case, the first to third permanent magnets, which extend in a straight line, are inserted into the trapezoidal magnet insertion holes.

[0042] The present invention is not limited to the configuration described in the embodiments, and various modifications, additions, and deletions are possible. In permanent magnet motors Regarding As explained, the present invention can be configured as various devices using a permanent magnet motor as the drive motor. For example, it can be configured as a compressor in which the compression mechanism is driven by a permanent magnet motor. The shape, number, and position of the magnet insertion holes formed in 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 changed as appropriate. Each of the configurations described in the embodiments can be used individually, or multiple configurations can be used in combination as appropriate. [Explanation of Symbols]

[0043] 100, 400 permanent magnet motor 110, 410 stator 111, 411 York 112, 412 teeth 113, 413 Teeth base 114, 414 Tooth tip 115, 415 Teeth tip surface (stator inner circumferential surface) 116, 416 slots 120, 220, 320, 420 rotors 120a, 220a, 320a, 420a First outer surface portion 120b, 220b, 320b, 420b Second outer surface portion 120c, 120d, 220c, 220d, 320c, 320d, 420c, 420dc connection part 121, 221, 321, 421 Inner surface 122, 222, 322 interior space 125 Central Bridge Section 126, 127 Outer perimeter bridge section 131, 132, 231, 331, 332, 333, 431, 432 Magnet insertion holes 131a, 132a Inner circumferential side wall portion 131b, 132b outer peripheral side wall 131c, 132c Inner circumferential end wall portion 131d, 132d Outer perimeter end wall 131e, 132e end wall 141, 142, 241, 341, 342, 342, 441, 442 permanent magnets 141a, 142a Inner circumferential outer wall surface 141b, 142b Outer wall surface on the perimeter 141c, 142c Inner circumferential end wall surface 141d, 142d Outer perimeter end wall

Claims

1. Equipped with a stator and a rotor, The stator comprises a plurality of teeth spaced apart along the circumferential direction, a plurality of slots formed by adjacent teeth in the circumferential direction, stator windings wound around each tooth, and an inner circumferential surface of the stator forming the inner space of the stator. The rotor is rotatably arranged within the inner space of the stator, and has alternating principal and auxiliary magnetic poles arranged along the circumferential direction, with permanent magnets inserted into magnet insertion holes formed in the principal magnetic poles. It is a permanent magnet motor, The stator winding is wound around the plurality of teeth in a distributed winding manner. The aforementioned main magnetic poles are provided in four units. The aforementioned teeth are provided in 24 units. The outer circumferential surface of the rotor has a first outer circumferential surface portion that intersects with the d-axis of the main magnetic pole and is formed in an arc shape with radius R1 centered at the rotation center, a second outer circumferential surface portion that intersects with the q-axis of the auxiliary magnetic pole and is formed in an arc shape with radius R2 (R2 < R1) smaller than radius R1 centered at the rotation center, and a connecting portion that connects the first outer circumferential surface portion and the second outer circumferential surface portion. The rotor diameter L is set to satisfy [55 mm ≤ L ≤ 67 mm]. The distance G between the first outer peripheral surface portion and the inner peripheral surface of the stator is set to satisfy [0.5 mm ≤ G ≤ 0.6 mm]. The width Wt of the teeth is set to satisfy [0.36 × (L + 2 × G) × π / 24 < Wt < 0.42 × (L + 2 × G) × π / 24], The opening angle K1 (mechanical angle) of the first outer peripheral surface portion with respect to the rotation center is set to satisfy [22.5 degrees ≤ K1 ≤ 23.5 degrees]. A permanent magnet motor characterized in that the radial distance H between the first outer peripheral surface portion and the second outer peripheral surface portion is set to satisfy [0.6 mm ≤ H ≤ 0.96 mm].

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

3. A permanent magnet motor according to claim 1 or 2, A permanent magnet motor characterized in that the stator and rotor are made of electromagnetic steel sheets in which the magnetic flux density transitions from a linear region to a nonlinear region within the range of 1.75 Tesla and 1.9 Tesla.

4. A compressor comprising a compression mechanism and an electric motor for driving the compression mechanism, wherein the electric motor is a permanent magnet electric motor as described in any one of claims 1 to 3.

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