Permanent magnet synchronous motor

Abstract

The permanent magnet (22) has a recess (25) for embedding into the protrusion (24) of the rotor core (21). When the shortest distance between the outermost part of the recess (25) and the outer diameter arc of the permanent magnet (22) is defined as L1, and the distance between the recess (25) of the permanent magnet (22) and the outer diameter arc of the permanent magnet (22) is defined as L2, the permanent magnet (22) has a recess of L2≥L1. The parallel line is the starting point of the conversion from the adhesion surface of the permanent magnet (22) and the rotor core (21) to the recess (25), and is parallel to the radial line from the center of the shaft (23) of the rotor (20) to the center of the permanent magnet (22).

Description

Technical Field

[0001] This application relates to permanent magnet synchronous motors. Background Technology

[0002] In permanent magnet synchronous motors used in machine tool industries, electric vehicle applications, and air conditioning compressors, the terminal voltage generated by the motor needs to be lower than the input voltage in order to output torque.

[0003] Typically, the torque T generated by a surface magnet type permanent magnet synchronous motor requires a q-axis current Iq; therefore, a decrease in the q-axis current Iq leads to a decrease in torque. Thus, to output large torque at high speeds or during high-speed rotation, effective field weakening control with a small d-axis current Id is required. To achieve this, the following existing technical documents describe techniques for effective field weakening control using a small d-axis current Id while increasing the d-axis inductance Ld.

[0004] In this prior art, by forming a protrusion that extends radially from the rotor core to embed multiple permanent magnets arranged on the surface of the rotor core, the d-axis inductance Ld is increased so that the weak magnetic field control can function effectively and the torque output at high speeds can be improved.

[0005] Existing technical documents

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-131070 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, in existing technology, a recess is provided in the central part of the permanent magnet, and a protrusion embedded in this part protrudes from the rotor core. Because the recess of the permanent magnet is rectangular in shape and the outer diameter of the permanent magnet is an arc, the magnet thickness becomes thinner at the corner of the recess. Typically, in permanent magnets, such as Nd-Fe-B neodymium magnets, irreversible demagnetization occurs due to the counter-magnetic field from the stator or exposure to high-temperature environments, resulting in a decrease in residual magnetic flux density. The existing technology has the following problem: as mentioned above, the thinning of the corner of the recess and the arc of the magnet's outer diameter makes irreversible demagnetization more likely, leading to a reduction in torque output.

[0010] This application is made to solve the problems mentioned above, and aims to obtain a permanent magnet synchronous motor that can suppress the reduction in torque characteristics caused by irreversible demagnetization and improve torque output at high speeds and during high-speed rotation.

[0011] Technical solutions for solving technical problems

[0012] Regarding the permanent magnet synchronous motor disclosed in this application, in a rotor having a rotor core composed of magnetic materials and a plurality of permanent magnets attached to the surface of the rotor core, the rotor core has one or more protrusions that protrude radially toward the stator, and the permanent magnets have one or more recesses for the protrusions to be embedded. When the shortest distance between the outermost part of the recess and the outer diameter arc of the permanent magnet is defined as L1, and the shortest distance between the recess of the permanent magnet and the outer diameter arc of the permanent magnet, which passes through the intersection of the tangent of the outermost part of the recess of the permanent magnet and the parallel line, is defined as L2, the permanent magnet synchronous motor has a recess where L2≥L1. The parallel line is taken from the conversion of the adhesion surface between the permanent magnet and the rotor core to the recess, and is parallel to a radial line from the axis center of the rotor to the center of the permanent magnet.

[0013] Invention Effects

[0014] The permanent magnet synchronous motor according to this application can suppress the reduction of torque characteristics and also improve the torque output at high speeds and high speeds. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the plane perpendicular to the axis of the permanent magnet synchronous motor of Embodiment 1.

[0016] Figure 2 This is a cross-sectional view obtained by magnifying the area near the permanent magnet in a cross-section of a plane perpendicular to the axis of the permanent magnet synchronous motor of Embodiment 1.

[0017] Figure 3 This is a cross-sectional view obtained by magnifying the area near the permanent magnet in a cross-section of a plane perpendicular to the axis of a prior art permanent magnet synchronous motor, which is compared with Embodiment 1.

[0018] Figure 4 A graph comparing the speed-torque characteristics of permanent magnet synchronous motors based on the presence or absence of protrusions / recesses.

[0019] Figure 5 This is a graph comparing the demagnetization rate distribution of the permanent magnets in the permanent magnet synchronous motor of Embodiment 1 with that of the permanent magnet synchronous motor used as a comparison.

[0020] Figure 6 This graph compares the rate of decrease in induced voltage after demagnetization of the permanent magnet synchronous motor of Embodiment 1 with that of the permanent magnet synchronous motor used for comparison.

[0021] Figure 7 This is a partially enlarged cross-sectional view showing a variation 1 of the permanent magnet synchronous motor according to Embodiment 1.

[0022] Figure 8 This is a partially enlarged cross-sectional view showing a variation 2 of the permanent magnet synchronous motor of embodiment 1.

[0023] Figure 9 This is a cross-sectional view obtained by magnifying the area near the permanent magnet in a cross-section of a plane perpendicular to the axis of the permanent magnet synchronous motor of Embodiment 2.

[0024] Figure 10 This is a graph comparing the demagnetization rate distribution of the permanent magnet synchronous motor of Embodiment 2 with that of the permanent magnet synchronous motor used for comparison.

[0025] Figure 11 This is a graph comparing the induced voltage of the permanent magnet synchronous motor in Embodiment 2 with that of the permanent magnet synchronous motor before demagnetization.

[0026] Figure 12 This graph compares the rate of decrease in induced voltage after demagnetization of the permanent magnet synchronous motor of Embodiment 2 with that of the permanent magnet synchronous motor used for comparison.

[0027] Figure 13 This is a partially enlarged cross-sectional view showing a variation 1 of the permanent magnet synchronous motor of embodiment 2.

[0028] Figure 14 This is a partially enlarged cross-sectional view showing a variation 2 of the permanent magnet synchronous motor according to embodiment 2.

[0029] Figure 15 This is a partially enlarged view showing a variation 3 of the permanent magnet synchronous motor according to embodiment 2.

[0030] Figure 16 This is a partially enlarged view showing a variation 4 of the permanent magnet synchronous motor according to embodiment 2.

[0031] Figure 17 This is a partially enlarged cross-sectional view showing a variation 5 of the permanent magnet synchronous motor of embodiment 2.

[0032] Figure 18 This is a cross-sectional view obtained by magnifying the area near the permanent magnet in a cross-section of a plane perpendicular to the axis of the permanent magnet synchronous motor of Embodiment 3.

[0033] Figure 19 This is a graph comparing the demagnetization rate distribution of the permanent magnet synchronous motor of Embodiment 3 with that of a comparative permanent magnet synchronous motor.

[0034] Figure 20 This is a graph comparing the induced voltage of the permanent magnet synchronous motor of Embodiment 3 before demagnetization with that of the permanent magnet synchronous motor used for comparison.

[0035] Figure 21 This is a graph comparing the rate of decrease in induced voltage after demagnetization of the permanent magnet synchronous motor of Embodiment 3 with that of the permanent magnet synchronous motor used for comparison.

[0036] Figure 22This is a partially enlarged cross-sectional view showing a variation 1 of the permanent magnet synchronous motor of embodiment 3.

[0037] Figure 23 This is a partially enlarged cross-sectional view showing a variation 2 of the permanent magnet synchronous motor of embodiment 3.

[0038] Figure 24 This is a partially enlarged cross-sectional view showing a variation 3 of the permanent magnet synchronous motor according to embodiment 3.

[0039] Figure 25 This is a partially enlarged cross-sectional view showing a variation 4 of the permanent magnet synchronous motor of embodiment 3.

[0040] Figure 26 This is a partially enlarged cross-sectional view showing a variation 5 of the permanent magnet synchronous motor of embodiment 3.

[0041] Figure 27 A cross-sectional view showing an example of the rotor in the permanent magnet synchronous motor of Embodiment 4.

[0042] Figure 28 A cross-sectional view showing another example of the rotor in the permanent magnet synchronous motor of embodiment 4.

[0043] Figure 29 A cross-sectional view showing another example of the rotor in the permanent magnet synchronous motor of embodiment 4.

[0044] Figure Labels

[0045] 10: Stator; 11: Stator core; 12: Back of core; 14: Coil; 20: Rotor; 21: Rotor core; 22: Permanent magnet; 23: Shaft; 24, 241a, 241b, 241c, 242a, 242b: Protrusions; 25, 251a, 251b, 251c, 252a, 252b: Recesses. Detailed Implementation

[0046] Implementation method 1.

[0047] The permanent magnet synchronous motor of Embodiment 1 will be described. Figure 1 This is a cross-sectional view showing the structure of the permanent magnet synchronous motor 100 of this embodiment, cut perpendicularly to the axial direction. Here, the direction along the axis of the rotor 20 in the permanent magnet synchronous motor 100 is defined as the axial direction. In the cross-section of the rotor 20 perpendicular to the axial direction, the direction along the radius of the rotor 20 is defined as the radial direction. The direction along the rotation direction of the rotor 20, that is, along the circumference centered on the axis of the rotor 20 in the above cross-section, is defined as the circumferential direction.

[0048] like Figure 1As shown, the permanent magnet synchronous motor 100 has a stator 10 and a rotor 20 rotatably disposed relative to the stator 10. The stator 10 is disposed around the outer periphery of the rotor 20 with a gap 15 serving as a magnetic gap. The stator 10 has a stator core 11 and a plurality of coils 14. The stator core 11 has a core back 12 formed on a ring and a plurality of teeth 13 protruding from the core back 12 toward the inner periphery.

[0049] Multiple coils 14 are wound around multiple teeth 13 respectively. Figure 1 The structure shown includes 12 teeth 13 and 12 coils 14. Although in this embodiment, multiple iron core blocks formed on an arc are connected to a ring to form the core back 12, the core back 12 can also be formed integrally. Alternatively, the core back 12 can be formed separately from each tooth 13.

[0050] The rotor 20, which forms part of a surface-side permanent magnet motor (SPM), includes a rotor core 21 and a plurality of permanent magnets 22 arranged circumferentially on the surface of the rotor core 21. The permanent magnets 22 are configured such that if one of the circumferentially adjacent permanent magnets has an N pole on its outer diameter side, the other has an S pole, thus resulting in different magnetization directions. That is, the permanent magnets are configured such that the polarities of the faces of adjacent permanent magnets opposite to the stator are different.

[0051] Here, although Figure 1 This is a so-called 8-pole 12-slot permanent magnet synchronous motor with 12 teeth 13, 12 coils 14, and 8 permanent magnets 22. However, the combination of the number of permanent magnets 22 with the number of teeth 13 and coils 14 is not limited to this. In addition, although the number of teeth 13 and the number of coils 14 are the same, their numbers can be different.

[0052] The rotor core 21 has a structure, for example, formed by stacking multiple iron chips in the axial direction. The rotor core 21 has a shaft 23 extending through it in the axial direction. The rotor core 21 has radially projecting protrusions 24, and the permanent magnet 22 has recesses 25 into which the protrusions 24 are embedded. Figure 2 The protrusion 24 and the recess 25 are described in detail.

[0053] Figure 2 for Figure 1An enlarged view of the portion surrounded by the dashed circle E. Define a radial line RL that extends radially from the axis center towards the center of the permanent magnet 22. Define the surface where the rotor core 21 contacts the permanent magnet 22 as the adhesion surface AS. Define a line parallel to the radial line RL, with the point where the adhesion surface AS changes towards the recess 25 as the starting point SP. Define a line tangent to the outermost part of the recess 25 and perpendicular to the radial line RL as the tangent TL. Define the point where the tangent TL intersects the parallel line PL as the intersection point A. When the shortest distance from the outermost part of the recess 25 of the permanent magnet 22 to the outer diameter arc of the permanent magnet 22 is defined as L1, and the shortest distance between the outer diameter arc of the permanent magnet 22 and the recess 25, passing through intersection point A, is defined as L2, the recess 25 has a shape where L1 ≤ L2. Figure 1 , Figure 2 In the middle, the corner of the concave part is rounded.

[0054] Figure 3 This is a cross-sectional view showing the structure of a conventional permanent magnet synchronous motor compared to the permanent magnet synchronous motor 100 of Embodiment 1, cut perpendicularly to the axial direction. The stator is omitted from the diagram here. Figure 3 In the text, for structures not explicitly defined, we assume they are related to... Figure 1 It is the same. Figure 3 In the rotor core 21, the protrusion 240 and the concave part 250 of the magnet 22 are rectangular in shape, with a relationship of L1 > L2.

[0055] The effects of this implementation method will be explained next.

[0056] A permanent magnet synchronous motor cannot generate a terminal voltage Vt that exceeds the motor input voltage Vi to output torque T. Typically, as the speed increases, the terminal voltage Vt increases according to the following equations (1) to (4).

[0057] Vt=√(Vd 2 +Vq 2 )……(1)

[0058] Vd=RId+ωLqIq……(2)

[0059] Vq=RIq+ωΦm+ωLdId……(3)

[0060] ω=2πf=2π(N / 60)pn……(4)

[0061] Here, Vd and Vq are the dq-axis voltages, R is the phase resistance, Id and Iq are the dq-axis currents, Φm is the magnetic flux, Ld and Lq are the dq-axis inductances, ω is the angular velocity, f is the frequency, N is the revolutions per minute, and pn is the number of pole pairs. In permanent magnet synchronous motors, as a control method to increase the torque output during high-speed rotation, there is a so-called field-weakening control that suppresses the increase of terminal voltage. This field-weakening control is a control method that connects the d-axis current Id in the direction that weakens the magnetic flux Φm. However, when the d-axis inductance Ld is small, a large d-axis current Id needs to flow. However, there is an upper limit to the current that can be supplied to the motor. When the current supplied from the inverter to the motor is set to Iinv, the following equation (5) is obtained.

[0062] √3×Iinv=√(Id 2 +Iq 2 )……(5)

[0063] The torque T output by an SPM type permanent magnet synchronous motor is typically as shown in equation (6), which is...

[0064] T=PnΦmIq……(6),

[0065] Therefore, when the d-axis current Id increases, the q-axis current Iq used for output torque T decreases, resulting in a reduction in torque output. Thus, to increase the torque T during high-speed rotation, effective field weakening control is required with a smaller d-axis current Id, necessitating an increase in the d-axis inductance Ld. This can be achieved by employing... Figure 3 The structure shown is used to increase the d-axis inductance Ld. Figure 4 This is a graph known as the speed-torque characteristic, where the horizontal axis represents speed (revolutions) and the vertical axis represents torque output. For example... Figure 4 As shown, by applying the protrusion 24 and the recess 25, the torque output at high speeds (high RPMs) is increased.

[0066] However, when the shape of the recess 250 of the permanent magnet 22 is rectangular, or when the outer diameter of the permanent magnet 22, such as in a rotating device, is arc-shaped, the distance between the corner of the recess 250 and the outer diameter of the permanent magnet 22 becomes extremely short. In permanent magnets, there exists a phenomenon called irreversible demagnetization, which occurs when the residual magnetic flux density Br of the permanent magnet decreases due to the temperature rise of the permanent magnet or a counter-magnetic field applied from the stator in the opposite direction to the magnetization direction. The ease of this irreversible demagnetization is related to the coercivity of the permanent magnet and the permeability Pc determined by the magnetic circuit. The permeability Pc depends on the magnetization direction thickness and magnetic reluctance of the magnet. In a magnetic circuit with a narrow magnetic gap between the stator and rotor, such as in a permanent magnet synchronous motor, when the magnetization direction thickness of the permanent magnet is set to Hm and the magnetic gap between the stator and rotor is set to gm, the permeability Pc can be approximated by the following equation (7).

[0067] Pc≈Hm / gm……(7)

[0068] Figure 5 The results are for calculating the demagnetization state of permanent magnet 22 through magnetic field analysis. Figure 5 (a) shows the demagnetization rate distribution when L1 > L2. Figure 5 (b) shows the demagnetization rate distribution when L1 = L2. Figure 5 (c) shows the demagnetization rate distribution when L1 < L2. Darker areas indicate higher demagnetization rates, and lighter areas indicate lower demagnetization rates. Figure 3 When the minimum distance L2 between the outer diameter of the permanent magnet 22 and the recess 250 becomes narrower, as shown, Figure 5 As shown in (a), demagnetization is improved over a wide range.

[0069] In this embodiment 1, as Figure 1 , 2 As shown, the recess 25 of the permanent magnet 22 is made into an arc shape so that the shortest distance L2 between the outer diameter of the permanent magnet 22 and the recess 25 is L1≤L2.

[0070] like Figure 5 As shown, increasing the length of L2 suppresses demagnetization. Furthermore, Figure 6 Shown in Figure 5 The graph showing the rate of decrease in induced voltage before and after demagnetization under the given shape is obtained by normalizing the rate of decrease in induced voltage for L1 > L2 to 1.0. Figure 6 As shown, compared to the prior art where L1 > L2, the rate of decrease in induced voltage is smaller. This results in a decrease in induced voltage, which in turn leads to a decrease in magnet flux Φm, and as mentioned above, a decrease in torque T, thus reducing torque in the low-speed range. Furthermore, according to Embodiment 1, Figure 4 The speed-torque characteristics shown will not change, and the same output improvement effect can be achieved.

[0071] Figure 7 This is a partially enlarged view of a variation 1 of the permanent magnet synchronous motor according to embodiment 1. Figure 1 and Figure 7 The only difference lies in whether the outermost shape of the recess 25 of the permanent magnet 22 is an arc or a flat shape with rounded corners; the effect obtained is the same regardless of the shape. Furthermore, Figure 8 This is also a partially enlarged view of a variation 2 of the permanent magnet synchronous motor of implementation method 1. Figure 8 and Figure 1 , Figure 7 The difference lies in the fact that the corner portion of the recess 25 of the permanent magnet 22 is formed at an angle, but even with this shape, the effect obtained is similar to... Figure 1The structures shown are no different.

[0072] Furthermore, although the protrusion 24 of the rotor core 21 shown in Embodiment 1 is in contact with all surfaces of the recess 25 of the permanent magnet 22, it is not necessary for all surfaces to be in contact; only one surface may be in contact. From a manufacturing point of view, to prevent cross-contamination or damage to the permanent magnet during manufacturing, it is preferable that the size of the recess 25 of the permanent magnet 22 is larger than the protrusion 24 of the rotor core 21. In addition, when considering the torque pulsation and increase in cogging torque caused by the installation offset of the permanent magnet 22, the offset of the installation position can be minimized by deflecting it towards a certain surface.

[0073] Implementation method 2.

[0074] The permanent magnet synchronous motor of Embodiment 2 will be described. Figure 9 To cut off the permanent magnet synchronous motor of Embodiment 2 perpendicular to the axis, and Figure 2 Similarly, a cross-sectional view obtained by magnifying the vicinity of permanent magnet 22 is shown. Figure 9 Although not illustrated, it is similar to Figure 1 Similarly, it includes stator 10 and rotor 20.

[0075] exist Figure 9 In this embodiment, the permanent magnet synchronous motor differs from the permanent magnet synchronous motor of Embodiment 1 in the following aspects.

[0076] The permanent magnet 22 has three recesses: recess 251a, recess 251b, and recess 251c. The rotor core 21 has three radial protrusions: protrusion 241a, protrusion 241b, and protrusion 241c.

[0077] Furthermore, in this embodiment 2, as Figure 9 As shown, the recess 251a and protrusion 241a located in the center of the permanent magnet 22 are located on the outermost diameter side.

[0078] The rotor core has an odd number of protrusions for each pole, and has a protrusion assembly consisting of multiple protrusions as a group of protrusions. On the circumferential outer side of the protrusion assembly, the shortest distance L2 between the concave part on the circumferential outer side and the outer diameter arc part of the permanent magnet is L1≤L2.

[0079] In Embodiment 2, the shortest distance L1 refers to the shortest distance between the outermost part of the recess 251a of the permanent magnet 22 and the outer diameter arc of the permanent magnet 22. Additionally, as... Figure 9As shown, the shortest distance L2 mentioned in Embodiment 2 is the shortest distance between the recess 251b or 251c and the outer diameter arc of the permanent magnet 22 passing through the intersection point A. The intersection point A is the intersection of the tangent line TL that is tangent to the outermost part of the recess 251a of the permanent magnet 22 and the parallel line PL. The parallel line PL takes the point SP where the adhesion surface AS of the permanent magnet 22 turns to the outermost part of the circumference of the recess 251b or 251c, and is parallel to the radial line RL that extends from the axis center of the rotor 20 toward the center of the permanent magnet 22.

[0080] Here, although in Figure 9 The recesses 251b and 251c are of the same size, but are not required to be the same size. However, from the viewpoint of reducing torque ripple, cogging torque, etc., it is preferable that they are of the same size.

[0081] The effects of Implementation Method 2 will be explained next.

[0082] Figure 10 A graph showing the demagnetization rate distribution of the permanent magnet 22 in Embodiment 2 and the demagnetization rate distribution of the prior art as a comparison. Figure 10 (a) shows the demagnetization rate distribution when L1 > L2. Figure 10 (b) shows the demagnetization rate distribution under Embodiment 2. Darker areas indicate higher demagnetization rates, and lighter areas indicate lower demagnetization rates. Figure 10 As shown, in Embodiment 2, the distribution of high demagnetization rates narrows, similar to Embodiment 1. Furthermore, Figure 11 , Figure 12 The diagram illustrates the difference between the induced voltage before demagnetization and the rate of decrease in induced voltage after demagnetization in Embodiment 2, as in the prior art where L1 > L2. Here, each diagram is obtained by normalizing the induced voltage and rate of decrease in induced voltage of the prior art to 1.

[0083] like Figure 11 , Figure 12 As shown, the induced voltage of this embodiment 2 is larger than that of the prior art, and the rate of decrease in induced voltage due to demagnetization is smaller than that of the prior art.

[0084] Based on the above, compared with the prior art, by employing a method that has multiple recesses in the permanent magnet 22 and multiple protrusions in the rotor core 21, Figure 9 This method can suppress the degradation of motor characteristics. Furthermore, due to the protrusion, it can interact with... Figure 4 Similarly, the speed-torque characteristic is increased in the high-speed range.

[0085] Figure 13 , Figure 14These are enlarged views of modified versions 1 and 2 of the permanent magnet synchronous motor according to embodiment 2. They differ from the original model in the following aspects. Figure 9 different.

[0086] The protrusions 241a to 241c of the rotor core 21 have different shapes from the recesses 251a to 251c of the permanent magnet 22. The permanent magnet 22 is not completely embedded between the protrusions 241a and 241b or between the protrusions 241a and 241c, and there is a gap. Figure 14 The gap in the middle is greater than Figure 13 The gaps in the structure. Typically, Nd-Fe-B based magnets used as permanent magnets employ heavy rare earth elements, making them expensive. By adopting this structure, the amount of permanent magnet 22 used can be reduced, lowering costs. Furthermore, it simplifies the processing of the permanent magnet, reducing processing expenses.

[0087] Through such Figure 13 , Figure 14 Although the induced voltage is slightly reduced with this configuration, the same effect as in embodiment 2 can be achieved, so there is no problem.

[0088] Figure 15 To illustrate embodiment 2 Figure 9 The enlarged view of deformation mode 3 shows that, apart from the protrusions 241a-241c and the recesses 251a-251c being rectangular in shape, they are different. Figure 15 It has the same structure as Embodiment 2. Therefore, the same effect as Embodiment 2 can be obtained, so there is no problem.

[0089] Figure 16 , Figure 17 The images shown are enlarged views of variations 4 and 5, illustrating variations of embodiment 2. Figure 13 , Figure 14 Examples of variations. Except for the fact that the protrusions 241a-241c and the recesses 251a-251c are rectangular, they are different. Figure 16 , Figure 17 To and Figure 13 , Figure 14 The same structure can be achieved. Therefore, there is no problem in obtaining the same effect as in embodiment 2.

[0090] Although this is embodiment 2 Figure 9 , Figures 13-17 The permanent magnet shown is in the shape of having 3 protrusions, but it is not a problem even if the number of protrusions is an odd number of 3 or more.

[0091] Implementation method 3.

[0092] The permanent magnet synchronous motor of embodiment 3 will be described. Figure 18 The diagram is an enlarged view of the area near the permanent magnet of the rotor of the permanent magnet synchronous motor of Embodiment 3, and is a cross-sectional view obtained by cutting perpendicular to the axis of the shaft.

[0093] exist Figure 18 In this embodiment, there are two protrusions from the rotor core 21, and two recesses in the permanent magnet 22. The shortest distance L1 is the shortest distance between the outermost edge of the recess 252a or 252b of the permanent magnet 22 and the outer diameter arc of the permanent magnet. Unlike embodiments 1 and 2, the shortest distance L1 is not near the center of the permanent magnet. Furthermore, the shortest distance L2 is defined as follows: a tangent TL is defined that is tangent to the outermost edge of the recess 252a or 252b of the permanent magnet. Define a parallel line PL, which starts at the transition point SP from the adhesion surface AS of the rotor core 21 and the permanent magnet 22 to the concave portion 252a or 252b of the permanent magnet, and is parallel to the radial line RL extending from the axis center of the rotor 20 towards the center of the permanent magnet 22. Then, regarding the shortest distance L2, the shortest distance between the concave portion 252a or 252b of the permanent magnet 22 and the outer diameter arc portion of the permanent magnet 22, passing through the intersection of the tangent line TL and the parallel line PL, is defined as L2. The relationship between L1 and L2 is the same as in embodiments 1 and 2: L1 ≤ L2.

[0094] In this way, the rotor core has an even number of protrusions for each pole, and has a protrusion assembly with multiple protrusions as a group of protrusions. On the circumferential outer side of the protrusion assembly, the shortest distance L2 between the concave part formed on the circumferential outer side and the outer diameter arc part of the permanent magnet is L1≤L2.

[0095] The effects of this third embodiment will now be explained.

[0096] Figure 19 A graph showing the demagnetization rate distribution of the permanent magnet 22 in this embodiment 3 and the demagnetization rate distribution of the prior art as a comparison. Figure 19 (a) shows the demagnetization rate distribution when L1 > L2. Figure 19 (b) shows the demagnetization rate distribution in Embodiment 3. Darker areas indicate higher demagnetization rates, and lighter areas indicate lower demagnetization rates. Figure 19 As shown, in Implementation 3, similar to Implementation 1 and 2, the distribution of high demagnetization rate becomes narrower. Figure 20 This is the result of comparing the induced voltage of the prior art (L1>L2) which is normalized to 1 with the induced voltage of this embodiment. Additionally, Figure 21 This graph compares the induced voltage reduction rate of the prior art (L1>L2) with that of this embodiment, which is standardized to 1.

[0097] like Figure 20As shown, by adopting this embodiment, the induced voltage is increased. Furthermore, as... Figure 21 As shown, the rate of decrease in induced voltage decreases. This is an effect of removing the concave portion of the magnet near the center of the magnet, because the fundamental frequency of the gap magnetic flux density of the magnet, which contributes to the torque generated between the stator 10 and the rotor 20, increases. Therefore, the torque in the low-speed range can be increased, and the decrease in magnet flux caused by irreversible demagnetization due to the countermagnetic field at high temperatures can also be suppressed. In other words, the torque decrease at high temperatures can be suppressed.

[0098] Figure 22 This is a partially enlarged view of a modified version 1 of the permanent magnet synchronous motor of Embodiment 3, which differs from the following aspects. Figure 18 different.

[0099] Figure 22 The difference lies in the fact that the permanent magnet 22 sandwiched between the two protrusions 242a and 242b does not extend to the rotor core 21 but extends halfway. The reason for this approach is that if the circumferential width of the portion sandwiched between the protrusions 242a and 242b is narrow, it could lead to cracking or damage to the magnet, and may even make manufacturing impossible. Therefore, considering production feasibility, it is preferable to adopt a structure where the bottom surface of the permanent magnet 22 is located further outward than the outer circumference. In this structure, it is also possible to obtain... Figure 18 The same effect is achieved in this embodiment 3.

[0100] In addition, such as Figure 23 As shown, a modified version 2, in which the rotor core sandwiched between protrusions 242a and 242b is located on the outer diameter side, can also be considered. The same effect as embodiment 3 can be achieved in this modified version 2.

[0101] Figures 24-26 The images show partial enlarged views of variations 3, 4, and 5 of the permanent magnet synchronous motor according to Embodiment 3. The protrusions and recesses are mirror-symmetrical about the circumferential center of the permanent magnet 22. Furthermore, this mirror-symmetrical shape structure of the protrusions and recesses is also present in other embodiments such as Embodiment 1 and Embodiment 2, where they are mirror-symmetrical about the radial line RL in each embodiment.

[0102] In addition, Figure 24 Deformation method 3 and Figure 25 In deformation mode 4, the outermost shape of the part forming the shortest distance L2 in the concave portion is an arc shape. Additionally, in... Figure 26 In variation 5, the shape of the portion forming the shortest distance L2 in the recess is formed at an angle. The same effect as in embodiment 3 can be achieved in these variations.

[0103] Implementation method 4.

[0104] The permanent magnet synchronous motor of embodiment 4 will be described. Figure 27 This is a cross-sectional view showing the structure obtained by cutting the rotor portion of the permanent magnet synchronous motor of Embodiment 4 perpendicularly to the shaft axis. The basic structure is the same as that of Embodiments 1 to 3, but differs in the following aspects.

[0105] In this embodiment, such as Figure 27 As shown, a gap 26 is provided in the rotor core 21 of the rotor. By configuring this gap 26, the q-axis inductance Lq in the permanent magnet synchronous motor can be reduced. Therefore, ωLqIq described in the aforementioned equations (1) to (4) can be reduced, resulting in a decrease in the d-axis voltage Vd and the terminal voltage Vt. In other words, voltage saturation is mitigated, and the speed-torque characteristics can be increased.

[0106] Figure 28 , Figure 29 It is also equipped with a gap of 26. Furthermore, Figure 27 and Figure 2 The structure corresponds to, Figure 28 and Figure 9 The structure corresponds to, Figure 29 and Figure 18 The structure corresponds to this.

[0107] Figures 27-29 This is one example of a slot configuration. It is not limited to these examples, but can be implemented as long as a slot is configured to increase the magnetic reluctance relative to the q-axis flux Φq in a permanent magnet synchronous motor. Furthermore, although in Figures 27-29 The standard configuration includes two slots for each pole, but configuring more than two slots is also acceptable.

[0108] Although this application describes various exemplary embodiments and examples, the various features, forms and functions described in one or more embodiments are not limited to the application of a specific embodiment, but can be applied to the embodiment alone or in various combinations.

[0109] Therefore, numerous variations not illustrated are contemplated within the scope of the technology disclosed in this application. These include variations, additions, or omissions of at least one constituent element, as well as extraction of at least one constituent element and combination with constituent elements of other embodiments.

Claims

1. A permanent magnet synchronous motor, comprising a stator and a rotor disposed with a gap between said stator, characterized in that, The rotor has a rotor core made of magnetic material, and multiple permanent magnets are arranged on the surface of the rotor core. Regarding the shape of the permanent magnets, the surface opposite the stator is arc-shaped. The rotor core has one or more protrusions that project radially toward the stator core, and the permanent magnet has a recess into which the protrusions are embedded. When the shortest distance between the outermost part of the concave portion and the outer diameter arc portion of the permanent magnet is defined as L1, and the shortest distance between the concave portion and the outer diameter arc portion, passing through the intersection of the tangent and the parallel line at the outermost part of the concave portion, is defined as L2, the permanent magnet synchronous motor includes a permanent magnet with the concave portion having L1≤L2, wherein... The parallel line originates from the point where the adhesion surface between the permanent magnet and the rotor core transitions to the concave portion of the permanent magnet, and is parallel to a radial line extending from the axial center of the rotor towards the center of the permanent magnet. The rotor core has multiple protrusions for each pole, forming a protrusion assembly with the multiple protrusions as a group. On the circumferential outer side of the protrusion assembly, the shortest distance L2 between the circumferentially outer recess and the outer diameter arc portion of the permanent magnet is L1≤L2. The multiple protrusions of the rotor core have different shapes from the concave portions of the permanent magnet, and the permanent magnet is not completely embedded between the multiple protrusions, leaving gaps.

2. The permanent magnet synchronous motor according to claim 1, characterized in that, The recess is in contact with at least one surface of the protrusion.

3. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that, In the recess, the outermost shape of the portion forming the shortest distance L2 is an arc shape.

4. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that, In the recess, the portion forming the shortest distance L2 is shaped at an angle.

5. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that, The number of the recesses is an odd number, which is 3 or more.

6. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that, The number of the recesses is an even number, which is 2 or more.

7. The permanent magnet synchronous motor according to claim 5, characterized in that, The number of protrusions is an odd number of 3 or more.

8. The permanent magnet synchronous motor according to claim 6, characterized in that, The number of protrusions is an even number of two or more.

9. The permanent magnet synchronous motor according to claim 5, characterized in that, The plurality of recesses and the plurality of protrusions are mirror-symmetrical about the circumferential center of the permanent magnet.

10. The permanent magnet synchronous motor according to claim 6, characterized in that, The plurality of recesses and the plurality of protrusions are mirror-symmetrical about the circumferential center of the permanent magnet.

11. The permanent magnet synchronous motor according to claim 1 or 2, characterized in that, The rotor is provided with a gap in such a way that the magnetic reluctance increases relative to the q-axis magnetic flux Φq in the permanent magnet synchronous motor.

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