Permanent magnet rotary electric machine and compressor using the same

Abstract

Permanent magnet type rotary electric machine has stator and rotor, the stator has stator core with multiple teeth and slot, motor coil, the rotor has rotor core and multiple permanent magnets embedded in the rotor core. The outer contour of the rotor core includes d-axis arc segment, q-axis arc segment / q-axis straight line segment and several connecting segments, the center of the d-axis arc segment coincides with the rotation center O of the rotor core; q-axis arc segment / q-axis straight line segment, the center of the q-axis arc segment coincides with the rotation center O of the rotor core, and the q-axis straight line segment is orthogonal to the q-axis; several connecting segments are connected between adjacent d-axis arc segment and q-axis arc segment, at least one of the several connecting segments has a center not coinciding with the rotation center O of the rotor core and located inside the rotor core, and the circular arc connecting segment tangent to the d-axis arc segment is arranged adjacent to the d-axis.

Description

Technical Field

[0001] This invention relates to a permanent magnet rotary motor for having a magnetic field in its rotor, and more particularly to a permanent magnet rotary motor suitable for use in compressors of air conditioners, refrigerators, freezers or food display cabinets, and compressors using permanent magnet rotary motors. Background Technology

[0002] Previously, in this type of permanent magnet rotary motor, the stator coils, which serve as the motor coils, were condensed, and rare-earth neodymium permanent magnets were used in the magnetic field to achieve miniaturization and high efficiency. However, with the increase in output density resulting from miniaturization and high efficiency, the nonlinear magnetic characteristics (hysteresis) of the iron core become significantly affected, and the spatial harmonic flux increases accordingly with the use of condensed winding. By employing concentrated windings in the stator coils and using permanent magnets with high flux density in the magnetic field, the efficiency of permanent magnet rotary motors has been dramatically improved. Conversely, in a structure where the stator coils are concentrated, harmonic flux theoretically increases, but this is a consequence of the high flux density permanent magnets amplifying these harmonic fluxes. That is, with the increase in output density resulting from miniaturization and high efficiency, the nonlinear magnetic characteristics of the core increase, and the magnetic force of the high flux density permanent magnets becomes stronger. Therefore, the vibration and noise of the permanent magnet rotary motor itself tend to increase, especially when assembled in a compressor, where there is a frequency band in the middle region that becomes the most jarring. To reduce compressor noise, it is necessary to minimize vibrations generated by the motor itself or prevent these vibrations from being transmitted to the compressor. Effective methods to reduce motor vibration include reducing harmonic components of the magnetic flux generated within the permanent magnet rotary motor (electric motor), thereby reducing pulsating torque and radial electromagnetic vibration force. Therefore, a permanent magnet rotary motor and a compressor using a permanent magnet rotary motor are proposed. Summary of the Invention

[0003] The purpose of this invention is to address the problem that, with the increase in output density resulting from miniaturization and high efficiency, the nonlinear magnetic characteristics (hysteresis) of the iron core become significant, and the spatial harmonic flux increases accordingly with the adoption of concentrated winding. Therefore, this invention proposes a permanent magnet rotary motor and a compressor using a permanent magnet rotary motor.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a permanent magnet rotary motor, comprising a stator and a rotor; the stator having an annular yoke, a plurality of teeth protruding radially inward from the yoke and arranged in a circumferential direction, and a stator core having a plurality of slots formed between the teeth; and a motor coil disposed in the slots and wound around the teeth; the rotor having a rotor core and a plurality of permanent magnets embedded in the rotor core and arranged in a circumferential direction, rotatably configured with the stator through a gap, characterized in that the rotor core has a plurality of permanent magnet slots spaced apart along the circumference of the rotor core, and in a plane perpendicular to the rotation center O axis of the rotor core, the outer contour of the rotor core includes: a d-axis arc segment, the center of which coincides with the rotation center O of the rotor core; a q-axis arc segment / q-axis straight segment; the q-axis arc segment The center of the circle coincides with the rotation center O of the rotor core; the straight segment of the q-axis is orthogonal to the q-axis; a plurality of connecting segments, wherein the connecting segments are located between adjacent arc segments of the d-axis and arc segments of the q-axis / straight segments of the q-axis, at least one of the plurality of connecting segments is an arc-shaped connecting segment whose center does not coincide with the rotation center O of the rotor core and is located inside the rotor core, and is tangent to the arc segment of the d-axis; the arc-shaped connecting segment is located adjacent to the d-axis; the arc segment of the d-axis... The radius is Rd, and the straight-line distance between the intersection of the q-axis arc segment / q-axis straight segment and the q-axis and the rotation center O of the rotor core is defined as Lq; the minimum gap between the tooth arc segment of the stator core and the d-axis arc segment is g, 0.1≤(Rd-Lq) / g≤1; the included angle of the d-axis arc segment is α; the included angle between the front end of the stator core tooth and the imaginary line connecting the rotation center O of the rotor core is β, 0.5≤α / β≤1.

[0005] Preferably, the radius of the arc-shaped connecting segment is smaller than the radius Rd of the d-axis arc segment.

[0006] Preferably, the area enclosed by the outer contour of the rotor core is S1; the area of ​​the circle containing the d-axis arc segment is S2, where S2 = πRd. 2 The area of ​​the circle containing the tooth arc segment of the stator core is S3, where S3 = π(Rd + g). 2 , 0.1≤(S2-S1) / (S3-S2)≤0.6; the rotor core has 8 poles and the stator core has 12 slots.

[0007] Preferably, the minimum width of the radial flux saturation portion between adjacent permanent magnet slots is no greater than 0.8 mm.

[0008] Preferably, the minimum width of the circumferential flux saturation portion between the permanent magnet slot and the outer contour of the rotor core is no greater than 0.6 mm.

[0009] Preferably, each pole of the permanent magnet embedded in the rotor core is composed of two permanent magnets; the two permanent magnets are arranged in a convex V-shape with the d-axis as the axis of symmetry and facing the rotation center O of the rotor core.

[0010] Preferably, the ratio of the number of poles of the rotor to the number of slots of the stator is 2:3.

[0011] Preferably, both the stator core and the rotor core are formed by stacking multiple silicon steel plates with a thickness of no more than 0.35 mm.

[0012] Preferably, at least one of the connecting segments is a straight connecting segment.

[0013] A compressor, characterized in that: the compressor is equipped with a permanent magnet rotary motor.

[0014] The beneficial effects of the present invention are that it enables the production of a small, efficient, and low-noise permanent magnet rotary motor and a compressor using the permanent magnet rotary motor. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the permanent magnet rotary motor of the present invention.

[0016] Figure 2 This is the present invention. Figure 1 A cross-sectional view of the rotor shape of a permanent magnet rotary electric motor.

[0017] Figure 3 This is a schematic diagram of the induced electromotive force distribution waveform of the permanent magnet rotary motor of the present invention.

[0018] Figure 4 This is a schematic diagram of the harmonic content of the induced electromotive force of the permanent magnet rotary motor of the present invention.

[0019] Figure 5 This is a schematic diagram of the air gap magnetic flux density distribution waveform of the permanent magnet rotary motor of the present invention.

[0020] Figure 6 This is a schematic diagram of the air gap magnetic flux density harmonic content of the permanent magnet rotary motor of the present invention.

[0021] Legend 1—Permanent magnet rotary motor; 2—Stator; 3—Rotor; 4—Gear; 4a—Arch segment of tooth; 4b, 4c—Front end of tooth; 5—Yoke; 6—Stator core; 7—Slot; 8—Motor coil; 8a—U-phase coil; 8b—V-phase coil; 8c—W-phase coil; 9—Rivet hole; 10—Outer contour of rotor core; 10a—Arch segment of d-axis; 10b—Arch segment of q-axis / straight segment of q-axis; 10c—Arch-shaped connecting segment; 10d—Straight connecting segment; 11—Permanent magnet slot; 11a, 11b—Protruding parts of permanent magnet slot; 12—Rotor core; 13—Permanent magnet; 14—Shaft hole; 15—Circumferential flux saturation part; 16—Radial flux saturation part. Detailed Implementation

[0022] The permanent magnet rotary motor and the compressor using the permanent magnet rotary motor described in this invention will now be further described with reference to the accompanying drawings.

[0023] In this embodiment, the application of the present invention to a permanent magnet rotary motor consisting of an 8-pole rotor and a 12-slot stator (8 poles, 12 slots) will be described. Furthermore, the ratio of the number of poles in the rotor to the number of slots in the stator is 2:3, but this can be applied similarly to other ratios of poles, slots, and rotor poles to stator slots, achieving substantially the same effect. For example, the number of poles in the rotor can be 4 poles, 6 poles, etc. Additionally, the permanent magnet rotary motor of this embodiment is a so-called embedded magnet type rotary motor where the permanent magnets are located in the rotor core.

[0024] In the following description, "axial" refers to the direction of the rotor's rotation axis, "radial" refers to the rotor's radial direction, and "circumferential" refers to the rotor's circumferential direction.

[0025] Figure 1 The cross-sectional view of the permanent magnet rotary electric motor of this embodiment shown is a cross-section in a direction perpendicular to the rotation axis (described later). Figure 2 (The same applies); In addition, this embodiment operates as a permanent magnet synchronous motor.

[0026] like Figure 1 As shown, the permanent magnet rotary motor 1 consists of a stator 2 and a rotor 3, which is disposed inside the stator 2 with a predetermined gap (gap) and rotates together with the shaft (not shown).

[0027] The stator 2 comprises a stator core 6 consisting of a ring-shaped yoke 5, 12 teeth protruding radially inward from the yoke 5 and arranged at approximately equal intervals along the circumferential direction, and motor coils 8 wound in a manner surrounding the teeth 4 in slots 7 between adjacent teeth 4 along the circumferential direction.

[0028] That is, the motor coil 8 is wound around the axis of the radially arranged teeth 4, and the three-phase coils U-phase coil 8a, V-phase coil 8b and W-phase coil 8c are arranged with gaps between each other in the circumferential direction.

[0029] In addition, the stator 2 is constructed by stacking the stator core 6 (electromagnetic steel plate) in the axial direction, and the slot 7 forms 12 slots in the adjacent tooth 4.

[0030] The rotor 3 consists of a rotor core 12 and 16 permanent magnets 13 embedded on the outer periphery of the rotor core 12 and arranged at approximately equal intervals in the circumferential direction, forming an 8-pole rotor. A shaft hole 14 is formed at the rotation center of the rotor 3, and a cylindrical shaft (not shown) is integrally fixed in the shaft hole 14. The rotor 3 is rotatably disposed on the inner circumferential surface of the stator 2 with a gap between them.

[0031] In this embodiment, the permanent magnet rotary motor 1 has 8 poles on the rotor 3 and 12 slots on the stator 2 (eight poles and twelve slots).

[0032] In the permanent magnet rotary motor 1 of this embodiment, if a three-phase alternating current is passed through the motor coil 8 composed of the three-phase coils 8a to 8c, a rotating magnetic field is generated. By utilizing this rotating magnetic field to act on the permanent magnet 13 embedded in the rotor 3 and the rotor core 12, the rotor 3 rotates.

[0033] In addition, in order to reduce iron losses such as eddy current losses generated on the stator core 6 and rotor core 12 when the permanent magnet rotary motor 1 is in operation, the stator core 6 and the rotor core 12 are preferably constructed by laminating multiple layers of thin plates made of magnetic steel plates such as silicon steel plates.

[0034] exist Figure 2 In this rotor 3, there is a rotor core 12 with a shaft hole 14 formed at its rotation center. Near the outer peripheral surface of the rotor core 12, a plurality of permanent magnet slots 11 are formed, arranged in a V-shape convex towards the rotation center O of the rotor core 12. Each magnetic pole has two permanent magnets 13, which are arranged in a convex V-shape relative to the shaft hole 14. Permanent magnets 13, made of magnetic material such as rare-earth neodymium, are inserted into these plurality of permanent magnet slots 11 in a flat and straight shape.

[0035] Here, in Figure 2In the rotor cross-section, the imaginary axis connecting the center of symmetry of the permanent magnet slot 11 and the rotation center O of the rotor core 12 is defined as the d-axis (magnetic flux axis), and the axis that is electrically orthogonal to the d-axis (the axis between permanent magnets) is defined as the q-axis. It can be understood that the q-axis also passes through the rotation center O of the rotor core 12.

[0036] The outer contour 10 of the rotor core 12 is described in more detail below. Specifically, the center of the d-axis arc segment 10a coincides with the rotation center O of the rotor core 12. The center of the q-axis arc segment 10b coincides with the rotation center O of the rotor core 12. The q-axis straight segment 10b is orthogonal to the q-axis.

[0037] Several connecting segments connect adjacent q-axis arc segments / q-axis straight segments 10b and d-axis arc segments 10a. At least one of the connecting segments is an arc-shaped connecting segment 10c whose center is located inside the rotor core 12 and tangent to the d-axis arc segment 10a of the rotor core 12. The arc-shaped connecting segment 10c is located adjacent to the d-axis, and its center does not coincide with the rotation center O of the rotor core 12. The radius r of the arc-shaped connecting segment 10c is smaller than the radius Rd of the d-axis arc segment. The straight-line distance between the intersection of the q-axis arc segment / q-axis straight segment 10b and the q-axis of the rotor core 12 and the rotation center O of the rotor core 12 is defined as Lq. The minimum gap between the tooth arc segment 4a of the stator core 6 and the d-axis arc segment 10a is defined as g, where 0.1 ≤ (Rd - Lq) / g ≤ 1.

[0038] It should be noted that, in the circumferential direction of the rotor core 12, the d-axis arc segment 10a, several connecting segments, and the q-axis arc segment / q-axis straight segment 10b are sequentially and cyclically connected to form the outer contour 10 of the rotor core 12. At least one of the connecting segments is an arc-shaped connecting segment 10c with its center located inside the rotor core 12, so that the outer contour of the rotor core 12 has a concave characteristic.

[0039] According to an embodiment of the present invention, the rotor core 12 is designed with (Rd-Lq) / g in the range of 0.1 to 1, and its outer contour is designed to have a concave shape. Furthermore, the arc-shaped connecting segment 10c connecting the d-axis arc segment 10a of the rotor core 12 is tangent to the d-axis arc segment 10a, resulting in a smooth connection of the outer contour of the rotor core 12 from the d-axis arc segment 10a to the q-axis arc segment / q-axis straight segment 10b. This connection structure enables the induced electromotive force waveform to be sinusoidal, thus the motor current can also be sinusoidal, reducing harmonic magnetic flux generated by the interaction between the induced electromotive force and the motor current. In other words, this structure suppresses motor reaction and reduces the harmonic components of the magnetic flux within the rotating motor.

[0040] in, Figure 3 This is the induced electromotive force waveform of the permanent magnet rotary motor 1 in this embodiment of the invention, and the induced electromotive force waveform has good sinusoidal properties. Figure 5 This is the air gap magnetic flux density distribution waveform of the permanent magnet rotary motor 1 in this embodiment of the invention, and the air gap magnetic flux density waveform distribution is relatively good.

[0041] Preferably, the area enclosed by the outer contour of the rotor core 12 is S1, and the area of ​​the circle containing the d-axis arc segment is S2, where S2 = πRd 2 The area of ​​the circle containing the tooth arc segment of the stator core is S3, where S3 = π(Rd + g). 2 0.1≤(S2-S1) / (S3-S2)≤0.6. By adjusting the ratio of (S2-S1) to (S3-S2), the structure of the rotor core 12 can be optimized.

[0042] According to some embodiments of the present invention, such as Figure 1 and Figure 2 As shown, the included angle of the d-axis arc segment 10d is α, and the included angle between the imaginary line connecting the front ends 4b and 4c of the stator core 6 teeth and the rotation center O of the rotor core 12 is β, where 0.5 ≤ α / β ≤ 1. By adjusting the ratio of included angle α to included angle β, the sine wave of the induced electromotive force is further optimized, the air gap flux distribution is further optimized, and the harmonic content of the air gap flux is further reduced. Simultaneously, the magnetic flux generated by the permanent magnet 11 can pass more smoothly through the gap between the d-axis arc segment 10a and the tooth arc segment 4a, thereby increasing the output torque of the permanent magnet rotary motor 1.

[0043] According to some embodiments of the present invention, the minimum width w1 of the radial flux saturation portion 16 between adjacent permanent magnet slots 11 is no greater than 0.8 mm. In other words, the permanent magnet slots 11 are closed slots, and the width of the portion of the rotor core 12 located between adjacent permanent magnet slots 11 in the circumferential direction of the rotor core 12 is designed to be sufficiently small to form a flux saturation portion. This effectively reduces the leakage flux of the permanent magnets 13, increases the main flux, and thereby increases the air gap flux value.

[0044] According to some embodiments of the present invention, the minimum width w2 of the circumferential flux saturation portion 15 between the permanent magnet slot 11 and the outer contour 10 of the rotor core 12 is not greater than 0.6 mm. For example, the permanent magnet slot protrusions 11a and 11b of the V-shaped permanent magnet slot 11 extend circumferentially along the rotor core 12 in a protruding manner. In this way, a better sinusoidal waveform of the induced electromotive force and a smaller air gap flux harmonic content are ensured.

[0045] Preferably, both the stator core 6 and the rotor core 12 are formed by stacking multiple silicon steel plates with a thickness of no more than 0.35 mm, which can effectively reduce iron losses such as eddy current losses and improve motor efficiency.

[0046] According to some embodiments of the present invention, such as Figure 1 and Figure 2 As shown, at least one of the connecting segments is a straight line. In other words, the d-axis arc segment 10a, at least one arc-shaped connecting segment 10c with its center located inside the rotor core 12, at least one straight connecting segment 10d, and the q-axis arc segment / q-axis straight segment 10b are cyclically connected to form the outer contour 10 of the rotor core 12. Optionally, the arc-shaped connecting segment 10c and the straight connecting segment 10d with their centers located inside the rotor core 12 can be directly connected or connected by rounded chamfers, thus simplifying the outer contour shape of the rotor core 12 and facilitating manufacturing.

[0047] Specifically, the outer contour 10 of the rotor core 12 is composed of a cyclically connected q-axis arc segment / q-axis straight segment 10b, a straight connecting segment 10d, an arc connecting segment 10c with its center located inside the rotor core 12, and a d-axis arc segment 10a. The portion of the outer contour 10 of the rotor core 12 located between adjacent q-axis is symmetrical about the corresponding d-axis. Wherein, Rd=28.95mm, Lq=28.75mm, g=0.55mm, α=16°, β=25°, the radius r of the arc-shaped connecting section 10c located inside the rotor core 12 is 10.95mm, and the distance L=18mm between its center and the rotation center O of the rotor core 12 satisfies r+L=Rd, that is, the arc-shaped connecting section 10c is tangent to the d-axis arc section 10a, and the radius r of the arc-shaped connecting section 10c is smaller than the radius Rd of the d-axis arc section 10a, so that the outer contour of the rotor core 12 is designed to have a concave shape.

[0048] According to an embodiment of the present invention, the rotor core 12 has (Rd-Lq) / g=0.36 and α / β=0.64. The rotor core 12 with this structure not only optimizes the sinusoidal nature of the induced electromotive force waveform and the air gap magnetic flux distribution of the motor, but also reduces pulsating torque and radial electromagnetic vibration force. Furthermore, it has a simple structure, facilitating mass production. Figure 3 The induced electromotive force waveform in this embodiment of the invention is close to a sine wave. Figure 4 This section describes the harmonic content of each order and the total harmonic content obtained by decomposing the induced electromotive force waveform using Fourier decomposition. Figure 5 The waveform of the air gap magnetic flux density distribution in this embodiment of the invention is close to a sine wave. Figure 6The harmonic content and distortion rate of each order are obtained by decomposing the waveform of the radial component of the air gap magnetic flux density using the Fourier decomposition method.

[0049] The area enclosed by the outer contour 10 of the rotor core 12 is S1 = 2611 mm². 2 The area of ​​the circle containing the arc segment 10a along the d-axis is S² = πRd. 2 =2633mm 2 The area of ​​the circle containing the tooth arc 4a of stator core 6 is S3 = π(Rd + g). 2 =2734mm 2 (S2-S1) / (S3-S2)=(2633-2611) / (2734-2633)=0.22. By adjusting the ratio of (S2-S1) to (S3-S2), the structure of the rotor core 12 can be optimized.

[0050] The permanent magnet rotary motor 1 according to an embodiment of the present invention can, on the one hand, make the induced electromotive force waveform sinusoidal and the current sinusoidal, thereby reducing the harmonic magnetic flux generated by the interaction of the induced electromotive force and the current. As a result, it can reduce pulsating torque and radial electromagnetic vibration force. On the other hand, it can optimize the air gap magnetic flux waveform and reduce the harmonic content of the air gap magnetic flux, thereby reducing the electromagnetic excitation ratio, vibration and noise, and making the structure simple and easy to mass-produce.

[0051] By incorporating a compressor with this small, high-efficiency permanent magnet rotary motor, compressor efficiency can be improved, and energy savings can be achieved.

[0052] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A permanent magnet rotary electric motor, comprising a stator and a rotor; the stator having an annular yoke, a plurality of teeth protruding radially inward from the yoke and arranged in a circumferential direction, and a stator core formed in a plurality of slots between the teeth; And a motor coil disposed in the slot and wound around the teeth; The rotor has a rotor core and a plurality of permanent magnets embedded in the rotor core and arranged circumferentially, and is rotatably configured with a gap between it and the stator. The permanent magnet rotary motor is characterized in that the rotor core has a plurality of permanent magnet slots spaced circumferentially on it. In a plane perpendicular to the rotation center O axis of the rotor core, the outer contour of the rotor core includes: a d-axis arc segment, the center of which coincides with the rotation center O of the rotor core; a q-axis arc segment / q-axis straight segment, the center of which coincides with the rotation center O of the rotor core; the q-axis straight segment being orthogonal to the q-axis; and several connecting segments, the connecting segments being adjacent to the d-axis arc segment and the q-axis arc segment / q-axis straight segment. Between the straight segments of the q-axis, at least one of the connecting segments is an arc-shaped connecting segment whose center does not coincide with the rotation center O of the rotor core and is located inside the rotor core, and is tangent to the arc segment of the d-axis; the arc-shaped connecting segment is located adjacent to the d-axis; the radius of the arc segment of the d-axis is Rd, and the straight-line distance between the intersection of the arc segment of the q-axis / straight segment of the q-axis and the rotation center O of the rotor core is defined as Lq; the minimum gap between the arc segment of the stator core teeth and the arc segment of the d-axis is g, 0.1≤(Rd-Lq) / g≤1; the included angle of the arc segment of the d-axis is α; the included angle between the front end of the stator core teeth and the imaginary line connecting the rotation center O of the rotor core is β, 0.5≤α / β≤1.

2. The permanent magnet rotary motor according to claim 1, characterized in that: The radius of the arc-shaped connecting segment is smaller than the radius Rd of the d-axis arc segment.

3. A permanent magnet rotary motor according to claim 1, characterized in that: The area enclosed by the outer contour of the rotor core is S1; the area of ​​the circle containing the d-axis arc segment is S2, where S2 = πRd. 2 The area of ​​the circle containing the tooth arc segment of the stator core is S3, where S3 = π(Rd + g). 2 , 0.1≤(S2-S1) / (S3-S2)≤0.6; the rotor core has 8 poles and the stator core has 12 slots.

4. A permanent magnet rotary motor according to claim 1, characterized in that: The minimum width of the radial flux saturation portion between adjacent permanent magnet slots is no greater than 0.8 mm.

5. A permanent magnet rotary motor according to claim 1, characterized in that: The minimum width of the circumferential flux saturation portion between the permanent magnet slot and the outer contour of the rotor core is no greater than 0.6 mm.

6. A permanent magnet rotary motor according to claim 1, characterized in that: Each pole of the permanent magnet embedded in the rotor core is composed of two permanent magnets; the two permanent magnets are arranged in a convex V-shape with the d-axis as the axis of symmetry and facing the rotation center O of the rotor core.

7. A permanent magnet rotary motor according to claim 1, characterized in that: The ratio of the number of poles of the rotor to the number of slots of the stator is 2:

3.

8. A permanent magnet rotary motor according to claim 1, characterized in that: Both the stator core and the rotor core are formed by stacking multiple silicon steel plates with a thickness of no more than 0.35 mm.

9. A permanent magnet rotary motor according to claim 1, characterized in that: At least one of the connecting segments is a straight connecting segment.

10. A compressor, characterized in that: The compressor is equipped with a permanent magnet rotary motor as described in any one of claims 1 to 9.

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