Permanent magnet synchronous motor and outer rotor thereof

Abstract

The application discloses a permanent magnet synchronous motor and an outer rotor thereof. The outer rotor comprises a rotor core, a plurality of magnetic steel grooves are arranged on the rotor core and are distributed in a circumferential direction at intervals, a rotor core area between circumferentially adjacent two magnetic steel grooves forms a magnetic isolation bridge, and a groove is arranged on an inner circumferential surface of the rotor core and corresponds to a position of the magnetic isolation bridge. The application increases the magnetic saturation degree of a local area of the magnetic isolation bridge through the groove, reduces magnetic leakage, improves utilization of a permanent magnet, and further reduces torque output loss and improves motor performance.

Description

Technical Field

[0001] This application relates to the field of motor equipment technology, specifically to a permanent magnet synchronous motor and its external rotor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) generate electromagnetic torque through the interaction between the stator armature magnetic field and the rotor permanent magnet magnetic field, driving the motor to rotate and output mechanical torque. For embedded PMSMs (where permanent magnets are embedded inside the rotor) operating at high speeds, the rotor strength requirements necessitate optimizing the magnetic isolation bridge design to improve mechanical reliability. This is especially true for external rotor motors, where the larger rotor diameter and stronger centrifugal force place even higher demands on the magnetic isolation bridge's strength. Widening the magnetic isolation bridge to increase strength reduces its magnetic saturation, increases leakage flux, and weakens the effective air gap magnetic flux density, leading to decreased permanent magnet flux utilization and reduced output torque. Therefore, how to reduce leakage flux and torque loss without widening the magnetic isolation bridge is a pressing issue that needs to be addressed. Utility Model Content

[0003] In view of this, based on one aspect of this application, an outer rotor of a permanent magnet synchronous motor is provided, including a rotor core, wherein a plurality of magnetic steel slots are provided on the rotor core at intervals along the circumference, and a magnetic isolation bridge is formed between two adjacent magnetic steel slots in the rotor core, and a groove is provided on the inner circumferential surface of the rotor core corresponding to the position of the magnetic isolation bridge.

[0004] In some embodiments, one or more grooves are provided on the inner circumferential surface of the rotor core corresponding to the position of each magnetic bridge.

[0005] In some embodiments, the minimum distance between the groove and the inner edge of the corresponding magnet groove is 0.5 mm.

[0006] In some embodiments, the groove is arc-shaped or formed by spline curves.

[0007] In some embodiments, the groove is arc-shaped, and the central angle of the groove is less than or equal to 180°.

[0008] In some embodiments, the grooves are circumferentially symmetrical about the axis of the corresponding magnetic bridge.

[0009] In some embodiments, the magnetic slots are arranged in a straight line, and the magnetic isolation bridge is formed between the circumferential ends of two adjacent magnetic slots. The inner circumferential surface of the rotor core is provided with the groove on the radial inner side of each magnetic isolation bridge.

[0010] In some embodiments, the magnetic slots are arranged in a V-shape, and the magnetic isolation bridge is formed between the radially inner ends of a pair of magnetic slots arranged in a V-shape. The inner circumferential surface of the rotor core is provided with the groove on the radially inner side of each magnetic isolation bridge.

[0011] In some embodiments, each of the magnet slots is embedded with a magnet, and the rotor core is formed by stacking multiple rotor laminations.

[0012] Based on another aspect of this application, a permanent magnet synchronous motor is provided, including an inner stator and an outer rotor of any one of the permanent magnet synchronous motors, the outer rotor being located outside the inner stator.

[0013] Compared with the prior art, the external rotor provided in this application reduces the width of the magnetic bridge at the groove by setting a groove on the inner circumferential surface of the rotor core corresponding to the position of the magnetic bridge. This causes local magnetic circuit saturation of the rotor core, which can promote more rotor magnetic flux to interact with the stator magnetic field through the air gap. In this way, without reducing the mechanical strength of the rotor core, leakage flux can be reduced, the utilization rate of permanent magnets can be improved, and the output torque loss can be reduced, thereby improving motor performance.

[0014] Since the permanent magnet synchronous motor provided in this application and the external rotor provided in this application belong to the same inventive concept, the permanent magnet synchronous motor provided in this application has at least all the beneficial effects of the external rotor provided in this application. Therefore, the beneficial effects of the permanent magnet synchronous motor provided in this application will not be described in detail here. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0016] Figure 1 This is a schematic diagram of the overall structure of the linear magnet-distributed outer rotor provided in some embodiments of this application;

[0017] Figure 2 yes Figure 1 A partial structural diagram of the inner and outer rotors;

[0018] Figure 3 This is a partial structural schematic diagram of a permanent magnet synchronous motor provided in some embodiments of this application, in which the outer rotor adopts a linear distribution of magnets;

[0019] Figure 4 yes Figure 3 A schematic diagram of a single magnetic pole with grooves at both ends circumferentially on the inner and outer rotors;

[0020] Figure 5This is a partial structural schematic diagram of a V-shaped magnet distributed external rotor provided in other embodiments of this application;

[0021] Figure 6 This is a comparison chart of the output torque of the comparative embodiment and the embodiment of this application. In the chart, the red line represents the embodiment of this application, the cyan line represents the comparative embodiment, the horizontal axis represents the rotor rotation angle (unit, °), and the vertical axis represents the output torque (unit, Nm).

[0022] [The following are the annotations in the attached diagram:] 10-Outer rotor, 11-Rotor core, 12-Magnet, 13-Magnet slot, 14-Magnetic bridge, 15-Groove, 20-Inner stator, L1-Magnetic bridge width, L2-Minimum distance. Detailed Implementation

[0023] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0024] The accompanying drawings illustrate various structural schematics according to embodiments of this application. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0025] In the context of this application, when a layer / element is referred to as being "on top of" another layer / element, the layer / element can be directly on top of the other layer / element, or there can be an intermediate layer / element between them. Furthermore, if a layer / element is "on top of" another layer / element in one orientation, then when the orientation is reversed, the layer / element can be "below" the other layer / element. To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] The purpose of this application is to provide a permanent magnet synchronous motor and its external rotor to solve the problem that existing permanent magnet synchronous motors cannot simultaneously achieve electromagnetic performance and mechanical strength at the magnetic bridge.

[0029] The core idea of ​​this application is to set a groove on the inner circumferential surface of the outer rotor corresponding to the position of the magnetic isolation bridge, so that the width of the magnetic isolation bridge at the location of the groove is the narrowest area of ​​the magnetic isolation bridge magnetic circuit. In this way, without reducing the mechanical strength of the rotor core, the magnetic saturation of the local area of ​​the magnetic isolation bridge can be increased, thereby reducing leakage flux, increasing the effective air gap magnetic density, improving the utilization rate of permanent magnets, and thus reducing the loss of output torque and improving motor performance.

[0030] The following description is in conjunction with the accompanying drawings.

[0031] like Figures 1 to 5 As shown, this application embodiment relates to an external rotor 10, which can be applied to a permanent magnet synchronous motor.

[0032] The permanent magnet synchronous motor provided in this application includes an outer rotor 10 and an inner stator 20; the outer rotor 10 is located outside the inner stator 20; the outer rotor 10 rotates while the inner stator 20 is fixed, and an air gap is provided between the inner circumference of the outer rotor 10 and the outer circumference of the inner stator 20. The inner stator 20 includes a stator core and stator windings; since this application does not improve its structure, it will not be described in detail.

[0033] The outer rotor 10 includes a rotor core 11. The rotor core 11 is typically formed by stacking multiple rotor laminations axially, and the stacked rotor laminations are connected to form a whole with sufficient mechanical strength. The inner circumferential surface of the rotor core 11 has a circular structure.

[0034] The rotor core 11 is provided with a plurality of circumferentially spaced magnetic slots 13. Specifically, magnetic slots 13 are formed on the plane of each rotor lamination. A magnet 12 is inserted into each magnetic slot 13, and each magnet 12 constitutes a magnetic pole. For distinction, when the lead line in the attached drawing points to the line area, it is a magnetic slot 13, and when it points to the non-line area, it is a magnet 12.

[0035] In some embodiments, the magnets 12 are rectangular or arc-shaped, and are fixed to the rotor core 11 with epoxy resin or a non-magnetic material to prevent displacement of the magnets 12 during high-speed rotation. The polarity (N or S) of each magnet 12 is symmetrically distributed in space. This application does not limit the specific number of magnets 12. For example, in an embodiment of this application, the outer rotor 10 is provided with 24 magnets 12, and the polarity of adjacent magnets 12 alternates (e.g., NSNS).

[0036] Furthermore, the outer rotor 10 of this application embodiment can cover various common magnet distribution methods in the art, and is not particularly limited thereto.

[0037] refer to Figures 1-4 As shown, in some embodiments, the magnets 12 on the outer rotor 10 are distributed in a straight line. In this case, a magnetic bridge 14 is formed between the circumferential ends of any two adjacent magnet slots 13.

[0038] refer to Figure 5 As shown, in some other embodiments, the magnets 12 on the outer rotor 10 are distributed in a single V-shape. In this case, a magnetic bridge 14 is formed between the radially inner ends of a pair of V-shaped magnet slots 13 near the center of the rotor core 11.

[0039] However, it should be noted that the magnet distribution in the embodiments of this application is not limited to a single V-shaped distribution. For example, it may also cover double V-shaped, multi-V-shaped, combined, or other distribution forms.

[0040] Regardless of the magnet distribution, a magnetic isolation bridge 14 is formed in the rotor core 11 region between two adjacent circumferential magnet slots 13. The magnetic isolation bridge 14 is the rotor core 11 region in the outer rotor 10 used to isolate adjacent permanent magnets. By saturating the leakage flux at the magnetic isolation bridge 14, leakage flux can be limited, and the utilization rate of permanent magnets can be improved.

[0041] Theoretically, the smaller the width of the magnetic isolation bridge 14, the greater the magnetic reluctance, the easier it is for the magnetic flux to saturate, and the better the effect of limiting magnetic leakage. However, the width of the magnetic isolation bridge 14 cannot be too small, otherwise the mechanical strength of the rotor laminations will deteriorate, especially under high-speed conditions. Therefore, in actual design, the circumferential width L1 of the magnetic isolation bridge 14 should be appropriate to achieve a balance between electromagnetic performance and structural strength, ensuring efficient and stable operation of the motor.

[0042] Based on this, this application improves the outer rotor 10 by providing a groove 15 on the inner circumferential surface of the outer rotor 10 at the position corresponding to the magnetic isolation bridge 14. The reason for this is that the area where the groove 15 is located is less affected by centrifugal force, or may even be unaffected by centrifugal force, thus not affecting the strength of the rotor core 11.

[0043] Specifically, such as Figure 4 As shown, during high-speed rotation of the permanent magnet synchronous motor, the centrifugal force is radially outward. The magnetic isolation bridge 14 in regions a and b of the rotor core 11 experiences greater stress, while the magnetic isolation bridge 14 at the groove 15 is almost unaffected by the centrifugal force (referred to as the low-stress region). Therefore, the magnetic isolation bridge 14 at region b must have a certain width to ensure the structural strength of the outer rotor 10. Since the groove 15 is almost unaffected by the centrifugal force, the thickness of the magnetic isolation bridge 14 at the groove 14 can be reduced. Therefore, making the groove 14 in the radially inner region of the magnetic isolation bridge 14 does not affect the structural strength of the outer rotor 10, but it can narrow the width of the magnetic isolation bridge 14 in the radially inner region, causing local magnetic circuit saturation of the rotor core 11. This encourages more rotor magnetic flux to interact with the stator 20 magnetic field through the air gap, thus limiting magnetic leakage.

[0044] Therefore, in this embodiment, the groove 15 is located in the low-stress region of the magnetic bridge 14. The low-stress region includes areas that are almost unaffected by centrifugal force. In this way, without reducing the mechanical strength of the rotor laminations, leakage flux can be reduced, the utilization rate of the permanent magnet can be improved, and the output torque loss can be reduced. It should be understood that the inner circumferential surface of the rotor core 11 is provided with grooves 15 corresponding to the positions of each magnetic bridge 14.

[0045] Furthermore, on the inner circumferential surface of the outer rotor 10, corresponding to the position of each magnetic bridge 14, a groove 15 can be continuously provided or multiple grooves 15 can be provided at intervals.

[0046] This application does not limit the shape and size of the groove 15, as long as it is easy to process. However, rectangular, trapezoidal, and other angular structures can cause stress concentration due to the sharp edges. Therefore, the groove 15 preferably adopts an arc-shaped structure, and more preferably a circular arc-shaped structure. In the embodiment of this application, the groove 15 is a circular arc groove, which can better narrow the width of the magnetic bridge 14 and facilitate stamping. Further, the central angle of the circular arc groove is less than or equal to 180°, that is, the groove 15 is a semi-circular arc or a minor arc. Alternatively, the groove 15 is formed by connecting spline curves, and the coordinates of each control point on the spline curve can be set by the user.

[0047] Furthermore, from the perspective of stamping process, the minimum distance L2 between the inner edge of the groove 15 and the corresponding magnet slot 13 near the center of the rotor core 11 satisfies the stamping process limit requirements. The stamping process limit requirements mainly include constraints on key indicators such as material properties, mold design, and process parameters. When stamping is feasible, reducing the distance between the groove 15 and the magnet slot 13 makes the magnetic circuit in a local area of ​​the magnetic bridge 14 more prone to saturation, thus effectively limiting magnetic leakage.

[0048] Ultimately, the minimum distance L2 between the location of the groove 15 and the corresponding inner edge of the magnetic groove 13 near the center of the rotor core 11 is the narrowest region on the magnetic circuit of the magnetic bridge 14, and the bottom of the groove 15 is not higher than the inner edge of the magnetic groove 13 near the center of the rotor core 11. Optionally, the minimum distance L2 between the groove 15 and the inner edge of the corresponding magnetic groove 13 near the center of the rotor core 11 is 0.5 mm.

[0049] The grooves 15 can be circumferentially symmetrically distributed or circumferentially asymmetrically distributed at positions corresponding to the magnetic bridge 14. Preferably, the grooves 15 are circumferentially symmetrically distributed about the axis of the corresponding magnetic bridge 14.

[0050] In some embodiments, when arranged in a straight line, the grooves 15 are circumferentially symmetrical about the intersection axis (q-axis).

[0051] In other embodiments, when the V-shaped distribution is used, the grooves 15 are circumferentially symmetrical about the straight axis (d-axis).

[0052] refer to Figures 1 to 4 When the magnetic steel slots 13 are arranged in a straight line, the inner circumferential surface of the rotor core 11 is provided with a groove 15 on the radial inner side of each magnetic bridge 14. The grooves 15 at both ends of each magnetic steel slot 13 are circumferentially symmetrical about the straight axis, and the grooves 15 themselves are circumferentially symmetrical about the cross axis.

[0053] refer to Figure 5 When the magnetic slots 13 are V-shaped, in the direction from the center of the rotor core 11 to the edge, a pair of magnetic slots 13 extend away from each other and are symmetrical about the d-axis. This pair of magnetic slots 13 form a magnetic bridge 14 between their radially inner ends close to each other. At the same time, the inner circumferential surface of the rotor core 11 is provided with a groove 15 on the radially inner side of each magnetic bridge 14, and the groove 15 itself is circumferentially symmetrical about the straight axis.

[0054] Next, refer to Figure 6As can be seen from the torque comparison experiment curves, the output torque of the permanent magnet synchronous motor is significantly improved after adopting the outer rotor 10 of this embodiment, effectively reducing torque loss. Moreover, under the same torque output conditions, adopting the outer rotor 10 of this embodiment can save 3-8% of the permanent magnet usage, significantly improving the utilization rate of the permanent magnets. Simultaneously, the optimized outer rotor 10 not only expands the design space but also provides more options for the permanent magnet arrangement scheme, which is beneficial for further improving motor performance.

[0055] While this application discloses the above, it is not limited thereto. Those skilled in the art can make various modifications and variations to this application without departing from its spirit and scope. Therefore, this application also intends to include any modifications and variations that fall within the scope of this application's specification and its equivalents.

Claims

1. An outer rotor of a permanent magnet synchronous motor, comprising a rotor core, characterized in that, The rotor core is provided with a plurality of circumferentially spaced magnetic slots, and the rotor core area between two adjacent circumferential magnetic slots forms a magnetic isolation bridge. The inner circumferential surface of the rotor core is provided with grooves corresponding to the positions of the magnetic isolation bridges.

2. The outer rotor of the permanent magnet synchronous motor according to claim 1, characterized in that, One or more grooves are provided on the inner circumferential surface of the rotor core corresponding to the position of each magnetic bridge.

3. The outer rotor of the permanent magnet synchronous motor according to claim 1, characterized in that, The minimum distance between the groove and the inner edge of the corresponding magnet groove is 0.5 mm.

4. The outer rotor of the permanent magnet synchronous motor according to claim 1, characterized in that, The groove is arc-shaped or formed by connecting spline curves.

5. The outer rotor of the permanent magnet synchronous motor according to claim 4, characterized in that, The groove is arc-shaped, and the central angle of the groove is less than or equal to 180°.

6. The outer rotor of the permanent magnet synchronous motor according to claim 1, characterized in that, The grooves are circumferentially symmetrical about the axis of the corresponding magnetic bridge.

7. The outer rotor of the permanent magnet synchronous motor according to claim 1 or 6, characterized in that, The magnetic slots are arranged in a straight line, and the magnetic isolation bridge is formed between the circumferential ends of two adjacent magnetic slots. The inner circumferential surface of the rotor core is provided with the groove on the radial inner side of each magnetic isolation bridge.

8. The outer rotor of the permanent magnet synchronous motor according to claim 1 or 6, characterized in that, The magnetic slots are arranged in a V-shape, and the magnetic isolation bridge is formed between the radially inner ends of a pair of magnetic slots arranged in a V-shape. The inner circumferential surface of the rotor core is provided with the groove on the radially inner side of each magnetic isolation bridge.

9. The outer rotor of the permanent magnet synchronous motor according to claim 1, characterized in that, Each of the said magnet slots is embedded with a magnet, and the rotor core is formed by stacking multiple rotor laminations.

10. A permanent magnet synchronous motor, characterized in that, It includes an inner stator and an outer rotor of a permanent magnet synchronous motor as described in any one of claims 1-9, wherein the outer rotor is located outside the inner stator.

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