Low eddy current loss permanent magnet unit for permanent magnet motors

Abstract

The present invention relates to a low eddy current loss permanent magnet unit for a permanent magnet motor, and belongs to the technical field of permanent magnet motors. [Solution] The permanent magnet unit has an electrical insulating layer, which includes a first set of insulating layers and a second set of insulating layers, where the first set of insulating layers is an adhesive layer that bonds adjacent permanent magnet segments together or adjacent non-conductive segments and permanent magnet segments together, and the second set of insulating layers is an electrical insulating layer, which has slits that can be filled with air or other insulating material that does not contain adhesive. By incorporating the adhesive layer and the electrical insulating layer simultaneously into the permanent magnet unit, it is possible to reduce eddy currents in the permanent magnet and the number of adhesive segments, and to alleviate the reduction in mechanical strength of the permanent magnet caused by the second set of insulating layers.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of designing permanent magnets related to rotors of permanent magnet motors. [Background technology]

[0002] A permanent magnet motor includes a stator and a rotor. FIG. 1A shows the rotor of an IPM motor. The rotor 100 consists of multiple permanent magnets 110 arranged in rotor slits 104 and a rotor core 102 made of laminated electromagnetic steel sheets. FIG. 1B shows the rotor of an SPM motor. The rotor 120 is formed by attaching permanent magnets 122 to the surface of the rotor core 102 by adhesive or other means. When current is applied to the stator coil, a rotating magnetic field is generated in the motor. The interaction between this rotating magnetic field and the magnetic field generated by the rotor's permanent magnets generates torque, causing the rotor to rotate. When a permanent magnet is subjected to an external magnetic field (including the magnetic field generated by the stator coil), eddy currents are induced in the permanent magnet, which increases its temperature. The increase in temperature of the permanent magnets causes magnetic flux loss, reducing the motor's output torque and efficiency.

[0003] Conventionally, the following methods have been used to reduce temperature rise and magnetic flux loss in permanent magnets due to eddy current induction: (1) A method for improving the heat resistance of permanent magnets, especially their magnetic properties at high temperatures, but this method significantly impacts the cost of permanent magnets; (2) A method for dividing and gluing permanent magnets to reduce eddy current loss, such as the invention disclosed in Chinese Patent CN104454852B (shown in Figure 2A); and (3) A method for reducing eddy current loss by removing a portion of a permanent magnet to form an electrical insulating layer, such as the invention disclosed in Chinese Patent CN1086314558B (shown in Figure 2B). U.S. Patents US10666099B1 and US6359359B1 (shown in Figures 2C and 2D, respectively) also use this method, although the slit placement method is different.

[0004] Although all three of the above-mentioned methods for reducing eddy current loss in magnetic materials can reduce to a certain extent the decrease in output torque and efficiency of permanent magnet motors caused by temperature rise in the magnetic material, they have had significant negative effects on the cost, magnetic flux, and mechanical strength of the permanent magnet material. DISCLOSURE OF THE INVENTION [Means for solving the problem]

[0005] In view of the negative effects of the above-mentioned permanent magnets on cost, magnetic flux, and mechanical strength, the present invention aims to provide a low eddy current loss permanent magnet unit for a permanent magnet motor that reduces the above-mentioned effects.

[0006] The permanent magnetic material unit of the present invention is provided with insulating layers, which are defined as a first set of insulating layers and a second set of insulating layers. The first set of insulating layers are adhesive layers extending along the height direction of the permanent magnetic material unit and the length or width direction of the permanent magnetic material unit, thereby bonding adjacent permanent magnetic material segments together. The second set of insulating layers are slits that can be filled with air or other insulating material other than adhesive, and are formed in the permanent magnetic material along the height direction of the permanent magnetic material unit.

[0007] The permanent magnetic material unit according to the present invention includes non-conductive segments, and the permanent magnetic material unit including the non-conductive segments also includes insulating layers. The insulating layers are defined as a first set of insulating layers and a second set of insulating layers. The first set of insulating layers are adhesive layers extending along the height and length of the permanent magnetic material unit, thereby bonding adjacent permanent magnetic material segments and the permanent magnetic material segments and the non-conductive segments together. The second set of insulating layers are slits that can be filled with air or other insulating material other than adhesive, and are formed in the permanent magnetic material along the height of the permanent magnetic material unit. [Effects of the Invention]

[0008] The above design reduces the eddy currents generated by the permanent magnets of the permanent magnet motor, reduces the number of adhesive segments, and alleviates the problem of reduced mechanical strength of the permanent magnets caused by the second insulating layer. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1 shows the rotor of an IPM motor. [Figure 1B] A diagram showing the rotor of an SPM motor. [Figure 2A] FIG. 1 is a diagram showing a typical prior art insulating layer bonded permanent magnetic body. [Figure 2B] FIG. 1 is a diagram showing a first insulating layer open-slit type permanent magnet, which is a typical prior art. [Figure 2C] FIG. 10 is a diagram showing a second insulating layer open-slit type permanent magnet, which is a typical prior art. [Figure 2D] FIG. 10 is a diagram showing a third insulating layer open-slit type permanent magnet, which is a typical prior art. [Figure 3] FIG. 1 is a diagram showing a permanent magnetic body that is a typical prior art. [Figure 4A] FIG. 1 is a diagram showing the distribution of eddy currents generated in a permanent magnetic material. [Figure 4B] 4B is a diagram showing the distribution of eddy currents generated at position B on the cross section of the permanent magnetic body in FIG. 4A. [Figure 4C] 4B is a diagram showing the distribution of eddy currents generated at position A on the cross section of the permanent magnetic body in FIG. 4A. [Figure 5] 1 is a diagram showing the structure of an insulating layer type permanent magnetic unit according to a first embodiment of the present invention; [Figure 6] FIG. 4 is a diagram showing the structure of an insulating layer type permanent magnetic unit according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing the structure of an insulating layer type permanent magnetic unit according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a diagram showing the structure of an insulating layer type permanent magnetic unit according to a fourth embodiment of the present invention. [Figure 9] FIG. 10 is a diagram showing the structure of an insulating layer type permanent magnetic unit according to a fifth embodiment of the present invention. [Figure 10]FIG. 1 is a diagram showing a comparative example 1 for verifying the effects of an embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing a comparative example 2 for verifying the effect of the embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing a comparative example 3 for verifying the effect of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The principles and features of the present invention will be described in detail below with reference to Figures 1 to 12. The following examples are used only to interpret the present invention and are not intended to limit the configuration of the present invention.

[0011] Figure 3 shows the structure of a typical permanent magnet used in an IPM motor. The permanent magnet in Figure 3 is block-shaped, magnetized along its height, and its length is aligned with the rotor's axis. Figure 4A shows the eddy current paths of a typical rectangular permanent magnet simulated using electromagnetic simulation software. The arrows indicate the eddy current paths. As shown in Figures 4B and 4C, eddy current loss in the permanent magnet is concentrated around the edges of the permanent magnet, with relatively low eddy current loss in the center and relatively high eddy current loss in the edges. While slitting the permanent magnet in areas with high eddy current loss can reduce eddy current loss, it also reduces the permanent magnet's mechanical strength. Similarly, slitting the permanent magnet in areas with high eddy current loss in a non-rectangular, polyhedral permanent magnet (e.g., a permanent magnet with a C-shaped cross section) also reduces the permanent magnet's mechanical strength.

[0012] In order to solve the problem of reduced mechanical strength caused by providing slits in the permanent magnet of a permanent magnet motor, the present invention incorporates an adhesive layer and other types of electrical insulating layers into the permanent magnet simultaneously. The present invention is applicable to permanent magnets of various shapes (rectangular, annular, tile-shaped, arch-shaped, etc.).

[0013] Example 1 5 shows one embodiment of the present invention. As shown in FIG. 5, adhesive layers 520A and 520B are formed along the length of the permanent magnet unit 500 to bond permanent magnet segments 510A, 510B, 510C, 510D, 510E, 510F, 510G, and 510H together to form the permanent magnet unit 500. Electrical insulating layers 530A, 530B, 530C, 530D, and 530E Stretching direction Adhesive layers 520A and 520B With respect to the stretching direction Vertical and permanent magnet unit 500 Width direction The permanent magnet unit 500 is formed with a slit (≦0.3 mm) filled with air or other insulating material in at least one of the electrical insulating layers 530A, 530B, 530C, 530D, and 530E. The adhesive layers 520A and 520B do not intersect with any of the electrical insulating layers. As shown in the figure, the height direction is the magnetization direction, and the extension direction of each electrical insulating layer is parallel to the magnetization direction (the same applies to Examples 2 to 5 below).

[0014] Example 2 6 shows another embodiment of the present invention. As shown in FIG. 6, an adhesive layer 620 is formed along the length of the permanent magnet unit 600, and permanent magnet segments 610A and 610B are bonded together to form the permanent magnet unit 600. Electrical insulating layers 630A, 630B, 630C, and 630D are also formed. Stretching direction Adhesive layer 620 With respect to the stretching direction Vertical and permanent magnet unit 600 Width direction The permanent magnet unit 600 is formed with a slit (≦0.3 mm) filled with air or other insulating material in at least one of the electrical insulating layers 630A, 630B, 630C, and 630D. The electrical insulating layers 630A, 630B, 630C, and 630D intersect with the adhesive layer 620. The electrical insulating layers 630A, 630B, 630C, and 630D are formed as slits not only between the permanent magnetic material segments as shown in the figure, but also in some of the permanent magnetic material segments.

[0015] Example 3 7 shows another embodiment of the present invention. As shown in FIG. 7, adhesive layers 720A and 720B are formed along the length of the permanent magnet unit 700 to integrally bond the permanent magnet segments 710A, 710B, 710C, 710D, and 710E and the non-magnetic segments 740A and 740B to form the permanent magnet unit 700. Electrical insulating layers 730A, 730B, 730C, and 730D Stretching direction are adhesive layers 720A and 720B With respect to the stretching direction Vertical and permanent magnet unit 700 Width direction The permanent magnet unit 700 was formed along the line 720A, 720B, 720C, and 720D. At least one of the electrical insulating layers 730A, 730B, 730C, and 730D had a slit (≦0.3 mm) filled with air or other insulating material. The adhesive layers 720A and 720B did not intersect any of the electrical insulating layers.

[0016] Example 4 8 shows a fourth embodiment of the present invention. As shown in FIG. 8, adhesive layers 820A and 820B are formed on the permanent magnet unit 800. Width direction The permanent magnet segments 810A, 810B, 810C, 810D, and 810E are bonded together to form the permanent magnet unit 800. Stretching direction are adhesive layers 820A and 820B With respect to the stretching direction Vertical and permanent magnet unit 800 Lengthwise The permanent magnet unit 800 is formed along the line 820A and 820B. At least one of the electrical insulating layers 830A and 830B has a slit (≦0.3 mm) filled with air or other insulating material. The adhesive layers 820A and 820B do not intersect with either of the electrical insulating layers. The permanent magnetic material segments 810D and 810E may be non-conductive segments as shown in FIG. 7 (third embodiment).

[0017] Example 5 9 shows another embodiment of the present invention, in which the permanent magnet is C-shaped, and the circumferential direction of the permanent magnet unit 900 is approximately the width direction. As shown in FIG. 9, an adhesive layer 920 is formed along the circumferential direction of the permanent magnet unit 900, and permanent magnet segments 910A, 910B, 910C, 910D, 910E, and 910F are integrally bonded to form the permanent magnet unit 900. Electrical insulating layers 930A, 930B, 930C, and 930D Stretching direction The adhesive layer is 920 With respect to the stretching direction Vertical and permanent magnet unit 900 Axial direction The permanent magnet unit 900 was formed along the line 930A, 930B, 930C, and 930D. At least one of the electrical insulating layers 930A, 930B, 930C, and 930D ​​was a slit (≦0.3 mm) filled with air or other insulating material. The adhesive layer 920 did not intersect any of the electrical insulating layers.

[0018] Below, the technical effects of permanent magnetic materials with various structures were compared by measuring the temperature change value of the permanent magnetic material after heating in an induction coil.

[0019] The sample was a rectangular parallelepiped Nd-Fe-B magnetic material, 47.5 mm long, 16.0 mm wide, and 5.0 mm high, with the magnetization direction being the height direction.

[0020] Measurements were made in comparison with the second embodiment of the present invention. Two rows of identical permanent magnet segments were bonded together in the width direction with an insulating adhesive. Two slits were placed along the length of the permanent magnet, offset in the width direction with a mirrored surface. The slits were filled with air, and the slit width was 0.15 mm and the slit length was two-thirds the width of the permanent magnet.

[0021] A permanent magnetic material with no adhesive or slits throughout is shown in FIG. 10 as Comparative Example 1.

[0022] The magnetic body was divided into three equal parts in the width direction and bonded together with an insulating adhesive to form Comparative Example 2, as shown in FIG.

[0023] Four slits were provided in the length direction of the magnetic material, and the slits were in the height direction of the permanent magnetic material, with the slit length being half the width and the slit width being 0.15 mm, which was used as one set of insulating slits. The insulating slit set was arranged with the positions of the mirror surface shifted in the width direction, which was used as Comparative Example 3 and is shown in Figure 12.

[0024] The samples were heated in an induction coil, placed in the same location within the coil, and heated for two minutes at the same frequency and current, after which the temperature change of each permanent magnetic material was measured, and each sample was also subjected to a three-point bending test. The comparative measurement results are shown in Table 1.

[0025] Table 1: Comparison of temperature rise, mechanical strength and relative cost of each sample after heating JPEG2026506838000021.jpg61127

[0026] The above measurement results reflect the temperature rise tendency of each permanent magnetic material sample, with Comparative Example 3 showing a significant temperature rise and a large yield range in mechanical strength. On the other hand, the examples of the present invention effectively solve the problem of the prior art, which has weak mechanical strength, and furthermore, the temperature rise is equivalent to that of the adhesive technology of Comparative Example 2, giving it an advantage in terms of cost.

[0027] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. All modifications and improvements made within the scope of the technical concept of the present invention fall within the scope of protection of the present invention.

Claims

1. A permanent magnetic unit, a plurality of permanent magnetic segments; at least one adhesive layer; At least one adhesive-free electrically insulating layer is embedded in the permanent magnetic unit. A permanent magnetic unit characterized by:

2. the adhesive layer is formed on the permanent magnetic unit along the height direction and length direction or the height direction and width direction of the permanent magnetic unit; 2. The permanent magnetic unit according to claim 1.

3. The adhesive layer and the permanent magnetic material segment are bonded to form the permanent magnetic material unit.

3. The permanent magnetic unit according to claim 2.

4. the adhesive layer is parallel to the length direction or width direction of the permanent magnetic unit; 3. The permanent magnetic unit according to claim 2.

5. the electrical insulating layer is formed on the permanent magnetic unit along the height direction of the permanent magnetic unit; 2. The permanent magnetic unit according to claim 1.

6. the electrically insulating layer is perpendicular to the adhesive layer; 2. The permanent magnetic unit according to claim 1.

7. The electrically insulating layer is a slit that can be filled with air or other insulating material.

2. The permanent magnetic unit according to claim 1.

8. the adhesive layer does not intersect with any of the electrical insulating layers; 2. The permanent magnetic unit according to claim 1.

9. At least one of the adhesive layers intersects with the electrical insulating layer.

2. The permanent magnetic unit according to claim 1.

10. A permanent magnetic unit, a plurality of permanent magnetic segments; a plurality of adhesive layers; a plurality of non-conductive segments; At least one adhesive-free electrically insulating layer is embedded in the permanent magnetic unit. A permanent magnetic unit characterized by:

11. a plurality of the adhesive layers are formed on the permanent magnetic unit along the height direction and the length direction of the permanent magnetic unit; 11. The permanent magnet unit according to claim 10.

12. the adhesive layer is parallel to the longitudinal direction of the permanent magnetic unit; 12. The permanent magnet unit according to claim 11.

13. the adhesive layer integrally bonds the permanent magnetic material segment and the non-conductive segment at both ends in the width direction of the permanent magnetic material segment to form the permanent magnetic material unit; 12. The permanent magnet unit according to claim 11.

14. the electrical insulating layer is formed on the permanent magnetic unit along the height direction of the permanent magnetic unit; 11. The permanent magnet unit according to claim 10.

15. the electrically insulating layer is perpendicular to the adhesive layer; 11. The permanent magnet unit according to claim 10.

16. The electrically insulating layer is a slit that can be filled with air or other insulating material.

11. The permanent magnet unit according to claim 10.

17. the adhesive layer does not intersect with any of the electrical insulating layers; 11. The permanent magnet unit according to claim 10.

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