Rotor assembly, motor and household appliance

Abstract

The utility model discloses a rotor assembly, a motor and a household electrical appliance, and relates to the technical field of motors. The rotor assembly comprises a plurality of fan-shaped parts, the plurality of fan-shaped parts of the rotor assembly are arranged around the circumferential direction of the rotating axis at intervals, and a mounting groove for accommodating the permanent magnet is formed between every two adjacent fan-shaped parts. The outer end face of the fan-shaped part comprises a first arc surface and a second arc surface, the first arc surface is located at one end of the fan-shaped part in the circumferential direction, and the second arc surface extends to the other end of the fan-shaped part in the circumferential direction. Therefore, the first arc surface is arranged at one end of the fan-shaped part along the circumferential direction, namely arc cutting is performed at one end of the fan-shaped part along the circumferential direction, and arc cutting is not performed at the other end. When the rotor assembly is applied to the motor, an asymmetric air gap is formed on one side of the rotor assembly, a specific harmonic component is effectively destroyed, and the distribution of electromagnetic force is more uniform, so that the torque pulsation is reduced, and the operation stability of the motor is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of motors, in particular to a rotor assembly, a motor and a household appliance. Background Art

[0002] The rotor assembly of a permanent magnet motor includes a rotor core, which includes multiple sector-shaped sections arranged around the rotation axis of the rotor assembly. As the motor rotates, the instantaneous output torque changes continuously over time and generates torque pulsation, which fluctuates around a certain average value. The greater the torque pulsation, the lower the stability of the motor and the greater the motor jitter. To improve the above situation, the motor's rotor will be clipped at the outer end of the sector to optimize the motor's air gap distribution and reduce torque pulsation. However, clipping can only eliminate part of the harmonic components, making it difficult to further improve the stability of the motor's operation. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a rotor assembly that can further reduce torque pulsation and improve the stability of motor operation.

[0004] The utility model also provides a motor and a household appliance having the rotor assembly.

[0005] According to the rotor assembly of the embodiment of the first aspect of the present invention, it includes: a plurality of fan-shaped portions, which are arranged at circumferential intervals around the rotation axis of the rotor assembly, and mounting grooves for accommodating permanent magnets are formed between adjacent fan-shaped portions, and the end of the fan-shaped portion facing away from the rotation axis has an outer end surface; wherein, the outer end surface includes a first arc surface and a second arc surface, and along the circumference of the rotor assembly, the first arc surface and the second arc surface are connected, the first arc surface is located at one end of the fan-shaped portion, and the second arc surface extends to the other end of the fan-shaped portion; the first arc surface and the second arc surface both protrude outward, and the first arc surface is located within the circular contour where the second arc surface is located.

[0006] The rotor assembly according to the embodiment of the present utility model has at least the following beneficial effects:

[0007] The rotor assembly is provided with a plurality of sector-shaped portions that are circumferentially spaced around the axis of rotation, and mounting grooves for accommodating permanent magnets are formed between adjacent sector-shaped portions. The outer end surface of the sector-shaped portion includes a first arc surface and a second arc surface, the first arc surface is located at one end of the sector-shaped portion along the circumferential direction, the second arc surface extends to the other end of the sector-shaped portion along the circumferential direction, and the first arc surface is located within the circular contour where the second arc surface is located. Therefore, the first arc surface is provided at one end of the sector-shaped portion along the circumferential direction, that is, the arc is cut at one end of the sector-shaped portion along the circumferential direction, while the arc is not cut at the other end. When the rotor assembly of this embodiment is applied to a motor, an asymmetric air gap is formed on one side of the rotor assembly, which effectively destroys specific harmonic components, making the distribution of electromagnetic force more uniform, thereby reducing torque pulsation, reducing vibration and noise of the motor, and improving the stability of motor operation.

[0008] According to some embodiments of the present invention, along the rotation direction of the rotor assembly, the first arc surface is located in front of the outer end surface.

[0009] According to some embodiments of the present invention, the radius of the first arc surface is R1, and the diameter of the circumscribed circle of the rotor assembly is D ro , the number of the installation slots is 2p, satisfying: R1= (D ro / 2)*Sin(π / 2p).

[0010] According to some embodiments of the present invention, the radius of the first arc surface is R1, and the radius of the second arc surface is R2, satisfying: 5≤R2 / R1≤8.

[0011] According to some embodiments of the present invention, in the radial direction of the second arc surface, the distance between the two ends of the first arc surface along the circumferential direction is h, which satisfies: 0.5 mm ≤ h ≤ 1 mm.

[0012] According to some embodiments of the present invention, the number of the mounting grooves is 2p, and on the projection surface perpendicular to the rotation axis, the line connecting the connection point of the first arc surface and the second arc surface and the center of the second arc surface is S2, the line connecting the endpoint of one end of the first arc surface away from the second arc surface and the center of the second arc surface is S3, and the angle between S2 and the line S3 is α, satisfying: α=k*α0, where 0.1≤k≤0.3, α0=360° / 2p.

[0013] According to some embodiments of the present invention, on a projection surface perpendicular to the rotation axis, a line connecting a connection point between the first arc surface and the second arc surface and a center point of the second arc surface is S2, a line connecting an endpoint of one end of the first arc surface away from the second arc surface and a center point of the second arc surface is S3, and an angle between S2 and the line S3 is α, satisfying: 2.5°≤α≤13.5°.

[0014] According to some embodiments of the present application, on a projection plane perpendicular to the rotation axis, a line connecting the connecting point of the first circular arc surface and the second circular arc surface and the center of the second circular arc surface is S2, a line connecting the midpoint of one end of the sector part close to the rotation axis and the center of the second circular arc surface is S1, and an included angle between the line S1 and the line S2 is θ, which satisfies: 8°≤θ≤16°.

[0015] The motor according to the second aspect of the present application comprises the rotor assembly according to the above embodiments.

[0016] The motor according to the present application has at least the following beneficial effects:

[0017] By adopting the rotor assembly according to the first aspect of the present application, the plurality of sector parts of the rotor assembly are arranged at intervals along the circumferential direction of the rotation axis, and the installation grooves for accommodating the permanent magnets are formed between the adjacent sector parts. The outer end surface of the sector part comprises the first circular arc surface and the second circular arc surface, the first circular arc surface is located at one end of the sector part along the circumferential direction, the second circular arc surface extends to the other end of the sector part along the circumferential direction, and the first circular arc surface is located within the circular contour of the second circular arc surface. Therefore, the first circular arc surface is arranged at one end of the sector part along the circumferential direction, that is, the sector part is chamfered at one end along the circumferential direction, and the other end is not chamfered. When the rotor assembly according to the present application is applied to the motor, an asymmetric air gap is formed on one side of the rotor assembly, specific harmonic components are effectively destroyed, the distribution of electromagnetic force is more uniform, the torque ripple is reduced, the vibration and noise of the motor are reduced, and the stability of the motor operation is improved.

[0018] The household appliance according to the third aspect of the present application comprises the motor according to the above embodiments.

[0019] The household appliance according to the present application has at least the following beneficial effects:

[0020] By adopting the motor according to the second aspect of the present application, the plurality of sector parts of the rotor assembly of the motor are arranged at intervals along the circumferential direction of the rotation axis, and the installation grooves for accommodating the permanent magnets are formed between the adjacent sector parts. The outer end surface of the sector part comprises the first circular arc surface and the second circular arc surface, the first circular arc surface is located at one end of the sector part along the circumferential direction, the second circular arc surface extends to the other end of the sector part along the circumferential direction, and the first circular arc surface is located within the circular contour of the second circular arc surface. Therefore, the first circular arc surface is arranged at one end of the sector part along the circumferential direction, that is, the sector part is chamfered at one end along the circumferential direction, and the other end is not chamfered. When the rotor assembly according to the present application is applied to the motor, an asymmetric air gap is formed on one side of the rotor assembly, specific harmonic components are effectively destroyed, the distribution of electromagnetic force is more uniform, the torque ripple is reduced, the vibration and noise of the motor are reduced, and the stability of the motor operation is improved.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is a schematic structural diagram of a rotor assembly according to an embodiment of the present invention;

[0024] Figure 2 This is a schematic structural diagram of a fan-shaped portion of an embodiment of the present invention;

[0025] Figure 3 This is a schematic structural diagram of a fan-shaped portion of another embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the structure of a sector-shaped portion of the utility model with arcs cut at both ends;

[0027] Figure 5 Schematic diagram of torque pulsation curve when the fan-shaped portion is not arc-cut in the related art;

[0028] Figure 6 Schematic diagram of torque pulsation curve when both ends of the sector portion along the circumferential direction are truncated in the related art;

[0029] Figure 7 This is a schematic diagram of a torque pulsation curve of a single-side arc cutting of a sector portion according to an embodiment of the present invention;

[0030] Figure 8 This is a torque waveform bar graph of the related art in which both ends of the sector portion along the circumferential direction are truncated;

[0031] Figure 9 This is a histogram of the torque waveform of the single-side arc cutting of the sector portion of an embodiment of the present utility model;

[0032] Figure 10 This is a schematic diagram of a torque pulsation curve of the rear side cutting arc of the sector portion along the rotation direction according to an embodiment of the present utility model;

[0033] Figure 11 Schematic diagram of a back electromotive force curve in the related art when both ends of the sector portion along the circumferential direction are clipped;

[0034] Figure 12 It is a schematic diagram of the back electromotive force curve of the single-side arc cutting of the fan-shaped portion of an embodiment of the present utility model.

[0035] Reference numerals:

[0036] Rotor assembly 100; sector 110; mounting groove 111; outer end surface 120; first circular arc surface 121; second circular arc surface 122. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only, and are used only for explaining the present application, and cannot be understood as a limitation of the present application.

[0038] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application.

[0039] In the description of the present application, the meaning of several is one or more, and the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, and above, below, etc. are understood as including the number. If it is described as first, second, etc. only for the purpose of distinguishing technical features, it cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0040] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and the skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0041] The rotor assembly of the permanent magnet motor includes a rotor core and a plurality of permanent magnets, and the rotor core includes a plurality of sectors, which are arranged around the rotation axis of the rotor assembly. Since the instantaneous output torque of the motor changes with time during rotation, it will fluctuate up and down around an average value. The greater the torque ripple, the lower the stability of the motor, and the greater the motor jitter. In order to improve the above situation, the rotor of the motor will be arc cut at the outer end of the sector to optimize the air gap distribution of the motor and reduce the torque ripple. Arc cutting refers to cutting a part of the end of the sector in the circumferential direction. In the related art, the arc cutting is symmetrical arc cutting at both ends of the sector in the circumferential direction. However, symmetrical arc cutting can only eliminate a part of the harmonic components, and it is difficult to reduce the other part of the harmonic components, and it is difficult to further improve the stability of the motor operation.

[0042] In order to solve the above problems, with reference to Figure 1 and Figure 2As shown, the rotor assembly 100 of the embodiment of the utility model can be used for motor, for example, the motor is permanent magnet motor. The rotor assembly 100 of the embodiment of the utility model includes multiple sector parts 110, multiple sector parts 110 are arranged at the circumferential interval around the rotation axis of rotor assembly 100, and the installation groove 111 for accommodating permanent magnet is formed between adjacent sector parts 110, and the outer end face 120 is formed at the end of sector part 110 away from the rotation axis. Wherein, the outer end face 120 includes the first circular arc surface 121 and the second circular arc surface 122 connected along the circumference of rotor assembly 100. Along the circumference of rotor assembly 100, the first circular arc surface 121 is located at one end of sector part 110, and the second circular arc surface 122 extends to the other end of sector part 110. The first circular arc surface 121 can be located at the front side or the rear side of the rotation direction of sector part 110. The first circular arc surface 121 and the second circular arc surface 122 are both outward convex, and outward convex refers to convex in the direction away from the rotation axis. The first circular arc surface 121 is located in the circular profile of the second circular arc surface 122. It should be noted that the first circular arc surface 121 in the circular profile refers to that at least part of the structure of the first circular arc surface 121 does not coincide with the circular profile and is located in the interior of the circular profile. For example, one end connected with the first circular arc surface 121 and the second circular arc surface 122 coincides with the circular profile, and the other end of the first circular arc surface 121 extends to the interior of the circular profile. Therefore, the scheme of the embodiment is to cut the arc at one end of sector part 110 along the circumference, and the other end is not cut, and the first circular arc surface 121 is formed after cutting the arc.

[0043] It should be noted that when the two ends of sector part 110 along the circumference are not cut, referring to Figure 5 As shown, from Figure 5 It can be known that when not cutting the arc, the motor torque ripple T1 is maximum, and T1 is 105.6163mNm. When the two ends of sector part 110 along the circumference are cut, referring to Figure 4 And Figure 6 As shown, Figure 4 The two ends of sector part 110 are cut. From Figure 6 It can be known that at this time, the motor torque ripple T2 is reduced, T2 is 21.6115mNm, and T2 Figure 7 As shown, from Figure 7 It can be known that at this time, the torque ripple is T3, T3=13.0905mNm, and it can be seen that T3

[0044] Therefore, the above solution is adopted, in which a first arc surface 121 is provided at one circumferential end of the sector portion 110. That is, the sector portion 110 is circumferentially truncated at one end, while the other end is not. When the rotor assembly 100 of this embodiment is used in a motor, an asymmetric air gap is formed on one side of the rotor assembly 100, effectively destroying specific harmonic components and making the electromagnetic force more evenly distributed, thereby reducing torque ripple and improving the stability of motor operation.

[0045] Among them, reference Figure 8 As shown, Figure 8 The torque waveform is obtained when both ends of the sector 110 along the circumferential direction are truncated. Figure 8 The horizontal axis represents the order of harmonics, for example, 1st harmonic, 2nd harmonic, 3rd harmonic, etc. The vertical axis represents the effective value of harmonics. The smaller the effective value, the better the stability of motor operation. Figure 8 As can be seen from the diagram, when both ends of the sector 110 are clipped along the circumferential direction, the effective values ​​of the sixth harmonic and the twelfth harmonic are relatively large, at 0.0048 mNm and 0.0054 mNm, respectively, while the effective values ​​of the other harmonics are relatively small. Therefore, compared with the solution without clipping, the torque ripple of the motor can be effectively reduced.

[0046] Reference Figure 9 As shown, Figure 9 The fan-shaped portion 110 is configured such that one end thereof along the circumferential direction is chamfered, while the other end thereof is not chamfered. Figure 9 The horizontal axis represents the order of harmonics, for example, 1st harmonic, 2nd harmonic, 3rd harmonic, etc. The vertical axis represents the effective value of harmonics. Figure 9 It can be seen that although the effective values ​​of 2 times and 3 times the frequency have increased slightly, it has little effect on the overall performance of the motor. The effective value of the 6 times the frequency is 0.0043mNm, and the effective value of the 12 times the frequency is 0.0008mNm. Figure 8 For the solution in [1], the effective value of the sixth frequency is reduced by 11%, and the effective value of the twelve frequency is reduced by 85%.

[0047] It is understandable that in a DC motor, torque fluctuations are mainly caused by the imbalance of electromagnetic forces and harmonic components. Single-sided arc clipping and double-sided arc clipping of the sector 110 will have different effects on the magnetic field distribution and air gap magnetic permeability characteristics of the motor. Single-sided arc clipping will form an asymmetric air gap distribution on one side of the rotor assembly 100, which can effectively destroy certain specific harmonic components, especially harmonics that have a greater impact on torque fluctuations, making the electromagnetic force distribution of the motor more uniform and reducing torque pulsation. Although double-sided arc clipping can also change the air gap distribution, due to its symmetry, it cannot effectively destroy the above-mentioned specific harmonics, and may also introduce new harmonics or enhance existing harmonics, thereby increasing torque fluctuations. In addition, double-sided arc clipping may also lead to an increase in the unevenness of the electromagnetic force distribution, further exacerbating torque fluctuations. Therefore, the adoption of a single-sided arc clipping solution can effectively destroy high-order harmonic components and further reduce torque pulsation, thereby improving the smoothness of motor operation and reducing the vibration and noise of the motor.

[0048] Among them, the back electromotive force of the motor can be increased to a certain extent when the arc is cut on one side. Back electromotive force, also known as counter electromotive force or self-induced electromotive force, is an electromagnetic phenomenon generated by the motor during operation. According to the law of electromagnetics, when the magnetic field changes, the nearby conductors will generate induced electromotive force. In the electric motor, when the rotor assembly 100 rotates and cuts the magnetic lines of force, an induced electromotive force is generated in the coil. The direction of the induced electromotive force is opposite to the direction of the applied voltage, so it is called the "back electromotive force" of the motor. The magnitude of the back electromotive force directly affects the torque coefficient and efficiency of the motor. The larger the back electromotive force, the greater the torque coefficient of the motor.

[0049] For example, refer to Figure 10 As shown, Figure 10 The back EMF of the double-sided arc cutting scheme is shown in the figure, and the effective value of the back EMF is 109.8457V. Figure 11 As shown, Figure 11 The figure in the middle shows the single-side arc-chopping scheme of this embodiment, and the effective value of the back EMF is 110.1096 V. Compared with the double-side arc-chopping scheme, the single-side arc-chopping scheme of this embodiment has a 0.2% improvement in back EMF, a slight increase in torque coefficient, and a certain degree of improvement in motor efficiency.

[0050] Reference Figure 1 and Figure 2 As shown, in the embodiment of the present invention, when designing the chamfer, it is necessary to determine the radius R1 of the first arc surface 121, the center of the first arc surface 121, the depth h of the chamfer, the arc length L of the chamfer, and the center angle α of the chamfer. Determine the radius R1 of the first arc surface 121: On the projection plane perpendicular to the rotation axis of the rotor assembly 100, the radius R1 of the first arc surface 121 can be calculated using the following formula: , where D rois the outer diameter of the rotor assembly, which refers to the diameter of the smallest circumscribed circle connected to the outer end faces of all the sectors; p is the number of pole pairs of the motor, that is, half of the number of mounting slots.

[0051] Determine the offset d between the center of the first arc surface and the center of the second arc surface: the offset d is calculated using the following formula: Among them, R ro D is the radius of the rotor assembly 100, that is, half of the outer diameter of the rotor assembly 100. Ri is the inner diameter of the rotor assembly 100. The inner diameter of the rotor assembly 100 refers to the diameter of the largest inscribed circle connected to the inner ends of all the sector-shaped portions 110. The inner end of the sector-shaped portion 110 refers to the end of the sector-shaped portion 110 facing the rotation axis.

[0052] Determine the arc length L and the chopping depth h of the first arc surface 121: The arc length L refers to the length of the first arc segment in the circumferential direction of the second arc segment. The depth h refers to the distance between the two ends of the first arc surface 121 along the radial direction of the second arc surface 122. The arc length L and the chopping depth h can be obtained by fitting the following formula: .

[0053] Determine the center position of the first arc surface 121: Assume that the center position of the first arc surface 121 is The starting point of the first arc surface 121 is a point on the outer end surface 120, namely point A. The position of point A is set to ,in, , . Reference Figure 2 As shown, on the projection surface perpendicular to the rotation axis of the rotor assembly 100, the center of the second arc surface 122 is point O, the connection point of the first arc surface 121 and the second arc surface 122 is point A, and the endpoint of the first arc surface 121 facing away from the second arc surface 122 is point B. The line connecting point A and point O is S2, and the line connecting point B and point O is S3. The line connecting the midpoint of the end of the sector 110 facing the rotation axis and point O is S1. The angle between the line S1 and the line S2 is θ. Therefore, θ is the angle at which the starting point of the arc cutting is offset from the center line of the rotor block. ΔR is the distance between the center of the first arc surface 121 and point A.

[0054] Determine the central angle of the first arc surface 121: α is the central angle of the first arc surface 121 relative to the center O, and the angle between the connecting line S2 and the connecting line S3 is α. The number of pole pairs of the motor is p, which is half the number of mounting slots 111. The mechanical angle of each pole is . Among them, kα is the arc cutting coefficient, and the value range of the arc cutting coefficient is 0.1≤k≤0.3.

[0055] It can be understood that by adopting the above scheme, the parameters such as the radius, central angle, offset, etc. of the first arc surface 121 can be designed, and the position of the first arc surface 121 can be further refined and designed based on design experience, which can effectively improve the situation of excessive motor torque pulsation and improve the stability and reliability of the motor during operation.

[0056] Reference Figure 2 As shown in FIG. 1 , in the embodiment of the present invention, along the rotation direction of the rotor assembly 100 , the first arc surface 121 is located at the front side of the outer end surface 120 . Figure 2 For example, when the rotor assembly 100 rotates counterclockwise, the first arc surface 121 is located on the left side of the front end surface; when the rotor assembly 100 rotates clockwise, the first arc surface 121 is located on the right side of the front end surface. Positioning the first arc surface 121 on the front side of the rotor assembly 100 in the rotational direction can more effectively reduce the torque ripple of the motor.

[0057] For example, taking the rotor assembly 100 rotating in a clockwise direction as an example, referring to Figure 7 As shown, Figure 7 The torque pulsation T3 of the solution in which the first arc surface 121 is designed on the left side of the front end surface is Figure 7 It can be seen that the torque ripple T3 = 13.0905mNm. Figure 12 As shown, Figure 12 The torque pulsation T4 of the solution in which the first arc surface 121 is designed on the right side of the front end surface is Figure 12 The torque ripple T4 is 27.8067 mNm, indicating that T4 > T3. Data comparison shows that chopping the arc at the front side of the sector 110 in the direction of rotation is more effective than chopping the arc at the rear side in the direction of rotation of the sector 110. This can further reduce the torque ripple of the motor, thereby reducing motor vibration and noise and improving the smoothness of motor operation.

[0058] Reference Figure 2As shown, in an embodiment of the present invention, the radius of the first arc surface 121 is R1, and the radius of the second arc surface 122 is R2, and the radius R1 of the first arc surface 121 is smaller than the radius R2 of the second arc surface 122. The radius R1 of the first arc surface 121 and the radius R2 of the second arc surface 122 satisfy: 5≤R2 / R1≤8. For example, the value of R2 / R1 can be 5, 6, 6.5, 7, 7.5, 8, etc. It should be noted that the radius R2 of the second arc surface 122 is generally fixed, and what needs to be changed is the value of the radius R1 of the first arc surface 121 to optimize the performance of the motor. When the value of R2 / R1 is less than 5, that is, the radius R1 of the first arc surface 121 is too large, resulting in an increase in the width of the air gap, an increase in magnetic resistance, and a decrease in the efficiency of the motor. When the value of R2 / R1 is greater than 8, that is, the radius R1 of the first arc surface 121 is too small, it is difficult to reduce the torque ripple of the motor, and the stability of the motor operation is poor. Therefore, by rationally designing the value of R2 / R1 within the range of 5 to 8, the air gap width of the motor can be kept within an appropriate range, and the torque ripple of the motor can be effectively reduced, thereby improving the stability of the motor operation.

[0059] Continue to refer to Figure 2 As shown, in the radial direction of the second arc surface 122, the distance between the two ends of the first arc surface 121 along the circumferential direction is h, where h is the arc cutting depth of the first arc surface 121, satisfying the following conditions: 0.5mm≤h≤1mm. For example, the value of h can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc. When h is less than 0.5mm, the arc cutting depth is too small, making it difficult to form an asymmetric air gap distribution and reduce torque pulsation. When h is greater than 1mm, the arc cutting depth is too large, which will increase the width of the air gap, increase the magnetic resistance, and reduce the efficiency of the motor. Therefore, by reasonably designing the value range of h within the range of 0.5mm to 1mm, an asymmetric air gap distribution can be effectively formed to reduce torque pulsation, while ensuring that the air gap width is within a suitable range to improve the working efficiency of the motor.

[0060] Continue to refer to Figure 2As shown, in an embodiment of the present invention, the angle between the connecting line S2 and the connecting line S3 is α, which satisfies: 2.5°≤α≤13.5°. For example, the value of α can be 2.5°, 4.5°, 6.5°, 8°, 10°, 13.5°, etc., and the appropriate central angle is selected according to the different number of poles, for example, it is calculated according to the relevant formula mentioned in the above embodiment. The size of the central angle α reflects the proportion of the first arc surface 121 on the front end surface. When the central angle α is less than 2.5°, the proportion of the first arc surface 121 is too small, and it is difficult to play the role of reducing torque pulsation. When the central angle α is greater than 13.5°, the proportion of the first arc surface 121 is too large, which will cause the torque pulsation of the motor to increase and the vibration of the motor to increase. Therefore, a reasonable design of the central angle α within the range of 2.5° to 13.5° can effectively reduce the torque pulsation of the motor, reduce the vibration and noise of the motor, and improve the stability and reliability of the motor operation.

[0061] Continue to refer to Figure 2 As shown, in an embodiment of the present invention, the angle between the connecting line S1 and the connecting line S2 is θ, which satisfies: 8°≤θ≤16°. For example, the value of θ can be 8°, 10°, 12°, 14°, 16°, etc., and a suitable angle is selected according to the motor with different pole numbers, for example, it is calculated according to the relevant formula mentioned in the above embodiment. For example, the value of θ for an 8-pole motor can be 16°, and the value of θ for a 12-pole motor can be 12°. The appropriate angle is selected according to the actual situation. When θ is less than 8°, the proportion of the first arc surface 121 is too large, resulting in increased torque pulsation of the motor and increased vibration during motor operation. When θ is greater than 16°, the proportion of the first arc surface 121 is too small, making it difficult to achieve the effect of reducing torque pulsation. Therefore, a reasonable design of θ within the range of 8° to 16° can effectively reduce the torque pulsation of the motor, reduce the vibration and noise of the motor, and improve the stability and reliability of the motor operation.

[0062] The motor of one embodiment of the present invention comprises the rotor assembly 100 and the stator assembly of the above embodiment. The stator assembly is annular, and the rotor assembly 100 is arranged inside the stator assembly. The rotor assembly 100 also includes a plurality of permanent magnets, the number of the permanent magnets is the same as the number of the mounting slots 111, and the plurality of permanent magnets are mounted in the plurality of mounting slots 111 in a one-to-one correspondence. The motor of the present invention embodiment adopts the rotor assembly 100 of the above embodiment, and the plurality of sector portions 110 of the rotor assembly 100 are arranged circumferentially spaced around the axis of rotation, and mounting slots 111 for accommodating permanent magnets are formed between adjacent sector portions 110. The outer end surface 120 of the sector portion 110 comprises a first arc surface 121 and a second arc surface 122, the first arc surface 121 is located at one end of the sector portion 110 along the circumferential direction, and the second arc surface 122 extends to the other end of the sector portion 110 along the circumferential direction, and the radius of the first arc surface 121 is smaller than the radius of the second arc surface 122. Therefore, a first arc surface 121 is provided at one circumferential end of the sector portion 110. That is, one circumferential end of the sector portion 110 is chopped, while the other end is not. When the rotor assembly 100 of this embodiment is used in a motor, an asymmetric air gap is formed on one side of the rotor assembly 100, effectively destroying specific harmonic components and making the electromagnetic force more evenly distributed, thereby reducing torque ripple and improving the stability of motor operation.

[0063] Since the motor adopts all the technical solutions of the rotor assembly 100 of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described in detail here.

[0064] A household appliance according to one embodiment of the present invention includes the motor of the above embodiment. The household appliance may be a refrigerator, an air conditioner, a fan, a dehumidifier, a range hood, etc. The household appliance according to the embodiment of the present invention adopts the motor of the above embodiment, and is provided with a plurality of sector-shaped portions 110 of a rotor assembly 100 arranged circumferentially spaced around the axis of rotation, and a mounting groove 111 for accommodating a permanent magnet is formed between adjacent sector-shaped portions 110. The outer end surface 120 of the sector-shaped portion 110 includes a first arc surface 121 and a second arc surface 122. The first arc surface 121 is located at one end of the sector-shaped portion 110 along the circumferential direction, and the second arc surface 122 extends to the other end of the sector-shaped portion 110 along the circumferential direction, and the radius of the first arc surface 121 is smaller than the radius of the second arc surface 122. Therefore, the first arc surface 121 is provided at one end of the sector-shaped portion 110 along the circumferential direction, that is, the sector-shaped portion 110 is chopped at one end along the circumferential direction, while the other end is not chopped. When the rotor assembly 100 of this embodiment is applied to a motor, an asymmetric air gap is formed on one side of the rotor assembly 100 , effectively destroying specific harmonic components and making the distribution of electromagnetic force more uniform, thereby reducing torque pulsation and improving the stability of motor operation.

[0065] Since the household appliance adopts all the technical solutions of the motor of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described in detail here.

[0066] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A rotor assembly, characterized in that: include: A plurality of sector-shaped portions are circumferentially spaced apart around the rotation axis of the rotor assembly, with mounting grooves for accommodating permanent magnets formed between adjacent sector-shaped portions, and an end of the sector-shaped portion facing away from the rotation axis having an outer end surface; In which, the outer end surface includes a first arc surface and a second arc surface. Along the circumference of the rotor assembly, the first arc surface and the second arc surface are connected, the first arc surface is located at one end of the fan-shaped portion, and the second arc surface extends to the other end of the fan-shaped portion; the first arc surface and the second arc surface both protrude outward, and the first arc surface is located within the circular outline where the second arc surface is located.

2. The rotor assembly according to claim 1, wherein: Along the rotation direction of the rotor assembly, the first arc surface is located in front of the outer end surface.

3. The rotor assembly according to claim 1, wherein: The radius of the first arc surface is R1, and the diameter of the circumscribed circle of the rotor assembly is D ro , the number of the installation slots is 2p, satisfying: R1= (D ro / 2)*Sin(π / 2p).

4. The rotor assembly according to claim 1, wherein: The radius of the first arc surface is R1, and the radius of the second arc surface is R2, satisfying: 5≤R2 / R1≤8.

5. The rotor assembly according to claim 1, wherein: In the radial direction of the second arc surface, the distance between the two ends of the first arc surface along the circumferential direction is h, which satisfies: 0.5 mm ≤ h ≤ 1 mm.

6. The rotor assembly according to claim 1, wherein: The number of the mounting grooves is 2p. On the projection surface perpendicular to the rotation axis, the line connecting the connection point of the first arc surface and the second arc surface and the center of the second arc surface is S2, and the line connecting the endpoint of one end of the first arc surface away from the second arc surface and the center of the second arc surface is S3. The angle between S2 and the line S3 is α, satisfying: α=k*α0, where 0.1≤k≤0.3, α0=360° / 2p.

7. The rotor assembly according to claim 1 or 6, characterized in that: On the projection surface perpendicular to the rotation axis, the line connecting the connection point of the first arc surface and the second arc surface and the center of the second arc surface is S2, the line connecting the endpoint of one end of the first arc surface away from the second arc surface and the center of the second arc surface is S3, and the angle between S2 and the line S3 is α, satisfying: 2.5°≤α≤13.5°.

8. The rotor assembly according to claim 1, wherein: On the projection surface perpendicular to the rotation axis, the line connecting the connection point of the first arc surface and the second arc surface and the center of the second arc surface is S2, the line connecting the midpoint of one end of the sector portion close to the rotation axis and the center of the second arc surface is S1, and the angle between the line S1 and the line S2 is θ, satisfying: 8°≤θ≤16°.

9. The motor is characterized by: Comprising a rotor assembly according to any one of claims 1 to 8.

10. A household appliance, characterized in that Including the motor according to claim 9.

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