Rotor core, rotor assembly, motor and food processor

Abstract

The invention provides a rotor core, a rotor assembly, a motor and a food processor, the rotor core is used for the motor, the motor comprises a stator assembly and a rotor assembly, the rotor assembly is located in the stator assembly, the rotor assembly comprises a rotor core, and the rotor assembly comprises a plurality of magnetic poles. The outer side wall surface of the rotor core comprises first outer side wall surfaces which are arranged in one-to-one correspondence with the plurality of magnetic poles, the outer contour line of each first outer side wall surface comprises two end points and a middle point, and the distance between the outer contour line and the circle center of the rotor core is reduced from the middle point to the two end points.

Description

Technical Field

[0001] The present application relates to the field of household appliances, and in particular to a rotor core, a rotor assembly, a motor and a food processor. Background Art

[0002] With improved living standards, users are placing higher demands on the noise and efficiency of blenders. As the core power component of blenders, the motor is closely linked to their vibration, noise, and service life. Permanent magnet motors, due to their cost advantages, are increasingly being used in blenders.

[0003] Among them, the rotor of the permanent magnet motor will generate cogging torque when the motor is running, which will cause the motor to generate vibration noise and affect the user experience.

[0004] Therefore, how to reduce the noise of permanent magnet motors has become an urgent problem to be solved. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0006] To this end, a first aspect of the present application provides a rotor core.

[0007] A second aspect of the present application provides a rotor assembly.

[0008] A third aspect of the present application provides a motor.

[0009] A fourth aspect of the present application provides a food processor.

[0010] In view of this, a first aspect of the present application provides a rotor core for use in an electric motor. The electric motor includes a stator assembly and a rotor assembly, wherein the rotor assembly is located within the stator assembly. The rotor assembly includes a rotor core. The rotor assembly includes a plurality of magnetic poles. The outer wall of the rotor core includes a first outer wall surface that is arranged in a one-to-one correspondence with the plurality of magnetic poles. The outer contour of the first outer wall surface includes two endpoints and a midpoint, and the distance between the outer contour line and the center of the rotor core decreases from the midpoint toward the two endpoints.

[0011] The rotor core proposed in this application is used in a motor, wherein the rotor core is provided with permanent magnets, and the permanent magnet arrangement enables the rotor core to form multiple magnetic poles. The outer wall of the rotor core is divided into multiple first outer walls, each corresponding to a magnetic pole. That is, the outer wall of the rotor core corresponding to each magnetic pole is a first outer wall. The distance between the first outer wall and the center of the rotor core decreases from the midpoint to the ends. That is, the outer wall of the rotor core corresponding to each magnetic pole is higher in the middle and lower at the ends, and the distance decreases toward the ends. That is, the distance between the midpoint of the first outer wall and the center of the rotor core is greatest, while it is smallest at the ends, and the distance decreases from the midpoint to the ends. This arrangement creates an uneven air gap structure between the rotor core and the stator assembly, thereby reducing the motor's cogging torque, reducing the harmonic content of the air gap flux density, and improving the sinusoidality of the air gap flux density waveform, resulting in smoother motor operation.

[0012] Optionally, the distance between any target point of the outer contour line and the center of the rotor core is R, and the air gap length lg(θ) of the motor at the target point and the inner diameter D of the stator assembly satisfy: R=D-lg(θ), where: the reciprocal of lg(θ) is distributed as a cosine function.

[0013] In this technical solution, lg(θ) is equal to the air gap length of the motor. That is, in this application, the air gap length between the rotor core and the stator assembly is an inverse cosine function, that is, the air gap between the rotor core and the stator assembly is not uniformly distributed. In conventional designs, the air gap structure of the motor is uniform, and there are many harmonics in the air gap magnetic flux. However, this application changes the air gap into an uneven structure by performing inverse cosine pole clipping on the outer circle side of the rotor core. The air gap length of the motor d axis (at the center line of the permanent magnet) is small, and the air gap length of the q axis (at the axis of symmetry of a pair of permanent magnets) is large, thereby achieving a sinusoidal distribution of the motor air gap magnetic flux. In this way, the distribution of the motor air gap magnetic flux is changed, achieving the purpose of reducing the motor cogging torque and torque pulsation.

[0014] Optionally, lg(θ) satisfies the following relationship:

[0015]

[0016] In the above formula, lg(θ) is the air gap length when the motor is at the target point, l gd is the air gap length of the motor at the midpoint, the first outer wall includes endpoints A and B, the center of the rotor core is O, the target point is point Q, the midpoint is P, and the angle formed by line segment AO and line segment PO is τ p , the angle formed by line segment PO and line segment QO is θ.

[0017] In this technical solution, the air gap length l of the motor after arc cosine pole clipping is g(θ) and the rotor mechanical position angle θ follow the above-mentioned law. The profile of the outer circle side of the rotor core is modified according to the corresponding function curve, which changes the distribution of the motor air gap magnetic flux density and achieves the purpose of reducing the motor slot torque and torque pulsation.

[0018] Among them, from the above formula, we can know that when θ approaches τ p When θ equals 0, meaning the rotor's mechanical position angle approaches half the pole pitch, the air gap length approaches infinity. When θ equals 0, meaning the rotor's position angle coincides with the d-axis, the air gap length reaches its minimum value. This cycle repeats, and the motor's air gap length varies from minimum to maximum in an inverse cosine pattern, achieving a sinusoidal distribution of the air gap flux density.

[0019] Among them, θ should be within a reasonable range, because when θ is too close to the pole pitch, that is, when the ratio of pole arc to pole pitch is close to 1, the air gap length is too large, which is not in line with the actual situation.

[0020] Optionally,

[0021] That is, the curve of the reciprocal of lg(θ) is not a complete cosine curve, but only a part of the cosine curve.

[0022] Optionally, the air gap length of the motor at either end is l gq , the air gap length of the motor at the midpoint is l gd , where l gq With l gd The ratio is greater than or equal to 2 and less than or equal to 2.5.

[0023] Among them, the ratio of pole arc to pole pitch affects the end magnetic barrier space and leakage of the motor permanent magnet, so it is necessary to determine the ratio of pole arc to pole pitch before further optimization. The ratio of pole arc to pole pitch can be determined by the d-axis air gap length l gd and q-axis air gap length l gq The ratio k reflects that k=l gq / l gd ∈[2,2.5], when k is less than 2, the air gap magnetic flux distortion rate is large and the cogging torque is not significantly improved. When k is greater than 2.5, in order to ensure that the rotor has sufficient mechanical strength, the permanent magnet needs to move closer to the inner circle of the motor rotor, resulting in a decrease in the utilization rate of the permanent magnet.

[0024] Optionally, an auxiliary groove is provided on the outer wall surface of the rotor core, and the auxiliary groove is provided at the connection between any two first outer wall surfaces.

[0025] The stator core slots and teeth are regularly staggered. When the rotor rotates, the core area corresponding to the permanent magnets changes periodically according to the distribution of the slots and teeth, resulting in a pulsating torque along the circumference, known as cogging torque. Cogging torque is the tangential force acting between the permanent magnets and the stator slots in a permanent magnet motor under no-load conditions. This force constantly attempts to align the centerline of the permanent magnets with the centerline of the stator teeth, pulling the rotor to a fixed position. However, the addition of auxiliary slots to the outer circumference of the rotor core alters the air gap structure, affecting the cogging torque and electromagnetic performance of the motor. Therefore, properly setting the parameters of the auxiliary slots can reduce the quadrature-axis inductance Lq while ensuring that the air gap magnetic flux sinusoidality and cogging torque do not deteriorate, thereby effectively improving the motor's overload capacity under high-speed operating conditions.

[0026] Among them, the position, width and depth of the auxiliary slot should be set reasonably. The position of the auxiliary slot will affect the magnetic resistance of the direct-axis and quadrature-axis magnetic circuits. If the width and depth of the auxiliary slot are too large, it will affect the rotor magnetic circuit, and if they are too small, the performance optimization of the motor will not be obvious.

[0027] Furthermore, the auxiliary slot is a circular slot, and the two auxiliary slots under one pole form an angle β with the center of the rotor, where β = 2×τ p , that is, the angle β and the angle corresponding to the pole distance are the same. Because, when β<2×τ p When , the cogging torque is reduced, but the magnetic resistance of the direct-axis magnetic circuit increases, resulting in a decrease in the utilization rate of the permanent magnet flux.

[0028] The auxiliary slot distribution position can be changed by adjusting the angle β. When β=2×τ p When the auxiliary slot position coincides with the rotor quadrature axis position, the auxiliary slot and the inverse cosine curve together form the rotor outer circular contour. At this time, the quadrature axis position air gap is further reduced, and the quadrature axis magnetic circuit reluctance increases, resulting in a further reduction in the quadrature axis inductance Lq. This can effectively improve the motor's overload capacity under high-speed operating conditions without significantly affecting the air gap magnetic flux distortion rate and cogging torque. The auxiliary slot size can be changed by adjusting the radius r. The auxiliary slot radius r should be smaller than the thickness of the magnetic isolation bridge. When the radius r approaches the thickness of the magnetic isolation bridge, the auxiliary slot is too close to the magnetic isolation slot at the permanent magnet pole tip, which affects the thickness of the magnetic isolation bridge, thereby reducing the mechanical strength of the rotor core and easily leading to poor permanent magnet assembly.

[0029] Optionally, the number of the auxiliary slots matches the number of the magnetic poles.

[0030] Among them, two auxiliary slots are set on the outer circle side of the rotor core corresponding to the permanent magnet under one pole. The two auxiliary slots are symmetrically distributed about the d axis (the center line of the permanent magnet). The number of auxiliary slots is n, the number of motor pole pairs is p, and n=2p.

[0031] Optionally, the auxiliary groove is a semicircular groove.

[0032] Optionally, the auxiliary slots are axisymmetric, with their axis of symmetry passing through the center of the rotor core. This arrangement allows for a symmetrical distribution of the auxiliary slots on the rotor core, thereby reducing the quadrature-axis inductance Lq while maintaining air gap flux sinusoidality and cogging torque, thereby effectively improving the motor's overload capacity under high-speed operating conditions.

[0033] Optionally, the radius of the circular slot is greater than or equal to 0.5 mm and less than or equal to 1 mm. The radius of the circular slot is set to r, r∈[0.5,1]. When r>1, the setting of the circular slot will reduce the thickness of the magnetic isolation bridge and affect the mechanical strength of the rotor core. When r<0.5, the circular slot has little effect on the performance of the motor.

[0034] Optionally, the rotor core is provided with a magnetic isolation groove and a mounting groove for mounting permanent magnets, wherein the magnetic isolation grooves are distributed on the outside of the mounting grooves along both ends of the rotor core, and the magnetic isolation grooves and the mounting grooves are connected; wherein the depth of the auxiliary groove along the radial direction of the rotor core is less than the distance between the magnetic isolation groove and the outer wall surface of the rotor core, wherein the distance between the magnetic isolation groove and the outer wall surface of the rotor core is the thickness of the magnetic isolation bridge. Because, when the depth of the magnetic isolation groove along the axial direction of the rotor core (i.e., the groove depth) is close to the thickness of the magnetic isolation bridge, the distance between the auxiliary groove and the magnetic isolation groove at the permanent magnet pole tip is too close, which will affect the thickness of the magnetic isolation bridge, thereby reducing the mechanical strength of the rotor core, and easily leading to poor assembly of the permanent magnet.

[0035] Optionally, the central portion of the rotor core is hollow. Alternatively, the central portion of the rotor core is enclosed, and a plurality of lightening holes are provided in the central portion of the rotor core. The plurality of lightening holes are symmetrically distributed along the center of the rotor core. Optionally, the number of lightening holes is four, and the lightening holes are of uniform size and shape.

[0036] The second aspect of the present application proposes a rotor assembly, comprising: a rotor core provided by any technical solution of the first aspect, wherein the rotor core is provided with a plurality of mounting slots for mounting permanent magnets; and a plurality of permanent magnets are mounted in the mounting slots in a one-to-one correspondence.

[0037] The rotor assembly proposed in this application is primarily composed of a rotor core and a plurality of permanent magnets. Furthermore, because the rotor assembly includes the rotor core provided by any of the technical solutions of the first aspect, the rotor assembly possesses all the beneficial effects of the rotor core provided by any of the technical solutions of the first aspect, and thus is not further elaborated here.

[0038] The mounting slots may be strip-shaped slots, such as straight slots, in which case the permanent magnets are strip-shaped. Furthermore, multiple mounting slots may be arranged in a group, such as a V-shaped arrangement, in which case the permanent magnets are distributed in the multiple mounting slots, and a pole may be formed by the multiple permanent magnets.

[0039] Optionally, the stator assembly includes a stator core and a stator winding. The stator core includes interconnected stator teeth and a stator yoke. There are multiple stator teeth. Stator slots are formed between adjacent stator teeth and the stator yoke.

[0040] In one specific embodiment, the number of stator teeth is 12. The width of the stator teeth is 4.5 mm. The thickness of the stator yoke is 4 mm. Furthermore, the upper and lower surfaces of the permanent magnets that contact the rotor core are coated with glue and inserted axially into the mounting slots of the core. The permanent magnets are fixed together by the attraction between the permanent magnets and the core and the glue filling. When the motor is running, the permanent magnets rotate in a circular motion around the axis with the core, and their relative positions remain unchanged.

[0041] The third aspect of the present application proposes a motor, comprising: a stator assembly; a rotor core provided by any technical solution of the first aspect or a rotor assembly provided by any technical solution of the second aspect; wherein the rotor core or the rotor assembly is located inside the stator assembly.

[0042] The motor proposed in this application includes the rotor core provided by any technical solution of the first aspect or the rotor assembly provided by any technical solution of the second aspect. Therefore, the motor has all the beneficial effects of the rotor core provided by any technical solution of the first aspect or the rotor assembly provided by any technical solution of the second aspect, which will not be described one by one here.

[0043] Optionally, the motor is a permanent magnet motor.

[0044] The fourth aspect of the present application provides a food processor, comprising: a rotor core provided by any technical solution of the first aspect or a rotor assembly provided by any technical solution of the second aspect; or a motor provided by any technical solution of the third aspect.

[0045] The food processor proposed in this application includes the rotor core provided by any technical solution of the first aspect or the rotor assembly provided by any technical solution of the second aspect or the motor provided by any technical solution of the third aspect. Therefore, the food processor has all the beneficial effects of the rotor core provided by any technical solution of the first aspect or the rotor assembly provided by any technical solution of the second aspect or the motor provided by any technical solution of the third aspect, which will not be described one by one here.

[0046] Among them, food processors include wall breakers, juicers or bread makers, etc.

[0047] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0049] Figure 1 A schematic structural diagram of a rotor core according to an embodiment of the present invention is shown;

[0050] Figure 2 A schematic cross-sectional view of a rotor core according to an embodiment of the present invention is shown;

[0051] Figure 3 A partial structural schematic diagram of a rotor assembly according to an embodiment of the present invention is shown;

[0052] Figure 4 A schematic structural diagram showing air gap variation of a motor according to an embodiment of the present invention is shown;

[0053] Figure 5 The figure shows the difference in cogging torque of a motor according to an embodiment of the present invention before and after optimization;

[0054] Figure 6 The figure shows the difference in back electromotive force waves of a motor before and after optimization according to an embodiment of the present invention;

[0055] Figure 7 The figure shows the difference in electromagnetic torque of a motor according to an embodiment of the present invention before and after optimization;

[0056] Figure 8 A schematic structural diagram of a motor according to an embodiment of the present invention is shown.

[0057] in, Figures 1 to 4 as well as Figure 8 The corresponding relationship between the reference numerals and component names is as follows:

[0058] 1 rotor core, 12 first outer side wall, 122 outer contour line, 14 auxiliary slot, 16 mounting slot, 18 magnetic isolation slot, 2 permanent magnet, 3 stator assembly, 32 stator teeth, 34 stator yoke. DETAILED DESCRIPTION

[0059] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0060] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0061] Refer to the following Figures 1 to 8 The rotor core and the motor according to some embodiments of the present invention are described.

[0062] like Figure 1 、 Figure 2 and Figure 3 As shown, the first aspect of the present application provides a rotor core 1 for use in an electric motor. The electric motor includes a stator assembly and a rotor assembly, wherein the rotor assembly is located within the stator assembly. The rotor assembly includes a rotor core 1. The rotor assembly includes a plurality of magnetic poles. The outer wall surface of the rotor core 1 includes a first outer wall surface 12 arranged in a one-to-one correspondence with the plurality of magnetic poles. The outer contour line 122 of the first outer wall surface 12 includes two endpoints and a midpoint. The distance between the outer contour line 122 and the center of the rotor core 1 decreases from the midpoint toward the two endpoints.

[0063] The rotor core 1 proposed in the present application is used for an electric motor, wherein a permanent magnet 2 is provided on the rotor core 1, and the arrangement of the permanent magnet 2 enables the rotor core 1 to form a plurality of magnetic poles. The outer wall of the rotor core 1 is divided into a plurality of first outer wall surfaces 12, and each first outer wall surface 12 corresponds to a magnetic pole arrangement. That is, the outer wall surface of the rotor core 1 corresponding to each magnetic pole is the first outer wall surface 12. The distance between the first outer wall surface 12 and the center of the rotor core 1 decreases from the midpoint to the two ends. That is, the outer wall surface of the rotor core 1 corresponding to each magnetic pole is high in the middle and low at the two ends, and the distance decreases as it moves towards the two ends. That is, the distance between the midpoint position of the first outer wall surface 12 and the center of the rotor core 1 is the largest, while the two ends are the smallest, and there is a trend of decreasing from the middle to the two ends. This setting can form an uneven air gap structure between the rotor core 1 and the stator assembly, thereby reducing the motor's cogging torque, reducing the air gap magnetic flux harmonic content, and improving the sinusoidality of the air gap magnetic flux waveform, making the motor run more smoothly.

[0064] Alternatively, as Figure 2 and Figure 3 As shown, the distance between any target point of the outer contour line 122 and the center of the rotor core 1 is R (for example Figure 3 The length of the line segment OP in the figure), the air gap length lg(θ) of the motor at the target point and the inner diameter D of the stator assembly satisfy: R=D-lg(θ), where: the reciprocal of lg(θ) is distributed in a cosine function.

[0065] In this embodiment, lg(θ) is equal to the air gap length of the motor. That is, in this application, the air gap length between the rotor core 1 and the stator assembly is an inverse cosine function, that is, the air gap between the rotor core 1 and the stator assembly is not uniformly distributed. In conventional designs, the air gap structure of the motor is uniform, and there are many harmonics in the air gap magnetic flux. However, in this application, by performing inverse cosine pole clipping on the outer circle side of the rotor core 1, the air gap is changed to an uneven structure, the air gap length of the motor d axis (at the center line of the permanent magnet 2) is small, and the air gap length of the q axis (at the pole tip of the permanent magnet 2) is large, thereby achieving a sinusoidal distribution of the motor air gap magnetic flux. In this way, the distribution of the motor air gap magnetic flux is changed, and the purpose of reducing the motor cogging torque and torque pulsation is achieved.

[0066] Optionally, lg(θ) satisfies the following relationship:

[0067]

[0068] In the above formula, l g (θ) is the air gap length when the motor is at the target point, l gd is the air gap length of the motor at the midpoint, the first outer wall 12 includes endpoints A and B, the center of the rotor core 1 is O, the target point is point Q, the midpoint is point P, and the angle formed by line segment AO and line segment PO is τ p , the angle formed by line segment PO and line segment QO is θ.

[0069] In this embodiment, the air gap length l of the motor after arc cosine pole clipping is g (θ) and the rotor mechanical position angle θ follow the above-mentioned law. The profile of the outer circle side of the rotor core 1 is modified according to the corresponding function curve, which changes the distribution of the motor air gap magnetic flux density and achieves the purpose of reducing the motor slot torque and torque pulsation.

[0070] Among them, from the above formula, we can know that when θ approaches τ p When θ equals 0, meaning the rotor's mechanical position angle approaches half the pole pitch, the air gap length approaches infinity. When θ equals 0, meaning the rotor's position angle coincides with the d-axis, the air gap length reaches its minimum value. This cycle repeats, and the motor's air gap length varies from minimum to maximum in an inverse cosine pattern, achieving a sinusoidal distribution of the air gap flux density.

[0071] Among them, θ should be within a reasonable range, because when θ is too close to the pole pitch, that is, when the ratio of pole arc to pole pitch is close to 1, the air gap length is too large, which is not in line with the actual situation.

[0072] in, Figure 4 Shown is a schematic diagram of the outer contour line corresponding to the outer side wall of half the pole pitch of the rotor core 1 and the air gap length between the outer side wall and the stator assembly. Figure 4 In, l gdIt means that when the rotor position angle coincides with the d-axis, the air gap length takes the minimum value.

[0073] Optionally,

[0074] That is, the curve of the reciprocal of lg(θ) is not a complete cosine curve, but only a part of the cosine curve.

[0075] Optionally, the air gap length of the motor at either end is l gq , the air gap length of the motor at the midpoint Q is l gd , where l gq With l gd The ratio is greater than or equal to 2 and less than or equal to 2.5.

[0076] Among them, the ratio of pole arc to pole pitch affects the end magnetic barrier space and leakage of the permanent magnet 2 of the motor, so it is necessary to determine the ratio of pole arc to pole pitch before further optimization. The ratio of pole arc to pole pitch can be calculated by the d-axis air gap length l gd and q-axis air gap length l gq The ratio k reflects that k=l gq / l gd ∈[2,2.5], when k is less than 2, the air gap magnetic flux distortion rate is large and the cogging torque is not significantly improved. When k is greater than 2.5, in order to ensure that the rotor has sufficient mechanical strength, the permanent magnet 2 needs to be moved closer to the inner circle of the motor rotor, resulting in a decrease in the utilization rate of the permanent magnet 2.

[0077] Alternatively, as Figures 1 to 4 As shown, auxiliary grooves 14 are provided on the outer wall surface of the rotor core 1 , and the auxiliary grooves 14 are provided at the connection between any two first outer wall surfaces 12 .

[0078] The stator core's slots and teeth are regularly and staggered. When the rotor rotates, the core area corresponding to the permanent magnets 2 undergoes periodic variations according to the regular distribution of the slots and teeth, resulting in a pulsating torque in the circumferential direction, known as cogging torque. Cogging torque is the tangential force acting between the permanent magnets 2 and the stator teeth in a permanent magnet motor under no-load conditions. This force always attempts to align the centerline of the permanent magnets 2 with the centerline of the stator teeth, pulling the rotor to a fixed position. Providing auxiliary slots 14 on the outer circumference of the rotor core 1 changes the air gap structure, affecting the motor's cogging torque and electromagnetic performance. Therefore, rationally setting the parameters of the auxiliary slots 14 can reduce the quadrature-axis inductance Lq while ensuring that the air gap magnetic flux sinusoidality and cogging torque do not deteriorate, thereby effectively improving the motor's overload capacity under high-speed operating conditions.

[0079] Among them, the position, width and depth of the auxiliary slot 14 should be set reasonably. The position of the auxiliary slot 14 will affect the magnetic resistance of the direct-axis and quadrature-axis magnetic circuits. If the width and depth of the auxiliary slot 14 are too large, it will affect the rotor magnetic circuit, and if they are too small, the performance optimization of the motor will not be obvious.

[0080] Furthermore, the auxiliary slots 14 are circular slots, and the two auxiliary slots 14 under one pole form an angle β with the center of the rotor, where β = 2×τ p That is, the angle β and the angle corresponding to the pole distance are the same. Because, when β<2×τ p When , the cogging torque is reduced, but the magnetic resistance of the direct-axis magnetic circuit increases, resulting in a decrease in the utilization rate of the permanent magnet flux.

[0081] The distribution position of the auxiliary grooves 14 can be changed by adjusting the angle β. When β = 2 × τ p When the auxiliary slot 14 is positioned at the position of the rotor's quadrature axis, the auxiliary slot 14 and the inverse cosine curve together form a modified shape for the rotor's outer circle. At this time, the air gap at the quadrature axis position is further reduced, and the quadrature axis magnetic circuit magnetic resistance increases, resulting in a further reduction in the quadrature axis inductance Lq, which can effectively improve the overload capacity of the motor under high-speed operation conditions without significantly affecting the air gap magnetic flux distortion rate and cogging torque. The size of the auxiliary slot 14 can be changed by adjusting the radius r. The radius r of the auxiliary slot 14 should be smaller than the thickness of the magnetic isolation bridge. When the radius r is close to the thickness of the magnetic isolation bridge, the distance between the auxiliary slot 14 and the magnetic isolation slot 18 at the pole tip of the permanent magnet 2 is too close, which will affect the thickness of the magnetic isolation bridge, thereby reducing the mechanical strength of the rotor core 1 and easily leading to poor assembly of the permanent magnet 2.

[0082] Optionally, the number of the auxiliary slots 14 is consistent with the number of the magnetic poles.

[0083] Among them, two auxiliary slots 14 are set on the outer circle side of the rotor core 1 corresponding to the permanent magnet 2 under one pole. The two auxiliary slots 14 are symmetrically distributed about the d axis (the center line of the permanent magnet 2). The number of auxiliary slots 14 is n, the number of motor pole pairs is p, and n=2p.

[0084] Alternatively, as Figures 1 to 4 As shown, the auxiliary groove 14 is a semicircular groove.

[0085] Optionally, the auxiliary slots 14 are axisymmetric, with the axis of symmetry of the auxiliary slots 14 passing through the center of the rotor core 1. This arrangement allows the plurality of auxiliary slots 14 to be symmetrically distributed on the rotor core 1. This reduces the quadrature-axis inductance Lq while ensuring that the air gap magnetic flux sinusoidality and cogging torque do not deteriorate, thereby effectively improving the overload capacity of the motor under high-speed operating conditions.

[0086] Alternatively, as Figures 1 to 4As shown in FIG, the radius of the circular slot is greater than or equal to 0.5 mm and less than or equal to 1 mm. The radius of the circular slot is set to r, r∈[0.5,1]. When r>1, the setting of the circular slot will reduce the thickness of the magnetic isolation bridge and affect the mechanical strength of the rotor core 1. When r<0.5, the circular slot has little effect on the motor performance.

[0087] Optionally, the rotor core 1 is provided with a magnetic isolation groove 18 and a mounting groove 16 for mounting the permanent magnet 2. The magnetic isolation groove 18 is distributed on the outer sides of the mounting groove 16 along both ends of the rotor core 1, and the magnetic isolation groove 18 and the mounting groove 16 are connected; wherein the groove depth of the auxiliary groove 14 is less than the thickness t of the magnetic isolation groove 18 (such as Figure 3 Because, when the width of the magnetic isolation slot 18 along the circumferential direction of the rotor core 1 approaches the thickness of the magnetic isolation bridge, the auxiliary slot 14 is too close to the magnetic isolation slot 18 at the pole tip of the permanent magnet 2, which will affect the thickness of the magnetic isolation bridge, thereby reducing the mechanical strength of the rotor core 1 and easily causing poor assembly of the permanent magnet 2.

[0088] like Figures 1 to 4 As shown, the second aspect of the present application proposes a rotor assembly, comprising: a rotor core 1 provided by any embodiment of the first aspect, the rotor core 1 being provided with a plurality of mounting grooves 16 for mounting permanent magnets 2; a plurality of permanent magnets 2 being mounted in the mounting grooves 16 in a one-to-one correspondence.

[0089] The rotor assembly proposed in this application is primarily composed of a rotor core 1 and a plurality of permanent magnets 2. Furthermore, since the rotor assembly includes the rotor core 1 provided in any embodiment of the first aspect, the rotor assembly possesses all the beneficial effects of the rotor core 1 provided in any embodiment of the first aspect, and thus is not further detailed here.

[0090] Furthermore, multiple permanent magnets 2 are coated with glue on their upper and lower surfaces in contact with the rotor core 1 and then inserted axially into mounting slots 16 of the rotor core 1. The two are secured together by the attractive force between the permanent magnets 2 and the rotor core 1 and the glue filling. During motor operation, the permanent magnets 2 rotate around the axis with the rotor core 1, while their relative positions remain unchanged.

[0091] like Figure 8 As shown, the third aspect of the present application proposes a motor, comprising: a stator assembly 3; a rotor core 1 provided by any embodiment of the first aspect or a rotor assembly provided by any embodiment of the second aspect; wherein the rotor core 1 or the rotor assembly is located in the stator assembly 3.

[0092] The motor proposed in the present application includes the rotor core 1 provided by any embodiment of the first aspect or the rotor assembly provided by any embodiment of the second aspect. Therefore, the motor has all the beneficial effects of the rotor core 1 provided by any embodiment of the first aspect or the rotor assembly provided by any embodiment of the second aspect, which will not be described one by one here.

[0093] Optionally, the motor is a permanent magnet motor.

[0094] Optionally, the stator assembly 3 includes a stator core and a stator winding, wherein the stator core includes stator teeth 32 and a stator yoke 34 .

[0095] In a specific embodiment, the number of stator teeth is 12, the number of permanent magnets is 8, the width of the stator teeth 32 is 4.5 mm, and the thickness of the stator yoke 34 is 4 mm.

[0096] The fourth aspect of the present application proposes a food processor (not shown in the figure), comprising: the rotor core 1 provided by any embodiment of the first aspect or the rotor assembly provided by any embodiment of the second aspect; or the motor provided by any embodiment of the third aspect.

[0097] The food processor proposed in this application includes the rotor core 1 provided by any embodiment of the first aspect or the rotor assembly provided by any embodiment of the second aspect or the motor provided by any embodiment of the third aspect. Therefore, the food processor has all the beneficial effects of the rotor core 1 provided by any embodiment of the first aspect or the rotor assembly provided by any embodiment of the second aspect or the motor provided by any embodiment of the third aspect, which will not be repeated here one by one.

[0098] Among them, food processors include wall breakers, juicers or bread makers, etc.

[0099] The following takes the permanent magnet brushless DC motor of a wall-breaking machine as an example to further introduce the rotor core 1, rotor assembly and motor provided in this application.

[0100] Blenders usually use DC series-excited motors, which have problems such as carbon powder pollution, short life, high noise, low motor efficiency, difficulty in speed regulation, and high machine base, which affect the user experience. The current variable frequency brushless motor solutions on the market are expensive and difficult to promote and apply to the main selling products.

[0101] With the improvement of living standards, users have higher requirements for the noise and efficiency of blenders. As the core power component of blenders, the motor is closely related to the vibration noise and service life of the blender. Currently, the blenders on the market mainly use brushed DC motors. Compared with brushed DC motors, permanent magnet brushless DC motors have advantages such as long life, low noise, high efficiency, adjustable speed, light structure, and no carbon powder pollution. However, due to the high cost of motors, their application is limited. With my country's restrictions on the export of rare earth resources, rare earth prices have gradually declined in recent years. The cost reduction of permanent magnet motors has further expanded their application scenarios.

[0102] Among them, there are permanent magnets 2 in the permanent magnet motor rotor structure, which will generate slot torque when the motor is running, thereby causing the motor to generate vibration noise and affect the user experience.

[0103] In order to solve the above noise problem, the present application reshapes the rotor outer circle of the permanent magnet motor and opens auxiliary slots 14, which can achieve the purpose of reducing the motor's slot torque, reducing the harmonic content of the air gap magnetic density, and improving the sinusoidality of the air gap magnetic density waveform, making the motor run more smoothly.

[0104] like Figure 3 As shown, the permanent magnet brushless DC motor rotor provided by the present application includes a rotor core 1 and a permanent magnet 2. The rotor core 1 has a mounting groove 16 for the permanent magnet 2 along the axial direction, which is evenly distributed in an array around the center of the core; an auxiliary groove 14 (also known as an auxiliary groove 14) is opened in the circumferential direction of the outer edge of the core, and two adjacent auxiliary grooves 14 are symmetrical about the mounting groove 16 in the middle, and the number of the two is the same. During the assembly process, the upper and lower surfaces of the permanent magnet 2 in contact with the core are smeared with glue, and the permanent magnet 2 is inserted axially into the slot hole (mounting groove 16) of the core. The two are fixed by the suction force between the permanent magnet 2 and the core and the filling glue. When the motor is running, the permanent magnet 2 rotates in a circle around the axis with the core, and the relative positions of the two remain unchanged.

[0105] The space between the outer circle of the rotor core 1 and the inner circle of the stator core forms the air gap structure. In conventional designs, the air gap structure of the motor is uniform, and there are many harmonics in the air gap flux density. By performing anti-cosine pole clipping on the outer circle of the rotor core 1, the air gap is changed to an uneven structure. The air gap length of the motor d-axis (at the center line of the permanent magnet 2) is small, and the air gap length of the q-axis (at the pole tip of the permanent magnet 2) is large, achieving a sinusoidal distribution of the motor air gap flux density. The air gap length l of the motor after anti-cosine pole clipping is g (θ) and the rotor mechanical position angle θ follow the rule of formula (1). The profile of the outer circle side of the rotor core 1 is modified according to the function curve, which changes the distribution of the motor air gap magnetic flux density and achieves the purpose of reducing the motor slot torque and torque pulsation.

[0106]

[0107] Where: l g (θ) is the air gap length when the rotor is at position angle θ; l gd is the air gap length corresponding to the d-axis (at the center line of the permanent magnet 2), i.e., the minimum air gap length; τ p It is half of the pole pitch (the pole pitch refers to the range occupied by each magnetic pole along the inner circle of the motor stator core) (expressed in mechanical degrees).

[0108] From formula (1), we can see that when θ approaches τ pWhen θ equals 0, meaning the rotor's mechanical position angle approaches half the pole pitch, the air gap length approaches infinity. When θ equals 0, meaning the rotor's position angle coincides with the d-axis, the air gap length reaches its minimum value. This cycle repeats, and the motor's air gap length varies from minimum to maximum in an inverse cosine pattern, achieving a sinusoidal distribution of the air gap flux density. θ should be within a reasonable range. When θ is too close to the pole pitch, meaning the ratio of pole arc to pole pitch approaches 1, the air gap length becomes excessively long and unrealistic.

[0109] The ratio of pole arc to pole pitch affects the end magnetic barrier space and magnetic leakage of the permanent magnet 2 of the motor. Therefore, the ratio of pole arc to pole pitch needs to be determined before further optimization. The ratio of pole arc to pole pitch can be calculated by the d-axis air gap length l gd and q-axis air gap length l gq The ratio k reflects that k=l gq / l gd ∈[2,2.5], when k is less than 2, the air gap magnetic flux distortion rate is large and the cogging torque is not significantly improved. When k is greater than 2.5, in order to ensure that the rotor has sufficient mechanical strength, the permanent magnet 2 needs to be moved closer to the inner circle of the motor rotor, resulting in a decrease in the utilization rate of the permanent magnet 2.

[0110] Furthermore, the rotor core 1 is provided with auxiliary slots 14. The stator core slots and teeth are regularly staggered. As the rotor rotates, the core area corresponding to the permanent magnets 2 undergoes periodic variations according to the distribution of the slots and teeth. This manifests as a pulsating torque along the circumference, known as cogging torque. Cogging torque is the tangential force acting between the permanent magnets 2 and the stator teeth in a permanent magnet motor under no-load conditions. This force constantly attempts to align the centerline of the permanent magnets 2 with the centerline of the stator teeth, pulling the rotor to a fixed position.

[0111] Providing auxiliary slots 14 on the outer circumference of the rotor core 1 changes the air gap structure, affecting the motor's cogging torque and electromagnetic performance. The position, width, and depth of the auxiliary slots 14 should be appropriately configured. The position of the auxiliary slots 14 affects the reluctance of the direct-axis and quadrature-axis magnetic circuits. Excessively large widths and depths of the auxiliary slots 14 can affect the rotor magnetic circuit, while too small widths and depths will not significantly improve motor performance.

[0112] Two auxiliary slots 14 are provided on the outer circumference of the rotor core 1 corresponding to the permanent magnet 2 under one pole. The two auxiliary slots 14 are symmetrically distributed about the d axis (the center line of the permanent magnet 2). The number of auxiliary slots 14 is n, and the number of motor pole pairs is p. The auxiliary slots 14 are preferably circular slots. The two auxiliary slots 14 under one pole form an angle β with the center of the rotor circle, wherein, as Figure 4 As shown, β = 2 × τ p , at this time n=2p. Because, when β<2×τ pWhen n = 4p, the cogging torque decreases, but the direct-axis magnetic circuit reluctance increases, resulting in a decrease in permanent magnet flux utilization. The radius of the auxiliary slot 14 is set to r, r∈[0.5,1]. When r>1, the auxiliary slot 14 reduces the thickness of the magnetic isolation bridge, affecting the mechanical strength of the rotor core 1. When r<0.5, the auxiliary slot 14 has little effect on motor performance.

[0113] The distribution position of the auxiliary grooves 14 can be changed by adjusting the angle β. When β = 2 × τ p When the auxiliary slot 14 is positioned at the position of the rotor's quadrature axis, the auxiliary slot 14 and the inverse cosine curve together form a modified shape for the rotor's outer circle. At this time, the air gap at the quadrature axis position is further reduced, and the quadrature axis magnetic circuit magnetic resistance increases, resulting in a further reduction in the quadrature axis inductance Lq, which can effectively improve the overload capacity of the motor under high-speed operation conditions without significantly affecting the air gap magnetic flux distortion rate and cogging torque. The size of the auxiliary slot 14 can be changed by adjusting the radius r. The radius r of the auxiliary slot 14 should be smaller than the thickness of the magnetic isolation bridge. When the radius r is close to the thickness of the magnetic isolation bridge, the distance between the auxiliary slot 14 and the magnetic isolation slot 18 at the pole tip of the permanent magnet 2 is too close, which will affect the thickness of the magnetic isolation bridge, thereby reducing the mechanical strength of the rotor core 1 and easily leading to poor assembly of the permanent magnet 2.

[0114] Figure 5 、 Figure 6 and Figure 7 The differences in the cogging torque, back electromotive force waveform, and electromagnetic torque of the motor of this embodiment before and after optimization are shown respectively. Figure 5 In the figure, the waveform of the cogging torque before optimization is S1, and the waveform of the cogging torque after optimization is S2. Figure 5 It can be clearly seen that the cogging torque is significantly improved after optimization.

[0115] Depend on Figure 6 It can be seen that the sinusoidality of the back electromotive force is also improved. The waveform of the back electromotive force before optimization is S3, and the waveform of the back electromotive force after optimization is S4.

[0116] Depend on Figure 7 It can be seen that the output capacity of the motor under high-speed operation conditions is improved after optimization. Among them, the waveform of the electromagnetic torque before optimization is S5, and the waveform of the electromagnetic torque after optimization is S6.

[0117] Based on the above improvements, this application achieves the following technical effects:

[0118] 1. The air gap between the stator and rotor of a motor is usually designed to be uniform. The air gap flux density distribution under the magnet will be closer to a trapezoidal wave and have more harmonics. If the air gap is changed to an unequal one, that is, the air gap is small at the center of the magnet and larger at the pole tip, the air gap flux density distribution under the magnet will be closer to a sine wave, which is beneficial to reducing the cogging torque.

[0119] 2. Based on precise mathematical functions, the core is injection-cut into a profile with a specific distribution along the circumferential position angle, changing the distribution of the air gap magnetic density harmonics, thereby reducing the cogging torque and torque ripple.

[0120] 3. The circular auxiliary slots on the quadrature axis of the rotor can reduce the quadrature axis inductance Lq while ensuring that the air gap magnetic flux sinusoidality and cogging torque do not deteriorate, thereby effectively improving the overload capacity of the motor under high-speed operation conditions.

[0121] In the present invention, the term "plurality" refers to two or more, unless otherwise specified. Terms such as "installed," "connected," "connected," and "fixed" should be broadly interpreted. For example, "connected" can mean fixed, removable, or integral; and "connected" can mean directly or indirectly through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0122] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0123] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A rotor core, characterized in that: For an electric motor, the motor includes a stator assembly and a rotor assembly, the rotor assembly is located inside the stator assembly, the rotor assembly includes the rotor core, the rotor assembly includes a plurality of magnetic poles, the outer wall of the rotor core includes a first outer wall arranged in a one-to-one correspondence with the plurality of magnetic poles, the outer contour line of the first outer wall includes two endpoints and a midpoint, and the distance between the outer contour line and the center of the rotor core decreases from the midpoint to the two endpoints.

2. The rotor core according to claim 1, characterized in that The distance between any target point of the outer contour line and the center of the rotor core is R, and the air gap length lg(θ) of the motor at the target point and the inner diameter D of the stator assembly satisfy: R=D-lg(θ), and the reciprocal of lg(θ) is distributed as a cosine function.

3. The rotor core according to claim 2, characterized in that: Among them, l g (θ) is the air gap length of the motor at the target point, l gd is the air gap length of the motor at the midpoint, the first outer wall includes endpoints A and B, the center of the rotor core is O, the target point is point Q, wherein the midpoint is P, and the angle formed by line segment AO and line segment PO is τ p , the angle formed by line segment PO and line segment QO is θ.

4. The rotor core according to claim 1, wherein: The air gap length of the motor at any of the end points is l gq , the air gap length of the motor at the midpoint is l gd , where l gq With l gd The ratio is greater than or equal to 2 and less than or equal to 2.

5.

5. The rotor core according to any one of claims 1 to 4, characterized in that: An auxiliary groove is provided on the outer wall surface of the rotor core, and the auxiliary groove is provided at the connection between any two of the first outer wall surfaces.

6. The rotor core according to claim 5, characterized in that The number of the auxiliary slots is consistent with the number of the magnetic poles; and or The auxiliary groove is a semicircular groove; and or The auxiliary slot is an axisymmetric structure, and the axis of symmetry of the auxiliary slot passes through the center of the rotor core.

7. The rotor core according to claim 5, characterized in that The auxiliary groove comprises a circular groove, and the radius of the circular groove is greater than or equal to 0.5 mm and less than or equal to 1 mm.

8. The rotor core according to claim 5, wherein: The rotor core is provided with a magnetic isolation groove and a mounting groove for mounting a permanent magnet, the magnetic isolation grooves are distributed on the outer sides of the mounting groove along both ends of the rotor core, and the magnetic isolation grooves are connected to the mounting grooves; Wherein, the depth of the auxiliary slot in the radial direction of the rotor core is smaller than the distance between the magnetic isolation slot and the outer wall surface of the rotor core.

9. A rotor assembly, characterized in that: include: The rotor core according to any one of claims 1 to 8, wherein the rotor core is provided with a plurality of mounting slots for mounting permanent magnets; A plurality of the permanent magnets are installed in a plurality of the installation slots.

10. A motor, characterized in that: include: stator assembly; The rotor core according to any one of claims 1 to 8, or the rotor assembly according to claim 9; Wherein, the rotor core or the rotor assembly is located inside the stator assembly.

11. A food processor, characterized in that: include: The rotor core according to any one of claims 1 to 8, or the rotor assembly according to claim 9; Or the motor as claimed in claim 10.

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