CN218498903U - Rotor and in-wheel motor comprising same - Google Patents

Abstract

A rotor of an in-wheel motor is provided, which includes a rotor frame and a plurality of sheet-like permanent magnets. The rotor frame is cylindrical and annular, and defines a rotor cavity therein. A plurality of sheet-like permanent magnets are arranged in the rotor cavity spaced apart from each other in the circumferential direction. The rotor has a polar arc coefficient in the range of 0.65-0.9, the polar arc coefficient referring to the ratio between the central angle of the permanent magnets with respect to the longitudinal axis of the rotor and the angle of the poles of the rotor, the angle of the poles of the rotor being 360 degrees divided by the number of permanent magnets.

Description

Rotor and in-wheel motor comprising same

Technical Field

The present disclosure relates to a rotor of an in-wheel motor and an in-wheel motor including the same.

Background

A27-slot 30-pole hub brushless motor belongs to the field of electric bicycles, the voltage of a common lithium battery pack is 36V, 48V and the like, and the voltage of the battery pack cannot be too high (such as 72V). This is because the high voltage is required to be connected in series with more battery cells and stronger battery protection function modules, and the battery cost is increased greatly, which directly results in increased vehicle purchase cost for users. Since the battery pack voltage cannot be too high, a high efficiency in-wheel motor is required. The motor includes a rotor. The design of the rotor needs to be optimized to improve the efficiency of the motor.

SUMMERY OF THE UTILITY MODEL

At least one embodiment of the present disclosure provides a rotor of an in-wheel motor, which includes a rotor frame and a plurality of sheet-like permanent magnets. The rotor frame is cylindrical and annular, and defines a rotor cavity therein. A plurality of sheet-like permanent magnets are arranged in the rotor cavity spaced apart from each other in the circumferential direction. The rotor has a polar arc coefficient in the range of 0.65-0.9, the polar arc coefficient referring to the ratio between the central angle of a single permanent magnet with respect to the longitudinal axis of the rotor and the angle of the poles of the rotor, which is 360 degrees divided by the number of permanent magnets.

For example, in some embodiments, the rotor further includes a magnetic isolation bridge having an annular body and magnetic isolation arms extending in an axial direction from the annular body. The magnetism isolating arm is inserted between the adjacent permanent magnets.

For example, in some embodiments, the number of permanent magnets is 30.

For example, in some embodiments, the permanent magnets are arcuate, and the two surfaces of the permanent magnets that face in the circumferential direction are parallel to each other.

For example, in some embodiments, the spacing distance between the permanent magnets is greater than 1.4mm.

At least one embodiment of the present disclosure provides an in-wheel motor including a stator and a rotor as described above.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present disclosure and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings may be obtained from the drawings without inventive effort.

Fig. 1 is a perspective view of a rotor according to an embodiment of the present disclosure;

FIG. 2 is a plan view of the rotor of FIG. 1;

FIG. 3 is an enlarged view of a portion of FIG. 2 shown in phantom;

FIG. 4 is an exploded perspective view of the rotor of FIG. 1;

FIG. 5 is a perspective view of a magnetic shield bridge of the rotor of FIG. 1;

FIG. 6 is a plan view of a magnetic shield bridge of the rotor of FIG. 1;

FIG. 7 is a cross-sectional view of a 27 slot 30 pole hub motor including a rotor according to an embodiment of the present disclosure;

FIG. 8 is a cogging torque for a motor including a conventional rotor; and is

Fig. 9 is a cogging torque of a motor including a rotor according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, a rotor and a hub motor including the same according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. To make the objects, technical solutions and advantages of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are some, but not all embodiments of the present disclosure.

Thus, the following detailed description of the embodiments of the present disclosure, presented in conjunction with the figures, is not intended to limit the scope of the claimed disclosure, but is merely representative of selected embodiments of the disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

The singular forms include the plural unless the context otherwise dictates otherwise. Throughout the specification, the terms "comprises," "comprising," "has," "having," "includes," "including," "having," "including," and the like are used herein to specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

In addition, even though ordinal terms such as "first," "second," etc., are used to describe various elements, the elements are not limited by the terms, and the terms are used only to distinguish one element from another.

The rotor includes a plurality of permanent magnets arranged in a circumferential direction, and rotates relative to the stator by interaction of the plurality of permanent magnets with the pole teeth of the stator around which the coils are wound. In a conventional rotor, the permanent magnets are arranged next to each other with almost no gaps between the permanent magnets. The south pole and the self-priming of north pole of two adjacent permanent magnets form from the return circuit, and this part magnetic field can't be used for the effective magnetic circuit of motor, belongs to useless magnetic circuit, causes the waste. Also, there is a magnetic saturation region at the surface where the adjacent permanent magnets face each other, additional harmonics and vibration are generated, deteriorating the motor performance.

The rotor according to the embodiment of the present disclosure has appropriate gaps between the permanent magnets, and effectively avoids the magnetic saturation effect. Therefore, harmonic waves and vibration caused by the magnetic saturation effect are avoided, and motor noise is reduced. In addition, the volume of the permanent magnet is reduced, so that the material usage amount and the cost of the permanent magnet are reduced, and rare earth resources are indirectly protected.

Fig. 1 is a perspective view of a rotor according to an embodiment of the present disclosure, fig. 2 is a plan view of the rotor in fig. 1, fig. 3 is an enlarged view of a dotted frame portion in fig. 2, and fig. 4 is an exploded perspective view of the rotor in fig. 1. As shown in fig. 1-4, the rotor includes a hub main body 210, a flux ring 220 disposed inside the cylindrical wall of the hub main body 210, a first bearing 250 mounted to the central hole of the hub main body 210, a plurality of permanent magnets 230, and a magnetic isolation bridge 240. To clearly show the structure of the interior of the rotor, fig. 1-4 do not show a hubcap closing the opening of the hub body 210 and a second bearing mounted at the center hole of the hubcap. The hub body 210 constitutes a hub shell together with a hub cover to define an inner space of a rotor, i.e., a rotor cavity. The hub body 210 and the hub cover may be made of an aluminum alloy material. The magnetic conductive ring 220 may be an iron ring for guiding the magnetic circuit of the permanent magnet 230. The plurality of permanent magnets 230 are arranged inside the flux ring 220 in the circumferential direction and are bonded to the flux ring 220.

Fig. 5 is a perspective view of the magnetic shield bridge 240 of the rotor of fig. 1, and fig. 6 is a plan view of the magnetic shield bridge 240 of the rotor of fig. 1. As shown in fig. 5 and 6, the magnetism isolating bridge 240 includes an annular body 241 and magnetism isolating arms 242 extending in an axial direction from the annular body 241. Returning to fig. 1-4, the plurality of permanent magnets 230 are arranged spaced apart from each other, and the magnetism isolating arms 242 of the magnetism isolating bridge 240 are inserted between the adjacent permanent magnets 230 to maintain the arrangement in which the permanent magnets 230 are spaced apart from each other. Alternatively, the permanent magnets 230 are inserted into recesses formed by the magnetism isolating arms 242 of the magnetism isolating bridge 240 to be spaced apart from each other, thereby being arranged to be spaced apart from each other. In this embodiment, the rotor is used for a 27 slot 30 pole hub motor. The rotor includes 30 permanent magnets 230.

The permanent magnet 230 is made of, for example, a sintered aluminum-iron-boron material, is plate-shaped, and is preferably arc-shaped plate-shaped to follow the shape of the annular magnetic conductive ring 220. For example, both surfaces of the permanent magnet 230 facing the circumferential direction are parallel to each other. In this example, the central angle of the permanent magnet 230 with respect to the longitudinal axis of the rotor remains constant in the axial direction. In other examples, the two surfaces of the permanent magnet 230 facing the circumferential direction are not parallel to each other. For example, the permanent magnet 230 is a trapezoidal sheet. In this example, the central angle of the permanent magnets 230 with respect to the longitudinal axis of the rotor varies in the axial direction. The central angle of the permanent magnets with respect to the longitudinal axis of the rotor is defined as the maximum measured central angle.

The power of the motor is divided into two parts, one part is useful work, the other part is useless work, and the efficiency of the motor refers to the ratio of the useful work to the total power. The more useful work the motor has, the higher the efficiency of the motor. The power consumed in the magnetic saturation region at the surface (i.e., the surface facing the circumferential direction) where the adjacent permanent magnets 230 face each other is useless work, and therefore, it is necessary to minimize the magnetic saturation intensity, and the distance between the N-pole magnet and the S-pole magnet of the adjacent permanent magnets 230 is positively correlated with the magnetic saturation intensity. For example, in this example, there are 30 permanent magnets 230, and there are 15 pairs of saturation regions of the NS pole that are circumferentially spaced in the rotor field, and the magnetic fields in these saturation regions are all such as to impede the circulation of the useful portion of the magnetic field during normal operation of the machine. Therefore, it is necessary to select a proper gap between the permanent magnets 230 to optimize the magnetic circuit arrangement between the permanent magnets 230, thereby achieving the maximum motor efficiency.

Here, a polar arc coefficient is defined, which refers to the ratio between the central angle θ (see fig. 6) of a single permanent magnet 230 with respect to the longitudinal axis of the rotor and the angle of the magnetic poles of the rotor, which is 360 degrees divided by the number of permanent magnets 230. In the present example, the angle of the magnetic poles of the rotor is 12 °. The embodiment of the disclosure sets the pole arc coefficient within the range of 0.65-0.9, and realizes the optimization of the motor efficiency. When the pole arc coefficient is greater than 0.9, the magnetic saturation effect cannot be effectively avoided and material waste is caused, and it is difficult to accurately maintain a small gap between the permanent magnets 230. When the pole arc coefficient is less than 0.65, the magnetic density is too small to meet the current and power requirements of the motor.

Further, the spacing distance between the permanent magnets 230 is greater than 1.4mm in consideration of the influence of the overall size of the rotor on the arrangement of the magnetic circuit.

Fig. 7 shows a cross-sectional view of a 27-slot 30-pole hub motor including a rotor according to an embodiment of the present disclosure. As shown in fig. 7, the motor includes a rotor and a stator. The stator includes a shaft 110, a stator core 130 fixed to the shaft 110 and including 27 pole teeth, and a coil assembly 140 wound on the pole teeth. As described above, the rotor includes the hub shell having the hub main body 210 and the hub cover 260, the magnetic conductive ring 220, the 30 permanent magnets 230, the first bearing 250 fixed to the hub main body 210, and the second bearing 270 fixed to the hub cover. The shaft 110 of the stator is supported on a first bearing 250 and a second bearing 270 so that the rotor can rotate relative to the stator.

Fig. 8 is a cogging torque of a motor including a conventional rotor, and fig. 9 is a cogging torque of a motor including a rotor according to an embodiment of the present disclosure. In the motor of the rotor shown in fig. 9, the pole arc coefficient is about 0.87, and in this conventional rotor, the pole arc coefficient is greater than 0.9. As shown in fig. 8 and 9, the cogging torque of the motor including the rotor according to the embodiment of the present disclosure is reduced from about 0.16N · m to about 0.06N · m, compared to the motor including the conventional rotor. The cogging torque can reflect the magnitude of the useless work of the motor in a magnetic saturation area. By choosing the appropriate gap between the permanent magnets 230, a maximum motor efficiency is achieved.

The above-mentioned embodiments only express several embodiments of the present disclosure, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present disclosure. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the concept of the present disclosure, and these changes and modifications are all within the scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

Claims (6)

1. A rotor for an in-wheel motor, comprising:

a rotor frame having a cylindrical ring shape and defining a rotor cavity therein;

a plurality of sheet-like permanent magnets arranged in the rotor cavity at a distance from each other in the circumferential direction, wherein

The rotor has a polar arc coefficient in the range of 0.65-0.9, the polar arc coefficient referring to the ratio between the central angle of a single permanent magnet with respect to the longitudinal axis of the rotor and the angle of the poles of the rotor, the angle of the poles of the rotor being 360 degrees divided by the number of permanent magnets.

2. The rotor of claim 1, further comprising:

a magnetic shield bridge having an annular body and magnetic shield arms extending from the annular body in an axial direction, the magnetic shield arms being interposed between adjacent ones of the permanent magnets.

3. The rotor of claim 1 or 2,

the number of the permanent magnets is 30.

4. The rotor of claim 1 or 2,

the permanent magnet is arc-shaped, and both surfaces of the permanent magnet facing the circumferential direction are parallel to each other.

5. The rotor of claim 1 or 2,

the spacing distance between the permanent magnets is greater than 1.4mm.

6. An in-wheel motor, comprising:

a rotor according to any one of claims 1-5.

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