Eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear and automobile wheel hub motor

Abstract

This invention provides an eccentric magnetic force self-cancelling symmetrical double-eccentric cycloidal magnetic gear and an automotive hub motor. The cycloidal magnetic gear includes a high-speed rotor, an intermediate rotor, a T-shaped adjusting magnetic ring stator, and a low-speed rotor. These four components are nested sequentially to form an axially modulated coaxial magnetic gear structure. The axis of the high-speed rotor is eccentric to the left relative to the axis of the intermediate rotor, and the axis of the low-speed rotor is eccentric to the right relative to the axis of the intermediate rotor, forming a symmetrical double-eccentric structure. The permanent magnets on both the high-speed and intermediate rotors are magnetized using a Halbach arrangement, while the permanent magnets on the low-speed rotor are radially magnetized. The T-shaped adjusting magnetic ring stator has dual modulation capabilities, modulating both the radial and axial magnetic fields. This invention solves the problems of insufficient transmission efficiency and uneven load distribution under low-speed, high-torque conditions in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to an eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear and an automotive wheel hub motor. Background Technology

[0002] With increasing global emphasis on energy efficiency and environmental protection, new energy vehicles have become a key research and application area. In the electric drive systems of new energy vehicles, in-wheel motors have attracted significant attention due to their high integration, small footprint, and high efficiency. In-wheel motors, with their excellent efficiency, high torque output, and compact structural design, have become an important power drive method in new energy vehicles. However, in-wheel motors are typically installed inside the wheel, in a confined space. Therefore, achieving higher torque density and improving low-speed, high-torque capability within this limited space has become a crucial challenge that urgently needs to be addressed in the design of in-wheel motors.

[0003] Magnetic gears, through magnetic field modulation technology, can effectively achieve bidirectional modulation of low-speed and high-speed magnetic fields, thereby improving the electromechanical energy conversion efficiency through harmonic magnetic field coupling. In magnetic gears, because the inner and outer rotors are driven by a modulated magnetic field and do not contact each other during transmission, magnetic gears offer significant advantages over traditional mechanical gears, including frictionless operation, vibration-free operation, no lubrication required, low noise, and compact structure. This makes magnetic gears a promising candidate for application in the field of hub motors for new energy vehicles.

[0004] Existing magnetic gears still suffer from problems such as poor magnetic field modulation, large device size, low torque density, and small transmission ratio. Eccentric magnetic gear structures, with their simplified modulation mechanism and good penetration transmission capability, have become an important direction for breaking through the bottlenecks of traditional magnetic gear technology. However, traditional eccentric magnetic gears still suffer from problems such as insufficient transmission efficiency and uneven load distribution under low-speed, high-torque conditions. Summary of the Invention

[0005] The purpose of this invention is to provide an eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear and an automobile wheel hub motor to solve the problems of insufficient transmission efficiency and uneven load distribution under low speed and high torque conditions in the prior art.

[0006] One aspect of the present invention provides an eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear, comprising a high-speed rotor, an intermediate rotor, a T-type adjusting magnetic ring stator, and a low-speed rotor;

[0007] The high-speed rotor, the T-type adjusting magnetic ring stator, the intermediate rotor, and the low-speed rotor are nested in sequence to form a coaxial magnetic gear structure for axial modulation.

[0008] The high-speed rotor's shaft center is eccentric to the left relative to the middle rotor's shaft center, and the low-speed rotor's shaft center is eccentric to the right relative to the middle rotor's shaft center, forming a symmetrical double-eccentric structure. The eccentricity of the high-speed rotor's shaft center relative to the middle rotor's shaft center is... The eccentricity of the low-speed rotor's shaft center relative to the intermediate rotor's shaft center is: And satisfy: ;

[0009] The permanent magnets on the high-speed rotor and the intermediate rotor are magnetized using the Halbach arrangement, while the permanent magnets on the low-speed rotor are magnetized radially.

[0010] The T-type magnetic ring stator has dual modulation capabilities, capable of modulating both the radial and axial magnetic fields.

[0011] A first axial air gap is provided between the high-speed rotor and the intermediate rotor, a first radial air gap is provided between the intermediate rotor and the T-type adjusting magnetic ring stator, a second radial air gap is provided between the high-speed rotor and the T-type adjusting magnetic ring stator, and a second axial air gap is provided between the intermediate rotor and the low-speed rotor.

[0012] The intermediate rotor and the high-speed rotor are magnetically modulated through a T-shaped adjusting magnetic ring stator to form a high-order harmonic dual-channel magnetic flux modulation coupling. The intermediate rotor and the low-speed rotor are directly modulated through a second axial air gap.

[0013] The transmission method of the magnetic gear is as follows: the low-speed rotor is used as the input end, and the high-speed rotor is driven to output through the intermediate rotor; or the intermediate rotor is used as the input end, and both the high-speed rotor and the low-speed rotor are driven to output simultaneously; or the high-speed rotor is used as the input end, and the low-speed rotor is driven to output through the intermediate rotor.

[0014] Another aspect of the present invention provides an automotive hub motor, which includes the aforementioned cycloidal magnetic gear.

[0015] The eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear and automobile wheel hub motor provided by the present invention have the following beneficial effects:

[0016] (1) The cycloidal magnetic gear of the present invention realizes a three-rotor structure through a high-speed rotor, an intermediate rotor and a low-speed rotor. The low-speed rotor can be used as the input rotor to drive the intermediate rotor and the low-speed rotor to rotate, thus achieving the effect of low speed and high torque, and having a large transmission ratio and stability.

[0017] (2) Compared with the traditional single eccentric cycloidal magnetic gear, the cycloidal magnetic gear of the present invention adopts a symmetrical double eccentric arrangement. When the rotor moves, most of the eccentric component of the magnetic pull on the rotor is canceled out, which effectively avoids the problems of load concentration and large total load on the swing arm bearing caused by eccentric asymmetry in the traditional structure, resulting in reduced life. It significantly improves the stability of torque transmission and the load uniformity of the overall system.

[0018] (3) The cycloidal magnetic gear of the present invention, through the revolution and rotation of the eccentric low-speed rotor, causes the relative area of ​​the air gap between the intermediate rotor and the low-speed rotor to change, thereby realizing the eccentric disturbance modulation. This design can generate multiple high-frequency harmonics in the magnetic field, which can not only realize the bidirectional magnetic field modulation in the axial and radial directions, but also effectively suppress the magnetic saturation phenomenon, improve the magnetic flux modulation effect, make the eccentric disturbance air gap periodically modulated, improve the modulation effect, and realize the transmission efficiency improvement under low speed and high torque conditions.

[0019] (4) The high-speed rotor and intermediate rotor are magnetized by Halbach arrangement, while the low-speed rotor is magnetized radially. Halbach arrangement focuses the magnetic flux on the air gap side and reduces back leakage. Radial magnetization is beneficial for manufacturing and demagnetization margin. This design can improve the effective magnetic density of the air gap, reduce losses and torque pulsation, thereby improving the torque density and transmission efficiency of the magnetic gear. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0021] Figure 2 This is a side view of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0022] Figure 3 This is an exploded view of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0023] Figure 4 This is a three-dimensional cross-sectional view of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of the structure of a T-type magnetic ring stator;

[0025] Figure 6 This is a front structural schematic diagram of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram of the back structure of the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear in an embodiment of the present invention.

[0027] Figure 8 This is a schematic diagram of the high-speed rotor.

[0028] Figure 9 This is a schematic diagram of the intermediate rotor.

[0029] Figure 10 This is a comparison diagram of the magnetic field strength in the air gap between the cycloidal magnetic gear of the present invention and the conventional cycloidal magnetic gear;

[0030] Figure 11 This is a comparison diagram of the spatial harmonic spectrum of magnetic induction intensity in the air gap of the cycloidal magnetic gear of the present invention and that of the conventional cycloidal magnetic gear. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figures 1 to 9 The eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear provided in this embodiment of the invention includes a high-speed rotor 1, an intermediate rotor 2, a T-type adjusting magnetic ring stator 3, and a low-speed rotor 4.

[0033] The high-speed rotor 1, the T-type adjusting magnetic ring stator 3, the intermediate rotor 2, and the low-speed rotor 4 are nested in sequence to form a coaxial magnetic gear structure for axial modulation.

[0034] The shaft center of high-speed rotor 1 is eccentric to the left relative to the shaft center of intermediate rotor 2, and the shaft center of low-speed rotor 4 is eccentric to the right relative to the shaft center of intermediate rotor 2, forming a symmetrical double-eccentric structure. The eccentricity of the shaft center of high-speed rotor 1 relative to the shaft center of intermediate rotor 2 is... The eccentricity of the shaft center of the low-speed rotor 4 relative to the shaft center of the intermediate rotor 2 is: And satisfy: Eccentricity and The settings can be optimized according to the target load and torque distribution. When the rotor moves, most of the eccentric component of the magnetic pull on the rotor is canceled out, achieving a more uniform distribution. This significantly reduces the load concentration in the cycloidal magnetic gear, reduces the total load on the swing arm bearing, and improves the stability of torque transmission.

[0035] Specifically in this embodiment, .

[0036] Furthermore, by introducing phase modulation into the symmetrical double-eccentric structure, the destructive effect between magnetic pull eccentric components of different frequencies can be achieved, thereby reducing the peak value of the main frequency load and suppressing torque pulsation.

[0037] The permanent magnets on the high-speed rotor 1 and the permanent magnets on the intermediate rotor 2 are magnetized using the Halbach arrangement, while the permanent magnets on the low-speed rotor 4 are magnetized radially.

[0038] For details, please refer to the following: Figure 8 , Figure 8 The arrows indicate the magnetization direction. The high-speed rotor 1 includes 16 high-speed rotor permanent magnet blocks, which are magnetized using a 45° Halbach array. This magnetization method can effectively improve torque and torque ripple. In this embodiment, the high-speed rotor permanent magnets are 4-pole pairs.

[0039] The intermediate rotor 2 includes an outer cohesive magnet core 11, a first outer permanent magnet 12, and a second outer permanent magnet 13. The volume of the second outer permanent magnet 13 is larger than that of the first outer permanent magnet 12. The first outer permanent magnet 12 is radially magnetized and is located in the inner ring of the intermediate rotor 2. The second outer permanent magnet 13 is tangentially magnetized and is located in the outer ring of the intermediate rotor 2. The intermediate rotor 2 adopts a non-fully permanent magnet Halbach structure. This structure effectively reduces magnetic leakage at the rotor end, increases the high-order harmonic components in the air gap, and is beneficial for increasing transmission torque and improving modulation efficiency.

[0040] In this embodiment, the intermediate rotor permanent magnet has 15 pole pairs, and the low-speed rotor permanent magnet has 16 pole pairs.

[0041] A first axial air gap 14 is provided between the high-speed rotor 1 and the intermediate rotor 2, a first radial air gap 15 is provided between the intermediate rotor 2 and the T-shaped adjusting magnetic ring stator 3, a second radial air gap 16 is provided between the high-speed rotor 1 and the T-shaped adjusting magnetic ring stator 3, and a second axial air gap 17 is provided between the intermediate rotor 2 and the low-speed rotor 4.

[0042] The intermediate rotor 2 and the high-speed rotor 1 are magnetically modulated through the T-shaped magnetic ring stator 3 to form a high-order harmonic dual-channel magnetic flux modulation coupling. The intermediate rotor 2 and the low-speed rotor 4 are directly modulated through the second axial air gap 17.

[0043] Because the axis of the low-speed rotor 4 is eccentric to the right relative to the axis of the intermediate rotor 2, the relative area of ​​the air gap between the intermediate rotor 2 and the low-speed rotor 4 changes due to the revolution and rotation of the eccentric low-speed rotor 4, thereby realizing the eccentric disturbance modulation.

[0044] In addition, the intermediate rotor 2 and the low-speed rotor 4 are directly modulated through the second axial air gap 17, which can realize a large transmission ratio of the cycloidal magnetic gear and further optimize the transmission efficiency of magnetic flux and the distribution of torque.

[0045] The T-type magnetic ring stator 3 has dual modulation performance, which can modulate both the radial magnetic field and the axial magnetic field. This can effectively enhance the high-order harmonic modulation effect of the magnetic field, reduce the leakage of permanent magnets, and suppress the magnetic saturation effect.

[0046] In this embodiment, the T-shaped adjusting magnetic ring stator 3 is composed of multiple adjusting magnetic cores, and each adjusting magnetic core is made of multiple silicon steel sheets stacked together.

[0047] Specifically, the magnetic core includes a first radial magnetic adjustment part 18, an axial magnetic adjustment part 19, and a second radial magnetic adjustment part 20. The axial magnetic adjustment part 19 is located between the first radial magnetic adjustment part 18 and the second radial magnetic adjustment part 20. The axial magnetic adjustment part 19 is connected to the high-speed rotor 1 and the intermediate rotor 2 respectively, and is used to realize the axial modulation effect of the intermediate rotor 2 and the high-speed rotor 1. The first radial magnetic adjustment part 18 and the second radial magnetic adjustment part 20 are used to realize the radial modulation effect of the intermediate rotor 2 and the high-speed rotor 1, and at the same time, they can suppress rotor leakage magnetic field.

[0048] In this embodiment, the distance between two adjacent tuning magnet cores is 6.67°.

[0049] Furthermore, in this embodiment, the volume of the high-speed rotor 1 is the same as that of the low-speed rotor 4, achieving torque balance. The volume of the intermediate rotor 2 is slightly larger than that of the high-speed rotor 1. This design can reduce end magnetic leakage caused by the eccentricity between the high-speed rotor 1 and the low-speed rotor 4.

[0050] In this embodiment, the magnetic gear satisfies the following formula:

[0051] ;

[0052] ;

[0053] in, To adjust the number of magnet cores on stator 3 of the T-type adjusting ring. Let be the number of pole pairs of the permanent magnets on the high-speed rotor 1. This represents the number of pole pairs of the permanent magnets on the intermediate rotor 2. This represents the number of pole pairs of the permanent magnets on the low-speed rotor 4.

[0054] Satisfying the condition: This results in the high-speed rotor 1, intermediate rotor 2, and T-shaped adjusting magnetic ring stator 3 forming an eccentric cycloidal magnetic gear structure with axial and radial high-order harmonic modulation.

[0055] Satisfying the condition: This results in the intermediate rotor 2 and the low-speed rotor 4 forming an axially modulated eccentric magnetic gear structure.

[0056] In this embodiment, the magnetic gear also satisfies the following formula:

[0057]

[0058]

[0059] in, This represents the transmission ratio between the high-speed rotor 1 and the intermediate rotor 2. This represents the transmission ratio between the intermediate rotor 2 and the low-speed rotor 4. The rotational speed of high-speed rotor 1 The rotational speed of the intermediate rotor 2. This refers to the rotational speed of the low-speed rotor 4.

[0060] The magnetic gear has multiple working modes and can flexibly switch the input mode according to different load conditions. Specifically, the transmission mode of the magnetic gear is as follows: the low-speed rotor 4 is used as the input end and transmitted through the intermediate rotor 2 to drive the high-speed rotor 1 to output; or the intermediate rotor 2 is used as the input end and simultaneously drives the high-speed rotor 1 and the low-speed rotor 4 to output; or the high-speed rotor 1 is used as the input end and transmitted through the intermediate rotor 2 to drive the low-speed rotor 4 to output.

[0061] A comparative analysis was conducted between the cycloidal magnetic gear of this invention and a traditional cycloidal magnetic gear. Figure 10 It can be seen that the magnetic field strength in the air gap of the cycloidal magnetic gear of the present invention is significantly higher than that of the conventional cycloidal magnetic gear, and the magnetic field modulation effect of the cycloidal magnetic gear of the present invention is significantly enhanced. From Figure 11 It can be seen that, compared with the traditional cycloidal magnetic gear, the peak value of the effective harmonic component in the air gap of the magnetic gear of the present invention is significantly improved, and there is a higher harmonic of 45th order, which is beneficial to improving the torque density of the magnetic gear.

[0062] An embodiment of the present invention also provides an automotive wheel hub motor, which includes the cycloidal magnetic gear described above.

[0063] In summary, the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear and automobile wheel hub motor provided by the present invention have the following beneficial effects:

[0064] (1) The cycloidal magnetic gear of the present invention realizes a three-rotor structure through a high-speed rotor, an intermediate rotor and a low-speed rotor. The low-speed rotor can be used as the input rotor to drive the intermediate rotor and the low-speed rotor to rotate, thus achieving the effect of low speed and high torque, and having a large transmission ratio and stability.

[0065] (2) Compared with the traditional single eccentric cycloidal magnetic gear, the cycloidal magnetic gear of the present invention adopts a symmetrical double eccentric arrangement. When the rotor moves, most of the eccentric component of the magnetic pull on the rotor is canceled out, which effectively avoids the problems of load concentration and large total load on the swing arm bearing caused by eccentric asymmetry in the traditional structure, resulting in reduced life. It significantly improves the stability of torque transmission and the load uniformity of the overall system.

[0066] (3) The cycloidal magnetic gear of the present invention, through the revolution and rotation of the eccentric low-speed rotor, causes the relative area of ​​the air gap between the intermediate rotor and the low-speed rotor to change, thereby realizing the eccentric disturbance modulation. This design can generate multiple high-frequency harmonics in the magnetic field, which can not only realize the bidirectional magnetic field modulation in the axial and radial directions, but also effectively suppress the magnetic saturation phenomenon, improve the magnetic flux modulation effect, make the eccentric disturbance air gap periodically modulated, improve the modulation effect, and realize the transmission efficiency improvement under low speed and high torque conditions.

[0067] (4) The high-speed rotor and intermediate rotor are magnetized by Halbach arrangement, while the low-speed rotor is magnetized radially. Halbach arrangement focuses the magnetic flux on the air gap side and reduces back leakage. Radial magnetization is beneficial for manufacturing and demagnetization margin. This design can improve the effective magnetic density of the air gap, reduce losses and torque pulsation, thereby improving the torque density and transmission efficiency of the magnetic gear.

[0068] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above 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 one or more embodiments or examples.

[0069] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A symmetrical double-eccentric cycloidal magnetic gear with self-cancelling eccentric magnetic force, characterized in that, Includes high-speed rotor, intermediate rotor, T-type adjusting magnetic ring stator, and low-speed rotor; The high-speed rotor, the T-type adjusting magnetic ring stator, the intermediate rotor, and the low-speed rotor are nested in sequence to form a coaxial magnetic gear structure for axial modulation. The high-speed rotor's shaft center is eccentric to the left relative to the middle rotor's shaft center, and the low-speed rotor's shaft center is eccentric to the right relative to the middle rotor's shaft center, forming a symmetrical double-eccentric structure. The eccentricity of the high-speed rotor's shaft center relative to the middle rotor's shaft center is... The eccentricity of the low-speed rotor's shaft center relative to the intermediate rotor's shaft center is: And satisfy: ; The permanent magnets on the high-speed rotor and the intermediate rotor are magnetized using the Halbach arrangement, while the permanent magnets on the low-speed rotor are magnetized radially. The T-type magnetic ring stator has dual modulation capabilities, capable of modulating both the radial and axial magnetic fields. A first axial air gap is provided between the high-speed rotor and the intermediate rotor, a first radial air gap is provided between the intermediate rotor and the T-type adjusting magnetic ring stator, a second radial air gap is provided between the high-speed rotor and the T-type adjusting magnetic ring stator, and a second axial air gap is provided between the intermediate rotor and the low-speed rotor. The intermediate rotor and the high-speed rotor are magnetically modulated through a T-shaped adjusting magnetic ring stator to form a high-order harmonic dual-channel magnetic flux modulation coupling. The intermediate rotor and the low-speed rotor are directly modulated through a second axial air gap. The transmission method of the magnetic gear is as follows: the low-speed rotor is used as the input end, and the high-speed rotor is driven to output through the intermediate rotor; or the intermediate rotor is used as the input end, and both the high-speed rotor and the low-speed rotor are driven to output simultaneously; or the high-speed rotor is used as the input end, and the low-speed rotor is driven to output through the intermediate rotor.

2. The eccentric magnetic force self-cancelling symmetrical double-eccentric cycloidal magnetic gear according to claim 1, characterized in that, The T-type adjusting magnetic ring stator is composed of multiple adjusting magnetic cores, each of which is made up of multiple silicon steel sheets stacked together.

3. The eccentric magnetic force self-cancelling type symmetrical double eccentric cycloidal magnetic gear according to claim 2, characterized in that, The magnetic core includes a first radial magnetic adjustment section, an axial magnetic adjustment section, and a second radial magnetic adjustment section. The axial magnetic adjustment section is located between the first and second radial magnetic adjustment sections. The axial magnetic adjustment section is connected to the high-speed rotor and the intermediate rotor respectively, and is used to realize the axial modulation effect of the intermediate rotor and the high-speed rotor. The first and second radial magnetic adjustment sections are used to realize the radial modulation effect of the intermediate rotor and the high-speed rotor.

4. The eccentric magnetic force self-cancelling type symmetrical double eccentric cycloidal magnetic gear according to claim 2, characterized in that, The distance between two adjacent tuning magnet cores is 6.67°.

5. The eccentric magnetic force self-cancelling type symmetrical double eccentric cycloidal magnetic gear according to claim 2, characterized in that, The magnetic gear satisfies the following formula: ； ； in, To adjust the number of magnet cores on the T-type adjusting ring stator. This represents the number of pole pairs of the permanent magnets on the high-speed rotor. This represents the number of pole pairs of the permanent magnets on the intermediate rotor. This represents the number of pole pairs of the permanent magnets on the low-speed rotor.

6. The eccentric magnetic force self-cancelling type symmetrical double eccentric cycloidal magnetic gear according to claim 5, characterized in that, The magnetic gear satisfies the following formula: in, This represents the transmission ratio between the high-speed rotor and the intermediate rotor. This represents the transmission ratio between the intermediate rotor and the low-speed rotor. The rotational speed of the high-speed rotor. The rotational speed of the intermediate rotor. This refers to the rotational speed of the low-speed rotor.

7. The eccentric magnetic force self-cancelling symmetrical double-eccentric cycloidal magnetic gear according to claim 1, characterized in that, The high-speed rotor consists of 16 high-speed rotor permanent magnet blocks, which are magnetized using a 45° Halbach array.

8. The eccentric magnetic force self-cancelling symmetrical double-eccentric cycloidal magnetic gear according to claim 1, characterized in that, The intermediate rotor includes an outer cohesive magnet core, a first outer permanent magnet, and a second outer permanent magnet. The volume of the second outer permanent magnet is larger than that of the first outer permanent magnet. The first outer permanent magnet is radially magnetized and is located in the inner ring of the intermediate rotor. The second outer permanent magnet is tangentially magnetized and is located in the outer ring of the intermediate rotor. The intermediate rotor adopts a non-fully permanent magnet Halbach structure.

9. The eccentric magnetic force self-cancelling type symmetrical double eccentric cycloidal magnetic gear according to claim 1, characterized in that, The high-speed rotor permanent magnet has 4 pole pairs, the intermediate rotor permanent magnet has 15 pole pairs, and the low-speed rotor permanent magnet has 16 pole pairs.

10. A hub motor for automobiles, characterized in that, Including the eccentric magnetic force self-cancelling symmetrical double eccentric cycloidal magnetic gear as described in any one of claims 1 to 9.

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