A high power density axial flux hub motor with a short axial structure

Abstract

The present invention relates to a high-power-density axial flux hub motor with a short axial structure. Compared with the prior art, it solves the problem of difficulty in ensuring high torque and high power density requirements under the condition of limited axial dimensions of the hub motor. The present invention includes a planetary reducer, wherein the output shaft of the rotor assembly is connected to the input shaft of the planetary reducer, and the reducer output shaft of the planetary reducer is connected to the hub bearing unit; the axial flux stator assembly includes a water-cooled shell, and a plurality of fins are provided on the inner wall of the water-cooled shell. The winding is wound on the stator core and embedded between adjacent fins on the inner wall of the water-cooled shell and fixed by glue potting. The present invention adopts a dual-rotor stator segmented yokeless axial flux topology structure with an internally integrated planetary reducer; it can provide high torque while having a small volume and weight.

Description

Technical Field

[0001] The present invention relates to the technical field of hub motors, and in particular to a high-power-density axial magnetic flux hub motor with a short axial structure. Background Art

[0002] The hub motor is installed in the wheel hub of an electric vehicle. Due to the limited space inside the wheel hub and the need to install the suspension, steering structure, and braking system at the same time, the space left for the hub motor is very limited.

[0003] like Figure 9 As shown, to achieve the vehicle's power and torque requirements, existing in-wheel motors require significant structural adjustments to the vehicle's chassis, suspension, and braking systems. Specifically, the braking system must be moved from the outside of the wheel to the inside, and the steering structure and suspension system must be customized based on the size of the in-wheel motor. Furthermore, existing in-wheel motors utilize a radial flux structure, resulting in a long axial length that takes up space in other vehicle components and hinders wide steering ranges. Due to the unique internal structure of in-wheel motors, adopting a traditional axial flux structure theoretically allows for a shorter axial length. However, this inevitably results in a lower power density and an inability to provide high torque, making it unsuitable for the practical needs of electric vehicles. The reasons for this are: 1. The presence of the yoke in traditional axial flux motors results in a heavier motor and higher overall losses. 2. The cooling system for traditional axial flux motors is integrated into the stator yoke. Heat generated in the motor windings must first be transferred to the yoke and then to the cooling system. This results in a long heat transfer path, high thermal resistance, and a large temperature difference between the stator and cooling system. Consequently, the motor's output power is limited by the motor's temperature. This also leads to a higher overall motor weight, a larger unsprung mass, and poor vehicle handling.

[0004] Therefore, how to ensure high torque and high power density of the hub motor under the condition of limited axial size of the hub motor has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to solve the defect in the prior art that it is difficult to ensure the requirements of high torque and high power density under the condition of limited axial size of the hub motor. At the same time, without making major changes to the chassis and suspension of the vehicle, a high-power density axial flux hub motor with a short axial structure is provided to solve the above problems.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A high-power-density axial flux hub motor with a short axial structure includes a motor housing, a motor rear end cover is installed at the rear end of the motor housing, a hub bearing unit and a motor front end cover are installed at the front end of the motor housing, a rotor assembly and an axial flux stator assembly are installed in the motor housing, and the rotor assembly and the axial flux stator assembly are installed in cooperation.

[0008] It also includes a planetary reducer, the output shaft of the rotor assembly is connected to the input shaft of the planetary reducer, and the reducer output shaft of the planetary reducer is connected to the hub bearing unit; the axial magnetic flux stator assembly includes a water-cooled shell, and a plurality of fins are provided on the inner wall of the water-cooled shell. The winding is wound on the stator core and embedded between adjacent fins on the inner wall of the water-cooled shell and fixed by glue potting.

[0009] The outer wall of the water-cooling shell is provided with a layer spacing protrusion that surrounds the water-cooling shell, and each fin is provided with an intra-fin water channel, one end of the intra-fin water channel is communicated with one side of the layer spacing protrusion on the outer wall of the water-cooling shell, and the other end of the intra-fin water channel is communicated with the other side of the layer spacing protrusion on the outer wall of the water-cooling shell.

[0010] The motor housing is divided into a stator assembly installation cavity and a planetary reducer installation cavity from back to front. The stator assembly installation cavity is connected to the center of the planetary reducer installation cavity and a bearing is installed at the center. The output shaft of the rotor assembly is installed on the bearing.

[0011] The cavity between the planetary reducer, the front end cover of the motor and the motor housing is filled with lubricating oil; it also includes a carbon fiber fixing plate, which is fixed to the fins on the axial surface of the water-cooling housing by glue.

[0012] The outer wall of the water-cooling shell is also provided with an off-chip water channel surrounding the water-cooling shell. The on-chip water channel is U-shaped. Several water channel partitions are provided on the outer wall of the water-cooling shell between the inner wall of the off-chip water channel and the layer spacing protrusion.

[0013] The rotor assembly includes two rotor yokes, the centers of the two rotor yokes are connected by a rotor connector, permanent magnets are installed on the opposite surfaces of the two rotor yokes, a rotating shaft is installed on the outer surface of any rotor yoke, and a water-cooling shell is installed on the rotor connector and located between the two rotor yokes.

[0014] The rotating shaft of the rotor assembly is mounted on the sun gear of the planetary reducer.

[0015] The water channel partitions are all located between adjacent fins.

[0016] The outer wall of the motor housing is provided with a brake caliper mounting hole, a water nozzle, a shock absorber mounting hole, a steering mechanism mounting hole and a chassis mounting hole. There are two water nozzles, and both water nozzles are connected to the outer wall of the water-cooled housing.

[0017] The winding is a round copper wire or a flat copper wire, and the stator core is formed by laminating two or more silicon steel sheets or pressing metal powder metallurgy materials.

[0018] Beneficial effects

[0019] The present invention features a high-power density, axial flux in-wheel motor with a short axial structure. Compared to existing technologies, it utilizes a dual-rotor stator, segmented yokeless axial flux topology, and an integrated planetary reducer. This motor delivers high torque while maintaining a compact size and weight. Compared to existing in-wheel motors, the present invention requires no modifications to the vehicle's suspension, steering, braking, or other systems, resulting in excellent versatility. Furthermore, while delivering the same power and torque, the in-wheel motor weighs approximately half that of existing in-wheel motors, significantly reducing the vehicle's unsprung mass and improving its handling.

[0020] The main advantages of the present invention are as follows:

[0021] 1. The planetary reducer and axial flux motor are highly integrated to form a new type of hub motor, which can provide high torque and output power while having a small size and weight;

[0022] 2. A water-cooling shell structure is added to the dual-rotor stator segmented yokeless axial flux topology structure. The water-cooling shell fins are provided with internal water channels, which can effectively increase the heat dissipation efficiency of the motor stator and improve the output power of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a longitudinal cross-sectional view of the present invention;

[0024] Figure 2 It is a three-dimensional structural diagram of the present invention;

[0025] Figure 3 Schematic diagram of the structure of the planetary reducer in the present invention;

[0026] Figure 4 Schematic diagram of the structure of the rotor assembly in the present invention;

[0027] Figure 5 Schematic diagram of the structure of the axial flux stator assembly of the present invention;

[0028] Figure 6a Schematic diagram of the structure of the water-cooling shell in the present invention;

[0029] Figure 6b A longitudinal cross-sectional view of the water-cooling housing of the present invention;

[0030] Figure 7 This is a schematic diagram of the parallel water channel design in the present invention;

[0031] Figure 8 This is a comparison chart of temperature rise tests between the motor of the present invention and a traditional motor;

[0032] Figure 9 This is an exploded diagram of the hub motor installation in the prior art;

[0033] Among them, 1-wheel hub bearing unit, 2-motor front end cover, 3-planetary reducer, 4-motor housing, 5-rotor assembly, 6-axial flux stator assembly, 7-motor rear end cover, 31-large ring gear, 32-planetary gear, 33-sun gear, 34-reducer output shaft, 41-brake caliper mounting hole, 42-water nozzle, 43-shock absorber mounting hole, 44-steering mechanism mounting hole, 45-chassis mounting hole, 51-rotor yoke, 52-permanent magnet, 53-rotor connector, 54-rotating shaft, 61-stator core, 62-winding, 63-carbon fiber fixing plate, 64-sealing ring, 65-water cooling shell, 651-fin, 652-layer spacing protrusion, 653-water channel partition, 654-outer water channel, 656-inner water channel. DETAILED DESCRIPTION

[0034] In order to provide a further understanding and appreciation of the structural features and effects achieved by the present invention, a detailed description is provided with reference to preferred embodiments and accompanying drawings as follows:

[0035] like Figure 1 As shown in FIG. 1 , a high-power-density axial flux hub motor with a short axial structure according to the present invention includes a motor housing 4. A motor rear end cover 7 is mounted at the rear end of the motor housing 4 in accordance with the prior art. A hub bearing unit 1 and a motor front end cover 2 are mounted at the front end of the motor housing 4 in accordance with the prior art. A rotor assembly 5 and an axial flux stator assembly 6 are both mounted within the motor housing 4, and the rotor assembly 5 and the axial flux stator assembly 6 are mounted in a coordinated manner.

[0036] The inside of the motor housing 4 is divided from back to front into a stator assembly mounting cavity and a planetary reducer mounting cavity. The stator assembly mounting cavity is close to the rear end cover 7 of the motor, and the planetary reducer mounting cavity is close to the front end cover 2 of the motor. The stator assembly mounting cavity is used to install the stator assembly, and the planetary reducer mounting cavity is used to install the planetary reducer 3. The stator assembly mounting cavity and the planetary reducer mounting cavity are relatively independent structures, communicating only at the center, and bearings are installed so that the output shaft of the rotor assembly 5 is installed on the bearings to output power. The purpose of the relatively independent structures of the stator assembly mounting cavity and the planetary reducer mounting cavity is to facilitate the installation of the planetary reducer. Because the planetary reducer must be lubricated, a special cavity is formed for the installation of the planetary reducer through the special design inside the motor housing 4. It not only accommodates the planetary reducer but also provides spatial redundancy in the planetary reducer mounting cavity for injecting lubricating fluid.

[0037] Here, the motor flux method adopts the axial flux method. Due to its short axial length and compact structure, the axial flux occupies a small space in the axial direction. However, the current common axial flux motor has low power density and poor heat transfer performance, and cannot meet the torque requirements of the entire vehicle within the limited space of the wheel hub. The role of the planetary reducer 3 is to increase the output torque of the entire machine to meet the power performance of the entire vehicle, such as Figure 3 As shown, the planetary reducer 3 includes a large ring gear 31, planetary gears 32, a sun gear 33, and a reducer output shaft 34. The unique axial magnetic flux method employed in this invention not only provides space for the installation of the planetary reducer 3, but also creates a cavity between the planetary reducer 3, the motor front end cover 2, and the motor housing 4 (within the planetary reducer mounting cavity). By filling this cavity with lubricating oil, this facilitates the installation and use of the planetary reducer 3. The output shaft of the rotor assembly 5 is connected to the input shaft of the planetary reducer 3, and the reducer output shaft 34 of the planetary reducer 3 is connected to the hub bearing unit 1. The power output of the rotor assembly 5 is increased in torque through the planetary reducer 3 and then provided to the hub bearing unit 1.

[0038] like Figure 4 As shown, the rotor assembly 5 includes two rotor yokes 51, the centers of the two rotor yokes 51 are connected by a rotor connector 53, permanent magnets 52 are installed on the opposite surfaces of the two rotor yokes 51, a rotating shaft 54 ​​is installed on the outer surface of any rotor yoke 51, a water-cooling housing 65 is installed on the rotor connector 53 and is located between the two rotor yokes 51, and the rotating shaft 54 ​​of the rotor assembly 5 is installed on the sun gear 33 of the planetary reducer 3.

[0039] like Figure 5 and Figure 6a 、 Figure 6b As shown, the axial flux stator assembly 6 includes a water-cooled shell 65, and a plurality of fins 651 are provided on the inner wall of the water-cooled shell 65. The fins 651 are used to clamp the stator core 61 in the radial direction. The number of fins 651 is designed according to the number of stator cores 61, and the shape between two fins 651 is designed according to the shape of the stator core 61. The winding 62 is wound on the stator core 61. The winding 62 can be round copper wire or flat copper wire. The stator core 61 has no yoke and is formed by stacking two or more silicon steel sheets or pressing metal powder metallurgy materials. This type of core can effectively reduce eddy current and hysteresis losses and improve the overall efficiency of the motor. After the stator core 61 is wound with the winding 62, it is embedded between adjacent fins 651 on the inner wall of the water-cooled shell 65 and is fixed by encapsulation with glue (traditional epoxy resin encapsulation), thereby achieving the installation of the stator core 61 between adjacent fins 651. Here, the special design of the water-cooling housing 65 reduces the thermal resistance of the heat path, improves the heat transfer efficiency, and increases the output power of the entire machine.

[0040] In order to further fix the stator core 61 in the axial direction, a carbon fiber fixing plate 63 can be used to fix it in the axial direction. The carbon fiber fixing plate 63 is fixed to the fin 651 on the axial surface of the water-cooled shell 65 by glue (conventional epoxy resin potting).

[0041] In order to increase the versatility of the motor, such as Figure 2 As shown, the outer wall of the motor housing 4 is provided with a brake caliper mounting hole 41, a water nozzle 42, a shock absorber mounting hole 43, a steering mechanism mounting hole 44 and a chassis mounting hole 45. There are two water nozzles 42, and both water nozzles 42 are connected to the outer wall (outer circumference) of the water-cooled housing 65.

[0042] In order to achieve high power density, the fin 651 is specially designed to clamp the stator core 61 in the radial direction. Figure 6a and Figure 6b As shown. The outer wall (outer circumference) of the water-cooling shell 65 is provided with a layer spacing protrusion 652 that surrounds the water-cooling shell 65. The layer spacing protrusion 652 divides the outer wall of the water-cooling shell 65 into two water channels in the axial direction: an inner water channel 656. Each fin 651 is provided with an inner water channel 656. The inner water channel 656 is preferably designed to be "U"-shaped. One end of the inner water channel 656 is connected to one side of the layer spacing protrusion 652 on the outer wall of the water-cooling shell 65, and the other end of the inner water channel 656 is connected to the other side of the layer spacing protrusion 652 on the outer wall of the water-cooling shell 65. This allows the inner water channel of the outer wall of the water-cooling shell 65 to flow in through the inner water channel 656 and then flow out from the outer water channel of the outer wall of the water-cooling shell 65 on the other side, realizing water circulation in the inner water channel 656, thereby achieving maximum efficiency and area for water cooling of the stator core 61.

[0043] To further enhance the water-cooling effect, an external water channel 654 can be provided on the outer wall of the water-cooling housing 65, surrounding the water-cooling housing 65. The external water channel 654 can also be designed as multiple channels to further cool the outer cylindrical shell of the water-cooling housing 65. To enhance the sealing effect, a sealing ring 64 can also be installed on the outer cylindrical shell of the water-cooling housing 65.

[0044] The use of the interlayer protrusions 652 and the internal water channels 656 here makes it possible to realize multiple water channel circulation processes. That is, to achieve a greater water cooling effect, a plurality of water channel baffles 653 can be designed on the outer wall of the water cooling shell 65 between the inner wall of the external water channel 654 and the interlayer protrusions 652. The water channel baffles 653 are preferably located between adjacent fins 651. Figure 7 As shown, by adjusting the position and number of the water channel parallel partitions 653, the number of parallel paths of the water channels 656 in the chip can be adjusted to achieve a better water cooling effect.

[0045] The motor using the cooling system of the present invention and the ordinary axial motor were tested for temperature rise under the conditions of output power of 65kw and heat generation power of 5kw. The cooling water inlet temperature was 28℃. The stator temperature of the motor of the present invention reached thermal equilibrium at 72℃, while the stator of the ordinary motor reached thermal equilibrium at 95℃, with a temperature difference of 23℃. Therefore, the output power of the motor of the present invention can be further improved than that of the ordinary motor. The temperature rise tests of the two motors are as follows: Figure 8 shown.

[0046] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A high power density axial flux hub motor with a short axial structure, comprising a motor housing (4), a motor rear end cover (7) installed at the rear end of the motor housing (4), a hub bearing unit (1) and a motor front end cover (2) installed at the front end of the motor housing (4), a rotor assembly (5) and an axial flux stator assembly (6) installed in the motor housing (4), the rotor assembly (5) and the axial flux stator assembly (6) being installed in cooperation, characterized in that: It also includes a planetary reducer (3), wherein the output shaft of the rotor assembly (5) is connected to the input shaft of the planetary reducer (3), and the reducer output shaft (34) of the planetary reducer (3) is connected to the hub bearing unit (1); the axial magnetic flux stator assembly (6) includes a water-cooled shell (65), a plurality of fins (651) are provided on the inner wall of the water-cooled shell (65), and the winding (62) is wound on the stator core (61) and embedded between adjacent fins (651) on the inner wall of the water-cooled shell (65) and fixed by glue potting; The outer wall of the water-cooling shell (65) is provided with a layer spacing protrusion (652) surrounding the water-cooling shell (65), and each fin (651) is provided with an internal water channel (656), one end of the internal water channel (656) is communicated with one side of the layer spacing protrusion (652) on the outer wall of the water-cooling shell (65), and the other end of the internal water channel (656) is communicated with the other side of the layer spacing protrusion (652) on the outer wall of the water-cooling shell (65); the outer wall of the water-cooling shell (65) is also provided with an external water channel (654) surrounding the water-cooling shell (65), and the internal water channel (656) is "U"-shaped and is on the outer wall of the water-cooling shell (65). A plurality of water channel partitions (653) are provided between the inner wall of the outer water channel (654) and the layer spacing protrusion (652); the rotor assembly (5) comprises two rotor yokes (51), the centers of the two rotor yokes (51) are connected via a rotor connector (53), permanent magnets (52) are mounted on opposite surfaces of the two rotor yokes (51), a rotating shaft (54) is mounted on the outer surface of any rotor yoke (51), a water-cooling housing (65) is mounted on the rotor connector (53) and is located between the two rotor yokes (51); the rotating shaft (54) of the rotor assembly (5) is mounted on the sun gear (33) of the planetary reducer (3).

2. The high power density axial flux hub motor with a short axial structure according to claim 1, characterized in that: The motor housing (4) is divided into a stator assembly mounting cavity and a planetary reducer mounting cavity from back to front. The stator assembly mounting cavity and the planetary reducer mounting cavity are connected at the center and a bearing is installed at the center. The output shaft of the rotor assembly (5) is installed on the bearing.

3. The high power density axial flux hub motor with a short axial structure according to claim 1, characterized in that: The cavity between the planetary reducer (3), the motor front end cover (2), and the motor housing (4) is filled with lubricating oil; and the carbon fiber fixing plate (63) is also included. The carbon fiber fixing plate (63) is fixed to the fin (651) on the axial surface of the water-cooling housing (65) by glue.

4. The high power density axial flux hub motor with a short axial structure according to claim 1, characterized in that: The water channel partitions (653) are all located between adjacent fins (651).

5. The high power density axial flux hub motor with a short axial structure according to claim 1, characterized in that: The outer wall of the motor housing (4) is provided with a brake caliper mounting hole (41), a water nozzle (42), a shock absorber mounting hole (43), a steering mechanism mounting hole (44) and a chassis mounting hole (45). There are two water nozzles (42), and both of the two water nozzles (42) are in communication with the outer wall of the water-cooling housing (65).

6. The high power density axial flux hub motor with a short axial structure according to claim 1, characterized in that: The winding (62) is a round copper wire or a flat copper wire, and the stator core (61) is formed by laminating two or more silicon steel sheets or pressing metal powder metallurgy materials.

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