Multi-disc axial flux permanent magnet motor based on lattice micro-channel composite cooling structure

Abstract

The application discloses a multi-disc axial flux permanent magnet motor based on a lattice micro-channel composite cooling structure, which comprises an end cover assembly, a hollow rotating shaft, a rotor assembly, a stator assembly, a lattice micro-channel framework, a porous medium filling layer and a machine shell; the stator assembly adopts a yokeless segmented structure, and the porous medium filling is used to replace traditional epoxy resin for filling, so that the heat dissipation path of the stator is reconstructed; the lattice micro-channel framework is integrated in the stator assembly, and a built-in liquid cooling circuit and a phase change material filling layer are arranged, so that the liquid cooling and the phase change are combined for cooling; the hollow rotating shaft is provided with a central air channel, and the double-path air cooling structure is formed in cooperation with the air vents on the machine shell and the end cover; and the direct-cooling rotor and the porous medium filling layer of the stator are arranged. Through the multi-medium collaborative heat dissipation, the application breaks through the global heat dissipation bottleneck of the multi-disc motor, and meanwhile, the high torque density and the lightweight characteristics are maintained, so that the application is suitable for new energy automobile traction, rail transit, aerospace and other high-performance driving scenes.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet motor cooling technology, specifically relating to a multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure, which is particularly suitable for electric drive scenarios with high power density, high torque density, and compact design. Background Technology

[0002] Multi-disc axial flux permanent magnet motors, due to their advantages such as compact axial dimensions, high torque density, high power density, and flexible topology expansion, have become core drive components in fields such as robot joints, hub motors, rail transit traction, and aerospace auxiliary drives. As electrification equipment develops towards lightweight, integrated, and high-performance directions, the requirements for the power density and torque density of multi-disc axial flux permanent magnet motors continue to increase. The structural design of the motor body is becoming increasingly compact, and the internal heat transfer space is severely compressed. This results in extremely high-density heat loads during operation, making motor temperature rise control a key bottleneck restricting its performance improvement and reliable operation.

[0003] The cooling methods for existing multi-disc axial flux permanent magnet motors are mainly divided into three categories: air cooling, liquid cooling, and phase change cooling. Each cooling method has obvious drawbacks in practical applications: air cooling mostly relies on fan-driven airflow for heat exchange, resulting in low heat exchange efficiency. Furthermore, external fans increase the overall size and weight of the motor, reducing the motor's torque density and failing to meet the heat dissipation requirements of high-power-density motors. Liquid cooling has higher heat transfer efficiency, but it often uses an external cooling circuit integrated with the motor body, resulting in complex piping and potential coolant leakage. In addition, liquid cooling systems have high thermal inertia, making them less responsive to transient peak heat loads and prone to causing excessively high local temperatures. Phase change cooling relies on the latent heat absorption of phase change materials to achieve rapid cooling, effectively suppressing temperature peaks. However, the heat dissipation sustainability of phase change materials is poor, and without an efficient outlet path, it cannot meet the steady-state heat dissipation requirements for long-term stable operation of the motor.

[0004] Meanwhile, existing cooling technologies mostly employ a single cooling method or simply combine multiple cooling methods externally, failing to achieve integrated design between the cooling system and the motor support structure. The cooling structure is independent of the stator and rotor support structures of the motor, which not only increases the structural redundancy of the motor but also leads to discontinuous heat exchange paths and a significant reduction in heat exchange efficiency. In addition, in multi-disc axial flux permanent magnet motors, the stator and rotor discs are stacked alternately, and the heat dissipation path of the intermediate rotor discs is blocked, becoming a heat dissipation blind zone, which can easily cause irreversible demagnetization of the permanent magnets. The axial magnetic pull generated during motor operation can cause rotor misalignment, and uneven air gaps further aggravate local overheating. Existing cooling technologies do not consider heat dissipation coordination with the bearing support structure, making it difficult to achieve efficient heat dissipation throughout the motor.

[0005] In summary, existing cooling technologies, when applied to multi-disc axial flux permanent magnet motors, cannot simultaneously meet the multiple requirements of efficient steady-state heat dissipation, transient thermal load bearing, and compact and lightweight structure. There is an urgent need for a composite cooling structure that organically combines liquid cooling, phase change cooling, and air cooling, and is integrated with the motor body, to overcome the physical limitations of heat dissipation in multi-disc axial flux permanent magnet motors. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure, which aims to solve the problem that when existing cooling technologies are applied to multi-disc axial flux permanent magnet motors, they cannot simultaneously meet the multiple requirements of efficient steady-state heat dissipation, transient thermal load bearing, and structural compactness and lightweight.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure is disclosed. The permanent magnet motor has a hollow shaft in the middle, with multiple central ventilation holes circumferentially opened in the middle of the hollow shaft. The central rotor is located directly opposite the ventilation holes on the hollow shaft. A lattice microchannel skeleton, a rotor disk, and an end cap are sequentially fitted on the hollow shaft from the central ventilation holes to both ends. A stator assembly is installed on the lattice microchannel skeleton, permanent magnets are attached to the rotor disks, and rotor ventilation holes are opened on the end caps. A housing is fitted over the lattice microchannel skeleton and rotor disks. Multiple lateral ventilation holes are circumferentially arranged in the housing, and the rotor ventilation holes are connected to the lateral ventilation holes through the permanent magnets. The central ventilation holes are connected to the lateral ventilation holes through the lattice microchannel skeleton and stator assembly, forming a dual-path air-cooling heat dissipation structure.

[0008] Furthermore, one end of the hollow rotating shaft is provided with an inlet and an outlet. A main liquid cooling channel and a lattice-shaped microchannel are provided inside the lattice microchannel framework. The inlet and outlet are connected to the main liquid cooling channel, which is connected to the lattice-shaped microchannel. The lattice microchannel framework has a multi-slot structure, with the stator assembly embedded in the slots. The lattice-shaped microchannels are arranged in the sidewalls of the slots of the lattice microchannel framework.

[0009] Furthermore, the lattice-shaped microchannel contains branched liquid-cooled heat exchange circuits arranged in a honeycomb grid pattern. Phase change material is filled in the gap regions of the branched liquid-cooled heat exchange circuits to form a phase change material filling layer. The main liquid-cooled channel is connected to the branched liquid-cooled heat exchange circuits.

[0010] Furthermore, the stator assembly is encapsulated on the lattice microchannel framework by a porous dielectric encapsulation layer, which is made of foam metal.

[0011] Furthermore, the stator assembly includes a yokeless segmented stator and stator windings, with the stator windings wound on the yokeless segmented stator.

[0012] Furthermore, the end cap surface is provided with multiple fan-shaped perforations spaced apart circumferentially.

[0013] Furthermore, the lateral ventilation holes of the end cap are evenly distributed in a matrix, with a diameter of 3mm to 8mm and a permeability of 20% to 40%.

[0014] The technical solution adopted in this invention has the following beneficial effects: This invention organically combines liquid cooling circulation with phase change material (PCM) cooling through lattice microchannels. The liquid cooling circulation achieves continuous and efficient heat dissipation during steady-state motor operation, while the PCM filling layer rapidly absorbs transient peak heat loads through latent heat of phase change, smoothing out temperature spikes. Combined with dual air-cooling channels, this achieves full-area auxiliary heat exchange, solving the technical problems of insufficient steady-state heat dissipation and weak transient response in existing cooling technologies, significantly improving the motor's thermal load-bearing capacity. Simultaneously, this invention uses a highly thermally conductive porous medium to replace traditional epoxy resin potting, reducing stator thermal resistance while providing a large heat exchange surface for air cooling, significantly improving stator convective heat transfer efficiency and overcoming the heat dissipation bottleneck of traditional potting structures. The main airflow directly runs through the motor, directly cooling the intermediate rotor, solving the problem of difficult heat dissipation of the intermediate rotor in multi-disc motors and effectively preventing irreversible demagnetization of permanent magnets. The auxiliary airflow directly cools the porous medium layer of the stator, achieving efficient heat dissipation throughout the stator and significantly improving the motor's operational reliability. In summary, the integrated design of the cooling system and motor support structure has been achieved. The lattice microchannel skeleton serves as the stator support structure, eliminating the need for external cooling pipes and fans, and adapting to the requirements of high torque density and lightweight traction motors. Attached Figure Description

[0015] Figure 1 This is an exploded view of the overall structure of the present invention; Figure 2 This is a schematic diagram of the external three-dimensional structure of the present invention; Figure 3 A schematic diagram of the main liquid cooling channel structure of the lattice microchannel framework; Figure 4 This is a schematic diagram of the lattice structure of the microchannel framework. Figure 5 This is a schematic diagram of the stator assembly structure; Figure 6 This is a schematic diagram of a porous medium potting layer structure; Figure 7 This is a schematic diagram of the dual-airflow cooling structure for the motor. Figure 8 A schematic diagram of the auxiliary air-cooling structure.

[0016] Explanation of reference numerals in the attached drawings: 1. End cap; 10. Rotor ventilation hole; 11. Fan-shaped hollow hole; 2. Hollow shaft; 20. Central ventilation hole; 21. Water inlet; 22. Water outlet; 3. Rotor disk; 4. Permanent magnet; 5. Lattice microchannel framework; 50. Main liquid cooling channel; 51. Lattice microchannel; 510. Branch liquid cooling heat exchange circuit; 511. Phase change material filling layer; 6. Porous medium potting layer; 60. Yokeless segmented stator; 61. Stator winding; 7. Housing; 70. Side ventilation hole; 8. Rotor. Detailed Implementation

[0017] like Figures 1 to 8 As shown, the present invention provides a multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure. The motor is an axial multi-disc stacked structure, and adopts a yokeless segmented stator, porous dielectric potting, lattice microchannel integrated skeleton, and dual-path air cooling highly integrated design, thereby achieving the comprehensive goals of efficient heat conduction throughout the stator, no blind spot heat dissipation in the middle rotor, rapid suppression of transient thermal load, and steady-state continuous heat dissipation.

[0018] That is: a hollow shaft 2 is set in the middle of the permanent magnet motor, and a rotor 8 is set in the hollow shaft 2. Multiple central ventilation holes 20 are opened in the circumferential direction in the middle of the hollow shaft 2. The ventilation holes are directly opposite the central rotor 8. From the central ventilation holes 20 to both ends, a lattice microchannel skeleton 5, a rotor disk 3 and an end cover 1 are sequentially fitted. A stator assembly is set on the lattice microchannel skeleton 5. A permanent magnet 4 is attached to the rotor disk 3. A rotor ventilation hole 10 is opened on the end cover 1. A housing 7 is fitted over the lattice microchannel skeleton 5 and the rotor disk 3. Multiple lateral ventilation holes 70 are opened in the circumferential array in the housing 7. The rotor ventilation holes 10 are connected to the lateral ventilation holes 70 through the permanent magnet 4. The central ventilation holes 20 are connected to the lateral ventilation holes 70 through the lattice microchannel skeleton 5 and the stator assembly, forming a dual-path air-cooling heat dissipation structure.

[0019] like Figure 1 , Figure 2 As shown, the motor is assembled on the hollow rotating shaft 2 in sequence along the axial direction by end cover 1, rotor disk 3, permanent magnet 4, lattice microchannel skeleton 5, porous medium potting layer 6 and housing 7. The whole is centrally symmetrical about the central rotor (8) and axially connected.

[0020] The end caps 1 are symmetrically installed at both ends of the motor axis. They adopt a hollow lightweight structure with evenly spaced circular rotor ventilation holes 10 on the surface to provide a stable air intake channel for external air cooling. The hollow shaft 2 runs through the entire machine along the motor axis and is the core load-bearing and fluid integration component of the motor. A central ventilation hole 20 is opened in the center to form a through airflow to directly cool the intermediate rotor assembly and stator assembly. The hollow rotating shaft 2 has a liquid cooling inlet 21 and an outlet 22 machined at both ends, which are directly connected to the main liquid cooling channel 50 of the internal lattice microchannel skeleton 5, so as to realize the direct access of the cooling liquid without external pipelines.

[0021] The rotor assembly consists of a rotor disk 3 and a permanent magnet 4. The permanent magnet 4 is fixed to the end face of the rotor disk 3 facing the stator by adhesive bonding. Multiple sets of rotor disks 3 and stator assemblies are alternately stacked along the hollow shaft 2. A uniform and stable working air gap is reserved between the rotor disk 3 and the stator assembly to ensure smooth axial magnetic flux and uniform air gap magnetic field.

[0022] The lattice microchannel framework 5 has a multi-slot structure, with the stator assembly embedded in the slots and the lattice microchannels 51 arranged in the sidewalls of the slots of the lattice microchannel framework 5. The lattice microchannel framework 5 is the core support substrate and cooling core of the stator assembly, and integrates the main liquid cooling channel 50, the lattice microchannels 51, and the phase change material filling cavity, thus having the triple functions of structural support, liquid cooling heat exchange, and phase change heat storage.

[0023] The porous dielectric potting layer 6 is made of high thermal conductivity foam metal, completely filling all gaps in the winding gaps, stator slots, and between the windings and the lattice microchannel framework 5 of the yokeless segmented stator 60. This replaces traditional epoxy resin potting, reconstructing a continuous heat dissipation path from the inside out of the stator, while providing a large amount of internal convection heat transfer surface for air cooling. The stator assembly adopts a yokeless segmented structure, eliminating the traditional stator yoke. The segmented stator is directly embedded in the positioning slots of the lattice microchannel framework 5, and the stator windings 61 are wound on the segmented stator core. The entire assembly is integrally potted and formed by the porous dielectric potting layer 6, significantly shortening the heat conduction path.

[0024] The housing 7 is mounted on the outside of the stator assembly, and the surface has matrix-distributed lateral ventilation holes 70 with a perforation rate of 20% to 40%. Together with the rotor ventilation holes 10 on the end cover 1 and the central ventilation holes 20 of the hollow shaft 2, it forms a closed and unobstructed dual-path air-cooling heat dissipation channel.

[0025] like Figure 3 , Figure 4As shown, the lattice microchannel framework 5 is the core component of the composite cooling structure. Its internal flow channels have a hierarchical structure, serving as the main structure for achieving a deep integration of liquid cooling circulation and phase change heat storage. The main liquid cooling channel 50 is arranged radially along the stator disk, with one end connected to the inlet 21 of the hollow rotating shaft and the other end connected to the outlet 22, forming a closed, series-connected liquid cooling circulation loop without external piping. The main liquid cooling channel 50 has a circular cross-section, ensuring a reasonable flow area and flow resistance. The coolant is evenly distributed radially to each level of branch flow channels, avoiding uneven local flow leading to heat dissipation deviations. The lattice-shaped microchannels 51 radiate from the main liquid cooling channel 50 towards the stator winding 61 and the core region, exhibiting a grid-like hierarchical distribution that evenly covers the entire stator area. The branch liquid-cooled heat exchange circuit 510 is embedded within the crystal lattice structure and is fully connected to the main liquid-cooled channel 50, forming a dense heat exchange network. The branch flow channels have small cross-sections and are numerous, greatly increasing the heat exchange area and heat exchange intensity, enabling the heat generated by the stator windings and core to be quickly transferred to the coolant. The coolant enters the main liquid-cooled channel 50 from the inlet 21 and is evenly distributed to each branch liquid-cooled heat exchange circuit 510, where it undergoes high-intensity inter-wall heat exchange with the stator heat source. After absorbing steady-state heat, it collects in the main liquid-cooled channel 50 on the other side and finally flows out from the outlet 22, completing a continuous cycle. The phase change material filling layer 511 is disposed in the gap cavity of the branch liquid-cooled heat exchange circuit 510 and is tightly bonded to the wall of the main liquid-cooled channel 50 and the porous medium potting layer 6. The material used is an organic phase change composite material. The phase change temperature is precisely matched with the rated operating temperature range of the motor, ensuring compatibility with all operating conditions of the motor. The filling method is vacuum injection, which ensures that the cavity is completely filled, without air bubbles or gaps, and the heat exchange interface is in close contact. The heat absorbed by the phase change is quickly transferred to the coolant through the wall of the lattice microchannel 51 and continuously discharged by the branch liquid cooling heat exchange circuit 510. The phase change material is gradually cooled and re-solidified, realizing repeated recycling and solving the defects of traditional phase change cooling heat dissipation with poor continuity and inability to work stably for a long time.

[0026] like Figure 5 As shown, the motor adopts a yokeless segmented stator structure. The stator assembly consists of a segmented stator core 60 and a concentrated winding 61. Each stator module is arranged independently. There are multiple gaps between the winding and the stator slot, and between the winding and the cooling frame. These are concentrated areas of weak points in contact thermal resistance and heat transfer in traditional structures.

[0027] like Figure 6As shown, the porous dielectric potting layer 6 is made of highly thermally conductive foam metal, completely filling the gaps in the stator windings 61, the interior of the stator slots, and the interface between the windings and the lattice microchannel framework 5. The porous dielectric potting layer 6 is tightly bonded to the lattice framework 5, replacing traditional epoxy resin, significantly reducing the overall thermal resistance of the stator. Heat from the windings can be quickly conducted to the lattice framework and then rapidly carried away by liquid cooling and phase change. In addition, the porous through-structure provides a more three-dimensional and comprehensive convective heat transfer surface for air cooling. Airflow can directly penetrate the interior of the potting layer, achieving forced convection throughout the windings and significantly improving the heat transfer efficiency on the stator side.

[0028] like Figure 1 and Figure 7 As shown, the motor has a dual-path air-cooled heat dissipation structure. The central air-cooling passage is the main air passage that runs through the axial direction and directly cools the middle rotor. The airflow enters from the openings at both ends of the hollow shaft 2, runs through the motor interior along the ventilation hole 20 in the middle of the shaft, and blows directly onto the rotor 8 in the middle, which is the most severely heated. It also provides forced cooling to the area in the middle that is the most difficult to dissipate heat in traditional multi-disc motors (this motor includes a porous medium potting layer 6 and the yokeless segmented stator inside it), and finally discharges through the matrix ventilation holes 70 on the casing.

[0029] like Figure 8 As shown, the motor end cover 1 adopts a hollow design with multiple fan-shaped hollow holes 11 on its surface, which are evenly distributed along the circumference of the end cover. On the one hand, this can effectively reduce the weight of the end cover 1 itself, reduce the overall rotational inertia of the motor, and optimize the lightweight performance of the motor; on the other hand, the end cover 1 is in close contact with the rotor disk 3, and external cooling air can be blown directly onto the rotor disk 3 through the fan-shaped hollow holes, achieving efficient air cooling of the rotor disk 3. This integrates weight reduction and heat dissipation into one, while also serving as an auxiliary function for the dual air cooling channels.

Claims

1. A multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure, characterized in that, The motor has a three-rotor, two-stator electromagnetic topology, with the rotor (8) located at the very center of the motor. A hollow shaft (2) is located in the middle of the motor, and multiple central ventilation holes (20) are opened in the circumferential direction in the middle of the hollow shaft (2). A lattice microchannel framework (5), a rotor disk (3), and an end cap (1) are sequentially fitted along both ends of the hollow shaft (2). A stator assembly is provided on the lattice microchannel framework (5), a permanent magnet (4) is attached to the rotor disk (3), and the end cap (1) is attached to the end cap (1). Ventilation holes (10) are provided. The lattice microchannel skeleton (5) and the rotor disk (3) are covered with a housing (7). Multiple lateral ventilation holes (70) are provided in a circumferential array on the housing (7). The ventilation holes (10) on the end cover are connected to the lateral ventilation holes (70) through the permanent magnet (4). The ventilation holes (20) in the middle of the rotating shaft are connected to the lateral ventilation holes (70) after passing through the central rotor (8) and scouring the lattice microchannel skeleton (5) and the stator assembly, thus forming a dual-path air-cooled heat dissipation structure.

2. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The hollow rotating shaft (2) has an inlet (21) and an outlet (22) at one end. The lattice microchannel skeleton (5) has a main liquid cooling channel (50) and a lattice microchannel (51). The inlet (21) and outlet (22) are connected to the main liquid cooling channel (50), and the main liquid cooling channel (50) is connected to the lattice microchannel (51). The lattice microchannel skeleton (5) has a multi-slot structure. The stator assembly is embedded in the slot, and the lattice microchannel (51) is arranged in the slot sidewall of the lattice microchannel skeleton (5).

3. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The lattice-shaped microchannel (51) contains a branched liquid-cooled heat exchange circuit (510) with a honeycomb grid distribution. The phase change material fills the gap area of ​​the branched liquid-cooled heat exchange circuit (510) to form a phase change material filling layer (511). The main liquid-cooled channel (50) is connected to the branched liquid-cooled heat exchange circuit (510).

4. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The stator assembly is encapsulated on the lattice microchannel framework (5) by a porous medium potting layer (6), which is made of foam metal.

5. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The stator assembly includes a yokeless segmented stator (60) and a stator winding (61) wound on the yokeless segmented stator (60).

6. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The end cap (1) has multiple fan-shaped perforated holes (11) spaced apart circumferentially on its surface.

7. The multi-disc axial flux permanent magnet motor based on a lattice microchannel composite cooling structure according to claim 1, characterized in that, The side ventilation holes (70) are evenly distributed in a matrix, with a diameter of 3mm to 8mm and a permeability of 20% to 40%.

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