Multiphase hybrid cooling system for axial flux electric machines

Abstract

A multiphase hybrid cooling system for an axial flux motor includes a housing, a stator system, a shaft, and a rotor system. The housing includes a drive end cover, a middle end cover, and a cooling end cover with cooling channels. The middle end cover has an oil supply hole for supplying oil to the cooling end cover. The cooling end cover has a cooling oil inlet, a cooling oil outlet, and a cooling oil flow channel. The cooling oil inlet and outlet are connected through the cooling oil flow channel inside the cooling end cover. The stator system includes a stator support, a stator core, windings, a stator core heat pipe, and a stator support heat pipe. The shaft is a hollow shaft with internal oil channels and external oil spray holes and a cooling oil inlet on its outer wall. The rotor system is a dual-rotor system, with each rotor symmetrically arranged on the left and right sides of the stator system along its axial direction. Each rotor system includes a rotor back iron and a permanent magnet. The internal pipes of the motor are filled with cooling oil to form an immersion oil cooling circuit.

Description

Technical Field

[0001] This invention relates to the field of axial flux motors, and more specifically to a multiphase hybrid cooling system for axial flux motors. Background Technology

[0002] As the demand for high performance in axial flux motors continues to increase, these motors are evolving towards higher power, smaller size, and lighter weight. These demands lead to increased losses and significantly higher motor temperatures, becoming key factors limiting their continuous operating capacity, thermal stability, and lifespan. Especially during continuous high-load operation, if the motor temperature rise is not effectively controlled, it will increase the risks of insulation aging, permanent magnet demagnetization, and winding burnout, seriously affecting the reliability and safety of the system. Therefore, how to improve the cooling effect of the motor without increasing its size has become a crucial technical problem that must be solved in the design of current axial flux motors.

[0003] Based on current application and research progress, existing technologies for axial flux motors typically employ air cooling, simple water jacket cooling, or oil cooling to control the motor's temperature rise. These cooling structures often revolve around the stator system, and the cooling medium cannot uniformly contact the heat-generating areas, leading to excessively high temperature rises in some areas. To control the maximum temperature rise, the amount of cooling medium needs to be increased, which not only increases consumption but also wastes energy, hindering green environmental protection and sustainable development.

[0004] Existing cooling solutions for axial flux motors have made various attempts in terms of structure and cooling medium, but the following pain points still exist: (1) Low liquid cooling efficiency. Existing indirect liquid cooling solutions remove heat through indirect heat exchange. However, due to the limited thermal conductivity of the materials, the heat exchange efficiency is low, requiring an increase in the volume of the cooling system or the flow rate of the cooling medium to ensure the cooling effect. In addition, when the motor power is large, the heat dissipation capacity of indirect heat dissipation is obviously insufficient while keeping the volume constant. In existing immersion cooling solutions, due to structural problems, there are blind spots in the flow path of the cooling medium, and the coolant flow rate is uneven, resulting in poor cooling effect.

[0005] (2) In high-power motors, current cooling solutions result in significant temperature differences between different parts of the stator system. Long-term uneven stator temperature, while not directly reaching the "overheating failure" threshold, gradually weakens the motor's efficiency, reliability, and lifespan through multiple pathways, including accelerated insulation aging, magnetic imbalance, accumulated mechanical stress, and decreased control precision. This is particularly problematic for automotive motors (which require high reliability, long lifespan, and wide operating condition adaptability), potentially becoming a hidden danger affecting the safety of the entire vehicle's powertrain. Therefore, it is necessary to optimize the cooling structure to balance the stator temperature distribution and reduce the impact of temperature differences.

[0006] (3) At present, most of the attention is focused on the cooling effect of the stator system of the axial flux motor, while relatively little research is done on the temperature of the rotor system. In high-power motors, the loss value of the rotor system will also increase. If a cooling system is not set up for it, the risk of permanent magnet failure and demagnetization at high temperature will also increase significantly.

[0007] (4) Because the air gap of the axial flux motor is small, the temperature rise of the stator end face will be significant. Furthermore, the temperature rise of the stator core will be significantly increased due to the insulation requirements. Current cooling solutions focus on winding cooling and cannot cool the stator. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a multiphase hybrid cooling system for axial flux motors.

[0009] The objective of this invention is achieved through the following solution: a multiphase hybrid cooling system for an axial flux motor, comprising a housing, a stator system, a shaft, and a rotor system. The housing includes a drive end cover, a middle end cover, and a cooling end cover with a cooling channel. The middle end cover has an oil supply hole for supplying oil to the cooling end cover. The cooling end cover has a cooling oil inlet, a cooling oil outlet, and a cooling oil flow channel. The cooling oil inlet is located on the circumference of the cooling end cover, and the cooling oil outlet is located at the center of the cooling end cover. The cooling oil inlet and the cooling oil outlet are connected through a cooling oil flow channel inside the cooling end cover. The stator system includes a stator support, a stator core, windings, a stator core heat pipe, and a stator support heat pipe. The stator core has a stator core hole. The winding has a winding gap, and the stator support has a stator support hole. The stator core heat pipe is inserted into the stator core hole and the winding gap, and the stator support heat pipe is inserted into the stator support hole. The shaft is a hollow shaft with shaft oil passages inside and shaft oil spray holes and shaft cooling oil inlets on the outer peripheral wall. The shaft cooling oil inlets are connected to the cooling channels of the cooling end cover. The rotor system is a dual-rotor system, with each rotor symmetrically arranged on the left and right sides of the stator system. Each rotor system includes a rotor back iron and a permanent magnet. The rotor back iron has rotor back iron oil passages and rotor back iron oil spray holes, and the rotor back iron oil passages are connected to the shaft oil spray holes on the shaft. The internal pipes of the motor are filled with cooling oil to form an immersion oil cooling circuit.

[0010] The upper two sides of the stator core heat pipe and the lower two sides of the stator support heat pipe are provided with heat dissipation fins.

[0011] Phase change material is installed in areas of the stator system where oil temperature fluctuations are likely to occur. The phase change material works in conjunction with the cooling oil and heat pipes to achieve multiphase mixed cooling.

[0012] The rotor back iron oil passage extends radially along the rotor back iron, and the rotor shaft oil injection holes are evenly distributed circumferentially along the hollow rotor shaft.

[0013] The left and right sides of the rotating shaft are rotatably connected to the drive end cover and the cooling end cover via bearings. The bearings are sealed bearings to prevent cooling oil leakage.

[0014] The heat dissipation fins of the stator core heat pipe extend into the cooling oil circuit of the stator system, and the heat dissipation fins of the stator support heat pipe are in contact with the winding and correspond to the oil injection holes of the rotating shaft.

[0015] The stator core is a yokeless stator core, and the stator core holes are evenly arranged along the circumference of the stator core, with the number consistent with the number of stator slots.

[0016] The advantages of this invention are: 1. By applying phase change materials in conjunction with an immersion oil cooling system, the oil flow can be made uniform, and the phase change materials can ensure cooling in areas where poor cooling is caused by oil temperature variations. This reduces the temperature difference between different parts of the stator system and improves its temperature uniformity; 2. It can effectively solve the problem of poor stator core cooling; 3. The present invention includes a cooling scheme for the rotor system. The cooling system, which is composed of a hollow shaft and a housing, can simultaneously cool the end faces of the rotor system and the stator core by means of oil spraying. This solves the problem of poor cooling effect of the stator system end faces while ensuring the cooling effect of the rotor system. 4. The cooling effect is good, which to some extent increases the motor's ability to operate under high load and its duration. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is an exploded view of the structure of the present invention; Figure 3 This is a schematic diagram of the middle end cap structure; Figure 4 This is a schematic diagram of the cooling end cap structure; Figure 5 This is a sectional view of the cooling end cap; Figure 6 This is a schematic diagram of the rotor system structure; Figure 7 This is a cross-sectional view of the rotor system; Figure 8 This is a schematic diagram of the rotating shaft structure; Figure 9 This is a sectional view of the rotating shaft; Figure 10 This is a schematic diagram of the stator system structure; Figure 11 This is a schematic diagram of the stator support structure; Figure 12 This is a schematic diagram of the stator core structure; Figure 13 This is a schematic diagram of the stator winding structure; Figure 14 This is a schematic diagram of the stator core heat pipe structure; Figure 15 This is a schematic diagram of the stator support heat pipe structure; Figure 16 This is a schematic diagram illustrating the working principle of oil injection from the rotor system to the stator system. Detailed Implementation

[0018] like Figures 1 to 16As shown, a multiphase hybrid cooling system for an axial flux motor includes a housing, a stator system 4, a shaft 3, and a rotor system 5. The housing includes a drive end cover 1, an intermediate end cover 2, and a cooling end cover 6 with a cooling channel. The intermediate end cover 2 has an oil supply hole 2-1 for supplying oil to the cooling end cover 6. The cooling end cover 6 has a cooling oil inlet 6-1, a cooling oil outlet 6-2, and a cooling oil flow channel 6-3. The cooling oil inlet 6-1 is located on the circumference of the cooling end cover 6, and the cooling oil outlet 6-2 is located at the center of the cooling end cover 6. The cooling oil inlet 6-1 and the cooling oil outlet 6-2 are connected by a channel inside the cooling end cover 6. The cooling oil flow channel 6-3 is connected; the stator system 4 includes a stator support 4-1, a stator core 4-2, windings 4-3, a stator core heat pipe 4-4, and a stator support heat pipe 4-5. The stator core 4-2 has a stator core hole 4-6, the windings 4-3 have a winding gap 4-9, and the stator support has a stator support hole 4-7. The stator core heat pipe 4-4 is inserted into the stator core hole 4-6 and the winding gap 4-9, and the stator support heat pipe 4-5 is inserted into the stator support hole 4-7. Heat dissipation fins 4-8 are provided on both sides of the upper end of the stator core heat pipe 4-4 and both sides of the lower end of the stator support heat pipe 4-5. A phase change material is installed in the areas of the stator system 4 where oil temperature fluctuations are likely to occur. The phase change material, cooling oil, and heat pipes work together to achieve multiphase mixed cooling. The heat dissipation fins 4-8 of the stator core heat pipe 4-4 extend into the cooling oil passage of the stator system 4. The heat dissipation fins 4-8 of the stator support heat pipe 4-5 are in contact with the winding 4-3 and correspond to the oil spray hole 3-1 of the rotating shaft 3. The stator core 4-2 is a yokeless stator core, and the stator core holes 4-4 are evenly arranged around the circumference of the stator core 4-2, with the number matching the number of stator slots. The rotating shaft 3 is a hollow shaft with an internal oil passage 3-3 and an outer peripheral wall with an oil spray hole 3-1 and a cooling oil inlet 3-2. The cooling oil inlet 3-2 is connected to the cooling channel 6-3 of the cooling end cover 6. The rotor system 5 is a dual-rotor system, with each rotor symmetrically arranged on the left and right sides of the stator system 4. Each rotor system includes a rotor back iron 5-1 and a permanent magnet 5-2. The rotor back iron 5-1 has an oil passage 5-3 and an oil spray hole 5-4, which are connected to the corresponding oil spray hole 3-1 on the rotating shaft 3. The internal pipes of the motor are filled with cooling oil to form an immersion oil cooling circuit. The rotor back iron oil passage 5-3 extends radially along the rotor back iron, and the oil spray hole 3-1 is evenly distributed circumferentially along the hollow shaft. The left and right sides of the rotating shaft 3 are rotatably connected to the drive end cover 1 and the cooling end cover 6 via bearings. The bearings are sealed bearings to prevent cooling oil leakage. The intermediate end cover 2 and the stator bracket 4-1 cooperate to seal the stator system 4, forming a closed cooling oil circuit. The oil supply hole 2-1 of the intermediate end cover 2 is connected to the cooling flow channel 6-3 of the cooling end cover 6, forming a cooling oil circulation path.The rotor back iron oil injection hole 5-4 is set towards the stator system 4. After the cooling oil is sprayed out from the rotor back iron oil injection hole 5-4 through the rotor back iron oil channel 5-3, it bounces and diffuses between the stator and rotor, while cooling the rotor back iron 5-1, permanent magnet 5-2, stator end face and winding 4-3.

[0019] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A multiphase hybrid cooling system for an axial flux motor, comprising a housing, a stator system (4), a shaft (3), and a rotor system (5), characterized in that: The housing includes a drive end cover (1), an intermediate end cover (2), and a cooling end cover (6) with a cooling channel. The intermediate end cover (2) is provided with an oil supply hole (2-1) for supplying oil to the cooling end cover (6). The cooling end cover (6) is provided with a cooling oil inlet (6-1), a cooling oil outlet (6-2), and a cooling oil flow channel (6-3). The cooling oil inlet (6-1) is located on the circumference of the cooling end cover (6), and the cooling oil outlet (6-2) is located at the center of the cooling end cover (6). The cooling oil inlet (6-1) and cooling oil outlet (6-2) are connected through a cooling oil flow channel (6-3) inside the cooling end cap (6); the stator system (4) includes a stator support (4-1), a stator core (4-2), windings (4-3), a stator core heat pipe (4-4), and a stator support heat pipe (4-5). A stator core hole (4-6) is provided on the stator core (4-2), and a winding gap (4-9) is provided on the windings (4-3). The stator support is provided with... A stator support hole (4-7) is provided, and a stator core heat pipe (4-4) is inserted into the stator core hole (4-6) and the winding gap (4-9). A stator support heat pipe (4-5) is inserted into the stator support hole (4-7). The shaft (3) is a hollow shaft, with a shaft oil passage (3-3) inside. The outer peripheral wall is provided with a shaft oil spray hole (3-1) and a shaft cooling oil inlet (3-2). The shaft cooling oil inlet (3-2) is connected to the cooling flow channel (6-3) of the cooling end cover (6). The rotor system (5) is a dual rotor system, with each rotor symmetrically arranged on the left and right sides of the stator system (4) along the axial direction. Each rotor system includes a rotor back iron (5-1) and a permanent magnet (5-2). The rotor back iron (5-1) is provided with a rotor back iron oil passage (5-3) and a rotor back iron oil spray hole (5-4). The rotor back iron oil passage (5-3) is connected to the rotor shaft oil spray hole (3-1) on the rotating shaft (3). The internal pipes of the motor are filled with cooling oil to form an immersion oil cooling circuit.

2. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: The upper two sides of the stator core heat pipe (4-4) and the lower two sides of the stator support heat pipe (4-5) are provided with heat dissipation fins (4-8).

3. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: Phase change material is installed in the area of ​​the stator system (4) where oil temperature fluctuations are likely to occur. The phase change material works in conjunction with the cooling oil and heat pipe to achieve multiphase mixed cooling.

4. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: The rotor back iron oil passage (5-3) extends radially along the rotor back iron, and the shaft oil injection holes (3-1) are evenly distributed circumferentially along the hollow shaft.

5. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: The left and right sides of the rotating shaft (3) are rotatably connected to the drive end cover (1) and the cooling end cover (6) through bearings. The bearings are sealed bearings to prevent cooling oil leakage.

6. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: The heat dissipation fins (4-8) of the stator core heat pipe (4-4) extend into the cooling oil circuit of the stator system (4), and the heat dissipation fins (4-8) of the stator support heat pipe (4-5) are in contact with the winding (4-3) and correspond to the rotating shaft oil injection hole (3-1) of the rotating shaft (3).

7. The multiphase hybrid cooling system for an axial flux motor according to claim 1, characterized in that: The stator core (4-2) is a yokeless stator core, and the stator core holes (4-4) are evenly arranged around the stator core (4-2), with the number being the same as the number of stator slots.

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