Phase change cooling method and structure of axial disc type permanent magnet motor

Abstract

The invention discloses an axial disc type permanent magnet motor phase change cooling method and structure. According to the cooling method, the rotation kinetic energy of the rotating shaft in the axial disc type permanent magnet motor is utilized, air flow is generated when the rotating shaft rotates, the air flow is introduced into the rotating shaft and cooled in the rotating shaft through the phase change material, and then the low-temperature air flow enters the air gap between the stator and the rotor, flows through the surface of the stator and the surface of the rotor along the air gap and then returns to the back face of the rotor to be discharged. According to the cooling structure, exhaust holes are formed in a shell of the axial disc type permanent magnet motor, an airflow channel is formed in the rotating shaft, the end, in the rotating shaft, of the airflow channel is communicated with the interior of the rotor, and phase-change materials are arranged in the airflow channel. On the basis of the internal structure of the motor, the temperature of air entering the motor is reduced through the characteristics of the phase change material, the cooling efficiency is improved, and the production cost and the maintenance cost are reduced.

Description

Technical Field

[0001] The invention relates to a method for cooling an axial disk type permanent magnet motor, belonging to the technical field of axial permanent magnet motor cooling. Background Art

[0002] The basic structure of axial disc permanent magnet motor can be found in Figure 3 , including a housing 13, a stator 5, a rotor 4 and a rotating shaft 10. The rotating shaft 10 is installed in the housing through a bearing. The rotating shaft 10 is connected to the rotor 4 through a flange 16 thereon, and one end of the rotating shaft 10 extends out of the housing 13. The rotor is composed of two rotor yokes 9 (two metal plates) and a patch magnetic pole 14 (in a circular ring structure) arranged on the inner side of the rotor yoke 9. When the two rotor yokes 9 move relative to each other in an alternating magnetic field, an electromagnetic force is generated between the two and they attract each other. The stator 5 and the rotor 4 are arranged in the housing 13, the stator 5 is in the rotor 4 (between the two rotor yokes 9), and there is an air gap between the stator 5 and the rotor yokes 9 on both sides. The electrical energy is converted into mechanical energy by generating a magnetic field between the stator 5 and the rotor 4. When the rotor 4 rotates during operation, copper loss, iron loss and eddy current loss will be generated, and the losses will eventually be converted into heat. The purpose of cooling the heat generated by the motor is to reduce the impact of temperature on the stator and rotor permanent magnets. The higher the power of the motor, the greater the temperature rise. A cooling method is needed to prevent the motor from being damaged. The existing cooling methods include natural cooling, air cooling, water cooling, and oil-gas mixed cooling. Different cooling methods have different structural complexity, maintenance costs, and failure points.

[0003] Since the axial permanent magnet motor adopts a closed process, the heat generated is not easy to dissipate. Poor heat dissipation is a problem that needs to be urgently solved for this motor.

[0004] In the prior art, axial permanent magnet motors use external auxiliary cooling air cooling or external circulating cooling water channels. Figure 1 As shown, an external fan 1 is used to force cold air into the motor for heat dissipation. This method is to install the fan on the motor shaft, which not only increases the axial length of the motor, increases additional fan loss, but also reduces the motor efficiency. Figure 2 As shown, it is necessary to cast the cooling water channel 2 in the shell, adopt the molding casting sand core method, fix it in the casting mold, and then take out the sand core after solidification and cooling to form the cooling water channel in the shell. Each casting requires the production of a new molding sand core, which is complex in process, inefficient and low in cost; it is also necessary to add an additional cooling circulation system 3 to provide circulating fluid for the cooling water channel 2, which not only increases the cost of the motor, but also increases the cost of regular maintenance and replacement of the coolant. External circulation cooling There is no industry unified standard for the cooling technology of the existing disc permanent magnet motor, and all refer to the temperature rise index of the radial permanent magnet motor. Summary of the invention

[0005] The present invention aims to solve the problems existing in the prior art of axial permanent magnet motor cooling and provides an axial disc permanent magnet motor phase change cooling method with high cooling efficiency and capable of reducing production cost and maintenance cost. At the same time, an axial disc permanent magnet motor phase change cooling structure for implementing the method is provided.

[0006] The phase change cooling method of the axial disk permanent magnet motor of the present invention is:

[0007] The rotational kinetic energy of the shaft in the axial disk permanent magnet motor is used to generate airflow when the shaft rotates. The airflow is introduced into the shaft and cooled by phase change materials (PCMs) inside the shaft. The low-temperature airflow then enters the air gap between the stator and the rotor, flows along the air gap through the stator surface and the rotor surface, and then returns to the back of the rotor (the side opposite to the inner wall of the casing) to be discharged, thereby releasing the heat inside the motor and achieving the purpose of cooling the heat inside the motor.

[0008] The heat dissipation Q generated when the shaft rotates is determined according to the following formula:

[0009] Q = a(tw-to)F, where Q is the heat dissipation, the unit is w.

[0010] tw is the surface temperature of the heat dissipation surface (i.e. the stator surface and the rotor yoke surface), °C.

[0011] to is the external ambient temperature (air temperature), ℃.

[0012] F is the area of ​​the heat dissipation surface (the stator surface and the rotor yoke surface), m 2 .

[0013] a is the comprehensive heat transfer coefficient, w / (℃×m 2 ).

[0014] The axial disc permanent magnet motor phase change cooling structure implementing the above method adopts the following technical solutions:

[0015] The cooling structure is to set an exhaust hole on the shell of the axial disc permanent magnet motor, set an airflow duct and a phase change material in the rotating shaft, one end of the airflow duct in the rotating shaft is connected with the air gap, and the phase change material is located in the rotating shaft outside the position where the airflow duct and the air gap are connected.

[0016] The airflow duct is in the shape of a round hole, a square hole, a triangular hole or other special-shaped holes.

[0017] The air flow duct is connected to the air gap by arranging a vent hole in the flange connecting the rotating shaft and the rotor.

[0018] Wind grooves are distributed on the inner wall of the airflow duct, and the wind grooves are axial grooves.

[0019] The phase change material is arranged in a closed space in the rotating shaft. The phase change material can be arranged at the bottom end of the airflow duct in the rotating shaft, or on the inner wall of the airflow duct, but cannot block the airflow duct and the vent hole connecting the airflow duct and the air gap.

[0020] When the shaft rotates, the outside air is sucked into the air flow channel inside the shaft, where it exchanges heat with the built-in phase change material to form a low-temperature cold air flow. The cold air flow enters the air gap between the stator and the rotor, flows through the surface of the stator and the rotor, then returns to the back of the rotor and is discharged from the exhaust holes on the outer casing, releasing the heat inside the motor to the outside of the motor.

[0021] Based on the internal structure of the disc permanent magnet motor, the present invention reduces the temperature of the air entering the motor through the characteristics of the phase change material, increases the comprehensive heat transfer coefficient by using the airflow channel, and changes the original non-flowing internal heat into a circulating positive pressure airflow. The comprehensive heat transfer coefficient is increased from the original 10 to about 150, greatly increasing the heat dissipation Q, reducing the working temperature of the motor, improving the cooling efficiency, achieving the rapid release of heat inside the motor, reducing the production cost and maintenance cost, ensuring the normal operation of the motor, and solving the problem that the axial disc permanent magnet motor structure is not easy to dissipate heat. Through testing, the surface temperature of the motor with this structure is about 15 degrees Celsius lower than the surface temperature of the motor without this structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the principle of the external air cooling structure of the existing axial disc permanent magnet motor.

[0023] Figure 2 It is a schematic diagram of the principle of the external circulation cooling structure of the existing axial disc permanent magnet motor.

[0024] Figure 3 It is a schematic diagram of the phase change cooling structure of the axial disc permanent magnet motor in the present invention.

[0025] Figure 4 It is a cross-sectional schematic diagram of the rotor in the cooling structure.

[0026] Figure 5 is a schematic diagram of the air flow channel in the shaft.

[0027] Figure 6 It is a schematic diagram of the air slots distributed on the inner wall of the air flow channel.

[0028] Figure 7 It is a schematic diagram of the heat transfer process of phase change materials.

[0029] In the figure: 1. External fan, 2. External cooling water channel, 3. Cooling circulation system, H. External dimensions of the motor;

[0030] 4. Rotor, 5. Stator, 6. Exhaust hole, 7. Air gap, 8. Phase change material, 9. Rotor yoke, 10. Rotating shaft, 11. Air flow channel, 12. Vent hole, 13. Casing, 14. Magnetic pole, 15. Wind slot, 16. Flange. DETAILED DESCRIPTION

[0031] The axial disc permanent magnet motor phase change cooling structure of the present invention is as follows: Figure 3 , Figure 4 and Figure 5 As shown, specifically, an exhaust hole 6 is provided on the housing, and an airflow duct 11 is provided in the rotating shaft 10. The airflow duct 11 is a blind hole, and the outer end thereof is connected to the atmosphere. The shape of the airflow duct 11 can be a round hole, a square hole, a triangular hole or other special-shaped holes. An axial wind slot 15 is provided on the inner wall of the airflow duct 11 (see Figure 5 and Figure 6 A vent hole 12 connected to the air duct 11 is provided on the flange 16 of the rotating shaft 10 (see Figure 3 and Figure 5 ), the air duct 11 is connected to the air gap 7 through the vent hole 12. The air flow structure is formed by the air duct 11 in the rotating shaft 10, the air duct 12 in the flange 16 and the exhaust hole 6 on the housing 13. Figure 3 The arrow in the middle represents the direction of airflow. The phase change material 8 is arranged in the rotating shaft 10, and the phase change material is in a closed space. Figure 5 The phase change material is at the bottom of the airflow duct 11 and is sealed by the end cover 17. A sealing ring is arranged between the end cover 17 and the rotating shaft so that the phase change material is in a closed cavity. The phase change material 8 can also be arranged on the inner wall of the airflow duct 11, but it cannot block the airflow duct 11 or the vent hole 12 that communicates with the air gap 7.

[0032] The cooling structure performs a partial hollowing process on the interior of the rotating shaft 10 to construct an airflow channel 11. According to aerodynamics, the rotational kinetic energy of the rotating shaft 10 in the motor is utilized to allow external airflow to enter the interior of the motor. When the rotating shaft 10 rotates, air enters through its built-in airflow channel 11, generating negative pressure at the shaft end, sucking the outside air into the airflow channel 11 inside the rotating shaft, forming a wind direction flow, which is guided by the airflow channel 11. When it reaches the inner end of the airflow channel 11, it exchanges heat with the built-in phase change material 8 (the phase change material 8 absorbs heat in the air), forming a low-temperature cold airflow. The cold airflow passes through the radial vents 12 distributed in the flange 16 on the rotating shaft 10 to form a rotating airflow layer (the flange 16 rotates with the rotating shaft 10) and enters the air gap 7 between the stator 5 and the rotor yokes 9 on both sides thereof, forming two airflows that flow along the air gap 7 through the surface of the stator 5 and the surface of the rotor 4, respectively. The airflow reaches the maximum outer diameter of the rotor 4 (the outermost side of the air gap 7) and returns to the back of the rotor 4 (rotor yoke 9), passes through the gap between the rotor 4 and the inner wall of the outer shell 13, and continues to flow to the exhaust hole 6 on the outer shell, and is finally discharged through the exhaust hole 6, releasing the internal heat of the motor to the outside of the motor, realizing the function of rapid heat exchange between the internal heat of the motor and the external cold air, thereby ensuring the normal operation of the motor.

[0033] Phase change material 8 is a prior art, which refers to a smart material that can absorb or release heat when a substance undergoes a phase change while the temperature of the substance itself remains unchanged or changes little. There are many types of phase change materials, and there are many classification methods. According to their phase change mode, they can be divided into gas-liquid, solid-gas, solid-liquid and solid-solid. Among them, solid-liquid can be divided into organic PCMs, inorganic PCMs and eutectic compounds according to their structure. The heat absorption and heat release process of phase change materials is shown in 7. The following table is the specific heat performance of RT70HC

[0034]

[0035] The heat dissipation Q when the shaft 10 rotates is based on the following formula:

[0036] Q = a(tw-to)F, where Q is the heat dissipation, the unit is w.

[0037] tw is the surface temperature of the heat dissipation surface (i.e. the stator surface and the rotor yoke surface), °C.

[0038] to is the external ambient temperature (air temperature), ℃.

[0039] F is the area of ​​the heat dissipation surface (the stator surface and the rotor yoke surface), m 2 .

[0040] a is the comprehensive heat transfer coefficient, w / (℃×m 2 ).

[0041] Through the characteristics of the phase change material 8, the ambient temperature to (external air temperature) entering the interior of the motor (the air flow channel 11 in the rotating shaft 10) is reduced, and the rotating shaft 10, the air flow channel 11 and the wind slot are used to increase the comprehensive heat transfer coefficient a, and the original non-flowing internal heat is converted into a circulating positive pressure airflow. The comprehensive heat transfer coefficient a is increased from the original 10 to about 150, and the heat dissipation Q is greatly improved, thereby reducing the operating temperature of the motor.

[0042] Through testing, it is found that the surface temperature of the motor with this structure is about 15 degrees Celsius lower than the surface temperature of the motor without this structure.

Claims

1. A phase change cooling method for an axial disk permanent magnet motor, characterized in that: The rotational kinetic energy of the shaft in the axial disk permanent magnet motor is used to generate airflow when the shaft rotates. The airflow is introduced into the shaft and cooled by the phase change material inside the shaft. The low-temperature airflow then enters the air gap between the stator and the rotor, flows along the air gap through the stator surface and the rotor surface, and then returns to the back of the rotor for discharge, releasing the heat inside the motor and achieving the purpose of cooling the heat inside the motor.

2. The phase change cooling method of the axial disk permanent magnet motor according to claim 1 is characterized in that: The heat dissipation Q generated when the shaft rotates is determined according to the following formula: Q = a(tw-to)F, where Q is the heat dissipation, the unit is w. tw is the surface temperature of the heat dissipation surface, °C. to is the external ambient temperature, ℃. F is the area of ​​the heat dissipation surface, m 2 . a is the comprehensive heat transfer coefficient, w / (℃×m 2 ).

3. An axial disc permanent magnet motor phase change cooling structure, used to implement the axial disc permanent magnet motor phase change cooling method according to claim 1, characterized in that: An exhaust hole is arranged on the shell of the axial disc permanent magnet motor, an airflow duct and a phase changer are arranged in the rotating shaft, one end of the airflow duct in the rotating shaft is connected with the air gap, and the phase changer is located in the rotating shaft outside the position where the airflow duct and the air gap are connected.

4. The axial disc permanent magnet motor phase change cooling structure according to claim 1 is characterized in that: The airflow duct is in the shape of a round hole, a square hole, a triangular hole or other special-shaped holes.

5. The axial disc permanent magnet motor phase change cooling structure according to claim 1 is characterized in that: The air flow duct is communicated with the air gap inside the motor by arranging a vent hole in a flange connecting the rotating shaft and the rotor of the motor.

6. The axial disc permanent magnet motor phase change cooling structure according to claim 1 is characterized in that: Wind grooves are distributed on the inner wall of the air flow duct.

7. The axial disc permanent magnet motor phase change cooling structure according to claim 1 is characterized in that: The phase change material is arranged in a closed space inside the rotating shaft.

8. The axial disc permanent magnet motor phase change cooling structure according to claim 3 or 7, characterized in that: The phase changer is arranged at the bottom end of the air flow channel in the rotating shaft.

9. The axial disc permanent magnet motor phase change cooling structure according to claim 3 or 7, characterized in that: The phase changer is arranged on the inner wall of the air flow duct.

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