Natural air-cooled direct-drive permanent magnet traction motor

Abstract

The application relates to the technical field of electric machines, in particular to a natural air-cooled direct-drive permanent-magnet traction motor, which comprises a rotor assembly, a stator assembly, a transmission end cover, a non-transmission end cover, a transmission end partition plate and a non-transmission end partition plate; the rotor assembly comprises a hollow shaft and a rotor iron core, and the part of the rotor iron core close to the hollow shaft is provided with an axial hole; the transmission end partition plate is connected between the transmission end cover and a transmission end stator pressing ring, and the inner side of the transmission end partition plate is provided with first fan blades; the non-transmission end partition plate is connected between the non-transmission end cover and a non-transmission end stator pressing ring, and the inner side of the non-transmission end partition plate is provided with second fan blades. The natural air-cooled direct-drive permanent-magnet traction motor provided by the application can accelerate the gas flow during work, so that a circulating air passage is formed between the air gap and the axial hole, the heat is dissipated through the inner circular surface of the hollow shaft when the circulating air passage passes through the axial hole, and therefore the direct-drive permanent-magnet traction motor can be applied to rail transit.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a naturally air-cooled direct-drive permanent magnet traction motor. Background Technology

[0002] Most existing rail transit vehicles use AC asynchronous traction motors, which transmit motor torque to wheelsets through gearboxes, couplings, and other transmission mechanisms. This transmission method is mature, but it has many drawbacks, including high noise, low efficiency, high cost, and frequent malfunctions.

[0003] If a direct-drive permanent magnet traction motor is used instead of a traditional AC asynchronous traction motor, the gearbox can be eliminated, and the wheelset can be driven directly, meaning the motor's output torque is directly transmitted to the wheels. This eliminates transmission losses associated with gear drives, reduces noise and maintenance costs, and improves transmission efficiency, thereby achieving overall system energy savings.

[0004] However, when installing direct-drive permanent magnet traction motors in rail transit, firstly, the rotor structure must be completely enclosed to prevent magnetic materials in the cooling air from adsorbing onto the rotor surface when the three-phase input power is cut off. Secondly, due to the vehicle installation method, undercarriage size limits, and operating characteristics, the motor's external dimensions are strictly limited, making it impossible to install cooling structures such as fans. These two factors make heat dissipation design extremely difficult when installing direct-drive permanent magnet traction motors in rail transit. Furthermore, the traction motor requires a very high output torque and torque density, resulting in significant heat generation per unit volume during operation. Therefore, a cooling structure is essential; otherwise, the temperature rise of critical components such as the motor windings, magnets, and bearings will be too high, threatening the safe operation of the motor. All these factors combined severely limit the application of direct-drive permanent magnet traction motors in rail transit. Summary of the Invention

[0005] To overcome the technical shortcomings of existing direct-drive permanent magnet traction motors, which are difficult to apply to rail transit due to heat dissipation issues, this invention provides a naturally air-cooled direct-drive permanent magnet traction motor.

[0006] This invention provides a naturally air-cooled direct-drive permanent magnet traction motor, comprising:

[0007] A rotor assembly includes a hollow shaft and a rotor core, wherein the rotor core is fitted onto the hollow shaft, and a plurality of axial holes are evenly distributed circumferentially on the portion of the rotor core near the hollow shaft.

[0008] A stator assembly includes a stator core and stator pressure rings at both axial ends of the stator core, a drive end stator pressure ring and a non-drive end stator pressure ring, the stator core being sleeved on the outside of the rotor core and forming an air gap, and the stator assembly having a stator natural air cooling structure.

[0009] The transmission end cap is connected to the side of the transmission end stator pressure ring away from the stator core, and the transmission end cap is supported on the transmission end of the hollow shaft by a first bearing assembly.

[0010] The non-drive end cap is connected to the side of the non-drive end stator pressure ring away from the stator core, and the non-drive end cap is supported on the non-drive end of the hollow shaft by a second bearing assembly.

[0011] A transmission end partition is connected between the transmission end cover and the transmission end stator pressure ring to seal one side of the transmission end of the rotor core. The inner side of the transmission end partition is provided with a first fan blade.

[0012] A non-drive end partition is connected between the non-drive end cover and the non-drive end stator pressure ring to seal the non-drive end side of the rotor core. A second fan blade is provided on the inner side of the non-drive end partition.

[0013] Optionally, the transmission end cover is provided with a first air inlet hole, the non-transmission end cover is provided with a second air inlet hole, the outer circular surface of the stator core is provided with a ventilation groove, and multiple ventilation holes are evenly distributed circumferentially on the side wall of the transmission end stator pressure ring and the side wall of the non-transmission end stator pressure ring.

[0014] Optionally, the outer circular surface of the stator core is provided with a plurality of ventilation slots along its axial direction. The ventilation slots are strip-shaped slots, and the two ends of the strip-shaped slots extend to the stator pressure ring at the transmission end and the stator pressure ring at the non-transmission end, respectively.

[0015] Optionally, the strip groove is inclined relative to the motor axis.

[0016] Optionally, the strip groove is rotated 7.5° clockwise relative to the motor axis.

[0017] Optionally, the rotor core near the air gap is provided with axial ventilation holes.

[0018] Optionally, the magnetic circuit structure of the rotor core is a radial V-shaped magnetic circuit.

[0019] Optionally, the number of poles is 12, the number of slots is 72, and the permanent magnet of the rotor core is a four-corner rounded arc structure.

[0020] The technical solution provided by this invention has the following advantages compared with the prior art:

[0021] The natural air-cooled direct-drive permanent magnet traction motor of the present invention has its rotor core enclosed at both ends by transmission end partitions and non-transmission end partitions, forming a completely enclosed rotor structure. This prevents small amounts of magnetic material in the cooling air from adsorbing onto the rotor surface when the three-phase input power is cut off. The shaft is a hollow shaft, and the part of the rotor core near the hollow shaft has an axial hole. An air gap is left between the rotor core and the stator core. Both the transmission end partition and the non-transmission end partition have fan blades on their inner sides. When the stator and rotor rotate relative to each other, the fan blades can accelerate the gas flow in the enclosed cavity of the rotor structure, thereby forming a circulating air path between the air gap and the axial hole. When the circulating air path passes through the axial hole, it dissipates heat through the inner surface of the hollow shaft. This avoids the decrease in heat dissipation capacity caused by the lack of a fan in the enclosed rotor structure, thus enabling the direct-drive permanent magnet traction motor to be used in rail transit. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the airflow structure of the naturally air-cooled direct-drive permanent magnet traction motor according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic cross-sectional view of the rotor core described in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the stator natural air cooling structure described in an embodiment of the present invention.

[0027] in:

[0028] 1. Hollow shaft; 2. Rotor core; 2.1 Axial hole; 2.2 Axial ventilation hole; 3. Stator core; 3.1 Ventilation slot; 4. Stator pressure ring at the drive end; 5. Stator pressure ring at the non-drive end; 6. Air gap; 7. End cover at the drive end; 7.1 First air inlet; 8. First bearing assembly; 9. End cover at the non-drive end; 9.1 Second air inlet; 10. Second bearing assembly; 11. Partition plate at the drive end; 11.1 First fan blade; 12. Partition plate at the non-drive end; 12.1 Second fan blade; 13. Ventilation hole. Detailed Implementation

[0029] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0031] In one embodiment, refer to Figures 1 to 3 The naturally air-cooled direct-drive permanent magnet traction motor includes a rotor assembly, a stator assembly, a drive end cover 7, a non-drive end cover 9, a drive end partition 11, and a non-drive end partition 12. The rotor assembly includes a hollow shaft 1 and a rotor core 2. The rotor core 2 is mounted on the hollow shaft 1, and the portion of the rotor core 2 near the hollow shaft 1 has multiple axial holes 2.1 evenly distributed circumferentially. The stator assembly includes a stator core 3 and drive end stator retaining rings 4 and non-drive end stator retaining rings 5 ​​located at both axial ends of the stator core 3. The stator core 3 is fitted around the outside of the rotor core 2 and forms an air gap 6. The stator assembly has a stator natural air-cooling structure. The drive end cover 7 is connected to the side of the drive end stator retaining ring 4 away from the stator core 3, and the drive end cover 7 is supported on the drive end of the hollow shaft 1 by a first bearing assembly 8. The non-drive end cover 9 is connected to the side of the non-drive end stator pressure ring 5 away from the stator core 3. The non-drive end cover 9 is supported on the non-drive end of the hollow shaft 1 by the second bearing assembly 10. The drive end partition 11 is connected between the drive end cover 7 and the drive end stator pressure ring 4 to close the drive end side of the rotor core 2. The inner side of the drive end partition 11 is provided with a first fan blade 11.1. The non-drive end partition 12 is connected between the non-drive end cover 9 and the non-drive end stator pressure ring 5 to close the non-drive end side of the rotor core 2. The inner side of the non-drive end partition 12 is provided with a second fan blade 12.1.

[0032] As is easily understood, the axial hole 2.1 is located in the part of the rotor core 2 near the hollow shaft 1. Its main purpose is to reduce the distance heat travels from the axial hole 2.1 to the inner circle of the hollow shaft 1, thereby improving heat dissipation efficiency. If the axial hole 2.1 is too far from the hollow shaft 1, the heat dissipation efficiency will be low; if the axial hole 2.1 is too close to the hollow shaft 1, it will affect the structural rigidity of the rotor laminations. The specific distance depends on factors such as the actual lamination size and shaft size, which is easily designed by those skilled in the art.

[0033] Specifically, the stator's natural air-cooling structure is as follows: the drive end cover 7 has a first air inlet 7.1, the non-drive end cover 9 has a second air inlet 9.1, the outer surface of the stator core 3 has a ventilation groove 3.1, and multiple ventilation holes 13 are evenly distributed circumferentially on the side walls of both the drive end stator pressure ring 4 and the non-drive end stator pressure ring 5. During vehicle operation, the traction motor drive end forms two air paths: the first path, where the traveling air enters through the first air inlet 7.1 and exits through the ventilation holes 13 of the drive end cover 7 (opposite to the traveling direction); the second path, where the traveling air enters through the ventilation holes 13 of the drive end cover 7 (above) and exits through the ventilation holes 13 of the drive end cover 7 (opposite to the traveling direction). The non-drive end of the traction motor follows the same pattern, which will not be elaborated here. The stator core 3 forms a natural air path at the ventilation groove 3.1, dissipating heat through the traveling air.

[0034] More specifically, the outer circumferential surface of the stator core 3 has multiple ventilation slots 3.1 distributed along its axial direction. Each ventilation slot 3.1 is a strip-shaped slot, with both ends extending along its length to the stator pressure ring 4 at the drive end and the stator pressure ring 5 at the non-drive end, respectively. This structure of ventilation slots 3.1 only requires multiple notches to be made circumferentially along the edge of each stator lamination; this structure is formed by stacking the stator laminations. It is relatively easy to manufacture, and the heat dissipation range covers the entire axial direction of the stator core 3, resulting in better heat dissipation. Of course, as an alternative implementation, multiple ventilation slots 3.1 can also be irregularly formed on the outer circumferential surface of the stator core 3.

[0035] Furthermore, when the ventilation slot 3.1 is configured as the aforementioned strip-shaped slot, the strip-shaped slot is inclined relative to the motor axis, i.e., not parallel to the motor axis. This creates a natural airflow path while also reducing harmonics, stray losses, and additional torque. Specifically, the strip-shaped slot is rotated 7.5° clockwise relative to the motor axis.

[0036] It should be noted that the above-described stator natural air cooling structure is only one specific structure in this embodiment. As an alternative implementation, the stator natural air cooling structure can also adopt other structures commonly used in the art, such as eliminating the ventilation holes 13 on the stator pressure ring 4 at the drive end and the stator pressure ring 5 at the non-drive end, and distributing multiple circumferentially arranged through holes evenly along the circumference on the stator core 3 to achieve the purpose of natural air cooling.

[0037] Specifically, both the first bearing assembly 8 and the second bearing assembly 10 include bearings, bearing covers, bearing limiting structures, etc., which are existing technologies and will not be described in detail here.

[0038] As is easily understood, both the drive end partition 11 and the non-drive end partition 12 are annular. Specifically, one end of the drive end partition 11 / non-drive end partition 12 is fixed to the corresponding end cover with screws, facilitating the disassembly and assembly of the end cover, while the other end is connected to the corresponding stator pressure ring via an annular sealing ring. Of course, as an alternative implementation, the other end of the drive end partition 11 / non-drive end partition 12 can also be connected to the corresponding stator pressure ring with screws; or other fixing methods such as clips or adhesive can be used instead of screws in any of the aforementioned solutions.

[0039] It should be noted that the first fan blade 11.1 or the second fan blade 12.1 is fixed, for example, a cast fan blade. It does not rotate on its own, but because of the rotation of the rotor structure itself, the fan blade and the rotor structure will rotate, which can accelerate the gas flow, hence the name fan blade.

[0040] In this embodiment, the natural air-cooled direct-drive permanent magnet traction motor has its rotor core 2 enclosed at both ends by a transmission end partition 11 and a non-transmission end partition 12, forming a completely enclosed rotor structure. This prevents small amounts of magnetic material in the cooling air from adsorbing onto the rotor surface when the three-phase input power is cut off. The shaft is a hollow shaft 1, and the part of the rotor core 2 near the hollow shaft 1 has an axial hole 2.1. An air gap 6 is left between the rotor core 2 and the stator core 3. Fan blades are provided on the inner side of the transmission end partition 11 and the non-transmission end partition 12. When the stator and rotor rotate relative to each other, the fan blades can accelerate the gas flow in the enclosed cavity of the rotor structure, thereby forming a circulating air path between the air gap 6 and the axial hole 2.1. When the circulating air path passes through the axial hole 2.1, it dissipates heat through the inner circular surface of the hollow shaft 1. This avoids the decrease in heat dissipation capacity caused by the lack of a fan in the enclosed rotor structure, thus enabling the direct-drive permanent magnet traction motor to be used in rail transit.

[0041] In some embodiments, the rotor core 2 is provided with axial ventilation holes 2.2 near the air gap 6.

[0042] Specifically, the axial ventilation holes 2.2 are provided in multiple sizes and are evenly distributed along the circumference.

[0043] In these embodiments, the axial ventilation hole 2.2 and the axial hole 2.1 form a new circulating air path, thereby improving the heat dissipation efficiency of the rotor.

[0044] In some embodiments, the magnetic circuit structure of the rotor core 2 is a radial V-shaped magnetic circuit. By varying the angle of the V-shaped slots, the utilization rate of the permanent magnets in the rotor is improved, the magnetic field distribution of the permanent magnets is made more reasonable, the cogging effect is weakened, and the motor torque output is made stable.

[0045] In some embodiments, the number of poles is 12 and the number of slots is 72, and the permanent magnet of the rotor core 2 has a four-corner rounded arc structure. The four-corner rounded arc design of the rotor permanent magnet can effectively reduce cogging torque, thereby reducing vibration and noise; at the same time, the combination of 12 poles and 72 slots can eliminate the 1st, 2nd, 3rd, 4th and 5th order radial force waves in the operating frequency range of the inner surface of the motor stator core 3, generating only the low-order 6th order radial force wave, which significantly reduces the electromagnetic vibration noise of the motor.

[0046] The above are merely specific embodiments of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A natural air-cooled direct-drive permanent-magnet traction motor, characterized in that, include: The rotor assembly includes a hollow shaft (1) and a rotor core (2), wherein the rotor core (2) is mounted on the hollow shaft (1), and the portion of the rotor core (2) near the hollow shaft (1) has a plurality of axial holes (2.1) evenly distributed circumferentially. The stator assembly includes a stator core (3) and a drive end stator pressure ring (4) and a non-drive end stator pressure ring (5) located at both ends of the axial direction of the stator core (3). The stator core (3) is sleeved on the outside of the rotor core (2) and forms an air gap (6). The stator assembly is provided with a stator natural air cooling structure. The transmission end cap (7) is connected to the side of the transmission end stator pressure ring (4) away from the stator core (3). The transmission end cap (7) is supported on the transmission end of the hollow shaft (1) by the first bearing assembly (8). The non-drive end cap (9) is connected to the side of the non-drive end stator pressure ring (5) away from the stator core (3), and the non-drive end cap (9) is supported on the non-drive end of the hollow shaft (1) by the second bearing assembly (10). A transmission end partition (11) is connected between the transmission end cover (7) and the transmission end stator pressure ring (4) to seal one side of the transmission end of the rotor core (2). The inner side of the transmission end partition (11) is provided with a first fan blade (11.1). The non-drive end partition (12) is connected between the non-drive end cover (9) and the non-drive end stator pressure ring (5) to seal the non-drive end side of the rotor core (2). The inner side of the non-drive end partition (12) is provided with a second fan blade (12.1). When the stator assembly and the rotor assembly rotate relative to each other, the fan blades can accelerate the gas flow in the closed cavity of the rotor structure, thereby forming a circulating air path between the air gap (6) and the axial hole (2.1). When the circulating air path passes through the axial hole (2.1), it dissipates heat through the inner circular surface of the hollow shaft (1).

2. The naturally air-cooled direct-drive permanent magnet traction motor according to claim 1, characterized in that, The transmission end cap (7) is provided with a first air inlet (7.1), the non-transmission end cap (9) is provided with a second air inlet (9.1), the outer circular surface of the stator core (3) is provided with a ventilation groove (3.1), and multiple ventilation holes (13) are evenly distributed circumferentially on the side wall of the transmission end stator pressure ring (4) and the side wall of the non-transmission end stator pressure ring (5).

3. The natural wind-cooling direct-drive permanent-magnet traction motor according to claim 2, characterized in that, The outer circular surface of the stator core (3) is provided with a plurality of ventilation slots (3.1) along its axial direction. The ventilation slots (3.1) are strip-shaped slots, and the two ends of the strip-shaped slots extend to the stator pressure ring (4) at the transmission end and the stator pressure ring (5) at the non-transmission end, respectively.

4. The natural wind-cooling direct-drive permanent-magnet traction motor according to claim 3, characterized in that, The strip groove is inclined relative to the motor axis.

5. The natural wind-cooling direct-drive permanent-magnet traction motor according to claim 4, characterized in that, The strip groove is rotated 7.5° clockwise relative to the motor axis.

6. The natural wind-cooling direct-drive permanent-magnet traction motor according to claim 1, characterized in that, The rotor core (2) near the air gap (6) is provided with an axial ventilation hole (2.2).

7. The natural wind-cooling direct-drive permanent-magnet traction motor according to any one of claims 1 to 6, characterized in that, The magnetic circuit structure of the rotor core (2) is a radial V-shaped magnetic circuit.

8. The natural wind-cooling direct-drive permanent-magnet traction motor according to any one of claims 1 to 6, characterized in that, The rotor core (2) has 12 poles and 72 slots, and the permanent magnets of the rotor core (2) are four-cornered rounded arc structures.

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