Flywheel energy storage device based on axial flux motor and hybrid magnetic bearing

Abstract

The application belongs to the field of flywheel energy storage, and discloses a flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing, which comprises a shell, a stator assembly fixed in the shell, and a rotor assembly rotatably arranged in the shell and comprising a rotor body and rotor shafts arranged on both sides of the rotor body, wherein the rotor body is arranged axially opposite to the stator assembly, one side of the rotor body is provided with a permanent magnet assembly, and the rotor shafts can axially move within a set range through a mechanical bearing assembly arranged on the shell; an axial magnetic bearing is arranged on the shell, and the axial magnetic bearing can provide an axial magnetic force for the rotor assembly, so that the sum of an axial permanent magnetic biasing force generated between the stator assembly and the rotor assembly and the axial magnetic force is balanced with the gravity of the rotor assembly in the axial direction. The application can solve the problem of improper matching of the axial magnetic suspension force in the current flywheel energy storage device.

Description

Technical Field

[0001] This application belongs to the field of flywheel energy storage, and more specifically, relates to a flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing. Background Technology

[0002] Flywheel energy storage is a highly efficient physical energy storage method. It stores kinetic energy through a high-speed rotating flywheel and converts electrical energy into mechanical energy through a motor. Axial flux motors (also known as disc motors) have shown promising application prospects in flywheel energy storage systems due to their compact structure, high power density, and short axial length.

[0003] However, in existing flywheel energy storage technologies using axial flux motors, some key technical issues remain unresolved, hindering further improvements in their reliability, safety, and performance: The risks and complexity of radial bearing instability: For example, Chinese invention patent application CN113131706A, entitled "Disc Permanent Magnet Synchronous Motor, Energy Storage Flywheel and Method," typically requires the addition of radial magnetic bearings to ensure the dynamic balance of a single-stator, single-rotor disc motor at high speeds and to resist radial electromagnetic forces. While the introduction of radial magnetic bearings solves the problem of non-contact levitation, it also significantly increases the system's control complexity, cost, and potential instability risks. Failure of the magnetic bearing control system could lead to catastrophic consequences. Furthermore, in traditional flywheel devices, the motor system and the magnetic levitation (bearing) system are often independent, resulting in reduced system integration.

[0004] The problem of mismatched axial magnetic levitation force: For a vertical flywheel, its own weight (gravity) is a constant load that must be precisely balanced by the axial levitation force. In existing technologies, whether using pure permanent magnet repulsion or pure electromagnetic force axial bearings, the precise matching between the flywheel's gravity and the static bias force (attraction or repulsion) provided by the axial electromagnetic bearing is often not systematically considered in the early stages of structural design. For example, although the aforementioned patent CN113131706A mentions axial passive magnetic bearings and states that "the attractive force of the upper stator disk on the rotor disk of the motor needs to be less than 1 / 2 times the axial repulsive force of the axial passive magnetic bearing," this is only a passive compensation. Mismatched axial forces can lead to the following problems: either the electromagnetic bearing needs to continuously output a large current to counteract the unbalanced force, increasing losses and heat generation; or, in severe cases, it may even cause axial movement of the flywheel, resulting in friction with the stator and endangering safety.

[0005] Heat dissipation issues: Axial flux motors, especially their stator core and windings, experience significant losses during high-speed, high-frequency operation. Traditional silicon steel sheets produce substantial iron losses at higher operating frequencies, leading to significant temperature rise in the stator yoke. The aforementioned patent CN113131706A proposes a solution using soft magnetic composite material (SMC) and water cooling with slotted magnetic disks at the top. Chinese invention patent application CN118117811A, entitled "A Magnetic Levitation Flywheel Energy Storage Device for Shared Axial Flux in a Motor and Magnetic Bearing System," discloses solutions such as opening heat dissipation holes in the outer casing and adding finned heat dissipation wings. However, these cooling measures are often localized and unsystematic. The flywheel rotor itself also generates heat through friction with the internal rarefied gas during high-speed rotation. If this heat cannot be dissipated promptly and evenly from the core heat-generating components of the entire device (motor stator, rotor, bearings, etc.), it will lead to localized overheating, reduced material performance, increased losses, and even thermal runaway, seriously threatening the long-term reliability and lifespan of the system.

[0006] Addressing the aforementioned issues, particularly how to simplify the system, achieve precise matching of axial forces, and construct an efficient global heat dissipation system while ensuring high reliability, has become a pressing technical challenge in this field. Summary of the Invention

[0007] In view of the deficiencies or improvement needs of the existing technology, this application provides a flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing, which aims to solve the problem of improper axial magnetic levitation force matching in current flywheel energy storage devices.

[0008] The above-mentioned technical objectives of this application are mainly achieved through the following technical solutions.

[0009] This application provides a flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing, comprising: a housing; a stator assembly fixed within the housing, the stator assembly including a stator core and an armature winding wound on the stator core; a rotor assembly rotatably disposed within the housing, the rotor assembly including a rotor body and rotor shafts disposed on both sides of the rotor body, the rotor body being axially opposite to the stator assembly, and a permanent magnet assembly being disposed on the side of the rotor body facing the stator assembly, the rotor shafts being axially movable within a set range via a mechanical bearing assembly disposed on the housing; and an axial magnetic bearing disposed outside the housing, the axial magnetic bearing providing axial magnetic force to the rotor assembly so that the sum of the axial permanent magnet bias force generated between the stator assembly and the rotor assembly and the axial magnetic force is axially balanced with the weight of the rotor assembly.

[0010] The core of this application's technical solution lies in constructing a hybrid axial magnetic bearing. It innovatively reuses the static bias magnetic force generated by the rotor permanent magnets of an axial flux motor, combined with an independent axial magnetic bearing for precise control. The magnetic flux generated by the rotor permanent magnets passes through the air gap, stator core, and armature windings to form a loop, creating an attractive force between the stator core and the rotor permanent magnets. By designing the magnetic energy product, quantity, arrangement, and air gap size of the permanent magnets, this attractive force can be made close to the total weight of the flywheel rotor (rotor assembly). This allows the motor's own magnetic circuit to naturally provide most of the static bias force to balance gravity, achieving "magnetic flux reuse." The axial magnetic bearing generates axial magnetic force on the flywheel rotor. Since the permanent magnet bias force and gravity partially cancel each other out, the axial magnetic bearing only needs to provide the remaining gravity and the force to resist dynamic disturbances to achieve precise and stable levitation of the flywheel rotor at the target position. This improves system efficiency and control stability, and solves the problem of improper axial force matching.

[0011] In a preferred embodiment of this application, the rotor shaft is arranged vertically, and the stator assembly and the axial magnetic bearing are located on the upper and lower sides of the rotor body, respectively. This vertical arrangement allows the rotor's gravity to act axially, facilitating the use of the axial attraction between the stator core and the rotor permanent magnets to balance the gravity. Simultaneously, the axial magnetic bearing, located below, effectively supports the rotor and enables precise control.

[0012] In a preferred embodiment of this application, the axial magnetic bearing is a bidirectional axial electromagnetic bearing, a unidirectional axial electromagnetic bearing, or a permanent magnet repulsion bearing. When the weight of the rotor assembly is greater than 0.8 times the axial permanent magnet bias force and less than 1.2 times the axial permanent magnet bias force, the axial magnetic bearing is the bidirectional axial electromagnetic bearing, which is configured to provide an adjustable axial magnetic attraction or repulsion force to the rotor assembly based on the axial position deviation of the rotor assembly. When the weight of the rotor assembly is less than or equal to 0.8 times the axial permanent magnet bias force, the axial magnetic bearing is the unidirectional axial electromagnetic bearing, which is configured to provide an adjustable axial magnetic attraction force to the rotor assembly based on the axial position deviation of the rotor assembly. When the weight of the rotor assembly is greater than or equal to 1.2 times the axial permanent magnet bias force, the axial magnetic bearing is the permanent magnet repulsion bearing, which provides an axial magnetic repulsion force to the rotor assembly such that the sum of the axial magnetic repulsion force and the axial permanent magnet bias force equals the weight of the rotor assembly. By using differentiated axial magnetic bearings based on the different relationships between the axial permanent magnet bias force and the rotor assembly gravity, the bearings can be made to use the least amount of material, have low losses, and be the most economical.

[0013] When using bidirectional and unidirectional axial electromagnetic bearings to achieve axial suspension support, the electromagnetic bearings can generate a controllable electromagnetic axial force on the flywheel rotor. Displacement sensors detect the axial position of the flywheel rotor in real time, and the controller outputs control current based on the position deviation. Since the permanent magnet bias force and gravity partially cancel each other out, the electromagnetic bearings only need to provide the remaining gravity and dynamic disturbance force to achieve precise and stable suspension of the flywheel rotor at the target position. This "permanent magnet bears the static load, electromagnetic bearings handle fine-tuning" mode further improves system efficiency and control stability, and solves the problem of improper axial force matching.

[0014] In a preferred embodiment of this application, the mechanical bearing assembly includes a mechanical bearing body and an elastic support ring sleeved on the outer periphery of the mechanical bearing body. A support chamber for mounting the mechanical bearing assembly is formed on the housing, and an annular groove is formed on the side wall of the support chamber. When the mechanical bearing assembly is installed in the support chamber, the elastic support ring is located within the annular groove. The elastic support ring absorbs radial vibration and impact, improving the stability and reliability of the system. Simultaneously, a small axial clearance is reserved on the outer ring side of the bearing within the chamber, allowing the bearing to perform a small range of axial movement within the chamber. This increases the tolerance space for magnetic bearing control, ensuring that the bearing can withstand small axial forces or be free from axial forces, and greatly improving bearing life.

[0015] In a preferred embodiment of this application, the housing includes a flywheel sleeve, an upper end cover, and a lower end cover. The flywheel sleeve has a cylindrical structure, and both the upper and lower end covers are end-cover disc structures, respectively fixedly mounted on both ends of the flywheel sleeve by screws. The stator assembly is fixedly mounted on the upper end cover, and the lower end cover has a through hole in its center for the rotor shaft to pass through. The axial magnetic bearing is fixedly mounted on the lower end cover. The upper and lower ends of the rotor shaft are respectively mounted to the upper and lower end covers via mechanical bearing assemblies. This structural design makes the installation, disassembly, and maintenance of each component very convenient. Furthermore, the flywheel sleeve, upper end cover, and lower end cover form a sealed internal space, which is beneficial for maintaining cleanliness and cooling.

[0016] In a preferred embodiment of this application, the upper end cover is provided with an upper end cover flow channel, which is used to introduce a cooling medium to cool the flywheel energy storage device.

[0017] In a preferred embodiment of this application, the flywheel sleeve is provided with a flywheel sleeve flow channel, which is used to introduce a cooling medium to cool the flywheel energy storage device.

[0018] In a preferred embodiment of this application, the lower end cover is provided with a lower end cover flow channel, which is used to introduce a cooling medium to cool the flywheel energy storage device.

[0019] By setting cooling channels in various parts of the housing to form a fully water-cooled structure, the heat generated during the operation of the motor and bearings can be effectively removed, ensuring the system can operate stably for a long time and avoiding excessive temperature rise that could lead to a decline in the performance of the permanent magnet.

[0020] In a preferred embodiment of this application, the upper end cover is provided with a wire hole for wires to pass through. The wire hole facilitates the lead-out of the armature winding wires, enabling the electrical connection of the motor.

[0021] In a preferred embodiment of this application, the bidirectional axial electromagnetic bearing includes a bearing housing, a guide disk, and a first electromagnetic coil disposed within the bearing housing. The bearing housing is located outside the housing and fixedly mounted on the lower end face of the lower end cover. The first electromagnetic coil is fixed inside the bearing housing and located on the upper and lower sides of the guide disk. One end of the rotor shaft passes through the bearing housing and is fixedly connected to the guide disk by screws. The first electromagnetic coil is located on the upper and lower sides of the guide disk. By controlling the direction and magnitude of the current in the upper and lower electromagnetic coils, the attractive or repulsive force on the guide disk can be flexibly adjusted, thereby achieving precise control of the axial position of the rotor assembly.

[0022] In a preferred embodiment of this application, the unidirectional axial electromagnetic bearing includes a second electromagnetic coil. The second electromagnetic coil is located inside the housing and is fixedly mounted on the upper end face of the lower end cover by a coil frame. The rotor body and the second electromagnetic coil are axially vertically opposite each other. The second electromagnetic coil is located on the lower side of the rotor body. By controlling the current of the second electromagnetic coil, the attractive force on the rotor body can be flexibly adjusted, thereby achieving precise control of the axial position of the rotor assembly.

[0023] In a preferred embodiment of this application, the permanent magnet repulsion bearing includes two bearing permanent magnets arranged opposite each other along the axial direction, and the two bearing permanent magnets are respectively fixedly installed on the upper end face of the lower end cover and the lower end face of the rotor body.

[0024] In a preferred embodiment of this application, the flywheel energy storage device further includes a position sensor for detecting the axial position of the rotor assembly. The bidirectional axial electromagnetic bearing and the unidirectional axial electromagnetic bearing are configured to output corresponding electromagnetic axial forces based on the detection data from the position sensor, thereby stabilizing the rotor assembly in an axial equilibrium position. The position sensor monitors the axial position of the rotor in real time, and the controller calculates the required control current based on the position deviation and outputs it to the electromagnetic coil, forming a closed-loop control system to ensure that the rotor assembly is always stable in the set axial equilibrium position.

[0025] In a preferred embodiment of this application, the permanent magnet assembly includes a permanent magnet disk and a plurality of permanent magnets mounted and fixed on the permanent magnet disk. The permanent magnets are arranged at intervals along the circumference according to a predetermined pattern, and the permanent magnet disk is fixedly mounted on the rotor body. The permanent magnets, arranged according to a predetermined pattern, cooperate with the armature windings on the stator core to generate a rotating magnetic field to drive the rotor to rotate, and also generate an axial attractive force to balance the rotor's gravity, thus achieving an organic combination of motor function and magnetic bearing function.

[0026] In a preferred embodiment of this application, the elastic support ring is an O-ring made of rubber or polyurethane. O-rings are simple in structure, low in cost, and have good elasticity, effectively absorbing radial vibrations. Rubber or polyurethane materials possess excellent elasticity and damping properties.

[0027] In summary, compared with the prior art, the technical solutions conceived in this application mainly possess the following technical features and advantages: 1. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing described in this application innovatively reuses the rotor permanent magnet of the axial flux motor to generate static bias magnetic force. It uses the axial attraction between the stator core and the rotor permanent magnet to balance part of the rotor's weight. Combined with independent axial magnetic bearings for axial support, it can achieve precise and stable levitation of the flywheel rotor at the target position, improve system efficiency and control stability, and solve the problem of improper axial force matching.

[0028] 2. The flywheel energy storage device based on an axial flux motor and hybrid magnetic bearings described in this application employs differentiated axial magnetic bearings according to the different relationships between the axial permanent magnet bias force and the gravity of the rotor assembly. This minimizes the material used in the bearings, reduces losses, and maximizes economic efficiency. When using bidirectional and unidirectional axial electromagnetic bearings to achieve axial suspension support, the electromagnetic bearings generate a controllable electromagnetic axial force on the flywheel rotor. Sensors detect the axial position of the flywheel rotor in real time, and the controller outputs control current based on the position deviation. Since the permanent magnet bias force has already offset part of the gravity, the electromagnetic coils within the electromagnetic bearings only need to provide the remaining force and dynamic disturbance force to achieve precise and stable suspension of the flywheel rotor at the target position. This "permanent magnet bears the static load, electromagnetic is responsible for fine-tuning" mode further improves system efficiency and control stability, and solves the problem of improper axial force matching.

[0029] 3. The flywheel energy storage device based on axial flux motor and hybrid magnetic bearing described in this application avoids the complex structure and control system of active radial magnetic bearing by using mechanical bearing assembly as radial support and providing a certain axial floating effect. This significantly reduces system complexity and cost. At the same time, the mechanical bearing has better stability under high-speed conditions, eliminating the risk of instability of active radial magnetic bearing and improving system reliability.

[0030] 4. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing described in this application forms a fully water-cooled structure by setting closed cooling channels inside the upper end cover, flywheel sleeve, and lower end cover. This effectively removes the heat generated during the operation of the motor and bearing, solves the heat dissipation problem during high-speed rotation, ensures stable operation of the system for a long time, and avoids the problem of excessive temperature rise leading to a decrease in the performance of permanent magnets and a reduction in system reliability. Attached Figure Description

[0031] Figure 1 This is a cross-sectional structural schematic diagram of the flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing described in this application; Figure 2 This is a cross-sectional structural schematic diagram of another embodiment of the flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing described in this application; Figure 3 This is a cross-sectional structural schematic diagram of another embodiment of the flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing described in this application; Figure 4 for Figure 1 A magnified view of part A in the middle; Figure 5 This is a schematic diagram of the rotor assembly described in this application; Figure 6 This is a schematic diagram of the magnetic circuit for generating permanent magnet bias by reusing permanent magnets within the rotor assembly described in this application. Figure 7 This is a schematic diagram of the structure of the bidirectional axial electromagnetic bearing described in this application; Figure 8 This is a schematic diagram of the structure of the upper end cover described in this application; Figure 9 This is a schematic diagram of the structure of the flywheel sleeve described in this application; Figure 10 This is a schematic diagram of the structure of the lower end cap described in this application.

[0032] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10. Shell; 11. Upper end cover; 111. Upper end cover body; 112. Upper cover plate; 113. Upper end cover flow channel; 114. Wire hole; 115. Support chamber; 12. Flywheel sleeve; 121. Flow channel ring; 122. Flywheel sleeve flow channel; 13. Lower end cover; 131. Lower end cover body; 132. Lower cover plate; 133. Lower end cover flow channel; 20. Stator assembly; 21. Stator core; 22. Armature winding; 30. Rotor assembly; 31. Rotor body; 32. Rotor shaft; 33. Permanent magnet disk; 34. Permanent magnet; 40. Mechanical bearing body; 41. Elastic support ring; 50. Axial magnetic bearing; 51. Bidirectional axial electromagnetic bearing; 511. Conductor disk; 512. First electromagnetic coil; 52. Unidirectional axial electromagnetic bearing; 521. Second electromagnetic coil; 522. Coil frame; 53. Permanent magnet repulsion bearing; 531. Bearing permanent magnet; 532. Permanent magnet frame. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] The flywheel energy storage device provided in this embodiment includes a housing 10, a stator assembly 20, a rotor assembly 30, a mechanical bearing assembly, and an axial magnetic bearing 50. For example... Figures 1 to 7As shown, the stator assembly 20 is fixed inside the housing 10. The stator assembly 20 includes a stator core 21 and an armature winding 22 wound on the stator core 21. The rotor assembly 30 is rotatably disposed inside the housing 10. The rotor assembly 30 includes a rotor body 31 and rotor shafts 32 disposed on both sides of the rotor body 31. The rotor body 31 is axially opposite to the stator assembly 20, and a permanent magnet assembly is provided on the side of the rotor body 31 facing the stator assembly 20. The rotor shaft 32 can move axially within a set range through a mechanical bearing assembly disposed on the housing 10. An axial magnetic bearing 50 is disposed on the housing 10. The axial magnetic bearing 50 can provide axial magnetic force to the rotor assembly 30 so that the sum of the axial permanent magnet bias force and the axial magnetic force generated between the stator assembly 20 and the rotor assembly 30 is balanced axially with the gravity of the rotor assembly 30.

[0035] By innovatively reusing the rotor permanent magnet of the axial flux motor to generate static bias magnetic force, and using the axial attraction between the stator core 21 and the rotor permanent magnet (permanent magnet assembly) to balance part of the rotor gravity, combined with the axial support of the independent axial magnetic bearing 50, the rotor assembly 30 can be accurately and stably suspended at the target position, which improves the system efficiency and control stability and solves the problem of improper axial force matching.

[0036] The following will describe in detail the specific structure of each part of the flywheel energy storage device described in this application, as well as the position and connection relationship between each part, with reference to the embodiments shown in the accompanying drawings.

[0037] The flywheel energy storage device includes a housing 10, such as Figures 1 to 3 As shown, the housing 10 includes an upper end cover 11, a flywheel sleeve 12, and a lower end cover 13. The flywheel sleeve 12 has a cylindrical structure, and both the upper end cover 11 and the lower end cover 13 are end cover-type disc structures. The two are fixedly installed at the upper and lower ends of the flywheel sleeve 12 by screws, forming a sealed internal space.

[0038] The flywheel energy storage device also includes a stator assembly 20, such as Figure 1 As shown, the stator assembly 20 is housed within the housing 10 and fixedly mounted on the lower side of the upper end cover 11. The stator assembly 20 includes a stator core 21 and an armature winding 22 wound on the stator core 21. The stator core 21 is made of laminated silicon steel sheets and is fixedly mounted on the lower side of the upper end cover 11. The armature winding 22 is a three-phase winding, which generates a rotating magnetic field in the air gap after being energized, driving the rotor assembly 30 to rotate. The upper end cover 11 has three wire holes 114 for wires to pass through, and the wires of the armature winding 22 are led out through the wire holes 114 to achieve electrical connection with the outside.

[0039] The flywheel energy storage device also includes a rotor assembly 30, such as Figure 1As shown, the rotor assembly 30 is rotatably disposed within the housing 10. The rotor assembly 30 adopts an integrated design of motor and flywheel, serving as both a motor rotor and a flywheel rotor. The rotor assembly 30 includes a rotor body 31 and rotor shafts 32 disposed on both sides of the rotor body 31. The rotor shafts 32 are arranged vertically, and the stator assembly 20 and the axial magnetic bearing 50 are located on the upper and lower sides of the rotor body 31, respectively.

[0040] The rotor body 31 has a flywheel disk structure, and a permanent magnet assembly is provided on the side of the rotor body 31 facing the stator assembly 20. For example... Figure 5 As shown, the permanent magnet assembly includes a permanent magnet disk 33 and multiple permanent magnets 34 mounted and fixed on the permanent magnet disk 33. The permanent magnets 34 are arranged at intervals along the circumference according to a preset pattern. Specifically, the permanent magnets 34 are made of neodymium iron boron permanent magnet material and are arranged with alternating N and S poles along the circumference, with adjacent permanent magnets 34 having opposite polarities. The permanent magnet disk 33 is fixedly mounted on the upper surface of the rotor body 31 by screws, and both ends of the rotor shaft 32 are fixedly connected to the rotor body 31.

[0041] The rotor shafts 32 at the upper and lower ends are respectively mounted to the upper end cover 11 and the lower end cover 13 via mechanical bearing assemblies. The mechanical bearing assembly includes a mechanical bearing body 40 and an elastic support ring 41 sleeved around the outer periphery of the mechanical bearing body 40. Support chambers 115 for mounting the mechanical bearing assembly are formed at positions on both the upper end cover 11 and the lower end cover 13 opposite to the axial direction of the rotor shaft 32. An annular groove is formed on the side wall of the support chamber 115. When the mechanical bearing assembly is installed in the support chamber 115, the elastic support ring 41 is located within the annular groove.

[0042] The elastic support ring 41 is an O-ring made of rubber or polyurethane material, possessing excellent elasticity and damping characteristics. It can absorb radial vibration and impact, improving system stability. The mechanical bearing body 40 uses a deep groove ball bearing. The inner ring mates with the rotor shaft 32, and the outer ring is installed in the support chamber 115 via the elastic support ring 41, achieving radial support. Simultaneously, an installation gap is provided between the outer ring and the support chamber 115. Due to the elastic support ring 41, the mechanical bearing body 40 can move axially, allowing the rotor shaft 32 to move axially within a set range via the mechanical bearing assembly. The mechanical bearing body 40 is not limited to deep groove ball bearings; depending on the actual application requirements, angular contact ball bearings, cylindrical roller bearings, and other commonly used mechanical bearing types in this field can also be used.

[0043] By using mechanical bearing assemblies as radial supports while providing a certain degree of axial floating effect, the complex structure and control system of active radial magnetic bearings are avoided, significantly reducing system complexity and cost. At the same time, mechanical bearings have better stability under high-speed conditions, eliminating the risk of instability of active magnetic bearings and improving system reliability.

[0044] The flywheel energy storage device also includes an axial magnetic bearing 50, such as Figures 1 to 3 As shown, the axial magnetic bearing 50 is a bidirectional axial electromagnetic bearing 51, a unidirectional axial electromagnetic bearing 52, or a permanent magnet repulsion bearing 53. The above three types of magnetic bearings are selected according to the relationship between the axial permanent magnet bias force and the gravity of the rotor assembly. By using different axial magnetic bearings 50 according to the relationship between the two, the bearing can use the least amount of material, have low loss, and be more economical.

[0045] When the gravity of rotor assembly 30 is greater than 0.8 times the axial permanent magnet bias force and less than 1.2 times the axial permanent magnet bias force, such as Figure 1 and Figure 7 As shown, the axial magnetic bearing 50 adopts a bidirectional axial electromagnetic bearing 51, which is configured to provide an adjustable axial magnetic attraction or repulsion force to the rotor assembly 30 according to the axial position deviation of the rotor assembly 30.

[0046] Specifically, such as Figure 1 and Figure 7 As shown, the lower end cover 13 has a through hole in its center for the rotor shaft 32 to pass through, and the bidirectional axial electromagnetic bearing 51 is fixedly installed on the lower end face of the lower end cover 13. The bidirectional axial electromagnetic bearing 51 includes a bearing housing, a guide disk 511 and a first electromagnetic coil 512 disposed within the bearing housing. The lower end of the rotor shaft 32 protrudes from the housing 10 and is fixedly connected to the guide disk 511 inside the bidirectional axial electromagnetic bearing 51. The bearing housing is fixedly installed on the lower end face of the housing 10, and the first electromagnetic coil 512 is fixed inside the bearing housing and located on the upper and lower sides of the guide disk 511. The lower end of the rotor shaft 32 passes through the lower end cover 13 and is fixedly connected to the guide disk 511 by screws. The guide disk 511 is made of silicon steel, and the upper and lower electromagnetic coils are respectively the upper electromagnetic coil and the lower electromagnetic coil. By controlling the direction and magnitude of the current in the upper and lower electromagnetic coils, an upward or downward electromagnetic force can be generated on the guide disk 511.

[0047] In this embodiment, the bidirectional axial electromagnetic bearing 51 is installed and fixed on the outside of the housing 10, but this is not a limitation. In another optional embodiment of this application, the bidirectional axial electromagnetic bearing 51 can also be provided inside the housing 10, and the bearing housing is fixedly installed on the upper end surface of the lower end cover 13. At the same time, it is necessary to ensure that the guide disk 511 inside the bidirectional axial electromagnetic bearing 51 is coaxially arranged with the rotor shaft 32 and the two are fixedly connected.

[0048] In this embodiment, the bidirectional axial electromagnetic bearing 51 can generate a controllable electromagnetic axial force (axial magnetic attraction or repulsion) on the rotor assembly 30. A displacement sensor detects the axial position of the rotor assembly 30 in real time, and the controller outputs a control current based on the position deviation. Since the permanent magnet bias force and gravity partially cancel each other out, the first electromagnetic coil 512 within the bidirectional axial electromagnetic bearing 51 only needs to provide the remaining force and dynamic disturbance force to achieve precise and stable levitation of the rotor assembly 30 at the target position. This "permanent magnet bears the static load, electromagnetic coil handles fine-tuning" mode further improves system efficiency and control stability, and solves the problem of improper axial force matching.

[0049] When the gravity of rotor assembly 30 is less than or equal to 0.8 times the axial permanent magnet bias force, such as Figure 2 As shown, the axial magnetic bearing 50 adopts a one-way axial electromagnetic bearing 52, which is configured to provide an adjustable axial magnetic force to the rotor assembly 30 according to the axial position deviation of the rotor assembly 30.

[0050] Specifically, such as Figure 2 As shown, the unidirectional axial electromagnetic bearing 52 includes a second electromagnetic coil 521. The second electromagnetic coil 521 is located inside the housing 10 and is fixedly mounted on the upper end surface of the lower end cover 13 by a coil frame 522. The rotor body 31 is axially and vertically opposite to the second electromagnetic coil 521.

[0051] In this embodiment, the unidirectional axial electromagnetic bearing 52 is installed and fixed inside the housing 10, but this is not a limitation; in another optional embodiment of this application, the unidirectional axial electromagnetic bearing 52 can also be provided outside the housing 10, the second electromagnetic coil 521 is fixedly installed on the upper end surface of the lower end cover 13, and an additional guide disk is fixedly connected to the rotor shaft 32.

[0052] In this embodiment, the unidirectional axial electromagnetic bearing 52 generates a controllable electromagnetic axial force (axial magnetic attraction) on the rotor assembly 30. A displacement sensor detects the axial position of the rotor assembly 30 in real time, and the controller outputs a control current based on the position deviation. Since the permanent magnet bias force exceeds the weight of the rotor assembly 30, the second electromagnetic coil 521 within the unidirectional axial electromagnetic bearing 52 needs to provide the remaining force to balance the permanent magnet bias force and dynamic disturbance force, thereby achieving precise and stable levitation of the rotor assembly 30 at the target position. This "permanent magnet bears the static load, electromagnetic coil is responsible for fine-tuning" mode further improves system efficiency and control stability, and solves the problem of improper axial force matching.

[0053] When the weight of the rotor assembly 30 is greater than or equal to 1.2 times the axial permanent magnet bias force, the axial magnetic bearing 50 adopts a permanent magnet repulsion bearing 53, which provides axial magnetic repulsion to the rotor assembly 30 so that the sum of the axial magnetic repulsion and the axial permanent magnet bias force is equal to the weight of the rotor assembly 30.

[0054] Specifically, such as Figure 3 As shown, the permanent magnet repulsion bearing 53 includes two axially opposed permanent magnets 531, which are respectively fixedly mounted on the upper end face of the lower end cover 13 and the lower end face of the rotor body 31. The upper permanent magnet 531 is embedded in a groove on the lower end face of the rotor body 31, while the lower permanent magnet 531 is mounted on the upper end face of the lower end cover 13 via a permanent magnet bracket. The opposing end faces of the two axially opposed permanent magnets 531 have the same polarity, thereby generating a certain axial magnetic repulsion force.

[0055] In this embodiment, the permanent magnet repulsion bearing 53 is installed and fixed inside the housing 10, but this is not the limitation. In another optional embodiment of this application, the permanent magnet repulsion bearing 53 can also be provided outside the housing 10, with one of the bearing permanent magnets 531 fixedly installed on the upper end face of the lower end cover 13 by means of a permanent magnet frame, and the other bearing permanent magnet 531 fixedly installed on the rotor shaft 32 by means of a permanent magnet frame.

[0056] Furthermore, the flywheel energy storage device also includes a position sensor for detecting the axial position of the rotor assembly 30. The position sensor is an eddy current displacement sensor, mounted on the bearing housing, to detect the axial position of the rotor assembly 30 (guide disk 511) in real time. Both the bidirectional axial electromagnetic bearing 51 and the unidirectional axial electromagnetic bearing 52 are configured to output corresponding electromagnetic axial forces based on the detection data from the position sensor, so as to stabilize the rotor assembly 30 in an axially balanced position.

[0057] like Figure 6 As shown, Figure 1 and Figure 2 The core technical feature of the provided embodiments lies in the working principle of the hybrid axial magnetic bearing, as detailed below.

[0058] An axial permanent magnet bias force is generated between the stator assembly 20 and the rotor assembly 30. This permanent magnet bias force originates from the magnetic attraction between the permanent magnet 34 on the rotor body 31 and the stator core 21.

[0059] Specifically, the magnetic flux generated by the permanent magnet 34 passes through the air gap, stator core 21, and armature winding 22 to form a closed magnetic circuit, generating an axial attraction between the stator core 21 and the permanent magnet 34. By designing the magnetic energy product, number, arrangement, and air gap size of the permanent magnet 34, this axial attraction can be made close to the total weight of the rotor assembly 30, thereby utilizing the motor's own magnetic circuit to naturally provide most of the static bias force to balance the gravity, achieving "magnetic flux reuse". The bidirectional axial electromagnetic bearing 51 or the unidirectional axial electromagnetic bearing 52 provides electromagnetic axial force to the rotor assembly 30 according to the axial position deviation of the rotor assembly 30, so that the sum of the axial permanent magnet bias force and the electromagnetic axial force generated between the stator assembly 20 and the rotor assembly 30 is axially balanced with the weight of the rotor assembly 30.

[0060] During system operation, the position sensor detects the axial position of the rotor assembly 30 in real time, and the controller outputs control current to the first electromagnetic coil 512 or the second electromagnetic coil 521 based on the position deviation. Since the permanent magnet bias force and the rotor assembly 30 have partially canceled each other out, the electromagnetic coil only needs to provide the remaining force and dynamic disturbance force to achieve precise and stable levitation of the rotor assembly 30 at the target position. This mode of "permanent magnets bearing static loads and electromagnetic coils handling fine-tuning" greatly reduces the capacity requirements, current losses, and heat generation of the electromagnetic bearings, and improves system efficiency and control stability.

[0061] According to one embodiment of this application, such as Figures 8 to 10 As shown, in order to solve the system heat dissipation problem, this embodiment has designed sealed water-cooling channels inside the upper end cover 11, flywheel sleeve 12, and lower end cover 13 to form a full water-cooling structure.

[0062] like Figure 8 As shown, the upper end cover 11 includes an upper end cover body 111 and an upper cover plate 112, and an upper end cover flow channel 113 is formed between the upper end cover body 111 and the upper cover plate 112. The upper end cover flow channel 113 is an annular flow channel. The cooling medium enters from the water inlet, circulates along the annular flow channel and is discharged from the water outlet, carrying away the heat generated by the stator assembly 20 during operation.

[0063] like Figure 9 As shown, a flow channel ring 121 is provided inside the flywheel sleeve 12, and a flywheel sleeve flow channel 122 is formed between the flow channel ring 121 and the inner wall of the flywheel sleeve 12. The flywheel sleeve flow channel 122 is arranged in a circumferential direction, and the cooling medium circulates in the flow channel to remove the heat from the outer wall of the flywheel sleeve 12.

[0064] like Figure 10As shown, the lower end cover 13 includes a lower end cover body 131 and a lower cover plate 132, and a lower end cover flow channel 133 is formed between the lower end cover body 131 and the lower cover plate 132. The lower end cover flow channel 133 is an annular flow channel. The cooling medium enters from the water inlet, circulates along the annular flow channel, and is discharged from the water outlet, carrying away the heat generated when the axial magnetic bearing 50 is working.

[0065] The upper end cover flow channel 113, flywheel sleeve flow channel 122 and lower end cover flow channel 133 are connected by pipelines to form a complete cooling circuit. The cooling medium is deionized water or other suitable coolant, which is driven by an external circulation pump to achieve full water cooling heat dissipation.

[0066] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0067] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0069] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing, characterized in that, include: Shell (10); A stator assembly (20) is fixed inside the housing (10), the stator assembly (20) including a stator core (21) and an armature winding (22) wound on the stator core (21); A rotor assembly (30) is rotatably disposed within the housing (10). The rotor assembly (30) includes a rotor body (31) and rotor shafts (32) disposed on both sides of the rotor body (31). The rotor body (31) is axially opposite to the stator assembly (20), and a permanent magnet assembly is provided on the side of the rotor body (31) facing the stator assembly (20). The rotor shafts (32) can move axially within a set range via a mechanical bearing assembly disposed on the housing (10). An axial magnetic bearing (50) is provided on the housing (10), which can provide axial magnetic force to the rotor assembly (30) so that the sum of the axial permanent magnet bias force generated between the stator assembly (20) and the rotor assembly (30) and the axial magnetic force is axially balanced with the gravity of the rotor assembly (30). The axial magnetic bearing (50) is a bidirectional axial electromagnetic bearing (51), a unidirectional axial electromagnetic bearing (52), or a permanent magnet repulsion bearing (53). When the gravity of the rotor assembly (30) is greater than 0.8 times the axial permanent magnet bias force and less than 1.2 times the axial permanent magnet bias force, the axial magnetic bearing (50) adopts the bidirectional axial electromagnetic bearing (51), which is configured to provide an adjustable axial magnetic attraction or repulsion force to the rotor assembly (30) according to the axial position deviation of the rotor assembly (30). When the gravity of the rotor assembly (30) is less than or equal to 0.8 times the axial permanent magnet bias force, the axial magnetic bearing (50) adopts the one-way axial electromagnetic bearing (52), which is configured to provide an adjustable axial magnetic attraction force to the rotor assembly (30) according to the axial position deviation of the rotor assembly (30). When the weight of the rotor assembly (30) is greater than or equal to 1.2 times the axial permanent magnet bias force, the axial magnetic bearing (50) adopts the permanent magnet repulsion bearing (53), which provides axial magnetic repulsion to the rotor assembly (30) so that the sum of the axial magnetic repulsion and the axial permanent magnet bias force is equal to the weight of the rotor assembly (30).

2. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 1, characterized in that, The rotor shaft (32) is arranged in a vertical direction, and the stator assembly (20) and the axial magnetic bearing (50) are located on the upper and lower sides of the rotor body (31), respectively.

3. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 2, characterized in that, The mechanical bearing assembly includes a mechanical bearing body (40) and an elastic support ring (41) sleeved on the outer periphery of the mechanical bearing body (40). A support chamber (115) for installing the mechanical bearing assembly is opened on the housing (10). An annular groove is opened on the side wall of the support chamber (115). When the mechanical bearing assembly is installed in the support chamber (115), the elastic support ring (41) is located in the annular groove.

4. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 1, characterized in that, The housing (10) includes a flywheel sleeve (12), an upper end cover (11), and a lower end cover (13). The flywheel sleeve (12) is a cylindrical structure. The upper end cover (11) and the lower end cover (13) are both end cover-type disc structures, and they are fixedly installed at both ends of the flywheel sleeve (12) by screws. The stator assembly (20) is fixedly installed on the upper end cover (11). The center of the lower end cover (13) has a through hole for the rotor shaft (32) to pass through. The axial magnetic bearing (50) is fixedly installed on the lower end cover (13). The upper and lower ends of the rotor shaft (32) are respectively installed to the upper end cover (11) and the lower end cover (13) through the mechanical bearing assembly.

5. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 4, characterized in that, The upper end cover (11) is provided with an upper end cover flow channel (113); and / or, the flywheel sleeve (12) is provided with a flywheel sleeve flow channel (122); and / or, the lower end cover (13) is provided with a lower end cover flow channel (133); the upper end cover flow channel (113), the flywheel sleeve flow channel (122) and the lower end cover flow channel (133) are all used to introduce cooling medium to cool the flywheel energy storage device.

6. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 4, characterized in that, The bidirectional axial electromagnetic bearing (51) includes a bearing housing, a guide disk (511) and a first electromagnetic coil (512) disposed inside the bearing housing. The bearing housing is located outside the housing (10) and is fixedly installed on the lower end face of the lower end cover (13). The first electromagnetic coil (512) is fixed inside the bearing housing and located on the upper and lower sides of the guide disk (511). One end of the rotor shaft (32) passes through the bearing housing and is fixedly connected to the guide disk (511) by screws. The unidirectional axial electromagnetic bearing (52) includes a second electromagnetic coil (521), which is located inside the housing (10) and is fixedly mounted on the upper end surface of the lower end cover (13) by a coil frame (522). The rotor body (31) and the second electromagnetic coil (521) are axially and vertically opposite to each other. The permanent magnet repulsion bearing (53) includes two bearing permanent magnets (531) arranged opposite each other along the axial direction. The two bearing permanent magnets (531) are respectively fixedly installed on the upper end face of the lower end cover (13) and the lower end face of the rotor body (31).

7. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 1, characterized in that, It also includes a position sensor for detecting the axial position of the rotor assembly (30), and the bidirectional axial electromagnetic bearing (51) and the unidirectional axial electromagnetic bearing (52) are configured to output corresponding electromagnetic axial forces based on the detection data of the position sensor, so as to stabilize the rotor assembly (30) in an axially balanced position.

8. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 1, characterized in that, The permanent magnet assembly includes a permanent magnet disk (33) and a plurality of permanent magnets (34) mounted and fixed on the permanent magnet disk (33). The permanent magnets (34) are arranged at intervals along the circumference according to a preset rule. The permanent magnet disk (33) is fixedly mounted on the rotor body (31).

9. The flywheel energy storage device based on an axial flux motor and a hybrid magnetic bearing according to claim 3, characterized in that, The elastic support ring (41) is an O-ring made of rubber or polyurethane material.

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