Magnetic suspension and air suspension hybrid bearing system and rotor structure and control method thereof

Abstract

The invention discloses a magnetic suspension and air suspension hybrid bearing system and a rotor structure and a control method thereof, and relates to the technical field of fans, and the system comprises a permanent magnet biased rotor structure, a stator core, a magnet exciting coil and an air dynamic pressure foil bearing assembly. The foil of the bearing assembly is made of a magnetic conductive material, so that the foil and the magnet exciting coil share the same radial air gap, and the air gap serves as a magnetic field channel and a dynamic pressure air film space at the same time. According to the operation control method, based on a rotating speed signal, magnetic suspension bearing is achieved through the magnet exciting coil in the starting and low-speed stages, and gas film complete bearing is switched in the high-speed stage. Through structure fusion and time-sharing control, the problem of magnetic circuit shielding is solved, the advantages of magnetic suspension friction-free starting and stopping and high speed and high efficiency of an air floating bearing are integrated, the state monitoring function is achieved, the system is compact and reliable, and the cost is optimized.

Description

Technical Field

[0001] This invention relates to the field of wind turbine technology, and in particular to a magnetic levitation-air levitation hybrid bearing system and its rotor structure and control method. Background Technology

[0002] Magnetic levitation bearings and pneumatic foil bearings are two advanced non-contact bearing technologies, each with distinct characteristics. Magnetic levitation bearings achieve rotor levitation through actively controlled electromagnetic force, offering advantages such as frictionless operation, high precision, and active vibration suppression. However, their systems are complex, manufacturing costs are high, and they require additional bearing protection and power-off safety measures. In contrast, pneumatic foil bearings rely on the air film pressure generated by the rotor's high-speed rotation for support. They are simple in structure, low in cost, highly reliable, and require no complex control system. However, they experience solid-state contact friction during start-up, shutdown, and low-speed phases, leading to wear, and their load-bearing capacity and stiffness are generally lower than those of magnetic levitation bearings.

[0003] To balance cost and performance, attempts have emerged in this field to combine two types of bearings. Existing hybrid approaches primarily involve arranging magnetic levitation bearings and air bearings side-by-side axially, each undertaking support tasks under different operating conditions. However, this simple physical combination has significant drawbacks: firstly, the two sets of bearings independently occupy axial space, resulting in a long axial dimension and a non-compact structure; secondly, there is complex dynamic coupling between the two sets of bearings, making control difficult; most importantly, this combination fails to resolve a fundamental contradiction—the metal foil in the air-dynamic foil bearing severely obstructs the magnetic field of the magnetic levitation bearing, and placing both in the same radial space leads to a sharp decrease in magnetic circuit efficiency or even failure. Therefore, existing technologies lack a solution that can deeply and efficiently integrate the principles of the two bearings in both physical space and control logic. Summary of the Invention

[0004] Objective of the Invention: The objective of this invention is to provide a magnetic levitation-air levitation hybrid bearing system, its rotor structure, and control method. By employing permanent magnet rings arranged in a Halbach array, the magnetic field strength on the working air gap side is significantly enhanced. Combined with a uniquely designed magnetic short-circuit isolation slot on the rotor shaft, the magnetic field is effectively constrained, preventing its axial diffusion from interfering with adjacent components or generating eddy current losses. This core rotor design provides crucial hardware assurance for the efficient realization of the magnetic levitation function and the stable operation of the entire hybrid system.

[0005] Technical solution:

[0006] A permanent magnet biased rotor structure for a hybrid magnetic levitation and air levitation bearing includes:

[0007] The rotor spindle has an annular mounting groove machined on its outer cylindrical surface;

[0008] A permanent magnet ring is embedded in the annular mounting groove. The permanent magnet ring is composed of multiple circumferentially magnetized fan-shaped permanent magnets arranged in a Halbach array.

[0009] A sheath layer that covers the outer surface of the permanent magnet ring;

[0010] The rotor spindle has magnetic short-circuit isolation grooves on both sides of the annular mounting groove.

[0011] Furthermore, the depth h of the annular mounting groove satisfies: 0.1R ≤ h ≤ 0.2R, where R is the radius of the rotor spindle.

[0012] Furthermore, the sheath layer is wrapped around the permanent magnet ring by an interference fit process, and radial preload is applied to the permanent magnet ring.

[0013] Furthermore, the outer surface of the sheath layer is coated with a molybdenum disulfide solid lubricant coating.

[0014] This invention also discloses a magnetic levitation-air levitation hybrid bearing system, comprising:

[0015] The aforementioned permanent magnet biased rotor structure;

[0016] The stator core is coaxially arranged with the permanent magnet biased rotor structure and forms a radial air gap with the outer surface of the sheath layer;

[0017] An excitation coil is disposed on the stator core;

[0018] An air-dynamic foil bearing assembly is provided at the radial air gap, wherein the foil of the air-dynamic foil bearing assembly is made of a magnetically conductive material;

[0019] The radial air gap serves as both a magnetic field channel and a dynamic pressure air film space.

[0020] Furthermore, it also includes a Hall sensor array disposed on the stator core for monitoring the magnetic field distribution in the radial air gap.

[0021] This invention also discloses an operation control method for the above-mentioned magnetic levitation-air levitation hybrid bearing system, comprising the following steps:

[0022] S1. During the start-up phase, power is supplied to the excitation coil to make the rotor magnetically levitate and drive the rotor to rotate to the first preset speed.

[0023] S2. During the switching phase, when the rotational speed exceeds the first preset speed, the excitation coil current is reduced to increase the proportion of air film bearing; when the rotational speed reaches the second preset speed, the current is cut off so that the rotor is completely carried by the air film.

[0024] S3, during the deceleration phase, when the speed drops to the second preset speed, the excitation coil is powered back to supply power, allowing the magnetic levitation to assist in the load until it stops.

[0025] Furthermore, the first preset speed is the speed at which the aerodynamic pressure effect begins to occur, and the second preset speed is the speed at which the air film can fully and stably bear the rated load of the rotor.

[0026] Furthermore, during the switching and deceleration phases, the current of the excitation coil is adjusted in a closed loop based on the changes in the magnetic field distribution monitored by the Hall sensor array.

[0027] Furthermore, during the deceleration phase, if the rotor vibration acceleration is detected to exceed the threshold, the excitation coil current is immediately restored to the starting value and an alarm is triggered.

[0028] Beneficial effects:

[0029] 1. By employing permanent magnet rings arranged in a Halbach array, the magnetic field strength on the working air gap side is significantly enhanced. Combined with a uniquely designed magnetic short-circuit isolation slot on the rotor shaft, the magnetic field is effectively constrained, preventing its axial diffusion from interfering with adjacent components or generating eddy current losses. This core rotor design provides crucial hardware support for the efficient realization of the magnetic levitation function and the stable operation of the entire hybrid system.

[0030] 2. By using magnetically conductive materials to manufacture the air bearing foil, the foil is transformed from a magnetic field barrier into part of the magnetic circuit, successfully resolving the core contradiction of the magnetic field being blocked by mechanical components in a shared radial air gap. This allows magnetic levitation and aerodynamic levitation principles to work collaboratively in the same space, achieving true technological integration.

[0031] 3. The integrated shared air gap design makes the system structure very compact. Utilizing a "time-sharing" control strategy, magnetic levitation is used to avoid wear during start-up and shutdown phases, while air-bearing bearings are used only during high-speed phases to save energy. This significantly optimizes the system's manufacturing cost and operating efficiency while ensuring high reliability.

[0032] 4. The intelligent control method based on real-time signals can automatically and smoothly switch between two support modes, and immediately activate protection in abnormal situations to prevent rotor drop damage, greatly improving the safety and service life of the system. Attached Figure Description

[0033] Figure 1 This is a perspective view of the magnetic levitation and air-floating hybrid bearing system of the present invention;

[0034] Figure 2 This is a perspective view of the permanent magnet biased rotor structure of the present invention;

[0035] Figure 3 This is a cross-sectional perspective view of the permanent magnet biased rotor structure of the present invention;

[0036] Figure 4 This is a schematic diagram of the installation of the magnetic levitation and air-floating hybrid bearing system of the present invention on a wind turbine;

[0037] Figure 5 This is an enlarged schematic diagram of the installation of the magnetic levitation and air-floating hybrid bearing system of the present invention on a wind turbine. Detailed Implementation

[0038] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] like Figure 1-5 As shown, a permanent magnet biased rotor structure for a hybrid magnetic levitation / air levitation bearing includes:

[0041] The rotor spindle 1 has an annular mounting groove 11 machined on its outer circular surface;

[0042] The permanent magnet ring 2 is embedded in the annular mounting groove 11. The permanent magnet ring 2 is composed of multiple circumferentially magnetized sector-shaped permanent magnets arranged in a Halbach array. Using a Halbach array arrangement enhances the magnetic field strength generated by the permanent magnet ring 2 on the working air gap side and weakens it on the inner side of the rotor main shaft 1, thereby concentrating the magnetic flux towards the working air gap and improving the efficiency of magnetic levitation. Simultaneously, the magnetic field waveform generated by this array is more sinusoidal, which is beneficial for improving control accuracy.

[0043] The sheath layer 4 covers the outer surface of the permanent magnet ring 2. The main function of the sheath layer 4 is to withstand the huge centrifugal force acting on the permanent magnet ring 2 during high-speed rotation, preventing it from flying off and failing. The sheath layer 4 is usually made of high-strength materials such as carbon fiber composite material or Inconel high-temperature alloy, and it is tightly bonded to the permanent magnet ring 2 through a specific assembly process.

[0044] The rotor spindle 1 has magnetic short-circuit isolation grooves 13 on both sides of the annular mounting groove 11. The magnetic short-circuit isolation grooves 13 are key structures that prevent the permanent magnet magnetic field from spreading along the axial direction of the rotor spindle 1. The principle is to create an annular air gap or fill it with non-magnetic material on the magnetically conductive rotor spindle 1, thereby significantly increasing the magnetic resistance of this path. This forces the magnetic field generated by the permanent magnet ring 2 to concentrate through the designed working air gap, effectively preventing the magnetic field from leaking to the bearings or seals at both ends of the spindle, and avoiding unnecessary eddy current losses and electromagnetic interference.

[0045] Furthermore, the depth h of the annular mounting groove 11 satisfies: 0.1R ≤ h ≤ 0.2R, where R is the radius of the rotor spindle 1. This design ratio achieves the optimal engineering balance between magnetic field strength and spindle stiffness. When the depth is less than 0.1R, the magnetic flux of the permanent magnet is insufficient, and the levitation force is limited; when the depth is greater than 0.2R, the spindle cross-section is excessively weakened, and the bending and torsional strength at high speeds decreases significantly, affecting operational safety.

[0046] Furthermore, the sheath layer 4 is wrapped around the permanent magnet ring 2 using an interference fit process, and a radial preload is applied to the permanent magnet ring 2. The interference fit process involves first heating and expanding the sheath layer 4, then fitting it over the permanent magnet ring 2, and finally allowing it to shrink upon cooling, thereby generating a continuous radial preload. This preload can counteract the centrifugal tensile stress experienced by the permanent magnet ring 2 during high-speed rotation and ensure that the permanent magnet ring 2 and the rotor shaft 1 maintain a stable unity under complex operating conditions.

[0047] Furthermore, the outer surface of the sheath layer 4 is coated with a molybdenum disulfide solid lubricant coating. This molybdenum disulfide solid lubricant coating provides a critical safety redundancy for the hybrid bearing system. In the event of system malfunctions, such as sudden failure of the aerodynamic film or contact during start-up and shutdown, this coating provides emergency lubrication between the sheath layer 4 and the foil bearing, preventing seizure or severe wear due to dry friction, and significantly improving the system's fault tolerance.

[0048] Example 2

[0049] like Figure 1 As shown, a magnetic levitation-air levitation hybrid bearing system includes:

[0050] The aforementioned permanent magnet biased rotor structure;

[0051] The stator core 5 is coaxially arranged with the permanent magnet biased rotor structure and forms a radial air gap with the outer surface of the sheath layer 4. The stator core 5 is made of stacked silicon steel sheets with high magnetic permeability and constitutes the main part of the magnetic circuit. A precise radial air gap is formed between its inner circular surface and the outer circular surface of the rotor sheath layer 4. This air gap is the physical space shared by the magnetic levitation magnetic field and the air dynamic pressure film. Its dimensional uniformity and stability directly determine the overall performance of the system.

[0052] The excitation coil 6 is mounted on the stator core 5. The excitation coil 6 is embedded in the slots of the stator core 5. When a controllable current is applied, it generates a control magnetic field that superimposes on or cancels the bias magnetic field of the permanent magnet ring 2. By adjusting the current of multiple excitation coils 6 in real time, electromagnetic forces in any direction can be synthesized, thereby achieving active and precise control of the rotor's radial position, ensuring its stable suspension at the center.

[0053] A pneumatic foil bearing assembly 7 is located at the radial air gap. The foil of the pneumatic foil bearing assembly 7 is made of a magnetically conductive material. The pneumatic foil bearing assembly 7 is fixed to the inner surface of the stator core 5 and typically consists of a corrugated foil providing elasticity and a top foil forming the air film surface. The top foil is made of a soft magnetic alloy strip with high magnetic permeability, which is the core for achieving deep integration of magnetic and air levitation. The magnetically conductive top foil provides a low magnetic reluctance path for the control magnetic field generated by the excitation coil 6, allowing the magnetic field to efficiently pass through the air gap and act on the rotor, thus solving the technical contradiction of mechanical foil obstructing the magnetic circuit.

[0054] The radial air gap serves as both a magnetic field channel and a dynamic pressure film space. This shared air gap is one of the core features of this invention. For magnetic levitation, the air gap is the medium for the magnetic field; for air bearings, the rotor rotation draws gas into the wedge-shaped air gap to form a dynamic pressure film. These two physical processes work collaboratively within the same space without interference. Magnetic levitation handles start-up, shutdown, and low-speed stability, while the dynamic pressure film provides primary support at high speeds, achieving a high degree of structural integration and perfect functional complementarity.

[0055] Furthermore, the system includes a Hall sensor array mounted on the stator core 5 to monitor the magnetic field distribution in the radial air gap. The Hall sensor array is typically installed on the teeth or yoke of the stator core 5 for non-contact, real-time monitoring of the magnetic field intensity distribution in the radial air gap. This magnetic field distribution directly reflects the instantaneous positional eccentricity of the rotor. This signal is fed back to the control system for closed-loop control of the magnetic levitation. Simultaneously, abnormal distortion patterns in the magnetic field distribution can also be used to diagnose rotor imbalance, misalignment, or early mechanical faults. The installation of Hall sensors is a common technique in existing magnetic levitation fans and will not be elaborated upon here.

[0056] Example 3

[0057] This invention also discloses an operation control method for the above-mentioned magnetic levitation-air levitation hybrid bearing system, comprising the following steps:

[0058] S1. During the startup phase, power is supplied to the excitation coil 6 to magnetically levitate the rotor and drive it to rotate to the first preset speed. During startup, the system relies entirely on active magnetic levitation to stably support the rotor at the center, achieving true zero-contact startup. At this time, the drive motor gradually increases the rotor's speed until it reaches the first preset speed. This phase completely avoids the frictional wear of traditional air-bearing bearings at low speeds.

[0059] S2. During the switching phase, when the rotational speed exceeds the first preset speed, the excitation coil current is reduced, increasing the proportion of air film load. When the rotational speed reaches the second preset speed, the current is cut off, allowing the rotor to be fully supported by the air film. As the rotational speed exceeds the first preset speed, an effective dynamic pressure air film begins to form in the air gap between the rotor and the foil bearing assembly 7, generating load-bearing capacity. The control system smoothly reduces the current of the excitation coil 6 according to a predetermined algorithm, gradually transferring the load-bearing task to the air film. When the rotational speed reaches a higher second preset speed, the air film can completely and stably support the rotor load. At this point, the current of the excitation coil 6 can be completely cut off, and the system enters a high-efficiency mode of pure air-floating operation.

[0060] S3, during the deceleration phase, when the speed drops to the second preset speed, power is restored to the excitation coil, allowing magnetic levitation to assist in bearing until the rotor stops. During deceleration or normal shutdown, when the speed returns to the second preset speed, the air film bearing capacity begins to decrease. The control system immediately restores power to the excitation coil 6, allowing magnetic levitation to re-engage and provide auxiliary support, ensuring the rotor decelerates smoothly until it comes to a complete stop. This effectively prevents rotor-bearing contact caused by the disappearance of the air film in the low-speed range.

[0061] Furthermore, the first preset speed is the speed at which the aerodynamic pressure effect begins to occur, and the second preset speed is the speed at which the air film can fully and stably bear the rated load of the rotor. The first preset speed N1 is usually low, corresponding to the critical point at which the air film effect can just begin. The second preset speed N2 is higher and needs to be determined through calculation and experimentation to ensure that at this speed, the stiffness and load-bearing capacity of the air film are sufficient to independently and stably support the rotor assembly and meet the operating requirements. N1 and N2 constitute the transition zone for the coordinated operation of magnetic levitation and air-bearing bearings.

[0062] Furthermore, during the switching and deceleration phases, the current of the excitation coil 6 is adjusted in a closed loop based on the changes in the magnetic field distribution monitored by the Hall sensor array. In the dynamic process of mode switching, relying solely on rotational speed is insufficient. The magnetic field signal monitored in real time by the Hall sensor array directly reflects the rotor's minute displacement. The control system uses this as feedback to dynamically adjust the current decay or recovery curve of the excitation coil 6, achieving precise guidance of the rotor trajectory, ensuring absolute smoothness during the transfer of support force, and avoiding vibration or impact.

[0063] Furthermore, during the deceleration phase, if the rotor vibration acceleration exceeds the threshold, the excitation coil current is immediately restored to the starting value and an alarm is triggered. This provision provides active safety protection for the system. During the deceleration phase, if the air film collapses prematurely due to a sudden fault, the rotor vibration will intensify. When the vibration sensor detects that the acceleration exceeds the safety threshold, the control system will immediately determine an emergency state, instantly restore the excitation coil current to its maximum, and fully lift the rotor to avoid rubbing damage, while simultaneously triggering an alarm to notify maintenance personnel.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A permanent magnet biased rotor structure for a hybrid magnetic-levitation air- bearing, characterized by, The application relates to a permanent-magnetic bias rotor structure. The rotor main shaft (1) is provided with an annular mounting groove (11) on the outer surface thereof; A permanent-magnetic ring (2) is embedded in the annular mounting groove (11), and the permanent-magnetic ring (2) is arranged in a Halbach array by a plurality of circumferential magnetized sector-shaped permanent magnets; A sheath layer (4) is coated on the outer surface of the permanent-magnetic ring (2); The annular mounting groove (11) is provided with a magnetic short-circuit isolation groove (13) on the two axial sides thereof.

2. The permanent magnet biased rotor structure for a hybrid magnetic- hydrodynamic bearing according to claim 1, wherein, The depth h of the annular mounting groove (11) satisfies the condition of 0.1R <= h <= 0.2R, and R is the radius of the rotor main shaft (1).

3. The permanent magnet biased rotor structure for a hybrid magnetic- hydrodynamic bearing according to claim 1, wherein The sheath layer (4) is assembled on the permanent-magnetic ring (2) through an interference heat assembly process, and a radial pre-compression stress is applied to the permanent-magnetic ring (2).

4. The permanent-magnetic biased rotor structure for a hybrid magnetic-levitation- hydrodynamic bearing according to claim 1 or 3, characterized in that The outer surface of the sheath layer (4) is coated with a molybdenum disulfide solid lubricating coating.

5. A hybrid magnetic-levitation air-bearing bearing system, characterized by, The application further relates to a permanent-magnetic bias rotor structure. A stator core (5) is coaxially arranged with the permanent-magnetic bias rotor structure, and a radial air gap is formed between the outer surface of the sheath layer (4) and the stator core (5); An excitation coil (6) is arranged on the stator core (5); An air dynamic pressure foil bearing assembly (7) is arranged at the radial air gap, and the foil of the air dynamic pressure foil bearing assembly (7) is made of a magnetically conductive material; The radial air gap simultaneously serves as a magnetic field channel and a dynamic pressure air film space. A Hall sensor array is further arranged on the stator core (5) and used for monitoring the magnetic field distribution in the radial air gap.

6. The hybrid magnetic-levitation air-foil bearing system of claim 5, wherein, The application further relates to a control method of the permanent-magnetic bias rotor structure.

7. A method for operating a magnetic bearing system according to claim 5 or 6, characterized in that S1, a starting stage, the excitation coil (6) is powered to magnetically suspend the rotor, and the rotor is driven to rotate to a first preset rotating speed; S2, a switching stage, when the rotating speed exceeds the first preset rotating speed, the excitation coil current is reduced to increase the air film bearing ratio; when the rotating speed reaches a second preset rotating speed, the current is cut off to make the rotor completely carried by the air film; S3, a speed reduction stage, when the rotating speed reduces to the second preset rotating speed, the excitation coil is powered again to assist in carrying the rotor by magnetic suspension until the rotor is stopped. The first preset rotating speed is the rotating speed at which the air dynamic pressure effect starts to generate, and the second preset rotating speed is the rotating speed at which the air film can completely and stably carry the rated load of the rotor.

8. The method of claim 7, wherein the magnetic bearing system is a hybrid magnetic- hydrodynamic bearing system. In the switching stage and the speed reduction stage, the current of the excitation coil (6) is closed-loop adjusted according to the change of the magnetic field distribution monitored by the Hall sensor array.

9. The method of claim 7, wherein the magnetic bearing system is a hybrid magnetic- hydrodynamic bearing system. In the speed reduction stage, if the rotor vibration acceleration is detected to exceed a threshold value, the excitation coil current is immediately restored to the starting value, and an alarm is triggered.

10. The method of claim 7, wherein the magnetic bearing system is a hybrid magnetic- aerodynamic bearing system. ​

Images