A method for designing parameters of a hybrid magnetic bearing and a permanent magnet magnetic group based on double deep groove ball bearing protection

Abstract

The application belongs to the technical field of electromagnetic-permanent magnetic hybrid magnetic transmission, and provides a hybrid magnetic bearing based on double deep groove ball bearing protection and a permanent magnet magnetic group parameter design method. The hybrid magnetic bearing realizes the limiting effect of the rotor under the biasing force, avoids the radial magnetic bearing from being stuck; the permanent magnetic bearing and the electromagnetic bearing are connected through the connecting cylinder, the permanent magnetic bearing is used to provide the biasing magnetic flux to bear most of the static load, the rotor is suspended, the control magnetic flux generated by the electromagnetic bearing is used to actively compensate the dynamic load generated due to vibration and impact, the current of the electromagnetic coil is adjusted through the controller, the rotor position is accurately controlled and stably suspended, the permanent magnetic bearing and the electromagnetic bearing are located on the two sides of the connecting cylinder, the magnetic field interference between the electromagnetic field and the permanent magnetic field can be reduced, and the hybrid magnetic bearing system is more stable. The application proposes the permanent magnet magnetic group parameter design method, the structure parameters of the permanent magnet magnetic group are inversely calculated based on the Maxwell stress tensor method, and the application has the advantages of rapidness and accuracy.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic-permanent magnet hybrid magnetic transmission technology, and relates to a hybrid magnetic bearing and permanent magnet magnetic assembly parameter design method based on double deep groove ball bearing protection. Background Technology

[0002] Magnetic levitation technology utilizes the magnetic force generated by magnets to achieve rotor levitation and stable rotation. Due to its contactless operation, lack of lubrication, and frictionless operation, coupled with high speed, high precision, and excellent stability, magnetic levitation bearings are widely used in aerospace, shipbuilding, and high-speed rail transportation. Based on their load-bearing methods, magnetic levitation bearings can be categorized into three types: active, passive, and hybrid magnetic bearings. Hybrid magnetic bearings combine the advantages of active and passive magnetic bearings. The passive magnetic bearing, i.e., a permanent magnet bearing, generates a bias magnetic flux to bear most of the static load, enabling rotor levitation. The active magnetic bearing, i.e., an electromagnetic bearing, generates a control magnetic flux to actively compensate for dynamic loads caused by vibration and impact. Furthermore, a controller adjusts the current in the electromagnetic coil to precisely control the rotor position and ensure stable levitation. However, current hybrid magnetic bearing structures often use a single deep groove ball bearing or other bearings as a protective bearing. While single-protection bearings are simple, the bias magnetic attraction can easily create bending moments at the protective bearing, causing friction between the inner ring of the bearing and the shaft, or even bearing seizure. Dual-protection bearings, on the other hand, provide protection on both sides of the magnetic radial bearing, making the support more reliable and reducing the risk of bearing seizure. Therefore, designing a hybrid magnetic bearing based on double deep groove ball bearing protection is of great significance for improving the support performance of hybrid magnetic bearings.

[0003] Regarding the structural composition issues of hybrid magnetic bearings, Han Jinchang of Beijing University of Chemical Technology proposed a structure with control coils on both sides of the permanent magnet ring in his doctoral dissertation "Design and Vibration Control Technology Research of Marine Hybrid Magnetic Bearing-Rotor System" in 2024. Although this structure provides relatively reliable support and rapid adjustment, it is prone to electromagnetic interference, affecting the stability of the system. Regarding the internal protective bearing structure of hybrid magnetic bearings, Cai Hua, Fu Chenfeng, and others proposed a structure in patent "Hybrid Magnetic Bearing with Magnetofluid Seal" CN 119196174 A, which places a pair of double angular contact ball bearings facing each other on one side of the magnetic radial bearing. Although it is also a double bearing protection structure, it only exists on one side of the magnetic radial bearing. This structure still causes the bias magnetic attraction to easily form a bending moment at the protective bearing, resulting in friction between the inner ring of the bearing and the shaft, and the support is still unreliable.

[0004] Therefore, proposing a design method for the parameters of hybrid magnetic bearings and permanent magnets based on double deep groove ball bearing protection is of great significance for the research on low electromagnetic interference, reliable support performance of hybrid magnetic bearings and rapid design of permanent magnet structures in the field of magnetic drive technology. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for designing the parameters of a hybrid magnetic bearing and permanent magnet assembly based on double deep groove ball bearing protection. The aim is to create a hybrid magnetic bearing with double deep groove ball bearing protection by placing a deep groove ball bearing on each side of the magnetic radial bearing. This makes the support more reliable and reduces the risk of bearing jamming. A connecting sleeve connects the electromagnetic bearing and the permanent magnet bearing, reducing interference between them and making the hybrid magnetic bearing system more stable. Furthermore, the structural parameters of the permanent magnet are inversely calculated using the Maxwell stress tensor method, enabling rapid and accurate design of the magnetic bearing assembly structure. This method is simple to operate, accurate in calculation, and highly practical in engineering applications.

[0006] The technical solution adopted in this invention is as follows:

[0007] A hybrid magnetic bearing based on double deep groove ball bearing protection: First, a permanent magnet assembly is inserted into a fixed groove formed by a radial magnetic bearing and its bearing bush. On one side, the connection between the protective bearing base and the radial magnetic bearing limits the permanent magnet assembly; on the other side, the connection between the connecting sleeve and the radial magnetic bearing also limits the permanent magnet assembly. Second, two deep groove ball bearings are placed between the protective bearing base and the radial magnetic shaft section, and between the connecting sleeve and the radial magnetic shaft section, respectively. These provide temporary support to the rotor during the start-up and shutdown of the radial magnetic bearing assembly, as well as in case of failure, preventing damage from bias magnetic attraction. The process involves causing the inner ring of the radial magnetic bearing to rub against the radial magnetic shaft section. Then, the deep groove ball bearing on one side of the protective bearing base is limited by the protective bearing cap, while the deep groove ball bearing on the connecting cylinder is limited by the stop and the hole on the connecting cylinder using an elastic retaining ring. Finally, the connecting cylinder connects the electromagnetic bearing and the radial magnetic bearing, reducing magnetic field interference between the electromagnetic field and the permanent magnetic field, making the hybrid magnetic bearing system more stable. Simultaneously, the displacement sensor assembly is connected to the electromagnetic bearing assembly to monitor the rotor's radial displacement in real time, thereby enabling real-time adjustment of the rotor position using the electromagnetic bearing.

[0008] A hybrid magnetic bearing based on double deep groove ball bearing protection includes:

[0009] The frame includes a radial magnetic bearing base 11 and a radial magnetic bearing 12, with the radial magnetic bearing 12 fixedly mounted on the radial magnetic bearing base 11.

[0010] The magnetic bearing assembly includes a radial magnetic bearing bush 21, a rotor 22, a permanent magnet assembly 23, a connecting cylinder 24, an electromagnetic bearing stator housing 25, a limiting ring 26, an electromagnetic bearing stator yoke 27, a control coil 28, and electromagnetic bearing rotor laminations 29. The radial magnetic bearing bush 21 is sleeved on the rotor 22, coaxial with the rotor 22, and fixed in the radial magnetic bearing 12. The permanent magnet assembly 23 is disposed in the radial magnetic bearing 12, with one side of the permanent magnet assembly 23 in contact with the radial magnetic bearing 12 and the other side in contact with the radial magnetic bearing bush 21, used to provide a static bias magnetic field and bear most of the static load. The electromagnetic bearing rotor laminations 29 are sleeved on the rotor 22. The electromagnetic bearing stator housing 25 is fixed on the connecting cylinder 24 and axially connected to the radial magnetic bearing 12 through the connecting cylinder 24, and axially restricts one side of the permanent magnet assembly 23; the electromagnetic bearing rotor lamination 29 is disposed inside the electromagnetic bearing stator housing 25 and is coaxially disposed with the electromagnetic bearing stator housing 25; the electromagnetic bearing stator yoke 27 is disposed in the electromagnetic bearing stator housing 25 and is coaxially disposed with the electromagnetic bearing stator housing 25, and is axially restricted in the electromagnetic bearing stator housing 25 by the limiting ring 26; the control coil 28 is wound on the electromagnetic bearing stator yoke 27, and is used to apply current to generate magnetic force to pull the rotor 22 back to the balanced state when the rotor 22 is not in the balanced position;

[0011] The displacement sensor includes a displacement sensor rotor lamination 31 and a displacement sensor stator 32. The displacement sensor rotor lamination 31 is sleeved on the rotor 22, and the displacement sensor stator 32 is fixed on the electromagnetic bearing stator housing 25 and coaxial with the rotor 22. The displacement sensor rotor lamination 31 and the displacement sensor stator 32 work together to output the rotor radial displacement signal.

[0012] The protective bearing assembly includes a protective bearing base 41, a first deep groove ball bearing 42, a protective bearing cap 43, a second deep groove ball bearing 44, a bore retaining ring 45, a double-controlled shaft end retaining ring 46, and a shaft end locking washer 47. The protective bearing base 41 is fixed on the radial magnetic bearing 12 and coaxially arranged with the rotor 22 to axially restrict one side of the permanent magnet assembly 23. The first deep groove ball bearing 42 is sleeved on the rotor 22. The protective bearing cap 43 is axially fixed on the protective bearing base 41 and coaxial with the rotor 22. The first deep groove ball bearing 42 is fitted with the protective bearing base 41 on one axial side and the protective bearing cover 43 on the other side; the second deep groove ball bearing 44 is disposed between the rotor 22 and the connecting cylinder 24 and is coaxial with the rotor 22. The hole is fixed to the connecting cylinder 24 by an elastic retaining ring 45 to limit the axial movement of the second deep groove ball bearing 44; the double-controlled shaft end retaining ring 46 is located at the right end of the rotor 22 and is coaxial with the rotor 22. It restricts the axial movement of the coupling 51 by cooperating with the shaft end stop washer 47.

[0013] The connecting components include a coupling 51, a first guide key 52, and a second guide key 53. The coupling 51 is fixed on the rotor 22 and is coaxially arranged with the rotor 22. The first guide key 52 is fixed on the coupling 51, and the two cooperate with each other to connect the rotor 22 with other transmission devices. The second guide key 53 is fixed on the left flange end face of the rotor 22 and is used to connect the rotor 22 with other transmission devices.

[0014] The first deep groove ball bearing 42 and the second deep groove ball bearing 44 are located on both sides of the radial magnetic bearing 12, so that both sides of the radial magnetic bearing 12 are protected, the support is reliable, and it is not easy to cause the bearing to seize.

[0015] The stator yoke 27 of the electromagnetic bearing includes a 4-pole structure, a 6-pole structure, or an 8-pole structure.

[0016] The stator yoke 27 and rotor laminations 29 of the electromagnetic bearing are both made of silicon steel sheets to enhance the magnetic circuit conductivity and reduce eddy current losses.

[0017] The permanent magnet assembly 23 includes multiple permanent magnets, which are sintered from neodymium iron boron material. They are radially magnetized, and adjacent permanent magnets in the axial direction are magnetized in opposite directions. The circumferential direction is composed of three permanent magnets with the same magnetization direction, and the circumferential coverage angle reaches 120 degrees.

[0018] A method for designing permanent magnet magnetic assembly parameters of a hybrid magnetic bearing protected by double deep groove ball bearings, comprising the following steps:

[0019] Step 1: Determine the key parameters of the radial magnetic bearing 12;

[0020] Key parameters include rotor radius r rotor Radial magnetic bearing inner radius r1, radial magnetic bearing outer radius r2, permanent magnet inner radius r3, permanent magnet radial thickness w m , the number of axial permanent magnets n, the circumferential coverage angle of the permanent magnets θ;

[0021] The second step is to calculate the magnetomotive force of a single axial permanent magnet.

[0022] First, calculate the coercivity of a single axial permanent magnet segment:

[0023]

[0024] Among them, H c For the coercivity of a single-segment permanent magnet in the axial direction, B r μ is the remanent magnetic flux density of the permanent magnet. r The relative permeability of a permanent magnet;

[0025] Secondly, calculate the magnetomotive force of a single-segment permanent magnet along the axis:

[0026]

[0027] Among them, F m It is an axial single-segment permanent magnet magnetomotive force;

[0028] Step 3: Calculate the magnetic reluctance of a single axial permanent magnet segment;

[0029] First, calculate the average radius of the permanent magnet:

[0030]

[0031] Where, r ma The average radius of the permanent magnet;

[0032] Secondly, calculate the average cross-sectional area of ​​a single axial segment of the permanent magnet:

[0033]

[0034] Among them, A m h is the average cross-sectional area of ​​a single axial permanent magnet segment. m The axial thickness of the permanent magnet;

[0035] Finally, the magnetic reluctance within the axial single-segment permanent magnet is calculated:

[0036]

[0037] Among them, R m The axial single-segment permanent magnet has a reluctance within its body, and μ0 is the free permeability, μ0 = 4π × 10⁻⁶. -7 H / m;

[0038] Step 4: Calculate the air gap magnetic reluctance generated by the axial single-segment permanent magnet in the air gap;

[0039] First, calculate the average radius of the air gap:

[0040]

[0041] Where, r ga The average radius of the air gap;

[0042] Secondly, calculate the average cross-sectional area of ​​the air gap corresponding to a single permanent magnet segment:

[0043]

[0044] Among them, A g0 This represents the average cross-sectional area of ​​the air gap corresponding to a single permanent magnet segment.

[0045] Finally, the air gap reluctance generated by the axial single-segment permanent magnet in the air gap is calculated:

[0046]

[0047] Among them, R g The air gap magnetic reluctance generated by an axial single-segment permanent magnet in the air gap;

[0048] Step 5: Calculate the air gap magnetic flux density of a single axial permanent magnet;

[0049] First, since the magnetic reluctance of the rotor and the radial bearing is small, it can be ignored. Therefore, only the magnetic reluctance within the permanent magnet and the magnetic reluctance of the two air gaps are considered when calculating the axial single-segment permanent magnet flux:

[0050]

[0051] Wherein, ϕ0 is the axial single-segment permanent magnet flux;

[0052] Further calculation of the air gap magnetic flux density of the axial single-segment permanent magnet:

[0053]

[0054] Step 6: Ignoring other factors and assuming that the air gap magnetic flux density of each permanent magnet segment is uniform, the axial thickness of the permanent magnet is calculated inversely based on Maxwell's stress tensor method.

[0055]

[0056] Summarized as follows:

[0057]

[0058] Among them, F y This is the required total radial permanent magnet force;

[0059] At this point, the calculation of the axial thickness of the permanent magnet is complete.

[0060] The beneficial effects of this invention are as follows: It proposes a hybrid magnetic bearing based on double deep groove ball bearing protection. This hybrid magnetic bearing uses deep groove ball bearings on both sides of the radial magnetic bearing to limit the rotor when subjected to bias force, thereby preventing the radial magnetic bearing from jamming and making the support more reliable. The permanent magnet bearing part is connected to the electromagnetic bearing part through a connecting cylinder. The permanent magnet bearing provides bias magnetic flux to bear most of the static load, enabling the rotor to levitate. The control magnetic flux generated by the electromagnetic bearing actively compensates for the dynamic load caused by vibration and impact. The current of the electromagnetic coil is adjusted by the controller, so that the rotor position is precisely controlled and the levitation effect is stable. Moreover, the permanent magnet bearing and the electromagnetic bearing are located on both sides of the connecting cylinder, which can reduce the magnetic field interference between the electromagnetic field and the permanent magnet field, making the hybrid magnetic bearing system more stable. In addition, this invention proposes a method for designing permanent magnet magnetic assembly parameters. Based on Maxwell's stress tensor method, the structural parameters of the permanent magnet magnetic assembly are calculated inversely. This method has the advantages of being fast and accurate, and is a calculation method with universality and practical application value. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of a hybrid magnetic bearing structure based on double deep groove ball bearing protection;

[0062] Figure 2 This is a schematic diagram of the magnetization direction of a permanent magnet;

[0063] Figure 3 This is a schematic diagram of the structural parameters of the radial magnetic bearing section;

[0064] In the diagram: 11-Radial magnetic bearing base, 12-Radial magnetic bearing, 21-Radial magnetic bearing bush, 22-Rotor, 23-Permanent magnet assembly, 24-Connecting cylinder, 25-Electromagnetic bearing stator housing, 26-Limiting ring, 27-Electromagnetic bearing stator yoke, 28-Control coil, 29-Electromagnetic bearing rotor lamination, 31-Displacement sensor rotor lamination, 32-Displacement sensor stator, 41-Protective bearing base, 42-First deep groove ball bearing, 43-Protective bearing cover, 44-Second deep groove ball bearing, 45-Elastic retaining ring for bore, 46-Double-controlled shaft end retaining ring, 47-Shaft end locking washer, 51-Coupling, 52-First guide key, 53-Second guide key. Detailed Implementation

[0065] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0066] In this embodiment, a hybrid magnetic bearing with a required total permanent magnet force of 2120N and protected by a double deep groove ball bearing was selected, and the structural parameters of its permanent magnet assembly were calculated.

[0067] Among them, the radial magnetic bearing 12 has an inner diameter of 154mm, the radial magnetic bearing bush 21 has an inner diameter of 131mm and an outer diameter of 138mm, the rotor 22 has an inner diameter of 129.4mm at the connection with the first deep groove ball bearing 42, an inner diameter of 130mm at the connection with the radial magnetic bearing bush 21, an inner diameter of 109.4mm at the connection with the second deep groove ball bearing 44, and an inner diameter of 74mm at the connection with the electromagnetic bearing rotor lamination 29. The permanent magnet magnetic assembly 23 has an inner diameter of 138mm, a radial thickness of 8mm, a total axial length of 125mm, and a circumferential coverage angle of 120 degrees. The first deep groove ball bearing 42 has an inner diameter of 130mm, an outer diameter of 165mm, and a thickness of 18mm. The second deep groove ball bearing 44 has an inner diameter of 110mm, an outer diameter of 140mm, and a thickness of 16mm. The electromagnetic bearing stator yoke 27 adopts an 8-pole structure, and the control coil 28 has a wire diameter of 0.8mm.

[0068] The installation steps for a hybrid magnetic bearing protected by double deep groove ball bearings are as follows:

[0069] First, the radial magnetic bearing 12 is installed on the radial magnetic bearing base 11 using eight M12×50 fixing bolts. The radial magnetic bearing bush 21 is installed inside the radial magnetic bearing 12, and the radial magnetic shaft section of the rotor 22 is placed inside the radial magnetic bearing bush 21. Then, the permanent magnet assembly 23 is inserted into the fixing groove between the radial magnetic bearing 12 and the radial magnetic bearing bush 21. The protective bearing base 41 is installed on the radial magnetic bearing 12 using twelve M5×26 double-ended screws, thus axially fixing the left side of the permanent magnet assembly 23. The first deep groove ball bearing 42 is sleeved on the radial magnetic shaft section of the rotor 22, and the protective bearing cap 43 is fixed to the protective bearing base 41 using twelve M4×12 bolts, thus axially limiting the first deep groove ball bearing 42. Finally, the connecting cylinder 24 is installed on the other side of the radial magnetic bearing 12 using twelve M5×20 bolts, thus axially fixing the right side of the permanent magnet assembly 23.

[0070] Next, the second deep groove ball bearing 44 is sleeved on the rotor 22 and placed inside the connecting cylinder 24. The axial fixation of the second deep groove ball bearing 44 is completed by the cooperation of the elastic retaining ring 45 in the hole and the groove inside the connecting cylinder 24.

[0071] The electromagnetic bearing rotor lamination 29 and electromagnetic bearing stator housing 25 are then successively fitted onto the electromagnetic bearing shaft section of rotor 22, and the electromagnetic bearing stator housing 25 is fixed to the connecting cylinder 24 with eight M10×35 bolts. Then, the control coil 28 is wound around the electromagnetic bearing stator yoke 27, and the electromagnetic bearing stator yoke 27 is fitted onto rotor 22 and placed inside the electromagnetic bearing stator housing 25. The electromagnetic bearing stator yoke 27 is axially fixed by the engagement of the limiting ring 26 with the internal slot of the electromagnetic bearing stator housing 25. After that, the displacement sensor rotor lamination 31 and displacement sensor stator 32 are successively fitted onto the electromagnetic bearing shaft section of rotor 22, and the displacement sensor stator 32 is fixed to the electromagnetic bearing stator housing 25 with eight M10×25 bolts.

[0072] Finally, the coupling 51 is fitted with the spline on the right side of the rotor 22, and the double-control shaft end retaining ring 46 is fixed to the right side of the rotor 22 with two M10×25 bolts to restrict the axial movement of the coupling 51. The second guide key 53 is installed on the left flange end face of the rotor 22 with two M5×10 screws, and the first guide key 52 is installed on the coupling 51 with two M5×10 screws to realize the connection between the rotor 22 and other transmission components.

[0073] The installation of a hybrid magnetic bearing based on double deep groove ball bearing protection is now complete.

[0074] In this invention, the first deep groove ball bearing 42 and the second deep groove ball bearing 44 are located on both sides of the radial magnetic bearing 12, so that both sides of the radial magnetic bearing 12 are protected, the support is reliable, and the bearing is not easy to jam.

[0075] In this invention, the stator yoke 27 of the electromagnetic bearing adopts an 8-pole structure.

[0076] Furthermore, both the stator yoke 27 and the rotor laminations 29 of the electromagnetic bearing are made of silicon steel sheets to enhance the magnetic circuit conductivity and reduce eddy current losses.

[0077] Furthermore, in this invention, the permanent magnet assembly 23 is made of neodymium iron boron material and is radially magnetized. The magnetization directions of adjacent permanent magnets in the axial direction are opposite, and the circumferential direction is composed of three permanent magnets with the same magnetization direction, with a circumferential coverage angle of 120 degrees.

[0078] Furthermore, the design process for the axial thickness of the permanent magnet assembly 23 of the hybrid magnetic bearing based on double deep groove ball bearing protection is as follows:

[0079] Step 1: Determine the key parameters of the radial magnetic bearing;

[0080] Key parameters include rotor radius Inner radius of radial magnetic bearing bush outer radius The inner radius of the permanent magnet body radial thickness Number of axial permanent magnets Permanent magnet circumferential coverage angle ;

[0081] The second step is to calculate the magnetomotive force of a single axial permanent magnet.

[0082] First, the coercivity of the axial single-segment permanent magnet is calculated using equation (1).

[0083] The magnetomotive force of the axial single-segment permanent magnet is further calculated using equation (2).

[0084] Step 3: Calculate the magnetic reluctance of a single axial permanent magnet segment;

[0085] First, the average radius of the permanent magnet is calculated using equation (3).

[0086] The average cross-sectional area of ​​a single axial permanent magnet segment is further calculated using equation (4).

[0087] Finally, the magnetic reluctance within the axial single-segment permanent magnet is calculated using equation (5).

[0088] Step 4: Calculate the air gap magnetic reluctance generated by the axial single-segment permanent magnet in the air gap;

[0089] First, the average radius of the air gap is calculated using equation (6).

[0090] The average cross-sectional area of ​​the air gap corresponding to a single permanent magnet segment is further calculated using equation (7).

[0091] Finally, the air gap magnetic reluctance generated by the axial single-segment permanent magnet in the air gap is calculated using equation (8).

[0092] Step 5: Calculate the air gap magnetic flux density of a single axial permanent magnet;

[0093] First, the axial single-segment permanent magnet flux is calculated using equation (9).

[0094] The axial single-segment permanent magnet air gap magnetic flux density is further calculated using equation (10).

[0095] Step 6: Inversely calculate the axial thickness of the permanent magnet using Maxwell's stress tensor method;

[0096] Substituting the results of equations (7) and (10) into equation (11), we can obtain the relationship between the required total radial permanent magnet force and the axial thickness of the permanent magnet: .

[0097] When the required total radial permanent magnet force is 2120N, the axial thickness Rounding down, i.e., taking the axial thickness. .

[0098] At this point, the calculation of the axial thickness of the permanent magnet is complete.

[0099] The hybrid magnetic bearing system, protected by double deep groove ball bearings, uses deep groove ball bearings on both sides of the radial magnetic bearing to limit the rotor under bias force, thus preventing the radial magnetic bearing from jamming and making the support more reliable. A connecting cylinder connects the permanent magnet bearing section and the electromagnetic bearing section. The permanent magnet bearing provides bias magnetic flux to bear most of the static load, enabling the rotor to levitate. The control magnetic flux generated by the electromagnetic bearing actively compensates for dynamic loads caused by vibration and impact. A controller adjusts the current of the electromagnetic coil, enabling precise control of the rotor position and stable levitation. Furthermore, the permanent magnet bearing and electromagnetic bearing are located on opposite sides of the connecting cylinder, reducing magnetic field interference between the electromagnetic and permanent magnet fields, making the hybrid magnetic bearing system more stable. In addition, this invention uses the Maxwell stress tensor method to inversely calculate the structural parameters of the permanent magnet, offering advantages in speed and accuracy. It is a calculation method with universality and practical application value.

Claims

1. A hybrid magnetic bearing based on double deep groove ball bearing protection, characterized in that, The hybrid magnetic bearing based on double deep groove ball bearing protection includes: The frame includes a radial magnetic bearing base (11) and a radial magnetic bearing (12), the radial magnetic bearing (12) being fixedly mounted on the radial magnetic bearing base (11); The magnetic bearing assembly includes a radial magnetic bearing bush (21), a rotor (22), a permanent magnet assembly (23), a connecting cylinder (24), an electromagnetic bearing stator housing (25), a limiting ring (26), an electromagnetic bearing stator yoke (27), a control coil (28), and electromagnetic bearing rotor laminations (29). The radial magnetic bearing bush (21) is fitted onto the rotor (22), coaxial with the rotor (22), and fixed in the radial magnetic bearing (12). The permanent magnet assembly (23) is disposed in the radial magnetic bearing (12), with one side of the permanent magnet assembly (23) in contact with the radial magnetic bearing (12) and the other side in contact with the radial magnetic bearing bush (21), used to provide a static bias magnetic field and bear most of the static load. The electromagnetic bearing rotor laminations (29) are fitted onto the rotor (22). On 22), the electromagnetic bearing stator housing (25) is fixed on the connecting cylinder (24) and axially connected to the radial magnetic bearing (12) through the connecting cylinder (24), and axially restricts one side of the permanent magnet assembly (23); the electromagnetic bearing rotor lamination (29) is arranged inside the electromagnetic bearing stator housing (25) and is coaxially arranged with the electromagnetic bearing stator housing (25); the electromagnetic bearing stator yoke (27) is arranged in the electromagnetic bearing stator housing (25) and is coaxially arranged with the electromagnetic bearing stator housing (25), and is axially restricted in the electromagnetic bearing stator housing (25) through the limiting ring (26); the control coil (28) is wound on the electromagnetic bearing stator yoke (27) and is used to generate magnetic force to pull the rotor (22) back to the balanced state when the rotor (22) is not in the balanced position; The displacement sensor includes a displacement sensor rotor lamination (31) and a displacement sensor stator (32). The displacement sensor rotor lamination (31) is sleeved on the rotor (22), and the displacement sensor stator (32) is fixed on the electromagnetic bearing stator housing (25) and coaxial with the rotor (22). The displacement sensor rotor lamination (31) and the displacement sensor stator (32) work together to output the rotor radial displacement signal. The protective bearing assembly includes a protective bearing base (41), a first deep groove ball bearing (42), a protective bearing cap (43), a second deep groove ball bearing (44), a bore retaining ring (45), a double-controlled shaft end retaining ring (46), and a shaft end locking washer (47). The protective bearing base (41) is fixed on the radial magnetic bearing (12) and coaxially arranged with the rotor (22) to axially restrict one side of the permanent magnet assembly (23). The first deep groove ball bearing (42) is sleeved on the rotor (22). The protective bearing cap (43) is axially fixed on the protective bearing base (41) and coaxially arranged with the rotor (22). Shaft configuration: The first deep groove ball bearing (42) is axially fitted on one side with the protective bearing base (41) and on the other side with the protective bearing cover (43); The second deep groove ball bearing (44) is set between the rotor (22) and the connecting cylinder (24) and is coaxial with the rotor (22). The hole is fixed on the connecting cylinder (24) with an elastic retaining ring (45) to limit the axial movement of the second deep groove ball bearing (44); The double-controlled shaft end retaining ring (46) is located at the right end of the rotor (22) and is coaxial with the rotor (22). It limits the axial movement of the coupling (51) by cooperating with the shaft end stop washer (47); The connecting parts include a coupling (51), a first guide key (52), and a second guide key (53). The coupling (51) is fixed on the rotor (22) and is coaxial with the rotor (22). The first guide key (52) is fixed on the coupling (51). The two cooperate with each other to connect the rotor (22) with other transmission devices. The second guide key (53) is fixed on the left flange end face of the rotor (22) to connect the rotor (22) with other transmission devices.

2. The hybrid magnetic bearing based on double deep groove ball bearing protection according to claim 1, characterized in that, The first deep groove ball bearing (42) and the second deep groove ball bearing (44) are located on both sides of the radial magnetic bearing (12) to provide protection for both sides of the radial magnetic bearing (12).

3. The hybrid magnetic bearing based on double deep groove ball bearing protection according to claim 1 or 2, characterized in that, The stator yoke (27) of the electromagnetic bearing includes a 4-pole structure, a 6-pole structure or an 8-pole structure.

4. The hybrid magnetic bearing based on double deep groove ball bearing protection according to claim 3, characterized in that, The electromagnetic bearing stator yoke (27) and the electromagnetic bearing rotor laminations (29) are both made of silicon steel sheets.

5. The hybrid magnetic bearing based on double deep groove ball bearing protection according to claim 4, characterized in that, The permanent magnet assembly (23) includes multiple permanent magnets, which are sintered from neodymium iron boron material. They are radially magnetized, and the magnetization directions of adjacent permanent magnets in the axial direction are opposite. The circumferential direction is composed of three permanent magnets with the same magnetization direction, and the circumferential coverage angle reaches 120 degrees.

6. A method for designing permanent magnet magnetic assembly parameters of a hybrid magnetic bearing protected by double deep groove ball bearings, characterized in that, The steps are as follows: Step 1: Determine the key parameters of the radial magnetic bearing (12); Key parameters include rotor radius r rotor Radial magnetic bearing inner radius r1, radial magnetic bearing outer radius r2, permanent magnet inner radius r3, permanent magnet radial thickness w m , the number of axial permanent magnets n, the circumferential coverage angle of the permanent magnets θ; The second step is to calculate the magnetomotive force of a single axial permanent magnet. First, calculate the coercivity of a single axial permanent magnet segment: Among them, H c For the coercivity of a single-segment permanent magnet in the axial direction, B r μ is the remanent magnetic flux density of the permanent magnet. r The relative permeability of a permanent magnet; Secondly, calculate the magnetomotive force of a single-segment permanent magnet along the axis: Among them, F m It is an axial single-segment permanent magnet magnetomotive force; Step 3: Calculate the magnetic reluctance of a single axial permanent magnet segment; First, calculate the average radius of the permanent magnet: Where, r ma The average radius of the permanent magnet; Secondly, calculate the average cross-sectional area of ​​a single axial segment of the permanent magnet: Among them, A m h is the average cross-sectional area of ​​a single axial permanent magnet segment. m The axial thickness of the permanent magnet; Finally, the magnetic reluctance within the axial single-segment permanent magnet is calculated: Among them, R m The axial single-segment permanent magnet has a reluctance within its body, and μ0 is the free permeability, μ0 = 4π × 10⁻⁶. -7 H / m; Step 4: Calculate the air gap magnetic reluctance generated by the axial single-segment permanent magnet in the air gap; First, calculate the average radius of the air gap: Where, r ga The average radius of the air gap; Secondly, calculate the average cross-sectional area of ​​the air gap corresponding to a single permanent magnet segment: Among them, A g0 This represents the average cross-sectional area of ​​the air gap corresponding to a single permanent magnet segment. Finally, the air gap reluctance generated by the axial single-segment permanent magnet in the air gap is calculated: Among them, R g The air gap magnetic reluctance generated by an axial single-segment permanent magnet in the air gap; Step 5: Calculate the air gap magnetic flux density of a single axial permanent magnet; First, since the magnetic reluctance of the rotor and the radial bearing is small, it can be ignored. Therefore, only the magnetic reluctance within the permanent magnet and the magnetic reluctance of the two air gaps are considered when calculating the axial single-segment permanent magnet flux: Wherein, ϕ0 is the axial single-segment permanent magnet flux; Further calculation of the air gap magnetic flux density of the axial single-segment permanent magnet: Step 6: Ignoring other factors and assuming that the air gap magnetic flux density of each permanent magnet segment is uniform, the axial thickness of the permanent magnet is calculated inversely based on Maxwell's stress tensor method. Summarized as follows: Among them, F y This is the required total radial permanent magnet force; At this point, the calculation of the axial thickness of the permanent magnet is complete.

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