Self-centering assembly device and design method for permanent magnetic thrust bearing

Abstract

This invention belongs to the field of permanent magnet thrust bearing assembly technology, and discloses a self-centering assembly device and design method for permanent magnet thrust bearings. The self-centering assembly device utilizes a long-stroke hydraulic cylinder to push the inner rotor of the permanent magnet thrust bearing into the outer stator. The rolling friction pair formed by the slide rail and slider continuously provides radial support to the piston rod of the hydraulic cylinder and the mounting shaft. After assembly, only the screws between the mounting shaft and the inner rotor of the permanent magnet thrust bearing need to be removed to quickly reset the self-centering assembly device. Simultaneously, the proposed design method cleverly transforms the force between the magnetic rings into internal force within the device, existing as static friction. The dimensions of the connecting parts are rationally designed to ensure the continuous function of static friction. A hydraulic damper is used to mitigate the impact vibration caused by sudden changes in the force between the magnetic rings. A conical surface mating scheme is adopted, achieving self-centering assembly without human intervention.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet thrust bearing assembly technology, and relates to a self-centering assembly device and design method for permanent magnet thrust bearings. Background Technology

[0002] As a key technology attracting significant attention in the fields of high-end equipment and green energy, permanent magnet thrust bearings use neodymium iron boron (NdFeB) permanent magnets as the force transmission medium. Utilizing the principle of "like poles repel, unlike poles attract," they provide axial non-contact support, significantly improving vibration reduction and isolation effects. They are widely used in high-speed motors, precision machine tools, and flywheel energy storage. However, NdFeB permanent magnets are installed in the stator and rotor of the permanent magnet thrust bearing. Their circumferential arrangement forms a magnetic ring, while the axial N and S poles alternate. While providing enormous axial support force, this inevitably increases the difficulty of assembling and disassembling the permanent magnet thrust bearing. Furthermore, as the inner rotor of the permanent magnet thrust bearing gradually moves into the outer rotor, the force between the magnetic rings gradually increases and changes periodically, easily generating vibration and impact, endangering the assembly device. In addition, the small air gap between the stator and rotor of the permanent magnet thrust bearing means that if the coaxiality is poor during assembly, the strong magnetic force will cause them to collide, further increasing assembly difficulty, reducing coaxiality, and even causing irreversible damage to the support structure. Therefore, there is an urgent need to develop a self-centering assembly device and design method for permanent magnet thrust bearings, which will provide important technical support for the high-precision, high-efficiency, safe and reliable assembly of permanent magnet thrust bearings.

[0003] Regarding a self-centering assembly device for permanent magnet thrust bearings, Gong Gao, Zhang Fang, et al., in their patent "Centering Device for Axial Magnetic Suspension Bearing, Axial Magnetic Suspension Bearing and Assembly Method" (CN 105299046 B), utilize the abutting relationship between the axial core, the axial core positioning ring, and the magnetic pole shell to ensure the coaxiality of the axial core and the thrust disk. While the positioning effect is significant, it increases processing costs, easily leads to error accumulation, and is inconvenient for assembly and disassembly. Therefore, providing a self-centering assembly device for permanent magnet thrust bearings is of great significance for the research of permanent magnet thrust bearings. Regarding the design method of the assembly device, Liu Mingxue of Wuhan University of Technology, in his 2015 master's thesis "Research on Load Characteristics of Small Magnetic Suspension Wind Turbine Generator," introduced the assembly process of the inner and outer magnetic rings of the permanent magnet bearing in a prototype of a small magnetic levitation wind turbine generator, but did not provide an overall assembly method for the inner and outer magnetic rings or a method for controlling the air gap between the magnetic fields. Therefore, providing a self-centering assembly device and design method for permanent magnet thrust bearings is essential. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a self-centering assembly device and design method for permanent magnet thrust bearings. The purpose is to utilize a long-stroke hydraulic cylinder to push the inner rotor of the permanent magnet thrust bearing into the outer stator. The rolling friction pair formed by the slide rail and slider consistently provides radial support to the hydraulic cylinder piston rod and mounting shaft. After assembly, simply removing the screws between the mounting shaft and the inner rotor of the permanent magnet thrust bearing allows for rapid repositioning of the self-centering assembly device, improving its structural rigidity, assembly accuracy, and assembly efficiency. Furthermore, the proposed design method cleverly transforms the inter-magnetic ring force into an internal force within the device, existing as static friction. The dimensions of the connecting parts are rationally designed to ensure the continuous function of static friction. A hydraulic damper mitigates the impact vibration caused by sudden changes in the inter-magnetic ring force. A conical surface mating scheme is employed, achieving self-centering assembly without human intervention. This provides theoretical guidance for the high-precision, high-efficiency, safe, and reliable assembly of permanent magnet thrust bearings.

[0005] The technical solution of the present invention:

[0006] A self-centering assembly device for a permanent magnet thrust bearing includes a mounting shaft, a sliding bearing housing A, an outer stator of the permanent magnet thrust bearing, an inner rotor of the permanent magnet thrust bearing, a baffle A, a sliding shaft, a sliding bearing housing B, a baffle B, a slider A, a hydraulic cylinder, a hydraulic cylinder support, a T-nut, a cast iron platform, a sliding bearing housing base B, a slider B, a slide rail A, a slide rail B, a permanent magnet thrust bearing base, and a sliding bearing housing base A.

[0007] The hydraulic cylinder support, slide rail A, slide rail B, permanent magnet thrust bearing base, sliding bearing base A, and cast iron platform are all fixed with T-nuts; the upper end faces of sliders B and A are connected to sliding bearing base B, and their lower end faces are respectively fitted with slide rail B and slide rail A to form a rolling friction pair that reciprocates along the assembly direction; sliding bearing base B and sliding bearing base B, and sliding bearing base A and sliding bearing base A are connected by screws; baffles A and B are installed on both sides of sliding bearing base B, respectively connected to sliding bearing base B by screws; the sliding shaft fits into sliding bearing base B, one side of which is connected to the hydraulic cylinder mounted on the hydraulic cylinder support by bolts and nuts, and the other side is connected to the mounting shaft mounted on sliding bearing base A by screws; the outer stator of the permanent magnet thrust bearing is fixed to the permanent magnet thrust bearing. On the bearing base, the inner rotor of the permanent magnet thrust bearing is fitted with the mounting shaft via a conical surface, and the end face is secured with screws. When the hydraulic cylinder piston rod extends, slider B and slider A move along slide rail B and slide rail A respectively. Accompanying this movement are the sliding bearing base B, baffle A, baffle B, sliding bearing seat B, sliding shaft, mounting shaft, and the inner rotor of the permanent magnet thrust bearing moving along the assembly direction. The inner rotor of the permanent magnet thrust bearing gradually enters the outer stator of the permanent magnet thrust bearing. Afterward, the screws between the mounting shaft and the inner rotor of the permanent magnet thrust bearing are removed, and the hydraulic cylinder piston rod is reset. At this time, the conical surface that fits between the inner rotor of the permanent magnet thrust bearing and the mounting shaft automatically separates. The sliding bearing base B, baffle A, baffle B, sliding bearing seat B, sliding shaft, and mounting shaft are reset. Subsequently, the inner rotor of the permanent magnet thrust bearing remains stationary under the action of the outer stator of the permanent magnet thrust bearing, completing the assembly task.

[0008] The outer stator and inner rotor of the permanent magnet thrust bearing constitute the core component of the permanent magnet thrust bearing. The permanent magnets are installed in the core component and are arranged closely around the circumference of the core component to form a magnetic ring. The magnetic ring is arranged with alternating N and N poles along the axial direction of the core component.

[0009] A design method for a self-centering assembly device for permanent magnet thrust bearings, comprising the following steps:

[0010] Step 1: Calculate the minimum screw size required to secure the T-nut;

[0011] The permanent magnet thrust bearing base and the cast iron platform, as well as the hydraulic cylinder support base and the cast iron platform, are connected by T-nuts and secured with screws. Static friction is generated between the permanent magnet thrust bearing base and the cast iron platform, and also between the hydraulic cylinder support base and the cast iron platform. These two static friction forces are equal in magnitude and opposite in direction, and their magnitude depends on the preload force on the screw and the screw type. The formula for calculating the preload force F1 on a single screw is:

[0012] (1)

[0013] Where R represents the lateral load on the screw, which is the maximum force between the magnetic rings; Z1 represents the number of screws, Z1=4; m represents the number of friction surfaces, which are the friction surfaces between the permanent magnet thrust bearing base and the cast iron platform, and between the T-nut and the cast iron platform; μ represents the coefficient of friction of the friction surfaces; where the cast iron platform is made of cast iron and has a dry surface, and the permanent magnet thrust bearing base and the T-nut are made of 45 steel and have a dry surface, with a coefficient of friction of 0.1~0.16, taken as 0.13; k f This represents the reliability coefficient, which is set to 1.35.

[0014] When a single screw is subjected to preload, the lateral load is balanced by the static friction generated between the friction surfaces. At this time, the screw is subjected to both tensile stress and torsional shear stress. The formula for calculating its minimum allowable size is:

[0015] (2)

[0016] Where, when i=1, d1 represents the diameter of the screw used to connect the permanent magnet thrust bearing base and the cast iron platform; when i=2, d2 represents the diameter of the screw used to connect the hydraulic cylinder support base and the cast iron platform; σ p σ represents the allowable tensile stress of the screw. p =σ s / S s , σ s The value indicates the yield point of the screw material. An 8.8 grade screw made of 45 steel is selected, with a yield point of 360 MPa. s S represents the safety factor. s =2.5;

[0017] The second step is to design the dimensions of the connecting parts used on the sliding shaft and the mounting shaft.

[0018] The sliding shaft is connected to the hydraulic cylinder by bolts and to the mounting shaft by screws. The mounting shaft is also connected to the inner rotor of the permanent magnet thrust bearing by screws. During assembly, the bolts or screws are subjected to tensile stress caused by the force between the magnetic rings, in addition to the preload. The formula for calculating the tensile stress F2 of a single bolt or screw is as follows:

[0019] (3)

[0020] Where Z2 represents the number of bolts or screws, Z2=6;

[0021] The formula for calculating the minimum allowable size of a single bolt or screw is:

[0022] (4)

[0023] Wherein, when j=1, d1 represents the diameter of the bolt used to connect the sliding shaft and the hydraulic cylinder; when j=2, d2 represents the diameter of the screw used to connect the sliding shaft and the mounting shaft; when j=3, d3 represents the diameter of the screw used to connect the mounting shaft and the inner rotor of the permanent magnet thrust bearing; F3 represents the maximum tensile force on the screw, F3=F0+F2, F0 represents the residual preload on the screw or bolt, F0=0.4F2;

[0024] Step 3: Design the dimensions of the connecting parts for fixing the outer stator of the thrust bearing;

[0025] The force between the magnetic rings is transmitted to the permanent magnet thrust bearing base through the outer stator of the permanent magnet thrust bearing. The latter remains stationary after being subjected to the force. Therefore, the force between the magnetic rings is completely canceled out by the static friction between the outer stator of the permanent magnet thrust bearing and the base of the permanent magnet thrust bearing. Thus, the size of the screw used to connect the outer stator of the permanent magnet thrust bearing and the base of the permanent magnet thrust bearing is obtained by the calculation formula of the preload F1 and its minimum allowable size.

[0026] Step 4: Improve the assembly equipment considering processing technology and assembly conditions;

[0027] First, a conical surface mating method is used to machine conical surfaces with a conical angle of 3° on both the mounting shaft and the inner rotor of the permanent magnet thrust bearing. Then, a hydraulic damper is added at the oil outlet of the hydraulic cylinder to absorb the vibration and impact caused by the sudden change in the direction of the force between the magnetic rings and to protect the assembly device. Finally, a process hole is machined at the connection between the sliding shaft and the mounting shaft to provide assembly and disassembly space for the screws connecting the mounting shaft and the inner rotor of the permanent magnet thrust bearing.

[0028] The beneficial effects of this invention are as follows: This invention proposes a self-centering assembly device for permanent magnet thrust bearings. It utilizes a rolling friction pair to release the degree of freedom of the sliding bearing seat B along the assembly direction. When the hydraulic cylinder piston rod extends or resets, the sliding bearing seat B continuously provides support. During assembly, the inner rotor of the permanent magnet thrust bearing slowly enters the outer stator of the permanent magnet thrust bearing under the action of the hydraulic cylinder until the force between the last ring of magnetic rings reaches a force balance state. During reset, the screws connecting the mounting shaft and the inner rotor of the permanent magnet thrust bearing are removed through the process hole. The hydraulic cylinder piston rod resets, and the inner rotor of the permanent magnet thrust bearing automatically separates from the mounting shaft and remains stationary, completing the assembly of the permanent magnet thrust bearing assembly. This device is designed for assembly tasks. It not only meets the requirements for high-precision and high-efficiency assembly and disassembly but is also easy to operate. The proposed design method for the self-centering assembly device of permanent magnet thrust bearings utilizes static friction to counteract the force between magnetic rings. At the same time, a hydraulic damper is added to weaken the impact vibration caused by the sudden change in the force between magnetic rings. The device adopts a conical surface mating scheme with automatic centering function, which allows the permanent magnet thrust bearing to be in a self-centering assembly state without human intervention. This ensures the uniformity of the magnetic field air gap between the outer stator and the inner rotor of the permanent magnet thrust bearing, making the self-centering assembly device of permanent magnet thrust bearings safer and more reliable, and highly practical in engineering. Attached Figure Description

[0029] Figure 1 This is a flowchart of a design method for a self-centering assembly device for permanent magnet thrust bearings.

[0030] Figure 2 This is a schematic diagram of a self-centering assembly device for a permanent magnet thrust bearing.

[0031] Figure 3 This is a schematic diagram of a permanent magnet thrust bearing assembly.

[0032] In the diagram: 1-Mounting shaft, 2-Sliding bearing seat A, 3-Outer stator of permanent magnet thrust bearing, 4-Inner rotor of permanent magnet thrust bearing, 5-Baffle A, 6-Sliding shaft, 7-Sliding bearing seat B, 8-Baffle B, 9-Slider A, 10-Hydraulic cylinder, 11-Hydraulic cylinder support seat, 12-T-nut, 13-Cast iron platform, 14-Sliding bearing seat base B, 15-Slider B, 16-Slide rail A, 17-Slide rail B, 18-Permanent magnet thrust bearing base, 19-Sliding bearing seat base A. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0034] Example

[0035] A permanent magnet thrust bearing with a maximum inter-ring force of 20kN (R=20kN) was selected. The assembly of the permanent magnet thrust bearing was completed using a design method for a self-centering assembly device. The inner rotor 4 of the permanent magnet thrust bearing has a total length of 420mm, and the hydraulic cylinder has a total stroke of 500mm, meeting the assembly requirements.

[0036] The installation steps of a self-centering assembly device for permanent magnet thrust bearings are as follows:

[0037] Fixed cast iron platform 13, insert the required T-nuts 12 into the reserved slots on cast iron platform 13; permanent magnet thrust bearing base 18 is connected to T-nuts 12 by 4 M20×65 socket head cap screws; permanent magnet thrust bearing outer stator 3 is connected to permanent magnet thrust bearing base 18 by 8 M20×65 socket head cap screws; sliding bearing base A19 is connected to T-nuts 12 by 4 M20×65 socket head cap screws; slide rail A16 and slide rail B17 are respectively connected to T-nuts 12 by screws. Female 12 is connected by seven M20×50 socket head cap screws; slider A9 is mounted on slide rail A16 via a mating surface, and slider B15 is mounted on slide rail B17 via a mating surface; slider A9 and slider B15 are respectively connected to sliding bearing seat base B14 by four M20×45 socket head cap screws; sliding bearing seat A2 is connected to sliding bearing seat base A19 by four M20×40 socket head cap screws; sliding bearing seat B7 is connected to sliding bearing seat base B14 by four... The hydraulic cylinder support 11 is connected to the T-nut 12 by four M20×65 socket head cap screws; the hydraulic cylinder support 11 is connected to the hydraulic cylinder 10 by six M16×40 socket head cap screws; the mounting shaft 1 and the inner rotor 4 of the permanent magnet thrust bearing are connected by a conical surface fit using six M12×15 socket head cap screws; the mounting shaft 1 and the sliding shaft 6 are connected by six M12×35 socket head cap screws; the assembled mounting shaft 1 and sliding shaft 6 are then connected. The moving shaft 6 and the inner rotor 4 of the permanent magnet thrust bearing are mounted on sliding bearing seats A2 and B7; the hydraulic cylinder 10 is connected to the sliding shaft 6 by six M12×35 hex bolts and six M12 nuts; the baffle B8 is connected to the sliding bearing seat base B14 by two M10×40 socket head cap screws; the baffle A5 is connected to the sliding bearing seat base B14 by two M10×40 socket head cap screws; thus, the installation of a self-centering assembly device for a permanent magnet thrust bearing is completed. Figure 2 As shown.

[0038] A flowchart illustrating the design method of a self-centering assembly device for permanent magnet thrust bearings, as shown below. Figure 1 As shown, the specific steps are as follows:

[0039] Step 1: Calculate the minimum screw size required to secure the T-nut;

[0040] From equation (1), the preload force F1 on the screws used to connect the permanent magnet thrust bearing base 18 and the cast iron platform 13, and the hydraulic cylinder support 11 and the cast iron platform 13 is obtained as 25.96kN; substituting into equation (2), the minimum allowable diameter of the screw is obtained as d1 = 17.27mm; therefore, the screws required between the permanent magnet thrust bearing base 18 and the cast iron platform 13, and between the hydraulic cylinder support 11 and the cast iron platform 13 are selected from the M20 series.

[0041] The second step is to design the dimensions of the connecting parts used on the sliding shaft and the mounting shaft.

[0042] The tensile stress F2 of the screw or bolt is obtained from equation (3) = 3333 N; the minimum allowable diameter of the screw or bolt is obtained from equation (4) = 7.32 mm; therefore, the bolts used to connect the sliding shaft 6 to the hydraulic cylinder 10, the screws used to connect the sliding shaft 6 to the mounting shaft 1, and the screws used to connect the mounting shaft 1 to the inner rotor 4 of the permanent magnet thrust bearing are all selected from the M12 series.

[0043] Step 3: Design the dimensions of the connecting parts for fixing the outer stator of the thrust bearing;

[0044] From equation (1), the preload force F1 on the screw used to connect the outer stator 3 of the permanent magnet thrust bearing and the base 18 of the permanent magnet thrust bearing is obtained as 25.96kN; substituting into equation (2), the minimum allowable diameter of the screw is obtained as d1 = 17.27mm; therefore, the screw used to connect the outer stator 3 of the permanent magnet thrust bearing and the base 18 of the permanent magnet thrust bearing is selected from the M20 series.

[0045] Step 4: Improve the assembly equipment considering processing technology and assembly conditions;

[0046] The conical fit method is used to ensure the coaxiality of the outer stator 3 and the inner rotor 4 of the permanent magnet thrust bearing, achieving high-precision self-centering. Figure 3 As shown; a hydraulic damper is installed at the oil outlet of the hydraulic cylinder 10 to reduce impact vibration and protect the assembly device; a process hole larger than the screw head diameter is designed at the connection between the sliding shaft 6 and the mounting shaft 1 to facilitate the assembly or disassembly of the screw with a wrench and improve the assembly efficiency of the permanent magnet thrust bearing.

[0047] This method cleverly transforms the force between magnetic rings during assembly into internal force of the device by utilizing static friction. At the same time, it uses a hydraulic damper to weaken the impact vibration caused by the sudden change in the force between magnetic rings. Then, a conical surface mating scheme is adopted, which can achieve a self-centering assembly state without human intervention. It is also easy to assemble and disassemble. This method has theoretical guiding significance for the high-precision, high-efficiency, safe and reliable assembly of permanent magnet thrust bearings.

Claims

1. A self-centering assembly device for a permanent magnet thrust bearing, characterized in that, The self-centering assembly device for the permanent magnet thrust bearing includes a mounting shaft (1), a sliding bearing seat A (2), an outer stator of the permanent magnet thrust bearing (3), an inner rotor of the permanent magnet thrust bearing (4), a baffle A (5), a sliding shaft (6), a sliding bearing seat B (7), a baffle B (8), a slider A (9), a hydraulic cylinder (10), a hydraulic cylinder support seat (11), a T-nut (12), a cast iron platform (13), a sliding bearing seat base B (14), a slider B (15), a slide rail A (16), a slide rail B (17), a permanent magnet thrust bearing base (18), and a sliding bearing seat base A (19). The hydraulic cylinder support (11), slide rail A (16), slide rail B (17), permanent magnet thrust bearing base (18), sliding bearing base A (19) and cast iron platform (13) are all fixed by T-nuts (12); the upper end faces of slider B (15) and slider A (9) are connected to sliding bearing base B (14), and the lower end faces are respectively engaged with slide rail B (17) and slide rail A (16) to form a rolling friction pair that reciprocates along the assembly direction; the sliding bearing base B (7) and sliding bearing base B (14) are connected by sliding shafts. The bearing seat A (2) is connected to the sliding bearing seat base A (19) by screws; the sliding bearing seat B (7) is equipped with baffles A (5) and B (8) on both sides, which are connected to the sliding bearing seat base B (14) by screws respectively; the sliding shaft (6) is fitted to the sliding bearing seat B (7), one side of which is connected to the hydraulic cylinder (10) installed on the hydraulic cylinder support seat (11) by bolts and nuts, and the other side of which is connected to the mounting shaft (1) installed on the sliding bearing seat A (2) by screws; the outer stator (3) of the permanent magnet thrust bearing is fixed to the permanent magnet thrust shaft. On the bearing base (18), the permanent magnet thrust bearing inner rotor (4) and the mounting shaft (1) are fitted by a conical surface and fastened at the end with screws; when the piston rod of the hydraulic cylinder (10) extends, the slider B (15) and slider A (9) move along the slide rail B (17) and slide rail A (16) respectively, accompanied by the sliding bearing seat base B (14), baffle A (5), baffle B (8), sliding bearing seat B (7), sliding shaft (6), mounting shaft (1), and permanent magnet thrust bearing inner rotor (4) moving along the assembly direction, the permanent magnet thrust bearing inner rotor (4) gradually The permanent magnet thrust bearing outer stator (3) is gradually moved in; then the screws between the mounting shaft (1) and the permanent magnet thrust bearing inner rotor (4) are removed, the piston rod of the hydraulic cylinder (10) is reset, at this time the conical surface of the permanent magnet thrust bearing inner rotor (4) and the mounting shaft (1) automatically separates, the sliding bearing seat base B (14), baffle A (5), baffle B (8), sliding bearing seat B (7), sliding shaft (6), and mounting shaft (1) are reset, and the permanent magnet thrust bearing inner rotor (4) is kept stationary by the action of the permanent magnet thrust bearing outer stator (3), thus completing the assembly task.

2. The self-centering assembly device for permanent magnet thrust bearings according to claim 1, characterized in that, The outer stator (3) and inner rotor (4) of the permanent magnet thrust bearing constitute the core component of the permanent magnet thrust bearing. The permanent magnets are installed in the core component and are arranged closely around the core component to form a magnetic ring. The magnetic ring is arranged with alternating N and N poles along the axial direction of the core component.

3. A design method for a self-centering assembly device for permanent magnet thrust bearings, characterized in that, The steps are as follows: Step 1: Calculate the minimum screw size required to fix the T-nut (12); The permanent magnet thrust bearing base (18) and the cast iron platform (13), and the hydraulic cylinder support base (11) and the cast iron platform (13) are connected by T-nuts (12) and fastened by screws; static friction is formed between the permanent magnet thrust bearing base (18) and the cast iron platform (13), and static friction is also formed between the hydraulic cylinder support base (11) and the cast iron platform (13). The two static friction forces are equal in magnitude and opposite in direction, and the magnitude of the static friction force depends on the magnitude of the preload force on the screw and the screw type; the formula for calculating the preload force F1 on a single screw is: Wherein, R represents the lateral load suffered by the screw, which is the maximum force between the magnetic rings; Z1 represents the number of screws, Z1=4; k f represents the reliability coefficient; m represents the number of friction surfaces, both between the permanent magnetic thrust bearing base (18) and the cast iron platform (13) and between the T-shaped nut (12) and the cast iron platform (13); μ represents the friction factor of the friction surface; When a single screw is subjected to preload, the lateral load is balanced by the static friction generated between the friction surfaces. At this time, the screw is subjected to both tensile stress and torsional shear stress. The formula for calculating its minimum allowable size is: Wherein, when i=1, d1 represents the diameter of the screw used to connect the permanent magnet thrust bearing base (18) and the cast iron platform (13); when i=2, d2 represents the diameter of the screw used to connect the hydraulic cylinder support base (11) and the cast iron platform (13); σ p σ represents the allowable tensile stress of the screw. p =σ s / S s , σ s S represents the yield point of the screw material. s S represents the safety factor. s =2.5; The second step is to design the dimensions of the connecting parts used on the sliding shaft and the mounting shaft. The sliding shaft (6) is bolted to the hydraulic cylinder (10) and screwed to the mounting shaft (1). The mounting shaft (1) is also screwed to the inner rotor (4) of the permanent magnet thrust bearing. During assembly, the bolts or screws are subjected to tensile stress caused by the force between the magnetic rings, in addition to the preload. The formula for calculating the tensile stress F2 of a single bolt or screw is as follows: Where Z2 represents the number of bolts or screws, Z2=6; The formula for calculating the minimum allowable size of a single bolt or screw is: Wherein, when j=1, d1 represents the diameter of the bolt used to connect the sliding shaft (6) and the hydraulic cylinder (10); when j=2, d2 represents the diameter of the screw used to connect the sliding shaft (6) and the mounting shaft (1); when j=3, d3 represents the diameter of the screw used to connect the mounting shaft (1) and the inner rotor (4) of the permanent magnet thrust bearing; F3 represents the maximum tensile force on the screw, F3=F0+F2, F0 represents the residual preload on the screw or bolt, F0=0.4F2; Step 3: Design the dimensions of the connecting parts for fixing the outer stator of the thrust bearing; The force between the magnetic rings is transmitted to the permanent magnet thrust bearing base (18) through the outer stator (3) of the permanent magnet thrust bearing. After the latter is subjected to force, it remains stationary. Therefore, the force between the magnetic rings is completely canceled by the static friction between the outer stator (3) of the permanent magnet thrust bearing and the base (18) of the permanent magnet thrust bearing. Thus, the screw size used to connect the outer stator (3) of the permanent magnet thrust bearing and the base (18) of the permanent magnet thrust bearing is obtained by the calculation formula of the preload F1 and its minimum allowable size. Step 4: Improve the assembly equipment considering processing technology and assembly conditions; First, a conical surface mating method is used to machine conical surfaces with a conical angle of 3° on the mounting shaft (1) and the inner rotor (4) of the permanent magnet thrust bearing respectively; then, a hydraulic damper is added at the oil outlet of the hydraulic cylinder (10) to absorb the vibration impact caused by the sudden change in the direction of the force between the magnetic rings and protect the assembly device; finally, a process hole is machined at the connection between the sliding shaft (6) and the mounting shaft (1) to provide assembly and disassembly space for the screws connecting the mounting shaft (1) and the inner rotor (4) of the permanent magnet thrust bearing.

4. The design method of the self-centering assembly device for permanent magnet thrust bearings according to claim 3, characterized in that, The cast iron platform (13) is made of cast iron and has a dry surface. The permanent magnet thrust bearing base (18) and the T-nut (12) are made of 45 steel and have a dry surface, with a friction coefficient of 0.

13. f Take 1.

35.

5. The design method of the self-centering assembly device for permanent magnet thrust bearings according to claim 3, characterized in that, The screws mentioned are grade 8.8 screws made of 45 steel, with a yield point of 360MPa and a safety factor S. s =2.5.

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