Magnetic levitation hybrid three-degree-of-freedom bearing and air compressor

Abstract

The application provides a magnetic suspension mixed three-degree-of-freedom bearing and an air compressor, wherein the bearing comprises a radial magnetic bearing assembly and an axial magnetic bearing assembly, a permanent magnet capable of providing a bias magnetic field is clamped between the radial magnetic bearing assembly and the axial magnetic bearing assembly, the axial magnetic bearing assembly comprises a first axial stator core and a second axial stator core, the first axial stator core has a first magnetic ring, the radial thickness of the first magnetic ring is la, the second axial stator core has a second magnetic ring, the radial thickness of the second magnetic ring is le, and la < le. The application increases the radial thickness of the side with smaller axial output, thereby improving the axial output of the second axial stator core, making the structures of the first axial stator core and the second axial stator core asymmetric, achieving axial force balance design without increasing the overall volume of the bearing, meeting the axial load demand, and thereby improving the rotor dynamics characteristics.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation bearing technology, specifically relating to a magnetic levitation hybrid three-degree-of-freedom bearing and an air compressor. Background Technology

[0002] Industrial air compressors operate at high speeds and have large pneumatic components. To ensure stable operation of the rotor in a rigid state, the rotor length should be minimized as much as possible. Based on this objective, existing technologies have developed magnetic levitation hybrid three-degree-of-freedom bearings, which integrate axial and radial magnetic bearings into one unit to achieve adjustment of the rotor's axial and radial positions. For example, patent application CN108869545A describes an invention with a radial magnetic bearing assembly and an axial magnetic bearing connected to one end. A permanent magnet is sandwiched between the two magnetic bearings, providing a bias magnetic field for both the radial and axial magnetic bearing assemblies. However, since the permanent magnet is located on one side of the axial stator of the axial magnetic bearing assembly (specifically, in this patent application, the permanent magnet is positioned on the right side of the axial stator), the path length of the bias magnetic field flowing through the right axial stator is shorter than that of the left axial stator. Furthermore, the structures of the left and right axial stators are symmetrical. Due to the asymmetry in electromagnetic characteristics, the axial force output of the left and right axial stators of the axial magnetic bearing is ultimately unequal. To ensure that the direction with the smaller output can also meet the axial load requirements, the current common solution is to increase the overall size of the bearing. This increases the volume of the magnetic bearing, which is detrimental to the rotor dynamics. Summary of the Invention

[0003] Therefore, the present invention provides a magnetic levitation hybrid three-degree-of-freedom bearing and an air compressor, which can solve the technical problem in the prior art where the stator structure of the left and right axes is symmetrical but the length of the permanent magnet bias magnetic circuit flow path is not equal, resulting in unequal axial output of the stator in the left and right axes. In order to ensure that the axial load requirement can also be met in the direction with smaller output, the volume of the magnetic bearing is increased, which is not conducive to the rotor dynamic characteristics.

[0004] To address the aforementioned problems, this invention provides a magnetically levitated hybrid three-degree-of-freedom bearing, comprising a radial magnetic bearing assembly and an axial magnetic bearing assembly located at one end of the radial magnetic bearing assembly. A permanent magnet capable of providing a bias magnetic field is sandwiched between the radial magnetic bearing assembly and the axial magnetic bearing assembly. The axial magnetic bearing assembly includes a first axial stator core and a second axial stator core, wherein the second axial stator core is located between the permanent magnet and the first axial stator core. The first axial stator core has a first magnetic ring with a radial thickness of la, and the second axial stator core has a second magnetic ring with a radial thickness of le, where la < le.

[0005] In some implementations, 0.8 ≤ la / le < 1.

[0006] In some embodiments, the first axial stator core includes a first stator body with an axial thickness of 1b, and the second axial stator core includes a second stator body with an axial thickness of 1d, where 1b < 1d.

[0007] In some implementations, 0.7 ≤ lb / ld ≤ 0.95.

[0008] In some embodiments, the axial magnetic bearing assembly further includes a thrust disk located between the first axial stator core and the second axial stator core, the axial thickness of the thrust disk being lp, where lp > la and lp > le.

[0009] In some implementations, lp ≤ la + le.

[0010] In some implementations, lp / (la+le)≥0.7.

[0011] In some embodiments, the radial magnetic bearing assembly includes a radial stator core with an axial thickness of lr, where lr > lp.

[0012] In some implementations, lr ≤ 2lp.

[0013] In some implementations, 1 < lr / lp ≤ 1.8.

[0014] The present invention also provides an air compressor, including the above-mentioned magnetic levitation hybrid three-degree-of-freedom bearing.

[0015] In some embodiments, the air compressor further includes a drive motor, the drive motor including a drive motor winding located at the end of the radial magnetic bearing assembly away from the axial magnetic bearing assembly, and the radial magnetic bearing assembly having a radial stator core with a laminated structure.

[0016] In some embodiments, the air compressor further includes an air compressor shaft on which an impeller is mounted. During operation of the impeller, the axial pneumatic load applied to the air compressor shaft is directed from the axial magnetic bearing assembly toward the radial magnetic bearing assembly.

[0017] The present invention provides a magnetic levitation hybrid three-degree-of-freedom bearing and air compressor. By increasing the radial thickness of the side with smaller axial output force, i.e., the radial thickness of the second magnetic ring, the axial output force of the second axial stator core is improved. This makes the structures of the first axial stator core and the second axial stator core asymmetrical, achieving axial force balance design without increasing the overall volume of the bearing, meeting axial load requirements, and thus improving rotor dynamic characteristics. Attached Figure Description

[0018] Figure 1 This is a schematic diagram (axial section) of the internal structure of the magnetic levitation hybrid three-degree-of-freedom bearing according to an embodiment of the present invention;

[0019] Figure 2 for Figure 1 Left side view;

[0020] Figure 3 This is a schematic diagram of the permanent magnet biasing magnetic circuit, radial control magnetic circuit, and axial control magnetic circuit of the magnetic levitation hybrid three-degree-of-freedom bearing according to an embodiment of the present invention.

[0021] The reference numerals in the attached figures are as follows:

[0022] 1. Radial magnetic bearing assembly; 11. Radial stator core; 12. Radial control winding; 13. Mounting ring; 14. Radial rotor core; 2. Axial magnetic bearing assembly; 211. First magnetic ring; 212. First stator body; 221. Second magnetic ring; 222. Second stator body; 23. Thrust disc; 24. Axial control winding; 25. Intermediate magnetic guide ring; 3. Permanent magnet; 4. Collar; 100. Air compressor shaft. Detailed Implementation

[0023] See also Figures 1 to 3 As shown, a magnetic levitation hybrid three-degree-of-freedom bearing is provided, including a radial magnetic bearing assembly 1 and an axial magnetic bearing assembly 2 located at one end of the radial magnetic bearing assembly 1. A permanent magnet 3 capable of providing a bias magnetic field is sandwiched between the radial magnetic bearing assembly 1 and the axial magnetic bearing assembly 2. The permanent magnet 3 is axially magnetized (i.e., Figure 1 (Horizontal direction of orientation), the permanent magnet 3 is a complete ring or a segmented sector-shaped magnet assembly covering more than 300° of the circumference, and the axial magnetic bearing assembly 2 includes an axial stator core, the axial stator core including a first axial stator core (i.e. Figure 1 The left-axis stator core in the indicated orientation), the second-axis stator core (i.e. Figure 1The diagram shows a right-hand axial stator core (as shown) and an intermediate magnetic ring 25 between them. The second axial stator core is located between the permanent magnet 3 and the first axial stator core. The first axial stator core includes a first stator body 212 and a first magnetic ring 211 thereon, with a radial thickness of la. The second axial stator core includes a second stator body 222 and a second magnetic ring 221 thereon, with a radial thickness of le, where la < le. In this technical solution, by increasing the radial thickness of the side with smaller axial output force, i.e., the radial thickness of the second magnetic ring 221, the axial output force of the second axial stator core is increased. This results in an asymmetrical structure between the first and second axial stator cores, achieving axial force balance design without increasing the overall bearing volume, meeting axial load requirements, and thus improving rotor dynamic characteristics.

[0024] See Figure 1 As shown, the axial magnetic bearing assembly 2 also includes a thrust disk 23 located between the first axial stator core and the second axial stator core. An axial gap 1 is formed between the first axial stator core and the thrust disk 23, and an axial gap 2 is formed between the second axial stator core and the thrust disk 23.

[0025] See further Figure 1 As shown, a mounting ring 13 is fitted on the outer circumference of the radial stator core 11. The permanent magnet 3 is clamped between the end face of the mounting ring 13 and the second stator body 222. In a specific embodiment, the end face of the mounting ring 13 facing the second stator body 222 is provided with a corresponding mounting groove, which can reliably position the permanent magnet 3.

[0026] The radial magnetic bearing assembly 1 also includes a radial rotor core 14, which is fitted onto a rotating shaft (specifically, for example, an air compressor shaft 100). This core can also be integrally formed with the shaft, preferably a laminated structure. The shaft also has a collar 4, which is preferably a solid structure. The collar 4 is used to determine the axial position of the thrust disc 23 and the radial rotor core 14, and to guide magnetic flux in the axial direction. The collar 4 can be integrally formed with the shaft or an assembled structure. It is understood that a single-coil axial control winding 24 is wound within the annular groove formed between the first and second axial stator cores.

[0027] See Figure 2 As shown, the radial stator core 11 has four poles, and each pole is wound with a radial control winding 12 to control and adjust the magnitude of the radial force in the quadrant where the four poles are located.

[0028] Specifically, such as Figure 3As shown, p1 is the permanent magnet bias magnetic circuit, p2 is the axial control magnetic circuit, and p3 is the radial control magnetic circuit. The direction of the permanent magnet bias magnetic circuit p1 remains unchanged. The axial control magnetic circuit p2 and the radial control magnetic circuit p3 can be changed by changing the direction of the winding current, thereby changing the magnitude of the magnetic flux in the radial air gap and the axial air gap, and thus adjusting the output direction. For ease of description, the axial stator core is divided into five parts: 8a, 8b, 8c, 8d, and 8e. Specifically, they can be combined into two parts, such as axial stator core one composed of 8a, 8b, and 8c and axial stator core two composed of 8d and 8e, or axial stator core one composed of 8a and 8b and axial stator core two composed of 8c, 8d, and 8e, etc. It can be understood that 8a corresponds to the first magnetic ring 211 part mentioned above, 8b corresponds to the first stator body 212, 8c corresponds to the intermediate magnetic guide ring 25 mentioned above, 8d corresponds to the second stator body 222, and 8e corresponds to the second magnetic ring 221. Axial air gap one is formed between 8a and the thrust plate 23, and axial air gap two is formed between 8e and the thrust plate 23.

[0029] by Figure 3 Taking the magnetic circuit direction as an example, let's analyze the magnetic circuit. Ignoring leakage flux, the magnetic flux in the axial direction mainly has the following paths:

[0030] ①Permanent magnet 3-8c-8b-8a-Axial air gap - Thrust disk 23-Collar 4-Radial rotor core 14-Radial air gap -Radial stator core 11-Permanent magnet 3;

[0031] ②Permanent magnet 3-8d-8e-Axial air gap 2-Thrust disk 23-Collar 4-Radial rotor core 14-Radial air gap-Radial stator core 11-Permanent magnet 3;

[0032] ③8a-Axial air gap one-Thrust disk 23-Axial air gap two-8e-8d-8c-8b-8a;

[0033] ④8a-8b-8c-8d-8e-Axial air gap two-Thrust disk 23-Axial air gap one-8a.

[0034] When there is no control current, the magnetic circuit is a combination of paths ① and ②, according to the magnetic reluctance formula... R is the magnetic reluctance, l is the magnetic path length, A is the magnetic path area, μ is the magnetic permeability, and the width la of 8a (i.e., the radial thickness of the first magnetic ring 211 mentioned above) is equal to the width le of 8e (i.e., the radial thickness of the second magnetic ring 221 mentioned above is le). The width lb of 8b (i.e., the axial thickness of the first stator body 212) is equal to the width ld of 8d (i.e., the axial thickness of the second stator body 222). Since the magnetic path lengths of 8a, 8b, and 8c in path ① are longer, the magnetic reluctance Rt1 in path ① and the magnetic reluctance Rt2 in path ② have Rt1>Rt2. Consequently, the axial air gap flux Φ01 in path ① and the axial air gap flux Φ02 in path ② have Φ01<Φ02. The thrust disk flux Φp=Φ01+Φ02.

[0035] When a positive control current i is applied, the magnetic circuit is a combination of paths ① and ② when i is small, Φp = Φ01 + Φ02. As i increases, the component of path ① increases and the component of path ② decreases. When the permanent magnet bias is just offset in the second axial stator core, the magnetic circuit only exhibits path ①, Φp = Φ01. If i is further increased, it will exhibit a combination of paths ① and ③, and the larger i is, the larger the component of path ③ is, Φp = Φ01 - Φ02.

[0036] When a control current -i is applied, the electrical excitation is opposite to the bias direction of the permanent magnet in the first axial stator core and the same as the bias direction of the permanent magnet in the second axial stator core. When the current -i is small, the magnetic circuit is a combination of paths ① and ②, Φp = Φ01 + Φ02, and as i increases, the component of path ① decreases while the component of path ② increases; when the permanent magnet bias is just offset in the first axial stator core, the magnetic circuit only exhibits path ②, Φp = Φ02; as i continues to increase, it will exhibit a combination of paths ② and ④, and the larger i is, the larger the component of path ④ is, Φp = Φ02 - Φ01.

[0037] According to the definition of magnetic flux Where B is the magnetic flux density, Φ is the magnetic flux, and A is the magnetic circuit area. Since Φ01 < Φ02 in the initial state without control current, the forward current must be greater than the reverse current to cancel the permanent magnet bias. That is, under the same current in different directions, the magnetic flux density of the second axial stator core is higher. Therefore, the core reluctances Rt1 and Rt2 at control current i and the core reluctances R't1 and R't2 at control current -i satisfy: Rt1<R't2,Rt2> R't1. Furthermore, the air gap fluxes Φ01 and Φ02 under control current i and the air gap fluxes Φ'01 and Φ'02 under control current -i satisfy: Φ01 > Φ'02, Φ02 < Φ'01. Therefore, Figure 3The maximum load-bearing capacity to the left is greater than the maximum load-bearing capacity to the right. Therefore, to balance the axial load-bearing capacity, the magnetic reluctance of magnetic circuit ② needs to be reduced, i.e., the magnetic circuit area of ​​magnetic circuit ② needs to be increased, requiring la < le and lb < ld. la and le directly determine the air gap area and also affect the core magnetic reluctance, thus affecting the bearing output. As le increases, the magnetic flux density and magnetic reluctance of the 8e portion decrease, Φ02 increases, and the bearing output to the right increases while the output to the left remains unchanged. However, at the same time, the increase in Φ02 increases the magnetic flux density and magnetic reluctance of the 8d portion. When 8e increases to a certain size, the magnetic reluctance of the 8d portion increases significantly, which leads to a slowdown in the rate of increase of axial output. If 8e continues to increase, the bearing output may decrease due to the excessively high magnetic flux density of the 8d portion. Therefore, an appropriate increase in le can balance the axial load-bearing capacity, but too much le can easily lead to a decrease in bearing output. The preferred value is 0.8 ≤ la / le < 1. Increasing ld within a certain range can reduce the magnetic flux density of the 8d portion of the second axial stator core, thereby increasing the backward load capacity. After ld increases to a certain value, the magnetic flux density of the 8d portion decreases, and the magnetic reluctance of the core decreases significantly, having little impact on the output force. Therefore, considering both load capacity and volume, there is an optimal value for the thickness of the second axial stator core, preferably lb / ld = 0.7 to 0.95.

[0038] Based on the aforementioned magnetic circuit analysis, since the axial bias magnetic circuit p1 passing through both axial stator core one and axial stator core two will pass through the thrust disk 23, the magnetic circuit area of ​​the thrust disk 23 must be larger than that of the core magnetic circuit. That is, the axial thickness lp of the thrust disk 23 must satisfy lp > la and lp > le. Depending on the magnitude of the applied control current, the thrust disk magnetic flux Φp can take several values: Φp = Φ01 + Φ02, Φp = Φ01, Φp = Φ02, Φp = Φ01 - Φ02, and Φp = Φ01 - Φ02. Therefore, lp ≤ la + le is sufficient. Simultaneously, to ensure that the thrust disk does not experience magnetic saturation, the value of lp should not be too small; preferably, lp / (la + le) ≥ 0.7.

[0039] The axial bias magnetic circuit p1 passing through the thrust disk 23 all passes through the radial stator core 11, and the radial stator core 11 also passes through the radial control magnetic circuit p3. Therefore, the axial thickness lr of the radial stator core 11 satisfies lr≥lp. Under the maximum radial control current, the radial bias magnetic field and the radial control magnetic field cancel each other out, and the magnetic flux Φr passing through the radial stator core 11 does not exceed twice the bias magnetic flux. Therefore, lr≤2lp. Since the radial stator core 11 generally adopts a silicon steel sheet laminated structure, which has better magnetic permeability than alloy materials such as the thrust disk, the thickness of the radial stator core 11 can be appropriately reduced, taking into account the bearing volume. Preferably, 1<lr / lp≤1.8.

[0040] According to embodiments of the present invention, an air compressor, particularly an industrial air compressor, is also provided, including the aforementioned magnetic levitation hybrid three-degree-of-freedom bearing. Furthermore, the air compressor also includes a drive motor, which includes drive motor windings located at the end of the radial magnetic bearing assembly 1 away from the axial magnetic bearing assembly 2. The radial magnetic bearing assembly 1 has a radial stator core 11 with a laminated structure, reducing eddy current heating generated by the end coils of the motor windings within the solid core and improving the reliability of the magnetic bearing operation.

[0041] In some embodiments, the air compressor also includes an air compressor shaft 100, on which an impeller is mounted. During the operation of the impeller, the axial pneumatic load applied to the air compressor shaft 100 is directed from the axial magnetic bearing assembly 2 toward the radial magnetic bearing assembly 1. This combination of the axial pneumatic load of the air compressor and the axial bearing capacity of the axial magnetic bearing assembly achieves a comprehensive design of the axial force of the air compressor shaft 100.

[0042] It should be noted that the left and right directions mentioned above are all based on... Figure 1 The directions shown are for reference only.

[0043] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A magnetically levitated hybrid three-degree-of-freedom bearing, comprising a radial magnetic bearing assembly (1) and an axial magnetic bearing assembly (2) located at one end of the radial magnetic bearing assembly (1), wherein a permanent magnet (3) capable of providing a bias magnetic field is sandwiched between the radial magnetic bearing assembly (1) and the axial magnetic bearing assembly (2), characterized in that, The axial magnetic bearing assembly (2) includes a first axial stator core and a second axial stator core, wherein the second axial stator core is located between the permanent magnet (3) and the first axial stator core. The first axial stator core has a first magnetic ring (211) with a radial thickness of la. The second axial stator core has a second magnetic ring (221) with a radial thickness of le. la < le to increase the axial output force of the second axial stator core on the side closer to the permanent magnet (3). 0.8 ≤ la / le < 1.

2. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 1, characterized in that, The first axial stator core includes a first stator body (212) with an axial thickness of lb. The second axial stator core includes a second stator body (222) with an axial thickness of ld, where lb < ld.

3. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 2, characterized in that, 0.7≤lb / ld≤0.

95.

4. The magnetic levitation hybrid three-degree-of-freedom bearing according to any one of claims 1 to 3, characterized in that, The axial magnetic bearing assembly (2) further includes a thrust disk (23) located between the first axial stator core and the second axial stator core, wherein the axial thickness of the thrust disk (23) is lp, lp > la and lp > le.

5. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 4, characterized in that, lp≤la+le.

6. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 5, characterized in that, lp / (la+le)≥0.

7.

7. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 4, characterized in that, The radial magnetic bearing assembly (1) includes a radial stator core (11) with an axial thickness of lr, where lr > lp.

8. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 7, characterized in that, lr≤2lp。 9. The magnetic levitation hybrid three-degree-of-freedom bearing according to claim 8, characterized in that, 1＜lr / lp≤1.8。 10. An air compressor, characterized in that, Includes the magnetic levitation hybrid three-degree-of-freedom bearing as described in any one of claims 1 to 9.

11. The air compressor according to claim 10, characterized in that, It also includes a drive motor, which includes a drive motor winding located at one end of the radial magnetic bearing assembly (1) away from the axial magnetic bearing assembly (2), and the radial magnetic bearing assembly (1) has a radial stator core (11) with a laminated structure.

12. The air compressor according to claim 10, characterized in that, It also includes an air compressor shaft (100), on which an impeller is mounted. During the operation of the impeller, the direction of the axial pneumatic load applied to the air compressor shaft (100) is from the axial magnetic bearing assembly (2) toward the radial magnetic bearing assembly (1).

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