Magnetic flux complete decoupling type three-degree-of-freedom magnetic bearing

Abstract

The invention discloses a magnetic flux complete decoupling type three-degree-of-freedom magnetic bearing which comprises a rotor part and a stator part. The stator part comprises a stator ring, an L-shaped axial stator iron core, a bias stator iron core, a radial stator iron core, a radial bias permanent magnet ring, an axial bias permanent magnet and a magnetic isolation sheet. The rotor part comprises an outer-layer thrust disc, an inner-layer thrust disc, a radial biased permanent magnet ring, an axial biased permanent magnet and a magnetic isolation sheet. A control winding is wound on each radial stator iron core in three directions, namely a 0-degree direction, a 60-degree direction and a 120-degree direction, and the two radial control windings in each direction are connected in series to finally form three radial control windings which are used for controlling the three directions and are driven by three switching power amplifiers. According to the magnetic flux complete decoupling type three-degree-of-freedom hybrid magnetic bearing, static suspension of the rotor is achieved through the two sets of opposite permanent magnets, dynamic displacement adjustment of the rotor is achieved through the suspension winding, a permanent magnet magnetic field and a suspension winding magnetic field do not share an air gap, loss caused by magnetic flux crossing is effectively reduced, and the bearing performance is improved. And the current sensitivity and the maximum axial and radial bearing capacity are improved.

Description

Technical Field

[0001] The present invention relates to the field of bearing manufacturing technology and proposes a simple-to-control three-degree-of-freedom hybrid magnetic bearing. The control magnetic flux and the bias magnetic flux generated by the permanent magnet are completely decoupled, which can effectively reduce the power consumption of the system during operation and generate greater axial and radial controllable suspension force. Background Art

[0002] Magnetic bearings (MBLs) achieve stable rotor suspension by controlling electromagnetic forces. Compared to traditional mechanical bearings, they offer numerous advantages, including the lack of lubrication, negligible friction losses, lower maintenance requirements, and higher rotational speeds. Consequently, MBLs have been widely used in a variety of high-speed rotating machinery. Their unique advantages have given them high application value and broad prospects in areas such as turbomolecular pumps, flywheel energy storage systems, and air compressors.

[0003] Although the classic three-degree-of-freedom hybrid magnetic bearing system has the advantage of high integration, there is generally a high coupling between the control flux and the bias flux. While increasing the system's operating power consumption, it also causes the rotor to demagnetize at high speeds, which is not conducive to rapid adjustment of the system. Summary of the Invention

[0004] Purpose of the invention: The present invention solves the problem of serious coupling between the bias flux and the control flux of the existing three-degree-of-freedom hybrid magnetic bearing, and proposes a three-degree-of-freedom magnetic bearing with completely decoupled magnetic flux, which makes the control flux and the bias flux completely independent, and the axial and radial control fluxes are completely independent of the bias flux circuit, effectively reducing the loss caused by flux crossing, reducing the heat generated by the system during operation, and improving the current sensitivity and the maximum axial and radial bearing capacity.

[0005] Technical solution: The present invention discloses a three-degree-of-freedom hybrid magnetic bearing with complete magnetic flux decoupling, comprising a rotor part and a stator part;

[0006] The rotor part includes a rotating shaft and an inner thrust disk. The left side axially offset inner permanent magnet and the right side axially offset inner permanent magnet are respectively provided on the left and right sides of the inner thrust disk, and an aluminum magnetic isolation ring is provided on the radial outer side thereof; the radial outer side of the aluminum magnetic isolation ring is connected to the outer suction disk, and the left and right sides of the outer suction disk are connected to the left inner groove and the right inner groove through an aluminum magnetic isolation sheet, which are respectively used to fix the left radially offset inner permanent magnet ring and the right radially offset inner permanent magnet ring;

[0007] The stator part includes an outer stator ring, and the left L-shaped axial stator core and the right L-shaped axial stator core are fixed on the left and right sides respectively, and the inner side of the outer stator ring is connected to the radial stator pole; the left and right L-shaped axial stator cores are both provided with axial control windings, and the left and right L-shaped axial stator cores are respectively connected to the left biased stator core and the right biased stator core through an aluminum magnetic isolation ring 2 near the rotating shaft, and a groove is opened near the inner thrust disk, and the left axial biased external permanent magnet and the right axial biased external permanent magnet are respectively installed; a radial control magnetic flux working air gap is provided between the radial stator pole and the outer suction disk, and a radial control winding is wound on the radial stator pole, and the left outer groove and the right outer groove are respectively connected on the left and right sides of the radial stator pole near the radial control magnetic flux working air gap through an aluminum magnetic isolation plate 2, which is used to fix the left radial biased external permanent magnet ring and the right radial biased external permanent magnet ring.

[0008] Furthermore, the left radially offset outer permanent magnet ring and the left radially offset inner permanent magnet ring are placed opposite each other in the radial direction to form a left radially offset working air gap; the right radially offset inner permanent magnet ring and the right radially offset outer permanent magnet ring are placed opposite each other in the radial direction to form a right radially offset working air gap, and they are all radially magnetized; the magnetization directions of each pair of magnetic poles are opposite, and the directions of the facing magnetic poles at the working air gap are both NN or SS, and the two pairs of permanent magnet rings work together to exert radial passive magnetic suspension force on the rotor for stability.

[0009] Furthermore, the left axially offset outer permanent magnet and the left axially offset inner permanent magnet are placed opposite each other in the axial direction to form a left axially offset working air gap; the right axially offset outer permanent magnet and the right axially offset inner permanent magnet are placed opposite each other in the axial direction to form a right axially offset working air gap; they are all axially magnetized, the magnetization direction of each pair of magnetic poles is opposite, and the directions of the facing magnetic poles at the working air gap are both NN or SS, and the two pairs of permanent magnets work together to exert axial passive magnetic levitation force on the rotor for stability.

[0010] Furthermore, in the three directions of 0 degree, 60 degree and 120 degree, two radial control windings in each direction are connected in series to finally form three radial control windings for controlling the three directions and driven by three switching power amplifiers, and a total of six control magnetic fields are generated after the windings are energized.

[0011] Furthermore, the axial control windings inside the left and right L-shaped axial stator cores are embedded inside the left and right L-shaped axial stator cores after being wound and insulated.

[0012] Furthermore, the parameters of the left axially offset outer permanent magnet and the right axially offset outer permanent magnet, and the left axially offset inner permanent magnet and the right axially offset inner permanent magnet are determined as follows:

[0013] First determine the axial offset load Fz , according to the formula The axial area S of a single permanent magnet can be pm , and then by the formula That is to say, the axial magnetization length of the permanent magnet ring is obtained; where B max is the air gap saturation magnetic induction intensity, R pm is the magnetic resistance inside the permanent magnet, H c is the coercive force of the permanent magnet, L pm is the axial magnetization length of the permanent magnet.

[0014] Furthermore, the maximum value of the axial suspension force is selected as the axial offset bearing capacity F z 1.2 times of the axial control winding to ensure that a 20% control margin is retained after the current is passed through the axial control winding.

[0015] Furthermore, the parameters of the left radially offset outer permanent magnet ring, the right radially offset outer permanent magnet ring, the left radially offset inner permanent magnet ring, and the right radially offset inner permanent magnet ring are determined as follows:

[0016] First determine the radial offset load F y , through the radial offset load F y The relevant parameters of the left radially offset outer permanent magnet ring, the right radially offset outer permanent magnet ring, the left radially offset inner permanent magnet ring, and the right radially offset inner permanent magnet ring are obtained by combining the following expressions:

[0017]

[0018] Among them, B r is the residual magnetic induction intensity of the air gap, R1, R2, R3, and R4 are the inner diameter of the left and right radially offset inner permanent magnet ring, the outer diameter of the left and right radially offset inner permanent magnet ring, the inner diameter of the left and right radially offset inner permanent magnet ring, and the outer diameter of the left and right radially offset inner permanent magnet ring, respectively; r1 and r2 represent the radii of the left and right radially offset inner permanent magnet ring, and the left and right radially offset inner permanent magnet ring; α and β represent the angular independent variables of the inner and outer permanent magnets during integration, and their value ranges are 0-2π; d r1 d r2 d α d β Respectively represent the differentials of r1, r2, α, and β; Δ x is the radial offset of the rotor, They are:

[0019]

[0020] Beneficial effects:

[0021] The present invention proposes a three-degree-of-freedom magnetic bearing with completely decoupled magnetic flux. Separate magnetic circuits are provided for radial and axial bias fluxes, which are not coupled with the magnetic circuit for the control flux, thus ensuring the stability of the magnetic circuit during high-speed operation. By isolating the radial-axial passive suspension portion from the active suspension portion to achieve complete decoupling of the bias flux from the control flux, the coupling between the radial-axial control flux and the bias flux generated by the permanent magnet is virtually eliminated, achieving greater radial and axial suspension forces at low control currents. This effectively reduces the nonlinearity of the control current vs. load-bearing capacity curve and improves the sensitivity of the control current for each phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the radial structure and radial control magnetic flux of a three-degree-of-freedom magnetic bearing with complete magnetic flux decoupling according to the present invention;

[0023] Figure 2 This is a schematic diagram of the axial structure and magnetic flux of a three-degree-of-freedom magnetic bearing with complete magnetic flux decoupling according to the present invention;

[0024] Figure 3 This is a comparison diagram of permanent magnet parameters of a three-degree-of-freedom magnetic bearing with complete magnetic flux decoupling according to the present invention;

[0025] Figure 4 This is a simulation diagram of the bias flux of a three-degree-of-freedom magnetic bearing with complete flux decoupling of the present invention.

[0026] Among them, 1- outer stator ring, 2- left L-shaped axial stator core, 3- right L-shaped axial stator core, 4- axial control winding, 5- left outer groove, 6- right outer groove, 7- left radially offset outer permanent magnet ring, 8- right radially offset outer permanent magnet ring, 9- left radially offset inner permanent magnet ring, 10- right radially offset inner permanent magnet ring, 11- left inner groove, 12- right inner groove, 13- axial suspension winding magnetic field, 14- left axially offset outer permanent magnet, 15- right axially offset outer permanent magnet, 16- left axially offset inner permanent magnet, 17- right axially offset inner permanent magnet, 18- rotor Shaft, 19-left axial offset working air gap, 20-right axial offset working air gap, 21-left offset stator core, 22-right offset stator core, 23-aluminum magnetic isolation ring 1, 24-left axial suspension winding air gap, 25-right axial suspension winding air gap, 26-outer suction disk, 27-left radial offset working air gap, 28-right radial offset working air gap, 29-radial control flux working air gap, 30-radial stator pole, 31-radial control winding, 32-control magnetic field, 33-inner thrust disk, 34-aluminum magnetic isolation plate 1, 35-aluminum magnetic isolation ring 2, 36-aluminum magnetic isolation plate 2. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] The invention discloses a magnetic flux completely decoupled three-degree-of-freedom magnetic bearing, comprising a rotor part and a stator part.

[0029] The rotor comprises a rotating shaft 18 and an inner thrust disc 33. The rotating shaft 18 extends through the inner thrust disc 33. The inner thrust disc 33 is provided with a left axially offset inner permanent magnet 16 and a right axially offset inner permanent magnet 17 on its left and right sides, respectively. An aluminum magnetic isolation ring 23 is provided radially outwardly of the inner thrust disc 33. The outer radial side of the aluminum magnetic isolation ring 23 is connected to the outer suction disc 26. The left and right inner grooves 11 and 12 are connected by aluminum magnetic isolation plates 34 on the left and right sides, respectively, to secure the left and right radially offset inner permanent magnet rings 9 and 10.

[0030] The stator section includes an outer stator ring 1. The left and right L-shaped axial stator cores 2 and 3 are fixed to the outer stator ring 1, respectively. Radial stator poles 30 are connected to the inner side of the outer stator ring 1. Axial control windings 4 are located within the L-shaped axial stator cores. After winding and insulation, the axial control windings 4 are embedded within the left and right L-shaped axial stator cores. During operation, the axial control windings 4 generate an axial suspension winding magnetic field 13.

[0031] A left axial suspension winding air gap 24 and a right axial suspension winding air gap 25 are formed between the left L-shaped axial stator core 2 , the right L-shaped axial stator core 3 and the outer suction disk 26 .

[0032] The left and right L-shaped axial stator cores are respectively connected to the left biased stator core 21 and the right biased stator core 22 near the rotating shaft 18 through an aluminum magnetic isolation ring 35. A groove is opened near the inner thrust plate 33 to install the left axial biased external permanent magnet 14 and the right axial biased external permanent magnet 15 respectively.

[0033] A radial control winding 31 is wound on the radial stator pole 30, and a radial control magnetic flux working air gap 29 is set between the radial stator pole 30 and the outer suction disk 26. The left outer groove 5 and the right outer groove 6 are respectively connected on the left and right sides near the radial control magnetic flux working air gap 29 through magnetic isolation plates 23, which are used to fix the left radial biased outer permanent magnet ring 7 and the right radial biased outer permanent magnet ring 8.

[0034] A pair of radially magnetized permanent magnet rings are located on either side of the radially controlled flux working air gap 29: a left radially offset outer permanent magnet ring 7, a left radially offset inner permanent magnet ring 9, a right radially offset inner permanent magnet ring 10, and a right radially offset outer permanent magnet ring 8. The left radially offset outer permanent magnet ring 7 and the left radially offset inner permanent magnet ring 9 are positioned radially opposite each other to form a left radially offset working air gap 27, while the right radially offset inner permanent magnet ring 10 and the right radially offset outer permanent magnet ring 8 are positioned radially opposite each other to form a right radially offset working air gap 28. Each pair of magnetic poles has opposite magnetization directions, and the facing magnetic poles at the working air gap are either NN or SS. The two pairs of permanent magnet rings work together to exert a radial passive magnetic levitation force that stabilizes the rotor.

[0035] The inner thrust disc 33 is flanked by a pair of axially magnetized permanent magnet rings on either side: an axially offset outer permanent magnet 14 and an axially offset inner permanent magnet 16 on the left side, and a right axially offset outer permanent magnet 15 and an axially offset inner permanent magnet 17 on the right side. The left axially offset outer permanent magnet 14 and the left axially offset inner permanent magnet 16 are axially opposed to each other, forming a left axially offset working air gap 19; the right axially offset outer permanent magnet 15 and the right axially offset inner permanent magnet 17 are axially opposed to each other, forming a right axially offset working air gap 20. Each pair of magnetic poles is magnetized in opposite directions, with the facing poles at the working air gap oriented in either NN or SS directions. The two pairs of permanent magnets work together to exert a stable axial passive magnetic levitation force on the rotor.

[0036] The coils of two adjacent radial control windings 31 in the 0-degree, 60-degree, and 120-degree directions are connected in series and driven by three switching amplifiers. When each winding is energized, a total of six control magnetic fields 32 are generated. The magnetic flux paths of the control magnetic fields 32 do not pass through the permanent magnet field, and there is no coupling between the two. This allows the magnetic flux amplitude of each magnetic flux at its respective working air gap to reach the saturation air gap magnetic flux density value, achieving higher magnetic flux utilization efficiency.

[0037] The parameters of the axial annular permanent magnets (the left axially offset outer permanent magnet 14 and the right axially offset outer permanent magnet 15, the left axially offset inner permanent magnet 16 and the right axially offset inner permanent magnet 17) are determined as follows:

[0038] First determine the axial offset load F z , according to the formula The axial area S of a single permanent magnet ring can be pm , and then by the formula The axial magnetization length of the permanent magnet ring can be obtained. max is the air gap saturation magnetic induction intensity, which is generally set to 1.2T and can be adjusted appropriately according to the material used. pm is the magnetic resistance inside the permanent magnet, H c is the coercive force of the permanent magnet, L pm is the axial magnetization length of the permanent magnet.

[0039] The maximum value of the axial suspension force is selected as the axial offset bearing capacity F z 1.2 times of the axial control winding 4, ensuring that a 20% control margin is retained after current is passed through the axial control winding 4.

[0040] Determine the parameters of the radial permanent magnet rings (left radial offset outer permanent magnet ring 7, right radial offset outer permanent magnet ring 8, left radial offset inner permanent magnet ring 9 and right radial offset inner permanent magnet ring 10). First, determine the radial offset bearing capacity F. y , through the radial offset load F y The relevant parameters of the radially magnetized permanent magnet ring can be obtained by combining the following expressions.

[0041]

[0042] Among them, B r is the residual magnetic induction intensity of the air gap, R1, R2, R3, and R4 are the inner diameters of the left and right radially offset inner permanent magnet rings 9 and 10, the outer diameters of the left and right radially offset inner permanent magnet rings 9 and 10, the inner diameters of the left and right radially offset inner permanent magnet rings 7 and 8, and the outer diameters of the left and right radially offset inner permanent magnet rings 7 and 8, respectively; r1 and r2 represent the radii of the left and right radially offset inner permanent magnet rings 9 and 10, and the left and right radially offset inner permanent magnet rings 7 and 8; α and β represent the angular independent variables of the inner and outer permanent magnets during integration, and their value ranges are both 0-2π; d r1 d r2 d α d β Respectively represent the differentials of r1, r2, α, and β; Δ x is the radial offset of the rotor, They are:

[0043]

[0044] Figure 4 This is a simulation diagram of the bias flux of a three-degree-of-freedom magnetic bearing with completely decoupled magnetic flux in the present invention. It can be seen from the figure that the magnetic flux generated by the radial and axial permanent magnets does not pass through the outer thrust plate, ensuring the complete independence of the control magnetic flux and the bias magnetic flux, and can minimize the coupling between the magnetic flux and the magnetic flux.

[0045] The technical means disclosed in the solutions of the present invention are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A three-degree-of-freedom hybrid magnetic bearing with complete magnetic flux decoupling, comprising a rotor portion and a stator portion; characterized in that: The rotor part includes a rotating shaft (18) and an inner thrust disk (33). The left and right sides of the inner thrust disk (33) are respectively provided with a left axially offset inner permanent magnet (16) and a right axially offset inner permanent magnet (17). An aluminum magnetic isolation ring (23) is provided on the radial outer side thereof. The radial outer side of the aluminum magnetic isolation ring (23) is connected to the outer suction disk (26). The left and right sides of the outer suction disk (26) are connected to the left inner groove (11) and the right inner groove (12) through an aluminum magnetic isolation sheet (34), which are respectively used to fix the left radially offset inner permanent magnet ring (9) and the right radially offset inner permanent magnet ring (10). The stator part comprises an outer stator ring (1), and the left L-shaped axial stator core (2) and the right L-shaped axial stator core (3) are fixed on the left and right sides of the outer stator ring (1), and the inner side of the outer stator ring (1) is connected to the radial stator magnetic pole (30); the left L-shaped axial stator core (2) and the right L-shaped axial stator core (3) are both provided with axial control windings (4) inside, and the left and right L-shaped axial stator cores are respectively connected to the left biased stator core (21) and the right biased stator core (22) through the aluminum magnetic isolation ring (35) at the position close to the rotating shaft, and a recess is provided at the position close to the inner thrust plate (33). The invention relates to a radial stator magnetic pole (30) and an outer layer suction disk (26). The radial stator magnetic pole (30) is provided with a radial control magnetic flux working air gap (29). The radial stator magnetic pole (30) is provided with a radial control winding (31). The radial stator magnetic pole (30) is provided with an aluminum magnetic isolation plate (36) on both sides thereof near the radial control magnetic flux working air gap (29). The left outer groove (5) and the right outer groove (6) are connected respectively to fix the left radial biased outer permanent magnet ring (7) and the right radial biased outer permanent magnet ring (8).

2. The flux-decoupled three-degree-of-freedom magnetic bearing according to claim 1, characterized in that: The left radially offset outer permanent magnet ring (7) and the left radially offset inner permanent magnet ring (9) are placed opposite each other in the radial direction to form a left radially offset working air gap (27); the right radially offset inner permanent magnet ring (10) and the right radially offset outer permanent magnet ring (8) are placed opposite each other in the radial direction to form a right radially offset working air gap (28), and both are radially magnetized; the magnetization directions of each pair of magnetic poles are opposite, and the directions of the facing magnetic poles at the working air gap are both NN or SS, and the two pairs of permanent magnet rings work together to exert radial passive magnetic suspension force on the rotor for stability.

3. The flux-decoupled three-degree-of-freedom magnetic bearing according to claim 1, characterized in that: The left axially offset outer permanent magnet (14) and the left axially offset inner permanent magnet (16) are placed opposite each other in the axial direction to form a left axially offset working air gap (19); the right axially offset outer permanent magnet (15) and the right axially offset inner permanent magnet (17) are placed opposite each other in the axial direction to form a right axially offset working air gap (20); They are all axially magnetized, and the magnetization direction of each pair of magnetic poles is opposite. The directions of the opposite magnetic poles at the working air gap are NN or SS. The two pairs of permanent magnets work together to exert a stable axial passive magnetic suspension force on the rotor.

4. The flux-decoupled three-degree-of-freedom magnetic bearing according to claim 1, characterized in that: In the three directions of 0 degree, 60 degree and 120 degree, two radial control windings (31) in each direction are connected in series to finally form three radial control windings for controlling the three directions and driven by three switching power amplifiers. After the radial control windings (31) are energized, a total of six control magnetic fields (32) are generated.

5. The flux completely decoupled three-degree-of-freedom magnetic bearing according to claim 1, characterized in that: The axial control windings (4) inside the left and right L-shaped axial stator cores are embedded inside the left and right L-shaped axial stator cores after winding and insulation.

6. The flux completely decoupled three-degree-of-freedom magnetic bearing according to claim 1, characterized in that: A left axial suspension winding air gap (24) and a right axial suspension winding air gap (25) are formed between the left L-shaped axial stator core (2), the right L-shaped axial stator core (3) and the outer suction disk (26).

7. A flux completely decoupled three-degree-of-freedom magnetic bearing according to any one of claims 1 to 6, characterized in that: The method for determining the parameters of the left axially biased outer permanent magnet (14) and the right axially biased outer permanent magnet (15), and the left axially biased inner permanent magnet (16) and the right axially biased inner permanent magnet (17) is as follows: First determine the axial offset load F z , according to the formula The axial area S of a single permanent magnet is obtained pm , and then by the formula That is to say, the axial magnetization length L of the permanent magnet ring is obtained. pm Where B max is the air gap saturation magnetic induction intensity, R pm is the magnetic resistance inside the permanent magnet, H c is the coercive force of the permanent magnet, L pm is the axial magnetization length of the permanent magnet; the maximum value of the axial suspension force is selected as the axial bias bearing capacity F z 1.2 times of the axial control winding (4), ensuring that a 20% control margin is retained after current is passed through the axial control winding (4).

8. A flux completely decoupled three-degree-of-freedom magnetic bearing according to any one of claims 1 to 6, characterized in that: The method for determining the parameters of the left radially offset outer permanent magnet ring (7), the right radially offset outer permanent magnet ring (8), the left radially offset inner permanent magnet ring (9) and the right radially offset inner permanent magnet ring (10) is as follows: First determine the radial offset load F y , through the radial offset load F y The relevant parameters of the left radially offset outer permanent magnet ring (7), the right radially offset outer permanent magnet ring (8), the left radially offset inner permanent magnet ring (9) and the right radially offset inner permanent magnet ring (10) are obtained by combining the following expressions: Among them, B r is the residual magnetic induction intensity of the air gap, R1, R2, R3, and R4 are respectively the inner diameter of the left and right radially offset inner permanent magnet rings (9, 10), the outer diameter of the left and right radially offset inner permanent magnet rings (9, 10), the inner diameter of the left and right radially offset inner permanent magnet rings (7, 8), and the outer diameter of the left and right radially offset inner permanent magnet rings (7, 8), r1 and r2 represent the radii of the left and right radially offset inner permanent magnet rings (9, 10), and the left and right radially offset inner permanent magnet rings (7, 8); α and β represent the angular independent variables of the inner and outer permanent magnets during integration, and both range from 0 to 2π; d r1 d r2 d α d β Respectively represent the differentials of r1, r2, α, and β; Δ x is the radial offset of the rotor, They are:

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