Double-stator radial two-degree-of-freedom hybrid magnetic bearing

Abstract

The invention discloses a double-stator radial two-degree-of-freedom hybrid magnetic bearing which comprises an outer stator, a rotor and an inner stator. The rotor is located between the inner stator and the outer stator, an inner air gap and an outer air gap exist between the rotor and the inner stator as well as between the rotor and the outer stator, the outer stator comprises three magnetic poles, a coil is wound on each magnetic pole, the coils in the 0-degree direction, the 120-degree direction and the 240-degree direction are respectively connected in parallel to form suspension windings in the 0-degree direction, the 120-degree direction and the 240-degree direction, and the suspension windings are driven by three switch power amplifiers. An inner permanent magnet ring is arranged on the inner side of the rotor, an outer permanent magnet ring is arranged on the outer side of the inner stator, and the outer permanent magnet ring and the inner permanent magnet ring are opposite in position and identical in polarity at the inner air gap. According to the double-stator radial two-degree-of-freedom hybrid magnetic bearing provided by the invention, the inner stator balances the static load of the rotor, the suspension winding on the outer stator is electrified to realize the dynamic adjustment of the radial displacement of the rotor, and the permanent magnetic field and the suspension winding magnetic field do not share an air gap, so that the energy consumption is reduced, the suspension force is increased, the suspension precision of the rotor is improved, and the dynamic and static performance is good.

Description

Technical Field

[0001] The present invention relates to the technical field of bearing manufacturing, and in particular to a permanent magnet biased two-degree-of-freedom magnetic bearing with simple control assembly, a semi-suspended state when there is no power amplifier between the stator and rotor, and mutual decoupling of the suspension winding magnetic flux and the permanent magnet magnetic field, which can effectively reduce system operating losses and control current. Background Art

[0002] Magnetic bearings have the advantages of no friction, wear, low noise, cleanliness, and no need for lubrication, which gives them irreplaceable unique advantages over traditional mechanical bearings. Therefore, they have broad application prospects in modern industry and mechanical manufacturing.

[0003] There are two main structures of existing radial two-degree-of-freedom hybrid magnetic bearings, namely heteropolar and homopolar types. The homopolar type uses two identical sheet-like stator and rotor structures, and then places a permanent magnet ring between the two stators to provide bias magnetic flux for the two sheet-like stators and rotors. The suspension winding on the stator magnetic pole is energized to generate suspension magnetic flux, and the two are superimposed in the air gap under the stator magnetic pole to generate suspension force; while the heteropolar two-degree-of-freedom hybrid magnetic bearing divides the magnetic poles on the stator into permanent magnetic poles and suspension poles, installs permanent magnets on the permanent magnetic poles, and winds suspension windings on the suspension poles to generate permanent magnetic fields and suspension magnetic flux respectively. Both pass through the suspension poles and are superimposed in the air gap under the suspension poles to generate suspension force.

[0004] The suspension flux and permanent magnetic field generated by the two radial two-degree-of-freedom hybrid magnetic bearings mentioned above must be superimposed within the same air gap to form a controllable suspension force. To ensure an unsaturated magnetic field, the permanent magnetic density and suspension flux density at the air gap can only be designed to be half the air gap saturation density, resulting in low static load-bearing capacity and controllable suspension force. Furthermore, the permanent magnets are installed between the two poles or inside the stator, making assembly difficult and requiring high precision. In other words, the suspension windings and permanent magnets of existing two-degree-of-freedom hybrid magnetic bearings share the stator space, and the suspension flux and bias flux share the core and air gap, resulting in a low maximum suspension force. Summary of the Invention

[0005] Purpose of the invention: In response to the technical difficulties in the background technology, the present invention proposes a dual-stator radial two-degree-of-freedom hybrid magnetic bearing. By setting an inner and outer stator, the outer stator has only a suspension winding, and permanent magnets are set on the inner side of the inner rotor and the outer side of the inner stator. The two permanent magnets have the same polarity facing the inner air gap, generating an uncontrollable suspension force that causes the rotor to be statically suspended. The design of this suspension force is based on balancing the static load of the rotor, and the suspension winding is energized to generate a controllable suspension force that adjusts the dynamic balance of the rotor. The permanent magnet flux and the suspension winding magnetic field do not share the air gap, the controllable suspension force is large, and the two magnetic fluxes are uncoupled.

[0006] Technical solution: The present invention discloses a dual-stator radial two-degree-of-freedom hybrid magnetic bearing, comprising a stator part and a rotor part.

[0007] The stator part includes an outer stator and an inner stator. The outer stator consists of three stator poles and a stator yoke, wherein each stator pole is wound with a coil; the inner stator includes a cylindrical inner stator core, the outer side of the inner stator core is provided with a groove, and an inner permanent magnet ring is arranged in the groove, and the inner permanent magnet ring is magnetized in the radial direction;

[0008] The rotor part includes a rotor and an outer permanent magnet ring fixed on the inner side of the rotor. The outer permanent magnet ring is magnetized radially, and the magnetic pole close to the rotor side is an S pole. The rotor and the outer permanent magnet ring are installed between the inner stator and the outer stator, and there is an inner air gap between the rotor and the inner stator, and an outer air gap between the rotor and the outer stator. The magnetic pole of the inner permanent magnet ring close to the inner air gap side is an N pole, and the magnetic pole of the inner permanent magnet ring close to the inner stator iron core side is an S pole.

[0009] Furthermore, the outer permanent magnetic ring and the inner permanent magnetic ring are placed opposite each other to generate two permanent magnetic fields;

[0010] The permanent magnetic field generated by the outer permanent magnetic ring starts from the N pole of the outer permanent magnetic ring, passes through the inner air gap, repels the permanent magnetic field generated by the inner permanent magnetic ring, passes through the rotor and returns to the S pole of the outer permanent magnetic ring, forming a complete circuit;

[0011] The second permanent magnetic field generated by the inner permanent magnetic ring starts from the N pole of the inner permanent magnetic ring, passes through the inner air gap, repels the permanent magnetic field generated by the outer permanent magnetic ring, passes through the inner stator core and returns to the S pole of the inner permanent magnetic ring, forming a complete circuit;

[0012] The magnetic poles at the inner air gap are all N or S poles, and the two permanent magnetic fields repel each other with the same polarity, generating an uncontrollable suspension force that balances the static suspension of the rotor.

[0013] Furthermore, the coils in the 0-degree, 120-degree and 240-degree directions are connected in parallel to form three suspension windings, which are driven by three switching power amplifiers. When each suspension winding is energized, three suspension winding magnetic fields are generated. The suspension winding magnetic field forms a closed path between the stator poles, stator yoke, rotor and external air gap.

[0014] Furthermore, the method for determining the parameters of the outer permanent magnet ring and the inner permanent magnet ring is as follows:

[0015] First, determine the static load based on the rotor's own gravity and the connected load, the total suspension force F s Selected as six times the rotor (6) weight G, that is, F s =6G, where F s The uncontrollable suspension force F r Combined with the controllable suspension force F, select F s =5G, F=G;

[0016] Furthermore, the maximum uncontrollable suspension force F can be calculated as follows: r The expressions are used to get the parameters related to permanent magnets:

[0017]

[0018] Where B r is the residual magnetic induction intensity of the inner and outer permanent magnet rings, which can be taken as 1.4T; μ0 is the magnetic permeability of air; δ is the radial air gap length; R1 is the average radius of the outer permanent magnet ring, and R2 is the average radius of the inner permanent magnet ring; the axial lengths of the inner and outer permanent magnet rings are equal and are taken as L.

[0019] The expression of the mean radius is:

[0020]

[0021] Among them, R oo Represents the outer diameter of the outer permanent magnet ring, R oi Represents the inner diameter of the outer permanent magnet ring, R io Represents the outer diameter of the inner permanent magnet ring, R ii Represents the inner diameter of the inner permanent magnet ring.

[0022] Furthermore, the coil parameters are determined by the maximum controllable suspension force requirement. The force exerted by the stator magnetic poles on the rotor in each direction has an angle, and the maximum magnetic pull F in the +Y direction is y The mathematical expression is:

[0023]

[0024] Where S represents the area of ​​each magnetic pole. After determining the radial air gap length δ and the area S of a single magnetic pole, the product of the number of turns N and the current I is obtained from the radial force, and its expression is:

[0025]

[0026] Similarly, the operations in the +X direction, -X direction, and -Y direction are the same.

[0027] Furthermore, the rotor, inner stator core, stator poles and stator yoke are all made of materials with radial magnetic conductivity, and the outer permanent magnet ring and the inner permanent magnet ring are both made of rare earth permanent magnet materials.

[0028] Beneficial effects:

[0029] The present invention utilizes an outer stator, rotor, and inner stator structure. A permanent magnet with the same polarity as the permanent magnet on the outer side of the inner stator is placed on the inner side of the rotor to generate a permanent magnetic field. The interaction between the two generates a static levitation force. The outer stator only has a suspension winding to generate a suspension winding magnetic field, which in turn generates a controllable levitation force. This levitation force is designed to balance the static load of the rotor. When the suspension winding is energized, a controllable levitation force is generated to adjust the dynamic balance of the rotor. The permanent magnet flux and the suspension winding magnetic field do not share an air gap, resulting in a large controllable levitation force and no coupling between the two magnetic fluxes. The controllable levitation force and the static levitation force now utilize separate air gaps, so the magnetic flux density of each air gap is not limited to 0.5 times the saturation magnetic flux density, completely resolving the technical drawback of low air gap magnetic flux density in conventional radial two-degree-of-freedom hybrid magnetic bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the radial structure and suspension winding magnetic field of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention;

[0031] Figure 2 Schematic diagram of the axial structure and bias magnetic flux of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention;

[0032] Figure 3 Schematic diagram of parameters of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention;

[0033] Figure 4 This is a simulation diagram of the bias flux of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] The present invention discloses a dual-stator radial two-degree-of-freedom hybrid magnetic bearing.

[0036] Figure 1 The figure is a schematic diagram of the radial structure and magnetic field of the suspension winding of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention. As shown in the figure, the present invention includes a stator part and a rotor part.

[0037] The stator consists of an outer stator and an inner stator. The outer stator consists of three stator poles 2 and a stator yoke 4, each of which is wound with a coil 3. The inner stator includes a cylindrical inner stator core 1 with a groove on the outside of the inner stator core 1, which houses an inner permanent magnet ring 8. The inner permanent magnet ring 8 is magnetized radially, with the pole closest to the inner air gap 10 being the north pole and the pole closest to the inner stator core 1 being the south pole.

[0038] The rotor section includes a rotor 6 and an outer permanent magnet ring 7 fixed inside the rotor 6. The outer permanent magnet ring 7 is magnetized radially, with the magnetic pole on the side closest to the rotor 6 being the S pole. The rotor 6 and the outer permanent magnet ring 7 are installed between the inner stator and the outer stator, with an inner air gap 10 between the rotor 6 and the inner stator and an outer air gap 9 between the rotor 6 and the outer stator.

[0039] Figure 2 The diagram below shows the axial structure and bias flux of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention. The outer permanent magnet ring 7 and the inner permanent magnet ring 8 are positioned opposite each other, generating two permanent magnetic fields, one 11 and two 12. The permanent magnetic field one 11 generated by the outer permanent magnet ring 7 originates from the N pole of the outer permanent magnet ring 7, passes through the inner air gap 10, repels the permanent magnetic field generated by the inner permanent magnet ring 8, and then returns to the S pole of the outer permanent magnet ring 7 through the rotor 6, forming a complete loop. The permanent magnetic field 12 generated by the inner permanent magnet ring 8 originates from the N pole of the inner permanent magnet ring 8, passes through the inner air gap 10, repels the permanent magnetic field generated by the outer permanent magnet ring 7, and then returns to the S pole of the inner permanent magnet ring 8 through the inner stator core 1, forming a complete loop.

[0040] The magnetic poles at the inner air gap 10 are all N or S poles, and the two permanent magnetic fields repel each other with the same polarity, generating an uncontrollable suspension force that balances the static suspension of the rotor.

[0041] A coil 3 is wound around each stator pole 2. The coils in the 0-degree, 120-degree, and 240-degree directions are connected in parallel to form three suspension windings, which are driven by three switching amplifiers. When each suspension winding is energized, three suspension winding magnetic fields 5 are generated. The suspension winding magnetic field 5 forms a closed path only between the stator pole 2, the stator yoke 4, the rotor 6, and the external air gap 11, and has no coupling with the permanent magnetic field 1 11 and the permanent magnetic field 2 12. This allows the magnetic flux density of the suspension winding magnetic field at the external air gap 9 to reach the maximum saturation magnetic flux density, eliminating the limitation of 0.5 times the saturation magnetic flux density at the air gap of traditional hybrid magnetic bearings.

[0042] Figure 3 This is a schematic diagram of the parameters of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention. The method for determining the parameters of the outer permanent magnet ring 7 and the inner permanent magnet ring 8 is as follows:

[0043] Step 1: Determine the static load and total suspension force F based on the rotor's own gravity and the connected load. s Selected as six times the rotor (6) weight G, that is, F s =6G. Among them, F s The uncontrollable suspension force F r Combined with the controllable suspension force F, select F s =5G, F=G.

[0044] In the second step, the maximum uncontrollable suspension force F r The expressions are used to get the parameters related to permanent magnets:

[0045]

[0046] Where B r is the residual magnetic induction intensity of the inner and outer permanent magnet rings, which can be taken as 1.4T; μ0 is the magnetic permeability of air; δ is the radial air gap length; R1 is the average radius of the outer permanent magnet ring 7, and R2 is the average radius of the inner permanent magnet ring 8; the axial lengths of the inner and outer permanent magnet rings are equal and are taken as L.

[0047] The expression of the mean radius is:

[0048]

[0049] R oo represents the outer diameter of the outer permanent magnet ring 7, R oi Represents the inner diameter of the outer permanent magnet ring 7, R io Represents the outer diameter of the inner permanent magnet ring 8, R ii Represents the inner diameter of the inner permanent magnet ring 8.

[0050] The parameters of coil 3 are determined by the maximum controllable suspension force requirement. The force exerted by the stator pole 2 on the rotor in each direction has an angle. The maximum magnetic pull F in the +Y direction y The mathematical expression is:

[0051]

[0052] Where S represents the area of ​​each magnetic pole. After determining the radial air gap length δ and the area S of a single magnetic pole, the product of the number of turns N and the current I is obtained from the radial force, and its expression is:

[0053]

[0054] Similarly, the operations in the +X direction, -X direction, and -Y direction are the same.

[0055] In this embodiment, the rotor 6, the inner stator core 1, the stator poles 2 and the stator yoke 4 are all made of materials with good radial magnetic conductivity. The outer permanent magnet ring 7 and the inner permanent magnet ring 8 are both made of rare earth permanent magnet materials.

[0056] Figure 4 This is a simulation diagram of the bias flux of the dual-stator radial two-degree-of-freedom hybrid magnetic bearing of the present invention. It can be seen from the figure that the magnetic flux generated by the permanent magnet in the present invention only flows in the rotor 6 and the inner stator core 1, and does not invade the stator pole 2, thereby realizing the decoupling of the suspended winding magnetic field 5 and the permanent magnet magnetic field 1 11 and the permanent magnet magnetic field 2 12.

[0057] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A dual-stator radial two-degree-of-freedom hybrid magnetic bearing, comprising a stator portion and a rotor portion, characterized in that: The stator part comprises an outer stator and an inner stator, wherein the outer stator is composed of three stator magnetic poles (2) and a stator yoke (4), wherein each stator magnetic pole (2) is wound with a coil (3); the inner stator comprises a cylindrical inner stator core (1), wherein a groove is formed on the outer side of the inner stator core (1), and an inner permanent magnet ring (8) is arranged in the groove, and the inner permanent magnet ring (8) is magnetized in the radial direction; The rotor part comprises a rotor (6) and an outer permanent magnet ring (7) fixed on the inner side of the rotor (6); the outer permanent magnet ring (7) is magnetized in the radial direction, and the magnetic pole close to the rotor (6) is an S pole; the rotor (6) and the outer permanent magnet ring (7) are installed between the inner stator and the outer stator, and there is an inner air gap (10) between the rotor and the inner stator, and an outer air gap (9) between the rotor and the outer stator; the magnetic pole of the inner permanent magnet ring (8) close to the inner air gap (10) is an N pole, and the magnetic pole of the inner permanent magnet ring (8) close to the inner stator core (1) is an S pole.

2. The dual-stator radial two-degree-of-freedom hybrid magnetic bearing according to claim 1, characterized in that: The outer permanent magnetic ring (7) and the inner permanent magnetic ring (8) are placed opposite each other to generate two permanent magnetic fields; The permanent magnetic field (11) generated by the outer permanent magnetic ring (7) starts from the N pole of the outer permanent magnetic ring (7), passes through the inner air gap (10), repels the permanent magnetic field generated by the inner permanent magnetic ring (8), passes through the rotor (6), and returns to the S pole of the outer permanent magnetic ring (7), forming a complete circuit; The second permanent magnetic field (12) generated by the inner permanent magnetic ring (8) starts from the N pole of the inner permanent magnetic ring (8), passes through the inner air gap (10), repels the permanent magnetic field generated by the outer permanent magnetic ring (7), passes through the inner stator core (1) and returns to the S pole of the inner permanent magnetic ring (8), forming a complete circuit; The magnetic poles at the inner air gap (10) are all N poles or S poles, and the two permanent magnetic fields repel each other with the same polarity, thereby generating an uncontrollable suspension force that balances the static suspension of the rotor.

3. The dual-stator radial two-degree-of-freedom hybrid magnetic bearing according to claim 1, characterized in that: The coils in the 0-degree direction, the 120-degree direction, and the 240-degree direction are connected in parallel to form three suspension windings, which are driven by three switch G amplifiers. When each suspension winding is energized, three suspension winding magnetic fields (5) are generated. The suspension winding magnetic fields (5) form a closed path between the stator pole (2), the stator yoke (4), the rotor (6), and the external air gap (9).

4. The dual-stator radial two-degree-of-freedom hybrid magnetic bearing according to claim 1, characterized in that: The method for determining the parameters of the outer permanent magnetic ring (7) and the inner permanent magnetic ring (8) is as follows: Step 1: Determine the static load and total suspension force F based on the rotor's own gravity and the connected load. s Selected as six times the rotor (6) weight G, that is, F s =6G, where F s The uncontrollable suspension force F r Combined with the controllable suspension force F, select F s =5G, F=G; Step 2: Through the following maximum uncontrollable suspension force F r The expressions are used to get the parameters related to permanent magnets: Where B r is the residual magnetic induction intensity of the inner and outer permanent magnet rings (8, 7), which is 1.4T; μ0 is the air magnetic permeability; δ is the radial air gap length; R1 is the average radius of the outer permanent magnet ring (7), and R2 is the average radius of the inner permanent magnet ring (8); the axial lengths of the inner and outer permanent magnet rings (8, 7) are equal, which is L; the average radius expression is: Among them, R oo represents the outer diameter of the outer permanent magnet ring (7), R oi represents the inner diameter of the outer permanent magnet ring (7), R io represents the outer diameter of the inner permanent magnet ring (8), R ii represents the inner diameter of the inner permanent magnet ring (8).

5. The dual-stator radial two-degree-of-freedom hybrid magnetic bearing according to claim 1, characterized in that: The parameters of the coil (3) are determined by the maximum controllable suspension force requirement. The force exerted by the stator pole (2) on the rotor in each direction has an angle. The maximum magnetic pull F in the +Y direction is y The mathematical expression is: Where S represents the area of ​​each magnetic pole. After determining the radial air gap length δ and the area S of a single magnetic pole, the product of the number of turns N and the current I is obtained from the radial force, and its expression is: Similarly, the operations in the +X direction, -X direction, and -Y direction are the same.

6. A dual-stator radial two-degree-of-freedom hybrid magnetic bearing according to any one of claims 1 to 5, characterized in that: The rotor (6), the inner stator core (1), the stator poles (2) and the stator yoke (4) are all made of materials with radial magnetic conductivity, and the outer permanent magnet ring (7) and the inner permanent magnet ring (8) are both made of rare earth permanent magnet materials.

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