Lorentz force type radial magnetic bearing

Abstract

The lorentz force type radial magnetic bearing comprises a stator and a rotor, the stator comprises a rectangular copper sheet, an arc-shaped copper sheet and a stator iron core, the rotor comprises a rotating shaft, a rotor iron core and a permanent magnet ring, and an axial air gap exists between the stator iron core and the rotor iron core. A rectangular copper sheet and an arc-shaped copper sheet are bonded on the surface of a stator core in an axial air gap through insulating materials, the arc-shaped copper sheet is connected with the rectangular copper sheet, then the rectangular copper sheet is connected to output terminals of switch power amplifiers in the X direction and the Y direction, the two switch power amplifiers generate control current according to rotor displacement signals, reaction suspension force is generated on a rotor, and the rotor is driven to rotate. And radial stable suspension of the rotor is realized. The lorentz force type radial magnetic bearing is simple in structure, convenient to manufacture, small in size, light in weight, capable of saving materials and space, easy to control and good in dynamic and static performance, and the radial suspension force is only related to the current.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor magnetic bearings, and particularly relates to a Lorentz force type radial magnetic bearing. Background Art

[0002] The radial hybrid magnetic bearing uses permanent magnets to generate a bias magnetic field and suspension windings to generate a control magnetic field. The two combined air-gap magnetic fields are enhanced on one side and weakened on the other side, and a displacement closed-loop control system is established to generate a controllable suspension force in the direction opposite to the rotor eccentricity direction, realizing the stable suspension of the rotor. It has the advantages of large suspension force density and low power consumption. However, existing radial hybrid magnetic bearings all have radial unbalanced forces. And during design, the bias magnetic field generated by the permanent magnets and the air-gap magnetic density generated by the suspension winding magnetic field can only be half of the air-gap saturation magnetic density. The suspension force mathematical model is not only related to the control current but also related to the rotor offset. The force / current relationship is non-linear. During the design of the control system, approximate linearization is performed, which results in poor accuracy of the control system. In particular, the unbalanced force caused by eccentricity will deteriorate the dynamic and static performance of the magnetic bearing, increasing the control difficulty and complexity and affecting the stability and accuracy of the system. In some application scenarios with strict requirements for space and weight, such as implantable medical devices, micro air vehicles, etc., due to the large volume and weight of traditional hybrid radial magnetic bearings, they cannot meet the actual requirements. Therefore, the present invention proposes a Lorentz force type radial magnetic bearing without radial unbalanced force, small volume, convenient manufacturing and installation, and with a linear force / current relationship, improving the dynamic and static performance of the radial magnetic bearing. Summary of the Invention

[0003] Object of the Invention: The present invention aims to solve the technical problem of poor control performance of existing radial hybrid magnetic bearings caused by unbalanced forces and non-linear force / current. A Lorentz force type radial magnetic bearing is proposed, which has no radial unbalanced force, and the force / current relationship is a strictly linear relationship, with good dynamic and static performance, small volume, and simple manufacturing and assembly.

[0004] Technical Solution: The present invention discloses a Lorentz force type radial magnetic bearing, including a rotor and a stator. The rotor includes a rotating shaft, a rotor core, and a permanent magnet ring; the stator includes a stator core and left and right copper sheets; there are left and right axial air gaps between the rotor core and the stator core, the rotor core is sleeved on the rotating shaft, and the permanent magnet ring is symmetrically inserted into the rotor core; the left and right copper sheets are arranged between the left and right axial air gaps and fixed to the stator core.

[0005] Further, the left and right copper sheets are respectively composed of 4 arc-shaped copper sheets and 8 square copper sheets. The 4 arc-shaped copper sheets form a ring and there are gaps between adjacent arc-shaped copper sheets. One square copper sheet is connected to both ends of the outer peripheral surface of each arc-shaped copper sheet.

[0006] Further, two of the four arc-shaped copper sheets that are opposite to each other form a group, and there are two groups in total. The two groups of arc-shaped copper sheets are in the X direction and the Y direction respectively. The four rectangular copper sheets in the X direction on the left copper sheet are connected in parallel in the same direction as the four rectangular copper sheets in the X direction on the right copper sheet. The four rectangular copper sheets in the Y direction on the left copper sheet are connected in parallel in the same direction as the four rectangular copper sheets in the Y direction on the right copper sheet. After the two groups are connected in parallel in the same direction, they are respectively connected to the output terminals of the switching power amplifiers in the X direction and the Y direction.

[0007] Further, the value ranges of the left and right axial air gaps are both 1 mm to 2 mm. The axial thickness of the left and right copper sheets (9, 10) is d, and the value of d is less than the value of the left and right axial air gaps (7, 8) minus 0.5 mm, that is, its value range is 0.5 mm to 1.5 mm. The air-gap magnetic density generated by the permanent magnet ring in the left and right axial air gaps is the saturation value B s , and its value is greater than 1.2 T.

[0008] Further, the permanent magnet ring is axially magnetized, and its magnetic circuit forms a unidirectional closed magnetic circuit through the rotor core, the left and right axial air gaps, the left and right copper sheets, and the stator core.

[0009] Further, the arc-shaped copper sheets of the left copper sheet are X l+ 、X l- 、Y l+ 、Y l- , and the square copper sheets of the right copper sheet are X1, X2, X3, X4, Y1, Y2, Y3, Y4; the arc-shaped copper sheets of the right copper sheet are X r+ 、X r- 、Y r+ 、Y r- , and the square copper sheets of the right copper sheet are X5, X6, X7, X8, Y5, Y6, Y7, Y8;

[0010] The square copper sheets X1, X3, X5, X7 are connected in parallel and then connected to the + output terminal of the switching power amplifier in the X direction. The square copper sheets X2, X4, X6, X8 are connected in parallel and then connected to the - output terminal of the switching power amplifier in the X direction. The square copper sheets Y1, Y3, Y5, Y7 are connected in parallel and then connected to the + output terminal of the switching power amplifier in the Y direction. The square copper sheets Y2, Y4, Y6, Y8 are connected in parallel and then connected to the - output terminal of the switching power amplifier in the Y direction.

[0011] Further, the current flows in from the positive output terminal of the switching power amplifier, passes through the arc-shaped copper sheets X l+ 、X l- 、Y l+ 、Y l- 、X r+ 、X r- 、Y r+ 、Y r-Then it flows out from the negative output terminal, generating independent radial magnetic fields in the X and Y directions on the stator surface, interacting with the magnetic field of the permanent magnet ring, and generating a radial suspension force F through the Lorentz force y+ , F y- , F x+ , F x- .

[0012] Furthermore, the parameter design process is as follows:

[0013] Step 1: Select the left and right axial air-gap lengths l g and the saturation value B of the air-gap magnetic flux density S ;

[0014] Step 2: The surface area A of the permanent magnet ring is expressed as:

[0015] A = π(R 2 - r 2 )

[0016] where R is the outer radius of the permanent magnet ring and r is the inner radius of the permanent magnet ring;

[0017] Step 3: Determine the reluctance R pm of the permanent magnet ring and the air-gap reluctance R g :

[0018]

[0019] where l pm is the thickness of the permanent magnet ring, A pm is the magnetization area of the permanent magnet ring, A g is the air-gap area, μ g and μ pm are the permeabilities of air and the permanent magnet ring respectively;

[0020] Step 4: The total magnetomotive force F pm generated by the permanent magnet ring is:

[0021] F pm = l pm H c ;

[0022] where H c is the coercivity of the permanent magnet;

[0023] Step 5: According to Kirchhoff's law of magnetic circuits, we have:

[0024] F pm = B s A(R pm + 2R g )

[0025] Step 6: Select the surface area, magnetization area and air-gap area of the permanent magnet ring to be equal, that is, let A pm= A g = A; The permeability of air and the permanent magnet is approximately equal, μ g = μ pm = μ0, then:

[0026]

[0027] The thickness l of the permanent magnet ring is obtained pm as:

[0028]

[0029] Step 7: According to the required maximum suspension force F, the outer radius R0 and inner radius r0 of the stator core (6) can be determined by the following formula:

[0030]

[0031] where, I density is the current density, and the value range is 6 A / mm 2 - 10 A / mm 2 ; The inner radius r0 of the stator core (6) is taken to be greater than the radius of the rotating shaft plus 2 mm, the outer radius R0 of the stator core (6) is obtained, and then the total current I0 can be obtained according to the following formula:

[0032] I0 = (R0 - r0)dI density

[0033] Furthermore, the rotor core and the stator core are made of magnetic conductive materials.

[0034] Compared with the prior art, the present invention has the following obvious advantages:

[0035] The Lorentz force type radial magnetic bearing of the present invention has the advantages of simple structure, convenient manufacturing, no radial unbalanced force, simple control, easy implementation, etc., can achieve high-precision control of the radial position of the rotor, ensure the stable and reliable operation of the magnetic bearing under various complex working conditions, and has a small volume, can save materials and space, and can be widely applied to fields with harsh requirements for bearing performance such as high-speed motors, aerospace equipment, precision instruments, etc., providing strong support for the performance improvement and technological development of related equipment. Brief Description of the Drawings

[0036] Figure 1 is the overall structure schematic diagram of the present invention;

[0037] Figure 2 is the left and right copper sheet structure schematic diagram of the present invention;

[0038] Figure 3 is the block diagram of generating Lorentz force of the present invention. Detailed Embodiments

[0039] 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 cannot be used to limit the protection scope of the present invention.

[0040] The present invention provides a Lorentz force type radial magnetic bearing.

[0041] As Figure 1 shown, the rotor 1 of the present invention includes: a rotating shaft 3, a rotor core 4, and a permanent magnet ring 5. The stator 2 includes: a stator core 6, arc-shaped copper sheets X l+ 、X l- 、Y l+ 、Y l- 、X r+ 、X r- 、Y r+ 、Y r- and left copper sheets 9 and right copper sheets 10 composed of rectangular copper sheets X1, X2, X3, X4, X5, X6, X7, X8; Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8. There are left and right axial air gaps 7 and 8 between the rotor core 4 and the stator core 6. The rotor core 4 is sleeved on the rotating shaft 3, and the permanent magnet ring 5 is symmetrically inserted into the rotor core 4. The rotor core 4 and the stator core 6 are made of magnetic conductive materials.

[0042] Figure 2 are schematic diagrams of the left copper sheet 9 and the right copper sheet 10 of the present invention. The left copper sheet 9 and the right copper sheet 10 are located in the left and right axial air gaps 7 and 8 and are fixedly pasted on the surface of the stator core 6. The left and right copper sheets 9 and 10 are respectively composed of 4 arc-shaped copper sheets and 8 square copper sheets. The 4 arc-shaped copper sheets form a ring and there is a gap between adjacent arc-shaped copper sheets. Both ends of the radial outer peripheral surface of each arc-shaped copper sheet are connected to a rectangular copper sheet. Two of the 4 arc-shaped copper sheets that are opposite to each other form a group, and there are a total of two groups. The two groups of arc-shaped copper sheets are respectively in the X direction and the Y direction. The 4 rectangular copper sheets in the X direction on the left copper sheet 9 are connected in parallel in the same direction with the 4 rectangular copper sheets in the X direction on the right copper sheet 10. The 4 rectangular copper sheets in the Y direction on the left copper sheet 9 are connected in parallel in the same direction with the 4 rectangular copper sheets in the Y direction on the right copper sheet 10. After the two groups are connected in parallel in the same direction, they are respectively connected to the output terminals of the switching power amplifiers in the X direction and the Y direction.

[0043] The left copper sheet 9 and the right copper sheet 10 are composed of arc-shaped copper sheets X l+ 、X l- 、Y l+ 、Y l- 、X r+ 、X r- 、Y r+ 、Y r-It is composed of rectangular copper sheets X1, X2, X3, X4, X5, X6, X7, X8; Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8. The arc-shaped copper sheet of the left copper sheet 9 is X l+ , X l- , Y l+ , Y l- . The rectangular copper sheets of the right copper sheet 9 are X1, X2, X3, X4, Y1, Y2, Y3, Y4; the arc-shaped copper sheet of the right copper sheet 10 is X r+ , X r- , Y r+ , Y r- . The rectangular copper sheets of the right copper sheet 10 are X5, X6, X7, X8, Y5, Y6, Y7, Y8.

[0044] Figure 3 This is the block diagram for generating Lorentz force in the present invention. The rectangular copper sheets X1, X3, X5, X7 are connected in parallel and then connected to the + output terminal of the X-direction switch power amplifier; the rectangular copper sheets X2, X4, X6, X8 are connected in parallel and then connected to the - output terminal of the X-direction switch power amplifier; the rectangular copper sheets Y1, Y3, Y5, Y7 are connected in parallel and then connected to the + output terminal of the Y-direction switch power amplifier; the rectangular copper sheets Y2, Y4, Y6, Y8 are connected in parallel and then connected to the - output terminal of the Y-direction switch power amplifier. The current flows in from the positive output terminal of the switch power amplifier, passes through the arc-shaped copper sheets X l+ , X l- , Y l+ , Y l- , X r+ , X r- , Y r+ , Y r- and then flows out from the negative output terminal, generating an independent radial magnetic field in the X / Y direction on the stator surface, which interacts with the magnetic field of the permanent magnet ring 5, and generating a radial suspension force F y+ , F y- , F x+ , F x- .

[0045] The permanent magnet ring 5 is axially magnetized, and its magnetic circuit forms a unidirectional closed magnetic circuit through the rotor core 4, the left and right axial air gaps 7, 8, the left and right copper sheets 9, 10, and the stator core 6. When the rotor deviates from the center, the controller adjusts the current polarity in the X / Y direction to enhance or weaken the magnetic field in the corresponding direction, so that the suspension force always points to the equilibrium position.

[0046] The parameter design process of the present invention is as follows:

[0047] First, select the lengths l g of the left and right axial air gaps 7, 8 and the saturation value B SAmong them, the value ranges of the left and right axial air gaps are both 1 mm to 2 mm. The axial thickness of the left and right copper sheets 9 and 10 is d, and the value of d is less than the value of the left and right axial air gaps 7 and 8 minus 0.5 mm, that is, its value range is 0.5 mm to 1.5 mm. The air gap magnetic density generated by the permanent magnet ring in the left and right axial air gaps is the saturation value B s , and its value is greater than 1.2 T.

[0048] Secondly, the surface area A of the permanent magnet ring 5 is expressed as:

[0049] A = π(R 2 -r 2 )

[0050] Among them, R is the outer radius of the permanent magnet ring, and r is the inner radius of the permanent magnet ring.

[0051] According to the thickness l of the permanent magnet ring 5 pm , the lengths l of the left and right axial air gaps 7 and 8 g , the magnetization area A of the permanent magnet ring pm , the air gap area A g , the air permeability μ g and the permanent magnet permeability μ pm . Determine the magnetic resistance R of the permanent magnet ring pm and the air gap magnetic resistance R g as:

[0052]

[0053] The total magnetomotive force F generated by the permanent magnet ring 5 pm can be expressed as:

[0054] F pm = l pm H c ;

[0055] Among them, H c is the coercivity of the permanent magnet.

[0056] According to Kirchhoff's law of magnetic circuit:

[0057] F pm = B s A(R pm +2R g )

[0058] Among them, select the surface area, magnetization area and air gap area of the permanent magnet ring 5 to be equal, that is, let A pm = A g = A; the air and permanent magnet permeabilities can be approximately equal, μ g = μ pm = μ0.

[0059] Substitute the above equation into the above equation: Obtain the thickness \(l\) of the permanent magnet ring 5 pm That is:

[0060]

[0061] After completing the parameter design of the permanent magnet ring 5, according to the required maximum suspension force \(F\), the outer radius \(R_0\) and inner radius \(r_0\) of the stator core (6) can be determined by the following formula:

[0062]

[0063] Where, \(I\) density is the current density, and the value range is \(6A / mm\) 2 - \(10A / mm\) 2 ; The inner radius \(r_0\) of the stator core (6) is taken to be greater than the radius of the rotating shaft plus \(2mm\), and the outer radius \(R_0\) of the stator core (6) is obtained. Then, the total current \(I_0\) can be obtained according to the following formula:

[0064] \(I_0=(R_0 - r_0)dI\) density

[0065] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A Lorentz force type radial magnetic bearing, comprising a rotor (1) and a stator (2), characterized in that: The rotor (1) comprises a rotating shaft (3), a rotor core (4) and a permanent magnet ring (5); the stator (2) comprises a stator core (6) and left and right copper sheets (9, 10); left and right axial air gaps (7, 8) are provided between the rotor core (4) and the stator core (6); the rotor core (4) is sleeved on the rotating shaft (3), and the permanent magnet ring (5) is symmetrically inserted into the rotor core (4); the left and right copper sheets (9, 10) are arranged between the left and right axial air gaps (7, 8) and are fixed on the stator core (6).

2. A Lorentz force type radial magnetic bearing according to claim 1, characterized in that: The left and right copper sheets (9, 10) are respectively composed of four arc-shaped copper sheets and eight square copper sheets, the four arc-shaped copper sheets form a circular ring, gaps are provided between adjacent arc-shaped copper sheets, and both ends of the radial outer peripheral surface of each arc-shaped copper sheet are connected to a square copper sheet.

3. A Lorentz force type radial magnetic bearing according to claim 2, characterized in that: Two of the four arc-shaped copper sheets that are opposite to each other form a group, which is divided into two groups in total. The two groups of arc-shaped copper sheets are in the X direction and the Y direction respectively. The four square copper sheets in the X direction on the left copper sheet (9) are connected in parallel with the four square copper sheets in the X direction on the right copper sheet (10). The four square copper sheets in the Y direction on the left copper sheet (9) are connected in parallel with the four square copper sheets in the Y direction on the right copper sheet (10). After being connected in parallel in the same direction, the two groups are connected to the output terminals of the switching power amplifier in the X direction and the Y direction respectively.

4. The Lorentz force type radial magnetic bearing according to claim 1, characterized in that: The left and right axial air gaps (7, 8) are both within a range of 1 mm to 2 mm. The axial thickness of the left and right copper sheets (9, 10) is d, and the value of d is the value of the left and right axial air gaps (7, 8) minus 0.5 mm, that is, the value range is 0.5 mm to 1.5 mm. The air gap magnetic flux density generated by the permanent magnet ring (5) in the left and right axial air gaps (7, 8) is a saturation value B. s , its value is greater than 1.2T.

5. The Lorentz force type radial magnetic bearing according to claim 1, characterized in that: The permanent magnet ring (5) is axially magnetized, and its magnetic circuit passes through the rotor iron core (4), left and right axial air gaps (7, 8), left and right copper sheets (9, 10), and the stator iron core (6) to form a unidirectional closed magnetic circuit.

6. The Lorentz force type radial magnetic bearing according to claim 3, characterized in that: The arc-shaped copper sheet of the left copper sheet (9) is X l+ , X l- , Y l+ , Y l- The square copper pieces of the right copper piece (9) are X1, X2, X3, X4, Y1, Y2, Y3, Y4; the arc copper pieces of the right copper piece (10) are X r+ , X r- , Y r+ , Y r- , the square copper pieces of the right copper piece (10) are X5, X6, X7, X8, Y5, Y6, Y7, Y8; The square copper sheets X1, X3, X5, and X7 are connected in parallel to the + output terminal of the X-direction switch amplifier, and the square copper sheets X2, X4, X6, and X8 are connected in parallel to the - output terminal of the X-direction switch amplifier; the square copper sheets Y1, Y3, Y5, and Y7 are connected in parallel to the + output terminal of the Y-direction switch amplifier, and the square copper sheets Y2, Y4, Y6, and Y8 are connected in parallel to the - output terminal of the Y-direction switch amplifier.

7. The Lorentz force type radial magnetic bearing according to claim 6, characterized in that: The current flows from the positive output terminal of the switching amplifier and passes through the arc-shaped copper sheet X l+ , X l- , Y l+ , Y l- , X r+ , X r- , Y r+ , Y r- Then it flows out from the negative output terminal, generating independent radial magnetic fields in the X and Y directions on the stator surface, which interact with the magnetic field of the permanent magnet ring (5) to generate a radial suspension force F through the Lorentz force. y+ 、F y- 、F x+ 、F x- .

8. The Lorentz force type radial magnetic bearing according to any one of claims 1 to 7, characterized in that: The parameter design process is as follows: Step 1: Select the length l of the left and right axial air gaps (7, 8) g and air gap magnetic flux saturation value B S ; Step 2: The surface area A of the permanent magnetic ring (5) is expressed as: A=π(R 2 -r 2 ) Wherein, R is the outer radius of the permanent magnet ring (5), and r is the inner radius of the permanent magnet ring (5); Step 3: Determine the magnetic resistance R of the permanent magnet ring (5) pm and air gap reluctance R g : Among them, l pm is the thickness of the permanent magnet ring (5), A pm is the magnetization area of ​​the permanent magnet ring (5), A g is the air gap area, μ g and μ pm are the magnetic permeabilities of air and permanent magnet ring respectively; Step 4: The permanent magnet ring (5) generates a total magnetomotive force F pm for: F pm =l pm H c ; Among them, H c is the coercive force of the permanent magnet; Step 5: According to Kirchhoff's law of magnetic circuit: F pm =B s A(R pm +2R g ) Step 6: Select the surface area, magnetization area and air gap area of ​​the permanent magnet ring (5) to be equal, that is, A pm =A g =A; the magnetic permeability of air and permanent magnet is approximately equal, μ g =μ pm =μ0, then: Calculate the thickness l of the permanent magnet ring (5) pm for: Step 7: According to the required maximum suspension force F, the outer radius R0 and inner radius r0 of the stator core (6) can be determined by the following formula: Among them, I density is the current density, the value range is 6A / mm 2 -10A / mm 2 The inner radius r0 of the stator core (6) is greater than the shaft radius plus 2 mm, and the outer radius R0 of the stator core (6) is obtained. Then, the total current I0 can be calculated according to the following formula: I0=(R0-r0)dI density。 9. The Lorentz force type radial magnetic bearing according to any one of claims 1 to 7, characterized in that: The rotor iron core (4) and the stator iron core (6) are made of magnetic conductive materials.

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