Axial magnetic bearing

Abstract

The invention discloses an axial magnetic suspension bearing, which comprises a rotating shaft, a magnetic conductive yoke, a permanent magnet, a magnetic barrier structure and an electromagnetic coil, the rotating shaft comprises a main shaft and a thrust disc; a first air gap and a second air gap with the projection area error smaller than 5% are formed between the magnetic conductive magnet yoke and the thrust disc. The permanent magnet is arranged on the magnetic conductive yoke, a third air gap is formed between the thrust disc and the permanent magnet, and a permanent magnetic circuit is formed among the thrust disc, the permanent magnet and the magnetic conductive yoke; the magnetic barrier structure is arranged on the magnetic conductive yoke and located in a path of the permanent magnet magnetic circuit, and the permanent magnet magnetic circuit passes through the magnetic barrier structure, the first air gap and the third air gap. The electromagnetic coil is arranged in the cavity of the magnetic conductive yoke and located on the radial outer side of the thrust disc, after control current is introduced into the electromagnetic coil, a control magnetic circuit is formed between the thrust disc and the magnetic conductive yoke, and the control magnetic circuit passes through the first air gap and the second air gap.

Description

Technical Field

[0001] The present invention relates to the technical field of bearings, and particularly to an axial magnetic bearing with a magnetic barrier structure, which decouples the control magnetic flux path from the permanent magnetic flux path, can bear a unidirectional heavy load, and satisfies that its control current is proportional to the bearing capacity of the bearing and has a linear control characteristic. Background Art

[0002] Magnetic bearings use electromagnets to control their output current to drive a ferromagnetic spindle so that the spindle rotates in a suspended state. Compared with traditional mechanical bearings, the magnetic bearing system provides a non-contact supporting force. Due to its characteristics of low friction resistance and no need for additional heat dissipation and lubrication, it is suitable for high-speed and enclosed rotating machinery applications. However, the supporting capacity of the magnetic bearing system is limited by the driving performance of the magnetic bearing hardware, and it is difficult to meet the usage requirements of heavy loads by simply using electromagnets for control.

[0003] A traditional five-axis magnetic levitation rotating machine consists of two sets of radial bearings, one set of axial bearings, one set of driving motors, and a high-speed spindle with a thrust disc structure. The radial bearings are used to constrain the rotation center position of the spindle, the axial bearings are used to prevent the spindle from moving along the rotation axis direction, and the driving motors are used to output shaft power. Among them, the axial bearings use two pairs of coils, which are respectively placed on both sides of the thrust disc of the spindle. By adjusting the driving current of the two sets of coils, the direction of the resultant magnetic suction force received by the thrust disc is controlled. By detecting the axial position of the thrust disc or the spindle with a position sensor, when its position deviates to one side and it is desired to move the spindle to the other side, it is necessary to control the driver to increase the current of the coil on the other side while reducing the current of the coil on this side, so that the direction of the resultant magnetic attraction force received by the thrust disc faces the other side and is lifted. Please refer to Figure 15 As shown, it has a driving circuit 901, a control circuit 902, and a thrust disc 903. Among them, the control circuit 902 receives the feedback signal x* and outputs a control command u* to drive the driving circuit 901. Regarding the working mode of the electromagnet and the thrust disc, if only considering a single-side axial bearing, the air gap length between it and the thrust disc 903 is g, the number of coil turns is N, the control current is i, and the cross-sectional area of the air gap is A. Under the limiting condition that the main magnetic path does not reach magnetic saturation, its magnetic attraction force can be expressed as follows:

[0004]

[0005] Obviously, the magnetic attraction force is proportional to the square of the control current and inversely proportional to the square of the air gap distance. It is necessary to use non-linear control technology to design a controller to achieve the control purpose. Please refer to Figure 16As shown in the figure, it has a drive circuit 901, a control circuit 902 and a thrust disk 903. Among them, the control circuit 902 receives the feedback signal x* and outputs a control command u* to drive the drive circuit 901. Assuming that the air gap is much larger than the displacement x of the thrust disk, identical coils 904 are placed on both sides of the thrust disk 903, with the air gap on both sides being g, and the current flowing through the two coils 904 is decomposed into a bias current i b and a control current i c . Fix the bias current i b . The resultant magnetic attraction force received by the thrust disk 903 is only linearly related to the control current i c (see the following equation), and the axial displacement of this system can be controlled by a linear controller.

[0006]

[0007] In short, in order to endow the traditional axial magnetic bearing with the characteristics of linear control, it is necessary to specially design a suitable air gap and paired electromagnetic coils in the mechanical structure, and a fixed bias current i b and a differential control current i c need to be applied to the drive circuit 901. In terms of assembly, the air gap positions of the two pairs of paired electromagnetic coils in this axial bearing structure need to be precisely adjusted to ensure that the lengths of the two air gaps are equal, and the requirements for assembly quality are very high. In addition, since the drive current is composed of a control current and a bias current, an excessive bias current will narrow the available control current range.

[0008] The drive circuit of a magnetic bearing generally adopts a circuit structure composed of a pair of switching elements and a pair of diodes, with a drive coil connected in series therebetween. When the switching element is short-circuited, the current flows from the voltage source into the coil. When the switching element is open-circuited, due to the inductance characteristic of the coil, the current will flow back to the voltage source through the diode; the switching element uses variable pulse modulation (PWM), and by adjusting the duty cycle to adjust the switching time ratio, the output current of the coil can be controlled. This circuit has the characteristic of current recovery, is simple and efficient and is widely used; however, since this control circuit uses diodes to control the current direction, it is only applicable to the application of unidirectional coil current.

[0009] Compared with a radial bearing, the structure of an axial bearing is complex, the number of assembled mating components is large, and its design position is in the middle section of the main shaft, which is not conducive to reducing the size of the thrust disk and subsequent adjustment and maintenance operations.

[0010] In view of this, in actual commercial applications, a magnetic bearing system structure with the thrust disk placed at the rear has been developed. By placing the thrust disk at the end of the main shaft, not only can the length of the main shaft and the size of the thrust disk be shortened, but the thrust disk can also be installed separately from the main shaft, reducing the operating costs of logistical maintenance such as thrust disk clearance adjustment.

[0011] To further reduce the complexity of the axial bearing and shrink the size of the thrust disk, permanent magnets are placed between the radial bearing and the axial bearing in commercial applications to provide a uniform bias magnetic field in the air gap of the axial bearing. An electromagnet coil is placed on the outer edge of the thrust disk, and its control current can increase / cancel the magnetic fields on both sides of the air gap simultaneously, thereby controlling the magnitude and direction of the resultant magnetic attraction force of the thrust disk. This can replace the design of traditional magnetic levitation bearings and achieve the goal of controlling the axial displacement of the main shaft using only a single set of coils.

[0012] However, this design also gives rise to the problem that the permanent magnet bias magnetic field needs to pass through the radial bearing. The local coupling of the magnetic fields of the axial bearing and the radial bearing makes the controller design rather difficult. In addition, using a single coil for control requires the current of the coil to be able to flow bidirectionally, increasing the cost of the drive circuit and controller design.

[0013] Many rotating machines operate in fields with large axial loads, such as blowers, ORC axial flow generators, flywheel energy storage systems, etc. In the aforementioned axial bearing design, when the rotating machine system is under low axial load, the axial magnetic levitation bearing operates under light load conditions. When the rotating machine operates under rated conditions, the axial magnetic levitation bearing operates under heavy load. In addition to energy consumption losses, the axial bearing is also prone to getting out of control under the impact of extreme working conditions.

[0014] To solve this problem, a single-side axial bearing system is designed to address the application scenario of single axial large load. This design uses permanent magnets to attract the thrust disk or the main shaft to counteract the axial force when the rotating machine operates at the rated point. An electromagnet coil is set on the other side of the permanent magnet to adjust the magnitude and direction of the resultant force borne by the thrust disk, so as to achieve the purpose of controlling the axial displacement. Adopting a single-side axial magnetic levitation bearing system requires breaking through the inherent limitations of non-linear control in control technology before it has the possibility of practical application.

[0015] There have been many patent literatures on axial permanent magnet bias magnetic levitation bearings, but most of them focus on the topology structure of shaft / radial hybrid bearings. The following only analyzes and discusses the existing patents of axial permanent magnet bias bearings with single-coil control or single-direction output.

[0016] For example, an existing US patent (Patent No. US8,102,088B2), "GENERATING ELECTROMAGNETIC FORCES WITH FLUX FEEDBACK CONTROL", designs a permanent magnet biased axial bearing that uses two sets of permanent magnets to create two bias magnetic paths with opposite directions along a specific bearing structure path. The two magnetic paths converge at the thrust disk, causing the thrust disk air gap to have a permanent magnet bias magnetic flux. An electromagnetic coil is provided, and when a control current is passed through it, the air gap of the thrust disk can be increased (or decreased) while the other air gap is decreased (or increased), thereby changing the force on the thrust disk. A magnetic field sensor is placed at the air gap position, and by directly measuring the magnetic flux, the differential magnetic field is controlled to achieve the control purpose. However, this existing technology requires a magnetic field sensor to be installed in the air gap structure to achieve the goal of linear control, which is difficult to achieve in practice. In addition, its electromagnetic coil requires a bidirectional current to achieve the goal of controlling the axial position, which is also one of the disadvantages of this existing bearing design.

[0017] Another example is another existing US patent (Patent No. US8,482,174B2), "ELECTROMAGNETIC ACTUATOR". This existing patent sets permanent magnets between the axial bearing and the radial bearing, and its permanent magnetic path flows through the axial bearing air gap and the radial bearing air gap. When a control current is passed through the electromagnetic coil, a control magnetic flux is generated, which increases (or decreases) the magnetic flux of one air gap and simultaneously decreases (or increases) the magnetic flux of the other air gap. By adjusting the magnitude and direction of the control current, the purpose of controlling the thrust disk is achieved. This existing patent uses a single electromagnetic coil for axial control, but a bidirectional current is still a necessary condition for its control. In addition, in order to achieve the purpose of sharing the axial and radial permanent magnetic paths, the path of this permanent magnetic path is long and its coupling with the axial magnetic path is high, which is its main disadvantage.

[0018] Another example is another existing US patent (Patent No. US11,005,336B1), "MAGNETIC BEARING ASSEMBLY FOR ROTATING MACHINERY". This existing patent uses four sets of single-sided axial actuators in combination with two sets of passive radial bearings to achieve the goal of five-axis suspension control. However, this existing patent does not solve the non-linear control problem of the single-sided axial bearing, and no method for reducing the manufacturing difficulty is proposed for the passive radial bearing, making it difficult to be applied in actual commerce.

[0019] For another example, another existing Chinese patent (Patent No. CN106286590B), "A Permanent Magnet Biased Axial Magnetic Bearing and a Centrifugal Compressor", is based on the aforementioned "ELECTROMAGNETIC ACTUATOR". The original radial air gap is changed to be arranged on the axial thrust disk, so that there are paired two air gaps and an independent air gap on both sides of the thrust disk respectively. The independent air gap provides an additional axial force support, making the axial bearing have an initial magnetic bias force. However, in this existing patent design, the permanent magnetic circuit must pass through three air gaps. This existing patent does not explain how to ensure that the permanent magnetic fluxes of the air gaps are equal in magnitude and opposite in direction, and the overlap of the permanent magnetic flux path and the control magnetic flux path is high, and it can be expected that the magnetic circuit coupling effect is significant.

[0020] Accordingly, how to develop an "axial magnetic floating bearing" that decouples the control magnetic flux path and the permanent magnetic flux path, can bear a unidirectional heavy load, and satisfies that its control current is proportional to the bearing capacity is an urgent problem to be solved by those skilled in the relevant technical fields. Summary of the Invention

[0021] In one embodiment, the present invention provides an axial magnetic floating bearing which is fixed to a structure and symmetric about a rotation axis. The axial magnetic floating bearing includes: a rotating shaft, including a main shaft and a thrust disk, the main shaft is coaxial with the rotation axis, and the thrust disk is concentrically arranged on the main shaft; a magnetic yoke, which includes opposite first and second sides, the first side and the second side are respectively arranged on the axial two sides of the thrust disk and do not contact the thrust disk, and one end corresponding to the first side and the second side has a chamber, and the chamber is located radially outside the thrust disk; the first side adjacent to the chamber has a first air gap surface, the second side adjacent to the chamber has a second air gap surface, a first air gap is formed between the first air gap surface and the thrust disk, a second air gap is formed between the second air gap surface and the thrust disk, and the error in the projected area sizes of the first air gap and the second air gap along the rotation axis direction is less than 5%; a permanent magnet, which is arranged on the surface of the magnetic yoke facing the thrust disk relative to the main shaft, the permanent magnet does not contact the thrust disk, and a third air gap is formed between the thrust disk and the permanent magnet, and a permanent magnetic circuit is formed among the thrust disk, the permanent magnet and the magnetic yoke; a magnetic barrier structure, which is arranged on the first side and located between the permanent magnet and the first air gap surface, the first side has a first cross-sectional area parallel to the rotation axis, the magnetic barrier structure has a second cross-sectional area parallel to the rotation axis, and the second cross-sectional area is smaller than the first cross-sectional area; the magnetic barrier structure is located in the path of the permanent magnetic circuit, and the permanent magnetic circuit passes through the magnetic barrier structure, the first air gap and the third air gap; and an electromagnetic coil, which is arranged in the chamber and does not contact the thrust disk. After the electromagnetic coil is energized with a control current, a control magnetic circuit is formed between the thrust disk and the magnetic yoke, and the control magnetic circuit passes through the first air gap and the second air gap. Brief Description of the Drawings

[0022] Figure 1Schematic diagram of a structure of an embodiment of the present invention;

[0023] Figures 2A to 2D Schematic diagram of different embodiment structures of the permanent magnet of the present invention;

[0024] Figure 3A and Figure 3B is Figure 1 Schematic diagram of the projected areas of the first air gap and the second air gap of the embodiment;

[0025] Figure 4 is Figure 1 Schematic diagram of the magnetic circuit path of the embodiment;

[0026] Figure 5 Schematic diagram of a structure of another embodiment of the present invention;

[0027] Figure 6 is Figure 1 Schematic diagram of the magnetic circuit path of the embodiment;

[0028] Figure 7 Schematic diagram of a structure of another embodiment of the present invention;

[0029] Figure 8A and Figure 8B is Figure 7 Schematic diagram of the projected areas of the first air gap and the second air gap of the embodiment;

[0030] Figure 9 is Figure 7 Schematic diagram of the magnetic circuit path of the embodiment;

[0031] Figure 10 Schematic diagram of a structure of yet another embodiment of the present invention;

[0032] Figure 11 is Figure 10 Schematic diagram of the magnetic circuit path of the embodiment;

[0033] Figure 12 Schematic diagram of the main magnetic flux path, air gap distance, displacement and area parameters of the present invention;

[0034] Figure 13 Schematic diagram of the magnetic resistance architecture of the present invention;

[0035] Figure 14 Relationship diagram of the force on the thrust disk and the control current of the present invention;

[0036] Figure 15 Schematic diagram of the structure of the air gap and the magnetic flux cross-sectional area of the existing axial bearing and the disc;

[0037] Figure 16 Schematic diagram of the structure of the existing differential current-controlled axial bearing disc.

[0038] Symbol Explanation

[0039] 100, 100A, 100B, 100C: Axial magnetic floating bearing

[0040] 101, 101A, 101B, 101C, 101D: Permanent magnet

[0041] 102: Magnetic conductive yoke

[0042] 1021: First side

[0043] 1022: Second side

[0044] 1023: Chamber

[0045] 1024: First air gap surface

[0046] 1025: Second air gap surface

[0047] 1026: Groove

[0048] 102A: Magnetic barrier structure

[0049] 102B: Magnetic force plate

[0050] 103A: First air gap

[0051] 103B: Second air gap

[0052] 103C: Third air gap

[0053] 104: Electromagnetic coil

[0054] 105: Control current

[0055] 106A: Permanent magnet magnetic circuit

[0056] 106B: Permanent magnet leakage magnetic circuit

[0057] 107A: Control magnetic circuit

[0058] 107B: Control leakage magnetic circuit

[0059] 108A, 108B: Radial bearing

[0060] 110: Structure

[0061] 120: Rotating shaft

[0062] 121: Thrust disc

[0063] 122: Main shaft

[0064] 901: Existing drive circuit

[0065] 902: Existing control circuit

[0066] 903: Existing thrust disk

[0067] 904: Existing coil

[0068] A: Existing air-gap cross-sectional area

[0069] AC: Axis of rotation

[0070] A 1 ,A 2 ,A 3 : Air-gap area

[0071] D1: First distance

[0072] D2: Second distance

[0073] D3: Third distance

[0074] F: Load

[0075] F 1 ,F 2 ,F 3 : Magnetic attractive force

[0076] g: Air-gap

[0077] ib: Fixed bias current

[0078] ic: Control current

[0079] R 1 : First air-gap magnetic resistance

[0080] R 2 : Second air-gap magnetic resistance

[0081] R 3 : Third air-gap magnetic resistance

[0082] R m : Magnet magnetic resistance

[0083] R c : Variable magnetic resistance

[0084] SA, SA1, SA2: Projection area

[0085] T1: First cross-sectional area

[0086] T2: Second cross-sectional area

[0087] x: Axial displacement

[0088] u*: Control command

[0089] x*: Feedback signal

[0090] φ C : Control current magnetic flux

[0091] φ M : Bias magnetic flux

[0092] φ L : Leakage magnetic flux Detailed implementation manners

[0093] Please refer to Figure 1 the illustrated embodiment. The axial magnetic floating bearing 100 of the present invention can be widely used in applications for supporting unidirectional axial loads. Figure 1 Only half of the structure symmetric about the rotation axis AC is shown.

[0094] The axial magnetic floating bearing 100 includes a permanent magnet 101, a magnetic yoke 102, a rotating shaft 120 and an electromagnetic coil 104.

[0095] The rotating shaft 120 is composed of a thrust disk 121 and a main shaft 122. The main shaft 122 is coaxial with the rotation axis AC, and the thrust disk 121 is concentrically arranged at an axial end of the main shaft 122.

[0096] The axial magnetic floating bearing 100 is fixed to a structure 110 and is symmetric about the rotation axis AC. The structure 110 can be made of non-magnetic material. The axial magnetic floating bearing 100 takes the magnetic yoke 102 as the main body. The magnetic yoke 102 does not need to be integrally formed and can be composed of a plurality of magnetic components.

[0097] The permanent magnet 101 is arranged on the surface of the magnetic yoke 102 facing the thrust disk 121 relative to the main shaft 122, and the permanent magnet 101 and the thrust disk 121 do not contact each other. The magnetization direction of the permanent magnet 101 is not limited to the direction along the rotation axis AC, and it can be fixed to the magnetic yoke 102 by bonding or by clamping with a fixture.

[0098] Please refer to Figures 2A to 2D as shown. The shape of the permanent magnet 101 is designed according to the actual usage conditions. For example Figure 2A the disk-shaped permanent magnet 101A shown, or as Figure 2B the ring-shaped permanent magnet 101B shown, or as Figure 2C composed of a plurality of sector-shaped permanent magnets 101C shown, or as Figure 2D composed of a plurality of rectangular permanent magnets 101D shown.

[0099] Please refer to Figure 1 as shown. The rotating shaft 120 is axisymmetric about the rotation axis AC, and the rotating shaft 120 bears a unidirectional load F. Radial bearings 108A and 108B are provided between the rotating shaft 120 and the structure 110 to maintain the radial relative position between the rotating shaft 120 and the structure 110 with the radial bearings 108A and 108B.

[0100] It should be noted that the present invention is not limited to setting the thrust disk 121 at one axial end of the main shaft 122. If the permanent magnet 101 is annular, the axial magnetic bearing 100 can also be designed between the two radial bearings 108A and 108B.

[0101] The main shaft 122 and the magnetic yoke 102 are spaced apart by a first distance D1. Since the main shaft 122 is a magnetic body, magnetic flux leakage is avoided through the first distance D1. The size of the first distance D1 is designed according to actual requirements. For example, the material of the main shaft 122, the size of the overall axial magnetic bearing 100, etc., as long as the main shaft 122 and the magnetic yoke 102 do not contact each other.

[0102] In addition, if the structure 110 is a magnetic body, the structure 110 and the thrust disk 121 must maintain a second distance D2 to avoid magnetic flux leakage. The size of the second distance D2 is designed according to actual requirements. For example, the material of the main shaft 122, the size of the overall axial magnetic bearing 100, etc., as long as the structure 110 and the thrust disk 121 do not contact each other.

[0103] Alternatively, if both the structure 110 and the main shaft 122 are magnetic bodies, the structure 110 and the main shaft 122 must maintain a third distance D3 to avoid magnetic flux leakage. The size of the third distance D3 is designed according to actual requirements. For example, the material of the main shaft 122, the size of the overall axial magnetic bearing 100, etc., as long as the structure 110 and the main shaft 122 do not contact each other.

[0104] In other words, when the structure 110 and the main shaft 122 are magnetic bodies, attention must be paid to the distances between the structure 110, the main shaft 122, the magnetic yoke 102 and the thrust disk 121 in the design.

[0105] Please refer to Figure 1 As shown, the magnetic yoke 102 includes a first side 1021 and a second side 1022 which are opposite to each other. The first side 1021 and the second side 1022 are respectively arranged on the axial two sides of the thrust disk 121 and do not contact the thrust disk 121.

[0106] One end of the first side 1021 corresponding to the second side 1022 has a chamber 1023, and the chamber 1023 is located radially outside the thrust disk 121. The first side 1021 adjacent to the chamber 1023 has a first air-gap surface 1024, and the second side 1022 adjacent to the chamber 1023 has a second air-gap surface 1025. A first air gap 103A is formed between the first air-gap surface 1024 and the thrust disk 121, and a second air gap 103B is formed between the second air-gap surface 1025 and the thrust disk 121.

[0107] The error in the projected area size of the first air gap 103A and the projected area size of the second air gap 103B along the direction of the rotation axis AC is less than 5%, and the geometric shape of the projected area is not limited.

[0108] Please refer to Figure 3A 、 Figure 3B As shown, the geometric shapes of the projected areas of the first air gap 103A and the second air gap 103B are both semi-circular ring shapes. If they are symmetric about the rotation axis AC, an air gap in the shape of a circular ring can be formed. The projected area sizes SA of the first air gap 103A and the second air gap 103B along the direction of the rotation axis AC are equal, and the projected range of the first air gap 103A completely overlaps with the projected range of the second air gap 103B.

[0109] Please refer to Figure 1 As shown, the electromagnetic coil 104 is arranged on the outer edge of the thrust disc 121, and a control current 105 can be passed through the electromagnetic coil 104, and the direction of its current is not limited.

[0110] Please refer to Figure 1 and Figure 4 As shown, the thrust disc 121 and the permanent magnet 101 do not contact each other, and a third air gap 103C is formed between the thrust disc 121 and the permanent magnet 101. A permanent magnet magnetic circuit 106A is formed among the thrust disc 121, the permanent magnet 101, and the magnetic conductive yoke 102.

[0111] A magnetic barrier structure 102A is provided on the first side 1021 of the magnetic conductive yoke 102. The magnetic barrier structure 102A is located between the permanent magnet 101 and the first air gap surface 1024, and the magnetic barrier structure 102A is located in the path of the permanent magnet magnetic circuit 106A. The permanent magnet magnetic circuit 106A passes through the magnetic barrier structure 102A, the first air gap 103A, and the third air gap 103C.

[0112] The function of the magnetic barrier structure 102A is to limit the magnetic flux of the permanent magnet magnetic circuit 106A. The magnetic barrier structure 102A can be achieved by reducing the cross-sectional area of the magnetic circuit. Alternatively, the material of the magnetic barrier structure 102A can be a material with a different magnetic permeability. For example, a material with a low magnetic permeability can be used to control the magnetic flux. Taking ferrite as an example, its magnetic permeability is 800 μH / m, while the magnetic permeability of electrical steel is 4000 μH / m. The magnetic permeability of ferrite is about one-fifth of that of electrical steel, and the effect of ferrite in limiting the magnetic flux is better than that of electrical steel.

[0113] For example Figure 1In the embodiment, a first side 1021 has a first cross-sectional area T1 parallel to the rotation axis AC. A groove 1026 is provided on the surface of the magnetic yoke 102 facing the thrust disk 121 to form a magnetic barrier structure 102A. The thickness of the magnetic barrier structure 102A parallel to the rotation axis AC in the axial direction is a second cross-sectional area T2, and the second cross-sectional area T2 is smaller than the first cross-sectional area T1. That is, the magnetic path cross-sectional area of the magnetic yoke 102 at the magnetic barrier structure 102A is smaller.

[0114] When the permanent magnetic circuit 106A flows through the magnetic barrier structure 102A, the magnetic flux of the permanent magnetic circuit 106A can be restricted.

[0115] However, the method of reducing the magnetic path cross-sectional area is not limited to Figure 1 as shown, and can be designed according to actual needs.

[0116] Please refer to Figure 1 and Figure 4 as shown, after the electromagnetic coil 104 is energized with a control current 105, a control magnetic circuit 107A will be formed between the thrust disk 121 and the magnetic yoke 102. The control magnetic circuit 107A passes through the first air gap 103A and the second air gap 103B.

[0117] Please refer to Figure 4 as shown. It should be noted that, in an ideal situation, the magnetic fluxes of the permanent magnetic circuit 106A and the control magnetic circuit 107A should be 100%. However, due to various factors such as structure and material, permanent magnetic leakage paths 106B and control leakage paths 107B will inevitably be generated.

[0118] The paths of the permanent magnetic leakage paths 106B and the control leakage paths 107B both pass through the magnetic barrier structure 102A, the second air gap 103B, and the third air gap 103C. Due to the physical limitation of the magnetic barrier structure 102A, the leakage magnetic flux can be reduced to be much smaller than the magnetic flux of the permanent magnetic circuit 106A, and even reach a negligible level. The permanent magnetic circuit 106A and the control magnetic circuit 107A are only coupled at the first air gap 103A, and the value of the permanent magnetic circuit 106A can be regarded as a constant and is independent of the magnitude of the control current 105.

[0119] Please refer to Figure 5 the embodiment shown. The structure of the axial magnetic floating bearing 100A is substantially the same as that of the Figure 1 axial magnetic floating bearing 100 shown. The axial magnetic floating bearing 100A includes a permanent magnet 101, a magnetic yoke 102, a rotating shaft 120, and an electromagnetic coil 104. The axial magnetic floating bearing 100A is fixed to a structure 110. The rotating shaft 120 is composed of a thrust disk 121 and a main shaft 122. Radial bearings 108A and 108B are provided between the rotating shaft 120 and the structure 110.

[0120] Figure 5 The embodiment andFigure 1 The main difference between the embodiments is that Figure 5 on the surface of the permanent magnet 101 of the embodiment facing the thrust disk 121, there is a magnetic force plate 102B with magnetic permeability.

[0121] Please refer to Figure 5 and Figure 6 As shown, a first air gap 103A is formed between the first air gap surface 1024 and the thrust disk 121, a second air gap 103B is formed between the second air gap surface 1025 and the thrust disk 121, and a third air gap 103C is formed between the thrust disk 121 and the permanent magnet 101. The projected area SA of the first air gap 103A and the second air gap 103B along the direction of the rotation axis AC is equal in size, and the projected range of the first air gap 103A completely overlaps with the projected range of the second air gap 103B, as Figure 3A , Figure 3B shown. However, due to manufacturing tolerances in actual production, the manufacturing error of the projected area SA can be less than 5%.

[0122] A magnetic barrier structure 102A is provided on the first side 1021 of the magnetic yoke 102. A permanent magnet magnetic circuit 106A is formed among the thrust disk 121, the permanent magnet 101, and the magnetic yoke 102.

[0123] After the electromagnetic coil 104 is energized with the control current 105, a control magnetic circuit 107A will be formed between the thrust disk 121 and the magnetic yoke 102. The control magnetic circuit 107A passes through the first air gap 103A and the second air gap 103B. The magnetic flux distribution in the third air gap 103C is made uniform through the magnetic force plate 102B.

[0124] The paths of the permanent magnet leakage magnetic circuit 106B and the control leakage magnetic circuit 107B both pass through the magnetic barrier structure 102A, the second air gap 103B, and the third air gap 103C. Due to the physical limitation of the magnetic barrier structure 102A, the leakage magnetic flux can be reduced to far less than the magnetic flux of the permanent magnet magnetic circuit 106A, even to the extent that it can be neglected.

[0125] Please refer to Figure 7 the embodiment shown. The structure of the axial magnetic floating bearing 100B is substantially the same as that of the axial magnetic floating bearing 100 shown in Figure 1 . The axial magnetic floating bearing 100B includes a permanent magnet 101, a magnetic yoke 102, a rotating shaft 120, and an electromagnetic coil 104. The axial magnetic floating bearing 100B is fixed to a structure 110. The rotating shaft 120 is composed of a thrust disk 121 and a main shaft 122. Radial bearings 108A and 108B are provided between the rotating shaft 120 and the structure 110.

[0126] The first side 1021 adjacent to the chamber 1023 has a first air gap surface 1024, and the second side 1022 adjacent to the chamber 1023 has a second air gap surface 1025.

[0127] Figure 7 The main difference between the embodiment and Figure 1 the embodiment is that Figure 7 the projection positions of the first air-gap surface 1024 and the second air-gap surface 1025 of the embodiment are misaligned along the direction of the rotation axis AC.

[0128] Please refer to Figure 8A and 8B As shown, the geometric shapes of the projected areas of the first air gap 103A and a second air gap 103B are both semi-circular ring shapes. If they are symmetric about the rotation axis AC, an air gap in the shape of a circular ring can be formed. The sizes of the projected areas SA1 and SA2 of the first air gap 103A and a second air gap 103B along the direction of the rotation axis AC are equal, and the projected ranges of the first air gap 103A and the second air gap 103B partially overlap.

[0129] Please refer to Figure 7 and Figure 9 As shown, a first air gap 103A is formed between the first air-gap surface 1024 and the thrust disk 121, a second air gap 103B is formed between the second air-gap surface 1025 and the thrust disk 121, and a third air gap 103C is formed between the thrust disk 121 and the permanent magnet 101.

[0130] A magnetic barrier structure 102A is provided on the first side 1021 of the magnetic yoke 102. A permanent magnetic circuit 106A is formed among the thrust disk 121, the permanent magnet 101, and the magnetic yoke 102.

[0131] After the electromagnetic coil 104 is passed through with a control current 105, a control magnetic circuit 107A will be formed between the thrust disk 121 and the magnetic yoke 102. The control magnetic circuit 107A passes through the first air gap 103A and the second air gap 103B.

[0132] The paths of the permanent magnetic leakage magnetic circuit 106B and the control leakage magnetic circuit 107B both pass through the magnetic barrier structure 102A, the second air gap 103B, and the third air gap 103C. Due to the physical limitation of the magnetic barrier structure 102A, the leakage magnetic flux can be reduced to be much smaller than the magnetic flux of the permanent magnetic circuit 106A, even to the extent that it can be negligible.

[0133] Please refer to Figure 10 the embodiment shown. The structure of the axial magnetic floating bearing 100C is substantially the same as that of Figure 7 the axial magnetic floating bearing 100B shown. The axial magnetic floating bearing 100C includes a permanent magnet 101, a magnetic yoke 102, a rotating shaft 120, and an electromagnetic coil 104. The axial magnetic floating bearing 100A is fixed to a structure 110. The rotating shaft 120 is composed of a thrust disk 121 and a main shaft 122. Radial bearings 108A and 108B are provided between the rotating shaft 120 and the structure 110.

[0134] Figure 10 The main difference between the embodiment and Figure 7 the embodiment lies in that Figure 10 on the surface of the permanent magnet 101 of the embodiment facing the thrust disk 121, a magnetic force plate 102B with magnetic permeability is provided.

[0135] Please refer to Figure 10 and Figure 11 As shown, a first air gap 103A is formed between the first air gap surface 1024 and the thrust disk 121, a second air gap 103B is formed between the second air gap surface 1025 and the thrust disk 121, and a third air gap 103C is formed between the thrust disk 121 and the permanent magnet 101. The projected areas SA1 and SA2 of the first air gap 103A and the second air gap 103B along the direction of the rotation axis AC are equal in size, and the projected range of the first air gap 103A partially overlaps with the projected range of the second air gap 103B, as Figure 8A 、 Figure 8B shown. However, considering the tolerances in actual manufacturing, the error of the projected areas SA1 and SA2 can be less than 5%.

[0136] A magnetic barrier structure 102A is provided on the first side 1021 of the magnetic yoke 102. A permanent magnet magnetic circuit 106A is formed among the thrust disk 121, the permanent magnet 101, and the magnetic yoke 102.

[0137] After the electromagnetic coil 104 is energized with the control current 105, a control magnetic circuit 107A will be formed between the thrust disk 121 and the magnetic yoke 102. The control magnetic circuit 107A passes through the first air gap 103A and the second air gap 103B. The magnetic flux distribution in the third air gap 103C is made uniform through the magnetic force plate 102B.

[0138] The paths of the permanent magnet leakage magnetic circuit 106B and the control leakage magnetic circuit 107B both pass through the magnetic barrier structure 102A, the second air gap 103B, and the third air gap 103C. Due to the physical limitation of the magnetic barrier structure 102A, the leakage magnetic flux can be reduced to far less than the magnetic flux of the permanent magnet magnetic circuit 106A, even to the extent that it can be ignored.

[0139] Figures 2A to 2D As shown, the different forms of permanent magnets 101A to 101D are all applicable to Figure 5 、 Figure 7 、 Figure 10 the axial magnetic floating bearings 100A, 100B, and 100C.

[0140] When the thrust disk 121 generates an axial displacement, the first air gap 103A, the second air gap 103B, and the third air gap 103C will change according to the displacement amount, just Figure 4 、 Figure 6 、 Figure 9 、Figure 11 Regarding the magnetic circuit shown, the present invention couples the magnetic field of the permanent magnet 101 with a part of the magnetic field path of the electromagnetic coil 104, such that only one side of the thrust disk 121 has the first air gap 103A and the second air gap 103B simultaneously passing through the magnetic flux of the permanent magnet 101 and the magnetic flux generated by the electromagnetic coil 104, and the two magnetic fluxes are in opposite directions.

[0141] In the magnetic field path of the permanent magnet 101, the present invention designs a magnetic saturation region to limit the magnetic flux of the permanent magnet 101 passing through the third air gap 103C, such that this magnetic flux does not change with the control current 105 of the electromagnetic coil 104.

[0142] Regarding the operating principle for achieving the above effects of this case, including the foregoing as Figure 4 shown, due to the physical limitation of the magnetic barrier structure 102A, the leakage magnetic flux can be reduced to far less than the magnetic flux of the permanent magnetic circuit 106A, and even to the extent that it can be ignored, which can be verified through the following mathematical calculation deduction formula and explanation.

[0143] Please refer to Figure 12 shown. Assume that the leakage magnetic phenomenon only exists inside the structure of the axial magnetic floating bearing 100, and the leakage magnetic paths of the permanent magnet 101 and the electromagnetic coil 104 are the same. The air gap areas of the first air gap 103A, the second air gap 103B, and the third air gap 103C are respectively A 1 、A 2 、A 3 . Define the control current magnetic flux φ C of the electromagnetic coil 104, the bias magnetic flux φ M of the permanent magnet 101, and the leakage magnetic flux φ L . The magnetic attraction forces F 1 、F 2 、F 3 generated by the first air gap 103A, the second air gap 103B, and the third air gap 103C can be respectively expressed as follows:

[0144]

[0145] Simplify the air gap areas into dimensionless parameters λ and λ′, as shown below:

[0146]

[0147] Then the resultant force received by the thrust disk 121 can be expressed by the following equation:

[0148]

[0149] Further expand the above equation and organize it as follows:

[0150]

[0151] φ controllable =(λ - 1)φ C 2 -2(λφ M +φ L )φ C

[0152] φ non-controllable =(λ + λ')φ M 2 +(λ' - 1)φ L 2 +2λ'φ M φ L

[0153] φ controllable is the magnetic flux related to the control current 105. The design area non - dimensional parameter λ is equal to 1, so that the resultant magnetic attraction force of the thrust disk 121 can be linearized with respect to the control magnetic flux. Based on the above assumptions, the magnetic flux φ non-controllable not related to the control current 105 can be further simplified as follows:

[0154] φ non-controllable =λ'(φ M +φ L ) 2 +(φ M -φ L )(φ M +φ L )

[0155] When the bias magnetic flux φ M is designed under the magnetic saturation condition, it can be assumed that the magnetic flux near its operating point is approximately constant. In other words, satisfying Under this condition, φ non-controllable can be regarded as a constant, and λ' can be designed arbitrarily. Since φ M is limited by the material properties, when the area ratio λ' of A 1 to A 3 is larger, the magnetic flux φ non-controllable not related to the control current 105 generates a larger magnetic flux.

[0156] Assume A = A 1 = A 2 , and Then the resultant force on the thrust disk 121 can be expressed by the following equation:

[0157]

[0158] Assume that the basic air - gaps are all g. When the thrust disk 121 generates an axial displacement x, the air - gap length of the A 1 surface is g + x, and the air - gap length of the A 2The air gap length on the surface is g - x. Its first air gap reluctance R 1 , and the second air gap reluctance R 2 are respectively expressed as follows:

[0159]

[0160] Please refer to Figure 12 , 13 as shown. Assuming the number of turns N of the electromagnetic coil 104 and the control current i c , the third air gap reluctance R 3 and the magnet reluctance R M , the variable reluctance R C , and its reluctance network is as shown in Figure 13 . From the main magnetic circuit loop of the control coil, the control current i C of the electromagnetic coil 104 and the relationship between the control current magnetic flux φ C can be solved as follows:

[0161]

[0162] Substitute into the aforementioned resultant force equation (1) of the thrust disk magnetic attraction force, and assume φ M = B sat A sat , where B sat is the saturation magnetic flux (regarded as a constant), and after arrangement, we can get:

[0163]

[0164] By designing the air gap area A 1 of the first air gap 103A of the coil magnetic circuit to be equal to the air gap area A 2 of the second air gap 103B, and designing the saturation magnetic flux φ M = B sat A sat on the main path of the permanent magnet magnetic circuit, the force on the thrust disk 121 can be made to have a linear relationship with the control current 105, and when the control current 105 is not applied, the thrust disk 121 bears an initial bias magnetic force. After the control current 105 is applied, the force on the thrust disk 121 gradually decreases as the control current 105 increases, as shown in Figure 14 .

[0165] In summary, a composite axial magnetic floating shaft using a permanent magnet and an electromagnet provided by the present invention has the characteristics of using a single coil, a unidirectional current, and providing a large unidirectional axial load. Without increasing the current output, it can carry a heavy unidirectional load and meet the linear control objective that its control current is proportional to the bearing capacity. In particular, the present invention has a magnetic barrier structure that forces the permanent magnetic circuit to pass only through the air gap on the same side of the thrust disk, making the leakage magnetic flux negligible compared to the magnetic flux of the permanent magnet. Furthermore, the control magnetic flux path is decoupled from the permanent magnetic flux path to achieve the linear control objective, and it is particularly suitable for application scenarios where the operating environment of the suspension spindle bears large axial offset forces.

[0166] Although the present invention is disclosed in combination with the above embodiments, it is not intended to limit the present invention. Any person of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. An axial magnetic floating bearing is fixed to a structure and is symmetrical about the rotation axis. The axial magnetic floating bearing includes: A rotating shaft, including a main shaft and a thrust disc. The main shaft is coaxial with the rotation axis, and the thrust disc is concentrically arranged on the main shaft; A magnetic conductive yoke, which includes opposite first and second sides. The first side and the second side are respectively arranged on the axial two sides of the thrust disc and do not contact the thrust disc. One end corresponding to the first side and the second side has a chamber, and the chamber is located radially outside the thrust disc; the first side adjacent to the chamber has a first air-gap surface, and the second side adjacent to the chamber has a second air-gap surface. A first air gap is formed between the first air-gap surface and the thrust disc, and a second air gap is formed between the second air-gap surface and the thrust disc. The error in the projected area sizes of the first air gap and the second air gap along the rotation axis direction is less than 5%; A permanent magnet is arranged on the surface of the magnetic conductive yoke facing the thrust disc relative to the main shaft. The permanent magnet does not contact the thrust disc, and a third air gap is formed between the thrust disc and the permanent magnet. A permanent magnetic circuit is formed among the thrust disc, the permanent magnet and the magnetic conductive yoke; A magnetic barrier structure is arranged on the first side and is located between the permanent magnet and the first air-gap surface. The first side has a first cross-sectional area parallel to the rotation axis, and the magnetic barrier structure has a second cross-sectional area parallel to the rotation axis. The second cross-sectional area is smaller than the first cross-sectional area; the magnetic barrier structure is located in the path of the permanent magnetic circuit, and the permanent magnetic circuit passes through the magnetic barrier structure, the first air gap and the third air gap; and An electromagnetic coil is arranged in the chamber and does not contact the thrust disc. After a control current is passed through the electromagnetic coil, a control magnetic circuit is formed between the thrust disc and the magnetic conductive yoke, and the control magnetic circuit passes through the first air gap and the second air gap.

2. The axial magnetic floating bearing according to claim 1, wherein the projected range of the first air gap and the projected range of the second air gap along the rotation axis direction are all or partially overlapped.

3. The axial magnetic floating bearing according to claim 1, wherein the main shaft is a magnetic body, and the main shaft and the magnetic conductive yoke are spaced apart by a first distance so that the main shaft and the magnetic conductive yoke do not contact each other.

4. The axial magnetic floating bearing according to claim 1, wherein the structure body is a magnetic body, and the structure body and the thrust disc are spaced apart by a second distance so that the structure body and the thrust disc do not contact each other.

5. The axial magnetic floating bearing according to claim 1, wherein both the structure body and the main shaft are magnetic bodies, and the structure body and the main shaft are spaced apart by a third distance so that the structure body and the main shaft do not contact each other.

6. The axial magnetic floating bearing according to claim 1, wherein a magnetic conductive magnetic force plate is provided on the surface of the permanent magnet facing the thrust disc to make the magnetic field distribution in the third air gap uniform.

7. The axial magnetic floating bearing according to claim 1, wherein the magnetic barrier structure, the second air gap and the third air gap are all located in the path of the permanent magnetic leakage path generated by the permanent magnetic circuit and the control magnetic leakage path generated by the control magnetic circuit.

8. The axial magnetic floating bearing according to claim 1, wherein the material of the magnetic barrier structure is a material with different magnetic permeabilities, including ferrite, thereby controlling the magnetic flux.

9. The axial magnetic levitation bearing according to claim 1, wherein a radial bearing is provided between the rotating shaft and the structure, so that the rotating shaft maintains a radial relative position with the structure by means of the radial bearing.

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