A Design Method for Axial Passive Magnetic Bearing

Abstract

The present invention discloses a design method for an axial passive magnetic bearing, wherein the axial passive magnetic bearing includes at least one permanent magnet group, and the design method includes: determining a first design parameter of the axial passive magnetic bearing according to the mechanical performance requirements of the axial passive magnetic bearing; obtaining a target stiffness of the axial passive magnetic bearing based on the first design parameter; determining a second design parameter of the axial passive magnetic bearing according to the structure and magnetization property requirements and magnetization parameters of the permanent magnet group; obtaining the bearing stiffness of each permanent magnet group based on the second design parameter; determining the number of permanent magnet groups according to the target stiffness and the bearing stiffness of each permanent magnet group; and designing the structure of the axial passive magnetic bearing according to the number of permanent magnet groups. The design method disclosed by the present invention realizes the quantitative design of the axial passive magnetic bearing, greatly improves the design accuracy, and effectively ensures the use safety of the axial passive magnetic bearing.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic bearings, and in particular to a design method for an axial passive magnetic bearing. Background Art

[0002] Compared with air static pressure bearings and mechanical bearings, magnetic bearings can achieve non-contact suspension support, with advantages such as simple structure, low processing and manufacturing precision requirements, low vibration and noise, and strong environmental adaptability. They have become important components of precision positioning workbenches. Magnetic bearings achieve stable suspension of the rotor part by balancing the gravity of the rotor part and the magnetic force of the stator part.

[0003] Existing magnetic bearings can be divided into active magnetic bearings and passive magnetic bearings according to whether the magnetic force is controllable. Active magnetic bearings can actively control the bearing stiffness and damping effect by controlling the size and direction of the current in the coil winding. They have the functions of active vibration control and active vibration suppression, but they need to be installed with high-precision and high-quality displacement sensors, controllers and power amplifiers. The system is complex, the cost is high, and the reliability is low. Passive magnetic bearings do not need to be used with components such as sensors and controllers. They have the advantages of simple structure, low cost, low power consumption, and high system reliability. They can meet the requirements of contactless suspension support of rotating motion machinery. However, most of the current patent documents only propose the structure of passive magnetic bearings, and lack corresponding analysis and design models. Summary of the invention

[0004] In order to overcome the problems existing in the related art, the present invention provides a design method for an axial passive magnetic bearing.

[0005] According to a first aspect of the present invention, a design method for an axial passive magnetic bearing is provided, wherein the axial passive magnetic bearing comprises at least one permanent magnet group, and the design method comprises:

[0006] Determining a first design parameter of the axial passive magnetic bearing according to the mechanical performance requirements of the axial passive magnetic bearing;

[0007] Based on the first design parameter, a target stiffness of the axial passive magnetic bearing is obtained;

[0008] Determining second design parameters of the axial passive magnetic bearing according to the structure and magnetization property requirements and magnetization parameters of the permanent magnet group;

[0009] Based on the second design parameter, obtaining the bearing stiffness of each of the permanent magnet groups;

[0010] Determining the number of the permanent magnet groups according to the target stiffness and the bearing stiffness of each of the permanent magnet groups;

[0011] The structure of the axial passive magnetic bearing is designed according to the number of permanent magnet groups.

[0012] In some embodiments, the structure and magnetization property requirements of the permanent magnet group include: the axial passive magnetic bearing includes a plurality of permanent magnet groups, and the magnetization intensity and radial thickness of each permanent magnet group are equal, so that the bearing stiffness of each permanent magnet group is equal;

[0013] The obtaining, based on the second design parameter, the bearing stiffness of each permanent magnet group comprises:

[0014] Based on the second design parameter, the bearing stiffness of a single permanent magnet group is obtained;

[0015] Determining the number of the permanent magnet groups according to the target stiffness and the bearing stiffness of each permanent magnet group includes:

[0016] The number of the permanent magnet groups is determined according to the target stiffness and the bearing stiffness of a single permanent magnet group.

[0017] In some embodiments, there is a spherical shell-shaped air gap between the stator and the rotor of the axial passive magnetic bearing;

[0018] The obtaining, based on the second design parameter, the bearing stiffness of each permanent magnet group comprises:

[0019] Establishing first configuration information, the first configuration information is used to characterize the relationship between the second design parameter and the magnetic field energy at the spherical shell-shaped air gap, the first configuration information includes a first parameter, and the first parameter is used to represent the axial displacement of the rotor;

[0020] Based on the first configuration information, determine second configuration information, where the second configuration information is obtained by taking the first parameter as the derivative twice and setting the first parameter to zero;

[0021] The bearing stiffness of each of the permanent magnet groups is determined according to the second configuration information.

[0022] In some embodiments, the structural requirements of the permanent magnet group include: each of the permanent magnet groups surrounds the circumference of the axial passive magnetic bearing and is arranged in sequence along the radial direction of the axial passive magnetic bearing, the permanent magnet group includes two sub-permanent magnet groups, the two sub-permanent magnet groups are respectively located on the stator and the rotor of the axial passive magnetic bearing and are arranged correspondingly, and the sub-permanent magnet group includes a first permanent magnet;

[0023] The magnetization direction of the first permanent magnet is parallel to the axial direction of the axial passive magnetic bearing, and the magnetization parameters of the permanent magnet group include the magnetization intensity of the first permanent magnet.

[0024] In some embodiments, the second design parameters include a base radius of the permanent magnet group, a radial thickness of the first permanent magnet, and a spacing between the two sub-permanent magnet groups in one permanent magnet group.

[0025] In some embodiments, the structural requirements of the permanent magnet group further include: the sub-permanent magnet group includes two second permanent magnets, and the two second permanent magnets are respectively located on both sides of the radial direction of the first permanent magnet in the sub-permanent magnet group;

[0026] The magnetization direction of the second permanent magnet points to the N pole of the first permanent magnet in the sub-permanent magnet group, and an angle is formed between the magnetization direction of the first permanent magnet and the magnetization direction of the second permanent magnet. The magnetization parameters of the permanent magnet group also include the magnetization intensity of the second permanent magnet and the size of the angle;

[0027] The second design parameter also includes a radial thickness of the second permanent magnet.

[0028] In some embodiments, the magnetization intensity and the radial thickness of the second permanent magnet are equal to those of the first permanent magnet.

[0029] In some embodiments, the first design parameter includes a maximum axial load force and a maximum allowable axial displacement.

[0030] In some embodiments, obtaining the target stiffness of the axial passive magnetic bearing based on the first design parameter includes:

[0031] Obtaining the deadweight of the rotor of the axial passive magnetic bearing and setting a safety factor;

[0032] Based on the first design parameter, the deadweight of the rotor and the safety factor, a target stiffness of the axial passive magnetic bearing is calculated.

[0033] According to a second aspect of the present invention, there is provided an axial passive magnetic bearing, wherein the axial passive magnetic bearing is designed using the design method described in any one of the above embodiments.

[0034] The beneficial effects of the present invention are:

[0035] In the design method of the axial passive magnetic bearing provided by the present invention, based on the requirements of multiple aspects of the axial passive magnetic bearing, its target stiffness and the bearing stiffness of each permanent magnet group are determined respectively, and then the number of permanent magnet groups is determined, thereby realizing the quantitative design of the axial passive magnetic bearing, greatly improving the design accuracy, and effectively ensuring the safety of the use of the axial passive magnetic bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic cross-sectional view of an axial passive magnetic bearing according to an exemplary embodiment.

[0038] Figure 2 The figure is a flow chart of a method for designing an axial passive magnetic bearing according to an exemplary embodiment.

[0039] Figure 3 FIG. 4 is a flowchart of step S400 according to an exemplary embodiment.

[0040] Figure 4 FIG. 1 is a flowchart of step S200 according to an exemplary embodiment.

[0041] In the figure: 10-stator; 20-rotor; 30-air gap; 1-permanent magnet group; 1a-permanent magnet group 1; 11-sub-permanent magnet group; 111-first permanent magnet; 112-second permanent magnet. DETAILED DESCRIPTION

[0042] like Figure 1 As shown, the passive magnetic bearing generally includes a stator 10 and a rotor 20, wherein the stator 10 and the rotor 20 are respectively provided with permanent magnets (refer to the first permanent magnet 111 and the second permanent magnet 112), and the stator 10 and the rotor 20 are axially spaced in the magnetic bearing ( Figure 1 The magnetization directions of the permanent magnets arranged opposite to each other in the y direction (as shown in the figure) are opposite, so that the permanent magnets on the stator 10 and the rotor 20 repel each other due to the magnetic field, and thus an air gap 30 is formed between the stator 10 and the rotor 20. In the working state of the passive magnetic bearing, the load and its own gravity on the rotor 20 are balanced with the repulsive force from the permanent magnets on the stator 10, and the rotor 20 can stably maintain a suspended state.

[0043] In the past, the design of passive magnetic bearings often used empirical values, and roughly estimated the relevant design parameter values ​​based on the actual usage of the magnetic bearings. However, this design method is qualitative design. On the one hand, the design accuracy is low, and it is difficult to ensure a good match with the usage scenario. On the other hand, the reliability is poor, and it is easy to have abnormal conditions and even cause safety accidents.

[0044] In order to solve the problems existing in the related art, an embodiment of the present invention provides a design method for an axial passive magnetic bearing, wherein the axial passive magnetic bearing includes at least one permanent magnet group. The design method includes: determining a first design parameter of the axial passive magnetic bearing according to the mechanical performance requirements of the axial passive magnetic bearing; obtaining the target stiffness of the axial passive magnetic bearing based on the first design parameter; determining a second design parameter of the axial passive magnetic bearing according to the structure and magnetization property requirements and magnetization parameters of the permanent magnet group; obtaining the bearing stiffness of each permanent magnet group based on the second design parameter; determining the number of permanent magnet groups according to the target stiffness and the bearing stiffness of each permanent magnet group; and designing the structure of the axial passive magnetic bearing according to the number of permanent magnet groups. In the design method for the axial passive magnetic bearing provided by the embodiment of the present invention, based on the requirements of multiple aspects of the axial passive magnetic bearing, the target stiffness and the bearing stiffness of each permanent magnet group are determined respectively, and then the number of permanent magnet groups is determined, so as to realize the quantitative design of the axial passive magnetic bearing, greatly improve the design accuracy, and effectively ensure the use safety of the axial passive magnetic bearing.

[0045] The technical scheme in the embodiment of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0046] like Figure 2 As shown, this embodiment provides a design method for an axial passive magnetic bearing. The designed axial passive magnetic bearing includes at least one permanent magnet group (refer to Figure 1 The permanent magnet group 1 shown in FIG. 1 ) is designed by the method comprising the following steps:

[0047] Step S100: determining first design parameters of the axial passive magnetic bearing according to the mechanical performance requirements of the axial passive magnetic bearing.

[0048] The requirements for mechanical properties of axial passive magnetic bearings vary depending on factors such as the location, purpose, and use environment. Therefore, when designing axial passive magnetic bearings, the requirements for mechanical properties (such as axial load and operating stability) can be determined first, and then the value of the first design parameter (such as maximum axial load and maximum allowable axial displacement) can be determined based on the mechanical performance requirements. The standard for determining the value of the first design parameter can be set according to actual conditions and is not limited here. For example, for the maximum axial load, 1.5-2.0 times the commonly used axial load of the axial passive magnetic bearing in the actual working environment can be set as its maximum axial load. For the maximum allowable axial displacement, for example, the displacement critical value of the unbalanced rotor 20 and the maximum allowable displacement fluctuation value of the rotating part of the equipment connected to the rotor 20 can be comprehensively considered, and 0.7-0.8 times the minimum of the two can be taken.

[0049] Step S200: Based on the first design parameter, obtain the target stiffness of the axial passive magnetic bearing.

[0050] Stiffness refers to the elastic properties of the bearing, which can reflect the ability of the bearing to resist deformation. The greater the stiffness, the smaller the deformation of the bearing when it is under load. Normally, the bearing is used to achieve movement between the components connected to the stator 10 and the components connected to the rotor 20. Therefore, the higher the stiffness of the bearing, the less likely the movement between the two parts will be disturbed by the outside world, thereby better ensuring the normal operation of the mechanical equipment. Based on the first design parameter, the target stiffness of the axial passive magnetic bearing can be obtained, which can ensure that the axial passive magnetic bearing can meet its mechanical performance requirements and has good operating stability. The target stiffness can be derived or characterized according to the operational relationship between it and the first design parameter (described in detail later), or it can also be simulated using relevant software to output a target stiffness value based on the first design parameter.

[0051] Step S300: Determine the second design parameters of the axial passive magnetic bearing according to the structure and magnetization property requirements and magnetization parameters of the permanent magnet group.

[0052] The space used for bearing installation and operation in mechanical equipment is often limited, so the value of the second design parameter of the axial passive magnetic bearing (such as the relevant structural dimensions of the permanent magnet group 1) can be determined first. In one example, the second design parameter may include the radius of the permanent magnet in the permanent magnet group 1, the radial thickness, and the thickness of the air gap 30 of the bearing, etc. The value of the determined second design parameter can make the size of the magnetic bearing less than or equal to its spatial size, so that the permanent magnet group 1 can meet the space limitations of the axial passive magnetic bearing. The specific value of the second design parameter can be set according to actual conditions. For example, when determining the radial thickness of the permanent magnet, the radial thickness of the permanent magnet of the existing specifications can be preferentially selected to facilitate subsequent bearing processing and manufacturing.

[0053] Step S400: Based on the second design parameter, the bearing stiffness of each permanent magnet group is obtained.

[0054] As mentioned above, the permanent magnet groups 1 on the stator 10 and the rotor 20 of the magnetic bearing repel each other and thus provide load capacity for the magnetic bearing. Therefore, the bearing stiffness of each permanent magnet group 1 can be determined to ensure that the load capacity provided by the permanent magnet group 1 can meet the needs of the axial passive magnetic bearing. After determining the value of the second design parameter, the bearing stiffness of each permanent magnet group 1 in the axial passive magnetic bearing can be obtained based on the second design parameter, and the sum of the bearing stiffness of each permanent magnet group 1 is the stiffness that the permanent magnet group 1 in the axial passive magnetic bearing can provide. The method for determining the bearing stiffness of the permanent magnet group 1 can refer to the target stiffness of the aforementioned axial passive magnetic bearing, and is obtained by the operational relationship with the second design parameter (described in detail later) or software simulation, etc., which will not be repeated here.

[0055] Step S500: Determine the number of permanent magnet groups according to the target stiffness and the bearing stiffness of each permanent magnet group.

[0056] When determining the number of permanent magnet groups 1, a larger number of groups can be appropriately selected so that the sum of the bearing stiffness of each permanent magnet group 1 is greater than the target stiffness of the axial passive magnetic bearing, ensuring that the stiffness provided by the permanent magnet group 1 can always meet the target stiffness requirements.

[0057] Step S600: designing the structure of the axial passive magnetic bearing according to the number of permanent magnet groups.

[0058] In this design method, based on the requirements of multiple aspects of the axial passive magnetic bearing, its target stiffness and the bearing stiffness of each permanent magnet group 1 are determined respectively, and then the number of permanent magnet groups 1 is determined. According to the determined number of permanent magnet groups 1, the structure of the axial passive magnetic bearing can be designed more accurately, and the quantitative design of the axial passive magnetic bearing is realized, which greatly improves the design accuracy and effectively ensures the safety of the use of the axial passive magnetic bearing.

[0059] In one embodiment, the structure and magnetization property requirements of the permanent magnet group 1 specifically include: the axial passive magnetic bearing includes multiple permanent magnet groups 1, and the magnetization intensity and radial thickness of each permanent magnet group 1 are equal. According to the calculation formula of the stiffness of the permanent magnet, it can be known that the bearing stiffness of each permanent magnet group 1 is equal at this time, so only the bearing stiffness of a single permanent magnet group 1 can be calculated to greatly reduce the amount of calculation and simplify the design process. At this time, step S400 and step S500 specifically include the following steps:

[0060] Step S401: Based on the second design parameter, obtain the bearing stiffness of a single permanent magnet group.

[0061] Step S501: Determine the number of permanent magnet groups according to the target stiffness and the bearing stiffness of a single permanent magnet group.

[0062] The number N of permanent magnet groups 1 can be determined by the following formula:

[0063]

[0064] In the formula, K a is the target stiffness of the axial passive magnetic bearing, K b is the bearing stiffness of the single permanent magnet group 1.

[0065] In one embodiment, if Figure 1 As shown, the opposite end faces of the permanent magnets on the stator 10 and the rotor 20 are both spherical surfaces, and the spherical surface on the stator 10 coincides with the spherical surface on the rotor 20, so that a spherical shell-shaped air gap 30 is provided between the stator 10 and the rotor 20 of the axial passive magnetic bearing. The spherical surface on the stator 10 can be an outward convex spherical surface, and the spherical surface on the rotor 20 corresponds to an inward concave spherical surface (refer to Figure 1 ), of course, the spherical surface on the stator 10 can also be a concave spherical surface, in which case the spherical surface on the rotor 20 corresponds to a convex spherical surface (not shown in the drawings), and this embodiment does not limit this. Since the centers of the two spherical surfaces coincide, when the rotor 20 is angularly deflected during rotation, the direction of the repulsive force on the rotor 20 is always along its axial direction and passes through the center of the spherical surface, so that the spherical shell air gap 30 can be kept uniform, thereby eliminating the torsional moment and improving the suspension accuracy of the magnetic bearing. In addition, the relative magnetic pole area of ​​the magnetic bearing can be significantly increased, thereby improving the bearing stiffness and bearing capacity.

[0066] like Figure 3 As shown, when the air gap 30 in the axial passive magnetic bearing is in the shape of a spherical shell, step S400 specifically includes the following steps:

[0067] Step S410: establishing first configuration information, the first configuration information is used to characterize the relationship between the second design parameter and the magnetic field energy at the spherical shell-shaped air gap 30, the first configuration information includes a first parameter, and the first parameter is used to represent the axial displacement of the rotor;

[0068] According to the virtual displacement principle, the derivative of the magnetic field energy at the spherical shell air gap 30 on the axial displacement is the axial load force of the permanent magnet group 1, so the first configuration information can be first established to characterize the magnetic field energy at the spherical shell air gap 30, and the first configuration information includes a first parameter for indicating the axial displacement of the rotor 20. The first configuration information can be obtained by deducing relevant physical formulas, and of course can also be established by other methods, which are not limited.

[0069] Step S420: determining second configuration information based on the first configuration information, where the second configuration information is obtained by derivatizing the first parameter twice using the first configuration information and setting the first parameter to zero;

[0070] Based on the first configuration information, the first parameter is first differentiated to obtain the axial load force of the permanent magnet group 1. As mentioned above, the bearing stiffness can reflect the ability of the bearing to resist deformation and can be expressed by the ratio between the load and the displacement. Therefore, the first parameter is differentiated for the second time and the first parameter is set to zero (that is, the axial displacement of the rotor 20 is zero) to obtain the second configuration information. The second configuration information can be used to characterize the bearing stiffness of the permanent magnet group 1.

[0071] Step S430: Determine the bearing stiffness of each permanent magnet group according to the second configuration information.

[0072] According to the obtained second configuration information, by performing numerical substitution or deformation on the second configuration information, the numerical value or expression of the bearing stiffness of each permanent magnet group 1 can be determined, and then the sum of the bearing stiffness of each permanent magnet group 1 can be determined.

[0073] In one embodiment, if Figure 1 As shown, the structural requirements of the permanent magnet group 1 include: each permanent magnet group 1 surrounds the circumference of the axial passive magnetic bearing and is along the radial direction of the axial passive magnetic bearing ( Figure 1 The permanent magnet group 1 includes two sub-permanent magnet groups 11, which are respectively located on the stator 10 and the rotor 20 of the axial passive magnetic bearing and are arranged correspondingly. The sub-permanent magnet group 11 includes a first permanent magnet 111. The magnetization property requirements of the permanent magnet group 1 include: the magnetization direction of the first permanent magnet 111 is parallel to the axial direction of the axial passive magnetic bearing ( Figure 1 The magnetization parameters of the permanent magnet group 1 include the magnetization intensity of the first permanent magnet 111.

[0074] According to magnetostatics theory, the surface magnetic charge density, main air gap magnetic field intensity, and air gap leakage magnetic field intensity of the first permanent magnet 111 at the spherical shell-shaped air gap 30 can be expressed based on the magnetization intensity of the first permanent magnet 111, so as to establish the first configuration information. The expressions of the surface magnetic charge density, main air gap magnetic field intensity, and air gap leakage magnetic field intensity of the first permanent magnet 111 are as follows:

[0075]

[0076]

[0077]

[0078] In the formula, σ * c is the surface magnetic charge density of the first permanent magnet 111, B zc The main air gap magnetic field strength of the first permanent magnet 111, B zclouis the air gap leakage magnetic field strength of the first permanent magnet 111, μ0 is the vacuum magnetic permeability (μ0=4π×10 -7 H / m), M is the magnetization intensity, B r is the residual magnetization intensity of the permanent magnet, δ is the thickness of the spherical shell-shaped air gap 30, and z is the axial displacement of the rotor 20 (ie, the first parameter).

[0079] In one embodiment, the second design parameter includes the reference radius of the permanent magnet group 1, the radial thickness of the first permanent magnet 111, and the distance between two sub-permanent magnet groups 11 in a permanent magnet group 1. The reference radius of the permanent magnet group 1 is the radial outermost permanent magnet group 1 of the axial passive magnetic bearing (reference Figure 1 The outer diameter of the permanent magnet group 1a) shown in FIG. 1 is the distance between two sub-permanent magnet groups 11 in a permanent magnet group 1, and the thickness of the spherical shell air gap 30. The first configuration information established based on the second design parameter can represent the magnetic field energy at the spherical shell air gap 30 when the first permanent magnet 111 is set.

[0080] In one embodiment, if Figure 1 As shown, the structural requirements of the permanent magnet group 1 also include: the sub-permanent magnet group 11 includes two second permanent magnets 112, and the two second permanent magnets 112 are respectively located on both sides of the radial direction of the first permanent magnet 111 in the sub-permanent magnet group 11. The magnetization property requirements of the permanent magnet group 1 also include: the magnetization direction of the second permanent magnet 112 points to the N pole of the first permanent magnet 111 in the sub-permanent magnet group 11, and the magnetization direction of the first permanent magnet 111 forms an angle with the magnetization direction of the second permanent magnet 112. The magnetization parameters of the permanent magnet group 1 also include the magnetization intensity of the second permanent magnet 112. The second design parameter also includes the radial thickness of the second permanent magnet 112.

[0081] A second permanent magnet 112 is arranged in the sub-permanent magnet group 11, so that the first permanent magnet 111 and the second permanent magnet 112 form a Halbach array structure together. On the one hand, it can effectively improve the air gap magnetic field fluctuation of the magnetic bearing caused by the splicing of permanent magnets, improve the uniformity of the air gap magnetic density, and thus improve the suspension accuracy of the magnetic bearing. On the other hand, it can also enable the stator 10 and the rotor 20 to produce a strong magnetic concentration effect, which can significantly enhance the air gap magnetic field strength, further improve the bearing capacity and stiffness of the magnetic bearing, and achieve the technical effect of both high suspension accuracy and high bearing stiffness.

[0082] According to magnetostatics theory, the surface magnetic charge density, main air gap magnetic field intensity, and air gap leakage magnetic field intensity of the second permanent magnet 112 at the spherical shell-shaped air gap 30 can also be expressed based on the magnetization intensity of the second permanent magnet 112, so as to establish the first configuration information. The expressions of the surface magnetic charge density, main air gap magnetic field intensity, and air gap leakage magnetic field intensity of the second permanent magnet 112 are as follows:

[0083]

[0084]

[0085]

[0086] In the formula, σ * s is the surface magnetic charge density of the second permanent magnet 112, B zb is the main air gap magnetic field strength of the second permanent magnet 112, B zblou is the air gap leakage magnetic field intensity of the second permanent magnet 112, and α is the angle between the normal direction of the end face of the permanent magnet ring and the magnetization direction.

[0087] In one embodiment, the magnetization intensity and radial thickness of the second permanent magnet 112 are equal to those of the first permanent magnet 111, so as to facilitate the design process of the axial passive magnetic bearing and the subsequent production of the bearing. At this time, the first configuration information can be shown as follows:

[0088] Where W is the magnetic field energy at the spherical shell air gap 30, R up and R down are the reference radii of the permanent magnet group 1 on the rotor 20 and the stator 10, respectively. pm is the radial thickness of the first permanent magnet 111 and the second permanent magnet 112 .

[0089]

[0090] Based on the first configuration information, the first parameter (z) is derived for the first time to obtain the axial load force of the permanent magnet group 1, and its expression is as follows:

[0091]

[0092] The first parameter is derivatized for the second time, and the first parameter is set to zero, and the second configuration information is obtained as shown below:

[0093]

[0094] In one embodiment, the first design parameters include a maximum axial load force and a maximum allowable axial displacement. The target stiffness of the axial passive magnetic bearing can be obtained based on the first design parameters. The target stiffness can ensure that the axial passive magnetic bearing can meet its mechanical performance requirements and have good operating stability.

[0095] In one embodiment, if Figure 4 As shown, step S200 specifically includes the following steps:

[0096] Step S210: Obtain the deadweight of the rotor of the axial passive magnetic bearing and set a safety factor;

[0097] Since the axial passive magnetic bearing is usually placed vertically, the gravity of its moving part is in the same direction as the axial load, and the load force required is the superposition of gravity and axial load. Therefore, when designing the axial passive magnetic bearing, it is also necessary to obtain the deadweight of the rotor 20. In addition, in order to ensure that the bearing can be stably and reliably suspended in the axial direction, a certain safety factor can be set additionally based on the superposition of gravity and axial load.

[0098] Step S220: Calculate the target stiffness of the axial passive magnetic bearing based on the first design parameter, the deadweight of the rotor and the safety factor.

[0099] The calculation formula for the target stiffness of the axial passive magnetic bearing is shown below:

[0100]

[0101] In the formula, k sc is the safety factor (can be between 2 and 3), F w is the maximum axial load force, m is the deadweight of the rotor 20, g is the gravitational acceleration, △z max is the maximum allowable axial displacement.

[0102] When the bearing stiffness K of each permanent magnet group 1 b When they are equal, the target stiffness K of the axial passive magnetic bearing can be calculated a and the bearing stiffness K of the single permanent magnet group 1 b The multiple relationship of is used to determine the number N of permanent magnet groups 1, which will not be elaborated here.

[0103] It can be understood that the values ​​of the parameters in the above design method can refer to the structural values ​​of the existing passive magnetic bearings, and on this basis, the above design method can be used for calculation to obtain a suitable size result (the number of permanent magnet groups 1) to meet the requirements of design accuracy and safety of use.

[0104] like Figure 1 As shown, this embodiment provides an axial passive magnetic bearing, which can be designed using the design method in any of the above embodiments. During the design process, based on the requirements of the axial passive magnetic bearing in multiple aspects, its target stiffness and the bearing stiffness of each permanent magnet group 1 are determined respectively, and then the number of permanent magnet groups 1 is determined, thereby realizing the quantitative design of the axial passive magnetic bearing. The axial passive magnetic bearing provided in this embodiment has a high design accuracy and can effectively ensure the safety of the use of the axial passive magnetic bearing.

[0105] The contents described in the embodiments of this specification are merely an enumeration of implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also includes equivalent technical means that can be thought of by those skilled in the art based on the inventive concept.

Claims

1. A design method for an axial passive magnetic bearing, characterized in that: The axial passive magnetic bearing comprises at least one permanent magnet group (1), and the design method comprises: Determining first design parameters of the axial passive magnetic bearing according to the mechanical performance requirements of the axial passive magnetic bearing, wherein the first design parameters include a maximum axial load force and a maximum allowable axial displacement; Based on the first design parameter, a target stiffness of the axial passive magnetic bearing is obtained, wherein based on the first design parameter, the target stiffness of the axial passive magnetic bearing is obtained, comprising: obtaining the deadweight of a rotor (20) of the axial passive magnetic bearing and setting a safety factor; based on the first design parameter, the deadweight of the rotor (20) and the safety factor, calculating the target stiffness of the axial passive magnetic bearing; Determining second design parameters of the axial passive magnetic bearing according to the structure and magnetization property requirements and magnetization parameters of the permanent magnet group (1), wherein the permanent magnet group (1) comprises two sub-permanent magnet groups (11), the two sub-permanent magnet groups (11) are respectively located on the stator (10) and the rotor (20) of the axial passive magnetic bearing and are arranged correspondingly, the sub-permanent magnet group (11) comprises a first permanent magnet (111), and the second design parameters comprise a reference radius of the permanent magnet group (1), a radial thickness of the first permanent magnet (111), and a spacing between two sub-permanent magnet groups (11) in the permanent magnet group (1); Based on the second design parameter, the bearing stiffness of each permanent magnet group (1) is obtained, wherein a spherical shell-shaped air gap (30) is provided between the stator (10) and the rotor (20) of the axial passive magnetic bearing, and based on the second design parameter, the bearing stiffness of each permanent magnet group (1) is obtained, comprising: establishing first configuration information, the first configuration information being used to characterize the relationship between the second design parameter and the magnetic field energy at the spherical shell-shaped air gap (30), the first configuration information comprising a first parameter, the first parameter being used to represent the axial displacement of the rotor (20); based on the first configuration information, determining second configuration information, the second configuration information being obtained by derivatizing the first parameter twice with the first configuration information and setting the first parameter to zero; and determining the bearing stiffness of each permanent magnet group (1) according to the second configuration information; Determining the number of permanent magnet groups (1) according to the target stiffness and the bearing stiffness of each permanent magnet group (1), wherein the axial passive magnetic bearing comprises a plurality of permanent magnet groups (1), the magnetization intensity and radial thickness of each permanent magnet group (1) are equal, so that the bearing stiffness of each permanent magnet group (1) is equal, and obtaining the bearing stiffness of a single permanent magnet group (1) based on the second design parameter, and determining the number of permanent magnet groups (1) according to the target stiffness and the bearing stiffness of a single permanent magnet group (1), wherein the number of permanent magnet groups (1) is the ratio of the target stiffness to the bearing stiffness of a single permanent magnet group (1); The structure of the axial passive magnetic bearing is designed according to the number of permanent magnet groups (1).

2. The design method according to claim 1, characterized in that: The structural requirements of the permanent magnet group (1) include: each of the permanent magnet groups (1) surrounds the circumference of the axial passive magnetic bearing and is arranged in sequence along the radial direction of the axial passive magnetic bearing; The magnetization direction of the first permanent magnet (111) is parallel to the axial direction of the axial passive magnetic bearing, and the magnetization parameters of the permanent magnet group (1) include the magnetization intensity of the first permanent magnet (111).

3. The design method according to claim 2, characterized in that: The structural requirements of the permanent magnet group (1) also include: the sub-permanent magnet group (11) comprises two second permanent magnets (112), and the two second permanent magnets (112) are respectively located on both sides of the radial direction of the first permanent magnet (111) in the sub-permanent magnet group (11); The magnetization direction of the second permanent magnet (112) points to the N pole of the first permanent magnet (111) in the sub-permanent magnet group (11), an angle is formed between the magnetization direction of the first permanent magnet (111) and the magnetization direction of the second permanent magnet (112), and the magnetization parameters of the permanent magnet group (1) also include the magnetization intensity of the second permanent magnet (112); The second design parameter also includes a radial thickness of the second permanent magnet (112).

4. The design method according to claim 3, characterized in that: The magnetization intensity and radial thickness of the second permanent magnet (112) are equal to those of the first permanent magnet (111).

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