Asymmetric hybrid magnetic bearing structure and multi-flow-port molecular pump

Abstract

The application provides a kind of asymmetric mixed magnetic bearing structure and multi-flow port molecular pump, the magnetic bearing structure includes stator core;The inside of stator core is divided into two two symmetrical distribution first function area and second function area along the circumferential direction, the first stator component of first function area includes permanent magnet and the first tooth part located on the two sides of permanent magnet, and the first tooth part is wound with first coil.Second stator component of second function area includes second tooth part and yoke, and the magnetic ring is arranged between yoke and the inner wall of stator core, and the second tooth part is wound with second coil.The application adopts asymmetric distribution stator topology, in the X direction of bearing small disturbance force, only the small area of pure electromagnetic pole is designed;In the Y direction of bearing gravity and pneumatic impact, the magnetic pole occupying larger pole arc area is designed, and the permanent magnet bias structure is introduced, so as to provide extremely high magnetic flux margin and bearing limit in Y direction, which fundamentally eliminates the risk of molecular pump shaft falling and machine damage due to insufficient lateral impact resistance.

Description

Technical Field

[0001] This invention relates to the field of magnetic bearing technology, and in particular to an asymmetric hybrid magnetic bearing structure and a multi-port molecular pump. Background Technology

[0002] In high-end analytical instruments such as mass spectrometers and helium mass spectrometer leak detectors, multi-port turbomolecular pumps (split-flow molecular pumps) are typically used to provide multi-stage differential vacuum to meet the pressure difference requirements between different chambers from the ion source to the mass analyzer. Due to the extremely compact space constraints within these instruments, these multi-port molecular pumps are usually installed horizontally (i.e., the pump shaft's rotation axis is horizontal) during system integration. Furthermore, to facilitate docking with the various vacuum chambers of the instrument, the multiple side inlets on the pump housing are typically arranged with upward-facing openings.

[0003] This unique installation and air intake method results in an extremely strong asymmetry in the forces acting on the high-speed rotating molecular pump shaft in the radial plane (XY plane):

[0004] High load-bearing direction (e.g., Y-direction): Since the molecular pump shaft is horizontal, it must constantly bear its own enormous weight in this direction. Simultaneously, because multiple outlets open upwards, when the instrument injects samples or introduces carrier gas, the gas flow rushes in from above, generating a continuous and strong downward aerodynamic impact force and steady-state asymmetric gas disturbance force on the high-speed molecular pump shaft. The superposition of gravity and aerodynamic load in this direction requires the radial magnetic bearing to possess extremely high static load-bearing capacity and dynamic stiffness.

[0005] Low load direction (e.g., horizontal X direction): This direction mainly bears the small high-frequency synchronous excitation force caused by the residual unbalance of the molecular pump shaft, as well as the weak stray airflow disturbance. The required load-bearing capacity and stiffness are much smaller than those in the Y direction.

[0006] Currently, in the field of magnetically levitated molecular pumps, the widely used radial magnetic levitation bearings are fully symmetrical 8-pole or 16-pole structures (including purely electromagnetic structures or symmetrical permanent magnet bias structures). A typical structure includes a stator assembly comprising a circular stator core with 8 or 16 stator poles of identical shape and polar arc area evenly distributed on its inner circumference. Each pole has a control coil wound with the same number of turns and wire diameter within its tooth groove. The molecular pump shaft is coaxially suspended within the inner hole formed by the stator pole shoes. During operation, sensors continuously detect the radial displacement of the molecular pump shaft in the X and Y directions. When the molecular pump shaft deviates from its geometric center, the controller, based on the deviation signal, supplies control current to the control coil in the corresponding direction. Because the pole areas are equal and the number of coil turns is the same in all directions, the maximum electromagnetic pull force provided in the X and Y directions is completely identical. For permanent magnet bias structures, permanent magnets are usually in the form of a complete circular ring or uniformly embedded in the symmetrical stator yoke, providing completely equal static bias magnetic flux in the X and Y directions.

[0007] Faced with the intense "unidirectional heavy load" conditions of horizontal multi-port molecular pumps, the aforementioned symmetrical structure must increase the stator outer diameter, pole shoe area, and coil volume of all magnetic poles to meet the requirements of the high load direction (Y direction). This inevitably leads to severe performance overkill in the low load direction (X direction), resulting in a significant waste of valuable stator slot space and volume.

[0008] Meanwhile, the space left for the molecular pump inside the mass spectrometer is extremely limited. If the overall size of the symmetrical magnetic bearing is forcibly reduced to meet the space constraints, the stator pole piece or stator yoke in the high-load direction (Y direction) is prone to magnetic saturation due to the superposition of gravity and instantaneous aerodynamic impact. Once magnetic saturation occurs, even if the control current is increased, it will not be able to generate sufficient electromagnetic attraction, which will directly cause the molecular pump shaft to become unstable and fall, resulting in a "crash".

[0009] Therefore, how to optimize the structure so that the magnetic bearing can meet the high load-bearing capacity requirement in the Y direction while minimizing the stator volume has become an urgent technical problem to be solved. Summary of the Invention

[0010] In view of the shortcomings of the prior art described above, the present invention proposes a radial magnetic bearing structure with asymmetric pole slots, hybrid excitation and magnetic circuit decoupling, and a multi-port molecular pump including the magnetic bearing structure, to solve the problem of insufficient load-bearing capacity in the Y direction.

[0011] To achieve the above and other related objectives, the present invention provides an asymmetric hybrid magnetic bearing structure, including an annular stator core with its axis arranged horizontally; the inner side of the stator core is divided into four functional areas along the circumference, including a first functional area and a second functional area symmetrically distributed in pairs, the first functional areas being arranged vertically and the second functional areas being arranged horizontally, each of the first functional areas being fixedly connected to a first stator assembly, the first stator assembly including a permanent magnet and first teeth located on both sides of the permanent magnet, the first teeth being wound with a first coil;

[0012] Each of the second functional areas is fixed with a U-shaped second stator assembly. The second stator assembly includes two second teeth and a yoke connecting the two second teeth. The yoke is connected to the inner wall of the stator core by a magnetic isolation ring. The second teeth are wound with a second coil.

[0013] The polar arc area of ​​the first stator assembly is greater than that of the second stator assembly.

[0014] Optionally, the pole shoe area of ​​the first tooth is larger than the pole shoe area of ​​the two second teeth.

[0015] Optionally, the number of turns of the first coil on the first tooth is greater than the number of turns of the second coil on the two second teeth.

[0016] Optionally, the permanent magnet flux generated by the permanent magnet starts from the permanent magnet, enters the stator core, and splits into two paths, passing through the first teeth on both sides and returning to the permanent magnet to form a closed loop.

[0017] Optionally, the control magnetic flux generated by the energization of the first coil forms a closed loop between the first tooth of the first functional area above, the stator core, and the first tooth on the same side of the first functional area below.

[0018] Optionally, the magnetic flux generated by energizing the second coil forms a closed loop between the two second teeth and the yoke connecting the two second teeth.

[0019] Optionally, the permanent magnet bias flux in the upper first functional area is superimposed in the same direction as the control flux of the first coil, while the permanent magnet bias flux in the lower first functional area is weakened in the opposite direction to the control flux of the first coil.

[0020] Optionally, electromagnetic differential control is performed between the second stator assemblies on the left and right sides by controlling the injected current.

[0021] The present invention also provides a multi-port molecular pump, the multi-port molecular pump comprising a horizontally placed cylindrical shell, an air outlet at one end of the shell, and an upward-facing air inlet on the side wall of the shell; a molecular pump shaft and blades capable of rotating synchronously with the molecular pump shaft are installed in the inner cavity of the shell; the molecular pump shaft is radially suspended and supported by the magnetic bearing structure.

[0022] Optionally, the multi-port molecular pump further includes an axial magnetic bearing.

[0023] As described above, this invention provides an asymmetric hybrid magnetic bearing structure and a molecular pump. The magnetic bearing structure includes a stator core. The inner side of the stator core is divided symmetrically into a first functional region and a second functional region along the circumferential direction. A first stator assembly is fixed in the first functional region. The first stator assembly includes a permanent magnet and first teeth located on both sides of the permanent magnet, with a first coil wound around the first teeth. A U-shaped second stator assembly is fixed in the second functional region. The second stator assembly includes second teeth and a yoke connecting the second teeth. A magnetic isolation ring is provided between the yoke and the inner wall of the stator core. A second coil is wound around the second teeth. This invention employs an asymmetric stator topology design. In the Y direction, which bears gravity and aerodynamic impact, three magnetic poles with large pole arc areas are designed; while in the X direction, which only bears minor disturbances, only two pure electromagnetic poles with smaller pole arc areas are designed. Simultaneously, a permanent magnet bias structure is introduced at the high-load end requiring high load resistance, and it is given a larger pole shoe area. The permanent magnet provides a strong basic static magnetic flux, while the large-area positive shoe reduces magnetic reluctance, completely solving the magnetic circuit saturation bottleneck in a compact volume. The large-area permanent magnet bias structure provides extremely high magnetic flux margin and load-bearing limit in the Y direction. When this magnetic bearing is used in a horizontal molecular pump, when a sudden intake of air at the upper multi-port generates a strong transient aerodynamic downward impact, the Y-direction magnetic pole can output a sufficiently large nonlinear electromagnetic pull-back force without magnetic saturation, fundamentally eliminating the risk of the molecular pump shaft falling and destroying the pump due to insufficient resistance to lateral impacts. Attached Figure Description

[0024] Figure 1 The diagram shows the functional area division of the magnetic bearing structure in this invention.

[0025] Figure 2 The diagram shows the components of the magnetic bearing structure in this invention.

[0026] Figure 3 The diagram shown is a schematic diagram of the magnetic flux of the permanent magnet in this invention.

[0027] Figure 4 This diagram illustrates the magnetic flux of the first coil in the energized state in this invention.

[0028] Figure 5 This diagram illustrates the magnetic flux of the second coil in the energized state in this invention.

[0029] Figure 6 The diagram shown is a schematic representation of the molecular pump in this invention.

[0030] Component designation explanation

[0031] 1. Permanent magnet, 2. First tooth, 3. First coil, 4. Magnetic isolation ring, 5. Second tooth, 6. Second coil, 7. Stator core, 11. First functional area, 12. Second functional area, 100. Magnetic bearing structure, 101. Air inlet, 102. Air outlet, 103. Blade, 104. Molecular pump shaft, 105. Axial magnetic bearing. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0034] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for the device in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or there may be one or more layers in between. The phrase “between” as used herein includes both endpoint values.

[0035] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0036] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0037] like Figures 1-2 As shown, the present invention provides an asymmetric hybrid magnetic bearing structure, including an annular stator core 7, the axis of which is arranged horizontally, and a molecular pump shaft 104 (see Figure 104) is installed in the inner hole of the stator core 7. Figure 6 The inner side of the stator core 7 is divided into four functional areas along the circumferential direction, including a first functional area 11 and a second functional area 12 symmetrically distributed in pairs. The first functional area 11 is arranged vertically, and the second functional area 12 is arranged horizontally. The arc length of the first functional area 11 is greater than the arc length of the second functional area 12. The stator core 7 is fixedly connected to a first stator assembly in the first functional area 11. The first stator assembly includes a permanent magnet 1 and a first tooth 2 located on both sides of the permanent magnet. The first tooth 2 is wound with a first coil 3.

[0038] The stator core 7 has a U-shaped second stator assembly fixed in the second functional area 12. The second stator assembly includes two second teeth 5 and a yoke connecting the two second teeth 5. The yoke is connected to the inner wall of the stator core 7 by a magnetic isolation ring 4. The second teeth 5 are wound with a second coil 6. The pole arc area of ​​the first stator assembly is greater than that of the second stator assembly. That is, the sum of the pole arc areas of the first stator assembly facing the axis is greater than the sum of the pole arc areas of the second stator assembly facing the axis. The pole arc area refers to the area occupied by the magnetic pole, that is, the arc length of the magnetic pole along the circumferential direction × the length of the magnetic pole along the axial direction.

[0039] Furthermore, an air gap is formed between the teeth and the molecular pump shaft 104. The air gap provides the molecular pump shaft 104 with a gap for non-contact levitation rotation, and also provides a safe clearance for the high-speed rotation of the molecular pump shaft 104.

[0040] Furthermore, the pole piece area of ​​the first tooth 2 is larger than that of the second tooth 5. Preferably, the pole piece area of ​​the first tooth 2 is larger than that of the two second tooth 5, meaning the pole piece area of ​​a single first tooth 2 is greater than the sum of the pole piece areas of the two second tooth 5, thus creating a more significant load difference. Since the electromagnetic attraction force is proportional to the magnetic pole area, the first tooth 2 with a larger pole piece area has a larger cross-sectional area, and therefore can generate a stronger electromagnetic force, thereby adapting to the load requirements in the high load-bearing direction (vertical direction); while the second tooth 5 with a smaller pole piece area is used to withstand only minor disturbances in the low load-bearing direction, thereby achieving anisotropic load-bearing capacity distribution.

[0041] Furthermore, the number of turns of the first coil 3 on the first tooth 2 is greater than the number of turns of the second coil 6 on the second tooth 5. Preferably, the number of turns of the first coil 3 on the first tooth 2 is greater than the number of turns of the second coil 6 on the two second teeth 5, that is, the number of turns of the first coil 3 on a single first tooth 2 is greater than the sum of the number of turns of the second coil 6 on the two second teeth 5, so as to form a more significant load difference. The larger number of turns of the first coil 3 means that it can generate a stronger magnetomotive force to meet the load requirements of the high load end (vertical direction).

[0042] Furthermore, the central arc length of the first functional area 11 is 1.5-3 times the central arc length of the second functional area 12. The arc length ratio can be flexibly adjusted within this range. When it is necessary to focus on improving the vertical bearing capacity, a larger ratio can be selected; when there is a large disturbance in the horizontal direction, such as external vibration, a smaller ratio can be selected to appropriately increase the control capability in the lateral horizontal direction.

[0043] Furthermore, the magnetic bearing structure also includes a displacement sensor for real-time detection of the radial position of the molecular pump shaft 104. The controller adjusts the current of each magnetic pole coil to ensure that the molecular pump shaft 104 is always suspended at the set center position.

[0044] Specifically, the stator system is divided into four functional zones in the circumferential direction and is physically and magnetically isolated by a magnetic isolation ring made of non-magnetic material. For ease of explanation, an XY rectangular coordinate system is established with the axis of the molecular pump shaft 104 as the origin. The plane of the XY rectangular coordinate system is perpendicular to the axis. The first functional zone 11 in the upper part (Y+) and the first functional zone 11 in the lower part (Y-) are symmetrical. The first stator assembly adopts an E-type 3-pole structure, with a main magnetic pole embedded with a permanent magnet 1 at the center, and two first teeth 2 with first coils 3 wound on both sides symmetrically distributed to form high load-bearing end magnetic poles.

[0045] Meanwhile, the second functional area 12 located on the left (X-) and the second functional area 12 located on the right (X+) are symmetrical. The second stator assembly adopts a U-shaped (including C-shaped and other similar shapes) 2-pole structure, containing two small-area second teeth 5 wound with second coils 6, forming a low-load end magnetic pole, without permanent magnets.

[0046] The above structural design achieves complete decoupling of the three magnetic circuits, ensuring they do not interfere with each other:

[0047] (1) High load-bearing end permanent magnet bias magnetic circuit (red path):

[0048] like Figure 3As shown, the permanent magnet 1 provides a static bias magnetic field. Taking the Y+ end as an example, the permanent magnet flux originates from the permanent magnet, enters the stator core 7, and splits into two paths. These paths pass through the first teeth 2 (high-load end magnetic poles) on both sides and return to the central permanent magnet 1, forming a local closed loop. The flux then passes through the air gap from the molecular pump shaft 104. Due to the blocking effect of the magnetic shielding ring 4, this strong bias magnetic flux will not leak to the low-load end magnetic pole of the second functional region 12.

[0049] (2) High load-bearing end electromagnetic control magnetic circuit (blue path):

[0050] like Figure 4 As shown, the control magnetic flux is generated by energizing the first coil 3. The control magnetic flux forms a local closed loop between the first tooth 2 (high load end magnetic pole) of the upper (Y+) first functional area 11, the stator core 7 (which bypasses or crosses the magnetic isolation ring area), and the first tooth 2 (high load end magnetic pole) of the lower (Y-) first functional area 11, and passes through the molecular pump shaft 104 through the air gap.

[0051] (3) Low-load end pure electromagnetic magnetic circuit (green path):

[0052] like Figure 5 As shown, after the second stator assembly is energized, the magnetic flux generated by the second tooth 5 (low load end magnetic pole) forms a short-path closed loop between the two second teeth 5 and the yoke connecting the two second teeth 5, and passes through the molecular pump shaft 104 through the air gap.

[0053] It should be understood that the direction of magnetic flux flow (e.g., clockwise or counterclockwise distribution in the closed loop formed by the stator core and the teeth) can be flexibly set. Specifically, by changing the energizing direction of the first and second coils, the magnetic flux direction can be reversed according to the right-hand screw rule, thereby meeting the active control requirements of levitation force.

[0054] This invention breaks away from the symmetrical structure of traditional magnetic bearings, adopting a stator topology with asymmetrical distribution in physical space. At the high-load end (Y direction) subjected to gravity and aerodynamic impact, three magnetic poles with a large pole arc area are designed; while at the low-load end (horizontal X direction) subjected to only minor disturbance forces, only two pure electromagnetic poles with a small pole arc area are designed.

[0055] This invention introduces a permanent magnet bias structure at the high-load-bearing end requiring strong resistance to large loads, and endows it with a larger pole shoe area. The permanent magnet provides a strong basic static magnetic flux, while the large-area pole shoes reduce magnetic reluctance. This completely solves the magnetic circuit saturation bottleneck in a compact volume. The large-area permanent magnet bias structure provides extremely high magnetic flux margin and load-bearing limit in the Y direction. When this magnetic bearing is used in a horizontal molecular pump, when a sudden intake of air at the upper multi-port generates a strong transient aerodynamic downward impact, the Y-direction magnetic poles can output a sufficiently large nonlinear electromagnetic pull-back force without magnetic saturation, fundamentally eliminating the risk of the molecular pump shaft falling and destroying the pump due to insufficient resistance to lateral impacts.

[0056] Furthermore, the bias magnetic flux of the permanent magnet in the first functional region 11 above the molecular pump shaft 104 is superimposed in the same direction as the control magnetic flux of the first coil 3, while the bias magnetic flux of the permanent magnet in the first functional region 11 below the molecular pump shaft 104 is weakened in the opposite direction to the control magnetic flux of the first coil 3.

[0057] Specifically, the levitation force in the Y direction is generated by the combined action of the red permanent magnet circuit and the blue electromagnetic circuit. When the multi-port molecular pump is subjected to downward gravity and unbalanced aerodynamic impact in the Y direction, the sensor detects that the molecular pump axis is deflected downward, and the controller injects control current into the first coil.

[0058] By controlling the direction of the current, at the Y+ (upper) air gap, the blue electromagnetic flux and the red permanent magnet flux superimpose in the same direction, increasing the magnetic flux density and generating a strong upward pull to resist gravity. Simultaneously, at the Y- (lower) air gap, the blue electromagnetic flux and the red permanent magnet flux subtract in opposite directions, decreasing the magnetic flux density and weakening the downward pull. Utilizing this differential superposition principle, a huge net levitation restoring force can be generated with a very small control current, exhibiting good linearity and effectively resisting the asymmetric transient impacts caused by multi-port air intakes.

[0059] In the X direction, only a weak disturbance force is applied, necessitating purely electromagnetic differential control. The controller injects a basic bias current (I0) and a control current (Ix) into the second coils on both sides, forming purely electromagnetic differential control. When the molecular pump shaft deviates in the X direction, the current on one side increases (I0 + Ix), while the current on the other side decreases (I0 - Ix), causing a change in the green magnetic flux and generating a horizontal restoring force that returns the molecular pump shaft to the center. By eliminating the permanent magnet, eddy current losses in the non-primary force direction of the high-speed molecular pump shaft are avoided.

[0060] This "peak shaving and valley filling" design transfers all the stator slot space and yoke volume saved in the low-load direction to the high-load direction. It achieves "precise allocation on demand" of internal electromagnetic resources without increasing the overall outer diameter and volume of the magnetic bearing, greatly improving space utilization and perfectly matching the extremely limited installation space of analytical instruments.

[0061] This invention innovatively employs an asymmetric hybrid excitation mode of "permanent magnet bias at high load end + pure electromagnetic at low load end," and sets up a "magnetic isolation ring" between the two magnetic circuits. In the Y direction, which is subjected to gravity, the permanent magnet provides static levitation force, and the coil only needs to be finely adjusted; in the X direction, which is lightly loaded, the permanent magnet is abandoned, and only the pure electromagnetic structure is used to suppress high-frequency micro-vibrations; the magnetic isolation ring physically cuts off the magnetic circuit of the stator yoke, preventing the strong Y-direction bias magnetic flux from interfering with the fragile X-direction pure electromagnetic circuit.

[0062] Because the Y-axis permanent magnet counteracts gravity, the heat generated by the coil copper loss in maintaining static levitation is significantly reduced, alleviating the critical bottleneck of heat dissipation in the molecular pump shaft in a vacuum and extending the equipment's lifespan. The introduction of the magnetic shielding ring ensures that the extremely asymmetrical strong and weak magnetic circuits do not interfere with each other, reducing the complexity of cross-coupling in the control system and guaranteeing high-precision and stable levitation of the molecular pump shaft under multi-port asymmetrical inlet conditions.

[0063] Based on the above-described magnetic bearing structure, the present invention also provides a multi-port molecular pump, which includes the above-described magnetic bearing structure.

[0064] The multi-port molecular pump includes a horizontally positioned cylindrical housing with an outlet 102 at one end and an upward-facing inlet 101 on the side wall for connecting to a process chamber in a vacuum system. A molecular pump shaft 104 and blades 103 are mounted inside the housing. The blades 103 rotate synchronously with the molecular pump shaft 104, and together they constitute the rotating components of the multi-port molecular pump. The molecular pump shaft 104 is radially suspended and supported by a magnetic bearing structure 100, which has at least two locations along the axial direction.

[0065] This multi-port molecular pump adopts a horizontal, upward-facing inlet layout, which facilitates compact installation in integrated systems such as semiconductor equipment. The pump has multiple independent inlets at different axial positions on the housing, each connected to a process chamber in the vacuum system with different pressure requirements. During operation, gas enters the pump body through each inlet, allowing for differentiated evacuation of multiple chambers within the same pump, eliminating the need for a separate pump for each chamber.

[0066] This multi-port molecular pump employs the aforementioned asymmetric magnetic bearing scheme. Specifically, a first stator assembly with a large pole arc area is provided in the vertical direction (Y direction), which bears greater gravity and blade aerodynamic loads; while in the horizontal direction (X direction), which only bears minor disturbances, two magnetic poles with smaller pole arc areas are provided. This asymmetric layout effectively reduces the power consumption and size of the bearing.

[0067] Furthermore, the molecular pump also includes an axial magnetic bearing 105 for limiting the axial movement of the molecular pump shaft 104.

[0068] Specifically, the axial magnetic bearing includes a thrust plate and axial electromagnets. The thrust plate is fixedly mounted on the end of the molecular pump shaft and rotates synchronously with the molecular pump shaft. Two axial electromagnets are respectively installed on both sides of the thrust plate, and an axial working air gap is maintained between the thrust plate and the electromagnets.

[0069] Similar to the radial magnetic bearing structure described above, an axial displacement sensor detects the axial position deviation at the end of the molecular pump shaft in real time. The controller adjusts the coil current of the two sets of axial electromagnets based on the deviation signal, ensuring that the thrust disk remains suspended at the set axial center position. The combined use of the axial and radial magnetic bearings enables high-speed, stable operation of the molecular pump shaft in a fully suspended state, while significantly reducing mechanical friction and power consumption.

[0070] In summary, this invention provides an asymmetric hybrid magnetic bearing structure and a multi-port molecular pump. The magnetic bearing structure includes a stator core. The inner side of the stator core is divided symmetrically into a first functional region and a second functional region along the circumferential direction. A first stator assembly is fixed in the first functional region, including a permanent magnet and first teeth located on both sides of the permanent magnet, with a first coil wound around the first teeth. A U-shaped second stator assembly is fixed in the second functional region, including second teeth and a yoke connecting the second teeth. A magnetic isolation ring is provided between the yoke and the inner wall of the stator core, and a second coil is wound around the second teeth. This invention employs an asymmetric stator topology design. In the Y direction, which bears gravity and aerodynamic impact, three magnetic poles with large pole arc areas are designed; while in the X direction, which only bears minor disturbances, only two pure electromagnetic poles with smaller pole arc areas are designed. Simultaneously, a permanent magnet bias structure is introduced at the high-load end requiring high load resistance, and it is given a larger pole shoe area. The permanent magnet provides a strong basic static magnetic flux, while the large-area positive shoe reduces magnetic reluctance, completely solving the magnetic circuit saturation bottleneck in a compact volume. The large-area permanent magnet bias structure provides extremely high magnetic flux margin and load-bearing limit in the Y direction. When this magnetic bearing is used in a horizontal molecular pump, when a sudden intake of air at the upper multi-port generates a strong transient aerodynamic downward impact, the Y-direction magnetic pole can output a sufficiently large nonlinear electromagnetic pull-back force without magnetic saturation, fundamentally eliminating the risk of the molecular pump shaft falling and destroying the pump due to insufficient resistance to lateral impacts.

[0071] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An asymmetric hybrid magnetic bearing structure, characterized in that, The stator core includes a ring-shaped stator core with its axis arranged horizontally. The inner side of the stator core is divided into four functional areas along the circumference, including a first functional area and a second functional area symmetrically distributed in pairs. The first functional area is arranged vertically, and the second functional area is arranged horizontally. Each first functional area is fixedly connected to a first stator assembly. The first stator assembly includes a permanent magnet and first teeth located on both sides of the permanent magnet. The first teeth are wound with a first coil. Each of the second functional areas is fixed with a U-shaped second stator assembly. The second stator assembly includes two second teeth and a yoke connecting the two second teeth. The yoke is connected to the inner wall of the stator core by a magnetic isolation ring. The second teeth are wound with a second coil. The polar arc area of ​​the first stator assembly is larger than that of the second stator assembly; The permanent magnet flux generated by the permanent magnet starts from the permanent magnet, enters the stator core, and splits into two paths, passing through the first teeth on both sides and returning to the permanent magnet, forming a closed loop; the control flux generated by the first coil forming a closed loop between the first tooth of the upper first functional area, the stator core, and the first tooth on the same side of the lower first functional area; the flux generated by the second coil forming a closed loop between the two second teeth and the yoke connecting the two second teeth.

2. The asymmetric hybrid magnetic bearing structure according to claim 1, characterized in that: The pole shoe area of ​​the first tooth is larger than the pole shoe area of ​​the two second teeth.

3. The asymmetric hybrid magnetic bearing structure according to claim 1, characterized in that: The number of turns of the first coil on the first tooth is greater than the number of turns of the second coil on the two second teeth.

4. The asymmetric hybrid magnetic bearing structure according to claim 1, characterized in that: The bias flux of the permanent magnet in the upper first functional area is superimposed in the same direction as the control flux of the first coil, while the bias flux of the permanent magnet in the lower first functional area is weakened in the opposite direction to the control flux of the first coil.

5. The asymmetric hybrid magnetic bearing structure according to claim 1, characterized in that: Electromagnetic differential control is achieved between the second stator assemblies on the left and right sides by controlling the injected current.

6. A multi-port molecular pump, characterized in that: The multi-port molecular pump includes a horizontally placed cylindrical shell with an outlet at one end and an upward-facing inlet on the side wall of the shell; the inner cavity of the shell is equipped with a molecular pump shaft and blades that can rotate synchronously with the molecular pump shaft; the molecular pump shaft is radially suspended and supported by a magnetic bearing structure as described in any one of claims 1-5.

7. The multi-port molecular pump according to claim 6, characterized in that: The multi-port molecular pump also includes an axial magnetic bearing.

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