Vacuum pump and magnetic bearing
By enhancing the thickness and positioning of the fastening components, the deformation problem caused by the difference in thermal expansion coefficients in the vacuum pump was solved, ensuring the accuracy of the sensor and the stability of the vacuum pump.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHIMADZU SEISAKUSHO LTD
- Filing Date
- 2023-03-17
- Publication Date
- 2026-07-10
AI Technical Summary
In existing vacuum pumps, the difference in thermal expansion rates between the thrust magnetic bearing and the base material causes the fastening parts to deform during thermal expansion, affecting the accuracy of axial position detection.
By increasing the thickness of the through hole in the fastening part in the depth direction and setting its center position higher than that of the second electromagnet, the strength of the fastening part is enhanced, the effects of thermal expansion are reduced, and deformation is avoided.
It effectively suppresses the deformation of the fastening parts during the thermal expansion of the base, ensuring that the sensor accurately detects the position of the shaft before and after heating, thus improving the stability and accuracy of the vacuum pump.
Smart Images
Figure CN116892527B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a vacuum pump and a magnetic bearing. Background Technology
[0002] A vacuum pump includes a rotor that is driven to rotate and a stator that works in conjunction with the rotor to expel gas. The rotor shaft is housed in a base and supported by magnetic bearings. The magnetic bearings include bearings that support the shaft radially (radial magnetic bearings) and bearings that support the shaft axially (thrust magnetic bearings) (e.g., Patent Document 1).
[0003] [Existing Technical Documents]
[0004] [Patent Literature]
[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-134886 Summary of the Invention
[0006] [The problem the invention aims to solve]
[0007] The thrust magnetic bearing in the magnetic bearing is fastened to the lower part of the base by fastening members such as bolts. The base contains aluminum or the like, while the thrust magnetic bearing contains a magnetic body such as an ferrous material. That is, there is a difference in the coefficient of thermal expansion between the base and the thrust magnetic bearing. In conventional vacuum pumps, the part of the thrust magnetic bearing fastened to the base deforms due to the difference in coefficient of thermal expansion, and the thrust magnetic bearing may deform during installation. Deformation of the thrust magnetic bearing can cause problems during the operation of the vacuum pump, such as making it difficult to accurately detect the axial position of the shaft.
[0008] [Technical means to solve the problem]
[0009] A vacuum pump according to one aspect of the present invention includes a rotor, a base, a thrust disk, and a magnetic bearing. The rotor has a shaft. The base rotatably houses the shaft. The thrust disk is located at the lower part of the shaft. The magnetic bearing supports the shaft axially by causing the thrust disk to float. The magnetic bearing has a first electromagnet and a second electromagnet. The first electromagnet is disposed facing the upper surface of the thrust disk. The second electromagnet is disposed facing the lower surface of the thrust disk. The second electromagnet includes a core and a coil. The core includes a fastening portion having a through hole through which a bolt for fastening the core to the base passes. In the vacuum pump, the depth direction thickness of the through hole of the fastening portion is greater than the nominal diameter of the bolt for fastening the fastening portion to the base. Alternatively, the center position of the depth direction of the through hole of the fastening portion is located higher than the center position of the second electromagnet in the vertical direction.
[0010] [The effects of the invention]
[0011] In the vacuum pump according to one aspect of the present invention, the thickness of the through hole in the fastening portion in the depth direction is greater than the nominal diameter of the bolt that fastens the fastening portion to the base. Since the strength of the fastening portion is increased by increasing its thickness, the fastening portion is less prone to deformation when the vacuum pump heats up, even if there is a difference in the coefficient of thermal expansion between the base and the fastening portion. This results in suppressing deformation of the magnetic bearing caused by heating. On the other hand, since the center position of the through hole in the fastening portion in the depth direction is higher than the center position in the vertical direction of the second electromagnet, the distance from the contact position between the base and the upper end face of the magnetic bearing to the contact position between the fastening portion and the base is shorter, thus the fastening portion is less susceptible to the effects of thermal expansion of the base. This also results in suppressing deformation of the magnetic bearing caused by heating. Attached Figure Description
[0012] Figure 1 This is a cross-sectional view of the vacuum pump according to the embodiment.
[0013] Figure 2 This is a diagram showing the overall structure of a magnetic bearing.
[0014] Figure 3 This is an enlarged view of a magnetic bearing.
[0015] Figure 4 This is a diagram showing a modified example of a magnetic bearing. Detailed Implementation
[0016] Hereinafter, a vacuum pump according to one embodiment will be described with reference to the accompanying drawings. Figure 1 This is a cross-sectional view of the vacuum pump 1 according to the embodiment. Figure 1 As shown, vacuum pump 1 includes housing 2, base 3, rotor 4 and stator 5.
[0017] The housing 2 includes a first end 11, a second end 12, and a first internal space S1. An intake port 13 is provided at the first end 11. The first end 11 is mounted to an exhaust target device (not shown). The exhaust target device is, for example, a processing chamber of a semiconductor manufacturing apparatus. The first internal space S1 communicates with the intake port 13. The second end 12 is located opposite to the first end 11 in the axial direction of the rotor 4 (hereinafter referred to as "axial direction A1"). The second end 12 is connected to a base 3. The base 3 includes a base end 14. The base end 14 is connected to the second end 12 of the housing 2. The base 3 is, for example, an aluminum component.
[0018] The rotor 4 includes a shaft 21. The shaft 21 extends along the axial direction A1. The shaft 21 is rotatably housed in the base 3. A thrust disk 21A is provided at the lower part of the shaft 21. Furthermore, a target 21B is screwed at the lower end of the shaft 21.
[0019] The rotor 4 includes multi-stage rotor blades 22 and a rotor cylindrical portion 23. The multi-stage rotor blades 22 are each connected to the shaft 21. The multi-stage rotor blades 22 are arranged at intervals along the axial direction A1. Although not shown in the figure, the multi-stage rotor blades 22 extend radially about the shaft 21. Furthermore, in the figures, only one of the multi-stage rotor blades 22 is indicated by a reference numeral, while the symbols for the other rotor blades 22 are omitted. The rotor cylindrical portion 23 is positioned below the multi-stage rotor blades 22. The rotor cylindrical portion 23 extends along the axial direction A1.
[0020] The stator 5 is disposed on the outer periphery of the rotor 4. The stator 5 includes multi-stage stator blades 31 and a stator cylindrical portion 32. The multi-stage stator blades 31 are connected to the inner surface of the housing 2. The multi-stage stator blades 31 are arranged at intervals along the axial direction A1. The multi-stage stator blades 31 are respectively disposed between the multi-stage rotor blades 22. Although not shown in the figure, the multi-stage stator blades 31 extend radially about the shaft 21. In addition, in the figure, only two of the multi-stage stator blades 31 are labeled, and the symbols for the other stator blades 31 are omitted. The stator cylindrical portion 32 is fixed in contact with the base 3. The stator cylindrical portion 32 is disposed opposite to the outer periphery of the rotor cylindrical portion 23 in the radial direction of the rotor cylindrical portion 23 with a slight gap. A helical groove is provided on the inner periphery of the stator cylindrical portion 32 opposite to the rotor cylindrical portion 23.
[0021] like Figure 1 As shown, an exhaust space S2 is provided further downstream of the exhaust downstream end of the rotor cylindrical portion 23 and the stator cylindrical portion 32. The exhaust target gas discharged from the exhaust target device is guided to the exhaust space S2. The exhaust space S2 communicates with the exhaust port 15. The exhaust port 15 is located on the base 3. Another vacuum pump (not shown) is connected to the exhaust port 15. Furthermore, the exhaust downstream side refers to the side closer to the exhaust space S2 in the axial direction A1. Moreover, the exhaust downstream direction refers to the direction facing the exhaust space S2.
[0022] The vacuum pump 1 includes a heater 6. The heater 6 heats the base 3 to regulate its temperature. By heating the base 3 with the heater 6, the accumulation of products in the components of the vacuum pump 1 can be suppressed.
[0023] The vacuum pump 1 includes bearings 41A and 41E, magnetic bearings 41B to 41D, and a motor 42. Bearings 41A and 41E are mounted on the base 3 at the location where the shaft 21 is housed. Bearings 41A and 41E rotatably support the shaft 21. Bearings 41A and 41E are ball bearings. Magnetic bearings 41B to 41D are bearings that support the shaft 21 using magnetic force. Among them, magnetic bearings 41B and 41C are radial magnetic bearings that support the shaft 21 radially. Magnetic bearing 41D is a thrust magnetic bearing that supports the shaft 21 axially.
[0024] Motor 42 drives rotor 4 to rotate. Motor 42 includes motor rotor 42A and motor stator 42B. Motor rotor 42A is mounted on shaft 21. Motor stator 42B is mounted on base 3. Motor stator 42B is configured opposite to motor rotor 42A.
[0025] In vacuum pump 1, multi-stage rotor blades 22 and multi-stage stator blades 31 constitute a turbomolecular pump section. Furthermore, rotor cylindrical section 23 and stator cylindrical section 32 constitute a grooved pump section. In vacuum pump 1, by rotating rotor 4 using motor 42, the target exhaust gas flows from intake port 13 to the first internal space S1. The target exhaust gas in the first internal space S1 is guided to exhaust space S2 through the turbomolecular pump section and the grooved pump section. The target exhaust gas in exhaust space S2 is discharged from exhaust port 15. As a result, the interior of the exhaust device installed at intake port 13 becomes a high vacuum state.
[0026] Next, use Figure 2 and Figure 3 The detailed structure of the magnetic bearing 41D is explained. Figure 2 This is a diagram showing the overall structure of the magnetic bearing 41D. Figure 3 This is an enlarged view of the magnetic bearing 41D. The magnetic bearing 41D includes a first electromagnet 411 and a second electromagnet 413.
[0027] The first electromagnet 411 is arranged facing the upper surface of the thrust disk 21A, generating a magnetic field to produce an upward force attracting the thrust disk 21A. The first electromagnet 411 includes a first inner core 411A, a first coil 411B, and a first outer core 411C. The first inner core 411A is a cylindrical component arranged facing the upper surface of the thrust disk 21A. The first inner core 411A contains a material with high magnetic permeability. For example, the first inner core 411A contains an ferrous material. A bearing 41E is arranged on the inner circumference of the first inner core 411A. The bearing 41E radially supports the shaft 21.
[0028] The first coil 411B is disposed on the outer periphery of the first inner core 411A, and generates a magnetic field through the flow of current. This magnetic field generates a force that attracts the push plate 21A upwards. The first outer core 411C is disposed in a manner that surrounds the lower side of the first coil 411B and the side near the base 3. The first outer core 411C contains a material with high magnetic permeability. For example, the first outer core 411C contains an iron-based material.
[0029] According to the structure described, in the first electromagnet 411, the first coil 411B is surrounded by a first inner core 411A and a first outer core 411C. The first inner core 411A is located closer to the shaft 21 than the first coil 411B, and the first outer core 411C is located closer to the base 3 than the first coil 411B. Because the first inner core 411A and the first outer core 411C have high permeability, the first electromagnet 411 with this structure can generate a large magnetic field towards the thrust plate 21A.
[0030] The second electromagnet 413 is arranged facing the lower surface of the thrust disk 21A, generating a magnetic field to produce a downward force attracting the thrust disk 21A. The second electromagnet 413 includes a second inner core 413A, a second coil 413B, and a second outer core 413C. The second inner core 413A is a cylindrical component arranged facing the lower surface of the thrust disk 21A. The second inner core 413A contains a material with high magnetic permeability. For example, the second inner core 413A contains an ferrous material. A target 21B is disposed at the lower end of the shaft 21 in the space on the inner circumference of the second inner core 413A.
[0031] The second coil 413B is disposed on the outer periphery of the second inner core 413A, and generates a magnetic field by the flow of current. This magnetic field is used to generate a force that attracts the thrust disk 21A downward. The second outer core 413C is disposed to surround the upper side of the second coil 413B and the side near the base 3. The second outer core 413C contains a material with high magnetic permeability. For example, the second outer core 413C contains an ferrous material.
[0032] According to the structure described, in the second electromagnet 413, the second coil 413B is surrounded by a second inner core 413A located on the side near the shaft 21 and a second outer core 413C located on the side near the base 3. Since the second inner core 413A and the second outer core 413C have high permeability, the second electromagnet 413 with the structure described can generate a large magnetic field toward the thrust plate 21A.
[0033] The second outer core 413C includes a fastening portion 413D. The fastening portion 413D is integral with the second outer core 413C and protrudes from the second outer core 413C toward the base 3. The fastening portion 413D has a through hole H1 through which a bolt B1 for fastening the second outer core 413C to the base 3 passes. Moreover, the second groove 3B of the base 3 has a threaded groove T1 for screwing the bolt B1. By abutting the upper end face 413E of the fastening portion 413D against the second groove 3B of the base 3, the bolt B1 passing through the through hole H1 is screwed into the threaded groove T1, and the fastening portion 413D is fastened to the second groove 3B of the base 3. By fastening the fastening portion 413D to the second groove 3B of the base 3, the second electromagnet 413 is fastened to the base 3.
[0034] If the fastening part 413D is fastened to the base 3 by bolt B1, the spacer member 415 disposed between the first electromagnet 411 and the second electromagnet 413 supports the lower surface of the first outer core 411C. Furthermore, the upper end face 411D of the first inner core 411A abuts against the first groove 3A of the base 3. With the spacer member 415 supporting the first outer core 411C from below and the upper end face 411D abutting against the first groove 3A, the first electromagnet 411 is fixed to the base 3. Thus, the entire magnetic bearing 41D is fixed to the base 3 by bolt B1.
[0035] The magnetic bearing 41D includes a sensor 417. The sensor 417 is mounted on the lower part of the second inner core 413A. Specifically, a sensor support member 417A, on which the sensor 417 is disposed, is fixed to the lower part of the second inner core 413A by bolt B2. Thus, the sensor 417 is positioned on the lower part of the second inner core 413A, facing the target 21B. The sensor 417 detects the vertical position of the shaft 21 by detecting the position of the target 21B. Furthermore, the term "vertical position" here refers to a direction parallel to the axial direction (axial direction A1) of the shaft 21.
[0036] The magnetic bearing 41D with the aforementioned structure can balance the force of the first electromagnet 411 attracting the thrust disk 21A upward and the force of the second electromagnet 413 attracting the thrust disk 21A downward, causing the thrust disk 21A to float between the first electromagnet 411 and the second electromagnet 413, thereby supporting the shaft 21 axially.
[0037] In vacuum pump 1, after the magnetic bearing 41D is fixed to the base 3, the reference position of shaft 21 is determined without heating the base 3. Specifically, when shaft 21 is positioned at the reference position without heating the base 3, the reference position is determined based on the position of target 21B detected by sensor 417.
[0038] On the other hand, as described above, since the materials constituting the base 3 are different from those constituting the fastening portion 413D, when the base 3 is heated, the fastening portion 413D may deform from its state before the base 3 was heated due to the difference in thermal expansion rates between the base 3 and the fastening portion 413D. Since the fastening portion 413D is integral with the second outer core 413C, and the second inner core 413A is fixed to the second outer core 413C, if the fastening portion 413D deforms, the sensor support member 417A fastened to the second inner core 413A may also deform. Due to the deformation of the sensor support member 417A, the position of the sensor 417 relative to the target 21B changes accordingly. As a result, when the base 3 is heated, the position of the sensor 417 changes from before the base 3 was heated, and the sensor 417 may erroneously detect the vertical position of the shaft 21.
[0039] Therefore, in vacuum pump 1, in order to suppress the deformation of the fastening part 413D when the base 3 is heated, such as... Figure 3 As shown, the thickness D1 in the depth direction of the through hole H1 of the fastening part 413D is greater than the nominal diameter M of the bolt B1. The "depth direction of the through hole H1" refers to the vertical direction, that is, the direction parallel to the axial direction of the shaft 21. Since the strength of the fastening part 413D is increased by increasing the thickness D1, the fastening part 413D is not easily deformed even if the base 3 is heated.
[0040] Furthermore, in the vacuum pump 1, the center position C1 of the through hole H1 of the fastening part 413D in the depth direction is located higher than the center position C2 of the second electromagnet 413 in the vertical direction. Therefore, the distance D2 between the contact position between the upper end face 411D of the first inner core 411A and the base 3, and between the contact position between the upper end face 413E of the fastening part 413D and the base 3, is shorter than before. Consequently, the fastening part 413D is less susceptible to the thermal expansion of the base 3, and therefore, the fastening part 413D is less prone to deformation even when heated by the base 3.
[0041] Thus, since the fastening part 413D is not easily deformed by the heating of the base 3, the deformation of the magnetic bearing 41D (sensor support member 417A) before and after the heating of the base 3 can be suppressed. As a result, since the position of the sensor 417 relative to the target 21B is not easily changed before and after the heating of the base 3, the sensor 417 can be prevented from erroneously detecting the vertical position of the shaft 21 when the base 3 is heated.
[0042] In addition, experiments have confirmed that by making the fastening part 413D as described above, when the base 3 is heated, the deformation of the fastening part 413D is suppressed to the extent that the sensor 417 will not erroneously detect the vertical position of the shaft 21.
[0043] Furthermore, in the vacuum pump 1, the fastening portion 413D is included in the second outer core 413C. The second outer core 413C has a simpler shape than the second inner core 413A. Therefore, the second outer core 413C has higher rigidity than the second inner core 413A. Therefore, by providing the fastening portion 413D in the second outer core 413C, the strength of the fastening portion 413D can be further improved.
[0044] As a comparative example, if the thickness of the fastening part is made less than the nominal diameter of the bolt B1, and the center position of the through hole of the fastening part in the depth direction is located lower than the center position of the second electromagnet in the vertical direction, then when the base 3 is heated, the fastening part will deform significantly, and the sensor 417 will sometimes erroneously detect the vertical position of the shaft 21.
[0045] The above describes one embodiment of the present invention, but the present invention is not limited to the described embodiment, and various modifications can be made without departing from the spirit of the invention.
[0046] like Figure 4 As shown, the second electromagnet 413' can also be formed by a second core 413A' and a second coil 413B' disposed inside the second core 413A'. Figure 4 This diagram shows a modified example of the magnetic bearing 41D. In this case, the fastening portion 413C' is provided on one side of the base 3 near the second core 413A'. Moreover, the thickness of the through hole H1 of the fastening portion 413C' in the depth direction is greater than the nominal diameter of the bolt B1, and the center position of the through hole H1 of the fastening portion 413C' in the depth direction is located higher than the center position of the second electromagnet 413' in the vertical direction.
[0047] Furthermore, the first electromagnet 411' can also be composed of a first core 411A' and a first coil 411B' disposed inside the first core 411A'.
[0048] Even if the thickness D1 of the through hole H1 of the fastening part 413D in the depth direction is made greater than the nominal diameter M of the bolt B1, or the center position C1 of the through hole H1 of the fastening part 413D in the depth direction is made higher than the center position C2 of the second electromagnet 413 in the vertical direction, the deformation of the fastening part 413D can be suppressed to the extent that the sensor 417 will not erroneously detect the position of the shaft 21 in the vertical direction.
[0049] The vacuum pump 1 in the described embodiment is a pump integrated with a turbomolecular pump including multi-stage rotor blades 22 and multi-stage stator blades 31, and a grooved pump including a rotor cylindrical portion 23 and a stator cylindrical portion 32. However, the grooved pump can be omitted. That is, the vacuum pump 1 can be a turbomolecular pump. Alternatively, the turbomolecular pump can also be omitted. That is, the vacuum pump 1 can also be a grooved pump.
[0050] Operators should understand that the above-mentioned exemplary implementation methods are specific examples of the following methods.
[0051] (First embodiment) The vacuum pump includes a rotor, a base, a thrust plate, and a magnetic bearing. The rotor has a shaft. The base rotatably houses the shaft. The thrust plate is located at the lower part of the shaft. The magnetic bearing supports the shaft axially by causing the thrust plate to float. The magnetic bearing has a first electromagnet and a second electromagnet. The first electromagnet is arranged facing the upper surface of the thrust plate. The second electromagnet is arranged facing the lower surface of the thrust plate. The second electromagnet includes a core and a coil. The core includes a fastening portion with a through hole through which a bolt for fastening the core to the base passes. In the vacuum pump, the depth direction thickness of the through hole of the fastening portion is greater than the nominal diameter of the bolt for fastening the fastening portion to the base. Alternatively, the center position of the depth direction of the through hole of the fastening portion is located higher than the center position of the second electromagnet in the vertical direction.
[0052] In the vacuum pump of the first type, the thickness of the through hole in the fastening part in the depth direction is greater than the nominal diameter of the bolt that fastens the fastening part to the base. Since the strength of the fastening part is increased by increasing its thickness, the fastening part is less prone to deformation when heated by the vacuum pump, even if there is a difference in the coefficient of thermal expansion between the base and the fastening part. This result suppresses deformation of the magnetic bearing caused by heating. On the other hand, since the center position of the through hole in the depth direction of the fastening part is higher than the center position in the vertical direction of the second electromagnet, the distance from the contact point between the base and the upper end face of the magnetic bearing to the contact point between the fastening part and the base is shorter, thus the fastening part is less affected by the thermal expansion of the base. This result also suppresses deformation of the magnetic bearing caused by heating.
[0053] (Second Method) In the vacuum pump of the first method, the thickness of the fastening part in the vertical direction may be greater than the nominal diameter of the bolt, and the center position of the fastening part in the vertical direction may be located higher than the center position of the second electromagnet in the vertical direction. In the vacuum pump of the second method, since the strength of the fastening part is improved and the fastening part is less affected by the thermal expansion of the base, the deformation of the magnetic bearing due to heating during installation can be further suppressed.
[0054] (Third Method) In the vacuum pumps of the first or second method, the core may also have an outer core including a fastening portion and an inner core located on a side closer to the shaft than the outer core. In the third type of vacuum pump, since the outer core, which has a higher rigidity than the inner core, has a fastening portion, the strength of the fastening portion can be improved.
[0055] (Fourth Method) Vacuum pumps of any of the first to third methods may also include a sensor mounted on the lower part of the core that detects the vertical position of the shaft. In the fourth method vacuum pump, the magnetic bearing is less prone to deformation before and after the base is heated. Therefore, the position of the sensor mounted on the lower part of the core remains almost unchanged before and after the base is heated. As a result, in the fourth method vacuum pump, the sensor's erroneous detection of the vertical position of the shaft during base heating can be suppressed.
[0056] (Fifth Method) The vacuum pump of any of the first to fourth methods may also include a heater for regulating the temperature of the base. In the vacuum pump of the fifth method, the accumulation of products due to heating of the base can be suppressed. Furthermore, deformation of the magnetic bearing before and after the heater heats the base can be suppressed.
[0057] (Sixth Method) In any of the vacuum pumps of methods one through five, the base may contain aluminum and the fastening part may contain an iron-based material. Even if the base and the fastening part contain materials with different coefficients of thermal expansion, the magnetic bearing is not easily deformed before or after the base is heated because the strength of the fastening part is increased or the fastening part is not easily affected by the thermal expansion of the base.
[0058] (Seventh Method) In a vacuum pump with a magnetic bearing comprising a rotor having a shaft, a base rotatably housing the shaft, and a thrust disk located at the lower part of the shaft, the shaft is axially supported by causing the thrust disk to float upwards. The magnetic bearing includes a first electromagnet and a second electromagnet. The first electromagnet is disposed facing the upper surface of the thrust disk. The second electromagnet is disposed facing the lower surface of the thrust disk. The second electromagnet includes a core and a coil. The core includes a fastening portion having a through hole H1 through which a bolt for fastening the core to the base passes. In the magnetic bearing, the thickness of the through hole in the depth direction of the fastening portion is greater than the nominal diameter of the bolt, or the center position of the through hole in the depth direction of the fastening portion is located higher than the center position in the vertical direction of the second electromagnet.
[0059] In the seventh type of magnetic bearing, the thickness of the through hole in the fastening part in the depth direction is greater than the nominal diameter of the bolt that fastens the fastening part to the base. Since the strength of the fastening part is increased by increasing its thickness, the fastening part is less prone to deformation during vacuum pump heating, even if there is a difference in the coefficient of thermal expansion between the base and the fastening part. This result suppresses deformation of the magnetic bearing caused by heating. Furthermore, since the center position of the through hole in the fastening part in the depth direction is higher than the center position in the vertical direction of the second electromagnet, the distance from the contact point between the base and the upper end face of the magnetic bearing to the contact point between the fastening part and the base is shorter, thus the fastening part is less affected by the thermal expansion of the base. This result also suppresses deformation of the magnetic bearing caused by heating.
[0060] [Explanation of Symbols]
[0061] 1: Vacuum pump
[0062] 2: Shell
[0063] 3: Base
[0064] 3A: First slot
[0065] 3B: Second slot
[0066] 4: Rotor
[0067] 5: Stator
[0068] 6: Heater
[0069] 11: First end
[0070] 12: Second end
[0071] 13: Intake port
[0072] 14: End of base
[0073] 15: Exhaust port
[0074] 21: Axis
[0075] 21A: Thrust plate
[0076] 21B: Target
[0077] 22: Rotor blades
[0078] 23: Rotor cylindrical section
[0079] 31: Stator blades
[0080] 32: Stator cylindrical section
[0081] 41A, 41E: Bearings
[0082] 41B~41D: Magnetic bearings
[0083] 42: Motor
[0084] 42A: Motor rotor
[0085] 42B: Motor stator
[0086] 411, 411': First electromagnet
[0087] 411A: First Core
[0088] 411A': The First Core
[0089] 411B, 411B': First coil
[0090] 411C: First outer core
[0091] 411D: Top surface
[0092] 413, 413': Second electromagnet
[0093] 413A: Second inner core
[0094] 413A': Second Core
[0095] 413B, 413B': Second coil
[0096] 413C: Second outer core
[0097] 413C', 413D: Fastening parts
[0098] 413E: Top surface
[0099] 415: Spacing Member
[0100] 417: Sensor
[0101] 417A: Sensor support component
[0102] B1, B2: Bolts
[0103] C1: Center position of the fastening part
[0104] C2: The center position of the second electromagnet
[0105] D1: Thickness of the fastening part
[0106] H1: Through hole
[0107] T1: Threaded groove
[0108] M: Nominal diameter
[0109] S1: First Internal Space
[0110] S2: Exhaust space.
Claims
1. A vacuum pump, comprising: A rotor, having a shaft; The base rotatably houses the shaft; A thrust disk is located at the lower part of the shaft; A magnetic bearing supports the shaft axially by causing the thrust disk to float. as well as The heater that heats the base The magnetic bearing includes: The first electromagnet is arranged facing the upper surface of the thrust disk; as well as The second electromagnet is arranged facing the lower surface of the thrust disk. The second electromagnet includes a core and a coil. The core includes a fastening portion with a through hole through which a bolt for fastening the core to the base passes. The base and the fastening part have different coefficients of thermal expansion. The thickness of the through hole in the fastening portion in the depth direction is greater than the nominal diameter of the bolt, or the center position of the through hole in the depth direction of the fastening portion is located higher than the center position of the second electromagnet in the vertical direction, thereby suppressing the deformation of the fastening portion caused by the difference in thermal expansion rates between the base and the fastening portion when the base is heated by the heater.
2. The vacuum pump according to claim 1, wherein The thickness of the fastening part in the vertical direction is greater than the nominal diameter of the bolt, and the center position of the fastening part in the vertical direction is located higher than the center position of the second electromagnet in the vertical direction.
3. The vacuum pump according to claim 1 or 2, wherein The core has an outer core including the fastening portion and an inner core located on a side closer to the shaft than the outer core.
4. The vacuum pump according to claim 1 or 2, wherein, Also includes: A sensor, installed at the lower part of the core, detects the vertical position of the shaft.
5. The vacuum pump according to claim 1 or 2, wherein, Also includes: A heater to regulate the temperature of the base.
6. The vacuum pump according to claim 1 or 2, wherein The base is made of aluminum, and the fastening part is made of ferrous material.
7. A magnetic bearing, comprising a rotor having a shaft, a base rotatably housing the shaft, a thrust disk disposed at the lower part of the shaft, and a heater for heating the base, wherein the shaft is axially supported by causing the thrust disk to float. The magnetic bearing includes: The first electromagnet is arranged facing the upper surface of the thrust disk; as well as The second electromagnet is arranged facing the lower surface of the thrust disk. The second electromagnet includes a core and a coil. The core includes a fastening portion with a through hole through which a bolt for fastening the core to the base passes. The base and the fastening part have different coefficients of thermal expansion. The thickness of the through hole in the fastening portion in the depth direction is greater than the nominal diameter of the bolt, or the center position of the through hole in the depth direction of the fastening portion is located higher than the center position of the second electromagnet in the vertical direction, thereby suppressing the deformation of the fastening portion caused by the difference in thermal expansion rates between the base and the fastening portion when the base is heated by the heater.