Vacuum pump

Abstract

Provided is a vacuum pump that can suppress the precipitation and accumulation of by-products in a flow path on the downstream side of a thread groove in a vacuum pump having a thread groove. A vacuum pump (1) includes: a housing (11) having a suction port (12) or an exhaust port (21); a rotor (30) having a plurality of rotor blades (32) and a rotor cylindrical portion (33); a drive unit (80); a bearing; stator blades (43); a thread groove stator (50) disposed on the downstream side of the stator blades (43) and having an inner peripheral surface facing the outer peripheral surface of the rotor cylindrical portion (33); and a heat insulating wall (90) disposed on the downstream side of the thread groove (51). The heat insulating wall (90) has an annular portion (92) and a wall portion (93) having a substantially cylindrical shape that extends upstream from the radially inner portion of the annular portion (92) and forms a flow path on the outer peripheral surface side; a first corner portion (97) is formed between the upstream surface of the annular portion (92) and the outer peripheral surface of the wall portion (93); the first corner portion (97) is formed in an arc shape.

Description

Technical Field

[0001] The present invention relates to a vacuum pump, and particularly to a vacuum pump used in semiconductor manufacturing apparatuses, analytical apparatuses, and the like. Background Art

[0002] When manufacturing semiconductor devices such as memories and integrated circuits, processes for forming insulating films, metal films, semiconductor films, etc. and processes for etching are carried out. These processes are carried out in a chamber in a high vacuum state in order to prevent the influence of dust in the air. The chamber is connected to a vacuum pump in order to exhaust the gas introduced into the interior to a specified high vacuum degree. As an example of the vacuum pump used, for example, a compound pump in which a turbo molecular pump and a scroll pump are combined can be cited.

[0003] A vacuum pump in which a turbo molecular pump and a scroll pump are combined is configured such that, as disclosed in Patent Document 1, a scroll pump is disposed downstream of a turbo pump having rotating blades and fixed blades alternately arranged in the axial direction. The exhaust gas taken in from the suction port is compressed by the turbo molecular pump and the scroll pump and discharged from the exhaust port to the outside of the vacuum pump.

[0004] The scroll pump is composed of a rotating rotor cylinder portion and a scroll stator on the housing side that houses the rotor. Thread grooves are formed on the opposing surfaces of the rotor cylinder portion or the scroll stator. Therefore, by rotating the rotor cylinder portion inside the scroll stator, the gas can be transferred toward the exhaust port side.

[0005] The exhaust gas exhibits a molecular flow behavior in the turbo molecular pump, but in the scroll pump and the flow path downstream thereof, since the pressure becomes relatively high, it exhibits a behavior like a viscous flow. Therefore, by-products are likely to precipitate at the portions where the flow of the exhaust gas in the scroll pump and the flow path downstream thereof stagnates. Therefore, the scroll stator is heated to a high temperature with a heater or the like so that the flow path is not blocked by the precipitation of by-products in the exhaust gas.

[0006] As by-products, generally, gases such as chlorine-based and sulfur fluoride-based gases are generated. The sublimation temperature of these gases becomes higher as the vacuum degree becomes lower and the pressure becomes higher, and the gases are more likely to solidify and accumulate inside the vacuum pump. If by-products accumulate inside the vacuum pump, there is a possibility that the by-products narrow the flow path and the compression performance and exhaust performance of the vacuum pump deteriorate.

[0007] On the other hand, the stator column that houses electrical components such as an electromagnet and a motor that rotationally drive the rotor is cooled with a water cooling pipe or the like to a temperature below a specified value in order to prevent deterioration of the performance and failure of the electrical components. Therefore, if a flow path is formed between the high-temperature portion that is heated to a high temperature and the cooling portion that is cooled, gas is likely to precipitate as a by-product in the low-temperature portion.

[0008] Therefore, a process is performed in which a part of a low-temperature component adjacent to a flow path on the downstream side of the screw groove is covered with a high-temperature heat-insulating wall. The heat-insulating wall restricts the exhaust gas on the downstream side of the screw groove from contacting the low-temperature part.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-090384. Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] The gas outlets of the screw groove pump are multiple in the circumferential direction corresponding to the number of threads. In contrast, the flow path connected to the exhaust port is only one place. Therefore, the heat-insulating wall is formed in a ring shape to transfer the gas to the discharge port provided at one place in the circumferential direction. If a concave portion is formed on the surface of the ring-shaped heat-insulating wall that forms the flow path, there is a problem that the flow of the gas stagnates and by-products are likely to precipitate and accumulate.

[0014] The present invention is made to solve the above problems, and an object thereof is to provide a vacuum pump capable of suppressing the precipitation and accumulation of by-products in a flow path on the downstream side of a screw groove of a vacuum pump having a screw groove.

[0015] Means for Solving the Problems

[0016] The vacuum pump according to the present invention for achieving the above object includes: a housing having an intake port for sucking gas from the outside or an exhaust port for discharging the sucked gas to the outside; a rotor rotatably disposed in the housing, having a plurality of rotor blades, and having a rotor cylinder portion on the downstream side of the rotor blades; a drive unit for rotationally driving the rotor; a bearing for rotatably supporting the rotor; stator blades alternately disposed with the rotor blades in the axial direction of the rotor; a screw groove stator disposed on the downstream side of the stator blades, having an inner peripheral surface facing the outer peripheral surface of the rotor cylinder portion; and a heat-insulating wall disposed on the downstream side of a screw groove formed on the outer peripheral surface of the rotor cylinder portion or the inner peripheral surface of the screw groove stator; characterized in that the heat-insulating wall has a ring-shaped portion and a wall portion having a substantially cylindrical shape extending upstream from the inner side portion in the radial direction of the ring-shaped portion and forming a flow path on the outer peripheral surface side; a first corner portion is formed between the upstream side surface of the ring-shaped portion and the outer peripheral surface of the wall portion; and in a cross section passing through the rotation axis of the rotor, the first corner portion is formed in an arc shape.

[0017] Advantages of the Invention

[0018] The vacuum pump of the present invention configured as described above has the first corner formed in an arc shape, so that the gas flowing circumferentially along the adiabatic wall on the downstream side of the thread groove and toward the exhaust port hardly stagnates at the first corner. Therefore, by-products hardly precipitate and accumulate at the first corner of the adiabatic wall. Thus, the present vacuum pump can suppress the precipitation and accumulation of by-products in the flow path on the downstream side of the thread groove of the thread groove pump.

[0019] Alternatively, the wall portion may have a cylindrical wall portion having a substantially cylindrical shape and an annular folded-back portion protruding radially outward from the upstream end of the cylindrical wall portion. Thereby, while ensuring that the radial thickness of the folded-back portion is an appropriate length, the cylindrical wall portion can be made thinner. By making the cylindrical wall portion thinner, a wider flow path can be ensured on the radially outer side of the cylindrical wall portion. Further, since the cross-sectional area of the cylindrical wall portion orthogonal to the rotation axis of the rotor becomes smaller, the thermal resistance of the cylindrical wall portion increases, and heat is difficult to transfer from the annular portion side to the folded-back portion. Therefore, the temperature rise of the folded-back portion can be restricted, and heat conduction from the adiabatic wall to the rotor can be reduced.

[0020] Alternatively, in a cross-section passing through the rotation axis of the rotor, a second corner is formed between the outer peripheral surface of the cylindrical wall portion and the downstream surface of the folded-back portion; the second corner is formed in an arc shape. Thus, the gas flowing circumferentially along the adiabatic wall on the downstream side of the thread groove and toward the exhaust port hardly stagnates at the second corner. Therefore, by-products hardly precipitate and accumulate at the second corner of the adiabatic wall. Thus, the present vacuum pump can suppress the precipitation and accumulation of by-products in the flow path on the downstream side of the thread groove pump.

[0021] Alternatively, the housing has a passage formed on the downstream side of the adiabatic wall and a substantially cylindrical exhaust pipe in which the exhaust port is formed; the inner wall surface of the passage and the inner wall surface of the exhaust pipe are continuously formed without a step. Thus, the gas flowing toward the exhaust port on the downstream side of the adiabatic wall hardly stagnates at the inlet of the exhaust pipe. Therefore, the present vacuum pump can suppress the precipitation and accumulation of by-products at the inlet of the exhaust pipe where the exhaust port is formed.

[0022] Alternatively, the adiabatic wall is arranged so as to cover the low-temperature portion of the housing that is arranged on the downstream side and / or radially inside of the adiabatic wall and has a temperature lower than that of the adiabatic wall. Thereby, the adiabatic wall can restrict the contact between the gas flowing toward the exhaust port and the low-temperature portion, and suppress the precipitation and accumulation of by-products at the low-temperature portion.

[0023] Alternatively, a heating heater may be disposed on the aforementioned threaded groove stator or a component connected to the aforementioned threaded groove stator; the aforementioned heat insulating wall is connected to the aforementioned threaded groove stator, or is connected to a component that is connected to the aforementioned threaded groove stator and is provided with a heating heater. Thus, the heat insulating wall is heated, so that precipitation and accumulation of by-products due to contact with the gas can be suppressed.

[0024] Alternatively, the end face on the upstream side of the aforementioned wall portion and the end face on the downstream side of the aforementioned rotor cylinder portion are axially close to and face each other. Thus, the end face of the heat insulating wall and the end face of the rotor cylinder portion form a sealing structure. Therefore, it is difficult for the gas to leak between the heat insulating wall and the rotor cylinder portion, and precipitation and accumulation of by-products at low-temperature portions can be suppressed.

[0025] Alternatively, a third corner portion is formed between the inner peripheral surface of the aforementioned heat insulating wall on the aforementioned threaded groove stator or a component connected to the aforementioned threaded groove stator and the upstream surface of the aforementioned annular portion; in a cross section passing through the rotation axis of the aforementioned rotor, the aforementioned third corner portion is formed in an arc shape. Thus, the gas flowing circumferentially along the heat insulating wall toward the exhaust port on the downstream side of the threaded groove is difficult to stagnate at the third corner portion. Therefore, it is difficult for by-products to precipitate and accumulate at the third corner portion of the heat insulating wall. Accordingly, this vacuum pump can suppress precipitation and accumulation of by-products in the flow path on the downstream side of the threaded groove of the threaded groove pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a cross-sectional view showing a vacuum pump according to the first embodiment.

[0027] Figure 2 is a schematic cross-sectional view orthogonal to the rotation axis of the heat insulating wall and the exhaust port of the vacuum pump.

[0028] Figure 3 is a partial cross-sectional view showing the vicinity of the exhaust pipe and the passage according to the first embodiment.

[0029] Figure 4 is a partial cross-sectional view showing the vicinity of the heat insulating wall and the threaded groove stator according to the first embodiment.

[0030] Figure 5 is a cross-sectional view showing a vacuum pump according to the second embodiment.

[0031] Figure 6 is a partial cross-sectional view showing the vicinity of the heat insulating wall and the threaded groove stator according to the second embodiment.

[0032] Figure 7 is a partial cross-sectional view showing the vicinity of the exhaust pipe and the passage according to the second embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the dimensions of the drawings may be exaggerated for convenience of explanation and may be different from the actual dimensions. Further, in this specification and the drawings, for components having substantially the same functional structure, the same reference numerals are given and repeated description is omitted. In addition, in the embodiments of the present invention, for convenience, the diameter direction of the rotor is defined as the "radial direction", and the direction perpendicular to the diameter direction of the rotor is defined as the "axial direction" for explanation.

[0034] <First Embodiment>

[0035] As shown in Figure 1 , the vacuum pump 1 according to the first embodiment of the present invention is a compound pump having a turbomolecular pump and a scroll pump disposed downstream of the turbomolecular pump. The turbomolecular pump high-speed rotates a rotor 30 having rotor blades 32 to bounce gas molecules, thereby exhausting the gas. The vacuum pump 1 has a vacuum pump main body 2 for sucking and exhausting gas and a control device 3 for controlling the vacuum pump main body 2.

[0036] The vacuum pump main body 2 sucks and exhausts gas from a chamber of, for example, a semiconductor manufacturing apparatus, an analysis apparatus, etc. The vacuum pump main body 2 has: a fixed portion 10 formed with a suction port 12 and an exhaust port 21; a rotor 30 capable of rotating inside the fixed portion 10; a bearing for rotatably supporting the rotor 30; a displacement sensor for detecting the displacement of the rotor 30; and a motor 80 (drive portion) for rotationally driving the rotor 30.

[0037] The fixed portion 10 has: a housing 11 formed with a suction port 12; a stationary vane portion 40 provided with stator vanes 43; a water-cooled spacer 14 connected to the housing 11; a scroll stator 50 formed with a scroll groove 51; an exhaust pipe 20 formed with an exhaust port 21; and a base 100. The fixed portion 10 further has: a heat insulating spacer 18 for heat insulating the scroll stator 50 and the water-cooled spacer 14; a heat insulating member 19 for heat insulating the scroll stator 50 and the water-cooled spacer 14 from the base 100; and a heat insulating wall 90 provided on the downstream side of the scroll groove 51.

[0038] The housing 11 has: a flange 13 mounted on a chamber of a semiconductor manufacturing apparatus or the like; and a suction port 12 communicating with the chamber.

[0039] The stationary vane portion 40 is disposed inside the housing 11. The stationary vane portion 40 has a multi-layered stator 41 and a plurality of stator spacers 42 laminated in such a manner as to sandwich each layer of the stator 41. Each stator 41 has a plurality of stator vanes 43. The stator vanes 43 are formed to be inclined at a prescribed angle from a plane perpendicular to the axial direction of the shaft 35. The stator vanes 43 are arranged in a staggered manner with the rotor vanes 32 of the rotor 30 described later. The end portions on the outer peripheral side of the stator vanes 43 are sandwiched between a plurality of laminated annular stator spacers 42 and supported thereby. The stator spacers 42 are laminated and disposed inside the housing 11. The stator vanes 43 and the rotor vanes 32 of the rotor 30 described later together constitute a turbo molecular pump.

[0040] The water-cooled spacer 14 is formed in a substantially cylindrical shape and is disposed on the downstream side of the housing 11. The water-cooled spacer 14 is connected to the housing 11 by bolts 15. In the water-cooled spacer 14, a water-cooling pipe 16 and a first temperature sensor 17 are embedded. The first temperature sensor 17 detects the temperature of the water-cooled spacer 14 in order to adjust the temperature of the water-cooled spacer 14. The flow of the cooling water in the water-cooling pipe 16 is controlled in order to adjust the temperature of the water-cooled spacer 14. Thereby, the water-cooled spacer 14 is maintained at a prescribed temperature (for example, 50°C to 100°C).

[0041] The grooved stator 50 is formed in a substantially cylindrical shape and is disposed inside the water-cooled spacer 14 with a gap therebetween for heat insulation from the water-cooled spacer 14. The grooved stator 50 has a structure that is heated in order to suppress the precipitation and accumulation of by-products in the grooves 51. Alternatively, a heat insulating member may be disposed between the water-cooled spacer 14 and the grooved stator 50.

[0042] On the inner peripheral surface of the grooved stator 50, spiral grooves 51 are formed. Further, in the grooved stator 50, a cylindrical heater 52 (heating heater) as a heating mechanism and a second temperature sensor 53 for detecting the temperature inside the grooved stator 50 are provided. In the present embodiment, the grooves 51 are formed on the inner peripheral surface of the grooved stator 50. However, conversely, grooves may be formed on the outer peripheral surface of the rotor cylindrical portion 33.

[0043] The direction of the helix of the thread groove 51 is the direction in which the molecules of the gas are transferred toward the exhaust port 21 when the molecules move in the rotation direction of the rotor 30. The thread groove stator 50 and the rotor cylinder part 33 constitute a thread groove pump. The thread groove stator 50 is made of a metal such as aluminum, stainless steel, copper, iron, or an alloy containing these metals as components. As an example, the thread groove stator 50 is made of aluminum. In addition, in the present embodiment, since the cartridge heater 52 as a heating mechanism is disposed in the thread groove stator 50, it is made of a material having a relatively high thermal conductivity. However, when the thread groove stator 50 has a structure different from the component (heater spacer) provided with the cartridge heater 52 as a heating mechanism, the component provided with the cartridge heater 52 may be made of a material having a relatively high thermal conductivity (such as aluminum), and the thread groove stator 50 may be made of a material having a relatively high strength (such as stainless steel) to ensure strength at high temperatures.

[0044] The second temperature sensor 53 detects the temperature of the thread groove stator 50 in order to adjust the temperature of the thread groove stator 50. The cartridge heater 52 is housed in the thread groove stator 50. The cartridge heater 52 generates heat when energized to adjust the temperature of the thread groove stator 50. The cartridge heater 52 is controlled for power supply based on the detection result of the second temperature sensor 53. Thus, the thread groove stator 50 is maintained at a specified temperature (for example, 100°C to 150°C).

[0045] The thread groove stator 50 is formed with one passage 54 penetrating radially on the downstream side of the portion where the thread groove 51 is formed. In addition, the component forming the passage 54 may be any component provided on the downstream side of the thread groove 51, and is not limited to the thread groove stator 50. As Figures 1 to 3 shown, the passage 54 allows the gas transferred from the thread groove 51 inside the thread groove stator 50 to flow toward the exhaust port 21 provided on the outer side in the radial direction. The passage 54 is formed with a constant inner diameter from the passage inlet portion 55 on the inner peripheral side of the thread groove stator 50 to the passage outlet portion 56 on the outer peripheral side of the thread groove stator 50. The extending direction of the passage 54 is orthogonal to the rotation axis of the rotor 30. The thread groove stator 50 is formed with a fitting portion 57 into which the exhaust pipe 20 is fitted on the exhaust port 21 side of the passage outlet portion 56, and a ring housing portion 58 for housing the O-ring 59 is formed on the outer side in the radial direction of the fitting portion 57. The inner diameter of the fitting portion 57 is larger than the inner diameter of the passage 54, and the inner diameter of the ring housing portion 58 is larger than the inner diameter of the fitting portion 57.

[0046] The exhaust pipe 20 is connected to the threaded groove stator 50 by bolts 22. The exhaust pipe 20 has: an exhaust pipe passage 23; an exhaust port 21 located on the exhaust side of the exhaust pipe passage 23; an exhaust pipe base end portion 24 that is fitted into a fitting portion 57 of the threaded groove stator 50 on the side opposite to the exhaust port 21; and an exhaust pipe flange 25 that abuts against the outer peripheral surface of the threaded groove stator 50. The exhaust port 21 is connected in a communicating manner to an auxiliary pump (not shown). The inner diameter of the exhaust pipe passage 23 is the same as the inner diameter of the passage 54. The inner peripheral surface of the exhaust pipe passage 23 and the inner peripheral surface of the passage 54 are smoothly continuous without a step difference. The extending direction of the exhaust pipe passage 23 is the same as the extending direction of the passage 54 and is orthogonal to the rotation axis of the rotor 30. The difference between the inner diameter of the exhaust pipe passage 23 and the inner diameter of the passage 54 at the boundary portion between the exhaust pipe passage 23 and the passage 54 is preferably as small as possible, for example, 0.6 mm or less, preferably 0.4 mm or less, and more preferably 0.2 mm or less. The deviation between the axis of the exhaust pipe passage 23 and the axis of the passage 54 at the boundary portion between the exhaust pipe passage 23 and the passage 54 is preferably as small as possible, for example, 0.3 mm or less, preferably 0.2 mm or less, and more preferably 0.1 mm or less. The exhaust pipe 20 penetrates through the water-cooling spacer 14 without contacting the water-cooling spacer 14. Therefore, the exhaust pipe 20 is provided with a cylindrical heater 52 to heat the high-temperature threaded groove stator 50. Therefore, in the exhaust pipe 20, by-products are difficult to precipitate and accumulate.

[0047] The heat insulation spacer 18 is a heat insulation mechanism that insulates between the high-temperature threaded groove stator 50 and the water-cooling spacer 14. The heat insulation spacer 18 is formed of a material with a low thermal conductivity, that is, a material through which heat is difficult to transfer. The constituent material of the heat insulation spacer 18 is, for example, aluminum, stainless steel, etc. In addition, the heat insulation spacer 18 is arranged in close contact with a plurality of stators 41 on the lower layer side (downstream side), and is spaced apart from the inner peripheral surface of the water-cooling spacer 14 connected to the plurality of stators 41 on the upper layer side (upstream side) with a gap for heat insulation.

[0048] Both the water-cooling spacer 14 and the threaded groove stator 50 are connected to the base body 101 of the base 100 via the heat insulation member 19. Therefore, both the water-cooling spacer 14 and the threaded groove stator 50 are insulated from the base 100 by means of the heat insulation member 19.

[0049] The base 100 has a base body 101 to which the threaded groove stator 50 and the water-cooling spacer 14 are connected, and a stator column 102 that protrudes upward (upstream side) from the center of the base body 101. The stator column 102 functions as a stator of the motor 80.

[0050] A water-cooling pipe 103 is embedded in the base body 101. By circulating cooling water inside, the water-cooling pipe 103 always cools the base body 101, the stator column 102, the magnetic bearings described later, the auxiliary bearing 65, the motor 80, etc. In the present embodiment, the water-cooling pipe 103 maintains a temperature of 25 to 70 °C by always circulating cooling water.

[0051] The heat-insulating wall 90 is, as Figure 4 shown, connected to the end face on the downstream side of the threaded groove stator 50 by bolts 91. Since the heat-insulating wall 90 is thermally connected to the threaded groove stator 50, it is heated to a high temperature. Therefore, the heat-insulating wall 90 is preferably made of a material with excellent thermal conductivity. Materials with excellent thermal conductivity are, for example, aluminum, etc. In addition, the component to which the heat-insulating wall 90 is connected only needs to be a component on the downstream side of the threaded groove 51, and it may not be the threaded groove stator 50. The component to which the heat-insulating wall 90 is connected is preferably a high-temperature part that is heated by a heating mechanism (heating heater) like the threaded groove stator 50. Thus, for example, when the threaded groove stator 50 has a structure different from the component provided with the heating mechanism, the heat-insulating wall 90 can also be connected to the component provided with the heating mechanism. The heat-insulating wall 90 covers at least a part of the stator column 102 and the base body 101, which are low-temperature parts, close to the flow path on the downstream side of the threaded groove 51. The heat-insulating wall 90 restricts the gas on the downstream side of the threaded groove 51 from contacting the low-temperature stator column 102 and the base 100 cooled by the water-cooling pipe 103, and suppresses the precipitation and accumulation of by-products at the low-temperature part.

[0052] The heat-insulating wall 90 is formed, as Figure 2 shown, so as to be able to transfer the gas discharged from the threaded groove 51 to a passage 54 communicating with an exhaust port 21 provided at one place in the circumferential direction. The heat-insulating wall 90 is, as Figure 4 shown, provided with an annular part 92 that extends from the part on the downstream side of the threaded groove stator 50 toward the inside in the radial direction, and a substantially cylindrical wall part 93 that extends from the inner part in the radial direction of the annular part 92 toward the upstream side and forms a flow path on the outer peripheral surface side. The wall part 93 has a cylindrical tubular wall part 94 on the side of the annular part 92, and a folded-back part 95 that protrudes outward in the radial direction from the upstream end of the tubular wall part 94.

[0053] The wall portion 93 is spaced apart from the outer peripheral surface of the stator column 102 with a lower temperature by a clearance for heat insulation. The end surface on the upstream side of the wall portion 93 faces the end surface on the downstream side of the rotor cylinder portion 33 of the rotor 30 in the axial direction. The radial thickness L3 of the cylindrical wall portion 94 is shorter than the radial thickness L1 of the folded-back portion 95. Therefore, it is possible to make the cylindrical wall portion 94 thinner while ensuring an appropriate length for the radial thickness L3 of the folded-back portion 95. By making the cylindrical wall portion 94 thinner, a wider flow path can be ensured on the outer side in the radial direction of the cylindrical wall portion 94. Furthermore, since the cross-sectional area of the cylindrical wall portion 94 orthogonal to the rotation axis of the rotor 30 becomes smaller, the thermal resistance of the cylindrical wall portion 94 increases, and heat is difficult to transfer from the annular portion 92 side to the folded-back portion 95. Therefore, it is possible to limit the temperature rise of the folded-back portion 95 and reduce the heat conduction from the heat insulation wall 90 to the rotor 30. Additionally, the folded-back portion 95 may not be provided.

[0054] A third corner portion 96 is formed between the inner peripheral surface (the inner peripheral surface of the fixing portion 10) on the downstream side of the thread groove stator 50 and the upstream side surface of the annular portion 92. In addition, a first corner portion 97 is formed between the upstream side surface of the annular portion 92 and the outer peripheral surface of the wall portion 93. In a cross-section passing through the rotation axis of the rotor 30, the third corner portion 96 and the first corner portion 97 are formed in an arc-shaped concave shape (arc shape (R shape)) so that gas is difficult to stagnate. In a cross-section passing through the rotation axis of the rotor 30, the radius of curvature of the third corner portion 96 and the first corner portion 97 is not particularly limited, but the larger the better. For example, it is 5 mm in the present embodiment.

[0055] [[ID=,6]]The clearance portion between the heat insulation wall 90 and the rotor 30 has a non-contact sealing structure. The end surface on the upstream side of the wall portion 93 faces the end surface on the downstream side of the rotor cylinder portion with an appropriate clearance G (gap) and an appropriate opposed area in order to ensure sealing performance. As an example, the axial clearance G between the end surface on the upstream side of the wall portion 93 and the end surface on the downstream side of the rotor cylinder portion is about 1.5 mm at rest. In addition, as an example, in order to form an appropriate opposed area, the radial thickness L1 of the end surface on the upstream side of the wall portion 93 is about 4 mm, and the radial thickness L2 of the end surface on the downstream side of the rotor cylinder portion 33 opposed to the heat insulation wall 90 is about 8 mm.

[0056] The rotor 30 is rotatably disposed inside the housing 11. The rotor 30 has a shaft rod 35, rotor blades 32 that are multi-layered in the axial direction, and a rotor cylinder portion 33 disposed downstream of the rotor blades 32. The rotor blades 32 constitute a turbo molecular pump and are blades for sucking and exhausting gas. A plurality of rotor blades 32 in each layer are radially arranged in the circumferential direction.

[0057] The rotor 30 has a substantially cylindrical shape, and a shaft rod 35 is fixedly penetrated inside. Each rotor blade 32 is formed to be inclined at a prescribed angle from a plane perpendicular to the axial direction of the shaft rod 35 in order to transfer gas molecules downward by means of collision. The rotor blades 32 are integrally formed on the outer peripheral surface of the rotor 30. Alternatively, the rotor blades 32 may also be fixed to the outer peripheral surface of the rotor 30.

[0058] The rotor cylindrical portion 33 is disposed downstream of the rotor blades 32 and is formed in a cylindrical shape. The rotor cylindrical portion 33 projects toward the inner peripheral surface of the thread groove stator 50. The rotor cylindrical portion 33 approaches the inner peripheral surface of the thread groove stator 50 with a prescribed gap therebetween.

[0059] The shaft rod 35 is disposed at the center of rotation of the rotor 30. The shaft rod 35 has a cylindrical main shaft portion 36 and a disk 37 in the shape of a circular plate disposed at the lower part of the main shaft portion 36. The main shaft portion 36 and the disk 37 are formed of a high magnetic permeability material (such as iron) that can be attracted by magnetism. The main shaft portion 36 is attracted by the magnetic forces of the upstream side radial electromagnet 61 and the downstream side radial electromagnet 62 described later to control its position.

[0060] The bearing is, for example, a so-called five-axis controlled magnetic bearing that suspends and supports the shaft rod 35 and performs position control. The bearing has an upstream side radial electromagnet 61 that attracts the upstream side of the main shaft portion 36, a downstream side radial electromagnet 62 that attracts the downstream side of the main shaft portion 36, axial electromagnets 63A and 63B that attract the disk 37, and an auxiliary bearing 65. The auxiliary bearing 65 comes into contact with the main shaft portion 36 when the shaft vibration of the rotor 30 becomes large, and suppresses direct contact between the rotor 30 and the stator side to prevent damage.

[0061] The upstream side radial electromagnet 61 has four electromagnets arranged in pairs on each of two axes orthogonal to each other in a plane perpendicular to the rotation axis. The downstream side radial electromagnet 62 has four electromagnets arranged in pairs on each of two axes orthogonal to each other in a plane perpendicular to the rotation axis. The axial electromagnets 63A and 63B are arranged sandwiching the disk 37 vertically.

[0062] The displacement sensor is disposed on the stator column 102 in order to detect the displacement of the rotor 30. The displacement sensor has an upstream side radial sensor 71, a downstream side radial sensor 72, and an axial sensor 73. The upstream side radial sensor 71 is four non-contact sensors arranged close to and corresponding to the four upstream side radial electromagnets 61. The upstream side radial sensor 71 is configured to detect the radial displacement of the upper part of the main shaft portion 36 of the shaft rod 35 and send its displacement signal to the control device 3. As an example of the sensor used as the upstream side radial sensor 71, there are an inductive sensor, an eddy current sensor, etc.

[0063] The downstream-side radial sensors 72 are four non-contact sensors arranged in proximity to and corresponding to the four downstream-side radial electromagnets 62. The downstream-side radial sensors 72 are configured to detect the radial displacement at the lower part of the spindle portion 36 and send the displacement signal thereof to the control device 3. As examples of the sensors used as the downstream-side radial sensors 72, there are inductive sensors, eddy current sensors, and the like.

[0064] The axial sensor 73 is arranged below the disk 37. The axial sensor 73 is configured to detect the axial displacement of the shaft 35 and send the displacement signal thereof to the control device 3.

[0065] Based on the displacement signal detected by the upstream-side radial sensor 71, the control device 3 performs excitation control on the upstream-side radial electromagnet 61 via a compensation circuit having a PID adjustment function to adjust the radial position on the upstream side of the spindle portion 36. This adjustment is independently performed on each of the two axes orthogonal to each other in the plane perpendicular to the rotation axis.

[0066] In addition, based on the displacement signal detected by the downstream-side radial sensor 72, the control device 3 performs excitation control on the downstream-side radial electromagnet 62 via a compensation circuit having a PID adjustment function to adjust the radial position on the downstream side of the spindle portion 36. This adjustment is independently performed on each of the two axes orthogonal to each other in the plane perpendicular to the rotation axis.

[0067] Furthermore, in the control device 3, based on the displacement signal detected by the axial sensor 73, excitation control is performed on the axial electromagnets 63A and 63B. At this time, the axial electromagnet 63A attracts the disk 37 upward by magnetic force, and the axial electromagnet 63B attracts the disk 37 downward. In this way, the magnetic bearing can magnetically levitate the shaft 35 by appropriately adjusting the magnetic force acting on the shaft 35 and can rotatably support the shaft 35 in a non-contact manner.

[0068] The motor 80 has a plurality of magnetic poles 81 as permanent magnets arranged on the rotor side and motor electromagnets 82 arranged on the stator side. The magnetic poles 81 are applied with a torque component for rotating the shaft 35 from the motor electromagnets 82. Thereby, the rotor 30 is rotationally driven.

[0069] In addition, a rotational speed sensor and a motor temperature sensor (not shown) are installed on the motor 80. The rotational speed sensor and the motor temperature sensor send the detected results to the control device 3 as detection signals. The control device 3 utilizes the signals received from the rotational speed sensor and the motor temperature sensor for the control of the rotation of the shaft 35.

[0070] If the shaft 35 is driven by the motor 80 in the above-described vacuum pump main body 2, the rotor blades 32 and the rotor cylindrical portion 33 rotate. Thereby, by the action of the rotor blades 32 and the stator blades 43, gas from the chamber is sucked in through the suction port 12.

[0071] The gas sucked in from the suction port 12 is transferred between the rotor cylinder portion and the grooved stator 50 by means of the rotor blades 32 and the stator blades 43. At this time, due to the frictional heat generated when the gas contacts the rotor blades 32, the conduction of heat generated by the motor 80, etc., the temperature of the rotor blades 32 rises. However, this heat is transferred to the stator blade 43 side by radiation or conduction brought by gas molecules of the gas. Further, the stator spacers 42 are joined to each other at the outer peripheral portion. Therefore, the heat received by the stator blades 43 from the rotor blades 32, the frictional heat generated when the gas contacts the stator blades 43, etc. are transferred to the outside via the stator spacers 42.

[0072] In addition, the gas transferred between the rotor cylinder portion 33 and the grooved stator 50 is transferred to the downstream side by means of the thread grooves 51 of the grooved stator 50. The grooved stator 50 is heated by the cylindrical heater 52. Thereby, the thread grooves 51, where by-products are likely to precipitate and accumulate if the temperature becomes low, are maintained at a high temperature, and the precipitation and accumulation of by-products in the thread grooves 51 are suppressed. Thus, it is possible to suppress the flow path of the thread grooves 51 from becoming narrow due to by-products.

[0073] In addition, the outer periphery of the electrical component section is covered by the stator column 102 so that the gas sucked from the suction port 12 does not intrude into the electrical component section composed of the motor 80, the downstream radial electromagnet 62, the downstream radial sensor 72, the upstream radial electromagnet 61, the upstream radial sensor 71, etc. The inside of the stator column 102 surrounding the electrical component section is maintained at a specified pressure by the purge gas. The stator column 102 is provided with a pipe (not shown), and the purge gas is introduced via this pipe. The introduced purge gas is sent to the exhaust port 21 through the gaps between the auxiliary bearing 65 and the shaft rod 35, between the motors 80, and between the stator column 102 and the rotor blades 32.

[0074] The base body 101 is cooled by the water-cooling pipe 103. Thereby, the base body 101 and the stator column 102, the magnetic bearing, the auxiliary bearing 65, the motor 80, etc. thermally connected to the base body 101 are always cooled. Thereby, the adhesion and accumulation of gas inside the vacuum pump body 2 are suppressed.

[0075] The gas transferred to the downstream side of the thread grooves 51 is as Figure 2 , Figure 4As shown, the downward movement is suppressed by means of the annular heat insulating wall 90 fixed to the downstream side of the threaded groove stator 50, and it is transferred to the passage inlet portion 55 of the threaded groove stator 50 provided at one place in the circumferential direction. The heat insulating wall 90 covers the low-temperature stator column 102 and the base body 101 close to the flow path on the downstream side of the threaded groove 51. Therefore, the heat insulating wall 90 restricts the gas on the downstream side of the threaded groove 51 from contacting the low-temperature stator column 102 and the base 100, and suppresses the precipitation and accumulation of by-products at the low-temperature portion. The third corner portion 96 and the first corner portion 97 of the heat insulating wall 90 are formed in an arc-shaped concave shape in the cross section passing through the rotation axis of the rotor 30. Therefore, in the third corner portion 96 and the first corner portion 97, it is difficult for the flow to stagnate, and the precipitation and accumulation of by-products are suppressed. In addition, since the heat insulating wall 90 is thermally connected to the threaded groove stator 50 and is heated to a high temperature, the precipitation and accumulation of by-products are further suppressed.

[0076] In addition, since the end face on the upstream side of the heat insulating wall 90 and the end face on the downstream side of the rotor cylinder portion 33 of the rotor 30 face each other with an appropriate gap G and an appropriate facing area, appropriate sealing performance is ensured. Thereby, it is suppressed that gas reaches the stator column 102, the base body 101, the inside of the stator column 102, etc. from the gap G between the heat insulating wall 90 and the rotor cylinder portion 33 and by-products precipitate and accumulate.

[0077] The gas transferred to the passage inlet portion 55 is as Figures 1 to 3 shown, passes through the passage 54 and reaches the exhaust pipe 20, and is exhausted to the outside from the exhaust port 21 of the exhaust pipe 20. The passage 54 of the threaded groove stator 50 and the exhaust pipe passage 23 are continuously connected smoothly without a step difference. Therefore, it is difficult for the flow to stagnate between the passage inlet portion 55 and the exhaust port 21, and the precipitation and accumulation of by-products are suppressed.

[0078] <Second Embodiment>

[0079] Regarding the vacuum pump 1 of the second embodiment of the present invention, as Figures 5 to 7 shown, only the shapes of the heat insulating wall 90 and the threaded groove stator 50 are different from those of the first embodiment.

[0080] The heat insulating wall 90 forms a second corner portion 98 between the outer peripheral surface of the cylindrical wall portion 94 and the surface on the downstream side of the folded-back portion 95. Moreover, the second corner portion 98 is formed in an arc-shaped concave shape in the cross section passing through the rotation axis of the rotor 30. Therefore, when the gas transferred from the threaded groove 51 flows along the heat insulating wall 90 in the circumferential direction, it is difficult for the flow to stagnate at the second corner portion 98. Therefore, the precipitation and accumulation of by-products at the second corner portion 98 are suppressed. The radius of curvature of the second corner portion 98 is not particularly limited, but the larger the better. For example, it is 2 mm in the present embodiment.

[0081] The threaded groove stator 50 is as follows Figure 7 As shown, in the axial direction, the position of the inner wall surface 54A on the downstream side in the inner wall surface of the passage 54 coincides with the position of the innermost part 99 on the most downstream side (the side opposite to the side where the suction port 12 is provided along the axial direction) between the third corner portion 96 and the first corner portion 97. Therefore, the passage inlet portion 55 of the threaded groove stator 50 penetrates the third corner portion 96 and is smoothly continuous with the innermost part 99. Thus, the gas flowing circumferentially along the heat insulating wall 90 can smoothly enter the passage 54 of the threaded groove stator 50 and smoothly flow toward the exhaust port 21. Thus, the precipitation and accumulation of by-products near the passage inlet portion 55 are suppressed. In addition, the heat insulating wall 90 is formed with the third corner portion 96 in the same manner as in the first embodiment except for the portion communicating with the passage inlet portion 55 in the circumferential direction. In addition, as a modification, the third corner portion 96 outside the portion communicating with the passage inlet portion 55 in the circumferential direction of the heat insulating wall 90 may not be circular arc-shaped in the cross section passing through the rotation axis of the rotor 30, and may be a concave shape with a substantially zero radius of curvature.

[0082] In addition, in the axial direction of the threaded groove stator 50, the position of the inner wall surface 54B on the upstream side in the inner wall surface of the passage 54 coincides with the position of the downstream side surface 95A of the folding portion 95. Therefore, the gas flowing circumferentially along the heat insulating wall 90 can smoothly enter the passage 54 of the threaded groove stator 50 from the flow path between the second corner portion 98 of the folding portion 95 and the first corner portion 97 of the annular portion 92 and smoothly flow toward the exhaust port 21. Thus, the precipitation and accumulation of by-products near the passage inlet portion 55 are suppressed.

[0083] In addition, the present invention is not limited to the above embodiments, and various changes can be made by those skilled in the art within the technical idea of the present invention. For example, the bearing may not be a magnetic bearing. In addition, the housing 11 may be formed with the exhaust port 21. In addition, the housing 11 may be formed with both the suction port 12 and the exhaust port 21.

[0084] Explanation of reference numerals

[0085] 1 Vacuum pump

[0086] 2 Vacuum pump main body

[0087] 11 Housing

[0088] 12 Suction port

[0089] 18 Heat insulating spacer

[0090] 20 Exhaust pipe

[0091] 21 Exhaust port

[0092] 23 Exhaust pipe passage

[0093] 30 Rotor

[0094] 32 Rotor blade

[0095] 41 Stator

[0096] 43 Stator blade

[0097] 50 Threaded groove stator

[0098] 51 Threaded groove

[0099] 54 Passage

[0100] 55 Passage inlet part

[0101] 80 Motor (drive unit)

[0102] 90 Heat-insulating wall

[0103] 92 Annular part

[0104] 93 Wall part

[0105] 94 Cylindrical wall part

[0106] 95 Folded-back part

[0107] 96 Third corner part

[0108] 97 First corner part

[0109] 98 Second corner part.

Claims

1. A vacuum pump, comprising: A housing having an intake port for sucking gas from the outside or an exhaust port for discharging the sucked gas to the outside; A rotor rotatably disposed within the housing, having a plurality of rotor blades, and having a rotor cylinder portion on the downstream side of the rotor blades; A drive unit for rotationally driving the rotor; A bearing for rotatably supporting the rotor; Stator blades alternately arranged with the rotor blades in the axial direction of the rotor; A grooved stator disposed on the downstream side of the stator blades, having an inner peripheral surface facing the outer peripheral surface of the rotor cylinder portion; And A heat insulating wall disposed on the downstream side of a thread groove formed on the outer peripheral surface of the rotor cylinder portion or the inner peripheral surface of the grooved stator; Characterized in that The heat insulating wall has an annular portion and a substantially cylindrical wall portion extending upstream from the inner side in the radial direction of the annular portion and forming a flow path on the outer peripheral surface side; A first corner portion is formed between the upstream surface of the annular portion and the outer peripheral surface of the wall portion; A third corner portion is formed between the inner peripheral surface of the grooved stator or a member connected to the grooved stator and the upstream surface of the annular portion; In a cross section passing through the rotation axis of the rotor, the first corner portion and the third corner portion are formed in an arc shape.

2. The vacuum pump according to claim 1, characterized in that The wall portion has a substantially cylindrical tubular wall portion and an annular folded-back portion protruding radially outward from the upstream end of the tubular wall portion.

3. The vacuum pump according to claim 2, characterized in that In a cross section passing through the rotation axis of the rotor, a second corner portion is formed between the outer peripheral surface of the tubular wall portion and the downstream surface of the folded-back portion; The second corner portion is formed in an arc shape.

4. The vacuum pump according to any one of claims 1 to 3, characterized in that The housing has a passage formed on the downstream side of the heat insulating wall and a substantially cylindrical exhaust pipe formed with the exhaust port; The inner wall surface of the passage and the inner wall surface of the exhaust pipe are continuously formed without a step difference.

5. The vacuum pump according to any one of claims 1 to 3, characterized in that The heat insulating wall is disposed so as to cover a low-temperature portion of the housing disposed on the downstream side and / or the inner side in the radial direction of the heat insulating wall and having a temperature lower than that of the heat insulating wall.

6. The vacuum pump according to any one of claims 1 to 3, characterized in that A heating heater is disposed on the grooved stator or a member connected to the grooved stator; The heat insulating wall is connected to the grooved stator or a member connected to the grooved stator and provided with a heating heater.

7. The vacuum pump according to any one of claims 1 to 3, characterized in that The upstream end surface of the wall portion and the downstream end surface of the rotor cylinder portion are axially close to each other and face each other.

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