vacuum pump

Abstract

To suppress generation of a reaction product to a base or the like.SOLUTION: A vacuum pump 1 comprises a rotor 4, a stator 5, a base 3, and a cover member 6. The rotor 4 has rotor blades 22 at a plurality of stages, and a rotor cylindrical part 23. The stator 5 has stator blades 31 at a plurality of stages, and a stator cylindrical part 32. The base 3 houses the rotor 4 and the stator 5. The cover member 6 covers an inner wall surface 15 of the base 3 positioned on an exhaust downstream side with respect to exhaust downstream end parts of the rotor cylindrical part 23 and the stator cylindrical part 32. The end of the cover member 6 on the inner peripheral side extends from a third internal space S3 to a position overlapping the inner peripheral surface of the rotor cylindrical part 23.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump. [Background technology]

[0002] Some vacuum pumps include a turbine pump section consisting of fixed and rotating blades, and a drag pump section located downstream of the turbine pump section in the exhaust direction. These vacuum pumps are used to create a high vacuum in a process chamber where processes such as dry etching or CVD (Chemical Vapor Deposition) are performed.

[0003] The above processes are performed by supplying gases into the process chamber. Therefore, when the vacuum pump exhausts the gases, reaction products may be generated on the surfaces of the vacuum pump that come into contact with the gas, and these reaction products may deposit on the surfaces that come into contact with the gas. These reaction products must be removed.

[0004] Therefore, in the vacuum pump of Patent Document 1, a protective member is provided on the gas-contacting surface of the exhaust path of the vacuum pump to prevent the accumulation of products in the vacuum pump, thereby eliminating the need to replace vacuum pump parts and reducing the maintenance costs of the vacuum pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-2856 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-described vacuum pump, a gap exists between the downstream exhaust end of the rotor cylindrical portion constituting the drag pump section and the end of the protective member. Therefore, exhaust gas exhausted from the drag pump section may enter the space between the rotor cylindrical portion and the base and / or the space between the protective member and the base. As a result, if the temperature of the base is low, reaction products may be generated in the base. Furthermore, the reaction products generated in the base may peel off and be exhausted into the exhaust path. An object of the present invention is to prevent exhaust gas from flowing into the space between the rotor cylindrical portion and the base and / or the space between the protective member and the base, thereby suppressing the generation of reaction products in vacuum pump components such as the base. [Means for solving the problem]

[0007] A vacuum pump according to one aspect of the present invention includes a rotor, a stator, a base, and a cover member. The rotor has multiple stages of rotor blades and a rotor cylindrical portion. The stator has multiple stages of stator blades and a stator cylindrical portion. The base houses the rotor and the stator. The cover member covers the inner wall surface of the base, which forms an internal space located downstream of the rotor cylindrical portion and the downstream end of the stator cylindrical portion in the exhaust direction. The inner peripheral end of the cover member extends from the internal space to a position overlapping the inner peripheral surface of the rotor cylindrical portion. [Effects of the Invention]

[0008] In the vacuum pump according to one aspect of the present invention, the inner peripheral edge of the cover member extends from the internal space to a position overlapping the inner peripheral surface of the rotor cylindrical portion. This prevents gases exhausted by the rotor and stator from entering the space between the rotor cylindrical portion and the base and / or the space between the cover member and the base. As a result, the generation of reaction products in the base can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a vacuum pump according to an embodiment. [Figure 2A] FIG. [Figure 2B] FIG. 2 is a cross-sectional view of the cover member taken along the line A2-A2. [Figure 3] FIG. 2 is an enlarged view of the rotor cylindrical portion and the stator cylindrical portion and their vicinity. [Figure 4] 10A and 10B are diagrams illustrating modified examples of the mounting position of the cover member. [Figure 5] 10A and 10B are diagrams showing other modified examples of the attachment position of the cover member. DETAILED DESCRIPTION OF THE INVENTION

[0010] A vacuum pump according to one embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of a vacuum pump 1 according to the embodiment. As shown in Fig. 1, the vacuum pump 1 includes a housing 2, a base 3, a rotor 4, and a stator 5.

[0011] The housing 2 includes a first end 11, a second end 12, and a first internal space S1. The first end 11 is provided with an intake port 13. The first end 11 is attached to an attachment object (not shown). The attachment object is, for example, a process chamber of a semiconductor manufacturing device. The first internal space S1 is connected to the intake port 13. The second end 12 is located opposite the first end 11 in the axial direction of the rotor 4 (hereinafter simply referred to as the "axial direction A1"). The second end 12 is connected to the 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.

[0012] The rotor 4 includes a shaft 21. The shaft 21 extends in an axial direction A1. The shaft 21 is rotatably housed in a base 3. A first gap G1 is formed between the shaft 21 and the base 3. A second internal space S2 is formed between an inner wall surface of the rotor 4 and the base 3.

[0013] The rotor 4 includes multiple stages of rotor blades 22 and a rotor cylindrical portion 23. The multiple stages of rotor blades 22 are each connected to the shaft 21. The multiple rotor blades 22 are arranged at intervals from one another in the axial direction A1. Although not shown, the multiple stages of rotor blades 22 each extend radially from the shaft 21 as a center. Note that in the drawings, only one of the multiple stages of rotor blades 22 is labeled with a reference numeral, and the reference numerals of the other rotor blades 22 are omitted. The rotor cylindrical portion 23 is arranged below the multiple stages of rotor blades 22. The rotor cylindrical portion 23 extends in the axial direction A1.

[0014] The stator 5 includes multiple stages of stator blades 31 and a stator cylindrical portion 32. The multiple stages of stator blades 31 are connected to the inner surface of the housing 2. The multiple stages of stator blades 31 are arranged at intervals in the axial direction A1. The multiple stages of stator blades 31 are respectively arranged between the multiple stages of rotor blades 22. Although not shown, the multiple stages of stator blades 31 each extend radially from the shaft 21. Note that in the drawings, only two of the multiple stages of stator blades 31 are labeled with reference numerals, and the other stator blades 31 are not labeled. The stator cylindrical portion 32 is fixed in thermal contact with the base 3. The stator cylindrical portion 32 is arranged facing the rotor cylindrical portion 23 with a small gap in the radial direction of the rotor cylindrical portion 23. A spiral groove is provided on the inner circumferential surface of the stator cylindrical portion 32.

[0015] As shown in FIG. 1, the inner wall surface 15 of the base 3 defines a third internal space S3 downstream of the exhaust downstream ends of the rotor cylindrical portion 23 and the stator cylindrical portion 32. Gas exhausted from the mounting object and a purge gas (described later) are exhausted into the third internal space S3. The third internal space S3 is in communication with an exhaust port 16. The exhaust port 16 is provided in the base 3. Another vacuum pump (not shown) is connected to the exhaust port 16. The exhaust downstream side refers to the side closer to the third internal space S3 in the axial direction A1. The exhaust downstream direction refers to the direction toward the third internal space S3.

[0016] The vacuum pump 1 includes a plurality of bearings 41A-41D and a motor 42. The plurality of bearings 41A-41D are attached to the base 3 at positions that house the shaft 21. The plurality of bearings 41A-41D rotatably support the rotor 4. The bearing 41A is, for example, a ball bearing. Meanwhile, the other bearings 41B-41D ​​are, for example, magnetic bearings. However, the plurality of bearings 41B-41D ​​may be other types of bearings, such as ball bearings.

[0017] The motor 42 drives the rotor 4 to rotate. The motor 42 includes a motor rotor 42A and a motor stator 42B. The motor rotor 42A is attached to the shaft 21. The motor stator 42B is attached to the base 3. The motor stator 42B is disposed opposite the motor rotor 42A.

[0018] In the vacuum pump 1, the multiple stages of rotor vanes 22 and the multiple stages of stator vanes 31 form a turbomolecular pump section. The rotor cylindrical section 23 and the stator cylindrical section 32 form a thread groove pump section. In the vacuum pump 1, gas flows into the first internal space S1 from the intake port 13 as the rotor 4 is rotated by the motor 42. The gas in the first internal space S1 passes through the turbomolecular pump section and the thread groove pump section and is exhausted into the third internal space S3. The gas in the third internal space S3 is exhausted from the exhaust port 16. As a result, the inside of the attachment object attached to the intake port 13 is placed in a high vacuum state.

[0019] When a process such as dry etching or CVD is performed inside the object attached to the intake port 13, the vacuum pump 1 exhausts gases used in these processes (referred to as "process gases"). As a result, reaction products may be generated in the exhaust path of the vacuum pump 1 using the process gas as a raw material. Therefore, in this embodiment, a cover member 6 is provided in the third internal space S3, which serves as the exhaust path of the vacuum pump 1, to suppress the generation of reaction products in the base 3 that constitutes the vacuum pump 1. The configuration of the cover member 6 will be specifically described below.

[0020] FIG. 2A is a plan view of the cover member 6. FIG. 2B is a cross-sectional view of the cover member 6 taken along the line A2-A2. FIG. 3 is an enlarged view of the rotor cylindrical portion 23 and the stator cylindrical portion 32 and their vicinity. The cover member 6 includes a first portion 61, a second portion 62, and a third portion 63. The first portion 61 is a ring-shaped planar member. When the cover member 6 is placed in the third internal space S3, the first portion 61 covers the bottom surface 15A of the inner wall surface 15 of the base 3. The cover member 6 is fixed to the base 3 by fastening the first portion 61 to the bottom surface 15A of the base 3 with bolts. This allows the cover member 6 to be easily detached from the base 3.

[0021] The second portion 62 is a ring-shaped wall portion and is connected to the outer periphery of the first portion 61. When the cover member 6 is placed in the third internal space S3, the second portion 62 covers the outer wall surface 15B of the inner wall surface 15 of the base 3. The third portion 63 is a ring-shaped wall portion and is connected to the inner periphery of the first portion 61. When the cover member 6 is placed in the third internal space S3, the third portion 63 covers the inner wall surface 15C of the inner wall surface 15 of the base 3.

[0022] The gaps between the first portion 61, the second portion 62, and the third portion 63 and the inner wall surface 15 of the base 3 covered by these portions are set as small as possible. This makes it possible to minimize the accumulation of reaction products on the inner wall surface 15 of the base 3 covered by the first portion 61, the second portion 62, and the third portion 63.

[0023] 2A and 2B, a cutout 62A is formed in a part of the second portion 62. When the cover member 6 is placed in the third internal space S3, the cutout 62A faces the exhaust port 16 (FIG. 1). Gas discharged to the exhaust side of the thread groove pump part formed by the rotor cylindrical part 23 and the stator cylindrical part 32 flows into the third internal space S3 and then passes through the cutout 62A to be discharged from the exhaust port 16.

[0024] The cover member 6 is formed by bending a plate material such as an aluminum alloy or stainless steel. Alternatively, the first portion 61, the second portion 62, and the third portion 63 may be formed from separate plate materials and then welded together to form the cover member 6. To improve corrosion resistance, the surface of the cover member 6 may be subjected to a surface treatment using nickel plating (e.g., electroless nickel plating). Furthermore, to facilitate absorption of radiation from the rotor 4, black plating such as black nickel plating with high emissivity may be formed. Furthermore, instead of nickel plating or black nickel plating, surface treatment using nickel plating containing fluororesin or black nickel plating may be performed.

[0025] 3, one end of the cover member 6 on the outer periphery is in contact with the end of the stator cylindrical portion 32 on the exhaust downstream side. Specifically, one end of the second portion 62 is in contact with the end of the stator cylindrical portion 32 on the exhaust downstream side. Meanwhile, the other end of the cover member 6 on the inner periphery extends from the third internal space S3 to a position overlapping with the inner periphery surface of the rotor cylindrical portion 23. Specifically, one end of the third portion 63 extends from the third internal space S3 to a position overlapping with the inner periphery surface of the rotor cylindrical portion 23.

[0026] As described above, in the vacuum pump 1, one end of the outer periphery of the cover member 6, i.e., one end of the second portion 62, is in contact with the downstream end of the stator cylindrical portion 32. This causes the cover member 6 to have approximately the same temperature as the stator cylindrical portion 32. To heat the stator cylindrical portion 32, the vacuum pump 1 includes a heater 7. The heater 7 is provided on the base 3. The heater 7 heats the base 3, thereby heating the stator cylindrical portion 32, which is in thermal contact with the base 3. The heater 7 may be fixed to the outer periphery of the base 3 as shown in FIG. 3 or may be embedded in the base 3. The heater 7 heats the stator cylindrical portion 32 to a temperature at which no reaction products are generated. The heating temperature of the stator cylindrical portion 32 can be set arbitrarily depending on the gas used inside the mounting target, the type of reaction products, and the like. This heating temperature is, for example, 150°C.

[0027] By heating the stator cylindrical portion 32 to the above temperature, the cover member 6 is also heated to a temperature at which no reaction products are generated, thereby suppressing the generation of reaction products on the cover member 6. Furthermore, the inner wall surface 15C of the base 3 is heated by radiation from the other end on the outer circumferential side of the cover member 6. This also suppresses the generation of reaction products on the base 3.

[0028] Furthermore, in the vacuum pump, the other end on the inner circumferential side of the cover member 6, i.e., one end of the third portion 63, extends from the third internal space S3 to a position overlapping the inner circumferential surface of the rotor cylindrical portion 23. This makes it possible to prevent gas exhausted to the third internal space S3 from entering the space between the rotor cylindrical portion 23 and the base 3 and / or the space between the third portion 63 of the cover member 6 and the base 3. As a result, the generation of reaction products in the base 3, the rotor cylindrical portion 23, and the cover member 6 (third portion 63) is suppressed.

[0029] The overlap length between the third portion 63 and the downstream exhaust side surface of the rotor cylindrical portion 23 is set to a length that prevents the rotor 4 from being excessively heated by the cover member 6. For example, this overlap length is 50% or less of the length of the rotor cylindrical portion 23, and preferably about 10% of the length of the rotor cylindrical portion 23. This prevents the rotor 4 from expanding and coming into contact with other components of the vacuum pump 1.

[0030] The vacuum pump 1 includes a purge gas supply device 8. The purge gas supply device 8 includes a purge port 81 and a gas flow path 82. The purge port 81 is connected to a purge gas supply source (not shown). The purge port 81 is connected to the gas flow path 82. The gas flow path 82 communicates with a first gap G1 between the base 3 and the shaft 21. The first gap G1 communicates with the second internal space S2. Purge gas introduced from the purge gas supply source to the purge port 81 passes through the gas flow path 82 and the first gap G1 and is introduced into the second internal space S2. The purge gas introduced into the second internal space S2 is exhausted in the exhaust downstream direction from a second gap G2 formed between the other end (third portion 63) of the inner periphery of the cover member 6 and the side surface of the inner periphery of the rotor cylindrical portion 23. As a result, the purge gas exhausted from the second gap G2 is exhausted into the third internal space S3, and further exhausted from the exhaust port 16. The purge gas is, for example, an inert gas such as nitrogen gas.

[0031] By discharging the purge gas from the second gap G2 to the third internal space S3, it is possible to prevent the gas discharged from the thread groove pump to the third internal space S3 from passing through the second gap G2 and entering the second internal space S2, thereby preventing the generation of reaction products on the side walls of the base 3 and the rotor 4 that constitute the second internal space S2.

[0032] The vacuum pump 1 includes a seal member 9. The seal member 9 has a ring shape in a plan view. The seal member 9 has an L-shaped cross section. The seal member 9 is disposed between the base 3 and the rotor cylindrical portion 23. Specifically, the short side of the L shape of the seal member 9 is fixed to a protrusion provided on the base 3. Meanwhile, the long side of the L shape of the seal member 9 faces the inner circumferential side of the rotor cylindrical portion 23 at the top of the other end of the inner circumferential side of the cover member 6. A thread groove is formed in the axial direction A1 on the surface of the long side of the L shape of the seal member 9 facing the rotor cylindrical portion 23. A third gap G3 is provided between the long side of the L shape of the seal member 9 and the inner circumferential side of the rotor cylindrical portion 23. The third gap G3 is sufficiently narrow.

[0033] By forming a thread groove on the surface of the long side of the L-shape of the seal member 9 facing the rotor cylindrical portion 23 and narrowing the third gap G3 between the seal member 9 and the rotor cylindrical portion 23, a gas flow is generated in the third gap G3 in the exhaust downstream direction, i.e., toward the third internal space S3, when the rotor 4 rotates at high speed. As a result, gas exhausted from the thread groove pump formed by the rotor cylindrical portion 23 and the stator cylindrical portion 32 to the third internal space S3 can be prevented from passing through the second gap G2 and the third gap G3 and entering the second internal space S2. Note that, as long as a gas flow in the exhaust downstream direction can be generated in the third gap G3 when the rotor 4 rotates at high speed, it is not necessary to form a thread groove on the long side of the L-shape of the seal member 9.

[0034] When assembling the vacuum pump 1, the cover member 6 is inserted from above the base 3 and attached to the inner wall surface 15, and then the rotor 4 is attached to the base 3. In this case, to overlap one end of the third portion 63 of the cover member 6 with the inner circumferential surface of the rotor cylindrical portion 23, the base 3 must be formed so that the gap between the base 3 and the rotor cylindrical portion 23 is equal to or greater than the thickness of the third portion 63. In the completed vacuum pump 1, if the gap between the base 3 and the rotor cylindrical portion 23 is equal to or greater than the thickness of the third portion 63, gas flow in the downstream exhaust direction is unlikely to occur in the gap, even when the rotor 4 is rotated at high speed. As a result, gas exhausted to the third internal space S3 is more likely to pass through the gap and enter the second internal space S2.

[0035] Therefore, by forming the seal member 9 as a separate member, inserting the cover member 6 from above the base 3 and attaching it to the inner wall surface 15, and then arranging the seal member 9 to face the rotor cylindrical portion 23, it is possible to form a narrow third gap G3 between the base 3 (seal member 9) and the rotor cylindrical portion 23. As a result, when the rotor 4 is rotated at high speed, a gas flow in the exhaust downstream direction is likely to occur in the third gap G3 between the seal member 9 and the rotor cylindrical portion 23.

[0036] In the vacuum pump 1 according to the present embodiment described above, the other end of the cover member 6, i.e., one end of the third portion 63, extends from the third internal space S3 to a position overlapping with the inner circumferential surface of the rotor cylindrical portion 23. This makes it possible to prevent gas exhausted by the rotor 4 and the stator 5 from entering the space between the rotor cylindrical portion 23 and the base 3 and / or the space between the cover member 6 and the base 3.

[0037] Furthermore, in the vacuum pump 1 according to this embodiment, the stator cylindrical portion 32 is heated by the heater 7, and one end (second portion 62) of the cover member 6 is in contact with the end of the stator cylindrical portion 32 on the exhaust downstream side in the third internal space S3. This heats the cover member 6, and also heats the vicinity of the cover member 6 on the base 3. As a result, the generation of reaction products on the cover member 6 and the base 3 can be suppressed.

[0038] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. For example, since the rotor cylindrical portion spontaneously heats up due to high-speed rotation, the temperatures of the stator cylindrical portion 32 and the cover member 6 may be raised only by radiant heat from the rotor cylindrical portion 23. Even when the heater 7 is provided, one end of the outer periphery of the cover member 6 may be indirectly heated by the heater 7 by contacting the side surface of the stator cylindrical portion 32 or the base, rather than at the end of the stator cylindrical portion 32 on the downstream side of the exhaust gas.

[0039] The vacuum pump 1 according to the above embodiment is a pump that integrates a turbomolecular pump configured with multiple stages of rotor blades 22 and multiple stages of stator blades 31, and a thread groove pump configured with a rotor cylindrical portion 23 and a stator cylindrical portion 32. However, the thread groove pump may be omitted. That is, the vacuum pump 1 may be a turbomolecular pump. Alternatively, the turbomolecular pump may be omitted. That is, the vacuum pump 1 may be a thread groove pump.

[0040] A member similar to the cover member 6 may be provided in the exhaust path other than on the inner wall surface 15 of the base 3 that forms the third internal space S3. For example, as shown in Fig. 4, a cover member 6A may be provided in the fourth internal space S4 formed between the turbomolecular pump and the thread groove pump. Also, as shown in Fig. 5, a cover member 6B may be provided on the inner wall surface of the exhaust port 16. Figs. 4 and 5 are diagrams showing modified examples of the attachment position of the cover member 6A.

[0041] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0042] (First aspect) A vacuum pump includes a rotor, a stator, a base, and a cover member. The rotor has multiple stages of rotor blades and a rotor cylindrical portion. The stator has multiple stages of stator blades and a stator cylindrical portion. The base houses the rotor and stator. The cover member covers the inner wall surface of the base, which forms an internal space located downstream of the rotor cylindrical portion and the downstream end of the stator cylindrical portion. The inner peripheral end of the cover member extends from the internal space to a position overlapping with the inner peripheral surface of the rotor cylindrical portion.

[0043] In the vacuum pump according to the first aspect, the inner peripheral edge of the cover member extends from the internal space to a position overlapping the inner peripheral surface of the rotor cylindrical portion. This prevents gases exhausted by the rotor and stator from entering the space between the rotor cylindrical portion and the base and / or the space between the cover member and the base. As a result, the generation of reaction products in the base can be suppressed.

[0044] (Second Aspect) In the vacuum pump according to the first aspect, the cover member may be formed in a ring shape. In the vacuum pump according to the second aspect, the cover member can be easily attached to the vacuum pump.

[0045] (Third Aspect) In the vacuum pump according to the first or second aspect, the cover member may have a first portion covering a bottom surface of the inner wall surface of the base, a second portion covering an outer wall surface of the inner wall surface of the base and connected to the first portion, and a third portion covering an inner wall surface of the inner wall surface of the base and connected to the first portion. The third portion may extend from the internal space to a position overlapping with the inner circumferential surface of the rotor cylindrical portion.

[0046] In the vacuum pump according to the third aspect, the third portion of the cover member extends from the internal space to a position overlapping the inner circumferential surface of the rotor cylindrical portion, thereby preventing gas exhausted by the rotor and the stator from entering the space between the rotor cylindrical portion and the base and / or the space between the cover member and the base.

[0047] (Fourth Mode) The vacuum pump according to any one of the first to third modes may further include a seal member. The seal member may be provided at an upper portion of the inner peripheral end of the cover member so as to face the inner peripheral side surface of the rotor cylindrical portion. In the vacuum pump according to the fourth mode, a narrow gap can be formed between the seal member and the rotor cylindrical portion, generating a gas flow in the exhaust downstream direction. As a result, it is possible to prevent the exhausted gas from entering through the gap.

[0048] (Fifth Mode) The vacuum pump according to any one of the first to fourth modes may further include a purge gas supply device. The purge gas supply device supplies purge gas in the exhaust downstream direction to a gap formed between the inner circumferential end of the cover member and the inner circumferential side surface of the rotor cylindrical portion. This makes it possible to prevent exhausted gas from entering through the gap formed between the inner circumferential end of the cover member and the inner circumferential side surface of the rotor cylindrical portion.

[0049] (Sixth Mode) In the vacuum pump of the fourth mode, the seal member may be formed as a separate member from the base and connected to the base. By forming the seal member as a separate member, inserting a cover member from above the base and attaching it to the inner wall surface, and then configuring the seal member to face the rotor cylindrical portion, a narrow gap can be formed between the seal member and the rotor cylindrical portion. As a result, gas flow in the exhaust downstream direction is more likely to occur.

[0050] (Seventh Mode) In the vacuum pump according to any one of the first to sixth modes, the length by which the inner peripheral end of the cover member overlaps with the inner peripheral surface of the rotor cylindrical portion may be 50% or less of the axial length of the rotor cylindrical portion. This can prevent the rotor 4 from expanding and coming into contact with other components of the vacuum pump 1.

[0051] (Eighth Mode) The vacuum pump according to any one of the first to seventh modes further includes a heater that heats the stator cylindrical portion, and the outer peripheral end of the cover member is heated by the heater. By heating the stator cylindrical portion and the outer peripheral end of the cover member by the heater, the vicinity of the cover member of the base is also heated. As a result, the generation of reaction products on the cover member and the base can be suppressed.

[0052] (Ninth Mode) The vacuum pump according to any one of the first to seventh modes further includes a heater that heats the stator cylindrical portion, and the outer peripheral end of the cover member contacts the exhaust downstream end of the stator cylindrical portion in the internal space. Because the stator cylindrical portion is heated by the heater and the outer peripheral end of the cover member contacts the exhaust downstream end of the stator cylindrical portion in the internal space, the cover member is heated and the vicinity of the cover member of the base is also heated. As a result, the generation of reaction products on the cover member and the base can be suppressed. [Explanation of symbols]

[0053] 1. Vacuum pump 2. Housing 11 First end 12 Second end 13 Air intake 3. Bass 14 Base end 15 Inner wall surface 15A bottom 15B Outside wall 15C Inner wall 16 Exhaust port 4 rotors 21 Shaft 22 rotor blades 23 Rotor cylindrical part 5 Stator 31 Stator blade 32 Stator cylindrical part 6, 6A, 6B Cover parts 61 Part 1 62 Part 2 62A Notch 63 Part 3 7 Heater 8 Purge gas supply device 81 Purge port 82 Gas flow path 9 Sealing material 41A-41D bearings 42 Motor 42A motor rotor 42B Motor Stator A1 Axial direction G1 First Gap G2 2nd Gap G3 3rd Gap S1 1st internal space S2 2nd internal space S3 3rd internal space S4 4th internal space

Claims

1. a rotor having multiple stages of rotor blades and a rotor cylindrical portion; a stator having a plurality of stages of stator blades and a stator cylindrical portion; a base that houses the rotor and the stator; a cover member that covers an inner wall surface of the base, which defines an internal space located downstream of downstream ends of the rotor cylindrical portion and the stator cylindrical portion; Equipped with an inner peripheral end of the cover member extends from the internal space to a position overlapping an inner peripheral surface of the rotor cylindrical portion; The cover member contacts at least the bottom surface of the inner wall surface of the base. Vacuum pump.

2. The vacuum pump according to claim 1 , wherein the cover member is formed in a ring shape.

3. The cover member is a first portion covering a bottom surface of the inner wall surface of the base; a second portion covering an outer wall surface of the inner wall surface of the base and connected to the first portion; a third portion covering the inner wall surface of the base and connected to the first portion; and The vacuum pump according to claim 1 or 2, wherein the third portion extends from the internal space to a position overlapping an inner circumferential surface of the rotor cylindrical portion.

4. 4. The vacuum pump according to claim 1, further comprising a seal member provided at an upper portion of an inner peripheral end of the cover member so as to face an inner peripheral side surface of the rotor cylindrical portion.

5. 5. The vacuum pump according to claim 1, further comprising a purge gas supply device that supplies a purge gas in an exhaust downstream direction to a gap formed between an inner peripheral end of the cover member and an inner peripheral side surface of the rotor cylindrical portion.

6. 5. The vacuum pump according to claim 4, wherein the seal member is formed as a separate member from the base and is connected to the base.

7. 7. The vacuum pump according to claim 1, wherein the length by which the inner peripheral end of the cover member overlaps with the inner peripheral surface of the rotor cylindrical portion is 50% or less of the axial length of the rotor cylindrical portion.

8. a heater for heating the stator cylindrical portion; 8. The vacuum pump according to claim 1, wherein an outer peripheral end of the cover member is heated by the heater.

9. a heater for heating the stator cylindrical portion; 8. The vacuum pump according to claim 1, wherein an outer peripheral end of the cover member contacts an exhaust downstream end of the cylindrical stator portion in the internal space.

Images