Turbo molecular vacuum pump and method for manufacturing the rotor thereof

Abstract

The turbo molecular vacuum pump (1) includes a stator (2) and a rotor (3) configured to rotate within the stator (2). The rotor (3) includes a hub (9) and at least one blade stage (10a - 10h) including blades (11a, 11b) regularly distributed around the hub (9). The blade (11a) of the at least one blade stage (10a) of the rotor (3) is hollow.

Description

Technical Field

[0001] The present invention relates to a turbo molecular vacuum pump. The present invention also relates to a method for manufacturing a rotor of a turbo molecular vacuum pump.

Background Art

[0002] In order to generate a high vacuum in a vacuum vessel, for example, it is necessary to use a turbo molecular vacuum pump having a stator with a rotor driven at a high rotational speed of 30,000 revolutions per minute or more inside.

[0003] In some applications of such vacuum pumps, especially in the semiconductor manufacturing industry, continuous efforts have been made to increase the pumping speed. As a result, the pumps are becoming increasingly larger. Also, in order to prevent reaction by-products from depositing in the pump, ensure an appropriate service life, and enhance the productivity of production equipment, the operating temperature of the vacuum pump is rising.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the volume of the vacuum pump increases, problems regarding the supply of raw materials may occur. Large vacuum pumps may take up too much space, making it difficult to install the pumps under a process chamber where a large number of accessories already necessary for operating the apparatus are present.

[0005] In particular, in some processes in the semiconductor manufacturing industry, new and complex chemical substances are used, and an increasing amount of by-products are generated. If the vacuum pump is not sufficiently heated, by-products may deposit in the vacuum pump. It is necessary to set the operating temperature of the turbo molecular vacuum pump, which was set at 50°C to 60°C several decades ago, to about 150°C at present.

[0006] The rotor of a modern turbo-molecular vacuum pump is usually made of a high-performance aluminum alloy, which has provided the best creep resistance so far. This solution provides a good compromise between the vacuum performance obtained with respect to the pump's rotational speed and the moment of inertia accumulated in the pump. Certainly, if the rotor is damaged, all of the rotor's kinetic rotational energy is confined within the vacuum pump's casing, ensuring the safety of people and property. However, when the turbo-molecular vacuum pump is under stress at a specific heating temperature, especially above 150 °C, there is a risk of rotor creep. Also, since the rotor is usually on a magnetic bearing and not in contact with the stator, it is difficult to cool the rotor.

[0007] One of the objectives of the present invention is to at least partially solve the drawbacks of the prior art, and in particular to provide a turbo-molecular vacuum pump that can reduce the kinetic energy stored in the vacuum pump. Another objective of the present invention is to increase the pumping speed and / or raise the operating temperature of the turbo-molecular vacuum pump without increasing the volume of the vacuum pump.

Means for Solving the Problems

[0008] For the above objectives, the turbo-molecular vacuum pump of the present invention comprises a stator and a rotor configured to rotate within this stator, wherein the rotor comprises a hub and at least one blade stage including blades regularly distributed around the hub, characterized in that the blades of the at least one blade stage of the rotor are hollow.

[0009] Since only the outer surface of the rotor is required to pump and convey the gas, the partially hollow rotor does not affect the pump performance. On the other hand, the hollow blade reduces the weight of the rotor, thereby reducing the kinetic energy stored in the vacuum pump, and enabling the rotor to be housed within the casing of the vacuum pump during an explosion. Further, at least a part of the rotor can be made of an alloy having a density higher than that of an aluminum alloy, improving creep resistance.

[0010] The vacuum pump can also have one or more of the features described below, either individually or in combination. For example, the rotor has four or more of the blade stages, and the first blade stage is disposed on the suction orifice side of the vacuum pump and has hollow blades. The skin thickness of the hollow blade is, for example, 3 mm or less and / or 0.2 mm or more. The diameter of the rotor is, for example, 160 mm or more and / or 450 mm or less.

[0011] The rotor has a cylindrical skirt downstream of at least one blade stage, and the cylindrical skirt is hollow. The hollow cylindrical skirt may have internal reinforcing elements that connect walls facing each other within the cavity of the cylindrical skirt. The hub may also be hollow.

[0012] The rotor is at least partially made of an alloy having a density higher than that of an aluminum alloy, i.e., a density exceeding 2.7 g / cm 3 and can be made of an alloy with a density exceeding 2.7 g / cm³. The rotor is, for example, at least partially made of stainless steel, a titanium alloy, or a nickel-based alloy.

[0013] These alloys have a higher density than aluminum alloys and are about two to three times heavier. Due to their high density, these alloys achieve better mechanical strength and creep resistance at high temperatures than aluminum alloys. Also, these alloys are excellent in corrosion resistance and oxidation resistance.

[0014] These materials, for example, enable heating a turbomolecular vacuum pump to a high temperature without the risk of creep. These materials also enable increasing the gas flow rate of a turbomolecular vacuum pump without the risk of creep of the rotor. These materials also enable the rotor to rotate faster than a prior art vacuum pump of the same size, so that the pumping speed can be increased without the risk of creep of the rotor. The use of these materials can also increase the rotational speed of the rotor to reduce the size of the vacuum pump and maintain the same pumping performance without the risk of creep of the rotor.

[0015] These alloys are more expensive and heavier than aluminum alloys, but a rotor with at least one blade stage with hollow blades helps reduce the weight of the rotor, reduce the kinetic energy in case the rotor explodes, reduce the raw materials used, reduce the raw material cost, and alleviate potential supply problems.

[0016] At least one blade stage of the rotor with the hollow blades can be manufactured by metal additive manufacturing. Stainless steel, titanium alloys, and nickel-based alloys are particularly suitable for metal additive manufacturing by laser melting. The radial ends of the hollow blades manufactured by metal additive manufacturing are, for example, open. The hollow cylindrical skirt can also be manufactured by metal additive manufacturing. The annular ends of the skirt manufactured by metal additive manufacturing are, for example, open.

[0017] The rotor can be integrally formed. The rotor can be manufactured by shrink-fitting at least one blade stage having a hollow blade manufactured by metal additive manufacturing to a hub. The rotor can be manufactured by manufacturing at least one blade stage having a hollow blade to the hub by metal additive manufacturing.

[0018] The present invention also relates to a method for manufacturing a rotor of a turbo molecular vacuum pump as described above, and the rotor is completely manufactured by metal additive manufacturing. The present invention also relates to a method for manufacturing a rotor of a turbo molecular vacuum pump as described above, manufacturing at least one blade stage having the hollow blade by metal additive manufacturing, and shrink-fitting it to a hub. The hollow cylindrical skirt can also be manufactured by metal additive manufacturing and shrink-fitted to the hub.

[0019] The present invention also relates to a method for manufacturing a rotor of a turbo molecular vacuum pump as described above, and at least one blade stage having the hollow blade is manufactured by metal additive manufacturing on a hub. The hollow cylindrical skirt can also be manufactured by metal additive manufacturing on the hub. Other advantages and features of the present invention are included in the description of specific embodiments of the present invention (which is in no way limiting) and the accompanying drawings.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0021] In the following figures, the same elements are denoted by the same reference numerals. The following examples are illustrative. The description refers to one or more examples, but this does not necessarily mean that each reference numeral refers to the same example, or that the features apply only to one example. The individual features of different examples can also be combined or exchanged to provide other examples.

[0022] In this specification, "upstream" means an element arranged in front of other elements with respect to the flow direction of the gas pumped by the pump. Conversely, "downstream" means an element arranged behind other elements with respect to the flow direction of the gas pumped by the pump. Also, the axial direction refers to a direction parallel to the rotation axis I-I of the rotor of the vacuum pump, and the radial direction refers to a direction perpendicular to the axial direction.

[0023] FIG. 1 is a longitudinal sectional view showing a first embodiment of a turbo molecular vacuum pump 1 of the present invention. This turbo molecular vacuum pump 1 includes a stator 2, and a rotor 3 is arranged in this stator so as to rotate at a high speed in the axial direction, for example, at 20,000 revolutions per minute or more. The gas pumped by the pump enters from the suction orifice 4 of the turbo molecular vacuum pump 1 and is discharged from the discharge orifice 5. During operation, the discharge orifice 5 is connected to a roughing pump.

[0024] The stator 2 in particular includes a casing 12, for example a casing assembled from a plurality of parts, at least two annular stator stages 6a to 6h fixed to the casing 12, and a high-pressure socket 7, in this example a high-pressure socket fixed to the casing 12 and in which the discharge orifice 5 of the vacuum pump 1 is arranged. The stator includes an annular inlet flange 8 surrounding the suction orifice 4 for connecting the vacuum pump 1 to a vacuum vessel whose pressure is to be reduced.

[0025] As clearly shown in FIGS. 2A and 3, the rotor 3 has a hub 9 and at least one blade stage 10a to 10h. Each blade stage 10a to 10h extends at an angle substantially radially from the hub 9 and includes a plurality of blades 11a, 11b evenly distributed around the hub 9. Each blade stage 10a to 10h has, for example, 20 to 30 blades 11a, 11b respectively, and in this example there are 22 blades.

[0026] The rotor 3 has, for example, four or more stages, for example 4 to 12 blade stages 10a to 10h (8 in the illustrated example). The first blade stage 10a is a blade stage located on the side of the suction orifice 4 of the turbomolecular vacuum pump 1. The annular stator stages 6a to 6h of the stator are respectively arranged between successive blade stages 10a to 10h of the rotor 3. The annular stator stages 6a to 6h and the blade stages 10a to 10h are axially continuous along the rotation axis I-I of the rotor 3 (see FIG. 1).

[0027] The rotor 3 has a cylindrical skirt 13, called a Horweck skirt, formed of a smooth cylinder, downstream of at least two blade stages 10a to 10h, and this skirt rotates in a direction opposite to the spiral groove 14 of the stator. The spiral groove 14 of the stator serves to compress the gas conveyed by the pump and guide it to the discharge orifice 5. The rotor 3 also has an internal bowl 15 that is arranged coaxially with the rotation axis I-I and projects downwardly from the rotor 3, below the cylindrical skirt 13 and in the opposite direction to the bell 17 of the stator 2. During operation, the rotor 3 rotates within the stator 2 without the internal bowl 15 and the bell 17 coming into contact.

[0028] The rotor 3 is fixed to the drive shaft 18 of the vacuum pump 1, for example, by a screw 19 passing through the hub 9 of the rotor 3. The rotor 3 is rotationally driven within the stator 2 by an internal motor 20 of the vacuum pump 1. The motor 20 is arranged, for example, within the bell 17 of the stator 2, the stator 2 is arranged below the internal bowl 15 of the rotor 3, and the drive shaft 18 passes through the bell 17 of the stator.

[0029] The rotor 3 is guided laterally and axially by magnetic and / or mechanical bearings 21 that support the drive shaft 18 of the rotor 3 arranged within the stator 2. For example, the first bearing 21 supports and guides the first end of the drive shaft 18 within the base of the bell 17 of the stator 2, and the second bearing 21 supports and guides the second end of the drive shaft 18 arranged above the bell 17. Other electrical or electronic components, such as a position sensor, can be accommodated within the bell 17 of the stator 2.

[0030] The vacuum pump 1 can include a heating device designed to heat the stator 2. This heating device can be an external resistance heating belt designed to heat the casing 12 of the vacuum pump 1, or, for example, a radiation element arranged within the gas flow path of the vacuum pump 1 designed to heat the high-voltage socket 7 of the stator 2 in which the spiral groove 14 is formed.

[0031] As shown in the longitudinal sectional view of FIG. 3, the blade 11a of at least one blade stage 10a of the rotor 3 is hollow. The cavity of the hollow blade 11a extends, for example, throughout the interior of each blade 11a. All the blades 11a of each blade stage 10a are hollow. The skin thickness e (see FIG. 2B) of the hollow blade 11a is, for example, such that the maximum thickness (the maximum thickness over the entire length of the cavity of the blade 11a) is 3 mm or less and / or the minimum thickness (the minimum thickness over the entire length of the cavity of the blade 11a) is 0.2 mm or more.

[0032] Since it is only necessary to pump the gas on the outer surface of the rotor 3, a partially hollow rotor 3 does not affect the pump performance. On the other hand, the hollow blade 11a reduces the weight of the rotor 3, thereby reducing the kinetic energy stored in the vacuum pump 1, and enabling the rotor 3 to be housed within the casing 12 of the vacuum pump 1 during an explosion.

[0033] In the first embodiment of the present invention shown in FIGS. 1 to 3, only the blades 11a of one blade stage 10a of the rotor 3 are hollow, and in particular, only the first blade stage 10a located on the suction orifice 4 side has hollow blades 11a. This is the stage with the largest blade 11a among the blade stages 10a of the rotor 3, and thus the maximum weight and material savings are achieved. The blades 11b of the other blade stages 10b to 10h are solid.

[0034] However, the blade stage provided with the hollow blade 11a may be other stages of the rotor 3. Furthermore, the rotor 3 may be made of an alloy having a density higher than that of an aluminum alloy, i.e., a density exceeding 2.7 g / cm 3 3.

[0035] The rotor 3 is made of, for example, at least partially stainless steel, or a titanium alloy, or a nickel-based alloy also known as a superalloy, such as Inconel® 600 (NiCr15Fe), Inconel® 625 (NiCr22Mo9Nb), or Inconel® 718 (NiCr19Fe19Nb5Mo3). The secondary alloying metals of Inconel® are mainly niobium, manganese, and molybdenum. These alloys have a higher density than aluminum alloys. These alloys are two to three times heavier than aluminum alloys. Due to the high density of these alloys, mechanical strength and creep resistance at high temperatures superior to those of aluminum alloys can be obtained. These alloys also have good resistance to corrosion and oxidation.

[0036] With these materials, for example, the turbo molecular vacuum pump 1 can be heated to a high temperature without the risk of creep. For example, the heating device is configured to heat the stator to a temperature of 150°C or higher, for example 200°C, thereby preventing the formation of reaction product deposits in the vacuum pump 1, particularly in semiconductor manufacturing applications. With these materials, the gas flow rate of the turbo molecular vacuum pump 1 can also be increased without the risk of creep of the rotor 3.

[0037] With these materials, the rotor 3 can also be rotated at a higher speed than a prior art vacuum pump 1 of the same size, so that the pumping speed can be increased without the risk of creep of the rotor 3. The rotational speed of the rotor 3 is, for example, 20,000 rpm or higher. The diameter D of the rotor 3 with which the radial ends of the blades 11a, 11b are inscribed is, for example, 160 mm or more and / or 450 mm or less (see Fig. 3).

[0038] Using these materials can reduce the size of the vacuum pump 1 and increase the rotational speed of the rotor 3, and maintain the same pumping performance without the risk of creep of the rotor 3.

[0039] These alloys are more expensive and heavier than aluminum alloys, but the rotor 3 with at least one blade stage 10a having a hollow blade 11a helps to reduce the weight of this rotor 3, reduce the kinetic energy in case the rotor 3 explodes, reduce the raw material cost by reducing the raw materials used, and mitigate potential supply problems.

[0040] The rotor 3 is integrally formed, for example. All or part of the rotor 3 can be made from a constituent metal such as stainless steel, titanium alloy, nickel-based alloy, etc. by, for example, metal additive manufacturing by laser melting or electron beam melting. In a laser melting process such as a direct energy deposition (DED) process (also called direct metal deposition (DMD)), the constituent metal in the form of metal powder is deposited and then melted by a laser beam and fused with the previous layer.

[0041] In an electron beam melting process such as electron beam additive manufacturing (EBAM), an electron beam melts the constituent metal in the form of a thick wire to create a 3D print. Stainless steel, titanium alloy, nickel-based alloy are particularly suitable for metal additive manufacturing by laser melting.

[0042] At least one blade stage 10a of the rotor 3 having a hollow blade 11a is made by metal additive manufacturing. In the first embodiment where the rotor 3 is integrally formed, the rotor 3 can be completely manufactured by metal additive manufacturing.

[0043] The radial end of the hollow blade 11a (the blade of the first blade stage 10a in this case) manufactured by metal additive manufacturing may be open (see FIG. 2B), which is easier to manufacture. The rotor 3 can also be coated after manufacturing, particularly to improve corrosion resistance. For example, the rotor is nickel-plated.

[0044] In the first embodiment of the present invention, there is only one blade stage 10a having a hollow blade 11a, but the turbo molecular vacuum pump 1 may have a plurality of blade stages having hollow blades. For example, the turbo molecular vacuum pump 1 has two blade stages having hollow blades. These blade stages do not necessarily have to be continuous in the gas pumping path. For example, as shown in FIG. 4, the first blade stage 10a and the sixth blade stage 10f on the suction orifice 4 side have hollow blades 11a.

[0045] The turbo molecular vacuum pump 1 may have two or more blade stages having hollow blades. For example, as shown in FIG. 5, the first blade stage 10a, the third blade stage 10c, and the sixth blade stage 1️0f have hollow blades 11a. Similarly, all the blades 11a of all the blade stages 10a to 10h of the rotor 3 may also be hollow (see FIG. 7).

[0046] The ends of the blades 11a of the blade stage manufactured by metal additive manufacturing, the first blade stage 10a and the sixth blade stage 10f in FIG. 4, or the first blade stage 10a, the third blade stage 10c, and the sixth blade stage 10f in FIG. 5, or all the blade stages 10a to 10h in FIG. 7 may be open type.

[0047] FIG. 6 shows another embodiment of the present invention. In this embodiment, the rotor 3 is manufactured by assembling a plurality of parts. First, a hub 9 (integrated with a cylindrical skirt 13 in this case) and blade stages provided with solid blades 11b (the second stage 10b, the fourth stage 10d, the fifth stage 10e, the seventh stage 10g, and the eighth stage 10h in this case) are assembled, and then at least one blade stage provided with hollow blades 11a (the first stage 10a, the third stage 10c, and the sixth stage 10f in this case) is assembled. The different parts can be made of the same material or different materials.

[0048] During the manufacture of the rotor 3, the hub 9, and in this case the cylindrical skirt 13, and each blade stage 10b, 10d, 10e, 10g, and 10h with a solid blade 11b can be manufactured by conventional methods, for example, by turning.

[0049] According to a first variant of the assembly of a plurality of parts, the rotor 3 is made by shrink-fitting at least one blade stage with a hollow blade 11a on the hub 9, in this case the first blade stage 10a, the third blade stage 10c, and the sixth blade stage 10f, and these blade stages 10a, 10c, 10f are made by metal additive manufacturing.

[0050] According to a second variant of the assembly of a plurality of parts, the rotor 3 is made by metal additive manufacturing of at least one blade stage with a hollow blade 11a on the hub 9. In other words, at least one blade stage with a hollow blade 11a, in this case the first blade stage 10a, the third blade stage 10c, and the sixth blade stage 10f, is added to the hub 9 by metal additive manufacturing.

[0051] In both variants, the ends of the hollow blades 11a made by metal additive manufacturing, in this case the ends of the first blade stage 10a, the third blade stage 10c, and the sixth blade stage 10f, may be open. The other features of the embodiments of FIGS. 4 to 6 are the same as those of the first embodiment already described.

[0052] In the embodiment of the present invention shown in FIG. 7, all of the blade stages 10a to 10h have hollow blades 11a. In this embodiment, the cylindrical skirt 13 is also hollow. The hollow cylindrical skirt 13 has internal reinforcing elements 22 that connect the walls facing each other within the cavity of the cylindrical skirt 13, and its mechanical strength can be enhanced. In this embodiment, the hub 9 is also hollow.

[0053] Other configurations are also possible. For example, some blade stages can have solid blades 11b, and the cylindrical skirt 13 or the hub 9 can be solid. During the manufacture of the rotor 3, the hub 9 can be manufactured by conventional methods or additive manufacturing methods.

[0054] The rotor 3 can also be produced by press-fitting at least one blade stage (in this case, all of the blade stages 10a to 10h) having hollow blades 11a made by metal additive manufacturing onto the hub 9, and / or by press-fitting the hollow cylindrical skirt 13 onto the hub 9. The rotor 3 can also be produced by manufacturing at least one blade stage 10a to 10h (in this case, all of the blade stages 10a to 10h) having hollow blades 11a and / or the hollow cylindrical skirt 13 by metal additive manufacturing on the hub 9. In other words, at least one blade stage 10a to 10h having hollow blades 11a and / or the cylindrical skirt 13 is added to the hub 9 by metal additive manufacturing.

[0055] It is also possible to press-fit at least one blade stage 10a to 10h having hollow blades 11a onto the hub 9. Attach the hollow blades 11a by metal additive manufacturing on the hub 9, and add a hollow skirt to the hub 9 by metal additive manufacturing on the hub 9. As all variations of the present invention, the ends of the hollow blades 11a and the cylindrical skirt 13 made by metal additive manufacturing may be open.

Explanation of Reference Numerals

[0056] 1 Turbo molecular vacuum pump 2 Stator 3 Rotor 4 Suction Orifice 5 Discharge Orifice 6a~6h Annular Stator Stage 7 High-Pressure Socket 8 Inlet Flange 9 Hub 10a~10h Blade Stage 11a, 11b Hollow Blade 12 Casing 13 Skirt 14 Spiral Groove of Stator

Claims

1. A turbo molecular vacuum pump comprising a stator (2) and a rotor (3) configured to rotate within the stator (2), wherein the rotor (3) includes a hub (9) and at least one blade stage (10a - 10h) including blades (11a, 11b) regularly distributed around the hub (9), characterized in that the blade (11a) of the at least one blade stage (10a) of the rotor (3) is hollow.

2. The turbo molecular vacuum pump according to claim 1, wherein the rotor (3) has four or more of said blade stages (10a - 10h), and the first blade stage (10a) disposed on the suction orifice (4) side of the vacuum pump (1) has the hollow blade (11a).

3. The turbo molecular vacuum pump according to claim 1, wherein the thickness (e) of the skin of the hollow blade (11a) is 3 mm or less and / or 0.2 mm or more.

4. The turbo molecular vacuum pump according to claim 1, wherein the diameter (D) of the rotor (3) is 160 mm or more and / or 450 mm or less.

5. The turbo molecular vacuum pump according to claim 1, wherein the rotor (3) has a cylindrical skirt (13) downstream of the at least one blade stage (10a), and the cylindrical skirt (13) is hollow.

6. The turbo molecular vacuum pump according to claim 5, wherein the hollow cylindrical skirt (13) has internal reinforcement elements (22) connecting walls facing each other within the cavity of the cylindrical skirt (13).

7. The turbo molecular vacuum pump according to claim 1, wherein the hub (9) is also hollow.

8. The turbo molecular vacuum pump according to claim 1, wherein the rotor (3) is made at least partially of stainless steel, titanium alloy, or nickel - based alloy.

9. The turbo molecular vacuum pump according to claim 1, wherein the at least one blade stage (10a) of the rotor (3) having the hollow blade (11a) is manufactured by metal additive manufacturing.

10. The turbo molecular vacuum pump according to claim 9, wherein the radially - outer ends of the hollow blade (11a) manufactured by metal additive manufacturing are open.

11. The turbo molecular vacuum pump according to claim 1, characterized in that the rotor (3) is integral.

12. The turbo molecular vacuum pump according to any one of claims 9 or 10, characterized in that at least one blade stage (10a) having the hollow blade (11a) manufactured by the metal laminated molding is press-fitted on the hub (9).

13. The turbo molecular vacuum pump according to any one of claims 9 or 10, characterized in that at least one blade stage (10a) having the hollow blade (11a) is manufactured by metal laminated molding on the hub (9).

14. A method for manufacturing the rotor (3) of the turbo molecular vacuum pump (1) according to claim 11, characterized in that the rotor (3) is entirely manufactured by metal laminated molding.

15. A method for manufacturing the rotor of the turbo molecular vacuum pump (1) according to claim 12, characterized in that at least one blade stage (10a) having the hollow blade (11a) is manufactured by metal laminated molding and press-fitted on the hub (9).

16. A method for manufacturing the rotor (3) of the turbo molecular vacuum pump (1) according to claim 13, characterized in that at least one blade stage (10a) having the hollow blade (11a) is manufactured by metal laminated molding on the hub (9).

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