Method for manufacturing a turbomolecular vacuum pump and its rotor

Abstract

A turbomolecular vacuum pump is proposed which at least partially overcomes the drawbacks of the prior art. [Solution] A turbomolecular vacuum pump (1) configured to drive a gas to be pumped from an inlet orifice (6) to an outlet orifice (7), wherein a surface of an inner bowl (15) of a rotor (3) arranged facing a shell (17) of a coolable stator (2) exhibits a higher emissivity than an outer surface (25) of the rotor (3) in fluid contact with the gas to be pumped, and wherein a surface of the shell (17) of the coolable stator (2) arranged facing the inner bowl (15) of the rotor (3) exhibits a higher emissivity in fluid contact with the gas to be pumped than the outer surface (25) of the rotor (3).

Description

[Technical Field]

[0001] This invention relates to a turbomolecular vacuum pump. Furthermore, this invention also relates to a method for manufacturing a turbomolecular vacuum pump rotor. [Background technology]

[0002] To generate a high vacuum inside the enclosure, it is necessary to use a turbomolecular vacuum pump inside the stator, in which the rotor rotates at high speed, for example, at over 90,000 revolutions per minute. In some manufacturing methods using turbomolecular vacuum pumps, such as those used to manufacture semiconductors and LEDs, deposits can form inside the vacuum pump. These deposits can restrict the play between the stator and rotor, potentially causing the rotor to stall. In fact, the deposits can heat the rotor through friction, which can cause creep and, consequently, cracking of the rotor.

[0003] Heating the stator to avoid condensation of reaction products within the pump is a well-known technique. However, care is taken to ensure that the rotor temperature does not exceed a certain high threshold in order to maintain the rotor's mechanical strength. In fact, the rotor's mechanical resistance to centrifugal force decreases as the temperature rises, and especially above 150°C in the case of aluminum. As the flow rate of gas being pumped increases, the temperature of the vacuum pump rises. Therefore, an increase in the operating temperature of the vacuum pump means that the maximum pump flow rate should be limited in order to maintain a rotor temperature that conforms to its operating specifications.

[0004] However, these constraints on the operating temperature and maximum pump flow rate of the vacuum pump contradict the product's expectations. In fact, it is required to raise the heating temperature as high as possible to limit deposit formation and thereby extend the pump's lifespan. At the same time, in order to increase the rate of production, it is required to maximize the flow rate of the gas being pumped, especially the flow rate of heavy gases such as argon. However, heavy gases have the disadvantage of causing further heating of the rotor. In fact, heat dissipation from the rotor is achieved on the one hand by heat transfer to molecules (convection) and on the other hand by infrared radiation. However, in the case of pumping heavy gases, heat exchange by convection is greatly reduced.

[0005] Furthermore, because the process gases used in manufacturing are highly aggressive, it may be necessary to protect the rotor by coating it with a protective layer such as nickel plating. However, the infrared emissivity of nickel coatings is very low, around 0.2. This low emissivity significantly limits heat exchange between the rotor and its surroundings, and as a result, limits the maximum flow rate of gas that can be transported by the pump. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] One of the objectives of the present invention is to propose a turbomolecular vacuum pump that at least partially solves the shortcomings of the latest prior art described above. [Means for solving the problem]

[0007] For this purpose, the subject of the present invention is a turbomolecular vacuum pump configured to transport gas from an intake orifice to an exhaust orifice, The turbomolecular vacuum pump comprises a stator, a rotor configured to rotate within the stator, and a purge device. The stator has at least one fin stage and a shell configured to allow cooling, The rotor has at least two stages of blade stages and an internal bowl, the blade stages and the fin stages follow alternately axially along the rotation axis of the rotor, and the internal bowl is coaxial with the rotation axis. In the purge device configured to inject a purge gas into a gap between the shell of the stator and the internal bowl of the rotor. The surface of the internal bowl of the rotor disposed facing the coolable shell of the stator is in fluid contact with the gas pumped and conveyed over at least a part of the surface of the internal bowl, and exhibits a higher emissivity than the outer surface of the rotor. The outer surface of the rotor in fluid contact with the gas pumped and conveyed exhibits a lower emissivity than the surface of the internal bowl of the rotor over at least a part of the surface of the internal bowl of the rotor. And / or, the surface of the shell of the stator disposed facing the internal bowl of the rotor and being coolable is in fluid contact with the gas pumped and conveyed, and exhibits a higher emissivity than the outer surface of the rotor over at least a part of the surface of the shell of the stator. The outer surface of the rotor in fluid contact with the gas pumped and conveyed exhibits a lower emissivity than the surface of the shell of the stator at least in a part of the surface of the shell of the stator, which is characterized.

[0008] In radiative transfer, emissivity corresponds to the radiative flux of thermal radiation emitted from a surface element at a specific temperature and is the ratio to a reference value that is the flux emitted by a blackbody at the same temperature. Most of the surface of the internal bowl excluding the centering surface, etc., most of the surface of the internal bowl, and / or most of the surface of the shell of the stator, for example, the entire surface of the shell of the stator excluding the centering surface, etc., exhibit a higher emissivity. One or more surfaces with high emissivity exhibit an emissivity of, for example, 0.4 or more. One or more surfaces in contact with the gas and fluid pumped can exhibit an emissivity of less than 0.3. In particular, the outer surface of the rotor in contact with the gas and fluid pumped can have a protective coating against corrosion such as nickel plating.

[0009] The inside of the rotor having a high emissivity surface, especially only this inside, enables promoting the radiative cooling of the rotor by heat dissipation. The shell of the stator on the lower side of the rotor having a high emissivity surface enables promoting the cooling of the rotor by radiation from the shell that is itself cooled.

[0010] The turbomolecular vacuum pump can be provided with a cooling device configured to cool the shell of the stator and / or a heating device configured to heat the sleeve of the stator surrounding the rotor. The sleeve of the stator surrounding the rotor is heated to avoid the formation of deposits on the inner surface of the stator. To not heat the rotor, the heat exchange between the sleeve and the rotor is reduced at the outer surface of the low emissivity rotor.

[0011] The shell of the stator protruding below the rotor is cooled to protect the electronic components and the motor below the rotor. The heat exchange between the shell and the rotor is promoted by the inner bowl of the rotor and / or the surface of the shell of the stator and has a high emissivity to better cool the rotor. To significantly promote heat exchange, it may be preferable in some cases that both the movable and fixed parts of the region not directly connected to the gas pumped are surfaces with a high emissivity.

[0012] To limit the intrusion of the gas pumped into the gap located between the shell of the stator and the inner bowl of the rotor, and to protect one or more surfaces with a high emissivity located between the inner bowl of the rotor and the shell of the stator, the cross-sectional area of the annular conductance between the end of the inner bowl of the rotor and the shell of the stator is such that the flow rate of the purge gas injected is, for example, 12 mm 2 / 1.69×10-3 Pa·m 3 / s(12mm 2 ( / sccm) is below this. The flow rate of the purge gas is, for example, 0.0845 Pa.m. 3 It is less than or equal to / s (or 50 sccm).

[0013] During operation, one or more highly emissive surfaces can facilitate heat exchange with the stator shell on the underside of the rotor, thereby promoting radiative cooling of the rotor. These highly emissive surfaces are protected on the one hand by the purge gas circulating in the gap on the underside of the rotor, and on the other hand by the annular conductance at the edge of the internal bowl, so as not to come into contact with potentially corrosive pump-carrying gases. The purge gas and cyclic conductance make it possible to protect the highly emissivity surfaces of the rotor and / or stator from attack by pumped gases that may penetrate beneath the rotor. Thus, only the protected surfaces are highly emissive, and these surfaces are not exposed to or are not exposed to potentially corrosive pumped gases.

[0014] Furthermore, a turbomolecular vacuum pump may have one or more of the features described below, either individually or in combination. One or more highly emissive surfaces of the rotor's internal bowl and / or the stator's shell are obtained by surface treatments such as anodizing, sandblasting, grooving, or texturing. For example, they are obtained by laser or soda treatment. Surface treatments of aluminum by anodizing, soda treatment, or laser texturing have the advantage of being able to obtain surfaces with an emissivity of more than 0.8 at a reasonable cost. High emissivity surfaces of the rotor's internal bowl and / or stator shell can be achieved by coating deposition. This includes solvent-free coatings such as KEPLA-COAT® type plasma vapor deposition chemical coatings, solvent-free paint-type coatings, or epoxy polymer coatings, more commonly known as "epoxy paints." The fact that only the rotor's internal bowl, particularly the surface of the Holwek skirt, can have a high emissivity coating offers the advantage that the robustness of the rotor coating is enhanced by the centrifugal pressing effect.

[0015] The coating thickness is, for example, between 30 μm and 100 μm. The coating or surface treatment may have, for example, a matte and / or dark appearance. In particular, it is possible to increase the emissivity of the rotor and / or stator within the gap by providing several surface treatments and / or coating layers. The coating or surface treatment is preferably solvent-free. The solvent must, in practice, be fully defined by the specific pumping device, and it is preferable not to use a solvent in a vacuum pump to avoid the risk of backscattering into the space being pumped. The purging device may be configured to inject the flow of purge gas into at least one bearing that supports and guides the rotor drive shaft such that the flow of purge gas passes through at least one bearing before exiting the stator shell. A turbomolecular vacuum pump may be equipped with a sensor to detect the presence of purge gas injected by a purging device. A vacuum pump is equipped with a cooling device, such as a hydraulic circuit, which is located inside the stator, inside the shell, or in thermal contact with the shell, for example, to cool the stator shell. This cooling device makes it possible to control the shell temperature to a temperature of 75°C or lower, such as 70°C, by circulating water at ambient temperature, for example.

[0016] A turbomolecular vacuum pump is preferably equipped with a temperature sensor configured to measure the rotor temperature using infrared radiation. The temperature sensor can be positioned on the stator shell so as to face the highly emissive surface of the internal bowl. The stator heating device is, for example, a heat-resistant shell, and is configured to heat the stator sleeve to a set temperature, such as 130°C, which is higher than 80°C. According to an exemplary embodiment, the rotor is provided with a Holweck skirt downstream of at least two stages of blades. This Holweck skirt is formed by smooth cylinders configured to rotate opposing helical grooves of the stator for pumping gas. An internal bowl facing the shell of the stator is also formed inside the Holweck skirt. In another embodiment, the vacuum pump is solely a turbomolecular pump, and the rotor has at least two blade stages, but does not have a Holweck skirt.

[0017] Another subject of the present invention is a method for manufacturing the turbomolecular vacuum pump rotor, The outer surface of the rotor, excluding the centering surface, is treated to obtain a high-emissivity surface, or a coating is deposited on the rotor to obtain a high-emissivity surface, excluding the centering surface. The outer surface of the rotor, intended to communicate with the gas and fluid being pumped, is nickel-plated by masking the rotor's internal bowl. Another subject of the present invention is a method for manufacturing the turbomolecular vacuum pump rotor, A surface treatment is performed on the first part of the rotor, including the inner bowl and Holweck skirt, to obtain a high-emissivity surface on the first part of the rotor, or a coating is deposited on the first part of the rotor, including the inner bowl and Holweck skirt, to obtain a high-emissivity surface on the first part of the rotor, and The surface of a first portion of the rotor, intended to come into contact with the gas and fluid being pumped, is nickel-plated, masking the inner bowl, and then the first portion of the rotor is fixed to a nickel-plated second portion of the rotor, which includes at least two stages of blades.

[0018] Another subject of the present invention is a method for manufacturing the turbomolecular vacuum pump rotor, wherein a component forming an inner bowl having a high emissivity surface is assembled, for example, by screwing or interference fitting, with a rotor body having a concave shape on the one hand that complements the inner bowl and on the other hand that has at least two blade stages. The component forming the inner bowl having a high emissivity surface is made, for example, anodized aluminum. [Brief explanation of the drawing]

[0019] [Figure 1] This is an axial cross-section of a turbomolecular vacuum pump according to a first exemplary embodiment of the present invention. [Figure 2] This is a cross-sectional view of the rotor of a turbomolecular vacuum pump according to another exemplary embodiment of the present invention. [Figure 3] This is a cross-sectional view of the rotor of a turbomolecular vacuum pump according to another exemplary embodiment of the present invention. [Figure 4] This is an axial cross-sectional view of a turbomolecular vacuum pump according to another exemplary embodiment of the present invention. [Modes for carrying out the invention]

[0020] Other advantages and features of the present invention will become apparent from the following description relating to specific, but non-limiting embodiments of the invention, and from the accompanying drawings. In the following drawings, identical elements are assigned the same reference number. The following embodiments are illustrative. While the following description refers to one or more embodiments of the present invention, this does not necessarily mean that each reference relates to the same embodiment or that features of the present invention apply only to a single embodiment. The present invention may also provide other embodiments by combining or substituting simple features of different embodiments. "Upstream" means that, in terms of the direction of gas circulation, one element is positioned before another element. On the other hand, "downstream" means that, with respect to the circulation direction of the gas being pumped, one element is positioned after another element.

[0021] Figure 1 shows a first exemplary embodiment of the turbomolecular vacuum pump 1 of the present invention. The turbomolecular vacuum pump 1 is equipped with a stator 2, within which a rotor 3 is configured to rotate at high speed, for example, at 90,000 revolutions per minute or more. In the exemplary embodiment shown in Figure 1, the turbomolecular vacuum pump 1 is a hybrid type and comprises a turbomolecular stage 4 and a molecular stage 5 located downstream of the turbomolecular stage 4 in the circulation direction of the pumped gas (direction of arrow F1 in Figure 1). The pumped gas enters the vacuum pump through the intake orifice 6, first passes through the turbomolecular stage 4, then through the molecular stage 5, and is discharged to the discharge orifice 7 of the turbomolecular vacuum pump 1. During operation, the discharge orifice 7 is connected to the primary pump transport means.

[0022] The annular inlet flange 8 surrounds, for example, the suction orifice 6 and connects the vacuum pump 1 to the housing where reduced pressure is required. In the turbo molecular stage 4, the rotor 3 has at least two stages of blades 9, and the stator 2 has at least one stage of fins 10. The blades 9 and fins 10 are arranged alternately in the axial direction along the rotation axis II of the rotor 3 within the turbo molecular stage 4. The rotor 3 has four or more stages of blades 9, such as between four and twelve stages (in the example shown in Figure 1, there are seven stages of blades). Each blade stage 9 of the rotor 3 comprises inclined blades that extend substantially radially from the hub 11 of the rotor 3, which are fixed to the drive shaft 12 of the vacuum pump 1, for example, by screws. These blades are regularly arranged around the hub 11.

[0023] Each fin stage 10 of the stator 2 is provided with a crown ring, from which multiple inclined fins, regularly distributed across the entire inner circumference, are formed to extend substantially radially. Each fin of the fin stage 10 of the stator 2 is located between two blades of a continuous blade stage 9 of the rotor 3. Each blade stage 9 of the rotor 3 and each fin stage 10 of the stator 2 are inclined to guide the pumped gas molecules to the molecular stage 5. The rotor 3 further includes an internal bowl 15 that protrudes from the underside of the rotor 3, coaxial with the rotation axis II. This internal bowl is positioned facing the shell 17 of the stator 2. During operation, the rotor 3 rotates within the stator 2 without the internal bowl 15 contacting the shell 17. The rotor 3 is further equipped with a Holweck skirt 13 downstream of at least two blade stages 9 in the molecular stage 5. This Holweck skirt is formed by a smooth cylinder that rotates in the helical groove 14 of the opposing stator 2. The helical groove 14 of the stator 2 allows for the compression of the pumped gas and its guidance to the discharge orifice 7. An internal bowl 15, located at the bottom of the rotor 3 and facing the shell 17 of the stator 2, is also formed inside the Holweck skirt 13.

[0024] The rotor 3 can be manufactured as a single piece (monoblock) or as an assembly of several parts. The rotor 3 is made of, for example, aluminum and / or nickel. The rotor 3 is fixed to a drive shaft 12, for example by screwing, which is rotationally driven by an internal motor 16 of the vacuum pump 1 within the stator 2. The motor 16 is located, for example, within the shell 17 of the stator 2, and the motor itself is located below the internal bowl 15 of the rotor 3, with its drive shaft 12 passing through the shell 17 of the stator 2. The rotor 3 is guided laterally and axially by magnetic or mechanical bearings 18a and 18b located within the stator 2, which support the drive shaft 12 of the rotor 3. For example, a first bearing 18a is located at the base of the shell 17 of the stator 2 to support and guide the first end of the drive shaft 12, and a second bearing 18b is located at the top of the shell 17 to support and guide the second end of the drive shaft 12.

[0025] The shell 17 of the stator 2 can house other electrical or electronic components, such as a position sensor or a sensor that indicates the presence of purge gas, as will be described later. The shell 17 is configured to be coolable in order to continuously cool the elements within the shell, particularly the bearings 18a, 18b, the motor 16, and other electrical or electronic components, so that they can operate. For this purpose, the vacuum pump 1 is equipped with a cooling device 19 configured to cool the shell 17 of the stator 2. This cooling device is, for example, housed within the stator 2 or the shell 17, or is in thermal contact with the shell 17 by a hydraulic circuit. The cooling device 19 can control the temperature of the shell 17 to a temperature of 75°C or lower, such as 70°C, by, for example, circulating water at ambient temperature.

[0026] The vacuum pump 1 is further equipped with a purge device 20, configured to inject a purge gas into the gap between the shell 17 of the stator 2 and the internal bowl 15 of the rotor 3. The purge gas is preferably air or nitrogen, but may be another neutral gas such as helium or argon. The flow rate of the purge gas is low, for example, 0.0845 Pa.m 3 / s (or 50 sccm) or less. The vacuum pump 1 can be provided with a sensor for detecting the presence of the purge gas injected by the purge device 20. The purge device 20 is configured to inject the purge gas, for example, into at least one of the bearings 18a, 18b that are located within the stator 2 and support and guide the drive shaft 12 of the rotor 3. As a result, the flow of the purge gas passes through at least one of the bearings 18a, 18b before exiting from the shell 17 of the stator 2 and circulating within the gap.

[0027] More specifically, according to an exemplary embodiment, the purge device 20 includes a duct 21 for introducing the purge gas into a cavity that receives the first bearing 18a that supports and guides the first end of the drive shaft 12. Furthermore, the cross-sectional area of the annular conductance C between the end of the rotor 3, here the annular end of the volute skirt 13, and the shell 17 of the stator 2 is 12 mm 2 / sccm or less, and the flow rate of the injected purge gas is, in international units, 12 mm 2 / 1.69×10 -3 Pa·m 3 / s. This is to limit the intrusion of the gas pumped into the gap between the shell 17 of the stator 2 and the inner bowl 15 of the rotor 3, and, as will become apparent later, to protect one or more surfaces with high emissivity between the inner bowl 15 of the rotor 3 and the shell 17 of the stator. Note that sccm is a unit of gas flow rate (standard cubic centimeters per minute at 101500 Pa, and in international units, 1 sccm = 1.69×10 -3 Pa·m 3 / s).

[0028] For example, when the purge flow rate is 50 sccm (0.0845 Pa·m 3 / s), the cross-sectional area of the conductance must be 600 mm 2 or less. Similarly, when the cross-sectional area of the conductance is 300 mm 2 , the flow rate of the injected purge gas is 25 sccm (42.25×10-3 Pa.m 3 It must be at least / s. The flow of the purge gas and its associated annular conductance form a barrier that limits the intrusion of the pumped gas into the underside of the rotor 3, thereby partially protecting the journal bearing elements of the turbomolecular vacuum pump 1, particularly the electrical connections, welds, and bearings 18a and 18b from aggressive pumped gases.

[0029] During operation, as schematically shown in the example in Figure 1, the purge gas passes through the first bearing 18a, rises along the drive shaft 12, passes through the second bearing 18b which supports and guides the second end of the drive shaft 12, exits from the shell 17 of the stator 2, circulates through the gap located between the shell 17 and the inner bowl 15, and then passes through the annular conductance C between the rotor 3 and the stator 2 under the Holweck skirt 13, and recombines with the pumped gas when the vacuum pump 1 is discharged (see arrow F2 in Figure 1). The turbomolecular vacuum pump 1 may be equipped with a heating device 22 for heating the stator 2, such as a heating resistance shell configured to heat the sleeve 24 of the stator 2 surrounding the rotor 3 to a set temperature of 130°C or higher, for example, 80°C. The surface of the inner bowl 15 of the rotor 3, positioned opposite the shell 17 of the coolable stator 2, exhibits a higher emissivity over at least a portion of the surface of the inner bowl 15 than the outer surface 25 of the rotor 3 that is in fluid contact with the pumped gas, while the outer surface 25 of the rotor 3 that is in fluid contact with the pumped gas exhibits a lower emissivity over at least a portion of the surface of the inner bowl 15 than the surface of the inner bowl 15 of the rotor 3.

[0030] As an alternative or additional measure, the surface of the coolable stator 2 shell 17 is positioned facing the internal bowl 15 of the rotor 3, and over at least a portion of the surface of the stator 2 shell 17, it exhibits a higher emissivity than the outer surface 25 of the rotor 3 that is in fluid contact with the pumped gas, and the outer surface 25 of the rotor 3 that is in fluid contact with the pumped gas exhibits a lower emissivity than the surface of the stator 2 shell 17 over at least a portion of the surface of the stator 2 shell 17. The emissivity of most of the surface of the inner bowl 15, for example, the entire surface of the inner bowl 15 excluding the centering surface, and / or the entire surface of the shell 17 of the stator 2, for example, the emissivity of most of the surface of the shell 17 of the stator 2 excluding the centering surface, is, for example, higher.

[0031] One or more high-emissivity surfaces exhibit an emissivity of 0.4 or higher, for example, 0.8 or higher. One or more surfaces that come into fluid contact with the gas being pumped exhibit an emissivity of less than 0.3, for example, 0.2, in the case of rotor 3 made of aluminum, nickel, or nickel-plated. The inside of the rotor 3, which has a highly emissivity surface, and only this inside, allows for radiative cooling of the rotor 3 by heat dissipation. The shell 17 of the stator 2 below the rotor 3, which also has a highly emissivity surface, allows for cooling of the rotor 3 by radiation from the shell 17, which is cooled itself. The heat flux is schematically represented by arrow F3 in Figure 1.

[0032] To prevent deposits from forming on the inner surface of the stator 2, the sleeve 24 of the stator 2 surrounding the rotor 3 can be heated. To avoid heating the rotor 3, heat exchange between the sleeve 24 and the rotor 3 is reduced on the low emissivity outer surface of the rotor 3. The shell 17 of the stator 2, which protrudes below the rotor 3, is cooled, protecting the electronic components and motor on the underside of the rotor 3. Heat exchange between the shell 17 and the rotor 3 is facilitated by the highly emissive surfaces of the inner bowl 15 of the rotor 3 and / or the shell 17 of the stator 2, in order to better cool the rotor 3. To significantly improve heat exchange, high emissivity surfaces can be prioritized in both the movable parts (internal bowl 15) and the fixed parts (shell 17) in areas that are not directly connected to the gas being pumped.

[0033] The outer surface 25 of the rotor 3, which is in fluid contact with the gas being pumped, can exhibit a low emissivity. In particular, this outer surface 25 of the rotor 3, which is in fluid contact with the gas being pumped, can be provided with a protective coating against corrosion, such as nickel plating. One or more high-emissivity surfaces of the internal bowl 15 of the rotor 3 and / or the shell 17 of the stator 2 are obtained by surface treatments such as anodizing, sandblasting, grooving, or texturing. For example, laser or soda blackening surface treatments are performed. Surface treatments of aluminum by anodizing, soda blackening, or laser offer the advantage of being able to obtain surfaces with an emissivity of more than 0.8 at a reasonable cost.

[0034] As an alternative or additional measure, one or more high-emissivity surfaces of the inner bowl 15 of the rotor 3 and / or the shell 17 of the stator 2 are obtained by coating deposition. This coating is a solvent-free paint-type coating such as a KEPLA-COAT® type plasma vapor deposition chemical coating or an epoxy polymer coating commonly referred to as "epoxy paint". The fact that only the surface of the inner bowl of the rotor 3 can have a high-emissivity epoxy polymer coating offers the advantage that the robustness of the coating is enhanced by the centrifugal pressing effect.

[0035] Preferably, the surfaces to be painted or coated are limited to surfaces parallel to the rotation axis II of the rotor 3, such as the inner bowl 15, and especially the cylindrical surface of the Holwek skirt 13, in order to prevent the paint or coating from peeling off due to centrifugal force. The thickness of the coating is, for example, between 30 μm and 100 μm. The coating or surface treatment may have a matte and / or dark appearance, preferably black or a shade of black. In particular, several surface treatments and / or coating layers can be provided to increase the emissivity of the rotor 3 and / or stator 2 within the gap. The coating or surface treatment is preferably solvent-free. The solvent should, in practice, be entirely formulated within the specific pumping device, and it is preferable not to use a solvent in the vacuum pump 1 in order to avoid the risk of backscattering into the space being pumped.

[0036] According to a first exemplary embodiment of the rotor 3, the first step of surface treatment is to perform an external surface treatment 25 on the rotor 3 to obtain a high emissivity surface of the rotor 3, excluding the centering surface, or to deposit a coating on the rotor 3, excluding the centering surface, to obtain a high emissivity surface of the rotor 3. The centering surface requires higher manufacturing precision because it allows the rotor 3 to be centered on the drive shaft 12 on the rotation axis II. Next, in the second step, the internal bowl 15 of the rotor 3 is masked and the external surface 25 of the rotor 3, which is intended to be in fluid contact with the pumped gas, is nickel-plated.

[0037] According to a second exemplary embodiment of the rotor 3, the surface treatment of the first portion 3a of the rotor 3 (see Figure 2), including the internal bowl 15 and the Holweck skirt 13, is performed to obtain a highly emissive surface of the first portion of the rotor 3, or a coating is deposited on the first portion of the rotor 3, including the internal bowl 15 and the Holweck skirt 13, thereby obtaining a highly emissive surface of the first portion of the rotor 3. Next, the surface of the first portion of the rotor 3, intended to be in fluid contact with the pumped gas, is nickel-plated, masking the internal bowl 15. Then, the first portion 3a of the rotor 3 is fixed to the nickel-plated second portion 3b of the rotor 3, including at least two stages of blades 9, for example, by screw fastening.

[0038] According to a third exemplary embodiment, the component forming the inner bowl 15 having a high emissivity surface is assembled, for example, by screwing or interlocking with a rotor body 23 (see Figure 3), which has a concave shape complementing the inner bowl 15 on one side and at least two blade stages 9 on the other. The component forming the inner bowl 15 having a high emissivity surface is made, for example, of anodized aluminum.

[0039] During operation, heat exchange between the stator 2 and the shell 17 is facilitated by one or more highly emissive surfaces beneath the rotor 3, which allow for radiative cooling of the rotor 3. These highly emissive surfaces are protected and therefore do not come into contact with potentially corrosive pump-carrying gases. This is done both by the purge gas circulating in the gap beneath the rotor 3 and by the annular conductance at the edges of the internal bowl 15. These highly emissive surfaces are protected both by the purge gas circulating in the gap beneath the rotor 3 and by the annular conductance at the edges of the rotor 3, thus preventing contact with potentially corrosive pump-carrying gases. The purge gas and annular conductance allow the highly emissive surfaces of the rotor 3 and / or stator 2 to be protected from potential attacks from pump-carrying gases that may penetrate beneath the rotor 3. Thus, only the protected surfaces are made highly emissive and encounter little to no potentially corrosive pump-carrying gases. The purge flow rate and low conductance allow for the relatively easy and inexpensive manufacture of high-emissivity surfaces, resulting in significant cost savings. For example, it has been found that the radiative cooling of the rotor 3, facilitated by the high-emissivity surface of the rotor 3 and the stator 2 below it, is combined with the flow of purge gas between the rotor 3 and the stator 2. This makes it possible to increase the flow rate of the pumped heavy gas to the shell 17 cooled to 70°C by 20-30%.

[0040] For example, and to better understand the present invention, the following symbols are used. Prs : Heat output radiated from rotor 3 to stator 2, T r : Rotor 3 temperature (K), T s :Temperature (K) of shell 17 of stator 2, ε r : Emissivity of the internal bowl 15 of rotor 3, ε s : Emissivity of shell 17 of stator 2, S sr : Opposing surfaces between the internal bowl 15 of rotor 3 and the shell 17 of stator 2. As a result, the output radiated from rotor 3 to stator 2 will be as follows: P1=S sr ·ε r ·σ·T r 4 σ = 5.67 × 10 -8 W·m -2 ·K -4 Stefan-Boltzmann constant (emission constant of a black body) The power reflected by stator 2 is as follows: P2=(1-ε s )·P1 The output radiated from stator 2 to rotor 3 is as follows: P3=S SR ·ε s ·σ·T s 4 The output reflected by rotor 3 is as follows: P4=(1-ε r )·P3 Therefore, the heat output transmitted from rotor 3 to stator 2 is as follows: P rs =P1-P2-P3+P4=S sr ·ε r ·ε s ·σ·(T r 4 -T s 4 ) Therefore, surface S sr 500cm 2If these values ​​are equal, the emissivity of the inner bowl 15 of the rotor 3 is 0.7, the emissivity of the shell 17 is 0.8, and when the temperature of the rotor 3 is 150°C and the temperature of the shell 17 is 70°C, the rotor 3 can transmit approximately 28W.

[0041] On the other hand, if the emissivity of shell 17 is 0.2 or less, the transmission output is 7.2W or less. As explained above, in order to increase the flow rate of the gas being pumped, the emissivity of the surface of the inner bowl 15 of the rotor 3 and the emissivity of the surface of the shell 17 of the stator 2 are maximized, thereby increasing the emissivity of the opposite radiating surface S on the underside of the rotor 3. sr It will be understood that it is possible to maximize this and increase the heat output that can be dissipated from rotor 3 by radiation.

[0042] Figure 4 also shows a second exemplary embodiment in which the vacuum pump 1 consists only of turbomolecules. This rotor 3 has at least two stages of blades 9 but does not have a Holweck skirt. In this example, the cross-sectional area of ​​the cyclic conductance C is constant over most of the height of the internal bowl 15. As described above, the surface of the inner bowl 15 of the rotor 3, which is positioned facing the shell 17 of the coolable stator 2, exhibits a higher emissivity than the outer surface 25 of the rotor 3, which is in fluid contact with the pumped gas, at least on a portion of the surface of the inner bowl 15. Alternatively or additionally, the surface of the coolable stator 2 shell 17, positioned facing the internal bowl 15 of the rotor 3, exhibits a higher emissivity over at least a portion of the surface of the stator 2 shell 17 than the outer surface 25 of the rotor 3, which is in fluid communication with the pumped gas.

[0043] During operation, as in the example described above, heat exchange between the stator 2 and the shell 17 is facilitated by the highly emissive surfaces on the underside of the rotor 3, thereby enhancing the radiative cooling of the rotor 3. These highly emissive surfaces are protected on the one hand by the purge gas circulating in the gap on the underside of the rotor 3, and on the other hand by the annular conductance at the edge of the internal bowl 15, and therefore are not potentially exposed to corrosive pumped gases. The purge gas and annular conductance make it possible to protect the highly emissive surfaces of the rotor 3 and / or stator 2 from potential attack by pumped gases that may penetrate the underside of the rotor 3. Thus, only the protected surfaces remain highly emissive and are exposed to little to no potentially corrosive pumped gases. [Explanation of symbols]

[0044] 1. Vacuum pump 2 staters 3 rotors 4 Turbo molecular stage 5 molecular stages 6. Inhalation orifice 7. Discharge Orifice 8. Annular inlet flange 9 blade stages 10 fin rows 11 Rotor hub 12 drive shafts 13 Holweck Skirt 14 Spiral groove 15 Inner bowl 17 Stator Shell 18a, 18b bearings 19 Cooling device 20 Purge device 21 Duct 22 Heating device 23 Rotor body 24 sleeves 25 Outer surface of the rotor II. Rotation axis

Claims

1. A turbomolecular vacuum pump (1) configured to transport gas from an intake orifice (6) to an exhaust orifice (7), The turbomolecular vacuum pump (1) comprises a stator (2), a rotor (3) configured to rotate within the stator (2), and a purge device (20). The stator (2) has at least one fin stage (10) and a shell (17) configured to allow cooling. The rotor (3) has at least two stages of blades (9) and an internal bowl (15), the blades (9) and fins (10) are arranged alternately in the axial direction along the rotation axis (I-I) of the rotor (3), the internal bowl (15) is coaxial with the rotation axis (I-I) and is positioned facing the shell (17) of the stator (2), The purge device (20) is configured to inject purge gas into the gap between the shell (17) of the stator (2) and the inner bowl (15) of the rotor (3), The inner surface of the inner bowl (15) of the rotor (3), which is positioned facing the coolable shell (17) of the stator (2), exhibits a high emissivity of 0.4 or more, which is higher than that of the outer surface (25) of the rotor (3) that is in fluid contact with the corrosive pumped gas. The outer surface (25) of the rotor (3) that is in fluid contact with the gas being pumped exhibits a low emissivity of less than 0.3, which is lower than the inner surface of the inner bowl (15) of the rotor (3). The high emissivity surface of the inner bowl (15) of the rotor (3) is obtained by surface treatment or coating deposition. A turbomolecular vacuum pump characterized in that the highly emissivity surface of the inner bowl (15) of the rotor (3) is protected on the one hand by the purge gas circulating in the gap below the rotor (3), and on the other hand by the annular conductance (c) of the end of the inner bowl (15), thus being protected from attack by the corrosive pumped gas.

2. A turbomolecular vacuum pump (1) configured to transport gas from an intake orifice (6) to an exhaust orifice (7), The turbomolecular vacuum pump (1) comprises a stator (2), a rotor (3) configured to rotate within the stator (2), and a purge device (20). The stator (2) has at least one fin stage (10) and a shell (17) configured to allow cooling. The rotor (3) has at least two stages of blades (9) and an internal bowl (15), the blades (9) and fins (10) are arranged alternately in the axial direction along the rotation axis (I-I) of the rotor (3), the internal bowl (15) is coaxial with the rotation axis (I-I) and is positioned facing the shell (17) of the stator (2), The purge device (20) is configured to inject purge gas into the gap between the shell (17) of the stator (2) and the inner bowl (15) of the rotor (3), The inner surface of the inner bowl (15) of the rotor (3), which is positioned facing the coolable shell (17) of the stator (2), exhibits a high emissivity of 0.4 or more, which is higher than that of the outer surface (25) of the rotor (3) that is in fluid contact with the corrosive pumped gas. The outer surface (25) of the rotor (3) that is in fluid contact with the gas being pumped exhibits a low emissivity of less than 0.3, which is lower than the inner surface of the inner bowl (15) of the rotor (3). The surface of the shell (17) of the stator (2), which is positioned facing the inner bowl (15) of the rotor (3), exhibits a high emissivity of 0.4 or more, which is higher than that of the outer surface (25) of the rotor (3) that is in fluid contact with the gas being pumped. The high emissivity surface of the inner bowl (15) of the rotor (3) and the high emissivity surface of the shell (17) of the stator (2) are obtained by surface treatment or coating deposition. A turbomolecular vacuum pump characterized in that the high emissivity surface of the inner bowl (15) of the rotor (3) and the high emissivity surface of the shell (17) of the stator (2) are protected on the one hand by the purge gas circulating in the gap below the rotor (3), and on the other hand by the annular conductance (c) of the end of the inner bowl (15), thus being protected from attack by the corrosive pumped gas.

3. A turbomolecular vacuum pump (1) configured to transport gas from an intake orifice (6) to an exhaust orifice (7), The turbomolecular vacuum pump (1) comprises a stator (2), a rotor (3) configured to rotate within the stator (2), and a purge device (20). The stator (2) comprises at least one fin stage (10), a shell (17) configured to be cooled by a cooling device (19), and a heating device (22) configured to heat the sleeve (24) of the stator (2) surrounding the rotor (3). The rotor (3) has at least two stages of blades (9) and an internal bowl (15), the blades (9) and fins (10) are arranged alternately in the axial direction along the rotation axis (I-I) of the rotor (3), the internal bowl (15) is coaxial with the rotation axis (I-I) and is positioned facing the shell (17) of the stator (2), The purge device (20) is configured to inject purge gas into the gap between the shell (17) of the stator (2) and the inner bowl (15) of the rotor (3), The inner surface of the inner bowl (15) of the rotor (3), which is positioned facing the coolable shell (17) of the stator (2), exhibits a high emissivity of 0.4 or more, which is higher than that of the outer surface (25) of the rotor (3) that is in fluid contact with the corrosive pumped gas. The outer surface (25) of the rotor (3) that is in fluid contact with the gas being pumped exhibits a low emissivity of less than 0.3, which is lower than the inner surface of the inner bowl (15) of the rotor (3), and the heat exchange between the sleeve (24) and the rotor (3) is reduced at the low emissivity outer surface (25) of the rotor (3) so as not to heat the rotor (3). The surface of the shell (17) of the stator (2), which is positioned facing the inner bowl (15) of the rotor (3), exhibits an emissivity of 0.4 or higher than that of the outer surface (25) of the rotor (3) which is in fluid contact with the gas being pumped. The high emissivity surface of the inner bowl (15) of the rotor (3) and the high emissivity surface of the shell (17) of the stator (2) are obtained by surface treatment or coating deposition. A turbomolecular vacuum pump characterized in that the high emissivity surface of the inner bowl (15) of the rotor (3) and the high emissivity surface of the shell (17) of the stator (2) are protected on the one hand by the purge gas circulating in the gap below the rotor (3), and on the other hand by the annular conductance (c) of the end of the inner bowl (15), thus being protected from attack by the corrosive pumped gas.

4. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 3, To limit the ingress of the pumped gas into the gap located between the shell (17) of the stator (2) and the inner bowl (15) of the rotor (3), and to protect one or more highly emissive surfaces located between the inner bowl (15) of the rotor (3) and the shell (17) of the stator (2), the cross-sectional area of ​​the annular conductance (c) between the edge of the inner bowl (15) of the rotor (3) and the shell (17) of the stator (2) is such that the flow rate of the injected purge gas is 12 mm ２ / 1.69 × 10 －３ Pa・m ３ / s (12mm) ２ A turbomolecular vacuum pump characterized by having a value of less than or equal to ( / sccm).

5. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 4, A turbomolecular vacuum pump characterized in that the outer surface (25) of the rotor (3), which is in fluid contact with the gas being pumped, has nickel plating to protect it from corrosion.

6. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 5, A turbomolecular vacuum pump characterized in that the high emissivity surfaces of the inner bowl (15) of the rotor (3) and / or the shell (17) of the stator (2) are obtained by a surface treatment of anodizing, sandblasting, grooving, or texturing.

7. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 5, A turbomolecular vacuum pump characterized in that the coating is deposited by plasma vapor deposition chemical coating or by deposition of a solvent-free paint-type coating.

8. In the turbomolecular vacuum pump (1) according to claim 6 or 7, A turbomolecular vacuum pump characterized in that the coating or surface treatment has a matte and / or dark appearance.

9. In the turbomolecular vacuum pump (1) according to any one of claims 6 to 8, A turbomolecular vacuum pump characterized in that the coating or surface treatment is a solvent-free treatment.

10. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 9, A turbomolecular vacuum pump characterized in that the purge device (20) is configured to inject the flow of the purge gas into at least one bearing (18a, 18b) that supports and guides the drive shaft (12) of the rotor (3), and the flow of the purge gas passes through at least one of the bearings (18a, 18b) before exiting the shell (17) of the stator (2).

11. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 10, A turbomolecular vacuum pump characterized by including a sensor that detects the presence of the purge gas injected by the purge device (20).

12. In the turbomolecular vacuum pump (1) according to claim 1 or 2, The system includes a heating device (22) configured to heat the sleeve (24) of the stator (2) that surrounds the rotor (3), A turbomolecular vacuum pump characterized in that, in order to prevent the rotor (3) from overheating, the heat exchange between the sleeve (24) and the rotor (3) is reduced at the low emissivity outer surface (25) of the rotor (3).

13. In the turbomolecular vacuum pump (1) according to any one of claims 1 to 12, The rotor (2) has a Holweck skirt (13) downstream of at least two stages of the blade stages (9), The Holweck skirt (13) is formed by a smooth cylinder configured to rotate the helical groove (14) on the opposite side of the stator (2) for pumping the gas. A turbomolecular vacuum pump characterized in that the internal bowl (15) positioned facing the shell (17) of the stator (2) is also formed by the interior of the Holweck skirt (13).

14. A method for manufacturing the rotor (3) of the turbomolecular vacuum pump (1) according to any one of claims 1 to 13, The treatment of the inner surface of the inner bowl (15) of the rotor (3) is carried out such that the surface treatment or coating deposition results in the high emissivity surface. A method for manufacturing a rotor for a turbomolecular vacuum pump, characterized in that the outer surface (25) of the rotor (3), which is intended to be in fluid contact with the gas being pumped, is nickel-plated by masking the inner bowl (15) of the rotor (3).

15. A method for manufacturing the rotor (3) of the turbomolecular vacuum pump (1) according to claim 13, The process includes a step of performing an inner surface treatment on the first portion of the rotor (3), including the inner bowl (15) and the Holweck skirt (13), to obtain a high-emissivity inner surface of the first portion of the rotor (3), or a step of depositing a coating on the inner surface of the first portion of the rotor (3), including the inner bowl (15) and the Holweck skirt (13), to obtain a high-emissivity inner surface of the first portion of the rotor (3), The outer surface of the first portion of the rotor (3), which is intended to be in fluid contact with the gas being pumped, is nickel-plated by masking the inner bowl (15). Next, a method for manufacturing a rotor for a turbomolecular vacuum pump, characterized in that the first portion of the rotor (3) is fixed to a second portion of the nickel-plated rotor (3) which includes at least two stages of blade stages (9).

16. A method for manufacturing the rotor (3) of the turbomolecular vacuum pump (1) according to any one of claims 1 to 12, A method for manufacturing a rotor for a turbomolecular vacuum pump, characterized in that the component forming the inner bowl (15) having a high emissivity surface has a concave shape on one side that complements the inner bowl (15), and on the other side has at least two stages of the blade stage (9).

Images