Vacuum pump

Description

[0001] The invention relates to a turbomolecular pump, with a rotor shaft rotating about a rotational axis during operation and with at least one rotor component attached to the rotor shaft.

[0002] The pumping action of such vacuum pumps results from the interaction of a pump-effective or pump-active area of ​​the rotor component with a pump-effective or pump-active area of ​​a respective stator component. A turbomolecular pump, for example, has several rotor disks as rotor components, each of which comprises several rotor blades as pump-effective areas and interacts with stator disks arranged relative to a pump housing. A Holweck pump comprises one or more Holweck sleeves that rotate during operation and are attached to a Holweck hub mounted on the rotor shaft. A Holweck sleeve interacts with one or more Holweck stators, wherein the cylindrical outer surface and / or the cylindrical inner surface of the Holweck sleeve constitutes the pump-effective area, which interacts with one or more Holweck grooves, each of which is designed as a pump-effective area on the respective Holweck stator.

[0003] Known turbomolecular pumps often have not only one or more turbomolecular pumping stages, but also one or more Holweck pumping stages arranged downstream of at least one turbomolecular pumping stage.

[0004] The pumping capacity of a vacuum pump is determined primarily by its (gas-dependent) pumping speed, which for a given gas depends essentially on the geometry of the rotor and stator components as well as on the rotational speed of the rotor components. The rotational speed is generally a fixed parameter for a given pump type, indicating the speed at which the pump can operate continuously under normal conditions. This speed is also referred to as the rated speed.

[0005] For any given pump type, however, it is not possible to arbitrarily increase the pumping capacity by simply increasing the rotational speed, as high speeds lead to increased stresses in the rotor component material and, due to higher gas friction, also to higher, unacceptable temperatures of the rotor components. Conditions must be avoided in which the rotor component material deforms beyond a tolerable level during operation and, in particular, begins to flow. Higher rotational speeds also increase the demands placed on any rolling bearing used to support the rotor shaft and its lubrication, especially on the lubricating oil used.Furthermore, the pumping capacity cannot simply be increased arbitrarily by increasing the diameter of the rotor and stator components, as this results in higher orbital speeds for the radially outer areas of the rotor components at the same rotational speeds, especially for the blade tips of the rotor blades of rotor disks.

[0006] The documents KR 101 758 033 B1 and EP 3 002 459 A1 describe rotor disks of known turbomolecular pumps.

[0007] These limitations make it difficult or impossible to increase the pumping capacity of existing vacuum pumps.

[0008] The purpose of the invention is to remedy this situation.

[0009] The solution to this problem is achieved in each case by the characteristics of the independent claims.

[0010] According to the invention, in a turbomolecular pump defined by claim 1 (hereinafter also referred to as embodiment 3) it is provided that the rotor disk has a rotor outer diameter DA, which is measured between two imaginary diametrically opposed blade ends, that the rotor disk has a flange outer diameter DB, which is measured between two diametrically opposed points of a radial outer surface of the flange, that the rotor disk has a base outer diameter DG, which is measured from blade base to blade base of two imaginary diametrically opposed rotor blades, wherein the ratio (DA - DG) / (DA - DB) is at least 0.94, preferably at least 0.95, and at most 0.97.

[0011] This concept, compared to conventional rotor discs, increases the proportion of the effective pumping area of ​​each rotor blade, measured from the blade base, relative to the blade length measured from the shoulder. This allows for a greater proportion of the effective pumping length of each rotor blade, thereby increasing the overall pumping capacity of the vacuum pump.

[0012] According to a preferred embodiment of the invention (hereinafter also referred to as embodiment 1), it is provided that at least one rotor component of the turbomolecular pump, which is either a rotor disk or a hollow section component, is made of an aluminum alloy comprising the following elements in weight %: Cu: 3.6 - 4.4 Mg: 1.2 - 1.4 Mn: 0.5 - 0.8 Zr: < 0.16 Ti: 0.01 - 0.05 Si < 0 , 21 Fe < 0 , 21 Zn < 0 , 26 other elements < 0.06, remainder aluminum.

[0013] This aluminum alloy will also be referred to simply as "the aluminum alloy" or as "the material according to the invention".

[0014] It was found that other geometries, higher rated speeds and higher rotor component temperatures are possible when those rotating components of a turbomolecular pump, which as a whole or of which at least relevant areas have a comparatively large radial distance from the axis of rotation of the rotor shaft, are made of the aforementioned aluminum alloy.

[0015] It may be provided that each rotor component of the turbomolecular pump is made of the material according to the invention. However, this is not mandatory. For example, it is possible that all rotor disks of a turbomolecular pump stage are made of the aluminum alloy, whereas the rotating components of one or more downstream Holweck pump stages are not made of this aluminum alloy.

[0016] It is also possible to manufacture only some rotor disks of a turbomolecular pump stage or only some rotating components of a Holweck pump stage from the aluminum alloy. For example, in a Holweck pump stage, the Holweck hub may be made of the aluminum alloy, but the Holweck sleeve(s) attached to the Holweck hub may not.

[0017] According to further aspects of the invention, it was found that certain geometries relating to one or more rotor components, namely certain dimensions and / or dimensional ratios as well as combinations thereof, enable a higher pumping performance.

[0018] According to an unclaimed aspect, in a vacuum pump defined by embodiment 2, it is particularly provided that the rotor disk has a rotor outer diameter DA, which is measured between two imaginary diametrically opposed blade ends, that the hollow hub has a hollow outer diameter DHW, which is measured between two diametrically opposed points of a radial outer surface of the hollow hub, and that the rotor outer diameter DA is larger than the hollow outer diameter DHW by a factor of at least 1.22, preferably at least 1.25, particularly preferably at least 1.30.

[0019] This concept involves a relative reduction in the diameter of the Holweck hub (and thus the diameter of a Holweck sleeve attached to the radially outer end of the Holweck hub) compared to the rotor disk's outer diameter. This reduction results in lower gas friction in the Holweck pump stage, which in turn allows for an increase in rotational speed and thus a higher blade tip velocity of the rotor disk. It was found that this concept results in an overall higher pumping capacity.

[0020] According to a further preferred embodiment of the invention, in a vacuum pump defined by embodiment 4, it is particularly provided that the rotor disk has a basic outer diameter DG, which is measured from blade base to blade base of two imaginary diametrically opposed rotor blades, that the rotor shaft has a shaft outer diameter DI, and that DG is larger than DI by a factor of at most 1.20, preferably at most 1.15, particularly preferably at most 1.10.

[0021] This concept leads to a relative reduction of the portion of the rotor disk – in relation to the radial direction – that has no or at most only a comparatively very low pumping efficiency.

[0022] The shaft outer diameter DI corresponds to the inner diameter of the flange of the rotor disk.

[0023] Preferably, the rotor discs are each a single-piece component, which is manufactured from a base material by milling and / or sawing.

[0024] Advantageous embodiments of the individual aspects of the invention are specified in the dependent claims, the following description, and the drawing. Unless otherwise stated, all embodiments relate to all aspects of the invention mentioned; that is, all aspects and embodiments can be combined with one another unless otherwise specified or combinations are clearly excluded.

[0025] In the turbomolecular pumps according to embodiments 2, 3 and 4, a particularly significant increase in pumping performance can be achieved if the respective rotor component(s) is / are made of the aluminum alloy. Under otherwise identical conditions, this material allows for higher rotational speeds without the problems mentioned in the introduction arising from excessive stresses in the rotor component material and / or excessive temperatures of the rotor components.

[0026] In some embodiments of the invention, it may be provided that the rotor disk has a rotor outer diameter DA that is greater than 5.0 cm, preferably in a range of 5.0 cm to 60 cm, wherein the rotor outer diameter DA is measured between two imaginary diametrically opposed blade ends.

[0027] According to some further developments of the invention, it can be provided that the Holweck hub has a Holweck outer diameter DHW which is measured between two diametrically opposed points of a radial outer surface of the Holweck hub, and wherein the rotor outer diameter DA is at least 135 mm and the Holweck outer diameter DHW is at least 108 mm or the rotor outer diameter DA is 120 mm and the Holweck outer diameter DHW is 99 mm.

[0028] According to some embodiments, the vacuum pump may include a second hollow hub having a hollow outer diameter DHW measured between two diametrically opposed points on a radial outer surface of the second hollow hub, wherein the hollow outer diameter DHW2 of the second hollow hub is at least 91 mm, and / or wherein the rotor outer diameter DA is larger than the hollow outer diameter DHW2 of the second hollow hub by a factor of at least 1.40, preferably at least 1.48.

[0029] The rotor shaft can be fitted with either a magnetic bearing or a hybrid bearing. If a hybrid bearing is used, a permanent magnet bearing is provided on the high-vacuum side and a rolling bearing on the fore-vacuum side. The design and arrangement of magnetic and rolling bearings for vacuum pump rotor shafts are generally known to those skilled in the art, so further discussion is unnecessary. Reference is also made to the following: Figs. 1 to 5 Reference is made to the described embodiment of a turbomolecular pump.

[0030] It has already been mentioned elsewhere that it is possible for all rotor disks of a turbomolecular pump stage to be made of the aluminum alloy defined by embodiment 1, but that this is not mandatory.

[0031] In other words, in some embodiments of the invention, several rotor disks may be mounted on the rotor shaft, with at least two rotor disks differing from one another in terms of the material from which they are made. It may be provided that at least one of the rotor disks is made of the aluminum alloy.

[0032] According to some further developments, it can be provided that one or more high-vacuum-side rotor disks are made of the aluminum alloy, whereas one or more forevacuum-side rotor disks are made of a different material. In other words, it is thus provided that the aluminum alloy according to the invention is not used for all rotor disks, but only for a high-vacuum-side portion of the rotor disks.

[0033] In some embodiments of the invention, it may be provided that the Holweck sleeve and / or the Holweck hub has or has an outer diameter DHH or DHW, which is measured between two diametrically opposed points of a radial outer surface of the Holweck sleeve or the Holweck hub and which is in the range of 5.0 cm to 60 cm.

[0034] According to some embodiments of the invention, the rotor component can have an outer diameter greater than 10 cm, preferably greater than 15 cm, and particularly preferably greater than 20 cm, wherein the outer diameter is measured between two diametrically opposed points, each located on a radial outer surface of the rotor component.

[0035] According to further embodiments, it can be provided that the collar of the rotor disk and / or the hollow hub has an axial height in the range of 3.0 mm to 5.9 mm, in particular up to 5.49 mm.

[0036] According to some embodiments of the invention, the rotor blades can each have a blade thickness in the range of 0.125 mm to 2.9 mm, if the blade thickness - viewed in the radial direction - is measured in the middle between the blade base and the blade tip.

[0037] In some embodiments, it may be provided that the rotor blades have a thickness of less than 9.8 mm, in particular less than 9.0 mm, at the base of the blades.

[0038] The blade thickness at any given point - viewed in the radial direction - is defined within the scope of the present disclosure as the smallest diameter of a cross-sectional surface of the rotor blade in a cross-sectional plane perpendicular to the radial direction.

[0039] The invention further relates to a method for operating a turbomolecular pump according to claim 12, wherein the turbomolecular pump is operated at a rotational speed of the rotor shaft such that the maximum permissible temperature of the rotor component is greater than 90°C, in particular greater than or equal to 98°C, and more preferably greater than or equal to 120°C. In particular, the rotor component is a rotor disk comprising a radially inner flange by which the rotor disk is mounted on the rotor shaft, and several rotor blades, each integrally connected to the flange and extending radially outwards from a blade base on the flange and having a free blade end radially outwards, or a hollow core component, in particular a hollow core hub or a hollow core sleeve.

[0040] A maximum permissible temperature of the rotor components exceeding 90°C enables the turbomolecular pump to operate at a higher rated speed than conventional turbomolecular pumps where the maximum permissible temperature of the rotor components is limited to 90°C. This higher speed allows for an increase in pumping capacity.

[0041] It was found that the aluminium alloy defined by embodiment 1 is a material which allows maximum permissible temperatures of more than 90°C for rotor components of turbomolecular pumps, in particular for rotor disks and / or hollow core components, without causing the aforementioned problems.

[0042] According to some embodiments of the method according to the invention, it can be provided that the turbomolecular pump is operated with a rotational speed of the rotor shaft such that the blade tip velocity of the rotor disk is more than 420 m / s, preferably more than 438 m / s, and particularly preferably more than 464 m / s.

[0043] In known turbomolecular pumps, the blade tip velocity of the rotor disk, i.e., the orbital speed of the blade tips during operation with the rotor shaft rotating at the rated speed, is limited to a maximum of 420 m / s. The higher rated speed allows the pumping capacity of the turbomolecular pump to be increased.

[0044] According to some embodiments of the invention, it can be provided that the turbomolecular pump is operated with a rotational speed of the rotor shaft that is more than 59,000 revolutions per minute, preferably more than 100,000 revolutions per minute, and particularly preferably more than 150,000 revolutions per minute.

[0045] In some embodiments of the invention, both of the turbomolecular pumps according to the individual aspects mentioned and of the method according to the invention, it may be provided that the rotor shaft is supported on the vacuum side by a rolling bearing lubricated with a synthetic oil having a kinematic viscosity in the range of 4.5 to 6.5 mm² / s at 100°C (viscosity measured according to ASTM D445-17a). A preferred example of such an oil is the oil designated "AeroShell Turbine Oil 560". For further properties and possible embodiments of a synthetic oil with the aforementioned viscosity properties, reference is made to European patent application EP 3 650 702 A1, published on May 13, 2020. .

[0046] The invention is described below by way of example with reference to the drawing. The drawing shows: Fig. 1 a perspective view of a turbomolecular pump, Fig. 2 a view of the underside of the turbomolecular pump of Fig. 1 , Fig. 3 a cross-section of the turbomolecular pump along the in Fig. 2 Section line AA shown, Fig. 4 a cross-sectional view of the turbomolecular pump along the in Fig. 2 Section line BB, Fig. 5 shows a cross-sectional view of the turbomolecular pump along the line shown in Fig. 2 The section line CC shown, Fig. 6 a section through a part of a turbomolecular pump to illustrate a dimensional ratio, Fig. 7 a sectional view of a rotor disk mounted on a rotor shaft to illustrate dimensions or dimensional ratios according to the invention, and Fig. 8 a section through a rotor blade to illustrate a dimension according to the invention.

[0047] The in Fig. 1The turbomolecular pump 111 shown comprises a pump inlet 115 surrounded by an inlet flange 113, to which a receiver (not shown) can be connected in a manner known per se. The gas from the receiver can be drawn out of the receiver via the pump inlet 115 and conveyed through the pump to a pump outlet 117, to which a backing pump, such as a rotary vane pump, can be connected.

[0048] The inlet flange 113 forms a Fig. 1 The upper end of the housing 119 of the vacuum pump 111. The housing 119 comprises a lower part 121, to which an electronics housing 123 is attached laterally. The electronics housing 123 contains electrical and / or electronic components of the vacuum pump 111, e.g., for operating an electric motor 125 located in the vacuum pump (see also Fig. 3The electronics housing 123 has several connections 127 for accessories. In addition, a data interface 129, e.g. according to the RS485 standard, and a power supply connection 131 are located on the electronics housing 123.

[0049] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0050] The housing 119 of the turbomolecular pump 111 has a flood inlet 133, in particular in the form of a flood valve, through which the vacuum pump 111 can be flooded. In the area of ​​the lower part 121, a purge gas connection 135, also referred to as a purge gas connection, is also arranged, through which purge gas can be supplied to protect the electric motor 125 (see e.g. Fig. 3The gas pumped by the pump can be introduced into the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111. Two coolant connections 139 are also arranged in the lower part 121, one of which serves as an inlet and the other as an outlet for coolant that can be directed into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) are operated exclusively with air cooling.

[0051] The lower side 141 of the vacuum pump can serve as a base, allowing the vacuum pump 111 to be operated standing upright on its underside 141. Alternatively, the vacuum pump 111 can be attached to a receiver via the inlet flange 113 and thus operated in a suspended position. Furthermore, the vacuum pump 111 can be designed to operate even when oriented differently than described. Fig. 1 As shown. It is also possible to implement embodiments of the vacuum pump in which the underside 141 can be arranged facing sideways or upwards instead of downwards. In principle, any angle is possible.

[0052] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in a standing position.

[0053] On the underside 141, which is in Fig. 2As shown, various screws 143 are arranged, by means of which components of the vacuum pump, not further specified here, are fastened to one another. For example, a bearing cover 145 is attached to the underside 141.

[0054] Mounting holes 147 are also arranged on the underside 141, via which the pump 111 can be attached to a support surface, for example. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0055] In the Figures 2 to 5 A coolant line 148 is shown, in which the coolant introduced and removed via the coolant connections 139 can circulate.

[0056] Like the sectional views of the Figures 3 to 5 As shown, the vacuum pump comprises several process gas pumping stages for conveying the process gas present at the pump inlet 115 to the pump outlet 117.

[0057] A rotor 149 is arranged in the housing 119, which has a rotor shaft 153 rotatable about a rotation axis 151.

[0058] The turbomolecular pump 111 comprises several turbomolecular pump stages connected in series to provide pumping action. These stages have several radial rotor disks 155 attached to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and fixed in the housing 119. Each rotor disk 155 and an adjacent stator disk 157 form a turbomolecular pump stage. The stator disks 157 are held at a desired axial distance from each other by spacer rings 159.

[0059] The vacuum pump also includes Holweck pump stages arranged radially within one another and connected in series to effectively pump the pump. Other turbomolecular vacuum pumps exist (not shown) that do not have Holweck pump stages.

[0060] The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical Holweck rotor sleeves 163, 165 attached to and supported by the rotor hub 161, which are oriented coaxially to the axis of rotation 151 and nested one inside the other in the radial direction. Furthermore, two cylindrical Holweck stator sleeves 167, 169 are provided, which are also oriented coaxially to the axis of rotation 151 and nested one inside the other in the radial direction.

[0061] The pump-active surfaces of the Holweck pump stages are formed by the outer surfaces, i.e., the radial inner and / or outer surfaces, of the Holweck rotor sleeves 163, 165 and the Holweck stator sleeves 167, 169. The radial inner surface of the outer Holweck stator sleeve 167 faces the radial outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together they form the first Holweck pump stage following the turbomolecular pumps. The radial inner surface of the outer Holweck rotor sleeve 163 faces the radial outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together they form a second Holweck pump stage. The radial inner surface of the inner Holweck stator sleeve 169 lies opposite the radial outer surface of the inner Holweck rotor sleeve 165, forming a radial Holweck gap 175, and together they form the third Holweck pumping stage.

[0062] At the lower end of the Holweck rotor sleeve 163, a radially extending channel can be provided, through which the radially outer Holweck slot 171 is connected to the central Holweck slot 173. Furthermore, a radially extending channel can be provided at the upper end of the inner Holweck stator sleeve 169, through which the central Holweck slot 173 is connected to the radially inner Holweck slot 175. This connects the nested Holweck pump stages in series. A connecting channel 179 to the outlet 117 can also be provided at the lower end of the radially inner Holweck rotor sleeve 165.

[0063] The aforementioned pump-active surfaces of the Holweck stator sleeves 167, 169 each have several Holweck grooves spiraling around the axis of rotation 151 in the axial direction, while the opposite outer surfaces of the Holweck rotor sleeves 163, 165 are smooth and drive the gas forward in the Holweck grooves for the operation of the vacuum pump 111.

[0064] For the rotatable mounting of the rotor shaft 153, a rolling bearing 181 is provided in the area of ​​the pump outlet 117 and a permanent magnet bearing 183 is provided in the area of ​​the pump inlet 115.

[0065] In the area of ​​the rolling bearing 181, a conical injection nut 185 with an outer diameter increasing towards the rolling bearing 181 is provided on the rotor shaft 153. The injection nut 185 is in sliding contact with at least one wiper of a fluid reservoir. In other existing turbomolecular vacuum pumps (not shown), an injection screw may be provided instead of an injection nut. Since different designs are thus possible, the term "injection tip" is also used in this context.

[0066] The operating fluid reservoir comprises several stacked absorbent discs 187, which are impregnated with an operating fluid for the rolling bearing 181, e.g. with a lubricant.

[0067] During operation of the vacuum pump 111, the operating fluid is transferred by capillary action from the fluid reservoir via the wiper to the rotating injection nut 185 and, as a result of centrifugal force, is conveyed along the injection nut 185 in the direction of the increasing outer diameter of the injection nut 185 towards the rolling bearing 181, where it performs, for example, a lubricating function. The rolling bearing 181 and the fluid reservoir are enclosed in the vacuum pump by a trough-shaped insert 189 and the bearing cover 145.

[0068] The permanent magnet bearing 183 comprises a rotor-side bearing half 191 and a stator-side bearing half 193, each containing a ring stack of several axially stacked permanent magnet rings 195, 197. The ring magnets 195, 197 face each other, forming a radial bearing gap 199, with the rotor-side ring magnets 195 arranged radially outside and the stator-side ring magnets 197 radially inside. The magnetic field present in the bearing gap 199 induces magnetic repulsion forces between the ring magnets 195, 197, which result in the radial support of the rotor shaft 153. The rotor-side ring magnets 195 are supported by a carrier section 201 of the rotor shaft 153, which radially surrounds the ring magnets 195 on the outside.The stator-side ring magnets 197 are supported by a stator-side support section 203, which extends through the ring magnets 197 and is suspended from radial struts 205 of the housing 119. Parallel to the axis of rotation 151, the rotor-side ring magnets 195 are fixed by a cover element 207 coupled to the support section 201. The stator-side ring magnets 197 are fixed parallel to the axis of rotation 151 in one direction by a retaining ring 209 connected to the support section 203 and a retaining ring 211 also connected to the support section 203. A disc spring 213 may also be provided between the retaining ring 211 and the ring magnets 197.

[0069] Within the magnetic bearing, an emergency or catch bearing 215 is provided, which runs freely without contact during normal operation of the vacuum pump 111 and only engages when there is excessive radial deflection of the rotor 149 relative to the stator, in order to form a radial stop for the rotor 149 and thus prevent a collision between the rotor-side and stator-side structures. The catch bearing 215 is designed as an unlubricated rolling bearing and forms a radial gap with the rotor 149 and / or the stator, which causes the catch bearing 215 to be disengaged during normal pump operation. The radial deflection at which the catch bearing 215 engages is dimensioned to be large enough so that the catch bearing 215 does not engage during normal operation of the vacuum pump, and simultaneously small enough to prevent a collision between the rotor-side and stator-side structures under all circumstances.

[0070] The vacuum pump 111 comprises the electric motor 125 for rotating the rotor 149. The armature of the electric motor 125 is formed by the rotor 149, whose rotor shaft 153 extends through the motor stator 217. A permanent magnet arrangement can be arranged radially on the outside or embedded in the section of the rotor shaft 153 extending through the motor stator 217. A space 219 is arranged between the motor stator 217 and the section of the rotor 149 extending through the motor stator 217. This space comprises a radial motor gap through which the motor stator 217 and the permanent magnet arrangement can magnetically influence each other to transmit the drive torque.

[0071] The motor stator 217 is fixed in the housing within the motor compartment 137 provided for the electric motor 125. A purge gas, also known as a sealing gas, which can be, for example, air or nitrogen, can enter the motor compartment 137 via the purge gas connection 135. This purge gas protects the electric motor 125 from process gas, e.g., from corrosive components of the process gas. The motor compartment 137 can also be evacuated via the pump outlet 117, meaning that the vacuum pressure in the motor compartment 137 is at least approximately equal to that produced by the backing pump connected to the pump outlet 117.

[0072] Between the rotor hub 161 and a wall 221 bounding the engine compartment 137, a so-called labyrinth seal 223, which is known per se, can also be provided, in particular to achieve a better seal of the engine compartment 217 against the radially outside Holweck pump stages.

[0073] The following will be based on the Figs. 6 to 8 Individual aspects and embodiments, in particular certain dimensions or dimensional ratios, of a vacuum pump according to the invention are explained, which is used in a turbomolecular pump as previously described in the Figs. 1 to 5 It has been described, but may have been realized.

[0074] In other words, a turbomolecular pump, as described by the Figs. 1 to 5 as described above, be designed in a manner according to the invention and in particular have one or more of the dimensions and / or one or more of the dimensional ratios as described above. Figs. 6 to 8 will be explained. The following will serve this purpose: Figs. 6 to 8 These figures are merely for illustrating dimensions and proportions and are therefore not to scale.

[0075] The turbomolecular pump according to Fig. 6The system comprises a turbomolecular pumping stage and a Holweck pumping stage. Several rotor disks 15 are mounted on a rotor shaft 13, which rotates about a rotary axis 11 during operation and is supported on the forevacuum side in a rolling bearing 37. The rolling bearing can be lubricated by a synthetic oil, as described in the introductory part of this disclosure.

[0076] A hollow shaft hub 17 is also attached to the rotor shaft 13, which carries a cylindrical hollow shaft sleeve 18 radially on its outer surface. The radial outer surface of the hollow shaft hub 17 lies on the same radius as the radial outer surface of the hollow shaft sleeve 18, namely on a radius of 1 / 2 * DHW, i.e., the outer diameter of the hollow shaft hub 17 is DHW.

[0077] The radially outer ends 25 of the rotor blades 21 lie on a radius of 1 / 2 * DA, i.e. the rotor disks 15 have an outer diameter DA.

[0078] As explained in the introductory part of the present disclosure, according to an unclaimed embodiment, the DA / DHW ratio is at least 1.22.

[0079] To achieve a pumping effect, the rotor blades 21 of a respective rotor disk 15 interact with stator blades of a respective stator disk 29. The stator disks 29 are mounted within a housing 27 of the turbomolecular pump in a manner generally known to those skilled in the art. To achieve a pumping effect, the Holweck sleeve 18 interacts with a radially outer Holweck stator 31 and a radially inner Holweck stator 33, each of which is provided with a Holweck groove arrangement facing the respective outer surface of the Holweck sleeve 18. Such a configuration of individual Holweck pump stages arranged one behind the other in the flow direction of the gas to be pumped, each comprising a Holweck stator and an opposing outer surface of a Holweck sleeve, and also referred to as radially nested or interleaved Holweck stages, is generally known to those skilled in the art.

[0080] In a further embodiment of this invention, the rotor disks 15 and the Holweck hub 17 can be made of the aluminum alloy. It is also possible, in principle, to manufacture the Holweck sleeve 18 from this aluminum alloy. Alternatively, the Holweck sleeve 18 can be made of a different material, for example, a carbon fiber reinforced plastic (CFRP), such as is generally known to those skilled in the art for the manufacture of Holweck sleeves.

[0081] Fig. 7 Figure 1 shows a rotor disk 15 mounted on a rotor shaft 13 of a turbomolecular pump. The rotor shaft 13 carries a high-vacuum magnetic bearing 35, of which in Fig. 7Two permanent magnet rings are shown. The high-vacuum magnetic bearing of a rotor shaft 13 of a turbomolecular pump is generally known to those skilled in the art, so that it need not be discussed in detail here. In this regard, reference is also made to the description of a turbomolecular pump based on the Figs. 1 to 5 referred.

[0082] The rotor disk 15 is a single-piece component manufactured from a base material by milling and / or sawing. This material is preferably an aluminum alloy. However, this material is not mandatory for the rotor disk 15. The dimensions and dimensional ratios described in more detail below can also be implemented on rotor disks 15 that are not made of this aluminum alloy.

[0083] The rotor disk 15 comprises a radially inner, hollow cylindrical collar 19, by means of which the rotor disk 15 is mounted on the rotor shaft 13. The rotor disk 15 also has a plurality of rotor blades 21, each integrally connected to the collar 19. Each blade extends radially outwards from a blade base 23 on the collar 19 and has a free blade end 25 at its outermost radial end. Each blade base 23 lies on a larger radius – relative to the central axis of the hollow cylindrical collar 19, which coincides with the axis of rotation 11 of the rotor shaft 13 when mounted on the rotor shaft 13 – than the radial outer surface of the collar 19.The outer diameter DB of the bund 19, which is measured between two diametrically opposed points of the radial outer surface of the bund 19, is therefore smaller than the base outer diameter DG, which is measured from blade base 23 to blade base 23 of two imaginary diametrically opposed rotor blades 21.

[0084] Furthermore, the rotor disk 15 has a rotor outer diameter DA, which is measured between two imaginary diametrically opposed blade ends 25.

[0085] The rotor shaft 13 has a shaft outer diameter DI which corresponds to the inner diameter of the collar 19 of the rotor disk 15.

[0086] As explained in the introduction, the radial length of each rotor blade 21, measured from the base 23 to the end 25, represents the pumping-effective portion of the total length of the rotor blade 21, which is measured from the collar 19 to the end 25.

[0087] According to the invention, the ratio (DA - DG) / (DA - DB) is at least 0.94, preferably at least 0.95, particularly preferably 0.97.

[0088] Rotor discs 15 with such a dimensional ratio can be operated at relatively high speeds, especially when they are made of the aluminum alloy. This leads to a particularly pronounced increase in the pumping capacity of the vacuum pump in question.

[0089] According to one embodiment of the invention, in a turbomolecular pump according to the invention, the base outer diameter DG is larger than the shaft outer diameter DI by a factor of at most 1.20, preferably at most 1.15, and particularly preferably at most 1.10. As already mentioned, the shaft outer diameter DI corresponds to the inner diameter of the collar 19 of the rotor disk 15. With respect to the outer diameter DI of the rotor shaft 13, the collar 19 of the rotor disk 15 according to the invention is therefore comparatively thin.

[0090] Rotor disks 15 with a flange 19 of such dimensions can then be operated at relatively high speeds if they are made of the aluminium alloy.

[0091] The axial height h of the collar 19 of the rotor disk 15 is preferably in a range of 3.0 mm to 5.9 mm, in particular up to 5.49 mm.

[0092] Preferred designs of the rotor blades 21 relate to their blade thickness. Fig. 8This illustrates how the blade thickness is defined within the scope of the present disclosure. Accordingly, at any radial location of a rotor blade 21, the blade thickness dG is the smallest diameter of a cross-sectional area of ​​the rotor blade 21 obtained at that radial location by a cut perpendicular to the radial direction through the rotor blade 21.

[0093] In a preferred embodiment, the blade thickness dG at the blade base is 23 (see Fig. 7 ) less than 9.8 mm, in particular less than 9.0 mm.

[0094] The blade thickness dG is preferably in the range of 0.125 mm to 2.9 mm in the midway between the blade base 23 and the blade end 25 (viewed in the radial direction).

[0095] Rotor disks 15, whose rotor blades 21 have the specified blade thickness dG at one or both of these radial points, can be operated at comparatively high speeds if the rotor disks 15 are made of the aluminum alloy. Reference symbol list

[0096] 11 Shaft of rotation 13 Rotor shaft 15 Rotor disc 17 Hollow hub 18 Hollow sleeve 19 Collar 21 Rotor blade 23 Blade base 25 Blade end 27 Housing 29 Stator disc 31 Hollow stator 33 Hollow stator 35 Magnetic bearing 37 Rolling bearing DHH Outer diameter Holweck sleeve DHW Outer diameter Holweck hub DI Shaft outer diameter DA Rotor outer diameter DBB Flange outer diameter DG Base outer diameter dG Rotor blade thickness h Axial height

Claims

1. A turbomolecular pump, comprising a rotor shaft (13) which rotates about an axis of rotation (11) during operation, and at least one rotor disc (15) which is fastened to the rotor shaft (13) and which comprises a radially inwardly disposed collar (19), via which the rotor disc (15) is fastened to the rotor shaft (13), and a plurality of rotor blades (21) which are each integrally connected to the collar (19), which each extend radially outwardly, starting from a blade base (23) at the collar (19), and which have a free blade end (25) radially at the outside, wherein the rotor disc (15) has a rotor outer diameter DA which is measured between two imaginary blade ends (25) disposed diametrically opposite one another, wherein the rotor disc (15) has a collar outer diameter DB which is measured between two points of a radial outer surface of the collar (19) that are disposed diametrically opposite one another, wherein the rotor disc (15) has a base outer diameter DG which is measured from blade base (23) to blade base (23) of two imaginary rotor blades (21) disposed diametrically opposite one another, characterized in that the ratio (DA - DG) / (DA - DB) is at least 0.94, preferably at least 0.95, and at most 0.97.

2. A turbomolecular pump according to claim 1, wherein the rotor shaft (13) has a shaft outer diameter DI, and wherein DG is greater than DI by a factor of at most 1.20, preferably of at most 1.15, particularly preferably of at most 1.10.

3. A turbomolecular pump according to claim 1 or 2, wherein the turbomolecular pump comprises one or more Holweck pump stages having at least one Holweck sleeve (18) which rotates during operation and which is attached to a Holweck hub (17) fastened to the rotor shaft (13).

4. A turbomolecular pump according to any one of the claims 1 to 3, wherein the rotor disc (15) is made of an aluminum alloy, or according to claim 3, wherein the rotor disc (15) and / or the Holweck hub (17) and / or the Holweck sleeve (18) is / are made of an aluminum alloy, wherein the aluminum alloy has the following composition in weight percent: Cu: 3.6 - 4.4 Mg: 1.2 - 1.4 Mn: 0.5 - 0.8 Zr: < 0.16 Ti: 0.01 - 0.05 Si < 0.21 Fe < 0.21 Zn < 0.26 other elements < 0.06, the remainder being aluminum.

5. A turbomolecular pump according to any one of the preceding claims, wherein the rotor outer diameter DA is greater than 5.0 cm, preferably lies in a range from 5.0 cm to 60 cm.

6. A turbomolecular pump according to claim 3 or according to one of the claims 4 or 5, when directly or indirectly referring back to claim 3, wherein the Holweck hub (17) has a Holweck outer diameter DHW which is measured between two points of a radial outer surface of the Holweck hub (17) that are disposed diametrically opposite one another, and wherein the rotor outer diameter DA is at least 135 mm and the Holweck outer diameter DHW is at least 108 mm, or wherein the rotor outer diameter DA is 120 mm and the Holweck outer diameter DHW is 99 mm.

7. A turbomolecular pump according to claim 3 or according to any one of the claims 4 to 6, when directly or indirectly referring back to claim 3, wherein the turbomolecular pump comprises a second Holweck hub that has a Holweck outer diameter DHW2 which is measured between two points of a radial outer surface of the second Holweck hub that are disposed diametrically opposite one another, wherein the Holweck outer diameter DHW2 of the second Holweck hub is at least 91 mm, and / or wherein the rotor outer diameter DA is greater than the Holweck outer diameter DHW2 of the second Holweck hub by a factor of at least 1.40, preferably of at least 1.48.

8. A turbomolecular pump according to any one of the preceding claims, wherein the rotor shaft (13) has a magnetic support or a hybrid support, namely a permanent magnet bearing (35) at the high-vacuum side and a rolling element bearing (37) at the fore-vacuum side.

9. A turbomolecular pump according to any one of the preceding claims, wherein a plurality of rotor discs (15) are fastened to the rotor shaft (13), wherein at least two rotor discs (15) differ from one another in terms of the material from which they are made, in particular wherein at least one of the rotor discs (15) is made of the aluminum alloy.

10. A turbomolecular pump according to claim 3 or according to any one of the claims 4 to 9, when directly or indirectly referring back to claim 3, wherein the Holweck sleeve (18) and / or the Holweck hub (17) has or have an outer diameter DHH or DHW, respectively, which is measured between two points of a radial outer surface of the Holweck sleeve (18) or the Holweck hub (17) that are disposed diametrically opposite one another and which lies in a range from 5.0 cm to 60 cm.

11. A turbomolecular pump according to any one of the preceding claims, wherein the rotor component (15, 17, 18) has an outer diameter greater than 10 cm, preferably greater than 15 cm, in particular preferably greater than 20 cm, wherein the outer diameter is measured between two points which are disposed diametrically opposite one another and which each lie on a radial outer surface of the rotor component (15, 17, 18).

12. A method for operating a turbomolecular pump according to claim 4 or according to any one of the claims 5 to 11, when directly or indirectly referring back to claim 4, wherein, in the method, the turbomolecular pump is operated at a rotational speed of the rotor shaft (13) such that the maximum permissible temperature of the rotor component (15, 17, 18) is greater than 90°C, in particular greater than or equal to 98°C, particularly preferably greater than or equal to 120°C.

13. A method according to claim 12, wherein the turbomolecular pump is operated at a rotational speed of the rotor shaft (13) such that the blade end speed of the rotor disc (15) is greater than 420 m / s, preferably greater than 438 m / s, preferably greater than 464 m / s.

14. A method according to claim 12 or 13, wherein the turbomolecular pump is operated at a rotational speed of the rotor shaft (13) which amounts to more than 59,000 revolutions per minute, preferably more than 100,000 revolutions per minute, particularly preferably more than 150,000 revolutions per minute.

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