VACUUM PUMP

Description

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

[0002] The pumping action of such vacuum pumps results from the interaction of a pumping-effective or pump-active region of the rotor component with a pumping-effective or pump-active region 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 pumping-effective regions and interacts with stator disks arranged relative to a housing of the pump. A Holweck pump comprises one or more Holweck sleeves that rotate during operation and are attached to a Holweck hub that is fastened to 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 represents the pumping-effective region, which interacts with one or more Holweck grooves, each of which is designed as a pumping-effective region on the respective Holweck stator.

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

[0004] The pumping performance of a vacuum pump is determined primarily by its (gas-dependent) pumping speed, which, for a given gas, essentially depends on the geometry of the rotor and stator components as well as the speed of the rotor components. The speed is usually a fixed parameter for a particular pump type, indicating the speed at which the pump can be continuously operated during normal operation. This speed is also referred to below as the nominal speed.

[0005] WO 2021 / 245345 A1 describes the use of an aluminum alloy composed, in weight percent, of 3.6-4.4% Cu, 1.2-1.4% Mg, 0.5-0.8% Mn, ≤0.15% Zr, 0.01-0.05% Ti, ≤0.20% Si, ≤0.20% Fe, ≤0.25% Zn, and <0.05% other elements, with the remainder being aluminum. DE 103 54 204 A1 and EP 4 006 349 A1 disclose a molecular pump in which the outer diameter of the blade ring of the turbo intake stage is larger than the outer diameter of the rotor on the intake side of the compressor stage designed as a Holweck pump.

[0006] However, for a particular pump type, it is not possible to arbitrarily increase the pumping capacity by increasing the speed, as high speeds lead to increased stresses in the material of the rotor components and, due to the increased gas friction, also to higher, unacceptable temperatures of the rotor components. Conditions must be avoided in which the material of the rotor components deforms beyond a tolerable level during operation and, in particular, begins to flow. Higher speeds also increase the demands on any rolling bearing used for the rotor shaft support and its lubrication, particularly the lubricating oil used for this purpose.Also, the pumping power cannot be increased arbitrarily simply by increasing the diameter of the rotor and stator components, since this results in higher orbital speeds for the radially outer regions of the rotor components, in particular for the blade ends of the rotor blades of rotor disks, at the same rotational speeds.

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

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

[0009] This problem is solved by the features of the independent claims.

[0010] According to a first aspect of the invention, it is provided that the at least one rotor component of the vacuum pump is a rotor disk, wherein the rotor disk has a rotor outer diameter DA, which is measured between two imaginary diametrically opposed blade ends, 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 the rotor outer diameter DA is larger than the Holweck outer diameter DHW by a factor of at least 1.22, preferably at least 1.25, particularly preferably at least 1.30, and wherein the at least one rotor disk is made of an aluminum alloy having the following elements 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, balance aluminum.

[0011] This aluminum alloy is also referred to hereinafter simply as "the aluminum alloy" or as "the material according to the invention".

[0012] It was found that other geometries, higher rated speeds and higher rotor component temperatures are possible if those rotating components of a vacuum 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 above-mentioned aluminum alloy.

[0013] It can be provided that each rotor component of the vacuum pump is made of the material according to the invention. However, this is not mandatory. For example, it is possible for all rotor disks of a turbomolecular pump stage to be made of the aluminum alloy, whereas the rotating components of one or more downstream Holweck pump stages are not made of this aluminum alloy.

[0014] It is also possible to manufacture only some of the rotor disks of a turbomolecular pump stage or only some of the 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 or sleeves attached to the Holweck hub may not be.

[0015] It has been found that certain geometries concerning one or more rotor components, namely certain dimensions and / or dimensional ratios and combinations thereof, enable higher pumping performance.

[0016] According to the invention, in a vacuum pump as defined by independent claim 1, 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 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 that the rotor outer diameter DA is larger than the Holweck outer diameter DHW by a factor of at least 1.22, preferably of at least 1.25, particularly preferably of at least 1.30.

[0017] 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 outer diameter of the rotor disk. This reduction results in lower gas friction in the Holweck pumping stage, which in turn enables an increase in rotational speed and thus a higher blade end speed of the rotor disk. This concept has been found to result in higher overall pumping performance.

[0018] According to a further aspect not according to the invention, in a vacuum pump it is provided in particular 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 collar outer diameter DB which is measured between two diametrically opposed points of a radial outer surface of the collar, 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, and that the difference DA - DG is greater than the difference DA - DB by a factor of at least 0.94, preferably of at least 0.95, particularly preferably of at least 0.97.

[0019] Compared to conventional rotor disks, this concept enlarges the proportion of the effective pumping area of ​​each rotor blade, measured from the blade base, to the blade length measured from the flange. This allows the proportion of the effective pumping length of each rotor blade to be increased, thus increasing the overall pumping performance of the vacuum pump.

[0020] According to a further aspect not according to the invention, it is provided in particular in a vacuum pump 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 greater than DI by a factor of at most 1.20, preferably of at most 1.15, particularly preferably of at most 1.10.

[0021] This concept leads to a relative reduction of that part of the rotor disk - related to the radial direction - which 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 collar of the rotor disc.

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

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

[0025] In the vacuum pump according to the invention, a particularly significant increase in pumping performance can be achieved by manufacturing the respective rotor component(s) from the aluminum alloy. This material allows for higher speeds under otherwise identical conditions without causing the problems mentioned in the introduction due to excessive stresses in the material of the rotor components and / or excessive temperatures of the rotor components.

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

[0027] According to some developments of the invention, it can be provided that the rotor disk has a rotor outer diameter DA which is measured between two imaginary diametrically opposite blade ends, wherein the Holweck hub has a Holweck outer diameter DHW which is measured between two diametrically opposite 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, according to an embodiment which does not fall within the scope of the claims, the rotor outer diameter DA is 120 mm and the Holweck outer diameter DHW is 99 mm.

[0028] According to some embodiments, it can be provided that the rotor disk has a rotor outer diameter DA which is measured between two imaginary diametrically opposite blade ends, and that the vacuum pump comprises a second Holweck hub which has a Holweck outer diameter DHW which is measured between two diametrically opposite points of a radial outer surface of the second Holweck hub, 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 larger 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.

[0029] The rotor shaft can be provided with a magnetic bearing or a hybrid bearing. If a hybrid bearing is provided, then a permanent magnet bearing is provided on the high-vacuum side and a rolling bearing on the forevacuum side. The design and arrangement of magnetic bearings and rolling bearings for rotor shafts of vacuum pumps are generally known to those skilled in the art, so there is no need to discuss this in detail. In this regard, reference is also made to the Fig. 1 to 5 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 independent claim 1, but that this is not mandatory.

[0031] In other words, in some embodiments of the invention, it can be provided that several rotor disks are 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 is provided that at least one of the rotor disks is made of the aluminum alloy.

[0032] According to some developments, it can be provided that one or more rotor disks on the high-vacuum side are made of the aluminum alloy, whereas one or more rotor disks on the forevacuum side 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 can be provided that the Holweck sleeve and / or the Holweck hub has or have an outer diameter DHH or DHW which is measured between two diametrically opposite points of a radial outer surface of the Holweck sleeve or the Holweck hub and which lies in the range of 5.0 cm to 60 cm.

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

[0035] According to further examples, it can be provided that the collar of the rotor disk and / or the Holweck hub has or 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 developments 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 - seen in the radial direction - is measured in the middle between the blade base and the blade end.

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

[0038] The blade thickness at a respective location - viewed in the radial direction - is defined in the context of the present disclosure as the smallest diameter of a sectional surface of the rotor blade in a sectional plane running perpendicular to the radial direction.

[0039] According to a further aspect of the invention, this relates to a method for operating the vacuum pump according to the invention, wherein the vacuum pump comprises a rotor shaft which rotates about an axis of rotation during operation and at least one rotor component fastened to the rotor shaft, wherein in the method the vacuum pump is operated at a 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, particularly preferably greater than or equal to 120°C. The rotor component is a rotor disk which comprises a radially inner collar, via which the rotor disk is fastened to the rotor shaft, and a plurality of rotor blades which are each integrally connected to the collar and which extend radially outwards from a blade base on the collar and have a free blade end radially outwards.

[0040] A maximum permissible temperature of the rotor components of more than 90°C allows the vacuum pump to operate as intended at a higher rated speed than conventional vacuum pumps, where the maximum permissible temperature of the rotor components is limited to 90°C. The higher speed can increase pump performance.

[0041] It has been found that the aluminum alloy defined by independent claim 1 is a material which allows for maximum permissible temperatures of more than 90°C for rotor components of vacuum pumps, in particular for rotor disks and / or Holweck components, without causing the problems mentioned above.

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

[0043] In conventional vacuum pumps, the blade end speed of the rotor disk, i.e., the path speed of the blade ends 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 performance of the vacuum pump to be increased.

[0044] According to some embodiments of the invention, it can be provided that the vacuum pump is operated at a rotor shaft speed of more than 59,000 revolutions per minute, preferably more than 100,000 revolutions per minute, particularly preferably more than 150,000 revolutions per minute. In some developments of the invention, both of the vacuum pump according to the invention and of the method according to the invention, it can be provided that the rotor shaft is supported on the forevacuum 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 configurations of a synthetic oil with the viscosity properties mentioned above, reference is made to European patent application EP 3 650 702 A1 published on 13 May 2020.

[0045] The invention is described below by way of example with reference to the drawings. They show: Fig. 1a perspective view of a turbomolecular pump, Fig. 2a view of the underside of the turbomolecular pump of Fig. 1 Fig. 3 a cross-section of the turbomolecular pump along the Fig. 2 shown section line AA, Fig. 4 a cross-sectional view of the turbomolecular pump along the Fig. 2 shown section line BB, Fig. 5 a cross-sectional view of the turbomolecular pump along the Fig. 2shown section line CC, Fig. 6 a section through a part of a turbomolecular pump to illustrate a dimensional ratio according to the invention, Fig. 7 a sectional view of a rotor disk mounted on a rotor shaft to illustrate further dimensions or dimensional ratios that are not part of the claimed invention, and Fig. 8 a section through a rotor blade to illustrate a further dimension which is not part of the claimed invention.

[0046] The Fig. 1The turbomolecular pump 111 shown comprises a pump inlet 115 surrounded by an inlet flange 113, to which a recipient (not shown) can be connected in a manner known per se. The gas from the recipient can be sucked out of the recipient 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.

[0047] The inlet flange 113 forms the vacuum pump alignment according to Fig. 1 the upper end of the housing 119 of the vacuum pump 111. The housing 119 comprises a lower part 121, on which an electronics housing 123 is arranged laterally. Electrical and / or electronic components of the vacuum pump 111 are housed in the electronics housing 123, e.g., for operating an electric motor 125 arranged in the vacuum pump (see also Fig. 3). Several connectors 127 for accessories are provided on the electronics housing 123. In addition, a data interface 129, e.g., according to the RS485 standard, and a power supply connector 131 are arranged on the electronics housing 123.

[0048] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0049] On the housing 119 of the turbomolecular pump 111, a flooding inlet 133, in particular in the form of a flooding valve, is provided, via which the vacuum pump 111 can be flooded. In the area of ​​the lower part 121, a sealing gas connection 135, which is also referred to as a purge gas connection, is also arranged, via which purge gas is supplied to protect the electric motor 125 (see e.g. Fig. 3) can be admitted into the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111, before the gas delivered by the pump. Furthermore, two coolant connections 139 are arranged in the lower part 121, one of which serves as an inlet and the other as an outlet for coolant, which can be fed into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) are operated exclusively with air cooling.

[0050] The lower side 141 of the vacuum pump can serve as a base, so that the vacuum pump 111 can be operated standing on the underside 141. However, the vacuum pump 111 can also be attached to a recipient via the inlet flange 113 and thus operated in a suspended position. Furthermore, the vacuum pump 111 can be designed so that it can also be operated when oriented in a different manner than in Fig. 1 As shown. Embodiments of the vacuum pump can also be realized in which the underside 141 is arranged facing either sideways or upwards, rather than downwards. In principle, any angle is possible.

[0051] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in an upright position.

[0052] 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 together. For example, a bearing cover 145 is attached to the underside 141.

[0053] Mounting holes 147 are also arranged on the underside 141, through which the pump 111 can be attached, for example, to a support surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0054] In the Figures 2 to 5 a coolant line 148 is shown in which the coolant introduced and discharged via the coolant connections 139 can circulate.

[0055] As the sectional views of the Figures 3 to 5 show, 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.

[0056] A rotor 149 is arranged in the housing 119 and has a rotor shaft 153 rotatable about a rotation axis 151.

[0057] The turbomolecular pump 111 comprises several turbomolecular pump stages connected in series for pumping purposes, with several radial rotor disks 155 attached to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and secured in the housing 119. A rotor disk 155 and an adjacent stator disk 157 each form a turbomolecular pump stage. The stator disks 157 are held at a desired axial distance from one another by spacer rings 159.

[0058] The vacuum pump also includes Holweck pump stages arranged radially one inside the other and connected in series for pumping efficiency. Other turbomolecular vacuum pumps (not shown) exist that do not have Holweck pump stages.

[0059] The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical-shell-shaped Holweck rotor sleeves 163, 165 attached to and supported by the rotor hub 161, which are oriented coaxially to the rotational axis 151 and nested within one another in the radial direction. Furthermore, two cylindrical-shell-shaped Holweck stator sleeves 167, 169 are provided, which are also oriented coaxially to the rotational axis 151 and nested within one another in the radial direction.

[0060] The pumping surfaces of the Holweck pump stages are formed by the lateral 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 lies opposite the radial outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together with the latter forms the first Holweck pump stage following the turbomolecular pumps. The radial inner surface of the outer Holweck rotor sleeve 163 lies opposite the radial outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together with the latter forms 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 forming the third Holweck pumping stage.

[0061] At the lower end of the Holweck rotor sleeve 163, a radially extending channel can be provided, via which the radially outer Holweck gap 171 is connected to the central Holweck gap 173. Furthermore, at the upper end of the inner Holweck stator sleeve 169, a radially extending channel can be provided, via which the central Holweck gap 173 is connected to the radially inner Holweck gap 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.

[0062] The above-mentioned pump-active surfaces of the Holweck stator sleeves 167, 169 each have a plurality of Holweck grooves extending spirally around the rotation axis 151 in the axial direction, while the opposite lateral surfaces of the Holweck rotor sleeves 163, 165 are smooth and propel the gas in the Holweck grooves for operating the vacuum pump 111.

[0063] 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.

[0064] In the area of ​​the rolling bearing 181, a conical spray nut 185 with an outer diameter increasing toward the rolling bearing 181 is provided on the rotor shaft 153. The spray nut 185 is in sliding contact with at least one wiper of a fluid reservoir. In other existing turbomolecular vacuum pumps (not shown), a spray screw can be provided instead of a spray nut. Since different designs are thus possible, the term "spray tip" is also used in this context.

[0065] The operating fluid storage comprises several stacked absorbent discs 187, which are impregnated with an operating fluid for the rolling bearing 181, e.g. with a lubricant.

[0066] During operation of the vacuum pump 111, the operating fluid is transferred by capillary action from the operating fluid reservoir via the wiper to the rotating injection nut 185. As a result of centrifugal force, it is conveyed along the injection nut 185 in the direction of the increasing outer diameter of the injection nut 185 to the rolling bearing 181, where it fulfills a lubricating function, for example. The rolling bearing 181 and the operating fluid reservoir are enclosed in the vacuum pump by a trough-shaped insert 189 and the bearing cover 145.

[0067] The permanent magnet bearing 183 comprises a rotor-side bearing half 191 and a stator-side bearing half 193, each comprising a ring stack of several permanent magnetic rings 195, 197 stacked one on top of the other in the axial direction. The ring magnets 195, 197 lie opposite one another, forming a radial bearing gap 199, with the rotor-side ring magnets 195 being arranged radially on the outside and the stator-side ring magnets 197 being arranged radially on the inside. The magnetic field present in the bearing gap 199 creates magnetic repulsion forces between the ring magnets 195, 197, which effect a radial bearing of the rotor shaft 153. The rotor-side ring magnets 195 are carried by a support section 201 of the rotor shaft 153, which surrounds the ring magnets 195 on the radial 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. The rotor-side ring magnets 195 are secured parallel to the rotation axis 151 by a cover element 207 coupled to the support section 201. The stator-side ring magnets 197 are secured parallel to the rotation axis 151 in one direction by a fastening ring 209 connected to the support section 203 and a fastening ring 211 connected to the support section 203. A disc spring 213 can also be provided between the fastening ring 211 and the ring magnets 197.

[0068] Within the magnetic bearing, an emergency or backup bearing 215 is provided, which runs idle without contact during normal operation of the vacuum pump 111 and only engages upon excessive radial deflection of the rotor 149 relative to the stator, forming a radial stop for the rotor 149 to prevent collision of the rotor-side structures with the stator-side structures. The backup bearing 215 is designed as an unlubricated rolling bearing and forms a radial gap with the rotor 149 and / or the stator, causing the backup bearing 215 to be disengaged during normal pumping operation. The radial deflection at which the backup bearing 215 engages is large enough so that the backup bearing 215 does not engage during normal operation of the vacuum pump, yet small enough so that collision of the rotor-side structures with the stator-side structures is prevented under all circumstances.

[0069] 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 portion of the rotor shaft 153 extending through the motor stator 217. Between the motor stator 217 and the portion of the rotor 149 extending through the motor stator 217, an intermediate space 219 is arranged, which comprises a radial motor gap, via which the motor stator 217 and the permanent magnet arrangement can magnetically influence each other to transmit the drive torque.

[0070] The motor stator 217 is secured in the housing within the motor compartment 137 provided for the electric motor 125. A purge gas, also referred to as a purge gas, which may be air or nitrogen, for example, can enter the motor compartment 137 via the purge gas connection 135. The purge gas can be used to protect 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, i.e., the vacuum pressure in the motor compartment 137 is at least approximately equal to the vacuum pressure created by the backing pump connected to the pump outlet 117.

[0071] Furthermore, a so-called labyrinth seal 223, which is known per se, can be provided between the rotor hub 161 and a wall 221 delimiting the motor compartment 137, in particular in order to achieve a better sealing of the motor compartment 217 with respect to the Holweck pump stages located radially outside.

[0072] Below, based on the Fig. 6 to 8 individual aspects and embodiments, in particular certain dimensions or dimensional ratios, of a vacuum pump are explained, which can be implemented individually or in any combination in a turbomolecular pump, for example in a turbomolecular pump as previously described with reference to the Fig. 1 to 5 In other words, a turbomolecular pump, as described in the Fig. 1 to 5 described, in particular have one or more of the dimensions and / or one or more of the dimensional ratios as described in the Fig. 6 to 8 The following are explained below. Fig. 6 to 8 merely to illustrate the dimensions or dimensional relationships, and are therefore not to scale.

[0073] The turbomolecular pump according to Fig. 6comprises a turbomolecular pump stage and a Holweck pump stage. Several rotor disks 15 are mounted on a rotor shaft 13, which rotates about a rotational axis 11 during operation and is supported on the forevacuum side in a rolling bearing 37. The rolling bearing can be lubricated with a synthetic oil, as described in the introductory part of the present disclosure.

[0074] Also mounted on the rotor shaft 13 is a Holweck hub 17, which radially outwardly carries a cylindrical Holweck sleeve 18. The radial outer surface of the Holweck hub 17 lies on the same radius as the radial outer surface of the Holweck sleeve 18, namely on a radius of 1 / 2 * DHW, ie, the outer diameter of the Holweck hub 17 is DHW.

[0075] The radially outer ends 25 of the rotor blades 21 lie on a radius of 1 / 2 * DA, ie the rotor disks 15 have an outer diameter DA.

[0076] As stated in the introductory part of the present disclosure, the DA / DHW ratio according to the invention is at least 1.22.

[0077] 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 lateral surface of the Holweck sleeve 18. Such a structure 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 opposite lateral 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.

[0078] In a further refinement of this embodiment of the invention, the rotor disks 15 and the Holweck hub 17 can be made of the aluminum alloy. In principle, it is also possible 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), as is generally known to those skilled in the art for the production of Holweck sleeves.

[0079] Fig. 7 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 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. In this regard, reference is also made to the description of a turbomolecular pump based on the Fig. 1 to 5 referred to.

[0080] The rotor disk 15 is a one-piece component manufactured by milling and / or sawing from a single raw material. This material is preferably an aluminum alloy. However, this material is not mandatory for the rotor disk 15. The dimensions and dimensional ratios explained in more detail below can also be implemented on rotor disks 15 that are not made of this aluminum alloy.

[0081] The rotor disk 15 comprises a radially inner, hollow-cylindrical collar 19, via which the rotor disk 15 is fastened to the rotor shaft 13. Furthermore, the rotor disk 15 has a plurality of rotor blades 21, each of which is integrally connected to the collar 19 and which each extend radially outward from a blade base 23 on the collar 19 and has a free blade end 25 on the radial outside. Each blade base 23 lies on a larger radius—relative to the center axis of the hollow-cylindrical collar 19, which coincides with the rotational axis 11 of the rotor shaft 13 when fastened to the rotor shaft 13—than the radial outer surface of the collar 19.The outer diameter DB of the collar 19, which is measured between two diametrically opposite points on the radial outer surface of the collar 19, is consequently smaller than the basic outer diameter DG which is measured from blade base 23 to blade base 23 of two imaginary diametrically opposite rotor blades 21.

[0082] Furthermore, the rotor disk 15 has a rotor outer diameter DA, which is measured between two imaginary diametrically opposite blade ends 25.

[0083] The rotor shaft 13 has an outer shaft diameter DI which corresponds to the inner diameter of the collar 19 of the rotor disk 15.

[0084] As explained in the introductory part, the radial length of a respective rotor blade 21 measured from the blade base 23 to the blade end 25 represents the pump-effective portion of the total length of the rotor blade 21, which is measured from the collar 19 to the blade end 25.

[0085] According to a non-inventive aspect, the ratio (DA - DG) / (DA - DB) is at least 0.94, preferably at least 0.95, particularly preferably 0.97.

[0086] Rotor disks 15 with such a dimensional ratio can be operated at relatively high speeds, especially when made of aluminum alloy. This leads to a particularly significant increase in the pumping performance of the vacuum pump in question.

[0087] According to a further aspect not according to the invention, which can be combined with the aspect described above, in a turbomolecular pump, 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, 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. Relative to the outer diameter DI of the rotor shaft 13, the collar 19 of the rotor disk 15 is thus comparatively thin.

[0088] Rotor disks 15 with such a dimensioned collar 19 can then be operated at relatively high speeds if they are made of the aluminum alloy.

[0089] The axial height h of the collar 19 of the rotor disk 15 is preferably in a range from 3.0 mm to 5.9 mm, in particular up to 5.49 mm.

[0090] Preferred embodiments of the rotor blades 21 relate to their blade thickness. Fig. 8 illustrates how the blade thickness is defined within the scope of the present disclosure. Accordingly, at a respective radial location of a rotor blade 21, the blade thickness dG is the smallest diameter of a sectional surface of the rotor blade 21, which is obtained at the radial location by a section through the rotor blade 21 running perpendicular to the radial direction.

[0091] In a preferred embodiment, the blade thickness dG at the blade base 23 (cf. Fig. 7 ) less than 9.8 mm, in particular less than 9.0 mm.

[0092] In the middle between the blade base 23 and the blade end 25 (seen in the radial direction), the blade thickness dG is preferably in the range of 0.125 mm and 2.9 mm.

[0093] Rotor disks 15, the rotor blades 21 of which have the respective blade thickness dG at one or both of these radial locations, can be operated at comparatively high speeds if the rotor disks 15 are made of the aluminum alloy. List of reference symbols

[0094] 11Rotation axis 13Rotor shaft 15Rotor disc 17Holweck hub 18Holweck sleeve 19Collar 21Rotor blade 23Blade base 25Blade end 27Housing 29Stator disc 31Holweck stator 33Holweck stator 35Magnetic bearing 37Rolling bearing DHHOuter diameter of Holweck sleeve DHWOuter diameter of Holweck hub DIOuter shaft diameter DAOuter rotor diameter DBBund outer diameter DGOuter base diameter dGThickness of the rotor blade hAxial height

Claims

1. A vacuum pump, in particular a turbomolecular pump, comprising a rotor shaft (13) rotating about an axis of rotation (11) during operation, at least one rotor disk (15) which is fastened to the rotor shaft (13) and which comprises a radially inwardly disposed collar (19), via which the rotor disk (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, and at least one Holweck hub (17) which is fastened to the rotor shaft (13) and to which at least one Holweck sleeve (18) is fastened, wherein the rotor disk (15) has a rotor outer diameter DA which is measured between two imaginary mutually diametrically oppositely disposed blade ends (25), wherein the Holweck hub (17) has a Holweck outer diameter DHW which is measured between two mutually diametrically oppositely disposed points of a radial outer surface of the Holweck hub (17), and wherein the rotor outer diameter DA is greater than the Holweck outer diameter DHW by a factor of at least 1.22, preferably of at least 1.25, particularly preferably of at least 1.30, wherein the at least one rotor disk (15) is made of an aluminum alloy which has the following composition in % by 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, the remainder being aluminum.

2. A vacuum pump according to claim 1, wherein the Holweck hub (17) and / or the Holweck sleeve (18) is / are made of the aluminum alloy.

3. A vacuum pump according to any one of the preceding claims, wherein the rotor disk (15) has a rotor outer diameter DA which is greater than 5.0 cm, preferably in a range from 5.0 cm to 60 cm, wherein the rotor outer diameter DA is measured between two imaginary mutually diametrically oppositely disposed blade ends (25).

4. A vacuum pump according to any one of the preceding claims, wherein the rotor disk (15) has a rotor outer diameter DA which is measured between two imaginary mutually diametrically oppositely disposed blade ends (25), wherein the Holweck hub (17) has a Holweck outer diameter DHW which is measured between two mutually diametrically oppositely disposed points of a radial outer surface of the Holweck hub (17), and wherein the rotor outer diameter DA is at least 135 mm and the Holweck outer diameter DHW is at least 108 mm.

5. A vacuum pump according to any one of the preceding claims, wherein the rotor disk (15) has a rotor outer diameter DA which is measured between two imaginary mutually diametrically oppositely disposed blade ends (25), wherein the vacuum pump comprises a second Holweck hub having a Holweck outer diameter DHW2 which is measured between two mutually diametrically oppositely disposed points of a radial outer surface of the second Holweck hub, 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 by a factor of at least 1.40, preferably of at least 1.48, than the Holweck outer diameter DHW2 of the second Holweck hub.

6. A vacuum 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.

7. A vacuum pump according to any one of the preceding claims, wherein a plurality of rotor disks (15) are fastened to the rotor shaft (13), wherein at least two rotor disks (15) differ from one another in terms of the material from which they are made.

8. A vacuum pump according to any one of the preceding claims, wherein the Holweck sleeve (18) and / or the Holweck hub (17) has / have an outer diameter DHH or DHW which is measured between two mutually diametrically oppositely disposed points of a radial outer surface of the Holweck sleeve (18) or the Holweck hub (17) and which lies in a range from 5.0 cm to 60 cm.

9. A vacuum 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 mutually diametrically oppositely disposed points which each lie on a radial outer surface of the rotor component (15, 17, 18).

10. A method of operating a vacuum pump according to any one of the preceding claims, wherein, in the method, the vacuum 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.

11. A method according to claim 10, wherein the vacuum pump is operated at a rotational speed of the rotor shaft (13) such that the blade end speed of the rotor disk (15) is more than 420 m / s, preferably more than 438 m / s, preferably more than 464 m / s.

12. A method according to claim 10 or 11, wherein the vacuum pump is operated at a rotational speed of the rotor shaft (13) that is more than 59,000 revolutions per minute, preferably more than 100,000 revolutions per minute, particularly preferably more than 150,000 revolutions per minute.