Turbomolecular vacuum pump

Abstract

The invention relates to a turbomolecular vacuum pump with at least one turbomolecular pump unit and at least one Holweck pump unit arranged downstream of the turbomolecular pump unit in the pumping direction, the Holweck pump unit having at least two Holweck stages arranged concentrically within one another with respect to a common axis of rotation and following one another in the pumping direction, wherein the Holweck stages each comprise a Holweck stator with a Holweck thread, which has Holweck webs projecting from a channel base and Holweck channels bounded by the walls of the Holweck webs and faces a common Holweck rotor of the Holweck pump unit, which rotates about the axis of rotation during operation and which, with one Holweck stator, defines a radially outer Holweck pumping area and, with the other Holweck stator, a radially inner Holweck pumping area.wherein in a transition region at the free end of the Holweck rotor an outlet region of the radially outer Holweck pumping region transitions into an inlet region of the radially inner Holweck pumping region, wherein in addition to an axial gas inlet into the radially outer Holweck pumping region a radial gas inlet into the Holweck pumping unit is provided, which opens either into the transition region or upstream of the transition region into the radially outer Holweck pumping region, and wherein the outlet region and the inlet region each have a free cross-sectional area defined by the Holweck channels in a cross-sectional plane perpendicular to the axis of rotation, in which the pumping action ends or begins, and the free cross-sectional area of ​​the inlet region is larger by a factor f > 1 than the free cross-sectional area of ​​the outlet region.

Description

[0001] The invention relates to a turbomolecular vacuum pump with at least one turbomolecular pump unit and at least one Holweck pump unit arranged downstream of the turbomolecular pump unit in the pumping direction, which has at least two Holweck stages which are concentrically arranged one inside the other with respect to a common axis of rotation and which follow one another in the pumping direction, wherein the Holweck stages each comprise a Holweck stator with a Holweck thread which has Holweck webs protruding from a channel base and Holweck channels delimited by the walls of the Holweck webs and faces a common Holweck rotor of the Holweck pump unit which rotates about the axis of rotation during operation and which delimits a radially outer Holweck pumping area with one Holweck stator and a radially inner Holweck pumping area with the other Holweck stator,wherein in a transition region at the free end of the Holweck rotor, an outlet region of the radially outer Holweck pumping region merges into an inlet region of the radially inner Holweck pumping region, and wherein in addition to an axial gas inlet into the radially outer Holweck pumping region, a radial gas inlet into the Holweck pumping unit is provided.

[0002] The invention further relates to a vacuum system comprising a turbomolecular vacuum pump as disclosed herein and comprising a recipient to be evacuated, wherein the turbomolecular vacuum pump is designed as a split-flow vacuum pump having one or more radial suction inlets which, during operation, are each connected to an opening of the recipient.

[0003] The invention further relates to a leak detection system comprising a turbomolecular vacuum pump as disclosed herein, which can be connected to a test object to be evacuated, and comprising a detector, in particular a mass spectrometer, for detecting a test gas, wherein the turbomolecular vacuum pump is connected to the detector via an axial or radial gas inlet and a radial gas inlet for the test gas into the Holweck pump unit is provided downstream of the gas inlet.

[0004] Such turbomolecular vacuum pumps are generally known, for example from EP 3 845 764 A2, EP 2 933 497 A2, and EP 3 657 021 A1. Vacuum systems and leak detection systems of the above type are also generally known.

[0005] Vacuum pumps are used in various fields of technology. Depending on the requirements, vacuum pumps have one or more pumping units. A Holweck pumping unit belongs to the class of molecular vacuum pumps and generates a molecular flow through the rotation of the Holweck rotor relative to the respective Holweck stator. A Holweck pumping unit can comprise one or more Holweck stages, with multiple Holweck stages being able to pump both serially and in parallel. Holweck pumping units are typically used in turbomolecular vacuum pumps and are arranged downstream of one or more turbomolecular pumping stages, which form a turbomolecular pumping unit.

[0006] A Holweck stage comprises a Holweck rotor and a Holweck stator, whereby the Holweck rotor is attached to a pump rotor by means of a disk-shaped Holweck hub, for example, which is set in rotation by a pump drive motor during pumping operation. The Holweck rotor is also referred to as a Holweck sleeve and is typically hollow-cylindrical in shape. A Holweck pump unit can have several Holweck sleeves that are concentrically attached to the Holweck hub. The Holweck stator is provided with a single or multi-start Holweck thread. The gas molecules to be conveyed are conveyed along the threads from an inlet to an outlet by the rotating movement of the Holweck rotor relative to the Holweck stator. A thread comprises a circumferential Holweck channel (also called a Holweck groove) defined by walls of Holweck webs, in which the gas molecules are conveyed when the Holweck rotor rotates relative to the Holweck stator.In order to minimize backflow losses, the width of the radial gap (Holweck gap) between the top side of the Holweck web, also known as the tip, and the Holweck sleeve is kept comparatively small compared to the web height.

[0007] So-called "folded" Holweck pump units are also known, in which several Holweck stages are arranged concentrically within one another (also referred to as "nested" Holweck stages), so that the gas flows of radially immediately adjacent Holweck stages oppose each other. Two consecutive Holweck stages, namely a (radially) outer Holweck stage and a (radially) inner Holweck stage, can comprise a common Holweck stator provided with a Holweck thread on both sides, hereinafter also referred to as a "double-sided" Holweck stator, which is located between two concentric Holweck rotors.

[0008] Furthermore, it is generally known to provide so-called "conical" Holweck stages, in which the Holweck stator is designed such that the web height decreases continuously in the pumping direction. The web height is the radial distance between the web tip and the channel base at a given axial location.

[0009] For many applications of turbomolecular vacuum pumps, for example in so-called split-flow applications or leak detection applications, it is necessary to provide at least one radial gas inlet – also known as an interstage port – in the Holweck pump unit. An axial position of such a radial gas inlet relatively close to the turbomolecular pump unit with respect to the rotation axis can be disadvantageous, in particular, adverse backflow effects can arise. Therefore, efforts are made to position the radial gas inlet in the Holweck pump unit at or near the transition area, in any case closer to the transition area than to the turbomolecular pump unit. Furthermore, it is desirable for such an interstage port to have the highest possible pumping speed.

[0010] The pumping speed is the volume flow of a gas being pumped through a specific cross-sectional area per unit of time.

[0011] Against this background, the object of the invention is to improve a turbomolecular vacuum pump of the type mentioned at the outset in such a way that, in connection with a radial gas inlet, backflow effects in the Holweck pump unit are minimized and the highest possible pumping speed is available for the radial gas inlet.

[0012] This object is achieved by the features of claim 1. According to the invention, it is accordingly provided that the radial gas inlet opens either into the transition region or upstream of the transition region into the radially outer Holweck pumping region, in particular into the downstream half or into the downstream third, quarter, fifth or sixth of the radially outer Holweck pumping region, and that the outlet region and the inlet region each have a free cross-sectional area defined by the Holweck channels in a cross-sectional plane running perpendicular to the axis of rotation, in which the pumping action ends or begins, and the free cross-sectional area of ​​the inlet region is larger by a factor f > 1 than the free cross-sectional area of ​​the outlet region.

[0013] The free cross-sectional area on the inlet and outlet sides is also referred to as openness.

[0014] The Holweck stators are preferably each designed to be multi-threaded, ie they each have a plurality, e.g. 4, 6 or 8, of parallel Holweck channels, which are separated from each other in pairs by one of the Holweck webs.

[0015] Investigations on known Holweck pump units have shown that the pumping speed decreases continuously in the pumping direction, i.e., from the inlet into the radially outer Holweck pump stage to the outlet from the radially inner Holweck pump stage. Depending on the respective conditions, a comparatively strong decrease in pumping speed is observed in the transition area between the radially outer Holweck pumping area and the radially inner Holweck pumping area. In many Holweck pump units, the pumping speed at the inlet area of ​​the radially inner Holweck pumping area is also generally lower than at the outlet area of ​​the radially outer Holweck pumping area. In other words, in some arrangements, a considerable reduction in pumping speed occurs at the transition area—also referred to as the reversal point.

[0016] It was found that the inventive enlargement of the inlet-side openness compared to the outlet-side openness considerably increases the pumping speed at the inlet area of ​​the radially inner Holweck pumping area and, while simultaneously minimizing backflow, also provides a significantly higher pumping speed for the radial gas inlet, even when the radial gas inlet opens into the radially outer Holweck pumping area upstream of the transition area. For example, in a real turbomolecular vacuum pump, it was found that enlarging the free cross-sectional area at the inlet area of ​​the radially inner Holweck pumping area from 142 mm² to 388 mm² results in an increase in pumping speed from 2.69 l / s to 6.70 l / s (where l / s = liters per second), with the geometric conditions of the Holweck pumping unit otherwise unchanged.

[0017] The invention thus enables a considerable increase in the performance of Holweck pump units and thus of turbomolecular vacuum pumps equipped with such Holweck pump units, which is of great advantage in practice, particularly for split-flow applications and leak detection applications that require one or more radial gas inlets.

[0018] Advantageous further developments of the invention are also specified in the dependent claims, the following description and in the figures.

[0019] According to some embodiments, it can be provided that the following applies: 1 < f < 3, preferably 1 < f < 2, preferably 1.2 < f < 1.5. It has been found that advantageous increases in suction capacity can be achieved in practice even if the factor f is less than 1.5, whereby a factor F of less than 2 or less than 3 has the advantage that comparatively little radial installation space is required.

[0020] The inlet openness can be varied in different ways.

[0021] In some embodiments, it can be provided that in the respective cross-sectional plane the height of the Holweck webs in the inlet area is greater than the height of the Holweck webs in the outlet area.

[0022] According to some embodiments, it can be provided that in the respective cross-sectional plane, the width of the Holweck webs measured in the circumferential direction is greater in the inlet area than in the outlet area.

[0023] According to some embodiments, it may be provided that the number of Holweck webs in the radially inner Holweck pumping region is smaller than the number of Holweck webs in the radially outer Holweck pumping region.

[0024] The measures mentioned above can also be combined with each other as desired.

[0025] The Holweck stator delimiting the radially inner Holweck pumping area can be a Holweck stator provided with a Holweck thread on both sides, which delimits a further Holweck pumping area radially further inward with a further Holweck rotor.

[0026] It can be provided that the Holweck stator provided with the Holweck thread on both sides has a wall thickness measured in the radial direction, wherein in the inlet area the wall thickness is smaller than the height of the Holweck webs of the radially inner Holweck pumping area.

[0027] In some embodiments, it can be provided that the radially outer Holweck pumping region and / or the radially inner Holweck pumping region are each conically designed such that the height of the Holweck webs continuously decreases in the pumping direction.

[0028] In this case, it can be provided that a conicity angle defined by the channel base of the radially outer Holweck pumping region and a conicity angle defined by the channel base of the radially inner Holweck pumping region are at least substantially equal to or different from one another. In particular, the conicity angle of the radially outer Holweck pumping region can be greater or smaller than the conicity angle of the radially inner Holweck pumping region.

[0029] Alternatively, the radially outer Holweck pumping area and / or the radially inner Holweck pumping area can also each be cylindrical.

[0030] According to some embodiments, it can be provided that at least one pump-effective section of the radially outer Holweck stator, which section delimits the radially outer Holweck pumping region with the Holweck rotor, is designed as a single piece. It can be provided that the radial gas inlet opens into the radially outer Holweck pumping region upstream of the transition region and extends through the single-piece pump-effective section of the radially outer Holweck stator. The single-piece design facilitates manufacture and assembly of the Holweck pumping unit. The greater inlet-side openness of the radially inner Holweck pumping region is also advantageous for a radial gas inlet located upstream of the transition region with regard to suction capacity and backflow minimization, i.e. there is no need for a two-part radially outer Holweck stator to ensure greater openness downstream of the opening of the radial gas inlet.

[0031] In some embodiments, it can be provided that the radial gas inlet into the Holweck pump unit extends through a pump housing above a lower part or intermediate component of the vacuum pump, in which the transition region is at least partially located. This is particularly advantageous if, for example, in a split-flow vacuum pump, one or more additional radial gas inlets are present upstream, since the outer side of the pump housing can then serve as a common sealing surface for the radial gas inlets.

[0032] According to some embodiments, it can be provided that at least one further radial gas inlet is arranged upstream of the radial gas inlet into the Holweck pump unit, in particular wherein the further radial gas inlet opens into the Holweck pump unit or into the turbomolecular pump unit.

[0033] As mentioned above, an outer side of a pump housing through which at least some of the plurality of radial gas inlets extend can advantageously be used as a common sealing surface.

[0034] In the vacuum system according to the invention, one of the radial suction inlets is the radial gas inlet opening into the transition region or upstream of the transition region into the radially outer Holweck pumping region.

[0035] In the leak detection system according to the invention, the radial gas inlet for the test gas is the radial gas inlet opening into the transition area or upstream of the transition area into the radially outer Holweck pumping area.

[0036] The invention is described below by way of example with reference to the drawings. They show: Fig. 1 is a perspective view of a turbomolecular vacuum pump according to the prior art, Fig. 2 is a view of the underside of the turbomolecular vacuum pump of Fig. 1 , Fig. 3 a cross-section of the turbomolecular vacuum pump along the Fig. 2 shown section line AA, Fig. 4 a cross-sectional view of the turbomolecular vacuum pump along the Fig. 2 shown section line BB, Fig. 5 a cross-sectional view of the turbomolecular vacuum pump along the Fig. 2 shown section line CC, Fig. 6 a schematic view of a turbomolecular vacuum pump according to the prior art, Fig. 7 partially a cross section parallel to the axis of rotation through a part of a turbomolecular vacuum pump according to the prior art Fig. 8 partially a cross section parallel to the axis of rotation through a part of a turbomolecular vacuum pump according to an embodiment of the invention, and Fig. 9 partially a cross section perpendicular to the axis of rotation through a Holweck pump unit of a turbomolecular vacuum pump according to the invention.

[0037] The Fig. 1 The turbomolecular vacuum pump 111 shown (hereinafter also referred to as turbomolecular pump or vacuum pump) 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.

[0038] 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.

[0039] 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 connections 127 for accessories are provided on the electronics housing 123.

[0040] In addition, a data interface 129, e.g. according to the RS485 standard, and a power supply connection 131 are arranged on the electronics housing 123.

[0041] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0042] 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.

[0043] 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.

[0044] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in an upright position.

[0045] On the underside 141, which is in Fig. 2 As 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.

[0046] 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.

[0047] In the Fig. 2 bis 5 a coolant line 148 is shown in which the coolant introduced and discharged via the coolant connections 139 can circulate.

[0048] As the sectional views of the Figuren 3 bis 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.

[0049] A rotor 149 is arranged in the housing 119 and has a rotor shaft 153 rotatable about a rotation axis 151.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The motor stator 217 is secured in the housing within the motor compartment 137 provided for the electric motor 125. A seal gas, also referred to as purge gas, which may be air or nitrogen, for example, can enter the motor compartment 137 via the seal gas connection 135. The seal 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.

[0064] 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.

[0065] Fig. 6 shows schematically some components of a turbomolecular vacuum pump according to the prior art, wherein the turbomolecular vacuum pump can furthermore be designed as described above in connection with the Fig. 1 bis 5 has been described.

[0066] In Fig. 6 Shown are a turbomolecular pump unit 11 and a Holweck pump unit 13. Both pump units 11, 13 have a common rotor 12, which rotates about a rotation axis 15 during pumping operation. The drive motor for the rotor 12 is in Fig. 6 not shown.

[0067] The turbomolecular pump unit 11 comprises a plurality of rotor disks 11a, which are non-rotatably connected to the rotor 12. Not shown in the turbomolecular pump unit 11 are the stator disks, which interact with the rotor disks 11a in a known manner for pumping purposes.

[0068] Of the Holweck pump unit 13, the Holweck hub 26, which is connected in a rotationally fixed manner to the rotor 12, the Holweck rotor 25, which is also referred to as a Holweck sleeve and is connected in a rotationally fixed manner to the Holweck hub 26, as well as a radially outer Holweck stator 17a and a radially inner Holweck stator 17b are shown.

[0069] Thus, in the embodiment illustrated here, the Holweck pump unit 13 comprises two Holweck stages arranged concentrically one within the other with respect to the rotation axis 15 and arranged one behind the other in the pumping direction. Each Holweck stage comprises the respective Holweck stator 17a, 17b, which comprises a multi-start Holweck thread having Holweck webs 21 projecting from a channel base 19 and Holweck channels 23 delimited by the walls of the Holweck webs 21. This Holweck thread faces the respective side of the Holweck rotor 25.

[0070] In a fundamentally known manner, the Holweck rotor 25 forms a radially outer Holweck pumping region 27 with the radially outer Holweck stator 17a and a radially inner Holweck pumping region 29 with the radially inner Holweck stator 17b.

[0071] The flow path of a gas to be pumped is Fig. 6 indicated by the arrows. The gas to be pumped initially flows via an axial pump inlet (not shown) in the pump housing (also not shown) into the turbomolecular pump unit 11, through this to an axial gas inlet 33 in the radially outer Holweck pumping region 27, through this to an outlet region 27a of the radially outer Holweck pumping region 27, into a transition region 31 at the free end of the Holweck rotor 25, into an inlet region 29a of the radially inner Holweck pumping region 29, through this and then via a flow path (not shown in detail) to an outlet of the turbomolecular vacuum pump.

[0072] The outlet region 27a of the radially outer Holweck pumping region 27 is located in a cross-sectional plane perpendicular to the rotation axis 15 in an axial position relative to the rotation axis 15, at which the pumping action of the radially outer Holweck pumping region 27 ends, i.e., where the Holweck channels 23 end. Accordingly, the pumping action of the radially inner Holweck pumping region 29 begins at its inlet region 29a and thus in a cross-sectional plane perpendicular to the rotation axis 15, in which the Holweck channels 23 begin.

[0073] The cross-sectional plane in which the outlet region 27a is located, and in which the pumping action of the radially outer Holweck pumping region 27 thus ends, and the cross-sectional plane in which the inlet region 29a is located, and in which the pumping action of the radially inner Holweck pumping region 29 consequently begins, can coincide. Depending on the specific design and arrangement of the two Holweck pumping stages, these two cross-sectional planes can also be spaced apart from each other in the axial direction.

[0074] In the respective cross-sectional plane, the outlet region 27a and the inlet region 29a have a respective free cross-sectional area defined by the Holweck channels 23. For the sake of simplicity, the respective free cross-sectional area is also referred to below as openness, i.e., the radially outer Holweck pumping region 27 has a specific outlet-side openness at its outlet region 27a, defined by the geometry of its Holweck channels 23. Correspondingly, the radially inner Holweck pumping region 29 has an inlet-side openness at its inlet region 29a, defined by the geometry of its Holweck channels 23.

[0075] You can see that in the Fig. 6 In the schematically illustrated example of the prior art, the inlet-side openness is significantly smaller than the outlet-side openness, since the height of the Holweck webs 21 of the radially inner Holweck pumping area 29 is smaller than the height of the Holweck webs 21 of the radially outer Holweck pumping area 27. For the sake of simplicity, it is assumed that there are no differences in the width of the Holweck webs 21 and the number of Holweck channels 23 - parameters which also determine the openness.

[0076] Furthermore, in Fig. 6 It can be seen that the radially outer Holweck pumping area 27 is conical in such a way that the height of the Holweck webs 21 decreases in the pumping direction. The radially outer Holweck pumping stage is therefore a conical pumping stage. The conicity or a respective conicity angle measured with respect to the rotational axis 15 is defined by the channel base 19. Such conical Holweck pumping stages are generally known. The radially inner Holweck stage is cylindrical in this case. It is also generally known to have both a radially outer Holweck pumping stage and a radially inner Holweck pumping stage, which - as in the example of the Fig. 6 - have a common Holweck rotor 25, each of which is conical.

[0077] While Fig. 6 a turbomolecular vacuum pump is only shown schematically, Fig. 7 a concrete example from the state of the art.

[0078] Unlike in Fig. 6 A pump housing 41 is also shown here. Furthermore, Fig. 7 a lower part 39 of the vacuum pump, on which the radially inner Holweck stator 17b is supported with its lower end. It can be seen that the transition region 31 between the outlet region of the radially outer pumping region 27 and the inlet region of the radially inner Holweck pumping region 29 is located within the lower part 39, since the free end of the Holweck rotor 25 extends into the lower part 39.

[0079] In the example of Fig. 7 The radially inner Holweck stator 17b is a Holweck stator provided with a Holweck thread on both sides. This double-sided Holweck stator 17b defines, with a further, radially inner Holweck rotor 25, a further Holweck pumping area 43. While the Holweck pumping areas 29 and 43 defined by the radially inner Holweck stator 17b are each cylindrical, the radially outer Holweck pumping area 27 is - as in the example of the Fig. 6 - conical in shape.

[0080] In Fig. 7 It can be seen that - with the same width of the Holweck webs and the same number of Holweck channels due to the different height of the Holweck webs 21 - the inlet-side openness of the radially inner Holweck pumping area 29 is again smaller than the outlet-side openness of the radially outer Holweck pumping area 27.

[0081] As will be explained below with reference to the embodiment of the invention Fig. 8 As described, the Holweck pump unit 13 of a turbomolecular vacuum pump according to the invention differs from the prior art, as described above by way of example with reference to Fig. 6 and 7 has been described, in that the inlet region 29a of the radially inner Holweck pumping region 29 has a greater openness than the outlet region 27a of the radially outer Holweck pumping region 27.

[0082] As explained in the introduction, this results in a higher pumping speed at the transition area and also for a radial gas inlet (interstage port) into the Holweck pump unit 13 as well as in a reduction of backflow effects.

[0083] The axial height of the radial gas inlet – relative to the rotation axis (not shown here) – can vary in practice. Two different possibilities are shown as examples in Fig. 8 shown. The arrow 35 represents a radial gas inlet, which opens into the transition region 31 between the outlet region 27a and the inlet region 29a. Alternatively, a radial gas inlet can open slightly further upstream into the radially outer Holweck pumping region 27, as shown in Fig. 8 by the arrow 35'. Such a radial gas inlet 35' located slightly upstream of the transition region 31 can, for example, be provided when - as in the example of the Fig. 7 shown - the transition region 31 is located within a pump base 39. Even with such a radial gas inlet 35', the higher pumping capacity generated by the greater openness at the inlet region 29a of the radially inner Holweck pump region 29 has an advantageous effect.

[0084] How Fig. 8 Furthermore, both Holweck pumping areas 27, 29 are conical, ie the height of the Holweck webs 21 decreases in the pumping direction. Consequently, gas to be pumped also enters the Fig. 8 - coming from the turbomolecular pump unit 11 - via an axial gas inlet 33 into the radially outer Holweck pumping area 27 and then passes via the transition area 31 into the radially inner Holweck pumping area 29 and from there either to a gas outlet of the vacuum pump or into one or more further Holweck pumping areas, for example according to the example of Fig. 7 . Thus, even in a turbomolecular vacuum pump according to the invention, the radially inner Holweck stator 17b of the Holweck pump unit 13 can be a "double-sided" Holweck stator, which is provided on both sides, i.e. radially outside and radially inside, with a Holweck thread, which cooperates in a pumping-effective manner with a respective Holweck sleeve 25 attached to the common Holweck hub 26.

[0085] As already mentioned elsewhere, the respective conicity of the Holweck pumping area 27, 29 is measured with respect to the rotation axis. The conicity angles βa and βi of the radially outer Holweck pumping area 27 and the radially inner Holweck pumping area 29 are shown in Fig. 8 drawn using dashed auxiliary lines. The conicity angles βa and βi can be the same or different.

[0086] Fig. 9 illustrates the geometry at the inlet area 29a of the radially inner Holweck pumping area 29, specifically in the cross-sectional plane running perpendicular to the rotation axis 15, in which the Holweck channels 23 delimited by the Holweck webs 21 begin, ie in the cross-sectional plane in which the pumping action of the radially inner Holweck pumping area 29 begins.

[0087] In Fig. 9 Also shown is the Holweck rotor 25, which interacts with the Holweck thread of the radially inner Holweck stator 17b, which comprises the Holweck webs 21. The Holweck thread on the cylindrical wall 17c of the Holweck stator 17b is multi-threaded and here comprises eight parallel pumping Holweck channels 23, each separated from each other in pairs by a Holweck web 21. The Holweck rotor 25 and stator wall 17c can begin in a different cross-sectional plane than the Holweck webs 21. The pumping action of the radially inner Holweck pumping area 29 nevertheless begins where the Holweck channels 23 begin, which are jointly delimited by the channel base 19, i.e., the outside of the stator wall 17c, and by the Holweck webs 21, and for whose pumping effectiveness the radial inside of the Holweck rotor 25 is required.

[0088] As in Fig. 9 schematically shown, one can imagine the geometric situation at the inlet area 29a in a Holweck pump unit 13 according to the invention - e.g. according to Fig. 8 - introduce. In Fig. 9 The radially outer Holweck stator 17a is not shown. However, the geometric situation is corresponding for the outer Holweck stator 17a, whereby the Holweck thread of the radially outer Holweck stator 17a interacts with the radial outer side of the Holweck rotor 25 and - as mentioned elsewhere - the pumping action of the radially outer Holweck pumping area can end in a cross-sectional plane that differs from the cross-sectional plane in which the pumping action of the radially inner Holweck pumping area 27a begins.

[0089] In a known manner, the tips of the Holweck webs 21 are slightly spaced from the facing inner side of the Holweck rotor 25. The actual size ratios are shown in Fig. 9 not shown to scale. In the cross-sectional view shown, the tips of the Holweck webs 21 lie on a circle around the rotation axis 15, which in Fig. 9 represented by a dashed line and which, as mentioned, has a smaller radius than the inside of the Holweck rotor 25.

[0090] As mentioned, the Holweck channels 23 are effective for pumping. The size of the effective free cross-sectional area at the inlet area 29a, i.e. in the Fig. 9 shown cross-sectional plane, is thus determined by the number of Holweck channels 23 and by their free cross-sectional areas, the latter being determined by the width B measured in the circumferential direction and the height H - i.e. by the distance between the web tip and the channel base 19 - of the respective delimiting Holweck webs 21. The comparatively narrow annular area between the tips of the Holweck webs 21 and the inside of the Holweck rotor 25 is not counted towards the free cross-sectional area at the inlet area 29a, and in this sense does not contribute to the inlet-side openness of the radially inner Holweck pumping area 29. The same applies to the outlet-side openness of the Fig. 9 not shown radially outer Holweck pumping area 27.

[0091] A variation of both the inlet-side openness and the outlet-side openness can therefore be achieved, for example, by changing the width B, the height H, or the number of Holweck webs 21. These measures can also be combined as desired. For example, with the number of Holweck webs 21 and thus the Holweck channels 23 remaining the same, the openness can be changed by changing the height H and the width B of the Holweck webs. The height H can be changed, with the radial distance between the tips of the Holweck webs 21 and the inside of the Holweck rotor 25 remaining the same, by providing the cylindrical region of the Holweck stator 17b, i.e. its wall 17c, from which the Holweck webs 21 protrude radially outwards, with a smaller wall thickness, whereby the channel base 19 is brought closer to the rotation axis 15.Alternatively or additionally, the height H of the Holweck webs 21 can also be changed by changing the radial distance between the web tips and the inside of the Holweck rotor 25, as far as this is possible in each case without impairing the basic functionality, i.e. pumping efficiency, of the Holweck pumping stage. Bezugszeichenliste

[0092] 11Turbomolecular pump unit 11aRotor disk 12Rotor 13Holweck pump unit 15Rotation axis 17aRadial outer Holweck stator 17bRadial inner Holweck stator 17cWall of the radially inner Holweck stator 19Channel base 21Holweck web 23Holweck channel 25Holweck rotor 26Holweck hub 27Radial outer Holweck pumping area 27aOutlet area 29Radial inner Holweck pumping area 29aInlet area 31Transition area 33Axial gas inlet 35, 35'Radial gas inlet 39Lower part or intermediate component 41Pump housing 43Further Holweck pumping area HHeight of the Holweck webs BWidth of the Holweck webs βaConicity angle of the radially outer Holweck pumping area βiConicity angle of the radially inner Holweck pumping area 111Turbomolecular pump 113Inlet flange 115Pump inlet 117Pump outlet 119Housing 121Lower section 123Electronics housing 125Electric motor 127Accessory connection 129Data interface 131Power supply connection 133Flood inlet 135Seal gas connection 137Motor compartment 139Coolant connection 141Underside 143Screw 145Bearing cover 147Mounting hole 148Coolant line 149Rotor 151Rotation axis 153Rotor shaft 155Rotor disc 157Stator disc 159Spacer ring 161Rotor hub 163Holweck rotor sleeve 165Holweck rotor sleeve 167Holweck stator sleeve 169Holweck stator sleeve 171Holweck gap 173Holweck gap 175Holweck gap 179Connecting channel 181Rolling bearing 183Permanent magnet bearing 185Injection nut 187Disc 189Insert 191Rotor-side bearing half 193Stator-side bearing half 195Ring magnet 197Ring magnet 199Bearing gap 201Support section 203Support section 205Radial strut 207Cover element 209Support ring 211Fastening ring 213Disc spring 215Emergency orFanglager 217Motorstator 219Zwischenraum 221Wandung 223Labyrinthdichtung.

Claims

1. A turbomolecular vacuum pump comprising at least one turbomolecular pump unit (11) and at least one Holweck pump unit (13) arranged downstream of the turbomolecular pump unit (11) in the pumping direction, said unit comprising at least two Holweck stages which are arranged concentrically one inside the other with respect to a common axis of rotation (15) and which follow one another in the pumping direction, wherein the Holweck stages each comprise a Holweck stator (17a, 17b) with a Holweck thread, which has Holweck webs (21) projecting from a channel base (19) and Holweck channels (23) delimited by the walls of the Holweck webs (21), and which faces a common Holweck rotor (25) of the Holweck pump unit (13) which rotates about the axis of rotation (15) during operation and which delimits a radially outer Holweck pumping region (27) with one Holweck stator (17a) and a radially inner Holweck pumping region (29) with the other Holweck stator (17b),wherein in a transition region (31) at the free end of the Holweck rotor (25) an outlet region (27a) of the radially outer Holweck pumping region (27) merges into an inlet region (29a) of the radially inner Holweck pumping region (29), , characterized by thatin addition to an axial gas inlet (33) in the radially outer Holweck pumping region (27), a radial gas inlet (35, 35') is provided in the Holweck pumping unit (13), which opens either into the transition region (31) or upstream of the transition region (31) into the radially outer Holweck pumping region (27), in particular into the downstream half or into the downstream third, quarter, fifth or sixth of the radially outer Holweck pumping region (27), and in that the outlet region (27a) and the inlet region (29a) each have a free cross-sectional area defined by the Holweck channels (23) in a cross-sectional plane running perpendicular to the axis of rotation (15), in which the pumping action ends or begins, and the free cross-sectional area of ​​the inlet region (29a) is larger by a factor f > 1 than the free cross-sectional area of ​​the outlet region (25a).

2. Vacuum pump according to claim 1, wherein: 1 < f < 3, preferably 1 < f < 2, preferably 1.2 < f < 1.

5.

3. Vacuum pump according to claim 1 or 2, wherein in the respective cross-sectional plane the height of the Holweck webs (21) in the inlet region (29a) is greater than the height (H) of the Holweck webs (21) in the outlet region (27a).

4. Vacuum pump according to one of the preceding claims, wherein in the respective cross-sectional plane the width (B) of the Holweck webs (21) measured in the circumferential direction is greater in the inlet region (29a) than in the outlet region (27a).

5. Vacuum pump according to one of the preceding claims, wherein the number of Holweck webs (21) in the radially inner Holweck pumping area (29) is smaller than the number of Holweck webs (21) in the radially outer Holweck pumping area (27).

6. Vacuum pump according to one of the preceding claims, wherein the Holweck stator (17b) delimiting the radially inner Holweck pumping region (29) is a Holweck stator provided with a Holweck thread on both sides, which delimits a further Holweck pumping region (43) radially further inward with a further Holweck rotor (25).

7. Vacuum pump according to claim 6, wherein the Holweck stator (17b) provided with the Holweck thread on both sides has a wall thickness measured in the radial direction, and wherein in the inlet region (29a) the wall thickness is smaller than the height of the Holweck webs (21) of the radially inner Holweck pumping region (29).

8. Vacuum pump according to one of the preceding claims, wherein the radially outer Holweck pumping region (27) and / or the radially inner Holweck pumping region (29) are each conically designed such that the height of the Holweck webs (21) continuously decreases in the pumping direction.

9. Vacuum pump according to claim 8, wherein a conicity angle (βa) defined by the channel base (19) of the radially outer Holweck pumping region (27) and a conicity angle (βi) defined by the channel base (19) of the radially inner Holweck pumping region (29) are at least substantially equal to or different from one another, in particular wherein the conicity angle (βa) of the radially outer Holweck pumping region (27) is greater or smaller than the conicity angle (βi) of the radially inner Holweck pumping region (29).

10. Vacuum pump according to one of the preceding claims, wherein at least one pump-effective section of the radially outer Holweck stator (17a) which delimits the radially outer Holweck pumping region (27) with the Holweck rotor (25) is formed in one piece, in particular wherein the radial gas inlet (35) opens into the radially outer Holweck pumping region (27) upstream of the transition region (31) and extends through the one-piece pump-effective section of the radially outer Holweck stator (17a).

11. Vacuum pump according to one of the preceding claims, wherein the radial gas inlet (35) extends above a lower part or intermediate component (39) of the vacuum pump, in which the transition region (31) is at least partially located, through a pump housing (41).

12. Vacuum pump according to one of the preceding claims, wherein at least one further radial gas inlet is arranged upstream of the radial gas inlet (35) into the Holweck pump unit (13), in particular wherein the further radial gas inlet opens into the Holweck pump unit (13) or into the turbomolecular pump unit (11).

13. Vacuum system with a vacuum pump according to one of the preceding claims and with a recipient to be evacuated, wherein the vacuum pump is designed as a split-flow vacuum pump having one or more radial suction inlets which, during operation, are each connected to an opening of the recipient, and wherein one of the radial suction inlets is the radial gas inlet (35) opening into the transition region (31) or upstream of the transition region (31) into the radially outer Holweck pump region (27).

14. Leak detection system with a vacuum pump according to one of claims 1 to 12, which can be connected to a test object to be evacuated, and with a detector, in particular a mass spectrometer, for detecting a test gas, and wherein the vacuum pump is connected to the detector via an axial or radial gas inlet and downstream of the gas inlet a radial gas inlet for the test gas into the Holweck pump unit (13) is provided, wherein the radial gas inlet for the test gas is the radial gas inlet (35) opening into the transition region (31) or upstream of the transition region (31) into the radially outer Holweck pump region (27).

Images