Turbomolecular pump

Abstract

The invention relates to a turbomolecular pump with an inlet, an outlet, a pumping system operating in a pumping direction from the inlet to the outlet and comprising at least one turbomolecular pumping stage, the pumping system comprising a rotor with rotor elements and stator elements that interact with the rotor elements during operation to effectively pump, and a spindle unit comprising a spindle housing and, within the spindle housing, a shaft rotatably connected to the rotor, and for the shaft a drive motor and a bearing arrangement, wherein the shaft can be driven into rotation about an axis of rotation by means of the drive motor and is rotatably mounted by the bearing arrangement, wherein the spindle housing is at least partially surrounded by the rotor, and wherein at least one blocking stage is arranged in an intermediate space between the spindle housing and the rotor, which blocks at least one direction, in particular for a process gas pumped by the pumping system,has a blocking effect and is formed by an area on the outside of the spindle housing and / or by an area on the inside of the rotor.

Description

[0001] The invention relates to a turbomolecular pump with an inlet, an outlet, a pumping system effective in a pumping direction from the inlet to the outlet and comprising at least one turbomolecular pumping stage, which has a rotor comprising rotor elements and stator elements that interact with the rotor elements during operation to effectively pump, and a spindle unit comprising a spindle housing and, within the spindle housing, a shaft rotatably connected to the rotor and, for the shaft, a drive motor and a bearing arrangement, wherein the shaft can be driven into rotation about an axis of rotation by means of the drive motor and is rotatably mounted by the bearing arrangement, and wherein the spindle housing is at least partially surrounded by the rotor.

[0002] Turbomolecular pumps are vacuum pumps with a fundamentally well-known structure and function, which are versatile and used in various applications and environments in industry and science.

[0003] The turbomolecular pump mentioned at the outset features a spindle unit that can be handled as a single unit. This unit comprises an outer spindle housing containing a shaft, a drive motor for the shaft, and a bearing assembly for the shaft. Such spindle units can be installed and removed as a single unit during pump assembly and disassembly. Turbomolecular pumps of this type are generally known. The spindle units, or—if the aforementioned components, particularly the bearing assembly, are combined into a subunit arranged within the spindle housing—these subunits are also referred to as magnetic bearing cartridges. The outer spindle housing faces the rotor's inner surface with that portion of its outer surface being surrounded by the rotor.

[0004] In Depending on the specific application and environment, external influences can affect the components of the spindle unit. This particularly affects the bearing system, especially when the shaft is supported by active magnetic bearings. External influences can include process gases that are pumped from the inlet to the outlet and can enter the spindle housing. Other external influences, such as ambient dust, can also affect the spindle unit components.

[0005] The object of the invention is to protect the spindle unit of a turbomolecular pump of the type mentioned above, and in particular the components located in the spindle housing, from external influences as effectively and simply as possible.

[0006] This problem is solved by the features of independent claim 1.

[0007] In particular, it is provided that at least one blocking stage is arranged in an intermediate space between the spindle housing and the rotor, which acts as a blocking stage at least in one direction, in particular for a process gas conveyed by the pumping system, and which is formed jointly by an area on the outside of the spindle housing and / or by an area on the inside of the rotor.

[0008] The space between the spindle housing and the rotor is used to make it more difficult or to completely prevent the ingress of process gas or other contaminants, thus protecting the relevant interior of the pump, and in particular the interior of the spindle housing of the spindle unit, from external influences.

[0009] The barrier step is therefore formed neither by surface roughness of the spindle housing or rotor, whether intentional or deliberately introduced for other reasons, nor by one or more separate components or materials deliberately placed in the gap. Rather, the barrier step is formed by a structure arranged on the outside of the spindle housing or on the inside of the rotor to achieve a barrier effect, or jointly by structures formed on both sides. Different possibilities for forming such a barrier step are discussed in more detail below.

[0010] In principle, the rotor can surround the spindle housing only radially or only axially. Preferably, the rotor surrounds the spindle housing both radially and axially. If the rotor surrounds the spindle housing radially, then—regardless of whether the rotor also surrounds the spindle housing axially—the rotor can surround the spindle housing over its entire axial length or only over a portion of its axial length. In the latter case, the spindle housing can project axially either beyond one open end of the rotor, or the rotor can be open at both ends and the spindle housing can project axially beyond both open ends.

[0011] According to a further embodiment, the rotor can be arranged to surround the spindle housing both radially and axially, with at least one axial locking stage located in an axial section of the gap and / or at least one radial locking stage located in a radial section of the gap. Preferably, the spindle housing is not surrounded by the rotor over its entire axial length, i.e., the spindle housing projects axially beyond an open end of the rotor.

[0012] In a particularly advantageous further development, both an axial section of the gap and a radial section of the gap are used to form a barrier step.

[0013] A gap with an axial section and a radial section can be formed, for example, by the rotor having a bell- or cup-shaped section with which the rotor at least partially surrounds the spindle housing.

[0014] At least one sealing stage can be formed by a labyrinth seal. In particular, the labyrinth seal can be designed as an axial sealing stage. In this case, an axial section of the gap is used to form a sealing stage. The advantage of such a sealing stage is that it can be located relatively far inwards radially, i.e., relatively close to the axis of rotation.

[0015] According to some embodiments, at least one blocking stage can be designed to act as a pump in the direction of the outlet. In this case, the blocking stage is not passive, but rather exerts an active blocking effect during operation by providing a pumping action in the opposite direction to where the blocking stage is intended to act. The rotation of the rotor relative to the spindle housing can be used to form a pumping blocking stage. For example, at least one pumping blocking stage can be formed by a sealing track. In particular, an axial section of the space between the rotor and the spindle housing can be formed as such a pumping sealing track in a relatively simple manner.

[0016] Alternatively or additionally, at least one blocking stage can be formed by a Holweck pump stage. The axial section of the space between the rotor and the spindle housing can be used to form such a Holweck pump stage.

[0017] The Holweck pump stage forming the locking stage can comprise a single- or multi-start Holweck thread on the outside of the spindle housing and a Holweck surface facing the Holweck thread on the inside of the rotor. In particular, it can be provided that the Holweck surface is formed by the radial inside of a Holweck sleeve of the rotor.

[0018] This Holweck sleeve can be a component of a Holweck pump system located downstream of the turbomolecular pump stage in the pumping direction, which additionally has one or more additional Holweck pump stages located radially outside the Holweck pump stage forming the barrier stage.

[0019] In other words, if such a Holweck pump system is provided, the Holweck pump stage forming the barrier stage can be the radially innermost stage of a multi-stage Holweck pump system comprising several radially nested Holweck pump stages. Such an arrangement of multiple Holweck pump stages is also referred to as a nested arrangement of Holweck pump stages or a nested Holweck pump system. Such Holweck pump systems are generally known and are regularly used in turbomolecular pumps. One outlet of the Holweck pump system is then connected to the outlet of the turbomolecular pump, which is formed, in particular, by a backing port.

[0020] In such a configuration, the output of the Holweck pumping system can lead, on the one hand, to at least one Holweck pumping stage that pumps in the same direction as the turbomolecular pumping stage, and on the other hand, either to the Holweck pumping stage forming the barrier stage or to at least one Holweck pumping stage downstream of the barrier stage that pumps in the same direction as the barrier stage.

[0021] In other words, the blocking stage can either lead directly to the outlet of the Holweck pumping system, i.e., without one or more downstream Holweck pumping stages, or the Holweck pumping stage forming the blocking stage can be extended by one or more Holweck pumping stages that pump in the same direction, i.e., against the blocking direction, and which are not formed by the space between the rotor and the spindle housing.

[0022] The design and function of a Holweck pump system are generally known, so there is no need to discuss them in more detail here.

[0023] Preferably, the rotor and the shaft are detachably connected. In this way, the spindle unit comprising the shaft can be assembled and disassembled independently of the rotor.

[0024] Alternatively, the rotor and shaft can be permanently joined. The rotor and spindle unit can then be handled and assembled as a single unit.

[0025] According to some embodiments, the rotor can comprise a holder connected to the shaft, to which the rotor elements are connected. The rotor elements are, in particular, rotor disks of the turbomolecular pumping stage and – if, according to preferred embodiments, a Holweck pumping system is arranged downstream of the turbomolecular pumping stage – one or more Holweck sleeves of the Holweck pumping system.

[0026] It may be provided that at least some rotor elements, preferably all rotor elements, are designed as separate components that are attached to the holder by suitable means. Methods for the rotationally fixed mounting of rotor disks of a turbomolecular pump stage and of Holweck sleeves of a Holweck pump system are generally known. Rotor disks can, for example, be mounted on a corresponding shaft- or shaft-like section of the rotor. Holweck sleeves, which may be made of a different material than the rotor holder or, for example, a hub-like support for the holder, can be bonded to the holder or support, for example. Such fastening methods are generally known, so there is no need to discuss them in detail here.One or more, in particular all, Holweck sleeves can also be made of the same material as the holder and in particular be formed in one piece with the holder.

[0027] The rotor elements, or at least some rotor elements, in particular all or part of the rotor disks of the turbomolecular pump stage and / or one or more, in particular all, Holweck sleeves of a Holweck pump system, can alternatively be formed integrally with the rotor holder. In particular, the entire rotor, including all rotor elements, in particular all rotor disks and all Holweck sleeves of a Holweck pump system, can be formed integrally. Such designs of rotors for turbomolecular pumps, and in particular for turbomolecular pump stages and Holweck pump systems, are also known in principle.

[0028] As mentioned elsewhere, the rotor can have a bell- or cup-shaped section that at least partially surrounds the spindle housing. This creates a gap between the rotor and the spindle housing with both an axial and a radial section. Such a bell- or cup-shaped rotor thus allows for the inclusion of multiple, and in particular, differently designed sealing stages. For example, an axial sealing stage, such as a labyrinth seal or a sealing track stage, can be formed in the axial section of the gap, while a Holweck pump stage can be provided as a radial sealing stage in the radial section of the gap.

[0029] According to some further developments, a section of the rotor surrounding the spindle housing can be formed by a hollow sleeve and a support for the hollow sleeve. The support and the hollow sleeve together can form a bell or cup shape.

[0030] A section of the rotor surrounding the spindle housing can be open in an axial direction pointing away from the turbomolecular pump stage, with the spindle unit projecting beyond the open end of the rotor. In particular, it can be provided that the spindle unit is surrounded outside the rotor by a stationary pump housing and / or a stationary pump lower section.

[0031] As mentioned elsewhere, the bearing arrangement for the shaft can include one or more active magnetic bearings. This can include one or more radial active magnetic bearings and one or more active axial magnetic bearings.

[0032] Alternatively, the shaft can be supported by one or more rolling bearings. A so-called hybrid bearing arrangement is also possible, meaning that the shaft can be supported by either one or more active magnetic bearings or one or more rolling bearings.

[0033] An active magnetic bearing is understood to be a bearing in which the bearing action is achieved by means of controlled electromagnets. The use of such magnetic bearings in vacuum pumps, including turbomolecular pumps, for supporting rapidly rotating rotors or shafts is generally known in the technical field under discussion, so that further explanation is not necessary here.

[0034] A rotary bearing arrangement for the shaft consisting solely of active magnetic bearings does not preclude the use of one or more rolling bearings, which serve as so-called backup or catch bearings. This concept is also generally known.

[0035] According to some advanced designs, the pump may be equipped with a barrier gas connection and a flow path for the barrier gas extending from this connection. The flow path for the barrier gas passes through the spindle unit and opens into the space between the spindles. The use of a barrier gas is advantageous in conjunction with one or more passive barrier stages, as well as with one or more pump-acting barrier stages and with a combination of at least one passive and at least one active barrier stage. An active, i.e., pump-acting, barrier stage, such as a Siegbahn stage or a Holweck pump stage, can deliver the barrier gas against the barrier direction, thereby further suppressing or even more reliably preventing the ingress of process gas or other contaminants.

[0036] It may be provided that the flow path for the barrier gas opens into the space at a point which, in a flow direction leading to the outlet, is located upstream of at least one barrier stage.

[0037] Furthermore, it may be provided that the flow path for the sealing gas leads through an emergency bearing arranged radially between the shaft and a section of the spindle housing surrounded by the rotor.

[0038] This allows, especially if the emergency bearing represents a potential entry point for external influences into the interior of the spindle housing, this entry point to be protected in a particularly effective manner.

[0039] The invention is described below by way of example with reference to the drawing. The drawing shows: Fig. 1 shows a section along the axis of rotation of an embodiment of a turbomolecular pump according to the invention, Fig. 2 shows a section along the axis of rotation of the spindle unit of the pump. Fig. 1 , Fig. 3 the spindle unit of Fig. 2 in one view, Fig. 4 the pump of Fig. 1 as well as, in enlarged representation, an axial locking stage and a radial locking stage, and Fig. 5 two different possibilities for the integration of a Holweck pump stage serving as a locking stage into the Holweck pump system of the pump of Fig. 1 .

[0040] The turbomolecular pump according to Fig. 1 The pump housing 49 comprises a cylindrical housing with a high-vacuum inlet 11 and a radial forevacuum outlet 13, which is formed in an intermediate section 50 of the housing 49 and is provided with a forevacuum connection. On the side facing away from the inlet 11, the housing 49 is provided with a lower section 51, which is closed at its underside by means of a cover element 52. A barrier gas connection 59, which will be discussed in more detail elsewhere, is shown here purely as an example on the lower section 51.

[0041] The pumping system of the turbomolecular pump comprises a turbomolecular pumping stage 15 with a plurality of alternately arranged rotor disks 17 and stator disks 23, as well as a Holweck pumping system 43 downstream of the turbomolecular pumping stage 15 in a pumping direction extending from the inlet 11 to the outlet 13. Of the rotor disks 17 and the stator disks 23 of the turbomolecular pumping stage 15, Fig. 1 Only a few are listed as examples, each with a reference mark.

[0042] The Holweck pump system 43, the construction of which will be discussed in more detail elsewhere, comprises a so-called nested arrangement of radially nested Holweck pump stages, which are formed by Holweck sleeves 19 and stator elements 23.

[0043] In addition to the aforementioned rotor elements, namely the rotor disks 17 of the turbomolecular pumping stage 15 and the Holweck sleeves 19 of the Holweck pumping system 43, a rotor 21 of the pumping system comprises a one-piece holder 22. This holder includes two essentially cylindrical sections of different diameters for the rotor disks 17 and an annular support 47 for the two Holweck sleeves 19. The rotor disks 17 of the section with the larger diameter are integrally formed with the holder 22. The other rotor disks 17, located closer to the inlet 11, are rotationally fixed to the holder 22 by being pressed onto the section with the smaller diameter.

[0044] During operation of the turbomolecular pump, which is then connected to a recipient to be evacuated, the rotor 21 rotates about an axis of rotation 35 that coincides with the central axis of the cylindrical pump housing 49, whereby the rotor disks 17 interact effectively with the stator disks 23 and the Holweck sleeves 19 interact effectively with the Holweck stators 23 to convey a respective process gas from the inlet 11 to the outlet 13.

[0045] The structure and function of such a pumping system, a turbomolecular pump, as explained above, are generally known.

[0046] In addition to the pump system consisting of rotor 21 and the stator elements 23 that interact with it, the turbomolecular pump includes a spindle unit 25, which is also fundamentally known in terms of its structure and function.

[0047] The spindle unit 25 can be handled as a single unit and thus assembled as a whole. In the assembled state shown, the spindle unit 25 is surrounded axially and radially by the rotor 21 and – axially adjoining the rotor 21 – radially by the intermediate piece 50 of the housing 49 and the lower part 51.

[0048] The spindle unit 25 comprises an outer spindle housing 27 in which a shaft 29, a drive motor, and a bearing assembly for this shaft 29 are arranged. This assembly of the spindle unit 25 will be described below with reference to Fig. 2 The spindle housing 27 comprises two cylindrical sections with different diameters, the cylindrical section with the smaller diameter being located closer to the rotor 21.

[0049] The rotor 21 is set in rotation during operation via the drive motor and thus the shaft 29. For this purpose, the holder 22 of the rotor 21 is connected to the shaft 29 by a screw 61. The rotating system of the turbomolecular pump therefore includes the shaft 29 in addition to the rotor 21.

[0050] During pumping operation, the turbomolecular pump is connected on the inlet side, for example, to a recipient to be evacuated. A gas to be pumped flows from the inlet 11 through the turbomolecular pumping stage 15 and the Holweck pumping system 43 to an outlet 45 of the Holweck pumping system 43, which leads to the outlet 13. For the process gas coming from the turbomolecular pumping stage 15, the Holweck pumping system 43 comprises three radially nested Holweck pumping stages. The third Holweck pumping stage, counting radially outwards, terminates at the aforementioned outlet 45.

[0051] The turbomolecular pump according to Fig. 1 is characterized by the fact that an intermediate space 37 between the outside of the spindle housing 27 and the inside of the rotor 21 is used to form one or more barrier stages - in the present embodiment two barrier stages 39, 41 - in order to protect the components located inside the spindle housing 27 - in particular the bearing assembly - from external influences, especially from the process gas conveyed to the outlet 45 of the Holweck pumping system 43, but also - as mentioned in the introduction - from other external influences such as impurities in the form of dust.

[0052] An axial sealing stage 39 in the form of a labyrinth seal is located in an axial section of the space 37. The labyrinth seal is formed by axially facing surfaces on the outside of the spindle housing 27 and the inside of the support 47 of the holder 22 of the rotor 21. The two facing sides of the spindle housing 27 and the support 47 thus jointly form the sealing stage 39, which is designed here as a labyrinth seal.

[0053] A radial barrier stage 41, located in a radial section of the space 37, is formed jointly by the radial inner surface of the radially inner Holweck sleeve 19 of the Holweck pumping system 43 and the outer surface of the cylindrical section of the spindle housing 27, which thus acts as a Holweck stator. This radial barrier stage 41 is therefore a Holweck pumping stage that is effective in pumping towards the outlet 45 of the Holweck pumping system 43.

[0054] If a barrier gas source is connected to the barrier gas port 49 during operation of the turbomolecular pump, then barrier gas can flow through the spindle unit 25, i.e. through the interior of the spindle housing 27, into the axial section of the intermediate space 37 in a manner not shown in detail here, and in particular through a radial emergency bearing.

[0055] Thus, the two sealing stages 39, 41 and, if applicable, the sealing gas together form a barrier against external influences, such as, in particular, the process gas conveyed to the outlet 45 of the Holweck pumping system 43, thereby preventing them from entering the interior of the spindle housing 27. The pumping action of the radial sealing stage 41, designed as a Holweck pumping stage, directed towards the outlet 45, is particularly advantageous. Instead of the labyrinth seal, a Siegbahn pumping stage, for example, can be provided as the axial sealing stage 39, which also provides a pumping action directed towards the outlet 45 of the Holweck pumping system 43.

[0056] Thus, the mutually facing sides of spindle housing 27 and rotor 21 are advantageously used to form a barrier in the space 37 created thereby against the ingress of contaminants that could otherwise impair the components located inside the spindle housing 27.

[0057] The design of the spindle unit 25 is also Fig. 2 The following are shown schematically: Active radial magnetic bearings 53, a drive motor 31, and an active axial magnetic bearing 55 for the shaft 29. The active axial magnetic bearing 55 interacts with a bearing disk 63 made of magnetizable material, which is formed on the shaft 29. An axial sensor 54 is provided to control the axial position of the shaft 29 and thus of the active axial magnetic bearing 55. This sensor measures the size of the axial gap formed between the axial sensor 54 and an end face 58 of the shaft 29.

[0058] Furthermore, in Fig. 2 Radial emergency bearings 57, designed as rolling bearings, are shown and are arranged at the two axial end regions of the shaft 29. Each outer bearing ring is supported on the stationary spindle housing 27, while each radial inner bearing ring of the respective emergency bearing 57 faces the radial outer side of a section of the shaft 29.

[0059] The emergency bearing 57, which is located closer to the axial sensor 54, is received by a bearing housing 56, which also serves as an axial support for the active axial magnetic bearing 55 and on which the axial sensor 54 is attached.

[0060] To form the based on Fig. 1 In accordance with the described locking stages 39, 41, a hollow thread 41a is formed on a cylindrical section of the outside of the spindle housing 27. This hollow thread 41a is single-start in this case. Alternatively, a multi-start hollow thread 41a can also be provided. As described in connection with Fig. 1 As explained, this Holweck thread 41a together with the radial inner side of the radially internal Holweck sleeve 19 of the Holweck pump system 43 forms a pump-effective Holweck pump stage.

[0061] An axially oriented annular surface of the spindle housing 27, located at the level of one of the emergency bearings 57, is provided with three concentrically arranged wall sections, each projecting axially, and thus forms one part of the aforementioned labyrinth seal, which constitutes the axial locking stage 39. This arrangement of concentric wall sections 39a engages with a corresponding arrangement of concentric wall sections 39b on the facing, axially oriented surface of the support 47 of the holder 22 of the rotor 21, in order to form the described labyrinth seal 39 as an axial locking stage.

[0062] A view of this spindle unit 25 is in Fig. 3 shown. Particularly visible is the hollow thread 41a, which is formed on the outside of the cylindrical section of the spindle housing 27 having the smaller outer diameter, which is attached to the rotor 21 (cf. Fig. 1 ) the end face of the shaft 29, which protrudes slightly beyond the spindle housing 27, and the section of the bearing housing 56 with the axial sensor 54 that protrudes from the spindle housing 27 on the other side.

[0063] In Fig. 4 is the turbomolecular pump of Fig. 1 together with enlarged sections, each showing one of the mentioned barrier levels 39, 41.

[0064] The image on the left in Fig. 4 shows the Holweck pumping system 43 with the two Holweck stators 43 and the two Holweck sleeves 19 attached to the support 47 of the holder 22 of the rotor 21.

[0065] The radially innermost Holweck pump stage of this Holweck pump system 43 constitutes the radial locking stage 41, which—as described above—is formed by the Holweck thread 41a on the outside of the spindle housing 27 and the Holweck surface 41b formed by the radial inside of the radially inner Holweck sleeve 19. This Holweck pump stage 41, which acts as a locking stage, and the three radially outer Holweck pump stages of the Holweck pump system 43, which are successive in the pumping direction, open at the common outlet 45, which leads to the outlet 13 of the pump (see Figure 1). Fig. 1 ).

[0066] The illustration on the right in Fig. 4 Figure 39 shows the labyrinth seal acting as an axial locking stage, which is formed from the two axially interlocking arrangements of concentric wall sections 39a, 39b.

[0067] This axial locking step 39 is therefore located in the axial section of the space 37 and lies axially at the level of the emergency bearing 57 between spindle housing 27 and shaft 29.

[0068] Furthermore, this right-hand representation includes in Fig. 4 partially one of the active radial magnetic bearings 53 (see Fig. 2 ) and a stator disk 23 of the turbomolecular pump stage 15 is shown (cf. Fig. 1 ).

[0069] Fig. 5 shows two possibilities for integrating the aforementioned radial locking stage 41 into the Holweck pump system 43.

[0070] The image on the left in Fig. 5 This corresponds to what was stated above, particularly in connection with the representation on the left. Fig. 4 This has been explained. The arrows indicate the flow of the process gas coming from turbomolecular pump stage 15, which is located on the left in Fig. 5 The variant shown is conveyed to the outlet 45 by the three radially nested Holweck pump stages, as well as the flow from the sealing gas connection 49 (not shown here) (cf. Fig. 4 ) incoming barrier gas, which flows through the interior of the spindle housing 27 into the space 37 and thereby through the emergency bearing 57 located there.

[0071] Of the four radially nested Holweck pump stages, only the radially innermost Holweck pump stage is effective as a blocking element, i.e., the Holweck pump stage in the radial section of the space 37 between spindle housing 27 and radially inner Holweck sleeve 19. The other three Holweck pump stages serve to pump the process gas coming from the turbomolecular pump stage 15.

[0072] In the right in Fig. 5 In the depicted variant, only the radially outermost Holweck pump stage serves to convey the process gas. The two other Holweck pump stages extend the radially innermost Holweck pump stage, i.e., the barrier stage 41, which in turn is formed by the outer surface of the spindle housing 27 and the radially inner Holweck sleeve 19. These two middle Holweck pump stages are thus different from the variant on the left. Fig. 5 by a correspondingly opposite orientation of the Holweck threads on the relevant Holweck stator 23, i.e. they are effective in the same direction as the locking stage 41. In The outlet 45 of the Holweck pumping system 43, which leads to the outlet 13 of the pump, is thus fed on the one hand by the Holweck pumping stage which conveys the process gas and is located radially furthest outwards, and on the other hand by the three other Holweck pumping stages which pump in the same direction.

[0073] The radial locking stage 41 in the radial space between inner Holweck sleeve 19 and spindle housing 27 is thus effectively extended by the two Holweck pump stages. Bezugszeichenliste

[0074] 11 Inlet 13 Outlet 15 Turbomolecular pump stage 17 Rotor element, rotor disk 19 Rotor element, Holweck sleeve 21 Rotor 22 Rotor holder 23 Stator element, stator disk or Holweck stator 25 Spindle unit 27 Spindle housing 29 Shaft 31 Drive motor 35 Shaft of rotation 37 Intermediate space 39 Axial barrier stage 39a Arrangement of concentric wall sections 39b Arrangement of concentric wall sections 41 Radial barrier stage 41a Holweck thread 41b Holweck surface 43 Holweck pump system 45 Outlet of the Holweck pump system 47 Support 49 Pump housing 50 Intermediate piece 51 Lower part 52 Cover element 53 Active radial magnetic bearing 54 Axial sensor 55 Active axial magnetic bearing 56 Position detection 57 Emergency bearing 58 End section 59 Bar gas connection 61 Screw 63 Bearing washer

Claims

1. Turbomolecular pump comprising: - an inlet (11), - an outlet (13), - a pumping system operating in a pumping direction from the inlet (11) to the outlet (13) and comprising at least one turbomolecular pumping stage (15), the pumping system comprising a rotor (21) with rotor elements (17, 19) and stator elements (23) which interact with the rotor elements (17, 19) to provide pumping action during operation, and - a spindle unit (25) comprising a spindle housing (27) and, within the spindle housing (27), a shaft (29) rotatably connected to the rotor (21), and for the shaft (29) a drive motor (31) and a bearing arrangement (53, 55, 57), wherein the shaft (29) can be driven into rotation about a rotary axis (35) by means of the drive motor (31) and is rotatably mounted by the bearing arrangement (53, 55, 57), wherein the spindle housing (27) is at least partially surrounded by the rotor (21),and wherein at least one blocking stage (39, 41) is arranged in an intermediate space (37) between spindle housing (27) and rotor (21), which acts as a blocking element at least in one direction, in particular for a process gas conveyed by the pumping system, and which is formed by a region on the outside of the spindle housing (27) and / or by a region on the inside of the rotor (21).

2. Turbomolecular pump according to claim 1, wherein the rotor (21) surrounds the spindle housing (27) both radially and axially, and wherein at least one axial locking stage (39) is arranged in an axial section of the space (37) and / or at least one radial locking stage (41) is arranged in a radial section of the space (37).

3. Turbomolecular pump according to claim 1 or 2, wherein the or a barrier stage (39) is formed by a labyrinth seal, in particular wherein the labyrinth seal is an axial barrier stage.

4. Turbomolecular pump according to one of the preceding claims, wherein the or a blocking stage (41) is designed to be pump-effective in the direction of the outlet (13).

5. Turbomolecular pump according to claim 4, wherein the or a blocking stage designed to be effective in the direction of the outlet (13) is formed by a sieve pumping stage.

6. Turbomolecular pump according to claim 4 or 5, wherein the or a blocking stage (41) designed to act in the direction of the outlet (13) is formed by a Holweck pump stage.

7. Turbomolecular pump according to claim 6, wherein the Holweck pump stage forming the barrier stage (41) comprises a single- or multi-start Holweck thread (41a) on the outside of the spindle housing (27) and a Holweck surface (41b) facing the Holweck thread (41a) on the inside of the rotor (21), in particular wherein the Holweck surface (41b) is formed by the radial inside of a Holweck sleeve (19) of the rotor (21).

8. Turbomolecular pump according to claim 6 or 7, wherein the Holweck pump stage forming the barrier stage (41) is the radially innermost stage of a multi-stage Holweck pump system (43) comprising several radially nested Holweck pump stages, which is arranged downstream of the turbomolecular pump stage (15) in the pumping direction and which has an outlet (45) leading to the outlet (13) of the pump, and wherein at least one Holweck pump stage effective in the same direction as the turbomolecular pump stage (15) leads to the outlet (45) of the Holweck pump system (43), and either the Holweck pump stage forming the barrier stage (41) or at least one Holweck pump stage downstream of the barrier stage (41) effective in the same direction as the barrier stage (41) leads to the outlet (45).

9. Turbomolecular pump according to one of the preceding claims, wherein the rotor (21) and the shaft (29) are detachably connected to each other, and / or wherein the rotor (21) comprises a holder (22) connected to the shaft (29), to which the rotor elements (17, 19) are connected, in particular wherein at least some rotor elements (17, 19) are separate components that are attached to the holder (22).

10. Turbomolecular pump according to one of the preceding claims, wherein the rotor (21) has a bell- or cup-shaped section (47, 19) with which the rotor (21) at least partially surrounds the spindle housing (27).

11. Turbomolecular pump according to one of the preceding claims, wherein a section of the rotor (21) surrounding the spindle housing (27) is formed by a Holweck sleeve (19) and a support (47) for the Holweck sleeve (19).

12. Turbomolecular pump according to one of the preceding claims, wherein a section (47, 19) of the rotor (21) surrounding the spindle housing (27) is open in an axial direction pointing away from the turbomolecular pump stage (15) and the spindle unit (25) projects beyond the open end of the rotor (21), in particular wherein the spindle unit (25) is surrounded outside the rotor (21) by a stationary housing (49) of the pump and / or by a stationary lower part (51) of the pump.

13. Turbomolecular pump according to one of the preceding claims, wherein the bearing arrangement (53, 55, 57) comprises one or more active magnetic bearings (53, 55) and / or one or more rolling bearings (57).

14. Turbomolecular pump according to one of the preceding claims, wherein the pump has a barrier gas port (59) and a flow path for a barrier gas extending from the barrier gas port (59), wherein the flow path for the barrier gas passes through the spindle unit (25) and opens into the space (37).

15. Turbomolecular pump according to claim 14, wherein the flow path for the barrier gas opens into the space (37) at a point which is arranged upstream of at least one barrier stage (39, 41) in a flow direction leading to the outlet (13), and / or wherein the flow path for the barrier gas passes through an emergency bearing (57) arranged radially between the shaft (29) and a section of the spindle housing (27) surrounded by the rotor (21).

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