EP3907406B1 - Vacuum pump - Google Patents

Description

The invention relates to a vacuum pump, in particular a turbomolecular vacuum pump, having at least one inlet, one outlet and at least two Holweck stages which are concentric with respect to a common axis of rotation and are arranged one after the other in the pumping direction between the inlet and the outlet.

Vacuum pumps are used in various areas of technology. Depending on the requirements, the vacuum pumps have one or more pump stages. A Holweck pump stage (also referred to herein simply as a Holweck stage) belongs to the genus of molecular vacuum pumps and generates molecular flow through the rotation of a rotating element relative to a static element. A vacuum pump can comprise one or more Holweck stages, whereby several Holweck stages can pump both in series and in parallel with one another. Holweck stages are typically used in turbomolecular vacuum pumps and are usually one or more turbomolecular pump stages (also turbo pump stages) downstream.

As briefly mentioned above, a Holweck stage comprises a Holweck rotor and a Holweck stator segment, the Holweck rotor having a rotor shaft to which one or more Holweck sleeves (often referred to as rotor sleeves) are concentrically attached by means of, for example, a disc-shaped Holweck hub. The Holweck stator segment is provided with a single or multi-threaded Holweck thread. The gas molecules to be conveyed are conveyed along the thread turns from an inlet side to an outlet side by the rotating movement of the Holweck sleeve relative to the Holweck stator segment assigned to it. A thread usually includes a through Walls of a web limited circumferential Holweck channel, in which the gas molecules are promoted when the rotor sleeve rotates relative to the Holweck stator segment. In order to minimize backflow losses, the width of the radial gap (Holweck gap) between the outside of the Holweck stator segment or the web tip diameter of the Holweck stator thread and the rotor sleeve must be kept small.

So-called “folded” Holweck arrangements are known, in which several Holweck stages are arranged concentrically one inside the other, so that the pumping devices of Holweck stages that follow one another radially are opposite to one another. Two successive Holweck stages, a (radial) outer Holweck stage and a (radial) inner Holweck stage, can comprise a common Holweck stator, which is provided with a Holweck thread on both sides and is also referred to as "double-sided" in the following, which is inserted into the radial gap between the concentrically arranged Holweck sleeves protrudes. The two Holweck stator segments of the two Holweck stages are thus arranged on both sides of the Holweck stator.

In order to build a vacuum pump as compact as possible in the axial direction, an axial distance or axial gap between the axial end of the Holweck stator and the Holweck hub is kept as small as possible. In conventional folded Holweck arrangements, therefore, there is generally only a narrow annular gap between the two components mentioned, which also contributes to minimizing backflow losses between the Holweck stages.

In many applications, the power consumption is an important parameter when integrating a vacuum pump into a system. For example, in a conventional turbomolecular vacuum pump with turbopump stage(s) and Holweck stage(s), a large part of the power consumption is often caused by the gas friction in the Holweck stage(s). A conventional pump of the above described type with the features of the preamble of claim 1 is in the

US6135709A shown.

According to the invention, it was recognized that there is potential in the area of the Holweck arrangement to influence the power consumption of the vacuum pump without compromising decisive performance parameters, such as pumping speed or fore-vacuum compatibility of the pump.

Based on a known vacuum pump with the features of the preamble of claim 1, contrary to the usual design principles, a comparatively large axial distance or space between the static element of the successive Holweck stages and the rotor hub is deliberately provided.

Specifically, this is achieved in that an axial distance between an axial end of at least one of the Holweck stator segments protruding into the intermediate space and the Holweck hub, which is designed in the shape of a disk, is greater than 25% of the axial extension of a section of the Holweck stator segments protruding into the radial intermediate space and/or is greater than 25% of the axial extent of at least one of the Holweck sleeves. If there is a need for a greater reduction in power consumption, the axial distance can also be selected to be larger and larger than 30%, 40% or 50% of the axial extent of the section of the Holweck stator segments protruding into the radial gap and/or larger than 30%, 40% or 50% of the axial extent of at least one of the Holweck sleeves.

In addition, the Holweck stator segments and the Holweck sleeves can be designed in such a way that an axial extent of a section protruding into the radial intermediate space of at least one of the Holweck stator segments is less than 75% of the axial extent of at least one of the Holweck sleeves. At a Such a configuration of the components mentioned above results in the comparatively large axial distance or axial gap. The axial extent of the section of at least one of the Holweck stator segments protruding into the radial intermediate space can, if required, also be less than 70%, 60% or 50% of the axial extent of at least one of the Holweck sleeves.

The concept described above is based on the finding that the power consumption of the vacuum pump depends on the effective (pumping-active) axial length of the Holweck stages. To put it simply, the higher the axial length of the active pumping area of the Holweck stages, the higher the power consumption.

In some applications it is not necessary to call up or provide the full pump power of the Holweck stages.

According to the invention, it is therefore proposed to reduce the axial extent of the Holweck stator segments in order to increase the axial distance defined above. This significantly reduces the power consumption of the vacuum pump without e.g. B. whose pumping speed or fore-vacuum compatibility (vacuum data) is excessively influenced. Since it has been recognized according to the invention that despite the above-described comparatively large axial gap, which is achieved by a suitable and above-defined dimensioning of the components relevant for this, approximately comparable or only slightly and for certain cases completely sufficient performance data of the pump can already be achieved proven vacuum pump concepts can be adapted without complex structural changes being necessary. All that needs to be done is to reduce the pump-active axial extension of the Holweck stator segments - i.e. the components of the Holweck stator that are provided with a Holweck thread and in the radial space between the Holweck or rotor sleeves - can be made in order to achieve a significant reduction in the power consumption of the vacuum pump. The rotating elements of the Holweck steps do not have to be changed.

For example, a Holweck stator with shortened, pump-active Holweck stator segments can be used in a conventional vacuum pump without structural changes having to be made to the rotating elements of the Holweck stages. Consequently, the desired goal is already achieved by a comparatively simple modification.

In particular, it was recognized that an increase in the axial clearance negatively affects the vacuum data to a lesser extent than expected, while at the same time the positive effect of the power consumption reduction has a disproportionate effect.

Further embodiments of the invention are indicated in the description, the claims and the accompanying drawings.

According to one embodiment, the Holweck stator segments and the Holweck sleeves are designed and/or arranged in such a way that the axial distance between an axial end of both Holweck stator segments projecting into the intermediate space and the rotor hub is greater than 25%, 30%, 40% or 50% of the axial extent of one The portion of the Holweck stator segments that protrudes into the gap and/or is greater than 25%, 30%, 40% or 50% of the axial extension of both Holweck sleeves and/or that the axial extension of the portion of the two Holweck stator segments that protrudes into the gap is less than 80%, 70 %, 60% or 50% of the axial extent of at least one of the Holweck sleeves.

Basically, the two Holweck stator segments of the two Holweck stages can have a different or the same axial extension. The same applies to the Holweck sleeves.

The vacuum pump may have at least a first and a second inlet, the first inlet being associated with a turbomolecular pumping stage and the second inlet being associated with the Holweck stages. In the case of so-called spliflow pumps, the concept according to the invention is particularly advantageous, since it is a simple way of adapting to the actual pumping power requirement that exists at the second inlet, and at the same time the power consumption caused by the Holweck stages is reduced.

For example, the second inlet—seen in the axial direction of the vacuum pump—is arranged in the area of the Holweck stages.

The second inlet can be a radial inlet, as a result of which a compact design is achieved.

The outer one of the two Holweck sleeves, together with a (third) Holweck stator segment surrounding the outer Holweck sleeve radially on the outside at least in sections, can form a third Holweck stage. In particular, the third stage Holweck stator segment has a recess or opening that forms the second inlet.

To improve the heat dissipation in the area of the Holweck stages, the Holweck stator can be provided with at least one heat exchanger element, which extends from the axial end of the Holweck stator protruding into the radial intermediate space to the rotor hub. The enlarged axial gap according to the invention is thus used to provide a non-pumping heat exchanger element that improves the heat management of the vacuum pump.

Since the heat exchanger element has no relevant active pumping effect, it does not lead to any relevant increase in the power consumption of the vacuum pump.

The heat exchanger element can be rod-shaped, sleeve-shaped or partially sleeve-shaped. It can have a perforation or a slit in order to improve the heat transfer between the gas flow and the element.

More flexibility is achieved if the at least one heat exchanger element is detachably connected to the Holweck stator, for example by screwing. This makes it possible to use the axial gap in a suitable manner and to adapt the heat exchange in the area of the Holweck stages as required.

The Holweck stator can be arranged in different positions in the axial direction. It can be provided that the axial position of the Holweck stator can be changed continuously or in discrete steps.

For example, a fastening concept is conceivable that allows the Holweck stator to be fixed in positions at different depths into the radial gap between the Holweck sleeves. The Holweck stator then does not have to be replaced or modified in order to achieve a needs-based adjustment of the Holweck stages.

According to one embodiment, the vacuum pump has an adjustment mechanism with which an axial positioning of the Holweck stator and/or at least one of the Holweck stator segments can be adjusted. The vacuum pump may include a controller that controls the adjustment mechanism, for example based on operator input, an operating mode of the vacuum pump, and/or an operating parameter of the vacuum pump. Adjusting the axial The Holweck stator can be positioned automatically, ie without the input of an operator.

According to a further embodiment, at least one of the Holweck stator segments is formed in one piece with the Holweck stator. This preferably applies to both Holweck stator segments. In principle, however, it is also conceivable that one of the two segments or both segments is or are detachably connected to a base body of the Holweck stator. For an adaptation of the Holweck stages that is suitable for the respective application, the entire stator does not then have to be exchanged, but an adaptation can take place by exchanging one or both segments.

The present invention further relates to a vacuum pump system comprising a vacuum pump according to at least one of the embodiments described above and at least one replacement Holweck stator comprising at least one Holweck stator segment having an axial extent which differs from the axial extent of the corresponding Holweck stator segment of the Holweck stator. In an embodiment with at least one Holweck stator segment detachably fastened to a main body of the Holweck stator, at least one replacement Holweck stator segment can be provided which has an axial extent that differs from the axial extent of the corresponding Holweck stator segment of the Holweck stator.

The system may also include multiple replacement Holweck stators having differently configured and/or sized Holweck stator segments. The replacement Holweck stators thus form a set that makes it easy to modify the vacuum pump as required. The same applies in an analogous form to a set of replacement Holweck stator segments.

Fig. 1

eine perspektivische Ansicht einer Turbomolekularpumpe,

Fig. 2

eine Ansicht der Unterseite der Turbomolekularpumpe von Fig. 1,

Fig. 3

einen Querschnitt der Turbomolekularpumpe längs der in Fig. 2 gezeigten Schnittlinie A-A,

Fig. 4

eine Querschnittsansicht der Turbomolekularpumpe längs der in Fig. 2 gezeigten Schnittlinie B-B,

Fig. 5

eine Querschnittsansicht der Turbomolekularpumpe längs der in Fig. 2 gezeigten Schnittlinie C-C,

Fig. 6

schematisch einen Längsschnitt durch die rechte Seite einer Holweck-Anordnung gemäß einer ersten Ausführungsform der Erfindung und

Fig. 7 bis 9

schematisch einen Längsschnitt durch die rechte Seite einer Holweck-Anordnung gemäß weiterer Ausführungsformen der Erfindung.

The invention is described below by way of example using advantageous embodiments with reference to the attached figures. They show, each schematically:

1

a perspective view of a turbomolecular pump,

2

a view of the bottom of the turbo molecular pump from 1 ,

3

a cross-section of the turbomolecular pump along the in 2 shown cutting line AA,

4

a cross-sectional view of the turbomolecular pump along the in 2 shown cutting line BB,

figure 5

a cross-sectional view of the turbomolecular pump along the in 2 shown cutting line CC,

6

schematically a longitudinal section through the right side of a Holweck arrangement according to a first embodiment of the invention and

Figures 7 to 9

schematically a longitudinal section through the right side of a Holweck arrangement according to further embodiments of the invention.

In the 1 The 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.

The inlet flange 113 forms when the vacuum pump is aligned 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 accommodated in the electronics housing 123, for example for operating an electric motor 125 arranged in the vacuum pump (cf. also 3 ). Several connections 127 for accessories are provided on the electronics housing 123 . In addition, a data interface 129, for example according to the RS485 standard, and a power supply connection 131 are arranged on the electronics housing 123.

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

A flood inlet 133, in particular in the form of a flood valve, is provided on the housing 119 of the turbomolecular pump 111, via which the vacuum pump 111 can be flooded. In the area of the lower part 121 there is also a sealing gas connection 135, which is also referred to as a flushing gas connection, through which flushing gas to protect the electric motor 125 (see e.g 3 ) before the pumped gas in the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111, can be admitted. Two coolant connections 139 are also arranged in the lower part 121, one of the coolant connections being provided as an inlet and the other coolant connection being provided as an outlet for coolant, which can be conducted into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) operate solely on air cooling.

The lower side 141 of the vacuum pump can serve as a standing surface, so that the vacuum pump 111 can be operated standing on the underside 141 . However, the vacuum pump 111 can also be fastened to a recipient via the inlet flange 113 and can thus be operated in a suspended manner, as it were. In addition, the vacuum pump 111 can be designed in such a way that it can also be operated when it is oriented in a different way than in FIG 1 is shown. It is also possible to realize embodiments of the vacuum pump in which the underside 141 cannot be arranged facing downwards but to the side or directed upwards. In principle, any angles are possible.

Other existing turbomolecular vacuum pumps (not shown), which in particular are larger than the pump shown here, cannot be operated standing.

At the bottom 141, the in 2 shown, various screws 143 are also arranged, by means of which components of the vacuum pump that are not further specified here are fastened to one another. For example, a bearing cap 145 is attached to the underside 141 .

In addition, fastening bores 147 are arranged on the underside 141, via which the pump 111 can be fastened, for example, to a support surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), which in particular are larger than the pump shown here.

In the Figures 2 to 5 a coolant line 148 is shown, in which the coolant fed in and out via the coolant connections 139 can circulate.

Like the sectional views of the Figures 3 to 5 show, the vacuum pump comprises several process gas pump stages for conveying the process gas present at the pump inlet 115 to the pump outlet 117.

A rotor 149 is arranged in the housing 119 and has a rotor shaft 153 which can be rotated about an axis of rotation 151 .

The turbomolecular pump 111 comprises a plurality of turbomolecular pumping stages connected in series with one another in a pumping manner, with a plurality of radial rotor disks 155 fastened to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and fixed in the housing 119. A rotor disk 155 and an adjacent stator disk 157 each form a turbomolecular pump stage. The stator discs 157 are held at a desired axial distance from one another by spacer rings 159 .

The vacuum pump also comprises Holweck pump stages which are arranged one inside the other in the radial direction and are connected in series with one another for pumping purposes. Other turbomolecular vacuum pumps (not shown) exist that do not have Holweck pumping stages.

The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two Holweck rotor sleeves 163, 165 in the shape of a cylinder jacket, fastened to the rotor hub 161 and carried by it, which are oriented coaxially to the axis of rotation 151 and are nested in one another in the radial direction. Also provided are two cylinder jacket-shaped Holweck stator sleeves 167, 169, which are also oriented coaxially with respect to the axis of rotation 151 and are nested in one another when viewed in the radial direction.

The pumping-active surfaces of the Holweck pump stages are formed by the lateral surfaces, ie by 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 forming with it the first Holweck pump stage following the turbomolecular pumps. The radially inner surface of the outer Holweck rotor sleeve 163 faces the radially outer surface of the inner Holweck stator sleeve 169 to form a radial Holweck gap 173 and therewith forms a second Holweck pumping stage. The radially inner surface of the inner Holweck stator sleeve 169 faces the radially outer surface of the inner Holweck rotor sleeve 165 to form a radial Holweck gap 175 and therewith forms the third Holweck pumping stage.

At the lower end of the Holweck rotor sleeve 163, a radially running channel can be provided, via which the radially outer Holweck gap 171 is connected to the middle Holweck gap 173. In addition, a radially extending channel can be provided at the upper end of the inner Holweck stator sleeve 169, via which the middle Holweck gap 173 is connected to the radially inner Holweck gap 175. As a result, the nested Holweck pump stages are connected in series with one another. Furthermore, a connecting channel 179 to the outlet 117 can be provided at the lower end of the radially inner Holweck rotor sleeve 165 .

The above-mentioned pumping-active surfaces of the Holweck stator sleeves 167, 169 each have a plurality of Holweck grooves running in a spiral shape around the axis of rotation 151 in the axial direction, while the opposite lateral surfaces of the Holweck rotor sleeves 163, 165 are smooth and the gas for operating the Advance vacuum pump 111 in the Holweck grooves.

A roller bearing 181 in the region of the pump outlet 117 and a permanent magnet bearing 183 in the region of the pump inlet 115 are provided for the rotatable mounting of the rotor shaft 153 .

In the area of the roller bearing 181 , a conical spray nut 185 is provided on the rotor shaft 153 with an outer diameter that increases towards the roller bearing 181 . The injection nut 185 is in sliding contact with at least one stripper of an operating fluid store. In other existing turbomolecular vacuum pumps (not shown), an injection screw may be provided instead of an injection nut. Since different designs are thus possible, the term "spray tip" is also used in this context.

The resource reservoir comprises a plurality of absorbent discs 187 stacked on top of one another, which are impregnated with a resource for the roller bearing 181, e.g. with a lubricant.

During operation of vacuum pump 111, the operating fluid is transferred by capillary action from the operating fluid reservoir via the scraper to the rotating spray nut 185 and, as a result of the centrifugal force, is conveyed along the spray nut 185 in the direction of the increasing outer diameter of the spray nut 185 to the roller bearing 181, where it e.g. fulfills a lubricating function. The roller bearing 181 and the operating fluid reservoir are surrounded by a trough-shaped insert 189 and the bearing cover 145 in the vacuum pump.

The permanent magnet bearing 183 comprises a bearing half 191 on the rotor side and a bearing half 193 on the stator side, which each comprise a ring stack of a plurality of permanent magnetic rings 195, 197 stacked on top of one another in the axial direction. The ring magnets 195, 197 lie opposite one another, forming a radial bearing gap 199, with the ring magnets 195 on the rotor side being arranged radially on the outside and the ring magnets 197 on the stator side being arranged radially on the inside are. The magnetic field present in the bearing gap 199 produces magnetic repulsive forces between the ring magnets 195, 197, which cause the rotor shaft 153 to be supported radially. The ring magnets 195 on the rotor side are carried by a support section 201 of the rotor shaft 153, which radially surrounds the ring magnets 195 on the outside. The ring magnets 197 on the stator side are carried by a support section 203 on the stator side, which extends through the ring magnets 197 and is suspended on radial struts 205 of the housing 119 . The ring magnets 195 on the rotor side are fixed parallel to the axis of rotation 151 by a cover element 207 coupled to the carrier section 201 . The stator-side ring magnets 197 are fixed parallel to the axis of rotation 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 magnet 197 .

An emergency or safety bearing 215 is provided within the magnetic bearing, which runs idle without contact during normal operation of the vacuum pump 111 and only engages in the event of an excessive radial deflection of the rotor 149 relative to the stator, in order to create a radial stop for the rotor 149 to form, so that a collision of the rotor-side structures is prevented with the stator-side structures. The backup bearing 215 is designed as an unlubricated roller bearing and forms a radial gap with the rotor 149 and/or the stator, which causes the backup bearing 215 to be disengaged during normal pumping operation. The radial deflection at which the backup bearing 215 engages is dimensioned large enough so that the backup bearing 215 does not engage during normal operation of the vacuum pump, and at the same time small enough so that the rotor-side structures collide with the stator-side structures under all circumstances is prevented.

The vacuum pump 111 includes the electric motor 125 for rotating the rotor 149. The armature of the electric motor 125 is formed by the rotor 149, the rotor shaft 153 of which extends through the motor stator 217. A permanent magnet arrangement can be arranged radially on the outside or embedded on the section of the rotor shaft 153 that extends through the motor stator 217 . Between the motor stator 217 and the section of the rotor 149 extending through the motor stator 217 there is an intermediate space 219 which includes a radial motor gap via which the motor stator 217 and the permanent magnet arrangement can influence each other magnetically for the transmission of the drive torque.

The motor stator 217 is fixed in the housing inside the motor room 137 provided for the electric motor 125 . A sealing gas, which is also referred to as flushing gas and which can be air or nitrogen, for example, can get into the engine compartment 137 via the sealing gas connection 135 . The sealing gas can protect the electric motor 125 from process gas, e.g. from corrosive components of the process gas. The engine compartment 137 can also be evacuated via the pump outlet 117, i.e. the vacuum pressure produced by the backing pump connected to the pump outlet 117 prevails in the engine compartment 137 at least approximately.

What is known as a labyrinth seal 223 can also be provided between the rotor hub 161 and a wall 221 delimiting the motor compartment 137, in particular in order to achieve better sealing of the motor compartment 217 in relation to the Holweck pump stages located radially outside.

A Holweck arrangement according to the invention, as exemplified below with reference to Figures 6 to 9 is described, in particular, instead of the Holweck arrangement of the above with reference to Figures 1 to 5 described vacuum pump are used.

The Figures 6 to 9 show only the right-hand part of a Holweck arrangement 11 of a vacuum pump, for example a turbomolecular pump, with three Holweck stages A, B, C. The vacuum pump comprises a rotor shaft 15 that is rotatably mounted about an axis of rotation 13. A rotor hub 17 is arranged on the rotor shaft 15 in a rotationally fixed manner, which carries two cylindrical, concentrically arranged rotor sleeves 19.

Furthermore, two Holweck stators 21, 23 are provided. The inner Holweck stator 21 positioned between the two rotor sleeves 19 is double-sided in a manner according to the invention, i. H. provided on both sides with a Holweck stator segment 25a, 25b. The segments 25a, 25b each have a pump-active Holweck thread. The segments 25a, 25b can be formed in one piece with the Holweck stator 21. For example, grooves forming Holweck threads are introduced into a base body of the stator 21 . However, it is also entirely conceivable to manufacture the segments 25a, 25b as separate components which are attached to the base body in order to form the stator 21.

Arranged radially outside of the outer rotor sleeve 19 is the outer Holweck stator 23, which can be formed by, for example, the pump housing or is connected to it. The outer Holweck stator 23 and the outer rotor sleeve 19 form the first Holweck stage A. The outer rotor sleeve 19 also forms the second Holweck stage B with the Holweck stator segment 25a, which is also referred to here as the outer pump or Holweck stage. The inner rotor sleeve 19 and the Holweck stator segment 25b form the third Holweck stage C, which is also referred to here as the inner pump or Holweck stage.

Arrows indicate the pumping direction and thus the conveying direction of the gas molecules conveyed in the Holweck stages A, B, C. The pumping direction runs from an inlet 33 of the Holweck arrangement 11 to an outlet 35.

The Holweck stators 21, 23 are also designed in the form of sleeves and are arranged coaxially to one another and to the rotor sleeves 19.

The Holweck stator 21 protrudes into a radial intermediate space between the Holweck sleeves 19. In the present example, an axial end of the Holweck segment 25a, 25b corresponds to the axial end of the stator 21 and is arranged at an axial distance X from the rotor hub 17. Compared to the corresponding distance of the axial end of the Holweck stator sleeve 169 from the rotor hub 161 of the vacuum pump according to FIGS Figures 1 to 5 the distance X is significantly greater, both when this distance X is set in relation to the axial extension of the sections of the Holweck stator segments 25a, 25b projecting into the intermediate space and in relation to the axial extension of the Holweck sleeves 19 (in each case significantly greater than 25%) . It also applies that the axial extent of the Holweck stator segments 25a, 25b projecting into the radial intermediate space between the sleeves 19 is significantly smaller than 75% of the axial extent of the Holweck sleeves 19.

The geometric relationships explained above and at the outset are the result of the basic idea of selecting the distance X to be relatively large in order to achieve a reduction in the power consumption caused by the Holweck arrangement 11 when the vacuum pump is in operation. The different definitions take into account the fact that the Holweck stator segments 25a, 25b can have different axial extents. This also applies to sleeves 19.

The comparatively large distance X according to the invention leads—compared to conventional Holweck arrangements—to a surprisingly greatly reduced power consumption of the arrangement 11 with approximately the same good or only slightly reduced vacuum data.

7 shows modifications of the in 6 shown concept. The Holweck stator 23 has a radial opening here, which forms the inlet 33 of the arrangement 11 . Inlet 33 may be an intermediate inlet of a split flow pump. It goes without saying that the Holweck stator 23 can also be omitted, so that gas molecules to be conveyed enter the pump-active part of the arrangement 11 in a region between the sleeve 19 and a base 37 to which the Holweck stator 21 is connected.

7 also shows an example of an optional measure with which heat transfer in the area of the Holweck arrangement 11 can be improved. For this purpose, a heat exchanger element 39 is arranged at the axial end of the Holweck stator 21 . It can be formed in one piece with the Holweck stator 21 . Alternatively, it is also possible for the element 39 to be detachably attached to the stator 21, for example by screwing. A plurality of elements 39 are preferably provided, which are arranged evenly distributed in particular in the circumferential direction of the sleeve-shaped stator 21 .

The element 39 can be a rod. However, it is also conceivable to provide a sleeve-shaped heat exchanger element 39 at the axial end of the stator 21 . It is also conceivable to provide only partial sections of the axial end of the stator 21 with curved surfaces which follow the sleeve shape of the stator 21 in sections (partial sleeves). The element 39 can have openings and/or slots.

8 FIG. 1 shows a Holweck stator 21 which is provided with Holweck stator segments 25a, 25b which have different axial extensions. To the power consumption of the Holweck arrangements 11 according to 6 to reduce the Holweckstator 21 was the 6 through the in 8 shown stator 21 replaced. In the case of embodiments with detachable segments 25a, 25b, it is also conceivable that only segments 25a, 25b were exchanged.

The axial end of the stator 21 protrudes beyond the axial end of the segments 25a, 25b. However, since it has no active pumping effect, the power consumption of the arrangement 11 is compared to the power consumption of the arrangement 11 according to FIG 6 reduced. The power consumption is reduced by increasing the distance X′ or X″ of the rotor hub 17 from the axial end of the pump-active segments 25a or 25b.

The embodiment according to 8 is only intended to convey by way of example that not only by changing the axial extension of the stator 21 (i.e. by a pure axial shortening of the stator 21 according to 6 ) but also by changing the axial extent of the segments 25a, 25b, the power consumption of the arrangement 11 can be influenced.

A change in the power consumption can be achieved not only by replacing the stator 21 or the Holweck stator segments 25a, 25b, but also by changing the axial position of the stator 21.

In the Holweck arrangement 11 according to 9 a Holweckstator 21 is used, which is geometrically essentially like the stator 21 of the 6 is trained. However, it was shifted downwards in the axial direction and fixed in this position, resulting in an increased distance X‴ between the rotor hub 17 and the axial end of the stator 21 . A corresponding fixing mechanism can be designed in such a way that the axial position of the stator 21 can be changed in discrete steps or continuously.

The axial position of the stator 21 can be adjusted manually, either directly or by means of an adjustment mechanism 41. According to one embodiment, a control device 43 is provided, with which the adjustment mechanism 41 can be controlled. A control of the mechanism 41 can, for example based on an operator input, an operating mode of the vacuum pump and/or an operating parameter of the vacuum pump.

In principle, it is also conceivable that not the stator 21 as a whole, but rather the Holweck stator segments 25a, 25b are arranged to be displaceable in the axial direction and/or can be fixed in different axial positions (directly or by means of a corresponding mechanism) in order to limit the axial extent of the pumping active To modify areas of Holweck levels B, C and thus also the power consumption associated with them.

Reference List

11

Holweck arrangement

13

axis of rotation

15

rotor shaft

17

rotor hub

19

rotor sleeve

21, 23

Holweck stator

25a, 25b

Holweck stator segment

33

inlet

35

outlet

37

Base

39

heat exchanger element

41

adjustment mechanism

43

control device

A, B, C

Holweck level

X, X', X", X‴

axial distance

111

turbomolecular pump

113

inlet flange

115

pump inlet

117

pump outlet

119

Housing

121

lower part

123

electronics housing

125

electric motor

127

accessory port

129

data interface

131

power connector

133

flood inlet

135

sealing gas connection

137

engine compartment

139

coolant connection

141

bottom

143

screw

145

bearing cap

147

mounting hole

148

coolant line

149

rotor

151

axis of rotation

153

rotor shaft

155

rotor disk

157

stator disc

159

spacer ring

161

rotor hub

163

Holweck rotor sleeve

165

Holweck rotor sleeve

167

Holweck stator sleeve

169

Holweck stator sleeve

171

Holweck fissure

173

Holweck fissure

175

Holweck fissure

179

connecting channel

181

roller bearing

183

permanent magnet bearing

185

injection nut

187

disc

189

Mission

191

rotor-side bearing half

193

stator bearing half

195

ring magnet

197

ring magnet

199

bearing gap

201

carrier section

203

carrier section

205

radial strut

207

cover element

209

support ring

211

mounting ring

213

disc spring

215

Emergency or catch camp

217

motor stator

219

space

221

wall

223

labyrinth seal

Claims (15)

1. A vacuum pump, in particular a turbomolecular vacuum pump, comprising at least one inlet (33), one outlet (35) and at least two Holweck stages (B, C) which are concentric with respect to a common axis of rotation (13), which follow one another in the pump direction between the inlet and the outlet and which each comprise a Holweck stator segment (25a or 25b), which has a Holweck thread, and a Holweck sleeve (19) rotating about the axis of rotation, wherein the Holweck stator segments are each arranged at a side of a common Holweck stator (21) which projects into a radial intermediate space between the concentrically arranged Holweck sleeves which are fastened to a Holweck hub (17) rotationally fixedly connected to a rotor of the vacuum pump,
   wherein
   the Holweck hub (17) is designed in disk shape, characterized in that an axial spacing (X, X', X", X‴) between an axial end of at least one of the Holweck stator segments that projects into the radial intermediate space and the Holweck hub is greater than 25% of the axial extent of a section of the Holweck stator segments that projects into the radial intermediate space and/or greater than 25% of the axial extent of at least one of the Holweck sleeves.
2. A vacuum pump in accordance with claim 1,

   wherein an axial spacing (X, X', X", X‴) between an axial end of both Holweck stator segments (25a, 25b) that projects into the radial intermediate space and the rotor hub (17) is greater than 25% of the axial extent of a section of the Holweck stator segments that projects into the radial intermediate space and/or greater than 25% of the axial extent of both Holweck sleeves and/or

   wherein an axial extent of a section of both Holweck stator segments that projects into the radial intermediate space is smaller than 75% of the axial extent of at least one of the Holweck sleeves (19).
3. A vacuum pump in accordance with claim 1 or claim 2,

   wherein the vacuum pump comprises at least a first and a second inlet (33),

   wherein the first inlet is associated with a turbomolecular pump stage and the second inlet is associated with the Holweck pump stages (B, C).
4. A vacuum pump in accordance with claim 3,
   wherein the second inlet (33) - viewed in the axial direction of the vacuum pump - is arranged in the region of the Holweck stages (B, C).
5. A vacuum pump in accordance with claim 3 or claim 4,
   wherein the second inlet (33) is a radial inlet.
6. A vacuum pump in accordance with at least one of the preceding claims,
   wherein the outer Holweck sleeve (19) forms a third Holweck stage (A) together with a Holweck stator segment (23) at least sectionally surrounding the outer Holweck sleeve radially at the outer side, in particular wherein the Holweck stator segment of the third Holweck stage has a recess or an opening which forms the second inlet (33).
7. A vacuum pump in accordance with at least one of the preceding claims,
   wherein the Holweck stator (21) is provided with at least one heat exchanger element (39) which extends from the axial end of the Holweck stator that projects into the radial intermediate space towards the rotor hub (17).
8. A vacuum pump in accordance with claim 7,
   wherein the heat exchanger element (39) is rod-shaped or sleeve-shaped or partly sleeve-shaped.
9. A vacuum pump in accordance with claim 7 or claim 8,
   wherein the heat exchanger element (39) has at least one aperture and/or slit.
10. A vacuum pump in accordance with claim 7, claim 8 or claim 9,
    wherein the heat exchanger element (39) is releasably connected to the Holweck stator (21).
11. A vacuum pump in accordance with at least one of the preceding claims,
    wherein the Holweck stator (21) can be arranged in different positions in the axial direction.
12. A vacuum pump in accordance with claim 11,
    wherein the vacuum pump has a setting mechanism (41) with which an axial positioning of the Holweck stator (21) and/or of at least one of the Holweck stator segments (25a, 25b) can be set.
13. A vacuum pump in accordance with claim 12,
    wherein the vacuum pump has a control device (43) which controls the setting mechanism (41), in particular on the basis of an operator input, an operating mode of the vacuum pump and/or an operating parameter of the vacuum pump.
14. A vacuum pump in accordance with at least one of the preceding claims,
    wherein at least one of the Holweck stator segments (25a, 25b), in particular both Holweck stator segments, is or are formed in one piece with the Holweck stator (21).
15. A vacuum pump system comprising

    a vacuum pump in accordance with least one of the preceding claims and

    at least one replacement Holweck stator which comprises at least one Holweck stator segment which has an axial extent that differs from the axial extent of the corresponding Holweck stator segment (25a, 25b) of the Holweck stator (21), and/or

    at least one replacement Holweck stator segment which has an axial extent that differs from the axial extent of the corresponding Holweck stator segment of the Holweck stator.

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