EP4194700A1 - Vacuum pump with a holweck pump stage with variable holweck geometry - Google Patents

Abstract

The present invention relates to a vacuum pump with at least one Holweck pump stage with an inlet and an outlet downstream of the inlet in the pumping direction. The Holweck pump stage includes a Holweck rotor with a rotor sleeve and a Holweck stator with a stator sleeve arranged coaxially with the Holweck rotor to form a Holweck gap. The stator sleeve has a Holweck thread with a plurality of thread grooves, which are delimited by webs formed on the stator sleeve and by a groove base formed by the stator sleeve. The stator sleeve is designed in one piece and at least one thread parameter of the Holweck thread from the group of thread parameters consisting of the number of lands, the thread pitch, the width of the thread grooves, the width of the lands and the height of the lands above the groove base changes over the axial extent of the stator sleeve.

Description

The present invention relates to a vacuum pump, also referred to here only as a pump, in particular a turbomolecular vacuum pump, according to the preamble of claim 1 with at least one Holweck pump stage.

Vacuum pumps are used in various areas of technology. Depending on the requirements, vacuum pumps can have one or more pump stages. In general, Holweck pump stages belong to the category of molecular vacuum pumps and generate a molecular flow by rotating a Holweck rotor relative to a stationary Holweck stator. In principle, a vacuum pump can comprise one or more Holweck pump stages, it being possible for a number of Holweck pump stages to be operated both in series and in parallel with one another. Typically, Holweck pumping stages are used in turbomolecular vacuum pumps, downstream of one or more turbomolecular pumping stages.

A Holweck pump stage usually comprises a Holweck rotor and a Holweck stator, the Holweck rotor having a rotor shaft on which one or more Holweck rotor sleeves are provided concentrically by means of a Holweck hub, for example in the form of a disk. The Holweck stator sleeve has a single or multi-start Holweck thread. The gas molecules to be pumped are pumped by the rotating movement of the Holweck rotor relative to the Holweck stator along the thread turns from an inlet to an outlet of the respective Holweck pump stage. A thread includes a spirally circumferential Holweck channel delimited by the walls of a web in the form of a thread groove, in which the gas molecules are conveyed when the rotor sleeve rotates relative to the stator sleeve.

Furthermore, so-called “folded” Holweck arrangements are known, in which several Holweck pump stages are arranged concentrically to one another and nested one inside the other, so that the pumping direction of Holweck pump stages that follow one another radially is opposite to one another. Two successive Holweck pump stages in the direction of flow - a (radial) outer Holweck pump stage and a (radial) inner Holweck pump stage - can thus comprise a common Holweck stator, which is provided with a Holweck thread on both sides and is located in the radial direction between two rotor sleeves.

Basically, the Holweck geometry and in particular the formation of the Holweck thread influences the characteristics of the Holweck pump stage, such as its suction and/or compression capacity and the power consumption of the pump motor. However, since the Holweck geometry usually does not change over the axial extent of a Holweck stator sleeve, the parameters in question can only be set to a limited extent when designing the pump.

In order to have more design freedom when designing the pump with regard to the parameters of a Holweck pump stage, such as its suction and/or compression capacity and its power consumption, the Holweck stator of a Holweck pump stage can be formed by several separate sleeve sections, which are arranged axially one behind the other or in parallel in the pumping direction are arranged immediately adjacent to each other. The individual sleeve sections can, for example, in terms of the number of webs or the distinguish threads formed by the webs, whereby the parameters in question are influenced.

However, the axial extent of Holweck stator sleeves is limited downwards, for example for manufacturing and assembly reasons. Since Holweck stator sleeves must not fall below a certain minimum axial extent, replacing one sleeve section with another one with, for example, a larger number of webs and/or a different thread pitch can only change the parameters of a Holweck pump stage in relatively large steps .

The invention is therefore based on the object of further developing a generic vacuum pump in such a way that the parameters of the Holweck pump stage can be changed in relatively small steps or in a finely dosed manner.

This object is achieved with a vacuum pump having the features of claim 1 and in particular in that in the case of a one-piece stator sleeve the thread geometry of the Holweck thread changes over the axial extent of the stator sleeve. In particular, it is provided according to the invention that, in the case of a one-piece stator sleeve, at least one thread parameter of the Holweck thread from the group of thread parameters consisting of the number of webs, the thread pitch, the width of the thread grooves, the width of the webs and the height of the webs over the groove bottom, changes over the axial extent of the stator sleeve.

For example, on the fore-vacuum side or at the outlet of the Holweck pump stage for a higher compression capacity and on the high-vacuum side or at the inlet of the Holweck pump stage for a lower compression capacity or a higher one To ensure pumping speed, the stator sleeve at the outlet of the Holweck pump stage can, for example, have a threaded section with a relatively small axial extent, in which the number of webs or the number of thread grooves is greater than in a threaded section located upstream thereof. Since the height dimension or the axial extension of the outlet-side threaded section can be made almost as small as desired due to the one-piece design of the stator sleeve, it is thus possible to change the compression capacity at the outlet of the Holweck pump stage in relatively small steps. This applies in particular when not only the number of webs changes over the axial extent of the stator sleeve, but also, for example, the thread pitch and/or the width of the thread grooves and the width of the webs over the axial extent of the stator sleeve.

In addition, the parameters of Holweck pump stages with a relatively small axial extent can also be modified, since a stator sleeve with a relatively small height dimension can also be designed in such a way that at least one thread parameter changes over the axial extent of the stator sleeve. In the case of such stator sleeves with a relatively small axial extent, on the other hand, a multi-part design of the stator sleeve from two separate sleeve sections to be arranged axially one behind the other is ruled out, since the sleeve sections must not have a minimum axial extent for manufacturing and/or assembly reasons.

Preferred embodiments of the invention will now be discussed below. Further embodiments can also result from the dependent claims, the description of the figures and the drawings themselves.

According to one embodiment, it can be provided that the Holweck thread has a first thread section, which extends in the axial direction over a first height dimension of the stator sleeve, and downstream of the first thread section a second thread section, which extends in the axial direction over a second height dimension of the stator sleeve and/or comprises at least one third threaded section downstream of the second threaded section, which extends in the axial direction over a third height dimension of the stator sleeve, wherein at least one threaded section of the three threaded sections extends from another threaded section of the three threaded sections by at least one thread parameter from the group differs from thread parameters.

For example, according to an exemplary embodiment, the number of webs in the third threaded section can be greater than in the second threaded section, it being possible in particular for the number of webs in the third threaded section to be twice as large as in the second threaded section. Due to the fact that on the fore-vacuum side or in the outlet of the Holweck pump stage the number of webs and thus the number of thread grooves is greater than at the inlet of the Holweck pump stage, a higher compression capacity can be achieved at the outlet of the Holweck pump stage than at the inlet of the Holweck Achieve pumping stage. Equally, because the number of webs in the third threaded section is greater than in the second threaded section, a higher pumping speed can be achieved on the high-vacuum side or at the inlet of the Holweck pump stage than at the outlet of the Holweck pump stage.

The pumping speed is considered to be the volume flow, ie the volume that can be conveyed through a cross-sectional area of a thread groove per unit of time. The compression capacity preferably relates to the component length, ie it is based on the compression capacity per overall length. The compression ratio can be regarded as the compression capacity, which can be reached by the respective threaded portion at its respective downstream end. In other words, the compression capacity describes the pressure ratio between the inlet and outlet of a respective thread groove.

The number of webs in the second threaded section can also be greater than the number of webs in the first threaded section, which would mean that the number of webs increases gradually starting from the inlet of the Holweck pump stage in the direction of the outlet of the same; However, the number of webs in the second threaded section can also be the same as the number of webs in the first threaded section, so that viewed from this perspective, the stator sleeve has, so to speak, only two threaded sections with a different number of webs.

According to a further embodiment, it can be provided that the width of the thread grooves in the third thread section is smaller than in the second thread section. In particular, it can be provided that the width of the thread grooves in the third thread section is less than half as large as in the second thread section. If, for example, the Holweck stator sleeve has a first set of spirally circumferential webs that extend from the inlet to the outlet of the Holweck pump stage, additional webs can be formed in the thread grooves formed thereby in the third thread section, through which the mutual spacing of the webs of the first set of ridges is reduced.

According to a further embodiment, it can be provided that the width of the thread grooves in the second thread section is the same as the width of the thread grooves in the first thread section, so that in this case the Holweck pump stage effectively has only two thread sections with different thread groove widths.

As already mentioned above, according to one embodiment it can be provided that the number of webs in the second threaded section is greater than in the first threaded section. With the web width remaining the same, this means that the width of the thread grooves in the third thread section is significantly smaller than in the first thread section, which means that the compression capacity tends to increase in the direction of the outlet of the Holweck pump stage, whereas the suction capacity increases in the direction of the inlet of the Holweck pump stage .

In addition or as an alternative to the embodiment in which the number of webs in the third threaded section is greater than in the second threaded section, it can be provided according to a further embodiment that the number of webs in the first threaded section is also greater than in the second threaded section is. In particular, it can be provided that the number of webs in the first threaded section is the same as the number of webs in the third threaded section. In other words, in this embodiment it is provided that the number of thread grooves in the central second thread section is less than in the first and third thread sections on the inlet and outlet side.

As an alternative to this, however, provision can be made for the number of thread grooves in the central second thread section to be greater than in the first and third thread sections on the inlet and outlet side.

Although the bottom of all thread grooves can lie on a cylindrical lateral surface; however, should it be desirable for the pumping speed to increase in the direction of the outlet of the Holweck pump stage, it can be provided according to a further embodiment that the groove base defines a base envelope which is conical in at least one of the three thread sections is. In particular, it can be provided that the groove base defines a conicity angle that has a different value in at least one of the three threaded sections than in another threaded section.

For example, the conicity angle in the first thread section can be smaller than in the second thread section and/or than in the third thread section, which means that the basic envelope in the first thread section tapers less in the direction of the outlet of the Holweck pump stage than in the second or in the third threaded section. This configuration can prove particularly advantageous when the Holweck pump stage has an intermediate inlet at the downstream end of the first threaded section, since in this case an increase in pumping speed can be recorded at the intermediate inlet.

According to a further embodiment, it can be provided that the height dimension of the respective threaded section makes up 15 to 50%, preferably 25 to 40% and particularly preferably 30 to 35% of the entire axial extent of the stator sleeve. In particular, when the height dimension of one of the threaded sections is only 30 to 35% of the axial extension of the stator sleeve - the threaded section in question therefore has a relatively small axial extension - the parameters such as the pumping speed, the compression capacity and/or the power consumption of the Holweck -Adjust the pump stage in relatively small steps.

In a single-stage Holweck pump, the stator sleeve usually surrounds the rotor sleeve. In this case, the Holweck thread is thus designed as an internal thread on the stator sleeve. If, on the other hand, the rotor sleeve surrounds the stator sleeve, then in this case the Holweck thread would have to be designed as an external thread on the stator sleeve.

According to a further embodiment, however, the vacuum pump can also comprise a "folded" Holweck arrangement, as was described in the introduction. In this case, the Holweck rotor comprises an inner rotor sleeve and an outer rotor sleeve concentrically surrounding the inner rotor sleeve, whereas the Holweck stator comprises an outer stator sleeve concentrically surrounding the outer rotor sleeve and an inner stator sleeve concentrically surrounding the inner rotor sleeve. In this case, the Holweck thread is designed as an internal thread on the outer stator sleeve, as an internal thread on the inner stator sleeve and/or as an external thread on the inner stator sleeve.

According to a further embodiment, it can be provided that instead of the first and/or third threaded section, the stator sleeve forms a section with a thread-free cylindrical lateral surface, into which a separately manageable ring is fitted as an additional component, which has a threaded section which, together with at least the second threaded section forms the Holweck thread of the stator sleeve, the threaded section of the ring differing from the second threaded section by at least one thread parameter from the aforementioned group of thread parameters. In addition, it can be provided that the groove base of the threaded portion of the ring defines a conical base envelope, with the base envelope tapering in the direction of the outlet of the Holweck pump stage.

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

eine Abwicklung einer herkömmlichen Holweck-Statorhülse in schematischer Darstellung;

Fig. 7

eine Abwicklung einer Ausführungsform einer erfindungsgemäßen Holweck-Statorhülse in schematischer Darstellung;

Fig. 8

eine Abwicklung einer weiteren Ausführungsform einer erfindungsgemäßen Holweck-Statorhülse in schematischer Darstellung;

Fig. 9

eine Abwicklung noch einer weiteren Ausführungsform einer erfindungsgemäßen Holweck-Statorhülse in schematischer Darstellung;

Fig. 10

eine schematische Schnittdarstellung durch eine gefaltete Holweck-Pumpstufe mit einer erfindungsgemäß ausgebildeten Holweck-Statorhülse gemäß einer weiteren Ausführungsform; und

Fig. 11

ein Diagramm zur Erläuterung des Saugvermögens bei der Holweck-Pumpstufe der Fig. 10; und

Fig. 12

eine schematische Schnittdarstellung durch eine gefaltete Holweck-Pumpstufe gemäß noch einer weiteren Ausführungsform.

The invention is described below with reference to the accompanying figures. Show it:

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

a development of a conventional Holweck stator sleeve in a schematic representation;

7

a development of an embodiment of a Holweck stator sleeve according to the invention in a schematic representation;

8

a development of a further embodiment of a Holweck stator sleeve according to the invention in a schematic representation;

9

a development of yet another embodiment of a Holweck stator sleeve according to the invention in a schematic representation;

10

a schematic sectional view through a folded Holweck pump stage with a Holweck stator sleeve designed according to the invention according to a further embodiment; and

11

a diagram to explain the pumping speed in the Holweck pump stage 10 ; and

12

a schematic sectional view through a folded Holweck pump stage according to yet another embodiment.

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 .

Attachment bores 147 are also arranged on the underside 141, via which the pump 111 can be attached to a support surface, for example. This is not possible with other existing turbomolecular vacuum pumps (not shown), which 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.

As 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. There are other turbomolecular vacuum pumps (not shown) 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 active pumping 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. Also, at the top end of the inner Holweck stator sleeve 169, a radially extending channel may be provided, 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 injection 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, for example 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, 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. 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 carrier 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 ring magnets 197 on the stator side 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, whose rotor shaft 153 extends through the motor stator 217 therethrough. 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 reach the engine compartment 137 via the sealing gas connection 135 . About the sealing gas, the electric motor 125 before process gas, for example corrosive components of the process gas are protected. The engine compartment 137 can also be evacuated via the pump outlet 117 , ie the vacuum pressure produced by the backing pump connected to the pump outlet 117 prevails in the engine compartment 137 at least approximately.

A labyrinth seal 223, known per se, 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.

When previously referring to the Figures 1 to 5 The turbomolecular vacuum pump 111 described, the Holweck stator sleeves 167, 169 can have an internal or external Holweck thread 16, as shown schematically as a development in FIG 6 is shown. As can be seen from this illustration, the Holweck geometry remains the same there over the entire axial extent of the Holweck stator sleeve 167, 169 between the inlet E and the outlet A of the Holweck pump stage, and in particular the number of webs 12 that form the Holweck Form thread 16 between the inlet E and the outlet A constant. The pitch of the thread, the width of the webs 12, the width of the thread grooves 14 and the height of the webs 12 is constant over the axial extent of the stator sleeves 167, 169.

Various embodiments of stator sleeves 10 are now described below, which can be installed in the turbomolecular vacuum pump 111 instead of the illustrated stator sleeves 167, 169, although the other structure of the turbomolecular vacuum pump 111 as well as the basic structure of the Holweck pump stage with three nested pump stages are retained can be.

How to settle the 7 can be seen, the stator sleeve 10 or the Holweck thread 16 formed by its thread ridges 12 between inlet E and outlet A has three thread sections I, II, III, with the number of thread ridges 12 in the most downstream third thread section III being twice as many is large as in the second threaded portion II. In contrast, the number of webs 12 in the second threaded portion II is equal to the number of webs 12 in the first threaded portion I, so that in the embodiment of 7 basically there are only two thread sections with different Holweck geometry.

Due to the fact that in the third thread section III the number of webs 12 is twice as large as in the first and second thread sections I, II and consequently the width of the thread grooves 14 in the third thread section III is significantly smaller than in the other two thread sections I, II, the compression capacity increases in the direction of outlet A, whereas in the direction of inlet E the pumping speed of the Holweck pump stage increases.

In the embodiment of 8 on the other hand, the stator sleeve 10 effectively has three threaded sections I, II and III, each with a different Holweck geometry. In particular, the number of webs 12 in the central second threaded section II is greater than in the first threaded section I on the inlet side and smaller than in the third threaded section III on the outlet side, with the result that the width of the thread grooves in the third threaded section III is significantly smaller than in the first thread section I.

According to the embodiment of 9 On the other hand, the number of webs 12 in the central threaded section II is smaller than both in the first threaded section I on the inlet side and in the third threaded section III on the outlet side. As an alternative to this, depending on the parameter to be achieved, the opposite conditions can also exist, so that, for example, in the central second threaded section II the number of webs 12 can be greater than in the first threaded section I on the inlet side and in the third threaded section III on the outlet side.

Although the thread pitch changes in the previously with reference to the Figures 7 to 9 described embodiments between the inlet E and the outlet A not; Depending on the design of the respective Holweck pump stage, however, the thread pitch can also change over the axial extent of the stator sleeve 10, as can the width of the thread grooves 14, the width of the webs 12 and/or the height of the webs 12 above the groove base 18 of the respective thread groove 14 may apply.

As best the embodiment in 9 can be removed, there the threaded sections I, II, III each have an axial extent between the inlet E and the outlet A, which is approximately 30 to 35% of the axial extent of the stator sleeve 10 . The axial extent of the respective threaded sections can therefore be very small, particularly when the stator sleeve 10 in its entirety already has a relatively small axial extent, as a result of which the parameters of the Holweck pump stage can be finely adjusted.

The 10 shows a further embodiment of a folded Holweck pump stage, in which the radially outer stator sleeve 10 is formed by two threaded sections I, II located between inlet E and outlet A. Both the groove base 18 of the first thread section I and the groove base 18 of the second thread section II, which is located downstream of the first thread section I, form a conical base envelope, with the embodiment shown here the conicity angle α being smaller in the first thread section I than in is the second threaded section II. As an alternative to this, however, the conicity angle α in the second threaded section II can also be smaller than in the first threaded section I.

Although the conicity angle α can also be the same size in both thread sections I and II; however, the conicity angle α in the second threaded section II is greater than in the first threaded section I, as in FIG 10 is shown, an increase in pumping speed of the order of up to 20% can be achieved at the transition from the first threaded section I to the second threaded section II, in particular when the admission pressure or the pressure at outlet A is relatively high and is in the range between 1 and approx. 10 mbar, see the diagram in the 11 . This can prove particularly advantageous when the Holweck pump stage as shown in FIG 10 has an intermediate inlet 20 in the transition area between the first and the second threaded section I, II, since in this case the increased pumping speed at the intermediate inlet 20 can prevent process gas sucked in thereby from flowing back in the direction of inlet E of the Holweck pump stage.

When referring to the 12 In the described embodiment, it is ultimately provided that the third threaded section III, which is located at the outlet of the Holweck pump stage, is formed by a ring 22 that can be handled separately and has an internal thread formed thereon, with the basic envelope of the thread grooves 14 being formed conically here as well tapers towards outlet A.

To accommodate ring 22, stator sleeve 10 has at its outlet end A a section 24 with a thread-free cylindrical lateral surface 26, into which ring 22 can be fitted, so that the two upstream threaded sections I, II together with the threaded section of the ring 22 form the Holweck thread 16 of the stator sleeve 10 . The threaded section of the ring 22 can differ from the other two threaded sections I, II by at least one thread parameter such as the thread pitch, the number of webs 12, the width of the thread groove 14, the width of the webs 12 and the height of the webs 12 differ above the groove base 18 in order to be able to finely adjust the parameters of the Holweck pump stage.

It is true that the ring 22 is to a certain extent a stator sleeve that can be handled separately; However, since the ring 22 is received by the section 24 with a thread-free cylindrical lateral surface 26 of the stator sleeve 10, the ring 22 can be manufactured with a relatively small axial extent without this leading to any loss of stability, since the ring 22 is to a certain extent through the section 24 with a thread-free cylindrical lateral surface 26 is supported and stiffened.

Reference List

E

inlet

A

outlet

10

stator sleeve

12

webs

14

thread grooves

16

Holweck thread

18

groove bottom

20

intermediate entry

22

ring

24

Section

26

lateral surface

I,II,III

threaded sections

a

taper angle

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 disc

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 (17)

Vacuum pump (111), in particular a turbomolecular vacuum pump (111), having at least one Holweck pump stage with an inlet (E) and an outlet (A) downstream of the inlet (E) in the pumping direction, the Holweck pump stage having a Holweck rotor with a rotor sleeve (163, 165) and a Holweck stator with a stator sleeve (10) which is arranged coaxially to the Holweck rotor, forming a Holweck gap (171, 173, 175), the stator sleeve (10) having a Holweck thread ( 16) with a plurality of thread grooves (14) which are delimited by webs (12) formed on the stator sleeve (10) and by a groove base (18) formed by the stator sleeve (10),
characterized in that
the stator sleeve (10) is designed in one piece and at least one thread parameter of the Holweck thread (16) is selected from the group of thread parameters consisting of the number of webs (12), the thread pitch, the width of the thread grooves (14), the width of the Webs (12) and the height of the webs (12) above the groove base (18) changes over the axial extent of the stator sleeve (10). Vacuum pump according to claim 1,
wherein the Holweck thread (16) has a first threaded portion (I) extending in the axial direction over a first height dimension of the stator sleeve (10), downstream of the first threaded portion (I) a second threaded portion (II) extending in the axial direction extends over a second height dimension of the stator sleeve (10), and downstream of the second threaded section (III) comprises at least one third threaded section (III), which extends in the axial direction over a third height dimension of the Stator sleeve (10), at least one thread section of the three thread sections (I, II, III) differing from another of the three thread sections (I, II, III) by at least one thread parameter from the group of thread parameters. Vacuum pump according to claim 2,
wherein the number of webs (12) in the third threaded section (III) is greater than in the second threaded section (II), it being provided in particular that the number of webs (12) in the third threaded section (III) is twice as large is as in the second thread portion (II). Vacuum pump according to claim 2 or 3,
wherein the number of webs (12) in the second threaded section (II) is the same as the number of webs (12) in the first threaded section (I). Vacuum pump according to one of claims 2 to 4,
wherein the width of the thread grooves (14) in the third thread section (III) is smaller than in the second thread section (II), and/or wherein the width of the thread grooves (14) in the second thread section (II) is the same as the width of the thread grooves (14) in the first thread section (I). Vacuum pump according to claim 2 or 3,
wherein the number of webs (12) in the second threaded section (II) is greater than in the first threaded section (I). Vacuum pump according to claim 6,
wherein the width of the thread grooves (14) in the third thread section (III) is smaller than in the first thread section (I). Vacuum pump according to claim 2 or 3,
wherein the number of webs (12) in the first thread section (I) is greater than in the second thread section, and/or wherein the number of webs (12) in the first thread section (I) is the same as the number of webs ( 12) in the third thread section (III). Vacuum pump according to claim 8, wherein the width of the thread grooves (14) in the third thread section (III) and in the first thread section (I) is smaller than in the second thread section (II), and/or wherein the width of the thread grooves (14) in the third thread section (III) is the same as the width of the thread grooves (14) in the first thread section (I). Vacuum pump according to one of the preceding claims,
the groove base (18) defining a base envelope which is conical in at least one of the three thread sections (I, II, III). Vacuum pump according to claim 10,
the groove base (18) defining a conicity angle (α) which has a different value in at least one of the three thread sections (I, II, III) than in another thread section. Vacuum pump according to claim 11,
wherein the conicity angle (α) in the first thread section (I) is smaller than in the second thread section (II) and/or in the third thread section (III). Vacuum pump according to one of the preceding claims,
the height dimension of the respective threaded section (I, II, III) being 15% to 50%, preferably 25 to 40%, and particularly preferably 30% to 35% of the axial extent of the stator sleeve (10). Vacuum pump according to one of the preceding claims, wherein the stator sleeve (10) surrounds the rotor sleeve (163, 165) and the Holweck thread (16) is designed as an internal thread on the stator sleeve (10); and or wherein the rotor sleeve (163) surrounds the stator sleeve (10) and the Holweck thread (16) is designed as an external thread on the stator sleeve (10). Vacuum pump according to one of the preceding claims,
the Holweck rotor comprises an inner rotor sleeve (165) and an outer rotor sleeve (163) concentrically surrounding the inner rotor sleeve (165), and the Holweck stator comprises an outer stator sleeve (10) concentrically surrounding the outer rotor sleeve (163) and an outer stator sleeve (10) surrounding the inner Rotor sleeve (165) concentrically surrounding inner stator sleeve (10), wherein the Holweck thread (16) as an internal thread on the outer stator sleeve (10), as an internal thread on the inner stator sleeve (10) and/or as an external thread on the inner stator sleeve ( 10) is formed. Vacuum pump according to one of claims 2 to 15,
the stator sleeve (10) forming a section (24) with a thread-free cylindrical lateral surface (26) instead of the first and/or third threaded section (I, III), which accommodates a ring (22) which can be handled separately and which has a threaded section which together with the second threaded section (II), the Holweck thread (16) of the stator sleeve (10) forms, with the threaded section of the ring (22) of which second thread section (II) differs by at least one thread parameter from the group of thread parameters. Vacuum pump according to claim 16,
the groove base (18) defining a conical base envelope.

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