Vacuum pump with Holweck pump stage having variable Holweck geometry - Patents.com

Abstract

To change a characteristic value of a Holweck pump stage with a comparatively small step or by finely adjusting the same in a vacuum pump which includes at least one Holweck pump stage having a suction port and an exhaust port and in which the Holweck pump stage has a Holweck rotor including a rotor sleeve, and a Holweck stator having a stator sleeve, the stator sleeve is disposed coaxially to the Holweck rotor with a Holweck clearance, and the stator sleeve has a Holweck screw portion having a plurality of screw grooves.SOLUTION: A stator sleeve 10 is constituted into one-piece, and at least one screw portion parameter of a Holweck screw portion 16 in a group of screw portion parameters composed of the number of webs 12, a screw pitch, a width of a screw groove 14, a width of the web, and a height of the web on a groove bottom 18 is changed over an axial extension length of the stator sleeve.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The invention relates to a vacuum pump, in particular a turbomolecular vacuum pump, also referred to herein simply as pump, according to the preamble of claim 1, which has at least one Holweck pump stage. [Background technology]

[0002] Vacuum pumps are used in various technical fields. Depending on the requirements, a vacuum pump may have one or more pump stages. Generally, Holweck pump stages belong to the category of molecular vacuum pumps, which generate a molecular flow by rotating a Holweck rotor relative to a fixed Holweck stator. In principle, a vacuum pump may have one or more Holweck pump stages, which can be operated in series or in parallel with one another. Typically, Holweck pump stages are used in turbomolecular vacuum pumps, where a Holweck pump stage is followed in the flow direction by one or more turbomolecular pump stages.

[0003] A Holbeck pump stage typically comprises a Holbeck rotor and a Holbeck stator, where the Holbeck rotor comprises a rotor shaft on which one or more Holbeck rotor sleeves are concentrically mounted, for example by means of a disk-shaped Holbeck hub. The Holbeck stator sleeve is provided with a single-start or multiple-start Holbeck thread. The gas molecules to be pumped are pumped along the thread from the inlet to the outlet of the respective Holbeck pump stage by the rotational movement of the Holbeck rotor relative to the Holbeck stator. The thread has a helically circulating Holbeck channel in the form of a screw groove, which is defined by the walls of the web, in which the gas molecules are pumped when the rotor sleeve rotates relative to the stator sleeve.

[0004] Furthermore, so-called "folded" Holbeck arrangements are known in which several Holbeck pump stages are arranged concentrically with one another and engage with one another inwardly, so that the pumping directions of directly successive Holbeck pump stages in the radial direction are opposite to one another. Thus, two successive Holbeck pump stages in the flow direction, i.e. the (radially) outer Holbeck pump stage and the (radially) inner Holbeck pump stage, may have a common Holbeck stator with a Holbeck thread on each side, which is located radially between two rotor sleeves.

[0005] Essentially, the Holweck geometry and in particular the configuration of the Holweck thread influence the characteristic values ​​of the Holweck pump stage, such as the pumping speed and / or compression performance of the Holweck pump stage as well as the power consumption of the pump motor. However, since the Holweck geometry usually does not change over the axial extension length of the Holweck stator sleeve, the characteristic values ​​in question can only be adjusted to a limited extent when designing the pump.

[0006] In order to allow more design latitude when designing the pump with regard to the characteristic values ​​of the Holweck pump stage, such as, for example, the pumping speed and / or the compression performance and the power consumption, the Holweck stator of the Holweck pump stage can be formed by a number of separate sleeve parts, which are arranged axially one after the other in the pumping direction or directly adjacent to one another, in which case the individual sleeve parts can differ, for example, with regard to the number of webs or the threads formed by the webs, which influences the characteristic values ​​in question.

[0007] However, there is a lower limit to the axial extension length of the Holweck stator sleeve, e.g. for manufacturing and assembly reasons, and therefore the characteristic values ​​of the Holweck pump stage can only be changed in relatively large steps, e.g. by replacing the sleeve part with another sleeve part having a larger number of webs and / or a different thread pitch, since the Holweck stator sleeve must not fall below a certain minimum axial extension length. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention is therefore based on the object of developing a vacuum pump of the type mentioned at the beginning, in such a way that the characteristic values ​​of the Holweck pump stages can be varied in relatively small steps or with fine adjustment. [Means for solving the problem]

[0009] This problem is solved by a vacuum pump having the features of claim 1, in particular in a stator sleeve designed in one piece, in that the thread geometry of the Holweck thread varies over the axial extension length of the stator sleeve. In particular, it is envisaged according to the invention that in a stator sleeve designed in one piece, 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 groove, the width of the webs and the height of the webs above the groove base varies over the axial extension length of the stator sleeve.

[0010] For example, in order to achieve a high compression performance at the pre-vacuum side or at the outlet of a Holbeck pump stage and a low compression performance or a high pumping speed at the high vacuum side or at the inlet of a Holbeck pump stage, the stator sleeve has a threaded section at the outlet of the Holbeck pump stage, for example with a relatively small axial extension, in which the number of webs or the number of grooves is greater than in the threaded section located upstream from it. The height dimension or axial extension of the threaded section on the outlet side can be made almost arbitrarily small due to the one-piece construction of the stator sleeve, so that the compression performance at the outlet of the Holbeck pump stage can be changed in relatively small steps. This applies in particular when not only the number of webs but also, for example, the thread pitch and / or the width of the grooves change over the axial extension of the stator sleeve, as well as when the width of the webs changes over the axial extension of the stator sleeve.

[0011] Furthermore, the characteristic values ​​of Holweck pump stages with a relatively small axial extension can also be modified, since even stator sleeves with a relatively small height dimension can be designed so that at least one thread parameter varies over the axial extension of the stator sleeve. On the other hand, for such stator sleeves with a relatively small axial extension, a multi-piece design of the stator sleeve consisting of two separate sleeve parts to be arranged axially one after the other is excluded, since for manufacturing and / or assembly reasons the minimum axial extension of the sleeve parts must not be exceeded.

[0012] Preferred embodiments of the invention will now be described below. Further embodiments are evident from the dependent claims, the description of the drawings and the drawings themselves.

[0013] Thus, according to one embodiment, it can be envisaged that the Holweck thread has a first thread portion extending axially across a first height dimension of the stator sleeve, a second thread portion extending axially across a second height dimension of the stator sleeve downstream of the first thread portion and / or at least one third thread portion extending axially across a third height dimension of the stator sleeve downstream of the second thread portion, wherein at least one of the three thread portions and another of the three thread portions differ in at least one thread parameter of a group of thread parameters.

[0014] Thus, for example, according to an exemplary embodiment, it can be envisaged that the number of webs in the third threaded section can be greater than the number in the second threaded section, in particular that the number of webs in the third threaded section is twice as large as the number in the second threaded section. Thus, the number of webs and therefore the number of thread grooves at the pre-vacuum side or outlet of the Holbeck pump stage is greater than the number at the inlet of the Holbeck pump stage, so that a higher compression performance can be achieved at the outlet of the Holbeck pump stage than at the inlet of the Holbeck pump stage. Similarly, the number of webs in the third threaded section is greater than the number at the second threaded section, so that a higher pumping speed can be achieved at the high vacuum side or inlet of the Holbeck pump stage than at the outlet of the Holbeck pump stage.

[0015] In this case, the volumetric flow rate, i.e. the volume that can be pumped through the cross section of the thread per unit time, is considered as the pumping speed. The compression performance is preferably related to the part length, i.e. tailored to the compression performance per structural length. In this case, the compression ratio that can be achieved by each threaded section at its downstream end can be considered as the compression performance. In other words, the compression performance represents the pressure ratio between the inlet and the outlet of each thread.

[0016] The number of webs in the second threaded portion may be greater than the number of webs in the first threaded portion, meaning that the number of webs increases in identical steps starting from the inlet of the Holweck pump stage towards the outlet, and the number of webs in the second threaded portion may be identical to the number of webs in the first threaded portion, so that from this point of view the stator sleeve in a sense only has two threaded portions with different numbers of webs.

[0017] According to another embodiment, it can be envisaged that the width of the thread in the third thread portion is smaller than the width in the second thread portion. In this case, it can be envisaged in particular that the width of the thread in the third thread portion is less than half the width in the second thread portion. For example, when the Holweck stator sleeve has a first set of spirally circumferential webs extending from the inlet to the outlet of the Holweck pump stage, additional webs can be formed in the thread formed thereby in the third thread portion, which reduces the mutual spacing between these webs and the first set of webs.

[0018] According to another embodiment, it can be envisaged that the width of the thread groove in the second thread portion is the same as the width of the thread groove in the first thread portion, so that the Holweck pump stage in this case effectively has only two thread portions with different thread groove widths.

[0019] As already mentioned above, according to one embodiment, it can be envisaged that the number of webs in the second threaded section is greater than in the first threaded section, which means that for the same web width, the width of the groove in the third threaded section is significantly smaller than in the first threaded section, which means that the compression performance increases towards the exhaust of the Holweck pump stage, while the exhaust velocity tends to increase towards the intake of the Holweck pump stage.

[0020] Additionally or alternatively to the embodiment in which the number of webs in the third threaded portion is greater than in the second threaded portion, it can be envisaged according to another embodiment that the number of webs in the first threaded portion is also greater than in the second threaded portion. In particular, it can be envisaged in this case that the number of webs in the first threaded portion is of the same magnitude as the number of webs in the third threaded portion. In other words, in this embodiment, it can be envisaged that the number of thread grooves in the central second threaded portion is less than the number in the first and third threaded portions on the inlet and outlet sides.

[0021] Alternatively to this, it can be envisaged that the number of threads in the central second threaded portion is greater than the number in the first and third threaded portions on the inlet and outlet sides.

[0022] The groove roots of all the thread grooves may be located on the cylindrical lateral surface, but it should be desired that the pumping speed increases towards the outlet of the Holweck pump stage, and therefore according to another embodiment it can be envisaged that the groove roots define a conically shaped bottom envelope in at least one of the three threaded sections, in which case it can be envisaged in particular that the groove roots define a taper angle in at least one of the three threaded sections which has an angle different from the angle in the other threaded sections.

[0023] Thus, for example, the taper angle of the first threaded portion may be smaller than the taper angle of the second and / or third threaded portion, meaning that the bottom envelope of the first threaded portion tapers less towards the outlet of the Holweck pump stage than the bottom envelope of the second or third threaded portion. This configuration may prove to be advantageous in particular if the Holweck pump stage has an intermediate inlet at the downstream end of the first threaded portion, since in this case an increase in the pumping speed at the intermediate inlet can be avoided.

[0024] According to another embodiment, it can be envisaged that the height dimension of each threaded portion is 15% to 50%, preferably 25% to 40%, particularly preferably 30% to 35% of the total axial extension length of the stator sleeve. In particular, the height dimension of one of the threaded portions is only 30-35% of the axial extension length of the stator sleeve, i.e. when the threaded portion in question has a relatively small axial extension length, characteristic values ​​such as, for example, the pumping speed, compression performance and / or power consumption of a Holweck pump stage can be adapted in relatively small steps.

[0025] In a single stage Holweck pump, the stator sleeve generally surrounds the rotor sleeve, so that the Holweck thread is configured as an internal thread on the stator sleeve, whereas when the rotor sleeve surrounds the stator sleeve, the Holweck thread is configured as an external thread on the stator sleeve.

[0026] Moreover, according to another embodiment, the vacuum pump may have a "folded" Holweck arrangement as described at the beginning, where the Holweck rotor has an inner rotor sleeve and an outer rotor sleeve concentrically surrounding the inner rotor sleeve, whereas the Holweck stator has an outer stator sleeve concentrically surrounding the outer rotor sleeve and an inner stator sleeve concentrically surrounding the inner rotor sleeve, where the Holweck thread is configured as an internal thread on the outer stator sleeve, an internal thread on the inner stator sleeve and / or an external thread on the inner stator sleeve.

[0027] According to another embodiment, it can be envisaged that the stator sleeve forms, instead of the first and / or third threaded portion, a portion with a cylindrical side without threads, into which is fitted, as an additional part, a separately addressable annulus with a threaded portion, which, together with at least the second threaded portion, forms the Holweck thread of the stator sleeve, in which case the threaded portion of the annulus differs from the second threaded portion in at least one thread parameter of the aforementioned group of thread parameters. Additionally, it can be envisaged that the groove base of the threaded portion of the annulus defines a conical bottom envelope, in which case the bottom envelope tapers towards the outlet of the Holweck pump stage.

[0028] The present invention will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 shows a perspective view of a turbomolecular pump. [Diagram 2] FIG. 2 shows a bottom view of the turbomolecular pump of FIG. [Diagram 3] 3 shows a cross-sectional view of a turbomolecular pump taken along the section line AA shown in FIG. 2. [Figure 4] 3 shows a cross-sectional view of the turbomolecular pump taken along the section line BB shown in FIG. 2. [Diagram 5] 3 shows a cross-sectional view of a turbomolecular pump taken along the section line CC shown in FIG. 2. [Figure 6] 1 shows a schematic development of a conventional Holweck Sterling sleeve. [Figure 7] 1 shows a schematic exploded view of one embodiment of a Holweck Stator Sleeve according to the present invention. [Figure 8] 1 shows a schematic exploded view of another embodiment of a Holweck Stator Sleeve according to the present invention. [Figure 9] 1 shows a schematic exploded view of yet another embodiment of a Holweck Stator Sleeve according to the present invention. [Figure 10]2 shows a schematic cross-sectional view of a folded-type Holweck pump stage having a Holweck stator sleeve constructed in accordance with the present invention according to another embodiment. [Figure 11] 11 is a diagram for explaining the pumping speed in the Holweck pump stage of FIG. 10. [Figure 12] 4 shows a schematic cross-sectional view of a folded type Holweck pump stage according to yet another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The turbomolecular pump 111 shown in Fig. 1 has a pump inlet 115 surrounded by an inlet flange 113. To the pump inlet 115, in a manner known per se, a recipient, not shown, may be connected. Gas coming from the recipient can be sucked from the recipient via the pump inlet 115 and pumped through the pump to a pump outlet 117. To the pump outlet 117, an auxiliary vacuum pump, for example a rotary vane pump, may be connected.

[0031] The inlet flange 113 forms the upper end of a housing 119 of the vacuum pump 111 in the orientation of the vacuum pump according to Fig. 1. The housing 119 has a lower part 121, on which an electronics housing 123 is arranged laterally. In the electronics housing 123, electrical and / or electronic components of the vacuum pump 111 are accommodated, for example for operating an electric motor 125 (see also Fig. 3) arranged in the vacuum pump. The electronics housing 123 is provided with a number of connections 127 for accessories. Furthermore, a data interface 129 (for example according to the RS485 standard) and a current supply connection 131 are arranged in the electronics housing 123.

[0032] There are also turbomolecular pumps that do not have this type of attached electronics housing, but are connected to external drive electronics.

[0033] A ventilation inlet 133, in particular in the form of a ventilation valve, is provided in the housing 119 of the turbomolecular pump 111. Via the ventilation inlet 133, the vacuum pump 111 can be vented. In the region of the lower part 121, a sealing gas connection 135 (also called purge gas connection) is also arranged. Via the sealing gas connection 135, a purge gas can be fed into a motor chamber 137 in order to protect the electric motor 125 (see, for example, FIG. 3) against the gas pumped by the pump. In the motor chamber 137, the vacuum pump 111 accommodates the electric motor 125. In the lower part 121, two coolant connections 139 are also arranged. In this case, one coolant connection is provided as an inlet for the coolant and the other coolant connection is provided as an exhaust. A coolant can be introduced into the vacuum pump for cooling purposes. The further turbomolecular vacuum pump present (not shown) is operated exclusively air-cooled.

[0034] The underside 141 of the vacuum pump can be used as a base, so that the vacuum pump 111 can be operated vertically with respect to the underside 141. Moreover, the vacuum pump 111 can be fixed to the recipient via the inlet flange 113 and thus operated in a suspended state, so to speak. Furthermore, the vacuum pump 111 can be configured so that it can be operated even when oriented in a different direction than shown in FIG. 1. Vacuum pump configurations are also feasible in which the underside 141 can be arranged not only downwards, but also sideways or upwards. In this case, in principle, any angle is conceivable.

[0035] In particular, other turbomolecular vacuum pumps (not shown) that are present and are larger than the pump shown cannot be operated in a vertical position.

[0036] Various screws 143 are further arranged on the underside 141 shown in Fig. 2. By means of these screws 143, components of the vacuum pump, not specified in detail here, are fixed to one another. For example, a bearing cover 145 is fixed to the underside 141.

[0037] Fastening holes 147 are furthermore arranged in the underside 141. Via the fastening holes 147, the pump 111 can be fixed, for example, to a mounting surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), in particular those larger than the pump shown.

[0038] 2 to 5 show a coolant line 148. In the coolant line 148 a coolant can be circulated which is introduced and discharged via the coolant connection 139.

[0039] As shown in the cross-sectional views of Figures 3 to 5, the vacuum pump has multiple process gas pumping stages for pumping process gas acting on a pump inlet 115 to a pump exhaust 117.

[0040] A rotor 149 is disposed within the housing 119. The rotor 149 has a rotor shaft 153 that is rotatable about a rotation axis 151.

[0041] The turbomolecular pump 111 has a number of turbomolecular pump stages connected in series to provide a pumping action. The turbomolecular pump stages have a number of radially extending rotor blades 155 fixed to the rotor shaft 153 and a number of stator vanes 157 arranged between the rotor blades 155 and fixed within the housing 119. In this case, each of the rotor blades 155 and the adjacent stator vanes 157 forms one turbomolecular pump stage. The stator vanes 157 are held at a desired axial distance from each other by spacer rings 159.

[0042] The vacuum pump further comprises Holweck pump stages arranged radially inside and outside one another and connected in series to provide a pumping action. There are alternative turbomolecular vacuum pumps (not shown) that do not comprise Holweck pump stages.

[0043] The rotor of the Holweck pump stage comprises a rotor hub 161 arranged on the rotor shaft 153 and two Holweck rotor sleeves 163, 165 with cylindrical flanks fixed to and supported by the rotor hub 161. The Holweck rotor sleeves 163, 165 are oriented coaxially with respect to the axis of rotation 151 and engage one another radially. Two Holweck stator sleeves 167, 169 with cylindrical flanks are further provided. The Holweck stator sleeves 167, 169 are likewise oriented coaxially with respect to the axis of rotation 151 and engage one another radially.

[0044] The pumping surfaces of the Holweck pump stages are formed by the lateral surfaces, i.e. by the radially inner and / or outer surfaces of the Holweck rotor sleeves 163, 165 and the Holweck stator sleeves 167, 169. The radially inner surface of the outer Holweck stator sleeve 167 faces the radially outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together with this outer surface forms the first Holweck pump stage following the turbomolecular pump. The radially inner surface of the outer Holweck rotor sleeve 163 faces the radially outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together with this outer surface forms the second Holweck pump stage. The radially inner surface of the inner Holweck stator sleeve 169 opposes the radially outer surface of the inner Holweck rotor sleeve 165 while forming a radial Holweck gap 175, and together with this outer surface forms the third Holweck pump stage.

[0045] The lower end of the Holweck rotor sleeve 163 may be provided with a radially extending channel, through which the radially outer Holweck gap 171 is connected to the central Holweck gap 173. The upper end of the inner Holweck stator sleeve 169 may be provided with a further radially extending channel, through which the central Holweck gap 173 is connected to the radially inner Holweck gap 175. In this way, the multiple mutually interlocking Holweck pump stages are connected in series with each other. The lower end of the radially inner Holweck rotor sleeve 165 may be further provided with a connecting channel 179 leading to the exhaust port 117.

[0046] The pumping surfaces of the Holweck stator sleeves 167, 169 each have a number of Holweck grooves extending in the axial direction and spiraling around the rotation axis 151, while the opposing sides of the Holweck rotor sleeves 163, 165 are smoothly formed and pump the gas for the operation of the vacuum pump 111 forward in the Holweck grooves.

[0047] For the rotatable support of the rotor shaft 153, a rolling bearing 181 is provided in the area of ​​the pump outlet 117 and a permanent magnetic bearing 183 is provided in the area of ​​the pump inlet 115.

[0048] In the region of the rolling bearing 181, the rotor shaft 153 is provided with a conical splash nut 185. The splash nut 185 has an outside diameter that increases towards the rolling bearing 181. The splash nut 185 is in sliding contact with at least one scraping member of the working medium reservoir. In other existing turbomolecular vacuum pumps (not shown), instead of a splash nut, a splash screw may be provided. Since various configurations are thereby possible, the term "splash tip" is also used in the above context.

[0049] The working medium reservoir comprises a number of absorbent discs 187 stacked one above the other, which are impregnated with a working medium for the rolling bearings 181, for example a lubricant.

[0050] During operation of the vacuum pump 111, the working medium is transferred by capillary action from the working medium reservoir via the scraping element to the rotating splash nut 185 and is then forced by centrifugal force along the splash nut 185 towards the increasing outer diameter of the splash nut 185 towards the rolling bearing 181, where it fulfills, for example, a lubrication function. The rolling bearing 181 and the working medium reservoir are enclosed in the vacuum pump by a trough-like insert 189 and a bearing cover 145.

[0051] The permanent magnetic bearing 183 has a rotor-side bearing half 191 and a stator-side bearing half 193. Each of these has a ring stack, which consists of several rings 195, 197 of permanent magnets stacked axially one above the other. The ring magnets 195, 197 face each other forming a radial bearing gap 199, with the rotor-side ring magnet 195 arranged radially outward and the stator-side ring magnet 197 arranged radially inward. The magnetic field present in the bearing gap 199 induces a magnetic repulsion between the ring magnets 195, 197. This repulsion provides a radial support for the rotor shaft 153. The rotor-side ring magnet 195 is supported by a support part 201 of the rotor shaft 153. The support part 201 surrounds the ring magnet 195 radially outward. The stator-side ring magnet 197 is supported by a support part 203 on the stator side. The support part 203 extends through the ring magnet 197 and is suspended on radial struts 205 of the housing 119. Parallel to the axis of rotation 151, the ring magnet 195 on the rotor side is fixed by a cover element 207 connected to the support part 203. The ring magnet 197 on the stator side is fixed in one direction parallel to the axis of rotation 151 by a fixing ring 209 connected to the support part 203 and a fixing ring 211 connected to the support part 203. Between the fixing ring 211 and the ring magnet 197, a disc spring 213 may further be provided.

[0052] An emergency or safety bearing 215 is provided in the magnetic bearing. During normal operation of the vacuum pump, the emergency or safety bearing 215 runs free without contact and only engages if the rotor 149 is displaced too far radially relative to the stator, thus forming a radial stop for the rotor 149, so that a collision between the rotor-side and stator-side structures is prevented. The safety bearing 215 is configured as a non-lubricated rolling bearing and forms a radial gap together with the rotor 149 and / or the stator. The gap ensures that the safety bearing 215 is not engaged during normal pump operation. The safety bearing 215 engages during radial displacement, which is dimensioned to be sufficiently large so that the safety bearing 215 is not engaged during normal operation of the vacuum pump and at the same time is sufficiently small so that a collision between the rotor-side and stator-side structures is prevented in all circumstances.

[0053] The vacuum pump 111 has an electric motor 125 which drives a rotor 149 in rotation. The armature of the electric motor 125 is formed by the rotor 149. A rotor shaft 153 of the rotor 149 extends through a motor stator 217. A permanent magnet assembly may be arranged radially outwardly or embedded in the part of the rotor shaft 153 which extends through the motor stator 217. An intermediate chamber 219 is arranged between the motor stator 217 and the part of the rotor 149 which extends through the motor stator 217. The intermediate chamber 219 has a radial motor gap. Through the motor gap, the motor stator 217 and the permanent magnet assembly may magnetically interact to transmit a driving torque.

[0054] The motor stator 217 is fixed in the housing in a motor chamber 137 provided for the electric motor 125. Via a seal gas connection 135, a seal gas (also called purge gas, which can be, for example, air or nitrogen) can reach the motor chamber 137. Via the seal gas, the electric motor 125 can be protected against process gases, for example against corrosive parts of the process gas. The motor chamber 137 can be evacuated via the pump outlet 117, i.e. a vacuum pressure acts in the motor chamber 137, which is realized at least approximately by an auxiliary vacuum pump connected to the pump outlet 117.

[0055] A so-called labyrinth seal 223, known per se, may furthermore be provided between the rotor hub 161 and the wall 221 which defines the motor chamber 137. This in particular achieves better sealing of the motor chamber 217 with respect to the radially outer Holweck pump stages.

[0056] In the turbomolecular vacuum pump 111 described above with reference to Figures 1 to 5, the Holweck stator sleeves 167, 169 can have an internally or externally located Holweck thread 16, as shown diagrammatically as an exploded view in Figure 6. As can be seen from this drawing, the Holweck geometry is constant over the entire axial extension of the Holweck stator sleeve 167, 169 between the inlet E and the outlet A of the Holweck pump stage, in which case in particular the number of webs 12 forming the Holweck thread 16 is constant between the inlet E and the outlet A. The pitch of the thread, the width of the webs 12, the width of the thread groove 14 and the height of the webs 12 are constant over the axial extension of the stator sleeves 167, 169.

[0057] In the following, various embodiments of the stator sleeve 10 are described which can be incorporated into the turbomolecular vacuum pump 111 instead of the stator sleeves 167, 169 shown here, while in this case the rest of the structure of the turbomolecular vacuum pump 111 and the basic structure of the Holweck pump stage with three pump stages mating inside and outside may be maintained.

[0058] As can be seen from the development of Fig. 7, there the stator sleeve 10 or the Holweck thread 16 formed by the thread webs 12 of the stator sleeve 10 has three thread sections I, II, III between the inlet E and the outlet A, where the number of thread webs 12 in the third thread section III, the most downstream, is twice as large as the number in the second thread section II, whereas the number of webs 12 in the second thread section II is the same as the number of webs 12 in the first thread section I, so that in the embodiment of Fig. 7 there are essentially only two thread sections with different Holweck geometries.

[0059] In the third threaded portion III, the number of webs 12 is twice as large as in the first and second threaded portions I, II, and therefore the width of the grooves 14 in the third threaded portion III is significantly smaller than in the other two threaded portions I, II, resulting in an increase in compression performance towards the outlet port A, whereas the pumping speed of the Holweck pump stage towards the inlet port E increases.

[0060] 8, the stator sleeve 10, in contrast, effectively has three threaded portions I, II, III with different Holweck geometries. In particular, the number of webs 12 in the central second threaded portion II is greater than the number in the inlet-side first threaded portion I and less than the number in the outlet-side third threaded portion III, so that the width of the thread groove in the third threaded portion III is significantly smaller than in the first threaded portion I.

[0061] 9, the number of webs 12 in the central threaded portion II is smaller than the number in both the first threaded portion I on the inlet side and the third threaded portion III on the outlet side, whereas, alternatively, depending on the characteristic values ​​to be achieved, the reverse situation may also exist, so that, for example, in the central second threaded portion II, the number of webs 12 may be greater than the number in both the first threaded portion I on the inlet side and the third threaded portion III on the outlet side.

[0062] In the embodiment described above with reference to Figures 7 to 9, the thread pitch does not change between the inlet port E and the outlet port A, but depending on the design of the respective Holweck pump stage, the thread pitch may vary over the axial extension length of the stator sleeve 10, which may equally apply to 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 each thread groove 14.

[0063] As can be best seen from the embodiment of Figure 9, in which threaded portions I, II, III each have an axial extension length between the inlet E and the outlet A that is approximately 30% to 35% of the axial extension length of the stator sleeve 10. The axial extension length of each threaded portion can therefore be quite small, especially when the stator sleeve 10 already has a relatively small axial extension length in its entirety, allowing fine tuning of the characteristics of the Holweck pump stage.

[0064] FIG. 10 shows another embodiment of a folded type Holweck pump stage, in which the radially outer stator sleeve 10 is formed by two threaded sections I, II located between the inlet E and the outlet A. In this case, both the groove bottom 18 of the first threaded section I and the groove bottom 18 of the second threaded section II located downstream of the first threaded section I form a conical bottom envelope, in which case in the embodiment shown here the taper angle α in the first threaded section I is smaller than the taper angle α in the second threaded section II. However, alternatively to this, the taper angle α in the second threaded section II may also be smaller than the taper angle α in the first threaded section I.

[0065] The taper angle α can be of the same magnitude in both threaded sections I and II, but as shown in Fig. 10, the taper angle α in the second threaded section II is greater than the taper angle α in the first threaded section I, so that an increase in the pumping speed of up to 20% can be achieved in the transition from the first threaded section I to the second threaded section II, in particular when the reserve pressure or the pressure at the exhaust port A is relatively high, in the range of 1 mbar to about 10 mbar, see diagram in Fig. 11. This can prove to be advantageous in particular when the Holweck pump stage according to the drawing in Fig. 10 has an intermediate inlet 20 in the transition area between the first threaded section I and the second threaded section II, since in this case the increase in the pumping speed at the intermediate inlet 20 makes it possible to prevent the process gas drawn in thereby from flowing back towards the inlet E of the Holweck pump stage.

[0066] Finally, in the embodiment described with reference to FIG. 12, the third threaded section III, located at the outlet A of the Holweck pump stage, is formed by a separately handleable annular body 22 with an internal thread, the bottom envelope of the thread groove 14 here likewise being conically formed and tapering towards the outlet A.

[0067] In this case, to accommodate the annulus 22, the stator sleeve 10 has at its outlet end A a portion 24 with a non-threaded cylindrical side surface 26 onto which the ring 22 can be pressed, so that the two upstream threaded portions I, II together with the threaded portion of the annulus 22 form the Holweck thread 16 of the stator sleeve 10. In this case, the threaded portion of the annulus 22 differs from the other two threaded portions I, II in at least one thread parameter, such as the thread pitch, the number of webs 12, the width of the thread grooves 14, the width of the webs 12 and the height of the webs 12 above the groove bottom 18, which allows fine-tuning of the characteristic values ​​of the Holweck pump stage.

[0068] Since the annulus 22 is received by the unthreaded cylindrical side 24 of the stator sleeve 10, the annulus 22 is, in a sense, a separately manipulable stator sleeve, but the annulus 22 can be manufactured with a relatively small axial extension without compromising stability, since the annulus 22 is supported and reinforced to some extent by the unthreaded cylindrical side 26 of the stator sleeve 10. This application relates to the invention described in the claims, but also includes the following as other aspects. 1. A vacuum pump (111), in particular a turbomolecular vacuum pump (111), at least one Holweck pump stage having an inlet (E) and an outlet (A) downstream of the inlet (E) in the pumping direction, The Holweck pump stage comprises a Holweck rotor having a rotor sleeve (163, 165) and a Holweck stator having a stator sleeve (10), the stator sleeve (10) being arranged coaxially with the Holweck rotor while defining a Holweck gap (171, 173, 175); A vacuum pump (111), wherein the stator sleeve (10) has a Holweck thread (16) having a plurality of thread grooves (14), the thread grooves (14) being defined by a web (12) formed on the stator sleeve (10) and a groove bottom (18) formed by the stator sleeve (10), A vacuum pump (111) in which the stator sleeve (10) is constructed in one piece and at least one thread parameter of the Holweck thread (16) from a group of thread parameters consisting of the number of webs (12), the thread pitch, the width of the thread groove (14), the width of the webs (12), and the height of the webs (12) above the groove bottom (18) varies over the axial extension length of the stator sleeve (10). 2. 10. The vacuum pump of claim 1, wherein the Holweck thread (16) has a first thread portion (I) extending axially across a first height dimension of the stator sleeve (10), a second thread portion (II) extending axially across a second height dimension of the stator sleeve (10) downstream of the first thread portion (I), and at least one third thread portion (III) extending axially across a third height dimension of the stator sleeve (10) downstream of the second thread portion (III), and at least one of the three thread portions (I, II, III) differs from another of the three thread portions (I, II, III) in at least one thread parameter of a group of thread parameters. 3. The vacuum pump of claim 2, wherein the number of webs (12) in the third threaded portion (III) is greater than the number in the second threaded portion (II), and in particular, the number of webs (12) in the third threaded portion (III) is twice as large as the number in the second threaded portion (II). 4. 4. The vacuum pump of claim 2 or 3, wherein the number of webs (12) in the second threaded portion (II) is the same as the number of webs (12) in the first threaded portion (I). 5. 5. Any one of the vacuum pumps as set forth above in 2 to 4, wherein the width of the thread groove (14) in the third thread portion (III) is smaller than the width in the second thread portion (II) and / or the width of the thread groove (14) in the second thread portion (II) is the same as the width of the thread groove (14) in the first thread portion (I). 6. 4. The vacuum pump according to claim 2 or 3, wherein the number of webs (12) in the second threaded portion (II) is greater than the number in the first threaded portion (I). 7. 7. The vacuum pump of claim 6, wherein the width of the thread groove (14) in the third thread portion (III) is smaller than the width in the first thread portion (I). 8. 4. The vacuum pump of claim 2 or 3, wherein the number of webs (12) in the first threaded portion (I) is greater than the number in the second threaded portion and / or the number of webs (12) in the first threaded portion (I) is the same as the number of webs (12) in the third threaded portion (III). 9. 9. The vacuum pump of claim 8, wherein the width of the thread groove (14) in the third thread portion (III) and the first thread portion (I) is smaller than the width in the second thread portion (II), and / or the width of the thread groove (14) in the third thread portion (III) is the same as the width of the thread groove (14) in the first thread portion (I). 10. 10. The vacuum pump according to any one of claims 1 to 9, wherein the groove bottom (18) defines a conically shaped bottom envelope in at least one of the three threaded portions (I, II, III). 11. 13. The vacuum pump of claim 10, wherein the groove bottom (18) sets a taper angle (α) in at least one of the three threaded portions (I, II, III) that has a different value from the taper angle (α) in another threaded portion. 12. 12. The vacuum pump according to claim 11, wherein the taper angle (α) in the first threaded portion (I) is smaller than the taper angle (α) in the second threaded portion (II) and / or the third threaded portion (III). 13. 13. The vacuum pump according to any one of claims 1 to 12, wherein the height dimension of each of the threaded portions (I, II, III) is 15% to 50%, preferably 25% to 40%, and particularly preferably 30% to 35% of the axial extension length of the stator sleeve (10). 14. 14. Any one of the vacuum pumps described above in 1 to 13, wherein the stator sleeve (10) surrounds the rotor sleeve (163, 165) and the Holweck thread portion (16) is configured as a female thread portion provided on the stator sleeve (10), and / or the rotor sleeve (163) surrounds the stator sleeve (10) and the Holweck thread portion (16) is configured as a male thread portion provided on the stator sleeve (10). 15. 15. The vacuum pump of any one of claims 1 to 14, wherein the Holweck rotor has an inner rotor sleeve (165) and an outer rotor sleeve (163) concentrically surrounding the inner rotor sleeve (165), the Holweck stator has an outer stator sleeve (10) concentrically surrounding the outer rotor sleeve (163) and an inner stator sleeve (10) concentrically surrounding the inner rotor sleeve (165), and the Holweck thread portion (16) is configured as a female thread portion provided on the outer stator sleeve (10), as a female thread portion provided on the inner stator sleeve (10), and / or as a male thread portion provided on the inner stator sleeve (10). 16. 16. The vacuum pump of any one of claims 2 to 15, wherein the stator sleeve (10) forms, instead of the first and / or third threaded portions (I, III), a portion (24) having a cylindrical side surface (26) without threads, said portion (24) housing a separately addressable annulus (22) having a threaded portion, the annulus (22) forming together with the second threaded portion (II) the Holweck threaded portion (16) of the stator sleeve (10), the threaded portion of the annulus (22) differing from the second threaded portion (II) in at least one threaded parameter of the group of threaded parameters. 17. The groove bottom (18) defines a conical bottom envelope of the vacuum pump of claim 16. [Explanation of symbols]

[0069] E. Air Intake A Exhaust port 10 Status Leave 12. Web 14 Thread groove 16 Holweck thread 18 Groove bottom 20 Intermediate air intake 22 ring body 24 parts 26 Side I, II, III Threaded section α Taper angle 111 Turbomolecular pump 113 Intake flange 115 Pump Inlet 117 Pump exhaust port 119 Housing 121 Lower part 123 Electronics Housing 125 Electric Motor 127 Accessory connection 129 Data Interface 131 Current supply connection 133 Ventilation Intake 135 Seal gas connection 137 Motor Room 139 Coolant Connection 141 Bottom surface 143 Screw 145 Bearing cover 147 Fixed hole 148 Coolant Line 149 Rotor 151 Rotation axis 153 rotor shaft 155 Moving blade 157 Stator blade 159 Spacer ring 161 rotor hub 163 Holbeck Rotor Sleeve 165 Holbeck Rotor Sleeve 167 Holbeck Sterling Sleeve 169 Holbeck Sterling Sleeve 171 Holbeck Gap 173 Holbeck Gap 175 Holbeck Gap 179 Connection Channels 181 Rolling bearings 183 Permanent magnet type magnetic bearing 185 Splash Nut 187 Disc 189 Insert 191 Rotor side bearing half 193 Stator side bearing half 195 Ring Magnet 197 Ring Magnet 199 Bearing clearance 201 Support part 203 Support part 205 Radial Struts 207 Cover Elements 209 Support Ring 211 Fixing ring 213 Disc spring 215 Emergency or safety bearings 217 Motor Stator 219 Intermediate Room 221 Wall 223 Labyrinth Seal

Claims

1. A vacuum pump (111), at least one Holweck pump stage having an inlet (E) and an outlet (A) downstream of the inlet (E) in the pumping direction, The Holweck pump stage comprises a Holweck rotor having a rotor sleeve (163, 165) and a Holweck stator having a stator sleeve (10), the stator sleeve (10) being arranged coaxially with respect to the Holweck rotor while forming a Holweck gap (171, 173, 175); A vacuum pump (111) in which a stator sleeve (10) has a Holweck thread (16) having a plurality of thread grooves (14), the thread grooves (14) being defined by a web (12) formed in the stator sleeve (10) and a groove base (18) formed by the stator sleeve (10), the stator sleeve (10) is of one-piece construction, and at least one thread parameter of the Holweck thread (16) from a 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 root (18) varies over the axial extension length of the stator sleeve (10); the Holweck thread (16) has a first thread portion (I) extending axially across a first height dimension of the stator sleeve (10), a second thread portion (II) extending axially across a second height dimension of the stator sleeve (10) downstream of the first thread portion (I), and at least one third thread portion (III) extending axially across a third height dimension of the stator sleeve (10) downstream of the second thread portion (II), wherein at least one of the three thread portions (I, II, III) differs from another of the three thread portions (I, II, III) in at least one thread parameter of a group of thread parameters; the number of webs (12) in the first threaded portion (I) is greater than the number in the second threaded portion, and the number of webs (12) in the first threaded portion (I) is the same as the number of webs (12) in the third threaded portion (III); A vacuum pump (111).

2. A vacuum pump as described in claim 1, wherein the number of webs (12) in the third threaded portion (III) is twice as large as the number in the second threaded portion (II).

3. 3. A vacuum pump according to claim 1 or 2, wherein the width of the thread groove (14) in the third threaded portion (III) is smaller than its width in the second threaded portion (II).

4. 2. The vacuum pump according to claim 1, wherein the width of the thread groove (14) in the third thread portion (III) and in the first thread portion (I) is smaller than the width in the second thread portion (II) and / or the width of the thread groove (14) in the third thread portion (III) is the same as the width of the thread groove (14) in the first thread portion (I).

5. 3. A vacuum pump according to claim 1 or 2, wherein the groove bottom (18) defines a conically shaped bottom envelope in at least one of the three threaded sections (I, II, III).

6. 6. A vacuum pump as claimed in claim 5, wherein the groove bottom (18) defines a taper angle (α) in at least one of the three threaded portions (I, II, III) that has a different value than a taper angle (α) in another one of the threaded portions.

7. 7. The vacuum pump according to claim 6, wherein the taper angle (α) in the first threaded portion (I) is smaller than the taper angle (α) in the second threaded portion (II) and / or the third threaded portion (III).

8. 3. A vacuum pump according to claim 1 or 2, wherein the height dimension of each of the threaded portions (I, II, III) is between 15% and 50% of the axial extension length of the stator sleeve (10).

9. 3. The vacuum pump according to claim 1 or 2, wherein the stator sleeve (10) surrounds the rotor sleeve (163, 165) and the Holweck thread (16) is configured as an internal thread on the stator sleeve (10) and / or the rotor sleeve (163) surrounds the stator sleeve (10) and the Holweck thread (16) is configured as an external thread on the stator sleeve (10).

10. 3. The vacuum pump according to claim 1, wherein the Holweck rotor comprises an inner rotor sleeve (165) and an outer rotor sleeve (163) concentrically surrounding the inner rotor sleeve (165), the Holweck stator comprises an outer stator sleeve (10) concentrically surrounding the outer rotor sleeve (163) and an inner stator sleeve (10) concentrically surrounding the inner rotor sleeve (165), and the Holweck thread (16) is configured 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).

11. 3. A vacuum pump according to claim 1 or 2, wherein the stator sleeve (10) forms, instead of the first and / or third threaded portions (I, III), a portion (24) with a cylindrical side surface (26) without threads, said portion (24) housing a separately addressable annulus (22) with a threaded portion, which annulus (22) forms, together with the second threaded portion (II), the Holweck threaded portion (16) of the stator sleeve (10), the threaded portion of the annulus (22) differing from the second threaded portion (II) in at least one threaded parameter of a group of threaded parameters.

12. 12. The vacuum pump of claim 11, wherein the groove bottom (18) defines a conical bottom envelope.

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