JP7670752B2 - Vacuum pump with Holweck pump stage having variable Holweck geometry - Patents.com - Google Patents

Description

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

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 each other. Typically, Holweck pump stages are used in turbomolecular vacuum pumps, where the Holweck pump stage is followed in the flow direction by one or more turbomolecular pump stages.

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 defined by the walls of the web, in which the gas molecules are pumped when the rotor sleeve rotates relative to the stator sleeve.

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 the two rotor sleeves.

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.

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 sections, which are arranged axially one after the other in the pumping direction or directly adjacent to one another. In this case, the individual sleeve sections 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.

However, there is a lower limit to the axial extension length of the Holweck stator sleeve, e.g. for manufacturing and assembly reasons. The Holweck stator sleeve must therefore not fall below a certain minimum axial extension length, so that 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.

The object of the present invention is therefore to improve 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.

This problem is solved by a vacuum pump having the features of claim 1, in particular in a one-piece stator sleeve, in which 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 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 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.

For example, in order to achieve a high compression performance at the pre-vacuum side or at the outlet of the Holbeck pump stage, and a low compression performance or a high pumping speed at the high vacuum side or at the inlet of the 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 thread 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 structure 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 thread 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.

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 configured 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 configuration 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 technical reasons the minimum axial extension of the sleeve parts must not be exceeded.

Hereinafter, preferred embodiments of the invention will be described. Further embodiments are evident from the dependent claims, the description of the drawings and the drawings themselves.

Thus, according to one embodiment, 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, and at least one of the three thread portions differs from another of the three thread portions in at least one thread parameter of the group of thread parameters.

Thus, for example, according to an exemplary embodiment, it can be envisaged that the number of webs in the third threaded portion may be greater than the number in the second threaded portion, in particular that the number of webs in the third threaded portion is twice as large as the number in the second threaded portion. Thus, the number of webs and therefore the number of thread grooves is greater at the pre-vacuum side or outlet of the Holbeck pump stage than 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 portion is greater than the number in the second threaded portion, 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.

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. adjusted 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 outlet of each threaded section.

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 equal 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 the same as the number of webs in the first threaded portion, so that in this respect the stator sleeve has in a sense only two threaded portions with different numbers of webs.

According to another embodiment, it may be envisaged that the width of the thread groove in the third thread portion is smaller than the width in the second thread portion. In this case, it may be envisaged in particular that the width of the thread groove 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 may be formed in the thread groove formed thereby in the third thread portion, which reduces the mutual spacing between these webs and the first set of webs.

According to another embodiment, 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 it can be envisaged that the Holweck pump stage in this case effectively has only two thread portions with different thread groove widths.

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. For the same web width, this means that the width of the thread 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.

Additionally or alternatively to the embodiment in which the number of webs in the third threaded portion is greater than the number in the second threaded portion, according to another embodiment, it can be envisaged that the number of webs in the first threaded portion is also greater than the number in the second threaded portion. In particular, in this case, it can be envisaged 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.

Alternatively, it may be envisaged that the number of thread grooves in the second central threaded portion is greater than the number in the first and third threaded portions on the intake and exhaust sides.

The groove bottoms of all the thread grooves may be located on the cylindrical side, but it should be desired that the pumping speed increases towards the exhaust of the Holweck pump stage, and therefore according to another embodiment it can be envisaged that the groove bottoms set a conically formed bottom envelope in at least one of the three threaded sections. In this case it can be envisaged in particular that the groove bottoms set a taper angle in at least one of the three threaded sections that has an angle different from the angle in the other threaded sections.

Thus, for example, the taper angle in the first threaded section may be smaller than the taper angle in the second and/or third threaded section, which means that the bottom envelope of the first threaded section tapers less towards the outlet of the Holweck pump stage than the bottom envelope of the second or third threaded section. 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 section, since in this case an increase in the pumping speed at the intermediate inlet can be avoided.

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.

In a single stage Holweck pump, the stator sleeve generally surrounds the rotor sleeve. In this case, the Holweck thread is therefore configured as an internal thread on the stator sleeve. In contrast, when the rotor sleeve surrounds the stator sleeve, the Holweck thread is then configured as an external thread on the stator sleeve.

Moreover, according to another embodiment, the vacuum pump may have a "folded" Holweck arrangement as described above. In this case, 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. In this case, 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.

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 a separately handleable annular body with a threaded portion is fitted as an additional part, 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 annular body differs from the second threaded portion in at least one threaded parameter of the aforementioned group of threaded parameters. Additionally, it can be envisaged that the groove bottom of the threaded portion of the annular body defines a conical bottom envelope, in which case the bottom envelope tapers towards the exhaust of the Holweck pump stage.

The present invention will now be described with reference to the accompanying drawings.

FIG. 1 shows a perspective view of a turbomolecular pump. FIG. 2 shows a bottom view of the turbomolecular pump of FIG. 3 shows a cross-sectional view of the turbomolecular pump taken along section line AA shown in FIG. 2. 3 shows a cross-sectional view of the turbomolecular pump taken along section line BB shown in FIG. 2. 3 shows a cross-sectional view of the turbomolecular pump taken along section line CC shown in FIG. 2. 1 shows a schematic development of a conventional Holweck Sterling sleeve. 1 shows a schematic exploded view of one embodiment of a Holweck Stator Sleeve according to the present invention. 1 shows a schematic exploded view of another embodiment of a Holweck Stator Sleeve according to the present invention. 1 shows a schematic exploded view of yet another embodiment of a Holweck Stator Sleeve according to the present invention. 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. FIG. 11 is a diagram for explaining the pumping speed in the Holweck pump stage of FIG. 10. 4 shows a schematic cross-sectional view of a folded type Holweck pump stage according to yet another embodiment.

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

The inlet flange 113 forms the upper end of the 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 on the electronics housing 123.

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

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 a purge gas connection) is also arranged. Via the sealing gas connection 135, a purge gas can be fed into the 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 intake 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. A separate turbomolecular vacuum pump (not shown) is present and is operated exclusively air-cooled.

The underside 141 of the vacuum pump can be used as a base, so that the vacuum pump 111 can be operated vertically with the underside 141 as a reference. 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 that shown in FIG. 1. Vacuum pump configurations are also possible 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.

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

Various screws 143 are further arranged on the underside 141 shown in FIG. 2. These screws 143 secure the vacuum pump components, not specified in detail here, to one another. For example, a bearing cover 145 is secured to the underside 141.

In the underside 141, furthermore, fastening holes 147 are arranged. 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.

2 to 5 show a coolant line 148. In the coolant line 148, a coolant can be circulated that is introduced and discharged via the coolant connection 139.

As shown in the cross-sectional views of Figures 3 to 5, the vacuum pump has multiple process gas pump stages. The process gas pump stages are for pumping process gas acting on the pump inlet 115 to the pump outlet 117.

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.

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 radial 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, one rotor blade 155 and one adjacent stator vane 157 each form one turbomolecular pump stage. The stator vanes 157 are held at a desired axial distance from each other by spacer rings 159.

The vacuum pump further comprises Holweck pump stages arranged radially inside and outside each other and connected in series to provide a pumping action. There are alternative turbomolecular vacuum pumps (not shown) that do not have Holweck pump stages.

The rotor of the Holweck pump stage has a rotor hub 161 arranged on the rotor shaft 153 and two Holweck rotor sleeves 163, 165 with cylindrical sides 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 with each other radially. Two Holweck stator sleeves 167, 169 with cylindrical sides are further provided. The Holweck stator sleeves 167, 169 are likewise oriented coaxially with respect to the axis of rotation 151 and engage with each other radially.

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

The lower end of the Holweck rotor sleeve 163 may be provided with a radially extending channel. The radially outer Holweck gap 171 is connected to the central Holweck gap 173 via the channel. The upper end of the inner Holweck stator sleeve 169 may be further provided with a radially extending channel. The central Holweck gap 173 is connected to the radially inner Holweck gap 175 via the channel. In this way, the multiple Holweck pump stages that engage with each other inwardly and outwardly are connected in series with each other. The lower end of the Holweck rotor sleeve 165 located in the radially inner direction may be further provided with a connecting channel 179 that leads to the exhaust port 117.

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

For rotatable support of the rotor shaft 153, a rolling bearing 181 is provided in the area of the pump exhaust port 117, and a permanent magnetic bearing 183 is provided in the area of the pump intake port 115.

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 outer 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), a splash screw may be provided instead of a splash nut. Since various configurations are possible hereby, the term "splash tip" is also used in the above context.

The working medium reservoir has a number of absorbent disks 187 stacked one above the other. These disks 187 are impregnated with a working medium, e.g. a lubricant, for the rolling bearings 181.

During operation of the vacuum pump 111, the working medium is transferred by capillary action from the working medium reservoir through the scraping member to the rotating splash nut 185 and then, due to centrifugal force, is forced 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.

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 causes 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 rotor-side ring magnet 195 is fixed by a cover element 207 connected to the support part 203. The stator-side ring magnet 197 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.

An emergency or safety bearing 215 is provided in the magnetic bearing. The emergency or safety bearing 215 runs free during normal operation of the vacuum pump 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.

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. The rotor shaft 153 of the rotor 149 extends through the motor stator 217. A permanent magnet assembly may be arranged radially outwardly or embedded in the portion 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 portion 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 drive torque.

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 may 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 gas, for example against corrosive parts of the process gas. The motor chamber 137 may be evacuated via the pump exhaust 117, i.e. a vacuum pressure is applied in the motor chamber 137, which is realized at least approximately by an auxiliary vacuum pump connected to the pump exhaust 117.

Between the rotor hub 161 and the wall 221 that defines the motor chamber 137, a so-called labyrinth seal 223, known per se, may further be provided. This achieves better sealing of the motor chamber 217, in particular against the radially outer Holweck pump stages.

In the turbomolecular vacuum pump 111 described above with reference to Figures 1 to 5, the Holweck stator sleeves 167, 169 can have the Holweck threads 16 located on the inside or on the outside, 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 length of the Holweck stator sleeves 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 threads 16 is constant between the inlet E and the outlet A. The pitch of the threads, the width of the webs 12, the width of the thread grooves 14 and the height of the webs 12 are constant over the axial extension length of the stator sleeves 167, 169.

Hereinafter, various embodiments of the stator sleeve 10 are described which can be incorporated into the turbomolecular vacuum pump 111 in place of the stator sleeves 167, 169 shown here, while still maintaining the basic structure of the Holweck pump stage with three pump stages mating inside and outside the rest of the turbomolecular vacuum pump 111.

As can be seen from the development of FIG. 7, 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, which is the most downstream, is twice as large as the number in the second thread section II. In contrast, 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.

In the third threaded section III, the number of webs 12 is twice as large as in the first and second threaded sections I, II, and therefore the width of the thread grooves 14 in the third threaded section III is significantly smaller than in the other two threaded sections I, II, resulting in an increase in compression performance towards the exhaust port A, whereas the exhaust speed of the Holweck pump stage towards the intake port E increases.

In the embodiment of FIG. 8, by contrast, the stator sleeve 10 effectively has three threaded portions I, II, III, each having a different Holweck geometry. In particular, the number of webs 12 in the central second threaded portion II is greater than the number in the first threaded portion I on the inlet side and less than the number in the third threaded portion III on the outlet side, so that the width of the thread groove in the third threaded portion III is significantly smaller than the width in the first threaded portion I.

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. Alternatively, the reverse situation may exist depending on the characteristic value to be achieved, so that, for example, in the central second threaded portion II, the number of webs 12 may be greater than the number in the first threaded portion I on the inlet side and the third threaded portion III on the outlet side.

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 each 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.

As can be best seen from the embodiment of FIG. 9, in which the threaded portions I, II, and 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. Thus, the axial extension length of each threaded portion can 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.

Figure 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 be smaller than the taper angle α in the first threaded section I.

The taper angle α may be the same 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 pre-pressure or pressure at the exhaust port A is relatively high, in the range of 1 mbar to about 10 mbar, see the 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 intake port 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 intake port 20 makes it possible to prevent the process gas sucked in thereby from flowing back towards the intake port E of the Holweck pump stage.

Finally, in the embodiment described with reference to FIG. 12, the third threaded portion III, located at the outlet A of the Holweck pump stage, is formed by a separately addressable 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.

In this case, to accommodate the annulus 22, the stator sleeve 10 has at its outlet end A a portion 24 with a cylindrical unthreaded side 26 into 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.

Since it is received by the portion 24 having the unthreaded cylindrical side 26 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 it is supported and reinforced to some extent by the portion 24 having the unthreaded cylindrical side 26.
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), comprising:
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),
1. A vacuum pump (111) comprising a stator sleeve (10) of one-piece construction, characterized in that 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 base (18) varies over the axial extension length of the stator sleeve (10).
2.
11. 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), 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.
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 described 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.
11. 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 a taper angle (α) in another one of the threaded portions.
12.
12. The vacuum pump of 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 of 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. The vacuum pump of any one of claims 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 a group of threaded parameters.
17.
17. The vacuum pump of claim 16, wherein the groove bottom (18) defines a conical bottom envelope.

E Inlet A Outlet 10 Stator sleeve 12 Web 14 Thread groove 16 Holweck thread 18 Groove bottom 20 Intermediate inlet 22 Annulus 24 Part 26 Side I, II, III Threaded part α 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 connection 129 Data interface 131 Current supply connection 133 Ventilating inlet 135 Seal gas connection 137 Motor chamber 139 Coolant connection 141 Lower surface 143 Screw 145 Bearing cover 147 Fixing hole 148 Coolant line 149 Rotor 151 axis of rotation 153 rotor shaft 155 rotor blade 157 stator blade 159 spacer ring 161 rotor hub 163 Holweck rotor sleeve 165 Holweck rotor sleeve 167 Holweck stator sleeve 169 Holweck stator sleeve 171 Holweck gap 173 Holweck gap 175 Holweck gap 179 connecting channel 181 rolling bearing 183 permanent magnetic bearing 185 splash nut 187 disk 189 insert 191 rotor-side bearing half 193 stator-side bearing half 195 ring magnet 197 ring magnet 199 bearing gap 201 support part 203 support part 205 radial strut 207 cover element 209 support ring 211 fixing ring 213 Disc spring 215 Emergency bearing or safety bearing 217 Motor stator 219 Intermediate chamber 221 Wall 223 Labyrinth seal

Claims (12)

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 according to 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. 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). 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 ). 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. 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. 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 ). 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). A 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 a female thread provided on the stator sleeve (10), and/or the rotor sleeve (163) surrounds the stator sleeve (10) and the Holweck thread (16) is configured as a male thread provided on the stator sleeve (10). The vacuum pump according to claim 1 or 2, 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). 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. The vacuum pump of claim 11 , wherein the groove bottom (18) defines a conical bottom envelope.