Vacuum pump

Abstract

The invention relates to a vacuum pump (90), preferably a vacuum pump (90) according to any one of claims 1 to 4, in particular a split-flow pump (92), with: - an inlet (94), - an outlet (96), - two or more pump stages (10) connected in series between the inlet (94) and the outlet (96) in the pumping direction (98), wherein the at least two or more pump stages (10) comprise at least one turbomolecular pump stage (10, 12) and at least one Holweck pump stage (14), wherein the turbomolecular pump stage (10, 12) is arranged upstream of the Holweck pump stage (14) in the pumping direction (98), and the at least one Holweck pump stage (14) comprises a Holweck stator (20) and a Holweck rotor (30) rotating about a rotational axis (102) during operation, wherein at least one intermediate inlet (40) is provided for gas (100) to be pumped. is located in a pump-active area of ​​one of the pump stages (10),or alternatively wherein at least one intermediate inlet (40) for gas (100) to be pumped is provided, which is arranged between two of the pump stages (10) or in a pump-active area of ​​one of the pump stages (10).

Description

[0001] The invention relates to a vacuum pump, in particular a split flow pump, with an inlet, an outlet, two or more pump stages connected in series in the pumping direction between the inlet and the outlet, wherein the at least two or more pump stages comprise at least one turbomolecular pump stage and at least one Holweck pump stage, wherein the turbomolecular pump stage is arranged upstream of the Holweck pump stage in the pumping direction and the at least one Holweck pump stage comprises a Holweck stator and a Holweck rotor rotating about a rotational axis during operation.

[0002] In the vacuum pump according to the invention, at least one intermediate inlet for gas to be pumped is provided, which is arranged in a pump-active area of ​​the Holweck pump stage, or alternatively between two of the pump stages or in a pump-active area of ​​one of the pump stages.

[0003] Vacuum pumps with one or more turbomolecular pumping stages are often referred to simply as turbomolecular pumps, since the turbomolecular pumping stages employed ultimately determine the pressure level achievable by the respective vacuum pump, particularly high vacuum or ultra-high vacuum. These turbomolecular pumps are fundamentally well-known vacuum pumps in terms of their construction and function, and are versatile and used in various applications and environments in industry and science.

[0004] Turbomolecular pumps are used in particular to create a vacuum in one or more vacuum chambers of a recipient. For this purpose, it is necessary that an inlet side of the vacuum pump is connected to one or more vacuum chambers of the recipient.

[0005] A vacuum pump, and in particular a turbomolecular pump, can be a so-called split-flow pump. Split-flow pumps are generally known. The terms "SplitFlow" and "SPLITFLOW" are registered trademarks of Pfeiffer Vacuum GmbH. Other names for such a vacuum pump include multi-inlet vacuum pump and multi-inlet vacuum pump. Various embodiments of a split-flow pump are described, among other places, in EP 4 108 932 A1.

[0006] A split-flow pump system typically comprises a turbomolecular pump system with at least one, but usually several, turbomolecular pump stages. Downstream of these, in the pumping direction, is a Holweck pump stage, or more commonly, an entire Holweck pump system, also referred to as a Holweck arrangement, with several radially nested Holweck pump stages. The rotating pumping components, namely the rotor disks of the turbomolecular pump system and one or more Holweck sleeves of the Holweck pump system, are mounted on a common shaft driven by an electric motor to rotate about a rotational axis.

[0007] The pumping system of a split-flow pump comprises at least one, and usually several, radial intermediate inlets arranged sequentially in the pumping direction (i.e., axially relative to the axis of rotation). These inlets enable a single split-flow pump to simultaneously evacuate multiple vacuum chambers of a receiver, thereby achieving different pressure levels within the chambers. Split-flow pumps can have their own external housing and be connected to a receiver via this housing. Alternatively, split-flow pumps can be integrated into a receiver's pumping chamber. In this case, the components of the split-flow pump can be arranged in a separate housing. Such a split-flow pump, also known as a cartridge pump, can be handled as a single unit and inserted into the receiver's pumping chamber. However, the use of a separate housing is not mandatory.It is also possible to mount the individual components of the split flow pump in the pumping chamber of the recipient without a separate housing.

[0008] In such split-flow pumps, one of the intermediate inlets may be located in the pumping-active area of ​​a Holweck pump stage or between the last turbomolecular pump stage and the Holweck pump stage following it in the pumping direction. In both cases, it has been found that this reduces the pumping speed of the Holweck pump stage with respect to the intermediate inlet compared to a theoretically achievable pumping speed.

[0009] The present invention is therefore based on the objective of providing a vacuum pump, in particular a split-flow pump, in which the disadvantages of the prior art described above are at least partially overcome. In particular, it is an objective of the present invention to provide a vacuum pump, in particular a split-flow pump, in which a Holweck pump stage, in whose pumping-active area an intermediate inlet is provided or which immediately follows an intermediate inlet, is provided in such a way that its pumping capacity with respect to the intermediate inlet is increased compared to known embodiments of the prior art.

[0010] The foregoing problem is solved by the independent claims. In particular, the foregoing problem is solved by a vacuum pump according to the invention having the features of independent claim 1. Alternatively or additionally, the foregoing problem is also solved by a vacuum pump having the features of independent claim 5. Further developments of the vacuum pumps according to the invention are described in the dependent claims, the description, and the drawings.

[0011] According to a first aspect of the invention, the problem is solved by a vacuum pump, in particular a split flow pump, with an inlet, an outlet, two or more pump stages connected in series in the pumping direction between the inlet and the outlet, wherein the at least two or more pump stages comprise at least one turbomolecular pump stage and at least one Holweck pump stage, wherein the turbomolecular pump stage is arranged upstream of the Holweck pump stage in the pumping direction, and the at least one Holweck pump stage comprises a Holweck stator and a Holweck rotor rotating about a rotational axis during operation, wherein at least one intermediate inlet for gas to be pumped is provided, which is arranged in a pump-active region of the Holweck pump stage.

[0012] The vacuum pump according to the first aspect of the invention is characterized in that the Holweck pump stage has an axial length with respect to the axis of rotation, comprising a first axial end facing at least one turbomolecular pump stage and a second axial end opposite the first axial end, wherein the intermediate inlet is arranged axially between the first axial end and the second axial end of the Holweck pump stage, and wherein the Holweck stator of the Holweck pump stage has a first axial region axially adjoining the intermediate inlet and a second axial region adjoining the intermediate inlet axially opposite to the first axial region, wherein the first axial region has pump-active structures configured and designed for pumping in the direction of the first axial end, and the second axial region has pump-active structures.which are designed and configured for pumping in the direction of the second axial end.

[0013] The vacuum pump according to the first aspect of the invention is therefore preferably a split-flow pump with at least one turbomolecular pumping stage and a Holweck pumping stage downstream of the vacuum pump along the pumping direction. Preferably, however, the vacuum pump according to the invention can have several turbomolecular pumping stages and / or Holweck pumping stages. In the following, the term "Holweck pumping stage" is used such that, unless explicitly stated otherwise, it refers to the Holweck pumping stage through which the gas to be pumped flows first in the pumping direction after the last turbomolecular pumping stage in the pumping direction.

[0014] The Holweck pump stage comprises the usual components, in particular a Holweck stator and a Holweck rotor. The Holweck rotor is designed and configured to rotate about a rotational axis during operation of the vacuum pump. Preferably, the Holweck rotor and a rotor of one or more turbomolecular pump stages share a common pump shaft, which is driven by an electric motor.

[0015] The Holweck rotor features, in particular, a Holweck sleeve which, together with the Holweck stator, forms the pump-active area of ​​the Holweck pump stage. Specifically, the pump-active area of ​​the Holweck pump stage is located where the respective axial extents of the Holweck sleeve and the Holweck stator overlap axially.

[0016] Furthermore, the vacuum pump according to the first aspect of the invention, as a split-flow pump, has at least one intermediate inlet for the gas to be pumped. This intermediate inlet is provided, in particular, in a pump-active region of the Holweck pump stage. In addition to this single intermediate inlet, the vacuum pump according to the first aspect of the invention may also have further intermediate inlets, each arranged in a pump-active region of one of the pump stages of the vacuum pump or between two pump stages of the vacuum pump. Unless explicitly stated otherwise, the term "intermediate inlet" hereafter refers to the intermediate inlet in the Holweck pump stage.

[0017] As explained above, the intermediate inlet is located in the pumping-active area of ​​the Holweck pump stage. This means that the intermediate inlet axially divides the Holweck stator into two parts along an axial length of the Holweck pump stage, i.e., an extension of the Holweck pump stage along its axis of rotation: a first axial section and a second axial section.

[0018] Here, the first axial section extends from the intermediate inlet to a first axial end of the Holweck pump stage, which is specifically oriented towards the turbomolecular pump stage. Similarly, the second axial section extends from the intermediate inlet to a second axial end of the Holweck pump stage, which is axially opposite to the first axial end.

[0019] A key aspect of the invention is that both the first axial region and the second axial region have pump-active structures. These pump-active structures are configured and designed such that in the first axial region, the gas flowing in through the intermediate inlet is pumped towards the first axial end, while in the second axial region, it is pumped towards the second axial end. In other words, in both the first and second axial regions, the incoming gas is pumped away from the intermediate inlet.

[0020] This enables a significant improvement in the pumping performance of the Holweck stage compared to conventional split-flow pumps, where the intermediate inlet is also located in the active area of ​​the Holweck pump stage, but the pumping directions are the same in both axial sections. As a result, only one of the two axial sections, usually the second axial section, is used for pumping the gas flowing in through the intermediate inlet.

[0021] Overall, the inventive design of the vacuum pump according to the first aspect of the invention makes it possible to increase the pumping performance of the Holweck pump stage, particularly with regard to the gas to be pumped which flows in through the intermediate inlet, compared to known designs of vacuum pumps of the prior art.

[0022] Furthermore, in the vacuum pump according to the first aspect of the invention, it can be provided that at least two Holweck pump stages are arranged sequentially along the pumping direction and radially one inside the other with respect to the axis of rotation, and wherein the intermediate inlet is located in the pumping-active area of ​​the Holweck pump stage that is radially outermost with respect to the axis of rotation. In other words, the Holweck pump stage is part of a Holweck pump system or a Holweck arrangement in which several Holweck pump stages are arranged concentrically to one another and nested within each other, so that, in particular preferably, the pumping direction of radially immediately successive Holweck pump stages is opposite to each other. This is also referred to as a "folded" Holweck arrangement.By positioning the intermediate inlet in the radially outermost Holweck pump stage, it can be ensured that the intermediate inlet is particularly easy to access.

[0023] Furthermore, it may be provided that two Holweck pump stages arranged successively in the direction of flow - a (radially) outer Holweck pump stage and a (radially) inner Holweck pump stage - thus comprise a common Holweck stator, provided on both sides with a pump-active structure, which is located radially between two rotor sleeves.

[0024] The vacuum pump according to the invention can also be designed such that the Holweck stator, as pump-active structures, has a first Holweck thread with at least one first thread parameter in the first axial region and a second Holweck thread with at least one second thread parameter in the second axial region, wherein the first thread parameter and the second thread parameter differ. The pumping behavior, in particular the pumping capacity, of a Holweck pump stage or a section of a Holweck pump stage is determined on the one hand by the rotational speed of the corresponding Holweck sleeve, and on the other hand also by the design of the respective pump-active structure.

[0025] In the present embodiment, the pump-active structures of the two axial sections are formed by Holweck threads. These Holweck threads are characterized by corresponding thread parameters. By designing the Holweck thread of the first axial section and the Holweck thread of the second axial section to differ by at least one thread parameter, it is possible to provide different pumping characteristics in the first and second axial sections, even though the first and second axial sections interact with the same Holweck sleeve. This increases the variability of the vacuum pump according to the invention and thus expands its range of applications.

[0026] It should be noted that the pumping direction of the respective axial area is also determined by thread parameters, in particular by the sign of the thread pitch. Therefore, Holweck threads are conceivable in the two axial areas that differ only in the thread parameter "sign of the thread pitch" and otherwise have identical thread parameters.

[0027] Furthermore, the vacuum pump according to the first aspect of the invention can be characterized in that the first Holweck thread and the second Holweck thread each have at least one, in particular several, thread grooves which are bounded by webs formed on the respective axial region and by a groove base formed by the respective axial region, and wherein the first thread parameters and the second thread parameters comprise at least one further of the following parameters: Absolute value of the thread pitch, number of webs, width of the thread grooves, width of the webs, height of the webs above the groove base, and taper angle.

[0028] This list is not exhaustive, so that further parameters, insofar as technically sensible and possible, can also be used to characterize the corresponding Holweck thread.

[0029] As previously mentioned, it should be noted that the Holweck threads of the two axial sections automatically differ in the parameter "sign of the thread pitch," as this results in the different axial pumping directions in the first and second axial sections. In other words, in this embodiment, the Holweck threads in the two axial sections differ not only in the thread parameter "sign of the thread pitch" but also in another of the listed thread parameters.

[0030] According to a second aspect of the invention, the problem is solved by a vacuum pump, preferably a vacuum pump according to the first aspect of the invention, in particular a split-flow pump, with an inlet, an outlet, two or more pump stages connected in series in the pumping direction between the inlet and the outlet, wherein the at least two or more pump stages comprise at least one turbomolecular pump stage and at least one Holweck pump stage, wherein the turbomolecular pump stage is arranged upstream of the Holweck pump stage in the pumping direction and the at least one Holweck pump stage comprises a Holweck stator and a Holweck rotor rotating about a rotational axis during operation, wherein at least one intermediate inlet for gas to be pumped is provided, which is arranged between two of the pump stages or in a pump-active region of one of the pump stages.

[0031] The vacuum pump according to the second aspect of the invention is characterized in that the Holweck rotor has a substantially radially extending Holweck hub on which at least one Holweck sleeve is arranged, wherein the Holweck hub has one or more axially through pump openings to create an axially effective fluid connection between an upstream and a downstream section of the vacuum pump.

[0032] The vacuum pump according to the second aspect of the invention is preferably configured as a vacuum pump according to the first aspect of the invention. In this configuration of the vacuum pump according to the second aspect of the invention, it has the same features and advantages as those described above with reference to the vacuum pump according to the first aspect of the invention.

[0033] Furthermore, the vacuum pump according to the second aspect of the invention is also designed, in particular, as a split-flow pump with at least one turbomolecular pumping stage and a Holweck pumping stage downstream of the vacuum pump along the pumping direction. Preferably, several turbomolecular pumping stages and / or Holweck pumping stages may also be provided. In the following, the term "Holweck pumping stage" is used again in such a way that, unless explicitly stated otherwise, it refers to the Holweck pumping stage through which the gas to be pumped flows first in the pumping direction after the last turbomolecular pumping stage in the pumping direction.

[0034] The Holweck pump stage of the vacuum pump according to the second aspect of the invention also comprises the usual components, in particular a Holweck stator and a Holweck rotor. To avoid repetition, reference is made to the corresponding descriptions above regarding the design of the Holweck pump stage of the vacuum pump according to the first aspect of the invention.

[0035] Furthermore, as a split-flow pump, the vacuum pump according to the second aspect of the invention also has at least one intermediate inlet for the gas to be pumped. In contrast to the design of the vacuum pump according to the first aspect of the invention, this intermediate inlet in the vacuum pump according to the second aspect of the invention can be arranged not only in a pump-active area of ​​one of the pump stages, but alternatively also between two of the pump stages.

[0036] In the vacuum pump according to the second aspect of the invention, it is provided that one or more axially through-hole pump openings are provided in a Holweck hub of the Holweck rotor. The singular form ("pump opening") is used below, but the descriptions apply analogously to multiple pump openings.

[0037] The pump opening provides, in particular, an axially effective fluid connection between an upstream and a downstream section of the vacuum pump. In other words, the pump opening ensures a continuous fluid connection along the pumping direction between the inlet and outlet of the vacuum pump. Specifically, the pump opening allows gas to be pumped from the turbomolecular stage, which is located last upstream of the Holweck pumping stage in the pumping direction, to and ultimately through the Holweck pumping stage.

[0038] The pump opening provided in the Holweck hub according to the invention makes it possible to introduce the gas to be pumped, coming from the turbomolecular pump stage upstream in the pumping direction, into the Holweck arrangement or the Holweck pumping system not via the first, radially outermost Holweck pump stage, but only downstream of this first Holweck pump stage in the pumping direction. In this way, it is possible to use the entire first Holweck pump stage for pumping the gas to be pumped, which is supplied through the intermediate inlet.

[0039] Following the concept of a split-flow pump, the intermediate inlet supplies additional gas to be pumped to the Holweck pump stage. If the intermediate inlet is arranged between two pump stages, and thus, according to the invention, upstream of the Holweck pump stage, this Holweck pump stage can be used to pump the gas supplied by the intermediate inlet along its entire axial length. If the intermediate inlet is arranged within the pumping section of the Holweck pump stage, the design of the Holweck pump stage according to the first aspect of the invention can also be used to achieve effective pumping of the gas supplied by the intermediate inlet along substantially the entire length of the Holweck pump stage.

[0040] Overall, the inventive design of the vacuum pump according to the second aspect of the invention also makes it possible to increase the pumping performance of the Holweck pump stage, particularly with regard to the gas to be pumped which flows in through the intermediate inlet, compared to known designs of vacuum pumps of the prior art.

[0041] Furthermore, in the vacuum pump according to the second aspect of the invention, the pump opening in the Holweck hub can be arranged radially within the Holweck sleeve, in particular between two Holweck sleeves. The Holweck sleeve, together with the Holweck stator, forms the pump-active area of ​​the Holweck pump stage. By arranging the pump opening radially within this Holweck sleeve, it can be ensured that the Holweck pump stage can be used completely and, in particular, exclusively for pumping gas supplied through the intermediate inlet, and, in particular, that no gas flowing through the pump opening has to be pumped through the Holweck pump stage.

[0042] Furthermore, at least two Holweck pump stages can be provided, arranged sequentially along the pumping direction and radially one inside the other with respect to the axis of rotation. In other words, in the vacuum pump according to the second aspect of the invention, the Holweck pump stage can also be part of a Holweck pump system, in particular a "folded" Holweck arrangement. In this case, an arrangement of the pump opening between two Holweck sleeves has proven particularly advantageous, since this ensures that the gas to be pumped is fed into the Holweck pump system precisely between two of the successive Holweck pump stages. This avoids or at least significantly reduces any impairment of the pumping process in the respective Holweck pump stages by the supplied gas.

[0043] The embodiments described below can be provided in both a vacuum pump according to the first aspect of the invention and in a vacuum pump according to the second aspect of the invention. Therefore, no further distinction is made below between the vacuum pumps according to the first aspect of the invention and the vacuum pumps according to the second aspect of the invention, since all the features and advantages described below can be provided by both variants of vacuum pumps.

[0044] In a vacuum pump according to the invention, a Holweck auxiliary pump stage with a Holweck auxiliary sleeve and a Holweck auxiliary stator can further be provided upstream of the Holweck hub in the pumping direction of the turbomolecular pump stage, the pumping direction of which corresponds to that of the turbomolecular pump stage. As explained above, the pump opening in the Holweck hub allows the entire Holweck stage to be used for pumping gas supplied through the intermediate inlet. However, this usually results in at least some of this gas being conveyed in the Holweck pump stage in the direction of the pump opening, i.e., against the pumping direction of the turbomolecular pump stage. In other words, the possibility of this gas entering the turbomolecular pump stage through the pump opening against its pumping direction cannot be ruled out.This can impair the overall pumping performance of the vacuum pump according to the invention. However, this can be reliably avoided by using an additional Holweck pumping stage, which is positioned upstream of the Holweck hub and thus also upstream of the pumping opening, and whose pumping direction corresponds to that of the turbomolecular pumping stage.

[0045] Furthermore, the vacuum pump according to the invention can also be designed such that the Holweck auxiliary stator is formed integrally with the Holweck stator. In other words, the Holweck stator extends axially beyond the first axial section and forms the Holweck auxiliary stator axially adjacent to the first axial section. This reduces the number of different individual parts required for the mechanical construction of the vacuum pump according to the invention. As a result, the entire design, and in particular the manufacturing process, of the vacuum pump according to the invention can be simplified. Sealing the transition between the Holweck auxiliary pump stage and the first axial section can also be ensured particularly easily.

[0046] It should be noted that a multi-part design of the Holweck stators is also conceivable. In this case, a separate component can be provided for each of the first axial section, the second axial section, and / or the Holweck auxiliary pump stage.

[0047] Furthermore, the vacuum pump according to the invention can be characterized in that the Holweck auxiliary sleeve is arranged on the Holweck hub on an axially opposite side to the Holweck sleeve. In other words, the Holweck auxiliary sleeve and the Holweck sleeve extend from the Holweck hub in opposite axial directions. Here, the Holweck auxiliary sleeve, analogous to the Holweck sleeve, is preferably aligned concentrically to the axis of rotation of the Holweck rotor. In particular, this arrangement makes the Holweck auxiliary sleeve, which together with the Holweck auxiliary stator forms a pump-active area of ​​the Holweck auxiliary stage, an integral part of the Holweck rotor and also an element of the Holweck pump stage. This allows the rotation of the Holweck auxiliary sleeve, necessary for the pumping action of the Holweck auxiliary stage, to be generated and ensured particularly easily.A separate connection of the Holweck auxiliary sleeve to the common pump shaft, or even a completely separate drive for the Holweck auxiliary stage, is therefore unnecessary.

[0048] Furthermore, in the vacuum pump according to the invention, the Holweck auxiliary sleeve can also be arranged radially inside the pump opening on the Holweck hub, and the Holweck auxiliary stator is arranged radially outside the Holweck auxiliary sleeve. This radial arrangement of these elements of the Holweck auxiliary stage ensures that the pump-active area of ​​the Holweck auxiliary stage, formed in the axial overlap between the Holweck auxiliary stator and the Holweck auxiliary sleeve, is located upstream of the pump opening in the pumping direction. The Holweck auxiliary stage thus conveys the gas to be pumped towards the pump opening, and preventing gas from flowing out of the Holweck pump stage through the pump opening towards the final turbomolecular pump stage can be prevented even more effectively and reliably.

[0049] The vacuum pump according to the invention can also be designed such that the Holweck auxiliary stage, as a pump-active structure, has a Holweck auxiliary thread formed on a Holweck auxiliary stator with auxiliary thread parameters, wherein the Holweck auxiliary thread comprises at least one, in particular several, thread grooves which are bounded by webs formed on the Holweck auxiliary stator and by a groove base formed by the Holweck auxiliary stator, and wherein the auxiliary thread parameters comprise at least one of the following parameters Absolute value of the thread pitch, number of webs, width of the thread grooves, width of the webs, height of the webs above the groove base, and taper angle.

[0050] This list is not exhaustive, so that further parameters, insofar as technically sensible and possible, can also be used to characterize the Holweck additional thread.

[0051] It should be noted that the parameter "sign of a thread pitch" is automatically predefined for the Holweck auxiliary thread, as this parameter determines the pumping direction of the underlying pump stage. However, this direction is fixed for the Holweck auxiliary stage, such that it corresponds to the pumping direction of the turbomolecular pump stage.

[0052] Furthermore, the vacuum pump according to the invention can be characterized in that the first thread parameters and the additional thread parameters are designed to be coordinated such that a flow of gas to be pumped through the first axial section through the Holweck additional stage against the pumping direction is prevented. As already explained above, the pumping action of the Holweck additional stage, simply by virtue of its pumping direction, which corresponds to that of the turbomolecular pumping stage, already counteracts a flow of gas to be pumped through the first axial section through the Holweck additional stage in the direction of the turbomolecular stage. By explicitly coordinating the first thread parameters and the additional thread parameters, the pumping action of the Holweck additional stage can also be dimensioned such that this unwanted gas flow against the pumping direction is reliably prevented.

[0053] Preferably, this adjustment can be achieved solely by setting the additional thread parameters. This allows the aforementioned advantage of preventing unwanted backflow to be realized without requiring changes to the first thread parameter(s), as these could potentially lead to undesirable limitations in the pumping action of the first axial section of the Holweck pump stage.

[0054] According to one embodiment of the vacuum pump according to the invention, a second Holweck pump stage can also be provided, wherein the second Holweck pump stage is effectively connected, in the pumping direction, exclusively to the second axial section of the first Holweck pump stage. As described above, the second axial section of the first Holweck pump stage extends only over a portion of its axial length. The pumping effect of this second axial section is therefore reduced compared to a theoretical Holweck pump stage extending over the entire axial length. This can be at least partially compensated for by a second Holweck pump stage that is connected exclusively to the second axial section. Preferably, the second axial section and the second Holweck pump stage can be arranged concentrically to each other and nested within one another, so that they form, in particular, a "folded" Holweck arrangement.

[0055] Alternatively, or additionally, a vacuum pump according to the invention can also be characterized by the provision of a further Holweck pumping stage, wherein the further Holweck pumping stage is arranged in the pumping direction both downstream of the intermediate inlet and downstream of one or more pump openings. The second Holweck pumping stage described above pumps gas that is supplied to it exclusively from the second axial section, i.e., that originally flowed into the Holweck pumping stage through the intermediate inlet. In contrast, the further Holweck pumping stage is connected downstream not only of the intermediate inlet but also of the pump opening in the pumping direction, with fluid communication between the two. The pump opening enables the supply of gas to be pumped along the general pumping direction of the vacuum pump, while the intermediate inlet enables the supply of gas in accordance with the design of the vacuum pump as a split-flow pump.By providing the additional Holweck pump stage, it is thus possible for the entire Holweck arrangement, comprising at least the Holweck pump stage and the additional Holweck pump stage, preferably also comprising the second Holweck pump stage, to be designed for pumping and conveying all gas present in this part of the vacuum pump.

[0056] Furthermore, the vacuum pump according to the invention can be designed such that a Holweck inner stator is provided, arranged radially within the Holweck stator with respect to the axis of rotation, wherein the Holweck inner stator is arranged concentrically to the Holweck stator and has pump-active structures for the second Holweck pump stage and / or the further Holweck pump stage. As already described in the introduction, a pump-active area of ​​a Holweck pump stage is usually formed by a stator element and a driveable rotating rotor element, in particular a sleeve element, which are arranged concentrically within one another and overlap axially along an extension of the pump-effective area to be formed. The second Holweck pump stage and / or the further Holweck pump stage can thus be implemented particularly easily by means of the Holweck inner stator as a further stator element.It is particularly preferred that the Holweck inner stator has pump-active structures on a radially outer side to form the second Holweck pump stage, and pump-active structures on a radially inner side to form the further Holweck pump stage.

[0057] The vacuum pump according to the invention can also be characterized in that the Holweck inner stator extends axially from the second axial end to a free end, the free end being located in a range of 25% to 75% of the axial length, particularly at the axial height of the intermediate inlet. The Holweck inner stator preferably has pump-active structures for the second Holweck pump stage and the further Holweck pump stage. By extending the Holweck inner stator such that its free end terminates in a range of 25% to 75% of the axial length, i.e., essentially in the middle of the axial length, the axial extension of the Holweck inner stator can be sufficient to provide the required pumping action of the second Holweck stage.At the same time, however, it can also be made possible that sufficient space remains above the Holweck inner stator, i.e. axially between its free end and the first end of the Holweck pump stage, so that gas to be pumped from the first axial area of ​​the Holweck pump stage and from the pump opening can combine with gas to be pumped from the second axial area of ​​the Holweck pump stage, in order to then be pumped further in the subsequent Holweck pump stage.

[0058] The accompanying drawings show, by way of example, the construction of a vacuum pump known per se, in particular a turbomolecular pump, as well as embodiments according to the aspects explained above. They show: Fig. 1 a perspective view of a turbomolecular pump, Fig. 2 a view of the underside of the turbomolecular pump of Fig. 1 , Fig. 3 a cross-section of the turbomolecular pump along the in Fig. 2Section line AA shown, Fig. 4 a cross-sectional view of the turbomolecular pump along the in Fig. 2 Section line BB, Fig. 5 shows a cross-sectional view of the turbomolecular pump along the line shown in Fig. 2 The section line CC shown, Fig. 6 a split flow pump with a Holweck arrangement according to the prior art, Fig. 7 a first possible embodiment of a Holweck arrangement of a split flow pump according to the invention, and Fig. 8 a first possible embodiment of a Holweck arrangement of a split flow pump according to the invention.

[0059] The following will be explained in more detail below to aid understanding, using the Figs. 1 to 5 An exemplary embodiment of a known turbomolecular pump 111 is described in order to explain the basic operating principle of turbomolecular pump stages, Holweck pump stages and other components (e.g., the bearing of a pump rotor). These concepts can also be applied analogously to split-flow pumps.

[0060] The in Fig. 1 The turbomolecular pump 111 shown comprises a pump inlet 115 surrounded by an inlet flange 113, to which a receiver (not shown) can be connected in a manner known per se. The gas from the receiver can be drawn out of the receiver via the pump inlet 115 and conveyed through the pump to a pump outlet 117, to which a backing pump, such as a rotary vane pump, can be connected.

[0061] The inlet flange 113 forms a Fig. 1 The upper end of the housing 119 of the vacuum pump 111. The housing 119 comprises a lower part 121, to which an electronics housing 123 is attached laterally. The electronics housing 123 contains electrical and / or electronic components of the vacuum pump 111, e.g., for operating an electric motor 125 located in the vacuum pump (see also Fig. 3The electronics housing 123 has several connections 127 for accessories. In addition, a data interface 129, e.g. according to the RS485 standard, and a power supply connection 131 are located on the electronics housing 123.

[0062] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0063] The housing 119 of the turbomolecular pump 111 has a flood inlet 133, in particular in the form of a flood valve, through which the vacuum pump 111 can be flooded. In the area of ​​the lower part 121, a purge gas connection 135, also referred to as a purge gas connection, is also arranged, through which purge gas can be supplied to protect the electric motor 125 (see e.g. Fig. 3The gas pumped by the pump can be introduced into the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111. Two coolant connections 139 are also arranged in the lower part 121, one of which serves as an inlet and the other as an outlet for coolant that can be directed into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) are operated exclusively with air cooling.

[0064] The lower side 141 of the vacuum pump can serve as a base, allowing the vacuum pump 111 to be operated standing upright on its underside 141. Alternatively, the vacuum pump 111 can be attached to a receiver via the inlet flange 113 and thus operated in a suspended position. Furthermore, the vacuum pump 111 can be designed to operate even when oriented differently than described. Fig. 1 As shown. It is also possible to implement embodiments of the vacuum pump in which the underside 141 can be arranged facing sideways or upwards instead of downwards. In principle, any angle is possible.

[0065] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in a standing position.

[0066] On the underside 141, which is in Fig. 2As shown, various screws 143 are arranged, by means of which components of the vacuum pump, not further specified here, are fastened to one another. For example, a bearing cover 145 is attached to the underside 141.

[0067] Mounting holes 147 are also arranged on the underside 141, through which the pump 111 can be attached to a support surface, for example. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0068] In the Figures 2 to 5 A coolant line 148 is shown, in which the coolant introduced and removed via the coolant connections 139 can circulate.

[0069] Like the sectional views of the Figures 3 to 5 As shown, the vacuum pump comprises several process gas pumping stages for conveying the process gas present at the pump inlet 115 to the pump outlet 117.

[0070] A rotor 149 is arranged in the housing 119, which has a rotor shaft 153 rotatable about a rotation axis 151.

[0071] The turbomolecular pump 111 comprises several turbomolecular pump stages connected in series to provide pumping action. These stages have several radial rotor disks 155 attached to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and fixed in the housing 119. Each rotor disk 155 and an adjacent stator disk 157 form a turbomolecular pump stage. The stator disks 157 are held at a desired axial distance from each other by spacer rings 159.

[0072] The vacuum pump also includes Holweck pump stages arranged radially within one another and connected in series to effectively pump the pump. Other turbomolecular vacuum pumps exist (not shown) that do not have Holweck pump stages.

[0073] The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical Holweck rotor sleeves 163, 165 attached to and supported by the rotor hub 161, which are oriented coaxially to the axis of rotation 151 and nested one inside the other in the radial direction. Furthermore, two cylindrical Holweck stator sleeves 167, 169 are provided, which are also oriented coaxially to the axis of rotation 151 and nested one inside the other in the radial direction.

[0074] The pump-active surfaces of the Holweck pump stages are formed by the outer surfaces, i.e., the radial inner and / or outer surfaces, of the Holweck rotor sleeves 163, 165 and the Holweck stator sleeves 167, 169. The radial inner surface of the outer Holweck stator sleeve 167 faces the radial outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together they form the first Holweck pump stage following the turbomolecular pumps. The radial inner surface of the outer Holweck rotor sleeve 163 faces the radial outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together they form a second Holweck pump stage. The radial inner surface of the inner Holweck stator sleeve 169 lies opposite the radial outer surface of the inner Holweck rotor sleeve 165, forming a radial Holweck gap 175, and together they form the third Holweck pumping stage.

[0075] At the lower end of the Holweck rotor sleeve 163, a radially extending channel can be provided, through which the radially outer Holweck slot 171 is connected to the central Holweck slot 173. Furthermore, a radially extending channel can be provided at the upper end of the inner Holweck stator sleeve 169, through which the central Holweck slot 173 is connected to the radially inner Holweck slot 175. This connects the nested Holweck pump stages in series. A connecting channel 179 to the outlet 117 can also be provided at the lower end of the radially inner Holweck rotor sleeve 165.

[0076] The aforementioned pump-active surfaces of the Holweck stator sleeves 167, 169 each have several Holweck grooves spiraling around the axis of rotation 151 in the axial direction, while the opposite outer surfaces of the Holweck rotor sleeves 163, 165 are smooth and drive the gas forward in the Holweck grooves for the operation of the vacuum pump 111.

[0077] For the rotatable mounting of the rotor shaft 153, a rolling bearing 181 is provided in the area of ​​the pump outlet 117 and a permanent magnet bearing 183 is provided in the area of ​​the pump inlet 115.

[0078] In the area of ​​the rolling bearing 181, a conical injection nut 185 with an outer diameter increasing towards the rolling bearing 181 is provided on the rotor shaft 153. The injection nut 185 is in sliding contact with at least one wiper of a fluid reservoir. In other existing turbomolecular vacuum pumps (not shown), an injection screw may be provided instead of an injection nut. Since different designs are thus possible, the term "injection tip" is also used in this context.

[0079] The operating fluid reservoir comprises several stacked absorbent discs 187, which are impregnated with an operating fluid for the rolling bearing 181, e.g. with a lubricant.

[0080] During operation of the vacuum pump 111, the operating fluid is transferred by capillary action from the fluid reservoir via the wiper to the rotating injection nut 185 and, as a result of centrifugal force, is conveyed along the injection nut 185 in the direction of the increasing outer diameter of the injection nut 185 towards the rolling bearing 181, where it performs, for example, a lubricating function. The rolling bearing 181 and the fluid reservoir are enclosed in the vacuum pump by a trough-shaped insert 189 and the bearing cover 145.

[0081] The permanent magnet bearing 183 comprises a rotor-side bearing half 191 and a stator-side bearing half 193, each containing a ring stack of several axially stacked permanent magnet rings 195, 197. The ring magnets 195, 197 face each other, forming a radial bearing gap 199, with the rotor-side ring magnets 195 arranged radially outside and the stator-side ring magnets 197 radially inside. The magnetic field present in the bearing gap 199 induces magnetic repulsive forces between the ring magnets 195, 197, which cause the rotor shaft 153 to be radially supported. The rotor-side ring magnets 195 are supported by a support section 201 of the rotor shaft 153, which radially surrounds the ring magnets 195 on the outside.The stator-side ring magnets 197 are supported by a stator-side support section 203, which extends through the ring magnets 197 and is suspended from radial struts 205 of the housing 119. Parallel to the axis of rotation 151, the rotor-side ring magnets 195 are fixed by a cover element 207 coupled to the support section 201. The stator-side ring magnets 197 are fixed in one direction, parallel to the axis of rotation 151, by a retaining ring 209 connected to the support section 203 and a retaining ring 211 also connected to the support section 203. A disc spring 213 may also be provided between the retaining ring 211 and the ring magnets 197.

[0082] Within the magnetic bearing, an emergency or catch bearing 215 is provided, which runs freely without contact during normal operation of the vacuum pump 111 and only engages when there is excessive radial deflection of the rotor 149 relative to the stator, in order to form a radial stop for the rotor 149 and thus prevent a collision between the rotor-side and stator-side structures. The catch bearing 215 is designed as an unlubricated rolling bearing and forms a radial gap with the rotor 149 and / or the stator, which causes the catch bearing 215 to be disengaged during normal pump operation. The radial deflection at which the catch bearing 215 engages is dimensioned to be large enough so that the catch bearing 215 does not engage during normal operation of the vacuum pump, and simultaneously small enough to prevent a collision between the rotor-side and stator-side structures under all circumstances.

[0083] The vacuum pump 111 comprises the electric motor 125 for rotating the rotor 149. The armature of the electric motor 125 is formed by the rotor 149, whose rotor shaft 153 extends through the motor stator 217. A permanent magnet arrangement can be arranged radially on the outside or embedded in the section of the rotor shaft 153 extending through the motor stator 217. A space 219 is arranged between the motor stator 217 and the section of the rotor 149 extending through the motor stator 217. This space comprises a radial motor gap through which the motor stator 217 and the permanent magnet arrangement can magnetically influence each other to transmit the drive torque.

[0084] The motor stator 217 is fixed in the housing within the motor compartment 137 provided for the electric motor 125. A purge gas, also known as a sealing gas, which can be, for example, air or nitrogen, can enter the motor compartment 137 via the purge gas connection 135. This purge gas protects the electric motor 125 from process gas, e.g., from corrosive components of the process gas. The motor compartment 137 can also be evacuated via the pump outlet 117, meaning that the vacuum pressure in the motor compartment 137 is at least approximately equal to that produced by the backing pump connected to the pump outlet 117.

[0085] Between the rotor hub 161 and a wall 221 bounding the engine compartment 137, a so-called labyrinth seal 223, which is known per se, can also be provided, in particular to achieve a better seal of the engine compartment 217 against the radially outside Holweck pump stages.

[0086] Fig. 6 Figure 92 shows a vacuum pump 90 designed as a split-flow pump 92 with a Holweck arrangement according to the prior art. Figure 90 "A" schematically shows the entire vacuum pump 90, while Figure 90 "B" shows an enlarged view of the area of ​​the vacuum pump 90 marked with a dashed line in Figure 92, in particular the Holweck arrangement. Both Figures "A" and "B" are described below. Fig. 6 jointly described.

[0087] At the in Fig. 6The prior art vacuum pump 90 shown is a multi-stage split-flow pump 92. The vacuum pump 90 has three turbomolecular pumping stages 12 (see Figure "A") and three Holweck pumping stages 14 (see Figure "B"), the latter being collectively referred to as a Holweck arrangement. During operation of the vacuum pump 90, the elements of the turbomolecular pumping stages 12 and those of the Holweck pumping stages 14 rotate about the same axis of rotation 102. This allows, as shown, a common pump shaft 104 to be used for all turbomolecular pumping stages 12 and Holweck pumping stages 14 in such vacuum pumps 90. Along a pumping direction 98 of the gas 100 to be pumped, the vacuum pump 90 extends from an inlet 94 to an outlet 96.

[0088] Figure "B" shows an enlarged view of the Holweck arrangement. In particular, it is clearly visible that the pump shaft 104 carries a Holweck rotor 30. In the illustrated embodiment, the Holweck rotor 30 has a Holweck hub 32 and two Holweck sleeves 34 arranged thereon and extending coaxially and parallel to the axis of rotation 102. Also coaxial are two Holweck stators 20, which have pump-active structures 60, in particular Holweck threads 62, on the side surfaces facing the Holweck sleeves 34.

[0089] In addition to the inlet 94, the vacuum pump 90 shown, as a split-flow pump 92, has three intermediate inlets 40. Two of these intermediate inlets 40 are arranged between the pump-active areas of two turbomolecular pump stages 12. The third intermediate inlet 40, however, as can be clearly seen in Figure "B", is arranged in the pump-active area of ​​one of the Holweck pump stages 14 and thus divides it axially into two sections.

[0090] Gas 100 is pumped or conveyed into the upper section of the radially outermost Holweck pumping stage 14, which is located with respect to the axis of rotation 102, coming from the turbomolecular pumping stage 12 (see Figure "A", not shown in Figure "B") located upstream in the pumping direction 98. Additional gas 100 to be pumped can now flow in through the intermediate inlet 40 and is then pumped further together with the gas 100 pre-pumped by the turbomolecular pumping stages 12. In the two subsequent Holweck pumping stages 12, all the gas present in the Holweck arrangement is then pumped further.

[0091] Due to this design, in split-flow pumps 92 known according to the prior art, only a portion of the entire Holweck pump stage 14 is used for the gas 100 to be pumped, which is supplied through the intermediate inlet 40. The pumping capacity for gas 100 flowing in through the intermediate inlet 40 is therefore reduced.

[0092] In Fig. 7 Figure 1 shows a first possible embodiment of a Holweck arrangement of a split-flow pump 92 according to the invention. The special features of this Holweck arrangement according to the invention are described below, with particular emphasis on the differences from known Holweck arrangements, such as those shown by way of example in Figure "B" of the [reference to Figure 1]. Fig. 6 It has been shown that it will be addressed.

[0093] In the embodiment according to the invention, a Holweck stage 14, radially outermost with respect to the axis of rotation 102, also has an intermediate inlet 40 in its Holweck stator 20. Along the axial length 50 of the Holweck stage 14, the Holweck stator 20 is thereby divided into a first axial region 22 and a second axial region 24. The first axial region 22 extends from the intermediate inlet 40 towards the first axial end 52, and the second axial region 24 extends oppositely from the intermediate inlet 40 towards the second axial end 54.

[0094] According to the invention, it can be provided in particular that the pump-active structures 60 of both axial regions 22, 24 are arranged and designed such that the gas 100 to be pumped, flowing in through the intermediate inlet 40, is pumped away from the intermediate inlet 40, namely from the first axial region 22 towards the first axial end 52, and correspondingly from the second axial region 24 towards the second axial end 54. The pumping capacity of the entire first, radially outermost Holweck stage 14 with respect to the gas 100 to be pumped, flowing in through the intermediate inlet 40, can thereby be significantly increased.

[0095] Preferably, the pump-active structures 60 of the two axial regions 22, 24 can be formed by corresponding Holweck threads 62. To coordinate the pumping capacities of the two axial regions 22, 24, the values ​​of the first thread parameters 64 of the Holweck thread 62 of the first axial region 22 and the values ​​of the corresponding second thread parameters 66 of the Holweck thread 62 of the second axial region 24 can be set differently. Such thread parameters 64, 66 include, in particular, properties of the thread grooves of the Holweck threads 62, such as the width and / or height of webs or the thread grooves, or a taper angle.

[0096] The preceding Holweck stage 14 is determined by the interaction of the Holweck stator 20, in particular its first and second axial sections 22, 24, and a Holweck sleeve 34 rotating during operation of the vacuum pump 90. The Holweck sleeve 34 is arranged on a Holweck hub 32, with which it forms a Holweck rotor 30. The Holweck rotor 30, in turn, is connected to the central pump shaft 104 and can rotate about the axis of rotation 102.

[0097] An alternative or additional feature of the Holweck arrangement of the vacuum pump 90 according to the invention is that at least one axially through-hole pumping opening 36 is provided in the Holweck hub 32. This makes it possible, in particular, for the gas 100 to be pumped, coming from a turbomolecular pumping stage 12 upstream of the Holweck arrangement in the pumping direction 98 (see Figure 100), to be pumped through the Holweck hub. Fig. 6) can be introduced into the Holweck arrangement without having to be pumped through the first, in particular radially outermost, Holweck pump stage 14.

[0098] This can enable, as in Fig. 7 The first Holweck pumping stage 14 is shown with divided axial sections 22, 24 with different pumping directions 98 for gas 100 from the intermediate inlet 40. Alternatively, but not shown, it is also possible to use the entire first Holweck pumping stage 14 to pump the gas 100 from the intermediate inlet 40, but now completely in one pumping direction 98 along the entire axial length 50. This is particularly advantageous for split-flow pumps 92, in which the intermediate inlet 40 is arranged between the last turbomolecular pumping stage 12 and the first Holweck pumping stage 14.

[0099] The at least one pump opening 36 is arranged radially inside the Holweck sleeve 34. Together with the arrangement of the Holweck stator 20 with its two axial sections 22, 24 radially outside this Holweck sleeve 34, this makes it particularly easy to ensure that the entire first Holweck pumping stage 14 is positioned radially outside the pump opening 34. This allows all gas 100 pumped through this first Holweck pumping stage 14 towards the Holweck hub 32 to be pumped further, together with the gas 100 supplied by the turbomolecular pumping stages 12.

[0100] A possible optional further development of the vacuum pump 90 according to the invention is in Fig. 7 Also shown is a Holweck additional pump stage 70, which is in pumping direction 98 of the turbomolecular pump stage 12 (see Fig. 6) is provided in front of the Holweck hub 32, and its pumping direction 98 corresponds to that of the turbomolecular pumping stage 12, i.e., in other words, points in the direction of the Holweck hub 32.

[0101] The Holweck auxiliary pump stage 70 comprises a Holweck auxiliary sleeve 72 and a Holweck auxiliary stator 74. The Holweck auxiliary stator 74 carries pump-active structures 60, in particular a Holweck auxiliary thread 76, which is characterized by auxiliary thread parameters 78. Analogous to the first and second thread parameters 64, 66, the auxiliary thread parameters 78 can also include, for example, properties of thread grooves of the Holweck auxiliary thread 76, such as the width and / or height of webs or the thread grooves, or a taper angle. The taper angle can refer to the groove base, the inner diameter of the web tips, or both.Preferably, the additional thread parameters 78 are set, in particular adapted to the first thread parameters 64, such that a flow of gas 100, which is pumped through the first axial area 22 in the direction of the turbomolecular pumping stages 12, is reliably prevented by the Holweck additional pumping stage 70 against its pumping direction 98.

[0102] The Holweck auxiliary stator 74 can, as shown, be configured separately from the Holweck stator 20 of the Holweck pumping stage 14. Preferably – though not shown – the Holweck auxiliary stator 74 can also be implemented as a single piece with the Holweck stator 20 of the Holweck pumping stage 14. Additionally or alternatively, it is also conceivable to provide the axial sections 22, 24 on separate components. An exemplary embodiment can comprise a "stacked" arrangement of separate components with the components 22, 24, 74.

[0103] The Holweck auxiliary sleeve 72 can also be arranged on the Holweck hub 32. This arrangement is preferably on an axially different side of the Holweck hub 32 than is the case with the Holweck sleeve 32 of the Holweck pumping stage 14. By the illustrated, further preferred arrangement of the Holweck auxiliary sleeve 72 radially inside the pumping opening 36, with the simultaneous arrangement of the Holweck auxiliary stator 74 radially outside the Holweck auxiliary sleeve 72, a particularly good, and in particular complete, supply of gas 100 to be pumped from the turbomolecular pumping stages 12 upstream in the pumping direction 98 through the pumping opening 36 into the Holweck arrangement can be ensured.

[0104] Fig. 8 shows a possible further development of the design form of the in Fig. 7The Holweck arrangement of a split-flow pump according to the invention 92 is illustrated. The additional features of this embodiment are described in particular below; for all features and elements not explicitly mentioned, reference is made to the above description of the Holweck arrangement in Fig. 7 referred.

[0105] The in Fig. 8 The illustrated Holweck arrangement features, in particular, a Holweck inner stator 26, which is arranged radially inside and concentrically with the radially outermost Holweck stator 20. The illustrated Holweck inner stator 26 carries pump-active structures 60 on both radial side faces, in particular Holweck threads 62, which together with Holweck sleeves 34 form Holweck pump stages 14. In alternative embodiments not shown, only one of the two radial side faces of the Holweck inner stator 26 may carry such pump-active structures 60.

[0106] The pump-active structures 60 on the radially outer side surface of the Holweck inner stator 26 form a second Holweck pump stage 14, 16, which, in the pumping direction 98, is exclusively connected to the second axial region 24 of the first Holweck pump stage 14. As shown, the pump-active structures 60 of both the second axial region 24 and the second Holweck pump stage 14, 16 interact with the same Holweck sleeve 34. This second Holweck pump stage 14, 16 supports the pumping action of the second axial region 24, which may be reduced due to its shortened axial extent caused by the presence of the intermediate inlet 40.

[0107] The pump-active structures 60 on the radially inner side surface of the Holweck inner stator 26 form a further Holweck pump stage 14, 18, which is arranged in the pumping direction 98 both after the intermediate inlet 40 and after one or more pump openings 36. As shown, an additional Holweck sleeve 34 is provided on the Holweck hub 32 for these pump-active structures 60. This further Holweck pump stage 14, 18 ensures that all gas 100 to be pumped by the Holweck arrangement is pumped and ultimately conveyed to the outlet 96 of the vacuum pump 90.

[0108] As shown, it is particularly preferred that, in the presence of several Holweck sleeves 34, the pump opening 36 is provided between two of these Holweck sleeves 34 in the Holweck hub 32, preferably between the two radially outermost Holweck sleeves 34.

[0109] Furthermore, as shown, the Holweck inner stator 26 can extend from the second axial end 54 towards the Holweck hub 32 to its free end 28, which is positioned in a range of 25% to 75% of the axial length 50. The free end 28 can be located in the region of the axial height of the intermediate inlet 40; however, this depends on the actual operating point of the vacuum pump 90 according to the invention. It has been found that such a shortened axial length of the Holweck inner stator 26 is advantageous for sufficient mixing of the various gas 100 flows coming from the intermediate inlet 40 and from one or more pump openings 36. At the same time, the axial length of the Holweck inner stator 26 is still sufficient to adequately provide the above-described support for the pumping action of the second axial area 24 as part of the second Holweck pumping stage 14, 16.However, other length ratios are certainly conceivable, depending on the application and design of the pump. Reference symbol list

[0110] 10 Pump stage 12 Turbomolecular pump stage 14 Holweck pump stage 16 Second Holweck pump stage 18 Further Holweck pump stage 20 Holweck stator 22 First axial section 24 Second axial section 26 Holweck inner stator 28 Free end 30 Holweck rotor 32 Holweck hub 34 Holweck sleeve 36 Pump opening 40 Intermediate inlet 50 Axial length 52 First axial end 54 Second axial end 60 Pump-active structure 62 Holweck thread 64 First thread parameter 66 Second thread parameter 70 Holweck auxiliary pump stage 72 Holweck auxiliary sleeve 74 Holweck auxiliary stator 76 Holweck auxiliary thread 78 Auxiliary thread parameter 90 Vacuum pump 92 Split flow pump 94 Inlet 96 Outlet 98 Pumping direction 100 Gas 102 Rotation axis 104 Pump shaft 111 Turbomolecular pump 113 Inlet flange 115 Pump inlet 117 Pump outlet 119 Housing 121 Bottom section 123 Electronics housing 125 Electric motor 127 Accessory connection 129 Data interface 131 Power supply connection 133 Flood inlet 135 Sealing gas connection 137 Motor compartment 139 Coolant connection 141 Bottom 143 Screw 145 Bearing cover147 Mounting hole 148 Coolant line 149 Rotor 151 Rotation shaft 153 Rotor shaft 155 Rotor disc 157 Stator disc 159 Spacer ring 161 Rotor hub 163 Holweck rotor sleeve 165 Holweck rotor sleeve 167 Holweck stator sleeve 169 Holweck stator sleeve 171 Holweck gap 173 Holweck gap 175 Holweck gap 179 Connecting channel 181 Rolling bearing 183 Permanent magnet bearing 185 Injection nut 187 Washer 189 Insert 191 Rotor-side bearing half 193 Stator-side bearing half 195 Ring magnet 197 Ring magnet 199 Bearing gap 201 Support section 203 Support section 205 Radial strut 207 Cover element 209 Support ring 211 Mounting ring 213 Disc spring 215 Emergency or catch bearing 217 Motor stator 219 Gap 221 Wall 223 Labyrinth seal

Claims

1. Vacuum pump (90), in particular split-flow pump (92), with - an inlet (94), - an outlet (96), - two or more pump stages (10) connected in series between the inlet (94) and the outlet (96) in the pumping direction (98), wherein the at least two or more pump stages (10) comprise at least one turbomolecular pump stage (10, 12) and at least one Holweck pump stage (14), wherein the turbomolecular pump stage (10, 12) is arranged upstream of the Holweck pump stage (14) in the pumping direction (98), and the at least one Holweck pump stage (14) comprises a Holweck stator (20) and a Holweck rotor (30) rotating about a rotational axis (102) during operation, wherein at least one intermediate inlet (40) for gas (100) to be pumped is provided, which is arranged in a pump-active region of the Holweck pump stage (14). is, characterized by the fact thatThe Holweck pump stage (14) has an axial length (50) with respect to the axis of rotation (102) with a first axial end (52) facing one of the at least one turbomolecular pump stage (10, 12) and a second axial end (54) opposite the first axial end (52), wherein the intermediate inlet (40) is arranged axially between the first axial end (52) and the second axial end (54) of the Holweck pump stage (14), and wherein the Holweck stator (20) of the Holweck pump stage (14) has a first axial region (22) axially adjoining the intermediate inlet (40) and a second axial region (24) adjoining the intermediate inlet (40) axially opposite to the first axial region (22), wherein the first axial region (22) has pump-active structures (60) configured for pumping in the direction of the first axial end (52) and are formed and the second axial area (24) has pump-active structures (60),which are designed and configured for pumping in the direction of the second axial end (54).

2. Vacuum pump (90) according to claim 1 wherein at least two Holweck pump stages (14) are provided which are arranged one after the other along the pumping direction (98) and radially in one another with respect to the axis of rotation (102), and wherein the intermediate inlet (40) is arranged in the pump-active area of ​​the Holweck pump stage (14) that is radially outermost with respect to the axis of rotation (102).

3. Vacuum pump (90) according to claim 1 or 2, wherein the Holweck stator (20) has as pump-active structures (60) in the first axial region (22) a first Holweck thread (62) with at least one first thread parameter (64) and in the second axial region (24) a second Holweck thread (62) with at least one second thread parameter (66), wherein the first thread parameter (64) and the second thread parameter (66) differ.

4. Vacuum pump (90) according to claim 3, wherein the first Holweck thread (62) and the second Holweck thread (62) each have at least one, in particular several, thread grooves which are bounded by webs formed on the respective axial region and by a groove base formed by the respective axial region, and wherein the first thread parameters (64) and the second thread parameters (66) comprise at least one of the following parameters: - absolute value of the thread pitch, - number of webs, - width of the thread grooves, - width of the webs, - height of the webs above the groove base, and - taper angle.

5. Vacuum pump (90), preferably a vacuum pump (90) according to any one of the preceding claims 1 to 4, in particular a split-flow pump (92), comprising: - an inlet (94), - an outlet (96), - two or more pump stages (10) connected in series in the pumping direction (98) between the inlet (94) and the outlet (96), wherein the at least two or more pump stages (10) comprise at least one turbomolecular pump stage (10, 12) and at least one Holweck pump stage (14), wherein the turbomolecular pump stage (10, 12) is arranged upstream of the Holweck pump stage (14) in the pumping direction (98), and the at least one Holweck pump stage (14) comprises a Holweck stator (20) and a Holweck rotor (30) rotating about a rotational axis (102) during operation, wherein at least one intermediate inlet (40) is provided for gas (100) to be pumped. which is located between two of the pump stages (10) or in a pump-active area of ​​one of the pump stages (10), characterized by the fact thatthe Holweck rotor (30) has a substantially radially extending Holweck hub (32) on which at least one Holweck sleeve (34) is arranged, wherein the Holweck hub (32) has one or more axially through pump openings (36) to create an axially effective fluid connection between an upstream and a downstream section of the vacuum pump (90).

6. Vacuum pump (90) according to claim 5, wherein the pump opening (36) is arranged in the Holweck hub (32) in the radial direction within the Holweck sleeve (34), in particular wherein the pump opening (36) is arranged in the radial direction between two Holweck sleeves (34).

7. Vacuum pump (90) according to one of claims 1 to 6, wherein in the pumping direction (98) of the turbomolecular pumping stage (10, 12) upstream of the Holweck hub (32) a Holweck auxiliary pumping stage (70) with a Holweck auxiliary sleeve (72) and a Holweck auxiliary stator (74) is provided, the pumping direction (98) of which corresponds to that of the turbomolecular pumping stage (10, 12).

8. Vacuum pump (90) according to claim 7, wherein the Holweck auxiliary stator (74) is formed integrally with the Holweck stator (20).

9. Vacuum pump (90) according to claim 7 or 8, wherein the Holweck auxiliary sleeve (72) is arranged on the Holweck hub (32) on an axially opposite side to the Holweck sleeve (34).

10. Vacuum pump (90) according to claims 7 to 9, wherein the Holweck auxiliary sleeve (72) is arranged inside the pump opening (36) on the Holweck hub (32) when viewed in a radial direction, and wherein the Holweck auxiliary stator (74) is arranged outside the Holweck auxiliary sleeve (72) when viewed in a radial direction.

11. Vacuum pump (90) according to one of claims 7 to 10, wherein the Holweck auxiliary pump stage (70) as a pump-active structure (60) comprises a Holweck auxiliary thread (76) formed on the Holweck auxiliary stator (74) with auxiliary thread parameters (78), wherein the Holweck auxiliary thread (76) comprises at least one, in particular several, thread grooves which are bounded by webs formed on the Holweck auxiliary stator (74) and by a groove base formed by the Holweck auxiliary stator (74), and wherein the auxiliary thread parameters (78) comprise at least one of the following parameters: - absolute value of the thread pitch, - number of webs, - width of the thread grooves, - width of the webs, - height of the webs above the groove base, and - taper angle.

12. Vacuum pump (90) according to claim 11, wherein the first thread parameters (64) and the additional thread parameters (78) are designed to be coordinated such that a flow of gas (100) conveyed through the first axial area (22) to be pumped through the Holweck additional pump stage (70) is prevented in the opposite direction of pumping (98).

13. Vacuum pump (90) according to one of claims 1 to 12, wherein a second Holweck pump stage (14, 16) is provided, wherein the second Holweck pump stage (14, 16) is connected in the pumping direction (98) exclusively to the second axial region (24) of the first Holweck pump stage (14) in a pumping effect.

14. Vacuum pump (90) according to one of the preceding claims 5 to 13, wherein a further Holweck pump stage (14, 18) is provided, wherein the further Holweck pump stage (14, 18) is arranged in the pumping direction (98) in a pumping-effective manner both after the intermediate inlet (40) and after one or more pump openings (36).

15. Vacuum pump (90) according to one of the preceding claims 13 or 14, wherein a Holweck inner stator (26) is provided arranged radially within the Holweck stator (20) with respect to the axis of rotation (102), wherein the Holweck inner stator (26) is arranged concentrically to the Holweck stator (20) and has pump-active structures (60) for the second Holweck pump stage (14, 16) and / or the further Holweck pump stage (14, 18).

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