Pumping system with electrically driven cooling device

Abstract

The present invention relates to a pumping system with a turbomolecular vacuum pump comprising a housing with at least one pump inlet and one pump outlet, a first pumping mechanism driven by a rotor shaft and having at least one turbomolecular pumping stage in the housing, and a second pumping mechanism driven by the rotor shaft in the housing, downstream of the first pumping mechanism and operating according to a different pumping principle than the first pumping mechanism. The first and second pumping mechanisms are arranged along the rotor shaft for jointly conveying a process gas from the pump inlet to the pump outlet and are located axially between the at least one pump inlet and the pump outlet.For cooling the housing, the pump system further comprises at least one electrically operated cooling device which is located in the axial direction with respect to the second pump mechanism on the side of the second pump mechanism facing the first pump mechanism.

Description

[0001] The present invention relates to a pumping system with an electrically operated cooling device for cooling a turbomolecular vacuum pump of the pumping system.

[0002] Turbomolecular vacuum pumps are typically used to generate a vacuum or negative pressure in physical measuring devices such as mass spectrometers. Especially when evacuating mass spectrometers, the goal is often to achieve a final pressure in the ultra-high vacuum range, i.e., between 10 -8 and 10 -11 mbar. To generate such low pressures, special turbomolecular vacuum pumps are often used. These pumps are characterized, among other things, by the fact that they have several turbomolecular pump stages connected in series, each with its own pump inlet.

[0003] Such turbomolecular vacuum pumps with multiple pump inlets are generally known and are also referred to as split-flow vacuum pumps. The terms "SplitFlow" and "SPLIT-FLOW" are registered trademarks of Pfeiffer Vacuum GmbH. Other names for such vacuum pumps include multi-inlet vacuum pumps or multi-inlet vacuum pumps.

[0004] However, in the ultra-high vacuum range, and especially at pressures below 10 -9< mbar, it has been observed that undesirable physical phenomena occur that negatively impact the achievable ultimate pressure. Desorption and / or permeation phenomena can occur, particularly at pressures below 10 -9< mbar, and in particular at pressures below 10 -10< mbar. The lower the pressure, the larger the proportion of these released gases in the ultra-high vacuum range that increases. As a result, the physical phenomena described above ultimately place a lower limit on the ultimate pressure that can be achieved. This, in turn, limits the accuracy of physical measuring devices such as mass spectrometers.

[0005] Accordingly, the object of the present invention is to provide a pumping system with which a lower pressure can be achieved compared to a pumping system with the same pumping configuration or compared to a pumping system having the same pumping mechanism as the pumping system according to the invention.

[0006] To solve this problem, a pumping system with an essentially conventional turbomolecular vacuum pump is presented, wherein the pumping system is characterized by the features of claim 1.

[0007] A substantially conventional turbomolecular vacuum pump is characterized, among other things, by the fact that it comprises a housing with at least one pump inlet and one pump outlet, in which two pump mechanisms driven by a rotor shaft are located. The first of the two pump mechanisms is a turbomolecular pump stage, which preferably comprises a plurality of rotor disks driven by the rotor shaft, whereas the second or the other pump mechanism of the two pump mechanisms is, for example, a Holweck pump stage, which is located downstream of the first pump mechanism or downstream of the turbomolecular pump stage. In principle, the second or other pump mechanism operates according to a different pumping principle than the first pump mechanism. In this respect, the second pump mechanism can also comprise, for example, a Siegbahn pump stage and / or a pump stage operating according to the side channel principle.The two pump mechanisms are arranged in a conventional manner for jointly conveying a process gas from the pump inlet to the pump outlet along the rotor shaft and are located in the axial direction between the at least one pump inlet and the pump outlet.

[0008] According to the invention, the pump system proposed here is characterized in particular by the fact that it has at least one electrically operated cooling device for cooling the housing, which is located in the axial direction relative to the second pump mechanism on the side of the second pump mechanism facing the first pump mechanism. Thus, it was recognized according to the invention that the mechanisms underlying the previously described desorption and / or permeation phenomena are, among other things, temperature-dependent. In particular, it was observed that the proportion of gases that dissolve from a solid surface increases with increasing temperature.

[0009] In order to prevent the operational heating of the turbomolecular vacuum pump and thus the described gas desorption and / or permeation phenomena, the invention therefore proposes for the first time to actively cool a turbomolecular vacuum pump in the region of the first pumping mechanism between the pump inlet and the pump outlet.

[0010] Although it is not uncommon to cool the electric motor of a turbomolecular vacuum pump using a fan, the drive motor of conventional

[0011] However, turbomolecular vacuum pumps are located on the side of the Holweck pump stage facing away from the turbomolecular pump stage, which consequently also applies to the fan for cooling the drive motor. The turbomolecular pump stage is thus, in a sense, separated from the drive motor and thus from the fan by the Holweck pump stage, so that cooling the drive motor has no or only a negligible effect on the turbomolecular pump stage. Therefore, cooling the drive motor cannot ensure adequate cooling of the high-vacuum-side turbomolecular pump stages.

[0012] According to the invention, it is therefore proposed for the first time to cool the turbomolecular pumping stage directly by means of an electrically operated cooling device in order to counteract the previously described desorption and / or permeation problems already in the high vacuum range of the turbomolecular vacuum pump.

[0013] Preferred embodiments of the invention will now be discussed below. Further embodiments may also emerge from the dependent claims, the description of the figures, and the drawings themselves.

[0014] Thus, according to one embodiment, it can be provided that the first pumping mechanism, as in a split-flow pump, has a first turbomolecular pumping stage and, downstream thereof, at least one second turbomolecular pumping stage. In this case, it can be provided that the at least one electrically operated cooling device is located in the axial direction with respect to the at least second turbomolecular pumping stage on the side of the at least second turbomolecular pumping stage facing the first turbomolecular pumping stage. The at least one electrically operated cooling device is therefore located in the axial direction closer to the first turbomolecular pumping stage than the Holweck pumping stage and thus closer to the pump inlet than the Holweck pumping stage. This is because the achievable final pressure decreases increasingly in the direction of the pump inlet, which is why it is necessary to reduce gas desorption or-permeation, it is advantageous to arrange the at least one electrically operated cooling device as close as possible to the (only) pump inlet, since the achievable final pressure is lowest there and thus the gas desorption or permeation tendency has the greatest influence on the resulting pressure.

[0015] Accordingly, in a split-flow pump with a first pump inlet and at least one second pump inlet located axially between the first turbomolecular pump stage and the second turbomolecular pump stage, it may be appropriate to arrange the at least one electrically operated cooling device axially such that, with respect to the second pump inlet, it is located on the side of the second pump inlet facing the first pump inlet. The at least one electrically operated cooling device is thus located even closer to the pump inlet located furthest upstream in the flow direction, which is also referred to throughout here as the first pump inlet, since the tendency toward gas permeation or desorption increases with increasing proximity to the first pump inlet.

[0016] If a split-flow pump comprises a third turbomolecular pumping stage in the axial direction between the first turbomolecular pumping stage and the second turbomolecular pumping stage, according to a further embodiment, in order to further reduce the tendency for gas desorption or permeation, it may be advisable to position the at least one electrically operated cooling device in the axial direction such that, with respect to the third turbomolecular pumping stage, it is located on the side of the third turbomolecular pumping stage facing the first pump inlet or on the side of the third turbomolecular pumping stage facing the first turbomolecular pumping stage. Unlike in the previously described embodiment, the at least one electrically operated cooling device is thus located even closer to the furthest upstream pump inlet, which is also referred to here as the first pump inlet.

[0017] If a split-flow pump has a third pump inlet in the axial direction between the first turbomolecular pumping stage and the third turbomolecular pumping stage, it may be advisable to arrange the at least one electrically operated cooling device in the axial direction in such a way that, with respect to the third pump inlet, it is located on the side of the third pump inlet facing the first pump inlet or on the side of the third pump inlet facing the first turbomolecular pumping mechanism.

[0018] The pump inlets in question can all open radially into the interior of the housing; alternatively, all pump inlets except the first pump inlet or the most upstream pump inlet can open radially into the interior of the housing, whereas the most upstream or first pump inlet opens axially into the interior of the housing at the head end of the housing opposite the second pump mechanism.

[0019] In order to be able to particularly effectively reduce the tendency toward gas desorption or permeation, according to a preferred embodiment, the at least one electrically operated cooling device can be located in the axial direction relative to the first pump mechanism on the side of the first pump mechanism facing the first pump inlet. The at least one electrically operated cooling device is thus located in the region most susceptible to gas desorption and / or permeation phenomena, since, especially in highly efficient split-flow pumps with multiple pump inlets and multiple turbomolecular pump stages, the lowest final pressure prevails in the region of the pump inlet located furthest upstream.

[0020] The at least one electrically operated cooling device is therefore preferably located in the axial direction of the turbomolecular vacuum pump in a region in which a final pressure is established inside the turbomolecular vacuum pump during operation, which final pressure is in the ultra-high vacuum range, wherein the final pressure which is established is preferably less than 10 -8< mbar, in particular less than 10 -9< mbar, and particularly preferably less than 10 -10< mbar.

[0021] If at least one electrically operated cooling device is mentioned here, each cooling device can be a fan that generates an air flow. According to one embodiment, this fan can be aligned such that the air flow generated by the fan strikes the housing in a radial direction or in an axial direction perpendicular to the housing, for example, the previously mentioned head end of the housing. Alternatively, at least one fan can be aligned such that the air flow generated by it brushes against the housing in a radial or axial direction, forming a turbulent boundary layer flow. The generated air flow therefore extends either parallel to the rotor shaft, without striking the head end of the housing, or perpendicular to it, with the air flow along the head end of the housing generating a turbulent boundary layer flow.

[0022] In order to intensify the cooling effect caused by the at least one fan, it can be provided according to a further embodiment that the housing of the turbomolecular vacuum pump has at least one heat sink, which preferably comprises a plurality of cooling fins, wherein the heat sink is exposed to the air flow generated by the at least one fan.

[0023] According to various embodiments, it can further be provided that at least one fan is fastened directly to the housing. Additionally or alternatively, it can be provided that at least one fan is fastened indirectly to the housing, for example by means of a spacer device which is in turn fastened to the housing and supports the at least one fan. Furthermore, in addition to or alternatively to the two previously described types of fastening, in which the fan is fastened directly or indirectly to the housing, according to a further embodiment, it can be provided that at least one fan is fastened to a support structure of a pumping station that is independent of the housing, so that the fan can be aligned as needed in order to cool different areas of the housing depending on the alignment.

[0024] In addition or alternatively to the previously described embodiments, in which the at least one electrically operated cooling device comprises at least one fan, a further embodiment may provide for the at least one electrically operated cooling device to comprise at least one Peltier element. According to one embodiment, the at least one Peltier element may be attached directly to the exterior of the housing. In addition or alternatively, a further embodiment may provide for the at least one Peltier element to be integrated into the wall of the housing.

[0025] For example, the housing can have at least one blind hole that accommodates at least one Peltier element. Preferably, the housing can have a plurality of blind holes that extend axially from the head end of the housing opposite the second pumping mechanism into the interior of the housing wall and each accommodates at least one Peltier element.

[0026] The accommodation of the Peltier elements in question in the aforementioned blind holes is particularly suitable because conventional split-flow pumps may already have such blind holes for accommodating heating elements. Using these heating elements, the pump can be heated up during initial commissioning at the factory in order to ensure that gas molecules are released by desorption from surfaces inside the pump, thus anticipating a large part of the gas desorption in advance. Since the blind holes in question may already be present, they can be used to accommodate Peltier elements after initial commissioning of the pump, meaning that no additional receptacles need to be provided in the housing wall. It may be advantageous to provide the Peltier elements on the same bracket that already supports the heating elements.

[0027] The invention is described below by way of example using advantageous embodiments with reference to the accompanying figures. They show, schematically: Fig. 1a perspective view of a turbomolecular pump, Fig. 2a view of the underside of the turbomolecular pump of Fig. 1 , Fig. 3 a cross-section of the turbomolecular pump along the Fig. 2 shown section line AA, Fig. 4 a cross-sectional view of the turbomolecular pump along the Fig. 2 shown section line BB, Fig. 5 a cross-sectional view of the turbomolecular pump along the Fig. 2 shown section line CC, Fig. 6 a schematic representation of a split-flow pump with three pump inlets and three turbomolecular pump stages, Fig. 7 a first embodiment of a pump system with the split-flow pump of the Fig. 6 and two fans, Fig. 8 a second embodiment of a pumping system with the split-flow pump of the Fig. 6and two fans and two heat sinks, Fig. 9 a third embodiment of a pumping system with the split-flow pump of the Fig. 6 and two fans, Fig. 10 a fourth embodiment of a pumping system with the split-flow pump of the Fig. 6 , a fan and a heat sink, Fig. 11 a fifth embodiment of a pumping system with the split-flow pump of the Fig. 6 and a Peltier element provided thereon, Fig. 12 a sixth embodiment of a pumping system with the split-flow pump of the Fig. 6 and several Peltier elements provided on a holder, and Fig. 13 a seventh embodiment of a pumping system with the split-flow pump of the Fig. 6 and Peltier and heating elements provided on a holder.

[0028] The Fig. 1The turbomolecular pump 111 shown comprises a pump inlet 115 surrounded by an inlet flange 113, to which a recipient (not shown) can be connected in a manner known per se. The gas from the recipient can be sucked out of the recipient via the pump inlet 115 and conveyed through the pump to a pump outlet 117, to which a backing pump, such as a rotary vane pump, can be connected.

[0029] The inlet flange 113 forms the vacuum pump alignment according to Fig. 1 the upper end of the housing 119 of the vacuum pump 111. The housing 119 comprises a lower part 121, on which an electronics housing 123 is arranged laterally. Electrical and / or electronic components of the vacuum pump 111 are housed in the electronics housing 123, e.g., for operating an electric motor 125 arranged in the vacuum pump (see also Fig. 3). Several connectors 127 for accessories are provided on the electronics housing 123. In addition, a data interface 129, e.g., according to the RS485 standard, and a power supply connector 131 are arranged on the electronics housing 123.

[0030] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0031] On the housing 119 of the turbomolecular pump 111, a flooding inlet 133, in particular in the form of a flooding valve, is provided, via which the vacuum pump 111 can be flooded. In the area of ​​the lower part 121, a sealing gas connection 135, which is also referred to as a purge gas connection, is also arranged, via which purge gas is supplied to protect the electric motor 125 (see e.g. Fig. 3) can be admitted into the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111, before the gas delivered by the pump. Furthermore, two coolant connections 139 are arranged in the lower part 121, one of which serves as an inlet and the other as an outlet for coolant, which can be fed into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) are operated exclusively with air cooling.

[0032] The lower side 141 of the vacuum pump can serve as a base, so that the vacuum pump 111 can be operated standing on the underside 141. However, the vacuum pump 111 can also be attached to a recipient via the inlet flange 113 and thus operated in a suspended position. Furthermore, the vacuum pump 111 can be designed so that it can also be operated when oriented in a different manner than in Fig. 1 As shown. Embodiments of the vacuum pump can also be realized in which the underside 141 is arranged facing either sideways or upwards, rather than downwards. In principle, any angle is possible.

[0033] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in an upright position.

[0034] 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 together. For example, a bearing cover 145 is attached to the underside 141.

[0035] Mounting holes 147 are also arranged on the underside 141, through which the pump 111 can be attached, for example, to a support surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0036] In the Figures 2 to 5 a coolant line 148 is shown in which the coolant introduced and discharged via the coolant connections 139 can circulate.

[0037] As the sectional views of the Figures 3 to 5 show, 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.

[0038] A rotor 149 is arranged in the housing 119 and has a rotor shaft 153 rotatable about a rotation axis 151.

[0039] The turbomolecular pump 111 comprises several turbomolecular pump stages connected in series for pumping purposes, with several radial rotor disks 155 attached to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and secured in the housing 119. A rotor disk 155 and an adjacent stator disk 157 each form a turbomolecular pump stage. The stator disks 157 are held at a desired axial distance from one another by spacer rings 159.

[0040] The vacuum pump also includes Holweck pump stages arranged radially one inside the other and connected in series for pumping efficiency. Other turbomolecular vacuum pumps (not shown) exist that do not have Holweck pump stages.

[0041] The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical-shell-shaped Holweck rotor sleeves 163, 165 attached to and supported by the rotor hub 161, which are oriented coaxially to the rotational axis 151 and nested within one another in the radial direction. Furthermore, two cylindrical-shell-shaped Holweck stator sleeves 167, 169 are provided, which are also oriented coaxially to the rotational axis 151 and nested within one another in the radial direction.

[0042] The pumping surfaces of the Holweck pump stages are formed by the lateral 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 lies opposite the radial outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together with the latter forms the first Holweck pump stage following the turbomolecular pumps. The radial inner surface of the outer Holweck rotor sleeve 163 lies opposite the radial outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together with the latter forms 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 forming the third Holweck pumping stage.

[0043] At the lower end of the Holweck rotor sleeve 163, a radially extending channel can be provided, via which the radially outer Holweck gap 171 is connected to the central Holweck gap 173. Furthermore, at the upper end of the inner Holweck stator sleeve 169, a radially extending channel can be provided, via which the central Holweck gap 173 is connected to the radially inner Holweck gap 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.

[0044] The above-mentioned pump-active surfaces of the Holweck stator sleeves 167, 169 each have a plurality of Holweck grooves extending spirally around the rotation axis 151 in the axial direction, while the opposite lateral surfaces of the Holweck rotor sleeves 163, 165 are smooth and propel the gas in the Holweck grooves for operating the vacuum pump 111.

[0045] 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.

[0046] In the area of ​​the rolling bearing 181, a conical spray nut 185 with an outer diameter increasing toward the rolling bearing 181 is provided on the rotor shaft 153. The spray nut 185 is in sliding contact with at least one wiper of a fluid reservoir. In other existing turbomolecular vacuum pumps (not shown), a spray screw can be provided instead of a spray nut. Since different designs are thus possible, the term "spray tip" is also used in this context.

[0047] The operating fluid storage comprises several stacked absorbent discs 187, which are impregnated with an operating fluid for the rolling bearing 181, e.g. with a lubricant.

[0048] During operation of the vacuum pump 111, the operating fluid is transferred by capillary action from the operating fluid reservoir via the wiper to the rotating injection nut 185. As a result of centrifugal force, it is conveyed along the injection nut 185 in the direction of the increasing outer diameter of the injection nut 185 to the rolling bearing 181, where it fulfills a lubricating function, for example. The rolling bearing 181 and the operating fluid reservoir are enclosed in the vacuum pump by a trough-shaped insert 189 and the bearing cover 145.

[0049] The permanent magnet bearing 183 comprises a rotor-side bearing half 191 and a stator-side bearing half 193, each comprising a ring stack of several permanent magnetic rings 195, 197 stacked one on top of the other in the axial direction. The ring magnets 195, 197 lie opposite one another, forming a radial bearing gap 199, with the rotor-side ring magnets 195 being arranged radially on the outside and the stator-side ring magnets 197 being arranged radially on the inside. The magnetic field present in the bearing gap 199 creates magnetic repulsion forces between the ring magnets 195, 197, which effect a radial bearing of the rotor shaft 153. The rotor-side ring magnets 195 are carried by a support section 201 of the rotor shaft 153, which surrounds the ring magnets 195 on the radial 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. The rotor-side ring magnets 195 are secured parallel to the rotation axis 151 by a cover element 207 coupled to the support section 201. The stator-side ring magnets 197 are secured parallel to the rotation axis 151 in one direction by a fastening ring 209 connected to the support section 203 and a fastening ring 211 connected to the support section 203. A disc spring 213 can also be provided between the fastening ring 211 and the ring magnets 197.

[0050] Within the magnetic bearing, an emergency or backup bearing 215 is provided, which runs idle without contact during normal operation of the vacuum pump 111 and only engages upon excessive radial deflection of the rotor 149 relative to the stator, forming a radial stop for the rotor 149 to prevent collision of the rotor-side structures with the stator-side structures. The backup bearing 215 is designed as an unlubricated rolling bearing and forms a radial gap with the rotor 149 and / or the stator, causing the backup bearing 215 to be disengaged during normal pumping operation. The radial deflection at which the backup bearing 215 engages is large enough so that the backup bearing 215 does not engage during normal operation of the vacuum pump, yet small enough so that collision of the rotor-side structures with the stator-side structures is prevented under all circumstances.

[0051] 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 portion of the rotor shaft 153 extending through the motor stator 217. Between the motor stator 217 and the portion of the rotor 149 extending through the motor stator 217, an intermediate space 219 is arranged, which comprises a radial motor gap, via which the motor stator 217 and the permanent magnet arrangement can magnetically influence each other to transmit the drive torque.

[0052] The motor stator 217 is secured in the housing within the motor compartment 137 provided for the electric motor 125. A seal gas, also referred to as purge gas, which may be air or nitrogen, for example, can enter the motor compartment 137 via the seal gas connection 135. The seal gas can be used to protect 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, i.e., the vacuum pressure in the motor compartment 137 is at least approximately equal to the vacuum pressure created by the backing pump connected to the pump outlet 117.

[0053] Furthermore, a so-called labyrinth seal 223, which is known per se, can be provided between the rotor hub 161 and a wall 221 delimiting the motor compartment 137, in particular in order to achieve a better sealing of the motor compartment 217 with respect to the Holweck pump stages located radially outside.

[0054] Having previously referred to the Fig. 1 to 5 The basic structure of a turbomolecular vacuum pump 111 has been explained, will be explained below with reference to the Fig. 6 the structure of a turbomolecular vacuum pump 300 designed as a split-flow pump is explained, with reference to the Fig. 7 ff. the cooling concept according to the invention is explained below. However, this cooling concept can be applied in a corresponding manner to the cooling concept described above with reference to the Fig. 1 to 5 Use the turbomolecular vacuum pump 111 described.

[0055] Since the basic structure of the Fig. 6 The turbomolecular vacuum pump 300 shown in FIG. 1 is the same as that described with reference to Fig. 1 to 5 described turbomolecular vacuum pump 111, the description of the turbomolecular vacuum pump 300 is limited to the essential differences compared to the turbomolecular vacuum pump 111 of Fig. 1 to 5 .

[0056] Similar to the turbomolecular vacuum pump 111, the turbomolecular vacuum pump 300 also has a housing 302 with a first pump inlet 304 and a pump outlet 310, but here the pump inlet 304 is different from the pump inlet 115 of the turbomolecular vacuum pump 111 of the Fig. 1 bi 5 does not open axially, but radially into the interior of the housing 302. A backing pump 312 is connected to the pump outlet 310, which discharges the process gas pumped by the turbomolecular vacuum pump 300 from the pump inlet 304 to the pump outlet 310 into the environment.

[0057] The process gas is pumped from the pump inlet 304 to the pump outlet 310 by means of three turbomolecular pump stages 314, 316, 318 and a downstream Holweck pump stage 320, all of which are arranged along a rotor shaft 322 and driven by it. The first turbomolecular pump stage 314 is located closest to the pump inlet 304 and downstream thereof. The third turbomolecular pump stage 318 is located downstream of the first turbomolecular pump stage 314, whereas the second turbomolecular pump stage 316 is in turn downstream of the third turbomolecular pump stage 316. The third turbomolecular pump stage 318 is thus located between the first and second pump stages 314, 316.

[0058] Again Fig. 6As can be seen, the three turbomolecular pump stages 314, 316, 318 are spaced apart from one another in the axial direction, wherein a second pump inlet 306 opens radially into the interior of the housing 302 in the distance between the third turbomolecular pump stage 318 and the second turbomolecular pump stage 316, whereas a third pump inlet 308 opens radially into the interior of the housing in the distance between the first turbomolecular pump stage 314 and the third turbomolecular pump stage 318.

[0059] As already mentioned in the Fig. 6As is schematically indicated by the two arrows, in the illustrated split-flow pump 300, it is provided according to the invention that the head end 324 of the housing 302, which is located at the head end 324 of the housing 302 opposite the Holweck pump stage 302, is cooled by fans (not shown) which direct an air flow illustrated by the arrows onto the housing 302. In the embodiment illustrated here, the fan(s) are provided at the head end 324 of the housing 302, since the lowest pressure prevails upstream of the first turbomolecular pump stage 314 or in the region of the first pump inlet 304 during pumping operation, and gas desorption there contributes to a non-negligible pressure increase.Basically, however, in the area of ​​the entire turbomolecular pumping mechanism, which is formed by the three turbomolecular pumping stages 314, 316, 318, there is an increased tendency for gas desorption due to the low pressures prevailing there during pumping operation, which is why it may also be advisable, depending on requirements, to cover the housing 302 in the area of ​​the . Fig. 6 to cool the areas marked "A", "B", "C" and "D".

[0060] Region "A" is located, relative to the second turbomolecular pumping stage 316, on the side of the second turbomolecular pumping stage 316 facing the first turbomolecular pumping stage 314. The second region "B" is located, in the axial direction, relative to the second pump inlet 306, on the side of the second pump inlet 306 facing the first pump inlet 304. The third region "C" is located, in the axial direction, relative to the third turbomolecular pumping stage 318, on the side of the third turbomolecular pumping stage 318 facing the first pump inlet 304. Finally, the fourth region "D" is located, in the axial direction, relative to the third pump inlet 308, on the side of the third pump inlet 308 facing the first pump inlet 304.

[0061] In principle, however, it proves advantageous to cool all those areas in which a pressure in the ultra-high vacuum range is established inside the turbomolecular vacuum pump 300 during operation using an electrically operated cooling device. In particular, these are areas in which a pressure of less than 10 -9 mbar and especially less than 10 -10 mbar prevails.

[0062] In the case of the Fig. 7In the pumping system described, the housing area upstream of the first turbomolecular pumping stage 314 is cooled by means of two fans 326, which are only schematically illustrated, wherein one fan 326 is oriented such that the air flow generated by it impinges on the housing 302 in a radial direction, whereas the other fan 326 is oriented such that the air flow generated by it impinges on the housing 302 in an axial direction and in particular on the head end 324 of the housing 302 opposite the Holweck pumping stage 320. If necessary, the pumping system can also have further fans 326, which are oriented such that their air flow impinges on the housing 302 in a radial direction in one or more of the areas "A", "B", "C" and / or "D", see the Fig. 6 . In the embodiment of the Fig. 7the fans 326 are not attached to the housing 302 itself, but to a support structure (not shown) independent of the housing 302, for example a pumping station or a mass spectrometer in which the split flow can be installed, which makes it possible to arrange and orient the fans 326 as required.

[0063] In contrast to the design of the Fig. 7 are in the design of the pump system of the Fig. 8 The two fans 326 are attached directly to the housing 302, with both fans 326 aligned so that the airflow they generate brushes the housing 302 in the radial and axial directions, respectively. Although two fans 326 are provided in the embodiment shown here, it may also be sufficient to cool only the top end 324 of the housing 302 with one fan 326.

[0064] To improve the cooling effect caused by the fans 326, it is in the embodiment of the Fig. 8It is further provided that each fan 326 is assigned a heat sink 328 with preferably a plurality of cooling fins, wherein the respective heat sink 328 is placed on the housing 302 such that it is exposed to the air flow generated by the fan 326 assigned to the respective heat sink 328.

[0065] In contrast to the design of the Fig. 8 are in the design of the pump system of the Fig. 9 the two fans 326 are not attached to the housing 302 directly, but indirectly with the aid of suitable spacer devices 330, whereby the fans 326, contrary to the embodiment of the Fig. 8 are oriented so that the air flow generated by them hits the housing 302 directly in the radial or axial direction.

[0066] The design of the Fig. 10The head end 324 of the housing 302 is cooled by a fan 326 attached to the housing 302 via a spacer device 330, which in this embodiment is also oriented such that the air flow generated by it impinges in the axial direction directly onto the housing 302 and in particular the head end 324 of the housing 302. In this case, a heat sink 328 with a plurality of cooling fins is located at the distance between the fan 326 and the head end 324 of the housing 302, which is attached to the housing 302 in order to enhance the cooling effect caused by the fan 326.

[0067] In the design of the Fig. 11The electrically operated cooling device is not formed by a fan, but by a Peltier element 332, which is attached there purely as an example to the outer circumference of the housing 302 in an area located upstream of the first turbomolecular pump stage 314. In addition or alternatively, however, Peltier elements can also be used in the areas "A", "B", "C" and / or "D" (see the Fig. 6 ) on the housing 302 in order to additionally or alternatively cool these areas.

[0068] In the design of the Fig. 12 The head end 324 of the housing 302 is cooled with four Peltier elements 332. The Peltier elements 332 are attached to a holder 334 and extend into respective blind holes 336 formed in the head end 324 of the housing 302.

[0069] In the design of the Fig. 13Ultimately, it is intended that the holder 334 carries not only two Peltier elements 332, but also two heating elements 340, wherein both the Peltier elements 332 and the heating elements 340 extend into blind holes 336 formed in the head end 324 of the housing 302. By means of the heating elements 340, the pump can be heated during initial commissioning at the factory in order to ensure in advance that gas molecules are released by desorption from surfaces inside the pump, whereby a large part of the gas desorption is, in a sense, already anticipated in advance. The Peltier elements 332, however, serve as in the embodiment of the Fig. 12 for cooling the turbomolecular vacuum pump 300 in order to limit gas desorption during its operation.

[0070] For the sake of good order, it should be noted at this point that with reference to the Fig. 7 to 13Specific arrangements of electrically operated cooling devices have been explained; however, as already partially noted above, the respective cooling devices can also be arranged and aligned, as required, to cool one or more of the areas "A", "B", "C" and / or "D". List of reference symbols

[0071] 111Turbomolecular pump 113Inlet flange 115Pump inlet 117Pump outlet 119Housing 121Lower section 123Electronics housing 125Electric motor 127Accessory connection 129Data interface 131Power supply connection 133Flood inlet 135Seal gas connection 137Motor compartment 139Coolant connection 141Underside 143Screw 145Bearing cover 147Mounting hole 148Coolant line 149Rotor 151Rotation axis 153Rotor shaft 155Rotor disc 157Stator disc 159Spacer ring 161Rotor hub 163Holweck rotor sleeve 165Holweck rotor sleeve 167Holweck stator sleeve 169Holweck stator sleeve 171Holweck gap 173Holweck gap 175Holweck gap 179Connecting channel 181Rolling bearing 183Permanent magnet bearing 185Injection nut 187Disc 189Insert 191Rotor-side bearing half 193Stator-side bearing half 195Ring magnet 197Ring magnet 199Bearing gap 201Support section 203Support section 205Radial strut 207Cover element 209Support ring 211Fastening ring 213Disc spring 215Emergency orSafety bearing 217Motor stator 219Gap 221Wall 223Labyrinth seal 300Turbomolecular vacuum pump 302Housing 304First pump inlet 306Second pump inlet 308Third pump inlet 310Pump outlet 312Backing pump 314First turbomolecular pump stage 316Second turbomolecular pump stage 318Third turbomolecular pump stage 320Holweck pump stage 322Rotor shaft 324Head end 326Fan 328Heat sink 330Spacer device 332Peltier element 334Bracket 336Blind hole 340Heating element.

Claims

1. A pumping system with a turbomolecular vacuum pump (300), comprising: - a housing (302) with at least one pump inlet (304, 306, 308) and one pump outlet (310); - a first pumping mechanism driven by a rotor shaft (322) with at least one turbomolecular pumping stage (314, 316, 318) in the housing (302); - a second pumping mechanism in the housing (302) driven by the rotor shaft (322) downstream of the first pumping mechanism, which operates according to a different pumping principle than the first pumping mechanism; wherein the first and second pumping mechanisms for jointly conveying a process gas from the pump inlet (304, 306, 308) to the pump outlet (310) are arranged along the rotor shaft (322) and are located in the axial direction between the at least one pump inlet (304, 306, 308) and the pump outlet (310);and wherein the pumping system for cooling the housing (302) further comprises at least one electrically operated cooling device (326, 332) which is located in the axial direction with respect to the second pumping mechanism on the side of the second pumping mechanism facing the first pumping mechanism; 2. Pumping system according to claim 1, wherein the first pumping mechanism comprises a first turbomolecular pumping stage (314) and downstream thereof at least one second turbomolecular pumping stage (316), wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction with respect to the at least second turbomolecular pumping stage (316) on the side of the at least one second turbomolecular pumping stage (316) facing the first turbomolecular pumping stage (314).

3. Pump system according to claim 2, wherein the housing (302) has a first pump inlet (304) and at least one second pump inlet (306) which is located in the axial direction between the first turbomolecular pumping stage (314) and the second turbomolecular pumping stage (316), wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction with respect to the second pump inlet (306) on the side of the second pump inlet (306) facing the first pump inlet (304).

4. Pumping system according to claim 2 or 3, wherein the first pumping mechanism further comprises at least one third turbomolecular pumping stage (318) which is located in the axial direction between the first turbomolecular pumping stage (314) and the second turbomolecular pumping stage (318), wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction with respect to the third turbomolecular pumping stage (318) on the side of the third turbomolecular pumping stage (318) facing the first pump inlet (304).

5. Pump system according to claim 4, wherein the housing (302) further comprises at least one third pump inlet (308) which is located in the axial direction between the first turbomolecular pumping stage (314) and the third turbomolecular pumping stage (318), wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction with respect to the third pump inlet (308) on the side of the third pump inlet (308) facing the first pump inlet (304).

6. Pump system according to at least one of the preceding claims, wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction with respect to the first pump mechanism on the side of the first pump mechanism facing the first pump inlet (304).

7. Pump system according to at least one of the preceding claims, wherein the at least one electrically operated cooling device (326, 332) is located in the axial direction of the turbomolecular vacuum pump (300) in a region in which a final pressure is established inside the turbomolecular vacuum pump (300) during operation, which final pressure is in the ultra-high vacuum range, wherein the final pressure that is established is preferably less than 10 -8 mbar, especially less than 10 -9 mbar, and particularly preferably less than 10 -10 mbar, is.

8. Pump system according to at least one of the preceding claims, wherein all pump inlets (304, 306, 308) open radially into the interior of the housing (302); or wherein all pump inlets (304, 306, 308) except the first pump inlet (304) open radially into the interior of the housing (302), whereas the first pump inlet (304) opens axially into the interior of the housing (302) at the head end of the housing (302) opposite the second pump mechanism.

9. Pump system according to at least one of the preceding claims, wherein the at least one electrically operated cooling device (326, 332) is at least one fan (326) generating an air flow.

10. Pump system according to claim 9, wherein at least one fan (326) is oriented such that the air flow generated by it strikes the housing (302) in a radial or axial direction.

11. Pump system according to claim 9 or 10, wherein at least one fan (326) is oriented such that the air flow generated by it brushes the housing (302) in the radial or axial direction to form a boundary layer flow.

12. Pump system according to claim 9, 10 or 11, wherein the housing (302) has at least one heat sink (328), which preferably comprises a plurality of cooling fins, the heat sink (328) being exposed to the air flow generated by the at least one fan (326).

13. Pump system according to at least one of claims 9 to 12, wherein at least one fan (326) is attached directly to the housing (302); and / or wherein at least one fan (326) is attached indirectly to the housing (302), preferably by means of a spacer device (330); and / or wherein at least one fan (326) is attached to a support structure independent of the housing (302).

14. Pump system according to at least one of the preceding claims, wherein the at least one electrically operated cooling device (326, 332) is at least one Peltier element (332).

15. Pump system according to claim 14, wherein the at least one Peltier element (332) is attached to the outside of the housing (302).

16. Pump system according to claim 14 or 15, wherein the housing (302) has at least one blind hole (336) which receives at least one Peltier element (332), wherein it is preferably provided that the housing (302) has a plurality of blind holes (336) which extend axially from the head end (324) of the housing (302) opposite the second pump mechanism into the interior of the housing wall and which each receive at least one Peltier element (332).

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