Vacuum pump system with electrically operated cooling unit

Description

[0001] The present invention relates to a pumping system according to the preamble of claim 1 with an electrically operated cooling device for cooling a turbomolecular vacuum pump of the pumping system, as is known essentially from EP 3 657 022 A1.

[0002] Further state of the art can also be found in documents US 2022 / 243 737 A1, EP 2 846 044 A1 and WO 2015 / 043 964 A1.

[0003] Turbomolecular vacuum pumps are typically used to generate a vacuum or low pressure in physical measuring instruments such as mass spectrometers. Especially when evacuating mass spectrometers, the goal is often to achieve an ultimate pressure in the ultra-high vacuum range, specifically between 10⁻⁸ and 10⁻¹¹ mbar. To generate such low pressures, specialized turbomolecular vacuum pumps are frequently employed. These pumps are characterized, among other things, by having several turbomolecular pump stages arranged in series, each with its own pump inlet.

[0004] 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 pump or multi-inlet vacuum pump.

[0005] In the ultra-high vacuum range, and especially at pressures below 10⁻⁹ mbar, undesirable physical phenomena have been observed that negatively affect the achievable ultimate pressure. Specifically, at pressures below 10⁻⁹ mbar, desorption and / or permeation phenomena can occur. The lower the pressure, the greater the proportion of these dissolved gases that represent in the ultra-high vacuum range. This ultimately limits the achievable ultimate pressure due to the described physical phenomena. This, in turn, limits the accuracy of physical measuring instruments such as mass spectrometers.

[0006] Accordingly, the present invention is based on the objective of providing a pumping system with which a lower pressure can be achieved compared to a pumping system with the same pump configuration or compared to a pumping system that has the same pumping mechanism as the pumping system according to the invention.

[0007] To solve this problem, a pumping system with a substantially conventional turbomolecular vacuum pump is presented, wherein the pumping system is characterized by the features of claim 1.

[0008] A conventional turbomolecular vacuum pump is characterized, among other things, by comprising a housing with at least one pump inlet and one pump outlet, containing two pumping mechanisms driven by a rotor shaft. The first of these two pumping mechanisms is a turbomolecular pumping stage, preferably comprising several rotor disks driven by the rotor shaft. The second pumping mechanism, for example, is a Holweck pumping stage located downstream of the first pumping mechanism, or downstream of the turbomolecular pumping stage. Fundamentally, the second pumping mechanism operates on a different pumping principle than the first. Therefore, the second pumping mechanism can also include, for example, a Siegbahn pumping stage and / or a side-channel pumping stage.The two pumping mechanisms are arranged in a conventional manner for the joint conveyance of 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.

[0009] According to the invention, the proposed pump system is characterized in particular by the fact that it has at least one electrically operated cooling device for cooling the housing. This cooling device is located axially on the side of the second pump mechanism facing the first pump mechanism. It was discovered according to the invention that the mechanisms underlying the desorption and / or permeation phenomena described above 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. According to the invention, the at least one electrically operated cooling device comprises at least one Peltier element attached to the outside of the housing.

[0010] In order to prevent the operational heating of the turbomolecular vacuum pump and thus the described gas desorption and / or permeation phenomena, it is proposed according to the invention to actively cool a turbomolecular vacuum pump in the area of ​​the first pumping mechanism between pump inlet and pump outlet.

[0011] While it is not uncommon to cool the electric motor of a turbomolecular vacuum pump using a fan, the drive motor of conventional turbomolecular vacuum pumps is located on the side of the Holweck pump stage facing away from the turbomolecular pump stage. This also applies to the fan used to cool the drive motor. The turbomolecular pump stage is thus effectively separated from the drive motor and therefore from the fan by the Holweck pump stage, meaning that cooling the drive motor has no or only a negligible effect on the turbomolecular pump stage. Consequently, cooling the drive motor alone cannot provide sufficient cooling for the high-vacuum side of the turbomolecular pump stage.

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

[0013] To reduce the tendency for gas desorption or permeation particularly effectively, the invention provides that the at least one electrically operated cooling device is located axially 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 area 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 ultimate pressure prevails in the region of the pump inlet furthest upstream.

[0014] The at least one electrically operated cooling device is therefore located in the axial direction of the turbomolecular vacuum pump in a region in which an ultimate pressure is established inside the turbomolecular vacuum pump during operation, which is in the ultra-high vacuum range, wherein the ultimate pressure established is preferably less than 10⁻⁸ < mbar, in particular less than 10⁻⁹ < mbar, and in particular preferably less than 10⁻¹⁰ < mbar.

[0015] Preferred embodiments of the invention will now be discussed. Further embodiments may also be apparent from the dependent claims, the description of the figures, and the drawings themselves.

[0016] According to one embodiment, the first pumping mechanism, as in a split-flow pump, may have a first turbomolecular pumping stage and at least a second turbomolecular pumping stage downstream of it. In this case, the at least one electrically operated cooling device may be located axially on the side of the second turbomolecular pumping stage facing the first turbomolecular pumping stage. Thus, the at least one electrically operated cooling device is located axially closer to the first turbomolecular pumping stage than the Holweck pumping stage and therefore closer to the pump inlet. This is because the achievable ultimate pressure decreases progressively towards the pump inlet, which is why, to reduce gas desorption, the cooling device is used.-permeation is advantageous to arrange at least one electrically operated cooling device as close as possible to the (single) pump inlet, since the achievable final pressure is lowest there and thus the tendency for gas desorption or permeation has the greatest influence on the resulting pressure.

[0017] Accordingly, in a split-flow pump with a first pump inlet and at least one second pump inlet located axially between the first and second turbomolecular pump stages, it may be advantageous to arrange the at least one electrically operated cooling device axially such that 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 furthest upstream in the flow direction, which is consistently referred to here as the first pump inlet, since the tendency for gas permeation or desorption increases with increasing proximity to the first pump inlet.

[0018] If a split-flow pump includes a third turbomolecular pump stage in the axial direction between the first and second turbomolecular pump stages, a further embodiment allows for a further reduction of the tendency for gas desorption or permeation by positioning at least one electrically operated cooling device in the axial direction such that it is located on the side of the third turbomolecular pump stage facing the first pump inlet, or on the side of the third turbomolecular pump stage facing the first turbomolecular pump stage. Unlike the embodiment described above, the at least one electrically operated cooling device is thus located even closer to the pump inlet furthest upstream, which is also referred to here as the first pump inlet.

[0019] If a split-flow pump has a third pump inlet in the axial direction between the first turbomolecular pump stage and the third turbomolecular pump stage, it may be advantageous to further reduce undesirable gas desorption and / or permeation phenomena by arranging at least one electrically operated cooling device in the axial direction such that 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 pump mechanism, with respect to the third pump inlet.

[0020] 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 the first pump inlet opens axially into the interior of the housing at the head end opposite the second pump mechanism.

[0021] If at least one electrically operated cooling device is mentioned here, this cooling device, in addition to the at least one Peltier element, can be a fan that generates an airflow. According to one embodiment, this fan can be oriented such that the airflow generated by the fan strikes the housing perpendicularly in the radial or axial direction, for example, the aforementioned head end of the housing. Alternatively, at least one fan can be oriented such that the airflow it generates passes over the housing in the radial or axial direction, forming a turbulent boundary layer flow. The generated airflow thus extends either parallel to the rotor shaft without striking the head end of the housing, or perpendicular to it, generating a turbulent boundary layer flow along the head end of the housing.

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

[0023] According to various embodiments, at least one fan may be directly attached to the housing. Additionally or alternatively, at least one fan may be indirectly attached to the housing, for example, by means of a spacer device that is itself attached to the housing and supports the at least one fan. Furthermore, in addition to or as an alternative to the two previously described attachment methods, where the fan is directly or indirectly attached to the housing, a further embodiment provides for at least one fan to be attached to a support structure of a pump stand that is independent of the housing, so that the fan can be oriented as needed to cool different areas of the housing.

[0024] In addition to or as an alternative to the embodiments described above, a further embodiment may provide that the at least one Peltier element is 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 several blind holes extending axially into the interior of the housing wall from the head end of the housing opposite the second pump mechanism, each accommodating at least one Peltier element.

[0026] The placement of the Peltier elements in question within the aforementioned blind holes is particularly advantageous because conventional split-flow pumps may already have such blind holes to accommodate heating elements. These heating elements allow the pump to be heated during initial factory commissioning, thus pre-heating the pump and causing gas molecules to desorb from internal surfaces, thereby pre-emptively handling a significant portion of the gas desorption process. Since these blind holes may already be present, they can be used to house the Peltier elements after the pump's initial commissioning, eliminating the need for additional recesses in the housing wall. Preferably, the Peltier elements can be mounted on the same bracket that already supports the heating elements.

[0027] The invention is described below by way of example with reference to advantageous embodiments and the accompanying figures. These show, schematically: 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. 2 Section 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 Section line CC shown, 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 pump system with the split-flow pump of the Fig. 6and two fans and two heat sinks, Fig. 9 a third embodiment of a pump system with the split-flow pump of the Fig. 6 and two fans, Fig. 10 a fourth embodiment of a pump system with the split-flow pump of the Fig. 6 , a fan and a heat sink, Fig. 11 a fifth embodiment of a pump system with the split-flow pump of the Fig. 6 and a Peltier element provided thereon, Fig. 12 a sixth embodiment of a pump 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 pump system with the split-flow pump of the Fig. 6 and Peltier and heating elements provided on a bracket.

[0028] The Figures 11 to 13 show embodiments according to the invention.

[0029] The in Fig. 1The 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.

[0030] 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.

[0031] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0032] 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.

[0033] 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.

[0034] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in a standing position.

[0035] 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.

[0036] Mounting holes 147 are also arranged on the underside 141, via which the pump 111 can be attached to a support surface, for example. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0037] 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.

[0038] Like the sectional views of the Figures 3 to 5As 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.

[0039] In A rotor 149 is arranged in the housing 119, which has a rotor shaft 153 rotatable about a rotation axis 151.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 result in the radial support of the rotor shaft 153. 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] After previously referring to the Figs. 1 to 5 The basic structure of a turbomolecular vacuum pump 111 has been explained, and will be described below with reference to the Fig. 6 The construction of a turbomolecular vacuum pump 300 designed as a split-flow pump is explained, based on which, with reference to the Fig. 7 The cooling concept according to the invention will then be explained below. This cooling concept can, however, be adapted accordingly to the previously mentioned cooling concept. Figs. 1 to 5 Use the described turbomolecular vacuum pump 111.

[0056] Since the basic structure of the in the Fig. 6 The turbomolecular vacuum pump 300 shown, which is described with reference to the Figs. 1 to 5 Since the turbomolecular vacuum pump 300 corresponds to the turbomolecular vacuum pump 111 described above, the description of the turbomolecular vacuum pump 300 is limited to the essential differences compared to the turbomolecular vacuum pump 111. Figs. 1 to 5 .

[0057] 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, although here the pump inlet 304 differs from the pump inlet 115 of the turbomolecular vacuum pump 111. Fig. 1 The outlet 310 opens radially, not axially, into the interior of the housing 302. A backing pump 312 is connected to the pump outlet 310, which discharges the process gas conveyed by the turbomolecular vacuum pump 300 from the pump inlet 304 to the pump outlet 310 into the environment.

[0058] The process gas is conveyed from pump inlet 304 to pump outlet 310 by means of three turbomolecular pump stages 314, 316, and 318, as well as 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 and downstream of the pump inlet 304. The third turbomolecular pump stage 318 is located downstream of the first turbomolecular pump stage 314, while the second turbomolecular pump stage 316 is located downstream of the third turbomolecular pump stage 316. The third turbomolecular pump stage 318 is therefore located between the first and second pump stages 314 and 316.

[0059] Again Fig. 6As can be seen, the three turbomolecular pump stages 314, 316, 318 are spaced apart from each other in the axial direction, wherein a second pump inlet 306 opens radially into the interior of the housing 302 in the space 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 space between the first turbomolecular pump stage 314 and the third turbomolecular pump stage 318.

[0060] As already mentioned in the Fig. 6As schematically indicated by the two arrows, in the illustrated split-flow pump 300, the head end 324 of the housing 302, located opposite the Holweck pump stage 302, is cooled by fans (not shown) that direct an airflow, illustrated by the arrows, onto the housing 302. In the embodiment shown here, the fan(s) are located at the head end 324 of the housing 302 because the lowest pressure prevails upstream of the first turbomolecular pump stage 314, or in the region of the first pump inlet 304, during pump operation, and gas desorption there contributes to a non-negligible pressure increase.However, in principle, the entire turbomolecular pumping mechanism, which is formed by the three turbomolecular pumping stages 314, 316, 318, has an increased tendency for gas desorption due to the low pressures prevailing there during pumping operation, which is why it may be advisable, depending on requirements, to enclose the housing 302 in the area of ​​the . Fig. 6 to cool the areas marked "A", "B", "C" and "D".

[0061] Area "A" is located on the side of the second turbomolecular pump stage 316 facing the first turbomolecular pump stage 314, relative to the second turbomolecular pump stage 316. Area "B" is located axially relative to the second pump inlet 306 on the side of the second pump inlet 306 facing the first pump inlet 304. Area "C" is located axially relative to the third turbomolecular pump stage 318 on the side of the third turbomolecular pump stage 318 facing the first pump inlet 304. Area "D" is located axially relative to the third pump inlet 308 on the side of the third pump inlet 308 facing the first pump inlet 304.

[0062] However, it is generally advantageous to cool all those areas by means of an electrically operated cooling device where a pressure in the ultra-high vacuum range is established inside the turbomolecular vacuum pump 300 during operation. In particular, these are areas where a pressure of less than 10⁻⁹ mbar and especially less than 10⁻¹⁰ mbar prevails.

[0063] With reference to the Fig. 7In the described pumping system, the housing area upstream of the first turbomolecular pumping stage 314 is cooled by means of two fans 326, which are only shown schematically. One fan 326 is oriented such that the airflow it generates strikes the housing 302 in a radial direction, while the other fan 326 is oriented such that the airflow it generates strikes the housing 302 in an axial direction, and in particular the head end 324 of the housing 302 opposite the Holweck pumping stage 320. If required, the pumping system can also have additional fans 326, which are oriented such that their airflow strikes 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 independent of the housing 302 (not shown), for example a pump stand or a mass spectrometer, in which the Splitflow can be installed, which makes it possible to arrange and orient the fans 326 as needed.

[0064] In contrast to the embodiment of the Fig. 7 are in the design of the pump system the Fig. 8 The two fans 326 are attached directly to the housing 302, with both fans 326 being oriented such that the airflow they generate sweeps across the housing 302 in a radial or axial direction. Although two fans 326 are provided in the embodiment shown here, it may also be sufficient to cool only the head end 324 of the housing 302 with one fan 326.

[0065] To improve the cooling effect caused by the fans 326, in the embodiment of the Fig. 8It is further provided that each fan 326 is assigned a heat sink 328 with preferably several cooling fins, wherein the respective heat sink 328 is placed on the housing 302 in such a way that it is exposed to the airflow generated by the fan 326 assigned to the respective heat sink 328.

[0066] In contrast to the embodiment of the Fig. 8 are in the design of the pump system the Fig. 9 the two fans 326 are not attached directly to the housing 302, but indirectly by means of suitable spacers 330, whereby the fans 326 are contrary to the embodiment of the Fig. 8 are oriented in such a way that the airflow they each generate hits the housing 302 directly in a radial or axial direction.

[0067] Even in the embodiment of the Fig. 10The head end 324 of the housing 302 is cooled by means of a fan 326 attached to the housing 302 via a spacer 330. In this embodiment, the fan is also oriented such that the airflow it generates strikes the housing 302, and in particular the head end 324, in an axial direction. A heat sink 328 with several cooling fins is located at a distance between the fan 326 and the head end 324 of the housing 302. This heat sink is attached to the housing 302 to enhance the cooling effect provided by the fan 326.

[0068] In the embodiment of the Fig. 11The electrically operated cooling device is not formed by a fan, but by a Peltier element 332, which, according to the invention, is attached to the outer circumference of the housing 302 in an area located upstream of the first turbomolecular pump stage 314. Peltier elements can also be installed in areas "A", "B", "C" and / or "D" (see the figure below). Fig. 6 ) are provided on housing 302 in order to additionally cool these areas as well.

[0069] In the embodiment of the Fig. 12 The head end 324 of the housing 302 is cooled by four Peltier elements 332. The Peltier elements 332 are attached to a holder 334 and extend into respective blind bores 336 formed in the head end 324 of the housing 302.

[0070] In the embodiment of the Fig. 13Ultimately, the mounting 334 is designed to support not only two Peltier elements 332, but also two heating elements 340, with both the Peltier elements 332 and the heating elements 340 extending into blind bores 336 formed in the head end 324 of the housing 302. The heating elements 340 allow the pump to be heated during initial factory commissioning, thus ensuring that gas molecules are released from surfaces inside the pump by desorption, thereby pre-emptively performing a large part of the gas desorption. The Peltier elements 332, on the other hand, 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.

[0071] For the sake of good order, it should be noted at this point that with reference to the Figs. 7 to 13Specific arrangements of electrically operated cooling devices have been explained; however, as has already been partly noted previously, the respective cooling devices can also be arranged and aligned as needed to cool one or more of the areas "A", "B", "C" and / or "D". Reference symbol list

[0072] 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 side 143 Screw 145 Bearing cover 147 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 or217 Catching bearing 219 Motor stator 219 Intermediate space 221 Wall 223 Labyrinth seal 300 Turbomolecular vacuum pump 302 Housing 304 First pump inlet 306 Second pump inlet 308 Third pump inlet 310 Pump outlet 312 Forevacuum pump 314 First turbomolecular pump stage 316 Second turbomolecular pump stage 318 Third turbomolecular pump stage 320 Holweck pump stage 322 Rotor shaft 324 Head end 326 Fan 328 Heat sink 330 Spacer 332 Peltier element 334 Mounting bracket 336 Blind hole 340 Heating element.

Claims

1. A pump system comprising a turbomolecular vacuum pump (300) which comprises: - a housing (302) having at least one pump inlet (304, 306, 308) and one pump outlet (310); - a first pump mechanism, which is driven by a rotor shaft (322) and which has at least one turbomolecular pump stage (314, 316, 318), in the housing (302); - a second pump mechanism, which is located downstream of the first pump mechanism and which is driven by the rotor shaft (322), in the housing (302), said second pump mechanism operating according to a different pumping principle than the first pump mechanism; wherein, for the joint conveying of a process gas from the pump inlet (304, 306, 308) to the pump outlet (310), the first and the second pump mechanism are arranged along the rotor shaft (322) and are disposed in the axial direction between the at least one pump inlet (304, 306, 308) and the pump outlet (310); and wherein, for the cooling of the housing (302), the pump system further comprises at least one electrically operated cooling device (326, 332) which is located in the axial direction with respect to the second pump mechanism on the side of the second pump mechanism that faces the first pump mechanism, characterized in that 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 that faces the first pump inlet (304); and in that the at least one electrically operated cooling device (326, 332) comprises at least one Peltier element (332) which is fastened to the outer side of the housing (302).

2. A pump system according to claim 1, wherein the first pump mechanism comprises a first turbomolecular pump stage (314) and, downstream thereof, at least a second turbomolecular pump 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 pump stage (316) on the side of the at least one second turbomolecular pump stage (316) that faces the first turbomolecular pump stage (314).

3. A pump system according to claim 2, wherein the housing (302) has a first pump inlet (304) and at least a second pump inlet (306) which is disposed in the axial direction between the first turbomolecular pump stage (314) and the second turbomolecular pump 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) that faces the first pump inlet (304).

4. A pump system according to claim 2 or 3, wherein the first pump mechanism further comprises at least a third turbomolecular pump stage (318) which is disposed in the axial direction between the first turbomolecular pump stage (314) and the second turbomolecular pump 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 pump stage (318) on the side of the third turbomolecular pump stage (318) that faces the first pump inlet (304).

5. A pump system according to claim 4, wherein the housing (302) further has at least a third pump inlet (308) which is disposed in the axial direction between the first turbomolecular pump stage (314) and the third turbomolecular pump 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) that faces the first pump inlet (304).

6. A 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, which is in the ultra-high vacuum range, is adopted in the interior of the turbomolecular vacuum pump (300) during the operation, wherein the final pressure that is adopted is preferably less than 10-8 mbar, in particular less than 10-9 mbar, and particularly preferably less than 10-10 mbar.

7. A pump system according to at least one of the preceding claims, wherein all the pump inlets (304, 306, 308) open radially into the interior of the housing (302); or wherein all the pump inlets (304, 306, 308) except for 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) that is disposed opposite the second pump mechanism.

8. A pump system according to at least one of the preceding claims, wherein the at least one electrically operated cooling device (326, 332) comprises at least one fan (326) generating an air flow.

9. A pump system according to claim 8, wherein at least one fan (326) is oriented such that the air flow generated by it impacts the housing (302) in a radial direction or in an axial direction.

10. A pump system according to claim 8 or 9, wherein at least one fan (326) is oriented such that the air flow generated by it brushes the housing (302) in a radial direction or in an axial direction while forming a boundary layer flow.

11. A pump system according to claim 8, 9 or 10, wherein the housing (302) has at least one heat sink (328) which preferably comprises a plurality of cooling fins, wherein the heat sink (328) is exposed to the air flow generated by the at least one fan (326).

12. A pump system according to at least one of the claims 8 to 11, wherein at least one fan (326) is directly fastened to the housing (302); and / or wherein at least one fan (326) is indirectly fastened to the housing (302), preferably by means of a spacer device (330); and / or wherein at least one fan (326) is fastened to a support structure which is independent of the housing (302).

13. A pump system according to claim 1, wherein the housing (302) has at least one blind bore (336) which receives at least one Peltier element (332), wherein it is preferably provided that the housing (302) has a plurality of blind bores (336) which extend axially into the interior of the housing wall, starting from the head end (324) of the housing (302) that is disposed opposite the second pump mechanism, and which each receive at least one Peltier element (332).

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