Turbo-molecular pump

Abstract

To provide a turbo-molecular pump having a means for lowering the temperature of a rotor.SOLUTION: The pump comprises a housing (340), a plurality of turbomolecular pump stages (312), at least one auxiliary pump stage (332) arranged downstream of the turbomolecular pump stages, a flow path (350) for a gas to be pumped, which flow path is partially defined by elements (314, 316, 374) having a pumping action of the turbomolecular pump stages and of the auxiliary pump stages, and a cooling element (360) which projects into the flow path upstream of the auxiliary pump stages and is configured to transfer a larger amount of heat to the housing than the respective elements having a pumping action of the turbomolecular pump stages for a predetermined period of time.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a turbomolecular pump comprising a housing, a plurality of turbomolecular pump stages and at least one auxiliary pump stage arranged downstream of the turbomolecular pump stages. [Background technology]

[0002] Turbomolecular pumps are typically operated at rotor speeds in the range of more than 10,000 revolutions per minute. The pumping elements of a turbomolecular pump, i.e., the rotor and stator, typically do not have good thermal contact with the housing of the turbomolecular pump, resulting in significant rotor temperature increases during operation. Rotor temperatures of over 90°C can be reached. Persistently high rotor temperatures can cause damage within the turbomolecular pump, shortening its service life. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION An object of the present invention is to provide a turbomolecular pump having means for reducing the temperature of the rotor. [Means for solving the problem]

[0004] This problem is solved by a turbomolecular pump having the features of claim 1. Advantageous developments of the invention are described in the dependent claims, the description and the drawings.

[0005] The turbomolecular pump includes a housing, a plurality of turbomolecular pump stages, and at least one auxiliary pump stage downstream of the turbomolecular pump stages. The turbomolecular pump further includes a flow path for the gas to be pumped. The flow path is defined in part by the pumping elements of the turbomolecular pump stages and the auxiliary pump stage.

[0006] The turbomolecular pump further includes a cooling element projecting into the flow path upstream of the auxiliary pump stage, the cooling element configured to transfer a greater amount of heat to the turbomolecular pump stage housing than the pumping elements of each turbomolecular pump stage during a predetermined period of time.

[0007] The flow path of the gas to be pumped through the turbomolecular pump, i.e., through multiple turbomolecular pump stages, through at least one auxiliary pump stage, and through the transition region between these stages, can be geometrically determined by the specific dimensions of the pumping elements, for example, by the respective inner and outer diameters of the blades on the stationary or rotating vanes that can form the pumping elements in the turbomolecular pump stages. The flow path through the turbomolecular pump can be determined as a volume with a favorable direction for the gas flow of the gas to be pumped, and therefore corresponds to the internal volume of a pipe or hose with the stated flow direction. In other words, the pumping elements of each pump stage of the turbomolecular pump define the flow path of the gas to be pumped in each section where the pumping elements of this pump stage are present.

[0008] Since the cooling element transfers more heat to the housing than the pumping elements of the respective turbomolecular pump stages during a given period, the cooling element is better thermally coupled to the housing of the turbomolecular pump than the pumping elements of the respective turbomolecular pump stages, in particular the stator vanes. The better thermal coupling can be achieved by the choice of material for the cooling element and its geometrical configuration. The cooling element therefore has properties that allow it to transfer more heat to the housing than the pumping elements of the respective turbomolecular pump stages during the same period, but with comparable dimensions.

[0009] During operation of the turbomolecular pump, the cooling element may, on the one hand, be in contact with the "cold" surfaces of the turbomolecular pump, i.e., surfaces and housing that have the operating temperature outside the housing, and thus approximately the ambient temperature, and, on the other hand, be in thermal contact with the hot gas present in the flow path of the turbomolecular pump.

[0010] The cooling element protrudes into the flow path as a so-called obstacle, thereby tapering the flow path at a certain point. Because the cooling element is arranged upstream of an auxiliary pump stage, such as at least one Holweck pump stage and / or at least one side-channel pump stage, the cooling element reduces the temperature of the gas flow in the turbomolecular pump stage due to intensive thermal contact with the housing. This reduces the temperature of the turbomolecular pump stage, and in particular the rotor temperature. Another advantage of the cooling element is that its implementation in the turbomolecular pump requires only relatively small structural changes. The cooling element can be implemented, for example, by reducing the inner diameter of an existing spacer element or an annular throttle.

[0011] According to one embodiment, the cooling element has a larger contact surface with the housing than the pumping elements of each turbomolecular pump stage. Furthermore, the cooling element may be made of a material with a higher thermal conductivity than the material of the pumping elements. A larger contact surface and / or a material with a higher thermal conductivity allows for an optimized heat transfer of the cooling element to the housing within a given construction space for the cooling element.

[0012] According to another embodiment, the cooling element is annularly configured and completely surrounds the flow path of the gas to be pumped, so that the flow path can be completely surrounded by the cooling element, and the structural space available for the cooling element is optimally available for heat transfer from the gas to be pumped via the cooling element to the housing of the turbomolecular pump.

[0013] The cooling element may further comprise two half rings or half disks to completely enclose the flow path of the gas to be pumped. The two half ring or half disk cooling element configuration allows for ease of manufacturing and packaging of the cooling element.

[0014] The pumping elements of the turbomolecular pump stage may have rotor blades with a predetermined outer diameter, and the inner diameter of the cooling element may be smaller than the outer diameter of the rotor blades. In addition to the rotor blades, the pumping elements of the turbomolecular pump stage may also have stator blades, the geometry of which likewise determines the flow path of the gas to be pumped. Since the inner diameter of the cooling element is smaller than the outer diameter of the rotor blades, the inner diameter of the cooling element determines how much the cooling element protrudes into the flow path. The cooling element may be located between the rotor blades and the stator vanes, i.e., within the turbomolecular pump stage, or downstream of the last rotor blade or stator vane, in the transition region leading to the auxiliary pump stage.

[0015] According to another embodiment, the cooling element can be arranged in the region of the pumping element of the turbomolecular pump stage, in which case the cooling element can significantly reduce the temperature of the rotor of the turbomolecular pump, for example due to the small distance between the cooling element and the rotor.

[0016] When the cooling element is arranged in the region of a turbomolecular pump stage, it may be configured as a spacer element between at least two stator vanes of the turbomolecular pump stage. In other words, the spacer element may be configured with respect to its geometry and material to act as a cooling element protruding into the flow path of the turbomolecular pump. This allows the cooling element to be implemented with little effort, since it only has to be substituted for an existing spacer element.

[0017] Furthermore, the cooling element may form part of at least one stator vane of the turbomolecular pump stage. Such a stator vane having a cooling element may, for example, have a reinforcement portion that protrudes into the flow path and at least partially covers a normally open area within the stator vane. Again, the cooling element can be implemented with relatively little effort, since it only requires modifying an existing stator vane.

[0018] Furthermore, the cooling elements may be configured as cooling ribs or cooling fins, which may improve or optimize the thermal contact between the hot gas present in the flow path and the surface of the cooling element.

[0019] Furthermore, the cooling element may be configured as a perforated orifice located between at least two stator vanes of the turbomolecular pump stage or alternatively downstream of the pumping element of the turbomolecular pump stage. Such a perforated orifice maximizes thermal contact between the gas to be pumped and the housing of the turbomolecular pump via the cooling element. Furthermore, the openings in the perforated orifice may be configured in such an embodiment so that the turbomolecular pump reaches a desired pumping speed with the turbomolecular pump stage. The desired pumping speed is defined by a specific number of liters / second of gas to be pumped.

[0020] According to another embodiment, the cooling element is configured as an annular throttle arranged in the transition region between the spatial region in which the turbomolecular pump stage is located and the auxiliary pump stage. The annular throttle as a cooling element can thus be located before the inlet region of the auxiliary pump stage for the gas to be pumped. The inlet region of the auxiliary pump stage can be connected to the outlet region of the turbomolecular pump stage so that a transition region is located between the outlet region of the turbomolecular pump stage and the inlet region of the auxiliary pump stage. In the transition region, the annular throttle forms a so-called taper that at least partially covers the inlet region of the auxiliary pump stage. This allows for intensive thermal contact between the gas to be pumped and the housing via the annular throttle. Furthermore, the cooling element as an annular throttle can be implemented more simply in the transition region than a cooling element, for example, between the rotor blades and the stator blades of a turbomolecular pump stage.

[0021] The annular restriction may at least partially cover the open inlet region of the auxiliary pump stage. Therefore, in such an embodiment, a positive internal pressure in the inlet region of the auxiliary pump stage may be maintained despite the annular restriction being located upstream of the auxiliary pump stage. The coverage by the annular restriction relates to a radial direction in the turbomolecular pump, which extends perpendicular to the rotational axis of the rotor of the turbomolecular pump. The rotational axis of the rotor, in turn, defines an axial direction in the turbomolecular pump.

[0022] Furthermore, the annular throttle may completely cover the open inlet area of ​​the auxiliary pump stage in the radial direction of the turbomolecular pump. It has been found that the rotor temperature can be significantly reduced by such an annular throttle configuration. Despite the annular throttle completely covering the inlet area in the radial direction, the inlet area of ​​the auxiliary pump stage remains open in the axial direction, so that the gas to be pumped can enter the auxiliary pump stage with a sufficient volumetric flow rate of liters per second.

[0023] The annular throttle may have an inner diameter smaller than the outer diameter of the rotor element of the auxiliary pump stage. In this case, the annular throttle has a so-called negative inner curvature in the radial direction relative to the inlet region of the auxiliary pump stage. It has been found that such a configuration allows the rotor temperature to be reduced most significantly. Moreover, in the axial direction, the inlet region of the auxiliary pump stage has a width appropriate for substantially maintaining the total pumping speed of the turbomolecular pump without significantly impairing the flow characteristics of the gas to be pumped, compared to a turbomolecular pump without such an annular throttle.

[0024] The cooling element may be fabricated from aluminum and may have an axial height in the range of 2 mm to 3 mm. Such a configuration may be used in all of the above-described embodiments. Aluminum cooling elements with such dimensions are relatively easy to manufacture.

[0025] The invention will now be described on the basis of exemplary advantageous embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0026] [Figure 1] 1 shows a perspective view of a turbomolecular pump. [Figure 2] The turbomolecular pump of FIG. 1 is shown in bottom view. [Figure 3] 3 shows a cross-sectional view of a turbomolecular pump taken along the section line AA shown in FIG. 2. [Figure 4] 3 shows a cross-sectional view of the turbomolecular pump taken along the section line BB shown in FIG. 2. [Figure 5] 3 shows a cross-sectional view of the turbomolecular pump taken along the section line CC shown in FIG. 2. [Figure 6] 1 shows a further cross-sectional view of a turbomolecular pump. [Figure 7] 7A-7C illustrate various embodiments of the arrangement of cooling elements in the turbomolecular pump of FIG. 6. [Figure 8] FIG. 8 is a diagram showing gas flow dependent rotor temperature for various inner diameters of the annular restrictor in the flow path of the turbomolecular pump of FIGS. 6 and 7; DETAILED DESCRIPTION OF THE INVENTION

[0027] The turbomolecular pump 111 shown in Figure 1 has a pump inlet 115 surrounded by an inlet flange 113. A recipient (not shown) may be connected to the pump inlet 115 in a manner known per se. Gas coming from the recipient can be drawn in from the recipient via the pump inlet 115 and pumped through the pump to a pump outlet 117. An auxiliary vacuum pump, such as a rotary vane pump, may be connected to the pump outlet 117.

[0028] The inlet flange 113 forms the upper end of a housing 119 of the vacuum pump 111 in the orientation of the vacuum pump according to Fig. 1. The housing 119 has a lower part 121. Arranged laterally on the lower part 121 is an electronics housing 123. The electronics housing 123 accommodates electrical and / or electronic components of the vacuum pump 111, for example for operating an electric motor 125 (see also Fig. 3) arranged in the vacuum pump. The electronics housing 123 is provided with a number of connections 127 for accessories. Furthermore, a data interface 129 (for example according to the RS485 standard) and a current supply connection 131 are arranged on the electronics housing 123.

[0029] There are also turbomolecular pumps that do not have this type of attached electronics housing, but are connected to external drive electronics.

[0030] The housing 119 of the turbomolecular pump 111 is provided with a ventilation inlet 133, particularly in the form of a ventilation valve. The vacuum pump 111 can be vented via the ventilation inlet 133. A seal gas connection 135 (also called a purge gas connection) is also arranged in the region of the lower part 121. A purge gas can be introduced into a motor chamber 137 via the seal gas connection 135 to protect the electric motor 125 (see, for example, FIG. 3 ) from the gas pumped by the pump. The electric motor 125 is accommodated in the motor chamber 137 of the vacuum pump 111. Two coolant connections 139 are also arranged in the lower part 121. One coolant connection serves as a coolant inlet and the other as an outlet. A coolant can be introduced into the vacuum pump for cooling purposes. The other turbomolecular vacuum pump present (not shown) is operated exclusively air-cooled.

[0031] The underside 141 of the vacuum pump can be used as a base, so that the vacuum pump 111 can be operated in a vertical position relative to the underside 141. Moreover, the vacuum pump 111 can be fixed to the recipient via the inlet flange 113 and thus operated in a suspended state, so to speak. Furthermore, the vacuum pump 111 can be configured so that it can be operated even when oriented in a different direction than that shown in FIG. 1. It is also possible to configure the vacuum pump in such a way that the underside 141 can be positioned not only facing downwards, but also facing sideways or upwards. In this case, in principle, any angle is conceivable.

[0032] In particular, other turbomolecular vacuum pumps (not shown) that exist, which are larger than the pump shown, cannot be operated in a vertical position.

[0033] 2 further comprises various screws 143. These screws 143 secure components of the vacuum pump, not specifically identified here, to one another. For example, a bearing cover 145 is secured to the lower surface 141.

[0034] Further fastening holes 147 are arranged in the underside 141. Via the fastening holes 147, the pump 111 can be fixed, for example, to a mounting surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), in particular those larger than the pump shown.

[0035] 2 to 5 show a coolant line 148 in which a coolant can be circulated, the coolant being introduced and withdrawn via the coolant connection 139.

[0036] As shown in the cross-sectional views of Figures 3-5, the vacuum pump has multiple process gas pumping stages for pumping process gas acting on a pump inlet 115 to a pump outlet 117.

[0037] A rotor 149 is disposed within the housing 119. The rotor 149 has a rotor shaft 153 that is rotatable about a rotation axis 151.

[0038] The turbomolecular pump 111 has multiple turbomolecular pump stages connected in series to provide a pumping action. Each turbomolecular pump stage has multiple radially extending rotor blades 155 fixed to the rotor shaft 153 and multiple stator vanes 157 arranged between the rotor blades 155 and fixed within the housing 119. In this case, each rotor blade 155 and its adjacent stator vane 157 form one turbomolecular pump stage. The stator vanes 157 are held at a desired axial distance from each other by spacer rings 159.

[0039] The vacuum pump further comprises Holweck pump stages arranged radially inside and outside one another and connected in series to provide a pumping action. There are alternative turbomolecular vacuum pumps (not shown) that do not have Holweck pump stages.

[0040] The rotor of the Holweck pump stage includes a rotor hub 161 disposed on the rotor shaft 153 and two cylindrically sided Holweck rotor sleeves 163, 165 fixed to and supported by the rotor hub 161. The Holweck rotor sleeves 163, 165 are oriented coaxially with respect to the rotation axis 151 and engage radially with one another. Two cylindrically sided Holweck stator sleeves 167, 169 are also provided. The Holweck stator sleeves 167, 169 are likewise oriented coaxially with respect to the rotation axis 151 and engage radially with one another.

[0041] The pumping surfaces of the Holweck pump stages are formed by the side surfaces, i.e., the radially inner and / or outer surfaces of the Holweck rotor sleeves 163, 165 and the Holweck stator sleeves 167, 169. The radially inner surface of the outer Holweck stator sleeve 167 faces the radially outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together with this outer surface forms the first Holweck pump stage following the turbomolecular pump. The radially inner surface of the outer Holweck rotor sleeve 163 faces the radially outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together with this outer surface forms the second Holweck pump stage. The radially inner surface of the inner Holweck stator sleeve 169 opposes the radially outer surface of the inner Holweck rotor sleeve 165, forming a radial Holweck gap 175, and together with this outer surface forms the third Holweck pump stage.

[0042] A radially extending channel may be provided at the lower end of the Holweck rotor sleeve 163. The radially outer Holweck gap 171 is connected to the central Holweck gap 173 via the channel. A further radially extending channel may be provided at the upper end of the inner Holweck stator sleeve 169. The central Holweck gap 173 is connected to the radially inner Holweck gap 175 via the channel. This allows multiple Holweck pump stages that engage with each other in series. A connecting channel 179 that leads to the exhaust port 117 may be provided at the lower end of the radially inner Holweck rotor sleeve 165.

[0043] The pumping surfaces of the Holweck stator sleeves 167, 169 each have a plurality of Holweck grooves that extend axially and spirally around the rotation axis 151. On the other hand, the opposing sides of the Holweck rotor sleeves 163, 165 are smoothly formed and pump gas for operating the vacuum pump 111 forward in the Holweck grooves.

[0044] For the rotatable support of the rotor shaft 153, a rolling bearing 181 is provided in the region of the pump outlet 117 and a permanent magnetic bearing 183 is provided in the region of the pump inlet 115.

[0045] In the region of the rolling bearing 181, the rotor shaft 153 is provided with a conical splash nut 185. The splash nut 185 has an outer diameter that increases towards the rolling bearing 181. The splash nut 185 is in sliding contact with at least one scraping element of the working medium reservoir. In other existing turbomolecular vacuum pumps (not shown), a splash screw may be provided instead of a splash nut. This allows for various configurations to be realised, so that the term "splash tip" is also used in this context.

[0046] The working medium reservoir comprises a number of absorbent discs 187 stacked one above the other, which are impregnated with a working medium, e.g., a lubricant, for the rolling bearings 181.

[0047] During operation of the vacuum pump 111, the working medium is transferred by capillary action from the working medium reservoir via the scraping element to the rotating splash nut 185 and is then forced by centrifugal force along the splash nut 185 towards the increasing outer diameter of the splash nut 185 towards the rolling bearing 181, where it performs, for example, a lubrication function. The rolling bearing 181 and the working medium reservoir are enclosed in the vacuum pump by a trough-like insert 189 and a bearing cover 145.

[0048] The permanent magnet type magnetic bearing 183 has a rotor-side bearing half 191 and a stator-side bearing half 193. Each of these has a ring stack, which consists of multiple rings 195, 197 of permanent magnets stacked one above the other in the axial direction. The ring magnets 195, 197 face each other, forming a radial bearing gap 199, with the rotor-side ring magnet 195 positioned radially outward and the stator-side ring magnet 197 positioned radially inward.

[0049] The magnetic field present in the bearing gap 199 generates a magnetic repulsion force between the ring magnets 195, 197. This repulsion force provides radial support for the rotor shaft 153. The rotor-side ring magnet 195 is supported by a support part 201 of the rotor shaft 153, which surrounds the ring magnet 195 radially outward. The stator-side ring magnet 197 is supported by a support part 203 on the stator side, which extends through the ring magnet 197 and is suspended on radial struts 205 of the housing 119. The rotor-side ring magnet 195 is fixed parallel to the rotation axis 151 by a cover element 207 connected to the support part 203. The stator-side ring magnet 197 is fixed in one direction parallel to the rotation axis 151 by a fixing ring 209 connected to the support part 203 and a fixing ring 211 connected to the support part 203. A disc spring 213 may further be provided between the fixed ring 211 and the ring magnet 197 .

[0050] An emergency or safety bearing 215 is provided within the magnetic bearing. During normal operation of the vacuum pump, the emergency or safety bearing 215 runs free and only engages if the rotor 149 is displaced excessively radially relative to the stator, thereby forming a radial stop for the rotor 149 so that collisions between rotor-side and stator-side structures are prevented. The safety bearing 215 is configured as a non-lubricated rolling bearing and forms a radial gap with the rotor 149 and / or the stator. This gap prevents the safety bearing 215 from engaging during normal pump operation. The radial displacement that the safety bearing 215 engages is dimensioned to be sufficiently large so that the safety bearing 215 does not engage during normal operation of the vacuum pump, and at the same time is sufficiently small so that collisions between rotor-side and stator-side structures are prevented under all circumstances.

[0051] The vacuum pump 111 includes an electric motor 125 that rotates a rotor 149. The rotor 149 forms an armature of the electric motor 125. A rotor shaft 153 of the rotor 149 extends through a motor stator 217. A permanent magnet assembly may be disposed radially outward or embedded in the portion of the rotor shaft 153 that extends through the motor stator 217. An intermediate chamber 219 is disposed between the motor stator 217 and the portion of the rotor 149 that extends through the motor stator 217, and the intermediate chamber 219 has a radial motor gap. Through the motor gap, the motor stator 217 and the permanent magnet assembly may magnetically interact to transmit a driving torque.

[0052] The motor stator 217 is fixed in the housing in a motor chamber 137 provided for the electric motor 125. A seal gas connection 135 allows a seal gas (also called purge gas, which may be, for example, air or nitrogen) to reach the motor chamber 137. The seal gas protects the electric motor 125 against process gases, for example corrosive parts of the process gas. The motor chamber 137 may be evacuated via the pump outlet 117, i.e., a vacuum pressure is applied to the motor chamber 137 at least approximately, which is achieved by an auxiliary vacuum pump connected to the pump outlet 117.

[0053] A so-called labyrinth seal 223, known per se, may further be provided between the rotor hub 161 and the wall 221 that defines the motor chamber 137. This achieves better sealing of the motor chamber 217, in particular with respect to the radially outer Holweck pump stages.

[0054] Figure 6 shows another turbomolecular pump 300 that is essentially similar to the turbomolecular pump 111 previously described and shown in Figures 1 to 5 (see in particular Figures 3 and 6). Thus, the above description of the turbomolecular pump 111 semantically also applies to the turbomolecular pump 300, unless otherwise stated or shown to the contrary.

[0055] Similar to the turbomolecular pump 111, the turbomolecular pump 300 has a rotor 302 that is supported by a magnetic bearing 304 on the high vacuum side and by a ball bearing 306 on the opposite side. The turbomolecular pump 300 further has a turbomolecular region 310 that has four turbomolecular pump stages 312. Each turbomolecular pump stage 312 is associated with a respective rotor blade 314, and each rotor blade 314 is attached to the rotor 302. One stator vane 316 is located between each of the rotor blades 314.

[0056] Downstream of the turbomolecular region 310, the turbomolecular pump 300 includes a transition region 320 and an auxiliary pumping region 330. The auxiliary pumping region 330 includes an auxiliary pumping stage 332 configured as a Holweck pumping stage.

[0057] Due to the high rotational speed of the rotor 302, which is typically well above 10,000 revolutions per minute in turbomolecular pumps, a significant temperature rise occurs in the turbomolecular region 310 during operation of the turbomolecular pump 300. Due to gas friction between the pumping elements of the turbomolecular pump 300, such as the rotor blades 314 and the stator vanes 316, the rotor 302 can heat up, for example, to above 90°C, especially at high gas loads. This is due, inter alia, to the fact that the stator vanes 316 do not have sufficient thermal contact with the housing 340 of the turbomolecular pump 300 to transfer the heat generated from the turbomolecular pump stage 312 to the housing 340.

[0058] The rotor blades 314 are thermally very well insulated from the housing 340 due to the magnetic bearing of the rotor 302 on the high vacuum side of the turbomolecular pump 300, the ball bearing 306, and the high vacuum that exists in the turbomolecular region 310 during operation of the turbomolecular pump 300. Due to this thermal insulation and the high rotational speed of the rotor 302, a temperature rise in the rotor 302 during operation of the turbomolecular pump 300 cannot be prevented or reduced by direct and simple means.

[0059] The turbomolecular pump 300 has a flow path 350 for the gas to be pumped, indicated in principle by the white arrow 350 in Figures 6 and 7. The flow path 350 for the gas to be pumped is defined in part by the pumping elements of the turbomolecular pump stage 312 and the auxiliary or Holweck pump stage 332. In other words, the pumping elements, i.e., the rotor blades 314 and the stator vanes 316, and the pumping elements of the Holweck pump stage 332, in part determine the geometrical course of the flow path 350. The flow path 350 therefore represents a volume within the turbomolecular pump 300 through which the gas to be pumped moves from the intake of the turbomolecular pump 300 to its exhaust. Furthermore, a preferred direction for the movement of the gas to be pumped is associated with the flow path 350, which in this case extends from the high vacuum side of the turbomolecular pump 300 to its exhaust.

[0060] To reduce the rotor temperature during operation of the turbomolecular pump 300, the turbomolecular pump 300 includes a cooling element (see FIG. 7). The cooling element 360 is located upstream of the auxiliary or Holweck pump stage 332 and projects into the flow path 350 of the turbomolecular pump 300. Several possibilities or embodiments for the placement and configuration of the cooling element 360 are shown in FIGS. 7A and 7B.

[0061] In Figure 7A, the cooling element 360 is located in the region 310 of the turbomolecular pump stage 312, or in the transition region 320, immediately below, i.e., downstream of, the last turbomolecular pump stage 312, immediately following the last rotor blade 314. In contrast, Figure 7B shows an arrangement of the cooling element 360 located immediately prior to the inlet region 370 of the auxiliary or Holweck pump stage 332.

[0062] Figure 7A shows an enlarged partial view of the turbomolecular pump 300 of Figure 6, including a portion of the turbomolecular region 310 and the transition region 320. The four rotor blades 314 of each of the turbomolecular pump stages 312 are numbered 1 through 4.

[0063] In a first embodiment of a cooling element 360, shown in the upper portion of FIG. 7A and labeled 362, the cooling elements 360, 362 form part of the stator vane 316 shown in FIG. 6 and thus protrude into the flow path 350. The cooling elements 360, 362 are annular and completely surround the flow path 350 of the gas to be pumped. Furthermore, the cooling elements 360, 362 have a larger contact surface with the housing 340 than the other stator vane 316-2, which does not have the cooling element 360. Thus, on the one hand, the cooling elements 360, 362 are in contact, and thus in thermal contact, with surfaces of the turbomolecular pump 300 that are at approximately the ambient temperature, i.e., the temperature of the housing of the turbomolecular pump 300 during operation. On the other hand, because the cooling elements 360, 362 protrude into the flow path 350, they are also in thermal contact with the hot gas in the flow path 350 during operation. This also applies to the embodiments of the cooling element 360 described below. Additionally, the cooling elements 360 may be configured as cooling ribs or cooling fins, which improve the thermal contact with the hot gas.

[0064] In a first embodiment of the cooling elements 360, 362, the cooling elements 360, 362 form a reinforcing portion of the stator vane 316-1. Thus, compared to the stator vane 316-2, which does not have the cooling element 360, the cooling element 360 protrudes into the flow path 350 as a reinforcing portion in the outer region of the stator vane 316-1. In the first embodiment, the cooling elements 360, 362 may be arranged at different axial positions, i.e., at different pump stages of the turbomolecular pump 300. In the example of FIG. 7A , one cooling element 360, 362 each is arranged between the rotor blades 314 numbered 1 and 2 and / or between the rotor blades 314 numbered 3 and 4. For clarity, a stator blade 317 is shown schematically as being obliquely positioned between the rotor blades 314 numbered 1 and 2 relative to the stator vane 316-1.

[0065] In short, due to their geometry and their material, e.g., aluminum, the cooling elements 360, 362 have improved thermal contact with the housing 340 compared to the vane 316-2 without the cooling element, thereby allowing the cooling elements 360, 362 to transfer a greater amount of heat to the housing 340 over a given period of time than the respective pumping elements of the turbomolecular pump stage 312, i.e., the vane 316-2 without the cooling element. This is equally true for the other embodiments of the cooling element 316, labeled 364 or 366, described below.

[0066] In another embodiment not shown, the cooling element 360 may form a spacer ring between at least two of the stator vanes 316 of the turbomolecular pump stage 312. In this embodiment, the cooling element protrudes into the flowpath 350 in an axial region of one of the rotor blades 314 and is therefore located at approximately the same axial height as the corresponding rotor blade 314.

[0067] In another embodiment of the cooling element 360 shown in the lower part of Figure 7A, the cooling element 360 is configured as a perforated orifice 364. The perforated orifice 364 is arranged downstream of the pumping elements 314, 316 of the turbomolecular pump stage 312. The perforated orifice 364 is therefore located approximately in the transition region 320 between the turbomolecular region 310 and the auxiliary pump region 330.

[0068] In contrast, in the embodiment shown in FIG. 7B, the cooling element 360 is configured as an annular throttle 366. The annular throttle 366 is located in the transition region 320 just before the inlet region 370 of the auxiliary or Holweck pump stage 332. In a radial direction extending perpendicular to an axial direction defined by the rotational axis of the rotor 302, the inlet region 370 of the Holweck pump stage 332 has an inner diameter 372. The inner diameter 372 represents the radial distance over which the inlet region 370 of the Holweck pump stage opens radially. Thus, as viewed along the rotational axis of the rotor 302, the inner diameter 372 defines an annular plane between the annular throttle 366 and a rotor element 374 of the Holweck pump stage 332. Within this annular plane, the inlet region 370 of the Holweck pump stage 332 is not covered by the cooling element 360 or the annular throttle 366 if the inner diameter 372 is greater than zero.

[0069] The aforementioned embodiments of the cooling element 360 may be combined with one another in any way in the turbomolecular pump 300, i.e., one or more cooling elements 360 corresponding to the aforementioned embodiments may be implemented in the turbomolecular pump 300. Alternatively, only a single cooling element 360 each may be used.

[0070] 8 shows a diagram in which the measured rotor temperature (°C) is plotted against the gas load (sccm) (standard cubic centimeters per minute) generated at the inlet of the turbomolecular pump 300. The measurement curve in FIG. 8 was obtained for nitrogen as the gas to be pumped at a pre-vacuum pressure of 2 mbar. Furthermore, the turbomolecular pump 300 was operated at a rotor 302 rotation frequency of 820 Hz (see FIG. 6).

[0071] The various measurement curves 380-388 shown in Figure 8 have different internal diameters 372 (see Figure 7B). Measurement curve 380 was taken with an internal diameter 372 of 9.6 mm, which corresponds to a configuration of turbomolecular pump 300 without annular restrictor 360. This configuration with maximum internal diameter 372 and no annular restrictor 366 is used as a reference for measurements with various internal diameters of annular restrictor 366, where the internal diameter 372 is gradually reduced until it completely covers the inlet area 370 of Holweck pump stage 332.

[0072] As can be seen based on the measurement curve 380, at a maximum internal displacement of 9.6 mm and a gas load of 150 sccm, the rotor temperature is about 75° C. During operation of the turbomolecular pump 300, the rotor temperature decreases as the gas load decreases, so that at a gas load of about 20 sccm, the rotor temperature is only about 65° C.

[0073] For measurement curve 382, ​​turbomolecular pump 300 was provided with cooling element 360 in the configuration of annular restrictor 366 (see FIG. 7B), specifically with an inner diameter of annular restrictor 366 having an inner diameter 372 of 4 mm. For other measurement curves 384 and 386, the inner diameter was reduced to 2 mm or 0 mm by shortening the inner diameter of annular restrictor 366, respectively. In the embodiment for measurement curve 386, annular restrictor 366 almost completely covers the inlet area 370 of Holweck pump stage 332 in the radial direction.

[0074] In contrast, in the embodiment for measurement curve 388, the inner diameter 372 is −5 mm, so that the annular throttle 366 completely covers the inlet area 370 of the Holweck pump stage 332 and protrudes radially into the area of ​​the rotor element 374 (see FIG. 7B) of the Holweck pump stage 332. In other words, in the embodiment for measurement curve 388, the inner diameter of the annular throttle 366 is smaller than the outer diameter of the rotor element 374 of the Holweck pump stage 332.

[0075] As can be seen based on measurement curves 382 through 388 in FIG. 8 , the presence of the annular restriction 366 generally reduces rotor temperature across the entire range of gas loads measured. This can be seen based on curve 382, ​​which already lies below reference curve 380 across the entire measurement range of gas loads at 4 mm inner diameter 372. Reducing inner diameter 372 to 2 mm (curve 284) further reduces rotor temperature across the entire measurement range, while further reducing inner diameter 372 to 0 mm further reduces rotor temperature, achieving a rotor temperature slightly above 50°C at a gas load of 20 sccm (see curve 386). Further reducing the inner diameter of cooling restriction 366 to a coverage of -5 mm inner diameter 372 finally results in a reduction in rotor temperature only at gas loads significantly above 50 sccm (see measurement curve 388).

[0076] Overall, measurement curves 382 through 388 show that cooling element 360 in the form of annular restriction 366 can significantly reduce rotor temperatures during operation of cooling element 360, as compared to measurement curve 380. This is equally true for the alternative embodiment of cooling element 360 described in connection with FIG. 7A.

[0077] That is, by simultaneously measuring the pumping speed of the turbomolecular pump 300 while obtaining the measurement curves 380 to 388 in FIG. 8 , it was found that the reduction in pumping speed was negligible when the annular restrictor 366 was present, even when the inner diameter 372 was 0 mm (curve 386 in FIG. 8 ). Even at an inner diameter of -5 mm (curve 388 in FIG. 8 ), the pumping speed was reduced by only about 10% at a relatively high inlet pressure of 0.01 mbar. At the same time, in the embodiment with the annular restrictor 366 inner diameter 372 of -5 mm (corresponding to curve 388 in FIG. 8 ), a slight increase in power consumption of the turbomolecular pump 300 was observed at higher gas loads, while in the embodiment with the annular restrictor 366 inner diameter 300 of 0 mm or greater, no increase in power consumption of the turbomolecular pump 300 was observed. [Explanation of symbols]

[0078] 111 Turbomolecular pump 113 Intake flange 115 Pump intake 117 Pump exhaust port 119 Housing 121 Lower part 123 Electronics Housing 125 electric motor 127 Accessory Connection 129 Data Interface 131 Current supply connection 133 Ventilation intake 135 Seal gas connection 137 Motor Room 139 Coolant Connection 141 Bottom surface 143 Screw 145 Bearing cover 147 Fixed hole 148 Coolant line 149 Rotor 151 Rotation axis 153 rotor shaft 155 Moving blade 157 Stator blade 159 Spacer ring 161 rotor hub 163 Holbeck Rotor Sleeve 165 Holbeck Rotor Sleeve 167 Holbeck Sterling Sleeve 169 Holbeck Sterling Sleeve 171 Holbeck Gap 173 Holbeck Gap 175 Holbeck Gap 179 Connection Channels 181 Rolling bearings 183 Permanent magnet type magnetic bearing 185 Splash Nut 187 discs 189 Insert 191 Rotor side bearing half 193 Stator side bearing half 195 Ring Magnet 197 Ring Magnet 199 Bearing clearance 201 Support part 203 Support part 205 Radial Struts 207 Cover Elements 209 Support Ring 211 Fixing ring 213 Disc spring 215 Emergency bearings or safety bearings 217 Motor Stator 219 Intermediate Room 221 Wall section 223 Labyrinth Seal 300 Turbomolecular Pump 302 Rotor 304 Magnetic Bearings 306 Ball bearing 310 Turbomolecular Region 312 Turbomolecular pump stage 314 Moving blade 316 Stator blade 316-1 Stator vanes with cooling elements 316-2 Stator blades without cooling elements 317 Stator Blade 320 Transition Zone 330 Auxiliary Pump Area 332 Auxiliary pump stage or Holbeck pump stage 340 Housing 350 Flow path of gas to be pumped 360 Cooling Element 362 Stator blade reinforcement area 364 Holed drawing 366 Annular aperture 370 Inlet area of ​​Holweck pump stage 372 Inside 374 Rotor elements of Holweck pump stage 380 Rotor temperature reference curve 382 Rotor temperature measurement curve, inner diameter 4 mm 384 Rotor temperature measurement curve, inner diameter 2 mm 386 Rotor temperature measurement curve, inner diameter 0 mm 388 Rotor temperature measurement curve, inner diameter -5mm

Claims

1. In a turbomolecular pump (300), a housing (340); a plurality of turbomolecular pump stages (312); at least one auxiliary pump stage (332) disposed downstream of the turbomolecular pump stage (312); a flow path (350) for the gas to be pumped, established in part by the pumping elements (314, 316, 374) of the turbomolecular pump stage (312) and the auxiliary pump stage (332); a cooling element (360) projecting into the flow path (350) upstream of the auxiliary pump stage (332) and configured to transfer a greater amount of heat to the housing (340) than the respective pumping elements (314, 316) of the turbomolecular pump stage (312) during a predetermined period of time; A turbomolecular pump (300) comprising:

2. 2. The turbomolecular pump (300) of claim 1, wherein the cooling element (360) has a larger contact surface with the housing (340) than the pumping elements (314, 316) of each turbomolecular pump stage (312).

3. 3. The turbomolecular pump (300) of claim 1 or 2, wherein the cooling element (360) is annularly shaped and completely surrounds the flow path (350) of the gas to be pumped.

4. The turbomolecular pump (300) of claim 3, wherein the cooling element (360) comprises two half rings or half disks.

5. The pumping elements (314, 316) of the turbomolecular pump stage (312) include rotor blades (314) having a predetermined outer diameter; The turbomolecular pump (300) of any one of claims 1 to 4, wherein an inner diameter (360) of the cooling element (360) is smaller than an outer diameter (314) of the rotor blades (314).

6. 6. The turbomolecular pump (300) according to any one of claims 1 to 5, wherein the cooling element (360) is arranged in the region of the pumping elements (314, 316) of the turbomolecular pump stage (312).

7. The turbomolecular pump (300) of claim 6, wherein the cooling element (360) is configured as a spacer element (362) between at least two stator vanes (316) of the turbomolecular pump stage (312).

8. The turbomolecular pump (300) of claim 6 or 7, wherein the cooling element (360) forms part of at least one stator vane (316) of the turbomolecular pump stage (312).

9. The turbomolecular pump (300) according to any one of claims 6 to 8, wherein the cooling elements (360) are configured as cooling ribs or cooling fins.

10. 10. The turbomolecular pump (300) according to any one of claims 6 to 9, wherein the cooling element (360) is configured as a perforated throttle (364) arranged between at least two stator vanes (316) of the turbomolecular pump stage (312) or downstream of the pumping element (314, 316) of the turbomolecular pump stage (312).

11. 11. The turbomolecular pump (300) according to claim 6, wherein the cooling element (360) is configured as an annular throttle (366) arranged in a transition region (320) between a spatial region (310) in which the turbomolecular pump stage (312) is located and the auxiliary pump stage (332).

12. The turbomolecular pump (300) of claim 11, wherein the annular throttle (366) at least partially covers the open inlet region (370) of the auxiliary pump stage (332).

13. 13. The turbomolecular pump (300) of claim 12, wherein the annular throttle (366) completely covers the open inlet area (370) of the auxiliary pump stage (332) in the radial direction of the turbomolecular pump (300).

14. The turbomolecular pump (300) of claim 13, wherein the annular throttle (366) has an inner diameter that is smaller than an outer diameter of the rotor element (374) of the auxiliary pump stage (332).

15. 15. The turbomolecular pump (300) of any one of claims 1 to 14, wherein the cooling element (360) is made from aluminum and has an axial height in the range of 2 mm to 3 mm.

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