Turbomolecular 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 Art

[0002] Turbomolecular pumps are normally operated at rotor speeds in the range exceeding 10000 revolutions per minute. Since the elements that provide the pumping action of a turbomolecular pump, namely the rotor and the stator, usually do not have good thermal contact with the housing of the turbomolecular pump, a significant temperature increase of the rotor occurs during operation of the turbomolecular pump. Rotor temperatures of 90°C or higher are reached. A permanently high rotor temperature can cause damage within the turbomolecular pump, which can shorten the service life. Summary of the Invention Problem to be Solved by the Invention

[0003] An object of the present invention is to provide a turbomolecular pump having a means for reducing the temperature of the rotor. Means for Solving the Problem

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

[0005] The turbomolecular pump comprises a housing, a plurality of turbomolecular pump stages, and at least one auxiliary pump stage arranged downstream of the turbopump stages. Furthermore, the turbomolecular pump has a flow path for the gas to be pumped. The flow path is partially defined by the pumping elements of the turbomolecular pump stages and the auxiliary pump stages.

[0006] Furthermore, the turbomolecular pump has a cooling element that protrudes into the flow path upstream of the auxiliary pump stage. The cooling element is configured to transfer a greater amount of heat to the turbomolecular pump stage housing than the elements that contribute to the pumping action of each turbomolecular pump stage for a predetermined period of time.

[0007] The flow path of the gas to be pumped through the turbomolecular pump, that is, through multiple turbomolecular pump stages, through at least one auxiliary pump stage, and through the transition regions between these stages, may be geometrically defined by specific dimensions of the pumping elements, for example, by the inner and outer diameters of the blades provided on the stator or rotor vanes that can form the pumping elements within the turbomolecular pump stages. The flow path through the turbomolecular pump may be defined as a volume having a favorable direction for the gas flow of the gas to be pumped, and therefore corresponds to the volume inside a pipe or hose having the described 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 portion of that pump stage where the pumping elements exist.

[0008] Since the cooling element transfers more heat to the housing than the elements responsible for the pumping action of each stage of the turbomolecular pump for a given period of time, a better thermal coupling occurs between the cooling element and the turbomolecular pump housing than between the cooling element and the elements responsible for the pumping action of each stage of the turbomolecular pump, particularly the stator vanes. This better thermal coupling can be achieved through the selection of the material of the cooling element and its geometric configuration. Therefore, the cooling element has properties that allow it to transfer more heat to the housing for the same period of time than the elements responsible for the pumping action of each stage, which have comparable dimensions.

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

[0010] Since the cooling element protrudes into the flow path as a so-called obstruction, the cooling element forms a tapered flow path in a given portion. Since the cooling element is located upstream of an auxiliary pump stage having, for example, at least one Holbeck pump stage and / or at least one side channel pump stage, the cooling element lowers the temperature of the gas flow within the turbomolecular pump stage based on concentrated thermal contact with the housing. This lowers the temperature of the turbomolecular pump stage, and in particular the rotor temperature. The cooling element further implements this within the turbomolecular pump. Ruta An advantage is that it requires relatively small structural changes. The cooling element can be implemented, for example, by reducing the inner diameter of an existing spacer element or annular throttling.

[0011] According to one embodiment, the cooling element has a contact surface with the housing that is larger than that of the elements that perform the pumping action of each stage of the turbomolecular pump. Furthermore, the cooling element may be made of a material having a higher thermal conductivity than the material of the elements that perform the pumping action. A larger contact surface and / or a material with higher thermal conductivity can optimize the heat transfer of the cooling element to the housing within a given structural space for the cooling element.

[0012] According to another embodiment, the cooling element is formed in an annular shape and completely encloses the flow path of the gas to be pumped. Thus, since the flow path can be completely surrounded by the cooling element, the structural space present for the cooling element can be optimally utilized for heat transfer from the gas to be pumped through the cooling element to the housing of the turbomolecular pump.

[0013] The cooling element may have two additional half-rings or half-disks to completely enclose the flow path of the gas to be pumped. This configuration of the cooling element, consisting of two half-rings or half-disks, facilitates the manufacturing and implementation of the cooling element.

[0014] The elements that perform the pumping action 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 elements that perform the pumping action of the turbomolecular pump stage may also have stator blades, and the geometry of the stator blades similarly sets 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 extent to which the cooling element protrudes into the flow path is predetermined by the inner diameter of the cooling element. The cooling element may be located between the rotor blades and the stator blades, i.e., within the turbomolecular pump stage, or in a transition region downstream of the last rotor blade or stator blade that leads to the auxiliary pump stage.

[0015] In another embodiment, the cooling element may be positioned in the region of the element that performs the pumping action of the turbomolecular pump stage. In this case, the cooling element can significantly reduce the temperature of the rotor of the turbomolecular pump, for example, based on a small distance between the cooling element and the rotor.

[0016] When the cooling element is positioned in the region of the 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 for implementation of the cooling element with minimal effort, as it only requires replacing 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 have, for example, a reinforcing 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, as it only requires modifying an existing stator vane.

[0018] Furthermore, the cooling element may be configured as a cooling rib or cooling fin. Such a configuration of the cooling element can improve or optimize the thermal contact between the high-temperature gas present in the flow path and the surface of the cooling element.

[0019] Furthermore, the cooling element may be configured as a perforated throttling positioned between at least two stator vanes of the turbomolecular pump stage or, alternatively, downstream of the element that performs the pumping action of the turbomolecular pump stage. Such a perforated throttling maximizes the thermal contact between the gas to be pumped and the housing of the turbomolecular pump via the cooling element. Moreover, in such embodiments, the opening in the perforated throttling may be configured so that the turbomolecular pump reaches a desired pumping speed by the turbomolecular pump stage. The desired pumping speed is defined by a specific number of gases to be pumped (liters / second).

[0020] In another embodiment, the cooling element is configured as an annular throttling positioned in the transition region between the space region where the turbomolecular pump stage is located and the auxiliary pump stage. Thus, the annular throttling as a cooling element may be positioned in front of the intake region of the auxiliary pump stage for the gas to be pumped. The intake region of the auxiliary pump stage may be connected to the exhaust region of the turbomolecular pump stage, such that the transition region is located between the exhaust region of the turbomolecular pump stage and the intake region of the auxiliary pump stage. In the transition region, the annular throttling forms a so-called taper that at least partially covers the intake region of the auxiliary pump stage. This allows for concentrated thermal contact between the gas to be pumped and the housing via the annular throttling. Furthermore, the cooling element as an annular throttling can be implemented in the transition region more easily than, for example, a cooling element between the rotor and stator blades of the turbomolecular pump stage.

[0021] The annular throttling may at least partially cover the open intake area of ​​the auxiliary pump stage. Therefore, in such embodiments, positive inlet clearance within the intake area of ​​the auxiliary pump stage can be maintained even though the annular throttling is located upstream of the auxiliary pump stage. The covering by the annular throttling relates to the radial direction within the turbomolecular pump, extending perpendicular to the rotation axis of the rotor of the turbomolecular pump. On the other hand, the rotation axis of the rotor defines the axial direction within the turbomolecular pump.

[0022] Furthermore, the annular throttling may completely cover the open intake region 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 annular throttling configuration. Despite the annular throttling completely covering the inlet region in the radial direction, the intake region of the auxiliary pump stage remains open in the axial direction, so that the gas to be pumped can enter the auxiliary pump stage at a sufficient volumetric flow rate of liters / 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 overlap with respect to the intake region of the auxiliary pump stage in the radial direction. It has been found that such a configuration can reduce the temperature of the rotor to the greatest extent. Moreover, in the axial direction, the intake region of the auxiliary pump stage, compared with a turbomolecular pump that does not have such an annular throttle, has an appropriate width to substantially maintain the overall pumping speed of the turbomolecular pump while hardly impairing the flow characteristics of the gas to be pumped.

[0024] The cooling element may be manufactured 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 aforementioned embodiments. A cooling element made of aluminum with such dimensions can be manufactured relatively easily.

[0025] Hereinafter, the present invention will be described based on exemplarily advantageous embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [Figure 1] A perspective view of a turbomolecular pump is shown. [Figure 2] A bottom view of the turbomolecular pump of Figure 1 is shown. [Figure 3] A cross-sectional view of the turbomolecular pump taken along the cutting line A-A shown in Figure 2 is shown. [Figure 4] A cross-sectional view of the turbomolecular pump taken along the cutting line B-B shown in Figure 2 is shown. [Figure 5] A cross-sectional view of the turbomolecular pump taken along the cutting line C-C shown in Figure 2 is shown. [Figure 6] A further cross-sectional view of a turbomolecular pump is shown. [Figure 7] Various embodiments of the arrangement of cooling elements in the turbomolecular pump of Figure 6 are shown. [Figure 8] It is a diagram showing rotor temperature dependent on gas flow for various inner diameters of an annular throttle in the flow path of the turbomolecular pump of Figures 6 and 7. [Modes for carrying out the invention]

[0027] The turbomolecular pump 111 shown in Figure 1 has a pump intake port 115 surrounded by an intake flange 113. A recipient (not shown) may be connected to the pump intake port 115, as is known in itself. Gas arriving from the recipient can be drawn in from the recipient through the pump intake port 115 and pumped through the pump to the pump exhaust port 117. An auxiliary vacuum pump, such as a rotary vane pump, may be connected to the pump exhaust port 117.

[0028] The intake flange 113 forms the upper end of the housing 119 of the vacuum pump 111 in the orientation of the vacuum pump shown in Figure 1. The housing 119 has a lower portion 121. An electronics housing 123 is located laterally within the lower portion 121. The electronics housing 123 houses the electrical and / or electronic components of the vacuum pump 111, for example, to operate an electric motor 125 (see also Figure 3) located inside the vacuum pump. The electronics housing 123 is provided with a number of connection points 127 for accessories. Furthermore, a data interface 129 (e.g., conforming to the RS485 standard) and a current supply connection point 131 are located within the electronics housing 123.

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

[0030] The housing 119 of the turbomolecular pump 111 is provided with a ventilation intake 133, particularly in the form of a ventilation valve. The vacuum pump 111 may be vented through the ventilation intake 133. Further above the lower portion 121, a seal gas connection 135 (also referred to as a purge gas connection) is located. Through the seal gas connection 135, purge gas may be introduced into the motor chamber 137 to protect the electric motor 125 (see, for example, Figure 3) from the gas being pumped by the pump. The electric motor 125 is housed in the vacuum pump 111 within the motor chamber 137. Further above the lower portion 121, two coolant connection 139 are located. In this case, one coolant connection is provided as a coolant intake, and the other coolant connection is provided as an exhaust port. Coolant can be introduced into the vacuum pump for cooling purposes. Other turbomolecular vacuum pumps (not shown) that exist are operated exclusively by air cooling.

[0031] Since the lower surface 141 of the vacuum pump can be used as a base, the vacuum pump 111 may be operated in a vertical orientation with the lower surface 141 as the reference point. Furthermore, the vacuum pump 111 may be fixed to the recipient via the intake flange 113 and thus operated in a suspended state. Moreover, the vacuum pump 111 may be configured to operate even when it is aligned in a direction other than that shown in Figure 1. It is also possible to realize a vacuum pump configuration in which the lower surface 141 can be positioned sideways or upward instead of downward. In this case, in principle, any angle is possible.

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

[0033] Various screws 143 are further positioned on the lower surface 141 shown in Figure 2. These screws 143 fasten components of the vacuum pump, which are not specifically identified here, to each other. For example, the bearing cover 145 is fixed to the lower surface 141.

[0034] The lower surface 141 is further provided with fixing holes 147. The pump 111 can be fixed to, for example, a mounting surface via these fixing holes 147. This is not possible with other turbomolecular vacuum pumps (not shown) that are larger than the pump shown.

[0035] Figures 2 to 5 show the coolant pipeline 148. Within the coolant pipeline 148, the coolant introduced and discharged via the coolant connection part 139 can be circulated.

[0036] As shown in the cross-sectional views of Figures 3 to 5, the vacuum pump has multiple process gas pump stages. The process gas pump stages are for pressurizing the process gas acting on the pump intake port 115 and sending it to the pump exhaust port 117.

[0037] A rotor 149 is positioned inside the housing 119. The rotor 149 has a rotor shaft 153 that is rotatable around a rotation axis 151.

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

[0039] The vacuum pump further comprises Holbeck pump stages arranged radially inward and outward from each other and connected in series to exert a pumping action. Another turbomolecular vacuum pump (not shown) exists that does not have Holbeck pump stages.

[0040] The rotor of the Holbeck pump stage has a rotor hub 161 positioned on the rotor shaft 153, and two cylindrical Holbeck rotor sleeves 163, 165 fixed to and supported by the rotor hub 161. The Holbeck rotor sleeves 163, 165 are oriented coaxially with respect to the axis of rotation 151 and are radially engaged with each other inward and outward. Two more cylindrical Holbeck status sleeves 167, 169 are provided. The Holbeck status sleeves 167, 169 are similarly oriented coaxially with respect to the axis of rotation 151 and are radially engaged with each other inward and outward.

[0041] The pumping surface of the Holbeck pump stage is formed by its sides, that is, by the radially inner and / or outer surfaces of the Holbeck rotor sleeves 163, 165 and the Holbeck status sleeves 167, 169. The radially inner surface of the outer Holbeck status sleeve 167 faces the radially outer surface of the outer Holbeck rotor sleeve 163, forming a radial Holbeck gap 171, and together with this outer surface, forms a first Holbeck pump stage that follows the turbomolecular pump. The radially inner surface of the outer Holbeck rotor sleeve 163 faces the radially outer surface of the inner Holbeck status sleeve 169, forming a radial Holbeck gap 173, and together with this outer surface, forms a second Holbeck pump stage. The radial inner surface of the inner Holbeck status sleeve 169 faces the radial outer surface of the inner Holbeck rotor sleeve 165, forming a radial Holbeck gap 175, and together with this outer surface, forms a third Holbeck pump stage.

[0042] A radially extending channel may be provided at the lower end of the Holbeck rotor sleeve 163. Through this channel, the radially outward-located Holbeck gap 171 is connected to the central Holbeck gap 173. A further radially extending channel may be provided at the upper end of the inner Holbeck stage sleeve 169. Through this channel, the central Holbeck gap 173 is connected to the radially inward-located Holbeck gap 175. This connects multiple Holbeck pump stages that engage with each other internally and externally in series. A further connecting channel 179 leading to the exhaust port 117 may be provided at the lower end of the radially inward-located Holbeck rotor sleeve 165.

[0043] The surfaces of the Holbeck status sleeves 167 and 169 that perform the aforementioned pumping action each have multiple Holbeck grooves that spiral around the rotation axis 151 and extend axially. On the other hand, the opposing sides of the Holbeck rotor sleeves 163 and 165 are smoothly formed and send the gas for operating the vacuum pump 111 forward within the Holbeck grooves.

[0044] For the rotatable support of the rotor shaft 153, a rolling bearing 181 is provided in the area of ​​the pump exhaust port 117, and a permanent magnet type magnetic bearing 183 is provided in the area of ​​the pump intake port 115.

[0045] In the region of the rolling bearing 181, a conical splash nut 185 is provided on the rotor shaft 153. The splash nut 185 has an outer diameter that increases toward the rolling bearing 181. The splash nut 185 is in sliding contact with at least one scraping member of the working medium reservoir. In other turbomolecular vacuum pumps (not shown), a splash screw may be provided instead of a splash nut. As a result, various configurations are possible, and in the above relationship, the term "splash tip" is also used.

[0046] The working medium storage unit has a plurality of absorbent disks 187 stacked vertically. These disks 187 are impregnated with a working medium for the rolling bearings 181, such as a lubricant.

[0047] During operation of the vacuum pump 111, the working fluid is transmitted by capillary action from the working fluid reservoir through the scraping member to the rotating splash nut 185, and then, based on centrifugal force, along the splash nut 185 toward the rolling bearing 181 toward the increasing outer diameter of the splash nut 185, where, for example, lubrication is performed. The rolling bearing 181 and the working fluid reservoir are surrounded within the vacuum pump by a tank-shaped 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 one ring stack, which consists of multiple rings 195, 197 of permanent magnets stacked vertically in the axial direction. The ring magnets 195 and 197 face each other, forming a radial bearing gap 199 between them. In this case, the ring magnet 195 on the rotor side is positioned radially outward, and the ring magnet 197 on the stator side is positioned radially inward.

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

[0050] An emergency bearing or safety bearing 215 is provided within the magnetic bearing. for The bearing or safety bearing 215 rotates freely without contact during normal operation of the vacuum pump, and only engages when the rotor 149 is excessively displaced radially relative to the stator, thereby forming a radial stopper for the rotor 149 so as to prevent collision between the rotor-side structure and the stator-side structure. The safety bearing 215 is configured as a non-lubricated rolling bearing and forms a radial gap with the rotor 149 and / or stator. This gap prevents the safety bearing 215 from engaging during normal pump operation. The safety bearing 215 engages upon radial displacement, and since the radial displacement is sufficiently large, the safety bearing 215 does not engage during normal operation of the vacuum pump, and at the same time is sufficiently small so that collision between the rotor-side structure and the stator-side structure is prevented in all situations.

[0051] The vacuum pump 111 has an electric motor 125 that rotates a rotor 149. The armature of the electric motor 125 is formed by the rotor 149. The rotor shaft 153 of the rotor 149 extends through a motor stator 217. A permanent magnet assembly may be positioned radially outward or embedded in the portion of the rotor shaft 153 that extends through the motor stator 217. An intermediate chamber 219 is positioned 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 influence each other to transmit driving torque.

[0052] The motor stator 217 is fixed within the housing, in a motor chamber 137 provided for the electric motor 125. A seal gas (also called a purge gas, which may be, for example, air or nitrogen) can reach the motor chamber 137 via a seal gas connection 135. The electric motor 125 can be protected from process gases, such as corrosive parts of the process gas, via the seal gas. The motor chamber 137 may be evacuated via a pump exhaust port 117. That is, a vacuum pressure, at least approximately, is acting within the motor chamber 137, achieved by an auxiliary vacuum pump connected to the pump exhaust port 117.

[0053] A so-called labyrinth seal 223, which is known in itself, may be further provided between the rotor hub 161 and the wall portion 221 defining the motor chamber 137. This achieves better sealing of the motor chamber 217, particularly to the Holbeck pump stage located radially outward.

[0054] Figure 6 shows another turbomolecular pump 300 that is fundamentally similar to the turbomolecular pump 111 described above and shown in Figures 1 to 5 (see Figures 3 and 6 in particular). Therefore, the above description of the turbomolecular pump 111 also applies to the turbomolecular pump 300, unless there is a semantically contradictory description or illustration.

[0055] The turbomolecular pump 300, like the turbomolecular pump 111, has a rotor 302, which is supported by a magnetic bearing 304 on the high vacuum side and by a ball bearing 306 on the opposite side. Furthermore, the turbomolecular pump 300 has a turbomolecular region 310 with four turbomolecular pump stages 312. Each turbomolecular pump stage 312 is associated with a rotor blade 314, and each rotor blade 314 is attached to the rotor 302. A stator blade 316 is located between each rotor blade 314.

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

[0057] In turbomolecular pumps, a significant temperature rise occurs within the turbomolecular region 310 during operation of the turbomolecular pump 300, due to the high rotational speed of the rotor 302, which typically exceeds 10,000 revolutions per minute. Based on the gas friction of the elements that contribute to the pumping action of the turbomolecular pump 300, such as the rotor blades 314 and stator blades 316, the rotor 302 can be heated to, for example, 90°C or higher, especially when the gas load is high. This is primarily because the stator blades 316 do not have sufficient thermal contact with the housing 340 of the turbomolecular pump 300 to transfer the generated heat from the turbomolecular pump stage 312 to the housing 340.

[0058] The rotor blades 314 are thermally insulated from the housing 340 based on the magnetic bearing portion of the rotor 302 on the high vacuum side of the turbomolecular pump 300, the ball bearing 306, and the high vacuum present in the turbomolecular region 310 during operation of the turbomolecular pump 300. Based on this thermal insulation, and due to the high rotational speed of the rotor 302, the temperature rise of 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, in principle, has a flow path 350 for the gas to be pumped, as indicated by the white arrows 350 in Figures 6 and 7. The flow path 350 for the gas to be pumped is partially defined by the pumping elements of the turbomolecular pump stage 312 and the auxiliary pump stage or Holbeck pump stage 332. In other words, the pumping elements, namely the rotor blades 314 and stator blades 316, and the pumping elements of the Holbeck pump stage 332, partially define the geometric course of the flow path 350. Thus, the flow path 350 represents the volume within the turbomolecular pump 300 as the gas to be pumped moves from the intake port to the exhaust port of the turbomolecular pump 300. Furthermore, a favorable direction for the movement of the gas to be pumped is associated with the flow path 350, in this case, extending from the high vacuum side of the turbomolecular pump 300 to its exhaust port.

[0060] To reduce the rotor temperature of the turbomolecular pump 300 during operation, the turbomolecular pump 300 has a cooling element (see Figure 7). The cooling element 360 is located upstream of the auxiliary pump stage or Holbeck pump stage 332 and protrudes into the flow path 350 of the turbomolecular pump 300. Figures 7A and 7B show several possible arrangements and embodiments of the cooling element 360.

[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, directly following the last rotor blade 314 downstream, i.e., immediately below the last turbomolecular pump stage 312. In contrast, Figure 7B shows the arrangement of the cooling element 360 located immediately before the intake region 370 of the auxiliary pump stage or Holbeck pump stage 332.

[0062] Figure 7A shows an enlarged section of the turbomolecular pump 300 of Figure 6, including the turbomolecular region 310 and part of the transition region 320. Each of the four rotor blades 314 of the turbomolecular pump stage 312 is numbered from 1 to 4.

[0063] In the first embodiment of the cooling element 360, shown in the upper part of A in Figure 7 and denoted by reference numeral 362, the cooling elements 360, 362 form part of the stator vane 316 shown in Figure 6, thereby protruding into the flow path 350. The cooling elements 360, 362 are annular in shape 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 another stator vane 316-2 that does not have a cooling element 360. Thus, on the one hand, the cooling elements 360, 362 are in contact, and thus thermal contact, with the surface of the turbomolecular pump 300 at approximately ambient temperature, i.e., the temperature of the housing during operation of the turbomolecular pump 300. On the other hand, since the cooling elements 360, 362 protrude into the flow path 350, they are also in thermal contact with the high-temperature gas in the flow path 350 during operation. This also applies to embodiments of the cooling element 360 described later. Furthermore, the cooling element 360 may be configured as a cooling rib or cooling fin, thereby improving thermal contact with the high-temperature gas.

[0064] In the 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 without the cooling elements 360, the cooling elements 360 protrude 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 positioned in various axial positions, i.e., at various pump stages of the turbomolecular pump 300. In the example of Figure 7A, one cooling element 360, 362 is positioned between the rotor vanes 314 labeled 1 and 2 and / or between the rotor vanes 314 labeled 3 and 4. For clarity, the stator blades 317 are schematically shown positioned obliquely between the rotor vanes 314 labeled 1 and 2 relative to the stator vane 316-1.

[0065] In short, based on their geometry and material, for example aluminum, the cooling elements 360 and 362 have improved thermal contact with the housing 340 compared to the stator vanes 316-2 without cooling elements. As a result, the cooling elements 360 and 362 are configured to transfer a greater amount of heat to the housing 340 over a given period than the elements that perform the pumping action of each turbomolecular pump stage 312, i.e., a greater amount of heat than the stator vanes 316-2 without cooling elements. This also applies to other embodiments of the cooling element 316, designated 364 or 366, as described later.

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

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

[0068] In contrast, in the embodiment shown in Figure 7B, the cooling element 360 is configured as an annular throttling 366. The annular throttling 366 is located in the transition region 320, directly in front of the intake port region 370 of the auxiliary pump stage or Holbeck pump stage 332. In the radial direction extending perpendicular to the axial direction defined by the rotation axis of the rotor 302, the intake port region 370 of the Holbeck pump stage 332 has a bevel 372. The bevel 372 represents the radial distance by which the intake port region 370 of the Holbeck pump stage opens radially. Thus, viewed along the rotation axis of the rotor 302, the bevel 372 defines an annular plane between the annular throttling 366 and the rotor element 374 of the Holbeck pump stage 332. Within this annular plane, the intake port region 370 of the Holbeck pump stage 332 is not covered by the cooling element 360 or the annular throttling 366 if the bevel 372 is greater than zero.

[0069] The aforementioned embodiments of the cooling element 360 may be optionally combined with each other in the turbomolecular pump 300; that is, 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 may be used.

[0070] Figure 8 shows a plot of measured rotor temperature (°C) with respect to the gas load (sccm) (standard cubic centimeters / min) generated at the intake of the turbomolecular pump 300. The measurement curve in Figure 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 Figure 6).

[0071] The various measurement curves 380-388 shown in Figure 8 have different inner diameters 372 (see B in Figure 7). Measurement curve 380 was obtained with an inner diameter 372 of 9.6 mm, corresponding to the configuration of the turbomolecular pump 300 without the annular aperture 360. This configuration, with the maximum inner diameter 372 and without the annular aperture 366, is used as a baseline for measurements with various inner diameters of the annular aperture 366, where the inner diameter 372 is gradually reduced until it completely covers the intake port area 370 of the Holbeck pump stage 332.

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

[0073] For measurement curve 382, ​​the turbomolecular pump 300 was provided with a cooling element 360, specifically in the form of an annular thrombus 366 (see Figure 7B) having an inner diameter of 4 mm, with an internal depth 372. For the other measurement curves 384 and 386, the internal depth was reduced to 2 mm or 0 mm by shortening the inner diameter of the annular thrombus 366, respectively. In the embodiment for measurement curve 386, the annular thrombus 366 almost completely covers the intake port area 370 of the Holbeck 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 the annular aperture 366 completely covers the intake port area 370 of the Holbeck pump stage 332 and protrudes radially into the area of ​​the rotor element 374 (see Figure 7B) of the Holbeck pump stage 332. In other words, in the embodiment for measurement curve 388, the inner diameter of the annular aperture 366 is smaller than the outer diameter of the rotor element 374 of the Holbeck pump stage 332.

[0075] As can be seen from measurement curves 382 to 388 in Figure 8, the presence of the annular throttler 366 generally reduces the rotor temperature across the entire range of the acquired gas load. This is already seen from curve 382, ​​which is below the reference curve 380 across the entire measurement range of the gas load with an inner depth of 4 mm 372. As the inner depth 372 is reduced to 2 mm (curve 284), the rotor temperature is further reduced across the entire measurement range, while as the inner depth 372 is further reduced to 0 mm, the rotor temperature is reduced even more significantly so that a rotor temperature slightly above 50°C is achieved at a gas load of 20 sccm (see curve 386). As the inner diameter of the cooling throttler 366 is further reduced to cover an inner depth of -5 mm 372, finally, a reduction in rotor temperature is only achieved at gas loads well above 50 sccm (see measurement curve 388).

[0076] Overall, measurement curves 382 to 388 show that the cooling element 360 in the form of an annular aperture 366 can significantly reduce the rotor temperature of the cooling element 360 during operation, compared to measurement curve 380. This is similarly true for another embodiment of the cooling element 360 described in relation to A in Figure 7.

[0077] In other words, by simultaneously obtaining the measurement curves 380 to 388 in Figure 8 and measuring the exhaust velocity of the turbomolecular pump 300, it was found that even when the annular throttle 366 is present, and even when the inner depth 372 is 0 mm (curve 386 in Figure 8), the decrease in exhaust velocity is negligible. Even with an inner depth of -5 mm (curve 388 in Figure 8), the exhaust velocity decreased by only about 10% at a relatively high intake pressure of 0.01 mbar. At the same time, in the embodiment with an annular throttle 366 having an inner depth 372 of -5 mm (corresponding to curve 388 in Figure 8), a slight increase in the power consumption of the turbomolecular pump 300 was observed in the higher gas load region, while in the embodiment with an annular throttle 366 having an inner depth 300 of 0 mm or more, no increase in the power consumption of the turbomolecular pump 300 was observed. This application relates to the invention described in the claims, but also includes the following other embodiments. 1. In the turbomolecular pump (300), Housing (340) and, Multiple turbomolecular pump stages (312), A turbomolecular pump stage (312) is configured with at least one auxiliary pump stage (332) located downstream of it, A flow path (350) for the gas to be pumped, partially set by elements (314, 316, 374) that perform the pumping action of the turbomolecular pump stage (312) and the auxiliary pump stage (332), A cooling element (360) is configured to protrude into the flow path (350) upstream of the auxiliary pump stage (332) and to transfer a larger amount of heat to the housing (340) than the elements (314, 316) that perform the respective pumping actions of the turbomolecular pump stage (312) for a predetermined period of time. A turbomolecular pump (300) equipped with the following. 2. The turbomolecular pump (300) described above has a cooling element (360) that has a larger contact surface with the housing (340) than the elements (314, 316) that perform the respective pumping actions of the turbomolecular pump stage (312). 3. The cooling element (360) is formed in an annular shape and completely surrounds the flow path (350) of the gas to be pumped, the turbomolecular pump (300) of the above 1 or 2. 4. The cooling element (360) is the turbomolecular pump (300) of the above 3, having two half-rings or half-disks. 5. The elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312) include a rotor blade (314) having a predetermined outer diameter. A turbomolecular pump (300) of any one of the above 1 to 4, wherein the inner diameter (360) of the cooling element (360) is smaller than the outer diameter (314) of the rotor blade (314). 6. The cooling element (360) is located in the region of the elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312), and is one of the turbomolecular pumps (300) described in 1 to 5 above. 7. The cooling element (360) is configured as a spacer element (362) between at least two stator vanes (316) of the turbomolecular pump stage (312) of the turbomolecular pump (300) of the above 6. 8. The cooling element (360) is part of the turbomolecular pump (300) of the turbomolecular pump stage (312), which is part of at least one stator vane (316) of the turbomolecular pump stage (312). 9. A cooling element (360) is configured as a cooling rib or cooling fin in one of the turbomolecular pumps (300) described in 6 to 8 above. 10. A turbomolecular pump (300) which is configured as a perforated throttling (364) located between at least two stator vanes (316) of the turbomolecular pump stage (312) or downstream of the elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312), any one of the above 6 to 9. 11. A turbomolecular pump (300) from any of the above 6 to 10, wherein the cooling element (360) is configured as an annular throttling (366) located in the transition region (320) between the space region (310) where the turbomolecular pump stage (312) is located and the auxiliary pump stage (332). 12. The annular throttling (366) of the turbomolecular pump (300) of the 11 above at least partially covers the open intake region (370) of the auxiliary pump stage (332). 13. The annular throttling (366) completely covers the open intake region (370) of the auxiliary pump stage (332) radially of the turbomolecular pump (300), as described in the 12 turbomolecular pumps (300). 14. The annular throttling (366) of the turbomolecular pump (300) has an inner diameter smaller than the outer diameter of the rotor element (374) of the auxiliary pump stage (332). 15. The cooling element (360) is made of aluminum and has an axial height in the range of 2 mm to 3 mm, and is one of the turbomolecular pumps (300) described above from 1 to 14. [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 part 129 Data Interfaces 131 Current supply connection 133 Ventilation intake 135 Seal gas connection 137 Motor Room 139 Coolant connection part 141 Bottom surface 143 screws 145 Bearing cover 147 Fixed hole 148 Coolant piping 149 Rotor 151 Rotation axis 153 Rotor Shaft 155 Moving blade 157 Static Wing 159 Spacer Ring 161 Rotor Hub 163 Holbeck Rotor Sleeve 165 Holbeck Rotor Sleeve 167 Holbeck Status Leaf 169 Holbeck Status Leaf 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 Inserts 191 Rotor-side bearing half 193 Stator-side bearing half 195 Ring Magnets 197 Ring Magnets 199 Bearing clearance 201 Support part 203 Support part 205 Radial support columns 207 cover elements 209 Support ring 211 Fixing ring 213 Disc spring 215 Emergency bearing or safety bearing 217 Motor Stator 219 Intermediate Room 221 Wall section 223 Labyrinth Seal 300 Turbomolecular Pumps 302 Rotor 304 Magnetic bearing 306 Ball bearing 310 Turbo Molecular Region 312 Turbomolecular pump stage 314 Moving blade 316 Static Wing 316-1 Stator vanes with cooling elements 316-2 Stator vanes without cooling elements 317 Stator Blade 320 Transition Area 330 Auxiliary pump area 332 Auxiliary pump stage or Holbeck pump stage 340 Housing 350 Flow path of gas to be pumped 360 Cooling Elements 362 Reinforcement area of ​​stationary wings 364-hole aperture 366 Ring-shaped aperture 370 Holbeck pump stage intake area 372 inside 374 Holbeck pump stage rotor element 380 Reference curve for rotor temperature 382 Rotor temperature measurement curve, inner depth 4mm 384 Rotor temperature measurement curve, inner thickness 2mm 386 Rotor temperature measurement curve, inner depth 0mm 388 Rotor temperature measurement curve, inner depth -5mm

Claims

1. In the turbomolecular pump (300), Housing (340) and Multiple turbomolecular pump stages (312), At least one auxiliary pump stage (332) located downstream of the turbomolecular pump stage (312), A flow path (350) for the gas to be pumped, partially set by elements (314, 316, 374) that perform the pumping action of the turbomolecular pump stage (312) and the auxiliary pump stage (332), A cooling element (360) is configured to protrude into the flow path (350) upstream of the auxiliary pump stage (332) and to transfer a larger amount of heat to the housing (340) than the elements (314, 316) that perform the respective pumping actions of the turbomolecular pump stage (312) for a predetermined period of time. Equipped with, The cooling element (360) is configured as an annular throttling (366) located in the transition region (320) between the space region (310) where the turbomolecular pump stage (312) is located and the auxiliary pump stage (332). The annular throttling (366) completely covers the open intake region (370) of the auxiliary pump stage (332) radially with respect to the turbomolecular pump (300). Turbomolecular pump (300).

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

3. The turbomolecular pump (300) according to claim 1 or 2, wherein the cooling element (360) is formed in an annular shape and completely surrounds the flow path (350) of the gas to be pumped.

4. The turbomolecular pump (300) according to claim 3, wherein the cooling element (360) has two half-rings or half-disks.

5. The elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312) include a rotor blade (314) having a predetermined outer diameter, The turbomolecular pump (300) according to claim 1 or 2, wherein the inner diameter (360) of the cooling element (360) is smaller than the outer diameter (314) of the rotor blade (314).

6. The turbomolecular pump (300) according to claim 1 or 2, wherein the cooling element (360) is located in the region of the elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312).

7. The turbomolecular pump (300) according to 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) according to claim 6, 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 claim 6, wherein the cooling element (360) is configured as a cooling rib or cooling fin.

10. The turbomolecular pump (300) according to claim 6, wherein the cooling element (360) is configured as a perforated throttling (364) located between at least two stator vanes (316) of the turbomolecular pump stage (312) or downstream of the elements (314, 316) that perform the pumping action of the turbomolecular pump stage (312).

11. The turbomolecular pump (300) according to claim 1, wherein the annular throttling (366) has an inner diameter smaller than the outer diameter of the rotor element (374) of the auxiliary pump stage (332).

12. The turbomolecular pump (300) according to claim 1 or 2, wherein the cooling element (360) is made of aluminum and has an axial height in the range of 2 mm to 3 mm.

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