Turbomolecular vacuum pump with optimized seal gas supply

Abstract

The present invention provides a turbomolecular vacuum pump in which the probability of the sealing gas absorbing oil particles from the bearing region is reduced. [Solution] The electric motor 125 is located in a motor chamber 310, which is surrounded by a cylindrical partition wall 314 and, on the side closer to the first pump mechanism, is defined by a radially extending partition wall 316, the radially extending partition wall surrounds the rotor 360, forming an annular gap 348, through which the motor chamber is flow-technically connected to an annular chamber 320 leading to the pump exhaust port, the rotor shaft 358 extends to an end supported by a rolling bearing 318, the housing has at least one seal gas connection portion 304, 305, and an inflow channel 312 is formed in the cylindrical partition wall, the inflow channel is in fluid communication with the seal gas connection portion on one side and with the fluid chamber 320 on the other side.

Description

Technical Field

[0001] The present invention relates to a turbomolecular vacuum pump with optimized seal gas supply. In particular, the present invention is a turbomolecular vacuum pump comprising a Holweck pump stage, within which the electric motor of the turbomolecular vacuum pump, which is here simply referred to as the turbomolecular pump or "pump", is located. The Holweck pump stage has a seal gas inlet opening, through which seal gas can be introduced from a part that may cause a corrosive effect and can be a constituent of the process gas to be pumped, in order to protect the motor region and the bearing region connected to the motor region. Such a part does not necessarily have to cause a corrosive effect; rather, it may be particles or dust that can contaminate the working medium or block the gaps. Furthermore, other components may also easily contaminate the working medium.

Background Art

[0002] Seal gas is usually introduced into the pump system in the vicinity of generally oil-lubricated rolling bearings. In particular, when a large amount of seal gas is introduced into the pump system, it can happen that the seal gas absorbs and entrains oil vapor, and the oil vapor can diffuse from the bearing region. The seal gas thus concentrated with oil then spreads within the pump system and may reach the equipment connected to the pump inlet, where it may cause measurements containing errors and / or damage. Similarly, the seal gas spreading within the pump system can reach the rough vacuum region located near the pump outlet. The rough vacuum region is in fluid communication with the outlet of the Holweck pump stage, where the oil particles present in the seal gas can deposit as an oil film, which may cause confusion on the user side of the pump.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, the fundamental problem of the present invention is to provide a turbomolecular vacuum pump equipped with a Holbeck pump stage and a seal gas intake port, in which the probability of the seal gas absorbing oil particles from the bearing region is reduced. [Means for solving the problem]

[0004] This problem is solved by a turbomolecular vacuum pump having the features of claim 1.

[0005] In this case, the problem is solved by the fact that a component of the motor cover, a cylindrical partition wall separating the motor chamber from the pre-vacuum region at the exhaust port of the Holbeck pump stage located furthest downstream, has at least one inflow channel formed within it, which is aligned substantially axially with respect to the axis of rotation, and the inflow channel is in fluid communication at one end with a seal gas connection and at the other end, via a flow path that may be complexly configured, is in fluid communication with the annular chamber of the motor cover that surrounds the cylindrical partition wall in question, at the pre-vacuum level. In this case, at least one inflow channel is aligned substantially axially and therefore extends within the cylindrical partition wall. To put it in other words, the end of the inflow channel that is in fluid communication with the seal gas connection is located in a plane that extends radially in an axial direction, separate from the other end of the inflow channel. Thus, the radial planes in which both ends of the inflow channel are located are spaced apart from each other in the axial direction.

[0006] Therefore, the seal gas is not introduced directly into the motor chamber radially. Based on the fact that the motor chamber is directly adjacent to the bearing area of ​​the pump rotor, there is a high probability that the seal gas will absorb oil coming from the bearing area. Instead, based on the fact that the inlet channel in question is formed in or within an axially extending cylindrical partition wall, the seal gas is first guided axially away from the bearing area through the inlet channel, and then toward the electric motor or the first pump mechanism, thereby reducing the probability of absorption of oil coming from the bearing area. After the seal gas has flowed through the inlet channel, if it is guided into the motor chamber near the radially extending partition wall of the motor cover, it may subsequently spread toward the bearing area through the motor / rotor gap, in which case the seal gas acts as a kind of buffer or barrier to the seal gas that subsequently flows through the inlet channel. Next, the seal gas flowing from behind passes through the annular gap between the rotor and the radially extending partition wall of the motor cover and reaches the annular chamber surrounding the cylindrical partition wall, which is at a pre-vacuum level. In this case, the seal gas flowing from behind does not come into contact with the bearing area due to the buffering effect of the seal gas that initially flows into the motor chamber, and therefore contains little to no oil vapor.

[0007] Therefore, according to the present invention, in a sense, the sealing gas spreading within the pump system is not made to come into contact with the bearing area, but rather the sealing gas is guided to first move axially away from the bearing area through an inlet channel that extends substantially axially, thereby reducing the probability of oil vapor absorption by the sealing gas. Consequently, a larger amount of sealing gas can be introduced.

[0008] Therefore, since the seal gas connection is also used for ventilation during pump shutdown, a larger volume of ventilation gas can be used, thereby shortening the time required for pump shutdown.

[0009] Preferred embodiments of the present invention will be discussed below. Further embodiments will become apparent from the dependent claims, the description of the drawings, and the drawings.

[0010] Accordingly, according to one embodiment, a seal gas connection is formed in the lower part of the housing of the turbomolecular vacuum pump, in which case the lower part of the housing may be intended to receive a rolling bearing or a bearing socket including a rolling bearing. In this case, a cylindrical partition wall that forms a motor cover in conjunction with a radially extending partition wall starts from the radial plane where the rolling bearing is located and extends axially to the upper part of the housing which is coupled to the lower part of the housing, where a first pump mechanism is located, and the upper part of the housing, together with the lower part of the housing, forms a housing chamber for a second pump mechanism including an electric motor.

[0011] In a further embodiment, it may be intended that at least one seal gas connection, which may be provided in the lower part of the housing, is in fluid communication with the inlet channel via a radially extending seal gas channel also formed in the lower part of the housing. Thus, there is a direct flow path from the seal gas connection to the inlet channel formed in the axially extending cylindrical partition wall of the motor cover, so that the seal gas cannot first reach the motor chamber, which is defined on the circumferential side by the cylindrical partition wall.

[0012] In yet another embodiment, the turbomolecular vacuum pump and, in particular, the lower part of the housing, may have at least two seal gas connections, one of which is located at the radially outer end of the seal gas channel, while the other seal gas connection is in fluid communication with the seal gas channel via a seal gas hole, the seal gas hole opening into the seal gas channel at a location radially inward from the radially outer end of the seal gas channel. For example, the other seal gas connection may be located on the underside of the lower part of the housing and may be connected to the seal gas channel by an axially extending seal gas hole. Thus, in confined space situations, the seal gas can be supplied radially or axially to the pump by a suitable seal gas supply line, as needed.

[0013] To distribute the seal gas as uniformly as possible within the pump system, according to a further embodiment, the inlet channel may open downstream into a circumferential annular channel, the annular channel being formed to circumfer within a cylindrical partition wall, and the annular channel itself being in fluid communication with the annular chamber via a complexly configured flow path, possibly through a motor chamber. Thus, the seal gas can spread and distribute circumferentially through the annular channel, thereby reaching the annular chamber surrounding the motor chamber and / or the cylindrical partition wall.

[0014] In order to enable the formation of an annular channel in a cylindrical partition wall, according to one further embodiment, the cylindrical partition wall may be composed of two cylindrical wall portions aligned axially with respect to each other, and the annular channel may be formed at the joint where both cylindrical wall portions are joined to each other. Specifically in this case, the first cylindrical wall portion of the two cylindrical wall portions may be intended to start from the bottom of the housing and extend toward a free end toward a first pump mechanism, at which point the first cylindrical wall portion is joined to a second cylindrical wall portion of the two cylindrical wall portions, the second cylindrical wall portion may be intended to start from there and similarly extend toward an end toward the first pump mechanism, at which point a radially extending partition wall is joined to the second cylindrical wall portion. Thus, for example, at the free end of the first cylindrical wall portion and / or the adjacent end of the second cylindrical wall portion, a recess may be formed, for example, that encircles the wall, and the recess in this case forms an annular channel with both cylindrical wall portions joined to each other.

[0015] In one preferred embodiment, the first cylindrical wall portion may have a circumferential first annular projection at its free end, the first annular projection having a thickness smaller than that of the first cylindrical wall portion. Correspondingly, the end of a second cylindrical wall portion, coupled to the free end of the first cylindrical wall portion, may have a circumferential second annular projection, the second annular projection surrounding the first annular projection and having a thickness smaller than that of the second cylindrical wall portion. In this case, the annular channel between the two annular projections can be formed by a chamfer or rounded portion formed along the inner edge of the free end of the second annular projection to circumferentially.

[0016] In a further embodiment, to allow the sealing gas to reach the motor chamber from the annular channel, the motor chamber may be intended to be in fluid communication with the annular channel via at least one distribution channel defined by a cylindrical partition wall. Preferably, in this case, there are a plurality of connecting channels located spaced apart from each other in the circumferential direction of the annular channel, and preferably uniformly spaced apart, so that the sealing gas is supplied to the motor chamber as uniformly as possible.

[0017] In a further embodiment, to ensure that as much of the seal gas as possible flows into the motor chamber through each of the distribution channels mentioned, it may be intended that the distribution channels have flow cross-sections of different sizes, at least partially, and / or that the flow cross-section of the annular channel increases circumferentially as the distance from the inlet channel increases. In this case, in particular, it may be intended that, circumferentially, distribution channels located further away from the inlet channel have a larger flow cross-section than distribution channels located near the inlet channel. Thus, as the seal gas seeks the path of least resistance, the seal gas arriving at the annular channel through the inlet channel can reach the distribution channels further away from the inlet channel without escaping from the annular channel through the distribution channels located near the inlet channel, and simultaneously, again mostly, through the distribution channels located near the inlet channel, thereby ensuring that ultimately, uniform distribution of the seal gas is achieved through all the distribution channels.

[0018] In yet another embodiment, a portion of each distribution channel may be formed by axially extending recesses in the first and / or second cylindrical wall portions, which are also preferably formed by axially extending recesses in the first and / or second annular projections. For example, an axially extending slot may penetrate the second cylindrical wall portion so that the seal gas can escape from the annular channel through the slot and thereby be directed toward the radially extending partition wall of the motor cover.

[0019] In yet another embodiment, the electric motor has a motor stator within a motor chamber, the motor stator contacting a cylindrical partition wall internally only along a circumferential central region. In contrast, on the side of the circumferential central region closer to the first pump mechanism, the motor stator is spaced apart from the cylindrical partition wall by a circumferential annular chamber. Therefore, the motor stator does not contact the cylindrical partition wall from the inside in the region of the annular chamber mentioned above, so that in this region, the aforementioned at least one distribution channel can open into the motor chamber. Thus, the sealing gas that reaches the annular chamber between the motor stator and the cylindrical partition wall through the distribution channel mentioned above may further expand axially within the motor chamber, thereby reaching a gap used as an expansion volume, through which the motor stator is spaced apart from the radially extending partition wall on the side closer to the first pump mechanism. The annular gap between the radially extending partition wall and the pump rotor connects directly to the expansion volume mentioned; therefore, the annular gap can be sealed by a sealing gas, thereby preventing corrosive components originating from the process gas from reaching the interior of the motor compartment in a desirable manner.

[0020] In short, according to the flow path described above, the seal gas can travel from the annular channel through the motor chamber to the annular gap, and from there, through the annular chamber surrounding the cylindrical partition wall, which is at a pre-vacuum level, to the exhaust port of the Holbeck pump stage. In addition to or alternatively, according to a further embodiment, the annular channel may be in direct fluid communication with the annular chamber on the radially outside of the cylindrical partition wall via at least one distribution channel extending radially through the cylindrical partition wall, and preferably, a plurality of distribution channels may be provided, preferably spaced uniformly apart from each other in the circumferential direction of the annular channel. In this embodiment, it may also be further intended that the distribution channels have flow cross-sections of at least partially different sizes from each other, and / or the flow cross-section of the annular channel increases with increasing distance from the inlet channel, thereby achieving the most uniform distribution of the seal gas possible.

[0021] According to yet another embodiment, in order to prevent the process gas pumped from the Holbeck pump stage to the pump exhaust port from flowing back into the motor chamber via an annular chamber surrounding the cylindrical partition wall, it may be contemplated that the cylindrical partition wall is surrounded on the outer peripheral surface side by a blocking geometry such as, for example, a circumferential annular flange. In this case, preferably, the blocking geometry is axially located closer to the radially extending partition wall of the motor cover than the distribution channel passing through the cylindrical partition wall. Thereby, the process gas exiting from the Holbeck pump stage cannot initially reach the blocking geometry at all, thereby ensuring that the annular chamber surrounding the cylindrical partition wall is also effectively protected from the corrosive components of the process gas. Additionally or alternatively, the blocking geometry may also be configured as a structure having a pumping action in the form of a Holbeck thread portion. The Holbeck thread portion reduces the probability of the inflow of the process gas into the annular chamber surrounding the cylindrical partition wall.

[0022] Paragraph. Hereinafter, the present invention will be described based on exemplary advantageous embodiments with reference to the accompanying drawings.

Brief Description of the Drawings

[0023] [Figure 1] A perspective view of a known turbomolecular pump is shown. [Figure 2] A bottom view of the turbomolecular pump of FIG. 1 is shown. [Figure 3] A cross-sectional view of the turbomolecular pump taken along the cutting line A-A shown in FIG. 2 is shown. [Figure 4] A cross-sectional view of the turbomolecular pump taken along the cutting line B-B shown in FIG. 2 is shown. [Figure 5] A cross-sectional view of the turbomolecular pump taken along the cutting line C-C shown in FIG. 2 is shown. [Figure 6] A cross-sectional view corresponding to FIG. 3 of a turbomolecular vacuum pump configured according to the present invention is shown. [Figure 7] Detail X of FIG. 6 is shown in a plan view by cross-section M-M. [Figure 8] The detailed view Y in FIG. 6 is shown as a plan view taken along the cross-section M-M. [Figure 9] The detailed view X shown in FIG. 6 is shown as an enlarged view. [Figure 10] The seal gas flow path of the turbo molecular vacuum pump according to FIG. 6 is shown. [Figure 11] The seal gas flow path according to a further embodiment of the turbo molecular vacuum pump is shown. [Figure 12] The seal gas flow path according to a further embodiment of the turbo molecular vacuum pump is shown. ]>

MODE FOR CARRYING OUT THE INVENTION

[0024] The turbo molecular pump 111 shown in FIG. 1 has a pump intake port 115 surrounded by an intake flange 113. A recipient (not shown) known per se may be connected to the pump intake port 115. The gas coming from the recipient can be sucked 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.

[0025] The intake flange 113 forms the upper end portion of the housing 119 of the vacuum pump in the orientation of the vacuum pump according to FIG. 1. The housing 119 has a lower portion 121. An electronics housing 123 is arranged laterally in the lower portion 121. The electronics housing 123 houses the electrical and / or electronic components of the vacuum pump 111 for operating, for example, an electric motor 125 (also see FIG. 3) arranged within the vacuum pump. The electronics housing 123 is provided with a plurality of connection portions 127 for accessories. Further, a data interface 129 (for example, compliant with the RS485 standard) and a current supply connection portion 131 are arranged in the electronics housing 123.

[0026] There are also turbomolecular pumps that do not have this type of attached electronic housing and are connected to external drive electronics.

[0027] 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.

[0028] 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.

[0029] In particular, other turbomolecular vacuum pumps (not shown) that are larger than the pump illustrated cannot be operated in a vertical configuration.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The turbomolecular pump 111 has multiple turbomolecular pump stages connected in series to perform 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.

[0036] The vacuum pump further comprises Holbeck pump stages, which are arranged radially inward and outward from each other and connected in series to perform a pumping action. There is another turbomolecular vacuum pump (not shown) that does not have Holbeck pump stages.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The working medium storage unit has multiple absorbent disks 187 stacked vertically. These disks 187 are impregnated with a working medium for the rolling bearings 181, such as a lubricant.

[0044] 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.

[0045] 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, 197 face each other, forming a radial bearing gap 199, in which case the rotor-side ring magnet 195 is positioned radially outward, and the stator-side ring magnet 197 is positioned radially inward. The magnetic field present in the bearing gap 199 causes a magnetic repulsive force between the ring magnets 195, 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 support portion 203 of the stator side. The support portion 203 extends through the ring magnet 197 and is suspended from the radial support members 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.

[0046] An emergency bearing or safety bearing 215 is provided within the magnetic bearing. The emergency 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In the aforementioned turbomolecular vacuum pump 111, the seal gas reaches the motor chamber 137 directly via the seal gas connection 135 in the manner already described. The motor chamber 137 is flow-through from the pre-vacuum region and is technically substantially separated from it by the exhaust port of the Holbeck pump stage, by the wall portion 221, also referred to as the motor cover, and especially by the labyrinth seal 223. However, since the bearing region and especially the oil-lubricated rolling bearing 181 are located within the motor chamber 137, the seal gas flowing into the motor chamber 137 can undesirably absorb oil vapor diffusing from the rolling bearing 181 into the motor chamber 137. This oil-concentrated seal gas can then flow through the gap 219 and the labyrinth seal 223. From there, the seal gas can reach the connection channel 179 at the exhaust port of the Holbeck pump stage, where it can deposit as an undesirable oil film.

[0051] To address this problem, in the turbomolecular vacuum pump 300 configured as a so-called split-flow pump, as described below with reference to Figure 6, the seal gas channel 302 extending radially inward from the seal gas connection 304 in the lower part of the housing 306 does not directly lead to the motor chamber 320. Instead, the seal gas channel 302 is intended to lead to an inflow channel 312 formed within the motor cover and, in particular, its cylindrical partition wall 314. Therefore, the seal gas flowing through the seal gas channel 302 is first guided axially away from the bearing region where the rolling bearing 318 is located, and thereby subsequently reaches the annular chamber 320 surrounding the cylindrical partition wall 314 via a flow path which will be described in more detail later. Although the pump in this drawing is a split-flow pump, the seal gas concept according to the present invention can, of course, also be realized in conventional turbomolecular pumps as shown in Figures 1 to 5.

[0052] Before we examine the structural design of the turbomolecular vacuum pump 300, shown in detail in Figure 6, it should be noted that the structural design of this pump 300 is largely equivalent to the pump described with reference to Figures 1 to 5, and therefore, only the main differences in this invention will be considered below.

[0053] As previously mentioned, in the turbomolecular vacuum pump 300 according to the present invention, a seal gas channel 302, starting from a seal gas connection 304 and extending radially inward within the lower part of the housing 306, is intended to continue to an axially extending inlet channel 312 formed within the cylindrical partition wall 314 of the motor cover. In addition to the radial seal gas connection 304, the pump 300 has an axially aligned seal gas connection 305, which is in fluid communication with the seal gas channel 302 via a seal gas hole 307, so that the seal gas can be supplied to the inlet channel 312 via the radial seal gas connection 304 and / or the axial seal gas connection 305 as needed.

[0054] In the embodiment shown herein, the cylindrical partition wall 314 surrounding the motor chamber 310 on its circumferential side is composed of a first cylindrical wall portion 322 and a second cylindrical wall portion 324. In this case, the first cylindrical wall portion 322 starts from the lower part of the housing 308 and extends toward the first pump mechanism. The first pump mechanism is formed by the rotor blades and stator blades of a turbomolecular pump mechanism. In this case, the free end of the first cylindrical wall portion 322 is connected to the second cylindrical wall portion 324 in a manner that will be described in detail below. The second cylindrical wall portion 324 extends radially from the free end of the first cylindrical wall portion 322 toward the first pump mechanism toward the end where the partition wall 316 is connected to the second cylindrical wall portion 324.

[0055] As can be seen from Figure 6 in conjunction with Figure 9, the first cylindrical wall portion 322 has a circumferential first annular projection 326 extending from its free end, and in this case, the thickness of this first annular projection 326 is smaller than the thickness of the first cylindrical wall portion 322. Correspondingly, the end of the second cylindrical portion 324, which is coupled to the free end of the first cylindrical wall portion 322, also has a circumferential second annular projection 328, and its thickness is smaller than the thickness of the second cylindrical wall portion 324. In this case, the second annular projection 328 surrounds the first annular projection 326 and may be screwed or press-bonded to the first annular projection 326, for example. As can be seen in particular from the detailed view in Figure 9, the inner edge of the free end of the second annular projection 328 is formed with a rounded edge. This rounded portion 330, which may alternatively be configured as a simple chamfered portion, forms a circumferential annular channel 332 between both annular projections 326 and 328. An inflow channel 312 opens from below into the annular channel 332. See also the detailed view in Figure 7 for more information.

[0056] As can be further seen from the plan view in Figure 7, the first annular projection 326 has a recess in the form of an axially extending slot 334, in which case this recess may continue as a groove inside the second cylindrical wall portion 324. Thus, the seal gas that reaches the annular channel 332 via the inflow channel 312 spreads axially inside the second cylindrical wall portion 324 through the distribution channel 336 formed as a slot 334 and the subsequent groove (not shown), thereby reaching the upper region of the motor chamber 310.

[0057] As can be seen from the plan view in Figure 8, another distribution channel 336 branches axially from the annular channel 332. The other distribution channel 336 is located on the opposite side of the annular channel 332 from the distribution channel 336 formed by the slot 334. Specifically, this distribution channel 336 is formed by an axially extending slot 338 in the lower annular projection 326 and a recess 340 in the second annular projection 328. This also extends axially, similar to the slot 338. In this case, the distribution channel 336 formed by the slot 338 and the recess 340 has a larger flow cross-section than the distribution channel 336 formed by the slot 334, thereby ensuring that approximately the same amount of seal gas can reach the motor chamber 310 through both distribution channels 336. To provide a clear and concise explanation, it should be noted that the flow cross-section formed by the slot 338 and the recess 340 may extend axially to the second cylindrical wall portion 324, thereby allowing the seal gas to flow into the motor chamber 310.

[0058] In the embodiment described herein, there are only two distribution channels branching axially from the annular channel 332. However, three or more distribution channels 336 may branch from the annular channel 332, as indicated by dashed lines in Figure 8 as semicircular recesses in both annular projections 326, 328. In this case, these additional distribution channels 336 should preferably be uniformly spaced apart from each other in the circumferential direction. In this case, it is preferable that the flow cross-section of each distribution channel 336 is larger as the distribution channel 336 moves circumferentially away from the inlet channel 312, thereby providing a uniform supply of seal gas to the motor chamber 310.

[0059] Alternatively, the flow cross-section of the annular channel 332 may increase as its distance from the inlet channel 312 increases. This is because, similarly, the distribution channel 336, which is further away from the inlet channel 312, can ensure that substantially the same amount of seal gas flows into the motor chamber 310 as would through the distribution channel 336, which is located closer to the inlet channel 312.

[0060] The fact that the seal gas can flow into the motor chamber 310 without obstruction through the aforementioned distribution channel 336 is due to the motor stator 342 contacting the cylindrical partition wall 314 only on the inside along the central region 344 around which it revolves. In contrast, on both sides of this central region 344, the motor stator 342 is separated from the cylindrical partition wall 314 by the annular chamber 346. Therefore, on the side of the central region 344 closer to the first pump mechanism, the seal gas can flow into the annular chamber 346 without obstruction from the distribution channel 336. From there, the seal gas can further spread toward the annular gap 348, which separates the rotor 356 from the radially extending partition wall 316. Specifically, in this case, the seal gas spreads toward the region used as the expansion volume 350. The expansion volume 350 is formed by the distance between the motor stator 342 and the radially extending partition wall 316.

[0061] Therefore, the sealing gas reaching the annular gap 48 along the aforementioned flow path reliably seals the annular gap 348, and in this case, based on the fact that the sealing gas does not come into contact with oil vapor arriving from the rolling bearing 380 on its way to the annular gap 348, the sealing gas can prevent the sealing gas from carrying oil particles arriving from the rolling bearing 318 on its way to the annular chamber 320 surrounding the cylindrical partition wall 314. Otherwise, the oil particles could deposit as an oil film in the pre-vacuum area at the exhaust port of the Holbeck pump stage in an undesirable manner.

[0062] As shown in the schematic diagram of Figure 10, a portion of the initially introduced seal gas passes through the motor / rotor gap 353 to the lower region of the motor chamber 310, and subsequently reaches the bearing region or the vicinity of the rolling bearing 318. However, this initial volume of seal gas flowing through the motor / rotor gap acts as a buffer for the seal gas that later flows into the expansion volume 350. Therefore, when seal gas is continuously supplied during pump operation, no further seal gas can flow into the lower region of the motor chamber 310. In other words, the lower region of the motor chamber 310 is not through which seal gas flows during pump operation, thereby preventing the seal gas from carrying oil particles arriving from the rolling bearing 318 on its way to the annular gap 348. Otherwise, the oil particles could subsequently deposit as an oil film in the pre-vacuum region.

[0063] In this embodiment, the seal gas first reaches the upper part of the motor chamber 310 via the inlet channel 312, and from there it reaches the annular chamber 320 outside the cylindrical partition wall 314 via the annular gap 348. Unlike the aforementioned embodiment schematically shown in Figure 10, in the very schematic embodiment shown in Figures 11 and 12, the seal gas is intended to bypass the motor chamber 310 and reach the annular chamber 320 surrounding the cylindrical partition wall 314. That is, in the embodiment of Figure 11, the inlet channel 312 leads to an annular channel 332 in the cylindrical partition wall 314, and in this case, this annular channel 223 is in fluid communication with the annular chamber 320 outside the cylindrical partition wall 314 via a plurality of distribution channels 336 that extend radially through the cylindrical partition wall 314.

[0064] Alternatively, in the embodiment shown in Figure 12, the seal gas channel 302 first transitions to an annular channel 332 in the lower part of the housing 306, from which multiple inflow channels 312 extend upward within the cylindrical partition wall 314, with these inflow channels 312 in fluid communication with the annular chamber 320 outside the cylindrical partition wall 314 via radial holes. Additionally, in this embodiment, the cylindrical partition wall 314 is surrounded on its outer circumferential side by a blocking geometry (blocking geometric member) 354, such as an annular flange, which prevents backflow of process gas into the motor chamber 310 through the annular chamber 320. Additionally or alternatively, the blocking geometry may be configured as a structure that performs a pumping action in the form of a Holbeck thread portion, reducing the probability of process gas flowing into the annular chamber surrounding the cylindrical partition wall. [Explanation of symbols]

[0065] 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 Seal gas channel 304 Radial seal gas connection 305 Axial seal gas connection 306 Lower part of housing 307 Seal gas hole 308 Housing top 310 Motor Room 312 Inflow Channels 314 Cylindrical partition wall 316 Partition walls extending in the radial direction 318 Rolling bearings 320 Ring chamber 322 First cylindrical wall section 324 Second cylindrical wall section 326 First annular projection 328 Second annular projection 330 Rounded part 332 ring channels 334 slots 336 distribution channels 338 slots 340 recess 342 Motor Stator 344 Central Area 346 Ring Chamber 348 Annular gap 350 expansion volume 353 Motor / Rotor Gap 354 Obstruction Geometry 356 Rotor 358 Rotor Shaft

Claims

1. In a turbomolecular vacuum pump (300), A housing (306, 308) having a pump intake port (115) and a pump exhaust port (117), A first pump mechanism having at least one turbomolecular pump stage within a housing (306, 308), A second pump mechanism located downstream of a first pump mechanism, having at least one Holbeck pump stage within a housing (306, 308), wherein both the first and second pump mechanisms are configured to pump process gas from a pump intake port (115) to a pump exhaust port (117), A rotor (360) having a rotor shaft (358) for both the first pump mechanism and the second pump mechanism, It comprises an electric motor (125) that drives a rotor shaft (358), The electric motor (125) is located in a motor chamber (310) situated radially inward of the second pump mechanism. The motor chamber (310) is surrounded on its circumferential side by a cylindrical partition wall (314) and, on the side closer to the first pump mechanism, is defined by a radially extending partition wall (316). The radially extending partition wall (316) surrounds the rotor (360) while forming an annular gap (348). Through the annular gap (348), the motor chamber (310) is technically connected to an annular chamber (320) that surrounds the cylindrical partition wall (314). The annular chamber (320) leads to the pump exhaust port. The rotor shaft (358) starts from the first pump mechanism, passes through the second pump mechanism and the motor chamber (310), and extends to an end that is pivotally supported within the housing (306, 308) by rolling bearings (318). The housing (306, 308) has at least one seal gas connection (304, 305) for introducing seal gas to protect the electric motor (125), A turbomolecular pump (300) has an inlet channel (312) formed within a cylindrical partition wall (314), the inlet channel (312) is in fluid communication with a seal gas connection section (304, 305) on one side and with an annular chamber (320) via a flow path on the other side.

2. The turbomolecular vacuum pump (300) according to claim 1, wherein the seal gas connections (304, 305) are formed in the lower part (306) of the housing (306, 308), the lower part (306) accommodates a rolling bearing (318), and a cylindrical partition wall (314) extends axially from the lower part (306) toward the upper part (308) which is coupled to the lower part (306), a first pump mechanism is located in the upper part (308), and the upper part (308), together with the lower part (306), forms a housing chamber in which a second pump mechanism is located.

3. The turbomolecular vacuum pump (300) according to claim 1 or 2, wherein at least one seal gas connection (304, 305) is in fluid communication with an inlet channel (312) via a radially extending seal gas channel (302).

4. The turbomolecular vacuum pump (300) has two seal gas connection parts (304, 305), one of which is provided at the radially outer end of the seal gas channel (302), and the other seal gas connection part (305) is in fluid communication with the seal gas channel (302) via a seal gas hole (307), the seal gas hole (307) opening into the seal gas channel (302) at a location radially inward from the radially outer end of the seal gas channel (302), as described in claim 3.

5. The turbomolecular vacuum pump (300) according to any one of claims 1 to 4, wherein the inlet channel (312) opens downstream to a revolving annular channel (332), the annular channel (332) is formed annularly on a cylindrical partition wall (314), and the annular channel (332) itself is in fluid communication with the annular chamber (320) at least indirectly.

6. The turbomolecular vacuum pump (300) according to claim 5, wherein the cylindrical partition wall (314) has a first cylindrical wall portion (332) and a second cylindrical wall portion (324), the first cylindrical wall portion (332) starting from the lower part of the housing (306) and extending toward the free end toward the first pump mechanism, the second cylindrical wall portion (324) is coupled to the free end of the first cylindrical wall portion (322), the second cylindrical wall portion (322) starting from there and extending toward the end toward the first pump mechanism, at the end a radially extending partition wall (316) is coupled to the second cylindrical wall portion (324), and an annular channel (332) is formed by the cylindrical wall portions (322, 324) at the point where the two cylindrical wall portions (322, 324) are joined.

7. The turbomolecular vacuum pump (300) according to claim 6, wherein the first cylindrical wall portion (322) has a circumferential first annular projection (326) at its free end, the first annular projection (326) having a thickness smaller than that of the first cylindrical wall portion (322), and the end of the second cylindrical wall portion (324) connected to the free end has a circumferential second annular projection (328), the second annular projection (328) surrounding the first annular projection (326) and having a thickness smaller than that of the second cylindrical wall portion (324), and an annular channel (332) between the two annular projections is formed by a chamfered or rounded portion (330) formed to circumfer along the inner edge of the free end of the second annular projection (328).

8. A turbomolecular vacuum pump (300) according to at least one of claims 5 to 7, wherein the motor chamber (310) is in fluid communication with an annular channel (332) via at least one distribution channel (336) defined by a cylindrical partition wall (314), and preferably a plurality of distribution channels are provided which are preferably uniformly spaced apart from each other in the circumferential direction of the annular channel (332).

9. The turbomolecular vacuum pump (300) according to claim 8, wherein the distribution channels have flow cross-sections of different sizes relative to each other in at least part, and / or the flow cross-section of the annular channel (332) increases as the distance from the inlet channel (312) increases.

10. A portion of each distribution channel (336) is formed by axially extending recesses (334, 338, 340) in the first and / or second cylindrical wall portion (324), preferably formed by axially extending recesses (334, 338, 340) in the first and / or second annular projection (328), the turbomolecular vacuum pump (300) according to claim 8 or 9.

11. A turbomolecular vacuum pump (300) according to at least one of claims 8 to 10, wherein an electric motor (125) has a motor stator (342) in a motor chamber (310), the motor stator (342) in contact with a cylindrical partition wall (314) only along a circumferential central region, and at least one distribution channel (336) opens into an annular chamber (346), and the annular chamber (346) positions the motor stator (342) apart from the cylindrical partition wall (314) on the side of the circumferential central region (344) closer to the first pump mechanism.

12. The turbomolecular vacuum pump (300) according to claim 11, wherein the motor stator (342) is located on the side closer to the first pump mechanism, spaced apart from a radially extending partition wall (316) by a spacing used as an expansion volume (350) for a sealing gas.

13. A turbomolecular vacuum pump (300) according to at least one of claims 5 to 12, wherein the annular channel (332) is in fluid communication with the annular chamber (320) on the radially outer side of the cylindrical partition wall (314) via at least one distribution channel (336) extending radially through the cylindrical partition (314), and preferably a plurality of distribution channels are provided which are preferably uniformly spaced apart from each other in the circumferential direction of the annular channel (332).

14. The turbomolecular vacuum pump (300) according to claim 13, wherein the distribution channels have flow cross-sections of different sizes relative to each other in at least part, and / or the flow cross-section of the annular channel (332) increases as the distance from the inlet channel (312) increases.

15. A turbomolecular vacuum pump (300) according to any one of claims 1 to 14, wherein a cylindrical partition wall (314) is surrounded on its outer surface by a barrier geometry (354) which prevents process gas from flowing back into the motor chamber (310) through an annular chamber (320).

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