VACUUM PUMP WITH AN AXIALLY ADJUSTABLE MAGNET CARRIER

Description

[0001] The invention relates to a vacuum pump, in particular a turbomolecular vacuum pump, with at least one pumping stage comprising a stator and a rotor rotating about an axis of rotation relative to the stator during operation, and at least one magnetic bearing for an end region of the rotor near the inlet, which comprises a magnetic bearing rotor and a magnetic bearing stator cooperating therewith, each of which has a stack of several permanent magnet rings, wherein the magnetic bearing rotor is attached to the rotor and the magnetic bearing stator is attached to a holder of the stator.

[0002] The invention also relates to a method for assembling, attaching and adjusting a magnetic bearing of such a vacuum pump.

[0003] Such vacuum pumps are generally known. Turbomolecular vacuum pumps are of particular importance in practice. The pumping action is based on an arrangement of stator blades associated with the stator and rotor blades connected to the rotor. In a typical turbomolecular vacuum pump design, the rotor's axis of rotation runs parallel to the pumping direction, which runs from the pump's intake side (also known as the high-vacuum side), which is equipped with a pump inlet, to the pump's outlet side (also known as the forevacuum side).

[0004] This arrangement of stator blades and rotor blades is also referred to as a turbopump stage, meaning a turbomolecular vacuum pump has one or more such turbopump stages. Typically, turbomolecular vacuum pumps also have one or more Holweck pump stages, which are connected in the pumping direction to the at least one turbopump stage. A Holweck pump stage consists of one or more cylindrical Holweck sleeves, which rotate during operation and are attached to a separate rotor or to a rotor shared by the turbopump stage(s) and Holweck pump stage(s), as well as a Holweck stator.

[0005] The stator of a vacuum pump—in a typical turbomolecular vacuum pump, the stator blades of the turbo pump stages and the Holweck stators of the Holweck pump stages—are in practice usually separate components that are arranged in a rotationally fixed manner inside a pump housing. In principle, it is also possible to form at least some of the stators as a single piece with the pump housing. In this respect, the pump housing can also be considered a component of the stator of a vacuum pump.

[0006] In practice, the rotor of a turbomolecular vacuum pump is typically supported by a so-called hybrid bearing. On the high-vacuum side, i.e., the inlet side, the aforementioned magnetic bearing is located between the rotor and stator. On the forevacuum side, i.e., the outlet side, the rotor is supported by a rolling bearing, particularly a ball bearing. However, there are also purely magnetically mounted rotors, which are supported by a magnetic bearing at both the end near the inlet and the end far from the inlet.

[0007] While the invention is particularly advantageous for the inlet-near magnetic bearing of a rotor of a turbomolecular pump stage, the invention is fundamentally applicable to any vacuum pump in which a magnetic bearing for an end region of the rotor near the inlet is present between a rotor carrying any pumping components and a stator having corresponding pumping components that interact with the rotating pumping components. The magnetic bearing has a stack of several permanent magnet rings on both the stator and rotor sides.

[0008] The assembly and adjustment of such magnetic bearings generally represents a challenge in practice, especially with regard to the magnetic bearing stator.

[0009] The magnetic bearing stator and the magnetic bearing rotor must be brought into a precise axial relative position with respect to the axis of rotation when assembling the vacuum pump. It must be taken into account that the rotor has a certain amount of axial play due to its bearing at the end farthest from the inlet, meaning it can move slightly in the axial direction. Therefore, when adjusting the magnetic bearing, which takes place as part of the pump assembly, the individual permanent magnet rings are first pre-assembled to a component of the stator. This component is typically a pin protruding into the pump housing. This pin is formed on a stator component located near the pump inlet. This component has a star-shaped structure and is therefore also referred to as a stator star. The pin for the magnetic bearing stator is cylindrical and arranged concentrically to the axis of rotation of the rotor.At the free end of the pin there is a disc spring assembly, with the permanent magnet rings arranged between this disc spring assembly and an adjusting ring that is screwed onto the pin.

[0010] By turning the adjustment ring, the permanent magnet rings can be pressed together against the restoring force of the disc spring assembly and adjusted together to adjust their axial position relative to the journal, in order to adjust the axial position of the magnetic bearing stator on the stator. The correct adjustment is achieved when the rotor, which has the aforementioned slight axial play, suddenly performs a small jump in the axial direction due to the interaction of the permanent magnet ring stacks of the stator and rotor, which are axially relative to one another during adjustment. The rotational position of the magnetic bearing stator on the journal at which this effect occurs is also referred to as the tilt angle. In practice, this adjustment of the magnetic bearing is typically carried out with the vacuum pump lying flat, i.e. with the rotor's axis of rotation running horizontally.

[0011] This procedure for adjusting the magnetic bearing of a vacuum pump is generally known to those skilled in the art and, in principle, enables reliable and precise axial positioning of the magnetic bearing stator. However, this adjustment concept is not without disadvantages. The assembly of the aforementioned disc spring assembly is time-consuming and error-prone. Furthermore, individual disc springs can "fold over" during assembly, requiring rework and thus resulting in additional costs. Furthermore, when turning the adjustment ring, friction between the adjustment ring and the permanent magnet rings or any spacers used can generate chips that can enter the pump interior.Furthermore, due to its design, the adjusting ring is only accessible from the inlet side of the pump via circular slots. This means that the adjusting tool used to rotate the adjusting ring must be repositioned several times, as the slotted holes limit the rotation to a relatively small angle. This makes automating the adjustment process, which is still performed manually in practice, difficult or practically impossible. Another problem is that the spring characteristic of the disc springs is not linear. Due to thermal expansion, individual disc springs can "fold over," causing the permanent ring stack to no longer be sufficiently preloaded.

[0012] Document EP 3 018 373 A1 discloses a vacuum pump in which the axial position of a support on a holding element is adjustable by means of a tool that can be passed through a plurality of through-bores. Document US 2003 / 155830 A1 discloses a vacuum pump in which the axial position of a support relative to a housing is adjustable by means of adjusting screws. Document EP 3 683 447 A1 discloses a vacuum pump with a support section that extends through ring magnets and is suspended from radial struts of a housing. Document US 2019 / 368499 A1 discloses a vacuum pump in which the axial position of a support section on a holder is adjustable.

[0013] The object of the invention is therefore to simplify the assembly and adjustment of a magnetic bearing for the rotor of a vacuum pump.

[0014] This problem is solved by the features of the independent claims.

[0015] In the device according to the invention, a separate magnet carrier is provided for the magnetic bearing stator, on which the permanent magnet rings can be fully assembled independently of the holder and which, together with the fully assembled permanent magnet rings, can be attached to the holder as a single unit. The axial position of the magnet carrier on the holder can be adjusted with respect to the rotational axis. The holder has a passage running parallel to the rotational axis, through which the magnet carrier is accessible from the inlet side of the pump for a manually or mechanically operable adjustment tool for adjusting the axial position of the magnet carrier.

[0016] In this context, "fully assembled" means that the permanent magnet rings are pressed together, meaning they can only move in the axial direction as a whole stack, but no longer relative to each other.

[0017] The invention represents a departure from the previous practice of individually arranging the permanent magnet rings of the magnetic bearing stator directly on the stator of the vacuum pump, only then compressing them and simultaneously moving them against the restoring force of a spring to adjust the required axial position. While in the prior art explained above, the compression of the permanent magnet rings and the adjustment of the axial position occur virtually simultaneously, meaning that essentially no distinction can be made between compression and adjustment, which leads to the problems explained above, the invention takes a completely different approach.

[0018] The separate magnet carrier created by the invention enables pre-assembly of the permanent magnet rings independently of the vacuum pump stator. The permanent magnet rings can be easily and precisely assembled on this separate magnet carrier, i.e., pressed together with a butt joint. This enables automation. The unit consisting of the magnet carrier and permanent magnet rings can thus be manufactured and assembled in large quantities.

[0019] The fully assembled units can be handled completely independently of the rest of the vacuum pump and, in particular, can be manufactured externally as a purchased part. During final assembly of the vacuum pump, this unit can be attached to the stator as a whole. Since the permanent magnet rings are already fully assembled, only the axial position remains during assembly on the vacuum pump stator. This adjustment is done by adjusting the axial position of the magnet carrier and thus the permanently mounted permanent magnet stack on the stator holder.

[0020] Another advantage is that if the magnetic bearing or magnetic bearing stator needs to be replaced during use of the vacuum pump in the field, it is no longer necessary to replace the individual permanent magnet rings of the magnetic bearing stator or the stator or the housing in whole or in part, but only the unit consisting of the magnet carrier and the permanent magnet ring stack, which can be handled as a whole, needs to be replaced.

[0021] The method according to the invention for assembling, attaching and adjusting a magnetic bearing of a vacuum pump according to the invention is characterized by the following steps: Mounting the magnetic bearing rotor on the rotor, providing a separate magnet carrier for the magnetic bearing stator, mounting the permanent magnet rings of the magnetic bearing stator on the magnet carrier independently of the stator of the vacuum pump, attaching the magnet carrier together with the fully assembled permanent magnet rings as a unit to a holder of the stator, and adjusting the magnetic bearing by adjusting the axial position of the magnet carrier on the holder with respect to the axis of rotation.

[0022] Possible further developments of the invention are specified in the dependent claims, the drawing and the following description.

[0023] In some embodiments, it may be provided that the magnet carrier has an actuating section for the adjustment tool on a side facing the inlet side of the pump and aligned with the passage.

[0024] The adjustment tool can, in particular, be a hexagon socket wrench that can be operated manually or by means of an automatic machine. The actuating section of the magnet carrier then comprises a corresponding hexagon profile for this tool.

[0025] According to some developments of the invention, the attachment of the magnet carrier to the holder and the adjustment of the axial position of the magnet carrier on the holder are carried out by screwing the magnet carrier to the holder.

[0026] The use of a separate magnetic carrier according to the invention enables complete revolutions of the adjustment tool, so that the multiple replugging explained at the beginning in connection with the prior art is no longer necessary and the assembly of the vacuum pump is thus accelerated.

[0027] According to some embodiments, the holder may comprise a retaining pin extending parallel to the axis of rotation, wherein the retaining pin and the magnet carrier are arranged to overlap one another in the axial direction.

[0028] It can be provided that the retaining pin protrudes into the stack of permanent magnet rings of the magnetic bearing stator mounted on the magnet carrier.

[0029] The magnet carrier can be attached to the retaining pin by screwing it into a recess formed in the retaining pin, particularly into the passage running parallel to the rotation axis. Alternatively, the magnet carrier can be attached by screwing it onto an outer side of the retaining pin.

[0030] The holder, to which the magnet carrier can be attached, is arranged in particular in the region of the pump inlet. The holder can be star-shaped and comprise a particularly annular outer section connected to a pump housing, a central section having the retaining pin, and a plurality of web sections distributed in the circumferential direction, by which the central section is connected to the outer section.

[0031] In particular, the holder can be a separate, one-piece component that is inserted into the pump housing on the inlet side and arranged in a rotationally fixed manner. In particular, the holder can be a so-called stator star, as already mentioned above.

[0032] In some embodiments, the magnet carrier may comprise a centering sleeve, on which the permanent magnet rings are seated radially outward, and two axially spaced abutments for the permanent magnet rings. In particular, it may be provided that the centering sleeve and the holder, in particular a retaining pin of the holder, overlap each other in the axial direction.

[0033] When fully assembled, the permanent magnet rings are clamped between these abutments, i.e. pressed together.

[0034] In this case, one abutment, in particular the one remote from the inlet, can be formed integrally with the centering sleeve, while the other abutment, in particular the one near the inlet, can be a separate component that is firmly connected to the centering sleeve. This separate abutment can be pressed or screwed to the centering sleeve to create the fully assembled state.

[0035] Furthermore, in some embodiments, the magnet carrier may comprise a central section arranged concentrically with the centering sleeve, having a reduced diameter compared to the centering sleeve. This central section may, in particular, be pin-shaped. The centering sleeve and the central section may be connected to one another by a connecting section located below the retaining pin of the holder. In particular, the centering sleeve and the central section may be integrally connected to one another. Depending on the specific embodiment of the magnet carrier, the central section may have different designs and fulfill different functions.

[0036] The central section and the centering sleeve can be arranged to overlap each other in the axial direction. Alternatively or additionally, the central section can protrude beyond the end of the centering sleeve remote from the inlet.

[0037] The centering sleeve can serve more than just as a seat for the permanent magnet rings. Additionally, the magnet carrier can be screwed onto a retaining pin of the holder, which extends parallel to the axis of rotation, using the centering sleeve. The centering sleeve thus serves to attach the magnet carrier to the holder of the vacuum pump's stator. Alternatively, the magnet carrier can be attached using a central section connected to the centering sleeve, by screwing it to a retaining pin of the holder, which extends parallel to the axis of rotation. In particular, the central section of the magnet carrier can be screwed into a recess formed in the retaining pin. This recess can, in particular, be the passage running parallel to the axis of rotation.

[0038] In a specific embodiment, the central section can therefore be a threaded pin with an actuating section for an adjustment tool, which is screwed into the passage of the retaining pin and is thus accessible for the adjustment tool from the inlet side.

[0039] According to the invention, one of two mutually associated bearing parts of a safety or emergency bearing for the rotor having the other bearing part is arranged on a free end region of the magnet carrier remote from the inlet. The provision of safety or emergency bearings for magnetically mounted rotors of vacuum pumps is known in principle. In these developments of the invention, the magnet carrier can simultaneously be used as a component of such a safety or emergency bearing. The corresponding bearing part for this safety or emergency bearing can be arranged, in particular, on a central section of the magnet carrier connected to a centering sleeve.

[0040] According to further embodiments of the invention, a clamping device acting in the axial direction between the magnet carrier and the holder can be provided. A set axial relative position between the magnet carrier and the holder can thereby be secured. This is particularly advantageous when the magnet carrier and the holder are screwed together, since the clamping device eliminates thread play. Furthermore, sufficient self-locking of the thread can be achieved by such a clamping device. The clamping device thus ensures very high protection against rotation and thus secures the respectively set axial position of the magnet carrier.

[0041] The tensioning device can, for example, be a spring. The spring can, for example, comprise a compression spring or a wave spring. There can be different possibilities for the arrangement of a spring serving as a tensioning device, depending on the specific design. For example, the spring can act between a connecting section that connects a central section and a centering sleeve of the magnet carrier to one another, and the end region of a retaining pin of the holder that extends parallel to the axis of rotation and is remote from the inlet. Alternatively or additionally, a spring serving as a tensioning device can surround a retaining pin of the holder and act between a shoulder region at the transition between the retaining pin and the holder, on the one hand, and the end region of the magnet carrier that is close to the inlet, on the other.

[0042] Alternatively or additionally, the clamping device can comprise a screw. The screw can be designed, for example, as a grub screw. A screw serving as a clamping device can be screwed to the holder and apply axial pressure to the magnet carrier. In particular, it can be provided that the screw serving as a clamping device is screwed into the passage formed in a retaining pin of the holder extending parallel to the rotation axis.

[0043] Furthermore, according to some embodiments, at least one recess acting as a chip pocket can be formed in at least one of two contact surfaces of the holder and the magnet carrier that touch each other and move relative to each other during attachment and adjustment of the magnet carrier. The recess can, for example, be an annular groove encircling the rotation axis.

[0044] One or more recesses acting as chip pockets can be formed, for example, on the inside of the centering sleeve. Alternatively or additionally, one or more recesses can also be formed on the outside of a retaining pin of the holder. The concept of the recesses acting as chip pockets is independent of the manner in which the magnet carrier is attached to the stator. In particular, regardless of whether the centering sleeve is screwed to the retaining pin to attach the magnet carrier to the stator or a central section of the magnet carrier is screwed into a recess formed in the retaining pin, in particular a passage, the concept of the recess(es) acting as chip pockets can be provided on at least one of the contact surfaces between the centering sleeve and the retaining pin.

[0045] The possible developments of the invention explained above and also those developments which result from the following description of the drawing are developments both of the vacuum pump according to the invention, in particular of the magnetic carrier according to the invention, and developments of the method according to the invention.

[0046] If, in connection with the explanation of combinable developments, individual components have the same designation, then in an inventive object comprising these developments in combination, the component in question can have several of the explained developments. For example, in some embodiments of the invention, a central section of the magnet carrier can be designed as a pin with an external thread and thus serve to screw the magnet carrier to a passage formed in a retaining pin of the holder, wherein the central section can simultaneously have the bearing part of the catch or emergency bearing on a free end region remote from the inlet, but this is not mandatory. This also applies analogously to other components explained in connection with different developments.

[0047] The invention is described below by way of example with reference to the drawings. Fig. 1 a perspective view of a known turbomolecular pump, Fig. 2 a view of the underside of the turbomolecular pump of Fig. 1 , Fig. 3 a cross-section of the turbomolecular pump along the Fig. 2 shown section line AA, Fig. 4 a cross-sectional view of the turbomolecular pump along the Fig. 2 shown section line BB, Fig. 5 a cross-sectional view of the turbomolecular pump along the Fig. 2 shown section line CC, Fig. 6a and 6b possible embodiment of a turbomolecular vacuum pump according to the invention, wherein Fig. 6b an enlarged section of Fig. 6a with the magnetic bearing, Fig. 7a and 7b show a further possible embodiment of the invention in a corresponding representation, Fig. 8a and 8b show a further possible embodiment of the invention in a corresponding representation, Fig. 9a and 9b show a further possible embodiment of the invention in a corresponding representation, and Fig. 10 shows a stator star of a vacuum pump serving as a holder with a magnet carrier attached thereto according to a further embodiment of the invention.

[0048] The Fig. 1 The turbomolecular pump 111 shown comprises a pump inlet 115 surrounded by an inlet flange 113, to which a recipient (not shown) can be connected in a manner known per se. The gas from the recipient can be sucked out of the recipient via the pump inlet 115 and conveyed through the pump to a pump outlet 117, to which a backing pump, such as a rotary vane pump, can be connected.

[0049] The inlet flange 113 forms when the vacuum pump is aligned according to Fig. 1 the upper end of the housing 119 of the vacuum pump 111. The housing 119 comprises a lower part 121, on which an electronics housing 123 is arranged laterally. Electrical and / or electronic components of the vacuum pump 111 are housed in the electronics housing 123, e.g., for operating an electric motor 125 arranged in the vacuum pump (see also Fig. 3 ). Several connectors 127 for accessories are provided on the electronics housing 123. In addition, a data interface 129, e.g., according to the RS485 standard, and a power supply connector 131 are arranged on the electronics housing 123.

[0050] There are also turbomolecular pumps that do not have such an attached electronics housing, but are connected to external drive electronics.

[0051] On the housing 119 of the turbomolecular pump 111, a flooding inlet 133, in particular in the form of a flooding valve, is provided, via which the vacuum pump 111 can be flooded. In the area of ​​the lower part 121, a sealing gas connection 135, which is also referred to as a purge gas connection, is also arranged, via which purge gas is supplied to protect the electric motor 125 (see e.g. Fig. 3 ) can be admitted into the motor compartment 137, in which the electric motor 125 is housed in the vacuum pump 111, before the gas delivered by the pump. Furthermore, two coolant connections 139 are arranged in the lower part 121, one of which serves as an inlet and the other as an outlet for coolant, which can be fed into the vacuum pump for cooling purposes. Other existing turbomolecular vacuum pumps (not shown) are operated exclusively with air cooling.

[0052] The lower side 141 of the vacuum pump can serve as a base, so that the vacuum pump 111 can be operated standing on the underside 141. However, the vacuum pump 111 can also be attached to a recipient via the inlet flange 113 and thus operated in a suspended position. Furthermore, the vacuum pump 111 can be designed so that it can also be operated when oriented in a different way than in Fig. 1 As shown. Embodiments of the vacuum pump can also be realized in which the underside 141 is arranged facing sideways or upwards rather than downwards. In principle, any angle is possible.

[0053] Other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here, cannot be operated in an upright position.

[0054] On the underside 141, which is Fig. 2 As shown, various screws 143 are arranged, by means of which components of the vacuum pump (not further specified here) are fastened together. For example, a bearing cover 145 is attached to the underside 141.

[0055] Mounting holes 147 are also arranged on the underside 141, via which the pump 111 can be attached, for example, to a support surface. This is not possible with other existing turbomolecular vacuum pumps (not shown), which are particularly larger than the pump shown here.

[0056] In the Figuren 2 bis 5 a coolant line 148 is shown in which the coolant introduced and discharged via the coolant connections 139 can circulate.

[0057] As the sectional views of the Figuren 3 bis 5 show, the vacuum pump comprises several process gas pumping stages for conveying the process gas present at the pump inlet 115 to the pump outlet 117.

[0058] A rotor 149 is arranged in the housing 119 and has a rotor shaft 153 rotatable about a rotation axis 151.

[0059] The turbomolecular pump 111 comprises several turbomolecular pumping stages connected in series for pumping purposes, with several radial rotor disks 155 attached to the rotor shaft 153 and stator disks 157 arranged between the rotor disks 155 and secured in the housing 119. A rotor disk 155 and an adjacent stator disk 157 each form a turbomolecular pumping stage. The stator disks 157 are held at a desired axial distance from one another by spacer rings 159.

[0060] The vacuum pump also includes Holweck pump stages arranged radially one inside the other and connected in series for pumping efficiency. Other turbomolecular vacuum pumps (not shown) exist that do not have Holweck pump stages.

[0061] The rotor of the Holweck pump stages comprises a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical-shell-shaped Holweck rotor sleeves 163, 165 attached to and supported by the rotor hub 161, which are oriented coaxially to the rotation axis 151 and nested within one another in the radial direction. Furthermore, two cylindrical-shell-shaped Holweck stator sleeves 167, 169 are provided, which are also oriented coaxially to the rotation axis 151 and nested within one another in the radial direction.

[0062] The pumping surfaces of the Holweck pump stages are formed by the lateral surfaces, i.e., the radial inner and / or outer surfaces, of the Holweck rotor sleeves 163, 165 and the Holweck stator sleeves 167, 169. The radial inner surface of the outer Holweck stator sleeve 167 lies opposite the radial outer surface of the outer Holweck rotor sleeve 163, forming a radial Holweck gap 171, and together with the latter forms the first Holweck pump stage following the turbomolecular pumps. The radial inner surface of the outer Holweck rotor sleeve 163 lies opposite the radial outer surface of the inner Holweck stator sleeve 169, forming a radial Holweck gap 173, and together with the latter forms a second Holweck pump stage. The radial inner surface of the inner Holweck stator sleeve 169 lies opposite the radial outer surface of the inner Holweck rotor sleeve 165, forming a radial Holweck gap 175 and together forming the third Holweck pumping stage.

[0063] At the lower end of the Holweck rotor sleeve 163, a radially extending channel can be provided, via which the radially outer Holweck gap 171 is connected to the central Holweck gap 173. Furthermore, at the upper end of the inner Holweck stator sleeve 169, a radially extending channel can be provided, via which the central Holweck gap 173 is connected to the radially inner Holweck gap 175. This connects the nested Holweck pump stages in series. A connecting channel 179 to the outlet 117 can also be provided at the lower end of the radially inner Holweck rotor sleeve 165.

[0064] The above-mentioned pump-active surfaces of the Holweck stator sleeves 167, 169 each have a plurality of Holweck grooves extending spirally around the rotation axis 151 in the axial direction, while the opposite lateral surfaces of the Holweck rotor sleeves 163, 165 are smooth and propel the gas in the Holweck grooves to operate the vacuum pump 111.

[0065] For the rotatable mounting of the rotor shaft 153, a rolling bearing 181 is provided in the area of ​​the pump outlet 117 and a permanent magnet bearing 183 is provided in the area of ​​the pump inlet 115.

[0066] In the area of ​​the rolling bearing 181, a conical spray nut 185 with an outer diameter increasing toward the rolling bearing 181 is provided on the rotor shaft 153. The spray nut 185 is in sliding contact with at least one wiper of a fluid reservoir. In other existing turbomolecular vacuum pumps (not shown), a spray screw can be provided instead of a spray nut. Since different designs are thus possible, the term "spray tip" is also used in this context.

[0067] The operating fluid storage comprises several stacked absorbent discs 187 which are impregnated with an operating fluid for the rolling bearing 181, e.g. with a lubricant.

[0068] During operation of the vacuum pump 111, the operating fluid is transferred by capillary action from the operating fluid reservoir via the wiper to the rotating injection nut 185. As a result of centrifugal force, it is conveyed along the injection nut 185 in the direction of the increasing outer diameter of the injection nut 185 to the rolling bearing 181, where it fulfills a lubricating function, for example. The rolling bearing 181 and the operating fluid reservoir are enclosed in the vacuum pump by a trough-shaped insert 189 and the bearing cover 145.

[0069] The permanent magnet bearing 183 comprises a rotor-side bearing half 191 and a stator-side bearing half 193, each comprising a ring stack of several permanent magnetic rings 195, 197 stacked one on top of the other in the axial direction. The ring magnets 195, 197 lie opposite one another, forming a radial bearing gap 199, with the rotor-side ring magnets 195 being arranged radially on the outside and the stator-side ring magnets 197 being arranged radially on the inside. The magnetic field present in the bearing gap 199 creates magnetic repulsion forces between the ring magnets 195, 197, which effect a radial bearing of the rotor shaft 153. The rotor-side ring magnets 195 are carried by a support section 201 of the rotor shaft 153, which surrounds the ring magnets 195 on the radial outside.The stator-side ring magnets 197 are supported by a stator-side support section 203, which extends through the ring magnets 197 and is suspended from radial struts 205 of the housing 119. The rotor-side ring magnets 195 are secured parallel to the rotation axis 151 by a cover element 207 coupled to the support section 201. The stator-side ring magnets 197 are secured parallel to the rotation axis 151 in one direction by a fastening ring 209 connected to the support section 203 and a fastening ring 211 connected to the support section 203. A disc spring 213 can also be provided between the fastening ring 211 and the ring magnets 197.

[0070] Within the magnetic bearing, an emergency or backup bearing 215 is provided, which runs idle without contact during normal operation of the vacuum pump 111 and only engages upon excessive radial deflection of the rotor 149 relative to the stator, forming a radial stop for the rotor 149 to prevent collision of the rotor-side structures with the stator-side structures. The backup bearing 215 is designed as an unlubricated roller bearing and forms a radial gap with the rotor 149 and / or the stator, causing the backup bearing 215 to be disengaged during normal pumping operation. The radial deflection at which the backup bearing 215 engages is large enough so that the backup bearing 215 does not engage during normal operation of the vacuum pump, and at the same time small enough so that collision of the rotor-side structures with the stator-side structures is prevented under all circumstances.

[0071] The vacuum pump 111 comprises the electric motor 125 for rotating the rotor 149. The armature of the electric motor 125 is formed by the rotor 149, whose rotor shaft 153 extends through the motor stator 217. A permanent magnet arrangement can be arranged radially on the outside or embedded in the portion of the rotor shaft 153 extending through the motor stator 217. Between the motor stator 217 and the portion of the rotor 149 extending through the motor stator 217, an intermediate space 219 is arranged, which comprises a radial motor gap, via which the motor stator 217 and the permanent magnet arrangement can magnetically influence each other to transmit the drive torque.

[0072] The motor stator 217 is fixed in the housing within the motor compartment 137 provided for the electric motor 125. A seal gas, also referred to as purge gas, which can be, for example, air or nitrogen, can enter the motor compartment 137 via the seal gas connection 135. The seal gas can be used to protect the electric motor 125 from process gas, e.g., from corrosive components of the process gas. The motor compartment 137 can also be evacuated via the pump outlet 117, i.e., the vacuum pressure in the motor compartment 137 is at least approximately the vacuum pressure generated by the backing pump connected to the pump outlet 117.

[0073] Furthermore, a so-called labyrinth seal 223, which is known per se, can be provided between the rotor hub 161 and a wall 221 delimiting the motor compartment 137, in particular in order to achieve a better sealing of the motor compartment 217 with respect to the Holweck pump stages located radially outside.

[0074] With regard to individual details of the turbomolecular vacuum pumps according to the invention described below, reference is made to the above description of the Fig. 1 bis 5 , ie all the configurations described therein can also be implemented in a vacuum pump according to the invention. Conversely, the embodiments of the invention described below can also be implemented in the vacuum pump according to the Fig. 1 bis 5 explained vacuum pump can be realized.

[0075] The Fig. 6a , 7a , 8a and 9aThe turbomolecular vacuum pumps shown each have a pump housing 33 in which two pump stages are located, namely a turbo pump stage 11 located closer to the inlet of the pump and a Holweck pump stage 13 adjoining it in the pumping direction. The individual stator blades 11a form the stator of the turbo pump stage 11. The Holweck pump stage 13 has a stator 13a which, viewed in the radial direction, is arranged between two Holweck sleeves 13b which are attached in a rotationally fixed manner to a common rotor 15 of the turbo pump stage 11 and the Holweck pump stage 13. The stator blades 11a of the turbo pump stage 11 interact with rotor blades 11b which, like the Holweck sleeves 13b, are connected in a rotationally fixed manner to the rotor 15.

[0076] This design of a turbomolecular pump stage is generally known. Also generally known is the inlet-side bearing of the rotor 15 by means of a magnetic bearing 17. The magnetic bearing 17 comprises a magnetic bearing rotor 19 and a magnetic bearing stator 21 (see FIG. Fig. 6b , 7b , 8b and 9b ), each of which has a stack of permanent magnet rings 19a (magnetic bearing rotor) and 21a (magnetic bearing stator) arranged one above the other in the axial direction. The axial direction here refers to the rotational axis 14 of the rotor 15.

[0077] The permanent magnet rings 19a of the magnetic bearing rotor 19 are pressed together by means of an abutment 61, for example a pressed-in or screwed-in ring, and are thus attached to the rotor 15 in an axially defined position and in a rotationally fixed manner.

[0078] The magnetic bearing stator 21 is part of a structural unit that can be handled as a whole and separately from the rest of the vacuum pump and that additionally comprises a magnet carrier 25. As explained in more detail below, the magnet carrier 25 is attached to a retaining pin 31 that is integrally formed on a so-called stator star 23, which comprises an annular outer part 35, a central section 37 provided with the retaining pin 31, and a plurality of web sections 39 arranged distributed in the circumferential direction, which connect the central section 37 to the outer section 35. This stator star is a one-piece, separate component that is non-rotatably inserted into the pump housing 33 on the inlet side. The magnet carrier 25 is a one-piece component that can be made, for example, of metal.

[0079] In all embodiments illustrated here, a passage 27 is formed in the cylindrical retaining pin 31, which is arranged concentrically to the rotational axis 14 and opens at a front end remote from the inlet at the free end region of the retaining pin 31. The function of the retaining pin 31 and its passage 27 will be discussed in more detail below.

[0080] The magnet carrier 25 comprises a cylindrical centering sleeve 41, on which the permanent magnet rings 21a are seated radially outward. At its end remote from the inlet, the centering sleeve 41 is provided with a radially outwardly projecting shoulder, which serves as an abutment 45 for the permanent magnet ring stack 21a. Furthermore, the centering sleeve 41 is connected to a pin-shaped central section 47 via an annular connecting section 49. On its side facing the inlet, the central section 47 is provided with an actuating section 29 in the form of a hexagon socket (Allen key). This actuating section 29 is accessible from the inlet side of the pump via the passage 27 formed in the retaining pin 31 for an adjustment tool (not shown), which serves to rotate the magnet carrier 25 about the rotation axis 14.

[0081] At its free end region remote from the inlet, the central section 37 carries a bearing part 51 of an emergency or safety bearing for the rotor 15, the other bearing part 53 being arranged on the rotor 15 (cf. Fig. 6b , 7b , 8b and 9b ).

[0082] The permanent magnet rings 21a of the magnetic bearing stator 21 are pressed together by means of an abutment 43, i.e., the stack of permanent magnet rings 21a is clamped between the two abutments 43, 45 on the magnet carrier 25 and is thus fully assembled on the magnet carrier 25. The abutment 43 is designed as a clamping ring, which is pressed or screwed onto the centering sleeve 41 of the magnet carrier 25 during assembly of the magnetic bearing stator 21 on the magnet carrier 25 - depending on the specific design.

[0083] The unit comprising the magnet carrier 25 and the magnetic bearing stator 21 fully assembled thereon is a separate assembly that can be handled as a whole and manufactured and assembled independently of the rest of the vacuum pump.

[0084] The embodiments described here differ in particular with regard to the manner in which the magnet carrier 25 is attached to the retaining pin 31 of the stator star 23 and with regard to the manner in which a clamping device is provided between the stator star 23 and the magnet carrier 25.

[0085] In the embodiment of the Fig. 6a and 6b The magnet carrier 25, together with the fully assembled magnetic bearing stator 21 and the centering sleeve 41, is screwed onto the retaining pin 31. A screw thread 63 is used for this purpose, ie in this area the inside of the centering sleeve 41 is provided with an internal thread and the outside of the retaining pin 31 with an external thread.

[0086] The screwing is carried out by turning the magnet carrier 25 by means of the adjustment tool already mentioned, which cooperates with the actuating section 29 formed on the central section 47.

[0087] To prevent any chips that may be formed from entering the pump interior, a recess 59 in the form of a circumferential groove is provided on the outside of the retaining pin 31, which serves as a chip pocket.

[0088] The aforementioned clamping device here comprises a compression spring 57, which is arranged between the end face of the free end of the retaining pin 31, which is remote from the inlet, and the side of the central section 47 facing the inlet. The compression spring 57 eliminates the play in the thread 63 and simultaneously ensures a sufficiently high self-locking force of this thread 63. This reliably secures the magnet carrier 25 against unintentional rotation.

[0089] The embodiment of the Fig. 7a and 7bdiffers from the embodiment described above in that a grub screw 57 is provided as the clamping device, which is screwed into the passage 27 in the holding pin 31, which passage is provided with a corresponding internal thread. With a cone 57a formed at its free end remote from the inlet, this clamping screw 57 acts on the central section 47 at a counter surface 57b surrounding the actuating section 29 with a corresponding cone angle. For clamping, the grub screw 57 can be turned using a tool (not shown), for example an Allen key, which cooperates with a corresponding profile (not shown) formed on the side of the clamping screw 57 facing the inlet.

[0090] The embodiment of the Fig. 8a and 8b combines the two variants in terms of the clamping device according to Fig. 6a and 6b on the one hand and Fig. 7a and 7bThe tensioning and thus the anti-twist protection is effected here both by a compression spring 57 according to Fig. 6a and 6b as well as by a grub screw 57 according to Fig. 7a and 7b This ensures a particularly high degree of anti-twist protection for the magnet carrier 25.

[0091] The clamping by means of the grub screw 57 only takes place when the required axial position of the magnet carrier 25 has been reached by turning.

[0092] In the embodiment of the Fig. 9a and 9bA wave spring 57 is provided as a tensioning device. The wave spring 57 is arranged at the base of the retaining pin 31, i.e., the wave spring 57 surrounds the retaining pin 31 and is supported with its side facing the inlet on a shoulder area at the transition between the retaining pin 31 and the central section 37 of the stator star 23. With its other end, the wave spring 57 acts on the assembly consisting of the magnet carrier 25 and the magnetic bearing stator 21.

[0093] In the embodiment of the Fig. 10 The magnet carrier 25 is not attached to the retaining pin 31 by screwing it using the centering sleeve 41 of the magnet carrier 25. Instead, the central section 47 of the magnet carrier 25 extends from the connecting section 49 to the inlet side of the pump, i.e. into the centering sleeve 51 and thus in the direction of the retaining pin 31. The length of this pin-shaped part of the central section 47 is dimensioned such that the central section 47 can be screwed into the passage 27 of the retaining pin 31. For this purpose, a screw thread 63 is provided, which comprises an external thread on the central section 47 and an internal thread of the retaining pin 31 formed in the passage 27.

[0094] The screwing of the magnet carrier 25 to the retaining pin 31 is again achieved by actuating the central section 47 on the actuating section 29, which is formed on the pin-shaped section of the central section 47 screwed into the retaining pin 31. A tensioning device, which here is arranged as a compression spring 57 between the front end of the retaining pin 31 and the connecting section 49 of the magnet carrier 25, serves to eliminate play and self-lock the thread 73 and thus to prevent rotation of the magnet carrier 25.

[0095] On at least one of the contact surfaces between the holding section 31 and the centering sleeve 41, one or more recesses can be provided which, as in the other embodiments, serve as chip pockets.

[0096] A bore 67 is formed in the connecting section 49, which prevents a so-called dead volume from forming within the centering sleeve 41 when the magnet carrier 25 is mounted. The bore 67 allows this space to be evacuated during operation of the vacuum pump. One or more corresponding evacuation openings, such as the bore 67, can also be provided in the other embodiments.

[0097] The fit between the permanent magnet rings 21a and the outside of the centering sleeve 41 is a clearance fit in all embodiments. This also applies to the fit between the outside of the retaining pin 31 and the inside of the centering sleeve 41 in the embodiment of the Fig. 10 , in which the screw connection does not take place between the retaining pin 31 and the centering sleeve 41.

[0098] In all embodiments described here, independent of the assembly of a respective vacuum pump, the magnetic bearing stator 21 can first be pre-assembled on the magnet carrier 25. The permanent magnet rings 21a can thus be arranged on the centering sleeve 41 completely independently of the rest of the vacuum pump and, in particular, independently of the retaining pin 31 of the stator star 23 and finally pressed against the other abutment 45 by means of the abutment 43, for example a press-on or screw-on ring, and thus pressed together in abutment and thus fully assembled.

[0099] This prefabricated assembly is then screwed to the retaining pin 31 in the manner described above, with the compression or wave spring 57 serving as a tensioning device being interposed if necessary.

[0100] Once the magnet carrier is screwed to the retaining pin 31, the correct relative axial position of the magnetic bearing stator 21 can be adjusted immediately thereafter or at a later time by adjusting the axial position of the magnet carrier 25 by turning it, as described in the introductory section.

[0101] If, instead of or in addition to a spring as a tensioning device, a grub screw is used which also serves as a tensioning device (cf. Fig. 7a , 7b and Fig. 8a , 8b ), then after setting the correct axial position, the grub screw 57 is tightened in order to eliminate the thread play between the retaining pin 31 and the centering sleeve 41 and to ensure the self-locking of this screw thread, thus ensuring a high degree of security against rotation.

Claims

1. A vacuum pump, in particular a turbomolecular vacuum pump, comprising - at least one pump stage (11, 13) which comprises a stator (11a, 13a) and a rotor (15) rotating relative to the stator (11a, 13a) about an axis of rotation (14) during operation, and - at least one magnetic bearing (17) for an end region of the rotor (15) near the inlet, said magnetic bearing (17) comprising a magnetic bearing rotor (19) and a magnetic bearing stator (21) interacting therewith, said magnetic bearing rotor and magnetic bearing stator each having a stack of a plurality of permanent magnet rings (19a, 21a), wherein the magnetic bearing rotor (19) is attached to the rotor (15) and the magnetic bearing stator (21) is attached to a holder (23) of the stator (11a, 13a), wherein a separate magnet carrier (25) is provided for the magnetic bearing stator (21), at which magnet carrier the permanent magnet rings (21a) can be completely mounted independently of the holder (23) and which magnet carrier can be attached together with the completely mounted permanent magnet rings (21a) as a unit to the holder (23), and wherein the axial position of the magnet carrier (25) at the holder (23) is adjustable with respect to the axis of rotation (14), wherein the holder (23) has a passage (27) which extends parallel to the axis of rotation (14) and through which the magnet carrier (25) is accessible, starting from the inlet side of the pump, for a manually or automatically operable setting tool for setting the axial position of the magnet carrier (25), characterized in that the one of two mutually associated bearing parts (51, 53) of a catch bearing or emergency bearing (55) for the rotor (15) having the other bearing part is arranged at a free end region of the magnet carrier (25) remote from the inlet.

2. A vacuum pump according to claim 1, wherein the magnet carrier (25) has an actuating section (29) for the setting tool at a side facing the inlet side of the pump and aligned with the passage (27).

3. A vacuum pump according to claim 1 or 2, wherein the attachment of the magnet carrier (25) to the holder (23) and the adjustment of the axial position of the magnet carrier (25) at the holder (23) take place by screwing the magnet carrier (25) to the holder (23).

4. A vacuum pump according to any one of the preceding claims, wherein the holder (23) comprises a holding pin (31) extending parallel to the axis of rotation, and wherein the holding pin (31) and the magnet carrier (23) are arranged overlapping one another in the axial direction.

5. A vacuum pump according to claim 4, wherein the holding pin (31) projects into the stack of the permanent magnet rings (21a) of the magnetic bearing stator (21) mounted at the magnet carrier (25), and / or wherein the magnet carrier (25) is screwed into a recess formed in the holding pin (31), in particular into the passage (27) extending parallel to the axis of rotation (14), or wherein the magnet carrier (25) is screwed onto an outer side of the holding pin (31).

6. A vacuum pump according to claim 4 or 5, wherein the holder (23), which is in particular arranged in the region of the pump inlet, is star-shaped and comprises an, in particular annular, outer section (35) connected to a pump housing (33), a central section (37) having the holding pin (31), and a plurality of web sections (39) which are arranged distributed in the circumferential direction and by which the central section (37) is connected to the outer section (35).

7. A vacuum pump according to any one of the preceding claims, wherein the magnet carrier (25) comprises a centering sleeve (41), on which the permanent magnet rings (21a) are seated radially at the outside, and two abutments (43, 45) spaced apart from one another in the axial direction for the permanent magnet rings (21a), in particular wherein the centering sleeve (41) and the holder (23), in particular a holding pin (31) of the holder (23), are arranged overlapping one another in the axial direction.

8. A vacuum pump according to claim 7, wherein the one abutment (45), in particular the one remote from the inlet, is formed in one piece with the centering sleeve (41) and the other abutment (43), in particular the one near the inlet, is a separate component which is connected, in particular pressed or screwed, to the centering sleeve (41).

9. A vacuum pump according to claim 7 or 8, wherein the magnet carrier (25) comprises a central section (47) which is arranged concentrically to the centering sleeve (41) and which has a reduced diameter compared to the centering sleeve (41), wherein the centering sleeve (41) and the central section (47) are connected to one another, in particular in one piece, by a connection section (49) of the centering sleeve (41) disposed below the holding pin (31) of the holder (23), and wherein the central section (47) and the centering sleeve (41) are arranged overlapping one another in the axial direction and / or the central section (47) projects beyond the end of the centering sleeve (41) remote from the inlet.

10. A vacuum pump according to any one of the claims 7 to 9, wherein the magnet carrier (25) is screwed by means of the centering sleeve (41) onto a holding pin (31) of the holder (23) that extends parallel to the axis of rotation (14), or wherein the magnet carrier (25) is screwed by means of a central section (47), which is connected to the centering sleeve (41), to a holding pin (31) of the holder (23) that extends parallel to the axis of rotation (14), in particular is screwed into a recess formed in the holding pin (31), in particular into the passage (27) extending parallel to the axis of rotation (14).

11. A vacuum pump according to any one of the preceding claims, wherein the free end region of the magnet carrier (25) remote from the inlet is an end region of a central section (47) of the magnet carrier (25) that is connected to a centering sleeve (41).

12. A vacuum pump according to any one of the preceding claims, wherein a tensioning device (57) is provided that is active in the axial direction between the magnet carrier (25) and the holder (23).

13. A vacuum pump according to claim 12, wherein the tensioning device (57) comprises a spring, preferably a compression spring or a wave spring, which is either active between a connection section (49), which connects a central section (47) and a centering sleeve (41) of the magnet carrier (25) to one another, and the end region of a holding pin (31) of the holder (23) remote from the inlet, said holding pin (31) extending parallel to the axis of rotation (14), or which surrounds the holding pin (31) of the holder (23) and is active between a shoulder region at the transition between the holding pin (31) and the holder (23) and the end region of the magnet carrier (25) near the inlet, and / or wherein the tensioning device (57) comprises a screw, preferably a grub screw, which is screwed to the holder (23) and acts on the magnet carrier (25) in the axial direction, in particular wherein the screw is screwed into the passage (27) which is formed in a holding pin (31) of the holder (23) that extends parallel to the axis of rotation (14).

14. A vacuum pump according to any one of the preceding claims, wherein at least one recess (59) active as a chip pocket, in particular a groove revolving about the axis of rotation (14), is formed in at least one of two contact surfaces of the holder (23) and the magnet carrier (25) that contact one another and that move relative to one another on the attachment and adjustment of the magnet carrier (25).

15. A method for mounting, attaching and setting a magnetic bearing (17) of a vacuum pump according to any one of the preceding claims, wherein the vacuum pump comprises at least one pump stage (11, 13), which comprises a stator (11a, 13a) and a rotor (15) rotating relative to the stator (11a, 13a) about an axis of rotation (14) during operation, and wherein the magnetic bearing (17) provided for the end region of the rotor (15) near the inlet comprises a magnetic bearing rotor (19) and a magnetic bearing stator (21) which each have a stack of a plurality of permanent magnet rings (19a, 21a), wherein the method comprises the steps: - mounting the magnetic bearing rotor (19) at the rotor (15), - providing a separate magnet carrier (25) for the magnetic bearing stator (21), - mounting the permanent magnet rings (21a) of the magnetic bearing stator (21) at the magnet carrier (25) independently of the stator (11a, 13a) of the vacuum pump, - attaching the magnet carrier (25) together with the completely mounted permanent magnet rings (21a) as a unit to a holder (23) of the stator (11a, 13a), and - setting the magnetic bearing (17) by adjusting the axial position of the magnet carrier (25) at the holder (23) with respect to the axis of rotation (14).