JP7534466B2 - Vacuum pump with improved suction capacity of Holweck pump stage - Google Patents

Description

The present invention relates to a vacuum pump, also referred to herein simply as a pump, in particular a turbomolecular vacuum pump, having a pump inlet, a pump outlet and at least one Holweck pump stage, in which the Holweck pump stage, in particular the stator sleeve of the Holweck pump stage, is specially designed to achieve improved suction capacity.

Vacuum pumps are used in various technical fields. Depending on the requirements, vacuum pumps comprise one or more pump stages. Holweck pump stages belong to the molecular vacuum pump family and generate a molecular flow by rotating a Holweck rotor relative to a stationary Holweck stator. A vacuum pump can comprise one or more Holweck stages, which can pump both in series and in parallel with each other. Holweck stages are typically used in turbomolecular vacuum pumps and are usually downstream of one or more turbomolecular pump stages.

The Holbeck pump stage comprises a Holbeck rotor and a Holbeck stator, the latter comprising a rotor shaft on which one or more Holbeck rotor sleeves are concentrically attached, for example by a disk-shaped Holbeck hub. The Holbeck stator sleeve is provided with a single-screw or multi-screw Holbeck thread. The gas molecules to be conveyed are conveyed along the threaded screw from the inlet end to the outlet end of the respective Holbeck pump stage by the rotational movement of the Holbeck rotor sleeve relative to the Holbeck stator sleeve. The threaded screw comprises a circumferential Holbeck channel bounded by the thread flanks of the webs, in which the gas molecules are conveyed when the Holbeck rotor sleeve rotates relative to the Holbeck stator sleeve.

Furthermore, so-called "folded" Holweck arrangements are known, in which several Holweck stages are nested inside one another, so that the pumping directions of the immediately radially adjacent Holweck pump stages are generally opposite to one another. For example, two Holweck pump stages that follow one another in the pumping direction, such as a radially outer Holweck pump stage and a radially inner Holweck pump stage, can have a common Holweck stator with a Holweck thread on each side, which is located radially between two Holweck rotor sleeves.

The suction capacity of the Holweck pump stages depends, among other things, on the inlet conductance at the inlet end of the respective Holweck pump stage. In this case, the inlet conductance is influenced, among other things, by the end faces of the thread web of the Holweck thread, which lie in the plane of the inlet end, since the gas molecules to be pumped are more likely to collide with these end faces and be desorbed back in the direction of the upstream turbomolecular pump stage. This reduces the inlet conductance, to the detriment of the suction capacity of the pump.

The object of the present invention is therefore to reduce the above-mentioned adsorption problems and thus to improve the suction capacity of vacuum pumps, such as turbomolecular vacuum pumps.

This problem is solved by a vacuum pump having the features of claim 1,
In particular, this is solved in that the webs of the Holweck thread at the inlet end of the Holweck pump stage each have a substantially radially aligned or substantially radially extending end face, which end face forms with the second thread flank a first reflex angle (smaller than 300°, preferably smaller than 270°). In particular, the first angle can be between 190° and 260°, preferably between 200° and 250°, particularly preferably between 205° and 245°.

In this case, the second thread flank is the one located on the opposite side of the respective web to the inlet end of the Holbeck pump stage. Thus, if the essentially radially aligned end face forms with the second thread flank a reflex angle of less than 300°, in particular less than 270°, this means that, due to the inclination angle of the Holbeck thread, which is usually less than 45°, the end face does not lie in the plane in which the inlet end of the Holbeck pump stage lies, as opposed to conventional Holbeck pump stages. For example, if the Holbeck thread has an inclination angle of the order of 30° and the first angle of the reflex angle in question is just under 270°, this means that the radially oriented end face encloses an angle of about 60° with the plane in which the inlet end of the Holbeck pump stage lies.

On the other hand, if the first angle of the reflex angle is, for example, 210°, this means that, for example, in the case of a Holweck thread inclination angle of 30°, the substantially radially aligned end face is bounded by an angle of 120° with the plane at the inlet end of the Holweck pump stage.

Due to the fact that the substantially radially aligned end faces according to the invention do not lie in a plane located at the inlet end of the Holweck pump stage, but are rather inclined relative to this plane, the spacing between adjacent webs at the inlet end and therefore the inlet area at the Holweck pump stage is increased. In this case, depending on the magnitude of the inclination angle and the first angle of the reflex angle, an increase in the inlet area, in particular of up to 20%, can be achieved.

In the following, preferred embodiments of the invention are described. Further embodiments can be taken from the dependent claims, the description of the drawings and the drawings themselves.

According to one embodiment, it can be provided that the respective substantially radially aligned end faces enclose a second reflex angle with the end face of the Holweck stator sleeve at the inlet end or with the plane in which the inlet end of the Holweck pump stage lies, the second reflex angle being smaller than the adjacent angle of the inclination angle of the Holweck thread at the inlet end. Thus, for example, if the inclination angle of the Holweck thread at the inlet end is 30°, the adjacent angle of the inclination angle is 150°, which means that the second reflex angle is smaller than 150°.

According to one embodiment, the second angle may be between 90° and 160°, in particular between 92° and 140°, preferably between 95° and 120°.

If the second angle is greater than 90°, this means that the radially aligned end faces of the respective webs form an undercut or overhang when viewed from the inlet end, so that the spacing between two adjacent webs in the circumferential direction is reduced by the end faces. Thus, due to the inclined end faces, there is an increase in the inlet area at the inlet end of the Holweck pump stage, which has a positive effect on the inlet conductance at the Holweck pump stage in the desired way.

Thus, by increasing the inlet area at the inlet end of the Holweck Stator Sleeve, the suction capacity of the pump for nitrogen can be increased by more than about 5%, while for helium the increase in suction capacity is only about 2%.

According to a further embodiment, it may be provided that the end face is enclosed with the inner or outer peripheral surface of the Holweck pump stage on which the Holweck thread is formed at a third angle smaller than 110°. According to an embodiment, the third angle may be smaller than 105°, in particular smaller than 100°. It may preferably be provided that the third angle is a right angle.

To further increase the inlet conductance at the inlet end of the Holweck pump stage, the end face of the Holweck stator sleeve at the inlet end is chamfered on the side (inner or outer) where the web of the Holweck thread has a radially aligned end face. This also reduces the possibility that gas molecules impinging on the inlet end will be desorbed back in the direction of the upstream pump stage, improving the suction capacity of the Holweck pump stage in the desired way.

The present invention will now be described, by way of example only, with reference to the accompanying drawings.

FIG. 1 is a perspective view of a turbomolecular pump not according to the present invention; A bottom view of the turbomolecular pump of FIG. FIG. 3 is a cross-sectional view of a turbomolecular pump taken along the line A-A shown in FIG. FIG. 3 is a cross-sectional view of a turbomolecular pump taken along the line B-B shown in FIG. FIG. 3 is a cross-sectional view of a turbomolecular pump taken along the line CC shown in FIG. FIG. 2 is a perspective top view of a portion of the inlet of the outer Holweck pump stage of the turbomolecular vacuum pump of FIG. 1; FIG. 2 is a perspective top view of a portion of the inlet of an outer Holweck pump stage of a vacuum pump according to the invention; FIG. 7 is a schematic internal view of the Holweck Sterling sleeve of FIG. 6 ;

The turbomolecular vacuum pump 111 shown in FIG. 1 has 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. Gas from the recipient can be drawn in through the pump inlet 115 and transferred via the pump to a pump outlet 117, to which a spare vacuum pump, for example a rotary vane pump, can be connected.

The inlet flange 113 constitutes the upper end of the housing 119 of the vacuum pump 111 when the vacuum pump is oriented according to FIG. 1. The housing 119 has a lower part 121 on which the electronics housing 123 is arranged laterally. In the electronics housing 123, the electric and/or electronic components of the vacuum pump 111 are accommodated, for example for operating an electric motor 125 arranged in the vacuum pump (see also FIG. 3). The electronics housing 123 is provided with a number of ports 127 for accessories. In addition, a data interface 129, for example according to the RS485 standard, and a power supply port 131 are arranged on the electronics housing 123.

There are also turbomolecular vacuum pumps that do not have an electronics housing attached in this way, but are connected to external drive electronics.

The housing 119 of the turbomolecular vacuum pump 111 is provided with a ventilation inlet 133, in particular in the form of a ventilation valve, through which the vacuum pump 111 can be vented. Furthermore, in the region of the lower part 121, a sealing gas port 135, also called scavenging gas port, is arranged, via which scavenging gas can be introduced into the motor space 137, in which the electric motor 125 is accommodated in the vacuum pump 111, in order to protect the electric motor 125 (see, for example, FIG. 3) from the gases transported by the pump. Furthermore, in the lower part 121, two coolant ports 139 are arranged, one of which is arranged as an inlet for a coolant and the other coolant port as an outlet for a coolant, which can be introduced into the vacuum pump for cooling. Other existing turbomolecular vacuum pumps (not shown) are operated with air cooling only.

The underside 141 of the vacuum pump can be used as a stand surface, so that the vacuum pump 111 can be operated standing on the underside 141. However, the vacuum pump 111 can also be fixed to the recipient via the inlet flange 113, and thus operated in a somewhat suspended state. In addition, the vacuum pump 111 can be configured to be operated when oriented differently than that shown in FIG. 1. It is also possible to realize embodiments of the vacuum pump in which the underside 141 can be oriented so that it faces sideways or upwards, rather than facing downwards. In this case, essentially any angle is possible.

Other existing turbomolecular vacuum pumps (not shown), particularly those larger than the pump illustrated here, cannot be operated in an upright position.

2 further comprises various bolts 143, by means of which the parts of the vacuum pump not further specified here are fixed to one another. For example, a bearing cover 145 is fixed to the lower side 141.

In addition, the underside 141 is provided with fixing holes 147, via which the pump 111 can be fixed, for example, to a mounting surface. This is not possible in the case of other existing turbomolecular vacuum pumps, which are in particular larger than the pumps shown individually.

Figures 2-5 show a coolant line 148 through which coolant can circulate, introduced and discharged via coolant port 139.

As shown in the cross-sectional views of Figures 3-5, the vacuum pump has multiple process gas pump stages to transfer process gas present at the pump inlet 115 to the pump outlet 117.

A rotor 149 is disposed within the housing 119 and includes a rotor shaft 153 that is rotatable about a rotation axis 151.

The turbomolecular vacuum pump 111 has a number of turbomolecular pump stages effectively interposed in series with one another in the pump, with a number of radial rotor disks 155 fixed to the rotor shaft 153 and a stator disk 157 arranged between the rotor disks 155 and fixed to the housing 119. In this case, each rotor disk 155 and adjacent stator disk 157 constitutes one turbomolecular pump stage. The stator disks 157 are held at a desired axial distance from one another by spacer rings 159.

In addition, the vacuum pump has Holweck pump stages nested radially within one another and effectively interposed in series with one another in the pump. There are other existing turbomolecular vacuum pumps that do not have Holweck pump stages.

The rotor of the Holweck pump stage has a rotor hub 161 arranged on the rotor shaft 153 and two cylindrical shell-shaped Holweck rotor sleeves 163, 165 fixed to and supported by the rotor hub 161, which are aligned coaxially with respect to the rotary shaft 151 and nested relative to one another in the radial direction. In addition, two cylindrical shell-shaped Holweck stator sleeves 167, 169 are provided, which are also aligned coaxially with respect to the rotary shaft 151 and nested relative to one another in the radial direction.

The pump active surface of the Holbeck pump stage is constituted by the shell surfaces, i.e. the radial inner and/or outer surfaces, of the Holbeck rotor sleeves 163, 165 and the Holbeck stator sleeves 167, 169. The radial inner surface of the outer Holbeck stator sleeve 167 faces the radial outer surface of the outer Holbeck rotor sleeve 163 while forming a radial Holbeck gap 171, and together with this radial outer surface constitutes the first Holbeck pump stage following the turbomolecular pump stage (wherein this first Holbeck pump stage is also called the outer Holbeck pump stage). The radial inner surface of the outer Holbeck rotor sleeve 163 faces the radial outer surface of the inner Holbeck stator sleeve 169 while forming a radial Holbeck gap 173, and together with this radial outer surface constitutes the second Holbeck pump stage (wherein this second Holbeck pump stage is also called the middle Holbeck pump stage). The radial inner surface of the inner Holbeck stator sleeve 169 faces the radial outer surface of the inner Holbeck rotor sleeve 165 while forming a radial Holbeck gap 175, and together with this radial outer surface constitutes a third Holbeck pump stage (here, this third Holbeck pump stage is also referred to as the inner Holbeck pump stage).

At the lower end of the Holbeck rotor sleeve 163, a radially extending passage can be provided, which connects the radially outer Holbeck gap 171 with the central Holbeck gap 173 and thus the outer Holbeck pump stage with the Holbeck pump stage. In addition, at the upper end of the inner Holbeck stator sleeve 169, a radially extending passage can be provided, which connects the central Holbeck gap 173 with the radially inner Holbeck gap 175 and thus the central Holbeck pump stage with the inner Holbeck pump stage. This means that the nested Holbeck pump stages are connected in series with each other, i.e. the outlet end of the outer Holbeck pump stage essentially corresponds to the inlet end of the middle Holbeck pump stage and the outlet end of the central Holbeck pump stage essentially corresponds to the inlet end of the inner Holbeck pump stage. Furthermore, at the lower end of the radially inner Holbeck rotor sleeve 165, a connecting passage 179 to the outlet 117 can be provided.

The pump active surfaces of the Holweck stator sleeves 167, 169 each include a number of Holweck grooves extending axially in a helical manner about the axis of rotation 151, which together form a Holweck screw, while the shell surfaces of the opposing Holweck rotor sleeves 163, 165 are formed smooth and propel gas through the Holweck grooves to operate the vacuum pump 111.

In this case, the Holbeck grooves are formed by webs 225 formed on the inside and/or outside of the Holbeck stator sleeves 167, 169, which run helically between the inlet and outlet ends of the respective Holbeck pump stages in the respective Holbeck stator sleeves 167, 169. Since the inner Holbeck stator sleeve 169 comprises both an inner and an outer Holbeck thread, the inlet end of the inner Holbeck pump stage, also formed by the Holbeck thread located on the inside of the Holbeck stator sleeve 169, corresponds to the outlet end of the middle Holbeck pump stage, also formed by the Holbeck thread located on the outside of the Holbeck stator sleeve 169, from which the gas to be pumped enters the inner Holbeck pump stage.

As can be seen from FIG. 6, which shows a perspective top view of a portion of the inlet end 229 of the outer Holweck pump stage, the webs 225 formed on the inside of the associated Holweck stator sleeve 167 typically each have an end face 227 at the inlet end of the Holweck stator sleeve 167, where these end faces 227 lie in the plane in which the inlet end 229 of the outer Holweck pump stage lies.

To rotatably support the rotor shaft 153, a rolling bearing 181 is provided in the region of the pump outlet 117, and a permanent magnetic bearing 183 is provided in the region of the pump inlet 115.

In the region of the rolling bearing 181, the rotor shaft 153 is provided with a conical spray nut 185 having an outer diameter that increases towards the rolling bearing 181. The spray nut 185 is in sliding contact with at least one wiper of the working medium accumulator. In the case of other existing turbomolecular vacuum pumps (not shown), a spray bolt can be provided instead of the spray nut. Since different configurations are therefore possible, the term "spray tip" is also used in this connection.

The working medium accumulator has a number of hygroscopic disks 187 stacked one on top of the other, which absorb the working medium, e.g., lubricant, for the rolling bearings 181.

During operation of the vacuum pump 111, the working medium is transferred by capillary action from the working medium accumulator through the wiper to the rotating spray nut 185 and, due to centrifugal force, is transported along the spray nut 185 in the direction of the increasing outer diameter of the spray nut 185 towards the rolling bearing 181, where it performs, for example, a lubrication function. The rolling bearing 181 and the working medium accumulator are surrounded in the vacuum pump by a trough-shaped insert 189 and a bearing cover 145.

The permanent magnet bearing 183 has a rotor-side bearing half 191 and a stator-side bearing half 193, each of which has a ring stack consisting of a number of permanent magnet rings 195, 197 stacked one on top of the other in the axial direction. The ring magnets 195, 197 face each other forming a radial bearing gap 199, with the rotor-side ring magnet 195 arranged radially outward and the stator-side ring magnet 197 arranged radially inward. The magnetic field present in the bearing gap 199 generates a magnetic repulsion force between the ring magnets 195, 197, which produces a radial bearing of the rotor shaft 153. The rotor-side ring magnet 195 is supported by a carrier part 201 of the rotor shaft 153, which surrounds the ring magnet 195 from the radial outside. The ring magnet 197 on the stator side is supported by a carrier part 203 on the stator side, which extends through the ring magnet 197 and is suspended on radial braces 205 of the housing 119. Parallel to the axis of rotation 151, the ring magnet 195 on the rotor side is fixed by a cover element 207 connected to the carrier part 201. The ring magnet 197 on the stator side is fixed in one direction, parallel to the axis of rotation 151, by a fixing ring 209 connected to the carrier part 203 as well as a fixing ring 211 connected to the carrier part 203. In addition, a disc spring 213 can be provided between the fixing ring 211 and the ring magnet 197.

In the magnetic bearing, an emergency or safety bearing 215 is provided, which during standard operation of the vacuum pump 111 runs free without contact and only engages to form a radial stop for the rotor 149 in the event of excessive radial displacement of the rotor 149 relative to the stator, in order to prevent collisions between structures on the stator side and structures on the rotor side. The safety bearing 215 is formed as a lubricated rolling bearing and together with the rotor 149 and/or the stator forms a radial gap which causes the safety bearing 215 to be released during standard pump operation. The radial displacement with which the safety bearing 215 engages is set to be large enough so that the safety bearing 215 does not engage during standard operation of the vacuum pump, and at the same time small enough so that collisions between structures on the stator side and structures on the rotor side are prevented under all circumstances.

The vacuum pump 111 has an electric motor 125 as a drive for rotating the rotor 149. The anchor of the electric motor 125 is constituted by the rotor 149, whose rotor shaft 153 extends through the motor stator 217. A permanent magnet device can be arranged on the part of the rotor shaft 153 extending through the motor stator 217, either radially outwardly or embedded. Between the motor stator 217 and the part of the rotor 149 extending through the motor stator 217, an intermediate space 219 is arranged, which has a radial motor gap, via which the motor stator 217 and the permanent magnet device can be magnetically influenced to transmit a drive torque.

The motor stator 217 is fixed in the housing in a motor space 137 provided for the electric motor 125. A sealing gas, also called scavenging gas and which may be, for example, air or nitrogen, can reach the motor space 137 via a sealing gas port 135. Via the sealing gas, the electric motor 125 can be protected from the process gas, for example from corrosive components of the process gas. The motor space 137 can also be evacuated via the pump outlet 117, i.e. the vacuum pressure generated by the auxiliary vacuum pump connected to the pump outlet 117 prevails in the motor space 137 at least approximately.

In addition, between the rotor hub 161 and the wall 221 defining the motor space 137, a so-called labyrinth seal 223, known per se, can be provided, in particular to achieve good sealing of the motor space 217 with respect to the radially outer Holweck pump stage.

Next, a Holweck stator sleeve 10 formed according to the present invention and which can be installed in place of the outer Holweck stator sleeve 167 in the turbomolecular vacuum pump 111 according to Figures 1 to 5 will be described below with reference to Figures 7 and 8.

The inner or internal surface of the Holweck stator sleeve 10 is formed with a plurality of helical circumferential webs 12 which together form an internal Holweck thread 14, each of which has a first thread flank 16 facing toward the inlet end 20 of the Holweck stator sleeve 10 and a second thread flank 18 facing away from the inlet end 20. In other words, the second thread flank 18 faces toward the outlet end of the Holweck stator sleeve 10.

As can also be seen in Figures 7 and 8, the web 12 comprises, near the inlet end 20, a second thread flank 18 and a substantially radially oriented end face 22 which surrounds a first reflex angle α ₁ (see Figure 8) of less than 300°, in particular less than 270°. In the embodiment depicted in Figure 7, the first angle α ₁ is approximately 210°, but according to other embodiments the first angle α ₁ may be between 190° and 260°. In particular, the first angle α ₁ may be between 200° and 250°, preferably between 205° and 225°.

As can be seen in particular from Figure 8, according to the invention, each substantially radially aligned end face 22 of the respective web 12 makes a reflex second angle α2 with the end face 26 of the Holweck stator sleeve 10 at the inlet end 20 or with the plane in which the inlet end 20 of the Holweck stator sleeve 10 lies, said second angle _α2 being smaller than the adjacent angle of inclination angle β of the Holweck thread 14 at the inlet end 20. In this case, the second angle _α2 is between 90° and ₁₆₀ °, in particular between 92° and 140°, preferably between 95° and 120°, which means that the end face 22 of the respective web 12 as viewed from the inlet end 20 of the Holweck stator sleeve 10 forms an undercut 24 or an overhang.

Thus, in comparison with the conventional Holweck stator sleeve formation according to FIG. 6, each web 12 is chamfered at the inlet end 20 such that the conventional end face 227 (FIG. 6) lying in the plane of the inlet end 229 is omitted. Instead, the chamfer 28 results in an end face 22 that is inclined relative to the inlet end 20 according to the invention. In this case, this chamfer 28 is shown by a shaded portion in FIG. 8.

Here, the chamfer 28 is formed such that the end face 22 has a flat shape or forms a flat surface, but the chamfer 28 can also be formed such that the end face 22 has a curved contour, which can be formed, for example, convexly or concavely. In this case, a first angle α ₁ of reflex angle extends between the second thread flank 18 and a tangent line which meets the curved contour of the end face 22 at any location. For example, considering the position or intersection point where the convexly or concavely curved end face 22 intersects with the second thread flank 18, a first angle α 1 of reflex angle extends there between the second thread flank 18 and a tangent line which meets the convexly or concavely curved end face 22 at the intersection point between the curved end face 22 and the second thread flank ₁₈ .

In the radial direction, the end face 12 encloses a third angle α ₃ with the inner or inner circumferential surface 30 of the Holweck stator sleeve 10 that is less than 110°, this angle lying in the plane in which the inlet end 20 or the end face 26 of the Holweck stator sleeve 10 at the inlet end 20 lies (see FIG. 7 ).

Although the chamfer 28 of the web 12 near the inlet end 20 allows the inlet area to be increased by up to 20% to the Holweck stator sleeve 10, which results in a higher inlet conductance and therefore an improved suction capacity, the suction capacity of the Holweck pump stage can be further improved by providing the end face 26 of the Holweck stator sleeve 10 at the inlet end 20 with a chamfer 32 (see here FIG. 7). In this case, this chamfer 32 is on the inside of the Holweck stator sleeve 10, i.e. at the inlet end 20 on the side of the Holweck stator sleeve 10 on which the web 12 with the radially aligned end face 22 is formed in the method according to the invention.

The construction of the Holbeck stator sleeve 10 having the internal Holbeck thread 14 has been described above, and this Holbeck stator sleeve can be used in the vacuum pump 111 of Figures 1 to 5 in place of the external Holbeck stator sleeve 167. However, the internal Holbeck stator sleeve 169 of the pump 111, and in particular its internal Holbeck thread, can be constructed in the same manner as the Holbeck stator sleeve 10.

Likewise, the outer Holbeck thread of the inner Holbeck stator sleeve 169, in particular its web, can be formed corresponding to its web 12 on the inlet side corresponding to the Holbeck stator sleeve 10 or at the inlet end 20. The outer web of the inner Holbeck stator sleeve 169 or of the two Holbeck stator sleeves 169 can also be provided with a radially aligned end face 22 on the inlet side, which end face encloses with the thread flank facing away from the inlet end of the central Holbeck pump stage a first angle of less than 300°, in particular less than 270°, so as to form an undercut or overhang in the web of the outer Holbeck thread.
This application relates to the invention described in the claims, but also includes the following as other aspects.
1.
A vacuum pump, in particular a turbomolecular pump (111),
The vacuum pump comprises a pump inlet (115), a pump outlet (117), and at least one Holweck pump stage;
The Holweck pump stage comprises a Holweck stator sleeve (10) having an inner side and an outer side and an inlet end (20) facing away from the pump inlet,
In this case, a Holweck thread (14) having a plurality of helical circumferential webs (12) is formed on the inner side (30) and/or the outer side of the Holweck stator sleeve (10),
The webs each have a first thread flank (16) facing the entry end (20) and a second thread flank (18) facing away from the entry end (20);
In this case, the web (12) at the inlet end (20) of at least one Holweck pump stage further comprises a radially aligned end face (22), which end face (22) encloses with the second thread flank (18) a first reflex angle (α 1 ) of _less than 300°, in particular less than 270°.
2.
2. The vacuum pump according to claim 1, wherein the first angle (α ₁ ) is between 190° and 260°, in particular between 200° and 250°, preferably between 205° and 245°.
3.
3. The vacuum pump according to claim 1 or 2, characterized in that each radially oriented end face (22) encloses a reflex second angle (α ₂ ) with a plane in which the inlet end (20) of at least one Holweck pump stage lies, said second angle (α ₂ ) being smaller than the adjacent angle of inclination (β) of the Holweck thread (14) of the inlet end (20).
4.
4. The vacuum pump according to any one of claims 1 to 3, characterized in that the second angle (α ₂ ) is between 90° and 160°, in particular between 92° and 140°, preferably between 95° and 120°.
5.
5. The vacuum pump according to any one of claims 1 to 4, characterized in that the radially oriented end face (22), as viewed from the inlet end (20) of the Horbeck pump stage, forms an undercut (24) on the web (12).
6.
6. The vacuum pump according to any one of claims 1 to 5, characterized in that the radially oriented end surface (26) subtends a third angle (α ₃ ) less than 110° with a peripheral surface (30) of the Holweck stator sleeve (10) on which the Holweck thread (14) is formed.
7.
7. The vacuum pump according to claim 6, characterized in that the third angle (α ₃ ) is smaller than 105°, in particular smaller than 100°, preferably the third angle (α ₃ ) is 90°.
8.
8. A vacuum pump according to any one of claims 1 to 7, characterized in that the end face (26) of the Holweck stator sleeve (10) at the inlet end (20) of the Holweck pump stage is chamfered on the side where the web (12) has the radially aligned end face (22).

10 Holweck stator sleeve 12 web 14 Holweck thread 16 first thread flank 18 second thread flank 20 inlet end 22 end face 24 undercut or overhang 26 inlet end end face 28 chamfer 30 inner surface or inner circumferential surface 32 chamfer 111 turbomolecular vacuum pump 113 inlet flange 115 pump inlet 117 pump outlet 119 housing 121 lower part 123 electronics housing 125 electric motor 127 accessory port 129 data interface 131 power supply port 133 vent inlet 135 seal gas port 137 motor space 139 coolant port 141 underside 143 bolt 145 bearing cover 147 fixing hole 148 coolant line 149 rotor 151 axis of rotation 153 rotor shaft 155 rotor disk 157 stator disk 159 spacer ring 161 rotor hub 163 Holweck rotor sleeve 165 Holweck rotor sleeve 167 Holweck stator sleeve 169 Holweck stator sleeve 171 Holweck gap 173 Holweck gap 175 Holweck gap 179 connecting passage 181 rolling bearing 183 permanent magnet bearing 185 spray nut 187 disk 189 insert 191 rotor-side bearing half 193 stator-side bearing half 195 ring magnet 197 ring magnet 199 bearing gap 201 carrier part 203 carrier part 205 radial brace 207 cover element 209 support ring 211 fixing ring 213 disc spring 215 emergency or safety bearing 217 motor stator 219 intermediate space 221 wall 223 labyrinth seal 225 web 227 end face 229 inlet end α ₁ first angle α ₂ second angle α _3. Third angle β: inclination angle

Claims (15)

A vacuum pump, in particular a turbomolecular pump (111),
The vacuum pump comprises a pump inlet (115), a pump outlet (117), and at least one Holweck pump stage;
The Holweck pump stage comprises a Holweck stator sleeve (10) having an inner side and an outer side and an inlet end (20) facing away from the pump inlet,
In this case, a Holweck thread (14) having a plurality of helical circumferential webs (12) is formed on the inner side (30) and/or the outer side of the Holweck stator sleeve (10),
The webs each have a first thread flank (16) facing the entry end (20) and a second thread flank (18) facing away from the entry end (20);
In this case, the web (12) at the inlet end (20) of at least one Holweck pump stage further comprises a radially aligned end face (22), said end face (22) enclosing with the second thread flank (18) a first reflex angle (α ₁ ) of less than 300°. 2. The vacuum pump according to claim 1, characterized in that each radially oriented end face (22) encloses a reflex second angle (α ₂ ) with a plane in which the inlet end (20) of at least one Holweck pump stage lies, said second angle (α ₂ ) being smaller than the adjacent angle of inclination (β) of the Holweck thread (14) of the inlet end (20). 2. The vacuum pump according to claim 1, characterized in that the radially oriented end faces (22) form an undercut (24) on the web (12), as viewed from the inlet end (20) of the Holweck pump stage. 2. The vacuum pump according to claim 1, characterized in that the radially oriented end surface (26) encloses a third angle (α ₃ ) less than 110° with a peripheral surface (30) of the Holweck stator sleeve (10) on which the Holweck thread (14) is formed. 2. A vacuum pump according to claim 1, characterized in that the end face (26) of the Holweck stator sleeve (10) at the inlet end (20) of the Holweck pump stage is chamfered on the side with the radially aligned end face (22) of the web ( 12 ). The first angle (α ₁ 2. The vacuum pump according to claim 1, wherein the angle θ is less than 270°. The first angle (α ₁ 2. The vacuum pump according to claim 1, wherein the angle θ is between 190° and 260°. The first angle (α ₁ 2. The vacuum pump according to claim 1, wherein the angle θ is between 200° and 250°. The first angle (α ₁ 2. The vacuum pump according to claim 1, wherein the angle θ is between 205° and 245°. The second angle (α ₂ 3. The vacuum pump according to claim 2, wherein the angle θ is between 90° and 160°. The second angle (α ₂ 3. The vacuum pump according to claim 2, wherein the angle θ is 92° to 140°. The second angle (α ₂ 3. The vacuum pump according to claim 2, wherein the angle θ is between 95° and 120°. The third angle (α ₃ 5. The vacuum pump according to claim 4, wherein the angle θ is less than 105°. The third angle (α ₃ 5. The vacuum pump according to claim 4, wherein the angle θ is less than 100°. The third angle (α ₃ 5. The vacuum pump according to claim 4, characterized in that the angle .theta.