EP3499041B1 - Screw vacuum pump - Google Patents

Screw vacuum pump Download PDF

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Publication number
EP3499041B1
EP3499041B1 EP17207558.2A EP17207558A EP3499041B1 EP 3499041 B1 EP3499041 B1 EP 3499041B1 EP 17207558 A EP17207558 A EP 17207558A EP 3499041 B1 EP3499041 B1 EP 3499041B1
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EP
European Patent Office
Prior art keywords
screw
section
vacuum pump
accordance
rotors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP17207558.2A
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German (de)
French (fr)
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EP3499041A1 (en
Inventor
Peter Huber
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pfeiffer Vacuum GmbH
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Pfeiffer Vacuum GmbH
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Filing date
Publication date
Application filed by Pfeiffer Vacuum GmbH filed Critical Pfeiffer Vacuum GmbH
Priority to EP17207558.2A priority Critical patent/EP3499041B1/en
Priority to JP2018232382A priority patent/JP2019143620A/en
Publication of EP3499041A1 publication Critical patent/EP3499041A1/en
Application granted granted Critical
Publication of EP3499041B1 publication Critical patent/EP3499041B1/en
Priority to JP2021011798A priority patent/JP7339973B2/en
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Anticipated expiration legal-status Critical

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/082—Details specially related to intermeshing engagement type pumps
    • F04C18/084—Toothed wheels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum

Definitions

  • the present invention relates to a screw vacuum pump having a housing, two screw rotors which are arranged in the housing and are in engagement with one another and which, in order to convey a process gas in cooperation with the housing, form repeatedly closed delivery volumes of the process gas and convey them in the direction of an outlet.
  • Screw vacuum pumps generally include complex pump-active geometries, in particular screw profiles of screw rotors and a corresponding housing for the screw rotors.
  • the interaction of these geometries requires high precision in their manufacture. It can therefore be very complex and expensive to manufacture or control the geometries.
  • a screw vacuum pump according to the preamble of claim 1 is in the DE 20 2016 005 209 U1 disclosed.
  • the DE 20 2016 005 208 U1 , the US 2002/031439 A1 , the DE 100 19 637 A1 and the JP 4 900270 B2 disclose further screw vacuum pumps with screw rotors, which have different sections.
  • a screw vacuum pump with the features of claim 1, and in particular by the fact that the screw rotors each have at least two sections adjacent along the screw axis, the screw rotors each having an at least substantially constant and in a first section closer to an inlet in a second section have a lower slope than in the first section, and wherein with respect to the screw axis, the first section is longer than a completed delivery volume in the first section.
  • a respective screw profile interacts with the housing to include a delivery volume.
  • the delivery volume to be closed reaches the second section opposite to the inlet, this means that the process gas is partially expelled back towards the inlet.
  • high manufacturing precision of the housing in the inlet area was previously necessary to ensure a precisely defined completion of the delivery volume. Precise manufacture of the inlet area is complex and is made more difficult, for example, by the fact that a mold for the housing wears out over several casting cycles.
  • the first section is longer than a completed delivery volume according to the invention, it is ensured that the second section is not reached before the delivery volume is completed.
  • the manufacturing precision of the housing in the inlet area can thus be reduced without running the risk of the process gas knocking back towards the inlet.
  • the reduced requirement for manufacturing precision considerably simplifies the manufacture of the vacuum pump. It allows a more stable manufacturing process with fewer defective components. This is particularly advantageous because the housing in the inlet area is often difficult to measure, in particular only with great effort using a 3D coordinate measuring system. Without a measurement, deviations may only be recognized during a final inspection of the screw vacuum pump, which in the event of a fault leads to high costs for reassembly.
  • the influence of manufacturing precision is reduced by the invention, so that deviations from a desired shape are less relevant or harmless.
  • the invention not only simplifies the manufacture of the housing, but also the manufacture of the screw rotors, since larger tools and / or tools with a higher chip volume can be used to produce the profile in the relatively long first section with a relatively large pitch. This reduces the processing time and the associated manufacturing costs. This can further reduce the processing time, for example be that a respective screw contour of the screw rotors, in particular only or also in the first section, is already formed during casting at least in a preliminary contour for further machining.
  • the screw vacuum pump according to the invention even has an improved pumping speed at relatively high suction pressures. This is attributed to the fact that, with the longer first section, the gaps in the first section which form between the rotors with one another and in particular with respect to the housing are longer. The process gas in the area of the internal compression, which results in particularly high internal pressures at high intake pressures, must therefore overcome longer gaps in order to flow back. The backflow is consequently made more difficult or better sealed.
  • the screw vacuum pump according to the invention is therefore not only particularly easy to manufacture with justifiable design restrictions, but also has improved vacuum performance in certain pressure ranges.
  • a closed delivery volume can generally be understood to be a closed area - apart from unavoidable gaps between the rotors and in relation to the housing - which extends between two screw threads of a respective rotor along the screw profile around the rotor and outwards from the housing and along the screw profile from each other rotor is limited.
  • the delivery volume moves during the pumping process along the respective screw rotor in its profile from the inlet to the Outlet, providing the pumping action.
  • the funding volume can decrease on the way between inlet and outlet. This is called internal compression.
  • the closed delivery volume can cover an angle of 360 ° around the screw axis of the respective rotor.
  • the first section corresponds to at least 1.25 times, in particular at least 1.5 times, in particular at least 1.75 times, in particular at least 2 times the length of the delivery volume.
  • An end face for the screw rotors is formed in a suction area of the pump, the shape of which is adapted to the screw rotors in such a way that a respective delivery volume can be opened for suction and can be closed for delivery.
  • the end face in particular runs at least substantially perpendicular to the screw axes.
  • the end surface forms e.g. one, in particular inner, end face of the housing.
  • the end surface can preferably be designed as a free-form surface and / or run at least substantially parallel to at least one corresponding screw profile.
  • two areas of the end face that are parallel to the screw profiles can be provided, which are brought together in particular to form an area that is raised, in particular lower, and / or lowered, in particular upper, with respect to the screw axis.
  • the end surface can generally be formed, for example, in the housing.
  • the housing can be designed as a cast part, for example.
  • the end surface is in a casting, in particular the housing, trained and unprocessed. This completely saves the manufacturing step of machining the end face, which further simplifies the manufacture of the housing.
  • a screw profile of a respective screw rotor is formed by a cycloid.
  • Such a screw profile can advantageously be designed as required.
  • a screw profile of a respective screw rotor is designed with two threads. This results in a particularly low imbalance of the corresponding screw rotor.
  • compensation elements such as Compensating masses that require additional installation space and / or compensating holes in which material can be deposited can be dispensed with.
  • higher speeds can be made possible.
  • the screw rotors each have an at least substantially constant pitch in the second section.
  • Such screw rotors are particularly easy to design and manufacture because the constant pitch forms a relatively simple geometry.
  • the screw rotors each have at least a third section and their pitch is smaller in the third section than in the second section. This allows additional internal compression to be achieved.
  • the slope in the third section can in particular be at least substantially constant.
  • the screw rotors each have a plurality of sections of different pitch over their entire active pumping length, the pitch in all sections, in particular is constant at least in areas or subsections, in particular in each case. Both contribute to a simplified design and manufacture.
  • the pitch of the screw profile along a screw axis basically only changes in transition areas between the sections.
  • a transition area is in particular smaller than a section, in particular than the adjacent sections.
  • all transition areas are smaller than all sections.
  • the screw vacuum pump can, for example, have an internal compression with a compression ratio of less than 5 to 1, in particular less than 4 to 1, in particular less than 3.5 to 1, and / or greater than 2 to 1, in particular greater than 3 to 1.
  • a respective screw profile can e.g. Form or promote more than 7, in particular more than 10, in particular more than 12, in particular 13, closed delivery volumes at the same time.
  • a respective screw rotor can in particular have a ratio of the length of its screw profile to its diameter of at least 2.0, in particular at least 2.5, in particular at least 3.0 and / or at most 5.0, in particular 4.0.
  • a screw vacuum pump 10 which has a motor 12, a gear box 14, a housing 16, a bearing plate 18 and a cover 20.
  • the screw vacuum pump 10 conveys a process gas from an inlet 22 to a downward, in Fig. 3 visible outlet 24.
  • An active liquid cooling is provided for the motor 12, which emerges from a housing of the motor 12.
  • an active liquid cooling is also provided, which has two cooling lines, which in Fig. 1 are not shown, but the course thereof by means of corresponding grooves 32 in the housing 16 is indicated, into which the cooling lines are pressed.
  • active liquid cooling systems are provided in the gearbox 14 and in the cover 20 and are each designed here as immersion coolers 34, which are described below with reference to FIG Fig. 5 are explained in more detail.
  • the housing 16 of the screw vacuum pump 10 has a waist 36.
  • the waist 36 is arranged in the region of the outlet 24.
  • Fig. 4 the screw vacuum pump 10 is shown in a sectional view, the sectional plane of the line AA in Fig. 3 corresponds.
  • Two screw rotors 28 and 30 are visible, each having two-start, interlocking screw profiles 38 and 40, which are generated with the aid of a cycloid profile and have a cylindrical envelope contour and a cylindrical basic shape of the screw base.
  • the screw profiles 38 and 40 form a pump-active area of the screw vacuum pump 10 and repeatedly convey closed delivery volumes of the process gas from the inlet 22 to the outlet 24, in Fig. 4 from left to right.
  • the pumping power of the screw vacuum pump 10 depends on the size and shape of various gaps in the pumping area, which are unavoidable due to the relative movement of the rotors 28, 30 and housing 16, but are small and as constant as possible for good pumping power. Temperature changes in the components involved lead to their shape change. The measures described here for avoiding, dissipating and, in general, controlling heat in the pump 10 thus bring about the least possible change in shape and consequently the most manageable gaps. The gaps can therefore be designed more precisely, which improves the pump performance and its efficiency.
  • the screw rotor 28 is driven directly by the motor 12, that is to say without an intermediate coupling.
  • the screw rotor 30 is driven via a synchronization gear 42 with gearwheels 43 in a defined angular relationship to the screw rotor 28.
  • the motor 12 comprises a housing 44, which is made of aluminum, for example, and in which cooling lines 26 are formed for the active liquid cooling.
  • the motor 12 also includes a wound stator 46 which, together with a magnet carrier 48 attached to a shaft end of the screw rotor 28, forms an electric motor and a direct drive for the screw rotor 28.
  • the screw rotor 28 forms a rotor of the motor 12.
  • the magnet carrier 48 comprises a plurality of permanent magnets.
  • the motor 12 thus forms a permanent magnet synchronous machine with internal magnets, which is also referred to as IPMSM.
  • the stator 46 is arranged in a potting body 50, which insulates electrical conductors (not shown in more detail) in the stator 46 and insulates them to a circuit board 52.
  • the potting body 50 here, in conjunction with the circuit board 52, forms a vacuum-tight connection of the motor 12 to control electronics provided in a range of atmospheric pressure.
  • control electronics provided in a range of atmospheric pressure.
  • an external frequency converter can be provided for the motor 12.
  • at least part of control electronics for the motor 12 can be provided on the circuit board 52.
  • the synchronizing gear 42 is arranged in the gear box 14.
  • oil is also provided as a lubricant, which is distributed by spray disks 54 via the synchronizing gear 42 and adjacent bearings 56.
  • the waist 36 forms a shield or a heat barrier, in particular for heat that is produced in the area of the screw rotors 28, 30 during pump operation. Due to the fact that a small material cross section remains, and because the change in shape extends a heat path, the heat from the screw rotor, which otherwise spreads in the housing 16, is prevented from reaching areas beyond. In particular, the oil in the gearbox 14 and the bearings 56 are protected from excessive temperatures.
  • the immersion cooler 34 arranged in the gearbox 14 also contributes to reducing the temperature. This is arranged in an oil bath (not shown) of the gear box 14 and thus cools the oil directly.
  • a lubricant discharge device designed as a deflector 58 is provided for a respective screw rotor 28 or 30 adjacent to the bearings 56, which form a fixed bearing here.
  • a respective deflector 58 forms a barrier for the oil in the gearbox so that it does not get into a pump-active area or a vacuum area, here in particular an outlet area.
  • the deflector 58 comprises a not shown edge for the oil. Opposite the fling edge, a drain groove is formed in the housing 16, which takes up flung oil and directs it back into the gear box 14 or into an oil bath there. The oil, which is conveyed or distributed by the spray disks 54 to the gear 42 and bearing 56, is thus removed again by the deflectors 58 from the rotors 28 and 30, respectively.
  • Piston rings are provided on a piston ring carrier 60 as a dynamic fluid seal. These form a non-contact seal and thus avoid frictional heat.
  • the deflectors 58 return as much oil as possible to the gearbox 14, so that as little oil as possible is present on the piston rings. An overall reliable sealing effect is achieved with particularly low heat production.
  • the screw rotors 28 and 30 have three sections of different pitch in their respective screw profile 38 and 40, respectively.
  • the first section 62 is longer than a closed delivery volume in the first section with respect to a screw axis 63 which runs along a respective rotor 28 or 30.
  • a second section 64 has a plurality of subsections, which are not referenced in any more detail, with different but in each case constant slopes in the screw profile 38 or 40, the slopes being lower than in the first section.
  • the second section 64 forms the longest section here.
  • a third section 66 with an even lower slope forms an ejection section. In the third section there is again a constant slope. Due to the reduced slope along the pump direction, an internal compression is brought about, which compresses the process gas before it is expelled.
  • the rotors 28, 30 and the screw profiles 38, 40 can be designed and manufactured particularly simply by providing the constant sections. As it is based on Fig. 4 It can be seen that an elongated first section 62 leads to correspondingly elongated gaps between the screw profiles 28, 30 and the housing 16, so that the path or the column from the internal compression at the transition of the sections 62 and 64 to a scooping area or suction area 67 is longer is. The sealing effect of the gaps is correspondingly increased, which leads to improved sealing of the internal compression with respect to the suction area 67, in particular at high differential pressures.
  • the screw vacuum pump 10 thus has an internal compression.
  • the screw rotors 28, 30 of the pump 10 include repeatedly closed delivery volumes. Their size is larger at an inlet end or in section 62 than at an outlet end End or in section 62.
  • the size of a delivery volume is determined by a cross section of a screw profile 38, 40 and its slope.
  • the size of a delivery volume on the inlet side or in section 62 determines a theoretical pumping speed of the screw pump 10.
  • the slope of the screw profile 38, 40 is constant on the inlet side via section 62, so that the delivery volume is only compressed after completion by the internal compression. If a respective rotor 28, 30 closes a respective delivery volume too early or too late or if the internal compression begins too early, the theoretical pumping speed of the pump drops.
  • the size of a respective delivery volume on the outlet side or in section 66 determines the power consumption of the pump in operation at an achievable final pressure.
  • the ratio of the sizes of the delivery volume on the inlet side and outlet side or in sections 62 and 66 corresponds to the ratio of the internal compression of the pump.
  • the pitch is constant over several revolutions of the screw profile 38, 40.
  • the slope corresponds approximately to the minimum of the slope that can be achieved by a specific machining tool and is therefore, particularly in consideration of costs, production-related. Because several revolutions, that is to say a plurality of closed delivery volumes, are provided in section 66, a backflow due to a pressure difference between the gaps is compensated.
  • the overall gradient course along the rotors 28, 30 and the size of the gaps formed between the rotors 28, 30 and between rotors 28, 30 and the housing 16 determine the vacuum performance data of the pump, in particular the pumping speed and an achievable final pressure.
  • the screw profiles 38, 40 have a particularly low unbalance due to their two-start design. For example, there are no compensating elements, e.g. Compensating compounds that require additional installation space and / or compensating holes in which material can be deposited are necessary.
  • the pump can be operated with the two-start cycloid screw profiles 38, 40 in a wide speed range, in particular with speed control, and / or, for example, in a stand-by mode.
  • the compression of the process gas generally generates heat, which in the screw pump 10 is dissipated primarily by liquid cooling.
  • the grooves 32 provided for this purpose are visible. Cooling lines of the liquid cooling extend here and preferably in the longitudinal direction over a wide range of the screw profiles, in particular over at least half the length of the screw profiles.
  • the liquid cooling is arranged in the area or in the vicinity of an internal compression.
  • the bearing plate 18 is fastened to an inlet-side end of the housing 16. Among other things, this carries a further bearing with bearings 68, which form a loose bearing. In contrast to an opposite bearing plate 70 arranged on an outlet-side housing end, which is formed integrally with the housing 16 but can also be formed separately, the bearing plate 68 is formed as a separate component, but can also be formed integrally.
  • Spray disks 54, deflectors 58 and a piston ring carrier 60 with a plurality of piston rings are also provided on the inlet side and operate in accordance with the arrangement on the outlet side.
  • a further oil bath which is carried out separately, is provided in the cover 20.
  • An immersion cooler 34 is also provided for this oil bath.
  • a cooling line can also be provided, in particular cast, in a wall of the end shield 14 and / or the cover 20
  • a biasing device in particular a spring, may be provided, which is provided in particular in the case of a loose bearing of the rotor and / or on the inlet side.
  • the pretensioning device can, for example, also absorb forces acting on the rotors through helically toothed gearwheels and / or generally ensure that the bearings are preloaded in accordance with the design, regardless of the operating state when the pressures or pressure conditions change.
  • FIG. 5 An immersion cooler 34 is shown as it is arranged in the gearbox 14 or in the cover 20 of the screw vacuum pump 10. In this embodiment, the immersion coolers 34 are therefore of identical design, which leads to a small number of parts and low manufacturing costs.
  • the immersion cooler 34 has a cooling line 72 which runs through a heat sink 74.
  • the heat sink has a structure for increasing the surface of the heat sink in order to optimize the heat transfer.
  • the immersion cooler 34 also has a flange 76 with which the immersion cooler 34 is fastened.
  • FIG. 6 the suction area 67 of the screw vacuum pump 10 is illustrated in a perspective sectional view.
  • the suction area 67 respective suction-side ends of the screw profiles 38 and 40 are arranged, which due to their rotation and in cooperation with an end surface 78 repeatedly close delivery volumes and convey them along the rotor axes to the outlet 24.
  • the end surface 78 is essentially designed as a free-form surface, ie it has a relatively complex shape that deviates from a simple plane.
  • the end surface 78 has a roof-like, lower area 80 and a valley-like or groove-like, upper area 82. Machining the end surface 78 would therefore be very complex, especially if high precision is required.
  • the end face 78 is unprocessed. It is formed by casting the housing 16 by an appropriate shape. Although this creates a relatively imprecise end face 78, this is essentially unproblematic because of the first section 62, which is relatively long in accordance with the invention. Machining can be saved here advantageously.
  • FIG. 6 The sectional view of the Fig. 6 is in Fig. 7 shown in a side view to further illustrate the course of the end surface 78. Only the screw rotor 30 is visible, since it hides the screw rotor 28 in this view.
  • the end face 78 runs in a region surrounding the screw rotor 30 essentially parallel or corresponding to its screw profile 40.
  • the distance between the screw profile 40 and the end face 78 decreases until the distance is zero and a delivery volume is closed in the corresponding profile space 84.
  • Fig. 8 the housing 16 of the screw vacuum pump 10 is shown in perspective view without the screw rotors 28, 30.
  • the complex end surface 78 can only be brought into a desired shape with great effort, in particular by machining processes such as ripping. Because of its complex shape, the end surface 78 cannot be measured or can only be measured with great effort and therefore also hides a danger for series production, since any defects can only be uncovered during a final inspection of the pump without extensive measurement. This goes hand in hand with high assembly and manufacturing costs and expensive rejects.
  • the invention generally reduces the influence of the accuracy of the end face 78 on the vacuum performance data.
  • Fig. 9 shows a diagram, the abscissa of which represents a pressure p in hectopascals of a process gas at the inlet of a screw vacuum pump under investigation and whose ordinate represents a pumping speed S in cubic meters per hour of the pump. Two curves 86 and 88 of the pumping speed as a function of the inlet pressure are shown.
  • the dashed curve 86 is based on an exemplary screw vacuum pump with an inlet area or with an end surface that has been machined to a desired contour.
  • the length of a first section of constant slope essentially corresponds to the length of a closed delivery volume in the first section.
  • the exemplary screw vacuum pump of the course 86 is therefore not designed according to the invention.
  • the curve 88 shown as a solid line was recorded for a further exemplary screw vacuum pump, in which an oversize intended for machining the end face was left and was not machined. Otherwise, the screw vacuum pump of the course 88 is identical to the screw vacuum pump of the course 86. The two pumps or end faces only differ by a certain allowance. The oversize is provided in the direction of the rotor axes, which is why with unchanged rotors a respective delivery volume is completed earlier and the first section is therefore longer than a delivery volume.
  • the screw vacuum pump of the course 88 is consequently designed according to the invention.
  • Both curves 86 and 88 have a pumping speed curve typical of screw vacuum pumps with internal compression.
  • the pumping speed is greatest in a medium pressure range.
  • the pumping speed at high pressures or at the beginning of a pumping process is in Fig. 9 right, lower.
  • the pumping speed drops when a final pressure is reached, in Fig. 9 left, to zero.
  • the course 86 shows a higher pumping speed. It is noticeable here that the delivery volumes are precisely closed due to the end surface being precisely manufactured to the target contour. This effect is indicated by arrow 90.
  • the pumping speed according to curve 86 essentially corresponds to a theoretical pumping speed. A backflow due to compression, in particular to a second section, is therefore not a dominant effect in this middle pressure range.
  • An arrow 92 indicates that the achievable final pressure in the screw vacuum pump with oversize, that is to say with the course 88, is lower or better. This is attributed to the fact that the overall pump-active length of the screw rotors is greater due to the measurement. The gaps between the rotors and the housing are correspondingly longer, so that overall a better seal against backflows from the outlet to the inlet is achieved.
  • the screw vacuum pump according to the invention in particular its housing, is particularly simple to manufacture, since the influence of the corresponding surface accuracy has been reduced. In particular, this eliminates the need for complex machining of the housing in the inlet area or on an end surface. A negative influence on the vacuum performance is small and in some pressure ranges the invention even leads to an improvement in the performance data.

Description

Die vorliegende Erfindung betrifft eine Schraubenvakuumpumpe mit einem Gehäuse, zwei in dem Gehäuse angeordneten und miteinander in Eingriff stehenden Schraubenrotoren, die zum Fördern eines Prozessgases in Zusammenwirkung mit dem Gehäuse wiederholt abgeschlossene Fördervolumina des Prozessgases bilden und in Richtung eines Auslasses fördern.The present invention relates to a screw vacuum pump having a housing, two screw rotors which are arranged in the housing and are in engagement with one another and which, in order to convey a process gas in cooperation with the housing, form repeatedly closed delivery volumes of the process gas and convey them in the direction of an outlet.

Schraubenvakuumpumpen umfassen generell komplexe pumpaktive Geometrien, insbesondere Schraubenprofile von Schraubenrotoren und ein korrespondierendes Gehäuse für die Schraubenrotoren. Ein Zusammenwirken dieser Geometrien erfordert eine hohe Präzision bei deren Fertigung. Es kann daher sehr aufwendig und teuer sein, die Geometrien herzustellen bzw. zu kontrollieren.Screw vacuum pumps generally include complex pump-active geometries, in particular screw profiles of screw rotors and a corresponding housing for the screw rotors. The interaction of these geometries requires high precision in their manufacture. It can therefore be very complex and expensive to manufacture or control the geometries.

Eine Schraubenvakuumpumpe nach dem Oberbegriff des Anspruchs 1 ist in der DE 20 2016 005 209 U1 offenbart. Die DE 20 2016 005 208 U1 , die US 2002/031439 A1 , die DE 100 19 637 A1 und die JP 4 900270 B2 offenbaren weitere Schraubenvakuumpumpen mit Schraubenrotoren, welche unterschiedliche Abschnitte aufweisen.A screw vacuum pump according to the preamble of claim 1 is in the DE 20 2016 005 209 U1 disclosed. The DE 20 2016 005 208 U1 , the US 2002/031439 A1 , the DE 100 19 637 A1 and the JP 4 900270 B2 disclose further screw vacuum pumps with screw rotors, which have different sections.

Es ist eine Aufgabe der Erfindung, eine erforderliche Fertigungspräzision zumindest für einen Teilbereich einer pumpaktiven Geometrie zu verringern.It is an object of the invention to reduce the required manufacturing precision at least for a sub-area of a pump-active geometry.

Diese Aufgabe wird durch eine Schraubenvakuumpumpe mit den Merkmalen des Anspruchs 1 gelöst, und insbesondere dadurch, dass die Schraubenrotoren jeweils zumindest zwei entlang der Schraubenachse benachbarte Abschnitte aufweisen, wobei die Schraubenrotoren jeweils in einem näher an einem Einlass gelegenen ersten Abschnitt eine zumindest im Wesentlichen konstante und in einem zweiten Abschnitt eine niedrigere Steigung als im ersten Abschnitt aufweisen, und wobei in Bezug auf die Schraubenachse der erste Abschnitt länger ist als ein abgeschlossenes Fördervolumen im ersten Abschnitt.This object is achieved by a screw vacuum pump with the features of claim 1, and in particular by the fact that the screw rotors each have at least two sections adjacent along the screw axis, the screw rotors each having an at least substantially constant and in a first section closer to an inlet in a second section have a lower slope than in the first section, and wherein with respect to the screw axis, the first section is longer than a completed delivery volume in the first section.

An einem Einlass der Schraubenvakuumpumpe wirkt ein jeweiliges Schraubenprofil mit dem Gehäuse zusammen, um ein Fördervolumen einzuschließen. Sofern das abzuschließende Fördervolumen vor seinem Abschluss gegenüber dem Einlass den zweiten Abschnitt erreicht, führt dies dazu, dass das Prozessgas teilweise zurück zum Einlass hin ausgestoßen wird. Deswegen war bisher eine hohe Fertigungspräzision des Gehäuses im Einlassbereich notwendig, um für einen präzise definierten Abschluss des Fördervolumens zu sorgen. Eine präzise Fertigung des Einlassbereichs ist aufwendig und wird z.B. dadurch erschwert, dass eine Gussform für das Gehäuse über mehrere Gießzyklen verschleißt.At an inlet of the screw vacuum pump, a respective screw profile interacts with the housing to include a delivery volume. Provided If the delivery volume to be closed reaches the second section opposite to the inlet, this means that the process gas is partially expelled back towards the inlet. For this reason, high manufacturing precision of the housing in the inlet area was previously necessary to ensure a precisely defined completion of the delivery volume. Precise manufacture of the inlet area is complex and is made more difficult, for example, by the fact that a mold for the housing wears out over several casting cycles.

Da der erste Abschnitt erfindungsgemäß länger als ein abgeschlossenes Fördervolumen ist, ist sichergestellt, dass der zweite Abschnitt nicht vor Abschluss des Fördervolumens erreicht wird. Die Fertigungspräzision des Gehäuses im Einlassbereich kann somit reduziert werden, ohne die Gefahr eines Zurückstoßens des Prozessgases zum Einlass hin einzugehen.Since the first section is longer than a completed delivery volume according to the invention, it is ensured that the second section is not reached before the delivery volume is completed. The manufacturing precision of the housing in the inlet area can thus be reduced without running the risk of the process gas knocking back towards the inlet.

Die verringerte Anforderung an die Fertigungspräzision vereinfacht die Herstellung der Vakuumpumpe erheblich. So erlaubt sie einen stabileren Herstellungsprozess mit weniger fehlerhaften Bauteilen. Dies ist insbesondere deshalb vorteilhaft, da das Gehäuse im Einlassbereich häufig schwierig, insbesondere nur aufwendig durch ein 3D-Koordinatenmesssystem, zu vermessen ist. Ohne eine Vermessung werden Abweichungen gegebenenfalls erst bei einer Endprüfung der Schraubenvakuumpumpe erkannt, was im Fehlerfall zu hohen Kosten für die erneute Montage führt. Durch die Erfindung wird der Einfluss der Fertigungspräzision reduziert, sodass Abweichungen von einer Sollform weniger relevant bzw. unschädlich sind.The reduced requirement for manufacturing precision considerably simplifies the manufacture of the vacuum pump. It allows a more stable manufacturing process with fewer defective components. This is particularly advantageous because the housing in the inlet area is often difficult to measure, in particular only with great effort using a 3D coordinate measuring system. Without a measurement, deviations may only be recognized during a final inspection of the screw vacuum pump, which in the event of a fault leads to high costs for reassembly. The influence of manufacturing precision is reduced by the invention, so that deviations from a desired shape are less relevant or harmless.

Hinzu kommt, dass die Erfindung nicht nur die Fertigung des Gehäuses, sondern auch die Fertigung der Schraubenrotoren vereinfacht, da in dem erfindungsgemäß relativ langen ersten Abschnitt mit relativ großer Steigung größere Werkzeuge und/oder Werkzeuge mit höherem Spanvolumen zur Profilherstellung verwendet werden können. Dies verringert die Bearbeitungszeit und die damit einhergehenden Herstellungskosten. Die Bearbeitungszeit kann weiter z.B. dadurch verringert werden, dass eine jeweilige Schraubenkontur der Schraubenrotoren, insbesondere nur oder auch im ersten Abschnitt, bereits beim Gießen zumindest in einer Vorkontur zur weiteren spanenden Bearbeitung ausgebildet wird.In addition, the invention not only simplifies the manufacture of the housing, but also the manufacture of the screw rotors, since larger tools and / or tools with a higher chip volume can be used to produce the profile in the relatively long first section with a relatively large pitch. This reduces the processing time and the associated manufacturing costs. This can further reduce the processing time, for example be that a respective screw contour of the screw rotors, in particular only or also in the first section, is already formed during casting at least in a preliminary contour for further machining.

Es hat sich gezeigt, dass sich trotz des verlängerten ersten Abschnitts effiziente Schraubenprofile bei vergleichbarer Gesamtlänge der Rotoren gestalten lassen. Die fertigungstechnischen Vorteile überwiegen also die vakuumtechnischen Einschränkungen erheblich, sodass sich durch die Erfindung eine effiziente Pumpe besonders einfach herstellen lässt.It has been shown that, despite the lengthened first section, efficient screw profiles can be designed with a comparable overall length of the rotors. The manufacturing advantages outweigh the vacuum restrictions, so that the invention makes it possible to manufacture an efficient pump in a particularly simple manner.

Es hat sich außerdem überraschend gezeigt, dass die erfindungsgemäße Schraubenvakuumpumpe sogar ein verbessertes Saugvermögen bei relativ hohen Ansaugdrücken aufweist. Dies wird darauf zurückgeführt, dass mit dem längeren ersten Abschnitt auch die Spalte im ersten Abschnitt, die sich zwischen den Rotoren untereinander und insbesondere gegenüber dem Gehäuse ausbilden, länger sind. Das Prozessgas im Bereich der inneren Verdichtung, die bei hohen Ansaugdrücken in besonders hohen inneren Drücken resultiert, muss also zum Zurückströmen längere Spalte überwinden. Die Rückströmung wird folglich erschwert bzw. besser abgedichtet. Die erfindungsgemäße Schraubenvakuumpumpe ist also nicht nur bei vertretbaren Auslegungseinschränkungen besonders einfach herzustellen, sondern weist sogar in bestimmten Druckbereichen eine verbesserte vakuumtechnische Leistung auf.It has also surprisingly been found that the screw vacuum pump according to the invention even has an improved pumping speed at relatively high suction pressures. This is attributed to the fact that, with the longer first section, the gaps in the first section which form between the rotors with one another and in particular with respect to the housing are longer. The process gas in the area of the internal compression, which results in particularly high internal pressures at high intake pressures, must therefore overcome longer gaps in order to flow back. The backflow is consequently made more difficult or better sealed. The screw vacuum pump according to the invention is therefore not only particularly easy to manufacture with justifiable design restrictions, but also has improved vacuum performance in certain pressure ranges.

Als abgeschlossenes Fördervolumen kann allgemein ein - abgesehen von unvermeidbaren Spalten zwischen den Rotoren und gegenüber dem Gehäuse - abgeschlossener Bereich verstanden werden, der sich zwischen zwei Schraubengängen eines jeweiligen Rotors entlang des Schraubenprofils um den Rotor herum erstreckt und nach außen vom Gehäuse und entlang des Schraubenprofils vom jeweils anderen Rotor begrenzt ist. Das Fördervolumen wandert beim Pumpvorgang entlang des jeweiligen Schraubenrotors in dessen Profil vom Einlass zum Auslass, wodurch die Pumpwirkung bereitgestellt wird. Das Fördervolumen kann auf dem Weg zwischen Einlass und Auslass kleiner werden. Hierbei spricht man von einer inneren Verdichtung.A closed delivery volume can generally be understood to be a closed area - apart from unavoidable gaps between the rotors and in relation to the housing - which extends between two screw threads of a respective rotor along the screw profile around the rotor and outwards from the housing and along the screw profile from each other rotor is limited. The delivery volume moves during the pumping process along the respective screw rotor in its profile from the inlet to the Outlet, providing the pumping action. The funding volume can decrease on the way between inlet and outlet. This is called internal compression.

Insbesondere kann das abgeschlossene Fördervolumen einen Winkel von 360° um die Schraubenachse des jeweiligen Rotors abdecken.In particular, the closed delivery volume can cover an angle of 360 ° around the screw axis of the respective rotor.

Bei einer Ausführungsform entspricht der erste Abschnitt mindestens dem 1,25-fachen, insbesondere mindestens dem 1,5-fachen, inbesondere mindestens dem 1,75-fachen, insbesondere mindestens dem 2-fachen der Länge des Fördervolumens. Die zuvor genannten Vorteile werden hierdurch entsprechend verstärkt.In one embodiment, the first section corresponds to at least 1.25 times, in particular at least 1.5 times, in particular at least 1.75 times, in particular at least 2 times the length of the delivery volume. The advantages mentioned above are thereby increased accordingly.

In einem Ansaugbereich der Pumpe ist eine Abschlussfläche für die Schraubenrotoren ausbildet, die derart hinsichtlich ihrer Form an die Schraubenrotoren angepasst ist, dass ein jeweiliges Fördervolumen zum Ansaugen eröffnet und zum Fördern abgeschlossen werden kann.An end face for the screw rotors is formed in a suction area of the pump, the shape of which is adapted to the screw rotors in such a way that a respective delivery volume can be opened for suction and can be closed for delivery.

Die Abschlussfläche verläuft insbesondere zumindest im Wesentlichen senkrecht zu den Schraubenachsen. Die Abschlussfläche bildet z.B. eine, insbesondere innere, Stirnfläche des Gehäuses. Die Abschlussfläche kann vorzugsweise als Freiformfläche ausgebildet sein und/oder zumindest im Wesentlichen parallel zu zumindest einem entsprechenden Schraubenprofil verlaufen. Inbesondere können zwei zu den Schraubenprofilen jeweils parallele Bereiche der Abschlussfläche vorgesehen sein, die insbesondere zu einem in Bezug auf die Schraubenachse erhöhten, insbesondere unteren, Bereich und/oder erniedrigten, insbesondere oberen Bereich, zusammengeführt sind.The end face in particular runs at least substantially perpendicular to the screw axes. The end surface forms e.g. one, in particular inner, end face of the housing. The end surface can preferably be designed as a free-form surface and / or run at least substantially parallel to at least one corresponding screw profile. In particular, two areas of the end face that are parallel to the screw profiles can be provided, which are brought together in particular to form an area that is raised, in particular lower, and / or lowered, in particular upper, with respect to the screw axis.

Die Abschlussfläche kann im allgemeinen z.B. im Gehäuse ausgebildet sein. Das Gehäuse kann beispielsweise als Gussteil ausgebildet sein. Bei einer Ausführungsform ist die Abschlussfläche in einem Gussteil, insbesondere dem Gehäuse, ausgebildet und unbearbeitet. Hierdurch wird der Fertigungsschritt einer spanenden Bearbeitung der Abschlussfläche komplett eingespart, was die Fertigung des Gehäuses weiter vereinfacht.The end surface can generally be formed, for example, in the housing. The housing can be designed as a cast part, for example. In one embodiment, the end surface is in a casting, in particular the housing, trained and unprocessed. This completely saves the manufacturing step of machining the end face, which further simplifies the manufacture of the housing.

Bei einer weiteren Ausführungsform ist ein Schraubenprofil eines jeweiligen Schraubenrotors durch eine Zykloide gebildet. Ein solches Schraubenprofil lässt sich vorteilhaft bedarfsgerecht gestalten.In a further embodiment, a screw profile of a respective screw rotor is formed by a cycloid. Such a screw profile can advantageously be designed as required.

Bei einer Weiterbildung ist ein Schraubenprofil eines jeweiligen Schraubenrotors zweigängig ausgebildet. Hierdurch wird eine besonders geringe Unwucht des entsprechenden Schraubenrotors erreicht. Somit kann auf Ausgleichselemente, wie z.B. Ausgleichsmassen, die zusätzlichen Bauraum erfordern, und/oder Ausgleichsbohrungen, in denen sich Material ablagern kann, verzichtet werden. Andererseits können so höhere Drehzahlen ermöglicht werden.In one development, a screw profile of a respective screw rotor is designed with two threads. This results in a particularly low imbalance of the corresponding screw rotor. Thus, compensation elements such as Compensating masses that require additional installation space and / or compensating holes in which material can be deposited can be dispensed with. On the other hand, higher speeds can be made possible.

Bei einer weiteren Ausführungsform weisen die Schraubenrotoren jeweils im zweiten Abschnitt eine zumindest im Wesentlichen konstante Steigung auf. Derartige Schraubenrotoren lassen sich besonders einfach auslegen und fertigen, da die konstante Steigung eine relativ einfache Geometrie bildet.In a further embodiment, the screw rotors each have an at least substantially constant pitch in the second section. Such screw rotors are particularly easy to design and manufacture because the constant pitch forms a relatively simple geometry.

Es kann vorgesehen sein, dass die Schraubenrotoren jeweils zumindest einen dritten Abschnitt aufweisen und ihre Steigung im dritten Abschnitt kleiner ist als im zweiten Abschnitt. Hierdurch kann eine zusätzliche innere Verdichtung realisiert werden.It can be provided that the screw rotors each have at least a third section and their pitch is smaller in the third section than in the second section. This allows additional internal compression to be achieved.

Die Steigung im dritten Abschnitt kann insbesondere zumindest im Wesentlichen konstant sein. Bei einem weiteren Ausführungsbeispiel weisen die Schraubenrotoren jeweils über ihre gesamte pumpaktive Länge eine Mehrzahl von Abschnitten unterschiedlicher Steigung auf, wobei die Steigung in allen Abschnitten, insbesondere zumindest Bereich- oder Unterabschnittsweise, insbesondere jeweils, konstant ist. Beides trägt zu einer vereinfachten Auslegung bzw. Fertigung bei.The slope in the third section can in particular be at least substantially constant. In a further exemplary embodiment, the screw rotors each have a plurality of sections of different pitch over their entire active pumping length, the pitch in all sections, in particular is constant at least in areas or subsections, in particular in each case. Both contribute to a simplified design and manufacture.

Zwischen zwei benachbarten Abschnitten konstanter Steigung verändert sich die Steigung des Schraubenprofils entlang einer Schraubenachse grundsätzlich lediglich in Übergangsbereichen zwischen den Abschnitten. Ein Übergangsbereich ist insbesondere kleiner als ein Abschnitt, insbesondere als die benachbarten Abschnitte. Insbesondere sind alle Übergangsbereiche kleiner als alle Abschnitte.Between two adjacent sections of constant pitch, the pitch of the screw profile along a screw axis basically only changes in transition areas between the sections. A transition area is in particular smaller than a section, in particular than the adjacent sections. In particular, all transition areas are smaller than all sections.

Die Schraubenvakuumpumpe kann beispielsweise eine innere Verdichtung mit einem Verdichtungsverhältnis kleiner als 5 zu 1, inbesondere kleiner als 4 zu 1, insbesondere kleiner als 3,5 zu 1, und/oder größer als 2 zu 1, insbesondere größer als 3 zu 1, aufweisen. Ein jeweiliges Schraubenprofil kann z.B. mehr als 7, insbesondere mehr als 10, insbesondere mehr als 12, insbesondere 13 abgeschlossene Fördervolumina gleichzeitig bilden bzw fördern. Ein jeweiliger Schraubenrotor kann insbesondere ein Verhältnis der Länge seines Schraubenprofils zu dessen Durchmesser von wenigstens 2,0, insbesondere wenigstens 2,5, insbesondere wenigstens 3,0 und/oder höchstens 5,0, insbesondere 4,0, aufweisen.The screw vacuum pump can, for example, have an internal compression with a compression ratio of less than 5 to 1, in particular less than 4 to 1, in particular less than 3.5 to 1, and / or greater than 2 to 1, in particular greater than 3 to 1. A respective screw profile can e.g. Form or promote more than 7, in particular more than 10, in particular more than 12, in particular 13, closed delivery volumes at the same time. A respective screw rotor can in particular have a ratio of the length of its screw profile to its diameter of at least 2.0, in particular at least 2.5, in particular at least 3.0 and / or at most 5.0, in particular 4.0.

Die Erfindung wird nachfolgend lediglich beispielhaft anhand der schematischen Zeichnung erläutert.

Fig. 1
zeigt eine Schraubenvakuumpumpe in perspektivischer Ansicht.
Fig. 2
zeigt die Schraubenvakuumpumpe der Fig. 1 in einer Draufsicht.
Fig. 3
zeigt die Schraubenvakuumpumpe der Fig. 1 und 2 in einer Seitenansicht.
Fig. 4
zeigt eine Schnittansicht der Schraubenvakuumpumpe entlang einer in Fig. 3 angedeuteten Schnittebene A-A.
Fig. 5
zeigt einen Tauchkühler der Schraubenvakuumpumpe der Fig. 1 bis 4.
Fig. 6
zeigt einen Ansaugbereich der Schraubenvakuumpumpe der Fig. 1 bis 4 in geschnittener, perspektivischer Ansicht.
Fig. 7
zeigt die Schnittdarstellung der Fig, 6 in einer Seitenansicht.
Fig. 8
zeigt ein Gehäuse der Schraubenvakuumpumpe in perspektivischer Ansicht.
Fig. 9
zeigt in einem Diagramm zwei Saugvermögensverläufe jeweils von einer Schraubenpumpe mit einer bearbeiteten bzw. unbearbeiteten Abschlussfläche.
The invention is explained below by way of example only with reference to the schematic drawing.
Fig. 1
shows a screw vacuum pump in perspective view.
Fig. 2
shows the screw vacuum pump of the Fig. 1 in a top view.
Fig. 3
shows the screw vacuum pump of the Fig. 1 and 2nd in a side view.
Fig. 4
shows a sectional view of the screw vacuum pump along an in Fig. 3 indicated cutting plane AA.
Fig. 5
shows an immersion cooler of the screw vacuum pump 1 to 4 .
Fig. 6
shows a suction area of the screw vacuum pump of the 1 to 4 in a cut, perspective view.
Fig. 7
shows the sectional view of the Fig. 6 in a side view.
Fig. 8
shows a housing of the screw vacuum pump in a perspective view.
Fig. 9
shows in a diagram two pumping speed curves, each from a screw pump with a machined or unprocessed end surface.

In den Fig. 1 bis 3 ist eine Schraubenvakuumpumpe 10 gezeigt, die einen Motor 12, einen Getriebekasten 14, ein Gehäuse 16, einen Lagerschild 18 sowie einen Deckel 20 aufweist. Die Schraubenvakuumpumpe 10 fördert ein Prozessgas von einem Einlass 22 zu einem nach unten gerichteten, in Fig. 3 sichtbaren Auslass 24.In the 1 to 3 A screw vacuum pump 10 is shown, which has a motor 12, a gear box 14, a housing 16, a bearing plate 18 and a cover 20. The screw vacuum pump 10 conveys a process gas from an inlet 22 to a downward, in Fig. 3 visible outlet 24.

Für den Motor 12 ist eine aktive Flüssigkeitskühlung vorgesehen, die aus einem Gehäuse des Motors 12 austritt. Für im Inneren des Gehäuses 16 angeordnete und in Fig. 4 sichtbare Schraubenrotoren 28 und 30 ist ebenfalls eine aktive Flüssigkeitskühlung vorgesehen, die zwei Kühlleitungen aufweist, welche in Fig. 1 nicht dargestellt sind, deren Verlauf aber durch entsprechende Nuten 32 des Gehäuses 16 angedeutet ist, in die die Kühlleitungen eingepresst werden. Des Weiteren sind aktive Flüssigkeitskühlungen im Getriebekasten 14 und im Deckel 20 vorgesehen und hier jeweils als Tauchkühler 34 ausgebildet, die unten anhand von Fig. 5 näher erläutert werden.An active liquid cooling is provided for the motor 12, which emerges from a housing of the motor 12. For arranged inside the housing 16 and in Fig. 4 visible screw rotors 28 and 30 an active liquid cooling is also provided, which has two cooling lines, which in Fig. 1 are not shown, but the course thereof by means of corresponding grooves 32 in the housing 16 is indicated, into which the cooling lines are pressed. Furthermore, active liquid cooling systems are provided in the gearbox 14 and in the cover 20 and are each designed here as immersion coolers 34, which are described below with reference to FIG Fig. 5 are explained in more detail.

Wie es in den Fig. 1 bis 4 ersichtlich ist, weist das Gehäuse 16 der Schraubenvakuumpumpe 10 eine Taillierung 36 auf. Die Taillierung 36 ist im Bereich des Auslasses 24 angeordnet.Like it in the 1 to 4 can be seen, the housing 16 of the screw vacuum pump 10 has a waist 36. The waist 36 is arranged in the region of the outlet 24.

In Fig. 4 ist die Schraubenvakuumpumpe 10 in einer Schnittansicht gezeigt, deren Schnittebene der Linie A-A in Fig. 3 entspricht. Es sind zwei Schraubenrotoren 28 und 30 sichtbar, die jeweils zweigängige, ineinandergreifende Schraubenprofile 38 und 40 aufweisen, die mit Hilfe eines Zykloidenprofil generiert sind und eine zylindrische Hüllkontur sowie eine zylindrische Grundform des Schraubengrundes aufweisen. Die Schraubenprofile 38 und 40 bilden in Zusammenwirkung mit dem Gehäuse 16 einen pumpaktiven Bereich der Schraubenvakuumpumpe 10 und fördern wiederholt abgeschlossene Fördervolumina des Prozessgases vom Einlass 22 zum Auslass 24, in Fig. 4 also von links nach rechts.In Fig. 4 the screw vacuum pump 10 is shown in a sectional view, the sectional plane of the line AA in Fig. 3 corresponds. Two screw rotors 28 and 30 are visible, each having two-start, interlocking screw profiles 38 and 40, which are generated with the aid of a cycloid profile and have a cylindrical envelope contour and a cylindrical basic shape of the screw base. In cooperation with the housing 16, the screw profiles 38 and 40 form a pump-active area of the screw vacuum pump 10 and repeatedly convey closed delivery volumes of the process gas from the inlet 22 to the outlet 24, in Fig. 4 from left to right.

Die Pumpleistung der Schraubenvakuumpumpe 10 hängt von Größe und Gestalt verschiedener Spalte im pumpaktiven Bereich ab, die aufgrund der Relativbewegung von Rotoren 28, 30 und Gehäuse 16 zwar unvermeidbar sind, jedoch zwecks guter Pumpleistung klein und möglichst konstant zu halten sind. Temperaturänderungen in den beteiligten Bauteilen führen zu deren Formänderung. Die hierin beschriebenen Maßnahmen zur Vermeidung, Abführung und im Allgemeinen Beherrschung von Wärme in der Pumpe 10 bewirken somit eine möglichst geringe Formänderung und in der Folge möglichst beherrschbare Spalte. Die Spalte können also präziser ausgelegt werden, was die Pumpleistung bzw. ihre Effizienz verbessert.The pumping power of the screw vacuum pump 10 depends on the size and shape of various gaps in the pumping area, which are unavoidable due to the relative movement of the rotors 28, 30 and housing 16, but are small and as constant as possible for good pumping power. Temperature changes in the components involved lead to their shape change. The measures described here for avoiding, dissipating and, in general, controlling heat in the pump 10 thus bring about the least possible change in shape and consequently the most manageable gaps. The gaps can therefore be designed more precisely, which improves the pump performance and its efficiency.

Der Schraubenrotor 28 wird direkt, also ohne zwischengeschaltete Kupplung, von dem Motor 12 angetrieben. Der Schraubenrotor 30 wird dagegen über ein Synchronisierungsgetriebe 42 mit Zahnrädern 43 in einem definierten Winkelverhältnis zum Schraubenrotor 28 angetrieben.The screw rotor 28 is driven directly by the motor 12, that is to say without an intermediate coupling. In contrast, the screw rotor 30 is driven via a synchronization gear 42 with gearwheels 43 in a defined angular relationship to the screw rotor 28.

Der Motor 12 umfasst ein Gehäuse 44, welches zum Beispiel aus Aluminium hergestellt ist und in welchem Kühlleitungen 26 für die aktive Flüssigkeitskühlung ausgebildet sind. Der Motor 12 umfasst außerdem einen gewickelten Stator 46, der zusammen mit einem auf einem Wellenende des Schraubenrotors 28 angebrachten Magnetträger 48 einen elektrischen Motor und einen Direktantrieb für den Schraubenrotor 28 bildet. Der Schraubenrotor 28 bildet einen Läufer des Motors 12. Der Magnetträger 48 umfasst eine Mehrzahl an Permanentmagneten. Der Motor 12 bildet also eine Permanentmagnetsynchronmaschine mit innenliegenden Magneten, welche auch als IPMSM bezeichnet wird.The motor 12 comprises a housing 44, which is made of aluminum, for example, and in which cooling lines 26 are formed for the active liquid cooling. The motor 12 also includes a wound stator 46 which, together with a magnet carrier 48 attached to a shaft end of the screw rotor 28, forms an electric motor and a direct drive for the screw rotor 28. The screw rotor 28 forms a rotor of the motor 12. The magnet carrier 48 comprises a plurality of permanent magnets. The motor 12 thus forms a permanent magnet synchronous machine with internal magnets, which is also referred to as IPMSM.

Der Stator 46 ist in einem Vergusskörper 50 angeordnet, welcher nicht näher dargestellte elektrische Leiter beim Stator 46 isoliert und diese isoliert zu einer Platine 52 führt. Der Vergusskörper 50 bildet hier in Verbindung mit der Platine 52 einen vakuumdichten Anschluss des Motors 12 an eine in einem Bereich atmosphärischen Drucks vorgesehene Steuerungselektronik. Es kann z.B. ein externer Frequenzumrichter für den Motor 12 vorgesehen sein. Alternativ oder zusätzlich kann auf der Platine 52 zumindest ein Teil einer Steuerungselektronik für den Motor 12 vorgesehen sein.The stator 46 is arranged in a potting body 50, which insulates electrical conductors (not shown in more detail) in the stator 46 and insulates them to a circuit board 52. The potting body 50 here, in conjunction with the circuit board 52, forms a vacuum-tight connection of the motor 12 to control electronics provided in a range of atmospheric pressure. For example, an external frequency converter can be provided for the motor 12. Alternatively or additionally, at least part of control electronics for the motor 12 can be provided on the circuit board 52.

In dem Getriebekasten 14 ist das Synchronisierungsgetriebe 42 angeordnet. Im Getriebekasten 14 ist außerdem Öl als Schmiermittel vorgesehen, welches durch Spritzscheiben 54 über das Synchronisierungsgetriebe 42 und benachbarte Lager 56 verteilt wird.The synchronizing gear 42 is arranged in the gear box 14. In the gear box 14, oil is also provided as a lubricant, which is distributed by spray disks 54 via the synchronizing gear 42 and adjacent bearings 56.

Die Tailllierung 36 bildet eine Abschirmung bzw. eine Wärmebarriere, und zwar insbesondere für Wärme, die im Bereich der Schraubenrotoren 28, 30 während des Pumpbetriebs produziert wird. Dadurch, dass ein geringer Materialquerschnitt verbleibt, und dadurch, dass durch die Formänderung ein Wärmepfad verlängert ist, wird die Wärme vom Schraubenrotor, die sich ansonsten im Gehäuse 16 ausbreitet, daran gehindert, in jenseitige Bereiche zu gelangen. So werden insbesondere das Öl im Getriebekasten 14 und die Lager 56 vor zu hohen Temperaturen geschützt. Der im Getriebekasten 14 angeordnete Tauchkühler 34 trägt ebenfalls zur Temperaturreduzierung bei. Dieser ist in einem nicht dargestellten Ölbad des Getriebekastens 14 angeordnet und kühlt somit das Öl direkt.The waist 36 forms a shield or a heat barrier, in particular for heat that is produced in the area of the screw rotors 28, 30 during pump operation. Due to the fact that a small material cross section remains, and because the change in shape extends a heat path, the heat from the screw rotor, which otherwise spreads in the housing 16, is prevented from reaching areas beyond. In particular, the oil in the gearbox 14 and the bearings 56 are protected from excessive temperatures. The immersion cooler 34 arranged in the gearbox 14 also contributes to reducing the temperature. This is arranged in an oil bath (not shown) of the gear box 14 and thus cools the oil directly.

Für einen jeweiligen Schraubenrotor 28 bzw. 30 ist benachbart zu den Lagern 56, die hier eine Festlagerung bilden, eine als Deflektor 58 ausgebildete Schmiermittel-Abführeinrichtung vorgesehen. Ein jeweiliger Deflektor 58 bildet eine Barriere für das Öl im Getriebekasten, damit es nicht in einen pumpaktiven Bereich oder einen Vakuumbereich, hier insbesondere einen Auslassbereich, gelangt. Der Deflektor 58 umfasst eine nicht näher veranschaulichte Abschleuderkante für das Öl. Gegenüber der Abschleuderkante ist im Gehäuse 16 eine Ablaufnut ausgebildet, die abgeschleudertes Öl aufnimmt und dieses zurück in den Getriebekasten 14 bzw. in ein dortiges Ölbad leitet. Das Öl, welches durch die Spritzscheiben 54 auf Getriebe 42 und Lager 56 gefördert bzw. verteilt wird, wird somit durch die Deflektoren 58 wieder von den Rotoren 28 bzw. 30 abgeführt.A lubricant discharge device designed as a deflector 58 is provided for a respective screw rotor 28 or 30 adjacent to the bearings 56, which form a fixed bearing here. A respective deflector 58 forms a barrier for the oil in the gearbox so that it does not get into a pump-active area or a vacuum area, here in particular an outlet area. The deflector 58 comprises a not shown edge for the oil. Opposite the fling edge, a drain groove is formed in the housing 16, which takes up flung oil and directs it back into the gear box 14 or into an oil bath there. The oil, which is conveyed or distributed by the spray disks 54 to the gear 42 and bearing 56, is thus removed again by the deflectors 58 from the rotors 28 and 30, respectively.

Als dynamische Fluiddichtung sind Kolbenringe auf einem Kolbenringträger 60 vorgesehen. Diese bilden eine berührungslose Dichtung und vermeiden somit Reibungswärme. Die Deflektoren 58 führen möglichst viel Öl zum Getriebekasten 14 zurück, sodass bereits möglichst wenig Öl an den Kolbenringen ansteht. So wird eine insgesamt zuverlässige Dichtwirkung bei besonders geringer Wärmeproduktion erreicht.Piston rings are provided on a piston ring carrier 60 as a dynamic fluid seal. These form a non-contact seal and thus avoid frictional heat. The deflectors 58 return as much oil as possible to the gearbox 14, so that as little oil as possible is present on the piston rings. An overall reliable sealing effect is achieved with particularly low heat production.

Die Schraubenrotoren 28 und 30 weisen in ihrem jeweiligen Schraubenprofil 38 bzw. 40 drei Abschnitte unterschiedlicher Steigung auf. Ein in Pumprichtung erster Abschnitt 62, in Fig. 4 links, bildet einen Ansaugabschnitt und weist eine konstante und die größte Steigung unter den drei Abschnitten auf. Der erste Abschnitt 62 ist in Bezug auf eine Schraubenachse 63, die entlang eines jeweiligen Rotors 28 bzw. 30 verläuft, länger als ein abschlossenes Fördervolumen im ersten Abschnitt. Ein zweiter Abschnitt 64 weist mehrere Unterabschnitte, die nicht näher referenziert sind, mit verschiedenen aber jeweils konstanten Steigungen im Schraubenprofil 38 bzw. 40 auf, wobei die Steigungen niedriger sind, als im ersten Abschnitt. Der zweite Abschnitt 64 bildet hier den längsten Abschnitt. Ein dritter Abschnitt 66 mit noch niedrigerer Steigung bildet einen Ausstoßabschnitt. Im dritten Abschnitt liegt wiederum eine konstante Steigung vor. Durch die entlang der Pumprichtung verminderte Steigung wird eine innere Verdichtung bewirkt, die das Prozessgas schon vor dem Ausstoßen verdichtet.The screw rotors 28 and 30 have three sections of different pitch in their respective screw profile 38 and 40, respectively. A first section 62 in the pumping direction, in Fig. 4 left, forms a suction section and has a constant and the largest slope among the three sections. The first section 62 is longer than a closed delivery volume in the first section with respect to a screw axis 63 which runs along a respective rotor 28 or 30. A second section 64 has a plurality of subsections, which are not referenced in any more detail, with different but in each case constant slopes in the screw profile 38 or 40, the slopes being lower than in the first section. The second section 64 forms the longest section here. A third section 66 with an even lower slope forms an ejection section. In the third section there is again a constant slope. Due to the reduced slope along the pump direction, an internal compression is brought about, which compresses the process gas before it is expelled.

Die Rotoren 28, 30 bzw. die Schraubenprofile 38, 40 lassen sich durch das Vorsehen der konstanten Abschnitte besonders einfach auslegen und fertigen. Wie es anhand von Fig. 4 ersichtlich ist, führt ein verlängerter erster Abschnitt 62 zu entsprechend verlängerten Spalten zwischen den Schraubenprofilen 28, 30 und dem Gehäuse 16, sodass der Weg bzw. die Spalte von der inneren Verdichtung am Übergang der Abschnitte 62 und 64 hin zu einem Schöpfraum oder Ansaugbereich 67 länger ist. Entsprechend erhöht ist also die Dichtwirkung der Spalte, was insbesondere bei hohen Differenzdrücken zu einer verbesserten Abdichtung der inneren Verdichtung gegenüber dem Ansaugbereich 67 führt.The rotors 28, 30 and the screw profiles 38, 40 can be designed and manufactured particularly simply by providing the constant sections. As it is based on Fig. 4 It can be seen that an elongated first section 62 leads to correspondingly elongated gaps between the screw profiles 28, 30 and the housing 16, so that the path or the column from the internal compression at the transition of the sections 62 and 64 to a scooping area or suction area 67 is longer is. The sealing effect of the gaps is correspondingly increased, which leads to improved sealing of the internal compression with respect to the suction area 67, in particular at high differential pressures.

Die Schraubenvakuumpumpe 10 weist also eine innere Verdichtung auf. Die Schraubenrotoren 28, 30 der Pumpe 10 schließen in Zusammenwirkung mit dem Gehäuse 16 wiederholt abgeschlossene Fördervolumina ein. Deren Größe ist an einem einlassseitigen Ende bzw. im Abschnitt 62 größer als an einem auslassseitigen Ende bzw. im Abschnitt 62. Die Größe eines Fördervolumens wird durch einen Querschnitt eines Schraubenprofils 38, 40 und dessen Steigung bestimmt.The screw vacuum pump 10 thus has an internal compression. In cooperation with the housing 16, the screw rotors 28, 30 of the pump 10 include repeatedly closed delivery volumes. Their size is larger at an inlet end or in section 62 than at an outlet end End or in section 62. The size of a delivery volume is determined by a cross section of a screw profile 38, 40 and its slope.

Die Größe eines Fördervolumens auf der Einlassseite bzw. im Abschnitt 62 bestimmt ein theoretisches Saugvermögen der Schraubenpumpe 10. Die Steigung des Schraubenprofils 38, 40 ist einlassseitig über Abschnitt 62 konstant, damit das Fördervolumen erst nach Abschluss durch die innere Verdichtung komprimiert wird. Schließt ein jeweiliger Rotor 28, 30 ein jeweiliges Fördervolumen zu früh oder zu spät bzw. beginnt die innere Verdichtung zu früh, sinkt das theoretische Saugvermögen der Pumpe.The size of a delivery volume on the inlet side or in section 62 determines a theoretical pumping speed of the screw pump 10. The slope of the screw profile 38, 40 is constant on the inlet side via section 62, so that the delivery volume is only compressed after completion by the internal compression. If a respective rotor 28, 30 closes a respective delivery volume too early or too late or if the internal compression begins too early, the theoretical pumping speed of the pump drops.

Die Größe eines jeweiligen Fördervolumens auf der Auslassseite bzw. im Abschnitt 66 bestimmt die Leistungsaufnahme der Pumpe im Betrieb bei einem erreichbaren Enddruck. Das Verhältnis der Größen des Fördervolumens an Einlassseite und Auslasseite bzw. in den Abschnitten 62 und 66 entspricht dem Verhältnis der inneren Verdichtung der Pumpe.The size of a respective delivery volume on the outlet side or in section 66 determines the power consumption of the pump in operation at an achievable final pressure. The ratio of the sizes of the delivery volume on the inlet side and outlet side or in sections 62 and 66 corresponds to the ratio of the internal compression of the pump.

In Abschnitt 66 ist die Steigung über mehrere Umdrehungen des Schraubenprofils 38, 40 konstant. Die Steigung entspricht dabei in etwa dem Minimum der durch ein bestimmtes Bearbeitungswerkzeug erreichbaren Steigung und ist somit, insbesondere unter Kostenabwägung, fertigungstechnisch bedingt. Dadurch, dass mehrere Umdrehungen, also mehrere abgeschlossene Fördervolumina, im Abschnitt 66 vorgesehen sind, wird eine Rückströmung infolge einer Druckdifferenz zwischen den Spalten ausgeglichen. Insgesamt bestimmen insbesondere der gesamte Steigungsverlauf entlang der Rotoren 28, 30 und die Größe der sich zwischen den Rotoren 28, 30 und zwischen Rotoren 28, 30 und dem Gehäuse 16 ausbildenden Spalte die vakuumtechnischen Leistungsdaten der Pumpe, also insbesondere das Saugvermögen und einen erreichbaren Enddruck.In section 66, the pitch is constant over several revolutions of the screw profile 38, 40. The slope corresponds approximately to the minimum of the slope that can be achieved by a specific machining tool and is therefore, particularly in consideration of costs, production-related. Because several revolutions, that is to say a plurality of closed delivery volumes, are provided in section 66, a backflow due to a pressure difference between the gaps is compensated. Overall, in particular the overall gradient course along the rotors 28, 30 and the size of the gaps formed between the rotors 28, 30 and between rotors 28, 30 and the housing 16 determine the vacuum performance data of the pump, in particular the pumping speed and an achievable final pressure.

Die Schraubenprofile 38, 40 weisen durch ihre zweigängige Ausgestaltung eine besonders geringe Unwucht auf. Es sind also beispielsweise keine Ausgleichselemente, wie z.B. Ausgleichsmassen, die zusätzlichen Bauraum erfordern, und/oder Ausgleichsbohrungen, in denen sich Material ablagern kann, notwendig. Die Pumpe kann mit den zweigängigen Zykloidenschraubenprofilen 38, 40 in einem weiten Drehzahlbereich, insbesondere mit Drehzahlregelung, und/oder beispielsweise in einer Stand-By-Betriebsart betrieben werden.The screw profiles 38, 40 have a particularly low unbalance due to their two-start design. For example, there are no compensating elements, e.g. Compensating compounds that require additional installation space and / or compensating holes in which material can be deposited are necessary. The pump can be operated with the two-start cycloid screw profiles 38, 40 in a wide speed range, in particular with speed control, and / or, for example, in a stand-by mode.

Die Verdichtung des Prozessgases im Allgemeinen erzeugt Wärme, die bei der Schraubenpumpe 10 vornehmlich durch eine Flüssigkeitskühlung abgeführt wird. In Fig. 4 sind die hierfür vorgesehenen Nuten 32 sichtbar. Kühlleitungen der Flüssigkeitskühlung erstrecken sich hier und vorzugsweise in Längsrichtung über einen weiten Bereich der Schraubenprofile, insbesondere über wenigstens die Hälfte der Länge der Schraubenprofile. Insbesondere ist die Flüssigkeitskühlung im Bereich oder in der Nähe einer inneren Verdichtung angeordnet.The compression of the process gas generally generates heat, which in the screw pump 10 is dissipated primarily by liquid cooling. In Fig. 4 the grooves 32 provided for this purpose are visible. Cooling lines of the liquid cooling extend here and preferably in the longitudinal direction over a wide range of the screw profiles, in particular over at least half the length of the screw profiles. In particular, the liquid cooling is arranged in the area or in the vicinity of an internal compression.

An einem einlassseitigen Ende des Gehäuses 16 ist der Lagerschild 18 befestigt. Dieser trägt unter anderem eine weitere Lagerung mit Lagern 68, die eine Loslagerung bilden. Im Gegensatz zu einem gegenüberliegenden, an einem auslassseitigen Gehäuseende angeordneten Lagerschild 70, der integral mit dem Gehäuse 16 ausgebildet ist aber auch separat ausgebildet sein kann, ist der Lagerschild 68 als separates Bauteil ausgebildet, kann jedoch auch integral ausgebildet sein.The bearing plate 18 is fastened to an inlet-side end of the housing 16. Among other things, this carries a further bearing with bearings 68, which form a loose bearing. In contrast to an opposite bearing plate 70 arranged on an outlet-side housing end, which is formed integrally with the housing 16 but can also be formed separately, the bearing plate 68 is formed as a separate component, but can also be formed integrally.

Einlassseitig sind ebenfalls Spritzscheiben 54, Deflektoren 58 und ein Kolbenringträger 60 mit mehreren Kolbenringen vorgesehen, die entsprechend der auslassseitigen Anordung arbeiten. Einlassseitig ist ein weiteres, separat ausgeführtes Ölbad im Deckel 20 vorgesehen. Auch für dieses Ölbad ist ein Tauchkühler 34 vorgesehen. Alternativ oder zusätzlich kann auch beispielsweise eine Kühlleitung in einer Wand des Lagerschildes 14 und/oder des Deckels 20 vorgesehen, insbesondere vergossen seinSpray disks 54, deflectors 58 and a piston ring carrier 60 with a plurality of piston rings are also provided on the inlet side and operate in accordance with the arrangement on the outlet side. On the inlet side, a further oil bath, which is carried out separately, is provided in the cover 20. An immersion cooler 34 is also provided for this oil bath. Alternatively or additionally, for example, a cooling line can also be provided, in particular cast, in a wall of the end shield 14 and / or the cover 20

Am Anfang eines Abpumpvorganges durch die Pumpe 10 herrscht gewöhnlich am Einlass 22 im Wesentlichen der gleiche Druck wie am Auslass. Während des Abpumpens sinkt dagegen der Druck am Einlass 22 bis hin zu einem Enddruck, der hinsichtlich resultierender Kräfte im Wesentlichen Null ist. Somit übt der Druck am Auslass 24 eine Kraft auf die Rotoren 28, 30 aus, die anders ist als am Anfang des Abpumpvorgangs. Um diese Kraft auszugleichen kann z.B. eine Vorspanneinrichtung, insbesondere eine Feder, vorgesehen sein, die insbesondere bei einem Loslager des Rotors und/oder einlassseitig vorgesehen ist. Die Vorspanneinrichtung kann beispielsweise auch durch schräg verzahnte Zahnräder auf die Rotoren wirkende Kräfte aufnehmen und/oder generell eine auslegungsgerechte Vorspannung der Lager unabhängig vom Betriebszustand bei sich verändernden Drücken bzw. Druckverhältnissen gewährleisten.At the beginning of a pumping process by the pump 10, there is usually essentially the same pressure at the inlet 22 as at the outlet. In contrast, during the pumping down, the pressure at the inlet 22 drops to a final pressure which is essentially zero with regard to the resulting forces. Thus, the pressure at the outlet 24 exerts a force on the rotors 28, 30 that is different than at the beginning of the pumping process. To balance this force e.g. a biasing device, in particular a spring, may be provided, which is provided in particular in the case of a loose bearing of the rotor and / or on the inlet side. The pretensioning device can, for example, also absorb forces acting on the rotors through helically toothed gearwheels and / or generally ensure that the bearings are preloaded in accordance with the design, regardless of the operating state when the pressures or pressure conditions change.

In Fig. 5 ist ein Tauchkühler 34 dargestellt, wie er im Getriebekasten 14 bzw. im Deckel 20 der Schraubenvakuumpumpe 10 angeordnet ist. In dieser Ausführungsform sind die Tauchkühler 34 also identisch ausgebildet, was zu einer geringen Teilevielfalt und geringen Herstellungskosten führt.In Fig. 5 An immersion cooler 34 is shown as it is arranged in the gearbox 14 or in the cover 20 of the screw vacuum pump 10. In this embodiment, the immersion coolers 34 are therefore of identical design, which leads to a small number of parts and low manufacturing costs.

Der Tauchkühler 34 weist eine Kühlleitung 72 auf, die durch einen Kühlkörper 74 verläuft. Der Kühlkörper weist eine Strukturierung zur Erhöhung der Oberfläche des Kühlkörpers auf, um die Wärmeübertragung zu optimieren. Der Tauchkühler 34 weist außerdem einen Flansch 76 auf, mit dem der Tauchkühler 34 befestigt wird.The immersion cooler 34 has a cooling line 72 which runs through a heat sink 74. The heat sink has a structure for increasing the surface of the heat sink in order to optimize the heat transfer. The immersion cooler 34 also has a flange 76 with which the immersion cooler 34 is fastened.

In Fig. 6 ist der Ansaugbereich 67 der Schraubenvakuumpumpe 10 in einer perspektivischen Schnittansicht veranschaulicht. Im Ansaugbereich 67 sind jeweilige ansaugseitige Enden der Schraubenprofile 38 und 40 angeordnet, die infolge ihrer Rotation und in Zusammenwirken mit einer Abschlussfläche 78 wiederholt Fördervolumina abschließen und entlang der Rotorachsen zum Auslass 24 fördern.In Fig. 6 the suction area 67 of the screw vacuum pump 10 is illustrated in a perspective sectional view. In the suction area 67, respective suction-side ends of the screw profiles 38 and 40 are arranged, which due to their rotation and in cooperation with an end surface 78 repeatedly close delivery volumes and convey them along the rotor axes to the outlet 24.

Die Abschlussfläche 78 ist im Wesentlichen als Freiformfläche ausgebildet, sie weist also eine von einer einfachen Ebene abweichende, relativ komplexe Form auf. Beispielsweise weist die Abschlussfläche 78 einen dachartigen, unteren Bereich 80 und einen tal- oder rinnenartigen, oberen Bereich 82 auf. Eine spanende Bearbeitung der Abschlussfläche 78 wäre also sehr aufwendig, insbesondere wenn eine hohe Präzision erforderlich ist. Die Abschlussfläche 78 ist dagegen unbearbeitet ausgeführt. Sie wird bei einem Gießen des Gehäuses 16 durch eine entsprechende Form ausgebildet. Zwar wird hierdurch eine relativ ungenaue Abschlussfläche 78 geschaffen, dies ist jedoch wegen des erfindungsgemäß relativ langen ersten Abschnitts 62 im Wesentlichen unproblematisch. Die spanende Bearbeitung lässt sich hier also vorteilhaft einsparen.The end surface 78 is essentially designed as a free-form surface, ie it has a relatively complex shape that deviates from a simple plane. For example, the end surface 78 has a roof-like, lower area 80 and a valley-like or groove-like, upper area 82. Machining the end surface 78 would therefore be very complex, especially if high precision is required. The end face 78, however, is unprocessed. It is formed by casting the housing 16 by an appropriate shape. Although this creates a relatively imprecise end face 78, this is essentially unproblematic because of the first section 62, which is relatively long in accordance with the invention. Machining can be saved here advantageously.

Die Schnittdarstellung der Fig. 6 ist in Fig. 7 in einer Seiteansicht gezeigt, um den Verlauf der Abschlussfläche 78 weiter zu verdeutlichen. Dabei ist nur der Schraubenrotor 30 sichtbar, da er in dieser Ansicht den Schraubenrotor 28 verdeckt.The sectional view of the Fig. 6 is in Fig. 7 shown in a side view to further illustrate the course of the end surface 78. Only the screw rotor 30 is visible, since it hides the screw rotor 28 in this view.

Wie in Fig. 7 ersichtlich, verläuft die Abschlussfläche 78 in einem den Schraubenrotor 30 umschließenden Bereich im Wesentlichen parallel bzw. korrespondierend zu dessen Schraubenprofil 40. Wenn sich der Rotor 30 in Bezug auf Fig. 6 gegen den Uhrzeigersinn dreht, verkleinert sich der Abstand zwischen dem Schraubenprofil 40 und der Abschlussfläche 78 bis der Abstand Null ist und ein Fördervolumen im entsprechenden Profilzwischenraum 84 abschlossen ist.As in Fig. 7 can be seen, the end face 78 runs in a region surrounding the screw rotor 30 essentially parallel or corresponding to its screw profile 40. When the rotor 30 is in relation to one another Fig. 6 rotates counterclockwise, the distance between the screw profile 40 and the end face 78 decreases until the distance is zero and a delivery volume is closed in the corresponding profile space 84.

In Fig. 8 ist das Gehäuse 16 der Schraubenvakuumpumpe 10 in perspektivischer Ansicht ohne die Schraubenrotoren 28, 30 gezeigt. Hier wird nochmals deutlich, dass die komplexe Abschlussfläche 78 nur unter hohem Aufwand präzise, insbesondere durch spanende Verfahren wie etwa Abzeilen, in eine gewünschte Form gebracht werden kann. Die Abschlussfläche 78 lässt sich wegen ihrer komplexen Form nicht oder nur unter großem Aufwand vermessen und birgt damit zusätzlich eine Gefahr für die Serienfertigung, da etwaige Mängel ohne aufwendige Vermessung womöglich erst im Rahmen einer Endprüfung der Pumpe aufgedeckt werden können. Damit gehen hohe Montage- bzw. Herstellungskosten und teure Ausschussteile einher. Durch die Erfindung wird allgemein der Einfluss der Genauigkeit der Abschlussfläche 78 auf die vakuumtechnischen Leistungsdaten verringert.In Fig. 8 the housing 16 of the screw vacuum pump 10 is shown in perspective view without the screw rotors 28, 30. Here it becomes clear once again that the complex end surface 78 can only be brought into a desired shape with great effort, in particular by machining processes such as ripping. Because of its complex shape, the end surface 78 cannot be measured or can only be measured with great effort and therefore also hides a danger for series production, since any defects can only be uncovered during a final inspection of the pump without extensive measurement. This goes hand in hand with high assembly and manufacturing costs and expensive rejects. The invention generally reduces the influence of the accuracy of the end face 78 on the vacuum performance data.

Fig. 9 zeigt ein Diagramm, dessen Abszisse einen Druck p in Hektopascal eines Prozessgases am Einlass einer untersuchten Schraubenvakuumpe und dessen Ordinate ein Saugvermögen S in Kubikmeter pro Stunde der Pumpe repräsentieren. Es sind zwei Verläufe 86 und 88 des Saugvermögens in Abhängigkeit des Einlassdrucks gezeigt. Fig. 9 shows a diagram, the abscissa of which represents a pressure p in hectopascals of a process gas at the inlet of a screw vacuum pump under investigation and whose ordinate represents a pumping speed S in cubic meters per hour of the pump. Two curves 86 and 88 of the pumping speed as a function of the inlet pressure are shown.

Dem gestrichelten Verlauf 86 liegt eine beispielhafte Schraubenvakuumpumpe zugrunde mit einem Einlassbereich bzw. mit einer Abschlussfläche, die spanend auf eine Sollkontur bearbeitet wurden. Dabei entspricht die Länge eines ersten Abschnitts konstanter Steigung im Wesentlichen der Länge eines abgeschlossenen Fördervolumens im ersten Abschnitt. Die beispielhafte Schraubenvakuumpumpe des Verlaufs 86 ist folglich nicht erfindungsgemäß ausgestaltet.The dashed curve 86 is based on an exemplary screw vacuum pump with an inlet area or with an end surface that has been machined to a desired contour. The length of a first section of constant slope essentially corresponds to the length of a closed delivery volume in the first section. The exemplary screw vacuum pump of the course 86 is therefore not designed according to the invention.

Der als Volllinie dargestellte Verlauf 88 wurde aufgenommen für eine weitere beispielhafte Schraubenvakuumpe, bei der ein zur spanenden Bearbeitung der Abschlussfläche vorgesehenes Aufmaß belassen und nicht bearbeitet wurde. Ansonsten ist die Schraubenvakuumpumpe des Verlaufs 88 identisch zur Schraubenvakuumpumpe des Verlaufs 86 ausgebildet. Die beiden Pumpen bzw. Abschlussflächen unterscheiden sich also lediglich um ein gewisses Aufmaß. Das Aufmaß ist in Richtung der Rotorachsen vorgesehen, weshalb bei unveränderten Rotoren ein jeweiliges Fördervolumen früher abgeschlossen wird und damit der erste Abschnitt länger ist als ein Fördervolumen. Die Schraubenvakuumpumpe des Verlaufs 88 ist folglich erfindungsgemäß ausgebildet.The curve 88 shown as a solid line was recorded for a further exemplary screw vacuum pump, in which an oversize intended for machining the end face was left and was not machined. Otherwise, the screw vacuum pump of the course 88 is identical to the screw vacuum pump of the course 86. The two pumps or end faces only differ by a certain allowance. The oversize is provided in the direction of the rotor axes, which is why with unchanged rotors a respective delivery volume is completed earlier and the first section is therefore longer than a delivery volume. The screw vacuum pump of the course 88 is consequently designed according to the invention.

Beide Verläufe 86 und 88 weisen einen für Schraubenvakuumpumpen mit innerer Verdichtung typischen Saugvermögensverlauf auf. Dabei ist das Saugvermögen in einem mittleren Druckbereich am größten. Dagegen ist das Saugvermögen bei hohen Drücken bzw. am Anfang eines Abpumpvorgangs, in Fig. 9 rechts, niedriger. Das Saugvermögen sinkt bei Erreichen eines Enddrucks, in Fig. 9 links, auf Null.Both curves 86 and 88 have a pumping speed curve typical of screw vacuum pumps with internal compression. The pumping speed is greatest in a medium pressure range. In contrast, the pumping speed at high pressures or at the beginning of a pumping process is in Fig. 9 right, lower. The pumping speed drops when a final pressure is reached, in Fig. 9 left, to zero.

Im mittleren Bereich zeigt der Verlauf 86 ein höheres Saugvermögen. Hier macht es sich bemerkbar, dass die Fördervolumina wegen der präzise auf Sollkontur gefertigten Abschlussfläche präzise abgeschlossen werden. Dieser Effekt ist durch Pfeil 90 angedeutet. Das Saugvermögen gemäß Verlauf 86 entspricht hier im Wesentlichen einem theoretischen Saugvermögen. Eine Rückströmung infolge einer Kompression, insbesondere zu einem zweiten Abschnitt, ist in diesem mittleren Druckbereich also kein dominanter Effekt.In the middle area, the course 86 shows a higher pumping speed. It is noticeable here that the delivery volumes are precisely closed due to the end surface being precisely manufactured to the target contour. This effect is indicated by arrow 90. The pumping speed according to curve 86 essentially corresponds to a theoretical pumping speed. A backflow due to compression, in particular to a second section, is therefore not a dominant effect in this middle pressure range.

Ein Pfeil 92 deutet an, dass der erreichbare Enddruck bei der Schraubenvakuumpumpe mit Aufmaß, also beim Verlauf 88, niedriger bzw. besser ist. Dies wird darauf zurückgeführt, dass durch das Aufmaß die gesamte pumpaktive Länge der Schraubenrotoren größer ist. Entsprechend länger sind die Spalte zwischen Rotoren und Gehäuse, sodass insgesamt eine bessere Abdichtung gegen Rückströmen vom Auslass zum Einlass erreicht wird.An arrow 92 indicates that the achievable final pressure in the screw vacuum pump with oversize, that is to say with the course 88, is lower or better. This is attributed to the fact that the overall pump-active length of the screw rotors is greater due to the measurement. The gaps between the rotors and the housing are correspondingly longer, so that overall a better seal against backflows from the outlet to the inlet is achieved.

Überraschend hat sich durch die der Fig. 9 zugrundeliegenden Versuche gezeigt, dass die Schraubenvakuumpumpe mit Aufmaß bzw. der Verlauf 88 auch ein verbessertes Saugvermögen bei hohen Drücken aufweist, was durch Pfeil 94 angedeutet ist. Dies wird darauf zurückgeführt, dass ein durch das Aufmaß verlängerter Spalt zwischen einer inneren Verdichtung der Pumpe und einem Ansaugbereich vorliegt, was wiederum zu einer entsprechend verbesserten Abdichtung gegen Rückströmung führt. Dies macht sich im Bereich hoher Drücke besonders bemerkbar, da hier die innere Verdichtung zu den höchsten Innendrücken bzw. über Spalten wirkenden Differenzdrücken führt.Surprised by the Fig. 9 underlying experiments showed that the screw vacuum pump with oversize or the course 88 also has an improved pumping speed at high pressures, which is indicated by arrow 94. This is attributed to the fact that there is a gap between an internal compression of the pump and a suction area which is lengthened due to the oversize, which in turn leads to a correspondingly improved sealing against backflow. This is particularly noticeable in the area of high pressures, since here the internal compression leads to the highest internal pressures or differential pressures acting via gaps.

Es zeigt sich, dass die erfindungsgemäße Schraubenvakuumpumpe, insbesondere deren Gehäuse, besonders einfach herzustellen ist, da der Einfluss der entsprechenden Oberflächengenauigkeit verringert wurde. Insbesondere kann dadurch auf eine aufwendige, spanende Bearbeitung des Gehäuses im Einlassbereich bzw. an einer Abschlussfläche verzichtet werden. Dabei ist ein negativer Einfluss auf die Vakuumleistung gering und in manchen Druckbereichen führt die Erfindung sogar zu einer Verbesserung der Leistungsdaten.It turns out that the screw vacuum pump according to the invention, in particular its housing, is particularly simple to manufacture, since the influence of the corresponding surface accuracy has been reduced. In particular, this eliminates the need for complex machining of the housing in the inlet area or on an end surface. A negative influence on the vacuum performance is small and in some pressure ranges the invention even leads to an improvement in the performance data.

BezugszeichenlisteReference list

1010th
SchraubenvakuumpumpeScrew vacuum pump
1212th
Motorengine
1414
GetriebekastenGear box
1616
Gehäusecasing
1818th
LagerschildEnd shield
2020
Deckelcover
2222
Einlassinlet
2424th
AuslassOutlet
2626
KühlleitungCooling pipe
2828
SchraubenrotorScrew rotor
3030th
SchraubenrotorScrew rotor
3232
NutGroove
3434
TauchkühlerImmersion cooler
3636
TaillierungWaist
3838
SchraubenprofilScrew profile
4040
SchraubenprofilScrew profile
4242
SynchronisierungsgetriebeSynchronization gear
4343
Zahnradgear
4444
Gehäusecasing
4646
Statorstator
4848
MagnetträgerMagnetic carrier
5050
VergusskörperPotting body
5252
Platinecircuit board
5454
SpritzscheibeWasher
5656
Lagercamp
5858
DeflektorDeflector
6060
KolbenringträgerPiston ring carrier
6262
erster Abschnittfirst section
6363
SchraubenachseScrew axis
6464
zweiter Abschnittsecond part
6666
dritter Abschnittthird section
6767
AnsaugbereichSuction area
6868
Lagercamp
7070
LagerschildEnd shield
7272
KühlleitungCooling pipe
7474
KühlkörperHeatsink
7676
Flanschflange
7878
AbschlussflächeFinishing area
8080
unterer Bereichlower area
8282
oberer Bereichupper area
8484
ProfilzwischenraumProfile space
8686
SaugvermögensverlaufPumping speed curve
8888
SaugvermögensverlaufPumping speed curve
9090
Pfeilarrow
9292
Pfeilarrow
9494
Pfeilarrow
pp
EinlassdruckInlet pressure
SS
SaugvermögenPumping speed

Claims (14)

  1. A screw vacuum pump (10) comprising
    a housing (16);
    two screw rotors (28, 30) which are arranged in the housing (16), which are in engagement with one another and which, for the conveying of a process gas, repeatedly form closed conveying volumes of the process gas in cooperation with the housing (16) and convey them in the direction of an outlet (24),
    wherein the screw rotors (28, 30) each have at least two sections (62, 64) which are adjacent along the screw axis (63);
    wherein the screw rotors (28, 30) each have an at least substantially constant pitch in a first section (62) disposed closer to an inlet (22) and have a lower pitch in a second section (64) than in the first section (62); and wherein the first section (62) is longer with respect to the screw axis (63) than a closed conveying volume in the first section (62),
    characterized in that
    a termination surface (78) for the screw rotors (28, 30) is formed in a suction region (67) of the pump and is adapted with respect to its shape to the screw rotors (28, 30) such that a respective conveying volume can be opened for suction and closed for conveying.
  2. A screw vacuum pump (10) in accordance with claim 1,
    characterized in that
    the closed conveying volume covers an angle of 360° about the screw axis (63) of the respective rotor (28, 30).
  3. A screw vacuum pump (10) in accordance with claim 1 or claim 2,
    characterized in that
    the first section (62) corresponds to at least 1.25 times the length of the conveying volume.
  4. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the first section (62) corresponds to at least 1.5 times the length of the conveying volume.
  5. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the first section (62) corresponds to at least 1.75 times the length of the conveying volume.
  6. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the first section (62) corresponds to at least twice the length of the conveying volume.
  7. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the termination surface (78) is formed in a casting (16) and is not machined.
  8. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the termination surface (78) is formed in the housing (16).
  9. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    a screw profile (38, 40) of a respective screw rotor (28, 30) is formed by a cycloid.
  10. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    a screw profile (38, 40) of a respective screw rotor (28, 30) is configured as a two-start screw profile.
  11. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the screw rotors (28, 30) each have an at least substantially and at least regionally constant pitch in the second section (64).
  12. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the screw rotors (28, 30) each have at least one third section (66) and their pitch is smaller in the third section (66) than in the second section (64).
  13. A screw vacuum pump (10) in accordance with claim 12,
    characterized in that
    the pitch is at least substantially constant in the third section (66).
  14. A screw vacuum pump (10) in accordance with at least one of the preceding claims,
    characterized in that
    the screw rotors (28, 30) each have a plurality of sections (62, 64, 66) of different pitches over their total pump-active length, with the pitch being constant in all the sections (62, 64, 66).
EP17207558.2A 2017-12-15 2017-12-15 Screw vacuum pump Active EP3499041B1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP17207558.2A EP3499041B1 (en) 2017-12-15 2017-12-15 Screw vacuum pump
JP2018232382A JP2019143620A (en) 2017-12-15 2018-12-12 Screw type vacuum pump
JP2021011798A JP7339973B2 (en) 2017-12-15 2021-01-28 screw vacuum pump

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP17207558.2A EP3499041B1 (en) 2017-12-15 2017-12-15 Screw vacuum pump

Publications (2)

Publication Number Publication Date
EP3499041A1 EP3499041A1 (en) 2019-06-19
EP3499041B1 true EP3499041B1 (en) 2020-07-01

Family

ID=60781573

Family Applications (1)

Application Number Title Priority Date Filing Date
EP17207558.2A Active EP3499041B1 (en) 2017-12-15 2017-12-15 Screw vacuum pump

Country Status (2)

Country Link
EP (1) EP3499041B1 (en)
JP (2) JP2019143620A (en)

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06288369A (en) * 1993-04-06 1994-10-11 Hitachi Ltd Suction port of screw compressor
JP3831115B2 (en) * 1998-04-06 2006-10-11 大晃機械工業株式会社 Dry vacuum pump
DE10019637B4 (en) * 2000-04-19 2012-04-26 Leybold Vakuum Gmbh Screw vacuum pump
US6508639B2 (en) * 2000-05-26 2003-01-21 Industrial Technology Research Institute Combination double screw rotor assembly
JP4853168B2 (en) * 2006-08-10 2012-01-11 株式会社豊田自動織機 Screw pump
JP4900270B2 (en) * 2008-02-08 2012-03-21 株式会社豊田自動織機 Screw pump
JP2009243280A (en) * 2008-03-28 2009-10-22 Hokuetsu Kogyo Co Ltd Surface treatment method for casing for screw fluid machine, and casing for screw fluid machine
JP5353521B2 (en) * 2009-07-22 2013-11-27 株式会社豊田自動織機 Screw rotor
DE102011054607A1 (en) * 2010-10-27 2012-06-21 Gebr. Becker Gmbh vacuum pump
DE202016005209U1 (en) * 2016-08-30 2017-12-01 Leybold Gmbh Screw vacuum pump
DE202016005208U1 (en) * 2016-08-30 2017-12-01 Leybold Gmbh Dry-compacting vacuum pump

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Also Published As

Publication number Publication date
JP2019143620A (en) 2019-08-29
EP3499041A1 (en) 2019-06-19
JP7339973B2 (en) 2023-09-06
JP2021102960A (en) 2021-07-15

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